Influence of paraformaldehyde and EDAC fixation on the demonstrability of hormones (histamine, endorphin, triiodothyronine) in rat immune cells: An immunocytochemical comparative analysis

The amount and localization of three hormones (histamine, endorphin and triiodothyronine [T(3)]) was measured in male and female rat peritoneal cells (lymphocytes, mast cells, monocyte-macrophage-granulocyte group [mo-gran]) using flow cytometry as well as confocal microscopy after paraformaldehyde (PFA) or EDAC fixation. In the EDAC fixed lymphocytes and mo-gran of female animals two-magnitude higher levels of histamine were measured after EDAC fixation and one magitude higher in mast cells. The amount of T(3) was almost four-fold in lymphocytes and 2.5-4-fold in mast cells and mo-gran. Endorphin content was not altered by the type of fixation. In each cell type in males one magnitude higher levels of histamine and T(3) were measured after EDAC fixation and a small, but significant, elevation of endorphin. Confocal microscopy supports the quantitative data. The results show that (1) the fixation with the crosslinking molecule, EDAC, is more suitable for immunocytochemical studies of amino-acid type hormones in immune cells, (2) more histamine and T(3) are present in the immune cells than it was supposed previously when studying PFA-fixed preparations, (3) the estimation of the amount of peptide hormones seems to be accurate after PFA fixation, (4) there is a quantitative difference comparing the results of PFA and EDAC fixation between males and females.

Expression of cell death-associated proteins in neuronal apoptosis associated with pontosubicular neuron necrosis

Expression of apoptosis-associated proteins p53, bcl-2, bax, and caspase-3/CPP32, activation of caspase-3, and modification of proteins via poly(ADP-ribosyl)ation was studied in pontosubicular neuron necrosis (PSN), a form of perinatal brain damage revealing the morphological hallmarks of neuronal apoptosis. Immunoreactivity for p53 was completely absent. The majority of cells stained with the bax and procaspase-3 antibodies did not show morphological signs of apoptosis. In contrast, an antibody against activated caspase-3 almost exclusively stained cells with apoptotic morphology. Poly(ADP-ribosyl)ated proteins were only rarely detected in cells with apoptotic morphology. The expression patterns of bax, procaspase-3, bcl-2, and p53 in PSN were similar to that found in age-matched control brains. However, activated caspase-3 and poly-ADP-ribosylated proteins were exclusively found in apoptotic cells. These data indicate that detection of active caspase-3 is a reliable marker for apoptosis in formalin-fixed human tissue, and that neuronal apoptosis in pontosubicular neuron necrosis is accompanied by a pronounced activation of caspase-3.

Subjective vs. objective analysis of the corneal endothelial cells in the rabbit cornea by scanning electron microscopy - a comparison of two different methods of corneal fixation

OBJECTIVE

To illustrate a method of quantitative scanning electron microscopy (SEM) for the evaluation of the corneal endothelia of small animals by comparing two commonly used fixation methods.

ANIMALS STUDIED

Female New Zealand white rabbits, aged 10-12 weeks.

PROCEDURES

The corneas were either dissected from the eye and placed in fixative (2% glutaraldehyde in 80 mm cacodylate, pH 7.4) or the whole eyeball immersed in fixative solution and the cornea dissected later. Lower (x 200) and high magnification (x 1,000-5,000) images were inspected for overall appearance. Magnification images (x 500) were used to measure the areas of 100 cells, and cell density (CD) calculated from the average area.

RESULTS

Both fixation protocols yielded an intact endothelial surface, but the dissect- then-fix protocol resulted in more creasing and distortion artifacts that were avoided with the whole-eyeball fixation. Overall, the CD values were higher if the dissect-then-fix method was used, and the uniformity of the cell mosaic was less. The median CD values for the central, mid-peripheral and peripheral regions following dissect-then-fix protocols were 7,693, 7,353, and 7,071 cells/mm(2) (average eight corneas at each location). If the whole-globe fixation was used, the median CD values were 6,098, 5,747, and 4,785 cells/mm(2).

CONCLUSION

Cell density values in SEM can be very different according to the fixation method used. A distinct regional difference in CD was evident, which was more pronounced if the cornea was fixed prior to being dissected from the eye.

Hippocampal theta state in relation to formalin nociception

In the present study using extracellular electrophysiological recording techniques, we explored the temporal characteristics of hippocampal theta activation in relation to formalin nociception. Results indicate that, compared to hind paw injection of saline, formalin injection in behaving rat evoked biphasic increase in duration of dorsal CA1 theta. Such an increase broadly paralleled animal biphasic behavioral activation, especially lick and moment-to-moment agitated behaviors. Correspondingly, theta-modulated cell firing was observed following formalin injection in anesthetized rat. The formalin-induced theta activation in behaving rat was most marked during peak of theta activation in the 2nd theta state (11-40 min post-injection) comprising 73% of the time in the 5 min block. An increase in theta peak frequency was also observed with respect to pre-injection control. However, the peak of theta in the 2nd theta state mostly preceded the peak of lick and flinch of the affected paw. In the 41-60 min, following formalin injection while the animals displayed robust nociceptive flinching and lifting, the theta activity approached control levels. Furthermore, the theta peak frequency at peak of theta was higher than the corresponding values of sustained theta observed in correlation with the nociceptive behaviors; in contrast, high frequency theta rhythm was observed during formalin-induced other moment-to-moment agitated behaviors. These findings favor the notion that in the formalin model the theta state of the hippocampus reflects a neural drive that is dissociated from the duration of nociceptive experience and is not selective to the typical nociceptive indices of lick, flinch, and lift of the injured paw.

Identification of N,N-dimethylamphetamine formed by methylation of methamphetamine in formalin-fixed liver tissue by multistage mass spectrometry

Methamphetamine is methylated in the presence of unbuffered formalin solutions within hours at room temperature. The product, N,N-dimethylamphetamine, is also found in human liver exposed to methamphetamine followed by incubation with formalin. In the present study, a direct mass spectrometric method was developed to identify N,N-dimethylamphetamine in human liver before and after treatment with formalin. Human liver samples were obtained from four deaths that were investigated by the West Virginia Office of Chief Medical Examiner. Full toxicological analysis was conducted on samples from the decedents and methamphetamine was among the positive findings in each case. The method used to expose liver tissue to formaldehyde involved treating a small piece of liver from each case with formalin solution (20% v/v) for 24 h at room temperature. The formalin treated tissues were homogenized and the resulting suspension was sonicated for 5 min, and then centrifuged. Supernatant aliquots were directly analyzed by electrospray ionization (ESI) mass spectrometry without chromatographic isolation. Positive ion multistage mass spectra recorded in MS, MS/MS and MS/MS/MS (MS3) modes were used to confirm the presence of N,N-dimethylamphetamine and methamphetamine in the mixture. Liver tissue not treated with formalin did not contain a detectable level of N,N-dimethylamphetamine. Decreases in methamphetamine concentrations in liver tissue resulting from treatment with formalin were measured using deuterium-labeled methamphetamine as internal standard. The method can be completed in less than 2 h on thawed tissue. The results suggest that the process of fixing tissues with formalin may lead to false negative findings for methamphetamine.

Multiscale analysis of surface thrombosis in vivo in a left ventricular assist system

Thrombosis limits the success of ventricular assist devices as the demand for alternatives to heart transplants is increasing. This study mapped the occurrence of thrombosis in a left ventricular assist system (LVAS) to better understand the biologic response to these devices. Nine calves divided into two groups were implanted with LVAS for 28 to 30 days. One group was anticoagulated, whereas the second group received no long-term anticoagulation. The blood-contacting poly(urethane urea) surfaces of blood sacs in the LVAS were examined for macroscopic thrombi upon retrieval. The sac was partitioned into eight sections and imaged for thrombi by scanning electron microscopy. No difference in thrombosis was observed macroscopically between the groups. Anticoagulation appeared to result in reduction of platelet-like structures, but the presence of fibrin-like structures remained similar between groups. Regional differences correlating with high and low shear stress regions were observed. At the macroscale, fewer thrombi were recorded in the high shear stress ports. At the microscale, features resembling fibrin were observed primarily in the ports and platelet-like features were common in lower shear stress regions. These variations in thrombosis with anticoagulation and location are likely due to varied fluid dynamics within the LVAS blood sac.

Oral epithelial cell antifungal activity: approaches to evaluate a broad range of clinical conditions

Anti-Candida activity by oral epithelial cells is considered one of several innate mucosal defense mechanisms against oropharyngeal candidiasis (OPC). OPC is the most common fungal infection in HIV disease. Previously we reported that oral epithelial cell anti-Candida activity is reduced in those with OPC, potentially representing a contributing factor to OPC. However, testing clinical epithelial cells possessing high levels of Candida has been limiting due to high background in the assay controls. HIV+ smokers often develop OPC sooner than non-smokers during progression to AIDS, suggesting additional immune aberrations. The purpose of this study was to design a means to reduce Candida associated with epithelial cells collected from saliva without affecting their in vitro growth inhibitory activity, and to employ that approach to evaluate antifungal activity in HIV+ smokers. To do so, oral epithelial cells with and without known levels of Candida were subjected to various treatments including azole, polyene, or echinocandin antifungal drugs or fixation followed by the standard growth inhibition (GI) assay. The results indicated that antifungal drugs, while effectively reducing cell-associated Candida, also affected epithelial cell function. In contrast, fixation with paraformaldehyde eliminated cell-associated Candida and had minimal effects on epithelial cell anti-Candida activity. Employing the fixation design that allowed a broad range of patients to be evaluated showed no difference in oral epithelial anti-Candida activity between HIV+ smokers and non-smokers. Therefore, oral epithelial cell antifungal activity does not appear compromised in those who smoke, reducing it as a contributing factor in susceptibility to premature OPC.

Mechanical strength repercussions of various fixative storage methods on bone

This study compensates for the lack of literature on the actual effects that various fixative storage methods have on the mechanical strength characteristics of bone and attempts to identify the ideal fixative method for preservation of all tissues while maintaining in vivo bone strength. Researchers currently use a wide variety of storage methods that lessen the mechanical strength to varying degrees. Differences could introduce error into a great number of bone fracture studies if an inexact discrepancy in the mechanical properties of fixed bone does actually exist. Furthermore, such disparities could go on to pose clinical risks for patients. This study focuses on the mechanical strength testing of four different groups of rat femora that were retrieved at various times and subjected to differing storage procedures. The first, Group N, were fresh, new femora retrieved just days before testing. The second, Group F, were femora that have been fixed in a 10% formalin bath for just over a year prior to testing. The third, Group W, are femora that have also been fixed in 10% formalin for just over a year but were washed out just prior to testing. The fourth, Group P, were femora that were retrieved from rats that were perfused with formalin immediately following euthanasia. Mechanical strength tests on the four groups revealed that fixing bone in a 10% formalin bath significantly reduces the mechanical fracture strength properties of the bone regardless of whether the formalin is washed out prior to testing. Testing also revealed that bone from perfused animals behaves more similarly to fresh bones from non-perfused animals suggesting that the formalin did not entirely infiltrate the bone and permanently fix the material. These results could have profound implications on how studies equate the behavior of in vitro bone to in vivo bone which could manifest as clinical complications for patients.

Assessment of fixatives, fixation, and tissue processing on morphology and RNA integrity

Molecular characterization of morphologic change requires exquisite tissue morphology and RNA preservation; however, traditional fixatives usually result in fragmented RNA. To optimize molecular analyses on fixed tissues, we assessed morphologic and RNA integrity in rat liver when sections were fixed in 70% neutral-buffered formalin, modified Davidson's II, 70% ethanol, UMFIX, modified Carnoy's, modified methacarn, Bouin's, phosphate-buffered saline, or 30% sucrose. Each sample was subjected to standard or microwave fixation and standard or microwave processing, and sections were evaluated microscopically. RNA was extracted and assessed for preservation of quality and quantity. Modified methacarn, 70% ethanol, and modified Carnoy's solution each resulted in tissue morphology representing a reasonable alternative to formalin. Modified methacarn and UMFIX best preserved RNA quality. Neither microwave fixation nor processing affected RNA integrity relative to standard methods, although morphology was modestly improved. We conclude that modified methacarn, 70% ethanol, and modified Carnoy's solution provided acceptable preservation of tissue morphology and RNA quality using both standard and microwave fixation and processing methods. Of these three fixatives, modified methacarn provided the best results and can be considered a fixative of choice where tissue morphology and RNA integrity are being assessed in the same specimens.

Structural elements of bulk chromatin within metaphase chromosomes

We have performed a very extensive electron microscopy investigation of the chromatin structures extruded from partially denatured metaphase chromosomes from HeLa cells under a wide variety of conditions. Denatured chromosomes having fibres as the dominant structural element are obtained in the presence of buffers of very low concentration or after incubation with water. At slightly higher ionic concentrations, metaphase chromosomes become granulated. The most frequently observed granules have a diameter of about 35 nm and show the same structural characteristics as the compact cylindrical chromatin bodies previously found in our laboratory in studies performed using small chromatin fragments. Our results suggest that fibres are formed by the face-to-face association of 35-nm chromatin bodies. We have observed a very compact morphology of chromosomes in solutions containing intracellular concentrations of monovalent cations and the Mg2+ concentration found in metaphase. The most abundant structural elements observed in chromatin extruded from partially denatured compact metaphase chromosomes are multilayered plate-like structures. This is the first time that these planar structures have been reported. The observation of the irregular plates found in some preparations and of the small planar structures seen in aggregates of small chromatin fragments suggests that plates are formed by side-by-side association of compact chromatin bodies.

Effect of tissue fixatives on telomere length determination by quantitative PCR

Telomere length is a well established marker of cellular senescence and thus biological age. Quantitative PCR allows the determination even from very low amounts of tissue by using telomere specific and single copy gene primers. Comparing a directly processed tissue sample to a 4% formaldehyde fixed one showed a significantly reduced efficiency of PCR reactions (mainly in single copy gene experiments) in a storage time-dependent manner resulting in an artificial increase in reported relative telomere length. This effect was not seen when the tissue was stored in RNA later solution. In summary, telomere length determination from formaldehyde fixed material by quantitative PCR is not a reliable method. Unfortunately therefore, many easily accessible tissue samples from pathology laboratories are unsuitable for this technique.

The influence of chronic exposure to antipsychotic medications on brain size before and after tissue fixation: a comparison of haloperidol and olanzapine in macaque monkeys

It is unclear to what degree antipsychotic therapy confounds longitudinal imaging studies and post-mortem studies of subjects with schizophrenia. To investigate this problem, we developed a non-human primate model of chronic antipsychotic exposure. Three groups of six macaque monkeys each were exposed to oral haloperidol, olanzapine or sham for a 17-27 month period. The resulting plasma drug levels were comparable to those seen in subjects with schizophrenia treated with these medications. After the exposure, we observed an 8-11% reduction in mean fresh brain weights as well as left cerebrum fresh weights and volumes in both drug-treated groups compared to sham animals. The differences were observed across all major brain regions (frontal, parietal, temporal, occipital, and cerebellum), but appeared most robust in the frontal and parietal regions. Stereological analysis of the parietal region using Cavalieri's principle revealed similar volume reductions in both gray and white matter. In addition, we assessed the subsequent tissue shrinkage due to standard histological processing and found no evidence of differential shrinkage due to drug exposure. However, we observed a pronounced general shrinkage effect of approximately 20% and a highly significant variation in shrinkage across brain regions. In conclusion, chronic exposure of non-human primates to antipsychotics was associated with reduced brain volume. Antipsychotic medication may confound post-mortem studies and longitudinal imaging studies of subjects with schizophrenia that depend upon volumetric measures.

Impact of preanalytical variables on granulocytic surface antigen expression: a review

BACKGROUND

There is a gradual but steady increase in the use of granulocytic surface marker studies to diagnose several inherited and acquired blood and bone marrow disorders. Diagnosis and follow-up of patients with inflammation and infection are other areas of quantitative flow cytometric application. Despite the increased use of flow cytometry to study granulocytes, there seems to be no well-established standards regarding specimen handling for these studies.

METHODS

This review summarizes the effect of preanalytical variables on granulocytic surface markers.

RESULTS AND CONCLUSIONS

Storing specimens in sodium heparin at room temperature for up to 72 h seems satisfactory. Other anticoagulants, although acceptable, may have a shorter storage time. Storage time could be prolonged further with the use of some preservation media. Lysed whole blood is the preferred technique. Techniques should avoid major temperature change and excessive manipulation and should maintain storage and methodologic temperature with minimal fluctuation. Fixation before staining with the antibody may result in decreased expression of some surface antigens.

Further evidence on the role of heparan sulfate as protamine acceptor during the decondensation of human spermatozoa

BACKGROUND

Human spermatozoa decondense in vitro upon exposure to heparin and glutathione. Glutathione is also the disulfide bond reducer in vivo, and heparan sulfate, a functional analogue of heparin, has been proposed as the protamine acceptor. The aim of this study was to evaluate the decondensing ability of chemically modified heparins and different glycosaminoglycans (GAGs) on isolated sperm nuclei in vitro, and to analyse the possible role of different GAGs as protamine acceptors.

METHODS

Capacitated spermatozoa and isolated sperm nuclei from normospermic semen samples were decondensed in the presence of heparin (or its equivalent) and glutathione. After fixation with glutaraldehyde, the percentage of decondensed spermatozoa and nuclei was determined under phase-contrast. Proteins were extracted from sperm nuclei previously incubated in the presence of gluhathione and different GAGs by incubation with urea-beta-meracptoethanol-NaCl, and analysed by acid polyacrylamide gel electrophoresis.

RESULTS

The ability of desulfated heparins and other GAGs to decondense isolated nuclei mirrored exactly the decondensation of capacitated spermatozoa, the only difference being the level of maximum decondensation achieved. Heparan sulfate and heparin, but not other GAGs, were able to release protamines from sperm chromatin.

CONCLUSIONS

Heparan sulfate could be functioning as protamine acceptor in vivo during human sperm nuclear decondensation.

Optical microscopy of Arabidopsis seedlings fixed in non-fresh FAA using Kennedy Fixation Tubes

Samples will be kept in non-fresh fixative for longer period than usual in Kennedy Space Center Fixation Tubes (KFT) when they will be fixed for microscopy in the International Space Station (ISS). It is necessary to examine characteristics of samples prepared under such conditions and to improve preservation of the samples. In this study, morphology of Arabidopsis tissues prepared under such conditions was examined under a light microscope. Deformation of cell shape was observed in tissues with well-developed intercellular spaces when they were fixed in non-fresh fixative for longer period in KFTs.

RT-PCR analysis of RNA extracted from Bouin-fixed and paraffin-embedded lymphoid tissues

In the present study, we have investigated whether RNA can be efficiently isolated from Bouin-fixed or formalin-fixed, paraffin-embedded lymphoid tissue specimens. To this aim, we applied a new and simple method that includes the combination of proteinase K digestion and column purification. By this method, we demonstrated that the amplification of long fragments could be accomplished after a pre-heating step before cDNA synthesis associated with the use of enzymes that work at high temperature. By means of PCR using different primers for two examined genes (glyceraldehyde-3-phosphate dehydrogenase [GAPDH]- and CD40), we amplified segments of cDNA obtained by reverse transcription of the isolated RNA extracted from Bouin-fixed or formalin-fixed paraffin-embedded tissues. Amplified fragments of the expected sizes were obtained for both genes tested indicating that this method is suitable for the isolation of high-quality RNA. To explore the possibility for giving accurate real time quantitative RT-PCR results, cDNA obtained from matched frozen, Bouin-fixed and formalin-fixed neoplastic samples (two diffuse large cell lymphomas, one plasmacytoma) was tested for the following target genes: CD40, Aquaporin-3, BLIMP1, IRF4, Syndecan-1. Delta threshold cycle (DeltaC(T)) values for Bouin-fixed and formalin-fixed paraffin-embedded tissues and their correlation with those for frozen samples showed an extremely high correlation (r > 0.90) for all of the tested genes. These results show that the method of RNA extraction we propose is suitable for giving accurate real time quantitative RT-PCR results.

DNA and RNA obtained from Bouin's fixed tissues

BACKGROUND

The use in many countries of acid fixatives, such as Bouin's solution, has limited the use of archival tissue for molecular analysis. An acidic environment is one of the main causes of DNA degradation. Moreover, RNA extraction is difficult in these types of fixed tissues.

AIMS

To amplify DNA and RNA from Bouin's fixed tissues.

METHODS

DNA and RNA were extracted from 20 breast cancer samples that had been routinely fixed in Bouin's fixative. Amplification of several genes using primers that produced amplicons of different lengths was carried out using the polymerase chain reaction (PCR) for DNA (with and without restoration) and reverse transcription PCR for RNA.

RESULTS

The acid environment of Bouin's fixative damaged both DNA and RNA. However, amplification was successful when the amplicon length was reduced to about 80 bp for RNA and 100-200 bp for DNA, especially if submitted to DNA reconstruction procedures.

CONCLUSIONS

It is possible to recover and analyse DNA and RNA from Bouin's fixed and paraffin wax embedded tissues.

Antimicrobial activity of UMFix tissue fixative

AIMS

The aim of this study was to determine the antimicrobial effects of UMFix, an alcohol based tissue fixative, on various microorganisms. The UMFix solution was compared with 10% neutral buffered formalin.

METHODS

Standard methods to determine microorganism colony counts were performed after exposure of the microorganisms to UMFix and 10% neutral buffered formalin.

RESULTS

After a short exposure, UMFix rapidly killed vegetative bacteria, yeasts, moulds, and viruses. Bacterial spores were resistant to killing by UMFix. All organisms were killed by the 10% neutral buffered formalin preparation.

CONCLUSIONS

UMFix was microbicidal for vegetative bacteria, yeasts, and aspergillus species after a short exposure, although it was not active against spore forming bacillus species. The methanol content of the fixative was responsible for the killing effect of this fixative. No killing was seen when polyethylene glycol was used alone.

Effect of one-step 100% ethanol fixation and modified manual microdissection on high-quality RNA recovery from esophageal carcinoma specimen

This paper attempts to determine an optimal fixation protocol for stabilizing RNA during microdissection so as to obtain high-quality RNA from specific cell populations procured from esophageal carcinoma specimens, and to develop a manual microdissection that can facilitate the procurement. The special features of our protocol include one-step dehydration of tissue sections in 100% ethanol immediately after cryosectioning, a self-made T-shape plate (T plate) and "exclusion microdissection" procedure. The quality of RNA isolated from dissected cells was analyzed by neutral agarose gel electrophoresis and reverse transcription-polymerase chain reaction (RT-PCR) to detect genes of different abundance levels. One-step 100% ethanol fixation of cryosections effectively stabilized RNA integrity for agelong period of time while maintaining histological morphology comparable to that using the conventional procedure, indicating that it is a valid protocol for preservation of RNA in microdissected samples. In conjunction with the application of the T plate and 'exclusion microdissection' procedure, which efficiently simplifies manual microdissection procedure, allowing maximal procurement of target cells from complex primary tissues, full use of every single specimen for maximal procurement of target cells from the sections was allowed. The RNA isolated from 5 different stage-specific cell populations of an esophageal carcinoma specimen was of high quality and sufficient in quantity for various downstream molecular analyses. Our method is suitable for a wide spectrum of expression analysis in diverse clinical settings.

Evaluation of leukocyte stabilisation in TransFix®-treated blood samples by flow cytometry and transmission electron microscopy

In this report, we have evaluated the effects of a TransFix-based stabilisation technique on leukocyte scatter characteristics, immunophenotyping, membrane permeability, absolute cell counting and morphology to extend previously reported flow cytometric data focused on the lymphocyte population. We show that scatter characteristics, immunophenotyping and absolute cell counting are well preserved, particularly in the lymphocyte population. Nevertheless, a general increase in membrane permeability, evaluated by propidium iodide (PI) uptake, was observed in TransFix-treated leukocyte subsets. Ultrastructural observations show selective morphological preservation (up to 10 days of storage) of lymphocytes and, to a lesser extent, of monocytes. In contrast, granulocytes have necrosis-like features, although the plasma membrane seems well preserved. Therefore, electron microscopy observations reflect modifications induced in different cell populations as evidenced by flow cytometry (FC). The data indicate that this short-term stabilisation method is particularly suitable for the analysis of human lymphocytes and it is a good procedure for quality control programmes for inter- and intra-laboratory performance evaluation; good results are obtained with respect to antigen definition and absolute cell counting procedures. Any apoptotic pathways in leukocyte subsets are blocked for at least 10 days.

Antigen presentation to celiac lesion-derived T cells of a 33-mer gliadin peptide naturally formed by gastrointestinal digestion

Celiac disease is an HLA-DQ2-associated disorder characterized by intestinal T cell responses to ingested wheat gluten proteins. A peptide fragment of 33 residues (alpha(2)-gliadin 56-88) produced by normal gastrointestinal proteolysis contains six partly overlapping copies of three T cell epitopes and is a remarkably potent T cell stimulator after deamidation by tissue transglutaminase (TG2). This 33-mer is rich in proline residues and adopts the type II polyproline helical conformation in solution. In this study we report that after deamidation, the 33-mer bound with higher affinity to DQ2 compared with other monovalent peptides harboring gliadin epitopes. We found that the TG2-treated 33-mer was presented equally effectively by live and glutaraldehyde-fixed, EBV-transformed B cells. The TG2-treated 33-mer was also effectively presented by glutaraldehyde-fixed dendritic cells, albeit live dendritic cells were the most effective APCs. A strikingly increased T cell stimulatory potency of the 33-mer compared with a 12-mer peptide was also seen with fixed APCs. The 33-mer showed binding maximum to DQ2 at pH 6.3, higher than maxima found for other high affinity DQ2 binders. The 33-mer is thus a potent T cell stimulator that does not require further processing within APC for T cell presentation and that binds to DQ2 with a pH profile that promotes extracellular binding.

Inactivation of SARS coronavirus by means of povidone-iodine, physical conditions, and chemical reagents

The efficacy of several povidone-iodine (PVP-I) products, a number of other chemical agents, and various physical conditions were evaluated for their ability to inactivate the severe acute respiratory syndrome coronavirus (SARS-CoV). Treatment of SARS-CoV with PVP-I products for 2 min reduced the virus infectivity from 1.17 x 10(6) TCID50/ml to below the detectable level. The efficacy of 70% ethanol was equivalent to that of PVP-I products. Fixation of SARS-CoV-infected Vero E6 cells with a fixative including formalin, glutaraldehyde, methanol, and acetone for 5 min or longer eliminated all infectivity. Heating the virus at 56 degrees C for 5 min dramatically reduced the infectivity of the virus from 2.6 x 10(7) to 40 TCID50/ml, whereas heating the virus for 60 min or longer eliminated all infectivity. Irradiation with ultraviolet light at 134 microW/cm2 for 15 min reduced the infectivity from 3.8 x 10(7) to 180 TCID50/ml; however, prolonged irradiation (60 min) failed to eliminate the remaining virus, leaving 18.8 TCID50/ml. We believe that these findings will be useful for the implementation of infection control measures against SARS, and for the establishment of effective guidelines for the prevention of SARS outbreaks.

Formaldehyde-induced DNA adducts as biomarkers of in vitro human nasal epithelial cell exposure to formaldehyde

Formaldehyde (FA) is a mutagen that, at high concentrations and long durations, has been reported to cause nasal cancer in rats and in some humans. The level of FA-induced modified DNA in nasal cells should serve as a biomarker of FA exposure and effect. In the present study, a high-performance liquid chromatography (HPLC)-ultraviolet (UV) method at 254 nm was developed and optimized to detect and quantify hydroxymethyldeoxynucleosides after the isolated DNA in exposed human nasal epithelial cells (HNEC) was enzymically digested. Normal and modified deoxynucleosides were successfully resolved from one another and from tissue and enzyme blank interferences. The viability of HNEC exposed to FA in solution for 24 h decreased, and there was a linear dose response between % nonviability and FA dose from 10 to 500 microg/mL. Amounts of 18.0 +/- 1.5 pmol N6-dA and 12.0 +/- 1.2 pmol N2-dG derivatives were determined in a 10 microL injection after 1.4 x 10(7) HNEC (106 microg DNA) were exposed to 500 microg/mL in solution. The respective tissue concentrations in pmol hydroxymethyldeoxynucleoside/mg DNA were 170 +/- 14 and 113 +/- 11. The lower quantifiable limits were about 97 and 88 pmol/mg DNA, respectively. Diffusive exposure of HNEC to air FA up to 100 ppm (v/v) for 24 h did not produce quantifiable hydroxymethylnucleosides. FA-modified deoxynucleosides may be useful biomarkers for FA exposure in biological monitoring samples taken by nasal lavage or brush biopsy.

Use of isopropyl alcohol in histological assays: dehydration of tissue, enbessing into paraffin, and processing of paraffin sections

Isopropyl alcohol (isopropanol) can be used as a substitute for ethyl alcohol in tissue dehydration during embedding into paraffin and dehydration of stained sections. The use of isopropyl alcohol during paraffinization allows us to exclude treatment with intermediate solvents of paraffin (chloroform, xylene, and benzene), which reduces the degree of tissue compaction and simplifies and accelerates histological assay.