The glucose-6-phosphatase system in rat hepatic microsomes displays hyperbolic kinetics at physiological glucose 6-phosphate concentrations

The kinetics of rat liver glucose-6-phosphatase (EC 3.1.3.9) were studied in intact and detergent-disrupted microsomes from normal and diabetic rats at pH 7.0 using two buffer systems (50 mM Tris-cacodylate and 50 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) and glucose-6-P varied from 20 microM to 10 mM. Identical data were obtained when the phosphohydrolase activity was quantified by a colorimetric determination of Pi or by measuring 32Pi formed during incubations with [32P]glucose-6-P. In every instance the initial rate data displayed excellent concordance with that expected for a reaction obeying Michaelis-Menten kinetics. The present findings agree with recently reported results of Traxinger and Nordlie (Traxinger, R. R., and Nordlie, R. C. 1987) J. Biol. Chem. 262, 10015-10019) that glucose-6-phosphatase activity in intact microsomes exhibits hyperbolic kinetics at concentrations of glucose-6-P above 133 microM, but fail to confirm their finding of sigmoid kinetics at substrate concentrations below 133 microM. We conclude that glucose-6-P hydrolysis conforms to a hyperbolic function at concentrations of glucose-6-P existing in livers of normal and diabetic rats in vivo.     

Reproductive and metabolic hormones during estrus after fasting in Holstein heifers

The estrous cycles of 23 Holstein heifers were synchronized with three prostaglandin F₂α (PG) injections at 0600 h 11 d apart, designated as Days ?11, 0 and 11. Twelve of the animals were randomly assigned to receive no solid food (Group F) from Day 6 to 14, while the other animals remained on full feed to serve as controls (Group C). Jugular blood samples were collected at 6-h intervals beginning with PG injection at 0600 h on Day 0 until 1800 h on Day 4 and at 0600, 1200 and 1700 h on Day 8 through 10. Samples were collected again at 6-h intervals from PG Day 11 (0600 h) until 1800 h on Day 15. Period 1 was defined as those samples collected from Day 0 through 4.5, Period 2 from Day 7 through 10, Period 3 from Day 11 through 14.25, and Period 4 from Day 14.5 through 15. Plasma growth hormone concentrations were increased (P<0.01) in F as compared with C animals during Periods 2, 3 and 4. Plasma concentrations of prolactin (P<0.01) were decreased in F as compared with C animals during Periods 2 and 3. Plasma urea concentrations were increased (P<0.01) in F as compared with C animals during the first 3 d of the fast (Period 2) but were decreased (P<0.01) during the remainder of the experiment (Periods 3 and 4). Thus, fasting was effective in altering several metabolic parameters. Although plasma progesterone and luteinizing hormone (LH) concentrations remained similar (P>0.05) between F and C animals, plasma estradiol-17β concentrations decreased in F as compared with C animals during Periods 2, 3 and 4. No differences (P>0.05) between F and C animals were found in duration to LH peak after PG injection, estrous behavior, or pregnancy rates. Results from this study indicate that fasting reduced plasma estradiol-17β concentrations during estrus but did not alter occurrence of estrus or pregnancy rate.     

MSI2通过下调circRNA_001214促进急性髓系白血病细胞HL60生长

Musashi-2（MSI2）是一种RNA结合蛋白质,对维持造血干细胞功能具有重要作用。研究表明,MSI2高表达能促进急性髓系白血病（acute myelocytic leukemia, AML）进展,但其作用机制尚不明确。本研究稳定沉默HL60细胞MSI2后,第1、2、3、4 d对照组的相对细胞生长率分别为1.931 ± 0.027、3.070 ± 0.073、4.017 ± 0.092和4.215 ± 0.246;敲减组分别为1.927 ± 0.035、2.564 ± 0.090、2.825 ± 0.097和3.223 ± 0.182,两组相比具有统计学差异,P<0.001;细胞凋亡明显增加(7.967% ± 0.698% vs 3.400% ± 0.322%., P<0.01);G₀/G₁期细胞比例明显增高（67.430% ± 4.390% vs. 50.360% ± 2.160%, P<0.01）;NUMB蛋白明显上调,LEF1明显下降。环状RNA（circular RNA, circRNA）芯片筛选和荧光定量PCR验证显示,MSI2沉默组circRNA_001214表达水平是对照组3.48倍。这一结果也在NALM6细胞得到证实。进一步用生物信息学分析,显示circRNA_001214最可能与miR-1273a、miR-1273e和miR 5095结合,进而影响参与细胞凋亡相关基因（CYCS、AKT1、BAX、TNFRSF10A、TNFRSF10D）、Wnt信号基因（WNT4、WNT2B、WNT7B、 DKK2、SFRP1、CSNKE1和LEF1）以及参与细胞代谢相关基因（RPE, PGAM4, PGAM1, TAT, CBS、RPE、SUCLG2、PGAM4、PGAM1和 IDNK）。总而言之,MSI2可能通过干扰circRNA_001214生成,减少靶miRNA对凋亡、Wnt信号及细胞代谢相关基因表达的影响,促进细胞生长。     

The biosynthesis of extracellular-matrix components by bovine retinal endothelial cells displaying distinctive morphological phenotypes.

Previous studies have indicated that the morphology and behaviour of bovine retinal microvessel endothelial cells are influenced by culture conditions in vitro. Data are presented here concerning the biosynthesis of matrix macromolecules by bovine retinal endothelial cells cultured under conditions in which the cells display either the 'cobblestone' or the 'sprouting' phenotype. Newly synthesized matrix proteins were identified by their characteristic electrophoretic mobilities, immunoprecipitation with specific antibodies, susceptibilities to enzymic digestions and chromatographic behaviour. Type IV procollagen was the major collagenous species synthesized by early-passage cells forming a 'cobblestone' monolayer. In contrast, cells displaying the 'sprouting' morphology switched to the predominant synthesis of interstitial fibrillar collagens (types I and III). Fibronectin was synthesized by retinal endothelial cells under all the experimental conditions studied. A non-collagenous glycoprotein of Mr approx. 47,000 was also a major biosynthetic product of these cells. The synthesis of thrombospondin was very much dependent on the nature of the substratum on which the cells were cultured. This glycoprotein was synthesized in large amounts by 'cobblestone' endothelial cells cultured on gelatin-coated dishes, whereas its synthesis was markedly decreased by culturing the cells on collagen gels, and the protein appeared to be absent when the cells were plated within collagen gels ('sprouting' cells). Late-passage retinal cells synthesized predominantly type I procollagen, variable amounts of type III procollagen and only traces of type IV procollagen, irrespective of whether the cells displayed a 'cobblestone' or 'sprouting' morphology.     

酪氨酸对大鼠离体Leydig细胞睾酮和cAMP生成的影响

本实验采用胶原酶消化,Ficoll 密度梯度离心,制备大鼠睾丸 Leydig 细胞悬浮液进行体外培养(每管内含有10~6 细胞),以研究酪氨酸对 Leydig 细胞睾酮和cAMP 生成的影响。实验结果表明,hCG(100mIU)能明显地促进Leydig 细胞睾酮和 cAMP的生成。睾酮从对照组的3.08±0.58ng(X±SD,下同)增加到41.61±1.52ng,cAMP 含量从19.62±2.56pmol增加到153.24±5.92pmol。若将酪氨酸(60μg)与hCG同时加入到细胞培养液中,则睾酮和cAMP 含量分别下降到 19.22±.0.52ng(P<0.01)和92.63±6.02pmol(P<0.05)。但是,酪氨酸羟化酶抑制剂(α-甲基酪氨酸)对酪氨酸抗hCG致睾酮生成作用无阻断效应,而酪氨酸对外源cAMP(2.5mM)诱导的睾酮生成,则有明显的抑制作用,睾酮含量从27.56±1.53ng降至 19.50±0.47ng(P<0.01)。以上实验结果表明,酪氨酸抗hCG致睾酮生成的作用机理与cAMP有关。     

云南叶螨属一新种(蜱螨目:叶螨科)

在鉴定云南叶螨标本时,发现叶螨属一新种,现记述如下。模式标本保存于上海农学院。本文量度单位均为微米。 食禾叶螨Tetranychus graminivorus新种(图1—14) 雌螨 体长(包括喙)454,宽298。椭圆形。浅黄绿色。须肢端感器圆柱形,长6.8,     

中国东北地区常见有瓣蝇类调查初步报告

与人类杂处的蝇类,在我国东北地区的分布情况尚少系统调查。作者于1956年5月、8月曾赴内蒙东北部(伊图里河、图里河),6月、7月赴营口、盘山(田庄台),借这些机会,顺便采集了蝇类标本;同年9月组内同志去绥中也采回部分标本;1957年5月至10月作者又赴吉林、辽宁两省各地进行了蝇类调查。其中有瓣蝇类已经定名的共计5科26属68种,有6种为国内新记录。兹将结果报告如下:     

我国赫坎按蚊群内中华按蚊不同类型的研究——Ⅳ.幼虫形态的比较

对于赫坎按蚊群内(Anopheles(A.)hyrcanus group.)用四龄幼虫的形态来区别不同种型,在国外曾有若干报导,如马来亚(Reid,1953;1963)、日本(Otsuru and Ohmori,1960)、菲律宾(Baisas et al.,1936等)及印澳(Bonne-Wepsrer and Swellengrebel,1953)等,但在国内对这方面的研究很少。1938年林樑城和姚永政对于南京地区中华按蚊(统称)幼     

酪氨酸对人离体滋养层细胞孕酮与hCG分泌的影响

本文观察三种剂量(2×10~(-5)mol/L,2×10~(-4)mol/L和2×10~(-3)mol/L)的酪氮酸对离体培养的滋养层细胞孕酮及hCG分泌的影响,并对其抑制效应的机理作了初步探讨。实验结果表明,三种剂量的酪氨酸均可抑制滋养层细胞孕酮分泌(P<0.01),但是,在孕酮分泌受酪氨酸抑制的同时,未见对hCG分泌发生影响(P>0.05),进一步观察了酪氨酸对滋养层细胞3β-羟甾脱氢酶活性的影响,结果表明,酪氨酸能显著抑制3β-羟甾脱氢酶活性,提示酪氨酸对滋养层细胞孕酮生成的抑制作用与抑制3β-羟甾脱氢酶活性有关。