Appearance of a factor stimulating oocyte maturation in the karyoplasm of the oocytes of the green toad, the clawed toad and the starred sturgeon

The karyoplasm (the contents of germinal vesicle) of the Bufo viridis, Xenopus laevis, and Acipenser stellatus oocytes maturing under the influence of progesterone acquires the ability to induce the maturation (germinal vesicle breakdown) of the full grown oocytes, when injected into them. This ability arises in the karyoplasm earlier than in the cytoplasm and is preserved until the germinal vesicle breakdown.     

Genotype and phenotype associations with drought tolerance in barley tested in North Africa

A review is presented of genetic strategies deployed in a 3-yr project on drought tolerance in barley. Data were collected on genetic, physiological and agronomic traits in non-irrigated and irrigated field trials in Egypt, Morocco and Tunisia. A wide range of barley germplasm (developed from African and European cultivars, adapted landraces and wild barleys) was tested, and positive traits were found in each gene pool. The contrasting environments of the three North African countries had major effects on plant/genotype performance. Genetic effects were also detected, as were genotype × environment interactions. A range of strategies were deployed to investigate the physiology and genetics of quantitative traits associated with field performance. Quantitative trait locus (QTL) analysis was performed using backcross lines, recombinant inbred lines and doubled haploid mapping populations. A detailed genetic map was generated in the Tadmor × (ER/Apm) recombinant inbred lines, an important mapping population specifically developed by ICARDA (Centre for Agricultural Research in Dry Areas) and CIMMYT (International Maize and Wheat Improvement Center) to study drought. Quantitative trait loci (QTLs) for grain yield and other important morphological and physiological traits were also identified in a population of doubled haploids derived from F2BCj plants from a cross between a cultivar and a wild barley accession. Significantly, the wild parental line was found to contribute a number of positive alleles for yield. Effects of major developmental genes could explain many of the responses observed. QTLs were found to cluster around major genes controlling flowering time (sghI), plant stature (sdwI and arie.GP) and ear type (vrsl), and it is highly likely that the associations represent pleiotropic effects. Some QTLs were associated with candidate genes such as dehydrins and rubisco activase. One of the most significant results was the identification and generation of material that out performed the best local standards in the three participating North African countries; the selected lines have now entered local breeding programmes. The strategies adopted provided information on physiological traits, genotypes and genetic markers that could be used for marker-assisted selection. Target QTLs and their associated genetic markers may be deployed in marker assisted selection programmes to match crop phenology to the field environment.     

Modifications of anionic-lipid domains preceding membrane fusion in guinea pig sperm

The relationship between anionic-lipid concentration and the functional properties of plasma-membrane domains was explored using the guinea-pig sperm membrane as a model, with polymyxin B (PXB) as a probe. Areas of plasmalemma specialized for fusion during the acrosome reaction had a higher affinity for the probe than adjacent nonfusigenic regions. In addition, capacitation--a process preceding acrosome:plasma-membrane fusion--markedly enlarged the area susceptible to PXB binding over the acrosomal cap. Protease treatment mimicked capacitation by increasing the acrosome-reaction incidence as well as PXB binding, at enzyme concentrations not affecting the surface coat nor altering filipin/sterol localization. Both proteolytic digestion and capacitation failed to augment PXB- or filipin-affinity in nonfusigenic zones, such as the post-acrosomal segment, including its particle-free maculae. Incubation of sperm in capacitating medium supplemented with 32P-labeled phosphate, followed by lipid extraction, thin-layer chromatography, and autoradiography, revealed a radioactive band comigrating with cardiolipin and phosphatidic acid. Vermiform protrusions elicited by PXB in the outer lamellae of cardiolipin- phosphatidylcholine liposomes resembled those seen in fusional regions of sperm membrane. We conclude that (a) differing concentrations of anionic lipids are found in adjacent domains of the sperm plasma membrane; (b) these domains mirror the functional regions of the membrane, with higher anionic-lipid concentrations localized over fusional zones; (c) the surface coat does not participate in the maintenance of such domains; (d) anionic-lipid synthesis may contribute to their formation; and (e) anionic-lipid concentrations increase as the membrane becomes fusionally competent, indicating that cellular modulation of lipid domains accompanies regulation of membrane function.     

Photosynthetic oxygen evolution and CO2 photoassimilation by cyanobacteria that form water-bloom spots in a sulfur spring with a high sulfide content

Cyanobacteria belonging mainly to the genera Anabaena and Oscillatoria were isolated from water-bloom spots of a sulfur spring in Staraya Matsesta. Their suspensions evolved O2 at a rate of 6--8 nM/min per 1 mg of dry cell weight at an intensity of solar radiation being 60--75 mV/cm2 per 1 sec. The cells were also capable of CO2 photoassimilation in the presence of solfide at a rate of 10(-4) mg C per mg per hour. DCMU at a concentration of 10(-5) M completely inhibited O2 evolution and inhibited CO2 fixation by 80%. Oxygen assimilation in dark by the suspensions did not depend on the addition of cyanide and was caused apparently by nonenzymatic reduction of O2 with sulfide dissolved in the spring water. Oxygen assimilation by the suspensions in light in the presence of DCMU was by 20--30% greater than in dark. Therefore, the cells of cyanobacteria are characterized by photorespiration at the level of photosystem I. Presumably, sulfide at a concentration of 9 mM cannot significantly inhibit the photosynthetic processes in cyanobacteria producing water-bloom spots in the sulfur spring.     

Enzymes of the xylotrophic basidiomycete Lentinus edodes F-249 in the course of morphogenesis

It has been shown that the fungus Lentinus edodes grown on a solid wort agar substrate produces intracellular enzymes, including Mn-dependent peroxidase, laccase, and tyrosinase as a family of isoforms. The composition of the complex (containing one to four forms of each enzyme) varied during the basidiomycete life cycle. The activity of oxidases was maximal at the stage of nonpigmented mycelium and at the stages of a brown mycelial mat and a fruit body. The activity of tyrosinase increased in the course of mycelium pigmentation and had two maxima: at the stage of a brown mycelial mat and at the stage of a fruit body. Laccase and tyrosinase activities were shown to increase sharply upon addition of oak sawdust extract to the culture medium as compared with the enzyme activities of mycelium grown on wort agar alone. It was established that the effect of phenol oxidase substrates on the growing mycelium consists in a twofold acceleration of the process of morphogenesis in the fungus L. edodes.     

Sentinel systems on the razor's edge: effects of warming on Arctic geothermal stream ecosystems

The Earth is experiencing historically unprecedented rates of warming, with surface temperatures projected to increase by 3–5 °C globally, and up to 7.5 °C in high latitudes, within the next century. Knowledge of how this will affect biological systems is still largely restricted to the lower levels of organization (e.g. species range shifts), rather than at the community, food web or ecosystem level, where responses cannot be predicted from studying single species in isolation. Further, many correlational studies are confounded with time and/or space, whereas experiments have been mostly confined to laboratory microcosms that cannot capture the true complexity of natural ecosystems. We used a ‘natural experiment’ in an attempt to circumvent these shortcomings, by characterizing community structure and trophic interactions in 15 geothermal Icelandic streams ranging in temperature from 5 °C to 45 °C. Even modest temperature increases had dramatic effects across multiple levels of organization, from changes in the mean body size of the top predators, to unimodal responses of species populations, turnover in community composition, and lengthening of food chains. Our results reveal that the rates of warming predicted for the next century have serious implications for the structure and functioning of these fragile ‘sentinel’ ecosystems across multiple levels of organization.     

Lectin activity of Lentinus edodes

The hemagglutinating activity of submerged mycelium and culture liquid for four strains of Lentinus edodes (Berk.) Sing [L. edodes (Berk.) Pegler] was studied in the search for lectins. The hemagglutinating activity of culture liquid was substantially higher, compared with mycelium. The carbohydrate-binding capacity of the agglutinins was established, and the lectin activity of extracts from mycelia grown on several agar media was elucidated in relation to fruiting. The lectin activity of L. edodes was examined at different morphogenetic steps: mycelium, brown mycelial film, primordium, and fruiting body. Hemagglutination titers at the brown film step were higher than in the mycelium, whereas activity at the primordial and fruiting bodies steps decreased. Lectins seem to be involved in the formation of hyphal aggregates of brown mycelial film.