Molecular characterization of de novo secondary trisomy 13.

Unbalanced Robertsonian translocations are a significant cause of mental retardation and fetal wastage. The majority of homologous rearrangements of chromosome 21 in Down syndrome have been shown to be isochromosomes. Aside from chromosome 21, very little is known about other acrocentric homologous rearrangements. In this study, four cases of de novo secondary trisomy 13 are presented. FISH using alpha-satellite sequences, rDNA, and a pTRI-6 satellite I sequence specific to the short arm of chromosome 13 showed all four rearrangements to be dicentric and apparently devoid of ribosomal genes. Three of four rearrangements retained the pTRI-6 satellite I sequence. Case 1 was the exception, showing a deletion of this sequence in the rearrangement, although both parental chromosomes 13 had strong positive hybridization signals. Eleven microsatellite markers from chromosome 13 were also used to characterize the rearrangements. Of the four possible outcomes, one maternal Robertsonian translocation, two paternal isochromosomes, and one maternal isochromosome were observed. A double recombination was observed in the maternally derived rob(13q13q). No recombination events were detected in any isochromosome. The parental origins and molecular chromosomal structure of these cases are compared with previous studies of de novo acrocentric rearrangements.     

BIOCHEMICAL HETEROZYGOSITY AND MORPHOLOGIC VARIATION IN A COLONY OF PAPIO HAMADRYAS HAMADRYAS BABOONS

This analysis examines the association between genetic heterozygosity and individual morphologic variation in a captive population of Papio hamadryas hamadryas consisting of 403 juveniles and adults. The population structure of the colony was artificially generated and maintained and is thus rigorously defined. Subpopulations delimited by age, sex, and degree of inbreeding are also explored. Heterozygosity, as enumerated from six simple Mendelian biochemical loci, is compared with the residual morphologic variation of each individual for each of 20 quantitative traits. Use of a sequential Bonferroni technique nullifies all significant correlations. Principal-components analysis reduces the morphometrics to a single or few significant axes in each population. The first axis of the total population contains 86.07% of the variation in the sample and the absolute values of the factor scores exhibit a significant positive correlation with heterozygosity at P < 0.05. Correcting for age- and sex-related variation in the total population with a linear model subsequently demonstrates that no significant correlation between heterozygosity and morphologic variation exists. No significant relationship is found in the inbred animals or subpopulations when age and sex are controlled. Previous studies have indicated that individuals proximal to the population mean for a specific polygenic trait exhibit a higher biochemical heterozygosity than individuals distant from the mean. The results presented here, which are based on more loci than many studies and a well-defined population, do not support this relationship. Substructuring of a population by age and sex can lead to spurious correlations with univariate or multivariate techniques. Comprehensive indices of genetic variation and rigorous statistical techniques should be used in future analyses. Studies that fail to recognize these design elements should be interpreted with caution.     

Analysis of Schizosaccharomyces pombe mitochondrial DNA replication by two dimensional gel electrophoresis

The entire mitochondrial genome of Schizosaccharomyces pombe ura4-294h ^-was analyzed by the 2D pulsed field gel electrophoresis technique developed by Brewer and Fangman. The genome consists of multimers with an average size of 100 kb and analysis of the overlapping restriction fragments of the complete mitochondrial DNA (mtDNA) genome resulted in simply Y 2D gel patterns. Large single-stranded DNA molecules or double-stranded DNA molecules containing large or numerous single-stranded regions were found in the S. pombe mtDNA preparation. The replication of mtDNA monomers was found to occur in either direction. On the basis of these results, a replication mechanism for S. pombe mtDNA that is most consistent with a rolling circle model is suggested.     

Chronic Nicotine Administration Differentially Affects Neurotransmitter Release from Rat Striatal Slices

Abstract: The objective of these experiments was to determine whether the chronic administration of nicotine, at a dose regimen that increases the density of nicotine binding sites, alters the nicotine-induced release of [³H]dopamine ([³H]DA), [³H]norepinephrine ([³H]NE), [³H]serotonin ([³H]5-HT), or [³H]acetylcholine ([³H]ACh) from rat striatal slices. For these experiments, rats received subcutaneous injections of either saline or nicotine bitartrate [1.76 mg (3.6 µmol)/kg, dissolved in saline] twice daily for 10 days, and neurotransmitter release was measured following preloading of the tissues with [³H]DA, [³H]NE, [³H]5-HT, or [³H]choline. Chronic nicotine administration did not affect the accumulation of tritium by striatal slices, the basal release of radioactivity, or the 25 mM KCl-evoked release of neurotransmitter. Superfusion of striatal slices with 1, 10, and 100 µM nicotine increased [³H]DA release in a concentration-dependent manner, and release from slices from nicotine-injected animals was significantly (p < 0.05) greater than release from saline-injected controls; release from the former increased to 132, 191, and 172% of release from the controls following superfusion with 1, 10, and 100 µM nicotine, respectively. Similarly, [³H]5-HT release increased in a concentration-related manner following superfusion with nicotine, and release from slices from nicotine-injected rats was significantly (p < 0.05) greater than that from controls. [³H]5-HT release from slices from nicotine-injected rats evoked by superfusion with 1 and 10 µM nicotine increased to 453 and 217%, respectively, of release from slices from saline-injected animals. The nicotine-induced release of [³H]NE from striatal slices was also concentration dependent but was unaffected by chronic nicotine administration. [³H]ACh release from striatal slices could not be detected when samples were superfused with nicotine but was measurable when tissues were incubated with nicotine. The release of [³H]ACh from slices from nicotine-injected rats was significantly (p < 0.05) less than release from controls and decreased to 36, 83, and 77% of control values following incubation with 1, 10, or 100 µM nicotine, respectively. This decreased [³H]ACh release could not be attributed to methodological differences because slices from nicotine-injected rats incubated with nicotine exhibited an increased [³H]DA release, similar to results from superfusion studies. In addition, it is unlikely that the decreased release of [³H]ACh from striatal slices from nicotine-injected rats was secondary to increased DA release because [³H]ACh release from slices from hippocampus, which is not tonically inhibited by DA, also decreased significantly (p < 0.05) in response to nicotine; hippocampal slices from nicotine-injected rats incubated with 1 and 10 µM nicotine decreased to 42 and 70%, respectively, of release from slices from saline-injected animals. Results indicate that the chronic administration of nicotine increases the ability of nicotine to induce the release of [³H]DA and [³H]5-HT and decreases the ability of nicotine to evoke the release of [³H]ACh but does not alter the nicotine-induced release of [³H]NE from brain slices.     

Effects of quality and developmental stage on the survival of IVF-derived bovine blastocysts cultured in vitro after freezing and thawing

Factors affecting viability of IVF-derived bovine blastocysts after freezing and thawing were investigated. A total of 1,101 ova matured and fertilized in vitro were cultured under 2 different conditions, 1) in TCM-199 on granulosa cell monolayers at 5% CO(2) in air and 2) in synthetic oviduct fluid (SOF) medium without somatic cell support at 5% CO(2), 5% O(2), 90% N(2). All blastocysts that developed from the 2 different culture systems were individually classified into 4 grades of embryo quality and were then frozen by conventional slow freezing. Developmental rates of the IVF-derived ova to blastocysts and the survival rates of the frozen-thawed blastocysts were not different between the SOF medium (16 and 49%) and the co-culture system (13 and 61%, respectively). Survival of frozen-thawed blastocysts was affected by embryo quality in both the SOF and co-culture systems (P<0.001). Blastocysts produced in vitro were also individually classified into 3 developmental stages and were then cultured for 3 d in the co-culture system with granulosa cells after freezing and thawing. There was a difference in the survival rate of frozen-thawed embryos between blastocyst developmental stages (early vs mid, P<0.05; mid vs expanded, P<0.01; early vs expanded, P<0.001). The post-thawing survival rate of blastocysts frozen at Day 7 (62%) of culture was higher compared with that of Day 8 (45%), but there was no difference in survival rate between Day 7 and 8 of culture. The results indicate that the quality and developmental stage of blastocysts are important factors influencing their survival after freezing and thawing.     

Rapid screening of an SH2-containing gene using PCR amplification method

Summary To isolate a novel gene that contains an SH2 domain, we devised a rapid and nonradioactive cDNA library screening method using polymerase chain reaction (PCR). For PCR amplification, we designed degenerate oligonucleotide primers from the multialigned DNA sequences of SH2 domains. This method offers an inexpensive and efficient approach for the isolation of clones of interest from cDNA libraries.     

Changes and Relationship of PAF and TNF in Rats with Myocardial Ischaemia and Reperfusion Injury

IN THIS STUDY IT IS REPORTED THAT: (1) the levels of blood platelet-activating factor and serum tumour necrosis factor significantly increased after coronary ligation and reperfusion, compared with sham-ligated controls, in an anaesthetized rat model; (2) compared with vehicle controls, pretreatment with the PAF antagonist BN 50739 (10 mg/kg, i.v.) produced significant decreases in infarct size (from 29.6 +/- 4.0% to 22.4 +/- 2.1%, p < 0.05 after 3 h ligation, and from 28.5 +/- 9.5% to 10.5 +/- 4.5%, p < 0.01 after 4 h reperfusion) and the level of serum TNF (from 10.4 +/- 7.7 U/ml to 3.9 +/- 4.8 U/ml, p < 0.05); and (3) a significan positive correlation was found between the level of blood PAF or serum TNF and infarct size. The present results indicate that PAF and TNF may be important mediators involved in myocardial ischaemia and reperfusion injury, and that PAF antagonists may exert a protective effect on ischaemic or reperfused myocardium by inhibiting the interaction of PAF and TNF.     

软紫草愈伤组织的初步培养

外植体来源不同的软紫草愈伤组织产生紫草色素的能力各异。６０Ｃｏ－ｒ射线辐照处理后的Ｈ２无性系愈伤组织生长量和色素产生均属上乘。改良ＭＳ基本培养基添加１毫克／升ＫＴ,０．５毫克／升ＩＡＡ,５％（Ｗ／Ｖ）蔗糖对愈伤组织培养较为适宜。马铃薯提取液对愈伤组织生长有明显的促进作用。     

三褶脉紫菀中的新二萜甙

三褶脉紫菀（ＡｓｔｅｒａｇｅｒａｔｏｉｄｅｓＴｕｒｃｚ．）系菊科多年生草本植物,遍布全国,是民间常用的中药,有清热解毒、祛痰镇咳的功效［１,２］。化学工作者们曾从其同属植物紫菀（ＡｓｔｅｒｔａｒａｒｉｃｕｓＬ．ｆ．）中分离到紫菀酮（ｓｈｉｏｎｏｎｅ）、槲皮素（ｑｕｅｒｃｅｔｉｎ）、无羁萜（ｆｒｉｅｄｅｌｉｎ）、表无羁萜（ｅｐｉｆｒｉｅｄｅｌｉｎｅｌ）、毛叶醇（ｌａｃｈｎｏｐｈｙｌｌｏｌ）、乙酸毛叶酯（ｌａｃｈｎｏｐｈｙｌｌｏｌａｃｅｔａｔｅ）、茴香醚（ａｎｅｔｈｏｌｅ）以及紫菀三萜皂甙［２—４］…     

解离增强镧系元素荧光免疫分析灵敏度的改进

为提高解离增强镧系荧光免疫分析(DELFIA)的灵敏度或信／噪比,进行了一些重要的方法学研究．观察到了对于不同的铕量,荧光响应和信／噪比都随着增强液体积而明显地变化．对于确定的铕量,存在一个最佳体积,且铕量越小,其最佳体积也越小．实验中选择最佳体积是重要的．研究了增强液制备技术,发展了微滴定板条有效的清洗和干燥方法,使本底荧光明显降低．