Glacial refugia and reticulate evolution: the case of the Tasmanian eucalypts

Tasmania is a natural laboratory for investigating the evolutionary processes of the Quaternary. It is a large island lying 40-44 degrees S, which was repeatedly glaciated and linked to southeastern continental Australia during the Quaternary. Climate change promoted both the isolation of species in glacial refugia, and an exchange between Tasmanian and mainland floras. Eucalyptus is a complex and diverse genus, which has increased in abundance in Australia over the past 100 kyr, probably in response to higher fire frequency. Morphological evidence suggests that gene flow may have occurred between many eucalypt species after changes in their distribution during the Quaternary. This paper summarizes recent genetic evidence for migration and introgressive hybridization in Tasmanian Eucalyptus. Maternally inherited chloroplast DNA reveals a long-term persistence of eucalypts in southeastern Tasmanian refugia, coupled with introgressive hybridization involving many species. Detailed analysis of the widespread species Eucalyptus globulus suggests that migration from mainland Australia was followed by introgression involving a rare Tasmanian endemic. The data support the hypothesis that changes in distribution of interfertile species during the Quaternary have promoted reticulate evolution in Eucalyptus.     

Two-dimensional polyacrylamide gel electrophoresis of chromatin proteins of normal rat liver and Novikoff hepatoma ascites cells

Chromatin was prepared from the citric acid nuclei of normal rat liver and Novikoff hepatoma ascites cells. After sulfuric acid extraction, the dehistonized chromatin was solubilized by digestion with deoxyribonuclease I. The proteins of normal liver and of Novikoff hepatoma chromatin fractions were analyzed by two-dimensional polyacrylamide gel electrophoresis. The liver pattern contained 69 components and the hepatoma pattern contained 84 components. Comparison of the two patterns revealed two dense protein spots migrating in the B region in the liver pattern that were absent from the tumor pattern and two dense protein spots migrating in the C region in the tumor pattern that were absent from the liver pattern.     

Gene expression profiling during thymus ontogeny and its association with TCRVβ8.1-Dβ2.1 rearrangements of inbred mouse strains

The V(D)J recombination of TCR and in early developing T-cells is a highly modulated phenomenon initiated and completed by recombinase complex (RAG-1 and RAG-2), and regulated by other gene products such as interleukins. To further evaluate the association of several other gene products with the evolution of TCRV8.1 V(D)J rearrangements in vivo, the mRNA expression levels of seven interleukins, three cytokines, receptors TCRV8.1 and IL-2R, MHC-I/MHC-II, RAG-1/RAG-2 and retroviral superantigen MMTV(SW) were measured by RT-PCR during the fetal development of the thymus of three inbred mouse strains (Balb-c, C57Bl/6 and CBA/J). Clustering using the Tree View software, was used to organize these genes based on similarity of expression patterns. Each strain displayed a different expression profile during thymus ontogeny.During the late developmental stage the most evident association was the kinetics of MMTV(SW) retrovirus, IL-2R and IL-7 overexpression with reduction of TCRV8.1-D2.1 rearrangement in the thymus of CBA/J mice. These data suggest a susceptibility of this strain to expression of MMTV(SW) upon reduction of the rearranged TCRV8.1-D2.1 segment in developing thymocytes, with parallel IL-7 overexpression.     

Cryopreservation of peripheral blood mononuclear cells does not significantly affect the levels of spontaneous apoptosis after 24-h culture

Studies performed with malaria patients living in endemic areas are frequently conducted in laboratories located hundreds of kilometer away from research centers, due to the difficulties in performing the assays in field conditions. Thus, we considered the potential indication of cryopreservation of peripheral blood mononuclear cells (PBMC), in most fieldwork, and decided to evaluate the effect of cryopreservation of PBMC on spontaneous apoptosis. The membrane integrity of PBMC was tested using three previously described protocols of cryopreservation. Cell samples were obtained from 19 healthy volunteers. Percentage of apoptotic nuclei in short-term PBMC cultures was determined by a sensitive method using 7-aminoactinomycin D followed by flow cytometry. Our results indicate that although cryopreservation can to some extent affect lymphocyte membrane integrity rates, flow cytometry analysis showed that frequencies of spontaneous apoptosis in cryopreserved cells were not significantly modified after 24-h culture. It is concluded that cryopreserved PBMC could be used for measuring spontaneous apoptosis and therefore, could be employed for the study of populations living in areas distant from research centers, allowing the comparative evaluation of samples obtained at different time.     

Disulfiram-based disulfides as narrow-spectrum antibacterial agents

Sixteen disulfides derived from disulfiram (Antabuse?) were evaluated as antibacterial agents. Derivatives with hydrocarbon chains of seven and eight carbons in length exhibited antibacterial activity against Gram-positive Staphylococcus, Streptococcus, Enterococcus, Bacillus, and Listeria spp. A comparison of the cytotoxicity and microsomal stability with disulfiram further revealed that the eight carbon chain analog was of lower toxicity to human hepatocytes and has a longer metabolic half-life. In the final analysis, this investigation concluded that the S-octylthio derivative is a more effective growth inhibitor of Gram-positive bacteria than disulfiram and exhibits more favorable cytotoxic and metabolic parameters over disulfiram.     

Karyotypic study of titi monkeys,Callicebus moloch brunneus

A karyotypic study on a subspecies of the dusky titi,Callicebus moloch brunneus, was carried out and a third karyotype ofC. moloch was discovered. The chromosome number of this subspecies is 48. The autosomes consist of 5 subtelocentric, 5 submeta- or metacentric, and 13 acrocentric chromosome pairs. The X chromosome and the Y chromosome are submetacentric and metacentric, respectively. A comparative study with other subspecies of theC. moloch group (i.e.,C. m. cupreus andC. m. ornatus with 2n=46 andC. m. donacophilus with 2n=50) suggests that the karyotype ofbrunneus occupies a position intermediate between the two other karyotypes ofC. moloch, but nearer to that of 2n=50. The presumed total differences betweenbrunneus andcupreus comprise one Robertsonian rearrangement, one centromeric transposition and four pericentric inversions, and those betweenbrunneus anddonacophilus involve one translocation or breakage (possibly corresponding to two events, that is, one Robertsonian rearrangement and one centromeric transposition).     

Swi1 Associates with Chromatin through the DDT Domain and Recruits Swi3 to Preserve Genomic Integrity

Swi1 and Swi3 form the replication fork protection complex and play critical roles in proper activation of the replication checkpoint and stabilization of replication forks in the fission yeast Schizosaccharomyces pombe. However, the mechanisms by which the Swi1-Swi3 complex regulates these processes are not well understood. Here, we report functional analyses of the Swi1-Swi3 complex in fission yeast. Swi1 possesses the DDT domain, a putative DNA binding domain found in a variety of chromatin remodeling factors. Consistently, the DDT domain-containing region of Swi1 interacts with DNA in vitro, and mutations in the DDT domain eliminate the association of Swi1 with chromatin in S. pombe cells. DDT domain mutations also render cells highly sensitive to S-phase stressing agents and induce strong accumulation of Rad22-DNA repair foci, indicating that the DDT domain is involved in the activity of the Swi1-Swi3 complex. Interestingly, DDT domain mutations also abolish Swi1's ability to interact with Swi3 in cells. Furthermore, we show that Swi1 is required for efficient chromatin association of Swi3 and that the Swi1 C-terminal domain directly interacts with Swi3. These results indicate that Swi1 associates with chromatin through its DDT domain and recruits Swi3 to function together as the replication fork protection complex.     

Global similarity and local divergence in human and mouse gene co-expression networks

Background  

A genome-wide comparative analysis of human and mouse gene expression patterns was performed in order to evaluate the evolutionary divergence of mammalian gene expression. Tissue-specific expression profiles were analyzed for 9,105 human-mouse orthologous gene pairs across 28 tissues. Expression profiles were resolved into species-specific coexpression networks, and the topological properties of the networks were compared between species.