Showing papers in "Microscopy Research and Technique in 1997"
TL;DR: In this paper, the structure and function of insect mechanoreceptors with respect to their cellular, subcellular, and cuticular organization are discussed and four types are described: 1, the bristles; 2, the trichobothria; 3, the campaniform sensilla; and 4, the scolopidia.
Abstract: This paper reviews the structure and function of insect mechanoreceptors with respect to their cellular, subcellular, and cuticular organization. Four types are described and their function is discussed: 1, the bristles; 2, the trichobothria; 3, the campaniform sensilla; and 4, the scolopidia. Usually, bristles respond to touch, trichobothria to air currents and sound, campaniform sensilla to deformation of the cuticle, and scolopidia to stretch. Mechanoreceptors are composed of four cells: a bipolar sensory neuron, which is enveloped by the thecogen, the trichogen, and the tormogen cells. Apically, the neuron gives off a ciliary dendrite which is attached to the stimulus-transmitting cuticular structures. In types 1–3, the tip of the dendrite contains a highly organized cytoskeletal complex of microtubules, the “tubular body,” which is connected to the dendritic membrane via short rods, the “membrane-integrated cones” (MICs). The dendritic membrane is attached to the cuticle via fine attachment fibers. The hair-type sensilla (types 1, 2) are constructed as first-order levers, which transmit deflection of the hair directly to the dendrite tip. In campaniform sensilla (type 3), there is a cuticular dome instead of a hair and the dendrite is stimulated by deformation of the cuticle. In these three types, a slight lateral compression of the dendrite tip is most probably the effective stimulus. In scolopidia, the dendritic membrane is most probably stimulated by stretch. On the subcellular level, connectors between the cytoskeleton, the dendritic membrane, and extracellular (cuticular) structures are present in all four types and are thought to be engaged in membrane depolarization. Microsc. Res. Tech. 39:506–531, 1997. © 1997 Wiley-Liss, Inc.
359 citations
TL;DR: Along with these developmental changes in the biliary tract, the peribiliary glands and the vascular plexus also develop in a step‐wise manner and their maturation is completed after birth.
Abstract: Microstructure and development of the normal biliary tract and the pathologies of several biliary tract diseases in humans are reviewed. The biliary tract, comprising the bile duct and peribiliary glands, is anatomically divided into the extrahepatic and intrahepatic biliary tree. The intrahepatic biliary tree is further divided into large bile ducts, corresponding to the right and left hepatic ducts and their first to third order branches, and into septal and interlobular bile ducts and bile ductules according to their size and location relative to the hepatic lobules and surrounding structures. The right and left hepatic ducts and the extrahepatic bile ducts are composed of dense fibrous duct walls lined by a layer of columnar biliary epithelium. The peribiliary glands, which may secrete mucinous and serous substances into the bile, are found along the extrahepatic and large intrahepatic bile ducts. They are divided in glands within and outside the duct wall. The former (intramural glands) drain directly into the lumen of the bile duct, while the latter (extramural glands) are composed of several lobules and drain into the ductal lumen via their own conduits. The biliary tract is supplied by a complex vasculature called the peribiliary vascular plexus. Afferent vessels of this plexus derive from hepatic arterial branches, and this plexus drains into the portal venous system or directly hepatic sinusoids. The development of the intrahepatic biliary tract is divided into three stages: the stage of the ductal plate, the stage of biliary cell migration into the mesenchyme, and the stage of bile duct formation in the portal tract. It remains unclear how the extrahepatic and intrahepatic biliary tract integrate. Along with these developmental changes in the biliary tract, the peribiliary glands and the vascular plexus also develop in a step-wise manner and their maturation is completed after birth. Pathologies of various biliary diseases are briefly reviewed noting their relevance to several histologic elements and the microenvironment of the biliary tract and the developmental anomalies of the biliary tract including ductal plate malformation.
265 citations
TL;DR: The zone of calcified cartilage (ZCC) forms an important interface between cartilage and bone for transmitting force, attaching cartilage to bone, and limiting diffusion from bone to the deeper layers of cartilage.
Abstract: The zone of calcified cartilage (ZCC) forms an important interface between cartilage and bone for transmitting force, attaching cartilage to bone, and limiting diffusion from bone to the deeper layers of cartilage. The height of the ZCC is a relatively constant percent of articular cartilage and the height is maintained by a balance between progression of the tidemark into the unmineralized cartilage and changing into bone by vascular invasion and bony remodeling. During its formation, the cells that form the ZCC have properties similar to the cells of the growth plate. In the adult, the ZCC becomes quiescent but not inactive. The ZCC may be reactivated in osteoarthritis and may progressively calcify the unmineralized cartilage. This might contribute to cartilage thinning which would increase the concentration of forces across the uncalcified cartilage leading to more damage. Although the subchondral bony plate remodels extensively in osteoarthritis, there is little evidence that a change in the biomechanics of the plate directly initiates the osteoarthritic process in cartilage. However, increased repair by endochondral ossification of vertical cracks in the ZCC that penetrate into the marrow space could contribute to progression via changes in the ZCC.
241 citations
TL;DR: It is concluded that changes in the subchondral mineralized tissues are not required for initiation of cartilage fibrillation, but may be necessary for progression, and that only changes in bone and calcified cartilage close to the joint are significant to the disease process.
Abstract: This paper reviews evidence for the role of subchondral bone and calcified cartilage in the initiation and progression of osteoarthrosis (OA). There is consensus that OA is characterized by subchondral sclerosis, but disagreement about whether bone changes are concurrent with, primary to, or secondary to cartilage deterioration. Clinical observation suggests that bone density and cartilage fibrillation are inversely related. Evidence from the rabbit impulsive loading model is consistent with early bone changes, but evidence from other models of subchondral stiffening, such as the sheep metallic implant model, do not strongly support this idea. However, evidence from tibial angulation models and from the Pond-Nuki (anterior cruciate ligament resection) model show evidence that bone changes precede cartilage fibrillation temporally, and are associated spatially within a single joint. Evidence is also presented for the importance of calcified cartilage changes in pre-disposing the joint towards progression to OA. Microdamage accumulation and repair by vascular invasion may be a component of the pathogenesis of OA in some cases, but more work is needed to demonstrate this conclusively. We conclude that changes in the subchondral mineralized tissues are not required for initiation of cartilage fibrillation, but may be necessary for progression, and that only changes in bone and calcified cartilage close to the joint are significant to the disease process.
225 citations
TL;DR: With age, and in some pathologic conditions, skinElastin may undergo irreversible structural and compositional changes, which seem to progress from localized deposition of osmiophilic materials to the substitution of the great majority of the amorphous elastin with interwoven filaments negative for elastIn specific antibodies.
Abstract: Elastin molecules aggregate in the extracellular space where they are crosslinked by stable desmosine bridges. The resulting polymer is structurally organized as branched fibers and lamellae, which, in skin, are wider (a few microns) in the deep dermis and become progressively thinner (fraction of a micron) towards the papillary dermis. Several general and local factors seem to regulate elastin gene expression, deposition and degradation. In skin, the volume density of the elastin network increases from birth up to maturity, when it accounts for about 3-4% of the tissue. However, its amount and distribution depend on dermis areas, which are different among subjects and change with age. Several matrix molecules (glycosaminoglycans, decorin, biglycan, osteopontin) have been found to be associated with elastin into the normal fiber, and several others have been recognized within pathologic elastic fiber (osteonectin, vitronectin, alkaline phosphatase in PXE). With age, and in some pathologic conditions, skin elastin may undergo irreversible structural and compositional changes, which seem to progress from localized deposition of osmiophilic materials to the substitution of the great majority of the amorphous elastin with interwoven filaments negative for elastin specific antibodies.
196 citations
TL;DR: Morphologic evidence suggests that the layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear.
Abstract: The ultrastructure of the round window membrane of humans, monkeys, felines, and rodents discloses three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Interspecies variations are mainly in terms of thickness, being thinnest in rodents and thicker in humans. Morphologic evidence suggests that the layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Different substances, including antibiotics, local anesthetics, and tracers such as cationic ferritin, horseradish peroxidase, and 1 mu latex microspheres, are placed in the middle ear side traverse the membrane. Cationic ferritin and 1 micron microspheres placed in perilymph become incorporated by the inner epithelial cells of the membrane. Permeability is selective; factors include size, concentration, liposolubility, electrical charge, and thickness of the membrane. Passage of substances through the round window membrane is by different pathways, the nature of which is seemingly decided at the outer epithelium of the round window membrane.
193 citations
TL;DR: A recent review as mentioned in this paper summarized associations of microalgae, protozoans, and bacteria with marine crustaceans, especially copepods, and suggested future research opportunities for microbial epibionts in aquatic environments.
Abstract: Although the occurrence of microbial (algal, protozoan, bacterial, and fungal) epibionts on marine crustaceans and other invertebrates has been documented repeatedly, the ecological context and significance of these relationships generally are not well understood. Recently, several studies have examined the population and community ecology of algal and protozoan epibionts on freshwater crustaceans. Even so, the study of microbial epibionts in aquatic environments is still in its infancy. In this review, we summarize associations of microalgae, protozoans, and bacteria with marine crustaceans, especially copepods. We note differences and commonalities across epibiont taxa, consider host-epibiont cycling of nutrients, generate hypotheses relevant to the ecology of the host and the epibiont, and suggest future research opportunities. Microsc. Res. Tech. 37:116–135, 1997. © 1997 Wiley-Liss, Inc.
171 citations
TL;DR: In truely vitrified tissue, a network of fine cross‐banded filaments with a periodicity characteristic of collagen fibrils is seen throughout the extracellular substance, even within the pericellular compartment, which has hitherto been deemed free of such components.
Abstract: The ultrastructure of adult human articular cartilage matrix is reexamined in tissue processed according to recently improved cryotechniques [Studer et al. (1995) J. Microsc., 179:321–332]. In truely vitrified tissue, a network of fine cross-banded filaments (10–15 nm in diameter) with a periodicity characteristic of collagen fibrils is seen throughout the extracellular substance, even within the pericellular compartment, which has hitherto been deemed free of such components. Proteoglycans fill the interstices between these entities as a homogeneously distributed granular mass; they do not manifest a morphologically identifiable reticular structure. Longitudinally sectioned collagen fibrils exhibit variations in thickness and kinking; they tend to align with their periodic banding in register and are frequently seen to split or fuse along their longitudinal course. The tendency of fibrils to form bundles is greater in deeper zones than in more superficial ones.
A duality in the orientation of fibrils and fibril bundles is observed within the interterritorial matrix compartment: superimposed upon the well-characterized arcade-like structure formed by one subpopulation is another, more randomly arranged one. The classical concepts of matrix organization thus need to be modified and refined to encompass these findings. Microsc. Res. Tech., 37:271–284, 1997. © 1997 Wiley-Liss, Inc.
168 citations
TL;DR: Freeze‐fracture electron microscopy has been used to investigate the structure of human airway tight junctions and their morphology comprehensively characterised at two airway levels (main and lobar bronchi).
Abstract: The flux of fluid, ions, macromolecules, and inflammatory cells across airway epithelium depends in part upon the integrity of its apico-lateral tight junctions. Without the correct balance of fluid and ions, the normal functioning of mucociliary clearance and the neural responsiveness of the airways cannot take place. Freeze-fracture electron microscopy has been used to investigate the structure of human airway tight junctions and their morphology comprehensively characterised at two airway levels (main and lobar bronchi). Further data is needed to establish if the fall in transepithelial electrical resistance found across progressively proximal disparate airway generations is correlated with an alteration in tight junction morphology. Altered epithelial permeability is associated with the development of the airway conditions: asthma, chronic bronchitis, and cystic fibrosis. However, few data have been published on the structure of tight junctions in asthma and chronic bronchitis. In patients with cystic fibrosis, airways obtained at transplantation and postmortem show a basal extension of the apico lateral tight junctional belt. This change is not unique to cystic fibrosis airways as it also occurs in non-respiratory systems postmortem. However the functional relevance of these changes remains uninvestigated and recently developed in vitro models may help answer this question. The data demonstrate that tight junctions are highly dynamic structures capable of rapid alterations in disease and in response to functional stress.
132 citations
TL;DR: The development and differentiation of bile ducts in the human and rodent liver are reviewed and periportal connective tissue, glucocorticoid hormones, and basal laminar components may play important roles in the differentiation.
Abstract: The development and differentiation of bile ducts in the human and rodent liver are reviewed. The liver primordium develops as a ventral diverticulum in the anterior intestinal portal region, which consists of endodermal and mesodermal components. The endodermal cells differentiate into hepatocytes and all epithelial cells of the bile ducts in the adult liver. The gallbladder and extrahepatic bile ducts also start to develop from hepatic endodermal cells and hepatoblasts just after liver primordium formation. The gallbladder and cystic duct do not develop through hepatic development in the rat. Intrahepatic bile ducts are formed from periportal hepatoblasts forming the “ductal plate” and expressing alpha-fetoprotein, and albumin and bile duct-specific cytokeratin and develop independently of extrahepatic bile duct formation. The first sign of intrahepatic bile duct differentiation is the increased expression of bile duct–specific cytokeratin and large lumina formation in periportal hepatoblasts, and then deposition of basal laminar components occurs on the basal side. Their development takes place discontinuously along portal veins at the early stage of development, and they then become confluent through development. Periportal connective tissue, glucocorticoid hormones, and basal laminar components may play important roles in the differentiation of bile ducts. Microsc. Res. Tech. 39:328–335, 1997. © 1997 Wiley-Liss, Inc.
130 citations
TL;DR: Results of all analyses were consistent with dominant sulfur‐based endosymbioses in the clam and mussel and the general absence of methane symbioses at the site, strengthening the analogy of the whale‐skeleton faunal community to those known from distant Pacific hydrothermal vent sites.
Abstract: To explore the microbial basis for a remarkable macrofaunal community at the site of a whale skeleton on the seafloor of the Santa Catalina Basin, we obtained samples of whale bone, bone-colonizing invertebrates, microbial mats, and the dominant fauna in the adjacent sulfide-rich sediments during Alvin expeditions in 1988 and 1991. Invertebrate tissues were examined by transmission electron microscopy (TEM) and mats and bone-penetrating bacteria by epifluorescence microscopy (EM). Tissues from the dominant bivalve Vesicomya c.f. gigas, the mytilid mussel Idasola washingtonia, and selected gastropods and limpets were also assayed chemically for enzymes diagnostic of sulfur- and methane-based chemoautotrophy and for stable carbon isotopic composition. Results of all analyses were consistent with dominant sulfur-based endosymbioses in the clam and mussel (the first record of endosymbiosis in the genus Idasola) and the general absence of methane symbioses at the site, strengthening the analogy of the whale-skeleton faunal community to those known from distant Pacific hydrothermal vent sites. Examples of minor endosymbionts, either nitrifying or methanotrophic cells according to internal membrane structures by TEM, raised the possibility of a supplemental mode of nutrition to the clam, or means to remove ammonia in the gill tissue, in the event of significant changes in the chemical environment.
TL;DR: Four distinct zones of cell generation were identified within the retina, each associated with either glial, vascular, or neuronal cytogenesis, confirming earlier studies.
Abstract: A method was developed for detecting cytogenesis in retinal whole-mount preparations by bromodeoxyuridine (BrdU) immunohistochemistry. Because BrdU is a nonspecific marker that labels all cells in the S phase of the cell cycle, it is ideally combined with other cell-specific markers to study the cytogenesis of specific cell types. Double-label protocols to visualize mitotically active astrocytes and cells associated with the forming vasculature have been developed and applied to the retina. This approach revealed that, during normal development of the kitten retina, vascular mitogenesis occurs predominantly in the ganglion cell and nerve fiber layers, where the inner retinal plexus is formed by a process involving transformation of mesenchymal precursor cells and division of vascular endothelial cells. The peak density of vascular mitogenesis moved in a central-to-peripheral manner and was associated with the leading edge of the forming capillary plexus. A small number of dividing vascular endothelial cells was also associated with angiogenesis, the process responsible for the formation of the outer retinal plexus, vessels at the area centralis, and the radial peripapillary capillaries. Cytogenesis associated with astrocytes occurred in the ganglion cell and nerve fiber layers but was apparent predominantly at or close to the optic nerve head. Confirming earlier studies, neuronal mitogenesis was shown to occur predominantly at the ventricular zone, first at the area centralis and spreading peripherally with increasing maturity. A second region of neuronal cytogenesis, at the subventricular zone, was also apparent. Tissue hyperoxia decreased the rate of vasculogenic cell division but had no apparent effect on neurogenic or astrocytic cell division. Four distinct zones of cell generation were therefore identified within the retina, each associated with either glial, vascular, or neuronal cytogenesis. Thus, BrdU immunohistochemistry in whole-mounted retinal preparations offers a fast and reliable alternative to [3H]thymidine autoradiography for the study of the topography of cytogenesis during development.
TL;DR: It is demonstrated that the stem villi and their precursors, the immature intermediate villi, can selectively be identified by anti‐γ‐smooth muscle (sm) actin staining and the existence of three different subtypes ofstem villi is shown; these differ regarding the presence and distribution of γ‐sm actin‐positive cells.
Abstract: The stem villi of the human placenta represent the central branches of the villous trees. They are characterized by a condensed fibrous stroma in which the fetal arteries and veins as well as the arterioles and venules are embedded. Functionally they are accepted as the mechanically supporting structures of the villous trees, and they are supposed to control fetal blood flow to the maternofetal exchange area, which is located in the peripheral villi. To obtain further insights into the functions of the stem villi, the recent literature has been reviewed, and some immunohistochemical, ultrastructural, and reconstruction studies have been added. These new studies were aimed at identifying immunohistochemically different subtypes of stem villi, their branching patterns, the distribution of macrophages, the stromal proliferation patterns, and the differentiation of extravascular stromal cells. Our findings demonstrate that the stem villi and their precursors, the immature intermediate villi, can selectively be identified by anti-gamma-smooth muscle (sm) actin staining. Furthermore, the existence of three different subtypes of stem villi is shown; these differ regarding the presence and distribution of gamma-sm actin-positive cells. These cells were immunohistochemically and ultrastructurally identified as smooth muscle cells and myofibroblasts. Increasingly complex coexpression patterns of cytoskeletal proteins reflect a clearly defined differentiation gradient of extravascular stromal cells, which covers the whole range of an undifferentiated germinative layer beneath the trophoblast to highly differentiated myofibroblasts surrounding the medias of the stem vessels. Possible functions of the extravascular contractile system include the regulation of villous turgor and the control of intervillous blood flow impedance.
TL;DR: While the intercellular domains in some of the studied keratinization disorders showed an impaired distribution of the EL, X‐chromosomal ichthyosis showed normal lipid architecture, dry and scaly skin disorders are therefore not always accompanied by an impairment of the water permeability barrier.
Abstract: The water permeability barrier of the stratum corneum (SC) seems primarily to be regulated by the lamellarly arranged lipid bilayers between the corneocytes, which originate largely from polar lipid precursors provided by the cells of stratum granulosum via exocytosis of the lamellar body (LB) content. In particular, the structural organization of these intercellular lipid lamellae seems to be responsible for the very low water permeability of the intact skin, and these lipid-rich structures might also influence the desquamation process in the SC. The aim of this study was to obtain further insight into the distribution and organization of the epidermal lipids (EL) and the mechanism involved in desquamation and barrier function in normal human skin and scaling skin disorders. Biopsies of healthy human skin (n = 12), of inflammatory skin diseases (atopic dry skin (n = 9), psoriatic skin lesions [n = 2]), and of hereditary keratinization disorders (autosomal recessive ichthyoses congenita (n = 3), X-chromosomal ichthyosis (XCI) [n = 3]) were analyzed utilizing a special fixation protocol with ruthenium tetroxide (RuO4) postfixation. While the atopic dry skin revealed normal barrier structures, the psoriasis lesions were characterized by severe alteration of the lipid structures leading to an abnormal interaction with the desmosomal unit. While the intercellular domains in some of the studied keratinization disorders showed an impaired distribution of the EL (autosomal recessive ichthyoses), X-chromosomal ichthyosis showed normal lipid architecture. Dry and scaly skin disorders are therefore not always accompanied by an impairment of the water permeability barrier. Microsc. Res. Tech. 38:361–372, 1997. © 1997 Wiley-Liss, Inc.
TL;DR: The understanding of basic mechanisms of taste perception in insects is likely to lead to better management of useful as well as harmful insects.
Abstract: Insects have been favorites for the study of taste perception in the last few decades. They have been used for anatomical, behavioral, developmental, genetic, and physiological studies related to gustation and feeding response. Several genes known to affect the formation of gustatory sensilla or alter the feeding behavior of insects such as Drosophila are known. Studies related to signal transduction, coding of gustatory information, and the nature and constitution of genes involved in taste perception have also been taken up with insects in recent years. The understanding of basic mechanisms of taste perception in insects is likely to lead to better management of useful as well as harmful insects.
TL;DR: The results of this study suggest that different irritants induce distinct and characteristic alterations to reflect the specific interaction with the epidermal permeability barrier.
Abstract: The stratum corneum (SC) controls the diffusion and penetration of chemical substances and drugs into and through the skin. Surprisingly, knowledge of the SC structure and reaction to the various irritants is still poorly understood. Routine transmission electron microscopy has not been effective in demonstrating the epidermal lipids (EL) of SC which are believed to morphologically represent the water permeability barrier. To gain a better understanding of the interaction of chemically different irritants with the SC, we investigated the ultrastructural changes of epidermal lipids resulting from the topical application of sodium dodecyl sulfate (SDS 0.5% and 1% w/v) and absolute acetone. The disturbance of barrier function by these irritants was determined by the increase of transepidermal water loss (TEWL). Punch biopsies from the treated sites showed a maximum increase of TEWL. To visualize the EL which derive from lamellar body (LB) lipids (sheets), we used a special fixation method utilizing 0.5% ruthenium tetroxide/0.25% KFe(CN)6 as the postfixative. The 0.5% SDS caused cell damage to the nucleated cells of the epidermis with disturbance of LB lipid extrusion and the transformation into the lipid bilayers. However, the upper portions of SC displayed intact intercellular lipid layers. With the acetone treatment, the EL lamellae showed disruption and loss of cohesion between the lamellae at all levels of the SC. The more polar LB lipids appeared more resistant to acetone. The results of this study suggest that different irritants induce distinct and characteristic alterations to reflect the specific interaction with the epidermal permeability barrier.
TL;DR: To elucidate sinusoidal cell structure and function under normal conditions and their behavior in diseased settings, an understanding of their developmental aspects is needed.
Abstract: To elucidate sinusoidal cell structure and function under normal conditions and their behavior in diseased settings, an understanding of their developmental aspects is needed. At day 10 of gestation in mice and rats or at 5 weeks of gestation in humans, the hepatic cords grow into the mesenchymal tissue of the septum transversum, and the primitive sinusoidlike structure is simultaneously observed between the liver cell cords. In the margin of the growing liver primordium, mesenchymal cells in the septum transversum are trapped in the subendothelial space. These subendothelial cells are at the early stages of organogenesis and become progenitors of the Ito cells. By days 12-14 of gestation in mice and rats or 8 weeks of gestation in humans, the basic structure of the sinusoids has developed. Embryonic hepatic sinusoids are usually lined by a continuous endothelium without basement membranes, and an incompletely fenestrated sinusoid appears at the middle gestational stage. In the late gestational stages, the Ito cells exhibit myofibroblastlike features in humans, mice, and rats. In association with this event, perisinusoidal reticular networks are gradually intensified. After birth until days 4-5 in mice and rats, the sinusoidal and perisinusoidal structures are almost completely formed, although slight morphological differences from those in adult livers still exist. What happens to sinusoidal endothelial cells and Ito cells in hepatic fibrosis-cirrhosis of the adult may be a deviated or uncontrolled occurrence of what goes on during the fetal period, i.e., a continuous nonfenestrated sinusoidal lining in the early embryonic stage and a myofibroblastlike transformation of Ito cells in late fetal life.
TL;DR: The ruminant placenta, concerning the fetal vascular tree, in many aspects is workable as a model for the human, and Converging and differing morphological vascular phenomena of ruminants and human Placenta are discussed in terms of maternofetal exchange related to placental efficiency.
Abstract: The microvasculature of both the ruminant placentomes of cattle, sheep, and goats and the human placenta were compared, using corrosion casts of blood vessels and scanning electron microscopy. The fetal vascular trees of ruminant and human placenta differ in form and size, which correlates with the degree of ramification; however, their architecture of stem, intermediate, and terminal villi is similar. In the human, the system of serially linked capillary convolutions of terminal villi is longer than that in ruminants. Therefore, in guaranteeing blood flow against flow resistance, the human vessels particularly need a straight course, anastomoses, and sinusoidal dilations. Specifically in the ruminants studied, the venous vessels outweigh the arterial ones by volume and by number. They are suggested to be absorptive for substances metabolized in the zone of the capillary complex. The most extreme interspecies difference relates to the maternal vasculature, which, in contrast to the fetal system, is a closed system in the ruminant septas and an open lacunal intervillous space in the human. Converging and differing morphological vascular phenomena of ruminants and human placenta are discussed in terms of maternofetal exchange related to placental efficiency. In summary, the ruminant placenta, concerning the fetal vascular tree, in many aspects is workable as a model for the human. Microsc. Res. Tech. 38:76–87, 1997. © 1997 Wiley-Liss, Inc.
TL;DR: The Ca2+‐dependent cell‐cell adhesion molecules, termed cadherins, are subdivided into several subclasses and E (epithelial)‐ and P (placental)‐cadherins are involved in the selective adhesion of epidermal cells.
Abstract: The Ca(2+)-dependent cell-cell adhesion molecules, termed cadherins, are subdivided into several subclasses. E (epithelial)- and P (placental)-cadherins are involved in the selective adhesion of epidermal cells. E-cadherin is expressed on the cell surfaces of all epidermal layers and P-cadherin is expressed only on the surfaces of basal cells. Ultrastructural studies have shown that E-cadherin is distributed on the plasma membranes of keratinocytes with a condensation in the intercellular space of the desmosomes. During human skin development P-cadherin expression is spatiotemporally controlled and closely related to the segregation of basal layers as well as to the arrangement of epidermal cells into eccrine ducts. In human skin diseases E-cadherin expression is markedly reduced on the acantholytic cells of tissues in pemphigus and Darier's disease. Cell adhesion molecules are now considered to play a significant role in the cellular connections of cancer and metastatic cells. Reduced expression of E-cadherin on invasive neoplastic cells has been demonstrated for cancers of the stomach, liver, breast, and several other organs. This reduced or unstable expression of E- and P-cadherin is observed in squamous cell carcinoma, malignant melanoma, and Paget's disease, but cadherin expression is conserved in basal cell carcinoma. Keratinocytes cultured in high calcium produce much more intense immunofluorescence of intercellular E- and P-cadherin than those cells grown in low calcium. E-cadherins on the plasma membrane of the keratinocytes are shifted to desmosomes under physiological conditions, and therein may express an adhesion function in association with other desmosomal cadherins. Soluble E-cadherins in sera are elevated in various skin diseases including bullous pemphigoid, pemphigus vulgaris, and psoriasis, but not in patients with burns. Markedly high levels in soluble E-cadherin are demonstrated in patients with metastatic cancers.
TL;DR: Rarely are there lymphatics associated with islets of Langerhans, and then only where lymphatic vessels in connective tissue septa pass close to a pancreatic lobule that contains an islet at its periphery.
Abstract: A network of lymphatic vessels exists within the pancreas. The majority of vessels forming this network lie in the interlobular septa of connective tissue that subdivide the pancreas into lobes and lobules. Peripheral extensions of these interlobular lymphatics can be found within the lobules, but these intralobular lymphatics are relatively sparse. In the main, the intimate relationships of these internal pancreatic lymphatics are with the blood vessels and associated connective tissue. However in random areas, both intra- and interlobular lymphatics come into close relationship with acinar cells. Rarely are there lymphatics associated with islets of Langerhans, and then only where lymphatic vessels in connective tissue septa pass close to a pancreatic lobule that contains an islet at its periphery. Intra- and interlobular lymphatics are similar in structure. Both are thin walled having an endothelial lining and a delicate component of connective tissue. The pattern of interendothelial cell contacts and the sparsity of gaps between adjacent cells suggest that fluid movement through the intracytoplasmic system of vesicles is important in lymph formation in the pancreas. However intercellular transport is also likely to occur by a dynamic process involving fluid movement through dilatations between cells from interstitium to lymphatic lumen. Both exocrine and endocrine secretions of the pancreas may enter thoracic duct lymph directly in pancreatic lymph, but in normal circumstances this route of entry is not quantitatively important. The structural relationships between lymphatics and pancreatic parenchymal cells also make clear that lymph is not a significant pathway for their secretory products. Rather, the arrangement of lymphatics in the pancreas supports the view that lymph is primarily the drainage medium for substances that, for whatever reason, enter the interstitium. In addition, the low flow of lymph compared with that of plasma lends credence to the view that lymph is not a functionally important pathway for endocrine secretions from the pancreas to reach the blood. Both structural and functional evidence suggests that the proper functioning of the lymphatic system is of critical importance in the homeostasis of the pancreas. The lymphatic system of the pancreas, like that in other organs, is essential in the removal of excess fluid from the interstitium. In this sense, the lymphatics may be considered to serve as an overflow, protective, or safety system. When the system is inadequate or its capacity is exceeded, as in inflammation of the pancreas, exocrine secretions entering the interstitium are not cleared and the proteolytic enzymes cause major damage to the tissue. This, in turn, exacerbates the edema, accentuates the inability of lymphatics to drain the fluid, and results in further damage. The fibrosis that ensues damages the lymphatics either directly or through stricture of the surrounding connective tissue. In consequence, they become inadequate at an even earlier stage in subsequent attacks of inflammation and thereby predispose to chronic and recurrent pancreatitis. The larger interlobular lymphatics formed by the junction of their tributaries emerge upon the surface of the pancreas. There they travel primarily with blood vessels and stream toward a ring of lymph nodes that intimately surrounds the pancreas. A second system of nodes extensively involved in drainage from the pancreas is related to the front and sides of the aorta from the level of the celiac trunk to the origin of the superior mesenteric artery. This second set of nodes receives lymph either directly from the pancreas or indirectly from the first echelon of nodes that rings the organ. Although there is general agreement on the disposition of the groups within these sets of nodes, confusion results from the different classifications used by various authors. These classifications range from being purely descriptive, through an alpha and num
TL;DR: The results suggested that the joint cartilage degeneration is influenced by the remodeling of the underlying subchondral bone.
Abstract: The present study has focused on the cartilage-bone interrelationships in the progression of osteoarthrosis in human knees. Eleven tibial condyles with osteoarthrosis were analyzed by histology and bonemorphometry. The data were evaluated according to the grade of joint cartilage degeneration in distinct areas of the tibial condyle. The bone morphometric data were also analyzed by the depth of subchondral bone. A parallel relationship between the bone volume/bone formation activity and the Mankin's grade of cartilage degeneration was observed in both medial and lateral condyles. In the lateral condyle, there was correlation among progression of cartilage degeneration and trabecular and osteoid thickness and bone formation activity. Osteoblasts and osteoclasts were most abundant in the external areas of the medial condyles. Bone resorption activity in the medial condyle was found only in the external and intermediate areas, but it was extremely low in all areas of the lateral condyle. The values of bone volume in relation to depth were highest in the superficial layer with a decrease as the depth increased in both condyles. The bone formation activity was high in the superficial layer of the lateral condyle, whereas in the medial condyle, it was high in the layer between 500 and 1,500 microns of depth. The bone volume and bone formation activity were higher in all layers of the medial condyle in comparison with the lateral condyle. The bone resorption activity was low in the superficial layer of the medial condyle as compared with deeper layers. These results suggested that the joint cartilage degeneration is influenced by the remodeling of the underlying subchondral bone.
TL;DR: Lysosomotropic agents are selectively taken up into lysosomes following their administration to man and animals and relate them to toxic side‐effects or pharmacological action, as was suggested by de Duve et al. (1974).
Abstract: Lysosomotropic agents are selectively taken up into lysosomes following their administration to man and animals [de Duve et al. (1974) Biochem. Pharmacol. 23:2494–2531] The effects of lysosomotropic drugs studied in vivo and in vitro can be used as models of lysosomal storage diseases. These agents include many drugs still used in clinical medicine: aminoglycosides used in antibiotics [Tulkens (1988)]; phenothiazine derivatives; such antiparasitic drugs as chloroquine and suramin; antiinflammatory drugs like gold sodium thiomalate; and cardiotonic drugs like sulmazol [Schneider (1992) Arch. Toxicol. 66:23–33]. Side-effects to these drugs can be caused by their lysosomotropic properties. In addition to drugs, other compounds to which man and animals are exposed (e.g., metals, cytostatics, vitamins, hormones) are also lysosomotropic. Liver cells, especially Kuppfer cells, are known to accumulate lysosomotropic agents. Here we review studies which evaluate lysosomal changes in the liver following administration of lysosomotropic agents to experimental animals, and relate them to toxic side-effects or pharmacological action, as was suggested by de Duve et al. (1974). Common features of lysosomal changes include, the overload of liver lysosomes by non-digestable material; increased size and number of liver lysosomes; inhibition of several lysosomal enzymes; secondary increase in the activity of some lysosomal enzymes; increased autophagy, and fusion disturbances. There was no significant change in endocytosis, except for an increase in the Triton WR 1339 model. Microsc. Res. Tech. 36:253–275, 1997. © 1997 Wiley-Liss, Inc.
TL;DR: Evidence to date suggests that P450 enzymes in man are regulated in a manner similar to that in other animals, and the balance between different individual enzymes of cytochrome P450 in foetuses and/or neonates is subject to modulation by xenobiotics.
Abstract: Several approaches, including immunoquantification of individual enzymes, profiling of substrate activities by immunoinhibition using highly specific polyclonal and monoclonal antibodies, and the estimation of corresponding mRNAs with nucleic acid probes, have been used to investigate the ontogeny of cytochromes P450 in livers of rodents and man. CYP1A1 is expressed very early in development in rodents, whereas most other enzymes either appear at or near birth (CYP2B, CYP2C23, and CYP3A) or between 2 and 4 weeks following birth (CYP2A, CYP2C6, CYP2C7, CYP2C11, CYP2C12, and CYP4A10). The constitutive expression of enzymes is subject to regulation by various transcriptional nuclear and/or hormonal factors (CYP2B and CYP2C) or in a sex-dependent manner (CYP2A, CYP2C11, CYP2C12, CYP3A, and CYP4A10). The enhanced sensitivity and specificity of immunocytochemical and in situ hybridisation studies have revealed differences, with age and xenobiotic treatment, in the intercellular expression of certain P450 enzymes of the liver. For example, in rats, the expression of CYP1A1 and 1A2 is differentially regulated at the level of the individual cell from as early as 24 hours before birth. The human foetal liver relative to rodents has a substantial level of CYP3A and also has the capacity to metabolise a greater repertoire of substrates. Evidence to date suggests that P450 enzymes in man are regulated in a manner similar to that in other animals. The balance between different individual enzymes of cytochrome P450 in foetuses and/or neonates is subject to modulation by xenobiotics, the consequences of which may lead to toxicologically compromised livers with respect to metabolic handling of certain substrates.
TL;DR: The most prominent aging changes in early stages of ARM are drusen and basal laminar deposit (BLD), both extracellular deposits, that are assumed to be important in the development of ARM.
Abstract: Age-related maculopathy (ARM) is a degenerative disorder of the central part of the retina with a rising prevalence in patients 50 years of age and older, and comprises different histopathological changes. The morphologic changes in ARM are described and illustrated with light-microscopical, electron microscopical, and fundus pictures. Furthermore, the most important biochemical data are given. The most prominent aging changes in early stages of ARM are drusen and basal laminar deposit (BLD), both extracellular deposits, that are assumed to be important in the development of ARM. Drusen accumulate within Bruch's membrane, whereas BLD is present between Bruch's membrane and the retinal pigment epithelium. Although the histopathologic characteristics of the deposits are well documented, the chemical composition has only been partly resolved. Biochemical analysis of these deposits is necessary to determine the source of the deposits and to find possible ways to avoid or treat them. The late stages of ARM, geographic atrophy, and neovascular (disciform) degeneration, are called age-related macular degeneration (AMD), and result in severe and irreversible visual impairment. Since there is still no adequate therapy for the majority of people disabled by AMD, and because of the aging population resulting in even more patients with this disease, it is necessary to intensify the research on ARM in order to prevent AMD or find a therapy for it.
TL;DR: Osteoarthritis is usually considered to be a primary disorder of chondrocyte function with secondary changes in bones, but a defect in the subchondral bone resulting in loss of its shock absorbing capacity could transfer the stress of loading directly to the articular cartilage.
Abstract: Osteoarthritis is usually considered to be a primary disorder of chondrocyte function with secondary changes in bones. However, a defect in the subchondral bone resulting in loss of its shock absorbing capacity could transfer the stress of loading directly to the articular cartilage with secondary changes in the cartilage. Review of histomorphometric and bone densitometric studies at sites of osteoarthritis at the hip or knee revealed that cartilage fibrillation could not be dissociated from bony changes even in the earliest stages of osteoarthritis and that subchondral trabeculae are thickened and more spaced in osteoarthritis. Microfractures of subchondral trabecular bone were less frequently seen in osteoarthritis compared to controls. Changes of the tidemark were found to be multiform and metabolically active in the osteoarthritic process. Endochondral ossification depletes the calcified cartilage at the cartilage/bone interface and the tidemark has been thought of as a calcification front advancing in the direction of non-calcified cartilage. Duplication of the tidemark is cited as evidence of this advancement. In the few experimental animal studies of subchondral bone in osteoarthritis, thicker trabeculae which were closer together were found in guinea pigs already when only mild cartilage changes were present. In the dog, with cruciate ligament transection, changes in bone were later than in the cartilage, but the changes in bone could still contribute to the progression of osteoarthritis. To study if bone changes may precede injury to the cartilage and if metabolic and systemic influences can also alter the subchondral bone, rendering it less able to withstand normal mechanical stresses, bone at different sites in the body has been studied extensively by the authors. Epidemiological and case control studies have revealed that osteoarthritis cases have more bone at all sites than expected and that bone in cases with generalized osteoarthritis shows both quantitative and qualitative differences, including increased contents of growth factors and hypermineralization. These findings suggest that a more generalized bone alteration may be the basis of the pathogenesis of osteoarthritis.
TL;DR: Results clearly indicate that aldosterone, the most potent mineralocorticoid, is synthesized in the zona glomerulosa cells, and glucocortioids, such as corticosterone and cortisol, are produced in theZona fasciculata‐reticularis cells.
Abstract: Recent immunohistochemical studies have revealed the precise localization of the enzymes involved in adrenal steroidogenesis. Light microscopical investigations showed that cytochromes P450 of cholesterol side-chain cleavage enzyme (P450scc) and of 11β-hydroxylase (P45011β), 3β-hydroxysteroid dehydrogenase/Δ5-4 isomerase (3βHSD), and 21-hydroxylase (P450C21) are localized in all the adrenocortical cells, especially in those of the zona fasciculata-reticularis. 17α-Hydroxylase/C17-20 lyase (P45017α, lyase) is present in the zona fasciculata-reticularis cells of human, bovine, pig, and guinea-pig adrenals, but absent in the adrenals of some rodents such as rat, hamster, and mouse. Aldosterone synthase (P450aldo) is contained only in the zona glomerulosa cells. In the rat adrenal, P45011β, which catalyzes the conversion of deoxycorticosterone to corticosterone, is localized in the zona fasciculata-reticularis cells. Electron microscopic investigations demonstrated that P450scc and P45011β are colocalized in the matrix side of inner mitochondrial membrane including cristae, while 3βHSD, P450C21, and P45017α, lyase are present in the membranes of smooth endoplasmic reticulum (SER). These results clearly indicate that aldosterone, the most potent mineralocorticoid, is synthesized in the zona glomerulosa cells, and glucocorticoids, such as corticosterone and cortisol, are produced in the zona fasciculata-reticularis cells. The conversion of cholesterol to pregnenolone and the final steps of corticosteroid synthesis occur in the mitochondria, while the intermediate steps, leading to the synthesis of deoxycorticosterone or deoxycortisol from pregnenolone, take place in the SER membranes. Microsc. Res. Tech. 36:445–453, 1997. © 1997 Wiley-Liss, Inc.
TL;DR: The use of microscopy to study free viruses is discussed and the ultrastructure of free viruses with bacteriophages and viruses which have been cultured from marine hosts are compared.
Abstract: Free viruses are abundant in the world's oceans. With this realization has come renewed interest in marine viruses and the role viruses play in structuring marine planktonic communities, primarily members of the microbial assemblage. The principal means of studying marine viruses has been by electron microscopy. This review discusses the use of microscopy to study free viruses and compares the ultrastructure of free viruses with bacteriophages and viruses which have been cultured from marine hosts. Many of the free viruses are smaller than typical cultured bacteriophages, which suggests that either many native phages are smaller than cultured phages or that many of the free viruses may be members of those phage families with smaller size classes or, in some cases, that many free viruses may be eukaryotic viruses. Some of the forms currently considered free viruses may be "defective phage" or "phage ghosts," noninfectious particles produced by bacteria, or virus-sized inorganic/organic colloids and warrant further study. Gross virus ultrastructure cannot be used as the sole criterion for determining marine virus diversity, since, as with many microbes, many unrelated viruses have similar morphological characters. Determination of DNA or RNA content as well as studies of protein and DNA relatedness of marine viruses will be needed if we are to understand the complexity of marine virus assemblages. Another important direction for future work is the need for marine bacteriophage/host and virus/host systems in order to study the biology of virus infection.
TL;DR: The ability to isolate intact native microfibrils from skin has enabled a combination of high resolution and biochemical techniques to be applied to elucidate their structure:function relationships, which have generated new information about their molecular organisation and physiological interactions in health and disease.
Abstract: Connective tissue microfibrils are key structural elements of the dermal matrix which play major roles in establishing and maintaining the structural and mechanical integrity of this complex tissue. Type VI collagen microfibrils form extensive microfibrillar networks which intercalate between the major collagen fibrils and are juxtaposed to cellular basement membranes, blood vessels and other interstitial structures. Fibrillin microfibrils define the continuous elastic network of skin, and are present in dermis as microfibril bundles devoid of measureable elastin extending from the dermal-epithelial junction and as components of the thick elastic fibres present in the deep reticular dermis. Electron microscopic analyses have revealed both classes of microfibrils to have complex ultrastructures. The ability to isolate intact native microfibrils from skin has enabled a combination of high resolution and biochemical techniques to be applied to elucidate their structure:function relationships. These approaches have generated new information about their molecular organisation and physiological interactions in health and disease.
TL;DR: Morphological studies of the microcirculatory system in the thymus were reviewed in regards to methodology and structural organization of blood and lymphatic vessels, suggesting a possible route for lymphocyte efflux into the lymphatic vessel from the PVS.
Abstract: Morphological studies of the microcirculatory system in the thymus were reviewed in regards to methodology and structural organization of blood and lymphatic vessels. The blood capillaries and postcapillary venules (PCVs) in the thymus are characterized by a double-walled structure. These vessels are surrounded more or less by perivascular spaces (PVSs) containing many lymphocytes. This space is delimited on the one side by abluminal surface of the vascular endothelium and on the other side by cytoplasmic processes of epithelial reticular cells. There are interruptions or gaps on the outer epithelial reticular layer. The lymphatic vessels can be distinguished histochemically from blood vessels based on strong 5′-nucleotidase (5′-Nase) activity. The 5′-Nase-positive lymphatic vessels were seen predominantly in the capsule and interlobular connective tissue but sometimes in the immediate vicinity of the PVS around the PCV, when a discrete opening in the lymphatic wall next to the PVS was found. Thus, it may be regarded as an initial part of lymphatics closely associated with the PVS, suggesting a possible route for lymphocyte efflux into the lymphatic vessel from the PVS. The endothelial cells of lymphatic vessels as well as PCVs are often infiltrated by lymphocytes, particularly more heavily during acute involution of the thymus. These images represent the migration of lymphocytes into the blood or lymphatic microcirculation. Microsc. Res. Tech. 38:287–299, 1997. © 1997 Wiley-Liss, Inc.
TL;DR: Findings of cell surface localization of gp91 and p22 components of the oxidase in chemoreceptive cells suggests that the heme‐linked cytochrome b558 component is associated with the plasma membrane.
Abstract: A potential candidate for an oxygen-sensing protein in chemoreceptor cells is a heme-linked multicomponent NADPH oxidase, originally described in neutrophils. The postulated function for the oxidase in chemoreceptor cells is to signal changes in oxygen levels (either in the blood or in the airway lumen) via changes in oxygen metabolite production. An alteration in either superoxide (or dismuted hydrogen peroxide) production may affect the gating properties of the O2-sensitive K+ channels. We have previously reported immunohistochemical localization of gp91 glycoprotein component of the oxidase to the plasma membrane of pulmonary neuroepithelial body (NEB) cells. In this study we have investigated the immunocytochemical localization of the other polypeptide components of the oxidase in NEB cells and in the glomus cells of the carotid body. Cultures of dissociated fetal rabbit NEB cells and newborn rat glomus cells were immunostained with specific antibodies recognizing the various polypeptide subunits of the oxidase using indirect immunofluorescence methods. Immunostaining with the anti-oxidase antibodies reveal strong positive reaction in both NEB and glomus cell clusters while other cells were unstained. The positive reaction product was localized to the plasma membrane and/or cytoplasm and no nuclear staining was observed. Live cell labelling studies with anti-p22 antibody showed positive immunofluorescence on the surface of NEB cells, suggesting that this component of the oxidase is also associated with the plasma membrane. In glomus cells, similar strongly positive immunofluorescence signal was observed for p22 and gp91 in paraformaldehyde-fixed cultures, regardless whether they were permeabilized or not. Taken together, our findings of cell surface localization of gp91 and p22 components of the oxidase in chemoreceptive cells suggests that the heme-linked cytochrome b558 component is associated with the plasma membrane. This association allows for direct interaction with the O2-sensitive K+ channel thus forming the molecular complex of membrane bound O2 sensor.