Properties of photoreceptor-specific phospholipase C encoded by the norpA gene of Drosophila melanogaster.

Mutations in the norpA gene drastically affect the phototransduction process in Drosophila. To study the biochemical characteristics of the norpA protein and its cellular and subcellular distributions, we have generated antisera against the major gene product of norpA. The antisera recognize an eye-specific protein of 130-kDa relative molecular mass that is present in wild-type head extracts but not in those of strong norpA mutants. The protein is associated with membranes and can be extracted with high salt. Immunohistochemical analysis at the light and electron microscopic levels indicates that the protein is expressed in all adult photoreceptor cells and specifically localized within the rhabdomeres, preferentially adjacent to, but not within, the rhabdomeric membranes. The results of the present study strongly support the previous suggestion that the norpA gene encodes the major phosphoinositol-specific phospholipase C in the photoreceptors. Moreover, insofar as the rhabdomeres are specialized structures for photoreception and phototransduction, specific localization of the norpA protein within these structures, in close association with the membranes, is consistent with the proposal that it has an important role in phototransduction.     

Behavioural variations among strains of Trichogramma spp.: Adaptability to field-temperature conditions

In order to select a candidate strain of Trichogramma sp. for inundative releases against lepidopteran pests in cabbage field-crops in the Netherlands, the parasitization activity of a collection of 60 different Trichogramma spp. strains was studied during 2 h and 24 h exposures at 12°C. Activity and parasitism varied significantly among strains and the two characteristics were not correlated, suggesting the action of two differentially temperature-dependent mechanisms influencing both characteristics. Native strains were characterized by a low activity at 12°C, making their usefulness for inundative releases doubtful. In three strains tested at 12, 17, 20, 25 and 30°C, activity increased linearly with temperature, until nearly all females parasitized at 20 or 25°C. Parasitism increased with increasing temperature to a maximum at 20–25°C and declined at 30°C. Handling time decreased asymptotically with increasing temperature. The results of this study suggest that Trichogramma strains vary in adaptability to low temperature, making this characteristic a useful criterion for evaluation of candidate strains.

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Résumé Afin de sélectionner une souche de Trichogramma sp. (Hymenoptera, Trichogrammatidae) candidate pour des lâchés inondatifs contre les Lépidoptères pestes de chou aux Pays-Bas, l'activité de parasitisation d'une collection de 60 souches différentes de Trichogramma spp. a été étudiée à 12°C pendant des durées d'exposition de 2 h et 24 h. L'activité proportionnelle et le degré de parasitisation des femelles varient significativement selon des souches et ne sont par corrélés. Ceci suggère l'action des deux mécanismes distincts, dépendant de la température et contrôlant independamment chacun de ces processus. Les souches indigènes sont caractérisées par une faible activité à 12°C, mettant en doute leur utilisation pour les lâchés inondatifs. Dans 3 souches testées à 12, 17, 20, 25 et 30°C, l'activité augmente linéairement avec la température, jusqu'a ce que quasi toutes les femelles parasitent les oeufs hôtes à 20°C et 25°C. Le taux de parasitisation augmente avec la température atteignant un maximum à 20–25°C puis diminue à 30°C. Le temps de manipulation d'un oeuf hôte diminue asymptotiquement lorsque la température croît. Les résultats de cette étude suggèrent que la capacité d'adaptation aux températures basses varie selon les souches de Trichogramma. Cette caractéristique constitue un critère utile pour l'évaluation de souches candidates potentielles.

     

A conserved role for the zinc finger polyadenosine RNA binding protein,ZC3H14, in control of poly(A) tail length

The ZC3H14 gene, which encodes a ubiquitously expressed, evolutionarily conserved, nuclear, zinc finger polyadenosine RNA-binding protein, was recently linked to autosomal recessive, nonsyndromic intellectual disability. Although studies have been carried out to examine the function of putative orthologs of ZC3H14 in Saccharomyces cerevisiae, where the protein is termed Nab2, and Drosophila, where the protein has been designated dNab2, little is known about the function of mammalian ZC3H14. Work from both budding yeast and flies implicates Nab2/dNab2 in poly(A) tail length control, while a role in poly(A) RNA export from the nucleus has been reported only for budding yeast. Here we provide the first functional characterization of ZC3H14. Analysis of ZC3H14 function in a neuronal cell line as well as in vivo complementation studies in a Drosophila model identify a role for ZC3H14 in proper control of poly(A) tail length in neuronal cells. Furthermore, we show here that human ZC3H14 can functionally substitute for dNab2 in fly neurons and can rescue defects in development and locomotion that are present in dNab2 null flies. These rescue experiments provide evidence that this zinc finger-containing class of nuclear polyadenosine RNA-binding proteins plays an evolutionarily conserved role in controlling the length of the poly(A) tail in neurons.     

Action of a homogeneous hydrogenation catalyst on living Tetrahymena mimbres cells

Various conditions were tested in an attempt to hydrogenate the unsaturated fatty acids of living Tetrahymena mimbres with the homogeneous catalyst palladium di-(sodium alizarine monosulfonate) without causing serious damage to the cells. Using a low (20 micrograms/ml) catalyst concentration in the external medium, hydrogenation of greater than 20% of surface membrane lipid double bonds were obtained, but hydrogenation of intracellular membranes was minimal. When exposed to H2, cells preincubated with inactive catalyst for several hours and visibly loaded with the catalyst lost viability as soon as hydrogenation exceeded trace levels. Material secreted by Tetrahymena into their medium effectively inhibited hydrogenation of added oleic acid, normally a good substrate. Mucus secreted by the cells, soluble proteins isolated from cell homogenates, bovine serum albumin, and cysteine were also inhibitory, but the inhibition could be overcome by employing higher catalyst concentrations. Although some enzymatic retroconversion of saturated lipids back to unsaturated lipids appeared to take place, the scale of the conversion was small, and further experimentation will be required to understand the mechanism involved. The selective hydrogenation of surface membranes achieved by these methods may be especially useful to those interested in fluidity effects on plasma membrane properties.     

Charge Transport Modulation of a Flexible Quantum Dot Solar Cell Using a Piezoelectric Effect

Colloidal quantum dots are promising materials for flexible solar cells, as they have a large absorption coefficient at visible and infrared wavelengths, a band gap that can be tuned across the solar spectrum, and compatibility with solution processing. However, the performance of flexible solar cells can be degraded by the loss of charge carriers due to recombination pathways that exist at a junction interface as well as the strained interface of the semiconducting layers. The modulation of the charge carrier transport by the piezoelectric effect is an effective way of resolving and improving the inherent material and structural defects. By inserting a porous piezoelectric poly(vinylidenefluoride‐trifluoroethylene) layer so as to generate a converging electric field, it is possible to modulate the junction properties and consequently enhance the charge carrier behavior at the junction. This study shows that due to a reduction in the recombination and an improvement in the carrier extraction, a 38% increase in the current density along with a concomitant increase of 37% in the power conversion efficiency of flexible quantum dots solar cells can be achieved by modulating the junction properties using the piezoelectric effect.     

New upper cambrian trilobites from the chopko river section

Six new genera, one new subgenus, and ten new species of trilobites are described from the Upper Cambrian Chopko Formation from a section of the Chopko River, Norilsk District, northwestern part of the Siberian Platform. These include one genus and two species of agnostids and five genera, one subgenus, and eight species of polymerids. The new taxa come from an interval of the section attributed to the upper two-thirds of the Upper Cambrian.