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Biomedical subjects

D Malamud

Publications and source records attributed to D Malamud.

At least 73 records · Page 4Linked to original sources
PubMed1981

Bacterial aggregating activity in human saliva: comparisons of bacterial species and strains.

Using a quantitative assay to measure saliva-mediated bacterial aggregating activity, we have surveyed 20 streptococcal strains with saliva samples obtained from a large population study. Individual saliva samples demonstrated characteristic levels of aggregating activity for Streptococcus sanguis M5. In general, high activity for this strain was associated with high activity for other strains of S. sanguis. Streptococcus mitis, and Streptococcus salivarius. The population distribution of aggregating activity for Streptococcus mutans, however, was different.

Humans↗
PubMed1979

A comparision of normal submaxillary gland proteins with proteins obtained from a transplantable murine salivary gland carcinoma (myoepithelioma).

A new transplantable murine salivary gland carcinoma (myoepithelioma) was further characterized by comparing total protein patterns with normal submaxillary gland proteins. Analysis by isoelectric focussing or by labelling studies with radioactive leucine showed considerable differences between tumour and normal proteins. In contrast, analysis of staining patterns after electrophoresis in sodium dodecyl sulphate containing gels revealed a striking similarity between normal proteins, tumour proteins and proteins obtained from metastatic growths. It thus appears that tumour proteins closely resemble the normal proteins from the tissue of origin with respect to molecular size as determined by electrophoretic mobility, while significant differences occur in charge and labelling kinetics.

Animals↗
PubMed1979

Bacterial aggregating activity in human saliva: simultaneous determination of free and bound cells.

Two new assays for saliva-mediated aggregation of oral bacteria have been developed, based on the use of [3H]thymidine-labeled cells. One assay separates free cells from aggregated cells by centrifugation through sucrose, whereas the other utilizes membrane filters (8 micrometers, Nuclepore) to effect the separation. Comparison of these assays with the turbidity method reveals that they are faster (X20 to 40) and require 10 times less saliva and bacteria. The aggregation of Streptococcus sanguis M5, as determined with these assays, is complete in 5 min and is dose dependent on added cells and saliva. The reaction exhibits a temperature optimum of 42 degrees C with no reaction at 0 degrees C. If the pH is reduced to below 5, saliva-dependent aggregation is inhibited. The salivary factor(s) are heat labile, losing 100% of their activity after 100 degrees C, 10 min or 70 degrees C, 30 min.

Bacterial Physiological Phenomena↗
PubMed1978

Cyclic AMP mediated increased amino acid transport: effect of isoproterenol administration.

A single injection of isoproterenol (IPR) stimulates cell proliferation in rodent salivary glands after a lag period of about 24 hrs. Among the many events occurring prior to stimulated DNA synthesis, there is an early increase in cAMP levels and elevated transport of amino acids into the parotid gland. Amino acid transport is also elevated in liver and pancreas, tissues not induced to proliferate by IPR. IPR-stimulated alpha-aminoisobutyric acid (AIB) transport in parotid, pancreas and liver is augmented by prior injection of theophylline and is mimicked by dibutyryl cAMP. In all three tissues, changes in cAMP levels and subsequent increases in AIB transport appear to be closely related events. Since only the parotid gland is stimulated to grow after IPR injection, amino acid transport and growth would not appear to be directly related.

Amino Acids↗
PubMed1978

Compensatory hyperplasia with increasing loss of renal mass.

When a rat with two kidneys is cross-circulated with an anephric rat, compensatory renal hypertrophy occurs as indicated by an increased ratio of RNA to DNA within 6 hours and an increased ratio of kidney weight to body weight within 12 hours. Removal of three kidneys between the rats further increases residual renal mass and RNA/DNA after 24 and 48 hours of cross-circulation as compared with results of removing two kidneys. Trinephrectomy triples the mitotic index and doubles the proliferative index. Increasing the magnitude of renal loss causes appreciable hyperplasia as well as increasing the magnitude of compensatory renal hypertrophy.

Animals↗
PubMed1977

Onset of cell proliferation in the shortened gut. Colonic hyperplasia after ileal resection.

Cytokinetics in colonic mucosa were studied after ileal resection in young female rats. The RNA content of the transverse colon was increased 32% after 7 days; after 14 days the increase was present throughout the colon. The DNA content of the ascending colon increased 29% after 10 days. Specific activity of DNA labeled with [3H-methyl]thymidine was elevated 29% in the ascending colon and elevated 49% in the descending colon on the 7th postoperative day. Colonic cell proliferation is stimulated within 1 week of ileal resection.

Animals↗
PubMed1977

Onset of cell proliferation in the shortened gut. Rapid hyperplasia after jejunal resection.

Early manifestations of cell proliferation were studied in the large and small bowel of young female rats after resection of the proximal one-third of the small bowel. On the 2nd day after resection, the absolute amounts of RNA and DNA increased in gut distal to the resection. As compared with values from sham-resected gut, nucleic acid levels in much of the distal small bowel and colon increased. Increased specific activity in DNA after injection of [3H]thymidine was present in the small bowel on the 2nd day. Changes were marked and persistent in midgut for 10 days, tending to be less intense and of shorter duration in segments progressively more distal. Compensatory cell proliferation in midgut occurs within 2 days of jejunectomy.

Animals↗
PubMed1976

Cyclic AMP metabolism in mouse parotid glands. Properties of adenylate cyclase, protein kinase and phosphodiesterase.

Catecholamines induce unique growth and secretory responses in salivary glands. An analysis of three enzyme activities involved in cyclic AMP metabolism was carried out to identify the specificity of these responses for salivary glands. Although parotid adenylate cyclase has an unusually high specific activity, its kinetic properties and responses to NaF, guanine nucleotides, and isoproterenol are similar to other tissues not stimulated to grow after isoproterenol stimulation. Solubilized adenylate cyclase was separated from other membrane proteins by isoelectric focusing on polyacrylamide gels. There was a single broad peak of activity witha pI of 5.9. Parotid protein kinase has a subcellular distribution and substrate preference similar to hepatic protein kinase. Activation by cyclic AMP is also similar to that reported for other tissues, with a Ka of 1.2 - 10(-7) M. Parotid cyclic AMP and cyclic GMP phosphodiesterases are a heterogeneous group of enzymes with relatively low specific activity as compared with mouse pancreas, liver and brain. Isoelectric focusing of supernatant phosphodiesterases revealed at least sixpeaks of enzyme activity in the pI range of 4-6. Previous reports of a large increase in parotid cyclic AMP levels after in vivo administration of catecholamines and specific growth and secretion could be the result of a relatively high specific activity adenylate cyclase associated with low specific activity cyclic AMP phosphodiesterases.

Adenosine Triphosphate↗
PubMed1976

Onset of cell proliferation in the shortened gut: growth after subtotal colectomy.

Cell proliferation and remodeling of the small intestine were studied after subtotal colectomy in the rat. After an initial fall in nucleic acid contents, there was a trend to increasing amounts of RNA throughout the intestine on the fourteenth postoperative day; by the thirtieth day RNA and DNA contents were increased about 20 percent. DNA synthesis increased after 5 days. Although initially villi became shorter and crypts shallower, higher villi, deeper crypts, and an increased rate of cell migration were present after 14 days. Subtotal colectomy stimulates nucleic acid synthesis and remodeling of the small bowel within 2 weeks. Changes are more marked in ileum.

Animals↗
PubMed1975

Differential labeling with orotic acid and uridine in compensatroy renal hypertrophy.

Using [5-3H]orotic acid and [5-3H]uridine as precursors, we compared the efficiency of labeling and the localization of labeled RNA during compensatory hypertrophy of the mouse kidney. [5-3H]orotic acid in tubules labeled RNA 15 times more intensely that [5-3H]uridine, presumably because of greater incorporation of orotic acid into tubular cells. Of the orotic acid label, 97% was in tubular cells, mostly in the proximal tubules. Only about 80% of the uridine label was in the tubules; the ratio in proximal tubules compared with that in distal tubules was 2:1. No changes in distribution within the nephron were produced during compensatory hypertrophy. [5-3H]uridine should be used as the precursor of generalized labeling is desired, but [5-3H5orotic acid is the better precursor of RNA for many studies of compensatory hypertrophy since it is more efficient and concentrates in the segments of greatest biologic activity.

Animals↗
PubMed1975

Rapid reversal of compensatory renal hypertrophy after withdrawal of the stimulus.

The permanence of the early phases of compensatory renal hypertrophy was tested by interrupting vascular parabiosis between an anephric rat and a normal rat after 48 hours. At the time of interruption, the weights and the ratio of ribonucleic acid (RNA) content to deoxyribonucleic acid (DNA) content of the kidneys were the same as those of the remaining kidney in a single rat subjected to unilateral nephrectomy, previously reported. Within 12 hours after parabiosis was stopped, renal mass and nucleic acid concentrations returned to normal. Compensatory hypertrophy could be produced again by unilateral nephrectomy. Regression of the early phase of compensatory hypertrophy appears to be faster than muscular atrophy produced by disuse or denervation. Compensatory hypertrophy can be activated at least twice.

Animals↗
PubMed1974

Transformation by simian virus 40 of spleen cells from a hyperimmune rabbit: demonstration of production of specific antibody to the immunizing antigen.

Extracts of spleen cells obtained from a rabbit hyperimmunized with Type III pneumococcal vaccine and transformed with simian virus 40, were subjected to agarose gel electrophoresis in the presence of an [(125)I]S3 polysaccharide-protein conjugate. Binding of radioactivity in the gamma globulin region was observed. Extracts and media obtained from labeled cell cultures contained a protein that bound to an S3, but not to an S8 or inactivated S3 immunoadsorbent. After elution, the bound protein showed a single band on isoelectric focusing which corresponded in isoelectric point to one of the serum anti-S3 antibodies of the donor rabbit. These observations strongly suggest that a normal committed lymphoid cell may be brought into continuous culture by virus transformation and yet retain its ability to synthesize specific antibody.

Animals↗