Should attractive males have more sons?

It is often argued that females with attractive partners shouldproduce more sons because these sons will inherit their father'sattractiveness. Numerous field and laboratory studies have addressedthis hypothesis, with inconsistent results, but there is surprisinglylittle theoretical work on the topic. Here, we present an extensiveinvestigation of the link between male attractiveness and offspringsex ratios, using evolutionary, individual-based computer simulations.In situations where sexual selection leads to the stable exaggerationof a costly male trait and a costly female preference, we findthat females with attractive partners produce more sons thanfemales with unattractive partners. This same qualitative patternis seen for a wide range of different models, with discreteor continuous variation in the male trait, under Fisherian orgood-genes sexual selection and for abrupt or gradual sex ratioadjustment. However, in all simulations, it takes a huge numberof generations to evolve, suggesting that selection acting onsex ratio adjustment is weak. Our models ignore many potentialcosts and constraints associated with manipulation, which impliesthat selection may be weaker still in natural populations. Theseresults may explain why published evidence for sex ratio biasin relation to male attractiveness is mixed.     

Isolation of a methyl parathion-degrading strain <Emphasis Type="Italic">Stenotrophomonas</Emphasis> sp. SMSP-1 and cloning of the <Emphasis Type="Italic">ophc2</Emphasis> gene

A rod-shaped, gram-negative bacterium Stenotrophomonas sp. SMSP-1 was isolated from the sludge of a wastewater treating system of a pesticide manufacturer. Strain SMSP-1 could hydrolyze methyl parathion to p-nitrophenol (PNP) and dimethyl phosphorothioate but could not degrade PNP further. Strain SMSP-1 was able to hydrolyze other organophosphate pesticides, including fenitrothion, ethyl parathion, fenthion, and phoxim, but not chlorpyrifos. A 4395-bp DNA fragment, including an organophosphorus hydrolase encoding gene ophc2, was cloned from the chromosome of strain SMSP-1 using the shotgun technique. Its sequence analysis showed that ophc2 was associated with a typical mobile element ISPpu12 consisting of tnpA (encoding a transposase), lspA (encoding a lipoprotein signal peptidase), and orf1 (encoding a CDF family heavy metal/H⁺ antiporter). The ophc2 gene was effectively expressed in E. coli. This is the second report of cloning the ophc2 gene and the first report of this gene from the genus of Stenotrophomonas.     

Novel type II cell wall architecture in dichlobenil-habituated maize calluses

Growth of maize (Zea mays L.) callus-culture cells was inhibited using dichlobenil (2,6 dichlorobenzonitrile, DCB) concentrations ≥1 μM; I ₅₀ value for the effect on inhibited fresh weight gain was 1.5 μM. By increasing the DCB concentration in the culture medium, DCB-habituated cells became 13 times more tolerant of the inhibitor (I ₅₀: 20 μM). In comparison with non-habituated calluses, DCB-habituated calluses grew slower, were less friable and were formed by irregularly shaped cells surrounded by a thicker cell wall. By using an extensive array of techniques, changes in type II cell wall composition and structure associated with DCB habituation were studied. Walls from DCB-habituated cells showed a reduction of up to 75% in cellulose content, which was compensated for by a net increase in arabinoxylan content. Arabinoxylans also showed a reduction in their extractability and a marked increase in their relative molecular mass. DCB habituation also involved a shift from ferulate to coumarate-rich cells walls, and enrichment in cell wall esterified hydroxycinnamates and dehydroferulates. The content of polymers such as mixed-glucan, xyloglucan, mannans, pectins or proteins did not vary or was reduced. These results prove that the architecture of type II cell walls is able to compensate for deficiencies in cellulose content with a more extensive and phenolic cross-linked network of arabinoxylans, without necessitating β-glucan or other polymer enhancement. As a consequence of this modified architecture, walls from DCB-habituated cells showed a reduction in their swelling capacity and an increase both in pore size and in resistance to polysaccharide hydrolytic enzymes.     

Pseudozyma aphidis induces ethylene-independent resistance in plants

Species of the epiphytic fungus Pseudozyma are not pathogenic to plants and can be used as biocontrol agents against plant pathogens. Deciphering how they induce plant defense might contribute to their use for plant protection and expand our understanding of molecular plant–pathogen interactions. Here we show that Pseudozyma aphidis isolate L12, which is known to induce jasmonic acid- and salicylic acid-independent systemic resistance, can also activate local and systemic resistance in an ethylene-independent manner. We also show that P. aphidis localizes exclusively to the surface of the plant leaf and does not penetrate the mesophyll cells of treated leaves. We thus propose that P. aphidis acts via several mechanisms, and is an excellent candidate biocontrol agent.     

The effect of mercury accumulation on the intestinal glycosidase activity in perch <Emphasis Type="Italic">Perca fluviatilis</Emphasis> L. from aquatic bodies of European Russia with different pH

The intestinal glycosidase activities and kinetic characteristics of carbohydrate hydrolysis change in different ways with mercury accumulation in the muscles of perch from aquatic bodies of European Russia. Amylolytic activity decreases in fish from aquatic bodies with a neutral pH with a growth in Hg content (0.05–0.30 mg per 1 kg fresh weight), whereas sucrase increases. A decrease in the Michaelis constant for carbohydrate hydrolysis reflects an adaptive increase in enzyme-substrate affinity. In fish from acid lakes, the muscle Hg accumulation amounts to 0.18–0.86 mg per 1 kg fresh weight. With a growth in Hg content, the glycosidase activities and enzyme-substrate affinity decrease in most cases, having a negative effect on the assimilation rate of the carbohydrate components of food.     

Genotypic and phenotypic differentiation of Flavobacterium indologenes Yabuuchi et al 1983 from Flavobacterium gleum Holmes et al 1984

The type and eight strains of Flavobacterium indologenes were clearly differentiated from the type and two reference strains of Flavobacterium gleum by deoxyribonucleic acid-deoxyribonucleic acid homology data and phenotypic characteristics. Phenotypic characteristics useful to differentiate the two species are presented.     

Inhibition of interleukin-2 receptor (CD25) expression induced on T cells from children with acute lymphoblastic leukemia

 Peripheral blood lymphocytes obtained from children with acute lymphoblastic leukemia (ALL) at onset were studied for the expression of interleukin-2 (IL-2) receptor α-chain (CD25) by two-color flow-cytometric analysis. Stimulated with anti-CD3 monoclonal antibody (mAb) alone, CD25 expression was significantly suppressed in CD4⁺ T cells from 27 of 48 (56.3%) cases and in CD8⁺ T cells from 29 of 48 (60.4%) cases. When stimulated with anti-CD3 mAb plus phorbol 12-myristate 13-acetate (PMA), CD25 expression was clearly restored in certain cases of ALL. When PMA plus ionomycin were used for stimulation of T cells, CD25 was inducible in a majority of cases. Interestingly CD25 expression upon anti-CD3 mAb stimulation was recovered after complete remission had been achieved. These observations suggest the presence in ALL children at onset of an in vitro defect in the signal transduction pathway of the T-cell-receptor/CD3 complex, resulting in inefficient CD25 expression. However, immune-staining analysis indicated that protein kinase C was normally translocated from the cytosol fraction to the cell membrane fraction. The mobilization of cytoplasmic free calcium is also normal. Received: 27 March 1996 / Accepted: 23 December 1996