Transferrin and sulfated glycoprotein-2 messenger ribonucleic acid levels in the testis and isolated Sertoli cells of hypophysectomized rats

Both FSH and testosterone act on Sertoli cells in the testis. It is possible that the action of these hormones on Sertoli cells results in an increased capacity for the cells to carry out their prescribed functions, among which are the synthesis and secretion of specific glycoproteins. Changes in the testicular levels of two specific mRNAs in hypophysectomized hormone-treated rats were determined by solution hybridization to cRNA probes. The mRNAs coding for transferrin and sulfated glycoprotein-2 (SGP-2), both of which are secretion products of Sertoli cells, decreased dramatically in the testis of hypophysectomized rats that were maintained for 20 days untreated with hormones. If hypophysectomy was done to rats at 20 days of age, daily injections for a subsequent 20 days with FSH or FSH in combination with testosterone partially maintained both transferrin and SGP-2 mRNA levels. Testosterone alone was ineffective in 20-day-old rats. In contrast, if hypophysectomy was performed on 40-day-old rats, daily injections of testosterone alone or in combination with FSH were most effective in maintaining higher levels of the specific mRNAs. When the Sertoli cells from rats hypophysectomized at 20 days of age were placed in cell culture, FSH again was most effective in the stimulation of transferrin mRNA above control levels. However, when the Sertoli cells from the rats hypophysectomized at 40 days of age were placed in culture, FSH was slightly stimulatory, but testosterone had no effect on the transferrin mRNA levels. Neither FSH nor testosterone affected the levels of SGP-2 mRNA in the cultured cells regardless of the age of the animal at the time of hypophysectomy. Additional in vivo studies were done in which the rats were hypophysectomized at 20 days of age, allowed to regress for 17 days, and then injected daily with hormones for 3 days. The levels of transferrin and SGP-2 mRNA in this experiment were stimulated by FSH alone or by a combination of FSH and testosterone to an extent similar to that in the cultured cells. These studies showed that FSH is most important in the younger rats and testosterone is most important in the older rats in the maintenance of specific mRNA levels. In addition, the level of stimulation observed with either hormone is different depending on whether the hormone is given in culture or in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)     

NLA-1: a 2-nitroimidazole radiosensitizer targeted to DNA by intercalation.

Targeting of electron affinic radiosensitizers to DNA via reversible non-covalent intercalative binding has potential for increasing sensitizer concentrations locally at the DNA target while decreasing accessibility to reductases responsible for bioactivation and cytotoxicity. We have prepared an DNA-targeted acridine-linked 2-nitroimidazole (NLA-1) as an example of such a compound. NLA-1 binds reversibly to DNA with an affinity similar to 9-aminoacridine, and is approximately 1000 times more potent than MISO as a cytotoxin, despite a similar reduction potential. It shows less enhancement of cytotoxicity under hypoxia (5- to 6-fold) than does MISO (approximately 11-fold), but is a potent hypoxia-selective radiosensitizer in AA8 cells with a concentration for an enhancement ratio of 1.6 (C1.6) of 9 microM. The mean intracellular concentration at the C1.6 is 400 microM, on which basis its potency is about twice that of MISO. The in vitro therapeutic index (aerobic cytotoxic potency/hypoxic C1.6) of NLA-1 is approximately 6-fold lower than that for MISO. NLA-1 lacks radiosensitizing activity against SCCVII or EMT6 tumors in vivo at the maximum tolerated dose (MTD) of 100 mumol.kg-1.     

Concentration response relationships of amiodarone and desethylamiodarone

Twelve patients with frequent ventricular premature depolarizations (VPDs) received amiodarone, 600 mg/day, for up to 8 weeks. On days 0, 1, 4, 8, 15, 22, 36, and 57 of treatment, 24-hour ambulatory ECGs were obtained, and multiple blood samples were taken for determination of amiodarone and desethylamiodarone plasma concentrations. All patients had at least 75% suppression of VPDs. The mean duration of therapy before the onset of antiarrhythmic effect was 13.2 days (range 1 to 36 days). Trough amiodarone and desethylamiodarone plasma concentrations at the time of onset of antiarrhythmic effect were 0.86 +/- 0.48 mg/L and 0.23 +/- 0.15 mg/L, respectively. Sixty-seven percent of patients responded at amiodarone concentrations below 1.0 mg/L. For each patient there was a progressive decrease in frequency of VPDs as both amiodarone and desethylamiodarone concentrations increased. Regression modeling indicated that both amiodarone and desethylamiodarone plasma concentrations explained significant variability in the frequency of VPDs, and amiodarone and desethylamiodarone plasma concentrations were highly correlated with each other. There was a trend for desethylamiodarone to explain more variability in frequency of VPDs than amiodarone.     

Effect of 6-hydroxydopamine lesions of the amygdala on intravenous cocaine self-administration under a progressive ratio schedule of reinforcement

Bilateral six-hydroxydopamine (6-OHDA) lesions were placed in the amygdala of rats self-administering cocaine (1.5 mg/kg per injection i.v.) under a progressive ratio schedule of reinforcement. Post-lesion access to three doses of cocaine (1.5, 0.75 and 0.37 mg/kg per injection i.v.) revealed a lesion effect only at the highest dose. At this dose, the lesion caused a significant increase in breaking point. No change in the breaking point was produced at the lower two doses. The biochemical results show a significant reduction in dopamine and DOPAC levels within the amygdala and an increase in dopamine within the NACC. In contrast, noradrenaline and serotonin (5-HT) levels were unaffected by the lesion in any of the dissected areas. These results demonstrate that no specific effect on cocaine reinforcement was produced by 6-OHDA lesions of the amygdala. The possibility that the lesion may have attenuated the anxiogenic qualities of the high dose of cocaine is discussed.     

Does desmopressin acetate prophylaxis reduce blood loss after valvular heart operations? A randomized, double-blind study.

The effectiveness of prophylactic desmopressin acetate in reducing hemorrhage after cardiopulmonary bypass operations is controversial. We conducted a prospective, randomized, placebo-controlled, double-blind trial to determine its effectiveness and safety in such patients. Eighty-three evaluable patients undergoing valvular heart operations were randomized to receive desmopressin (0.3 microgram/kg) (41) or placebo (42) after cardiac bypass. Demographic characteristics were similar in both groups. There was no significant difference in total 24-hour blood loss between groups (desmopressin 1064.8 +/- 647.1 ml versus placebo 844.4 +/- 507.6 ml; p greater than 0.05), or in the requirement for red blood cell, platelet, or fresh frozen plasma transfusion, or for reexploration for control of hemorrhage. Neither was there a difference in the occurrence of thrombotic complications between groups. Analysis of factor VIII activity, von Willebrand factor, or von Willebrand factor multimers failed to show significant correlations with blood loss or differences between groups except for factor VIII activity, which was significantly higher in the desmopressin group 1 hour after operation than in the placebo group. A detailed comparative analysis of similar trials to determine the reasons for different outcomes suggests that desmopressin should not be used routinely as a prophylactic agent to reduce postsurgical hemorrhage, but that it may be beneficial when used in patients who already manifest excessive bleeding postoperatively.