Subsociality and female reproductive success in a mycophagous thrips: An observational and experimental analysis

Oviparous females of the haplodiploid, facultatively viviparous thrips Elaphrothrips tuberculatus(Thysanoptera: Phlaeothripidae) guard their eggs against female conspecifics and other egg predators. The intensity of maternal defense increases with clutch size. Field and laboratory observations indicate that cannibalism by females is an important selective pressure favoring maternal care. Experimental removals of guarding females showed that egg guarding substantially increases egg survivorship and that the survivorship of undefended eggs is higher in the absence of nonguarding female conspecifics than in their presence. The fecundity of viviparous females increases with the number of eggs cannibalized. The reproductive success of oviparous females increases with body size and local food density and decreases with local density of breeding females. Social behavior may not have advanced beyond maternal care in Elaphrothrips tuberculatusbecause, relative to Hymenoptera, capabilities for helping relatives are few or nonexistent, and the causes of variation in female reproductive success are not influenced easily by cooperation among females.     

High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans

We compared male-reproductive-tract polypeptides of Drosophila melanogaster and D. simulans by using two-dimensional gel electrophoresis. Approximately 64% of male-reproductive-tract polypeptides were identical between two randomly chosen isofemale lines from these two species, compared with 83% identity for third-instar imaginal wing-disc polypeptides. Qualitatively similar differences were found between reproductive tracts and imaginal discs when D. sechellia was compared with D. melanogaster and with D. simulans. When genic polymorphism was taken into account, approximately 10% of male- reproductive-tract polypeptides were apparently fixed for different alleles between D. melanogaster and D. simulans; this proportion is the same as that found for soluble enzymes by one-dimensional gel electrophoresis. Strikingly, approximately 20% of male-reproductive- tract polypeptides of either D. melanogaster or D. simulans had no detectable homologue in the other species. We propose that proteins of the Drosophila male reproductive tract may have diverged more extensively between species than have other types of proteins and that much of this divergence may involve large changes in levels of polypeptide expression.      

Fasciation induction by the phytopathogen Rhodococcus fascians depends upon a linear plasmid encoding a cytokinin synthase gene.

Rhodococcus fascians is a nocardiform bacteria that induces leafy galls (fasciation) on dicotyledonous and several monocotyledonous plants. The wild-type strain D188 contained a conjugative, 200 kb linear extrachromosomal element, pFiD188. Linear plasmid-cured strains were avirulent and reintroduction of this linear element restored virulence. Pulsed field electrophoresis indicated that the chromosome might also be a linear molecule of 4 megabases. Three loci involved in phytopathogenicity have been identified by insertion mutagenesis of this Fi plasmid. Inactivation of the fas locus resulted in avirulent strains, whereas insertions in the two other loci affected the degree of virulence, yielding attenuated (att) and hypervirulent (hyp) bacteria. One of the genes within the fas locus encoded an isopentenyltranferase (IPT) with low homology to analogous proteins from Gram-negative phytopathogenic bacteria. IPT activity was detected after expression of this protein in Escherichia coli cells. In R.fascians, ipt expression could only be detected in bacteria induced with extracts from fasciated tissue. R.fascians strains without the linear plasmid but containing this fas locus alone could not provoke any phenotype on plants, indicating additional genes from the linear plasmid were also essential for virulence. These studies, the first genetic analysis of the interaction of a Gram-positive bacterium with plants, suggest that a novel mechanism for plant tumour induction has evolved in R.fascians independently from the other branches of the eubacteria.     

The fas operon of Rhodococcus fascians encodes new genes required for efficient fasciation of host plants.

Three virulence loci (fas, att, and hyp) of Rhodococcus fascians D188 have been identified on a 200-kb conjugative linear plasmid (pFiD188). The fas locus was delimited to a 6.5-kb DNA fragment by insertion mutagenesis, single homologous disruptive recombination, and in trans complementation of different avirulent insertion mutants. The locus is arranged as a large operon containing six open reading frames whose expression is specifically induced during the interaction with host plants. One predicted protein is homologous to P-450 cytochromes from actinomycetes. The putative ferredoxin component is of a novel type containing additional domains homologous to transketolases from chemoautotrophic, photosynthetic, and methylotrophic microorganisms. Genetic analysis revealed that fas encodes, in addition to the previously identified ipt, at least two new genes that are involved in fasciation development, one of which is only required on older tobacco plants.     

Three conditions for the evolution of eusociality: Are they sufficient?

Summary I hypothesize that three conditions, (1) food-shelter coincidence, (2) strong selection for defense, and (3) ability to defend, are sufficient, although not necessary, for the evolution of eusociality in group-living animals. Reasons for this association between ecology and eusociality include extremely high value of the habitat, possibilities for habitat inheritance, high relatedness in claustral situations, self-sufficiency of juveniles, greater ability of workers to reproduce, and trade-offs between defensive ability and dispersal.     

Microelectrode studies of the active Na transport pathway of frog skin

When the outer surface of short-circuited frog skin was penetrated with microelectrodes, stable negative potentials that averaged near -100 mV were recorded consistently, confirming the results of Nagel (W. Nagel. 1975. Abstracts of the 5th International Biophysics Congress, Copenhagen. P-147.). The appearance of these stable potentials, V(O), concurrent with the observations that (a) a high resistance outer barrier R(O) accounting for approximately 75 percent or more of the transcellular resistance of control skins had been penetrated and that (b) 10(-5) M amiloride and reduced [Na] outside caused the values of V(O) to increase towards means value near -130 mV while the values of percent R(O) increased to more than 90 percent. It was of relationships were the same as the values of E(1) observed in studies of the current-voltage relationships were the same as the values of E’(1) defined as the values of voltage at the inner barrier when the V(O) of the outer barrier was reduced to zero by voltage clamping of the skins. Accordingly, these data are interpreted to mean that the values of E(1), approximately 130 mV, represent the E(Na) of the sodium pump at the inner barrier. 2,4-DNP was observed to decrease the values of transepithelial voltage less than E(1) the V(O) was negative. These data can be interpreted with a simple electrical equivalent circuit of the active sodium transport pathway of the frog skin that includes the idea that the outer membrane behaves as an electrical rectifier for ion transport.     

The location of retinal in the purple membrane profile by neutron diffraction.

The trans-membrane location of retinal in the purple membrane of Halobacterium halobium, has been determined by low-angle neutron scattering studies on aqueous dispersions of the membranes. The membrane was bleached and regenerated with deuterated and with hydrogen-containing retinal. The modified retinal was obtained by extraction from bacteria grown in a totally deuterated medium. The determination of the retinal position is based on the differences in neutron scattering between a purple membrane sample with normal, protonated retinal and another sample with deuterated retinal. A distinct scattering density difference between the two preparations was observed. A direct structure determination was used with the retinal localized from a Fourier difference density profile. We conclude that the β-ionone ring portion of the retinal is situated centrally in the membrane.     

Fructose as a carbohydrate source yields stable pH and redox parameters in microcarrier cell culture

The pH and cytosolic NADH/NAD⁺ redox potential in microcarrier cultures of Madin-Darby canine kidney cells remain within physiological range when fructose is substituted for glucose in medium formulation. This difference is accounted for by the low rate of lactic acid production in cultures utilizing fructose as a primary carbohydrate source.     

Probing antioxidant activity of 2′-hydroxychalcones: Crystal and molecular structures, in vitro antiproliferative studies and in vivo effects on glucose regulation

In order to better understand the antioxidant behavior of a series of polyphenolic 2′-hydroxychalcones, we describe the results of several chemical and biological studies, in vitro and in vivo. Single crystal X-ray methods elucidated their molecular structures and important intermolecular interactions such as H-bonding and molecular stacking in the crystal structures that contribute to our knowledge in explaining antioxidant activity. The results of experiments using the 1,1-diphenyl-2-dipicrylhydrazyl (DPPH) UV–vis spectroscopic method indicate that a hydroxyl group in position 5′ induces the highest antioxidant activity. Consequently, 2,2′,5′-trihydroxychalcone was selected for further study in vitro towards ROS scavenging in L-6 myoblasts and THP-1 human monocytes, where it shows an excellent antioxidant activity in a concentration range lower than that reported by most studies of related molecules. In addition, this chalcone shows a very selective activity: it inhibits the proliferation of leukemic cells, but it does not affect the normal L-6 myoblasts and human fibroblasts. In studying 2,2′,5′-trihydroxychalcone's effect on weight gain and serum glucose and insulin levels in Zucker fatty (fa⁻/fa⁻) rats we found that supplementing the diet with a 10 mg/kg dose of this chalcone (3 times weekly) blunted the increase in glucose that co-occurs with weight gain over the 6-week treatment period. It is concluded that 2,2′,5′-trihydroxychalcone has the potential to serve as a protective agent for some debilitating diseases.