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1.
Nutr Hosp ; 40(5): 919-923, 2023 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-37732341

RESUMEN

Introduction: Introduction: scientific evidence on the appropriate nutritional support in the treatment of post-operative head and neck cancer (HNC) patients is still limited. Objectives: our aim was to evaluate nutritional status and quality of life in HNC patients in post-operative phase with different nutritional support. Methods: fifty-four HNC patients (26 with enteral nutrition [EN] via percutaneous endoscopic gastrostomy [PEG] and 28 with oral nutrition [ON]) were included. Nutritional status was evaluated with biochemical parameters and quality of life through the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30). Results: ON patients reported significantly (p < 0.05) lower levels of hemoglobin, lymphocytes, iron, folic acid, and vitamin D than EN patients, with greater percentage of ON patients found to be below the reference limits for hemoglobin (21.4 % vs 19.4 %), and significantly for serum iron (17.9 % vs 0 %) and vitamin D (78.6 % vs 30.8 %). Furthermore, EN patients had a better quality of life (63.8 ± 17.6) than ON (55.4 ± 20.3), although ON patients reported less symptoms related to dyspnea (-5.8 %), loss of appetite (-11.3 %) and vomiting (-23.1 %). Conclusions: these results suggest that the use of EN in post-operative HNC patients could have a positive effect on the nutritional status and quality of life of these patients. However, further research is needed to optimize the nutritional support in these patients in order to avoid malnutrition and improve their well-being.


Introducción: Introducción: la evidencia científica sobre el soporte nutricional más apropiado en pacientes con cáncer de cabeza y cuello (CCC) en el periodo postoperatorio es aún limitada. Objetivos: el objetivo de este estudio fue evaluar el estado nutricional y la calidad de vida en pacientes con CCC en el periodo postoperatorio. Métodos: se incluyeron 54 pacientes con CCC (26 con nutrición enteral [NE] mediante gastrostomía endoscópica percutánea [PEG] y 28 con nutrición oral NO]). El estado nutricional se evaluó mediante parámetros bioquímicos y la calidad de la vida, con el cuestionario European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30). Resultados: los pacientes con NO reportaron valores significativamente (p < 0,05) menores de hemoglobina, linfocitos, hierro sérico, ácido fólico y vitamina D respecto a los pacientes con NE, con un mayor porcentaje de pacientes con NO por debajo de los límites de referencia de hemoglobina (21,4 % vs. 19,4 %) y significativamente de hierro sérico (17,9 % vs. 0 %) y vitamina D (78,6 % vs. 30,8 %). Además, los pacientes con NE reportaron una mejor calidad de vida (63,8 ± 17,6) respecto los pacientes con NO (55,4 ± 20,3), aunque los pacientes con NO refirieron menos síntomas cómo disnea (-5,8 %), pérdida de apetito (-11,3 %) y vómitos (-23,1 %). Conclusión: estos resultados sugieren que el uso de NE en pacientes con HNC tras cirugía podría tener un efecto positivo sobre su estado nutricional y su calidad de vida. Sin embargo, es necesario seguir investigando para optimizar el soporte nutricional en estos pacientes a fin de evitar la desnutrición y mejorar su bienestar.

2.
Nutr Metab Cardiovasc Dis ; 33(8): 1490-1500, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37246076

RESUMEN

AIMS: Over the past years, interest in chrono-nutrition has grown enormously as the fundamental role of circadian rhythms in regulating most physiological and metabolic processes has become clearer. Recently, the influence of circadian rhythms on the gut microbiota (GM) composition has also emerged, as more than half of the total microbial composition fluctuates rhythmically throughout the day. At the same time, other studies have observed that the GM itself synchronises the host's circadian biological clock through signals of a different nature. Therefore, it has been hypothesised that there is a two-way communication between the circadian rhythms of the host and the GM, but researchers have only just begun to identify some of its action mechanisms. The manuscript aim is, therefore, to gather and combine the latest evidence in the field of chrono-nutrition with the more recent research on the GM, in order to investigate their relationship and their potential impact on human health. DATA SYNTHESIS: Considering current evidence, a desynchronization of circadian rhythms is closely associated with an alteration in the abundance and functionality of the gut microbiota with consequent deleterious effects on health, such as increased risk of numerous pathologies, including cardiovascular disease, cancer, irritable bowel disease, and depression. A key role in maintaining the balance between circadian rhythms and GM seems to be attributed to meal-timing and diet quality, as well as to certain microbial metabolites, in particular short-chain fatty acids. CONCLUSIONS: Future studies are needed to decipher the link between the circadian rhythms and specific microbial patterns in relation to different disease frameworks.


Asunto(s)
Microbioma Gastrointestinal , Neoplasias , Humanos , Ritmo Circadiano/fisiología , Dieta/efectos adversos , Estado Nutricional
3.
World J Gastroenterol ; 28(18): 1965-1980, 2022 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-35664958

RESUMEN

BACKGROUND: Fibromyalgia (FM) syndrome is mainly characterized by widespread pain, sleeping disorders, fatigue, and cognitive dysfunction. In many cases, gastrointestinal distress is also reported, suggesting the potential pathogenic role of the gut microbiota (GM). The GM is deeply influenced by several environmental factors, especially the diet, and recent findings highlighted significant symptom improvement in FM patients following various nutritional interventions such as vegetarian diet, low-fermentable oligosaccharides, disaccharides, monosaccharides, and polyols based diets, gluten-free diet, and especially an ancient grain supplementation. In particular, a recent study reported that a replacement diet with ancient Khorasan wheat led to an overall improvement in symptom severity of FM patients. AIM: To examine the effects of ancient Khorasan wheat on the GM, inflammation, and short-chain fatty acid production in FM patients. METHODS: After a 2-wk run-in period, 20 FM patients were enrolled in this randomized, double-blind crossover trial. In detail, they were assigned to consume either Khorasan or control wheat products for 8 wk and then, following an 8-wk washout period, crossed. Before and after treatments, GM characterization was performed by 16S rRNA sequencing while the fecal molecular inflammatory response and the short-chain fatty acids (SCFAs) were respectively determined with the Luminex MAGPIX detection system and a mass chromatography-mass spectrometry method. RESULTS: The Khorasan wheat replacement diet, in comparison with the control wheat diet, had more positive effects on intestinal microbiota composition and on both the fecal immune and SCFAs profiles such as the significant increase of butyric acid levels (P = 0.054), candidatus Saccharibacteria (P = 9.95e-06) and Actinobacteria, and the reduction of Enterococcaceae (P = 4.97e-04). Moreover, the improvement of various FM symptoms along with the variation of some gut bacteria after the Khorasan wheat diet have been documented; in fact we reported positive correlations between Actinobacteria and both Tiredness Symptoms Scale (P < 0.001) and Functional Outcome of Sleep Questionnaire (P < 0.05) scores, between Verrucomicrobiae and both Widespread Pain Index (WPI) + Symptom Severity scale (SS) (P < 0.05) and WPI (P < 0.05) scores, between candidatus Saccharibacteria and SS score (P < 0.05), and between Bacteroidales and Sleep-Related and Safety Behaviour Questionnaire score (P < 0.05). CONCLUSION: The replacement diet based on ancient Khorasan wheat results in beneficial GM compositional and functional modifications that positively correlate with an improvement of FM symptomatology.


Asunto(s)
Fibromialgia , Microbioma Gastrointestinal , Dieta Sin Gluten , Ácidos Grasos Volátiles , Fibromialgia/diagnóstico , Humanos , Inflamación , Dolor , ARN Ribosómico 16S , Triticum
4.
Nutr Cancer ; 74(8): 2868-2874, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35196919

RESUMEN

The aims of this study were to assess the presence of dysgeusia in patients receiving anticancer therapy and to explore possible factors influencing its occurrence. A total of 242 adult patients with histological diagnoses of malignant neoplasia and undergoing all types of anticancer treatment were included in the analysis. Data were collected from May 2019 to November 2019 at the Unit of Medical Oncology of Careggi University Hospital, Florence, Italy. Dysgeusia was assessed using the Chemotherapy-induced Taste Alteration Scale (CiTAS), while treatment-related symptoms were assessed using the Common Terminology Criteria for Adverse Events (CTCAE). Patients were aged 68 ± 13 years, mostly males (65%). A large proportion of them was undergoing chemotherapy (42.2%), while the others were receiving immunotherapy (20.7%), hormone therapy (15.5%), targeted therapy (12.8%), or a combination of them. Overall, 21.5% of patients reported dysgeusia, 17.4% nausea, 10.7% dysosmia, 9.9% xerostomia, 4.5% mucositis, and only 3.7% vomiting. The targeted therapy showed the greatest adverse effects, followed by chemotherapy, immunotherapy, and hormone therapy. When patients with dysgeusia were analyzed, phantogeusia and parageusia was the most affected dimension of gustatory disorders. Significant differences (p < 0.05) in CiTAS scores were found according to treatment-related symptoms for nausea and mucositis.


Asunto(s)
Mucositis , Neoplasias , Adulto , Disgeusia/inducido químicamente , Disgeusia/epidemiología , Femenino , Hormonas/efectos adversos , Humanos , Masculino , Náusea/inducido químicamente , Neoplasias/tratamiento farmacológico
5.
Adv Nutr ; 13(1): 269-281, 2022 02 01.
Artículo en Inglés | MEDLINE | ID: mdl-34549270

RESUMEN

Chronotype is a behavioral manifestation of the internal circadian clock system. It refers to the specific activity-rest preference of an individual over a 24-h period and can be assessed using different methodologies that classify individuals into morning or evening chronotype. In recent years, several studies have suggested a relation between individual chronotype, eating habits, and the risk of developing obesity and other conditions. Our aim was to evaluate the association between chronotype, energy intake, and health status through a meta-analytic approach. A comprehensive search of MEDLINE, Embase, Scopus, Web of Science, and Cochrane Database was conducted. Observational studies that reported a measure of association between chronotype, energy intake, and health indicators were considered eligible. Overall, 39 observational studies (37 cross-sectional studies, 2 prospective cohort studies) were included in the systematic review, with a total of 377,797 subjects. By comparing morning and evening subjects, pooled analyses of cross-sectional studies showed significantly (P < 0.001) higher concentrations of blood glucose [mean difference (MD): 7.82; 95% CI: 3.18, 12.45], glycated hemoglobin (MD: 7.64; 95% CI: 3.08, 12.21), LDL cholesterol (MD: 13.69; 95% CI: 6.84, 20.54), and triglycerides (MD: 12.62; 95% CI: 0.90, 24.35) in evening subjects. Furthermore, an association between evening type and the risk of diabetes (OR: 1.30; 95% CI: 1.20, 1.41), cancer (OR: 1.18; 95% CI: 1.08, 1.30), and depression (OR: 1.86; 95% CI: 1.20, 2.88) was reported. Regarding the other outcomes examined, no significant differences were observed between the groups in terms of energy intake, anthropometric parameters, blood pressure, insulin, total and HDL cholesterol, and hypertension risk. In conclusion, evening chronotype was associated with a worse cardiometabolic risk profile and higher risk of diabetes, cancer, and depression. Further studies are needed to confirm these results and to better elucidate the interplay between chronotype, nutrition, and health status. This systematic review was registered at www.crd.york.ac.uk/prospero/ as CRD42021231044.


Asunto(s)
Enfermedades Cardiovasculares , Neoplasias , Enfermedades Cardiovasculares/etiología , Ritmo Circadiano/fisiología , Estudios Transversales , Depresión , Ingestión de Energía , Humanos , Neoplasias/epidemiología , Neoplasias/etiología , Estudios Prospectivos
6.
Eur J Clin Invest ; 51(9): e13576, 2021 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-33955547

RESUMEN

BACKGROUND: The aim of the present study was to assess the effects of a lacto-ovo-vegetarian diet (VD), compared to a Mediterranean diet (MD), on kidney function in a group of subjects with medium-to-low cardiovascular risk profile. METHODS: We analysed 107 subjects (82 women, 25 men; median age 52) who followed a VD (n = 54) and a MD (n = 53) for 3 months in the CARDIVEG study, a randomized, open, crossover trial that compared the effects of these 2 diets on cardiovascular disease risk. RESULTS: The effect of the two diets on kidney function markers was evaluated by conducting a general linear model for repeated measurements adjusted for possible confounding factors such as age, sex, physical activity, alcohol, smoking, hypertension, LDL cholesterol, glucose and body weight change. A significant reduction in creatinine (-5.3%; P < .001), urea nitrogen levels (-9%; P = .001), blood urea nitrogen (BUN) (-8.7%; P = .001) and BUN/creatinine ratio (-5.8%; P < .001), and an increase in estimated glomerular filtration rate (eGFR) (+3.5%; P = .001) was observed during the VD period. On the contrary, no significant changes were noted in the MD group. Variations obtained in the two dietary interventions were significantly different (P < .0001) for creatinine levels, BUN/creatinine and eGFR, for which opposite trends were observed in the VD and MD groups. CONCLUSIONS: In a selected group of subjects with medium-to-low cardiovascular risk profile, a 3 month VD period determined significant improvements in kidney function markers. Further trials are needed to confirm these results.


Asunto(s)
Nitrógeno de la Urea Sanguínea , Enfermedades Cardiovasculares/prevención & control , Creatinina/sangre , Dieta Mediterránea , Dieta Vegetariana , Tasa de Filtración Glomerular , Adulto , Anciano , Estudios Cruzados , Femenino , Factores de Riesgo de Enfermedad Cardiaca , Humanos , Pruebas de Función Renal , Modelos Lineales , Masculino , Persona de Mediana Edad , Conducta de Reducción del Riesgo , Ácido Úrico/sangre , Adulto Joven
7.
Int J Food Sci Nutr ; 72(3): 367-374, 2021 May.
Artículo en Inglés | MEDLINE | ID: mdl-32718191

RESUMEN

The aim of this study was to compare the effect of consumption of ancient grain "Verna" bread obtained by two different leavening agents, sourdough (SD) and baker's yeast (BY), on inflammatory parameters and cardiometabolic risk factors. Seventeen clinically healthy subjects were included to consume SD or BY bread for 4 weeks each, and blood analyses were carried out. The consumption of "Verna" bread obtained with both leavening agents led to a significant improvement of LDL cholesterol. A reduction of -10.6% and -8.53% was observed after replacement with SD and BY bread, respectively. A significant increase in fasting blood glucose (+6%) was observed only after the intervention with BY bread. A 10.7% decrease of vascular endothelial growth factor was found after the SD bread replacement period. The consumption of "Verna" bread resulted significantly associated with an improvement in the cardiometabolic and inflammatory profile. However, only consumption of BY bread determined a significant increase in blood glucose levels.


Asunto(s)
Pan/análisis , Dieta , Grano Comestible , Saccharomyces cerevisiae , Adolescente , Adulto , Anciano , Análisis Químico de la Sangre , Pan/microbiología , Colesterol , Estudios Cruzados , Método Doble Ciego , Femenino , Fermentación , Manipulación de Alimentos/métodos , Humanos , Italia , Masculino , Persona de Mediana Edad , Factor A de Crecimiento Endotelial Vascular/análisis , Adulto Joven
8.
Nutrients ; 12(9)2020 Aug 20.
Artículo en Inglés | MEDLINE | ID: mdl-32825400

RESUMEN

Fibromyalgia (FM) is a multifactorial syndrome of unknown etiology, characterized by widespread chronic pain and various somatic and psychological manifestations. The management of FM requires a multidisciplinary approach combining both pharmacological and nonpharmacological strategies. Among nonpharmacological strategies, growing evidence suggests a potential beneficial role for nutrition. This review summarizes the possible relationship between FM and nutrition, exploring the available evidence on the effect of dietary supplements and dietary interventions in these patients. Analysis of the literature has shown that the role of dietary supplements remains controversial, although clinical trials with vitamin D, magnesium, iron and probiotics' supplementation show promising results. With regard to dietary interventions, the administration of olive oil, the replacement diet with ancient grains, low-calorie diets, the low FODMAPs diet, the gluten-free diet, the monosodium glutamate and aspartame-free diet, vegetarian diets as well as the Mediterranean diet all appear to be effective in reducing the FM symptoms. These results may suggest that weight loss, together with the psychosomatic component of the disease, should be taken into account. Therefore, although dietary aspects appear to be a promising complementary approach to the treatment of FM, further research is needed to provide the most effective strategies for the management of FM.


Asunto(s)
Fibromialgia/dietoterapia , Terapia Nutricional/métodos , Fenómenos Fisiológicos de la Nutrición/fisiología , Acetilcarnitina/administración & dosificación , Ácido Ascórbico/administración & dosificación , Chlorella , Dieta Vegana , Suplementos Dietéticos , Síndrome , Ubiquinona/administración & dosificación , Ubiquinona/análogos & derivados , Vitamina E/administración & dosificación
9.
Pain Med ; 21(10): 2366-2372, 2020 10 01.
Artículo en Inglés | MEDLINE | ID: mdl-32488245

RESUMEN

OBJECTIVE: To investigate the effects of a replacement diet with Khorasan wheat products in patients with fibromyalgia, in comparison with a similar replacement diet with control products made from organic semi-whole-grain modern wheat. DESIGN: Randomized, double-blinded crossover trial. SETTING: Outpatient clinic. SUBJECTS: Twenty subjects (19 female and one male, mean age = 48.9 ± 12.3 years) with fibromyalgia. METHODS: Participants were randomly assigned to consume either Khorasan or control wheat products (pasta, bread, crackers, biscuits) for eight weeks and then crossed. Validated self-administered questionnaires were collected from each subject at the beginning and end of each intervention period. RESULTS: A general linear model for repeated measurement, adjusted for potential confounders, showed that the overall score reported from each questionnaire improved after both intervention and control periods, but the effect was more evident after the intervention with Khorasan. In particular, a statistically significant difference in Widespread Pain Index (WPI) + Severity Scale (SS) and Functional Outcome of Sleep Questionnaire (FOSQ) was observed, which decreased significantly by 21.5% and 11.7% respectively, only after the Khorasan period, while no statistically significant variations were reported after the control period. Similarly, FM Impact Questionnaire scores decreased significantly only after the Khorasan period, with a reduction that was significantly different between the intervention and control periods (-22.5% vs -0.3%, P = 0.037). The improvement was even greater in people with higher symptom severity. CONCLUSIONS: A dietary intervention with Khorasan wheat products seems to benefit patients with fibromyalgia, especially those with greater symptom severity.


Asunto(s)
Fibromialgia , Triticum , Adulto , Dieta , Femenino , Humanos , Masculino , Persona de Mediana Edad , Dolor , Calidad de Vida
10.
J Reconstr Microsurg ; 35(3): 189-193, 2019 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-30112753

RESUMEN

BACKGROUND: The creation of skin flaps based on small perforator vessels is an increasingly popular procedure nowadays; the optimization of their blood supply enhances surgical success. This study evaluates the effects on the flowmetries of 7 days' negative pressure application on the skin surface overlying the muscle fascia emergence of periumbilical perforators of the deep inferior epigastric artery (DIEA). METHODS: Ten volunteer participants were enrolled. In each subject, one periumbilical perforator of the DIEA was identified on each side of the abdomen using an eco-color-Doppler. One of them was used as the control group, while the other (the study group) underwent 80 mm Hg negative pressure for 7 days. The flowmetries of both perforators were measured before and after the application of negative pressure wound therapy. RESULTS: After the application of negative pressure, randomly applied on the skin surface over one of the two selected periumbilical perforators, an increase in the flowmetries was observed in both groups of perforators (2.74 cm/s; p < 0.0001). The relative flowmetry increase in the control group was 9.55% (2.735 cm/s), while in the study group it was 44.03% (8.748 cm/s). CONCLUSION: The application of negative pressure system on the skin surface over the muscle fascia emergence of the selected periumbilical perforators showed an increase in flowmetry. Although this is a preliminary study, this simple and economical procedure before surgery could be usefully employed to increase the rate of success in microsurgical procedures.


Asunto(s)
Arterias/diagnóstico por imagen , Terapia de Presión Negativa para Heridas , Colgajo Perforante/irrigación sanguínea , Adulto , Arterias/fisiología , Femenino , Voluntarios Sanos , Humanos , Masculino , Ultrasonografía Doppler en Color , Adulto Joven
11.
J Am Coll Nutr ; 37(6): 508-514, 2018 08.
Artículo en Inglés | MEDLINE | ID: mdl-29652567

RESUMEN

OBJECTIVE: KAMUT khorasan is an ancient grain with widely acclaimed health benefits. The aim of this study was to investigate the effects of a replacement diet with ancient khorasan wheat products in patients with NAFLD, in comparison to a similar replacement diet with control products made from organic semi-whole-grain modern wheat. METHODS: Forty NAFLD patients (12 M/28 F; age 55.2 ± 10.4 years) with mild to moderate liver steatosis were included. The experimental design was a randomized, double-blind, parallel-arm study with 20 participants assigned to consume either KAMUT khorasan or control wheat products (pasta, bread, crackers, biscuits) over a 3-month period. Anthropometric measurements, blood analyses, and ultrasonography examination were performed at both the beginning and end of each dietary intervention. RESULTS: After the implementation of a general linear model for repeated measurements adjusted for baseline demographic details, risk factors, and medication, alanine aminotransferase (ALT) was significantly reduced by 12%, aspartate aminotransferase (AST) by 14%, alkaline phosphatase (ALP) by 8%, and cholesterol by 6% only in the khorasan group (p < 0.05 for all). Similarly, significant reductions in circulating proinflammatory tumor necrosis factor-alpha by 50%, interleukin l-receptor antagonist-alpha by 37%, interleukin-8 by 24%, and interferon gamma by 24% were evident only in participants who consumed the khorasan products (p < 0.05 for all). Finally, significant improvements in the liver steatosis grading, Doppler perfusion index values, and reactive oxygen species (ROS) production were evident after consumption of both the khorasan and control products. CONCLUSIONS: This study suggests that a short-term replacement diet with ancient KAMUT khorasan products is most effective in reducing metabolic risk factors and ameliorating the liver profile in patients with NAFLD.


Asunto(s)
Pan , Dieta , Enfermedad del Hígado Graso no Alcohólico/dietoterapia , Triticum/clasificación , Anciano , Alanina Transaminasa/sangre , Aspartato Aminotransferasas/sangre , Colesterol/sangre , Método Doble Ciego , Grano Comestible , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estrés Oxidativo/efectos de los fármacos , Factores de Riesgo
12.
J Proteome Res ; 15(10): 3666-3678, 2016 10 07.
Artículo en Inglés | MEDLINE | ID: mdl-27571187

RESUMEN

Understanding the relationship between physical exercise, reactive oxygen species, and skeletal muscle modification is important in order to better identify the benefits or the damages that appropriate or inappropriate exercise can induce. Heart and skeletal muscles have a high density of mitochondria with robust energetic demands, and mitochondria plasticity has an important role in both the cardiovascular system and skeletal muscle responses. The aim of this study was to investigate the influence of regular physical activity on the oxidation profiles of mitochondrial proteins from heart and tibialis anterior muscles. To this end, we used the mouse as animal model. Mice were divided into two groups: untrained and regularly trained. The carbonylated protein pattern was studied by two-dimensional gel electrophoresis followed by Western blot with anti-dinitrophenyl hydrazone antibodies. Mass spectrometry analysis allowed the identification of several different protein oxidation sites, including methionine, cysteine, proline, and leucine residues. A large number of oxidized proteins were found in both untrained and trained animals. Moreover, mitochondria from skeletal muscles and heart showed almost the same carbonylation pattern. Interestingly, exercise training seems to increase the carbonylation level mainly of mitochondrial proteins from skeletal muscle.


Asunto(s)
Mitocondrias Musculares/química , Proteínas Mitocondriales/análisis , Carbonilación Proteica , Animales , Western Blotting , Ratones , Proteínas Mitocondriales/metabolismo , Miocardio/ultraestructura , Oxidación-Reducción , Condicionamiento Físico Animal
13.
Biophys J ; 98(11): 2582-90, 2010 Jun 02.
Artículo en Inglés | MEDLINE | ID: mdl-20513402

RESUMEN

The cross-bridge stiffness can be used to estimate the number of S1 that are bound to actin during contraction, which is a critical parameter for elucidating the fundamental mechanism of the myosin motor. At present, the development of active tension and the increase in muscle stiffness due to S1 binding to actin are thought to be linearly related to the number of cross-bridges formed upon activation. The nonlinearity of total stiffness with respect to active force is thought to arise from the contribution of actin and myosin filament stiffness to total sarcomere elasticity. In this work, we reexamined the relation of total stiffness to tension during activation and during exposure to N-benzyl-p-toluene sulphonamide, an inhibitor of cross-bridge formation. In addition to filament and cross-bridge elasticity, our findings are best accounted for by the inclusion of an extra elasticity in parallel with the cross-bridges, which is formed upon activation but is insensitive to the subsequent level of cross-bridge formation. By analyzing the rupture tension of the muscle (an independent measure of cross-bridge formation) at different levels of activation, we found that this additional elasticity could be explained as the stiffness of a population of no-force-generating cross-bridges. These findings call into question the assumption that active force development can be taken as directly proportional to the cross-bridge number.


Asunto(s)
Actinas/metabolismo , Contracción Muscular/fisiología , Fibras Musculares Esqueléticas/fisiología , Tono Muscular/fisiología , Miosinas/metabolismo , Animales , Elasticidad , Técnicas In Vitro , Soluciones Isotónicas , Modelos Biológicos , Contracción Muscular/efectos de los fármacos , Fibras Musculares Esqueléticas/efectos de los fármacos , Tono Muscular/efectos de los fármacos , Periodicidad , Rana esculenta , Solución de Ringer , Sarcómeros/efectos de los fármacos , Sarcómeros/fisiología , Sulfonamidas/farmacología , Factores de Tiempo , Tolueno/análogos & derivados , Tolueno/farmacología
14.
Biophys J ; 97(11): 2922-9, 2009 Dec 02.
Artículo en Inglés | MEDLINE | ID: mdl-19948121

RESUMEN

Force generation and movement in skeletal muscle result from a cyclical interaction of overlapping myosin and actin filaments that permits the free energy of ATP hydrolysis to be converted into mechanical work. The rapid force recovery that occurs after a step release imposed on a muscle is thought to result from a synchronized tilting of myosin lever arms toward a position of lower free energy (the power stroke). We investigated the power stroke mechanism in intact muscle fibers of Rana esculenta using a fast stretch to detach forcibly cross-bridges. Stretches were applied either with or without a conditioning step release. Cross-bridge rupture tension was not significantly influenced by the release, whereas sarcomere elongation at the rupture point increased immediately after the release and returned to the prerelease condition within 15-20 ms, following a slower time course compared to the recovery of tension. These observations suggest that the rupture force of a bridge is unaltered by a conditioning release, but rupture must first be preceded by a power stroke reversal, which restores the prepower stroke state. The sarcomere extension at the rupture point indicates both the extent of this power stroke reversal and the time course of strained bridge replenishment.


Asunto(s)
Movimiento , Fibras Musculares Esqueléticas/fisiología , Miosinas/metabolismo , Animales , Fenómenos Biomecánicos , Cinética , Modelos Biológicos , Fibras Musculares Esqueléticas/metabolismo , Rana esculenta , Termodinámica
15.
J Physiol ; 578(Pt 1): 337-46, 2007 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-17023505

RESUMEN

The aims of this study were to investigate the effects of solution tonicity on muscle properties, and to verify their consistence with the lever arm theory of force generation. Experiments were made in single muscle fibres and in fibre bundles from the frog, using both fast stretches and time-resolved X-ray diffraction, in isotonic Ringer solution (1T), hypertonic (1.4T) and hypotonic (0.8T) solutions. Fast stretches (0.4-0.6 ms duration and 16-25 nm per half-sarcomere (nm hs(-1)) amplitude) were applied at various tensions during the force development in isometric tetani. Force increased during the stretch up to a peak (critical tension, Pc) at which it started to fall, in spite of continued stretching. In all solutions, Pc was proportional to the initial isometric tension developed. For a given isometric tension, Pc increased with solution tonicity and occurred at a precise sarcomere elongation (critical length, Lc) which also increased with tonicity. M3 meridional layer line intensity (I M3) was measured during the application of sinusoidal length oscillations (1 kHz frequency, and about 2% fibre length amplitude) at tetanus plateau. I M3 changed during the length oscillations in a sinusoidal manner in phase opposition to length changes, but a double peak distortion occurred at the peak of the release phase. The presence of the distortion, which decreased with tonicity, allowed calculation of the mean position of the myosin head (S1) during the oscillation cycle. In agreement with the lever arm theory, both X-ray diffraction and mechanical data show that solution tonicity affects S1 mean position and consequently crossbridge individual extension and force, with no effect on crossbridge number. The force needed to break the single crossbridge was insensitive to solution tonicity suggesting a non-ionic nature of the actomyosin bond.


Asunto(s)
Fibras Musculares Esqueléticas/fisiología , Miosinas/fisiología , Actinas/fisiología , Animales , Soluciones Hipertónicas , Técnicas In Vitro , Contracción Isométrica , Contracción Muscular/fisiología , Husos Musculares/fisiología , Miosinas/química , Concentración Osmolar , Rana esculenta , Sarcómeros/fisiología , Difracción de Rayos X
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