Effects of a Plant Growth Regulator, Prohexadione Calcium (BX-112), on the Elongation of Rice Shoots Caused by Exogenously Applied Gibberellins and Helminthosporol, Part II

Prohexadione calcium (BX-112) is a novel plant growth regulatorthat inhibits the late stages of the biosynthesis of gibberellinsin plants. Fourteen kinds of gjbberellin, helminthosporol and'helminthosporic acid were applied simultaneously with BX-112to rice seedlings (Oryza sativa L. ), and their growth-promotingactivities in terms of shoot elongation were examined. The growth-promotingactivities of GA₁, GA₄, GA₁₈, GA₂₂, GA₂₃, GA₃₈, helminthosporoland helminthosporic acid were not inhibited by BX-112, but thoseof GA₅, GA₉, GA₁₅, GA₁₉, GA₂₀, GA₃₁, GA₄₄ and GA₅₃ were inhibited.These results suggest that 3ß-hydroxylation is animportant and necessary step in the biosynthesis of gibberellinsthat promote shoot elongation in rice seedlings. The weak promotionof shoot elongation by GA₂₂ in the presence of BX-112 suggeststhat the effect of a hydroxyl group at C-18 of GA₂₂ might beable to mimic the effect of the 3ß-hydroxyl groupof GA₁. Helminthosporol and helminthosporic acid may promotethe shoot elongation of rice by mimicking physiologically activegibberellins and not by stimulating their biosynthesis. ¹Part I is the previous paper by Nakayama et al. (1990a) ³Present address: Frontier Research Program RIKEN, Wako-shi,Saitama, 351-01 Japan. (Received June 26, 1991; Accepted September 4, 1991)     

Cell movements in a living mammalian tissue: Long-term observation of individual cells in wounded corneal endothelia of cats

Although the cells in tissues are known to be motile under special conditions (e.g., during tissue turnover or wound healing), there are not many reports that polygonal cells covering an area without leaving any gaps are also capable of movement. In the present study, cell movements (cell shifting and rearrangement) in a living mammalian eye tissue were documented by identifying and locating individual cells over intervals as long as 100 days. Cat corneal endothelium, a monolayered cell sheet, was wounded by removing a small number (about 180) of endothelial cells from the internal lining of the cornea. Healing of the wounded tissue was observed with a wide-view specular microscope applied to the outer surface of the cornea, enabling us to identify individual cells for as long as two to three months. Cells surrounding the wound underwent areal enlargement, elongated toward the wound, and shifted to cover the wound surface. During days 4–7, cells became rearranged by changing neighbors in such a way that they retained their enlarged size but recovered their non-elongated, original shape. This pattern of cell rearrangement was interpreted by a computer simulation which assumed that cells shorten their boundary length while maintaining contacts with contiguous cells. After day 7, the enlarged cells adjacent to the wounded area gradually contracted and pulled surrounding cells toward the wounded area. These movements were followed by a temporary halt in cell shifting, then by a recovery of shifting and cell elongation. These movements are interpreted as a result of the contractility of endothelial cell microfilaments.     

Apparent binding activity of [H]glutathione in rat central and peripheral tissues

An apparent binding activity of [³H]glutathione (GSH) was detected in the synaptic membranous preparations obtained from the rat brain. Both methionine- and leucine-enkephalins exhibited a profound diminution of the apparent binding at 100 μM in a naloxone-insensitive fashion. The retina was found to have the highest binding activity amongst various central structures examined, followed by the hypothalamus, striatum, spinal cord, midbrain, hippocampus, medulla-pons, cerebellum and cerebral cortex. In peripheral organs employed, the pituitary possessed an apparent binding activity higher than that in the retina, with progressively lower activities in the adrenal, liver, spleen, skeletal muscle and heart. No significant activity was detected in the kidney. These results suggest that specific binding sites of GSH may be located in the central and peripheral excitable tissues.     

Significance of exercise and bed rest in pregnancy--pregnancy and walking (1)

Prior to evaluating the significance of bed rest in managing obstetric diseases, characteristics of physiology of pregnant women were examined on the basis of 24 hours heart rate changes in eight pregnant women at the third trimester and also distances covered in walking by a total of 53 multiparas and of 87 primiparas during free-living daily activities were measured by means of a pedometer. A significantly higher mean heart rate was observed in those pregnant women even during sleep than in non-pregnant control. The primiparas showed significant decreases in the pedometer readings in all stages except for 15-27 weeks of gestation, while the multiparas of less than 28 weeks exhibited no decrease as compared with non-pregnant control. The decrease in the pedometer readings were marked in both primiparas and multiparas, the value being much lower than that of any other week of gestation. However, the equation of weight x distance covered in walking remains rather constant throughout gestation.