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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe the SEM appearance of the rat endosteal bone lining cell ( BLC ) population, and the sequence of morphological changes of these cells as they self-incorporate into unmineralized bone matrix (osteoid), establish intercellular connections, and construct lacunae. The osteoblast/nascent osteocyte series was progressively unsheathed by gentle digestion of the osteoid with 0.25% collagenase. The osteoblasts which leave the polygonally packed BLC compartment rapidly develop numerous complexly branched processes that contact the processes elaborated by previous generations of maturing and mature osteocytes. As osteoblasts mature and approach the mineralization front, they appear to lose processes. The mature cells begin to form osteocyte lacunae by depositing an asymmetric perimeter of woven collagen fibrils, such that as the cells roof-over, the lacunae appear as pocketlike constructions. The collagen fibrils on the perilacunar matrix are oriented in a tangential or circular pattern, while those in the more distal matrix are arranged in a parallel pattern. With the completion of a lacuna, its wall appears to mineralize quickly, for lacunae could be recognized only when they are forming.
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PMID:From bone lining cell to osteocyte--an SEM study. 632 38

The extent of the odontoblast cell process has been the subject of controversy for many years. Using SEM we have examined the extent and morphology of the process on dentine surfaces of human teeth which were partially demineralized and collagenase digested. Third molars were extracted and split; the dentine surface was demineralized, digested by bacterial collagenase, fixed with glutaraldehyde, postfixed in osmium tetroxide, and prepared for SEM investigation. The SEM study revealed the presence of many processlike structures which extended from the odontoblast cell bodies up to the dentinoenamel junction (DEJ). These processes demonstrated lateral and terminal branching and some of them terminated in distended spheres. We have also applied an immunofluorescence technique at the light microscope level to these exposed dentinal surfaces to localize the intracellular microtubules. For this, a second series of third molars was processed in the same manner as for the SEM up to the fixation stage. Teeth were then fixed in periodate-lysine-paraformaldehyde, postfixed in -20 degrees C acetone, and then incubated with affinity-purified rabbit antitubulin antibodies, followed by fluorescein-conjugated goat antirabbit IgGs. Intratubular immunofluorescence labelling for tubulin was evident from the odontoblast cell bodies up to the DEJ. The presence of the tubulin-containing structures extending to the DEJ supports the hypothesis that the structures observed with the SEM are odontoblast processes and that the odontoblast processes do extend to the DEJ.
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PMID:A combined scanning electron microscopy and immunofluorescence study demonstrating that the odontoblast process extends to the dentinoenamel junction in human teeth. 639 20

Triiodothyronine (T3) production from thyroxine (T4) was studied in isolated rat hepatocytes. With an initial T4 concentration of 0.56 microM, hepatocyte T3 production was 0.029 +/- 0.003 (SEM) pmoles/min/mg protein. T3 production was greater in hepatocytes than in homogenates from the same liver prepared either before or after liver perfusion with collagenase. Most T3 produced remained within the cells under the conditions employed. Hepatocyte T3 production was dependent on cell number, medium bovine serum albumin concentration and temperature. It was stimulated by dithiothreitol, and inhibited by propylthiouracil, 3,3',5'-triiodothyronine and dinitrophenol; glutathione and ouabain had no effect. Alterations in medium glucose concentration and exposure to insulin or glucagon at several glucose concentrations in vitro did not alter T3 production. These results indicate that in hepatic tissue T3 production is enhanced when intact cellular organization is present and that insulin and glucagon do not acutely influence cell production of T3 in vitro.
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PMID:Triiodothyronine production by isolated rat hepatocytes: characterization and lack of glucoregulatory hormone effects. 639 64

Morphologic features of the cell surface were studied in isolated cardiac myocytes obtained from 12 and 48 week old Spontaneously Hypertensive Rats (SHR) and normotensive Wistar-Kyoto (WKY) control rats. Hearts obtained from ether-anesthetized animals were perfused with Ca++-free Hanks' solution containing EGTA and 0.1% collagenase. The hearts were minced and the suspended cells fixed in 2% phosphate buffered glutaraldehyde. Cells mounted on Nuclepore membrane filters were dehydrated in alcohol and critical point dried for SEM. Quantitative evaluation of myocyte length, width and volume was done with a sonic digitizer on H and E stained cells by light microscopy. At both ages studied there was a significant increase in heart weight to body weight ratio, systolic blood pressure and cell size in SHR compared to WKY controls. In the older animals there appeared to be increased numbers of cell junction areas and deep grooves in the cell surface which appeared more pronounced in SHR than in WKY. The cell surface of the myocytes from 48 week old animals had deep capillary grooves surrounded by protruding longitudinal bundles of myofibrils. These changes would result in increased surface area of the larger cells and diminish the effect of increased cell size on diffusion distance from capillary to tissue. These changes in cell morphology were interpreted as providing a protective effect against development of functional impairment in the hypertrophied hearts.
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PMID:Surface morphology of isolated cardiac myocytes from hypertrophied hearts of aging spontaneously hypertensive rats. 644 76

In this paper the ultrastructural features of the epithelial-mesenchymal interface in mandibular processes of embryonic chicks have been examined using scanning electron microscopy. Mandibular epithelium is required for the mesenchyme to differentiate as osteoblasts and to deposit the membrane bones of the mandible. The surface morphology of the epithelium changes from the lateral to the medial face of the mandible from rounded cells, each with a central cilium to flattened cells with numerous microvilli. Treatment with trypsin and pancreatin was used to digest the basal lamina so as to separate epithelium from mesenchyme. This exposed a thick, fibrillar basement membrane (reticular lamina), which was thicker underlying the caudal epithelium than under the cephalad epithelium. Addition of collagenase to the trypsin/pancreatin solution degraded some of the basement lamella, especially that underlying epithelium on the caudal portion of each mandibular process. Selective degradation of basement lamella is postulated as one means of regulating inductive epithelial-mesenchymal interactions. EDTA was used to isolate basal laminae on mandibular mesenchyme. SEM was used to confirm the integrity of the basal lamina, its structure, and its association with overlying epithelial cells and underlying basement lamella.
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PMID:An SEM analysis of the epithelial--mesenchymal interface in the mandible of the embryonic chick. 673 22

The neural retina of avian embryos was spread on a membrane filter and cut in any desired orientation. Strips cut across the retina of 4- to 7-day chick or 3- to 6-day quail embryos were explanted onto collagen gels. Vigorous neurite outgrowth was seen for about 3 days, by which time many neurites were 3 mm long. Horseradish peroxidase (HRP) labeling showed that the cells producing the neurites were large and formed a layer near the inner limiting membrane, indicating that the neurites in vitro were axons of retinal ganglion cells. The size of the neurite population and the regions from which neurites emerged varied with the donor age, while most neurites sprouted from the side of the explant formerly closest to the optic fissure. This pattern closely resembled that of axon growth in the normal retina, as revealed by SEM, silver staining, and HRP labeling. Mitotic inhibitors (Ara-C and FUdR) did not alter the neurite outgrowth. Pretreatment of retinae with trypsin or collagenase did not disorganize axons at the time of explanation, but tended to equalize neurite emergence on each side of the retinal strips. We suggest that microenvironmental factors, especially the enzyme-labile inner limiting membrane, are important for axon guidance in the retina.
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PMID:Oriented axon outgrowth from avian embryonic retinae in culture. 682 32

The current study was conducted to determine if physical activity and/or weight control could influence the age-related decrease in beta cell insulin response noted in earlier studies. As such, virgin, male Sprague-Dawley rats were maintained in our facility for 1 yr on three differential experimental programs; in the first group, control rats lived under standard laboratory conditions; the second group of rats ran several miles a day in exercise wheels, and the third group was given a calorie-restricted diet designed to keep the rats weight-matched with the exercising rats. The results showed that the 12-mo-old sedentary control rats weighed an average of 800g. From the time these rats were 4 mo old, they were significantly hyperinsulinemic, with mean (+/- SEM) serum insulin levels of 55 +/- 6 microU/ml. Morphological studies on the pancreas of these rats at the end of the year revealed enlarged, multilobulated, fibrotic islets. After collagenase digestion, the most normal-appearing islets from the 12-mo-old controls were used for insulin secretion studies, these islets showed significantly reduced glucose-induced insulin release (0.83 microU insulin/min per volume islet) compared with islets from young rats (1.80 microU insulin/min per volume islet). In contrast, 12-mo-old exercised or calorie-restricted rats weighed approximately 500 g and did not show the changes in serum insulin levels or pancreas pathology exhibited by the sedentary control animals. However, islets from the calorie-restricted group functioned in vitro no better than islets from he sedentary control group. Islets from the exercised rats were somewhat improved in this regard. In summary, we believe exercise and weight control diminishes the animals' need for insulin-resulting in youthful-appearing islets after a year's time. However, these regimes do not appear able to correct the beta cell decline in function previously described.
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PMID:Structure and function changes in the endocrine pancreas of aging rats with reference to the modulating effects of exercise and caloric restriction. 701 47

The present study details a new method for the exposure and viewing of individual microvessels located within the small intestine of rats. This procedure will selectively and consistently remove the outer muscle layers and underlying submucosa of the intestinal wall and thereby expose a variety of arterioles in their normal location within the tissue, with their normal relationship to each other undisturbed. The small intestine of the rat was initially fixed by vascular perfusion with 2.5% glutaraldehyde in 0.1 M cacodylate/HCL buffer, reinfused with heparinized whole blood, removed from the animal, and secured to a dissecting petri dish for further fixation. Subsequently, the external muscularis was dissected from the sample which exposed the submucosa. In order to remove the connective tissue elements from this layer and uncover the submucosal vasculature, the samples were first transferred to a solution of 30% potassium hydroxide for 2-5 minutes and then to a final digesting solution containing collagenase. Thereafter, the samples were routinely processed for light microscopy and for scanning (SEM) or transmission (TEM) electron microscopy. Examination of the samples revealed excellent preservation of the three-dimensional organization of the arteriolar wall with minimal membrane damage. This new technique now makes it possible to visualize the shape and position of individual smooth muscle cells along arterioles of differing size and branching order.
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PMID:A new morphological procedure for viewing microvessels: a scanning electron microscopic study of the vasculature of small intestine. 713 4

Equine oxyntic mucosal cells were obtained by sequential exposure to pronase and collagenase. Acid production by parietal cells was assessed by uptake of [14C]aminopyrine (AP), a weak base that accumulates in intracellular acidic spaces. Incubation for various times revealed a maximal AP uptake at 10 minutes for histamine and carbachol. Similar secretagogue responses were observed for parietal cells from the mucosal cell preparation or after enrichment by elutriation. Histamine and isobutyl-methylxanthine (IBMX) stimulated AP uptake with a dose-dependent response and maximal effective concentration of 100 microM. Carbachol, 1 to 100 microM, and pentagastrin (PG), 1 to 1,000 nM, were ineffective stimulants of AP uptake. The AP uptake values for 100 microM IBMX, 1 microM carbachol, or 100 nM PG were 77 +/- 6%, 50 +/- 3.2%, and 40 +/- 4.5%, respectively, of that observed with maximal stimulation by 100 microM histamine (mean +/- SEM, n = 4 to 14). Uptake of AP by nonstimulated control cells was 36 +/- 3.6% of maximal histamine stimulation. The AP accumulations during control conditions and after stimulation with 100 microM histamine and IBMX, 1 microM carbachol, or 100 nM PG were 1.18 +/- 0.39, 2.81 +/- 0.85, 1.93 +/- 0.48, 1.44 +/- 0.36, and 1.23 +/- 0.33 pmol of AP/10(5) parietal cells, respectively. Individual histamine dose-response curves were shifted to the right by increasing ranitidine and cimetidine concentrations (0.1 to 50 microM). These results indicate that isolated equine parietal cells are maximally stimulated by histamine and minimally stimulated by carbachol and PG.
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PMID:Secretagogue-induced [14C]aminopyrine uptake in isolated equine parietal cells. 751 58

Cirrhotic livers are considered to regenerate less actively than normal livers after hepatic resection. Little is known about the mechanisms responsible for impaired capacity of regeneration in cirrhotic liver. In the present study, we investigated the effect of phorbol ester on hepatocyte proliferation in healthy and cirrhotic hepatocytes, using one of the phorbol esters, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), which has a direct effect on activation of protein kinase C (PKC). Cirrhosis was established by the administration of carbon tetrachloride and phenobarbital to rats. Healthy and cirrhotic hepatocytes were isolated from Wistar male rats by a two-step collagenase perfusion technique. DNA synthesis was estimated by [3H]thymidine incorporation into DNA and by autoradiographic nuclear labeling index. [3H]Thymidine incorporation was measured 24 hr after hepatocytes were stimulated by appropriate reagents. TPA (50 nM) stimulated [3H]thymidine incorporation in healthy hepatocytes (control vs TPA, 991 +/- 247 vs 2569 +/- 766 mean +/- SEM cpm/microgram DNA; P < 0.05), whereas TPA (50 nM) failed to stimulate in cirrhotic hepatocytes (control vs TPA, 1144 +/- 184 vs 1304 +/- 187 cpm/microgram DNA; NS). Staurosporine, a specific PKC inhibitor, suppressed [3H]thymidine incorporation in TPA-stimulated healthy hepatocytes (806 +/- 263 cpm/microgram DNA; P < 0.05); however, it had no effect on cirrhotic hepatocytes (1295 +/- 180 cpm/microgram DNA; NS). An autoradiographic nuclear labeling index exhibited the same results with [3H]thymidine incorporation. We conclude that TPA stimulates hepatocyte proliferation in healthy rat hepatocytes but has no effect on cirrhotic hepatocytes.
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PMID:Impaired phorbol ester-induced hepatocyte proliferation in cirrhosis. 772 25


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