Differential diagnosis between freshwater drowning and saltwater drowning based on intrapulmonary aquaporin-5 expression

Diagnosing fatal drownings: A review of the postmortem findings

The lack of drowning-specific pathological findings postmortem complicates medico-legal investigations when bodies are recovered in water. This review provides an in-depth analysis of macroscopic and microscopic findings, as well as biochemical and molecular approaches typically used to diagnose drownings. To ensure that only studies fulfilling established scientific criteria were selected to form conclusions in this review, existing literature was systematically assessed using SPICOT for evaluation of scientific evidence and risk of bias. Analysis of selected studies indicates that several pathophysiological findings following suspected drowning lack scientific evidence, while others are supported by the literature. However, the shortage of suitable controls in drowning research, specifically addressing non-drowned immersed bodies significantly limits investigations on postmortem drowning pathology, and further research is warranted.

Application of Aquaporins as Markers in Forensic Pathology: A Systematic Review of the Literature

The study of aquaporins (AQPs) in various forensic fields has offered a promising horizon in response to the need to have reliable elements for the identification of the manner of death and for the individuation of forensic markers for the timing of lesions and vitality of injury. In the literature, various tissues have been studied; the most investigated are the lungs, brain, kidneys, skin, and blood vessels. A systematic literature review on PubMed following PRISMA 2020 guidelines enabled the identification of 96 articles. In all, 34 of these were enrolled to identify Aquaporin-like (AQP-like) forensic markers. The analysis of the literature demonstrated that the most significant markers among the AQPs are as follows: for the brain, AQP4, which is very important in brain trauma and hypoxic damage; AQP3 in the skin lesions caused by various mechanisms; and AQP5 in the diagnosis of drowning. Other applications are in organ damage due to drug abuse and thrombus dating. The focus of this review is to collect all the data present in the literature about the forensic application of AQPs as forensic markers in the most important fields of application. In the current use, the individuation, validation, and application of markers in forensic investigation are very useful in real forensic applications in cases evaluated in court.

Applicable Forensic Biomarker for Drowning Diagnosis: Extracellular Signal-Regulated Kinase 2 (ERK2)

Drowning is a common cause of accidental death worldwide, and it continues to be a serious public health problem. However, diagnosing drowning is a challenging task in forensic investigation because it is difficult to prove actual drowning and other submerged deaths with the autopsy techniques that are currently in use. Here, we show biomarkers that may be helpful for the diagnosis of drowning. We divided the experimental animals into four groups (drowning, postmortem submersion, hypoxia, and control) to evaluate the expression patterns of extracellular signal-regulated kinase 1/2 (ERK1/2). On gene expression analysis, only ERK2 was found to be significantly increased in the drowning groups compared to the other cases. In the immunoblot analysis, phosphorylated ERK2 (p-ERK2) was found to be upregulated in the drowning groups. Immunohistochemical staining also showed that p-ERK in alveolar cells revealed a granular pattern in the drowning groups. However, the expression pattern of ERK2 over time after drowning differed between the freshwater and seawater drowning groups. Taken together, these results indicate that ERK2 may be useful for distinguishing between drowning and postmortem submersion if the postmortem interval (PMI) of drowning is short. Conversely, if the PMI is long from the time that death occurs until the discovery of dead bodies, it is possibly more helpful for identifying between freshwater and seawater drowning.

Forensic application of aquaporins

Aquaporins (AQPs) are a family of water channel proteins that primarily elicit the basic functions of water transport and osmotic homeostasis. To date, at least 17 mammalian AQPs have been identified, AQP-0 to -12 have been found in higher orders including human, and AQP-13 to -16 have been described in older lineages. Moreover, these proteins have recently been shown to regulate many biological processes through unique activities, such as cell proliferation, migration, apoptosis, and mitochondrial metabolism. Several studies have focused on the involvement of AQPs in cell biology aspect, showing that they are involved in a variety of physiological processes and pathophysiological conditions. Furthermore, in the field of forensic medicine, studies on whether AQPs can be a useful marker for diagnosing various causes of death have been conducted using autopsy samples and animal experiments, which have produced interesting results. Herein, we review certain observations regarding AQPs and discuss their potential to contribute to the future practice of forensic research.

Drowning versus postmortem submersion: Biochemical and histopathological examination and estimation of postmortem intervals (an experimental study)

Estimation of the postmortem interval (PMI) is a very essential task for forensic experts especially in criminal cases. drowning is still the most difficult tasks for forensic pathologists to be diagnosed and differentiated from a body disposed of in water following death especially after long post-mortem period. The objective of this study was to estimate the PMI in drowning in comparison to postmortem submersion using mRNA expression of AQP1 in addition to histological and immunohistochemical examination of caspase-3 in the adrenal and thyroid glands of adult albino rats. Adult albino rats were divided into 2 groups; group A (drowning) and group B (post-mortem submersion). Thyroid and adrenal glands were examined at different PMI. The results revealed significant differences at AQP1 levels between drowning and postmortem submersion at different PMI. Histological changes and caspase-3 expression immunologically in both glands were helpful.

Forensic Diagnosis of Freshwater or Saltwater Drowning Using the Marker Aquaporin 5: An Immunohistochemical Study

Background and Objectives: Aquaporins are a family of water channel proteins. In this study, the renal and intrapulmonary expression of aquaporin-5 (AQP5) was examined in forensic autopsy cases to evaluate it as a drowning marker and to differentiate between freshwater drowning and saltwater drowning. Materials and Methods: Cases were classified into three groups: freshwater drowning (FWD), saltwater drowning (SWD), and controls (CTR). Samples were obtained from forensic autopsies at less than 72 h postmortem (15 FWD cases, 15 SWD cases, and 17 other cases) and were subjected to histological and immunohistochemical investigations. Results: In FWD group, intrapulmonary AQP5 expression was significantly suppressed compared with SWD and CTR; there was no significant difference in AQP5 expression among the other two groups. The same differences in expression were also observed in the kidney. Conclusions: These observations suggest that AQP5 expression in alveolar cells was suppressed by hypotonic water to prevent hemodilution. Moreover, it is possible to hypothesize that in the kidney, with the appearance of hypo-osmotic plasma, AQP5 is hypo-expressed, as a vital reaction, to regulate the renal reabsorption of water. In conclusion, the analysis of renal and intrapulmonary AQP5 expression would be forensically useful for differentiation between FWD and SWD, or between FWD and death due to other causes.

Mini Review: Forensic Value of Aquaporines

Forensic pathologists are routinely confronted with unclear causes of death or findings. In some scenarios, it can be difficult to answer the specific questions posed by criminal investigators or prosecutors. Such scenarios may include questions about wound vitality or causes of death when typical or landmark findings are difficult to find. In addition to the usual subsequent examinations to clarify unclear causes of death or special questions, immunohistochemical analysis has become increasingly important since its establishment in the early 40s of the 20th century. Since then, numerous studies have been conducted to determine the usefulness and significance of immunohistochemical investigations on various structures and proteins. These proteins include, for example, aquaporins, which belong to the family of water channels. They enable the transport of water and of small molecules, such as glycerol, through biological channels and so far, 13 classes of aquaporins could have been identified in vertebrates. The classic aquaporin channels 1, 2, 4 and 5 are only permeable to water. The aquaporin channels 3, 7, 9, and 10 are also called aquaglycerolporins since they can also transport glycerol. This mini review discusses the immunohistochemical research on aquaporins, their range of applications, and respective forensic importance, their current limitations, and possible further implementations in the future.

Acute or chronic pulmonary emphysema? Or both?-A contribution to the diagnosis of death due to violent asphyxiation in cases with pre-existing chronic emphysema

The diagnosis of death due to violent asphyxiation may be challenging if external injuries are missing, and a typical acute emphysema (AE) "disappears" in pre-existing chronic emphysema (CE). Eighty-four autopsy cases were systematically investigated to identify a (histo-) morphological or immunohistochemical marker combination that enables the diagnosis of violent asphyxiation in cases with a pre-existing CE ("AE in CE"). The cases comprised four diagnostic groups, namely "AE", "CE", "acute and chronic emphysema (AE + CE)", and "no emphysema (NE)". Samples from all pulmonary lobes were investigated by conventional histological methods as well as with the immunohistochemical markers Aquaporin 5 (AQP-5) and Surfactant protein A1 (SP-A). Particular attention was paid to alveolar septum ends ("dead-ends") suspected as rupture spots, which were additionally analyzed by transmission electron microscopy. The findings in the four diagnostic groups were compared using multivariate analysis and 1-way ANOVA analysis. All morphological findings were found in all four groups. Based on histological and macroscopic findings, a multivariate analysis was able to predict the correct diagnosis "AE + CE" with a probability of 50%, and the diagnoses "AE" and "CE" with a probability of 86% each. Three types of "dead-ends" could be differentiated. One type ("fringed ends") was observed significantly more frequently in AE. The immunohistochemical markers AQP-5 and SP-A did not show significant differences among the examined groups. Though a reliable identification of AE in CE could not be achieved using the examined parameters, our findings suggest that considering many different findings from the macroscopical, histomorphological, and molecular level by multivariate analysis is an approach that should be followed.

Determining the effect of water temperature on the T1 and T2 relaxation times of the lung tissue at 9.4 T MRI: A drowning mouse model

Japanese individuals have a unique culture of soaking in a bathtub, and forensic pathologists have experienced fatal cases due to drowning. However, T1 and T2 relaxation times of a drowning lung are poorly documented. In the present study, we investigated the relationship between drowning water temperature and T1 and T2 relaxation times of drowning lung tissues at 9.4 T MRI (Bruker, BioSpec94/20USR). The mice used as animal drowning models were directly submerged in freshwater. Water temperature was set to 8 °C-10 °C (cold), 20 °C-22 °C (normal), 30 °C, and 45 °C. The regions of interest (ROIs) on the axial section of the third slice were set at the central and peripheral areas of each-the left and the right-lung. T1 relaxation times measured immediately after death differed by the presence or absence of soaking water, except in case of cold water temperature. In the drowning groups, T1 relaxation time showed a linear dependency on water temperature. By contrast, T2 relaxation time was almost constant regardless of the presence of drowning under the same temperature condition; when compared in the lung areas of the same individuals, the times were uniformly reduced in drowning models. To minimize the effects of hypostasis and decomposition, we performed measurements immediately after death and were able to determine the noticeable difference in drowning water temperature. These results may be useful for qualitative assessments of a drowning lung and may serve as a basis when imaging the human body during forensic autopsy cases.

Intrathrombotic appearances of AQP-1 and AQP-3 in relation to thrombus age in murine deep vein thrombosis model

Aquaporins (AQPs) are membrane-bound proteins for water transportation and are useful for diagnosing drowning and wound vitality in forensic pathology. Here, we examined intrathrombotic expression of AQP-1 and AQP-3 using deep vein thrombosis models in mice. To perform immunohistochemical analyses, we used anti-AQP-1 and anti-AQP-3 antibodies. In thrombus samples with the post-ligation intervals of 1 to 5 days, AQP-1⁺ areas were over 70%. At 7 days after the IVC ligation, AQP-1⁺ areas became less than 50%, eventually decreasing to 11% at 21 days. At 3 days after the IVC ligation, AQP-3⁺ cells started to appear from the peripheral area. Thereafter, the positive cell number progressively increased and reached to a peak at 10 days after the IVC ligation. When the intrathrombotic AQP-1⁺ area was as large as the intrathrombotic collagen area or smaller, it would indicate a thrombus age of ≥ 10 days. AQP-3⁺ cell number of > 30 would indicate a thrombus age of 10–14 days. Collectively, our study implied that the detection of AQP-1 and AQP-3 would be useful for the determination of thrombus age.

MicroRNAs: An Update of Applications in Forensic Science

MicroRNAs (miRNAs) are a class of non-coding RNAs containing 18–24 nucleotides that are involved in the regulation of many biochemical mechanisms in the human body. The level of miRNAs in body fluids and tissues increases because of altered pathophysiological mechanisms, thus they are employed as biomarkers for various diseases and conditions. In recent years, miRNAs obtained a great interest in many fields of forensic medicine given their stability and specificity. Several specific miRNAs have been studied in body fluid identification, in wound vitality in time of death determination, in drowning, in the anti-doping field, and other forensic fields. However, the major problems are (1) lack of universal protocols for diagnostic expression testing and (2) low reproducibility of independent studies. This review is an update on the application of these molecular markers in forensic biology.

Immunohistochemical renal expression of aquaporin 2, arginine-vasopressin, vasopressin receptor 2, and renin in saltwater drowning and freshwater drowning

The diagnosis of drowning is considered one of the most difficult in forensic medicine. Due to the paucity of signs, it is a classical diagnosis by exclusion. For this reason, specific immunohistochemical markers would be useful. Far too little has been done to analyze in-depth the differences between SWD and FWD. We focused on the renal immunohistochemical expression of aquaporin 2, AVP, V2R, and renin in cases of drowning. This study has two purposes: (1) to better understand the differences between saltwater drowning (SWD) and freshwater drowning (FWD), which may indicate different pathophysiology and (2) to eventually identify markers useful for the diagnosis of drowning. We retrospectively investigated 10 cases of SWD gathered from the Institute of Legal Medicine in Genoa (Italy), and 10 cases of FWD from the University Center of Legal Medicine in Geneva (Switzerland). As a control group, we investigated 10 cases of death by gunshot to the head. A strong expression of AQP2 and AVP was significantly (p < 0.05) more evident in cases of SWD than in FWD and control cases. Regarding the V2R, no statistically significant differences were found between the studied groups. The renin tubular expression was particularly intense (p < 0.05) both in SWD and in FWD compared controls. According to our results, AQP2 and AVP represent potential useful markers for the differential diagnosis between SWD and other causes of death, including FWD. Renin may be a useful marker in the diagnosis of drowning but it does not allow for differentiation between FWD and SWD.

Immunohistochemical expression of P-selectin, SP-A, HSP70, aquaporin 5, and fibronectin in saltwater drowning and freshwater drowning

The diagnosis of drowning is one of the most difficult in forensic medicine. The aim of this study was to analyze pulmonary tissue reactions in death by drowning. In particular, we focused on the immunohistochemical expression of P-selectin, SP-A, HSP70, AQP-5, and fibronectin to investigate our expression in drowning and to understand whether there are differences between saltwater drowning (SWD) and freshwater drowning (FWD), which may indicate a different pathophysiology. We retrospectively investigated 10 cases of SWD (Mediterranean Sea) from the Institute of Legal Medicine of Genoa (Italy), and 10 cases of FWD (Lake of Geneva) from the University Center of Legal Medicine of Geneva (Switzerland). As control group, we examined 10 cases of death by acute external bleeding, characterized by minimal respiratory distress. As compared with controls, in SWD cases, the results showed a decrease of SP-A expression with membrane patterns. Furthermore, we observed a greater SP-A expression with granular pattern in drowning cases without statistically significant difference between SWD and FWD. For the markers AQP-5, HSP70, fibronectin, and P-selectin, no statistically significant differences were found between SWD, FWD, and controls.

Potential forensic application of receptor for advanced glycation end products (RAGE) and aquaporin 5 (AQP5) as novel biomarkers for diagnosis of drowning

Drowning is the most common cause of unnatural death worldwide. There is no single biomarker to diagnose drowning, so the diagnosis of drowning is one of the most difficult tasks in forensic medicine. Especially, distinguishing a victim of drowning from a body disposed of in water following death remains a problem. The objective of this study was to identify specific biomarkers of drowning compared with other causes of death such as hypoxia and postmortem submersion. The present study investigated the intrapulmonary expression of receptor for advanced glycation end products (RAGE), aquaporin-5 (AQP5), surfactant protein-A (SP-A), interleukin 6 (IL-6) and interleukin 1β (IL-1β) as markers of drowning. In animal experiments, all rats (n = 45) were classified into four groups (drowning, postmortem-submersion, hypoxia and control group). The lungs of experimental animals were analyzed as mRNA expression, immunoblot expression and immunohistochemical staining. qRT-PCR demonstrated increased mRNA expression of RAGE and AQP5 in drowning group compared with that in control, hypoxia and postmortem-submersion group, but not other molecules. Western blotting also showed high expression of RAGE and AQP5 in drowning group, immunostaining of RAGE and AQP5 was highly detected in a linear pattern in type I alveolar epithelial cells, compared with control and postmortem-submersion group. These observations indicate a difference of expression in pulmonary molecular pathology compared with other causes, suggesting RAGE and AQP5 may be useful for differentiation between drowning and postmortem-submersion.

Forensic application of epidermal AQP3 expression to determination of wound vitality in human compressed neck skin

In forensic practices, it is often difficult to determine wound vitality in compression marks of the neck with naked eyes. AQP1 and AQP3 are the major water channels associated with skin. Thus, we immunohistochemically examined the expression of AQP1 and AQP3 in neck skin samples to discuss their forensic applicability to determination of the wound vitality. Skin samples were obtained from 56 neck compression cases (hanging, 35 cases; strangulation, 21 cases). The intact skin from the same individual was taken as a control. Although AQP1 was immnunostained in dermal capillaries in both the neck compression marks and intact skin samples, there was no significant difference in the magnitude of AQP1 expression between both groups. On the contrary, AQP3-positive signals could be faintly detected in uninjured skin samples, and the positive signals seemed more intense in the keratinocytes in compression regions. Morphometrical analyses revealed that the ratio of AQP3-expressed keratinocytes was significantly enhanced in neck compression regions, compared with control groups. From the viewpoints of forensic pathology, immunohistochemical detection of AQP3 in the neck skin can be considered a valuable marker to diagnose the trace of antemortem compression.

Animal experimentation in forensic sciences: How far have we come?

In the third millennium where ethical, ethological and cultural evolution seem to be leading more and more towards an inter-species society, the issue of animal experimentation is a moral dilemma. Speaking from a self-interested human perspective, avoiding all animal testing where human disease and therapy are concerned may be very difficult or even impossible; such testing may not be so easily justifiable when suffering-or killing-of non human animals is inflicted for forensic research. In order to verify how forensic scientists are evolving in this ethical issue, we undertook a systematic review of the current literature. We investigated the frequency of animal experimentation in forensic studies in the past 15 years and trends in publication in the main forensic science journals. Types of species, lesions inflicted, manner of sedation or anesthesia and euthanasia were examined in a total of 404 articles reviewed, among which 279 (69.1%) concerned studies involving animals sacrificed exclusively for the sake of the experiment. Killing still frequently includes painful methods such as blunt trauma, electrocution, mechanical asphyxia, hypothermia, and even exsanguination; of all these animals, apparently only 60.8% were anesthetized. The most recent call for a severe reduction if not a total halt to the use of animals in forensic sciences was made by Bernard Knight in 1992. In fact the principle of reduction and replacement, frequently respected in clinical research, must be considered the basis for forensic science research needing animals.

Forensic application of microRNA-706 as a biomarker for drowning pattern identification

Forensic research using microRNA has been used so far only for the identification of body fluids, but its use in understanding biological processes in post-mortem pathology has not been studied before. Therefore, we performed experiments in mice to compare between freshwater and saltwater drowning models, and miRNA expression was analyzed in the brain through a forward bioinformatics screening approach. In this study, we identified eight specific microRNAs whose expression increased in freshwater and decreased in saltwater. Among them, miR-706 - targeting HCN1 - was identified as a potent biomarker for the drowning pattern identification. A higher expression of miR-706 was detected in the freshwater drowning compared to the control and saltwater drowning group (p<0.05, and p<0.01, respectively). HCN1 mRNA expression, a suggested candidate target for miR-706, was lower in the freshwater (p<0.01) than in the saltwater drowning group, and showed statistical difference between freshwater and saltwater drowning (p<0.01). miR-706 was specifically expressed in the hippocampal neurons as detected by in situ hybridization. Our data suggest that a specific microRNA may provide clues to understanding some crime scene investigations and pathobiological processes in the dead body.

Forensic diagnosis of ante- and postmortem burn based on aquaporin-3 gene expression in the skin

In order to diagnose death associated with fire, it is essential to show that the person was exposed to heat while still alive. We investigated both AQP1 and AQP3 expression in the skin of an experimental burn model, as well as in forensic autopsy cases, and discuss its role in the differential diagnosis of ante- and postmortem burns. In animal experiments, there was no difference in AQP1 gene expression among four groups (n=4): antemortem burn, postmortem burn, mechanical wound, and control. However, AQP3 expression in the antemortem burn was increased significantly compared with that of the other groups even at 5min after burn. Water content of the skin was decreased significantly by the burn procedure. Consistent with animal experiments, AQP3 gene expression in the skin of antemortem burn cases was increased significantly compared with postmortem burns, mechanical wounds, and controls (n=12 in each group). These observations suggest that dermal AQP3 gene expression was increased to maintain water homeostasis in response to dehydration from burn. Finally, our results suggest that AQP3 gene expression may be useful for forensic molecular diagnosis of antemortem burn.

Forensic molecular pathology: its impacts on routine work, education and training

The major role of forensic pathology is the investigation of human death in relevance to social risk management to determine the cause and process of death, especially in violent and unexpected sudden deaths, which involve social and medicolegal issues of ultimate, personal and public concerns. In addition to the identification of victims and biological materials, forensic molecular pathology contributes to general explanation of the human death process and assessment of individual death on the basis of biological molecular evidence, visualizing dynamic functional changes involved in the dying process that cannot be detected by morphology (pathophysiological or molecular biological vital reactions); the genetic background (genomics), dynamics of gene expression (up-/down-regulation: transcriptomics) and vital phenomena, involving activated biological mediators and degenerative products (proteomics) as well as metabolic deterioration (metabolomics), are detected by DNA analysis, relative quantification of mRNA transcripts using real-time reverse transcription-PCR (RT-PCR), and immunohisto-/immunocytochemistry combined with biochemistry, respectively. Thus, forensic molecular pathology involves the application of omic medical sciences to investigate the genetic basis, and cause and process of death at the biological molecular level in the context of forensic pathology, that is, 'advanced molecular autopsy'. These procedures can be incorporated into routine death investigations as well as guidance, education and training programs in forensic pathology for 'dynamic assessment of the cause and process of death' on the basis of autopsy and laboratory data. Postmortem human data can also contribute to understanding patients' critical conditions in clinical management.

Svechnikov's sign as an indicator of drowning in immersed bodies changed by decomposition: an autopsy study

PURPOSE

Bodies recovered from water often present as a difficult problem in forensic pathology. The aim of this study was to examine the presence and amount of free liquid in the sphenoid sinus in cases of freshwater drowning, and to compare this to the amount found in putrefied bodies recovered from freshwater, as well as in putrefied bodies found in an indoor environment.

METHODS

Free liquid from the sphenoid sinuses was aspirated using a syringe and a needle, after piercing the hypophyseal fossa. Non-putrefied drowning cases were also examined for hemolytic staining of the intima of the aortic root.

RESULTS

In 29 non-putrefied cases of freshwater drowning there was 1.36 ± 1.48 ml in the sphenoid sinuses, with 21 of them having hemolytic staining of aortic intima. In putrefied bodies recovered from freshwater (22 cases) there was 1.26 ± 1.40 ml within the sphenoid sinuses, and in putrefied bodies found in an indoor environment (52 cases), there was significantly less-0.57 ± 0.92 ml.

CONCLUSIONS

Free liquid in the sphenoid sinuses (Svechnikov's sign) may be considered a vital reaction in drowning non-putrefied cases. Hemolytic staining of the aortic intima could be a significant sign of freshwater drowning. In putrefied bodies recovered from water, an amount of 0.55 ml of free liquid in the sphenoid sinuses may imply that the victim was alive upon their contact with the water, but the presence of free liquid in the sphenoid sinuses does not necessarily indicate that drowning had been the cause of death.

Estimating time of death based on the biological clock

The biological clock may stop at the time of death in a dead body. Therefore, the biological clock seems useful for estimating the time of death. In this study, we tried to read the biological clock in tissues from dead bodies to estimate the time of death using molecular biological techniques. At first, we examined real-time RT-PCR analysis of gene expression for mPer2 and mBmal1, which constitutes a feedback loop in the oscillation system, in the kidney, liver, and heart of mice. We could detect circadian oscillation of these gene expressions in mouse tissues even at <48 h after death. Thus, the ratio of mPer2/mBmal1 was found to be useful for estimating the time of death. We next applied this method to the liver, kidney, and heart obtained from forensic autopsy cases with less than 72 h of postmortem interval. Significant circadian oscillation of hPer2/hBmal1 ratio could be detected in these autopsy samples. We further examined gene expression for hRev-Erbα, a component of another feedback loop. The ratios of hRev-Erbα/hBmal1 showed higher amplitude of oscillation than those of hPer2/hBmal1 and are considered more suitable for estimating the time of death. In particular, a hRev/hBmal1 ratio of >50 indicated the time of death as 0200-0900 hours, and a hRev/hBmal1 ratio that considerably exceeded 75 indicated the time of death as 0200-0800 hours. On the other hand, a hRev/hBmal1 ratio of less than 25 strongly indicated the time of death as 1000-2300 hours. Taken together, these findings indicate that gene expression analyses of the biological clock could be powerful methods for estimation of the time of death.

Immunohistochemical examination of intracerebral aquaporin-4 expression and its application for differential diagnosis between freshwater and saltwater drowning

Human brain samples were collected from 70 autopsy cases including 22 freshwater drowning (FWD), 26 saltwater drowning (SWD), and 22 non-drowning cases as controls. Then, immunohistochemical study combined with morphometry was carried out in order to examine the differential expression of AQP1 and AQP4 in the brain samples. Immunohistochemically, star-shaped cells bearing highly branched processes, often surrounding blood vessels, showed positive reactions for AQP1 and AQP4 in FWD, SWD, as well as control groups. Additionally, with double-color immunofluorescence analysis, AQP1- or AQP4-positive cells could be identified as GFAP-positive astrocytes. Moreover, AQP1-positive reaction was also observed in blood vessels. Morphometrically, there were no significant differences in AQP1 expression in astrocytes or in blood vessels among the three groups. In contrast, the average value of AQP4-positive astrocytes was significantly higher in FWD cases than in SWD and control groups. Moreover, AQP4 expression was significantly lower in SWD than in the control group (p < 0.05). Moreover, there was no significant correlation between post-submerged interval and AQP expression in drowning cases. Therefore, immunohistochemical analysis of intracerebral AQP4 expression would be forensically useful for differentiation between FWD and SWD.

Immunohistochemical identification of prevalent right ventricular ischemia causing right heart failure in cases of pulmonary fat embolism

Pulmonary fat embolism is a life-threatening event that may result to potentially determining right ventricular failure. Even if the pathophysiology of this phenomenon has been widely investigated, no immunohistochemical demonstration of right ventricular failure following pulmonary fat embolism has been reported till now. We performed an immunohistochemical investigation with the markers fibronectin and C5b-9 in 21 cases of polytrauma with bone fractures (study group-nine females and 12 males; mean age 64.6 years) compared to a control group of 21 forensic cases with various causes of death (nine females and 12 males; mean age 68.6 years). In each case at least one tissue slide from both cardiac ventricles (free wall of the right ventricle, anterior and/or posterior wall of the left ventricle) was available. The reactions were semi-quantitatively classified, and the two groups were compared. In the study group, the occurrence of ischemic changes at the right ventricle was significantly higher than in controls. The determining aspect, however, seems to be the prevalent ischemic lesion at the right ventricle compared to the left one. This may indicate the primary involvement of the right ventricle, thus, demonstrating a right ventricular failure.