Biomedical subjects

Xin Lin

Publications and source records attributed to Xin Lin.

At least 55 records · Page 3Linked to original sources

PubMed2004

Human glycolipid transfer protein: probing conformation using fluorescence spectroscopy.

Glycolipid transfer protein (GLTP) is a soluble 24 kDa protein that selectively accelerates the intermembrane transfer of glycolipids in vitro. Little is known about the GLTP structure and dynamics. Here, we report the cloning of human GLTP and characterize the environment of the three tryptophans (Trps) of the protein using fluorescence spectroscopy. Excitation at 295 nm yielded an emission maximum (lambda(max)) near 347 nm, indicating a relatively polar average environment for emitting Trps. Quenching with acrylamide at physiological ionic strength or with potassium iodide resulted in linear Stern-Volmer plots, suggesting accessibility of emitting Trps to soluble quenchers. Insights into reversible conformational changes accompanying changes in GLTP activity were provided by addition and rapid dilution of urea while monitoring changes in Trp or 1-anilinonaphthalene-8-sulfonic acid fluorescence. Incubation of GLTP with glycolipid liposomes caused a blue shift in the Trp emission maximum but diminished the fluorescence intensity. The blue-shifted emission maximum, centered near 335 nm, persisted after separation of glycolipid liposomes from GLTP, consistent with formation of a GLTP-glycolipid complex at a glycolipid-liganding site containing Trp. The results provide the first insights into human GLTP structural dynamics by fluorescence spectroscopy, including global conformational changes that accompany GLTP folding into an active conformational state as well as more subtle conformational changes that play a role in GLTP-mediated transfer of glycolipids between membranes, and establish a foundation for future studies of membrane rafts using GLTP.

Amino Acid Sequence↗

PubMed2004

Design, synthesis, and biological evaluation of 2,4-diamino-5-methyl-6-substituted-pyrrolo[2,3-d]pyrimidines as dihydrofolate reductase inhibitors.

2,4-diamino-5-methyl-6-(substituted-phenyl)thiopyrrolo[2,3-d]pyrimidines 4-11 were synthesized as dihydrofolate reductase (DHFR) inhibitors against opportunistic pathogens that afflict patients with AIDS. Synthesis was achieved from 2,4-diamino-5-methypyrrolo[2,3-d]pyrimidine and substituted phenylthiols under modified conditions reported by Gangjee et al. Some of these compounds were potent and selective against DHFR from both Toxoplasma gondii and Mycobacterium avium compared to mammalian DHFR. Compound 11 with a 1-naphthyl substituent is 16-fold more potent and equally selective against Toxoplasma gondii DHFR as the clinically used trimethoprim.

Animals↗

PubMed2004

MALT1/paracaspase is a signaling component downstream of CARMA1 and mediates T cell receptor-induced NF-kappaB activation.

T cell receptor (TCR) induces a series of signaling cascades and leads to activation of multiple transcription factors, including NF-kappaB. Although the mechanism of TCR-induced NF-kappaB activation is not fully understood, recent studies indicate that Bcl10 and CARMA1, two adaptor/scaffold proteins, play essential roles in mediating TCR-induced NF-kappaB activation. MALT1/paracaspase is a caspase-like protein that contains an N-terminal death domain, two Ig-like domains, and a C-terminal caspase-like domain. It binds to Bcl10 through its Ig-like domains and cooperates with Bcl10 to activate NF-kappaB. Recently, it has been shown that MALT1 is involved in mediating TCR signal transduction, leading to activation of NF-kappaB. In this study, we show that MALT1 is recruited into the lipid rafts of the immunological synapse following activation of the TCR and the CD28 coreceptor (CD3/CD28 costimulation). This recruitment of MALT1 is dependent on CARMA1 because CD3/CD28 costimulation failed to recruit MALT1 into lipid rafts in CARMA1-deficient T cells. In addition, we also found that MALT1 not only binds to Bcl10 directly, but also associates with CARMA1 in a Bcl10-independent manner. Therefore, MALT1, Bcl10, and CARMA1 form a trimolecular complex. Expression of a MALT1 deletion mutant containing only the N-terminal death domain and the two Ig-like domains completely blocked CD3/CD28 costimulation-induced, but not tumor necrosis factor-alpha-induced, NF-kappaB activation. Together, these results indicate that MALT1 is a crucial signaling component in the TCR signaling pathway.

Apoptosis Regulatory Proteins↗

PubMed2004

Cell signalling through thromboxane A2 receptors.

Thromboxane A2 receptors (TPs) are widely distributed among different organ systems and have been localized on both cell membranes and intracellular structures. Following the initial cloning of this receptor class from human placenta, the deduced amino acid sequence predicted seven-transmembrane spanning regions, four extracellular domains and four intracellular domains, making TP a member of the seven-transmembrane G-protein-coupled receptor (GPCR) super family. A single gene on chromosome 19p13.3 leads to the expression of two separate TP isoforms: TPalpha which is broadly expressed in numerous tissues, and a splice variant termed TPbeta which may have a more limited tissue distribution. Mutagenesis, photoaffinity labelling, and immunological studies have indicated that the ligand binding domains for this receptor may reside in both the transmembrane (TM) and extracellular regions of the receptor protein. In addition, separate studies have provided evidence that this receptor can couple to at least four separate G protein families. As a consequence, TP signalling has been shown to result in a broad range of cellular responses including phosphoinositide metabolism, calcium redistribution, cytoskeletal arrangement, integrin activation, kinase activation, and the subsequent nuclear signalling events involved in DNA synthesis, cell proliferation, cell survival and cell death. While activation of these different signalling cascades can all derive from TP stimulation, the relative signalling preference for a given cascade appears to be both tissue and cell specific. Finally, separate studies have indicated that TP signalling capacity can be both down-regulated by protein kinase activation and up-regulated by GPCR cross-signalling. Thus, the multitude of signalling events which derive from TP activation can themselves be modulated by endogenous cellular messengers.

Cells, Cultured↗

PubMed2004

The roles of CARMA1, Bcl10, and MALT1 in antigen receptor signaling.

Lymphocyte activation plays a critical role in immune responses. Dysregulation of lymphocyte activation can cause autoimmune, immunodeficient diseases, or leukemia/lymphoma. Lymphocyte activation is triggered by stimulation of antigen receptors, T cell receptors (TCR) or B cell receptors (BCR), on the surfaces of T or B lymphocyte, respectively. Stimulation of TCR or BCR induces a series of signal transduction cascades leading to activation of multiple transcription factors including NF-kappaB. Recent studies demonstrate that CARMA1, a scaffold protein, plays an essential role in mediating TCR- or BCR-induced NF-kappaB activation by recruiting two adaptor proteins, Bcl10 and MALT1, to lipid rafts following stimulation of antigen receptors. In this review, we will discuss the mechanism by which proximal signaling components connect antigen receptor signaling to CARMA1, and how CARMA1 regulates Bcl10 and MALT1, leading to activation of NF-kappaB. In addition, the roles of CARMA1, Bcl10, and MALT1 in lymphocyte activation and development will also be discussed.

Adaptor Proteins, Signal Transducing↗

PubMed2004

CD3/CD28 costimulation-induced NF-kappaB activation is mediated by recruitment of protein kinase C-theta, Bcl10, and IkappaB kinase beta to the immunological synapse through CARMA1.

CARMA1 (also known as CARD11) is a scaffold molecule and contains a caspase-recruitment domain (CARD) and a membrane-associated guanylate kinase-like (MAGUK) domain. It plays an essential role in mediating CD3/CD28 costimulation-induced NF-kappaB activation. However, the molecular mechanism by which CARMA1 mediates costimulatory signals remains to be determined. Here, we show that CARMA1 is constitutively associated with the cytoplasmic membrane. This membrane association is essential for the function of CARMA1, since a mutant of CARMA1, CARMA1(L808P), that is defective in the membrane association cannot rescue CD3/CD28 costimulation-induced NF-kappaB activation in JPM50.6 CARMA1-deficient T cells. Although CD3/CD28 costimulation effectively induces the formation of the immunological synapse in CARMA1-deficient T cells, the recruitment of protein kinase C-theta (PKC-theta), Bcl10, and IkappaB kinase beta (IKKbeta) into lipid rafts of the immunological synapse is defective. Moreover, expression of wild-type CARMA1, but not CARMA1(L808P), restores the recruitment of PKC-theta, Bcl10, and IKKbeta into lipid rafts in CARMA1-deficient T cells. Consistently, expression of a mutant CARMA1, CARMA1(DeltaCD), that cannot associate with Bcl10 failed to restore CD3/CD28 costimulation-induced NF-kappaB activation in JPM50.6 cells, whereas expression of Bcl10-CARMA(DeltaCD) fusion protein effectively restored this NF-kappaB activation. Together, these results indicate that CARMA1 mediates CD3/CD28 costimulation-induced NF-kappaB activation by recruiting downstream signaling components into the immunological synapse.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Restoration of NF-kappaB activation by tumor necrosis factor alpha receptor complex-targeted MEKK3 in receptor-interacting protein-deficient cells.

Receptor-interacting protein (RIP) plays a critical role in tumor necrosis factor alpha (TNF-alpha)-induced NF-kappaB activation. However, the mechanism by which RIP mediates TNF-alpha-induced signal transduction is not fully understood. In this study, we reconstituted RIP-deficient Jurkat T cells with a fusion protein composed of full-length MEKK3 and the death domain of RIP (MEKK3-DD). In these cells, MEKK3-DD substitutes for RIP and directly associates with TRADD in TNF receptor complexes following TNF-alpha stimulation. We found that TNF-alpha-induced NF-kappaB activation was fully restored by MEKK3-DD in these cells. In contrast, expression of a fusion protein composed of NEMO, a component of the IkappaB kinase complex, and the death domain of RIP (NEMO-DD) cannot restore TNF-alpha-induced NF-kappaB activation in RIP-deficient cells. These results indicate that the role of RIP is to specifically recruit MEKK3 to the TNF-alpha receptor complex, whereas the forced recruitment of NEMO to the TNF-alpha receptor complex is insufficient for TNF-alpha-induced NF-kappaB activation. Although MEKK2 has a high degree of homology with MEKK3, MEKK2-DD, unlike MEKK3-DD, also fails to restore TNF-alpha-induced NF-kappaB activation in RIP-deficient cells, indicating that RIP-dependent recruitment of MEKK3 plays a specific role in TNF-alpha signaling.

Blotting, Western↗

PubMed2004

Endomorphins, endogenous opioid peptides, induce apoptosis in human leukemia HL-60 cells.

Opioids play a role in the apoptosis machinery. We studied the induction of apoptosis in endomorphin 1 (EM1) and endomorphin 2 (EM2), 2 newly isolated endogenous mu-opioid receptor agonists. These endomorphins were able to reduce the viability of cultured HL-60 cells. The antiproliferative properties of endomorphins appeared to be attributable to their induction of apoptotic cell death as determined by ultrastructural change, internucleosomal DNA fragmentation, and increased proportion of the subdiploid cell population. To elucidate molecular events in the apoptosis, protein expressions of Bcl-2, Bax, Fas, and FasL were measured by western blotting using specific antibodies in HL-60 cells. The level of Bcl-2 indicated down-regulation, but the Bax, Fas, and FasL expression showed up-regulation as compared with the untreated control cells. These data support the idea that endomorphins induce apoptosis in HL-60 cells through the activation of the Bcl-2-Bax and the Fas-FasL pathway. We suggest that endomorphins may play an important role in the regulation of tumor cell death.

Apoptosis↗

PubMed2004

The effects of hydroxyethyl starch on lung capillary permeability in endotoxic rats and possible mechanisms.

UNLABELLED: In this study we examined the effects of hydroxyethyl starch (HES 200/0.5) on lung capillary permeability in endotoxic rats and explored the possible mechanisms. Male Wistar rats were randomly divided into seven groups treated with saline, lipopolysaccharide (LPS; 6 mg/kg), LPS plus HES (3.75, 7.5, 15, or 30 mL/kg), or HES (30 mL/kg) alone for 4 or 2 h. Lung capillary permeability, lung neutrophil accumulation, expression of CD11b on the blood neutrophil cell surface, lung cytokine-induced neutrophil chemoattractant protein level, and nuclear factor kappa B (NF-kappaB) activation in blood neutrophils and lungs were measured. HES at doses of 3.75 and 7.5 mL/kg significantly reduced LPS-induced increases of lung capillary permeability. HES was found to inhibit lung neutrophil accumulation, cytokine-induced neutrophil chemoattractant protein, and NF-kappaB activation in parallel and to inhibit CD11b expression in a dose-dependent manner. These findings demonstrate that HES has beneficial effects on capillary leak in acute lung injury and that the mechanisms underlying this action involve an antiinflammatory effect of HES, including inhibition of NF-kappaB activation. IMPLICATIONS: A randomized, controlled laboratory experiment indicated that hydroxyethyl starch (HES) could reduce increased lung capillary permeability in endotoxemia. This effect may be due to an antiinflammatory effect of HES.

Animals↗

PubMed2004

Genome-wide search for type 2 diabetes/impaired glucose homeostasis susceptibility genes in the Chinese: significant linkage to chromosome 6q21-q23 and chromosome 1q21-q24.

This genome-wide search for susceptibility genes to type 2 diabetes/impaired glucose homeostasis (IGH) was performed on a relatively homogeneous Chinese sample with a total number of 257 pedigrees and 385 affected sibpairs. Two regions showed significant linkage to type 2 diabetes/IGH in the Chinese. The region showing linkage to type 2 diabetes/IGH from the entire sample group analysis was located on chromosome 6q21-q23 (128.93 cM, 1-LOD [logarithm of odds] support interval between 124 and 142 cM, according to the Marshfield genetic map), with a maximum likelihood score of 6.23, a nonparametric linkage (all) score of 4.48, and empirical P value <0.001. With a subanalysis based on 101 affected sibpairs with age at diagnosis of type 2 diabetes/IGH <40 years, we detected significant evidence for linkage to chromosome 1q21-q24 (192.1 cM, 1-LOD support interval between 182 and 197 cM), with a maximum likelihood score of 8.91, a nonparametric linkage (all) score of 5.70, and empirical P value <0.001. No interaction was observed between these two regions. Our independent replication of the region on chromosome 1q that has been shown to be linked significantly to type 2 diabetes/IGH in Chinese supports the notion that gene(s) in this region may be universally important in the development of human type 2 diabetes.

Asian People↗

PubMed2004

[Scanning HNF-1 alpha gene mutation in Chinese early-onset and/or multiplex diabetes pedigrees].

OBJECTIVE: To investigate the prevalence of mutations of hepatocyte nuclear factor (HNF)-1 alpha gene in Chinese families with early-onset and/or multiplex diabetes mellitus. METHODS: The studied population consisted of 247 unrelated Chinese residents in Shanghai, including 93 healthy controls and 154 probands of early-onset and/or multiplex diabetes pedigrees. The ten exons, flanking introns and minimal promoter region of HNF-1 alpha gene were screened using polymerase chain reaction-single strand conformation polymorphism and DNA sequencing. RESULTS: Fourteen substitutions were identified in 154 probands. Three variants were not observed in 93 healthy controls. Two of them (nt-128T-->G IVS2 nt+21G-->A) were not reported previously and all co-segregated with diabetes. The genotype and allele frequencies of the other eleven variants in the diabetic patients were not significantly different from those in the healthy controls. There were no significant relationships between the eleven variants of HNF-1 alpha gene and clinical variables (plasma glucose, insulin, C-peptide and fasting lipid profile). CONCLUSION: HNF-1 alpha gene is not a major cause of early-onset or multiplex diabetes pedigrees in this Chinese population in Shanghai.

Asian People↗

PubMed2004

[Surgical treatment for laryngeal condyloma acuminata in children].

OBJECTIVE: To investigate the therapeutic methods of laryngeal condyloma acuminata in children. METHOD: Operative treatment was performed in 43 cases of laryngeal condyloma acuminata in children. Direct laryngoscopy with removal of laryngeal tumor under surface anesthesia was performed in 26 cases, and trachea cannula, retaining laryngoscopy with removal of laryngeal tumor under general anesthesia were performed in 17 cases, hypodermic implantation of the removal condyloma acuminata at medial upper arm and submucous injection of interferon at vocal fold were performed in 13 cases at the same time. RESULT: Cases were followed-up, 26 cases were cured, 7 cases were improved, 2 cases were dead, 7 cases needed tracheotomy, 3 cases had difficulty of decannulation. CONCLUSION: Wide affected part and high recurrence rate are characters of this disease, the tumor can be removed more accurately and the recurrence rate can be decreased when performing self-retaining laryngoscopy with removal of laryngeal tumor combined with hypodermic implantation of the removal condyloma acuminata at medial upper arm and submucous injection of interferon at vocal fold. Difficulty of decannulation can also be avoided after tracheotomy.

Child, Preschool↗

PubMed2004

[The measurement frequency distribution in tissue impedance spectroscopy measurement].

In the research of tissue impedance spectroscopy measurement, the authors constructed a frequency sets that produce angularly equidistant points on the Nyquist loci. The studies of simulation data model demonstrate that, by use of the same quantity of frequency points and in comparison with the frequency sets that are logarithmic and quasi-linear, the angularly equidistant frequency sets can improve the estimate accuracy of tissue electrical model parameters of alpha and fc.

Biomedical Engineering↗

PubMed2004

[Treatment of vertebral hemangioma with percutaneous vertebroplasty].

OBJECTIVE: To investigate the efficacy of percutaneous vertebroplasty in the treatment of vertebral hemangioma. METHODS: Seven patients with vertebral hemangiomas were treated by percutaneous vertebroplasty, including one case of cervical, three cases of thoracic, and three cases of lumbar hemangiomas. The average score of the 6-point behavioral pain rating scale was 2.67 +/- 0.41, and the average score of ambulation was 2.83 +/- 0.33. Guilty vertebral bodies were orientated with fluoroscopy. The procedures were performed under local anesthesia. The image features were also analyzed. Unipedicular or bipedicular approaches were used in 6 cases of thoracic and lumbar hemangiomas. The cervical anterior-lateral approach was adopted in one case of cervical hemangioma. 4-7 ml of 15%-20% bone cement was mixed and injected into the vertebral body to form a cast in the lesions. Re-examination of clinical symptoms, plain film, and CT were made for 1, 3, and 9 months of post-procedure follow-up. RESULTS: Good results were achieved in all the seven cases. Pain was completely relieved in 5 cases and partially relieved in 2 cases. Symptom was also recovered in 2 patients with radiculopathy. No recurrence was found after 1-9 months of postoperative follow-up. CONCLUSION: Treatment of vertebral hemangioma with percutaneous vertebroplasty is safe and effective with minimal invasion.

Adult↗

PubMed2004

Microbial changes in rhizospheric soils contaminated with petroleum hydrocarbons after bioremediation.

Effects of bioremediation on microbial communities in soils contaminated with petroleum hydrocarbons are a scientific problem to be solved. Changes in dominate microbial species and the total amount of microorganisms including bacteria and fungi in rhizospheric soils after bioremediation were thus evaluated using field bioremediation experiments. The results showed that there were changed dominant microorganisms including 11 bacterial strains which are mostly Gram positive bacteria and 6 fungal species which were identified. The total amount of microorganisms including bacteria and fungi increased after bioremediation of microbial agents combined with planting maize. On the contrary, fungi in rhizospheric soils were inhibited by adding microbial agents combined with planting soybean.

Biodegradation, Environmental↗

PubMed2003

Endomorphins, endogenous opioid peptides, provide antioxidant defense in the brain against free radical-induced damage.

Oxidative stress has been considered to be a major cause of cellular injuries in a variety of chronic health problems, such as carcinogenesis and neurodegenerative disorders. The brain appears to be more susceptible to oxidative damage than other organs. Therefore, the existence of antioxidants may be essential in brain protective systems. The antioxidative and free radical scavenging effects of endomorphin 1 (EM1) and endomorphin 2 (EM2), endogenous opioid peptides in the brain, have been investigated in vitro. The oxidative damage was initiated by a water-soluble initiator 2,2'-azobis(2-amidinopropane hydrocholoride) (AAPH) and hydrogen peroxide (H2O2). The linoleic acid peroxidation, DNA and protein damage were monitored by formation of hydroperoxides, by plasmid pBR 322 DNA nicking assay and single-cell alkaline electrophoresis, and by SDS-polyacrylamide gel electrophoresis. Endomorphins can inhibit lipid peroxidation, DNA strand breakage, and protein fragmentation induced by free radical. Endomorphins also reacted with galvinoxyl radicals in homogeneous solution, and the pseudo-first-order rate constants were determined spectrophotometrically by following the disappearance of galvinoxyl radicals. In all assay systems, EM1 was more potent than EM2 and GSH, a major intracellular water-soluble antioxidant. We propose that endomorphins are one of the protective systems against free radical-induced damage in the brain.

Amidines↗

PubMed2003

Structure determination, apoptosis induction, and telomerase inhibition of CFP-2, a novel lichenin from Cladonia furcata.

A great deal of experimental evidence has accumulated in the past several decades, suggesting that polysaccharides have wide bioactivities. Cladonia furcata polysaccharide, CFP-2, a water-soluble lichenin with a mean Mr 7.6 x 10(4), was first obtained by 0.25 M NaOH solution extraction, ethanol precipitation, DEAE-cellulose, and Sephadex G-200 column chromatography. Gas chromatography of acid hydrolyzate of CFP-2 suggested that it was composed of D-glucose, D-galactose, and D-mannose in the molar ratios of 8:1:1. Periodate oxidation, Smith degradation, IR, and NMR spectroscopy analysis revealed that CFP-2 had a backbone consisting of alpha-(1-->3) and alpha-(1-->4)-linked D-glucopyranosyl residues substituted at O-6 with beta-(1-->6)-linked D-galactopyranosyl residue and alpha-(1-->6)-linked D-mannopyranosyl residue. CFP-2 was able to reduce viability of cultured HL-60 and K562 cells. The antiproliferative properties of CFP-2 appeared to be attributable to its induction of apoptotic cell death as determined by ultrastructural change, internucleosomal DNA fragmentation, and increased proportion of the subdiploid cell population. To elucidate molecular events in the apoptosis, protein expressions of Bcl-2, Bax, Fas, and FasL were measured by Western blotting using specific antibodies in HL-60 cells. The level of Bcl-2 remained largely unchanged, but the Bax, Fas, and FasL expression showed up-regulation. Moreover, the telomerase activity analyzed by TRAP-ELISA assay in HL-60 cells treated with CFP-2 decreased as compared with the untreated control cells. These results suggest that CFP-2 could have a possible cancer therapeutic potential.

Apoptosis↗

PubMed2003

Study on therapeutic mechanism and clinical effect of mild hypothermia in patients with severe head injury.

BACKGROUND: The therapeutic mechanism and clinical effect of mild hypothermia in patients with severe head injury were studied. METHODS: All 396 patients with severe head injury [Glasgow Coma Scale score (GCS) equal to or less than 8 on admission] were randomly divided into the hypothermic group (198 cases) and the control group (198 cases). Hypothermia was induced within 24 hours of injury. Rewarming began 1 to 7 days (average 62.4 +/- 27.6 h) after the rectal temperature (RT) reached 32.0 to 35.0 degrees C. Meanwhile, the vital signs, intracranial pressure (ICP), blood gas values, blood electrolytes, brain tissue oxygen pressure (P(bt)O2), brain tissue temperature (BT), cerebral blood flow (CBF), and jugular venous oxygen saturation (S(jv)O2) were measured. The rectal temperature of control patients was induced to 36.5 to 37.0 degrees C. According to GOS, the prognosis of the patients was evaluated. RESULTS: In comparison with control group, during mild hypothermia the high level of ICP, hyperglycemia and blood lactic acid significantly decreased (p < 0.05) and cerebral flow improved dominantly. The vital signs, blood gas values, and blood electrolytes did not change significantly. Decreased mortality and good recovery were also found in hypothermia group. CONCLUSIONS: Mild hypothermia is safe and effective for preventing brain damage on patients with severe head injury, as well as reducing mortality and improving the prognosis. It is important to monitor P(bt)O2, BT, CBF, and S(jv)O2 in hypothermic therapy.

Adolescent↗