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J van den Berg

Publications and source records attributed to J van den Berg.

At least 37 records · Page 2Linked to original sources
PubMed1994

Membrane changes associated with lysis of red blood cells by hypochlorous acid.

This study was carried out to investigate HOCl-induced lysis of human erythrocytes. Using reagent HOCl with isolated red cells, we showed that the rate of lysis was dependent on the dose of HOCl per red cell rather than on the concentration of oxidant. The process was inhibited by scavengers such as methionine and taurine, but only if they were present at the time of addition of HOCl. Lysis was preceded by a decrease in cell density, a change in the deformability of the membrane as evidenced by ektacytometry, and an increase in K(+)-leak. Electron microscopy showed extensive disruption of the membrane. Increasing doses of HOCl caused progressive loss of membrane thiols, but complete thiol oxidation by N-ethylmaleimide did not result in an equivalent rate of lysis. Restoration of oxidised thiols by incubation with glucose did not significantly alter the pattern of lysis. Taken together, these results suggest that thiol oxidation was not responsible for HOCl-mediated lysis. There was evidence of increasing crosslinking of membrane proteins on electrophoresis, only some of which was due to the formation of disulfides. TLC of the membrane lipids indicated that there may be formation of chlorohydrins by reaction of HOCl with the fatty acid double bonds. This reaction results in the formation of a more polar species which, if formed, would be extremely disrupting to the lipid bilayer. The results indicate that HOCl-mediated damage to the membrane proteins or to the lipid bilayer comprises an initial damaging event that sets the cells on a path toward eventual lysis.

Diamide↗
PubMed1993

Detection and differentiation of diffuse liver disease by quantitative echography. A retrospective assessment.

RATIONALE AND OBJECTIVES: The detectability of diffuse liver diseases by quantitative echography was retrospectively investigated using scans of patients with known pathologic findings (n = 103) and of normal subjects (n = 129). The authors determined the best set of quantitative parameters for this task. METHODS: Quantitative echography was comprised of acoustospectrographic parameters (frequency dependence of attenuation and backscattering) and image texture parameters. The disease processes studied included: acute hepatitis, hepatitis/cirrhosis, alcoholic hepatitis/cirrhosis, primary biliary cirrhosis, and steatosis. RESULTS: Correct differentiation of these diseases ranged from 88% to 97%. Correlations between histologic grading and echographic parameters were poor. With only one exception, the differentiation between any two of the diseases could be made in 60% to 99% of cases. Different parameters better differentiated abnormal from normal scans than among diseases. CONCLUSIONS: The detection of diffuse liver diseases can be based on echographic parameters, related to a diffuse scattering model, whereas the differentiation among diseases needs additional parameters derived from a structural scattering model. Further studies are indicated to assess the prospective potential of the devised methods.

Discriminant Analysis↗
PubMed1993

[Complete dentures in the Dutch population 1981-1992].

In the period 1981-1992 the percentage of people with a full set of dentures dropped from 31.6 to 22.5 in the Netherlands (persons > or = 16 years). This is particularly due to the relatively strong decrease in the number of young people with full dentures. Regional differences are remarkable: in the northern provinces the percentage is relatively high; in the province of Utrecht it is relatively low. Recently regional differences appear to be (very) small among the young age groups. Many people with a full set of dentures use the same dentures for a long period: about 20% of them have had their current prostheses for 16-25 years, another 20% for over 25 years. Taking into account the total adult population, it appears that the socio-economic status (SES) negatively correlates with the probability of having a full set of dentures. This holds for all three SES indicators in the study: education, income and type of insurance. But among the young age groups this correlation is only valid for education.

Adolescent↗
PubMed1992

No counterregulation after breaking the external restraint of children.

At the present, it is unknown how restraint and binge eating/counterregulation are exactly related. Earlier studies on this relationship suffer from two main shortcomings: the studies are all correlational in nature or could not rule out the contribution of confounding variables such as weight loss. The present study investigated whether a break of restraint is a sufficient condition for the occurrence of counterregulation by studying a restrained sample which is not liable to dieting practices and weight loss. The externally imposed restraint on children with regard to eating sweets was broken. However, after breaking their external restraint the children did not counterregulate. It is discussed whether restraint of food intake is really as important for binge eating as it is claimed to be or whether it is merely a consequence or an epiphenomenon of binge eating.

Bulimia↗
PubMed1987

Butyrate stimulates tissue-type plasminogen-activator synthesis in cultured human endothelial cells.

Incubation of cultured human endothelial cells with 5 mM-dibutyryl cyclic AMP led to an approx. 2-fold increase in tissue-type plasminogen-activator (t-PA) production over a 24 h incubation period. The stimulating effect of dibutyryl cyclic AMP could be explained by the slow liberation of butyrate, as the effect could be reproduced by addition of free butyrate to the medium, but not by addition of 8-bromo cyclic AMP or forskolin, agents known to raise intracellular cyclic AMP levels. With butyrate, an accelerated accumulation of t-PA antigen in the conditioned medium (CM) was observed after a lag period of about 6 h. Increasing amounts of butyrate caused an increasingly stimulatory effect, reaching a plateau at 5 mM-butyrate. The relative enhancement of t-PA production in the presence of 5 mM-butyrate varied among different endothelial cell cultures from 6- to 25-fold in 24 h CM. Such an increase in t-PA production was observed with both arterial and venous endothelial cells. The butyrate-induced increases in t-PA production were accompanied by increased t-PA mRNA levels. Analysis of radiolabelled CM and cell extracts by SDS/polyacrylamide-gel electrophoresis indicated that the potent action of butyrate is probably restricted to a small number of proteins. The accumulation of plasminogen activator inhibitor type 1 (PAI-1) in CM from butyrate-treated cells varied only moderately. In our study of the relationship between structure and stimulatory activity, we found that a straight-chain C4 monocarboxylate structure with a methyl group at one end and a carboxy moiety at the other seems to be required for the optimal induction of t-PA in cultured endothelial cells.

Butyrates↗
PubMed1987

[Reconsideration of the 'bacteriological examination' of slaughter stock].

A comparative trial was made by six meat inspection services to attain uniform indications for the 'Bacteriological Examination' of slaughtered animals in accordance with the 'Meat Inspection Regulations' of the Dutch 'Meat Inspection Act'. The results of the study compelled the investigators to scrutinize these regulations. The 'Bacteriological Examination' which is prescribed, is designed to exclude septicaemic animals from human consumption. Applying the rules will result in condemnation of animals harbouring a small number of bacteria which have a minimum significance for the health of consumers, whereas animals harbouring organisms potentially pathogenic for man are overlooked. It is concluded that the 'Meat Inspection Regulations' should be considered.

Animals↗
PubMed1986

Quantification of tissue-type plasminogen activator (t-PA) mRNA in human endothelial-cell cultures by hybridization with a t-PA cDNA probe.

We describe the construction of a recombinant DNA plasmid, consisting of the vector pBR322 and full-length tissue-type plasminogen-activator (t-PA) cDNA, by using polyadenylated RNA from cultured Bowes melanoma cells as substrate. A 1280-base-pair PstI restriction fragment, covering the 3' untranslated region and part of the coding region for the t-PA L-chain, was used as a radiolabelled probe to determine the size and the number of t-PA mRNA molecules in cultured endothelial cells of different origin from the same individual. Northern blotting showed that in all these cells a t-PA mRNA is synthesized of about 2500 nucleotides, indicating that transcriptional initiation, splicing and polyadenylation is similar. The number of t-PA mRNA molecules per cell measured, by using a dot-blotting technique and t-PA mRNA made in vitro, with a plasmid DNA preparation harbouring a specific promotor of the Salmonella typhimurium bacteriophage SP6, t-PA cDNA and SP6 RNA polymerase as standard, is approx. 10,000 in all cultured endothelial cells from adult vessels. However, the amount of t-PA antigen synthesized and/or secreted differs by a factor of 6-20. Relatively large amounts of t-PA antigen secreted were detected in conditioned medium from vena-cava-derived cells, whereas low amounts were found in conditioned medium from arteria-iliaca-derived cells.

Antigens↗
PubMed1985

[Disorders in slaughtering animals. V. Endocarditis in slaughtering pigs, sows and cattle].

Bacteriological studies were done in 673 slaughtered animals (pigs, sows and cattle) in which post-mortem examination had revealed the presence of endocarditis. The studies were positive for the presence of bacteria in 453 cases. Lesions were not observed on ante-mortem inspection in 386 cases. Isolation of Corynebacterium pyogenes was extremely common in cattle, whereas beta-haemolytic streptococci and Erysipelothrix insidiosa were very frequently isolated in slaughtered pigs.

Animals↗
PubMed1985

Lack of cross-resistance to X-irradiation in oxygen-resistant mammalian cell lines.

HeLa and Chinese hamster ovary cells capable of proliferating at O2 levels that are ordinarily lethal to cells in tissue culture were selected by chronic adaptation to stepwise increased oxygen tensions. A popular hypothesis, originally proposed by Gerschman et al., states that the toxic action of both hyperoxia and X rays is based on a common mechanism involving the formation of oxidizing free radicals. Contrary to what may be predicted from this hypothesis we found that our oxygen-resistant substrains were not cross-resistant to X rays, as determined by a clonogenic cell survival assay. These results show that cellular properties governing increased resistance to killing by O2 do not necessarily contribute to cellular X ray tolerance.

Animals↗
PubMed1985

Effect of hypothermia on cell kinetics and response to hyperthermia and X rays.

Hyperthermia is a potent radio enhancer. Studies using hypothermia in combination with irradiation have given confusing results due to lack of uniformity in experimental design. This report shows that hypothermia might have potential significance in the treatment of malignant cells with both thermo- and radiotherapy. Reuber H35 hepatoma cells, clone KRC-7 were used to study the effect of hypothermia on cell kinetics and subsequent response to hyperthermia and/or X rays. Cells were incubated at 8.5 degrees C or between 25 and 37 degrees C for 24 hr prior to hyperthermia or irradiation. Hypothermia caused sensitization to both hyperthermia and X rays. Maximum sensitization was observed between 25 and 30 degrees C and no sensitization was found at 8.5 degrees C. At 25 degrees C maximum sensitization was achieved in approximately 24 hr, cell proliferation was almost completely blocked, and cells gradually accumulated in the G2 phase of the cell cycle. In contrast to the effect of hypothermia on either hyperthermia or X rays alone, thermal radiosensitization was decreased in hypothermically pretreated cells (24 hr at 25 degrees C) compared to control cells (37 degrees C). The expression of thermotolerance and the rate of development at 37 degrees C after an initial heating at 42.5 degrees C were not influenced after preincubation at 25 degrees C for 24 hr. The expression of thermotolerance for heat or heat plus X rays during incubation at 41 degrees C occurred in a significantly smaller number of cells after 24 hr preincubation at 25 degrees C. The enhanced thermo- and radiosensitivity in hypothermically treated cells disappeared in approximately 6 hr after return to 37 degrees C.

Acclimatization↗
PubMed1984

[Main point].

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Adolescent↗
PubMed1984

Effect of thermotolerance on thermal radiosensitization in hepatoma cells.

The interaction between hyperthermia and X irradiation was determined in cultured Reuber H35 hepatoma cells with different states of thermosensitivity. Incubation at 41 degrees C followed by 4-Gy X rays resulted after 2 hr in a stabilization of cell survival for heat or plus X rays, with a maximum synergism factor of 1.6. Thermotolerance did not develop during incubation at 41.7 or 42.5 degrees C. When heat treatment of cells was followed by irradiation, the synergism factor for thermal radiosensitization increased with both the amount of thermal cell killing and the amount of X-ray cell killing; the influence of thermal exposure on the synergism factor was greater than that of the X-ray dose. Cells were made thermotolerant either by incubation at 42.5 degrees C for 30 or 60 min followed by an interval at 37 degrees C, or by continuous incubation at 41 degrees C. In both cases thermotolerance was measured by incubation at 42.5 degrees C. No difference was observed between the maximum thermotolerance achieved with both methods. When cells were irradiated in addition to the second heat treatment, thermal radiosensitization was strongly reduced concomitant with the decreased sensitivity to killing by heat.

Acclimatization↗
PubMed1984

Thermotolerance in cultured hepatoma cells: cell viability, cell morphology, protein synthesis, and heat-shock proteins.

Heat treatment at 42 degrees C of cultured Reuber H35 rat hepatoma cells induced both a rapid decrease of the rate of protein synthesis and the rounding up of the cells. Reincubation at 37 degrees C resulted in a gradual flattening of the cells, resumption of protein synthesis, and the synthesis of heat-shock proteins. During the recovery period cells developed a resistance toward a treatment which otherwise should lead to heat-induced cell death. Thermotolerance measured in terms of cell survival was paralleled by thermal resistance of protein synthesis and the cellular ability to refrain from rounding up under heat stress.

Acclimatization↗