Biomedical subjects
Publications and source records attributed to J H Ross.
To understand managed care, it is important to look at its origins, growth and development, including prospects for the future. Managed care systems today are a major factor in health care delivery and may well dominate the delivery system in America during the 1990s.
The autoperfused heart-lung preparation was developed as a method for extending the acceptable donor-to-recipient interval in clinical heart-lung transplantation. Metabolic substrate enhancement has been shown to be necessary for the survival and homeostasis of the functioning preparation. To define basic metabolic requirements and to determine the resting energy expenditure of the working canine heart-lung preparation, two groups were studied. Ten canine heart-lung blocks were placed in a normothermic autoperfusion circuit. In Group 1 (n = 5), a hyperalimentation solution of balanced substrate was infused (15% dextrose, 4.25% amino acids, 8 meq magnesium sulfate, 30 IU/dl insulin, and 10% lipids). In Group 2 (n = 5), no substrate was given. The preparations were ventilated with a mixture of room air and 5% CO2 at a rate of 4 breaths/min to maintain physiological pH. Myocardial function was assessed by cardiac output determinations and mixed venous gases. Pulmonary function was assessed with arterial blood gases. The oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured with a Metabolic Cart, and the resting energy expenditure was calculated. The mean survival time for Group 1 was 360 minutes, and all preparations were terminated electively. The mean survival time for Group 2 was 219 +/- 43 minutes (p less than 0.01) with congestive heart failure as the common terminal event. All parameters of cardiac function and blood gases remained within physiological limits without significant differences between groups. The resting energy expenditure, a measure of metabolic rate, was 2.5 +/- 0.3 kcal/hr in Group 1 and 1.0 +/- 0.2 in Group 2 at termination (mean +/- SD) (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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The effects of severe repetitive exercise on certain haematological measurements were studied. Decreases in haematocrit and haemoglobin (13% in one group of participants) took place during the first 2 weeks but not the third week of increasingly severe exertion and the reasons for this are discussed. Haemolysis probably plays only a small part and plasma volume expansion is likely to be the main cause of this phenomenon. It is suggested that there is no stimulus for the haemoglobin concentration to be increased to match the increased plasma volume as tissue oxygen tension is maintained satisfactorily.
Two groups of young men taking part in a 24-day training course involving increasingly severe exercise were studied. Serum myoglobin, creatine kinase, creatine kinase-MB, transaminases, lactate dehydrogenase, urea, creatinine, calcium and uric acid were estimated at intervals. During the first few days, increases in myoglobin and muscle enzymes correlated with the severity of the preceding exercise. Increases in myoglobin and muscle enzymes after the final most severe exercising were less than with the initial exercising, demonstrating the effect of physical training. The changes in myoglobin and the muscle enzymes correlated closely. Elevated myoglobin levels persisted for over 24 hours. There was no consistent correlation between changes in myoglobin and uric acid, both of which have been considered responsible for the renal failure which may occur with rhabdomyolysis.
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8 patients who developed proteinuria whilst receiving penicillamine for rheumatoid arthritis have been studied. Light microscopy of renal biopsy specimens showed evidence of an extramembranous nephropathy in 6 cases, with epimembranous spikes infrequently described previously in association with penicillamine.
Duckweed (Spirodela oligorrhiza, Kurz) is a sensitive indicator of 1,1'-alkyl-4,4'-bipyridylium salt (viologen) herbicidal potency. A homologous series of viologens were tested to determine relative herbicidal potency which was related to alkyl inductive and steric effects of N-alkyl side chains. Chlorosis was assessed after 48 hr of continuous illumination to establish herbicidal potency. Herbicidally effective concentrations were 2.7, 12, 236, 71, 31, 51, 13 and 43 microM for methyl (paraquat), propyl, isopropyl, butyl, methyl-pentyl, hexyl, octyl and benzyl viologen, respectively. A biphasic relationship of herbicidal potency versus steric effect was established in which compounds with the least bulky side chains were most phytotoxic. Comparison of rat lethality (acute, subcutaneous) and herbicidal potency of these compounds indicates that none of the viologens tested are less toxic to mammals than plants compared to the commercial herbicide methyl biologen (paraquat).
Methyl (paraquat), propyl, isopropyl, butyl, methyl-pentyl, hexyl, octyl and benzyl viologens (1,1'-Alkyl-4,4'-bipyridylium salts) were administered subcutaneously to female Sprague-Dawley rats to determine relative toxicities. These compounds all produce the spectrum of effects previously reported for paraquat and additionally produce a focal necrosis at the injection site, nonemptying of the stomach and adrenal enlargement. A lethal dose of propyl, hexyl or benzyl viologen often produced a yellow to red serous fluid in the pleural cavity. Many of the signs observed with viologen poisoning are similar to adrenal hormone effects and the suggestion is made that the adrenals may be contributing to toxicity.
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Current methods of estimating absorbed dosage (AD) of chemicals were evaluated to determine residue transfer from a carpet treated with chlorpyrifos (CP) to humans who performed a structured exercise routine. To determine the dislodgeability of residue, a California Department of Food and Agriculture (CDFA) roller was applied to a flat cotton cloth upon a treated carpet. Levels ranged from 0.06 to 0.99 microg CP/cm2. Cotton whole body dosimeters (WBD) were also used to assess residue transfer. The dosimeters retained 1.5 to 38 mg CP/person. Urine biomonitoring (3 days) for 3,5,6-trichloro-2-pyridinol (TCP) of persons who wore only swimsuits revealed a mean AD of 176 microg CP equivalents/person. The results show that the AD depends on the extent of contact transfer and dermal absorption of the residue. Default exposure assessments based upon environmental levels of chemicals and hypothetical transport pathways predict excessive exposure. The cotton WBD retains chemical residues and may be effectively used to predict dermal dose under experimental conditions.
This report summarizes the deliberations of an eight-member panel of scientists convened by Dow AgroSciences in cooperation with the U.S. Environmental Protection Agency (EPA). The panel was charged with evaluating the scientific literature on the health effects potentially associated with exposure to the insecticide chlorpyrifos. Specifically, the panel was asked to (1) evaluate human experience data available and address the adequacy of the available current literature; (2) develop a list of recommendations for epidemiology studies, including appropriate endpoints and study populations, and strengths and weaknesses of each approach; and (3) draft a report to summarize its recommendations. The panel assessed the quality of the existing epidemiologic literature on chlorpyrifos and specific outcomes such as neuropathy (including organophosphate induced delayed neurotoxicity), behavior (cognition and affect), immunologic, and multiple complaints (also referred to as multiple chemical sensitivities). The majority of panel members (five members) agreed that the literature reviewed provided little or no scientific evidence that chlorpyrifos exposure causes harm to human health other than its known cholinergic effects associated with acute poisoning. Those panel members voting in the minority (three members) agreed that the studies reviewed provided inadequate evidence to preclude the possibility of adverse effects to human health from chlorpyrifos exposure at levels associated with its manufacture or professional application. Those voting in the minority suggested further investigation of cohort(s) of workers engaged in either the manufacture or the professional application of chlorpyrifos, or both. Compared to the general population, these groups have relatively high levels of exposure to chlorpyrifos. The primary health outcomes recommended for study were cognitive and affective disorders, with consideration of the assessment of peripheral neuropathy also suggested for at least a subset of the cohort.