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Biomedical subjects

N Chetty

Publications and source records attributed to N Chetty.

At least 19 recordsLinked to original sources
PubMed2000

Cell adhesion molecules - can they be used to predict coronary artery disease in patients with familial hypercholesterolaemia?

Adhesion of leukocytes to endothelial cells via cell adhesion molecules (CAMS) is thought to be pivotal in the initiation of atherosclerosis. As patients with familial hypercholesterolaemia (FH) are known to develop severe, premature coronary artery disease (CAD), we investigated the usefulness of soluble forms of CAMS namely vascular cellular adhesion molecule-1 (VCAM), intercellular cell adhesion molecule-1 (ICAM) and E-selectin as predictive markers of the presence and severity of atherosclerosis in this patient group. Twenty heterozygous FH patients without CAD; 24 heterozygous FH patients with CAD; 17 homozygous FH patients without documented CAD; nine homozygous FH patients with overt CAD; and 50 healthy controls were studied. Carotid artery intima media thickness (IMT) was also measured in the homozygous patients. Levels of the adhesion molecules VCAM, ICAM and E-selectin were not significantly elevated in homozygous FH patients and heterozygous FH patients, both with and without CAD, compared to the normal control subjects. In addition the range of results was so wide and the overlap of values with normal controls so great, that the use of an individual level of either VCAM, ICAM or E-selectin was not predictive of either the presence or degree of atherosclerosis in the FH subjects.

Adult↗
PubMed1998

Ruthenium red preserves glycoprotein peplomers of C-type retroviruses for transmission electron microscopy.

Peplomers, the glycoprotein projections of the outer viral envelope, are distinctive for many viruses. Peplomers of retroviral C-type particles are fragile and are not preserved in standard preparations for transmission electron microscopy of thin sections, whereas the peplomers of B- and D- type retroviruses are usually preserved. Ruthenium red, extensively used in transmission electron microscopy to enhance the preservation of glycosylated proteins, was used in the preparation of three retrovirus-producing lymphoblastoid cell lines: murine SC-1 cells producing the C-type murine leukemia retrovirus LP-BM5 that causes immunodeficiency, human DG-75 cells producing a murine leukemia retrovirus, and human C5/MJ cells producing human T-cell lymphotropic virus type I (HTLV-I). Fixation of cells was carried out with ruthenium red present in the glutaraldehyde, osmium tetroxide, and the ethanol dehydration through the 70% ethanol step. The detailed structure of peplomers of these three different viruses was well preserved.

Animals↗
PubMed1997

The in vitro effect of ridogrel on platelet function in normocholesterolaemic and familial hypercholesterolaemic type IIa subjects.

Platelets from familial hypercholesterolaemia type IIa patients are hyperreactive and produce increased amounts of thromboxane A2. These modifications of platelet function may play an important role in the occurrence of premature atherosclerosis. One approach to the prevention of the thromboembolic complications of atherosclerosis is the use of antiplatelet agents which depress platelet function. Ridogrel, a combined thromboxane synthase inhibitor and thromboxane A2/prostaglandin endoperoxide receptor blocker inhibits platelet aggregation. This study was designed to investigate the in vitro effect of ridogrel on platelet function in normocholesterolaemic and familial hypercholesterolaemia type IIa subjects. In citrated platelet rich plasma ridogrel significantly inhibited platelet aggregation and thromboxane A2 production in response to collagen, ADP and arachidonic acid stimulation. In washed platelets ridogrel significantly decreased aggregation and serotonin release. Ridogrel significantly increased cAMP levels in response to thrombin stimulation. In conclusion, ridogrel at low concentrations significantly inhibited the in vitro function of platelets in a dose dependant manner in both normocholesterolaemic subjects and familial hypercholesterolaemia IIa subjects.

Adult↗
PubMed1997

Plasma fatty acid levels in South African interethnic male high school pupils at different ultimate risks of coronary heart disease.

While coronary heart disease (CHD) is responsible for about a quarter of deaths in South African white, coloured and Indian populations, the rate is very low in the black population. Dietary risk factors for CHD include high intakes of saturated fatty acids and cholesterol, with low intakes of mono and polyunsaturated fatty acids. In a characterization study, plasma fatty acid profiles have been determined in seven groups of high school pupils aged 16-18 years, namely, white, rural black, urban black and middle-class and lower socio-economic class coloureds and Indians. Plasma fatty acids were measured by gas liquid chromatography in 20 subjects from each group. Contrary to expectation, urban and rural black pupils had the highest mean molar composition of saturated fatty acids, largely myristic (14:0) and palmitic (16:0) acids. Rural blacks and middle-class coloureds had the highest molar percentage composition of monounsaturated fatty acids, primarily oleic acid (18:1). Again unexpectedly, white, coloured and Indian groups had the highest level of polyunsaturated fatty acids, due entirely to linoleic acid (18:2). As the findings are unrelated to proneness to CHD mortality in the particular communities studied, plasma fatty acid levels are not predictive of the disease. Epidemiologically, there are many examples of lack of correlation in serum lipid levels and proneness to CHD.

Adolescent↗
PubMed1995

An anatomic and physiological model of hepatic vascular system.

Hepatic function can be characterized by the activity/time curves obtained by imaging the aorta, spleen, and liver. Nonparametric deconvolution of the activity/time curves is clinically useful as a diagnostic tool in determining organ transit times and flow fractions. The use of this technique is limited, however, because of numerical and noise problems in performing deconvolution. Furthermore, the interaction of part of the tracer with the spleen and gastrointestinal tract, before it enters the liver, further obscures physiological information in the deconvolved liver curve. In this paper, a mathematical relationship is derived relating the liver activity/time curve to portal and hepatic behavior. The mathematical relationship is derived by using transit time spectrum/residence time density theory. Based on this theory, it is shown that the deconvolution of liver activity/time curves gives rise to a complex combination of splenic, gastrointestinal, and liver dependencies. An anatomically and physiologically plausible parametric model of the hepatic vascular system has been developed. This model is used in conjunction with experimental data to estimate portal, splenic, and hepatic physiological blood flow parameters for eight normal volunteers. These calculated parameters, which include the portal flow fraction, the splenic blood flow fraction, and blood transit times are shown to adequately correspond to published values. In particular, the model of the hepatic vascular system identifies the portal flow fraction as 0.752 +/- 0.022, the splenic blood flow fraction as 0.180 +/- 0.023, and the liver mean transit time as 13.4 +/- 1.71 s. The model has also been applied to two portal hypertensive patients. The variation in some of the model parameters is beyond normal limits and is consistent with the observed pathology.

Blood Flow Velocity↗
PubMed1992

Platelet hyperreactivity in hyperlipidaemia with specific reference to platelet lipids and fatty acid composition.

Platelet function after thrombin stimulation, the fatty acid composition of individual phospholipids, and levels of lipid components (cholesterol, cholesterol ester, phospholipids and triglycerides) were determined in total membranes of platelets from hyperlipidaemic (HL) and control subjects. Platelet aggregation, thromboxane (TX) B2 production and serotonin release was significantly greater in HL patients than in controls. Levels of platelet cholesterol, total phospholipids, cholesterol ester and triglycerides, were significantly higher in the HL patients. Small differences between the two groups were observed for the phospholipid fatty acid patterns. However, levels of arachidonic acid (AA) were significantly higher in phosphatidylinositol (PI) of HL patients (40.01 +/- 6.59 mol%) as compared to the controls (31.52 +/- 9.91 mol%) (P = 0.002). The higher levels of AA in PI, which is considered a donor pool for eicosanoid synthesis, may be an additional mechanism for the well documented platelet hyperfunction and greater TXB2 production in hyperlipidaemic subjects.

Adult↗
PubMed1992

Patency of side branches after peripheral placement of metallic biliary endoprostheses.

During a 28-month period, the authors placed 91 Wallstent endoprostheses in 55 patients with malignant obstructive jaundice. Five patients developed recurrent jaundice between 2 and 60 weeks after stent insertion due to stent occlusion by tumor overgrowth on seven occasions. To assess long-term segmental side-branch drainage through the walls of such endoprostheses, the cholangiograms obtained following stent occlusion were reviewed. In all five patients, evidence of drainage of intrahepatic ducts through the side of the mesh was observed. Although the number of patients in the series is small, this initial experience suggests that long metallic endoprostheses can be placed peripherally in the intrahepatic bile ducts without the potential risk of infection or occlusion of undrained, noninvolved segments. This policy may delay or prevent endoprosthesis occlusion in many patients.

Adenoma, Bile Duct↗
PubMed1991

Methylmalonic acid metabolism and nervous-system fatty acids in cobalamin-deficient fruit bats receiving supplements of methionine, valine and isoleucine.

Cobalamin neuropathy was produced in Cape fruit bats (Rousettus aegyptiacus) by a cobalamin-free diet combined with intermittent exposure to nitrous oxide, which inactivates cobalamin. Cobalamin-deficient bats had low hepatic methylmalonyl-CoA mutase holoenzyme activity, with elevated plasma and urinary methylmalonic acid levels. No significant changes could be demonstrated in the concentration of odd- or branched-chain fatty acids in the nervous system. Supplementation of the cobalamin-free diet with methionine, valine or isoleucine delayed the onset of neuropathy, despite persistence of methylmalonic acid accumulation. Supplementation with any of the three amino acids was associated with elevation of hepatic methionine concentration. The action of valine and isoleucine in delaying the onset of neuropathy can be explained by their methionine-sparing effect. These results emphasize the central role of methionine in the cobalamin neuropathy and do not support the hypothesis that the neuropathy is related to an effect of cobalamin deficiency on the propionic acid pathway.

Amino Acids↗
PubMed1991

Self-expandable stainless steel endoprostheses for treatment of malignant bile duct obstruction.

The Wallstent biliary endoprosthesis is a mesh of stainless steel that is delivered percutaneously over a 7-French catheter but expands to achieve a 1-cm lumen when released across a bile-duct stricture. The small transhepatic track required makes insertion easier, less painful, and probably safer when compared with plastic stents, and the large internal lumen reduces the rate of occlusion by encrusted bile. Wallstent endoprostheses were inserted under local anesthesia in 41 consecutive patients with malignant obstructive jaundice. Biliary drainage was considered the treatment of choice in all of these patients. The diagnosis was based on biopsy results in 32 patients and on radiologic appearances in nine. The patients were followed up in outpatient clinics for 16 months and had repeated radiologic examinations only if they had symptoms suggesting stent occlusion. No cases of hemobilia due to damaged hepatic vessels occurred. Two patients had septicemia treated with antibiotics. Three patients had recurrent jaundice due to growth of tumor below or above the stents. Endoprosthesis migration was not seen. No cases of stent occlusion due to encrustation of bile occurred. The median survival of patients was 105 days (range, 10-545 days). Our experience shows that Wallstent endoprostheses can be inserted with little discomfort for the patient and with relatively few complications. They provide good palliation in patients with malignant obstructive jaundice.

Adult↗