RESUMO
In human medical practice, a hematological rule of three has been validated for healthy human populations. One such formula is estimating hemoglobin (Hb) levels as 1/3rd of Packed Cell Volume (PCV). However, no such hematological formulae have been devised and validated for veterinary medical practice. The present study was devised with an aim to evaluate the relationship between hemoglobin (Hb) concentration and Packed Cell Volume (PCV) in camels (n = 215) being reared under pastoralism, and to devise a simple pen-side hematological formula for estimation of Hb from PCV. The PCV was determined through microhematocrit method whereas Hb estimation by cyanmethaemoglobin method (HbD). The Hb was also calculated as 1/3rd of PCV and was dubbed as calculated Hb (HbC). Overall HbD and HbC were significantly (P≥0.05) different. Similar results were attained for all study groups i.e. males (n = 94) and females (n = 121), and young (n = 85) and adult (n = 130) camels. The corrected Hb (CHb) was deduced through regression prediction equation attained from linear regression model. Scatterplots were drawn, linear regression was carried out, and Bland Altman chart was built for agreement of both methods of Hb estimation. A non-significant (P≥0.05) difference was noticed between HbD and CHb. Bland Altman agreement analysis revealed satisfactory agreement between HbD and CHb and the data was distributed closely around the mean difference line (Mean = 0.1436, 95% CI = 3.00, -2.72). A simplified pen-side hematological formula for deducing Hb concentration from PCV is accordingly recommended viz. Hb concentration (g/dL) = 0.18(PCV)+5.4 for all age and gender groups of camels instead of its calculation as one-third of PCV.
Assuntos
Camelus , Alimentos Formulados , Masculino , Feminino , Animais , Humanos , Hematócrito/veterinária , Modelos Lineares , Tamanho Celular , Hemoglobinas/análiseRESUMO
Along with different life strategies, organisms have evolved dramatic cellular composition differences. Understanding the molecular basis and fitness effects of these differences is key to elucidating the fundamental characteristics of life. TOR/insulin pathways are key regulators of cell size, but whether their activity determines cell size in a systemic or tissue-specific manner awaits exploration. To that end, we measured cells in four tissues in genetically modified Drosophila melanogaster (rictorΔ2 and Mnt1) and corresponding controls. While rictorΔ2 flies lacked the Rictor protein in TOR complex 2, downregulating the functions of this element in TOR/insulin pathways, Mnt1 flies lacked the transcriptional regulator protein Mnt, weakening the suppression of downstream signalling from TOR/insulin pathways. rictorΔ2 flies had smaller epidermal (leg and wing) and ommatidial cells and Mnt1 flies had larger cells in these tissues than the controls. Females had consistently larger cells than males in the three tissue types. In contrast, dorsal longitudinal flight muscle cells (measured only in males) were not altered by mutations. We suggest that mutations in cell cycle control pathways drive the evolution of systemic changes in cell size throughout the body, but additional mechanisms shape the cellular composition of some tissues independent of these mutations.
Assuntos
Drosophila melanogaster , Insulinas , Feminino , Masculino , Animais , Drosophila melanogaster/genética , Mutação , Tamanho Celular , Fatores de Transcrição/genética , Ciclo CelularRESUMO
Bacteria dynamically regulate cell size and growth to thrive in changing environments. While previous studies have characterized bacterial growth physiology at steady-state, a quantitative understanding of bacterial physiology in time-varying environments is lacking. Here we develop a quantitative theory connecting bacterial growth and division rates to proteome allocation in time-varying nutrient environments. In such environments, cell size and growth are regulated by trade-offs between prioritization of biomass accumulation or division, resulting in decoupling of single-cell growth rate from population growth rate. Specifically, bacteria transiently prioritize biomass accumulation over production of division machinery during nutrient upshifts, while prioritizing division over growth during downshifts. When subjected to pulsatile nutrient concentration, we find that bacteria exhibit a transient memory of previous metabolic states due to the slow dynamics of proteome reallocation. This allows for faster adaptation to previously seen environments and results in division control which is dependent on the time-profile of fluctuations.
Assuntos
Bactérias , Proteoma , Bactérias/genética , Adaptação Fisiológica , Nutrientes , Tamanho CelularRESUMO
Biological tissues acquire various characteristic shapes through morphogenesis. Tissue shapes result from the spatiotemporally heterogeneous cellular activities influenced by mechanical and biochemical environments. To investigate multicellular tissue morphogenesis, this study aimed to develop a novel multiscale method that can connect each cellular activity to the mechanical behaviors of the whole tissue by constructing continuum-based particle models of cellular activities. This study proposed mechanical models of cell growth and proliferation that are expressed as volume expansion and cell division by extending the material point method. By simulating cell hypertrophy and proliferation under both free and constraint conditions, the proposed models demonstrated potential for evaluating the mechanical state and tracing cells throughout tissue morphogenesis. Moreover, the effect of a cell size checkpoint was incorporated into the cell proliferation model to investigate the mechanical behaviors of the whole tissue depending on the condition of cellular activities. Consequently, the accumulation of strain energy density was suppressed because of the influence of the checkpoint. In addition, the whole tissues acquired different shapes depending on the influence of the checkpoint. Thus, the models constructed herein enabled us to investigate the change in the mechanical behaviors of the whole tissue according to each cellular activity depending on the mechanical state of the cells during morphogenesis.
Assuntos
Modelos Biológicos , Simulação por Computador , Morfogênese , Proliferação de Células , Tamanho CelularRESUMO
During hypocotyl development, an asymmetric auxin gradient causes differential cell elongation, leading to tissue bending and apical hook formation. Recently, Ma et al. identified a molecular pathway that links auxin with endoreplication and cell size through cell wall integrity sensing, cell wall remodeling, and regulation of cell wall stiffness.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Endorreduplicação , Ácidos Indolacéticos/metabolismo , Tamanho Celular , Regulação da Expressão Gênica de PlantasRESUMO
How the production of biomass is controlled as cells increase in size and proceed through the cell cycle events is important for understanding the regulation of global cellular growth. This has been studied for decades but has not yielded consistent results, probably due to perturbations induced by the synchronisation methods used in most previous studies. To avoid this problem, we have developed a system to analyse unperturbed exponentially growing populations of fission yeast cells. We generated thousands of fixed single-cell measurements of cell size, cell cycle stage and the levels of global cellular translation and transcription. We show that translation scales with size, and additionally, increases at late S-phase/early G2 and early in mitosis and decreases later in mitosis, suggesting that cell cycle controls are also operative over global cellular translation. Transcription increases with both size and the amount of DNA, suggesting that the level of transcription of a cell may be the result of a dynamic equilibrium between the number of RNA polymerases associating and disassociating from DNA.
Assuntos
Proteínas de Schizosaccharomyces pombe , Schizosaccharomyces , Schizosaccharomyces/genética , Ciclo Celular/fisiologia , Mitose , Proteínas de Schizosaccharomyces pombe/genética , Tamanho CelularRESUMO
Along with differences in life histories, metazoans have also evolved vast differences in cellularity, involving changes in the molecular pathways controlling the cell cycle. The extent to which the signalling network systemically determines cellular composition throughout the body and whether tissue cellularity is organized locally to match tissue-specific functions are unclear. We cultured genetic lines of Drosophila melanogaster on food with and without rapamycin to manipulate the activity of target of rapamycin (TOR)/insulin pathways and evaluate cell-size changes in five types of adult cells: wing and leg epidermal cells, ommatidial cells, indirect flight muscle cells and Malpighian tubule epithelial cells. Rapamycin blocks TOR multiprotein complex 1, reducing cell growth, but this effect has been studied in single cell types. As adults, rapamycin-treated flies had smaller bodies and consistently smaller cells in all tissues. Regardless, females eclosed with larger bodies and larger cells in all tissues than males. Thus, differences in TOR activity and sex were associated with the orchestration of cell size throughout the body, leading to differences in body size. We postulate that the activity of TOR/insulin pathways and their effects on cellularity should be considered when investigating the origin of ecological and evolutionary patterns in life histories.
Assuntos
Proteínas de Drosophila , Insulinas , Animais , Masculino , Feminino , Drosophila melanogaster/genética , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Sirolimo/farmacologia , Sirolimo/metabolismo , Tamanho Celular , Insulinas/metabolismo , Tamanho CorporalRESUMO
BACKGROUND: Myricetin, a type of flavonol commonly found in fruits and herbs, has demonstrated anticancer properties by triggering the process of apoptosis or programmed cell death in tumor cells. Despite the absence of mitochondria and nuclei, erythrocytes can undergo programmed cell death, also known as eryptosis.This process is characterized by cell shrinkage, externalization of phosphatidylserine (PS) on the cell membrane, and the formation of membrane blebs. The signaling of eryptosis involves Ca2+ influx, the formation of reactive oxygen species (ROS), and the accumulation of cell surface ceramide. The present study explored the effects of myricetin on eryptosis. METHODS AND RESULTS: Human erythrocytes were exposed to various concentrations of myricetin (2-8 µM) for 24 h. Flow cytometry was used to assess the markers of eryptosis, including PS exposure, cellular volume, cytosolic Ca2+ concentration, and ceramide accumulation. In addition, the levels of intracellular ROS were measured using the 2',7'-dichlorofluorescin diacetate (DCFDA) assay. The myricetin-treated (8 µM) erythrocytes significantly increased Annexin-positive cells, Fluo-3 fluorescence intensity, DCF fluorescence intensity, and the accumulation of ceramide. The impact of myricetin on the binding of annexin-V was significantly reduced, but not completely eliminated, by the nominal removal of extracellular Ca2+. CONCLUSION: Myricetin triggers eryptosis, which is accompanied and, at least in part, caused by Ca2+ influx, oxidative stress and increase of ceramide abundance.
Assuntos
Eriptose , Humanos , Espécies Reativas de Oxigênio/metabolismo , Estresse Oxidativo , Eritrócitos/metabolismo , Ceramidas , Anexinas/metabolismo , Anexinas/farmacologia , Cálcio/metabolismo , Fosfatidilserinas/metabolismo , Fosfatidilserinas/farmacologia , Tamanho Celular , HemóliseRESUMO
The variation of nutrient supply not only leads to the differences in the phytoplankton biomass and primary productivity but also induces the long-term phenotypic evolution of phytoplankton. It is widely accepted that marine phytoplankton follows Bergmann's Rule and becomes smaller with climate warming. Compared with the direct effect of increasing temperature, the indirect effect via nutrient supply is considered to be an important and dominant factor in the reduction of phytoplankton cell size. In this paper, a size-dependent nutrient-phytoplankton model is developed to explore the effects of nutrient supply on the evolutionary dynamics of functional traits associated with phytoplankton size. The ecological reproductive index is introduced to investigate the impacts of input nitrogen concentration and vertical mixing rate on the persistence of phytoplankton and the distribution of cell size. In addition, by applying the adaptive dynamics theory, we study the relationship between nutrient input and the evolutionary dynamics of phytoplankton. The results show that input nitrogen concentration and vertical mixing rate have significant effects on the cell size evolution of phytoplankton. Specifically, cell size tends to increase with the input nutrient concentration, as does the diversity of cell sizes. In addition, a single-peaked relationship between vertical mixing rate and cell size is observed. When the vertical mixing rate is too low or too high, only small individuals are dominant in the water column. When the vertical mixing rate is moderate, large individuals can coexist with small individuals, so the diversity of phytoplankton is elevated. We predict that reduced intensity of nutrient input due to climate warming will lead to a trend towards smaller cell size and will reduce the diversity of phytoplankton.
Assuntos
Clima , Fitoplâncton , Humanos , Nutrientes , Tamanho Celular , NitrogênioRESUMO
The distribution of fluorescence signals measured with flow cytometry can be influenced by several factors, including qualitative and quantitative properties of the used fluorochromes, optical properties of the detection system, as well as the variability within the analyzed cell population itself. Most of the single cell samples prepared from in vitrocultures or clinical specimens contain a variable cell cycle component. Cell cycle, together with changes in the cell size, are two of the factors that alter the functional properties of analyzed cells and thus affect the interpretation of obtained results. Here, we describe the association between cell cycle status and cell size, and the variability in the distribution of fluorescence intensity as determined with flow cytometry, at population scale. We show that variability in the distribution of background and specific fluorescence signals is related to the cell cycle state of the selected population, with the 10% low fluorescence signal fraction enriched mainly in cells in their G0/G1 cell cycle phase, and the 10% high fraction containing cells mostly in the G2/M phase. Therefore we advise using caution and additional experimental validation when comparing populations defined by fractions at both ends of fluorescence signal distribution to avoid biases caused by the effect of cell cycle and cell size.
Assuntos
Fase G2 , Citometria de Fluxo/métodos , Divisão Celular , Ciclo Celular/fisiologia , Tamanho CelularRESUMO
Cell swelling as a result of hypotonic stress is counteracted in mammalian cells by a process called regulatory volume decrease (RVD). We have recently discovered that RVD of human keratinocytes requires the LRRC8 volume-regulated anion channel (VRAC) and that Ca2+ exerts a modulatory function on RVD. However, the ion channel that is responsible for Ca2+ influx remains unknown. We investigated in this study whether the Ca2+-permeable TRPV4 ion channel, which functions as cell volume sensor in many cell types, may be involved in cell volume regulation during hypotonic stress response of human keratinocytes. We interfered with TRPV4 function in two human keratinocyte cell lines (HaCaT and NHEK-E6/E7) by using two TRPV4-specific inhibitors (RN1734 and GSK2193874), and by creating a CRISPR/Cas9-mediated genetic TRPV4-/- knockout in HaCaT cells. We employed electrophysiological patch clamp analysis, fluorescence-based Ca2+ imaging and cell volume measurements to determine the functional importance of TRPV4. We could show that both hypotonic stress and direct activation of TRPV4 by the specific agonist GSK1016790A triggered intracellular Ca2+ response. Strikingly, the Ca2+ increase upon hypotonic stress was neither affected by genetic knockout of TRPV4 in HaCaT cells nor by pharmacological inhibition of TRPV4 in both keratinocyte cell lines. Accordingly, hypotonicity-induced cell swelling, downstream activation of VRAC currents as well as subsequent RVD were unaffected both in TRPV4 inhibitor-treated keratinocytes and in HaCaT-TRPV4-/- cells. In summary, our study shows that keratinocytes do not require TRPV4 for coping with hypotonic stress, which implies the involvement of other, yet unidentified Ca2+ channels.
Assuntos
Queratinócitos , Canais de Cátion TRPV , Animais , Humanos , Pressão Osmótica , Canais de Cátion TRPV/metabolismo , Linhagem Celular , Queratinócitos/metabolismo , Tamanho Celular , Cálcio/metabolismo , Soluções Hipotônicas/farmacologia , Soluções Hipotônicas/metabolismo , Mamíferos/metabolismoRESUMO
A highly invasive subpopulation of circulating tumor cells (CTCs) may constitute seeds for metastases, which are therefore considered functional CTCs. However, there are few effective strategies to detect CTCs based on invasive phenotypes. Herein, we focused on functional CTCs with high invasiveness and designed an integrated microfluidic system to differentiate the invasive potential of CTCs for more accurate metastasis prediction. By combining size-based enrichment and invasiveness-based analysis, the system managed to continuously remove most hemocytes by 8 µm gaps and analyze the invasiveness of the enriched CTCs by Matrigel loading. In addition to a device, a single pump and a Petri dish were included to provide an FBS gradient for driving cell invasion and maintain a long-term cell culture. The system successfully identified functional CTCs derived from different types of cancer patients, including colorectal, kidney and bladder cancer patients, using whole blood without any sample pretreatment process. Within 28 cases of colorectal cancer patients, functional CTCs were detected in 61.54% of patients with metastases, along with stronger invasiveness evaluated by migration/invasion distance than those from patients without metastases (P < 0.05). Furthermore, one bladder cancer patient was diagnosed with recurrence six months after detection, indicating the excellent value for cancer metastases prediction. In addition, great phenotypic heterogeneity of CTCs was also observed at the single-cell level, including invasion, proliferation and dormancy, which provided an effective strategy for metastasis prediction based on CTC function as a single cell.
Assuntos
Técnicas Biossensoriais , Células Neoplásicas Circulantes , Neoplasias da Bexiga Urinária , Humanos , Células Neoplásicas Circulantes/patologia , Microfluídica , Separação Celular , Tamanho Celular , Linhagem Celular TumoralRESUMO
Benzodiazepine (BZD) abuse is a global problem, including pregnant women. For this population, the drug of choice is usually alprazolam, which acts as a GABAergic agonist and may compromise the development of integrative areas of the nervous system, such as the dentate gyrus (DG) of the hippocampus. In this context, we studied the changes in the DG of the offspring of rats treated with alprazolam during gestation: control, treatment 1 (T1: 1.25 mg/animal), and an overdose group (T2: 30 mg/animal). Alprazolam was administered orally ten days before mating and during the gestational period. After birth, newborns were counted, sexed, and the body mass of each pup was measured. The newborns' brains were extracted and processed for morphological study of the DG or for total protein extraction of the hippocampus. The results showed that alprazolam can affect the cell number and area, and increased euchromatin in both granular and molecular layers of the DG, especially in the overdose group. Also, alprazolam upregulated the NF-κB and reduced GFAP and caspase-3. Based on our findings, we conclude that the DG is a plausible region of influence by BZDs during embryogenesis. An overdose during gestation may cause structural changes in the DG.
Assuntos
Giro Denteado , Masculino , Feminino , Animais , Ratos , Ratos Wistar , Alprazolam/farmacologia , Giro Denteado/efeitos dos fármacos , Giro Denteado/metabolismo , Gravidez , Peso Corporal , Proliferação de Células , Tamanho Celular , NF-kappa B/metabolismo , Peroxidação de LipídeosRESUMO
Cell volume regulation is an essential strategy for the maintenance of life under unfavorable osmotic conditions. Mechanisms aimed at minimizing the physiological challenges caused by environmental changes are crucial in anisosmotic environments. However, aquatic ecosystems experience multiple stressors, including variations in salinity and heavy metal pollution. The accumulation of heavy metals in aquatic ecosystems has a significant effect on the biota, leading to impaired function. The aim of this study was to investigate the capacity of volume regulation in isolated cells of the sea anemone Bunodosoma cangicum exposed to nominal copper (Cu) concentrations of 5 and 50 µg L-1, associated or not with hypoosmotic (15) or hyperosmotic (45) shock for 15 min. In the absence of the metal, our results showed volume maintenance in all osmotic conditions. Our results showed that cell volume was maintained under all osmotic conditions in the absence of Cu. Similarly, no significant differences were observed in cell volumes under isosmotic and hyperosmotic conditions in the presence of both Cu concentrations. A similar homeostatic response was observed under the hypoosmotic condition with 5 µg L-1 Cu. Our results showed an increase in cell volume with exposure of the cells to the hypoosmotic condition and 50 µg L-1 Cu. The response could be associated with the increased bioavailability of Cu, reduced ability to resist multixenobiotics and their efflux pathways, and the impairment of water efflux in specialized transmembrane proteins. Therefore, B. cangicum pedal disk cells can tolerate osmotic variations in aquatic ecosystems. However, the capacity to regulate cell volume under hypoosmotic conditions can be affected by the presence of a metal contaminant (50 µg L-1 Cu), which could be due to the inhibition of water channels.
Assuntos
Metais Pesados , Anêmonas-do-Mar , Poluentes Químicos da Água , Animais , Cobre/metabolismo , Anêmonas-do-Mar/metabolismo , Ecossistema , Metais Pesados/metabolismo , Tamanho Celular , Poluentes Químicos da Água/metabolismoRESUMO
The volume of adhered cells has been shown experimentally to decrease during spreading. This effect can be understood from the pump-leak model, which we have extended to include mechano-sensitive ion transporters. We identify a novel effect that has important consequences on cellular volume loss: cells that are swollen due to a modulation of ion transport rates are more susceptible to volume loss in response to a tension increase. This effect explains in a plausible manner the discrepancies between three recent, independent experiments on adhered cells, between which both the magnitude of the volume change and its dynamics varied substantially. We suggest that starved and synchronized cells in two of the experiments were in a swollen state and, consequently, exhibited a large volume loss at steady state. Nonswollen cells, for which there is a very small steady-state volume decrease, are still predicted to transiently lose volume during spreading due to a relaxing viscoelastic tension that is large compared with the steady-state tension. We elucidate the roles of cell swelling and surface tension in cellular volume regulation and discuss their possible microscopic origins.
Assuntos
Tensão Superficial , Transporte de Íons , Tamanho CelularRESUMO
Adherent cells use actomyosin contractility to generate mechanical force and to sense the physical properties of their environment, with dramatic consequences for migration, division, differentiation, and fate. However, the organization of the actomyosin system within cells is highly variable, with its assembly and function being controlled by small GTPases from the Rho family. To understand better how activation of these regulators translates into cell-scale force generation in the context of different physical environments, here we combine recent advances in non-neuronal optogenetics with micropatterning and traction force microscopy on soft elastic substrates. We find that, after whole-cell RhoA activation by the CRY2/CIBN optogenetic system with a short pulse of 100 ms, single cells contract on a minute timescale in proportion to their original traction force, before returning to their original tension setpoint with near perfect precision, on a longer timescale of several minutes. To decouple the biochemical and mechanical elements of this response, we introduce a mathematical model that is parametrized by fits to the dynamics of the substrate deformation energy. We find that the RhoA response builds up quickly on a timescale of 20 s, but decays slowly on a timescale of 50 s. The larger the cells and the more polarized their actin cytoskeleton, the more substrate deformation energy is generated. RhoA activation starts to saturate if optogenetic pulse length exceeds 50 ms, revealing the intrinsic limits of biochemical activation. Together our results suggest that adherent cells establish tensional homeostasis by the RhoA system, but that the setpoint and the dynamics around it are strongly determined by cell size and the architecture of the actin cytoskeleton, which both are controlled by the extracellular environment.
Assuntos
Actinas , Actomiosina , Actinas/fisiologia , Actomiosina/fisiologia , Citoesqueleto de Actina/fisiologia , Tamanho CelularRESUMO
Flow batteries are a promising energy storage solution. However, the footprint and capital cost need further reduction for flow batteries to be commercially viable. The flow cell, where electron exchange takes place, is a central component of flow batteries. Improving the volumetric power density of the flow cell (W/Lcell) can reduce the size and cost of flow batteries. While significant progress has been made on flow battery redox, electrode, and membrane materials to improve energy density and durability, conventional flow batteries based on the planar cell configuration exhibit a large cell size with multiple bulky accessories such as flow distributors, resulting in low volumetric power density. Here, we introduce a submillimeter bundled microtubular (SBMT) flow battery cell configuration that significantly improves volumetric power density by reducing the membrane-to-membrane distance by almost 100 times and eliminating the bulky flow distributors completely. Using zinc-iodide chemistry as a demonstration, our SBMT cell shows peak charge and discharge power densities of 1,322 W/Lcell and 306.1 W/Lcell, respectively, compared with average charge and discharge power densities of <60 W/Lcell and 45 W/Lcell, respectively, of conventional planar flow battery cells. The battery cycled for more than 220 h corresponding to >2,500 cycles at off-peak conditions. Furthermore, the SBMT cell has been demonstrated to be compatible with zinc-bromide, quinone-bromide, and all-vanadium chemistries. The SBMT flow cell represents a device-level innovation to enhance the volumetric power of flow batteries and potentially reduce the size and cost of the cells and the entire flow battery.
Assuntos
Líquidos Corporais , Brometos , Tamanho Celular , Fibras na Dieta , ZincoRESUMO
Fission yeast undergoes premeiotic nuclear oscillation, which is dependent on microtubules and is driven by cytoplasmic dynein. Although the molecular mechanisms have been analyzed, how a robust oscillation is generated despite the dynamic behaviors of microtubules has yet to be elucidated. Here, we show that the oscillation exhibits cell length-dependent frequency and requires a balance between microtubule and viscous drag forces, as well as proper microtubule dynamics. Comparison of the oscillations observed in living cells with a simulation model based on microtubule dynamic instability reveals that the period of oscillation correlates with cell length. Genetic alterations that reduce cargo size suggest that the nuclear movement depends on viscous drag forces. Deletion of a gene encoding Kinesin-8 inhibits microtubule catastrophe at the cell cortex and results in perturbation of oscillation, indicating that nuclear movement also depends on microtubule dynamic instability. Our findings link numerical parameters from the simulation model with cellular functions required for generating the oscillation and provide a basis for understanding the physical properties of microtubule-dependent nuclear movements.
Assuntos
Schizosaccharomyces , Schizosaccharomyces/metabolismo , Dineínas/genética , Microtúbulos/metabolismo , Núcleo Celular/metabolismo , Tamanho CelularRESUMO
Each bacterial species possesses a specific cell size and morphology, which constitute important and recognizable physical traits. How bacteria maintain their particular cell size and morphology remains an essential question in microbiology. Cyanobacteria are oxygen-evolving photosynthetic prokaryotes. Although monophyletic, these organisms are highly diverse in their cell morphology and cell size. How these physical traits of cyanobacteria are controlled is poorly understood. Here, we report the identification of a two-component signaling system, composed of a histidine kinase CdgK and a response regulator CdgS, involved in cell size regulation in the filamentous, heterocyst-forming cyanobacterium Anabaena sp. PCC 7120. Inactivation of cdgK or cdgS led to reduction of cell length and width with little effect on cell growth capacity. CdgS has a GGDEF domain responsible for the synthesis of the second messenger c-di-GMP. Based on genetic and biochemical studies, we proposed a signaling pathway initiated by CdgK, leading to the phosphorylation of CdgS, and thereby an enhanced enzymatic activity for c-di-GMP synthesis of the latter. The GGDEF domain of CdgS was essential in cell size control, and the reduction of cell size observed in various mutants could be rescued by the expression of a c-di-GMP synthetase from E. coli. These results provided evidence that a minimal threshold of c-di-GMP level was required for maintaining cell size in Anabaena. IMPORTANCE Cyanobacteria are considered the first organisms to produce oxygen on Earth, and their activities shaped the evolution of our ecosystems. Cell size is an important trait fixed early in evolution, with the diversification of micro- and macrocyanobacterial species during the Great Oxidation Event. However, the genetic basis underlying cell size control in cyanobacteria was not understood. Our studies demonstrated that the CdgK-CdgS signaling pathway participates in the control of cell size, and their absence did not affect cell growth. CdgK has multiple domains susceptible to signal input, which are necessary for cell size regulation. This observation suggests that cell size in Anabaena could respond to environmental signals. These studies paved the way for genetic dissection of cell size regulation in cyanobacteria.
Assuntos
Anabaena , Cianobactérias , Escherichia coli/metabolismo , Ecossistema , Transdução de Sinais , Anabaena/genética , Anabaena/metabolismo , Tamanho Celular , Oxigênio/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão GênicaRESUMO
BACKGROUND: Pre-operative anaemia is common and associated with adverse outcomes. We hypothesised that pre-operative anaemia would be evident more than 1 month pre-operatively, and that peri-operative changes in haemoglobin and post-operative outcomes differed between red cell size-based subsets of anaemia. METHODS: A retrospective single-centre cohort study, including all patients 18 years and older undergoing their first surgery at Landspitali between January 2006 and December 2018 with available measurement of haemoglobin (Hb) within 30 days preceding surgery. Clinical data were compared between patients with subgroups of anaemia classified by mean corpuscular volume (MCV) into microcytic (MCV < 80 fl), normocytic (MCV 80-100 fl), and macrocytic (MCV > 100 fl) anaemia. The development of haemoglobin measurements from a nationwide database was plotted from 1 year pre-operatively to 2 years post-operatively. RESULTS: Of 40,979 patients, 10,505 (25.6%) had pre-operative anaemia, of which 1089 (10.4%) had microcytic anaemia, 9243 (88.0%) had normocytic anaemia, and 173 (1.6%) had macrocytic anaemia. Patients within all subgroups of pre-operative anaemia had a higher degree of comorbidity and frailty burden and a low haemoglobin evident for more than 100 days pre-operatively and similar changes post-operatively. Post-operative prolonged recovery of haemoglobin was slower for macrocytic anaemia than other types of anaemia. All groups of patients with anaemia had a higher incidence of 30-day mortality, acute kidney injury, and rate of readmission compared with patients without anaemia. CONCLUSIONS: Pre-operative anaemia is evident long prior to the procedure and its association with worse outcomes is similar regardless of red cell size.
