Reduction In Pdi Research Articles

No effect of aerobic fitness on exercise-induced diaphragm fatigue in females.

We tested the hypothesis that the incidence and magnitude of diaphragm fatigue following high-intensity exercise would be lower in females with a high aerobic capacity (Hi-Fit) compared with healthy females with an average aerobic fitness (Avg-Fit). Participants were assigned to groups based on their peak O2 uptake (V̇o2peak) obtained during cycle exercise: Hi-Fit n = 9, V̇o2peak ≥ 56.1 ± 3.4 mL·kg-1·min-1 versus Avg-Fit n = 9, V̇o2peak ≤ 35.7 ± 4.9 mL·kg-1·min-1. On the second day, diaphragm fatigue was assessed before and after constant load exercise test to exhaustion. Magnetic stimulation of the phrenic nerve roots was used to nonvolitionally assess diaphragm fatigue by measurement of transdiaphragmatic twitch pressure (Pdi,tw). Both groups exercised at >90% of V̇o2peak for a similar duration (Hi-Fit: 546.1 ± 177.8 vs. Avg-Fit: 559.3 ± 175.0 s, P = 0.9). Diaphragm fatigue was defined as a ≥15% reduction in Pdi,tw, approximately two times greater than the coefficient of variation. The mean group average reduction in Pdi,tw following exercise in the Hi-Fit (17.5%) and Avg-Fit groups (12.2%) was not different between groups (P = 0.2). The Hi-Fit group performed exercise at a higher absolute work rate that elicited significantly greater ventilatory work and inspiratory muscle force output. The Hi-Fit group did not experience greater fatigue compared with the Avg-Fit group, which we attribute to a greater reliance on accessory respiratory muscle recruitment, to training-induced increases in the aerobic capacity of the diaphragm, or a combination of the two. In summary, aerobic fitness is not predictive of exercise-induced diaphragm fatigue in healthy females.NEW & NOTEWORTHY We hypothesized that females with a high aerobic capacity would be resistant to exercise-induced diaphragm fatigue relative to healthy but untrained females. We assessed the pressure generated by the diaphragm following exhaustive exercise by stimulating the phrenic nerves. The magnitude and incidence of fatigue were similar between groups. Despite having higher ventilatory demands during exercise highly trained females were resistant to greater diaphragm fatigue. Aerobic fitness is not predictive of exercise-induced diaphragm fatigue in females.

Cervical spinal cord hemisection impacts sigh and the respiratory reset in male rats.

Cervical spinal cord injury impacts ventilatory and non-ventilatory functions of the diaphragm muscle (DIAm) and contributes to clinical morbidity and mortality in the afflicted population. Periodically, integrated brainstem neural circuit activity drives the DIAm to generate a markedly augmented effort or sigh-which plays an important role in preventing atelectasis and thus maintaining lung function. Across species, the general pattern of DIAm efforts during a normal sigh is variable in amplitude and the extent of post-sigh "apnea" (i.e., the post-sigh inter-breath interval). This post-sigh inter-breath interval acts as a respiratory reset, following the interruption of regular respiratory rhythm by sigh. We examined the impact of upper cervical (C2 ) spinal cord hemisection (C2 SH) on the transdiaphragmatic pressure (Pdi ) generated during sighs and the post-sigh respiratory reset in rats. Sighs were identified in Pdi traces by their characteristic biphasic pattern. We found that C2 SH results in a reduction of Pdi during both eupnea and sighs, and a decrease in the immediate post-sigh breath interval. These results are consistent with partial removal of descending excitatory synaptic inputs to phrenic motor neurons that results from C2 SH. Following cervical spinal cord injury, a reduction in the amplitude of Pdi during sighs may compromise the maintenance of normal lung function.

Bioagent consortia assisted suppression in grey blight disease with enhanced leaf nutrients and biochemical properties of tea (Camellia sinensis)

Microbial bioagents and botanicals contrastingly different in modes of action, and despite being used over the years, their comparative efficacy are not yet fully explored with regard to management of grey blight disease caused by Pseudopestalotiopsis curvatispora Petch in tea plantation of Assam, India. Four microbial antagonists-based formulations and seven botanicals at 2.5–10% concentration were tesed against mycelial growth of grey blight pathogen through dual culture assay and poisoned food technique, respectively, under in vitro conditions. Resultantly, two botanicals viz., Pongamia pinnata L. and Xanthium strumarium L. and two microbial bioformulations viz., Biometa as Metarhizium anisopliae and Biogreen as Trichoderma viride -based consortium of microbial antagonists were evaluated, singly and in combination through field studies in a grey blight affected 12-year -old tea plantation (grey blight susceptible clone TV-23) established on acidic Inceptisol with regard to suppression in grey blight disease incidence (PDI), green tea yield, culturable soil microbial population, leaf nutrients composition, and biochemical properties of tea. The consortium of microbial antagonists (Biogreen + Biometa) registered 11.34% higher suppression in grey blight disease at 4% concentration over combination of P. pinnata + X. strumarium at 10% concentration, both sprayed 5 times at 30 days interval in 150- days period, besides single microbial antagonist (Biometa) being inferior to consortium of microbial antagonists (Biogreen). Such a reduction in PDI resulted in 22.9% higher yield of green tea leaves with consortium of bioagents over botanicals due to significant elevation in soil culturable microbial population, and leaf nutrient composition. These responses were eventually associated with an improvement in biochemical properties (Polyphenols, caffeines, and antioxidants acivity) of tea. Our study, hence, provided both, in vitro and field evidence in favor of multipronged benfits of consortium of microbial antagonists for an extended control of grey blight disease of tea, a reliable alternative to conventionally used chemical fungicides towards tea health care with enhanced quality parameters.

Sex differences in diaphragmatic fatigue: Effects of hypoxia during inspiratory loading.

Under normoxic conditions, both healthy female and male diaphragms fatigue at a similar degree when matched for absolute diaphragmatic work during inspiratory loading. We investigated whether similarities in diaphragm fatigability persist under acute hypoxic conditions. We found that, in acute hypoxia, fatigue of the diaphragm is greater in women compared to men, whereas the magnitude of fatigue in normoxia did not differ between sexes. When matched for maximal diaphragm strength, women and men had a similar pressor response to work-matched inspiratory loading, independent of oxygen availability. In normoxia, women and men display a comparable magnitude of diaphragmatic fatigue (DF) after work-matched inspiratory loading. Whether these sex similarities are maintained under acute hypoxic conditions is unknown. We investigated the influence of acute hypoxia during work-matched inspiratory pressure-threshold loading (PTL) on DF in healthy women (n=8) and men (n=8). Two 5min isocapnic PTL tasks targeting a transdiaphragmatic pressure (Pdi ) of 92cmH2 O in normoxia and hypoxia (8% O2 ) were performed on separate days (≥48h). DF was quantified by twitch Pdi (Pdi,tw ) via cervical magnetic stimulation post-PTL. Women and men had similar maximal Pdi (Pdi,max ; women: 171±16, men: 178±20cmH2 O) and relative target workload (women: 54±5%, men: 53±6% Pdi,max ). The absolute cumulative diaphragmatic work did not differ between sexes in normoxia (women: 12,653±1796cmH2 Os-1 , men: 13,717±1231cmH2 Os-1 ; P=0.202) or hypoxia (women: 11,624±1860cmH2 Os-1 , men: 12 722±1502cmH2 Os-1 ; P=0.189). In normoxia, the magnitude of reduction in Pdi,tw post-PTL was similar between sexes (women: -21.1±8.4%, men: -22.5±4.9 %; P=0.193); however, a higher degree of DF was observed in women compared to men following PTL in acute hypoxia (women: -27.6±7.7%, men: -23.4±9.6%, P=0.019). We conclude that the female diaphragm is more susceptible to fatigue after inspiratory loading under acute hypoxic conditions. This finding may be related to sex differences in diaphragm muscle metabolism, such as fibre type composition, contractile properties, substrate utilisation and blood perfusion.

Effective chemical protection against Maydis Leaf Blight of Maize incited by Helminthosporium maydis under the in-vitro and in-vivo condition

Maydis leaf blight, a serious devastating disease affecting maize crop throughout the country, is characterized by long, spindle-shaped elliptical and tan lesion which appears first on lower leaves caused by Helminthosporium maydis. In the present study, different fungicides were tested under in-vitro as well as in-vivo condition. The result revealed that among the fungicides used under in vitro at 50,100,150,200 and 250 ppm concentration, Propiconazole was effective against the pathogen followed by Mancozeb, Carbendazim, Chlorothalonil and COC over control respectively. While under field condition, One, two and three sprays of 4 fungicides along with seed treatment with SAAF @ 3gm/kg seed were evaluated and found that Propiconazole @ 0.1% showed a reduction in PDI (%) at all spray i.e. One (28.67%), two (31.00%) and three (34.75%) over control which showed PDI of 64.01%, 61.09% and 56.38% at all three sprays respectively. Based on antifungal efficiency, Chlorothalonil @ 0.1 % found less effective with 63.50%, 67.50% and 73.20% PDI at all three consecutive sprays.

Diaphragm fatigue and inspiratory muscle metaboreflex in men and women matched for absolute diaphragmatic work during pressure-threshold loading.

The female diaphragm fatigues at a slower rate compared to that of males, with blunted cardiovascular consequences (i.e. inspiratory muscle metaboreflex). It is unclear if these findings are a function of relative or absolute diaphragmatic work. We asked if sex differences in diaphragm fatigue and the inspiratory muscle metaboreflex persisted during inspiratory loading performed at equal absolute intensities. We found that matching men and women for absolute diaphragmatic work resulted in an equal degree of diaphragm fatigue, despite women performing significantly greater work relative to body mass. Metabolite-induced reflex influences in sympathetic outflow originating from the diaphragm are attenuated in women, with potential implications for blood flow distribution during exercise. In response to inspiratory pressure-threshold loading (PTL), women have greater inspiratory muscle endurance time, slower rate of diaphragm fatigue development, and a blunted pressor response compared to men. It is unclear if these differences are due to discrepancies in absolute diaphragm force output. We tested the hypothesis that following inspirations performed at equal absolute intensities, females would develop a similar level of diaphragm fatigue and an attenuated cardiovascular response relative to men. Healthy young men (n=8, age=24±3years) and women (n=8, age=23±3years) performed PTL whilst targeting a transdiaphragmatic pressure (Pdi ) of 92cmH2 O for 5min. Diaphragm fatigue was assessed via twitch Pdi (Pdi,tw ) using cervical magnetic stimulation. Heart rate (HR) and mean arterial blood pressure were monitored continuously. During PTL, the absolute amount of diaphragm work was not different between men (13,399±2019cmH2 Os) and women (12,986±1846cmH2 Os; P>0.05); however, women performed the PTL task at a higher relative di /Pdi,max . Following inspiratory PTL, the magnitude of reduction in Pdi,tw was similar between men (-27.1±7.2%) and women (-23.8±13.8%; P>0.05). There were significant increases in HR over time (P<0.05), but this did not differ on the basis of sex (P>0.05). Mean arterial blood pressure increased significantly over time in both men and women (P<0.05); however, the rate of change was higher in men (6.24±2.54mmHgmin-1 ) than in women (4.15±2.52mmHgmin-1 ) (P<0.05). We conclude that the female diaphragm is protected against severe fatigue when inspiratory work is excessive and as a result does not evoke overt sympathoexcitation.

Acute Impact of Disrupting BDNF/TrkB Signaling on Diaphragm Muscle Force Generation across Motor Behaviors

Brain‐derived neurotrophic factor (BDNF) binds with high affinity to tropomyosin‐related kinase receptor subtype B (TrkB), and plays an important role in neuromuscular junction (NMJ) function (regulating neuromuscular transmission and muscle innervation). We previously showed impaired neuromuscular transmission following acute inhibition of TrkB kinase activity in TrkBF616A mice harboring a point mutation that renders the kinase domain susceptible to inhibition by 1NMPP1 treatment. Neuromuscular transmission failure is expected to predominantly affect the ability of more fatigable motor units to generate force and thus primarily impair higher force motor behaviors. Accordingly, we hypothesized that acute administration of 1NMPP1 will impair the ability of the diaphragm muscle to accomplish higher force behaviors in adult, 6‐month old TrkBF616A mice. Transdiaphragmatic pressure (Pdi) measurements were conducted across a range of motor behaviors in lightly anesthetized mice during eupnea, exposure to hypoxia (10% O2)/hypercapnia (5% CO2), tracheal occlusion, spontaneous deep breaths (“sighs”) and during maximal activation elicited by bilateral phrenic nerve stimulation. Adult male and female TrkBF616A mice at 6 months were injected with 1NMPP1 or vehicle (DMSO) one hour prior to Pdi measurements. The Pdi generated during eupnea and hypoxia/hypercapnia was ~8 cm H20 compared to ~70 cm H20 during maximal stimulation. There was a significant reduction in Pdi during maximal force with bilateral phrenic nerve stimulation in the 1NMPP1 group compared to the vehicle control (p=0.01). There was no effect of 1NMPP1 on Pdi during eupnea, hypoxia/hypercapnia, tracheal occlusion, or sigh behaviors. The reduction in Pdi is generally similar to the impairment in neuromuscular transmission consistent with a predominant effect on motor units innervating fast‐twitch fatigable muscle fibers in the diaphragm muscle. Thus, impaired trophic BDNF/TrkB signaling can be expected to limit the range of motor behaviors accomplished by the diaphragm muscle and may be an important contributor to neuromuscular dysfunction.Support or Funding InformationThis study was supported by NIH grant R01 AG057052.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Sex differences in diaphragmatic fatigue: the cardiovascular response to inspiratory resistance.

Diaphragmatic fatigue (DF) elicits a sympathetically mediated metaboreflex resulting in increased heart rate, blood pressure and limb vascular resistance. Women may be more resistant to DF compared to men, and therefore it was hypothesised that women would experience an attenuated inspiratory muscle metaboreflex during inspiratory pressure-threshold loading (PTL) performed to task failure. At the time of PTL task failure, the severity of DF was not different between sexes; however, inspiratory muscle endurance time was significantly longer in women than in men. For a given cumulative diaphragmatic force output, the severity of DF was less in women than in men. Women exhibited a blunted cardiovascular response to inspiratory resistance (i.e. metaboreflex) that may have implications for exercise tolerance. Diaphragmatic fatigue (DF) elicits reflexive increases in sympathetic vasomotor outflow (i.e. metaboreflex). There is some evidence suggesting women may be more resistant to DF compared to men, and therefore may experience an attenuated inspiratory muscle metaboreflex. To this end, we sought to examine the cardiovascular response to inspiratory resistance in healthy young men (n=9, age=24±3years) and women (n=9, age=24±3years). Subjects performed isocapnic inspiratory pressure-threshold loading (PTL, 60% maximal inspiratory mouth pressure) to task failure. Diaphragmatic fatigue was assessed by measuring transdiaphragmatic twitch pressure (Pdi,tw ) using cervical magnetic stimulation. Heart rate (HR) and mean arterial pressure (MAP) were measured beat-by-beat throughout PTL via photoplethysmography, and low-frequency systolic pressure (LFSBP ; a surrogate for sympathetic vasomotor tone) calculated from arterial waveforms using power spectrum analysis. At PTL task failure, the degree of DF was similar between sexes (∼23% reduction in Pdi,tw ; P=0.33). However, time to task failure was significantly longer in women than in men (27±11vs. 16±11min, respectively; P=0.02). Women exhibited less of an increase in HR (13±8vs. 19±12bpm; P=0.02) and MAP (10±8vs. 14±9mmHg; P=0.01), and significantly lower LFSBP (23±11vs. 34±8mmHg2 ; P=0.04) during PTL compared to men. An attenuation of the inspiratory muscle metaboreflex may influence limb and respiratory muscle haemodynamics with implications for exercise performance.

Sex Differences in Diaphragmatic Fatigue

Inspiratory muscle fatigue (IMF) is associated with a sympathetically mediated metaboreflex, resulting in time-dependent sympathoexcitation, including increased heart rate, mean arterial pressure and limb vascular resistance that impairs tolerance to exercise. Women may be more resistant to IMF relative to men and therefore, may experience an attenuated inspiratory muscle metaboreflex. PURPOSE: To examine sex-based differences in a) the cardiovascular response to inspiratory pressure-threshold loading (PTL) and b) the effect of prior-induced IMF on subsequent exercise performance. METHODS: Healthy men (n = 9) and women (n = 9) completed a maximal incremental cycle test on day 1. On day 2, subjects performed PTL to task failure followed by a constant load submaximal time-to-exhaustion (TTE) exercise test (85% peak work rate). On day 3, subjects performed the same exercise test without prior-induced IMF. Diaphragmatic fatigue was assessed by measuring transdiaphragmatic twitch pressure (Pdi,tw) in response to cervical magnetic stimulation. Heart rate (HR) and mean arterial pressure (MAP) were measured beat-by-beat throughout PTL via photoplethysmography, and low-frequency systolic pressure (LFSBP, surrogate for sympathetic vasomotor tone) calculated from arterial waveforms using power spectrum analysis. RESULTS: At task failure of PTL, the severity of IMF was similar between sexes (W = 23 ± 6%, M = 24 ± 8% reduction in Pdi,tw, p = 0.33). However, time to task failure was significantly longer in women than men (27 ± 11 vs. 16 ± 11 min, p = 0.02) and consequently, women tended to produce greater cumulative diaphragmatic pressure (46,805 ± 16,723 vs. 32,288 ± 20,752 cmH O⋅s-1; p = 0.06). Furthermore, women exhibited less of an increase in HR (13 ± 8 vs. 19 ± 12 bpm, p = 0.01) and MAP (10 ± 8 vs. 14 ± 9 mmHg, p = 0.02) during PTL, and significantly lower LFSBP (27 ± 12 vs. 38 ± 7 mmHg2, p = 0.04) compared to men. Prior-induced IMF resulted in the premature termination of exercise that did not differ on the basis of sex (W = 15 ± 19%, M = 16 ± 19% decrease in TTE, p = 0.89). CONCLUSIONS: Inspiratory muscle endurance time is significantly longer in women than men. Fatiguing contractions of the diaphragm elicit a blunted cardiovascular response in women, whilst IMF contributes to exercise impairment independent of sex.

Compensatory effects following unilateral diaphragm paralysis

Injury to nerves innervating respiratory muscles such as the diaphragm muscle results in significant respiratory compromise. Electromyography (EMG) and transdiaphragmatic pressure (Pdi) measurements reflect diaphragm activation and force generation. Immediately after unilateral diaphragm denervation (DNV), ventilatory behaviors can be accomplished without impairment, but Pdi generated during higher force non-ventilatory behaviors is significantly decreased. We hypothesized that 1) the initial reduction in Pdi during higher force behaviors after DNV is ameliorated after 14 days, and 2) changes in Pdi over time after DNV are associated with concordant changes in contralateral diaphragm EMG activity and ventilatory parameters. In adult male rats, the reduced Pdi during occlusion (∼40% immediately after DNV) was ameliorated to ∼20% reduction after 14 days. Contralateral diaphragm EMG activity did not significantly change immediately or 14days after DNV compared to the pre-injury baseline for any motor behavior. Taken together, these results suggest that over time after DNV compensatory changes in inspiratory related muscle activation may partially restore the ability to generate Pdi during higher force behaviors.

Quadriceps and respiratory muscle fatigue following high-intensity cycling in COPD patients.

Exercise intolerance in COPD seems to combine abnormal ventilatory mechanics, impaired O2 transport and skeletal muscle dysfunction. However their relatie contribution and their influence on symptoms reported by patients remain to be clarified. In order to clarify the complex interaction between ventilatory and neuromuscular exercise limiting factors and symptoms, we evaluated respiratory muscles and quadriceps contractile fatigue, dynamic hyperinflation and symptoms induced by exhaustive high-intensity cycling in COPD patients. Fifteen gold II-III COPD patients (age = 67±6 yr; BMI = 26.6±4.2 kg.m-2) performed constant-load cycling test at 80% of their peak workload until exhaustion (9.3±2.4 min). Before exercise and at exhaustion, potentiated twitch quadriceps strength (Qtw), transdiaphragmatic (Pdi,tw) and gastric (Pga,tw) pressures were evoked by femoral nerve, cervical and thoracic magnetic stimulation, respectively. Changes in operational lung volumes during exercise were assessed via repetitive inspiratory capacity (IC) measurements. Dyspnoea and leg discomfort were measured on visual analog scale. At exhaustion, Qtw (-33±15%, >15% reduction observed in all patients but two) and Pdi,tw (-20±15%, >15% reduction in 6 patients) were significantly reduced (P<0.05) but not Pga,tw (-6±10%, >15% reduction in 3 patients). Percentage reduction in Qtw correlated with the percentage reduction in Pdi,tw (r=0.66; P<0.05). Percentage reductions in Pdi,tw and Pga,tw negatively correlated with the reduction in IC at exhaustion (r=-0.56 and r=-0.62, respectively; P<0.05). Neither dyspnea nor leg discomfort correlated with the amount of muscle fatigue. In conclusion, high-intensity exercise induces quadriceps, diaphragm and less frequently abdominal contractile fatigue in this group of COPD patients. In addition, the rise in end-expiratory lung volume and diaphragm flattening associated with dynamic hyperinflation in COPD might limit the development of abdominal and diaphragm muscle fatigue. This study underlines that both respiratory and quadriceps fatigue should be considered to understand the complex interplay of factors leading to exercise intolerance in COPD patients.

Oxidative carbonylation of glycerol to glycerol carbonate catalyzed by PdCl 2(phen)/KI

We present a direct and highly efficient approach for synthesizing glycerol carbonate, via the catalytic oxidative carbonylation of glycerol, using PdCl 2(phen) (phen = 1,10-phenanthroline) as catalyst with the aid of KI. The palladium catalyst loading as low as 0.25 mol% is sufficient for high conversion (92%) and selectivity (99%) at the reaction condition: 2.0 MPa CO, 1.0 MPa O 2, 140 °C, 2 h. The turnover frequency (TOF) reaches 184 h −1. Furthermore, using crude glycerol, we achieved 85% conversion of glycerol. We discuss in detail a plausible mechanism based on PdI 2(phen) as an intermediate. We propose that there is synergistic effect of I − and 1,10-phenanthroline on the performance of the Pd complex catalyst. Based on the cyclic voltammograms, the reduction of PdI 2(phen) occurred at a more positive potential than that of PdCl 2(phen). This may explain why the catalytic activity of PdI 2(phen) was more effective than that of PdCl 2(phen).

Sex differences in exercise-induced diaphragmatic fatigue in endurance-trained athletes

There is evidence that female athletes may be more susceptible to exercise-induced arterial hypoxemia and expiratory flow limitation and have greater increases in operational lung volumes during exercise relative to men. These pulmonary limitations may ultimately lead to greater levels of diaphragmatic fatigue in women. Accordingly, the purpose of this study was to determine whether there are sex differences in the prevalence and severity of exercise-induced diaphragmatic fatigue in 38 healthy endurance-trained men (n = 19; maximal aerobic capacity = 64.0 +/- 1.9 ml x kg(-1) x min(-1)) and women (n = 19; maximal aerobic capacity = 57.1 +/- 1.5 ml x kg(-1) x min(-1)). Transdiaphragmatic pressure (Pdi) was calculated as the difference between gastric and esophageal pressures. Inspiratory pressure-time products of the diaphragm and esophagus were calculated as the product of breathing frequency and the Pdi and esophageal pressure time integrals, respectively. Cervical magnetic stimulation was used to measure potentiated Pdi twitches (Pdi,tw) before and 10, 30, and 60 min after a constant-load cycling test performed at 90% of peak work rate until exhaustion. Diaphragm fatigue was considered present if there was a >or=15% reduction in Pdi,tw after exercise. Diaphragm fatigue occurred in 11 of 19 men (58%) and 8 of 19 women (42%). The percent drop in Pdi,tw at 10, 30, and 60 min after exercise in men (n = 11) was 30.6 +/- 2.3, 20.7 +/- 3.2, and 13.3 +/- 4.5%, respectively, whereas results in women (n = 8) were 21.0 +/- 2.1, 11.6 +/- 2.9, and 9.7 +/- 4.2%, respectively, with sex differences occurring at 10 and 30 min (P < 0.05). Men continued to have a reduced contribution of the diaphragm to total inspiratory force output (pressure-time product of the diaphragm/pressure-time product of the esophagus) during exercise, whereas diaphragmatic contribution in women changed very little over time. The findings from this study point to a female diaphragm that is more resistant to fatigue relative to their male counterparts.

Protein Disulfide Isomerase: A Critical Evaluation of Its Function in Disulfide Bond Formation

Disulfide bond formation is probably involved in the biogenesis of approximately one third of human proteins. A central player in this essential process is protein disulfide isomerase or PDI. PDI was the first protein-folding catalyst reported. However, despite more than four decades of study, we still do not understand much about its physiological mechanisms of action. This review examines the published literature with a critical eye. This review aims to (a) provide background on the chemistry of disulfide bond formation and rearrangement, including the concept of reduction potential, before examining the structure of PDI; (b) detail the thiol-disulfide exchange reactions that are catalyzed by PDI in vitro, including a critical examination of the assays used to determine them; (c) examine oxidation and reduction of PDI in vivo, including not only the role of ERo1 but also an extensive assessment of the role of glutathione, as well as other systems, such as peroxide, dehydroascorbate, and a discussion of vitamin K-based systems; (d) consider the in vivo reactions of PDI and the determination and implications of the redox state of PDI in vivo; and (e) discuss other human and yeast PDI-family members.

Effects of diaphragm activation on airway pressure generation during lower thoracic spinal cord stimulation

Lower thoracic spinal cord stimulation (SCS) results in the generation of large positive airway pressures. The potential effects of diaphragm co-activation during SCS were investigated in 10 anesthetized dogs. Diaphragm compound action potentials (CMAPs) were present during SCS at the T10 and T12 levels. In group 1, airway (Paw) and trans-diaphragmatic (Pdi) pressures were monitored during supramaximal SCS before and after phrenicotomy. In group 2, pressures were monitored before and after C2 section to evaluate the potential influence of supraspinal centers. Following phrenicotomy in group 1, the reduction in Pdi during SCS was associated with increases in Paw. In group 2, diaphragm CMAPs and active Pdi increased following C2 section, while Paw fell. Following phrenicotomy, Paw increased significantly. In intact animals therefore, changes in Paw during SCS are affected by the interaction between inhibitory and excitatory influences on diaphragm activation. We conclude that lower thoracic SCS results in substantial diaphragm co-activation and secondary reductions in airway pressure generation.

Induction of systemic resistance in faba bean (Vicia faba L.) to bean yellow mosaic potyvirus (BYMV) via seed bacterization with plant growth promoting rhizobacteria

In a greenhouse experiment, two plant growth promoting rhizobacteria „Pgpr“ strains (Pseudomonas fluorescens FB11 and a Rhizobium leguminosarum bv. viceae FBG05) isolated from roots of faba bean plants were tested singly and in combination as seed inoculants for induction of systemic resistance in faba bean against bean yellow mosaic potyvirus (BYMV). The results demonstrated that BYMV challenged plants emerged from Pseudomonas inoculated seeds not only showed a pronounced and significant reduction in percent disease incidence (PDI) but also a significant reduction in virus concentration (ELISA) in the challenged plants, compared to the nonbacterized, challenged plants. Rhizobium singly also showed a significant reduction in both Pdi and ELISA value, but the reduction was less pronounced than that resulting from Pseudomonas inoculation. Combined inoculation with Pseudomonas and Rhizobium showed no additional significant reduction in Pdi or ELISA value compared with Pseudomonas singly. Appreciable and significant increase in both salicylic acid level and peroxidase activity was observed in leaves of all Pgpr inoculated plants compared to other treatments. Since the Pgpr inoculants (Pseudomonas and Rhizobium) and the pathogen (BYMV) remained spatially separated, it can be concluded that the tested Pseudomonas or Rhizobium strains induced systemic resistance in faba bean against BYMV.

Effects of fatigue, fiber length, and aminophylline on human diaphragm contractility.

The clinical relevance of methylxanthines as therapeutic agents for improving diaphragmatic contractility is controversial. In a double-blind, placebo-controlled trial, we investigated the effect of aminophylline on the contractility of fresh and fatigued human diaphragm at different lung volumes, and therefore as a function of fiber length. The diaphragmatic contractility of normal subjects was assessed by measurements of transdiaphragmatic pressure changes (Pdi,T) in response to single, bilateral, supramaximal phrenic-nerve shocks during relaxation from total lung capacity (TLC) to functional residual capacity (FRC). Fatigue was induced by resistive breathing. Therapeutic levels of theophylline were reached in all subjects. Under fresh (i.e., nonfatigue) conditions, aminophylline significantly increased Pdi,T at lung volumes above 75% of the inspiratory capacity (IC). Fatigue in the absence of aminophylline caused a disproportionately greater reduction of Pdi,T at high than at low lung volume (J. Appl. Physiol. 1992; 72:1064), which was rapidly reversible with rest. With aminophylline, the disproportionate decrease in diaphragmatic contractility at short fiber lengths was not observed. Aminophylline potentiates diaphragmatic contractility to a proportionately greater extent at short than at long fiber lengths, under both fresh and fatigued conditions. We explain these findings by known effects of muscle shortening, fatigue, and methylxanthines on excitation-contraction coupling mechanisms.

A new method for the preparation of highly dispersed metal/carbon catalyst—Pd/C catalyst and its properties

Highly dispersed Palladium/Carbon catalyst was prepared by the reduction of PdI 2 which was precipitated on the surface of activated carbon. The essential steps are: (I) the functionalization of the surface of the carbon with preadsorption of I −; (II) the precipitation of Pd 2+ on the carbon surface; (III) the reduction of PdI 2 on the carbon surface. The effects of preadsorption of different halogen ions and the reduction of temperature on Pd particle size and the crystal structure were studied by transmission electron microscopy (TEM) and selected area diffraction (SAD) methods. As a comparison, carbon oxidized with HNO 3 was also used as support. The effects on particle size and crystal structure were also studied with TEM and SAD. The adsorption characteristics of Pd 2+ and halogen ions on the carbon were measured by an argentimetry method. The results of the electrocatalytic reduction of oxygen showed that the catalysts prepared with this new method were more active than those prepared with the carbon preoxidation method.

The preparation of a highly dispersed Pd + Ag/carbon electrocatalyst and its properties

A new method for the preparation of fairly dispersed Pd + Ag alloy catalysts on carbon is described. The method involves three steps: (1) the functionalization of the surface of activated carbon with I − preadsorption; (2) the coprecipitation of Pd 2+ and Ag + on the carbon surface; (3) the reduction of PdI 2 and AgI codeposits on the carbon surface. The majority of metal particles are in the size range 2–8 nm. The effects of different halogen ion preadsorption and different initial Pd:Ag ratios on Pd + Ag particle size distribution were studied by transmission electron microscopy. Pd + Ag particle crystal structure and its composition were studied by selected area diffraction and energy dispersive spectrometry analysis. The unique feature of this method is that the bimetallic alloys could be formed at room temperature. The results of the electrocatalytic reduction of oxygen on these catalysts showed that this new method can increase the catalytic activity of the catalysts, mainly as a result of a decrease in metal particle size.

Diaphragmatic Rest During Negative Pressure Ventilation by Pneumowrap: Assessment in Normal and COPD Patients

In the present study, we assessed the occurrence of respiratory muscle rest during long lasting INPV runs using a pneumowrap ventilator at different pressure levels. We measured two indices of diaphragmatic activity: transdiaphragmatic pressure and the electrical activity of the diaphragm. Five healthy volunteers and six COPD patients were studied during spontaneous breathing and during 30-minute runs of INPV at a pressure of -2, -15 and -30 cmH2O. Ventilation, rib cage and abdomen motion were measured by inductive plethysmography; Pdi was obtained as the difference between gastric and esophageal pressures; Edi was recorded with surface electrodes. About 10 minutes of INPV (adaptation phase) were needed to obtain stable values in all the variables recorded. Ventilation increased in both groups up to threefold by increasing the negative pressure applied, this being due to changes in tidal volume. Changes in Pga swings mainly accounted for the reduction in Pdi that became negative during the run at -30 cmH2O. In both groups, Edi, after adaptation, showed no change during INPV at -2 cmH2O but a progressive reduction from control, during INPV at -15 and -30 cmH2O. We conclude that INPV by a pneumowrap ventilator can induce partial respiratory muscle rest in normal subjects and COPD patients.