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J R Connor

Publications and source records attributed to J R Connor.

157 records · Page 9Linked to original sources
PubMed1982

Plasticity of the aging cerebral cortex.

The results we have presented indicate that during aging the changes occurring in the different layers are similar in some instances and not in others. The environment does affect the different layers in separate ways. By using only our standard colony environment we learned that there were greater decrease in the cell number per unit area in the lower half of the cortex compared with the upper half during the first 100 days of life. Thereafter, there were no such differences at least until 650 days of age. Our results also showed that the environment can affect the dendrites in the cortical layers differently. Different dendritic patterns were noted between layers II and III and layer Vb, for example. In layer II and III there were more and longer oblique dendrites in the old standard colony animals than in the old isolated animals. Whereas, in layer Vb there were longer oblique dendrites in the isolated animals than in the standard colony animals. There were more nubbin type spines in the isolated rats than in the standard colony rats in both layers II and III and in Vb, but not in Va. The lollipop spines were always more frequent than the nubbin spines and in layer Vb there were more L spines in IC than in SC. These results continue to add information to the general pool indicating the importance of the role of the external environment in studying the aging nervous system and also the importance of considering more than one region of the brain at a time when mapping aging patterns.

Aging↗
PubMed1980

Environmental influences on serotonin and cyclic nucleotides in rat cerebral cortex.

The response to different environmental conditions and negative air ions was investigated on cerebral cortical serotonin and cyclic nucleotides. The results indicated that negative air ions alter the weight of the cerebral cortex and that concentrations of serotonin and cyclic nucleotides can be altered both by different environments and by negative air ions. The data stress the importance of the role of the environment when studying the structure and chemistry of the cerebral cortex.

Animals↗
PubMed1980

A study of atherosclerosis regression in Macaca mulatta: III. Chemical changes in arteries from animals with atherosclerosis induced for 19 months and regressed for 48 months at plasma cholesterol concentrations of 300 or 200 mg/dl.

The influence of two levels of plasma cholesterol concentration on the long-term regression of atherosclerotic plaques in rhesus monkeys (Macaca mulatta) was studied. Forty-eight young adult male rhesus monkeys were fed an atherogenic diet for 19 months, then diets designed to maintain plasma cholesterol concentrations at 280-320 mg/dl (actual 316 +/- 10 mg/dl; mean +/- SEM) of 180-220 mg/dl (actual 204 +/- 4 mg/dl). Twelve animals were killed after 19 months to evaluate the atherosclerosis produced. The remaining 36 monkeys were studied after 48 months of atherosclerosis regression. Significantly greater amounts of accumulated nonesterififed and esterified cholesterol were lost from the arteries of monkeys that underwent regression at about 200 mg/dl, in comparison with 300 mg/dl. Regression at both plasma cholesterol concentrations resulted in increased collagen and decreased elastin content in the thoracic aorta but not in the other arteries studied. After regression at 300 mg/dl there was no change (83%) in the frequency of calcification of the thoracic aorta, while at 200 mg/dl the frequency of calcification was reduced to 50%. When compared with monkeys whose athersclerotic lesions were produced in an identical manner but were regressed for only 24 months, after 48 months had increased cholesterol concenrations in the thoracic aorta and carotid artery but not the abdominal aorta of iliaco-femoral artery, regardless of the plasma cholesterol concentration. The lipid composition of the regressed plaque suggested a change in plaque lipid toward the character of extracellular deposits described physically as crystalline in nature. The physical state was influenced by the length of the regression period and the plasma cholesterol concentration during regeression. In the thoracic aorta, principally as a result of changes in elastin content, the collagen-to-elastin ratio increased between 24 and 48 months of regression. It is proposed that the differences in removal of cholesterol from the thoracic and abdominal aorta after 24 and 48 months of regression in animals at 300 mg/dl may be influenced by the rearrangement of connective tissue. On the basis of the lipid and mineral content of uncomplicated atherosclerotic plaques after 4 yers of regression, it appears that the plasma cholesterol concentration during the regression period is a signigicant factor influencing the extent of plaque regression as well as the potential for further progression.

Animals↗
PubMedDate not supplied

D-Phe7-substituted peptide bradykinin antagonists are not substrates for kininase II.

The bradykinin receptor antagonists [D-Phe7]bradykinin, D-Arg[Hyp3,D-Phe7]bradykinin and D-Arg[Hyp3,Thi5,8,D-Phe7]bradykinin were tested for their ability to serve as substrates for kininase II (angiotensin converting enzyme) purified from rabbit lung. By HPLC, the peptides were not measurably degraded over 30 minutes. Under identical conditions, bradykinin was completely degraded to bradykinin (1-7). When hippuryl-His-Leu was used as a substrate for kininase II, the D-Phe7-substituted bradykinins acted as weak noncompetitive inhibitors. While the peptides were poor substrates for kininase II, they were short-lived when injected intravenously. D-Arg[Hyp3,D-Phe7]bradykinin was completely degraded to small fragments in less than 2 minutes. In diluted serum in vitro, a single product was observed with elution consistent with loss of arginine, suggestive of metabolism by kininase I.

Animals↗