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Biomedical subjects

R Cornelis

Publications and source records attributed to R Cornelis.

At least 55 records · Page 3Linked to original sources
PubMed1992

Behaviour of 12 trace elements in serum of uremic patients on hemodiafiltration.

The concentrations of the trace elements As, Au, Cd, Cs, Cu, Fe, Hg, Mo, Rb, Se and Zn were studied in the serum of 5 patients with end-stage renal failure who were undergoing treatment with hemodiafiltration. The concentrations of the following elements differ significantly from the reference values: As, Cd, Cu, Hg and Mo are higher, while Rb, Se, Zn and some of the Cs values are lower. The observed concentration deviations may be due to the uremic state and/or the dialysis process. To asses the contribution of the latter, the elements were determined in the substitution fluid and in the dialysate before and after blood contact and passage through the artificial kidney. Our findings suggest that the concentration abnormalities could be related to the substitution fluid for Cs, Rb, Se and Zn and to the dialysate for Mo and Rb.

Aged↗
PubMed1990

Localization of the essential histidine and carboxylate group in D-xylose isomerases.

D-Xylose isomerases from different bacterial strains were chemically modified with histidine and carboxylate-specific reagents. The active-site residues were identified by amino acid sequence analysis of peptides recognized by differential peptide mapping on ligand-protected and unprotected derivatized enzyme. Both types of modified residues were found to cluster in a region with consensus sequence: Phe-His-Asp-Xaa-Asp-Xaa-Xaa-Pro-Xaa-Gly, conserved in all D-xylose isomerases studied so far. These results are consistent with the recently published X-ray data of the enzyme active centre from Streptomyces rubiginosus showing hydrogen bond formation between Asp-57 and His-54 which locks the latter in one tautomeric form. A study of the pH-dependence of the kinetic parameters suggests the participation of a histidine group in the substrate-binding but not in the isomerization process. Comparison of the N-terminal amino acid sequences of several D-xylose isomerases further revealed a striking homology among the Actinomycetaceae enzymes and identifies them as a specific class of D-xylose isomerases.

Aldose-Ketose Isomerases↗
PubMed1989

[Epidemiological aspects of Campylobacter infections in Belgium].

In the context of a surveillance programme for infectious diseases in Belgium, a network of microbiological laboratories, since February 1983, weekly registers the isolation of a number of pathogenic agents, among which Campylobacter. Some epidemiological characteristics of Campylobacter in Belgium are discussed. Between 54 and 58% of the isolations are reported from males. About 50% of the cases are observed in children under 5 years of age. The mean weekly number of isolations per laboratory is rising in May and remains high until October-November.

Adolescent↗
PubMed1989

[Epidemiologic aspects of infections due to Neisseria gonorrhoea in Belgium].

In the context of a surveillance programme for communicable diseases in Belgium, a network of microbiological laboratories has, since February, 1983, made weekly registrations of a number of pathogenic agents, among them, N. gonorrhoeae. Some epidemiological characteristics of N. gonorrhoeae in Belgium are discussed. Although only a portion of Belgian laboratories participate in the programme, the total of cases registered from 1983 through 1986 was 2 to 5 times greater than obtained through the notifiable diseases reporting system. More than 75% of the cases registered concerned those between 20 and 39 years of age, with a maximum for the 20-29-year age group. In 1985, 82% of the diagnoses were based on one culture alone (or one + ELISA); in 1986, this percentage was only 66%.

Adolescent↗
PubMed1988

Kinetics of chromium during peritoneal dialysis.

This study describes investigations on the possible mechanisms involved in the transfer of Cr from the dialysate to the blood during peritoneal dialysis. The ability of Cr(III) compounds to penetrate across a membrane at physiological pH seems rather questionable, as it is well known that Cr(III) tends to form polymeric chains. Therefore, a systematic study was undertaken to describe the pathways involved in this transport. The characteristics during 'in vitro' dialysis were compared to the behaviour of Cr during acute 'in vivo' experiments on anesthetized rabbits. It appeared that lactate, a common substance of the dialysate, plays an extremely important role in the mobility and subsequent transfer of Cr(III) across the peritoneum.

Carbon Radioisotopes↗
PubMed1988

Metal ion binding to D-xylose isomerase from Streptomyces violaceoruber.

The binding of two activating cations, Co2+ and Mg2+, and of one inhibitory cation, Ca2+, to D-xylose isomerase from Streptomyces violaceoruber was investigated. Equilibrium-dialysis and spectrometric studies revealed that the enzyme binds 2 mol of Co2+/mol of monomer. Difference absorption spectrometry in the u.v. and visible regions indicated that the environment of the first Co2+ ion is markedly different from that of the second Co2+ ion. The first Co2+ appears to have a six-co-ordinate. The conformational change induced by binding of Co2+ to the first site is maximum after the addition of 1 equivalent of Co2+ and yields a binding constant greater than or equal to 3.3 x 10(6) M-1. Binding of Co2+ to the second, weaker-binding, site caused a visible difference spectrum. The association constant estimated from Co2+ titrations at 585 nm agrees satisfactorily with the value of 4 x 10(4) M-1 obtained from equilibrium dialysis. Similarly, the enzyme undergoes a conformational change on binding of Mg2+ or Ca2+, the binding constants being estimated as 1 x 10(5) M-1 and 5 x 10(5) M-1 respectively. Competition between the activating Mg2+ and Co2+ and the inhibitory Ca2+ ion for both sites was further evidenced by equilibrium dialysis and by spectral displacement studies.

Aldose-Ketose Isomerases↗
PubMed1987

Tool for validation of the network of sentinel general practitioners in the Belgian health care system.

Morbidity registration by a network of sentinel general practitioners (SGPs) in Belgium raises a number of problems related to possible biases in the network procedure, such as unequal geographical distribution, non-participation of a segment of the target population of practitioners and difficulties in the estimation of the denominator population at risk for the health problems under study. Through the application of two hierarchical clustering procedures, the initial number of 43 districts in the country has been reduced to 15 homogeneous district clusters. These represent the new geographical framework from which the geographical spread of the network is checked. This network is subsequently corrected for such socio-demographic parameters as age, sex and occupation in order to match more closely the total population of Belgian general practitioners (GPs). The population covered by the network is estimated on the basis of the annual number of patient contacts. Application of the described procedures should result in a network allowing valid estimations for a number of health issues as seen by Belgian GPs.

Adult↗
PubMed1986

Evaluation of trace elements in human lung tissue. I. Concentration and distribution.

The lungs of eight individuals were investigated for 27 elements by neutron activation analysis and atomic absorption spectrometry. Thirteen segments of each lung pair were analyzed, together with hilar lymph nodes. The trace element distribution in the lungs and the inter-individual concentration differences reveal the existence of two groups of elements. A similar situation is observed in the lymph nodes. The elements Br, Cs, Cu, K, Na, Rb, Se and Zn are relatively homogeneously distributed over a lung pair and show little inter-individual concentration differences. On the other hand, Cd, Co, Cr, Pb, Sb, Sc and V are very inhomogeneosly distributed. The inhomogeneity and the concentrations increase with age. The existence of a concentration gradient within the lung and of relatively higher levels in the lymph nodes point to an enrichment in the lung tissue by inhaled atmospheric contaminants.

Adolescent↗
PubMed1986

Evaluation of trace elements in human lung tissue. II. Recovery and analysis of inhaled particulates.

Inhaled particulate material, deposited in the lungs of eight Belgian individuals, is differentiated from the tissue with a digestion procedure using the enzyme ficin. This method is simple and efficient and yields a small amount of insoluble dust. The total element concentration of the tissue samples was determined by neutron activation analysis. The radioactive residues obtained after the digestion of the tissue were counted and are considered to represent the insoluble dust fraction. A major part of the Co, Cr, Sb and Sc was recovered in the residues, but only small fractions of the Cs, Rb and Zn. These findings confirm the assumption that Co, Cr, Sb and Sc are enriched in the lungs as a result of the accumulation of atmospheric contaminants. Further proof can be derived from the analogy between the elemental composition of the residue and that of atmospheric particulate matter collected in Belgium.

Adolescent↗
PubMed1986

Evaluation of trace elements in human lung tissue. III. Correspondence analysis.

The concentrations of 22 trace elements in 13 segments of both lungs of eight individuals were subjected to correspondence analysis, a display method based on principal components analysis. Sample groups were isolated which coincide with the age of the individuals. The firmness of the clusters decreased however with aging. The elements Br, Cd, Co, Cr, Cs, Pb, Sc, Se and V had the most important influence on the grouping. It can be assumed that they are enriched in the tissue by inhaled particulate matter, deposited and accumulated in an insoluble form. The correlation between the elements is proof for their similar behaviour in the lungs: Co, Cr, Sb, Sc and V have a long biological half-life in the tissue, whereas Zn and K are easily removed.

Adolescent↗
PubMed1986

Trace elements in serum, packed cells, and dialysate of CAPD patients.

Neutron Activation Analysis (NAA) was used to investigate trace element patterns in serum, packed cells, and dialysate of CAPD patients. The concentrations of the elements Cs, Cu, Fe, and Mn in serum and packed cells appeared to be maintained within the normal range, while the levels of the non-essential element Br in both serum and packed cells were subnormal. The serum Cr values were extremely high (20 to 50 times higher than the normal serum level). The amount of Cr absorbed from the dialysate was calculated to be ten times higher than the daily dietary uptake. The Co concentrations were normal in packed cells but were significantly increased in serum. The Rb content in packed cells was slightly lower than normal, while the serum value was normal. Se was maintained within the normal range in packed cells, but the serum concentration was slightly lower than normal. The concentrations of Zn were low in serum and appeared to be higher than normal in packed cells. In conclusion, this analysis of the trace element status of CAPD patients reveals two major abnormalities. There is an apparent loss of Br from the blood towards the dialysate and on the other hand, a dramatic accumulation of Cr into the blood as a result of the very high Cr content in the dialysate.

Erythrocytes↗
PubMed1986

Epidemiological surveillance of measles through a network of sentinel general practitioners in Belgium.

Measles morbidity data were collected during 1982-1983 through a network of sentinel general practitioners. The annual incidence rate of the disease in the country was 80.3 per 1000 population with most of the cases seen between 2 and 6 years of age. Complications were encountered in 13.8% of all cases. Emphasis is put on developing a strategy for immunization against measles on a nationwide scale.

Adolescent↗