Plant Regeneration from Isolated Microspore of Indica Rice

Isolated microspores of rice (Oryza saliva L.) cultivars, IR36and IR43, belonging to the recalcitrant indica subspecies werecultured. Two types of microspores were observed after isolationfrom the fresh anthers and from pre-cultured anthers—onetype consisted of vacuolated, larger-sized grains, while theother was composed of microspores of smaller sizes with densecytoplasm. Within few days in culture, all the smaller sizedgrains were dead, and only the large grains were viable andproduced pollen embryos. After 30 days from culture, microcalliwere transferred to semisolid modified Murashige and Skoog mediumcontaining 1 mg/liter each of kinetin and naphthaleneaceticacid and kept under continuous light at 25?C. IR36 showed onlycell division while IR43 gave 32 green plants from these experiments. (Received January 18, 1990; Accepted July 4, 1990)     

let-60, a gene that specifies cell fates during C. elegans vulval induction, encodes a ras protein

Genetic analysis previously suggested that the let-60 gene controls the switch between vulval and hypodermal cell fates during C. elegans vulval induction. We have cloned the let-60 gene, and shown that it encodes a gene product identical in 84% of its first 164 amino acids to ras gene products from other vertebrate and invertebrate species. This conservation suggests that the let-60 product contains all the biochemical functions of ras proteins. Extrachromosomal arrays of let-60 ras DNA cause cell-type misspecification (extra vulval fates) phenotypically opposite to that caused by let-60 ras loss-of-function mutations (no vulval fates), and suppress the vulvaless phenotype of mutations in two other genes necessary for vulval induction. Thus, the level and pattern of let-60 ras expression may be under strict regulation; increase in let-60 ras activity bypasses or reduces the need for upstream genes in the vulval induction pathway.     

Functional profile of the human fetal gamma-globin gene upstream promoter region.

We performed a systematic functional analysis of the human gamma-globin promoter to identify its activator domains. We used a panel of truncation and scanning mutants as well as transfection in human K562 fetal erythroid cells. The various mutations produced relatively small changes in promoter function in both transient and stable transfection assays. The CACCC region and the region containing the binding sites for protein GATA-1 behaved as activator domains. We also obtained evidence for a minor activator site in the - 200 to - 190 region. The results are consistent with the interpretation that gamma-globin gene regulation may occur in part through multiple small effects of promoter elements.     

Common denominators in the etiology and pathology of visceral lesions of cystic fibrosis and Keshan disease

The common denominator of a unique disseminated multi-focal milliary myocardial hyaline necrosis and fibrosis in Keshan disease (KSD) and cystic fibrosis (CF) and a commonality of the affected age groups of fetuses and preschool children led to the review of existing KSD autopsy material to search for pancreatic and hepatic lesions considered pathognomonic for CF. Pancreatic lesions considered pathognomonic for CF were found in 595, or 35% of 1700 documented cases of KSD. The pancreatic lesions were limited to tissues of fetuses and preschool children. Adults dying of KSD had diagnostic lesions limited to the cardiovascular system, liver, and skeletal muscle. Varying degrees of focal biliary cirrhosis were identified in 850, or 50% of the KSD autopsies, and 85, or 5% developed severe lobular cirrhosis. The common denominator in CF and KSD appears to be a primary or induced secondary selenium deficiency in age-susceptable humans, prenatally at or around 22 wk of fetal life, during early postnatal life, or during the rapid-growth preschool years. The basic difference between the natural history of CF and KSD is that the selenium deficiency is totally environmental in KSD and appears to be the result of a maternal malabsorptive syndrome or an abnormality of selenium transfer in CF.     

Variability of entrainment of cohesive sediments in freshwater

Estimates of sediment entrainment are required for models of particle transport in lakes and estuaries but are difficult to make because of the multiplicity of factors affecting cohesiveness of surficial sediments. We present results of sediment resuspension studies performed in an annular flume calibrated with laser-Doppler velocimetry. In our experiments, using sediments collected from two sites in the R. Raisin which flows into L. Erie and from one site in the western basin of L. Erie near the mouth of the R. Raisin, we applied shear stresses at the sediment-water interface in steps from 2 to 12 dyne/cm². Percent water content at the surface of the sediments was either 77 or 74%, and trials were run with and without oxygenating the water overlying the sediments. Entrainment rates as a function of shear stress at the sediment-water interface were best described by a power-law relationship. All but 14% of the variability in the power law expression was due to shear stress and percent water content; the variability not accounted for was due to differences in particle size distributions, chemical properties, and biological activity in the sediments.     

Comparison of DMO and flow cytometric methods for measuring intracellular pH and the effect of hyperthermia on the transmembrane pH gradient

Intracellular pH (pHi) was measured in both unheated and heated cells by the distribution of the weak acid, 5,5-dimethyl-2,4-oxazolidinedione-2-14C (14C-DMO), and by the fluorescence intensity ratio (I530/I630) of the pH sensitive fluorescent dye, 2',7'-bis(carboxyethyl)-5,6-carboxy-fluorescein (BCECF), analyzed by flow cytometry (FCM). BCECF-loaded Chinese hamster ovary (CHO) cells were analyzed by FCM after they had incubated in fresh medium at 37 degrees C for 90 min, during which time a decrease in fluorescence ratio stabilized. After stabilization, the pHi determined for CHO cells by the FCM method at pHe values of 6.0-8.1 agreed-within 0.1 pH units with that determined by the 14C-DMO method. There is a pH gradient across the plasma membrane that is not affected by heat. In CHO cells, the gradient, determined by DMO and FCM, is less or greater than pHe by 0.30 and 0.15 pH units at pHe 7.4 and 6.3, respectively, and in NG108-15 cells, the gradient determined by DMO increases to 0.50 pH units at pHe 6.3. Both cells maintained their pH gradients for at least 4 h after heating, although 99.9% of the cells were reproductively dead (survival of 10(-3)) after heating at 45.5 degrees C either at the normal pHe of 7.4 or at a low pHe of 6.4-6.7.     

GABA神经元在金黄地鼠视觉中枢的分布

本文用免疫细胞化学技术研究了GABA在金黄地鼠视觉中枢的分布特征,同时用统计学方法作了定量分析,结果表明:GABA阳性神经元分布在整个视皮层和上丘中,呈不均匀分布,外膝体中GABA阳性神经元密度较低.视皮层中GABA阳性神经元密度为781mm~2,占视皮层细胞总数的19.7%,上丘中其密度为812/mm~2,占22.3%,视皮层Ⅰ层中GABA阳性神经元为52%,上丘表层(浅灰层及视觉层GABA阳性神经元为56%,GABA阳性神经元包括不同类型的细胞.在视皮层中可观察到GABA免疫疫应阳性的锥体细胞.     

L7811鼠腹水肿瘤细胞^31P核磁共振的研究

用~(31)P核磁共振技术(~(31)P-NMR)研究了L_(7811)鼠腹水肿瘤细胞和615系鼠胸腺细胞(正常对照细胞)。结果发现在肿瘤晚期阶段,L_(7811)腹水肿瘤细胞的含磷化合物未进入完全不活跃状态。此外,腹水肿瘤细胞的磷脂组成与含量亦有明显改变。因此,~(31)P-NMR谱可做为观察肿瘤细胞内能量生成和某些磷脂合成宏观动态过程的一项参考指标。