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Biomedical subjects

B Dalton

Publications and source records attributed to B Dalton.

At least 19 recordsLinked to original sources
PubMed1999

Sodium bicarbonate can be used as an ergogenic aid in high-intensity, competitive cycle ergometry of 1 h duration.

The aim of this study was to determine whether a dose of 300-mg x kg(-1) body mass of sodium bicarbonate would effect a high-intensity, 1-h maximal cycle ergometer effort. Ten male, well-trained [maximum oxygen consumption 67.3 (3.3) ml x kg(-1) x min(-1), mean (SD)] volunteer cyclists acted as subjects. Each undertook either a control (C), placebo (P), or experimental (E) ride in a random, double-blind fashion on a modified, air-braked cycle ergometer, attached to a personal computer to which the work and power data was downloaded at 10 Hz. Fingertip blood was sampled at 10-min intervals throughout the exercise. Blood was also sampled at 1, 3, 5, and 10 min post-exercise. Blood was analysed for lactate, partial pressure of Carbon dioxide and oxygen, pH and plasma bicarbonate (HCO-) concentration. Randomly chosen pairs of subjects were asked to complete as much work as possible during the 60-min exercise periods in an openly competitive situation. The sodium bicarbonate had the desired effect of increasing blood HCO3- prior to the start of the test. The subjects in E completed 950.9 (81.1) kJ of work, which was significantly more (F(2,27) = 5.28, P < 0.01) than during either the C [835.5 (100.2) kJ] or P [839.0 (88.6) kJ] trials. No differences were seen in peak power or in the power:mass ratio between these three groups. The results of this study suggest that sodium bicarbonate may be used to offset the fatigue process during high-intensity, aerobic cycling lasting 60 min.

Adult↗
PubMed1999

Inosine supplementation has no effect on aerobic or anaerobic cycling performance.

The two basic aims of this study were to add to the limited literature concerning Inosine as an ergogenic aid, and to determine the effects of Inosine supplementation over a period of 5 and 10 days, at a dosage of 10,000 mg.d-1 on measures associated with aerobic and anaerobic performance. Seven trained, volunteer male subjects (body mass = 63.0 +/- 8.7 kg, VO2max = 67.9 +/- 3.3 ml.kg-1.min-1) participated in this study. The subjects completed three test sessions, each comprising three tests (5 x 6-s sprint, 30-s sprint, and 20-min time trial). Supplementation was carried out in a random, double-blind manner, and the test sessions were undertaken prior to (Baseline, B), on Day 6, and on Day 11. Blood was sampled prior to supplementation as well as on Days 6 and 11 and was analyzed for uric acid and 2,3 DPG. An analysis of the data indicated no performance benefit of supplementation and no improvement in 2,3 DPG concentration. Uric acid concentration increased significantly after both Days 6 and 11 (p < 0.03 and p < 0.004, respectively). It is concluded that Inosine has no ergogenic effects but may cause possible health problems if taken over long periods of time.

2,3-Diphosphoglycerate↗
PubMed1998

The effects of creatine supplementation on high-intensity exercise performance in elite performers.

The aim of this research was to determine whether creatine supplementation at a dose of 20 g x day(-1), given in 4 x 6-g doses (5 g creatine monohydrate and 1 g glucose) for 5 days, was effective in improving kayak ergometer performances of different durations. Sixteen male subjects with the following characteristics [mean (SEM)]: age 21 (1.2) years, height 170.2 (1.7) cm, weight 75.3 (2.3) kg, sigma8 skinfolds 59.3 (2.6) mm, and maximal oxygen consumption 67.1 +/- (4.3) ml x kg x min(-1), undertook three maximal kayak ergometer tests of 90, 150 and 300 s duration on a wind-braked kayak ergometer (CON). Two groups were then randomly formed, with one group taking the supplement (SUP) while the other took a placebo (PLAC). No pre-test differences existed between the SUP and the PLAC groups in any of the variables measured. After supplementation each group then repeated the same kayak ergometer tests as performed previously and after a 4-week "washout period" the groups took either the PLAC or SUP for another 5 days and then completed the final tests. The SUP group completed significantly more work than either the CON or PLAC groups in all of the tests (90 s, P < 0.01; 150 s, P < 0.001; 300 s, P < 0.05). Body mass remained stable throughout the test period in both the CON and PLAC groups, but both were significantly less than the SUP body mass of 77.3 (1.0) kg (P < 0.01). The results of this work indicate that creatine supplementation can significantly increase the amount of work accomplished during kayak ergometer performance at durations ranging from 90 to 300 s.

Adult↗
PubMed1997

Circadian rhythms have no effect on cycling performance.

The aim of this research was to determine if circadian rhythms have an effect on time trial cycling performance of 15 min duration. Seven males (Mean+/-SD): age, 22.3+/-4.9 yr; height 179.0+/-7.9 cm, body mass 74.5+/-15.5 kg; VO2max 68.0+/-5.7 ml x kg(-1) x min(-1) who were all competitive cyclists or triathletes with previous experience in laboratory testing procedures volunteered to participate in this study. Each of the seven subjects underwent a series of four tests; one VO2 max test, and three 15 min maximal performance tests, at varying times during a 24 hr period. Testing times were at 08.00-10.00; 14.00-16.00 and 20.00-22.00 hours. Heart rate was recorded during the last 10-15 seconds of each minute and blood lactate levels were taken at 5 and 10 min during exercise and again immediately post-exercise. O2 consumption was measured continuously using open circuit spirometry. RPE was measured using the Borg scale at 5 and 10 min during, and again immediately following the completion of testing. Resting oral temperature was the only variable to show a significant time of day effect (p<0.05). Oral temperature during the afternoon was higher than both morning and evening results by 0.76 degrees C and 0.09 degrees C respectively. Total work (kJ) and average power output (W) were recorded at their highest during the morning session and reached a trough during the afternoon session, but these differences were not significant (p = 0.9997 and 0.9972 respectively). The results obtained in this study indicate that while certain biological rhythms are present, they appear to have no effect on this type of cycling performance. Although athletic performance may be enhanced by training programs that are compatible with an individuals body clock, the ability to perform and train at various times has an adaptive response which appears to over-ride these naturally inherent rhythms.

Adaptation, Physiological↗
PubMed1992

Percutaneous endoscopic gastrostomy. What are the benefits, what are the risks?

One way to nutritionally support patients who cannot swallow is to administer formula directly into the stomach. Placing a gastrostomy tube percutaneously using endoscopy avoids the risks of general anesthesia and wound healing that accompany surgical gastrostomy. Although certain conditions (eg, sepsis, coagulation disorder, portal hypertension) are contraindications to the procedure, it can be done in patients who have had previous abdominal surgery and in those with severe illness. A commercially available feeding formula is used. The type chosen and the frequency of administration are based on the patient's specific needs. With regular medical monitoring and daily care of the gastrostomy site, appropriately selected patients may be safely maintained with enteral feeding for months. An advantage of the percutaneously inserted tube is that it is easily removed when the patient regains the ability to eat, and the fistula heals rapidly.

Enteral Nutrition↗
PubMed1991

Demographic and health characteristics of participants and nonparticipants in a work site health-promotion program.

Work site health-promotion programs represent an increasingly common attempt by industry to improve the health of employees. The potential impact of programs is limited by nonparticipation, especially among demographic subgroups and those who could most benefit from health behavior change. The present study prospectively examined the relationship of personnel data and self-reported health habits and health status to participation in the health-promotion program at a research and development work site. Thirty-four percent of the 505 employees enrolled in the health-promotion program. White employees were 2.47 times as likely to participate as nonwhites (95% confidence interval, 1.59, 3.83). Those with health maintenance organization health insurance were 1.43 times as likely to participate as were employees with fee-for-service insurance (1.11, 1.84). There was no difference between participants and nonparticipants in self-reported health status, and only slightly more positive health habits were noted among participants. Seatbelt use was 1.65 times more common among participants (1.10, 2.49). The study results are reassuring that such programs do not enroll only the very healthy or those with healthy habits. However, the diminished enrollment of nonwhite employees supports concern that health-related programs may not equally reach all segments of the work force.

Adult↗
PubMed1991

Psychosocial predictors of participation in a work site health-promotion program.

An understanding of psychosocial factors associated with participation in health promotion programs could lead to targetted interventions to increase enrollment. This study used questionnaires to measure employees' perception of program efficacy, health attitudes, beliefs, social support, and stress prior to the introduction of a comprehensive health promotion program at a research and development work site. The association of these factors with enrollment in the program was then prospectively determined. In addition, open-ended questionnaires were used retrospectively to determine additional factors associated with participation. Of the above factors, only program efficacy was significantly associated with participation in the entire sample. Perceived social support was associated with participation among non-white employees. In open-ended questionnaires, a desire for health information, a desire for help with behavior change, and concern about health status were the most commonly given reasons for participating. The study findings imply that environmental factors operating during the enrollment period at the work site may be more powerful than preexisting attitudes and beliefs in determining participation.

Community Participation↗
PubMed1982

Chemical modification of mouse interferons.

Mouse interferon (MuIFN) preparations containing both the alpha and beta species were treated with chemical modifying reagents specific for lysine, cysteine and tryptophan residues. The purpose was to ascertain whether reagents which modify specific amino acid residues distinguished MuIFN-alpha from MuIFN-beta, and if biologic properties could be correlated with specific amino acid residues. MuIFN species were characterized by their activity on homologous and heterologous cells and by antibody neutralization. Modification of lysine residues with increasing concentrations of fluorescamine resulted in a concomitant loss of biologic and antigenic activities of both MuIFN species. Modification of cysteine residues with 5,5'-dithio-bis (2-nitrobenzoic acid) showed an enhancement of antiviral activity of MuIFN-alpha but a gradual decrease in all activities of MuIFN-beta. Modification of tryptophan residues with 2-methoxy-5-nitrobenzyl bromide enhanced somewhat MuIFN-alpha activity, but resulted in the loss of MuIFN-beta activity. These results show that amino-modifying reagents rendered both major species of MuIFN inactive; however, they can be distinguished by reagents which affect cysteine and tryptophan residues. The fact that biologic activity is accompanied by the loss of antigenicity implies that the biologic and antigenic sites may be the same or closely associated. Chemical modification of interferons may provide a useful approach for relating the properties of interferons to their primary structure.

Amino Acid Sequence↗
PubMed1981

Immune reactions and long-term therapy with human leukocyte interferon.

Twenty patients with osteosarcoma were treated with exogenous human leukocyte interferon for periods ranging from 6 to 18 months. Eleven of them remained free from detectable tumour growth during this treatment. Blood samples from all patients were tested for antibodies against interferon and against impurities in the interferon preparations. No patient developed detectable levels of neutralizing antibodies against interferon. All patients formed antibodies against contaminants in the concentrated crude interferon and the partially purified interferon preparation which had been used for treatment.

Adolescent↗
PubMed1980

Lymphocyte blastogenesis and interferon production in adult human leukocyte cultures stimulated with cytomegalovirus antigens.

Lymphocyte blastogenesis and interferon production were measured in adult human leukocyte cultures stimulated with purified or crude cytomegalovirus antigens. Leukocytes from seropositive adults underwent blastogenesis when stimulated with purified or crude Towne strain antigen, whereas neither antigen stimulated blastogenesis in cultures from seronegative donors. The concentrations of antigens yielding maximal blastogenesis varied among the individuals tested. When cultures from seropositive individuals were stimulated with antigens prepared from three different CMV strains--AD-169, Towne, and Davis--comparable levels of blastogenesis were detected. Type 1 interferon was detected in supernatants of cultures stimulated with crude antigens regardless of the immune status of the donor. In contrast, when purified antigen was used as the stimulant, only cultures obtained from seropositive individuals produced detectable levels of interferon, which appeared to be predominantly type 2 or immune interferon.

Antigens, Viral↗