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Biomedical subjects

W J Krause

Publications and source records attributed to W J Krause.

At least 91 records · Page 5Linked to original sources
PubMed1986

Scanning electron microscopic observations on developing opossum embryos: days 9 through 12.

During the first 9 d of development in Didelphis, the 3 germ layers are established and the initial formation of their derivatives occurs. During this time the embryos float within uterine secretions, each separated from the uterine mucosa by a shell membrane. Organogenesis begins during the last 3 1/2 d of the 12 1/2 d gestation period and corresponds to the time when the yolk sac placenta is associated with the uterine epithelium. During this period development proceeds at an explosive rate, culminating in a fetus-like creature capable of surviving in the pouch. Early in d 10, the forelimbs are present as limb buds. Late in the 10th d the embryo descends into and becomes enveloped by its own yolk sac. Mandibular and hyoid arches, and prominent digital ridges on the forefeet are characteristic external features. By d 11, the hindlimb is represented by a bud the eyes and external auditory meatus are established and an open mouth with protruding tongue is characteristic of this stage. Digits are present on the forefeet but lack claws. During the 12th d the oral shield develops, curved claws are prominent features of the forefeet and digital ridges are seen on the hindfeet. Prior to birth the periderm covers the eyes, ear pinnae and sides of the mouth.

Animals↗
PubMed1985

The allantois of the North American opossum (Didelphis virginiana) with preliminary observations on the yolk sac endoderm and trophectoderm.

During the middle of prenatal day 10, the opossum allantois forms as a ventral outgrowth of the hindgut. By day 11 it appears as a large, fluid filled sac and by the middle of day 12 (just prior to birth) it reaches its maximal development. The simple squamous epithelium lining the allantois consists of only one cell type that often contains numerous filaments in the apical cytoplasm. At the luminal surface, the apices of the cells are united by junctional complexes and desmosomes are present between adjacent cells. The luminal surface is irregular, whereas laterally and basally the cell membranes show few if any infoldings. Mitotic figures and presumptive degenerating cells occasionally occur in the allantoic epithelium which rests on a delicate basal lamina. The allantois is covered by a simple squamous mesothelium that lacks a distinct basal lamina. Between the two epithelial sheets lie mesenchymal cells, collagen fibers, and blood vessels. No specializations of cell membranes were noted in either of the epithelial layers. The yolk sac endoderm consists of a single layer of squamous cells whose cytoplasm contains scattered profiles of rough endoplasmic reticulum and mitochondria. Extensive lateral and basal infoldings of the plasmalemma were not observed in these endodermal cells. The morphology of the trophectodermal (trophoblastic) cells indicates a cell type that is active in the transport of materials. Since the endodermal cells that line the allantois lack morphological features that would suggest the presence of mechanisms for transport or exchange, and because they remain relatively unchanged throughout pregnancy, it is thought that the allantois functions primarily in the storage of urinary wastes during prenatal life.(ABSTRACT TRUNCATED AT 250 WORDS)

Allantois↗
PubMed1985

Prostaglandin protection of the gastric mucosa against alcohol injury--a dynamic time-related process. Role of the mucosal proliferative zone.

The aim of the present study was first to resolve controversies regarding the extent of prostaglandin protection ("cytoprotection") of the gastric mucosa against injury produced by 100% ethanol and second to determine time sequence and histologic, ultrastructural, and functional features of this protection. Fasted rats received intragastrically (A) 0.9% NaCl alone as a control, (B) 5 micrograms/kg of 16,16-dimethyl prostaglandin E2 dissolved in 0.9% NaCl, and (C) 100 micrograms/kg of 16,16-dimethyl prostaglandin E2 dissolved in 0.9% NaCl. Thirty minutes later, 2 ml of 100% ethanol was instilled. The gastric mucosa was assessed macroscopically, by quantitative histology, and by scanning and transmission electron microscopy for [3H]thymidine uptake, mitotic activity, ion fluxes, and gastric potential difference determined at several time intervals (between 10 min and 16 h) after ethanol administration. Between 10 min and 16 h after ethanol administration macroscopic necrosis involved 27% +/- 3% to 41% +/- 4% of the mucosal area in controls (group A), but necrosis was prevented in groups receiving 16,16-dimethyl prostaglandin E2 (groups B and C). In the control group, histology and electron microscopy showed extensive disruption of the surface epithelium and deep necrosis (greater than 0.2 mm) involving greater than 46% +/- 4% of the mucosa between 15 min and 16 h after ethanol administration. Deep necrotic lesions were completely prevented by either dose of 16,16-dimethyl prostaglandin E2 (groups B and C). The mucosal proliferative zone was severely damaged in controls (68% +/- 5%) within the first hour after ethanol administration, whereas 16,16-dimethyl prostaglandin E2 protected the zone from damage (less than 5% +/- 1%). Neither dose of 16,16-dimethyl prostaglandin E2 prevented the occurrence of initial (at 15-30 min) morphologic and functional disruption of the surface epithelium after ethanol administration. However, initial disruption of the surface epithelium by 16,16-dimethyl prostaglandin E2 (groups B and C) was followed by migration of cells from the mucosal proliferative zone; the result was prompt restoration of the surface epithelium and resumption of its barrier and transport functions.

16,16-Dimethylprostaglandin E2↗
PubMed1985

Protective effect of sucralfate against alcohol-induced gastric mucosal injury in the rat. Macroscopic, histologic, ultrastructural, and functional time sequence analysis.

Histologic or ultrastructural evidence of the ability of sucralfate to protect the gastric mucosa against ethanol injury is lacking. Therefore we analyzed morphologic and functional changes in the mucosa of 120 rats receiving, intragastrically, 2 ml of either sucralfate 500 mg/kg body wt or a control solution and 1 h later 2 ml of 100% ethanol. At 15 min, 1, 4, 6, and 24 h after ethanol instillation, mucosal changes were assessed by macroscopic examination, quantitative histology, scanning electron microscopy, recordings of gastric potential difference, and measurements of volume, pH, and electrolytes in the gastric contents. Between 15 min and 24 h after ethanol instillation, macroscopic necrotic lesions in controls involved greater than 33% of mucosal area and in the sucralfate-treated group less than 4% (p less than 0.001 for each period). In controls, ethanol instillation produced surface epithelial cell disruption and deep (greater than 0.2 mm) mucosal necrosis involving greater than 55% +/- 3% of the mucosal length. In sucralfate-pretreated animals, disruption of the surface epithelium was present at 15 min, 1 h, and 4 h after ethanol instillation, but deep necrotic lesions were virtually absent (0%-2%; p less than 0.001 vs. controls) during the entire study period. The surface epithelium was mostly reestablished by 6 h after ethanol instillation in the sucralfate group but not in the controls. We concluded that sucralfate protects the gastric mucosa against ethanol-induced injury by preventing deep mucosal necrosis and as a consequence the mucosal proliferative zone cells rapidly restitute mucosal integrity.

Aluminum↗
PubMed1985

Morphological observations on the mesodermal cells in the 8 day opossum embryo.

Cells of the mesodermal layer of the 8 day opossum were examined by scanning and transmission electron microscopy after removal of the ectoderm. The mesodermal layer is formed by a multilayered network of large somewhat flattened, stellate-shaped cells, whose broad surfaces usually lie parallel to the external surface of the embryo. The mesodermal cells show numerous cytoplasmic processes which often appear as long delicate threads that may branch. The processes may course for considerable distances and establish contact with adjacent mesodermal cells. Contact points between processes, processes and cells, and between adjacent cell bodies showed junctional complexes. Most of the junctional complexes appeared morphologically similar to the nexus (communicating) type. Occasional desmosome-like junctions also were observed. Extracellular fibers were not observed.

Animals↗
PubMed1985

Placentation in the opossum, Didelphis virginiana.

For the first 9 days of gestation, opossum embryos float in uterine secretions, separated from maternal tissues by a shell membrane. Each embryo is part of the wall of its hollow embryonic sphere. By the 10th day of development, the embryo becomes enveloped by both the amnion and yolk-sac. The yolk-sac consists of vascular and non-vascular portions and, together with the surrounding trophectoderm (trophoblast), forms the yolk-sac placenta of the opossum: the allantois does not contribute to formation of the placenta. The vascular portion of the yolk-sac placenta establishes an intimate relationship with the uterine epithelium soon after loss of the shell membrane. The yolk-sac placenta is non-invasive. Cells of the trophoblast exhibit numerous microvilli, an apical endocytic complex and the lateral and basal cell membrane are elaborately folded. These features suggest a cell that is active in the transport of materials. Junctional complexes between cells of the trophoblast and uterine epithelium were not observed. The uterine epithelium changes from ciliated pseudostratified columnar with few infoldings of lateral and basal cell membranes, to non-ciliated simple columnar in which these membranes show elaborate infoldings. The cells show numerous inclusions and mitochondria are polarized to the basal half of the cell. These features suggest a cell that also is active in the transport of materials.

Animals↗
PubMed1985

Quantitative distribution of enteroendocrine cells in the gastrointestinal tract of the adult opossum, Didelphis virginiana.

The distribution and quantification of enteroendocrine cells exhibiting immunoreactivities to nine peptides and one amine were examined in the gastrointestinal mucosa of the adult opossum using specific immunocytochemical methods. In the stomach, 90% of the enteroendocrine cells are confined to the pyloric glands and this region contained 73% of the gastrin-containing cells, 60% of the somatostatin-containing cells and 9% of cells reactive for 5-HT. Enteroendocrine cells showing immunoreactivities to glucagon, pancreatic polypeptide, somatostatin and 5-HT were observed scattered within the oxyntic glands. Only somatostatin and 5-HT positive cells were found in the cardiac glands. Immunoreactivities to CCK, glucagon, gastrin, BPP, somatostatin, secretin, motilin, neurotensin, GIP and 5-HT were observed in the epithelium of the small intestine. Although considerable variation exists in the distribution of individual enteroendocrine cell types along the intestinal tract, nearly equal numbers of enteroendocrine cells were observed in each segment. The percentage of enteroendocrine cells increases distally in the colon. Of the three enteroendocrine cell types present, somatostatin- and 5-HT-immunoreactive cells are evenly distributed, whereas neurotensin-immunoreactive cells increase in numbers distally, resulting in an increase in total number.

Animals↗
PubMed1984

Scanning electron microscopic observations on the 9-day opossum (Didelphis virginiana) embryo.

All three germ layers are present in the opossum embryo by the 9th prenatal day. The embryo proper is part of, and continuous with, the remainder of the chorionic wall. The wall of the yolk sac-chorion away from the embryo consists only of an outer covering of ectoderm and an inner layer of endoderm. Ectodermal cells covering the neural folds have dome-shaped apices and often show large, bleb-like expansions. Microvilli are short and few in number. The apical surfaces of ectodermal cells that overlie the parietal mesoderm are relatively smooth and show scattered, short microvilli that tend to be concentrated at cell junctions. The apices of ectodermal cells that cover the extraembryonic region are more rounded, and the cells balloon from the surface. Each cell shows abundant elongate microvilli and occasional cytoplasmic blebs. Endodermal cells that line the chorion and form the third (innermost) layer of the embryo are similar in their surface morphology.

Animals↗
PubMed1984

Scanning electron microscopic observations on the opossum yolk sac chorion immediately prior to uterine attachment.

The 10 day opossum embryo is enclosed by a yolk sac chorion in which distinct vascular and non-vascular regions are established before attachment to the uterine epithelium. The embryo is closely associated with the vascular region which becomes adherent to the uterine lining. Cells of the external layer bear abundant, closely packed, long microvilli, which may serve to absorb nutrients from the uterine secretions. Cells of the inner surface show only scattered microvilli and microplicae on their apical surfaces.

Animals↗
PubMed1983

Ultrastructural observations on the shell membrane of the North American opossum (Didelphis virginiana).

Each developing opossum embryo is surrounded by a shell membrane which completely separates embryonic and maternal tissues. During the eighth and ninth prenatal days, the embryos together with their limiting shell membranes float freely within the uterine lumen, surrounded only by the secretions of the uterus. The shell membrane is transparent, nonelastic, tough, and capable of extreme deformation. It consists of a mat of interwoven fibers which vary in external diameter, are electron dense, and show no apparent substructure. The morphology and arrangement of component fibers are similar throughout the width of the shell membrane.

Animals↗
PubMed1983

An immunohistochemical survey of endocrine cells and nerves in the proximal small intestine of the platypus, Ornithorhynchus anatinus.

The relative frequencies of endocrine cells and peptidergic nerve elements in the proximal small intestine of the adult platypus were studied by immunohistochemistry. Six kinds of endocrine cells - serotonin (5-HT)-, somatostatin-, gastrin-, motilin-, cholecystokinin (CCK)- and bovine pancreatic polypeptide (BPP)-immunoreactive cells - were identified in this study. These endocrine cells were found most frequently in the intestinal glands, in moderate numbers in the tubular ducts and were infrequent in the surface folds. 5-HT-immunoreactive cells were most numerous, somatostatin-, gastrin-, motilin- and BPP-immunoreactive cells were moderately numerous, whereas CCK-immunoreactive cells were rare. Five kinds of neuropeptides: substance P, vasoactive intestinal polypeptide (VIP), gastrin releasing peptide (GRP), somatostatin and leu-enkephalin, were detected in the intramural nerve elements. Substance P-, VIP- and GRP-immunoreactive nerve fibers were found most frequently in the lamina propria mucosae of the surface folds. The relationships between the possible functions of the peptides and amine detected in this study as well as the characteristic structure of the digestive tract of the adult platypus are discussed.

Animals↗
PubMed1983

Morphological observations on the parathyroid of the opossum (Didelphis virginiana).

Parathyroid III of the opossum, Didelphis virginiana, lies on the medial surface of the internal carotid artery at its origin just above the bifurcation of the common carotid artery. It is limited externally by a capsule and is subdivided into lobule-like structures by connective tissue septae. The parenchyma consists solely of chief (principal) cells, arranged in irregular cords and clumps supported by a delicate vascular connective tissue. Ultrastructurally, the chief cells are polyhedral in shape and have centrally placed nuclei. The cytoplasm contains small, randomly distributed, rod-shaped mitochondria, scattered profiles of granular endoplasmic reticulum, free ribosomes, and small perinuclear Golgi complexes. Secretory granules are small, electron-dense, and appear to be limited by a delicate membrane. The granules are related both to the Golgi complex and the basal cell membrane. Capillaries that lie immediately adjacent to the chief cells show an extensively fenestrated endothelium.

Animals↗
PubMed1983

Postnatal development of the thyroid gland in the opossum (Didelphis virginiana).

Thyroid lobes of the newborn opossum consist of small epithelial cords or plates, the constituent cells of which are joined by tight junctions and surround a minute lumen that courses throughout the length of each cord. Occasional cells, not directly associated with the lumina of the cords, show central nuclei and clusters of small electron-dense granules: these may represent parafollicular cells at an early state of development. By the end of the 1st week after birth, parafollicular cells are well established and appear as groups between the epithelial cords and as scattered individual cells within the cords. Growth of the thyroid occurs as the cords continue to elongate and branch. 11 days after birth, thyroid development in the opossum corresponds morphologically to that of eutherians just prior to birth. Primary follicles are present near the periphery of the thyroid lobes, having formed from evaginations of the epithelial cords. There is evidence of synthetic activity by the epithelial cells and colloid is present. Secondary follicles form as a result of evaginations from the epithelium of the primary follicles. At the end of the 2nd postnatal week, epithelial cords are no longer a prominent feature of the opossum thyroid, and the organ is now characterized by numerous, small colloid-filled follicles. As development progresses, the follicles increase in size and number and, by 35 days after birth, the thyroid shows adult features.

Animals↗
PubMed1983

Arachidonic acid protection of gastric mucosa against alcohol injury: sequential analysis of morphologic and functional changes.

We have shown previously that arachidonic acid (AA) prevents gastric mucosal injury by ethanol (ETOH). The present study was designed to determine the sequence of morphological and functional changes in the gastric mucosa during ETOH-induced injury and AA-promoted protection. Fasted male rats received intragastrically 1 ml of vehicle (PL) or 1 ml of 120 mM AA followed 1 hr later by 2 ml of absolute ETOH. Mucosal changes were assessed at 10, 15, and 30 min and 1, 2, 3, 6, and 15 hr after ETOH: (1) macroscopically, histologically, and by scanning EM; and (2) by determinations of (a) mitotic activity and 3H-thymidine incorporation in vivo, (b) gastric volume, pH, and electrolytes, and (c) gastric PD. Macroscopic necrotic changes were present in PL-but not AA-pretreated animals throughout the 15 hr after ETOH. Histological examination and scanning EM showed desquamation of the surface epithelium at 10 min to 2 hr and deep necrotic lesions throughout the 15 hr after ETOH in PL-pretreated animals. In AA-pretreated rats, deep necrotic lesions did not occur, but desquamation of the surface epithelium was seen during the initial 30 min after ETOH. A continuous layer of the surface epithelium was restored within 3 hr after ETOH in AA group, with resumption of the transport and barrier functions. The main feature of AA protection of gastric mucosa against ETOH injury is preservation of the mucosal proliferative zone.

Animals↗
PubMed1983

Comparison of fiberoptic endoscope and Quinton tube human gastric biopsies.

Morphological examination of human gastric mucosa is being increasingly reported with the widespread use of upper gastrointestinal endoscopy. To our knowledge no studies have been reported comparing gastric mucosal tissue obtained with pinch biopsies through the endoscope with those taken by the Quinton hydraulic biopsy instrument for light and electron microscopic examination. We report such a study. Gastric biopsies were obtained from healthy volunteers. Gastric biopsies taken with the Quinton hydraulic tube have a number of distinct advantages over those taken with the standard pinch biopsy forceps. These relate primarily to the size, shape and depth of the specimens obtained. Quinton samples are large (2-3 mm in diameter), flat, discshaped specimens which are relatively free of contaminating debris on the mucosal surface. Because of their disc shape, Quinton biopsies are easily orientated for light microscopy. 55 percent of all Quinton biopsies contained muscularis mucosae. In contrast, samples taken by the standard forceps method are small (0.5--1 mm in diameter), have a tendency to roll-up into a ball, and show considerable surface debris making scanning electron microscopy of the mucosa difficult. Consistent orientation of the surface epithelium for light microscopy is more difficult with the pinch biopsies because of the small size and irregular shape of the samples. Crushing and tearing artifacts at the periphery of biopsy specimens are common. Light microscopic sections of forceps' biopsies provide a mean +/- SE of only 227 +/- 17 consecutive surface cells for examination compared to 730 +/- 24 (p less than 0.001) for Quinton biopsies. Only 7% of all pinch biopsies included muscularis mucosae.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗