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Biomedical subjects

C Cohen

Publications and source records attributed to C Cohen.

At least 397 records · Page 22Linked to original sources
PubMed1980

Protein switches in muscle contraction.

Two types of Ca2+-sensitive protein complexes control the contraction of muscle: Troponin (TN) and tropomyosin (TM) are associated with the thin actin filaments, and a specific light chain is a regulatory subunit of myosin itself. Most muscles have both types of regulation. X-ray diffraction diagrams from whole muscle have shown changes in the position of tropomyosin and changes in the pattern of myosin crossbridge attachment associated with different states of the regulatory switches. The full interpretation of these diagrams is often ambiguous, however, and structural studies of the purified proteins provide essential information. Recent crystallographic results reveal that the TM molecule has unusual local domains of marginal stability, leading to extensive motions of the tropomyosin filaments. Electron microscopy of negatively stained thin filaments decorated with subfragments of scallop myosin yields unusually detailed images that show marked conformational changes in myosin crossbridges that are dependent on the presence or absence of the regulatory light chain. These observations suggest that both the special dynamic design of tropomyosin and the striking structural changes in the myosin crossbridges are significant clues for detailed models for the regulatory mechanism.

Actins↗
PubMed1980

Periportal hepatic necrosis in Reye's syndrome. One case in a review of eight patients.

Hepatic necrosis, usually periportal and mild but occasionally of significant extent, is described in the liver of patients with Reye's syndrome, in addition to diffuse microvesicular fatty change. Review of clinical and pathologic findings of eight cases of Reye's syndrome diagnosed between 1970-1978 showed extensive peripheral lobular necrosis of hepatocytes in one case. Other than biochemical evidence of greater liver damage, the latter case showed no significant differences in clinical and laboratory findings from the seven cases with diffuse fatty change of hepatocytes but no liver cell necrosis. The significance of this periportal hepatic necrosis is discussed in the light of current theories concerning the etiology and pathogenesis of Reye's syndrome.

Adolescent↗
PubMed1979

Crystal structure and molecular interactions of tropomyosin.

The three-dimensional structure of tropomyosin filaments has been determined by X-ray crystallography. The ends of the molecules were located by reference to the single pair of cysteine residues. Departures from the alpha-helical-coiled coil conformation may occur in localised domains along the molecule as well as at the overlapping ends.

Amino Acid Sequence↗
PubMed1979

Liver cell dysplasia: association with hepatocellular carcinoma, cirrhosis and hepatitis B antigen carrier status.

Liver cell dysplasia was noted on histological examination of nontumorous liver from 24 of 50 (48%) black southern African males with hepatocellular carcinoma (HCC). Macronodular cirrhosis was present in 40 (80%). There was no statistically significant difference between the frequency of dysplasia in 50% of 40 cirrhotic and 40% of 10 noncirrhotic livers, or in 52.6% of 38 hepatitis B antigen (HBAg) positive and 33.3% of 12 HBAg negative HCC patients. HBAg positivity was present in 80% of 40 cirrhotic and in 60% of 10 noncirrhotic HCC patients. This lack of significant correlation between liver cell dysplasia, and both cirrhosis and HBAg positivity in HCC patients in contrast to findings in Uganda and the United States, suggests a different pathogenetic mechanism for dysplasia in southern Africa. Liver cell dysplasia in man appears to be analogous to preneoplastic experimentally-induced hyperplastic foci or areas.

Africa, Southern↗
PubMed1979

Generalizability and durability of treatment effects in an intervention program for coronary-prone (Type A) managers.

To test the reliability and durability of positive treatment effects obtained in a type A intervention project for healthy managers, the analysis was extended to data available from a third treatment group (a special behavior therapy group for participants eliminated from the main sample because of manifestations of clinical CHD) and to measures obtained 6 months following the end of treatment. Immediately after treatment all three groups showed a similar pattern of improvement, although the two behavior therapy groups did show a greater decrease in serum cholesterol levels. Six months after treatment the sample as a whole showed good maintenance of treatment effects, but the differences between groups had become somewhat sharper, with the special behavior therapy group faring best, the regular behavior therapy group intermediate, and the psychotherapy group worst. The logical consistency of these findings increases our confidence in the initial treatment results, as well as permitting cautious optimism concerning the possibility of developing effective intervention programs for coronary-type (type A) behavior.

Analysis of Variance↗
PubMed1979

Influence of vagal tone on rheology and transportability of canine tracheal mucus.

The influence of vagal tone on the rheology of tracheal mucus was studied in 6 conscious, tracheostomized dogs. Mucus was sampled via the tracheostomy with a cytology brush before and after administration of atropine. After vagal blockade, a clear decrease in the mucus collection rate was seen. The viscoelastic properties of the mucus were not altered by atropine when control elasticity was high, but when control elasticity was low, administration of atropine led to increased elasticity. In neither case was there a significant change in transportability of the mucus samples. The increase in elasticity from a small initial value was consistent with the blocking of moderate vagal activity, because administration of methacholine in the same group of dogs had been shown to cause a decrease in mucus elasticity.

Animals↗
PubMed1979

Chronic bronchitis and bronchial asthma in a rural community in Israel: relation to socioenvironmental factors.

Prevalence rates of chronic bronchitis and asthma in a rural community in Israel in 1976 were 2.5 and 2.1%, respectively. The relationships with age, sex, country of origin, marital status, number of children, household crowding, education, occupation and cigarette-smoking habits were studied. A number of significant univariate associations were found. A multiple regression analysis showed a significant independent association between chronic bronchitis and age. Age alone accounted for 4.6% of the variance in chronic bronchitis. Five other variables were significantly associated with chronic bronchitis. Together, these accounted for an additional 1.3% of the variance in chronic bronchitis. The multivariate analysis showed that only one variable--the number of children--had an independent relationship with asthma. It accounted for 0.8% of the variance. All the variables together accounted for 1.3% of the variance observed in bronchial asthma.

Adult↗
PubMed1979

Hypertension and ischemic heart disease in a rural family practice in Israel.

Prevalence rates of hypertension and ischemic heart disease in a rural community in Israel in 1976 were 9.3% and 2.3%, respectively. The rates were related to age, sex, country of origin, education, occupation, marital status, household crowding, and smoking habits. A multiple regression analysis of all variables showed a significantly positive association between the prevalence of hypertension and age, number of children, Cochin or Moroccan origin, and divorce or widowhood. A negative association was found with agricultural work. The prevalence rate of ischemic heart disease correlated positively with age, Cochin origin, and divorce or widowhood. A stepwise linear regression analysis revealed that these variables accounted for 11.3% and 2.8% of the total variance observed, in hypertension and ischemic heart disease respectively.

Adult↗