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Biomedical subjects

M H Harrison

Publications and source records attributed to M H Harrison.

At least 37 records · Page 2Linked to original sources
PubMed1984

Intravascular volume and protein responses to running exercise.

The roles of posture and mean skin temperature (Tsk) in determining intravascular volume and protein responses to running exercise were examined in 12 male subjects. Moving from a sitting to a standing position before exercise was always accompanied by a decrease in blood volume (BV), as indicated by increases in the hematocrit and hemoglobin concentration. Although neither the onset of running nor alterations in Tsk during running caused any further consistent change in BV, there was an acceleration of the rate at which protein entered the intravascular space. At the end of exercise and in recovery this led to an augmentation of intravascular protein. It is concluded that intravascular volume responses to running exercise are determined by the accompanying postural hemoconcentration, and that running per se and any imposed thermal stress have minimal effects on BV thereafter. A hypothesis is presented which accounts for the reportedly diverse effects of different forms of exercise on BV in terms of the posture-dependent BV being obtained immediately before exercise begins.

Adult↗
PubMed1983

Blood volume and protein responses to skin cooling and warming during cycling exercise.

The effects of alterations in mean skin temperature (Tsk) on intravascular volume and protein responses to 90 min of bicycle ergometer exercise have been studied in six male subjects. The onset of exercise was accompanied by an initial rapid haemoconcentration, followed by a slower, progressive haemoconcentration as core and skin temperatures increased. Cooling the skin after 30 min of exercise abolished the slow haemoconcentration, and thereafter, even when Tsk was raised to the pre-exercise level during the final 30 min of exercise, little further change in blood volume was observed. During skin warming, and during recovery from exercise, there was an increase in the total intravascular protein content compared with before exercise. It is concluded that the progressive haemoconcentration often described during cycling exercise may be attributed to an increase in skin blood flow occurring as a result of rises in core and skin temperature, the associated increase in filtration through the cutaneous capillaries causing a progressive loss of plasma volume. The mechanism of the augmentation of intravascular protein remains unclear.

Adult↗
PubMed1983

Blood volume and protein responses to skin heating and cooling in resting subjects.

The effects of alterations in skin temperature on intravascular volume and protein content have been investigated in resting subjects. With a normal core temperature (Tac) both skin cooling and skin heating caused hemoconcentration, and heating was associated with an increased rate of protein loss from the intravascular space. Raising of the skin temperature after cooling, with Tac depressed, and cooling of the skin after heating, with Tac raised, were associated with an immediate reversal of the hemoconcentration, and gain of protein by the intravascular space. It is concluded that intravascular volume responses to thermal stress are dependent on the skin and core temperatures obtaining immediately prior to imposition of the stress and that, in particular, a low skin temperature predisposes toward hemodilution on subsequent exposure to heat; sweating per se does not necessarily result in hemoconcentration. The association of hemodilution with augmentation of intravascular protein, and the rapidity with which extravascular protein can apparently gain entry to the intravascular space, is taken as indicating a possible direct return of protein through capillary walls.

Adult↗
PubMed1983

The sagging rope sign: a critical appraisal.

Certain features of the sagging rope sign recently analysed by Apley and Weintroub (1981) are examined in detail. Evidence is presented to show that the line is a radiological shadow cast by the lateral edge of a severely deformed femoral head rather than a condensation of the spongiosa within the neck. An explanation is offered to explain the common association of the presence of this radiological sign with premature epiphysial fusion.

Adolescent↗
PubMed1983

Painful sequelae of coxa plana.

Thirty-one patients with an average age of twenty-seven years had painful hips as the result of coxa plana in childhood. The pain was severe enough for surgical relief to be considered. Radiographically the lesions could be subdivided into three groups: severe mushroom deformity of the femoral head, 43 per cent; less severe dysplasia of the hip, 27 per cent; and severe osteoarthritis, 30 per cent. Twenty-three hip operations were done on theses patients. Fifteen hips showed radiographic evidence of definitive premature closure of the femoral capital epiphysis. The series is presented to illustrate that coxa plana may be followed by major disability in the hip within the first three decades of life.

Adolescent↗
PubMed1981

Blood volume and plasma protein responses to heat acclimatization in humans.

The effects of heat acclimatization on intravascular volume and protein responses to acute heat stress and exercise were studied in six male subjects. Absolute values for hematocrit and hemoglobin concentration were lower after, than before, acclimatization, indicating hemodilution. Also, after acclimatization, the magnitude of the hemoconcentration response to exercise in the heat was significantly increased. There ws no change in the concentration of plasma protein during or after acclimatization compared with before acclimatization, but there was a net increase in the total intravascular protein content. It is suggested that the hemodilution associated with heat acclimatization may be explained in terms of an increase in the intravascular oncotic pressure following an exercise-induced augmentation of protein, occurring at the expense of the interstitial compartment. It is concluded that this hemodilution is unlikely to be primarily responsible for the cardiovascular adjustment accompanying heat acclimatization and that it should be regarded as a secondary feature of adaptation to heat.

Acclimatization↗
PubMed1981

Effect of saline loading during heat acclimatization on adrenocortical hormone levels.

Six male subjects were acclimatized to heat; once they were given sufficient 1% saline to prevent the occurrence of a salt deficit during acclimatization, and another time they were given no saline. Plasma aldosterone (PA), plasma cortisol (PC), plasma renin activity (PRA), and plasma electrolytes were measured before, during, and after and sweat electrolytes before and after the 11-day acclimatization program. PRA and PA were significantly increased by the acute stress of heat and exercise but were unaffected by acclimatization. These increases were attenuated, but not prevented, by drinking saline, whereas sweat [Na] and PC were reduced by acclimatization but were unaffected by saline. Thus adrenocortical activity has been shown not to be increased after heat acclimatization, and mineralocorticoid activity, although potentiated by a Na deficit, appears to be determined primarily by the acute stress of heat and of exercise. Hence, the increased Na conservation with acclimatization is likely to be a normal response to heat and exercise even in the absence of a negative Na balance.

Acclimatization↗
PubMed1980

A study of the "normal" hip in children with unilateral Perthes' disease.

The radiographs of 153 children suffering from Perthes' disease of one hip were studied to examine the bony outline of the femoral capital epiphysis in the unaffected hip. In 48.4 per cent of patients irregularity of the surface, flattening or dimpling, were noted; in the majority of instances (37.2 per cent) these changes were present in the initial anteroposterior radiograph. By contrast, these changes were present in only 10.4 per cent of a control series of 153 children in whom intravenous urography was being performed, these children being matched for age and sex with the children with Perthes' disease. A second unmatched control series of 49 children whose pelves were being radiographed after injury showed a 6.1 per cent incidence of contour irregularities in 98 femoral capital epiphyses. In the patients with Perthes' disease and in the control series obtained at urography the incidence of changes was inversely related to age. The possible cause and significance of contour irregularities in normal children and in those with Perthes' disease is disscussed.

Age Factors↗
PubMed1980

Maximal oxygen uptake: its measurement, application, and limitations.

Maximal aerobic power (VO2 max) was determined by direct measurement in 10 male subjects whilst exercising on a bicycle ergometer, and whilst running uphill on a treadmill at speeds of 10 and 12 km/h. There was no significant difference between VO2 max measured at the two treadmill speeds, but the VO2 max measured on the bicycle was 20% lower than on the treadmill. An estimate of the variance of the treadmill determined VO2 max was obtained from repeated measurements on five subjects. The 95% tolerance interval about a single measurement of VO2 max was +/- 7.8 ml.kg-1.min-11. It is recommended that when indirect methods for determining VO2 max are calibrated against the direct method, the latter should be based upon the treadmill. Reservations are expressed concerning the value of the direct method for determining VO2 max, and of the concept of VO2 max as a measure of physical fitness.

Adult↗
PubMed1980

A comparison of some indirect methods for predicting maximal oxygen uptake.

Nine male subjects took part in a comparative evaluation of four indirect tests commonly used for predicting maximum aerobic power (VO2 max). In three of these tests (involving cycling, stepping and walking) VO2 max was predicted from submaximal heart rates; in the fourth, VO2 max was predicted from the time taken to run 2 km. Additionally, VO2 max was predicted from the body fat content. All predicted values were compared with the VO2 max determined directly on a treadmill. The best estimates of VO2 max were provided by the timed run, and by the step test. Both heart rate measured during walking and body fat content proved totally inadequate for the reliable prediction of VO2 max. Taking into account such factors as cost, safety, and the time required for testing, it is concluded that the timed run is the submaximal test most suited to the indirect determination of VO2 max.

Adult↗
PubMed1979

Congenital abnormalities and Perthes' disease. Clinical evidence that children with Perthes' disease may have a major congenital defect.

This paper reports a high incidence of minor congenital anomalies in boys and girls with Perthes' disease compared with that in a control population. There is a similarity of the incidence of minor anomalies in the children with Perthes' disease to that in babies with a single major congenital defect. Multiple major defects were more numerous and more severe than in the control children. It is speculated that there may be a congenital abnormality affecting skeletal development which in some way makes the hip susceptible to Perthes' disease at a later date.

Abnormalities, Multiple↗
PubMed1979

A prospective study of children with untreated Catterall group 1 Perthes' disease.

Twenty-four hips in twenty children affected by Group 1 Perthes' disease have been reviewed to assess the radiographic result after a minimum follow-up of four years. The children were allocated to Group 1 prospectively after examination of the early radiographs and no specific treatment of the affected hip was provided. The radiographic end results assessed by three methods were good even in those cases in which the additional stress of containment splintage of the contralateral hip was applied.

Age Factors↗
PubMed1979

The correction of angular deformities of long bones by osteotomy-osteoclasis.

The correction of angular deformities of long bones by incomplete osteotomy, followed three weeks later by manual osteoclasis, overcomes the problem of secondary displacement sometimes seen after correction by complete osteotomy and makes internal fixation unnecessary. This paper presents an experience of twenty-six operations in eighteen patients. In all cases the deformity was corrected with excellent cosmetic and functional results. Complete bony union was achieved and there were no problems with displacement at the osteotomy site. Four cases are described in detail to illustrate use of the technique in different clinical situations.

Adolescent↗
PubMed1979

Cockpit thermal stress and aircrew thermal strain during routine Jaguar operations.

Thermal data have been obtained from Jaguar aircraft flying routine, warm-weather operations in Sardinia. These data have been analysed in terms of the ambient and cockpit wet bulb globe temperatures (WBGT) and the mean body temperature (Tb) of the pilot. In contrast to similar data previously obtained from Harrier and Buccaneer aircraft, no interrelationships could be demonstrated between ambient WBGT at ground level and either cockpit WBGT or pilot Tb. Relationships which could be described by equations of negative slope were obtained between Tb and sortie time and between cockpit WBGT and sortie time. A model has been derived for predicting aircrew thermal strain in the Jaguar from cockpit temperature and sortie time.

Aerospace Medicine↗