First record of a possible trypanotolerant cattle breed in Latin America: Parasitological, serological, and clinical aspects.

Trypanosoma vivax infections are endemic in Africa, where they provoke trypanosomosis against which some local taurine breeds are tolerant and are thus named trypanotolerant. In Latin America, T. vivax was imported in 1919, since when it has been responsible for periodic outbreaks of the disease. This study assessed whether a South American taurine breed resilient to several parasitic and infectious diseases (Curraleiro Pé-Duro-CPD) can meet trypanotolerant criteria (control parasite proliferation, prevent anemia, survive without treatment, and maintain productivity). Three groups were established, each consisting of six animals (Group 1: CPD-infected; Group 2: Holstein/Gyr-infected; Group 3: Holstein/Gyr-uninfected, negative control). Groups 1 and 2 were infected with T. vivax on Day 0 and evaluated until day 532. Throughout the experimental period, parasitological (Woo and Brener), molecular (cPCR), serological (enzyme-linked immunosorbent assay - ELISA, indirect fluorescent antibody test - IFAT, immunochromatographic assay - IA), and clinical (hemogram, fever, weight loss) aspects were evaluated. During the acute phase of the disease, T. vivax was initially detected in Holstein/Gyr. Notably, the CPD animals restored their packed cell volume (PCV) values to the normal range 74 days after inoculations. In the chronic phase, two of the six CPD animals were positive by cPCR until D + 522 following immunosuppression with dexamethasone. Regarding serological aspects, the two CPD animals had positive tests until D + 532. The absence of T. vivax in blood during the chronic phase did not correspond to "self-cure". Holstein/Gyr animals exhibited fever on more evaluation days than CPD animals. Both breeds experienced weight loss, with Holstein/Gyr animals losing significantly more weight. On D + 25, the Holstein/Gyr group required treatment. During the 532 days, none of the CPD animals required treatment, even after being sensitized with dexamethasone. Animals from Group 3 tested negative for T. vivax throughout the experiment. This study demonstrated that CPD cattle fulfill the mentioned trypanotolerant criteria.

SNX10 regulates osteoclastogenic cell fusion and osteoclast size in mice.

Bone-resorbing osteoclasts (OCLs) are formed by differentiation and fusion of monocyte precursor cells, generating large multi-nucleated cells. Tightly-regulated cell fusion during osteoclastogenesis leads to formation of resorption-competent OCLs, whose sizes fall within a predictable physiological range. The molecular mechanisms that regulate the onset of OCL fusion and its subsequent arrest are, however, largely unknown. We have previously shown that OCLs cultured from mice homozygous for the R51Q mutation in the vesicle trafficking-associated protein sorting nexin 10, a mutation that induces autosomal recessive osteopetrosis in humans and in mice, display deregulated and continuous fusion that generates gigantic, inactive OCLs. Fusion of mature OCLs is therefore arrested by an active, genetically-encoded, cell-autonomous, and SNX10-dependent mechanism. In order to directly examine whether SNX10 performs a similar role in vivo, we generated SNX10-deficient (SKO) mice and demonstrated that they display massive osteopetrosis and that their OCLs fuse uncontrollably in culture, as do homozygous R51Q SNX10 (RQ/RQ) mice. OCLs that lack SNX10 exhibit persistent presence of DC-STAMP protein at their periphery, which may contribute to their uncontrolled fusion. In order to visualize endogenous SNX10-mutant OCLs in their native bone environment we genetically labelled the OCLs of wild-type, SKO and RQ/RQ mice with EGFP, and then visualized the three-dimensional organization of resident OCLs and the pericellular bone matrix by two-photon, confocal, and second harmonics generation microscopy. We show that the volumes, surface areas and, in particular, the numbers of nuclei in the OCLs of both mutant strains were on average 2-6 fold larger than those of OCLs from wild-type mice, indicating that deregulated, excessive fusion occurs in the mutant mice. We conclude that the fusion of OCLs, and consequently their size, are regulated in vivo by SNX10-dependent arrest of fusion of mature OCLs.

Osteoclasts (OCLs) are cells that degrade bone. These cells are generated by fusion of monocyte precursor cells, but the mechanisms that regulate this process and eventually arrest it are unknown. We had previously shown that OCLs cultured from mice carrying the R51Q mutation in the protein sorting nexin 10 (SNX10) lose their resorptive capacity and become gigantic due to uncontrolled fusion. To examine whether SNX10 is required for OCL fusion arrest also in vivo, we inactivated the Snx10 gene in mice and fluorescently labelled their OCLs and OCLs of R51Q SNX10 mice, isolated their femurs, and used advanced 3D microscopy methods to visualize OCLs within the bone matrix. As expected, mice lacking SNX10 exhibited excessive bone mass, indicating that their OCLs are inactive. OCLs within bones of both mutant mouse strains were on average 2-6-fold larger than in control mice, and contained proportionally more nuclei. We conclude that OCL fusion is arrested in control, but not SNX10 mutant, mice, indicating that the sizes of mature OCLs are limited in vivo by an active, SNX10-dependent mechanism that suppresses cell fusion.

Cell volume regulation modulates macrophage-related inflammatory responses via JAK/STAT signaling pathways.

Cell volume as a characteristic of changes in response to external environmental cues has been shown to control the fate of stem cells. However, its influence on macrophage behavior and macrophage-mediated inflammatory responses have rarely been explored. Herein, through mediating the volume of macrophages by adding polyethylene glycol (PEG), we demonstrated the feasibility of fine-tuning cell volume to regulate macrophage polarization towards anti-inflammatory phenotypes, thereby enabling to reverse macrophage-mediated inflammation response. Specifically, lower the volume of primary macrophages can induce both resting macrophages (M0) and stimulated pro-inflammatory macrophages (M1) to up-regulate the expression of anti-inflammatory factors and down-regulate pro-inflammatory factors. Further mechanistic investigation revealed that macrophage polarization resulting from changing cell volume might be mediated by JAK/STAT signaling pathway evidenced by the transcription sequencing analysis. We further propose to apply this strategy for the treatment of arthritis via direct introduction of PEG into the joint cavity to modulate synovial macrophage-related inflammation. Our preliminary results verified the credibility and effectiveness of this treatment evidenced by the significant inhibition of cartilage destruction and synovitis at early stage. In general, our results suggest that cell volume can be a biophysical regulatory factor to control macrophage polarization and potentially medicate inflammatory response, thereby providing a potential facile and effective therapy for modulating macrophage mediated inflammatory responses. STATEMENT OF SIGNIFICANCE: Cell volume has recently been recognized as a significantly important biophysical signal in regulating cellular functionalities and even steering cell fate. Herein, through mediating the volume of macrophages by adding polyethylene glycol (PEG), we demonstrated the feasibility of fine-tuning cell volume to induce M1 pro-inflammatory macrophages to polarize towards anti-inflammatory M2 phenotype, and this immunomodulatory effect may be mediated by the JAK/STAT signaling pathway. We also proposed the feasible applications of this PEG-induced volume regulation approach towards the treatment of osteoarthritis (OA), wherein our preliminary results implied an effective alleviation of early synovitis. Our study on macrophage polarization mediated by cell volume may open up new pathways for immune regulation through microenvironmental biophysical clues.

51Cr Red Blood Cells in the Study of Hematologic Disease: A Historical Review.

The early years of nuclear medicine included the development and clinical use of several in vitro or nonimaging procedures. The use of radionuclides as replacements for nonradioactive dyes brought improved accuracies and less subjective measurements to indicator dilution studies of body compartments such as the gastrointestinal system, lungs, urinary system, and vascular space. A popular nuclear medicine procedure was the radionuclide dilution method for quantitation of whole-blood volume or red blood cell volume or mass using 51Cr-labeled red blood cells-an important diagnostic element in patients suspected of having polycythemia vera, congestive heart failure, hypertension, shock, syncope, and other abnormal blood volume disorders. The radionuclide dilution method led to improved evaluation of red blood cell survival, which is important for clinical treatment planning in anemia and confirmation of splenic sequestration of damaged red blood cells. Although it was discovered that 51Cr was a chemically stable radiolabel of red blood cells after binding to intracellular hemoglobin, few nuclear medicine departments offered the clinical study for referring physicians because it required laboratory expertise for technologists, patient coordination, and a time-consuming procedure. The introduction of improved methods that are less time-consuming and have clinically acceptable results, along with the discontinuation of the sodium chromate 51Cr injection radiopharmaceutical by manufacturers, has consigned 51Cr red blood cells for red blood cell volume, mass, or survival evaluation to the list of retired nuclear medicine studies.

Risk of low levels of blood group antibodies mediating hemolysis in ABO-incompatible neonates with negative three hemolysis tests.

Objective: To explore the risk of low-level blood group antibody-mediated hemolysis in ABO-incompatible newborns with negative three hemolysis tests, aiming to assist in the identification and management of neonatal jaundice. Methods: A retrospective case-control study was performed in 892 children with jaundice. The patients were divided into three groups: group I, ABO compatible, negative three hemolysis tests; group II, ABO incompatible, negative three hemolysis tests; and group III, ABO incompatible, positive three hemolysis tests. We analyzed the differences in clinical data, blood routine and biochemical laboratory results. Results: (1) Patients in group II had higher levels of mean corpuscular volume (MCV), standard deviation of red blood cell volume distribution width (RDW-SD), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and bile acid (BA) than those in group I (P < 0.05). However, there were no statistically significant differences in the MCV, ALT, ALP and BA levels between groups II and III (P > 0.05). (2) Mean corpuscular hemoglobin concentration (MCHC) >359.5 g/L, cell volume distribution width (RDW-CV) >15.95%, and reticulocyte count (RET) >4.235% were identified as independent predictors of positive hemolysis test results (P < 0.001). The combination of MCHC, RDW-CV, and RET% yielded an AUC of 0.841. Conclusion: Low-level blood group antibody-mediated hemolysis may occur in ABO-incompatible neonates even when three hemolysis tests are negative. Changes in liver function parameters must be monitored. The combination of MCHC, RDW-CV, and RET% can be used to improve the detection rate of HDN.

RhoB plays a central role in hyperosmolarity-induced cell shrinkage in renal cells.

The small Rho GTP-binding proteins are important cell morphology, function, and apoptosis regulators. Unlike other Rho proteins, RhoB can be subjected to either geranylgeranylation (RhoB-GG) or farnesylation (RhoB-F), making that the only target of the farnesyltransferase inhibitor (FTI). Fluorescence resonance energy transfer experiments revealed that RhoB is activated by hyperosmolarity. By contrast, hyposmolarity did not affect RhoB activity. Interestingly, treatment with farnesyltransferase inhibitor-277 (FTI-277) decreased the cell size. To evaluate whether RhoB plays a role in volume reduction, renal collecting duct MCD4 cells and Human Kidney, HK-2 were transiently transfected with RhoB-wildtype-Enhance Green Fluorescence Protein (RhoB-wt-EGFP) and RhoB-CLLL-EGFP which cannot undergo farnesylation. A calcein-based fluorescent assay revealed that hyperosmolarity caused a significant reduction of cell volume in mock and RhoB-wt-EGFP-expressing cells. By contrast, cells treated with FTI-277 or expressing the RhoB-CLLL-EGFP mutant did not properly respond to hyperosmolarity with respect to mock and RhoB-wt-EGFP expressing cells. These findings were further confirmed by 3D-LSCM showing that RhoB-CLLL-EGFP cells displayed a significant reduction in cell size compared to cells expressing RhoB-wt-EGFP. Moreover, flow cytometry analysis revealed that RhoB-CLLL-EGFP expressing cells as well as FTI-277-treated cells showed a significant increase in cell apoptosis. Together, these data suggested that: (i) RhoB is sensitive to hyperosmolarity and not to hyposmolarity; (ii) inhibition of RhoB farnesylation associates with an increase in cell apoptosis, likely suggesting that RhoB might be a paramount player controlling apoptosis by interfering with responses to cell volume change.

Neutrophils actively swell to potentiate rapid migration.

While the involvement of actin polymerization in cell migration is well-established, much less is known about the role of transmembrane water flow in cell motility. Here, we investigate the role of water influx in a prototypical migrating cell, the neutrophil, which undergoes rapid, directed movement to sites of injury, and infection. Chemoattractant exposure both increases cell volume and potentiates migration, but the causal link between these processes are not known. We combine single-cell volume measurements and a genome-wide CRISPR screen to identify the regulators of chemoattractant-induced neutrophil swelling, including NHE1, AE2, PI3K-gamma, and CA2. Through NHE1 inhibition in primary human neutrophils, we show that cell swelling is both necessary and sufficient for the potentiation of migration following chemoattractant stimulation. Our data demonstrate that chemoattractant-driven cell swelling complements cytoskeletal rearrangements to enhance migration speed.

The effects of ACE inhibitor Enalapril on Mytilus galloprovincialis: Insights into morphological and functional responses.

In the last decades, pharmaceuticals have emerged as a new class of environmental contaminants. Antihypertensives, including angiotensin-converting enzyme (ACE) inhibitors, are of special concern due to their increased consumption over the past years. However, the available data on their putative effects on the health of aquatic animals, as well as the possible interaction with biological systems are still poorly understood. This study analysed whether and to which extent the exposure to Enalapril, an ACE inhibitor commonly used for treating hypertension and heart failure, may induce morpho-functional alterations in the mussel Mytilus galloprovincialis, a sentinel organism of water pollution. By mainly focusing on the digestive gland (DG), a target tissue used for analysing the effects of xenobiotics in mussels, the effects of 10-days exposure to 0.6 ng/L (E1) and 600 ng/L (E2) of Enalapril were investigated in terms of cell viability and volume regulation, morphology, oxidative stress, and stress protein expression and localization. Results indicated that exposure to Enalapril compromised the capacity of DG cells from the E2 group to regulate volume by limiting the ability to return to the original volume after hypoosmotic stress. This occurred without significant effects on DG cell viability. Enalapril unaffected also haemocytes viability, although an increased infiltration of haemocytes was histologically observed in DG from both groups, suggestive of an immune response. No changes were observed in the two experimental groups on expression and tissue localization of heat shock proteins 70 (HSPs70) and HSP90, and on the levels of oxidative biomarkers. Our results showed that, in M. galloprovincialis the exposure to Enalapril did not influence the oxidative status, as well as the expression and localization of stress-related proteins, while it activated an immune response and compromised the cell ability to face osmotic changes, with potential consequences on animal performance.

The TSC22D, WNK, and NRBP gene families exhibit functional buffering and evolved with Metazoa for cell volume regulation.

The ability to sense and respond to osmotic fluctuations is critical for the maintenance of cellular integrity. We used gene co-essentiality analysis to identify an unappreciated relationship between TSC22D2, WNK1, and NRBP1 in regulating cell volume homeostasis. All of these genes have paralogs and are functionally buffered for osmo-sensing and cell volume control. Within seconds of hyperosmotic stress, TSC22D, WNK, and NRBP family members physically associate into biomolecular condensates, a process that is dependent on intrinsically disordered regions (IDRs). A close examination of these protein families across metazoans revealed that TSC22D genes evolved alongside a domain in NRBPs that specifically binds to TSC22D proteins, which we have termed NbrT (NRBP binding region with TSC22D), and this co-evolution is accompanied by rapid IDR length expansion in WNK-family kinases. Our study reveals that TSC22D, WNK, and NRBP genes evolved in metazoans to co-regulate rapid cell volume changes in response to osmolarity.

Pump up the volume.

An influx of water molecules can help immune cells called neutrophils to move to where they are needed in the body.

Chondrocyte deformation during the unloading phase of cyclic compression loading.

Cell volume and shape changes play a pivotal role in cellular mechanotransduction, governing cellular responses to external loading. Understanding the dynamics of cell behavior under loading conditions is essential to elucidate cell adaptation mechanisms in physiological and pathological contexts. In this study, we investigated the effects of dynamic cyclic compression loading on cell volume and shape changes, comparing them with static conditions. Using a custom-designed platform which allowed for simultaneous loading and imaging of cartilage tissue, tissues were subjected to 100 cycles of mechanical loading while measuring cell volume and shape alterations during the unloading phase at specific time points. The findings revealed a transient decrease in cell volume (13%) during the early cycles, followed by a gradual recovery to baseline levels after approximately 20 cycles, despite the cartilage tissue not being fully recovered at the unloading phase. This observed pattern indicates a temporal cell volume response that may be associated with cellular adaptation to the mechanical stimulus through mechanisms related to active cell volume regulation. Additionally, this study demonstrated that cell volume and shape responses during dynamic loading were significantly distinct from those observed under static conditions. Such findings suggest that cells in their natural tissue environment perceive and respond differently to dynamic compared to static mechanical cues, highlighting the significance of considering dynamic loading environments in studies related to cellular mechanics. Overall, this research contributes to the broader understanding of cellular behavior under mechanical stimuli, providing valuable insights into their ability to adapt to dynamic mechanical loading.

Use of membrane transport models to design cryopreservation procedures for oocytes.

Oocyte cryopreservation is increasingly being used in reproductive technologies for conservation and breeding purposes. Further development of oocyte cryopreservation techniques requires interdisciplinary insights in the underlying principles of cryopreservation. This review aims to serve this purpose by: (1) highlighting that preservation strategies can be rationally designed, (2) presenting mechanistic insights in volume and osmotic stress responses associated with CPA loading strategies and cooling, and (3) giving a comprehensive listing of oocyte specific biophysical membrane characteristics and commonly used permeation model equations. It is shown how transport models can be used to simulate the behavior of oocytes during cryopreservation processing steps, i.e., during loading of cryoprotective agents (CPAs), cooling with freezing as well as vitrification, warming and CPA unloading. More specifically, using defined cellular and membrane characteristics, the responses of oocytes during CPA (un)loading were simulated in terms of temperature- and CPA type-and-concentration-dependent changes in cell volume and intracellular solute concentration. In addition, in order to determine the optimal cooling rate for slow programmable cooling cryopreservation, the freezing-induced cell volume response was simulated at various cooling rates to estimate rates with tolerable limits. For vitrification, special emphasis was on prediction of the timing of reaching osmotic tolerance limits during CPA exposure, and the need to use step-wise CPA addition/removal protocols. In conclusion, we present simulations and schematic illustrations that explain the timing of events during slow cooling cryopreservation as well as vitrification, important for rationally designing protocols taking into account how different CPA types, concentrations and temperatures affect the oocyte.

Bacterial cell volume regulation and the importance of cyclic di-AMP.

SUMMARYNucleotide-derived second messengers are present in all domains of life. In prokaryotes, most of their functionality is associated with general lifestyle and metabolic adaptations, often in response to environmental fluctuations of physical parameters. In the last two decades, cyclic di-AMP has emerged as an important signaling nucleotide in many prokaryotic lineages, including Firmicutes, Actinobacteria, and Cyanobacteria. Its importance is highlighted by the fact that both the lack and overproduction of cyclic di-AMP affect viability of prokaryotes that utilize cyclic di-AMP, and that it generates a strong innate immune response in eukaryotes. In bacteria that produce the second messenger, most molecular targets of cyclic di-AMP are associated with cell volume control. Besides, other evidence links the second messenger to cell wall remodeling, DNA damage repair, sporulation, central metabolism, and the regulation of glycogen turnover. In this review, we take a biochemical, quantitative approach to address the main cellular processes that are directly regulated by cyclic di-AMP and show that these processes are very connected and require regulation of a similar set of proteins to which cyclic di-AMP binds. Altogether, we argue that cyclic di-AMP is a master regulator of cell volume and that other cellular processes can be connected with cyclic di-AMP through this core function. We further highlight important directions in which the cyclic di-AMP field has to develop to gain a full understanding of the cyclic di-AMP signaling network and why some processes are regulated, while others are not.

The Structure and Function of the Bacterial Osmotically Inducible Protein Y.

The ability to adapt to osmotically diverse and fluctuating environments is critical to the survival and resilience of bacteria that colonize the human gut and urinary tract. Environmental stress often provides cross-protection against other challenges and increases antibiotic tolerance of bacteria. Thus, it is critical to understand how E. coli and other microbes survive and adapt to stress conditions. The osmotically inducible protein Y (OsmY) is significantly upregulated in response to hypertonicity. Yet its function remains unknown for decades. We determined the solution structure and dynamics of OsmY by nuclear magnetic resonance spectroscopy, which revealed that the two Bacterial OsmY and Nodulation (BON) domains of the protein are flexibly linked under low- and high-salinity conditions. In-cell solid-state NMR further indicates that there are no gross structural changes in OsmY as a function of osmotic stress. Using cryo-electron and super-resolution fluorescence microscopy, we show that OsmY attenuates plasmolysis-induced structural changes in E. coli and improves the time to growth resumption after osmotic upshift. Structure-guided mutational and functional studies demonstrate that exposed hydrophobic residues in the BON1 domain are critical for the function of OsmY. We find no evidence for membrane interaction of the BON domains of OsmY, contrary to current assumptions. Instead, at high ionic strength, we observe an interaction with the water channel, AqpZ. Thus, OsmY does not play a simple structural role in E. coli but may influence a cascade of osmoregulatory functions of the cell.

Measurement of protein concentration in bacteria and small organelles under a light transmission microscope.

Protein concentration (PC) is an essential characteristic of cells and organelles; it determines the extent of macromolecular crowding effects and serves as a sensitive indicator of cellular health. A simple and direct way to quantify PC is provided by brightfield-based transport-of-intensity equation (TIE) imaging combined with volume measurements. However, since TIE is based on geometric optics, its applicability to micrometer-sized particles is not clear. Here, we show that TIE can be used on particles with sizes comparable to the wavelength. At the same time, we introduce a new ImageJ plugin that allows TIE image processing without resorting to advanced mathematical programs. To convert TIE data to PC, knowledge of particle volumes is essential. The volumes of bacteria or other isolated particles can be measured by displacement of an external absorbing dye ("transmission-through-dye" or TTD microscopy), and for spherical intracellular particles, volumes can be estimated from their diameters. We illustrate the use of TIE on Escherichia coli, mammalian nucleoli, and nucleolar fibrillar centers. The method is easy to use and achieves high spatial resolution.

Clinical importance of distinguishing true anemia from dilutional pseudo-anemia: Consequences of a 3-year follow-up volume assessment in a heart failure patient.

In chronic heart failure, dilutional anemia and hypervolemia may occur due to plasma volume expansion, the latter sometimes exacerbated by an increase in red cell volume. Diagnosis and a therapeutic strategy require determination of vascular volumes.

Functional expression of the proton sensors ASIC1a, TMEM206, and OGR1 together with BKCa channels is associated with cell volume changes and cell death under strongly acidic conditions in DAOY medulloblastoma cells.

Fast growing solid tumors are frequently surrounded by an acidic microenvironment. Tumor cells employ a variety of mechanisms to survive and proliferate under these harsh conditions. In that regard, acid-sensitive membrane receptors constitute a particularly interesting target, since they can affect cellular functions through ion flow and second messenger cascades. Our knowledge of these processes remains sparse, however, especially regarding medulloblastoma, the most common pediatric CNS malignancy. In this study, using RT-qPCR, whole-cell patch clamp, and Ca2+-imaging, we uncovered several ion channels and a G protein-coupled receptor, which were regulated directly or indirectly by low extracellular pH in DAOY and UW228 medulloblastoma cells. Acidification directly activated acid-sensing ion channel 1a (ASIC1a), the proton-activated Cl- channel (PAC, ASOR, or TMEM206), and the proton-activated G protein-coupled receptor OGR1. The resulting Ca2+ signal secondarily activated the large conductance calcium-activated potassium channel (BKCa). Our analyses uncover a complex relationship of these transmembrane proteins in DAOY cells that resulted in cell volume changes and induced cell death under strongly acidic conditions. Collectively, our results suggest that these ion channels in concert with OGR1 may shape the growth and evolution of medulloblastoma cells in their acidic microenvironment.

Ion channel-mediated mitochondrial volume regulation and its relationship with mitochondrial dynamics.

The mitochondrion, one of the important cellular organelles, has the major function of generating adenosine triphosphate and plays an important role in maintaining cellular homeostasis, governing signal transduction, regulating membrane potential, controlling programmed cell death and modulating cell proliferation. The dynamic balance of mitochondrial volume is an important factor required for maintaining the structural integrity of the organelle and exerting corresponding functions. Changes in the mitochondrial volume are closely reflected in a series of biological functions and pathological changes. The mitochondrial volume is controlled by the osmotic balance between the cytoplasm and the mitochondrial matrix. Thus, any disruption in the influx of the main ion, potassium, into the cells can disturb the osmotic balance between the cytoplasm and the matrix, leading to water movement between these compartments and subsequent alterations in mitochondrial volume. Recent studies have shown that mitochondrial volume homeostasis is closely implicated in a variety of diseases. In this review, we provide an overview of the main influencing factors and research progress in the field of mitochondrial volume homeostasis.

Physiological role of potassium channels in mammalian germ cell differentiation, maturation, and capacitation.

BACKGROUND: Ion channels are essential for differentiation and maturation of germ cells, and even for fertilization in mammals. Different types of potassium channels have been identified, which are grouped into voltage-gated channels (Kv), ligand-gated channels (Kligand ), inwardly rectifying channels (Kir ), and tandem pore domain channels (K2P ). MATERIAL-METHODS: The present review includes recent findings on the role of potassium channels in sperm physiology of mammals. RESULTS-DISCUSSION: While most studies conducted thus far have been focused on the physiological role of voltage- (Kv1, Kv3, and Kv7) and calcium-gated channels (SLO1 and SLO3) during sperm capacitation, especially in humans and rodents, little data about the types of potassium channels present in the plasma membrane of differentiating germ cells exist. In spite of this, recent evidence suggests that the content and regulation mechanisms of these channels vary throughout spermatogenesis. Potassium channels are also essential for the regulation of sperm cell volume during epididymal maturation and for preventing premature membrane hyperpolarization. It is important to highlight that the nature, biochemical properties, localization, and regulation mechanisms of potassium channels are species-specific. In effect, while SLO3 is the main potassium channel involved in the K+ current during sperm capacitation in rodents, different potassium channels are implicated in the K+ outflow and, thus, plasma membrane hyperpolarization during sperm capacitation in other mammalian species, such as humans and pigs. CONCLUSIONS: Potassium conductance is essential for male fertility, not only during sperm capacitation but throughout the spermiogenesis and epididymal maturation.

Unveiling the Intricate Connection: Cell Volume as a Key Regulator of Mechanotransduction.

The volumes of living cells undergo dynamic changes to maintain the cells' structural and functional integrity in many physiological processes. Minor fluctuations in cell volume can serve as intrinsic signals that play a crucial role in cell fate determination during mechanotransduction. In this review, we discuss the variability of cell volume and its role in vivo, along with an overview of the mechanisms governing cell volume regulation. Additionally, we provide insights into the current approaches used to control cell volume in vitro. Furthermore, we summarize the biological implications of cell volume regulation and discuss recent advances in understanding the fundamental relationship between cell volume and mechanotransduction. Finally, we delve into the potential underlying mechanisms, including intracellular macromolecular crowding and cellular mechanics, that govern the global regulation of cell fate in response to changes in cell volume. By exploring the intricate interplay between cell volume and mechanotransduction, we underscore the importance of considering cell volume as a fundamental signaling cue to unravel the basic principles of mechanotransduction. Additionally, we propose future research directions that can extend our current understanding of cell volume in mechanotransduction. Overall, this review highlights the significance of considering cell volume as a fundamental signal in understanding the basic principles in mechanotransduction and points out the possibility of controlling cell volume to control cell fate, mitigate disease-related damage, and facilitate the healing of damaged tissues.