Invasion of hereditary ovalocytes by Plasmodium falciparum in vitro and its relation to intracellular ATP concentration

Hereditary ovalocytes (stomatocytic ovalocytes), when examined within 1-2 days from the time that the blood sample is drawn, are invaded by Plasmodium falciparum in culture to the extent of at least 55% of normal control cells. The ovalocytes have extremely rigid membranes, characterised by a shear elastic modulus some 3-4 times greater than that of normal cells. The extent of invasion falls off very much more rapidly than that into normal cells on storage, and we surmise that this is the reason for earlier reports of resistance of ovalocytes to malarial invasion in vitro. The initial loss of susceptibility to invasion with time is not accompanied by any change in membrane rigidity, but is primarily a consequence of a rapid decline in intracellular ATP concentration: this falls to below the threshold level required for invasion (approx. 0.1 mM) over a period in which the ATP in normal cells remains almost constant. Incubation in a metabolic regenerating medium leads to a rise in the intracellular ATP concentration and invasion by P. falciparum is recovered, though to a much lower extent than in normal cells. The resistance of ovalocytes to invasion becomes irreversible, due possibly to degradative processes in the membrane, on further storage. The developing parasites in ovalocytes have a reduced number of merozoites and show distinct morphological abnormalities.     

Rapid, sensitive procedure to determine buspirone levels in rat brains using gas chromatography with nitrogen-phosphorus detection

Reported here is a rapid, sensitive and relatively inexpensive procedure using gas chromatography with nitrogen-phosphorus detection (GC-NPD) to quantify buspirone levels in brains of rats. The analyte was directly extracted from brain homogenate with toluene after basification and then subjected to GC-NPD analysis using a capillary column. The calibration curves were linear over the range of 10 to 320 ng per 2 ml of brain homogenate, with typical r2 values >0.99. The assay was highly reproducible and gave peaks with excellent chromatographic properties.     

In vivo formation of 8-Epi-prostaglandin F2 alpha is increased in hypercholesterolemia

F2-isoprostanes are bioactive prostaglandin (PG)-like compounds that are produced from arachidonic acid through a nonenzymatic process of lipid peroxidation catalyzed by oxygen free-radicals. 8-Epi-PGF2 alpha may amplify the platelet response to agonists, circulates in plasma, and is excreted in urine. We examined the hypothesis that the formation of 8-epi-PGF2 alpha is altered in patients with hypercholesterolemia and contributes to platelet activation in this setting. Urine samples were obtained from 40 hypercholesterolemic patients and 40 age- and sex-matched control subjects for measurement of immunoreactive 8-epi-PGF2 alpha. Urinary excretion of 11-dehydro-thromboxane (TX) B2, a major metabolite of TXA2, was measured as an in vivo index of platelet activation. Low-dose aspirin, indobufen, and vitamin E were used to investigate the mechanism of formation and effects of 8-epi-PGF2 alpha on platelet activation. Urinary 8-epi-PGF2 alpha was significantly (P = .0001) higher in hypercholesterolemic patients than in control subjects: 473 +/- 305 versus 205 +/- 95 pg/mg creatinine. Its rate of excretion was inversely related to the vitamin E content of LDL and showed a positive correlation with urinary 11-dehydro-TXB2. Urinary 8-epi-PGF2 alpha was unchanged after 2-week dosing with aspirin and indobufen despite complete suppression of TX metabolite excretion. Vitamin E supplementation was associated with dose-dependent reductions in both urinary 8-epi-PGF2 alpha and 11-dehydro-TXB2 by 34% to 36% and 47% to 58% at 100 and 600 mg daily, respectively. We conclude that the in vivo formation of the F2-isoprostane 8-epi-PGF2 alpha is enhanced in the vast majority of patients with hypercholesterolemia. This provides an aspirin-insensitive mechanism possibly linking lipid peroxidation to amplification of platelet activation in the setting of hypercholesterolemia. Dose-dependent suppression of enhanced 8-epi-PGF2 alpha formation by vitamin E supplementation may contribute to the beneficial effects of antioxidant treatment.     

Acute effects of estradiol infusion and naloxone on luteinizing hormone secretion in pubertal boys

We have shown previously in pubertal boys that testosterone (T) suppresses the nocturnal augmentation of luteinizing hormone (LH) secretion principally by decreasing LH pulse frequency. As T can be aromatised to estradiol (E2), and E2 effects on LH secretory dynamics may be separate from those of T, we examined the effects of acute E2 infusion on LH secretion in pubertal boys. Opioid receptor blockade has been reported to increase LH secretion after estradiol suppression in adult men, so we also examined whether naloxone might augment LH secretion during E2 treatment in pubertal boys. Starting at 1000 h, eight pubertal boys were given a 33 h saline infusion, followed 1 week later by an E2 infusion at 4.6 nmol/m2/h. During both infusions, four iv boluses of saline were given hourly beginning at 1200 h on the first day, and four naloxone iv boluses, 0.1 mg/kg each, were given hourly beginning at 1200 h on the second day. Blood was obtained every 15 min for LH, and every 60 min for T and E2, from 1200 h until the end of the infusion. Pituitary responsiveness to gonadotropin-releasing hormone (GnRH) was assessed after both infusions by iv administration of 250 ng/kg synthetic GnRH. Estradiol infusion increased the mean plasma E2 concentration from 23 +/- 4 to 46 +/- 6 pmol/L (P < 0.01) and suppressed mean plasma T from 4.9 +/- 1.4 to 3.0 +/- 3.5 nmol/L (saline vs. E2 infusion, P < 0.05). The overall mean LH was suppressed by E2 infusion from 3.7 +/- 0.5 to 2.2 +/- 0.4 IU/L (saline vs. E2 infusion, P < 0.01). LH pulse frequency was suppressed by 50%, whereas mean LH pulse amplitude was not different between saline and E2 infusions. Administration of naloxone did not alter the mean LH, LH pulse frequency, or amplitude during either saline or E2 infusions. Pituitary responsiveness to exogenous GnRH was similar during both infusions. These studies indicate that E2 produces its negative feedback in pubertal boys principally by suppression of LH pulse frequency, and naloxone does not reverse these suppressive effects. Thus E2 suppression of LH secretion is mediated by a decrease of hypothalamic GnRH secretion that is independent of endogenous opioid pathways.     

New quinoline di-Mannich base compounds with greater antimalarial activity than chloroquine, amodiaquine, or pyronaridine

We have compared the ex vivo antimalarial activity of 12 new quinoline di-Mannich base compounds containing the 7-dichloroquinoline or 7-trifluoromethylquinoline nucleus with amodiaquine, chloroquine, and pyronaridine using the Saimiri-bioassay model. Each compound was administered orally (30 mg/kg of body weight) to three or more noninfected Saimiri sciureus monkeys, and serum samples were collected at various times after drug administration and serially diluted with drug-free (control) serum. In vitro activity against the multidrug-resistant K1 isolate of Plasmodium falciparum was determined in serum samples by measuring the maximum inhibitory dilution at which the treated monkey serum inhibited schizont maturation in vitro. Of the 12 Mannich bases tested, 8 were associated with levels of ex vivo antimalarial activity in serum greater than those of amodiaquine, chloroquine, or pyronaridine 1 to 7 days after drug administration. Further studies were carried out with four of these compounds, and the results showed that the areas under the serum drug concentration-time curves for the four compounds were between 7- and 26-fold greater than that obtained for pyronaridine. Activity against four multidrug-resistant strains of P. falciparum was also much greater in serum samples collected from monkeys after administration of these four compounds than in serum samples collected after administration of pyronaridine or chloroquine. These findings suggest that these four quinoline Mannich base compounds possess a very marked and prolonged antimalarial activity and that further studies should be performed to determine their value as antimalarial drugs.     

Myosin isoforms in skeletal muscle in patients with chronic heart decompensation: distribution and correlation with with exercise tolerance

Chronic heart failure (CHF) is accompanied by a reduced exercise capacity, and the symptoms can be at least in part explained by qualitative and quantitative changes in the skeletal muscle composition and metabolism. We have correlated the myosin heavy chain (MHC) composition of the gastrocnemius in 20 patients with different degrees of CHF to expiratory gases measured during maximal cardiopulmonary exercise testing, NYHA functional class and echocardiographic parameters. MHC composition was determined electrophoretically in skeletal muscle needle microbiopsies and the percent distribution calculated by laser densitometry. There was no correlation between ejection fraction, left ventricular end-diastolic and end-systolic diameters and MHC composition. The percentage of MHC 1 (slow aerobic isoform) was positively correlated with peak VO2 (r2 = 0.5, p = 0.0004), ventilatory threshold (VT, r2 = 0.33, p = 0.008), and O2 pulse (peak VO2/HR, r2 = 0.40, p = 0.003). There was a negative correlation between MHC 2a and 2b (fast isoforms) and peak VO2 (r2 = 0.38 and 0.37, p = 0.004, respectively), VT (r2 = 0.2, p = 0.05; r2 = 0.34, p = 0.007, respectively) and O2 pulse (r2 = 0.39, p = 0.003; r2 = 0.23, p = 0.03, respectively). NYHA functional class was also negatively correlated with the same parameters (r2 = 0.2, p = 0.01; r2 = 0.4, p = 0.001; r2 = 0.34, p = 0.006, respectively) as well as with MHC 1 (r2 = 0.62, p = 0.0001). A positive correlation was found between NYHA functional class and MHC 2a and 2b (r2 = 0.46, p = 0.001; r2 = 0.41, p = 0.002, respectively). The severity of heart failure is paralleled by a shift of the MHC pattern toward the fast MHC 2b. The correlation between the magnitude of the MHCs shift, from the slow aerobic to the fast type, with both clinical parameters (NYHA functional class) and functional measurements (peak VO2, VT, O2 pulse) of exercise capacity seem to suggest that changes in skeletal muscle composition may play a key role in exercise tolerance in patients with CHF.     

Maternal use of antiepileptic drugs and the risk of major congenital malformations: a joint European prospective study of human teratogenesis associated with maternal epilepsy

PURPOSE: To quantify the risks of intrauterine antiepileptic drug (AED) exposure in monotherapy and polytherapy. METHODS: Data from five prospective European studies totaling 1,379 children were pooled and reanalyzed. Data were available for 1,221 children exposed to AED during pregnancy and for 158 children of unexposed control pregnancies. RESULTS: Overall, when comparing a subgroup of 192 children exposed to AED with 158 children of matched nonepileptic controls, there was an increased risk of major congenital malformations (MCA) in children exposed to AED during gestation [relative risk (RR) 2.3; 95% confidence interval (CI): 1.2-4.7]. A significant increase in risk was found for children exposed to valproate (VPA) (RR 4.9; 95% CI: 1.6-15.0) or carbamazepine (CBZ) (RR 4.9; 95% CI: 1.3-18.0) in monotherapy. When comparing different AED regimens during all 1,221 pregnancies, risks of MCA were significantly increased for the combination of phenobarbital (PB) and ethosuximide (RR 9.8; 95% CI: 1.4-67.3) and the combination of phenytoin, PB, CBZ, and VPA (RR 11.0; 95% CI: 2.1-57.6). Offspring of mothers using > 1,000 mg VPA/day were at a significantly increased risk of MCA, especially neural tube defects, compared to offspring exposed < or =600 mg VPA/day (RR 6.8; 95% CI: 1.4-32.7). No difference in risk of MCA was found between the offspring exposed to 601-1,000 mg/day and < or =600 mg/day. CONCLUSIONS: This reanalysis shows that VPA is consistently associated with an increased risk of MCA in babies born to mothers with epilepsy. Significant associations were also observed with CBZ. Larger prospective population-based studies are needed to evaluate the risks of many other less frequently prescribed treatment regimens, including newly marketed AEDs.