Spatial synchronization of cortical electrical activity at different stages of visual set in preschool children

Changes in the alpha-rhythm synchronization were revealed at different stages of cognitive visual set in 5- to 7-year-old children. We found a clear-cut correlation of these changes with set plasticity. In children with a plastic set, the EEG synchronization between the frontal and other brain regions substantially increased in the period of set-shifting (the actualization stage). At the set extinction stage, after set-shifting has already taken place, the EEG-synchronization becomes minimal. On the contrary, in children who formed a rigid set, EEG coherence considerably increases at the set extinction stage. This finding suggests that the rigid set still affects the cognitive activity even after (judging from oral reports) the set shift has been completed. The age-related differences in cognitive set formation clearly correlate with the time course of the EEG synchronization between the frontal and other brain regions. We think that the ability to form a plastic visual set depends on the frontal cortex maturation, which occurs at the age of 6-7 years, and its age-related effect on the brain cognitive functions.     

Retention of the skill of adaptive biocontrol of cortical bioelectric activity synchronization in argon-nitrogen-oxygen atmosphere with different oxygen concentrations

A decreased oxygen concentration in the air (hypoxia) is an efficient preventive measure against fire in spacecrafts and other habitable pressurized modules. Addition of argon to the air may increase the human tolerance of this hypoxia. In order to estimate the human mental performance in argon-nitrogenoxygen atmosphere (ANOA) with different oxygen concentrations, the following characteristics were determined: (i) the retention of the skill of adaptive biocontrol (ABC) of bioelectric activity synchronization in the frontoparietal and parietooccipital cortical areas with the use of EEG; (ii) emotional and mental states estimated using Luscher’s test; and (iii) performance parameters estimated using the computer games Tetris and Minesweeper as models. Despite fluctuations of the anxiety level, ANOA did not decrease the parameters of the performance of the model activity or long-term retention of the ABC skill (for 24 h), specific characteristics of the ABC skill retention being related to the type of activity.     

Spatial organization of the cortical electrical activity at different stages of visual set in children of preschool and junior school age

Set-forming and set-shifting were studied in children of three age groups: five to six-, six to seven- and nine to ten-year-old. Set effect displayed itself in contrast illusions in most of the subjects (69 of 73). Age differences in set plasticity and in reaction time to a probe stimulus were revealed. Five to six-year-old children formed a more rigid set than older ones. According to EEG coherence function in theta- and alpha-bands and behavioral data, a hypothesis of two systems being involved in set-forming and set-shifting is proposed. These systems are: a fronto-talamic system of selective attention, and a system of cortico-hippocampal connections that are involved in cortical processing of novel visual information and in episodic memory. The age of 6-7 years is shown to be critical in forming a plastic type of cognitive set.     

Interregional cortical interactions at different stages of natural sleep and the hypnotic state: EEG evidence

The characteristic patterns of EEG spatial organization at different stages of natural sleep and the hypnotic state were studied in 26 volunteers aged 18–22 years. EEGs were recorded using 12 monopolar leads, and EEG cross-correlation coefficient matrices were calculated for consecutive epochs (4 and 8 s). Matrices averaged for each state were treated using factor analysis. The EEG correlation matrices were compared element by element for the states studied and the waking state. Relatively similar changes in the spatial structure of EEG correlations were observed at different stages of natural sleep, with the correlations tending to intensify, especially in the posterior temporal region of the right hemisphere. In the light and deep (somnambular) phases of hypnosis, the interaction between cortical zones that was characteristic of distant relationships of the EEGs of frontal regions, especially the posterior inferior frontal region of the right hemisphere, decreased. The systemic reorganization of the interregional EEG correlations during natural sleep was considerably more pronounced than in the hypnotic state. Notwithstanding, the highly orderly spatial organization of the cortical biopotential field that was typical of the waking state was retained at different stages of natural sleep and hypnosis. Thus, the coordination of the activities of distant nerve centers oriented to providing for a certain function or maintaining a certain functional state occurs against the background of a relatively invariant pattern of interregional integration at the level of the whole brain.Translated from Fiziologiya Cheloveka, Vol. 31, No. 2, 2005, pp. 34–48.Original Russian Text Copyright © 2005 by A. Shepovalnikov, Tsitseroshin, Rozhkov, Galperina, Zaitseva, R. Shepovalnikov.     

Organization of cortical microtubules at the plasma membrane in Arabidopsis

 To understand the role of microtubules in the regulation of cell elongation, we characterized microtubule patterns in fass, a cell shape mutant of Arabidopsis thaliana (L.) Heynh. Examining microtubule patterns via immunocytochemistry, we found that fass cells were able to organize their microtubules into mitotic spindles and phragmoplasts. During interphase or preprophase, fass cells had cortical microtubules, verified by transmission electron microscopy, but these microtubules were not organized into the cortical array or preprophase band. Using chromatin condensation and tubulin localization on the nuclear envelope as preprophase stage markers, we found that although fass cells lacked the preprophase band and cortical array, their cell division cycle appeared normal. To pinpoint the defect in fass cells, we delineated the sequential events leading to cortical array formation in Arabidopsis cells and found that fass cells initiated and recolonized cortical microtubules in the same manner as wild-type cells, but failed to order them into the cortical array. Taken together, these results suggest fass cells are impaired in a component of the microtubule organizing center(s) required for the proper ordering of cortical microtubules at the plasma membrane. Received: 23 August 1996 / Accepted: 25 September 1996     

Examination of transpositional activity of nDart1 at different stages of rice development

As a useful tool to elucidate gene functions, a rice transposon tagging line has been developed using an active endogenous DNA transposon, nDart1. It was highly desirable to evaluate the transposition timing and frequency of the nDart1 elements during rice development to facilitate the generation of an efficient mutant isolation system. Comparison of the detected new insertions at different stages of rice development by transposon display analysis demonstrated that the last heading tiller carry a higher number of nDart1 elements than the main culm. Moreover, it was revealed that the last heading tiller could produce progeny that carried more new insertions of nDart1 elements, mainly as a result of the accumulation of somatic insertions in the parental plant. This report demonstrates that late tillers increase the probability of producing independent mutant lines.     

FSH and LH activity of PMSG from mares at different stages of gestation

Blood was collected from each of four mares at approximately 60, 90 and 120 days of pregnancy. Pregnant mare serum gonadotrophin (PMSG) was prepared in a relatively impure form from each serum sample. Biological activities of FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone) were determined for each sample. FSH activity was greatest at 60 days of gestation and was reduced by day 90; this reduction persisted through day 120. LH activity was highly variable among mares at 60 and 120 days, and variability and mean values were lowest at 90 days. The mean ratio of FSH to LH was greatest at 90 days. The mean ratio of FSH to LH was greatest at 90 days and somewhat lower at both 60 and 120 days. The results suggest that the composition and biological activity of PMSG, as prepared and assayed by these procedures, may vary during gestation as well as among mares.     

Requirement for N-ethylmaleimide-sensitive factor activity at different stages of bacterial invasion and phagocytosis

Bacterial invasion, like the process of phagocytosis, involves extensive and localized protrusion of the host cell plasma membrane. To examine the molecular mechanisms of the membrane remodeling that accompanies bacterial invasion, soluble NSF attachment protein receptor (SNARE)-mediated membrane traffic was studied in cultured cells during infection by Salmonella typhimurium. A green fluorescent protein-tagged chimera of VAMP3, a SNARE characteristic of recycling endosomes, was found to accumulate at sites of Salmonella invasion. To analyze the possible role of SNARE-mediated membrane traffic in bacterial infection, invasion was measured in cells expressing a dominant-negative form of N-ethylmaleimide-sensitive factor (NSF), an essential regulator of membrane fusion. Inhibition of NSF activity did not affect cellular invasion by S. typhimurium nor the associated membrane remodeling. By contrast, Fcgamma receptor-mediated phagocytosis was greatly reduced in the presence of the mutant NSF. Most important, dominant-negative NSF significantly impaired the fusion of Salmonella-containing vacuoles with endomembranes. These observations indicate that the membrane protrusions elicited by Salmonella invasion, unlike those involved in phagocytosis, occur via an NSF-independent mechanism, whereas maturation of Salmonella-containing vacuoles is NSF-dependent.     

Changes in the activity of enzyme systems of xenobiotic metabolism at different stages of insect development

The cytochrome P-450 content, activity of microsomal monooxygenases, nonspecific esterases and glutathione S-transferases were studied at different stages of development of the Colorado beetle, cotton bollworm, cabbage butterfly, wax moth from the laboratory and natural populations. The data obtained demonstrate significant species, sexual and age differences in the activity of enzyme systems of insecticide detoxication. The toxic efficiency of insecticides at certain developmental stages depends on the level of activity of the enzyme systems involved in their metabolism. These data are discussed with respect to the problem of insects' sensitivity to insecticides at different developmental stages.     

Bacterial diversity at different stages of the composting process

Background  

Composting is an aerobic microbiological process that is facilitated by bacteria and fungi. Composting is also a method to produce fertilizer or soil conditioner. Tightened EU legislation now requires treatment of the continuously growing quantities of organic municipal waste before final disposal. However, some full-scale composting plants experience difficulties with the efficiency of biowaste degradation and with the emission of noxious odours. In this study we examine the bacterial species richness and community structure of an optimally working pilot-scale compost plant, as well as a full-scale composting plant experiencing typical problems. Bacterial species composition was determined by isolating total DNA followed by amplifying and sequencing the gene encoding the 16S ribosomal RNA.     

棉铃虫不同虫态及虫龄血淋巴中酚氧化酶活力的比较

分别测定了棉铃虫Helicoverpa armigeraHübner不同虫态及虫龄血清和血细胞中酚氧化酶(phenoloxidase,PO)的活力。结果显示血清和血细胞中都有酚氧化酶活性,且血细胞中高于血清中。不同虫态及虫龄的血清和血细胞中酚氧化酶活力有很大的不同,血清和血细胞中酚氧化酶活力变化规律一致。3龄幼虫酶活力最高,5龄幼虫最低。酶活力大小依次为:3龄幼虫>预蛹>4龄幼虫>蛹>5龄幼虫