Effect of tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate on induction of sister-chromatid exchanges in Chinese hamster V79 cells treated with mutagens

The effect of a tumor promoter, 12-O-tetradecanoyl-phorbol 13-acetate (TPA) alone and in combination with mitomycin C (MMC) or cyclophosphamide (CPP) on the induction of sister-chromatid exchanges (SCE) in Chinese hamster V79 cells was investigated. TPA alone at various doses and durations caused no increase of SCE frequency. MMC either at the dose of 0.03 or 0.003 μg/ml alone or in combination with TPA (2 μg/ml) all caused a significant increase of SCE frequencies. There was no difference in SCE frequencies between the cultures treated with MMC alone at 0.03 μg/ml and those treated with MMC plus TPA. However, cultures treated with MMC at 0.003 μg/ml plus TPA had significantly and consistently higher SCE frequencies than those treated with MMC alone at all durations. Treatment of CPP at 1 μg/ml activated by S9 mix caused significant increase of SCE frequencies. Surprisingly, the cultures treated with CPP, S9 mix plus TPA (2 μg/ml) caused a drastic reduction of SCE frequencies as compared to those treated with CPP and S9 mix only at all durations. These results indicate that TPA alone had no effect on SCE in V79 cells. TPA enhanced the SCE induction in V79 cells treated with MMC at a low dose, i.e. 0.003 μg/ml, but it inhibited SCE induction in cultures treated with the indirect mutagen CPP. Thus, TPA has no direct effect on genetic materials but it may indirectly alter the effects of a mutagen.     

cis-Platinum(II)diaminodichloride-induce mutagenesis in E. coli K12: crowding depression of mutagenesis

cis-Platinum(II)diamminodichloride (cis-PDD)-induced mutations to prototrophy were studied in Escherichia coli. Mutagenesis was not detected in a recA nor in a lexA mutant, but as greater in uvrA strain than in a repair-proficient strain, at a given treatment of cis-PDD. Increasing the plating density above 10⁵ cells per plate did not give an equivalent increase in revertants per plate [crowding depression of mutagenesis (Bockrath et al., 1980)]. Growth rates were similar at different plating densities and crowdign depression of mutagenesis was observed in both excision-proficient and excision-deficient strains.

A filtrate of a plate wash from crowded plates, of either treated or untreated cultuers, further reduced the mutation frequenciews over that due to crowding depression of mutagenesis.     

Transfer cells and solute uptake in minor veins of Pisum sativum leaves

Morphometric and physiological studies were conducted to determine whether the wall ingrowths of transfer cells in the minor-vein phloem of Pisum sativum L. leaves increase the capacity of the cells for solute influx. Size and number of wall ingrowths are positively correlated to the photon flux density (PFD) at which the plants are grown. An analysis of plasmodesmatal frequencies indicated that numerous plasmodesmata are present at all interfaces except those between the sieveelement-transfer-cell complex (SE-TCC) and surrounding cells where plasmodesmata are present but few in number. Flux of exogenous sucrose into the SE-TCC was estimated from kinetic profiles of net sucrose influx into leaf discs, quantitative autoradiography, and measurements of sucrose translocation. Flux based both on the saturable (carrier-mediated) and the linear components of influx was 47% greater in leaves of plants grown at high PFD (1000 mol·m^–2·s^–1) than those grown in low PFD (200 mol·m^–2·s^–1) and was paralleled by a 47% increase in SE-TCC plasmalemma surface area. Flux of endogenous photosynthate across the SE-TCC plasmalemma was calculated from carbon balance and morphometric data. The increase in flux in high-light leaves over that in low-light leaves can be explained on the basis of an increase in plasmalemma surface area. In intact leaves, a standing osmotic gradient may facilitate transport of solute into transfer cells with extensive wall elaborations.Abbreviations LPI leaf plastochron index - PCMBS p-chloromercuribenzenesulfonic acid - PFD(s) photon flux density (densities) - SE-TCC sieve-element-transfer-cell complex This research was supported by National Science Foundation Grant DCB-9104159, U.S. Department of Agriculture Competitive Grant 90000854, and Hatch funds.     

Effective number of pollen parents in clonal seed orchards

Summary A method for quantifying mating behavior in clonal seed orchards of forest tree species is presented. It involves the estimation of effective numbers of pollen parents from seed samples collected from individual ramets in such orchards. These effective numbers are variance effective numbers for populations of male gametes that are successful in uniting with ovules to produce viable seed. Three such effective numbers are defined for clonal seed orchards:N _p (a) for male gamete populations for ramets within clones,N _p (b) for male gamete populations for clones, andN _p (c) for male gamete populations for entire orchards. Estimators for these effective numbers and for standardized variances of allele frequencies in the male gametic populations are presented. Expressions are also given for the confidence intervals for each of the three effective numbers. Estimates of these parameters and the corresponding confidence intervals for two seed orchards are presented and interpreted.     

油松种群自然更新格局的研究

种群的空间格局系指某一种群个体在其生存空间内相对静止的散布形式。它是种群的重要属性之一,是种的生物学特性对其所生存的环境条件在特定时期适应和选择的结果。空间格局的阐明,无论在理论生态学的研究上抑或     

Studies of the T1 and T2 of intracellular water as a function of frequency in normal and transformed fetal cells

Frequency-dependent values of the spin-lattice relaxation time (T₁) and the spin-spin relaxation time (T₂) have been obtained for intracellular water in normal and transformed Syrian hamster fetal fibroblasts. Values of T₁ and T₂ were obtained for normal and transformed cells at 24.3 (0.57 T), 100 (2.4 T), 300 (7.0 T), and 400 MHz (9.4 T). At each frequency, values of T₁ were the same for both normal and transformed cells, whereas values of T₂ were lower for one passage of transformed cells. As expected, T₁ increased with frequency. However, T₂ decreased with frequency for both normal and transformed cells. The frequency dependence of T₂, was similar for all cells; thus, the ability of T₂ to make a distinction between normal and transformed cells did not change with field.     

Vegetation structure and dynamics of Pinus gerardiana forests in Balouchistan,Pakistan

Abstract. 44 forest stands, including 42 stands with Pinus gerardiana Wall, ex Lamb dominant and two stands with broad-leaved trees, were sampled in the Suleiman Range in Balouchistan. Density oi Pinus gerardiana trees ranged from 24 to 930 trees / ha with a mean of 266 individuals / ha; the average basal area was 25.5 m² ha^-1. Adequate recruitment of Pinus seedlings was observed; higher seedling density is recorded from east-facing slopes, while tree density was higher on west-facing slopes. The average growth rate was estimated as 0.08 cm / yr radial growth. However, trees on high elevations and cooler slopes grow faster. Soil variables showed no correlation with density, basal area or importance values. It is suggested that the present degraded stage of the forests in the study area is of anthropogenic origin.     

利用各世代小区平均数的加权最小二乘法在玉米数量性状遗传分析上的应用

本文根据作者在参考文献[3]所提出的利用各世代小区平均数估计遗传参数的加权最小二乘法对玉米穗粒重的遗传特性进行了分析。结果表明:(1)在本次试验中,可用加性-显性-二基因互作模型来描述玉米穗粒重的遗传特性;其加性效应[d]、加性效应与显性效应的互作[j]在α=0.01水平上显著,显性效应[h]、显性效应与显性效应的互作[l]在α=0.10水平上显著,加性效应与加性效应的互作[i]不显著;[d]与[h]的差异在α=0.10水平上不显著,但([d] [h])与([i] [j] [l])在α=0.05水平上显著;(2)与利用6个世代平均数相比,利用8个世代小区平均数的加权最小二乘法既节约、又灵敏。