Phosphorylation of Adenosine with Trimetaphosphate Under Simulated Prebiotic Conditions

The phosphorylation of adenosine withtrimetaphosphate in solution, in solid phase and usingwet-dry cycles was carried out and it was found thatwet-dry cycles were the most efficient. The catalytic effectsof some metal ions on the phosphorylation were alsostudied and it was discovered that Ni(II) is the mosteffective. The combination of wet-dry cycles (4 cycles)and catalysis by Ni(II) led to an unprecedented highconversion of adenosine to phosphorylated products (30%)near neutral pH. The main phosphorylated products were2', 3'-cyclic AMP (10.4%) and 5'-ATP (13.0%).     

The biology of the trematodes Nenimandijea kashmirensis and Pleurogenoides medians (Pleurogenidae)--parasites of frogs in the Maritime Territory

The experimental study of life cycles of the trematodes Nenimandijea kashmirensis Kaw, 1950 and Pleurogenoides medians Olsson, 1876 was carried out. It was found out, that their life cycles include: the first intermediate host--the mollusc Boreoelona contortrix ussuriensis, the second intermediate host--dragonfly larvae of the genus Cordulia, and the final host--the frogs Rana nigrimaculata and R. semiplicata. Based on obtained data it is suggested, that Pleurogenoides japonicus (Yamaguti) should not be considered as a separate species.     

The ontogeny of bone growth in two species of dormice: Reconstructing life history traits

Though bone histology has become a powerful tool to reconstruct life history strategies and physiology in living and extinct reptiles and amphibians, it is of limited use in mammals. Dormice (Myoxidae) are good candidates for assessing the relation between bone microstructure and life history due to their long life span, marked physiological cycles and negligible bone remodelling. We carried out the most comprehensive study so far analyzing 16 wild individuals of unknown age belonging to two different species of dormice, Glis glis and Eliomys quercinus. Our study shows a high degree of consistency in the number of resting lines present in bones of the same individual, with femora providing the most accurate age estimations. Moreover, the presence of a single LAG in some juveniles allows discerning between offspring from different reproductive events (early or late litters).     

Population cycles in voles and lemmings: state of the science and future directions

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Herpes Simplex Virus and Human Cytomegalovirus Replication in WI-38 Cells I. Sequence of Viral Replication

A comparison, under standardized conditions, of herpes simplex virus (HSV) and human cytomegalovirus (CMV) revealed differences in viral morphology, in the timing of their infectious cycles, and in several morphological events during those cycles. Structural distinctions between the two viruses included the coating of unenveloped cytoplasmic CMV capsids, but not those of HSV, and a variation in the structure of their cores. Since the two cycles were carried out in the same host cell strain under conditions of one-step growth (input multiplicity = 10 PFU/cell), it was possible to construct time scales locating the major events of each cycle. Comparison of the two showed that HSV replicated and released progeny within 8 h postinfection, whereas CMV required 4 days. These results correlated well with those of concurrent plaque assays. Within the longer CMV cycle, most of the major events appeared retarded to a similar degree, and no obvious limiting step in particle production could be identified. Distinctions between the two cycles included the following: condensation of the chromatin in HSV- but not CMV-infected cells; the greater tendency of HSV to produce membrane alterations; and the appearance of cytoplasmic dense bodies in CMV- but not HSV-infected cells. Identification of these differences even under identical conditions of culture and infection strongly implies that they result from intrinsic differences in the nature of the viruses, and are not caused by variations in experimental conditions.     

Growth of high-elevation <Emphasis Type="Italic">Cryptococcus</Emphasis> sp. during extreme freeze–thaw cycles

Soils above 6000 m.a.s.l. are among the most extreme environments on Earth, especially on high, dry volcanoes where soil temperatures cycle between ?10 and 30 °C on a typical summer day. Previous studies have shown that such sites are dominated by yeast in the cryophilic Cryptococcus group, but it is unclear if they can actually grow (or are just surviving) under extreme freeze–thaw conditions. We carried out a series of experiments to determine if Cryptococcus could grow during freeze–thaw cycles similar to those measured under field conditions. We found that Cryptococcus phylotypes increased in relative abundance in soils subjected to 48 days of freeze–thaw cycles, becoming the dominant organisms in the soil. In addition, pure cultures of Cryptococcus isolated from these same soils were able to grow in liquid cultures subjected to daily freeze–thaw cycles, despite the fact that the culture medium froze solid every night. Furthermore, we showed that this organism is metabolically versatile and phylogenetically almost identical to strains from Antarctic Dry Valley soils. Taken together these results indicate that this organism has unique metabolic and temperature adaptations that make it able to thrive in one of the harshest and climatically volatile places on Earth.     

Tubulin dynamics during the cytoplasmic cohesiveness cycle in artificially activated sea urchin eggs

Sedimentation studies and [³H]colchicine-binding assays have demonstrated a relationship between the cytoplasmic cohesiveness cycles and the changes in tubulin organization in Paracentrotus lividus eggs activated by 2.5 mM procaine. The same amount of tubulin (20–25 % of the total egg tubulin) is involved in these cyclic process and appears to undergo polymerization and depolymerization cycles. Electron microscopy studies reveal that the microtubules formed during these cytoplasmic cohesiveness cycles are under a particulate form which is sedimentable at low speed. Activation experiments carried out in the presence of cytochalasin B (CB) show that the increase in the cytoplasmic cohesiveness is highly reduced while tubulin polymerization and depolymerization cycles and pronuclear centration are not affected. Although tubulin or actin polymerization can be independently triggered in procaine-activated eggs, the increase in cytoplasmic cohesiveness requires the polymerization of both proteins. However, the cytoplasmic cohesiveness cycles appear to be regulated by tubulin polymerization and depolymerization cycles.     

Exploring the Interdependence of Couples' Rest‐Wake Cycles: An Actigraphic Study

Within western societies, it is commonplace for couples to share a bed. Yet there has been remarkably little research carried out on couples' sleep. This paper draws upon actigraphy, audio diary, and questionnaire data from both partners of 36 heterosexual couples (age 20–59 yrs) and aims to quantify the extent to which it is important to take into account the dyadic nature of sleep‐wake cycles. It achieves this through two interrelated aims: to use hierarchical linear models to measure dyadic interdependence in actigraphically recorded variables, and to investigate how much of this dyadic interdependence truly results from couple dynamics. The variables with the most significant couple interdependency were actual bed time, sleep latency, light/dark ratio, and wake bouts. The paper concludes by suggesting that interdependence may be the defining feature of couples' sleep, and that we need to employ analytic approaches that both acknowledge this and are sensitive to the possibilities that not all aspects of sleep will behave in the same way.     

State of actin during the cycle of cohesiveness of the cytoplasm in parthenogenetically activated sea urchin egg

By the DNase I inhibition assay it is shown that the cytoplasmic matrix isolated 60 min after procaine activation of Paracentrotus lividus eggs contains about 20% of the total egg actin, mostly in polymerized form (85%). Electron microscopy studies on this cytoplasmic structure after treatment with heavy meromyosin (HMM), reveal that the decorated actin filaments are organized in bundles which are distributed radially, with the arrowheads pointing towards the central region. In addition few microtubules and a network of non-decorated microfilaments of about 3 nm diameter are observed. From the cytoplasmic pH determination and the DNase I inhibition assay on homogenates of eggs which were taken at different times of activation, it cannot be inferred that a direct relationship between the increase in the cytoplasmic pH and the increase in the amount of polymerized actin or of cytoplasmic matrix exists. Activation experiments carried out in the presence of colchicine shows that, although the formation of the cytoplasmic matrix is inhibited, polymerization of actin still occurs. Moreover, from the inhibition effects of cytochalasin B (CB) added before the activator it is shown that polymerization of actin is a necessary step for the organization of the cytoplasmic matrix. However, the cycles of cohesiveness of the cytoplasm observed in the course of the activation process do not appear to depend on cycles of polymerization and depolymerization of actin.     

The beta-geometric distribution applied to comparative fecundability studies

A convenient measure of fecundability is time (number of menstrual cycles) required to achieve pregnancy. Couples attempting pregnancy are heterogeneous in their per-cycle probability of success. If success probabilities vary among couples according to a beta distribution, then cycles to pregnancy will have a beta-geometric distribution. Under this model, the inverse of the cycle-specific conception rate is a linear function of time. Data on cycles to pregnancy can be used to estimate the beta parameters by maximum likelihood in a straightforward manner with a package such as GLIM. The likelihood ratio test can thus be employed in studies of exposures that may impair fecundability. Covariates are incorporated in a natural way. The model is illustrated by applying it to data on cycles to pregnancy in smokers and nonsmokers, with adjustment for covariates. For a cross-sectional study, when length-biased sampling is taken into account, the pre-interview attempt time is shown to follow a beta-geometric distribution, so that the same methods of analysis can be applied even though all of the available data are right-censored. For a cohort followed prospectively, there will be some couples enrolled whose fecundability is effectively 0, and for such applications, the beta could be considered to be contaminated by a distribution degenerate at 0. The mixing parameter (proportion sterile) can be estimated by application of the expectation-maximization (EM) algorithm. This, too, can be carried out using GLIM.     

Factor analysis of the structure of nocturnal sleep and the results of psychodiagnostic examination in man

Factor analysis was carried out of sleep structure and results of complex psychodiagnostic study in 35 subjects. Seven orthogonal factors were singled out. It is shown that alarm level is connected with fast sleep general presentation; the system of psychological defences is linked with the fast sleep in the second cycle; the self-control in alert state and the transfer from alertness to sleep are interrelated, and duration of the first and last sleep cycles are reciprocally connected.     

The role of lysosomes in iron metabolism and recycling

Iron is the most abundant transition metal in the earth's crust. It cycles easily between ferric (oxidized; Fe(III)) and ferrous (reduced; Fe(II)) and readily forms complexes with oxygen, making this metal a central player in respiration and related redox processes. However, 'loose' iron, not within heme or iron-sulfur cluster proteins, can be destructively redox-active, causing damage to almost all cellular components, killing both cells and organisms. This may explain why iron is so carefully handled by aerobic organisms. Iron uptake from the environment is carefully limited and carried out by specialized iron transport mechanisms. One reason that iron uptake is tightly controlled is that most organisms and cells cannot efficiently excrete excess iron. When even small amounts of intracellular free iron occur, most of it is safely stored in a non-redox-active form in ferritins. Within nucleated cells, iron is constantly being recycled from aged iron-rich organelles such as mitochondria and used for construction of new organelles. Much of this recycling occurs within the lysosome, an acidic digestive organelle. Because of this, most lysosomes contain relatively large amounts of redox-active iron and are therefore unusually susceptible to oxidant-mediated destabilization or rupture. In many cell types, iron transit through the lysosomal compartment can be remarkably brisk. However, conditions adversely affecting lysosomal iron handling (or oxidant stress) can contribute to a variety of acute and chronic diseases. These considerations make normal and abnormal lysosomal handling of iron central to the understanding and, perhaps, therapy of a wide range of diseases.     

Studies on repository compound stability in DMSO under various conditions

The chemical stability of repository compounds is affected by various environmental conditions during long-term storage. Studies were carried out to evaluate the effects of the following potential causes of instability of compounds in DMSO at a 10-mM concentration: water, oxygen, freeze/thaw cycles, and storage container material. A set of compounds was selected for the study based on structural diversity and functional group representation. Compound concentration was determined with liquid chromatography/ultraviolet spectroscopy/mass spectrometry (LC/UV/MS) analysis relative to an internal standard added to each sample. An accelerated study was conducted, and results demonstrate that most compounds are stable for 15 weeks at 40 degrees C. Water is more important in causing compound loss than oxygen. The freeze/thaw cycle study was done with freezing at -15 degrees C and thawing under nitrogen atmosphere at 25 degrees C. Two methods were used to redissolve compounds after thawing: agitation and repeated aspiration/dispense. The results indicate no significant compound loss after 11 freeze/thaw cycles. Compound recovery was also measured from glass and polypropylene containers for 5 months at room temperature, and no significant difference was found for these 2 types of containers.     

Collective behavior in gene regulation: metabolic clocks and cross-talking

Biological functions governed by the circadian clock are the evident result of the entrainment operated by the earth's day and night cycle on living organisms. However, the circadian clock is not unique, and cells and organisms possess many other cyclic activities. These activities are difficult to observe if carried out by single cells and the cells are not coordinated but, if they can be detected, cell-to-cell cross-talk and synchronization among cells must exist. Some of these cycles are metabolic and cell synchronization is due to small molecules acting as metabolic messengers. We propose a short survey of cellular cycles, paying special attention to metabolic cycles and cellular cross-talking, particularly when the synchronization of metabolism or, more generally, cellular functions are concerned. Questions arising from the observation of phenomena based on cell communication and from basic cellular cycles are also proposed.     

Model of "standing water" of Baikalian phytoplankton interannual dynamics

A "standing waves" model is presented which is based on the idea that an energy impulse accumulated from the spring bloom outburst of phytoplankton moves along a food chains. When its "echo" comes back, it generates a new bloom outburst, and a next cycle occurs. It is supposed that the resonance of self-supporting oscillations in populations with periodic solar influences led to standing waves, which provide for biosystem stability and cyclic recurrence of phytoplankton bloom. To test the model, an analysis of the interannual dynamics (from 1941 to 1998) of the pelagic phytoplankton in the southern basin of the lake Baikal was carried out. The discovered 11-year cycles with 3 2/3-year cycles within them conform well to the model, which made it possible to explain not only the cyclic recurrence but also a number of other obscure aspects of phytoplankton life in the lake Baikal. The next bloom burst is predicted to take place in 2001.     

Mechanisms and regulation of the degradation of cyclin B

The degradation of the cyclin B subunit of protein kinase Cdk1/cyclin B is required for inactivation of the kinase and exit from mitosis. Cyclin B is degraded by the ubiquitin pathway, a system involved in most selective protein degradation in eukaryotic cells. In this pathway, proteins are targeted for degradation by ligation to ubiquitin, a process carried out by the sequential action of three enzymes: the ubiquitin-activating enzyme E1, a ubiquitin-carrier protein E2 and a ubiquitin-protein ligase E3. In the system responsible for cyclin B degradation, the E3-like function is carried out by a large complex called cyclosome or anaphase-promoting complex (APC). In the early embryonic cell cycles, the cyclosome is inactive in the interphase, but becomes active at the end of mitosis. Activation requires phosphorylation of the cyclosome/APC by protein kinase Cdk1/cyclin B. The lag kinetics of cyclosome activation may be explained by Suc1-assisted multiple phosphorylations of partly phosphorylated complex. The presence of a Fizzy/Cdc20-like protein is necessary for maximal activity of the mitotic form of cyclosome/APC in cyclin-ubiquitin ligation.     

Study of implanted biomaterial functionality by diphosphonate molecules labeled with radioactive99mTc

An implanted biomaterial can be transformed into young bone after some months, but it has not necessary reached full biofunctionality. Mineral concentration kinetics and crystal-structure studies, still being carried out in our group, are completed here by biofunctionality determinations. A natural coral is implanted in vivo at the cortical level of the femoral diaphyse in rabbits. Diphosphonates molecules labeled with radioactive^99mTc are then injected in rabbits and the fixation of the radioactivity is analyzed in several sites for 8 mo after the implantation. Nuclear instruments and methods are used for the measurements. Four successive cycles of osseous remodeling are determined before reaching a biofunctional phase.     

The consequences of growth of a mutator strain of Escherichia coli as measured by loss of function among multiple gene targets and loss of fitness

We have examined the composition of members of mutator populations of Escherichia coli by employing an extensive set of phenotypic screens that allow us to monitor the function of >700 genes, constituting approximately 15% of the genome. We looked at mismatch repair deficient cells after repeated cycles of single colony isolation on rich medium to generate lineages that are forced through severe bottlenecks, and compared the results to those for wild-type strains. The mutator lineages continued to accumulate mutations rapidly with each increasing cycle of colony isolation. By the end of the 40th cycle, after approximately 1000 generations, most of the lineages had reduced colony size, 4% had died out, 55% had auxotrophic requirements (increasing to 80% after 60 cycles), and 70% had defects in at least one sugar or catabolic pathway. In addition, 33% had a defect in cell motility, and 26% were either temperature-sensitive or cold-sensitive lethals. On the other hand, only 3% of the wild-type lineages had detectable mutations of any type after 40 cycles. By the 60th cycle, the typical mutator cell carried 4-5 inactive genes among the 15% of the genome being monitored, indicating that the average cell carried at least 24-30 inactivated genes distributed throughout the genome. Remarkably, 30% of the lineages had lost the ability to utilize xylose as a carbon source. DNA sequencing revealed that most of the Xyl(-) mutants had a frameshift in a run of eight G's (GGGGGGGG) in the xylB gene, either adding or deleting one -G-. Further analysis indicated that rendering E. coli deficient in mismatch repair unmasks hypermutable sites in certain genes or intergenic regions. Growth curves and competition tests on lineages that passed through 90 cycles of single colony isolation showed that all lineages suffered reduced fitness. We discuss these results in terms of the value of mutators in cellular evolution.     

The behaviour of microcracks in compact bone

This paper summarises four separate studies carried out by our group over the past number of years in the area of bone microdamage. The first study investigated the manner by which microcracks accumulate and interact with bone microstructure during fatigue testing of compact bone specimens. In a series of fatigue tests carried out at four different stress ranges between 50 and 80 MPA, crack density increased with loading cycles at a rate determined by the applied stress. Variations in the patterns of microdamage accumulation suggest that that at low stress levels, larger amounts of damage can build up without failure occurring. In a second study using a series of four-pont bending tests carried out on ovine bone samples, it was shown that bone microstructure influenced the ability of microcracks to propagate, with secondary osteons acting as barriers to crack growth. In a third study, the manner by which crack growth disrupts the canalicular processes connecting osteocytes was investigated. Analysis of individual cracks showed that disruption of the canalicular processes connecting osteocytes occurred due to shear displacement at the face of propagating microcracks, suggesting that this may play some role in the mechanism that signals bone remodelling. In a fourth in vivo study, it was shown that altering the mechanical load applied to the long bones of growing rats causes microcrack formation. In vivo microdamage was present in rats subjected to hindlimb suspension with a higher microcrack density found in the humeri than the femora. Microdamage was also found in control animals. This is the first study to demonstrate in vivo microcracks in normally loaded bones in a rat model.     

Clustering in large networks does not promote upstream reciprocity

Upstream reciprocity (also called generalized reciprocity) is a putative mechanism for cooperation in social dilemma situations with which players help others when they are helped by somebody else. It is a type of indirect reciprocity. Although upstream reciprocity is often observed in experiments, most theories suggest that it is operative only when players form short cycles such as triangles, implying a small population size, or when it is combined with other mechanisms that promote cooperation on their own. An expectation is that real social networks, which are known to be full of triangles and other short cycles, may accommodate upstream reciprocity. In this study, I extend the upstream reciprocity game proposed for a directed cycle by Boyd and Richerson to the case of general networks. The model is not evolutionary and concerns the conditions under which the unanimity of cooperative players is a Nash equilibrium. I show that an abundance of triangles or other short cycles in a network does little to promote upstream reciprocity. Cooperation is less likely for a larger population size even if triangles are abundant in the network. In addition, in contrast to the results for evolutionary social dilemma games on networks, scale-free networks lead to less cooperation than networks with a homogeneous degree distribution.