Characteristics of the leaf photosynthetic machinery in broad bean grown in zinc chloride aqueous solutions

The structural and functional characteristics of bean leaves (the content of chlorophyll, the rate of oxygen production, the slow fluorescence induction, and light-induced changes in the EPR signal I from oxidized reaction centers P700+) were investigated to obtain insight into the mechanism of influence of zinc chloride on the photosynthetic apparatus. Seedlings were grown on hydroponic medium containing ZnCl2 at concentrations from 10(-7) to 10(-3) M. At low concentrations of ZnCl2, a decrease in the content of chlorophyll per one unit of leaf mass was observed, while the rate of oxygen production per chlorophyll was increased. High concentrations of ZnCl2 in the hydroponic medium caused the slowed down the plant development and inhibited the light-induced production of oxygen. The changes in biophysical characteristics of leaves the parameter FM/FT of the slow fluorescence induction, and kinetics of redox transients of P700 induced by ZnCl2 were of similar character and correlated with the changes in photosynthetic activity. The data obtained demonstrate that structural and functional changes in the photosynthetic apparatus induced by the variations of growth conditions have adaptive character.     

Mitochondrial DNA variation in populations of the chum salmon Oncorhynchus keta (Walbaum) from rivers of the Prymorye and Sakhalin

Mitochondrial DNA (mtDNA) variation was studied using restriction fragment length polymorphism (RFLP) in chum salmon populations from three rivers in southern Primorye and one river in Sakhalin Island. Significant differences were detected between the samples from Primorye and Sakhalin Island. No differences were found between the samples from the rivers of Primorye, which can be explained by a high rate of gene flow due to transplantation of spawn from one river to another. The effect of fish breeding on the chum salmon populations correlated with the indices of haplotype and nucleotide diversity (h and pi, respectively). The lowest diversity was found in the completely artificial population from the Ryazanovka River; the highest, in natural populations from the Narva and Naiba rivers. Frequencies of haplotypes in consecutive generations were significantly different, which confirms the effects of genetic drift on the small-size chum salmon populations of Primorye.     

Evoked potentials in the brain of adolescents in norm and those with attention deficit during recognition of short-term acoustic stimuli

The effect of stimulus duration on auditory event-related potentials and performance of oddball task was studied in normal children and those with attention-deficit symptoms. Mismatch negativity was absent on presentation of short-term (11 ms) stimuli and present with longer stimuli (50 ms). The adolescents with deficit of attention performed much worse (errors of omission) with the short stimuli. The RT was significantly larger in subjects with attention-deficit with all types of tested stimulus duration. They also manifested a smaller P3b amplitude in response to task-relevant deviant stimuli and larger N2b peaks in response to the standard stimuli. It was possible to differentiate between the MMN and the N2b components owing to the fact that the MMN was absent with shorter stimuli. The findings suggest that there is a deficit in processing of sensory information at the cortical level in subjects with the attention-deficit symptoms.     

The role of antioxidative status in development of the consequences of biological action under low dose and low intensity irradiation

The scale and direction of changes of a number of biophysical, biochemical and physiological parameters in SHK mice (male) tissues were studied depending on their initial values for mice control groups within 1 day after low intensity gamma-irradiation (15 cGy). The reciprocal dependences between the scales of the lipid antioxidative activity (AOA) in brain or the spleen mass changes and their values for mice control groups were found. The external dependences were revealed between the amounts of lipid peroxidation secondary products in spleen, liver and blood plasma of the control mice and a scale of their change after irradiation. The most substantial changes of this parameter were observed in blood plasma and the changes of the phospholipid content within the total lipid composition were found in spleen and blood erythrocytes of the irradiated mice, that is in the lipids of tissues, which had the lowest level of AOA for mice control groups. The experimental data obtained indicate that the initial antioxidant status of animal tissues plays the important role for the development of consequences of the biological action under low dose and low intensity irradiation.     

The structure of the micromycete complexes of oligotrophic peat deposits in the southern taiga subzone of West Siberia

The analysis of the micromycete complexes of oligotrophic peat deposits in the Vasyugan Marsh by direct count and culture methods showed that the micromycete carbon comprises no more than 3% of the total peat carbon and that the microscopic fungal biomass varies from 2 to 13 tons/hectare, depending on the season and the peat deposit thickness. Fungal spores were found in all layers of the peat deposits, whereas the mycelium was found only in the active peat layer. The high abundance of eukaryotic cells in the peats was due to the presence of yeastlike cells rather than fungal spores. Analyses by culture methods showed that micromycetes were present in all peat layers and that their abundance tended to decrease with depth, except for yeasts, which were uniformly distributed in a vertical direction. The micromycete complexes of the peat deposits were similar in the diversity and abundance of dominant species but differed in the composition of minor species. Peat yeasts were dominated by ascomycetes.     

Functional topography of afferent projections of the horizontal division of the nucleus of the diagonal band in the dorsolateral neocortex of the cat

EPs recording under Nembutal anaesthesia during stimulation of the medial section of the horizontal part of the diagonal band nucleus (HNDB) shows a wide spreading of HNDB afferentation over the neocortex: from the frontal area to the medial and some posterior parts of the auditory, parietal areas and Ep zone, with the least activation of the latter three regions and activation increasing intensity correspondingly in the somatic zones II, I (SII, SI), motor and frontal cortex. Such reduction of signals flow intensity oriented both in caudal and ventral directions of the cortex goes with foci of maximal activity of these signals in the motor, parietal areas and zones of representation of various body parts in SI and SII. Traits of similarity and differences of signal's projections in the neocortex from HNDB and thalamic relay nuclei have been revealed. A hypothesis is substantiated on different mechanisms underlying peculiarities of influences of these subcortical nuclei on the cortex depending on the type of their afferent-neuronal links in the latter and their functional role in the brain activity.     

Features of corticofugal effects of the motor area of the cortex on processing of heterogeneous afferentation in the parafascicular complex of the thalamus in the cat

Evoked potentials to somatic and visual stimuli were recorded in the parafascicular complex (parafascicular nuclei--centrum medianum--Pf--CM) of the thalamus of cats anaesthetized by nembutal. Cooling of the motor cortex was also used. The influence of the motor cortex on processing of the visual and somatic afferent signals at the thalamic level was found to be direct but different by its character. The motor cortex exerted unidirectional facilitatory modulatory action of a tonic type on the processing of visual afferentation and general facilitatory influence against the background of which particular excitatory and inhibitory effects were seen which it exerted on the processing of somatic signals. Episodically the motor cortex completely controlled the afferent inputs activated by somatic impulses. The motor cortical area non-equally influenced afferentation of the same modality forming the different components of the evoked potentials in Pf--CM. On the base of our present and earlier obtained data an idea has been formed of existence of a general principle of differentiated influences of polysensory areas on heterogeneous afferentation on nonspecific and association thalamic nuclei, and of realization of these influences through separation of functionally isolated subsystems in descending pathways. Each of the subsystems by closing separate thalamo-cortical circuits might transmit signals of a single modality.     

SO2 污染油菜对桃蚜的影响

ＳＯ_２污染油菜对桃蚜的影响龚佩瑜,吴坤君,李秀珍（中国科学院动物研究所北京１０００８０）ＳＯ２是我国大气污染的主要成分,它是一种对生物影响很大的污染物。ｓｏ。曾被用作熏蒸剂来防治害虫,但只有在浓度很高时才有效。更多的观察表明,ｓｏ：污染有利于蚜虫的?..