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Biomedical subjects

R A Snyder

Publications and source records attributed to R A Snyder.

16 recordsLinked to original sources
PubMed1986

Inhibition of angiotensin-converting enzyme by des-Leu10-angiotensin I: a potential mechanism of endogenous angiotensin-converting enzyme regulation.

Des-Leu10-angiotensin I is a nonapeptide generated from angiotensin I by the action of carboxypeptidase-like activities residing in the human platelet and mast cell. This nonapeptide was found to inhibit rabbit lung angiotensin-converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.1) with a Ki of 3.1 X 10(-7) M. The mechanism of inhibition was competitive. Inhibition of human serum angiotensin-converting enzyme by des-Leu10-angiotensin I was comparable in magnitude to inhibition by bradykinin and angiotensin III. These results suggest that limited proteolysis of angiotensin I by cells resident in vascular tissue may result in the generation of an endogenous inhibitor of angiotensin-converting enzyme. Such pathways may play roles in controlling levels of vasoactive peptides at local vascular sites.

Angiotensin I↗
PubMed1986

Pyoderma gangrenosum involving the head and neck.

In six patients with pyoderma gangrenosum, the head and neck region was a major site of ulcerative skin disease. In two patients, the disease was limited to this anatomic site. Corticosteroids were effective therapy in five cases. In one case, occurring in association with ulcerative colitis, total proctocolectomy was required to control ulcerative scalp disease. Detailed histologic examination of a primary lesion in one case with 0.5-micron sections demonstrated morphologic evidence of mast cell activation, suggesting that mast cells may contribute to the pathogenesis of the inflammatory process in pyoderma gangrenosum.

Adrenal Cortex Hormones↗
PubMed1985

A human platelet angiotensin I-processing system. Identification of components and inhibition of angiotensin-converting enzyme by product.

Mechanisms controlling the local generation of angiotensin II by vascular tissue are incompletely understood. Human platelets were examined for their ability to metabolize angiotensin I. Platelet-dependent angiotensin I metabolism was detected by a high performance liquid chromatography assay which allowed quantitation of angiotensin I substrate utilized and products formed. The major product of platelet-dependent angiotensin I metabolism was identified as des-Leu10-angiotensin I. The platelet des-Leu10-angiotensin I-generating activity had a pH optimum of 6.0-6.5 and was inhibited 100% by mersalyl acid (10(-4) M), 86% by leupeptin (10(-4) M), and 95% by iodoacetamide (10(-2) M). The activity had an approximate Mr = 70,000 as determined by Sephacryl S-200 gel filtration. Intact human platelets stimulated with calcium ionophore (1-10 microM) released 13.7-30.8% of the des-Leu10-angiotensin I-generating activity. Des-Leu10-angiotensin I, the major product of platelet angiotensin I metabolism, inhibited human serum and purified rabbit lung angiotensin-converting enzymes with an I50 of 3.7 X 10(-6) and 2.0 X 10(-6) M, respectively. These results suggest that the platelet may control local angiotensin II formation at vascular sites both by metabolism of the precursor peptide angiotensin I and by generation of an endogenous angiotensin-converting enzyme inhibitor, des-Leu10-angiotensin I. This platelet-dependent pathway may contribute to the control of local levels of vasoactive peptides, such as bradykinin and angiotensin II, so as to alter local tissue blood flow.

Angiotensin I↗
PubMed1985

Chemistry of a human monocyte-derived cell line (U937): identification of the angiotensin I-converting activity as leukocyte cathepsin G.

Angiotensin-converting enzyme, a dipeptidyl carboxypeptidase, catalyzes the conversion of angiotensin I to the vasoactive peptide angiotensin II. The finding of angiotensin-converting enzyme in dexamethasone-stimulated cultured monocytes and alveolar macrophages prompted the examination of a human monocyte-like cell line (U937) for angiotensin I-converting activity. Conversion of angiotensin I (5 X 10(-5) mol/L) to angiotensin II by U937 cell extracts (10(4) - 4 X 10(6) cells) was detected, and the pH optimum for the reaction was 7.0 to 8.0. The U937 cell angiotensin I-converting activity was purified to homogeneity by carboxymethylcellulose chromatography and trasylol affinity chromatography. The purified protein performed similarly to purified human neutrophil cathepsin G on sodium dodecyl sulfate-gradient polyacrylamide gel electrophoresis (SDS-gradient PAGE), elicited a reaction of complete identity with neutrophil cathepsin G when diffused against anti-cathepsin G antiserum, and had quantitatively similar angiotensin I-converting activity as neutrophil cathepsin G. Neutrophils and U937 cells had 143 and 52 times greater angiotensin I-converting capability than cultured monocytes or peripheral blood mononuclear cells, suggesting the relative importance of mobile cells containing cathepsin G in the local generation of angiotensin II. These data identify the angiotensin I-converting activity of the U937 cell as leukocyte cathepsin G and provide evidence that the U937 cell has neutrophil-like as well as monocyte-like characteristics.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1984

Alopecia mucinosa. Report of a case with diffuse alopecia and normal-appearing scalp skin.

A 69-year-old man had reversible generalized thinning of the scalp hair and normal-appearing scalp skin that proved to be secondary to follicular mucinosis. This case illustrates that when mild degrees of follicular degeneration and inflammation occur in this disorder, physical findings other than alopecia may be absent. In rare instances, follicular mucinosis can occur as a chronic diffuse noncicatricial alopecia.

Aged↗
PubMed1981

The influence of sow dietary lipids and choline on piglet survival, milk and carcass composition.

Twenty-one crossbred gilts and 75 crossbred sows were randomly assigned to six treatments for examination of the effect of lipid feeding and choline level on baby pig survival. Dietary variables were supplemental fat and choline in a 3 X 2 factorial arrangement. Fat treatments were no supplemental fat, 10% corn oil and 10% animal fat; choline treatments were 0 and 500 ppm supplemental choline from choline chloride. Baby pig survival and litter weight at 21 days were improved (P less than .05) by supplemental fat. Lipid treatments also improved (P less than .05) percentage survival among piglets in the weight ranges of 909 g or less, 1,136 to 1,362 g and 1,363 to 1,589 grams. Lipid feeding increased survival by 18.5% among the piglets weighing less than 909 grams. Piglets fasted for 60 hr had 47.7% less (P less than .05) total lipids and 90.5% less (P less than .05) glycogen than 12-hr-old, nonfasted piglets. The feeding of corn oil significantly affected percentages of carcass fatty acids. Percentages of palmitic, palmitoleic, oleic and linoleic acids decreased during fasting, indicating good utilization, while percentages of stearic and arachidonic acids increased, indicating poorer utilization during fasting. Milk from control sows, which had received a gestation diet containing 4% added poultry fat prior to treatment, was only slightly lower in energy and lipid content (nonsignificant) than milk from sows on the lipid treatment. Corn oil affected (P less than .05) the percentage of fatty acids in milk. Additional choline appeared to have no beneficial effect in any phase of the experiment. Choline did not increase lipid mobilization or piglet survival.

Animals↗