異数体を含むレンゲ人為同質４倍体集団での全兄弟と半兄弟の共分散の計算

Full and half sib covariances were investigated in an artificial autotetraploid population with random mating in Astragalus sinicus L.. Since a set of homologous chromosomes is not necessarily involved in aneuploidy, the covariances must be averaged for two cases, that is, with and without involvement. To average the covariances, the probability that a set of homologous chromosomes was involved in aneuploidy was assumed as 3/8, where “8” and “3” represent the chromosome number of a genome and the mean number of quadrivalent chromosomes formed in a euploid, respectively. The covariances were calculated under the assumption that quadrivalent chromosomes were distributed to the poles by 2-2 and 1-3 with probabilities κ＝ 0.8 and λ ＝0.2 (κ＋λ＝1) respectively, and that trisomic and pentasomic chromosomes were distributed by 1-2 and 2-3 both with a probability of 1. It was also assumed that the inbreeding coefficient of the parents was F＝ 0, and that 2x and 2x＋ 1 pollens and all female gametes could fertilize equally. The covariance of a family was taken as an average of the covariance of each sib combination in a family. As a result, the covariance of a population could be obtained as an average of the covariance of each family in a population. The coefficients of variance components calculated under these assumptions were different from those calculated under the same condition except that 2x＋ 1 pollen could not fertilize. Differences in the coefficient of additive genetic variance components were about 3.3% and 7.2% for full and half sib covariances, respectively. Coefficients of the other variance components were also different between the two cases. However, 2x＋1 pollen could rarely fertilize, since their ability to fertilize in a practical population were lower than 2x pollen. Therefore, it would be valid to calculate full and half sib covariances in an artificial autotetraploid population of Astragalus sinicus L. under the condition thatonly 2x pollen could fertilize.任意交配するレンゲ人為同質４倍体集団における全兄弟と半兄弟の共分散を計算した．特定の相同染色体が必ずしも異数体に関わるとは限らないので，特定の相同染色体が関わる場合と関わらない場合について共分散を計算し，平均しなければならない．共分散を平均するため，特定の相同染色体が異数性に関わる確率を３/８とした“８”と“３”はゲノム染色体数と正４倍体で形成される４価染色体数の平均値である．４価染色体は MI で確率κ＝ 0.8とλ＝ 0.2（κ＋λ＝１）で２-２と１-３に分配され，Ⅲ価染色体とⅤ価染色体は確率１で１-２と２-３に分配されるとし，２xと２x＋１花粉と雌性配偶子は等しく受精するとして共分散を計算した．両親の近交系数はＦ＝０であると仮定した．次いで家族の共分散を家族内の兄弟間の共分散の平均として計算し，集団の共分散を家族の共分散の平均として計算した．仮定に基づき求めた共分散の分散成分の係数は２x花粉のみが受精するとして計算した値と違っていた．相加遺伝分散成分の係数は全兄弟と半兄弟でそれぞれ3.3％と7.2％ずつ違っていた．他の分散成分も同様であった．実際のレンゲ人為同質４倍体集団では２x＋１花粉は受精能力が２x花粉より低く稀にしか受精しないので，２x花粉のみが受精するとして全兄弟と半兄弟の共分散を計算しても問題はないであろう

Evaluation of forest decontamination using radiometric measurements

An experiment has been conducted to evaluate the additional dose reduction by clear felling contaminated forestry in Fukushima Prefecture, Japan, and using the timber to cover the areas with wood chips. A portable gamma spectrometry system, comprising a backpack containing a 3x3” NaI(Tl) detector with digital spectrometer and GPS receiver, has been used to map dose rate and radionuclide activity concentrations before, after and at stages during this experiment. The data show the effect of the different stages of the experiment on dose rate at different locations around the site. The spectrometric data have allowed the assessment of the contributions of natural and anthropogenic radionuclides to the dose rate at different parts of the site before and after the experiment. This has clearly demonstrated the value of radiometric methods in evaluating remediation, and the effect of other environmental processes. The value of spectrometric methods which directly measure radionuclide concentrations has also been shown, especially through the identification of the contribution of natural and anthropogenic activity to the measured dose rate. The experiment has shown that clearing trees and applying wood chips can reduce dose rates by 10-15% beyond that achieved by just clearing the forest litter and natural redistribution of radiocaesium

人為同質４倍体集団における全兄弟及び半兄弟共分散の数学モデル

For the estimation of genetic variance of an artificial autotetraploid population, a mathematical model of full and half sib covariances between sibs with various chromosome numbers, which were derived from euploid or aneuploid parents, was devised for a case where the inbreeding coefficient of the parents was F＝0. The coefficients defined in Kempthorne's model were separated into two parts: (i) A, D, T and Q, and (ii) φ and ψ. The former four parameters were defined as probabilities of factor combinations, which could be compared between various sibs, for additive, digenic, trigenic, and quadrigenic effects, and were mutually independent. The latter two parameters, which were the numbers of the identical allele and the identical allele pair combinations that two sibs inherited from a parent, were defined as linear functions of the probabilities that two sibs inherited allele or allele pair from a parent, respectively. These probabilities depend on chromosome behavior during meiosis and the chromosome number of the gametes. For the estimation, it was assumed that quadrivalent chromosomes were distributed by 2-2 and 1-3 with probabilities κ and λ (κ＋λ＝ 1), respectively. The distribution of trisomic and pentasomic chromosomes to the poles was assumed to be 1-2 and 2-3. Then, the probabilities were estimated for the simple case where all male and female gametes could equally fertilize irrespective of their chromosome number, provided that tetrasomic chromosomes completely formed a quadrivalent chromosome. 　The constitution of variance components were different according to the sib combinations and family. Therefore, for the calculation of the covariance of a family, the covariances between various sibs were averaged by the combination frequency in a family, and for the calculation of the covariance of population, the family's covariances were averaged by the family's frequency in the population.人為同質４倍体集団の遺伝分散を求めるため，両親が近交系数Ｆ＝０の同質４倍体家族の全兄弟と半兄弟の共分散を検討した．Kempthorne のモデルにおいて定義された分散の係数を①Ａ，Ｄ，Ｔ，Ｑと②φ，ψの２つに分割し た．①は互いに独立な相加，２遺伝子，３遺伝子，４遺伝子効果の組み合わせの確率である．②は兄弟が片親から受け取る同一対立遺伝子の数と対立遺伝子ペアの数である．これは兄弟が片親から対立遺伝子と対立遺伝子の組を受け取る確率の関数であり，この確率は減数分裂での染色体行動と配偶子の染色体数によって決まる.この確率を推定するため，Ⅳ価染色体は確率κ，λ（κ＋λ＝１）で２-２と１-３で分配され，Ⅲ価染色体とⅤ価染色体は１-２と２-３に分配されると仮定した．本報告では，四染色体が完全にⅣ価染色体を形成するとして，全ての雌雄の配偶子がその染色体数に関係なく受精できる単純な場合について検討した．共分散の分散成分の構造は兄弟の組み合わせと家族によって異なる．したがって，家族の共分散は各兄弟の共分散 とその組み合わせ頻度を用い平均すれば求めることができ，集団の平均の共分散は家族の共分散と集団での家族の頻度を用い平均すれば求めることができる

A novel magnetic resonance imaging postprocessing technique for the assessment of intervertebral disc degeneration-Correlation with histological grading in a rabbit disc degeneration model.

Introduction:Estimation of intervertebral disc degeneration on magnetic resonance imaging (MRI) is challenging. Qualitative schemes used in clinical practice correlate poorly with pain and quantitative techniques have not entered widespread clinical use. Methods:As part of a prior study, 25 New Zealand white rabbits underwent annular puncture to induce disc degeneration in 50 noncontiguous lumbar discs. At 16 weeks, the animals underwent multi-echo T2 MRI scanning and were euthanized. The discs were stained and examined histologically. Quantitative T2 relaxation maps were prepared using the nonlinear least squares method. Decay Variance maps were created using a novel technique of aggregating the deviation in the intensity of each echo signal from the expected intensity based on the previous rate of decay. Results:Decay Variance maps showed a clear and well demarcated nucleus pulposus with a consistent rate of decay (low Decay Variance) in healthy discs that showed progressively more variable decay (higher Decay Variance) with increasing degeneration. Decay Variance maps required significantly less time to generate (1.0 ± 0.0 second) compared with traditional T2 relaxometry maps (5 (±0.9) to 1788.9 (±116) seconds). Histology scores correlated strongly with Decay Variance scores (r = 0.82, P < .01) and weakly with T2 signal intensity (r = 0.32, P < .01) and quantitative T2 relaxometry (r = 0.39, P < .01). Decay Variance had superior sensitivity and specificity for the detection of degenerate discs when compared to T2 signal intensity or Quantitative T2 mapping. Conclusion:Our results show that using a multi-echo T2 MRI sequence, Decay Variance can quantitatively assess disc degeneration more accurately and with less image-processing time than quantitative T2 relaxometry in a rabbit disc puncture model. The technique is a viable candidate for quantitative assessment of disc degeneration on MRI scans. Further validation on human subjects is needed