Pyridostigmine bromide does not alter thermoregulation during exercise in cold air.

This study examined the effects of acute and chronic pyridostigmine bromide (PB) administration on thermoregulatory and metabolic responses to exercise in cold air (5 degrees C). Seven healthy men completed two 7-day trials in a double-blind, crossover experimental design: during one trial they received PB (30 mg three times daily) and during the other trial they received placebo. For each trial, subjects attempted four (3 h) exercise tests: low-intensity exercise (approximately 25% VO2max) and moderate-intensity exercise (approximately 50% VO2max), on days 2 and 3 and again on days 6 and 7.

Blood-to-lymph migration of small lymphocytes through the liver of the sheep.

The process of lymphocyte migration is required for the systemic dissemination of immunological memory and immune surveillance. We report here experiments to quantitate the normal traffic of lymphocytes that occurs from blood to lymph through the liver and hepatic node in the sheep. Comparisons were made with known lymphocyte homing pools.

The Effects of Illumination on the Xanthophyll Composition of the Photosystem II Light-Harvesting Complexes of Spinach Thylakoid Membranes.

The xanthophyll composition of the light-harvesting chlorophyll a/b proteins of photosystem II (LHCII) has been determined for spinach (Spinacia oleracea L.) leaves after dark adaptation and following illumination under conditions optimized for conversion of violaxanthin into zeaxanthin. Each of the four LHCII components was found to have a unique xanthophyll composition.

Induction of Nonphotochemical Energy Dissipation and Absorbance Changes in Leaves (Evidence for Changes in the State of the Light-Harvesting System of Photosystem II in Vivo).

Simultaneous measurements of nonphotochemical quenching of chlorophyll fluorescence and absorbance changes in the 400- to 560-nm region have been made following illumination of dark-adapted leaves of the epiphytic bromeliad Guzmania monostachia. During the first illumination, an absorbance change at 505 nm occurred with a half-time of 45 s as the leaf zeaxanthin content rose to 14% of total leaf carotenoid. Selective light scattering at 535 nm occurred with a half-time of 30 s.

Role of thermal factors on aerobic capacity improvements with endurance training.

This investigation studied the importance of the rise in body temperature during exercise for aerobic capacity adaptations produced by endurance training. The approach used was to compare training effects produced by subjects exercising in hot (35 degrees C) water vs. cold (20 degrees C) water.

Lymphocyte recirculation and life span in vivo.

The physiological process of lymphocyte migration is a complex and dynamic process. The differential migration and life span of lymphocyte subsets is inherent to the normal function of the mammalian immune system. Adequate assessment of the involved processes requires the presence of an intact blood and lymphatic circulatory system and the ability to isolate individual tissues.

Sequence homology and absence of mRNA defines a possible pseudogene member of the Trypanosoma cruzi gp85/sialidase multigene family.

A genomic clone, pTt21, containing DNA apparently transcribed specifically in Trypanosoma cruzi trypomastigotes, was obtained by differentially screening a genomic library with trypomastigote and epimastigote cDNA. This 3444-bp clone contained open reading frames at each end, separated by a 1.8-kb non-coding region.

Increased arterial pressure after acclimatization to 4300 m: possible role of norepinephrine.

Both systemic arterial pressure and sympathetic activity increase at high altitude, but neither the time course of these increases nor the relationship between them are known. Examination of resting and exercising data from our prior studies at sea level and on Pikes Peak indicated that blood epinephrine concentrations either showed little change (from sea level) or rose early in altitude exposure and then declined with acclimatization. By contrast, norepinephrine concentrations in blood and urine were not increased on arrival but consistently rose later in the acclimatization process.

Methane prediction in dry and lactating Holstein cows.

Data from six experiments (two with dry cows) were used to predict partitioning of gross energy to CH4 in Holstein cows using selected independent variables, some of which were intercorrelated, and a stepwise backward elimination regression procedure. Methane outputs ranged from 3.1 to 8.

Human tolerance to heat strain during exercise: influence of hydration.

This study determined whether 1) exhaustion from heat strain occurs at the same body temperatures during exercise in the heat when subjects are euhydrated as when they are hypohydrated, 2) aerobic fitness influences the body temperature at which exhaustion from heat strain occurs, and 3) curves could be developed to estimate exhaustion rates at a given level of physiological strain. Seventeen heat-acclimated men [maximal oxygen uptake (VO2max) from 45 to 65 ml.kg-1.

Human thermoregulatory responses during cold water immersion after artificially induced sunburn.

Thermoregulatory responses during cold-water immersion (water temperature 22 degrees C) were compared in 10 young men before as well as 24 h and 1 wk after twice the minimal erythemal dose of ultraviolet-B radiation that covered approximately 85% of the body surface area. After 10 min of seated rest in cold water, the mean exercised for 50 min on a cycle ergometer (approximately 51% of maximal aerobic power). Rectal temperature, regional and mean heat flow (hc), mean skin temperature from five sites, and hearrt rate were measured continuously for all volunteers while esophageal temperature was measured for six subjects.

Erythrocyte, plasma, and blood volume of healthy young men.

Insufficient data are readily available concerning the vascular fluid volumes of healthy young men. The primary purpose of this study was to develop a normative database for the erythrocyte volume, plasma volume, and blood volume of healthy young men. The secondary purposes were to relate these vascular fluid volumes to the person's body size and physical fitness level and to develop equations that enable their prediction.

Oxygen transport during exercise at altitude and the lactate paradox: lessons from Operation Everest II and Pikes Peak.

It seems unlikely that oxygen-limited metabolism explains the increased lactate concentrations in blood or muscle during exercise at high altitude compared with sea level values because: 1. Even marked hypoxia equivalent to that at the summit of Mt. Everest may not be sufficiently severe to impair function or to impair muscle oxidative metabolism markedly during exercise; 2.

Control of the light-harvesting function of chloroplast membranes by aggregation of the LHCII chlorophyll-protein complex.

A new hypothesis is presented to explain the major molecular process that regulates the efficiency of light harvesting by chloroplast membranes. It is proposed that in excess light the decrease in the thylakoid lumen pH causes an increase in aggregation of the light harvesting complexes of photosystem II resulting in formation of an efficient pathway for non-radiative dissipation of excitation energy. The aggregation is potentiated by the conversion of violaxanthin to zeaxanthin.

Effect of estradiol and progesterone on long chain fatty acyl-coenzyme A levels in the rat uterus.

Fatty acyl-CoAs are potential in vivo inactivators of glucose-6-phosphate dehydrogenase (G6PD). Ovariectomized mature rats (n = 74) were given 5 micrograms of estradiol intravenously, then killed 0, 24, 36, 48 and 72 h later. Control levels of myristoyl-, palmitoyl-, stearoyl-, arachidonoyl-, oleoyl- and linoleoyl-CoA were 0.

Hypohydration does not impair skeletal muscle glycogen resynthesis after exercise.

The purpose of this investigation was to examine the effects of moderate hypohydration (HY) on skeletal muscle glycogen resynthesis after exhaustive exercise. On two occasions, eight males completed 2 h of intermittent cycle ergometer exercise (4 bouts of 17 min at 60% and 3 min at 80% of maximal O2 consumption/10 min rest) to reduce muscle glycogen concentrations (control values 711 +/- 41 mumol/g dry wt). During one trial, cycle exercise was followed by several hours of light upper body exercise in the heat without fluid replacement to induce HY (-5% body wt); in the second trial, sufficient water was ingested during the upper body exercise and heat exposure to maintain euhydration (EU).

Effects of aging on human cold tolerance.

The risk of hypothermia is widely considered to be greater for older than younger persons due to a reduced ability to maintain body temperature during cold exposure. Epidemiological surveys of body temperature normally maintained by older persons while in their own homes do not indicate a large incidence of hypothermia. Uncontrolled ambient conditions during body temperature measurements may have influenced those observations.

Effect of beta-adrenergic blockade on plasma lactate concentration during exercise at high altitude.

When unacclimatized lowlanders exercise at high altitude, blood lactate concentration rises higher than at sea level, but lactate accumulation is attenuated after acclimatization. These responses could result from the effects of acute and chronic hypoxia on beta-adrenergic stimulation. In this investigation, the effects of beta-adrenergic blockade on blood lactate and other metabolites were studied in lowland residents during 30 min of steady-state exercise at sea level and on days 3, 8, and 20 of residence at 4300 m.

Failure of gonadotropin-releasing hormone or human chorionic gonadotropin to enhance the fertility of repeat-breeder cows when administered at the time of insemination.

Repeat-breeder dairy cows failing to conceive to two previous inseminations were injected with saline (2 cc i.m.), gonadotropin-releasing hormone (GnRH, 2 cc i.

Association of Ig L chain-like protein lambda 5 with a 16-kilodalton protein in mouse pre-B cell lines is not dependent on the presence of Ig H chain protein.

Using a polyclonal rabbit antiserum against recombinant mouse lambda 5 protein, we determined that the pre-B cell specific mouse lambda 5 gene encodes a 22-kDa protein. The lambda 5 protein, which is related to conventional Ig lambda L chain proteins forms a complex with Ig mu H chain protein and an as yet unidentified 16-kDa protein (p16) in mu+ pre-B cell lines carrying a functionally rearranged VH-DH-JH allele. In pre-B cell lines which carry DH-JH rearrangements and do not express mu H chain protein, lambda 5 protein is associated with p16.

In vitro regulation of mammary glucose-6-phosphate dehydrogenase activity by palmitoyl coenzyme A, acetate, and polyamines.

An in vitro study was conducted to determine whether bovine mammary glucose-6-phosphate dehydrogenase (G6PD) activity was regulated by palmitoyl coenzyme A (CoA), acetate, spermidine, and putrescine and whether these effects were dependent upon stage of lactation. Early lactation explants incubated in media containing palmitoyl CoA or acetate had reduced (P less than 0.01) G6PD activity compared with incubated control explants.

Human and mouse LSP1 genes code for highly conserved phosphoproteins.

With use of the mouse LSP1 cDNA we isolated a human homologue of the mouse LSP1 gene from a human CTL cDNA library. The predicted protein sequence of human LSP1 is compared with the predicted mouse LSP1 protein sequence and regions of homology are identified in order to predict structural features of the LSP1 protein that might be important for its function. Both the human and mouse LSP1 proteins consist of two domains, an N-terminal acidic domain and a C-terminal basic domain.

Decreased exercise muscle lactate release after high altitude acclimatization.

Blood lactate concentration during exercise decreases after acclimatization to high altitude, but it is not clear whether there is decreased lactate release from the exercising muscle or if other mechanisms are involved. We measured iliac venous and femoral arterial lactate concentrations and iliac venous blood flow during cycle exercise before and after acclimatization to 4,300 m. During hypoxia, at a given O2 consumption the venous and arterial lactate concentrations, the venous and arterial concentration differences, and the net lactate release were lower after acclimatization than during acute altitude exposure.