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Biomedical subjects

G Fox

Publications and source records attributed to G Fox.

At least 55 records · Page 3Linked to original sources
PubMed1984

Thrombin stimulates Na+-H+ exchange across the human platelet plasma membrane.

We have investigated the release of protons from thrombin-stimulated platelets. Addition of thrombin to suspensions of washed platelets resulted in fast liberation of H+. In the presence of 0.1 mM amiloride, a potent inhibitor of the Na+/H+ transport system, the amount of protons liberated was decreased by about 50%, and was further reduced to about 15% by 1 mM amiloride. Similar inhibition of H+ release was observed after Na+ in the incubating medium had been replaced by choline. We conclude that one of the earliest events in thrombin-stimulated platelets consists of the activation of an Na+/H+ countertransport, which leads to an increase in intracellular pH.

Amiloride↗
PubMed1984

The effect of carbonic anhydrase inhibition on the velocity of thrombin-stimulated platelet aggregation under physiological conditions.

We have studied the effect of ethoxzolamide , a specific carbonic anhydrase inhibitor, on the velocity of thrombin-stimulated platelet aggregation. After preincubation of platelet rich plasma with 10(-6) M ethoxzolamide the velocity of platelet aggregation was reduced by about 40%. Between 10(-11) M and 10(-10)M ethoxzolamide was necessary to achieve a half-maximal diminution of the aggregation velocity. An identical maximal reduction of the velocity of aggregation as with ethoxzolamide could be achieved by a nearly complete removal of CO2 from the platelet rich plasma. These results suggest that the intracellular CO2 hydration-dehydration reaction is involved in the activation of human platelets by thrombin. It is possible that the cytosolic carbonic anhydrase of platelets provides a rapid source of the protons that are transferred across the plasma membrane during the activation process.

Blood Platelets↗
PubMed1984

Muscle pressure and flow during expiration in infants.

The postinspiratory activity of the inspiratory muscles (Pmusl) was estimated in 12 infants (2 to 4 days old) by analysis of the rise in mask pressure after airway occlusion at end inspiration. We reasoned that if at the end of inspiration Pmusl instantaneously ceased, the mask pressure would immediately increase to the relaxation pressure value corresponding to that volume. Any delay would suggest some degree of Pmusl. In 9 infants, Pmusl reached zero before the end of an average expiration (TE), although lasting for a long portion of TE (83% +/- 25 SD). We then compared the expiratory tidal flow-volume curves during resting breathing with the curves of "relaxed" expirations. In general, the tidal curve shows a linear portion that can be extrapolated to zero flow. From this extrapolation it is apparent that the end-expiratory level (FRC) is above the resting volume of the respiratory system (Vr), the FRC-Vr difference averaging 3.11 ml/kg. In 6 infants, the tidal expiratory flow-volume curve was displaced to the left of the "relaxed" curve, whereas in the remaining infants the two curves superimposed. These analyses suggest that in infants during tidal breathing (1) Pmusl can substantially contribute to the rise in FRC, and (2) the final portion of expiration is in most cases "relaxed." In some infants, however, a braking mechanism, probably of laryngeal origin, further decreases the expiratory flow and may contribute in maintaining the mean lung volume elevated.

Functional Residual Capacity↗
PubMed1982

Effect of morphine on the hypothalamic-pituitary axis in postmenopausal women.

In this study, 10 postmenopausal women were given 5 mg of morphine intravenously; and the serum level of prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and growth hormone (GH) were measured before and after morphine injection. A significant increase in serum prolactin as well as a significant decrease in LH were observed following the administration of morphine. It is suggested that morphine may affect a common neurotransmitter that controls both prolactin and LH secretion. It is also of interest that the increase in serum prolactin following morphine injection is of similar magnitude as observed in premenopausal patients.

Female↗
PubMed1982

Dynamics of breathing in infants.

Passive compliance (C) has been measured in 10 infants at 10--90 min after birth and in 10 infants at a few days of life by recording mouth pressure after airways occlusions at end inspiration. From the slope of the expiratory flow-volume curve, the passive time constant (tau) and resistance (R = tau/C) have been also computed. Examination of the changes of C with time and of the expiratory flow-volume curves indicates that the end-expiratory volume is maintained above functional residual capacity at both ages, but significantly more so at a few days (7.6 ml) than at 10--90 min (3.5 ml). The passive time constant (tau = C . R) is shorter at the early age due to the smaller C. The active compliance (C') and resistance (R') values have been estimated from the pressure generated by the infant when the airways are occluded at end expiration. The active time constant of the respiratory system (tau' = C' . R') is less than tau, due to a smaller active compliance, particularly at a few days. The active resistance is on the contrary similar to R. The active stiffening of the respiratory system provides more stability of the infant's respiratory system and a more ready volume response for any given change in pressure; its price, however, is a higher work of breathing. At optimal breathing rates, in fact, the active work is 127% (10--90 min) to 183% (a few days) higher than that computed from the passive values. The inspiratory flow wave tends to be squared at both ages minimizing the energy losses due to friction.

Airway Resistance↗
PubMed1980

[Baker's eczema through chromium compound in flour (author's transl)].

In several former papers on baker's eczema authors happened to hint at hypersensitivity to chromium in bakers suffering from eczema. To our knowledge however the question, if there is any connection between chromium-hypersensitivity and a baker's occupation, has not been investigated later on. In a baker with eczema of the hands relapses occurred obviously as a consequence of exclusive contact to flour, only hypersensitivity to chromium was revealed. Thus 4 sorts of flour used in GDR were analysed. Chromium content ranged between 0.01 and 0.09 mg%. It may be concluded, that even those comparatively low chromium levels are capable of giving rise to eczema.

Chromium↗
PubMed1973

Skew deviation.

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Adult↗