Sodium-glucose cotransporter 2 inhibitor dapagliflozin prevents ejection fraction reduction, reduces myocardial and renal NF-κB expression and systemic pro-inflammatory biomarkers in models of short-term doxorubicin cardiotoxicity.

Background: Anthracycline-mediated adverse cardiovascular events are among the leading causes of morbidity and mortality in patients with cancer. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) exert multiple cardiometabolic benefits in patients with/without type 2 diabetes, chronic kidney disease, and heart failure with reduced and preserved ejection fraction. We hypothesized that the SGLT2i dapagliflozin administered before and during doxorubicin (DOXO) therapy could prevent cardiac dysfunction and reduce pro-inflammatory pathways in preclinical models. Methods: Cardiomyocytes were exposed to DOXO alone or combined with dapagliflozin (DAPA) at 10 and 100 nM for 24 h; cell viability, iATP, and Ca++ were quantified; lipid peroxidation products (malondialdehyde and 4-hydroxy 2-hexenal), NLRP3, MyD88, and cytokines were also analyzed through selective colorimetric and enzyme-linked immunosorbent assay (ELISA) methods. Female C57Bl/6 mice were treated for 10 days with a saline solution or DOXO (2.17 mg/kg), DAPA (10 mg/kg), or DOXO combined with DAPA. Systemic levels of ferroptosis-related biomarkers, galectin-3, high-sensitivity C-reactive protein (hs-CRP), and pro-inflammatory chemokines (IL-1α, IL-1ß, IL-2, IL-4, IL-6, IL-10, IL-12, IL17-α, IL-18, IFN-γ, TNF-α, G-CSF, and GM-CSF) were quantified. After treatments, immunohistochemical staining of myocardial and renal p65/NF-kB was performed. Results: DAPA exerts cytoprotective, antioxidant, and anti-inflammatory properties in human cardiomyocytes exposed to DOXO by reducing iATP and iCa++ levels, lipid peroxidation, NLRP-3, and MyD88 expression. Pro-inflammatory intracellular cytokines were also reduced. In preclinical models, DAPA prevented the reduction of radial and longitudinal strain and ejection fraction after 10 days of treatment with DOXO. A reduced myocardial expression of NLRP-3 and MyD-88 was seen in the DOXO-DAPA group compared to DOXO mice. Systemic levels of IL-1ß, IL-6, TNF-α, G-CSF, and GM-CSF were significantly reduced after treatment with DAPA. Serum levels of galectine-3 and hs-CRP were strongly enhanced in the DOXO group; on the other hand, their expression was reduced in the DAPA-DOXO group. Troponin-T, B-type natriuretic peptide (BNP), and N-Terminal Pro-BNP (NT-pro-BNP) were strongly reduced in the DOXO-DAPA group, revealing cardioprotective properties of SGLT2i. Mice treated with DOXO and DAPA exhibited reduced myocardial and renal NF-kB expression. Conclusion: The overall picture of the study encourages the use of DAPA in the primary prevention of cardiomyopathies induced by anthracyclines in patients with cancer.

Machine learning applied to ambulatory blood pressure monitoring: a new tool to diagnose autonomic failure?

BACKGROUND: Autonomic failure (AF) complicates Parkinson's disease (PD) in one-third of cases, resulting in complex blood pressure (BP) abnormalities. While autonomic testing represents the diagnostic gold standard for AF, accessibility to this examination remains limited to a few tertiary referral centers. OBJECTIVE: The present study sought to investigate the accuracy of a machine learning algorithm applied to 24-h ambulatory BP monitoring (ABPM) as a tool to facilitate the diagnosis of AF in patients with PD. METHODS: Consecutive PD patients naïve to vasoactive medications underwent 24 h-ABPM and autonomic testing. The diagnostic accuracy of a Linear Discriminant Analysis (LDA) model exploiting ABPM parameters was compared to autonomic testing (as per a modified version of the Composite Autonomic Symptom Score not including the sudomotor score) in the diagnosis of AF. RESULTS: The study population consisted of n = 80 PD patients (33% female) with a mean age of 64 ± 10 years old and disease duration of 6.2 ± 4 years. The prevalence of AF at the autonomic testing was 36%. The LDA model showed 91.3% accuracy (98.0% specificity, 79.3% sensitivity) in predicting AF, significantly higher than any of the ABPM variables considered individually (hypotensive episodes = 82%; reverse dipping = 79%; awakening hypotension = 74%). CONCLUSION: LDA model based on 24-h ABPM parameters can effectively predict AF, allowing greater accessibility to an accurate and easy to administer test for AF. Potential applications range from systematic AF screening to monitoring and treating blood pressure dysregulation caused by PD and other neurodegenerative disorders.

Levodopa/carbidopa intestinal gel infusion and weight loss in Parkinson's disease.

BACKGROUND AND PURPOSE: Weight loss (WL) is a frequent yet under-recognized complication of levodopa/carbidopa intestinal gel (LCIG) infusion, as well as a milestone of Parkinson's disease (PD) disability progression. The complex association between WL, poor nutritional status, motor complications and PD progression, however, remains unclear. METHODS: Consecutive consenting patients with PD treated with LCIG (n = 44; PD duration, 18.3 ± 6.5 years) were enrolled in an open-label observational study assessing the extent of WL occurring during LCIG treatment. As secondary aims, we correlated the nutritional status, as detected by the Mini Nutritional Assessment, with the severity of motor symptoms [Movement Disorder Society Unified Parkinson's Disease Rating Scale part III], motor complications (Unified Parkinson's Disease Rating Scale part IV), activities of daily living (Schwab and England scale), cognitive impairment (Mini Mental State Examination), depression (Beck Depression Inventory), difficulties in feeding (Edinburgh Feeding Evaluation in Dementia Questionnaire) and levodopa equivalent daily dose (LEDD). RESULTS: There was an average WL of 9.9 ± 10.5% (7.6 ± 7.1 kg) over an LCIG treatment period of 51.6 ± 28.5 months. The extent of WL correlated with the percentage of the waking day spent with dyskinesia (P < 0.05). The nutritional status correlated with motor symptom severity (P < 0.01), dysphagia (P < 0.01) and LEDD (P < 0.01). CONCLUSIONS: Weight loss may occur in patients with PD undergoing LCIG in correlation with the percentage of the waking day spent with dyskinesia. Regardless of the extent of WL, the nutritional status correlated with higher LEDD, as well as with indices of disease progression, such as motor symptom severity and dysphagia.

Subthalamic deep brain stimulation and trunk posture in Parkinson's disease.

OBJECTIVES: We sought to assess the efficacy of subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson's disease (PD)-associated trunk posture abnormalities retrospectively analyzing data from 101 patients reporting mild-to-severe trunk posture abnormalities of a cohort of 216 PD patients treated with STN-DBS at our center. METHODS: Abnormal trunk posture was rated on a scale of 0 (normal) to 4 (marked flexion with an extreme abnormality of posture) as per the grading score reported in the Unified Parkinson's Disease Rating Scale. The independent effect of STN-DBS on trunk posture was assessed comparing Medication-Off (presurgery) vs Stimulation-On/Medication-Off (post-surgery). The combined effect of STN-DBS plus levodopa was evaluated comparing Medication-On (presurgery) vs Stimulation-On/Medication-On (post-surgery). Analyses were conducted considering both the entire cohort of patients and the subgroup with camptocormia (CMC) and Pisa syndrome (PS). RESULTS: The independent effect of STN-DBS resulted in a 41.4% improvement in abnormal trunk posture severity (P < .001), with 78.2% of patients (n = 79) reporting an improvement of at least 1 point. The combined effect of STN-DBS and levodopa resulted in a 30.9% improvement (P = .061), with 54.5% of patients (n = 55) reporting an improvement of at least 1 point. The subanalysis of patients with CMC (n = 23) and PS (n = 5) showed a 42.7% improvement in abnormal posture severity when considering the independent effect of STN-DBS (P < .001) and 30.5% when considering the combined effect of STN-DBS and levodopa (P < .001). CONCLUSIONS: STN-DBS may have the potential for improving posture in patients with advanced PD.

A forward modelling approach for the estimation of oxygen extraction fraction by calibrated fMRI.

The measurement of the absolute rate of cerebral metabolic oxygen consumption (CMRO2) is likely to offer a valuable biomarker in many brain diseases and could prove to be important in our understanding of neural function. As such there is significant interest in developing robust MRI techniques that can quantify CMRO2 non-invasively. One potential MRI method for the measurement of CMRO2 is via the combination of fMRI and cerebral blood flow (CBF) data acquired during periods of hypercapnic and hyperoxic challenges. This method is based on the combination of two, previously independent, signal calibration techniques. As such analysis of the data has been approached in a stepwise manner, feeding the results of one calibration experiment into the next. Analysing the data in this manner can result in unstable estimates of the output parameter (CMRO2), due to the propagation of errors along the analysis pipeline. Here we present a forward modelling approach that estimates all the model parameters in a one-step solution. The method is implemented using a regularized non-linear least squares approach to provide a robust and computationally efficient solution. The proposed framework is compared with previous analytical approaches using modelling studies and in vivo acquisitions in healthy volunteers (n=10). The stability of parameter estimates is demonstrated to be superior to previous methods (both in vivo and in simulation). In vivo estimates made with the proposed framework also show better agreement with expected physiological variation, demonstrating a strong negative correlation between baseline CBF and oxygen extraction fraction. It is anticipated that the proposed analysis framework will increase the reliability of absolute CMRO2 measurements made with calibrated BOLD.

Peripheral neuropathy associated with levodopa-carbidopa intestinal infusion: a long-term prospective assessment.

BACKGROUND AND PURPOSE: Subacute and chronic peripheral neuropathies (PNP) have been reported in Parkinson's disease (PD) patients treated with levodopa/carbidopa intestinal gel infusion (LCIG), although several aspects of their incidence and pathogenesis still remain to be clarified. This study main objective is to prospectively report the 2-year incidence of PNP in patients treated with LCIG. METHODS AND RESULTS: The clinical, hematological, nutritional and electrophysiological assessments of 33 consecutive patients have been prospectively collected and evaluated. At baseline (before the start of LCIG therapy), 3/33 (9%) patients showed symptomatic PNP and 7/33 (21%) subclinical PNP. During a follow-up of 24.36 ± 12.18 months, 2/23 patients with normal baseline clinical-electrophysiological assessment developed a subacute PNP, 2/23 developed a chronic PNP and 7/23 developed a subclinical PNP. LCIG was immediately halted in the subacute cases, while the infusion therapy was not interrupted in chronic and subclinical forms. All PNP were supplemented with vitamin B1 and B12, showing a clinical improvement and/or substantial stability at the following evaluations. Higher levodopa-equivalent daily dose (P: 0.024) and homocysteine levels (P: 0.041) were found in chronic PNP, while no correlations were observed with vitamin B12, folate and UPDRS values. A trend towards BMI reduction was observed in both PNP and unaffected subjects and one patient developed a symptomatic PNP associated with a relevant weight loss. CONCLUSIONS: Serial clinical-electrophysiological evaluations are mandatory in patients treated with LCIG, given the possible risk of subacute and chronic PNP. No clear causative factors has been recognized in the subacute forms, whilst homocysteine-mediated neurotoxicity seems to underlie the pathogenesis of chronic forms.

Long-term outcome of subthalamic nucleus DBS in Parkinson's disease: from the advanced phase towards the late stage of the disease?

BACKGROUND: Deep Brain Stimulation of the Subthalamic Nucleus (STN-DBS) is an effective treatment for Parkinson's disease (PD), but only few studies investigated its long-term efficacy. Furthermore, little is known about the role of PD-subtype on STN-DBS long-term outcome. OBJECTIVE: To report the results of a long-term follow-up (mean 11 years, range 10-13) on 26 patients bilaterally implanted in two centres. METHODS: Patients were assessed preoperatively and 1, 5 and 11 years after the implant by the Unified Parkinson's Disease Rating Scale (UPDRS) and a battery of neuropsychological tests. Stimulation parameters, drugs dosages, non-motor symptoms and adverse events were also recorded. RESULTS: At 11 years, stimulation significantly improved the motor symptoms by 35.8%, as compared to the preoperative off-state. Motor complications were well controlled, with a 84.6% improvement of dyskinesias and a 65.8% improvement of motor fluctuations. Despite this, the UPDRS-II-on score worsened by 88.5%, mainly for the worsening of poorly levodopa-responsive symptoms. More than 70% of the patients performed in the normal range in most of the neuropsychological tests, despite the development of dementia in 22.7%. Age at disease onset, axial subscore in off-condition and presence of REM behaviour disorder at baseline were found to be associated with a higher risk of developing disability over time. CONCLUSIONS: Our study confirms the long-term safety and efficacy of STN-DBS in PD. Nevertheless, the functionality of patients worsens over time, mainly for the onset and progression of levodopa-resistant and non-motor symptoms. The role of PD-subtype seems to be relevant in the long-term outcome.

Levodopa/carbidopa intestinal gel infusion in advanced Parkinson's disease: a 7-year experience.

BACKGROUND AND PURPOSE: Levodopa/carbidopa intestinal gel (LCIG) infusion is nowadays becoming an established therapeutic option for advanced Parkinson's disease (PD) patients with fluctuating symptoms unresponsive to conventional oral treatment. As the implementation of LCIG therapy is increasing, there is a need for safety and efficacy data from current clinical practice. METHODS: All PD patients treated with LCIG at our centre over a 7-year period were analysed to determine the duration of treatment, retention rate, reasons for discontinuation, LCIG efficacy in motor complications, modifications of concomitant therapy and adverse events. RESULTS: Of the 59 patients, seven subjects (12%) died of causes unrelated to LCIG infusion and 11 patients (19%) discontinued therapy prior to the cut-off date. Duodopa improved motor complications and over 90% of patients reported an improvement in their quality of life, autonomy and clinical global status. The most common adverse events were dislocation and kinking of the intestinal tube. CONCLUSIONS: LCIG infusion is effective for the long-term treatment of advanced PD patients and exerts a positive and clinically significant effect on motor complications with a relatively low dropout rate.

Prospective assessment of peripheral neuropathy in Duodopa-treated parkinsonian patients.

BACKGROUND: Although peripheral neuropathies (PN) have been described in patients with Parkinson's disease (PD) treated with oral dopaminergic therapies, anecdotal reports of subacute severe PN have been reported during treatment with enteral levodopa/carbidopa infusion (Duodopa). AIM OF THE STUDY: We prospectively assessed clinical and electrophysiological data of 15 consecutive patients with PD treated with Duodopa for a mean follow-up of 9 months. METHODS: Nerve conduction studies and a clinical evaluation with a standardized battery of peripheral neuropathy scales were performed at baseline and after a mean follow-up of 9 months. RESULTS: At baseline, mild signs of PN were observed in three subjects, and vitamin B12 serum levels were found to correlate with the amplitude of sural sensory action potentials. Follow-up data were available for 10/15 subjects: one patient developed a subacute sensory-motor PN and three subjects with pre-existing PN showed a moderate worsening of electrophysiological and clinical features. Subclinical electrophysiological alterations of peripheral nerves were observed in two subjects. No significant changes were observed in vitamin B12, folate, homocysteine and methylmalonic acid levels. CONCLUSIONS: In this consecutive series of patients treated with Duodopa, we observed one subacute sensory-motor PN and few length-dependent alterations of peripheral nerves, similar to those described during oral levodopa treatment.

Sleep improvement with levodopa/carbidopa intestinal gel infusion in Parkinson disease.

BACKGROUND: Sleep disorders are common in patients with advanced Parkinson's disease (PD). Nocturnal akinesia and sleep fragmentation frequently coexist with daytime sleepiness, influencing daytime functioning. Levodopa/carbidopa intestinal gel (LCIG) infusion has been shown to improve motor complications in advanced PD, and preliminary findings suggest that sleep might improve following LCIG infusion. OBJECTIVE: To analyze the impact of LCIG infusion on sleep symptoms and daytime sleepiness in patients with PD. METHODS: Twelve consecutive patients with PD completed the PD-Sleep-Scale-version-2 (PDSS-2) and the Epworth-Sleepiness-Scale (ESS) at baseline and after 2-4 months of LCIG treatment. Activities of daily living, motor symptoms and complications were assessed with the Unified-PD-rating-Scale section II, III, and IV. RESULTS: Nocturnal sleep improved substantially in all patients switched to LCIG infusion. PDSS-2 total score and subscores for 'Disturbed sleep', 'Motor symptoms at night', and 'PD symptoms at night' were significantly reduced. ESS measures of daytime sleepiness also improved. Motor complications and activities of daily living improved significantly with LCIG. CONCLUSION: Subjective measures of sleep quality and daytime sleepiness improve in patients with advanced PD undergoing LCIG infusion. Further studies with a larger number of patients and polysomnographic recordings are needed to confirm the beneficial effect on sleep and clarify the underlying mechanisms.

[Role of a mini-invasive approach in the diagnosis and treatment of tubo-peritoneal infertility as an altenative to IVF]. / Il ruolo di un approccio chirurgico mini-invasivo nello diagnosi e trattamento della sterilità tubo-peritoneale in alternativa alla FIVET.

AIM: Tubal factor infertility accounts for approximately 25-35% of cases of female infertility. Identifiable causes of tubal infertility are postinfectious tubal damage, postsurgical adhesion formation, and endometriosis-related adhesions. Aim of this study was to evaluate the results of a diagnostic/therapeutic minimally invasive approach in patients with suspect or ascertained mechanical infertility in terms of obtained pregnancies. METHODS: The study enrolled 143 patients who underwent diagnostic or operative laparoscopy, with chromopertubation, peritoneal or endometrial culture, salpingoscopy when indicated and diagnostic or operative hysteroscopy. Nine patients with submucous-intramural or multiple intramural fibroids underwent miomectomy by minilaparotomy following hysteroscopy and chromopertubation. Patients were contacted periodically by telephone to monitor the onset and outcome of pregnancy. The mean length of follow- up was 49 months (range: 11 to 118 months). RESULTS: Of the 152 patients considered in the study, 61 became pregnant (40%). Twenty-three pregnancies resulted in miscarriage, two in tubal pregnancy and one patient aborted after a diagnosis of Down syndrome. In total, 32% of the patients achieved a term pregnancy. CONCLUSION: The diagnostic/therapeutic mini-invasive approach allows women to become pregnant naturally and it is, therefore, an option for couples with ethical and religious concerns. The percentage of pregnancies is higher than after in-vitro fertilization. When efficacious, this approach allows additional spontaneous conceptions without renewed therapy and the course of pregnancy and the type of delivery will not differ from those in a normal population.

Multiple cerebral aneurysms associated with atrial myxoma. A case report.

Cardiac myxoma is a tumor of mesenchymal origin accounting for half of all primary cardiac neoplasms. Intracranial involvement by atrial myxoma is a rare cause of neurologic deficit. When the myxoma arises in the left atrium, systemic emboli from a cardiac myxoma can lead to infarction, cerebral hemorrhage and aneurysm formation. In the light of the potentially preventable nature of these lesions, the diagnosis of myxomatous aneurysms should be considered in any patient with neurologic symptoms and a history of cardiac myxoma. Because aneurysms are often stable over several years, conservative management with careful clinical and radiological follow-up with MRI and angiography seems sensible. We describe a case in which MR imaging and angiography were used to diagnose multiple cerebral aneurysms caused by left atrial myxoma.

Multiple sclerosis relapses: a multivariable analysis of residual disability determinants.

BACKGROUND: Recovery from multiple sclerosis (MS) relapses is variable. The factors influencing persistence of residual disability (RD) after a relapse are still to be thoroughly elucidated. AIMS OF STUDY: To assess RD after MS relapses and to define the factors associated with persistence of RD. METHODS: Data were retrospectively collected for all relapses in a population of relapsing-remitting MS patients during 3 years. Relapse severity and RD after 1 year were calculated on Expanded Disability Status Scale basis. A multivariable analysis for factors influencing RD and relapse severity was performed (variables: age, gender, disease duration, oligoclonal bands, relapse severity, monosymptomatic/polysymptomatic relapse, immunomodulating treatment, incomplete recovery at 1 month). RESULTS: A total of 174 relapses were assessed. RD after 1 year was observed in 54.5% of the relapses. Higher risk of RD was associated with occurrence of a severe relapse (P = 0.024). Incomplete recovery at 1 month was highly predictive of RD at 1 year (P < 0.0001). Risk of a severe relapse was associated with age

A nonlinear lumped parameters model to analyze the dynamics of venous reflux.

The aim of this work is to formulate a lumped parameters model of the venous tree of the lower limbs in order to study the effects and the possible clinical treatments for Chronic Venous Insufficiency (CVI). CVI is a pathology characterized by an important socio-economic impact due to its relevant prevalence, the costs for its diagnosis and treatment being more frequently widespread among the working population. The planning of haemodynamic surgical operations is critical to treat a pathological pattern of venous blood flow; such planning, in turn, depends on the right analysis of the possible consequences of flow modification. To this regard, the blood flow correction allows to solve the most important venous pathologies, in order to guarantee the restoration of normal blood flow by means of proper modifications of the venous tree. The developed model preserves the geometry of the venous network and considers some non linear resistive and capacitive effects. In fact, the study of the variability of some parameters (i.e. vessel radius) is very important to allow a correct diagnosis of vascular diseases. This variability causes a non linear behaviour of resistance and compliance effects. With the aid of the developed model we evaluate the time profile of blood velocity, flow and pressure in the entire venous network, both in physiological and pathological cases. The obtained results are discussed in comparison with available experimental data.

A haemodynamic model of the venous network of the lower limbs.

The pathologies of the venous system are characterized by a relevant socioeconomic impact in western countries. To this regard, the blood flow correction allows to solve the most important venous pathologies. In these cases, in order to guarantee the restoration of normal blood flow by means of proper modifications of the venous network, the correct planning of haemodynamics surgical operations is needed; such planning in turn depends on the right analysis of the possible consequences of flow modification. To this end, a mathematical model, that allows to precisely study the physiological and pathological behaviour of the venous network of the lower limbs, has been developed. The final goal is to use this model as an instrument helpful to plan surgical operations and give guidelines for the design and the test of new artificial devices. As for the modelling processing, a lumped parameters model has been derived with a resolution which allows to take into account the anatomic characteristics of the venous system.

Is an excessive number of prenatal echographies a risk for fetal growth?

AIM: To assess whether a very high number of prenatal ultrasonographies affects birthweight. POPULATION AND METHODS: We studied 1203 consecutive women who delivered in Siena Hospital. Exclusion criteria were the following: twin pregnancy, maternal smoke or alcohol ingestion in pregnancy, gestational diabetes, placenta or umbilical cord defects, gestational age at birth <37 weeks, and major malformations. We analysed birthweights in relation to the number of ultrasound examinations. 120 women had undergone a minimum number (three or less-base group) and 167 a maximum number (nine or more-intensive group) of fetal US scans. We compared the birthweight of the children born in these two groups and the correlation between number of US scans and birthweight in the whole population. RESULTS: Mean birthweights of the base and the intensive groups were 3389.5+/-434 g and 3268+/-438 g, respectively (p=0.0206). Nevertheless, the regression study did not show a significant correlation between birthweight and number of US scans. The mean age of the base group was 30.1+/-5.3 years and that of the intensive group was 32.09+/-4.99 years (p=0.0018). Eighteen women of base group underwent amniocenteses vs. 71 in the intensive group (p<0.001). In the base group 57.5% of the mothers had low school level vs. 24.4% in the intensive group (p<0.01). CONCLUSION: More studies are needed to confirm or exclude any relationship between an intensive use of prenatal ultrasounds and birthweight, and to exclude other effects of ultrasounds on children's health. Moreover, our study shows an excess of prenatal diagnostic procedures, the causes of which should be investigated.

Superoxide scavengers augment contractile but not energetic responses to hypoxia in rat diaphragm.

Acute exposure to severe hypoxia depresses contractile function and induces adaptations in skeletal muscle that are only partially understood. Previous studies have demonstrated that antioxidants (AOXs) given during hypoxia partially protect contractile function, but this has not been a universal finding. This study confirms that specific AOXs, known to act primarily as superoxide scavengers, protect contractile function in severe hypoxia. Furthermore, the hypothesis is tested that the mechanism of protection involves preservation of high-energy phosphates (ATP, creatine phosphate) and reductions of P(i). Rat diaphragm muscle strips were treated with AOXs and subjected to 30 min of hypoxia. Contractile function was examined by using twitch and tetanic stimulations and the degree of elevation in passive force occurring during hypoxia (contracture). High-energy phosphates were measured at the end of 30-min hypoxia exposure. Treatment with the superoxide scavengers 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron, 10 mM) or Mn(III)tetrakis(1-methyl-4-pyridyl) porphyrin pentachloride (50 microM) suppressed contracture during hypoxia and protected maximum tetanic force. N-acetylcysteine (10 or 18 mM) had no influence on tetanic force production. Contracture during hypoxia without AOXs was also shown to be dependent on the extracellular Ca(2+) concentration. Although hypoxia resulted in only small reductions in ATP concentration, creatine phosphate concentration was decreased to approximately 10% of control. There were no consistent influences of the AOX treatments on high-energy phosphates during hypoxia. The results demonstrate that superoxide scavengers can protect contractile function and reduce contracture in hypoxia through a mechanism that does not involve preservation of high-energy phosphates.

Sources for superoxide release: lessons from blockade of electron transport, NADPH oxidase, and anion channels in diaphragm.

Isolated diaphragm releases low levels of superoxide (O2*-) at rest and much higher levels during heat stress. The molecular source is unknown. The hypothesis was tested that heat stress stimulates mitochondrial complex activity or NADPH oxidases, resulting in increased O2*- release. The mitochondria within intact rat diaphragm were inhibited at complex I (amobarbital or rotenone) or complex I and II (rotenone plus thenoyltrifluoroacetone). NADPH oxidases were blocked by diphenyliodonium. None of these treatments inhibited O2*- release. Conversely, most blockers stimulated O2*- release. As intracellular O2*- generators require a mechanism for O2*- transport across the membrane, anion channel blockers, probenecid and 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid, were also tested. Neither blocker had any inhibitory effect on O2*- release. These results suggest that O2*- released from diaphragm is not directly dependent on mitochondrial complex activity and that it is not a reflection of passive diffusion of O2*- through anion channels. Although the molecular source for extracellular O2*- remains elusive, it is clearly sensitive to temperature and conditions of "chemical hypoxia" induced by partial or complete mitochondrial inhibition.