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Biomedical subjects

M McCabe

Publications and source records attributed to M McCabe.

At least 109 records · Page 6Linked to original sources
PubMed1984

Favorable balance of prostacyclin and thromboxane A2 improves early patency of human in situ vein grafts.

Graft thrombosis soon after reconstruction remains a major obstacle to the use of reversed vein grafts in infrapopliteal reconstruction. Our clinical experience with in situ vein grafts corroborates Leather's results by demonstrating an overall graft patency of 95% below the knee at 1 year and 94% in the infrapopliteal group. It has been postulated that this improved early patency rate of in situ vein grafts is the result of more optimal preservation of the endothelium of the vein graft. To investigate this hypothesis, human saphenous veins were handled by an in situ and a reversed technique. The intact vein segments were then tested for luminal production of prostacyclin and thromboxane A2 and fixed for scanning electron microscopic analysis of the surface morphology. This study demonstrated that endothelial cell prostacyclin release is enhanced in human in situ vein segments but not in reversed vein segments. In addition, luminal production of thromboxane A2 is significantly greater in the reversed than in the in situ vein segments. These findings are associated with marked endothelial structural damage in the reversed veins and minimal endothelial disruption in the in situ veins. Therefore the ratio of the antiaggregatory vasodilator prostacyclin to the proaggregatory vasoconstrictor thromboxane A2 is significantly more favorable for the in situ vein segment than for the reversed vein segment. The observed excellent early patency of the in situ vein grafts in our poor-risk patient population may in part be the result of this favorable balance of prostacyclin and thromboxane A2 and the more optimally preserved endothelial morphology.

Aged↗
PubMed1984

Luminal release of prostacyclin and thromboxane A2 by arteries distal to small-caliber prosthetic grafts.

Myointimal hyperplasia distal to prosthetic grafts may be due to a local imbalance of prostacyclin and thromboxane A2 that exaggerates platelet adherence. This study evaluated prostacyclin and thromboxane A2 production by arteries distal to prosthetic grafts. In 12 dogs, control segments of both iliac arteries were excised and a 5 cm segment of polytetrafluoroethylene was grafted end to end. One iliac artery was circumferentially dissected from the distal anastomosis to the inguinal ligament. The contralateral artery was not dissected. Of the 24 grafts, 19 remained patent and the arteries distal to these grafts were studied. After excision, each artery was analyzed for its ability to produce prostacyclin and thromboxane A2. Our data indicate that the luminal surface of a normal artery spontaneously produces both prostacyclin and thromboxane A2 and that the arterial wall distal to a prosthetic graft produces increased levels of these arachidonic acid metabolites. However, only those arteries not surgically dissected maintain a normal balance of prostacyclin and thromboxane A2. The dissected artery may thus be more susceptible to platelet interaction and myointimal hyperplasia.

Animals↗
PubMed1983

The effects of arsenic compounds on human and bovine lymphocyte mitogenesis in vitro.

The response of human and bovine peripheral blood lymphocytes to PHA stimulation was measured in the presence of low concentrations of sodium arsenite and sodium arsenate. In bovine lymphocytes, 41% augmentation of the response occurred at 10(-6) M arsenite with a return to the normal response at 2.5 X 10(-6) M. Complete inhibition of mitogenesis occurred at 6 X 10(-6) M. In the presence of sodium arsenate, similar results were obtained but at the higher concentrations of 2 X 10(-5) (for 57% augmentation), 5.2 X 10(-5), and 1.9 X 10(-4) M, respectively. The possible significance of these findings in view of the known relationship between chronic arsenicalism and human skin cancer is discussed. It is suggested that arsenic compounds may, by potentiating mitogenesis, increase the possibility of errors in DNA replication, some of which could be potentially carcinogenic. Additionally, interference with the immune response could enable potentially cancerous cells to escape immune surveillance.

Animals↗
PubMed1983

Neural control of acid-induced serotonin release from rabbit duodenum.

The neural mediation of acid-stimulated serotonin release was studied in isolated sheets of rabbit duodenal mucosa mounted in Ussing chambers. The serosal side of the mucosa was exposed to Ringer-HCO3 at pH 7.4, and the mucosal side was exposed to citrate-phosphate buffer at pH 3-6.8. Immunoreactive serotonin release occurred onto the luminal surface at pH 6 and below and onto the serosal surface at pH 5 and below, but was greater on the luminal side at each pH. The effect of cholinergic and adrenergic agonists and antagonists on mucosal serotonin release was measured at luminal pH 7.4, 5, and 4. Acid-stimulated luminal release was significantly inhibited by atropine, hexamethonium, and propranolol at pH 4 and 5 but not by phentolamine. Serotonin release was stimulated at pH 7.4 and 4 by carbachol and isoproterenol but not by norepinephrine or nicotine at pH 7.4. It is concluded that acid-induced and nonacid-induced mucosal serotonin release is partly neurally mediated by muscarinic cholinergic and beta-adrenergic mechanisms.

Animals↗
PubMed1978

Lipoid proteinosis; a clinical, pathological and genetic study.

The clinical, pathological, and genetic findings in two closely related families in which a number of cases of lipoid proteinosis occurred are described. The necropsy findings, particularly the neuropathological aspects, in a patient who died from a coincidental pancreatic carcinoma are detailed. The genetic aspects are reviewed.

Aged↗
PubMed1975

Diffucison of OXYGEN, Nitrogen and water in hyluronate solutions.

A method is reported for the measurement of the diffusion coefficients in water of some sparingly soluble gases. The results obtained for the diffusion coefficients of oxygen and nitrogen gas through water at 25 degrees C are 2.12. 10-5 and 2.61 . 10-5 cm-2 . s-1, respectively. A check on the accuracy of the teachnique using tritiated water as the diffusing substance gave a value of 2.15 . 10-5 cm-2 . s-1 which agrees within 3% with recent values from the literature. The method was applied to the measurement of oxygen, nitrogen, and tritiated water diffusion coefficients through agarose gels and through agarose gels containing hyluronate. The results indicate that the hyaluronate had only a small effect as a barrier to the diffusion of such low molecular weight substance.

Diffusion↗
PubMed1972

The diffusion coefficient of caffeine through agar gels containing a hyaluronic acid-protein complex. A model system for the study of the permeability of connective tissues.

A hyaluronic acid-protein complex was embedded into agar gel. This gel complex resembles in some respects the physiological situation in connective tissue, but still permits precise physicochemical measurements to be made. The diffusion coefficient of caffeine into and from such gels has been measured as a function of both agar and hyaluronate concentration. The value for the diffusion coefficient of caffeine was also measured by using a Gouy type diffusiometer. From both types of measurement the value for D (Fick) for caffeine when extrapolated to zero caffeine and agar concentrations agreed at (6.79+/-0.01)x10(-6)cm(2).s(-1) at 25 degrees C. Although agar concentration had only a small effect on caffeine diffusion, hyaluronic acid caused a large decrease in caffeine diffusion co-efficient. The presence of the hyaluronic acid-protein complex within the gel tended to oppose gel syneresis, a concentration of 1.7mg/ml abolishing the effect and higher concentrations reversing it. The possible physiological implications of these results are discussed.

Agar↗
PubMed1967

Mitochondria and pH.

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Hydrogen-Ion Concentration↗