PubMed Health⌕ Search

Biomedical subjects

K Larson

Publications and source records attributed to K Larson.

At least 37 records · Page 2Linked to original sources
PubMed1989

Energy expenditure during normo- and overfeeding in peripubertal children of lean and obese Pima Indians.

We investigated the hypothesis that peripubertal children born to obese parents have a lower 24-h energy expenditure during "weight maintenance" and/or in response to overfeeding when compared with children born to normal-weight parents. Sixteen Southwestern American Indians (12.4 +/- 1.4 yr, 55.5 +/- 14.1 kg, 30 +/- 8% body fat), eight offspring from obese parents [body mass index (BMI) = 40 +/- 6 kg/m2], and eight offspring from thin parents (BMI = 24 +/- 3 kg/m2) were admitted for 8 days to our metabolic ward. The 24-h energy expenditure was measured under eucaloric conditions and on the 3rd day of progressive overfeeding of a mixed diet, i.e., 150, 200, and 200% of weight maintenance on day 1, 2, and 3 of overfeeding. At base line, offspring of obese parents were heavier (64 +/- 15 vs. 47 +/- 6 kg, P less than 0.05) and tended to be fatter (34 +/- 8 vs. 26 +/- 9% body fat, P = 0.07), with a higher absolute fat mass (22 +/- 9 vs. 13 +/- 4 kg body fat, P less than 0.05) when compared with offspring of thin parents. During both normo- and over-feeding, the larger part of the variance in 24-h energy expenditure in the conditions of a respiratory chamber was accounted for by differences in fat-free body mass (54 and 68%, respectively), whereas differences in the level of spontaneous physical activity accounted for another 19 and 21%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Journal of Manipulative & Physiological Therapeutics: a bibliographic analysis.

The first 9 years of the Journal of Manipulative and Physiological Therapeutics (JMPT) (1978-1986) were surveyed to determine concentrations of research activity, educational backgrounds of contributors, sources of funding for chiropractic science, and the volume and kinds of research in chiropractic. Most articles were authored by chiropractors but a fourth of all articles included contributors with scientific/academic doctorates. Most chiropractors were affiliated with a chiropractic college, but collaboration among chiropractic colleges was rare. A recent increase in contributions from private practitioners was also evident. Authors with medical training were uncommon (6%). National College and Canadian Memorial together accounted for 43% of all articles, and 72% of papers whose authors gave chiropractic college affiliations. Authors acknowledged 30 funding sources, and the Foundation for Chiropractic Education and Research (FCER) accounted for a third of all grants (18 of 55). Empirical studies increased in frequency from 1978 to 1986, but accounted for less than half of the papers. Case reports have been the most common form of original data report; 39 were published in JMPT during the 9 year period. Controlled clinical trials of chiropractic healing methods were extremely rare (3 of 334 papers). A need for greatly expanded clinical research in chiropractic is suggested.

Abstracting and Indexing↗
PubMed1988

An interdisciplinary psychoeducation program for schizophrenic patients and their families in an acute care setting.

A psychoeducation program in an acute care inpatient psychiatric setting involves schizophrenic patients and their families in a range of educational interventions that are responsive to their particular strengths and vulnerabilities. Patients receive one-on-one instruction about their illness from a psychiatrist and the nursing staff and learn community living skills in classes and tutorials conducted by occupational therapists. Families discuss ways of coping with the patients' illness in a series of meetings with a social worker, and they attend workshops led by a team of clinicians and an administrator, who advise them of current perspectives on the illness and its management and about how to negotiate the mental health system. A mental health library keeps staff, family, and patients abreast of recent literature about schizophrenia. The authors believe the program prepares patients to live in the community better than do programs whose goals are limited to symptom reduction or crisis intervention.

Adaptation, Psychological↗
PubMed1987

Inhibition of postbinding target cell lysis and of lymphokine-induced enhancement of human natural killer cell activity by in vitro exposure to ultraviolet B radiation.

In vitro exposure of human peripheral blood mononuclear cells (PBMC) to ultraviolet B (uvB) radiation has been shown to inhibit natural killer (NK) cell-mediated cytotoxicity in a dose-dependent fashion. The purpose of this study was to examine the manner by which uvB produced these deleterious effects. Inhibition of NK activity was not due to lethal injury to NK cells since the viability of cell populations enriched for NK activity was greater than 90% with the uvB doses employed. uvB appeared to directly affect NK cells since procedures which removed suppressor mechanisms, such as removal of monocytes and pharmacologic inhibition of the cyclooxygenase pathway, failed to reverse the response. Furthermore, no suppression of activity of unirradiated NK cells could be produced by coincubation of unirradiated NK cells with uv-irradiated NK cells. When the single cell assay for binding and killing was employed to determine at which stage in the lytic sequence inhibition occurred, it was found that binding was normal but lysis of bound targets and the recycling capacity of active NK cells were markedly reduced. At uvB doses above 50 J/m2, both interferon alpha (IFN-alpha) and interleukin 2 (IL-2) were ineffective in augmenting NK cell-mediated cytotoxic reactions after cells had been irradiated with uvB. Furthermore, incubation of NK cells with IFN-alpha prior to irradiation failed to protect against the inhibitory effects. These studies provide evidence that in vitro exposure of NK cells to uvB radiation inhibits their function by a direct nonlethal effect and that this inhibition occurs selectively at the postbinding stage of target cell lysis.

Cytotoxicity, Immunologic↗
PubMed1985

In vitro models of mutagenesis.

The bypass of lesions in DNA with insertion of nucleotides opposite damaged bases has been studied as a model for mutagenesis in an in vitro system. Lesions introduced by dimethyl sulfate at adenines and by ultraviolet light at pyrimidine dimers act as termination sites on both double- and single-stranded DNA templates. Base selection opposite noninformational lesions is, in part, a property of the polymerases: different polymerases have different selectivities although all polymerases tested seem to prefer purines. The ability to insert "incorrect" bases is determined in part by the sequence 5' to the lesion on the template strand. The hypothesis that damaged purines tend to result in transversions can be applied to published data on activation of the c-ras oncogene.

Base Sequence↗
PubMed1983

Cellular aspects of DNA repair.

DNA repair reactions are under cellular control. In bacteria, the reactions removing 0(6)-methylguanine and 3-methyladenine are inducible. It is not clear whether similar inducibility occurs in human lymphoblastoid cells. Nonetheless, the ability to manufacture the 0(6)-methylguanine acceptor protein does seem to be controlled by some chromosomal mechanism which is superimposed on the structural gene. This control system may affect reactions other than the removal of 0(6)-methylguanine. Insofar as this is so, transformed human lymphoblastoid cells have a system reminiscent of that found in bacteria.

Animals↗
PubMed1982

Minerals in the hair and nutrient intake of autistic children.

The concentrations of calcium, magnesium, zinc, copper, lead, and cadmium were determined in scalp hair samples from a group of 12 autistic children and a group of 12 nonautistic control children. The only statistically significant difference between median concentrations of minerals in the hair from the two groups was a 62% decrease in the concentration of cadmium in the hair of autistic children. This decrease was probably not physiologically significant. The nutrient intake of autistic children as a group was found to be adequate and typical of well-fed American children. It was concluded that the children in neither the autistic nor the nonautistic control group showed evidence of toxicity or deficiency of the minerals or nutrients studied, but because of food idiosyncracies nutrient intake should be monitored.

Animals↗
PubMed1982

Regulation of the capacity for O6-methylguanine removal from DNA in human lymphoblastoid cells studied by cell hybridization.

Hybrids were made between a ouabain-resistant, thioguanine-resistant human lymphoma line able to remove O6-methylguanine from its DNA (Mex+) and human lymphoblastoid lines deficient in this capability (Mex-). The formation of hybrids was confirmed by chromosomal analysis. Hybrid cells had an O6-methylguanine removal capacity per mole of guanine about one third to one half that of the Mex+ parents, i.e., about the same per cell. Cell hybrids removed the same amount of the alkylation adduct 3-methyladenine as did their parents per mole of guanine, i.e., about twice as much per cell. Although the cell hybrids had intermediate resistance to the cytotoxic action of N-methyl-N'-nitro-N-nitrosoguanidine used to induce O6-methylguanine and 3-methyladenine, there is evidence that the ability to remove O6-methylguanine and resistance to the cytotoxic effect of N-methyl-N'-nitro-N-nitrosoguanidine are dissociable characteristics.

Adenosine↗
PubMed1978

Characterization of glutathione reductase from porcine erythrocytes.

Glutathione reductase (NAD(P)H: oxidized-glutathione oxidoreductase, EC 1.6.4.2) was purified to homogeneity from porcine erythrocytes by use of affinity chromatography on 2',5'-ADP-Sepharose 4-B. Analytical ultracentrifugation experiments were analysed to give the following physical parameters for the enzyme: s20,w = 5.7 S, D20,w = 50 microgram2/s, and Mw = 103 000 (protein concentration, 0.5 mg/ml). The frictional ratio was 1.37 and the Stokes radius was 4.3 nm. The enzyme molecule is a dimer composed of subunits of equal size each containing a FAD molecule. The amino acid compositions and circular dichroism spectra of the porcine and human enzymes indicated extensive structural similarities. The isoelectric point was at pH 6.85 (at 4 degrees C). The absorption spectrum of the oxidized enzyme had maxima at 377 and 462 nm. In vivo the enzyme appears to be partially reduced. At a physiological concentration of reduced glutathione the apparent Michaelis constants for glutathione disulfide and NADPH were higher than in the absence of reduced glutathione. At 0.15 M ionic strength the catalytic activity obtained with NADPH as reductant was optimal at pH 7 and more than 200 times higher than that obtained with NADH. S-sulfoglutathione and some mixed disulfides of glutathione were poor substrates with the exception of the mixed disulfide of coenzyme A and reduced glutathione. The purified enzyme displayed low transhydrogenase activity with oxidized pyridine nucleotide analogs and diaphorase activity with 2,6-dichlorophenolindophenol as acceptor substrates; both NADPH and NADH served as donors.

Amino Acids↗
PubMed1978

Topical effects of 16,16 dimethyl prostaglandin E2 on gastric acid secretion and mucosal permeability to hydrogen ions in dogs.

The effects of luminal instillation of 16,16 dimethyl PGE2 (dmPGE2) on gastric acid secretion and back diffusion of H+ were studied in anaesthetised dogs which were prepared with a segment of the greater curvature of the stomach mounted in a double lumen chamber. This model permitted simultaneous evaluation of two segments of mucosa, one control and the other test, supplied by the same vascular pedicle. Imfusion of histamine (1.0 microgram/kg/min, intravenously) stimulated brisk acid secretion in both chambers. Topical application of 25 microgram dmPGE2 in 20 ml 0.3 M HC1 to the test chamber for 30 minutes prevented acid secretion from the test mucosa during a second histamine infusion. Since the control chamber showed no evidence of inhibition this indicates that dmPGE2 acted directly on the secretory cells, rather than after absorption from the bloodstream. This observation, however, does not exclude a possible local effect on mucosal blood flow. Direct exposure of the gastric mucosa to dmPGE2 increased the rate of back diffusion of H+ because of disruption of the permeability barrier, indicated by increased H+ back diffusion, Na+ efflux, and a reduction in potential difference. However, H+ loss was small compared to the reduction in acid output.

Animals↗
PubMed1978

Oxygen consumption during cimetidine and prostaglandin E2 inhibition of acid secretion.

Oxygen consumption was determined during cimetidine and 16,16-dimethyl prostaglandin E2 inhibition of acid secretion in exteriorized segments of the greater curvature of dog stomach. Steady-state acid secretion during histamine infusion correlated well with O2 consumption (r = 0.85, P less than 0.01). Cimetidine and 16,16-dimethyl prostaglandin E2 inhibition of acid secretion produced a reduction of oxygen consumption to resting levels. In contrast, oxygen consumption did not decrease appreciably during thiocyanate inhibition of acid secretion. These observations suggest that the inhibitory action of cimetidine and 16,16-dimethyl prostaglandin E2 precedes, whereas that of thiocyanate is at a point beyond the transfer of energy to the process of acid production.

Animals↗