Convection as one of the limiting factors of human respiration during normoxic exercise.

Each of the pathways within respiration has been suspected of limiting maximal performance, suggesting that O2 transport may be affected by each single pathway. The use of the stable, isotopic O2 molecules 16O2 and 16O18O is presented as a novel method for assessing respiration. Because of their different molecular weights, 16O2 diffuses 3% more rapidly than 16O18O, whereas 16O2 is convectively transported as rapidly as 16O18O.

Development of REM and slow wave sleep in the rat.

Active sleep (AS) in the neonate has been considered to be an immature form of rapid eye movement (REM) sleep. Quiet sleep (QS) has been thought to represent an immature form of slow wave sleep (SWS). To determine the relationship between the behaviorally determined states of AS and QS and electrographically determined REM sleep and SWS, we examined sleep ontogeny in the developing rat using an experimental routine that permitted long-term recordings and minimized the effects of maternal separation.

Spiral computerized tomography in the evaluation of acute flank pain: a replacement for excretory urography.

Purpose: We determined the value of noncontrast enhanced spiral computerized tomography (CT) in the evaluation of suspected renal colic.

Materials And Methods: Thin section (5 mm.) noncontrast enhanced CT was used to evaluate 100 patients presenting to the emergency room with flank pain.

Body composition and endocrine function in women with acquired immunodeficiency syndrome wasting.

The acquired immunodeficiency syndrome (AIDS) wasting syndrome is a devastating complication of human immunodeficiency virus (HIV) infection characterized by progressive weight loss and severe inanition. In men, the wasting syndrome is characterized by a disproportionate decrease in lean body mass and relative fat sparing. In contrast, relatively little is known about the gender-specific changes in body composition that characterize AIDS wasting in women.

Metabotropic glutamate receptor activation modulates kainate and serotonin calcium response in astrocytes.

Although metabotropic glutamate receptor (mGluR) modulation has been studied extensively in neurons, it has not been investigated in astrocytes. We studied modulation of glutamate-evoked calcium rises in primary astrocyte cultures using fura-2 ratiometric digital calcium imaging. Calcium plays a key role as a second messenger system in astrocytes, both in regulation of many subcellular processes and in long distance intercellular signaling.

Comparison of the effects of medium-chain triacylglycerols, palm oil, and high oleic acid sunflower oil on plasma triacylglycerol fatty acids and lipid and lipoprotein concentrations in humans.

Although medium-chain triacylglycerols (MCTs, composed of medium-chain fatty acids 8:0 and 10:0) have long been described as having neutral effects on serum cholesterol concentrations, experimental evidence supporting this claim is limited. In a randomized, crossover, metabolic-ward study, we compared the lipid effects of a natural food diet supplemented with either MCTs, palm oil, or high oleic acid sunflower oil in nine middle-aged men with mild hypercholesterolemia. Rather than having a neutral effect, MCT oil produced total cholesterol concentrations that were not significantly different from those produced by palm oil (MCT oil: 5.

Functional inhomogeneities in interstitial lung disease, assessed using (16)o(18)o.

Abstract We investigated the contribution of diffusion limitation and functional inhomogeneities to the impairment of pulmonary oxygen (O(2)) transfer in interstitial lung disease (ILD). Analyses of (16)O(18)O/(16)O(2) ratios were performed on expiratory gas mixtures obtained from 6 ILD patients and 6 healthy humans at rest, applying respiratory mass spectrometry. We assessed O(2) transport by using the overall fractionation factor of respiration (α(0)) which is predicted to increase in the case of diffusion limitation.

Appropriate thermal manipulations eliminate tremors in rats recovering from halothane anesthesia.

Tremors are common in mammals emerging from anesthesia. To determine whether appropriate thermal manipulations immediately before emergence from anesthesia are sufficient to eliminate these tremors, electroencephalographic (EEG) and electromyographic (EMG) activities, hypothalamic temperature (Thy), and O2 consumption were monitored in 12 rats recovering from halothane anesthesia under three thermal regimes. EEG and EMG activities were recorded throughout anesthesia and served as feedback signals for controlling anesthetic depth.

Loss of lean body and muscle mass correlates with androgen levels in hypogonadal men with acquired immunodeficiency syndrome and wasting.

The acquired immunodeficiency syndrome (AIDS) wasting syndrome (AWS) is a devastating complication of human immunodeficiency virus infection characterized by a disproportionate decrease in lean body mass. The pathogenesis of the AWS is unknown, but recent data suggest that endogenous secretion of the potent anabolic hormone, testosterone; is decreased in 30-50% of men with AIDS. However, it is unknown whether decreased androgen levels are associated with decreased lean body mass and/or functional decreases in muscle strength and aerobic capacity in hypogonadal men with the AWS.

Siberian hamsters free run or become arrhythmic after a phase delay of the photocycle.

Body temperature (Tb) and locomotor activity were recorded telemetrically from male Siberian hamsters (Phodopus sungorus sungorus) that were 3 or 12 mo of age and maintained in a light-dark (LD) cycle of 16 h light/day for 2-4 mo. After 3 wk of Tb recording, the LD cycle was phase delayed by extending the light phase by 5 h for 1 day; animals remained on a 16:8-h LD cycle for the remainder of the experiment. Tb and activity rhythms of all animals were stably entrained to the LD cycle before the phase shift.

Ablation of suprachiasmatic nucleus alters timing of hibernation in ground squirrels.

Hibernation patterns were monitored continuously for 2.5 years in female squirrels that were neurologically intact or in which the hypothalamic suprachiasmatic nucleus (SCN) was completely ablated (SCNx). The number of hibernation bouts in SCNx squirrels increased by 159%, total hibernation time increased by 58%, and periodic arousals from hibernation were 47% longer in SCNx than in control squirrels; the duration of individual torpor bouts was 2 days shorter and far more variable in SCNx than in control animals.

Temperature sensitivity of the suprachiasmatic nucleus of ground squirrels and rats in vitro.

Temperature compensation of circadian rhythms in neuronal firing rate was investigated in the suprachiasmatic nucleus (SCN) of ground squirrels and rats in vitro. A reduction in SCN temperature from 37 to 25 degrees C reduced peak firing rates by > 70% in rats but only by approximately 21% in squirrels; trough firing rates were marginally altered in both species. In the rat SCN at 25 degrees C, the peak in neuronal activity decreased progressively on successive days and circadian rhythms no longer were present by Day 3.

Temperature sensitivity of sleep homeostasis during hibernation in the golden-mantled ground squirrel.

Brain temperature (Tbr), vigilance state, and electroencephalograph slow-wave activity (EEG SWA, 1.0-4.0 Hz) were measured during hibernation and spontaneous arousals to euthermia in seven golden-mantled ground squirrels (Spermophilus lateralis).

Chromosomal distribution of the hamster intracisternal A-particle (IAP) retrotransposons.

The retrotransposon-like elements of the intracisternal A-particle (IAP) sequences occur in about 900 copies per haploid hamster cell genome. By applying the fluorescent in situ hybridization (FISH) technique and four different, cloned segments of the IAP element as hybridization probes, these elements were found to be distributed in specific patterns over many of the 44 hamster chromosomes. The hybridization patterns were very similar regardless of whether all four probes or only the IAPI probe carrying the long terminal repeat (LTR) region were used.

Adenosine pre- and postsynaptic modulation of glutamate-dependent calcium activity in hypothalamic neurons.

1. Within the hypothalamus, adenosine has been reported to influence temperature regulation, sleep homeostasis, and endocrine secretions. The effects of adenosine on hypothalamic neurons have not been studied at the cellular level.

Evidence for normal vitamin D receptor messenger ribonucleic acid and genotype in absorptive hypercalciuria.

Absorptive hypercalciuria (a stone-forming condition) is characterized by gut hyperabsorption of calcium, hypercalciuria, and reduced bone density. Inasmuch as these features implicate enhanced calcitriol action in gut and bone, we analyzed the vitamin D receptor (VDR) gene to ascertain whether an abnormality of this gene marks patients with intestinal hyperabsorption of calcium. We have compared the frequency of a restriction fragment length polymorphism (Bsm I) associated with different alleles of the VDR gene in a group of 33 well characterized absorptive hypercalciuric patients and a group of 36 normal race- and age-matched control subjects.

Apamin, a selective SK potassium channel blocker, suppresses REM sleep without a compensatory rebound.

To determine the role of neuronal potassium conductance in rapid-eye-movement (REM)-sleep homeostasis, we have administered small doses of apamin (2-5 ng), a selective blocker of the calcium-dependent SK potassium channel, injected into the lateral ventricle in rats, and characterized the resultant effects on REM-sleep expression. Apamin produces a dose-dependent reduction in REM-sleep expression without an increase in the frequency of attempts to enter REM sleep, suggesting that accumulation of REM-sleep propensity is suppressed. The vast majority (84-95%) of lost REM sleep is not recovered 40 h after apamin administration.

Stimulation of A1 adenosine receptors mimics the electroencephalographic effects of sleep deprivation.

N6-Cyclopentyladenosine (CPA), an A1 adenosine receptor agonist, increased EEG slow-wave activity in nonREM sleep when administered either systemically (0.1-3 mg/kg) or intracerebroventricularly (3.5-10 micrograms) in the rat.

Chromosomal insertion of foreign (adenovirus type 12, plasmid, or bacteriophage lambda) DNA is associated with enhanced methylation of cellular DNA segments.

Insertion of foreign DNA into an established mammalian genome can extensively alter the patterns of cellular DNA methylation. Adenovirus type 12 (Ad12)-transformed hamster cells, Ad12-induced hamster tumor cells, or hamster cells carrying integrated DNA of bacteriophage lambda were used as model systems. DNA methylation levels were examined by cleaving cellular DNA with Hpa II, Msp I, or Hha I, followed by Southern blot hybridization with 32P-labeled, randomly selected cellular DNA probes.

Monoaminergic and cholinergic modulation of REM-sleep timing in rats.

The effects on sleep structure of systemic administration of benchmark cholinergic, serotonergic, and noradrenergic antagonists (QNB, ritanserin, metergoline, and prazosin) were characterized in rats using a new technique for identifying transitions (NRTs) from non-REM (NREM) sleep to REM sleep. In agreement with previous studies, all agents tested reduced REM-sleep expression (by 36-86%). In addition, the serotonergic and noradrenergic antagonists reduced NRT frequency (by 58-81%).

On the insertion of foreign DNA into mammalian genomes: mechanism and consequences.

We have studied the integration of adenovirus type 12 (Ad12) DNA in transformed and hamster tumor cells over many years. Upon infection of hamster cells with Ad12, viral DNA has been found in association with hamster chromosomes, possibly in part integrated into the host genome. Ad12 DNA integration is not sequence specific.

Quantitative and qualitative characterization of apolipoprotein B containing lipoproteins produced by the visceral rat yolk sac in two different in vitro systems: organ culture and isolated epithelial cells in suspension culture.

Tissue pieces as well as isolated epithelial cells taken from visceral rat yolk sacs at the 18th day of gestation were able to synthesize and to secrete apo B containing lipoproteins floating in the density ranges of VLDL, IDL and LDL. In all three density classes only the high molecular weight apo B was detectable. VLDL secreted from yolk sac tissue or isolated epithelial cells lacked apo E and apo C.