Molecular evolutionary dynamics of cytochrome b in strepsirrhine primates: the phylogenetic significance of third-position transversions

DNA sequences of the complete cytochrome b gene are shown to contain robust phylogenetic signal for the strepsirrhine primates (i.e., lemurs and lorises). The phylogeny derived from these data conforms to other molecular studies of strepsirrhine relationships despite the fact that uncorrected nucleotide distances are high for nearly all intrastrepsirrhine comparisons, with most in the 15%-20% range. Cytochrome b sequences support the hypothesis that Malagasy lemuriforms and Afro-Asian lorisiforms each comprise clades that share a sister- group relationship. A study (Adkins and Honeycutt 1994) of the cytochrome c oxidase subunit II (COII) gene placed one Malagasy primate (Daubentonia) at the base of the strepsirrhine clade, thereby suggesting a diphyletic Lemuriformes. The reanalysis of COII third- position transversions, either alone or in combination with cytochrome b third-position transversions, however, yields a tree that is congruent with phylogenetic hypotheses derived from cytochrome b and other genetic data sets.      

The effect of relaxed functional constraints on the photosynthetic gene rbcL in photosynthetic and nonphotosynthetic parasitic plants

The photosynthetic gene rbcL has been lost or dramatically altered in some lineages of nonphotosynthetic parasitic plants, but the dynamics of these events following loss of photosynthesis and whether rbcL has sustained functionally significant changes in photosynthetic parasitic plants are unknown. To assess the changes to rbcL associated with the loss of functional constraints for photosynthesis, nucleotide sequences from nonparasitic and parasitic plants of Scrophulariales were used for phylogeny reconstruction and character analysis. Plants in this group display a broad range of parasitic abilities, from photosynthetic ("hemiparasites") to nonphotosynthetic ("holoparasites"). With the exception of Conopholis (Orobanchaceae), the rbcL locus is present in all parasitic plants of Scrophulariales examined. Several holoparasitic genera included in this study, including Boschniakia, Epifagus, Orobanche, and Hyobanche, have rbcL pseudogenes. However, the holoparasites Alectra orobanchoides, Harveya capensis, Harveya purpurea, Lathraea clandestina, Orobanche corymbosa, O. fasciculata, and Striga gesnerioides have intact open reading frames (ORFs) for the rbcL gene. Phylogenetic hypotheses based on rbcL are largely in agreement with those based on sequences of the nonphotosynthetic genes rps2 and matK and show a single origin of parasitism, and loss of photosynthesis and pseudogene formation have been independently derived several times in Scrophulariales. The mutations in rbcL in nonparasitic and hemiparasitic plants would result in largely conservative amino acid substitutions, supporting the hypothesis that functional proteins can experience only a limited range of changes, even in minimally photosynthetic plants. In contrast, ORFs in some holoparasites had many previously unobserved missense substitutions at functionally important amino acid residues, suggesting that rbcL genes in these plants have evolved under relaxed or altered functional constraints.      

Frequency of spontaneous chromosome aberrations in mice: effects of age

In this paper, we present data on chromosome aberration frequencies in mice which served as unexposed controls in a variety of radiation and chemical toxicology experiments conducted in our laboratory in recent years. All chromosome aberration data were obtained by chromosome painting. In peripheral blood lymphocytes from 102 animals, the frequencies of translocations and insertions increased significantly with age. No increase with age was seen for dicentrics or acentric fragments. When the data were analyzed by strain, the age-related increase in translocation frequencies was observed only in the 71 homozygous C57BL/6 mice and not in any of the three heterozygous strains. Very few aberrations of any type were observed in 62 bone marrow samples, and no effect of age was seen for any aberration type in this tissue. These results are similar to those observed in unexposed humans, and suggest that the increase in translocations is not the result of accumulated damage from chronic 'background' environmental exposures but instead may be due to biological processes associated with aging.     

In vitro production of llama (Lama glama) embryos by IVF and ICSI with fresh semen

The interest for South American camelids has increased in the last years. The aim of the present research was to compare the in vitro production of Lama glama embryos using two techniques: in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). For IVF technique, we compared the effect of adding or not, heparin, penicillamine and hypotaurine as sperm capacitating agents. In the oocyte group subjected to ICSI, activation with or without, ionomycin and 6-dimethylaminopurine (6-DMAP) was assessed. Semen samples were obtained by electroejaculation and incubated at 38 degrees C in a 25% (v/v) collagenase solution. The cleavage and embryo development rates were compared between the different experimental groups. Only the number of cleaved oocytes was less when ICSI with no activation was used (p<0.05).     

Collection method, season and individual variation on seminal characteristics in the llama (Lama glama)

The objective of the present study was to evaluate the effect of semen collection method (electroejaculation "EE" as compared with the artificial vagina "AV"), the season (summer versus winter) and the male used on macroscopic and microscopic characteristics of ejaculates in llamas. A total of 110 ejaculates were collected from six males and 92 of them were analyzed. Ejaculate volume, concentration, total sperm and the following sperm characteristics were studied: motility, membrane function (HOS test), membrane integrity (CFDA/PI fluorochromes) and morphology. A mixed linear model, that considered season and collection method as the fixed variables and the male as the random variable, was used for the statistical analysis. Variability was found between males (p相似文献   

Alternative splicing and protein function

Background  

Alternative splicing is a major mechanism of generating protein diversity in higher eukaryotes. Although at least half, and probably more, of mammalian genes are alternatively spliced, it was not clear, whether the frequency of alternative splicing is the same in different functional categories. The problem is obscured by uneven coverage of genes by ESTs and a large number of artifacts in the EST data.     

Gene therapy for mitochondrial disease by delivering restriction endonucleaseSmaI into mitochondria

The restriction endonucleaseSmaI has been used for the diagnosis of neurogenic muscle weakness, ataxia and retinitis pigmentosa disease or Leigh's disease, caused by the Mt8993TG mutation which results in a Leu156Arg replacement that blocks proton translocation activity of subunit a of F₀F₁-ATPase. Our ultimate goal is to applySmaI to gene therapy for this disease, because the mutant mitochondrial DNA (mtDNA) coexists with the wild-type mtDNA (heteroplasmy), and because only the mutant mtDNA, but not the wild-type mtDNA, is selectively restricted by the enzyme. For this purpose, we transiently expressed theSmaI gene fused to a mitochondrial targeting sequence in cybrids carrying the mutant mtDNA. Here, we demonstrate that mitochondria targeted by theSmaI enzyme showed specific elimination of the mutant mtDNA. This elimination was followed with repopulation by the wild-type mtDNA, resulting in restoration of both the normal intracellular ATP level and normal mitochondrial membrane potential. Furthermore, in vivo electroporation of the plasmids expressing mitochondrion-targetedEcoRI induced a decrease in cytochromec oxidase activity in hamster skeletal muscles while causing no degenerative changes in nuclei. Delivery of restriction enzymes into mitochondria is a novel strategy for gene therapy of a special form of mitochondrial diseases.     

Comparison of tetrachromic VOF stain to other histochemical staining techniques for characterizing stromal soft and hard tissue components

The components of hard tissues including dentin, enamel, cementum, bone and other calcified deposits, and mature and immature collagen pose problems for identification in routine hematoxylin and eosin (H & E) stained sections. Use of combinations of stains can demonstrate the components of hard tissues and soft tissues distinctly. We assessed the efficacy of the Verde Luz-orange G-acid fuchsin (VOF) stain for differentiating hard and soft connective tissues and compared results with other histochemical staining techniques. Eighty tissue sections comprising developing tooth (30), ossifying fibroma (30) and miscellaneous pathologies (20) expected to contain varying types of calcified tissues were stained with H & E, VOF, and Masson's trichrome (MT). In developing tooth, VOF demonstrated better differentiation of hard tissues, while it was comparable to MT for ossifying fibroma and miscellaneous pathologies. The intensity of staining was greater with VOF than with the other stains studied. VOF stains hard tissue components distinctly and gives good contrast with the surrounding connective tissue. VOF is comparable to MT, but has added advantages including single step staining, rapid and easy procedures, and it distinguishes the maturity of the tissues.     

Interactions of neural glycosaminoglycans and proteoglycans with protein ligands: assessment of selectivity, heterogeneity and the participation of core proteins in binding

The method of affinity coelectrophoresis was used to study the binding of nine representative glycosaminoglycan (GAG)-binding proteins, all thought to play roles in nervous system development, to GAGs and proteoglycans isolated from developing rat brain. Binding to heparin and non-neural heparan and chondroitin sulfates was also measured. All nine proteins-laminin-1, fibronectin, thrombospondin-1, NCAM, L1, protease nexin-1, urokinase plasminogen activator, thrombin, and fibroblast growth factor-2-bound brain heparan sulfate less strongly than heparin, but the degree of difference in affinity varied considerably. Protease nexin-1 bound brain heparan sulfate only 1.8- fold less tightly than heparin (Kdvalues of 35 vs. 20 nM, respectively), whereas NCAM and L1 bound heparin well (Kd approximately 140 nM) but failed to bind detectably to brain heparan sulfate (Kd>3 microM). Four proteins bound brain chondroitin sulfate, with affinities equal to or a few fold stronger than the same proteins displayed toward cartilage chondroitin sulfate. Overall, the highest affinities were observed with intact heparan sulfate proteoglycans: laminin-1's affinities for the proteoglycans cerebroglycan (glypican-2), glypican-1 and syndecan-3 were 300- to 1800-fold stronger than its affinity for brain heparan sulfate. In contrast, the affinities of fibroblast growth factor-2 for cerebroglycan and for brain heparan sulfate were similar. Interestingly, partial proteolysis of cerebroglycan resulted in a >400- fold loss of laminin affinity. These data support the views that (1) GAG-binding proteins can be differentially sensitive to variations in GAG structure, and (2) core proteins can have dramatic, ligand-specific influences on protein-proteoglycan interactions.      

布雷费尔德对真菌的进化观点在真菌分类中所起的影响

布雷费尔德(O. Brefeld)虽对真菌纯培养方法的改进和真菌发育与生理知识作出了不少贡献,但他的主要贡献还是对真菌系统发育的观点。按照他的这种观点,卵菌不是真正的真菌,它应与粘菌一起排除在真菌之外,而真正的真菌应从接合菌开始。他并将子囊菌和担子菌分别分为半子囊菌和真子囊菌,半担子菌和真担子菌。