Showing papers on "Apical cytoplasm published in 1998"

Origin and secretion of milk lipids.

Abstract: The cream fraction of milk comprises droplets oftriacylglycerol coated with cellular membranes. In thisreview, we discuss how these droplets are formed andsecreted from mammary epithelial cells during lactation. This secretory system is especiallyinteresting because the assembled lipid droplets aresecreted from the cytoplasm enveloped by cellularmembranes. In other cells, such as hepatocytes andenterocytes, lipid is secreted by exocytosis frommembrane-bounded compartments of the secretory pathway.Milk lipids originate as small droplets oftriacylglycerol, synthesized in or on the surfaces ofrough endoplasmic reticulum (ER)4 membranes. Thesedroplets are released into the cytoplasm as microlipiddroplets (MLDs) with a surface coat of protein and polarlipid. MLDs may fuse with each other to form largercytoplasmic lipid droplets (CLDs). Droplets of varyingsize, are transported to the apical cytoplasm by unknownmechanisms and are secreted from the cell coated with anouter bilayer membrane. CLDs may increase in size in all regions of the cell, especially atthe plasma membrane during secretion. Two possiblemechanisms for lipid secretion have been proposed: anapical mechanism, in which lipid droplets are enveloped with apical plasma membrane, and asecretory-vesicle mechanism, in which fat droplets aresurrounded by secretory vesicles in the cytoplasm andare released from the surface by exocytosis fromintracytoplasmic vacuoles. A combination of both mechanisms maybe possible. Following secretion, a fraction of themembrane surrounding the globules may be shed from thedroplets and give rise to membrane fragments in the skimmilk phase.

Epithelial cytology and function in the digestive gland of thenus orientalis (decapoda: scyllaridae)

Abstract: The morphology and epithelial cytology of the digestive gland of the slipper lobster Thenus orientalis is described. The primary ducts possess extensive musculature which indicate that they may move fluid into and out of the glands. Immunohistochemical localization of trypsin demonstrated that it is synthesized and secreted solely by the F-cells in the digestive gland. Trypsin is absent from tissue in the oral region, proventriculus, and hindgut, but is present in digestive fluid throughout the alimentary tract, indicating that it has a role in extracellular digestion. Substantial accumulations of lipid in the cytoplasm of R-cells indicate a role in the absorption and storage of digestion products. Residual bodies in the apical cytoplasm are consistent with metal-storing granular inclusions and supranuclear vacuoles in the R-cells of other decapods. Based on the presence of an apical complex of pinocytotic vesicles and subapical vacuoles, an absorptive role for B-cells is evident. The presence of trypsin in the central vacuole is consistent with a digestive role, although our results cannot distinguish whether the enzyme is endogenous (lysosomal versus digestive) or was absorbed from the tubule lumen for excretion.

Histology and ultrastructure of the gut of the tilapia (Tilapia spp.), a hybrid teleost.

Abstract: Summary The morphology of the intestine has been studied in a species of warm water fish, Tilapia spp., a hybrid teleost of notable economic importance. Light and electron microscope results show that the intestine is a relatively undifferentiated muscular tube lined with a simple columnar epithelium interspersed with goblet cells. The proximal region has a greater surface area, manifested by elongated mucosal ridges. The enterocytes are covered apically with uniform microvilli and exhibit the typical ultrastructural features of pinocytosis, namely extensive invaginations of the luminal plasma membrane and massive accumulation of vesicles in the apical cytoplasm. The distal intestine mucosa is thinner and less elaborately folded and consists of columnar cells with shorter and sparser microvilli. Their supranuclear cytoplasm contains abundant clear vacuoles. Numerous endocrine cells can also be seen. Regional cellular ultrastructural features are correlated with digestive functions.

Early development of an identified serotonergic neuron in Helisoma trivolvis embryos: Serotonin expression, de-expression, and uptake

Abstract: In early-stage embryos of Helisoma trivolvis, a bilateral pair of identified neurons (ENC1) express serotonin and project primary descending neurites that ramify in the pedal region of the embryo prior to the formation of central ganglia. Pharmacological studies suggest that serotonin released from ENC1 acts in an autoregulatory pathway to regulate its own neurite branching and in a paracrine or synaptic pathway to regulate the activity of pedal ciliary cells. In the present study, several key features of early ENC1 development were characterized as a necessary foundation for further experimental studies on the mechanisms underlying ENC1 development and its physiological role during embryogenesis. ENC1 morphology was determined by confocal microscopy of serotonin-immunostained embryos and by differential-interference contrast (DIC) microscopy of live embryos. The soma was located at an anteriolateral superficial position and contained several distinguishing features, including a large spherical nucleus with prominent central nucleolus, large granules in the apical cytoplasm, a broad apical dendrite ending in a sensory-like structure at the embryonic surface, and a ventral neurite. ENC1 first expressed serotonin immunoreactivity around stage E13, followed immediately by the appearance of an immunoreactive neurite (stage E14). Both the intensity of immunoreactivity and primary neurite length were consistently greater in the right ENC1 at early stages. Serotonin uptake, as indicated by 5,7-dihydroxytryptamine-induced fluorescence, first occurred between stages E18 and E25. At later stages of embryogenesis (after stage E65), serotonin immunoreactivity disappeared, whereas serotonin uptake and normal cell morphology were retained.

Detection of Anionic Antimicrobial Peptides in Ovine Bronchoalveolar Lavage Fluid and Respiratory Epithelium

Abstract: Three small antimicrobial anionic peptides (AP) were originally isolated from an ovine pulmonary surfactant. However, their presence in bronchoalveolar lavage (BAL) fluid and tissues of the respiratory tract is unknown. In this study, we made affinity-purified rabbit polyclonal and mouse monoclonal antibodies to synthetic H-DDDDDDD-OH. Antibody specificity was assessed by a competitive enzyme-linked immunosorbent assay (ELISA), and the exact epitope binding sites were determined with analog peptides synthesized on derivatized cellulose. These antibodies were used to detect AP in BAL fluid by ELISA and in respiratory tissues by Western blot analysis and immunocytochemistry. BAL fluid from 25 sheep contained 0.83 ± 0.33 mM AP (mean ± standard deviation; range, 0.10 to 1.59 mM) and was antimicrobial. The presence of AP in BAL fluid was confirmed by reverse-phase high-pressure liquid chromatography fractionation followed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry on those fractions which were positive by competitive ELISA and demonstrated antimicrobial activity. In Western blots, polyclonal antibody PAB96-1 and monoclonal antibody 1G9-1C2 (5.0 μg/ml) detected four bands in solubilized turbinate and tracheal epithelial cells (53.7, 31.2, 28.0, and 25.7 kDa) and five bands in lung homogenates (53.5, 37.1, 31.2, 28.0, and 25.7 kDa). Only a single band was seen in solubilized liver and small-intestine homogenates, and no bands were seen in blots containing BAL fluid, albumin, or kidney or spleen homogenates. In pulmonary-tissue sections, both antibodies PAB96-1 and 1G9-1C2 identified accumulated protein in the apical cytoplasm of the bronchial and bronchiolar epithelia, in the cytoplasm of pulmonary endothelial cells, and in an occasional alveolar macrophage. As a first step in identifying a candidate AP precursor gene(s), degenerate oligonucleotides representing all possible coding combinations for H-GADDDDD-OH and H-DDDDDDD-OH were synthesized and used to probe Southern blots of sheep genomic DNA. Following low-stringency washes and a 2-day exposure, strongly hybridizing bands could be identified. One degenerate oligonucleotide, SH87, was used as a hybridization probe to screen a sheep phage genomic library. Two independent phage contained the H-GADDDDD-OH coding sequence as part of a larger predicted protein. AP may originate as part of an intracellular precursor protein, with multistep processing leading to the release of the heptapeptide into mucosal secretions. There it may interact with other innate pulmonary defenses to prevent microbial infection.

Temporal expression and cellular localization of a gastrin-releasing peptide-related gene in ovine uterus during the oestrous cycle and pregnancy.

Abstract: Synthesis of both mRNA and peptide for gastrin-releasing peptide (GRP) has been demonstrated in the pregnant endometrium of sheep and women. However, it is not known whether GRP is synthesized in the sheep uterus during the oestrous cycle. Furthermore the cellular site of GRP mRNA synthesis in the uterus has not been determined. Therefore we examined the synthesis of GRP and determined the cellular location of GRP peptide and mRNA in sheep uterus taken at different times during the oestrous cycle (duration 17 days) and pregnancy (duration 145 days). Northern blot analysis of RNA isolated from ovine endometrium revealed low or no GRP mRNA at days 4, 10, 12 and 14 of the oestrous cycle and a 24-fold rise in GRP mRNA (normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA) between days 14 and 16. A similar pattern was observed during early pregnancy, with a 12-fold rise in GRP mRNA:GAPDH mRNA between days 17 and 20 of pregnancy. Levels of GRP peptide were determined by RIA and found to be low in endometrium isolated at days 4, 10, 12 and 14 of the oestrous cycle (1.0-1.6 pmol/g) and 4 to 5-fold higher at day 16. In situ hybridization localized GRP synthesis to the epithelial cells of the uterine glands at day 16 of the oestrous cycle and at days 17, 20, 40 and 50 of pregnancy. At day 140 of pregnancy diffuse hybridization to cells of the myometrium was also observed. Immunohistochemistry localized GRP peptide to the apical cytoplasm of uterine glandular epithelial cells at day 16 of the oestrous cycle. For samples obtained at day 20 of pregnancy, the area surrounding the glands also showed moderately strong staining. Further staining in the glandular lumen and the stromal tissue surrounding the glands was apparent at day 140 of pregnancy. No GRP immunoreactivity could be detected in the peripheral plasma during the oestrous cycle or the first 20 days of pregnancy. Sizing chromatography of GRP immunoreactivity extracted from endometrial tissue taken at day 10 of the oestrous cycle revealed two peaks that co-eluted with GRP(1-27) and GRP(18-27). However, during luteolysis and oestrus the major peak of GRP immunoreactivity extracted from endometrial tissue was larger than GRP(1-27) and similar to that seen previously in the gravid ovine endometrium. These studies demonstrate that a peptide similar to, but larger than, GRP is a major product of the glandular epithelium of the ovine uterus during the luteal regression phase of the oestrous cycle and post-blastocyst implantation in pregnancy and provide further evidence that GRP-related peptides have important regulatory roles in uterine function.

Frequency specificity of vibration dependent discharge of nematocysts in sea anemones

Abstract: Hair bundles on tentacles of sea anemones are similar to vertebrate hair bundles in terms of structure and function. Anemone hair bundles are involved in regulating discharge of nematocysts, "stinging capsules," used to capture prey. N-acetylated sugars from the prey includ- ing N-acetylneuraminic acid (NANA) induce hair bundles to elongate while shifting vibration dependent discharge of nematocysts to lower frequencies matching prey movements. In the present study, we find that vibration dependent discharge of nematocysts exhibits sharp frequency dis- crimination to within one Hz. Testing at one-Hz intervals over the range of frequencies spanning 1-75 Hz, we find that seven of these are stimulatory in seawater alone. A total of twenty-six frequencies are stimulatory in the presence of NANA. Stimulatory frequencies in NANA are lower than those in seawater alone. We find that antagonists of ryanodine receptors including ryanodine, procaine and tetracaine shift discharge to lower frequencies. Fluorescently tagged ryanodine labels numerous small loci in the apical cytoplasm of supporting cells. We propose that calcium induced calcium release (CICR) via ryanodine receptors may sharpen frequency specificity and/or cause shortening of hair bundles to shift frequency specificity to higher fre- quencies. J. Exp. Zool. 281:582-593, 1998. © 1998 Wiley-Liss, Inc. Sea anemones are slow moving, predominantly sessile invertebrates that rely on prey locomotion or water currents to bring prey into contact with their tentacles. Anemones with small, fine ten- tacles or long, filamentous tentacles are prima- rily planktivorous (Shick, '91). Prey are captured by nematocysts and other cnidae, complex secre- tory products consisting of capsules containing eversible tubules (Mariscal, '74, '84). In response to appropriate chemical and mechanical stimuli (Pantin, '42), effector cells called cnidocytes trig- ger cnida discharge, rapid eversion of the tubule (Skaer and Picken, '65; Holstein and Tardent, '84). Depending on the type of cnida, the everting tubule may adhere to the surface of the prey, en- tangle its appendages, or penetrate its integu- ment to inject potent toxins (Mariscal, '74, '84). In anemones, most of the published work on the regulation of cnida discharge has concerned microbasic p-mastigophore nematocyts, selected for study because this nematocyst type is abun- dant in the cnidom (complement of cnidae) of the tentacle. Furthermore, microbasic p-mastigophore nematocysts discharged into gelatin coated test probes are relatively easy to count using phase contrast optics (e.g., Watson and Hudson, '94). Mechanical stimuli alone are sufficient to trig- ger discharge. Relevant mechanical stimulation can comprise contact alone or contact with a vi- brating test probe. Contact between a tentacle and nonvibrating test probe elicits discharge of a baseline number of nematocysts. Provided the test probe is vibrating at a preferred frequency (here- after referred to as a "key" frequency), about twice as many cnidocytes discharge nematocysts into the test probe as baseline. The number of nema- tocysts discharged into test probes vibrating at frequencies other than key frequencies is compa- rable to baseline (reviewed in Watson and Mire- Thibodeaux, '94). Thus far, two chemoreceptors are known to affect discharge of nematocysts. These chemore- ceptors bind N-acetylated sugars and amino com- pounds, respectively, compounds derived from prey (Thorington and Hessinger, '88). N-acety- lated sugars are contained in prey mucins and other glycoproteins. Amino compounds are con- tained in hemolymph of prey. Chemical stimuli

Cells in the duct system of the rat submandibular gland.

Abstract: The duct system of the rat submandibular gland (granular convoluted tubule [GCT], striated duct, excretory duct, main excretory duct [MED] and salivary bladder) was studied using scanning and transmission electron microscopy, with special reference to the dark and tuft cells. The MED was subjected to histochemistry for horseradish peroxidase (HRP) uptake. The epithelium of the duct system was composed of a heterogeneous cell population. On scanning electron-microscopic observation, principal, dark, and tuft cells were easily distinguished by their microvilli. Principal cells had small microvilli and microridges on their surface. The principal cells of the striated duct had secretory granules in the apical cytoplasm, but those of the excretory duct, the MED, and the salivary bladder had electron-lucent vesicles. Except for the GCT and salivary bladder, the basal infoldings of the epithelial cells were well developed. The dark cells were characterized by regular microvilli, and many tubules and vesicles confined to the apical cytoplasm. They existed in the striated duct, the excretory duct, the MED, and salivary bladder. The so-called pillar cells in the GCT appeared to be identical to the dark cells. Tuft cells had on their surface long, blunt microvilli with prominent rootlets. Many vesicles were observed in the apical cytoplasm. It was concluded that dark and tuft cells were common in the striated duct, the excretory duct, the MED and salivary bladder. Dark cells were observed also in the GCT. Dark and principal cells of the MED showed HRP uptake but tuft cells did not.

Characterization of stage-specific tyrosinated α-tubulin immunoperoxidase staining patterns in Sertoli cells of rat seminiferous tubules by light microscopic image analysis

Abstract: Microtubules are involved in many structural and functional changes that occur in Sertoli cells during the cycle of the seminiferous epithelium. However, few studies have addressed stage-specific changes in the distribution of microtubules that accompany the process of spermatogenesis. This study provides a stage-by-stage immunohistochemical evaluation of Sertoli cell microtubules in paraffin sections of whole rat testes using an antibody to tyrosinated α-tubulin. Microtubules that contain tyrosinated tubulin are considered to be less stable and are therefore expected to populate Sertoli cells undergoing dynamic changes during spermatogenesis. A quatitative method was developed to analyze the relative tyrosinated α-tubulin staining in different stages of the cycle. Immunostaining patterns of the stages were separated into five different groups. Stages VII–VIII had the least amount of tyrosinated α-tubulin, while stages IX–XI contained the greatest amount. The staining patterns were consistent with established structural changes in the seminiferous epithelium, such as the formation of ectoplasmic specializations, the presence of microtubule nucleation sites along the periphery of the apical cytoplasm, and the translocation of elongate spermatids from deep crypts in the Sertoli cell to the tubule lumen. These data should provide improved methods for the evaluation of microtubules in the study of Sertoli cell responses to environmental toxicants and testicular diseases.

Sperm aggregations in the spermatheca of female desmognathine salamanders (Amphibia: Urodela: Plethodontidae)

Abstract: The alignment of sperm in a cloacal sperm storage gland, the spermatheca, was studied in female desmognathine salamanders by scanning and transmission electron microscopy. Females representing nine species and collected in spring, late summer, and fall in the southern Appalachian Mountains contained abundant sperm in their spermathecae. The spermatheca is a compound tubuloalveolar gland connected by a single common tube to the middorsal wall of the cloaca. Sperm enter the common tube in small groups aligned in parallel along their axes, and continue in a straight course until encountering divisions of the common tube (neck tubules) or luminal borders of distal bulbs, which can act as barriers. Sperm may form tangles, in which small clusters retain their mutual alignment, at the branches of the neck tubules from the common tube, or in the lumen of the distal bulbs, where subsequent waves of sperm collide with sperm already present. The nuclei of some sperm from the initial group to encounter the walls of the distal bulbs appear to become embedded in secretory material on the luminal border or in the apical cytoplasm of the spermathecal epithelial cells. We propose that these sperm become trapped in the spermatheca and are ultimately degraded. J. Morphol. 238:143-155, 1998. © 1998 Wiley-Liss, Inc.

Cutaneous glands of male and female impalas (Aepyceros melampus): seasonal activity changes and secretory mechanisms

Abstract: The cutaneous glands of the forehead and the metatarsus were studied by histological and histochemical methods and electron microscopy in adult male and female impalas in various seasons of the year. All glandular areas consist of apocrine and holocrine glands, which, however, occur in different proportions. Our findings in the apocrine gland cells suggest (1) the synthesis and exocytosis of a glycoproteinaceous secretory product stored in secretory granules, (2) typical apocrine secretion of the transformed apical cytoplasm, and (3) transepithelial fluid transport. The Golgi apparatus and apical membrane have binding sites for several lectins (PNA, HPA, RCA I, WGA). Cytokeratins 7, 14 and 19 are expressed at various intracellular localizations, suggesting an active role in the secretory mechanisms. The glands of the male forehead show marked seasonal changes in activity that are correlated with the main phases of the reproductive cycle, with the highest cellular activity occurring during the rut in April/May. The female forehead glands are only moderately developed and do not undergo seasonal changes. The metatarsal glands are of equal size in males and females and show no seasonal changes in activity. This study supports the hypothesis that (1) forehead glands in the male have a signaling role in the rut and (2) the metatarsal glands have a more general, probably social role maintaining and restoring contact between herd members.

Aural polyp associated with cryptosporidiosis in an iguana (Iguana iguana)

Abstract: Figure 2. Electron micrograph. Aural polyp; green iguana. Pseudostratified columnar epithelial cells with numerous cryptosporidial trophozoites (arrowheads). Bar 5 2 mm. Cryptosporidiosis is well recognized as a gastroenteric pathogen in many mammalian species, as both an enteric and respiratory pathogen in domestic fowl, and as a gastric pathogen in several reptilian species.2,3,5 This report describes the first documented case of cryptosporidiosis in a green iguana (Iguana iguana) and an association of the organism with an inflammatory polyp within the middle ear canal, an anatomic location where Cryptosporidium has not been previously recognized. An adult female green iguana was presented because of a protruding right tympanic membrane; the protrusion had been present for approximately 2 weeks. The referring veterinarian had detected an irregular 1.0–1.5-cm-diameter firm mass that filled the right tympanic cavity, had surgically excised the mass, and had submitted the tissue, fixed in 10% neutral-buffered formalin, for diagnostic evaluation. The tissue was routinely processed for histopathology. An accompanying swab of the mass was submitted for routine aerobic bacteria culture; no bacteria were isolated from the swab. Histologically, the mass consisted of a core of dense fibrous connective tissue covered by hyperplastic pseudostratified columnar epithelium with scattered mucous goblet cells. There were moderate numbers of heterophils within the connective tissue just beneath the epithelium, with some exocytosis of heterophils. Few lymphocytes and plasma cells were scattered through the connective tissue. Along the outer ciliated border of the epithelium, there were numerous 2–3mm-diameter basophilic protozoal organisms associated with the apical cytoplasm; these organisms were consistent with Cryptosporidium (Fig. 1).2 Tissues were postfixed in glutaraldehyde and routinely prepared for transmission electronmicroscopy. Many epithelial cells contained one or more spherical protozoa beneath the host cell plasma membrane; the cell membranes had lost their cilia in the areas associated with the organisms (Figs. 2, 3). Most of the organisms were consistent with trophozoites, although occasional forms resembling schizonts and gametocytes were also present.2 Trophozoites were an average of 2.0 3 2.5 mm, had a single prominent nucleus and a distinct feeder organelle in the zone of attachment to the host cell, and were surrounded by a parasitophorous vacuole bounded by a plasma membrane (Fig. 3). This is the first report of Cryptosporidium in an iguana,

Increasing frequency of occurrence of tuft cells in the main excretory duct during postnatal development of the rat submandibular gland

Abstract: Tuft cells, a widespread cell type that is present in the mucosal epithelia of hollow organs, including the main excretory duct (MED) epithelia of the rat salivary gland, are well documented morphologically. However, studies of their development are few. The purpose of the present study was to examine the perinatal and postnatal development of tuft cells in the main excretory duct of the rat submandibular gland. Main excretory ducts of the submandibular gland were obtained from five male Wistar rats at the ages of 0, 1, 7, 14, 17, 21, 23, 28, and 56 postnatal days and were prepared for scanning and transmission electron microscopy. The tuft cells, which are distinguished easily by their long microvilli protruding into the lumen, were recognizable first at 17 postnatal days. They showed a remarkable increase in number between 3 and 4 postnatal weeks. The percentages of tuft cells were 0.4% at 17 postnatal days and 0.8% at 3 postnatal weeks. The number of tuft cells represented approximately 5% of the total epithelial cells by 4 postnatal weeks. There was a significant difference between 3 and 4 postnatal weeks (P < 0.01). The microvilli of the tuft cells at the time of weaning had almost the same width as in the adult, but they were shorter. Microfilaments extending from the tips of the microvilli and microtubules and many electron-lucent vesicles in the supranuclear cytoplasm also were observed. These results indicate that tuft cells appeared in the MED of the submandibular gland during weaning and had abundant vesicles in their apical cytoplasm.

Lectin histochemistry study in the human vas deferens.

Abstract: The oligosaccharide sequences of glycoconjugates in the normal human vas deferens and the nature of the saccharide linkage were studied by lectin histochemistry The cytoplasm of all epithelial cell types (principal cells, basal cells, and mitochondria-rich cells) and luminal contents reacted positively with WGA, MAA, PNA, DSA, LTA, UEA-I, AAA, and ConA The reaction was more intense in the stereocilia of principal cells Cytoplasmic staining was diffuse except for PNA and DSA labeling which was limited to the apical cytoplasm and stereocilia of columnar cells The cytoplasm of all cell types also reacted diffusely with HPA, although staining was weak and was not observed in the stereocilia Positive reaction with SBA only was encountered in the stereocilia of principal cells SNA, LTA, and DBA were unreactive GNA-labeling showed a granular distribution in the supranuclear cytoplasm of columnar epithelial cells Reactions with MAA, PNA, DSA, AAA, HPA and SBA disappeared after the beta-elimination reaction Reactions with WGA and UEA-I decreased after beta-elimination or Endo-F digestion Reactions with ConA and GNA were suppressed by Endo-F digestion Reactions with PNA, HPA, and SBA increased after desialylation Of all the lectins that label the luminal contents of the vas deferens, only UEA-I was not found in the luminal contents of seminiferous tubules and epididymis and, thus, this lectin would probably bind to glycoproteins secreted by the vas deferens The chemical treatments used suggest that this secretion contains fucose residues located in both N- and O-linked oligosaccharides The other lectins may label secreted proteins, but also structural proteins or proteins reabsorbed from the luminal fluid The lectin- binding pattern of mitochondria-rich cells in the vas deferens differed from that found in the epididymis

Ultrastructure of the Vacuolar Apparatus in the Renal Proximal Tubule Microinfused in vivo with the Cytological Stain Light Green

Abstract: To obtain insight into the basic mechanisms controlling endocytosis, we tested the effects of different perfusates containing the cytological stain light green on endocytosis and ultrastructure of the vacuolar apparatus in renal proximal tubule cells Rat proximal tubules were microinfused in vivo for 2 min in the presence or absence of light green with the following solutions: (A) perfusates containing inorganic salts and (B) perfusates with organic components or protein In other experiments, the tubules were first microinfused for 2 min with 09% NaCl in the presence or absence of light green, then 15 min later further microinfused with or without light green using either group A or B solutions in order to either aggravate or reverse possible changes All infused tubules were fixed after 5 min with 1% glutaraldehyde and examined by electron microscopy In tubules microinfused without light green, the endocytic vacuolar apparatus in the apical cytoplasm showed a normal ultrastructure However, microinfusion of solutions containing light green in either inorganic salts or a low concentration of protein caused significant changes in the apical endocytic apparatus Large endocytic vacuoles were absent, and invaginations and small endocytic vacuoles were decreased in frequency On the other hand, the amount of dense apical tubules was significantly increased, and in some cells dense apical tubules had transformed into a cisternalike network These changes were aggravated in tubules which received a second microinfusion of NaCl and reversed in tubules that received a second infusion of protein Furthermore, in the tubules microinfused with light green using perfusates containing organic components or protein, the apical cytoplasm of proximal tubule cells showed an essentially normal endocytic apparatus The present study demonstrates that microinfusion of renal proximal tubules with light green disrupted normal endocytic membrane trafficking and recycling These changes could be prevented or reversed by microinfusion of solutions containing protein or organic components

Intracellular electrolyte levels and transport of secretory granules in exocrine gland cells

Abstract: We demonstrate the intracellular transport of secretory granules of a silk protein, fibroin, from the Golgi region to the apical cytoplasm with special reference to microtubule organization, electrolyte concentrations and the acidic intragranular pH of normal and mutant posterior silk gland cells, using the techniques of electrophysiological microelectrode and microprobe analysis and of light and electron microscopic autoradiography. The silk gland cells of a recessive mutant making only flimsy cocoons were defective in the microtubule systems, did not stain with an anti-tubulin antibody in immunofluorescent microscopy, and accumulated intracellular granules in the apical and basal cytoplasm. The increase in intracellular calcium concentration and levels of chloride secretion were also reduced in the mutant cells. A carboxylic ionophore, monensin, which collapsed the granular H+ gradient, induced the transport of chloride and an increase in the intracellular calcium concentration, while it blocked the intracellular transport of granules from the Golgi region to the apical cytoplasm in normal cells. Thus, we conclude that the H+ gradient across the membrane of secretory granules is responsible for the intracellular transport of the secretory granules along the microtubule systems in silk gland cells, while Ca2+ is thought to be required for the exocytosis of the granules.

Gene cloning of BM180, a lacrimal gland enriched basement membrane protein with a role in stimulated secretion.

Abstract: Dry eye is the ocular manifestation of a collective secretory deficiency by lacrimal acinar cells.1 Lacrimal acinar cells are polarized tear protein factories, with tear protein-filled secretory granules packed in the apical cytoplasm adjacent to the acinar lumen into which tear proteins are released. These cells are wrapped into acini by a poorly characterized basement membrane2 sheet, the complex cellular adhesiveness of which is the molecular basis for exocrine cell polarity.3 Abnormality of the basement membrane-cell interface is the primary lesion in several autoimmune and genetic diseases.4 In Goodpasture’s syndrome, for example, nephrotoxic autoantibodies appear as a consequence of infection-associated exposure of a sequestered epitope in the α3 chain of collagen IV. In Alport’s syndrome, function-altering point mutations in the collagen IV α3 chain have been detected.

An unusual parotid gland in the tent‐building bat, Uroderma bilobatum: Possible correlation of interspecific ultrastructural differences with differences in salivary pH and buffering capacity

Abstract: The tent-building bat, Uroderma bilobatum, is a small, frugivorous phyllostomid bat with a broad neotropical distribution. Generally found in humid forest, this bat lives in small groups that create daytime ‘‘roosts’’ from large leaves of a variety of tropical plants. Fruit eating engenders a variety of ecological and physiological challenges for bats, some of which could require adaptive features in their salivary glands. The parotid salivary glands of Uroderma bilobatum were prepared for transmission electron microscopy by using methods that have become standard for field work. The parotid gland is extremely unusual in structure. Although the secretory endpieces still produce serous granules with a complex substructure, they are modified into quasi striated ducts. Their basal folds, which are extensive, occasionally harbor some vertically oriented mitochondria, imparting a resemblance to striated ducts. Other evidence for the endpiece origin of these parenchymal components is a well-developed system of intercellular canaliculi, structures that never occur in bona fide striated ducts. The long but sparse intercalated ducts consist of two types of cells, each of which elaborates a modest number of secretory granules of differing substructure. Striated ducts are of conventional morphology, except that a few dark cells shaped like wine glasses are present in their walls. The striated duct cells produce no secretory granules, but their apical cytoplasm may contain some small, empty vesicles. Capillaries lie in longitudinal grooves in the base of the duct cells, an arrangement that might enhance electrolyte exchange. Excretory ducts consist of simple cuboidal epithelium composed of cytologically unspecialized cells that sometimes includes a dark cell. It was concluded that salivary glands could have a major role in adapting species to acquire nutrients from marginal sources, such as tropical fruits, which have a low protein and sodium content. The unusual parotid acinar cells in Uroderma bilobatum are discussed in the context of salivary pH and buffering capacity. Comparisons are made with four other bat species, including an insectivorous species with a salivary pH .

Localization of glucose-6-phosphatase activity and carbohydrates in boar caput epididymal principal cells.

Abstract: Unidentified tubulovesicular profiles have been reported in the apical cytoplasm of boar caput epididymal principal cells in addition to vesicles considered to be involved in endocytosis and secretion. The main aim of the present study was to clarify the character of these organelles and to differentiate them from the endocytic apparatus. Glucose-6-phosphatase (G6Pase) activity was determined as the reporter enzyme of the endoplasmic reticulum (ER) and phosphotungstic acid was used to visualize carbohydrate moieties in both the proximal and distal caput. Phosphotungstic acid revealed the glycocalyx of the endocytic apparatus, which was similar in both regions studied, and also stained specific granules of the proximal caput. Glucose-6-phosphatase showed the tubulovesicular profiles to be sparsely granulated ER that was poorly developed in the proximal caput and very abundant in the apical cytoplasm of the distal caput principal cells. The function of such large amounts of sparsely granulated ER with corresponding G6Pase activity in caput epididymal principal cells is unknown.

BRIEF COMMUNICATIONS Aural polyp associated with cryptosporidiosis in an iguana (Iguana iguana)

Abstract: Cryptosporidiosis is well recognized as a gastroenteric pathogen in many mammalian species, as both an enteric and respiratory pathogen in domestic fowl, and as a gastric pathogen in several reptilian species. 2,3,5 This report describes the first documented case of cryptosporidiosis in a green iguana (Iguana iguana) and an association of the organism with an inflammatory polyp within the middle ear canal, an anatomic location where Cryptosporidium has not been previously recognized. An adult female green iguana was presented because of a protruding right tympanic membrane; the protrusion had been present for approximately 2 weeks. The referring veterinarian had detected an irregular 1.0‐1.5-cm-diameter firm mass that filled the right tympanic cavity, had surgically excised the mass, and had submitted the tissue, fixed in 10% neutral-buffered formalin, for diagnostic evaluation. The tissue was routinely processed for histopathology. An accompanying swab of the mass was submitted for routine aerobic bacteria culture; no bacteria were isolated from the swab. Histologically, the mass consisted of a core of dense fibrous connective tissue covered by hyperplastic pseudostratified columnar epithelium with scattered mucous goblet cells. There were moderate numbers of heterophils within the connective tissue just beneath the epithelium, with some exocytosis of heterophils. Few lymphocytes and plasma cells were scattered through the connective tissue. Along the outer ciliated border of the epithelium, there were numerous 2‐3mm-diameter basophilic protozoal organisms associated with the apical cytoplasm; these organisms were consistent with Cryptosporidium (Fig. 1). 2 Tissues were postfixed in glutaraldehyde and routinely prepared for transmission electronmicroscopy. Many epithelial cells contained one or more spherical protozoa beneath the host cell plasma membrane; the cell membranes had lost their cilia in the areas associated with the organisms (Figs. 2, 3). Most of the organisms were consistent with trophozoites, although occasional forms resembling schizonts and gametocytes were also present. 2 Trophozoites were an av

Ultrastructural and biochemical studies on the intestinal absorption of a medium-chain triglyceride (MCT), tricaprylin

Abstract: The intestinal absorption of a medium-chain triglyceride (MCT) was studied by electron microscopy and biochemical analysis. In jejunal absorptive cells of rats fed tricaprylin, the smooth endoplasmic reticulum in the apical cytoplasm appeared to increase in number and contained one or two particles about 40–80 nm in diameter that were less electron dense and similar in size and profile to very low density lipoprotein. Similar particles were also observed packed in the dilated Golgi sacs and in the extended intercellular spaces. These particles were remarkably increased in number as compared with those in fasted rats. Biochemical analysis of lymph from the main intestinal lymph duct showed that caprylate was apparently demonstrated only in the lymph of rats given tricaprylin at the maximum rate 3h after oral administration. The study strongly suggests that medium-chain triglyceride is at least in part transported via lacteal, possibly in the form of very low density lipoprotein.