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Biomedical subjects

N Brown

Publications and source records attributed to N Brown.

At least 217 records · Page 12Linked to original sources
PubMed1984

Pressure rise at arterial bifurcations.

The increase in cross-sectional area within an arterial bifurcation is shown to be much larger than that predicted by the conventional area ratio beta. Modified area ratios which better describe this increase are presented and their values are assessed both from theoretical considerations and from physiological data. The results suggest that the pressure rise within an arterial bifurcation may be much more severe than that suggested by the conventional area ratio beta, and that local flow separation may be far more common. These conditions may adversely affect endothelial tissue and orderly flow within the bifurcation region.

Animals↗
PubMed1984

The molluscicidal properties of Ambrosia maritima L. (Compositae). 2. Results from a field trial using dry plant material.

A field trial in Egypt of the plant molluscicide, Ambrosia maritima is described. Applications of 140, 70 and 35 mg/l-1 dry, whole plant were made to irrigation canals and drains in June. The treatment effect took between 1 and 5 weeks to become fully established. The reduction in the numbers of alive Biomphalaria alexandrina snails was generally more than 90% and was virtually the same at all treatment levels and in both types of watercourse. The snail population remained at a low level for at least 3 months until September-October. The possible use of a single, annual application in April or May in controlling snails throughout the main schistosomiasis transmission season in Lower Egypt is suggested.

Animals↗
PubMed1984

Nutrient intake of patients with cystic fibrosis.

Nutrient intake, anthropometric measurements, and pulmonary function were assessed in 26 young adult patients with cystic fibrosis (CF). Mean nutrient intakes, excluding those from vitamins and nutrient supplements, were less than the Recommended Dietary Allowances for folate for men and women and for iron and vitamin B-6 for women. Male cystic fibrosis patients consumed significantly more of 11 of 16 nutrients in comparison with men with Crohn's disease and men with functional gastrointestinal complaints. Female cystic fibrosis patients consumed significantly more of 9 of 16 nutrients than did women with gastrointestinal complaints. The relative body weight was less than 85% of standard in 65% of men and 50% of women with CF. Relative body weight was correlated with variables indicative of airflow obstruction, reduced vital capacity, and hyperinflation of lung volumes.

Adolescent↗
PubMed1983

Improving the medical record for clinical oncology research by adaptation to a microcomputer.

In clinical oncology, much of the research is conducted in the milieu of patient care and the traditional medical record is used for collection of data. A clinical study manager reviewing medical records is frequently faced with problems such as omissions of data, illegible notes, and inconsistent locations of data within the various formats. At the Children's Hospital in Birmingham, Alabama, we developed a microcomputer-based medical record system in an attempt to improve the quality of clinical research. Our system is based within our division and provides for a single point of transcription of clinical data when the patient is initially seen. Our entire practice is managed on the system, with numerous reports available that range from individual patient information to summary reports on protocol studies.

Computers↗
PubMed1983

The embryotoxic effects of ultrasound exposure in pregnant ICR mice.

The embryotoxicity of ultrasound exposure during pregnancy was investigated in DUB:(ICR) mice. On day 0 of gestation (day of plug), pregnant mice were assigned to one of five groups: cage control, sham exposed (0 W/cm2), 0.05 W/cm2, 0.50 W/cm2. or 1.00 W/cm2. Females were anesthetized on day 8 of gestation and their abdomens were shaved to assure good acoustic coupling. The animals were strapped on a lucite board and placed vertically into a distilled degassed water bath (30 degrees C) so that the abdomen was fully submerged and centered in the axis of the ultrasonic beam. Insonation was carried out using a PZT transducer with a radius of 1.27 cm and a frequency of 1 MHz under continuous wave conditions. Each animal was placed at a distance of 25 cm from the transducer and exposed to the appropriate intensity for 120 seconds. On day 17 of gestation, the maternal animals were killed, the uterine contents were examined, and live fetuses were weighed and then shipped in cold lactated Ringer's solution from Maryland to Arkansas. Fetuses were examined on the day following maternal sacrifice for external and visceral defects and skeletons were prepared and examined subsequently. Slight but significant differences were detected between the cage control and sham-exposed groups. No statistically significant changes were seen that could be attributed to ultrasound exposure, although there was a slight increase in the incidence of malformed fetuses and the occurrence of multiple malformations in individual fetuses as intensity of the ultrasonic exposure increased.

Animals↗
PubMed1983

Internal geometry of arterial bifurcations.

The internal geometries of 137 arterial bifurcations were measured, using enlarged angiographic pictures, to determine the position of the apex of each bifurcation in relation to the ostium of the parent artery. The measurements, relating to different parts of the cardiovascular system of man and some to that of rabbit and pig, were compared with each other and with a theoretical model of an 'optimum' arterial bifurcation. The results were found to be consistent with a position of the apex which is optimum from the point of view of local hemodynamics. In that position, the apex lies on a straight dividing streamline which divides the flow in the parent artery in the proportion required by the two branches.

Animals↗
PubMed1983

Effects of hepatic function on vancomycin clinical pharmacology.

Using a recently developed radioimmunoassay, we performed 15 vancomycin pharmacology studies in cancer patients with infections. Vancomycin (500 mg) was infused intravenously for 30 min every 6 h for up to 7 days. The plasma disappearance curve was biphasic, with an initial half-life of less than 30 min. The second half-life (t1/2 beta), not dose related, varied from 1.4 to 231 h among the patients. In six studies of patients with normal hepatic functions, the t1/2 beta was 2.6 h; the rate of total clearance was 162 ml/min. In contrast, nine studies of patients with impaired liver function had a much longer t1/2 beta (37 h) and a decrease in the rate of total clearance to 48 ml/min. These factors resulted in an increase in the value of area under the concentration-time curve from 59 to 3,434 micrograms X h/ml. These results have demonstrated the importance of the effects of liver function on vancomycin disposition. The vancomycin dose and schedule should be adjusted for patients with liver impairment.

Adult↗
PubMed1983

Chronic exposure of the eggs and adults of Biomphalaria glabrata (Say) to the molluscicide, nicotinanilide.

Some effects of chronic, low-dosage treatment of Biomphalaria glabrata eggs and adults with nicotinanilide, are reported. The susceptibility of eggs decreased with age. The development and hatching of 0-1 day old eggs could be prevented by continuous exposure to 0.0005-0.001 mg/l-1 whereas prehatch stages had a susceptibility similar to that of adult snails (0.1-0.2 mg/l-1). The possible use of slow-release formulations of nicotinanilide in the control of field populations of snails and schistosomiasis transmission is discussed.

Aging↗
PubMed1982

The effects of marijuana use during pregnancy. I. A preliminary epidemiologic study.

We conducted a prospective study of the effects of marijuana use in 35 pregnancies. Thirty-six age-and parity-matched nonuser pregnancies were selected for comparison. (Users of other illicit drugs were excluded from study.) Users and nonusers were similar with respect to most potentially confounding prenatal risk factors, although users tended to come from lower income and educational backgrounds. Most adverse outcomes of pregnancy were too infrequent to allow reliable comparisons between the groups, but the infants born to users exhibited significantly more meconium staining (57% versus 25% in nonusers). Significant differences in duration of labor were also observed. The findings were not altered by statistical adjustments for various prenatal differences between the groups. Possible reasons for these findings are discussed. We also address the implications of these findings for further research.

Adolescent↗
PubMed1982

Arterial branching in various parts of the cardiovascular system.

Angiographic pictures of vascular beds in various parts of the cardiovascular system were analyzed to study the geometrical structure of arterial bifurcations. The sites of arterial bifurcations were enlarged individually, and measurements were made of the branching angles and branch diameters at each site. Results from various parts of the cardiovascular system of man, and some from rabbit and pig, were compared with each other. The measurements were also compared with "optimum" values of branching angles and branch diameters which have been predicted by various theoretical studies. In general the measurements were found to give support to the theoretical premise that branching angles and branch diameters in the cardiovascular system are dictated by certain optimality principles which aim to maximize the efficiency of the system in its fluid-conducting function. In some parts of the system, however, the measured angles and diameters were found to be decidedly lower than those predicted by theory.

Animals↗
PubMed1982

Phosphorylation and methylation of proteins during Myxococcus xanthus spore formation.

Post-translational modification of proteins was examined during the life cycle of Myxococcus xanthus. A specific pattern of protein phosphorylation was observed in vegetative cells. When spore formation was induced by glycerol, significant changes in the pattern of protein phosphorylation were observed, including the phosphorylation of two membrane proteins. In in vitro experiments, the same membrane proteins were phosphorylated by ATP when the membrane preparation from cells treated with glycerol was used. Changes in the pattern of protein methylation were also observed during spore formation induced by glycerol or fruiting body formation. These results suggest that post-translational protein modification may be required for spore formation or fruiting body formation.

Adenosine Triphosphate↗
PubMed1982

Protein kinase activity of purified Leydig cells: low protein kinase activity causes impaired steroidogenesis by band two cells.

Using a 0-32% continuous metrizamide density gradient, interstitial cells could be separated into five distinct bands. Cells localized in bands 1 (B1), 2 (B2), and 3 (B3) were isolated and incubated for 1h with or without human chorionic gonadotropin (hCG). Both B2 and B3 cells responded to hCG with increased cyclic AMP formation, but only B3 cells produced significantly more testosterone. Protein kinase activity of B2 cells was found to be extremely low compared with B1 and B3 cells. Additional treatment of B3 cells with collagenase did not cause any change in protein kinase activity. These results indicate that decreased protein kinase activity may be responsible for impaired testosterone synthesis in B2 cells.

Animals↗
PubMed1982

Structure and gametogenic potential of seminiferous tubules in ageing mice.

The gametogenic potential of young male CBA/Ca mice aged 4-5 months was compared with that of animals 20-23 months of age which had recently ceased to sire offspring. The older mice had substantially lower circulating levels of testosterone and smaller testes. Testicular and epididymal spermatozoa were reduced in number, had more abnormal forms and fewer were progressively motile. Ageing seminiferous tubules varied in the degree of functional atrophy from complete depletion of germ cells to maintenance of sperm production. They were enclosed by a thickened basal lamina and more collagenous connective tissue and occasionally allowed the penetration of lanthanum between Sertoli cells into the ad-luminal compartment. There was no evidence of autosensitization to sperm antigens.

Aging↗
PubMed1982

The influence of the size of the lens in ocular disease.

The mechanism of normal lens growth is considered. This involves both the surface accretion of new fibres and the central compaction of aging fibres. When lens growth is abnormal, it is shown to be retarded in most conditions, but accelerated in diabetes. The relationship between lens growth and ocular disease, in particular angle-closure glaucoma, is discussed.

Aging↗