Decrease In Pdi Research Articles

Comparative study of endophytic bacterial strains from non-host crops for enhancing plant growth and managing early blight in tomato.

Bacillus pseudomycoides, Paenibacillus polymyxa, and B. velezensis are potent bacterial endophytes, which typically exhibit host-specific interactions. However, comparative studies of these endophytes in vitro and in planta in non-host crops are lacking. Therefore, in this study, we evaluated the potential of endophytes B. pseudomycoides strain HP3d, P. polymyxa strain PGSS1, B. velezensis strain A6, and P42, isolated from various crop ecosystems in promoting plant growth and inducing systemic resistance against early blight disease in tomato. In vitro, endophytes exhibited 44.44-55.56% and 37.50-87.50% inhibition of Alternaria solani in dual culture and volatilome bioassay, respectively. In the glasshouse, individual and combined applications via seed treatment (ST), seedling dip (SD), and foliar spray (FS) significantly enhanced shoot growth (23.63-57.61%), root growth (43.27-118.23%), number of leaves (77.52-93.58%), number of shoots (33.42-45.28%) and root dry matter (42.17-43.86%), reducing early blight (PDI) by 70.95-76.12% compared to uninoculated control. Enzymatic activities, including such as polyphenol oxidase (30-40 fold), peroxidase (65.00-75.00 fold), superoxide dismutase (34.20-37.20 fold) and phenylalanine ammonia-lyase (44.44-45.56 fold) were elevated post-inoculation in endophytes treated tomato plants challenged with A. solani compared to control treated only with A. solani and declined after the fifth day. The total chlorophyll content declined from the 0th to the 10th day, but endophyte treated plants exhibited lesser reductions (2.03-2.09) than uninoculated control. Field trials confirmed the glasshouse findings, showing reduced early blight and improved growth parameters in tomato where the ST + SD + FS combination emerged as the most effective treatment for all endophytes showing 1.06-1.88 fold increase in fruit yield per plant and 28.92-32.52% decrease in PDI compared to untreated control. Thus, the study highlights the broad-spectrum potential of these strains in promoting plant growth and controlling early blight in tomato, demonstrating non-host specificity. These endophytes offer eco-friendly alternatives to chemical pesticides, supporting sustainable agriculture. Their success in field trials suggests the potential for commercialization and large-scale use across diverse crops and pave the way for further interdisciplinary research to optimize their application in integrated pest management strategies.

Impact of the tripartite interaction between rice, sheath blight and diverse crop-associated endophytes on phenotypic and biochemical responses in rice

Endophytes stimulate plant growth and inhibit phytopathogens. Most of the known endophytes are host-specific and only a few strains are effective for practical field use. Thus, this study focuses on the evaluation of endophytes viz., Bacillus pseudomycoides strain HP3d, Paenibacillus polymyxa strain PGSS1, B. velezensis strain A6 and P42 isolated from diverse crop ecosystems for their potential to promote plant growth and induce systemic resistance against sheath blight disease in rice. The endophytes were studied for plant growth promoting traits in vivo conditions and were found to exhibit ammonia (light to strong), siderophore (yellow zone on the CAS agar plate), indole-3-acetic acid (15.20–22.19 μg mL−1) production and phosphorus solubilization (1.2–1.5 cm). In the glasshouse, when applied individually and in combinations through various methods like seed treatment, seedling dip, and foliar spray these endophytes significantly reduced lesion size (2.06–2.37 fold) and ShB severity (2.60–2.58 fold), enhancing growth parameters viz., shoot (1.09–1.11 fold), root (1.02–1.20 fold), number of tillers (1.2–1.6 fold), shoot (80.58–82.64 %) and root (62.01–66.66 %) dry matter over untreated control. Consequently, enzyme activity viz., polyphenol oxidase (2.20–3.00 U−1min−1g−1), peroxidase (0.31–0.35 min−1g−1), superoxide dismutase (118.50–123.00 Ug−1 FW), and phenylalanine ammonia lyase (0.84–0.90 min⁻1g⁻1FW) was found to increase up to the fourth day after the pathogen challenge and subsequently decrease thereafter. Chlorophyll content post inoculation of ShB declined over time but endophyte treated plants exhibited lesser reductions over uninoculated control. Field trials corroborated the in vitro findings, demonstrating reduced ShB (1.71–1.88 fold decrease in PDI) and enhanced growth (1.1–1.2 fold increase in shoot length) over untreated controls. The combined application of seedling dip, seed treatment, and foliar spray proved to be the most optimum treatment. The findings highlight the potential of diverse crop-derived endophytes, emphasizing their non-host specificity and effectiveness as broad-spectrum bioagents in actual field conditions.

Study on the bacteriostasis of lemon essential oil and the application of lemon essential oil nanoemulsion on fresh-cut kiwifruit

Fresh-cut fruit has been popularized for use by consumers in recent years, but its shelf life is very short. Plant essential oils have received attention for their bioactive properties, such as antibacterial and antioxidant properties, but their volatile nature limited their application in foods. In this study, the bacteriostasis of lemon essential oil (LEO) was verified, and LEO nanoemulsion was prepared to preserve fresh-cut kiwifruit. Compared with those of gram-negative bacteria, the inhibition zone diameters of LEO against gram-positive bacteria were significantly greater, measuring 12.20 ± 0.67 mm (Staphylococcus aureus) and 14.23 ± 0.61 mm (Listeria monocytogenes), compared to 9.50 ± 1.08 mm (Escherichia coli). At a concentration of 50 mg/mL, LEO exhibited DPPH and ABTS radical scavenging rates of 84.88 and 83.01%, respectively, which were comparable to those of 10 mg/L vitamin C (VC). Konjac glucomannan, whey protein and LEO were used to prepare nanoemulsion. When 2.0% LEO was added, the nanoemulsion exhibited great stability, which resulted in a decrease in particle size to 220.80 nm, a decrease in PDI to 0.238, and an increase in zeta potential to-27.83 mV. The stability of the nanoemulsion with added LEO was superior to that of the nanoemulsion without LEO on the 15th day. Preservation tests on fresh-cut kiwifruit demonstrated that, on the 8th day, compared with no treatment, nanoemulsion containing 2.0% LEO reduced the weight loss rate from 3.20 to 1.16%, increased the firmness from 20.459 to 38.23, and decreased the decay rate from 80.69 to 41.74% compared to untreated kiwifruit. It also effectively maintained the original color of fresh-cut kiwifruit and had positive effects on the soluble solid content, titratable acid content, VC content, and total colony count. LEO has great bacteriostatic and antioxidant activity, and the use of LEO nanoemulsions on fresh-cut kiwifruit can effectively maintain various indicators of fresh kiwifruit after a 8-day storage period.

Voluntary activation of the diaphragm after inspiratory pressure threshold loading.

After a bout of isolated inspiratory work, such as inspiratory pressure threshold loading (IPTL), the human diaphragm can exhibit a reversible loss in contractile function, as evidenced by a decrease in transdiaphragmatic twitch pressure (PDI,TW ). Whether or not diaphragm fatigability after IPTL is affected by neural mechanisms, measured through voluntary activation of the diaphragm (D-VA) in addition to contractile mechanisms, is unknown. It is also unknown if changes in D-VA are similar between sexes given observed differences in diaphragm fatigability between males and females. We sought to determine whether D-VA decreases after IPTL and whether this was different between sexes. Healthy females (n=11) and males (n=10) completed an IPTL task with an inspired duty cycle of 0.7 and targeting an intensity of 60% maximal transdiaphragmatic pressure until task failure. PDI,TW and D-VA were measured using cervical magnetic stimulation of the phrenic nerves in combination with maximal inspiratory pressure maneuvers. At task failure, PDI,TW decreased to a lesser degree in females vs. males (87 ± 15 vs. 73 ± 12% baseline, respectively, p=0.016). D-VA decreased after IPTL but was not different between females and males (91 ± 8 vs. 88 ± 10% baseline, respectively, p=0.432). When all participants were pooled together, the decrease in PDI,TW correlated with both the total cumulative diaphragm pressure generation (R2 =0.43; p=0.021) and the time to task failure (TTF, R2 = 0.40; p = 0.30) whereas the decrease in D-VA correlated only with TTF (R2 =0.24; p=0.041). Our results suggest that neural mechanisms can contribute to diaphragm fatigability, and this contribution is similar between females and males following IPTL.

Diaphragm Voluntary Activation After Inspiratory Pressure Threshold Loading In Healthy Humans

Inspiratory pressure threshold loading (IPTL) elicits a reduction in diaphragm contractile function (transdiaphragmatic twitch pressure; PDI,TW). It is unknown if diaphragm fatigability after IPTL is also mediated by neural mechanisms (diaphragm voluntary activation; D-VA) or if it differs on the basis of sex. PURPOSE: We sought to determine if D-VA decreases after IPTL and whether this was different between sexes. METHODS: Healthy participants (11F; 10 M) performed IPTL to task failure with an inspired duty cycle of 0.7 at 60% PDI,MAX. Cervical magnetic stimulation of the phrenic nerves was used to assess PDI,TW and D-VA. The relationship between fatigability outcomes (PDI,TW and D-VA), time to task failure, and cumulative diaphragm work were tested to explore how each factor contributes to diaphragm fatigability. RESULTS: Main effects of time (p < 0.001) and sex (p = 0.030), along with an interaction effect (p = 0.007) were observed when examining the changes in PDI,TW after IPTL. Specifically, immediately following IPTL, the decrease in PDI,TW was greater in males compared to females (24 ± 17 vs. 13 ± 15%points; p = 0.016). D-VA was 91 ± 8%baseline in males and 88 ± 11%baseline in females immediately following IPTL. We observed main effects of time, (p < 0.001) but neither the effect of sex (p = 0.177) nor the interaction between sex and time (p = 0.304) were significant, suggesting that D-VA decreases after IPTL similarly in males and females. The decrease in PDI,TW correlated with both the total cumulative diaphragm work (R2 = 0.43; p = 0.021) and time to task failure (R2 = 0.40; p = 0.030), whereas the decrease in D-VA was significantly correlated with time to task failure (R2 = 0.24; p = 0.041) and not cumulative diaphragm work (R2 = 0.19; p = 0.079). CONCLUSION: Our results indicate that neural mechanisms contribute to diaphragm fatigability and this contribution is similar between females and males after IPTL. A decrease in contractile function can be partially explained by both the amount of work performed and the total time of the IPTL task. Decreases in D-VA appear to be influenced primarily by the total time spent performing the IPTL task rather than the amount of work performed. Moreover, these contributing factors appear to be independent of sex. Supported by the Natural Sciences and Engineering Research Council of Canada.

Maternal Blood Pressure, Cord Glucocorticoids, and Child Neurodevelopment at 2 Years of Age: A Birth Cohort Study.

Pregnancy hypertensive disorders have impaired neurodevelopment in offspring. We aimed to explore the association of normal range maternal blood pressure (BP) with child neurodevelopment, as well as the possible role of placental 11-beta-hydroxysteroid dehydrogenase type 2 (11β-HSD2) therein. Among 1,008 mother-child pairs recruited in Wuhan, China, in 2013-2015, we measured maternal third-trimester BP (systolic BP (SBP) and diastolic BP (DBP)) and cord glucocorticoids (cortisol and cortisone), a marker reflecting placental 11β-HSD2 activity. We evaluated child neurodevelopment using the Bayley Scales of Infant Development (BSID) with obtaining the Mental and Psychomotor Development Index (MDI and PDI). Multiple regression and mediation analysis were performed to estimate the effect. Each 5 mm Hg increase in maternal third-trimester SBP was associated with 1.54 points decrease in MDI (95% confidence interval (CI) = -2.60, -0.48) and 1.23 points decrease in PDI (95% CI = -2.14, -0.31); similar association was observed between DBP and BSID (adjusted β = -1.32; 95% CI = -2.53, -0.10 for MDI and -1.37; 95% CI = -2.42, -0.33 for PDI). Also, we found significant associations between cord cortisol/cortisone ratio and PDI (adjusted β = 2.95; 95% CI = 0.91, 4.99), as well as between maternal BP and cord cortisol/cortisone ratio (adjusted β = -0.03; 95% CI = -0.06, -0.01 for both SBP and DBP). Mediation analysis revealed that cord cortisol/cortisone ratio explained 6.29% of the association between SBP and PDI, and 6.85% between DBP and PDI. Increased maternal normal range BP may affect child neurodevelopment. Furthermore, placental 11β-HSD2 activity might be involved in the process.

Temporal characteristics of exercise-induced diaphragmatic fatigue.

There is evidence suggesting diaphragmatic fatigue (DF) occurs relatively early during high-intensity exercise; however, studies investigating the temporal characteristics of exercise-induced DF are limited by incongruent methodology. Eight healthy adult males (25 ± 5 yr) performed a maximal incremental exercise test on a cycle ergometer on day 1. A constant-load time-to-exhaustion (TTE) exercise test was conducted on day 2 at 60% delta between the calculated gas exchange threshold and peak work rate. Two additional constant-load exercise tests were performed at the same intensity on days 3 and 4 in a random order to either 50 or 75% TTE. DF was assessed on days 2, 3, and 4 by measuring transdiaphragmatic twitch pressure (Pdi,tw) in response to cervical magnetic stimulation. DF was present after 75 and 100% TTE (≥20% decrease in Pdi,tw). The magnitude of fatigue was 15.5 ± 5.7%, 23.6 ± 6.4%, and 35.0 ± 12.1% at 50, 75, and 100% TTE, respectively. Significant differences were found between 100 to 75 and 50% TTE (both P < 0.01), and 75 to 50% TTE ( P < 0.01). There was a significant relationship between the magnitude of fatigue and cumulative diaphragm force output ( r = 0.785; P < 0.001). Ventilation, the mechanical work of breathing (WOB), and pressure-time products were not different between trials ( P > 0.05). Our data indicate that exercise-induced DF presents a relatively late onset and is proportional to the cumulative WOB; thus the ability of the diaphragm to generate pressure progressively declines throughout exercise. NEW & NOTEWORTHY The notion that diaphragmatic fatigue (DF) occurs relatively early during exercise is equivocal. Our results indicate that DF occurs during high-intensity endurance exercise in healthy men and its magnitude is strongly related to the amount of pressure and work generated by respiratory muscles. Thus we conclude that the work of breathing is the major determinant of exercise-induced DF.

Antifungal Properties of Phytoextracts of Certain Medicinal Plants Against Leaf Spot Disease of Mulberry, Morus spp

The fungi toxicant use checks the pathogen, yet its use in the organic farming system is least permitted because of their eco-toxic properties. Hence, the use of plants for their anti-fungal properties which could be used against the pathogen in the organic farming system becomes an area of interest for the eco-friendly mode of disease management. Six commonly available medicinal plants were selected based on their wide application in the state and for their valuable use as ethano-medicines. Cold water extracts of the six plants were tested in vitro against three identified leaf spot pathogens, Cercospora moricola Cooke, Alternaria alternata and Cladosporium cladosporiodes and extracts of plants viz. Artemisia absanthemum, Allium sativa L, uphorbia ligularia Roxb, Zingiber officinale and Datura metel showed more than 85% conidial inhibition in vitro with a 94.56% in A. absanthemum and more than 50% decrease in leaf spot disease incidence and severity in field conditions except A. sativa L and E. ligularia Roxb.at 0.05% decrease in PDI. All the plant extracts screened showed more than 50% percent mycelial inhibition with respect to control (water). The highest mycelial inhibition of more than 70% was found in E. ligularia Roxb. Followed by Z. officinale in all the three pathogens. So these plants with anti-fungal properties could be utilized against these pathogens, at least to lessen the impact of these pathogens. Similar eco-friendly means of disease control has been appreciated by the present environment conscious generation. Thus exploring new plants for their anti-fungal activity would bring about more resource base for use in eco-friendly and sustainable mode of agriculture especially in organic farming.

413 Transcatheter management of failed melody valves after successful placement

rapid postoperative recovery. Subjects requiring postoperative ECMO were assigned a score of 7, the highest possible score, to reflect the most severe morbidity. RESULTS: 171 subjects met inclusion criteria, 25 died, 46 were excluded (27 Bayley III, 12 chromosomal abnormality, 6 hearing loss, 1 cerebralpalsy), and1was lost to follow-up.Theremaining99subjects were analyzed. Surgical procedures were: arterial switch (36), Norwood (26), repair of total anomalous pulmonary venous connection (16), and other (21). The distribution of clinical outcome scores among subjects is shown (Figure). Four subjects had postoperative ECMO.Clinicaloutcomescoreswerehighest in theNorwoodgroup (mean 4.1, SD 1.4) compared to the arterial switch group (1.9 1.6) (P 0.001), TAPVC group (1.6 2.0) (P 0.001), and other group (3.3 1.6, P NS). A mean decrease in PDI of 10.9 points (95% CI 4.9-16.9, P 0.0005) was observed among children who had a clinical outcome score 3, compared to those with a clinical outcome score 3. Time until lactate 2.0 mmol/L increased with increasing clinical outcome score (P 0.014) as did highest postoperative inotrope score (P 0.0001). CONCLUSION: Clinical outcome scores of 3 were associated with a significantly lower PDI at 18-24 months. The clinical outcome score was associated with time until normalization of lactate and highest inotropescore.This score iseasytocalculate,canbereadilyadoptedby clinical programs, and may be valuable as an endpoint when evaluating novel potential therapies for this high risk population. 413 TRANSCATHETER MANAGEMENT OF FAILED MELODY VALVES AFTER SUCCESSFUL PLACEMENT

Midazolam-Induced Muscle Dysfunction and Its Recovery in Fatigued Diaphragm in Dogs

Midazolam, widely used for sedation and anesthesia, decreases contractility in nonfatigued diaphragm; however, its effects on contractility in fatigued diaphragm that are implicated as a cause of respiratory failure have not been established. We therefore studied the effects of midazolam on diaphragm muscle function and recovery in fatigued diaphragm. Dogs were divided into three groups of eight each. In each group, diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20-Hz stimulation for 30 min. When fatigue was established, Group I received no study drug; Group II was infused with a sedative dose (0.1 mg x kg(-1) x h(-1)) of midazolam; and Group III was infused with an anesthetic dose (0.5 mg x kg(-1) x h(-1)) of midazolam. We assessed diaphragm muscle function (contractility and electrical activity) by transdiaphragmatic pressure (Pdi) and integrated electrical activity of the diaphragm (Edi). In the presence of fatigue, Pdi at low-frequency (20-Hz) stimulation decreased from baseline values (P < 0.05), Pdi at high-frequency (100-Hz) stimulation did not change, and Edi to each stimulus did not change. With an infusion of midazolam, in Groups II and III, Pdi at both stimuli and Edi at 100-Hz stimulation decreased from fatigued values (P < 0.05). The decrease in Pdi and Edi was more in Group III than in Group II (P < 0.05). At 60 min after the cessation of midazolam administration, in Group II, Pdi and Edi recovered from midazolam-induced values (P < 0.05) and returned to fatigued values. In Group III, Pdi and Edi did not change from midazolam-induced values. We conclude that midazolam causes, in a dose-related manner, diaphragm muscle dysfunction in fatigued canine diaphragm and that at a sedative dose, but not at an anesthetic dose, midazolam does not delay its recovery.

The Dose-Related Efficacy of Diltiazem for Enhancing Diaphragmatic Fatigability in Dogs

Nicardipine, a calcium channel blockade, enhances the production of diaphragmatic fatigue. We studied the dose-related effects of diltiazem, another calcium channel blockade, on diaphragmatic fatigability in dogs. Animals were divided into three groups of eight each. In each group, diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. During this fatigue-producing period, Group I received no study drug, Group II was infused with diltiazem 0.1 mg. kg(-1). h(-1), and Group III was infused with diltiazem 0.5 mg. kg(-1). h(-1). We assessed diaphragmatic contractility by transdiaphragmatic pressure (Pdi). After the fatigue-producing period, in Group I, Pdi at low-frequency (20-Hz) stimulation decreased from baseline values (P < 0.05), whereas there was no change in Pdi at high-frequency (100-Hz) stimulation. In Groups II and III, with an infusion of diltiazem, Pdi at both stimuli decreased from baseline values (P < 0.05). The decrease in Pdi to each stimulus was more in Group III than in Group II (P < 0.05). We conclude that diltiazem causes a dose-related augmentation of fatigability in the diaphragm of dogs. Diaphragmatic muscle fatigue is implicated as a cause of respiratory failure. Diltiazem, a calcium channel blockade, enhances diaphragmatic fatigability in dogs in a dose-related manner.

The dose-range effects of propofol on the contractility of fatigued diaphragm in dogs.

Diaphragmatic fatigue may contribute to the development of respiratory failure. We studied the dose-range effects of propofol on the contractility of fatigued diaphragm in dogs. Animals were divided into three groups of eight each. In each group, diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20-Hz stimulation for 30 min. Immediately after the end of a fatigue-producing period, Group 1 received no study drug; Group 2 was infused with small-dose propofol (0.1 mg/kg initial dose plus 1.5 mg x kg(-1) x h(-1) maintenance dose); Group 3 was infused with large-dose propofol (0.1 mg/kg initial dose plus 6.0 mg x kg(-1) x h(-1) maintenance dose). We assessed diaphragmatic contractility by transdiaphragmatic pressure (Pdi). After the fatigue-producing period, in each group, Pdi at low-frequency (20-Hz) stimulation decreased from baseline values (P < 0.05), whereas there was no change in Pdi at high-frequency (100-Hz) stimulation. In Groups 2 and 3, with an infusion of propofol, Pdi at 20-Hz stimulation decreased from fatigued values (P < 0.05). Compared with Group 1, Pdi at 20-Hz stimulation decreased from fatigued values (P < 0.05) during propofol administration in Groups 2 and 3. The decrease in Pdi was more in Group 3 than in Group 2 (P < 0.05). We conclude that propofol decreases the contractility of fatigued canine diaphragm in a dose-related fashion. Propofol is a widely used IV anesthetic for the induction and maintenance of general anesthesia and sedation. It decreases, in a dose-related fashion, the contractility of fatigued diaphragm in dogs.

Dose-response characteristics of midazolam for reducing diaphragmatic contractility.

A sedative dose of midazolam decreases contractility of the diaphragm, but no data are available concerning the relationship between dose and diaphragmatic contractility. We studied the dose-response characteristics of midazolam for reducing the diaphragmatic contractility in dogs. Animals were divided into three groups of eight each: Group 1 received no study drug, Group 2 was infused with a sedative dose of midazolam (0.1 mg/kg initial dose plus 0.1 mg x kg(-1) x h(-1) maintenance dose), and Group 3 was infused with an anesthetic dose of midazolam (0.1 mg/kg initial dose plus 0.5 mg x kg(-1) x h(-1) maintenance dose). We assessed the diaphragmatic contractility by transdiaphragmatic pressure (Pdi). With an infusion of midazolam in Groups 2 and 3, Pdi at low-frequency (20 Hz) and high-frequency (100 Hz) stimulation decreased from the baseline values (P < 0.05), and the integrated electrical activity of diaphragm (Edi) at 100-Hz stimulation decreased from the baseline values, whereas Edi at 20-Hz stimulation did not change. Compared with Group 1, Pdi and Edi for each stimulus decreased during midazolam infusion in Groups 2 and 3 (P < 0.05). The decrease in Pdi and Edi was more in Group 3 than in Group 2 (P < 0.05). We conclude that midazolam decreases, in a dose-dependent manner, contractility of the diaphragm in dogs.

Retracted: Midazolam versus propofol for reducing contractility of fatigued canine diaphragm

The effects of midazolam and propofol on the contractility of fatigued canine diaphragm were examined. Diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. After fatigue had been induced, group I (n=10) received no study drug, group II (n=10) was given a propofol infusion (0.1 mg kg(-1) loading dose plus 1.5 mg kg(-1) h(-1) maintenance dose) and group III (n=10) was given a midazolam infusion (0.1 mg kg(-1) loading dose plus 0.1 mg kg(-1) h(-1) maintenance dose). Diaphragmatic contractility was assessed by measuring transdiaphragmatic pressure (Pdi). After the fatigue-inducing period in each group, Pdi at low-frequency (20 Hz) stimulation was lower than the baseline values (P<0.05), whereas no change in Pdi at high-frequency (100 Hz) stimulation was observed. In group II, Pdi at 20 Hz stimulation was lower than fatigued values (P<0.05); Pdi at 100 Hz stimulation did not change. In group III, Pdi at both stimulation frequencies was lower than fatigued values (P<0.05). Compared with group I, Pdi at 20 Hz stimulation was lower than fatigued values (P<0.05) during administration of the study drug in groups II and III. The decrease in Pdi was greater in group III than in group II (P<0.05). In conclusion, midazolam compared with propofol is associated with an inhibitory effect on contractility in the fatigued canine diaphragm.

Propofol decreases diaphragmatic contractility in dogs.

Volatile anesthetics depress diaphragmatic muscle function; however, no data are available regarding the effect of propofol on diaphragmatic contractility. We therefore studied this effect in dogs. Pentobarbital-anesthetized animals were divided into three groups of 10 each. Group I received only maintenance fluid; Group II was infused with a subhypnotic dose of propofol (0.1-mg/kg initial dose plus 1.5-mg x kg(-1) x h(-1) maintenance dose); Group III was infused with an anesthetic dose of propofol (0.1-mg/kg initial dose plus 6.0-mg x kg(-1) x h(-1) maintenance dose). We assessed diaphragmatic contractility by transdiaphragmatic pressure (Pdi). With an infusion of propofol in Groups II and III, Pdi at low-frequency (20-Hz) stimulation decreased from the baseline values (P < 0.05), whereas Pdi at high-frequency (100-Hz) stimulation did not change. Compared with Group I, Pdi at 20-Hz stimulation decreased during propofol administration in Groups II and III (P < 0.05). The decrease in Pdi was more in Group III than in Group II (P < 0.05). We conclude that propofol is associated with a dose-related inhibitory effect on diaphragmatic contractility in dogs. Propofol is an effective IV anesthetic for the induction and maintenance of anesthesia. Subhypnotic and anesthetic doses of propofol decrease diaphragmatic contractility in dogs.

Central and peripheral components of diaphragmatic fatigue during inspiratory resistive load in cats.

The development of fatigue was investigated in the diaphragm of anaesthetized, tracheostomized, spontaneously breathing cats during restricted air flow. Ventilation, transdiaphragmatic pressure (Pdi), integrated electrical activity of diaphragm (Edi) and phrenic nerve (Eph) were measured simultaneously and expressed as a percentage of values at unloaded breathing. Inspiratory loads were 60, 70 and 80% of Pdi max. The Pdi max was measured by airway occlusion at functional residual capacity. The duration of loads was 40-60 min. The diaphragmatic fatigue developed only during heavy inspiratory loading (80% Pdi max). During the first 10 min of heavy load Pdi, Edi and Eph increased to 905 +/- 60%, 248 +/- 20% and 229 +/- 24%, respectively (P < 0.01), and then began to fall gradually. Ventilation declined to 39 +/- 3% after 60 min of heavy load (P < 0.01), resulting in acute hypercapnia and hypoxia. Initial fatigue appeared as a decrease in Pdi (to 781 +/- 63%) and parallel decline in Edi (to 233 +/- 21%) after 30 min of load (P < 0.05). Phrenic nerve activity did not change during this stage. These data suggest a peripheral basis of diaphragmatic fatigue, related to disorders in neuromuscular transmission. After 60 min of heavy load, Pdi fell to 675 +/- 49%, Edi declined to 209 +/- 28% and Eph decreased to 189 +/- 25%. We interpret the decrease in phrenic nerve activity as a weakening of central inspiratory drive and development of the central component of diaphragmatic fatigue in the last stage.

RETRACTED ARTICLE: Effects of nicardipine on diaphragmatic fatigue in the dog: The relationship between dosage and fatigability

We examined the dose-related effects of nicardipine on the diaphragmatic fatigability in 24 anesthetized, mechanically ventilated dogs. Animals were divided into three groups of eight each: the control group (group C), the nicardipine 3 μg·kg(-1) I.V. group (group N1) and the nicardipine 5 μg·kg(-1)·min(-1) I.V. group (group N2). Diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. In groups N1 and N2, nicardipine was continuoulsy infused intravenously during this fatigueproducing period. Diaphragmatic contractility was assessed by changes in transdiaphragmatic pressure (Pdi). After induction of diaphragmatic stimulation at low-frequency (20 Hz), Pdi decreased significantly in all groups compared with the prefatigue value (P<0.05), whereas no change was observed in Pdi at high-frequency (100 Hz) stimulation. The Pdi at 20 Hz stimulation was significantly lower in groups N1 and N2 compared with that in group C (P<0.05). The decrease in Pdi at 20 Hz stimulation was significantly larger in group N2 than in group N1 (P<0.05). The speed of recovery of Pdi at 20 Hz stimulation was dose dependent. The integrated diaphragmatic electric activity (Edi) in each group did not change at any frequency of stimulation throughout the study. Our results demonstrate that nicardipine causes a dose-dependent reduction of the contractility of the fatigued diaphragm.

Diaphragmatic failure during group B streptococcal sepsis in piglets: the role of thromboxane A2

Group B Streptococcus (GBS) causes an impairment of diaphragmatic pressure generation (Pdi) in 2-wk-old piglets, whereas 4-wk-old piglets are unaffected. In this study, we examined the effect on 4-wk-old piglets of a higher dose of GBS than previously utilized. We sought to determine whether an eicosanoid product of arachidonic acid metabolism accounted for the decrease in Pdi during GBS infusion and whether thromboxane A2 (TxA2) is the putative eicosanoid mediator of decreased Pdi during GBS infusion. Measuring Pdi during phrenic nerve stimulation, we studied four groups of anesthetized spontaneously breathing 4-wk-old piglets. Group 1 (GBS) was infused with live GBS, which caused a decrease in Pdi by 1 h at 20-, 30-, 50-, and 100-Hz stimulation frequencies. Group 2 [GBS + indomethacin (Indo)] was pretreated with Indo before GBS infusion. In the GBS + Indo group, Pdi did not decrease throughout 4 h of GBS infusion. Because Indo proved to be protective of Pdi during GBS infusion, we examined the role of TxA2, the only eicosanoid present at 1 h in the serum of GBS-infused piglets. Group 3 was infused with the TxA2 analogue U-46619 only for 1 h. Group 4 was treated with the TxA2-receptor antagonist SQ-29548 before and concomitant with GBS infusion for 1 h; the SQ-29548 was then discontinued, and GBS was continued for 1 h more. In the U-46619-infused group, Pdi decreased at 1 h, and in the SQ-29548-treated group, Pdi did not decrease during GBS infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of isoflurane on contractile properties of diaphragm.

Isoflurane has been shown to depress skeletal muscle force in vitro, but data are not available regarding the effects of isoflurane on diaphragmatic muscle function in vivo. To answer this question, 15 rats anesthetized with pentobarbital and mechanically ventilated were studied. They were divided into three groups of five animals each, according to the administered concentration of isoflurane. Diaphragmatic function was assessed by measuring the transdiaphragmatic pressure (Pdi) generated during bilateral supramaximal phrenic nerve stimulation at 0.5 Hz, 20 Hz, 50 Hz, and 100 Hz under quasi-isometric conditions. After a control measurement (C), isoflurane was administered at a constant concentration (0.5, 1, or 1.5 MAC) and Pdi measurements were repeated after 30 min of isoflurane exposure (T1) and 30 min after discontinuing isoflurane (T2). In the group breathing 1.5 MAC isoflurane, the time constant of diaphragmatic relaxation (tau) and integrated electrical activity of the diaphragm (Edi) were also assessed. The Pdi amplitude generated by single twitch (0.5 Hz) was unchanged at the three isoflurane concentrations. A significant increase in Pdi at 20 Hz was observed at T1, which returned to control after 30 min recovery (T2). No change in Pdi during 50 Hz stimulation was noted during 0.5 and 1 MAC isoflurane exposure, whereas it was reduced at T1 during 1.5 MAC. For 100 Hz stimulation, a significant decrease in Pdi was noted for all groups at T1, which returned toward control values at T2. Edi was markedly reduced for 50 and 100 Hz stimulation, but this reduction was also transient, since Edi returned toward control values at T2.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of fatiguing resistive loads on the level and pattern of respiratory activity in awake goats

The effect of respiratory muscle fatigue on inspiratroy muscle electrical activity (EMG), transdiaphragmatic pressure and ventilation during spontaneous breathing was examined in three awake goats. Studies were performed during progressive hypercapnia before and immediately after inspiratory muscle fatigue induced by flow resistive loading (IRL). IRL caused a decrease in the high-low ratio of the diaphragm and intercostal EMG and a decrease in Pdi during electrophrenic stimulation. After IRL, inspiratory time, the breathing duty cycle (inspiratory time/total breath cycle time), peak integrated activity of the diaphragm and external intercostal EMG per breath and per minute were all decreased at any given level of P CO 2 . Changes in the timing of respiratory motor activity and reduced muscle performance after IRL resulted in a decrease in transdiaphragmatic pressure and ventilation during hypercapnia. In conscious goats studied during spontaneous, chemically stimulated breathing, inspiratory muscle fatigue is associated with reductions in diaphragm and external intercostal muscle electrical activity and reductions in transdiaphragmatic pressure and ventilation.