Biomedical subjects

W Quint

Publications and source records attributed to W Quint.

At least 19 recordsLinked to original sources

PubMed2006

g-Factor of heavy ions: a new access to the fine structure constant.

A possibility for a determination of the fine structure constant in experiments on the bound-electron g-factor is examined. It is found that studying a specific difference of the g-factors of B- and H-like ions of the same spinless isotope in the Pb region to the currently accessible experimental accuracy of 7 x 10(-10) would lead to a determination of the fine structure constant to an accuracy which is better than that of the currently accepted value. Further improvements of the experimental and theoretical accuracy could provide a value of the fine structure constant which is several times more precise than the currently accepted one.

Journal Article↗

PubMed2004

Electronic g factor of hydrogenlike oxygen 16O7+.

We present an experimental value for the g factor of the electron bound in hydrogenlike oxygen, which is found to be g(expt)=2.000 047 025 4 (15)(44). The experiment was performed on a single 16O7+ ion stored in a Penning trap. For the first time, the expected line shape of the g-factor resonance is calculated which is essential for minimizing the systematic uncertainties. The measurement agrees within 1.1 sigma with the predicted theoretical value g(theory)=2.000 047 020 2 (6). It represents a stringent test of bound-state quantum electrodynamics to a 0.25% level. Assuming the validity of the underlying theory, a value for the electron mass is obtained: m(e)=0.000 548 579 909 6 (4) u. This value agrees with our earlier determination on and allows a combination of both values which is about 4 times more precise than the currently accepted one.

Journal Article↗

PubMed2001

Assessment of Helicobacter pylori vacA and cagA genotypes and host serological response.

Helicobacter pylori strains can be distinguished by genotyping of virulence-associated genes, such as vacA and cagA. Because serological discrimination between strain types would reduce the need for endoscopy, 61 patients carrying H. pylori were studied by vacA and cagA genotyping of H. pylori in gastric biopsy specimens and by detection of specific serum antibodies. Serological responses to H. pylori were determined by Helicoblot (versions 2.0 and 2.1). Antibodies to CagA also were determined by a rapid anti-CagA assay (Pyloriset screen CagA) as well as by two noncommercially developed enzyme immunoassays, each using a recombinant CagA protein. Assessment of performance of the Helicoblot assays indicated substantial interobserver variation, with kappa values between 0.20 and 0.93. There was no relationship between the serological profiles on the Helicoblot and the genotypes from the same patients, except for strong associations between the presence of anti-CagA and the cagA-positive and vacA s1 H. pylori genotypes. Detection of anti-CagA by the five different assays varied considerably, with kappa values ranging from 0.21 to 0.78. Using the cagA genotype as the "gold standard," the sensitivity and specificity of the anti-CagA assays varied from 71.4 to 85.7% and from 54.2 to 100%, respectively. Thus, serological profiles of antibodies to H. pylori are heterogeneous and, with the exception of anti-CagA antibodies, show no relation to the H. pylori vacA and cagA genotypes. Detection of anti-CagA antibodies is strongly dependent on the test used.

Antibodies, Bacterial↗

PubMed2000

High-accuracy measurement of the magnetic moment anomaly of the electron bound in hydrogenlike carbon.

We present a new experimental value for the magnetic moment of the electron bound in hydrogenlike carbon (12C5+): g(exp) = 2.001 041 596 (5). This is the most precise determination of an atomic g(J) factor so far. The experiment was carried out on a single 12C5+ ion stored in a Penning trap. The high accuracy was made possible by spatially separating the induction of spin flips and the analysis of the spin direction. The current theoretical value amounts to g(th) = 2.001 041 591 (7). Together experiment and theory test the bound-state QED contributions to the g(J) factor of a bound electron to a precision of 1%.

Journal Article↗

PubMed2000

The prevalence and incidence of hepatitis C virus infections among dialysis patients in the Netherlands: a nationwide prospective study.

A nationwide prospective survey on hepatitis C virus (HCV) infections among dialysis patients in The Netherlands was performed. Patients were recruited from 34 dialysis centers and were tested for antibodies and HCV RNA in 1995 and 1997. Seronegative serum samples were analyzed by reverse-transcriptase polymerase chain reaction in pools. HCV-RNA-positive serum samples were genotyped and were partly sequenced. In the first and second rounds, 67 (2.9%) of 2281 and 76 (3.4%) of 2286 patients were HCV positive, respectively. Of 960 patients with paired serum samples, 35 were HCV positive in both rounds, and 9 HCV-positive cases were newly identified in the second round. The incidence of HCV infection was 0.5 per 100 dialysis years. Phylogenetic analysis revealed clustered sequences that indicated nosocomial transmission. Sixty percent of HCV infections, however, can be attributed to 4 interdependent risk factors (i.e., hemodialysis before 1992, kidney transplantation before 1994, and birth or dialysis in a foreign country). In conclusion, the prevalence of HCV infections in The Netherlands does not decline, and transmission within dialysis units continues. Adequate screening of HCV infections and strict enforcement of universal infection control practices are required.

Case-Control Studies↗

PubMed2000

Observation of the continuous stern-gerlach effect on an electron bound in an atomic Ion

We report on the first observation of the continuous Stern-Gerlach effect on an electron bound in an atomic ion. The measurement was performed on a single hydrogenlike ion ( 12C5+) in a Penning trap. The measured g factor of the bound electron, g = 2.001 042(2), is in excellent agreement with the theoretical value, confirming the relativistic correction at a level of 0.1%. This proves the possibility of g-factor determinations on atomic ions to high precision by using the continuous Stern-Gerlach effect. The result demonstrates the feasibility of conducting experiments on single heavy highly charged ions to test quantum electrodynamics in the strong electric field of the nucleus.

Journal Article↗

PubMed2000

The efficacy of laboratory diagnosis of Helicobacter pylori infections in gastric biopsy specimens is related to bacterial density and vacA, cagA, and iceA genotypes.

A total of 500 consecutive patients undergoing upper endoscopy were biopsied and tested for H. pylori infection by the Campylobacter-like organism (CLO) test, culture, histology, and PCR. Serum samples were tested by two different serological assays. Patients were considered H. pylori positive if at least two of the four biopsy specimen-based methods yielded positive results. PCR had the highest diagnostic sensitivity (99.4%), followed by histology (92.2%), culture (89.5%), and the CLO test (89.0%). The specificities of all methods were higher than 98%. Of the organisms from the 181 PCR-positive patients, the vacA (s and m regions), cagA, and iceA genotypes were determined by reverse hybridization (line probe assay) or an allele-specific PCR. Organisms that were detected by PCR but that remained undetected by the CLO test were significantly more often vacA s1 (P = 0.006), m1 (P = 0.028), and cagA positive (P = 0.029) than vacA s2, m2, and cagA negative, respectively. Organisms that were detected by PCR but that remained undetected by culture or histology more often contained iceA1 (P = 0. 034 and P = 0.029, respectively) than iceA2. Higher H. pylori density was associated with vacA s2 (P = 0.024), vacA m2 (P = 0.050), and cagA-negative (P = 0.035) genotypes. Also, the diagnostic results of the CLO test (P = 0.001) and culture (P = 0.031) but not those of the PCR (P = 0.130) were significantly associated with the H. pylori density. The rate of detection by the four biopsy specimen-based tests was lower for patients who used proton pump inhibitors, but this was independent of the H. pylori genotypes. These observations may be explained by different bacterial densities, as established by the distinct genotypes of H. pylori, and confirm that the biologies of strains with such genotypes are considerably different.

Antigens, Bacterial↗

PubMed2000

Perceptions of aging and their relation with age, death depression, and sex.

The relations of knowledge and attitudes about aging to one's age, sex, and depression about death were examined. 111 undergraduate and graduate students completed the multiple-choice form of the Facts on Aging Quiz and the Death Depression Scale. Present results extend previous research showing that people's perceptions of aging change with age. How such perceptions change is twofold: (1) perceptions of aging do not become more positive with age but do have less negative bias, and (2) they show more knowledge of aging on test measures. No sex differences were found in knowledge and attitudes about aging. No significant relationship was found between scores on measures of attitudes toward aging and depression about death. Sex differences were found on scores for death depression, with women reporting greater depression about death.

Adult↗

PubMed1999

[Nosocomial transmission of hepatitis C virus in a Dutch dialysis center].

OBJECTIVE: To describe the transmission of hepatitis C virus (HCV) in a dialysis centre in the Netherlands, to analyse risk factors and to redefine additional preventive measures. DESIGN: Descriptive. METHODS: The data of patients attending the dialysis centre of the Deventer Hospital, the Netherlands, who had participated in a national prospective survey on the epidemiology of HCV among Dutch dialysis patients, were examined. In addition, patients who developed signs of hepatic failure in the ensuing year were included in this study. To diagnose an HCV-infection serology as well as polymerase chain reaction were used. Genotyping and sequence analysis were used to assess phylogenetic relations. Infection control practices were audited. RESULTS: In the dialysis centre a cluster of four almost identical HCV isolates genotype 2a was found. Within a period of one year another cluster of four HCV-infected dialysis patients was detected in the same centre. These four isolates were almost identical to a fifth isolate, genotype 2b, found in the earlier study from another patient dialysing in the same unit. It was observed that possibly contaminating procedures were not strictly separated. Some of the shared medical equipment was not sterilised but only cleaned. Also blood-contaminated gloves might have played a role in the transmission of HCV. CONCLUSION: Nosocomial transmission plays an important role in the epidemiology of HCV in dialysis patients. Shared medical equipment and blood-contaminated gloves may constitute a potential route of transmission. There is a need for stringent implementation and regular auditing of infection control measures.

Cluster Analysis↗

PubMed1999

Risk factors for human papillomavirus and cervical precancerous lesions, and the role of concurrent HIV-1 infection.

OBJECTIVES: To identify risk factors for human papillomavirus (HPV) infection and squamous intraepithelial lesions (SIL) of the cervix, and to measure the impact of concurrent HIV-1 infection. METHODS: Women were studied at a family planning clinic in Nairobi, Kenya. Demographic and historical information was obtained using a semi-structured questionnaire and specimens were collected for sexually transmitted diseases (STDs), HPV, cervical cytology, and HIV-1 testing. RESULTS: HPV was detected in 87 of 513 women (17%), including 81 (93%) oncogenic types (16, 18, 31, 33 and others) and six (7%) non-oncogenic types (6 and 11). HIV-1 prevalence was 10%. HPV detection was associated with HIV-1 infection [adjusted odds ratio (aOR) 3.9, 95% confidence interval (CI), 2.0-7.7], sexual behavior indicators including the number of sex partners and inflammatory STDs, as well as the number of pregnancies (0 or 1 vs. > or = 3, aOR 0.4; 95% CI, 0.2-0.9). SIL was detected in 61 women (11.9%), including 28 (46%) with low-grade lesions (LSIL) and 33 (54%) with high-grade lesions (HSIL). HPV infection was strongly associated with HSIL (OR 14.9; 95% CI, 6.8-32.8). In a multivariate model predictors of HSIL included HIV-1 serpositivity (aOR 4.8; 95% CI, 1.8-12.4), the number of lifetime sex partners (0-1 vs. > or = 4; aOR 3.8; 95% CI, 1.1-13.5), and older age (< 26 vs. > 30; OR 3.9; 95% CI, 1.1-13.6). An analysis stratified by HIV-1 showed a stronger association between HPV and HSIL in HIV-1 negative women (OR 17.0; 95% CI, 6.4-46.3) then in HIV-1 positive women (OR 4.5; 95% CI, 0.8-27.4). CONCLUSION: Our results indicate that HSIL and even invasive cancer are highly prevalent in this setting of women on reproductive age considered to be at low risk for STDs, suggesting that routine Pap smear screening may save lives.

Adult↗

PubMed1999

Relationship between human papillomavirus type 16 in the cervix and intraepithelial neoplasia.

OBJECTIVE: To evaluate a temporal relationship between the presence of cervical human papilloma virus (HPV) type 16 and the risk of developing cervical intraepithelial neoplasia (CIN). METHODS: Fifty-four women with HPV 16 polymerase chain reaction (PCR)-positive tests were selected from the gynecologic outpatient clinic of the Reinier de Graaf Hospital, Delft, The Netherlands. At least three successive PCR tests were performed in each woman at intervals of 6 months. The PCR HPV 16 assay was performed in conjunction with cervical smear, and colposcopy and biopsy, if indicated. Women with at least three consecutive positive PCR tests were defined as having persistent HPV 16 infections. Women with one positive test followed by two negative tests were defined as having transient infections. Subdivided into two groups, 25 women had persistent infections and 29 had transient infections. RESULTS: In significantly more women in the persistent group compared with the transient group, CIN developed (11 of 25 versus six of 29, P = .036). Lesions in women with persistent HPV 16 infection were more severe (six of 11 were CIN III versus one of six P = .041). CONCLUSION: Persistent infection with HPV 16 is associated with a higher risk of developing CIN, which is often high-grade.

Adult↗

PubMed1999

Development and clinical evaluation of a highly sensitive PCR-reverse hybridization line probe assay for detection and identification of anogenital human papillomavirus.

Human papillomavirus (HPV) can be detected by amplification of viral DNA. A novel PCR primer set generating a short PCR fragment (SPF PCR) was used for amplification of a fragment of only 65 bp from the L1 region and permitted ultrasensitive detection of a broad spectrum of HPV genotypes. The intra- and intertypic sequence variations of the 22-bp interprimer region of this amplimer were studied. Among 238 HPV sequences from GenBank and clinical specimens, HPV genotypes were correctly identified based on the 22-bp sequence in 232 cases (97.2%). Genotype-specific probes for HPV genotypes 6, 11, 16, 18, 31, 33 to 35, 39, 40, 42 to 45, 51 to 54, 56, 58, 59, 66, 68, 70, and 74 were selected, and a reverse hybridization line probe assay (LiPA) (the INNO-LiPA HPV prototype research assay) was developed. This LiPA permits the use of amplimers generated by the SPF as well as the MY 09/11 primers. The assay was evaluated with a total of 1, 354 clinical specimens, comprising cervical scrapes (classifications ranging from normal cytology to severe dyskaryosis) and formalin-fixed, paraffin-embedded cervical carcinoma samples. LiPA results were highly concordant with sequence analysis of the SPF amplimer, genotype-specific PCR, and sequence analysis of amplimers generated by MY 09/11 primers. The sensitivity of the SPF primers was higher than that of the GP5(+)/6(+) primers over a broad range of HPV types, especially when multiple HPV genotypes were present. In conclusion, the SPF LiPA method allows extremely sensitive detection of HPV DNA as well as reliable identification of HPV genotypes in both cervical smears and paraffin-embedded materials.

Base Sequence↗

PubMed1999

Evaluation of an in-house polymerase chain reaction for detection of Neisseria gonorrhoeae in urogenital samples.

AIM: To develop and evaluate a one day in-house polymerase chain reaction (PCR) assay for the detection of Neisseria gonorrhoeae DNA in urogenital samples. METHODS: 429 urogenital specimens were tested for the presence of N gonorrhoeae by in-house PCR and by Gen-Probe. The PCR assay amplifies target sequences within the N gonorrhoeae cppB gene on the 4.2 kb cryptic plasmid, after which amplicons are detected by a streptavidinbiotin based enzyme immunoassay using an internal probe. Discordant specimens were further evaluated by repeating the PCR and the Gen-Probe assay, and by an additional PCR using another set of 16S primers followed by radioactive detection of amplicons on a Southern blot. RESULTS: Of the 429 samples tested, 15 were found positive by in-house PCR, eight of which were confirmed by Gen-Probe. Of the seven discrepant samples, five were confirmed by 16S PCR and are also considered true positive. The remaining two samples were positive in the in-house PCR only, and are considered false positive. After resolution of discrepant samples, the sensitivities of the N gonorrhoeae assays were 100% and 61.5% for the in-house PCR and Gen-Probe, respectively, while specificities were comparable at 99.5% and 100%. CONCLUSIONS: The in-house PCR for the detection of N gonorrhoeae DNA is at least comparable to Gen-Probe in performance. An extended evaluation period should elucidate if the additional five GO-PCR positive specimens, confirmed by 16S PCR, are caused by persistence of DNA or whether the method is indeed more sensitive.

Cervix Uteri↗

PubMed1998

Novel short-fragment PCR assay for highly sensitive broad-spectrum detection of anogenital human papillomaviruses.

A novel set of polymerase chain reaction (PCR) primers, designated SPF1 and SPF2 and located in the L1 region, was developed for universal detection of human papillomavirus (HPV). A short PCR fragment (SPF) of only 65 pb was synthesized. SPF amplimers were detected in a microtiter-based hybridization system, using a mixture of oligonucleotide probes. The SPF system allowed detection of at least 43 different HPV genotypes. The clinical performance of the novel SPF system was assessed in three different patient groups. 1) Analysis of 534 cervical scrapes, obtained from treated patients, showed that the detection rate in 447 (83.7%) scrapes with normal cytology was significantly higher using the SPF system as compared with the universal primer set GP5+/6+ (P < 0.001). 2) The SPF assay detected HPV DNA in 299 (98.4%) of 304 scrapes with cytological dyskaryosis. 3) The SPF system detected HPV DNA in 100% of 184 formalin-fixed, paraffin-embedded cervical carcinoma specimens. In conclusion, the novel SPF system permitted universal and highly sensitive detection of HPV DNA in diverse clinical materials and may improve the molecular diagnosis and epidemiology of this important virus.

Blotting, Southern↗

PubMed1998

Clinical relevance of the cagA, vacA, and iceA status of Helicobacter pylori.

BACKGROUND & AIMS: Clinical outcome of Helicobacter pylori infection may be associated with specific virulence-associated bacterial genotypes. The aim of this study was to assess the relationships between H. pylori cagA, vacA, and iceA status and severity of disease. METHODS: Gastric biopsy specimens from 94 patients in The Netherlands were analyzed by polymerase chain reaction and reverse hybridization. RESULTS: cagA was present in 63 (67%) of 94 cases and was associated with peptic ulcer disease (P = 0.0019). vacA geno-types s1a/m1, s1b/m2, s1b/m1, s1b/m2, and s2/m2 were found in 36.2%, 23.4%, 2.1%, 5.3%, and 20.2%, respectively. Ten isolates (10.6%) contained multiple vacA genotypes. The presence of peptic ulcers was associated with type s1 strains (P = 0.0006) but not with the m type (P = 0.2035). cagA and vacA s1 were strongly associated (P < 10(-5)). iceA1 was found in 53 (56.4%) and iceA2 in 25 (26.6%) of the 94 cases. In 14 isolates (14.9%), both iceA alleles were found, and 2 (2.1%) were negative for both iceA1 and iceA2. iceA1 was also associated with peptic ulcer disease (P = 0.0042). The iceA allelic type was independent of the cagA and vacA status. CONCLUSIONS: vacA s1, cagA, and iceA1 are markers of H. pylori strains that are more likely to lead to ulcer disease.

Adult↗

PubMed1998

Radiotherapy for oesophagus carcinoma: the impact of p53 on treatment outcome.

BACKGROUND AND PURPOSE: Wildtype p53 protein plays an important role in the cellular response to ionizing radiation and other DNA damaging agents and is mutated in many human tumours. We evaluated the relationship of the immunohistochemically determined p53 protein status and the disease control with radiotherapy alone for carcinoma of the oesophagus. MATERIALS AND METHODS: Immunostaining for p53 protein was performed on paraffin-embedded specimens from 69 patients with adeno- and squamous cell carcinoma of the oesophagus. All patients were treated by radiotherapy exclusively, consisting of a combination of external irradiation and intraluminal brachytherapy, using two different dose levels. RESULTS: Fifty-four percent (37/69) of the tumours showed overexpression of the p53 protein. No difference in pre-treatment parameters for p53-positive and p53-negative cases was detected. In multivariate analysis p53 was significantly associated with overall survival (OS) next to weight loss, tumour stage and N-stage. For metastatic-free survival (MFS) p53 status proved to be the sole independent prognostic factor. The influence of p53 on local recurrence-free survival (LRFS), however, was not as strong as on OS and MFS. CONCLUSIONS: Immunohistochemically detected overexpression of mutated p53 protein in oesophagus carcinoma was an independent prognostic factor in a group of patients treated with radiotherapy alone.

Adenocarcinoma↗

PubMed1998

Hepatitis C virus infections in dialysis centers in The Netherlands: a national survey by serological and molecular methods.

A national survey of hepatitis C virus (HCV) infections among dialysis patients in The Netherlands was performed. The study involved 2,653 patients (2,108 hemodialysis patients and 545 chronic ambulatory peritoneal dialysis [CAPD] patients) from 39 of the 49 dialysis centers in the country. Patient sera were analyzed by both serological and molecular methods. Screening by a third-generation enzyme immunoassay (EIA) yielded 79 reactive sera. The presence of anti-HCV antibodies was confirmed in 70 patients by a line immunoassay. All seropositive samples were tested by reverse transcriptase PCR, and 57 samples were found to contain HCV RNA. Of the nine EIA-positive and line immunoassay-negative or indeterminate samples, four were HCV RNA positive. All seronegative samples were screened for the presence of HCV RNA in pools of five sera. Of 2,576 antibody-negative samples, 6 contained HCV RNA. All antibody-positive and RNA-positive samples were also tested by a second serological assay. The prevalence of HCV infections among Dutch dialysis patients as determined by serology or the presence of HCV RNA was 3% (80 of 2,653), i.e., 3.5% (73 of 2,108) in patients treated on hemodialysis and 1.3% (7 of 545) in patients on CAPD. Of these 80 HCV-infected dialysis patients, 67 (84%) were HCV RNA positive. Serological screening alone would have diagnosed only 70 infected patients. Therefore, antibody screening combined with detection of HCV RNA should be considered as the "gold standard" for diagnosing HCV infection in dialysis patients. The prevalence of HCV-infected patients in Dutch dialysis centers ranged from 0 to 8%, suggesting the existence of local risk factors for acquiring HCV infection. Genotyping analysis by reverse hybridization line probe assay revealed the presence of genotypes la (23%), 1b (46%), 2 (3%), 2a (13%), 2b (1%), 3a (7%), and 4a (4%). In four (6%) samples multiple genotypes were detected. The genotype distribution of HCV isolates among Dutch dialysis patients was similar to the distribution among nondialysis patients from the Benelux, except for subtype 1a, which was significantly more prevalent among dialysis patients. In only one center, a high prevalence of an uncommon genotype was suggestive of infection from a common source.

Ambulatory Care Facilities↗

PubMed1998

Hepatitis G virus: prevalence and sequence analysis in blood donors of São Paulo, Brazil.

BACKGROUND AND OBJECTIVES: Hepatitis G virus (HGV) is a recently discovered viral agent transmitted by blood, which was firstly identified in patients with acute or chronic liver disease. HGV prevalence in US blood donors was recently found to average 1-2%. We report a much higher HGV frequency among blood donors of São Paulo, Brazil. MATERIALS AND METHODS: 200 serum samples were submitted to RT-PCR using primers directed to the 5' untranslated region and nonstructural 5A (NS5A) region. PCR products were analyzed by gel electrophoresis and Southern blot hybridization. RESULTS: Of the 200 specimens, 18 (9%; 95% CI 5.4-13.8%) were positive by both sets of primers. Sequence analysis of the NS5A PCR products revealed a homology of 96.3%. Of the 18 HGV-positive samples, only one was positive for anti-HBc and all were anti-HCV- and HCV-RNA-negative. CONCLUSION: Such a high prevalence of HGV in a nonsymptomatic population suggests that this is a benign agent.

Base Sequence↗