Brain gangliosides in monotremes, marsupials and placentals: phylogenetic and thermoregulatory aspects

The concentration and composition of brain gangliosides of 17 mammalian species belonging to the subclasses of Prototheria (monotremes), Metatheria (marsupials), and Eutheria (placentals) were investigated. The mean concentration of brain gangliosides ranges from 525 to 610 micrograms NeuAc/g wet wt in monotremes, 445-900 micrograms in marsupials and from 630 to 1130 micrograms in the placentals. In the phylogenetic series of mammals, a decrease in the complexity of brain ganglioside composition becomes obvious: a drastic reduction in the number of individual ganglioside fractions particularly those of the c-pathway of biosynthesis, took place from the level of monotremes to that of the marsupials and placentals. In monotremes, marsupials and "lower" placentals (insectivores) the percentage of alkali-labile gangliosides is relatively low (between traces and 5%), whereas in the higher evolved mammals it amounts to about 20% of all gangliosides. The ratio of the contents of the two major mammalian ganglioside fractions GD1a and GT1b is generally in the range of 1.0 and even higher; in the heterothermic platypus from the monotremes and in hibernators among the placental mammals, however, it is much lower (about 0.8). These data support the hypothesis that the brain ganglioside composition not only depends on the phylogenetic level of nervous organization (cephalization) but is additionally correlated with the state of thermal adaptation.     

Prolonged and daily torpor in the feathertail glider, Acrobates pygmaeus (Marsupialia: Acrobatidae)

Deep and prolonged torpor in marsupials is only known from the pygmy possums, family Burramyidae. We investigated the pattern of torpor in the feathertail glider Acrobates pygmaeus (Acrobatidae) to determine whether members of other marsupial families also possess the ability of remaining torpid for several days with body temperatures (T_b) approaching 0°C. At high air temperatures (T_a) of 15 and 20°C, A. pygmaeus usually exhibited daily torpor. Torpor bouts at T_a 12°C usually lasted for about 2˙5 days and at T_a 8°C up to 5˙5 days. The metabolic rate during torpor was reduced to about 1% of that in normothermic, resting individuals. The T_b during torpor was regulated at about 2°C when T_a fell below about 0˙8 °C. Arousal from torpor was rapid and the mean fastest rewarming rate was 0˙88°C/min. While A. pygmaeus exhibited deep and prolonged torpor, its pattern differed somewhat from deep hibernation. Acrobates pygmaeus did not show prehibernation fattening and a subsequent prolonged hibernation period and it appears that prolonged torpor is used only in emergency situations.     

Saccharomyces cerevisiae genes required in the absence of the CIN8-encoded spindle motor act in functionally diverse mitotic pathways.

Kinesin-related Cin8p is the most important spindle-pole-separating motor in Saccharomyces cerevisiae but is not essential for cell viability. We identified 20 genes whose products are specifically required by cell deficient for Cin8p. All are associated with mitotic roles and represent at least four different functional pathways. These include genes whose products act in two spindle motor pathways that overlap in function with Cin8p, the kinesin-related Kip1p pathway and the cytoplasmic dynein pathway. In addition, genes required for mitotic spindle checkpoint function and for normal microtubule stability were recovered. Mutant alleles of eight genes caused phenotypes similar to dyn1 (encodes the dynein heavy chain), including a spindle-positioning defect. We provide evidence that the products of these genes function in concept with dynein. Among the dynein pathway gene products, we found homologues of the cytoplasmic dynein intermediate chain, the p150Glued subunit of the dynactin complex, and human LIS-1, required for normal brain development. These findings illustrate the complex cellular interactions exhibited by Cin8p, a member of a conserved spindle motor family.     

The metamorphic switch in hemoglobin phenotype ofXenopus laevis involves erythroid cell replacement

Summary To elucidate the cellular basis of hemoglobin transition inXenopus laevis the distribution of larval and adult hemoglobins was analyzed by indirect immunofluorescence in the circulating erythrocytes during metamorphosis. In addition, the morphological characteristics as well as the capacity for synthesis of DNA and hemoglobin in the erythrocytes were followed during the same developmental period. Our quantitative analysis on the distribution of larval and adult hemoglobins suggests that they are localized in different cells. Hemoglobin transition, therefore, most likely reflects replacement of the larval erythrocyte population by new cells which are committed to adult globin synthesis. Since hemoglobin transition is not accompanied by an increase in the abundance of immature erythroid cells with active DNA synthesis, we assume that the presumptive adult erythroid cells are released into circulation at a relatively advanced stage of maturation. The decline in the synthesis of DNA and larval hemoglobin further indicates that cessation of cell renewal in the larval erythrocyte population may represent a decisive step in hemoglobin transition.     

Efficient transformation of Bacillus thuringiensis and B. cereus via electroporation: Transformation of acrystalliferous strains with a cloned delta-endotoxin gene

Summary Electroporation was used as a method to transform intact cells of Bacillus thuringiensis and B. cereus. With our optimized method a range of plasmid vectors could be transformed into strains of B. thuringiensis at frequencies of up to 10⁷ transformants/g DNA. This high frequency allows cloning experiments to be bone directly in B. thuringiensis. A bifunctional vector capable of replicating in Escherichia coli and in Bacillus spp. was constructed. The kurhd1 protoxin gene was cloned into this shuttle vector to produce plasmid pXI93, then transformed into B. thuringiensis HDl cryB and B. cereus 569K. The cloned protoxin gene was expressed in sporulating cultures of both strain HD1 cryB (pXI93) and 569K (pXI93), producing crystal protein active in biotests against larvae of Heliothis virescens. This demonstrates the usefulness of the electroporation method for the introduction of cloned toxin genes, in either their native or modified form, into a variety of host strains.     

Long-term effects of ungulates on phytophagous insects

Abstract.  1. Most plants interact with a diverse suite of herbivores, allowing the opportunity for the existence of positive and negative interactions between highly dissimilar organisms. However, most studies on herbivorous interactions have been performed under the assumption that they occur mainly between similar species. Consequently, ecologists are still far from a full understanding of the ecological factors that determine insect population dynamics.
2. In this study, a 7-year field experiment was conducted that manipulated the presence of ungulates to evaluate their effects on the abundance, attack rate, and survival of four guilds of co-occurring herbivorous insects living on the same host plant: seed predators, stem borers, gall makers and sap suckers. These four guilds differed in habits and behaviour, the first three being sessile and endophytic and the last being free-living.
3. This study shows that the abundance of all four guilds was negatively affected by ungulates. However, the effect on attack rate differed among guilds, as mammals do not affect the seed predator attack rate. Ungulates also differentially affected insect survival, ingesting only seed predators and gall makers.
4. In summary, this study suggests that diverse mechanisms may affect different insect guilds in different ways. Therefore, competition between disparate herbivores appears to be complex and can be provoked by multiple mechanisms.