用正交实验法筛选营养缺陷型酿酒酵母原生质体的最佳实验条件

为了提高原生质体的再生率,用正交实验筛选了制备营养缺陷型酿酒酵母PW208菌株原生质体的条件。最佳条件为用柠檬酸缓冲液配制1％蜗牛酶,在30℃酶解60min后再经后处理可得99％的形成率和43％的再生率。     

双单抗的免疫层析一步法用于早妊诊断的研究

在试管式、微孔式和斑点式的酶免测定法测定人绒毛膜促性腺激素（ＨＣＧ）的基础上,发展了应用双单克隆抗体的免疫层析一步法测定ＨＣＧ。此法用胶体金标记抗βＨＣＧ单克隆抗体,将抗αＨＣＧ单克隆抗体包被在硝酸纤维素膜上。无需分离步骤,特别是在进行测定时除加入样品外无需再加任何试剂,此方法特别迅速、简便,２～５ｍｉｎ即可得结果。凡ＨＣＧ浓度＞２５ＩＵ／Ｌ的样品可得到阳性结果。在人体血或尿中可能出现的高浓度的干扰物质,如抗坏血酸、乙酰水杨酸、雌二醇、蛋白质、胆红素、甘油三酯等对本测定均无干扰作用,在促黄体激素（ＬＨ）浓度高达５００ＩＵ／Ｌ时仍与ＨＣＧ没有交叉反应。能进行测定的最高值大于３００ＩＵ／ｍｌ,这表示,当ＨＣＧ浓度达到妊娠期的最高值时仍不会有假阴性结果。     

冻干青春型双歧杆菌DM8504存活期的加速预测

本文介绍了加速贮存实验预测冻干活菌制品存活期的方法,并用此法对冻干青春型双歧杆菌ＤＭ８５０４的存活期进行了预测。结果表明,预测结果与实验测试结果非常接近,两者没有显著性统计学差异,笔者认为加速贮存实验法是预测冻干活菌稳定性的一种快速而可行的方法。     

抑菌生亚急性毒性实验研究

本项研究的目的：是在一系列毒性试验的基础上进一步观察大鼠皮下给予由枯草芽孢杆菌ＢＳ２２４菌株制成的抑菌生后,对机体产生毒性反应的情况。结果表明：给药组大鼠饮食、活动正常。各项检测指标及病理组织学检查未发现异常,与对照组比较均无差异（Ｐ＞０．０５）,说明抑菌生无毒性反应。     

DNA damage and repair in somatic and germ cells in vivo

Alkylation-induced germ cell mutagenesis in the mouse versus Drosophila is compared based on data from forward mutation assays (specific-locus tests in the mouse and in Drosophila and multiple-locus assays in the latter species) but not including assays for structural chromosome aberrations. To facilitate comparisons between mouse and Drosophila, forward mutation test results have been grouped into three categories. Representatives of the first category are MMS (methyl methanesulfonate) and EO (ethylene oxide), alkylating agents with a high s value which predominantly react with ring nitrogens in DNA. ENU (N-ethyl-N-nitrosourea), MNU (N-methyl-N-nitrosourea), PRC (procarbazine), DEN (N-nitrosodiethylamine), and DMN (N-nitrosodimethylamine) belong to the second category. These agents have in common a considerable ability for modification at oxygens in DNA. Cross-linking agents (melphalan, chlorambucil, hexamethylphosphoramide) from the third category.The most unexpected, but encouraging outcome of this study is the identification of common features for three vastly different experimental indicators of genotoxicity: hereditary damage in Drosophila males, genetic damage in male mice, and tumors (TD₅₀ estimates) in rodents. Based on the above three category classification scheme the following tentative conclusions are drawn. Monofunctional agents belonging to category 1, typified by MMS and EO, display genotoxic effects in male germ cell stages that have passed meiotic division. This phenomenon seems to be the consequence of a repair deficiency during spermiogenesis for a period of 3–4 days in Drosophila and 14 days in the mouse. We suggest that the reason for the high resistance of premeiotic stages, and the generally high TD₅₀ estimates observed for this class in rodents, is the efficient error-free repair of N-alkylation damage. If we accept this hypothesis, then the increased carcinogenic potential in rodents, seen when comparing category 2 (ENU-type mutagens) to category 1 (MMS-type mutagens), along with the ability of category 2 genotoxins to induce genetic damage in premeiotic stages, must presumably be due to their enhanced ability for alkylations at oxygens in DNA; it is this property that actually distinguishes the two groups from each other. In contrast to category 1, examination of class 2 genotoxins (ENU and DEN) in premeiotic cells of Drosophila gave no indication for a significant role of germinal selection, and also removal by DNA repair was less dramatic compared to MMS. Thus category 2 mutagens are expected to display activity in a wide range of both post- and premeiotic germ cell stages. A number of these agents have been demonstrated to be among the most potent carcinogens in rodents. In terms of both hereditary damage and the initiation of cancers (low TD₅₀), cross-linking agents (category 3) comprise a considerable genotoxic hazard. Doubling doses for the mouse SLT have been determined for four cross-linking agents not requiring metabolic conversion and in all four cases the doubling doses for these agents were lower than those for MMS, DES and EMS. In support of this conclusion, two of 10 genotoxic agents, for which data on chromosomal aberrations were available for both somatic cells and germ cells in mice, were cross-linking agents and again the doubling dose estimates are lower than for monofunctional agents. Four cross-linking agents induced mutations in stem cell spermatogonia indicating that this type of agent can be active in a wide range of germ cell stages.Quite in contrast to what is generally observed in unicellular systems and in mammalian cells in culture, both cross-linking agents and MMS-type mutagens (high s value) predominantly produce deletion mutations in postmeiotic male germ cell stages. This is the uniform picture found for both Drosophila and the mouse. It is concluded that in vitro systems, in contrast to Drosophila germ cells, fail to predict this very intriguing feature of mouse germ line mutagenesis. In addition to their potential for induction of deletions and other rearrangements, cross-linking agents are among the most efficient inducers of mitotic recombination in Drosophila. Thus there are several mechanisms by which cross-linking agents may cause loss of heterozygosity for long stretches of DNA sequences, leading to expression of recessive genes. Since a substantial portion of agents used in the chemotherapy of cancers have cross-linking potential, the potential hazards of hereditary damage and cancers associated with this class of genotoxins should, in our opinion, receive more attention than they have in the past.     

数理统计方法优化单细胞蛋白发酵培养基研究

采用正交试验和中心组合设计相结合的数理统计方法,在２Ｌ发酵罐中对紫云英汁液培养单细胞蛋白发酵培养基进行筛选、优化,试验结果表明较优培养基为：初糖２．３％,酵母粉０．１６％,ＫＨ_２ＰＯ_４０．２％,ＭｇＳＯ_４０．０５％。酵母浓度最高达１０．４６ｇ／Ｌ,基质生长得率为０．５５ｇ菌体／ｇ基质,基质转化率为８３％。研究结果同时说明采用数理统计方法设计实验,工作量小,效率高,结果准确。     

Molecular clocks and the incompleteness of the fossil record

Molecular clocks can be evaluated by comparing absolute rates of evolution and by performing relative-rate tests. Typically, calculations of absolute rates are based on earliest observed occurrences in the fossil record. Relative-rate tests, on the other hand, merely require an unambiguous outgroup. A major disadvantage of relative-rate tests is their insensitivity to concomitant and equal rate changes in all lineages. Apparent differences in absolute rates, in turn, may be artifacts that are attributable to an incomplete fossil record.Recently developed methods in quantitative biostratigraphy recognize the incompleteness of the fossil record and allow us to place confidence intervals on the endpoints of taxon ranges. These methods are applicable to taxa whose fossil records are of markedly different quality. When we extend these methods and integrate molecular and paleontologic data, we can test the null hypothesis that seemingly disparate rates of molecular evolution are in fact equal under the simplifying assumption that fossils are randomly and independently distributed over their temporal ranges and that fossils can be accurately placed in a phylogenetic context. We can also estimate the range of ticking rates, if any, that are compatible with known fossil data. Ultimately, more accurate rate estimates for widely divergent taxa should allow for more meaningful comparisons of evolutionary rates.DNA hybridization data for monotremes and marsupials suggest a 17-fold difference for 14 different rate calculations with a mean value of approximately 1% divergence per million years. Variation among marsupials is sevenfold. However, when we apply appropriate statistical tests and make additional allowances for fossils of uncertain taxonomic assignment, etc., all 14 rates are compatible with a molecular clock ticking at approximately 0.4% divergence per million years. In addition, this analysis brings relative- and absolute-rate tests into accord.     

Swim Stress Increases the Potency of Glycine at the N-Methyl-d-Aspartate Receptor Complex

Abstract: We have previously demonstrated that chronic administration of antidepressants results in a reduction in the potency of glycine to displace 5,7-[³H]dichlorokynurenic acid (5,7-[³H]-DCKA) from the strychnine-insensitive glycine recognition site of the NMDA receptor complex. We now report that exposure of rats to the forced swim test results in a 56% increase in the potency of glycine to displace 5,7-[³H]DCKA from frontal cortical homogenates. These data are consistent with the hypothesis that the forced swim test, a preclinical screen sensitive to acute administration of antidepressant drugs and NMDA receptor antagonists, also results in adaptation of the NMDA receptor complex. Moreover, these data lend further support to the hypothesis that glutamatergic pathways are involved in the neurobiological response to stress and, potentially, in the pathophysiology of depression.