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Biomedical subjects

M J White

Publications and source records attributed to M J White.

At least 109 records · Page 6Linked to original sources
PubMed1984

Different effects of ageing on the mechanical properties of human arm and leg muscles.

The effect of ageing on voluntary and electrically evoked muscle force was investigated. A group of 70-year-old men and a control group of young men took part in the study. The muscles studied were the elbow flexor group and the triceps surae group of the leg. With ageing both muscle groups showed a reduction in maximum voluntary force and in the force of electrically evoked tetani. The reduction was greatest in the leg muscles. The time to peak of the twitch was prolonged with age in the leg muscles. The findings are discussed in relation to the changes in fibre type known to occur in elderly muscle.

Adult↗
PubMed1984

Racial and ethnic succession in four cities.

"The concept of succession is well established in both ecological and economic models of urban residential change, yet much remains unknown about the determinants of succession in urban neighborhoods. Employing longitudinal census tract data for four [U.S.] cities, this article predicts racial composition of neighborhoods as a function of earlier-period racial, ethnic, socioeconomic, and physical characteristics. There is support for aspects of the ecological and filtering models of succession, although many elements of the process are not generally applicable across time and place."

Americas↗
PubMed1984

The effect of specific and nonspecific immunotherapy on natural killer cell activity in patients with non-small-cell lung cancer.

Fourteen patients with stages I and II non-small-cell lung carcinoma receiving adjuvant immunotherapy after surgery were studied serially for natural killer (NK) cell cytotoxicity assays. Seven patients received active nonspecific immunotherapy with Freund's complete adjuvant alone and seven patients received active specific immunotherapy with tumor-associated antigen plus Freund's complete adjuvant. Both groups were analyzed as a single group in view of the lack of any difference in the results. The results indicated that NK-cell cytotoxicity v K562 was lower in untreated patients than in normal controls, but the difference was not significant. There was no evidence of specific cytotoxicity v the lung cell line A549 in untreated patients when compared with normal controls. Compared with pretreatment values, elevated cytotoxicity v both K562 and A549 was observed at every post-treatment time point tested, and this was statistically significant at several time points by a paired t test. No specific effect was noted after immunization with lung antigen on cytotoxicity against the lung cell line A549. Other correlations studied did not show any relationship between delayed hypersensitivity skin testing or serum carcinoembryonic antigen levels and NK-cell cytotoxicity. It is concluded that NK-cell reactivity was increased nonspecifically by active specific and nonspecific immunotherapy. This increase seems to peak at the 12-month period and was significant when compared with pretreatment levels.

Adjuvants, Immunologic↗
PubMed1983

Muscle function in children.

Electrically evoked mechanical and contractile properties of the triceps surae have been measured in 52 children aged 11 and 14 years, and results compared with previously reported data for adults (Davies and White 1982). The results show that the time to peak tension (TPT), half relaxation time (1/2RT) and supramaximal tension (Pt) of the twitch were not significantly (P greater than 0.1) different in girls and boys and independent of age. The 14-year-old girls and boys were stronger in terms of their supramaximal 10, 20, and 50 Hz tetanic tensions and maximal voluntary contraction (MVC) than their younger counterparts, and both groups of children were significantly (P less than 0.001) weaker than the young adults. However, if standardisation was made for an anthropometric estimate of calf muscle (plus bone) cross-sectional area (CSA), the differences in strength disappeared. Electrically stimulated and voluntary maximal force per unit CSA measured at the knee were 17.1 and 20.5 N X cm2 respectively and independent of sex and age. The loss of force during a 2-min stimulated fatigue test was the same in the children as the adults. The average fatigue indices ranged from 0.52 to 0.72 in the children, compared with 0.68 in the adults. It is concluded that absolute differences in muscle strength in children are a function of muscle mass. The force generating capacity expressed in N X cm2, fatiguability, contraction and relaxation times of the triceps surae would appear to remain unchanged through adolescence and early adulthood.

Adolescent↗
PubMed1983

Electrically evoked and voluntary maximal isometric tension in relation to dynamic muscle performance in elderly male subjects, aged 69 years.

The dynamic performance and electrically evoked mechanical properties of elderly triceps surae muscle have been investigated in 9 men, aged 69 yr. Dynamic performance consisted of cycling on a force bicycle and a vertical jump off two feet from a force platform. The results showed that the time to peak tension (TPT) and half relaxation time (1/2 RT) were significantly greater (p less than 0.001) by 30 ms and 22 ms and the supramaximal twitch (Pt) and tetanic (20 Hz-P020) tensions and maximal voluntary contraction (MVC) were less by 45 N (-33%), 708 N (-49%), and 899 N (-43%) in the elderly compared with young male control subjects. On the force platform, the height jumped (Ht), maximal force exerted (P), take-off velocity (VT), net impulse (NI) and peak power output (W) were less by 18.6 cm, 173 N, 0.9 ms-1, 52 Ns and 1120 w respectively. Similar differences of power, force and velocity were observed on the force bicycle. The reduction of W in the elderly was associated with the contractile characteristics of the leg muscle. The loss of contractile speed and capacity to to generate force in old people was reflected in their inability to develop power during the performance of a maximal vertical jump and cycling.

Aged↗
PubMed1983

Prevention of cadmium-induced sterility by zinc in the male rat.

The potential of zinc (Zn) to antagonize the adverse effects of cadmium (Cd) on the male reproductive processes was studied. A significant reduction in the weights of the testis and epididymis, the testicular sperm population and oligospermia to azoospermia in the epididymis was recorded in rats treated once s.c. with 2 mg/kg Cd and sacrificed 20 days later. This was accompanied by a significantly reduced serum T and a loss of fertility. Administration of a single s.c. injection of Zn (80 mg/kg) did not alter significantly any of the reproductive parameters studied. On the other hand, Zn given 1/2 to 2 h after Cd resulted in partial recovery. Organ weights and sperm population in these groups were maintained and the fertility rate was 67% and 50% at 5 and 20 days as compared to 67% and 0% at corresponding period in Cd-exposed males. The protective effect diminished when Zn was given more than 2 h after Cd exposure. The most effective regimen of Zn therapy was an administration of a total dose of 80 mg/kg Zn given in 3 injections (15 mg/kg before, 50 mg/kg at the time and 15 mg/kg 2 h after Cd). The results provide evidence that Zn, if given before or within 2 h of Cd exposure, is capable of at least partially reversing its deleterious effects on spermatogenesis, steroidogenesis and fertility of the male rat.

Animals↗
PubMed1983

Reassessment of Graham-Steele closure in acute perforated peptic ulcer.

We studied 67 patients who had operation for perforated peptic ulcer. Operative treatment included plication with omentum (Graham closure) in 27 patients, vagotomy and pyloroplasty in 32 patients, or vagotomy and antrectomy in eight patients, depending on antecedent ulcer history, degree of contamination, and general patient condition. Mortality was high with simple closure in patients with long-standing perforation or associated disease. Early complications associated with Graham closure included rebleeding, perforation, and obstruction. There were no deaths or major complications related to vagotomy and pyloroplasty. In selected patients, definitive operation is safe and produces excellent long-term results.

Acute Disease↗
PubMed1983

Contractile properties of elderly human triceps surae.

Maximal electrically evoked and voluntary contractions of the triceps surae were repeatedly measured over several weeks in 13 elderly men, mean age 69.6 +/- 1.3 years. All subjects were found to be tolerant of supramaximal single twitch stimuli from the first occasion of measurement onwards and were habituated to supramaximal tetanic stimulation at frequencies of 10 and 20 Hz after three occasions of measurement. There was a significant increase in maximal voluntary contraction between the first and second occasions of measurement, but thereafter it remained unchanged. The coefficient of variation for maximal twitch and tetanic tensions and MVC were 12.5, 9.0 and 8.3%, respectively. Comparison with previously reported data showed that elderly muscle had an increased time-to-peak twitch tension development (148 +/- 15 ms) compared with young subjects (113 +/- 11 ms). The respective half relaxation times were 99 +/- 13 and 78 +/- 4 ms. Maximal tetanic tensions at frequencies of 10 and 20 Hz were significantly lower in the elderly men, 520 +/- 168 and 716 +/- 193 N respectively compared with 742 +/- 133 and 1,162 +/- 199 N respectively in the young subjects. A 2-min test involving repeated tetanisation of the triceps surae showed that though the absolute loss of tension was the same the relative loss was greater in the older than the younger men. It is concluded that muscle function in the elderly can be reliably assessed. The results suggest that the triceps surae of the elderly are weaker, more slowly contracting and show a greater relative force loss, when subjected to a standard "fatigue' test procedure, than young triceps surae.

Aged↗
PubMed1983

Effects of dynamic exercise on muscle function in elderly men, aged 70 years.

The maximal electrically evoked and voluntary contractions of the triceps surae were measured, before and after 30 min of continuous uphill walking, in 8 elderly men aged 67-71 years. The exercise was performed on a motor-driven treadmill and corresponded to 66-74% of their predicted maximal aerobic power output. During the control period, before exercise, twitch tension (Pt), time-to-peak tension (TPT) and half relaxation time (1/2RT) of the maximal twitch response were 102 +/- 29 N, 156 +/- 15 ms and 98 +/- 11 ms; the tetanic responses at frequencies of 10 Hz (PO10) and 20 Hz (PO20) and the maximal voluntary contraction (MVC) averaged 600 +/- 103, 766 +/- 106 and 1,225 +/- 185 N, respectively. The fatigue index in response to a 2-min test involving repeated tetanisation of the triceps surae was 0.40 +/- 0.14. None of these variables (except TPT which was decreased to 145 +/- 11 ms, p less than 0.001) was significantly changed following exercise. It was concluded that exercise of relatively high intensity and duration in healthy elderly men does not impair the force-generating capacity of the lower leg muscles nor increase their fatigability.

Aged↗
PubMed1982

Contractile properties of the human triceps surae with some observations on the effects of temperature and exercise.

The contractile properties of the triceps of five healthy male subjects (mean age 22 years) during electrically stimulated and voluntary isometric muscle contractions were investigated and some observations made on the effects of muscle heating and cooling and dynamic exercise. The times to peak twitch tension (TPT) and half relaxation time (1/2RT) were 111 +/- 20 ms and 83 +/- 13 ms respectively. Heating and prior exercise decreased, and cooling severely prolonged, TPT and 1/2RT. Exercise and heating had no effect on supramaximal twitch tension (Pt0) but cooling the muscle to a temperature of 24.3 degrees C reduced it by 52%. The effects of repetitive stimuli on Pt0 were dependent on frequency; at 0.2 Hz potentiation was observed but at 2 Hz, Pt0 was depressed under control conditions. Heating had no effect on these responses but cooling reversed the 2 Hz and abolished 0.2 Hz response. Post-tetanic potentiation of the twitch was observed under all conditions of measurement. At submaximal stimulation voltages, heating and exercise enhanced twitch and tetanic tensions, but at supramaximal voltages heating reduced tetanic tension (P0) at 10 Hz (by 115 N), though not at 20 Hz. Exercise decreased P0 at both frequencies of stimulation. Cooling significantly reduced the maximal voluntary contraction and P0 at 20 Hz. At submaximal voltages, heating enhanced and cooling severely depressed tetanic tensions at high frequency (100 Hz) stimulation. A 2-min fatigue test was unaffected by heating but cooling reduced force generation at the onset of, and the decline of force during, the test. It was concluded that studies of the contractile properties of human muscle in vivo should be based on supramaximal stimulation, and that temperature and prior exercise should be carefully standardised in order to obtain reliable and meaningful results.

Adult↗
PubMed1982

Computed tomography in the preoperative evaluation of bronchogenic carcinoma.

Preoperative determination of the extent of bronchogenic carcinoma at presentation was assessed by CT using a 4th generation scanner with a 3-second scan time in 98 patients whose disease was later surgically staged. Prospective CT interpretations correctly staged 33 of 35 (94%) resectable lesions, and disease in 41 of 45 (91%) patients who had lesions that were not resectable for cure. No definite opinion was rendered on the scans of the remaining 18 patients. Retrospectively analysis using slightly modified criteria resulted in a correct prediction of resectability in 28 of 30 (93%) patients (scans showed a normal mediastinum with no lymph node larger than 1 cm in diameter), and nonresectability for cure in 34 of 34 (100%) patients (scans showed either direct extension of the primary neoplasm into the mediastinum or mediastinal lymph-node enlargement greater than 2 cm in diameter). However, scans of 34 of 98 (35%) patients showed inconclusive findings (mediastinal lymph-nodes with 1-cm to 2-cm diameters, neoplasms abutting but not definitely invading the mediastinum, pleural or pericardial thickening, or additional noncalcified nodules).

Adenocarcinoma↗
PubMed1982

Muscle weakness following dynamic exercise in humans.

Electrical stimulation of the triceps surae in five healthy male subjects showed that following 1-2 h level running and uphill walking, at submaximal voltages of stimulation, exercise enhanced the twitch and tetanic responses, but the supramaximal time to peak tension (TPT), twitch (Pto) and tetanic tensions (Po) at 10 and 20 Hz were reduced by 16 ms (-12.6%), 11 (-8.9%), 163 (-17.5%), and 230 N (-18.1%), respectively. High-frequency (50 and 100 Hz) tetanic stimulation produced qualitatively similar changes to the 20-Hz response, but the stimulus response curve for the two frequencies was different and the ratio of 20- to 50-Hz response (20/50) (cf. Edwards et al., J. Physiol, London 272: 769-778, 1977) was voltage dependent. The reduction in Po at 100 Hz was associated with a decrease in maximal voluntary contraction (MVC). The effects of exercise on Pto and Po at 10, 20, 50, and 100 Hz were short lived and recovered within approximately 2 h. In contrast box-stepping produced a greater fall in Pto and Po at 10 and 20 Hz, which was long lasting (at least (22 h), and there was a consistent fall in the 20/50 ratio. a 2-min "fatigue" test showed that the muscles were weaker but not more fatigable after exercise. Our results seriously question the validity of using submaximal stimulation voltages and ratios for testing human muscle function and suggest that long-lasting muscle weakness is not associated with recovery from prolonged walking, running, and only observed after box-stepping exercise.

Adult↗
PubMed1982

Cytogenetics of the parthenogenetic grasshopper Warramaba virgo and its bisexual relatives. VIII. Karyotypes and C-banding patterns in the clones of W. virgo.

Eleven cytological clones of the parthenogenetic grasshopper Warramaba virgo are defined in this paper on the basis of their karyotypes and the C-banding patterns of their chromosomes. These clones are additional to the 16 clones previously described. Seven of the new clones have the standard karyotype and differ only in minor features of the C-bands, the result of amplification or diminution of heterochromatic segments. The remaining 4 clones carry translocations. Of the total of 27 clones of W. virgo now known, 9 carry translocations or fusions. The X + A chromosome is involved in five of these rearrangements and the 1(169) chromosome in four, suggesting a marked nonrandomness with regard to involvement in rearrangements. All the clones with translocations or fusions are known from single localities, suggesting that they are short-lived and do not spread far from their point of origin. A clone that apparently carries a paracentric inversion in one chromosome is more widespread. Clonal diversity in W. virgo seems to be maximal in the Kalgoorlie region of Western Australia, where W. virgo is believed to have arisen, on two separate occasions, by hybridization between two bisexual species. A classification of the clones on the basis of their C-banding patterns is tentatively proposed.

Animals↗