Frontiers in Physiology最新文献

Introduction: Chronic injury to the rectus femoris muscle induces and exacerbates the progression of knee osteoarthritis (KOA). However, the lesion characteristics of the rectus femoris muscle in KOA at different stages have not been fully characterized. The aim of this study was to analyze the pattern of lesion characteristics of the rectus femoris muscle at different stages of KOA and to investigate the mechanism by which ultrasound-guided acupotomy operations can prevent and control KOA.

Methods: Early, middle, and late-stage rabbit KOA models were constructed using the modified Videman method. Ultrasonography was used to record the elastic modulus and cross-sectional area of the rectus femoris muscle, and morphology was used to observe the ultramicroscopic changes in the rectus femoris muscle and assess the degree of fibrosis. Additionally, ultrasound-guided acupotomy operations were performed on the rabbit model of late-stage KOA, and alterations in the key molecular markers of rectus femoris fibrosis were determined using Western Blot and qPCR methods.

Results: As the disease progressed, the elastic modulus of the rectus femoris muscle in KOA rabbits gradually increased, the cross-sectional area gradually decreased, and the degree of fibrosis increased. In contrast, the degree of fibrosis in the rectus femoris muscle improved after ultrasound-guided acupotomy intervention.

Conclusion: These findings highlight the gradual increase in the modulus of elasticity, the gradual decrease in cross-sectional area, and the increased fibrosis of the rectus femoris muscle in KOA rabbits as the disease progressed. Ultrasoundguided acupotomy operations have been shown to have a protective effect on KOA cartilage and to delay the progression of KOA by ameliorating pathological changes in the rectus femoris muscle. The mechanism may involve reducing chronic injury to the rectus femoris muscle and protecting joint homeostasis by attenuating the degree of rectus femoris fibrosis.

Background: Previous studies have shown that athletes accustomed to higher chronic workloads are less susceptible to injury than those exposed to lower chronic workloads. However, few studies have evaluated whether previous injury influences them. Therefore, this study investigated the impact of previous injuries on subsequent training loads, physical fitness, and injury rates in female youth basketball players.

Methods: Training load, physical fitness, and injuries of 18 young female basketball players (age 16.8 ± 1.4 years) were monitored. Previous injury status was clustered using the K-means clustering algorithm to separate players into high-risk and low-risk groups. Linear mixed models were used to analyze the effects of previous injury status on subsequent training load and physical fitness. Meanwhile, the differences between the players' injury groups were analyzed.

Results: Previous injury status can significantly impact a player's subsequent training loads, including acute loads, chronic loads, skill-based training loads, training monotony, and training strain (all p < 0.05). The two groups had no significant differences in physical fitness (all p > 0.05). Furthermore, the incidence of non-contact injuries was significantly higher in the high-risk group than low-risk group, which would result in more training time lost (all p < 0.05).

Conclusion: This study identified the impact of previous injury status on subsequent training load, physical fitness, and injuries in youth female basketball players. These findings provide valuable insight for coaches to optimize training loads according to previous injury status, aiming to minimize the likelihood of subsequent injuries.

The discovery of nitric oxide (NO) and the role of endothelial cells (ECs) in its production has revolutionized medicine. NO can be produced by isoforms of NO synthases (NOS), including the neuronal (nNOS), inducible (iNOS), and endothelial isoforms (eNOS), and via the non-classical nitrate-nitrite-NO pathway. In particular, endothelium-derived NO, produced by eNOS, is essential for cardiovascular health. Endothelium-derived NO activates soluble guanylate cyclase (sGC) in vascular smooth muscle cells (VSMCs), elevating cyclic GMP (cGMP), causing vasodilation. Over the past four decades, the importance of this pathway in cardiovascular health has fueled the search for strategies to enhance NO bioavailability and/or preserve the outcomes of NO's actions. Currently approved approaches operate in three directions: 1) providing exogenous NO, 2) promoting sGC activity, and 3) preventing degradation of cGMP by inhibiting phosphodiesterase 5 activity. Despite clear benefits, these approaches face challenges such as the development of nitrate tolerance and endothelial dysfunction. This highlights the need for sustainable options that promote endogenous NO production. This review will focus on strategies to promote endogenous NO production. A detailed review of the mechanisms regulating eNOS activity will be first provided, followed by a review of strategies to promote endogenous NO production based on the levels of available preclinical and clinical evidence, and perspectives on future possibilities.

Introduction: Cardiotocography (CTG) is used to monitor and evaluate fetal health by recording the fetal heart rate (FHR) and uterine contractions (UC) over time. Among these, the detection of late deceleration (LD), the early marker of fetal mild hypoxemia, is important, and the temporal relationship between FHR and UC is an essential factor in deciphering it. However, there is a problem with UC signals generally tending to have poor signal quality due to defects in installation or obesity in pregnant women. Since obstetricians evaluate potential LD signals only from the FHR signal when the UC signal quality is poor, we hypothesized that LD could be detected by capturing the morphological features of the FHR signal using Artificial Intelligence (AI). Therefore, this study compares models using FHR only (FHR-only model) and FHR with UC (FHR + UC model) constructed using a Convolutional Neural Network (CNN) to examine whether LD could be detected using only the FHR signal.

Methods: The data used to construct the CNN model were obtained from the publicly available CTU-UHB database. We used 86 cases with LDs and 440 cases without LDs from the database, confirmed by expert obstetricians.

Results: The results showed high accuracy with an area under the curve (AUC) of 0.896 for the FHR-only model and 0.928 for the FHR + UC model. Furthermore, in a validation using 23 cases in which obstetricians judged that the UC signals were poor and the FHR signal had an LD-like morphology, the FHR-only model achieved an AUC of 0.867.

Conclusion: This indicates that using only the FHR signal as input to the CNN could detect LDs and potential LDs with high accuracy. These results are expected to improve fetal outcomes by promptly alerting obstetric healthcare providers to signs of nonreassuring fetal status, even when the UC signal quality is poor, and encouraging them to monitor closely and prepare for emergency delivery.

[This corrects the article DOI: 10.3389/fphys.2024.1407215.].

Background: In patients with chronic coronary syndromes (CCS), increased ventilation/carbon dioxide production ( $\dot{V}$ _E/ $\dot{V}$ CO₂) slope has been found to predict disease progression and mortality, similarly to patients with heart failure (HF); however, increased chemosensitivity, a well-established predictor for mortality in patients with HF, has rarely been assessed in patients with CCS.

Method: Patients with CCS, HF with reduced ejection fraction (EF < 50%), healthy controls (45+ years), and young healthy adults (<35 years) were recruited. For patients, a $\dot{V}$ _E/ $\dot{V}$ CO₂ slope ≥36 was an inclusion criterion. The Duffin rebreathing method was used to determine the resting end-expiratory partial pressure of carbon dioxide (P_ETCO₂), ventilatory recruitment threshold (VRT), and slope (sensitivity) during a hyperoxic (150 mmHg O₂) and hypoxic (50 mmHg O₂) rebreathing test to determine the central and peripheral chemosensitivity.

Results: In patients with CCS, HF, controls, and young healthy adults, median $\dot{V}$ _E/ $\dot{V}$ CO₂ slopes were 40.2, 41.3, 30.5, and 28.0, respectively. Both patient groups had similarly reduced hyperoxic VRT (at P_ETCO₂ 42.1 and 43.2 mmHg) compared to 46.0 and 48.8 mmHg in the control and young healthy adults. Neither hypoxic VRT nor hyper- or hypoxic slopes were significantly different in patients compared to controls. Both patient groups had lower resting P_ETCO₂ than controls, but only patients with HF had increased breathing frequency and rapid shallow breathing at rest.

Conclusion: In patients with HF and/or CCS and excess ventilation, central chemoreflex VRT was reduced independently of the presence of HF. Low VRTs were related to resting excess ventilation in patients with CCS or HF; however, rapid shallow breathing at peak exercise was present only in patients with HF.

Clinical trial registration number: NCT05057884.

Introduction: The periaqueductal gray (PAG) has been previously established to play a key role in producing the vital changes in respiration occurring in response to threat. However, it is not fully understood how PAG activation alters the ongoing respiratory output, nor it is understood which pathways mediate these effects, as several regions have been previously identified to influence respiratory activity.

Methods: We used optogenetic tools in conjunction with EMG recordings of inspiratory and expiratory musculature to determine how PAG activation on short (250 ms) and longer (10-15 s) timescales alters respiratory muscle activity. Through cFOS mapping, we also identified key downstream brain regions which were likely modulated by PAG activation including the preBötzinger Complex (preBötC) and the lateral parafacial area (pFL). We then stimulated PAG terminals in those regions to determine whether their activity can account for the observed effects of PAG stimulation.

Results: Directly stimulating the PAG resulted in prominent changes to all recorded muscle activities and reset the breathing rhythm in either a phase-independent or phase-dependent manner. In contrast, stimulating PAG terminals in either preBötC or pFL with long or shorter timescale stimuli could not completely replicate the effects of direct PAG stimulation and also did not produce any respiratory reset.

Conclusions: Our results show that the effects of PAG activity on respiration are not mediated solely by PAG inputs to either the preBötC or pFL and more likely involve integration across a larger network of brainstem areas.

Background: Recent studies that investigated the effects of systemic doxycycline as an adjuvant to scale and root planing (SRP) in the treatment of diabetic periodontitis have yielded controversial results. The aim of this meta-analysis is to evaluate the effect of systemic doxycycline as an adjunct to SRP against SRP alone for improving clinical outcomes of periodontitis in diabetic individuals.

Methods: A systematic literature search was performed using PubMed, Cochrane library, China National Knowledge Infrastructure (CNKI), and VIP Data from the beginning of the database until March 2024. For probing depth (PD), clinical attachment level (CAL), plaque index (PI), gingival index (GI), and bleeding on probing (BOP), mean difference (MD) and the 95% confidence interval (CI) were computed. Heterogeneity was assessed using the Q test and the I² statistic. Evaluation of publication bias was conducted using Egger's and Begg's tests.

Results: A total of 12 articles were included for meta-analysis. No statistically significant difference was indicated in the improvement of PD, CAL, PI and GI between a treatment group receiving SRP combined with short-term antimicrobial dose doxycycline and controls receiving SRP alone. However, short-term antimicrobial dose doxycycline plus SRP significantly reduced BOP by 8.14% (95%CI 2.23-14.05) at 3 months. Furthermore, after the adjunctive use of long-term sub-antimicrobial dose doxycycline, significant reductions in GI (MD: 0.72, 95% CI: 0.34-1.10) and BOP (MD: 12.8, 95% CI: 0.24-25.36) were observed at 3 months. The robustness of the results was further confirmed by sensitivity analysis, despite the truth that significant heterogeneity was found among the included studies.

Conclusion: Gingival inflammation in diabetic patients can be reduced more successfully by SRP combined with systemic doxycycline than by SRP alone, but this is insufficient in preventing periodontal tissue destruction.