The pancreatic glucagon and C-peptide secretion during hyperinsulinemia in euglycemic glucose clamp with or without somatostatin infusion in normal man

6 normal subjects received two times of 2 hr euglycemic glucose clamp studies (insulin infusion rate 40 mU/M2/min) one with and the other without somatostatin (SRIF) infusion (500 microgram/hr). Serum C-peptide and glucagon levels were measured during clamp to study the sensitivity of pancreatic alpha and beta cells to the suppressive effects of exogenous hyperinsulinemia during normoglycemia in normal subjects and to find whether SRIF had any modulative effects on endocrine pancreas secretion at the status of hyperinsulinemia. The results showed that in normal man the degree of suppression of pancreatic glucagon secretion by hyperinsulinemia (approximately 100 uU/ml) during euglycemic glucose clamp without SRIF infusion was less than that of C-peptide with mean value of 62 +/- 4% of basal glucagon remained at the end of clamp study; while only about 30 +/- 2% of basal C-peptide concentrations remained. But during SRIF infused glucose clamp studies (SRIF was infused from 60 to 120 min), 32 +/- 2% of mean basal C-peptide concentrations and 38 +/- 6% of mean basal glucagon concentrations left at the end of 2 hr clamp studies when serum insulin level was about 100 uU/ml. For the glucose infusion rate (M value), it was significantly greater in our normal subjects in response to insulin + SRIF as compared to insulin alone (12.0 + 0.9 vs 8.8 +/- 1.4; P less than 0.01). We concluded: during hyperinsulinemia (100 uU/ml), the sensitivity of pancreatic alpha cells to insulin seems less than that of beta cells in normal man at normoglycemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

中国木兰属和含笑属导管分子的比较解剖

本文对我国木兰科的39种木兰属和含笑属植物次生木质部的导管分子进行了初步分析。两属导管分子的长度和宽度略有差异。木兰属中多数种的导管分于有单穿孔板,但有的可见到梯状穿孔板。含笑属植物的导管分子大多具有梯状穿孔板,仅有一种可看到单穿孔板。在具有梯状穿孔板的木兰属植物中,穿孔板的横隔数目较含笑属的多。木兰属的导管壁上一般无螺纹加厚;含笑属则相反。此外,在两属之间,导管尚存在一些其它差异。     

芦苇胚性愈伤组织的形成及植株的再生

以芦苇种子为外植体,其愈伤组织的诱导率最高。叶鞘和叶片不发生脱分化。培养基中最合适的蔗糖浓度为4%。维生素 B 类、肌醇对愈伤组织的生长起促进作用。而酵母提取物对愈伤组织的诱导和生长具有明显的抑制作用。这种抑制效应,将随酵母提取物浓度的提高而增大。愈伤组织的继代培养,随培养基中2,4-D 浓度的提高,其平均鲜重明显降低。脱分化培养基中2,4-D 浓度对胚性愈伤组织的诱导形成具有一定的相关性。胚性愈伤组织经30代继代培养依然具有90%的分化频率,只是每块愈伤组织的分化苗数减少。反之,非胚性愈伤组织则完全丧失形态发生的能力。对两类愈伤组织进行扫描电镜的观察,发现其表面结构有很大差异。其过氧化物酶、酯酶同工酶谱以及可溶性蛋白的含量均有明显的差别。     

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.     

Purification and Characterization of a Substrate-Size-Recognizing Metalloendopeptidase from Streptococcus cremoris H61

During the ripening of Gouda-type cheese, two kinds of endopeptidases were found to participate in the degradation of αs1-CN(f1-23), a specific product from αs1-casein hydrolyzed by chymosin. One of the endopeptidases, lactic acid bacteria endopeptidase (LEP-II), which can recognize the size of its substrates, has already been purified and characterized (T. R. Yan, N. Azuma, S. Kaminogawa, and K. Yamauchi, Eur. J. Biochem. 163:259-265, 1987). The other endopeptidase, LEP-I, was purified to homogeneity by conventional chromatographic techniques from Streptococcus cremoris H61. The enzyme appeared to be monomeric, with an apparent molecular weight of 98,000, and its isoelectric point was 5.1. For the hydrolysis of αs1-CN(f1-23), the enzyme had an optimum pH and temperature of 7.0 to 7.5 and 40°C, respectively. Its activity was inhibited by such chelating agents as EDTA and 1,10-phenanthrolin, and it could be fully reactivated by Mn²⁺. Inhibitors specific for serine and thiol proteases had no effect on the protease activity. The enzyme showed a high affinity toward the Glu-Asn peptide bond of αs1-CN(f1-23) and αs1-CN(f91-100) but showed no hydrolysis activity toward αs1-CN(f1-52), αs1-CN(61-122), αs1-CN(136-196), αs1-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin. The K_m and V_max of LEP-I for αs1-CN(f1-23) were 14.2 pM and 139 U, respectively.     

Metabolism of progesterone by preimplantation mouse blastocysts in culture

This study examined the question whether or not preimplantation mouse blastocysts can metabolize progesterone (P). When young (Day 4) and implanting (Day 5) blastocysts were cultured in supplemented Eagle's minimum essential medium containing 0.4 microM [3H]P, metabolism of P and formation of metabolites were noticed at 10 h of culture. The metabolites accumulated in medium as the culture continued to 118 h. Three of the four metabolite fractions were identified, by crystallization to constant sp. act., to be 5 alpha-pregnane-3,20-dione and 3 beta-hydroxy-5 alpha-pregnan-20-one (or allopregnanolone), accounting for 22 and 57% of radioactivity, respectively, and a small amount (1-10%) of 3 alpha-hydroxy-5 alpha-pregnan-20-one. This suggests that both delta 4-5 alpha-reductase and 3 alpha- and 3 beta-hydroxysteroid dehydrogenase are active. Day 5 blastocysts were much more active than Day 4 blastocysts in P metabolism. It is suggested that the ability of blastocysts to metabolize P could produce the following effects in the adjacent endometrium: a lessening of P effects; and consequently a change in P-estrogen interaction; and possible effects from the metabolites. These local effects of embryos on the endometrium may be important for embryonic development and implantation.     

Gene mapping on maize pachytene chromosomes by in situ hybridization

A sensitive in situ hybridization technique which was effective for mapping genes of low copy number on human metaphase chromosomes was used for gene mapping on maize pachytene chromosomes. A cloned genomic EcoR1 fragment of 10.8 kb, containing most or all of the sequence encoding the Waxy locus mRNA, was used as the probe. Southern DNA blotting analyses performed by Shure et al. (1983) indicated that the Waxy locus was a single copy sequence. In our in situ hybridization experiment, the probe hybridized to a specific site on chromosome 9. Labeling at this site was detected in 48.6% of 154 randomly selected copies of chromosome 9. To test the sensitivity of the method, subclones of the fragment with insert sizes of 6.6, 4.7, 3.5, 2.3, 1.9 and 0.8 kb were used for in situ hybridizations. Labeling efficiency for each probe was determined. The data showed that a single copy probe of 1.9 kb could be detected at the correct position in 18% of 183 randomly selected number 9 chromosomes.     

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.     

Purification and characterization of a novel metalloendopeptidase from Streptococcus cremoris H61. A metalloendopeptidase that recognizes the size of its substrate

An endopeptidase (LEP-II), which has a unique substrate specificity, was purified to homogeneity by conventional chromatographic techniques from Streptococcus cremoris H61. The enzyme was a metalloendopeptidase since it was inhibited by EDTA and 1,10-phenanthroline; the metal-depleted enzyme could be fully reactivated by micromolar levels of Zn2+ and was not inhibited by specific inhibitors for serine or thiol protease. The molecular mass of the enzyme was estimated to be 80 kDa by Sephacryl S-300 gel filtration and high-performance liquid chromatography with a TSK-G3000SW column. The enzyme consisted of two identical subunits and the N-terminal sequence of LEP-II was determined up to the 19th residue. Although the enzyme had a broad substrate specificity it specifically hydrolyzed the peptide bonds involving the amino groups of hydrophobic amino acid residues. Various small polypeptides, such as alpha s1-CN(f1-23), alpha s1-CN(f91-100), oxidized insulin B chain, glucagon and some biologically active peptides were hydrolyzed. However, a variety of larger polypeptides or proteins, such as alpha s1-CN(f1-54), alpha s1-CN(f61-123), alpha s1-CN(f136-196), alpha s1-casein, beta-casein, and kappa-casein were not hydrolyzed. LEP-II recognized the size of its substrates, which were limited below a molecular mass of about 3.5 kDa.