5-HT3 Receptor-independent Inhibition of the Depolarization-induced 86Rb Efflux from Human Neuroblastoma Cells,TE671, by Ondansetron

The 5-HT₃-receptor antagonist, ondansetron, has been shown to have positive effects in selected in-vivo models of memory impairment and anxiety. The exact mechanisms underlying such bioactivities are unknown. In the present work, an ⁸⁶Rb efflux bioassay was used to show that ondansetron has a unique ability to block voltage-gated potassium channels in TE671 human neuroblastoma cells. This intrinsic potassium-channel-blocking (KCB) property is relatively weak (IC50 20 (M), but is not shared by other 5-HT₃-receptor ligands including zatosetron, MDL 72222, LY 278, 584, zacopride, 1-phenylbiguanide, and ICS 205–930 (tropisetron). Pre-incubation of the target neuroblastoma cells with several 5-HT-receptor ligands including 5-hydroxytryptamine, 8-OH-DPAT, ketanserin, 2-methyl-5-HT, as well as a number of potent 5-HT₃ agonists and antagonists and two selective neurotoxins, failed to abolish the KCB action of ondansetron. A preliminary structure-activity relationship analysis indicates that the KCB activity of ondansetron is almost entirely attributable to its structural nucleus, 2,3-dihyro-9-methyl-4(lH)-carbazolone. It is hypothesized that the KCB action of ondansetron is mediated through receptors other than 5-HT₃ receptors. The KCB activity of ondansetron may be a significant factor in the in-vivo cognition-enhancing activities of this compound, conceivably due to depolarization of the hippocampal synaptic membranes and a consequent augmentation of neurotransmission.     

The Alcohol Beverage Warning Label: When Did Knowledge Increase?

This article presents data on the awareness of the alcohol beverage warning label among a sample of 5,169 inner city African-American gravidas seeking prenatal care. While the label law was implemented in November 1989, a significant increase in knowledge of the label did not occur until March 1990. Women who predominantly consumed wine coolers and beer, and those under age 30 were more likely to know about the label than their counterparts.     

Erythrocyte autoantibodies, autoimmune haemolysis, and carcinoma.

AIMS--To examine a large series of patients in whom both red cell autoantibodies and carcinoma are present; and to determine whether this rare occurrence is a true association or a chance event. METHODS--The laboratory records of 160 patients (76 men, 84 women; mean age 68 years) with erythrocyte autoantibodies and confirmed carcinoma were examined for site of tumour origin and clinical and immunohematological findings. To test whether the concomitant occurrence of autoantibodies and carcinoma was fortuitous, data on total population and carcinoma incidence were included in a chi 2 analysis. RESULTS--The association was significant (chi 2 = 97.5, p < 0.0005); erythrocyte autoantibodies and carcinoma were found together 12-13 times more often than expected from their relative frequencies. Autoantibodies occurred with a variety of carcinomas, particularly those of breast, lung, colon, rectum, and prostate; this largely reflected tumour incidence. Adenocarcinoma, squamous, anaplastic, and transitional cell types were all represented. Warm, cold, and mixed autoantibodies were not associated with particular tumour sites or histology. Eighty six patients had haemolysis of varying severity, 37 had metastatic disease, and 28 died within a few months of presentation. CONCLUSIONS--The presence of erythrocyte autoantibodies and carcinoma in the same patient is a true association and probably reflects a fundamental disturbance in immune homeostasis. It tends to occur with a large tumour mass and metastatic disease, and generally indicates a poor prognosis.     

Gentamicin-induced increases in cytosolic calcium in pig kidney cells (LLC-PK1)

LLC-PK1 cells, an established epithelial cell line derived from pig kidney, were tested as a model system for assessing the role of calcium in gentamicin-induced nephrotoxicity. Cell viability was evaluated by a vital dye exclusion procedure, and intracellular free calcium [Ca2+]i was measured employing Fura-2 fluorescence. Exposing cell suspensions (10(6)/ml) to concentrations of the drug, which had no apparent effect on viability, produced a rapid and prolonged increase in intracellular [Ca2+]. The perturbation of calcium homeostasis could be blocked by the addition of mepiperphenidol, an inhibitor of the organic cation transport system. We propose that LLC-PK1 cells are an appropriate model to study drug-induced nephrotoxicity. Gentamicin disrupts calcium homeostasis and causes plasma membrane alterations. Since mepiperphenidol blocked the gentamicin-induced Ca2+ increases, the data suggest that aminoglycosides enter the cell via the organic cation transporter.     

Distribution of quorum-sensing genes in the Burkholderia cepacia complex

The distribution of quorum-sensing genes among strains from seven genomovars of the Burkholderia cepacia complex was examined by PCR. cepR and cepI were amplified from B. cepacia genomovars I and III, B. stabilis, and B. vietnamiensis. cepR was also amplified from B. multivorans and B. cepacia genomovar VI. bviIR were amplified from B. vietnamiensis. All genomovars produced N-octanoyl-L-homoserine lactone and N-hexanoyl-L-homoserine lactone. B. vietnamiensis and B. cepacia genomovar VII produced additional N-acyl-L-homoserine lactones.     

Characterization of chloroquine-induced autophagic vacuoles isolated from rat liver

Studies have been undertaken to investigate the role of cellular autophagy in the accommodation of stress in a biological system. Chloroquine (Aralen hydrochloride), an antimalarial and anti-inflammatory drug, was used to induce autophagy in rat liver. A method is presented which uses differential and discontinuous sucrose gradient centrifugation for the preparation of autophagic vacuole-enriched fractions from rat liver. Ultrastructural studies of the autophagic vacuole fractions showed that the integrity of the autophagic vacuoles was maintained throughout the isolation procedure and that they were morphologically similar to those seen in situ. Assay of glucose-6-phosphatase, NADPH-DCIP reductase, and acid phosphatase confirm the presence of membranes derived from the endoplasmic reticulum, as well as lysosomes, in the autophagic vacuole fractions. The distribution of [¹⁴C]-chloroquine suggested a preferential binding of the drug to the autophagic vacuoles may have occurred. These results suggest that cellular autophagy may play an important role in the accommodation of chemically induced alterations in hepatocytes by preferentially sequestering chloroquine, as well as restoring cellular ultrastructure.     

Production and utilization of pyochelin by clinical isolates of Pseudomonas cepacia.

Forty-three Pseudomonas cepacia isolates were screened for the production of pyochelin. Twenty-one (49%) produced pyochelin, and 22 (51%) were pyochelin negative. Of the 21 strains producing pyochelin, 18 were from patients with severe infections, 11 of which resulted in death. Of the 22 strains which did not produce pyochelin, 13 were from patients with mild or moderate infections. Pyochelin production by P. cepacia isolates infecting cystic fibrosis patients correlates with morbidity and mortality in these patients. Pyochelin was shown to stimulate the in vitro growth of P. cepacia in the presence of transferrin. P. cepacia isolates were able to accumulate 59Fe-pyochelin regardless of whether they produced this siderophore.     

Normative reproductive indices for male and female adult Sprague-Dawley rats.

The Sprague-Dawley rat is traditionally used as the experimental model for the study of contraceptive agents and reproductive toxicants. Until recently, the normative values used to compare hormone levels after drug exposure were based on the values generated by radioimmunoassay methods developed 30 years ago. To ascertain normative reproductive indices for adult female and male Sprague-Dawley rats over a 6-month age period, we measured luteinizing hormone, testosterone, and estradiol using commercially available kits that employ updated assay techniques. In addition, sperm indices were correlated with reproductive hormones over the same time period. Animals were killed at 107, 128, 156, 212, and 268 days of age irrespective (for females) of cycle stage. Serum LH levels did not change with increasing age; however, the female rats had significantly higher LH values than did the males at comparable ages (p < 0.001). Testosterone levels and sperm parameters did not significantly change with increasing age. Estradiol levels were significantly higher in 107-day-old female rats than they were in female rats in all older age groups (p < 0.01). The values reported can be used in designing and interpreting data generated in ongoing, long term toxicological and contraceptive studies using the rat animal model.