Effect of the Nematode Contortylenchus brevicomi on Gallery Construction and Fecundity of the Southern Pine Beetle

Field-collected Dendroctonus frontalis were reared in a controlled environment. Male-female beetle pairs retrieved from galleries 1, 2, or 5 wk after introduction into pine bolts were examined for nematode parasites. Data were obtained for each pair on gallery length, egg niche construction, egg viability, and progeny survival. In a separate study, beetle pairs were reared under laboratory conditions for 10 wk. The number of emerged adult progeny of each pair was recorded. Contortylenchus brevicomi, a nematode parasite, was found in 25% of all beetles that established galleries. After 2 and 3 wk, female beetles infected with the nematode had produced fewer eggs and shorter galleries than did uninfected females. Uninfected females mated with nematode-infected males showed similar trends, although the differences in the 2- and 3-wk tests were not significant. Progeny survival or egg viability was not affected by nematode parasitism of either parent beetle. Unikaryon minutum, a microsporidian parasite found in 65% of all colonizing beetles, had no effect on measured variables. The lower fecundity of beetles parasitized by C. brevicomi continued throughout the insect''s reproductive cycle. After 10 wk, nematode-infected beetle pairs produced fewer emerged adult progeny than did uninfected pairs.     

Effect of light and temperature on epicuticular fatty acid and fatty alcohol of tobacco

Genetically uniform burley tobacco (Nicotiana tabacum) was grown under field and various controlled-environment conditions to determine whether environment influenced epicuticular alkane, fatty acid, and fatty-alcohol composition of the leaves. Quantity and quality of alkanes, fatty acids, and fatty alcohols were greatly influenced by environmental conditions. Highest light intensity did not result in the largest total long aliphatic carbon-chain production. Generally, long photoperiod and cool temperature were associated with highest long aliphatic carbon-chain production on a leaf area basis. Quantity of the individual alkane, fatty acid, or fatty alcohol classes present under the different growth conditions varied in relation to the leaf metabolic status and not leaf size.     

Dilatometric study of binary mixtures of phosphatidylcholines.

Volumes of lipid dispersions as a function of temperature have been measured for two different kinds of binary mixtures of lecithins, (1) DMPC and DSPC and (2) DMPC and DC20PC. Emphasis was placed on DMPC-rich compositions so as to resolve ambiguities regarding solid-phase immiscibility in DMPC-DSPC mixtures. Special attention has been paid to problems of equilibration in the low-temperature phase and to methods of mixing the lipids. We find that there is no solid-solid immiscibility in DMPC-DSPC mixtures, although this system is close to exhibiting such immiscibility, and that DMPC-DC20PC mixtures exhibit pronounced solid immiscibility.     

A comparison of chromosomal and allozymal variation across a narrow hybrid zone in the grasshopper Caledia captiva

A hybrid zone between the Moreton and Torresian taxa of the grasshopper Caledia captiva in S.E. Queensland has been characterised in terms of allozyme and chromosome variation within the same individuals. — On chromosomal criteria (pericentric rearrangements), the zone is asymmetrical with evidence of high levels of introgression of Torresian chromosomes into the Moreton taxon. This is apparent from the analysis of two independent transects across the hybrid zone. Major changes in chromosomal frequency occur over distances of less than 0.5 km. and the level of introgression differs between the two transects, with much higher levels in the northern Moreton populations, characterised by an acrocentric X-chromosome, when compared with the southern metacentric-X Moreton populations. Chromosome analysis of samples taken from the same transect over two years has revealed no major changes in the structure of the zone. Moreover, a Moreton population located only 0.5 km. from the null point was found to be stable over 6 generations with evidence for a new balanced genome having originated following the differential incorportation of Torresian chromosomes. — Contrary to the chromosomal situation, the same hybrid zone was found to be symmetrical with respect to allozyme variation with evidence of movement of diagnostic alleles in both directions across the zone. The alleles are independent and not tightly linked to any of the pericentric rearrangements. Thus these 5 alleles are acting as markers of the background genome and reveal the relatively free movement of genes which are located outside the pericentric rearrangements. — It is proposed that the hybrid zone in Caledia captiva is unstable and is moving slowly in a westerly direction into the Torresian territory. This is due to the ability of the Moreton taxon to incorporate more readily into its genome those Torresian chromosomes or chromosome segments which increase the fitness of the Moreton taxon. On chromosomal criteria, the Torresian taxon does not share the same capacity. — It is suggested that, so long as the two taxa retain their ability to hybridise with subsequent asymmetrical introgression, the zone will continue to move westwards and eventually lead to the selective incorporation of the Torresian genome into the Moreton taxon. This will result in a polymorphic situation with clinal variation in chromosomal frequencies. The structure of the zone is dependent upon a fine balance between genomic reorganisation in recombinant genotypes and the relative dispersal capacities of the two hybridising taxa.     

The effects of chemotactic factors on the adhesiveness of rabbit neutrophil granulocytes.

A range of chemotactic factors has been shown to affect the adhesion of rabbit peritoneal neutrophil granulocytes to cultured endothelial cells and to serum-coated glass. At chemotactically optimal concentrations, α_s-casein, β-casein, alkali denatured human serum albumin (HSA) and several synthetic formyl-peptides reduced the number of adherent neutrophils after 30 min to around 50% of control values. These effects were still observed after neutrophils, but not endothelium or serum-coated glass had been exposed to chemotactic factors and washed before use in assays. Two non-chemotactic analogues, native HSA and a non-formyl-peptide were ineffective. The dose responses for adhesion after 30 min in the presence of α_s-casein and formyl-methionyl-leucyl-phenylalanine (FMLP) were found to be inversely related to those for migration towards these substances. After incubation for 60 min in high (10^?8–10^?7 M) concentrations of FMLP, neutrophil adhesion was found to be enhanced. Neutrophil aggregation was also affected by the presence of chemotactic factors in a similar time- and dose-dependent manner to the adhesion to substratum assays. Using FMLP, it was also shown that the timing of the adhesive changes depended on the concentration of chemotactic factor present.     

Bdellovibrio-like parasite of cyanobacteria symbiotic in marine sponges

A bdellovibrio-like bacterium was observed infecting unicellular symbiotic cyanobacteria in two coral reef sponges, Neofibularia irata and Jaspis stellifera. The infecting bacterium, which was located between the cell wall and the cytoplasmic membrane of the cyanobacteria, was similar in size and appearance to previously described bdellovibrios. This observation is believed to extend the host range of the bdellovibrios.     

Lecithin bilayers. Density measurement and molecular interactions.

Density measurement are reported for bilayer dispersions of a series of saturated lecithins. For chain lengths with, respectively, 14, 15, 16, 17, and 18 carbons per chain, the values for the volume changes at the main transition are 0.027, 0.031, 0.037, 0.040 and 0.045 ml/g. The main transition temperature extrapolates with increasing chain length to the melting temperature of polyethylene. Volume changes at the lower transition are an order of magnitude smaller than the main transition. Single phase thermal expansion coefficients are also reported. The combination of X-ray data and density data indicated that the volume changes are predominantly due to the hydrocarbon chains, thus enabling the volume vCH2 of the methylene groups to be computed as a function of temperature. From this and knowledge of intermolecular interactions in hydrocarbon chains, the change in the interchain van der Waals energy, delta UvdW, at the main transition is computed for the lecithins and also for the alkanes and polyethylene at the melting transition. Using the experimental enthalpies of transition and delta UvdW, the energy equation is consistently balanced for all three systems. This yields estimates of the change in the number of gauche rotamers in the lecithins at the main transition. The consistency of these calculations supports the conclusion that the most important molecular energies for the main transition in lecithin bilayers are the hydrocarbon chain interactions and the rotational isomeric energies, and the conclusion that the main phase transition is analogous to the melting transition in the alkanes from the hexagonal phase to the liquid phase, but with some modifications.     

The optical birefringence of DNA solutions induced by oscillatory electric and hydrodynamic fields

The optical birefringence induced in DNA solutions by both oscillating hydrodynamic fields (flow birefringence) and oscillating electric fields (Kerr effect) is measured over a wide frequency range. The observed frequency response of the birefrigence is compared with theories for rigid ellipsoidal particles and for Gaussian chains. DNA at 6 × 10⁵ molecular weight is found to exhibit rigid particle hydrodynamic behavior, while DNA at 5 × 10⁶ molecular weight behaves like a flexible chain. Characterization of the hydrodynamic relaxation spectra for the DNA's by oscillatory flow birefringence allows precise comparison between theory and the experimental Kerr effect response. The dielectric model for DNA contains both permanent and dispersionless induced dipole moments. The dielectric behavior of DNA has the character of a permanent dipole but with anomalous low-frequency dispersion in the Kerr effect. The existing theories do not adequately describe this dispersion. A fluctuation dipole mechanism with relaxation times comparable to those associated with the hydrodynamic motion could possibly demonstrate the observed polar behavior.     

Automated adsorption isotherm device.

A device is described for the automated determination of the water adsorption isotherms of biological materials. The vapor pressure and weight of the adsorbate are measured directly with appropriate transducers, and equilibrium is defined on the basis of constant pressure. The accuracy of the device, determined on two samples with well-known water binding properties, is +/- 5%. Automation is achieved by electronic control.