Changes in myocardial capillary diffusion capacity during infusion of vasoactive drugs.

The present study investigated how variations in coronary vascular resistance and metabolic demand affected myocardial capillary diffusion capacity. Hearts from Wistar rats were perfused with Krebs-Henseleit-albumin buffer in a Langendorff preparation, where heart rate (HR), contractility (dP/dtmax) and myocardial oxygen consumption (MVO2) were recorded continuously. Myocardial capillary diffusion capacity was measured as the permeability surface area product (PS) for Cr-EDTA and vitamin B12 by the single injection colorimetric indicator dilution method.

Capillary diffusion capacity for Cr-EDTA and cyanocobalamine in spontaneously beating rat hearts.

In order to obtain a functional estimate of the diffusional capacity of the myocardial capillary bed, the permeability surface area product (PS) for Cr-EDTA (mol. wt = 341) and cyanocobalamine (vitamin B12, mol. wt = 135) was determined in spontaneously beating Langendorff-perfused rat hearts over a wide range of coronary flow rates (700-3000 ml min-1 100 g-1).

Vasodilators inhibit acute alpha 1-adrenergic receptor-induced trophic responses in the vasculature.

Cardiovascular hypertrophy plays an important role in the development and maintenance of hypertension. Hyperactivity of the sympathetic nervous system may be one of the initiating factors responsible for the stimulation of growth processes involved in these structural alterations. We have used a well-established early biochemical marker of cellular growth processes, induction of ornithine decarboxylase (ODC), to determine whether alpha 1-adrenergic receptor-induced vascular trophic responses are dependent on arterial pressure elevation.

Functional and stereologic estimations of myocardial capillary exchange capacity in treated and untreated spontaneously hypertensive rats.

Myocardial capillary exchange capacity was investigated by stereologic and functional techniques in parallel during pressure-overload cardiac hypertrophy and after long-term antihypertensive therapy with the vasodilator felodipine. In 26-week-old female spontaneously hypertensive rats (SHR) blood pressure increased by 25% and left ventricular weight (LVW/BW) increased by 18% compared to Wistar-Kyoto rats (WKY). Myocardial capillary surface and volume densities normalized for organ weight were similar in both ventricles for both strains.

Influence of early antihypertensive treatment on vascular and cardiac design in SHR with and without renal hypertension.

The present study was designed to explore to what extent pressure reduction by antihypertensive therapy and pressure elevation by renal hypertension are able to affect structural vascular and cardiac changes in young spontaneously hypertensive rats (SHR). Pressure elevation in SHR was induced by means of superimposing 2 kidney, 1 clip renal hypertension (2K1C). Pressure reduction was achieved by means of the vasoselective calcium antagonist felodipine from 6 to 13 weeks of age in both clipped and unclipped SHR.

Molecular abundances in the Sagittarius A molecular cloud.

We have obtained column densities for HCO+, HCO, HCS+, C3H2, HC5N, SiO, OCS, HCOOH, CH3CH2OH, and CH3CCH toward Sgr A. The fractional abundance of SiO relative to molecular hydrogen in Sgr A is comparable to that for the Orion plateau, approximately 10(-7)-10(-8), which may be a typical value for hot clouds. The abundances of HCO, CH3CH2OH and CH3CCH all appear to be enhanced relative to other molecular clouds such as Sgr B2.

Left ventricular insulin-like growth factor I increases in early renal hypertension.

Increasing interest has been directed toward the possible role of trophically acting molecules as modulators or initiators, or both, of myocardial hypertrophy. The aim of the present study was to investigate the possible role of one such molecule, namely, insulin-like growth factor I, in myocardial hypertrophy developed in response to renal artery stenosis. Two-kidney, one clip Goldblatt hypertension was induced in Wistar rats weighing 180 g, and sham-operated animals were used as controls.

Exercise training lowers resting renal but not cardiac sympathetic activity in humans.

Endurance exercise training has previously been shown to reduce the plasma concentration of norepinephrine. Whether reduction in sympathetic activity is responsible for the blood pressure-lowering effects of exercise training is unknown. Using a radiotracer technique, we measured resting total, cardiac, and renal norepinephrine spillover to plasma in eight habitually sedentary healthy normotensive men (aged 36 +/- 3 years, mean +/- SEM) after 1 month of regular exercise and 1 month of sedentary activity, performed in a randomized order.

Left ventricular blood flow during aortic pressure reduction in hypertensive dogs.

We measured left ventricular blood flow with radioactive microspheres during aortic pressure reduction in 10 open-chest, anesthetized dogs with left ventricular hypertrophy due to chronic hypertension and in 10 matched normotensive dogs. Heart rate and left atrial pressure were held constant, and autonomic reflexes were abolished with ganglionic blockade. Aortic diastolic pressure was lowered from baseline to 90, 75, and 60 mm Hg with an arteriovenous fistula.

Norepinephrine overflow and renin pattern of the individual kidney in patients with unilateral renal artery stenosis.

This study was performed to determine divided renal efferent sympathetic nerve activity from kidneys in seven patients with renin-positive, unilateral renal artery stenosis before and 30 minutes after an acute intravenous dose of 1.25 mg enalaprilat. Renal norepinephrine release was calculated from split renal plasma flow, venoarterial plasma concentration gradients across the kidney, and the fractional extraction of tritiated norepinephrine.

Right ventricular coronary blood flow patterns during aortic pressure reduction in renal hypertensive dogs.

We measured right ventricular coronary blood flow with radioactive microspheres during graded aortic pressure reduction in 13 normal dogs and in 13 renal hypertensive dogs with left ventricular hypertrophy. Under anaesthesia and controlled loading conditions, mean aortic pressure was lowered from control (128 mmHg in normal and 146 mmHg in hypertensive dogs) to approximately 100, 90 and 80 mmHg. In normal dogs, right ventricular blood flow was not affected by this pressure reduction, consistent with effective right ventricular autoregulation.

Abundance and chemistry of interstellar HOCO+.

We derive HOCO+ column densities approximately 10(15) cm-2 toward the Galactic center and < or = 10(12) cm-2 for cold dark clouds from observations and an LVG model. We mapped the HOCO+ 4(04)-3(03) line toward Sgr A. The fractional abundance of HOCO+ in the Galactic center region is three orders of magnitude larger than predicted by quiescent ion-molecule chemistry and an order of magnitude larger than predicted by a MHD shock model.

Cardiac and vascular structural adaptation in experimental hypertension.

Various colonies of the spontaneously hypertensive rat (SHR) of the same age demonstrate different forms of the left ventricle (LV) in end-diastole. SHR from breeders in Australia and Switzerland exhibit concentrically hypertrophied LV, evident from an increased wall thickness to internal radius ratio (w/ri), while SHR from a Danish colony show an unchanged w/ri ratio, indicating eccentrically hypertrophied LV. These differences may be related to changes in arterial blood pressure and/or altered cardiac filling patterns.

Evidence for increased renal norepinephrine overflow during sodium restriction in humans.

To investigate the differentiated pattern of efferent sympathetic nerve activity by means of analyzing norepinephrine kinetics in response to sodium restriction, cardiorenal sympathetic activity during rest and mental stress was studied in 12 subjects (33.3 +/- 2.6 years old, SEM) exposed to a low and a normal sodium diet; 5-40 mmol and 160-200 mmol/24 hours, respectively (crossover design).

Interstellar cyanomethane.

We have made an observational study of the newly identified cyanomethane radical CH2CN and the possibly related species CH3CN with the goals of (1) elucidating the possible role of reactions of the type CnHm(+) + N in astrochemistry, and (2) providing a possible test of Bates's models of dissociative electron recombination. We find a remarkably different abundance ratio CH2CN/CH3CN in TMC-1 and Sgr B2, which we deduce is a result of the large difference in temperature of these objects. Studies of CH2CN and CH3CN in other sources, including two new detections of CH2CN, support this conclusion and are consistent with a monotonic increase in the CH2CN/CH3CN ratio with decreasing temperature over the range 10-120 K.

Detection of formic acid in the cold, dark cloud L134N.

We report the first detection of formic acid (HCOOH) in a cold, dark interstellar cloud (L134N). The observed abundance of 3x10(-10) relative to H2 is between one and two orders of magnitude lower than that calculated by published ion molecule models of dark cloud chemistry, but is quite consistent with recent model revisions based on new reaction rates. Formic acid was not detected in the archetypical dark cloud TMC-1, and was tentatively detected in the region of massive star formation, W51.

Effect of endurance exercise on cardiac secretion and renal clearance of atrial natriuretic peptide in normal humans.

Previous work from our laboratory has shown that (i) regular endurance exercise lowers blood pressure (BP), and (ii) acute exercise increases circulating levels of atrial natriuretic peptide (ANP). We hypothesised that increased ANP release may contribute to the antihypertensive effect of regular exercise. Using arterial and selective venous (coronary sinus and renal vein) catheterization and sampling, we measured cardiac secretion and renal clearance of ANP at rest in 7 normal healthy males (mean age 36 years), before and after 4 weeks of training.

Cardiac secretion and renal clearance of atrial natriuretic peptide in normal man: effect of salt restriction.

1. Previous studies of endogenous atrial natriuretic peptide (ANP) in humans have examined changes in plasma levels, rather than regional secretion and clearance of the peptide. Using arterial and selective venous catheterization and sampling, and measurement of regional organ flow, we measured haemodynamics, cardiac secretion of ANP and renal clearance of ANP in six healthy volunteers at rest, on a normal sodium diet.

Autonomic control of the diurnal variation in arterial blood pressure and heart rate in spontaneously hypertensive and Wistar-Kyoto rats.

The relative influences of sympathetic and parasympathetic neural modulation on mean arterial pressure (MAP) and heart rate (HR), and their respective variabilities, were studied in young spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). An on-line computerized system was used for continuous intra-arterial measurements of MAP and HR in unrestrained rats. In addition, the autonomic nervous control of MAP and HR was studied in ageing SHR and WKY.

Resistance control in hypertension.

In hypertension the small arteries undergo structural changes that increase vascular resistance, both in vivo and in vitro. The hallmark of a physiological vascular amplifier is that enhanced resistance responses must occur about the resting value. For this to happen, the average radius of the resistance vessels must be narrower than normal; increased wall thickness without narrowing does not result in this type of amplification.

Interstellar SiO as a tracer of high-temperature chemistry.

The J = 2-1 transition of SiO has been searched for toward both hot and cold molecular gas. SiO was not detected toward the dark clouds TMC-1, L134 N, and B335, down to column density upper limits of N < 2-4 x 10(10) cm-2. The species, however, has been observed toward all sources with a kinetic temperature greater than or equal to 30 K, with the largest column densities (N approximately 10(13)-10(17) cm-2) measured in the warmest (TK > or = 100 K) material.

Observations of some oxygen-containing and sulfur-containing organic molecules in cold dark clouds.

Observations of nine oxygen- and sulfur-containing organic molecules have been made toward the cold dark clouds TMC-1 and L134N. We have confirmed the presence of para-ketene (H2C2O) in TMC-1, have for the first time observed ortho-ketene, and find a total ketene column density approximately 1 x 10(13) cm-2. Thioformaldehyde (H2CS) is easily detectable in both TMC-1 and L134N, with a column density about 5 times larger in the former source (approximately 3 x 10(13) cm-2).

A survey of cyclopropenylidene (C3H2) in galactic sources.

We report the results of an initial survey in a variety of Galactic sources for cyclopropenylidene (C3H2), the first interstellar hydrocarbon ring molecule. C3H2 is found to be very widespread throughout the Galaxy. This, together with its large dipole moment and many observable transitions, makes cyclopropenylidene a promising probe for physical conditions in the interstellar medium.

Electrophysiological and mechanical characteristics of isolated hearts from spontaneously hypertensive (SHR) and normotensive (WKY) rats on very high- and low-sodium diets.

Electrophysiological, mechanical, dimensional and coronary flow characteristics were studied on papillary strips and on isolated hearts, from spontaneously hypertensive (SHR) and normotensive (WKY) rats respectively, which from 5 to 15 weeks of age had been on either 'low' (LNa, 0.5 mmol 100 g-1 food), control (CNa, 5) 'high' (HNa, 50) or 'very high' (vHNa, 120) sodium diets. With respect to cardiac electrophysiological characteristics, contractility, and maximal stroke volume capacity only minor, if any, differences were observed between the various Na diet groups, both in WKY and SHR.