大鼠缺氧预处理心肌酶活性及其ATP酶的电镜细胞化学观察

本实验通过对大鼠反复４次缺氧５ｍｉｎ（常压,氧浓度１０±０．５％）的缺氧预处理与经典的缺血预处理（Ｍｕｒｙ法）的对比观察表明,两者均能明显降低心肌丙二醛含量和肌酸激酶的漏出,提高心肌超氧化物岐化酶,Ｃａ２＋Ｍｇ２＋－ＡＴＰａｓｅ、细胞色素氧化酶、琥珀酸脱氢酶活性及维持细胞超微结构的完整性,提示这种非创伤性缺氧预处理具有与缺血预处理相类似的抗心肌缺血的作用     

Hematopoietic stem cell subtypes expand differentially during development and display distinct lymphopoietic programs

Adult hematopoietic stem cells (HSCs) with serially transplantable activity comprise two subtypes. One shows a balanced output of mature lymphoid and myeloid cells; the other appears selectively lymphoid deficient. We now show that both of these HSC subtypes are present in the fetal liver (at a 1:10 ratio) with the rarer, lymphoid-deficient HSCs immediately gaining an increased representation in the fetal bone marrow, suggesting that the marrow niche plays a key role in regulating their ensuing preferential amplification. Clonal analysis of HSC expansion posttransplant showed that both subtypes display an extensive but variable self-renewal activity with occasional interconversion. Clonal analysis of their differentiation programs demonstrated functional and molecular as well as quantitative HSC subtype-specific differences in the lymphoid progenitors they generate but an indistinguishable production of multipotent and myeloid-restricted progenitors. These findings establish a level of heterogeneity in HSC differentiation and expansion control that may have relevance to stem cell populations in other hierarchically organized tissues.     

The MIG-2/integrin interaction strengthens cell-matrix adhesion and modulates cell motility

Integrin-mediated cell-matrix adhesion plays an important role in control of cell behavior. We report here that MIG-2, a widely expressed focal adhesion protein, interacts with beta1 and beta3 integrin cytoplasmic domains. Integrin binding is mediated by a single site within the MIG-2 FERM domain. Functionally, the MIG-2/integrin interaction recruits MIG-2 to focal adhesions. Furthermore, using alphaIIbbeta3 integrin-expressing Chinese hamster ovary cells, a well described model system for integrin activation, we show that MIG-2 promotes integrin activation and enhances cell-extracellular matrix adhesion. Although MIG-2 is expressed in many cell types, it is deficient in certain colon cancer cells. Expression of MIG-2, but not of an integrin binding-defective MIG-2 mutant, in MIG-2-null colon cancer cells strengthened cell-matrix adhesion, promoted focal adhesion formation, and reduced cell motility. These results suggest that the MIG-2/integrin interaction is an important element in the cellular control of integrin-mediated cell-matrix adhesion and that loss of this interaction likely contributes to high motility of colon cancer cells.     

Functional utrastructure of Genlisea (Lentibulariaceae) digestive hairs

BACKGROUND AND AIMS: Digestive structures of carnivorous plants produce external digestive enzymes, and play the main role in absorption. In Lentibulariaceae, the ultrastructure of digestive hairs has been examined in some detail in Pinguicula and Utricularia, but the sessile digestive hairs of Genlisea have received very little attention so far. The aim of this study was to fill this gap by expanding their morphological, anatomical and histochemical characterization. METHODS: Several imaging techniques were used, including light, confocal and electron microscopy, to reveal the structure and function of the secretory hairs of Genlisea traps. This report demonstrates the application of cryo-SEM for fast imaging of whole, physically fixed plant secretory structures. KEY RESULTS AND CONCLUSION: The concentration of digestive hairs along vascular bundles in subgenus Genlisea is a primitive feature, indicating its basal position within the genus. Digestive hairs of Genlisea consist of three compartments with different ultrastructure and function. In subgenus Tayloria the terminal hair cells are transfer cells, but not in species of subgenus Genlisea. A digestive pool of viscous fluid occurs in Genlisea traps. In spite of their similar architecture, the digestive-absorptive hairs of Lentibulariaceae feature differences in morphology and ultrastructure.     

Fatty acid efficiency profile in uncoupling of <Emphasis Type="Italic">Acanthamoeba castellanii</Emphasis> mitochondria

A profile of free fatty acid (FFA) specificity in Acanthamoeba castellanii mitochondrial uncoupling is described. The FFA uncoupling specificity was observed as different abilities to stimulate resting respiration, to decrease resting membrane potential, and to decrease oxidative phosphorylation efficiency. Tested unsaturated FFA (C18–20) were more effective as uncouplers and protonophores when compared to tested saturated FFA (C8–18), with palmitic acid (C16:0) as the most active. As FFA efficiency in mitochondrial uncoupling is related to physiological changes of fatty acid composition (and thereby FFA availability) during growth of amoeba cells, it could be a way to regulate the activity of an uncoupling protein and thereby the efficiency of oxidative phosphorylation during a cell life of this unicellular organism. Aleksandra Swida and Małgorzata Czarna contributed equally to this work.     

Chinese white Rongchang pig does not have the dominant white allele of KIT but has the dominant black allele of MC1R

The mast/stem cell growth factor receptor (KIT) and melanocortin receptor 1 (MC1R) mutations are responsible for coat color phenotypes in domestic pigs. Rongchang is a Chinese indigenous pig breed with a white coat color phenotype. To investigate the genetic variability of the KIT and MC1R genes and their possible association with the coat color phenotype in this breed, a gene duplication and splice mutation of KIT were diagnosed in a sample of 93 unrelated Rongchang animals. The results show that Rongchang pigs have a single copy of KIT without the splice mutation at the first nucleotide of intron 17, indicating that the dominant white I allele of KIT is not responsible for their white phenotype. The KIT mRNA and MC1R coding sequences were also determined in this breed. Three putative amino acid substitutions were found in the KIT gene between Rongchang and Western white pigs, their association with the Rongchang white phenotype remains unknown. For the MC1R gene, Rongchang pigs were demonstrated to have the same dominant black allele (E(D1)) as other Chinese breeds, supporting the previous conclusion that Chinese and Western pigs have independent domestication origin. We also clarified that the Rongchang white phenotype was recessive to nonwhite color phenotypes. Our results provide a good starting point for the identification of the mutations underlying the white coat color in Rongchang pigs.     

Lysine 77 is a Key Residue in Aggregation of Equinatoxin II, a Pore-forming Toxin from Sea Anemone Actinia equina

Among eighteen point mutants of equinatoxin II produced in E. coli, containing a single cystein substitution at variable position, EqtIIK77C was chosen for its peculiar properties. It was almost 100 times less hemolytic than the wild-type, but its hemolytic activity could be restored by chemical modification of the thiol group, provided that a positive charge was reintroduced. This indicates that a positive charge at this position is necessary for toxin activity. The mutant formed larger pores as compared to the wild type, but displayed the same cation selectivity. The pores reverted to normal size upon reintroduction of the positive charge. The conformation of EqtIIK77C and its binding to lipid membranes, either vesicles or red blood cells, was almost normal. However the kinetics of calcein release from lipid vesicles was substantially slower than that of the wild-type. Taken together with the different size of the pore formed, this is an indication that mutation of Lys77 → Cys influences the normal development of the aggregate which is required for assembling the functional pore. Received: 18 May 1999/Revised: 18 September 1999