PubMed Health⌕ Search

Biomedical subjects

S Dodd

Publications and source records attributed to S Dodd.

65 records · Page 4Linked to original sources
PubMed1987

Silicone-induced hypercalcaemia in haemodialysis patients.

Silicone spallation from the roller-pump insert in dialysis blood lines leads to the accumulation of silicone in haemodialysis patients, which in turn leads to a foreign-body reaction with granuloma formation. We have studied two patients in whom documented silicone accumulation has been associated with both granuloma formation and significant, persistent hypercalcaemia. In both patients plasma levels of immunoreactive parathyroid hormone and 1,25-dihydroxyvitamin D were low or undetectable. In one patient, hypercalcaemia responded only partially to corticosteroids, but completely to naproxen. Both patients were changed to silicone-free blood lines and their hypercalcaemia subsequently resolved. The results indicate that in some haemodialysis patients, silicone accumulation and granuloma formation may lead to hypercalcaemia that is independent of 1,25-dihydroxyvitamin D, and that may instead reflect altered prostaglandin metabolism.

Adult↗
PubMed1986

Caffeine alters ventilatory and gas exchange kinetics during exercise.

The purpose of these experiments was to determine the effects of oral caffeine ingestion on the kinetics of oxygen uptake (VO2), expired carbon dioxide output (VCO2), and expired ventilation (VE) in the transition from rest to exercise. Nine male subjects underwent three repetitions of constant load cycle ergometer exercise (approximately 80% ventilatory threshold) on two occasions. A single blind experimental procedure was followed, with one trial being performed 60 min after the subject ingested caffeine (7 mg X kg-1), while the second trial required the subject to ingest a placebo with the treatment order being counterbalanced. Ventilation and gas exchange were monitored by open circuit techniques. The data from three repetitions of the same protocol were pooled and modeled with a single-component exponential function incorporating a time delay: (formula; see text) Kinetic analysis of VO2 revealed no significant difference (P greater than 0.05) in the mean response time between treatments. In contrast, the mean response time for VCO2 and VE were longer (P less than 0.05) for the caffeine trial when compared to the control experiment. These data suggest that caffeine will influence both VCO2 and VE kinetics in the transition from rest to work and should be considered by investigators when planning experiments to study ventilatory and gas exchange kinetics during exercise.

Caffeine↗
PubMed1985

Oxygen uptake kinetics in trained athletes differing in VO2max.

Previous work has shown that when VO2 kinetics are compared for endurance trained athletes and untrained subjects, the highly trained athletes have a faster response time. However, it remains to be determined whether the more rapid adjustment of VO2 toward steady state in athletes is due to VO2max differences or training adaptation alone. One approach to this problem is to study the time course of VO2 kinetics at the onset of work in athletes who differ in VO2max but have similar training habits. Therefore, the purpose of these experiments was to compare the time course of VO2 kinetics at the onset of exercise in athletes with similar training routines but who differ in VO2max. Ten subjects (VO2max range 50-70 ml . kg-1 . min-1) performed 6-minutes of cycle ergometer exercise at approximately 50% VO2max. Ventilation and gas exchange were monitored by open circuit techniques. The data were modeled with a single component exponential function incorporating a time delay, (TD); delta VO2t = delta VO2ss (1-e-t-TD/tau), where tau is the time constant delta VO2t is the increase in VO2 at time t and delta VO2ss is the steady-rate increment above resting VO2. Kinetic analysis revealed a range of VO2 half times from 21.6 to 36.0 s across subjects with a correlation coefficient of r = -0.80 (p less than 0.05) between VO2max and VO2 half time. These data suggest that in highly trained individuals with similar training habits, those with a higher VO2max achieve a more rapid VO2 adjustment at the onset of work.

Adult↗
PubMed1984

Precision of ventilatory and gas exchange alterations as a predictor of the anaerobic threshold.

Anaerobic threshold has been defined as the oxygen uptake (VO2) at which blood lactate (La) begins to rise systematically during graded exercise (Davis et al. 1982). It has become common practice in the literature to estimate the anaerobic threshold by using ventilatory and/or gas exchange alterations. However, confusion exists as to the validity of this practice. The purpose of this study was to examine the precision with which ventilatory and gas exchange techniques for determining anaerobic threshold predicted the anaerobic threshold resolved by La criteria. The anaerobic threshold was chosen using three criteria: (1) systematic increase in blood La (ATLa), (2) systematic increase in ventilatory equivalent for O2 with no change in the ventilatory equivalent for CO2 (ATVE/VO2), and (3) non-linear increase in expired ventilation graphed as a function of VO2 (ATVE). Thirteen trained male subjects performed an incremental cycle ergometer test to exhaustion in which the load was increased by 30 W every 3 minutes. Ventilation, gas exchange measures, and blood samples for La analysis were obtained every 3rd min throughout the test. In five of the thirteen subjects tested the anaerobic threshold determined by ventilatory and gas exchange alterations did not occur at the same VO2 as the ATLa. The highest correlation between a gas exchange anaerobic threshold and ATLa was found for ATVE/VO2 and was r = 0.63 (P less than 0.05). These data provide evidence that the ATLa and ATVE do not always occur simultaneously and suggest limitations in using ventilatory or gas exchange measures to estimate the ATLa.

Adult↗
PubMed1984

Haemoglobin saturation during incremental arm and leg exercise.

There are few reports concerning the alterations in the percent of haemoglobin saturated with oxygen (%SO2) during non-steady state incremental exercise. Further, no data exist to describe the %SO2 changes during arm exercise. Therefore, the purpose of this study was made to assess the dynamic changes in %SO2 during incremental arm and leg work. Nine trained subjects (7 males and 2 females) performed incremental arm and leg exercise to exhaustion on an arm crank ergometer and a cycle ergometer, respectively. Ventilation and gas exchange measurements were obtained minute by minute via open circuit spirometry and changes in %SO2 were recorded via an ear oximeter. No significant difference (p greater than 0.05) existed between arm and leg work in end-tidal oxygen (PETO2), end-tidal carbon dioxide (PETCO2), or %SO2 when compared as a function of percent VO2 max. These results provide evidence that arterial O2 desaturation occurs in a similar fashion in both incremental arm and leg work with the greatest changes in %SO2 occurring at work rates greater than 70% VO2 max.

Arm↗
PubMed1984

Blood lactate disappearance at various intensities of recovery exercise.

Numerous studies have reported that following intense exercise the rate of blood lactate (La) disappearance is greater during continuous aerobic work than during passive recovery. Recent work indicates that a combination of high- and low-intensity work may be optimal in reducing blood La. We tested this hypothesis by measuring the changes in blood La levels following maximal exercise during four different recovery patterns. Immediately following 50 S of maximal work, subjects (n = 7) performed one of the following recovery treatments for 40 min: 1) passive recovery (PR); 2) cycling at 35% maximal O2 uptake (VO2 max) (35% R); 3) cycling at 65% VO2 max (65% R); 4) cycling at 65% for 7 min followed by cycling at 35% for 33 min (CR). The treatment order was counterbalanced with each subject performing all treatments. Serial blood samples were obtained throughout recovery treatments and analyzed for La. The rate of blood La disappearance was significantly greater (P less than 0.05) in both the 35% R and CR when compared with either the 65% R or PR. No significant difference (P greater than 0.05) existed in the rate of blood La disappearance between the 35% R and CR. These data do not support the hypothesis that exercise recovery at a combination of intensities is superior to a recovery involving continuous submaximal exercise in lowering blood La following maximal work.

Adult↗
PubMed1981

Distribution of lactoferrin in human fetal tissues.

We used an immunoperoxidase method to study the distribution of lactoferrin in seven human fetuses from 11 to 21 weeks of age. Lactoferrin was found in mononuclear cells, presumably granulocytes, in various organs from thirteen weeks of gestation onwards. In addition to the liver, spleen, lung and thymus, lactoferrin-positive mononuclear cells were also found close to vessel walls in human pancreas in fetuses more than 20 weeks old. This finding might suggest that there is significant granulopoiesis in the pancreas at this stage of maturation. In addition to the mononuclear cells, lactoferrin could be found in Hassal's corpuscles of the thymus from 13 weeks and in glandular cells of the tongue from 20 weeks onwards. The present results are in good agreement with the maturation of humoral and cellular acquired immunity and the onset of synthesis of lysozyme and interferon.

Female↗
PubMedDate not supplied

Caffeine and endurance performance.

The belief among athletes that caffeine is an ergogenic aid is common, and several governing bodies of sport have barred use of the drug during competition. At the cellular level, caffeine has been implicated to affect the translocation of calcium in muscle, promote an increase in cellular levels of cyclic AMP and cause a blockade of adenosine receptors in the central nervous system. The general systemic effect of caffeine is to cause central nervous system arousal, mobilisation of free fatty acids and other metabolites, and possibly enhance the contractile status of muscle. At present, the scientific community remains divided as to whether caffeine ingestion will indeed produce an ergogenic effect upon sport performance. Some evidence suggests that caffeine may improve performance in events relying upon strength and power; however, the lack of in vivo research in humans makes it difficult to form firm conclusions. In addition, reports concerning caffeine's effect on VO2max and performance during incremental exercise are not in agreement. On the other hand, recent studies suggest that caffeine might indeed have ergogenic potential in endurance events (e.g. marathon running). It is hypothesised that the mechanism behind these findings is related to the increased availability of free fatty acids for muscle metabolism which has a glycogen-sparing effect.

Caffeine↗
PubMedDate not supplied

Antidepressants and breast-feeding: a review of the literature.

For every antidepressant so far investigated in the breast milk of mothers prescribed these medications, findings indicate that some amount of drug will be excreted into the breast milk. Nursing infants will be exposed to some, usually a very low, amount of drug and drug metabolites. Levels of drug exposure to infants for the many antidepressants available are examined, discussing milk to plasma drug concentration ratios and the infant dose as a percentage of the maternal dose. Drug concentrations in infant plasma and adverse effects of drug exposures to infants are reviewed. Factors influencing the decision on whether to breast or bottle feed an infant nursed by a mother taking antidepressants are discussed, concluding that the decision needs to be made on an individual basis. The lactating mother, in consultation with her doctor, should be in a position to make an informed decision on whether or not to breast feed. Under certain circumstances the decision to bottle feed may be wise, but more commonly the advantages of breast-feeding will outweigh the very low risk of an adverse event from drug exposure to the infant.

Adult↗