Effect of oxidant challenge on contractile function of the aging rat diaphragm

Although controversial, growing evidence indicates that reactive oxygen species (ROS) alter contractions of skeletal muscle, including the diaphragm. However, the impact of ROS on contractility of the aging diaphragm is unknown. The xanthine oxidase (0.01 U/ml) system was used as an ROS generator, imposing an oxidant challenge. Contractile function [twitch tension; twitch time to peak tension; twitch one-half relaxation time; tension at 10 and 20 Hz; maximal tetanic tension (Po) at 100 Hz] of costal diaphragm fiber bundles from young (4 mo) and old (25 mo) Fischer 344 rats was examined in vitro before and after treatment with control Krebs solution [young control (YC) and old control (OC)], or with xanthine oxidase (XO; 0.01 U/ml) plus hypoxanthine (0.29 mg/ml) substrate [young XO treated (YXO) and old XO treated (OXO)]. Contractile function of fiber bundles was reassessed after oxidant challenge in an unfatigued state (Post-u) or 10 min after a fatiguing stimulation protocol (Post-f). Oxidant challenge in the unfatigued fiber bundles increased twitch tension and tension at 10 and 20 Hz in YXO, but not OXO, without increasing Po. Conversely, XO significantly depressed fatigued diaphragm twitch and low-frequency tension in both OXO and YXO, compared with controls. Po was depressed Post-f in OXO but not YXO. Oxidant challenge also increased twitch one-half relaxation time of the fatigued diaphragm in both age groups. Furthermore, fiber bundles from old rats suffered greater fatigue during the stimulation protocol. We conclude that the response to oxidant challenge and increased contractile demand is impaired in the aging diaphragm.

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N-acetylcysteine depresses contractile function and inhibits fatigue of diaphragm in vitro

Journal of Applied Physiology ◽

10.1152/jappl.1994.77.1.317 ◽

1994 ◽

Vol 77 (1) ◽

pp. 317-324 ◽

Cited By ~ 86

Author(s):

F. A. Khawli ◽

M. B. Reid

Keyword(s):

Antioxidant Enzymes ◽

Contractile Function ◽

Fiber Bundles ◽

Clinical Use ◽

Time To Peak ◽

Antioxidant Agents ◽

Dose Dependent Decrease ◽

Diaphragm In Vitro ◽

The Right

We have previously shown that antioxidant enzymes (superoxide dismutase and catalase) depress contractility of unfatigued diaphragm fiber bundles and inhibit development of acute fatigue. In the present study, we tested for similar effects of N-acetyl-cysteine (NAC), a nonspecific antioxidant approved for clinical use. Diaphragms were excised from deeply anesthetized rats. Fiber bundles were removed, mounted isometrically at 37 degrees C, and stimulated directly using supramaximal current intensity. Studies of unfatigued muscle showed that 10 mM NAC reduced peak twitch stress (P < 0.0001), shortened time to peak twitch stress (P < 0.002), and shifted the stress-frequency curve down and to the right (P < 0.05). Fiber bundles incubated in 0.1–10 mM NAC exhibited a dose-dependent decrease in relative stresses developed during 30-Hz contraction (P < 0.0001) with no change in maximal tetanic (200 Hz) stress. NAC (10 mM) also inhibited acute fatigue. Throughout 10 min of intermittent contraction at 30–40 Hz, treated bundles developed higher stresses than time-matched control bundles (P < 0.0001). NAC concentrations > or = 30 mM were toxic, causing a prompt irreversible decrease in maximal tetanic stress (P < 0.0001). Because NAC effects mimic the effects of other antioxidant agents with different mechanisms of action, we conclude that exogenous antioxidants exert stereotypical effects on contractile function that differ between unfatigued and fatiguing muscle. Unlike antioxidant enzymes, however, NAC has been approved for clinical use and may be used in future studies of human muscle fatigue.

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Contractile properties of expiratory abdominal muscles: effect of elastase-induced emphysema

Journal of Applied Physiology ◽

10.1152/jappl.1987.62.6.2314 ◽

1987 ◽

Vol 62 (6) ◽

pp. 2314-2319 ◽

Cited By ~ 6

Author(s):

J. S. Arnold ◽

A. J. Thomas ◽

S. G. Kelsen

Keyword(s):

Relaxation Time ◽

Contractile Function ◽

Isometric Tension ◽

Contractile Properties ◽

Abdominal Muscles ◽

Force Frequency ◽

Contraction Time ◽

Transverse Abdominis ◽

External Oblique

The present study examined the intrinsic contractile properties and endurance of the transverse abdominis and external oblique abdominal expiratory muscles in adult hamsters and compared their performance with the diaphragm. Experiments were performed in vitro on isolated bundles of muscle stimulated electrically. In control animals peak twitch tension was similar in the two muscles. In contrast, the twitch contraction time and one-half relaxation time of the transverse abdominis were significantly greater than that of the external oblique. The isometric tension generated over a range of stimulus frequencies (i.e., the force-frequency relationship) was a greater percent of the maximum value in response to subtetanizing frequencies (10–40 Hz) in the transverse abdominis than in the external oblique. For both abdominal muscles, however, the tension generated over this range of stimulus frequencies was less than that of the diaphragm. The endurance of the transverse abdominis during repeated contractions was significantly greater than that of the external oblique but similar to the diaphragm. The effect of chronic hyperinflation produced by elastase-induced emphysema on the contractile function of the two muscles was assessed in a second group of adult hamsters. In emphysematous animals peak twitch tension, contraction time, and one-half relaxation time of the twitch and force-frequency curves of muscles from emphysematous animals were similar to values obtained in control animals for both the external oblique and transverse abdominis. However, the endurance of both the transverse abdominis and external oblique muscles was greater in emphysematous than control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

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The Toothbrush Microbiome: Impact of User Age, Period of Use and Bristle Material on the Microbial Communities of Toothbrushes

Microorganisms ◽

10.3390/microorganisms8091379 ◽

2020 ◽

Vol 8 (9) ◽

pp. 1379 ◽

Cited By ~ 1

Author(s):

Marc-Kevin Zinn ◽

Laura Schages ◽

Dirk Bockmühl

Keyword(s):

Bacterial Colonization ◽

Low Frequency ◽

Antibiotic Resistance Genes ◽

In Vitro Tests ◽

Bacterial Survival ◽

Microbial Composition ◽

Growth And Survival ◽

Ngs Data ◽

The Impact

Toothbrushes play a central role in oral hygiene and must be considered one of the most common articles of daily use. We analysed the bacterial colonization of used toothbrushes by next generation sequencing (NGS) and by cultivation on different media. Furthermore, we determined the occurrence of antibiotic resistance genes (ARGs) and the impact of different bristle materials on microbial growth and survival. NGS data revealed that Enterobacteriaceae, Micrococcaceae, Actinomycetaceae, and Streptococcaceae comprise major parts of the toothbrush microbiome. The composition of the microbiome differed depending on the period of use or user age. While higher fractions of Actinomycetales, Lactobacillales, and Enterobacterales were found after shorter periods, Micrococcales dominated on both toothbrushes used for more than four weeks and on toothbrushes of older users, while in-vitro tests revealed increasing counts of Micrococcus on all bristle materials as well. Compared to other environments, we found a rather low frequency of ARGs. We determined bacterial counts between 1.42 × 106 and 1.19 × 107 cfu/toothbrush on used toothbrushes and no significant effect of different bristles materials on bacterial survival or growth. Our study illustrates that toothbrushes harbor various microorganisms and that both period of use and user age might affect the microbial composition.

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Human Newborn Monocytes Demonstrate Distinct BCG-Induced Primary and Trained Innate Cytokine Production and Metabolic Activation In Vitro

Frontiers in Immunology ◽

10.3389/fimmu.2021.674334 ◽

2021 ◽

Vol 12 ◽

Author(s):

Asimenia Angelidou ◽

Joann Diray-Arce ◽

Maria-Giulia Conti ◽

Mihai G. Netea ◽

Bastiaan A. Blok ◽

...

Keyword(s):

Cytokine Production ◽

Colorimetric Assay ◽

Age Groups ◽

Metabolic Activation ◽

Human Monocyte ◽

Autologous Serum ◽

Live Attenuated Vaccine ◽

Cytokine Responses ◽

The Impact

BackgroundNewborns exhibit distinct immune responses and are at high risk of infection. Neonatal immunization with BCG, the live attenuated vaccine against tuberculosis (TB), is associated with broad protection against a range of unrelated pathogens, possibly reflecting vaccine-induced training of innate immune cells (“innate memory”). However, little is known regarding the impact of age on BCG-induced innate responses.ObjectiveEstablish an age-specific human monocyte in vitro training platform to characterize and compare BCG-induced primary and memory cytokine responses and immunometabolic shifts.Design/MethodsHuman neonatal and adult CD33-selected monocytes were stimulated for 24h with RPMI (control) or BCG (Danish strain) in 10% autologous serum, washed and cultured for 5 additional days, prior to re-stimulation with the TLR4 agonist LPS for another 24h. Supernatants were collected at Day 1 (D1) to measure primary innate responses and at Day 7 (D7) to assess memory innate responses by ELISA and multiplex cytokine and chemokine assays. Lactate, a signature metabolite increased during trained immunity, was measured by colorimetric assay.ResultsCytokine production by human monocytes differed significantly by age at D1 (primary, BCG 1:750 and 1:100 vol/vol, p<0.0001) and D7 (innate memory response, BCG 1:100 vol/vol, p<0.05). Compared to RPMI control, newborn monocytes demonstrated greater TNF (1:100, 1:10 vol/vol, p<0.01) and IL-12p40 (1:100 vol/vol, p<0.05) production than adult monocytes (1:100, p<0.05). At D7, while BCG-trained adult monocytes, as previously reported, demonstrated enhanced LPS-induced TNF production, BCG-trained newborn monocytes demonstrated tolerization, as evidenced by significantly diminished subsequent LPS-induced TNF (RPMI vs. BCG 1:10, p <0.01), IL-10 and CCL5 production (p<0.05). With the exception of IL-1RA production by newborn monocytes, BCG-induced monocyte production of D1 cytokines/chemokines was inversely correlated with D7 LPS-induced TNF in both age groups (p<0.0001). Compared to BCG-trained adult monocytes, newborn monocytes demonstrated markedly impaired BCG-induced production of lactate, a metabolite implicated in immune training in adults.ConclusionsBCG-induced human monocyte primary- and memory-innate cytokine responses were age-dependent and accompanied by distinct immunometabolic shifts that impact both glycolysis and training. Our results suggest that immune ontogeny may shape innate responses to live attenuated vaccines, suggesting age-specific approaches to leverage innate training for broad protection against infection.

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‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material

Crystals ◽

10.3390/cryst10040297 ◽

2020 ◽

Vol 10 (4) ◽

pp. 297 ◽

Cited By ~ 1

Author(s):

Aleksandra Drozd-Rzoska

Keyword(s):

Relaxation Time ◽

Nematic Phase ◽

Liquid Crystalline ◽

Strong Electric Field ◽

Low Frequency ◽

Ionic Species ◽

Crystalline Material ◽

Isotropic Liquid ◽

The Impact ◽

Liquid Crystalline Material

Results of dielectric studies in the nematic and isotropic liquid phases of pentylcyanobiphenyl (5CB), a model rod-like liquid crystalline material, are shown. They are based on the discussion of the evolution of dielectric constant ( ε ), its changes under the strong electric field (nonlinear dielectric effect, NDE), and finally, the primary relaxation time. It is shown that changes in ε T and NDE are entirely dominated by the impact of pretransitional fluctuations (pre-nematic and pre-isotropic, respectively) which are associated with the weakly discontinuous character of the isotropic–nematic phase transition. This influence also extends for the low-frequency, ionic species dominated, region. Notable, that the derivative-based and distortions sensitive analysis revealed the tricritical nature of the I-N transition. Although the glass transition in 5CB occurs in the deeply supercooled state at T g ≈ − 68 ° C , the dynamics (changes of the primary relaxation time) follow a previtreous pattern both in the isotropic and in the nematic phase. Finally, the discussion of the ’molecular’ vs. ‘quasi-critical’ characterizations of the isotropic and nematic phases is presented. It shows the evident prevalence of the ‘quasi-critical-picture’, which offers the consistent temperature parameterization in the total tested temperature range.

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Effect of General Impact of Weak Low Frequency Vortex Magnetic Field on the System of Natural Antitumor Resistance of the Body

Medical Radiology and radiation safety ◽

10.12737/1024-6177-2019-64-6-44-50 ◽

2019 ◽

Vol 64 (6) ◽

pp. 44-50

Author(s):

Yu. Rybakov ◽

V. Gukasov ◽

Yu. Kozlov

Keyword(s):

Breast Cancer ◽

Magnetic Field ◽

Functional Activity ◽

Low Frequency ◽

The Body ◽

General Effect ◽

Healthy Donors ◽

The Impact ◽

Observation Period

Purpose: Experimental study of the antitumor mechanism of increasing the functional activity of phagocytes with a general effect on the body of a weak low-frequency vortex magnetic field (VMP). Material and methods: The functional activity of phagocytes was assessed upon activation by the intensity of chemiluminescence (CHL) on a Biolumat instrument (model LB 9500, by Berthold, Germany). Samples for in vitro and in vivo experiments were prepared according to generally accepted protocols. The impact of the VMP (Vmax = 3.0 mTl, f = 100 Hz) was performed using a Magnitoturbotron magnetotherapeutic installation (developed by NPF Az). Results: It was found in vitro experiments that the exposure of a suspension of VMP cells stimulated an increase in CHL by 58 % relative to the control, while the main contribution to the intensity of the signal of the CHL was made by neutrophils. In the study of the blood CHL of mice with subcutaneously inoculated melanoma B-16, it was established that the value of the specific CHL in the experiment with VFM by the end of the observation period (day 17) increased sharply (3 times) relative to the beginning of the observation and to the control at the same observation period was 3.3 times more. Experiments with whole blood of healthy donors and patients with breast cancer showed that the CHL curves over time were biphasic in nature and had two maxima, but the phase ratio was different. At donors, the main luminescence developed by the 100th minute, and a maximum of 30–40 min was mild. In patients with breast cancer, the first maximum at 30–40 min was the main, the second maximum was weak and came later than that of donors. Experiments with the effects of VMP on the organism of healthy and patients with breast cancer of people showed an increase in the functional activity of neutrophils as a result of exposure to VMP, but in patients with breast cancer, the level of CHL was significantly (3 times) higher than of healthy donors. Based on the research, it was concluded that exposure to the VMP is able to form a priming neutrophil. Сonclusion: It is shown that the overall effect of weak low-frequency VFM increases the level of nonspecific resistance of the organism to the tumor process, which expands the possibilities of rehabilitation of patients, allows expanding the compensatory capabilities of the body and reduce the risk of disease.

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Reactive oxygen in skeletal muscle. I. Intracellular oxidant kinetics and fatigue in vitro

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.5.1797 ◽

1992 ◽

Vol 73 (5) ◽

pp. 1797-1804 ◽

Cited By ~ 308

Author(s):

M. B. Reid ◽

K. E. Haack ◽

K. M. Franchek ◽

P. A. Valberg ◽

L. Kobzik ◽

...

Keyword(s):

Superoxide Dismutase ◽

High Frequency ◽

Low Frequency ◽

Reactive Oxygen ◽

Muscular Contraction ◽

Fiber Bundles ◽

Reactive Oxygen Intermediates ◽

Oxygen Intermediates ◽

Low Frequency Fatigue

We hypothesized that muscle fiber bundles produce reactive oxygen intermediates and that reactive oxidant species contribute to muscular fatigue in vitro. Fiber bundles from rat diaphragm were mounted in chambers containing Krebs-Ringer solution. In studies of intracellular oxidant kinetics, bundles were loaded with 2′,7′-dichlorofluorescin, a fluorochrome that emits at 520 nm when oxidized; emissions were quantified using a fluorescence microscope. Emissions from unstimulated muscles increased over time (P < 0.001). Accumulation of fluorescence was slowed by addition of catalase (P < 0.001) or superoxide dismutase (P < 0.001) and was accelerated by repetitive muscular contraction (P < 0.05). To determine effects of reactive oxygen intermediates on fatigue, curarized bundles were stimulated to contract isometrically; force was measured. Catalase, superoxide dismutase, and dimethyl sulfoxide were screened for effects on low- and high-frequency fatigue. Antioxidants inhibited low-frequency fatigue [after 5 min of repetitive contractions, force at 30 Hz was 20% greater than control (P < 0.015)] and increased the variability of fatigue at 30 Hz (P < 0.03). Antioxidants did not alter high-frequency (200-Hz) fatigue. We conclude that 1) diaphragm fiber bundles produce reactive oxygen intermediates, including O2-. and H2O2; 2) muscular contraction increases intracellular oxidant levels; and 3) reactive oxygen intermediates promote low-frequency fatigue in this preparation.

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Lengthening-contractions in isolated myocardium impact force development and worsen cardiac contractile function in the mdx mouse model of muscular dystrophy

Journal of Applied Physiology ◽

10.1152/japplphysiol.00253.2010 ◽

2011 ◽

Vol 110 (2) ◽

pp. 512-519 ◽

Cited By ~ 5

Author(s):

Ying Xu ◽

Dawn A. Delfín ◽

Jill A. Rafael-Fortney ◽

Paul M. L. Janssen

Keyword(s):

Contractile Function ◽

Wild Type Mouse ◽

Mdx Mouse ◽

Mdx Mice ◽

Wild Type ◽

Cardiac Contractile Function ◽

Lengthening Contractions ◽

Peak Tension ◽

The Impact

Lengthening-contractions exert eccentric stress on myofibers in normal myocardium. In congestive heart failure caused by a variety of diseases, the impact of lengthening-contractions of myocardium likely becomes more prevalent and severe. The present study introduces a method to investigate the role of stretching imposed by repetitive lengthening-contractions in myocardium under near-physiological conditions. By exerting various stretch-release ramps while the muscle is contracting, consecutive lengthening-contractions and their potential detrimental effect on cardiac function can be studied. We tested our model and hypothesis in age-matched (young and adult) mdx and wild-type mouse right ventricular trabeculae. These linear and ultrathin muscles possess all major cardiac cell types, and their contractile behavior very closely mimics that of the whole myocardium. In the first group of experiments, 10 lengthening-contractions at various magnitudes of stretch were performed in trabeculae from 10-wk-old mdx and wild-type mice. In the second group, 100 lengthening-contractions at various magnitudes were conducted in trabeculae from 10- and 20-wk-old mice. The peak isometric active developed tension (Fdev, in mN/mm2) and kinetic parameters time to peak tension (TTP, in ms) and time from peak tension to half-relaxation (RT50, in ms) were measured. Our results indicate lengthening-contractions significantly impact contractile behavior, and that dystrophin-deficient myocardium in mdx mice is significantly more susceptible to these damaging lengthening-contractions. The results indicate that lengthening-contractions in intact myocardium can be used in vitro to study this emerging contributor to cardiomyopathy.

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Cardiomyocyte-specific overexpression of an active form of Rac predisposes the heart to increased myocardial stunning and ischemia-reperfusion injury

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00367.2012 ◽

2013 ◽

Vol 304 (2) ◽

pp. H294-H302 ◽

Cited By ~ 13

Author(s):

M. A. Hassan Talukder ◽

Mohammad T. Elnakish ◽

Fuchun Yang ◽

Yoshinori Nishijima ◽

Mazin A. Alhaj ◽

...

Keyword(s):

Nadph Oxidase ◽

Ischemia Reperfusion Injury ◽

Contractile Function ◽

Ischemia Reperfusion ◽

Active Form ◽

Mutant Form ◽

Cardiac Contractile Function ◽

The Impact

The GTP-binding protein Rac regulates diverse cellular functions including activation of NADPH oxidase, a major source of superoxide production (O2·−). Rac1-mediated NADPH oxidase activation is increased after myocardial infarction (MI) and heart failure both in animals and humans; however, the impact of increased myocardial Rac on impending ischemia-reperfusion (I/R) is unknown. A novel transgenic mouse model with cardiac-specific overexpression of constitutively active mutant form of Zea maize Rac D (ZmRacD) gene has been reported with increased myocardial Rac-GTPase activity and O2·− generation. The goal of the present study was to determine signaling pathways related to increased myocardial ZmRacD and to what extent hearts with increased ZmRacD proteins are susceptible to I/R injury. The effect of myocardial I/R was examined in young adult wild-type (WT) and ZmRacD transgenic (TG) mice. In vitro reversible myocardial I/R for postischemic cardiac function and in vivo regional myocardial I/R for MI were performed. Following 20-min global ischemia and 45-min reperfusion, postischemic cardiac contractile function and heart rate were significantly reduced in TG hearts compared with WT hearts. Importantly, acute regional myocardial I/R (30-min ischemia and 24-h reperfusion) caused significantly larger MI in TG mice compared with WT mice. Western blot analysis of cardiac homogenates revealed that increased myocardial ZmRacD gene expression is associated with concomitant increased levels of NADPH oxidase subunit gp91phox, O2·−, and P21-activated kinase. Thus these findings provide direct evidence that increased levels of active myocardial Rac renders the heart susceptible to increased postischemic contractile dysfunction and MI following acute I/R.

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