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Biomedical subjects

M Chen

Publications and source records attributed to M Chen.

At least 955 records · Page 53Linked to original sources
PubMed1976

Hin D restriction mapping of upaired regions in simian virus 40 superhelical DNA I: considerations regarding structure-function relationships.

Superhelical simian virus 40 (SV40) DNA I was reacted with N-cyclohexyl-N'-beta-(4-methylmorpholinium)ethylcarbodiimide (CMC), and the location of CMC sites was mapped using the Hin D restriction endonuclease. The use of 14C-labeled CMC allows a quantitative analysis of the binding to the respective Hin D restriction endonuclease fragments. The percentage of reactivity was 6.54% for fragment A, 3.87% for fragment B, and 2.74% for fragment G. No CMC radioactivity was detected in other fragments. This reactivity is in agreement with the evaluation of binding by buoyant density measurements. The above fragments also contain the sites susceptible to S1 endonuclease action. This adds further support to the view that superhelical DNA can contain regions of localized interrupted secondary structure which may be capable of forming intrastrand hairpin structures if sequence relationships are favorable. The possible structure-function relationships for this model are discussed with the emphasis on transcription.

Binding Sites↗
PubMed1976

Density of perivascular nerves on some cerebral and extracerebral blood vessels.

The perivascular adrenergic nerves were counted as they crossed a grid-line superimposed on rat cerebral or femoral arteries and arterioles, and on the portal vein and its tributaries. The nerves were visualized with the formaldehyde-vapor, fluorescence technique. No support was received for the hypothesis that cerebral vessels are better innervated than extracerebral vessels. In fact, the density of nerves was significantly greater on the femoral and portal vessels than on the cerebral.

Adrenergic Fibers↗
PubMed1976

The effect of rate and dose of glucose infusion on the acute insulin response in man.

Two types of studies have been done to determine the importance of the rate of plasma glucose concentration change to the magnitude of the acute insulin response following an intravenous glucose injection in normal men. When an identical amount of glucose (20 g) was given at varying infusion rates (1.67 g/min to 66.7 g/min), the magnitude of the acute insulin response was found to be proportional to the rate. When various doses (5 g to 20 g) were given at the identical rate (1.67 g/min) the acute insulin response did not change. When 5 g of glucose was given in 0.3 and 3 minutes, a sub-maximal acute insulin response resulted which was still rate-dependent (delta peak IRI=35.5 +/- 5 at 5 g/0.3 minutes, 21.8 +/- 3 at 5 g/3 minutes). We have concluded that the human islet acts as a sensor for both the concentration of plasma glucose and the rate of change in plasma glucose. Islet perception of both these phenomena are critical factors in the determination of the magnitude of the acute insulin response.

Adult↗
PubMed1976

Brain serotonin concentration and crude synaptosomal uptake in mice with the Chediak-Higashi syndrome.

The Chediak-Higashi syndrome is characterized by a serotonin platelet defect and neuronal dysfunction. Whole blood serotonin concentration, serotonin brain concentration, and synaptosomal uptake of serotonin were determined in mice with the syndrome. While brain serotonin uptake in the affected mice was not significantly different from that in nonaffected mice, whole blood serotonin concentration was markedly reduced. These data suggest that in human neuropathies with platelet serotonin defect, a parallel neuronal serotonin disorder may not be assumed.

Animals↗
PubMed1975

Renal glucose utilization in genetically diabetic microangiopathy.

Glucose uptake into kidney tissue is not influenced by the development of glomerulosclerosis in KK mice. Glucosyltransferase activity remains at a normal level even at an age having a highest incidence of serious development of glomerulosclerosis. The observation suggests that biosynthesis of basement membrane reflected by its glucosyltransferase activity does not accelerate in genetically transmitted microangiopathy.

Animals↗
PubMed1975

Thyroxine binding by hepatitis B surface antigen.

Thyroxine and triiodothyronine binding sites are present on the 20-nm spherical particles associated with hepatitis B surface antigen (HBsAg). Thyroxine-treated HBsAg has a buoyant density of 1.26 g/cm-3 in CsCl and appears under the electron microscope as a hexagonal particle with a center-to-vertex distance of 10 nm. These results provoke questions concerning the origin of thyroid hormone binding sites on HBsAg and a possible relationship between thyroid status and HBsAg antigenemia in humans.

Binding Sites, Antibody↗
PubMed1975

Effects of nutritional copper deficiency on the biomechanical properties of bone and arterial elastin metabolism in the chick.

Increased bone fragility was observed in chickens fed diets containing less than 1 ppm copper. Using a device that was designed to measure torsion during fracture, it could be demonstrated that bone from copper-deficient chicks fractured with less deformation and torque than bone from control chicks. The collagen of bone from copper-deficient chicks appeared to contain fewer cross-links than normal bone. The introduction of artificial cross-links into collagen from copper-deficient chick bone by formaldehyde and NaBH4 treatments improved bone strength and strain (deformation) so that it was comparable with normal bone. Copper deficiency blocks the formation of cross-links in collagens and elastin from various tissues. It is felt that the bone fragility related to nutritional copper deficiency is the result of decreased bone collagen cross linking. Arterial elastin metabolism was also investigated. By radioactively labeling arterial soluble elastin (tropoelastin) in vivo by an intraperitoneal injection of [G-3H]valine, it could be demonstrated that copper deficiency appeared to reduce its rate of metabolic turnover. Soluble elastin or tropoelastin is assumed to be the precursor of mature or insoluble elastin. The observations presented here are consistent with the view that by retarding the steps associated with elastin cross-link formation, the incorporation of soluble elastin into mature elastin may be retarded as well.

Animal Nutritional Physiological Phenomena↗
PubMed1975

Hydrophobic chromatography of hepatitis B surface antigen on 1,9-diaminononane or 1,10-diaminodecane linked to agarose.

A series of omega-aminoalkyl-agarose differing in the number of carbon atoms in the alkyl chains was prepared and used for chromatography of hepatitis B surface antigen (HBSAg). HBSAg was separated from the major part of serum proteins by adsorption to columns of 1,9-diaminononane or 1,10-diaminodecane linked to agarose beads (Sepharose 4B or 2B) followed by elution with 4 M-NaSCN.

Alkanes↗
PubMed1975

Effect of cerebral intraventricular insulin on pancreatic insulin secretion in the dog.

The effect of cerebral intraventricular insulin on pancreatic insulin secretion was investigated. An extracorporeal pancreatic blood circuit was established after laparotomy to monitor blood flow and insulin concentration directly from the superior pancreaticoduodenal vein. Phentolamine was infused throughout (0.2 mg./min. intravenously) to block alpha-adrenergic effects of any catecholamine secretion induced by surgical stress. Glucose (1.5 mg./kg./min. intravenously) was infused to maintain a constant baseline stimulation of insulin secretion. Six dogs received insulin and six control dogs received saline through a spinal needle stereotaxically placed into the left lateral cerebral ventricle. After central injection of insulin (0.2 U./kg.) there was a significant increase of pancreatic output as early as five minutes. It is concluded that the pancreatic beta-cells are under the influence of insulin-sensitive cells of the CNS.

Animals↗
PubMed1975

Central factors in the control of insulin and glucagon secretion.

A complete system for neural regulation of insulin and glucagon secretion from the ventral hypothalamus to the autonomic cholinergic and adrenergic nerves of the endocrine pancreas is described. Both physiologic and pathophysiologic states of altered metabolism can be partly explained by activation of this neural system. Direct hypothalamic humoral control of the endocrine pancreas has been evaluated by studies of the hypothalamic hormone somatostatin, or somatotrophin release inhibiting factor (SRIF). Somatostatin has been shown to inhibit pancreatic glucagon and insulin secretion when infused into the pancreatic artery of intact dogs in vivo in the absence of a change of systemic glucose concentration. Although less inhibition is observed when the same amount of hormone is infused intraportally, the potency of somatostatin when given directly into the liver suggests extrapancreatic effects as well as direct pancreatic effects on insulin and glucagon secretion.

Animals↗
PubMed1974

Inhibition of the metabolism of streptococci and salmonella by specific antisera.

Streptococcal and salmonella antisera inhibited carbohydrate metabolism for groups A, B, C, and D streptococci and group E salmonella, as measured by the formation of [(14)C]dioxide from [(14)C]glucose metabolism. For salmonella, the inhibition was type specific since group E salmonella were inhibited only by salmonella E antisera and not by anti-salmonella A or C(1). For streptococci, quantitative differences were demonstrated, but major cross-reactivity was observed. At high concentrations, the antisera were bactericidal; at more dilute concentrations, for both salmonella and streptococci, carbohydrate metabolism was suppressed, but subculture on chocolate agar showed abundant growth. Cross-reacting antibodies could be absorbed by incubation with either antigen, e.g., streptococcal antisera versus heat-killed salmonella. The results suggest that the radiometric technique can be more sensitive than either capillary flocculation or visual detection of bacterial growth for detecting the inhibition of streptococci and salmonella by specific antibodies. The use of specific antisera may prove useful for bacterial species identification in an automated system for detection of bacterial growth.

Absorption↗