Sex-related Resistance in Hamsters to Adenovirus-12 Oncogenesis II. Influence of Virus Dose

A significantly higher proportion of female hamsters developed tumors than did males given the same dose of adenovirus-12 (Huie) at birth over a dose range from 10(5.0) to 10(7.0)tcd(50) for human embryonic kidney cells. The 50% tumor dose (td(50)) was calculated to be 10(5.90)tcd(50) for females and 10(6.27) for males. Tumor response patterns induced with approximate td(50) inocula, 10(6.0) for females and 10(6.3) for males, were quite similar. The greater susceptibility of females was not found to be characteristic of a single strain of hamsters; nor was it attributable to a single lot of virus, to a single type of human cell used to produce the virus, nor to the degree of purification of the virus inoculum. The inoculation route did not appear to be of importance. Inasmuch as the foregoing extrinsic factors were of little influence, it was concluded that the mechanism is host-mediated, presumably hormonally controlled. The possibility that female cells, independent of host control, are more susceptible to adenovirus-12 oncogenesis than male cells has not been explored. Tumor regression occurred in 20% of the 211 tumors in males and in 15% of the 355 tumors in females. Adenovirus-12 T-antibody was detected in all but six of 473 sera tested from tumor-bearing hamsters and in 50% of 94 sera tested from non-tumor-bearing animals given virus at birth. Antibodies in the latter group were detected almost exclusively by indirect immunofluorescence. This technique appears to be extremely sensitive for detection of low levels of adeno-12 T-antibodies. The implications of T-antibody in nontumor-bearing virus-injected hamsters are discussed. Sera from normal hamsters were free of T-antibody.     

Genetic structure of Glycine canescens,a perennial relative of soybean

Summary Allozyme variation as detected by starch gel electrophoresis was used to assess the extent and spatial organization of genetic variation across the entire range of Glycine canescens sensu lato. Eleven enzyme systems were assayed in 116 accessions of this taxon and 102 alleles were detected at a total of 31 loci. Eighty-one percent of loci were polymorphic. Most of this variation occurred between and very little within accessions. Three major groupings were detected. These groupings (groups 1, 2, and 3) also differed with respect to mean seed size and their geographic distribution. A further ten accessions stood out from these distinct groups. These accessions were most closely related to group 3 but were variable among themselves. In general, they were collected from highly dissected terrain, often in the remote interior of the continent. A final group of 18 problematic accessions (group X), originally tentatively identified as G. canescens on morphological grounds, was shown to be isozymically distinct from this species and was reclassified as one form of the polytypic species G. clandestina.     

小鼠巨核系祖细胞增殖,分化特性的研究

小鼠骨髓细胞经7d培养后进行细胞形态学观察,可见不同发育阶段的巨核细胞及不同大小的巨核细胞集落。通过计数每个集落中的细胞数,可确定相应祖细胞的有丝分裂能力。结果表明,具有不同有丝分裂能力的祖细胞的体外增殖动力学有所不同。祖细胞的数量与其有丝分裂次数呈负相关(r=-0.986)。进行0、1、2和3次有丝分裂的祖细胞的阿糖胞苷自杀率分别为48.9,58.7,48.0和41.2％;放射敏感性的D_O值(Gy)分别为1.71,1.24,1.03和0.77,D_O值的大小与有丝分裂次数呈负相关(r=-0.958)。经3Gy全身照射后CFU-Meg与CFU-GM的恢复动态过程具有不同特点。     

Plant community structure in an oligohaline tidal marsh

An oligohaline tidal marsh on the northern shore of Lake Pontchartrain, LA was characterized with respect to the distributions and abundances of plant species over spatial and temporal gradients using Detrended Correspondence Analysis (DCA). In addition, the species distributions were correlated to several physical environmental factors using Detrended Canonical Correspondence Analysis (DCCA). The distributions of species were best correlated with distance from Lake Pontchartrain, and to a lesser extent with elevation and substrate organic matter. They were least correlated with mean soil salinity (referred to here as background salinity). Of the three mid-seasonal dominant species, the perennial grass, Spartina patens, is the most salt tolerant and was found closest to the lake. Further inland the dominant perennial was Sagittaria lancifolia, which has a salt tolerance less than that of Spartina patens. The perennial sedge, Cladium jamaicense, which is the least salt tolerant of the three, was dominant furthest inland. Background salinity levels were generally low (<5 ppt.) and did not explain species distributions. We hypothesize that the distribution of species is regulated by occasional storm-generated salt pulses that generate strong, short-lived salinity gradients as a function of distance from the lake. Biotic interactions likely also play a role in structuring the plant community. The distributions of several annuals depended on the size and life history of the mid-seasonal dominant perennials. Most of the annuals frequently co-occurred with Sagittaria lancifolia, which was the shortest in stature and had the least persistent canopy of the three mid-seasonal dominant perennials.Abbreviations DCA Detrended Correspondence Analysis - DCCA Detrended Canonical Correspondence Analysis     

A leaf disc method for measuring cuticular conductance

This paper describes a new method for the measurement of cuticularconductance (g_o;) using a leaf disc sealed in a specially-designedenvelope. Conductances for astomatous (adaxial) and stomatous(abaxial) surfaces of beech {Fagus sylvatica L.) were determinedfrom measurements of water flux. Leaf discs were punched outfrom attached leaves and placed inside individual envelopesthat provided a water supply. Water flux from an exposed epidermalsurface of the leaf discs was measured gravimetrically. Allmeasurements were made under darkness. Conductance of the adaxialsurface was referred to as g_c, whereas conductance of the abaxialsurface was considered as a minimum leaf surface conductance()- The main advantage of this method is that it enables measurement of g_c and from leaf samples with intact cuticles and a highrelative water content [RWC) for periods of up to 12 d. Conductancesof leaf discs in envelopes were compared with those of wholeleaves and leaf discs without envelopes. Data demonstratinga strong positive relationship between conductance and RWC ispresented. Key words: Cuticular conductance, leaf disc, relative water content     

华北棉区夏播棉田害虫发生特点分析

分析和比较了华北棉区夏季播种与春季播种的棉田主要害虫（棉铃虫与棉蚜）的发生特点,探讨了它们的管理对策。