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Biomedical subjects

C C Chen

Publications and source records attributed to C C Chen.

At least 739 records · Page 41Linked to original sources
PubMed1975

In vitro studies of effects of light and riboflavin on DNA and HeLa cells.

The widespread use of phototherapy for neonatal hyperbilirubinemia has caused some concern since substances other than bilirubin may be photoactivated. The toxic properties of these photoactivated substances might prove to be more harmful to the neonatal infant than bilirubin. The purpose of the present study was to investigate the effect of photoactivated riboflavin in low concentration, on purified DNA. The results demonstrate extensive changes in the structure of DNA (see Table 1) manifested by (1) a change in the peak absorbance in the ultraviolet, (2) a decrease in the temperature of the thermal helix-coil transition, (3) a slight decrease in the sedimentation coefficient, and (4) an increase in the buoyant density values (1.704-1.709). These observations are consistent with the interpretation that there has been an alteration of one of the base moieties with minimal cleavage of the phosphodiester linkages. Results with human cells in tissue culture indicate that a similar photodynamic effect of riboflavin on the DNA occurs in living cells.

Animals↗
PubMed1974

Coronary hemodynamics and regional myocardial metabolism in experimental aortic insufficiency.

Acute aortic valvular insufficiency was induced in open chest dogs by employing a special intravascular cannula, or by rupturing an aortic valve leaflet. Phasic and mean coronary flow were assessed in some animals, while in others data were obtained on arterial and coronary sinus blood lactate, pyruvate, P(O2), P(CO2), and pH, and on myocardial tissue lactate, pyruvate, and water content in the outer and inner halves of the free wall of the left ventricle. Results showed that in acute aortic insufficiency diastolic coronary flow decreased as a function of aortic diastolic pressure, but systolic coronary flow increased in such proportion that mean coronary flow did not decrease. With moderate reductions in aortic diastolic pressure due to aortic insufficiency, myocardial blood flow was judged to be nutritionally adequate in both the outer and inner regions of the left ventricle. With more severe reductions in aortic diastolic pressure, the inner region exihibited biochemical signs of anaerobic metabolism. The presence of these metabolic changes could be correlated with either of two previously described pressure indexes. These findings suggest that the reduced coronary perfusion pressure and the intramyocardial tissue pressure gradient can be compensated for by autoregulation in some cases of aortic insufficiency, but in others such compensation may be incomplete, in which case oxygen delivery to the subendocardium will be inadequate to meet local tissue oxygen needs.

Anaerobiosis↗
PubMed1974

Current status of biomedical book reviewing: Part IV. Major American and British biomedical book publishers.

This is the fourth part of a comprehensive, quantitative study of biomedical book reviews. The data base of the total project was built from statistics of 3,347 reviews of 2,067 biomedical books taken from all 1970 issues of fifty-four reviewing journals. This part of the study identifies the major American and British biomedical book publishers in terms of their quantitative production of book titles reviewed, and determines the relationships among these publishers. It is found that Williams & Wilkins, Charles C Thomas, Academic Press, and Springer Verlag are the most productive biomedical book publishers in terms of books reviewed in 1970. These four publishers accounted for 32% of the 1,674 books available in the United States and reviewed in the reviewing media in 1970. Williams & Wilkins is especially significant by virtue of reprint activity. The present study also explores the price trend of biomedical books. It is found that the mean price for 1,077 books studied was $16.20 per volume, with a standard deviation of $9.42.

Biology↗
PubMed1974

Current status of biomedical book reviewing: Part III. Duplication patterns in biomedical book reviewing.

This is the third part of a comprehensive, quantitative study of biomedical book reviewing. The data base of the total project was built from statistics of 3,347 reviews of 2,067 biomedical books appearing in all 1970 issues of fifty-four reviewing journals. This part of the study explores the duplication patterns in book reviewing among these media. It is found that 35.17% (727 books) of the 2,067 titles were reviewed more than once in 1970, these titles accounting for 2,007 of the total of 3,347 reviews. For the most part, reviews of the most frequently reviewed titles appeared in such journals as British Medical Journal, Annals of Internal Medicine, Lancet, Journal of the American Medical Association, and New England Journal of Medicine. These five journals covered 93.53% of the 727 books reviewed more than once in 1970.

Biology↗
PubMed1974

Current status of biomedical book reviewing. I. Key biomedical reviewing journals with quantitative significance.

This is the first part of a comprehensive, quantitative study of biomedical book reviewing. The data base of the total project was built from statistics taken from all 1970 issues of biomedical journals held in the Science Library of the Massachusetts Institute of Technology. Of 285 so-called "life sciences" journals held by that library, fifty-four English journals (excluding Science and Nature) were found to contain bona fide book reviews (as contrasted with mere author-title lists) and were therefore selected for close study. The statistical results reveal that there were 3,347 reviews of 2,067 biomedical books in these fifty-four selected journals in 1970. Part I of the study identifies key biomedical reviewing journals of quantitative significance. The top ten journals, British Medical Journal, Lancet, Annals of Internal Medicine, Journal of the American Medical Association, Archives of Internal Medicine, New England Journal of Medicine, Quarterly Review of Biology, Bioscience, Canadian Medical Association Journal,(*) and American Journal of the Medical Sciences, accounted for 63.03% of the total number of reviews in 1970.

Book Reviews as Topic↗
PubMed1974

Current status of biomedical book reviewing. II. Time lag in biomedical book reviewing.

This part of the study explores the effectiveness of the review media in terms of speed of reviewing, comprehensiveness of review treatment, and authority. The time lags for the fifty-four journals varied widely, the mean ranging from 5.8 months to forty-two months. The time lags for all 3,347 reviews varied even more widely, ranging from less than a month to 108 months after a book was off the press. The 3,347 reviews had a mean time lag of 10.43 months and a standard deviation of 6.63 months.

Book Reviews as Topic↗
PubMed1973

Trends in biophysical research and their implications for medical libraries.

This is a statistical survey of the trends in biophysical research as reflected by papers presented at four Biophysical Society (BPS) annual meetings between 1958 and 1972 and by the funding sources of the reported projects. The study reveals that biophysical research has grown quite substantially, particularly since 1968. Although biophysics is truly interdisciplinary, since 1968 there has been more pronounced emphasis on biomedically oriented problems and a tendency toward more specific and more highly specialized problems. Between 1958 and 1972, most biophysicists were academic researchers, 50% of whom were biomedical scientists. Over three quarters of the ongoing biophysical research projects during this period were supported by governmental agencies, and among them, the National Institutes of Health was the largest single funding source.

Biology↗