Verapamil impairs secretion of stimulated atrial natriuretic factor in humans.

The adaptation of the secretory rate of atrial natriuretic factor to repeated adequate stimuli and the influence of the calcium antagonist verapamil on the release of atrial natriuretic factor were investigated in 16 patients. In eight patients (Group 1) right atrial pressure was abruptly increased by rapid right ventricular pacing for 4 min (stimulation I). After a 15 min interval, the identical stimulation was repeated (stimulation II).

Location and nucleotide sequence of two tRNA genes and a tRNA pseudo-gene in the maize mitochondrial genome: evidence for the transcription of a chloroplast gene in mitochondria.

We report the nucleotide sequence of three tRNA genes from maize mitochondria. The genes are located in two BamHI fragments, 3.55 and 5.

Possible gender differences in the effect of exercise on hypoxic ventilatory response.

Gender differences in resting ventilation and hypoxic ventilatory response (HVR) have been reported. Ventilation and HVR are closely related to changes in metabolic rate in men. However, it is unclear whether there is a comparable relationship between metabolic rate and ventilation or HVR in women.

Is cyclic GMP a clinically useful marker for ANF action?

The action of ANF is, at least in part, mediated by the activation of particulate guanylate cyclase. Increases in plasma ANF levels induce a marked increase in the plasma levels and urinary excretion of cyclic GMP. In contrast to agents that stimulate particulate guanylate cyclase, activators of soluble guanylate cyclase, such as the bioactive molsidomine metabolite, SIN 1, induce only a modest, not significant, increase in plasma cyclic GMP levels.

Influence of diurnal rhythm, posture and right atrial size on plasma atrial natriuretic peptide levels.

A diurnal rhythm of plasma atrial natriuretic peptide (ANP) and cyclic 3'5'guanosine monophosphate (cGMP) was found in nine healthy adult volunteers. Significantly higher levels of both parameters were found in the morning (8 a.m.

Increased carotid body hypoxic sensitivity during acclimatization to hypobaric hypoxia.

Mechanisms of ventilatory acclimatization to chronic hypoxia remain unclear. To determine whether the sensitivity of peripheral chemoreceptors to hypoxia increases during acclimatization, we measured ventilatory and carotid sinus nerve responses to isocapnic hypoxia in seven cats exposed to simulated altitude of 15,000 ft (barometric pressure = 440 Torr) for 48 h. A control group (n = 7) was selected for hypoxic ventilatory responses matched to the preacclimatized measurements of the experimental group.

Interindividual variation in hypoxic ventilatory response: potential role of carotid body.

There is considerable interindividual variation in ventilatory response to hypoxia in humans but the mechanism remains unknown. To examine the potential contribution of variable peripheral chemorecptor function to variation in hypoxic ventilatory response (HVR), we compared the peripheral chemoreceptor and ventilatory response to hypoxia in 51 anesthetized cats. We found large interindividual differences in HVR spanning a sevenfold range.

Propranolol blocks metabolic rate increase but not ventilatory acclimatization to 4300 m.

Previously, we found resting metabolic rate increased at high altitude but the mechanism and consequences of this increase were unclear. We sought to test the role of beta-sympathetic activation for increasing metabolic rate and the contribution of an increase in metabolic rate to raising total ventilation at altitude. Following baseline studies at sea level, two groups of six healthy male subjects received either placebo or propranolol (80 mg/8 h) for 3 days prior to ascent to Pikes Peak (4300 m) where treatment was continued for 15 days.

Antiarrhythmic agents diminish thiourea-induced pulmonary vascular protein leak in rats.

Drugs possessing membrane stabilizing activity might act to diminish the augmented microvascular permeability resulting from acute lung injury. To test this rats were pretreated with quinidine, procainamide, or lidocaine and then given the lung injury-inducing agent thiourea. Vascular permeability, assessed as the extravascular accumulation of radiolabeled protein, was increased more than threefold by thiourea.

Biphasic ventilatory response of adult cats to sustained hypoxia has central origin.

Hypoxia stimulates ventilation, but when it is sustained, a decrease in the response is often seen. The mechanism of this depression or "roll off" is unclear. In this study we attempted to localize the responsible mechanism at one of three possible sites: the carotid bodies, the central nervous system (CNS), or the ventilatory apparatus.

Increased plasma cyclic guanosine monophosphate concentrations in children with high levels of circulating atrial natriuretic peptide.

Simultaneous measurements of plasma atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (GMP) concentrations were performed in children with various forms of cardiac diseases (n = 22) and in control children (n = 29). In healthy children, plasma ANP and cyclic GMP levels ranged between 2.4 and 98.

NHLBI workshop summary. Respiratory disorders of sleep. Pathophysiology, clinical implications, and therapeutic approaches.

The extensive investigation into complex interactions of breathing and sleep have produced answers to numerous important questions, but it is clear that many of the most important questions in this area remain unanswered. Our understanding of the mechanisms through which sleep alters breathing and how disordered breathing can, in turn, effect sleep is rudimentary. Although a large body of recent work has done much to elucidate the factors that act to maintain the patency of the upper airway during sleep, our understanding of such mechanisms and the relative importance of structure and function in this context remains primitive.

[Homozygous infant in a family with hereditary protein C deficiency].

We report on a female infant homozygous for protein C deficiency in a Jordanian family with frequent intermarriage. A protein C antigen of 0.6% was determined.

Internal carotid and vertebral arterial flow velocity in men at high altitude.

Cerebral blood flow increases at high altitude, but the mechanism of the increase and its role in adaptation to high altitude are unclear. We hypothesized that the hypoxemia at high altitude would increase cerebral blood flow, which would in turn defend O2 delivery to the brain. Noninvasive Doppler ultrasound was used to measure the flow velocities in the internal carotid and the vertebral arteries in six healthy male subjects.

Altitude acclimatization: influence on periodic breathing and chemoresponsiveness during sleep.

Although the influence of altitude acclimatization on respiration has been carefully studied, the associated changes in hypoxic and hypercapnic ventilatory responses are the subject of controversy with neither response being previously evaluated during sleep at altitude. Therefore, six healthy males were studied at sea level and on nights 1, 4, and 7 after arrival at altitude (14,110 ft). During wakefulness, ventilation and the ventilatory responses to hypoxia and hypercapnia were determined on each occasion.

Localization, sequence and expression of the gene coding for tRNA(Pro) (UGG) in plant mitochondria.

The four Sal I fragments of wheat mitochondrial DNA containing the 18S and 5S ribosomal RNA genes were screened for the presence of tRNA genes. Upon sequencing, a tRNA(Pro) (UGG) gene was found in two of these four fragments. The localization of the corresponding gene on the maize mitochondrial genome was established.

In vitro synthesis of bean (Phaseolus vulgaris) chloroplastic and cytoplasmic leucyl-tRNA synthetases. Characterization and processing of a precursor polypeptide for the chloroplast enzyme.

Bean (Phaseolus vulgaris) chloroplastic and cytoplasmic leucyl-tRNA synthetases differ in their structural and catalytic properties and do not share common antigenic determinants. Polyadenylated mRNAs, prepared from young bean leaves, have been translated in vitro in a rabbit reticulocyte lysate cell-free system. The newly synthesized polypeptides have been submitted to immunoadsorption on protein A-Sepharose in the presence of the antibodies raised against the chloroplastic or the cytoplasmic leucyl-tRNA synthetase.

[The AMDP scales in a phase II evaluation of psychotropic drugs].

Four multicentre double blind trials (two studies comparing placebo to a marketed activating drug and two comparing placebo to a new drug with central adrenergic modulating properties) were pooled, totalling 77 placebo Ss, 30 reference drug Ss and 73 study drug Ss. The AMDP-4 and -5 scales were filled out at day 0 and 7 by trained raters. Four statistical analyses were performed on the pre- vs.

Acute increase in right atrial pressure by intracardiac stimulation releases atrial natriuretic peptide.

We studied the effect of an increase in heart rate and/or in right atrial pressure (RAP) on the release of atrial natriuretic peptide (ANP) in 18 patients. In group 1 (n = 6), right ventricular stimulation (100, 120, 140 and 150 bpm) was used to increase RAP by asynchronous contraction of the right atrium and ventricle. Mean RAP increased from 3.

Adjustment of the tRNA population to the codon usage in chloroplasts.

In chloroplasts there is a correlation between the amounts of tRNAs specific for a given amino acid and the codons specifying this amino acid. Furthermore, for the amino acids coded for by more than one codon, the population of isoaccepting tRNAs is adjusted to the frequency of synonymous codons used in chloroplast protein genes. A comparison by two-dimensional gel electrophoresis of the tRNA populations extracted from chloroplasts and from chloroplast polysomes shows that all chloroplast tRNAs are involved in protein biosynthesis.