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S Chong

Publications and source records attributed to S Chong.

At least 37 records · Page 2Linked to original sources
PubMed2001

Cost-effectiveness of screening swab or urine specimens for Chlamydia trachomatis from young Canadian women in Ontario.

BACKGROUND: Undetected and untreated Chlamydia trachomatis infections can result in a significant health burden. Diagnostic testing refers to tests performed on patients with symptoms, whereas screening refers to testing specimens in asymptomatic patients. The goal of diagnostic testing and screening programs are early identification of infections to prevent upper tract infection and transmission to other partners. GOAL: To compare the costs and outcomes of alternative diagnostic testing and screening programs for women ages 15 to 24 years in the province of Ontario, Canada. STUDY DESIGN: Using outcome probabilities from the literature and a consensus group, together with the costs from insurance billing, a decision analytic model was constructed to determine the baseline risk of C trachomatis and related sequelae. Seven diagnostic testing and screening programs were compared over a 10-year period. The programs compared included the use of nucleic acid amplification assays collected from urine or endocervical swab specimens. RESULTS: Largely because of lower sensitivity the urine-based testing or screening programs were dominated by the swab-based programs. The move from swab-based testing to a swab-based screening program for high-risk women costs $1873 per case of C trachomatis averted. Expanding the program further to include all women in Ontario between 15 and 24 years of age is considerably more costly at $5990 per case averted. CONCLUSIONS: It is more costly and more effective to screen and treat high-risk women ages 15 to 24 years for C trachomatis than to perform only swab-based diagnostic testing on symptomatic women. Expanding the screening program to include all women ages 15 to 24 years is considerably more expensive and only moderately more effective than screening only high-risk women.

Adolescent↗
PubMed2001

Circulating nucleic acids of Chlamydia pneumoniae and cytomegalovirus in patients undergoing coronary angiography.

Peripheral blood mononuclear cells from 208 consecutive patients undergoing elective coronary angiography or angioplasty were collected before, immediately after, and 4 h after the procedure. Nucleic acids of Chlamydia pneumoniae and of cytomegalovirus (CMV) were detected by PCR and confirmed by hybridization. Circulating C. pneumoniae DNA was identified in 24 patients (11.5%) and was associated with current smoking (odds ratio [OR] = 4.5, 95% confidence interval [CI] = 1.6 to 12.2, P = 0.004) but not with arterial narrowing on coronary angiogram or with serological results positive for C. pneumoniae. Circulating CMV DNA was identified in 36 patients (17.3%) and was associated with anti-CMV immunoglobulin G (OR = 2.7, 95% CI = 1.2 to 6.3, P = 0.02) but not with angiographic arterial narrowing or with the need for revascularization. Neither C. pneumoniae nor CMV DNA detection increased after angioplasty, a procedure in which endothelium is disrupted. Larger prospective studies are needed to determine the prognostic significance of DNA detection.

Adult↗
PubMed2001

Evaluation of the NucliSens Basic Kit for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in genital tract specimens using nucleic acid sequence-based amplification of 16S rRNA.

We evaluated a new RNA amplification and detection kit, the NucliSens Basic Kit (Organon Teknika), for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in genitourinary specimens. The Basic Kit provides an open platform for RNA amplification and detection and contains isolation reagents for nucleic acid extraction, nucleic acid sequence-based amplification (NASBA) reagents (enzymes and buffers), and a generic ruthenium-labeled probe for electrochemiluminescent (ECL) detection of amplified product. Using freshly purified and titrated stocks of C. trachomatis and N. gonorrhoeae and in vitro-generated RNA transcripts for sensitivity determinations, the Basic Kit detected 1 inclusion-forming unit of C. trachomatis, 1 CFU of N. gonorrhoeae, and 100 RNA molecules of 16S rRNA for both bacteria. The clinical performance of the Basic Kit was evaluated by testing a total of 250 specimens for N. gonorrhoeae by culture and NASBA and a total of 96 specimens for C. trachomatis by PCR and NASBA. The Basic Kit detected 139 of 142 N. gonorrhoeae culture-positive specimens and gave a negative result for 73 of 74 culture-negative specimens, for a sensitivity and specificity of 97.9 and 98.7%, respectively. For C. trachomatis, the Basic Kit detected 24 of 24 PCR-positive specimens and gave a negative result for 71 of 72 PCR-negative specimens, for a sensitivity and specificity of 100 and 98.6%, respectively. The Basic Kit also detected specimens containing both N. gonorrhoeae and C. trachomatis, using a multiplex NASBA assay using primers for both bacteria. The NucliSens Basic Kit offers a versatile platform for the development of sensitive RNA detection assays for sexually transmitted diseases.

Cervix Uteri↗
PubMed2001

Replicate PCR testing and probit analysis for detection and quantitation of Chlamydia pneumoniae in clinical specimens.

Nucleic acid amplification of clinical specimens with low target concentration has variable sensitivity. We examined whether testing multiple aliquots of extracted DNA increased the sensitivity and reproducibility of Chlamydia pneumoniae detection by PCR. Nested and non-nested C. pneumoniae PCR assays were compared using 10 replicates of 16 serial dilutions of C. pneumoniae ATCC VR-1310. The proportion positive versus the C. pneumoniae concentration was modeled by probit regression analysis. To validate the model, 10 replicates of 26 previously positive patient specimens of peripheral blood mononuclear cells (PBMC), sputum, or nasopharyngeal swabs (NPS) were tested. The proportion of replicates that were positive varied with the concentration of C. pneumoniae in the sample. At concentrations above 5 infection-forming units (IFU)/ml, both nested and non-nested PCR assay sensitivities were 90% or greater. The nested PCR was more sensitive (median detection, 0.35 versus 0.61 IFU/ml; relative median detection, 0.58; 95% confidence interval, 0.31 to 0.99; P = 0.04). In clinical specimens, replicate PCR detected 15 of 26 (nested) versus 1 of 26 (non-nested, P < 0.001). For PBMC specimens, testing 1, 3, or 5 replicates detected 3, 5, or 9 of 10 positive specimens, respectively. Median C. pneumoniae concentrations were estimated at 0.07 IFU/ml for PBMC and at <0.03 IFU/ml for NPS specimens. We conclude that performing 5 or 10 replicates considerably increased the sensitivity and reproducibility of C. pneumoniae PCR and enabled quantitation for clinical specimens. Due to sampling variability, PCR tests done without replication may miss a large proportion of positive specimens, particularly for specimens with small amounts of target C. pneumoniae DNA present.

Chlamydophila Infections↗
PubMed2000

A rapid screening system to determine drug affinities for the intestinal dipeptide transporter 1: system characterisation.

PURPOSE: To establish an in vitro system for the rapid assessment of the affinities of potential substrates for the di/tri/oligopeptide transport system (DTS). METHODS: Monolayers of Caco-2 cells were cultured in plastic wells for 7-9 days and the uptake of Gly-[3H]L-Pro, a specific and relatively stable substrate for the DTS was used as an affinity probe. Gly-[3H]L-Pro (50 nM), together with excess L-Pro (10 mM), to suppress uptake of any [3H]L-Pro produced by degradation of the probe, was incubated with the test compound (usually 1 mM) at pH 6 for 3 min. The uptake of radiolabel was determined by liquid scintillation counting. RESULTS: High specific-uptake (> 85%) of Gly-[3H]L-Pro was obtained with cells grown for 7-9 days. Gly-[3H]L-Pro uptake had a substantial active concentration-dependent component (Km of 0.39 +/- 0.02 mM, Vmax of 0.98 +/- 0.04 nmol min(-1) (mg protein)(-1). This process was shown to be specific for the DTS as evidenced by the significant inhibition by compounds reported to be transported by this system and the lack of inhibition by amino acids. The use of low competitor concentrations (1 mM) enabled a range of inhibition values (0-89%) of a series of competitors (amino acids, dipeptides and beta-lactam antibiotics) to be estimated, illustrating that structurally similar compounds can be ranked for affinity to the DTS. CONCLUSION: A screening system, using Caco-2 cells and the dipeptide Gly-[3H]L-Pro as a displaceable probe, was developed to assess a variety of compounds for recognition by the di/tri/oligopeptide transport system. This fully describes the first system that allows structurally related compounds to be ranked on the basis of their affinity for the DTS recognition site.

Algorithms↗
PubMed2000

A rapid screening system to determine drug affinities for the intestinal dipeptide transporter 2: affinities of ACE inhibitors.

PURPOSE: To assess the affinities of a series of ACE inhibitors for the di/tri/oligopeptide transport system (DTS) using a rapid in vitro system. METHODS: Monolayers of Caco-2 cells were cultured in plastic wells for 7-9 days and the uptake of Gly-[3H]L-Pro was used as an affinity probe. Gly-[3H]L-Pro (50 nM), together with excess L-Pro (10 mM), to suppress uptake of any [3H]L-Pro produced by degradation of the probe, was incubated with the test compound (usually 1 mM) at pH 6 for 3-mins. The uptake of radiolabel was determined by liquid scintillation counting. RESULTS: A 2-dimensional six-domain model of the transporter based on the structure of a phosphinate ACE inhibitor (SQ-29852) was constructed to facilitate interpretation of the competitor affinities. The SQ-29852 molecule was divided into six binding domains (A-F) based on functional groups within these regions and the effects of structural variation in four of these domains (A, C-E) were explored. A series of dipeptide-like compounds varying within specific domains were selected from a large number of commercially available ACE inhibitors and SQ-29852 analogues. Domain A had a preference for an uncharged group, with bulky hydrophobic groups reducing affinity. Domain C exhibited a preference for a positive charge over a neutral function, with the space this functional group occupies contributing to affinity. Domain D favoured lipophilic residues and domain E retained activity when the carboxylic acid was esterified. CONCLUSION: The test system is able to reveal structure-activity relationships of peptidomimetic agents and may well serve as a design tool to optimise affinity for the DTS.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Discovery of (R)-7-cyano-2,3,4, 5-tetrahydro-1-(1H-imidazol-4-ylmethyl)-3- (phenylmethyl)-4-(2-thienylsulfonyl)-1H-1,4-benzodiazepine (BMS-214662), a farnesyltransferase inhibitor with potent preclinical antitumor activity.

Continuing structure-activity studies were performed on the 2,3,4, 5-tetrahydro-1-(imidazol-4-ylalkyl)-1,4-benzodiazepine farnesyltransferase (FT) inhibitors. These studies demonstrated that a 3(R)-phenylmethyl group, a hydrophilic 7-cyano group, and a 4-sulfonyl group bearing a variety of substituents provide low-nanomolar FT inhibitors with cellular activity at concentrations below 100 nM. Maximal in vivo activity in the mutated K-Ras bearing HCT-116 human colon tumor model was achieved with analogues carrying hydrophobic side chains such as propyl, phenyl, or thienyl attached to the N-4 sulfonyl group. Several such compounds achieved curative efficacy when given orally in this model. On the basis of its excellent preclinical antitumor activity and promising pharmacokinetics, compound 20 (BMS-214662, (R)-7-cyano-2,3,4, 5-tetrahydro-1-(1H-imidazol-4-ylmethyl)-3-(phenylmethyl)-4-(2-thie nyl sulfonyl)-1H-1,4-benzodiazepine) has been advanced into human clinical trials.

3T3 Cells↗
PubMed2000

Prevalence and predictors of human papillomavirus infection in women in Ontario, Canada. Survey of HPV in Ontario Women (SHOW) Group.

BACKGROUND: Human papillomavirus (HPV) is thought to be the primary cause of cervical intraepithelial neoplasia and cervical cancer. We determined the age-specific prevalence of HPV infection and its risk factors in Ontario women. METHODS: We obtained 2 cervical specimens from randomly selected women (in 5-year age categories, from 15 to 49 years) who were being seen in 32 family practices for cytologic screening. The specimens were tested for carcinogenic HPV by the hybrid capture II assay (Digene Corp., Silver Spring, Md.) and by polymerase chain reaction (PCR) and genotyping. RESULTS: Of 1004 women eligible to participate, samples were obtained from 955 (95.1%). The prevalence of HPV (as determined by the hybrid capture II method) was highest, at 24.0% (95% confidence interval [CI] 16.5% to 31.5%), among women 20 to 24 years of age and was progressively lower in older age groups, reaching 3.4% (95% CI 0.1% to 6.7%) in women 45 to 49 years old. The prevalence of HPV (any type) as determined by PCR showed a similar pattern but was significantly higher (p = 0.01) among women 45 to 49 years old than among those 40 to 44 years old (13.0% [95% CI 6.4% to 19.6%] v. 3.3% [95% CI 0.1% to 6.5%]). Risk factors for positivity with the hybrid capture II method were never-married status, divorced or separated status, more than 3 lifetime partners, more than 1 partner in the preceding year, cigarette smoking and current use of oral contraceptives. The presence of squamous intraepithelial lesions on cytologic examination was strongly associated with positivity with the hybrid capture II assay (odds ratio 96.0, 95% CI 22.3 to 413.4; p < 0.01). INTERPRETATION: The highest prevalence of HPV was 24.0%, in women 20 to 24 years old. Risk factors supported a sexual mode of transmission, and there was a strong association between HPV and abnormal cervical cytologic results.

Adolescent↗
PubMed2000

Comparison of self-collected vaginal, vulvar and urine samples with physician-collected cervical samples for human papillomavirus testing to detect high-grade squamous intraepithelial lesions.

BACKGROUND: Certain types of human papillomavirus (HPV) in cervical samples are strongly associated with squamous intraepithelial lesions (SIL) and invasive cervical carcinoma. We determined and compared the test characteristics of testing for HPV with samples obtained by patients and with samples obtained by their physicians. METHODS: In a consecutive series of women referred to a colposcopy clinic at a teaching hospital because of abnormalities on cervical cytologic screening, 200 agreed to collect vulvar, vaginal and urine samples for HPV testing. The physician then collected cervical samples for HPV testing, and colposcopy, with biopsy as indicated, was performed. Presence of HPV was evaluated using the hybrid capture II assay (Digene Corp., Silver Spring, Md.) with a probe cocktail for 13 carcinogenic types. Cervical specimens were also tested for HPV by polymerase chain reaction and hybridization with type-specific probes. Cervical smears for cytologic examination were obtained from all women. RESULTS: High-grade lesions (high-grade squamous intraepithelial lesions [HSIL], equivalent to cervical intraepithelial neoplasia [CIN] grade 2 or 3, and adenocarcinoma) were found in 58 (29.0%) of the 200 women. Carcinogenic types of HPV were detected in the self-collected vaginal samples of 50 (86.2%) of these 58 women, in the self-collected vulvar samples of 36 (62.1%) and in the self-collected urine samples of 26 (44.8%). Carcinogenic types of HPV were detected in the cervical samples collected by physicians for 57 (98.3%) of these 58 women. The remaining 142 women (71.0%) had normal findings or low-grade squamous intraepithelial lesions (LSIL, CIN grade 1). Test results were negative or noncarcinogenic types of HPV were detected in the self-collected vaginal samples of 76 (53.5%) of these 142 women, in the self-collected vulvar samples of 89 (62.7%) and in the self-collected urine samples of 99 (69.7%). The sensitivity for self-collected samples ranged from 44.8% to 86.2%, and the specificity from 53.5% to 69.7%. For the samples collected by physicians, the sensitivity was 98.3% and the specificity 52.1%. The self-sampling methods were generally acceptable to the women: 98.4% of respondents (126/128) deemed urine sampling acceptable, 92.9% (118/127) found vulvar sampling acceptable, and 88.2% (112/127) found vaginal sampling acceptable. INTERPRETATION: Self-collection of samples for HPV testing was acceptable to women attending a colposcopy clinic for investigation of suspected cervical lesions and shows sufficient sensitivity to warrant further evaluation as a screening test for cervical cancer prevention programs.

Adenocarcinoma↗
PubMed2000

Analytical sensitivity, reproducibility of results, and clinical performance of five PCR assays for detecting Chlamydia pneumoniae DNA in peripheral blood mononuclear cells.

Chlamydia pneumoniae has been associated with atherosclerosis and coronary artery disease (CAD), and its DNA has been detected in atheromatous lesions of the aorta, carotid, and coronary arteries by a variety of PCR assays. The objective of this study was to compare the performances of five published PCR assays in the detection of C. pneumoniae in peripheral blood mononuclear cells (PBMCs) from patients with coronary artery disease. The assays included two conventional PCRs, one targeting a cloned PstI fragment and one targeting the 16S rRNA gene; two nested PCRs, one targeting the 16S rRNA gene and one targeting ompA; and a touchdown enzyme time release (TETR) PCR, targeting the 16S rRNA gene. All PCRs had similar analytical sensitivities and detected a minimum of 0.005 inclusion-forming units (IFU) of C. pneumoniae; the ompA nested PCR and the TETR PCR were slightly more sensitive and detected 0.001 IFU. Assay reproducibility was examined by testing 10 replicates of C. pneumoniae DNA by each assay. All five assays showed excellent reproducibility at high levels of DNA, with scores of 10 out of 10 for 0.01 IFU, but exhibited decreased reproducibility for smaller numbers of C. pneumoniae IFU for all tests. Pairwise comparison of test results indicated that there was a significant difference between tests (Cochran Q = 32.0, P<0.001), with the PstI fragment (P<0.001) and 16S rRNA (P = 0.002) assays having lower reproducibility than the nested ompA and TETR assays. To further analyze assay sensitivity, C. pneumoniae-infected U-937 mononuclear cells were added to whole blood, and extracted mononuclear-cell DNA was tested by each assay. All five assays showed similar sensitivities, detecting 15 infected cells; three assays detected 3 infected cells, while all assays were negative at the next dilution (1.5 infected cells). A striking difference in performance of the five assays was seen, however, when PBMCs from CAD patients were tested for C. pneumoniae DNA. The ompA nested PCR detected C. pneumoniae DNA in 11 of 148 (7.4%) specimens, the 16S rRNA nested PCR detected 2 positives among the 148 specimens (1.4%) (P<0.001), and the other 3 assays detected no positive specimens (P<0.001, compared with the ompA assay). These results indicate that analytical sensitivity alone does not predict the ability of an assay to detect C. pneumoniae in whole-blood-derived PBMCs. Before standardized assays can be used in wide-scale epidemiological studies, further characterization of these assays will be required to improve our understanding of their performance in the detection of C. pneumoniae in clinical material.

Bacterial Outer Membrane Proteins↗
PubMed2000

Loss of G(1)/S checkpoint in human immunodeficiency virus type 1-infected cells is associated with a lack of cyclin-dependent kinase inhibitor p21/Waf1.

Productive high-titer infection by human immunodeficiency virus type 1 (HIV-1) requires the activation of target cells. Infection of quiescent peripheral CD4 lymphocytes by HIV-1 results in incomplete, labile reverse transcripts and lack of viral progeny formation. An interplay between Tat and p53 has previously been reported, where Tat inhibited the transcription of the p53 gene, which may aid in the development of AIDS-related malignancies, and p53 expression inhibited HIV-1 long terminal repeat transcription. Here, by using a well-defined and -characterized stress signal, gamma irradiation, we find that upon gamma irradiation, HIV-1-infected cells lose their G(1)/S checkpoints, enter the S phase inappropriately, and eventually apoptose. The loss of the G(1)/S checkpoint is associated with a loss of p21/Waf1 protein and increased activity of a major G(1)/S kinase, namely, cyclin E/cdk2. The p21/Waf1 protein, a known cyclin-dependent kinase inhibitor, interacts with the cdk2/cyclin E complex and inhibits progression of cells into S phase. We find that loss of the G(1)/S checkpoint in HIV-1-infected cells may in part be due to Tat's ability to bind p53 (a known activator of the p21/Waf1 promoter) and sequester its transactivation activity, as seen in both in vivo and in vitro transcription assays. The loss of p21/Waf1 in HIV-1-infected cells was specific to p21/Waf1 and did not occur with other KIP family members, such as p27 (KIP1) and p57 (KIP2). Finally, the advantage of a loss of the G(1)/S checkpoint for HIV-1 per se may be that it pushes the host cell into the S phase, which may then allow subsequent virus-associated processes, such as RNA splicing, transport, translation, and packaging of virion-specific genes, to occur.

CDC2-CDC28 Kinases↗
PubMed2000

A survey of antibiotic use in dentistry.

BACKGROUND: Antibiotics are important in the management and prophylaxis of infection in patients at risk of experiencing microbial disease. As a result of the increase in antimicrobial resistance, the authors conducted a survey to assess current antibiotic use in dental practice. METHODS: The authors mailed a two-page, pretested survey to all licensed dental practitioners in British Columbia, Canada. A total of 2,542 surveys were mailed; 19.9 percent were returned by fax or mail. The authors examined an association between factors analyzed using a chi 2 test. RESULTS: Respondents were demographically consistent with all registered dentists in British Columbia. They reported writing an average of 4.45 prescriptions per week. Antibiotics prescribed after treatment primarily were penicillin and its derivatives. Recommended adult doses of penicillin were prescribed by 59.2 percent of respondents; recommended daily doses of amoxicillin were prescribed by 72.2 percent of respondents. The average prescription duration was 6.92 days. Respondents prescribed prophylactic antibiotics an average of 1.15 times per week for prophylaxis of bacterial endocarditis; 17.5 percent reported postoperative dosing for prophylaxis, ranging from a one- to seven-day prescription with an average of 6.91 postoperative doses. Preoperative antibiotics were prescribed for patients with a history of rheumatic fever or any heart murmur or prosthetic hip. Antibiotics were prescribed more frequently for surgical procedures and patients with acquired immunodeficiency syndrome than for other circumstances. CONCLUSIONS: More than 80 percent of respondents reported that they followed current American Heart Association prophylaxis guidelines. The authors, however, noted discrepancies in prophylactic use of antibiotics for bacterial endocarditis and for patients with large joint prostheses, as well as in prescribing antibiotics in the presence of clinical infection. In therapeutic use, approximately 85 percent of respondents followed appropriate prescription guidelines for dosing and duration of therapy. CLINICAL IMPLICATIONS: Appropriate and correct use of antibiotics is essential to ensure that effective and safe treatment is available and that practices that may enhance microbial resistance are avoided. To improve standards of care, dentists need up-to-date pharmacology in dental education, as well as continuing education, further outcome studies and continuous assessment of dental practices.

Adult↗
PubMed1999

Discovery and structure-activity relationships of imidazole-containing tetrahydrobenzodiazepine inhibitors of farnesyltransferase.

2,3,4,5-Tetrahydro-1-(imidazol-4-ylalkyl)-1,4-benzodiazepines were found to be potent inhibitors of farnesyltransferase (FT). A hydrophobic substituent at the 4-position of the benzodiazepine, linked via a hydrogen bond acceptor, was important to enzyme inhibitory activity. An aryl ring at position 7 or a hydrophobic group linked to the 8-position through an amide, carbamate, or urea linkage was also important for potent inhibition. 2,3,4, 5-Tetrahydro-1-(1H-imidazol-4-ylmethyl)-7-(4-pyridinyl)-4-[2-(t rifluo romethoxy)benzoyl]-1H-1,4-benzodiazepine (36), with an FT IC(50) value of 24 nM, produced 85% phenotypic reversion of Ras transformed NIH 3T3 cells at 1.25 microM and had an EC(50) of 160 nM for inhibition of anchorage-independent growth in soft agar of H-Ras transformed Rat-1 cells. Selected analogues demonstrated ip antitumor activity against an ip Rat-1 tumor in mice.

3T3 Cells↗
PubMed1999

Characterization of a self-splicing mini-intein and its conversion into autocatalytic N- and C-terminal cleavage elements: facile production of protein building blocks for protein ligation.

The determinants governing the self-catalyzed splicing and cleavage events by a mini-intein of 154 amino acids, derived from the dnaB gene of Synechocystis sp. were investigated. The residues at the splice junctions have a profound effect on splicing and peptide bond cleavage at either the N- or C-terminus of the intein. Mutation of the native Gly residue preceding the intein blocked splicing and cleavage at the N-terminal splice junction, while substitution of the intein C-terminal Asn154 resulted in the modulation of N-terminal cleavage activity. Controlled cleavage at the C-terminal splice junction involving cyclization of Asn154 was achieved by substitution of the intein N-terminal cysteine residue with alanine and mutation of the native C-extein residues. The C-terminal cleavage reaction was found to be pH-dependent, with an optimum between pH6.0 and 7.5. These findings allowed the development of single junction cleavage vectors for the facile production of proteins as well as protein building blocks with complementary reactive groups. A protein sequence was fused to either the N-terminus or C-terminus of the intein, which was fused to a chitin binding domain. The N-terminal cleavage reaction was induced by 2-mercaptoethanesulfonic acid and released the 43kDa maltose binding protein with an active C-terminal thioester. The 58kDa T4 DNA ligase possessing an N-terminal cysteine was generated by a C-terminal cleavage reaction induced by pH and temperature shifts. The intein-generated proteins were joined together through a native peptide bond. This intein-mediated protein ligation approach opens up novel routes in protein engineering.

Amino Acid Sequence↗
PubMed1999

Single-shot echo-planar imaging of multiple sclerosis: effects of varying echo time.

Our aim was to determine the relative merits of short and long echo times (TE) with single-shot echo-planar imaging for imaging cerebral lesions such as multiple sclerosis. We examined seven patients with clinically definite multiple sclerosis were imaged at 1.5 T. Patients were scanned with spinecho, single-shot echo-planar imaging, using TEs of 45, 75, 105, and 135 ms. Region of interest (ROI) measurements were performed on 36 lesions at or above the level of the corona radiata. The mean image contrast (IC) was highest (231.1) for a TE of 45 ms, followed by 75 ms (218.9), 105 ms (217.9), and 135 ms (191.6). When mean contrast-to-noise ratios (C/N) were compared, the value was again highest (29.7) for TE 45 ms, followed by 75 ms (28.9), 105 ms (28.5), and 135 ms (26.3). In a lesion-by-lesion comparison, TE 45 ms had the highest IC and C/N in the largest number of cases (50 % and 47.2 %, respectively). IC and C/N for TE 45 ms were superior to those of 75 ms in 64% and 58%, respectively. These results support the use of relatively short TEs for single-shot echo-planar imaging in the setting of cerebral lesions such as multiple sclerosis.

Cerebral Cortex↗