Cell Cycle And The Concept Of Physiological Age With Special Reference To Pyruvate Kinase Activity In Wi-38 Cells

Wi-38 Cells Were Synchronized By Mitotic Collection And Periodically Assayed For Pyruvate Kinase Activity. The Kinetics Of The Synchronous Cohort Were Determined By Continuous Labelling Index And By Mitotic Index. The Experimental Data Were Analysed By Computer Using A State Vector Model To Yield The Probability Density Functions For Phase Transit Times And For Cell Physiological Ages. Pyruvate Kinase Activity For These Cells As A Function Of Physiological Age Was Then Examined Using The Computer Model. Considering Dna Synthesis, Pyruvate Kinase Activity And Mitosis To Be Markers Of Physiological Age, It Was Found That A Model Which Assumes That A Cohort Of Synchronized Cells Desynchronizes Irreversibly And Uniformly From One Age Marker To The Next Is Incompatible With The Experimental Data. For Example, The Times Over Which Cells Entered The S Phase Were Too Widely Distributed To Be Consistent With The Mitotic Index Data. Also, For Pyruvate Kinase Activity To Be A Function Of Physiological Age Alone, The Cell Ages Were Probably Too Dispersed To Be Compatible With The Experimental Enzyme Data. Alternative Models For Cell Physiological Ageing Are Presented, Which Are Compatible With The Experimental Data.     

Model of For3p-Mediated Actin Cable Assembly in Fission Yeast

Formin For3p nucleates actin cables at the tips of fission yeast cells for polarized cell growth. The results of prior experiments have suggested a possible mechanism for actin cable assembly that involves association of For3p near cell tips, For3p-mediated actin polymerization, retrograde flow of actin cables toward the cell center, For3p dissociation from cell tips, and cable disassembly. We used analytical and computational modeling to test the validity and implications of the proposed coupled For3p/actin mechanism. We compared the model to prior experiments quantitatively and generated predictions for the expected behavior of the actin cable system upon changes of parameter values. We found that the model generates stable steady states with realistic values of rate constants and actin and For3p concentrations. Comparison of our results to previous experiments monitoring the FRAP of For3p-3GFP and the response of actin cables to treatments with actin depolymerizing drugs provided further support for the model. We identified the set of parameter values that produces results in agreement with experimental observations. We discuss future experiments that will help test the model''s predictions and eliminate other possible mechanisms. The results of the model suggest that flow of actin cables may establish actin and For3p concentration gradients in the cytoplasm that could be important in global cell patterning.     

Characterization of two different 2-oxoglutarate:ferredoxin oxidoreductases from Hydrogenobacter thermophilus TK-6

A thermophilic, chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, fixes carbon dioxide via the reductive TCA cycle. 2-Oxoglutarate:ferredoxin oxidoreductase (OGOR) is one of the key enzymes of this cycle. Strain TK-6 has two distinct OGOR enzymes termed For and Kor. These enzymes were purified and characterized following heterologous expression in Escherichia coli. The specific activity of For was approximately one-tenth of that of Kor. Additionally, For showed higher thermo-stability than Kor under both aerobic and anaerobic conditions. Western blot analysis showed that both of For and Kor were expressed when strain TK-6 was grown under aerobic conditions. In contrast, only Kor was expressed when the strain was grown under anaerobic conditions using nitrate as a terminal electron acceptor. These results indicate that For supports the optimal growth of strain TK-6 in the presence of oxygen.     

E.s.r. of spin-trapped radicals in gamma-irradiated polycrystalline amino acids, N-acetyl amino acids and dipeptides

The radicals produced in several polycrystalline amino acids, N-acetyl amino acids and dipeptides by gamma-radiolysis at room temperature were investigated by spin-trapping. After irradiation in the solid state, the samples were dissolved in aqueous solutions f t-nitrosobutane and the trapped radicals identified by e.s.r. For alpha-amino acids, deamination radicals were found, and in some cases H-abstraction radicals were also observed. No decarboxylation radicals could be detected. For N-acetyl amino acids, except for N-acetylglycine, the major radical was the decarboxylation radical. For N-acetyglycine the H-abstraction radical from the glycine residue was observed. For dipeptides of the x-glycine, the radical formed by removal of H from the alpha-carbon of the carboxyl-terminal residue was always spin-trapped. Some primary deamination radicals and minor amounts of decarboxylation radicals could also be observed. For dipeptides of the type x-alanine, glycine-x and alanine-x, the decarboxylation radical was always the major spin-trapped radical. Some primary and secondary deamination radicals were also detected.     

Targeting multi-cellular organisms

For many years, biologists' efforts in achieving gene targeting by homologous recombination in multicellular organisms have been hampered by the difficulty in culturing pluripotent stem cells. Recent advances have eliminated this requirement for several animal species. For large mammals, cloning by nuclear transfer has led to the first knockout sheep and pigs. For Drosophila, whole organism gene targeting was accomplished by a method for the generation of linear DNA in vivo.     

Greenhouse and field trials of the bacterial antagonists in pelletformulations to suppress sheath blight of rice caused by Rhizoctoniasolani

Bacterial formulations, produced using both Bacillus megaterium andB. pumilus individually with pharmaceutical technology, were testedunder both greenhouse and field conditions. In the greenhouse testing,some bacterial formulations, for instance For 7 minus Lac and For 16 minusLac, performed as well as freshly prepared bacterial antagonists insuppress sheath blight disease. In the field testing, For 16 minus Lac wasnot effective in suppressing sheath blight development. Failure of the For16 minus Lac to suppress sheath blight disease in the field trial may be dueto the dilution and inactivation of antibiotics produced by B.megaterium in the aquatic environment in the rice field and climaticconditions during the formulation application.     

Addendum to the Morphology of Steinernema scapterisci

This paper provides additional information on the morphology of Steinernema scapterisci. For females, the amphids are shown for the first time, and clearer scanning electron microscope (SEM) photographs of the six labial and four cephalic papillae are presented. For males, six labial and four cephalic papillae, one or two pairs of additional genital papillae, and the death shape are shown. For infective juveniles, six labial and four cephalic papillae and an elevated oral disc are shown.     

Polarized signal classification by complex and quaternionic multi-layer perceptrons

For polarized signals, which arise in many application fields, a statistical framework in terms of quaternionic random processes is proposed. Based on it, the ability of real-, complex- and quaternionic-valued multi-layer perceptrons (MLPs) of performing classification tasks for such signals is evaluated. For the multi-dimensional neural networks the relevance of class label representations is discussed. For signal to noise separation it is shown that the quaternionic MLP yields an optimal solution. Results on the classification of two different polarized signals are also reported.     

Necessary and sufficient conditions for the existence of certain quadratic invariants under a phylogenetic tree.

Invariants are functions of the probabilities of state configurations among lineages, with expected values equal to zero under certain phylogenies. For two-state sequences, the existence of certain quadratic invariants requires a symmetric substitution model. For sequences with more than two states, the necessary condition for the existence of certain quadratic invariants in terms of independent events is much stronger than symmetry. For DNA sequences, only three parameters are allowed in the substitution model, which includes Kimura's two-parameter model as a special case.     

Statistics of hits to bone cell nuclei

The statistics of hits to the nuclei of bone cells irradiated from alpha sources labeling bone tissue is described. It is shown that the law of remodeling of a bone structural unit (BSU), which describes the distribution of quiescence periods of this unit, affects the statistics of hits. It the irradiation of bone cells occurs during the whole cell cycle, the mean number of hits is independent of the law of remodeling. In this case the variance of hits has the minimum value for constant quiescence periods of BSUs (deterministic remodeling) and the maximum value for exponentially distributed quiescence periods (random remodeling). For the first generation of bone cells, i.e. for the cells which existed at the moment of the uptake of the nuclide, the mean number of hits depends on the law of remodeling. For random remodeling the mean number is equal to the mean value for the complete remodeling cycle. For deterministic remodeling the mean is only half this value. For the first generation of bone cells, changing the law of remodeling from random to deterministic increases the probability of no hits to the nuclei of bone cells. For the same mean value of hits, the difference does not exceed 13.3 % of the total number of cells. For the subsequent generations of bone cells, such a change of the law of remodeling decreases the probability of no hits by 20.4%.     

Selection in Complex Genetic Systems I. the Symmetric Equilibria of the Three-Locus Symmetric Viability Model

The symmetric equilibria of the three-locus symmetric viability model are determined and their stability analyzed. For tight linkage there may be four stable equilibria, each characterized by having one pair of complementary chromosomes in high frequencies, with all others low. For looser linkage the only stable symmetric equilibrium is that with complete linkage equilibrium. For intermediate recombination values both types of equilibria may be stable. A new class of equilibria with all pairwise linkage disequilibria zero, but with third order linkage disequilibrium, has been discovered. It may be stable for tight linkage.     

PAIRED PREFERENCE TESTS: d' VALUES FROM MEXICAN CONSUMERS WITH VARIOUS RESPONSE OPTIONS

Three groups, each comprising 200 consumers, performed paired preference tests between two flavors of potato chips. For one group, a “No Preference” option was allowed, while for the second group, it was not. For a third group, a “No Preference” option was allowed while the preference responses were differentiated as “Strong Preference” and “Weak Preference.” For all three groups, d′ values representing overall strength of preference did not differ significantly.     

The chromosome number of several species of flowering plants from the flora of the Aragats mountain massif

The chromosome numbers are given for 10 species of the flora from the Aragatz mountainous massif. For 7 species the chromosome numbers are presented for the first time or they differ from those already published by other authors. For the rest 3 species the chromosome numbers are confirmed. Five species of the 10 above-mentioned ones proved to be polyploids of various degree of ploidy, the rest--diploids. For the first time the new pentaploid chromosome race with 2n=30 was found in Scilla sibirica.     

Docking unbound proteins using shape complementarity, desolvation, and electrostatics

A comprehensive docking study was performed on 27 distinct protein-protein complexes. For 13 test systems, docking was performed with the unbound X-ray structures of both the receptor and the ligand. For the remaining systems, the unbound X-ray structure of only molecule was available; therefore the bound structure for the other molecule was used. Our method optimizes desolvation, shape complementarity, and electrostatics using a Fast Fourier Transform algorithm. A global search in the rotational and translational space without any knowledge of the binding sites was performed for all proteins except nine antibodies recognizing antigens. For these antibodies, we docked their well-characterized binding site-the complementarity-determining region defined without information of the antigen-to the entire surface of the antigen. For 24 systems, we were able to find near-native ligand orientations (interface C(alpha) root mean square deviation less than 2.5 A from the crystal complex) among the top 2,000 choices. For three systems, our algorithm could identify the correct complex structure unambiguously. For 13 other complexes, we either ranked a near-native structure in the top 20 or obtained 20 or more near-native structures in the top 2,000 or both. The key feature of our algorithm is the use of target functions that are highly tolerant to conformational changes upon binding. If combined with a post-processing method, our algorithm may provide a general solution to the unbound docking problem. Our program, called ZDOCK, is freely available to academic users (http://zlab.bu.edu/~rong/dock/).     

Evolutionary game dynamics in finite populations

We introduce a model of stochastic evolutionary game dynamics in finite populations which is similar to the familiar replicator dynamics for infinite populations. Our focus is on the conditions for selection favoring the invasion and/or fixation of new phenotypes. For infinite populations, there are three generic selection scenarios describing evolutionary game dynamics among two strategies. For finite populations, there are eight selection scenarios. For a fixed payoff matrix a number of these scenarios can occur for different population sizes. We discuss several examples with unexpected behavior.     

The Association between Leptin Level and Breast Cancer: A Meta-Analysis

Background

Contradictory results have been reported regarding the association between leptin level and breast cancer. Therefore, a meta-analysis was performed to investigate this issue.

Methods

Published literature from PubMed and the Chinese National Knowledge Infrastructure (CNKI) Database was retrieved. This study was performed based on different cases and control groups. The combined effect () with 95% confidence interval (CI) was calculated using fixed-effects or random-effects model analysis.

Results

Overall, the mean serum leptin level of case groups was significantly higher than that of control groups. A) For 9 studies comparing breast cancer cases and healthy controls the combined effect was 0.58 with 95% CI (0.48, 0.68). B) For 4 studies comparing premenopausal breast cancer cases and healthy controls the was 0.32 (0.12, 0.52). C) For 5 studies comparing postmenopausal cases and healthy controls the was 0.65 (0.46, 0.84). D) For 4 studies comparing breast cancer cases and breast benign controls the was 0.38 (0.17, 0.59). E) For 2 studies comparing premenopausal breast cancer cases and breast benign controls the was 0.33 (-0.25, 0.91). F) For 6 studies comparing postmenopausal breast cancer cases and breast benign controls the was 0.39 (0.19, 0.60). G) For 4 studies comparing lymph node metastasis positive cases and negative controls the was 0.72 (0.45, 1.00). H) For 3 studies comparing breast benign cases and healthy controls the was 0.71 (0.41, 1.01).

Conclusion

This meta-analysis suggests that leptin level plays a role in breast cancer and has potential for development as a diagnostic tool.     

Effect of the anti-microtubule compound tubulozole on Leishmania protozoan parasites in vitro

Abstract For the cis and trans stereoisomers of the synthetic anti-microtubule compound tubulozole, at micromolar concentrations, tubulozole-C is cytotoxic to mammalian cells whereas tubulozole-T is not. The effect of tubulozoles on the parasitic protozoan Leishmania was tested. For the promastigote stage of L. mexicana amazonensis , both isomers inhibited parasite growth. For the amastigote stage of L. mexicana amazonensis and L. major , within murine J774 macrophage line as host cells in vitro, tubulozole-T reduced the infective index. Despite the observation of macrophage cytotoxicity of tubulozole-T, this compound may be a potentially useful and novel anti-leishmanial drug.     

The use of Taylor's power law to describe the aggregated distribution of gastro-intestinal nematodes of sheep.

The distribution of gastro-intestinal nematodes collected from lambs was investigated using the Taylor's power law index of aggregation beta, which is known to be independent of the mean population size. For 12 out of the 15 nematode species investigated the estimate of beta was not significantly different from 2.0. For these species a logarithmic transformation would stabilize the variance of the distributions prior to further statistical analysis. The remaining species had values of beta which were significantly lower than 2.0. For these species a variance-stabilizing transformation is given by z = x1-beta/2.     

The geometry of the aortic root in health, at valve disease and after valve replacement

For the design of aortic valve prostheses with a separation-free flow field and minimum pressure drop the geometry of the aortic root is of high importance, since an appropriate adjustment of the prostheses to the surrounding geometry could largely reduce the risk of thromboembolic complications. For the investigation of the geometry of the aortic root 604 angiographic films out of a total stock of 15,000 of the Medical Clinic I were evaluated. The film material was preclassified into five clinical categories according to the patient's data. For each category characteristic geometries could be derived in non-dimensional form.     

Improved properties of systems for computer-assisted motility analysis]

For a number of years, computer-assisted methods have been employed for the motility analysis of spermatozoa. In addition to a number of advantages, such as short processing time and good reproducibility, they have certain shortcomings in the recognition and tracking of spermatozoa at high densities. For example, sperm cells and contaminating particles of the same size cannot be distinguished. The tracking of crossing sperm cell trajectories is also a problem. For this reason, procedures that are free from such shortcomings have been introduced. Their application leads to an improvement in the performance of computer-assisted semen analysis methods.