The effect of naloxone on the preoperative gastric volume and pH

The effect of 4 mg oral naloxone on preoperative gastric volume and pH of gastric aspirate was studied in a double-blind, randomized study. Twenty patients received 10 ml of naloxone (4 mg) mixed with 10 ml of orange juice, and 20 patients received 10 ml of isotonic saline mixed with 10 ml of orange juice, 2 h before surgery. Gastric content was obtained immediately after intubation of the trachea. No significant difference in gastric volume and pH of gastric aspirate was found between the two groups. It is concluded that naloxone does not affect gastric emptying and gastric acid secretion to a degree great enough to protect against aspiration of gastric contents into the lungs.     

Alpha-ketoacids stimulate rat renal cysteine conjugate beta-lyase activity and potentiate the cytotoxicity of S-(1,2-dichlorovinyl)-L-cysteine

Renal cysteine conjugate beta-lyase (beta-lyase) catalyzes the bioactivation of nephrotoxic cysteine S-conjugates. beta-Lyase activity is present in both renal cytosolic and mitochondrial fractions, and, although the cytosolic beta-lyase is identical to glutamine transaminase K, the mitochondrial beta-lyase has not been characterized. Because beta-lyase is a pyridoxal phosphate (PLP)-dependent enzyme, pyridoxamine phosphate (PMP) formation may occur during the metabolism of cysteine S-conjugates. In this study, the effects of alpha-ketoacids, which may convert the PMP form of the enzyme to the pyridoxal phosphate form, on the metabolism and cytotoxicity of cysteine S-conjugates were examined; the PMP enzyme is catalytically inactive in beta-elimination reactions, but is catalytically active in transamination reactions. Both alpha-keto-gamma-methiolbutyrate (KMB) and alpha-ketobutyrate enhanced the metabolism of S-(2-benzothiazolyl)-L-cysteine (BTC) to 2-mercaptobenzothiazole by rat renal cytosol or mitochondria. KMB and phenylpyruvate potentiated both the cytotoxicity of S-(1,2-dichlorovinyl)-L-cysteine (DCVC) in isolated rat renal proximal tubular cells and the inhibition of mitochondrial respiration produced by DCVC. These results are consistent with the formation of PMP during the renal cytosolic or mitochondrial metabolism of cysteine S-conjugates. Mitochondrial beta-lyase was previously localized in the outer membrane. To examine whether beta-lyase activity is present in mitoplasts, but in the PMP form, the effects of KMB on the metabolism of BTC to 2-mercaptobenzothiazole and on the DCVC-induced inhibition of state 3 respiration in mitoplasts were studied. The majority of the mitochondrial beta-lyase activity was present in the outer membrane, and the specific activity of the outer membrane beta-lyase was greater than that of the mitoplast beta-lyase. KMB produced equivalent stimulation of beta-lyase activity in intact mitochondria, in mitochondrial outer membranes, and in mitoplasts and potentiated DCVC-induced inhibition of respiration in intact mitochondria, but not in mitoplasts. These results provide additional evidence for the central role of beta-lyase in the bioactivation of nephrotoxic cysteine S-conjugates.     

Smoking and female infertility: a systematic review and meta-analysis

The high prevalence of smoking among women in their reproductive years continues to be a matter of concern. The negative effects of smoking on general health are well known, but smoking may also affect fertility. The objective of the present study was to perform a systematic review of the literature to determine whether there is an association between smoking and risk of infertility in women of reproductive age, and to assess the size of this effect. In the 12 studies used for this meta- analysis, the overall value of the odds ratio (OR) for risk of infertility in women smokers versus non-smokers was 1.60 [95% confidence interval (CI) 1.34-1.91]. Studies of subfertile women undergoing in-vitro fertilization (IVF) treatment also show a reduction in fecundity among women smokers. A meta-analysis of nine studies found an OR of 0.66 (95% CI 0.49-0.88) for pregnancies per number of IVF- treated cycles in smokers versus non-smokers. Despite the potential limitations of meta-analyses of observational studies, the evidence presented in this review is compelling because of the consistency of effect across different study designs, sample size and types of outcome. However, continued reassurance is needed that the calculated overall effect is not in fact due to confounding variables.