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Biomedical subjects

J A Downey

Publications and source records attributed to J A Downey.

At least 19 recordsLinked to original sources
PubMed1992

Effect of fever on menopausal hot flashes.

Some women report that they have fewer hot flashes when they have a fever. This is the first case of physiological monitoring of hot flashes during fever in a subject with a well documented pattern of frequent hot flashes when afebrile. During fever, there were fewer hot flashes than during afebrile periods, and these hot flashes also tended to be less intense. For most of the period of reduced hot flashes, internal (core) temperature was elevated, above 37.5 degrees C. When the fever broke, hot flashes resumed in a pattern similar to that of afebrile periods. Possible explanations for the reduction in hot flashes during a fever include: (1) a hot flash is triggered, but the characteristic physiological changes do not occur due to competing thermoregulatory drives, (2) the febrile core temperature inhibits whatever it is that triggers a hot flash; or (3) some product of the fever process inhibits the hot flash trigger or masks the physiological changes that occur during hot flashes.

Body Temperature↗
PubMed1992

In vitro inhibition of struvite crystal growth by acetohydroxamic acid.

Struvite (MgNH4PO46H2O) crystals were produced by Proteus mirabilis growth in artificial urine, in the presence and absence of the urease inhibitor, acetohydroxamic acid (AHA). In the absence of AHA, struvite crystals assumed an "X-shaped" or dendritic crystal habit due to rapid growth along their 100 axis. When AHA was present, crystal growth, as monitored by phase contrast light microscopy, was greatly slowed, and the crystals assumed an octahedral crystal habit. Scanning electron microscopy revealed that crystals grown in the presence of AHA were pitted on their surface. This pitting was absent in control samples. While most of this inhibition by AHA was due to lowered urease activity, some crystal growth inhibition occurred in struvite produced in the absence of urease activity through NH4OH titration of artificial urine. We conclude that while AHA is primarily a urease inhibitor, it may also disrupt struvite growth and formation directly through interference with the molecular growth processes on crystal surfaces.

Animals↗
PubMed1990

The cold face test (diving reflex) in clinical autonomic assessment: methodological considerations and repeatability of responses.

1. Cold stimulus applied to the face causes bradycardia and peripheral vasoconstriction (i.e. the diving reflex), and has been suggested as a test of the autonomic pathways involved. The purpose of this study was to define standard procedures for conducting the test and analysing the responses to the cold face test, to evaluate variability in responses between subjects and within subjects when the same test is repeated, and to examine its usefulness in clinical autonomic assessment. 2. Sixteen (nine female, seven male) healthy adult (21-35 years old) subjects were used. Cold stimulus was applied with gel-filled compresses. Forehead temperature under the compress as an indication of stimulus magnitude, heart rate, blood flow in the finger, toe and calf by venous occlusion plethysmography, and systolic and diastolic blood pressure were monitored. Three protocols were carried out in which the temperature (0, 5, 10, 15 degrees C), placement (whole face, unilateral, forehead) and duration (20, 40, 60, 120 s) of the cold compress application were varied. 3. The data indicate that 0 degrees C compresses applied bilaterally for 40 s produced the maximum bradycardia and peripheral vasoconstriction. No subject found this test to be obnoxious, but a 120 s application was objectionable to some subjects. This cold face test resulted in 22%, 72%, 59% and 44% reductions in heart rate and blood flow to the finger, toe and calf, respectively. There was significant between-subject variability, but good consistency in responses to tests repeated in the same subject on different days, at different times of day and in different seasons.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Ultrastructural study of microbiologic colonization of urinary catheters.

We examined ten urinary catheters, associated with catheter-related urinary tract infections, by scanning and transmission electron microscopy to study the morphology of bacterial adherence. We confirmed that the bacteria associated with catheter-associated urinary tract infections grow in glycocalyx-enclosed microcolonies in a biofilm on the catheter surface. The bacterial populations demonstrated a heterogeneity that was not evident from the culture results, and it was demonstrated that only a small proportion of the microorganisms, including fungi, identified morphologically by scanning or transmission electron microscopy are recovered by routine culture methods. The persistence of the bacterial pathogens in catheter-associated infection, even in the face of antibiotic treatment, may be attributed to their adherent mode of growth in protected biofilms and their production of extensive enveloping anionic glycocalyces.

Bacterial Adhesion↗
PubMed1987

Thermoregulatory physiology of menopausal hot flashes: a review.

Hot flashes during the climacteric years have long been a frequent clinical complaint, generally considered within the realm of the internist, gynecologist, or endocrinologist. Yet the underlying mechanism of hot flashes remains unknown. Only within the past 10 years has there been significant research on hot flashes as a disturbance of thermoregulation. This paper focuses on thermoregulatory aspects of hot flashes, reviewing current knowledge of the thermoregulatory physiology and endocrinology of hot flashes and discussing future avenues for research. Hot flashes are compared with fever in terms of thermoregulatory changes and speculated mechanisms. Although several substances in the peripheral circulation are found in increased concentrations during hot flashes, none is a trigger for a hot flash. The pattern of hot flash occurrence is striking in its regularity, and the possibility of endogenous rhythmicity is discussed. Recently, investigators have begun to explore a primate model of menopausal hot flashes. These studies are summarized. Finally, the multiple effects of estrogen on various systems of the body and their interrelationships are discussed. An understanding of the mechanism of hot flashes would not only be of importance to women suffering with hot flashes but would further our knowledge of thermoregulatory function and the interactions between thermoregulatory and reproductive systems.

Body Temperature↗
PubMed1987

The differential importance of weight and body image among college men and women.

Among a sample of American college students, body image and the degree of desired weight change were associated with academic self-rankings, with social and psychological well-being, and with the development of eating difficulties. The effects of body image and desired weight change on eating disorders were generally found to be greater for women than for men, and their effects on student self-rankings of academic ability, social, and psychological traits were more pervasive for women than for men. The less attractive a woman perceived herself to be and the more weight she wanted to lose, the greater was her overall sense of academic, social, and psychological impairment. Women who had poor body images and who desired to lose weight were more likely to report eating difficulties.

Body Image↗
PubMed1979

Vascular effects of etilefrine. Further studies to substantiate the predominant indirect sympathomimetic action of this agent.

The suggested use of etilefrine in the treatment of patients with orthostatic hypotension is based on the premise that it has an action similar to that of noradrenaline (Miller, Wiener and Bloomfield, 1973). However, earlier work from this laboratory (Frost, Frewin and Gerke, 1977; Frost, Frewin, Gerke and Downey, 1978; Frost, Halloran, Frewin, Gerke and Downey, 1978) on blood vessels in the rat tail has suggested that the drug acts predominantly as an indirect sympathomimetic agent. The present study examined the action of etilefrine on the central artery of the rabbit ear. This vessel is known to have a rich sympathetic innervation (de la Lande, Frewin and Waterson, 1967) and has the added advantage that it can be surgically denervated. It therefore became possible to examine the effects of etilefrine on both normal and denervated arteries and to quantitate the extent to which the drug relied on the symphathetic nerves for its vasoconstrictor effects.

Animals↗
PubMed1978

The effects of agents modifying sympathetic nerve function on the response of the isolated rat tail artery to etilefrine and tyramine.

The effects of etilefrine on the ventral caudal artery of the rat have been examined in the presence of agents modifying sympathetic nerve function. Catecholamine levels were also measured in adjacent segments of artery to those studied pharmacologically and an attempt made to relate vascular response to etilefrine (and tyramine) with catecholamine content. Both guanethidine and reserpine produced significant attenuation of the vascular effects of etilefrine and tyramine. Pre-treatment with a monoamine oxidase inhibitor caused an increase in tissue catecholamine levels but, paradoxically, depressed the vascular response to etilefrine. The significance of some of the findings in terms of an indirect component to etilefrine's action are discussed.

Animals↗
PubMed1978

The indirect sympathomimetic activity of etilefrine--a comparison with tyramine and ephedrine using [3H] noradrenaline.

The indirect sympathomimetic activity of etilefrine has been examined using the ventral caudal artery of the rat. This vessel has a rich sympathetic innervation and lends itself to studies on [3H]noradrenaline efflux from these sites. Etilefrine possessed significant indirect activity on the artery and this action, although less than that of tyramine, was equivalent to that caused by ephedrine. Pretreatment of the vessels with a mixture of iproniazid, doca, cocaine and UO521 (3',4'-dihydroxy-2-methyl propiophenone) significantly enhanced[3H]-noradrenaline efflux from the artery.

Animals↗
PubMed1978

The dead zone of thermoregulation in normal and paraplegic man.

Independent heating and cooling of the core and skin were performed to a normal and a paraplegic subject. It was found that the core threshold temperature for vasoconstriction release was between that for shivering and sweating. After the onset of sweating, vasodilation of the forearm was observed to increase sharply. The core threshold temperature of sweating of the paraplegic was 0.7 degrees C higher than that of the normal at corresponding mean sentient skin temperatures. No sweating was observed in the spinal man without raising his core temperature. It appeared that the dead zone of thermoregulation is shifted up in the spinal patient and the possible reasons for this are discussed.

Adult↗
PubMed1977

The effect of aspirin pretreatment on the sweating response of older female subjects.

Seven healthy female volunteers (aged 50 to 67 years) have been subjected to a thermal stress and their sweat rates evaluated using hygrosensors on five different locations on their body surface. It was found that the sweating rate was highest on the forehead in all but one of the subjects with the chest being the next most prominent site for the response. Five of the subjects were restudied after aspirin pretreatment. In the presence of this drug, resting body temperature was lowered, sweating occurred at a lower oral temperature and the mean sweating rate at a standardized body temperature was significantly higher. These findings are consistent with aspirin's known pharmacological actions, although in this study the increased sweating rate have been demonstrated in afebrile subjects.

Age Factors↗
PubMed1976

The effect of ambient temperature on the growth hormone and prolactin response to exercise.

The effect of a standardised exercise procedure on plasma growth hormone (HGH) and prolactin has been assessed in 10 normal human subjects. Each subject was tested in an ambient temperature of 40 degrees and on a subsequent day at a temperature of 10 degrees. At 40 degrees exercise produced an increase in HGH in all 10 subjects, while in the cold only 1 showed a rise in the hormone during exercise. An increase in prolactin with exercise at 40 degrees occurred in some of the subjects, but these changes were small in comparison with those of HGH. Prolactin levels did not increase during exercise in the cold.

Adolescent↗
PubMed1976

Sweating responses to central and peripheral heating in spinal man.

Studies of central and peripheral heating of a resting spinal man (T6) were performed under various ambient temperatures (20-34 degrees C). It was found that at a constant core temperature, sweating could not be initiated by sentient skin heating alone, but skin cooling alone did produce a rapid decrease in sweating response. Central heating alone induced sweating responses and the central temperature thresholds of sweating were inversely related to the ambient (sentient skin) temperatures. The local and mean sweating rates were found to be linearly related to the core temperature. The slopes of local sweating rates versus the core temperature vary increasingly with the following locations: chest, forearm, and forehead; but the slopes of mean sweating rates versus core temperature were essentially constant.

Adult↗
PubMed1976

Relationship between evaporation rate of sweat and mean sweating rate.

The rate of evaporation of sweat under a step change of ambient temperature (30-45 degrees C) was compared with the mean sweating rate (MSR) computed from five simultaneous resistance hygrometric measurements. Empirical equations derived for the conditions studied enabled a direct conversion from hygrometric measurements into real evaporative sweat losses and skin wetness for all phases of sweat evaporation. From five chosen skin areas, forehead, forearm, chest, thigh, and calf, it was found that none of these sites gave a local sweating response close to the MSR. In the subjects with a forehead sweating rate within +/- 39% of the MSR, at least four hygrometric sensors were needed to predict the rate of sweat evaporation. For subjects with higher forehead sweating rates, at least five sensors were necessary to calculate the evaporative sweat loss.

Adult↗
PubMed1976

Standstill of nailfold capillary blood flow during cooling in scleroderma and Raynaud's syndrome.

Capillary blood flow in nailfold capillaries, observed continuously by capillary microscopy during standardized cold exposure (16 degrees C) has been compared in 15 patients with scleroderma (SD), 6 patients with Raynaud's syndrome (RS) without known organic pathology, and 9 normal controls. Capillary microscopy affords direct observation of capillary blood flow and allows one to determine if standstill of capillary circulation occurs (as defined by the movement of the red blood cell column), a state impossible to differentiate from near zero flow by conventional methods. Complete standstill of capillary blood flow occurred in 10 of 15 patients with SD and in 1 of 6 patients with RS. Intermittent standstill was observed in 5 of 15 SD and in 4 of 6 RS patients. In all normal subjects and in 1 of 6 patients with RS the capillary blood flow continued throughout the cooling period. Thus all 15 patients with SD and 5 of 6 patients with RS could be distinguished from control subjects by the development of capillary standstill on cooling. It is concluded that capillary microscopy can separate SD and RS patients from control subjects during cold exposure and may be useful in early diagnosis and prognosis of rheumatic syndromes and in the evaluation of therapy designed to improve the nutritional capillary blood flow of the skin. Whereas the complete standstill of capillary blood flow appears to be definitely associated with pathology, the intermittent standstill pattern as defined in this study may be an exaggerated form of flow fluctuation also seen in normal subjects. A larger number of subjects will have to be studied to determine whether patients with RS of the vasopastic type without connective tissue disease can be distinguished from normal subjects with low finger blood flow rates in cold conditions.

Cold Temperature↗