Impact of the quality of resected thyroid cancer tissue sample on next-generation sequencing testing.

Activating rearranged during transfection (RET) proto-oncogene alterations can be identified using next-generation sequencing (NGS) of tumor DNA/RNA. We assessed factors associated with NGS (Oncomine Dx Target Test [ODxTT]) success for resected thyroid cancer (TC) specimens, including sample age, processing conditions, and DNA/RNA quality. TC samples were from three Japanese hospitals, with sample age <1-<10 years, fixative 10%/15% neutralized buffered formalin (NBF), and fixation time ≤48 h/>48 h-≤72 h. NGS success rate was defined as the percentage of samples returning validated NGS results (RET fusion-positive/negative [RNA] or RET mutation-positive/negative [DNA], detected using ODxTT). DNA/RNA quality was assessed with indexes based on electrophoresis (DNA/RNA integrity number, DV200 ) and quantitative polymerase chain reaction (DNA/RNA integrity score [ddCq/ΔCq]). NGS success rate (N = 202) was 90%/93% (DNA/RNA) overall, 98%-100% (DNA and RNA) for samples <3 years old, and 91% (DNA and RNA) for samples ≥3-<5 years old fixed in 10% NBF for ≤48 h. Multivariate logistic regression analysis identified ddCq and ΔCq as significant predictors of DNA and RNA NGS success rates, respectively. Quality assessment of nucleic acid extracted from archival tissue samples is important for achieving high NGS success rates in clinical practice, especially for samples ≥3 years old.

Human umbilical cord blood cells suffer major modification by fixatives and anticoagulants.

Introduction: Developing techniques for the tagless isolation of homogeneous cell populations in physiological-like conditions is of great interest in medical research. A particular case is Gravitational Field-Flow Fractionation (GrFFF), which can be run avoiding cell fixation, and that was already used to separate viable cells. Cell dimensions have a key role in this process. However, their dimensions under physiological-like conditions are not easily known since the most diffused measurement techniques are performed on fixed cells, and the fixation used to preserve tissues can alter the cell size. This work aims to obtain and compare cell size data under physiological-like conditions and in the presence of a fixative. Methods: We developed a new protocol that allows the analysis of blood cells in different conditions. Then, we applied it to obtain a dataset of human cord blood cell dimensions from 32 subjects, comparing two tubes with anticoagulants (EDTA and Citrate) and two tubes with different preservatives (CellRescue and CellSave). We analyzed a total of 2071 cells by using confocal microscopy via bio-imaging to assess dimensions (cellular and nuclear) and morphology. Results: Cell diameter measured does not differ when using the different anticoagulants, except for the increase reported for monocyte in the presence of citrate. Instead, cell dimensions differ when comparing anticoagulants and cell preservative tubes, with a few exceptions. Cells characterized by high cytoplasm content show a reduction in their size, while morphology appears always preserved. In a subgroup of cells, 3D reconstruction was performed. Cell and nucleus volumes were estimated using different methods (specific 3D tool or reconstruction from 2D projection). Discussion: We found that some cell types benefit from a complete 3D analysis because they contain non-spherical structures (mainly for cells characterized by poly-lobated nucleus). Overall, we showed the effect of the preservatives mixture on cell dimensions. Such an effect must be considered when dealing with problems highly dependent on cell size, such as GrFFF. Additionally, such information is crucial in computational models increasingly being employed to simulate biological events.

Nationwide differences in cytology fixation and processing methods and their impact on interlaboratory variation in PD-L1 positivity.

Programmed death ligand-1 (PD-L1) immunostaining, which aids clinicians in decision-making on immunotherapy for non-small cell lung cancer (NSCLC) patients, is sometimes performed on cytological specimens. In this study, differences in cytology fixation and cell block (CB) processing between pathology laboratories were assessed, and the influence of these differences on interlaboratory variation in PD-L1 positivity was investigated. Questionnaires on cytology processing were sent to all Dutch laboratories. Information gathered from the responses was added to data on all Dutch NSCLC patients with a mention of PD-L1 testing in their cytopathology report from July 2017 to December 2018, retrieved from PALGA (the nationwide network and registry of histo- and cytopathology in the Netherlands). Case mix-adjusted PD-L1 positivity rates were determined for laboratories with known fixation and CB method. The influence of differences in cytology processing on interlaboratory variation in PD-L1 positivity was assessed by comparing positivity rates adjusted for differences in the variables fixative and CB method with positivity rates not adjusted for differences in these variables. Twenty-eight laboratories responded to the survey and reported 19 different combinations of fixation and CB method. Interlaboratory variation in PD-L1 positivity was assessed in 19 laboratories. Correcting for differences in the fixative and CB method resulted in a reduction (from eight (42.1%) to five (26.3%)) in the number of laboratories that differed significantly from the mean in PD-L1 positivity. Substantial variation in cytology fixation and CB processing methods was observed between Dutch pathology laboratories, which partially explains the existing considerable interlaboratory variation in PD-L1 positivity.

The effect of different combinations of fixatives and decalcifying agents on rat and rabbit hard tissues, a guide for histologic processing.

BACKGROUND AND PURPOSE: In order to acquire the best method that can simultaneously maximize tissue morphology and staining quality, we compared the effect of different fixative and decalcifying solutions on the quality of rabbit and rat bone histology. METHOD: Fifty-four rat hemimaxillae and 54 rabbit quarter-parietal bones were allocated into 3 fixation groups (formalin, 10 %sodium-phosphate-buffered-formalin and 10 %calcium-phosphate-buffered-formalin). Each fixative was divided into 6 groups and decalcified with 5 % and 10 % nitric acid (NA), 5 % and 10 % formic acid (FA), Gooding-Stewart liquid (GSL) and EDTA. Slide quality was evaluated on hematoxylin/eosin slides by 3 observers and mean-scores for total-cell-characteristics (TCC) and total-tissue-characteristics (TTC) were statistically analyzed. RESULT: Significant differences in decalcification-time were observed in different combinations of decalcifiers and fixatives in both animals. In rats, TCC was better preserved when using 10 %NA/calcium-phosphate-buffered-formalin compared to 10 %NA/sodium-phosphate-buffered-formalin (P = 0.03). GSL/sodium-phosphate-buffered-formalin performed better than both other fixatives (P < 0.001). TCC differed among the decalcifiers in each of the fixatives. In rabbits, there were differences in TCC among the decalcifiers when formalin (P = 0.001) and sodium-phosphate-buffered-formalin (P = 0.01) were used. TTC only showed significant difference when 10 %FA was used in rats (P = 0.044), with formalin performing better than sodium-phosphate-buffered-formalin (P = 0.01). CONCLUSION: Based on our results, if time is an issue, 10 %NA/calcium-phosphate-buffered-formalin could provide good cellular quality and if time is not a consideration, FA (5 % or 10 %) with sodium-phosphate-buffered-formalin followed by EDTA with formalin, would have the best performance. In rabbits, GSL provides the fastest results, regardless of the fixative and FA/sodium-phosphate-buffered-formalin gives the best cellular quality.

Honey as a Cytological Fixative: A Comparative Study With 95% Alcohol.

Background Ninety-five percent (95%) ethyl alcohol (ethanol) has been used as a standard cytological fixative but it is expensive, difficult to procure, and has addictive properties. Alternate substitutes like methanol, which give similar results to ethanol, have toxic potential. Honey, a known preservative, is an eco-friendly fixative and is of great value when ethanol is unavailable and economizing on cost is necessary. The present study was done to assess and compare the fixation property and cytomorphological features of smears fixed in 20% honey in comparison to 95% ethyl alcohol and to determine whether the former can be used as an alternative cytological fixative in routine practice. Material and methods The present prospective study was done in the cytology section of the Department of Pathology for one and a half years on 300 cytological samples comprising 100 samples each of various body fluids (peritoneal, pleural, bronchoalveolar lavage, and urine), cervical smears, and fine-needle aspiration samples. The smears from all the 300 cytological samples were fixed separately in 95% ethanol and 20% unprocessed natural honey for a minimum of 15 minutes and were then stained with Papanicolaou (Pap) stain. The cytomorphological parameters of both the smears were compared based on set criteria. Relevant statistical analysis was done using the student t-test, chi-square test, and test of agreement (kappa statistics). Results A comparable and good-quality staining pattern, preservation of morphology, and crisp nuclear and cytoplasmic staining were observed between the two fixatives for all three types of samples with a strong agreement between them (kappa value varying between 0.896 and 0.942) and a p-value of <0.05. Conclusion Natural honey is a readily available and non-toxic alternative to ethanol as a cytological fixative and can be used in routine practices, especially in resource-constrained settings.

Nuances of the Papanicolaou stain.

The impressive list of achievements of Dr. G. N. Papanicolaou and his tedious journey from normal to abnormal human cell includes the importance of wet fixation of cells and the development of the unique polychromatic Pap stain. The 5-dye Pap stain method evolved through 2 salient phases. The first being the development of wet fixation using alcohol-ether to enhance cellular transparency and the second phase saw the introduction of various cytoplasmic counterstaining methods using orange G and EA (light green, Bismarck brown, eosin) and phosphotungstic acid, facilitating the distinction of cell types. The specific characteristics of the staining method is, the cellular transparency combined with crisp nuclear staining, achieved through tailored cellular fixation and cytoplasmic staining using variable dye and pH combinations. With little modifications if any the Pap stain continues to be applied uniformly globally. However, institutional supply of dyes and chemicals from different companies make minor modifications, that remain consistent, an essential part of the staining protocol. This chapter describes the preparation and principles of various components of the stain that are being currently used in our department.

Development of a fixative protocol using formaldehyde and gluteraldehyde for preservation of microbial art on agar plates.

AIMS: Agar art bridges the gap between science and art using microbes instead of paint. Afterwards, the art can change in response to microbial fluctuation, meaning preservation of the original art is essential. Here, formaldehyde and glutaraldehyde were investigated as preservatives, involving techniques used in healthcare settings to preserve samples. METHODS AND RESULTS: Formaldehyde was tested at 1.0%, 2.0% and 3.7%, w/v, whereas glutaraldehyde was tested at 1% and 2.5%, w/v. Both compounds and respective concentrations were tested for different time periods. Escherichia coli, Serratia marcescens, Staphlococcus aureus and Micrococcus luteus were used as bacteria for "drawing" the works of art. The effectiveness of fixation was determined using integrated densities and visual assessment. Initially, both compounds showed potential promise, albeit with a loss of bacteria. Ser. marcescens was prone to colour changes and glutaraldehyde caused discolouration of agar and bacteria. These could be caused by a pH decrease in the agar, due to residual free aldehyde groups. Reduction of this was tested using 300 mM sodium metabisulfite to neutralize excess aldehydes. This initially led to reduced bacterial loss and avoided colour changes, however measurements 24 h post-fixation showed colour loss to some bacterial clusters. CONCLUSIONS: Here, at least 2% formaldehyde for a short fixation period, typically 1 min, depending on the species, was most promising for the preservation of art. Given the success of this with different bacteria, it would make a good starting combination for anyone trying to fix agar art, although methodology refinement may be needed for optimisation depending on the bacterial species used. SIGNIFICANCE AND IMPACT OF STUDY: This study shows, for the first time, successful fixation and preservation of different bacterial species on agar. The impact of this is to preserve agar art while making it safe and non-infective to those in contact with the microbial art.

Histology of human teeth: Standard and specific staining methods revisited.

OBJECTIVE: Histological techniques have long been an integral part of dental research. Especially the processing of complex tissues poses specific challenges, however, literature offers only few technical references. Objectives of this study were therefore to optimize histological staining methods and compile detailed protocols for preparation and staining of dental tissues. METHODS: Human teeth were collected and fixed with 4 % formaldehyde solution after extraction. Subsequently, teeth were decalcified in 17 % EDTA or Morse's solution over a period of 28 days. The extent of decalcification was determined by weight loss and radiography. After sectioning, histological staining methods were optimized for their use on teeth. These included hematoxylin-eosin, Masson trichrome, Masson-Goldner trichrome and May-Gruenwald-Giemsa staining. Nerve fibres were visualized by luxol fast blue staining and Bodian silver staining. In addition, specific methods like TRAP, modified Brown and Brenn as well as picrosirius red staining with light polarization or fluorescence were applied and optimized. RESULTS: Preparation of an artificial access to the pulp chamber was essential to ensure prompt penetration of the chemicals. Decalcification with Morse's solution took at least two weeks but was more efficient than 17 % ETDA, where thorough demineralization was achieved only after three weeks. The staining methods exhibited differences not only regarding their ability to display specific structures of interest, but also in terms of reproducibility. CONCLUSION: High-quality histology of teeth can only be achieved after optimal tissue preparation and accurate staining. A complementary use of staining techniques is necessary to answer specific research questions.

Antibodies validated for routinely processed tissues stain frozen sections unpredictably.

Background: Antibody validation for tissue staining is required for reproducibility; criteria to ensure validity have been published recently. The majority of these recommendations imply the use of routinely processed (formalin-fixed, paraffin-embedded) tissue. Materials & methods: We applied to lightly fixed frozen sections a panel of 126 antibodies validated for formalin-fixed, paraffin-embedded tissue with extended criteria. Results: Less than 30% of the antibodies performed as expected with all fixations. 35% preferred one fixation over another, 13% gave nonspecific staining and 23% did not stain at all. Conclusion: Individual antibody variability of the paratope's fitness for the fixed antigen may be the cause. Revalidation of established antibody panels is required when they are applied to sections whose fixation and processing are different from the tissue where they were initially validated.

Biochemical synthesis of palladium nanoparticles: The influence of chemical fixatives used in electron microscopy on nanoparticle formation and catalytic performance.

Palladium nanoparticles (PdNPs) can catalyse a range of reductive chemical reactions transforming both organic and inorganic environmental pollutants. PdNPs that ranged from <2 to 2-40 nm were synthesized using chemical methods, and bacterial biomass with/without chemical fixatives. PdNP formation was enhanced by adsorption of Pd(II) to bacterial biomass, followed by fixation with formate or glutaraldehyde. TEM-SAED analyses confirmed that the cell associated PdNPs were polycrystalline with a face-centered cubic structure. Chemically formed PdNPs possessed a higher Pd(0):Pd(II) ratio and produced structurally similar nanoparticles as the biotic systems. These PdNPs were employed to catalyze two, reductive chemical reactions, transforming 4-nitrophenol (4-NP) and hexavalent chromium [Cr(VI)], into 4-aminophenol and Cr(IV), respectively. In the reduction of 4-NP, the catalytic performance was directly proportional to PdNP surface area, i.e., the smallest PdNPs in formate-PdCH34 cells had the fastest rate of reaction. The mass of Pd(0) as PdNPs was the main contributor to Cr(VI) reduction; the chemically synthesized PdNPs showed the highest removal efficiency with 96% at 20 min. The use of glutaraldehyde enhanced the reduction of Pd(II) and promoted PdNPs formation, i.e., creating an artefact of fixation; however, this treatment also enhanced the catalytic performance of these PdNPs.

Use of fixatives for immunohistochemistry and their application for detection of retinoic acid synthesizing enzymes in the central nervous system.

Retinoic acid (RA) is a lipid signaling molecule that has a crucial role in growth and survival of neurons as well as regulation of neuronal plasticity in the central nervous system. Complete understanding of the distribution of RA is necessary to identify foci of RA signaling. However, RA itself is very difficult to detect by immunohistochemistry as there are few effective antibodies to this lipid and it can be difficult to fix in place in tissue. A set of retinaldehyde dehydrogenases (RALDHs) catalyze the last step of RA synthesis and their distribution can be used as a proxy for RA distribution. This protocol uses the example of RALDH2 expression in the motor neurons of the spinal cord as a demonstration of the approach and describes methods that can improve its effectiveness. Immunodetection is impacted by protein cross linking and protein denaturation as well as antigen/epitope masking by various fixatives. Finding a suitable fixative that preserves morphology and tissue structure by linking cellular component such as proteins and lipids in an indissoluble macromolecular network while keeping functional groups, including antigens, intact is essential. Here, we discuss fixatives in general and also describe a fixation protocol that allows detection of multiple antigens in the same section with a periodate-lysine-paraformaldehyde (PLP) fixative. This keeps tissue structure and antigen well preserved in the adult spinal cord to show RALDH2 expression in motor neurons.

Histomorphological Assessment of Formalin versus Nonformalin Fixatives in Diagnostic Surgical Pathology.

Introduction Fixation is the critical step in the preservation of tissues in diagnostic pathology. The formalin is an economical and excellent fixative with the inherent property of adequate fixation. The well-established side effects of formalin include mucosal irritation, upper respiratory diseases, and corrosive injury to the gastrointestinal tract. In addition, substantial evidence exists regarding the potential role of formaldehyde as a human carcinogen. The carcinogenic and toxic effects of formalin encourage searching for alternative fixatives for tissue fixation. However, "the formalin dogma" has severely hampered the search for alternative fixatives for many years. Material and Methods Ninety tissues of liver and skeletal muscle obtained during autopsies were immersed in adequate amounts of the following fixatives: formalin (10%), methyl alcohol (70%), and acetone (100%). The comparison among the three was made based on time for fixation, preservation of tissue architecture, cell borders, cytoplasm, nuclear contours, chromatin texture, and uniformity of staining. Results The tissue preserved in formalin undergoes rapid fixation compared with alcohol and acetone. The tissue architecture, cell border characteristics of alcohol and acetone was found satisfactory compared with formalin. The cytoplasm and nuclear contour were superior with the formalin. The chromatin texture and uniformity of staining were similar with all the three fixatives. Conclusion The formalin is considered superior to most of the parameters, whereas both methyl alcohol and acetone showed nearly equivalent scores. Hence, owing to the potential human health hazards and carcinogenicity of formalin, no rational reasons hamper the complete substitution of formalin with alternative fixatives such as alcohol and acetone in diagnostic pathology and medical research.

A Simple and Rapid Staining Technique for Sex Determination of Trichinella Larvae Parasites by Confocal Laser Scanning Microscopy.

The roundworms of Trichinella genus are worldwide distributed and their prevalence in nature is high. Trichinella genus parasites are the causative agents of foodborne zoonosis trichinellosis. The main prevention and control of the infection are meat inspection by the magnetic stirrer method for the detection of Trichinella larvae in muscle samples. The treatment can be effective if the parasite is discovered early in the intestinal phase. Once the Trichinella larva has reached the muscle tissue, the parasite remains therein and there is no treatment for this life cycle stage. The Trichinella species is dioecious with separate male and female individuals. The developed staining technique that uses confocal laser scanning microscopy (CLSM) displays sufficient results for Trichinella larvae examination and this protocol is applicable to study the internal and external structures and for the sex determination of T. britovi and T. spiralis larvae samples. In the present study, a luminescent derivative was synthesized and used for staining of T. spiralis and T. britovi larvae samples for the examination by CLSM. Various fixatives, such as AFA, 70% ethanol, and Bouin's and Carnoy's solutions were tested for sample preparation. The synthesized luminescent compound demonstrates best visualization results for samples fixed in Bouin's fixative.

The Optimal Concentration of Formaldehyde is Key to Stabilizing the Pre-Fusion Conformation of Respiratory Syncytial Virus Fusion Protein.

BACKGROUND: To date, there is no licensed vaccine available to prevent respiratory syncytial virus (RSV) infection. The valuable pre-fusion conformation of the fusion protein (pre-F) is prone to lose high neutralizing antigenic sites. The goals of this study were to stabilize pre-F protein by fixatives and try to find the possibility of developing an inactivated RSV vaccine. METHODS: The screen of the optimal fixative condition was performed with flow cytometry. BALB/c mice were immunized intramuscularly with different immunogens. The serum neutralizing antibody titers of immunized mice were determined by neutralization assay. The protection and safety of these immunogens were assessed. RESULTS: Fixation in an optimal concentration of formaldehyde (0.0244%-0.0977%) or paraformaldehyde (0.0625%-1%) was able to stabilize pre-F. Additionally, BALB/c mice inoculated with optimally stabilized pre-F protein (opti-fixed) induced a higher anti-RSV neutralization (9.7 log2, mean value of dilution rate) than those inoculated with unstable (unfixed, 8.91 log2, p < 0.01) or excessively fixed (exce-fixed, 7.28 log2, p < 0.01) pre-F protein. Furthermore, the opti-fixed immunogen did not induce enhanced RSV disease. CONCLUSIONS: Only the proper concentration of fixatives could stabilize pre-F and the optimal formaldehyde condition provides a potential reference for development of an inactivated RSV vaccine.

Transmission Electron Microscopy of the Phloem with Minimal Artifacts.

It is a universal feature of seed plants that their phloem consists of a continuous sieve-tube system throughout the plant that is highly pressurized by its sugar contents. Cellular continuity and the pressure flow, osmotically generated in the source leaves, allow the assimilates to reach all sinks organs. However, both phloem features, the cellular continuity and the high pressure, are challenges when fixing the phloem for transmission electron microscopy. With very few exceptions, the tissue preparation necessary for the fixation evokes rapid wound responses that eventually result in artifacts.This chapter describes the steps necessary to minimize development of artifacts in the phloem and includes preparation of fixatives, a dissection procedure that optimizes penetration of the fixatives and application to axial and lateral plant organs. Moreover, as alternative to the established fixation of fresh hand sections, we suggest a xylem-assisted perfusion fixation method for herbaceous plants. After the initial fixation, the subsequent dehydration, embedding, and ultrathin sectioning of the material follow routine procedures, which are briefly discussed, as is the orientation of samples for obtaining transverse and longitudinal phloem sections.

Comparative evaluation of the quality of Papanicolaou staining at different intervals of fixation times using 96% ethyl alcohol / Avaliação comparativa da qualidade da coloração de Papanicolaou em diferentes tempos de fixação em álcool etílico a 96%

ABSTRACT Introduction: Fixation of cytological smears consists of immediate immersion in appropriate fixative, in order to preserve cellular morphological characteristics, it is essential for the microscopic examination and diagnostic interpretation. Objective: To evaluate the influence of fixation times on the morphological and staining characteristics of samples fixed in ethanol and stained by the Papanicolaou method. Method: Experimental, quantitative and qualitative research was carried out on 99 samples of the jugal mucosa scrapings from 33 participants, fixed in 96% ethyl alcohol in three different times. Group A: 15 minutes; group B: 30 minutes; group C: seven days. The quality of staining was categorized in Optimal, Good, Regular and Poor, with subsequent recategorization at optimal and non-optimal. To verify the association among the groups and the categories, Fisher's exact test was performed, with significance level of 0.05. Results: From the 99 stained slides, 19 were discarded due to acellularity, remaining 80 slides. From these, 28 in group A, 26 in group B and 26 in group C were evaluated. In Group A, optimal quality was found in 60.7% (n = 17), good in 28.6% (n = 8), regular in 10.7% (n = 3) and poor in 0% (n = 0). In group B optimal was found in 61.5% (n = 16), good in 30.8% (n = 8), regular in 7.7% (n = 2) and poor in 0% (n = 0). In group C, optimal was found in 92.3% (n = 24), good in 7.7% (n = 2), regular in 0% (n = 0) and poor in 0% (n = 0). In the three groups, there was no representation of the Poor category. Conclusion: The results suggest that there is a significant difference in the staining quality (p-value = 0.01) according to the fixation time.

RESUMEN Introducción: La fijación de extensiones citológicas consiste en la inmersión inmediata en fijador adecuado para preservar la morfología celular, siendo esencial para el análisis microscópico y la interpretación diagnóstica. Objetivo: Evaluar la influencia de los tiempos de fijación en las características morfológicasy de tinción de muestras fijadas con metanoly tenidas con el método de Papanicolaou. Método: Se realizó una investigación experimental, cuantitativa y cualitativa de 99 muestras de raspado de la mucosa yugal de 33 participantes, fijadas con etanol al 96% en tres tiempos distintos. Grupo A: 15 minutos; grupo B: 30 minutos; grupo C: 7 días. La calidad de la tinción fue categorizada en óptima, buena, regular y mala, con posterior reclasificación en óptima y no óptima. Para determinar la asociación entre los grupos y las categorias, se realizó la prueba exacta de Fisher, con un nivel de significación del 0,05. Resultado: De las 99 muestras tenidas, 19 fueron desechadas por acelularidad, quedando 80 para ser analizadas. De estas muestras, 28 fueron evaluadas en el grupo A, 26 en el grupo B y 26 en el grupo C. En el grupo A, hemos encontrado calidad óptima - 60,7% (n =17); buena - 28,6% (n = 8); regular -10,7% (n = 3) y mala - 0% (n = 0). En el grupo B, óptima - 61,5% (n = 16); buena - 30,8% (n = 8); regular - 7,7% (n = 2); y mala - 0% (n = 0). En el grupo C, óptima - 92,3% (n = 24); buena - 7,7% (n = 2); regular - 0% (n = 0) y mala - 0% (n = 0). En los tres grupos no hubo representación en la categoria mala. Conclusión: Los resultados sugieren que hay diferencia significativa en la calidad de la tinción (p = 0,01) de acuerdo con el tiempo de fijación.

RESUMO Introdução: A fixação dos esfregaços citológicos consiste na imersão imediata em fixador adequado para preservar as características morfológicas celulares, sendo essencial para a análise microscópica e a interpretação diagnóstica. Objetivo: Avaliar a influência dos tempos de fixação nas características morfológicas e tintoriais de amostras fixadas em álcool etílico e coradas pelo método de Papanicolaou. Método: Realizou-se pesquisa experimental, quantitativa e qualitativa de 99 amostras de raspado da mucosa jugal de 33participantes, fixadas em álcool etílico 96% em três tempos diferentes. Grupo A: 15 minutos; grupo B: 30 minutos; grupo C: sete dias. A qualidade da coloração foi categorizada em ótima, boa, regular e ruim, com posterior recategorização em ótimo e não ótimo. Para verificar a associação entre os grupos e as categorias, realizou-se teste exato de Fisher, com nível de significância de 0,05. Resultado: Das 99 lâminas coradas, 19 foram desprezadas por acelularidade, restando 80 lâminas para serem analisadas. Destas, foram avaliadas 28 no grupo A, 26 no grupo B e 26 no grupo C. No grupo A, foi encontrada qualidade ótima - 60,7% (n = 17); boa - 28,6% (n = 8); regular - 10,7% (n = 3) e ruim - 0% (n = 0). No grupo B, ótima - 61,5% (n = 16); boa - 30,8% (n = 8); regular - 7,7% (n = 2); e ruim - 0% (n = 0). E no Grupo C, ótima - 92,3% (n = 24); boa - 7,7% (n = 2); regular - 0% (n = 0); e ruim - 0% (n = 0). Nos três grupos não houve representação na categoria ruim. Conclusão: Os resultados sugerem que há diferença significativa na qualidade da coloração (p = 0,01) de acordo com o tempo de fixação.

The impact of cell fixation on coherent anti-stokes Raman scattering signal intensity in neuronal and glial cell lines.

A number of studies require sample fixation, aimed to preserve cells in a physiological state with minimal changes of morphology and intracellular molecular content. Sample fixation may significantly distort experimental data, which makes the data interpretation process more challenging. It is particularly important for study of lipid-related diseases, where the biochemical and morphological characteristics of the cells need to be well preserved for an accurate data analysis. This study investigates the effects of formaldehyde and ethanol (EtOH) fixatives on coherent anti-stokes Raman scattering (CARS) signal of proteins and lipids in major cellular compartments of neuronal and glial cells. We found that both fixatives induce alteration of proteins and lipids signal in studied cell lines. Furthermore, the impact of sample preservation methods on CARS signal varies between cell lines. For instance, our data reveals that EtOH fixation induces ~45% increase of CARS signal of proteins in the nucleolus of neuronal cells and ~35% decrease of CARS signal in glial cells. The results indicate that aldehyde fixation is a preferable method for preservation of neuronal and glial cells prior to CARS imaging, as it less affects both CARS signal and intracellular distribution of proteins and lipids.

Evaluation of two eco-friendly neutralizers for a spectrum of tissue fixatives for biomedical applications.

Formaldehyde is a widely used aldehyde in biomedical applications, including tissue fixation. It is this same fixative property that can result in toxicity if aldehydes are improperly discarded. A proper neutralization of aldehyde waste products can address this, thereby reducing both health and environmental toxicity concerns. In this study two commercially available products designed to neutralize formaldehyde were evaluated, including neutralization of laboratory derived tissue fixative waste. The primary selection criteria for inclusion in the study were: their ease of use (based on product instructions); the two products assert high levels of formaldehyde neutralization (below 20 ppm) relative to other neutralizing products and their lack of generation of polymeric residues that can clog drains. Both products tested were relatively easy to use and both achieved <10 ppm residual levels of formaldehyde from standard formalin and glutaraldehyde preparations used in research and clinical laboratories.

Procedures for chemical fixation in immunohistochemical analyses of PIN proteins regulating polar auxin transport: Relevance to spaceflight experiments.

The mechanism by which gravity controls the polar transport of auxin, a plant hormone regulating multiple physiological processes in higher plants, remains unclear, although an important role of PIN proteins as efflux carriers/facilitators in polar auxin transport is suggested. We are going to study the effect of microgravity on the polar transport of auxin, focusing on the cellular localization of its efflux carrier, PsPIN1 in etiolated pea seedlings and ZmPIN1a in etiolated maize seedlings grown under microgravity conditions on the International Space Station (ISS) using immunohistochemical analyses according to space experimental plans (Ueda, 2016). To obtain adequate results regarding the cellular localization of functional proteins, prolonged chemical fixation processes as well as chemical fixatives should be well-matched to the properties of functional proteins as antigens since experimental analyses will be performed on the ground after keeping samples for a long duration on the ISS. As a result of ground verification, clear detection of the cellular localization of PsPIN1 and ZmPIN1a immunohistochemically was successful based on the results of several kinds of chemical fixation tested, even when etiolated pea and maize seedlings were fixed by immersion in chemical fixative for a long duration. The addition of 0.1% (w/v) Nonidet P-40 to chemical fixative composed of 50% (v/v) ethanol and 5% (v/v) acetic acid or that of 50% (v/v) methanol and 5% (v/v) acetic acid has led to a significant improvement in the immunohistochemical detection of PsPIN1 or ZmPIN1a. These chemical fixatives were also shown to be storage-stable for a long time before use. In this study, adequate chemical fixatives and fixation protocols were developed, which can be used to detect localization of PsPIN1 and ZmPIN1a proteins in young etiolated pea and maize seedlings, respectively, using anti PsPIN1 and ZmPIN1a antibodies. These protocols can be used in spaceflight experiments to investigate the effects of the microgravity environment on the ISS on PIN protein localization in pea and maize seedlings.

Comparison of efficacy of local anesthetic solution, distilled water and normal saline as emergency fixatives.

CONTEXT: Adequate tissue fixation is fundamental to good quality histological sections. Owing to undesirable effects of 10% buffered formalin, its availability in clinics is questionable. Thus, the present study was conducted with a novel approach to fixation, together with the scope of finding fixative properties of more commonly used reagents available at the clinics. AIMS: The present study was aimed to compare the efficacy of local anesthetic solution, normal saline (NS) and distilled water (DW) with that of 10% neutral-buffered formalin. SETTINGS AND DESIGN: It is a single-blinded study where histological assessment of fixation was done to assert if the tissues procured were sufficient or insufficient for the clinical diagnosis with/without any problems. SUBJECTS AND METHODS: Forty soft-tissue specimens obtained from 2 goat tongue were used. Tissues each were directly immersed in local anesthesia, DW, NS solution and formalin for 12 and 24 h each and labeled as Group I and Group II, respectively. The sections were evaluated for staining quality and were subjected to statistical analysis. STATISTICAL ANALYSIS USED: Kruskal-Wallis test was employed to assess the differences in histological quality scores. Comparison between the tissues of the two groups was estimated with Mann-Whitney U-test. Kappa Statistic was used to measure the interobserver variation. RESULTS: There was a significant difference (P ≤ 0.05) in the efficacy of all the three emergency fixatives. CONCLUSIONS: On the basis of the results obtained, local anesthetic solution can be used as an emergency fixative.