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Biomedical subjects

A van Dalen

Publications and source records attributed to A van Dalen.

At least 19 recordsLinked to original sources
PubMed2006

Definite involuntary childlessness: associations between coping, social support and psychological distress.

BACKGROUND: Around 4% of all couples remain involuntarily childless. These people often experience insufficient social support, which further aggravates the distress symptoms such as physical health problems, anxiety, depression and complicated grief. This study investigates the association of coping style and the degree of satisfaction regarding social support from primary support groups with distress symptoms of involuntarily childless individuals. MATERIALS AND METHODS: Subjects in this cross-sectional study were people who wanted to have children with their partner but were unable to conceive and had acknowledged their involuntary childlessness. The sample consisted of 116 persons (response 88%) with an average age of 39 years (SD = 6.0), with 75% women. The sample group completed a questionnaire consisting of passive and active coping styles from the Utrecht Coping List (UCL), the discrepancy variant of the Social Support List (SSL-D), the short version of the Questionnaire on Experienced Health Complaints (VOEG-21), the Hospital Anxiety and Depression Scale (HADS) and the Inventory of Complicated Grief-Revised (ICG-R), adapted for this study. RESULTS: Women especially experienced more health complaints, more anxiety and depression symptoms and more complicated grief than the general population. Regression analysis shows that when controlled for sex and the duration of involuntary childlessness, the concepts passive coping style and dissatisfaction with social support were positively associated with health complaints, depression, anxiety and complicated grief. The concept active coping style was negatively associated with depression, anxiety and complicated grief. Explained variance of the different distress symptoms varied from 30 to 65%. A moderating association of perceived social support is only found between a passive coping style and health complaints. CONCLUSIONS: Psychosocial interventions should be continued after the childlessness has become definite. By teaching couples how to cope actively with their childlessness and how to ask for support, the negative consequences of their childlessness may be decreased.

Adaptation, Psychological↗
PubMed2003

Clinical utility of biochemical markers in colorectal cancer: European Group on Tumour Markers (EGTM) guidelines.

In recent years, numerous serum and cell/tissue-based markers have been described for colorectal cancer (CRC). The aim of this article was to provide guidelines for the routine clinical use of some of these markers. Lack of sensitivity and specificity preclude the use of any available serum markers such as carcinoembryonic antigen (CEA), CA 19-9, CA 242, CA 72-4, tissue polypeptide antigen (TPA) or tissue polypeptide-specific antigen (TPS) for the early detection of CRC. However, preoperative measurement of CEA is desirable as this may give independent prognostic information, help with surgical management and provide a baseline level for subsequent determinations. For patients with stage 2 (Dukes' B) and 3 (Dukes' C) disease who may be candidates for liver resection, CEA levels should be measured every 2-3 months for at least 3 years after diagnosis. For monitoring treatment of advanced disease, CEA should also be tested every 2-3 months. Insufficient evidence is presently available to recommend the routine use of other serum markers for monitoring purposes. Similarly, the new cell and tissue-based markers (e.g, ras, P53) cannot yet be recommended for routine clinical use.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed2003

[Cantilever resin-bonded bridges with one adhesive surface. A review of the literature].

Conventional resin-bonded bridges are designed with adhesive surfaces on both sides of the dummy. As a consequence both abutment teeth are rigidly connected to each other. Loading of the abutment teeth or dummy will lead to wringing forces in the cement. Adhesive bridges with one adhesive surface are actually cantilever bridges. Theoretically this type of bridges will be less prone to wringing forces due to loading. However, long term research into the performance of cantilever resin-bonded bridges (RBBs) is hardly available. The results of research into the longevity of conventional RBBs differ remarkably between Europe, and the United States and Japan. These difference are discussed in this article. This article compares the fixed-fixed design RBBs with the cantilever RBBs. The differences are discussed based on eight articles, the earliest being published in 1991, which are dedicated, completely or partially, to the subject of cantilever adhesive bridges. One can conclude that in The Netherlands RBBs are wrongly considered to be unreliable. On the contrary, they appear to be reliable and predictable restorations provided their preparations meet the right standards. Although a number of authors conclude that cantilever RBBs are performing better than their fixed-fixed design counterparts in similar situations, further research is needed concerning the longevity of this type of adhesive bridges.

Dental Abutments↗
PubMed2002

Lateralisation and depth of the internal mammary chain determined by scintigraphy and by ultrasonography: a comparative study in 124 primary breast cancer patients.

In 124 primary breast cancer patients the maximum values of the lateralisation of the internal mammary chain (IMC) and their corresponding depths could be determined by scintigraphy and ultrasonography in 77% and 85% of the cases, respectively. With respect to the lateralisation it appeared that these values were uncorrelated between the two methods. With respect to depth correlation was found (correlation coefficient 0.34; P=0.001). We conclude that substantial differences are noted. Irradiation of the IMC based on computed tomography treatment planning might be a better alternative.

Breast Neoplasms↗
PubMed2001

The acute effects of norharman on cocaine self-administration and sensorimotor function in male Wistar rats.

The purpose of the present study was to determine the acute effects of the beta-carboline norharman on cocaine dependence. Male Wistar rats were allowed to self-administer cocaine for 3 h for seven sessions. A single injection of norharman (0.2-20 mg/kg, i.p.) was given 30 min before the onset of the seventh session. It was shown that norharman decreased the cocaine intake in a U-shaped manner with the dose of 10 mg/kg having the most potent effect. These results indicate that several receptor mechanisms mediate the effects of norharman. In addition, 15 min following the administration of norharman on session 7, motor and sensory skill tests were performed. Six naïve animals were tested with the dose, which has the most pronounced effect on cocaine self-administration intake, in order to examine whether the observed effects were due to norharman or due to the combination of norharman and cocaine. It was observed that norharman in both the naïve and cocaine-exposed animals significantly increased the response time in the somato-sensory orienting test. However, only in the naïve animals a significant effect of norharman on the grasp reflex was observed.

Animals↗
PubMed2001

Minimally invasive surgery for solitary parathyroid adenomas in patients with primary hyperparathyroidism: role of US with supplemental CT.

PURPOSE: To determine the role of ultrasonography (US) with supplemental computed tomography (CT) in patients with primary hyperparathyroidism who undergo minimally invasive surgery instead of conventional neck exploration. MATERIALS AND METHODS: US and CT were performed in 61 consecutive patients with primary hyperparathyroidism (part 1) to identify and localize solitary adenomas for resection by means of minimally invasive surgery and to provide a surgical road map. In part 2, involving 33 consecutive patients, CT was performed only when no solitary adenoma was identified with US or for road map information. Minimally invasive surgery was considered successful when serum calcium levels normalized and remained stable. RESULTS: In part 1, 46 definite solitary adenomas were found with US and two additional ones with CT. Minimally invasive surgery was successful in 45 patients and failed once. In part 2, US helped identify 23 solitary adenomas, and CT helped to find one. Minimally invasive surgery was successful in 22 patients and failed in two. Combined results in 94 patients demonstrated successful minimally invasive surgery in 67 (71%), with 64 of them selected with US alone (95% CI: 61, 80). The sensitivity of US in the diagnosis of solitary adenoma was 78% (95% CI: 67%, 86%), with a positive predictive value of 96% (95% CI: 88%, 99%). CONCLUSION: US examination of patients with primary hyperparathyroidism allowed successful selection for minimally invasive surgery in more than two-thirds of the cases, with additional CT useful chiefly for surgical road mapping.

Adenoma↗
PubMed2000

Tissue polypeptide specific antigen (TPS), a marker for differentiation between pancreatic carcinoma and chronic pancreatitis. A comparative study with CA 19-9.

BACKGROUND: The value of serum tissue polypeptide specific antigen (TPS) as a complement to CA 19-9 in the detection of pancreatic carcinoma was determined prospectively. TPS and CA 19-9 levels obtained at the time of diagnosis in patients suspected of having chronic pancreatitis or pancreatic carcinoma were evaluated in receiver operating characteristic (ROC) curve analysis. METHODS: Serum TPS and CA 19-9 levels were measured by immunoassays in 122 subjects, 48 with pancreatic carcinoma and 74 with chronic pancreatitis. RESULTS: Elevated levels of CA 19-9 were detected preoperatively in 70% of pancreatic carcinoma patients and in 19% of chronic pancreatitis patients. Elevated levels of TPS were detected in 100% of patients with pancreatic carcinoma and in 22% of patients with chronic pancreatitis. The median levels of TPS and CA 19-9 for pancreatic carcinoma were significantly higher than those for chronic pancreatitis (P < 0.0001). Increasing the upper reference value of TPS allowed for better discrimination between chronic pancreatitis and pancreatic carcinoma. ROC curve analysis showed that the introduction of 200 U/L as a decision criterion for TPS did not reduce its sensitivity but significantly improved its specificity. At a specificity of 98% for TPS, discrimination between pancreatic carcinoma and chronic pancreatitis was found to be 97%. Increasing the upper reference level for CA 19-9 to attain a specificity of 98% decreased its sensitivity from 70% to 33%. CONCLUSIONS: At an elevated cut-off level for TPS (200 U/L), almost complete discrimination between pancreatic carcinoma and chronic pancreatitis was obtained. TPS will be more useful than CA 19-9 in the differential diagnosis of pancreatic carcinoma and chronic pancreatitis.

Adult↗
PubMed2000

Prognostic significance of CA 125 and TPS levels after 3 chemotherapy courses in ovarian cancer patients.

OBJECTIVE: To evaluate the prognostic significance of and predictive value for survival of CA 125 and TPS levels after three chemotherapy courses in ovarian cancer patients. METHODS: We analyzed in a prospective multicenter study the 1- and 2-year overall survival (OS) in ovarian carcinoma patients. The prognostic significance of CA 125 and TPS levels above the discrimination value (25 kU/L and 100 U/L, respectively) was examined by univariate and multivariate analyses. RESULTS: Of the 213 cases included, 64 patients were staged as FIGO I + II and 149 patients were staged as FIGO III + IV. Tumor marker levels in stage I + II were not correlated with survival. However, stage III and IV patients with elevated levels of CA 125 or TPS after three chemotherapy courses had a worse 2-year OS (69% vs 26%, P < 0.0001 and 57% vs 20%, P < 0.0001, respectively) than patients with normal levels of the markers. In univariate analysis the result of operation (staging laparatomy and partial debulking) and advanced FIGO stage (IV) were also adverse prognostic factors. Independent factors predictive of low 2-year OS by multivariate analysis were staging laparotomy, TPS elevated, and CA 125 elevated. The only factors predictive of low 1-year OS were TPS elevated and staging laparotomy. CONCLUSIONS: Ovarian cancer patients with elevated CA 125 levels after three chemotherapy courses have a poor prognosis. However, the prognostic accuracy can be significantly increased by the parallel determination of serum TPS.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Efficient membrane assembly of the KcsA potassium channel in Escherichia coli requires the protonmotive force.

Very little is known about the biogenesis and assembly of oligomeric membrane proteins. In this study, the biogenesis of KcsA, a prokaryotic homotetrameric potassium channel, is investigated. Using in vivo pulse-chase experiments, both the monomeric and tetrameric form could be identified. The conversion of monomers into a tetramer is found to be a highly efficient process that occurs in the Escherichia coli inner membrane. KcsA does not require ATP hydrolysis by SecA for insertion or tetramerization. The presence of the proton-motive force (pmf) is not necessary for transmembrane insertion of KcsA; however, the pmf proved to be essential for the efficiency of oligomerization. From in vivo and in vitro experiments it is concluded that the electrical component, deltapsi, is the main determinant for this effect. These results demonstrate a new role of the pmf in membrane protein biogenesis.

Adenosine Triphosphate↗
PubMed2000

Direct, minimally invasive adenomectomy for primary hyperparathyroidism: An alternative to conventional neck exploration?

OBJECTIVE: To evaluate the feasibility and efficacy of a direct, minimally invasive adenomectomy (MIA) as an alternative to conventional neck exploration (CNE) in patients with primary hyperparathyroidism. SUMMARY BACKGROUND DATA: Because primary hyperparathyroidism is caused by a solitary adenoma in 85% to 90% of patients, a direct adenomectomy through a mini-incision would theoretically suffice whenever an adenoma is correctly localized on preoperative imaging. If effective, a less invasive method could spare the patient an unnecessary bilateral neck exploration, thus saving time and rendering future surgical procedures in the neck less problematic. METHODS: Between October 1994 and October 1998, 110 consecutive patients with biochemically proven primary hyperparathyroidism who were to undergo surgery were enrolled in this study. Ultrasound and spiral CT were routinely performed as standard preoperative imaging modalities in the first series of 65 patients. In the second series of 45 patients, ultrasound was performed as the sole initial modality; it was supplemented by CT only in case of inconclusive test results. If test results were unequivocal (one adenoma), the patient was offered MIA. CNE was performed if the results were equivocal or if multiglandular disease was suspected. RESULTS: Overall, 84 patients were selected for MIA and 26 for CNE. In the first series, 2 MIA procedures (2/51) were converted to CNE because of negative perioperative findings. All 65 procedures resulted in normocalcemia. In the second series, all but five (4/33 MIAs, 1/12 CNEs) resulted in normocalcemia. A reexploration (CNE) was performed in three patients, resulting in normocalcemia after resection of a second or third adenoma. Two patients are still awaiting reexploration. In both series together, 78 of the 110 patients were successfully treated with MIA and spared CNE. CONCLUSION: MIA is a safe and effective alternative to CNE that may replace CNE in approximately two thirds of all patients.

Adenoma↗
PubMed1999

Delta psi stimulates membrane translocation of the C-terminal part of a signal sequence.

For several proteins in Escherichia coli it has been shown that the protonmotive force (pmf) dependence of translocation can be varied with the signal sequence composition, suggesting an effect of the pmf on the signal sequence. To test this possibility, we analyzed the effect of the membrane potential on translocation of the signal sequence. For this purpose, a precursor peptide was used (SP+7), corresponding to the signal sequence of PhoE with the first seven amino acids of the mature part that can be processed by purified leader peptidase. Translocation was studied in pure lipid vesicles containing leader peptidase, with its active site inside the vesicles. In the presence of a positive inside Delta psi, the amount of processing of SP+7 was significantly higher than without a Delta psi, indicating that the translocation of the cleavage region is stimulated by Delta psi. Replacement of the helix-breaking glycine residue at position -10 in the signal sequence for a leucine abolished the effect of Delta psi on the translocation of the cleavage region. It is concluded that Delta psi directly acts on the wild type signal sequence by stimulating the translocation of its C terminus. We propose that Delta psi acts on the signal sequence by stretching it into a transmembrane orientation.

Amino Acid Sequence↗
PubMed1998

The orientation of nisin in membranes.

Nisin is a 34 residue long peptide belonging to the group A lantibiotics with antimicrobial activity against Gram-positive bacteria. The antimicrobial activity is based on pore formation in the cytoplasmic membrane of target organisms. The mechanism which leads to pore formation remains to be clarified. We studied the orientation of nisin via site-directed tryptophan fluorescence spectroscopy. Therefore, we engineered three nisin Z variants with unique tryptophan residues at positions 1, 17, and 32, respectively. The activity of the tryptophan mutants against Gram-positive bacteria and in model membrane systems composed of DOPC or DOPG was established to be similar to that of wild type nisin Z. The tryptophan fluorescence emission maximum showed an increasing blue-shift upon interaction with vesicles containing increased amounts of DOPG, with the largest effect for the 1W peptide. Studies with the aqueous quencher acrylamide showed that all tryptophans became inaccessible from the aqueous phase in the presence of negatively charged lipids in the vesicles. From these results it is concluded that anionic lipids mediate insertion of the tryptophan residues in at least three positions of the molecule into the lipid bilayer. The depth of insertion of the tryptophan residues was determined via quenching of the tryptophan fluorescence by spin-labeled lipids. The results showed that the depth of insertion was dependent on the amount of negatively charged lipids. In membranes containing 50% DOPG, the distances from the bilayer center were determined to be 15.7, 15.0, and 18.4 A for the tryptophan at position 1, 17, and 32, respectively. In membranes containing 90% DOPG, these distances were calculated to be 10.8, 11.5, and 13.1 A, respectively. These results suggest an overall parallel average orientation of nisin in the membrane, with respect to the membrane surface, with the N-terminus more deeply inserted than the C-terminus. These data were used to model the orientation of nisin in the membrane.

Acrylamide↗
PubMed1998

Serotoninergic status in patients with hereditary vascular retinopathy syndrome.

AIM/BACKGROUND: In a new autosomal dominant syndrome (which the authors called hereditary vascular retinopathy (HVR)) cerebral ischaemia, Raynaud's phenomenon, and migraine are the most striking features. As serotonin (5-HT) is known to play a role in vasospastic processes, Raynaud's phenomenon, and migraine they wondered whether the serotoninergic status in patients with HVR is different. Therefore, it was decided to investigate some serotoninergic variables in these patients. METHODS: The study was conducted in 12 patients with HVR, 10 relatives, and 19 healthy controls. The levels of intraplatelet and plasma 5-HT were measured, as well as the plasma levels of its precursor amino acid tryptophan and the ratio of tryptophan to the large neutral amino acids, which compete with the transport of tryptophan through the blood-brain barrier. RESULTS: In both the patients with HVR and in nine relative the concentrations of 5-HT in plasma and platelets were significantly lower than in controls. The plasma levels of tryptophan and the tryptophan ratio were also found to be lower in the patient group compared with the control group, but not in the relatives. CONCLUSION: The observed alterations in 5-HT and its precursor tryptophan strongly suggest the existence of a malfunctioning of the serotoninergic system in the HVR syndrome.

Adult↗
PubMed1998

Epitope specificity of 30 monoclonal antibodies against cytokeratin antigens: the ISOBM TD5-1 Workshop.

The epitope specificities of 30 monoclonal antibodies (MAbs) against the most common human cytokeratins. i.e., Nos. 8, 18, and 19, in epithelial cells were investigated in the ISOBM TD-5 Workshop. Seven research groups from universities or companies participated independently in the evaluation of the antibody specificities. The complex assembly of cytokeratins in vivo, with obligatory heterologous dimeric combinations of different cytokeratins from each of the two major groups, comprising together more than 20 different individual cytokeratins, made analysis of the antibody reactivity patterns with isolated single cytokeratins necessary. The concordance of the evaluations was striking and independent of the technologies used. As antigens purified individual cytokeratins, chemically degraded purified cytokeratins, recombinant intact and truncated cytokeratins, as well as specific synthesized shorter peptides were used. In order to elucidate the epitope specificity, reactivity patterns in ELISA assays and immunoblots with partial enzymatic degradation of the antigens were performed. Competitive cross-inhibition experiments between antibodies using antigens and antibodies in all possible combinations were performed with radioimmunometric assays, BIAcore, and ELISA technology. All 30 antibodies could convincingly be classified with regard to target cytokeratin. One MAb (192) had to be deleted due to dual specificities in both isotype and epitope specificity against its target. Six antibodies bound selectively to cytokeratin 8, 14 to cytokeratin 18, and 10 to cytokeratin 19, as demonstrated by using native, recombinant, and synthesized antigens. The immunodominant part of the molecule for all three types of cytokeratins was located in the region of amino acid (aa) 270-400. Out of the six MAbs reactive with cytokeratin 8, four MAbs, i.e., 178, 199, 202, and 206, were reactive with a sequence in the interval aa 340-365, and MAb 191 reacted with a closely related epitope. The remaining antibody, 192, presented dual specificities. At least two closely related major immunogenic epitopes could be identified in cytokeratin 8. In cytokeratin 18 four distinct epitopes could be documented, again with the dominating sequence region 270-429 as target for 10 (181, 184, 186, 188, 189, 190, 193, 196, 198, and 200) out of 14 antibodies. Since MAb 193 is known to react with the M3 epitope, aa 322-342 in cytokeratin 18, this entire group is reactive in the region close to the charge shift, in the middle of the rod 2B region, as shown by competitive binding. The remaining four anticytokeratin 18 antibodies (180, 185, 203, and 205) displayed unique, noncompetitive binding to this filament. Cytokeratin 19, reactive with altogether ten antibodies, displayed two major epitopes, all of them also within the large immunodominant region. MAbs 179, 195, 197, and 204 were reactive with the peptides aa 311-335 also known as the KS 19.1 epitope, and MAbs 182, 183, 187, 194, and 201 bound to peptide aa 346-367, known as the BM 19.21 epitope. One antibody, 231, was selectively reactive with aa 356-370 in cytokeratin 19. A complex pattern of binding specificities comprising at least ten different, noncompetitive epitopes, mainly situated in the rod portion, 2A and 2B, situated close to the charge shift in the rod of all three cytokeratins was documented. Out of the 29 classifiable antibodies, altogether 22 were reactive in this very short region, i.e., from aa 311 to 370 in all cytokeratin filaments. The remaining seven antibodies displayed unique binding properties. The implications of the findings are of significance both for immunohistochemistry and for assaying circulating heterodimeric, partially degraded complexes in patients' blood for tumor marker evaluation.

Amino Acid Sequence↗
PubMed1998

Successful minimally invasive surgery in primary hyperparathyroidism after combined preoperative ultrasound and computed tomography imaging.

The hypothesis that due to the high prevalence of solitary adenoma and the accuracy of modern imaging techniques it should be possible to cure a considerable number of patients by direct adenomectomy through a minimally invasive approach was tested in a consecutive series of 66 patients with primary hyperparathyroidism. Preoperative parathyroid imaging consisted of a combination of (Doppler) ultrasound and spiral computed tomography with cine-loop reconstruction potentiality. If only one parathyroid adenoma was identified preoperatively, a minimally invasive approach was advised. If more than one adenoma was located, or when the imaging results were equivocal, the patient was advised to undergo a conventional bilateral neck exploration. Sixty-six patients (54 female, 12 male) with a median age of 60 years and a median serum calcium of 2.90 mmol L(-1) were studied. Fifty-one of these patients underwent minimally invasive surgery, which was successful in 49 patients, while conversion to conventional neck exploration was necessary in two patients. Conventional neck exploration was chosen for the other 15 patients. Six of these proved to have multiglandular disease or a retro-sternal adenoma, while in nine patients only one parathyroid adenoma was found. All patients became normocalcaemic postoperatively. Morbidity consisted of a transient unilateral vocal cord paralysis in one patient. These results support the original hypothesis: successful minimally invasive surgery was possible in 74% (49 of 66) of patients, thus avoiding conventional neck exploration. This strategy further simplifies the operative treatment of primary hyperparathyroidism without loss of efficiency.

Female↗
PubMed1997

The diagnostic accuracy of core biopsy in palpable and non-palpable breast lesions.

OBJECTIVE: To assess the accuracy of large-core needle biopsy in evaluating palpable and nonpalpable breast lesions. METHODS AND PATIENTS: Stereotaxic and ultrasound (US) guided core biopsies were performed in 103 breast lesions in 97 patients. Subsequently, all patients underwent surgery. All specimens (core biopsy and surgical) underwent radiography for evaluation of microcalcifications. The histopathologic findings of the core biopsies and the surgical specimens were correlated. RESULTS: Core biopsies and surgery findings were concordant in 100% of the 27 palpable lesions and in 89% of the 76 nonpalpable lesions. One case of malignancy, ductal carcinoma in situ (DCIS), was not diagnosed by core biopsy. In 102 (99%) of the 103 breast lesions, a correct choice for additional diagnostic procedure or definitive treatment could have been made upon histopathologic findings of core biopsy. CONCLUSION: Stereotaxic and ultrasound-guided core biopsy are safe, reliable and less traumatic than excisional biopsy. Special attention is necessary when atypical ductal hyperplasia (ADH) or DCIS without invasive carcinoma is found. Radiography of the biopsy specimens for detection of microcalcifications is essential.

Adult↗