砂鼠利什曼原虫(Leishmania gerbilli)的亚显微结构

砂鼠利什曼原虫(Leishmania gerbilli)存在于我国西北甘肃某地的砂土鼠或大砂鼠(Rhombomys opimus)体内,是中国特有的种类,王捷等60年代分离培养成功。对L.gerbilli的前鞭毛体的亚显微结构的观察表明:1.质膜下微管间距约为50nm,比别的利什曼原虫的宽;2.鞭毛基部极少观察到基板(basal plate);3.线粒体发达,从动基体所在部位伸向虫体各个部位,内有复杂的结构;4.在通常情况下,L.gerbilli的动基体呈棒状,但当细胞膨胀后则无论在光镜或电镜下动基体均呈扁环结构;5.虫体后部有发达的复片层结构。这一结构由一系列的膜卷绕成,其意义不明。     

Leaf ultrastructure of C4 species possessing different Kranz anatomical types in the cyperaceae

The leaf ultrastructure of NADP-malic enzyme type C₄ species possessing different anatomical features in the Cyperaceae was examined: types were the Rhynchosporoid type, a normal Kranz type in which mesophyll cells are adjacent to Kranz cells, and Fimbristyloid and Chlorocyperoid types, unusual Kranz types in which nonchlorophyllous mestome sheath intervenes between the two types of green cells. They show structural characteristics basically similar to the NADP-malic enzyme group of C₄ grasses, that is, centrifugally located chloroplasts with reduced grana and no increase of mitochondrial frequency in the Kranz cells. However, the Kranz cell chloroplasts of the Fimbristyloid and Chlorocyperoid types exhibit convoluted thylakoid systems and a trend of extensive development of peripheral reticulum, although those of the Rhynchosporoid type do not possess such particular membrane systems. The suberized lamella, probably a barrier for CO₂ diffusion, is present in the Kranz cell walls of the Rhynchosporoid type and in the mestome sheath cell walls of the other two types, and tightly surrounds the Kranz cells (sheaths) that are the sites of the decarboxylation of C₄ acids. These ultrastructural features are discussed in relation to C₄ photosynthetic function.     

Polyamines in liver and their influence on chromatin condensation after 17-β estradiol treatment of Atlantic salmon

Atlantic salmon (Salmo salar) were treated with 17- estradiol to induce vitellogenin synthesis in liver. This led to an increase in liver wet weight and total DNA. After incubation with micrococcal nuclease (EC 3.1.31.1) less soluble chromatin was obtained from nuclei of the estradiol treated than the control fish, but active gene regions were solubilized by the nuclease. Thus, in the estradiol treated fish soluble mononucleosomes contained hybridizable vitellogenin gene sequences. As a result of estradiol treatment the content in total liver of putrescine rose 3-fold, that of spermidine 2-fold, while spermine was unchanged. In muscle no significant changes were observed. The regulatory functions of polyamines during gene expression were investigated by binding (¹⁴C)spermine to isolated liver nuclei depleted of endogenous polyamines. The number of binding sites was higher in nuclei of estradiol treated than control fish. (^14C)spermine associated preferentially with micrococcal nuclease insensitive chromatin. Thus, the high content of putrescine and spermidine in liver supported the view of polyamine accumulation in proliferating tissues. The preferential binding to condensed chromatin indicated a stabilizing effect of polyamines on the organization of inactive chromatin structures.Abbreviations MNase micrococcal nuclease - PMSF phenylmethylsulfonylfluoride     

Key regulators of mitochondrial biogenesis are increased in kidneys of growth hormone receptor knockout (GHRKO) mice

The growth hormone receptor knockout (GHRKO) mice are remarkably long-lived and highly insulin sensitive. Alterations in mitochondrial biogenesis are associated with aging and various metabolic derangements. We have previously demonstrated increased gene expression of key regulators of mitochondriogenesis in kidneys, hearts and skeletal muscles of GHRKO mice. The aim of the present study was to quantify the protein levels of the following regulators of mitochondriogenesis: peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), AMP-activated protein kinase α (AMPKα), phospho-AMPKα (p-AMPKα), sirtuin-3 (SIRT-3), endothelial nitric oxide synthase (eNOS), phospho-eNOS (p-eNOS), nuclear respiratory factor-1 (NRF-1) and mitofusin-2 (MFN-2) in skeletal muscles and kidneys of GHRKOs in comparison to normal mice. We also were interested in the effects of calorie restriction (CR) and visceral fat removal (VFR) on these parameters. Both CR and VFR improve insulin sensitivity and can extend life span. Results: The renal levels of PGC-1α, AMPKα, p-AMPKα, SIRT-3, eNOS, p-eNOS and MFN-2 were increased in GHRKOs. In the GHRKO skeletal muscles, only MFN-2 was increased. Levels of the examined proteins were not affected by CR (except for PGC-1α and p-eNOS in skeletal muscles) or VFR. Conclusion: GHRKO mice have increased renal protein levels of key regulators of mitochondriogenesis, and this may contribute to increased longevity of these knockouts.     

Growth and ultrastructure of the marine unicellular alga <Emphasis Type="Italic">Dunaliella salina</Emphasis> (Chlorophyta) after chronic selenium intoxication

The effects of selenium (0.01, 0.5, 1, 5 and 10 mg/liter) on the growth and ultrastructure of the microalga Dunaliella salina were investigated following its transfer into clean water. Selenium concentrations of 5 and 10 mg/liter were toxic to D. salina, and reinoculation of microalga into clean water did not prevent it from total mortality. When reinoculated from medium with 0.01 mg Se/liter, the cell population density of D. salina was restored in 14 days. The number of ultrastructural alterations in cells was the same as in the control, while the excretory activity of microalga between days 4 and 10 of this experiment was higher. Cell population growth of D. salina transferred from 0.5 and 1 mg Se/liter was lower than in the control. No ultrastructural defects were observed in microalga reinoculated from medium with a selenium concentration of 0.5 mg/liter and the excretion level corresponded to that at 0.01 mg/liter. Various types of ultrastructural damage were found in microalga from medium with 1 mg Se/liter, which was previously reported to be threshold for D. salina; however, the number of cell injuries decreased with increasing time in clean medium. Excretory activity was decreased at the beginning of experiment; but after 7 days, it was restored to the control level. Though there were no ultrastructural alterations in microalgal cells from medium with 0.5 mg Se/liter, we assume that they had molecular defects that could inhibit the cell population growth. The study of microalgae following their reinoculation from medium containing toxicants into clean medium can be a useful method for evaluating algal survival after toxic exposure.     

COMPARATIVE ULTRASTRUCTURE OF THE VALVES OF SOME CYCLOTELLA SPECIES (BACILLARIOPHYCEAE)1

Cyclotella atomus Hust., C. meneghiniana Kütz., C. comta (Ehr.) Kütz., C. antiqua W. Sm., C. michiganiana Skv., C. ocellata Pant., C. glomerata Bachmann, C. pseudostelligera Hust., and C. stelligera (Cleve et Grun.) V. H., were selected for ultrastructure investigations on the basis of their ready availability. Specimens were examined employing both transmission and scanning electron microscopy. Strutted processes, labiate processes, spines and other special features were surveyed in all species. On the basis of these observations the species of Cyclotella observed seem to be in one of 3 morphological groups, the meneghiniana group, the comta group, and the stelligera group.     

Organization of connectin/titin filaments in sarcomeres of differentiating chicken skeletal muscle cells

Very long, elastic connectin/titin molecules position the myosin filaments at the center of a sarcomere by linking them to the Z line. The behavior of the connectin filaments during sarcomere formation in differentiating chicken skeletal muscle cells was observed under a fluorescent microscope using the antibodies to the N terminal (located in the Z line), C terminal (M line), and C zone (myosin filament) regions of connectin and was compared to the incorporation of -actinin and myosin into forming sarcomeres. In early stages of differentiating muscle cells, the N terminal region of connectin was incorporated into a stress fiber-like structure (SFLS) together with -actinin to form dots, whereas the C terminal region was diffusely distributed in the cytoplasm. When both the C and N terminal regions formed striations in young myofibrils, the epitope to the C zone of A-band region, that is the center between the A-I junction and the M-line, initially was diffuse in appearance and later formed definite striations. It appears that it took some time for the N and C terminal regions of connectin to form a regular organization in a sarcomere. Thus the two ends of the connectin filaments were first fixed followed by the specific binding of the middle portion onto the myosin filament during sarcomere formation.     

慢性低O_2高CO_2性肺动脉高压大鼠脑超微结构改变与MDA、SOD变化及培哚普利的治疗作用

目的 :探讨慢性低O2 高CO2 时神经元线粒体及髓鞘的改变与氧自由基的变化关系及培哚普利的治疗作用。方法 :采用慢性低O2 高CO2 肺动脉高压模型 ,应用培哚普利治疗 ,电镜观察大鼠脑超微结构并测定MDA和SOD。结果 :观察到脑血管内皮细胞锯齿状突起 ,管腔狭窄 ,神经元线粒体空泡变及髓鞘分层断裂 ,测得实验大鼠MDA升高 ,SOD降低 ,用药组大鼠脑血管和神经元结构损害明显减轻。结论 :提示慢性低O2 高CO2 时神经元线粒体及髓鞘改变与MDA升高有关 ,培哚普利对慢性低O2 高CO2 时脑损害有保护作用。     

猪的骨骼肌生长发育研究进展

瘦肉率对生猪产业来说是一个极其重要的经济指标,而这一指标完全取决于骨骼肌的生长发育。因此,猪骨骼肌生长发育机理的研究是十分必要的。然而,在早期由于各种因素的限制,猪骨骼肌单个基因的研究一直进展缓慢;相反,以小鼠为模型,其骨骼肌单基因的功能研究却取得了较大进展。在这一时期,影响肌决定和肌分化的基因,如MRFs家族和MEF2家族相继被发现,这些基因在猪的肌肉发育中也发挥着同样的作用。然而,这些结果并不能很好地揭示骨骼肌发育过程中复杂的基因间互作关系。随着近年来芯片和测序技术的不断发展,更多人试图从整个转录谱的水平来阐述猪肌肉发育的分子机理,并且也取得了较大的进展。为了对猪骨骼肌生长发育有一个更为清晰的认识,该文将以目前猪骨骼肌生长发育研究结果为基础,同时结合模式动物小鼠骨骼肌单基因的研究成果,对猪的骨骼肌生长发育分子调控机理进行详细的阐述。     

松突圆蚧雄成虫触角感器的扫描电镜观察

松突圆蚧(Hemiberlesia pitysophila Takagi)是我国南方重要的外来林业害虫。本研究利用扫描电镜对该蚧雄成虫的触角形态和感器进行了观察。结果表明:松突圆蚧雄成虫触角呈线状,由柄节、梗节和鞭节组成,共10节。触角感器共有5种,分别为Bhm氏鬃毛、毛形感器、乳头形感器、锥形感器、火柴形感器,其中,火柴形感器为首次在松突圆蚧雄成虫触角上发现并描述。不同感器在触角各节的数量和分布各不相同,其中,毛形感器数量最多,分布最广,乳头形感器次之,火柴形感器最少。此外,根据感器的分布、形态特征,结合已有的文献描述,推测了感器可能的功能。