Enhancement of intestinal water absorption and sodium transport by glycerol in rats

Advances in screening technologies allowing the identification of growth factor receptors solely by virtue of DNA or protein sequence comparison call for novel methods to isolate corresponding ligand growth factors. The EPH-like receptor tyrosine kinase (RTK) HEK (human EPH-like kinase) was identified previously as a membrane antigen on the LK63 human pre-B-cell line and overexpression in leukemic specimens and cell lines suggested a role in oncogenesis. We developed a biosensor-based approach using the immobilized HEK receptor exodomain to detect and monitor purification of the HEK ligand. A protein purification protocol, which included HEK affinity chromatography, achieved a 1.8 X 10(6)-fold purification of an approximately 23-kDa protein from human placental conditioned medium. Analysis of specific sHEK (soluble extracellular domain of HEK) ligand interactions in the first and final purification steps suggested a ligand concentration of 40 pM in the source material and a Kd of 2-3 nM. Since the purified ligand was N-terminally blocked, we generated tryptic peptides and N-terminal amino acid sequence analysis of 7 tryptic fragments of the S-pyridylethylated protein unequivocally matched the sequence for AL-1, a recently reported ligand for the related EPH-like RTK REK7 (Winslow, J.W., Moran, P., Valverde, J., Shih, A., Yuan, J.Q., Wong, S.C., Tsai, S.P., Goddard, A., Henzel, W.J., Hefti, F., Beck, K.D., & Caras, I.W. (1995) Neuron 14, 973-981). Our findings demonstrate the application of biosensor technology in ligand purification and show that AL-1, as has been found for other ligands of the EPH-like RTK family, binds more than one receptor.     

Validity of self-reported rheumatoid arthritis in elderly women

OBJECTIVE: To determine the validity of a self-reported physician diagnosis of rheumatoid arthritis (RA) in elderly women. METHODS: Women with self-reported RA were contacted and permission requested to contact their physician. Physicians were mailed a questionnaire requesting information on the subject's arthritic condition. Hand radiographs obtained at study entry were read for changes of RA. RESULTS: The self-reported diagnosis of RA could be confirmed in 26 (21%) individuals. CONCLUSION: The positive predictive value of self-reported RA was low in this cohort. Caution needs to be exercised in the use and interpretation of self-report data concerning arthritic conditions in epidemiologic studies.     

Some biochemical properties of the new potential antidepressant agent N-methyl-N-propargyl-2-(1-methyl-5-methoxyindolyl)methylamine

The biochemical properties of the new methyl indole derivative IM-24 (N-methyl-N-propargyl-2(1-methyl-5-methoxyindolyl)methylamine HCl) have been investigated. The activity on both forms of monoamine oxidase MAO was tested in several nervous and non nervous tissues ex vivo after chronic administration. IM-24 is mainly an inhibitor of the activity of MAO A without any effect on intestinal MAO B at the doses studied. IM-24 was compared with tricyclic antidepressants in tests for serotonin (5HT), noradrenaline (NA) and dopamine (DA) uptake inhibition in vitro. IM-24 is mainly an inhibitor of the 5HT uptake mechanism but is less active than paroxetine and chlorimipramine which are very potent 5HT-uptake inhibitors. Radioligand binding techniques in rat brain ex vivo showed that IM-24 after chronic administration (21 days) produces no change in the number or the affinity of the alpha 2-adrenoceptors. IM-24 reduces by 70% the number of 5HT2 receptors but does not modify the affinity for the ligand. IM-24 is thus an interesting compound which combines monoamine oxidase inhibition with inhibition of 5HT uptake. Both these actions will lead to an increase of the availability of serotonin at the synaptic site.     

ThioTEPA pharmacokinetics during intravesical chemotherapy: the influence of dose and volume of instillate on systemic uptake and dose rate to the tumour

Hereditary tyrosinaemia type I (HTI), an autosomal recessive inborn error of metabolism, is caused by a deficiency of the enzyme fumarylacetoacetate hydrolase. The highest incidence of HTI is observed in the Saguenay-Lac-St-Jean region (SLSJ) (Québec, Canada), where 1 out of 22 individuals is thought to be a carrier. A splice mutation (IVS12 + 5G-->A) has recently been identified in this particular region. Here, we have determined the frequency of this mutation in a population of obligate carriers from the SLSJ region by allele-specific oligonucleotide hybridization and a method using a restriction enzyme digestion. Over 95 per cent of the HTI carriers were found to have the IVS12 + 5G-->A splice mutation. Screening for this mutation based on the two methods reported here is thus a reliable and rapid way of detecting carriers of hereditary tyrosinaemia type I in that region at high risk.     

The use of neuronal networks on multielectrode arrays as biosensors

Mammalian spinal neuronal networks growing on arrays of photoetched electrodes in culture provide a highly stable system for the long-term monitoring of multichannel, spontaneous or evoked electrophysiological activity. In the absence of the homeostatic control mechanisms of the central nervous system, these networks show remarkable sensitivities to minute chemical changes and mimic some of the properties of sensory tissue. These sensitivities could be enhanced by receptor up-regulation and altered by the expression of unique receptors. The fault-tolerant spontaneous network activity is used as a dynamic platform on which large changes in activity signify detection of chemical substances. We present strategies for the expression of novel supersensitivities to foreign molecules via genetic engineering that involves the grafting of ligand binding cDNA onto truncated native receptor DNA and the subsequent expression of such chimeric receptors.     

Nuclear and cytoplasmic pH increase at fertilization in Urechis caupo

Intracellular pH (pHi) was measured in Urechis caupo (Echiura) eggs during fertilization using the pH-sensitive dye BCECF [bis(carboxyethyl)carboxyfluorescein] and fluorescence microscopy. When eggs were inseminated at pH 8, pHi began to rise 22-36 sec (n = 7) after sperm contact and reached a plateau by 3 min (2.8 +/- 1 SD; n = 14). The net increased was 0.25-0.3 pH units and the alkalinization persisted through 1 hr after insemination (after second polar body formation). Separate measurements of germinal vesicles and cytoplasm revealed that pH rose dramatically within the nuclei well before germinal vesicle breakdown (GVBD), as well as in cytoplasm. When eggs were fertilized at pH 6.9 (previously shown to inhibit proton release and egg activation despite sperm entry; see Paul, 1970, 1975; Holland et al., 1984), there was no net pH increase in either cytoplasm or germinal vesicles. When fertilization was at pH 7.45, the average pHi increase in whole eggs was 58% of that at pH 8, and 61% of the eggs activated partially or completely. These results show that the pHi rise is correlated with GVBD and egg activation.