Accurate estimation of viral abundance by epifluorescence microscopy

Virus enumeration by epifluorescence microscopy (EFM) is routinely done on preserved, refrigerated samples. Concerns about obtaining accurate and reproducible estimates led us to examine procedures for counting viruses by EFM. Our results indicate that aldehyde fixation results in rapid decreases in viral abundance. By 1 h postfixation, the abundance dropped by 16.4% +/- 5.2% (n = 6), and by 4 h, the abundance was 20 to 35% lower. The average loss rates for glutaraldehyde- and formaldehyde-fixed samples over the first 2 h were 0.12 and 0.13 h(-1), respectively. By 16 days, viral abundance had decreased by 72% (standard deviation, 6%; n = 6). Aldehyde fixation of samples followed by storage at 4 degrees C, for even a few hours, resulted in large underestimates of viral abundance. The viral loss rates were not constant, and in glutaraldehyde- and formaldehyde-fixed samples they decreased from 0.13 and 0.17 h(-1) during the first hour to 0.01 h(-1) between 24 and 48 h. Although decay rates changed over time, the abundance was predicted by using separate models to describe decay over the first 8 h and decay beyond 8 h. Accurate estimates of abundance were easily made with unfixed samples stained with Yo-Pro-1, SYBR Green I, or SYBR Gold, and slides could be stored at -20 degrees C for at least 2 weeks or, for Yo-Pro-1, at least 1 year. If essential, samples can be fixed and flash frozen in liquid nitrogen upon collection and stored at -86 degrees C. Determinations performed with fixed samples result in large underestimates of abundance unless slides are made immediately or samples are flash frozen. If protocols outlined in this paper are followed, EFM yields accurate estimates of viral abundance.

Alcoholic fixation of blood to surgical instruments—a possible factor in the surgical transmission of CJD?

While developing a new protein removal test for the quality control of surgical instrument cleaning, it was noted that alcohol firmly binds blood to stainless steel. Creutzfeldt-Jacob disease is one of the transmissible spongiform encephalopathies (TSE) that has been transmitted between humans and chimpanzees by electroencephalogram electrodes, previously 'sterilized' using ethanol and formaldehyde. Although ethanol has a bactericidal action, it also binds protein to metal. Prion proteins found in TSE are thought to be the causal agents of spongiform disease and it is likely that these proteins are also bound to the stainless steel of surgical instruments by alcohols. Where spongiform disease is a possibility, alcohol, and probably formaldehyde, should not be used to decontaminate neurosurgical instruments.

The role of methyl salicylate in prey searching behavior of the predatory mite phytoseiulus persimilis

Many carnivorous arthropods use herbivore-induced plant volatiles to locate their prey. These plant volatiles are blends of up to hundreds of compounds. It is often unknown which compounds in such a complex volatile blend represent the signal to the foraging carnivore. We studied the role of methyl salicylate (MeSA) as part of the volatile blend in the foraging behavior of the predatory mite Phytoseiulus persimilis by using a Y-tube olfactometer. MeSA is one of the compounds released by lima bean, infested with Tetranychus urticae--a prey species of the predatory mite. MeSA attracted satiated predatory mites in a dose-dependent way with optimum attraction at a dose of 0.2 microg. Predatory mites did not discriminate between a prey-induced lima bean volatile blend (that contains MeSA) and a prey-induced volatile blend to which an extra amount of synthetic MeSA had been added. However, they preferred a MeSA-containing volatile blend (induced by T. urticae) to an otherwise similar but MeSA-free blend (induced by jasmonic acid). Adding synthetic MeSA to the MeSA-free blend significantly increased the mites' choice for this odor, suggesting an important role for MeSA. This study is a new step toward unraveling the role of herbivore-induced plant volatiles in the foraging behavior of predatory arthropods.

[Study on the formaldehyde-induced DNA damage with comet assay]

Formaldehyde is known as a genotoxic substance. Numerous studies have shown that formaldehyde could induce DNA-DNA and DNA-protein crosslinks. However, scholars have disagreed with each other on the formaldehyde-induced DNA strand breaks. We chose buccal cells as materials to evaluate the genotoxicity of formaldehyde with comet assay--especially for DNA strand breaks. The results showed that formaldehyde of low concentration induced DNA strand breaks, while formaldehyde of high concentration induced DNA-DNA and DNA-protein crosslinks. According to our experimental results, we proposed the concept of the "peak point of break" at which formaldehyde induced DNA strand breaks most.

ADAPT-treated porcine valve tissue (cusp and wall) versus Medtronic Freestyle and Prima Plus: crosslink stability and calcification behavior in the subcutaneous rat model

BACKGROUND AND AIM OF THE STUDY

The study aim was to compare the crosslink stability and calcification behavior of porcine tissue (cusp and wall), treated with a new antimineralization process (ADAPT) with that of commercially prepared Freestyle and Prima Plus bioprosthetic tissues.

METHODS

Porcine aortic roots were divided into two groups: (i) tissue zero pressure-fixed with 0.625% glutaraldehyde (GA) for seven days and stored in 0.25% GA (as control); and (ii) tissue exposed to the ADAPT process for four days and stored in 0.25% buffered GA. These groups were compared with Freestyle and Prima Plus tissues (cusp and wall). Crosslink stability was assessed by shrinkage temperature and resistance to pronase degradation. Calcification behavior was assessed histologically (Von Kossa staining) and by atomic absorption spectrophotometry of explanted tissue after eight weeks. in a subcutaneous rat model.

RESULTS

Crosslink stability and calcification potential of ADAPT-treated porcine valve cusps were comparable to those of Freestyle and Prima Plus cusps (p = NS). ADAPT-treated porcine wall tissue showed improved crosslink stability (p <0.05) and significantly (p <0.001) reduced calcification (-95.95%) compared to control (-0.00%), Freestyle (-47.87%) and Prima Plus (-51.95%) tissues.

CONCLUSION

The ADAPT process is effective in reducing calcification in both porcine cusp and wall tissues in a subcutaneous rat model, and further suggest that enhanced crosslinking plays an important role in minimizing aortic wall calcification.

Repeated low level formaldehyde exposure produces enhanced fear conditioning to odor in male, but not female, rats

Multiple chemical sensitivity (MCS) is an ill-defined disorder in humans attributed to exposure to volatile organic compounds. This study draws on apparent parallels between individuals with posttraumatic stress disorder (PTSD) and panic disorder and a subset of those reporting MCS, using a conditioned fear task in rats. Male and female Sprague-Dawley rats were given repeated exposure to 2 ppm formaldehyde (Form) (1 h/day x 5 days/week x 4 week) or air, and after 2-3 weeks, rats were trained on the conditioned fear task. One half of Air and Form rats were given odor (orange oil, the conditioned stimulus, CS) paired with footshock (PRD) and the other half was given the same stimuli in an unpaired manner (UNP). After 24 h, rats were placed into the same context without the CS or footshock. Male and female PRD groups demonstrated contextual freezing 5-15% of the time, while the UNP groups showed freezing 30-50% of the time, with no effect of Air or Form pretreatment. For the next 5 days, rats were placed into a novel context and tested for freezing in the absence or presence of the CS. In male rats, Form pretreatment produced a significantly greater freezing response in both UNP and PRD groups in the presence of the CS, with no differences in freezing in the absence of the CS. In female rats, no significant differences between Form pretreated rats and Air controls were observed in either the PRD or UNP groups. The increase in conditioned fear responding to the CS after Form exposure in males suggests that repeated low-level Form may act as a stressor to produce sensitized responding within olfactory/limbic pathways, and may help explain the panic-like responses observed in a subset of individuals reporting MCS. Furthermore, the male/female differences suggest a gonadal hormonal contribution to this behavior.

A method to preserve sputum for delayed examination

Examination of sputum cell counts is limited by the need to process samples within hours of expectoration. The validity and repeatability of a method to preserve sputum for delayed processing and examination were investigated in this study. Portions of selected sputum from 39 subjects were dispersed with dithiothreitol (routine method), or were fixed in a dithiothreitol-formaldehyde mixture for 48-72 h before dispersal with trypsin (preservation method). Total and differential cell counts using the two methods were compared; within-method repeatability of the preservation method was also examined. The intraclass correlation coefficient (ICC) for total cell counts and percentage of eosinophils, neutrophils and macrophages in sputum processed by the two methods was 0.89, 0.86, 0.91 and 0.90, respectively. Within-method repeatability (ICC) of the preservation method for the same cellular indices was 0.99, 0.94, 0.97 and 0.97, respectively. The interobserver repeatability for eosinophils, neutrophils and macrophages was 0.96, 0.97 and 0.97 using the preservation method, and 0.96, 0.99 and 0.99 using the routine method, respectively. This method of sputum preservation and dispersal is valid, reliable and convenient, and may be used for delayed processing and examination.

Two distinct distributions of F-actin are present in the hyphal apex of the oomycete Achlya bisexualis

We show that two distinct distributions of F-actin are present in the hyphal apex of the oomycete Achlya bisexualis, that have been chemically fixed with a combination of methylglyoxal and formaldehyde and stained with Alexa phalloidin. In approximately one half of the hyphae examined, an F-actin depleted zone within the apical F-actin cap was observed. The remaining hyphae had a continuous apical cap. In live, growing hyphae two types of cytoplasmic organization were observed at the tips, one in which a clear zone was present which may correlate with the F-actin depleted zone, and one where no such clear zone existed which may represent the continuous cap. We suggest that the F-actin depleted zone may be a structural component of the actin network in a subpopulation of oomycete hyphae and may be comparable to similar F-actin depleted zones at the apices of other tip growing cells such as pollen tubes and root hairs. This observation has implications with regard to models of hyphal extension. Hyphae fixed with formaldehyde alone showed continuous apical F-actin caps. Our ability to resolve the F-actin depleted zone likely reflects the cross-linking capabilities of methylglyoxal. The methylglyoxal-formaldehyde combination fixative gave more stained hyphae, brighter staining and more complete staining of F-actin compared to formaldehyde alone.

Formalin-induced changes of NMDA receptor subunit expression in the spinal cord of the rat

Using RT-PCR, the present study investigated the effects of formalin administration on mRNA expression coding for NMDA receptor (NR) subunits and splice variants in rat lumbar spinal cord. Subsequent to formalin injection (5%; subcutaneously) into the hind paw of Sprague-Dawley rats, the animals exhibited the typical biphasic behavioural pain response. Spinal cord (L3-6) was prepared six hours after formalin injection. In controls, NR1-b predominated over NR1-a, and NR1-2 and NR1-4 exceeded over NR1-1 and NR1-3, respectively. Regarding the NR2 subunit expression in controls, NR2B exhibited the highest expression, followed by decreasing proportions of NR2C, NR2A, and NR2D. Formalin treatment did not affect NR1 splice variant expression but significantly increased and decreased the proportion of NR2A and NR2C, respectively. In summary, the present data demonstrate adaptive changes in the NR subunit expression pattern in rat spinal cord due to formalin injection.

Effect of the cytoskeletal fixation agent phalloidin on transcapillary albumin transport and interstitial fluid pressure following subdermal prostaglandin E1 administration in the rat

AIM

Lowering of interstitial fluid pressure (Pif) facilitates fluid filtration across the capillary membrane and oedema formation in acute inflammation. The cellular mechanism behind this lowering of Pif involves beta1-integrins mediating contact between dermal cells and the extracellular matrix fibres, and also the cell cytoskeleton as disruption of actin filaments using cytochalasin-D induced a lowering of Pif and oedema formation. Fixation of actin with phalloidin attenuates oedema formation and abolishes lowering of Pif in anaphylaxis in the rat. The objective of this study was to determine whether phalloidin modifies lowering of Pif and albumin extravasation in rat skin also after prostaglandin E1 (PGE1).

METHODS

Pif was measured using micropipettes connected to a servo-controlled counterpressure system. Microvascular permeability was estimated as the albumin extravasation (Ealb) using radiolabelled human serum albumin.

RESULTS

Subdermal injection of PGE1 (0.85 mg mL-1) lowered Pif from -0.8 +/- 0.8 mmHg (SD) in control to -3.5 +/- 0.9 mmHg (P < 0.05) within 30 min. Pre-treatment with phalloidin (500 microg kg-1) before PGE1 resulted in Pif of -1.7 +/- 1.0 mmHg (P < 0.05 compared with PGE1). Ealb after subdermal saline was 0.07 +/- 0.04 mL g-1 DW and increased to 0.32 +/- 0.32 mL g-1 DW with PGE1 (P < 0.05) but was unaffected by pre-treatment with phalloidin given before PGE1 0.32 +/- 0.35 mL g-1 DW (P > 0.05 compared with PGE1 alone).

CONCLUSION

These results are consistent with the concept that the cytoskeleton actin filaments participate in control of Pif.

Tissue regeneration patterns in acellular bovine pericardia implanted in a canine model as a vascular patch

It was noted in our previous study that acellular tissues can provide a natural microenvironment for host cell migration and proliferation to accelerate tissue regeneration. The purpose of this study was to further investigate the tissue regeneration patterns in acellular bovine pericardia fixed with glutaraldehyde or genipin as a biological patch to repair a defect in the pulmonary trunk in a canine model. The implanted samples were retrieved at distinct durations postoperatively. The structural remodeling of retrieved samples was then examined. It was found that the degree of inflammatory reaction observed for the genipin-fixed acellular patch was significantly less than its glutaraldehyde-fixed counterpart. At 1 month postoperatively, intimal thickening was found on the inner surfaces of both studied groups. The intimal thickening observed on the glutaraldehyde-fixed acellular patch was significantly thicker than its genipin-fixed counterpart. An intact layer of endothelial cells was found on the intimal thickening of the genipin-fixed acellular patch, whereas endothelial cells did not universally and totally cover the entire surface of the glutaraldehyde-fixed acellular patch. Additionally, fibroblasts with neocollagen fibrils and myofibroblasts were observed in the acellular patches for both studied groups, an indication of tissue regeneration. This phenomenon was more prominent for the genipin-fixed acellular patch than its glutaraldehyde-fixed counterpart. At 6 months postoperatively, foci of chondroid and/or bony metaplasia were found in each retrieved sample for both studied groups. The observed adverse response of chondroid metaplasia may be attributed to a compliance mismatch at the implanted site of the canine pulmonary trunk after implantation or a lack of angiogenesis in the regenerated tissue observed at 1 month postoperatively. Bony metaplasia may then develop as in other chondroid tissues. It was reported that ischemia is a usual cause of metaplasia.

Platelets stimulate fibroblast-mediated contraction of collagen gels

BACKGROUND

Platelets are thought to play a role in a variety of inflammatory conditions in the lung, some of which may lead to fibrosis. In the current study we tested the hypothesis that whole platelets and platelet lysate can mediate remodelling of extracellular matrix in vitro by affecting fibroblast-mediated contraction of a collagen gel. We also sought to determine to what extent platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) contribute to this effect.

METHODS

Washed platelets, isolated from healthy blood donors, and platelet lysate (freezing and thawing), were cast together with human lung fibroblasts in three-dimensional collagen gels. The gels were then released and cultured for four days. PDGF and TGF-beta1 concentrations were measured in culture supernatants by ELISA.

RESULTS

Both platelets and platelet lysate augmented fibroblast-mediated gel contraction in a time and concentration dependent manner (19.9% +/- 0.1 (mean +/- SEM) of initial area vs. 48.0% +/- 0.4 at 48 hours; P < 0.001 and 41.5% +/- 0.6 vs. 60.6% +/- 0.3 at 48 hours; P < 0.001, respectively). Fixed platelets had no effect in the system. Both TGF-beta1 and PDGF-AA/AB were released in co-culture. PDGF-AA/AB had a maximum release at 24 hours whereas TGF-beta1 release increased with longer culture periods. Neutralising antibodies to these mediators partially inhibited platelet-induced gel contraction.

CONCLUSION

We conclude that platelets may promote remodelling of extracellular matrix in vitro and that PDGF and TGF-beta partially mediate this effect, also indicating a role for other mediators. The findings may be an important mechanism in regulating repair processes after injury.

Dynamic alterations of glomerular charge density in fixed rat kidneys suggest involvement of endothelial cell coat

In a previous paper, we found that low ionic strength (I) reversibly reduced the glomerular charge density, suggesting increased volume of the charge-selective barrier. Because glutaraldehyde makes most structures rigid, we considered the isolated, perfusion-fixed rat kidney to be an ideal model for further analysis. The fixed kidneys were perfused with albumin solutions containing FITC-Ficoll at two different Is (I = 151 and 34 mM). At normal I, the fractional clearance () for albumin was 0.0049 (SE -0.0017, +0.0027, n = 6), whereas for neutral Ficoll35.5A of similar size was significantly higher 0.104 (SE 0.010, n = 5, P < 0.001). At low I, for albumin was 0.0030 (SE -0.0011, +0.0018, n = 6, not significant from albumin at normal I) and for Ficoll35.5A was identical to that at normal I, 0.104 (SE 0.015, n = 6, P < 0.01 compared with albumin at low I). According to a heterogeneous charged fiber model, low I reduced the fiber density from 0.056 to 0.0315, suggesting a 78% gel volume expansion. We conclude that 1) there is a significant glomerular charge barrier. 2) Solutions with low I increase the volume of the charge barrier even in kidneys fixed with glutaraldehyde. Our findings suggest that polysaccharide-rich structures, such as the endothelial cell coat, are key components in the glomerular barrier.

Effect of formalin fixation on the near-infrared Raman spectroscopy of normal and cancerous human bronchial tissues

Raman spectroscopy is a vibrational spectroscopic technique that can be used to probe molecular changes associated with tissue malignancy. In this report, the effect of formalin fixation on human bronchial tissues was studied by near-infrared (NIR) Raman spectroscopy to determine if the variations of Raman spectra caused by formalin fixation would affect the potential diagnostic ability for lung cancer detection. A rapid dispersive-type NIR Raman system with an excitation wavelength of 785 nm was used for this study. Bronchial tissue samples were obtained from six patients with known or suspected malignancies of the lung. Raman spectra of fresh normal and tumor tissue were compared with spectra of formalin-fixed normal and tumor tissue. Changes of the ratios of Raman intensities at 1445 to 1655 cm(-1) and 1302 to 1265 cm(-1) versus formalin fixing times varying from 2 to 24 h were also examined. The major tissue Raman peaks at 1265, 1302, 1445, and 1655 cm(-1) were found in both fresh and fixed bronchial tissues. However, bronchial tissue preserved in formalin showed a progressive decrease in overall intensities of these Raman peaks. Raman contaminations due to formalin were also found in the 980-1100, and 1480-1650 cm(-1) ranges with notable formalin peaks (1041 and 1492 cm(-1)) appearing in the fixed normal and tumor tissues. The results showed that NIR Raman spectra of human bronchial tissues were significantly affected by formalin fixing and tissue hydration. Diagnostic markers at the 980-1100, and 1500-1650 cm(-1) regions derived from fixed tissues do not appear to be applicable for in vivo lung cancer detection. To yield valid Raman diagnostic information for in vivo applications, fresh tissue should be used. If only fixed tissue is available, thorough rinsing of specimens in phosphate-buffered saline (PBS) before spectral measurements may help reduce the formalin fixation artifacts on tissue Raman spectra.

Studies on the internalization mechanism of cationic cell-penetrating peptides

A great deal of data has been amassed suggesting that cationic peptides are able to translocate into eucaryotic cells in a temperature-independent manner. Although such peptides are widely used to promote the intracellular delivery of bioactive molecules, the mechanism by which this cell-penetrating activity occurs still remains unclear. Here, we present an in vitro study of the cellular uptake of peptides, originally deriving from protegrin (the SynB peptide vectors), that have also been shown to enhance the transport of drugs across the blood-brain barrier. In parallel, we have examined the internalization process of two lipid-interacting peptides, SynB5 and pAntp-(43-58), the latter corresponding to the translocating segment of the Antennapedia homeodomain. We report a quantitative study of the time- and dose-dependence of internalization and demonstrate that these peptides accumulate inside vesicular structures. Furthermore, we have examined the role of endocytotic pathways in this process using a variety of metabolic and endocytosis inhibitors. We show that the internalization of these peptides is a temperature- and energy-dependent process and that endosomal transport is a key component of the mechanism. Altogether, our results suggest that SynB and pAntp-(43-58) peptides penetrate into cells by an adsorptive-mediated endocytosis process rather than temperature-independent translocation.

New red blood cell lysing fixative for use in fine needle aspiration and fluid cytology

OBJECTIVE

To describe a new red blood cell (RBC) lysing fixative, Devine's lysing solution (DLS), that increases the diagnostic utility of fine needle aspiration (FNA) and fluid cytology.

STUDY DESIGN

Twenty bloody FNA cases were fixed with either DLS or 95% ethanol, and the ability to render a diagnosis on these materials was analyzed. DLS was compared to the red cell lysing fixative CytoRich Red (CRR) (TriPath Care Technologies, Burlington, North Carolina, U.S.A.) in its ability to lyse RBCs by mixing human RBCs with the U266 multiple myeloma cell line. DLS was compared to CRR in its ability to suitably preserve materials for Papanicolaou and immunocytochemical analysis.

RESULTS

Comparison of DLS with 95% ethanol fixation in 20 bloody FNA cases prepared in duplicate showed that DLS reduced from 17 to 3 the number of cases that had RBCs obscuring > or = 25% of the diagnostic material. In 3 cases, DLS enabled the rendering of a definitive diagnosis of malignancy, which could not be made on the ethanol-fixed material. DLS was compared to CRR, and both fixatives were similarly effective at lysing RBCs, preserving the cellular morphology of diagnostic cells in FNA and fluid cytology, and preserving cells for use in immunocytochemistry.

CONCLUSIONS

DLS increases the visualization of diagnostic cellular material when compared to ethanol fixation. DLS is comparable to CRR in RBC lysing ability, diagnostic cell preservation and preservation of materials for immunocytochemistry.

Impact of brief exposure to balanced salts solution or cetylpyridinium chloride on the surface appearance of the rabbit corneal epithelium--a scanning electron microscopy study

PURPOSE

To examine the surface of pre-corneal mucous layer by scanning electron microscopy (SEM) with the view to assessing whether it was an amorphous, fibrous or porous structure.

METHODS

Healthy female albino rabbits (2 kg) were euthanised at 15.00 h and the corneal surface immediately fixed with buffered glutaraldehyde fixative pH 7.2 to 7.4 at 35 degrees C, carefully rinsed with balanced salts solution (BSS) and then fixed, or treated with the same fixative containing 0.05 to 0.25% w/v cetylpyridinium chloride (CPC). The corneas were critical point dried and gold-palladium coated, prior to examination at 1000x or 15000x magnification.

RESULTS

Buffered glutaraldehyde fixation resulted in an SEM image of polygonal cells, with very contrasting electron reflexes (light, medium and dark) and distinct cell surface microplicae and large crater-like features (average diameter 2.8 +/- 0.9 microm). Along the cell-cell borders was a distinct line (referred to as "caulking"), perhaps composed of mucous. Rinsing of the corneal surface with BSS just before fixation reduced the cell contrast, the surface was then covered with very short strands or small clumps of presumed mucus, the cell-cell border features were changed, but the crater-like features were largely unchanged (average diameter 2.5 +/- 0.7 microm). Fixation in the presence of 0.05% or 0.1% CPC resulted in the appearance of very short fine strands and occasional coarse mucous strands or even small plaques of mucous on the cell surfaces. The microplicae and craters were still often evident. Fixation with 0.2 or 0.25% CPC however yielded a surface with a uniform grey reflex that included numerous ultramicroscopic debris particles (average diameter of 72 nm) and was punctuated by numerous pores. No microplicae or craters were evident. The average pore diameter was 70 nm, their density averaged 59/5 microm(2), but a radial distribution analysis indicated no substantial pattern.

CONCLUSIONS

The pre-corneal mucous layer can be dispersed, by careful rinsing with a divalent cation containing solution, into small fibrils or clumps, but the cell surface craters are unaffected. After precipitation with a low concentrations of a polycation, some coarse fibrils are also formed. The use of high concentrations of a polycation in the fixative transforms the more superficial aspects of the pre-corneal mucous layer into a pore-like gel. The crater-like features therefore do not appear to be mucous, but the pore-like structure may be indicative of the organisation of the mucous layer on the surface of the living eye.

Porcine stentless bioprostheses: prevention of aortic wall calcification by dye-mediated photo-oxidation

PURPOSE

Aortic wall calcification is problematic in stentless porcine valves. We evaluated the possible anticalcification effect of photo-oxidation on the aortic wall portion of porcine stentless bioprostheses. A comparison with glutaraldehyde-fixed tissue was made.

METHODS

Six Photofix and six Freestyle valves were implanted in juvenile sheep in pulmonary position. Valves were explanted after 3 or 6 months and examined macroscopically, by x-ray, light, and transmission electron microscopy. Calcium content was determined by atomic absorption spectrometry.

RESULTS

The aortic wall portion of all Photofix valves remained free from calcification, while the wall portion of glutaraldehyde-fixed valves calcified strongly, both after 3 and 6 months. Calcium content of the aortic wall portion was: 0.71 +/- 1.27 in the Photofix valves versus 10.78 +/- 77.22 in the Freestyle valves (P < 0.05).

CONCLUSION

Photo-oxidation of a porcine stentless valve prevents calcification not only in the cusps but also in the aortic wall portion.

Electrocardiographic changes associated with the nasopharyngeal reflex in conscious rabbits: vago-sympathetic co-activation

Electrocardiographic responses were assessed in conscious rabbits when the nasopharyngeal reflex was elicited by inhalation of formaldehyde vapour. There was a profound fall in heart rate (224+/-5 to 64+/-4 beats per min (bpm)) associated with abnormal or absent P-waves. There were no changes in the QRS complex. The R-T interval (control value 118+/-4 ms) was initially shortened to 107+/-3 ms and then prolonged to 130+/-4 ms. Heart rate and P-wave changes were prevented by muscarinic cholinergic blockade with methylscopolamine. The R-T shortening was reduced by 79+/-4% by beta-adrenergic blockade with propranolol. Methylscopolamine also unmasked small tachycardic responses (5-25 bpm) in 5/7 animals. This tachycardia was prevented by propranolol. Thus both parasympathetic vagal cardiac nerves and sympathetic cardiac nerves are activated during the nasopharyngeal reflex, with increased vagal effects in the sino-atrial node, and increased sympathetic effects in the ventricular myocardium.

Histological preparation of developing vestibular otoconia for scanning electron microscopy

The unique nature of vestibular otoconia as calcium carbonate biominerals makes them particularly susceptible to chemical deformation during histological processing. We fixed and stored otoconia from all three otolith endorgans of embryonic, hatchling and adult Japanese quail in glutaraldehyde containing either phosphate or non-phosphate buffers for varying lengths of time and processed them for scanning electron microscopy. Otoconia from all age groups and otolith endorgans processed in 0.1 M phosphate buffer (pH 7.4) showed abnormal surface morphology when compared to acetone fixed controls. Otoconia processed in 0.1 M sodium cacodylate or HEPES buffered artificial endolymph (pH 7.4) showed normal morphology that was similar to controls. The degree of otoconial deformation was directly related to the time exposed to phosphate buffer. Short duration exposure produced particulate deformations while longer exposures resulted in fused otoconia that formed solid sheets. Otoconial surface deformation and fusing was independent of the glutaraldehyde component of the histological processing. These findings should help vestibular researchers to develop appropriate histological processing protocols in future studies of otoconia.

Treatment of hemorrhagic radiation proctitis with 4 percent formalin

PURPOSE

The purpose of this study was to review our results in patients undergoing treatment with 4 percent formalin for radiation-induced injury to the rectum.

METHODS

A retrospective review of office charts was performed, identifying all patients undergoing formalin treatment. Patient gender, initial malignancy, prior treatments, response to treatment with formalin, complications, and length of follow-up were reviewed. All patients had flexible endoscopy to assess for proximal sources of bleeding. The indication for treatment was a symptomatic patient with endoscopic evidence of radiation injury. A cotton pledget was used for direct application of 4 percent formalin to the affected area via a rigid proctoscope or anoscope. The treatment was repeated if blanching did not occur or if bleeding continued. Patients were followed up at three-week to four-week intervals and treatment was repeated based on the above indications. Treatments were continued until cessation of bleeding occurred or, when treatment failed, operative treatment was required.

RESULTS

Thirty-six patients were identified. Three were lost to follow-up. Symptoms included bleeding in all but one patient, who presented with an ulcer. There were 33 (26 male) patients. Seventeen (51.5 percent) patients had prior treatment. The number of formalin treatments ranged from 1 to 13, with a mean of 3.4. The follow-up ranged from 1 to 60 months, with a mean of 18 months. Twenty-nine (88 percent) patients had improvement or cessation of symptoms. Four (12 percent) patients failed treatment. Two patients were noted to have full-thickness ulcers and both failed formalin treatment. No complications were noted related to formalin treatment.

CONCLUSION

We conclude that formalin therapy is a safe and effective form of treatment that can be performed in the office with minimal discomfort and no complications. It can be performed multiple times until results are achieved. Formalin therapy may be useful as a first-line treatment for chronic radiation proctitis, however, a prospective controlled trial comparing modalities is required to prove this to be true.

To fix or not to fix: the role of 2-phenoxyethanol in rabbit, Oryctolagus cuniculus, chin gland secretion

The European rabbit (Oryctolagus cuniculus) uses the secretion of the chin gland to maintain dominance hierarchies in the wild. Recent work has investigated changes in the secretion when social status is manipulated in the rabbit. When a rabbit becomes dominant, a new compound appears in his secretion, 2-phenoxyethanol. This compound is used as a fixative in the perfume industry. This study investigates whether the compound performs a similar function in the secretion of the rabbit. 2-Phenoxyethanol is not detected olfactorially by rabbits, and slows the release rate of some of the compounds that occur naturally in rabbit chin gland secretion. We suggest that when a rabbit becomes dominant, he adds a fixative to his secretion so that his scent will persist in the environment and not dissipate. He will thus come to dominate the olfactory environment, in much the same way as he does the physical environment.

A novel method to determine specificity and sensitivity of the TUNEL reaction in the quantitation of apoptosis

Apoptosis is an important mode of cell death under both physiological and pathophysiological conditions. Numerous techniques are available for the study and quantitation of apoptosis in cell culture, but only few are useful when applied to complex tissues. Among these, the terminal transferase-mediated dUTP nick end-labeling (TUNEL) assay remains the most widely used technique. However, its specificity and sensitivity for the detection of apoptosis remain controversial. We developed a technique consisting of staining live cells and tissues with Hoechst 33342 and the vital dye propidium iodide (PI), followed by fixation and the TUNEL reaction. We demonstrate excellent retention of PI in necrotic cells after fixation. We also examined the distribution of TUNEL staining among necrotic and apoptotic cells in various models of cell injury in vitro and in vivo. We show that the sensitivity of the TUNEL varied between 61 and 90% in the models examined. The specificity exceeded 87% in all models but fell to 70% when a predominantly necrotic injury was induced. This novel and simple method will permit the determination of indices of sensitivity and specificity for the TUNEL assay in other tissues and experimental conditions.