Toxic effects of 2-methyl-4-dimethylaminoazobenzene in normal and partially hepatectomized rats

In order to obtain a more precise definition of the conditions under which 2-methyl-4-dimethylaminoazobenzene (2-Me-DAB) and liver cell proliferation play a role in the initiation of hepatocarcinogenesis, the toxicity of 2-Me-DAB for normal and partially hepatectomized rats was investigated. Continuous feeding of a basal low protein, low riboflavin diet supplemented with 2-Me-DAB was found to be highly toxic for male albino rats. All animals fed on such a diet died before 200 days. Sham operation and partial hepatectomy (PH) at 30 days of 2-Me-DAB feeding reduced the median survival time from 122 days to 107 and 94 days, respectively. Transfer to the basal diet after 30 days of 2-Me-DAB feeding and PH prolonged the median survival time to 216 days while 97% of the rats returned to the normal complete diet after the same treatments survived for more than 300 days. 2-Me-DAB was not necrogenic and there was no evidence of reparative proliferation or hepatic tumor formation in any group. Feeding rats with the 2-Me-DAB containing diet for 1 month delayed and strongly inhibited the mitotic response of the liver to the stimulus of partial hepatectomy. This is the result of a blockage of the cells in G1 as revealed by the fact that only 1% of the hepatocytes became labeled when 2-Me-DAB fed animals were injected with tritiated thymidine prior to sacrifice at 24 h post-hepatectomy, as compared to 40% in rats fed the normal or the control basal diet. This inhibitory effect of 2-Me-DAB is reversible however since rats returned to the normal diet for 1 or 2 months after 2-Me-DAB feeding showed percentages of mitoses and labeling indices comparable to those of control animals following PH. The number of abnormal mitoses was high (13%) in regenerating livers of rats fed 2-Me-DAB and the lesions responsible for this effect are apparently not repaired since 2-Me-DAB fed rats partially hepatectomized after being transferred to the normal diet for 1 or 2 months showed the same number of mitotic irregularities. The present results suggest that assays with 2-Me-DAB as 'pure initiator' or agent of selective toxicity should be pursued in attempts to improve existing experimental models of hepatocarcinogenesis.     

Persistence of Bacillus thuringiensis parasporal crystal insecticidal activity in soil

Spores and parasporal crystals of a Bacillus thuringiensis var. aizawai (H-serotype 7), strain HD137, streptomycin-resistant mutant were added to acidic (pH 5.0) natural and autoclaved soil and incubated at ?0.10 MPa, 25°C. Populations of B. thuringiensis in both soil treatments showed exponential rates of mortality which were represented by linear regression, the loss of viability being greater in natural than autoclaved soil. In natural soil, parasporal crystal insecticidal activity was lost at a complex, nonexponential rate. The initial, rapid decrease of activity gradually slowed, and the level of activity stabilized at 10% of the original inoculum level after 250 days incubation, until the cessation of sampling at >2 years. In autoclaved soil no significant (P > 0.2) loss of parasporal crystal insecticidal activity was detected over the same period, which suggested that soil microorganisms were responsible for the loss of crystal insecticidal activity in the natural, nonsterilized soil. The rate of loss of crystal activity in natural soil correlated well with assay data reported in the literature using Galleria mellonella, which measures the combined activity of spore and crystal. In autoclaved soil correlation was poor, probably due to variability in the bioassay data.     

贵州部分森林群落物种多样性初步研究

 本文根据贵州省178个森林群落样地的数据研究了群落物种的多样性。测定的指标有群 落物种丰富度,群落Simpson多样性指数和群落均匀度。测定结果表明;不同垂直带生物气 候条件下的森林群落有不同的多样性。相同垂直带生物气候条件下,基质生境相同时,不同森林植被亚型的群落的多样性近似,基质生境不同时,群落多样性则不同;同一群落类型的各个样地的多样性也有变化,结构不同的群落个体,其多样性指数不同,演替趋势也不同。乔木第二亚层的多样性普遍地高于乔木第一亚层。同一演替系列中,越接近顶极阶段多样性越高。多样性指数与群落物种丰富度,均匀度呈紧密的正相关,与群落个体总数没有相关。认为多样性测定在比较、说明群落的结构、类型、组织特征、生境、演替等方面有一定意义。     

Dry matter and nitrogen accumulation and partitioning in selected soybean genotypes of different derivation

Summary Experiments were conducted to determine if changes in the accumulation and partitioning of dry matter (DM) and nitrogen (N) in soybean [Glycine max (L.) Merr.] were associated with agronomic improvements and to assess the degree of genetic variation present for these traits. Fifteen maturity group II soybean genotypes including three ancestral cultivars, three modern cultivars, and nine agronomically superior plant introductions (PI's) were grown in replicated tests at four locations in the eastern U.S. The DM and N of stems, pod walls, and seeds were determined at maturity, and the apparent harvest indices (HI) and the apparent nitrogen harvest indices (NHI) were calculated. Pod DM partitioning was calculated as the ratio of seed DM to total pod DM and pod N partitioning was the ratio of seed N to total pod N. The mean DM accumulation of the modern cultivars was significantly greater than that of the ancestral cultivars and PI's. The apparent HI and the pod DM partitioning of both the modern and ancestral cultivars were significantly higher than that of the PI's. The three modern cultivars demonstrated the highest N accumulation. As a group, the modern cultivars consistently showed maximal accumulation and partitioning of DM and N suggesting that these physiological traits are associated with agronomic improvement. No individual PI was found to possess DM or N accumulation or partitioning which significantly exceeded the best modern cultivar or ancestral cultivar, indicating that genotypes with accumulation or partitioning characteristics which exceed available germplasm may be difficult to identify. Seed yield was correlated (P<0.05) with both DM (r=0.61) and N (r=0.57) accumulation.     

In vitro response of leaf tissues from Lolium multiflorum — a comparison with leaf segment position,leaf age and in vivo mitotic activity

Summary Immature gramineous leaves provide a convenient system for comparing the response of cells in culture with their state of differentiation. Callusing frequency is compared with leaf segment position, leaf age and in vivo mitotic activity in Lolium multiflorum. (1) In a succession of one millimeter sections from the immature leaf base, callus was formed from the first and second sections but not the third or subsequent sections. The frequency of those explants callusing decreased with distance from the base of the leaf and with leaf age (or leaf extension growth). (2) In vivo, the proportion of cells in mitosis declined from around 10–14% at the base of young leaves to zero at 5 mm from the base and beyond. Mitotic activity also declined in leaves as they aged, and dividing cells were not observed in leaves 30 days from initiation or older. (3) A high frequency of callus formation was associated with a high mitotic index in the explant. But for corresponding mitotic indices, cells further away from the leaf base were less responsive in culture. (4) It is proposed that cells are becoming differentiated even in highly meristematically active regions of the leaf and concomitantly losing their ability to respond in culture.     

Regulation by kinetin and abcisic acid of correlative senescence in relation to grain maturation,source-sink relationship and yield of rice (Oryza sativa L.)

When kinetin was applied to the source organ (flag leaf) of rice (Oryza sativa L. cv. Ratna), foliar senescence was delayed and grain yield per plant (as evidenced by grain weight, grain/straw weight ratio and 1,000 grain growth) was increased through the increase of sink activity (increase in dry weight of the grains/plant), duration of sink capacity as well as photosynthetic ability of the glumes (as determined by the chlorophyll content of the glumes of the developing grains). However, application of kinetin to the sink organs (fruits), promoted senescence of the source but increased the yield by increasing the sink capacity and 1,000 grain growth mostly at the earlier stage of reproductive development. Lower sterility percentage was associated with higher grain yield of the plant by kinetin treatments. ABA applied either to the source or the sink promoted leaf senescence and reduced the grain yield by reducing the sink activity, harvest index, sink capacity duration and increasing the sterility percentage. Thousand grain dry weight at harvest did not vary significantly amongst the treatments. It was concluded that nutrient drainage was associated with the correlative influence of fruit on the monocarpic senescence of rice plant and that a competetion for differential allocation of cytokinin and ABA in the source and sink organs initiates this senescence syndrome.     

水蒸汽蒸馏巴柑檬叶和果皮精油化学成分的研究

巴柑檬是我们第一次从国外引种成功的一种名贵香料植物。用色谱-质谱-计算机联用技术、毛细管气相色谱保留指数法和标准品叠加法分析了水蒸汽蒸馏巴柑檬叶和果皮精油的化学成分。从叶和果皮精油分离出来的220个和200个成分中,分别鉴定出48个和57个成分。鉴定组分的含量分别占叶和果皮精油的99.80％和98.54％。叶精油与果皮精油在化学成分方面的主要区别是叶油中萜烃化合物含量较低,而萜醇类化合物含量较高。     

Climate and the evolution of brachycephalization

Significant associations of cranial shape for 82 ethnic groups and seven climate variables are described. Variation among current populations is partially attributed to cold adaptation throughout the Pleistocene. Application of data files tabulated by the authors is described for a number of problems. Temporal distribution of 115 specimens indicates a geometric trend (CI = 76.7-1.96 log time X 10(3) ). Cranial indices are summarized within alternative taxonomic models and between climatic ecotypes. Evidence supports the hypothesis of cold adaptation among "Classic" Neandertals. Limitations of the thermodynamic model are discussed. It is probable that a decrease of the cranial index occurs from the Middle to Upper Paleolithic. During the Holocene, the index increases under all climatic conditions.     

Regulation of leaf senescence, grain-filling and yield of rice by kinetin and abscisic acid

Senescence of rice ( Oryza sativa L. cv. Jaya) leaves was regulated with kinetin and abscisic acid (ABA) sprays at the reproductive stage. The effect of such sprays on grain-filling and yield was analyzed. Spraying 100-day-old plants with kinetin solution (100 μg ml^-1) significantly delayed senescence as indicated by higher total chlorophyll and protein levels in the three uppermost leaves compared with the controls. In contrast, spraying with ABA (15 μg ml^-1) significantly promoted foliar senescence. The number of spikelets per panicle, number of panicles, percentage filled grains, panicle weight and grain yield per plant and the mobilization and harvest indices were significantly increased by kinetin treatment, while ABA decreased most of them. The possibility of increased grain-filling and thus, yield due to delayed foliar senescence by kinetin treatment and decreased grain-filling due to hastening of senescence by ABA is discussed.     

The effects of time of seed production on the germination response of Spergularia marina

Germination studies were carried out with seeds of Spergularia marina L. Griseb produced over an interval of six months (June-November). The response of the seeds to light and dark, various constant and alternating temperature regimes, and salinity were determined. In addition, the effects of soil moisture status at the time of seed production on the subsequent germination response of seeds were also determined. Light was an absolute requirement for germination. While a constant temperature regime did not generally favour germination of seed of any month, alternating temperature greatly enhanced germination with an optimum at 5/15°C in all seeds. When imbibed in solutions of different salinities, seeds collected in July and October behaved like true halophyte seeds whereas those collected in June. August, September and November behaved like glycophyte seeds.
High concentration of gibberellic acid (3 000 μ M ) stimulated dark germination in the June and November seed lots, but in light, low GA3 concentration (300 μ M ) stimulated germination most. The addition of kinetin (30 μ M ) plus gibberellic acid enhanced germination in the dark in contrast to GA3 alone; kinetin alone stimulated a very low percentage germination.
The moisture status of the soil at the time seeds were produced did not affect the germination response of an early seed crop (July) but affected that of the later seeds (August).
Judging from the different germination responses, it appears that the seeds belong to at least two physiological groups, one which appears to need either a dark-wet or cold-wet pretreatmem for high germination to occur; and the other group which does not need pretreatmem. The ecological significance of these varied responses is discussed in relation to the survival of the species in its habitat.