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Biomedical subjects

C Foster

Publications and source records attributed to C Foster.

At least 109 records · Page 6Linked to original sources
PubMed1991

Multiple K-ras codon 12 mutations in cholangiocarcinomas demonstrated with a sensitive polymerase chain reaction technique.

By using a modified polymerase chain reaction strategy, we have devised an approach to detect a K-ras oncogene mutated at codon 12 in the presence of 1000 normal alleles. This is a considerable improvement in sensitivity on previous assays. Application of this assay to 15 cholangiocarcinomas showed that all contained a K-ras mutation to codon 12 and that nine of the tumors contained two or more mutations. In 11 cases, mutations were present in less than 10% of the cells in the sample. In common with pancreatic adenocarcinomas, in which 75 to 95% of cases contain a mutation in K-ras, cholangiocarcinomas show a very high frequency of ras gene mutation, but within a tumor only a fraction of cells contain a ras mutation. The presence of multiple mutations and the low frequency of mutant alleles in the samples argue against K-ras mutations being the initiating genetic lesion in this tumor, but suggest that ras gene mutation is involved in the stepwise progression of neoplastic cells to full malignancy.

Adenoma, Bile Duct↗
PubMed1991

Uniqueness of interval and continuous training at the same maintained exercise intensity.

The present study sought to evaluate the inconsistencies previously observed regarding the predominance of continuous or interval training for improving fitness. The experimental design initially equated and subsequently maintained the same relative exercise intensity by both groups throughout the program. Twelve subjects were equally divided into continuous (CT, exercise at 50% maximal work) or interval (IT, 30 s work, 30 s rest at 100% maximal work) training groups that cycled 30 min day-1, 3 days.week-1, for 8 weeks. Following training, aerobic power (VO2max), exercising work rates, and peak power output were all higher (9-16%) after IT than after CT (5-7%). Vastus lateralis muscle citrate synthase activity increased 25% after CT but not after IT. A consistent increase in adenylate kinase activity (25%) was observed only after IT. During continuous cycling testing the CT group had reduced blood lactate (lab) levels and respiratory quotient at both the same absolute and relative (70% VO2max) work rates after training, while the IT group displayed similar changes only at the same absolute work rates. By contrast, both groups responded similarly during intermittent cycling testing with lower lab concentrations seen only at absolute work rates. These results show that, of the two types of training programs currently employed, IT produces higher increases in VO2max and in maximal exercise capacity. Nevertheless, CT is more effective at increasing muscle oxidative capacity and delaying the accumulation of lab during continuous exercise.

Adult↗
PubMed1991

Memory and attention in patients with senile dementia of the Alzheimer type and in normal elderly subjects.

Previous studies have shown that cholinergic blockade in normal subjects induces impairment of vigilance as well as memory deficits. In the present investigation we have examined the validity of this pharmacological model of dementia by administering a battery of cognitive tasks to patients with mild and moderate senile dementia of the Alzheimer type and to age-matched controls. In contrast to volunteers receiving scopolamine all the mildly demented patients, and half of those moderately affected, performed normally on tests of vigilance whilst exhibiting the expected memory deficits. These data suggest that the mechanism of memory loss in Alzheimer's disease may differ from that found in scopolamine-induced amnesia.

Aged↗
PubMed1991

Functional translation of exercise responses during combined arm-leg ergometry.

Previous studies have shown that the absolute power output required to produce a desired training heart rate could be predicted from the power output-heart rate relationship during exercise testing. The intent of this study was to develop an equation for the functional translation of exercise responses using combined arm-leg ergometry. Volunteer subjects (n = 16) performed exercise testing and three, 20-min exercise training sessions at different intensities on the combined arm-leg ergometer. Power output during exercise testing and training were well related (r = 0.905) with a small standard error estimate (12.1 W). Cross-validation of the regression equation developed from the validation sample yielded a high correlation (r = 0.969) with no differences between predicted and observed training heart rates.

Adult↗
PubMed1991

Stressful life events and symptom onset in HIV infection.

OBJECTIVE: The authors' goal is to provide basic epidemiologic data on the issue of reactivity to stress and HIV symptom onset by studying the relationship between a broad set of naturally occurring stressor events and HIV natural history in a large longitudinal community sample of HIV-seropositive homosexual men. METHOD: Subjects were recruited from a cohort of 1,011 homosexual men enrolled in the Chicago site of the Multicenter AIDS Cohort Study who also participated in the Coping and Change Study. The men were given self-administered questionnaires assessing behavioral, psychological, and psychosocial variables. Relationships between reports of stressful life events and longitudinal biomedical data measuring illness progression were examined. Life events were assessed by reports on the numbers of lovers, friends, and acquaintances who were diagnosed with AIDS or had died of AIDS and by scores on a checklist of 24 more general serious stressor events. The variables indicating progression of illness among initially asymptomatic men were a drop in T-helper lymphocyte percent (CD4%) between pairs of examinations of at least 25% and onset between examinations of thrush and/or fever lasting a minimum of 2 weeks. RESULTS: The authors found no evidence that serious stressor events have any meaningful effect on symptom onset indicated by either a drop in CD4% or onset of fever or thrush. CONCLUSIONS: There is no need for asymptomatic people with HIV infection to restrict their lives in order to avoid exposure to stressful life experiences or to develop special skills for coping with stress to forestall the progression of HIV illness.

Acquired Immunodeficiency Syndrome↗
PubMed1990

The evaluation of a cognitive behavioural treatment programme in outpatients with chronic pain.

This study is an attempt to investigate the efficacy of an outpatient cognitive behavioural group programme for the rehabilitation of patients with chronic pain. The programme, which took place over one afternoon per week for seven weeks and was conducted by a multidisciplinary team, aimed to increase patients' skills for coping with chronic pain and its social, emotional and physical consequences. Measures of pain intensity, mood, coping skills, physical disability and medication consumption were obtained on four separate occasions: twice pre-treatment, immediately post-treatment and at one month follow-up. Repeated measures analysis of variance showed significant improvements in mood, coping skills, physical disability and analgesic consumption despite less clear-cut improvement in ratings of pain intensity. These results parallel the findings of similar studies in the U.S.A. and their implications for the provision of services to chronic pain patients in the U.K. is discussed.

Adaptation, Psychological↗
PubMed1990

Small peptide inhibitors of smooth muscle myosin light chain kinase.

The pentapeptide Ser-Asn-Val-Phe-Ala-OBzl has been identified as the smallest inhibitory peptide of myosin light chain kinase (MLCK) derived from the primary sequence of the light chain phosphorylation site. The specific contributions of individual amino acid side chains and backbone elements of this pentapeptide toward the stabilization of the enzyme-inhibitor (E-I) complex have been evaluated. The potency of these peptides as inhibitors of MLCK has been enhanced by the incorporation of synthetic nonnatural amino acids into the sequence. Finally, it has been demonstrated that these peptide sequences could be converted into pseudopeptides with synthetic nonpeptide subunits designed to mimic peptide bonds, and that certain pseudopeptides retained the high-affinity inhibition of the parent pentapeptides.

Animals↗
PubMed1990

Serial gastric emptying studies: effect of preceding drinks.

A widely used method for evaluating gastric emptying is the serial recovery method, in which several different test drinks are given and recovered in rapid succession. Recently, the validity of this method has been challenged (Brouns et al., Int. J. Sports Med. 8:175-189, 1987) by suggestions that the duodenal contents remaining from previous drinks may influence the gastric emptying of subsequent drinks. To evaluate whether this methodological issue might influence the results of gastric emptying studies, we studied six volunteer subjects. The gastric emptying rate of water was measured following a previous trial with either water or a concentrated maltodextrin solution (23% CHO). All trials were conducted at rest and consisted of a volume of 400 ml. The emptying rate of water was not different following either water or maltodextrin solution (14.9 vs 16.3 ml.min-1). We conclude that the serial recovery method remains a valid technique for measuring the rate of gastric emptying during rest and exercise.

Drinking↗
PubMed1989

Prehospital care by EMTs and EMT-Is in a rural setting: prolongation of scene times by ALS procedures.

Because the initiation of IV lines by emergency medical technicians-Intermediates (EMT-Is) appeared to delay the patient's transport to the hospital, we undertook a retrospective study of 370 patients to compare prehospital care rendered by EMTs (EMT-A equivalent) and EMT-Is in a rural setting. Our study was limited to acute medical conditions in which protocols called for IV lines (124 patients with chest pain, 122 with acute respiratory distress, 99 with seizures, and only 25 with cardiac arrest) (the cardiac arrest cases were too few for statistical significance). We found that the difference in scene times for EMTs and EMT-Is not attempting IV lines was 6.1 and 6.9 minutes, respectively. The average scene time of EMT-Is attempting an IV line was 19.6 minutes (P less than .001) compared with EMT times, or times for EMT-Is not attempting an IV line. One hundred twenty-eight of 370 patients received IV medication within ten minutes of arrival in the emergency department, and ten of these patients had their IV lines initiated successfully in the field. Thirty-nine percent of patients with ED IV lines received IV medication within ten minutes of arrival, while only 21% of patients with a field IV line received medication in this period (P less than .05). We conclude that initiating a field IV line in this specific patient population significantly increased scene time and did not improve the chances of these patients receiving IV medication within ten minutes of arrival in the emergency department.

Allied Health Personnel↗
PubMed1988

Normalization of the blood lactate profile in athletes.

The power output-blood lactate or velocity-blood lactate relationship, the lactate "profile", is a widely used method for the evaluation of athletes. Recent observations have suggested a shift in the blood lactate profile when athletes are fatigued, as at training camps. This study was designed to determine whether the blood lactate profile could be corrected for progressive muscle glycogen depletion by normalizing for the peak exercise blood lactate concentration. Ten well-trained subjects performed incremental cycle ergometer exercise followed by supramaximal exercise (Wingate test) following 3 days of usual and 3 days of heavier than usual training. Following heavier than usual training, blood lactate accumulation was reduced during submaximal exercise such that the power output associated with a lactate concentration of 4 mM was significantly increased (3.08 vs 3.51 W/kg). The maximal blood lactate concentration was also reduced (14.8 vs 12.7 mM) although average supramaximal power output was unchanged (9.03 vs 8.92 W/kg). When the submaximal blood lactate concentrations were normalized for the maximal blood lactate concentration, there were no significant differences in the power output associated with 20% (2.6 vs 2.7 W/kg), 25% (3.1 vs 3.2 W/kg), or 30% (3.3 vs 3.5 W/kg) of maximal lactate. The results suggest that normalization based on peak exercise blood lactate may be a useful strategy for circumventing one of the primary practical barriers to the use of the blood lactate profile in athletes.

Adult↗
PubMed1988

Potential for strength and endurance training to amplify endurance performance.

The impact of adding heavy-resistance training to increase leg-muscle strength was studied in eight cycling- and running-trained subjects who were already at a steady-state level of performance. Strength training was performed 3 days/wk for 10 wk, whereas endurance training remained constant during this phase. After 10 wk, leg strength was increased by an average of 30%, but thigh girth and biopsied vastus lateralis muscle fiber areas (fast and slow twitch) and citrate synthase activities were unchanged. Maximal O2 uptake (VO2max) was also unchanged by heavy-resistance training during cycling (55 ml.kg-1.min-1) and treadmill running (60 ml.kg-1.min-1); however, short-term endurance (4-8 min) was increased by 11 and 13% (P less than 0.05) during cycling and running, respectively. Long-term cycling to exhaustion at 80% VO2max increased from 71 to 85 min (P less than 0.05) after the addition of strength training, whereas long-term running (10 km times) results were inconclusive. These data do not demonstrate any negative performance effects of adding heavy-resistance training to ongoing endurance-training regimens. They indicate that certain types of endurance performance, particularly those requiring fast-twitch fiber recruitment, can be improved by strength-training supplementation.

Adenosine Triphosphate↗
PubMed1987

Effect of age and training on aerobic capacity and body composition of master athletes.

Maximum oxygen uptake (VO2max) and body composition have been shown to deteriorate with age. How much of the decline is attributable to aging and how much is affected by reduced physical activity is not known. The purpose of this investigation was to determine the aerobic capacity and body composition of 24 master track athletes and to evaluate the relationship to age and maintenance of training over a 10-yr period. The subjects (50-82 yr of age) were retested after a 10.1-yr follow-up (T2). All continued their aerobic training, but only 11 were still highly competitive (COMP) and continued to train at the same intensity. The other 13 athletes studied became noncompetitive (post-COMP) and reduced their training intensity. The results showed the COMP group to maintain its VO2max and maximum O2 pulse while the post-COMP group showed a significant decline (54.2-53.3 vs. 52.5-45.9 ml X kg-1 X min-1; 20.7-20.8 vs. 22.4-20.0 ml/beat from test one (T1) to T2 for the COMP vs. post-COMP groups, respectively). Maximum heart rate declined 7 beats/min for both groups. Body composition showed no difference between groups from T1 to T2. For both groups body weight declined slightly (70.0-68.9 kg), percent fat increased significantly (13.1-15.1%), and fat-free weight decreased significantly (61.0-59.0 kg). Thus, when training was maintained, aerobic capacity remained unchanged over the follow-up period. Body composition changed for both groups and may have been related to aging and/or the type of training performed.

Aged↗
PubMed1986

Functional translation of exercise responses from graded exercise testing to exercise training.

This study attempts to develop a quantitative approach to the prescription of absolute exercise intensity during level ground ambulation (min/mile) or cycle ergometry (kpm) from responses observed during GXT. A total of 345 subjects performed GXT and exercise training sessions with either the Bruce treadmill protocol and level ground ambulation (N = 154) or cycle ergometry (N = 191). Responses from 90% of each group were used to generate equations for predicting training pace (or power output) from the time (or power output) during the GXT when target HR was achieved. FAI was also included in the prediction of training pace (or power output). The remaining 10% of subjects in each group were used to cross-validate the prediction equations. The correlation between the time (or power output) during GXT when the training HR was observed and the pace of ambulation (or power output) was 0.70 for treadmill walking and 0.88 for cycle-cycle. Correlations were increased by the addition of FAI to the prediction equation. The results of this investigation suggest that the absolute intensity of exercise for training can be predicted accurately from GXT results.

Cardiac Rehabilitation↗
PubMed1986

Tryptic digestion of myosin light chain kinase produces an inactive fragment that is activated on continued digestion.

Trypsin digestion of chicken gizzard myosin light chain kinase at limiting trypsin concentrations proceeds in stages. In the first stage, catalytic activity in the presence or absence of calcium and calmodulin decreases. In the second stage, activity in the absence of calcium increases, and the calcium-calmodulin complex no longer stimulates activity. The initial loss of activity is associated with the appearance of a 59,000-Da peptide that has been isolated and shown to have low catalytic activity. This peptide was further digested to a 55,000-Da peptide that has calcium-independent catalytic activity. This peptide has been isolated, and its affinities for the peptide substrate Kemptamide (Lys-Lys-Arg-Pro-Gln-Arg-Ala-Thr-Ser-Asn-Val-Phe-Ser-NH2) and ATP have been shown to be the same as those of the intact enzyme. Neither the 59,000-Da nor the 55,000-Da fragment binds calmodulin.

Calcium↗