Thermoregulatory shivering during exercise

Three subjects with lowered internal body temperatures performed brief bouts of bicycle ergometer exercise at 150 and 200 W. Oxygen uptake during exercise was consistently greater than that required by the working muscles, the increase being the result of the additional cost of shivering. Increases in metabolism during exercise above control levels were inversely proportional to internal temperature (with skin temperature constant) below a given internal temperature threshold. Observations of intense shivering during exercise which is proportional to lowered internal temperature in the same manner as during rest provides further evidence against the concept of a decrease in the thermoregulatory set point during exercise in man.     

Thermoregulatory mechanisms in Sarcophaga

Summary The flesh fly, Sarcophaga, is frequently seen feeding on flowers during periods of high radiation when other flies of comparable size avoid exposure because of the dangers of overheating. Sarcophaga is able to maintain its intermittent flower visits due to a cuticle of high thermal reflectance, giving low intrinsic heating rates, and to an ability to shunt blood between thorax and abdomen according to its needs. The fly thus achieves partial thermoregulation and can keep its body temperature within the preferred range for longer periods than its potential entomophilous competitors.     

Thermoregulatory responses of diabetic rats

1. Thermal responses and skin microcirculation were measured in streptozotocin-induced diabetic (SD) rats during acute and chronic exposure to ambient (Ta) temperatures ranging from about 5 to 35 degrees C. 2. At 28 degrees C, SD rats had higher rate of oxygen consumptions (VO2), tail skin blood flow (SKBF), but lower rectal temperatures (Tre) than saline-injected controls. 3. Chronic exposure of the SD rats to 35 and 5 degrees C caused a sharp rise and decline in Tre, respectively. 4. At 35 degrees C, hyperthermia in the SD rats was associated with greater increase in VO2 than controls, but changes in SKBF were similar in both groups. 5. At 5 degrees C, VO2 changed similarly in both the SD and control rats, but vasoconstriction was greater in the controls. 6. The data suggest that hypothermia in SD rats may be associated with impairment of vasoconstriction and hyperthermia may be related to an increase VO2 not accompanied by greater vasodilation.     

Thermoregulatory Activity of Dermorphin Fragments

We studied the effect of C-terminal truncation of the dermorphin (DM) molecule and analogs of its N-terminal tetrapeptide, [DOrn²]-DM_1–4, [DArg²]-DM_1–4, [DAla⁴]-DM_1–4, [DArg², DAla⁴]-DM_1–4, Arg-DM_1–4, Arg-[DArg²]-DM_1–4, Arg-[DAla⁴]-DM_1–4, and Arg-[DArg², DAla⁴]-DM_1–4, on the functional status of the thermoregulation system in rats at different ambient temperatures. For the first time, we demonstrate that the N-terminal tetrapeptide is the minimal fragment with the hypothermic effect. Only the N-terminal octapeptide exerted the vasomotor effect. Amino acid substitutions in the tetrapeptide affected its hypothermic effect. [DArg²]-DM_1–4 and [DArg², DAla⁴]-DM_1–4 had the greatest effect. Addition of Arg to the N-terminus of DM_1–4 analogs changed their thermoregulatory activity. The greatest thermoregulatory effect was observed for Arg-[DArg²]-DM_1–4 and Arg-[DArg², DAla⁴]-DM_1–4.     

Paleoclimatic Variation and Brain Expansion during Human Evolution

One of the major adaptations during the evolution of Homo sapiens was an increase in brain size. Here we present evidence that a significant and substantial proportion of variation in brain size may be related to changes in temperature. Based on a sample of 109 fossilized hominid skulls, we found that cranial capacities were highly correlated with paleoclimatic changes in temperature, as indexed by oxygen isotope data and sea-surface temperature. Indeed, as much as 52% of the variance in the cranial capacity of these skulls could be accounted for by temperature variation at 100 ka intervals. As an index of more short-term seasonal fluctuations in temperature, we examined the latitude of the sites from which the crania originated. More than 22% of the variance in cranial capacity of these skulls could be accounted for by variation in equatorial distance.     

Thermoregulatory effects of purines and caffeine

Purines are putative neurotransmitters which appear to be involved in regulating several vegetative functions. We examined the effect of purines and their antagonist, caffeine, on colonic temperature of rats. Adenosine injected ip lowered colonic temperature in a dose responsive manner at ambient room temperatures. Adenine and AMP also lowered body temperature whereas 7-methylinosine and inosine only slightly influenced colonic temperature. Caffeine (50 mg/kg) injected sc, increased colonic temperature and when injected within 60 seconds of adenosine, counteracted the hypothermic effect of adenosine (50 mg/kg). Low ambient temperature (4°C) accentuated the thermoregulatory effects of adenosine. Thus adenosine appears to have a hypothermic effect on body temperature regulation when administered peripherally which can be reversed by caffeine.     

Large-Scale In Vitro Expansion of Polyclonal Human Switched-Memory B Lymphocytes

Polyclonal preparations of therapeutic immunoglobulins, namely intravenous immunoglobulins (IVIg), are essential in the treatment of immunodeficiency and are increasingly used for the treatment of autoimmune and inflammatory diseases. Currently, patients’ accessibility to IVIg depends exclusively upon volunteer blood donations followed by the fractionation of pooled human plasma obtained from thousands of individuals. Presently, there are no in vitro cell culture procedures allowing the preparation of polyclonal human antibodies. All in vitro human therapeutic antibodies that are currently generated are based on monoclonal antibodies, which are mostly issued from genetic engineering or single cell antibody technologies. Here, we describe an in vitro cell culture system, using CD40-CD154 interactions, that leads to a 1×10⁶-fold expansion of switched memory B lymphocytes in approximately 50 days. These expanded cells secrete polyclonal IgG, which distribution into IgG₁, IgG₂, IgG₃ and IgG₄ is similar to that of normal human serum. Such in vitro generated IgG showed relatively low self-reactivity since they interacted moderately with only 24 human antigens among a total of 9484 targets. Furthermore, up to one liter of IgG secreting cells can be produced in about 40 days. This experimental model, providing large-scale expansion of human B lymphocytes, represents a critical step toward the in vitro production of polyclonal human IgG and a new method for the ex vivo expansion of B cells for therapeutic purposes.     

Expansion of Multipotent Stem Cells from the Adult Human Brain

The discovery of stem cells in the adult human brain has revealed new possible scenarios for treatment of the sick or injured brain. Both clinical use of and preclinical research on human adult neural stem cells have, however, been seriously hampered by the fact that it has been impossible to passage these cells more than a very few times and with little expansion of cell numbers. Having explored a number of alternative culturing conditions we here present an efficient method for the establishment and propagation of human brain stem cells from whatever brain tissue samples we have tried. We describe virtually unlimited expansion of an authentic stem cell phenotype. Pluripotency proteins Sox2 and Oct4 are expressed without artificial induction. For the first time multipotency of adult human brain-derived stem cells is demonstrated beyond tissue boundaries. We characterize these cells in detail in vitro including microarray and proteomic approaches. Whilst clarification of these cells’ behavior is ongoing, results so far portend well for the future repair of tissues by transplantation of an adult patient’s own-derived stem cells.     

Thermoregulatory responses to upper body exercise

The purpose of this study was to compare thermoregulatory responses between upper body and lower body exercise. Nine male subjects performed 60 min of arm crank (AC) and cycle (CY) exercise at the same absolute intensity (oxygen uptake = 1.61 X min-1) and at the same relative intensity (60% of ergometer specific peak oxygen uptake) in a temperate (24 degrees C, 20% rh) environment. During the absolute intensity experiments, rectal temperature and sweating rate responses were essentially the same for both modes of exercise. In addition, no differences were found for chest, back, arm, or thigh skin temperatures, but calf skin temperature was significantly (P less than 0.05) lower during arm crank than cycle exercise. During the relative intensity experiments, thermoregulatory responses were lower during arm crank than cycle exercise. In addition, we found no difference between esophageal and rectal temperature values elicited by arm crank exercise. These results indicate that the examined thermoregulatory responses are independent of the skeletal muscle mass employed and dependent upon the absolute metabolic intensity.     

Thermoregulatory adjustments during continuous heat exposure

Body temperature regulation was studied in 6 male subjects during an acclimation procedure involving uninterrupted heat exposure for 5 successive days and nights in a hot dry environment (ambient temperature = 35 degrees C, dew-point temperature = 7 degrees C; air velocity = 0.2 m.s-1). Data were obtained at rest and during exercise (relative mechanical workload = 35% VO2max). At rest, hourly measurements were made of oesophageal and 4 local skin temperatures, to allow the calculation of mean skin temperature, and of body motility and heart rate. During the working periods these measurements were made at 5 min intervals. Hourly whole-body weight loss was measured at rest on a sensitive platform scale while in the working condition just before starting and immediately after completing the bicycle exercise. The results show that, in both exercise and at rest, the successive heat exposures increased the sweat gland output during the first 3 days. Afterwards, sweat rate decreased without any corresponding change in body temperature. For the fixed workload, the sweat rate decline was associated with a decrease in circulatory strain. Adjustments in both sweating and circulatory mechanisms occur in the first 3 days of continuous heat exposure. The overall sweat rate decline could involve a redistribution of the regional sweating rates which enhances the sweat gland activities of skin areas with maximal evaporative efficiencies.     

Thermoregulatory control of finger blood flow.

Three men exercised on a bicycle ergometer at 30, 50, asd 70 per cent of maximal aerobic power in ambient temperatures of 15, 25, and 35 degrees C with water vapor pressure less than 18 Torr. Exercies was used to vary internal temperature during as experiment, and different ambient temperatures were used to vary skin temperatures independently of internal temperature. Finger temperature was fixed at about 35.7 degrees C. Espohageal temperature (Tes) was measured with a thermocouple at the level of the left atrium, and mean skin temperature (Tsk) was calcualted from a weighted mean of thermocouple temperatures at eight skin sites. Finger blood flow (BF) was measured by electrocapacitance plethysmography. Although some subjects showed small and equivocal vasomotor effects of exercise, our data are well accounted for by an equation of the form BF equal to alTes + a2Tsk + b, independent of exercise intensity. For these subjects, the ratios a1/a2 (5.9, 8.6, 9.4) were similar to the ratios of the corresponding coefficients recently reported for thermaoregulatory sweating (8.6, 10.4) and for forearm blood flow (9.6).     

Self-Renewing Human Bone Marrow Mesenspheres Promote Hematopoietic Stem Cell Expansion

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Reduced Lymphoid Lineage Priming Promotes Human Hematopoietic Stem Cell Expansion

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