具有生育脉冲的Lotka-Volterra合作系统的正周期解的存在性

研究具有生育脉冲的两种群Lotka-Volterra合作系统,利用重合度理论,获得正周期解的存在的充分条件。     

矫正型大动脉转位合并心内畸形的外科治疗

目的：为探讨矫正型大动脉转位的病理解剖特点及手术技术。方法：本组6例均为SLL型,手术包括：室间隔缺损修补4例、肺动脉瓣切开1例、静脉室肺动脉外通道1例、房室瓣替换1例。结果：全组手术死亡1例。主要手术并发症为低心排4例、完全性房室传导阻滞1例及残余左房室瓣关闭不全1例。结论：矫正型大动脉转位的病理解剖有一定的特殊性,应按不同的合并畸型选择不同术式,正确处理室间隔缺损、肺动脉流出道狭窄及左房室瓣关闭不全是外科手术的关键。     

Maximum Likelihood Estimation of Genetic Parameters in Cell Populations

In this paper we consider a cell population such as bacteria consisting of two types of cells, mutant and nonmutant. Under the mutation and homogeneous pure birth processes, this paper derives a maximum likelihood estimation procedure for estimating mutation rate and birth rate. The method is applied to Newcombe's data; further some Monte Carlo studies are generated. The numerical results indicate that the method is quite efficient for estimating genetic parameters in cell populations.     

The Relativistic Quantum Defect Orbital Method and some of its Applications

Justification of a simple and reliable relativistic procedure for the prediction of a large body of transition probability data is made. The main features of the Relativistic Quantum Defect Orbital (RQDO) formalism are described, and several examples of the data yielded by this method are presented in tabular and graph forms.     

A re-examination of parturition scars on the human female pelvis

Pits, cavities and depressions located on the dorsal surface of the pubic symphysis of females have been attributed to the trauma of parturition. Earlier research based on human skeletal remains provides inadequate information on the individual's obstetrical history. The 68 female pubic bones that were studied had comprehensive medical records indicating whether or not each female had given birth. Fourteen and one-half percent of the females who had not given birth exhibited trace to small scarring of the pubic symphysis and 23.4% of the females who had not given birth exhibited medium to large scarring. It is suggested that bony changes previously used as an indicator of child bearing must be re-examined in light of the fact that “birth scarring” has been found in women known not to have had children.     

Mortality and birth weight in Philadelphia Blacks: an example of stabilizing selection

It has been suggested that as a result of the action of natural selection the mean value of any biological measurement would be the most normal value and associated with the most favorable survival rate. Selection is said to be stabilizing (or normalizing or balancing) if individuals with intermediate values for a given quantitative trait have the highest fitness. Birth weight is perhaps the most clear-cut example of a human character subject to stabilizing selection. This paper presents the distribution of birth weights among 8382 Philadelphia Black infants and the rate of perinatal mortality for the birth weight classes. Using these data, several analyses of stabilizing selection are made. The data were taken from the Collaborative Study on Cerebral Palsy, Mental Retardation, and other Neurological and Sensory Disorders of Infancy and Childhood.     

Higher serum homocysteine and lower thyroid hormone levels in pregnant women are associated with neural tube defects

BackgroundThis study tested the hypothesis that abnormal maternal metabolism of both homocysteine and thyroid hormone network in pregnant women is associated with neural tube defects (NTDs) in a part of China with high NTD prevalence.MethodsA case–control study was performed between 2007 and 2009 in Lüliang Mountains, Shanxi Province. This study included 83 pregnant women who had fetuses with NTDs (cases) and 90 pregnant women with normal fetuses (controls). In addition, a cell model to illustrate the epidemiological findings was established.ResultsFetuses of mother who had both high total homocysteine (tHcy) and inadequate free thyroxine were 3 times more at risk of developing NTDs (adjusted odds ratio = 3.5; 95 % confidence interval = 1.2–10.4; cases vs. controls) using multivariate logistic regression models. Furthermore, biological interaction between metabolisms of Hcy and thyroid hormones was demonstrated in vitro. In homocysteine thiolactone of a metabolite of Hcy-treated mouse embryonic neural stem NE4C cells, genes (Bmp7, Ctnnb1, Notch 1, Gli2, and Rxra) related to both neural tube closure and thyroid hormone network were shown to be regulated by H3K79 homocysteinylation, which increased their expression levels.ConclusionsThe effect of maternal serum high tHcy on risk of developing NTDs is depended on maternal serum level of thyroxine. Meanwhile, a higher level of tHcy might also affect both maternal metabolism of thyroid hormone and neural tube closure in embryogenesis through homocysteinylation of histones.     

Severe Impairment of Nucleotide Synthesis Through Inhibition of Mitochondrial Respiration

Since de‐novo synthesis of pyrimidine nucleotides is coupled to the mitochondrial respiratory chain (RC) via dehydroorotic acid dehydrogenase (DHODH), respiratory chain dysfunction should impair pyrimidine synthesis. To investigate this, we used specific RC inhibitors, Antimycin A and Rotenone, to treat primary human keratinocytes and 143B cells, a human osteosarcoma cell line, in culture. This resulted in severe impairment of de novo pyrimidine nucleotide synthesis. The effects of RC inhibition were not restricted to pyrimidine synthesis, but concerned purine nucleotides, too. While the total amount of purine nucleotides was not diminished, they were significantly broken down from triphosphates to monophosphates, reflecting impaired mitochondrial ATP regeneration. The effect of Rotenone was similar to that of Antimycin A. This was surprising since Rotenone inhibits complex I of the respiratory chain, which is upstream of ubiquinone where DHODH interacts with the RC. In order to avoid unspecific effects of Rotenone, we examined the consequences of a mitochondrial DNA mutation that causes a specific complex I defect. The effect was much less pronounced than with Rotenone, suggesting that complex I inhibiton cannot fully explain the marked effect of Rotenone on pyrimidine nucleotide synthesis.