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Biomedical subjects

V Scott

Publications and source records attributed to V Scott.

At least 55 records · Page 3Linked to original sources
PubMed1992

Organochlorine pesticides and polychlorinated biphenyls in the Arctic Ocean food web.

Polychlorinated biphenyls (PCBs), polychlorinated camphenes (PCCs) and isomers of DDT and DDE were the predominant organochlorine (OC) hydrocarbons measured in epontic particulate matter, zooplankton, pelagic and benthic amphipods and liver tissue from an abyssal fish collected in the Arctic Ocean. Chlordane, dieldrin and other cyclodienes and hexachlorocyclohexane (HCH) isomers were present at lower concentrations. Levels on a dry weight basis in plankton of various sizes less than 63 microns to 2 mm were similar to those in epontic particulate matter, but on a lipid weight basis, concentrations in smaller plankton were two to five times higher. Organochlorines in amphipods and liver from the glacial eelpout Lycodes frigidus exceeded levels in zooplankton by up to an order of magnitude. Large benthic lysianassid amphipods (Tmetonyx cicada, Anonyx nugax and Eurythenes gryllus) accumulated higher concentrations on a dry and lipid weight basis than small species (Onisimus spp. and Andaniexis spp.) or the under-ice gammaridean amphipod (Gammarus wilkitzkii). No significant differences in OC levels were measured in benthic amphipods collected at different times. However, concentrations in large zooplankton (greater than 500 microns) collected in August, dominated by adult copepods and ctenophores, contained concentrations of alpha-HCH, chlordane isomers and other cyclodienes that were two to four times higher than levels in May. Ratios of alpha-HCH: gamma-HCH (5 to 10) were similar to those in seawater collected simultaneously but there was no difference in ratios in various size categories of planktonic and benthic crustaceans indicating no selective accumulation or metabolic alteration of these isomers. Ratios of cis-chlordane:trans-chlordane concentrations were lower in all sizes of zooplankton (2 to 3) than in shelf amphipods (3 to 6) which corresponded to an increase in the ratio with depth. Higher ratios of DDT:DDE in plankton (2 to 6) than in amphipods (1 to 2) reflects the metabolism of DDT to the more stable DDE isomers in amphipods. Metabolites of trans-chlordane were also measured in plankton and benthic amphipods. Although some OCs are degraded or metabolically transformed, accumulation in lipid-rich tissues results in the highest total concentrations in long-lived large-bodied arctic marine organisms.

Animals↗
PubMed1992

Effects of organic acids on the edema of the stria vascularis induced by furosemide.

Furosemide is a loop diuretic which is ototoxic. Investigations have shown the stria vascularis to be the target tissue of this ototoxic drug. The purpose of the present study was to investigate the effects of furosemide on the stria vascularis in chinchillas, in controls and in animals pretreated with the above organic acids. Control animals were injected with 0.5 ml alkalinized saline followed by furosemide IV 30 min later. Experimental animals received probenecid, penicillin or sodium salicylate IV. Thirty minutes later, furosemide was injected in the same dose as in the controls. The basal turn of the stria vascularis was rapidly removed at various times from 10 to 30 min after furosemide administration and processed for transmission electron microscopy. Control animals were found to have reversible edema of the stria vascularis. Experimental animals had variable findings. Those animals pretreated with penicillin had virtually no edema of the stria vascularis at any time. Salicylate and probenecid pretreated animals had significantly less edema from one to 10 min after furosemide injection, but more edema than controls at later times. These findings suggest a discrepancy between ultrastructural pathology and functional status of the cochlea in experimental animals pretreated with probenecid or sodium salicylate followed by furosemide. On the other hand, good structure function correlations were seen in controls and in experimental animals pretreated with penicillin.

Acids↗
PubMed1992

Development of endocochlear potential and compound action potential in the rat.

The present study was designed to investigate the developmental changes of the endocochlear potential and compound action potential simultaneously from rat pups of various ages. Animals were anesthetized with ketamine/xylazine, and the endocochlear potential was measured with a glass microelectrode. At the same time, a wire electrode was placed on the round window to record the click-evoked compound action potential. The endocochlear potential was found to be very low during the first few days of postnatal life. A rapid increase in the value of the endocochlear potential was noted between eleven and thirteen days of age, and adult-like values were recorded by seventeen days of age. Compound action potential responses were recorded at thirteen days of age to high intensity clicks, followed by a progressive improvement of thresholds and reduction of latencies. The development of the endocochlear potential and compound action potential was found to be reciprocally related - as the magnitude of the endocochlear potential increased, the compound action potential threshold declined with increasing age. The development of the endocochlear potential was found to closely approximate the development of enzymatic activity of sodium, potassium-ATPase in the stria vascularis reported by Kuijpers (1974).

Action Potentials↗
PubMed1991

Two proteins act as the IUF1 insulin gene enhancer binding factor.

IUF1 is a pancreatic beta cell-specific factor which binds to the sequence 5'-CPyCTAATG-3' (CT box) within the human insulin gene enhancer. Here we show that IUF1 is composed of 2 binding activities that can be separated by DEAE ion exchange chromatography. South Western blot analysis indicates that these distinct binding activities have apparent molecular weights of 115 kDa and 46 kDa.

Animals↗
PubMed1991

Comparative acute ototoxicity of loop diuretic compounds.

A microelectrode was used to measure endocochlear potentials (EP) in adult chinchillas and to study the effects of a series of loop diuretics. EP was measured before, during and for several hours after the intravenous injection of the following loop diuretics: furosemide, piretanide, bumetanide, ethacrynic acid, indacrinone stereoisomers and ozolinone. The first four loop diuretics caused a substantial dose-related reduction of EP. The (-) isomer of indacrinone was found to cause a dose-related reduction of EP to a moderate degree. The (+) isomer of indacrinone and ozolinone caused very little change of EP, even in very high doses. Findings are consistent with data on the mechanism of action of these agents in the kidney.

Acute Disease↗
PubMed1991

Rat as a potential model for hearing loss in biotinidase deficiency.

Biotinidase deficiency is an inborn error of metabolism that is transmitted as an autosomal recessive disorder. Symptoms include hearing loss, ataxia, blindness, mental retardation, and seizures. The metabolic defect is an inability to recycle the vitamin biotin, which is an important cofactor in key enzymes. We therefore sought to develop an animal model for this disorder by inducing biotin deficiency. Rat pups were divided into control and experimental groups. Control rats were fed a normal diet whereas experimental animals were given a diet deficient in biotin. Animals from both groups underwent brain stem auditory evoked potential testing at various ages. Wave I thresholds at various ages were similar in both groups. Latencies for wave I, however, and interpeak latencies (I-IV) were prolonged in the biotin-deficient groups compared to controls. Scanning electron microscopy of the organ of Corti in biotin-deficient animals showed no significant hair cell loss. The biotin-deficient developing rat appears to acquire functional changes in the auditory brain stem. These effects may be caused by defective myelination, since biotin is important in fatty acid metabolism.

Amidohydrolases↗
PubMed1991

Ototoxicity of furosemide during development.

The rat is an altricial animal which serves as a useful model for human auditory development. The purpose of the present study was to investigate the effects of furosemide on cochlear function and the stria vascularis ultrastructure at various postnatal ages. Rat pups anesthetized with ketamine hydrochloride/xylazine hydrochloride received furosemide 35 mg/kg intravenously (IV), and the endocochlear potential and compound action potential of the eighth nerve were recorded. The stria vascularis was removed and prepared for transmission electron microscopy. Rat pups 9 to 28 days of age had a much greater reduction of endocochlear potential and elevation of the compound action potential threshold than animals older than 30 days. These physiologic changes were accompanied by edema of the stria on transmission electron microscopy only in animals at susceptible ages. These findings support the concept of a critical period of susceptibility to ototoxic drugs during development and could have important clinical implications in premature infants.

Animals↗
PubMed1990

Organic acids do not alter the cochlear effects of ethacrynic acid.

Previous studies have shown a reduction of the ototoxicity of furosemide in chinchillas pretreated with organic acid transport inhibitors. The current studies were designed to investigate whether such a protective effect could be observed in chinchillas receiving ethacrynic acid. Chinchillas weighing 400-600 g were injected with saline followed by ethacrynic acid 12.5 mg/kg i.v. (controls) or one of three organic acids (probenecid, penicillin G and or sodium salicylate) 50 mg/kg i.v., thirty minutes prior to ethacrynic acid injection (experimentals). Endocochlear potential (EP) and compound action potential of the eighth nerve (CAP) elicited by click stimuli were simultaneously monitored before and after injection in both groups. The mean change in EP and CAP findings are consistent with observations by other investigators of the actions of these loop diuretics in the isolated loop of Henle. In the latter tissues, the 'furosemide-like loop diuretics' appear to have a different mechanism of action than does ethacrynic acid. It appears from the findings of the present study that the actions of furosemide and ethacrynic acid on the cochlea are by different mechanisms as well.

Action Potentials↗
PubMed1990

Crohn's disease in black patients.

Crohn's disease is less prevalent in blacks than in whites. However, when it does occur, it is associated with a high degree of morbidity and is frequently unrecognized at initial presentation. Forty-three patients with Crohn's disease presented to Howard University Hospital between 1965 and 1987. There were 156 hospital admissions, 47 emergency room visits, and 76 clinic visits over this 22-year period. Twenty-eight patients were female and 15 were male. The age of presentation for males ranged from 18 to 63 years and for females, 12 to 74 years. Crohn's disease should be considered in black patients who present with chronic abdominal pain and diarrhea. With correct diagnosis and appropriate medical therapy, patients should have an enhanced quality of life with less morbidity.

Adolescent↗
PubMed1987

Naturally occurring antibodies to phosphocholine as a potential index of antibody responsiveness to polysaccharides.

Naturally occurring antibodies reactive with the phosphocholine (PC) determinant of pneumococcal teichoic acids may be useful for evaluating the potential of patients to make antibodies to polysaccharides. Antibodies to PC are present in most adults under the age of 60 years, are absent in very young children, and are present at low levels in Wiscott-Aldrich patients and in IgG2-deficient adults. These last three groups respond very poorly to polysaccharide antigens. Antibodies to PC are also found at low levels in the elderly, a group that has previously been shown to have low levels of antibody to blood groups A and B carbohydrates. The levels of antibody to PC over time were constant in most individuals and, in adults, seemed to show slightly less variation than did titers of antibody to blood group B. Our findings suggest that titers of antibody to PC may be superior to titers of antibody to blood group A or B for monitoring responsiveness to carbohydrate antigens.

ABO Blood-Group System↗
PubMed1981

Pain perception in competitive swimmers.

The pain perception of 30 competitive swimmers was studied using experimentally induced ischaemic pain. The pain thresholds and tolerances of this group were compared with those of 30 club swimmers and 26 non-competitive athletes. While pain thresholds showed little difference between the groups, pain tolerances were considerably different. Pain tolerances of the competitive swimmers varied according to the stage of the training season. The relation between ischaemic pain and that experienced during swimming training was studied using a pain questionnaire composed of several systematically structured verbal categories. Both types of pain were classified along similar dimensions, and it was concluded that the experimentally demonstrated pain tolerances could be generalized to the normal pain perception of the subjects. The origins of the enhanced pain tolerances of the competitive swimmers would seem to lie in their systematic exposure to brief periods of intense pain. These data could have relevance for the treatment of chronic pain in certain diseases.

Arm↗
PubMed1981

Extrahepatic bile duct carcinoma: a case report.

The potential of local radiotherapy with intraoperative electron beam irradiation and trans t-tube iridium(192) brachytherapy for the management of carcinoma of the extrahepatic ducts is illustrated by this case report.

Adenocarcinoma, Papillary↗
PubMed1981

Spirometric standards for healthy black adults.

Forced expiratory spirometric studies were performed on 512 nonsmoking black adult men and women with negative cardiorespiratory histories. Regression equations were calculated for forced vital capacity (FVC), percent vital capacity in 1 second (% FEV(1)), and forced midexpiratory flow rate FEF(25-75)%), using height and age. These equations resulted in predicted values 3.5 to 23 percent lower than commonly used standards. The wide range of variation means that a single correction factor is inadequate when considering ethnic differences. In contrast, FEV(1)/FVC was within the accepted range of normal for all ethnic groups. In the 30 percent of subjects in whom sitting height was measured, it was not significantly different from one half the standing height; thus, sitting height is also an inadequate correction factor. Tables of predicted values were constructed for easy reference, with the hope that use of racespecific standards for pulmonary function testing will become widespread.

Adult↗