Small increments in plasma calcium concentration reduce the responsiveness of forearm resistance vessels to verapamil in men with primary hypertension.

The effect on the forearm resistance vessels of small increases in the local plasma concentration of calcium and magnesium has been examined in 20 men with primary hypertension. Studies were carried out by a standard plethysmographic method with infusion of drugs into the brachial artery. Infusion of calcium at 10 mumol/min into the forearm caused basal blood flow to fall by 9% (n = 17;0.

Effect of small increments in plasma calcium concentration on the responsiveness of forearm resistance vessels to verapamil in normal subjects.

The effect of a small increase in local plasma calcium concentration on the responsiveness of the forearm resistance vessels to verapamil has been examined in normal subjects, by using a plethysmographic method with infusion of calcium and other agents into the brachial artery. Infusion of calcium at a rate which increased the concentration in forearm venous blood by about 0.5 mmol/l caused basal blood flow to fall by 19% and the dilator response to verapamil to fall by 35% (n = 8; P less than 0.

The dilator response to K+ is reduced in the forearm resistance vessels of men with primary hypertension.

The dilator response to local infusion of K+ has been assessed in the forearm resistance vessels of 17 men with primary hypertension and 11 controls, by using a standard plethysmographic method. The response to infusion of K+ at 0.1 mmol/min was smaller in the patients with hypertension than in the normal controls (P less than 0.

Effect of treatment with chlorthalidone and atenolol on response to dilator agents in the forearm resistance vessels of men with primary hypertension.

The forearm resistance vessels of men with primary hypertension respond to verapamil with a greater than normal dilatation relative to that induced by sodium nitroprusside. We have examined the effect on this functional abnormality of treatment with chlorthalidone (50 mg daily in 16 patients) and atenolol (100 mg daily in eight patients and 200 mg daily in two). The responsiveness of the forearm resistance vessels to local intra-arterial infusion of verapamil and sodium nitroprusside was assessed before treatment and again after a minimum of 1 month of drug therapy.

Effect of local infusion of ouabain on human forearm vascular resistance and on response to potassium, verapamil and sodium nitroprusside.

The effect of local infusion of ouabain into the forearm vascular bed has been examined in 15 normotensive male volunteers in an attempt to define the nature of the functional abnormalities of the resistance vessels in primary hypertension. Ouabain and other drugs were infused into the brachial artery and forearm blood flow was measured by venous occlusion plethysmography. Infusion of ouabain at 2 micrograms/min for 1 h caused a 26% reduction in forearm blood flow with a small rise in systemic arterial pressure; the increase in vascular resistance was unaffected by prior treatment with phentolamine.

Homologous genes for X-linked chondrodysplasia punctata in man and mouse.

X-linked dominant chondrodysplasia punctata is a human gene defect characterized by punctate foci of epiphyseal calcification, cataracts, ichthyosis, and systematized atrophoderma. In a comparative study, the murine X-linked mutant 'bare patches' was found to display strikingly similar skeletal, ocular, and cutaneous anomalies. The human as well as the murine phenotypes occur exclusively in the female sex, apparently because the underlying mutations are lethal for male embryos.

Use of an inversion to test for induced X-linked lethals in mice.

A long X-chromosomal inversion in the mouse was used to suppress crossing-over and thereby to scan 85% of the X-chromosome, or 5% of the genome, for recessive lethal mutations induced by radiation. After a fractionated absorbed dose of 500 + 500 rad X-rays 24 h apart to spermatogonia, 2/536 irradiated and 0/529 control X-chromosomes carried a confirmed lethal. This corresponds to a rate for recessive lethals of 1.

Tectonics and evolution of venus.

The global tectonics of Venus differs significantly from that of Earth, most markedly in that the surface is covered predominately by gently rolling terrain; there apparently are no features like ocean rises; the gravity is positively correlated with topography at all wavelengths; and the few highlands are estimated to be supported or compensated at a depth of approximately 100 kilometers. The surface of Venus appears to be covered mainly by an ancient crust, the high surface temperature making subduction difficult. It seems likely that well over 1 billion years ago water was destabilized at the surface and, soon after, plate tectonics ceased.

A comparison of colour and visual texture as codes for use as area symbols on thematic maps.

Three experiments compared colour and texture as methods of coding area symbols for thematic maps. Most previous research has been limited to displays with, at most, eight codes. This study employed displays containing 16 types of symbol coded either by colour, texture, or a non-redundant combination of the two.

Ganymede: a relationship between thermal history and crater statistics.

An approach for factoring the effects of a planetary thermal history into a predicted set of crater statistics for an icy satellite is developed and forms the basis for subsequent data inversion studies. The key parameter is a thermal evolution-dependent critical time for which craters of a particular size forming earlier do not contribute to present-day statistics. An example is given for the satellite Ganymede and the effect of the thermal history is easily seen in the resulting predicted crater statistics.

Why is lower case better? Some data from a search task.

Words set in capital letters are less legible than in lower case when reading text, searching for newspaper headlines, or finding a name on a map. The difference is usually attributed to the distinctive shape of lower case words, but lower case setting also emphasises capital letters at the start of sentences and for proper names. In the experiment reported here people searched for names on a map-like display.

Dose-response curves for radiation-induced gene mutations in mouse oocytes and their interpretation.

Previous work, in which female mice had been given fractionated doses of 20 X 10 rad X-rays, had confirmed and extended Russell's observations that the dose-response relationship for specific-locus mutations in mature-mouse oocytes is curved at low doses. The present work was intended to study the relationship at relatively high doses. Adult female mice were given doses of 200, 400 or 600 rad x-rays at 52 or 72 rad/min, and mated immediately.

Gravity field of venus: a preliminary analysis.

The line-of-sight gravity field for Venus has been mapped by tracking the Pioneer Venus spacecraft in the vicinity of periapsis for a 45 degrees swath of longitude eastward of 294 degrees . There are consistent and systematic variations in the gravity signature from orbit to orbit, attesting to the reality of observed anomalies. Orbit 93 passes over a large positive topographic feature, the "northern plateau," for which there is no corresponding gravity signature.

Recognition of upright and inverted faces: a correlational study.

An investigation of ninety-five university admission candidates failed to replicate the finding by Yin of a negative correlation between the ability to recognise upright and inverted faces. A zero correlation was obtained when unknown faces were both learned and recognised upside down, but when well-known faces were presented normally and upside down for identification, a significant positive correlation appeared. Rock has suggested that inverted faces are difficult to recognise because they overtax a mechanism for correcting disoriented stimuli.

Searching for names in two city street maps.

Two experiments investigated the speed with which names could be found on maps from two London street atlases. Differences in grid referencing between the maps accounted for large differences in search times. However, small statistically significant differences were still present when grid references were not being used, and these cannot be explained in terms of map scale, nor in terms of greater familiarity with the faster map.

Specific locus mutation rates after repeated small radiation doses to mouse oocytes.

When female mice were given a dose of 20 X 20 rad X-rays, the specific locus mutation rate among offspring conceived up to 7 weeks after the end of treatment was 1/39887 or 0.18-10(-7)/rad/locus, whereas when the same total dose of 200 rad was given in a single exposure the mutation rate was 9/34813 or 1.85-10(-7)/rad/locus.