PDE5 inhibitors: considerations for preference and long-term adherence.

INTRODUCTION: Erectile dysfunction (ED) is a highly prevalent condition affecting nearly one in five men worldwide. The advent of phosphodiesterase type 5 inhibitors (PDE5i) has revolutionised the ED treatment landscape and provided effective, minimally invasive therapies to restore male sexual function. MATERIALS AND METHODS: A pubmed search was performed of all English language articles from 1996 to present reviewing PDE5i, including pharmacokinetics, efficacy profiles and comparisons, where available. RESULTS: Currently available PDE5i in the United States include sildenafil, vardenafil, tadalafil and avanafil, each of which has unique side effect, pharmacokinetic and outcome profiles. Sildenafil is associated with increased rate of visual changes, vardenafil with QT prolongation and tadalafil with lower back pain. Avanafil and vardenafil orodispersible tablet rapidly achieve peak plasma concentration, which results in faster onset of action, whereas tadalafil exhibits the longest half-life. First time response to PDE5i is approximately 60-70%, with no significant differences in efficacy noted among therapies. The literature does not clearly demonstrate a preference for one drug. High-treatment success rates (89%) were reported when patients were prescribed all available PDE5i. Daily dosing with tadalafil is associated with improved erectile function (EF) over time. Finally, novel modes of patient-provider interaction, including internet-based education, communication and prescribing, may also improve long-term adherence. CONCLUSIONS: PDE5i represent first line therapy for ED with excellent overall efficacy and satisfactory side effect profiles. Enhanced communciation, coupled with increased knowledge of drug characteristics, comparative treatment regimens and optimal prescribing patterns, offer compelling tools to improve long-term treatment success.

Understanding the course of Peyronie's disease.

AIMS: To correct common misconceptions about Peyronie's disease (PD) that present obstacles to early recognition and treatment. METHODS: The prevalence, natural disease course, psychosocial effects and treatment considerations for patients with PD were reviewed. RESULTS: Studies over the past decade have shown that the prevalence of PD may be higher (up to 20%) than previously thought. PD can lead to emotional and relationship distress. Nearly 10% of men who present with PD are younger than 40. Both younger age and comorbid vascular disease have been associated with more severe and progressive PD. In the majority of patients, symptoms will either deteriorate or remain stable. PD is often associated with erectile dysfunction (ED). Effective, minimally invasive treatments used early in the disease course include unapproved and/or investigational intralesional injection therapy with verapamil, interferon (IFN) α-2b, or collagenase clostridium histolyticum (CCH). Surgical intervention is considered in patients with ED and/or penile deformity that impairs sexual functioning; however, preoperative discussion of appropriate expectations is important. DISCUSSION: The availability of effective minimally invasive and surgical therapies for PD suggests that active management should be considered over a 'wait-and-see' approach. CONCLUSION: Providing early intervention and improved education/awareness of PD as a chronic and progressive disorder may result in improved physical and psychosocial outcomes for PD patients. As general practitioners are often the first contact for men with PD, they are well positioned to recognise symptoms early and promptly refer patients for further evaluation and treatment.

Development of a new grading system to assess the foster performance of lactating sows.

Increasing litter size has created the need for more sophisticated, accurate, and welfare-oriented systems for assessing the foster performance of lactating sows. The estimation of milk yield alone is not sufficient for meeting these requirements. Therefore, the aim of the current study was to develop a grading system for assessing the foster performance of lactating sows that can be easily applied in commercial farm practice. Data were collected in two German conventional farrow-to-feeder farms with a total sample size of 639 sows (4.05 ± 2.86 parities) and 1 728 litters. Besides general performance data, the piglets were weighed individually within the first 24 hours after birth and at the peak of lactation (day 18.22 ± 2.48). Based on these data, we proposed a new score referring to the milk score (MS). This score was compared with the commonly used formula for estimating milk yield (est. MY), which solely involves litter weight gain and litter size. The improvement of the developed MS allowed us to distinguish between the birth and foster performances of the lactating sows through considering cross-fostering, litter size, individual piglet weights, and piglet mortality during lactation. Both scores showed a similar progression across parities. It was found that litter size had a significant impact on the performance of lactating sows. A high est. MY was found to be associated with a significantly higher number of piglets per litter (15.79 ± 2.20), lower weight gain per piglet, and increased piglet mortality during lactation compared with sows with high MS, which showed a smaller litter size (13.51 ± 2.18) (P < 0.05). The focus on smaller litter size indicates a performance limitation, which seems to be related to the average teat number of 13-15 teats per sow. We recommend the consideration of the number of functional teats, because a litter size above it will not result in a sow having higher foster performance. In conclusion, as an extension of the common est. MY calculation, the MS considers cross-fostering as current farm-management practice when dealing with larger litters. Our recommendations emphasise the importance of an MS which indicates smaller litter size, higher piglet weight gain, and lower piglet mortality during lactation; these factors are related to an improvement in animal welfare for sows and piglets. Moreover, the presented MS could be used to develop a management tool for farmers to assess the foster performance of lactating sows, considering individual farm-management practices.

The mitochondrial permeability transition in cell death: a common mechanism in necrosis, apoptosis and autophagy.

Using confocal microscopy, onset of the mitochondrial permeability transition (MPT) in individual mitochondria within living cells can be visualized by the redistribution of the cytosolic fluorophore, calcein, into mitochondria. Simultaneously, mitochondria release membrane potential-indicating fluorophores like tetramethylrhodamine methylester. The MPT occurs in several forms of necrotic cell death, including oxidative stress, pH-dependent ischemia/reperfusion injury and Ca2+ ionophore toxicity. Cyclosporin A (CsA) and trifluoperazine block the MPT in these models and prevent cell killing, showing that the MPT is a causative factor in necrotic cell death. During oxidative injury induced by t-butylhydroperoxide, onset of the MPT is preceded by pyridine nucleotide oxidation, mitochondrial generation of reactive oxygen species, and an increase of mitochondrial free Ca2+, all changes that promote the MPT. During tissue ischemia, acidosis develops. Because of acidotic pH, anoxic cell death is substantially delayed. However, when pH is restored to normal after reperfusion (reoxygenation at pH 7.4), cell death occurs rapidly (pH paradox). This killing is caused by pH-dependent onset of the MPT, which is blocked by reperfusion at acidotic pH or with CsA. In isolated mitochondria, toxicants causing Reye's syndrome, such as salicylate and valproate, induce the MPT. Similarly, salicylate induces a CsA-sensitive MPT and killing of cultured hepatocytes. These in vitro findings suggest that the MPT is the pathophysiological mechanism underlying Reye's syndrome in vivo. Kroemer and coworkers proposed that the MPT is a critical event in the progression of apoptotic cell death. Using confocal microscopy, the MPT can be directly documented during tumor necrosis factor-alpha induced apoptosis in hepatocytes. CsA blocks this MPT and prevents apoptosis. The MPT does not occur uniformly during apoptosis. Initially, a small proportion of mitochondria undergo the MPT, which increases to nearly 100% over 1-3 h. A technique based on fluorescence resonance energy transfer can selectively reveal mitochondrial depolarization. After nutrient deprivation, a small fraction of mitochondria spontaneously depolarize and enter an acidic lysosomal compartment, suggesting that the MPT precedes the normal process of mitochondrial autophagy. A model is proposed in which onset of the MPT to increasing numbers of mitochondria within a cell leads progressively to autophagy, apoptosis and necrotic cell death.

Important cutaneous manifestations of inflammatory bowel disease.

Inflammatory bowel disease (IBD) has many extraintestinal manifestations. Cutaneous manifestations are usually related to the activity of the bowel disease but may have an independent course. Anyone presenting with IBD should be examined for cutaneous manifestations. Pyoderma gangrenosum is a severe painful ulcerating disease that requires moist wound management and, in the absence of secondary infection, systemic corticosteroids, cyclosporine, or both. Infliximab may also be used. Erythema nodosum is a common cause of tender red nodules of the shins. Management includes leg elevation, NSAIDs, and potassium iodide. Oral manifestations of IBD include aphthous stomatitis, mucosal nodularity (cobblestoning), and pyostomatitis vegetans. Treatment should be directed both at the cutaneous lesions and at the underlying systemic condition.

Comparison of infrapubic versus transcrotal approaches for inflatable penile prosthesis placement: a multi-institution report.

Inflatable penile prostheses (IPP) are associated with excellent long-term outcomes. To date, no study has evaluated the significance of surgical approach on IPP intraoperative variables. High-volume surgeons placing the Titan 0-degree prosthesis from March-July 2012 completed questionnaires including pre-/intraoperative variables. Intraoperative data were compared between surgeons performing an infrapubic versus transcrotal approach for total length of prosthesis, proximal and distal measurements, rear-tip extender (RTE) length, reservoir size and fill volume and ability to place the reservoir in the space of Retzius. Forty-six surgeons placed 256 IPPs, with a median of 5 (range 1-10) inserted. Transcrotal placement was performed most commonly (80%). Revision procedures accounted for 13% of cases, with 19% previously undergoing robotic-assisted prostatectomy. Compared with infrapubic, transcrotal placement resulted in a longer total prosthesis (22.3 cm vs 20.6 cm, P < 0.0001), increased proximal dilation (10.1 cm vs 8.6 cm, P < 0.0001), longer RTEs (1.9 cm vs 1.2 cm, P < 0.0001) and larger reservoir fill volume (79 cc vs 71 cc, P = 0.0003). No differences were noted in distal measurements or ability to place the reservoir in the space of Retzius. Compared with the infrapubic approach, high-volume surgeons placing the Titan 0-degree IPP transcrotally achieved increased proximal dilation with an ~1-2-cm-longer prosthesis inserted.

The direction and severity of penile curvature does not have an impact on concomitant vasculogenic erectile dysfunction in patients with Peyronie's disease.

Although the association between Peyronie's disease (PD) and erectile dysfunction (ED) is well established, limited data are available correlating penile curvature and penile hemodynamic parameters. We sought to examine this association in a cohort of PD men undergoing penile duplex Doppler ultrasound (PDDU). PD patients were retrospectively evaluated to correlate the extent and direction of penile curvature with measured vascular parameters. Demographic variables, disease characteristics and PDDU parameters were tabulated and statistically compared based on extent (≤ 45° and >45°) and direction (dorsal, ventral, lateral, ventrolateral, dorsolateral) of curvature. A total of 220 PD patients (mean age of 55.0 ± 9.2 years) underwent PDDU at one institution from January 2008 to December 2010. Overall, 69.5% of patients were found to have vasculogenic ED (arterial insufficiency (AI): 10%; veno-occlusive dysfunction (VOD): 43.2%; AI + VOD: 16.4%). Mean curvature was similar among all PDDU groups (AI: 41.7 ± 5.2°; VOD: 41.3 ± 2.5°; AI+VOD: 37 ± 4.1°; no-ED: 37.3 ± 3°; P > 0.85). No significant differences were noted in the presence or type of ED among various directions of curvature (P = 0.34) or when curvatures were stratified by ≤ 45° and >45°. The direction and extent of penile curvature are not associated with altered rates of vasculogenic ED on PDDU in PD patients.

Confocal microscopy of the mitochondrial permeability transition in necrotic and apoptotic cell death.

Opening of a high-conductance pore in the mitochondrial inner membrane induces onset of the mitochondrial permeability transition (mPT). Cyclosporin A and trifluoperazine inhibit this pore and block necrotic cell death in oxidative stress, Ca2+ ionophore toxicity, Reye-related drug toxicity, pH-dependent ischaemia/reperfusion injury and other models of cell injury. Confocal fluorescence microscopy directly visualizes the increased mitochondrial membrane permeability of the mPT from the movement of calcein from the cytosol into the matrix space. Pyridine nucleotide oxidation, increased mitochondrial Ca2+ and mitochondrial generation of reactive oxygen species (ROS) all contribute to the onset of the mPT in situ. Confocal microscopy also shows directly that the mPT is a critical link in apoptotic signalling by tumour necrosis factor-alpha at a point downstream of caspase 8 and upstream of caspase 3. Cyclosporin A blocks this mPT, preventing release of pro-apoptotic cytochrome c from mitochondria and subsequent apoptotic cell killing. Progression to necrosis or apoptosis after the mPT depends on the availability of ATP, which blocks necrosis but promotes the apoptotic programme. Given the pathophysiological importance of the mPT, development of agents to modulate the mPT represents an important new goal for pharmaceutical drug discovery.

Epilepsy in a managed care organization.

Lovelace Healthcare Systems in Albuquerque, New Mexico has developed a comprehensive approach to managing the care of seizure disorder patients through a larger project called Episodes of Care (EOC). The Seizure Disorder EOC was created to design tools and initiatives to make that care more efficient, more appropriate, and more effective by integrating primary care, specialty care, and all other aspects of a seizure disorder patient's management. Creation and methods of the EOC project are discussed, as well as implementation issues and clinical outcome and process indicators. Advice for other organizations planning similar disease management programs is outlined.

Painless ischemia provoked by mental stress in the coronary care unit.

A 30-year-old man suffered a cardiac arrest after setting fire to his home. Continuous ST segment electrocardiographic monitoring in the Coronary Care Unit detected painless ST segment depression during an interview with a police officer. At angiography, the patient proved to have severe three-vessel coronary artery disease. This case demonstrates the clinical value of continuous ST segment monitoring in the ICU. In addition, the case illustrates that mental stress is a potential trigger for acute myocardial ischemia in the ICU.

Confocal microscopy of the mitochondrial permeability transition in necrotic cell killing, apoptosis and autophagy.

Onset of the cyclosporin-A-sensitive mitochondrial permeability transition (MPT) in individual mitochondria within living cells can be visualized by laser scanning confocal microscopy. The MPT is a causative event in many types of necrotic and apoptotic cell death, including oxidative stress, ischemia/reperfusion injury, Ca2+ ionophore toxicity and tumor necrosis factor alpha (TNF alpha) induced apoptosis, and may contribute to Reye's-related drug toxicity. Pyridine nucleotide oxidation, mitochondrial generation of reactive oxygen species, and increased mitochondrial Ca2+ and pH can each promote onset of the MPT in situ. The MPT can also be directly visualized during TNF alpha-induced apoptosis to hepatocytes. Mitochondria spontaneously depolarize in situ after nutrient deprivation before entering an acidic lysosomal compartment, suggesting that the MPT precedes the normal process of mitochondrial autophagy. We propose a model in which onset of the MPT to increasing numbers of mitochondria leads progressively to autophagy, apoptosis and necrotic cell death.

Helicobacter pylori: seroprevalence and colorectal cancer.

BACKGROUND: Previous studies have published controversial results regarding a connection between Helicobacter pylori infection and colorectal cancer. One possible mechanism is increased gastrin secretion in subjects infected with H. pylori, insofar as gastrin is known to be a trophic factor for the colonic mucosa. OBJECTIVES: To investigate a possible role of gastrin secretion in H. pylori infection associated with colorectal cancer, and determine whether H. pylori infection is a factor in this disease. METHODS: The serum gastrin levels and the presence of H. pylori IgG antibodies were measured in 51 colorectal cancer patients and 51 control subjects. The cancer patients were also tested for carcinoembryonic antigen and CA 19-9. RESULTS: H. pylori IgG antibodies were found in the serum of 41 (80.4%) of the cancer patients compared to 32 (62.7%) of the control subjects (P = 0.05). A significant correlation was found between CA 19-9 (r = 0.3432, n = 49, P = 0.01) and seropositive H. pylori IgG antibodies in the serum of the cancer patients (odds ratio 2.43, and 95% confidence limit 0.99-5.95), but none between CEA and H. pylori IgG antibodies nor between the serum gastrin level and the presence of colorectal cancer. CONCLUSIONS: The results of this study indicate a significant association between seropositive H. pylori IgG antibodies and elevated CA 19-9 in colorectal cancer patients, but no correlation between the serum gastrin level and the presence of this cancer. H. pylori seropositivity is more prevalent in patients with colorectal cancer.

Multimodality management in severe pediatric spleen trauma.

BACKGROUND: Trauma is the leading cause of death in children. In abdominal lesions the spleen is the most commonly involved organ. During the last two decades much effort has focused on spleen tissue conservation. OBJECTIVES: To analyze the rationale of a multimodality management policy that includes autotransfusion and mesh wrapping. METHODS: Data gathered over 14 years illustrate the introduction of new techniques and their impact on cases of severe spleen rupture. RESULTS: A total of 122 children were treated during the 14 year period, 1985-98. In 16 children an absorbable mesh wrapping, alone or in combination with other techniques, was used to obtain hemostatis and save spleen tissue. CONCLUSIONS: Mesh wrapping, partial splenectomy and autotransfusion can be used, alone or in combination, to preserve severely injured spleens. According to our records, all children survived with a functional spleen. There were no cases of rebleeding. In only one case of prolonged postoperative fever could the cause be traced to an infected spleen hematoma that was drained transcutaneously. Autotransfusion is performed simply and without the use of a "cell saver." Its use can be crucial in small or field hospitals or in a situation of mass casualty.

Adipose tissue-derived stem cell therapy for prevention and treatment of erectile dysfunction in a rat model of Peyronie's disease.

Peyronie's disease (PD) is a localized connective tissue disorder that involves the tunica albuginea (TA) of the penis. While surgical correction remains the gold standard, the search for an effective and less invasive therapy continues. The objective of this study was to evaluate the effects of intratunical injection of adipose tissue-derived stem cells (ADSCs) for the prevention and treatment of erectile dysfunction in a rat model of PD. Twenty-four male Sprague-Dawley rats (300-350 g) were randomly divided into four groups: sham, PD, PD + ADSC (prevention) and PD + ADSC (treatment). All rats underwent penile injections into the TA with 50 µL vehicle (sham) or 0.5 µg transforming growth factor (TGF)-ß1 (remaining groups). The ADSC groups received intratunical injections with 0.5 million rat-labelled ADSCs on day 0 (prevention) or day 30 (treatment). Forty-five days following TGF-ß1 injection, rats underwent cavernous nerve stimulation (CNS) with total intracavernous-to-mean arterial pressure ratio (ICP/MAP) and total ICP recorded to measure response to therapy. Tissues were evaluated histologically and for mRNA expression of tissue inhibitors of metalloproteinases (TIMPs), matrix metalloproteinases (MMPs) and zymographic activity of MMPs. Statistical analysis was performed by analysis of variance followed by the Tukey test for post hoc comparisons. In both prevention and treatment groups, intratunical injection of ADSCs resulted in significantly higher ICP/MAP and total ICP in response to CNS compared with the PD group. Local injection of ADSCs prevented and/or reduced Peyronie's-like changes by decreasing the expression of TIMPs, and stimulating expression and activity of MMPs. This study documents the preventive and therapeutic benefits of ADSC on penile fibrosis and erectile function in an animal model of PD.

The pre-treatment prevalence and types of sexual dysfunction among patients diagnosed with prostate cancer.

Erectile dysfunction (ED) following prostate cancer therapy is a common condition that is well documented in literature. Despite the significant focus placed on ED and prostate cancer, very little is known regarding the baseline prevalence of other aspects of sexual dysfunction (SD) in this specific cohort of patients. The objective of the current manuscript was to assess the prevalence of subtypes of SD, including ED, ejaculatory dysfunction (EjD) and decreased libido among men with newly diagnosed prostate cancer. To achieve this objective, patients presenting to our clinic with a new diagnosis of prostate cancer from July 2011 and May 2012 completed the Male Sexual Health Questionnaire (MSHQ) to assess baseline sexual function. A total of 60 patients completed an MSHQ, with a mean age of 60.28 ± 6.25 (range 44-73 years). Of patients surveyed, 14% reported no sexual activity within the previous month, while 53% had sex at least once weekly. The percentage of patients reporting ED, EjD and decreased sexual desire ≥50% of the time was 37, 26 and 48% respectively. Eleven to 18% of patients reported that these symptoms were 'very' or 'extremely' bothersome. Patients noted dissatisfaction with the quality of their sexual relationship, frequency of sexual activity and quality of sex in 18, 31 and 20%, respectively. Overall findings suggest that patients with newly diagnosed prostate cancer experience a high rate of SD at baseline. Knowledge of these prevalence rates may assist physicians managing patient's expectations with planned therapies.

Bicycle accidents - do we only see the tip of the iceberg? A prospective multi-centre study in a large German city combining medical and police data.

INTRODUCTION: Bicycles are becoming increasingly popular. In Münster, a German town with a population of 273,000, bicycles were the main method of transportation in 2009, used more often (37.8%) than cars (36.4%). Each day in Münster, bicycles are used around 450,000 times. In 1982, they were only used around 270,000 times a day. However, the increased use of bicycles has also led to an increased number of bicycle accidents. METHODS: Between February 2009 and January 2010, data on bicycle-accidents leading to injuries were collected by the Police of Münster and in all emergency units of the six hospitals in Münster. A systematic acquisition of technical data from the police and the medical data from the hospitals were combined anonymously. None of the forms contained personal data of patients involved, except for patient age and sex as well as time and place of bicycle accidents to match the questionnaires. The data were entered into a central database (MS Access for input/MySQL for data retrieval). RESULTS: 2250 patients were included in this study. For each of these patients either a patient record or a hospital record or a police record or a combination of any of these different records existed in our database. In total, 1767 patients received medical treatment at a hospital and 484 people included in the study did not go to a hospital. Three fatalities occurred as a result of bicycle accidents. Considering reasons for hospital admission, traumatic brain injuries were the leading cause (25.7%). However, the largest resource consumption was attributed to fractures of the upper extremities (36.8%) and lower extremities (29.9%) with major surgery. DISCUSSION: Bicycle accidents occur more frequently than indicated by police records. The results of the Münster Bicycle Study have shown that the actual number of bicycle accidents exceeds the officially reported number by nearly two times. Since bicycle helmets cannot prevent accidents it is recommended not only to focus on helmet use as the only injury prevention method. Other factors, such as weather, pavement and default of traffic, roadworthiness of the bicycles or alcohol/drug abuse also affect the accident rates.

The mitochondrial permeability transition: a new pathophysiological mechanism for Reye's syndrome and toxic liver injury.

Aspirin, Neem oil, valproic, adipic, benzoic, isovaleric, 3-mercaptopropionic and 4-pentenoic acids are implicated in the pathogenesis of Reye's syndrome, Jamaican vomiting sickness, and related chemical toxicities. These disorders are characterized by hyperammonemia, hypoglycemia, microvesicular steatosis and encephalopathy. The goal of this study was to determine whether chemicals implicated in Reye's-related disorders induce the mitochondrial permeability translation (MPT). The MPT is induced by opening of a high-conductance, cyclosporin-sensitive pore in the mitochondrial inner membrane, causing swelling, depolarization and uncoupling of oxidative phosphorylation. In freshly isolated rat liver mitochondria, unhydrolyzed aspirin (300 microM) did not induce the MPT in the presence of 50 microM CaCl2. Salicylate, the hydrolysis product of aspirin and its active metabolite, was much more potent causing dose-dependent onset of the MPT in a therapeutic range of concentrations (37.5-300 microM). Similarly, Neem oil and valproic, adipic, benzoic, isovaleric, 3-mercaptopropionic and 4-pentenoic acids induced onset of the MPT. In all cases, cyclosporin A (200 nM), a specific inhibitor of the permeability transition pore, blocked the MPT caused by these inducers. Induction of the MPT by these agents was not caused by mitochondrial depolarization because concentrations of valproic acid and salicylate inducing the MPT had little effect on mitochondrial delta psi. Moreover, equivalent uncoupling caused by 5 nM carbonyl cyanide p-trifluoromethoxyphenylhydrazone did not induce an MPT. These data suggest that induction of the MPT is a common pathophysiological mechanism causing mitochondrial injury in Reye's syndrome and Reye's-related drug toxicities.

Role of the mitochondrial permeability transition in salicylate toxicity to cultured rat hepatocytes: implications for the pathogenesis of Reye's syndrome.

Aspirin is strongly implicated in the pathogenesis of Reye's syndrome, a childhood disorder characterized by hyperammonemia, microvesicular steatosis, and encephalopathy. Previously, we showed that salicylate, the active metabolite of aspirin, induces the mitochondrial permeability transition (MPT) in isolated mitochondria, as do several other chemicals implicated in Reye's-related disorders. Opening of a high conductance, cyclosporin A-sensitive pore in the mitochondrial inner membrane causes the MPT, leading to swelling, depolarization, and uncoupling of oxidative phosphorylation. The goal of this study was to characterize the role of the MPT in salicylate toxicity to cultured rat hepatocytes. Salicylate (0.3-5 mM) caused concentration-dependent cell killing. In Krebs-Ringer buffer, half-maximal cell killing occurred 150 min after 3 mM salicylate. Increasing Ca2+ enhanced salicylate lethality. Salicylate-dependent cell killing was blocked by 0.5-5 microM cyclosporin A and its nonimmunosuppresive analog, 4-methylvaline cyclosporin, implicating the MPT in the pathogenesis of cell killing. The contribution of the MPT to lethal cell injury was confirmed by laser scanning confocal microscopy, which demonstrated the redistribution of the fluorophore calcein from the cytosol into mitochondria prior to cell killing, an event blocked by cyclosporin A. Salicylate toxicity was enhanced at high extracellular Ca2+. In the range of 10-100 microM, several chemically diverse calcium antagonists blocked or reduced salicylate toxicity including verapamil, diltiazem, chlorpromazine, nifedipine, and nisoldipine. Calcium antagonists also blocked the increase of mitochondrial free Ca2+ in high Ca2+ buffer, as determined by confocal imaging of the fluorophore Rhod-2. These data with salicylate suggest that onset of the MPT may be the common pathophysiologic mechanism causing mitochondrial injury in Reye's syndrome and Reye's-related drug toxicities. Further, elevated intramitochondrial Ca2+ may be a predisposing condition promoting onset of the MPT by Reye's-related chemicals.

A cytotoxicity assay for tumor necrosis factor employing a multiwell fluorescence scanner.

Tumor necrosis factor (TNF) is an important mediator of many biological processes. This study sought to develop a sensitive bioassay allowing quantitative determination of TNF. The assay is based on uptake of the membrane impermeant dye, propidium iodide, by L929 cells when their viability is lost. L929 cells were plated on 96-well plates and cultured overnight in Eagle's minimum essential medium containing 10% horse serum. Propidium iodide (30 microM) was added, and fluorescence was monitored with a multiwell fluorescence scanner using 560-nm excitation and 645-nm emission filters. Human recombinant TNF caused a dose- and time-dependent increase in fluorescence, indicating onset of cell death. Cycloheximide (50 micrograms/ml) and actinomycin D (5 micrograms/ml) sensitized L929 cells to TNF-induced killing. By measuring cell killing early (12 h) and late (30 h), responses proportional to TNF concentration were obtained over a dynamic range of 1 to 5000 pg/ml. These findings serve as the basis for a simple TNF assay that is easy to perform and sensitive over a very broad range of TNF concentrations.