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Biomedical subjects

J P Bökkerink

Publications and source records attributed to J P Bökkerink.

At least 19 recordsLinked to original sources
PubMed2001

Analysis of handwriting of children during treatment for acute lymphoblastic leukemia.

BACKGROUND: Children treated for acute lymphoblastic leukemia (ALL) often complain about handwriting problems. PROCEDURE: Using a computerized writing task, we have prospectively studied the processes necessary for the production of handwriting movements in 11 children (5-12 years old) during treatment for ALL. Children were tested at time points closely related to the vincristine administration. RESULTS AND CONCLUSIONS: Children treated for ALL drew slower, with longer pause durations and increased drawing pressure. Children were able to overcome the problems, except for a consistently increased drawing pressure. This increased drawing pressure may be an attempt of the children to obtain sufficient kinesthetic information and thus can be seen as an adequate adaptation mechanism in case of peripheral neuropathy due to the neurotoxic effects of vincristine. However, neurotoxic effects of other cytostatic drugs cannot be excluded.

Analysis of Variance↗
PubMed2000

The saddle prosthesis in pelvic primary and secondary musculoskeletal tumors: functional results at several postoperative intervals.

The first purpose of this study was to evaluate the saddle prosthesis in patients with periacetabular tumors in terms of the functional results obtained after several postoperative intervals. The second purpose was to evaluate the complications and how they might be prevented in the future. Functional results according to the MSTS functional rating system were evaluated at several postoperative intervals in 15 patients treated with internal hemipelvectomy and reconstruction with the saddle prosthesis because of periacetabular primary (n = 9) or secondary (n = 6) malignancies. All complications were evaluated. Three months postoperatively, 7/9 patients with a primary tumor and 2/4 patients with a secondary tumor were able to walk outside without pain. Median functional results 3 and 6 months postoperatively were 40% and 50%, respectively. Deep infection occurred in 4 patients and fracture of the iliac remnant in 2. Heterotopic ossifications along the interpositional component were seen in 5 patients, but they did not negatively influence the functional outcome. Three (relative) contraindications to reconstruction with the saddle prosthesis could be ascertained: osteoporosis, extended involvement of the iliac wing by tumor, and insufficient soft-tissue quality after previous procedures. (Short-term) functional results after reconstruction with the saddle prosthesis are satisfactory if the above-mentioned contraindications are taken into consideration.

Acetabulum↗
PubMed2000

Mild axonal neuropathy of children during treatment for acute lymphoblastic leukaemia.

Neurophysiological functioning was studied prospectively in children treated for acute lymphoblastic leukaemia with a low dose vincristine regime (8 x 1.5 mg/m2/dose), to obtain more insight into vincristine neuropathy. A WHO neurotoxicity score was estimated and vibration sense and electrophysiological measurements were taken at standardized times during vincristine treatment. The WHO neurotoxicity score showed decreased or disappearance of Achilles tendon reflexes, and mild sensory disturbances, but a grade 3-4 neurotoxicity was not demonstrated by any of the children. Vibration perception thresholds increased progressively during treatment and amplitudes of action potentials of peroneal and sensory ulnar and median nerves decreased, whereas nerve conduction velocities stayed unchanged. Both vibration perception thresholds and the electrophysiological findings hardly exceeded the limits of normality. We conclude that children treated for acute lymphoblastic leukaemia with a low dose vincristine regimen have mild axonal neuropathy which may be responsible for the motor problems in these children.

Achilles Tendon↗
PubMed2000

SIOP treatment guidelines for renal tumours in small infants: fact or fantasy?

AIMS: Since as far back as 1980, SIOP (Société Internationale d>>Oncologie Pédiatrique) have advocated primary nephrectomy (PN) only for unilateral renal tumours in patients </=6 months of age. Patients aged 7-12 months have been pre-treated with chemotherapy before nephrectomy is performed. The aims of this study were: (1) to evaluate how the SIOP guidelines for infants 0-6 months and 7-12 months of age were followed in three Dutch centres for Paediatric Oncology before and after 1980, and (2) to carry out an inventory of the incidence of benign tumours in this patient population below 12 months of age. METHODS: Retrospective analysis of 67 patients under 12 months of age (1969-1995) with a unilateral renal tumour at diagnosis was carried out. Demographics, pathology, staging and treatment variables were analysed. RESULTS: Of 67 patients, 39 were male and 28 female. Twenty-six (39%) infants were 0-6 months of age (group A) and 41 (61%) were 7-12 months old (group B). In group A there were five patients (19%) with congenital mesoblastic nephroma (CMN), out of which one was still-born and therefore received no treatment, and 21 patients with a unilateral Wilms>> tumour (WT). Fourteen of the 25 patients (56%) were treated with PN, including four patients with CMN. In group B there was one patient (2%) with CMN and 40 patients with WT. Thirteen of the patients (31%) were treated with PN. A total of 15 patients were treated before 1980 and 26 after 1980. Eight of 15 (53%) patients were treated with PN before 1980 and 21/26 (81%) were pre-treated after 1980, according to the protocol. CONCLUSION: Despite the SIOP recommendations, only 56% of patients </=6 months were treated with PN. The percentage of pre-treated patients in group B increased after changing the protocol in 1980 to 81%. In the age group included in the SIOP studies the protocol had been used significantly more often compared to the group included in the guidelines only. The known excellent survival rate justifies a primary nephrectomy approach in the youngest age group, however, in cases of a large tumour, pre-operative chemotherapy in reduced doses may still be considered. In our study fewer CMN were found (19%) than reported in the SIOP studies (20-70%), most likely due to a low registration rate, as a consequence of excluding this very young age group (0-6 months) from the SIOP protocol.

Combined Modality Therapy↗
PubMed1999

Intensive treatment of children with acute lymphoblastic leukemia according to ALL-BFM-86 without cranial radiotherapy: results of Dutch Childhood Leukemia Study Group Protocol ALL-7 (1988-1991).

In The Netherlands from July 1988 to October 1991, children (0 to 16 years of age) with de novo acute lymphoblastic leukemia (ALL) were treated according to protocol ALL-7 of the Dutch Childhood Leukemia Study Group (DCLSG). In this protocol, chemotherapy and treatment stratification were identical to the ALL-BFM-86 protocol (Reiter et al, Blood 84:3122, 1994), but cranial irradiation was restricted to patients with initial central nervous system (CNS) involvement. Patients were stratified into 3 risk groups, based on leukemia cell mass and response to initial treatment: standard-risk group (SRG), risk group (RG), and experimental group (EG). As in ALL-BFM-86, a randomized study on late intensification (protocol S) was performed in RG patients, and during the study (since October 1990), early reinduction treatment (protocol II) was introduced for SRG patients. Treatment duration for all patients was 18 months. Two hundred eighteen children entered the study: 74 SRG, 127 RG, and 17 EG patients. The overall complete remission (CR) rate was 98%. The 5-year event-free survival (EFS) for all DCLSG ALL-7 patients was 65. 3% (standard error [SE] 3.2%), which was significantly different from the 73% (SE 1%) 5-year EFS achieved in the ALL-BFM-86 study (P =.02, Z-test). However, restricting the analysis to SRG patients receiving protocol II with a total duration of treatment of 18 months, the 5-year EFS rates were 64.6% (SE 4.0%) and 67% (SE 4%), respectively, and no significant difference could be established (P =.67, Z-test). The 5-year EFS rates for SRG, RG, and EG patients were 63.5% (SE 5.6%), 66.6% (SE 4.2%), and 63.3% (SE 12.0%), respectively. SRG patients receiving protocol II fared better than patients not receiving protocol II (5-year EFS 76.7% [SE 7.7] and 54. 5% [SE 7.5], respectively). No difference in 5-year EFS was observed in RG patients randomized to receive or not to receive late intensification with protocol S. The overall CNS relapse rate at 5 years was 5.5%. The incidence rate at 5 years was 11.4% in SRG patients not receiving protocol II, whereas no CNS relapses occurred in SRG patients receiving protocol II. Six children died in first complete remission and 2 children developed a second malignancy (thyroid carcinoma and acute nonlymphoblastic leukemia). Systemic high-dose methotrexate (MTX) and intrathecal chemotherapy is a safe and effective method of CNS prophylaxis in the context of BFM-oriented treatment for all children with ALL, regardless of the risk group (with the possible exception of T-ALL patients with high white blood cell counts). The results of the DCLSG ALL-7 study confirm those of the ALL-BFM-86 study showing that early reinduction with protocol II is essential in the treatment of SRG patients and that late intensification with protocol S does not improve the prognosis for RG patients.

Adolescent↗
PubMed1999

Osteosarcoma: oncologic and functional results. A single institutional report covering 22 years.

BACKGROUND AND OBJECTIVES: The oncologic and functional results in patients treated because of osteosarcoma (OS) were evaluated. METHODS: Fifty-one patients with high-grade OS were treated between 1974 and 1996 at our hospital. All patient records were studied, and the surviving patients were evaluated according to the American Musculoskeletal Tumor Society functional rating system. The majority of patients received adjuvant chemotherapy (prior to 1983) or neoadjuvant chemotherapy (from 1983). Until 1987, all patients with extremity OS had ablative surgery; from 1987, the majority had limb-saving surgery. Lung metastases were resected in most cases. RESULTS: Overall 2-year and 5-year disease-free survival (DFS) rates were 27 of 51 and 16 of 42, respectively. Patients with vertebral or pelvic OS or contaminated margins after resection had a very bad outcome. In all other subgroups, including patients with various types of chemotherapy, response to chemotherapy, diameter of tumor, presence or absence of metastatic spread, and location of tumor, a 5-year DFS of about 50% was found. Recurrent disease in patients who had achieved a 2-year disease-free interval was relatively low (4/23 patients). CONCLUSIONS: Survival in our series was worse than in most other studies. A very bad outcome was found in patients with vertebral or pelvic OS or with contaminated margins after resection.

Adolescent↗
PubMed1998

Teratomas in infancy and childhood.

BACKGROUND AND PROCEDURE: Outcomes in children with teratomas collected between October 1982 and December 1995 in cooperative protocols of the German Society of Pediatric Oncology and Hematology (GPOH) were analyzed. Teratomas were diagnosed in 329 (42%) of 780 registered patients with germ cell tumors. The annual incidence was 0.24/100,000. Main primary sites were coccygeal (n = 132, 2.2:1 female predominance), ovary (n = 81), testis (n = 40) and brain (n = 15, 2.8:1 male predominance). RESULTS: Two hundred seventy cases of extracranial non-testicular teratoma were evaluated: In mature teratomas (n = 154) the observed relapse rate was 10%. Incomplete resection was the main risk factor for relapse. After complete resection, the relapse-free survival (RFS, Kaplan-Meier-estimation) was 0.96 +/- 0.01 (n = 126, observation time 18-155 months) in comparison to an RFS of 0.56 +/- 0.09 in incompletely resected teratomas grade 0 (n = 28, observation time 28-94 months) (P < 0.01). Im-mature teratomas were treated by surgery alone in 76 cases and by surgery and adjuvant chemotherapy in 40 cases. The observed relapse risk was 18%. Main risk factors for relapse were incomplete tumor resection (n = 38) as well as immaturity in incompletely resected teratomas. Fifteen of 29 relapsing patients presented with malignant tissue in the recurrent tumor (mainly yolk sac tumor); in contrast, seven of 40 patients with immature teratoma relapsed despite adjuvant chemotherapy without showing malignant components (P = 0.014). Nine of 36 (25%) relapsing patients died of disease. Eleven of the 27 (41%) surviving children suffered from mutilation after repeated surgery. COMMENTS: It is suggested that an international randomized trial for patients with incompletely resected high risk teratoma be initiated to evaluate the effect of adjuvant chemotherapy on specific end-points: 1) influence on relapse rate in general; 2) reduction of the proportion of malignant relapses; 3) avoidance of mutilating surgery.

Adolescent↗
PubMed1998

Inhibition of DNA methylation in malignant MOLT F4 lymphoblasts by 6-mercaptopurine.

Treatment of MOLT F4 lymphoblasts with 6-mercaptopurine (6-MP) resulted in a decrease of ATP and a depletion of S-adenosylmethionine (AdoMet). To investigate whether this might affect the methylation of DNA, we treated MOLT F4 lymphoblasts with increasing concentrations of 6-MP, followed by labeling with [methyl-14C]methionine and [methyl-3H]thymidine. After DNA isolation, we measured the incorporated radioactivity and determined the 14C/3H ratio as a measure for the methylation of newly formed DNA. The 14C/3H ratio was decreased by 17% with 1 mumol/L 6-MP; treatment with increasing concentrations of 6-MP up to 10 mumol/L showed a further decrease to 70%, in comparison with untreated cells. To demonstrate that the methylation of deoxycytidine residues in DNA was reduced, we quantified hydrolyzed DNA by HPLC. The 14C/3H ratio showed a decrease with increasing 6-MP concentrations, indicating that treatment with 6-MP resulted in hypomethylation of DNA.

Carbon Radioisotopes↗
PubMed1997

DNA methylation patterns in the calcitonin gene region at first diagnosis and at relapse of acute lymphoblastic leukemia (ALL).

Aberrant DNA methylation can occur early in neoplastic transformation and may lead to the development of cancer. We describe the alterations of methylation patterns at the DNA sequence level which occurred in the 5' region of the calcitonin gene in lymphoblasts from 14 pediatric patients with acute lymphoblastic leukemia (ALL). The DNA methylation status of 25 CpG sites was determined by sequence analysis after bisulfite treatment of the DNA. This method showed that 13 out of 14 patients had increased numbers of methylated CpG sites in the calcitonin gene region at initial diagnosis when compared to control DNA from healthy individuals. The 5' region of the calcitonin gene appears to be methylated to a significantly higher degree in T lineage ALL compared to B lineage ALL (P < 0.01). Each of six ALL patients who were investigated at initial diagnosis and at relapse showed alterations in DNA methylation between the two stages. These six cases were also investigated by Southern blot analysis with methylcytosine-sensitive restriction enzymes and this method showed an increase in DNA methylation in only four of the six cases. The DNA sequencing method thus appears to be better suited to assess alterations of DNA methylation than Southern blot analysis. There are marked regional differences in the frequency of methylation of individual CpG sites and in the frequency of alterations between the two stages. Our results show that alterations in DNA methylation continue to occur from the initial stage to the relapse stage of ALL, suggesting that aberrant DNA methylation may play a role in tumor progression.

Base Sequence↗
PubMed1996

Effects on transmethylation by high-dose 6-mercaptopurine and methotrexate infusions during consolidation treatment of acute lymphoblastic leukemia.

6-mercaptopurine (6MP) cytotoxicity is caused by thioguanine and methylthioinosine nucleotides. Thiopurine methylation occurs to a large extent in vivo and in vitro. In this reaction, S-adenosyl-L-methionine (AdoMet), produced from methionine and ATP, is converted into S-adenosyl-L-homocysteine (AdoHcy) which, in turn, is hydrolyzed into homocysteine. Remethylation of homocysteine into methionine is inhibited by methotrexate (MTX). In cultured lymphoblasts, AdoMet: AdoHcy ratio and DNA methylation decrease after incubation with 6MP. The aim of the present study was to investigate the influence of high-dose 6MP on the methylation capacity in children with acute lymphoblastic leukemia. Five patients received 4 courses with high-dose intravenous MTX (5' g.m-2 in 24 hr) immediately followed by high-dose 6MP (1300 mg.m-2 in 24 hr). Five control patients received high-dose MTX and oral 6MP (25 mg.m -2 daily for 8 weeks). Leucovorin rescue was started at 36 hr in both groups. In the intravenous 6MP group, 6-methylmercaptopurine, its riboside, and 6-methylmercapto-8-hydroxypurine were detectable in plasma in concentrations of 0.3-2.6 muM (6MP steady state levels: 11.6 muM). In red blood cells, mean methylthioinosine nucleotide levels were one third of those of ATP (13.1 nmol/10(8)). AdoHcy levels (10 pmol/10(8)) remained constant in both groups and AdoMet was not detectable ( < 20 pmol/10(8)). In both groups, plasma homocysteine increased and methionine decreased following administration of MTX. The delay in the recovery of methionine in the intravenous 6MP group after MTX infusion is probably the result of an increased demand on methyl groups during 6MP infusion.

Antimetabolites, Antineoplastic↗
PubMed1996

Metabolism of intravenously administered high-dose 6-mercaptopurine with and without allopurinol treatment in patients with non-Hodgkin lymphoma.

PURPOSE: We investigated the metabolism of high dose 6 mercaptopurine (HD-6MP) infusions and its influence on the metabolism by allopurinol, an inhibitor of xanthine oxidase, the enzyme that catabolizes 6MP into thioxanthine and thiouric acid. PATIENTS AND METHODS: Nine patients (aged 2-11 years) with non-Hodgkin lymphoma (NHL) were treated with HD-6MP (1300 mg/m(2).24h) within a therapeutic window after diagnosis. Four patients received oral allopurinol (200 mg/m(2).day) to prevent urate nephropathy, and five did not. Plasma and RBC were isolated before and 4, 20, 24, 28, and 48h after the start of the infusion. All measurements were performed with HPLC. RESULTS: Considerable variations were found in the plasma levels of 6MP, thioxanthine, and thiouric acid and of RBC-MeTIN levels. 6MP-riboside was not detectable, and MeMP and MeMPR levels were <1.3 muM in the plasma. In general, 6MP, thioxanthine, and MeMP levels in plasma were higher, and thiouric acid plasma levels and RBC-MeTIN levels were lower in the patients treated with allopurinol compared to those who did not receive allopurinol. CONCLUSIONS: 6MP is extensively metabolized in patients with NHL treated with HD-6MP. Thiopurine methylation, at the levels of nucleotide, nucleoside, and base, is an important metabolic pathway after HD-6MP. Co-administration of allopurinol can result in both a decreased catabolism and anabolism of 6MP compared to treatment with HD-6MP alone. This observation may have consequences for the therapeutic efficacy and toxic effects of 6MP in combination with allopurinol.

Allopurinol↗
PubMed1995

Determination of extracellular and intracellular thiopurines and methylthiopurines by high-performance liquid chromatography.

The thiopurine antimetabolites 6-thioguanine and 6-mercaptopurine are important chemotherapeutic drugs in the treatment of childhood acute lymphoblastic leukaemia. Measurement of metabolites of these thiopurines is important because correlations exist between levels of these metabolites and the prognosis in childhood acute lymphoblastic leukaemia. The reversed-phase method for the determination of extracellular thiopurine nucleosides and bases was previously developed and has been modified such that methylthiopurine nucleosides, bases, thioxanthine and thiouric acid can be measured also. The anion-exchange method enables the determination of intracellular mono-, di- and triphosphate (methyl)thiopurine nucleotides in one run. Extraction on ice with perchloric acid and dipotassium hydrogenphosphate results in good recoveries for (methyl)thiopurine nucleotides in lymphoblasts and peripheral mononuclear cells and for methylthioinosine nucleotides in red blood cells. Measurement of the low concentrations of mono-, di- and triphosphate thioguanine nucleotides in red blood cells (detection limit 20 pmol/10(9) cells) is possible after extraction with methanol and methylene chloride, followed by oxidation of thioguanine nucleotides with permanganate and fluorimetric detection.

Calibration↗
PubMed1995

Reversal of methylmercaptopurine ribonucleoside cytotoxicity by purine ribonucleosides and adenine.

6-Methylmercaptopurine ribonucleoside-5'-phosphate (MeSPuRMP), the sole metabolite of 6-methylmercaptopurine ribonucleoside (MeSPuRib), is a strong inhibitor of purine de novo synthesis, inducing depletion of intracellular purine nucleotides and subsequent cell death in several tumor cell lines. In this study prevention of MeSPuRib cytotoxicity by compounds of the purine salvage pathway was studied in Molt F4 human malignant T-lymphoblasts. Adenosine, adenine and inosine were able to prevent depletion of the adenine nucleotide pool when used in combination with 0.5 microM MeSPuRib, but had virtually no effect on depletion of guanine nucleotides. Nevertheless, these three purine compounds were able to reduce the cytotoxic effects induced by MeSPuRib. Addition of guanosine to cells treated with 0.5 microM MeSPuRib normalized the guanine nucleotide pool, but adenine nucleotides remained depleted. Under these conditions, inhibition of cell growth was significantly decreased. With the combination of guanosine and 10 microM MeSPuRib, cytotoxicity was increased compared to 10 microM MeSPuRib alone, associated with a depletion of adenine nucleotides to 9% of untreated cells. Since cell growth and cell viability of Molt F4 cells are less inhibited by MeSPuRib under conditions where adenine nucleotide depletion is prevented by purine compounds (and where the other nucleotides are depleted) we conclude that depletion of adenine nucleotides is an important factor in MeSPuRib cytotoxicity.

Adenine↗
PubMed1994

Decrease in S-adenosylmethionine synthesis by 6-mercaptopurine and methylmercaptopurine ribonucleoside in Molt F4 human malignant lymphoblasts.

6-Mercaptopurine (6-MP) and methylmercaptopurine ribonucleoside (Me-MPR) are purine anti-metabolites which are both metabolized to methylthio-IMP (Me-tIMP), a strong inhibitor of purine synthesis de novo. Me-MPR is converted directly into Me-tIMP by adenosine kinase. 6-MP is converted into tIMP, and thereafter it is methylated to Me-tIMP by thiopurine methyltransferase, an S-adenosylmethionine (S-Ado-Met)-dependent conversion. S-Ado-Met is formed from methionine and ATP by methionine adenosyltransferase, and is a universal methyl donor, involved in methylation of several macromolecules, e.g. DNA and RNA. Therefore, depletion of S-Ado-Met could result in an altered methylation state of these macromolecules, thereby affecting their functionality, leading to dysregulation of cellular processes and cytotoxicity. In this study the effects of 6-MP and Me-MPR on S-Ado-Met, S-adenosylhomocysteine (S-Ado-Hcy), homocysteine and methionine concentrations are determined. Both drugs cause a decrease in intracellular S-Ado-Met concentrations and an increase in S-Ado-Hcy and methionine concentrations in Molt F4 human malignant lymphoblasts. The effects of both 6-MP and Me-MPR can be ascribed to a decreased conversion of methionine into S-Ado-Met, due to the ATP depletion induced by the inhibition of purine synthesis de novo by Me-tIMP. Both 6-MP and Me-MPR thus affect the methylation state of the cells, and this may result in dysregulation of cellular processes and may be an additional mechanism of cytotoxicity for 6-MP and Me-MPR.

Adenosine Triphosphate↗