Influence of nutritional status on CAPD peritonitis

To investigate the effect of nutritional status of continuous ambulatory peritoneal dialysis (CAPD) patients on the development of peritonitis, a cross-sectional study of the nutritional status of 79 CAPD patients and a retrospective study on the incidence of peritonitis in these patients were done. The incidences of peritonitis were compared according to the nutritional status of these patients on CAPD. Protein-caloric malnutrition assessed by a score system based on triceps skinfold thickness, mid-arm circumference, serum albumin level and relative body weight was demonstrated in 27 patients (34%) among 79 total CAPD patients. The incidence of peritonitis was significantly higher in poor nutritional status patients, with 1.09 +/- 0.86/patient-year, than that in normal nutritional status patients with 0.64 +/- 0.72/patient-year (p less than 0.05). In patients with the same nutritional status, patients using Dianeal solution had a trend of a lower incidence of peritonitis than those using Peritosol solution. In conclusion, the nutritional status and possibly the type of CAPD solution may influence CAPD peritonitis as risk factors.

High-performance liquid chromatographic assay for mitoxantrone in plasma using electrochemical detection

A sensitive and specific high-performance liquid chromatographic (HPLC) assay was developed for the quantitation of mitoxantrone in plasma using electrochemical detection. Bisantrene was chosen as the internal standard. A reversed-phase, 10-microns muBondapak C18 analytical column (30 cm X 3.9 mm) with an isocratic mobile phase of 28% acetonitrile in 80 mM sodium formate buffer (pH 3.0) was used. The eluent was monitored by both electrochemical detection at an applied potential of +0.75 V vs. Ag/AgCl and visible absorbance at 660 nm. Only electrochemical detection was able to quantitate the internal standard and provided ten times higher sensitivity than visible absorbance for mitoxantrone with a detection limit as low as 0.1 ng/ml. Calibration curves in the range 0.1-1000 ng/ml showed good linearity (r = 0.998) and precision (coefficient of variation less than 10%). This HPLC method utilized a reproducible and inexpensive liquid-liquid extraction procedure. Using methylene chloride, the extraction efficacy of mitoxantrone from plasma was 85.3% with a coefficient of variation less than 2.1%. This new assay was then applied to measure mitoxantrone concentrations in plasma obtained from two leukemic patients receiving 12 mg/m2 mitoxantrone as a 1-h infusion.

A clinical and pharmacokinetic study of mitoxantrone in acute nonlymphocytic leukemia

Twenty-two patients with relapsed or refractory acute leukemia received 31 treatment courses of mitoxantrone (10 to 12 mg/m2/d) as a one-hour infusion for five days. Seven of the 13 patients who had greater than or equal to 95% reduction in the leukemia cell mass, calculated using the bone marrow examination on day 6, achieved a complete remission (CR). These remissions lasted up to 14 months without additional therapy. There were no CRs among the 18 patients who had less than 95% cytoreduction by day 6. The sequential addition of 5-azacytidine (200 mg/m2/d) for three days in those patients with residual disease on day 6 provided little additional benefit. Nonhematological toxicity from mitoxantrone was mild, although fever and infection were common. A new high-performance liquid chromatography (HPLC) assay was used to describe the clinical pharmacokinetics of mitoxantrone. Neither clinical response nor toxicity was strongly correlated with the peak plasma mitoxantrone concentration on the first day (mean +/- SD, 510 +/- 206 ng/mL), nor the area under the concentration-time curve (484 +/- 229 ng X h/mL), nor the systemic clearance (405 +/- 124 mL/min/m2). Mitoxantrone causes rapid cytoreduction in acute nonlymphocytic leukemia (ANLL), but the optimal dose and schedule remain to be determined.

Control of renin secretion by Ca2+ and cyclic AMP through two parallel mechanisms

The cellular mechanism of action of cyclic AMP (cAMP) mediating the beta-adrenergic stimulation of renin secretion was studied, with special reference to its interactions with the inhibitory pathway of renin secretion by Ca2+ calmodulin. Forskolin, a potent stimulator of adenyl cyclase that bypasses the hormone-receptor interactions, stimulated renin secretion in vitro from rabbit renal cortical slices in a concentration-dependent manner. Renin secretion stimulated by submaximal concentration of forskolin was partly or completely antagonized or blocked by raising intracellular Ca2+ concentration by incubating slices in a high-K+ depolarizing medium, but renin secretion stimulated by the maximal effective concentration of forskolin was not inhibited by Ca2+. In addition, the maximal effective concentration of forskolin (10(-5) M) increased renin secretion by a fixed amount independent of medium (by inference, intracellular) Ca2+ concentration in the range of 10(-8) to 10(-6) M in a high-K+ medium. Furthermore, the degree of stimulation of renin secretion by forskolin was greater with greater removal of the inhibitory effect of Ca2+ calmodulin pathway on renin secretion with use of potent calmodulin antagonists, suggesting that the stimulatory effect of cAMP on renin secretion may be maximal in the absence of the inhibitory influence of Ca2+. These results are consistent with the hypothesis that cAMP (by inference, the beta-adrenergic stimulus) stimulates renin secretion through a cellular mechanism independent of that through the Ca2+ -calmodulin pathway.

Calcium in the control of renin secretion: Ca2+ influx as an inhibitory signal

The mechanism for the inhibition of renin secretion in vitro from renal cortical slices by angiotensin II, antidiuretic hormone, ouabain, and high K+ concentration was studied. The inhibitory effect of these agents was blocked by a Ca antagonist, verapamil. In addition, epinephrine stimulated renin secretion and its stimulatory action was blocked by ouabain. These results support the hypothesis that Ca2+ influx into juxtaglomerular cells plays a role as an inhibitory signal whereas Ca2+ efflux is a stimulatory signal for renin secretion. Renin secretion was greatly stimulated by lowering incubation temperature, indicating that renin secretion is not energy dependent. The possibility is discussed that Ca2+ of juxtaglomerular cells might activate an enzyme(s) that then modulates some sequential steps of renin secretory processes, thereby controlling the rate of renin secretion.