Methane cycle in different types of water bodies during the ice period

Studies conducted on different types of water bodies from January to March showed that microbial processes of the CH₄ cycle during the ice period are significant for degradation of organic carbon and trophic webs of the ecosystems. In productive polluted lakes, CH₄ formation occurs in sediments and in the water column, with its total output reaching the high summer level of 300–680 mL CH₄ /(m² day).     

Features of cardiovascular functioning during different phases of the menstrual cycle

The purpose of the present study was to determine whether there is a menstrual cycle effect on heart rate, blood pressure and heart rate variability. 10 healthy regularly cycling females (age 19-23 years) were studied during the follicular phase and luteal phase over two month. We found significant changes in heart rate, AMo and stress index during the menstrual cycle with a minimum in the follicular phase and maximum in the luteal phase. The HF and LF components decreased more during the luteal phase than during the follicular phase (p < 0.05), whereas a tendency for increase LF/HF was observed in the luteal phase. In the follicular phase SDNN, pNN50, Mo, MxDMn were significantly higher than in the luteal phase. Furthermore, the VIK was higher in the luteal phase compared to the follicular phase (p = 0.003). Blood pressure did not show any significant change during both these phases of the menstrual cycle. These findings indicate that sympathetic nervous activity in the luteal phase is greater than in the follicular phase, whereas parasympathetic nervous activity is predominant in the follicular phase. A difference of the balance of ovarian hormones may be responsible for these changes of autonomic functions during the menstrual cycle.     

月经周期对女性睡眠-觉醒和静息-活动的影响

目前有关月经周期对睡眠影响的研究结果并不一致,而对月经周期中昼夜睡眠-觉醒及静息-活动节律尚缺乏系统性的研究.本研究旨在观察正常育龄期女性月经周期中睡眠-觉醒及静息-活动昼夜节律的变化.我们采用静息-活动监测仪(actigraphy)和睡眠日志,调查了12个自然生活状态下健康育龄期妇女在月经周期不同阶段,即行经期、围排卵期、黄体早期及黄体晚期中睡眠与活动节律的变化.结果显示,睡眠-觉醒节律参数在四期之间无统计学显著差异;而静息-活动节律方面,所有受试女性静息-活动节律的平均日周期长度为(24.01±0.29)h,并且四期之间无显著性差异.行经期日间稳定系数(interdaily stability,IS)比黄体早期显著增加(P＜0.05).黄体早期日间活动开始时间明显较黄体晚期提前(P＜0.05);黄体早期的活动峰值时相比围排卵期显著提前(P＜0.05).月经周期可以影响静息-活动昼夜节律时相.而总体静息-活动数量与质量未发生显著变化;健康育龄期妇女在月经周期的各阶段中睡眠-觉醒节律亦无明显变异.     

Conservation of bone marrow CFUc in different phases of the cell cycle during cryopreservation

The effect of low temperature (-196 degrees C) preservation on the recovery of colon-forming units (CFUs) of bone marrow at different phases of the cell cycle before cryopreservation is dealt with. The intact bone marrow "enriched" with CFUs in S phase of the cell cycle and the bone marrow without colony-forming units in S phase were exposed to cryopreservation. After cryopreservation of the bone marrow enriched with CFUs in S phase and th bone marrow without colony-forming units in S phase the number of CFUs decreases by the same value as in the cryopreserved bone marrow obtained from intact mice.     

Reproduction of the bank vole, Clethrionomys glareolus, in northern and southern Sweden during several seasons and in different phases of the vole population cycle

The breeding biology of the bank vole was studied in northern and southern populations in Sweden in the years 1973–76. Trapped specimens supplied organ weights and histological data, which were utilized to describe the breeding season, number and size of litters, reproductive losses, spermatogenesis, and sexual maturation. In the north the populations are cyclic. During the increase phase of the cycle the breeding season was long, litter sizes and gonad weights were large, and there was maturation of yearlings in the summer. During the peak phase reproduction was impaired in all these respects. In southern Sweden there was no cyclicity, and the reproductive events varied less, but in 1976 the litters were larger than usual and the season was much extended.
In the south the voles born during the early part of the season regularly became sexually mature during their first summer. The differences in reproductive biology are related to population dynamics and discussed in terms of different hypotheses concerning vole population cyclicity.     

Entamoeba shows reversible variation in ploidy under different growth conditions and between life cycle phases

Under axenic growth conditions, trophozoites of Entamoeba histolytica contain heterogenous amounts of DNA due to the presence of both multiple nuclei and different amounts of DNA in individual nuclei. In order to establish if the DNA content and the observed heterogeneity is maintained during different growth conditions, we have compared E. histolytica cells growing in xenic and axenic cultures. Our results show that the nuclear DNA content of E. histolytica trophozoites growing in axenic cultures is at least 10 fold higher than in xenic cultures. Re-association of axenic cultures with their bacterial flora led to a reduction of DNA content to the original xenic values. Thus switching between xenic and axenic growth conditions was accompanied by significant changes in the nuclear DNA content of this parasite. Changes in DNA content during encystation-excystation were studied in the related reptilian parasite E. invadens. During excystation of E. invadens cysts, it was observed that the nuclear DNA content increased approximately 40 fold following emergence of trophozoites in axenic cultures. Based on the observed large changes in nuclear size and DNA content, and the minor differences in relative abundance of representative protein coding sequences, rDNA and tRNA sequences, it appears that gain or loss of whole genome copies may be occurring during changes in the growth conditions. Our studies demonstrate the inherent plasticity and dynamic nature of the Entamoeba genome in at least two species.     

Acetylcholinesterase in blood vessels of the guinea-pig ovary during different phases of the reproductive cycle

Synopsis The distribution of acetylcholinesterase-containing blood vessels in the ovary has been investigated histochemically during the reproductive cycle of the guinea-pig. Whole mounts as well as frozen sections have been studied. Stained vessels were found in the stroma throughout the oestrous cycle and pregnancy. In the corpus luteum the vascular reaction varied at different stages of the oestrous cycle; while never very pronounced it was more marked in lactating than in non-lactating animals. A few vessels in the corpus luteum of early pregnancy showed some reaction but as pregnancy advanced an increasing number of vessels were strongly stained. At the end of pregnancy, stained vessels were less prominent.acetylcholinesterase appeared to be localized principally in the vessels themselves (possibly in muscle cells) rather than is associated nerves. Experiments in which ovaries were injected, via their arterial or venous supply, with starch or coloured gelatine suggested that most stained vessels were arterioles but a reaction also occurred in some vessels which were probably arteries and others which could have been the postulated arterio-venous shunts. Capillaries were unstained; whether the veins were also totally unreactive could not be established.The significance of the changes in acetylcholinesterase staining in varying functional states remains obscure; they may or may not reflect the emergence of certain types of vessel at different stages.     

Gradient in seaweed vegetation patterns along the North Icelandic coast,related to hydrographic conditions

The benthic algal vegetation of the North Icelandic coast exhibits particular features, different from those found in southern and western Iceland on the one hand and in eastern Iceland on the other. It is characterised by low-eulittoral belts of Devaleraea ramentacea, Petalonia species and Chordaria flagelliformis as well as by meadows of diverse Acrosiphonia species. In the tide pools Atlantic and typical North Icelandic associations occur side by side. This area thus represents an intermediate region between Atlantic and subarctic growth conditions. A certain gradient in the west-east direction was observed within the North Icelandic vegetation type and is possibly related to the gradual cooling and dilution of the water masses which pass the North Icelandic shelf. The hydrographic discontinuity in the extreme NW creates a sharp floristic and vegetational boundary for benthic algae, whereas in the NE a gradual transition towards the subarctic East Icelandic vegetation was observed. The Atlantic character of the vegetation was more pronounced in the western than in the eastern part of the north coast. An enclave of warm water vegetation was interposed along the western banks of the Tjörnes peninsula.This paper is based on a presentation at the XIII^th International Seaweed Symposium in Vancouver, Canada.     

Distribution and abundance of European hake Merluccius merluccius (L.), eggs and larvae in the North East Atlantic waters in 1995 and 1998 in relation to hydrographic conditions

Plankton samples from surveys in 1995 and 1998 were analysedin order to study the spatial distribution of hake (Merlucciusmerluccius) eggs and larvae. The cruises covered an extensivearea from the south of the Bay of Biscay to the north-west ofIreland. This spatial distribution has been interpreted in relationto the direction and intensity of the dominant winds. An importantdecrease of eggs (69%) and larvae (27%) was observed from 1995to 1998. Hake showed continuous spawning from February to Julyin the area. The centroids of hake egg distribution indicateda northward displacement of the peak of spawning as the seasonprogresses. Spawning of hake was located close to the 200 mdepth isobath in the southern area (Bay of Biscay) and it spreadover the shelf in the area of the Celtic Sea. Eggs were mostabundant at 20 m depth temperatures between 12 and 12.5°C.The centroids of hake larvae distribution also showed a northwarddisplacement although not as strong as that of hake eggs. Thespatial distribution of hake larvae by size ranges showed importantdifferences between years: in 1995 it suggested inshore transportof larvae, from the spawning areas (close to the 200 m depthisobath) to nursery areas (closer to the coast) while in 1998it suggested offshore transport. This transport does not correspondwith the general wind regimes during those years. Thereforeit is concluded that the transport of the hake larvae to nurseryareas must be controlled by different hydrographic mechanismssuch as geostrophic currents in the Bay of Biscay and tidalcurrents in the northern areas.     

月经周期不同阶段游离皮质醇昼夜节律的变化

为了研究皮质醇分泌的昼夜节律在月经周期中的变化,实验对15位月经周期正常的育龄期健康妇女,在月经周期的不同阶段分别于24h内每隔两小时采样,检测唾液昼夜游离皮质醇水平。采用非线性回归分析模型分析皮质醇昼夜节律。结果显示,皮质醇昼夜节律在整个月经周期都具有复杂的明显受到亚节律(ultradian)影响的分泌形式;与月经期相比,围排卵期和黄体晚期昼夜节律波峰宽度(peak-width)明显减低(P=0．005与0．031),而昼夜节律波谷(trough)有抬高趋势(P=0．0622与0．066);黄体晚期的亚节律波幅(ultradian amplitude)与月经期相比显著减低(P=0．002)而与围排卵期相比有减低趋势(P=0．05)。这些结果提示月经周期的不同阶段对皮质醇分泌的昼夜节律有影响。     

Spatial distribution of extractable organohalogens in northern pink shrimp in the North Atlantic

Extractable organohalogens (EOX) are organic compounds that contain chlorine, bromine and/or iodine, which can be separated from the matrix by liquid/liquid or liquid/solid extraction. A combination of instrumental neutron activation analysis (INAA) and solvent extraction methods has been developed for the determination of EOX from the shrimpPandalus borealis. Levels of EOX were evaluated for spatial trends for shrimp caught in several areas off the Labrador coast, off the coast of Nova Scotia, and off the coast of Maine. Muscle contained 1.09–6.05 Μg EOCl/g tissue and 105–498 Μg extractable organochlorine (EOCl)/g lipid; 0.0607–0.288 Μg extractable organobromine (EOB)r/g tissue and 4.74-10.5 Μg EOBr/g lipid; and 0.014–0.048 Μg extractable organoiodine (EOI)/g tissue and 1.03–1.76 Μg EOI/g lipid, respectively. The levels of EOC1 in roe were 1.60–12.34 Μg/g tissue and 39.0-146 Μg/g lipid. In roe, the EOBr levels were 0.707–1.03 Μg/g tissue and 6.96–13.5 Μg/g lipid; and EOI levels were 0.123–0.349 Μg/g tissue and 1.42–4.11 Μg/g lipid. The EOCl, EOBr, and EOI levels in roe increased noticeably from north to south along the coast of Labrador. Samples taken from the coast of Maine and from Canso Hole were typically higher in EOCl levels than those taken from Labrador. The results for EOBr and EOI were in the same range as those from Labrador.     

Differential response of lymphocytes to free and sepharose-linked anti-immunoglobulin during different phases of the cell cycle

During proliferation induced by anti-immunoglobulins, B lymphocytes undergo cell volume increases prior to onset of DNA synthesis. Although both Sepharose-linked and free anti-immunoglobulin evoked essentially identical increases in cell volume, the Sepharose-linked antibody induced a significantly greater DNA synthesis than free antibody as judged from [3H]thymidine incorporation studies using mass cell culture technique, as well as by using autoradiographic analysis of individual cells. These findings are considered in terms of possible differences in triggering cell volume increases and DNA synthesis by free and linked anti-immunoglobulin and/or the possible existence of B cell subpopulations responding differentially to free and to linked antibody.     

Associative thoughts in women in different phases of the menstrual cycle

In this study female students in different phases of the menstrual cycle made a test of word association. The results were represented and compared in a pathfinder-network. This special network is a model of knowledge representation in which words are portrayed as nodes, and links between nodes represent associations. This method (pathfinder), developed by Schvaneveldt (1990), generates associative networks from individual's ratings of similarity of word pairs. 51 women had to judge 45 words of the three categories sexual, romantic and neutral in similarity. These networks were compared regarding probability of contraception, partnership and level of testosterone. The number and weights of links differed between women with high and low probability of contraception. The level of testosterone had a large influence on the density of associations, especially in sexual contents.     

A diatom based transfer function for reconstructing sea ice concentrations in the North Atlantic

A diatom based sea ice transfer function is developed using 99 surface sediment samples from the North Atlantic and the associated modern sea ice concentrations. Canonical correspondence analysis (CCA) is applied to the species assemblages of the surface sediment samples and the association of the species with two environmental parameters, August sea surface temperature and May sea ice concentration, is assessed. The results of this analysis indicate negative correlation between sea ice and sea surface temperature and that a group of diatom species is strongly associated with sea ice, especially May sea ice concentration. The results of the CCA legitimate the development of a diatom based sea ice transfer function. The maximum likelihood method has been applied as the transfer function method, as it has been proven most suitable with this particular data set. The newly developed transfer function is then used to reconstruct May sea ice concentration in three cases, each focusing on a different time period: the Last Glacial Maximum, the Younger Dryas and the Holocene. In all three cases the transfer function produces reasonable results when compared to other paleoclimatic proxy results. This suggests that the sea ice concentration reconstructed by the diatom based sea ice transfer function is a valid and reliable method, which can be applied as a valid proxy for May sea ice concentration.     

The corpus luteum periodicum in the bitch: histochemical and biochemical investigations during different phases of the cycle.

The corpus luteum periodicum (c.l.p.) of the bitch was studied using enzyme histochemistry, clinical and biochemical methods. Assessment of variations of the serum progesterone level during different stages of the ovarian cycle and the study of enzymatic activity of the luteal tissue furnished informations on vitality and biosynthetic capacity of luteinizing cells: The period of functional activity of the c.l.p. nearly ceased about day 60 of the cycle (proestrus included) in the animals examined. In the light microscope the neo-synthesis of progesterone in the c.l.-tissue can be made visible by histochemical demonstration of the activity of Delta(5)-3 beta-hydroxysteroiddehydrogenase (3 beta-HSD) only up to a progesterone level exceeding 6.7 ng/ml plasma. The data obtained contribute to our baseline knowledge of the mechanism involved in the etiology of pseudopregnancylike conditions in the bitch.