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Biomedical subjects

M H Maxwell

Publications and source records attributed to M H Maxwell.

232 records · Page 13Linked to original sources
PubMedDate not supplied

Characterisation of embryonic cardiac-derived troponin T in broiler chicks bled one to 168 hours after hatching.

Troponin T, a cardiac-specific protein released only from damaged or injured heart tissue and cells, was measured in the sera from fowl chicks bled one, 12, 24, 48, 96 and 168 hours after hatching. A peak troponin T response was observed 12 hours after hatching in two experiments conducted six months apart. In the second experiment the heterophil/lymphocyte (H/L) ratios were also increased at one and 12 hours after hatching. The data suggest that the troponin T response in chicks bled 12 hours after hatching, together with the raised H/L ratios at the same age, may indicate a physiological stress reaction to the process of hatching, rather than a process which is under direct genetic control.

Aging↗
PubMedDate not supplied

Inhibition of furosemide-induced increases in plasma renin activity by amiloride.

The effect of the potassium-sparing diuretic, amiloride, was studied in conscious rabbits bearing chronic indwelling cannulas to assess whether its reported in vitro kallikrein-inhibiting activity may produce a suppressive effect on furosemide-induced renin secretion similar to that previously demonstrated with another kallikrein inhibitor, aprotinin. Furosemide elicited a rapid and persistent rise in plasma renin activity (PRA), but pretreatment of the same rabbits with a 15-minute intravenous infusion of amiloride, which amounted to 1 mg/kg and commenced at 30 minutes before furosemide, completely prevented this rise. Amiloride also prevented furosemide-induced kaliuresis without an attenuation of the diuretic or natriuretic response and did not alter plasma potassium concentration in the absence of any change in external potassium balance, indicating that suppression of the PRA response is due neither to prevention of extracellular fluid volume contraction nor to the known suppressive effect of hyperkalemia. Mean arterial pressure tended to fall slightly but not significantly with or without amiloride pretreatment. On the basis of these findings and those of our antecedent study with aprotinin, we conclude that the striking similarity between the suppressive effects of two dissimilar inhibitors of kallikrein on pharmacologically evoked renin secretion is consistent with the hypothesis that renal kallikrein participates in the mechanism of renin secretion in vivo.

Amiloride↗
PubMedDate not supplied

Erythrocyte Na+,K+ cotransport and Na+,K+ pump in black and caucasian hypertensive patients.

Alterations in red blood cell (RBC) Na+,K+ pump and in Na+,K+ cotransport (CoT) have been described in essential hypertension (EH). We examined pump and CoT in 50 normotensive (NT) subjects and 58 EH subjects subdivided by race and family history of hypertension (+ FH). RBCs were preloaded with Na+ to obtain intracellular levels of 25 mM/liter cells by using the p-chloromercuribenzene sulfonic acid (pCMBS) method. Na+ and K+ efflux rates into a magnesium-sucrose medium were quantitated in the presence of ouabain and ouabain plus furosemide to define pump and CoT activity respectively. Mean intracellular Na+ content was higher (p less than 0.05) in black NT and HT subjects compared to Caucasians. Mean RBC CoT was lower in black EH compared to NT and compared to Caucasian NT and HT subjects. Conversely, Caucasian HT patients had higher mean CoT than NT subjects. Subdivision into + FH revealed very little effect of + FH on CoT in black NT and HT subjects. In Caucasian NT and HT subjects with + FH, mean CoT was significantly reduced (less than 0.3 mM/liter cells/hr) compared to those without + FH. A subgroup of Caucasian EH subjects displayed high CoT (greater than 0.6 mM/liter cells/hr); a + FH had little impact on the high CoT group. There was no correlation between RBC CoT activity and age, sex, severity of hypertension, urinary sodium excretion, and plasma aldosterone. There was a positive correlation (r = + 0.47; p less than 0.01) between CoT and upright plasma renin activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Sorbent regeneration of peritoneal dialysate: an approach to ambulatory dialysis.

Sorbent regeneration of peritoneal dialysate has been shown to be feasible in experimental and preliminary clinical studies and provides a realistic basis for the optimization of dialysis therapy and the potential development of an ambulatory dialysis system. Peritoneal dialysis efficiency can be significantly enhanced by continuous dialysate flow techniques and the mass transfer of uremic solutes can be theoretically augmented by the increased dialysis time made possible by a wearable design. Further optimization of end stage renal failure therapy may be achieved by the combined use of various methods for blood purification.

Adsorption↗
PubMedDate not supplied

Systolic blood pressure as an independent predictor of mortality in the Hypertension Detection and Follow-up Program.

The Hypertension Detection and Follow-up Program (HDFP) findings demonstrate the predictive value of baseline systolic blood pressure (SBP) and of pulse pressure (PB) in five-year mortality from all causes. Grouping participants into four SBP strata revealed an approximately two-fold increase in age-adjusted mortality rate from SBP stratum I to SBP stratum IV. This effect remained after the contributions of other risk factors were controlled by multivariate analysis. In contrast, baseline diastolic blood pressure (DBP) had little demonstrable effect on mortality in this particular population. The predictive power of pulse pressure was similar to that of SBP. The group mean SBP of every stratum fell progressively during the trial, the change being of greater magnitude in the stepped care (SC) group than in the referred care (RC) group. Also, the reduction in all-cause mortality associated with SC treatment was observed at all levels of baseline SBP. An analysis using life table regression with SBP as a time-dependent variable showed that the postrandomization reduction in SBP was a significant factor in reducing mortality. Similarly, reduced DBP was also contributory. Prospective studies are required to answer definitively the question of the efficacy of treatment of systolic hypertension. Nevertheless, the present analysis of the HDFP data, despite design limitations, supports the advisability of reducing elevated systolic blood pressure.

Actuarial Analysis↗