Enhanced stability of microRNA expression facilitates classification of FFPE tumour samples exhibiting near total mRNA degradation

BACKGROUND

As degradation of formalin-fixed paraffin-embedded (FFPE) samples limits the ability to profile mRNA expression, we explored factors predicting the success of mRNA expression profiling of FFPE material and investigated an approach to overcome the limitation.

METHODS

Bladder (n=140, stored 3-8 years) and cervix (n=160, stored 8-23 years) carcinoma FFPE samples were hybridised to Affymetrix Exon 1.0ST arrays. Percentage detection above background (%DABG) measured technical success. Biological signal was assessed by distinguishing cervix squamous cell carcinoma (SCC) and adenocarcinoma (AC) using a gene signature. As miR-205 had been identified as a marker of SCC, precursor mir-205 was measured by Exon array and mature miR-205 by qRT-PCR. Genome-wide microRNA (miRNA) expression (Affymetrix miRNA v2.0 arrays) was compared in eight newer FFPE samples with biological signal and eight older samples without.

RESULTS

RNA quality controls (QCs) (e.g., RNA integrity (RIN) number) failed to predict profiling success, but sample age correlated with %DABG in bladder (R=-0.30, P<0.01) and cervix (R=-0.69, P<0.01). Biological signal was lost in older samples and neither a signature nor precursor mir-205 separated samples by histology. miR-205 qRT-PCR discriminated SCC from AC, validated by miRNA profiling (26-fold higher in SCC; P=1.10 × 10(-5)). Genome-wide miRNA (R=0.95) and small nucleolar RNA (R=0.97) expression correlated well in the eight newer vs older FFPE samples and better than mRNA expression (R=0.72).

CONCLUSION

Sample age is the best predictor of successful mRNA profiling of FFPE material, and miRNA profiling overcomes the limitation of age and copes well with older samples.

Chromatin composition is changed by poly(ADP-ribosyl)ation during chromatin immunoprecipitation

Chromatin-immunoprecipitation (ChIP) employs generally a mild formaldehyde cross-linking step, which is followed by isolation of specific protein-DNA complexes and subsequent PCR testing, to analyze DNA-protein interactions. Poly(ADP-ribosyl)ation, a posttranslational modification involved in diverse cellular functions like repair, replication, transcription, and cell death regulation, is most prominent after DNA damage. Poly(ADP-ribose)polymerase-1 is activated upon binding to DNA strand-breaks and coordinates repair by recruitment or displacement of proteins. Several proteins involved in different nuclear pathways are directly modified or contain poly(ADP-ribose)-interaction motifs. Thus, poly(ADP-ribose) regulates chromatin composition. In immunofluorescence experiments, we noticed artificial polymer-formation after formaldehyde-fixation of undamaged cells. Therefore, we analyzed if the formaldehyde applied during ChIP also induces poly(ADP-ribosyl)ation and its impact on chromatin composition. We observed massive polymer-formation in three different ChIP-protocols tested independent on the cell line. This was due to induction of DNA damage signaling as monitored by γH2AX formation. To abrogate poly(ADP-ribose) synthesis, we inhibited this enzymatic reaction either pharmacologically or by increased formaldehyde concentration. Both approaches changed ChIP-efficiency. Additionally, we detected specific differences in promoter-occupancy of tested transcription factors as well as the in the presence of histone H1 at the respective sites. In summary, we show here that standard ChIP is flawed by artificial formation of poly(ADP-ribose) and suppression of this enzymatic activity improves ChIP-efficiency in general. Also, we detected specific changes in promoter-occupancy dependent on poly(ADP-ribose). By preventing polymer synthesis with the proposed modifications in standard ChIP protocols it is now possible to analyze the natural chromatin-composition.

Effect of glutaraldehyde fixation on bacterial cells observed by atomic force microscopy

Atomic force microscopy (AFM) is a promising microscopy technique that can provide high-resolution images of bacterial cells without fixation. Three species of bacteria, Xanthomonas campestris, Pseudomonas syringae, and Bacillus subtilis, were used in this study. AFM images were obtained from unfixed and glutaraldehyde-fixed cells, and cell height was measured. The mean height of bacterial cells prepared by fixation was higher than that of those prepared by nonfixation. However, the height changes were different between Gram-negative and Gram-positive bacteria: the mean height of two fixed Gram-negative bacteria, X. campestris and P. syringae, increased by 112.31 and 84.08%, respectively, whereas Gram-positive bacterium, B. subtilis, increased only by 38.79%. The results above indicated that glutaraldehyde fixation could affect the measured height of cells imaged by AFM; further more, the effect of glutaraldehyde fixation on the measured height of Gram-negative bacterial cells imaged by AFM seemed much more than on that of Gram-positive bacterial cells.

Genome-wide comparison of paired fresh frozen and formalin-fixed paraffin-embedded gliomas by custom BAC and oligonucleotide array comparative genomic hybridization: facilitating analysis of archival gliomas

Array comparative genomic hybridization (aCGH) is a powerful tool for detecting DNA copy number alterations (CNA). Because diffuse malignant gliomas are often sampled by small biopsies, formalin-fixed paraffin-embedded (FFPE) blocks are often the only tissue available for genetic analysis; FFPE tissues are also needed to study the intratumoral heterogeneity that characterizes these neoplasms. In this paper, we present a combination of evaluations and technical advances that provide strong support for the ready use of oligonucleotide aCGH on FFPE diffuse gliomas. We first compared aCGH using bacterial artificial chromosome (BAC) arrays in 45 paired frozen and FFPE gliomas, and demonstrate a high concordance rate between FFPE and frozen DNA in an individual clone-level analysis of sensitivity and specificity, assuring that under certain array conditions, frozen and FFPE DNA can perform nearly identically. However, because oligonucleotide arrays offer advantages to BAC arrays in genomic coverage and practical availability, we next developed a method of labeling DNA from FFPE tissue that allows efficient hybridization to oligonucleotide arrays. To demonstrate utility in FFPE tissues, we applied this approach to biphasic anaplastic oligoastrocytomas and demonstrate CNA differences between DNA obtained from the two components. Therefore, BAC and oligonucleotide aCGH can be sensitive and specific tools for detecting CNAs in FFPE DNA, and novel labeling techniques enable the routine use of oligonucleotide arrays for FFPE DNA. In combination, these advances should facilitate genome-wide analysis of rare, small and/or histologically heterogeneous gliomas from FFPE tissues.

[The effect of treatment of temporalis muscle fascia grafts with formaldehyde on the success rates of tympanoplasty]

OBJECTIVES

This study aims to investigate the effect of formaldehyde treatment of temporalis muscle fascia grafts used during tympanoplasty on the postoperative success rates.

PATIENTS AND METHODS

Fifty-four patients who underwent tympanoplasty between January 2006 and January 2007 in the Department of Otolaryngology, Medicine Faculty of Uludağ University and who were under regular follow-up were included in this prospectively planned study and divided into two groups: the study group (n=24) and the control group (n=30). Temporal muscle fascia grafts were used in all patients. The grafts were treated with formaldehyde in the study group. All the controls of the patients were performed by otomicroscopy. Audiometric tests were performed at the 6th month controls.

RESULTS

It was found out that perforation was permanently repaired in 79.2% of the study group and in 73.3% of the control group (p>0.05). We obtained an evident improvement in the average airway bone gap in both groups. We could not detect any statistical significance in the comparison of the operation duration between the groups although the operation duration in the study group was shorter (the study group: 735 seconds, the control group: 775 seconds).

CONCLUSION

The formaldehyde treatment of the temporalis muscle fascial graft used in tympanoplasty was not superior in closing perforation and operation length compared to its direct dry use. However, we concluded that the graft could be more easily manipulated during the operation.

[Effect of formaldehyde in low concentrations on the proliferation and organization of the cytoskeleton of cultured cells]

3-4% (1.07-1.42 M) formaldehyde is one of the most popular and well-known organs, tissues and cells fixer. In this manuscript we have shown that formaldehyde in concentrations of up to 60 microM (0.0002%) does not have any negative effect on the viability of cell lines A431, HEK293 and primary rat fibroblasts, but it is also increases the proliferative activity of A431. The influence on A431 cells might be explained by the activation of epidermal growth factor receptors as a result of their interaction with formaldehyde.

Influence of formalin fixation on the biomechanical properties of human diaphyseal bone

Owing to the lack of fresh human bones, formalin-fixed specimens are frequently used in biomechanical testing. However, formalin fixation is assumed to affect the biomechanical properties of bone. The aim of this study was to compare axial and torsional stiffness and bone mineral density in fresh and embalmed human bones. The subtrochanteric regions of 12 pairs of fresh human femora were randomised into two groups for paired comparison. After bone mineral density measurement, one group was preserved in 4% formalin. After 6 weeks, bone mineral density was remeasured and each specimen underwent axial and torsional loading. The formalin group showed significant higher stiffness values for torsional and axial loads than the fresh group. Axial stiffness increased by 14.1%, whereas torsional stiffness increased by 14.3%. These differences were not reflected in bone mineral density values. Formalin fixation significantly influences the stiffness of human cadaveric bones. Fresh bones represent the in vivo conditions better than formalin fixed bones.

Effects of formalin fixation on magnetic resonance indices in multiple sclerosis cortical gray matter

PURPOSE

To investigate changes in magnetic resonance imaging (MRI) indices following formalin fixation of postmortem multiple sclerosis (MS) cortical gray matter (CGM). Postmortem MS brain is being used to establish pathological correlates of changes detected using MRI, with recent emphasis on CGM. Fixation induces tissue alterations that may confound inference of in vivo observations from MRI/histology correlation studies.

MATERIALS AND METHODS

T(2)-weighted scans were obtained alongside quantitative T(1), magnetization transfer ratio (MTR), and macromolecular proton fraction (f(B)) measurements before and after formalin fixation of 15 postmortem brain samples. Type and size of CGM lesions (CGML) was identified on sections immunostained for myelin basic protein.

RESULTS

MRI indices obtained in unfixed MS CGM were similar to values obtained in subjects with MS in vivo. Fixation led to reduction in T(1) (617 msec [standard deviation = 114] vs. 1156 msec [216]) and MTR (24.1 [3.3] percent units [pu] vs. 29.1 [2.5] pu) and increase in f(B) (5.4 [0.7] pu vs. 3.2 [2.3] pu) (all P < 0.01). The proportion of CGM affected by demyelination did not alter the MRI data.

CONCLUSION

MRI indices in the CGM are significantly altered following tissue fixation.

[Role of the surgical pathology laboratory in the pre-analytical approach of molecular biology techniques]

The advent of the targeted cancer therapies administered to patients, according to the results of molecular biology techniques (in particular, in situ hybridization, "polymerase chain reaction" amplification and sequencing), has modified the practice of the surgical pathology laboratories. The necessity to answer to the needs of physicians for optimizing the medical care for patients who develop cancer has led to a policy of national debate, spurred by the National Institute of Cancer (INCa), in order to implement new procedures in the pathology laboratories. Thus, in addition to the structuring of molecular biology platforms and their labeling by INCa, the upstream control of the steps present between resection of tumor samples and molecular analysis has proved to be crucial. Indeed, the quality of this upstream time, called "pre-analytical" phase, determines the reliability of the molecular biology results and therefore the therapeutic strategy. We describe here the main steps to be checked in the pre-analytical phase. The optimization of this pre-analytical phase within the surgical pathology laboratory aims to reduce or render insignificant the risk of errors of molecular biology tests. These errors can indeed lead to false negative or false positive results whose therapeutic consequences can be particularly harmful to patients with cancer.

Comparison of red blood cell membrane microstructure after different physicochemical influences: atomic force microscope research

PURPOSE

After the influence of different actions on the blood, the erythrocytes may change their macrostructure. At the same time, the microstructure of cell membrane will be changed as well. This study provides the results of comparison of red blood cell membrane microstructure after they have been affected by different factors.

MATERIALS AND METHODS

Images and spatial profiles of the cell surface were obtained by atomic force microscope. It was proposed to use spatial Fourier transform to decompose the initial complex profile into series of simple ones. This made it possible to compare surface parameters after exposure of red blood cells to different external actions.

RESULTS

Quantitative differences between membrane profile harmonic composition parameters (amplitude and spatial period) after physical impact (impulse electrical field, osmotic swelling) and after chemical impact (the fixing fluid glutaraldehyde and the drug Esmeron) were experimentally confirmed.

CONCLUSIONS

Such experimental and theoretical approach may lay down the foundations of mechanisms of different factors' effect on red blood cells both in research and in clinics.

Immunocytochemical detection of tissue antigens after prolonged storage of specimens in methylsalicylate

The aim of the present work was to verify the possibility of detecting various tissue antigens using standard immunocytochemical methods in paraffin sections of specimens stored in methylsalicylate for two years and longer before embedding in paraffin. Using the immunocytochemical reaction for the intermediate filament proteins nestin, vimentin, and GFAP, the neuron marker NeuN, neuron-specific enolase, and doublecortin as examples, these experiments showed that prolonged storage of dehydrated specimens in methylsalicylate does not prevent detection of antigens using immunocytochemical reactions.

[Application of polyguanidine solution for fixation of biological and anatomical specimens]

A new method for fixation of biological material is described, and its effectiveness is compared to that one of formalin fixation. As an embalming agent, polyhexamethylenguanidine (PHMG) hydrochloride was used. Using the proposed method of fixation, the anatomical and histological preparations of human organs and of chick embryos at developmental 12 days, were produced. The anatomical preparations obtained show the appearance, similar to that of the recently removed organs. Histological preparations were free from significant distortions of the microscopic characteristics of the specimens, which are typical to the material fixed with formalin. The results of the study suggest the possibility of PHMG application in the morphological studies.

In vitroantioxidant activities of antioxidant-enriched toothpastes

Several forms of periodontal diseases (PD) are often associated with modified phagocytosing leukocytes and contemporary free radical production. Host antioxidant defenses could benefit from toothpastes used as adjuncts to counteract plaque-associated bacteria. The aim of the present study was to determine possible antioxidant activity (AA) of 12 differently antioxidant-enriched toothpastes, regardless of their efficacy as antimicrobial agents. Toothpastes were enriched alternatively with sodium ascorbyl phosphate, alpha-tocopherol acetate, pycnogenol, allantoin and methyl salycilate or a mixture of these. AA was tested in a cell-free system with a ABTS-decolorization assay improved by means of a flow injection analysis device. Comet assay, using NCTC 2544 keratinocytes, was performed to test if it was possible to identify any protection against in vitro DNA fragmentation provoked by a challenge with H(2)O(2) in cultures pre-incubated with toothpaste extracts. Only toothpastes containing sodium ascorbyl phosphate displayed clear AA with I(50) values ranging between 50 and 80 mg of toothpaste/ml water. COMET analysis of cells challenged with H(2)O(2) in presence of toothpaste extracts revealed a limited protection exerted by sodium ascorbyl phosphate. The results described herein indicate that toothpastes containing sodium ascorbyl phosphate possess AA. All the data were obtained in systems in vitro and the demonstration of in vivo AA is desirable. These findings could be useful in the treatment and maintenance of some forms of PD and should be considered when arranging new toothpaste formulations.

Chromosome shattering: a mitotic catastrophe due to chromosome condensation failure

Chromosome shattering has been described as a special form of mitotic catastrophe, which occurs in cells with unrepaired DNA damage. The shattered chromosome phenotype was detected after application of a methanol/acetic acid (MAA) fixation protocol routinely used for the preparation of metaphase spreads. The corresponding phenotype in the living cell and the mechanism leading to this mitotic catastrophe have remained speculative so far. In the present study, we used V79 Chinese hamster cells, stably transfected with histone H2BmRFP for live-cell observations, and induced generalized chromosome shattering (GCS) by the synergistic effect of UV irradiation and caffeine posttreatment. We demonstrate that GCS can be derived from abnormal mitotic cells with a parachute-like chromatin configuration (PALCC) consisting of a bulky chromatin mass and extended chromatin fibers that tether centromeres at a remote, yet normally shaped spindle apparatus. This result hints at a chromosome condensation failure, yielding a "shattered" chromosome complement after MAA fixation. Live mitotic cells with PALCCs proceeded to interphase within a period similar to normal mitotic cells but did not divide. Instead they formed cells with highly abnormal nuclear configurations subject to apoptosis after several hours. We propose a factor depletion model where a limited pool of proteins is involved both in DNA repair and chromatin condensation. Chromosome condensation failure occurs when this pool becomes depleted.

Preliminary evidence that regular vinegar ingestion favorably influences hemoglobin A1c values in individuals with type 2 diabetes mellitus

This report examined whether daily acetic acid ingestion as vinegar, dill pickle, or commercial vinegar pill influenced hemoglobin A1c in diabetic patients. Hemoglobin A1c values fell 0.16% with vinegar use but rose 0.06% and 0.22% for pill and pickle use respectively (p=0.018). Hence, regular vinegar use modestly improved glycemic control.

Reduced antigenicity of formaldehyde-fixed arterial allografts and their potential clinical application

This study was performed to examine the antigenicity of formaldehyde-fixed arterial allografts and their potential clinical application for hemodialysis access. Human femoral arteries were fixed with formaldehyde. New Zealand white rabbits were immunized with antigens prepared from fixed or unfixed grafts followed by anti-serum collection. The antigenicity of fixed grafts was evaluated using double-diffusion in two dimensions. Seventy-six fixed allografts were transplanted into 50 patients with end-stage renal diseases as hemodialysis access and monitored for acute rejection, blood flow, and patency rates. Anti-HLA antibody was evaluated using a panel-reactive antibody (PRA) assay in 6 patients. Formaldehyde-fixed grafts demonstrated reduced antigenicity as determined using double-diffusion in two dimensions when compared with unfixed grafts. Histological evaluation of allografts demonstrated absence of cell-mediated acute rejection after transplantation. Allografts demonstrated satisfactory blood flow with primary and secondary patency rates at 1, 2, and 3 years after allotransplantation. Serum collected from 6 patients after transplantation (mean, 3.3 +/- 3.2 years) did not demonstrate increased anti-HLA antibody levels. The allograft intimal hyperplasia was characterized by proliferation of actin-expressing smooth muscle cells. This study demonstrated that formaldehyde fixation reduced the antigenicity of arterial allografts. Acute rejection was absent after allotransplantation. The lack of increased PRA levels after allotransplantation suggested that allo-sensitization is not induced by fixed allografts. The use of formaldehyde-fixed allografts as hemodialysis access demonstrated blood flow and patency rates. Intimal hyperplasia of allografts is characterized by proliferation of actin-expressing cells. Our results supported the clinical use of formaldehyde-fixed arterial allografts for hemodialysis access.

Preparative procedures markedly influence the appearance and structural integrity of protein storage vacuoles in soybean seeds

In legumes, vacuoles serve as the final depository for storage proteins. The protein storage vacuoles (PSVs) of soybean contain electron-transparent globoid regions in which phytic acid ( myo-inositol-1,2,3,4,5,6-hexakisphosphate) is sequestered. This paper reports the effect of preparative procedures on the appearance and ultrastructural integrity of PSVs in soybeans. Electron microscopy examination of both developing and mature soybean seeds that were postfixed with osmium tetroxide revealed PSVs that had a homogeneous appearance with very few globoid crystals dispersed in them. Numerous electron-dense lipid bodies were readily seen in these cells. Omission of osmium tetroxide strikingly altered the appearance of PSVs and aided the visualization of the location of the globoids in the PSVs. In contrast to the osmicated tissue, lipid bodies appeared as electron-transparent spheres. The choice of dehydration reagent or staining procedure had little influence on the appearance of the PSVs. The results of this study demonstrate the profound effect of osmium tetroxide on the appearance and structural integrity of PSVs in soybean.

Effect of modified Davidson's fixative on examined number of lymph nodes and TNM-stage in colon carcinoma

AIMS

We evaluated the effect of modified Davidson's fixative (mDF) on the number of lymph nodes examined and staging in patients with colon carcinoma.

METHODS

The results of two different fixation methods used in the pathological preparation of the resection specimens were analyzed. A traditional formalin preparation with manual dissection of all nodes was performed in 117 colon specimens between January 2003 and July 2004. After July 2004, the resected specimens of 125 patients was fixated in mDF. Differences in the retrieval and number of nodes and size of suspected nodal metastases were measured. All lymph nodes were stained with conventional H&E methods.

RESULTS

The median number of examined nodes increased from 5 (0-17) to 13 (0-35) nodes after the introduction of mDF (p<0.001). The type of resection and the T-stage influenced the number of retrieved nodes significantly. The percentage of node-positive cases increased from 30% to 41% (p=0.077) with mDF, the median size of the retrieved lymph nodes decreased from 9 mm before to 6 mm after mDF (p<0.001) and more micrometastases were found (6% vs. 16%, p=0.03).

CONCLUSIONS

With mDF technique more lymph nodes were retrieved in the resected colon specimens. Smaller nodes and more micrometastases were found, leading to more node positive patients.

Real-time polymerase chain reaction assays for rapid detection and quantification of Noctiluca scintillans zoospore

Application and availability of real-time polymerase chain reaction (PCR) assay to detect and quantify the Noctiluca scintillans zoospore were investigated seasonally. Specific primer set for N. scintillans 18S rDNA was designed and applied to real-time PCR assay using the serial dilutions of N. scintillans zoospores. The real-time PCR assays with Ns63F and Ns260R primers were applied to sea water samples collected weekly in Manazuru Port of Sagami Bay, Japan from April 2005 to June 2006. We developed effective DNA preparation steps for collecting the template DNA of N. scintillans zoospore: size fraction and filter concentration of the water samples, fixation with Lugol solution, cell lysis, and purification. This method is useful for the monitoring of the zoospores of N. scintillans, and can also be used for other small and physiologically fragile planktonic cell. Variation in the density of zoospore was successfully detected in the field samples. The peak density of N. scintillans zoospore was observed to occur just before or at the same time as the peak of the vegetative cells. Moreover, zoospores were detected in seawater even when the vegetative cells were not observed. The presence of zoospore was found all year round in the present study. In this regards, this information is essential for the study of the life cycle and seasonal variation of N. scintillans in the coastal waters.

The effect of paraformaldehyde fixation and PBS storage on the water content of the human lens

PURPOSE

Fixation and phosphate buffered saline (PBS) storage are frequently used before studies of the morphological, biochemical, and optical properties of the human lens begin. It is assumed that this does not alter the properties being examined. The present study was undertaken to determine the effects of fixation and PBS storage on the human lens wet weight.

METHODS

Human donor lenses were incubated in a buffered paraformaldehyde (PF) solution or in PBS and their wet weights were monitored for up to 44 and 13 days, respectively.

RESULTS

PF fixation resulted in a large decrease in wet weight, averaging 25%+/-2.3% at 30 days for 14 human donor lenses, aged 49-80 years. The loss was essentially complete by 21 days. Out of the 10 lenses, aged 52-71 years, which were incubated in PBS alone, six of them increased in weight by an average of 38% over 13 days and four ruptured within four days. Comparison of literature data for a fixed eight-year-old lens with those for an unfixed seven-year-old lens indicated that the decrease in wet weight was due mainly to a loss of water from the cortex, which resulted in virtual disappearance of the water/protein gradient and the formation of a plateau containing 58% water in over 90% of the lens.

CONCLUSIONS

Fixation substantially alters the amount and distribution of water in the human lens. Caution should be exercised when interpreting data on water and protein distributions as well as cell dimensions obtained with lenses which have been fixed. In addition, prolonged storage of a lens in PBS will result in substantial water uptake, which may affect measurements of their dimensions and optical properties.

Comparison of the fixative properties of five disinfectant solutions

Following a French circular published in 2001, the use of glutaraldehyde for the disinfection of reusable medical devices was abandoned in favour of non-fixative disinfectants such as peracetic-acid-based solutions. Data published regarding the fixative properties of alternative disinfectants remain contradictory. We compared the effect of repetitive treatments of polytetrafluoroethylene (PTFE) tubes, contaminated by a liquid medium inoculated with Pseudomonas aeruginosa, using five different disinfectant solutions: two peracetic acid solutions (with and without an activator), glutaraldehyde, ortho-phthaldehyde and succine dialdehyde. The results confirmed that repeated treatments of a PTFE tube with a 2% glutaraldehyde solution induce an important accumulation and/or fixation of protein, compared to peracetic-acid-based disinfectants, for which the accumulation and/or fixation of proteins remain low and vary from one formulation to another.

A protocol for isolation and visualization of yeast nuclei by scanning electron microscopy

This article describes a protocol that details methods for the isolation of yeast nuclei from budding yeast (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe), immunogold labelling of proteins, and visualization by Field Emission Scanning Electron Microscopy (FESEM). This involves the removal of the yeast cell wall and isolation of the nucleus from within, followed by subsequent processing for high resolution microscopy. The nuclear isolation step is performed by enzymatic treatment of yeast cells to rupture the cell wall and generate spheroplasts (cells that have partially lost their cell wall and their characteristic shape), followed by isolation of nuclei by centrifugation. This protocol has been optimized for the visualization of the yeast nuclear envelope (NE), nuclear pore complexes (NPCs), and associated cytoskeletal structures. Samples, once processed for FESEM, can be stored under vacuum for weeks, allowing considerable time for image acquisition.

Long term formalin preserved stool specimens for detection of intestinal parasites from school aged children in Tripoli, Libya

A total of 949 single stool samples were collected from school aged children (5-14 years old) in the city of Tripoli. The samples were preserved in 10% formalin and examined by routine microscopy using normal saline and Lugol's iodine preparations as well as the formol ethyl concentration method after a storage period of twelve months at room temperature. Of 949 samples examined 4.5% were positive. Giardia lamblia and Entamoeba coli were the only protozoan parasites identified with an infection rate of 3.2% & 1.3% respecttively. No helminthes were detected in any of the samples. About 14% of the children had intestinal yeast infection Candida albicans in their stool of which 0.63% was infected with intestinal parasites. No distortion or alteration of morphology was observed particularly in G. lamblia. Preservation in 10% formalin is a very productive means for the accurate identification of protozoan parasites.

Clinical studies of hemodialysis access through formaldehyde-fixed arterial allografts

Efficient hemodialysis requires establishing a permanent stable vascular access. Our study was designed to evaluate formaldehyde-fixed arterial allografts as hemodialysis access for end-stage renal disease. Various parameters were determined for 68 formaldehyde-fixed, cadaver-derived allografts transplanted into 43 hemodialysis patients. The sources of the allografts were determined to be free of cytomegalovirus, hepatitis B and hepatitis C, and HIV infections. These allografts were monitored for rejection, blood flow, patency rates, and complications. Overall, antigenicity of the allografts was reduced after formaldehyde fixation with no acute rejection. The mean access blood flow was 696+/-282 ml with reasonable primary and secondary patency rates even after 3 years. Allograft intimal hyperplasia, determined by immunohistochemistry, was evident as the proliferation of smooth muscle-like cells expressing actin but cells not expressing the endothelial markers von Willebrand factor or CD34. The incidence of thrombus formation was about 37% after allograft transplant with other limited complications of pseudoaneurysms and local infection. Our results support the clinical use of formaldehyde-fixed arterial allografts for hemodialysis access.