Mitochondrial phylogeography and population history of pine martens Martes martes compared with polecats Mustela putorius

The flora and fauna of Europe are linked by a common biogeographic history, most recently the Pleistocene glaciations that restricted the range of most species to southern refugial populations. Changes in population size and migration, as well as selection, have all left a signature on the genetic differentiation. Thus, three paradigms of postglacial recolonization have been described, inferred from the patterns of DNA differentiation. Yet some species, especially wide-ranging carnivores, exhibit little population structuring between the proposed refugia, although relatively few have been studied due to the difficulty of obtaining samples. Therefore, we investigated mitochondrial variation in pine martens, Martes martes, in order to understand the extent to which they were affected by glacial cycles, and compared the results with an analysis of sequences from polecats, Mustela putorius. A general lack of ancient lineages, and a mismatch distribution that is consistent with an expanding population, is evidence that the present-day M. martes and Mu. putorius in central and northern Europe colonized from a single European refugium following a recent glaciation. There has also been interspecific mitochondrial introgression between M. martes and the sable M. zibellina in Fennoscandia.     

Presence of haemocyte-like cells in coccinellid reflex blood

Abstract.  Contrary to current assumptions, the reflex blood of two-spot ladybirds, Adalia bipunctata , and seven-spot ladybirds, Coccinella septempunctata , contains haemocyte-like cells. Furthermore, DNA can be extracted and amplified from coccinellid reflex blood, confirming the presence of haemocyte-like cells and demonstrating a nondestructive method of DNA extraction.     

Effects of fructose on human fibroblast metabolism: the application of DNA measurements as a basis for interpretation

Summary A fluorometric procedure for measuring DNA was used to study growth and metabolic responses of eight cell strains of human foreskin fibroblasts. In preliminary studies this procedure gave more precise specific activity changes inN-acetyl-β-d-glucosaminidase (NAG) than did a protein activity basis, when changes in this enzyme's specific activity were investigated as a function of experimental cell manipulation. When fibroblast growth in eight cell strains was compared in 134 mM d-fructose vs. 13.4 mM glucose-supplemented minimum essential media, a significant increase in cellular DNA (50%) and protein (45%) occurred over an 11-d period. No significant differences in media pH change, lactate production, or carbohydrate uptake occurred on a DNA basis when cell metabolism was compared over the last 24 h of culture in the two media. Cells grown in fructose-containing media tended to show a reduction in NAG specific activity when compared with those grown in glucose-containing media.     

Nuclear DNA content in differentiated tissues of sunflower (Helianthus annuus L.)

Summary Scanning cytophotometry following Feulgen-staining was used to determine nuclear DNA content in many differentiated tissues of nine cultivars, hybrids or selfed lines ofHelianthus annuus. Apart from such ephemeral tissues as endosperm and anther tapetum, it was found that tissue differentiation in sunflower occurs in the diploid condition, cells being arrested in the DNA presynthetic phase (G₁). In certain cases, however, the nuclear DNA content of differentiated G₁ cells does not exactly match the 2C DNA content found in meristematic cells, but may be either higher or lower. In endosperm and anther tapetum cells, nuclear DNA content may be as high as 24 C and 32 C, respectively. Cytological and autoradiographic analyses after³H-thymidine incorporation reveal that polyploidy in the tapetal cells is due to chromosome endoreduplication. No detectable difference between male-fertile and male-sterile plants exists as far as occurrence and level of cell polyploidy are concerned. The results are discussed in the context of previous investigations on the nuclear condition of differentiatedHelianthus annuus tissue.     

白细胞介素2受体α链基因转录起始点和5'调控区结合蛋白的初步研究

 借助于5'和3'末端删切后重建的IL-2R a链基因调控区次级克隆,在体外合成有放射性同位素参入的反意义RNA探针与总RNA进行液相杂交,结果表明TPA或PHA分别活化的T细胞在IL-2R a链表达过程中都在不同程度上有选择地利用了调控区内分别为-58(5')和+1(3')位两个转录起始点中3'转录起始点。热休克使PHA活化细胞更明显地利用+1位点。PHA诱导Jurkat细胞表达IL-2RamRNA斑点杂交证实,Jurkat细胞在活化16小时表达IL-2Ra基本达到高峰,至24小时已明显下降。根据这一规律提取PHA诱导活化15小时的Jurkat细胞S100和NE,进行有关结合蛋白的研究,初步结果显示磷酸纤维素柱的KCI洗脱组分中存在着DNA结合蛋白,有关结合蛋白性质的研究正在进行中。     

Molecular biology and systematics of an extinct Lemur:Pachylemur insignis

The systematic position of the extinctPachylemur insignis has been controversial: some authors consideredPachylemur as a lemur, whereas others viewed it closer toVarecia. Its classification in the genusLemur orVarecia thus remained an open question. DNA extraction from subfossil bones, using a non-destructive method, allowed us to obtain enough material to make a Southern blot. The hybridization ofPachylemur withEulemur fulvus, Lemur catta, andVarecia variegata highly repeated DNA probes showed that only theVarecia probe gave a positive signal on hybridization on thePachylemur blot. These results indicate thatPachylemur must be considered closer to the genusVarecia than toEulemur andLemur.     

The methylation status of DNA derived from potato plants recovered from slow growth

The in vitro conservation of potato using tissue culture medium supplemented with the growth retardant mannitol causes morphological changes in the propagated material. These culture conditions seem to have an affect on the DNA extracted from the regenerated plants, when it is digested by the methylation sensitive restriction enzymes Hpa II/Msp I and Eco RII/Bst NI, compared to the control material. In most of these plants, there appears to be preferential methylation of nuclear domains that contain Eco RII/Bst NI recognition sites in contrast to those that contain Hpa II/Msp I sites. The refractory nature of the isolated DNA to these restriction enzymes was attributed to hypermethylation of genomic DNA and the ribosomal RNA genes. These findings indicate that methylation of DNA sequences may be an adaptive response to conditions of high osmotic stress. The importance of these results for the conservation of potato germplasm and international exchange is discussed.     

The evolutionary origin of the 35 kb circular DNA of Plasmodium falciparum: new evidence supports a possible rhodophyte ancestry

In common with other Apicomplexan parasites, Plasmodium falciparum carries two extrachromosomal DNAs, one of which, the 6 kb element, is undoubtedly mitochondrial. The second, generally referred to as the 35 kb circle, is of unknown provenance, but the nature and organization of its genetic content makes a mitochondrial association unlikely and the molecule has features reminiscent of plastid genomes. We now report the occurrence on the circle of an open reading frame specifying a predicted 470 amino acid protein that shares more than 50% identity with a gene currently known only on the plastome of red algae. This high degree of conservation confirms the 35 kb circle's plastid ancestry, and we speculate that it may have originated from the rhodoplast of an ancient red algal endosymbiont in the progenitor of the Apicomplexa.     

A minichromosome-like structure in wheat embryos

A crude nuclear fraction of resting wheat embryos was used as the source of putative plant minichromosomes: unique DNA sequences the size of genes and flanked by telomere-type repeats. Preliminary separation of low-molecular-weight DNA species from chromosomal DNA (Hirt's method), velocity sedimentation, and isopycnic centrifugation were followed by PCR amplification of minichromosome-like sequences. The most abundant PCR product was cloned and sequenced. In addition to telomeric repeats (defined by a PCR primer), which were the expected sequences, the linear DNA molecule (637 pb) contained an ARS-like element, RAP1-binding site, and two relatively long ORFs. The whole sequence seems to represent a naturally occurring plant minichromosome.