Postmortem Vitreous Humor Research Articles

Nanoscale potassium sensing based on valinomycin-anchored fluorescent gold nanoclusters.

Gold nanoclusters are a smart platform for sensing potassium ions (K+). They have been synthesized using bovine serum albumin (BSA) and valinomycin (Val) to protect and cap the nanoclusters. The nanoclusters (Val-AuNCs) produced have a red emission at 616nm under excitation with 470nm. In the presence of K+, the valinomycin polar groups switch to the molecule's interior by complexing with K+, forming a bracelet structure, and being surrounded by the hydrophobic exterior conformation. This structure allows a proposed fluorometric method for detecting K+ by switching between the Val-AuNCs' hydrophilicity and hydrophobicity, which induces the aggregation of gold nanoclusters. As a result, significant quenching is seen in fluorescence after adding K+. The quenching in fluorescence in the presence of K+ is attributed to the aggregation mechanism. This sensing technique provides a highly precise and selective sensing method for K+ in the range 0.78 to 8µM with LOD equal to 233nM. The selectivity of Val-AuNCs toward K+ ions was investigated compared to other ions. Furthermore, the Val-AuNCs have novel possibilities as favorable sensor candidates for various imaging applications. Our detection technique was validated by determining K+ ions in postmortem vitreous humor samples, which yielded promising results.

Postmortem Analysis of Vitreous Urea Nitrogen, Creatinine, and Magnesium of Renal and Post-Renal Disease in Cats.

Analysis of vitreous urea nitrogen (VUN) and creatinine (CREA) has been shown to be a useful indicator of azotemia in human postmortem examinations. Previous studies in cats, dogs, horses, and cattle have shown a good correlation between serum and postmortem ocular fluid for urea and creatinine. The aim of this study was to evaluate differences in VUN, CREA, and magnesium (MG) concentrations in vitreous humor collected postmortem from cats that presented with renal or post-renal disease and cats without renal or post-renal disease. Nine cats with renal or post-renal disease and twenty cats without renal or post-renal disease that underwent autopsy were used in this study. Collection of postmortem vitreous humor was performed, and vitreous samples were frozen at -80 °C for a minimum of 24 h prior to analysis using an in-clinic dry chemistry analyzer. Overall, there were statistically significant differences for VUN, CREA, and MG between cats with renal or post-renal disease and cats without renal or post-renal disease. Analysis of vitreous humor from cats suspected to have renal or post-renal disease can provide useful diagnostic information pertaining to renal function and issues in the urethra and urinary bladder. Future studies exploring postmortem vitreous chemistry in cats are warranted.

Ethylene glycol poisoning may be associated with elevated post-mortem vitreous glucose level

Ethylene glycol (EG) is a toxic chemical that is sometimes used as ethanol substitute. Besides the desired intoxicating effects, the intake of EG may often lead to death unless timely treatment measures are provided by medical professionals.We examined 17 fatal EG poisonings between 2016 and March 2022 in Finland in terms of forensic toxicology and biochemistry results and demographic information. Most of the deceased were male and the median (range) age was 47 (20–77) years. Of the cases, 6 were suicides, 5 accidents and in 7 cases the intent remained undetermined. In all cases, vitreous humour (VH) glucose was above the limit of quantitation 0.35 mmol/L (mean: 5.2 mmol/L; range 0.52–19.5 mmol/L). Other markers of the glycaemic balance were within the normal range in all except one case.As EG is not routinely screened for in most laboratories but only analysed in cases where the intake of EG is suspected, some fatal EG poisonings may remain unrecognised in post-mortem (PM) investigations. Although various conditions may induce hyperglycaemia, it is worthwhile keeping in mind that elevated PM VH glucose levels that cannot be otherwise explained may suggest intake of ethanol substitutes.

Vitreous Humor Biomarkers Reflect Pathological Changes in the Brain for Alzheimer's Disease and Chronic Traumatic Encephalopathy.

Patients with eye disease have an increased risk for developing neurodegenerative disease. Neurodegenerative proteins can be measured in the eye; however, correlations between biomarker levels in eye fluid and neuropathological diagnoses have not been established. This exploratory, retrospective study examined vitreous humor from 41 postmortem eyes and brain tissue with neuropathological diagnoses of Alzheimer's disease (AD, n = 7), chronic traumatic encephalopathy (CTE, n = 15), both AD + CTE (n = 10), and without significant neuropathology (controls, n = 9). Protein biomarkers i.e., amyloid-β (Aβ40,42), total tau (tTau), phosphorylated tau (pTau181,231), neurofilament light chain (NfL), and eotaxin-1 were quantitatively measured by immunoassay. Non-parametric tests were used to compare vitreous biomarker levels between groups. Spearman's rank correlation tests were used to correlate biomarker levels in vitreous and cortical tissue. The level of significance was set to α= 0.10. In pairwise comparisons, tTau levels were significantly increased in AD and CTE groups versus controls (p = 0.08 for both) as well as AD versus AD+CTE group and CTE versus AD+CTE group (p = 0.049 for both). Vitreous NfL levels were significantly increased in low CTE (Stage I/II) versus no CTE (p = 0.096) and in low CTE versus high CTE stage (p = 0.03). Vitreous and cortical tissue levels of pTau 231 (p = 0.02, r = 0.38) and t-Tau (p = 0.04, r = -0.34) were significantly correlated. The postmortem vitreous humor biomarker levels significantly correlate with AD and CTE pathology in corresponding brains, while vitreous NfL was correlated with the CTE staging. This exploratory study indicates that biomarkers in the vitreous humor may serve as a proxy for neuropathological disease.

Determination of postmortem interval and cause of death: Do the levels of biochemical parameters in vitreous humor provide an additional assistance to medico legal expert?

An upward rise has been observed in the pattern of unnatural deaths in the recent years and the same has been found during the post mortem examination. During the trial in the court of law prosecution as well as defense require the time passed death before examination and the cause of death in particular circumstances, as it is mandatory to fix the exact duration either to punish the guilty or NOT to punish the innocent. Vitreous humor is different from other body fluids as it has relative stability in its composition so as also biochemical parameters. It was further hypothesized that postmortem vitreous humor biochemistry closely mimics antemortem serum biochemistry and may be a useful aid in establishing postmortem diagnoses. Various studies have been carried out on vitreous electrolyte concentration changes to arrive at postmortem interval. Many workers found the importance of potassium in the determination of postmortem interval, whereas among all the biochemical parameters, vitreous potassium is found to be more useful to find out time since death. Postmortem biochemical analysis of vitreous humor may be helpful in the establishment of antemortem disease or metabolic disorder. The present study was carried out jointly in department of Forensic Medicine and Toxicology and department of Biochemistry of Surat Municipal Institute of Medical Education & Research (SMIMER), Surat. A total of 100 subjects were taken up for this study. The samples were collected from dead bodies during postmortem examination with all aseptic precautions. A detailed performa was made with all the details of age, sex, length, weight and date and time of admission, date and time of death and manner of death such as suicide, homicide, sudden death and accidents was recorded. Cases below 15 years of age were not considered in this study. Out of 100 cases there were 24 (24%) females and 76 (76%) were males, out of these 56% were between 15-35 years, 32% were of 36-55 years, 9% were of 56-65 years, and 3% were of 66-77 years age group. According to the manner of death 50 subjects were of accident, 26 subjects were of sudden death, 21 subjects were of suicide and 3 subjects were of homicide. According to time interval between sample collection and time of death, 47 subjects were of 0-24 hours, 36 subjects were of 24-48 hours, 11 subjects were of 48-72 hours and 6 subjects were of 72-96 hours. In present study we observed that there is definitive correlation between time of death and changes in level of these biochemical parameters. This was a preliminary study in this region and can be considered as a pilot study. The levels of vitreous Potassium have been found to be significantly altered as the time progresses after death. A progressive decrease in sodium/potassium and increase in potassium/ calcium ratios was also observed.

Use of vitreous humor electrolytes in estimating postmortem interval in infant population (

ABSTRACT Using post-mortem vitreous humour (VH) electrolyte in estimating the post-mortem interval (PMI) is not well studied in the infant population. We hypothesize that VH can be useful in estimating PMI in shorter PMI. This 5-year retrospective study investigated the changes in VH electrolytes (Na+, Cl− and K+) with respect to shorter PMI. This study examined PMI <48 hours and stratified the PMI into two groups (i.e. <24 hours and 24–48 hours). The electrolyte levels were compared and linear regression analysis was performed between the two groups. Our result showed that K+ increases with PMI and is a relatively good estimator (compared to adults) for PMI especially when PMI was <24 hours. Na+ and Cl− showed some evidence that they decrease with PMI but have no use in estimating PMI. The results from this study suggested K+ is useful in estimating PMI but limited to only when the PMI is <24 hours.

Spectroscopy as a useful tool for the identification of changes with time in post-mortem vitreous humor for forensic toxicology purposes

Vitreous humor (VH) is an alternative biological matrix with a great advantage of longer availability for analysis due to the lack of many enzymes. The use of VH in forensic toxicology may have an added benefit, however, this application requires rapid, simple, non-destructive, and relatively portable analytical analysis methods. These requirements may be met by Fourier transform infrared spectroscopy technique (FT-IR) equipped with attenuated total reflection accessory (ATR). FT-IR spectra of vitreous humor samples, deposited on glass slides, were collected and subsequent chemometric data analysis by means of Hierarchical Cluster Analysis and Principal Component Analysis was conducted. Differences between animal and human VH samples and human VH samples stored for diverse periods of time were detected. A kinetic study of changes in the VH composition up to 2 weeks showed the distinction of FT-IR spectra collected on the 1st and 14th day of storage. In addition, data obtained for the most recent human vitreous humor samples—collected 3 and 2 years before the study, presented successful discrimination of all time points studied. The method introduced was unable to detect mephedrone addition to VH in the concentration of 10 µg/cm3.Graphic abstract

Determination of Methadone and Tramadol in Vitreous Humor Specimens Using Dispersive LiquidLiquidMicroextractionandUltraHighPerformance Liquid Chromatography

Background: Drug abuse is spreading rapidly all over the world. Methadone and tramadol are among not only the most abused opioids but also important from the forensic point of view. Therefore, we need to devise a simple and sensitive method for the sample preparation and identification of abused drugs in postmortem specimens. Methods: A simple and rapid Dispersive Liquid-Liquid Microextraction (DLLME) technique coupled with Ultrahigh Performance Liquid Chromatography (UHPLC) was developed for the extraction and analysis of methadone and tramadol from postmortem vitreous humor samples. Different parameters affecting the extraction recovery, such as the type and volume of extraction and dispersion solvents, pH value, sensitivity, and specificity, were optimized and studied. Results: Under optimized conditions, the recovery ranges were 82.3%-89.6% and 85.4%-87.1% for methadone and tramadol, respectively. The linear range was 25-100 ng/mL for both methadone and tramadol with a correlation coefficient (R2) of more than 0.98. Limit of Detection (LoD) and Limit of Quantification (LoQ) were 3 and 8 ng/mL for methadone and 6 and 16 ng/mL for tramadol. The accuracy level of the methods for methadone and tramadol detection were 99.4%-100% and 99.7%-99.9%, respectively. The method was specific enough for the qualitative and quantitative determination of methadone and tramadol. Conclusion: The obtained results showed that DLLME combined with UHPLC is a fast and straightforward method for determining methadone and tramadol in postmortem vitreous humor specimens.

Postmortem Vitreous Humor Analysis in Dogs, Cats and Horses.

Postmortem chemistry can be a useful ancillary technique that the forensic pathologist can use during a death investigation. In stark contrast, there is limited information available for use of postmortem vitreous humor analysis in animals. In order to use postmortem vitreous humor in veterinary forensic investigations, validation of a method to analyze vitreous humor is required. The goal of this study was to determine the precision, bias, TEobs and sigma (σ) of the Element DC chemistry analyzer; assess its precision using the vitreous humor collected postmortem from dogs, cats and horses and assess the stability of postmortem vitreous humor from all the three species. Analysis of quality control material (QCM) and pooled vitreous humor samples for the three species was used to test for sodium (Na), chloride (Cl), potassium (K), magnesium (Mg), creatinine (Crea) and blood/vitreous urea nitrogen. Analysis of QCM showed that the Element DC was both precise and accurate. When analyzing the pooled vitreous humors, most within-run coefficients of variance (CVs) were found to be <5% and the between-run CVs for five out of six analytes were found to be <5% for dogs, cats and horses. In all the three species, the capped samples of vitreous humor were stable out of refrigeration for up to 5 h. The results of this study show that the Element DC can successfully be used to analyze the postmortem vitreous humor from dogs, cats and horses.

Acidic Drug Concentrations in Postmortem Vitreous Humor and Peripheral Blood.

Vitreous humor is a potential alternative matrix for postmortem toxicology drug screens when peripheral blood is unavailable. It is easily and reliably collected and may not suffer from the same postmortem redistribution as seen in blood. Here, we compared the concentrations of 7 acidic drugs (acetaminophen, ibuprofen, naproxen, salicylic acid, carbamazepine, phenobarbital and phenytoin) in peripheral blood and vitreous fluid collected in 89 autopsy cases. Analysis was done by high-performance liquid chromatography with diode-array detection. Overall, we found that vitreous drug concentrations were significantly lower than peripheral blood with median vitreous to peripheral blood (V/PB) ratios ranging from 0.0 to 0.6 (mean, 0.1-0.6). The correlations between the concentrations of over-the-counter analgesics in peripheral blood versus vitreous fluid were poor, with acetaminophen exhibiting the best linearity (R2=0.72). The antiepileptic drugs (carbamazepine, phenytoin and phenobarbital) exhibited good correlations between peripheral blood and vitreous humor, with all exhibiting an R2≥0.95. Overall, we have demonstrated the potential of vitreous fluid as an alternative matrix for the detection of select acidic drugs.

Elevation of Postmortem Cerebrospinal Fluid Sodium and Chloride Levels Is a Potential Adjunct Test in the Diagnosis of Salt Water Drowning.

Postmortem vitreous humor biochemistry is a useful test in the diagnosis of salt water drowning (SWD). A significant limitation of vitreous humor is the potential effect of prolonged immersion. A recent animal study and case report suggested that cerebrospinal fluid biochemistry may be an alternative to vitreous because it is more resistant to the effects of immersion, given its protected anatomical location. This study compared postmortem cerebrospinal fluid sodium and chloride (PMCSC) levels collected via ventricular aspiration (PMCSC_V) and via lumbar puncture (PMCSC_L) in 13 SWD and 31 nonimmersion deaths. It showed a significant elevation in PMCSC levels in SWD deaths for both PMCSC_V and PMCSC_L (P < 0.05). The areas under the curve on the receiver operating characteristic curves for PMCSC_V and PMCSC_L were 0.73 and 0.83, respectively. The optimal cutoff for PMCSC_V was 216 mmol/L (sensitivity, 0.60; specificity, 0.72; likelihood ratio, 1.80; positive predictive value, 0.45) and for PMCSC_L was 241 mmol/L (sensitivity, 0.78; specificity, 0.73; likelihood ratio, 2.89; positive predictive value, 0.46). This study supports PMCSC levels as another biochemical test that can potentially aid in the diagnosis of SWD, particularly in cases where vitreous humor samples are unavailable or uninterpretable.

Prospective Anaylysis of Electrolytic Changes in Vitreous Humour Regarding Estimation of Time Since Death

Prospective Anaylysis of Electrolytic Changes in Vitreous Humour Regarding Estimation of Time Since Death

Combining Postmortem Vitreous Sodium and Chloride and Lung-Body Ratio in Aiding the Diagnosing Saltwater Drowning

Diagnosing death due to drowning can be difficult, and several postmortem findings have been postulated to aid the diagnosis. Increased lung weights are often seen in drowning deaths. Lung-body (LB) ratio was described to be the best anatomical lung measurement in diagnosing drowning. Postmortem vitreous humor sodium and chloride (PMVSC) was reported to be a useful biochemical test in diagnosing saltwater drowning when the immersion time is less than 1 hour (SWD1). The presented study compared the diagnostic accuracies between LB ratio, PMVSC, and their combination in diagnosing SWD1 in 20 SWD1 and 50 nonimmersion deaths. Classification tree models were used for analysis and revealed that combination of PMVSC and LB ratio was most accurate in diagnosing SWD1 (misclassification rate, 4%), followed by PMVSC (misclassification rate, 10%) and LB ratio (misclassification rate, 24%). A quantifiable diagnostic improvement was established when both LB ratio and PMVSC were used. After adjusting for interlaboratory variations, the developed tree models can be a reliable way in aiding the diagnosis of SWD1.

Validation of the i-STAT®1 Analyzer for Postmortem Vitreous Humor Electrolytes and Glucose Analysis.

The analytical value of vitreous humor as a specimen in postmortem forensic toxicology has been known for some time. Numerous medical examiner laboratories outsource the analysis of this important specimen for electrolyte and glucose measurements. This can be both time-consuming and costly. The utility of the i-STAT®1 medical device to measure electrolytes and glucose in whole blood samples has been demonstrated for over two decades in a clinical setting through single-use disposable cartridges that introduce samples to the i-STAT®1. Different cartridge types allow for the analysis of various analytes including sodium, potassium, chloride, creatinine, urea nitrogen and glucose. With only 100 μL of sample, results are obtained in under 4 min. In this study, we utilized the i-STAT®1 using an alternative specimen matrix, postmortem vitreous humor and quantitatively determined the validity and reliability of the instrument for this purpose. Acceptable criterion was used for each test as suggested by the Scientific Working Group for Forensic Toxicology. All analytes of interest, except creatinine, demonstrated a percent error < ±10% for both accuracy and precision studies. Drug interference and stability studies were performed with many of the analytes demonstrating a percent error < ±20%. Throughout drug interference and stability studies, all analytes of interest were detectable except for potassium, which gave inconclusive results. Significant interference with commonly found drugs were shown for creatinine and chloride but must be evaluated carefully. Volume additions to ethanol spiked samples caused significant interference for all analytes and is considered a limitation for this method of analysis that requires additional studies. As vitreous humor continues to be used in forensic medicine to aid in diagnostic interpretation, the i-STAT®1 has the potential to give accurate results in a timely and cost-effective manner.

Ocular disposition of diazepam in rabbits: understanding its level in vitreous humour for forensic applications

The disadvantages associated with routine toxicological samples, such as blood samples, have encouraged the forensic toxicologist to use vitreous humour as an alternative matrix. However, its use is still limited. The reason for this is the lack of a systematic study in this domain. Moreover, the phenomena of drug disposition in ocular tissues are mostly unexplored. This paper presents a controlled study to investigate the distribution of diazepam in post-mortem blood, vitreous humour and ocular tissues using rabbit as an animal model. This study reveals that diazepam levels in vitreous and aqueous humour increase with their decrease in whole blood at post-mortem. A further study on the distribution of diazepam in ocular tissues reveals that the anterior and posterior segment tissues might be responsible for the increase in diazepam levels in aqueous humour and vitreous humour respectively. The present study strengthens the possibility of using vitreous humour as a complementary sample to blood in forensic toxicological investigations.

Immersion of Bovine Eyeballs After 1 Hour in Seawater Does Not Result in Elevation of Postmortem Vitreous Humor Sodium and Chloride Levels.

Elevations in postmortem vitreous sodium chloride (PMVSC) levels may help in differentiating saltwater/seawater drowning (SWD) deaths from immersion deaths not related to drowning (DNRD). It is unclear whether the elevation is related to blood/plasma electrolyte changes after inhalation of seawater as hypothesized in SWDs or possibly caused by electrolyte diffusion and/or osmosis across the outer coats of the eyeball during immersion. To investigate the changes in bovine PMVSC levels at different time points while immersed in seawater. Bovine eyeballs were obtained from an abattoir and randomized into 2 groups: a) submerged in seawater ("wet" group) or b) placed in an impermeable plastic bag that was immersed in seawater ("dry" group). The PMVSC levels from 6 eyeballs were measured from each group (without replacement) at 30 minutes, 1 hour, 6 hours, and 12 hours. There was no significant difference in mean PMVSC levels between the 2 groups at 30-minute and 1-hour intervals. A significant difference was noted from 6 hours onward. There is no statistically significant elevation in bovine PMVSC levels when immersed in seawater for up to 1 hour. Assuming similar physical properties in humans, any elevations in PMVSC levels in bodies immersed in seawater for less than 1 hour should not be caused by immersion.

Immersion of bovine eyeballs after one hour in seawater does not result in elevation of post-mortem vitreous humor sodium and chloride levels

Immersion of bovine eyeballs after one hour in seawater does not result in elevation of post-mortem vitreous humor sodium and chloride levels

Simultaneous analysis of biochemical markers in vitreous humour and serum: a preliminary study on the effect of storage time at –20°C

Vitreous humour (VH) is a quite stable and well-protected biological fluid from post-mortem degradation and contamination, making it a usable specimen in forensic pathology. We aimed to analyse the biochemical markers in VH stored for one month at –20°C and to compare them with those of serum samples of the same deceased people. To the best of our knowledge this is the first time this has been reported in the literature. Serum levels of sodium, potassium and calcium, phosphorous and VH levels of calcium, creatinine, and urea were not statistically different between fresh and stored samples. There was no significant difference in VH urea and creatinine levels whereas serum levels were significantly decreased by the 15th and 30th days. In conclusion, urea and creatinine levels in VH showed adequate stability after one month of storage at –20°C, whereas large variations were seen in the stability of inorganic components such as Na, K, Mg, Cl, and P. Our results indicate the validity of using post-mortem VH samples for urea and creatinine but not for VH stored at –20°C for a limited time frame. The differences in sample handling before being stored at –20°C may introduce bias on some components of VH.

Vitreous Humor: A Short Review on Post-mortem Applications

Vitreous humor has been investigated since the 1960s, with many debates occurring over the years with regard to the usefulness of its specific applications. The composition of several electrolytes in post-mortem vitreous humour has been extensively studied. Using the fluid for determining the cause of death has also become commonplace, including testing glucose levels of diabetic related deaths, as well as alcohol and drug related fatalities. The debate regarding the composition between two eyes of the same individual has been an issue in the past, but has since been resolved.

Estimation of time since death from electrolyte, glucose and calcium analysis of postmortem vitreous humour in semi-arid climate

Estimating time since death (TSD) with fair accuracy from postmortem changes still remains an important but difficult task to be performed by every autopsy surgeon in medicolegal scenario. The aim of the present study was to estimate TSD from electrolyte analysis of postmortem vitreous humour collected from samples under semi-arid climate. Vitreous humour was collected from 210 dead bodies brought to University College of Medical Sciences and Guru Teg Bahadur Hospital, Delhi, during the period of November 2010 to April 2012. The vitreous samples were analysed for sodium, potassium, calcium, chloride and glucose. The results showed a significant positive relationship between TSD and potassium (r = 0.841, p = 0.000) and a weak negative relationship between TSD and sodium (r = -0.137, p = 0.048) and glucose (r = -0.241, p = 0.000), whereas no significant relationship could be established between TSD and calcium (r = 0.055, p = 0.429) and chloride (r = 0.075, p = 0.11).