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Biomedical subjects

D Sherman

Publications and source records attributed to D Sherman.

At least 145 records · Page 8Linked to original sources
PubMed1980

Phylogeny of enteric serotonergic neurons.

Serotonergic neurons have previously been identified in the enteric nervous systems of humans, subhuman primates, rodents, and rabbits. The distribution of enteric serotonergic neurons in lower vertebrates was examined in order to determine if these neurons are restricted to mammals and, if they are found more generally amongst vertebrates, when they first appear in vertebrate phylogeny. Since mammalian enteric serotonergic neurons take up 3H-serotonin by a highly specific mechanism, the radioautographic demonstration of axonal uptake of 3H-serotonin was used as the primary tool in looking for these neurons. As controls, conditions known to interfere with 3H-serotonin uptake by mammalian enteric neurons were also examined. These controls included incubation with 10 microM fluoxetine, a specific antagonist, incubation in Na+-free medium, and incubation in the presence of a 100-fold excess of nonradioactive serotonin. Radio-autographic labeling had to be absent or greatly reduced under all three control conditions for labeling by 3H-serotonin to be considered specific. Labeled enteric axons were found in cyclostomes (hagfish), teleosts (goldfish), and amphibia (bull-frog) but not in tunicates (sea squirt; sea vase) or echinoderms (sea cucumber). In addition, the serotonin concentration was measured in the intestine of two vertebrates, hagfish and goldfish, that do not have serotonin-containing enterochromaffin cells. Serotonin was found in both; in hagfish, the amine concentration was highest in preparations of muscularis externa containing the myenteric plexus. It is concluded that enteric serotonergic neurons arose early in vertebrate evolution, possibly in an ancestral chordate resembling amphioxus, although probably not in more primitive prevertebrates, and that they are a general feature of the vertebrate bowel.

Animals↗
PubMed1980

Quantitative ultrastructural analysis of the human parietal cell during acid inhibition and increase of gastric potential difference by glucagon.

Glucagon inhibits gastric acid secretion and increases the negativity of gastric mucosal potential difference (PD) in man. To test the hypothesis that the increased negativity of PD after glucagon in man could be due to decreased parietal cell canalicular membrane area, a quantitative ultrastructural analysis was carried out. Four healthy volunteers with normal gastric mucosa were submitted to biopsy before and 20 minutes after intravenous injection of 2 mg glucagon (G). This time corresponded with the maximal change in PD and a decrease in gastric acid secretion. Canalicular and tubulovesicular membrane area of 80 parietal cells (40 cells before glucagon and 40 cells after glucagon) were quantified by the Loud morphometric method. After glucagon, the oxyntic cell canalicular membrane area was reduced by one-fourth (P less than 0.05), while tubulovesicular membrane area showed an increase (P less than 0.05) at the same time. The decrease in the area of parietal cell canalicular membrane caused by glucagon may in part be responsible for increased negativity of the gastric PD caused by this hormone.

Adult↗
PubMed1980

Effects and interactions of 24R,25(OH)2D3 and 1,25(OH)2D3 on bone.

The effects of various combinations of therapy with 1 alpha,25-dihydroxycholecalciferol (1,25(OH)2D3) and 24R,25-dihydroxycholecalciferol (24R,25(OH)2D3) on structural and dynamic parameters of bone were evaluated in 40 chicks raised on a vitamin D-deficient diet from time of hatching and supplemented with the dihydroxylated metabolites. The results showed that: 1) the maintenance of volumetric density of bone is dependent on the presence of 1,25(OH)2D3, 2) lack of 1,25(OH)2D3 is associated with an increase in the number of osteocytes per unit volume of bone, most probably due to decreased amounts of bone formed by each osteoblast before becoming an osteocyte, 3) adequate quantities of either 24R,25(OH)2D3 or 1,25(OH)2D3 are needed to prevent accumulation of osteoid or the production of endosteal fibrosis, and 4) maintenance of normal tetracycline label width requires both hydroxylated compounds with one of them in sufficient amounts. The data of this study demonstrate that the integrity of certain parameters of bone structure could be maintained only with 1,25(OH)2D3, others with either dihydroxylated metabolites, and still others with a combination of both. These data underscore the biological activity of 24R,25(OH)2D3 by demonstrating its effectiveness on bone.

Animals↗
PubMed1980

High-risk neighborhoods and high-risk families: the human ecology of child maltreatment.

Based on multiple regression analysis to identify the socioeconomic, demographic, and attitudinal correlates of neighborhood differences in the rate of child abuse and neglect, a pair of neighborhoods matched for socioeconomic level was selected, one high risk, the other low risk. Interviews with expert informants ranging from elementary school principals to mailmen were used to develop neighborhood profiles. Samples of families were drawn from each neighborhood and interviews conducted to identify stresses and supports, with special emphasis on sources of help, social networks, evaluation of the neighborhood, and use of formal family support systems. The results lend support to the concept of neighborhood "risk." Families in the high-risk neighborhood, though socioeconomically similar to families in the low-risk neighborhood, report less positive evaluation of the neighborhood as a context for child and family development. Furthermore, they reveal a general pattern of "social impoverishment" in comparison with families in the low-risk neighborhood.

Adolescent↗
PubMed1980

Ventilatory and occlusion-pressure responses to hypercapnia in divers and non-divers.

Ventilatory (VE/PCO2) and occlusion-pressure (P0.1/PCO2) responses to progressive hypercapnia (rebreathing method of Read (1)) were estimated in 20 normal subjects and 22 scuba divers. Indexes of CO2 sensitivity (slopes of response curves) and absolute response values under strong CO2 drive (PCO2 = 60 mmHg) were significantly lower in the diver group. Individual CO2 sensitivity did not correlate with either diving experience or current diving activity. Positively skewed (log-normal) frequency distribution curves of individual CO2 sensitivities were drawn for the divers and for a larger sample of normal controls (using data from other studies). All divers' values fell in the lower range of non-diver control values and about one-third were below the normal range (mean +/- 2 SD) for CO2 sensitivity. We concluded that our divers did not represent a distinct population different from the normal one but rather a group of normal healthy subjects with either an inherent or acquired relatively low CO2 response. The rebreathing technique is strongly advocated as a tool for investigating divers' CO2 sensitivity and its implications in underwater environments.

Adult↗
PubMed1978

Nasality and precision of articulation.

Two reading passages, one with nasal consonants and one without, were tape-recorded for 72 subjects: 34 selected as having precise articulation and 38 selected as having imprecise articulation. These speech samples were evaluated for degree of precision and also for degree of nasality by the psychological scaling method of equal-appearing intervals employing a 7-point scale. Analysis indicated a relationship between degree of precision and degree of unpleasant nasality, that is, a tendency for decreases in precision to be accompanied by increased nasality and a tendency for males to be more imprecise in articulation and more nasal than females.

Female↗
PubMed1975

The ultrastructure of dyserythropoiesis in aplastic anaemia.

Electron microscopy of erythropoiesis in aplastic anaemia has demonstrated some unique features of dyserythropoiesis at the ultrastructural level, which contribute to understanding of the morphological features which are seen in the light microscope. The findings provide further evidence for the presence of qualitative defects in erythropoiesis in aplastic conditions. The alterations seen included bi- and multinucleated cells, intercellular bridges containing microtubules, internuclear chromatin bridges, irregular nuclear shapes, juxta-nuclear and peripheral cisternal structures, ringed sideroblasts, a diversity of intranuclear inclusions, nuclear clefts in both eu- and heterochromatin, and a variety of anomalies of the nuclear membrane. The significance of the occurrence of these anomalies in aplastic anaemia is considered and the role of the nuclear membrane and of endoplasmic reticulum in the pathogenesis of aplastic anaemia is discussed.

Adult↗
PubMed1973

Action of yeast killer factor: a resistant mutant with sensitive spheroplasts.

Yeast killer factor proteins bind to cells of both sensitive and killer-producing strains, although the latter are immune to killer action. Spheroplasts prepared from sensitive cells bind less than 1% of the killer bound to whole cells, but remain fully sensitive to killer. This finding and those obtained from binding studies of partially purified, radioactive killer protein suggest that most of the toxins remain bound to the yeast cell wall and do not function further in the killing process. A killer-resistant mutant R(18) was isolated from a sensitive strain. Whole cells of the mutant were unable to bind killer and were fully resistant. In contrast, spheroplasts of R(18) were fully sensitive to killer. These data suggest that the sites exposed to killer in spheroplasts are distinct from those on the cell wall. These wall sites appear to be necessary for killer action in whole cells.

Binding Sites↗