新疆绿蟾蜍的染色体组型初步研究

近年来,有关两栖类的染色体组型已有不少报道。无尾两栖类中蜍蟾属(Bufo)的染色体数目分为两类:2n=22和2n=20(Blain,1972)。我们对采自新疆4个地区的绿蟾蜍进行了染色体组型分析,发现其二倍体细胞染色体数均为44,是四倍体。现将我们的初步研究报道如下。     

Variations of susceptibility to alloxan induced diabetes in the rabbit

The variations of susceptibility to alloxan induced Diabetes in a total of seventeen rabbits was described. Our study was designed to explore dosage schedules which might improve rabbit responsiveness to and survival after alloxan treatment. A wide range of response to intravenously administered alloxan was observed. Permanent diabetes (blood glucose 350 mg/dl) was found in three rabbits after a single injection (60 mg/kg in one, 100 mg/kg in two). This effect has persisted for eight months. By contrast, two other rabbits injected with a single dose of alloxan (60 mg/kg) developed only transient hyperglycemia. Similarly, four other rabbits either did not respond or had an incomplete response after receiving a total dose of 120 mg/kg. These data suggest that there is extreme variability in individual rabbits susceptibility to the diabetogenic affects of alloxan.     

pH-dependent structural transition in rabbit skeletal troponin C

Although the crystal structure of troponin C is known (Herzberg, O., and James, M. N. G. (1985) Nature 313, 653-659; Sundaralingam, M., Bergstrom, R., Strasburg, G., Rao, S. T., Roychowdhury, P., Greaser, M., and Wang, B. C. (1985) Science 227, 945-948), its structure in solution, particularly under physiological conditions, has not been established. We examined the conformation of troponin C under a variety of conditions by measuring the distance between sites located in the N- and C-terminal domains using the technique of resonance energy transfer. The donor was the luminescent lanthanide ion Tb3+ bound at the low affinity metal sites in the N-terminal domain. The acceptor was 4-dimethylaminophenylazophenyl-4'-maleimide attached at Cys-98 in the C-terminal domain. The distance between these sites was found to be greater than 5.2 nm at pH 5.0, 2.7 nm at pH 6.8 for uncomplexed troponin C, and 4.1 nm for troponin C complexed with troponin I at pH 6.8. These findings suggest that uncomplexed troponin C undergoes a pH-dependent transition from an elongated conformation, compatible with the crystal structure at acidic pH, to a more compact conformation at neutral pH. When complexed with troponin I, troponin C adopts a conformation of intermediate length compared to the uncomplexed molecule at pH 6.8 and 5.0.     

Ligand recombination to the alpha and beta subunits of human hemoglobin

The rebinding of CO, O2, NO, methyl, ethyl, n-propyl, and n-butyl isocyanide to isolated alpha and beta chains and intact hemoglobin at pH 7, 20 degrees C was examined both during and after a 30-ns dye laser pulse. The resultant absorbance changes were analyzed in terms of a linear three-step reaction scheme: Hb + X in equilibrium with C in equilibrium with B in equilibrium with A or HbX, where A is the final bound state, and C and B are geminate states. Rate constants were assigned for each of the transitions in this mechanism using fitting procedures described previously for analyzing ligand rebinding to sperm whale myoglobin at room temperature (Gibson, Q. H., Olson, J. S., McKinnie, R. E., and Rohlfs, R. J. (1986) J. Biol. Chem. 261, 10228-10239). Five major conclusions were obtained. First, initial geminate recombination phases for the NO and O2 complexes of hemoglobin and its isolated subunits exhibit half-times equal to approximately 12 and approximately 440 ps, respectively. These values are in excellent agreement with more direct, picosecond measurements of the geminate recombination of HbNO (Cornelius, P. A., Hochstrasser, R. M., and Steele, A. W. (1983) J. Mol. Biol. 163, 119-128) and HbO2 (Friedman, J. M., Scott, T. W., Fisanick, G. J., Simon, S. R., Findsen, E. W., Ondrias, M. R., and MacDonald, V. W. (1985) Science 229, 187-229) following extremely short laser pulses. Second, the correspondence between our nanosecond measurements and the published picosecond data suggests strongly that the intrinsic photochemical yield of all ferrous, hexacoordinate heme complexes approaches one. Third, the major differences between the isolated alpha and beta chains involve the rate of ligand migration to the solvent, kC----X and the extent of recombination from the second geminate state, C, as measured by the ratio kC----B/kC----X. Fourth, for both isolated chains and intact hemoglobin, the rate and equilibrium constants for the formation of the initial O2 geminate state starting from ligand in the solvent (i.e. kX----B and KX----B) are 5-10 times greater than the corresponding parameters for the formation of the first CO geminate state. Fifth, the rate-limiting step for NO, O2, and isonitrile binding to hemoglobin and its isolated subunits is ligand migration up to the initial geminate state (i.e. kX----B). In the case of CO binding, both migration to state B and iron-ligand bond formation (kB----A) affect the overall, bimolecular association rate constant.     

Formation of lymphocyte colonies under serum-free culture conditions in normal individuals and patients with chronic lymphocytic leukemia

This paper describes a culture system which supports the formation of B cell and some T cell colonies under serum-free conditions in peripheral blood samples of normal individuals and patients with chronic lymphocytic leukemia (CLL) of B cell type. In this system, serum is replaced by bovine serum albumin, transferrin, cholesterol, insulin and catalase or horseradish peroxidase. In addition, it is necessary to add staphylococcus protein A, mitomycin-treated T cells as feeders and phytohemagglutinin leukocyte-conditioned medium as a source of growth factors. The plating efficiency is greatly enhanced when normal cells are incubated with galactose oxidase prior to plating and when CLL cells are exposed sequentially to neuraminidase and galactose oxidase.     

An immunocytochemical method for the localization of fibronectin in Araldite-embedded specimens

Summary The detection of fibronectin (FN) in osmium-fixed and Araldite-embedded frog skin fragments was studied using a modification of Baskin's procedure (Baskin et al. 1979). Following the removal of Araldite from the semi-thin sections (0.5–1.0 m) with ethanol-NaOH solution, the sections were bleached with hydrogen peroxide. FN was detected by indirect immunoperoxidase method. For precise localization of FN, careful attention was paid to the temperature, antibody concentrations and the quality of the ethanol-NaOH solution. Our results were in agreement with those that we had obtained previously for polyethylene glycol (PEG) sections, suggesting that the present procedure is useful for the detection of FN in Araldite-embedded biological specimens.     

An antibody to the receptor for insulin-like growth factor I inhibits the growth of MCF-7 cells in tissue culture

Alpha IR-3, a monoclonal antibody to the insulin-like growth factor I receptor which blocks insulin-like growth factor I binding and inhibits its activity, inhibits the binding of 125I-insulin-like growth factor I to MCF-7 cells (an estrogen dependent human breast carcinoma cell line) with an IC-50 of approximately 100 ng/ml. It also inhibits the growth of MCF-7 cells cultured in 5% calf serum with approximately the same IC-50. Inhibition of growth occurs both when cells are cultured in the presence and absence of estrogen and is more pronounced when cells are grown at a low density. These findings demonstrate a requirement for insulin-like growth factor I for optimal growth of MCF-7 cells and suggest that it is an autocrine growth factor in these cells.     

Contractility, ATP, and creatine phosphate during myocardial ischaemia and reperfusion: the effects of adenosine and inhibition of adenosine catabolism in the dog heart

Provision of AMP or adenosine to heart cells during recovery from episodes of myocardial ischaemia accelerates physiological, biochemical, and structural recovery. Inhibition of adenosine loss from the tissue during ischaemia should have a similar effect. This hypothesis was tested in dog heart by infusion of adenosine and inhibitors of adenosine catabolism prior to, during, and following ischaemia. Post-ischaemic recovery of ATP and contractile function was accelerated significantly by adenosine and by inhibitors of adenosine catabolism both singly and in combination. Contractility and ATP levels during ischaemia were also increased by these inhibitors.