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Biomedical subjects

D Peterson

Publications and source records attributed to D Peterson.

At least 181 records · Page 10Linked to original sources
PubMed1992

Cloning, expression, and nucleotide sequence of glgC gene from an allosteric mutant of Escherichia coli B.

The Escherichia coli B mutant strain CL1136 accumulates glycogen at a 3.4- to 4-fold greater rate than the parent E. coli B strain and contains an ADPglucose synthetase with altered kinetic and allosteric properties. The enzyme from CL1136 is less dependent on the allosteric activator, fructose 1,6-bisphosphate, for activity and less sensitive to inhibition by AMP than the parent strain enzyme. The structural gene, glgC, for the allosteric mutant enzyme was selected by colony hybridization and cloned into the bacterial plasmid pBR322 by insertion of the chromosomal DNA at the PstI site. One recombinant plasmid, designated pKG3, was isolated from the genomic library of CL1136 containing glgC. The cloned ADPglucose synthetase from the mutant CL1136 was expressed and characterized with respect to kinetic and allosteric properties and found to be identical to the enzyme purified from the CL1136 strain. The mutant glgC was then subcloned into pUC118/119 for dideoxy sequencing of both strands. The mutant glgC sequence was found to differ from the wild-type at the deduced amino acid residue 67 where a single point mutation resulted in a change from arginine to cysteine.

Allosteric Regulation↗
PubMed1992

Cadmium effects on bone metabolism: accelerated resorption in ovariectomized, aged beagles.

The purpose of this study was to evaluate, in an animal whose skeleton is comparable to humans, the combined effects of estrogen depletion and Cd exposure on bone resorption by monitoring skeletal release of 45Ca and to determine whether Cd-induced bone resorption occurred independent of osteotropic hormone changes and renal dysfunction. Cd exposure following ovariectomy or sham surgery was for 7 months: 1 month by oral ingestion of capsules (1, 5, 15, 50 ppm) and 6 months via drinking water (15 ppm). Serum and fecal 45Ca were increased at 1 week following ovariectomy (OV) (54 +/- 9% and 122 +/- 40%, respectively), but this response was attenuated by 2 weeks. Five of seven exposed dogs had increased serum and fecal 45Ca during the 50-ppm Cd capsule period (15-40% and 15-190%, respectively). Serum 45Ca levels in OV/+Cd dogs showed a significant and consistent increase within 1 week of initiating each of three separate Cd.H2O exposure cycles. Blood Cd levels increased over time from 2 to 15 micrograms/l, coinciding with the elevated serum 45Ca concentrations. No correlation was observed between serum 45Ca increases and parathyroid hormone, 1,25-(OH)2-vitamin D, or calcitonin. No effects of ovariectomy and/or Cd were observed in total serum Ca, calciotropic hormone concentrations, serum or urinary phosphorus and creatinine, creatinine clearance, or urinary specific gravity. Urinary Cd concentrations ranged from 7 to 50 micrograms/l in exposed dogs but were not detectable in nonexposed dogs. Urinary protein concentrations showed no differences between groups. Cd increased bone resorption (skeletal 45Ca release) in ovariectomized and sham-operated dogs without renal dysfunction or calciotropic hormone interaction. Based on our results, Cd is an exogenous factor which exacerbates bone mineral loss in postmenopausal osteoporosis.

Aging↗
PubMed1992

Effect of superoxide dismutase and catalase on regional dysfunction after exercise-induced ischemia.

This study was designed to test the hypothesis that the oxygen free radical scavengers superoxide dismutase (SOD) and catalase may reduce myocardial "stunning" after exercise-induced ischemia. To test this hypothesis, 8 mongrel dogs performed treadmill exercise for 10 min in the presence of a flow-limiting coronary artery stenosis. Regional left ventricular function was measured with ultrasonic microcrystals implanted to measure regional wall thickening. Regional myocardial perfusion was measured with radioactive microspheres. The combination of SOD (5 mg/kg iv) and catalase (5 mg/kg iv) did not affect heart rate, blood pressure, coronary artery flow, or regional myocardial blood flow at rest, during exercise, or in the postexercise period. SOD and catalase had no effect on regional wall thickening at rest before exercise. During exercise in the absence of a coronary artery stenosis, thickening was slightly lower during SOD and catalase infusion (27 +/- 11.0 vs. 30.8 +/- 11.5%, SOD vs. control P = 0.05). During exercise in the presence of a coronary artery stenosis, there was no difference in thickening. Infusion of SOD and catalase affected neither the transient rebound function occurring early after exercise nor the prolonged period of stunning. These results indicate that the myocardial stunning that follows exercise-induced ischemia is unlikely to be mediated by oxygen free radicals.

Animals↗
PubMed1992

Vitamin B12 and folate status of a selected group of free-living older persons.

Vitamin B12 and folate status was determined in 50 male and 47 female free-living subjects (65-77 years) in winter and summer. The mean intake calculated from 3-day food records met the Canadian recommended intake (RNI) for both gender and season, however, probability analysis of dietary data revealed a number of subjects at risk of deficiency. Although the mean plasma levels were within the acceptable range for both vitamins, some 9 to 14% of individual subjects had folate plasma levels below normal. Fewer subjects had subnormal plasma vitamin B12 levels. Although mean values for dietary intake and plasma concentration of folate and vitamin B12 may indicate nutritional adequacy, a proportion of an older population may be at nutritional risk.

Aged↗
PubMed1992

Clinical, epidemiologic, and virologic studies in four clusters of the chronic fatigue syndrome.

BACKGROUND: The purpose of this study is to provide a case definition of chronic fatigue syndrome in an outbreak occurring in the Nevada-California region to evaluate candidate etiologic agents and observe the natural history of the illness. METHODS: Patients diagnosed as having chronic fatigue syndrome were studied by repeated interviews, questionnaires, and blood collection over a 3-year period. Serum samples were tested for antibodies to Epstein-Barr virus, human herpesvirus-6, and human T-lymphotropic viruses I and II. Leukocytes from typical cases were also assayed for human T-lymphotropic viruses I and II. RESULTS: Cases were defined as persons who had: (1) severe persistent fatigue following an acute illness appearing in an individual with no previous physical or psychological symptoms; (2) presenting signs and symptoms of an acute infection; (3) severe and persistent headache and/or myalgias; and (4) abrupt change in cognitive function or the appearance of a new mood disorder. After 3 years of follow-up, almost all study subjects were able to return to pre-illness activity. None of the viruses evaluated--human T-lymphotropic viruses I and II, Epstein-Barr virus, or human herpesvirus-6--could be etiologically linked to these outbreaks. CONCLUSION: Clinical features of outbreaks of chronic fatigue syndrome differ sufficiently to suggest different etiologic agents. Giardiasis appears to have precipitated one of the four clusters in this study but the cause(s) of the other three outbreaks is as yet uncertain. The overall prognosis of chronic fatigue syndrome is usually favorable.

Antibodies, Viral↗
PubMed1991

Prevalence of hepatitis C in tropical communities: the importance of confirmatory assays.

The prevalence of antibody to hepatitis C virus (HCV) was estimated in 3 tropical populations using 2 screening ELISAs to detect antibody to the c100-3 antigen and 2 supplementary assays designed to test the specificity of these tests. Two hundred and eighty-six of 385 (74.2%) sera from Kiribati, 17 of 138 (12.3%) sera from Vanuatu, and 39 of 173 (22.5%) sera from Zaire were reactive in the initial screening assay. The proportion of reactive sera which were also reactive in the second screening ELISA varied between populations (55.1% in Kiribati, 85.1% in Vanuatu, and 39.2% from Zaire). Reactive sera were selected at random for confirmatory testing. Only 3 of 49 (6.12%) of sera from Kiribati and 1 of 14 (4.76%) of sera from Vanuatu positive in the initial ELISA were reactive in the confirmatory assays. The proportion of confirmed positive sera from Zaire was higher 8 of 28 (28.5%). Based on the results of these supplementary assays the estimated prevalence of anti-HCV in these populations is 4.8% in Kiribati, less than 1% in Vanuatu, and 6.4% in Zaire. Reliance on a single screening ELISA to estimate the prevalence of anti-HCV in stored sera from tropical communities may lead to a gross over-estimate of the true prevalence in these populations.

Antibody Specificity↗
PubMed1991

Dietary tocotrienols reduce concentrations of plasma cholesterol, apolipoprotein B, thromboxane B2, and platelet factor 4 in pigs with inherited hyperlipidemias.

Normolipemic and genetically hypercholesterolemic pigs of defined lipoprotein genotype were fed a standard diet supplemented with 50 micrograms/g tocotrienol-rich fraction (TRF) isolated from palm oil. Hypercholesterolemic pigs fed the TRF supplement showed a 44% decrease in total serum cholesterol, a 60% decrease in low-density-lipoprotein (LDL)-cholesterol, and significant decreases in levels of apolipoprotein B (26%), thromboxane-B2 (41%), and platelet factor 4 (PF4; 29%). The declines in thromboxane B2 and PF4 suggest that TRF has a marked protective effect on the endothelium and platelet aggregation. The effect of the lipid-lowering diet persisted only in the hypercholesterolemic swine after 8 wk feeding of the control diet. These results support observations from previous studies on lowering plasma cholesterol in animals by tocotrienols, which are naturally occurring compounds in grain and palm oils and may have some effect on lowering plasma cholesterol in humans.

Animals↗
PubMed1991

Hospital-physician relations. Beyond courtship to the ties that bind.

Years ago, perhaps when relationships were simpler and possibly more enduring, physicians had one request of hospitals, namely, "Give us a good workshop in which to practice." With increased diversification and competition in the health care environment, their demands have become more complex, even as hospitals have become more eager to please. Hospitals and physicians know they need each other, but the hospital usually plays the role of the suitor. It is a role that can involve wasteful investments in time, energy and money if the courtship isn't inspired by real knowledge of what physicians actually want from the relationship.

Data Collection↗
PubMed1991

Role of gastric colonization in the development of pneumonia in critically ill trauma patients: results of a prospective randomized trial.

Critically ill trauma patients were entered in a prospective, randomized trial to determine the role of gastric colonization in the development of pneumonia. Trauma patients admitted to the SICU were randomized to receive antacids (n = 27), continuous IV cimetidine (n = 32), or sucralfate (n = 30). Quantitative nasogastric tube (NGT) cultures were obtained biweekly and correlated with gastric pH, the incidence of pneumonia, and the incidence of pneumonia caused by an organism previously isolated from the stomach (percentage of gastric source of pneumonia--% GSP). Patients receiving antacids had a significantly greater pH than those receiving cimetidine (5.6 +/- 1.03 vs. 4.7 +/- 1.03; p = 0.006). However, there was no significant difference between the overall incidence of pneumonia, the percentage of NGT isolates greater than 10(6)/ml, or the % GSP. The gastric bacteriology of the three subgroups was nearly identical, with Candida albicans, Enterococci, and beta-hemolytic Streptococci being the most frequently isolated organisms. Gastric growth of organisms preceding their appearance in the blood occurred in 5 of 89 (5.6%) patients. These results suggest that 1) in trauma patients, the incidence of pneumonia is not increased by the use of stress ulcer prophylactic agents that elevate gastric pH; 2) increases in gastric pH progressively increased the number of intragastric bacteria but this did not correlate with an increased incidence of % GSP; and 3) while organisms in the upper intestinal tract may be pathogens for pneumonia, they are uncommonly a source of bacteremia in seriously injured patients.

Adolescent↗