TMS-MEP评价大鼠脊髓损伤后运动功能障碍程度的研究

目的探讨采用TMS-MEP评价大鼠脊髓损伤后运动功能障碍的可行性,并评价其在法医学中的应用价值。方法 SD雌性大鼠100只,分为3个损伤组、1个假手术组和1个正常对照组。损伤组采用Allen’s打击装置制作脊髓损伤模型;各组均于实验前、损伤后1d、1周、2周、4周,根据大鼠脊髓运动功能评定标准进行运动功能评分,并在70%刺激强度下记录腓肠肌的TMS-MEP;采用SPSS 19.0软件进行数据处理,单因素方差分析比较组间差异。结果损伤组随打击能量的增加,脊髓损伤程度加重,双下肢运动功能缺失明显,与正常对照组、假手术组和实验前之间均存在显著性差异（P〈0.05）。损伤组MEP潜伏期和波幅较正常对照组均延长,差异具有显著意义（P〈0.05）。TMS-MEP回归方程Y=0.465 1X＋4.602 4（R2=1,P〈0.001）,回归得出的结果与观察评分之间存在高度吻合。结论采用本文方法可为肌力的评定提供客观依据,有望在法医鉴定实践中应用。     

采用无创性核磁共振技术进行损伤时间推断初探

目的建立大鼠皮肤损伤核磁共振（nuclear magnetic resonance,NMR）检测方法,探讨其在法医学中应用的意义。方法雄性SD大鼠36只,随机分为皮肤切创和挫伤组,分别在大鼠背部制作皮肤切创和挫伤,各组分别在损伤后0h、4h、8h取皮肤组织及对侧无损伤部位皮肤,检测NMR一维1H谱,观察受创皮肤的分子代谢产物随损伤时间的变化规律。结果挫伤组、切创组背部损伤处皮肤的1H-NMR图谱在损伤后4h和8h分别检测到较多NMR波峰,波峰的高度和总面积也发生了改变,与对照部位皮肤相比,存在显著性差异（P〈0.05）。结论核磁共振技术检测组织代谢产物有望用于损伤经过时间的法医学检验。     

Fatal paradoxical air embolism diagnosed by postmortem imaging and autopsy

The recognition and visualization of an arterial gas embolism are difficult. We report a case of sudden death caused by paradoxical air embolism of coronary and cerebral arteries, diagnosed by the pre autopsy computed tomography (CT) scanning. A 54-year-old woman suddenly died after the self-removal of the jugular vein catheter. Postmortem imaging examination using CT scanning showed multiple gas embolisms in the cerebral arteries, pulmonary artery, right atrium and ventricle, left ventricle, aorta, and coronary arteries. These findings suggested that the occurrence of acute ischemia of the brain and heart caused by massive air inflow to the artery. Conventional autopsy revealed a patent foramen ovale of the heart. These results indicated that the patient died of paradoxical air embolization of the coronary and cerebral arteries through a patent foramen ovale because of right-to-left shunting. The use of postmortem imaging as an aid for conventional autopsy has proved to be of advantage in the case of gas embolism.     

The use of a 3-D laser scanner to document ephemeral evidence at crime scenes and postmortem examinations

Proper documentation of physical evidence at both crimes scenes and postmortem examination is crucial for downstream analysis, interpretation, and presentation in court. Ephemeral or transient evidence poses particular challenges to investigators, as its very nature renders it difficult or impossible to seize and maintain in its original physical state. The use of a hand-held three-dimensional (3-D) laser scanner is proposed to capture and document such evidence, both in the field and at autopsy. Advantages of the scanner over traditional means of documentation such as photography or casting include the ability to obtain measurements in all dimensions, the ability to reconstruct missing elements, and the ease with which generated images can be interpreted by the jury at trial. Potential scenarios warranting the use of the scanner are identified, and the limitations of its use are discussed.     

Massive systemic fat embolism detected by postmortem imaging and biopsy*

Postmortem computed tomography (pmCT) and pmCT angiography (pmCTA) provide a minimally invasive method to determine the cause of death. Postmortem image-guided biopsy allows for precise sampling of histological specimens. This case study describes the findings of lethal systemic fat embolism (FE) on whole-body unenhanced pmCT, pmCTA, and image-guided biopsy, with autopsy and histopathologic correlation. Unenhanced pmCT revealed a distinct fat level on top of sedimented layers of corpuscular blood particles and serum in the arterial system and pulmonary trunk. Subsequent pmCTA showed reproducible results, and image-guided biopsy confirmed fatal FE. pm CT/pmCTA combined with image-guided biopsy established the cause of death as right heart failure as a result of systemic fatal FE prior to autopsy. All imaging findings were consistent with traditional autopsy and histological specimens. This unique case demonstrates new imaging findings in massive, fatal FE and highlights that postmortem imaging, supplemented by image-guided biopsy, may detect the cause of death prior to traditional autopsy.     

单体素~1H-MRS推断死亡时间的初步研究

目的检测脑内N-乙酰天门冬氨酸、胆碱复合物及磷酸肌酸和肌酸的变化规律,并探讨其与死亡时间的关系。方法选取12只白兔,利用单体素氢质子磁共振波谱测定死后0.5、1、2、4、6、8、12、16、24h脑内N-乙酰天门冬氨酸、胆碱复合物及磷酸肌酸和肌酸峰下面积;分析其在上述时间点的变化规律,建立与死亡时间相关的回归方程。结果在死后24h内N-乙酰天门冬氨酸、磷酸肌酸和肌酸峰下面积随死亡时间的延长而降低(各时间点比较P<0.05),胆碱复合物在死后24h内无明显变化(各时间点比较P>0.05)。回归方程为:Naa:y=0.7425x2-27.282x+299.984(R2=0.962);Cr:y=0.3234x2-12.007x+210.503(R2=0.986)。结论死后24h内兔脑N-乙酰天门冬氨酸、磷酸肌酸和肌酸呈现出一定的变化规律,其与死亡时间相关程度较高,可用于对一定条件下死亡时间的推断。     

多体素~1H-MRS推断不同温度下死亡时间的研究

目的利用多体素质子磁共振波谱(1H-MRS)技术推断不同温度下的死亡时间。方法选取24只白兔,分为两组,利用多体素质子磁共振波谱测定死后30m in、1h、2h、4h、6h、8h、12h、16h、24h脑内N-乙酰天门冬氨酸、胆碱复合物、磷酸肌酸和肌酸各代谢物之间峰下面积的比值。结果死后24h内N-乙酰天门冬氨酸与磷酸肌酸和肌酸的比值随死亡时间的延长而降低,胆碱复合物与磷酸肌酸和肌酸的比值随死亡时间的延长而升高。Naa/Cr、Ch/Cr与PM I进行回归分析:自变量为Naa/Cr的二次多项式方程为:y=0.0020x2-0.0815x+1.4532(R2=0.971);自变量为Ch/Cr的二次多项式方程为:y=-0.0024x2+0.0870x+1.1876(R2=0.962)。用Naa/Cr的方程推测PM I,当PM I<24h时,平均偏离时间为1.70~50.27m in,用Ch/Cr的方程推测PM I,当PM I<24h时,平均偏离时间为1.12~98.11m in。结论Naa/Cr、Ch/Cr的死后变化与时间呈强相关性,可用于死亡时间推断。     

Positive identification of the principal component of a white powder as scopolamine by quantitative one-dimensional and two-dimensional NMR techniques

An unidentified white powder collected as evidence in an intelligence investigation was characterized exclusively by nuclear magnetic resonance (NMR) analysis. A small fraction of the powder dissolved in D2O was subjected to a series of one- and two-dimensional techniques which were used to elucidate the molecular structure of the powder's major component and positively identify it as the scopolamine biotoxin. Quantitative one-dimensional experiments identified individual proton and carbon atom sites, and conventional 14N spectroscopy detected a single nitrogen atom site. Heteronuclear single quantum coherence data correlated all protons to their directly bonded carbon atom, and together with the quantitative spectra, were used to determine the number of protons directly bonded to each carbon atom. The presence of a methyl, carboxyl, and a benzyl group was also identified from these data. Correlation spectroscopy detected a three proton and a nine proton JH,H network, representing a CH2CH moiety and seven carbon atom ring, respectively. These five elements were assembled into an almost complete molecular structure by using long-range, J-coupled, 1H-13C pairs detected by heteronuclear multiple bond correlation (HMBC) spectroscopy and 1H-1H dipolar-coupled pairs found from nuclear Overhauser effect spectroscopy (NOESY) data. Additional oxygen atom sites were inferred from 1H-13C correlation intensities in the HMBC spectra along with 1H and 13C chemical shift values, or directly from NOESY correlations. Only a single oxygen atom site could not be inferred from NMR data, but its presence was inferred from comparisons to target analyte structures to complete the structure of the scopolamine molecule. To confirm these results, an ethanol/H2O solution of the powder was analyzed by direct infusion into an ion trap mass spectrometer. A prominent base signal was observed at m/z 304.1 amu, corresponding to the protonated molecular ion of scopolamine. Subsequently, the ion was selected and subjected to collision-induced dissociation, producing characteristic major MS/MS fragments at m/z 138.1 and 156.1. Comparisons of 1H and 13C chemical shift values and JH,H values measured from our NMR data were found to agree very favorably with previously reported values for scopolamine in D2O.     

Chlorinated Opium Alkaloid Derivatives Produced by the Use of Aqueous Sodium Hypochlorite During the Clandestine Manufacture of Heroin

Abstract:  A clandestine chemist was observed producing heroin from crude morphine utilizing a solution of sodium hypochlorite during the process. Numerous chlorinated opium alkaloid derivatives were created when the morphine acetylation reaction was quenched and neutralized with a solution of sodium hypochlorite and ammonium hydroxide. Four of these compounds, 1-chloroheroin, 1-chloroacetylcodeine, 1-chloro-O⁶-monoacetylmorphine, and 2'-chloropapaverine, were characterized via preparative isolation, gas chromatography/mass spectrometry, nuclear magnetic resonance spectroscopy, and independent synthesis. These chlorinated derivatives were formed via electrophilic aromatic substitution with free chlorine during the illicit process. Although no illicit heroin exhibits containing these compounds have been observed in seizures to date, mass spectral data are provided for several of these compounds for their identification should they be seen within future seizures of illicit heroin.     

The Use of Hemastix® and the Subsequent Lack of DNA Recovery Using the Promega DNA IQTM System

Abstract:  Following implementation of our automated process incorporating the Promega DNA IQ^TM system as a DNA extraction method, a large number of blood-containing exhibits failed to produce DNA. These exhibits had been tested with the Hemastix^® reagent strip, commonly used by police investigators and forensic laboratories as a screening test for blood. Some exhibits were even tainted green following transfer of the presumptive test reagents onto the samples. A series of experiments were carried out to examine the effect of the Hemastix^® chemistries on the DNA IQ^TM system. Our results indicate that one or more chemicals imbedded in the Hemastix^® reagent strip severely reduce the ability to recover DNA from any suspected stain using the DNA IQ^TM magnetic bead technology. The 3,3',5,5'-tetramethylbenzidine (TMB) used as the reporting dye appears to interact with the magnetic beads to prevent DNA recovery. Hydrogen peroxide does not seem to be involved. The Hemastix^® chemistries do not interfere in any way with DNA extraction performed using phenol-chloroform. The incompatibility of the Hemastix^® chemistries on the DNA IQ^TM system forced us to adopt an indirect approach using filter paper to carry out the presumptive test.