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Biomedical subjects

R Thatcher

Publications and source records attributed to R Thatcher.

At least 19 recordsLinked to original sources
PubMed2005

Comparison of the Lactate Pro and Analox GM7 blood lactate analysers.

The purpose of this study was firstly, to determine the level of agreement between the Lactate Pro and Analox GM7 for the measurement of blood lactate, and secondly, to examine whether these analysers may be used interchangeably to identify lactate parameters routinely used in the physiological assessment of athletes. Twenty well-trained male cyclists performed an incremental cycle ergometry test; duplicate blood samples were taken simultaneously throughout the test for lactate determination using the two analysers. Power output and heart rate at LT, LT1, 2 mmol.L-1, and 4 mmol.L-1 were calculated from the lactate values obtained from the two analysers. There was a strong linear relationship between the two analysers (Lactate Pro=1.4541xAnalox GM7-0.1287; R2=0.969, p<0.001; SEE=0.704) though the Lactate Pro overestimated blood lactate when compared to the Analox GM7; 95% ratio limits of agreement (Lactate Pro/Analox GM7) were 1.40x//1.35. Differences were found between analysers for power output and heart rate at LT1 (p<0.01), 2 mmol.L-1 (p<0.001), and 4 mmol.L-1 (p<0.001); no differences were found between analysers for power output or heart rate at LT. In conclusion, the average difference in blood lactate concentration measured by the Lactate Pro and the Analox GM7 was 40%, with 95% of measures differing by between 4% and 89%. This poor level of agreement and the significant differences between the two analysers in power output and heart rate associated with a number of lactate parameters indicate that these analysers should not be used interchangeably.

Adult↗
PubMed2004

Development and validation of a sport-specific exercise protocol for elite youth soccer players.

AIM: The aims of the current study were, firstly, to quantify the motion characteristics of professional youth soccer players and, secondly, to develop and validate a soccer-specific exercise protocol (SSEP). METHODS: The motion characteristics of 12 first team members and 12 scholars (under 19s), signed to an English Premiership club were determined via motion analysis. Motion profiles from the analysis were then used to develop a SSEP for a non-motorised treadmill. Validity of the protocol was checked with 6, healthy, male soccer players who completed the SSEP and, on a separate occasion, a soccer match. Heart rates were recorded during both trials, in addition, capillary blood and expired air samples were taken, and RPE recorded, during the SSEP. RESULTS: Youth team players covered 10274+/-609 m, compared to 9741+/-882 m by the first team players (t=1.72, p>0.05; 95% CI for the difference = -1174 m to 109 m). The trend for greater mean distance covered by youth players could be attributed to the distances covered while jogging and running. Mean heart rate response was 166+/-9 beatsxmin(-1) during match play and 166+/-12 beatsxmin(-1) during the SSEP (t=0.164, p>0.05). Mean .VO(2) during the SSEP was 70+/-3% of .VO(2max). Blood lactate concentration fell from a mean value of 5.37+/-1.15 mmol x L(-1) during the first half to 4.74+/-1.25 mmol x L(-1) during the 2(nd) half (t=2.52, p<0.05). CONCLUSION: The findings of this study suggest that the protocol developed induced a similar physiological load to soccer match play and provides the opportunity to study the physiological demands of soccer.

Adult↗
PubMed2004

Gender differences in the pre-competition temporal patterning of anxiety and hormonal responses.

AIM: This study examined gender differences in the pre-competition temporal patterning of anxiety and hormonal responses. METHODS: Six male and 6 female field hockey players completed the modified Competitive State Anxiety Inventory-2, including both intensity and direction subscales, and provided saliva and urine samples 24, 2, and 1 hour prior to competition. These samples were analyzed for cortisol, and noradrenaline and adrenaline, respectively. RESULTS: Two x 3 repeated measures ANOVAs revealed significant gender x time interactions for cognitive and somatic anxiety intensity and adrenaline and noradrenaline, but not cortisol. While males' anxiety and hormonal responses demonstrated no significant changes, significant increases in females' anxiety, and significant decreases in their adrenaline and noradrenaline were observed over time. Moreover, while males' anxiety and hormonal responses mirrored each other, this was not the case for the females with increases in females' cognitive and somatic anxiety intensity levels accompanied by decreases in adrenaline and noradrenaline. CONCLUSIONS: Although this study has extended this line of research by adopting a psycho-physiological approach and measuring anxiety intensity and direction in male and female athletes, replication is required with larger samples from a greater diversity of sports.

Adolescent↗
PubMed1999

Repeated measures of cognitive processing efficiency in adolescent athletes: implications for monitoring recovery from concussion.

OBJECTIVE: The objective of this study was to determine whether an adolescent athlete, in the absence of concussion, would be expected to show an improvement in cognitive function during the course of a high school football season. BACKGROUND: At least 60,000 American high school football players suffer cerebral concussion every year, and symptoms may persist for 4 or more years in as many as 24%. METHOD: 34 members of a cohort of healthy athletes, aged 13-18, were administered a computerized neuropsychologic test battery from the Automated Neuropsychological Assessment Metrics (ANAM) before and after the 1997 high school football season, with a mean interval of 16.1 (range 12.3-20.4) weeks between tests. Preseason and postseason scores on eight tests were compared, with significance determined by paired t-test. For those tests in which an improvement was noted, one-way analysis of variance and Wilcoxon tests were used with both preseason and postseason data to determine if there was a measurable difference in cognitive processing efficiency between older and younger subjects. RESULTS: Improvements in processing efficiency (p < 0.001) were noted on tests designed to measure visual scanning and sustained attention (CDS), immediate recall (CDI), and short-term memory (CDD). Older subjects generally performed better on each of these tests, though the difference was significant in only one case (postseason CDI, 17-18 year olds vs. 13-14 year olds, Wilcoxon, p = 0.043). CONCLUSIONS: Our findings suggest that ANAM is sensitive to differences and improvements in cognitive function during a 4 month interval in adolescence. They also suggest that using "return to baseline" cognitive function as the criterion for evidence of recovery from concussion may be insufficient, especially when the baseline measurement was obtained 4 or more months prior to the date of "full recovery."

Adolescent↗
PubMed1999

The demography of centenarians in England and Wales.

Using a new database, the article investigates the causes of the current 'explosion' in the numbers of centenarians. It then examines the latest official projections for the future and their implications for the highest ages which are likely to be attained.

Aged↗
PubMed1994

Event-related desynchronization and movement-related cortical potentials on the ECoG and EEG.

Event-related desynchronization (ERD) 2.0 sec before and 1.0 sec after movement in the frequency bands of 8-10, 10-12, 12-20 and 20-30 Hz and movement-related cortical potentials (MRCPs) to self-paced movements were studied from subdural recordings over the central region in 3 patients, and from scalp-recorded EEGs in 20 normal volunteers. In direct cortical recordings, the peak ERD response and peak MRCP amplitude to self-paced finger movements were maximal over recording sites in the contralateral hand motor representations. The topography and time of onset of the ERD response to finger and foot movements suggest that the ERD responses in the 8-10 Hz and 10-12 Hz bands are more somatotopically restricted than the responses in the higher frequency bands. The power recovery and subsequent overshoot in the different frequency bands occurred in an orderly fashion with the faster frequencies recovering earlier. The ERD responses on the scalp-recorded EEGs were of lower magnitude and more widely distributed than those occurring on the subdural recordings. Across the population, there was no relation between the magnitude of the ERD response in any of the frequency bands studied and the peak amplitude of the negative slope (pNS') and the frontal peak of the motor potential (fpMP) of the MRCPs. MRCPs and ERD responses originate in similar cortical regions and share some common timing features, but the magnitude and spatial distribution of the two responses appear to be independent of each other, which suggests that the physiological mechanisms governing these two events are different and may represent different aspects of motor cortex activation. Differences in the timing and topographical features of the ERD responses in the various frequency bands also suggest a distinct functional significance for the various spectral components of the electrical activity in the motor cortex.

Adult↗
PubMed1991

Iron absorption by hypotransferrinaemic mice.

Iron absorption rates by homozygous and wild-type mice from a hypotransferrinaemic mouse colony were examined with in vivo tied-off duodenal segments and in vitro incubated duodenal fragments. Enhanced initial rates of mucosal uptake and carcass transfer by homozygotes, compared to wild-types, were observed. The changes in vivo and in in vitro uptake kinetics resemble changes seen in iron deficient or hypoxic mice, suggesting that the liver iron loading shown by homozygotes is due to a failure of the normal mechanism for regulation of iron absorption. In vivo mucosal uptake and carcass transfer of radioiron showed an inverse correlation with liver non-haem iron content in homozygous hypotransferrinaemic mice, suggesting that some degree of control of absorption, albeit at markedly reduced sensitivity, can operate in these mice. No correlation between haemoglobin level and iron absorption was observed in homozygous hypotransferrinaemic mice, suggesting that this regulator of iron absorption does not function in these mice. The precise pathogenic mechanism of the enhanced iron absorption in hypotransferrinaemia remains to be determined. Mucosal transferrin levels were found to parallel serum transferrin levels in homozygotes, heterozygotes and wild-type mice. This supports previous suggestions that mucosal transferrin is derived from plasma transferrin and that the enhancement of iron absorption, by physiological mechanisms, does not require the presence of mucosal transferrin.

Absorption↗
PubMed1985

The effects of ACTH on the renin-aldosterone system in normotensive man.

The present study examined the effects of low dose ACTH administration (0.1 mg/day for 2 days) on plasma renin concentration, (PRC), activity (PRA) and substrate (PRS), cortisol and aldosterone in man. Six healthy male volunteers on a diet calculated to contain 150 mmol Na/day received an infusion of 5% dextrose (6 ml/h) for 24 hours, then ACTH (Synacthen, Ciba-Geigy) was added to the infusion at the rate of 100 micrograms per day, for 48 h. Blood samples were taken four hourly for determination of plasma cortisol, aldosterone, PRC, PRA and PRS. There was a highly significant increase in plasma cortisol and aldosterone concentrations during ACTH infusion compared with dextrose infusion, but no significant increase in active or inactive PRC, PRA or PRS. In a separate study of 15 healthy male volunteers, dexamethasone (1 mg at 2300 h) suppressed plasma cortisol but had no effect on PRC. These results do not support the view that stimulation of aldosterone by ACTH is mediated through the renin angiotensin system.

Adrenocorticotropic Hormone↗
PubMed1984

Renin-angiotensin-aldosterone system in nephrotic syndrome.

Previous studies on the renin-angiotensin-aldosterone system and fluid volumes in patients with nephrotic syndrome have not considered the nature of the underlying renal lesion. We compared plasma renin concentration (PRC), plasma aldosterone (PA), and plasma volume in three groups of patients: five nephrotic patients with minimal change disease on renal biopsy, seven nephrotic patients with other renal histopathology, and a control group of eight patients investigated for glomerulonephritis with no past or present nephrosis. PRC and PA were significantly greater in nephrotic patients with minimal change disease than other renal histopathology (Supine PRC 42 +/- 7 microIU/mL compared with 14 +/- 4, P less than 0.01; ambulant PRC 56 +/- 7 microIU/mL compared with 29 +/- 10, P less than 0.05; supine PA 158 +/- 55 pg/mL compared with 53 +/- 13, P less than 0.05; and ambulant PA 167 +/- 57 pg/mL compared with 29 +/- 10, P less than 0.05. Plasma volume was similar in all three groups, contrary to predictions from the Starling capillary fluid exchange hypothesis. Nephrosis may be characterized by different pathophysiologic groups according to the underlying renal histopathology. High plasma renin and aldosterone levels may be markers for minimal change disease.

Adolescent↗
PubMed1983

Blood pressure and metabolic effects of ACTH in normotensive and hypertensive man.

ACTH administration (0.5 mg Synacthen Depot I/M 12 hourly for 5 days) significantly increased systolic blood pressure in normotensive subjects (n=6) and mild essential hypertensives (n=6) but not in 2 Addisonian women, indicating that the pressure rise was adrenally dependent. ACTH administration was associated with urinary sodium retention, hypokalaemia, elevation of fasting blood glucose, lymphopaenia and eosinopaenia. Body weight was increased only in the normotensive subjects. Plasma renin concentration fell and renin substrate rose. Inactive renin fell in the hypertensive subjects only. Plasma cortisol, 11-deoxycortisol, corticosterone, deoxycorticosterone, 17 alpha-hydroxyprogesterone and 17-hydroxy, 20-dihydroprogesterone were all increased by ACTH treatment. Plasma aldosterone rose initially in the normotensives but then fell. ACTH administration in man produces metabolic and hormonal changes similar to those produced by ACTH in sheep but the rise in blood pressure is systolic only in man. The steroid(s) responsible for the blood pressure rise with ACTH in man have not been defined.

Addison Disease↗
PubMed1982

Primary hyperaldosteronism in pregnancy.

We report a case of primary hyperaldosteronism in a 37-year-old woman presenting early in pregnancy with hypertension and hypokalaemia. Plasma renin concentration was suppressed and unaffected by sodium restriction or upright posture at 16 and 35 weeks gestation, or seven days post-partum. Recumbent plasma aldosterone was elevated, and normal postural response lost both at 35 weeks gestation and seven days post-partum. Vaginal delivery, following induction at 38 weeks, was uncomplicated. Two months postpartum C.T. scan and adrenal venous catheterisation studies indicated a left sided adenoma and left adrenalectomy was performed. Within seven days the patient was normotensive with normal serum potassium and urinary aldosterone on no treatment.

Adenoma↗
PubMed1982

Changes in active and inactive renin with haemodialysis.

Active (A) and inactive (I) plasma renin concentrations (PRC) were examined during haemodialysis in relation to blood pressure and body weight changes. Patients had either one (n = 15) or two (n = 51) remnant kidneys in situ, or were anephric (n = 4). 6 of the two remnant kidney patients had non-functioning renal allografts. Inactive renin was activated by acidification. Renin assay was by enzyme kinetic technique using sheep substrate and angiotensin I radioimmunoassay. Cryoactivation during handling was excluded. For the whole patient group the proportion of IPRC was inversely related to APRC in pre-dialysis plasma (p less than 0.001). APRC and IPRC did not change with heparinisation nor did activation of renin occur across the dialyser. Dialysis with up to 3 kg reduction in body weight did not consistently raise APRC or IPRC. Blood pressure was not significantly correlated with IPRC or APRC during dialysis. In all situations a high APRC was associated with a low IPRC:APRC ratio consistent with preferential secretion of the active form and/or consumption of the inactive renin zymogen.

Adolescent↗
PubMed1981

Blood pressure, renal and metabolic effects of ACTH in normotensive man.

1. The blood pressure, renal and metabolic effects of adrenocorticotropic hormone (ACTH) have been studied in six normotensive subjects and two patients with Addison's disease on maintenance steroid therapy. 2. In normotensive subjects, 5 days ACTH treatment (0.5 mg 12 hourly) was associated with a rise in systolic blood pressure and mean arterial pressure. There was a small rise in diastolic pressure but no consistent change in heart rate. Plasma sodium increased and plasma potassium fell. Serum creatinine and urea concentrations were unchanged. Fluid intake increased and urine output was unchanged but ACTH withdrawal was associated with a diuresis. There was an initial reduction in urinary sodium excretion and a natriuresis after ACTH withdrawal. Plasma volume and body weight rose. 3. ACTH produced increases in plasma cortisol, 11-deoxycortisol, corticosterone, deoxycorticosterone, aldosterone, 17 alpha-hydroxyprogesterone and 17 alpha,20 alpha-dihydroxyprogesterone. Plasma renin concentration fell. 4. Patients with Addison's disease showed no change in blood pressure or in any other metabolic variable studied. 5. The effects of ACTH in man resembled those found in sheep.

Adolescent↗
PubMedDate not supplied

Differential blood pressure and metabolic effects of 9 alpha-fluorocortisol in man.

The blood pressure and metabolic effects of 9 alpha-fluorocortisol at 0.15 mg/day and 1.5 mg/day were examined in man. At high dose, systolic pressure and body weight rose, and plasma [K+], urinary sodium excretion and renin concentration fell. At low dose similar metabolic effects were seen but blood pressure was unchanged. 9 alpha-Fluorocortisol has 'mineralocorticoid' effects in man at a dose which does not alter blood pressure. These studies do not provide evidence of a 'hypertensinogenic' class of steroid hormone action in man.

Blood Pressure↗