Biomedical subjects
Publications and source records attributed to C Brown.
Explore the source record for details and available documents.
We assessed the role of the renin-angiotensin system in the response of the renal circulation to restriction of sodium intake in 38 normal patients. Both saralasin (10 to 30 ng/kg/min), an angiotensin antagonist, and SQ 20881 (30 to 300microgram/kg), a converting enzyme inhibitor, induced a dose-related increase in renal blood flow (xenon 133 washout) only when the resin-angiotension system was activated by restriction of sodium intake to 10 MEq/day. Increasing doses of saralasin (100 to 1,000 ng/kg/min) reduced renal blood flow, presumably due to the angiotensin-like action of this partial agonist. The renal vascular response to SQ 20881 paralleled the endocrine response: An identical threshold dose (30 microgram/kg) increased renal blood flow and reduced plasma angiotensin II concentration, which fell despite a progressive rise of plasma renin activity. Plasma bradykinin concentration did not change in response to SQ 20881, which also blocks kininase II. Both agents also induced a small but consistent and statistically significant reduction in arterial blood pressure, which will be important in assessing the pathogenetic significance of a blood pressure reduction in patients with hypertension. This study indicates that angiotensin mediates the renal vascular response to restriction of salt intake in normal man and provides an approach to assessing the role played by angiotensin in the pathogenesis of functional renal disease.
Treatment of gently prepared lysates of Escherichia coli with single-strand-specific endonuclease (SI or from mung beans) results in the release of about 90% of the DNA from membranes, as determined by the M band technique. The released DNA has an average molecular weight of about 1.2 X 10(8). Data obtained with endonuclease S1 fit a mathematical model in which substrate sites are at or near membrane attachment sites. Data obtained with pancreatic deoxyribonuclease or x-rays fit a model for double-strand breaks at random sites along the DNA. Fitting data to these models, we estimate that there are 18+/-5 membrane attachment sites. The DNA remaining after S1 nuclease treatment is enriched for the region near the origin of chromosome replication. Therefore, attachment at this region near the origin of chromosome replication. Therefore, attachment at this region appears to be chemically different from that at the other sites along the DNA.
A test for homogeneity of the effect of a factor in inducing disease in the various strata of a population should relate to the scaling in which homogeneity is anticipated. Popularity, it is the multiplicative effect on the odds ratio in which homogeneity is anticipated. An asymptotic test by M. Zelen (Biometrika 58:129-137, 1971) for homogeneity in this scaling is indicated to be invalid. Further, a test by J. L. Fleiss (Statistical Methods for Rates and Proportions. NY, Wiley, 1973) for homogeneity of the standardized difference is shown to be the same as the Zelen test, to be invalid in any case, and not to correspond to any scaling. The examples given include one in which results of two studies are apparently inhomogeneous by the test even though they give effectively identical results. It is advised that tests for homogeneity be conducted with care, and that thought be given to how effects might be made homogeneous rather than to trying to demonstrate the existence of heterogeneity.
It was the purpose of this research to define the progression over several days of changes in pulmonary function and structure and to document the phases of recovery following transfusions to dogs of sublethal quantities of stored blood containing microaggregates. Ten dogs underwent partial exchange transfusions averaging 60% of blood volume through standard blood transfusion filters. Average screen filtration pressure (SFP) of the blood was 85 mm Hg. Pulmonary hypertension did not develop, but there were striking decreases in O2 consumption, increases in Qs/Qt and decreases in Do2. Changes became progressively more marked over the first 48 to 72 hours after the transfusions. Pulmonary function of surviving animals returned nearly to normal by the sixth day after transfusions. Pathologic examinations of the lungs of animals sequentially sacrificed over 6 days showed intravascular microemboli, alveolar cell hyperplasia and interstitial and alveolar pulmonary edema. Progressive recovery was associated with progressive resolution of all detrimental changes. In 6 animals exchange transfused 100% of their blood volumes through dacron wool (Swank) filters and in three control animals that were not transfused, there were no significant changes in pulmonary function or structure. These experiments define the progression of deterioration and recovery over 6 days of pulmonary function in dogs after sublethal pulmonary microembolism occurring during blood transfusion.
Explore the source record for details and available documents.
The major fissure when directed in the sagittal plane is visualized on a frontal roentgenogram. It is reported in infants and children as the vertical fissure line and may occur with cardiomegaly and/or respiratory infection which rotates or partially collapses the lower lobe. Its presence in a normal adult chest is presented. It is believed to represent a congenital positional variant.
Explore the source record for details and available documents.
The effect of salicylate treatment on the kidney, particularly medullary function, was investigated. In a retrospective analysis patients with rheumatoid arthritis (RA) treated with high doses of salicylates were shown to have inferior urinary concentrating power and increased excretion of N-acetyl-beta-D-glucosaminidase (NAG) when compared with patients who had not received salicylate treatment. A prospective study of renal funcition in healthy people and patients with RA starting salicylate in therapeutic doses showed that while epithelial cell excretion was only transiently raised in both groups the excretion of NAG was increased in all cases at three days and this increase was sustained at 10 days, all values being much higher in the patients than in the healthy subjects. Thus salicylate treatment does cause renal tubular damage but this damage results in only minimal impairment of function and does not constitute a reason for withholding salicylate treatment.
Forty-five patients, of whom most were children, underwent extensive exposure of the thoracolumbar spine to correct serious orthopedic abnormalities. The spine was exposed through a combined thoracotomy and retroperitoneal approach that gave excellent access with minimal morbidity. The diaphragm was opened circumferentially after the peritoneum had been dissected from its muscular portion. This permitted repair of the diaphragm with no detectable loss of function. Although this approach was developed for exposure of the spine, it can also be utilized to expose the entire aorta, both kidneys and their blood supply, and the retroperitoneal area for possible excision of large tumors.
Explore the source record for details and available documents.
A case control study of patients discharged from hospitals revealed fourfold differences in geographic variation in stomach cancer risk within the Department of Narino (Colombia). Data from gastroscopic surveys of population groups, samples of water supplies, and urine and saliva in Narino also indicated a generally positive correlation among the following parameters: 1) gastric cancer risk, 2) prevalence of chronic atrophic gastritis and intestinal metaplasia, 3) nitrate content of well waters, and 4) nitrate excretion by the population. Urinary excretion reflected the ingestion of nitrates, and this implied a higher average intake of nitrates in the populations at high risk for stomach cancer. The Narino data could be construed as presumptive epidemiologic evidence for the role of nitrate availability in the etiology of stomach cancer.
The premalignant process in the gastric mucosa was studied by gastroscopic surveys of Colombian populations, and the prevalence of superficial gastritis, chronic atrophic gastritis, and intestinal metaplasia was calculated for population samples having a very high gastric cancer risk (Nariño), very low risk (Cartagena), and intermediate risk (Cali). The prevalence of individuals with normal mucosa in successive age groups was used to estimate "depletion" curves, which were taken as indicators of the dynamics of the premalignant process in each community. Differences corresponding to the geographic variation in stomach cancer risk were found: In the high-risk areas of Nariño, around 75% of the population developed some type of gastritis by 45 years of age, whereas in the low- and intermediate-risk population of Cartagena and Cali, the proportion of such lesions did not exceed 50% at age 45 or thereafter. The effect of environmental factors in early life seemed to be important in determining the prevalence of lesions in each population.
Explore the source record for details and available documents.
Methods for the determination and quantitation of homovanillic, isohomovanillic, 3,4-dihydroxyphenylacetic and 3-methoxy-4-hydroxymandelic acids in single samples of biological material by gas chromatography, gas chromatographic mass spectrometry and selected ion monitoring during gas chromatographic mass spectrometry are described. Examples of the levels of these four acid metabolites of catecholamines in serum and CSF of untreated dog, cat and human, in urine of parkinsonian subjects treated with varying doses of L-DOPA and in CSF of dogs which had received 1 g of L-DOPA per day for 7 weeks are presented.
A review has been undertaken of the 47 patients who have had open pancreatic biopsy performed at the Royal Free Hospital between 1967 and 1972. It is concluded that not only is the procedure safe when using the technique described but also it is a valuable and accurate diagnostic procedure.
The phenotypic and nucleic acid properties of Klebsiella pneumoniae have been studied on cultures obtained from six different habitats (humans, vegetables, seeds, trees, rivers, and pulp mills). The 19 cultural reactions of 107 isolates varied significantly only in tryptophanase activity and dulcitol fermentation. The percentage of guanine plus cytosine base composition of 41 isolates varied from 53.9 to 59.2%. The range of percentage of guanine plus cytosine base composition for environmental klebsiellas was broader than that for the cultures of human origin. The range of deoxyribonucleic acid relative reassociation (homology) to the human K. pneumoniae reference strain extended from 5% to 100% and the chromosome molecular weights ranged from 2,200 x 10(6) to 3,000 x 10(6). The species of K. pneumoniae is thus molecularly more heterogeneous than previously thought and most isolates of human, pulp mill, and river origin are genetically indistinguishable. The presence of K. pneumoniae therefore represents a deterioration of the microbiological quality of the environment and should be considered of public health significance. At the present time the health significance of the molecularly more divergent strains, primarily of vegetable and seed origin, their relationship to klebsiellas of human origin, or to other genera of the Enterobacteriaceae is unclear.