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Biomedical subjects

A Jansen

Publications and source records attributed to A Jansen.

At least 19 recordsLinked to original sources
PubMed2003

[Determinants of paroxysmal atrial fibrillation in patients with arterial hypertension].

INTRODUCTION: Atrial fibrillation represents an important arrhythmia, in particular in patients with arterial hypertension. Hitherto, the connection between paroxysmal atrial fibrillation, left atrial size and left ventricular muscle mass has not been investigated sufficiently. In the present study, determinants of paroxysmal atrial fibrillation in patients with arterial hypertension were evaluated. METHODS: 104 consecutive patients were enrolled into this study. All of them suffered from arterial hypertension for more than one year. Persistent or permanent atrial fibrillation was not documented. In all of these patients, clinical, echocardiographic and rhythmologic variables were evaluated. RESULTS: In 10.3% of the patients, paroxysmal atrial fibrillation was found. These patients showed a significantly larger left atrium (43.3 +/- 6.7 vs 37.5 +/- 4.9 mm, p < 0.001), a significantly higher muscle mass of the left ventricle (152.38 +/- 43.57 vs 134.41 +/- 27.19 g/m2, p < 0.01) and significantly more frequent a mild mitral regurgitation (38.1 vs 28.6%, p < 0.01). The multivariate regression analysis revealed as independent factors for paroxysmal atrial fibrillation the size of the left atrium and the presence of mild mitral regurgitation. Independent factors for an enlarged left atrium were mitral insufficiency and left ventricular muscle mass. CONCLUSION: This study shows that paroxysmal atrial fibrillation in aterial hypertension is based on the left atrial size, and left atrial size on left ventricular muscle mass. Therefore, these results should lead to a causal therapy for treatment of paroxysmal atrial fibrillation in these patients.

Adult↗
PubMed2003

Neurological involvement in a case of hypophosphatemia.

Hypophosphatemia occasionally underlies neurological disorders such as encephalopathy, myopathy and neuropathy. Although several cases have been reported in the literature, severe hypophosphatemia as a cause of neurological disorders is rarely mentioned in neurological textbooks and is seldom thought of in practice. We present a 69-year-old woman who develops encephalopathy and rapidly progressive weakness due to hypophosphatemia. The cause of hypophosphatemia is often iatrogenic and multifactorial. Signs and symptoms are mostly non-specific, thus complicating correct diagnosis and appropriate treatment.

Journal Article↗
PubMed2003

How atypical is atypical language dominance?

Atypical, right-hemisphere language dominance is poorly understood. It is often observed in patients with brain reorganization due to lesions early in life. It can also be encountered in seemingly normal individuals. We compared the patterns of neural language activation in 7 individuals with left- and 7 with right-hemisphere language dominance, none of whom had any evidence of brain lesions. We speculated that incongruencies in the activation patterns in atypical, right-hemisphere language dominance could indicate a reorganized neural language system after undetected early brain damage. Functional magnetic resonance imaging analysis of brain activation during phonetic word generation demonstrated (1). no increased activation in the subdominant hemisphere in right compared to left language dominance, (2). a similar variability in the pattern of activation in both groups, and (3). a mirror reverse pattern of activation in right- compared to left-hemisphere dominant subjects. These findings support the view that in individuals with an unrevealing medical history right-hemispheric dominance constitutes a natural rather than an abortive variant of language lateralization.

Adult↗
PubMed2002

cAMP and cGMP do not mediate the vasorelaxation induced by iodinated radiographic contrast media in isolated swine renal arteries.

PURPOSE: Vasodilatation is a frequent side effect of radiographic contrast media, partially due to a direct effect on vascular smooth muscles. Our purpose was therefore to examine any possible implication of the cyclic adenosine monophospate (cAMP) and cyclic guanosine monophosphate (cGMP) pathways in contrast media induced vasorelaxation. MATERIAL AND METHODS: Isolated segments of swine renal arteries were precontracted with 10 microM phenylephrine and relaxed with iomeprol before and after blockade of the cAMP and cGMP pathways. RESULTS: 80 mM and 160 mM of iomeprol significantly relaxed about 52% and 68% of the precontracted arterial rings, respectively. 10 microM of IBMX, a phosphodiesterase inhibitor, did not increase the relaxant effect of 80 mM iomeprol but increased the relaxations induced by 400 nM forskolin by about 1.9 times (which stimulates the production of cAMP), and by 1 microM sodium nitroprusside (which stimulates the production of cGMP). 1 microM of H89 (an inhibitor of the cAMP-dependent protein kinase), was able to reduce the relaxation induced by 4 microM forskolin by about 2.5 times but had no significant effect on the relaxation induced by 160 mM iomeprol. 10 microM of ODQ (an inhibitor of the soluble guanylate cyclase), could reduce the relaxation induced by 10 microM of SNP but not the one induced by 160 mM iomeprol. Moreover, the absence of endothelial cells did not alter the relaxation induced by iomeprol. CONCLUSION: The activation of the cAMP and cGMP pathways are not involved in the in vitro relaxation induced by iomeprol in swine renal arteries.

Animals↗
PubMed2002

The genetic diversity of Brazilian Trypanosoma cruzi isolates and the phylogenetic positioning of zymodeme 3, based on the internal transcribed spacer of the ribosomal gene.

There is a high level of genetic diversity among the clinical isolates of the taxon Trypanosoma cruzi. The results of recent studies on well defined gene loci have revealed that T. cruzi can be divided into two major phylogenetic lineages, designated T. cruzi I and T. cruzi II. Further intra-lineage polymorphisms were explored, in clinical isolates from five representative regions of Brazil, using the internal transcribed spacers that flank the 5.8S ribosomal RNA gene. These regions were amplified in a PCR and the products were digested with six restriction enzymes before being subjected to RFLP analysis in polyacrylamide gels. The results were used to construct a complex evolutionary tree, in which the isolates were clustered into two major phylogenetic lineages with a low level of similarity. To investigate the evolutionary relationships between the isolates, the PCR products were cloned and sequenced. The results of the subsequent phylogenetic analysis confirmed the presence of the two major groups of T. cruzi and showed that zymodeme 3, a third iso-enzymatic sub-group, is closer to T. cruzi I than to T. cruzi II.

Animals↗
PubMed2001

Specific ligands of the peripheral benzodiazepine receptor induce apoptosis and cell cycle arrest in human colorectal cancer cells.

The peripheral benzodiazepine receptor (PBR) has been implicated in growth control of various tumour models. Although colorectal cancers were found to overexpress PBR, the functional role of PBR in colorectal cancer growth has not been addressed to date. Using primary cell cultures of human colorectal cancers and the human colorectal carcinoma cell lines HT29, LS174T, and Colo320 DM we studied the involvement of PBR in the growth control and apoptosis of colorectal cancers. Both mRNA and protein expression of PBR were detected by RT-PCR and flow cytometry. Using confocal laser scanning microscopy and immunohistochemistry the PBR was localized in the mitochondria. The specific PBR ligands FGIN-1-27, PK 11195, or Ro5-4864 inhibited cell proliferation dose-dependently. FGIN-1-27 decreased the mitochondrial membrane potential, which indicates an early event in apoptosis. Furthermore, FGIN-1-27, PK 11195 or Ro5-4864 increased caspase-3 activity. In addition to their apoptosis-inducing effects, PBR ligands induced cell cycle arrest in the G(1)/G(0)-phase. Thus, our data demonstrate a functional involvement of PBR in colorectal cancer growth and qualify the PBR as a possible target for innovative therapeutic approaches in colorectal cancer.

Adult↗
PubMed2001

Time-action analysis of instrument positioners in laparoscopic cholecystectomy.

BACKGROUND: Instrument positioners can position and lock a laparoscopic instrument. This study uses time-action analysis to evaluate objectively whether IPs can substitute for a surgical assistant efficiently and safely. METHODS: In four hospitals, 78 laparoscopic cholecystectomies were randomly assisted by a surgical assistant or an instrument positioner (AESOP and PASSIST) The efficiency and safety of laparoscopic cholecystectomies were analyzed with respect to time, number and type of actions, positioning accuracy, and peroperative complications. A questionnaire evaluated the difficulties for each operation and the comfort of instrument positioner use. RESULTS: The PASSIST and AESOP were able to replace the surgical assistant during laparoscopic cholecystectomies without significantly changing either the efficiency or the safety of the operation. The questionnaire showed that the surgeons preferred to operate with an instrument positioner. CONCLUSION: This study assessed objectively that instrument positioners can substitute for a surgical assistant efficiently and safely in elective laparoscopic cholecystectomies.

Cholecystectomy, Laparoscopic↗
PubMed2001

Towards effective treatment of eating disorders: nothing is as practical as a good theory.

There is much room for improvement in the treatment of eating disorders, anorexia nervosa in particular. It is argued that for more effective treatment a radical change in thinking and doing is needed. First, the wide-spread multicausal model of eating disorders must be abandoned and replaced by (a) fundamental strategic research into the most parsimonious explanation of eating disorders and (b) interventions solely directed on the specific maintaining mechanisms. Second, evidence-based working is needed in mental health care. In daily practice, two of three psychotherapists do not treat their eating disordered patients with the best treatment available, i.e. cognitive behaviour therapy. The Dutch Ministry of Health, Welfare and Sport tried to improve the care for eating disorder patients by the nomination of several specialist hospital units. These units are, however, not selected for their treatment quality or the use of evidence-based treatment protocols. It is argued that this ministerial operation will not increase the supply of effective treatment. The Minister obviously should have done two other things to improve the amount and quality of treatment supply for eating disorders: First, she better could invest in a broad array of workshops, training and supervision programs in cognitive behaviour therapy for all psychotherapists working with eating disorders. Second, since nothing is so practical as a good theory, the facilitation of research into parsimonious models of the relevant mechanisms as well as the experimental tests of interventions on these mechanisms would have been a promising move to effective treatment.

Cognitive Behavioral Therapy↗
PubMed2001

Seeing mum drinking a 'light' product: is social learning a stronger determinant of taste preference acquisition than caloric conditioning?

OBJECTIVE: It was examined whether caloric conditioning or social learning strategies dominate in taste preference acquisition in children. The caloric learning paradigm predicts that eating or drinking artificially sweetened products, which deliver virtually no energy, will not lead to a taste preference whereas the social learning paradigm predicts that seeing important others modelling the eating and drinking of these 'light' products will induce a preference for the taste of light products in the child. DESIGN: In a 2 x 2 between subjects factorial design, the amount of energy and social modelling was varied. SETTING: The study was undertaken at primary schools in Maastricht, The Netherlands. SUBJECTS: Forty-five children participated and six children dropped out. The 39 children who completed the study (14 boys and 25 girls) had a mean age of 67 months (range 51--81, s.d. 5.6). INTERVENTIONS: Each subject took part in nine conditioning trials with an individually selected tasting yoghurt which was not preferred very much at the pre-test. RESULTS: The children in the combined caloric and social condition showed an increase in their preference for the conditioned taste which was larger than a regression-to-the-mean effect (P=0.007), whereas children in the other groups did not. CONCLUSION: Caloric and social learning combined, ie modelling the consumption of energy-rich foods or drinks, is the best way to establish taste preferences. Children more easily learn a preference for energy-rich food that is eaten by significant others than for food that is low in energy and eaten by significant others.

Child↗
PubMed2001

AT1 receptor antagonist telmisartan administered peripherally inhibits central responses to angiotensin II in conscious rats.

The effects of systemic treatment with the AT1 receptor antagonist telmisartan on central effects of angiotensin II (Ang II), namely, increase in blood pressure, vasopressin release into the circulation, and drinking response, were investigated in conscious, normotensive rats. The central responses to i.c.v. Ang II (30 ng/kg) were measured at 0.5, 2, 4, and 24 h following acute i.v. or acute and chronic oral telmisartan application. At a dose of 10 mg/kg i.v., the drinking response to i.c.v. Ang II was completely blocked over 4 h, while the pressor response and the release of vasopressin in response to i.c.v. Ang II were blocked by 60 to 80%. The inhibition of the centrally mediated pressor and drinking response to Ang II was sustained over 24 h. The lower doses of telmisartan (0.3 and 1 mg/kg) significantly inhibited the Ang II-induced actions over 4 h. A consistent 24-h inhibition of the central responses to i.c.v. Ang II was obtained after acute and chronic oral treatment with 30 mg/kg telmisartan. Oral treatment with 1 and 3 mg/kg telmisartan produced a slight but inconsistent inhibition of the central actions of Ang II. Telmisartan concentrations measured in the cerebrospinal fluid following 8 days of consecutive daily oral treatment (1-30 mg/kg) ranged from 0.87 +/- 0.27 ng/ml (1 mg/kg/day) to 46.5 +/- 11.6 ng/ml (30 mg/kg/day). Our results demonstrate that, following peripheral administration, the AT1 receptor antagonist telmisartan can penetrate the blood-brain barrier in a dose- and time-dependent manner to inhibit centrally mediated effects of Ang II.

Angiotensin II↗
PubMed2000

Nuclear localization and transactivating capacities of the papillary renal cell carcinoma-associated TFE3 and PRCC (fusion) proteins.

The papillary renal cell carcinoma-associated t(X;1)(p11;q21) leads to fusion of the transcription factor TFE3 gene on the X-chromosome to a novel gene, PRCC, on chromosome 1. As a result, two putative fusion proteins are formed: PRCCTFE3, which contains all known domains for DNA binding, dimerization, and transactivation of the TFE3 protein, and the reciprocal product TFE3PRCC. Upon transfection into COS cells, both wild type and fusion proteins were found to be located in the nucleus. When comparing the transactivating capacities of these (fusion) proteins, significant differences were noted. PRCCTFE3 acted as a threefold better transactivator than wild type TFE3 both in a TFE3-specific and in a general (Zebra) reporter assay. In addition, PRCC and the two fusion proteins were found to be potent transactivators in the Zebra reporter assay. We propose that, as a result of the (X;1) translocation, fusion of the N-terminal PRCC sequences to TFE3 alters the transactivation capacity of the transcription factor thus leading to aberrant gene regulation and, ultimately, tumor formation.

Animals↗
PubMed2000

Cephalic phase responses, craving and food intake in normal subjects.

Cephalic phase responses (CPRs) are elicited during exposure to food cues. They gear up the body to optimize digestion or they compensate for unwanted changes during a meal. The cue reactivity model of binge eating predicts that CPRs are experienced as craving for food, thereby increasing food intake and playing a role in abnormal eating behaviour. The present experiment was designed to measure CPRs in normal women and to examine its relationship with craving, food intake and restraint. Results show that normal subjects do react to food exposure with changes in heart rate, heart rate variability (HRV), salivation, blood pressure, skin conductance and gastric activity. These CPRs presumably gear up the body and presumably do not reflect compensatory responses. Significant correlations between restraint and blood pressure, between blood pressure and craving, and between craving and food intake were also found. These results are in line with the cue reactivity model and suggest that research into physiological CPRs and craving in the field of eating disorders is valuable.

Adult↗
PubMed2000

GABA(C) receptors in neuroendocrine gut cells: a new GABA-binding site in the gut.

Although GABA(C) receptors play a crucial role in the mammalian central nervous system, their functional expression in peripheral tissues has not yet been studied. Using the gut neuroendocrine tumor cell line STC-1 as a model, we provide first evidence for the functional expression of GABA(C) receptors in the gut: mRNAs of the GABA(C) receptor subunits rho1 and rho2 were detected in STC-1 cells by reverse transcription polymerase chain reaction (RT-PCR). Applying anti-rho-antibodies, specific immunostaining for GABA(C) receptors was observed. For functional characterization, the effects of GABA(C) receptor activation on [Ca2+]i and hormone secretion were studied. The selective GABA(C) receptor agonist cis-4-aminocrotonic acid (CACA) induced dose-dependent increases both of [Ca2+]i and of hormone (cholecystokinin) secretion. The stimulatory effects of CACA were antagonized by the GABA(C) receptor blockers (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) and 3-aminopropyl(methyl)phosphinic acid (3-APMPA). These results demonstrate that GABA(C) receptors play an important role in neuroendocrine gastrointestinal secretion.

Acrylates↗
PubMed2000

Trans-complementation of vector replication versus Coxsackie-adenovirus-receptor overexpression to improve transgene expression in poorly permissive cancer cells.

Gene therapy of cancer requires high-level expression of therapeutic transgenes in the target cells. Poor gene transfer is an important limitation to adenovector-mediated cancer gene therapy. We investigated two fundamentally different approaches to improve transgene expression in poorly permissive cancer cells. First, overexpression of the adenovirus attachment receptor CAR to facilitate receptor-mediated adenovector (AdV) uptake into the target cells; second, co-infection of this vector together with traces of replication competent adenovirus (RCA) accidentally arising by back-recombination during large-scale vector preparation. Among eight gastrointestinal cancer cell lines, the colorectal cancer lines showed particularly poor vector-mediated transgene expression (down to 67-fold lower than in HeLa cells). Expression of the adenovirus receptors CAR, alpha(v)beta5- and alpha(v)beta3-integrin were highly variable between cell lines. AdV uptake was significantly associated with CAR levels on the cell surface, but not with those of the integrins. AdV-mediated CAR overexpression increased CAR density on the surface of all investigated tumor cells and led to enhancement of transgene expression by 1.8- to 6.7-fold. The other principle to enhance transgene expression was 'trans-complementation' of the therapeutic vector, ie induction of its replication within the target cells. Traces of RCA in a vector preparation, as well as purified RCA were found to provide sufficient E1-region transcripts to induce replication of the therapeutic vector genome. The number of adenovector-based transgene expression cassettes was greatly amplified by this principle, notably without any influence on the rate of vector entry. Co-infection of four colorectal cancer cell lines with marker vector plus RCA (at around 240:1 particle ratio) resulted in far stronger enhancement of transgene expression (up to 46-fold) as compared with CAR overexpression, even in cancers almost refractory to standard adenovector-mediated gene transfer. Whereas RCAs need to be strictly avoided in gene therapy of non-malignant diseases for safety reasons, the magnitude of helper virus-induced therapeutic transgene expression could possibly warrant application of this principle to overcome the resistance of highly malignant cancers against gene therapy.

Adenoviridae↗
PubMed2000

Choroidal calcifications in patients with Gitelman's syndrome.

Gitelman's syndrome is a renal tubular disorder characterized by a sodium and chloride reabsorption defect in distal tubular cells that determines hypokalemia, metabolic alkalosis, hypomagnesemia, and low calcium excretion. The presence of choroidal calcifications was sought in five patients with Gitelman's syndrome by ophthalmic examination, fluorescein angiography, indocyanine green angiography, and ocular ultrasonography. Calcifications observed in the choroid of two patients were shown by ultrasonography in both patients. Ophthalmic and fluorangiographic examinations detected this alteration in one of the two subjects. Chondrocalcinosis was found in one patient with choroidal calcifications. These findings suggest that precipitation of calcium salts can occur in the choroidal tissue of patients with Gitelman's syndrome. Deposits appeared to be well seen by ultrasonography because of their depth in ocular tissues. Sclerochoroidal calcifications may be favored by the low calcium excretion, which is associated with normal intestinal calcium absorption in patients with Gitelman's syndrome.

Adolescent↗
PubMed2000

Comparison of efficiencies of three techniques for colon surgery.

PURPOSE: To determine the most efficient technique for performing a colectomy, we used the methodology of time-motion analysis. METHODS: The efficiency of five hand-assisted and six regular laparoscopic colectomies and one open colectomy, performed by four surgeons in three different hospitals, was measured. The open colectomy was analyzed as a reference procedure. RESULTS AND CONCLUSIONS: The hand-assisted laparoscopic technique was the most efficient. Hand-assisted laparoscopy was therefore less time consuming than laparoscopic surgery. Open surgery was the fastest technique, because the time for every surgical motion is a factor of three shorter than for the two laparoscopic techniques.

Colectomy↗