Cutaneous evaporimetry. VIII. Cutaneous water loss in Somalian newborn infants

The cutaneous water loss (CWL) were investigated in 21 new-born infants by Evaporimeter Ep-1. The mean value of the CWL resulted 13,3 +/- 7,5 g/h. This result is much greater compared with the value of european new-born infants equal to 6,4 +/- 1,8 g/h.     

Cutaneous evaporimetry. VII. Cutaneous water loss in Basedow's disease

The cutaneous water loss was investigated in 12 patients affected with Basedow's disease by Evaporimeter Ep-1. The mean value of the CWL resulted 49,8 +/- 18,2 g/h. This result is significantly higher compared with the value of normal somali people equal to 25,24 +/- 14,6 g/h.     

Development of skin structure and cutaneous water loss in nestling desert house sparrows from Saudi Arabia

The outer layer of the epidermis, the stratum corneum (SC), contains lipids and corneocytes, which together form layers that limit cutaneous water loss (CWL). We examined the development of structure of the SC and CWL in nestling House Sparrows (Passer domesticus) from Saudi Arabia. We measured CWL of nestlings, and characterized development of their epidermis using electron microscopy. We tested two antagonistic hypotheses, that CWL decreases as nestlings age, a response to increased thickness of SC, and an opposite idea that CWL increases as nestlings age even though the number of layers of the SC remains constant. CWL of nestling House Sparrows varied with developmental stages, in a non-linear fashion, but not significantly so. CWL of nestlings averaged 7.31+/-1.5 g H(2)O/(m(2) h), whereas for adults it was 4.95 g/(m(2) h); adult CWL was 67.7% that of nestlings. We found that morphology of the SC did not change linearly with age, but seemed to vary with developmental stage. CWL decreased as the SC thickness increased and as the total thickness of the corneocytes increased. Further, we found that CWL decreased as the thickness of the extracellular space increased, number of corneocytes increased, and proportion of the SC that is extracellular space increased.     

Cutaneous water evaporation--I. Its significance in heat-stressed birds

In a comparative study on avian cutaneous evaporation, two species of Phasianidae, Japanese quail Coturnix coturnix japonica and chukar partridge Alectoris chukar, and three species of Columbidae, palm dove Streptopelia senegalensis, collared turtle dove Streptopelia decaocto and rock pigeon Columbia livia, were investigated. The skin resistance to vapor diffusion (rs) and cutaneous water loss (CWL) were studied in these birds exposed to air temperatures (Ta) between 20 and 52 degrees C. The skin resistance was measured with Lambda instrument diffusive resistance meter. Skin resistance within the thermo-neutral zone varied between a minimum of 62 sec/cm in the palm dove exposed to 20 degrees C and a maximum of 309.1 sec/cm in the partridge exposed to 36 degrees C. The CWL values were 2.5 mg H2O/cm2.hr and 0.51 mg H2O/cm2.hr respectively. Maximum CWL of the quail and partridge was 1.9-2.1 mg H2O/cm2.hr, equivalent to a cooling capacity of about 17% of metabolic heat production at 45 degrees C Ta. In the palm dove, collared dove and pigeon CWL reached 6.8, 13.1 and 20.9 mg H2O/cm2.hr and rs values reached 31.2, 16.2 and 9.4 sec/cm respectively. The cooling capacity amounted to 51.5, 86.1 and 96.5% of metabolic heat during heat stress (52 degrees C). The significance of skin evaporation in body temperature regulation of heat-stressed birds is discussed.     

Biodiesel production from isolated oleaginous fungi Aspergillus sp. using corncob waste liquor as a substrate

The study documented the potential of isolated filamentous fungus Aspergillus sp. as whole cell biocatalyst for biodiesel production using Sabourauds dextrose broth medium (SDBM) and corncob waste liquor (CWL) as substrates. SDBM showed improvement in both biomass production (13.6 g dry weight/1000 ml) and lipid productivity (23.3%) with time. Lipid extraction was performed by direct (DTE) and indirect (IDTE) transesterification methods. DTE showed higher transesterification efficiency with broad spectrum of fatty acids profile over IDTE. CWL as substrate showed good lipid productivity (22.1%; 2g dry biomass; 48 h) along with efficient substrate degradation. Lipids derived from both substrates depicted high fraction of saturated fatty acids than unsaturated ones. Physical characteristics of fungal based biodiesel correlated well with prescribed standards. CWL derived biodiesel showed relatively good fuel properties (acid number, 0.40 mg KOH/g of acid; iodine value, 11 g I?/100 g oil; density, 0.8342 g/cm3) than SDBM derived biodiesel.     

Cutaneous and respiratory water loss in larks from arid and mesic environments

Birds from deserts generally have lower total evaporative water loss (TEWL), the sum of cutaneous (CWL) and respiratory water loss (RWL), than species from mesic areas. We investigated the role of CWL and RWL as a function of air temperature (T(a)) in hoopoe larks (Alaemon alaudipes) and Dunn's larks (Eremalauda dunni) from the Arabian Desert and skylarks (Alauda arvensis) and woodlarks (Lullula arborea) from temperate mesic grasslands. The proportional contribution of CWL to TEWL in all larks at moderate T(a) ranged from 50% to 70%. At high T(a) (40 degrees -45 degrees C), larks enhanced CWL by only 45%-78% and relied on an increase in RWL by 676%-2,733% for evaporative cooling. Surface-specific CWL at 25 degrees C was 29% lower in the arid-zone species than in the mesic larks. When acclimated to constant T(a), 15 degrees C-acclimated hoopoe larks increased CWL by 22% compared with 35 degrees C-acclimated birds, but the other species did not change CWL. This study is consistent with the hypothesis that larks from deserts have a reduced CWL at moderate and low T(a) but provided no support for the hypothesis that at high T(a) larks from arid regions rely more on CWL than larks from mesic environments. Interspecific differences in CWL cannot be attributed to acclimation to environmental temperature and are possibly the result of genetic differences due to natural selection or of phenotypically plastic responses to divergent environments during ontogeny.     

Phenotypic flexibility in cutaneous water loss and lipids of the stratum corneum in house sparrows (Passer domesticus) following acclimation to high and low humidity

Resistance to water-vapor diffusion through the skin is thought to be conferred by lipids in the stratum corneum (SC), the outer layer of the epidermis. We tested the effect of ambient humidity on cutaneous water loss (CWL) and lipid composition of the SC by acclimating house sparrows (Passer domesticus) to either a dry (6.5 g/m(3) absolute humidity) or a humid (31 g/m(3)) environment for 3 wk at a thermoneutral temperature (30 degrees C). Sparrows in the dry-acclimated group reduced CWL by 36% compared with those in the humid environment. Relative to initial values, both groups of sparrows decreased CWL, 45% in the dry-acclimated group and 23% in the humid group, suggesting that temperature is also an important stimulus for CWL apart from humidity. Both groups of acclimated sparrows decreased quantities of cholesterol, free fatty acids, and cerebrosides and increased the proportion of ceramides in their SC. Lipid amounts or proportions in the SC did not differ between dry- and humid-acclimated sparrows, but the free fatty acid : ceramide ratio was significantly lower in dry-acclimated birds. Also, lipid composition was only correlated with CWL in dry-acclimated sparrows, suggesting that structural changes to SC lipids are more tightly linked to CWL regulation in response to low humidity. Our results demonstrate phenotypic flexibility in CWL and lipid composition of the SC and provide support for a functional relationship between these traits.     

The Relationship between Cutaneous Water Loss and Thermoregulatory State in Kuhl's Pipistrelle Pipistrellus kuhlii, a Vespertillionid Bat

Abstract Total evaporative water loss is the sum of respiratory water loss (RWL) and cutaneous water loss (CWL) and constitutes the main avenue of water loss in bats. Because bats fly and have large surface-to-volume ratios, they potentially have high rates of RWL and CWL. Most species of small insectivorous bats have the ability to reduce their body temperature (T(b)) at rest, which substantially reduces energy expenditure and water loss. We hypothesized that bats reduce evaporative water loss during bouts of deep hypothermia (torpor) by decreasing RWL and CWL. We measured T(b), RWL, CWL, and resting metabolic rate (RMR) in Kuhl's pipistrelle Pipistrellus kuhlii, a small insectivorous bat. In support of our hypothesis, we found that RWL decreased with decreasing RMR. We found that CWL was lower in torpid individuals than in normothermic bats; however, bats in deep torpor had similar or higher CWL than bats in shallow torpor, suggesting that they exert a less effective physiological control over CWL when in deep torpor. Because insectivorous bats spend most of their lives in torpor or hibernation, the regulation of CWL in different heterothermic states has relevant ecological and evolutionary consequences.     

Measurement of cutaneous evaporation. 5. Cutaneous water loss in peripheral vascular disease

The purpose of this research is the measurement of the cutaneous water loss in 19 angiopathie patients by the Evaporimeter. Ep I in order to compare it with the values of normal people. We found a statistical significant increase of the CWL without difference between the normal and pathologic limb.     

Cysteamine can induce duodenal ulceration in rats without depletion of immunoreactive somatostatin.

Single subcutaneous administration of cysteamine (2-aminoethanethiol, CSH) produces duodenal ulceration in rats within 24 h. Depletion of circulating and tissue somatostatin (SOM), hypergastrinemia and gastric acid hypersecretion have all been postulated as the pathophysiological response to CSH leading to ulceration. The purpose of this study was to analyze the synthesis, storage and secretion of gastrin and SOM as well as structural changes in SOM peptide after CSH treatment. Injection of 300 mg/kg (s.c.) of CSH caused macroscopic duodenal ulcers in seven out of eight rats at 24 h. Hypergastrinemia was seen within 30 min (from 23 +/- 4 to 74 +/- 20 pmol/l), and persisted for 4 h. Antral gastrin content was elevated at 30 min (2539 +/- 114 pmol/g) when compared to saline controls (1589 +/- 101 pmol/g). Plasma SOM did not change over the 24 h but antral SOM increased at 30 min (from 120 +/- 3 to 230 +/- 23 pmol/g) and remained elevated at 2 h (374 +/- 48 pmol/g) and 4 h (357 +/- 37 pmol/g). Fundic and duodenal SOM followed a similar pattern. Antral SOM mRNA was also elevated over the first 4 h (3-fold increase, P less than 0.05). HPLC analysis of antral tissue extracts revealed the presence of additional molecular forms of SOM which, however, differed from the major products of in vitro reduction with either CSH or dithiothreitol. Thus, the in vivo effect of CSH on SOM cannot be solely explained by a reductive opening of the disulphide bond. These results suggest that duodenal ulceration in rats treated with CSH is not related in a simple fashion to depletion of immunoreactive SOM. Early induction of hypergastrinemia may be important in the onset of ulceration. The value of CSH as a SOM depleting tool in gastrointestinal tissue must remain in doubt.     

Cutaneous water loss and lipids of the stratum corneum in two syntopic species of bats

The lipid matrix of the stratum corneum (SC), the outer layer of the epidermis of mammals and birds, constitutes the barrier to diffusion of water vapor through the skin. The lipids of the SC are structured in the intercellular spaces of the mammalian epidermis in ordered layers, called lamellae, which have been postulated to prevent water loss. Lipids in the mammalian SC are mainly cholesterol, free fatty acids and ceramides, the latter forming the structural support for the lamellae. However, knowledge on how the lipid composition of the SC alters cutaneous water loss (CWL) in mammals is rudimentary, and is largely derived from studies on laboratory animals and humans. We measured CWL of individuals of two species of syntopic bats, Tadarida brasiliensis and Myotis velifer. In the first study of its kind on wild mammals, we correlated CWL with the lipid composition of the SC, measured using thin layer chromatography and high performance liquid chromatography coupled with atmospheric pressure photoionization mass spectrometry. Surface-specific CWL was 20.6% higher in M. velifer than in T. brasiliensis, although differences were not significant. Compared with individuals of M. velifer, individuals of T. brasiliensis had more classes, and a higher proportion, of polar ceramides in the SC, a feature associated with lower CWL. Individuals of T. brasiliensis also had a class of non-polar ceramides that presumably spans the lamellae and gives more cohesiveness to the lipid matrix of the SC. We conclude that qualitative and quantitative modifications of the lipid composition of the SC contribute to regulate CWL of these two species of bats.     

Cutaneous water loss and the development of the stratum corneum of nestling house sparrows (Passer domesticus) from desert and mesic environments

Evaporation through the skin contributes to more than half of the total water loss in birds. Therefore, we expect the regulation of cutaneous water loss (CWL) to be crucial for birds, especially those that live in deserts, to maintain a normal state of hydration. Previous studies in adult birds showed that modifications of the lipid composition of the stratum corneum (SC), the outer layer of the epidermis, were associated with changes in rates of CWL. However, few studies have examined the ontogeny of CWL and the lipids of the SC in nestling birds. In this study, we measured CWL and the lipid composition of the SC during development of nestlings from two populations of house sparrows, one from the deserts of Saudi Arabia and the other from mesic Ohio. We found that desert and mesic nestlings followed different developmental trajectories for CWL. Desert nestlings seemed to make a more frugal use of water than did mesic nestlings. To regulate CWL, nestlings appeared to modify the lipid composition of the SC during ontogeny. Our results also suggest a tighter regulation of CWL in desert nestlings, presumably as a result of the stronger selection pressures to which nestlings are exposed in deserts.     

beta-Glucocerebrosidase activity in the stratum corneum of house sparrows following acclimation to high and low humidity

Skin is an important avenue of water loss in terrestrial birds, so environmental conditions that necessitate water conservation should favor physiological mechanisms that reduce cutaneous water loss (CWL). Skin resistance to CWL is conferred by a barrier of lipid molecules located in the stratum corneum (SC), the outer layer of the epidermis. In mammals, SC barrier function depends on the conversion of cerebrosides to ceramides by the enzyme beta -glucocerebrosidase ( beta -GlcCer'ase). Avian SC contains both cerebrosides and ceramides, suggesting that observed plasticity in CWL may be mediated by changes in beta -GlcCer'ase activity and resultant SC lipid composition. We tested the hypothesis that changes in ambient humidity would alter beta -GlcCer'ase activity by acclimating house sparrows (Passer domesticus) to either dry (6.5 g H(2)O m(-3) absolute humidity) or humid (31 g H(2)O m(-3)) conditions for 5 and 21 d at 30 degrees C and then measuring beta -GlcCer'ase activity from SC homogenates. Our results provide the first characterization of beta -GlcCer'ase activity in any nonmammalian vertebrate. Relative to nonacclimated controls, both dry- and humid-acclimated sparrows had significantly elevated beta -GlcCer'ase activity at 21 d postacclimation. Across individuals, we observed negative correlations between beta -GlcCer'ase activity and both CWL and SC ceramide content. Although dry- and humid-acclimated sparrows did not differ in beta -GlcCer'ase activity, these results are consistent with our findings that both humidity treatments caused a reduction in CWL and similar changes in SC lipid composition. Our results demonstrate physiological plasticity in CWL and provide tentative support for a role of beta -GlcCer'ase in mediating this response.     

The purine nucleotide cycle in the regulation of ammoniagenesis during induction and cessation of chronic acidosis in the rat kidney.

The effect of chronic acid feeding and its subsequent withdrawal was determined on the amounts of the metabolic intermediates and enzymic activities of the purine nucleotide cycle. Sprague-Dawley rats were given 1.5% (w/v) NH4Cl in their drinking water for 5 days. The renal excretion of NH3 rose 70-fold and the rats developed acidosis. The amount of renal IMP rose from a control value of 4.5 +/- 2.2 to 20.4 +/- 3.7nmol/g of kidney after 48h of acid feeding (P less than 0.001) and fell to normal within 48h of the recovery. Adenylosuccinate concentrations fell from a control value of 4.5 +/- 0.9nmol/g of kidney to 1.2 +/- 0.3nmol/g (P less than 0.005) by day 5 of acidosis and continued to fall to undetectable values by 48h after recovery. The amount of AMP remained constant through the acid-feeding and the recovery periods. The activity of adenylosuccinate synthetase, the rate-limiting enzyme of the purine nucleotide cycle, paralleled the rise and fall in NH3 excretion. The activities of phosphate-dependent glutaminase and glutamate dehydrogenase were elevated during the acid-feeding and the recovery period. Thus changes in the purine nucleotide cycle correlate with changes in NH3 excretion to a more parallel degree than does the activity of glutaminase or glutamate dehydrogenase.     

Regional hemodynamics during postexercise hypotension. II. Cutaneous circulation.

After an acute bout of exercise, there is an unexplained elevation in systemic vascular conductance that is not completely offset by an increase in cardiac output, resulting in a postexercise hypotension. The contributions of the splanchnic and renal circulations are examined in a companion paper (Pricher MP, Holowatz LA, Williams JT, Lockwood JM, and Halliwill JR. J Appl Physiol 97: 2065-2070, 2004). The purpose of this study was to determine the contribution of the cutaneous circulation in postexercise hypotension under thermoneutral conditions (approximately 23 degrees C). Arterial blood pressure was measured via an automated sphygmomanometer, internal temperature was measured via an ingestible pill, and skin temperature was measured with eight thermocouples. Red blood cell flux (laser-Doppler flowmetry) was monitored at four skin sites (chest, forearm, thigh, and leg), and cutaneous vascular conductance (CVC) was calculated (red blood cell flux/mean arterial pressure) and scaled as percent maximal CVC (local heating to 43 degrees C). Ten subjects [6 men and 4 women; age 23 +/- 1 yr; peak O(2) uptake (Vo(2 peak)) 45.8 +/- 2.0 ml.kg(-1).min(-1)] volunteered for this study. After supine rest (30 min), subjects exercised on a bicycle ergometer for 1 h at 60% of their Vo(2 peak) and were then positioned supine for 90 min. Exercise elicited a postexercise hypotension reaching a nadir at 46.0 +/- 4.5 min postexercise (77 +/- 1 vs. 82 +/- 2 mmHg preexercise; P < 0.05). Internal temperature increased (38.0 +/- 0.1 vs. 36.7 +/- 0.1 degrees C preexercise; P < 0.05), remaining elevated at 90 min postexercise (36.9 +/- 0.1 degrees C vs. preexercise; P < 0.05). CVC at all four skin sites was elevated by the exercise bout (P < 0.05), returning to preexercise values within 50 min postexercise (P > 0.05). Therefore, although transient changes in CVC occur postexercise, they do not appear to play an obligatory role in mediating postexercise hypotension under thermoneutral conditions.     

Uterine contractile activity in rats induced by mifepristone (RU 486) in relation to changes in concentrations of prostaglandins E-2 and F-2 alpha.

Pregnant rats were injected with mifepristone (RU 486) on Day 15 of pregnancy. The force and frequency of uterine contractions, recorded by a microballoon technique, were significantly greater at 12, 24 and 36 h in treated than in control rats (11.9 +/- 1.9 vs. 8.9 +/- 1.2 units, 17.7 +/- 3.0 vs. 10.5 +/- 2.3 units and 16.8 +/- 2.9 vs. 8.8 +/- 1.8 units for force and 51.3 +/- 9.1 vs. 29.4 +/- 3.8/h, 35.4 +/- 6.4 vs. 22.1 +/- 4.9/h and 35.6 +/- 3.2 vs. 24.6 +/- 4.6/h for frequency, respectively). There was no significant difference in concentrations of prostaglandin (PG) E-2 or PGF-2 alpha between treated and control rats at 12 h and 24 h after injection. At 36 h, 7 of 12 rats were aborting and uterine PG concentrations in these were significantly greater than in the others (1.5 +/- 0.2 vs. 0.9 +/- 0.2 ng PGE-2/g and 38.6 +/- 19.2 vs. 16.9 +/- 5.4 ng PGF-2 alpha/g), but there was no significant difference between control and treated rats that were not aborting. Concentrations of PGE-2 and PGF-2 alpha were significantly higher at 48 h when abortion had occurred in all animals (6.5 +/- 2.6 vs. 2.4 +/- 1.7 ng PGE-2/g and 30.4 +/- 8.9 vs. 9.3 +/- 5.6 ng PGF-2 alpha/g). Thus, the increase in uterine contractile activity induced by mifepristone preceded significant changes in concentrations of PGE-2 and PGF-2 alpha in the uterus and so could not have been caused by these changes.     

Caffeine increases exogenous carbohydrate oxidation during exercise.

Both carbohydrate (CHO) and caffeine have been used as ergogenic aids during exercise. It has been suggested that caffeine increases intestinal glucose absorption, but there are also suggestions that it may decrease muscle glucose uptake. The purpose of the study was to investigate the effect of caffeine on exogenous CHO oxidation. In a randomized crossover design, eight male cyclists (age 27 +/- 2 yr, body mass 71.2 +/- 2.3 kg, maximal oxygen uptake 65.7 +/- 2.2 ml x kg(-1) x min(-1)) exercised at 64 +/- 3% of maximal oxygen uptake for 120 min on three occasions. During exercise subjects ingested either a 5.8% glucose solution (Glu; 48 g/h), glucose with caffeine (Glu+Caf, 48 g/h + 5 mg x kg(-1) x h(-1)), or plain water (Wat). The glucose solution contained trace amounts of [U-13C]glucose so that exogenous CHO oxidation could be calculated. CHO and fat oxidation were measured by indirect calorimetry, and 13C appearance in the expired gases was measured by continuous-flow IRMS. Average exogenous CHO oxidation over the 90- to 120-min period was 26% higher (P < 0.05) in Glu+Caf (0.72 +/- 0.04 g/min) compared with Glu (0.57 +/- 0.04 g/min). Total CHO oxidation rates were higher (P < 0.05) in the CHO ingestion trials compared with Wat, but they were highest when Glu+Caf was ingested (1.21 +/- 0.37, 1.84 +/- 0.14, and 2.47 +/- 0.23 g/min for Wat, Glu, and Glu+Caf, respectively; P < 0.05). There was also a trend (P = 0.082) toward an increased endogenous CHO oxidation with Glu+Caf (1.81 +/- 0.22 g/min vs. 1.27 +/- 0.13 g/min for Glu and 1.12 +/- 0.37 g/min for Wat). In conclusion, compared with glucose alone, 5 mg x kg(-1) x h(-1) of caffeine coingested with glucose increases exogenous CHO oxidation, possibly as a result of an enhanced intestinal absorption.     

The effect of sex on central histaminergic responses and corticosterone bioperiodicity in Sprague-Dawley rats

Male and female rats demonstrate a difference in the relationship between food intake and H(1) receptor binding, which may be due to hormonal differences that exist. The relationship between the endocrine and histaminergic regulation and synchronization of food intake needs to be elucidated. Male and female rats fed 25% protein displayed bioperiodicity in mean corticosterone levels of 148.95+/-33.71 and 288.48+/-47.84 ng/ml, respectively. Accompanying bioperiodic times were of 22.43+/-1.35 h (males) and a period of 21.42+/-1.96 h (females). Central H(1) receptors in male rats had a mean bioperiodic value of 102.37+/-1.95 pmol/g protein with a period of 21.66+/-1.85 h, while that for females was 97.42+/-4.19 pmol/g protein with a period of 10.23+/-0.95 h. Central histaminergic activity affects feeding in rats with distinct gender variation that is bioperiodic in nature and functions as a major regulatory mechanism.     

Body-weight-support treadmill training improves blood glucose regulation in persons with incomplete spinal cord injury.

The impact of a 6-mo body-weight-supported treadmill training program on glucose homeostasis and muscle metabolic characteristics was investigated. Nine individuals (31 +/- 3 yr, 8.1 +/- 2.5 yr postinjury; means +/- SE) with incomplete spinal cord injury trained three times weekly for a total of 6 mo. Training session duration and intensity (velocity) increased by 54 +/- 10% (P < 0.01) and 135 +/- 20%, respectively. Muscle biopsies and a modified glucose tolerance test (100 g glucose with [U-(13)C]glucose) were performed before (Pre) and after training (Post). Training resulted in a reduction in area under the curve of glucose x time (-15 +/- 4%) and insulin x time (-33 +/- 8%; both P < 0.05). Oxidation of exogenous (ingested) glucose increased as a result of training (Pre = 4.4 +/- 0.7 g/h, Post = 7.4 +/- 0.6 g/h; P < 0.05), as did oxidation of endogenous (liver) glucose (Pre = 3.8 +/- 0.3 g/h, Post = 5.2 +/- 0.3 g/h; P < 0.05). Training resulted in increased muscle glycogen (80 +/- 23%; P < 0.05) and GLUT-4 content and hexokinase II enzyme activity (126 +/- 34 and 49 +/- 4%, respectively, both P < 0.01). Resting muscle phosphocreatine content also increased after training (Pre = 62.1 +/- 4.3, Post = 78.7 +/- 3.8, both mmol/kg dry wt and P < 0.05). Six months of thrice-weekly body-weight-supported treadmill training in persons with an incomplete spinal cord injury improved blood glucose regulation by increasing oxidation and storage of an oral glucose load. Increases in the capacity for transport and phosphorylation glucose in skeletal muscle likely play a role in these adaptations.     

Cutaneous active vasodilation in humans during passive heating postexercise.

The hypothesis that exercise causes an increase in the postexercise esophageal temperature threshold for onset of cutaneous vasodilation through an alteration of active vasodilator activity was tested in nine subjects. Increases in forearm skin blood flow and arterial blood pressure were measured and used to calculate cutaneous vascular conductance at two superficial forearm sites: one with intact alpha-adrenergic vasoconstrictor activity (untreated) and one infused with bretylium tosylate (bretylium treated). Subjects remained seated resting for 15 min (no-exercise) or performed 15 min of treadmill running at either 55, 70, or 85% of peak oxygen consumption followed by 20 min of seated recovery. A liquid-conditioned suit was used to increase mean skin temperature ( approximately 4.0 degrees C/h), while local forearm temperature was clamped at 34 degrees C, until cutaneous vasodilation. No differences in the postexercise threshold for cutaneous vasodilation between untreated and bretylium-treated sites were observed for either the no-exercise or exercise trials. Exercise resulted in an increase in the postexercise threshold for cutaneous vasodilation of 0.19 +/- 0.01, 0.39 +/- 0.02, and 0.53 +/- 0.02 degrees C above those of the no-exercise resting values for the untreated site (P < 0.05). Similarly, there was an increase of 0.20 +/- 0.01, 0.37 +/- 0.02, and 0.53 +/- 0.02 degrees C for the treated site for the 55, 70, and 85% exercise trials, respectively (P < 0.05). It is concluded that reflex activity associated with the postexercise increase in the onset threshold for cutaneous vasodilation is more likely mediated through an alteration of active vasodilator activity rather than through adrenergic vasoconstrictor activity.