银木种内化学类型研究

毛细管气相色谱／质谱／计算机联用仪器分析结果表明,在四川省成都市一人工种植的银木（Ｃｉｎｎａｍｏｍｕｍｓｅｐｔｅｎｔｒｉｏｎａｌｅ）种群中,其枝叶精油主要化学组成在各植株间存在很大差异,发现精油存在１,８－桉叶油素,樟脑,异丁香酚甲醇和９－氧代橙花叔醇等四个化学类型．除异丁香酚甲醚类型外,其余类型均为第一次报道．综观樟属其它种的化学类型研究可见,化学类型在樟属植物中普遍存在种内多型性和种间共性．     

组建昆虫系统生物学的目的性和可行性探索

通过作在昆虫生物学方面近五十年研究工作的体会．提出了组建昆虫系统生物学的目的性和可行性探索．拟以昆虫分类序列目、科、属、种为单元,将一些已知种类的有关生物学环节．一一列叙．编成《中国农林昆虫系统生物学手册》．再以目、科、属、种为主体,探求彼此间在生物学各环节间的共性和个性,分别加以比较、归纳和分析．作为这—分支学科的蘸本。     

A NEW SPECIES OF GENUS HABROPHLEBIODES ULMER (EPHEMEROPTERA: LEPTOPHLEBIIDAE)

Abstract  The present paper deals with a new species Habrophlebiodes zijinensis sp. nov. collected in Nanjing, Jiangsu Povince, China.     

A gene encoding a truncated large subunit of Rubisco is transcribed and salt-inducible in rice

Using the rice salt-tolerant mutant 20 as material, a cDNA library was constructed and two salt-inducible clones, SIR5.5 and SIR8.1, were isolated by differential screening. Homology analysis revealed that the two clones together constituted a chimeric rbcL which encoded a truncated large subunit of Rubisco with 337 amino-acids, plus 64 amino-acids of unknown origin. The expressions of both the normal and the chimeric locus appeared to be developmentally regulated and salt-inducible in shoots of the salt-tolerant mutant 20 and its original variety 77–170. In roots, their expressions were salt-inducible in the salt-tolerant mutant 20 whereas no, or only premature, forms were present in the salt-treated original variety 77–170. Higher concentrations of salt reduced the expressions of both normal rbcL and the chimeric locus. ABA showed no effect on their expression.     

RFLP tagging of a salt tolerance gene in rice

A salt tolerant rice mutant (M-20) was obtained through selection in vitro. Its tolerance was stably inherited over eight generations and most traints between M-20 and its sensitive original 77–170 (Oryza sativa) were very similar. By deriving an F₂ population of M-20 × 77–170 and splitting every F₂ individual into two parts, with one part planted in normal conditions and another part in saline conditions, the inheritance of salt tolerance in rice was studied. Under normal conditions, there was no apparent segregation among F₂ individuals. Under saline conditions, however, the segregation of traits was obvious. According to our standards, the ratio of salt sensitive:moderately-tolerant:tolerant plants was 25:42:18, in accordance with a 1:2:1 ratio. It suggested that the improvement of salt tolerance in our materials was induced by the mutation of a major tolerant gene which showed incomplete dominance. By use of 130 RFLP probes distributed throughout the rice genome, the gene was tagged by a single copy DNA probe, RG4, which was located on chromosome 7. The genetic distance between the salt tolerant gene and RG4 was 7.0 ± 2.9 cM. Based on the split method, a method which could be currently used to evaluate the damage of salt stress in rice was proposed.     

Phospholipid surface density determines the partitioning and permeability of acetic acid in DMPC:cholesterol bilayers

Relationships between the permeability coefficient (P_HA) and partition coefficient (K _m/w) of acetic acid and the surface density of DMPC:cholesterol bilayers have been investigated. Permeability coefficients were measured in large unilamellar vesicles by NMR line broadening. Bilayer surface density, , was varied over a range of 0.5–0.9 by changing cholesterol concentration and temperature. The temperature dependence of P_HA for acetic acid exhibits Arrhenius behavior with an average apparent activation energy (E _a ) of 22±3 kcal/mole over a cholesterol mole fraction range of 0.00–0.40. This value is much greater than the enthalpy change for acetic acid partitioning between bulk decane and water (H° = 4.8±0.8 kcal/mole) and the calculated E _a (= 8.0 kcal/mole) assuming a bulk phase permeability model which includes the enthalpy of transfer from water to decane and the temperature dependence of acetic acid's diffusion coefficient in decane. These results suggest that dehydration, previously considered to be a dominant component, is a minor factor in determining E _a . Values of 1n P_HA decrease linearly with the normalized phospholipid surface density with a slope of = -12.4±1.1 (r = 0.90). Correction of P_HA for those temperature effects considered to be independent of lipid chain order (i.e., enthalpy of transfer from water to decane and activation energy for diffusion in bulk hydrocarbon) yielded an improved correlation ( = -11.7±0.5 (r = 0.96)). The temperature dependence of K_m/w is substantially smaller than that for P_HA and dependent on cholesterol composition. Values of 1n K_m/w decrease linearly with the surface density with a slope of = -4.6±0.3 (r = 0.95), which is 2.7-fold smaller than the slope of the plot of 1n P_HA vs. . Thus, chain ordering is a major determinant for molecular partitioning into and transport across lipid bilayers, regardless of whether it is varied by lipid composition or temperature.This work was supported by grants from Glaxo, INTERx/Merck, and University of Utah Research Committee.     

Cell cycle and cell size dependence of susceptibility to hydrodynamic forces

Exposure of animal cells to intense hydrodynamic forces exerted in turbulent capillary flow, and by controiled agitation and aeration, resulted in preferential destruction of S and G(2) cells and the extent of destruction of these cells was dependent upon the intensity of the action. The loss of these cells was possibly due to their larger size. However, the appearance of large numbers of membrane-bound vesicular structures similar to apoptotic bodies as well as cells with low DNA stainability (in a sub-G(1) peak) suggested that the action of adverse hydrodynamic forces on these large cells may at least in part be to induce an apoptotic response. (c) 1995 John Wiley & Sons, Inc.     

Side-chain accessibilities in the pore of a K+ channel probed by sulfhydryl-specific reagents after cysteine-scanning mutagenesis.

To gain insight into the secondary structure of the ion conduction pathway of a voltage-gated K+ channel, we used sulfhydryl-specific reagents of different diameters to probe amino acid side-chain accessibilities in the pore of the channel after cysteine-substitution mutagenesis. We identified five positions at which modified amino acid side chains are accessible from the aqueous lumen of the external channel vestibule. Covalent coupling of the 2-trimethylammonium-thioethyl group to cysteine thiols leads to position-dependent current reduction, suggesting a gradual narrowing of the pore. The fact that the modified side chains of two adjacent amino acids are reactive is not compatible with the ion conduction pathway forming a regular beta-pleated sheet at these positions. The smaller thiol reagent Cd2+ reacts with modified side chains that are also accessible to the larger (2-trimethylammoniumethyl)methanethiosulfate (MTSET) [corrected]. Our results imply that the outer vestibule of a potassium-selective ion channel narrows over a short distance of three amino acids near a position where a regular beta-structure is unlikely.     

Evolutionary Endocrinology of Juvenile Hormone Esterase in Gryllus Assimilis: Direct and Correlated Responses to Selection

Hemolymph juvenile hormone esterase (JHE) activity on the third day of the last stadium in the cricket, Gryllus assimilis, exhibited a significant response to selection in each of six replicate lines. Mean realized heritability was 0.26 +/- 0.04. The response was due to changes in whole-organism enzyme activity as well as to changes in the proportion of enzyme allocated to the hemolymph compartment. In vivo juvenile hormone metabolism differed between some lines selected for high vs. low enzyme activity. Only minimal differences were observed between lines with respect to hemolymph protein concentration or whole-cricket activity of juvenile hormone epoxide hydrolase, the other major JH-degrading enzyme. Dramatic correlated responses to selection, equal in magnitude to the direct response, were observed for JHE activity on each of three other days of the last juvenile stadium. In contrast, no correlated responses in JHE activity were observed in adults. This indicates that JHE activities throughout the last stadium will evolve as a highly correlated unit independent of adult activities and the evolution of endocrine mechanisms regulating juvenile development can be decoupled from those controlling adult reproduction. This study represents the first quantitative-genetic analysis of naturally occurring endocrine variation in an insect species.