ABSTRACT
Really Interesting New Gene (RING) finger proteins are highly conserved molecules that participate in a variety of biological processes such as regulation of development, apoptosis and antiviral immunity in vertebrates. However, the functions of RING finger proteins are still poorly understood in crustaceans. Previously, we found that the transcript of a homolog of RING finger protein 152 (CqRNF152-like) was up-regulated in a differentially expressed transcriptome library of the haematopietic tissue (Hpt) cells from red claw crayfish Cherax quadricarinatus upon white spot syndrome virus (WSSV) infection, which is one of the most devastating viral diseases for crustaceans like shrimp and crayfish. The full-length cDNA sequence of CqRNF152-like was then identified with 975 bp, including an ORF of 685 bp that encoded a 195 amino acids protein, a 5'- UTR of 180 bp, and a 3'-UTR with a poly (A) tail of 207 bp. The conserved domain prediction showed that CqRNF152-like contained a conserved RING-finger domain. Gene expression analysis showed that CqRNF152-like was distributed in all tissues examined and the transcript is significantly up-regulated after WSSV challenge both in vivo in Hpt tissue and in vitro in cultured Hpt cells. Furthermore, the transcripts of both an immediate early gene ie1 and a late envelope protein gene vp28 of WSSV were clearly increased in the Hpt tissues, hemocytes and cultured Hpt cells after gene silencing of CqRNF152-like, which were further proved to be significantly decreased after overloading of recombinant CqRNF152-like protein in Hpt cell cultures. Meanwhile, CqRNF152-like was found to bind with WSSV envelope protein VP28 by proteins pull-down assay. Similar to most of RNF proteins, CqRNF152-like protein sequence contained a conserved RING-finger domain and showed self-ubiquitination activity in a RING finger domain dependent manner. Taken together, CqRNF152-like is likely to function as an antiviral molecular against WSSV infection through interaction with the envelope protein VP28 in a crustacean C. quadricarinatus. This is the first report that a RING finger protein with directly antiviral functions via interaction with viral protein and self-ubiquitination activity in crustacean, which sheds new light on the molecular mechanism of WSSV infection and the control of white spot disease.
Subject(s)
Astacoidea/genetics , Astacoidea/immunology , Gene Expression Regulation/immunology , Immunity, Innate/genetics , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/immunology , Amino Acid Sequence , Animals , Arthropod Proteins/chemistry , Arthropod Proteins/genetics , Arthropod Proteins/immunology , Base Sequence , Gene Expression Profiling , Phylogeny , Sequence Alignment , Ubiquitin-Protein Ligases/chemistryABSTRACT
Past studies have shown that the Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) is commonly downregulated in gastric cancer, which contributes to elevated activation of PI3K/Akt signaling, proliferation and tumorigenesis of gastric cancer cells. However, the mechanisms underlying the reduced expression of SHIP2 in gastric cancer remain unclear. While gene copy number variation analysis and exon sequencing indicated the absence of genomic alterations of SHIP2, bisulfite genomic sequencing (BGS) showed promoter hypomethylation of SHIP2 in gastric cancer cells. Analysis of transcriptional activity of SHIP2 promoter revealed Specificity protein 1 (Sp1) was responsible for the regulation of SHIP2 expression in gastric cancer cells. Furthermore, Sp1 expression, but not Sp3, was frequently downregulated in gastric cancer compared with normal gastric mucosa, which was associated with a paralleled reduction in SHIP2 levels in gastric cancer. Moreover, overexpression of Sp1 inhibited cell proliferation, induced apoptosis, suppressed cell motility and invasion in gastric cancer cells in vitro, which was, at least in part, due to transcriptional activation of SHIP2 mediated by Sp1, thereby inactivating Akt. Collectively, these results indicate that decreased expression of transcription factor Sp1 contributes to suppression of SHIP2 in gastric cancer cells.
Subject(s)
Down-Regulation/genetics , Gene Expression Regulation, Neoplastic , Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases/genetics , Sp1 Transcription Factor/metabolism , Stomach Neoplasms/genetics , Cell Line, Tumor , Humans , Mutation/genetics , Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases/metabolism , Promoter Regions, Genetic , Transcription, GeneticABSTRACT
BACKGROUND: Cholangiocarcinoma (CCA) is a highly malignant cancer, characterized by frequent mucin overexpression. MUC1 has been identified as a critical oncogene in the progression of CCA. However, the comprehensive understanding of how the mucin family influences CCA progression and prognosis is still incomplete. AIM: To investigate the functions of mucins on the progression of CCA and to establish a risk evaluation formula for stratifying CCA patients. METHODS: Single-cell RNA sequencing data from 14 CCA samples were employed for elucidating the roles of mucins, complemented by bioinformatic analyses. Subsequent validations were conducted through spatial transcriptomics and immunohistochemistry. The construction of a risk evaluation model utilized the least absolute shrinkage and selection operator regression algorithm, which was further confirmed by independent cohorts and diverse data types. RESULTS: CCA tumor cells with elevated levels of MUC1 and MUC4 showed activated nucleotide metabolic pathways and increased invasiveness. MUC5AC-high cells were found to promote CCA progression through WNT signaling. MUC5B-high cells exhibited robust cellular oxidation activities, leading to resistance against antitumoral treatments. MUC13-high cells were observed to secret chemokines, recruiting and transforming macrophages into the M2-polarized state, thereby suppressing antitumor immunity. MUC16-high cells were found to promote tumor progression through interleukin-1/nuclear factor kappa-light-chain-enhancer of activated B cells signaling upon interaction with neutrophils. Utilizing the expression levels of these mucins, a risk factor evaluation formula for CCA was developed and validated across multiple cohorts. CCA samples with higher risk factors exhibited stronger metastatic potential, chemotherapy resistance, and poorer prognosis. CONCLUSION: Our study elucidates the functional mechanisms through which mucins contribute to CCA development, and provides tools for risk stratification in CCA.
ABSTRACT
Corporate financial risks not only endanger the financial stability of digital industry but also cause huge losses to the macro-economy and social wealth. In order to detect and warn digital industry financial risks in time, this paper proposes an early warning system of digital industry financial risks based on improved K-means clustering algorithm. Aiming to speed up the K-means calculation and find the optimal clustering subspace, a specific transformation matrix is used to project the data. The feature space is divided into clustering space and noise space. The former contains all spatial structure information; the latter does not contain any information. Each iteration of K-means is carried out in the clustering space, and the effect of dimensionality screening is achieved in the iteration process. At the same time, the retained dimensions are fed back to the next iteration. The dimensional information of the cluster space is discovered automatically, so no additional parameters are introduced. Experimental results show that the accuracy of the proposed algorithm is higher than other algorithms in financial risk detection.
Subject(s)
Algorithms , Cluster AnalysisABSTRACT
Background: Epithelial ovarian tumors (EOTs) are a group of heterogeneous neoplasms. It is importance to preoperatively differentiate the histologic subtypes of EOTs. Our study aims to investigate the potential of radiomics signatures based on diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps for categorizing EOTs. Methods: This retrospectively enrolled 146 EOTs patients [34 with borderline EOT(BEOT), 30 with type I and 82 with type II epithelial ovarian cancer (EOC)]. A total of 390 radiomics features were extracted from DWI and ADC maps. Subsequently, the LASSO algorithm was used to reduce the feature dimensions. A radiomics signature was established using multivariable logistic regression method with 3-fold cross-validation and repeated 50 times. Patients with bilateral lesions were included in the validation cohort and a heuristic selection method was established to select the tumor with maximum probability for final consideration. A nomogram incorporating the radiomics signature and clinical characteristics was also developed. Receiver operator characteristic, decision curve analysis (DCA), and net reclassification index (NRI) were applied to compare the diagnostic performance and clinical net benefit of predictive model. Results: For distinguishing BEOT from EOC, the radiomics signature and nomogram showed more favorable discrimination than the clinical model (0.915 vs. 0.852 and 0.954 vs. 0.852, respectively) in the training cohort. In classifying early-stage type I and type II EOC, the radiomics signature exhibited superior diagnostic performance over the clinical model (AUC 0.905 vs. 0.735). The diagnostic efficacy of the nomogram was the same as that of the radiomics model with NRI value of -0.1591 (P = 0.7268). DCA also showed that the radiomics model and combined model had higher net benefits than the clinical model. Conclusion: Radiomics analysis based on DWI, and ADC maps serve as an effective quantitative approach to categorize EOTs.
ABSTRACT
Protein phosphatase 2A (PP2A) is an important serine/threonine phosphatase, a highly conserved enzyme widely expressed in eukaryotic cells, which accounts for a majority of the serine/threonine phosphatase activity in cells implicated in regulation of immune signaling pathways and antiviral response. However, most of studies about PP2A have been conducted in mammals but few in crustaceans. In this study, two subunits of PP2A (named as CqPP2Ab and CqPP2Ac) were characterized to be involved in white spot syndrome virus (WSSV) infection in the haematopoietic tissue (Hpt) cells from red claw crayfish Cherax quadricarinatus. The open reading frame (ORF) of CqPP2Ab was 1341 bp encoding 446 amino acids with seven WD40 domains, and the ORF of CqPP2Ac was 930 bp encoding 309 amino acids with a PP2Ac domain. Tissue distribution analysis showed that the mRNA transcript of CqPP2Ab and CqPP2Ac were both widely expressed in all the tested tissues with the highest expression in hemocyte, followed by high expression in Hpt. The gene expressions of CqPP2Ab and CqPP2Ac were both significantly down-regulated at 6 h post WSSV infection (6 hpi) in Hpt cells. Importantly, the expression of viral immediate early gene IE1 and late viral gene envelope protein VP28 were both significantly increased post WSSV infection after gene silencing of CqPP2Ab or CqPP2Ac in Hpt cells, suggesting that CqPP2Ab and CqPP2Ac could inhibit WSSV infection in Hpt cells, probably by increasing the antimicrobial substances expression in consideration to the significantly reduced expression of anti-lipopolysaccharide factor, crustin, and lysozyme after gene silencing of CqPP2Ab or CqPP2Ac, respectively. These findings provide a new light on the mechanism of WSSV infection and the antiviral response in crustaceans.
Subject(s)
Antimicrobial Peptides/immunology , Arthropod Proteins/immunology , Astacoidea/immunology , Gene Expression Regulation/immunology , Protein Phosphatase 2/immunology , White spot syndrome virus 1/immunology , Amino Acid Sequence , Animals , Antimicrobial Peptides/genetics , Antimicrobial Peptides/metabolism , Arthropod Proteins/genetics , Arthropod Proteins/metabolism , Astacoidea/genetics , Astacoidea/virology , Base Sequence , Gene Expression Profiling/methods , Hematopoietic System/cytology , Hematopoietic System/immunology , Hematopoietic System/metabolism , Hemocytes/cytology , Hemocytes/immunology , Hemocytes/metabolism , Host-Pathogen Interactions/immunology , Immunity, Innate/genetics , Immunity, Innate/immunology , Protein Phosphatase 2/genetics , Protein Phosphatase 2/metabolism , Protein Subunits/genetics , Protein Subunits/immunology , Protein Subunits/metabolism , Sequence Analysis, DNA/methods , Sequence Homology, Amino Acid , White spot syndrome virus 1/physiologyABSTRACT
In contrast to that hypoacetylation of histones is associated with condensed chromatin and gene silencing, the hyperacetylation of histones can promote an "open chromatin" conformation and transcriptional activation, which is recruited by some viruses to enhance the viral genome replication in host cells. However, the function of histone acetylation modification in the infection of white spot syndrome virus (WSSV), one of the most virulent pathogens for crustaceans like shrimp and crayfish at present, is still unknown. Previously, we found that the transcript of a histone K-Lysine acetyltransferase CqKAT2A-like gene was down-regulated in a differentially expressed transcriptome library of the haematopietic tissue (Hpt) cells from red claw crayfish Cherax quadricarinatus upon WSSV infection at 12 hpi. To further reveal its possible role in anti-WSSV response, CqKAT2A-like gene was then identified with an open reading frame (ORF) of 2523 bp encoding 840 amino acids, which contained a conserved PCAF-N domain, acetyltransf1 domain and bromo domain. Gene expression analysis showed that CqKAT2A-like was distributed in all tissues examined with high presence in haemocyte and muscle, and the transcript was significantly down-regulated after WSSV infection in Hpt cells. Furthermore, the level of histone H3 acetylation (H3ac) was strongly reduced by gene silencing of CqKAT2A-like, which was accompanied with the significantly decreased gene expression of WSSV in Hpt cells, suggesting that CqKAT2A-like gene can promote the activity H3ac and the replication of WSSV. When the H3ac was induced by histone deacetyltransferase inhibitor TSA, the transcription of WSSV genes including both IE1 and VP28 genes was significantly increased, indicating that H3ac participated in WSSV infection in Hpt cells. Taken together, these data suggest that CqKAT2A-like gene might promote the replication of WSSV by regulating H3ac, which sheds new light on the pathogenesis of WSSV in crustaceans.
Subject(s)
Arthropod Proteins/genetics , Astacoidea/physiology , DNA Virus Infections/immunology , Hemocytes/physiology , Histone Acetyltransferases/genetics , White spot syndrome virus 1/physiology , Acetylation , Animals , Arthropod Proteins/metabolism , Cells, Cultured , Cloning, Molecular , Gene Expression Regulation , Histone Acetyltransferases/metabolism , Histones/metabolism , Humans , Immunity , Sequence Alignment , Transcriptome , Virus ReplicationABSTRACT
BACKGROUND: Pancreatic ductal adenocarcinoma has a devastatingly poor prognosis, and most prognostic factors reflected the tumor stage more than the tumors' biology. The peripheral nerve plexus is densely distributed in the tumor micro-environment, and there are interactions between tumor cells and these nerves. Perineural invasion is an important risk factor for tumor recurrence and metastasis in pancreatic head adenocarcinoma, but the concrete types of extrapancreatic neuropathy and its role in predicting prognosis are still not clear. OBJECTIVE: To clarify the role of extrapancreatic neuropathy in the early postoperative liver metastasis and tumor-related mortality in pancreatic head adenocarcinoma and to study the mechanism of tumor recurrence and liver metastasis in pancreatic head adenocarcinoma. METHODS: We reported a retrospective study of 60 patients with resectable pancreatic head adenocarcinoma, all of whom accepted radical pancreaticoduodenectomy. Plexus pancreaticus capitalis II (PLX-II) was the representation of extrapancreatic plexus in our study, and all of these plexus had immunohistochemical staining. We defined the postoperative tumor recurrence and tumor-related mortality within 6 months as the early prognostic indicators and analyzed the pathological alterations in PLX-II among different prognosis groups. RESULTS: There were 18 patients suffering early postoperative liver metastasis; these two groups differed significantly in the average number of nerve trunks (P<0.001), the proportion of neuritis (P=0.003), the content of sympathetic nerve fibers (P=0.004) and parasympathetic nerve fibers (P<0.001) per unit area of PLX-II. There were 15 patients suffering early postoperative mortality, and there were significant differences between these two groups in the average number of nerve trunks (P<0.001), the proportion of neuritis (P=0.009), the content of sympathetic nerve fibers (P=0.023) and parasympathetic nerve fibers (P<0.001) per unit area of PLX-II. CONCLUSION: The patterns of extrapancreatic neuropathy could reflect the biological behavior of resectable pancreatic head adenocarcinoma, and the pathological features of PLX-II were closely related to early liver metastasis and mortality.
ABSTRACT
The aim of the present study was to evaluate the biological and prognostic implications of the superior mesenteric artery (SMA) boundary on preoperative abdominal contrast-enhanced computed tomography (CE-CT) for resectable adenocarcinoma of the pancreatic head. A total of 121 patients treated over a 6-year period at Peking University Third Hospital (Beijing, China) were included in the present study. The pattern of the SMA boundary was investigated on preoperative CE-CT and detailed pathological analysis of the extrapancreatic plexus [the pancreatic head plexus II (PLX-II) located on the right edge of the SMA] was performed. The results revealed that the radiological SMA boundary was associated with the grade of parasympathetic neurogenesis (P=0.014) in PLX-II, and was predictive of postoperative disease-free survival (P=0.014) and liver metastasis (P=0.013). Therefore, it was proposed that extrapancreatic parasympathetic neurogenesis may account for the different patterns of the SMA boundary on preoperative abdominal CE-CT, and affect the prognosis, particularly for liver metastasis in resectable pancreatic head adenocarcinoma.
ABSTRACT
Ganoderma lucidum polysaccharides have protective effects against apoptosis in neurons exposed to ischemia/reperfusion injury, but the mechanisms are unclear. The goal of this study was to investigate the underlying mechanisms of the effects of ganoderma lucidum polysaccharides against oxidative stress-induced neuronal apoptosis. Hydrogen peroxide (H2O2) was used to induce apoptosis in cultured cerebellar granule cells. In these cells, ganoderma lucidum polysaccharides remarkably suppressed H2O2-induced apoptosis, decreased expression of caspase-3, Bax and Bim and increased that of Bcl-2. These findings suggested that ganoderma lucidum polysaccharides regulate expression of apoptosis-associated proteins, inhibit oxidative stress-induced neuronal apoptosis and, therefore, have significant neuroprotective effects.
ABSTRACT
In this paper, the complete mitochondrial genome of Chlorophthalmus nigromarginatus has been determined. The mitochondrial genome (17,663 bp) had the canonical mitochondrial gene content and arrangement, including 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and 2 non-coding regions. The overall base composition of the heavy-strand is 25.66% A, 25.71% T, 17.82% G, and 30.81% C, with an AT content of 51.37%. It shared 86.6% identities with Chlorophthalmus agassizi. The phylogenetic analyses indicated the close relationship between the mitochondrial genome we presented and other species in order Aulopiformes.
Subject(s)
Fishes/genetics , Genome, Mitochondrial/genetics , AT Rich Sequence/genetics , Animals , Base Composition/genetics , DNA, Mitochondrial/genetics , Fishes/classification , Phylogeny , RNA, Ribosomal/genetics , RNA, Transfer/genetics , Sequence Analysis, DNAABSTRACT
BACKGROUND: The Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) is implicated in diabetes, arthrosclerosis, and cancer. However, the role of SHIP2 in human gastric cancer remains unclear. METHODS: The expression levels of SHIP2 in gastric cancer tissues, a panel of gastric cancer cell lines, and normal gastric epithelial cells were analyzed by immunohistochemistry (IHC), Western blot, and real-time quantitative RT-PCR (qRT-PCR). Gastric cancer cells with either overexpressed SHIP2 or co-overexpressed SHIP2 and Akt were analyzed to determine cell proliferation, colony formation, apoptosis, cell migration, and invasion assays. Normal gastric epithelial cells with knockdown SHIP2 or co-knockdown SHIP2 and Akt were subjected by anchorage-independent growth assays. The effect of SHIP2 on tumor growth in vivo was detected by xenograft tumorigenesis assays. RESULTS: SHIP2 was commonly downregulated in gastric cancer compared with normal gastric mucosa, and overexpression of SHIP2 inhibited cell proliferation, induced apoptosis, suppressed cell motility and invasion in gastric cancer cells in vitro, and retarded the growth of xenograft gastric tumors in vivo, while knockdown of SHIP2 in normal gastric epithelial cells promoted anchorage-independent growth. Moreover, overexpression of SHIP2 inactivated Akt, and upregulated p21, p27, and the pro-apoptotic protein Bim. Restoring Akt activation in gastric cancer cells largely blocked the inhibition of PI3K/Akt signaling by SHIP2 and reversed the inhibitory effect of SHIP2 on tumorigenesis and proliferation. CONCLUSIONS: This study demonstrates, for the first time, that SHIP2 is frequently downregulated in gastric cancer, and reduced SHIP2 expression promotes tumorigenesis and proliferation of gastric cancer via activation of the PI3K/Akt signaling.
Subject(s)
Cell Transformation, Neoplastic/metabolism , Phosphoric Monoester Hydrolases/physiology , Proto-Oncogene Proteins c-akt/physiology , Stomach Neoplasms/pathology , Animals , Cell Proliferation , Cell Survival/physiology , Cell Transformation, Neoplastic/pathology , Down-Regulation , Gastric Mucosa/cytology , Gastric Mucosa/metabolism , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Heterografts , Humans , Mice, Nude , Neoplasm Invasiveness , Neoplasm Transplantation , Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases , Phosphoric Monoester Hydrolases/genetics , Phosphoric Monoester Hydrolases/metabolism , Signal Transduction/physiology , Stomach Neoplasms/genetics , Stomach Neoplasms/metabolism , Tumor Cells, CulturedABSTRACT
In liver injuries, the quiescent hepatic stellate cells (HSCs) promptly change to activated HSCs, which are easily identified by the intense immunoreactivity for alpha-smooth muscle actin. However, reproducible markers for quiescent HSCs in formalin-fixed, paraffin-embedded liver tissue sections have not yet been reported. We immunohistochemically examined the expression of vinculin, one major protein of dense plaques, on cultured LI90 cells and on HSCs in normal and diseased human and rat livers. In cultured LI90 cells, vinculin appeared as small linear patches. Although vinculin was consistently negative in the routine liver tissue sections, an antigen retrieval technique using microwave oven heating yielded excellent effects. Using this technique, the formalin-fixed, paraffin-embedded human and rat normal liver tissue sections showed the vinculin immunoreactivity along the sinusoidal wall. Immunoelectron microscopic observation of hepatic parenchyma demonstrated that the vinculin was exclusively expressed in quiescent HSCs. In fetal rat livers, vinculin-positive quiescent HSCs gradually increased in number with gestation. In diseased livers the activated HSCs showed more intense immunoreaction for vinculin. These results indicate that, using microwave pretreatment, vinculin is expressed in quiescent and activated HSCs in routinely processed liver tissue sections. It could allow us to evaluate the development and distribution of quiescent HSCs and to examine the relationship between quiescent and activated HSCs.
Subject(s)
Kupffer Cells/metabolism , Liver/cytology , Vinculin/metabolism , Adult , Aged , Animals , Animals, Newborn , Biomarkers/analysis , Cell Line , Female , Fluorescent Antibody Technique , Humans , Immunoenzyme Techniques , Kupffer Cells/ultrastructure , Liver/embryology , Liver/metabolism , Male , Microscopy, Confocal , Microscopy, Immunoelectron , Middle Aged , Rats , Rats, WistarABSTRACT
We examined regeneration and fibrosis in the necrotic areas of hepatic stellate cells (HSCs). Acute hepatic injury was induced in rats by administration of an intraperitoneal injection of high-dose dimethylnitrosamine (50 mg/kg body weight). Liver samples were obtained from rats 6, 12, 24, 36 h and 2, 3, 5, 7, 10, and 14 days after the injection. They were examined by light and electron microscopy and by immunohistochemical methods. Hemorrhagic necrosis became most prominent 36 h after treatment and extended into zones 3 and 2. In the submassive necrotic areas the sinusoidal structure was destroyed. No HSCs positive for alpha-smooth muscle actin or desmin were present. On day 5, when necrotic tissues were almost removed by infiltrating macrophages, HSCs strongly positive for alpha-smooth muscle actin and desmin appeared along the surface of the preserved parenchyma and migrated into the necrotic areas along the residual reticulin fibers. By day 14 most of the necrotic areas were almost completely replaced by the regeneration of hepatocytes and central to central (C-C) bridging fibrosis. Our results indicate that following submassive complete necrosis, HSCs in the preserved liver parenchyma have roles in the formation of sinusoidal wall for remodeling in necrotic areas via their activation, proliferation, and migration into the necrotic areas.
Subject(s)
Dimethylnitrosamine , Hemorrhage/pathology , Liver Cirrhosis, Experimental/pathology , Liver Regeneration , Liver/ultrastructure , Actins/metabolism , Animals , Cell Division , Cell Movement , Desmin/metabolism , Dimethylnitrosamine/administration & dosage , Disease Models, Animal , Hemorrhage/etiology , Injections, Intraperitoneal , Kupffer Cells/drug effects , Kupffer Cells/metabolism , Kupffer Cells/pathology , Liver/drug effects , Liver/metabolism , Liver Cirrhosis, Experimental/complications , Liver Cirrhosis, Experimental/metabolism , Male , Necrosis , Rats , Rats, WistarABSTRACT
We observed postnecrotic tissue remodeling to examine vascularization in adult rat livers. Livers, bone marrow, and peripheral blood from rats at 24 h to 14 days after an injection of dimethylnitrosamine (DMN) were examined by light microscopic, immunohistochemical, and ultrastructural methods. Numerous ED-1 (a marker for rat monocytes/macrophages)-positive round mononuclear cells infiltrated in the necrotic areas at 36 h after DMN treatment. On day 5, when necrotic tissues were removed, some of the cells were transformed from round to spindle in shape. On day 7, these cells were contacted with residual reticulin fibers and became positive for SE-1, a marker of hepatic sinusoidal endothelial cells and Tie-1, an endothelial cell-specific surface receptor, associated with frequent occurrence of ED-1/SE-1 and ED-1/Tie-1 double-positive spindle cells. Ultrastructurally, the spindle cells simultaneously showed phagocytosis and endothelial cell-like morphology. With time necrotic areas diminished, and on day 14, the necrotic tissues were almost replaced by regenerated liver tissues and thin bundles of central-to-central bridging fibrosis. Bone marrow from 12 h to day 2 showed an increase of BrdU-positive mononuclear cells. Some of them were positive for ED-1. The BrdU-labeled and ED-1-positive cells appeared as early as 12 h after DMN injection and reached a peak in number at 36 h. They were similar in structure to ED-1-positive cells in necrotic liver tissues. These findings suggest that round mononuclear ED-1-positive cells proliferate first in bone marrow after DMN treatment, reach necrotic areas of the liver through the circulation, and differentiate to sinusoidal endothelial cells. Namely, hepatic sinusoids in DMN-induced necrotic areas may partly be reorganized possibly by vasculogenesis.