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Biomedical subjects

H Visser

Publications and source records attributed to H Visser.

At least 19 recordsLinked to original sources
PubMed2006

[Gynaecomastia and male infertility as symptoms of a nonpalpable Leydig cell tumour].

A 35-year-old man and his partner were referred for intracytoplasmic sperm injection treatment (ICSI) because of secondary infertility due to severe oligoasthenoteratospermia. Three years earlier he had presented elsewhere with left unilateral gynaecomastia. A hypertrophic mammary gland had been excised one year later. Histopathological investigation showed benign hypertrophy. One year later he developed gynaecomastia on the other side. Physical examination and incomplete hormonal screening showed no abnormalities. The couple were referred to our tertiary clinic for ICSI treatment. The patient still had unilateral gynaecomastia. Hormonal screening showed not only severe oligoasthenoteratospermia, but also an elevated serum oestrogen level. Scrotal ultrasound revealed a 17 mm mass in his right testicle. Subsequently unilateral orchidectomy was performed. Histology showed a benign Leydig cell tumour for which no further therapy was required. Four months after surgery the gynaecomastia diminished, oestrogen levels became normal and improvement in semen parameters followed. Patients with severe male infertility or gynaecomastia are at a higher risk of developing a testicular neoplasm. Besides history taking, physical examination of breasts and testicles, hormonal screening and scrotal sonography should be performed as some testicular neoplasms are not apparent on palpation.

Adult↗
PubMed2005

A comparison of the diagnostic accuracy and prognostic value of the first and second anti-cyclic citrullinated peptides (CCP1 and CCP2) autoantibody tests for rheumatoid arthritis.

OBJECTIVES: To compare the diagnostic performance and prognostic value of the anti-cyclic citrullinated peptide (CCP1) and anti-CCP2 autoantibody tests in a clinical setting. METHODS: Anti-CCP1 and anti-CCP2 antibody tests were performed on the same serum samples obtained from 467 patients with early arthritis from the Leiden Arthritis Cohort. The sensitivity, specificity, positive predictive value, and negative predictive value for discriminating between rheumatoid arthritis (RA) and non-RA at 1 year's follow up were calculated for both tests. Results were graphically presented using receiver operating characteristic curves. Progression of radiological joint damage was assessed over 4 years in patients with RA and used to assess the prognostics values of the CCP tests. RESULTS: At a similar specificity the CCP2 test had a higher sensitivity than the CCP1 test. Both tests identified a subgroup of patients with RA with an increased rate of joint damage progression. The anti-CCP2 test identified more patients with an increased rate of joint damage progression than the anti-CCP1 test, and in multiple regression analysis CCP2 was the better predictor of joint damage. CONCLUSIONS: The CCP2 test had better diagnostic and prognostic ability than the CCP1 test.

Adolescent↗
PubMed2002

Early and aggressive treatment of rheumatoid arthritis patients affects the association of HLA class II antigens with progression of joint damage.

OBJECTIVE: The presence of certain HLA class II antigens is strongly associated with the progression of joint destruction in rheumatoid arthritis (RA). Such antigens may be more effective than other class II antigens in inducing the formation of autoreactive T cells after presentation of (auto)antigens. We investigated whether early and aggressive treatment with disease-modifying antirheumatic drugs could modify this relationship. METHODS: We analyzed data from 2 studies of patients with early RA treated according to different strategies. The first study consisted of 2 cohorts, one (n = 109; median disease duration before treatment 4 months) was treated according to the pyramid strategy (initial nonsteroidal antiinflammatory drugs, followed by chloroquine [CQ] or sulfasalazine [SSZ] when necessary), and the other (n = 97; median disease duration before treatment 2 weeks) was immediately treated with CQ or SSZ. The second study comprised 155 patients (median disease duration 4 months) from the Combinatietherapie Bij Reumatoide Artritis (COBRA) trial, in which patients were randomly assigned to combination treatment with step-down prednisolone, methotrexate (MTX), and SSZ (n = 76) or with SSZ alone (n = 79). Prednisolone and MTX dosages were tapered and stopped after 28 and 40 weeks, respectively. The extent of joint damage was measured by the modified Sharp method. RESULTS: In the pyramid treatment cohort, the median increase in Sharp score after 2 years was 12 in patients positive for the shared epitope (SE) and 1 in SE- patients. In the immediate treatment cohort, the median increase was 3 in SE+ patients and 2 in SE- patients. In the SSZ group of the COBRA study, the median increase in Sharp score after 1 year was 11 in DR4+ patients and 3 in DR4- patients. In the combination treatment group, the median increase was 4 in DR4+ patients and 2 in DR4- patients. Significance was confirmed by multiple regression using log-transformed scores. CONCLUSION: Early and aggressive antirheumatic drug treatment affects the association of HLA class II alleles with progression of joint damage in RA.

Adult↗
PubMed2002

Sarcoid arthritis: clinical characteristics, diagnostic aspects, and risk factors.

OBJECTIVES: (a) To describe the clinical characteristics of acute sarcoid arthritis and the diagnostic value of its presenting clinical features; (b) to evaluate whether disease onset is seasonal; and (c) to evaluate whether smoking behaviour or the presence of HLA class II alleles is a risk factor for the disease. METHODS: 579 consecutive patients with recent onset arthritis who had been newly referred to a rheumatology outpatient clinic were included in a prospective cohort study. The presenting clinical features, the smoking behaviour, and the results of HLA-DQ and HLA-DR DNA typing of 55 patients with sarcoid arthritis, 524 patients with other arthritides of recent onset, and samples of the normal population were compared. RESULTS: In all cases the disease showed a self limiting arthritis and overall good prognosis. The diagnostic ability of a combination of four clinical features--symmetrical ankle arthritis, symptoms of less than two months, age below 40 years, and erythema nodosum--was exceptionally high. When test positivity is defined as the presence of at least three of four criteria the set rendered a sensitivity of 93%, a specificity of 99%, a positive predictive value of 75%, and a negative predictive value of 99.7%. The disease clustered in the months March-July. The disease was negatively associated with smoking (odds ratio (OR) 0.09; 95% confidence interval (95% CI) 0.02 to 0.37) and positively associated with the presence of the DQ2 (DQB1*0201)-DR3 (DRB1*0301) haplotype (OR 12.33; 95% CI 5.97 to 25.48). CONCLUSION: The disease entity acute sarcoid arthritis has highly diagnostic clinical features. The seasonal clustering, the protective effect of smoking, and the association with specific HLA class II antigens support the hypothesis that it results from exposure of susceptible hosts to environmental agents through the lungs.

Adult↗
PubMed2001

Early versus delayed treatment in patients with recent-onset rheumatoid arthritis: comparison of two cohorts who received different treatment strategies.

PURPOSE: To compare the effect of delayed and early treatment strategies on disease outcome in patients with rheumatoid arthritis. SUBJECTS AND METHODS: Between 1993 and 1995, 109 patients diagnosed with probable or definite rheumatoid arthritis of recent onset were initially treated with analgesics; if they had persistent active disease, they were treated subsequently with the disease-modifying drugs chloroquine or salazopyrine (delayed treatment). Between 1996 and 1998, similar patients (n = 97) were promptly treated with either chloroquine or salazopyrine (early treatment). RESULTS: The median lag to the initiation of disease-modifying treatment was 15 days in the early treatment group and 123 days in the delayed treatment group. There was less radiologic joint damage after 2 years in the early treatment group (median Sharp score, 3.5; 95% confidence interval [CI]: 1 to 7) compared with the delayed treatment group (median Sharp score, 10; 95% CI: 5 to 15; P <0.05). The median area under the curve of the 2-year disease activity score was lower in the early treatment group (64 units; 95% CI: 59 to 69 units) compared with the delayed treatment group (73 units; 95% CI: 69 to 77 units; P = 0.002). CONCLUSION: In this nonrandomized comparison, early introduction of disease-modifying antirheumatic drugs was associated with a better disease outcome after 2 years.

Activities of Daily Living↗
PubMed2001

Attenuated total reflection design for in situ FT-IR spectroelectrochemical studies.

A versatile spectroelectrochemical apparatus is introduced to study the changes in IR spectra of organic and inorganic compounds upon oxidation or reduction. The design is based on an attenuated total reflection device, which permits the study of a wide spectral range of 16,700 (600 nm)-250 cm(-1), with a small opaque region of 2250-1900 cm(-1). In addition, an IR data collection protocol is introduced to deal with electrochemically nonreversible background signals. This method is tested with ferrocene in acetonitrile; concentrations as low as 1 mM produce results that agree with those in the literature.

Electrochemistry↗
PubMed2001

Absence of Mn-centered oxidation in the S(2) --> S(3) transition: implications for the mechanism of photosynthetic water oxidation.

A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen-evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S(3) --> [S(4)] --> S(0) transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn Kbeta X-ray emission spectroscopy (Kbeta XES) to this problem for the first time. The Kbeta XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S(2) --> S(3) transition, in contrast to the S(0) --> S(1) and S(1) --> S(2) transitions, does not involve a Mn-centered oxidation. On the basis of new structural data from the S(3)-state, manganese mu-oxo bridge radical formation is proposed for the S(2) --> S(3) transition, and three possible mechanisms for the O-O bond formation are presented.

Electron Spin Resonance Spectroscopy↗
PubMed2001

Mn K-edge XANES and Kbeta XES studies of two Mn-oxo binuclear complexes: investigation of three different oxidation states relevant to the oxygen-evolving complex of photosystem II.

Two structurally homologous Mn compounds in different oxidation states were studied to investigate the relative influence of oxidation state and ligand environment on Mn K-edge X-ray absorption near-edge structure (XANES) and Mn Kbeta X-ray emission spectroscopy (Kbeta XES). The two manganese compounds are the di-mu-oxo compound [L'2Mn(III)O2Mn(IV)L'2](ClO4)3, where L' is 1,10-phenanthroline (Cooper, S. R.; Calvin, M. J. Am. Chem. Soc. 1977, 99, 6623-6630) and the linear mono-mu-oxo compound [LMn(III)OMn(III)L](ClO4)2, where L- is the monoanionic N,N-bis(2-pyridylmethyl)-N'-salicylidene-1,2-diaminoethane ligand (Horner, O.; Anxolabéhère-Mallart, E.; Charlot, M. F.; Tchertanov, L.; Guilhem, J.; Mattioli, T. A.; Boussac, A.; Girerd, J.-J. Inorg. Chem. 1999, 38, 1222-1232). Preparative bulk electrolysis in acetonitrile was used to obtain higher oxidation states of the compounds: the Mn(IV)Mn(IV) species for the di-mu-oxo compound and the Mn(III)Mn(IV) and Mn(IV)Mn(IV) species for the mono-mu-oxo compound. IR, UV/vis, EPR, and EXAFS spectra were used to determine the purity and integrity of the various sample solutions. The Mn K-edge XANES spectra shift to higher energy upon oxidation when the ligand environment remains similar. However, shifts in energy are also observed when only the ligand environment is altered. This is achieved by comparing the di-mu-oxo and linear mono-mu-oxo Mn-Mn moieties in equivalent oxidation states, which represent major structural changes. The magnitude of an energy shift due to major changes in ligand environment can be as large as that of an oxidation-state change. Therefore, care must be exercised when correlating the Mn K-edge energies to manganese oxidation states without taking into account the nature of the ligand environment and the overall structure of the compound. In contrast to Mn K-edge XANES, Kbeta XES spectra show less dependence on ligand environment. The Kbeta1,3 peak energies are comparable for the di-mu-oxo and mono-mu-oxo compounds in equivalent oxidation states. The energy shifts observed due to oxidation are also similar for the two different compounds. The study of the different behavior of the XANES pre-edge and main-edge features in conjunction with Kbeta XES provides significant information about the oxidation state and character of the ligand environment of manganese atoms.

Electrochemistry↗
PubMed2001

High-resolution X-ray spectroscopy of rare events: a different look at local structure and chemistry.

The combination of large-acceptance high-resolution X-ray optics with bright synchrotron sources permits quantitative analysis of rare events such as X-ray fluorescence from very dilute systems, weak fluorescence transitions or X-ray Raman scattering. Transition-metal Kbeta fluorescence contains information about spin and oxidation state; examples of the characterization of the Mn oxidation states in the oxygen-evolving complex of photosystem II and Mn-consuming spores from the marine bacillus SG- are presented. Weaker features of the Kbeta spectrum resulting from valence-level and 'interatomic' ligand to metal transitions contain detailed information on the ligand- atom type, distance and orientation. Applications of this spectral region to characterize the local structure of model compounds are presented. X-ray Raman scattering (XRS) is an extremely rare event, but also represents a unique technique to obtain bulk-sensitive low-energy (<600 eV) X-ray absorption fine structure (XAFS) spectra using hard (approximately 10 keV) X-rays. A photon is inelastically scattered, losing part of its energy to promote an electron into an unoccupied level. In many cases, the cross section is proportional to that of the corresponding absorption process yielding the same X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) features. XRS finds application for systems that defy XAFS analysis at low energies, e.g. liquids or highly concentrated complex systems, reactive compounds and samples under extreme conditions (pressure, temperature). Recent results are discussed.

Bacillus↗
PubMed2001

Human leukocyte antigen-DQ and DR polymorphisms predict rheumatoid arthritis outcome better than DR alone.

Conflicting data have been published on the value of the shared epitope (SE) hypothesis in predicting disease outcome in rheumatoid arthritis (RA). Recently we have proposed an alternative hypothesis, referred to as the RA protection (RAP) model. In this model, the HLA-DQ loci carry predisposition while HLA-DRB1 alleles encoding the motif DERAA provide protection against severe RA. In the present study, we have compared the respective values of the models in predicting both remission and erosions in early RA patients. We made use of an early arthritis clinic in which 158 RA patients and 138 patients with undifferentiated arthritis were enrolled. Patients were typed for HLA-DQ and -DR using high resolution DNA typing methods. Homozygosity for predisposing HLA-DQ alleles was associated with no remission and high erosion score. The presence of DERAA-bearing DRB1 alleles was negatively associated with erosions in otherwise predisposed individuals and increased the chance of being in remission. We found that the RAP model was significantly better than the SE model in predicting remission rate and erosion scores at one and two years in early RA patients. We conclude that HLA polymorphism does not only affect RA susceptibility, but also protects against severe disease at early stage.

Alleles↗
PubMed2001

Dose reduction by direct-digital cephalometric radiography.

Patient radiation exposure was determined for conventional and direct-digital cephalometric radiography. An anthropomorphic phantom was positioned to expose lateral cephalographs from the patient's left side. The conventional radiographs were exposed with a Siemens Orthophos C unit (77 kV, 14 mA, 0.5 s) and a film-screen system of a relative speed of 400. The direct-digital radiographs were exposed with a Siemens Orthophos DS Ceph (73 kV, 15 mA, 15.8 s). A set of 108 thermoluminescence detectors (TLDs; Bicron STI/Harshaw, Solon, Ohio) was used for dose measurements. For each measurement, 84 TLDs were placed at the surface of the head and neck, as well as inside the phantom, at anatomically relevant positions. The remaining detectors were employed for calibration purposes and quality control. The highest absorbed doses were recorded for the conventional technique at the skin of the left parotid region (132 microGy), in the left parotid gland (103 microGy), and in the ocular lens of the left eye (81 microGy). Digital cephalometry resulted in an absorbed dose about 2 times lower than the dose received by the conventional technique. The effective doses had the same relation (conventional 2.3 microSv; digital 1.1 microSv). The results demonstrate that direct-digital cephalometric radiography cuts the patient's dose in half compared with the conventional screen-film technique. Direct-digital cephalometry is more advantageous than the conventional technique from the perspective of radiation protection.

Cephalometry↗
PubMed2000

Increased gelatinase-A and gelatinase-B activities in malignant vs. benign breast tumors.

Matrix metalloproteinases (MMP) types 2 and 9 (also known as gelatinase A and B) are thought to be causally involved in cancer invasion and metastasis. In normal as well as in malignant tissue, both these MMPs occur in multiple forms such as inactive precursors, active enzymes and enzyme-inhibitor complexes. Using newly developed quantitative activity assays, the levels of active MMP-2, total (active and activatable) MMP-2 and total MMP-9 were found to be significantly higher in breast carcinomas than in fibroadenomas. In addition, active MMP-2 and MMP-9 were detected more frequently in malignant than in benign breast carcinoma. These new quantitative activity assays are likely to be of use in studying the mechanism of action of both MMP-2 and -9, assessing their potential prognostic value in different cancers and in the design of MMP inhibitors for preventing cancer metastasis.

Breast Neoplasms↗
PubMed2000

The diagnostic properties of rheumatoid arthritis antibodies recognizing a cyclic citrullinated peptide.

OBJECTIVE: Since modern treatment of rheumatoid arthritis (RA) is shifting toward aggressive antirheumatic therapy in an early phase of the disease, diagnostic tests with high specificity are desirable. A new serologic test (anti-cyclic citrullinated peptide [anti-CCP] enzyme-linked immunosorbent assay [ELISA]) was developed to determine the presence of antibodies directed toward citrullinated peptides, using a synthetic peptide designed for this purpose. METHODS: A cyclic peptide variant that contains deiminated arginine (citrulline) was designed and used as antigenic substrate in ELISA. Test parameters and diagnostic characteristics of the test were studied in patients with and without RA, in patients with various infectious diseases, and in a group of patients from an early arthritis clinic (EAC). RESULTS: Using prevalent RA and non-RA sera, the anti-CCP ELISA proved to be extremely specific (98%), with a reasonable sensitivity (68%). Also, in the EAC study group, the anti-CCP ELISA appeared to be highly specific for RA (96%). In comparison with the IgM rheumatoid factor (IgM-RF) ELISA, the anti-CCP ELISA had a significantly higher specificity (96% for CCP versus 91% for IgM-RF; P = 0.016) at optimal cut-off values. The sensitivity of both tests for RA was moderate: 48% and 54% for the anti-CCP ELISA and the IgM-RF ELISA, respectively (P = 0.36). Combination of the anti-CCP and the IgM-RF ELISAs resulted in a significantly higher positive predictive value of 91% (P = 0.013) and a slightly lower negative predictive value of 78% (P = 0.35) as compared with the use of the IgM-RF ELISA alone. The ability of the 2 tests performed at the first visit to predict erosive disease at 2 years of followup in RA patients was comparable (positive predictive value 91%). CONCLUSION: The anti-CCP ELISA might be very useful for diagnostic and therapeutic strategies in RA of recent onset.

Adolescent↗
PubMed2000

Cloning and characterization of an epoxide hydrolase-encoding gene from Rhodotorula glutinis.

We cloned and characterized the epoxide hydrolase gene, EPH1, from Rhodotorula glutinis. The EPH1 open reading frame of 1230 bp was interrupted by nine introns and encoded a polypeptide of 409 amino acids with a calculated molecular mass of 46.3 kDa. The amino acid sequence was similar to that of microsomal epoxide hydrolase, which suggests that the epoxide hydrolase of R. glutinis also belongs to the alpha/beta hydrolase fold family. EPH1 cDNA was expressed in Escherichia coli and resting cells showed a specific activity of 200 nmol min(-1)(mg protein)(-1) towards 1,2-epoxyhexane.

Amino Acid Sequence↗
PubMed2000

[Dose measurements comparing conventional and digital panoramic radiography].

OBJECTIVE: The purpose of our study was to measure and compare patient exposure by direct digital and conventional panoramic radiography. MATERIAL AND METHODS: Dose measurements were carried out on an anthropomorphic phantom, which was specially developed for dental radiography. Panoramic radiographs were taken with three different conventional devices (Orthopantomograph 10E, Orth Oralix FD, Siemens Orthophos) and two direct digital devices (Orthopantomograph 100 Digipan, Siemens Orthophos DS Ceph). The exposure conditions were according to clinical routine. The energy dose was measured at 28 places inside and on the surface of the phantom by using a set of 108 thermoluminescence detectors. Additionally, exposure time, tube voltage, central-beam dose, and dose-area products were measured. The effective doses were calculated on the basis of the absorbed doses. RESULTS: In each case, the highest energy doses were recorded at the parotid gland, the mandibular angle, the submandibular gland, and the skin in the neck. Panoramic radiographs taken with the conventional units yielded in effective doses in the range of 16-21 microSv, the digital units caused 5 or 14 microSv. CONCLUSION: In comparison with conventional techniques, patient exposure can be reduced by direct digital panoramic radiography. The extent of dose reduction depends on the device employed and is generally smaller than the dose reduction that can be achieved by digital imaging devices in intraoral radiography.

Humans↗
PubMed2000

The diagnostic value of streptococcal serology in early arthritis: a prospective cohort study.

OBJECTIVE: To evaluate the diagnostic value of streptococcal serology in adult early arthritis patients in discriminating between post-streptococcal reactive arthritis (PSRA) and arthritis with other causes. METHODS: The antistreptolysin-O (ASO) and anti-DNase B tests were performed at baseline in 366 consecutive, newly referred early arthritis patients. After 1 yr of follow-up the patients were classified according to international classification criteria and were evaluated for the presence of persistent arthritis. The outcome measures were the predictive value of streptococcal serology for the diagnosis of PSRA and the ability of this serology to discriminate at the first visit between the self-limiting and persistent forms of arthritis. RESULTS: With a positive serological result, the probability of having PSRA increased from 2 to 9%, whereas the probabilities of having rheumatoid arthritis or undifferentiated arthritis continued to be high (23 and 29%). The serological tests did not discriminate between the self-limiting and persistent forms of arthritis. The major Jones criteria apart from arthritis were not observed. CONCLUSION: Streptococcal serology has no diagnostic value in adult early arthritis patients in whom major Jones criteria other than arthritis are not present.

Adult↗
PubMed1999

MMP-9 activity in urine from patients with various tumors, as measured by a novel MMP activity assay using modified urokinase as a substrate.

Matrix metalloproteinases (MMPs) play an important role in many pathologic processes, but their activities are difficult to determine since no simple specific and/or chromogenic substrate exists. We have developed a novel MMP activity assay using a modified urokinase as a substrate. Protein engineering enabled the plasmin activation site in this urokinase to be substituted by a specific activation site recognized by MMPs. In this way the MMP activity can be monitored via urokinase activity as measured by a simple chromogenic assay. The assay was made specific for MMP-9 by a capture step using MMP-9-specific antibodies that do not interfere with MMP-activity. This assay monitors the amount of active enzyme as well as the latent, but potentially active proform. Using this assay the levels of MMP-9 were investigated in urine from patients with various kinds of carcinoma. High levels of both active and latent MMP-9 were detected in urine from patients with carcinoma of the bladder, whereas hardly any activity was observed in urine from healthy controls. MMP-9 in urine was present in its intact form. Surprisingly, MMP-9 was also increased in the urine of patients with nonurogenital carcinoma. Therefore, measurement of urinary MMP-9 activity levels may be a convenient diagnostic tool for various types of carcinoma.

Adult↗