Body fluid responses of heat-tolerant and intolerant men to work in a hot wet environment.

Acclimatization to heat before proceeding underground is a requirement for each South African mine laborer. Certain individuals among this large population cannot be acclimatized to heat (33.3 degrees C db, 31.7 degrees C wb) and are classified as heat intolerant. In this study certain body fluid responses to heat and work were compared between a group of 19 heat-tolerant (HT) and of 15 heat-intolerant (HI) subjects. To the factors known to affect heat tolerance such as age, weight, and oxygen consumption must now be added differences in body fluid responses. The HI group of subjects failed to hemodilute to the same degree as the HT group though working at the same relative work loads (30% and 50% VO2 max). As the 4-h work period (33.3 degrees C db, 31.7 degrees C wb) continued, the HI group did not maintain hemodilution in spite of the lower absolute work loads, sweat rates, and water deficits suffered by this group. From analysis of blood constituent changes it was suggested that the reason for the differences noted in body fluid dynamics concerned plasma protein equilibrium across capillary walls as well as the protein population of interstitial spaces.     

Using fish guilds to assess community responses to temperature and flow regimes in unregulated and regulated Canadian rivers

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Elevation of body temperature is an essential factor for exercise-increased extracellular heat shock protein 72 level in rat plasma

This study examined whether the exercise-increased extracellular heat shock protein 72 (eHsp72) levels in rats was associated with body temperature elevation during exercise. In all, 26 female Sprague-Dawley rats (3 mo old) were assigned randomly to control (CON; n = 8), exercise under warm temperature (WEx; n = 9), or exercise under cold temperature (CEx; n = 9). The WEx and CEx were trained at 25 degrees C or 4 degrees C, respectively, for nine days using a treadmill. Before and immediately after the final exercise bout, the colonic temperatures were measured as an index of body temperature. The animals were subsequently anesthetized, and blood samples were collected and centrifuged. Plasma samples were obtained to assess their eHsp72 levels. Only the colonic temperature in WEx was increased significantly (P < 0.05) by exercise. The eHsp72 level in WEx was significantly higher (P < 0.05) than that of either the CON or CEx. However, no significant difference was found between CON and CEx. Regression analyses revealed that the eHsp72 level increased as a function of the body temperature. In another experiment, the eHsp72 level of animals with body temperature that was passively elevated through similar kinetics to those of the exercise was studied. Results of this experiment showed that mere body temperature elevation was insufficient to induce eHsp72 responses. Collectively, our results suggest that body temperature elevation during exercise is important for induction of exercise-increased eHsp72. In addition, the possible role of body temperature elevation is displayed when the exercise stressor is combined with it.     

Effects of exercise detraining and deacclimation to the heat on plasma volume dynamics

The effects of the discontinuation (DET) of an endurance training/heat acclimation (T/A) program on vascular volumes were studied in 16 adult males. Resting and exercise blood volume dynamics were examined prior to and during an exercise task performed after completion of T/A (CT1) and again at the end of DET (CT2). T/A consisted of cycling at 60% of peak VO2 for 90 min per day, 6 days per week, for 4 weeks. Ambient temperature was 20 degrees C for the first 3 weeks and 40 degrees C for the last week (rh = 30-35%). Subjects were randomly assigned to one of the following DET conditions: 1) cycling one day per week at 40 degrees C, 2) cycling one day per week at 20 degrees C, 3) resting one day per week at 40 degrees C, 4) control. The exercise tasks consisted of 60 min of continuous cycle ergometer exercise at 50% of peak VO2 (Ta = 30 degrees C, rh = 35%). Although significant differences were found between CT1 and CT2, there were no interactions between the various DET conditions. Resting red cell volume decreased 98 ml and plasma volume decreased 248 ml following DET. A reduction in plasma protein content accounted for 97% of the decrease in plasma volume. Hemoconcentration occurred during exercise in both CT1 and CT2, while there were slight increases in plasma [Na+] and [Cl-] and a rapid rise in [K+]. It appears that a single exercise and/or heat exposure per week was not different from complete cessation of endurance exercise in the heat with regard to maintenance of the various vascular volumes.     

The effects of body position and exercise on plasma volume dynamics

We examined the plasma volume changes associated with a protocol of either exercise or controlled rest under identical positional and ambient conditions. Nine healthy adult males rode (E) and on another occasion sat quietly (C) on a cycle ergometer for 30 min. Ten minutes of cycle exercise immediately followed the resting C protocol. Ambient temperature was 30 degrees C (rh = 35%) and exercise load was equal to 50% of peak VO2. Venous blood samples were obtained with subjects both in the supine and seated positions prior to all experiments. Additional blood was drawn during minutes 1, 5, 10, and 30 in both experimental conditions. A final sample was taken during C after the 10 min exercise. Moving from the supine to a seated position resulted in an average loss of 162 ml of plasma across all experiments. During the E condition a further reduction in plasma volume (76 ml) occurred by one minute of exercise. Plasma volume stabilized by 5 min of exercise under the E protocol. During the C condition, subsequent fluid loss (98 ml) was not apparent until 10 min after the first seated sample and totalled 176 ml at the end of 30 min of rest. Ten minutes of cycling at the end of the C experiment resulted in a further plasma volume reduction of 137 ml. Plasma protein and albumin contents decreased by 5 min of exercise in E and by 30 min of rest in C. [Na+] and [Cl-] did not change in either condition but a rapid increase in [K+] during exercise indicated an addition of potassium to the vascular volume.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic Variability of Vancomycin-Resistant Enterococcus faecium and Enterococcus faecalis Isolates from Humans,Chickens, and Pigs in Malaysia

Vancomycin-resistant enterococci (VRE) have been reported to be present in humans, chickens, and pigs in Malaysia. In the present study, representative samples of VRE isolated from these populations were examined for similarities and differences by using the multilocus sequence typing (MLST) method. Housekeeping genes of Enterococcus faecium (n = 14) and Enterococcus faecalis (n = 11) isolates were sequenced and analyzed using the MLST databases eBURST and goeBURST. We found five sequence types (STs) of E. faecium and six STs of E. faecalis existing in Malaysia. Enterococcus faecium isolates belonging to ST203, ST17, ST55, ST79, and ST29 were identified, and E. faecium ST203 was the most common among humans. The MLST profiles of E. faecium from humans in this study were similar to the globally reported nosocomial-related strain lineage belonging to clonal complex 17 (CC17). Isolates from chickens and pigs have few similarities to those from humans, except for one isolate from a chicken, which was identified as ST203. E. faecalis isolates were more diverse and were identified as ST4, ST6, ST87, ST108, ST274, and ST244, which were grouped as specific to the three hosts. E. faecalis, belonging to the high-risk CC2 and CC87, were detected among isolates from humans. In conclusion, even though one isolate from a chicken was found clonal to that of humans, the MLST analysis of E. faecium and E. faecalis supports the findings of others who suggest VRE to be predominantly host specific and that clinically important strains are found mainly among humans. The infrequent detection of a human VRE clone in a chicken may in fact suggest a reverse transmission of VRE from humans to animals.     

Combined MRI–PET dissects dynamic changes in plant structures and functions

Unravelling the factors determining the allocation of carbon to various plant organs is one of the great challenges of modern plant biology. Studying allocation under close to natural conditions requires non-invasive methods, which are now becoming available for measuring plants on a par with those developed for humans. By combining magnetic resonance imaging (MRI) and positron emission tomography (PET), we investigated three contrasting root/shoot systems growing in sand or soil, with respect to their structures, transport routes and the translocation dynamics of recently fixed photoassimilates labelled with the short-lived radioactive carbon isotope ¹¹C. Storage organs of sugar beet ( Beta vulgaris ) and radish plants ( Raphanus sativus ) were assessed using MRI, providing images of the internal structures of the organs with high spatial resolution, and while species-specific transport sectoralities, properties of assimilate allocation and unloading characteristics were measured using PET. Growth and carbon allocation within complex root systems were monitored in maize plants ( Zea mays ), and the results may be used to identify factors affecting root growth in natural substrates or in competition with roots of other plants. MRI–PET co-registration opens the door for non-invasive analysis of plant structures and transport processes that may change in response to genomic, developmental or environmental challenges. It is our aim to make the methods applicable for quantitative analyses of plant traits in phenotyping as well as in understanding the dynamics of key processes that are essential to plant performance.