Doxepin, a tricyclic antidepressant, binds to normal, intact astroglial cells in cultures and inhibits the isoproterenol-induced increase in cyclic AMP production

Doxepin binds to intact astrocytes in primary cultures. The binding is competitively displaceable by excess cold doxepin and it is pronounced (Bmax = 27 nmol/mg protein) but the affinity is rather low (KD = 30 microM). The binding is inhibited by other antidepressants (amitriptyline, desipramine, tranylcypromine, iprindole) and propranolol but not by isoproterenol. Nevertheless, doxepin counteracts effectively the increase in the production of cyclic AMP evoked by isoproterenol.     

Leishmania donovani: a chemically defined medium suitable for cultivation and cloning of promastigotes and transformation of amastigotes to to promastigotes

A chemically defined medium using commercially available alpha-MEM supplemented with hemin, HEPES, L-glutamine, D-glucose, folic acid, D-biotin and adenine supports the luxuriant growth and propagation of Leishmania donovani promastigotes. A peak parasite population of about 7.0 x 10(7)/ml at stationary phase and a population doubling time of 11.4 h for high-subpassage promastigotes were obtained. The medium was suitable for transformation of isolated amastigotes from infected hamster spleen. Promastigotes could be detected by culturing kala-azar patients' bone-marrow aspirate or spleen puncture material in this medium. Four out of six freshly transformed isolates gradually adapted and grew well in this medium. Macroscopic colonies appeared on agar plates prepared with the medium within 16-20 days after inoculation. The cloning efficiency was increased about five-fold by glycerol supplementation.     

Investigation on the role of nodule cytokinins in regulation of nitrate reductase activity ofPhaseolus mungo (L.)

The effects of some nodular cytokinis, zeatin (Z), zeatin riboside (ZR), N⁶ (²-isopentenyl) adenine (IPA), and N⁶ (²-isopentenyI) adenosine (IPAS) on nitrate reductase (E.C 1.9.6.1) activity of root nodules ofPhaseolus mungo were investigated. The cytokinis were also tested for their effect on nitrate uptake by nodules. The results show that IPAS is the most effective of all the four cytokinins tested. Z and IPA, which caused higherin vivo activity than ZR and IPAS, stimulated uptake of nitrate by nodules. The other two (ZR and IPAS) while inhibiting uptake showed greaterin vitro activity than Z and IPA. It may be concluded that some cytokinins, in addition to their direct effects on the enzyme, may increase the substrate availability to it, whereas others may have only an direct effect on the enzyme activation or degradation.Deceased.     

Evaluation of Nosema locustae (Microsporida) as a control agent of grasshopper populations in Saskatchewan

A quantitative study of the effect of a microsporidan, Nosema locustae, as a control agent against grasshopper populations in Saskatchewan, Canada, revealed that 50% of the populations of Melanoplus sanguinipes, M. packardii, and Camnula pellucida were infected between 4 and 5 weeks (400 to 424 degree-days) after application of the pathogen. Maxima of 95–100% infection were evident between 9 and 12 weeks (600–700 degree-days) after application. The percentage reduction in surviving populations of M. sanguinipes, i.e., those that did not die from natural causes, reached about 20% by the 4th week (400 degree-days) after inoculation, about 50% by the 9th week (600 + degree-days), and a maximum of about 60% by the 12th week (700 degree-days). An exponential relationship was obtained between percentage reduction and percentage infection in all three species. However, a similar percentage infection resulted in different percentage reduction in the populations. Results also revealed that the rate of reduction in populations reached its peak by about 40–80 degree-days before the maximum rate of infection was attained for each species. Egg production in the two Melanoplus species in treated plots was significantly lower (P < 0.05) than in the control plot.     

Evidence for two uroporphyrinogen decarboxylase isoenzymes in human erythrocytes

In animals and plants, uroporphyrinogen decarboxylase catalyzes the stepwise decarboxylations of uroporphyrinogen, the precursor of heme and chlorophyll. To better understand its metabolic roles, we characterized the enzyme purified to electrophoretic homogeneity (about 11,000-fold) from human erythrocytes by a novel uroporphyrin-sepharose affinity chromatographic method. Native polyacrylamide disc gel electrophoresis of the purified enzyme preparation showed two bands detected by staining either for protein or with uroporphyrin-I. Each individual protein eluted from the gel when subjected to re-electrophoresis on SDS-polyacrylamide gel, appeared as a single protein band with molecular masses of approximately 54,000 and approximately 35,000 daltons respectively. Both proteins were able to catalyze all four decarboxylation steps, though the ratios of enzyme activity using octa-, hepta-, hexa- to pentacarboxylic porphyrinogen substrates were distinctly different. Also, their kinetic analysis with heptacarboxylic porphyrinogen-I substrate provided distinctly different apparent Michaelis constants. This provides the first evidence that decarboxylations of uroporphyrinogen to coproporphyrinogen are catalyzed by two isoenzymes.     

Measurement of nitrite reductase in leaf tissue of Vigna mungo

The enzyme nitrite reductase (EC 1.6.6.4) is generally assayed in terms of disappearance of nitrite from the assay medium. We describe a technique which allowed estimation of the enzyme level in leaf tissues of Vigna mungo (L). Hepper in terms of the release of the product (NH₃) of the enzyme reaction. The technique is offered as an alternative, possibly more convenient method for assay of nitrite reductase in plant tissue in vivo.     

Immunological Characterization and Transmembrane Topology of 5-Hydroxytryptamine3 Receptors by Functional Epitope Tagging

Abstract: 5-Hydroxytryptamine₃ (5-HT₃) receptors are the only known monoamine receptors mediating fast excitatory responses in mammalian neurons. Their primary structure as well as their electrophysiological and pharmacological properties show a phylogenetic relation to nicotinic acetylcholine, GABA_A, and glycine receptors. As a prototypical member of this gene superfamily, we investigated the membrane topology of functional homomeric 5-HT₃ receptors by using epitope tagging of the channel subunits expressed in heterologous systems. Visualization of 5-HT₃ receptors in transfected COS-7 cells, either in western blot (molecular mass 61.2 ± 0.8 kDa) or in situ, was performed with previously characterized antibodies recognizing artificial epitopes as well as with anti-fusion protein antibodies directed against a wild-type receptor intracellular domain. The extracellular location of the distal C-terminal tagged domain demonstrates the presence of a fourth transmembrane domain in 5-HT₃ serotonin-gated channels. In this region, the significant homology between members of this class of neurotransmitter-gated channels suggests strongly that they have a common transmembrane organization basically different from glutamate-gated and ATP-gated channels.