Medium Stress Research Articles

Reflection and transmission of plane waves in stressed media with an imperfectly bonded interface

SUMMARY The reflection and transmission of elastic waves are of great significance for predicting reservoir physical properties, interpreting seismic data and detecting crustal structures. Most studies only consider the initial vertical stress state when studying the reflection and transmission of elastic waves at imperfectly bonded interfaces, but few studies consider the influence of initial stress on boundary conditions. Moreover, the effect of initial stress on the energy distribution of elastic waves at imperfectly bonded interfaces has rarely been investigated. We propose a unified method to calculate the energy reflection and transmission coefficients for different incident waves at welded or imperfectly bonded interfaces in stressed media. The effects of initial stress on the equation of motion, the elastic properties of the medium and the boundary conditions at the interface are considered. The elastic properties of rocks under initial stress are described by acoustoelasticity theory. In addition, we define a new stress tensor to modify the linear-slip model for describing boundary conditions at the imperfectly bonded interface in the presence of initial stress. Numerical results show that the energy reflection and transmission coefficients at the non-welded interface in stressed media depend on the elastic properties of the incident and transmitted media, the initial stress, the type and magnitude of the interfacial compliance and the frequency and propagation direction of the incident wave. The initial vertical and horizontal stresses dominate the reflection and transmission coefficients at small and large angles, respectively. The discontinuity in displacement across the imperfectly bonded boundary results in the frequency dependence of the reflection and transmission coefficients. Imperfect bonding enhances P-wave and SV-wave energy reflection and weakens P-wave energy transmission. However, imperfect bonding can enhance the energy transmission of the SV wave for the imperfectly bonded interface with high contrast between tangential and normal compliance and a resonance peak appears at a specific frequency. We also notice that imperfectly bonded interfaces with interfacial compliance less than $1.0 \times {10}^{ - 11}$ m Pa−1 can be regarded as welded interfaces in the seismic frequency band (lower than 100 Hz). In addition, the initial stress greatly influences the reflection coefficients at high frequencies and the transmission coefficients at low frequencies. The initial vertical stress can reduce the energy transmission of SV waves at imperfectly bonded interfaces. In contrast, the initial horizontal stress can significantly increase the energy transmission of low-frequency SV waves and may lead to the disappearance of the resonant peak in the transmission coefficients.

Ab initio calculations of third-order elastic coefficients

Third-order elasticity (TOE) theory predicts strain-induced changes in second-order elastic coefficients (SOECs) and can model elastic wave propagation in stressed media. Although third-order elastic tensors have been determined based on first principles in previous studies, their current definition is based on an expansion of thermodynamic energy in terms of the Lagrangian strain near the natural, or zero pressure, reference state. This definition is inconvenient for predictions of SOECs under significant initial stresses. Therefore, when TOE theory is necessary to study the strain dependence of elasticity, the seismological community has resorted to an empirical version of the theory. This study reviews the thermodynamic definition of the third-order elastic tensor and proposes using an ``effective'' third-order elastic tensor. An explicit expression for the effective third-order elastic tensor is given and verified. We extend the ab initio approach to calculate third-order elastic tensors under finite pressure and apply it to two cubic systems, namely, NaCl and MgO. As applications and validations, we evaluate (a) strain-induced changes in SOECs and (b) pressure derivatives of SOECs based on ab initio calculations. Good agreement between third-order elasticity-based predictions and numerically calculated values confirms the validity of our theory.

Study of Mechanical Stresses in Thin-Walled Pressure Vessels Using Ultrasonic Methods

This paper presents an experimental study of the propagation of ultrasonic Rayleigh waves in the walls of a pressure vessel in order to estimate mechanical stresses. The ability to assess stresses using ultrasonic methods is based on the acoustoelastic effect, ie. the change of velocity of propagation of the ultrasonic Rayleigh waves (URW) in stressed media. The experiments were carried out using a hydraulic test conducted in a pressure vessel. Measurements of the travel time of the URW over the walls of the vessel in the axial and circumferential direction were carried out with a pressure change of up to 7 MPa at a constant temperature. Relations between the relative changes in the travel time of waves and the change in pressure were found. The influence of temperature and thermal stresses on the velocities of ultrasonic waves was not taken account. The conducted experiments confirmed the finding that the difference in the relative changes in the travel time of URW in circumferential and axial directions changes linearly with the change in the pressure in the vessel.

In-vitro propagation and phytochemical profiling of a highly medicinal and endemic plant species of the Himalayan region (Saussurea costus)

Efficient protocols for callus induction and micro propagation of Saussurea costus (Falc.) Lipsch were developed and phytochemical diversity of wild and in-vitro propagated material was investigated. Brown and red compact callus was formed with frequency of 80–95%, 78–90%, 70–95% and 65–80% from seeds, leaf, petiole and root explants, respectively. MS media supplemented with BAP (2.0 mgL−1), NAA (1.0 mgL−1) and GA3 (0.25 mgL−1) best suited for multiple shoot buds initiation (82%), while maximum shoot length was formed on media with BAP (1.5 mgL−1), NAA (0.25 mgL−1) and Kinetin (0.5 mgL−1). Full strength media with IAA (0.5 mgL−1) along with IBA (0.5 mgL−1) resulted in early roots initiation. Similarly, maximum rooting (87.57%) and lateral roots formation (up to 6.76) was recorded on full strength media supplemented with BAP (0.5 mgL−1), IAA (0.5 mgL−1) and IBA (0.5 mgL−1). Survival rate of acclimatized plantlets in autoclaved garden soil, farmyard soil, and sand (2:1:1) was 87%. Phytochemical analysis revealed variations in biochemical contents i.e. maximum sugar (808.32 µM/ml), proline (48.14 mg/g), ascorbic acid (373.801 mM/g) and phenolic compounds (642.72 mgL−1) were recorded from callus cultured on different stress media. Nonetheless, highest flavenoids (59.892 mg/g) and anthocyanin contents (32.39 mg/kg) were observed in in-vitro propagated plants. GC–MS analysis of the callus ethyl acetate extracts revealed 24 different phytochemicals. The variability in secondary metabolites of both wild and propagated plants/callus is reported for the first time for this species. This study may provide a baseline for the conservation and sustainable utilization of S. costus with implications for isolation of unique and pharmacologically active compounds from callus or regenerated plantlets.

Therapeutic Potential of Mesenchymal Stem Cells in a Pre-Clinical Model of Diabetic Kidney Disease and Obesity.

Diabetic kidney disease (DKD) is a worldwide microvascular complication of type 2 diabetes mellitus (T2DM). From several pathological mechanisms involved in T2DM-DKD, we focused on mitochondria damage induced by hyperglycemia-driven reactive species oxygen (ROS) accumulation and verified whether mesenchymal stem cells (MSCs) anti-oxidative, anti-apoptotic, autophagy modulation, and pro-mitochondria homeostasis therapeutic potential curtailed T2DM-DKD progression. For that purpose, we grew immortalized glomerular mesangial cells (GMCs) in hyper glucose media containing hydrogen peroxide. MSCs prevented these cells from apoptosis-induced cell death, ROS accumulation, and mitochondria membrane potential impairment. Additionally, MSCs recovered GMCs’ biogenesis and mitophagy-related gene expression that were downregulated by stress media. In BTBRob/ob mice, a robust model of T2DM-DKD and obesity, MSC therapy (1 × 106 cells, two doses 4-weeks apart, intra-peritoneal route) led to functional and structural kidney improvement in a time-dependent manner. Therefore, MSC-treated animals exhibited lower levels of urinary albumin-to-creatinine ratio, less mesangial expansion, higher number of podocytes, up-regulation of mitochondria-related survival genes, a decrease in autophagy hyper-activation, and a potential decrease in cleaved-caspase 3 expression. Collectively, these novel findings have important implications for the advancement of cell therapy and provide insights into cellular and molecular mechanisms of MSC-based therapy in T2DM-DKD setting.

Effects of Biotin on survival, ensheathment, and ATP production by oligodendrocyte lineage cells in vitro.

Mechanisms implicated in disease progression in multiple sclerosis include continued oligodendrocyte (OL)/myelin injury and failure of myelin repair. Underlying causes include metabolic stress with resultant energy deficiency. Biotin is a cofactor for carboxylases involved in ATP production that impact myelin production by promoting fatty acid synthesis. Here, we investigate the effects of high dose Biotin (MD1003) on the functional properties of post-natal rat derived oligodendrocyte progenitor cells (OPCs). A2B5 positive OPCs were assessed using an in vitro injury assay, culturing cells in either DFM (DMEM/F12+N1) or "stress media" (no glucose (NG)-DMEM), with Biotin added over a range from 2.5 to 250 μg/ml, and cell viability determined after 24 hrs. Biotin reduced the increase in OPC cell death in the NG condition. In nanofiber myelination assays, biotin increased the percentage of ensheathing cells, the number of ensheathed segments per cell, and length of ensheathed segments. In dispersed cell culture, Biotin also significantly increased ATP production, assessed using a Seahorse bio-analyzer. For most assays, the positive effects of Biotin were observed at the higher end of the dose-response analysis. We conclude that Biotin, in vitro, protects OL lineage cells from metabolic injury, enhances myelin-like ensheathment, and is associated with increased ATP production.

Spray-drying process as a suitable tool for the formulation of Bacillus velezensis RC218, a proved biocontrol agent to reduce Fusarium Head Blight and deoxynivalenol accumulation in wheat

ABSTRACTFusarium Head Blight is a worldwide disease affecting small grain cereals. Among the different management strategies, biocontrol is an environmentally-friendly approach to counteract this disease. Biocontrol effectiveness of Bacillus velezensis RC218 was demonstrated under greenhouse and field trials, but formulation conditions were not specified. Bacillus velezensis RC218 was grown on a sucrose and yeast extract basal medium (control) and in the same medium osmotically modified with NaCl to reach a 0.98 and 0.97 aW for physiological improvement. Before spray-drying process, MgSO4 (10% w/v) was added to the cells as a protective agent. Water, phosphate buffer and skimmed milk (10% w/v) were evaluated as rehydration agents. Shelf-life of the product was evaluated during 180 days at different storage temperatures (4°C and 25°C). The viability of control cells after the drying process decreased from 3.2 × 108 to 1.12 × 106 colony forming units per gram of dry weight (cfu/g dry w), meanwhile cells grown in stressed media retained a viability of 5 × 106 cfu/g dry w. Water and phosphate buffer resulted in the best rehydration agents. After 180 days, the best storing condition was observed for cells grown in NaCl at 0.97 aW and stored at 4°C, =4 × 106 cfu/g dry w, 80% of the initial viability. Spray drying was found to be a good method for conserving long term shelf-life of B. velezensis RC218 dried cells.

Visualizing the blast-induced stress wave and blasting gas action effects using digital image correlation

Rock blasting fragmentation is a result of the combined action of a blast-induced stress wave and the blasting gas. Incorporating high-speed camera technology, an experimental system of high-speed digital image correlation is established and is extended to blasting research. Using two-dimensional model experiments, the action effects of a blast-induced stress wave and blasting gas on the formation of the crush and fracture zones are studied, and the blasting attenuation law in the elastic vibration zone is also analyzed. The results show that the blast-induced stress wave and the blasting gas are respectively the main driving forces for the crush zone and fracture zone formation. The effect of the blasting gas reduces the crush zone size and increases the crack propagation length as well as the medium's stress peak. In the elastic vibration zone, the radial and circumferential stress of the medium are both first compressive and then tensile. The radial and circumferential stress are respectively dominated by compressive and tensile stress, and the radial stress decays more rapidly. With increased distance from the borehole, the medium's stress state gradually turns from mainly circumferential tensile to mainly radial compressive. In addition, in decoupled charge blasting, the stress attenuation index shows a trend of initially increasing and then decreasing with the increase of the decoupling coefficient. Compared with the attenuation of the circumferential stress, the air filling in the decoupled charge blasting more significantly affects the radial stress attenuation.

OsPUB75, an Armadillo/U-box protein interacts with GSK3 kinase and functions as negative regulator of abiotic stress responses

It has become increasingly evident that the protein degradation mediated by E3 ligases is a crucial cellular process that regulates both biotic and abiotic stresses in plants. Previously, we have reported the microarray expression analysis of ARM/U-box proteins during abiotic stress conditions. In this study, we have performed a detailed functional analysis of OsPUB75/ARM, which is transcriptionally repressed during stress conditions. OsPUB75/ARM is a cytosolic RING-type E3 ubiquitin (Ub) ligase that negatively regulates drought and salinity induced osmotic stress response in Arabidopsis. The phenotypic analysis of OsPUB75/ARM-OE showed inhibition of growth due to enhanced ROS production during salinity and mannitol induced oxidative stress conditions. Yeast two-hybrid screening using OsPUB75/ARM as bait identified OsSK41 (Shaggy-like kinase 41) as its target, which belongs to the Glycogen Synthase kinase 3 (GSK3) family. A specific interaction between OsPUB75/ARM and OsSK41 and auto-ubiquitination activity of OsPUB75/ARM were demonstrated in planta and in vitro. The subcellular localization and protein interaction by BiFC assay in Nicotiana benthamiana showed that OsPUB75/ARM and OsSK41 co-localize to the cytosolic spherical body, which lies in close proximity to the plasma membrane. The sensitivity of OsPUB75/ARM-OE lines on stress media indicates that this protein might be involved in the negative regulation of antioxidant system, which sets the redox-status of the cell upon activation by OsSK41. Collectively, our results suggest that OsPUB75/ARM is an important negative regulator of abiotic stress responses in Arabidopsis.

An embedded couple stress micro-/nano-obstacle with micro-inertia incident upon by SH-waves

An elliptic micro-/nano-obstacle bonded to an infinite body incident upon by SH-waves, where both domains are couple stress media with micro-inertia, is of major concern. The formulation of this problem in the mathematical framework of couple stress elasticity with micro-inertia leads to angular and radial Mathieu differential equations which are solved analytically. These equations carry two characteristic lengths which are peculiar to the discrete nature of each domain enabling the capture of size effect, dispersion phenomenon, as well as the enhancement of the accuracy of the results. For verification, the ratio of the semi-axis of the elliptic obstacle is set equal to 1, and the result associated with the circular fiber which was previously considered by Shodja et al. (Int J Solids Struct 58:73–90, 2015) is recovered. The distribution of the induced stresses along an elliptic obstacle boundary, depending on its major-to-minor semi-axis ratio (e.g., 2), can significantly differ from that pertinent to a circular one.

Negative and positive perceptions of media sources and PTSD symptoms among older adults exposed to missile attacks

This study examined the relationship between negative and positive perceptions of media sources during wartime and posttraumatic stress disorder (PTSD) symptoms among older adults with varying levels of physical functioning.We examined perception of media sources as stressful or helpful, PTSD symptoms and physical functioning among 170 older adults (mean age=66.87) four months after the 2014 Israel-Gaza conflict.After controlling for previous PTSD symptoms, the number of media sources perceived as stressful was positively related to PTSD symptoms, particularly among respondents with low physical functioning. The number of helpful media sources was unrelated to PTSD symptoms.The findings suggest that stressful media is especially maladaptive for older adults with low physical functioning, who are at a higher risk of being homebound. Moreover, favorable perception of media was not beneficial for older adults in the specific context of PTSD symptoms. Helping older adults regulate their perceptions regarding the media may restrict their negative outcomes.

Degradation pathways study of the natriuretic and β-adrenoceptor antagonist tienoxolol using liquid chromatography–electrospray ionization multistage mass spectrometry

Tienoxolol is a pharmacologically active molecule designed with the functional groups ketothiophene, alkyl benzoate and arylpropanolamine so as to combine a diuretic and a β-adrenoreceptor antagonist into a single molecule. Its degradation products generated in several stress media have been determined by high-pressure liquid chromatography (HPLC) coupled to a hybrid mass spectrometer with a triple quadrupole-linear trap. A Polaris® column with a C18-A stationary phase and a linear gradient mobile phase composed of a mixture of trifluoroacetic acid 1% (v/v) and acetonitrile allowed for optimal separation. Structural elucidation of the degradation products has been based on MS/MS techniques, by comparing their fragmentation patterns to the precursor's data. Up to seven degradation products of the active ingredient, resulting from hydrolysis, oxidation, dehydration and transamidation have been identified, covering a range of possible degradation pathways for derivatives with such functional groups. Kinetics have been studied to assess the molecule's shelf life and to identify the most important degradation factor.

Identification of the specified impurities of silver sulfadiazine using a screening of degradation products in different stress physico-chemical media

Determination of silver sulfadiazine degradation products in several stress media was carried out by high pressure liquid chromatography (HPLC) with diode array detector (DAD) and hybrid mass spectrometer triple quadrupole-linear trap. The optimal chromatographic method used a Hypercarb column with a stationary phase 100% carbon, a mobile phase composed by a mixture 45:55 formic acid 1% solution and acetonitrile and detection at 275nm. Structure elucidation was carried out on the mass spectrometry system using same chromatographic conditions and based on MS/MS techniques. Under these conditions up to 9 possible impurities were demonstrated to be degradation products respecting silver sulfadiazine evolution under different stress conditions: temperature, acid, basic, oxidation, reduction and catalyzed photodegradation. Sulfacetamide, sulfanilic acid (4-aminobenzenesulfonic acid), aniline, pyrimidin-2-amine, 4-aminobenzenesulfonamide, 4-methylidenesulfanilaniline, 4-aminophenol, 4-amino-n-methyl benzenesulfonamide and benzenesulfonic acid were identified by mass spectrometry in order to cover the possible degradation paths of silver sulfadiazine. Kinetics were also evaluated to obtain the prediction of shelf life of the substance. The linearity domain for the method was between 0.0005mg/ml and 0.25mg/ml for each compound. Recovery factors in accuracy determination were between 95 and 105% relative to target concentrations of silver sulfadiazine and the quantitation limit was 0.00025mg/ml.

Effect of Water Chemistry on Growth Performance of Some Freshwater Fish Exposed to Some Heavy Metals Mixture

This studied was conducted to evaluate the correlation between water physico-chemical parameters and the growth performance of two fish species viz . Ctenopharyngodon idella and Hypophthalmichthys molitrix . Fish were exposed to sub-lethal (1/3rd of LC 50 ) concentrations of metal mixture under controlled laboratory condition for 90 days. All physical and chemical parameters were determined twice a day through out experimental period. Water pH (7.25), total hardness (225 mg/L as CaCO 3 ) and temperature (30℃) of water were kept constant during each trail for fish. Correlation and regression analyses were computed to find-out relationships among various parameters defined for this study. During growth periods of 90 day, both fish species were monitored weekly for their increase in average wet weights (g), fork and total lengths (mm), specific growth rate, condition factor, feed intakes and feed conversion efficiency. No fish species showed any mortality during the entire period of growth trails under chronic stress of metal mixture. The relationships among all phyisco-chemical and growth parameters were investigated after 90-day growth trail. The obtained results showed that physico-chemistry of metal mixture stressed media exerted significant effect on both fish growth. Significantly better feed intake increased the ammonia production and excretion by both fish resulting fish weight increments positively non-significant correlated with contents of stressed media and also cause significant effect on growth of fish. Total ammonia content of test media exhibited significantly direct relationship with dissolve oxygen. However, calcium showed significantly inverse correlation with magnesium by the both fish species. It is also concluded that not only toxicity of metals but also the deficiency of consumed oxygen cause frequent deaths of fish in water due to biological decomposition of heavy metals.

The relationships between uniaxial stress and reflection coefficients

The direct relationships between uniaxial stress and reflection coefficients are presented for an interface between an isotropic overburden and an anisotropic medium induced by horizontal uniaxial stress based on the known weak-anisotropy approximations for the anisotropic parameters in stressed media and the reflection coefficients in anisotropic media. The approximate reflection coefficients in stressed media are given based on the known weak-anisotropy approximations and are used to obtain the simple relationships between uniaxial stress and reflection coefficients. The approximate anisotropic parameters and S- and P-wave reflection coefficients are compared with the exact ones in stressed media by numerical calculations, and the direct relationships are used to estimate the magnitude of stress. The results show that (i) the positive and negative signs of the values of anisotropic parameters ɛ(v) and γ can be used as an indicator of horizontal uniaxial stress-induced anisotropy, (ii) under the weak anisotropy induced by horizontal uniaxial stresses, magnitude of stress can be estimated by S-wave reflection coefficients at small incidence angle and (iii) the study of the azimuthal variation in the P-wave reflection coefficients can help to find the orientation of the principal stresses. This paper offers a new method to analyse the source of anisotropy and estimate stresses.

Influences of different stress media and high light intensities on accumulation of astaxanthin in the green alga Haematococcus pluvialis

Haematococcus pluvialis Flotow is used in the aquaculture, pharmaceutical and cosmetic industries. The aim of this study was to compare the effect of various stress media and high light intensities on astaxanthin accumulation. The experimental design was achieved by four different stress media and two different light intensities for 14 days of induction period. The astaxanthin concentrations of 29.62 mg g(-1) and 30.07 mg g(-1) were obtained in distilled water with CO(2) and N-free medium, respectively, with no significant difference between them at 546 micromol photons m(-2)s(-1). Because of the morphological changes of H. pluvialis, microscopic observation was considered during the induction period to facilitate the selection of stress medium. It was clear that the rate of astaxanthin accumulation was much faster in distilled water with the addition of CO(2). The main point is that, this medium is more economical than others, especially for the large-scale productions.

Effective elastic constants in acoustoelasticity

In the context of studies on ultrasonic wave propagation in stressed media (acoustoelasticity), a classic formalism can be considered (second order) by replacing the elastic constants with effective elastic constants (EECs) for which the influence of stress is taken into account. Up until now, this formalism presented some limitations since certain EEC split, which meant the authors have to consider the pseudo-orthotropy or pseudohexagonality to describe the symmetry of the materials with respect to ultrasonic wave propagation. In this letter, the possibility of avoiding these degenerations by carrying out the developments using the natural coordinates of the material is shown.

Effects of SAPK/JNK inhibitors on preimplantation mouse embryo development are influenced greatly by the amount of stress induced by the media

Stress-activated protein kinase/c-Jun kinase (SAPK/JNK) is thought to be necessary for preimplantation embryonic development (Maekawa et al., 2005). However, media increases SAPK/JNK phosphorylation and these levels negatively correlate with embryonic development (Wang et al., 2005). Culture-induced stress could confuse analysis of the role of SAPK in development. In this study, we tested how SAPK/JNK inhibitors influence embryonic development in optimal and non-optimal media and define the contribution of cell survival and proliferation to the embryonic response to these media. SAPK/JNK inhibitors retard embryonic development in suboptimal Ham's F10, but improve development in optimal potassium (K+) simplex optimized media (KSOM) +AA. In KSOM + amino acids (KSOM+AA), two SAPK/JNK inhibitors increase the rate of cavitation and hatching. These data suggest that (i) SAPK/JNK mediates the response to culture stress, not normal preimplantation embryonic development and (ii) SAPK/JNK inhibitors may be useful in ameliorating embryo stress caused by culture. To define the effects of media, we assayed the contribution of cell survival and proliferation and the differences in total cell number of cultured embryos. Embryos cultured from E3.5+24 h in the suboptimal medium (Ham's F10) induced significant but small increases in TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labelling (TUNEL) positive cells. Bromodeoxyuridine (BrdU) incorporation in suboptimal Ham's F10 was significantly lower than in optimal KSOM+AA, suggesting that cell cycle arrest also contributes to slower increase in cell number in stressful media. This is the first report where TUNEL and BrdU were both assayed to define the relative contribution of cell cycle/S phase commitment and apoptosis to lessened cell number increase during embryo culture.

A new approach to inversion of surface wave dispersion relation for determination of depth distribution of non-uniform stresses in elastic materials

Ultrasonic surface (Rayleigh) waves become dispersive when propagating on non-uniformly stressed media. In light of this, the Acoustoelastic effect on their propagation in deformed but initially isotropic materials has been investigated in the past, in order to determine the surface stress and gradients of stress with depth. An energy perturbation approach considerably reduces the complexity in the treatment of the Acoustoelastic effect and inversion of the perturbation relation offers an advantageous route to obtaining the stress gradients. This paper presents a new mechanism for effecting this inversion, which tries to overcome the effects of the ill-posed nature of the problem. Preliminary simulation results for commonly occurring stress profiles are presented.

Isolation and functional analysis of a gene, tcsB, encoding a transmembrane hybrid-type histidine kinase from Aspergillus nidulans.

We cloned and characterized a novel Aspergillus nidulans histidine kinase gene, tcsB, encoding a membrane-type two-component signaling protein homologous to the yeast osmosensor synthetic lethal N-end rule protein 1 (SLN1), which transmits signals through the high-osmolarity glycerol response 1 (HOG1) mitogen-activated protein kinase (MAPK) cascade in yeast cells in response to environmental osmotic stimuli. From an A. nidulans cDNA library, we isolated a positive clone containing a 3,210-bp open reading frame that encoded a putative protein consisting of 1,070 amino acids. The predicted tcsB protein (TcsB) has two probable transmembrane regions in its N-terminal half and has a high degree of structural similarity to yeast Sln1p, a transmembrane hybrid-type histidine kinase. Overexpression of the tcsB cDNA suppressed the lethality of a temperature-sensitive osmosensing-defective sln1-ts yeast mutant. However, tcsB cDNAs in which the conserved phosphorylation site His(552) residue or the phosphorelay site Asp(989) residue had been replaced failed to complement the sln1-ts mutant. In addition, introduction of the tcsB cDNA into an sln1delta sho1delta yeast double mutant, which lacked two osmosensors, suppressed lethality in high-salinity media and activated the HOG1 MAPK. These results imply that TcsB functions as an osmosensor histidine kinase. We constructed an A. nidulans strain lacking the tcsB gene (tcsBdelta) and examined its phenotype. However, unexpectedly, the tcsBdelta strain did not exhibit a detectable phenotype for either hyphal development or morphology on standard or stress media. Our results suggest that A. nidulans has more complex and robust osmoregulatory systems than the yeast SLN1-HOG1 MAPK cascade.