皮质醇的周年变化与雌性虹鳟性腺成熟的关系

利用放射免疫分析法对饲养于恒定水温和自然光照下的雌性虹鳟血浆中皮质醇和性激素含量的周年变化进行了测定．结果表明：１）根据性腺结构指数和性激素分泌量判断,三龄时,雌性虹鳟达到性成熟;２）在血浆中不仅性激素而且皮质醇的变化水平与性腺结构指数的变化高度相关．排卵前性激素的水平都较高,伴随着排卵的进行性激素水平下降．而且在产卵季节虹鳟血浆中皮质醇水平也较高,三龄时皮质醇水平与性腺结构指数的相关系数为０．８６．这些结果提示,皮质醇在虹鳟的繁殖过程中可能发挥某种作用．     

Organelle DNA Synthesis in the Quiescent centre of Arabidopsis thaliana (Col.)

The behaviour of cell nuclei and organelle nucleoids (organellenuclei) was studied in the root apical meristem of 3-d-old seedlingsof Arabidopsis thaliana (Col.). Samples were embedded in Technovit7100 resin, cut into thin sections and stained with 4'-6-diamidino-2-phenylindole(DAPI) for observation of DNA. DNA synthesis in cell nucleiand organelle nucleoids was investigated using the incorporationof [³H] thymidine or 5-bromo-2'-deoxyuridine (BrdU). Incorporated[³H] thymidine and BrdU were detected by microautoradiographyor immunofiuorescence microscopy, respectively. Central cellsand cells just above the central cells of the quiescent centre(QC) showed an extremely low activity of DNA synthesis. However,DNA synthesis occurred in at least one organelle nucleoid ofall cells in the QC within 24 h. This suggests the cells inthe QC are quiescent with regard to nuclear DNA synthesis, butnot with regard to the organelle nucleoids. Key words: Arabidopsis thaliana, quiescent centre, root apical meristem, mitochondrial nucleoid (nuclei), plastid nucleoid (nuclei)     

TRANSCELLULAR BIOSYNTHESIS OF CYSTEINYL LEUKOTRIENES BY KUPFFER CELL—HEPATOCYTE COOPERATION IN RAT LIVER

We previously proposed that an enzymatic cooperation between Kupffer cells and hepatocytes may play an important role in cysteinyl leukotriene (LT) production in rat liver. Anin vitrotranscellular synthesis cysteinyl LTs by a Kupffer cell—hepatocyte coculture system was characterized here. Kupffer cells alone, with A23187 stimulation, did not generate cysteinyl LTs until supplemented either with isolated hepatocytes or with LTC₄synthase and glutathione, indicating that Kupffer cells can synthesize LTA₄but not convert it into LTC₄. In contrast, hepatocytes converted the LTA₄into cysteinyl LTs and further degraded the cysteinyl LTs. Cysteinyl LT production by the Kupffer cell—hapatocyte coculture system was optimized by addition of 1–3% serum albumin to the culture and by bringing the cell—cell distance closer to less than 3μ. Tumour necrosis factor also stimulated cysteinyl LT production by the coculture system. From these results, it is expected that the Kupffer cell—hepatocyte transcellular system for cysteinyl LT production actually functionsin vivo.     

Cellular Basis of Neuralization of Induced Neurectoderm in Amphibian Embryogenesis: Changes of Cell Shape, Cell Size, and Cytodifferentiation of the Neurectoderm after Neural Induction

Cellular alterations of the neurectoderm after primary embryonic induction were examined by measuring several indices of shape, volume, and cytodifferentiation of the neurectodermal cells of Cynops embryos during gastrulation and early neurulation.
Results showed that cellular alterations occurs just after the 18 hr embryo stage (stage 13b). The thickness of the neurectoderm layer decreases like that of the epidermal ectoderm during early and middle gastrulation. After the 18 hr embryo stage, however, the neurectoderm thickens, mainly due to formation of columnar cells. Measurement of cell volume indicates that the neurectoderm of the early and middle gastrulae consists of a cell population of heterogeneous size. The heterogeneity diminishes sharply after the 18 hr embryo stage and the neural plate of the 36 hr embryo (stage 18) consists of cells of homogeneous size.
Stages before the 12 hr embryo (stage 12b) and after the 18 hr embryo (stage 13b) also showed differed in cell adhesion to the culture flask and in cytodifferentiating potency. Single cells dissociated from the neurectoderm of 18 hr embryos could adhere to the substratum and differentiate into both nerve-like cells and pigment cells. Both capacities increase during further development.
These results are discussed in relation to the neuralizing determination of neurectoderm after primary embryonic induction.     

Species Specificity of the Insect Prothoracicotropic Hormone (PITH): the Presence of Bombyx-and Samia-Specific PTTHs in the Brain of Bombyx mori

Crude extracts of Bombyx mori brains can provoke adult development when injected into brain-removed dormant pupae of Bombyx mori and Samia Cynthia ricini. From this fact the prothoracicotropic hormone (PTTH) of Bombyx has long been thought to be species-nonspecifically active on Samia. Chemical fractionation of Bombyx brain or head extracts by fractional precipitation with acetone, Sephadex G-50 gel-filtration, and DEAE-Sepharose CL-6B chromatography, however, separated the fractions which activated Bombyx brainless pupae from those which activated Samia. Those results reveal the existence of two species-specific PTTHs.     

Distribution of Intramembrane Particles and Its Changes during the Acrosome Reaction in Spermatozoa of the Japanese Abalone

The distribution of intramembrane particles in the plasma and acrosomal membranes of sperm of the Japanese abalone, Haliotis discus , and its changes during the acrosome reaction were studied by the freeze-fracture replica technique. The P face of the plasma membrane covering the acrosome has sparse membrane particles except in the apical region, which includes the trigger and 'truncated cone' regions. Large particles with an average diameter of 10 nm are located in this apical region. The E face of the plasma membrane has only a few particles. On the outer acrosomal membrane, many particles are randomly distributed throughout the P face, but only a small number of particles are found on the E face. Numerous particles on the P face of the inner acrosomal membrane show a regular arrangement as a dense lattice or with a concentric circular pattern. The initial change in the acrosome reaction is clearance of membrane particles from both the P and E faces of the plasma and outer acrosomal membranes around the apical region, where fusion of the two membranes occurs. As the acrosomal process elongates, the dense arrangement of particles on the inner acrosomal membrane changes via a loose lattice arrangement to a patchy distribution with particle-free areas. Then the arrangement is further disorganized becoming a sparse, random distribution.     

DOES COLCHICINE AFFECT AGGREGATION OF NORMAL AND TRANSFORMED BHK CELLS DIFFERENTLY?

The effect of colchicine and vinblastine on cell aggregation was studied, using BHK cells and their transformed derivatives (pyBHK cells). When cells were dissociated with EDTA and the assay was made in a Ca²⁺-containing medium, the aggregation of transformed cells was prevented by colchicine and vinblastine, whereas the aggregation of normal cells was unaffected. When a Ca²⁺-free medium was used for aggregation, neither type of cell was influenced by these drugs. BHK and pyBHK cells, dissociated by trypsin in the presence of Ca²⁺, can aggregate only in the Ca²⁺-containing medium and the aggregation of both cell types was equally prevented by colchicine and vinblastine. Based on these results, it was concluded that colchicine and vinblastine inhibited the Ca²⁺-dependent mechanism of cell adhesion, but not the Ca²⁺-independent one which occurs in the Ca²⁺-free aggregation medium.     

Activities of Enzymes Relating to Starch Synthesis and Endogenous Levels of Growth Regulators in Potato Stolon Tips During Tuberization

Changes in contents of starch and protein, and activities of enzymes involved in starch synthesis were studied during tubcrization of stolon tips of Solanum tuberosum L. cv. Irish Cobbler. Starch content and activities of phosphorylase and granule-bound starch synthctase based on fresh weight increased rapidly in the early phase (stage I, the stolon tips just before swelling; stage 2, the swelling tips; stage 3, young tubers of 0.2–0.5 cm diameter), and they all remained nearly unchanged in the later phase (stage 3 to stage 6, young tubers of 3.5 cm diameter). The content of soluble protein based on fresh weight remained unchanged. Activities of soluble starch snythetase and ADP-glucose pyrophosphorylase were not detected at stage 1 and 2, but increased at later stages. Endogenous levels of auxin, cytokinin and gibberellin were assayed for the materials at the corresponding developmental stages. Auxin content was high at stages 1 and 2, and lowered at later stages. Cytokinin content increased abruptly at stage 6. Gibberellin content was low at all stages. The internal conditions for starch deposition and tuberization in potato were discussed in regard to regulation of enzyme activities by growth regulators.