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Biomedical subjects

L De Ridder

Publications and source records attributed to L De Ridder.

At least 55 records · Page 3Linked to original sources
PubMed1996

Effects of ionizing radiation on cartilage: emphasis on effects on the extracellular matrix.

In this report, we review data dealing with radiation effects on cartilage. More specifically, we emphasize on alterations caused in the extra-cellular cartilage matrix. Although radiation studies predominantly describe the effect on the structure of DNA and on the mitotic activity of cells, alterations caused by the effect on the non-mitotic activity can also be important. Cartilage, having an extracellular matrix composed of 2 major components, aggrecan and collagen, provides a good model to study this kind of radiation effects. The following topics concerning literature data are summarized: effects on the amount of matrix synthesized, effects on the activity of certain enzymes and effects on the structure and morphology of the matrix. Some new findings concerning the radiation effect on the size distribution of aggrecan-aggregate populations, de novo synthesized by chondrocyte cultures, either derived from calcifying or from non-calcifying cartilage, are given.

Animals↗
PubMed1995

Micronucleus induction in peripheral blood lymphocytes of patients under radiotherapy treatment for cervical cancer or Hodgkin's disease.

The genetic damage present in peripheral blood lymphocytes of patients treated with fractionated partial-body radiation therapy for cervical cancer or Hodgkin's disease was followed during treatment by means of the cytokinesis-block micronucleus assay. For each patient a dose-response relationship with respect to the number of micronuclei after in vitro irradiation of blood samples pretreatment was also determined. Comparing the individual in vivo-in vitro data, the micronucleus yields after the equivalent whole-body dose during radiotherapy were found to differ substantially from the in vitro dose-response. Contrary to the linear-quadratic dose dependence after in vitro irradiation the initial increase in the micronucleus yield during radiotherapy levelled off at elevated doses. The observed differences cannot be attributed only to the effects of interphase death and the partial irradiation of the lymphocyte pool. The correlation between the micronucleus yield and the equivalent whole-body dose for values up to 2 Gy, observed for the pooled data of the first part of the radiotherapy treatment, demonstrates the suitability of the cytokinesis-block micronucleus assay as a biological dosemeter after accidents involving partial-body irradiation.

Adult↗
PubMed1994

Micronuclei induced by fast neutrons versus 60Co gamma-rays in human peripheral blood lymphocytes.

Here we compared the effectiveness of neutrons ( = 5.5 MeV) versus 60Co gamma-rays in producing micronuclei (MN) in human lymphocytes. To obtain dose-response data, blood samples of six donors were irradiated with doses ranging from 0.1 to 5 Gy for gamma-rays and 0.1-3 Gy for neutrons. A linear dependence of MN yield with dose was found for fast neutrons while for gamma-rays a nonlinear dependence existed. For both radiation qualities no significant interindividual differences were found. Derived relative biological effectiveness values decreased with increasing dose. The MN frequency distributions were overdispersed with respect to the Poisson distribution, with neutrons showing higher dispersion values than with gamma-rays. To compare the repair kinetics of both radiation qualities split-dose experiments were performed. A dose of 4 Gy gamma-rays (3 Gy neutrons) was delivered either as a single exposure or in two equal fractions separated by time intervals ranging from 30 min to 10 h (30 min to 7 h for neutrons). The data showed for gamma-rays a significant decline (30% +/- 10%) in MN yield with interfraction time due to repair of DNA damage. This repair is a continuous process starting almost immediately after the first of the two doses and lasting 3-5 h. For fast neutrons no decline was observed indicating irreparable damage.

Cells, Cultured↗
PubMed1994

[Relationship between endocrinology and craniofacial growth. I: Puberty and craniofacial growth. II: Growth of the craniofacial skeleton].

In this literature, a review is given of the endocrinology and morphology of the craniofacial complex. This article reviews in a first part the endocrinology of puberty and general growth aspects. Afterwards the adolescence growth spurt of the face and the hormonal regulation will be focused. In a second part the morphogenetic aspects together with growth area's and growth theories of the craniofacial complex will be discussed. At last a detailed description of the maxillary and mandibular growth is given.

Adolescent↗
PubMed1994

Comparative and combined effects of interleukin 6, interleukin 1 beta, and tumor necrosis factor alpha on proteoglycan metabolism of human articular chondrocytes cultured in agarose.

OBJECTIVE: To study the effects of recombinant tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta) and interleukin 6 (IL-6) on proteoglycan metabolism of isolated chondrocytes. METHODS: Human articular cartilage cells were cultured in agarose gel. In these culture conditions, chondrocytes keep their phenotypic stability. They release cartilage specific proteoglycans into the surrounding artificial matrix. Proteoglycan synthesis was measured by the incorporation of 35sulfate (35S). RESULTS: TNF-alpha and IL-1 beta depressed proteoglycan synthesis and induced proteoglycan degradation. The effects of both cytokines were additive, when used in submaximal doses. No mutual induction of TNF-alpha and IL-1 beta was shown, but both cytokines stimulated the chondrocytes to release IL-6, up to 100,000 pg/ml. Equal amounts of human recombinant IL-6 did not affect proteoglycan synthesis. IL-6 did not alter proteoglycan quality, nor did it modulate the IL-1 beta activities on proteoglycan metabolism. CONCLUSION: These findings illustrate the role of IL-1 beta and TNF-alpha in cartilage degradation and suggest that the role of the large amounts of IL-6 released in response to IL-1 in chronic arthritis is not directly protective with regard to proteoglycan metabolism.

Arthritis↗
PubMed1993

Radiation effects on the matrix synthesis in non-ossifying embryonic cartilage in vitro: a functional and morphological study.

Radiation effects on collagen and glycosaminoglycan (GAG) synthesis were studied in non-ossifying embryonic chick cartilage, in vitro. Fragments of the non-calcifying region of 15-day-old chick sterna were irradiated with 20, 50 and 100 Gy. The counterparts served as controls. Fragments were cultured up to 14 days. Pulse labeling experiments with 3H-proline and 3H-glucosamine started immediately after irradiation and on day 3, 6 and 13 post-irradiation. Fragments for morphological evaluation were fixed on day 1, 4, 7 and 14, simultaneously with the end of the labeling period. The same dose- and time-dependent inhibition was observed for the collagen and GAG synthesis. Radiation doses of 20, 50 and 100 Gy cause respectively and inhibition of about 20, 35 and 60% at the end of the culture period. Morphological alterations were observed after radiation doses of 50 and 100 Gy. Dose- and time-dependent necrosis all over the sternum was observed. A restricted number of cells showed an increased GAG synthesis after irradiation (50 Gy). This could explain the levelling off of the radiation effect on the incorporation of the labeled precursors towards the end of the culture period for radiation doses up to 50 Gy.

Animals↗
PubMed1993

Radiation damage to endothelial cells in vitro, as judged by the micronucleus assay.

The aim of our study was to optimize the cytokinesis-blocked (CB) micronucleus (MN) assay for the evaluation of radiation induced chromosomal damage in endothelial cells (EC) in vitro. After irradiation of confluent monolayers of rat and bovine aortic EC, with various doses of 250 kV X rays (0-3 Gy), the cells were trypsinized, resuspended in medium with cytochalasin B and then replated. After 3 days of growth they were again trypsinized and after fixing and staining of the cells, 1000 CB cells were scored for MN. The MN dose-response curves showed a rapid increase in the MN yield after low doses (< 0.25 Gy) of irradiation. This points to the high radiosensitivity of EC, with rat EC being more radiosensitive than bovine EC. A further slow increase (< 1 Gy) was observed after the initial fast increase. The occurrence of a fast and a slow component can be attributed to differences in radiosensitivity of EC in different stages of the cell cycle. For doses higher than 1 Gy, no further increase occurred due to severe damage at the spindle apparatus, as a result of which the division of many cells was inhibited.

Animals↗
PubMed1992

Study of dose-rate and split-dose effects on the in vitro micronucleus yield in human lymphocytes exposed to X-rays.

This paper reports the effects of changes in dose-rate and dose-fractionation on the micronucleus (MN) yield in human lymphocytes exposed to 250 kV X-rays. For the investigation of dose-rate effects whole blood samples of four healthy donors were irradiated with doses ranging from 1 to 4 Gy given at various dose-rates between 0.2 and 40 Gy/h. For the higher doses (3 and 4 Gy) a decline in the MN yield became apparent when the dose-rate was reduced below 1.6 Gy/h. This effect was enhanced systematically by a further lowering of the dose-rate. For lower doses (1 and 2 Gy) the reduction in the MN yield was less pronounced: only a small effect was observed for two donors when a dose of 2 Gy was administered at a dose-rate of 0.2 Gy/h. In the split-dose experiment a dose of 4 Gy was delivered either as a single exposure or in two fractions of 2 Gy, separated by time intervals ranging from 30 min to 10 h. A continuous decrease of the MN yield with increasing interfraction time is observed: after an initial fast decline a further slight reduction in the MN yield occurs. The observed dose-rate and split-dose effects on the MN yield can be attributed to repair of sublethal damage.

Chromosome Aberrations↗
PubMed1991

Nimodipine decreases resuscitability in a cardiopulmonary arrest model in the rat.

Although calcium has been implicated in ischemia-induced brain death or dysfunction, many animal studies do not show a beneficial effect of calcium-entry blockers given after resuscitation from a cardiopulmonary arrest (CPA). This may be due to the fact that treatment was started too late; we, therefore, evaluated the effect of the calcium-entry blocker nimodipine administered at the earliest feasible postischemic moment, i.e. at the start of the resuscitation attempts. In anesthetized Wistar rats, CPA was induced by an intra-cardiac injection of KCl, and maintained for 7 min by chest restriction. At the start of the resuscitation attempts, 50 rats were blindly and randomly assigned to intravenous treatment with either nimodipine (10 micrograms/kg over 2 min, followed by 1 micrograms/kg per min for 60 min; n = 25) or saline (n = 25). In the nimodipine group, significantly less rats could be resuscitated (11/25 versus 20/25) and the survival rate at the end of the 7 days evaluation period tended to be lower (5/25 versus 11/25). In the rats surviving after 7 days, there was no difference between both groups in incidence of seizures, neurological status and histological lesions in the hippocampus. It is concluded that nimodipine, in the dose tested and given during resuscitation in this rat model, has a detrimental effect on resuscitability and no beneficial effect on the neurological outcome in the surviving animals.

Animals↗
PubMed1991

The healing of cranial defects by demineralized osseous implants: a radiographic, histological and radioisotope-uptake study in rats.

The purpose of this study was to evaluate by different techniques the healing effect of demineralized allogeneic bone in parietal cranial defects in rats. 45Ca incorporation was measured for nine consecutive weeks in groups of control and implanted rats. Repeated 99mTc MDP uptake measurements were performed for nine weeks on the same group of rats. Each measurement was preceded by a cranial radiography. At the end of the study the animals were sacrificed for histologic evaluation. The results of the 45Ca incorporation, 99mTc MDP uptake measurements and the histologic pictures confirmed the osteogenic capacity of demineralized allogenic bone. From the results it can concluded that 99mTc MDP uptake measurements are a powerful tool in the evaluation of the healing process. It can be utilized sequentially in the same animal and gives detailed information about the progress of osteogenic activity over the entire implant area.

Animals↗
PubMed1990

Nimodipine has no beneficial effect on neurological outcome in a cardiopulmonary arrest model in the rat.

Brain damage after resuscitation from cardiac arrest is believed to be related to calcium influx in ischaemic neurons and to postischaemic calcium-dependent vasospasm. We therefore evaluated the potentially protective effects of the calcium-entry blocker nimodipine in a cardiopulmonary arrest model in the rat. Male Wistar rats were anaesthetized with ketamine (group I) or hexobarbital (group II) and subjected to a KCl-induced cardiac arrest during 7 min (group I) or 12 min (group II). Five minutes after resuscitation, the rats were treated intravenously in a randomized and blind fashion. Group I received either saline or 1 microgram.kg-1.min-1 or 5 micrograms.kg-1.min-1 of nimodipine and group II either saline or 1 microgram.kg-1.min-1 of nimodipine. Survival, occurrence of seizures and neurological status were assessed daily during 7 days after resuscitation. On day 7, the brains of the surviving rats were perfusion-fixed and a histopathological evaluation of the hippocampus was performed. Nimodipine, in the doses tested, had no beneficial influence on the 7 day survival rate, nor on the occurrence of seizures and the neurological and histopathological scores in the rats surviving after 7 days. With the highest dose of nimodipine, there was even a trend towards a decrease of the survival rate, probably related to the drug's hypotensive effect. Therefore, our data do not show a protective effect of nimodipine after cardiac arrest.

Animals↗
PubMed1990

Development of larval Echinococcus granulosus confronted with chicken heart tissue in vitro.

Vesiculated protoscoleces (VP) were produced by culturing freshly collected protoscoleces from Echinococcus granulosus horse liver hydatids in RPMI 1640 monophasic medium at 37 degrees C for 18 days. Half of the VP were used as such, the other half used after killing them by freeze-thawing. Nine-day-old chicken heart fragments (CHF) were cultured in MEM at 37 degrees C for 72 h. Subsequently, CHF were put together with live and dead VP, respectively, for up to 53 days, on a semisolid medium consisting of agar, Ringer's and MEM. Time-dependent histological observations revealed that dead VP were surrounded by CHF cells. Dead VP tissue was eventually internalized and disintegrated in about 1 week. Live VP penetrated into the CHF tissue and further developed into small hydatid cysts, located within the boundaries of the experimental 'host' tissue. The amorphous-looking contact region PAP-stained positively only with anti-E. granulosus serum and not with anti-CHF serum; it was considered identical to the normal laminated layer. The invasion of VP in CHF tissue proved to be different from a tumour or a bacterial invasion: it was concluded that the confrontation of VP and CHF had resulted in an 'in vitro cohabitation' rather than in an 'in vitro infection'.

Animals↗
PubMed1990

Dose- and time-dependent radiation inhibition of RNA and glycosaminoglycan synthesis in embryonic cartilage: an in vitro study.

Radiation effects on the RNA and glycosaminoglycan (GAG) synthesis of embryonic cartilaginous tibiae were studied in vitro during a 4- or 7-day culture period. Before being cultured, tibiae received single radiation doses of 20, 50 or 100 Gy. The counterparts served as sham-irradiated controls. At different times after irradiation, irradiated and control tibiae were pulse-labelled for 2 h with [3H]uridine or [3H]glucosamine. The incorporated radioactivity was measured by liquid scintillation counting. Histochemical demonstration of acid phosphatase (AP), a lysosomal enzyme, was carried out using beta-glycerophosphate as substrate. A limited, dose-dependent immediate effect on RNA and GAG synthesis was found. This effect was unchanged for 2 days. After this period a time-dependent delayed effect was observed. For each radiation dose, and for each precursor, the same time-related pattern was found. At the end of the culture period AP activity, an early indicator for apoptosis, was higher in the irradiated tibiae than in the controls. No other morphological ultrastructural differences were observed at this time. We conclude that the metabolic alterations are probably due to stimulation of the initial stages of the apoptotic process in the irradiated cartilage cells.

Animals↗
PubMed1987

Invasiveness, proliferative activity and ultrastructural phenotypes of hepatocytes from diethylnitrosamine-induced neoplastic nodules and hepacarcinomas in vitro.

The invasive behavior of hepatocytes from diethylnitrosamine (DENA) induced neoplastic nodules and hepatocarcinomas was studied in a confronting culture system in vitro. These observations confirm our previous report, demonstrating that hepatocytes from hepatocarcinomas and from neoplastic nodules invaded into embryonic chick precultured heart fragments (PHF), a property associated with malignancy (Mareel, 1979). We now further demonstrate that: (1) Invasiveness was expressed by the hepatocytes in 10 out of 12 samples from hepatocarcinomas, and in 13 out of 36 confronted nodular samples. The hepatocytes from the other two-thirds of nodule samples died off in the confrontation as did all normal hepatocytes. (2) Invasive hepatocytes from tumors and from nodules showed the same arrangement of invasive liver cells in relation to the heart tissue, and the same ultrastructural phenotypes. The latter did not differ from those in the non-invading subpopulations, with the exception perhaps of a higher proportion of cells with an indented nucleus. (3) None of the scored ultrastructural alterations was present in all the invasive cells, thus excluding any specific requisite in this respect. (4) When 3H-TdR was made continuously available to the cultures, starting at the time of confrontation between heart and liver tissues, unlabelled as well as labelled invasive hepatocytes were found inside the PHF in about equal proportions. It is concluded that nodular hepatocytes deviate from normality by at least 2 different properties that may or may not be related to each other and are revealed under in vitro conditions, namely the ability to survive and to proceed through S-phase and mitosis under such conditions and to actively invade precultured chick heart fragments. The latter property indicates that at least some of the nodules contain hepatocytes that have performed one step in malignant progression.

Animals↗
PubMed1983

Interaction between embryonic rat superior cervical ganglion and syngeneic heart fragments in a confronting culture.

Freshly dissected 17-19 days embryonic superior cervical ganglia are confronted with 0.5 mm diameter heart fragments of the same Wistar rat. Incubation in vitro at 37 degrees C of confronting heart-ganglion pairs is carried out in Dulbecco's medium on a gyratory shaker. Fixation and staining followed after 2 hr, 1, 3 and 6 days of incubation. Histological analysis with light and electron microscopy revealed the interaction between the sympathetic ganglion and its target organ. Ingrowth of axons rich in neurofilaments and neurotubules and containing light and dense core vesicles, is observed.

Animals↗
PubMed1981

Malignancy of neurogenic cells characterized by their invasiveness in vitro.

15 continuous neurogenic cell lines, originated from the off-spring of ethylnitrosourea treated BD IX rats are screened for invasions in vitro. Confrontations of precultured embryonic chick heart fragments with aggregates of the neurogenic cells are studied in a three dimensional system. Invasion of the neurogenic cells into the heart fragment is scored on histological sections. Invasion in vitro was correlated with malignancy in vivo. The reproducibility in our experiments strengthen the idea that invasiveness in vitro is a criterion of malignancy. Different cell lines express various patterns of invasion in vitro. Alterations are observed as well in the invading cells as in the heart tissue. These alterations represents cellular activities during invasion. The observed activities are probably the result of cell growth, penetration, destruction and phagocytosis.

Animals↗