Actin Gene Sequence from Euglena gracilis

ABSTRACT The full length coding sequence of the Euglena gracilis actin gene was determined by RT-PCR of Euglena gracilis mRNA. Conserved regions in the actin amino acid sequence were used as guides for the synthesis of degenerate primers. Sequence was obtained for 1.238 nucleotides, of which 1.131 were coding for 377 amino acids. Sequence comparisons showed a similarity with other actins of 56% to 80%. Even though most of the actin amino acid sequence was conserved, some regions showed high divergence, i.e. the DNase I-binding loop at the N-terminal region. The construction of a phylogenetic tree based on actin sequences from different organisms placed Euglena gracilis in a cluster with Trypanosoma brucei and Leishmania major.     

An aminomethylpyrimidine DPP-IV inhibitor with improved properties

A recently identified DPP-IV inhibitor (1) was found to induce phospholipidosis and to inhibit CYP3A4. A small series of less lipophilic and less amphiphilic analogues was synthesized in an effort to overcome these issues. One compound from this series was equipotent to 1, did not induce phospholipidosis and showed a reduced CYP3A4 inhibition.     

The linear double-stranded DNA of phage Bam35 enters lysogenic host cells, but the late phage functions are suppressed

Bam35, a temperate double-stranded DNA bacteriophage with a 15-kb linear genome, infects gram-positive Bacillus thuringiensis cells. Bam35 morphology and genome organization resemble those of PRD1, a lytic phage infecting gram-negative bacteria. Bam35 and PRD1 have an outer protein coat surrounding a membrane that encloses the viral DNA. We used electrochemical methods to investigate physiological changes of the lysogenic and nonlysogenic hosts during Bam35 DNA entry and host cell lysis. During viral DNA entry, there was an early temporal decrease of membrane voltage associated with K+ efflux that took place when either lysogenic or nonlysogenic hosts were infected. Approximately 40 min postinfection, a second strong K+ efflux was registered that was proposed to be associated with the insertion of holin molecules into the plasma membrane. This phenomenon occurred only when nonlysogenic cells were infected. Lysogenic hosts rarely were observed entering the lytic cycle as demonstrated by thin-section electron microscopy.     

Hmi1p from Saccharomyces cerevisiae mitochondria is a structure-specific DNA helicase

Hmi1p is a Saccharomyces cerevisiae mitochondrial DNA helicase that is essential for the maintenance of functional mitochondrial DNA. Hmi1p belongs to the superfamily 1 of helicases and is a close homologue of bacterial PcrA and Rep helicases. We have overexpressed and purified recombinant Hmi1p from Escherichia coli and describe here the biochemical characteristics of its DNA helicase activities. Among nucleotide cofactors, the DNA unwinding by Hmi1p was found to occur efficiently only in the presence of ATP and dATP. Hmi1p could unwind only the DNA substrates with a 3'-single-stranded overhang. The length of the 3'-overhang needed for efficient targeting of the helicase to the substrate depended on the substrate structure. For substrates consisting of duplex DNA with a 3'-single-stranded DNA overhang, at least a 19-nt 3'-overhang was needed. In the case of forked substrates with both 3'- and 5'-overhangs, a 9-nt 3'-overhang was sufficient provided that the 5'-overhang was also 9 nt in length. In flap-structured substrates mimicking the chain displacement structures in DNA recombination process, only a 5-nt 3'-single-stranded DNA tail was required for efficient unwinding by Hmi1p. These data indicate that Hmi1p may be targeted to a specific 3'-flap structure, suggesting its possible role in DNA recombination.     

Sexual differences in growth strategies of the wolf spider Hygrolycosa rubrofasciata

In invertebrates, the size at maturation is considered to be important for adult fitness. In the wolf spider Hygrolycosa rubrofasciata, however, it is only females that clearly benefit of larger size through augmented egg production, while male mating success is determined by display activity not related to size. Thus, we can expect conflicting growth patterns for the sexes. Additionally, populations differ greatly in adult size: individuals from dry habitats are smaller than those from wet habitats. To study the sexual differences in reaction norms of growth, we reared spiderlings from seven populations at two food levels under controlled laboratory conditions and compared size at sexual maturity. The shapes of reaction norms for adult size differed between the sexes. In females, the reaction norms were parallel, but individuals from dry habitats tended to grow larger at the given food levels. In males, there was a significant interaction between food level and population without any consistent differences between populations. Maturation time was a plastic character in both sexes with no genetic differences among populations. However, females on low food level matured later and significantly smaller in size than those on high food level. Males also matured later on low food level, but they were nearly of the same size as males that received more food. Female growth patterns reflected the strong selection for large size at maturity. However, the patterns for males were highly variable, which could be explained by the weak overall selection on male size, which means that any environmental factors can affect male growing patterns. This revised version was published online in November 2006 with corrections to the Cover Date.     

Geographic variation in adult and embryonic desiccation tolerance in a terrestrial-breeding frog

Intraspecific variation in the ability of individuals to tolerate environmental perturbations is often neglected when considering the impacts of climate change. Yet this information is potentially crucial for mitigating deleterious effects of climate change on threatened species. Here we assessed patterns of intraspecific variation in desiccation tolerance in the frog Pseudophryne guentheri, a terrestrial-breeding species experiencing a drying climate. Adult frogs were collected from six populations across a rainfall gradient and their dehydration and rehydration rates were assessed. We also compared desiccation tolerance of embryos and hatchlings originating from within-population parental crosses from four of the populations. Embryos were reared on soil at three soil–water potentials and their desiccation tolerance was assessed across a range of traits. We found significant and strong patterns of intraspecific variation in almost all traits, both in adults and first-generation offspring. Adult frogs exhibited clinal variation in their water balance responses, with populations from drier sites both dehydrating and rehydrating more slowly compared to frogs from more mesic sites. Similarly, desiccation tolerance of first-generation offspring was significantly greater in populations from xeric sites. Our findings suggest that populations within this species will respond differently to the regional reduction in rainfall predicted by climate change models.     

Temporal associations between daytime physical activity and sleep in children

Objectives

We examined temporal associations between objectively-measured physical activity (PA) during the day and in the evening, and sleep quantity and quality.

Study Design

PA and sleep were measured by actigraphs for an average of one week in an epidemiological cohort study of 275 eight-year-old children.

Results

For each one standard deviation (SD) unit of increased PA during the day, sleep duration was decreased by 0.30, sleep efficiency by 0.16, and sleep fragmentation increased by 0.08 SD units that night. For each one SD unit increase in sleep duration and efficiency the preceding night, PA the following day decreased by 0.09 and 0.16 SD units, respectively. When we contrasted days with a high amount of moderate to vigorous activity during the day or in the evening to days with a more sedentary profile, the results were essentially similar. However, moderate to vigorous PA in the evening shortened sleep latency.

Conclusions

The relationship between a higher level of PA and poorer sleep is bidirectional. These within-person findings challenge epidemiological findings showing that more active people report better sleep. Since only a few studies using objective measurements of both PA and sleep have been conducted in children, further studies are needed to confirm/refute these results.