Background The pathogenesis of silicosis has not been fully elucidated, and microRNAs (miRNA) may be involved in the occurrence and development of silicosis. Objective To investigate the effect of miR-204-3p inhibitor on the epithelial-mesenchymal transition (EMT) process and silicosis fibrosis in silicon dioxide dust-induced alveolar epithelial cells. Methods A co-culture model of macrophages and epithelial cells was established using a Transwell chamber. NR8383 macrophages were seeded into the upper chamber of the Transwell, and RLE-6TN cells were seeded into the lower chamber. After 24 h of culture, the medium in the lower chamber was discarded, washed three times with phosphate-buffered saline (PBS), and replaced with serum-free medium. The cells were divided into four groups: control group, silicosis group, miRNA NC group, and miR-204-3p inhibitor group. The lower chamber was transfected with miRNA NC for the miRNA NC group or the miR-204-3p inhibitor for the miR-204-3p inhibitor group. The lower chambers of the remaining two groups were added by equal amounts of serum-free medium. After 24 h, except for the control group that received an equal volume of serum-free medium, the upper chambers of the remaining three groups were treated with 800 μg·mL⁻¹ silicon dioxide dust. Morphological changes in each group were observed under a microscope. The mRNA and protein expression levels of EMT-related factors, including α-smooth muscle actin (α-SMA), Vimentin, N-Cadherin, and E-Cadherin, were detected by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and Western blot. The mRNA and protein expression levels of fibrosis-related factors, including Collagen I, Collagen III, and Fibronectin, were also assessed by RT-qPCR and Western blot. The fluorescence expression intensities of α-SMA, N-Cadherin, and E-Cadherin were evaluated by immunofluorescence. Results The morphological observation revealed that RLE-6TN cells in the control group exhibited a regular oval shape. After treatment with silicon dioxide, the cells predominantly displayed a long spindle shape. Following the intervention with the miR-204-3p inhibitor, the number of long spindle-shaped cells increased, and the intercellular gaps widened. The RT-qPCR results showed that, compared with the control group, the silicosis group exhibited significantly higher relative mRNA expression levels of EMT-related markers (α-SMA, Vimentin, and N-Cadherin) (P<0.05), while the relative mRNA expression level of E-Cadherin was significantly reduced (P<0.05); the relative mRNA expression levels of fibrosis-related markers (Collagen I, Collagen III, and Fibronectin) were also significantly elevated (P<0.05). Compared with the miRNA NC group, the miR-204-3p inhibitor group showed significantly increased relative mRNA expression levels of α-SMA, Vimentin, and N-Cadherin (P<0.05), decreased E-Cadherin mPNA expression (P<0.05), and elevated mPNA expression of Collagen I, Collagen III, and Fibronectin (P<0.05). The Western blot analysis indicated that, compared with the control group, the silicosis group had significantly higher protein expression levels of α-SMA, Vimentin, and N-Cadherin (P<0.05), lower E-Cadherin protein expression (P<0.05), and increased protein expression of Collagen I, Collagen III, and Fibronectin (P<0.05). Compared with the miRNA NC group, the miR-204-3p inhibitor group exhibited significantly elevated protein expression levels of α-SMA, Vimentin, and N-Cadherin (P<0.05), reduced E-Cadherin expression (P<0.05), and increased protein expression of Collagen I, Collagen III, and Fibronectin (P<0.05). The immunofluorescence analysis demonstrated that, compared with the control group, the silicosis group showed enhanced fluorescence intensities of α-SMA and N-Cadherin and reduced fluorescence intensity of E-Cadherin. Compared with the miRNA NC group, the miR-204-3p inhibitor group exhibited increased fluorescence intensities of α-SMA and N-Cadherin and decreased fluorescence intensity of E-Cadherin. Conclusion The miR-204-3p inhibitor may exacerbate the EMT process and silicosis fibrosis in silicon dioxide-induced RLE-6TN cells. miR-204-3p plays a negative regulatory role in silicosis fibrosis.

Objective To explore the role of miR-204-3p in silicosis and to elucidate the mechanism by which it affects silicosis fibers by regulating silica dust-induced alveolar epithelial-mesenchymal transition(EMT)in rats.Methods Forty SD rats were divided randomly into 4 groups:Control,Silicosis,AAV-Control,and AAV-miR-204-3p groups.The pathology of lung tissue damage was detected by hematoxylin and eosin(HE)and Masson staining.Relative expression levels of miR-204-3p and EMT marker genes in lung tissues from rats in each group were analyzed by real-time fluorescence reverse transcription quantitative PCR(RT-qPCR),and protein expression levels of EMT-related markers in lung tissues were detected by Western blot.Results The alveolar structure was damaged,the lung septa showed interstitial fibrosis,and expression levels of mesenchymal markers were elevated in the Silicosis group compared with the Control group(P＜0.05,P＜0.01,P＜0.001).The alveolar structure was more complete,the EMT process was alleviated,fibrosis was improved,and mesenchymal marker expression was reduced in the AAV-miR-204-3p group compared with the AAV-Control group(P＜0.05,P＜0.01,P＜0.001).Conclusions Free silica dust induces EMT in rat lung tissue.Overexpression of miR-204-3p can attenuate the EMT process induced by free silica dust in rats,and may thus affect silicosis fibrosis.

Objective To explore the role of miR-204-3p in silicosis and to elucidate the mechanism by which it affects silicosis fibers by regulating silica dust-induced alveolar epithelial-mesenchymal transition(EMT)in rats.Methods Forty SD rats were divided randomly into 4 groups:Control,Silicosis,AAV-Control,and AAV-miR-204-3p groups.The pathology of lung tissue damage was detected by hematoxylin and eosin(HE)and Masson staining.Relative expression levels of miR-204-3p and EMT marker genes in lung tissues from rats in each group were analyzed by real-time fluorescence reverse transcription quantitative PCR(RT-qPCR),and protein expression levels of EMT-related markers in lung tissues were detected by Western blot.Results The alveolar structure was damaged,the lung septa showed interstitial fibrosis,and expression levels of mesenchymal markers were elevated in the Silicosis group compared with the Control group(P＜0.05,P＜0.01,P＜0.001).The alveolar structure was more complete,the EMT process was alleviated,fibrosis was improved,and mesenchymal marker expression was reduced in the AAV-miR-204-3p group compared with the AAV-Control group(P＜0.05,P＜0.01,P＜0.001).Conclusions Free silica dust induces EMT in rat lung tissue.Overexpression of miR-204-3p can attenuate the EMT process induced by free silica dust in rats,and may thus affect silicosis fibrosis.

ObjectiveTo explore the effects of different dosage forms of Kaixinsan （KXS） on the morphology and function of mitochondria in rat models of Alzheimer's disease （AD） and potential mechanisms of action. MethodsMale SD rats were randomly assigned to a sham group， model group， treatment groups receiving KXS decoction， powders， and granules （3.08 g·kg^-1）， as well as donepezil group （0.51×10^-3 g·kg^-1）， with 10 rats in each group. AD model was created using intracerebroventricular injection of streptozocin （STZ）. After 30 days of administration， behavioral assessments were conducted， and mitochondrial morphology was observed using transmission electron microscopy. Mitochondrial respiratory chain complex content was measured via enzyme-linked immunosorbent assay （ELISA）. Changes in mitochondrial membrane potential were measured via JC-1 staining， and superoxide dismutase （SOD） activity and reactive oxygen species （ROS） levels were measured via biochemical assays. The mRNA expression of adenosine 5'-monophosphate-activated protein kinase （AMPK）， peroxisome proliferator-activated receptor gamma coactivator-1α （PGC-1α）， and silent information regulator 3 （SIRT3） was detected by real-time fluorescent quantitative polymerase chain reaction （Real-time PCR）， and Western blot was used to examine the protein expression levels of optic atrophy protein1 （OPA1）， mitochondrial fission protein 1 （FIS1）， AMPK， p-AMPK， PGC-1α， and SIRT3. ResultsCompared with the sham group， rats in the model group had significantly lower recognition index， spontaneous alternation rate， escape latency， number of platform crossings， time spent in the target quadrant， and percentage of distance traveled in the target quadrant distance （P<0.05， P<0.01）. Significant mitochondrial damage was observed in the hippocampal tissue， with a marked decrease in mitochondrial respiratory chain complex content （P<0.01） and reduced mitochondrial membrane potential （P<0.05）. Additionally， the SOD activity was reduced， while ROS levels were elevated （P<0.01）. The mRNA expression of PGC-1α and SIRT3 was significantly downregulated （P<0.01）， along with decreased protein expression levels of OPA1， p-AMPK/AMPK， PGC-1α， and SIRT3， whereas FIS1 protein expression was significantly upregulated （P<0.05， P<0.01）. Compared with the model group， rats in KXS-treated groups （various dosage forms） showed significant improvement in behavioral indexes （P<0.05， P<0.01）， reduced hippocampal mitochondrial damage， and more organized mitochondrial cristae. Mitochondrial respiratory chain complex content was significantly increased （P<0.05， P<0.01）， and mitochondrial membrane potentials were elevated （P<0.05）. SOD activity was elevated， and ROS levels were significantly reduced （P<0.05， P<0.01）. Furthermore， the mRNA expression of PGC-1α and SIRT3 was upregulated， with increased protein levels of OPA1， p-AMPK/AMPK， PGC-1α， and SIRT3， while FIS1 protein expression levels were significantly reduced （P<0.05， P<0.01）. Across the KXS-treated groups， the granule group showed a higher spontaneous alternation rate than the decoction and powder groups （P<0.05）. ConclusionKXS decoction， powders， and granules can improve the learning and memory ability of rats， with granules being the most effective. The mechanism of action may involve activation of the AMPK/PGC-1α/SIRT3 signaling pathway， improvement of the mitochondrial function， and subsequent amelioration of the brain energy metabolism disorders.

ObjectiveTo explore the effects of different dosage forms of Kaixinsan （KXS） on the morphology and function of mitochondria in rat models of Alzheimer's disease （AD） and potential mechanisms of action. MethodsMale SD rats were randomly assigned to a sham group， model group， treatment groups receiving KXS decoction， powders， and granules （3.08 g·kg^-1）， as well as donepezil group （0.51×10^-3 g·kg^-1）， with 10 rats in each group. AD model was created using intracerebroventricular injection of streptozocin （STZ）. After 30 days of administration， behavioral assessments were conducted， and mitochondrial morphology was observed using transmission electron microscopy. Mitochondrial respiratory chain complex content was measured via enzyme-linked immunosorbent assay （ELISA）. Changes in mitochondrial membrane potential were measured via JC-1 staining， and superoxide dismutase （SOD） activity and reactive oxygen species （ROS） levels were measured via biochemical assays. The mRNA expression of adenosine 5'-monophosphate-activated protein kinase （AMPK）， peroxisome proliferator-activated receptor gamma coactivator-1α （PGC-1α）， and silent information regulator 3 （SIRT3） was detected by real-time fluorescent quantitative polymerase chain reaction （Real-time PCR）， and Western blot was used to examine the protein expression levels of optic atrophy protein1 （OPA1）， mitochondrial fission protein 1 （FIS1）， AMPK， p-AMPK， PGC-1α， and SIRT3. ResultsCompared with the sham group， rats in the model group had significantly lower recognition index， spontaneous alternation rate， escape latency， number of platform crossings， time spent in the target quadrant， and percentage of distance traveled in the target quadrant distance （P<0.05， P<0.01）. Significant mitochondrial damage was observed in the hippocampal tissue， with a marked decrease in mitochondrial respiratory chain complex content （P<0.01） and reduced mitochondrial membrane potential （P<0.05）. Additionally， the SOD activity was reduced， while ROS levels were elevated （P<0.01）. The mRNA expression of PGC-1α and SIRT3 was significantly downregulated （P<0.01）， along with decreased protein expression levels of OPA1， p-AMPK/AMPK， PGC-1α， and SIRT3， whereas FIS1 protein expression was significantly upregulated （P<0.05， P<0.01）. Compared with the model group， rats in KXS-treated groups （various dosage forms） showed significant improvement in behavioral indexes （P<0.05， P<0.01）， reduced hippocampal mitochondrial damage， and more organized mitochondrial cristae. Mitochondrial respiratory chain complex content was significantly increased （P<0.05， P<0.01）， and mitochondrial membrane potentials were elevated （P<0.05）. SOD activity was elevated， and ROS levels were significantly reduced （P<0.05， P<0.01）. Furthermore， the mRNA expression of PGC-1α and SIRT3 was upregulated， with increased protein levels of OPA1， p-AMPK/AMPK， PGC-1α， and SIRT3， while FIS1 protein expression levels were significantly reduced （P<0.05， P<0.01）. Across the KXS-treated groups， the granule group showed a higher spontaneous alternation rate than the decoction and powder groups （P<0.05）. ConclusionKXS decoction， powders， and granules can improve the learning and memory ability of rats， with granules being the most effective. The mechanism of action may involve activation of the AMPK/PGC-1α/SIRT3 signaling pathway， improvement of the mitochondrial function， and subsequent amelioration of the brain energy metabolism disorders.

Objective : To investigate the effect of chromosome instability(CIN) associated gene polypeptide N-acetylgalactosaminyltransferase 7(GALNT7) on proliferation and apoptosis of HCT116 colon cancer cells. Methods : The HCT116 cell line withGALNT7knockdown was constructed by lentiviral infection. The correlation betweenGALNT7and CIN was verified by chromosome spread assay. The effect ofGALNT7on cell proliferation was detected by live cell counting, and the effect ofGALNT7on cell cycle distribution was detected by flow cytometry and Western blot. Caspase-3 activity and Western blot assays were used to detect the effect ofGALNT7on apoptosis. Results : HCT116 cells showed a slower proliferation rate upon knocking down ofGALNT7, and exhibited a more scattered karyotype distribution and a phenotype of increased degree of CIN. Inhibition ofGALNT7in HCT116 cells resulted in cell cycle arrest, upregulation of P21 and downregulation of CDK6 protein levels, as well as increased levels of Caspase-3 activity, cleaved PARP1 and PUMA protein expression, and decreased levels of BCL-2 protein expression. Conclusion TheGALNT7gene may promote proliferation and inhibit apoptosis of HCT116 colon cancer cells through the suppression of CIN generation.

OBJECTIVE: To evaluate the safety and clinical therapeutic effect of in-line mechanical in-exsufflation to assist sputum clearance in patients with invasive mechanical ventilation. METHODS: A prospective observational study was conducted at the department of critical care medicine, the First Affiliated Hospital of Sun Yat-sen University from April 2022 to May 2023. Patients who were invasively ventilated and treated with in-line mechanical in-exsufflation to assist sputum clearance were enrolled. Baseline data were collected. Sputum viscosity, oxygenation index, parameters of ventilatory function and respiratory mechanics, clinical pulmonary infection score (CPIS) and vital signs before and after day 1, 2, 3, 5, 7 of use of the in-line mechanical in-exsufflation were assessed and recorded. Statistical analyses were performed by using generalized estimating equation (GEE). RESULTS: A total of 13 invasively ventilated patients using in-line mechanical in-exsufflation were included, all of whom were male and had respiratory failure, with the main cause being cervical spinal cord injury/high-level paraplegia (38.46%). Before the use of the in-line mechanical in-exsufflation, the proportion of patients with sputum viscosity of grade III was 38.46% (5/13) and decreased to 22.22% (2/9) 7 days after treatment with in-line mechanical in-exsufflation. With the prolonged use of the in-line mechanical in-exsufflation, the patients' CPIS scores tended to decrease significantly, with a mean decrease of 0.5 points per day (P < 0.01). Oxygenation improved significantly, with the oxygenation index (PaO₂/FiO₂) increasing by a mean of 23.3 mmHg (1 mmHg ≈ 0.133 kPa) per day and the arterial partial pressure of oxygen increasing by a mean of 12.6 mmHg per day (both P < 0.01). Compared to baseline, the respiratory mechanics of the patients improved significantly 7 days after in-line mechanical in-exsufflation use, with a significant increase in the compliance of respiratory system (Cst) [mL/cmH₂O (1 cmH₂O ≈ 0.098 kPa): 55.6 (50.0, 58.0) vs. 40.9 (37.5, 50.0), P < 0.01], and both the airway resistance and driving pressure (DP) were significantly decreased [airway resistance (cmH₂O×L^-1×s^-1): 9.6 (6.9, 10.5) vs. 12.0 (10.0, 13.0), DP (cmH₂O): 9.0 (9.0, 12.0) vs. 11.0 (10.0, 15.0), both P < 0.01]. At the same time, no new lung collapse was observed during the treatment period. No significant discomfort was reported by patients, and there were no substantial changes in heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure before and after the in-line mechanical in-exsufflation treatment. CONCLUSIONS The combined use of the in-line mechanical in-exsufflation to assist sputum clearance in patients on invasive mechanical ventilation can effectively improve sputum characteristics, oxygenation and respiratory mechanics. The in-line mechanical in-exsufflation was well tolerated by the patients, with no treatment-related adverse events, which demonstrated its effectiveness and safety.
Humans ; Prospective Studies ; Respiration, Artificial/methods* ; Respiratory Insufficiency/therapy* ; Sputum

Objective To evaluate the application of evidence-based perioperative patient-controlled analgesia(PCA)management in patients with liver cancer receiving transcatheter arterial chemoembolization(TACE)treatment.Methods By using the application model of clinical evidence-based practice,the review indicators were formulated based on the best evidence.The baseline assessment was conducted,the barrier factors were analyzed,the best clinical decision was made,the implementation steps of PCA management,including training,monitoring,education,etc.were refined,and two rounds of clinical review were carried out.The knowledge-belief-practice level and the implementation of review indicators in 50 medical and nursing staff engaged in PCA management,as well as the changes in pain scores,the incidence of adverse reactions due to PCA management,and the patient's satisfaction in 159 patients after the application of evidence were compared with their corresponding values determined before the application of evidence.Results After implementing the evidence-based practice plan and applying the evidence,at multiple time points the pain scores and the incidences of adverse reactions were decreased significantly(P＜0.05),the patient's satisfaction increased remarkably(P＜0.01),the execution rate of medical and nursing staff for the review indicators were strikingly increased(P＜0.01),and the knowledge-belief-practice level concerning PCA management was prominently improved(P＜0.01).Conclusion The implementation of perioperative PCA management in patients with liver cancer receiving TACE treatment can help to reduce the perioperative pain level,improve the patient discomfort,increase the patient's satisfaction degree,and improve the ability of medical staff in performing PCA management and evidence-based practices.

Objective To investigate the effect of long-chain non-coding RNA00963 (LINC00963) on lipopolysaccharide (LPS) induced apoptosis in rat renal tubular epithelial cells via microRNA-150-5p (miR-150-5p)/interleukin-1 receptor-associated kinase 1 (IRAK1) axis. Methods Rat renal tubular epithelial cells NRK-52E were cultured in vitro. NRK-52E cells were divided into control group (Con),LPS group,LPS+si-NC group,LPS+si-LINC00963 group,LPS+si-LINC00963+inhibitor NC group,LPS+si-LINC00963+miR-150-5p inhibitor group,LPS+si-LINC00963+oe-NC group,and LPS+si-LINC00963+oe-IRAK1 group. MTT and EdU methods were used to detect cell proliferation. Flow cytometry was used to detect cell apoptosis rate. ELISA kits were used to detect TNF-α,IL-6,and IL-10 levels,and commercial reagent kits were used to analyze malondialdehyde (MDA),superoxide dismutase (SOD),glutathione peroxide dismutase (GSH-Px) levels. The qRT-PCR was used to detect the expression levels of LINC00963,miR-150-5p,and IRAK1 genes in each group. Western blot was used to detect the expression of cysteine aspartic acid specific protease-3(Caspase-3),Bax,Bcl-2,and IRAK1 proteins in cells. Dual luciferase reporter gene and RNA pull down experiment were used to verify the relationship between miR-150-5p and LINC00963 and IRAK1. Results Compare with the Con group,the expression of LINC00963 and IRAK1 mRNA,the levels of TNF-α,IL-6,the content of MDA,apoptosis rate,the expression of Caspase-3,Bax,and IRAK1 proteins in NRK-52E cells were obviously increased (P<0.05),the expression of miR-150-5p,A490 (24 hours,48 hours) values,proliferation rate,the level of IL-10,the activities of SOD and GSH-Px,and the expression of Bcl-2 protein were obviously reduced (P<0.05) in the LPS group and LPS+si-NC group. Compare with the LPS+si-NC group,the expression of LINC00963 and IRAK1 mRNA,the levels of TNF-α,IL-6,the content of MDA,apoptosis rate,the expression of Caspase-3,Bax,and IRAK1 proteins in NRK-52E cells were obviously reduced (P<0.05),the expression of miR-150-5p,A490 (24 hours,48 hours) values,proliferation rate,the level of IL-10,the activities of SOD and GSH-Px,and the expression of Bcl-2 protein were obviously increased (P<0.05) in the LPS+si-LINC00963 group. Down-regulation of miR-150-5p expression or overexpression of IRAK1 could reduce the improvement effect of interference LINC00963 on LPS induced NRK-52E cell damage (P<0.05). Conclusions Interference with LINC00963 can regulate the miR-150-5p/IRAK1 axis to alleviate LPS-induced oxidative stress,inflammatory response,and apoptosis in NRK-52E cells.

Background Long-term exposure to free silica particles will lead to fibrosis of lung tissue, and abnormal expression of microRNA (miRNA) may affect the occurrence and process of fibrosis. Objective To observed possible intervention effect of miR-204-3p overexpression adenovirus on silicosis fibrosis induced by silica dust using a silicosis rat model via non-exposed intratracheal instillation. Methods Forty SD rats were randomly divided into four groups: control group, silicosis model group, miRNA-NC group, and miR-204-3p intervention group. Under ether anesthesia, rats in the silicosis model group, miRNA-NC group, and miR-204-3p intervention group were injected with 1 mL (50 mg·mL⁻¹) of free silica dust suspension into the trachea, while the control group was injected with the same volume of normal saline. After 30 d of dust exposure, the miR-204-3p intervention group was injected with rno-mir-204 adenovirus vector to overexpress miR-204-3p, and the miRNA-NC group was given empty virus vector. After 30 d of normal feeding, the animals were sacrificed by chloral hydrate anesthesia, and the lung tissue was taken for subsequent experiments. The relative expression level of miR-204-3p in lung tissue of rats in each group was detected by real-time fluorescence quantitative PCR (RT-qPCR). HE staining, Masson staining, and Sirius red staining were used for pathological observation. Immunohistochemistry was used to detect the expression of Fibronectin and Collagen I in lung tissue of rats in each group. RT-qPCR was used to detect the relative gene expression levels of fibrosis markers Fibronectin, Vimentin, Collagen I, and Collagen III in lung tissue of rats in each group. Western blot was used to detect the protein expression levels of fibrosis markers Fibronectin, Vimentin, Collagen I, and Collagen III in lung tissue of rats in each group. Results The anatomical features of lung tissue in the control group were pink lung tissue with soft texture and smooth surface, while those in the silicosis model were grayish white tissue with hard texture and scars and grayish white silicon nodules on the surface. Compared with the silicosis model group, the color of lung tissue in the miR-204-3p intervention group became ruddy, the surface was smooth, and the texture became soft. The staining results showed that the alveolar wall of the control group was thin, there were a small number of capillaries in the alveoli, and the alveolar structure was clear and complete. In the silicosis model group, the alveolar wall became thicker, the pulmonary septum was partially broken, the alveolar structure was defective, and a large amount of collagen fibers were deposited. The alveolar structure of the miR-204-3p intervention group was relatively clear and there was a small amount of collagen fiber deposition. RT-qPCR results showed that compared with the control group, the relative expression levels of miR-204-3p in lung tissue of the silicosis model group and the miRNA-NC group were decreased (P<0.05), and the relative expression level of miR-204-3p in lung tissue of the miR-204-3p intervention group was increased (P＜0.05). The results of immunohistochemistry showed that compared with the control group, the expression levels of Fibronectin and Collagen I in lung tissue of the silicosis model group were increased (P＜0.05). Compared with the silicosis model group, the relative expression levels of Fibronectin and Collagen I in lung tissue of the rats in the miR-204-3p intervention group were significantly decreased (P<0.05). The results of RT-qPCR and Western blot showed that compared with the control group, the relative protein and gene expression levels of fibrosis factors Fibronectin, Vimentin, Collagen I, and Collagen III in lung tissue of the silicosis model group increased (P＜0.05). Compared with the silicosis model group, the relative gene and protein expression levels of fibrosis factors Fibronectin, Vimentin, Collagen I, and Collagen III in lung tissue of rats in the miR-204-3p intervention group were decreased (P＜0.05). Conclusion Silica dust can cause lung fibrosis in rats, and overexpression of miR-204-3P in vivo can reduce silicosis fibrosis in rats caused by silica dust.