Proliferation of human-derived osteoblast-like cells depends on the cycle number and frequency of uniaxial strain

We tested the hypothesis whether the number of applied load cycles and the frequency of uniaxial strain have an effect on proliferation of human bone derived osteoblast-like cells. A new approach was developed in order to differentiate between the effects of frequency and the effects of cycle number and strain duration. Monolayers of subconfluently grown cells were stretched in rectangular silicone dishes with cyclic predominantly uniaxial movement along there longitudinal axes. Strain was applied over 2 days varying the number of applied load cycles (4-3600) at a constant frequency (1Hz) or varying the frequency (0.1-30Hz) at a constant number of applied cycles (1800) or at a constant strain duration (5min). At a constant frequency, proliferative response increases (103%) with the number of applied cycles until a cycle number maximum (1800 cycles) was reached. 3600 cycles reduced cell number (43%) in contrast to the maximum. The variation of the frequency of applied strain tended to result in slight differences with regard to cell proliferation when cycle number was left constant. However, combined with an appropriate number of cycles there was an optimal frequency (1Hz) as stimulus for bone cell proliferation (84%). A higher frequency (30Hz) in combination with a high cycle number (9000) reduced cell number to control level (4%). This study demonstrates a frequency and cycle number dependent proliferative response of human osteoblast-like cells. It could be shown that effects of the frequency should not be considered separately from the effects of the cycle number.     

Estimation of the Number of Sex Alleles and Queen Matings from Diploid Male Frequencies in a Population of APIS MELLIFERA

The distribution of diploid males in a population of Apis mellifera was obtained by direct examination of the sexual phenotypes of the larvae. Using these data, estimates are derived for the number of sex alleles and the number of matings undergone by the queen. The number of sex alleles is estimated to be 18.9. The estimate is larger than previous ones, which have ranged between 10 and 12. However, the increase in the number of sex alleles can be explained by the large effective population number for our data. The best estimator of the number of matings by a queen is a maximum likelihood type that assumes a prior distribution on the number of matings. For the data presented here, this estimate is 17.3. This estimate is compared to others in the literature obtained by different approaches.     

Effects of number of flowers per raceme and number of racemes per plant on bumblebee visits and female reproductive success in <Emphasis Type="Italic">Salvia nipponica</Emphasis> (Labiatae)

We studied the adaptive arrangement of raceme flowers in dense and sparse habitats of Salvia nipponica. We recorded bumblebee visits and collected mature seeds to estimate outcrossing rates from allozyme genotypes. To examine the resource investment in flowering stalks, we measured their length and dry mass. We found that a greater number of open flowers in a raceme enhanced bumblebee visits and successive probings in both density plots. However, greater height of a raceme did not enhance these in plots of either density. In the high-density plot, both a greater mean number of open flowers in a raceme and a greater number of flowering racemes on a plant enhanced bumblebee visits, successive probings, and also enhanced outcrossing rate in spite of an increase in successive probings. Although the number of flowers per raceme had a greater positive effect on seed-to-ovule ratios than did the number of racemes, the number of flowers per raceme may be constrained because a longer flowering stalk needs greater buckling strength. Hence, it may be advantageous for plants in high-density plots to increase both number of flowers per raceme and number of racemes. In the low-density plot, a greater number of flowering racemes on a plant enhanced pollinator visits, but a greater mean number of open flowers in a raceme did not. Hence, it may be advantageous for plants to increase the number of racemes while keeping the numbers of flowers per raceme small. Thus, the adaptive number of flowers per raceme and number of racemes per plant may differ between high- and low-density plots.     

Sources of variability in numbers of live births in wild golden lion tamarins (Leontopithecus rosalia)

We examined the effects of several variables on the number of live births in multiparous females in a wild population of golden lion tamarins (Leontopithecus rosalia). Independent variables included the number of infants born to a female the previous breeding season, the number of infants weaned the previous breeding season, the female's age and body mass, the number of adult males and helpers in the group, and the inbreeding coefficient of the offspring. We also tested the hypothesis that trapping and chemical immobilization during pregnancy affected the number of live births. Female body mass was the only statistically significant predictor of the number of live-born infants in the current season when both first and second peaks were included. Characteristics that predicted higher numbers of infants in the first peak of a season were the number of infants born the previous season and the body mass of the female. The greater the number of infants born the previous season, the greater the number of infants born in the first peak of the current season. Factors positively correlated with the number of live births in the second peak within a season included the number of infants born the previous season, as well as the number of available helpers. Due to sample size constraints, the analysis of litters in the second peak did not include body mass of the female as a variable. Inbreeding and handling did not affect the number of live births. We found no evidence that current reproduction negatively impacts future reproduction in this species. We also found no evidence for an age-related reduction in fertility.     

On the estimation of the number of antibody-forming cells

The variability of the number of antibody-forming cells (AbFC) on using the plaque method is discussed. In the first part of the study it is shown on the basis of experimental data that the number of AbFC in a standard number of spleen cells has approximately Poisson distribution in one animal if the number of AbFC in a suspension is small, but that as the number of AbFC rises (even if the number of test cells in the given volume remains the same), variance increases more rapidly than the mean value and negative binomial distribution is a better probability model. The maintenance of conditions for Poisson distribution is evidently also related to the absolute number of test cells in a given volume, however. If the number of spleen cells in a given volume is raised, it is impossible to maintain complete homogeneity of the suspension; the cells form agglomerates, resulting in greater variability of the number of cells in individual drops. Under certain conditions, however, negative binomal distribution tends to Poisson distribution. In the second part, the question of determination of the error of estimation of the number of AbFC, expressed as percentages of the true value, is studied. Presuming Poisson distribution, it is pointed out that it is impossible to predetermine a fixed limit of the experiment, i.e one which will ensure for a given confidence level that the empirically determined value will not differ from the true value by more than a predetermined percentage of the true value; for routine use, however, a nomogram for the approximate estimation of the degree of error with which we work is suggested. Alternatively, the sequential method can be employed for estimating the number of AbFC with a given degree of error, but this statistical method is more exacting as regards both the preparation and the execution of the experiment. Dedicated to Academician Ivan Málek on the occasion of his 60th birthday     

Effects of distinct types of disturbance on seed rain in the Atlantic forest of NE Brazil

In disturbed sites, some groups of seeds might be excluded from the seed rain due to their dispersal modes or seed size, and some groups might be successful as a result of disturbance effects. In the present study, we examined the seed rain in natural treefall gaps and in an area of regenerating forest following an accidental burning, which occurred 4 years before this study. Both of these disturbed areas were compared with nearby forest understorey. The number of seeds, number of species, and proportion of wind-dispersed seeds were compared between these disturbed and undisturbed areas. The treefall gaps have received lower numbers of seeds and species than the nearby understorey, but the number of wind-dispersed seeds did not differ between these areas. The lowest seed number observed in treefall gaps can be attributed to a lower number of animal-dispersed seeds, suggesting that animals may be avoiding treefall gap areas. A higher number of seeds and a lower number of species were observed in the burned area when compared to the adjacent understorey. The high number of small-sized seeds and of wind-dispersed seeds in the burned area was almost surely a consequence of the local production of the pioneer plants established after the burning. In this study, substantial differences were observed in the characteristics of the seed rain at disturbed sites, when compared with undisturbed understorey. However, these two distinct types of disturbance showed quite differing patterns, as treefall gaps received lower number of seeds while the burned area received a higher number of seeds, with a greater proportion of wind-dispersed seeds. The exception was for species richness, which was quite low at both these disturbed sites.     

The effect of remating on sperm number in the spermatophores of Teleogryllus commodus (Gryllidae)

Factors controlling sperm production in members of the Orthoptera have not been fully elucidated. In this study, the influence of intermating interval and ad libidum mating on sperm number was investigated in black field crickets (Teleogryllus commodus). Remating at a variety of time intervals was not characterized by a significant change in sperm number compared with the first mating. Ad libitum mating (i.e., continuous availability of unmated females) had two main effects on spermatophore production and sperm number: first, there was a trend toward increased time between copulations with each successive remating, and second, the number of spermatozoa encapsulated in the transferred spermatophore declined after most rematings, with 61.8% of the initial sperm number being produced for the second spermatophore and 51.3% of the initial sperm number being produced for the third. The decrease in mean sperm number was accompanied by increased variance in sperm number in later rematings. This study suggests that males are willing to suffer a decrease in sperm number if a mating opportunity occurs before the completion of sperm production.     

Circular binary segmentation for the analysis of array-based DNA copy number data

DNA sequence copy number is the number of copies of DNA at a region of a genome. Cancer progression often involves alterations in DNA copy number. Newly developed microarray technologies enable simultaneous measurement of copy number at thousands of sites in a genome. We have developed a modification of binary segmentation, which we call circular binary segmentation, to translate noisy intensity measurements into regions of equal copy number. The method is evaluated by simulation and is demonstrated on cell line data with known copy number alterations and on a breast cancer cell line data set.     

The Effect of Change in Population Size on DNA Polymorphism

The expected number of segregating sites and the expectation of the average number of nucleotide differences among DNA sequences randomly sampled from a population, which is not in equilibrium, have been developed. The results obtained indicate that, in the case where the population size has changed drastically, the number of segregating sites is influenced by the size of the current population more strongly than is the average number of nucleotide differences, while the average number of nucleotide differences is affected by the size of the original population more severely than is the number of segregating sites. The results also indicate that the average number of nucleotide differences is affected by a population bottleneck more strongly than is the number of segregating sites.     

The reproductive strategy of the gregarious parasitoid,Pteromalus puparum (Hymenoptera: Pteromalidae)

Summary Host size of Pteromalus puparum, a gregarious pupal parasitoid, shows a wide inter- and intraspecific variation. Experiments were made to study the regulation of the number and sex ratio of progeny per host by the parasitoid. The parasitoid could discriminate inter- and intraspecific size differences of the host and regulate the number of eggs according to the host size when a single female attacked the host. The sex ratio of progeny (proportion males) was about 0.1. The number of progeny laid by the female agreed with the energetically most efficient number og eggs in order to maximize total weight of progeny per host but not with the reproductively most efficient number of eggs to maximize the total fecundity of the progeny. The parasitoid laid smaller number of eggs in a half buried host, but the number was much larger than a half of those in a fully exposed host. When more than one female attacked a single host, the number and sex ratio of progeny per host increased with the number of females attacking the host, but the number of progeny per female decreased. The change of the sex ratio agreed with the prediction of the local mate competition model.     

Relationship between the Number of Homoeologues, Chiasma Frequency and the Frequency of Telosome Pairing in Wheat

Pairing frequencies of a single telosome in groups of two, three, four, five and six equally related homoeologues were calculated for a range of values of c (the ratio of actual chiasma frequency to the total possible number of chiasmata, as described by Driscoll, Bielig and Darvey 1979). At low c values, the frequency of telosome pairing is little affected by the number of homoeologues. At high c values, the frequency is little affected by the number of homoeolgues if the number is even; if the number is odd, the frequency is dependent on the number of homoeologues and increases with increasing numbers of homoeologues. At intermediate c values, the pairing frequency is dependent on the number of homoeologues for both even and odd numbers of homoeologues.     

The roles of cell size and cell number in determining ovariole number in Drosophila

All insect ovaries are composed of functional units called ovarioles, which contain sequentially developing egg chambers. The number of ovarioles varies between and within species. Ovariole number is an important determinant of fecundity and thus affects individual fitness. Although Drosophila oogenesis has been intensively studied, the genetic and cellular basis for determination of ovariole number remains unknown. Ovariole formation begins during larval development with the morphogenesis of terminal filament cells (TFCs) into stacks called terminal filaments (TFs). We induced changes in ovariole number in Drosophila melanogaster by genetically altering cell size and cell number in the TFC population, and analyzed TF morphogenesis in these ovaries to understand the cellular basis for the changes in ovariole number. Increasing TFC size contributed to higher ovariole number by increasing TF number. Similarly, increasing total TFC number led to higher ovariole number via an increase in TF number. By analyzing ovarian morphogenesis in another Drosophila species we showed that TFC number regulation is a target of evolutionary change that affects ovariole number. In contrast, temperature-dependent plasticity in ovariole number was due to changes in cell-cell sorting during TF morphogenesis, rather than changes in cell size or cell number. We have thus identified two distinct developmental processes that regulate ovariole number: establishment of total TFC number, and TFC sorting during TF morphogenesis. Our data suggest that the genetic changes underlying species-specific ovariole number may alter the total number of TFCs available to contribute to TF formation. This work provides for the first time specific and quantitative developmental tools to investigate the evolution of a highly conserved reproductive structure.     

Analysis of trinomial responses from reproductive and developmental toxicity experiments.

This paper presents a Dirichlet-trinomial distribution for modelling data obtained from reproductive and developmental studies. The common endpoints for the evaluation of reproductive and developmental toxic effects are the number of dead fetuses, the number of malformed fetuses, and the number of normal fetuses for each litter. With current statistical methods for the evaluation of reproductive and developmental effects, the effect on the number of deaths and the effect on the number of malformations are analyzed separately. The Dirichlet-trinomial model provides a procedure for the analysis of multiple endpoints simultaneously. This proposed Dirichlet-trinomial model is a generalization of the beta-binomial model that has been used for handling the litter effect in reproductive and developmental experiments. Likelihood ratio tests for differences in the number of deaths, the number of malformations, and the number of normals among dosed and control groups are derived. The proposed test procedure based on the Dirichlet-trinomial model is compared with that based on the beta-binomial model with an application to a real data set.     

Evolutionary rate of the mammalian karyotype

Making pairwise comparisons of karyotypes of species belonging to a genus, we have calculated the probabilities that two randomly chosen species from a genus have the same karyotype. This probability decreases exponentially with time. Thus if we know the divergence time of species from a common ancestor, we can know the rate at which a karyotype changes in unit time. According to our result, mammalian karyotypes appear to be evolving at a rate of one change of either chromosomal number or arm number in every two and half million years. Data indicate that the rate of evolution in chromosome number and arm number are fairly similar in most of mammalian genera. The genus Peromyscus is, however, an exception and exhibits a rather rapid change in the arm number due to heterochromatin changes, but a very slow evolution in the chromosome number.     

Theory of oviposition strategy of parasitoids. I. Effect of mortality and limited egg number

The optimal oviposition strategies of parasitoids, the host range, and the number of eggs laid per host which result in the maximum lifetime performance of reproduction, are investigated. To study the effects of parasitoid mortality and of limiting total number of eggs laid by a parasitoid, a standard criterion used in previous theories of optimal diet and optimal patch use, the maximization of the foraging rate, is no longer suitable. The model is solved analytically by using dynamic programming. The results are as follows: The host preference of solitary parasitoids depends on the mortality during handling times; i.e., the forager tends to avoid hosts with high risk of foraging mortality. If the total number of eggs produced by a parasitoid is limited, and if the mortality during handling is negligible, the host range is wider when a larger number of eggs remains in the parasitoid's body. In general, however, the mortality-cost of forager and the egg-cost interplay, because the loss of future reproduction by mortality increases with the number of available eggs. In an example with two host types, host range is widest with an intermediate number of eggs available in the body. The optimal number of eggs per host laid by a gregarious parasitoid is also affected by the differential mortality of the forager, and by the number of available eggs.     

贵州五种菊头蝠的核型分析 *

采用常规骨髓细胞空气干燥法,研究了贵州5种菊头蝠的核型。贵州菊头蝠和中菊头蝠2n=62,两者染色体臂数(NF)均为60;托氏菊头蝠、小菊头蝠和栗黄菊头蝠的染色体数是2n=36,其中托氏菊头蝠和小菊头蝠染色体臂数(NF)是58,栗黄菊头蝠是60。5种菊头蝠的性别决定机制均是xY。     

The number of Great Tit mobbers influences the mobbing response of heterospecific birds

Many species mob predators to drive them away. Mobbing carries personal risk, but the risk of injury or death declines and the likelihood of repelling the predator increases in larger groups. The capacity to evaluate the number of mobbers before joining a mobbing group may be highly beneficial for individuals when deciding to join. Although recent studies have found that birds can use individual vocal discrimination to assess the number of conspecifics involved in initiating mobbing events, it is little known whether birds are able to evaluate the number of heterospecific mobbers. In this study, we investigated whether the number of heterospecifics responding to mobbing calls of Great Tits Parus major was influenced by the number of callers (a mix of Great Tit callers simulated by playbacks and live Great Tits attracted to playbacks, range one to seven callers). The total number of responding heterospecific individuals and species was positively influenced by the total number of callers, with heterospecifics responding more to larger than smaller Great Tit groups. However, these results may be driven by the total number of calls, call overlap and increased noise generated by the additional mobbers, and not the number per se. These findings therefore allow us to assess whether birds are more inclined to join a mobbing group when it consists of more heterospecific callers, but we cannot tell whether birds use individual vocal discrimination to assess the number of heterospecific callers.     

Two Types of Well Followed Users in the Followership Networks of Twitter

In the Twitter blogosphere, the number of followers is probably the most basic and succinct quantity for measuring popularity of users. However, the number of followers can be manipulated in various ways; we can even buy follows. Therefore, alternative popularity measures for Twitter users on the basis of, for example, users'' tweets and retweets, have been developed. In the present work, we take a purely network approach to this fundamental question. First, we find that two relatively distinct types of users possessing a large number of followers exist, in particular for Japanese, Russian, and Korean users among the seven language groups that we examined. A first type of user follows a small number of other users. A second type of user follows approximately the same number of other users as the number of follows that the user receives. Then, we compare local (i.e., egocentric) followership networks around the two types of users with many followers. We show that the second type, which is presumably uninfluential users despite its large number of followers, is characterized by high link reciprocity, a large number of friends (i.e., those whom a user follows) for the followers, followers'' high link reciprocity, large clustering coefficient, large fraction of the second type of users among the followers, and a small PageRank. Our network-based results support that the number of followers used alone is a misleading measure of user''s popularity. We propose that the number of friends, which is simple to measure, also helps us to assess the popularity of Twitter users.     

The Influence of Sucrose and Abscisic Acid on the Determination of Grain Number in Wheat

Using detached ears of wheat cultured in nutrient solution theeffect of sucrose and ABA supply on grain number was examined.In ears detached prior to ear emergence, to correspond withthe time of pollen mother cell meiosis, higher levels of sucroseuptake were associated with higher grain number per ear. ABAindirectly caused a reduction in grain number by decreasinguptake of sucrose through decreasing stomatal conductance andtranspiration. There was possibly also a direct effect of ABAon grain number. At higher levels of ABA the negative effecton grain number was decreased by increasing the sucrose concentration.In ears detached one to three days after anthesis grain numberwas also influenced by the amount of sucrose taken up. althoughgrain number was not as sensitive to the sucrose supply at thistime as it was at meiosis. The influence of ABA following anthesiswas limited to an indirect effect on grain number through reductionsin sucrose uptake. Key words: Wheat, Sucrose, ABA, Grain number     

Inheritance of five quantitative characters of bread wheat

Summary Heritability estimates of five characters of the wheat plant were studied in five crosses involving six cultivars of bread wheat. Parents, F₁, F₂ and backcrosses to both parents were used in the estimation of the genetic parameters.Heritability was low for number of fertile spikes/plant, moderate for number of spikelets/spike, number of kernels/spike, 1000-kernel weight and moderately high for number of kernels/spike. Evidence for mainly nonadditive gene effects were observed in the expression of number of fertile spikes and 1000-kernel weight. Although nonadditives contributed to a lesser degree to the gene action, additives seemed to be the most important genetic expression regulating number of spikelets/spike, number of kernels/spike, and number of kernels/spikelet. Except for number of fertile spikes/plant, selection in F₂-populations seems to be promising.