Formalin pigment artifact deposition in autopsy tissue: predisposing factors, patterns of distribution and methods for removal.

Formalin pigment deposition is a known artifact of autopsy histology, often anecdotally associated with decomposition of bodies. However, there is minimal data within the forensic literature demonstrating an association between formalin pigment deposition and length of postmortem interval. Furthermore, there is minimal data concerning other predisposing factors and patterns of distribution of formalin pigment deposition. In this study, we compare the amount and patterns of formalin deposition on histology slides from three categories of death: 1) decomposed bodies, 2) critically ill at time of death, and 3) sudden cardiac death. We also compare the effectiveness of two relatively simple histology laboratory methods to remove formalin pigment deposition from histology slides. Amongst the three categories of death, formalin deposition was highest in the decomposed category, second highest in the critically ill category, and lowest in the sudden cardiac death category. The organs most severely affected by formalin deposition were liver/spleen/pancreas and kidneys, and the organs least affected were brain and lung. Formalin pigment deposition correlated with length of postmortem interval. Histologic patterns of formalin deposition included the endothelial lining of vessels, perinuclear compartment of neurons and myocytes, and the basal epithelial compartment of renal tubular epithelial cells. The alcoholic ammonium hydroxide method (AAH) was slightly more effective than the alkylphenol ethoxylate (APE) method for removing formalin pigment, though both methods were effective. Because formalin pigment is strongly refractile under polarized light, a polarization filter can also be useful for distinguishing formalin pigment from other pigments.

The bottom-up approach to bounding potential low-dose cancer risks from formaldehyde: An update.

In 2013, we proposed a novel bottom-up approach to bounding low-dose cancer risks that may result from small exogenous exposures to chemicals that are always present in the body as a result of normal biological processes. The approach utilizes the background cancer risk and the background (endogenous) concentration of a cancer-related exposure biomarker in specific target tissues. After allowing for statistical uncertainty in these two parameters, the ratio of the background risk to background exposure provides a conservative slope factor estimate that can be utilized to bound the added risk that may be associated with incremental exogenous exposures. Our original bottom-up estimates were markedly smaller than those obtained previously by the US Environmental Protection Agency (USEPA) with a conventional top-down approach to modeling nasopharyngeal cancer and leukemia mortality data from a US worker cohort. Herein we provide updated bottom-up estimates of risk for these two cancers that are smaller still, and rely upon more robust estimates of endogenous and exogenous formaldehyde-DNA adducts in monkeys and a more robust estimate of the DNA adduct elimination half-life in rats, both obtained very recently. We also re-examine the worker mortality data used by USEPA in developing its estimate of human leukemia incidence from lifetime exposure to 1 ppm airborne formaldehyde. Finally, we compare a new bottom-up slope estimate of the risk of rat nasal cancer with conventional top-down estimates obtained with empirical dose-response modeling of rat nasal cancer bioassay data.

Aldehyde fixative solutions alter the water relaxation and diffusion properties of nervous tissue.

Chemically-fixed nervous tissues are well-suited for high-resolution, time-intensive MRI acquisitions without motion artifacts, such as those required for brain atlas projects, but the aldehyde fixatives used may significantly alter tissue MRI properties. To test this hypothesis, this study characterized the impact of common aldehyde fixatives on the MRI properties of a rat brain slice model. Rat cortical slices immersion-fixed in 4% formaldehyde demonstrated 21% and 81% reductions in tissue T(1) and T(2), respectively (P < 0.001). The T(2) reduction was reversed by washing slices with phosphate-buffered saline (PBS) for 12 h to remove free formaldehyde solution. Diffusion MRI of cortical slices analyzed with a two-compartment analytical model of water diffusion demonstrated 88% and 30% increases in extracellular apparent diffusion coefficient (ADC(EX)) and apparent restriction size, respectively, when slices were chemically-fixed with 4% formaldehyde (P

Are one or two dangerous? Methyl salicylate exposure in toddlers.

Serious toxicity can result from exposure to small amounts of methyl salicylate. Methyl salicylate is widely available as a component in many over-the-counter brands of creams, ointments, lotions, liniments and medicated oils intended for topical application to relieve musculoskeletal aches and pains. Among the most potent forms of methyl salicylate is oil of wintergreen (98% methyl salicylate). Other products with varying concentrations of methyl salicylate are ubiquitous throughout many parts of the world, including a number of products marketed as Asian herbal remedies. The toxic potential of all of these formulations is often underestimated by health care providers and the general public. A comprehensive review of the existing medical literature on methyl salicylate poisoning was performed, and data compiled over the past two decades by the American Association of Poison Control Centers (AAPCC) was examined. Methyl salicylate continues to be a relatively common source of pediatric exposures. Persistent reports of life-threatening and fatal toxicity were found. In children less than 6 years of age, a teaspoon (5 mL) or less of oil of wintergreen has been implicated in several well-documented deaths. More needs to be done to educate both health care providers and the general public regarding the dangers of these widely available formulations.

Detection of nitric oxide in the guinea pig inner ear, using a combination of aldehyde fixative and 4,5-diaminofluorescein diacetate.

Localization of nitric oxide (NO) production sites in the inner ear of the guinea pig was investigated using a combination of glutaraldehyde fixative and a new fluorescence NO indicator. 4,5-diaminofluorescein diacetate (DAF-2DA). The cochlea and vestibular end organs were examined to locate NO production sites. The fluorescence persisted after glutaraldehyde fixation and embedding with water-soluble resin. NO production in the cochlea was observed in the outer and inner hair cells, nerve endings, nerve fibers and supporting cells of the organ of Corti, stria vascularis, spiral ligament, ganglion cells, etc. In the vestibular end organs, both type I and type II sensory cells, nerve fibers, blood vessels and dark cells displayed fluorescence. This localization was exactly identical to that of NO synthase. Thus, detection of intracellular NO production by using a combination of glutaraldehyde fixation and DAF-2DA is useful for examining the function of NO in cells, both in situ and in vivo.

Potentiation of warfarin anticoagulation associated with topical methyl salicylate.

OBJECTIVE: To report a case of international normalized ratio (INR) elevation resulting from the administration of topical methyl salicylate in a patient whose INR was previously stable while she received warfarin anticoagulation. CASE SUMMARY: A 22-year-old white woman presented with an INR of 12.2 after applying a topical pain-relieving gel to her knees daily for eight days. The potentiation of the warfarin anticoagulation was attributed to the low-dose methyl salicylate contained in the product. DISCUSSION: Methyl salicylate is systemically absorbed through the skin in measurable amounts, and may increase warfarin action by affecting vitamin K metabolism or by displacing warfarin from protein-binding sites. While several investigators have reported this interaction with use of high-dose methyl salicylate, this case indicates that a significant interaction can occur with the use of lower topical doses of methyl salicylate as well. CONCLUSIONS: Healthcare providers and patients taking warfarin must be aware of the potential hazard of using topical methyl salicylate in combination with warfarin.

Metabolism and disposition of dimethyl hydrogen phosphite in rats and mice.

A study of dimethyl hydrogen phosphite (DMHP) by the National Toxicology Program (NTP) indicated that chronic administration by oral gavage resulted in an increased incidence of neoplastic lesions in the lungs and forestomachs of Fischer 344 rats but not in B6C3F1 mice. The current study was designed to evaluate the metabolic basis, if any, of this species selectivity by studying the metabolism and disposition of [14C]DMHP in the respective strains of rats and mice. Results of this study indicate that DMHP administered at a range of dose of 10-200 mg/kg was readily and near completely absorbed from the gastrointestinal tracts of rats and mice. DMHP-derived radioactivity was eliminated primarily as CO2 in the expired air, 44-57%, and urine, 28-49%, and very little was collected in feces, 1-2%, or as volatile organics, 2-3%. DMHP-derived radioactivity was widely distributed in tissues of rats and mice, with the highest concentrations observed in the liver, kidneys, spleen, lungs, and forestomach, and the lowest in brain, skeletal muscle, and adipose tissue. The disappearance of radioactivity from mouse tissues was approximately twice as rapid as from rat tissues. In vitro, DMHP was metabolized to formaldehyde by the microsomal fractions of liver, lungs, kidneys, forestomach, and glandular stomach. In vivo, DMHP was metabolized to the product of demethylation, monomethyl hydrogen phosphite (MMHP), which was excreted in urine. Results of this study indicate that the NTP carcinogenicity study with DMHP was carried out within the dose range in which the absorption, metabolism, and disposition of DMHP are linear in both species. Apparent species-dependent differences in the metabolism and disposition of DMHP are limited to the more rapid metabolism and elimination by the mouse. Therefore, the species-dependent variations in the carcinogenicity of DMHP are most likely attributable to factors other than metabolism and disposition.

Critical time of exposure of the rabbit inferior alveolar nerve to Carnoy's solution.

To reduce the recurrence of keratocysts, tanning of the epithelial lining with modified Carnoy's solution has been advocated as an ancillary procedure. This agent has occasionally been reported to induce long-lasting local neurotoxicity, when the inferior alveolar nerve (IAN) was located within the bony cavity of larger cysts. As the severity of the neurologic damage depends on the tissue penetration of the solution, a critical exposure time must be assumed. To substantiate this hypothesis, rabbit IANs were decorticated over an approximate length of 1 cm and soaked with modified Carnoy's solution for periods from 30 seconds to 10 minutes. Sensory nerve function was monitored using somatosensory evoked potentials. Exposures up to 2 minutes did not result in any electrophysiologic abnormality. Exposure for 3 minutes led to either normal or rudimentary evoked potentials. After exposure of 5 minutes, and invariably after 10 minutes, the evoked potentials from the IAN were absent. Nerve segments were removed for histologic examination and the penetration depth of the Carnoy's solution was identified by staining with the Berlin-blue reaction. The involved areas were morphometrically evaluated and they reflected the electrophysiological findings. Transmission electron microscopy showed morphologic changes confined to the outer nerve sheaths (epineurium and perineurium) after exposure of 3 minutes. Exposure of 5 minutes and longer resulted in involvement of both the nerve sheaths and their axonal contents, with disruption and disintegration of the neural tissue. This study clearly supports the hypothesis that contact of a peripheral nerve (ie, IAN) with Carnoy's solution carries a time-related risk to produce acute sensory impairment.(ABSTRACT TRUNCATED AT 250 WORDS)

Glutaraldehyde in dentistry--a review.

The disinfective and fixative properties of glutaraldehyde are now widely investigated. Glutaraldehyde is effective against micro-organisms and their spores. Recently, studies have shown the effectiveness of glutaraldehyde against the HIV virus. 2% glutaraldehyde is now recommended for the sterilisation of surgical instruments, operating areas, dental impressions and root canals during endodontic therapy. Studies have also shown that glutaraldehyde is an effective fixative with minimum side effects, limited penetration and quick acting. Pulpotomy studies using glutaraldehyde as the fixative agent produce high success rates. The important feature is the vital pulpal tissue at the apical third suggesting its limited penetration. The small amounts that get distributed systemically are quickly metabolised and excreted in the urine or exhaled as carbon dioxide.

Penetration of glutaric dialdehyde into human dentine as measured by changes in dentine microhardness and dentine dimensions.

Microhardness indentation lengths were measured on human dentine sections unfixed and fixed with glutaric dialdehyde (GDA) at pH 7. Fixed dentine was found to be softer than unfixed dentine. Indentation length increased by approximately 10% after fixation in a buffered 5% GDA solution at pH 7. Using this effect the variation of indentation length in the direction of the penetrating GDA as a function of fixation time was measured. Describing the penetration in the mineralized matrix as diffusion in a plane sheet, a diffusion coefficient of 0.5.10(-12); m2/s was calculated. Dimensional changes of the dentine due to fixation were also measured. Dentine was found to expand in both the direction parallel (approximately 0.4%) and perpendicular (approximately 2%) to the tubules.

Diffusion barriers impeding the flow of solutes to the ciliary body epithelium during immersion fixation of rabbit eyes. Assessment of ultrastructural preservation quality by examination of mitochondrial profiles in the electron microscope.

Various manipulations of rabbit anterior eye segments were carried out during the initial stages of glutaraldehyde fixation in order to assess the contribution made by particular tissues in restricting the flow of solutes to the ciliary body epithelium. Ultrastructural preservation quality was monitored by inspection of mitochondrial profiles. These organelles are structurally extremely sensitive to environmental disturbances, and hence changes in their morphological appearance may be used as an early indication of such adverse conditions. The results indicate that the principal barriers to diffusion are represented by the vitreous, posteriorly, and by the cornea at the anterior face. Since the cortical vitreous is strongly attached to the inner basement membrane of the ciliary epithelium, its removal may cause damage to this layer. A simpler and equally effective means of improving flow of fixative to the ciliary epithelium is to remove the cornea.

Kinetics of glutaraldehyde fixation of erythrocytes: size, deformability, form, osmotic and hemolytic properties.

Red blood cells interact with glutaraldehyde (GA) in a complex kinetic pattern of events. At a given GA concentration in phosphate buffered saline (PBS), the sequence of cell 'volume' response, as measured by resistive pulse spectroscopy (RPS), includes: an immediate response to the overall solution osmolality; a constant volume, latent phase; a rapid swelling phase; an intermediate constant volume phase; and a shrinkage phase to a final steady state volume. The final volume depends on fixative solution osmolality; for GA concentrations between 0.05% and 0.25% w/v, fixative osmolalities of less than 355 mosM, including 'isotonic', or greater than 355 mosM, lead to final cell volumes greater or less than native, respectively. Cell-membrane deformability decreases continuously and monotonically with time, as assessed by RPS. The rate of fixation is a direct function of GA concentration, in accordance with a derived empirical expression. The measured kinetic responses are related to considerations of cell size, deformability, and form, and to mechanisms involved in abrupt osmotic hemolysis.