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Biomedical subjects

M Brown

Publications and source records attributed to M Brown.

At least 865 records · Page 48Linked to original sources
PubMed1976

Isolation and characterization of proteoglycans from chick limb bud chondrocytes grown in vitro.

Chick limb bud mesenchyme cells from stage 23-24 embryos were isolated and grown in culture under conditions facilitating chondrogenic development. Dissociative extraction methods were used to isolate proteoglycans from Day 8 cultures, at which time the incorporation of [35S]sulfate into these macromolecules occurred at maximal rates. The monomer (D1) fraction contained 85 to 90% of the proteoglycans originally present in the matrix of the cultures. The composition of this fraction was approximately 7 to 8% protein, 7% keratan sulfate, and 85% chondroitin sulfate. The proportions of nonsulfated, 4-sulfated, and 6-sulfated disaccharides in chondroitinase digests were about 11%, 31%, and 58%, respectively. The D1 fraction exhibited a single, polydisperse component on Sepharose 2B chromatography and in the ultracentrifuge (so = 19 S). In associative density gradients about 35% of the proteoglycans were recovered in a gel at the top of the gradient. The remainder were recovered at the bottom of the gradient in the aggregate (A1) fraction. The A1 fraction exhibited two components, aggregate (about 70% of the total) and monomer, upon Sepharose 2B chromatography and in the ultracentrifuge (so = 120 S for aggregate; 18 S for monomer). The aggregate preparation contained only one of the two link proteins (molecular weight of about 45,000) which occur in proteoglycan preparations from many hyaline cartilages.

Amino Acids↗
PubMed1976

Surface architecture of the plant cell: biogenesis of the cell wall, with special emphasis on the role of the plasma membrane in cellulose biosynthesis.

Cell wall structure and biogenesis in the unicellular green alga, Oocystis apiculata, is described. The wall consists of an outer amorphous primary layer and an inner secondary layer of highly organized cellulosic microfibrils. The primary wall is deposited immediately after cytokinesis. Golgi-derived products contribute to this layer. Cortical microtubules underlie the plasma membrane immediately before and during primary wall formation. They function in maintaining the elliptical cell shape. Following primary wall synthesis, Golgi-derived materials accumulate on the cell surface to form the periplasmic layer. This layer functions in the deposition of coating and cross-linking substances which associate with cellulosic microfibrils of the incipient secondary wall. Secondary wall microfibrils are assembled in association with the plasma membrane. Freeze-etch preparations of untreated, living cells reveal linear terminal complexes in association with growing cellulosic microfibrils. These complexes are embedded in the EF fracture face of the plasma membrane. The newly synthesized microfibril lies in a groove of the outer leaflet of the plasma membrane. The groove is decorated on the EF fracture face by perpendicular structures termed "ridges". The ridges interlink with definitive rows of particles associated withe PF fracture face of the innter leaflet of the plasma membrane. These particles are termed "granule bands", and they function in the orientation of the newly synthesized microfibrils. Microfibril development in relation to a coordinated multienzyme complex is discussed. The process of cell wall biogenesis in Oocystis is compared to that in higher plants.

Cell Membrane↗
PubMed1976

Diagnosis of Barrett's esophagus by pertechnetate radionuclide.

In Barrett's esophagus the normal stratified squamous epithelium of esophagus is replaced by columnar epithelium and other charcteristics of gastric mucosa. Barrett's esophagus has an increased tendency to bleed and is more prone to undergo malignant change. There are many procedures used to diagnose this entity, but only by serial and multiple esophageal mucosal biopsies can the diagnosis be confirmed. Harper et al (2) demonstrated an early and intense uptake of 99m Tc pertechnetate by the stomach in animals. Since the Barrett's esophagus is lined by gastric mucosa, pertechnetate scintigraphy was used as a screening procedure. The criteria for a postive scan was an area of increased uptake of technetium extending above the normal dense uptake of stomach configuration. Pertechnetate scintigraphy was performed in 4 patients with Barrett's esophagus and 6 controls with only one false negative result. Thus pertechnetate scintigraphy is a rapid, safe, and atraumatic screening procedure.

Betazole↗
PubMed1976

Genome localization of simian virus 40 RNA species.

The topographical locations on the simian virus 40 (SV40) genome of the templates for virus-specific RNA species present late in the lytic infection were determined by RNA-DNA hybridization experiments with the Hind restriction enzyme fragments. Two classes of late virus-specific cytoplasmic mRNA's can be separated on the basis of either sedimentation properties in neutral sucrose or electrophoretic mobility in polyacrylamide gels. In the 16S class, two species of RNA were identified by hybridization experiments. One of these species was complementary to sequences of the early template on the minus (E) strand (0.175 to 0.655 map units), and the other more abundant species was complementary to sequences present in the late template on the plus (L) strand (0.655 to 0.175 map units). In addition two species were detected in the 16S class of late cytoplasmic virus-specific mRNA. One of these species was the major late RNA detected and consisted of a polyadenylated transcript complementary to the plus (L) DNA strands of Hind fragments K, F, J, and G (0.945 to 0.175 map units). This species appears to specify the major capsid protein (VP1). A less abundant nonpolyadenylated 16S RNA species complementary to the plus (L) strands of Hind fragments C, D, and E (0.655 to 0.945 map units) may result from post-transcriptional processing or nonspecific degradation of the 19S viral RNA complementary to the plus (L) strand.

Base Sequence↗
PubMed1976

Correlation between plasma growth hormone and insulin and blood glucose concentrations in premature infants.

Plasma growth hormone, insulin and blood glucose levels were measured longitudinally during the first 60 days of life in 21 premature infants (8 males and 13 females) born between the 6th and 8th month of gestation. When these variables were related to age it was found that insulin and glucose, which are lower than in the prepubertal children and adults, rise simultaneously. Whereas growth hormone, which is higher than in older prepubertal children, decreases during the first 2 weeks of life. The decrease in growth hormone continues during the first 2 months of life, in contrast to the increases in insulin and glucose which do not persist in as long a period.

Blood Glucose↗
PubMed1976

Biological activity of somatostatin and somatostatin analogs on inhibtion of arginine-induced insulin and glucagon release in the rat.

Somatostatin and dihydrosomatostatin (H2somatostatin) are equipotent in inhibiting insulin and glucagon release induced by arginine in the rat. The ID50 of H2somatostatin on insulin and glucagon secretion induced by arginine are 14 +/- 6 and 6 +/- 10 mug/100 g BW respectively, similar to the ID50 of H2somatostatin (18 +/- 10 mug/100 g BW) on inhibition of insulin release induced by glucose. Thyrotropin releasing factor, luteinizing hormone releasing factor, alpha-MSH, and the N-terminus decapeptide of the beta-chain of porcine hemoglobin did not alter the secretion of insulin and glucagon induced by arginine. With the exception of [Ala2[-somatostatin and [Ala5]-somatostatin, alanine substituted analogs of somatostatin were less potent than somatostatin. [D-Trp8]-somatostatin is 6-8 times as potent as somatostatin in inhibiting insulin and glucagon release induced by arginine. The relative potencies of these analogs to inhibit the secretion of the pancreatic hormones are in good agreement with our previously reported values based on the inhibition of GH secretion in vitro.

Animals↗
PubMed1976

Effects of neurotensin and substance P on plasma insulin, glucagon and glucose levels.

Neurotensin and substance P given iv 5, 10, 20 and 30 minutes prior to blood collection produce hypoinsulinemia, hyperglucagonemia and hyperglycemia in the rat. Glucagon similarly produces hyperglycemia in rats but results in hyperinsulinemia. On a molar basis neurotensin is ca. 10 and 30 times more active in inducing hyperglycemia than substance P and glucagon, respectively. The enhanced glucogenic effects of neurotensin and substance P over glucagon may well result from their inhibition of insulin release. Neurotensin and substance P may be important in glucose homeostasis.

Animals↗