Domains required for nucleic acid binding activities in chloroplast ribonucleoproteins.

Five ribonucleoproteins (or RNA-binding proteins) from tobacco chloroplasts have been identified to date; each of these contains an acidic N-terminal domain (24-64 amino acids) and two conserved RNA-binding domains (82-83 amino acids). All five ribonucleoproteins can bind to ssDNA and dsDNA but show high specificity for poly(G) and poly(U). Here we present the nucleic acid binding activity of each domain using a series of deletion mutant proteins made in vitro from the chloroplast 29 kDa ribonucleoproteins. The acidic domain does not have a positive effect on binding activities and proteins lacking this domain show higher affinities for nucleic acids than the wild-type proteins. Mutant proteins containing single RNA-binding domains can bind to poly(G) and poly(U), though with lower affinities than proteins containing two RNA-binding domains. The spacer region (11-37 amino acids) between the two RNA-binding domains does not interact with poly(G) or poly(U) by itself, but is required for the additive activity of the two RNA-binding domains. Proteins consisting of two RNA-binding domains but lacking the spacer have the same activity as those containing only one RNA-binding domain. Possible roles for each domain in chloroplast ribonucleoproteins are discussed.     

热应激时大鼠肺组织中β—肾上腺素受体的变化与膜磷...

To explore the relationship between the change of beta-adrenoceptor and the metabolism of phospholipids in lung tissue from acute heat stressed rats, the Bmax of beta-adrenoceptors, the activity of phospholipase A2 (PLA2), the content of phosphatidylcholine (PC) and phosphatidylserine (PS), and membrane fluidity in lung tissue of normal and heat stressed rats were investigated. The relevant parameter values mentioned above were 479 +/- 94 fmol/mg protein, 78.5 +/- 8.2 U, 53.5 +/- 1.7 mg/g.wet. w. and 425.1 +/- 68.1 micrograms/g.wet. w. respectively. Whereas in the heat stressed rats with rectal temperature raised to 42 degrees C for 15 min, the Bmax of beta-adrenoceptor was decreased by 43% (P less than 0.01), the activity of PLA2 increased by 83% (P less than 0.01), the contents of PC and PS decreased by 50% and 47% (P less than 0.01) respectively. A lower membrane fluidity in lung tissue for heat stressed rats was also demonstrated. The results suggest that the decreased binding sites of beta-adrenoceptor in lung tissue of rat during hyperthermia may be contributed to the activation of PLA2, which then accelerated the catabolism of phospholipids such as PC and PS in the cell plasma membrane, with a consequent alteration of membrane fluidity.     

Genomic groups,morphology, and sectional delimitation in EurasianElymus (Poaceae,Triticeae)

Seven tetraploid species ofElymus, viz.E. sibiricus, E. caninus, E. gmelinii, E. semicostatus, E. caucasicus, E. parviglume, andE. longearistatus subsp.canaliculatus, representing five sections were studied morphologically and used in interspecific hybridizations. The aim was to investigate whether the present sectional delimitation of the genus was in agreement with genomic data and if there was a correlation between genome constitution and morphology. The study revealed: (i) further information on the genomic affinities between the different species, (ii) that there is no congruence between genome constitution of the species and current sectional delimitation, and (iii) that there is a correlation between genome constitution and morphology in the palea apex shape and in the size of cilia of the palea.     

小麦体细胞再生株（R1）的染色体变异分析

本文研究了普通小麦(Triticum aestivum)、“宁麦三号”等5个基因型的体细胞再生株(R_1)减数分裂各期的染色体异常行为。结果表明:再生株 R_1代有丝分裂时表现为染色体数量上的变异,最常见的有2n-2类型,其次是2n-1类型,也有少数为2n 1和2n-4等变异类型;再生株 R_1花粉母细胞减数分裂过程中出现单价体、多价体、染色体桥、落后染色体、断片和微核等异常现象,并与各基因型细胞遗传程度上差异有关。     

鹅掌楸种子和胚胎发育的研究

应用控制授粉、软 X-射线法、常规石蜡制片法和荧光检测等手段,研究了鹅掌楸(Lirio-dendron chinense(Hemsl.)Sarg.胚胎发育和控制授粉与结籽率的相关性。控制授粉后2小时花粉萌发,6小时萌发率最高,柱头可授期持续30小时左右。花粉管借助于柱头毛之间的分泌物进入柱头沟,经花柱沟、珠孔塞和珠心冠原进入胚囊,行珠孔受精。授粉后2周,胚乳为2至3细胞厚的狭组织;第6周,胚乳充满胚囊腔,珠心随之解体殆尽;第7到8周,球形胚、心形胚发生;第14到16周,子叶形成;第22周种子或熟,胚乳丰富。单株自然授粉结籽率不足1%。控制授粉后,单个聚合果的最高结籽率可达39%,9个聚合果的平均结籽率为17.7%。     

Resolution and stability of oxazepam enantiomers

A solvent mixture containing dioxane, acetonitrile, and hexane was found to be suitable as a mobile phase to resolve oxazepam enantiomers by chiral stationary phase high performance liquid chromatography using covalent Pirkle columns. The resolved oxazepam enantiomers in this solvent mixture had a racemization half-life greater than 3 days at 23°C. When desiccated at 0°C as dried residue, OX enantiomers were stable for at least 50 days with less than 2% racemization. The conditions which stabilized OX enantiomers significantly facilitated the determination of racemization half-lives of OX enantiomers in a variety of aqueous and nonaqueous solvents and at different temperatures. © 1992 Wiley-Liss, Inc.     

Carbon Assimilation and Leaf Water Status in Sugar Beet Leaves during a Simulated Natural Light Regimen

Carbon assimilation and leaf water status were studied in sugar beet (Beta vulgaris L., Klein E-type multigerm) leaves during a light period in which illumination either increased rapidly to full irradiance or changed gradually in a sinusoidal manner as generally occurs during a natural day. A light regimen that simulated the light of a natural day was produced by adjusting irradiance with a neutral-density filter under the control of a computer. Under this light regimen, photosynthesis, transpiration, and stomatal conductance followed the irradiance pattern very closely and ribulose bisphosphate carboxylase was nearly fully activated. When illumination was increased rapidly at the beginning of a light period, transpiration also increased quickly, causing leaves to wilt to some extent. The activation state of ribulose bisphosphate carboxylase increased to only 52%, but ribulose bisphosphate level was nearly twice as high as during the simulated natural day. In spite of the differences in activation state and ribulose bisphosphate levels, photosynthesis rates were very similar under both regimens. Nevertheless, differences in parameters between leaves under the two irradiance regimens can affect how a plant responds to internal or external factors, and therefore, the rate at which irradiance increases at the beginning of a light period is an important consideration when interpreting data.     

Cytogenetic studies of the intergeneric hybrids between Secale cereale and Elymus caninus,E. brevipes,and E. tsukushiensis (Triticeae: Poaceae)

Summary Integeneric hybridizations were carried out between Secale cereale L. (2n = 14, RR) and three Elymus species, namely, E. caninus (L.) L. (2n = 28, SSHH), E. brevipes (Keng) Löve (2n = 28, SSYY) and E. tsukushiensis Honda (2n = 42, SSHHYY). Chromosome pairing was studied at metaphase I in the parental species and the hybrids. Meiotic configurations of the hybrids were 20.74 1+0.14 II for E. caninus x S. cereale (SHR), 16.35 I+2.17 II+0.09 III for E. brevipes x S. cereale (SYR) and 25.84 I+1.10 II+0.02 III for E. tsukushiensis x S. cereale (SHYR), in addition to some secondary associations in the different hybrids. It is concluded from the study that (1) a certain, different homoeologous relationship exists among S, H and Y genomes in the investigated Elymus species; (2) low homoeology is present between genomes of Elymus (S or H or Y) and rye (R); (3) the Secale genome affects homoeologous chromosome pairing between different genomes in E. brevipes and E. tsukushiensis.     

Bioactivity of plasma prolactin in ovariectomized, diethylstilbestrol-treated Long-Evans and Holtzman rats after thyrotropin-releasing hormone or bromocriptine administration

The objective of this study was to determine the effects of thyrotropin-releasing hormone (TRH) and bromocriptine on plasma levels of biologically active prolactin in ovariectomized, diethylstilbestrol (DES)-treated rats. Female Long-Evans and Holtzman rats were ovariectomized and each was given a subcutaneous implant of diethylstilbestrol (DES). One week later, groups of DES-treated rats were fitted with indwelling intra-atrial catheters, and 2 days later blood samples were withdrawn before and at 1, 2, 5, 10, and 20 min after intravenous administration of TRH (250, 500, or 1000 ng/rat). Blood samples were obtained from other groups at 4 weeks of DES treatment by orbital sinus puncture under ether anesthesia before and at 30, 60, and 120 min after bromocriptine administration (2.5 mg/rat sc). Plasma was assayed for prolactin by conventional radioimmunoassay (RIA) and by Nb2 lymphoma bioassay (BA). Holtzman rats released significantly more prolactin following TRH than did Long-Evans rats when the RIA was used to measure prolactin. However, when the BA was used to assay prolactin in the same samples, the Long-Evans rats released more prolactin than did the Holtzman rats. In addition, the ratio of the BA to RIA values was significantly increased in both strains following TRH, but the greatest increase was observed in the Long-Evans rats, in which the ratio was 4.5 at the peak of the TRH-induced rise in plasma prolactin. Gel filtration chromatography of plasma obtained at 5 min after TRH treatment in Long-Evans rats revealed large molecular forms of prolactin with BA to RIA ratios of 4-5. In addition, monomeric prolactin had a BA to RIA ratio of 2. Bromocriptine treatment reduced prolactin levels in both strains, but the effect was more rapid in Holtzman than in Long-Evans rats. In addition, bromocriptine treatment of Holtzman, but not Long-Evans, rats significantly reduced the BA to RIA ratio of plasma prolactin. The results indicate that TRH and bromocriptine affect the release of biologically active prolactin to a greater extent than prolactin detected by antibody in the RIA, and that Long-Evans and Holtzman rats respond to these secretagogues differently with regard to BA to RIA comparisons.