CELL DIVISION IN RELATION TO CYTODIFFERENTIATION IN CULTURED PEA ROOT SEGMENTS

One mm-thick segments cut 10–11 mm proximal to the root tip of germinating seeds of garden pea Pisum sativum were cultured in sterile nutrient medium containing auxin in the presence and absence of kinetin. In the absence of added cytokinin, pericyclic proliferation occurred, the cortical tissues showed no proliferation and were sloughed off, and a callus tissue of diploid cells was formed. In the presence of kinetin concentrations from 0.1–1.0 ppm cortical cells of the segments were induced to divide, beginning at the third day. From experiments with ³H-thymidine incorporation at different times of culture, from cytological squash preparations and from histological sections it was shown that the cortical cells stimulated to divide by cytokinin underwent DNA synthesis prior to division, were polyploid, and following cell division rapidly underwent cytodifferentiation at 5–7 days to form mature tracheary elements. At 10 days, when over 300,000 new cells had been formed per segment about 16% of these cells had formed tracheary elements. It was concluded that cytokinin, together with auxin, was essential for the initiation of DNA synthesis in the cortical cells, for their subsequent division, and finally for their specific cytodifferentiation.     

布氏田鼠种群数量的季节动态与鼠洞的关系

布氏田鼠种群和鼠洞数量均呈单峰型季节动态,新洞口和鼠丘上洞口的季节动态与鼠的季节动态存在-种正相关关系。盗洞率随堵洞后记录时间的推延而增加,并于堵洞后3天趋于最大值。盗洞率(r″′ )春季为40～50%;夏季为8O%以上;秋季为70～80% 。但每鼠盗洞数春季最高,夏季下降到最低,秋季又有所回升。样方内鼠只数／真实盗洞率(K_3max )比较理想,鼠只数／堵洞数(K₁ )比较实用。洞口系数K₁具有显著性季节变化,春季为口0.05995,夏季为O.2336,秋季为0.141。     

RELATION OF PROTEIN SYNTHESIS TO THE DIVISION CYCLE IN MAMMALIAN CELL CULTURES

The distribution of the reaction product of a staining method for adenosine triphosphatase (ATPase) in rat small intestine, kidney, and liver was studied with electron microscopy. Several procedures were tried but the best results were obtained from tissue that had been quenched in liquid nitrogen, sectioned at 25 µ in a cryostat, fixed for 30 to 90 minutes at 4°C in formalin-sucrose buffered to pH 7.2, incubated with substrate, and then osmicated and prepared for electron microscopy in the usual way. This procedure enabled the localization of mitochondrial ATPase to be studied. In tissue fixed in small blocks in osmium tetroxide for 3 minutes prior to incubation with substrate, good preservation was noted, and the reaction product for ATPase was localized on the cell membrane and nuclei. The reaction product was present in abundant amount in the nuclei, and particularly within nucleoli, of all tissues studied. Because the histochemical localization of nuclear enzymes poses numerous interpretative problems at the present time, the significance of this nuclear localization is uncertain. Cell (plasma) membranes were the site of localization, especially at areas where it has been proposed that active transport mechanisms may occur, namely, on the microvilli of intestinal epithelium, endothelial lining of capillaries, glomerular epithelial cell membranes, basal infoldings of the cell membrane of renal tubules, on the microvilli of bile canaliculi, and on the microvilli of proximal convoluted tubular epithelial cells. ATPase localization on the cristae mitochondriales was also demonstrated.     

蔷薇属38个野生种果实的维生素含量及其与分组的关系

对蔷薇属 (Rosa) 38个野生种果实 (以下简称蔷薇果 )的经济性状进行了分析 ,并测定了 VC、VE 和胡萝卜素等重要维生素的含量。蔷薇果 VC 含量在该属种间差异很大 ,以秦岭蔷薇 (R.tsinglingensis)的含量为最高 (2 576mg/ 1 0 0 g) ,德钦蔷薇 (R.deqenensis)的含量为最低 (49mg/ 1 0 0 g)。胡萝卜素含量种间差异明显 ,以软条七蔷薇 (R.henryi)的含量为最高 (1 9.2 4 mg / 1 0 0 g) ,黄刺玫 (R.xanthina)的含量为最低 (0 .0 6 mg/ 1 0 0 g)。 VE 含量种间差异较小 ,在 1 .34 mg/ 1 0 0 g(黄刺玫 )至 3.86 mg/ 1 0 0 g(硕苞蔷薇R.bracteata)之间。对蔷薇亚属 54种野生种果实重要维生素含量的统计分析表明 ,维生素含量与分组具有一定相关性 ,尤以 VC 含量与分组的相关性最为明显 ,桂味组和小叶组 Vc含量很高 (均值都高于 1 80 0mg/ 1 0 0 g) ;合柱组、月季组、木香组和硕苞组含量很低 (均值都在 30 0 mg/ 1 0 0 g以下 ) ,芹叶组除宽刺蔷薇 (R.platyacantha) VC含量很高外 ,其余种类含量都很低 (均值为 1 90 mg/ 1 0 0 g)。胡萝卜素含量与分组也具有一定相关性 ,桂味组、芹叶组、合柱组和硕苞组的胡萝卜素含量较高 ,均值在 6 mg/ 1 0 0 g以上 ;月季组、小叶组和木香组含量较低 ,均值在 0 .4mg/ 1 0 0 g以下。V     

CHANGES IN ENDOGENOUS CYTOKININ CONCENTRATIONS IN CHLORELLA (CHLOROPHYCEAE) IN RELATION TO LIGHT AND THE CELL CYCLE1

Endogenous cytokinins were quantified in synchronized Chlorella minutissima Fott et Novákova (MACC 361) and Chlorella sp. (MACC 458) grown in a 14:10 light:dark (L:D) photoperiod. In 24 h experiments, cell division occurred during the dark period, and cells increased in size during the light period. Cytokinin profiles were similar in both strains, consisting of five cis‐zeatin (cZ) and three N⁶‐(2‐isopentenyl)adenine (iP) derivatives. Cytokinin concentrations were low during the dark period and increased during the light period. In 48 h experiments using synchronized C. minutissima (MACC 361), half the cultures were maintained in continuous dark conditions for the second photoperiod. Cell division occurred during both dark periods, and cells increased in size during the light periods. Cultures kept in continuous dark did not increase in size following cell division. DNA analysis confirmed these results, with cultures grown in light having increased DNA concentrations prior to cell division, while cultures maintained in continuous dark had less DNA. Cytokinins (cZ and iP derivatives) were detected in all samples with concentrations increasing over the first 24 h. This increase was followed by a large increase, especially during the second light period where cytokinin concentrations increased 4‐fold. Cytokinin concentrations did not increase in cultures maintained in continuous dark conditions. In vivo deuterium‐labeling technology was used to measure cytokinin biosynthetic rates during the dark and light periods in C. minutissima with highest biosynthetic rates measured during the light period. These results show that there is a relationship between light, cell division, and cytokinins.     

百合生殖细胞分裂过程中微管分布的显微荧光观察

用抗微管蛋白抗体和荧光标记技术,观察了百合生殖细胞经有丝分裂形成精细胞过程中微管的变化。生殖细胞在分裂的前期,存在于核外围以及细胞两端胞质内的微管大都以微管束的形式沿细胞长轴方向平行排列。在靠近核的部位,有些微管有时会斜向排列。分裂进入中期后,染色体集中排列在赤道面。在染色体周围可以见到有多束与细胞长轴平行排列着的微管,但这些微管束是在分裂中期时新形成的或是在前期已存在,尚难以断定。这些微管束有一个特点,就是当它们延伸至赤道板部位时,在每一条微管束上都有一个无荧光的小圆区;这个小圆区可能代表着丝粒的位置。细胞分裂进入后期,姊妹染色单体分别向两极移动形成两组染色体。在它们之间近赤道板位置出现了一个具有强烈荧光的区域,显示在这一部位,微管相当浓密。从这一强烈荧光区向两极分别伸出多条微管束。因此,在这一强烈荧光区内可能有多个微管束重叠。到细胞分裂末期,在这一强烈的荧光区的中央出现了一条横向的无荧光区。这一区域有可能为胞质完成分裂后新形成的细胞板所在的部位。     

CELL SHAPE AND WALL PATTERN IN RELATION TO CYTOPLASMIC ORGANIZATION IN PEDIASTRUM SIMPLEX

P. simplex is a single-pronged, fenestrated species of Pediastrum. Comparison is made in regard to cell differentiation and structure with P. boryanum, a 2-pronged, unfenestrated species, with emphasis on the origin of cell wall pattern and the regulation of cell shape. The characteristic wall pattern is initiated with the deposition of plaques of wall material of the outer wall layer when zoospores have assembled in the colony. The pattern is postulated to be templated in the plasma membrane. The inner, thicker wall layer is fibrillar and deposited from vesicles derived from the golgi apparatus. In P. simplex 2–4 dictyosomes are present in contrast to the single dictyosome of P. boryanum. The dictyosomes lie at the concave inner face of the nucleus. Blebs of its ribosome-free outer membrane are contributed to the forming face of the golgi apparatus. Parallel microtubules underlie the plasma membrane in the aggregating zoospores and disappear after the initiation of wall formation. The possible role of microtubules and other organelles in the determination of cell shape in Pediastrum is discussed.     

NUCLEAR GLYCOCONJUGATES AND THEIR RELATION TO MALIGNANCY

1. The nucleus has a distinctive carbohydrate chemistry, the main features of which are the lack of glycosphingolipid, the high density of carbohydrate per unit area of nuclear membrane, the presence of glycosaminoglycan in the nuclear matrix and possibly the nuclear membranes, and the existence of glycosylated non-histone proteins. 2. The nucleus has considerable autonomy in its metabolism of glycosaminoglycan and has a capacity for glycosyl transfers involving glycosyl dolichyl phosphates and pyrophosphates. This latter activity probably resides in the nuclear membranes. 3. The soluble fraction of the nucleoplasm contains the total cellular CMP-sialic-acid synthetase and, hence, all sialic acid metabolism passes through the nucleus, which may have a regulatory role. Uncertainty remains as to the sialic acid content of the glycoproteins of the nucleus and it is likely to vary between cell types. 4. Malignancy is associated with several alterations in the glycosylation of nuclear membranes, including increased levels of sialic acids in the glycoproteins of the inner nuclear membrane: changes in glycosylation of the matrix and chromatin are not yet well defined. In malignancy, some nuclear glycoproteins may possibly appear in other cellular membranes.