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Biomedical subjects

R Richardson

Publications and source records attributed to R Richardson.

At least 19 recordsLinked to original sources
PubMed1992

Developmental constraints on the expression of behavioral and heart-rate orienting responses: II. The role of ambient temperature.

The effect of ambient temperature on the expression of behavioral and heart-rate orienting responses to a novel olfactory stimulus was examined in rats 1-18 days of age. There was no effect of ambient temperature on the behavioral orienting responses at any age. Ambient temperature did influence the expression of the heart-rate orienting response and did so differentially as a function of age. The implications of these findings for developmental models of attention and cognition are discussed.

Animals↗
PubMed1992

Emergency center arteriography.

From 1983 through 1989, 1,882 emergency center arteriograms were performed on 1,802 patients suspected of having peripheral vascular injuries. The most common indication for emergency center arteriography (ECA) was the proximity of an injury to a major vascular structure. This was the only indication in 1,712 injured extremities (91%). There were 1,510 true negative arteriograms, 294 true positives, 7 false negatives, and 14 false positives. Accordingly, the sensitivity was 95.5% and the specificity was 97.7%. The remaining 57 arteriograms were either equivocal or technically inadequate. Further evaluation of these patients uncovered an additional 11 vascular injuries. Operative intervention was required for 196 (64.3%) injuries detected by emergency arteriography. The remaining 109 injuries were considered minor and were not repaired. No complications developed in 91 patients (88%) with minor vascular injuries who were available for a mean follow-up duration of 12 months. One thousand forty-eight patients (69.4%) with negative arteriograms were followed for a mean of 18 months, and no vascular complications were noted. Emergency center arteriography is a rapid, accurate, and cost-effective technique. It is of particular value in detecting the presence of occult arterial injuries when proximity of a major vascular structure is the sole indication for arteriography. When formal arteriographic support is either unavailable or time consuming, ECA is recommended.

Adolescent↗
PubMed1992

Neurologic consequences of cerebrovascular injury.

Because of ongoing controversy, the issue of vascular repair or ligation for patients with cerebrovascular injuries and preoperative central neurologic deficits is frequently debated. A total of 133 patients with penetrating cerebrovascular injuries were analyzed. The frequency of preoperative neurologic deficit was 20% (27 patients). The common carotid and internal carotid arteries were the most frequently injured structures, with a 29% and 15% incidence of preoperative neurologic deficits, respectively. The results of carotid repair in all patients whose preoperative deficit was limited to weakness or paralysis were favorable (seven patients normal or improved, two patients unchanged). The results of repair in patients whose preoperative deficit was characterized by obtundation were variable (four patients improved, four patients worsened or died). The results of carotid ligation were also variable (one improved, one unchanged, three worsened or died). Limited numbers of patients with preoperative neurologic deficits and the retrospective nature of this review prohibit definite conclusions. Therefore a multicenter, prospective, randomized trial of ligation or vascular repair for comatose patients with cerebrovascular injuries is proposed.

Carotid Artery Injuries↗
PubMed1992

Developmental changes in the duration of attention to unfamiliar stimuli in the rat.

The purpose of the present study was to examine developmental changes in the duration of attention to novel auditory stimuli in rats from infancy to adulthood. In all experiments, the cardiac component of the orienting response was used as the index of attention. In the first experiment 16-, 23-, 30-, and 75-day-old rats were exposed to a novel auditory stimulus for 60 s. Animals of all four ages exhibited a marked decrease in heart rate in response to this stimulus. Although there were no significant effects of age on the magnitude of the cardiac response, there were dramatic developmental differences in the persistence of the response. The 16-day-olds maintained a decrease in heart rate for the entire stimulus period, whereas heart rate returned to baseline in the 75-day-olds after only 40 s. The duration of the cardiac response of the 23- and 30-day-olds was between these extremes. In Experiments 2A and 2B the effect of stimulus complexity on duration of the cardiac response was examined. Increasing stimulus complexity prolonged the deceleratory response in the 30-day-olds (Experiment 2A), and decreasing stimulus complexity decreased the duration of the cardiac response in the 16-day-olds (Experiment 2B). The results of these experiments were discussed in the context of Cohen's and Porges's two-phase theories of attention. The findings demonstrate that the initial attention-getting or reactive phase of attention did not change with age, but that the duration of the attention-holding or sustained phase decreased substantially during development.

Acoustic Stimulation↗
PubMed1992

The multiple choice true/false question: what does it measure and what could it measure?

Multiple choice questions of the true/false type are widely used in medical education. Evidence is given which suggests that they only tap a low level of intellectual skill. By using them in a slightly different manner it is suggested that they could be ideal techniques for measuring concept mastery. Some of the consequences of this idea are discussed.

Education, Medical, Undergraduate↗
PubMed1991

Effects of cardiac surgery and intraoperative hypothermia on energy expenditure as measured by doubly labelled water.

Total energy expenditure (TEE) was measured over two 10-day periods, before and after operation in 16 patients undergoing coronary artery surgery and randomized to have cardiopulmonary bypass with an intraoperative blood temperature of either 28 or 20 degrees C. TEE was measured with doubly labelled water containing stable isotopes of hydrogen and oxygen to allow calculation of TEE over fixed periods from the differential rate of excretion of the two isotopes. Results were available for eight patients in the 28 degrees C group but for only seven in the 20 degrees C group (one patient in this group was excluded as the temperature allocated was not achieved). The groups were similar with respect to body-weight and lean body mass. The 20 degrees C group received more grafts than the 28 degrees C group, resulting in an increase in cross-clamp and bypass times. Mean preoperative TEE was similar in both groups. The mean difference in fractional turnover rates of hydrogen and oxygen was not significantly different in the postoperative period. There was a non-significant increase in the mean 10-day postoperative TEE, calculated in total calories, of 4.7 per cent in the 28 degrees C and 5.1 per cent in the 20 degrees C group. When changes in postoperative TEE were calculated according to lean body mass, the mean increases were respectively 3.7 and 3.2 per cent. Cardiac surgery utilizing cardiopulmonary bypass and intraoperative hypothermia results in only a modest increase in postoperative TEE. In this study a more profound level of intraoperative hypothermia did not influence the change in postoperative TEE.

Adult↗
PubMed1991

Developmental constraints on the expression of behavioral and heart-rate orienting responses: I. The role of cardiosomatic coupling.

The ontogeny of behavioral and heart-rate orienting responses to a novel olfactory stimulus was examined in three experiments. The results of Experiment 1 demonstrated that behavioral responses to the olfactory stimulus were observed as early as Day 1, although heart-rate deceleration in response to the stimulus was not observed until Day 9. In Experiment 2, bradycardia was observed in 6-day-old pups if stimulus-elicited motor activity was reduced with haloperidol. Thus, the developmental asynchrony in the expression of behavioral and heart-rate orienting responses was due, at least in part, to cardiosomatic coupling in the very young animal. The results of Experiment 3 demonstrated that although cardiosomatic coupling interferes with the expression of the heart-rate orienting response very early in development, it has increasingly less impact over the course of the preweaning period.

Aging↗
PubMed1991

Outcome for delayed operation of penetrating colon injuries.

It has been stated that delay in operative repair of penetrating injuries to the gastrointestinal tract will result in a high rate of complications related to infection. To test this assertion, a group of patients with penetrating injuries to the colon were analyzed who had operative repair delayed (usually because of triage considerations) more than 6 hours after admission to the hospital. Nine hundred six patients who survived at least 48 hours after injury were divided into two groups. The immediate group of 769 patients was treated within 6 hours of admission and the delayed group of 137 patients was treated more than 6 hours after admission. The mortality for the immediate group was 4.0% vs. 1.5% for the delayed group. Colon-related infectious complications, defined as abscess or colon suture-line failure, occurred in 10% of the immediate group and 4.4% of the delayed group. To eliminate the effect of associated injuries, the group of patients with colon injuries only was analyzed separately. There was no mortality for 128 patients with colon injuries only operated on within 12 hours of injury, and the colon-related infectious morbidity rate was 3%. Eleven patients with colon injuries only were treated after 12 hours with a mortality of 9% and colon-related infectious morbidity of 18%. These data demonstrate that even patients with fecal contamination can have operative repair delayed for up to 12 hours without undue morbidity related to infection.

Adult↗
PubMed1990

Effects of four beta-adrenergic receptor antagonists on male rat sexual behavior.

Antihypertensive medication has been reported to cause serious sexual side effects in men. Frequently mentioned as causing sexual dysfunction are beta-adrenergic receptor antagonists. The purpose of this study was to examine in detail the effects of beta blockers on adult male rat sexual behavior. Thirty minutes following a single subcutaneous injection of propranolol, pindolol, atenolol or labetalol, mating tests were conducted. The mixed beta 1- and beta 2-adrenergic antagonists, propranolol and pindolol, profoundly inhibited male sexual behavior. At the 5 and 10 mg/kg doses, propranolol inhibited ejaculatory behavior to the extent that only 9.1 and 8.3% respectively showed the behavior while pindolol reduced this behavior to 36.4% (16 mg/kg). These drugs also adversely affected various parameters of behavior in a dose-dependent manner. The selective beta 1 antagonist, atenolol, had only minor effects and labetalol even less so at the doses tested. It was suggested that the strongly inhibitory effects of propranolol and pindolol on male rat sex behavior may well be due to their 5-HT1A antagonistic binding properties rather than their beta-antagonistic properties.

Adrenergic beta-Antagonists↗
PubMed1990

Retroperitoneal vascular injury.

Retroperitoneal vascular injuries are among the greatest challenges that confront the surgeon. Problems in resuscitation, exposure, and repair are numerous. Techniques to improve such perioperative tactics result in improved survival.

Blood Vessels↗
PubMed1990

Plasma and dialysate levels of pefloxacin and its metabolites in CAPD patients with peritonitis.

Six patients with acute peritonitis undergoing continuous ambulatory peritoneal dialysis for end-stage renal failure received an 800 mg loading dose of pefloxacin mesylate orally followed by 400 mg twice daily orally for 10 or 21 days. Plasma and dialysate levels of both pefloxacin and its metabolites were measured. Plasma levels in excess of the MIC for all infective bacteria were achieved within 90 min and in dialysate within 4 h. No significant accumulation of pefloxacin or its metabolite norfloxacin was noted. However, both serum and dialysate levels of the metabolite pefloxacin N-oxide rose continuously during treatment. Plasma and dialysate levels of all three agents fell rapidly during the five days after treatment had stopped. No major side effects were observed, although two patients developed Achilles tendonitis.

Adult↗
PubMed1990

Infant mortality and undernutrition in the squatter settlements of Karachi.

The socio-demographic and biological processes contributing to infant mortality and undernourishment were studied in five urban squatter settlements of Karachi. All those families who had experienced an infant death in the past 2 years (N = 106) were recruited into the study. Comparative children were selected by random numbers with geographical matching from families with at least one live infant and without a history of infant deaths in the past 2 years. The comparison children were weighed and those found underweight (27 per cent) were studied for the presence of risk factors. Forty-one per cent of all deaths were in the neonatal period, and in 47 per cent of cases deaths had occurred in infants with a birth order of 5 and above. Age, duration of breast feeding, birth interval, and the live/dead status of the previous sibling were significant biological variables accounting for 23 per cent of the variance for survival. Socio-economic status accounted for 22 per cent of the variance and health-seeking behaviour (antenatal care, immunization, etc.) for 28 per cent. Sixty-eight per cent of those underweight were more than 6 months old. Age, female sex, birth interval less than 24 months, duration of breast feeding, adolescent mother, alive/dead status of the previous child were significant influences accounting for 12 per cent of the variance. Socio-economic status and health seeking behaviour were also important determinants, but not to the same extent as in the case of infant death.

Adolescent↗
PubMed1990

Disruption and recovery of the orienting response following shock or context change in preweanling rats.

Previous research has shown that placement of preweanling rats in an unfamiliar environment inhibits both heart rate and behavioral orienting responses to an auditory stimulus, and that the orienting response gradually reappears during the following 15 min. Four experiments designed to evaluate two potential explanations of this effect were conducted. If the arousal induced by an unfamiliar environment disrupts sensory information processing, so should the arousal induced by mild electric shock. In two experiments, the orienting response was inhibited in proportion to number of shocks received and rate of recovery was comparable to that observed in the unfamiliar environment. New environments also contain many unfamiliar stimuli which may overload the rats' limited information processing capacity. In two experiments a change in environmental stimulation was shown to inhibit the orienting response. Recovery of the orienting response followed the same time course as that seen following shock or placement in an unfamiliar environment. Although the results of this study clearly demonstrate environmental inhibition of the orienting response, they provide little support for either the "arousal" or the "information overload" hypotheses of orienting response inhibition. The implications of these data for current theoretical conceptualizations of the orienting response are discussed.

Acoustic Stimulation↗
PubMed1989

Effect of maternal presence on the cardiac and behavioral responses to shock in rats as a function of age.

In two experiments the effects of the presence of an anesthetized lactating dam on the developing rat's response to a series of mildly painful shocks was examined. Both cardiac and behavioral responses to the shock stimulus were recorded. In the first experiment animals were tested at either 16, 20, or 24 days of age. The presence of the anesthetized dam markedly reduced the behavioral response to shock of the 16-day-old but not the older rats. A similar pattern of results was obtained with the shock-elicited tachycardia. The second experiment replicated these results with the 16-day-old rat and also demonstrated that being shocked in the presence of a lactating dam influences the animal's reaction to a subsequent series of shocks given when it is alone. The results of these two experiments are discussed in terms of other studies that have examined the influence of maternal presence on the developing animal's response to stressful or painful stimuli.

Aging↗