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Biomedical subjects

R D Specian

Publications and source records attributed to R D Specian.

At least 73 records · Page 4Linked to original sources
PubMed1987

Characterization and localization of the putative 'link' component in rat small-intestinal mucin.

Rat intestinal mucin is polymerized by a putative 'link' component of Mr 118,000 that can be released from the native mucin by thiol reduction [Fahim, Forstner & Forstner (1983) Biochem. J. 209, 117-124]. To confirm that this component is an integral part of the mucin and independent of the mucin purification technique, rat mucin was purified in the present study by three independent techniques. In all cases, the 118,000-Mr component was released after reduction. The 118 kDa band was electroeluted from SDS/polyacrylamide gels and its composition shown to resemble closely that of the link component of human intestinal mucin [Mantle, Forstner & Forstner (1984) Biochem. J. 224, 345-354]. Carbohydrates were present, including significant (10 mol/100 mol) amounts of mannose, suggesting the presence of N-linked oligosaccharides. Monospecific antibodies prepared against the rat 118,000-Mr component established its tissue localization in intestinal goblet cells. Mucins subjected to SDS/polyacrylamide-gel electrophoresis and Western blots using the same antibody, established that the link components of rat and human intestinal mucin are similar antigenically. Brief exposure (10 min) of native rat mucin to trypsin or Pronase (enzyme/mucin protein, 1:500, w/w) also released a 118,000-Mr component that reacted with the monospecific antibody. Thus the 118,000-Mr component is an integral part of the mucin and, although linked to large glycopeptides by disulphide bonds, this component also has proteinase-sensitive peptide bonds, presumably at terminal locations such that brief treatment with proteinases releases the molecule in a reasonably intact form. Under physiological conditions, therefore, one might expect that, after mucin is secreted into the intestinal lumen, luminal proteinases would rapidly remove the link component, thereby causing the mucin to depolymerize.

Amino Acids↗
PubMed1987

Endocytosis and vesicular traffic in fetal and adult colonic goblet cells.

Structural and functional differences between adult and fetal colonic goblet cells have not been clearly defined. To compare the binding, uptake, and intracellular pathway of internalized apical membrane in fetal and adult goblet cells, cationic ferritin (CF) was used as a nonspecific probe. The initial distribution of membrane anionic sites was determined in segments of proximal and distal colon from fetal (18-22 days) and adult rats that were fixed prior to a 10-minute exposure to CF at 4 degrees C. Uniform binding along the apical membrane and microvilli was noted at all ages. To assess uptake and intracellular transport, segments of proximal and distal colon from fetal and adult rats were exposed to CF for 10 minutes at 4 degrees C prior to a saline wash and incubation in saline or Liebovitz L-15 medium for 3, 6, 15, 30, or 60 minutes at 37 degrees C. In addition, fetal rats between 18 and 22 days gestation (birth) were exposed to CF continuously for 10-30 minutes via an intracaecal injection. The results showed extensive uptake of CF in the fetal goblet cells and a more variable intracellular pathway than in with the adult. Within 3 minutes, numerous CF positive vesicles and tubules were present within the apical cytoplasm as well as interspersed among the secretory granules of the fetal goblet cell. Most of these vesicles were smooth surfaced, although some were coated. By 15 minutes, CF was frequently seen in multivesicular bodies, and occasionally in vacuoles in the vicinity of the Golgi. No CF was detected in Golgi cisternae.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Translocation of indigenous bacteria from the gastrointestinal tract of mice after oral ricinoleic acid treatment.

A single dose of ricinoleic acid, the active component of castor oil, administered intragastrically to specific pathogen-free mice produced significant alterations in the proximal small intestinal mucosa. Two hours after drug administration, the duodenal villi were markedly shortened with massive exfoliation of columnar and goblet cells. This disruption of the mucosal barrier resulted in continuity between the intestinal lumen and the lamina propria of the villi. Because of the loss of the mucosal barrier, bacteria of the indigenous gastrointestinal flora translocated from the gastrointestinal lumen to the mesenteric lymph nodes, spleen, and liver. The peak incidence of bacterial translocation occurred 4 days after the ricinoleic acid treatment. Strictly anaerobic bacteria, which normally colonize the gastrointestinal tract at greater levels than aerobic or facultatively anaerobic bacteria, were translocated at a greater incidence to the mesenteric lymph nodes than were the other indigenous bacteria. The mucosa began regenerating within 4 h after the ricinoleic acid treatment and viable translocated bacteria were no longer cultured from the mesenteric lymph nodes by 7 days after treatment.

Animals↗
PubMed1986

Electrical stimulation of mandibular osteotomies in rabbits.

The use of electrical stimulation to accelerate mandibular healing was studied in rabbits that had undergone bilateral mandibular slot osteotomies. Stimulation on the day of surgery and for 3 successive days thereafter (2 hours per day) produced accelerated healing as evaluated histologically 8 days after surgery. Stimulation during the entire postoperative period did not result in accelerated healing. Intermittent stimulation in the early postoperative period may be clinically useful for accelerating the healing of mandibular fractures.

Animals↗
PubMed1986

Functional repair of rabbit gastrocnemius tendons using carbon fibers.

The ability of carbon fibers to form a secure anastomosis with soft tissue will have an important bearing on any future clinical uses. A secure anastomosis in rabbit Achilles tendons has been observed for up to 12 weeks after operation using a locking-weave suture, without immobilization. Impaired function occurred from slippage of the carbon fibers, which began by six weeks after operation, and which increased progressively at 13 and 42 weeks after operation. Satisfactory results were obtained using a modified Bunnell suture (with immobilization) in which the free ends of the carbon fibers were glued together with bone cement. In another study, carbon fibers that were weaved through intact rabbit Achilles tendons did not attach to the tendons during the postoperative time interval studied (18 weeks). It is possible, although difficult, to obtain a functional repair of the rabbit Achilles tendon using carbon fibers.

Animals↗
PubMed1984

Cytoskeleton of intestinal goblet cells in rabbit and monkey. The theca.

The ultrastructure and function of the cytoskeleton in intestinal goblet cells was investigated in colonic mucosa from rabbits and monkeys. This exocrine cell is unusual in that its secretory granules are stored as a compact apical mass limited by a dense, cup-shaped layer of cytoplasm called the "theca." Ultrastructural analysis of this cytoplasmic layer in rabbit goblet cells permeabilized with Triton X-100, treated with S4 fragments of heavy meromyosin, and fixed in the presence of tannic acid revealed that it contains an orderly arrangement of microtubules and intermediate filaments, but no detectable actin filaments. Microtubules are arranged vertically, like barrel staves, along the inner aspect of the theca. Intermediate filaments are arranged in two contiguous layers: an inner, basket-like network and an outer series of circumferential bundles resembling the hoops of a barrel. Autoradiography of [3H]glucosamine-labeled human and rabbit cells maintained in organ culture without secretagogues had provided preliminary data suggesting that labeled secretory granules migrate preferentially along the periphery of the apical granule mass, adjacent to the theca, toward the luminal cell surface. In this study, we confirm this observation and show that colchicine inhibits this movement. Cholinergic secretagogues induce rapid release of mucin by compound exocytosis of the granules stored in the theca. This secretory activity is not inhibited by colchicine, presumably because it does not require granule movement. The cuplike shape of the theca is unaltered during rapid release of stored granules. Because the shape is unaltered after 6 h of colchicine treatment, it appears to be maintained by the intermediate filament layers.

Animals↗
PubMed1982

Regulation of intestinal goblet cell secretion. I. Role of parasympathetic stimulation.

The in vivo effects of the parasympathomimetic drug pilocarpine on rat intestinal goblet cells were analyzed by autoradiography, light microscopy (LM), and electron microscopy (EM). Pilocarpine accelerated the release of mucus by compound exocytosis from crypt (but not surface) goblet cells throughout the small and large intestine. Pilocarpine-induced mucus secretion was blocked by atropine alone in ileum and colon, but total inhibition in proximal small intestine required a combination of atropine and tubocurarine. The sensitivity of morphological-autoradiographic methods for detection of goblet cell secretion was compared with that of a biochemical detection method, separation of labeled high-molecular-weight glycoproteins by Sepharose 4B gel filtration of luminal washings. Even when secretion of labeled mucus by compound exocytosis was clearly demonstrated by LM, EM, and autoradiography, gel filtration assay of luminal washings from pilocarpine-injected rats failed to reveal an increase in labeled high-molecular-weight glycoproteins. Autoradiographs of mucosal tissue after luminal washing showed that newly secreted, labeled mucus was retained in the crypts and was thus unavailable to the biochemical assay. Thus, direct observation of exocytosis in individual goblet cells provides a qualitative, but sensitive, assay for short-term acceleration of intestinal mucus secretion.

Animals↗
PubMed1982

Regulation of intestinal goblet cell secretion. II. A survey of potential secretagogues.

The factors that regulate the rate of mucus secretion in intestinal goblet cells are only partially defined. Autoradiographic and ultrastructural studies demonstrated that muscarinic cholinergic agents accelerate the exocytosis of mucus from goblet cells in the crypts throughout the small and large intestine, both in vivo and in mucosal organ culture. The present study seeks to identify other factors that may alter mucous secretory rates. Mucosal explants were exposed to potential secretagogues and inhibitors in the organ-culture system and analyzed by light and electron microscopy, alpha- and beta-Adrenergic agents, gastrointestinal regulatory peptides, serotonin, histamine, and dibutyryl cyclic nucleotides were tested over wide concentration ranges. With the exception of histamine, none of these agents accelerated or inhibited the exocytosis of mucous granules. Histamine was effective at the concentration of 10(-4) M and induced rapid, compound exocytosis by crypt goblet cells in mucosal explants from the colon but not from small intestine. The response to histamine was unaffected by atropine. Goblet cells on the mucosal surface released mucus by compound exocytosis when exposed to mustard oil, a nonspecific chemical irritant, but not when exposed to histamine or cholinergic agents.

Acetylcholine↗
PubMed1981

The surface topography of the colonic crypt in rabbit and monkey.

Scanning electron microscopy (SEM) was used to investigate the epithelial topography of the surface and crypt in rabbit and monkey colon. Crypt openings in monkey colon are arranged in a hexagonal pattern, in sharp contrast to rabbit colon where they are randomly arrayed and frequently hidden by epithelial folds. Crypt lumens were exposed by freezing ethanol-dehydrated tissue in liquid nitrogen and fracturing the tissue with a razor blade. The resulting overview of crypt-cell luminal surfaces showed that as columnar cells mature and migrate up the crypt and onto the colonic surface, their microvilli become progressively more abundant. Goblet cells were readily identified in the cross-fractured crypt epithelium; their luminal surfaces are characterized by short, sparse microvilli. The changing appearance of the luminal surface of goblet cells was visualized by SEM during the exocytosis of single mucous granules from unstimulated crypt goblet cells, and during the compound exocytosis of multiple granules in response to acetylcholine.

Animals↗
PubMed1981

Histochemical, cytochemical and autoradiographic studies on the rostellum of Hymenolepis diminuta.

Histochemical studies on the rostellum of Hymenolepis diminuta revealed diastase-stable, protein/neutral carbohydrate-rich material localized in the rostellum tegument. The remainder of the rostellum, primarily composed of the glycogen-rich myocytons of the rostellum musculature, is protein-poor, but rich in diastase-labile, neutral and acidic carbohydrates. Ultrastructural cytochemical studies, using the periodic acid-thiocarbohydrazide osmium (PATCO) technique, indicated that the granules of the rostellar tegumental cytons and distal cytoplasm are carbohydrate-rich. Lipids are present in the rostellar myocytons but not in the tegumental cytons. Autoradiography using a pulse-labeling with [3H]leucine revealed an apical translocation of tegumental granules, but at a slower rat than had been reported for the strobilar tegument of the same organism. Neither [3H]galactose nor [3H]glucose were incorporated into the rostellar tegumental granules. The function of the secretory glycoprotein(s) produced in the rostellar tegument and its (their) possible role in the regulation of maturation and/or strobilization remain enigmatic.

Animals↗
PubMed1981

The value of cuticular fine structure in identification of juvenile anisakine nematodes.

Juveniles of the ascarid nematodes Anisakis sp. and Phocanema sp. from marine teleosts, have been implicated as major causative agents of human anisakiasis. Whereas juveniles of the related genus Thynnascaris sp. have not been reported from humans, this nematode may occur in fish concurrently with the aforementioned species. The juvenile anisakine nematodes are not readily identified, and reliable morphological markers would provide a valuable aid in identification of potentially pathogenic individuals. In this study of cuticular fine structure, the following characteristic difference appeared to be most significant: a wide electron lucent area containing partitions and previously unreported electron dense rods occurred in the basal layer of the Phocanema sp. cuticle, but not in that of Anisakis sp. or of Thynnascaris sp. Juveniles of Thynnascaris sp. possessed a cuticle that was structurally similar to that of Anisakis sp., but only about one-half as thick. Comparatively, the third stage Ascaris lumbricoides cuticle was poorly developed, and less definitively layered than those of the anisakines.

Animals↗
PubMed1980

The microanatomy and fine structure of the rostellum of Hymenolepis diminuta.

The microanatomic arrangement of the muscular, nervous, and excretory systems as well as the organization of the tegument are described for the rostellum of Hymenolepis diminuta. An inner circular and an outer longitudinal layer of muscle comprise the rostellar capsule, delimiting the rostellum from the scolex proper. A similar muscular arrangement surrounds an apical invagination of the rostellar tegument, the anterior canal. Elements of the excretory and nervous systems enter the rostellum basally through a discontinuous region of the capsule. Although excretory canals extend into the rostellum, flame cells and their associated collecting ducts are absent. The rostellar nervous system is comprised of a single bilateral pair of ganglia, which provide motor innervation of the anterior canal, and the circular muscles of the rostellar capsule; it also receives dendrites from apical uniciliate sensory receptors. The tegument lining the anterior canal and covering the apical rostellum is syncytial and continuous with the tegument of the scolex proper. Twelve to 15 cytons are radially arranged around the anterior canal. They stain selectively with paraldehyde-fuchsin between days 3 and 35 postinfection, but are clearly tegumental, not neurosecretory elements. The appearance of ovoid granules in the rostellar tegumentary cytons coincides with the onset of fuchsinophilia, but the granules persist despite the subsequent loss of this staining characteristic. Intact granules are secreted into the lumen of the anterior canal, although their function has not been ascertained.

Animals↗
PubMed1980

Mechanism of rapid mucus secretion in goblet cells stimulated by acetylcholine.

The parasympathetic control of goblet cell secretion and the membrane events accompanying accelerated mucus release were studied in large intestinal mucosal biopsies maintained in an organ culture system. The secretory response of individual goblet cells to 10(-6) M acetylcholine chloride with 3 x 10(-3) M eserine sulfate (a cholinesterase inhibitor) was assessed by light microscopy and autoradiography, by scanning and transmission electron microscopy, and by freeze-fracture. Goblet cells on the mucosal surface are unaffected by acetylcholine. In crypt goblet cells acetylcholine-eserine induces rapid fusion of apical mucous granule membranes with the luminal plasma membrane (detectable by 2 min), followed by sequential, tandem fission of the pentalaminar, fused areas of adjacent mucous granule membranes. These events first involve the most central apical mucous granules, are then propagated to include peripheral granules, and finally spread toward the most basal granules. By 60 min, most crypt cells are nearly depleted. The apical membrane, although greatly amplified by these events, remains intact, and intracellular mucous granules do not coalesce with each other. During rapid secretion membrane-limited tags of cytoplasm are observed attached to the cavitated apical cell surface. These long, thin extensions of redundant apical membrane are rapidly lost, apparently by being shed into the crypt lumen.

Acetylcholine↗
PubMed1979

A unicellular endocrine gland in cestodes.

Unicellular glands are reported from the scolex and anterior neck region of Hymenolepis diminuta and H. nana. Despite positive staining reactions with the presumptive neurosecretory stains, paraldehyde-fuchsin and chrome-alum-hematoxylin, ultrastructurally these glands exhibit many non-neural characteristics. Glandular cell processes are frequently found in close proximity to muscular tissue, particularly in the suckers, suggesting a regulatory role in muscle modulation as a possible function. Two types of putative, neurosecretory cells are reported from the cephalic ganglia and the lateral nerve cords. Neurosecretory regulation of the unicellular endocrine glands is postulated based on the lack of direct innervation of the glands and the frequent close proximity of axons containing putative, neurosecretory granules.

Animals↗
PubMedDate not supplied

Effects of protein malnutrition and endotoxin on the intestinal mucosal barrier to the translocation of indigenous flora in mice.

Since protein malnourished or endotoxemic patients are at increased risk of developing nosocomial infections with enteric organisms, we investigated the effects of these risk factors alone and in combination on the intestinal mucosal barrier to bacteria. Protein malnutrition resulted in severe ileal atrophy that was directly related to the length of time the mice were protein malnourished. Although protein malnutrition did not promote bacterial translocation from the gut to systemic organs, the protein-malnourished mice were more susceptible to endotoxin-induced bacterial translocation than normally nourished mice (p less than 0.01). Since the gross epithelial damage documented after endotoxin administration in normally nourished mice was diminished after protein malnutrition, there was no correlation between the gross appearance of the epithelial mucosal barrier and the extent of endotoxin-induced bacterial translocation. These results suggest that the synergistic effect of endotoxin plus protein malnutrition on bacterial translocation is not primarily related to failure of the gut mucosal barrier. Nonetheless, it appears that protein-malnourished mice are less able to clear translocating bacteria than normally nourished mice.

Animals↗
PubMedDate not supplied

Bulk prevents bacterial translocation induced by the oral administration of total parenteral nutrition solution.

The effects of a fat and glutamine-free orally administered total parenteral nutrition (TPN) solution on intestinal mucosal mass, morphology, barrier function, and cecal bacterial population levels were measured in CD-1 mice. Ileal mucosal protein content decreased by 63% (p less than 0.01) in the oral TPN-fed mice, although they gained weight on this diet. These TPN-fed mice also exhibited changes in mucosal structure and the normal ecology of their cecal microflora was disrupted leading to overgrowth with Gram-negative enteric bacilli. These changes in intestinal mucosal mass, morphology, and gut bacterial ecology were associated with an increased incidence of bacterial translocation (BT) (TPN group 70% BT vs control group 15% BT: p less than 0.01). The administration of cellulose fiber or kaolin (bulk-forming agents), but not of citrus-pectin (a fully-fermentable, nonresidue fiber) reduced the incidence of BT in the TPN-fed mice to control levels. The beneficial effects of these bulk-forming agents appeared to be due to their ability to prevent TPN-induced disruption of the intestinal microflora and alterations in intestinal morphology, even though they did not prevent ileal mucosal protein levels from decreasing. These results suggest that the administration of bulk forming agents will prevent the loss of intestinal barrier function against luminal bacteria that occurs in mice fed an oral TPN solution.

Administration, Oral↗