Role of three basic light reactions in photomovement of desmids

Photoaccumulations in light trap experiments have been studied in the desmids, Cosmarium, Micrasterias and Euastrum. Dependence of accumulation density on exposure time follows saturation curves, while dose response curves show optima. Time-lapse microcinematography and population methods have revealed that all three basic light-induced motor responses known in microorganisms participate in producing photoaccumulations in desmids. During the initial phase the cells are phototactically attracted towards the trap by scattered light. In low light intensity traps photokinetic reactions may play only a minor role, since photokinesis could be evoked only by light intensities100 lx in Cosmarium cucumis. True photophobic reactions have been demonstrated for the first time in desmids. There are two types of phobic responses in desmids: either the cell reverses its movement or it swings sidewise into the new direction. Behaviour of partially shadowed cells suggests that perception of light direction is brough about by simultaneous intensity measurement at two or more sites within the cell.     

Sister chromatid exchange studies for monitoring DNA damage and repair capacity after cytostatics in vitro and in lymphocytes of leukaemic patients under cytostatic therapy.

The effect of various cytostatic drugs was studied on the frequency of sister chromatid exchanges (SCEs) in vitro and in PHA-stimulated lymphocytes of leukaemic patients under cytostatic therapy. The lymphocyte system is a sensitive one for the detection of DNA damage after administration of cytostatic drugs in vitro. Mitomycin C, busulphan, vincristine, chlorambucil, cytosine arabinoside, cyclophosphamide and lycurim were tested. All except cyclophosphamide induced high frequencies of SCEs in the first mitosis after their administration. The experiments with PHA-stimulated lymphocytes in vivo from patients treated with cytostatics showed that cytosine arabinoside, in combination with thioguanine, did not induce higher frequencies of SCEs, whereas in patients who were treated with cyclophosphamide alone or in combination with other cytostatic drugs, there was a higher incidence of SCEs during treatment. About 10 days after the termination of the treatment the elevated freuqencies of SCEs returned to the initial level. After administration of some mutagens, especially alkylating agents in vivo, the lymphocyte system can be used to assess induced DNA repair by continuously monitoring for SCEs.     

畜禽遗传资源冷冻保存中的取样方法探讨

本文基于遗传学和数理统计原理,提出了运用冷冻生殖细胞的方法长期保存畜禽遗传资源时,冷冻生殖细胞的4种取样方法,并推证了其误差公式和最低保存数量的估计公式。最后通过实例对公式的实际应用作了说明和讨论分析。     

Intracellular ion concentrations and cell volume during cholinergic stimulation of eccrine secretory coil cells

Summary Methacholine (MCh)-induced changes in intracellular concentrations of Na, K, and Cl ([Na]_i, [K]_i, and [Cl]_i, respectively) and in cellular dry mass (a measure of cell shrinkage) were examined in isolated monkey eccrine sweat secretory coils by electron probe X-ray microanalysis using the peripheral standard method. To further confirm the occurrence of cell shrinkage during MCh stimulation, the change in cell volume of dissociated clear and dark cells were directly determined under a light microscope equipped with differential interference contrast (DIC) optics. X-ray microanalysis revealed a biphasic increase in cellular dry mass in clear cells during continuous MCh stimulation; an initial increase of dry mass to 158% (of control) followed by a plateau at 140%, which correspond to the decrease in cell volume of 37 and 29%, respectively. The latter agrees with the MCh-induced cell shrinkage of 29% in dissociated clear cells. The MCh-induced increase in dry mass in myoepithelial cells was less than half that of clear cells. During the steady state of MCh stimulation, both [K]_i and [Cl]_i of clear cells decreased by about 45%, whereas [Na]_i increased in such a way as to maintain the sum of [Na]_i+[K]_i constant. There was a small (12–15mm) increse in [Na]_i and a decrease in [K]_i in myoepithelial cells during stimulation with MCh. Dissociated dark cells failed to significantly shrink during MCh stimulation. The decrease in [Cl]_i in the face of constant [Na]_i+[K]_i suggests the accumulation of unknown anion(s) inside the clear cell during MCh stimulation. While the decrease in [K]_i and [Cl]_i may be instrumental in facilitating influx of ions via Na–K–2Cl cotransporters, the functional significance of MCh-induced cell shrinkage remains unknown.     

氧合血红蛋白Fe-O2键合态 ab initio 研究

本文报道用自旋非限制Hartree-Fock方法(spin unrestricted Hartree-Fock method简写UHF)对氧合血红蛋白的Fe-O₂键合态进行ab initio研究。结果表明Fe^(Ⅱ)、Oc和Or的Mulliken布居值分别为24.18、8.19和7.64。这说明氧合血红蛋白的Fe-O₂键合态不发生电子转移。研究模型所得到的频率与实验频率基本一致。研究结果不支持Weiss提出的Fe³⁺O₂^-模型,为解释血红蛋白传输氧的作用机理提供了新的理论依据。     

Determination of chemical biodegradation by direct and indirect methods

Summary Degradation of 10 organic chemicals by pre-acclimated microorganisms in BOD dilution water was determined directly by UV spectrophotometry and indirectly by a modified BOD method. Residual chemical concentrations were periodically measured and pseudo-first-order biodegradation rate constants (k ₁) were calculated. Thek ₁ spectrophotometry values ranged from 0.006/h to 0.077/h andk ₁-BOD values from 0.002/h to 0.043/h for 1-methylnaphthalene and indole, respectively. The ratios ofk spectrophotometry to k₁-BOD were between 1.5 for salicylic acid and 3.0 for 1-methylnaphthalene with a mean of 2.7. A significant (=0.001) linear correlation (r ²=0.854,F=46.630) existed between the two sets of rate constants. Results from this study suggest that the modified BOD method may be used to estimate chemical biodegradation rates in synthetic media.     

Ecological release in feeding behaviour: the case of bluegills in Japan

The stomach contents were analyzed monthly for each year-class to elucidate the foraging pattern of bluegills in a small vegetated lake by the frequency occurrence and the points methods. Seasonal dietary changes of the year-classes were considered comparing the monthly fluctuations in abundance of major prey organisms. Though these bluegills are dietary generalists and opportunists like those in North America, their foraging pattern was characterized by a relatively clearer dietary shift during ontogeny and a wider food niche including piscivorous than those of bluegills with congeners in their home land. Therefore this finding provides evidence of the ecological release caused by the absence of congeners.     

Phylogenetic continuum indicates “Galaxies” in the protein universe: Preliminary results on the natural group structures of proteins

Summary The markedly nonuniform, even systematic distribution of sequences in the protein universe has been analyzed by methods of protein taxonomy. Mapping of the natural hierarchical system of proteins has revealed some dense cores, i.e., well-defined clusterings of proteins that seem to be natural structural groupings, possibly seeds for a future protein taxonomy.The aim was not to force proteins into more or less man-made categories by discriminant analysis, but to find structurally similar groups, possibly of common evolutionary origin. Single-valued distance measures between pairs of superfamilies from the Protein Identification Resource were defined by two ²-like methods on tripeptide frequencies and the variable-length subsequence identity method derived from dot-matrix comparisons. Distance matrices were processed by several methods of cluster analysis to detect phylogenetic continuum between highly divergent proteins.Only well-defined clusters characterized by relatively unique structural, intracellular environmental, organismal, and functional attribute states were selected as major protein groups, including subsets of viral and Escherichia coli proteins, hormones, inhibitors, plant, ribosomal, serum and structural proteins, amino acid synthases, and clusters dominated by certain oxidoreductases and apolar and DNA-associated enzymes.The limited repertoire of functional patterns due to small genome size, the high rate of recombination, specific features of the bacterial membranes, or of the virus cycle canalize certain proteins of viruses and Gram-negative bacteria, respectively, to organismal groups.