Genetic and cytogenetic studies of malic enzyme in Drosophila melanogaster

The genetic and cytogenetic locations of the structural gene (Men) for malic enzyme have been determined. Men maps genetically between kar and ry at 51.73±0.02. Cytogenetically, Men probably lies in the proximal edge of 87D1,2, based on the results of mapping utilizing a number of deficiencies with breakpoints in that region. A number of null alleles have been recovered; heterozygotes for these nulls and a Men deficiency are both viable and fertile. These findings are related to the one band, one functional unit model of salivary gland chromosome structure.     

Encapsulation of 8-azaguanine in single multiple compartment liposomes

Incorporation of [2-¹⁴C]-8-azaguanine into positively charged single and multiple component dipalmitoyl-DL-α-phosphatidylcholine and egg yolk phosphatidylcholine liposomes has been established. The extent of encapsulation in single compartment liposomes is 0.70–1.80% and it depends on the concentration of the added 8-azaguanine and the sonication time. Utilizing dialysis, the leakage of the drug from the single compartment liposomes after 20 hours was determined to be 4–34%. At high concentration of the added drug it is possible to encapsulate 18×10^?9 pmole of 8-azaguanine per liposome. Percentages of uptake into multicompartment liposomes are 3.6–5.4%. A preliminary study has been carried out on the effects of free and single and multiple compartment encapsulated 8-azaguanine on the survival and weight gains of leukemia L-1210 bearing mice.     

Inhibitory effect of antidepressants on the NMDA-evoked [H]noradrenaline release from rat hippocampal slices

We have previously shown that monoamine uptake blocker-type antidepressants with different chemical structure and selectivity are able to inhibit neuronal nicotinic acetylcholine receptors (nAChRs) in concentrations observed during antidepressant treatment. The mechanism of action of these drugs is similar to that of mecamylamine, a channel blocker-type antagonist of nAChRs. Since mecamylamine has been shown to block also NMDA receptors, our aim was to investigate whether the monoamine uptake blockers may affect the function of these ionotropic glutamate receptors.We studied, therefore the effect of the two most potent nicotinic antagonist antidepressants, the tricyclic desipramine and the selective serotonin reuptake inhibitor fluoxetine on the NMDA-induced [³H]noradrenaline ([³H]NA) release from rat hippocampal slices. The NMDA-induced hippocampal [³H]NA release was effectively blocked by the selective, non-competitive NMDA antagonist MK-801 (IC₅₀ = 0.54 μM), indicating that the [³H]NA release was mediated through NMDA receptors. This response was also dose-dependently inhibited by desipramine (IC₅₀ = 14.57 μM) and fluoxetine (IC₅₀ = 41.06 μM). The Na⁺-channel blocker TTX equally inhibited both the electrical stimulation- and the NMDA-evoked [³H]NA release (the IC₅₀ was 55 nM and 66 nM, respectively), whereas the antidepressants inhibited only the NMDA-evoked response. These data suggest that the inhibitory effect of fluoxetine and desipramine on the NMDA-evoked [³H]NA release is exerted directly on NMDA receptors rather than indirectly on Na⁺-channels.Due to accumulation processes the concentration of desipramine and fluoxetine in the brain might be in the same range as the observed IC₅₀ values, thus our data indicate that monoamine uptake blocker-type antidepressants are able to influence the function of NMDA receptors during antidepressant treatment, and the inhibitory effect on NMDA receptors might contribute to the therapeutic effects of these drugs.     

Characterization of the Photochemical Reaction Cycle of Proteorhodopsin

Absorption changes in the photocycle of the recently described retinal protein, proteorhodopsin, are analyzed. The transient spectra at pH 9.5, where it acts as a light-driven proton pump, reveal the existence of three spectrally different intermediates, K, M, and N, named in analogy with the photointermediates of bacteriorhodopsin. Model analysis based on time-dependent absorption kinetic signals at four wavelengths suggested the existence of two more spectrally silent intermediates and lead to a sequential reaction scheme with five intermediates, K, M₁, M₂, N, and PR′, before decay to the initial state PR. An L-like intermediate was not observed, probably for kinetic reasons. By measuring the light-generated electric signal of an oriented sample, the electrogenicity of each intermediate could be determined. The electrogenicities of the first three intermediates (K, M₁, and M₂) have small negative value, but the last three components, corresponding to the N and PR′ intermediates and PR, are positive and two-orders-of-magnitude larger. These states give the major contributions to the proton translocation across the membrane. The energetic scheme of the photocycle was calculated from the temperature-dependence of the absorption kinetic signals.     

Female collared flycatchers adjust yolk testosterone to male age, but not to attractiveness

The differential allocation hypothesis predicts that femalesinvest more resources into reproduction when mating with attractivemales. In oviparous animals this can include prefertilizationdecisions such as the production of larger eggs and the depositionof hormones, such as the steroid testosterone, into yolks. Onthe other hand, a compensatory hypothesis posits that femalesallocate more resources into the eggs when mated with malesof inferior quality. In the present study, we show that free-livingfemales of the collared flycatcher (Ficedula albicollis), asmall passerine bird, do not produce larger eggs or depositmore testosterone into eggs when mating with attractive malesreflected by a large forehead patch size, which is contraryto the prediction of the differential allocation hypothesis.However, we found higher yolk testosterone concentrations ineggs laid for young than older males. Because in young malesgenetic quality, parental experience, or willingness to investinto paternal care is likely to be low, high yolk testosteronelevel in their clutches may indicate that their females followa compensatory tactic. They may elicit more paternal care fromyoung, inexperienced males by hormonally increasing nestlingbegging. Laying date was also correlated with yolk testosteronelevel; however, when we controlled for it, male age still remaineda strong determinant of testosterone allocation.     

Alterations in EEG activity and sleep after influenza viral infection in GHRH receptor-deficient mice.

Viral infections induce excess non-rapid eye movement sleep (NREMS) in mice. Growth hormone-releasing hormone receptor (GHRH receptor) was previously identified as a candidate gene responsible for NREMS responses to influenza challenge in mice. The dwarf lit/lit mouse with a nonfunctional GHRH receptor was used to assess the role of the GHRH receptor in viral-induced NREMS. After influenza A virus infection the duration and intensity [electroencephalogram (EEG) delta power] of NREMS increased in heterozygous mice with the normal phenotype, whereas NREMS and EEG delta power decreased in homozygous lit/lit mice. Lit/lit mice developed a pathological state with EEG slow waves and enhanced muscle tone. Other influenza-induced responses (decreases in rapid eye movement sleep, changes in the EEG high-frequency bands during the various stages of vigilance, hypothermia, and decreased motor activity) did not differ between the heterozygous and lit/lit mice. GH replacement failed to normalize the NREMS responses in the lit/lit mice after influenza inoculation. Decreases in NREMS paralleled hypothermia in the lit/lit mice. Lung virus levels were similar in the two mouse strains. Lit/lit mice had a higher death rate after influenza challenge than the heterozygotes. In conclusion, GHRH signaling is involved in the NREMS response to influenza infection.