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Biomedical subjects

J M Walker

Publications and source records attributed to J M Walker.

At least 217 records · Page 12Linked to original sources
PubMed1987

Air-fluidized beds or conventional therapy for pressure sores. A randomized trial.

STUDY OBJECTIVE: To compare the effectiveness and adverse effects of air-fluidized beds and conventional therapy for patients with pressure sores. DESIGN: Randomized trial with both masked and unmasked comparisons of outcome after a median follow-up of 13 days (range, 4 to 77 days). SETTING: Urban, academic referral, and primary care medical center. PATIENTS: Of 140 potentially eligible hospitalized patients with pressure sores, 72 consented to randomization; 65 (90%) completed the study. INTERVENTIONS: Thirty-one patients on air-fluidized beds (Clinitron Therapy, Support Systems International, Inc., Charleston, South Carolina) repositioned every 4 hours from 0700h to 2300h without use of other antipressure devices. Thirty-four patients on conventional therapy used an alternating air-mattress covered by a foam pad (Lapidus Air Float System, American Pharmaceal Company, Cincinnati, Ohio) on a regular hospital bed; were repositioned every 2 hours; and had elbow or heel pads as needed. Topical therapy was standardized for both groups. MEASUREMENTS AND MAIN RESULTS: Pressure sores showed a median decrease in total surface area (-1.2 cm2) on air-fluidized beds, but showed a median increase (+ 0.5 cm2) on conventional therapy; 95% confidence interval (CI) for the difference between medians, -9.2 to -0.6 cm2 (p = 0.01). Improvement, as assessed from serial color photographs by investigators masked to treatment group, occurred in 71% and 47%, respectively; 95% CI for the difference, 1% to 47% (p = 0.05). For pressure sores 7.8 cm2 or greater, outcome differences between air-fluidized beds and conventional therapy were greater: median total surface area change was -5.3 and +4.0 cm2, respectively; 95% CI for the difference, -42.2 to -3.2 cm2 (p = 0.01). Improvement rates were 62% and 29% respectively; 95% CI for difference, 1% to 65% (p = 0.05). After adjusting for other factors associated with sore outcome, the estimated relative odds of showing improvement with air-fluidized beds were 5.6-fold (95% CI, 1.4 to 21.7) greater than with conventional therapy (p = 0.01). No significant increase in adverse effects was seen with air-fluidized beds. CONCLUSIONS: Our findings suggest that air-fluidized beds are more effective than conventional therapy, particularly for large pressure sores. Studies are needed to determine the effectiveness of air-fluidized beds in long-term care settings.

Adult↗
PubMed1986

[3H]dynorphin A binding and kappa selectivity of prodynorphin peptides in rat, guinea-pig and monkey brain.

We have previously demonstrated that [3H]dynorphin A selectively labels kappa opioid receptors in guinea-pig whole brain. In these current studies, using protection from inactivation by beta-chloronaltrexamine (beta-CNA), we are able to demonstrate that although dynorphin A prefers kappa receptors, it will label mu receptors when kappa receptors are not available, or present in only a small number. Thus, differences in numbers of mu and kappa receptors present in brain preparations are critical in determining the receptor binding profile of [3H]dynorphin A across species. Additionally, although all the prodynorphin derived peptides show kappa preference, the ability of the other prodynorphin derived peptides to compete with [3H]dynorphin A for its receptor varies across species. Consequently, in a highly enriched kappa preparation such as monkey cerebral cortex, [3H]dynorphin A appears to label kappa receptors with substantial selectivity, and the other prodynorphin-derived peptides show less ability to compete with dynorphin A for its receptor. In contrast, in a kappa-poor tissue such as rat brain, all of the prodynorphin-derived peptides, including dynorphin A-(1-8), show very similar potency. Thus, differences in mu and kappa receptor numbers across brain regions and species lead to differences in the receptor binding profile of dynorphin A.

Alkylating Agents↗
PubMed1986

Lack of difference between malignant and accelerated hypertension.

The clinical features and survival rates of 200 consecutive patients with malignant and accelerated hypertension admitted to a district hospital were investigated. Ninety five patients had bilateral haemorrhages and exudates and papilloedema (grade IV retinopathy) and 31 had bilateral haemorrhages and exudates with no papilloedema (grade III). A further 74 patients had bilateral retinopathy but failed to meet the criteria for grade IV or III and were investigated separately. No overall differences were found in survival when comparing the various grades of retinopathy. Cigarette smoking was significantly commoner only in grade IV patients compared with those with non-malignant hypertension matched for age, sex, and race. In patients with grade III retinopathy excess smoking was not statistically significant. In conclusion, the clinical features and survival rate showed that malignant and accelerated hypertension are one and the same disease.

Female↗
PubMed1986

Evaluation of a coronary lysing system: results of a preclinical safety and efficacy study.

The purpose of this study was to evaluate the efficacy and safety of a recently developed transluminal lysing system in the removal of coronary stenotic lesions from a human cadaver heart and in the cannulation of coronaries in the anesthetized dog. The left coronary arteries of three dogs were cannulated on separate occasions, with coronary arteriography and translation of the transluminal lysing system cutter to the distal segments of the coronary vessels performed each time. Proximal and distal coronary pressures were recorded from the guiding catheter and the transluminal lysing system cutter, demonstrating no significant pressure differential and minimal damping. Pathological examination of the dog coronaries after sacrifice demonstrated minor intimal irregularities with no significant thrombosis or vessel perforation. A significant portion of the occlusive stenotic lesions were removed from coronary vessels of a human cadaver heart with subsequent reestablishment of angiographic dye flow to the distal coronary vessels without evidence of debris loss from the transluminal lysing system cutter or the appearance of occlusions in the distal vessels. We conclude that the transluminal lysing system can be introduced into the coronary artery of a living dog on repeated occasions without causing significant coronary damage, coronary occlusive thrombosis, myocardial destruction, morbidity, or mortality; furthermore, occlusive stenotic lesions can be removed from cadaver coronary vessels by the transluminal lysing system with the establishment of angiography patency.

Animals↗
PubMed1986

Thermoregulation, metabolism, and stages of sleep in cold-exposed men.

Four naked men, selected for their ability to sleep in the cold, were exposed to an ambient temperature (Ta) of 21 degrees C for five consecutive nights. Electrophysiological stages of sleep, O2 consumption (VO2), and skin (Tsk), rectal (Tre), and tympanic (Tty) temperatures were recorded. Compared with five nights at a thermoneutral Ta of 29 degrees C, cold induced increased wakefulness and decreased stage 2 sleep, without significantly affecting other stages. Tre and Tty declined during each condition. The decrease in Tre was greater at 21 degrees C than at 29 degrees C, whereas Tty did not differ significantly between conditions. Increases in Tty following REM sleep onset at 21 degrees C were negatively correlated with absolute Tty. VO2 and forehead Tsk also increased during REM sleep at both TaS, whereas Tsk of the limb extremities declined at 21 degrees C. Unsuppressed REM sleep in association with peripheral vasoconstriction and increased Tty and VO2 in cold-exposed humans, do not signify an inhibition of thermoregulation during this sleep stage as has been observed in other mammals.

Adult↗
PubMed1986

Ear oximetry to detect apnea and differentiate rapid eye movement (REM) and non-REM (NREM) sleep. Screening for the sleep apnea syndrome.

Ear oximetry is commonly employed in screening patients for the sleep apnea syndrome, but the lack of objective information regarding the duration of sleep, including the presence of rapid-eye-movement (REM) sleep, is a major limitation. Based on the premise that both apnea and sleep-state-dependent changes in ventilation give rise to distinctive patterns in the arterial oxygen saturation, we developed a systematic technique to analyze ear oximetric tracings for wakefulness, REM sleep, and non-REM (NREM) sleep. Fifty-four patients were studied by both all-night polysomnography and ear oximetry. A careful comparison of ear oximetric data for sleep states and apnea was then made, using polysomnography as the correct classification to determine sensitivity, specificity, predictive value positive, and predictive value negative of the ear oximetric tracings. When classification of sleep state was compared, ear oximetry correctly classified 280.5 (82 percent) of 340.9 hours of sleep that was either REM or NREM sleep. The sensitivity for classifying NREM sleep was 0.85, for REM sleep was 0.70, and for wakefulness was 0.49. The sensitivity by ear oximetry for apnea was 0.80, with a predictive value negative of 0.87. We conclude that although polysomnography must be performed for definitive evaluation, ear oximetry is a valuable screening test for sleep apnea because the presence or absence of apnea can be determined, total duration of sleep can be estimated, and NREM vs REM sleep can be differentiated.

Adult↗
PubMed1986

Pressure sores among hospitalized patients.

A cross-sectional survey was done to determine the prevalence of pressure sores in hospitalized patients and the factors associated with having a pressure sore in the hospital. Among 634 adult patients, 30 (4.7%; 3.1% to 6.3%, 95% confidence interval) had a pressure sore and 78 (12.3%; 9.8% to 14.8%) were at risk for a pressure sore because they had been confined to a bed or chair for at least 1 week. Comparing these two groups of patients, we found that fecal incontinence, diarrhea, fractures, urinary catheter use, decreased weight, dementia, and hypoalbuminemia were associated with having pressure sores (p less than or equal to 0.05). Using logistic regression analysis, hypoalbuminemia, fecal incontinence, and fractures remained significantly and independently associated with having a pressure sore (odds ratios = 3.0, 3.1, and 5.2, respectively; p less than or equal to 0.05). Our findings suggest that 17% (14% to 20%) of hospitalized patients have pressure sores or are at risk for them, and that hypoalbuminemia, fecal incontinence, and fractures may identify bedridden patients at greatest risk.

Adult↗
PubMed1985

Electrophysiological effects of dynorphin peptides on hippocampal pyramidal cells in rat.

Single-unit extracellular recording was carried out in rats to characterize the effects of dynorphin and several structurally related peptides on hippocampal pyramidal cell activity. Dynorphin, applied electrophoretically or by pneumatic pressure, produced a dose-dependent depression of both spontaneous and glutamate-evoked discharge in a majority (63%) of CA1 and CA3 cells tested. In addition, a small number of cells in both cellular fields responded to the peptide with a prolonged elevation in firing. The inhibitory effects of dynorphin were not blocked by naloxone. Moreover, administration of des-tyrosine-dynorphin depressed the firing of pyramidal cells in a manner similar to that of the parent compound. Ethylketocyclazocine produced a mixed pattern of excitatory and inhibitory effects, whereas naloxone-sensitive elevations in firing were most often observed with the application of dynorphin-(1-8). Application of [Leu5]enkephalin produced only facilitations in pyramidal cell firing. The possibility is raised that biologically significant non-opiate actions, in addition to potent opiate-mediated effects, may occur upon release of pro-dynorphin peptides in the hippocampus.

Animals↗
PubMed1985

Rising from a chair. Influence of age and chair design.

We studied the effect of age on the act of rising from a standard armchair in a younger (means = 24 years) and an older (means = 75 years) group of healthy adult women. Rising from a standard armchair and an armchair specially designed for comfort in sitting of the elderly was studied in the older group to determine the influence of the special chair. We used electrogoniometry, EMG, and videotape analysis to record the activity for both groups. The older group placed their feet farther back and showed greater vastus lateralis muscle activity than did the younger group to rise from the standard chair. These results suggest that rising from the standard chair was more difficult for the older than for the younger group. In the special chair, the older subjects showed even more vastus lateralis muscle activity, greater knee flexion, and greater trunk forward lean. Rising from the special chair, therefore, appeared to be more difficult than rising from a standard chair; this finding suggests that both comfort and function must be considered in chair selection for certain groups.

Adult↗
PubMed1985

Effects of intracoronary and intravenous amrinone infusions in patients with cardiac failure and patients with near normal cardiac function.

The effects of intracoronary and intravenous infusions of amrinone were studied to distinguish the drug's direct cardiac actions from its peripheral vascular and neuroendocrine properties. Intracoronary infusions of amrinone were found to have no haemodynamic effect other than producing a slight reduction in the left ventricular ejection fraction and some suggestion of coronary vasodilatation in patients with impaired left ventricular function. They did not improve contractility, cardiac output, or filling pressures and had no significant effect on myocardial metabolism, although therapeutic concentrations of the drug were detected in coronary sinus blood. Intravenously administered amrinone reduced filling pressures and improved the cardiac index in all patients, but haemodynamic improvements were most pronounced in the patients with the worst cardiac function. These changes were accompanied by improvements in the indices of contractility only in patients in whom alterations in concentrations of free fatty acid, glycerol, and glucose suggested peripheral catecholamine release. In the patients with the best basal cardiac function intravenously administered amrinone produced a reduction in myocardial work and evidence of myocardial ischaemia, as a result of excessive reduction of coronary perfusion pressure and increased heart rate, without any appreciable increase in cardiac index. It is concluded that, at the concentrations of the drug that can be achieved in man without adverse effects, amrinone has no direct positive inotropic effect. Haemodynamic changes are predominantly the result of vasodilatation, although catecholamines may be released in some patients.

Adult↗
PubMed1985

A review of some nonopioid actions of dynorphin.

The evidence for several sites of activity within the dynorphin sequence is reviewed. A number of endocrine and CNS peptides are believed to contain several sites of biological activity. Data from a number of laboratories is consistent with such a mechanism for the opioid peptide dynorphin. These findings stem from structure-activity studies in which nonopiate fragments of dynorphin sometimes show biological activity and from the failure of naloxone to reverse some effects of dynorphin. These results are discussed in terms of the possible physiological relevance of such nonopiate actions.

Animals↗
PubMed1985

Cigarette smoking, blood pressure and the control of blood glucose in the development of diabetic retinopathy.

We have investigated the relationship between diabetic retinopathy and cigarette smoking, blood pressure, control of blood glucose, duration of diabetes and insulin requirement in a cross sectional study of 193 adult patients attending 2 diabetic follow-up clinics. Multiple discriminate analysis demonstrated that the duration of diabetes was closely related to the development of retinopathy in both sexes. Cigarette smoking was related to retinopathy in men but not in women, although in that group the prevalence of smoking was low. The average blood glucose whilst attending the clinic was weakly related to retinopathy in men only whereas the presence of hypertension was weakly related in women only. Cigarette smoking in men at least may be an aggravating factor for diabetic retinopathy.

Age Factors↗
PubMed1984

Inotropic and vasodilator effects of amrinone on isolated human tissue.

The effects of amrinone on human umbilical artery and human myocardium were studied. Amrinone produced dose related increases in tension, dT/dtmax and dT/dtmin in myocardium from patients who were NYHA grade I (n = 1) and II (n = 4). The responses to amrinone of these tissues were similar to the response seen in normal guinea-pig myocardium (n = 34). The drug had no inotropic effect on tissue from NYHA grade III patients (n = 5). The inotropic response of the tissues to amrinone was inversely related to length of history and severity of heart failure in the patients from whom the tissues were obtained. Amrinone caused dose related relaxation of the human umbilical artery. The vasodilator properties, but not the positive inotropic effects of amrinone were detectable at concentrations of the drug obtained during oral therapy (0.4 to 4.0 micrograms X ml-1). These findings support the view that in patients with congestive cardiac failure amrinone acts by vasodilatation with no clinically important positive inotropic effect.

Aminopyridines↗
PubMed1984

Active mobility of the extremities in older subjects.

The purposes of this study were to expand the data base of active range of motion (ROM) in the upper and lower extremities of older persons measured by goniometry and to determine if differences exist related to age, sex, and physical activity. Active ROM was measured with a clinical goniometer in 28 joint motions of the upper and lower extremities of the right side in 60 older subjects. Thirty men and 30 women were equally divided in two age groups of 60 to 69 and 75 to 84 years of age. Multivariate analysis of variance showed no significant differences in ROM that were attributable to sex and age. In univariate tests, however, 12 motions were significantly different (p less than .05) between the sexes, but only in 4 motions was the difference greater than intertester error. Physical activity, as assessed by a questionnaire and a rating scale, was not related to specific changes of joint range. Within the older subjects, however, a significant relationship between ROM and age or ROM and physical activity cannot be assumed. These results suggest that a data base of normative values is needed for older individuals.

Aged↗