Chronic liver diseases are a group of diseases in which the liver is subjected to a variety of injuries over a long period of time， resulting in irreversible pathological changes that last longer than 6 months. Emodin （EMO） is a natural anthraquinone derivative derived from Rheum officinale， and its pharmacological effect has been extensively studied， exhibiting a variety of biological properties and involving multiple signaling molecules and pathways. Western medicine or surgical treatment is currently the main treatment regimen for chronic liver diseases， and the advance in treatment is limited by various reasons such as side effects and high costs. Due to its natural origin and efficacy， EMO has unique advantages in the treatment of chronic liver diseases and has now become a research hotspot. This article summarizes the therapeutic effect of EMO on chronic liver diseases and its mechanism， in order to provide a certain scientific basis for the traditional Chinese medicine treatment of chronic liver diseases and the development of drugs in clinical practice.

ObjectiveThis study aims to explore the effect of Feiyanning granules on ferroptosis in lung cancer cells and its regulatory function within the nuclear transcription factor E₂-related factor 2 （Nrf2）/mouse solute carrier family 7 member 11 （SLC7A11）/glutathione peroxidase 4 （GPX4） signaling pathway. MethodsThe cell counting kit-8 （CCK-8） method was used to detect the effect of Feiyanning granule on the proliferation of A549 lung cancer cells. A549 lung cancer cells were categorized into a blank group， a ferroptosis inhibitor-1 （Fer-1） group （10 μmol·L^-1）， a Feiyanning granules （600 mg·L^-1） group， and a Feiyanning granules + Fer-1 group. After 48 hours of intervention， the activity and morphology of the cells were observed. The CCK-8 method was employed to measure cell viability. Biochemical assays were carried out to measure the levels of reactive oxygen species （ROS）， malondialdehyde （MDA）， glutathione （GSH）， and ferrous ions （Fe²⁺） in A549 cells. Western blot was utilized to evaluate the expression levels of Kelch-like ECH-associated protein 1 （Keap1）， Nrf2， SLC7A11， and GPX4 proteins. A549 lung cancer cells were categorized into a blank group and a Feiyanning Granule group （600 mg·L^-1）， and mitochondrial morphology was examined via transmission electron microscopy （TEM）. ResultsAfter the intervention of Feiyaning granules， the proliferation of A549 cells was significantly inhibited in a concentration-dependent manner compared with that in the blank group （P<0.01）. Compared with the blank group， the Feiyanning granules group exerted an significantly inhibitory effect on the viability of lung cancer cells （P<0.01）. Compared with that in the Feiyanning granules group， the cell viability in the Feiyanning granules +Fer-1 group was obviously restored （P<0.05）. Compared with the blank group， the Feiyanning Granule group showed a significant increase in the levels of ROS， MDA， and Fe²⁺ （P<0.01）， a significant decrease in the GSH level （P<0.01）， and facilitated ferroptosis. Compared with the blank group， the Feiyanning granules group showed significantly decreased expression of Nrf2， SLC7A11， and GPX4 proteins and enhanced expression of Keap1 （P<0.01）. Compared with those in the Feiyanning Granule group， the protein levels of Nrf2， SLC7A11， and GPX4 increased significantly （P<0.01）， and the expression of Keap1 decreased significantly in the Feiyanning granules + Fer-1 group （P<0.01）. Compared with the blank group， the Feiyaning granules group exhibited reduced mitochondrial size and increased matrix electron density. ConclusionFeiyanning granules can induce ferroptosis in lung cancer cells， and its underlying mechanism might be associated with the inhibition of the Nrf2/SLC7A11/GPX4 signaling pathway.

ObjectiveTo investigate the effect of quercetin on acute gouty arthritis （GA） in rats by inhibiting the reactive oxygen species （ROS）/NOD-like receptor protein 3 （NLRP3）/interleukin-1β （IL-1β） signaling pathway. MethodsSixty SPF-grade male SD rats were randomized into normal， model， colchicine （0.3 mg·kg^-1）， and low-， medium-， and high-dose （25， 50， 100 mg·kg^-1， respectively） quercetin groups （n=10）. The rats in the dosing groups were administrated with the corresponding drugs （10 mL·kg^-1） by gavage once a day for one week. An equal volume of normal saline was given by gavage to rats in normal and model groups. One hour after drug administration on day 5， an acute GA model was established in other groups except the control group via intra-articular injection of monosodium urate （MSU） suspension into the right posterior ankle joint cavity. The joint swelling and gait were scored at the time points of 6， 12， 24， 48 h after modeling. Histopathological alterations in the ankle joint tissue from each group were assessed by hematoxylin-eosin （HE） staining. Malondialdehyde （MDA）， xanthine oxidase （XOD）， and total superoxide dismutase （T-SOD） assay kits were used to assess the levels of MDA， XOD， and T-SOD in the serum. The levels of tumor interleukin-6 （IL-6）， necrosis factor-α （TNF-α）， and IL-1β in the rat serum， as well as ROS in the ankle joint tissue， were measured by enzyme-linked immunosorbent assay （ELISA）. Western blot was performed to determine the protein levels of NLRP3， thioredoxin-interacting protein （TXNIP）， apoptosis-associated speck-like protein containing a CARD domain （ASC）， precursor cysteinyl aspartate-specific proteinase-1 （pro-Caspase-1）， cleaved Caspase-1 （Caspase-1 p20）， and IL-1β in the ankle joint tissue. Real-time PCR was employed to assess the mRNA levels of TXNIP， NLRP3， ASC， IL-1β， and TNF-α in the ankle joint tissue. ResultsCompared with the normal group， the model group exhibited decreased spontaneous activity， mental fatigue， increased ankle joint swelling and gait scores （P<0.01）， aggravated synovial tissue edema and inflammatory cell infiltration （P<0.01）， elevated levels of XOD， MDA， TNF-α， IL-1β， and IL-6 in the serum and ROS in the joint tissue （P<0.01）， a declined level of T-SOD （P<0.01）， up-regulated protein levels of NLRP3， TXNIP， ASC， pro-Caspase-1， Caspase-1 p20， and IL-1β in the ankle joint tissue （P<0.01）， and up-regulated mRNA levels of NLRP3， TXNIP， ASC， IL-1β， and TNF-α in the ankle joint tissue （P<0.01）. Compared with the model group， the medium- and high-dose quercetin groups showed improved general conditions， decreased gait scores （P<0.05， P<0.01）， reduced joint swelling （P<0.01）， alleviated synovial tissue edema and inflammatory cell infiltration （P<0.05， P<0.01）， lowered levels of XOD， MDA， TNF-α， IL-1β， and IL-6 in the serum and ROS in the joint tissue （P<0.01）， increased levels of T-SOD （P<0.01）， down-regulated protein levels of TXNIP， NLRP3， ASC， pro-Caspase-1， Caspase-1 p20， and IL-1β in the ankle joint tissue （P<0.05， P<0.01）， and down-regulated mRNA levels of TXNIP， NLRP3， ASC， IL-1β， and TNF-α in the ankle joint tissue （P<0.01）. Low-dose quercetin also ameliorated some of the above parameters （P<0.05， P<0.01）. ConclusionQuercetin exerts anti-GA effects by blocking the ROS/NLRP3/IL-1β signaling pathway， downregulating NLRP3 inflammasome activation， and inhibiting the production of pro-inflammatory cytokines including TNF-α， IL-1β， and IL-6.

Chronic obstructive pulmonary disease （COPD） is a chronic respiratory disease that poses a significant threat to global health， exhibiting high morbidity， disability and mortality rate， with its prevention and treatment situation becoming increasingly critical. The pathogenesis of COPD is complex， and the underlying cellular and molecular biological mechanisms remain incompletely elucidated. Programmed cell death （PCD） is the process wherein cells actively undergo demise to maintain internal environmental stability in response to certain signals or specific stimuli. Contemporary medical research indicates that the dysregulation of PCD patterns such as apoptosis， necroptosis， pyroptosis， autophagy， and ferroptosis is closely related to the onset and progression of COPD. Clarifying the molecular mechanisms of PCD in COPD may provide novel perspectives for in-depth understanding and prevention of the disease. Traditional Chinese medicine （TCM） is characterized by holistic regulation. In recent years， extensive research has been conducted in the TCM field focusing on modulating apoptosis， necroptosis， pyroptosis， autophagy， and ferroptosis for the treatment of COPD， yielding remarkable achievements. Therefore， this study systematically explored the molecular mechanism of PCD in COPD and reviewed the potential mechanisms and intervention status of TCM targeting PCD in COPD， aiming to provide insights and references for the clinical prevention， treatment and in-depth research of COPD.

BACKGROUND:Living microecological hydrogels are a hot topic in the field of wound dressing and have received widespread attention.OBJECTIVE:To summarize the basic features and advantages of living microecological hydrogels,review the progress in the application of hydrogels loaded with different living organisms in skin wound repair in recent years.METHODS:The articles published from database inception to 2024 were retrieved from Web of Science,PubMed,CNKI,and WanFang databases with"cell,probiotics,phage,chlorella,algae,living microecological,hydrogel,skin,wound healing,wound repair"as search terms in English and Chinese.The articles for inclusion were screened according to the inclusion and exclusion criteria.Finally,108 articles were included for review.RESULTS AND CONCLUSION:The living microecological hydrogels have good biocompatibility,and the hydrogel can provide a suitable living environment for the loaded organisms,and play a barrier role between the living organisms and the wound to avoid potential threats.Compared with traditional wound dressings,the effect of living microecological hydrogels is sustainable and renewable.Biological regulation can keep the microenvironment at the wound site relatively stable,which can provide suitable conditions for wound healing for a long time and reduce the additional trauma caused by frequent dressing changes.Compared with the direct use of living organisms to promote wound healing,living microecological hydrogels can improve the survival rate of organisms and ensure their biological regulation.Living microecological hydrogels promote wound healing mainly by regulating the"inflammation"and"proliferation"stages in the wound healing process.The existing living microecological hydrogels mainly load organisms such as cells,probiotics,algae,and phages,which give hydrogels with different biological properties,so that they can promote wound healing by releasing substances required for wound healing or improving the wound environment,and have great application potential.To further expand the actual clinical application of living microecological hydrogels,it is necessary to further control the biosafety risks of active organisms in hydrogels in the future,avoid potential biological threats,and research the hydrogel matrix that can better adapt to the complex changes of human skin wounds and can support living organisms.

BACKGROUND:3D-printed bone tissue engineering scaffolds have obvious advantages in the research and clinical treatment of bone defect repair.As one of the important raw materials for 3D printed bone scaffolds,poly-L-lactic acid has a great potential for application in performing bone defect repair,but clinical patients with different bone defect causative factors have different requirements for the comprehensive performance of poly-L-lactic acid bone scaffolds.OBJECTIVE:To summarize and review the development of 3D printing technology and poly-L-lactic acid scaffolds and the design strategies chosen for scaffolds for bone repair in the setting of bone diseases such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis.METHODS:Literature from CNKI,WanFang,PubMed,Science Direct,and Web of Science databases were searched and screened from 1994 to 2024.Search terms were"3D printing,polylactic acid,bone tissue engineering scaffold,osteomyelitis,bone tumor,osteonecrosis,osteoporosis,bone defect"in Chinese and English.The screened 62 articles were systematically summarized and analyzed.RESULTS AND CONCLUSION:(1)Poly-L-lactic acid is considered to be an ideal raw material for artificial bone scaffold design due to its non-toxicity,processability,biocompatibility,and ability to self-degrade in the human environment.The application of 3D printing technology has enabled poly-L-lactic acid bone scaffolds to meet the multilayered and porous structural design requirements of biomimetic artificial bone repair materials,and to optimize the mechanical properties for better bone repair.(2)According to different bone disease microenvironments,timely adjustment of the functional design of poly-L-lactic acid scaffolds is important for the comprehensive osteogenic efficacy of the scaffolds.The article discusses the application of poly-L-lactic acid scaffolds in bone disease environments such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis,and highlights the importance of rationally grasping the timing of bone disease treatment and bone tissue regeneration for bone defects caused by different bone diseases.(3)Although poly-L-lactic acid scaffolds show potential in bone repair,there are still some problems,such as the need to further optimize the structural design of the scaffolds to fit new bone regeneration,enhance the bioactivity of the scaffolds,and take into account other functions(e.g.,antimicrobial,anti-tumor,and anti-osteoporosis)in order to adapt to the needs of bone tissue repair in different pathological environments.

BACKGROUND:The incidence rate of chronic non-specific neck pain is high and the etiology is unknown.Myofascial pain and deep cervical flexor atrophy are the key factors.Extracorporeal shockwave therapy can improve microcirculation,relieve local pain,and delay the degenerative development of the cervical spine,while motion control training can significantly improve neck muscle strength and endurance and reduce neck pain.However,both methods have limited effectiveness when applied individually.OBJECTIVE:To explore the therapeutic efficacy of extracorporeal shock wave intervention combined with motion control training at the upper trapezius muscle on chronic non-specific neck pain.METHODS:Forty-two patients with chronic non-specific neck pain recruited from Shenyang Sport University were randomly divided into three groups:a shock wave group(n=14),in which extracorporeal shockwave intervention at the upper trapezius muscle was given for 10-15 minutes,once a week for 4 weeks;a training group(n=14),in which motion control training was given for 40-50 minutes,three times a week for 4 weeks;and a combination group(n=14),in which extracorporeal shockwave intervention at the upper trapezius muscle combined with motion control training was performed for 4 weeks.Patients were assessed for pain intensity,cervical spine function,upper trapezius muscle thickness,hemodynamic parameters,and serum interleukin 6 and tumor necrosis factor α levels before intervention,1 week and 4 weeks after intervention.RESULTS AND CONCLUSION:(1)Compared with the pre-intervention period,the visual analogue scale scores and neck disability index in the three groups were lower after 1 and 4 weeks of intervention(P＜0.05),and the visual analogue scale scores and neck disability index in the combination group were lower than those of the shock wave group and the training group(P＜0.05).(2)Compared with the pre-intervention period,the upper trapezius thickness increased in the training group and the combination group after 4 weeks of intervention(P＜0.05);the upper trapezius thickness was greater in the combination group than in the shock wave group and the training group after 4 weeks of intervention(P＜0.05).(3)The shock wave group and the combination group had an increase in the peak systolic velocity of the ascending segment of the transverse carotid artery(P＜0.05)and a decrease in the resistance index(P＜0.05)after 1 and 4 weeks of intervention,while the training group showed an increase in the peak systolic velocity of the ascending segment of the transverse carotid artery(P＜0.05)and a decrease in the resistance index(P＜0.05)after 4 weeks of intervention.The peak systolic velocity of the ascending segment of the transverse carotid artery in the combination group was higher(P＜0.05)and the resistance index was lower(P＜0.05)than those in the shockwave group and the training group after 1 and 4 weeks of intervention.(4)Compared with the pre-intervention period,the levels of interleukin 6 and tumor necrosis factor α were reduced in the shock wave and combination groups after 1 and 4 weeks of intervention(P＜0.05),and in the training group after 4 weeks of intervention(P＜0.05).After 1 and 4 weeks of intervention,the levels of interleukin 6 and tumor necrosis factor α were lower in the combination group than in the shock wave group and the training group(P＜0.05).To conclude,extracorporeal shock wave combined with motion control training for chronic non-specific neck pain significantly reduces pain and improves neck function,and the mechanism of action may be to promote the blood flow velocity at the trigger point,reduce blood flow resistance,reduce the serum levels of interleukin 6 and tumor necrosis factor α,and increase the thickness of the upper trapezius muscle.

ObjectiveThe malaria parasites remodel the host erythrocyte structure by exporting parasite proteins that interact with the membrane skeleton proteins of red blood cells (RBCs), facilitating their intracellular survival and pathogenicity. Skeleton-binding protein 1 (SBP1) is a conserved exported protein across Plasmodium species. In Plasmodium falciparum, SBP1 has been reported to interact with erythrocyte membrane skeleton proteins 4.1R and spectrin, while its contribution to erythrocyte remodeling and parasite virulence in Plasmodium berghei (Pb) remains unclear. This study aims to determine whether PbSBP1 associates with the host cytoskeletal protein 4.1R and to investigate its role in the remodeling of host RBCs and the pathogenicity of Plasmodium berghei. MethodsIn Plasmodium berghei, the relationship between PbSBP1 and the erythrocyte cytoskeletal protein 4.1R was examined using co-immunoprecipitation. A Pbsbp1 gene knockout mutant of Plasmodium berghei (Pbsbp1∆) was generated based on the principle of double crossover homologous recombination. The deformability of erythrocytes infected with Pbsbp1∆ parasites was assessed using microfluidic methods. Microchannels with an array of cylindrical pillars were used to detect modifications in infected RBC deformability. The infected RBCs were squashed between the rows and recovered between the columns and the transit velocity (μm/s) of infected RBCs travelling through the microchannel was recorded. The component of the erythrocyte membrane skeleton junctional complex, tropomodulin (TMOD), was fluorescently labeled, and the cytoskeletal network of infected erythrocytes was imaged using super-resolution stochastic optical reconstruction microscopy (STORM) to analyze ultrastructural changes in the cytoskeleton of wild-type (WT) and Pbsbp1∆-infected erythrocytes. Actin-based junctional complexes were displayed as individual clusters by the labeled TMOD in the STORM images, and the cluster densities and distances between adjacent clusters of infected RBCs were calculated. Additionally, rodent malaria models (BALB/c mice) and experimental cerebral malaria models (C57BL/6 mice) were employed to monitor the growth of Pbsbp1∆ and WT parasites during the intraerythrocytic stage and their capacity to induce cerebral malaria in mice. ResultsPbSBP1 may participate in the remodeling of infected erythrocytes through direct or indirect interaction with the erythrocyte cytoskeletal protein 4.1R. Microfluidic assays revealed that the deformability of erythrocytes infected with Pbsbp1∆ parasites was significantly enhanced compared to those infected with WT parasites. STORM imaging further demonstrated that the ultrastructure of the erythrocyte cytoskeleton in Pbsbp1∆-infected cells was altered relative to that in WT-infected erythrocytes. The distances between nearest neighbors of clusters had a tendency to increase while the cluster densities were decreased in Pbsbp1∆-infected RBCs compared to WT-infected RBCs. Subsequent phenotypic analysis indicated that the growth rate of Pbsbp1∆ parasites during the intraerythrocytic stage was significantly slower than that of WT parasites, and their ability to induce cerebral malaria in mice was also attenuated. These findings suggest that PbSBP1 is involved in the remodeling of the erythrocyte membrane skeleton, likely through its direct or indirect interaction with protein 4.1R, thereby regulating the deformability of infected erythrocytes and influencing the pathogenicity of the blood-stage parasites. ConclusionThis study establishes a role for PbSBP1 in host erythrocyte remodeling and parasite virulence, providing new research strategies for the prevention and treatment of malaria.

ObjectiveZheng’s San Qi San (ZSQS) power, a classic traditional Chinese medicine (TCM) formula, is used for treating soft tissue injuries involving muscles, tendons, and ligaments. However, its underlying therapeutic mechanisms remain unclear. This study aimed to screen and identify pharmaceutically active ingredients and their candidate biomolecule targets, and further elucidate the molecular mechanism of ZSQS in the treatment of skeletal muscle injury. MethodsNetwork pharmacology was employed to construct “ZSQS-component-target”, “protein-protein interaction (PPI)” and “active ingredient-core protein-pathway” networks to predict the key active ingredients and potential core targets of ZSQS for skeletal muscle injury. The predicted results were then validated via microarray data from the GEO database. Molecular docking was then performed to assess the binding ability between the screened active ingredients of ZSQS and the candidate core targets. Moreover, liquid chromatography-mass spectrometry (LC-MS) was used for qualitative and quantitative analysis to verify the active components of the drug and ZSQS serum. Finally, an animal model of eccentric exercise-induced skeletal muscle injury and a myotube cell model of oxidative stress-induced injury were established to validate the effects of ZSQS and its interventional effects on the biological functions of critical targets, thereby demonstrating the potential therapeutic mechanism of ZSQS. ResultsAmong the 111 active components identified in ZSQS and their corresponding 204 targets related to the skeletal muscle injury repair process, 14 core targets (including AKT1) and 4 core active components (quercetin, luteolin, kaempferol, and β‑sitosterol) were screened out, while the corresponding metabolites of quercetin, luteolin and kaempferol were detected in the ZSQS serum. Among these targets, 5 candidate genes (IL-6, CASP3, HIF1A, STAT3, and JUN) overlapped with the differential expression screening results with GEO data, and IL-6 was confirmed to be enriched in the PI3K/AKT pathway. Combined with the prediction results of the AKT expression levels, these findings suggest that the phosphorylation level of AKT1 plays a core role in the therapeutic mechanism of ZSQS. Molecular docking analysis further revealed that the PH domain of AKT1 had high binding energy with all 4 core active components, as verified by LC-MS. Finally, animal model studies have shown the promoting effect of ZSQS administration on skeletal muscle injury repair and its possible antioxidant damage mechanism. Cell model studies further demonstrated that ZSQS-containing serum, core active ingredient combination therapy, and quercetin monomer could increase the phosphorylation level of AKT, promote the nuclear translocation of Nrf2, upregulate the expression of downstream antioxidant enzymes (SOD, GPx, and GR), and inhibit the expression of inflammatory factors (IL-6 and TNF-α), thereby alleviating oxidative stress and the inflammatory response. ConclusionZSQS alleviates skeletal muscle injury mainly by activating the AKT/Nrf2 signaling pathway, enhancing cellular antioxidant and anti-inflammatory capabilities. The results of this study provide a scientific basis for the clinical application and modernized development of ZSQS.

ObjectiveThe widespread adoption of portable fundus cameras for primary care and community screening is hindered by limitations in current autofocus(AF) technologies. Image-based methods relying on sharpness evaluation require iterative searches, resulting in slow convergence, while projection-based techniques are susceptible to optical artifacts and calibration errors. To address these challenges, this study introduces a novel AF system based on direct wavefront sensing, designed to deliver simultaneous high speed, high precision, and operational robustness within the compact form factor essential for portable ophthalmic devices. MethodsOur approach fundamentally reimagines the AF process by directly measuring the ocular wavefront aberration. We developed a custom portable fundus camera integrating a miniaturized Shack-Hartmann wavefront sensor (SHWS) into the optical path. An 850 nm laser diode projects a point source onto the retina via oblique illumination to minimize corneal reflections. Light scattered from this spot carries the eye’s refractive error through the imaging optics and is directed to the SHWS, positioned at a plane optically conjugate to the primary color CMOS imaging sensor. A microlens array within the SHWS samples the incident wavefront, generating a pattern of focal spots on a CCD. Real-time centroid analysis of these spots provides a map of local wavefront slopes. These measurements are processed through a singular value decomposition (SVD) algorithm to fit a Zernike polynomial basis set, enabling real-time reconstruction of the wavefront phase. The defocus component (S) is extracted from the second-order Zernike coefficients, providing a direct, quantitative measure of the refractive error in diopters. This value serves as a precise error signal in a closed-loop control system, which commands a voice-coil actuated focusing lens to its null position in a single, deterministic step, eliminating the need for iterative search algorithms. ResultsComprehensive evaluation demonstrated the system’s high performance. Testing on a calibrated model eye (OEMI-7) established a highly linear relationship between the computed defocus S and the focusing lens position across a ±20 Diopter (D) compensation range, achievable within a 5 mm mechanical travel. The system achieved a focusing precision of 0.08 D, corresponding to an 18-fold improvement over a conventional projection spot-size method tested under identical conditions. The total focus acquisition time, encompassing wavefront measurement, computation, and lens actuation, averaged under 0.5 s. Clinical validation with 25 human volunteers (50 eyes, refractive range -15 D to +10 D) confirmed practical efficacy. The wavefront-sensing AF succeeded in 92% of attempts with a mean time of 0.5 s, substantially outperforming a projection-based benchmark which achieved only a 32% success rate with an average time of 4.25 s. The system provided instantaneous directional guidance and maintained stability during minor ocular movements. Objective assessment of image quality, via amplitude contrast of retinal vasculature, showed consistent and significant enhancement following AF correction across the entire tested diopter range. ConclusionThis work successfully implements and validates a direct wavefront-sensing autofocus paradigm for portable fundus cameras. By directly quantifying and compensating for the optical defocus aberration, this method bypasses the fundamental limitations of image-processing and projection-based techniques, enabling rapid, precise, and deterministic diopter compensation. The developed system delivers an exceptional combination of a wide operational range (±20 D), high accuracy (0.08 D), fast convergence (0.5 s), and a compact physical footprint. This technology provides a practical and high-performance focusing solution capable of enhancing the reliability, throughput, and diagnostic utility of portable retinal imaging in large-scale screening applications. Future efforts will be directed towards system cost optimization and performance adaptation for diverse ocular conditions.