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Biomedical subjects

J Exner

Publications and source records attributed to J Exner.

9 recordsLinked to original sources
PubMed2004

Different cardiorespiratory responses to hemorrhage and hyperoxia in normotensive (WKY) and spontaneously hypertensive (SHR) rats.

OBJECTIVE: To compare the cardiorespiratory responses underlying the beneficial effects of hyperoxia during blood loss between normotensive (WKY) and hypertensive (SHR) rats. METHODS: Experiments were carried out in anesthetized animals with both carotid bifurcations either innervated or denervated. The effects of breathing 60% O2 in N2 were studied either in combination with non-hypotensive hemorrhage or during hemorrhagic hypotension. RESULTS: In normoxia arterial pressure fell more in SHR than in WKY for a given blood loss. During hyperoxia, nerve-intact rats showed initial suppression of ventilation, but bifurcation-denervated rats a powerful enhancement. In all groups, hyperoxia increased the overall tone of venous capacitance vessels. CONCLUSIONS: The greater blood loss in SHR than in WKY when bleeding down to a given arterial pressure results from a stronger constriction of venous capacitance vessels. Hyperoxia improves the ability of the cardiorespiratory system to resist the effects of hemorrhage by increasing the overall venous tone, thus supporting cardiac filling, and in some cases also by increasing alveolar ventilation, probably secondary to improved cerebral oxygenation. The beneficial effects of hyperoxia were: (i) not prevented by carotid denervation, and thus were presumably direct tissue effects of oxygen, (ii) strikingly weaker in SHR than in normotensive (WKY) rats.

Animals↗
PubMed2002

Reduced tolerance of simulated altitude (4200 m) in young men with borderline hypertension.

BACKGROUND: Primary hypertensives who are acutely exposed to hypoxic hypoxia show an enhanced reactivity of arterial chemoreceptors as well as an exaggerated response of the sympathetic nervous system. Since these phenomena could influence their ability to tolerate sustained hypoxic hypoxia, this study was performed to determine whether persons predisposed to hypertension have a normal tolerance of simulated high altitude. METHODS: Subjects were 18 young men with a family history of hypertension (sons of hypertensives, SOHT) whose BP values were in the upper normal or borderline hypertensive range. Controls were 15 young men without parental hypertension (sons of normotensives, SONT) who had normal BP values. Each subject underwent both a control and an altitude experiment. The latter consisted of an 8-h exposure to hypobaric hypoxia (equivalent to 4200 m) while resting supine in an altitude chamber. Fluids were administered by mouth and by intravenous line to produce sustained diuresis. Variables measured included heart rate, BP, respiratory rate, O2 saturation, urine flow rate, and sodium excretion. RESULTS: All subjects tolerated the control experiment and all SONT also completed altitude exposure. However, 8 of 18 SOHT developed antidiuresis and had to leave the chamber early due to symptoms of mild acute mountain sickness. Compared with SONT, SOHT exhibited more stable cardiorespiratory parameters at altitude. CONCLUSIONS: The data support the hypothesis that borderline hypertensives have stronger cardiorespiratory responses to altitude than controls, a response that is compatible with higher excitability of their arterial chemoreceptors. However, their altitude tolerance is reduced even at rest, probably because of the renal effects of an exaggerated response in the sympathetic nervous system.

Adaptation, Physiological↗
PubMed2001

Clinical utility of the Rorschach with African Americans.

In this study we sought to identify Rorschach differences between African Americans and White Americans and to understand these differences within a social and cultural framework. Data from the Exner (1993) Comprehensive System normative sample (N = 700) was used to form a group of 44 African Americans and 44 White Americans matched for age, sex, education, and socioeconomic status. Twenty-three Rorschach variables were chosen a priori and group differences were analyzed. The only clinically significant difference found was that African Americans offered significantly less cooperative movement. This lower frequency of cooperative movement may suggest African Americans do not anticipate cooperative interactions with others as a routine event. This may reflect a shared feeling among African Americans that most members of our society are less likely to be sensitive to or responsive to their needs relative to others. However, the study demonstrates a striking similarity between the groups, supporting the clinical use of the Rorschach with African Americans.

Adult↗
PubMed1996

Effects of acute hypoxia and hyperoxia on ventilation in spontaneously hypertensive and normotensive rat.

The aim of this study was to investigate whether there are differences between particular characteristics of the ventilatory responses to acute hypoxia and hyperoxia in primary hypertensive and normotensive states which might indicate significant differences in arterial chemoreceptor reflex function. Pneumotachographic monitoring of ventilation was carried out in anesthetized, spontaneously breathing, normotensive randomly bred Wistar rats (NWR), Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Under air breathing conditions, minute ventilation in SHR (50 +/- 2 ml/min per 100 g) was not significantly different from that of WKY (54 +/- 3 ml/min per 100 g) but NWR had a significantly lower minute ventilation (39 +/- 1 ml/min per 100 g) than both SHR and WKY. Our data indicate that there is no elevation of the ventilatory drive under air breathing conditions which can be unequivocally associated with primary hypertension in adult animals. During acute hypoxia, minute ventilation increased by a similar magnitude in SHR and NWR (by 97 and 77%, respectively, above baseline values), whereas in WKY the increase was only 58%. When exposed to acute hyperoxia, minute ventilation was inhibited by a similar degree in all animals investigated. We conclude that there is no characteristic pattern of peripheral chemoreceptor-mediated ventilatory responses in close association with primary hypertension.

Animals↗
PubMed1995

Cardiorespiratory responses to acute hypoxia and hyperoxia in adult and neonatal spontaneously hypertensive and normotensive rats.

The aim of this study was to investigate whether there are differences between particular characteristics of breathing regulation in primary hypertensive and normotensive states which might indicate significant differences in arterial chemoreceptor reflex function. Under air-breathing conditions, minute ventilation was similar in adult spontaneously hypertensive rats (SHR) (50 +/- 2ml/min x 100 g) and in Wistar-Kyoto rats (WKY) (54 +/- 3 ml/min x 100 g) but significantly lower in randomly bred normotensive Wistar rats (NWR) (39 +/- 1 ml/min x 100 g). In seven-day-old rats minute ventilation was 10.5 +/- 1.2ml/min x 10 g in SHR and 10.2 +/- 1.4 ml/min x 10 g in WKY. Our data indicate that there is no elevation of the ventilatory drive under air-breathing conditions which can be unequivocally associated with primary hypertension in adult and neonatal animals. Acute inhibition of ventilation caused by hyperoxia indicated that oxygen dependent peripheral chemoreceptor activity during air-breathing was similar in SHR and normotensive controls both in the unanesthetized neonatal state and in anesthetized adult animals. No well defined association between the characteristics of the hypoxic ventilatory response and primary hypertension could be demonstrated although responses in adult anesthetized SHR tended to be faster and of higher amplitude than in normotensive controls.

Acute Disease↗
PubMed1991

Radioimmunoassay of dibenzazepines and dibenzcycloheptanodienes in body fluids and tissues.

In an attempt to establish a radioimmunoassay (RIA), imipramine and amitriptyline immunogens were prepared; desmethyl derivatives were converted into hemisuccinates, conjugated with bovine serum albumin and used for rabbit immunization. [3H]Amitriptyline (4.3 TBq/mmol) and [3H]imipramine (2.9 TBq/mmol) were prepared by catalytic dehalogenation or reductive alkylation. Dibenzazepines and dibenzcycloheptanodienes were determined in biological fluids by a direct method without deproteinization (lower detection limit of 0.5 microgram.l-1); using high-yield methods they were extracted from cell membranes. Assay of tricyclic antidepressants in humans showed that these substances disappear from plasma much earlier than from cell membranes. Dissociation of the antidepressants bound to cell membranes is slow and their plasma concentrations are not influenced by standing for 2 h at 4 degrees C. During preparing the membranes for binding studies these substances are not removed, and they may affect the results of the binding studies.

Amitriptyline↗
PubMed1976

New types of synthetic infusion solutions. III. Elimination and retention of poly-[N-(2-hydroxypropyl)methacrylamide] in a test organism.

The elimination and retention of a new, fully synthetic plasma prosthesis of Czechoslovak origin under the working name of Duxon (poly[N-(2-hydroxypropyl)methacrylamide]) was investigated in experiments on rabbits by using a 14C-labeled polymer. Results published earlier on elimination have been confirmed and extended. Retention was examined after repeated application. The effect of molecular weight prevailed both in elimination and in retention. Polymers of lower molecular weights, which possess a good therapeutical effect, are not permanently deposited in the organism.

Acrylic Resins↗