Sperm viability in the reproductive tract of females in a population of Sceloporus mucronatus exhibiting asynchronous reproduction

Asynchronous reproduction is a common phenomenon in high-elevation populations of lizards from Central México. Sperm storage in the reproductive tract of females is the mechanism for making oocyte fertilization possible. Our study addresses questions related to functional oviductal sperm storage of females mating on different dates throughout the reproductive season. A population of Sceloporus mucronatus with copulation in the summer and ovulation in the fall was chosen for this experiment. Eleven females that copulated in the field during June and 13 females that copulated in captivity during August were maintained in the laboratory until parturition. The number of pregnant females and the litter sizes produced in each experimental group were indicative of the viability of the stored sperm. Sperm stored in the reproductive tract of females were able to fertilize eggs after 4 months. No significant differences were found in the number of pregnant females between the 2 experimental groups nor in the litter sizes that they produced. We found that the amount of time sperm were held in the female reproductive tract (ca. 3 months) had no effect on the capacity of sperm to fertilize eggs. Histological examination of 8 oviducts collected before the mating season eliminated the possibility of sperm storage from one year to the next. In this system, sperm retention could have evolved as a response mechanism to deal with the asynchrony between sexes in the reproductive cycles. However, we cannot rule out alternative hypotheses.     

Role of serum components in the binding and phagocytosis of oxidatively damaged erythrocytes by autologous mouse macrophages

To investigate the role of autologous serum components in the recognition of damaged cells by macrophages, we examined the binding and phagocytosis of damage oxidatively damaged red blood cells with Cu2+ and ascorbate (oxRBCs) by autologous resident mouse peritoneal macrophages. The binding of oxRBCs by macrophages was independent of the presence of serum. However, phagocytosis by macrophages increased with serum concentration, and macrophages showed little ingestion of oxRBCs in a serum-free medium. Macrophages neither bound nor appreciably ingested native RBCs (before oxidation) in either the absence or presence of autologous serum. Mouse macrophages ingested significantly more native as well as oxRBCs in the presence of heat-inactivated fetal calf serum than in the presence of heat-inactivated mouse serum. Pretreated oxRBCs with normal serum were rarely ingested by macrophages in a serum-free medium. Phagocytosis of oxRBCs was significantly inhibited by depletion of IgG or calcium from serum, by heat inactivation of complement, or by antiserum against mouse C3. These results demonstrate that serum components such as IgG, C3, and calcium are involved in phagocytosis of oxRBCs by autologous macrophages.     

钼-硫氰酸盐-甲基紫高灵敏离子缔合体系的研究和应用

本文研究了在聚乙烯醇存在下,钼(Ⅵ)—SCN—甲基紫高灵敏离子缔合体系,在0·10—0·14M硫酸介质中,该体系λ_(max)=530nm,表观摩尔吸光系数_(530)=9·20×10~5l·mol~(-1)·cm~(-1),0～μgM_0/25ml符合比尔定律,选择性较好,并用于钢铁中钼的测定。对显色反应机理作了初步探讨。     

Zr(0001)-(2×2)-O表面结构的分析

LEED强度的多重散射分析,进一步确定Zr与氧作用在低覆盖量下(<1ML),形成(2×2)-O结构,是氧吸附后进入Zr表面原子层下,占据八面体空位,形成有两层氧的under layer结构,Zr表面原子层有Fcc重构。分析得到的Zt-O键距为0.232nm,而Zr-Zr间距增大为0.268nm,比原来的距离增大约4.3％,这是由于氧插入的结果。     

On the complexity of self.

Self peptides bound to self major histocompatibility complex (MHC) molecules have been implicated both in positive and in negative selection of T cells during intrathymic development. We report here that the novel MHC-restricted monoclonal antibody Y-Ae detects the MHC class II bound form of a major self peptide. Y-Ae binds approximately 12% of the relevant MHC class II molecules on self antigen presenting cells. The peptide detected by Y-Ae is one of several major peptides eluted from the MHC molecule. These data suggest that self peptides presented by self MHC class II molecules at densities sufficient to signal a CD4 T cell are of very limited complexity. Furthermore, as Y-Ae stains antigen presenting cells that mediate negative selection but not thymic cortical epithelial cells that drive positive selection, differential expression of self peptide:self MHC class II complexes may be a key feature of intrathymic selection.     

Homeobox gene expression correlated with the bifurcation process of limb cartilage development.

The complex architecture of the limb cartilage pattern probably develops by the sequential segmentation and branching process of precartilaginous cell condensation under the control of positional signalling provided by the zone of polarizing activity (anteroposterior) and the apical ectodermal ridge (proximodistal). This signalling is monitored and interpreted in the mesenchymal cells and induces the position-specific response of subsets of genes. Homeobox genes may be responsible for the interpretation of signalling. A correlation between limb pattern and expression domains of the homeobox genes in the upstream region of Hox/Chox-4 has been proposed. We have analysed the spatial expression pattern of the Chox-1 genes during development of chick limb buds. In contrast to genes in Hox/Chox-4 expressed coordinately along the anteroposterior axis, homeobox genes in Chox-1 have unique and mutually exclusive expression domains along the proximodistal axis. We report here that the expression domains of the Chox-1 genes are closely related to the segmental structure of cartilage along the proximodistal axis, whereas the expression domains of the Chox-4 genes are related to the cartilage branching pattern.     

Hsp104 is a highly conserved protein with two essential nucleotide-binding sites

Most eukaryotic cells produce proteins with relative molecular masses in the range of 100,000 to 110,000 after exposure to high temperatures. These proteins have been studied only in yeast and mammalian cells. In Saccharomyces cerevisiae, heat-shock protein hsp104 is vital for tolerance to heat, ethanol and other stresses. The mammalian hsp110 protein is nucleolar and redistributes with growth state, nutritional conditions and heat shock. The relationships between hsp110, hsp104 and the high molecular mass heat-shock proteins of other organisms were unknown. We report here that hsp104 is a member of the highly conserved ClpA/ClpB protein family first identified in Escherichia coli and that additional heat-inducible members of this family are present in Schizosaccharomyces pombe and in mammals. Mutagenesis of two putative nucleotide-binding sites in hsp104 indicates that both are essential for function in thermotolerance.     

Enhancement of T-cell activation by the CD43 molecule whose expression is defective in Wiskott-Aldrich syndrome

CD43 (sialophorin, leukosialin, leukocyte large sialoglycoprotein), a heavily sialylated molecule found on most leukocytes and platelets, was initially identified as a major glycoprotein of mouse, rat and human T cells. CD43 expression is defective on the T cells of males with the Wiskott-Aldrich syndrome, an X chromosome-linked recessive immunodeficiency disorder. Affected males are susceptible to opportunistic infections and do not respond to polysaccharide antigens, reflecting defects in cytotoxic and helper T-cell functions. Anti-CD43 monoclonal antibodies have a modest costimulatory effect on T cells, natural killer cells, B cells and monocytes, and one such antibody has been shown to activate T cells directly. To investigate a possible physiological role for CD43, a complementary DNA encoding the human protein was introduced into an antigen-responsive murine T-cell hybridoma. We observed that CD43 enhances the antigen-specific activation of T cells and that the intracellular domain of CD43, which is hyperphosphorylated during T-cell activation, is required for this function. We also found that antigen-presenting cells can bind specifically to immobilized purified CD43 and that the binding can be inhibited by liposomes containing CD43 as well as by anti-CD43 monoclonal antibodies.     

The bcl-2 gene encodes a novel G protein

Little is known about the biochemical or functional nature of the proteins encoded by the bcl-2 gene, which undergoes chromosomal translocation in approximately 85% of follicular lymphoma, 20% of diffuse large cell lymphoma and 10% of chronic lymphocytic leukaemia of B cells. Translocation of bcl-2 sequences from chromosome 18 to the JH segment of the immunoglobulin gene at chromosome band 14q32 in B cells results in deregulated expression of this gene, causing high steady state levels of bcl-2 messenger RNA2. DNA sequence data indicate that bcl-2 encodes two proteins by virtue of alternative splicing, designated as Bcl-2 alpha and Bcl-2 beta, with relative molecular masses of 26,000 and 22,000 respectively. Cell fractionation experiments indicate that the bcl-2 alpha gene product is located at the inner surface of the cell membrane, suggesting a possible role in mitogenic signal transduction. We report here that Bcl-2 alpha has GTP-binding activity and a protein sequence that suggests it belongs to the small molecular weight GTP-binding protein (G protein) family.