THE RELATION BETWEEN BIOCHEMICAL AND MORPHOLOGICAL DIFFERENTIATION IN BLASTOCLADIELLA EMERSONII. II. NITROGEN METABOLISM IN SYNCHRONOUS CULTURES

Lovett, James S., and Edward C. Cantino. (Michigan State University, East Lansing, Michigan.) The relation between biochemical and morphological differentiation in Blastocladiella emersonii. II. Nitrogen metabolism in synchronous cultures. Amer. Jour. Bot. 47(7): 550–560. Illus, 1960.—A procedure was developed for growing well-synchronized, large-scale cultures of resistant-sporangial plants of Blastocladiella throughout one complete generation period in a glucose-peptone-yeast medium containing NaHCO₃. The increase in size and dry weight of individual plants and a photomicrographic record of their developmental morphology were obtained during the growth of such cultures. The activity of glucosamine synthetase, glucose-6-phosphate dehydrogenase, and phosphoglucoisomerase was determined during development in synchronous culture. The sequence for synthesis of chitin, lipid, melanin, and nitrogenous materials was also established. The free-N pools in developing resistant sporangial plants underwent both quantitative and qualitative changes during differentiation. The significance of the alteration in cellular components and their relationship to the structure and function of the developing thallus were discussed.     

THE RELATION BETWEEN BIOCHEMICAL AND MORPHOLOGICAL DIFFERENTIATION IN BLASTOCLADIELLA EMERSONII. I. ENZYMATIC SYNTHESIS OF GLUCOSAMINE-6-PHOSPHATE

Lovett , James S., and Edward C. Cantino . (Michigan State U., East Lansing.) The relation between biochemical and morphological differentiation in Blastocladiella emersonii. I. Enzymatic synthesis of glucosamine-6-phosphate. Amer. Jour. Bot. 47(6): 499–505. Illus. 1960.—The enzyme glucosamine synthetase (glutamine-fructose-6-phosphate transamidase) was purified ca. 19-fold from extracts of the aquatic phycomycete, Blastocladiella emersonii, by centrifugation, protamine sulfate fractionation, and adsorption on Ca₃(PO₄)₂ gel The pH optimum, time course, and relation between enzyme concentration and reaction rate were established for the partially purified synthetase. The reaction was the same as that of the enzyme of Neurospora crassa: D-fructose-6- phosphate + L-glutamine —> D-glucosamine-6-phosphate + L-glutamic acid. The 20-fold purification attained resulted in an enzyme preparation with a specific activity 40 times greater than that reported for other organisms to date.     

烟草愈伤组织分化和芽原基形成期间呼吸代谢途径的改变

接种在继代培养基上的柳叶烟草愈伤组织,未观察到组织分化和芽原基形成。在分化培养基上生长的愈伤组织,接种后第6天可见拟分生组织和管胞分化,9—12天有芽原基形成,15—18天可观察到苗端结构。根据碘乙酸、Na_3PO_4和丙二酸抑制试验,以及3-磷酸甘油醛脱氢酶与琥珀酸脱氢酶活性测定结果,初步表明烟草愈伤组织呼吸中存在有EMP、HMP和TCAC代谢途径.在发生输导组织和芽原基分化的愈伤组织中(接种后第6—12天),HMP途径的运行程度较高;而芽原基的继续生长(培养12天以后),则与EMP途径的增加有关;分化培养基上生长的愈伤组织,始终较继代培养愈伤组织具有较高的FCAC活性水平。     

花生叶片衰老过程中氮素代谢指标变化

以鲁花11和辐8707两个花生（Arachis hypogea L.)品种为材料,对大田条件下花生叶片衰老过程中N素代谢指标变化进行了研究,结果表明,花生叶叶片展开至衰老过程中,蛋白酶活性逐渐升高,叶中N含量逐渐降低;硝酸还原酶（NR）活性、叶绿素、游离氨基酸和可溶性蛋白质含量呈抛物线型变化,最先开始降低的是NR活性,其次是叶绿素含量,最后是游离氨基酸和可溶性蛋白质含量。     

SYNTHESIS AND METABOLISM OF l-KYNURENINE IN RAT BRAIN

Abstract— A method for the quantitative analysis of femtomole amounts of kynurenine (along with tryptophan, 3-hydroxykynurenine and kynuramine) in rat brain using high pressure liquid chroma-tography and electron-capture GLC is described. Endogenous concentrations of these substances in rat brain regions were measured, and their formation after the injection of radioactive tryptophan or kynurenine was determined. Kynurenine was formed from tryptophan in brain and was also taken up from the periphery. Extracerebral kynurenine was calculated to account for 60% of the cerebral pool of kynurenine. The cerebral rates of synthesis of kynurenine and 3-hydroxykynurenine were 0.29 and 0.17nmol/g/h. The turnover rate of kynurenine in the brain was 1.02 nmol/g/h measured from [¹⁴C]tryptophan or 1.14 nmol/g/h from [³H]kynurenine injected intraperitoneally. Kynuramine levels in different areas of the brain were similar to those of tryptamine. Following intraperitoneal injection of [¹⁴C]tryptophan, the presence of anthranilic, 3-hydroxyanthranilic, xanthurenic, kynurenic and quinaldic acids was demonstrated in the brain.     

氮素水平对花生氮素代谢及相关酶活性的影响

 在大田高产条件下研究了氮素水平对花生(Arachis hypogaea)可溶性蛋白质、游离氨基酸含量及氮代谢相关酶活性的影响, 结果表明, 适当提高氮素水平既能增加花生各器官中可溶性蛋白质和游离氨基酸的含量, 又能提高硝酸还原酶、谷氨酰胺合成酶和谷氨酸脱氢酶等氮素同化酶的活性, 使其达到同步增加; 氮素水平过高虽能提高硝酸还原酶和籽仁蛋白质含量, 但谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(GDH)的活性下降; N素施肥水平不改变花生植株各器官中可溶性蛋白质、游离氨基酸含量以及硝酸还原酶(NR)、谷氨酰胺合成酶、谷氨酸脱氢酶活性的变化趋势, 但适量施N (A2和A3处理)使花生各营养器官中GS、GDH活性提高; 氮素水平对花生各叶片和籽仁中GS、GDH活性的高低影响较大, 但对茎和根中GDH活性大小的影响较小。     

AUTORADIOGRAPHIC STUDY OF RNA SYNTHESIS DURING SECONDARY RHIZOID CELL DIFFERENTIATION IN PTERIS VITTATA

The pre- and postmitotic stages of rhizoid cell differentiation in Pteris vittata L. were pulsed in radioactive uridine for 30 min and the data analyzed quantitatively by autoradiography. The total grain count rises from 594 in the nondifferentiating cell to 1,369 in the corona stage; increases to 2,745 in the internally segmented rhizoid cell (IRC) and to 2,779 in the wheel; and then drops to 1,306 in the protrusion and to 1,261 in the early rhizoid. The significant increase in nucleolar labeling in the corona reflects an increase in ribosomal RNA synthesis for mitosis-associated syntheses. The two-fold increase in grains over the cellular compartments of the IRC and wheel reflects an increase in RNA synthesis in these postmitotic stages. The similarity of labeling profiles between these stages suggests that they are not far enough separated to show a difference in their roles. The decline in total grain counts in the protrusion and early rhizoid stages to half the maximum levels suggests that an overall decrease in RNA synthesis is attended by a shift from a differentiating phase to a steady-state growth system.     

PROTEIN SYNTHESIS AND RNA SYNTHESIS DURING MITOSIS IN ANIMAL CELLS

Protein synthesis and RNA synthesis during mitosis were studied by autoradiography on mammalian tissue culture cells. Protein synthesis was followed by incubating hamster epithelial and human amnion cells for 10 or 15 minutes with phenylalanine-C¹⁴. To study RNA synthesis the hamster cells were incubated for 10 minutes with uridine-C¹⁴. Comparisons of the synthetic capacity of the interphase and mitotic cells were then made using whole cell grain counts. The rate of RNA synthesis decreased during prophase and reached a low of 13 to 16 per cent of the average interphase rate during metaphase-anaphase. Protein synthesis in the hamster cells showed a 42 per cent increase during prophase with a subsequent return to the average interphase value during metaphase-anaphase. The human amnion cells showed no significant change at prophase but there was a 52 to 56 per cent drop in phenylalanine incorporation at metaphase-anaphase as compared to the average interphase rate. Colcemide was used on the hamster cells to study the effect of a prolonged mitotic condition on protein and RNA synthesis. Under this condition, uridine incorporation was extremely low whereas phenylalanine incorporation was still relatively high. The drastic reduction of RNA synthesis observed under mitotic conditions is believed to be due to the coiled condition of the chromosomes. The lack of a comparable reduction in protein synthesis during mitosis is interpreted as evidence for the presence in these cells of a relatively stable messenger RNA.     

包囊游仆虫包囊形成和解脱过程中纤毛器的分化

包囊游仆虫(Euplotes encysticus)形成包囊时,各类纤毛器中的纤毛杆被部分地或全部地吸收,毛基体被保留下来。休眠包囊中,背纤毛器的定位无明显变化,但原腹面纤毛器中的口围带和波动膜、额腹棘毛和横棘毛,以及左、右尾棘毛都按序陷入在细胞质内深处,并相互汇聚在一起。脱包囊时,纤毛结构在原毛基体上再分化,新纤毛器按口围带、横棘毛、额腹棘毛和左、右尾棘毛的顺序从细胞内显露出来。