Showing papers in "Journal of Anatomy in 1996"

Gray's Anatomy

Abstract: MEDICAL LITERATURE has been deluged during the past few years with books and papers on penicillin; but a book which has been produced under the general editorship of Sir Alexander Fleming himself represents a complete and authoritative summary of penicillin therapy as it stands today.' The book contains a series of independent contributions by \"experienced and eminent men who have worked with penicillin in Great Britain\". Their opinions and practical methods differ slightly, and there is some overlapping; but these are not disadvantageous, comparison and contrast lending interest to the reading. In the first or general section of the book Fleming contributes two chapters, one on the history and development of penicillin, introducing some interesting sidelights in the romance of discovery, the other on the bacteriological control of penicillin therapy. In both chapters the information is set out in meticulous detail and with a clarity and simplicity which can be enjoyed by all readers. Fleming also gives the right perspective to the place of penicillin amongst the antibiotics and lays down the principles of treatment. Both chapters are well illustrated and are the most outstanding in the book. Included in this first section also are chapters on the chemistry and manufacture of penicillin and its pharmacy, pharmacology and methods of administration. The second section of the book is entirely clinical, giving each author's view on the use of penicillin therapy in a disease or an infection of some particular region of the body. The entire range of peniCillin-sensitive conditions is considered in twenty authoritative and clearly written chapters; these contain many references and illustrations. Dental and veterinary diseases are also given fairly full consideration. The final section is a condensed resume of much of the preceding chapters and is written for. the general practttioner. This chapter is superttuous: it does not contain enough detall to be of much practical value. The book as a Whole, however, will undoubtedly be considered a classical contribution to medical literature and is strongly recommended, not only because of the general interest of its topic, but as a reference book on penicillin therapy of hitherto unequalled excellence. The typography, although conforming to war economy standards, is clear and the paper is good. There is an excellent list of references and the index is satisfactory.

'If you assume, you can make an ass out of u and me': a decade of the disector for stereological counting of particles in 3D space.

Abstract: The year 1984 was a watershed in stereology. It saw the introduction of highly efficient and unbiased design-based methods for counting the number of arbitrary objects in 3-dimensional (3D) space using 2D sectional images. The only requirement is that the objects be unambiguously identifiable on parallel sections or successive focal planes. The move away from the ?assumption-based' and ?model-based' methods applied previously has been a major scientific advance. It has led to the resolution of several problems in different biomedical areas. The basic principle which makes possible 3D counting from sections is the disector. Here, we review the disector principle and consider its impact on the counting and sizing of biological particles. From now on, there can be no excuse for applying the biased counting methods of yesteryear. Their continued use, despite the availability of unbiased alternatives, should be seen as paying homage to History rather than advancing Science.

Tendon cells in vivo form a three dimensional network of cell processes linked by gap junctions.

Abstract: Tendons respond to mechanical load by modifying their extracellular matrix. The cells therefore sense mechanical load and coordinate an appropriate response to it. We show that tendon cells have the potential to communicate with one another via cell processes and gap junctions and thus could use direct cell/cell communication to detect and/or coordinate their load responses. Unfixed cryosections of adult rat digital flexor tendons were stained with the fluorescent membrane dye DiI to demonstrate cell shape. Similar sections were immunolabelled with monoclonal antibodies to rat connexin 32 or connexin 43 to demonstrate gap junctions and counterstained with propidium iodide to show nuclei, or the membrane stain DiOC7 to show cell membranes. Sections were examined with a laser scanning confocal microscope and 3-dimensional reconstructions were prepared from optical section series to demonstrate cell shape and the position of connexin immunolabel. Cells had a complex interconnected morphology with gap junctions at points of contact with other cells. Cell bodies contained the nucleus and extended broad flat lateral cell processes that enclosed collagen bundles and interacted with similar processes from adjacent cells. They also had long thin longitudinal processes interacting with the cell process network further along the tendon. Connexin 43 occurred where cell processes met and between cell bodies, whereas connexin 32 was only found between cell bodies. The results indicate the presence of a 3-dimensional communicating network of cell processes within tendons. The intimate relationship between cell processes and collagen fibril bundles suggests that the cell process network could be involved in load sensing and coordination of response to load. The presence of 2 different types of connexins suggests that there could be at least 2 distinct communicating networks.

Nanoparticles and microparticles for drug and vaccine delivery

Abstract: Nanoparticles are polymeric particles in the nanometer size range whereas microparticles are particles in the micrometre size range. Both types of particle are used as drug carriers into which drugs or antigens may be incorporated in the form of solid solutions or solid dispersions or onto which these materials may be absorbed or chemically bound. These particles have been shown to enhance the delivery of certain drugs across a number of natural and artificial membranes. In addition, the particles were shown to accumulate in areas of the intestine that appear to be the Peyer's patches. Possibly because of the combination of both effects these particles were able to significantly improve the bioavailability of some drugs after peroral administration in comparison with solutions. Recently nanoparticles coated with polysorbate 80 enabled the passage of small peptides and other drugs across the blood-brain barrier and the exhibition of a pharmacological effect after intravenous injection. Without the use of this type of nanoparticles the drugs did not cross this barrier and yielded no effect.

Innervation of vasculature and microvasculature of the human vagina by NOS and neuropeptide-containing nerves.

Abstract: The aims of the present study were to determine whether nerves that contain nitric oxide synthase (NOS), calcitonin gene-related peptide (CGRP) or substance P (SP) are present in the human vagina and, if so, to determine the pattern of innervation relative to that of other neurotransmitters, particularly vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY). Surgical specimens of vaginal tissue (n = 10) from pre- and postmenopausal women were fixed and processed for immunohistochemistry of peptides and NOS and for histochemistry of NADPH-diaphorase. SP-immunoreactive nerves were very sparse, being absent from 9 of the 10 tissue samples. For other peptides and NOS, the innervation of the deep arteries and veins was greater than that of blood vessels in the propria. Capillaries in the epithelial papillae also appeared to be innervated by nerves containing NOS, CGRP, NPY and VIP. Beneath the epithelium nerve fibres formed a subepithelial plexus; no nerve cell bodies were seen. The relative density of innervation by immunoreactive fibres was PGP-9.5 > NPY > VIP >> NOS > CGRP > SP. These results imply that nerves that utilise nitric oxide or NPY, VIP or CGRP as a neurotransmitter may play a role in controlling blood flow and capillary permeability in the human vagina. The origin and function of all these nerves is discussed.

Degenerating and regenerating skeletal muscles contain several subpopulations of macrophages with distinct spatial and temporal distributions.

Abstract: Macrophages of different phenotypes can be detected using a panel of antibodies. We have used such antibodies to demonstrate that the macrophages in freeze-lesioned skeletal muscles are heterogeneous, with each subtype having a distinct location within the lesion as well as distinct times of arrival and departure from the lesion. ED1+ monocytes and macrophages began invading the lesion within 3 h and were abundant until necrotic tissue had been removed. In some macrophages, the ED1 antigen aggregated into a single or a few clumps and such cells persisted in the regenerated area for at least 21 d. ED2+/Ox6-/ED1-/RM1- cells are one of the major subpopulations of resident macrophages within skeletal muscle. Cells of this phenotype accumulated in the epimysia and perimysia surrounding the lesions but did not penetrate into the lesion until extensive phagocytosis had occurred (usually 1 or 2 d). ED2+ cells were subsequently concentrated in the regenerating connective tissues and empty remnants of phagocytosed fibres. They only rarely invaded necrotic tissue, even when immediately adjacent to it, suggesting that this type of macrophage has a specialised function which is unrelated to removal of damaged tissue. The ED2+ macrophages were CD4+ and it is probably that macrophages of this type have been previously misclassified as CD4+ T cells. Skeletal muscles also contain numerous Ox6(Ia)+/ED2- resident macrophages. Unlike ED2+ macrophages, Ox6+ macrophages invaded the damaged muscles half a day after lesioning and were abundant in necrotic tissue. As regeneration occurred, the Ox6+ macrophages became restricted to the connective tissues of the muscle, which is their normal location.

Ultrastructure of the human spinal arachnoid mater and dura mater.

Abstract: Human spinal dura and arachnoid, obtained during neurosurgical operations, were studied by transmission electron microscopy. The ultrastructure of spinal meninges largely conformed to the morphology of the cranial meninges, but some minor differences were detected. The dura was composed of an outermost loosely arranged fibroelastic layer, a middle basically fibrous portion and an innermost cellular layer (dural border cell layer). The dural border cell layer was characterised by multiple interdigitating cell processes, no extracellular collagen, significant extracellular spaces and few cell junctions. Paravascular vesiculated nerve profiles were encountered within the fibroadipose epidural tissue. The arachnoid was composed of an outermost portion (arachnoid barrier cell layer), presenting tightly packed cells, numerous tight junctions and no extracellular collagen. In view of its numerous tight junctions, the arachnoid barrier cell layer is considered to represent an effective morphological and physiological meningeal barrier between the cerebrospinal fluid in the subarachnoid space and the blood circulation in the dura. The arachnoid barrier layer was always characterised by a distinct continuous basal lamina on its inner surface towards the innermost collagenous portion of the arachnoid (arachnoid reticular cell layer). The interweaving arachnoid trabecular cells within this layer possessed numerous mitochondria and were anchored to the inner surface of the arachnoid barrier cell layer by desmosomes. An additional layer of flattened branching cells was demonstrated along the inner surface of the arachnoid reticular cell layer and assumed to be an "arachnoid border cell layer'. Morphological data suggest that the dura and arachnoid closely adhere at spinal levels in man without any naturally occurring "subdural space'. However, structurally, the dural border cell layer forms a weak cell layer at the dura-arachnoid continuum that is easily disrupted. The creation of an artifactual subdural space at spinal levels is discussed.

The intestinal uptake of particles and the implications for drug and antigen delivery

Abstract: A number of researchers from different scientific disciplines have independently described the uptake of a variety of particulates across the gastrointestinal tract in animal models. The reports of particle uptake are briefly reviewed and the alternative mechanisms and proposed sites of uptake are discussed. Following these observations, some researchers have exploited the phenomenon of particulate uptake by using microparticles and nanoparticles as oral delivery systems for active agents, such as drugs and vaccines. The potential use of particulate carrier systems as drug and vaccine delivery systems is also briefly discussed.

Targeting to intestinal M cells.

Abstract: The specialised, antigen-transporting, epithelial M cells in the follicle-associated epithelium (FAE) overlying gut-associated lymphoid tissues constitute the primary target for oral delivery of vaccines. Our studies have shown that polystyrene microspheres selectively bind to, and are efficiently transcytosed by, rabbit Peyer's patch M cells in closed intestinal loops. Binding of biodegradable poly(DL-lactide-co-glycolide) microspheres to rabbit Peyer's patch FAE is an order of magnitude lower than that of polystyrene microspheres. Although poly(DL-lactide-co-glycolide) microspheres are not selectively targeted to M cells, a high proportion of those which bind to M cells are transcytosed, supporting the potential of such microspheres as vehicles for oral vaccine delivery. Comparison of the binding of polystyrene microspheres by murine FAE revealed this to be markedly less extensive than by rabbit FAE. These data demonstrate that microsphere binding by M cells depends on the surface properties of both cells and microspheres and suggest that surface modification may enhance the efficacy of microsphere delivery vehicles. One such approach is the incorporation of molecules with inherent binding specificity for M cells. Lectin-binding studies have revealed that M cells exhibit pronounced regional and species variation in glycoconjugate expression. In murine intestine, certain lectins bind selectively to M cells either in Peyer's patches or caecum, or at both sites. Selective targeting to, and transcytosis of, lectin-conjugates by M cells in ligated segments of murine intestine have also been demonstrated. While several lectins display strong selectivity for rabbit caecal M cells, none to date have been identified with specificity for rabbit or rat Peyer's patch M cells. Knowledge of human M cells is limited and no lectin has yet been identified with specificity for these cells. However, at least one lectin exhibits binding specificity for FAE in the human ileum. In the future, knowledge of the regional patterns of M cell carbohydrate expression within a species may allow lectins to be utilised to target selectively antigenic material to the mucosal immune system at specific locations.

Blood supply to the human femoral diaphysis in youth and senescence.

Abstract: The nutrient foramina in the human femoral diaphysis were counted in 109 cleaned and dried bones, ranging in age from 38 to 98 y. Although statistical analysis for univariate associations found that foramen number was not linked to age, sex (male/female) or side (R/L), multivariate logistic analysis revealed a significant interaction between the effects of sex and side (P < 0.01). Univariate analysis for sex and for side separately revealed a significant difference in for men number between the results for men and women for R bones 62% (18/29) vs 33% (8/24) (P < 0.04), but not for L bones 35% (9/26) vs 48% (13/27) (P < 0.28). One lower limb from 15 cadavers was perfused with a barium sulphate suspension to show the blood supply of the femoral diaphysis. Twelve were in the age group 59-88 y and considered to be senescent material. In addition, 3 more femora were perfused, 1 from a young male aged 21 y, another from a 42-y-old male considered to show early senescent changes, and a third from a man aged 56 y with a hip prosthesis in situ, to provide an example of a cortex deprived entirely of its medulla. All perfused femora were fixed and decalcified, and sections were then radiographed. Cross-sections through the middiaphysis showed that aged bone cortex is supplied predominantly from the periosteum in contrast to the medullary supply in young human and animal material. The change is attributed to increasingly severe medullary ischaemia with age, brought on by atherosclerosis of the marrow vessels. An examination of the findings reported by investigators of animal bone blood supply in the past 40 y shows a large measure of agreement. Long standing controversy seems to be based on a failure to recognise that marrow ischaemia accompanies natural senescence, affecting transcortical haemodynamics, and entraining an increasing periosteal supply for bone survival in old age. The change over from a medullary to a periosteal blood supply to bone cortex is the consequence of medullary ischaemia and reduced marrow arterial pressure, brought about by medullary atherosclerosis.

Expression of the vascular endothelial growth factor receptor, KDR, in human placenta.

Abstract: Vascular endothelial growth factor (VEGF) is a heparin-binding growth factor known to act directly on vascular endothelial cells by promoting cell proliferation and permeability. To date, 3 structurally related cell surface receptors for VEGF, Flt-1, Flt-4 and KDR, have been identified and shown to be human type III receptor tyrosine kinases. The establishment of a vascular network is crucial to the development of the placenta and occurs through both angiogenesis and vasculogenesis. The signals controlling these processes are unclear. Immunohistochemical and in situ hybridisation techniques have localised VEGF in the trophoblast layers and VEGF binding to placental vascular endothelial cells and haemangioblasts has been shown, suggesting a role for VEGF and its receptors in development of the vascular network. In this study we have used specific antibodies to localise KDR and endothelial cells in 1st and 3rd trimester human placenta. The staining showed a colocalisation of KDR with endothelial cells and haemangioblasts. No staining of trophoblast cells was observed, but strong staining of the endothelial cells was seen in the villous stroma adjacent to areas of trophoblast proliferation.

Quantitative comparison of soft tissue-bone interface at chondral ligament insertions in the rabbit knee joint.

Abstract: At chondral ligament insertions the calcified fibrocartilage interdigitates deeply with the lamellar bone. The shape of this interface is formed under physiological loading conditions. For the purpose of morphological comparison between different ligament entheses in the rabbit knee, the number and frequency of interdigitations and thickness of calcified fibrocartilage were quantitated at the femoral insertion of the medial collateral ligament, both insertions of the cruciate ligaments, and the tibial insertion of the patellar ligament. Among the insertions, the femoral insertion of the medial collateral ligament showed the lowest frequency and depth of interdigitations at the soft tissue-bone interface, but had the thickest zone of calcified fibrocartilage. An inverse relationship was found at the insertion interface of the cruciate and patellar ligaments. The frequency and depth of interdigations at the bone-soft tissue interface at different chondral entheses seem to be related to the mechanical strength of the respective ligament; meanwhile it may be hypothesised that the thickness of the calcified fibrocartilage might be more related to the amount of motion which takes place at an insertion.

The development of articular cartilage: I. The spatial and temporal patterns of collagen types.

Abstract: Articular cartilage is both morphologically and biochemically heterogeneous. Its susceptibility to degenerative diseases such as arthritis and its limited repair capacity have made cartilage the focus of intense study; surprisingly, little is known of its development. Using a panel of specific antibodies, we have documented the temporal and spatial patterns of collagen types I, II, III, VI and X in the developing knee cartilage of the marsupial Monodelphis domestica from parturition to adulthood. Type I collagen was initially detected in the presumptive articular cartilage of the epiphyses in addition to the perichondrium. By 14 d postparturition, type I collagen was not detectable in the epiphyseal cartilage apart from insertion sites of ligaments and tendons of the joint. Similarly, type III collagen was detected at insertion sites of the major ligaments and tendons and within the perichondrium/periosteum but was never detected in the cartilage per se. Type II collagen was predictably distributed throughout the cartilage matrix and was also detected in the perichondrium. Type VI collagen was widely distributed throughout the cartilage matrix at parturition, but during development became restricted to a pericellular location particularly towards the presumptive articular cartilage, i.e. the epiphysis. Interestingly, generalised matrix immunopositivity was only retained in the hypertrophic cartilage of the secondary centre of ossification. After the formation of the secondary centre, type VI collagen became localised pericellularly in the deeper regions of the articular cartilage but was absent in the cartilage of the growth plate. Type X collagen showed a novel distribution pattern. In addition to being synthesised by hypertrophic chondrocytes, this collagen type was also expressed transiently by some cells at the presumptive articular surface. Furthermore, these surface chondrocytes also stained histochemically for alkaline phosphatase, suggesting that they were terminally differentiated. The fate of these terminally differentiated cells is unknown.

Normal and healing ligament vascularity : a quantitative histological assessment in the adult rabbit medial collateral ligament

Abstract: Normal and healing adult rabbit medial collateral ligaments (MCL) have been assessed for microvascular anatomy using a quantitative image analysis methodology. MCL preparation by ink-gelatin perfusion enabled acceptable visualisation of microvascular channels within the tissue. Fifteen adult rabbits were studied; 3 normal rabbits formed an external time-zero control group; 12 animals received a standardised gap injury to the right MCL. The ligament injury was permitted to heal for 3, 6, 17 or 40 wk (3 animals in each healing group). Results confirmed that the normal MCL is hypovascular (about 1.46% vascularity by area) and that microvascular channels are highly organised and oriented longitudinally deep within the tissue. Healing MCL scar becomes twice as vascular as normal ligament early on, but returns to near normal values by 40 wk. Microvascular channels appear less organised in scar than in contralateral controls, but remodel with time. The directional scatter and spatial extent of ligament microvascular channels is quantifiable in normal and healing tissues.

Structural changes in fluorosed dental enamel of red deer (Cervus elaphus L.) from a region with severe environmental pollution by fluorides.

Abstract: A macroscopic, microradiographic and scanning electron microscope study was performed on the structure of fluorosed dental enamel in red deer from a fluoride polluted region (North Bohemia, Czech Republic) As was revealed by analysis of mandibular bone fluoride content, the rate of skeletal fluoride accumulation in the fluorotic deer was about 6 times that in controls taken from a region not exposed to excessive fluoride deposition In all fluorosed mandibles, the 1st molar was consistently less fluorotic than the other permanent teeth This was related to the fact that crown formation in the M1 takes place prenatally and during the lactation period Fluorosed teeth exhibited opaque and posteruptively stained enamel, reduction or loss of enamel ridges, moderately to grossly increased wear and, in more severe cases, also enamel surface lesions of partly posteruptive, partly developmental origin Microradiographically, fluorosed enamel was characterised by subsurface hypomineralisation, interpreted as a result of fluoride interference with the process of enamel maturation In addition, an accentuation of the incremental pattern due to the occurrence of alternating bands with highly varying mineral content was observed in severely fluorosed teeth, denoting fluoride disturbance during the secretory stage of amelogenesis A corresponding enhancement of the incremental pattern was also seen in the dentine The enamel along the more pronounced hypoplasias consisted of stacked, thin layers of crystals arranged in parallel, indicating that the ameloblasts in these locations had lost the distal (prism-forming) portions of their Tomes processes The findings of the present study indicate that red deer are highly sensitive bioindicators of environmental pollution by fluorides

Targeting of drugs and delivery systems to specific sites in the gastrointestinal tract

Abstract: Particle uptake and translocation occur at specific sites in the gastrointestinal tract. Several drugs are also absorbed from solution only through narrow "windows' in the small intestine. In these circumstances, optimum therapeutic benefit would be obtained if the active agent was targeted to the appropriate site in the gastrointestinal tract. Targeting relies on exploiting a unique feature of the intended site and protecting the active agent until it reaches that site. This minireview highlights the problems in achieving site specificity in the gastrointestinal tract and examines possible solutions to the problem for 2 regions, the stomach and the colon.

Expression of tenascin in joint-associated tissues during development and postnatal growth.

Abstract: The extracellular matrix protein, tenascin, is selectively expressed in a variety of connective tissues during development. In this study, the distribution of tenascin in tissues contributing to the knee joint during embryonic development and postnatal growth in the rat has been investigated by immunohistochemistry. In recently formed embryonic knee joints, tenascin expression was abundant in the territorial matrix of superficial articular cartilage. Site of attachment of cruciate and patellar ligaments to cartilage were strongly stained; staining of ligaments weakened with distance from the attachment site. In rapidly growing 4-wk-old rats, tenascin was present in a fine line on the surface of articular cartilage, but at 10 wk of age tenascin staining was absent from most of the articular surface. In postnatal rats, there was strong tenascin staining of the synovial lining, but not of subintimal tissue. Cruciate ligaments were histologically fibrocartilaginous in 4 and 10-wk-old rats; within these ligaments strong pericellular tenascin staining was seen in association with rounded chondrocyte-like cells. Tenascin was absent from the cartilaginous growth plates of 4 and 10-wk-old rats, but intense tenascin staining was seen at the junction between epiphyseal bone and growth plate. Within the metaphysis, tenascin staining on bone surfaces increased with distance from the hypertrophic chondrocytes. Osteocytes within epiphyseal trabecular bone were strongly stained for tenascin, whereas those in the metaphysis were mostly unstained. The results presented here demonstrate that tenascin expression in joint-associated tissues changes markedly with cell type and stage of differentiation.

The vomeronasal organ of the cat.

Abstract: The vomeronasal organ of the cat was studied macroscopically, by light microscopy and by immunohistochemical techniques. Special attention was paid to the general distribution of the various soft tissue components of this organ (duct, glands, connective tissue, blood vessels and nerves). Examination of series of transverse sections showed that the wall of the vomeronasal duct bears 4 different types of epithelium: simple columnar in the caudal part of the duct, respiratory and receptor respectively on the lateral and medial walls of the middle part of the duct, and stratified squamous rostrally. The pattern of distribution of other soft tissue components was closely associated with that of epithelium types. In areas where the duct wall was lined with receptor epithelium, nerves and connective tissue were present between the epithelium and the medial sheet of the vomeronasal cartilage. Most glands and blood vessels were located lateral to those areas of the duct wall lined with respiratory epithelium. Numerous basal cells were present in the sensory epithelium. Understanding of the distribution of the soft tissue components of this organ may shed light on its function.

Morphological characteristics of mouse incisor enamel

Abstract: Maxillary and mandibular incisors of mice aged 5 wk were sectioned and ground along various planes, acidetched and observed by scanning electron microscopy (SEM). The general design of the enamel structure resembled rat incisor enamel with an uniserial lamellar pattern of prisms in the inner enamel and incisally directed parallel prisms in the outer enamel. The centrolabial thickness of the enamel was about 60 microns in the maxillary and about 95 microns in the mandibular incisor. The angle between prism rows and enamel-dentine junction was about 70 degrees in the maxillary and about 45 degrees in the mandibular incisor, while the angle of decussation, which increased from the enamel-dentine junction towards the outer enamel, was 50-95 degrees and 30-80 degrees respectively. The angle between outer enamel prisms and enamel surface was about 12 degrees in the maxillary and 5-15 degrees in the mandibular incisor. The outer 1/2-1/3 of the outer enamel contained iron and was more acid-resistant than the rest of the enamel. The superficial 3-5 microns was prismless with a Fe/Ca ratio of about 25/75 in the maxillary and about 10/90 in the mandibular incisor. The latter concentration of iron was insufficient to give visible pigmentation to the enamel. The extreme mesial and lateral enamel was neither typical of inner nor of outer enamel. Assuming that the length of the zone of enamel secretion is half the corresponding length in the rat, it could be calculated that ameloblasts in mouse mandibular incisors produce enamel at a rate of about 6 microns per day, about half the corresponding rate in the rat. In spite of this, the mouse mandibular incisor has a relatively thick layer of enamel, since the ameloblasts spend a relatively long time in the zone of enamel secretion due to a fairly slow eruption rate.

The morphology of ligament insertions after failure at low strain velocity: an evaluation of ligament entheses in the rabbit knee.

Abstract: The morphology of failed rabbit knee entheses is described after in vitro load to failure testing at low strain velocity. Avulsion fracture was the dominant failure mode both for the cruciate ligaments and the medial collateral ligament. The patellar ligament became avulsed in most cases from the patellar insertion. The ligamentous anterior attachment of the medial meniscus failed by a midsubstance rupture and the posterior fibrocartilaginous attachment by a rupture near to the meniscal horn. On histological inspection the failure characteristics usually appeared more elaborate, involving to different degrees all portions of the bone-ligament-bone complexes. Avulsion fracture through subchondral bone was often combined with a partial ligament midsubstance rupture. In few cases avulsion from the cement line was combined with a rupture between the uncalcified fibrocartilage and the ligament. The medial collateral ligament failed in one case entirely at the cement line of its femoral insertion. Horizontal rupture through the calcified fibrocartilage and a vertical cleavage crossing the tidemark were also observed. The superficial portion of the patellar ligament failed with a midsubstance rupture, and the deeper part with an avulsion through the calcified fibrocartilage or an avulsion fracture. The complex failure characteristics may be attributed to uneven loading, nonuniformity of the structure, and specific anatomical location. Subchondral bone beneath femoral and tibial insertions seems to be weaker than the transitional zone between soft tissue and hard bone at the enthesis. The overall inferior structural quality of a ruptured ligament has to be taken into account when parts of the original structure are used for suturing or reconstruction.

An ultrastructural study of the phagocytic activity of astrocytes in adult rat brain.

Abstract: The role of adult astrocytes in the removal of cell debris and foreign particles following injury to the brain is controversial. This study was undertaken to elucidate the response of adult astrocytes to needle injury of the rat cerebral cortex, using a suspension of colloidal carbon as a marker for phagocytosis. Either a single or 2 successive injections of colloidal carbon suspension were made into the cerebral cortex. The animals were allowed to survive for periods of from 1 to 30 d. Unequivocal involvement of astrocytes in the removal of carbon particles was evident only in those brains which had been subjected to 2 successive injections of carbon. The particles were located in membrane-bound vacuoles and were subsequently sequestered in lysosomes. Carbon-containing astrocytes were observed in the immediate vicinity of the lesion, in the adjacent parenchyma, around blood vessels and abutting carbon-containing macrophages. This study demonstrates that adult astrocytes are involved in phagocytosis, but only as a second line of defence. The possible significance of carbon-laden astrocytes further away from the site of the lesion is discussed.

Ultrastructure of fibrocartilages at the insertion of the rat Achilles tendon.

Abstract: The ultrastructure of 3 fibrocartilages is described at the insertion of the adult rat Achilles tendon Enthesial fibrocartilage lies at the tendon-bone junction, sesamoid fibrocartilage in the deep surface of the tendon where it presses on the calcaneus, and periosteal fibrocartilage covers the opposing surface of the bone All had some features that could be interpreted as typical of fibrous tissues and other features that were more characteristic of cartilage The general extracellular matrix was largely fibrous and had relatively little visible proteoglycan In contrast, the cells had features more common in cartilage--dilated rough endoplasmic reticulum, glycogen and lipid, and pericellular matrix rich in proteoglycans and fine collagen fibrils The periosteal fibrocartilage was the most 'cartilaginous' in character, probably because it develops rapidly after birth as a secondary cartilage from the calcaneal periosteum whereas enthesial and sesamoid fibrocartilages develop by metaplasia of tendon fibroblasts A major difference between the 3 fibrocartilages was the arrangement of their collagen fibrils There were parallel bundles in enthesial fibrocartilage but interweaving networks in the sesamoid and periosteal fibrocartilages This probably reflects different functional demands of the tissues The sesamoid and periosteal fibrocartilages directly formed the boundaries of the retrocalcaneal bursa and were not covered by synovium Both were lined by an electron dense, articular surface lamina that prevented cell contact with the bursa It significance is unclear, but it could protect against wear and tear, represent material being shed into the bursal cavity or control nutrient exchange with the synovial fluid

Intestinal absorption of PLAGA microspheres in the rat.

Abstract: Rhodamine B-labelled poly (DL-lactide-co-glycolide) (PLAGA) microspheres of 2 different sizes, 1-5 microns and 5-10 microns, were administered as a single dose (1.44 x 10(9) and 1.83 x 10(8) particles, respectively) into the ileal lumen of adult rats. The content of rhodamine in the mesenteric vein and ileal lumen was analysed periodically from 10 min to 48 h as well as the distribution of microspheres in the intestinal mucosa and various other tissues. The concentration of rhodamine decreased progressively in the intestinal lumen and was negligible after 24 h. The number of microspheres in the mesenteric vein increased rapidly and reached a maximum after 4 h whatever the size of the particles. It then decreased progressively, but more rapidly with microspheres > 5 microns than with microspheres 5 microns were retained in the ileal lumen. A few small microspheres were occasionally observed in the epithelial cells. Only the smallest particles were recovered in the liver, lymph nodes and spleen while basement membranes were always labelled. It is concluded that PLAGA microspheres could be useful for the oral delivery of antigens if their size is between 1 and 5 microns.

Ontogeny of four blood-brain barrier markers: an immunocytochemical comparison of pial and cerebral cortical microvessels.

Abstract: Pial and cortical microvessels possess many blood-brain barrier (BBB) properties in common, including impermeability to electron dense tracers, high transendothelial electrical resistance and specialised endothelial cell ultrastructural features. To compare pial and cortical microvessels further, a developmental, immunocytochemical study was undertaken of 4 BBB markers in the rat: OX-47, EBA, GLUT-1 and s-laminin. The appearance of the markers was monitored from embryonic d 16, to postnatal and adult stages. Each of the 4 markers appeared simultaneously in both pial and cortical vessels. GLUT-1 and OX-47 were present in endothelial cells of the BBB from E 16 to the adult. EBA and s-laminin appeared from postnatal d 7 through to the adult. Pial microvessels lack the ensheathment of astrocytes which may be involved in the induction and/or maintenance of BBB markers in the cortex. It is possible that astrocyte-derived factors diffusing from the brain surface are responsible for induction of BBB properties in the pial microvessels.

Particle uptake and translocation across epithelial membranes.

Abstract: Oral delivery of drugs and vaccines has many advantages over other routes of administration. For example, for vaccination, enteric delivery may result in the induction of a mucosal immune response against pathogens which colonise and invade the mucosa. However, the oral delivery of peptide or protein drugs or antigens is beset with problems, such as gastrointestinal breakdown of labile molecules, low level of macromolecular absorption and, for vaccines, the poor immune response usually elicited by orally administered soluble antigens. Investigations are therefore in progress to develop means of increasing intestinal absorption and decreasing digestion of orally administered molecules. Molecules can be incorporated into biodegradable microparticles to reduce the effect of gut secretions and to enable the absorption of bioactive agents in an unaltered form. The uptake of microparticulates through the gut wall is accepted as a true biological phenomenon but the mechanism and route of uptake have not been established. Furthermore, in general, only small numbers of microparticles are translocated across epithelial membranes, possibly making these systems inappropriate for drug or vaccine delivery. This paper reviews particle uptake across the gastrointestinal tract and describes studies carried out to determine whether a humoral response can be elicited following oral administration of an antigen associated with biodegradable poly(DL lactide-coglycolide) microparticles. The use of lipid delivery vehicles to enhance microparticle uptake and the selective transport of microspheres across M cells is also described.

Anatomy of the ostia venae hepaticae and the retrohepatic segment of the inferior vena cava.

Abstract: In 30 normal adult livers the retrohepatic segment of inferior vena cava had a length of 6.7 cm and was totally encircled by liver substance in 30% of cases. Altogether 442 ostia venae hepaticae were found, averaging 14.7 per liver and classified as large, medium, small and minimum. The localisation of the openings was studied according to the division of the wall of the retrohepatic segment of the inferior vena cava into 16 areas.

Immunohistochemical study of the corpora cavernosa of the human clitoris

Abstract: The microarchitecture of the corpora cavernosa of the human clitoris was investigated by immunohistochemistry. The distribution pattern of the nerve network was demonstrated by S-100 and neuron specific enolase immunoreactivity. Vascular and nonvascular muscle cells were identified by desmin and/or vimentin expression, and fibroblasts and endothelial cells by vimentin immunoreactivity. The findings show that tissue organisation in the corpora cavernosa of the clitoris is essentially similar to that of the penis except for the absence of the subalbugineal layer interposed between the tunica albuginea and erectile tissue. This has functional implications, suggesting that the clitoral erection cycle differs from that of the penis.

Immunohistochemical study of amoeboid microglial cells in fetal rat brain.

Abstract: The present study examined the expression of different antigens in amoeboid microglial cells (AMC) in fetal rat brain extending from 12 to 20 d postconception (E12-E20) using a panel of monoclonal antibodies which recognised the major histocompatibility complex (MHC) class I (OX-18) and class II (OX-6) antigens, leucocyte common antigen (OX-1), CD4 receptor (OX-35), complement type 3 receptor (OX-42) or macrophage antigens of unknown function (ED1 and ED2). Of the above-mentioned antigens, ED1 and ED2-labelled AMC were observed in the neuroepithelia as early as embryonic day 12 (E12); other antigens were not detected at this stage. At E14, except for MHC class I antigen, all other antigens were expressed by AMC distributed predominantly in the developing white matter. At E16, AMC in the intermediate zone lateral to the striatum were endowed with all the above-mentioned antigens including MHC class I. At E18, the immunoreactivities of AMC stained with OX-6, OX-18, OX-35 and OX-42 antigens were noticeably reduced when compared with those cells at E16. At E20, amoeboid microglial cells exhibited full complement of antigen expression similar to those cells at E16; some of the labelled cells emitted a variable number of cytoplasmic processes. It is suggested that the successive and differential expression of various macrophage related antigens on AMC in fetal brain is related to the specific requirement of local environment in different stages of development.