Current Assessment of Sperm DNA Integrity

Conventional semen analysis is rapidly losing its place as the gold standard of diagnosis and the cornerstone of treating the infertile male in modern times. Recent technology allows scientists to analyze sperm fertilizing potential and subsequent embryonic growth by studying factors that have previously escaped traditional parameters. It has become increasingly evident that nuclear DNA arrangement is essential to the fertilizing potential of sperm. A vast array of tests are now available to examine the genetic makeup of individual spermatozoa, ranging the entire gamut from simple bench top assays performed routinely to complex flow cytometric assays requiring highly-skilled technologists. Future research to compare these new tests to those more commonly in use, correlating them with reproductive outcome promises to fill the current void in the field of male infertility, paring innovative diagnostic (and prognostic) technological standards to the already existing sophisticated assortment of successful treatment modalities.     

Mitochondrial bioenergetics and drug-induced toxicity in a panel of mouse embryonic fibroblasts with mitochondrial DNA single nucleotide polymorphisms

Mitochondrial DNA (mtDNA) variations including single nucleotide polymorphisms (SNPs) have been proposed to be involved in idiosyncratic drug reactions. However, current in vitro and in vivo models lack the genetic diversity seen in the human population. Our hypothesis is that different cell strains with distinct mtDNA SNPs may have different mitochondrial bioenergetic profiles and may therefore vary in their response to drug-induced toxicity. Therefore, we used an in vitro system composed of four strains of mouse embryonic fibroblasts (MEFs) with mtDNA polymorphisms. We sequenced mtDNA from embryonic fibroblasts isolated from four mouse strains, C57BL/6J, MOLF/EiJ, CZECHII/EiJ and PERA/EiJ, with the latter two being sequenced for the first time. The bioenergetic profile of the four strains of MEFs was investigated at both passages 3 and 10. Our results showed that there were clear differences among the four strains of MEFs at both passages, with CZECHII/EiJ having a lower mitochondrial robustness when compared to C57BL/6J, followed by MOLF/EiJ and PERA/EiJ. Seven drugs known to impair mitochondrial function were tested for their effect on the ATP content of the four strains of MEFs in both glucose- and galactose-containing media. Our results showed that there were strain-dependent differences in the response to some of the drugs. We propose that this model is a useful starting point to study compounds that may cause mitochondrial off-target toxicity in early stages of drug development, thus decreasing the number of experimental animals used.     

指甲游离缘及毛发中核DNA抽提方法的探讨

目的探讨指甲游离缘及毛发中抽提核DNA的方法,并对抽提结果进行评估。方法采集5名健康成人志愿者指甲游离缘、发根及发干样本各30份。分别用无水乙醇和蒸馏水浸泡样本,去除外源性DNA。每份指甲游离缘样本为3 mg指甲游离缘碎片;每份发根或发干样本各为3段0.3～0.5 cm发根或发干。分别采用酚氯仿法、Chelex-100法和QIAamp DNA Investigator试剂盒法抽提3种样本的核DNA,并运用PCR扩增对抽提DNA进行评估。扩增片段位于不同染色体上,长度分别为188、248、300和741 bp。PCR扩增产物用1.8%琼脂糖凝胶电泳检测。为探讨样本量对抽提结果的影响,任意取指甲游离缘1、3和5 mg,发根及发干各1、3和5根重复实验,并比较结果。初步探讨增加Taq酶量对黑色素抑制的消除作用。结果在3种抽提方法中长度为248 bp的引物扩增成功率均为最高。指甲游离缘样本使用试剂盒法抽提核DNA PCR扩增成功率显著高于酚氯仿法及Chelex-100法（P<0.05）。发干样本使用试剂盒法抽提核DNA PCR扩增成功率显著高于酚氯仿法（P<0.05）。发根样本3种方法抽提核DNA PCR扩增成功率差异无统计学意义（P>0.05）。指甲游离缘样本的PCR扩增成功率显著高于发根及发干样本（P<0.05）,发根和发干样本的PCR扩增成功率差异无统计学意义。试剂盒法抽提指甲游离缘、发根和发干核DNA PCR扩增成功率随样本量增加而提高。酚氯仿法和Chelex-100法抽提发根或发干样本核DNA PCR扩增成功率随样本量增加呈下降趋势,提示可能存在黑色素抑制作用。增加Taq酶量对于消除黑色素抑制有一定作用。结论①3种抽提方法均能成功从指甲游离缘及毛发中抽提到核DNA,试剂盒法成功率最高。②指甲游离缘、发根和发干均可作为核DNA采样源,从指甲游离缘抽提DNA成功率最高。     

Highly resistant macromolecular components and low rate of generation of endogenous damage: two key traits of longevity

Key characteristics relating oxidative damage to aging and longevity are reviewed. Available information indicates that the specific composition of tissue macromolecules (proteins, lipids and mitochondrial DNA) in long-lived animal species gives them an intrinsically high resistance to modification that likely contributes to the superior longevity of these species. This is obtained in the case of lipids by decreasing fatty acid unsaturation, and in the proteins by lowering their methionine content. Long-lived animals also show low rates of reactive oxygen species (ROS) generation and oxidative damage at their mitochondria. On the other hand, dietary restriction decreases mitochondrial ROS production and oxidative damage to mitochondrial DNA and proteins. These changes are due to the decreased intake of dietary proteins (not of lipids or carbohydrates) of the dietary restricted animals. In turn, these effects of protein restriction seem to be specifically due to the lowered methionine intake of the protein and dietary restricted animals. It is emphasized that both a low rate of generation of endogenous damage and an intrinsically high resistance to modification of tissue macromolecules are key traits of animal longevity.     

指甲游离缘及毛发中核DNA抽提方法的探讨

目的探讨指甲游离缘及毛发中抽提核DNA的方法,并对抽提结果进行评估。方法采集5名健康成人志愿者指甲游离缘、发根及发干样本各30份。分别用无水乙醇和蒸馏水浸泡样本,去除外源性DNA。每份指甲游离缘样本为3mg指甲游离缘碎片;每份发根或发干样本各为3段0．3～0．5cm发根或发干。分别采用酚氯仿法、Chelex-100法和QIAamp@DNA Investigator试剂盒法抽提3种样本的核DNA,并运用PCR扩增对抽提DNA进行评估。扩增片段位于不同染色体上,长度分别为188、248、300和741bp。PCR扩增产物用1．8％琼脂糖凝胶电泳检测。为探讨样本量对抽提结果的影响,任意取指甲游离缘1、3和5mg,发根及发干各1、3和5根重复实验,并比较结果。初步探讨增加Taq酶量对黑色素抑制的消除作用。结果在3种抽提方法中长度为248bp的引物扩增成功率均为最高。指甲游离缘样本使用试剂盒法抽提核DNAPCR扩增成功率显著高于酚氯仿法及Chelex-100法（P〈0．05）。发干样本使用试剂盒法抽提核DNAPCR扩增成功率显著高于酚氯仿法（P〈0．05）。发根样本3种方法抽提核DNAPCR扩增成功率差异无统计学意义（P〉0．05）。指甲游离缘样本的PCR扩增成功率显著高于发根及发干样本（P〈0．05）,发根和发干样本的PCR扩增成功率差异无统计学意义。试剂盒法抽提指甲游离缘、发根和发干核DNAPCR扩增成功率随样本量增加而提高。酚氯仿法和Chelex-100法抽提发根或发干样本核DNAPCR扩增成功率随样本量增加呈下降趋势,提示可能存在黑色素抑制作用。增加Taq酶量对于消除黑色素抑制有一定作用。结论①3种抽提方法均能成功从指甲游离缘及毛发中抽提到核DNA,试剂盒法成功率最高。②指甲游离缘、发根和发干均可作为核DNA采样源,从指甲游离缘抽提DNA成功率最高。     

我国山丘疫区和平原疫区利什曼原虫分离株基因组DNA基因型分析

目的：分析我国山丘和平原疫区利什曼原虫分离株基因组DNA（nDNA）的多态性。方法：对基因组DNA进行内切酶酶切、Southern杂交、染色体定位。探针采用地高辛标记。结果：采用gp63探针，显示杜氏利什曼原虫（Leishmaniadonovani，L．d．）江苏人株和L．d．Jeddah nDNA之间有相似的染色体杂交带，L．d．四川人株和L．infantum nDNA之间有相似的染色体杂交带；采用β－tubulin探针，显示L．d．江苏人株与L．d．Jeddah nDNA之间有两条相似的染色体杂交带，L．d．四川犬株与L．d．甘肃犬株nDNA之间有三条相似的染色体杂交带、与L．d．汶川人株nDNA之间有两条相似的染色体杂交带。结论：提示平原疫区的江苏人株与L. d. J eddah 之间存在同源性, 山丘疫区的L. d. 四川人株与L. infantum 之间存在同源性, L. d. 四川犬株与L. d. 甘肃犬株之间存在同源性、与L. d. 汶川人株之间既存在同源性又存在差异, 山丘疫区与平原疫区分离株之间存在异源性。     

用RAPD技术分析利什曼原虫DNA多态性

为了建立ＲＡＰＤ技术分析利什曼原虫ＤＮＡ多态性的方法，并进一步揭示Ｌｉｎｆａｎｔｕｍ和Ｌｔｒｏｐｉｃａ之间的亲缘关系，本文应用筛选的两种随机引物（Ｍ１３，３３０１）分别扩增了Ｌｉｎｆａｎｔｕｍ和Ｌｔｒｏｐｉｃａ的ｎＤＮＡ和ｋＤＮＡ。结果显示，两种利什曼原虫ｎＤＮＡ及ｋＤＮＡ均扩增出各自特有的带型，两虫种间ｎＤＮＡ、ｋＤＮＡ的扩增片段共享度Ｆ值分别为０７２７２和０８５７１。表明ＲＡＰＤＰＣＲ可作为利什曼原虫虫种分析鉴别的工具     

Early and delayed cardioprotective intervention with dexrazoxane each show different potential for prevention of chronic anthracycline cardiotoxicity in rabbits

Despite incomplete understanding to its mechanism of action, dexrazoxane (DEX) is still the only clearly effective cardioprotectant against chronic anthracycline (ANT) cardiotoxicity. However, its clinical use is currently restricted to patients exceeding significant ANT cumulative dose (300 mg/m²), although each ANT cycle may induce certain potentially irreversible myocardial damage. Therefore, the aim of this study was to compare early and delayed DEX intervention against chronic ANT cardiotoxicity and study the molecular events involved. The cardiotoxicity was induced in rabbits with daunorubicin (DAU; 3 mg/kg/week for 10 weeks); DEX (60 mg/kg) was administered either before the 1st or 7th DAU dose (i.e. after ≈300 mg/m² cumulative dose). While both DEX administration schedules prevented DAU-induced premature deaths and severe congestive heart failure, only the early intervention completely prevented the left ventricular dysfunction, myocardial morphological changes and mitochondrial damage. Further molecular analyses did not support the assumption that DEX cardioprotection is based and directly proportional to protection from DAU-induced oxidative damage and/or deletions in mtDNA. Nevertheless, DAU induced significant up-regulation of heme oxygenase 1 pathway while heme synthesis was inversely regulated and both changes were schedule-of-administration preventable by DEX. Early and delayed DEX interventions also differed in ability to prevent DAU-induced down-regulation of expression of mitochondrial proteins encoded by both nuclear and mitochondrial genome. Hence, the present functional, morphological as well as the molecular data highlights the enormous cardioprotective effects of DEX and provides novel insights into the molecular events involved. Furthermore, the data suggests that currently recommended delayed intervention may not be able to take advantage of the full cardioprotective potential of the drug.     

Assessment of human nuclear and mitochondrial DNA qPCR assays for quantification accuracy utilizing NIST SRM 2372a

In forensic DNA casework, a highly accurate real-time quantitative polymerase chain reaction (qPCR) assay is recommended per the Scientific Working Group on DNA Analysis Methods (SWGDAM) (SWGDAM Validation Guidelines for DNA Analysis Methods [1]) to determine whether a DNA sample is of sufficient quantity and robust quality to move forward with downstream short tandem repeats (STR) or sequencing analyses. Most of these assays rely on a standard curve, referred to herein and traditionally as absolute qPCR, in which an unknown is compared, relative to that curve. However, one fundamental issue with absolute qPCR is the quantifiable concentration of commercial assay standards can vary depending on (1) origin, i.e., whether from a cell line or a human subject, (2) supplier, (3) lot number, (4) shipping method, etc. In 2018, the National Institute for Standards and Technology (NIST) released a human DNA standard reference material for evaluating qPCR quantification standards, Standard Reference Material (SRM) 2372a, Romsos et al. (2018) [2] which contains three well-characterized human genomic DNA samples: Component A) a single male₁ donor, Component B) a single female₁ donor, and Component C) a 1:3 male₂:female₂ donor, each with certification data for nDNA and informational mitochondrial DNA(mtDNA)/nuclear DNA (nDNA) ratio data. The SRM 2372a was used to assess four qPCR assays: (1) Quantifiler Trio (Thermo Fisher Scientific, Waltham, MA) for nDNA quantification, (2) NovaQUANT (EMD Millipore Corporation, San Diego, CA) for nDNA and mtDNA quantification, (3) a custom duplex mtDNA assay, and (4) a custom triplex mtDNA assay. Additionally, extracts from eighteen (18) skeletal remains were tested with the latter three assays for concordance of DNA concentration and with assays (2) and (3), for the degradation state. Our assessment revealed that an accurate, efficient, and reproducible qPCR assay is dependent on (1) the quality and reliability of the DNA standard, (2) the qPCR chemistry, and (3) the specific primers, and probes (if applicable), used in an assay. Our findings indicate qPCR assays may not always quantify as expected and that performance of each lot should be verified using a well-characterized DNA standard such as the NIST SRM 2372a and adjusted if warranted.     

Mediating effect of ROS on mtDNA damage and low ATP content induced by arsenic trioxide in mouse oocytes

Mitochondria provide most of the adenosine triphosphates (ATP) necessary for the maturation of oocytes. Various environmental toxicants would lead damage to mitochondrial DNA (mtDNA) and hence interfere with oocytes development. In the current study, the effect of arsenic trioxide (As₂O₃) on the common 3867 bp deletion and the copy number of mtDNA in mitochondria of mouse oocytes in vivo or in vitro, as well as the molecular pathway leading to the damage were investigated. PCR strategy was used to detect the damage of mtDNA. Reactive oxygen species (ROS) and ATP content in oocytes were checked to determine the influence of As₂O₃ on oxidative stress and activity of mitochondria. The results showed that As₂O₃ could obviously decrease the copy number of mtDNA and cause severe 3867 bp deletion in mitochondria together with elevated ROS level, while ATP content was decreased. Co-treatment with N-Acetyl-Cysteine (NAC) efficiently eliminated ROS induced by As₂O₃, lessened the mtDNA damage and enhanced ATP content in mouse oocytes both in vivo and in vitro. Taken together, the present study revealed that As₂O₃ could cause severe mtDNA damage and decrease ATP content by inducing excessive ROS, and this damage would then probably restrain the further development of mouse oocytes.