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Biomedical subjects

G Nichols

Publications and source records attributed to G Nichols.

At least 19 recordsLinked to original sources
PubMed1989

Umbilical cord occlusion but not increased plasma T3 or norepinephrine stimulate brown adipose tissue thermogenesis in the fetal sheep.

Nonshivering thermogenesis is normally inactive in utero but increases with supplemental oxygenation and again after occlusion of the umbilical cord. To test the hypothesis that brown fat responses are triggered by the surge in triiodothyronine (T3) which occurs at birth, we studied 7 fetal sheep at 132-143 days gestation. Fetuses were first cooled 2-3 degrees C by circulating cold water through an external coil in the amniotic fluid and then ventilated with oxygen in utero to raise arterial PO2 to 109 +/- 10 (SEM) mmHg. An hour later T3 was infused intravenously to elevate and maintain plasma levels at 39.8 +/- 6.1 nmol/l, some 40-50 times basal levels. Indices of brown heat production did not rise during the next 30 min. Following snaring of the umbilical cord, however, plasma free fatty acid levels increased 400% to 423 +/- 91 mEq/l, plasma glycerol rose 350% to 766 +/- 168 mmol/1, and the temperature difference between brown fat and body core widened to 0.59 +/- 0.13 degrees C during the next 30 min. Whole body oxygen consumption peaked at 23.1 +/- 2.8 ml.min-1.kg-1 body weight. These responses to cord occlusion were similar with and without T3 administration. Changes in plasma catecholamines during these experiments did not correlate with the onset of nonshivering thermogenesis. We conclude that the rise in T3 or the changes in plasma catecholamines which occurs at birth are not causally related to the onset of nonshivering thermogenesis.

Adipose Tissue, Brown↗
PubMed1988

Progressive isoinertial lifting evaluation. I. A standardized protocol and normative database.

Dynamic tests of trunk strength and lifting capacity have become more popular in recent years, offering certain advantages over static isometric tests in measuring patient progress in functional restoration programs for spinal disorders. However, equipment for performing such tests is expensive to buy, complex to run, and requires technical expertise and clinical volume unavailable in most physician offices. In this study, a new dynamic test known as Progressive Isoinertial Lifting Evaluation (PILE) is described, which draws upon prior psychophysical and isoinertial methods. An industrial sample of 61 male and 31 female incumbent workers were tested using the PILE, and a variety of anthropometric normalizing factors were evaluated. The isolation of an "Adjusted Weight" (AW) normalizing factor is documented, after which normative data are presented for male and female workers utilizing lumbar (0-30 inches) and cervical (30-54 inches) dynamic protocols.

Adult↗
PubMed1988

Progressive isoinertial lifting evaluation. II. A comparison with isokinetic lifting in a disabled chronic low-back pain industrial population.

The Progressive Isoinertial Lifting Evaluation (PILE), as described in Part I of this series of articles, is a simplified test combining psychophysical and isoinertial protocols to provide an unconstrained lifting assessment. In the second part of this study, 100 chronically disabled low-back pain patients (57 men and 43 women) were studied at two points: 1) at initial evaluation, when referred for possible entry into a comprehensive Functional Restoration treatment program; and 2) at the conclusion of the treatment (an average 7 weeks later). Results of simultaneous lumbar PILE and Cybex Liftask (Lumex, Ronkonkoma, NY) tests are presented, showing that patients may frequently double or triple initial lifting capacity after undergoing the functional restoration training program, achieving lifting levels at or above normal for incumbent industrial workers. Overall, results demonstrate that the PILE test can be an effective baseline screening test for lifting capacity under certain circumstances. Although several drawbacks affecting the PILE as an isolated test are discussed, its usefulness as part of a battery of physical capacity tests making up a quantitative functional evaluation is clearly demonstrated. Finally, the potential use of PILE as a safe, inexpensive, simple, and relevant screening test for frequent lifting capacity in worker selection is discussed.

Back Pain↗
PubMed1987

Flow cytometric measurement of antiplatelet antibodies.

A flow cytometric technic was developed to detect platelet surface-bound immunoglobulin in patients with thrombocytopenia. Elevated platelet surface IgG and/or IgM was detected in 90.9% of patients with immune thrombocytopenia purpura (ITP). False positive results occurred in 9.3% of patients with nonimmune thrombocytopenia usually associated with sepsis. False negatives occurred most frequently in adults with chronic ITP. Measurement of platelet surface immunoglobulin with this flow cytometric technic helps differentiate immune from nonimmune thrombocytopenia.

Blood Platelets↗
PubMed1985

Studies on uptake and catabolism of vascular histamine in spontaneously hypertensive rats.

Reduced vascular histamine content is postulated to contribute to increased peripheral vascular resistance in experimental hypertension in rats. Experiments were conducted to examine histamine content, in vitro uptake ability and in vitro catabolism of histamine in blood vessels from 12-week-old spontaneously hypertensive rats (SHR) and age-matched normotensive controls. Histamine content of mesenteric artery and abdominal aorta from SHR was significantly reduced (P less than .05) when compared to Wistar-Kyoto normotensive controls. This finding confirms a similar observation of reduced vascular histamine content in deoxycorticosterone acetate salt hypertensive rats reported from our laboratory. This reduction in histamine content may be more prevalent in arteries because the decrease was not observed in the portal vein from SHR. Uptake of [14C]histamine into mesenteric artery and abdominal aorta was unchanged in SHR compared to Wistar-Kyoto controls. No significant differences between slopes for uptake regression lines were observed for either mesenteric artery or abdominal aorta. Mesenteric artery exhibited a greater capacity of [14C]histamine accumulation than aorta and significant reductions in accumulation of labeled histamine after 20 and 60 min were found in this vessel from SHR. Because metabolism of histamine was inhibited by aminoguanidine, this reduction may reflect diminished retention by histamine storage sites. In vitro I-[14C]histidine uptake was significantly increased in abdominal aorta and iliac artery but not mesenteric artery from SHR. These differences were also present at the later accumulation periods of 20 and 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

U.K. deep diving trials.

Using a breathing medium of 40 kPa oxygen, remainder helium, 18 volunteer subjects participated in a series of 15 exposures to pressures equivalent to depths of 180-540 m s.w. The time of exposure at these pressures was mostly 2 days, except for the 540 m s.w. exposure, when 6 days were spent at full pressure. Compression procedures, based upon placing 'stages' at 60 m s.w. intervals, evolved with experience and proved to be a highly successful way of achieving acceptable pressure-time courses. Decompression combined slow linear release of pressure with overnight halts for sleep. On one occasion a depth of 660 m s.w. was reached by breathing 40 kPa oxygen, 10% nitrogen, remainder helium. Throughout all exposures, teams of investigators followed the changes in cardiovascular, respiratory, haematological, neurophysiological and metabolic status, and mental performance of the volunteers. Some major findings were that the neurophysiological and behavioural changes could be assigned to the motor, or vestibular, or cerebral, or autonomic systems, and were mainly first observed during compression. The subjects suffered, apparently from severe nitrogen narcosis, when breathing 10% (by volume) nitrogen in oxygen-helium at 420 m s.w. Lung ventilation was remarkably adaptable to the oxygen requirements of exercise at all depths, but cardiac output was adversely affected at 540 m s.w., particularly for heavier workloads. Ventilatory responses to carbon dioxide were significantly elevated after diving. Thermal balance was seen to be precarious, but nevertheless it was achieved by the normal subjective assessments of comfort. Water loss was affected by diminished evaporation from the skin. Skin temperature sensitivity was changed and took many days after the dives to return to normal. Energy requirements increased for work purposes, but basal metabolic rate was undisturbed. Body chemistry altered at pressures in excess of 300 m s.w., for example thyroid hormone and nitrogen balances were affected. No decompression sickness was encountered until the pressures were low, but marked haematological changes could occur during decompression. Every change that occurred during these dives reverted to normal, mostly before the end of the decompression. It is concluded that diving with oxygen-helium breathing mixtures to depths as great as 540 m s.w. can be effective and safe. An attempt is made to assess the physiological significance of the principal findings.

Adult↗
PubMed1984

Histamine uptake and metabolism in the blood vessels of rats.

In vitro radiolabeled histamine uptake and metabolism were investigated in abdominal aorta, iliac artery, mesenteric artery and hepatic portal vein of the rat. Histamine uptake was rapid and remained linear over the initial 10 min of the accumulation period. The uptake rate was temperature sensitive with marked reduction in rate at 0 degrees C. The accumulation at 0 degrees C represents nonspecific uptake. The uptake of histamine was observed to be related to the amount of tissue stores of histamine as well as extracellular sodium ion concentration. The only histamine metabolite detected in the vasculature examined was imidazoleacetic acid representing almost 80% of the chromatogram radioactivity. This observation indicates the primary metabolic pathway for histamine in rat vasculature involves the enzyme, diamine oxidase.

Animals↗
PubMed1983

Skin antisepsis during steady-state hyperbaric exposure and subsequent decompression.

A custom-made container for the transfer of bacteriological sampling pads was used in a trial to test the feasibility of human skin disinfection during saturation or steady-state diving and subsequent decompression. Analysis of the results of colony counting and typing from 6 days of pre- and postcleansing samples taken during a recent saturation dive indicates that the skin of hyperbaric chamber occupants can be effectively sterilized in the event of a need to prepare for anesthetic or surgical procedures while still under pressure. A separate survey was also made to establish any pattern of change in bacterial flora of the chamber interior during the trial. Results of this survey are briefly discussed.

Antisepsis↗
PubMed1978

Femoral hypoplasia-unusual facies syndrome, from another viewpoint.

A female infant with the "femoral hypoplasia-unusual facies" syndrome is presented. Most of the findings observed in this child have also been described in the "caudal regression syndrome". The similarity and probable identity between these two syndromes is discussed on the basis of our patient and others from the literature.

Abnormalities, Multiple↗
PubMed1978

Synthesis and antiinflammatory activity of some 1,2,3- and 1,2,4-triazolepropionic acids.

All possible "nonadjacent" phenyltriazolepropionic acids were synthesized and tested for antiinflammatory activity. Two of the isomers displayed activity approximately equal to phenylbutazone: the 4-phenyl-1,2,3,-triazole-2-propionic acid (7) and its reverse counterpart, 2-phenyl-1,2,3-triazole-4-propionic acid (6). The other five isomers were inactive. Since these seven acids are geometrically congruent and possess similar lipophilic characters, antiinflammatory activity must depend on some property that is a function of how the carbon and nitrogen atoms are arranged in the triazole ring.

Animals↗