Cyclosporin A inhibits apical secretory K+ channels in rabbit cortical collecting tubule principal cells

We used the cell-attached patch clamp configuration to examine the effect of basolateral cyclosporin A (CsA) exposure on low conductance K+ channels found in the principal cell apical membrane of rabbit cortical collecting tubule (CCT) primary cultures. Baseline K+ channel activity, measured as mean NPo (number of channels x open probability), was 2.7 +/- 1.1 (N = 29). NPo fell by 69% (0.84 +/- 0.32; N = 32) in cultures pretreated with 500 ng/ml CsA for 30 minutes prior to patching. Chelation of intracellular [Ca2+]i (10 mM BAPTA/AM; N = 8) or removal of extracellular Ca2+ (N = 9), but not prevention of [Ca2+]i store release (10 microM TMB-8; N = 7), abolished CsA-induced inhibition. This suggested that CsA effects were mediated by an initial rise in [Ca2+]i via Ca2+ influx. Either 25 nM AVP (N = 10) or 0.25 microM thapsigargin (N = 8) (causing IP3-dependent and -independent release of [Ca2+]i stores, respectively) augmented, while 25 pM (N = 6) or 250 pM AVP (N = 8) reversed CSA-induced channel inhibition. Apical membrane protein kinase C (PKC) activation with 0.1 microM phorbol ester, PMA (N = 8) or 10 microM synthetic diacylglycerol, OAG (N = 7), mimicked (mean NPo = 0.99 +/- 0.40) the inhibitory effect of CsA. Apical PKC inhibition by prolonged apical exposure to PMA (N = 10) or 100 microM D-sphingosine (N = 6) blocked CsA's effect. Cyclic AMP increasing maneuvers, 10 microM forskolin (N = 5) or 0.5 mM db-cAMP (N = 8), stimulated basal K+ channel activity in the absence of CsA. In Conclusion: (1) basolateral exposure to CsA inhibits the activity of apical membrane 13 pS channels responsible for physiologic K+ secretion in rabbit CCT principal cells. (2) The inhibition is mediated by changes in intracellular Ca2+ and activation of apical PKC. (3) Pharmacologic AVP (nM) augments CsA-induced inhibition by releasing intracellular Ca2+ stores; more physiologic AVP (pM) attenuates channel inhibition, probably through cAMP generation. (4) Inhibition of apical secretory K+ channels by CsA likely contributes to decreased kaliuresis and clinical hyperkalemia observed in patients on CsA therapy.     

Testosterone replacement increases fat-free mass and muscle size in hypogonadal men

To test the hypotheses that plasma volume (PV) expansion 24 h after intense exercise is associated with reduced transcapillary escape rate of albumin (TERalb) and that local changes in transcapillary forces in the previously active tissues favor retention of protein in the vascular space, we measured PV, TERalb, plasma colloid osmotic pressure (COPp), interstitial fluid hydrostatic pressure (Pi), and colloid osmotic pressure in leg muscle and skin and capillary filtration coefficient (CFC) in the arm and leg in seven men and women before and 24 h after intense upright cycle ergometer exercise. Exercise expanded PV by 6.4% at 24 h (43.9 +/- 0.8 to 46.8 +/- 1.2 ml/kg, P < 0.05) and decreased total protein concentration (6.5 +/- 0.1 to 6.3 +/- 0.1 g/dl, P < 0.05) and COPp (26.1 +/- 0.8 to 24.3 +/- 0.9 mmHg, P < 0.05), although plasma albumin concentration was unchanged. TERalb tended to decline (8.4 +/- 0.5 to 6.5 +/- 0.7%/h, P = 0.11) and was correlated with the increase in PV (r = -0.69, P < 0.05). CFC increased in the leg (3.2 +/- 0.2 to 4.3 +/- 0.5 microl . 100 g-1 . min-1 . mmHg-1, P < 0. 05), and Pi showed a trend to increase in the leg muscle (2.8 +/- 0. 7 to 3.8 +/- 0.3 mmHg, P = 0.08). These data demonstrate that TERalb is associated with PV regulation and that local transcapillary forces in the leg muscle may favor retention of albumin in the vascular space after exercise.     

Malignant peripheral nerve sheath tumors: the St. Jude Children's Research Hospital experience

BACKGROUND: Malignant peripheral nerve sheath tumors (MPNSTs) are uncommon in young patients. To contribute to the understanding of these tumors, we reviewed the records of all patients treated for PNSTs at one institution over a 30-year period. METHODS: We reviewed the records of eight patients treated for benign PNSTs and 28 patients treated for 29 MPNSTs. We focused on the latter group, statistically testing several clinical factors for their significance in affecting survival. RESULTS: Five-year survival in patients with MPNSTs was 39%. The most significant prognostic factor was gross tumor resectability (p = 0.0004). Five-year survival for patients with resectable tumors was 65%, whereas no patient with unresectable disease survived > 25 months. Tumor grade, site, and patient race were also significant factors by univariate analysis but were not significant when adjusted for resectability. CONCLUSION: Gross tumor resection is crucial in treating malignant PNSTs. Supplemental radiation therapy is recommended for positive microscopic margins. More effective treatment is still being sought for unresectable disease.     

A comparison of a 30-cluster survey method used in India and a purposive method in the estimation of immunization coverages in Tamil Nadu

The reaction mechanisms of p-nitrophenyl phosphate hydrolysis catalyzed by two rat liver isoenzymes of the low M(r) phosphotyrosine protein phosphatase (AcP1 and AcP2) were compared. Furthermore, the effect of some heterocyclic compounds on their activities were tested. Cyclic GMP and guanosine causes a particularly high activation of the isoenzyme AcP2, whereas its effect on AcP1 is very poor. A study on the mechanism of cyclic GMP activation was carried out. The results suggest that cyclic GMP activates the AcP2 isoenzyme by increasing the rate of the step that leads to the hydrolysis of the covalent enzyme-substrate phosphorylated complex formed during the catalytic process. The physiological significance of cyclic GMP activation of only one of the two isoenzymes (AcP2) remains uncertain.     

Safety assessment of polylactide (PLA) for use as a food-contact polymer

This report constitutes a safety assessment of polylactide (PLA), a polymer of lactic acid intended for use in fabricating various food-contact articles. Migration studies were conducted on samples of the polymer following guidelines issued by the Food and Drug Administration. Potential migrants from PLA include lactic acid, lactide (the monomer), and lactoyllactic acid (the linear dimer of lactic acid). The studies were designed to model reasonable 'worst' case extraction situations when the polymer is used (a) in houseware articles for short and intermediate time periods at various temperatures and (b) in food-packaging materials. The limited migration observed during the trials represents no significant risk since migrating species are expected to convert to lactic acid, a safe food substance. It is concluded that PLA is safe and 'Generally Recognized As Safe' for its intended uses as a polymer for fabricating articles that will hold and/or package food.     

Complete primary structure of the major component myoglobin of California gray whale (Eschrichtius gibbosus)

The complete primary structure of the major component myoglobin from the California gray whale, Eschrichtius gibbosus, was determined by specific cleavage of the protein to obtain large peptides for degradation by the automatic sequenator. Cleavage at the two methionine residues of the apomyoglobin with cyanogen bromide and at the three arginine residues of the methyl acetimidated protein with trypsin resulted in three and four easily separable peptides, respectively, which when sequenced accounted for 85% of the primary structure. The remainder of the covalent structure was obtained by further digestion of the central cyanogen bromide peptide with trypsin and S. aureus strain V8 protease. This protein differs from that of the sperm whale, Physeter catodon, at 12 positions, from that of the common porpoise, Phocoena phocoena, and the Black Sea dolphin, Delphinus delphis, at 14 positions, and from that of the Amazon River dolphin, Inia geoffrensis, at 7 positions. All substitutions observed in this sequence fit easily into the tertiary structure of sperm whale myoglobin.