Precursor supply for insect juvenile hormone III biosynthesis in a cockroach

The biosynthesis of the sesquiterpenoid juvenile hormone III (JH III) was studied using corpora allata of the cockroach Diploptera punctata incubated in vitro and a radiochemical assay for the hormone produced. The influence of several exogenous precursors such as glucose, trehalose, acetate, amino acids, and mevalonate on JH synthetic rates was studied. Glucose or trehalose were needed for an optimal rate of JH synthesis. Highest rates were achieved at trehalose concentrations below the normal hemolymph levels (35-40 mM). About one-third of the glucose utilized for the biosynthesis of JH III was metabolized through a pentose pathway, but acetyl-CoA derived from glucose was significantly diluted by acetyl-CoA from other sources. Amino acids provided both a source of carbon for JH III synthesis and a source of energy that allowed JH III synthesis from acetate and stimulated JH III synthesis from glucose. Acetate was a poor substrate, because it could not support JH III synthesis in long term incubations. The incorporation of exogenous mevalonate into JH III was dependent on the physiological state of the glands, but there was a significant dilution with endogenous mevalonate. This dilution reflected in part the poor penetration of mevalonate into the corpora allata cells, because JH synthesis in mevinolin-treated cells was not fully rescued by mevalonate.     

Prenyl proteins in eukaryotic cells: a new type of membrane anchor

Recent studies have indicated that eukaryotic cells contain proteins that are post-translationally modified by long-chain, thioether-linked prenyl groups. These proteins include yeast mating factors, ras proteins and nuclear lamins. The modification occurs on a cysteine residue near the C terminus and appears to initiate a set of additional protein modification reactions that promote attachment of the proteins to specific membranes.     

A barrier to diffusion in pseudoplasmodia of Dictyostelium discoideum

Several enzymatic activities have been reported to be preferentially localized in the anterior portions of pseudoplasmodia of Dictyostelium discoideum. Since anterior cells are responsible for formation of the stalk during fruiting body construction, it has been suggested that accumulation of these enzymes may direct the cells toward stalk differentiation. However, the evidence for enzyme localization has come only from histochemical studies. We have assayed for succinoxidase and several dehydrogenase activities in cell free extracts of isolated anterior and posterior fragment and found no significant differences in specific activities, although by histochemical techniques each is apparently localized in the anterior cells. The preferential staining appears to be a consequence of a barrier to diffusion that is more effective at the back than at the front in limiting entry of the histochemical chromogen into pseudoplasmodia. The barrier appears to be the glycoprotein surface sheath that surrounds the pseudoplasmodium. The consequences of a barrier to diffusion of compounds into and out of pseudoplasmodia are discussed in relation to a mechanism that could give cells information concerning their position in this organism.     

Human lamin B contains a farnesylated cysteine residue

We recently showed that HeLa cell lamin B is modified by a mevalonic acid derivative. Here we identified the modified amino acid, determined its mode of linkage to the mevalonic acid derivative, and established the derivative's structure. A cysteine residue is modified because experiments with lamin B that had been biosynthetically labeled with [3H]mevalonic acid or [35S]cysteine and then extensively digested with proteases yielded 3H- or 35S-labeled products that co-chromatographed in five successive systems. A thioether linkage rather than a thioester linkage is involved because the mevalonic acid derivative could be released from the 3H-labeled products in a pentane-extractable form by treatment with Raney nickel but not with methanolic KOH. The derivative is a farnesyl moiety because the Raney nickel-released material was identified as 2,6,10-trimethyl-2,6,10-dodecatriene by a combination of gas chromatography and mass spectrometry. The thioether-modified cysteine residue appears to be located near the carboxyl end of lamin B because treatment of 3H-labeled lamin B with cyanogen bromide yielded a single labeled polypeptide that mapped toward this end of the cDNA-inferred sequence of human lamin B.     

Allometric analysis of Sitka spruce branches: mechanical versus hydraulic design principles

The geometry of tree branches can have considerable effect on their efficiency in terms of carbon export per unit carbon investment in structure. The purpose of this study was to evaluate different design criteria using data describing the form of Picea sitchensis branches. Allometric analysis of the data suggests that resources are distributed to favour shoots with the greatest opportunity for extension into new space, with priority to the extension of the leader. The distribution of allometric relations of links (branch elements) was tested against two models: the pipe model, based on hydraulic transport requirements, and a static load model based on the requirement of shoots to provide mechanical resistance to static loads. Static load resistance required the load parameter to be proportional to the link radius raised to the power of 4. This was shown to be true within a 95% statistical confidence limit. The pipe model would require total distal length to be proportional to link radius squared but the measured branches did not conform well to this model. The comparison suggests that the diameters of branch elements were more related to the requirements for mechanical load. The cost of following a hydraulic design principle (the pipe model) in terms of mechanical efficiency was estimated and suggested that the pipe model branch would not be mechanically compromised but would use structural resources inefficiently. Resource allocation among branch elements was found to be consistent with mechanical stability criteria but also indicated the possibility of allocation based on other criteria, such as potential light interception by shoots. The evidence suggests that whilst branch topology increments by reiteration of units of morphogenesis, the geometry follows a functional design pattern.     

3S,24S,25-Trihydroxytirucall-7-ene from Ailanthus excelsa

A new triterpene has been isolated from the root bark of Ailanthus excelsa (Simaroubaceae) and identified as 3S,24S,25-trihydroxytirucall-7-ene.     

A monoclonal antibody targeting a highly conserved epitope in influenza B neuraminidase provides protection against drug resistant strains

All influenza viral neuraminidases (NA) of both type A and B viruses have only one universally conserved sequence located between amino acids 222–230. A monoclonal antibody against this region has been previously reported to provide broad inhibition against all nine subtypes of influenza A NA; yet its inhibitory effect against influenza B viral NA remained unknown. Here, we report that the monoclonal antibody provides a broad inhibition against various strains of influenza B viruses of both Victoria and Yamagata genetic lineage. Moreover, the growth and NA enzymatic activity of two drug resistant influenza B strains (E117D and D197E) are also inhibited by the antibody even though these two mutations are conformationally proximal to the universal epitope. Collectively, these data suggest that this unique, highly-conserved linear sequence in viral NA is exposed sufficiently to allow access by inhibitory antibody during the course of infection; it could represent a potential target for antiviral agents and vaccine-induced immune responses against diverse strains of type B influenza virus.     

Can Nocturnal Flight Calls of the Migrating Songbird,American Redstart,Encode Sexual Dimorphism and Individual Identity?

Bird species often use flight calls to engage in social behavior, for instance maintain group cohesion and to signal individual identity, kin or social associations, or breeding status of the caller. Additional uses also exist, in particular among migrating songbirds for communication during nocturnal migration. However, our understanding of the information that these vocalizations convey is incomplete, especially in nocturnal scenarios. To examine whether information about signaler traits could be encoded in flight calls we quantified several acoustic characteristics from calls of a nocturnally migrating songbird, the American Redstart. We recorded calls from temporarily captured wild specimens during mist-netting at the Powdermill Avian Research Center in Rector, PA. We measured call similarity among and within individuals, genders, and age groups. Calls from the same individual were significantly more similar to one another than to the calls of other individuals, and calls were significantly more similar among individuals of the same sex than between sexes. Flight calls from hatching-year and after hatching-year individuals were not significantly different. Our results suggest that American Redstart flight calls may carry identifiers of gender and individual identity. To our knowledge, this is the first evidence of individuality or sexual dimorphism in the flight calls of a migratory songbird. Furthermore, our results suggest that flight calls may have more explicit functions beyond simple group contact and cohesion. Nocturnal migration may require coordination among numerous individuals, and the use of flight calls to transmit information among intra- and conspecifics could be advantageous. Applying approaches that account for such individual and gender information may enable more advanced research using acoustic monitoring.     

Reductions in abscisic acid are linked with viviparous reproduction in mangroves

We investigate physiological mechanisms behind the convergent evolutionary loss of seed dormancy in plant lineages, focusing on mangroves as a model system. More than 60 angiosperm families, including several mangrove taxa, contain species with seeds that are intolerant of drying and do not undergo dormancy. These desiccation-intolerant species occur with disproportionate frequency in wet or coastal tropical habitats. In plants, the hormone abscisic acid (ABA) coordinates both the development of desiccation tolerance during the onset of seed dormancy and whole-organism responses to flooding. Thus, changes in ABA levels and/or modes of action in different plant compartments are implicated in the repeated evolutionary loss of seed dormancy among species of wet habitats. We compare ontogenetic dynamics of ABA levels in embryonic, maternal, and mature vegetative tissue of four phylogenetically independent pairs of related viviparous mangroves and nonviviparous nonmangroves. We demonstrate that ABA levels are consistently lower in embryos of viviparous mangrove taxa than embryos of nonmangrove, nonviviparous sister taxa. In contrast, elevated tissue concentrations of ABA characterize leaves of all mangrove species tested, while ABA levels in maternal tissues vary among mangrove species. These commonalities suggest a functionally important trade-off between the maintenance of embryonic development and the adjustment of the parent tree to salinity stress. This study yields comparative data on seed physiology in naturally occurring desiccation-intolerant species, for which these data are currently scarce, and demonstrates a potentially significant role of phytohormones in the evolution of plant life histories.