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H de Vries

Publications and source records attributed to H de Vries.

At least 37 records · Page 2Linked to original sources
PubMed2002

Diagnostic, surgical and medical aspect of the midgut carcinoids.

This review covers the incidence, prognosis, diagnosis and treatment of midgut carcinoids with emphasis on the surgical and peri-operative aspects. Midgut carcinoids are rare neuro-endocrine tumours which become manifest once they have metastasized to the liver. Treatment of metastatic disease may include radical resection but is usually palliative. The tumour grows relatively slow. Besides the biochemical effects resulting in the carcinoid syndrome, patients may suffer from mechanical mass effects of the tumour. Medical treatment can alleviate the biochemical effects of the tumour, but has a limited effect on tumour growth. The introduction of octreotide was a milestone in palliation of these symptoms and has led to more aggressive treatment protocols. Treatment aimed at cytoreduction of hepatic metastasis and diminished secretion of bioactive amines may achieve good palliation. Cytoreduction may be performed by means of surgery, hepatic arterial ligation, (chemo)embolization, cryosurgery, radio-frequency ablation, internal radiation or even liver transplantation. The role of these options will be discussed in this review.

Antineoplastic Agents↗
PubMed2001

Rank and grooming reciprocity among females in a mixed-sex group of captive hamadryas baboons.

In a mixed-sex, captive group of hamadryas baboons (Papio hamadryas hamadryas) we investigated whether female grooming relationships are affected by their dominance ranks. Seyfarth's [1977] grooming for support model and Barrett et al.'s [1999] biological market model both predict that in primate groups where competition for monopolizable resources is high, grooming among females is based, at least partly, on the interchange of grooming for rank-related benefits, and that rank thus influences the distribution of grooming in females. Contrary to this prediction, our results show that despite the existence of a linear dominance hierarchy, rather strict dominance relationships, and high food-related aggression rates, grooming among female hamadryas baboons is not affected by rank and is only exchanged for itself. This is understandable since rank differences in our study group only result in differential access to limited, preferred food items that are not actively shared. Although some females are more likely to tolerate one another at the food pile, this tolerance is not determined by their grooming efforts and interchange of grooming for rank-related benefits does not occur. We conclude that female hamadryas baboons groom others in order to be groomed by them, which is supported by our observation that grooming reciprocity within a dyad increases when more grooming occurs in this dyad. Our results indicate that grooming is indeed a valuable commodity in itself, probably because of its stress- and tension-reducing effect. Based on our findings, the existing groom trade model is extended to include circumstances in which monopolizable resources are available but are not traded for grooming.

Aggression↗
PubMed2001

"Kicking the initiation": do adolescent ex-smokers differ from other groups within the initiation continuum?

BACKGROUND: Current research on the continuum of smoking initiation has largely focused on phases of progressing frequency of smoking. To gain more insight into reasons some adolescents do, and others do not, proceed to advanced levels of smoking behavior, a continuum in which two categories of ex-smoking are proposed is examined. METHODS: Standardized scores on psychosocial predictors of smoking among adolescent nonsmoking deciders and quitters were compared cross-sectionally with those of the categories of never smokers, triers, experimenters, and regular smokers (n = 23,317). RESULTS: Never smokers, triers, experimenters, and regular smokers had significantly different characteristics with regard to psychosocial predictors of smoking (P < 0.01), with scores of never smokers indicating that they were least at risk of smoking in the future and those of regular smokers indicating that they were most at risk. Scores of nonsmoking deciders showed that they were less at risk than triers and experimenters and more at risk than never smokers. Quitters seemed to have less risky psychosocial characteristics than experimenters and more risky characteristics than nonsmoking deciders. CONCLUSIONS: Studying transitions of smoking behavior based on six possible phases (i.e., never smoking, nonsmoking deciding, trying, experimenting, regular smoking, and quitting) might lead to more valid insights into predictors of adolescent smoking behavior.

Adolescent↗
PubMed2001

Determinants of albuminuria in people with Type 2 diabetes mellitus.

This study sought to identify determinants of albuminuria in people with Type 2 diabetes. In 335 primary care patients, we assessed albumin-creatinine ratio (ACR) in two 24-h urine samples, and its cross-sectional associations with protein and alcohol intake, cigarette smoking, body weight and height, glycosuria, blood pressure, hypoglycaemic and antihypertensive treatment, gender, age, age at diagnosis, diabetes duration, family history of diabetes and cardiovascular diseases, ethnic origin, and education. The prevalence of micro- or macro-albuminuria (ACR> or =2.0 mg/mmol) was 33%. Among these patients, compared to those with normo-albuminuria, there were more men, protein intake (g/kg) estimated from urinary urea as well as systolic blood pressure and glycosuria were higher, there were more smokers, men were shorter, and a family history of diabetes was less prevalent (all P<0.05). In linear and logistic regression (n=270) albuminuria was independently associated (P<0.05 unless indicated otherwise) with systolic blood pressure (OR(10 mmHg)=1.32), smoking (OR(ex/never)=2.36, OR(current/never)=4.89), glycosuria (OR(> or =7/<1 g/l)=2.41), gender (OR(men/women)=2.50), age in men (OR(10 year)=1.60) (P<0.10) and, inversely, in women (OR(10 year)=0.63) (P>0.10). On aggregation, the modifiable determinants systolic blood pressure, smoking and glycosuria explained 12% of the variation in albuminuria. These factors thus are, although to a moderate extent only, potential determinants of albuminuria. We also observed an independent, inverse association with body height (OR(0.10 m)=0.47). This is in line with the hypothesis that development in utero or during early life influences kidney function in later life.

Aged↗
PubMed2001

A qualitative study on detecting cancer symptoms and seeking medical help; an application of Andersen's model of total patient delay.

Patient delay is the interval between the day someone first becomes aware of an unexplained symptom and the day they seek medical consultation. This pre-diagnostic period is comprised of several stages which may involve delay on the part of the individual. This study investigated factors influencing the process of detecting cancer symptoms and consulting a general practitioner (GP). Twenty-three patients were interviewed about their experiences during this process. Among factors stimulating the process of detection and consultation were associating symptoms with cancer, and discussing symptoms with others. Being ashamed or embarrassed about the symptoms and attributing symptoms to common ailments were among the impeding factors. The findings of the present study suggest that future health education on early detection of cancer should focus on increasing knowledge and providing positive information about early detection of cancer. It is recommended that educational materials be disseminated to the general public via more channels, including non-medical channels.

Adult↗
PubMed2000

Human pre-mRNA cleavage factor II(m) contains homologs of yeast proteins and bridges two other cleavage factors.

Six different protein factors are required in vitro for 3' end formation of mammalian pre-mRNAs by endonucleolytic cleavage and polyadenylation. Five of the factors have been purified and most of their components cloned, but cleavage factor II(m) (CF II(m)) remained uncharacterized. We have purified CF II(m) from HeLa cell nuclear extract by several chromatographic steps. During purification, CF II(m) activity separated into two components, one essential (CF IIA(m)) and one stimulatory (CF IIB(m)) for the cleavage reaction. CF IIA(m) fractions contain the human homologs of two yeast 3' end processing factors, Pcf11p and Clp1p, as well as cleavage factor I(m) (CF I(m)) and several splicing and transcription factors. We report the cloning of hClp1 and show that it is a genuine subunit of CF IIA(m). Antibodies directed against hClp1 deplete cleavage activity, but not polyadenylation activity from HeLa cell nuclear extract. hClp1 interacts with CF I(m) and the cleavage and polyadenylation specificity factor CPSF, suggesting that it bridges these two 3' end processing factors within the cleavage complex.

Amino Acid Sequence↗
PubMed2000

Perturbation of myelination by activation of distinct signaling pathways: an in vitro study in a myelinating culture derived from fetal rat brain.

An in vitro myelinating mouse-derived model system has been adapted and optimized for fetal rat brain. In these mixed brain cell (MBC) cultures, myelinogenesis was studied by examining the effect of signaling pathways that are involved in the timing of oligodendrocyte differentiation. When PMA, a protein kinase C (PKC) activator, was kept present during development, the early myelin protein, CNP, was expressed in oligodendrocytes as promptly as in control MBC cultures. In contrast, continuous activation of signaling pathways triggered by FGF-2 caused a delay in the expression of CNP. The expression of the late myelin proteins MBP and PLP in oligodendrocytes was impeded by both PMA- and FGF-2-treatment, and, as a consequence, also myelin formation. Surprisingly, the continuous presence of PDGF during development also prevented myelin formation, even though all myelin-specific proteins were significantly expressed. Taken together, the data indicate that this in vitro myelinating culture system represents an excellent system to study signaling events necessary for the onset of myelination. Moreover, the present results demonstrate that oligodendrocyte differentiation in the presence of neurons and astrocytes can be manipulated both by extracellular and intracellular signaling factors. Importantly, differentiation per se is not necessarily culminating into myelination.

Animals↗
PubMed2000

Balloon angioplasty of coarctation of the aorta: a safe alternative for surgery in adults: immediate and mid-term results.

Patients with coarctation of the aorta can be treated either with surgery or with balloon angioplasty. So far, the last method has proved to be successful in children, but results of this treatment in (young) adults are virtually unknown. The aim of this study was to evaluate the immediate and mid-term follow-up results of balloon angioplasty of native coarctation in (mainly young) adults. Coarctation of the aorta was diagnosed by means of ultrasound or angiography, and defined as a stenosis with a pressure gradient greater than 20 mm Hg. The balloon angioplasty-procedure was carried out under complete anesthesia, and was considered to be successful, if the pressure gradient was reduced to less than 20 mm Hg. Nineteen consecutive adults (12 males, 7 females; aged 14-67 years, median 29) with native coarctation were treated from 1995-99. Mean pressure gradient decreased from 49.3+/- 20.8 to 4.8+/-8.2 mm Hg (P<0.0001). One patient showed a suboptimal result with a residual pressure gradient of 28 mm Hg. In one other patient a stent was placed on request of the referring physician. Follow-up was 100% complete and ranged from 3-47 months (mean 20.2+/- 12.9). At 1-year follow-up mean systolic blood pressure was reduced from 159.4+/-19.5 to 132.5+/-17.6 mm Hg (n = 18; P<0.0001), and mean ankle-arm pressure index improved from 0.73+/-0.09 to 0.96+/-0.05 (n = 18; P<0.0001). Anti-hypertensive medication could either be reduced or stopped in 7 patients (53.8%). With ultrasound or angiography or MRI, no patients had signs of aneurysm formation or worsening restenosis during follow-up. In adult patients with uncomplicated native coarctation of the aorta, balloon angioplasty (without stenting) would seem to be an excellent and safe alternative for surgery. In our hospital it has completely replaced surgical correction in such patients.

Adolescent↗
PubMed2000

PDGF and FGF-2 signaling in oligodendrocyte progenitor cells: regulation of proliferation and differentiation by multiple intracellular signaling pathways.

In this paper we address the linking of platelet-derived growth factor (PDGF) and basic fibroblast growth factor (FGF-2) to intracellular signaling molecules in oligodendrocyte progenitors. It is demonstrated that both growth factors activate downstream targets similar to those shown for protein kinase C (PKC) activation. Yet, neither the arrest of terminal oligodendrocyte differentiation nor the proliferation induced by PDGF or FGF-2 can be antagonized by inhibition of PKC. Rather, p42/p44 mitogen-activated protein kinase (MAPK), p38 MAPK, and pp70 S6 kinase were found to be necessary for the mitogenic activity of PDGF and FGF-2. Paradoxically, these kinases were also necessary for the onset of oligodendrocyte differentiation in control cells. In addition, cAMP-dependent kinase A (PKA) activation inhibited the mitogenic response of oligodendrocyte progenitors to FGF-2. Taken together, the molecular mechanism that controls oligodendrocyte lineage progression is operated by at least two signal pathways, which interfere either with proliferation and/or differentiation of oligodendrocyte progenitors.

Animals↗
PubMed2000

Photochemical decomposition of lomefloxacin in vitro and in vivo.

To obtain an idea of the photostability of Lomefloxacin (Lom) under in vivo conditions the compound was exposed to UV-A (310-360 nm) in PBS buffer pH 7.4. Exposure of 10 microg/ml of Lom in PBS pH 7.4 led to more than 50% decomposition within 10 min. Loss of the fluorine atom at C-8 and partial breakdown of the piperazine ring occurred. The only two photoproducts formed under these conditions were AEA, 1-ethyl-6-fluoro-1,4-dihydro-7-(2-aminoethyl-amino)-4-oxo-3-quinolinecarboxylic acid, and APA, 1-ethyl-6-fluoro-1,4-dihydro-7-(2-aminopropyl-amino)-4-oxo-3-quinolinecarboxylic acid. When Lom was exposed in whole blood in vitro, the same photochemical decomposition was observed in the plasma as in PBS buffer: APA and AEA were the only products. During UV-A exposure, Lom was shown to be taken up by the leukocytes. This process appeared to be less rapid during UV-A exposure than in the dark. As soon as UV-A exposure commenced, AEA and APA were found. As in the plasma, the total amount of Lom and the two photoproducts in the leukocytes was not significantly different from the amount of Lom found in unexposed cells at the same time point. The erythrocytes did not take up Lom, but exposure of whole blood to Lom and UV-A under the above conditions led to more than 7% haemolysis. Treatment of rats with a combination of Lom and UV-A demonstrated photodecomposition of Lom in vivo. In urine produced during exposure and by the irradiated rats during the twilight period after exposure, a considerable amount of AEA and APA was found. The blood plasma from rats exposed simultaneously to UV-A and Lom proved to contain AEA and APA and, in the leukocytes, APA. This was not the case with animals kept in twilight.

Animals↗
PubMed2000

Adherence to protein restriction in patients with type 2 diabetes mellitus: a randomized trial.

OBJECTIVE: To describe the extent to which diet counselling can decrease protein intake, and to identify predictors of adherence. DESIGN: (1) Randomized trial; (2) observational longitudinal study. SUBJECTS: (1) 125 type 2 diabetic patients in primary care; (2) 59 patients in the experimental group. INTERVENTION: For a period of 12 months, dieticians provided guidance on protein restriction (experimental group, n=59) or the usual dietary advice (control group, n=66). OUTCOME MEASURES: Adherence was estimated primarily from urinary urea excretion (UUE), but also from food-frequency questionnaires (FFQ). RESULTS: After 6 months protein intake was, according to the UUE and the FFQ, respectively, 8 g/day (95% CI -2, 13) (8%) and 15 g/day (95%-CI 9, 22) (16%) lower in the experimental than in the control group. After 12 months these differences were smaller. Linear regression analysis indicated that protein restriction was greater in patients who were well satisfied with their pre-existing diet (r=0.32, bper 1/10=3.6 (1, 6) g), in patients who were less overweight (r=0.32, bper kg.m-2=1.1 (0.2, 2. 0) g), and in patients living alone (r=0.22, b=7.7 (-2, 17) g). These combined factors explained only 11% of variation in adherence. Adherence was not predicted by the number of barriers reported by the patients or by coinciding changes in diet satisfaction. CONCLUSIONS: The diet counselling resulted in a very moderate degree of protein restriction only. Predictors of adherence could be identified, but only a few, and their predictive power was limited.

Aged↗
PubMed2000

Motives for protective behavior against carcinogenic substances in the workplace: a pilot study among Dutch workers.

Exposure to carcinogenic substances in the workplace creates an increased risk of certain types of cancer among employees. In The Netherlands, more than one million of the total working population of 10 million are exposed to toxic substances in more than 100,000 Dutch companies. To motivate workers to comply with protective recommendations, it is important to know their reasons for complying or not complying. The goal of the present study was to analyze the differences between workers who show a relatively high degree of protective behavior and those who show a relatively low degree of such behavior. The beliefs of workers exposed to carcinogenic substances at four worksites were analyzed. Data on attitudes, perceptions of social support, and self-efficacy expectations toward compliance with protective behavior were collected among 164 workers. The results showed that non-compliant workers perceived fewer benefits, encountered less social support, and, most importantly, encountered more barriers to complying with safety recommendations. It is concluded that health education programs must address these specific items to motivate non-compliant workers to comply more fully with protective recommendations.

Adult↗
PubMed2000

Major stressful life events in relation to prevalence of undetected type 2 diabetes: the Hoorn Study.

OBJECTIVE: To test whether chronic psychological stress is positively associated 1) with the prevalence of type 2 diabetes; 2) with visceral adiposity; and to test whether 3) the relationship between stress and diabetes is mainly mediated by visceral adiposity RESEARCH DESIGN AND METHODS: In a general Caucasian population aged 50-74 years without a history of diabetes (n = 2,262), the number of major stressful life events experienced during the past 5 years was assessed by self-report before the administration of an oral glucose tolerance test. RESULTS: Diabetes was newly diagnosed among 5% of the subjects. The number of stressful events was positively associated with the prevalence of hitherto undetected diabetes. The highest quintile had a 1.6-fold (95% CI 1.0-2.6) increased probability of undetected diabetes compared with the remaining four quintiles (P<0.05 by logistical regression analysis adjusted for age and sex). This increased probability remained significant after additional adjustment for family history of diabetes, heavy alcohol consumption, physical activity, and low level of education. The number of stressful events was weakly positively associated with waist-to-hip ratio (WHR) (men, P<0.01; women, P = 0.05 by multiple regression analysis adjusted for age). The age- and sex-adjusted association between stress and diabetes was only marginally reduced by adding the WHR into the logistical regression model (odds ratio 1.5 [0.9-2.4]; P = 0.08). CONCLUSIONS: These cross-sectional findings are partially consistent with Björntorp's theory that stressful life events, which indicate chronic psychological stress, are indeed associated with undetected type 2 diabetes and with visceral adiposity. However, in this white middle-aged population, visceral adiposity does not seem to be the main link between stress and diabetes.

Aged↗
PubMed1999

Protein kinase C prevents oligodendrocyte differentiation: modulation of actin cytoskeleton and cognate polarized membrane traffic.

In a previous study, we showed that activation of protein kinase C (PKC) prevents oligodendrocyte differentiation at the pro-oligodendrocyte stage. The present study was undertaken to identify downstream targets of PKC action in oligodendrocyte progenitor cells. Activation of PKC induced the predominant phosphorylation of an 80-kD protein, identified as myristoylated alanine-rich C-kinase substrate (MARCKS). Upon phosphorylation, MARCKS is translocated from the plasma membrane to the cytosol. Furthermore, PKC activation perturbed the organization of the actin cytoskeleton, causing a redistribution of actin filaments to the submembranous or cortical actin cytoskeleton. As a consequence, transport of a protein traffic marker, the vesicular stomatitis virus glycoprotein, from the trans-Golgi network to the plasma membrane becomes perturbed. The effect of disruption of the actin filament network by cytochalasin D perfectly matched the effect of PKC. These data thus favor the existence of a causal relationship between actin rearrangement and docking and/or fusion of proteins to the plasma membrane. Interestingly, neither in control cells nor in PKC-activated cells did another protein traffic marker, influenza hemagglutinin (HA), reach the cell surface. However, an eminent and specific accumulation of HA just underneath the plasma membrane became apparent upon PKC activation. Yet, this effect could not be simulated by cytochalasin D treatment. Therefore, these observations imply that although MARCKS represents a prominent PKC target site in regulating differentiation, another target involves the differential control of cognate polarized trafficking pathways, which are apparently operating in oligodendrocyte progenitor cells.

Actins↗
PubMed1999

Reproducibility and biomarker-based validity and responsiveness of a food frequency questionnaire to estimate protein intake.

This study, conducted in the Netherlands in 1994-1996, assessed the reproducibility, validity, and responsiveness of a food frequency questionnaire (FFQ) used with older subjects with type 2 diabetes. During a period of 6 months, 93 subjects had a stable protein intake according to their urinary urea excretion (UUE). An FFQ was completed before and after this period. Reproducibility was evaluated on the basis of the correlation (0.80) between duplicate FFQ estimates of protein intake. At the group level, the smallest detectable difference was 3 g. For 354 subjects, average protein intake according to the FFQ was similar to that from UUE estimates. Validity was evaluated on the basis of the crude and deattenuated correlations, which were 0.31 and 0.39, respectively. The crude correlation was highest for former smokers (r = 0.39) and for patients with a higher body mass index (r = 0.37), and it was very low for current smokers (r = 0.14, p > 0.20). The correlation did not vary with age or gender. Responsiveness was judged on the crude correlation between changes in intake according to the FFQ and UUE; the correlation was 0.22 (n = 134). The responsiveness ratio was 0.73. The authors concluded that FFQ estimates are well reproducible. At the group level, protein intake was estimated correctly, whereas individual protein intake and changes in intake were reflected to a moderate extent only.

Aged↗
PubMed1999

Computer-tailored interventions motivating people to adopt health promoting behaviours: introduction to a new approach.

This issue of Patient Education and Counseling discusses the development, application and effectiveness of computer-tailored interventions. Computer-tailored interventions are a relatively new health education approach. The interventions are characterised by the fact that the content of the materials is adapted, with the aid of computers, to the specific characteristics of a particular person. The use of computers also facilitates addressing large segments of the population, who can now receive materials that are not general but highly individualized. This thematic issue features papers dealing with a wide range of topics. These articles describe the application of behavioural change theories to this new approach, the advantages of computer-tailored interventions over more general mass media approaches, their effectiveness and future directions for research on computer-tailored interventions. This editorial paper introduces computerised tailoring and provides a brief overview of its elements and applications as well as of the papers in this issue, and summarises the main conclusions and suggestions for future research on computer-tailored interventions.

Attitude to Health↗