Genetic dissection of monoamine neurotransmitter synthesis in Drosophila

The biogenic monoamine neurotransmitters octopamine, dopamine and serotonin have been detected in nervous tissue from many insects. We report here that intact Drosophila melanogaster brains, when incubated with the radioactive amino acids tyrosine and tryptophan, synthesized and accumulated labelled monoamines. In two mutant strains monoamine synthesis was abnormal. The per o mutation abolishes the normal circadian rhythm. Brains from per o flies, when incubated in tritiated tyrosine, accumulated one-third as much labelled octopamine as did brains from wild-type flies, but had normal dopamine and serotonin synthesis. In contrast, dopa decarboxylase (Ddc) mutations decreased dopamine and serotonin synthesis but did not affect octopamine synthesis. These results suggest that there are two different aromatic amino acid decarboxylases in Drosophila brains, one that decarboxylates L-dopa and 5-hydroxytryptophan and another that decarboxylates tyrosine. Direct measurement of L-dopa, 5-hydroxytryptophan and tyrosine decarboxylase activities in the different strains confirmed this suggestion.     

Motility and mechanosensitivity of macrocilia in the ctenophore Bero?

Mechanical activation of the microtubule sliding mechanism in cilia and flagella by local passive bending has been postulated to be essential for the initiation and propagation of bending waves along the axoneme. In addition, responsiveness of cilia to hydrodynamic forces imposed externally by their neighbours is thought to be responsible for metachronal coordination of ciliary activity, as well as for synchronal beating of component cilia within compound ciliary organelles. Direct tests of the mechanosensitivity of motile cilia are limited, but generally support these views. It remains problematical, however, whether mechanical interaction between cilia operates continuously during both the effective and recovery phases of the asymmetrical beat cycle. Moreover, the directional sensitivity and temporal responsiveness of motile cilia to mechanical stimuli have been explored in only a few cases. Finally, the continuous nature of the ciliary beat cycle has hindered investigation of the 'switch point hypothesis' in which doublet sliding is assumed to be activated sequentially on the two halves of the axoneme to produce bends in opposite directions. Here we report that macrocilia on the ctenophore Bero? beat discontinuously with separate effective and recovery strokes, resulting in 'split-cycle' waves of metachronal coordination. This new pattern of ciliary beating is used to investigate the motile responses of cilia to controlled mechanical stimuli during each phase of the beat cycle.     

SB-restricted presentation of influenza and herpes simplex virus antigens to human T-lymphocyte clones

The HLA-D region of the human major histocompatibility complex (MHC) has been shown to be homologous to the murine I region in terms of both structure and function. Both regions encode class II MHC molecules which restrict T-lymphocyte interactions with antigen-presenting cells. We have recently described the MHC restriction and antigen specificities of human T-lymphocyte clones directed at strain A influenza virus. The majority of T-lymphocyte clones recognized antigen in the context of cell surface interaction products encoded by HLA-D/DR genes. However, a few clones recognized antigen presented by cells histoincompatible for D/DR antigens. We report here that some of these clones recognized viral antigens in association with antigens encoded by genes identical with or closely linked to the recently described secondary B-cell (SB) locus of the MHC. This is the first report that SB-restricted antigen recognition may form an integral part of normal, human immune responses.     

Evolution and ecological correlates of uniparental reproduction in freshwater snails

We review the spatial and temporal correlates of uniparental reproduction in freshwater snails as they pertain to the ecological hypotheses for the maintenance of biparental sex. The biogeographic evidence from two species (Potamopyrgus antipodarum andBulinus truncatus) presently supports the Red Queen hypothesis that biparental reproduction is selected as a way to reduce the risk to progeny of parasite attack. Uniparental reproduction in these species is associated with low levels of infection by parasites (castrating digenetic trematodes), suggesting that parthenogenesis or self-fertilization can replace cross-fertilization when the risk of infection is low. In addition, inB. truncatus, the opportunity for cross-fertilization coincides with the season in which parasite attack is highest. In a third species (Campeloma decisum), parthenogenetic reproduction is correlated with latitude and the presence of a non-castrating trematode that may prevent cross-fertilization; these patterns suggest that parthenogenesis has been selected as a mechanism to assure reproduction. Finally, we discuss the spotty taxonomic distribution of parthenogenetic species.     

On the pathway of the rectosphincteric reflex

In several rat models, including those with circular and semicircular rectal aganglionosis, the rectosphincteric reflex was examined. The reflex was confirmed to be essentially an intramural one and its route is considered to run mainly in the longitudinal and partly in the oblique directions.     

Comparative distribution of vasoactive intestinal polypeptide (VIP), substance P and PHI in the enteric sphincters of the cat

In the feline gastrointestinal tract, the neuropeptides, substance P, VIP and PHI were investigated by specific radioimmunoassays and immunocytochemistry. The concentrations of all 3 peptides and the level of peptidergic innervation were significantly less in the anal sphincter than elsewhere, whereas no significant differences were seen between other sphincter and non-sphincter regions.     

Antiviral activity of coralloid root ofCycas revoluta extract against some viruses of tomato plant

Summary Crude coralloid root extract ofCycas revoluta showed significant antiviral activity against viruses of the tomato plant (PVX, PVY, TMV, TAV and TRSV) when applied 24 h before virus inoculation, or when mixed with different virus inocula before virus inocultion, in hypersensitive and systemic hosts. No such inhibition was observed when extract was applied 24 h after virus inoculation. TAV did not show any inhibitory response in a systemic host.Authors are thankful to Dr S. N. Gupta and Dr (Smt.) K. Shukla for their valuable guidance and providing laboratory facilities and U.G.C. for financial assistance.     

Cadmium-induced inhibition of brain monoamine oxidase in the freshwater catfish

Summary The freshwater catfishClarias batrachus (L.), exposed to 50 ppm of cadmium (Cd) chloride for a period of 135 days exhibited marked inhibition of brain monoamine oxidase (MAO) (p<0.001). The retarded gonadal growth observed in the present study suggests that Cd may be capable of creating imbalance in the aminergic activity of the hypothalamus, which modulates the secretion and release of gonadotropins.Acknowledgment. Financial assistance from the Council of Scientific and Industrial Research of India made this work possible.