Pflugers Archiv : European journal of physiology最新文献

The purpose was to investigate the changes in cytosolic Ca²⁺ and force output during post-tetanic potentiation (PTP) during pre-fatigue and during prolonged low-frequency force depression (PLFFD) following fatigue. Intact single myofibers from the flexor digitorum brevis of mice were electrically stimulated to record force (n = 8) and free cytosolic Ca²⁺ concentration ([Ca²⁺]_c) with FURA-2 (n = 6) at 32 °C. Initially, force and [Ca²⁺]_c were measured during brief (350 ms) trains of stimuli at 30, 50, 70, and 200 Hz at ~ 2 s intervals (Force-frequency protocol, FFP). Then, a conditioning stimulus (CS) of six 120 Hz stimuli, separated by ~ 3 s, was used to induce PTP, immediately followed by an FFP. Myofiber fatigue was produced by 150 Hz trains every 3 s until peak force decayed 70% of the initial. Thirty minutes after the fatigue, the CS was repeated to assess the effect of PTP on force and [Ca²⁺]_c during PLFFD. The CS in unfatigued myofibers induced PTP as the submaximal force was enhanced and accompanied by increased peak [Ca²⁺]_c with no change in myofilament Ca²⁺ sensitivity. After fatigue, PLFFD was due to lowered peak [Ca²⁺]_c. Inducing PTP during PLFFD enhanced submaximal force primarily through greater peak [Ca²⁺]_c, mitigating the submaximal force deficits. Despite the impaired force during PLFFD, myofibers remained sensitive to PTP, and this mitigated the submaximal force deficits through increased peak [Ca²⁺]_c without a change in myofilament Ca²⁺ sensitivity. Therefore, force adjustments of intact single myofibers due to activation history are principally accomplished by opposing adjustments in [Ca²⁺]_c.

The prevalence of panic disorder is two to four times higher in women compared to that in men, and hormonal changes during the menstrual cycle play a role in the occurrence of panic attacks. Here, we investigated the effect of the estrous cycle on the ventilatory and behavioral responses to CO₂ in mice. Female mice in proestrus, estrus, metestrus, or diestrus were exposed to 20% CO₂, and their escape behaviors, brain monoamines, and plasma levels of 17β-estradiol (E₂) and progesterone (P₄) were measured. Pulmonary ventilation (V̇_E), oxygen consumption (V̇O₂), and body core temperature (T_B) were also measured during normocapnia followed by CO₂. Females exposed to 20% CO₂ exhibited an escape behavior, but the estrous cycle did not affect this response. Females in all phases of the estrous cycle showed higher V̇_E and lower T_B during hypercapnia. In diestrus, there was an attenuation of CO₂-induced hyperventilation with no change in V̇O₂, whereas in estrus, this response was accompanied by a reduction in V̇O₂. Hypercapnia also increased the concentration of plasma P₄ and central DOPAC, the main dopamine metabolite, in all females. There was an estrous cycle effect on brainstem serotonin, with females in estrus showing a higher concentration than females in the metestrus and diestrus phases. Therefore, our data suggest that hypercapnia induces panic-related behaviors and ventilatory changes that lead to an increase in P₄ secretion in female mice, likely originating from the adrenals. The estrous cycle does not affect the behavioral response but interferes in the ventilatory and metabolic responses to CO₂ in mice.

Autosomal dominant polycystic kidney disease (ADPKD) is a debilitating disease characterized by renal cysts. It arises from mutations in proteins expressed in part in the primary cilia of renal epithelial cells. One of these, polycystin-2 (PC2), is an ion-conducting channel. To date, ion channels in the cilium have only been characterized in standard normosmolar external solutions, but the osmolality of the renal filtrate bathing the cilia varies widely. Here I report that urine, which better represents the filtrate, activates a large cation-conducting current in the cilia. With defined external solutions, hyperosmolality through addition of urea, NaCl, or D-mannitol activates a similar current. Most but not all of this current is conducted through TRPM4 channels. It is greatly reduced by internal MgATP or 9-phenanthrol, which inhibit TRPM4, or by shRNA knockdown of TRPM4. However, part of the current activated by urea conducts Ca²⁺ through channels that remain to be identified. External hyperosmolality also greatly increases the activity of ciliary PC2 channels; this is the first physiological stimulus identified for these channels. Possibilities are discussed for the mechanisms of channel activation and the roles for these activities in regulatory volume increase and cystogenesis.

The Notch signaling pathway is crucial for skeletal muscle development, regeneration, inflammation, and aging. This study investigated the association between interleukin-10 (IL-10) and the Notch pathway in C2C12 cells, as well as explored the effects of combined endurance and resistance exercise on the Notch and autophagy pathways in the skeletal muscle of senescence-accelerated mouse-resistant 1 Sedentary (SAMR1 CT), SAMR1 exercised (SAMR1 EX), senescence-accelerated prone mouse 8 Sedentary (SAMP8 CT), and SAMP8 exercised (SAMP8 EX). C2C12 myoblasts were transfected with siIL-10. Histological analysis, reverse transcription-quantitative polymerase chain reaction, and immunoblotting were performed on the quadriceps and tibialis anterior muscles. A publicly available dataset was analyzed to assess the Notch pathway in older men. In summary, IL-10 knockdown in myoblasts reduced the Notch pathway gene and protein expression. In SAMP8 mice, combined exercise improved muscle fiber organization, enhanced balance and coordination, and increased Notch2 and Hes1 mRNA levels. NOTCH2 mRNA levels were also higher in older men compared to young subjects with similar physical activity levels. These findings suggest that combined physical exercise enhances muscle regeneration via the Notch pathway in aged muscle.

Personalised nutrition (PN) as a new endeavour emerged in the background of the human genome project with the ease to analyse genetic heterogeneity. First commercial offers with recommendations for diet and lifestyle changes, usually based on a few polymorphisms, entered markets soon after the presentation of the human genome blueprint. Although PN has seen many attempts, meanwhile, with the inclusion of other biomedical measures such as microbiome and/or continuous glucose monitoring, scientific assessments of such approaches in various settings revealed limited success. Although personalisation improved general compliance over generic advice, particular benefits in referring to biomedical measures and individual risks did, in most cases, not provide any significant advantage. Moreover, scholars criticised such approaches as of limited impact from a public health perspective by attracting mainly technology-open individuals of high social status and proper financial capabilities. Based on these experiences, new avenues for personalising dietary advice are developed, and those are going beyond pure biomedical data by assessing the entire food environment of the individual with its capabilities and constraints in the given life setting. Embedded into digital environments for data collection but also for bidirectional communication, new possibilities emerge. Artificial intelligence methods allow for the multitude of input data and highly complex decision trees to be derived to customize advice. And that can be delivered on the spot and in time in any language whenever decisions are made on what to buy or what to eat. But systems can also be employed to increase physical activity levels and for the adoption of a more healthy lifestyle in general.

Plasma thyroid hormone (TH) binding proteins (THBPs), including thyroxine-binding globulin (TBG), transthyretin (TTR), and albumin (ALB), carry THs to extrathyroidal sites, where THs are unloaded locally and then taken up via membrane transporters into the tissue proper. The respective roles of THBPs in supplying THs for tissue uptake are not completely understood. To investigate this, we developed a spatial human physiologically based kinetic (PBK) model of THs, which produces several novel findings. (1) Contrary to postulations that TTR and/or ALB are the major local T4 contributors, the three THBPs may unload comparable amounts of T4 in Liver, a rapidly perfused organ; however, their contributions in slowly perfused tissues follow the order of abundances of T4TBG, T4TTR, and T4ALB. The T3 amounts unloaded from or loaded onto THBPs in a tissue acting as a T3 sink or source respectively follow the order of abundance of T3TBG, T3ALB, and T3TTR regardless of perfusion rate. (2) Any THBP alone is sufficient to maintain spatially uniform TH tissue distributions. (3) The TH amounts unloaded by each THBP species are spatially dependent and nonlinear in a tissue, with ALB being the dominant contributor near the arterial end but conceding to TBG near the venous end. (4) Spatial gradients of TH transporters and metabolic enzymes may modulate these contributions, producing spatially invariant or heterogeneous TH tissue concentrations depending on whether the blood-tissue TH exchange operates in near-equilibrium mode. In summary, our modeling provides novel insights into the differential roles of THBPs in local TH tissue distribution.

Increased dietary inorganic phosphate (P_i) intake stimulates renal P_i excretion, in part, by parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23) or dopamine. High dietary P_i may also stimulate sympathetic outflow. Rodent studies provided evidence for these regulatory loops, while controlled experiments in healthy humans examined periods of either a few hours or several weeks, and often varied dietary calcium intake. The effects of controlled, isolated changes in dietary P_i intake over shorter periods are unknown. We studied the effects of a low or high P_i diet on parameters of mineral metabolism in 10 healthy young men. Participants received a standardized diet (1000 mg phosphorus equivalent/day) supplemented with either a phosphate binder (low P_i diet) or phosphate capsules (750 mg phosphorus, high P_i diet) in a randomized cross-over trial for 5 days with a 7-day washout between diets. High P_i intake increased plasma P_i levels and 24-h excretion and decreased urinary calcium excretion. High P_i intake increased intact FGF23 (iFGF23) and suppressed plasma Klotho without affecting cFGF23, PTH, calcidiol, calcitriol, Fetuin-A, dopamine, epinephrine, norepinephrine, metanephrine, or aldosterone. Higher iFGF23 correlated with lower calcitriol and higher PTH. These data support a role for iFGF23 in increasing renal P_i excretion and reducing calcitriol in healthy young men during steady-state high dietary P_i intake. High dietary P_i intake elevated blood P_i levels in healthy young subjects with normal renal function and may therefore be a health risk, as higher serum P_i levels are associated with cardiovascular risk in the general population.

Many synaptic vesicles undergo exocytosis in motor nerve terminals during neuromuscular communication. Endocytosis then recovers the synaptic vesicle pool and presynaptic membrane area. The kinetics of endocytosis may shape neuromuscular transmission, determining its long-term reliability. Here, using fluorescent dyes, the time course of endocytosis induced by intense activity of the phrenic nerve was studied at the mouse diaphragm neuromuscular junction. It was found that a significant portion of endocytic events occurs after the end of tetanic stimulation. Pitstop 2, clathrin inhibitor, and more profoundly dynole 34-2, dynamin antagonist, suppressed endocytic FM1-43 dye uptake both during and after tetanus. Furthermore, synaptic vesicles formed in the presence of the endocytic blockers released FM-dye during subsequent evoked exocytosis at a lower rate. 25-Hydroxycholesterol (25HC) is an oxysterol, ubiquitously synthetized from excessive cholesterol. In addition, its production greatly increases by activated macrophages. 25HC accelerated FM-dye endocytosis and its sequential evoked exocytosis, and dynole (but not pitstop) prevented 25HC-mediated enhancement of endocytic FM-dye uptake. The positive effects of 25HC were interfered with chelation of cytosolic Ca²⁺ with a slow Ca²⁺ buffer EGTA-AM, Ca²⁺ antagonist TMB8, and sphingomyelin-hydrolyzing enzyme. In contrast to amphiphilic FM1-43 dye capture, 25HC reduced uptake of hydrophilic high molecular weight markers (labeled dextrans and toxin), which utilize bulk endocytosis to enter into nerve terminals. Thus, synaptic vesicle endocytosis had a relatively slow kinetics following the tetanic activity and can be accelerated by 25HC. The positive effect of 25HC on endocytosis engages a dynamin-dependent pathway, interconnected with cytoplasmic Ca²⁺ and sphingomyelin integrity.

Epilepsy is a chronic neurological disease characterized by recurrent seizures caused by abnormal electrical activity in the brain. The aim of our study was to investigate the effect of tDCS on oxidative stress, Ca²⁺, glutamate, GABA, AMPAR1, and NMDAR1 levels in kindling-induced epilepsy model. Behavioral tests evaluated motor and cognitive functions, while assessing oxidative stress, Ca²⁺, glutamate, GABA, AMPAR1, and NMDAR1 levels in hippocampal tissue. tDCS stimulation therapy demonstrates a neuroprotective effect on motor and cognitive function postepilepsy. Our study reveals an increase in TOC, Ca²⁺, glutamate, GABA, AMPAR1, and NMDAR1 levels and a decline in total antioxidant capacity (TAC) following PTZ-induced seizures. However, tDCS treatment led to a significant decrease of Ca²⁺, total oxidant capacity (TOC), glutamate, GABA, AMPAR1, and NMDAR1 levels in the epilepsy cohorts, while simultaneously causing a spike in TAC levels. The study's results showed that tDCS treatment could have a therapeutic effect on oxidative stress, Ca²⁺, TOC, glutamate, GABA, AMPAR1, NMDAR1, and TAC in both acute and chronic kindling epilepsy models.

Psychologic stress induces behavioral and autonomic responses such as acceleration of respiration. The lateral habenula (LHb) is noted to be involved in stress-induced behavioral responses. However, its involvement in stress-induced respiratory responses is unknown. In this study, we aimed to analyze whether and how the LHb regulates respiration. Electrical stimulation of the LHb of anesthetized Wistar male rats increased respiratory frequency and minute ventilation, calculated by respiratory frequency × thoracic movement amplitude. Systemic administration of a dopaminergic receptor antagonist, clozapine, suppressed the LHb-induced respiratory responses. On the other hand, administration of a serotonergic receptor antagonist, methysergide, significantly accelerated the LHb-induced increase in respiratory frequency, together with suppressing the thoracic movement amplitude. To clarify the source of dopaminergic modulation, we inhibited the ventral tegmental area (VTA), which contains dopaminergic neurons and receives inputs from the LHb, by administering microinjections of a GABA_A agonist, muscimol. The bilateral inhibition of the VTA almost abolished the LHb-induced respiratory responses. These results suggest that LHb activation causes respiration acceleration, mainly mediated by dopaminergic neurons in the VTA and suppressively modulated by the serotonergic system. Neural circuits originating in the LHb may be a key modulator for respiration during psychological stress.