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Biomedical subjects

G M Mitchell

Publications and source records attributed to G M Mitchell.

36 records · Page 2Linked to original sources
PubMed1988

Long microvenous allografts in rabbit femoral arteries and veins.

In this study the patency of long microvenous allografts in rabbits with and without immunosuppressive drug therapy was investigated. Eighty-two microvenous autografts (controls) and allografts were transplanted into rabbit femoral vessels. Veno-venous autograft controls were 100% patent at 3 weeks. Rejection of non-immunosuppressed veno-venous allografts consistently produced occlusion between 15-20 days. Thrombus filled the lumen, and a leucocyte invasion destroyed the graft wall. In contrast vein allografts into arteries were 100% patent at 3 weeks; this was reduced to 50% at 4 weeks. Low (5 mg/kg/day) and high (20 mg/kg/day) doses of hydrocortisone over 21 days improved the 3 week patency in veno-venous allografts to 28.5% and 57.0% respectively. Cyclosporin A (15 mg/kg/day) over 8 or 22 days significantly increased the patency rate of veno-venous allografts to 100%. Only cyclosporin A treated rabbits maintained allografts of normal vein morphology to 3 weeks.

Animals↗
PubMed1988

The long-term fate of microvenous autografts.

Changes in length, external diameter, wall thickness, and morphology were examined in 60 intraarterial vein grafts and 30 intravenous vein grafts inserted in rabbit femoral vessels. Half of each graft type was explored at 6 or 12 months, giving four experimental groups. The overall patency for intraarterial grafts at exploration was 98 percent and for intravenous grafts 100 percent. In comparison with the initial graft length resected, all four groups were significantly shorter at the completion of anastomosis, and three of the four groups also were significantly shorter at exploration. The overall loss in length of grafts varied between 26 and 30 percent of original length. External diameter was significantly increased (from between 133 and 201 percent) in all four groups at exploration compared to the normal femoral vein. Intravenous grafts maintained normal vein morphology to 12 months. Intraarterial grafts were modified by the ingrowth of smooth-muscle cells from the recipient artery, thereby creating a neointima that significantly thickened their walls at both 6 and 12 months.

Animals↗
PubMed1986

The nature and extent of histopathologic injury in human avulsed arteries and veins and in experimentally avulsed monkey arteries.

To determine the end point of histopathologic damage in avulsed arteries, the forearm arteries of five monkeys being sacrificed were avulsed longitudinally and samples of proximal and distal arteries prepared for light microscopy and transmission and scanning electron microscopy. A severe and consistent circumferential skip lesion was found on the luminal surface involving the intima and media. In 30 percent of vessels, histopathologic damage extended more than 3.0 cm from the rupture point. Similar circumferential tears occurred on the luminal surface of resected human avulsed arteries collected at the time of replantation surgery. No consistent lesions were noted in resected veins from human avulsed amputations. It is possible that in the human artery (as in the monkey) circumferential lesions frequently extend many centimeters from the rupture point and therefore beyond resection distances. Lesions present in the vessel after resection and microsurgical repair might be the site of thrombosis and subsequent occlusion.

Animals↗
PubMed1985

A study of the extent and pathology of experimental avulsion injury in rabbit arteries and veins.

A comparison was made between operating microscope observations and histopathological examination of the ruptured ends of experimentally avulsed rabbit femoral arteries and veins. Under the operating microscope no damage was evident in arteries or veins more than 0.8 cm (on average) from the rupture site, the common lesions being tears, holes, bruising, sleeving and dilatations. In light microscope and electron microscope studies arterial and venous lesions were often noted up to 4 cm from the rupture site both proximally and distally. Severe circumferential skip lesions involving the tunica intima and media in the arteries were noted, and commonly deep clefts also extended through all three tunicae at arterial bifurcations. In avulsed veins complete tears through all tunicae or partial loss of intima and media were observed. The extensive nature of these lesions is the most likely reason for the lower success rate of avulsed digits in replantation surgery.

Animals↗
PubMed1983

Epizootic bovine abortion: histogenesis of the fetal lesions.

The development of the fetal lesions of epizootic bovine abortion (EBA) was studied in a series of experiments and field cases of the disease. Thirty-six experimentally infected fetuses were recovered at periods of 29 to 126 days after their dams had been infected by allowing the vector tick Ornithodorus coriaceus to feed on them. The sequential development of the fetal lesions was studied and the lesions compared with those in both naturally occurring and experimentally induced infections of the dams which either aborted or carried to term. The early changes observed in the fetuses consisted of transformation and proliferation of lymphocytes and mononuclear phagocytes. These changes were marked by 50 days after tick exposure of the dams, but fetal lesions specific enough to permit making the diagnosis of the disease did not develop until 100 days after dams were exposed by tick feeding. In the fetuses which were either aborted or carried to term after prolonged infection, acute necrotizing lesions were superimposed on the chronic proliferative fetuses. Acute necrotizing foci developed in several organs, but most commonly in lymph nodes and spleen. These foci frequently formed pyogranulomas. Acute vasculitis developed at the same time as the acute focal-necrotizing lesions. These lesions were similar to immune-mediated lesions that result from the deposition of toxic complexes in the tissues. Immunofluorescent examination demonstrated that immunoglobulins (Ig)G and IgM were present in the vascular lesions.

Abortion, Veterinary↗
PubMed1982

Whole blood viscosity in preeclampsia.

Whole blood viscosity was measured in 41 patients with preeclampsia and in 51 normotensive control subjects. The mean viscosity in the preeclamptic group had a highly significant elevation (t = 9.752, p less than 0.001, at a shear rate of 0.1 sec-1 and t = 4.223, p less than 0.001, at a shear rate of 100 sec-1). The slower shear rate gave the better discrimination between the two groups as only four patients with preeclampsia had a value within 1 SD of the mean of the control group. It is suggested that the measurement of whole blood viscosity may be clinically useful in the management of patients with preeclampsia.

Blood Pressure↗
PubMed1982

Morphogenesis of the renal juxtaglomerular apparatus and peripolar cells in the sheep.

The morphogenesis of the juxtaglomerular apparatus and peripolar cells was studied in the metanephros of fetal sheep (from 24 to 147 days of gestation) using light and electron microscopy. The first juxtaglomerular apparatus was detected at 45 days of gestation, following constriction of the edges of Bowman's capsule and formation of the vascular pole of the renal corpuscle. Mesenchymal cells gave rise to lacis cells and to smooth muscle and epithelioid cells of the juxtaglomerular arterioles. Epithelioid cells developed only sparse cytoplasmic granulation, first detectable at 92 days. The macula densa developed from tubular cells at the junction of the middle and upper limbs of the S-shaped body of the developing nephron. Peripolar cells arose from epithelial cells in the lower limb of the S-shaped body, at the constricting edges of Bowman's capsule, and formed a cuff around the origin of the glomerular tuft. Cytoplasmic granules were first detected in peripolar cells at 53 days, and remained more prominent than epithelioid cell granulation throughout gestation.

Animals↗
PubMed1981

National Poisons Information Services: report and comment 1980.

The National Poisons Information Services (NPIS) covering the United Kingdom and the Republic of Ireland currently receive over 40,000 telephone inquiries a year. Over the years there has been little change in the proportion of inquiries related to each of the main categories of poisons (drugs, household, chemical, agricultural, animals, and plants). More detailed analysis, however, shows pronounced changes in the inquiries relating to specific types of poisoning, particularly with drugs. By monitoring these trends and assessing the risks of toxicity, the NPIS has an important role in informing the medical profession of the need for preventive measures and for improved methods of treatment. At present, the NPIS cannot make full use of the available data due to inadequate staffing and lack of computer facilities. It is argued that for a modest increase in funding a much more comprehensive service could be provided.

Adolescent↗
PubMed1968

Oxytocic drugs.

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Animals↗