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Biomedical subjects

T J Stevens

Publications and source records attributed to T J Stevens.

24 records · Page 2Linked to original sources
PubMed1983

Decreased catecholamine content caused by slicing of frozen human post mortem brain with an electric blade.

A deleterious effect on dopamine and norepinephrine levels was observed in cortical Brodmann area 25 tissue dissected from mechanically cut coronal slices of frozen human brain. Catecholamine concentrations were found to be 10 (NE) and 7 (DA) fold higher in similar tissue dissected directly from the frozen hemisphere without cutting. A heat-related breakdown in endogenous catecholamine content is suspected. An alternative method is presented for cutting coronal slices of frozen human brain which involves much less heat and friction and provides slices with excellent morphological appearance.

Brain Chemistry↗
PubMed1983

Comparison of clofibrate and ethyl-5-(p-chlorophenoxy)-3-hydroxy-3-methylpentanoate induced changes in serum lipoprotein cholesterol and hepatic peroxisome proliferation in the normal rat.

Clofibrate and ethyl-5(p-chlorophenoxy)-3-hydroxy-3-methylpentanoate (HMP), at 0.1 and 0.25% in the diet, were evaluated in normal rats. Effects on serum lipoprotein cholesterol, liver cholesterol and peroxisome proliferation changes were compared. Both doses of HMP significantly lowered high density lipoprotein cholesterol (HDL-C) and total cholesterol (mean 22% and 18%). The distribution of cholesterol in the lipoproteins was altered (p less than 0.05) and liver weights were increased 18% by the 0.25 dose of HMP. Clofibrate treatment increased (p less than 0.01) the combination of very low and low density lipoprotein cholesterol (VLDL + LDL-C) by 42% at the 0.1% dose and lowered HDL-C by 28% at the 0.25% dose; total-C was not changed from control values. Both levels of clofibrate shifted the distribution of lipoprotein cholesterol, increased liver weights (mean 69%) and reduced liver cholesterol (mean 33%). Image analysis of peroxisome changes showed that both doses of HMP and clofibrate increased peroxisome numbers (mean 71% vs 218%), with activity of HMP significantly lower than clofibrate. Measurement of carnitine acetyltransferase (CAT) activity (nmCoASH released/mg protein/minute) showed no significant increases in liver samples from HMP-treated rats, while clofibrate induced large increases in CAT activity, which were significant compared to control and HMP values. While having chemical structural similarity to clofibrate, HMP appears to cause comparable hypocholesterolemic activity without comparable levels of hepatomegaly and peroxisome proliferation.

Animals↗
PubMed1982

Dopamine and homovanillic acid concentrations in striatal and limbic regions of human brain.

In an attempt to further define the dopaminergic nature of the limbic nucleus accumbens from the morphologically similar striatal caudate and putamen, the levels of dopamine (DA), homovanillic acid (HVA), and HVA/DA ratios, an index of dopamine turnover, were measured in these three structures of human brain. The levels of dopamine in the accumbens (2.49 ng/mg), caudate (2.39 ng/mg), and putamen (3.00 ng/mg) were similar. The homovanillic acid concentration in the accumbens (7.44 ng/mg) and putamen (6.54 ng/mg) were comparable, while its concentration was considerably lower in the caudate (3.61 ng/mg). The most striking difference between the limbic accumbens and the striatum was observed in the HVA/DA ratio. This index of turnover was significantly higher in the accumbens (3.64) when compared to the caudate (1.80), and was 59% higher than that found in the putamen (2.53). The data provide evidence for differences in dopamine activity in the mesolimbic versus the nigrostriatal pathways.

Adult↗
PubMedDate not supplied

Activity of ethyl 5-(p-chlorophenoxy)-3-hydroxy-3-methylpentanoate, a new hypocholesterolemic compound, in male rats and SEA Japanese quail.

Ethyl 5-(p-chlorophenoxy)-3-hydroxy-3-methylpentanoate (HMP), a new hypocholesterolemic compound, was evaluated in male rats at dosage levels ranging from 25-800 mg/kg/day and in SEA Japanese quail at approximately 200 mg/kg/day. In the rat, the atherogenic lipoprotein cholesterol, that is, the combination of very low density plus low density lipoprotein cholesterol (VLDL-C + LDL-C), was reduced 20-27% at dosage levels over 100 mg/kg/day, while high density lipoprotein cholesterol (HDL-C) and total serum cholesterol (TSC) were significantly decreased 25-46%, respectively, at all dose levels of HMP. Liver weights with HMP treatment were significantly elevated (11-26%) in the rat. HMP was not active in the SEA Japanese quail, since an initial reduction in artery cholesterol could not be confirmed in subsequent tests.

Animals↗