Biomedical subjects

F Li

Publications and source records attributed to F Li.

At least 325 records · Page 18Linked to original sources

PubMed1998

Imaging brain activity in conscious animals using functional MRI.

Functional magnetic resonance imaging (fMRI) in humans has helped improve our understanding of the neuroanatomical organization of behavior. Unfortunately, fMRI in animal studies has not kept pace with the human work. Experiments are limited because animals must be anesthetized to prevent motion artifacts, precluding most studies involving neuroimaging of brain activity during behavior. The present study tested a newly developed head and body holder for performing fMRI in fully conscious animals. Significant changes in signal intensities were observed in the somatosensory cortex of conscious rats in response to electrical shock of the hindpaw. These changes in evoked signal ranged between 4 and 19% and were accompanied by significant increases in local cerebral blood flow. The fMRI study was performed with a 2.0-Tesla spectrometer. Using this non-invasive method of imaging brain activity in conscious animals, it is now possible to perform developmental studies in animal models of neurological and psychiatric disorders.

Animals↗

PubMed1998

Cytomegalovirus infection enhances the neointima formation in rat aortic allografts: effect of major histocompatibility complex class I and class II antigen differences.

BACKGROUND: The development of chronic rejection has emerged as a major cause of long-term graft failure. Previous studies have demonstrated that cytomegalovirus (CMV) infection is associated with an increased incidence of chronic allograft rejection in renal, cardiac, and aortic allografts. This study was designed to investigate the effects of the major histocompatibility complex (MHC) class I or class II mismatches on CMV-enhanced chronic rejection. METHODS: Aortic transplantation was performed between different inbred rat strain combinations; the Lewis to RP combination was class I-mismatched and Wag/Rij to RP class II-mismatched. At 7, 28, and 90 days after transplantation, the intensity of chronic rejection in mismatched grafts with or without CMV infection was evaluated using histological and immunohistological analysis. RESULTS: The results of this study demonstrated that CMV infection led to an increased influx of monocytes/ macrophages in class I-mismatched grafts at 1 week after transplantation and enhanced infiltration of T lymphocytes in class II-mismatched grafts at 4 weeks. Although more vascular lesions were observed in the class II-mismatched combinations, an intensified neointima formation by CMV infection was observed only in the MHC class I-mismatched allografts. CONCLUSIONS: CMV infection may increase neointima formation of allografts when an MHC class I disparity between donor and recipient is present. This may be associated with the increased perivascular influx of monocytes/macrophages observed in CMV-infected animals early after transplantation.

Animals↗

PubMed1998

Mass screening for lung cancer with mobile spiral computed tomography scanner.

BACKGROUND: The incidence of and mortality from lung cancer have increased steadily. Most lung cancers are not localised when first detected, but early detection is mandatory to improve prognosis. Since curable early cases are hard to visualise with conventional chest radiography, a new diagnostic means must be found. We assessed whether population-based mass screening with a spiral computed tomography scanner could contribute substantially to detection of smaller cancers, and decrease mortality. METHODS: In 1996, we screened in a mobile unit 5483 individuals from the general population of Matsumoto, Japan, aged between 40 years and 74 years who had undergone annual chest radiography (miniature fluorophotography) and cytological assessment of sputum. All participants had a low-dose X-ray spiral computed tomography (CT) scan of the thorax; 3967 also underwent miniature fluorophotography. We compared smokers and non-smokers. Further assessments were done for probably benign but suspicious lesions; suspicion of cancer; and indeterminate small nodules by chest radiography and conventional CT, with additional transbronchial biopsy when possible. Thoracotomy was recommended when it was strongly suspected that the patients had lung cancer. FINDINGS: 19 patients were diagnosed as having lung cancer--14 with suspicion of lung cancer, three with benign but suspicious lesions, and two with indeterminate small nodules. 18 cases were surgically confirmed, and one was clinically diagnosed. The mean size of lesions was 17 mm (range 6-47). In four of 19 patients, lung abnormality was seen on CT and miniature fluorophotography. The lung-cancer detection rate with CT was 0.48%, significantly higher than the 0.03-0.05% for standard mass assessments done previously in the same area. CT missed one case that was found solely on a sputum cytology examination. INTERPRETATION: Our results show that miniature fluorophotography or conventional chest radiography, which have been the main diagnostic techniques for lung cancer, showed few small cancers. CT was more accurate in mass screening for lung cancer and led to early detection and an accurate diagnosis of lung cancer, and should be considered in future health plans.

Adult↗

PubMed1998

Induction of rat aortic smooth muscle cell growth by the lipid peroxidation product 4-hydroxy-2-nonenal.

BACKGROUND: Atherosclerotic lesion formation is a complex process, in part mediated by inflammatory and oxidative mechanisms including lipid peroxidation. To further characterize the potential role of lipid peroxidation products in atherogenesis, we studied the effects of 4-hydroxy-2-nonenal (HNE) on rat aortic smooth muscle cell growth. METHODS AND RESULTS: HNE, at concentrations of 1.0 and 2.5 micromol/L, significantly stimulated rat aortic smooth muscle cell growth as determined by cell counts, [3H]-thymidine uptake, and incorporation of bromo-deoxyuridine. To characterize the mechanism of HNE-induced mitogenesis, its effect on activation of intracellular growth signaling pathways was examined. Treatment with HNE resulted in activation of extracellular signal-regulated protein kinases ERK1 and ERK2, induction of c-fos and c-jun protein expression, and an increase in transcription factor AP-1 DNA binding activity. In addition, HNE induced expression of platelet-derived growth factor-AA (PDGF-AA) protein, and an anti-PDGF-AA antibody specifically inhibited HNE-mediated DNA synthesis, suggesting that growth factor induction may play a role in HNE-induced vascular smooth muscle cell growth. The role of redox-sensitive mechanisms in this process was further supported by the observation that HNE-induced DNA synthesis and AP-1 activation were inhibited by the antioxidants N-acetylcysteine and pyrrolidine dithiocarbamate. CONCLUSIONS: These data demonstrate that HNE, one of several important lipid peroxidation products, induces rat aortic smooth muscle cell growth through redox-sensitive mechanisms and growth factor expression. These observations are consistent with a role for lipid peroxidation products in vascular smooth muscle cell growth in atherogenesis.

Aldehydes↗

PubMed1998

Two CD95 (APO-1/Fas) signaling pathways.

We have identified two cell types, each using almost exclusively one of two different CD95 (APO-1/Fas) signaling pathways. In type I cells, caspase-8 was activated within seconds and caspase-3 within 30 min of receptor engagement, whereas in type II cells cleavage of both caspases was delayed for approximately 60 min. However, both type I and type II cells showed similar kinetics of CD95-mediated apoptosis and loss of mitochondrial transmembrane potential (DeltaPsim). Upon CD95 triggering, all mitochondrial apoptogenic activities were blocked by Bcl-2 or Bcl-xL overexpression in both cell types. However, in type II but not type I cells, overexpression of Bcl-2 or Bcl-xL blocked caspase-8 and caspase-3 activation as well as apoptosis. In type I cells, induction of apoptosis was accompanied by activation of large amounts of caspase-8 by the death-inducing signaling complex (DISC), whereas in type II cells DISC formation was strongly reduced and activation of caspase-8 and caspase-3 occurred following the loss of DeltaPsim. Overexpression of caspase-3 in the caspase-3-negative cell line MCF7-Fas, normally resistant to CD95-mediated apoptosis by overexpression of Bcl-xL, converted these cells into true type I cells in which apoptosis was no longer inhibited by Bcl-xL. In summary, in the presence of caspase-3 the amount of active caspase-8 generated at the DISC determines whether a mitochondria-independent apoptosis pathway is used (type I cells) or not (type II cells).

Adaptor Proteins, Signal Transducing↗

PubMed1998

Bcl-xL functions downstream of caspase-8 to inhibit Fas- and tumor necrosis factor receptor 1-induced apoptosis of MCF7 breast carcinoma cells.

Stimulation of the Fas or tumor necrosis factor receptor 1 (TNFR1) cell surface receptors leads to the activation of the death effector protease, caspase-8, and subsequent apoptosis. In some cells, Bcl-xL overexpression can inhibit anti-Fas- and tumor necrosis factor (TNF)-alpha-induced apoptosis. To address the effect of Bcl-xL on caspase-8 processing, Fas- and TNFR1-mediated apoptosis were studied in the MCF7 breast carcinoma cell line stably transfected with human Fas cDNA (MCF7/F) or double transfected with Fas and human Bcl-xL cDNAs (MCF7/FB). Bcl-xL strongly inhibited apoptosis induced by either anti-Fas or TNF-alpha. In addition, Bcl-xL prevented the change in cytochrome c immunolocalization induced by anti-Fas or TNF-alpha treatment. Using antibodies that recognize the p20 and p10 subunits of active caspase-8, proteolytic processing of caspase-8 was detected in MCF7/F cells following anti-Fas or TNF-alpha, but not during UV-induced apoptosis. In MCF7/FB cells, caspase-8 was processed normally while processing of the downstream caspase-7 was markedly attenuated. Moreover, apoptosis induced by direct microinjection of recombinant, active caspase-8 was completely inhibited by Bcl-xL. These data demonstrate that Bcl-xL can exert an anti-apoptotic function in cells in which caspase-8 is activated. Thus, at least in some cells, caspase-8 signaling in response to Fas or TNFR1 stimulation is regulated by a Bcl-xL-inhibitable step.

Apoptosis↗

PubMed1998

Heparan sulfate proteoglycans recognize ghost Pick bodies.

An anti-heparan sulfate proteoglycan (HSPG) monoclonal antibody (3G10) recognized irregular round structures (IRSs) of various sizes adjacent to tau-positive intracellular Pick bodies (PBs) in the granular cell layer of the dentate gyrus and the superficial layers of the parahippocampal and other temporal gyri in Pick's disease. Some intracellular PBs were also weakly immunostained with 3G10. Only part of the IRSs were double-immunostained with 3G10 and anti-tau antibody. Immunoelectron-microscopic examination revealed that IRSs were composed of aggregated fibrillary structures with a diameter of 10-20 nm, corresponding to the appearance of ghost PBs. These findings suggest that 3G10 identifies ghost PBs better than intracellular PBs, and that heparan sulfate proteoglycans are involved in the process of PBs extinction.

Antibodies, Monoclonal↗

PubMed1998

Synthesis and secretion of the pancreatic-type carboxyl ester lipase by human endothelial cells.

Human aortic extracts contain significant cholesteryl ester hydrolytic activity. The enzymic activity was shown to be activated by trihydroxylated bile salt, but not by dihydroxylated bile salt. Monospecific antibodies prepared against rat pancreatic carboxyl ester lipase (CEL, cholesterol esterase) immunoprecipitated cholesteryl ester hydrolytic activity from human aorta, demonstrating that the neutral CEL in aorta is highly similar to and probably identical with the pancreatic enzyme. Reverse transcriptase PCR amplification of mRNA from human aortic endothelial cells revealed de novo synthesis of the pancreatic-type CEL by these cells. Preincubating human aortic endothelial cells with oxidized or native low-density lipoprotein resulted in an 8- and 3-fold increase in CEL activity secreted into the culture medium respectively. A potential physiological role for the endothelial CEL was demonstrated by studies showing its ability to confer partial protection against the cytotoxic effects of lysophosphatidylcholine. The protective effect of CEL is related to its bile-salt-independent lysophospholipase activity. However, CEL hydrolysis of lysophosphatidylcholine can be inhibited by excess cholesterol. Taken together, these results indicate that pancreatic-type CEL is synthesized by cells lining the vessel wall. Moreover, vascular CEL may interact with cholesterol and oxidized lipoproteins to modulate the progression of atherosclerosis.

Animals↗

PubMed1998

Trypanosoma brucei brucei: characterization of an ODC null bloodstream form mutant and the action of alpha-difluoromethylornithine.

Ornithine decarboxylase (ODC) is a key enzyme in the polyamine synthesis pathway in African trypanosomes. We report here the characterization of an ODC null bloodstream form Trypanosoma brucei brucei mutant, created by replacing the ODC gene with antibiotic resistant marker genes through transfection and homologous recombination. The null mutant expresses no ODC mRNA or protein and does not have ODC enzymatic activity. We tested the attenuation of the bloodstream form ODC- mutants in mice, and showed that these mutants cannot multiply and are quickly cleared from the blood. We also tested the effect of DFMO on this ODC null mutant.

Animals↗

PubMed1998

Expression of the integrin-linked kinase (ILK) in mouse skin: loss of expression in suprabasal layers of the epidermis and up-regulation by erbB-2.

Integrin-linked kinase (ILK) is a newly identified serine/threonine protein kinase implicated in integrin signaling. To investigate the functions of ILK in vivo, we have analyzed the expression and regulation of ILK in the skin, in which proper control of cell-extracellular matrix interactions and cell proliferation is essential for its normal development and homeostasis. We report here that ILK is abundantly expressed throughout the extracellular matrix-rich dermis. ILK mRNA was also detected in the hair follicles and the basal cells of the interfollicular epidermis. However, ILK expression is lost in the suprabasal layers of keratinocytes that are undergoing terminal differentiation. PINCH, an ILK-binding protein, exhibited a similar expression pattern in the skin. Recent studies have indicated that erbB-2, a member of the epidermal growth factor receptor family, plays a pivotal role in epidermal growth, differentiation, and hair follicle morphogenesis. Using a transgenic mouse system in which an activated erbB-2 is overexpressed in the epidermis, we show that ILK expression is regulated by erbB-2. The in vivo expression and regulation patterns of ILK, together with its biochemical activities, suggest an important role of ILK in coordinating the integrin signaling pathways and the growth factor signaling pathways in the development of the skin and the pathogenesis of skin diseases.

Adaptor Proteins, Signal Transducing↗

PubMed1998

Identification and characterization of a serpin with differential expression during the life cycle of the sea lamprey.

We have cloned a member of the serine proteinase inhibitor gene superfamily from the sea lamprey, Petromyzon marinus. The predicted translation product contains a putative signal peptide and mRNA expression is localized mainly to the liver. Northern blot analysis indicates that the mRNA increases in the larvae and peaks in late larval life. At the onset of metamorphosis there is a approximately 10-fold drop after which it remains low. These changes correspond with levels of circulating thyroid hormone suggesting that this serpin is involved in or regulated by molecular signals that induce metamorphosis in the lamprey. Use of alignments and structural information from other serpins indicates that the lamprey serpin has the potential to be inhibitory. In addition the lamprey serpin contains methionine and serine at the P1 and P1' positions, respectively. Appropriate residues at positions important in allowing the insertion of strand s4A into beta-sheet A that occurs upon cleavage in inhibitory serpins are also found in the lamprey serpin.

Amino Acid Sequence↗

PubMed1998

Molecular cloning, sequence analysis and expression distribution of rainbow trout (Oncorhynchus mykiss) cystatin C.

Cystatin C is one of a family of proteinase inhibitors of cathepsins and other cysteine proteinases. Among warm-blooded vertebrates, small functional regions of cystatin amino acid sequences are well conserved among species, but major portions of cystatin amino acid sequences vary evolutionarily. Although considerable attention has been given to mammalian and avian cystatins, little data exist on cystatins from other vertebrates. A cDNA clone for trout cystatin C was isolated from a lambda gt11 cDNA library of rainbow trout (Oncorhynchus mykiss) liver. An apparently full-length cDNA clone of 674 bp encoding 132 amino acid residues was obtained. Sequence analysis indicated that trout cystatin C contains an N-terminal signal sequence extension of 21 amino acids and a mature sequence of 111 amino acid residues, with amino acid residues conserved in functional regions relative to mammalian and avian cystatin C. Using cloned cDNA as a probe, we investigated expression of the cystatin C gene in trout tissues, several cell lines of trout liver or liver tumor, and cell cultures of liver tumor origin. Cystatin C mRNA was in high abundance in trout embryo tissue, a tumor-derived liver cell line and some normal adult tissues. Southern hybridization analysis indicated one copy of the trout cystatin C gene per haploid genome, and sequence comparisons indicated considerable divergence in large portions of the coding region of the trout cystatin C gene relative to a variety of species.

Amino Acid Sequence↗

PubMed1998

One step microelectroelution concentration method for efficient coupling of sodium dodecylsulfate gel electrophoresis and matrix-assisted laser desorption time-of-flight mass spectrometry for protein analysis.

The coupling of the widely used separation technique of conventional sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) with the mass accuracy measurement capability of mass spectrometry (MS) provides a very powerful analytical technique. However, at present, there is no simple, definitive method for coupling the two methods. Typically, separated proteins are extracted from the gel, either as the native protein or as a peptide mixture after in-gel proteolytic digestion, and then analyzed by mass spectrometry. However, the various extraction techniques described previously have been labor intensive and require a large number of steps. The mass spectrometry analysis of very low concentrations of in vivo derived proteins requires minimum sample handling and on-line concentration. Therefore, we have developed an efficient microelectroelution technique that is applied in a single step manner and contains an on-line concentration device. Initial results from this system have shown a high efficiency of analyte elution from the gel and a simple, robust technique for the coupling of SDS-containing gels with MALDI-TOF-MS analysis and a capability of analyzing proteins at the subpicomole level.

Amino Acids↗

PubMed1998

Measuring self-monitoring ability and propensity: a two-dimensional Chinese scale.

Self-monitoring characterizes individual differences in a person's ability and propensity to regulate self-presentation (M. Snyder, 1974, 1979). On the basis of this idea and existing scale items (R. D. Lennox & R. N. Wolfe, 1984; M. Snyder, 1974), a 23-item 2-dimensional Chinese Self-Monitoring Scale was devised with subscales measuring the Ability and the Propensity to regulate self-presentation according to situational cues. The two subscales displayed different correlational patterns with the Psychoticism, Extraversion, Neuroticism, and Lie subscales of the Eysenck Personality Questionnaire (EPQ; S. B. G. Eysenck & H. J. Eysenck, 1975). The new scale, with stable factor structure and satisfactory internal consistency, may discriminate among self-presentational styles beyond the prototypes of high and low self-monitoring.

China↗

PubMed1998

Confirmatory factor analysis of the Task and Ego Orientation in Sport Questionnaire with cross-validation.

Although a number of factor analytic studies have been conducted on the factorial validity of the Task and Ego Orientation in Sport Questionnaire (TEOSQ), the results have been equivocal. To further substantiate its evidence of validity, this study cross-validated the measurement model using a rigorous structural equation modeling (SEM) approach. Data collected from a college student sample were first analyzed on a calibration sample (n = 439). Results confirmed the two-factor orthogonal structure representing the underlying task and ego orientations. The results were cross-validated on a validation sample (n = 439) using various SEM-based cross-validation procedures. Collectively, these findings support the construct validity of the TEOSQ as a measure of achievement goal orientation.

Achievement↗

PubMed1998

Nck-2, a novel Src homology2/3-containing adaptor protein that interacts with the LIM-only protein PINCH and components of growth factor receptor kinase-signaling pathways.

Many of the protein-protein interactions that are essential for eukaryotic intracellular signal transduction are mediated by protein binding modules including SH2, SH3, and LIM domains. Nck is a SH3- and SH2-containing adaptor protein implicated in coordinating various signaling pathways, including those of growth factor receptors and cell adhesion receptors. We report here the identification, cloning, and characterization of a widely expressed, Nck-related adaptor protein termed Nck-2. Nck-2 comprises primarily three N-terminal SH3 domains and one C-terminal SH2 domain. We show that Nck-2 interacts with PINCH, a LIM-only protein implicated in integrin-linked kinase signaling. The PINCH-Nck-2 interaction is mediated by the fourth LIM domain of PINCH and the third SH3 domain of Nck-2. Furthermore, we show that Nck-2 is capable of recognizing several key components of growth factor receptor kinase-signaling pathways including EGF receptors, PDGF receptor-beta, and IRS-1. The association of Nck-2 with EGF receptors was regulated by EGF stimulation and involved largely the SH2 domain of Nck-2, although the SH3 domains of Nck-2 also contributed to the complex formation. The association of Nck-2 with PDGF receptor-beta was dependent on PDGF activation and was mediated solely by the SH2 domain of Nck-2. Additionally, we have detected a stable association between Nck-2 and IRS-1 that was mediated primarily via the second and third SH3 domain of Nck-2. Thus, Nck-2 associates with PINCH and components of different growth factor receptor-signaling pathways via distinct mechanisms. Finally, we provide evidence indicating that a fraction of the Nck-2 and/or Nck-1 proteins are associated with the cytoskeleton. These results identify a novel Nck-related SH2- and SH3-domain-containing protein and suggest that it may function as an adaptor protein connecting the growth factor receptor-signaling pathways with the integrin-signaling pathways.

3T3 Cells↗

PubMed1998

Endoscopic diagnosis of lower intestinal lesions of leukaemia and malignant lymphoma.

There have been only a few endoscopic studies with respect to lower intestinal lesions of leukaemia and malignant lymphoma, although there have been many autopsy studies of these lesions. The aim of this study was to clarify these lesions using endoscopy. Colonoscopy was performed on 11 of 341 patients with leukaemia and on 32 of 105 patients with malignant lymphoma for frequent diarrhoea, anal bleeding or abnormal findings on barium enema examination, between April 1984 and September 1994. In eight of the 11 patients with leukaemia on whom endoscopy was performed, nine lesions were found; aphthoid ulcers, small ulcers or large tumours due to leukaemic infiltration were found in five, and colorectal adenoma was found in only one patient. Antibiotic-associated haemorrhagic colitis or pseudomembranous colitis was found in one patient each. In 10 of the 32 patients with malignant lymphoma, 11 lesions were found. The following were found in one patient each: large lymphomatous tumours, a large lymphomatous ulcer, multiple small polypoid lesions, multiple lymphomatous polyposis; and colorectal cancer or adenoma in six patients. However, the autopsy findings in patients with both diseases were mostly pseudomembrane formation or ulcers due to fungal and/or bacterial infection. It is concluded that accurate endoscopic diagnosis of lower intestinal lesions in patients with leukaemia or malignant lymphoma is essential for staging and treatment of these diseases and for determining their prognosis. Most lesions in leukaemia are aphthoid and small ulcers are due to leukaemic infiltration or antibiotics; most lesions in malignant lymphoma are elevated lesions such as cancer, adenoma or lymphomatous lesions as determined by endoscopy. This is in contrast to pseudomembrane formation or ulcers due to fungal and/or bacterial infection which are detected at autopsy.

Adult↗

PubMed1998

The S2 gene of equine infectious anemia virus is dispensable for viral replication in vitro.

Equine infectious anemia virus (EIAV) contains the simplest genome among lentiviruses in that it encodes only three putative regulatory genes (S1, S2, S3) in addition to the canonical gag, pol, and env genes, presumably reflecting its limited tropism to cells of monocyte/macrophage lineage. Tat and Rev functions have been assigned to S1 and S3, respectively, but the specific function for the S2 gene has yet to be determined. Thus, the function of S2 in virus replication in vitro was investigated by using an infectious molecular viral clone, EIAVUK. Various EIAVUK mutants lacking S2 were constructed, and their replication kinetics were examined in several equine cell culture systems, including the natural in vivo target equine macrophage cells. The EIAV S2 mutants showed replication kinetics similar to those of the parental virus in all of the tested primary and transformed equine cell cultures, without any detectable reversion of mutant genomes. The EIAVUK mutants also showed replication kinetics similar to those of the parental virus in an equine blood monocyte differentiation-maturation system. These results demonstrate for the first time that the EIAV S2 gene is not essential and does not appear to affect virus infection and replication properties in target cells in vitro.

Amino Acid Sequence↗