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R De Vries

Publications and source records attributed to R De Vries.

11 recordsLinked to original sources
PubMed2005

A low-saturated-fat, low-cholesterol diet decreases plasma CETP activity and pre beta-HDL formation but does not affect cellular cholesterol efflux to plasma from type 1 diabetic patients.

The aim of this study was to evaluate the effect of a low-saturated-fat, low-cholesterol diet on plasma lipopoproteins, pre beta-high density lipoprotein (HDL) formation, lecithin:cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) activities, as well as on the ability of plasma to stimulate cellular cholesterol efflux. Twelve male type 1 diabetic patients with plasma cholesterol >5.0 mmol/L were studied while consuming their usual diet and after 6 weeks of a low-fat, low-cholesterol diet. Pre beta-HDL formation was measured using crossed immuno-electrophoresis. Plasma LCAT, CETP and PLTP activities were assayed by exogenous substrate methods. The ability of plasma to promote cellular cholesterol efflux out of Fu5AH rat hepatoma cells and out of human skin fibroblasts was also determined. Saturated fat intake was lowered (p = 0.001) due to replacement with carbohydrates, while mono- and polyunsaturated fat intake remained unchanged. Cholesterol intake decreased as well (p = 0.003). The changes in plasma total cholesterol, very low and low-density lipoprotein (VLDL+LDL) cholesterol, HDL cholesterol, HDL phospholipids, apolipoprotein (apo) A-I, plasma LCAT activity and PLTP activity were not significant. Plasma CETP activity (p = 0.008) and pre beta-HDL formation (p = 0.008) decreased. The ability of plasma to promote cholesterol efflux out of fibroblasts and Fu5AH cells remained unchanged. Reduction in dietary saturated fat and cholesterol intake does not adversely affect cellular cholesterol efflux to plasma from type 1 diabetic patients, despite a drop in pre beta-HDL formation.

Carrier Proteins↗
PubMed2004

Type 2 diabetes mellitus is associated with differential effects on plasma cholesteryl ester transfer protein and phospholipid transfer protein activities and concentrations.

BACKGROUND: Human plasma contains two lipid transfer proteins, cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP), which are crucial in reverse cholesterol transport. METHODS: Plasma CETP and PLTP activity levels and concentrations in 16 type 2 diabetic patients and 16 matched healthy subjects were determined, and these data were correlated to clinical variables, including insulin sensitivity and lipid levels. RESULTS: Plasma triglycerides were higher (p<0.02) and high-density lipoprotein (HDL) cholesterol (p<0.02) was lower in diabetic patients. Plasma CETP activity and concentrations were not significantly different between diabetic and healthy subjects, but CETP specific activity was lower in diabetic patients (p<0.001). Multiple regression analysis showed that plasma CETP activity was positively related to CETP concentration (p=0.0001) and negatively to the diabetic state (p<0.002) or to HbA1c (p<0.02). PLTP activity (p<0.05) and specific activity were higher (p<0.05), whereas there was no difference in PLTP concentration between the two groups. There was no significant bivariate correlation between PLTP concentration and activity, in either healthy or diabetic subjects. Multiple regression analysis did disclose positive relationships of PLTP activity with PLTP concentration (p=0.0001), plasma triglycerides (p=0.0001) and waist/hip ratio (p=0.0001), but not with the diabetic state or HbA1c. CONCLUSIONS: Neither CETP nor PLTP activity was independently associated with insulin sensitivity. Specific CETP activity is decreased in type 2 diabetes mellitus. In contrast, specific PLTP activity is higher in diabetes, as a result of the association of plasma PLTP activity with plasma triglycerides and obesity. Measurement of both plasma lipid transfer protein activity and mass levels may thus provide extra information in diabetes mellitus.

Apolipoproteins↗
PubMed2003

Alterations in high-density lipoprotein metabolism and reverse cholesterol transport in insulin resistance and type 2 diabetes mellitus: role of lipolytic enzymes, lecithin:cholesterol acyltransferase and lipid transfer proteins.

Insulin resistance and type 2 diabetes mellitus are generally accompanied by low HDL cholesterol and high plasma triglycerides, which are major cardiovascular risk factors. This review describes abnormalities in HDL metabolism and reverse cholesterol transport, i.e. the transport of cholesterol from peripheral cells back to the liver for metabolism and biliary excretion, in insulin resistance and type 2 diabetes mellitus. Several enzymes including lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyltransferase (LCAT), as well as cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP), participate in HDL metabolism and remodelling. Lipoprotein lipase hydrolyses lipoprotein triglycerides, thus providing lipids for HDL formation. Hepatic lipase reduces HDL particle size by hydrolysing its triglycerides and phospholipids. A decreased postheparin plasma LPL/HL ratio is a determinant of low HDL2 cholesterol in insulin resistance. The esterification of free cholesterol by LCAT increases HDL particle size. Plasma cholesterol esterification is unaltered or increased in type 2 diabetes mellitus, probably depending on the extent of triglyceride elevation. Subsequent CETP action results in transfer of cholesteryl esters from HDL towards triglyceride-rich lipoproteins, and is involved in decreasing HDL size. An increased plasma cholesteryl ester transfer is frequently observed in insulin-resistant conditions, and is considered to be a determinant of low HDL cholesterol. Phospholipid transfer protein generates small pre beta-HDL particles that are initial acceptors of cell-derived cholesterol. Its activity in plasma is elevated in insulin resistance and type 2 diabetes mellitus in association with high plasma triglycerides and obesity. In insulin resistance, the ability of plasma to promote cellular cholesterol efflux may be maintained consequent to increases in PLTP activity and pre beta-HDL. However, cellular cholesterol efflux to diabetic plasma is probably impaired. Besides, cellular abnormalities that are in part related to impaired actions of ATP binding cassette transporter 1 and scavenger receptor class B type I are likely to result in diminished cellular cholesterol efflux in the diabetic state. Whether hepatic metabolism of HDL-derived cholesterol and subsequent hepatobiliary transport is altered in insulin resistance and type 2 diabetes mellitus is unknown. Specific CETP inhibitors have been developed that exert major HDL cholesterol-raising effects in humans and retard atherosclerosis in animals. As an increased CETP-mediated cholesteryl ester transfer represents a plausible metabolic intermediate between high triglycerides and low HDL cholesterol, studies are warranted to evaluate the effects of these agents in insulin resistance- and diabetes-associated dyslipidaemia.

Biological Transport↗
PubMed2001

A comparison of urinary nuclear matrix protein-22 and bladder tumour antigen tests with voided urinary cytology in detecting and following bladder cancer: the prognostic value of false-positive results.

OBJECTIVES: To evaluate the diagnostic and prognostic value of the nuclear matrix protein-22 (NMP22) and bladder tumour antigen (BTAstat) tests compared with voided urinary cytology (VUC) in detecting and following bladder cancer, assessing particularly the prognostic value of false-positive test results in patients followed up for bladder cancer. PATIENTS AND METHODS: From 739 patients suspected of having bladder cancer, voided urine samples for the NMP22 and BTAstat tests, and for VUC and urine analysis, were collected before cystoscopy. All patients underwent transurethral resection of bladder lesions or mapping. and were followed for a mean (range) of 27.3 (3-65) months. RESULTS: In the 406 patients with bladder cancer, the overall sensitivity was 85% for NMP22, 70% for BTAstat and 62% for VUC. For histological grades 1-3 the sensitivity in detecting transitional cell carcinoma was 82%, 89% and 94% for NMP22, 53%, 76% and 90% for BTAstat, and 38%, 68% and 90% for VUC, respectively. Although the sensitivity in detecting invasive carcinoma was >85% for all the tests. NMP22 and BTAstat were statistically more sensitive than VUC for superficial tumours. The optimal threshold value for NMP22, calculated using the receiver operating characteristics curve was 8.25 U/mL. The specificity was 68% for NMP22, 67% for BTAstat, and 96% for VUC. The specificity of VUC remained >87% and was independent of benign histological findings. In contrast, in patients with no apparent genitourinary disease on histology, NMP22 and BTAstat had significantly higher specificity (94% and 92%, respectively: P=0.003) than in the group with chronic cystitis (52% for both tests). Forty patients having no bladder cancer at biopsy had a recurrence after a mean (range) follow-up of 7.7 (3-15) months: all had a previous history of bladder cancer. According to subsequent recurrence, the prognostic positive and negative predictive values were 18% and 91% for NMP22, 13% and 88% for BTAstat, and 79% and 91% for VUC. Both false-positive VUC and NMP22 tests predicted recurrence (log-rank test, P<0.001 and P=0.004, respectively), but the BTAstat test produced no similar correlation (P=0.778). CONCLUSION: The NMP22 and BTAstat tests are better than VUC for detecting superficial and low-grade bladder cancer but they have significantly lower specificity. After excluding diseases with the potential to interfere in these tests the overall specificity of both tests is increased considerably. False-positive results from NMP22 and VUC but not from BTAstat in patients followed up for bladder cancer correlate with future recurrences.

Adult↗
PubMed1997

Anticonvulsant activity of new and potent inhibitors of nitric oxide synthase.

The effects of new and potent NOS inhibitors, S-methyl-L-thiocitrulline (S-Me-TC), 3-bromo 7-nitro indazole (3-Br-7-NI), and 1-(2-trifluoromethylphenyl) imidazole (TRIM), were examined on the pilocarpine-induced seizures in mice. 3-Br-7-NI and TRIM decreased the frequency of status epilepticus and mortality, while TRIM. In addition, significantly reduced the incidence of seizures. The latencies to onsets of seizures, status epilepticus, and mortality were significantly prolonged by all three NOS inhibitors, while duration of seizures was reduced by 3-Br-7-NI and TRIM. These data suggest an excitatory effect of NO in the neuronal structure involved in the pilocarpine-induced seizures.

Animals↗
PubMed1995

7-Nitro indazole, an inhibitor of neuronal nitric oxide synthase, attenuates pilocarpine-induced seizures.

7-Nitro indazole (25-100 mg/kg i.p.), an inhibitor of neuronal nitric oxide (NO) synthase, attenuated the severity of pilocarpine (300 mg/kg i.p.)-induced seizures in mice. This indicates that the decreased neuroexcitability of the central nervous system (CNS) following administration of 7-nitro indazole may be due to inhibition of neuronal NO synthase, implying that NO acts as an excitatory and proconvulsant factor in the CNS.

Animals↗
PubMed1994

Nitric oxide synthase inhibition reduces wakefulness.

The effect of NG-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide (NO) synthase and L-arginine, a precursor of NO, was examined on the sleep-waking pattern in rats. L-NMMA (3.75-15 mg/kg, i.p.) reduced wakefulness with a corresponding increase of slow wave sleep and rapid eye movement sleep. The effect of L-NMMA on vigilance was limited to the first hour following drug administration. The effect of L-NMMA was abolished by intracerebroventricular administration of L-arginine (600 micrograms). This indicates that the inhibitory effect of L-NMMA on wakefulness is mediated by decreased NO synthesis and that central NO exerts an excitatory role in vigilance. It further implicates that factors facilitating a release and/or synthesis of NO might lead to increased wakefulness and sleep disturbances.

Amino Acid Oxidoreductases↗
PubMed1992

Analysis of a conjugate between anti-carcinoembryonic antigen monoclonal antibody and alkaline phosphatase for specific activation of the prodrug etoposide phosphate.

The selective targeting of tumors by enzymes conjugated to monoclonal antibodies (mAb) may be an ideal approach to convert relatively nontoxic prodrugs into active agents at the tumour site. We used the anti-carcinoembryonic antigen mAb BW431/26 conjugated to alkaline phosphatase (AP) and phosphorylated etoposide (etoposide-P) as a prodrug to study the feasibility of this concept. Etoposide was phosphorylated with POCl3. Quantitative hydrolysis of etoposide-P to etoposide occurred within 10 min in the presence of AP. BW431/26 and AP were conjugated using a thioether bond. The AP conjugate retained 93% of its calculated activity. 125I-labelled AP conjugate did not show a reduction of immunoreactivity as determined by a cell-binding assay. SW1398 colon cancer cells were used to analyse the cytotoxicity of etoposide and etoposide-P. Etoposide (IC50 22 microM) was 100 times more toxic than etoposide-P (20% growth inhibition at 200 microM). Pretreatment of the cells with BW431/26-AP prior to etoposide-P exposure resulted in a dramatic increase in cytotoxicity (IC50 70 microM). The pharmacokinetics and tumour-localizing properties of BW431/27 and the AP conjugate were assessed in nude mice bearing SW1398 tumours. BW431/26 showed excellent tumour localization (10% of the injected dose/g tissue retained from 8 h to 120 h), whereas the AP conjugate showed a reduced tumour uptake (3%-0.3% of the injected dose/g tissue at 8-120 h), a faster clearance from the circulation and a high liver uptake. Radiolabelled AP showed a similar pharmacokinetic profile to the AP conjugate. Gel filtration analysis of blood, liver, and tumour samples indicated good stability of the conjugate.

Alkaline Phosphatase↗
PubMed1986

Quantitative and qualitative differences in HLA-DR molecules correlated with antigen-presentation capacity.

The monoclonal antibodies 7.3.19.1 (anti-DRw52-like) and B8.11.2 (anti-DR framework) were used for the isolation and characterization of HLA class II molecules expressed by HLA-DR3 and DR5 homozygous B cell lines. Sequential immunoprecipitation studies demonstrated that from these cells class II molecules can be isolated which are characterized by the presence or absence of DR framework (DR) and DRw52-like (DRw62) determinants: (DR+, DRw52+), (DR+, DRw52-) and (DR-, DRw52+). The DR3 donor cells appeared to express only the (DR+, DRw52+) and (DR-, DRw52+) class II molecules whereas DR5-positive cells express only the (DR+, DRw52+) and (DR+, DRw52-) class II molecules. Besides qualitative differences some of the above-mentioned molecules appeared to differ in their levels of expression. To investigate whether this might have functional implications, cells with the HLA-DR3 and -5 haplotypes were used to present antigen purified protein derivative of tuberculin (PPD) to PPD-specific T cell lines and the blocking capacity of the two monoclonal antibodies 7.3.19.1 and B8.11.2 was determined. A remarkable correlation was observed between the type of class II molecule blocked by these monoclonal antibodies and its quantitative expression. However, (DR-, DRw52+) molecules, clearly expressed by DR3 cells, were not involved in the presentation of PPD. This indicates that not only quantitative but also qualitative aspects may play a role in the selection of the type of class II molecule that will be involved in antigen presentation.

Antibodies, Monoclonal↗