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M Wolfe

Publications and source records attributed to M Wolfe.

At least 37 records · Page 2Linked to original sources
PubMed1992

Stable isotope tracer analysis by GC-MS, including quantification of isotopomer effects.

In metabolic tracer studies it is frequently useful to infuse tracers that are differently labeled variants of the same molecule. These tracers are known as isotopomers. Analysis of the enrichment of each isotopic analogue can be accomplished by gas chromatography-mass spectrometry (GC-MS). However, the raw GC-MS data must be corrected to give the information required. This paper addresses how to transform the raw GC-MS data, consisting of relative abundance ratios at specific ion masses, into relative molar ratios of tracer and tracee molecules. Several correction factors are necessary. First, the background must be measured and corrected for, since it is always present in the sample. Second, the abundances in the spectrum of the labeled molecule are different from those in the unlabeled molecule, and this proportionality "skew" is corrected. A third correction factor accounts for the overlapping spectra of two or more isotopomers that cannot be measured independently. The final correction removes the "double vision" effect that may appear in some spectra due to the presence of (M - H)+ species.

Drug Stability↗
PubMed1987

Effect of severe burn injury on substrate cycling by glucose and fatty acids.

Increases in metabolic rate and core temperature are common responses to severe injury. We have investigated the hypothesis that these responses are due to increases in substrate cycling. A substrate cycle exists when opposing, nonequilibrium reactions catalyzed by different enzymes are operating simultaneously. At least one of the reactions must involve the hydrolysis of ATP. Thus, a substrate cycle both liberates heat and increases energy expenditure, yet there is not net conversion of substrate to product. In studies in volunteers (n = 18) and in patients with severe burns who were in a hypermetabolic state (n = 18), we used stable-isotope tracers to quantify substrate cycling in the pathways of glycolysis and gluconeogenesis and a cycle involving the simultaneous breakdown and synthesis of stored triglyceride (triglyceride-fatty acid cycle). The total rates of triglyceride-fatty acid and glycolytic-gluconeogenic cycling were elevated in the patients by 450 and 250 percent, respectively (P less than 0.01). An infusion of propranolol in the patients greatly reduced triglyceride-fatty acid cycling but did not affect gluconeogenic-glycolytic cycling. We conclude that increased substrate cycling contributes to the increased thermogenesis and energy expenditure following severe burns and that the increased triglyceride-fatty acid cycling is due to beta-adrenergic stimulation.

Adolescent↗
PubMed1987

Luteinizing hormone and progesterone concentrations in serum of heifers administered a short half-life prostaglandin (PGF(2alpha)) or long half-life prostaglandin analogue (fenprostalene) on days six or eleven of the estrous cycle.

Two trials were conducted to measure the progesterone (P(4)) decline and luteinizing hormone (LH) surge in serum subsequent to administration of a short half-life (short t (1 2 )) prostaglandin (PGF(2alpha)) or a long half-life (long t (1 2 )) prostaglandin analogue (fenprostalene) on Days 6 or 11 of the estrous cycle. Twenty-five crossbred Shorthorn and five Hereford heifers with a mean weight of 331.4 +/- 29.8 kg were used in both trials. The heifers were randomly allotted to receive either a short t (1 2 ) or long t (1 2 ) prostaglandin treatment on Day 6 or 11 of the estrous cycle. A crossover design for the main effect, treatment (type of prostaglandin), was conducted. Heifers that received PGF(2alpha) in Trial I were given fenprostalene in Trial II and vice versa. Stage of the estrous cycle (day) was the same for each heifer in both trials. Stage of estrous cycle was standardized to either Day 6 or 11 by administering Syncro-Mate B (SMB). Blood was collected every hour for 80 h post injection to quantify LH and P(4) concentrations. There were no significant differences (P > 0.05) between the short t (1 2 ) or long t (1 2 ) for either P(4) or LH profiles. In addition, no differences were detected between stages of the estrous cycle for the timing of the preovulatory surge of LH after prostaglandin administration.

Journal Article↗
PubMed1986

The value of standardized exercise testing in the noninvasive evaluation of mitral stenosis.

The determination of functional impairment is an important portion of the evaluation of patients with mitral stenosis and frequently is instrumental in the determination to proceed with invasive testing. To test the hypothesis that patients with slowly evolving disability from mitral stenosis frequently do not recognize the degree of their limitations and to determine the utility of formal exercise testing, 24 consecutive patients with pure or predominant mitral stenosis were evaluated for NYHA functional category (NYHA class) by historical determination of functional impairment, echocardiographic mitral valve area (echo MVA), exercise duration, estimated maximum oxygen consumption, and functional aerobic impairment during a symptom-limited Bruce protocol exercise test and multiple catheterization-derived parameters. The data revealed no difference in exercise duration or mitral valve area between NYHA classes, but demonstrated an excellent correlation between exercise duration and severity of mitral valve stenosis determined at cardiac catheterization (cath MVA). This relationship was similar to that of echo MVA to cath MVA and exceeded that of exercise time to any other parameter measured during catheterization. Estimation of maximum oxygen consumption or functional aerobic impairment did not improve the exercise duration to valve area relationship. The data presented thus demonstrate that Bruce protocol exercise testing is a valuable adjunct to other noninvasive tests in the initial evaluation of selected patients with mitral stenosis. By virtue of being easily repeated at low risk, exercise testing may also be useful in long term follow-up of medically treated mitral stenosis patients.

Adult↗
PubMed1984

Laboratory basis for the medical management of necrotizing enterocolitis (NEC).

Necrotizing enterocolitis (NEC) is a serious condition affecting the neonate that may be responsive to medical management. This study evaluates the efficacy of supplemental oxygen (FiO2 40% and 50%), systemic antibiotics (ampicillin and gentamicin, cephamandole) and oral antibiotics (trimethoprim-sulfamethoxazole, neomycin and gentamicin) in a weanling rat bowel ischemia model induced by a transient (one minute) occlusion of the superior mesenteric artery. Animals were evaluated for overall survival, duration of survival, presence of bowel necrosis or perforation at seven days. Mortality in ischemic controls was 83.8%. This was reduced to 52% by FiO2 of 50%, and 40% with systemic ampicillin and gentamicin (with or without FiO2 50%) (P less than .001). Length of survival was 3.4 days in controls and increased from 5.4 to 5.9 days in rats given FiO2 50% and/or ampicillin and gentamicin (P less than .001). The incidence of bowel necrosis in controls was 60% and was reduced to 25% in rats given systemic ampicillin and gentamicin and 23.3% with 50% FiO2 and the same antibiotics (P less than .001). Systemic cephamandole and oral antibiotics had no beneficial effects.

Animals↗
PubMed1983

Comparative effects of indomethacin, prostaglandin E1, and ibuprofen on bowel ischemia.

This study evaluates the effects of Indomethacin (IND), Prostaglandin E1 (PGE1), and Ibuprofen (IBP) in a bowel ischemia model. Laparotomy was performed in 80-gram rats (n = 260). Transient ischemia was induced by a one minute occlusion of the superior mesenteric artery. Animals were placed in five experimental groups: (I) ischemic controls (n = 80), (II) PGE1, 80 micrograms/kg IV (n = 20), (III) IBP, 12.5 mg/kg IV (n = 60), (IV) IND 15 mg/kg IV (n = 80) and (V) PGE1 + IND (n = 20). All medications were given just prior to laparotomy. Animals were evaluated for survival, length of survival and the presence of bowel necrosis and/or perforation at seven days. Survival was 18% in controls and was reduced to 5% by IND (p less than .005). Improved survival was observed with PGE1 (35%), TBP (31%) and PGE1 + IND (35%). IND resulted in early death, while PGE1, IBP, and PGE1 + IND all increased the length of survival (p less than .05). IND-treated rats had a high incidence of bowel perforation (greater than 40%). PGE1 reversed this effect when given concomitantly with IND. IBP had a significantly lower incidence of intestinal necrosis. These data suggest that infants treated with IND who are at risk for NEC should be carefully monitored for evidence of bowel necrosis. PGE1 and IBP may have a cytoprotective role in subjects at risk for bowel ischemia.

Alprostadil↗
PubMed1982

Mineral oil vacuum distillation method for nitrosamines in fried bacon, with thermal energy analyzer: collaborative study.

Nine laboratories participated in a collaborative study of a method for determining 6 nitrosamines, dimethylnitrosamine, diethylnitrosamine, dibutylnitrosamine, nitrosopiperidine, nitrosopyrrolidine, and nitrosomorpholine, in the 5-17 ppb range. The coefficients of variation for repeatability were 10.8, 8.5, 10.4, 8.5, 8.7, and 7.8% with corresponding coefficients of variation for reproducibility of 16.4, 12.0, 13.6, 10.8, 11.2, and 10.3% and recoveries of 89.6, 91.6, 84.7, 90.0, 89.6, and 88.1%, respectively. The method was adopted official first action.

Animals↗
PubMed1981

Parasitic disease control in a residential facility for the mentally retarded: failure of selected isolation procedures.

Asymptomatic infection with either Entamoeba histolytica or Giardia lamblia was found in 60 per cent of the residents in an institution for the mentally retarded one year after eradication of these parasites. The residents were then segregated into infected and noninfected groups and drug therapy was again successfully undertaken. The two groups remained separated except during periods of play. A one-year follow-up showed that both study and control groups were equally infected. The failure of segregation was confounded by patient age and infection with nonpathogenic parasites.

Adolescent↗
PubMed1979

Parasitic disease control in a residential facility for the mentally retarded.

Asymptomatic infection with either Entameba histolytica or Giardia lamblia was found in 61 per cent of the residents of a dormitory in an institution for the mentally retarded; two other dormitories had rates of 20 per cent and 22 per cent. Drug therapy was successfully undertaken in all three dormitories, and environmental improvements were introduced in the heavily infected dormitory. A one-year follow-up showed a reduction in parasitic disease in two dormitories but, in the most heavily infected dormitory, infection had returned to pretreatment levels.

Adolescent↗
PubMed1977

Lassa fever: response to an imported case.

In February, 1976, a Peace Corps worker returned to the United States from Sierra Leone with an undiagnosed illness later recognized as Lassa fever. To assess the risk of transmission and to contain a potential outbreak, we identified 552 contacts as having had exposure to the patient before the start of strict isolation procedures, and maintained intensive surveillance on these contacts for 21 days. At the end of the surveillance period, no illness had developed in contacts. One month later, a serologic survey among 29 of the contacts judged to be at high risk gave no evidence of infection. In response to the importation of this communicable and highly fatal disease, procedures for the isolation of the patient, the identification, surveillance and management of contacts and the handling of laboratory specimens were developed and implemented. These procedures could be adapted to future introductions of highly contagious diseases.

Adult↗
PubMed1975

Therapeutic groups for patients with spinal cord injuries.

A preliminary study was conducted to determine the effectiveness of therapeutic patient groups in a rehabilitation setting. A spinal cord knowledge "Inventory" test was designed to evaluate the success of the group method in disseminating information to patients. The first part of this test assesses the patient's knowledge about body physiology and functioning, health care, and community resources. The second part attempts to evaluate the patient's feelings regarding his body image, sexual attractiveness, and family relationships. The test was administered to 31 spinal cord injured patients upon admission and again just prior to discharge. Eighteen patients participated in a therapeutic patient group, which met twice a week for a month. The other group did not participate in such sessions. The purpose of the meetings was to help the patient adjust to his disability by exchanging commonly needed information and discussing experiences and feelings. Initial results suggest that therapeutic groups can provide an effective means for imparting information to patients. The test also indicates that many patients experience changes in their attitudes and feelings around such sensitive areas as personal worth and self-esteem.

Adolescent↗
PubMed1969

Punishment of shock-induced aggression.

Squirrel monkeys were restrained in a chair equipped with a tail-shock apparatus and a pneumatic bite hose located in front of the subject's face. An aggressive response was recorded when the monkey bit the hose. Initial sessions in which no shocks were delivered produced some biting. When biting during these sessions stabilized at a near-zero level, regularly scheduled shocks were delivered to the monkey's tail, causing a consistently higher rate of biting. After several sessions under these conditions, a punishment phase was introduced in which the previous shock conditions were maintained, and every bite was followed immediately by another, more intense shock. Biting under these conditions was suppressed to a near-zero level. When the punishment contingency was removed, biting increased. With one subject, two additional bite-contingent stimuli were examined: (1) a milder shock that, when made contingent upon hose biting, also suppressed that response, and (2) a contingent tone that had no obvious suppressing or facilitating effect. Individual differences among subjects were extreme, but the effect of bite-contingent shock was consistent. Observations of the subjects during the punishment sessions indicated the existence of certain side effects that resulted from the use of punishment to suppress shock-induced aggression.

Aggression↗