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Biomedical subjects

A Jackson

Publications and source records attributed to A Jackson.

At least 361 records · Page 20Linked to original sources
PubMed1983

Variations in the pattern of muscle innervation by the L5 and S1 nerve roots.

Evidence based on electrical studies is presented for the standard and anomalous patterns of innervation of muscles supplied by the fifth lumbar and first sacral nerve roots. Although considerable controversy still exists, previous work in this field suggests that the L5 nerve root supplies tibialis anterior, extensor hallucis longus, extensor digitorum brevis, and the lateral head of gastrocnemius, while the S1 nerve root innervates the medial head of gastrocnemius, soleus, and abductor hallucis. In order to confirm the reliability of this data, the L5 and S1 nerve roots of 50 patients were electrically stimulated during surgery, and distally evoked responses in the relevant muscles were recorded, using surface electrodes. The results confirm the essential reliability of the proposed table of segmental innervation and also demonstrate that most muscles have a dual innervation, with one nerve root being dominant. However, eight patients (16%) exhibited a marked departure from the normal pattern. For example, it is clear that on occasion the extensor digitorum brevis and the lateral head of gastrocnemius can be supplied by S1 and the soleus and medial head of gastrocnemius can be supplied by L5. In a prospective study of 100 patients presenting with clinical evidence of lumbosacral nerve root entrapment, the level of nerve root involvement, as predicted by electromyography, was compared with the operative findings. Correct preoperative nerve root localization was achieved in 84%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

Effects of posture on flow-volume curve configuration in normal humans.

Tien et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 46: 565-570, 1979) found reproducible details in the configuration of averaged maximal expiratory flow-volume curves and suggested that these details may correspond to sudden relocations of airway choke points. The occurrence of choke points depends on factors affecting local airway pressure-diameter behavior. We postulated that changes in posture as they affect the distribution of lung recoil on airways might change the locations of choke points and thereby alter flow-volume configuration. Twenty normal adults performed five flow-volume curves in each of four postures (standing, supine, right, and left lateral recumbent). Volume was measured with a Krogh spirometer and airflow with a Fleisch No. 4 pneumotachometer. Curves were digitally filtered and plotted relative to upright total lung capacity. Five curves in each posture were averaged at increments of 0.1 l/s of flow and average volumes at given flows were compared using the Student's t test. Significant differences (P less than 0.01) in mean volumes at given flows occurred in all subjects from standing to supine and/or right to left lateral postures. Large changes in configuration were apparent in one of the two postural pairs in eight subjects. We conclude that changes in posture result in significant changes in flow-volume configuration in most normal adults. These findings are consistent with the wave-speed theory of flow limitation and suggest that small changes in local airway stresses can significantly alter the location and motion of airway choke points during forced expiration.

Adult↗
PubMed1982

Randomized comparative trial of a ward discussion group.

A randomized controlled study of 38 catchment unit psychiatric in-patients in a discussion group showed no significant additional benefit compared with 36 in-patients in an activity group. Symptom change scored by three rating groups agreed closely, average r = +0.64. Patients treated with ECT showed 2.6 times as much reduction in morbidity as those not so treated, but there was still no appreciable difference between discussion and activity groups when this was allowed for. Other treatment factors and the Hawthorne effect appeared to obscure any effect due to group therapy.

Adult↗
PubMed1981

Subthalamic projection to nucleus tegmenti pedunculopontinus in the rat.

A projection from the subthalamic nucleus to the nucleus tegmenti pedunculopontinus has been demonstrated in the rat using retrograde and anterograde transport of horseradish peroxidase. Small, well-localized injections of peroxidase in nucleus pedunculopontinus gave rise to retrogradely labelled cell bodies in the subthalamic nucleus. Injections of peroxidase restricted to the subthalamic nucleus gave terminal labelling in nucleus pedunculopontinus.

Animals↗
PubMed1981

Ammonia partitioning between glutamine and urea: interorgan participation in metabolic acidosis.

The distribution of precursor nitrogen between urea and glutamine was studied in control and acidotic rats. Acidosis, either acutely induced with hydrochloric acid or chronically induced with ammonium chloride, resulted in a rise in ammonia and a fall in urinary urea excretion; the percent of urinary nitrogen excreted as ammonia rose from 3.5 +/- 0.4 and 4.9 +/- 0.5 in fed and pair-fed controls to 25.9 +/- 3.9 and 37 +/- 5 in acidosis induced by hydrochloric acid and ammonium chloride. Hepatoportal vein urea concentration differences were significantly reduced, whereas glutamine concentration differences were significantly elevated, consistent with a shift of nitrogen from ureagenesis to glutamine; alanine and ammonia concentration differences were significantly decreased and increased respectively in the acidotic animals, suggesting that former supported urea synthesis whereas ammonia may preferentially support glutamine synthesis. Evidence of a feed-forward involvement of the gut in influencing hepatic nitrogen distribution was suggested by an increased ammonia and decreased alanine release in acidotic rats. Bilateral ureteral ligation was performed on control and acidotic rats to determine the fate of the redirected urinary ammonia. Ammonia did not accumulate in the blood, rather it was initially incorporated into glutamine, elevating the plasma level, and then it was subsequently deposited into urea. The shift of nitrogen back into urea in acidotic animals was confirmed by the greater postligation urea production rates supported by hepatic uptake of both alanine and glutamine. These results are discussed in terms of interorgan participation involving the liver, gut, and muscle in the partitioning of nitrogen between glutamine and urea.

Acidosis, Renal Tubular↗
PubMed1981

Comparison of heart rate measurement protocols used during autonomic function tests.

The five most used cold pressor test heart rate protocols were compared to the true R-R interval responses recorded during a cold hand test. Forty-one nonsmoking male volunteers between 18 and 55 yr were given a cold hand pressor test. Heart rate was evaluated by averaging the R-R interval within 2-, 5-, 6-, 10-, and 30-s time intervals and by the true R-R interval measurement. No significant physiological differences existed at rest; however, during stress the maximum values obtained were successively diminished the greater the time utilized to average the heart rate pressure (P less than 0.05). During recovery an underestimation of the true response was observed that increased as the averaging time increased (P less than 0.05). Comparison between the R-R interval measure and the 6-s average data indicated a 18% decrease in the time of peak response. Therefore, the responses recorded with the 6-s averaged data were less sensitive and obscured the rapidity of autonomic changes. Hence, when sensitivity and absolute response are a primary concern in determining autonomic function, measurements should include R-R interval measures of heart rate or the average of the number of R-R intervals in 2-s time blocks.

Adolescent↗
PubMed1981

Airway permeability to horseradish peroxidase in guinea pigs: the repair phase after injury by cigarette smoke.

Airway permeability was examined in the 24-h period immediately after injury by cigarette smoke in 30 guinea pigs studied in groups of five at 30 min and 1, 6, 12, and 24 h after smoke exposure, and in 1 control group. The animals were anesthetized, tracheostomized, a carotid cannula inserted, and purified horseradish peroxidase was instilled on the airway surface via the tracheostomy tube. Blood samples (0.8 ml) were drawn and replaced with heparinized saline before and at 10, 15, 20, 30, and 40 min after horseradish peroxidase instillation. The animals were then killed, and samples of trachea and lung tissue taken for wet/dry wt determinations and for light and electron microscopic examination. The HRP concentrations in the blood were determined using an Elisa plate assay. We found the acute exposure to 100 puffs cigarette smoke resulted in a transient increase in airway epithelial permeability of HRP with a maximum at 30 min and a return to control values by 12 h after insult. These changes in mucosal permeability occurred in relation to a well-defined inflammatory reaction where increased permeability occurred during the exudative phase, which was monitored by measuring airway wet wt/dry wt ratios and the infiltration of polymorphonuclear cells. The return to the control value of permeability was associated with the repair phase of the inflammatory reaction, which was measured by monitoring basal cell mitoses.

Animals↗
PubMed1981

The heart rate, perceived exertion, and pace of the 1.5 mile run.

The logical validity of a 1.5-mile run as a measure of aerobic capacity, and the validity of Borg's laboratory model of perceived exertion (RPE) were examined in a field setting on a 440-yd cinder track. Performance time, heart rate (HR), and RPE were described for college-age males (N=67) instructed to achieve the lowest time possible during an "all-out" effort. Alpha and canonical factor analyses revealed three robust factors for performance times: 1) lap 1, 2) laps 2.5, 3) lap 6; two robust factors for HR: 1) laps 3-6, 2) laps 1 and 2; and four factors for RPE: 1) lap 6, 2) laps 1-3, 3) laps 4 and 5, 4) first 220 yd of lap 1. Results indicated distinct pacing characteristics of an initial sprint, a stable speed reduction, and a finishing sprint. This pace was generally independent of Ss HR (r's, mean lap 1 = 0.09; mean laps 2-5 = 0.19, mean lap 6 = 0.21) and RPE (r's, mean lap 1 = -0.15; mean laps 2-5 = 0.12; mean lap 6 = 0.07), and in part these findings at least implicate confounding influences by anaerobic metabolism and Ss motivation on performance. This possibility was supported by the fact that 95% of performance variance could be accounted for by pace factors of the initial and finishing sprints. Both HR and RPE response followed a linear-like increase as a function of cumulative time and distance. However, only a small relationship between HR and RPE (r, mean = 0.16) was observed during the run, and the obtained correlations did not support a central RPE-control model based on cardiovascular stress.

Adult↗