PubMed Health⌕ Search

Biomedical subjects

S Cai

Publications and source records attributed to S Cai.

At least 19 recordsLinked to original sources
PubMed2003

Comparative antimicrobial activities of gatifloxacin, sitafloxacin and levofloxacin against Mycobacterium tuberculosis replicating within Mono Mac 6 human macrophage and A-549 type II alveolar cell lines.

Mycobacterium tuberculosis (MTB) is capable of invading not only macrophages (Mphis) but also type II pneumocytes. In this study, we compared the antimicrobial activities of fluoroquinolones, including gatifloxacin, sitafloxacin and levofloxacin, against the MTB replication in the Mono Mac 6 human Mphi cell line (MM6-Mphis) and the A-549 human type II alveolar epithelial cell line (A-549 cells). When test quinolones were added at the MIC (0.125, 0.06 and 0.25 mg/l for gatifloxacin, sitafloxacin and levofloxacin, respectively) to the culture media of MTB-infected cells, these drugs exerted growth-inhibitory activity against intracellular organisms in the order of sitafloxacin > gatifloxacin > levofloxacin. On the other hand, when test quinolones were added at Cmax in the blood (1.7, 1.0 and 2.0 mg/l for gatifloxacin, sitafloxacin and levofloxacin, respectively), these drugs exhibited bactericidal activity against intracellular MTB in the order of gatifloxacin > sitafloxacin > or = levofloxacin. In addition, when test drugs were added at 1/8 C(max) to 1/2 C(max), the efficacy was in the order of sitafloxacin > gatifloxacin > levofloxacin. Thus, it appears that the MIC values of fluoroquinolones are not always predictive of their antimicrobial activity against intracellular MTB. In this context, it was also found that intracellular uptake of these quinolones by MM6-Mphis and A-549 cells was in the order of sitafloxacin > gatifloxacin > levofloxacin. This implies that the cellular permeability of these quinolones is an important factor that determines their efficacy to eliminate intracellular MTB organisms.

Anti-Infective Agents↗
PubMed2003

Molecular characterization of a distinct potyvirus from whitegrass in China.

Apotyvirus isolated from perennial whitegrass ( Pennisetum centrasiaticum Tzvel.) in North China was characterized at the molecular level. The 3' terminal nucleotide (nt) sequence of 1669 nt of the viral RNA genome has been determined, which covered the coding region of the C-terminal part of the large nuclear inclusion protein (NIb, RNA polymerase), capsid protein (CP) gene and the 3' nontranslated region (NTR). The CP gene consisted of 909 nt (including the stop codon) encoding 302 amino acid residues, and the 3' NTR was 241 nt in length excluding the polyadenylated tract. Sequence comparison of the amino acids of CPs showed that this virus was most closely related to Sorghum mosaic virus and Maize dwarf mosaic virus with percent identities of 77% to 78% while that of the 3' NTRs suggested that it was most closely related to Zea mosaic virus with identity of 72%. This virus isolate was to some extent closely related to other members of the Sugarcane mosaic virus subgroup of potyviruses for the CP amino acid sequences. Phylogenetic analyses of the sequences indicated that this virus isolate represented a distinct potyvirus, and the name Pennisetum mosaic virus (PenMV) is proposed.

Capsid Proteins↗
PubMed2003

Efficacy of a 0.5% chlorhexidine gel on the control of gingivitis in Brazilian mentally handicapped patients.

OBJECTIVE: To evaluate the effectiveness of a 0.5% chlorhexidine gel on the reduction of interdental gingival bleeding. MATERIAL AND METHODS: Forty-three mentally handicapped subjects, living in an institution (Casas André Luiz, Brazil), were enrolled in a double-blind randomised clinical trial. The subjects were randomly divided into two groups: test (chlorhexidine gel) and control (placebo gel). The gel was applied with trays, twice a day, over a period of 8 weeks. The interdental bleeding index (IBI) was recorded before and after the period in which the gel was used. RESULTS: Statistical analysis showed that baseline IBI scores were similar (p=0.82) for test and control groups (55.6% and 54.5%, respectively). After 8 weeks, a statistically significant (p<0.001) decrease in IBI means took place in the test group (33.2%). The control group presented a small increase (60.6%) in IBI scores. The difference between groups was significant at the end of the study (p<0.001). CONCLUSION: The results indicated that the use of a 0.5% chlorhexidine gel was effective in reducing interdental gingival bleeding in special patients.

Adolescent↗
PubMed2002

Neuronal nitric oxide synthase gene transfer promotes cardiac vagal gain of function.

Nitric oxide (NO) generated from neuronal nitric oxide synthase (NOS-1) in intrinsic cardiac ganglia has been implicated in parasympathetic-induced bradycardia. We provide direct evidence that NOS-1 acts in a site-specific manner to promote cardiac vagal neurotransmission and bradycardia. NOS-1 gene transfer to the guinea pig right atrium increased protein expression and NOS-1 immunolocalization in cholinergic ganglia. It also increased the release of acetylcholine and enhanced the heart rate (HR) response to vagal nerve stimulation (VNS) in vitro and in vivo. NOS inhibition normalized the HR response to VNS in the NOS-1-treated group compared with the control groups (enhanced green fluorescent protein and sham) in vitro. In contrast, an acetylcholine analogue reduced HR to the same extent in all groups before and during NOS inhibition. These results demonstrate that NOS-1-derived NO acts presynaptically to facilitate vagally induced bradycardia and that upregulation of NOS-1 via gene transfer may provide a novel method for increasing cardiac vagal function.

Acetylcholine↗
PubMed2001

Role of the disulfide cleavage induced molten globule state of type a botulinum neurotoxin in its endopeptidase activity.

Botulinum neurotoxins are produced by anaerobic Clostridium botulinum in an inactive form. The endopeptidase activity of type A botulinum neurotoxin (BoNT/A) is triggered by reduction of its disulfide bond between its heavy chain and light chain. By using circular dichroism spectroscopy, we show that, upon reduction of BoNT/A and under physiological temperature (37 degrees C), the BoNT/A loses most of its native tertiary structure, while retaining most of its secondary structure. This type of structure is characterized as a molten globule type conformation, which was further confirmed for BoNT/A by the characteristic binding of 1-anilinonaphthalene-8-sulfonic acid. Under nonreducing conditions where the interchain disulfide bond is intact, the enzymatically inactive BoNT/A did not show a molten globule type of structure. A temperature profile of the structure and enzyme activity of BoNT/A revealed that, under reducing conditions, there was a strong correlation in the existence of the molten globule structure and optimum endopeptidase activity at about 37 degrees C.

Anilino Naphthalenesulfonates↗
PubMed2001

Cyanide complexes of iron corrolates: spin delocalization and autoreduction.

Complex formation of (7,13-dimethyl-2,3,8,12,17,18-hexaethylcorrolato)iron chloride, [(7,13-Me(2)Et(6)C)FeCl], with cyanide ion in dimethylformamide, DMF-d(7), was studied by (1)H NMR spectroscopy. It is found that a bis-cyanide complex is formed initially, in which the electron configuration is a low-spin Fe(III) corrolate(2-*). This complex is not stable, and it is readily reduced with an excess of cyanide in the solution. The reduction occurs at the corrole ring instead of on the iron center giving the monocyanide complex of the low-spin Fe(III) corrole, [(7,13-Me(2)Et(6)C)FeCN](-). Thus, this is a case where an axial ligand serves as a reducing agent of the macrocycle and not of the metal.

Cations↗
PubMed2001

Nitric oxide synthase (nNOS) gene transfer modifies venous bypass graft remodeling: effects on vascular smooth muscle cell differentiation and superoxide production.

BACKGROUND: Pathological vascular remodeling in venous bypass grafts (VGs) results in smooth muscle cell (SMC) intimal hyperplasia and provides the substrate for progressive atherosclerosis, the principal cause of late VG failure. Nitric oxide (NO) bioactivity is reduced in VGs, in association with increased vascular superoxide production, but how these features relate to pathological VG remodeling remains unclear. We used gene transfer of the neuronal isoform of nitric oxide synthase (nNOS) to investigate how increased NO production modulates vascular remodeling in VGs and determined the effects on late VG phenotype. METHODS AND RESULTS: New Zealand White rabbits (n=60) underwent jugular-carotid interposition bypass graft surgery with intraoperative adenoviral gene transfer of nNOS or beta-galactosidase. Vessels were analyzed after 3 days (early, to investigate acute injury/inflammation) or 28 days (late, to investigate SMC intimal hyperplasia). In early VGs, nNOS gene transfer significantly increased NOS activity and substantially reduced adhesion molecule expression and inflammatory cell infiltration. In late VGs, recombinant nNOS protein was no longer evident, but there were sustained effects on VG remodeling, resulting in a striking reduction in SMC intimal hyperplasia, a more differentiated intimal SMC phenotype, and reduced vascular superoxide production. CONCLUSIONS: Intraoperative nNOS gene transfer has sustained favorable effects on VG remodeling and on the vascular phenotype of mature VGs. These findings suggest that early, transient modification of the response to vascular injury is a powerful approach to modulate VG biology and highlight the potential utility of NOS gene transfer as a therapeutic strategy in VGs.

Adenoviridae↗
PubMed2001

Effect of H-7 on cultured human trabecular meshwork cells.

PURPOSE: To determine the effect of the serine-threonine kinase inhibitor H-7, which blocks actomyosin contractility and increases outflow facility in live monkeys, on morphology, cytoskeleton, and cellular adhesions of human trabecular meshwork (HTM) cells in culture. METHODS: Cultured HTM cells were videographically recorded and evaluated before and after exposure to H-7 at different concentrations. The subcellular distribution of the actin-based cytoskeleton and associated anchor proteins including vinculin, paxillin, and beta-catenin, as well as phosphotyrosine-containing proteins were evaluated by fluorescence immunocytochemistry and digital fluorescence microscopy. RESULTS: H-7 induced pronounced but reversible HTM cell thickening toward the cell center and deterioration of the actin cytoskeletal network. Cell-extracellular matrix (ECM) and cell-cell adhesions were also affected, but the beta-catenin-rich, vinculin-containing adherens junctions were clearly more resistant than focal contacts. Phosphotyrosine labeling in focal contacts was highly sensitive to H-7. CONCLUSIONS: H-7 induces alterations in cell shape, actin cytoskeleton, and associated focal adhesions in cultured HTM cells, which may be responsible for the effects of H-7 on outflow facility in live monkey eyes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2001

Determination of interaction sites of phospholipase D1 for RhoA.

Phospholipase D (PLD) is regulated by many factors, including protein kinase C (PKC) and small G-proteins of the Rho and ADP-ribosylation factor families. Previous studies revealed that the interaction site of human PLD(1) for RhoA is located in its C-terminus, but the exact locus has not been determined. The purpose of the present study was to determine the interaction site of rat PLD(1) (rPLD(1)) with RhoA. Selection with phage display of different peptides of rPLD(1) confirmed that GTP-bound RhoA interacted with a site in the amino acid sequence 873-1024 at the C-terminus of rPLD(1). RhoA also associated with this peptide in a GTP-dependent manner in COS-7 cell lysates and the peptide inhibited RhoA stimulation of PLD activity in membranes from COS-7 cells expressing rPLD(1). A series of alanine mutations of non-conserved residues were made in this sequence, and the enzymes were expressed in COS-7 cells and checked for responses to activation of PKC, which interacts with the N-terminus of PLD(1), and also to the constitutively active V14RhoA. Mutations in the C-terminus of rPLD(1) (K946A, V950A, R955A and K962A) caused partial loss of V14RhoA stimulation, and double mutations (K946A/K962A, K946A/V950A and K962A/V950A) caused an almost total loss. Co-immunoprecipitation studies also showed that the mutated forms of rPLD(1) described above failed to bind V14RhoA compared with wild-type rPLD(1), whereas rPLD(1) with mutations outside the region K946-K962 bound V14RhoA normally. It is concluded that basic amino acids in a restricted C-terminal region of rPLD(1) are important for binding of RhoA and its activation of PLD activity.

Animals↗
PubMed2001

A correlation between differential structural features and the degree of endopeptidase activity of type A botulinum neurotoxin in aqueous solution.

Botulinum neurotoxin type A is one of the most toxic substances known to man (LD(50) for mouse 0.1 ng/kg). It is also an effective therapeutic drug against involuntary muscle disorders and for pain management. BoNT/A is a Zn(2+) endopeptidase which selectively cleaves SNAP-25 (synaptosomal-associated protein of 25 kDa), a critical component of the exocytotic machinery. Based on nucleotide sequence, BoNT/A is a 145 kDa protein, which appears as a 145 kDa protein band on sodium dodecyl sulfate--polyacrylamide gel electrophoresis. We have examined the structure of BoNT/A in aqueous solution, and found the structure in aqueous solution differs dramatically from that resolved by X-ray crystallography, both at secondary and at quaternary levels. In terms of secondary structure, BoNT/A in aqueous solution has about 47% beta-sheet structure as revealed by infrared spectroscopy, while X-ray crystallography revealed only 17% beta-sheet structure. In terms of quaternary structure, the estimated molecular mass of the native BoNT/A in aqueous solution ranged between 230 and 314 kDa, based on results from different chemical and biophysical techniques (native gel electrophoresis, chemical cross-linking, size exclusion chromatography, and fluorescence anisotropy). These results indicate that BoNT/A exists as a dimer in aqueous solution, which contrasts with the reported monomeric structure of BoNT/A based on X-ray crystallography. The dimeric form of BoNT/A can self-dissociate into the monomeric form at a concentration lower than 50 nM. This concentration-dependent structural change has a significant impact on the endopeptidase activity of BoNT/A: the catalytic efficiency of the monomeric BoNT/A is about 4-fold higher than that of its dimeric form. This difference implies a sterically restricted catalytic site of BoNT/A in the dimeric form of BoNT/A.

Botulinum Toxins, Type A↗
PubMed2001

Characterization of the prfA virulence gene cluster insertion site in non-hemolytic Listeria spp.: probing the evolution of the Listeria virulence gene island.

The prfA virulence gene cluster is present between prs and ldh in the pathogenic L. monocytogenes and L. ivanovii, but absent from the non-pathogenic L. innocua and L. welshimeri. To probe the evolution of this virulence gene cluster, we sequenced the prs-ldh intergenic region in L. welshimeri and L. innocua. Two ORFs (ORFA and ORFB) were found in both species as well as in L. monocytogenes. Another ORF of unknown function (ORFZ) was found in L. monocytogenes and L. innocua, while two unique ORFs were present in L. welshimeri. ORFA and ORFB showed significant functional constraint, suggesting that further investigations in the functions of these genes, including possible roles in horizontal gene transfer or sequence deletion, are warranted. DNA sequences homologous to Tn1545 integration consensus sequences were found downstream of prs and ORFB, thus defining the likely junctions of the virulence gene island and indicating that the prs-ldh intergenic region may represent a Tn insertion hot spot. Our results are consistent with the hypothesis that a combination of horizontal gene transfer and deletion events mayhave been involved in the evolution of the prfA virulence gene cluster in Listeria.

Animals↗
PubMed2001

Subgingival occurrence and antimicrobial susceptibility of enteric rods and pseudomonads from Brazilian periodontitis patients.

The occurrence and in vitro antimicrobial sensitivity of isolates of enteric rods and pseudomonads were examined in 80 periodontitis patients, 17 to 58 years of age, in São Paulo, Brazil. Speciation and in vitro antimicrobial susceptibility testing were performed using the BBL Crystal enteric/nonfermenter system and the Etest for amoxicillin/clavulanic acid, ciprofloxacin and doxycycline. A total of 30 strains were isolated from 25 (31.2%) of the study subjects. Pseudomonas aeruginosa occurred in nine patients, Serratia marcescens in seven, and five other species were recovered in lower prevalence. All study organisms demonstrated high susceptibility to ciprofloxacin but exhibited variable susceptibility patterns to the other antimicrobial agents tested. In conclusion, the high occurrence of enteric rods and pseudomonads in these subjects may be important in the pathogenesis of periodontitis, and ciprofloxacin might be the antibiotic of choice to eradicate these pathogens from periodontal pockets.

Adolescent↗
PubMed2001

Phylogenetic analysis based on 18S rRNA gene and matK gene sequences of Panax vietnamensis and five related species.

Panax vietnamensis was discovered recently in Vietnam. Its bamboo-like rhizomes, called Vietnamese Ginseng, have attracted considerable attention because of their specific pharmacological activities. In order to define the taxonomic position of this new species and include it in the molecular authentication of Ginseng drugs, the 18S ribosomal RNA gene and matK gene sequences of P. vietnamensis were determined and compared with those of its related taxa, P. japonicus var. major and P. pseudo-ginseng subsp. himalaicus, besides previously reported P. ginseng, P. japonicus and P. quinquefolius. The 18S rRNA gene sequences were found to be 1809 bps in length. The sequence of P. vietnamensis was identical to that of P. quinquefolius, and presented one base substitution from those of both P. japonicus var. major and P. pseudo-ginseng subsp. himalaicus. The matK gene sequences of 6 taxa were found to be 1509 bps in length. The sequence of P. vietnamensis differed from those of P. japonicus var. major, P. pseudo-ginseng subsp. himalaicus, P. ginseng, P. japonicus and P. quinquefolius at 4, 5, 9, 9 and 10 nucleotide positions, respectively. The phylogenetic tree reconstructed by the combined 18S rRNA-matK gene analysis using the maximum parsimony method showed that P. vietnamensis was sympatric with other Panax species and had a close relationship with P. japonicus var. major and P. pseudo-ginseng subsp. himalaicus.

Amino Acid Sequence↗
PubMed2001

Tumor necrosis factor modulates fibroblast apoptosis, PMN recruitment, and osteoclast formation in response to P. gingivalis infection.

P. gingivalis is an important oral pathogen, which has been closely linked to periodontal disease as well as lesions of endodontic origin. Both infections are associated with a decrease in fibroblast numbers, formation of an inflammatory infiltrate, and bone resorption. The goal of this study was to investigate the role that the host response plays in the capacity of P. gingivalis to stimulate fibroblast apoptosis, PMN recruitment, and osteoclastogenesis. This was accomplished by the use of an in vivo calvarial model in mice with targeted deletion of TNF receptors p55 and p75 and matched wild-type mice. The results indicate that P. gingivalis induces fibroblast apoptosis in vivo and establish for the first time that this involves the stimulation of a host response. Moreover, bacteria-stimulated PMN recruitment and osteoclastogenesis were also dependent upon the host response. The results suggest that much of the damage caused by P. gingivalis infection, including fibroblast apoptosis, at least under some circumstances, results from stimulation of the host response rather than the direct effect of bacterial products. Furthermore, this may represent a more general mechanism by which bacterial challenge induces apoptosis of matrix-producing cells through the induction of TNF.

Animals↗
PubMed2001

Investigation on the rheological properties of hepatocellular carcinoma cells and their relevance to cytoskeleton structure.

OBJECTIVE: To investigate the relevance of the rheological properties, i.e., viscoelasticities and adhesion to basement membrane components coated surface, of both hepatocytes and hepatocellular carcinoma (HCC) cells to the cytoskeleton structure. METHODS: Micropipette aspiration technique was adopted to measure viscoelastic coefficients and adhesion forces to 2 microg/ml collagen IV/1.25 microg/ml laminin coated surface of the cells. Two kinds of cytoskeleton perturbing agents, colchicine and cytochalasin D, were used to treat both HCC cells and hepatocytes and the effects of these treatments on cell viscoelastic coefficients and cell adhesion forces were investigated. RESULTS: Upon treatment of cells with colchicine in a concentration range of 1 to 60 mg/L, the elastic coefficients, especially the first elastic coefficient K1, and adhesion forces of hepatocytes generally tended to increase or increased significantly while, in contrast, viscoelastic coefficients and adhesion forces of HCC cells decreased obviously. Upon treatment of cells with cytochalasin D in a concentration range of 0.25-5.00 mg/L, viscoelastic coefficients of both hepatocytes and HCC cells decreased uniformly, with a larger magnitude for the decrease in elastic coefficients and adhesion forces of HCC cells than for those of hepatocytes. Adhesion forces of hepatocytes and HCC cells onto collagen IV/laminin coated surface varied similarly as viscoelastic coefficients under the action of the cytoskeleton perturbing agents. A significant positive correlation existed between changes of HCC cell adhesion forces on collagen IV/laminin coated surfaces and those of cell elastic coefficients (P<0.01). CONCLUSIONS: The effects of cochicine and cytochalasin D on rheological properties of HCC cells differed significantly either in ways or extents from those on rheological properties of hepatocytes. These results might reflect the difference in the state of cytoskeleton structure and function among these two kinds of cells.

Carcinoma, Hepatocellular↗
PubMed2001

[Investigation on the mechanics of adhesion to the selective extracellular matrix coated surfaces of lung cancer cells].

The adhesion properties of tumor cells with extracellular matrix(ECM) are closely associated with their invasion and metastasis. Our work reported here was intended reveal the relevant biomechanical and biorheological manifestations of human lung cancer. Using micropipette aspiration technique, we investigated quantitatively the adhesive mechanics properties of high metastatic human giant cell carcinoma(PG) cells as well as low metastatic adenocarcinoma(PAa) cells of lung based on cell culture in vitro. The results showed that the adhesion forces of PAa and PG cells to collagen IV were significantly higher than those to glass surfaces, but at the lower concentrations(1.00 microgram/ml and 2.00 micrograms/ml) of collagen IV, the amplitude for the increase of adhesion forces of PG cells were less than the amplitude for that of PAa cells, and most of the adhesion force values of PAa cells to the coated surfaces of incorporation of laminin along with 2 micrograms/ml collagen IV were significantly greater than those of PG cells. At the lower concentrations(0.625 microgram/ml for PAa cells, and 0.625 microgram/ml, 1.25 micrograms/ml for PG cells) of laminin tested, the adhesion force values of PAa and PG cells all decreased, but the amplitude and level for the decreased values of adhesion forces of PG cells were greater than those for the PAa cells. In conclusion, the adhesive and proteolytic behaviour of cancer cells to extracellular matrix might be mediated mainly by tumor cell membrane receptors such as integrin receptors and laminin receptors, it might affect the biological characteristics and the metastasis of the tumor cells. The results may benefit to explain some questions in biomechanical views about how the highly metastatic PG cells are prone to migration and invasion.

Adenocarcinoma↗