Alternative to xylene as a clearing agent in histopathology

Retrograde dye perfusion of the proximal aorta - A postmortem technical study

Introduction

Multiple cardiovascular conditions can lead to unexpected fatality, which is defined as sudden cardiac death. One of these potentially underlying conditions is aortic regurgitation, which can be caused by discrete changes of the geometry of the proximal aorta. To analyze aortic valve competency and furthermore to elucidate underlying pathological alterations of the coronary arteries and the vasa vasorum a perfusion method to simulate a diastolic state was designed.

Material and methods

A postmortem approach with retrograde perfusion of the ascending aorta with methylene blue was applied to three bodies. The procedure comprised cannulation of the brachiocephalic trunk, clamping of the aortic arch between brachiocephalic trunk and left carotid artery, infusion of 250 ml of methylene blue, and optical clearing of the superficial tissue layers after perfusion. Organs were examined directly following perfusion and after optical clearing.

Results

Assessment and visualization of aortic valve competency and the vasa vasorum were possible in all three instances. Visualization of the coronary perfusion was impaired by postmortem thrombus formation. Optical clearing did not provide additional information.

Discussion

The method presented here is a time- and cost-efficient way of visualizing aortic valve competency and the vasa vasorum. The visualization of the vasa vasorum highlights the potential of this method in basic research on diseases of the great arteries and coronaries. However, for a time-efficient functional analysis of the coronaries, other methods must be applied.

Automated variable power cold microwave tissue processing: A novel universal tissue processing protocol without using formaldehyde and xylene

The tissue processing technique is used to preserve the biological structure of tissue samples harvested from biopsy as closely as possible to their in vivo state for the diagnoses and study of disease on the cellular level. This process includes fixation, dehydration, clearing, paraffin infiltration. The protocol follows paraffin block embedding, microtome slicing, staining, and microscope slide studying. Tissue processing is a time-sensitive task as histopathologists must rapidly prevent the decomposition of tissue samples and promptly provide diagnoses on time. However, there are different tissue processing protocols for processing tissues with different types and sizes. Fatty tissues and tissues thicker than 1.5 mm are more susceptible to human errors when choosing a proper tissue processing protocol when preparing separate batches of tissues. In this research, a novel automated variable power cold microwave tissue processor was developed using a universal tissue processing protocol (processing time of 97 min) to simultaneously process all tissue types up to 4 mm in thickness. The tissue processor operated with a relatively smaller number of reagents without formaldehyde or xylene. These materials cause severe health and safety issues for humans and the environment. The quality of healthy and diseased processed tissues (sizes 1×1×1 to 24×15×4 mm) of fatty, thyroid, breast, placenta, skin, prostate, stomach, and bladder was examined under a light microscope by defining MAS (morphology, artifacts, and staining) criteria for evaluating cellular details, tissue arrangement, tissue integrity, stain uptake, and visual distinction of a tissue structure in light microscopy. It was found that the new tissue processor has successfully processed both healthy and diseased fatty and nonfatty tissue samples, while all tissue samples also met MAS criteria. Light microscopy showed outstanding integrity and arrangement in the tissue structures with an excellent visual distinction.

A Paraffin Microtomy Method for Improved and Efficient Production of Standardized Plastic Microfibers

Microfibers are one of the most abundant microplastic particle types found in the environment, where they cause negative impacts on organisms and possibly on human health. Microfibers should be included in a wide range of laboratory studies; however, microfibers for scientific studies are not commercially available. Current methods to make microfibers generally create particles with large size ranges and poor precision, and efficient production of particles ≤100 µm is difficult. Laboratory studies of the biological and toxicological effects and chemical interactions of microfibers require uniform, small microfibers in sufficient numbers for environmentally relevant experiments. We developed a novel fiber embedding technique and modified a seminal cryomicrotomy method to produce precise microfibers in quantities suitable for environmentally relevant concentrations. Polyethylene terephthalate (PET) and nylon fibers were strategically wound onto a spindle, embedded in paraffin wax, and sectioned using a standard paraffin microtome. After processing with a suitable organic solvent to remove the wax, microfiber size distributions were assessed. The small microfibers (10-42 µm) were accurate to the target lengths with excellent precision and a production rate ≥13.5 times higher than previous methods. As a proof of application, three lengths of manufactured PET fibers were stained with Nile red and exposed to eastern oyster larvae (Crassostrea virginica) for 24 h. Larvae ingested the smaller fiber lengths (14 and 28 µm), and the Nile red-stained fibers were visible and distinguishable in the guts of the larvae. This experiment was the first to demonstrate ingestion of plastic particles other than microspheres by oyster larvae. The present method facilitates the use of small microfibers in laboratory experiments, allowing for a more complete understanding of microplastic effects in the environment. Environ Toxicol Chem 2022;41:944-953. © 2021 SETAC.

Cedarwood oil as an alternative to xylene as a clearing agent in histopathological tissue processing - A comparative study

Background:

Clearing in histopathological tissue processing should be able to make the tissues translucent and clear for the tissues to be visible under light microscopy and should render the clearing agent to be miscible with the dehydrant and the impregnation wax in the preceding and following processing steps. Xylene is a gold standard clearing agent but increasing concerns about the potential carcinogenicity, implementing eco-friendly agents in routine histopathology is necessary.

Aim:

The aim of the study is to assess the clearing ability of Cedarwood oil as an alternative to Xylene in routine tissue processing.

Materials & Methods:

The study was carried out in the Department of Oral Pathology and Microbiology. Formalin fixed 50 tissue samples of size 3-7mm were taken and subsequent dehydration done with acetone and alcohol. The dehydrated tissue is later processed using 90ml of Cedarwood oil with few drops of Xylene and Thymol. After clearing the tissues were subjected to impregnation and embedded in paraffin wax, later which sections were made and stained using H & E stain.

Results:

The results of our study on comparison showed better outcome in tissues processed with cedarwood oil than xylene. Statistical Significant correlation was observed in nuclear staining (p value = 0.001) ; cytoplasmic staining (p value = 0.08) and background staining ( p value = 0.045) indicating a positive results on using cedarwood oil as clearing agent.

Conclusion:

The cedarwood oil can be considered as a safer natural alternative to xylene in laboratories. The cedarwood oil is eco - friendly and easily available with enhanced tissue processing qualities.

Cost and pollution by the use of xylene in cervical cytology in four Peruvian hospitals

Background: Cytological samples are cleared with xylene in two or three baths during a Pap test, however, this solvent has a high degree of toxicity, and being a controlled reagent infers high costs for its purchase and implications for environmental pollution. We estimated the impact of xylene during the Pap test in terms of the number of liters and cost of two baths of xylene, and also estimated the impact with three baths  Methods: This cross-sectional study was carried out in four hospitals of EsSalud in Peru in two stages. First, the analysis of the impact due to the use of two baths of xylene was conducted during the period 2015-2019, and second, the estimates were calculated based on the assumption of three baths of xylene for the years 2020-2025. The assumption was based on the recommendations of the 2018 EsSalud cytology guideline. The monthly amount of xylene was ~10 liters per bath/month and the cost per liter was estimated at 8.13 USD (27 soles).  Results: For the staining of 594,898 cytology tests, 7,848 liters of xylene were necessary, resulting in a cost of 60,861 USD (202,068 soles) during the period 2015-2019. The estimates showed a maximum assumption of 9,483 liters and 77,110 USD (256,040 soles) for the use of three baths of xylene in the four EsSalud hospitals (p = 0.0025) during the period 2020-2025.   Conclusions: We determined that there was a high economic impact of using xylene with two baths from 2015 to 2019 and a dramatic increase in costs with the possible use of three baths of xylene in the Pap test for the following five years.

Cost and pollution by the use of xylene in cervical cytology in four Peruvian hospitals

Background: Cytological samples are cleared with xylene in two or three baths during a Pap test, however, this solvent has a high degree of toxicity, and being a controlled reagent infers high costs for its purchase and implications for environmental pollution. We estimated the impact of xylene during the Pap test in terms of the number of liters and cost of two baths of xylene, and also estimated the impact with three baths  Methods: This cross-sectional study was carried out in four hospitals of EsSalud in Peru in two stages. First, the analysis of the impact due to the use of two baths of xylene was conducted during the period 2015-2019, and second, the estimates were calculated based on the assumption of three baths of xylene for the years 2020-2025. The assumption was based on the recommendations of the 2018 EsSalud cytology guideline. The monthly amount of xylene was ~10 liters per bath/month and the cost per liter was estimated at 8.13 USD (27 soles).  Results: For the staining of 594,898 cytology tests, 7,848 liters of xylene were necessary, resulting in a cost of 60,861 USD (202,068 soles) during the period 2015-2019. The estimates showed a maximum assumption of 9,483 liters and 77,110 USD (256,040 soles) for the use of three baths of xylene in the four EsSalud hospitals (p = 0.0025) during the period 2020-2025.   Conclusions: We determined that there was a high economic impact of using xylene with two baths from 2015 to 2019 and a dramatic increase in costs with the possible use of three baths of xylene in the Pap test for the following five years.

Cost and pollution by the use of xylene in cervical cytology in four Peruvian hospitals

Background: Cytological samples are cleared with xylene in two or three baths during a Pap test, however, this solvent has a high degree of toxicity, and being a controlled reagent infers high costs for its purchase and implications for environmental pollution. We estimated the impact of xylene during the Pap test in terms of the number of liters and cost of two baths of xylene, and also estimated the impact with three baths  Methods: This cross-sectional study was carried out in four hospitals of EsSalud in Peru in two stages. First, the analysis of the impact due to the use of two baths of xylene was conducted during the period 2015-2019, and second, the estimates were calculated based on the assumption of three baths of xylene for the years 2020-2025. The assumption was based on the recommendations of the 2018 EsSalud cytology guideline. The monthly amount of xylene was ~10 liters per bath/month and the cost per liter was estimated at 8.13 USD (27 soles).  Results: For the staining of 594,898 cytology tests, 7,848 liters of xylene were necessary, resulting in a cost of 60,861 USD (202,068 soles) during the period 2015-2019. The estimates showed a maximum assumption of 9,483 liters and 77,110 USD (256,040 soles) for the use of three baths of xylene in the four EsSalud hospitals (p = 0.0025) during the period 2020-2025.   Conclusions: We determined that there was a high economic impact of using xylene with two baths from 2015 to 2019 and a dramatic increase in costs with the possible use of three baths of xylene in the Pap test for the following five years.

Exposure and Management of the Health Risk for the Use of Formaldehyde and Xylene in a Large Pathology Laboratory

BACKGROUND

Formaldehyde and xylene are two hazardous chemicals widely used in pathology laboratories all over the world. The aim of this work was to survey a large volume pathology lab, measuring exposure of workers and residents to formaldehyde and xylene, and verify the efficacy of the undertaken preventive actions and the accomplishment with occupational limit values.

METHODS

Environmental, personal, and biological monitoring of exposure to formaldehyde and xylene in different lab rooms and in 29 lab attendants was repeated yearly from 2017 to 2020. Continuous monitoring of airborne formaldehyde was performed to evaluate the pattern of airborne concentrations while specific tasks were performed. Several risk management and mitigation measures, including setting a new grossing room, reducing the number of samples to be soaked in formaldehyde, and improving the lab practices and equipment, such as the use of chemical hoods, were undertaken after each monitoring campaign, based on the results obtained from the exposure monitoring.

RESULTS

Significant exposures to formaldehyde in pathologists and residents, especially during the grossing of samples, were observed in the first 2 years, with exposure exceeding the occupational exposure limit value; the following surveys showed that the risk management and mitigation measures were effective in reducing airborne concentrations and personal exposure. Xylene, assessed with both environmental and biological monitoring, was always well below the occupational exposure limit value and biological limit values, respectively.

CONCLUSION

Critical exposure to air formaldehyde in attendants of a pathology laboratory could be reduced with the re-organization of lab spaces, new and improved work procedures, and awareness and training initiatives.

A substitute to xylene in deparaffinization and clearing prior to coverslipping in histopathology

INTRODUCTION:

Deparaffinization and clearing prior to coverslipping are important steps in all staining methods in histopathology. Xylene is the most commonly used agent worldwide. However, xylene is toxic. We evaluated safer alternative dewaxing and clearing agents prior to coverslipping in a histopathology laboratory.

MATERIALS AND METHODS:

Thirteen different fresh surgical tissues were cut into two halves. One half processed using xylene and the other half processed using UltraClear™. Five groups were designed. For each Group of A, B, C, and D, 100 slides were cut from xylene-processed blocks. For Group E, 100 slides were cut from UltraClear™-processed blocks. Group A is the standard method. Group B evaluates UltraClear™ as a dewaxing agent only. Group C evaluates UltraClear™ as a clearing agent prior to coverslipping only. Group D evaluates UltraClear™ as both dewaxing and clearing agents prior to coverslipping. Group E evaluates UltraClear™ as both dewaxing and clearing agents prior to coverslipping. Six parameters were evaluated: nuclear staining, cytoplasmic staining, cell morphology, clarity of staining, uniformity of staining, and cost.

RESULTS:

Groups B, C, and D showed 79% (P = 0.054), 83% (P = 0.221), and 80% (P = 0.079) adequacy when compared with Group A (89%), respectively. However, Group E showed only 76% (P = 0.016) adequacy. UltraClear™ is more expensive than xylene.

CONCLUSION:

UltraClear™ is a promising dewaxing agent. It is also a good clearing agent for use prior to coverslipping in histopathology laboratory. Cost-benefit balance between safety of laboratory workers, good quality staining, and cost-effective strategy needs to be further studied.