Biomedical subjects

S Chai

Publications and source records attributed to S Chai.

At least 19 recordsLinked to original sources

PubMed2006

Defects in articular cartilage metabolism and early arthritis in fibroblast growth factor receptor 3 deficient mice.

Fibroblast growth factor (FGF) receptor 3 has been identified as a key regulator of endochondral bone development and of post-natal bone metabolism through its action on growth plate chondrocytes and osteoblasts, respectively. It has also been shown to promote chondrogenesis and cartilage production by cultured pre-chondrogenic cells in response to FGF18. In the current studies, we show that the absence of signaling through Fgfr3 in the joints of Fgfr3(-/-) mice leads to premature cartilage degeneration and early arthritis. Degenerative changes in cartilage matrix included excessive proteolysis of aggrecan core protein and type II collagen, as measured by neo-epitope immunoreactivity. These changes were accompanied by increased expression of metalloproteinase MMP13, type X collagen, cellular hypertrophy and loss of proteoglycan at the articular surface. Using a novel micro-mechanical indentation protocol, it was shown that articular cartilage in the humeral head of 4-month-old Fgfr3(-/-) mice was less resistant to compressive force and less stiff than that of littermate controls. These results identify Fgfr3 signaling as a potential target for intervention in degenerative disorders of cartilage metabolism.

Aggrecans↗

PubMed2001

Antenatal syphilis in sub-Saharan Africa: missed opportunities for mortality reduction.

PURPOSE: Between 4-15% of pregnant women are believed to be infected with syphilis in sub-Saharan Africa. Active infection with syphilis in pregnant women results in foetal or infant death or disability for 50-80% of affected pregnancies, and is a major cause of adult morbidity as well. Antenatal syphilis screening is cheap and effective; however, it is often poorly implemented in countries with high syphilis risk. This study sought to estimate the missed opportunities for antenatal syphilis screening in sub-Saharan Africa. METHODS: Survey data were collected from 22 ministries of health in sub-Saharan Africa, complemented by data from published sources and key informants. Informants described their country's policies and experience with antenatal syphilis screening and estimated their national syphilis screening rates. FINDINGS: Seventy-three percent of women are reported by WHO to receive antenatal care in the study countries. Of women in antenatal care, 38% were estimated by survey respondents to be screened for syphilis. Costs and the organization of services were the principal reported obstacles to screening. With syphilis seroprevalence estimated at 8.3%, approximately 1 640 000 pregnant women with syphilis are undetected annually, including 1 030 000 women who attend antenatal care. DISCUSSION: Syphilis testing and treatment is a cost-effective intervention that deserves much greater attention, particularly in sub-Saharan Africa and other countries where syphilis infection is high.

Africa South of the Sahara↗

PubMed2001

Nicotine metabolism and CYP2A6 allele frequencies in Koreans.

CYP2A6 is a major catalyst of nicotine metabolism to cotinine. Previously, we demonstrated that the interindividual difference in nicotine metabolism is related to a genetic polymorphism of the CYP2A6 gene in Japanese. To clarify the ethnic differences in nicotine metabolism and frequencies of CYP2A6 alleles, we studied nicotine metabolism and the CYP2A6 genotype in 209 Koreans. The cotinine/nicotine ratio of the plasma concentration 2 h after chewing one piece of nicotine gum was calculated as an index of nicotine metabolism. The genotypes of CYP2A6 gene (CYP2A6*1A, CYP2A6*1B, CYP2A6*2, CYP2A6*3, CYP2A6*4 and CYP2A6*5) were determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism or allele specific (AS)-PCR. There were ethnic differences in the allele frequencies of CYP2A6*1A, CYP2A6*1B, CYP2A6*4 and CYP2A6*5 between Koreans (45.7%, 42.8%, 11.0% and 0.5%, respectively) and Japanese (42.4%, 37.5%, 20.1% and 0%, respectively, our previous data). Similar to the Japanese, no CYP2A6*2 and CYP2A6*3 alleles were found in Koreans. The homozygotes of the CYP2A6*4 allele (four subjects) were completely deficient in cotinine formation, being consistent with the data among Japanese. The heterozygotes of CYP2A6*4 tended to possess a lower metabolic ratio (CYP2A6*1A/CYP2A6*4, 4.79 +/- 3.17; CYP2A6*1B/CYP2A6*4, 7.43 +/- 4.97) than that in subjects without the allele (CYP2A6*1A/CYP2A6*1A, 7.42 +/- 6.56; CYP2A6*1A/CYP2A6*1B, 9.85 +/- 16.12; CYP2A6*1B/CYP2A6*1B, 11.33 +/- 9.33). The subjects who possess the CYP2A6*1B allele appeared to show higher capabilities of cotinine formation. It was confirmed that the interindividual difference in nicotine metabolism was closely related to the genetic polymorphism of CYP2A6. The probit plot of the metabolic ratios in Koreans (8.73 +/- 11.88) was shifted to a higher ratio than that in the Japanese (3.78 +/- 3.09). In each genotype group, the Korean subjects revealed significantly higher metabolic ratios than the Japanese subjects. The ethnic difference in cotinine formation might be due to environmental and/or diet factors as well as genetic factors.

Adult↗

PubMed2001

[Effect of rare earth elements on the seedling ratio of crops].

The effects of rare earth elements(REEs) on the relative seedling ratio of three crops(rice, rape and soybean) in three soil(red soil, yellow fluvo-aquic soil and yellow cinnamon soil) were studied according to OECD method, and the LC50 were obtained. Toxicity effect of REEs on rice was minimum among the crops tested. The toxicity on crops in yellow cinnamon soil was lower, whereas on soybean in yellow fluvo-aquic soil and on rape in red earth were higher.

Crops, Agricultural↗

PubMed2000

Failure to regulate TNF-induced NF-kappaB and cell death responses in A20-deficient mice.

A20 is a cytoplasmic zinc finger protein that inhibits nuclear factor kappaB (NF-kappaB) activity and tumor necrosis factor (TNF)-mediated programmed cell death (PCD). TNF dramatically increases A20 messenger RNA expression in all tissues. Mice deficient for A20 develop severe inflammation and cachexia, are hypersensitive to both lipopolysaccharide and TNF, and die prematurely. A20-deficient cells fail to terminate TNF-induced NF-kappaB responses. These cells are also more susceptible than control cells to undergo TNF-mediated PCD. Thus, A20 is critical for limiting inflammation by terminating TNF-induced NF-kappaB responses in vivo.

Animals↗

PubMed2000

The overlapping angB and angG genes are encoded within the trans-acting factor region of the virulence plasmid in Vibrio anguillarum: essential role in siderophore biosynthesis.

Products encoded in the trans-acting factor (TAF) region are necessary for the biosynthesis of anguibactin and for maximal expression of iron transport and biosynthesis genes in the plasmid-encoded iron-scavenging system of Vibrio anguillarum. Here we identify angB, a locus located in the TAF region, which encodes products essential for anguibactin biosynthesis. We demonstrate that a 287-amino-acid polypeptide, encoded by angB and designated AngB, has an isochorismate lyase activity necessary for the synthesis of 2, 3-dihydroxybenzoic acid, an anguibactin biosynthesis intermediate. Complementation of various angB mutations provided evidence that an additional, overlapping gene exists at this locus. This second gene, designated angG, also has an essential biosynthetic function. The angG gene directs the expression of three polypeptides when overexpressed in Escherichia coli, all of which are translated in the same frame as AngB. The results of site-directed mutagenesis and in vivo phosphorylation experiments suggest that the carboxy-terminal end of AngB and the AngG polypeptide(s) function as aryl carrier proteins involved in the assembly of the anguibactin molecule. Our results also show that the regulatory functions of the TAF are encoded in a region, TAFr, which is distinct from and independent of the angB and angG genes.

Alleles↗

PubMed2000

[Cluster analysis methods appropriate for classification of drought-resistant wheat ecotypes].

The appropriate cluster analysis methods for classification of drought-resistant wheat ecotypes were investigated, based on the analysis of 21 morphologic and agronomic characters of 15 winter wheat cultivars. According to the proximity degree to the results from experts experiences, the cluster results using original data were orderly better than those using Varimax orthogonal rotation, Promax skew intersection rotation, and principal component analysis with phenotypic mean's correlation matrix. The results using Euclidean distance were greater than those using Mahalanobis distance. The clustering methods of correspondent analysis and fuzzy cluster were better than those of nearest distance, furthest distance or group average method (UPGMA). Among all cluster results from various methods combined, the two cluster results from the fuzzy cluster using original data and from the correspondence analysis method were closest to the results of experts' experience. Based on both comparisons of results and examination of the performance of different strategies with several statistical properties, the two methods mentioned above were also acceptable.

Cluster Analysis↗

PubMed2000

[Protective efficacy of H2 strain live attenuated hepatitis A vaccines in an outbreak of hepatitis A].

OBJECTIVE: To investigate the protective efficacy of H(2) strain live attenuated hepatitis A vaccine (H(2)-strain vaccine) locally produced in an outbreak of hepatitis A (HA). METHODS: A nonrandomized controlled design was used in a trial for HA vaccination. Five thousand five hundred and fifty-one children at preschool classes and at grades 1 - 3 of primary schools were selected in 14 villages. Epidemiological and serological methods were used to evaluate its protective efficacy of the vaccines and serum immunoglobulin M against hepatitis A virus (IgM anti-HAV) was detected with ELISA for 271 subjects in vaccinated group and 341 in the control one. RESULTS: An outbreak of HA occurred one year after the vaccination with 26 cases in the vaccinated group, including one vaccine-related case with an attack rate of 0.28% (1/356), and 25 cases in the control group with an attack rate of 5.92% (25/422). The protective efficacy of vaccines was 95.27% (95% confidence interval of 85.83% to 104.72%). Positivity of IgM anti-HAV, i.e., newly-infected cases, was 4.43% (12/271) in the vaccinated group and 13.38% (42/314) in the control group, respectively. Clinically apparent cases accounted for 8.33% (1/12) and 50.00% (21/42) in newly-infected cases in vaccinated and control groups, respectively. CONCLUSION: Vaccination with H(2) strain vaccines locally produced was effective in reducing occurrence of HA during its outbreak, but not so effective in preventing its infection. A booster dose of HA vaccine should be vaccinated for children in adequate time.

Adolescent↗

PubMed1999

Solution structure of carnobacteriocin B2 and implications for structure-activity relationships among type IIa bacteriocins from lactic acid bacteria.

Carnobacteriocin B2 (CbnB2), a type IIa bacteriocin, is a 48 residue antimicrobial peptide from the lactic acid bacterium Carnobacterium pisicola LV17B. Type IIa bacteriocins have a conserved YGNGVXC sequence near the N-terminus and usually contain a disulfide bridge. CbnB2 seemed to be unique in that its two cysteines (Cys9 and Cys14) could be isolated as free thiols [Quadri et al. (1994) J. Biol. Chem. 26, 12204-12211]. To establish the structural consequences of the presence or absence of a disulfide bridge and to investigate if the YGNGVXC sequence is a receptor-binding motif [Fleury et al. (1996) J. Biol. Chem. 271, 14421-14429], the three-dimensional solution structure of CbnB2 was determined by two-dimensional (1)H nuclear magnetic resonance (NMR) techniques. Mass spectroscopic and thiol modification experiments on CbnB2 and on model peptides, in conjunction with activity measurements, were used to verify the redox status of CbnB2. The results show that CbnB2 readily forms a disulfide bond and that this peptide has full antimicrobial activity. NMR results indicate that CbnB2 in trifluoroethanol (TFE) has a well-defined central helical structure (residues 18-39) but a disordered N terminus. Comparison of the CbnB2 structure with the refined solution structure of leucocin A (LeuA), another type IIa bacteriocin, indicates that the central helical structure is conserved between the two peptides despite differences in sequence but that the N-terminal structure (a proposed receptor binding site) is not. This is unexpected because LeuA and CbnB2 exhibit >66% sequence identity in the first 24 residues. This suggests that the N-terminus, which had been proposed [Fleury et al. (1996) J. Biol. Chem. 271, 14421-14429] to be a receptor binding site of type IIa bacteriocins, may not be directly involved and that recognition of the amphiphilic helical portion is the critical feature.

Amino Acid Sequence↗

PubMed1998

Characterization of the interaction between Fur and the iron transport promoter of the virulence plasmid in Vibrio anguillarum.

The expression of iron transport genes fatDCBA in Vibrio anguillarum strain 775 is negatively regulated by two iron-responsive repressors, the Fur protein and the antisense RNA, RNAalpha. Here we report the identification of the promoter for the iron transport genes and studied the interaction between the V. anguillarum Fur protein and this promoter. The iron transport promoter was localized in a region approximately 300 base pairs upstream of fatD by both primer extension and S1 mapping analysis. High activity of the promoter was measured in response to iron depletion in the wild-type strain when a promoter-lacZ fusion was examined, whereas the promoter was constitutive in the Fur-deficient strain. Gel retardation and DNase I footprint analysis showed that Fur binds specifically to two contiguous sites comprising the promoter region and the region downstream of the transcription start site. The identified Fur binding sites showed a low degree of homology to each other as well as to the consensus sequence for the Escherichia coli Fur protein. DNase I footprints pattern suggested a sequential interaction of Fur with these two sites that renders a protection in the template strand and a hypersensitivity to the nuclease in the nontemplate strand. The periodicity of the hypersensitive sites suggested that the promoter DNA undergoes a structural change upon binding to Fur, which might play a role in the repression of gene expression.

Bacterial Proteins↗

PubMed1998

IL-15 receptor maintains lymphoid homeostasis by supporting lymphocyte homing and proliferation.

The IL-15 receptor alpha subunit (IL-15Ralpha) mediates high-affinity binding of IL-15, a pleiotropic cytokine implicated in the development of innate immune cells. We have generated IL-15Ralpha null (IL-15Ralpha-/-) mice to understand the role of IL-15Ralpha in immune development and function. IL-15Ralpha-/- mice are markedly lymphopenic despite grossly normal T and B lymphocyte development. This lymphopenia is due to decreased proliferation and decreased homing of IL-15Ralpha-/- lymphocytes to peripheral lymph nodes. These mice are also deficient in natural killer cells, natural killer T cells, CD8+ T lymphocytes, and TCRgammadelta intraepithelial lymphocytes. In addition, memory phenotype CD8+ T cells are selectively reduced in number. Thus, IL-15Ralpha has pleiotropic roles in immune development and function, including the positive maintenance of lymphocyte homeostasis.

Animals↗

PubMed1997

The complete nucleotide sequence and functional organization of Bacillus subtilis bacteriophage SPP1.

The complete nucleotide sequence of the B. subtilis bacteriophage SPP1 is described. The genome is 44,007 bp in size and has a base composition of 43.7% dG + dC. Only 32.2 kb are essential for phage amplification under laboratory conditions. Transcription using only the 'heavy strand' is asymmetric. Eighty-one orfs organized in five early and four late operons were identified. Experiments have shown that 25 orfs are essential. Of the remaining orfs, functions could be predicted for the products of five of the orfs on the basis of comparison of the deduced amino acid sequence to known proteins. Intergenic regions include most of the 5 PE and the 4 PL promoters. Transcripts are polycistronic. Transcription from the PE promoters is mediated by host RP, whereas recognition of the PL promoters requires an additional unidentified phage-encoded product. Translation of mRNA transcribed from most of the orfs seems to be initiated independently, each from its own ribosomal binding and initiation site, although a few cases of coupled translation have been reported. The organization of SPP1 genes involved in the replication, DNA packaging and phage assembly proteins resembles the organization of genes of equivalent regions of different E. coli double-stranded DNA phages. Absence of aa sequence similarity between analogous proteins of different phages suggested that the conserved gene organization is representative of a primordial bacteriophage.

Bacillus Phages↗

PubMed1997

The replisome organizer (G38P) of Bacillus subtilis bacteriophage SPP1 forms specialized nucleoprotein complexes with two discrete distant regions of the SPP1 genome.

Initiation of Bacillus subtilis bacteriophage SPP1 DNA replication requires the products of genes 38, 39 and 40 (G38P, G39P and G40P). G38P specifically binds two discrete regions, which are 32.1 kb apart in a linear map of the SPP1 genome. One of these target sites, which maps at the left end of the phage genome, within gene 38, was shown to function as an origin of replication and was therefore termed left origin (oriL). The other site, which lies within a non-coding segment in the late transcribed region on the right end of the genome, was termed oriR. Both sites contain two types of repeated elements (termed Box AB and A + T-rich region). The K(app) for the G38P-oriL DNA and G38P-oriR DNA complexes was estimated to be 1 nM and 4 nM, respectively. G38P binds to the distant oriL and oriR sites cooperatively. DNase I footprinting experiments showed protection by G38P in Box AB, but not in the A + T-rich region. Electron microscopy analysis showed that G38P forms a higher-order nucleoprotein structure with the SPP1 oriL and oriR sites through protein-protein interaction. G38P binding at its cognate sites does not seem to modify the length of the DNA, but to bend it. These results suggest that G38P forms a nucleoprotein complex on the regions where the SPP1 replication origins were previously predicted.

Bacillus Phages↗

PubMed1997

Bacillus subtilis bacteriophage SPP1 terminase has a dual activity: it is required for the packaging initiation and represses its own synthesis.

The B. subtilis bacteriophage SPP1 terminase, encoded by genes 1 and 2, is required for the initiation of headful packaging. The DNA segment to which gene 1 product (G/P) binds includes the pacL and pacR sites and the late PL1 and PL2 promoters from which genes 1 to 7 are transcribed. When SPP1wt or SPP1sus115 (gene 6-) phages were used to infect a B. subtilis sup0 strain, the gene 1 to 7 mRNA synthesis was reduced at late times of infection. This was not observed, however, when either chloramphenicol was added 7 min after infection with SPP1wt or when SPP1sus114 (gene 1-) or SPP1sus19 (gene 2-) were used to infect B. subtilis sup0 cells. These results suggest that the terminase enzyme functions as a repressor of its own transcription. G/P and B. subtilis RNA polymerase (RP) bind to the pacL segment, which contains the PL1 and PL2 promoter region. The binding of G/P to the pacL site does not seem to exclude RP from the promoters, despite of the overlapping of their binding sites. It is likely that the terminase protein does not repress transcription by a mere steric hindrance of RP binding.

Bacillus Phages↗

PubMed1997

Obstacles to nutrition labeling in restaurants.

OBJECTIVE: This study determined the major obstacles that foodservices face regarding nutrition labeling. DESIGN: Survey questionnaire was conducted in May 1994. In addition to demographic questions, the directors were asked questions addressing willingness, current practices, and perceived obstacles related to nutrition labeling. SUBJECTS/SETTING: Sixty-eight research and development directors of the largest foodservice corporations as shown in Restaurants & Institutions magazine's list of the top 400 largest foodservices (July 1993). STATISTICAL ANALYSES PERFORMED: P tests were used to determine significance within a group for the number of foodservices that were currently using nutrition labeling, perceived impact of nutrition labeling on sales, and perceived responsibility to add nutrition labels. Regression analysis was used to determine the importance of factors on willingness to label. RESULTS: Response rate was 45.3%. Most companies were neutral about their willingness to use nutrition labeling. Two thirds of the respondents were not currently using nutrition labels. Only one third thought that it was the foodservice's responsibility to provide such information. Several companies perceived that nutrition labeling would have a potentially negative effect on annual sales volume. Major obstacles were identified as menu or personnel related, rather than cost related. Menu-related obstacles included too many menu variations, limited space on the menu for labeling, and loss of flexibility in changing the menu. Personnel-related obstacles included difficulty in training employees to implement nutrition labeling, and not enough time for foodservice personnel to implement nutrition labeling. APPLICATIONS: Numerous opportunities will be created for dietetics professionals in helping foodservices overcome these menu- or personnel-related obstacles.

Food Labeling↗

PubMed1996

Distamycin-induced inhibition of formation of a nucleoprotein complex between the terminase small subunit G1P and the non-encapsidated end (pacL site) of Bacillus subtilis bacteriophage SPP1.

The small subunit of the Bacillus subtilis bacteriophage SPP1 terminase (G1P) forms a sequence-specific nucleoprotein complex with the SPP1 non-encapsidated end (pacL site) during initiation of DNA encapsidation. Gel mobility shift assay was used to study the G1P-pacL interaction. Distamycin, a minor groove binder that induces local distortion of the DNA, inhibits G1P-pacL complex formation. The competition of G1P with distamycin for DNA binding at the pacL site is independent of the order of addition of the reactants. Other minor groove binders, such as spermine or Hoechst 33258, which do not distort DNA, failed to compete with G1P for pacL DNA binding. Cationic metals, which generate a repertoire of DNA structures different from that caused by the minor groove binders, can partially reverse the distamycin-induced inhibition of G1P binding to pacL DNA. The major groove binder methyl green, which does not distort sequence-directed bending of pacL DNA, competes with G1P for binding at the pacL site. Our data suggest that the natural sequence-directed bend that exists within the pacL site is the architectural element that facilitates assembly of a nucleoprotein complex and hence initiation of DNA encapsidation by bacteriophage SPP1.

Anti-Bacterial Agents↗

PubMed1995

The small subunit of the terminase enzyme of Bacillus subtilis bacteriophage SPP1 forms a specialized nucleoprotein complex with the packaging initiation region.

Initiation of SPP1 DNA packaging requires the gene 1 and gene 2 products (G1P and G2P), which are different subunits of the terminase enzyme. G1P specifically recognizes the phage packaging initiation region (pac). The apparent equilibrium constant for the G1P-pac-DNA complex was estimated to be 9 nM. DNase I footprinting experiments reveal that the pac region can be subdivided into three discrete sites (pacL, pacC and pacR). G1P binds co-operatively to the non-adjacent pacL and pacR sites. Several G1P protomers bind to the target sequences which map close to the pac cleavage site (pacC site), but do not overlap with it. G1P interacts in a different fashion with the encapsidated (pacR site) and with the non-encapsidated (pacL site) end of the phage genome. G1P interaction with the intrinsically bent pacL DNA occurs only on one face of the DNA double helix. G1P binding to the pacL and in the pacR region results in a DNA loop. Electron microscopy of purified G1P shows that the protein is an oligomer in solution. G1P binding to the core region of the pacL site could facilitate the formation of a higher-order nucleoprotein structure. This specialized complex would allow the pac DNA to form a loop between binding sites brought together by interaction with G1P. The results presented here suggest that G1P could provide a tool to discriminate the first encapsidated end, which contains pacR, from the non-encapsidated pacL end.

Bacillus Phages↗

PubMed1995

Lead acetate-induced contraction in rabbit mesenteric artery: interaction with calcium and protein kinase C.

Animal studies have demonstrated that low-level lead exposure produces hypertension and that lead can cause contraction of vascular smooth muscle directly. The physiological effects of lead have been associated with both stimulation and inhibition of protein kinase C (PKC). Given that vascular smooth muscle contractility is generally enhanced when protein kinase C is activated, we have tested the hypothesis that lead contracts vascular smooth muscle via stimulation of PKC. Helically-cut strips of rabbit mesenteric artery were mounted in muscle baths for measurement of isometric force development. Cumulative addition of lead acetate (10(-10)-10(-3) M) to the muscle bath produced contractions (concentration necessary to produce half-maximal response -log EC50 = 5.16 +/- 0.07). Maximal contraction to lead acetate in arteries denuded of endothelium did not differ from those in intact vessels, supporting the hypothesis that lead-induced contraction is an endothelium-independent event. Contractions to lead acetate were potentiated by the PKC activators, phorbol 12-myristate 13-acetate (TPA; 3 x 10(-7) M) and mezerein (3 x 10(-7) M), as indicated by leftward shifts in the concentration-response curve and increase in the potency of lead (-log EC50 with TPA: 6.94 +/- 0.07; -log EC50 with mezerein: 6.07 +/- 0.04). H-7 (6 x 10(-6) M), an inhibitor of PKC, decreased maximal contraction to lead approximately 65% and slightly, but insignificantly, decreased the potency of lead (-log EC50 = 4.82 +/- 0.1). The inactive phorbol ester, phorbol 12-myristate 13-acetate 4-0-methyl ether (1 x 10(-6) M), did not alter contractile responses to lead (-log EC50 = 4.92 +/- 0.09). Vascular contraction to lead partially depends on extracellular calcium as the L-type voltage-gated calcium channel antagonist, verapamil (3 x 10(-6) M), decreased lead-induced contractions by 50%. These data indicate that lead interacts with PKC in an endothelium-independent, calcium-dependent manner to cause vascular smooth muscle contraction and suggest that lead-induced increases in vascular contractility may play a role in lead-induced hypertension.

Analysis of Variance↗