Changes in intracellular pH during repeated exercise

The rates of change in intracellular pH during repeated exercise sessions with rest periods was determined by 31 phosphorus-nuclear magnetic resonance spectroscopy (³¹P-MRS). Five long-distance runners and six healthy male subjects as controls performed a 2-min femoral flexion at 20 kg · m · min^–1 in a 2.1 T superconducting magnet with a 67-cm bore and repeated this exercise four times with 2-min rest periods intervening. In all cases during exercise the inorganic phosphate (P_i) peak split into two, the earlier increased rapidly (high-pH P_i) and the later (low-pH P_i) increased more slowly. The P_i peaks were separated by a fitting procedure using the least square mean method. The high-pH P_i area during exercise decreased as the number of repeated exercise periods increased, while the low-pH P_i area gradually increased. Although the total P_i area decreased exponentially during the recovery period, the high-pH P_i area decreased first and then the low-pH P_i area reduced gradually. The pH values were estimated from the chemical shift between the phosphocreatine peak and each split peak in the P_i. The high-pH in pooled data ranged from 6.6 to 7.0 during exercise and recovery, while the low pH decreased to 6.2 during exercise. As the number of exercise periods increased, each pH value gradually became less acidic, although there was a tendency to more acidity in the control subjects than in the long-distance runners. In conclusion, it was possible to obtain by non-invasive, continuous³¹P-MRS, a split pattern of P_i peaks during exercise and there were at least tow different intracellular pH values during exercise, suggesting that each P_i peak might be attributed to the types of muscle fibre recruited.     

Carbamylcholine-induced morphological changes and spatial dynamics of [Ca2+]c in Harderian glands of guinea pigs: calcium-dependent lipid secretion and contraction of myoepithelial cells

To determine whether lipid-secreting cells have cytosolic Ca²⁺ concentration ([Ca²⁺]_c)-related secretory mechanisms, morphological changes and intracellular calcium dynamics of Harderian glands of guinea pigs stimulated by secretagogs were studied by electron microspy and Fura-2/AM digital image analysis. Control glandular cells contained large lipid vacuoles that were bordered by multi-layered membranes. Rough-surfaced endoplasmic reticulum, mitochondria, and smooth-surfaced endoplasmic reticulum may be involved in lipid vacuole formation. Myoepithelial cells surrounded alveoli. After carbamylcholine (CCh, 10^–6, 10^–5, and 10^–3 M) stimulation, lipid materials within the membranous structures were frequently discharged by an exocytotic mechanism. Conspicuous deformation of glandular cells caused by vigorous contraction of myoepithelial cells was observed in isolated alveoli after 10^–6M CCh stimulation, whereas the deformaties of glandular tissues perfused via vessels were small even after 10^–3M CCh stimulation. Connective tissue between glandular alveoli inhibited unbridled myoepithelial-cell contraction. Fura-2/AM digital imaging analysis revealed that CCh stimulation caused an increase in [Ca²⁺]_c in isolated alveoli. The morphological reactions and changes in [Ca²⁺]_c were prevented by atropine. When extracellular calcium ions were absent, enhanced extrusion of lipid vacuoles, myoepithelial-cell contraction, and a rise in [Ca²⁺]_c after CCh stimulation were not observed. Nicotine and catecholamines had no effect on the secretion or on the dynamics of [Ca²⁺]_c. It can be concluded that acetylcholine elicits exocytosis in glandular cells and contraction of the myoepithelial cells of Harderian glands, accompanied by an increase in [Ca²⁺]_c. The dynamics of [Ca²⁺]_c of the gland alveoli are mostly dependent on extracellular Ca²⁺.     

Chemical probes for investigating protein liquid-liquid phase separation and aggregation

Protein liquid-liquid phase separation drives the dynamic assembly of membraneless organelles for fulfilling different physiological functions. Under diseased condition, protein may undergo liquid-to-solid condensation to form pathological amyloid aggregates closely associated with neurodegenerative diseases. Chemical probe serves as an important chemical tool not only for exploring the basic principle of the dynamic assembly of different protein condensates in vitro and in cell but also for clinical diagnosis and therapeutics of the related diseases. In this review, we first introduce chemical probes to image and regulate protein condensates. Then, we summarized three different categories of chemical probes including general amyloid dye, selective positron emission tomography tracer, and disaggregating binder, which feature distinct interaction pattern and activity upon binding to different pathological amyloid fibrillar aggregates. Next, we discuss the development of chemical probes for tracking protein amorphous aggregates in cells. Finally, we point out future direction in expanding the probes’ chemical space and applications.     

Early response of herbaceous vegetation to Rhododendron ponticum subsp. baeticum invasion in European Atlantic forests

Questions

Rhododendron ponticum subsp. baeticum is an invasive shrub of growing concern in continental Europe, but little is known about its impact on native plant communities. Here we ask: do environmental conditions differ between forest stands invaded by it and uninvaded stands? Do these differences correlate with R. ponticum's cover? Are these differences associated with differences in taxonomic and functional diversity of vascular plant species of the herb layer? Can these vegetation changes be explained by the sorting of certain life-history traits by R. ponticum-induced environmental changes?

Location

Several forests invaded by R. ponticum in the French Atlantic domain.

Methods

We recorded vegetation composition and a number of environmental variables in 400-m² plots that were established in 64 paired forest stands (32 invaded vs 32 uninvaded). We compiled traits from existing databases. We computed several metrics of taxonomic and functional diversity. We compared environmental variables and diversity metrics between invaded and uninvaded stands. We used correlation and regression analyses to relate them with R. ponticum's cover. We ran RLQ and fourth-corner analyses to explore the relationships between R. ponticum invasion, environmental variables, species traits, and vegetation composition.

Results

Independent of its abundance, R. ponticum invasion was associated with lower light arrival at the forest floor and increased litter thickness. Concomitantly, species richness and diversity and trait diversity were reduced. The major driver of species assemblages was soil pH, which strongly interacted with the invasion gradient. R. ponticum did not sort species according to traits associated with shade tolerance and thick-litter tolerance. However, tree and shrub saplings were more abundant in invaded than uninvaded stands, at the expense of graminoid and fern species.

Conclusions

As R. ponticum becomes the dominant shrub, it exerts new selection forces on life-history traits of extant species, mostly via reduced light availability, increased litter thickness, and physical competition, thereby reducing taxonomic and functional diversity of the herb layer, without impeding tree and shrub self-regeneration, at least in the short term.     

A trait-based approach to assess niche overlap and functional distinctiveness between non-indigenous and native species

Our understanding of the community assembly processes acting on non-indigenous species (NIS), as well as the relationship with native species is limited, especially in marine ecosystems. To overcome this knowledge gap we here develop a trait-based approach based on the functional distinctiveness metric to assess niche overlap between NIS and native species, using high-resolution data on benthic invertebrate communities in the Baltic Sea. Our results show that NIS retain a certain degree of similarity with native species, but display one or a few singular unique traits (e.g., bioturbation ability). Furthermore, we demonstrate that community assembly processes, including both environmental filtering and limiting similarity affect NIS establishment, but that their effects may be highly context dependent, as illustrated by pronounced spatial patterns in distinctiveness. Finally, our trait-based approach provides a generic framework applicable to other areas and organisms, to better understand and address biological invasions.     

Trade-offs and synergies between ecosystem productivity and stability in temperate grasslands

Aim

It is crucial to monitor how the productivity of grasslands varies with its temporal stability for management of these ecosystems. However, identifying the direction of the productivity–stability relationship remains challenging because ecological stability has multiple components that can display neutral, positive or negative covariations. Furthermore, evidence suggests that the direction of the productivity–stability relationship depends on the biotic interactions and abiotic conditions that underlie ecosystem productivity and stability. We decipher the relationships between grassland productivity and two components of its stability in four habitat types with contrasting environments and flora.

Location

France.

Time period

2000–2020.

Major taxa

Grassland plant species.

Methods

We used c. 20,000 vegetation plots spread across French permanent grasslands and remotely sensed vegetation indices to quantify grassland productivity and temporal stability. We decomposed stability into constancy (i.e., temporal invariability) and resistance (i.e., maximum deviation from average) and deciphered the direct and indirect effects of abiotic (namely growing season length and nitrogen input) and biotic (namely plant taxonomic diversity, trait diversity and community-weighted mean traits) factors on productivity–stability relationships using structural equation models.

Results

We found a positive relationship between productivity and constancy and a negative relationship between productivity and resistance in all habitats. Abiotic factors had stronger effects on productivity and stability compared with biotic factors. A longer growing season enhanced grassland productivity and constancy. Nitrogen input had positive and negative effects on grassland productivity and resistance, respectively. Trait values affected the constancy and resistance of grassland more than taxonomic and trait diversity, with effects varying from one habitat to another. Productivity was not related to any biotic factor.

Main conclusions

Our findings reveal how vital it is to consider both the multiple components of stability and the interaction between environment and biodiversity to gain an understanding of the relationships between productivity and stability in real-world ecosystems, which is a crucial step for sustainable grassland management.     

Self-assembly of molecular beacons through metal ion coordination for fluorescence imaging of miRNA in living cells

Fluorescence nanosensors based on functional nucleic acids have been explored as a powerful sensing platform for disease-relevant miRNAs. This work developed a new hybrid nanosensor (Zr-B) through coordination-driven self-assembly of Zr ions and beacons. The prepared nanosensor exhibited high loading efficiency of beacons and could achieve sensitive and specific detection for miRNAs. The hybrid nanosensor could transfer beacons into living cells efficiently and maintain high stability and biocompatibility in the biological environment, achieving effective miRNA fluorescence imaging in living cells. Therefore, the resultant nanosensor holds potential for applications in disease diagnostics.     

Use of 31P magnetisation transfer magnetic resonance spectroscopy to measure ATP changes after 670 nm transcranial photobiomodulation in older adults

Mitochondrial function declines with age, and many pathological processes in neurodegenerative diseases stem from this dysfunction when mitochondria fail to produce the necessary energy required. Photobiomodulation (PBM), long-wavelength light therapy, has been shown to rescue mitochondrial function in animal models and improve human health, but clinical uptake is limited due to uncertainty around efficacy and the mechanisms responsible. Using ³¹P magnetisation transfer magnetic resonance spectroscopy (MT-MRS) we quantify, for the first time, the effects of 670 nm PBM treatment on healthy ageing human brains. We find a significant increase in the rate of ATP synthase flux in the brain after PBM in a cohort of older adults. Our study provides initial evidence of PBM therapeutic efficacy for improving mitochondrial function and restoring ATP flux with age, but recognises that wider studies are now required to confirm any resultant cognitive benefits.     

Meta-analysis of iron metabolism markers levels of Parkinson’s disease patients determined by fluid and MRI measurements

BackgroundParkinson’ s disease (PD) is a progressive neurodegenerative disease featured neuropathologically by the loss of dopaminergic neurons of the substantia nigra (SN). Iron overload in the SN is mainly relative to the pathology and pathogenesis of PD. Postmortem samples of PD has indicated the increased levels of brain iron. However, there is no consensus on iron content through iron-sensitive magnetic resonance imaging (MRI) techniques and the alteration of iron and iron related metabolism markers levels in blood and cerebrospinal fluids (CSF) are still unclear based on the current studies. In this study, we performed a meta-analysis to explore the iron concentration and iron metabolism markers levels through iron-sensitive MRI quantification and body fluid.MethodsA comprehensive literature search was performed in PubMed, EMBASE and Cochrane Library databases for relevant published studies that analyzed iron load in the SN of PD patients using quantitative susceptibility mapping (QSM) or susceptibility weighting imaging (SWI), and iron metabolism markers, iron, ferritin, transferrin, total iron-binding capacity（TIBC）in CSF sample or serum/plasma sample (from Jan 2010 to Sep 2022 to filter these inaccurate researches attributed to unadvanced equipment, inaccurate analytical methods). Standardized mean differences (SMD) or mean differences (MD) and 95% confidence intervals (CI) with random or fixed effect model was used to estimate the results.ResultsForty-two articles fulfilled the inclusion criteria including 19 for QSM, 6 for SWI, and 17 for serum/plasma/CSF sample including 2874 PD patients and 2821 healthy controls (HCs). Our meta-analysis results founded a notable difference for QSM values increase (19.67, 95% CI=18.69–20.64) and for SWI measurements (−1.99, 95% CI= −3.52 to −0.46) in the SN in PD patients. However, the serum/plasma/CSF iron levels and serum/plasma ferritin, transferrin, total iron-binding capacity (TIBC) did not differ significantly between PD patients and HCs.ConclusionsOur meta-analysis showed the consistent increase in the SN in PD patients using QSM and SWI techniques of iron-sensitive MRI measures while no significant differences were observed in other iron metabolism markers levels.