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V de Haas

Publications and source records attributed to V de Haas.

13 recordsLinked to original sources
PubMed2002

The TEL-AML1 real-time quantitative polymerase chain reaction (PCR) might replace the antigen receptor-based genomic PCR in clinical minimal residual disease studies in children with acute lymphoblastic leukaemia.

Prospective studies in children with B-precursor acute lymphoblastic leukaemia (ALL) have shown that polymerase chain reaction (PCR)-based detection of minimal residual disease (MRD) using immunoglobin (Ig) and T-cell receptor (TCR) gene rearrangements as targets can be used to identify patients with a high relapse risk. The disadvantage of this approach is that for each patient preferably two different targets have to be identified. The t(12;21)(p13;q22) with the TEL-AML1 fusion gene is present in approximately 25% of children with B-precursor ALL. In these patients, sensitive reverse transcription (RT)-PCR analysis of the TEL-AML1 fusion transcript might be a more simple and less laborious alternative approach. However, it is unknown how stable the mRNA is and whether the number of transcripts per leukaemic cell remains constant during follow-up. We investigated whether the MRD results obtained using RT-PCR of TEL-AML1 transcripts correlated with the clinically validated genomic PCR for Ig and TCR gene rearrangements. Therefore, we used real-time quantitative (RQ)-PCR analysis for both types of targets and assessed the MRD levels in 36 follow-up bone marrow samples (obtained during the first 1.5 years after diagnosis) from 13 patients with B-precursor ALL. In 34/36 bone marrow samples the Ig/TCR RQ-PCR and TEL-AML1 RQ-PCR revealed equal levels of MRD and these results had a strong correlation (P < 0.0001, R2 = 0.84). Therefore, we conclude that the TEL-AML1 RQ-PCR can, in principle, replace Ig/TCR RQ-PCR in B-precursor ALL with t(12;21).

Child↗
PubMed2001

Quantification of minimal residual disease in children with oligoclonal B-precursor acute lymphoblastic leukemia indicates that the clones that grow out during relapse already have the slowest rate of reduction during induction therapy.

Antigen receptor gene rearrangements are applied for the PCR-based minimal residual disease (MRD) detection in acute lymphoblastic leukemia (ALL). It is known that ongoing rearrangements result in subclone formation, and that the relapsing subclone(s) can contain antigen receptor rearrangement(s) that differ from the rearrangements found in the major clone(s) at diagnosis. However, the mechanism leading to this so-called clonal evolution is not known, particularly at which time point in the disease the relapsing subclone obtains its (relative) therapy resistance. To obtain insight in clonal evolution, we followed the kinetics of several subclones in three oligoclonal ALL patients during induction therapy. Clone-specific nested PCR for immunoglobulin heavy chain or T cell receptor delta gene rearrangements were performed in limiting dilution assays on bone marrow samples taken at diagnosis, at the end of induction therapy and at possible relapse in three children with oligoclonal B-precursor ALL. We demonstrated that in all three patients the subclones were behaving differently in response to therapy. Moreover, in the two patients who relapsed, the clones that grew out during relapse showed the slowest regression or even evoluated during induction therapy and the clones that were not present at relapse showed good response to induction therapy. These results support the hypothesis that at least in some patients already at diagnosis or in the very first weeks, subclones have important differences in respect to resistance. Hence, these data give experimental evidence for the need to develop, during the first months after diagnosis, quantitative PCR assays for at least two different Ig/TCR gene rearrangement targets for every ALL patient.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Minimal residual disease studies are beneficial in the follow-up of TEL/AML1 patients with B-precursor acute lymphoblastic leukaemia.

The t(12;21)(p13;q22) translocation has been identified as the most common chromosomal abnormality in childhood acute lymphoblastic leukaemia (ALL). Initially, several investigators reported an excellent prognosis in paediatric leukaemias with this translocation, but other studies showed a 20% incidence in relapsed ALL. We performed an extensive analysis of 90 ALL patients. In 17 (19%) cases a TEL/AML1 fusion was found. However, this group was not representative as it included a high number of relapsed patients compared with the normal incidence in B-precursor ALL [54 in continuous complete remission (CCR) and 36 relapsed patients] and only a slightly better prognosis for TEL/AML1-positive patients was found (not significant) (four relapses in 17 TEL/AML1-positive patients vs. 32 relapses in 73 TEL/AML1-negative patients). Comparison of known prognostic factors (age, sex, ploidy, white blood cell count and immunophenotype) between relapsed TEL/AML1-positive and TEL/AML1-positive patients in CCR did not reveal differences, except that the white blood cell count was significantly higher in the relapsed group (P = 0.001). Time between diagnosis and relapse was not different for the relapsed TEL/AML1-positive group vs. the relapsed TEL/AML1-negative group. In 11 TEL/AML1-positive patients, the minimal residual disease (MRD) level at the end of induction therapy was quantified in a limiting dilution assay using IGH or TCRD junctional regions as polymerase chain reaction (PCR) targets. In all four relapsed patients, the level of MRD at the end of induction therapy was high (range 0.24-1.2%), whereas in all seven CCR patients, the MRD level was extremely low (0.02 to < 0.001%). In agreement with previous studies in which MRD levels at the end of induction therapy were found to be the strongest risk factor independent of other risk factors, in the present study we show that the MRD level remains a risk factor independent of the presence of a TEL/AML1 fusion gene.

Chromosomes, Human, Pair 12↗
PubMed1998

The success of dietary protein restriction in alkaptonuria patients is age-dependent.

Alkaptonuria is characterized by an increased urinary excretion of homogentisic acid, pigmentation of cartilage and connective tissues, and ultimately the development of inflammatory arthropathy. Various diets low in protein have been designed to decrease homogentisic acid excretion and to prevent the ochronotic pigmentation and arthritic lesions. However, limited information is available on the long-term beneficial effects of these diets. We reviewed the medical records of 16 patients aged 3-27 years (4 > 18 years) to ascertain the age of diagnosis, growth, development, social behaviour, signs of complications and longitudinal dietary compliance. The diagnosis of alkaptonuria was made at an average age of 1.4 years (2 months-4 years); following the diagnosis all patients were prescribed a diet with a protein content of 1.5 g/kg per day. All patients showed normal growth and development, and no major complications of the disease. Behavioural problems associated with poor dietary compliance emerged as the main problem. Dietary compliance decreased progressively with age. The effect of dietary protein restriction in homogentisic acid excretion was studied by fixing the amounts of protein in the diet at 1 g/kg per day and 3.5-5 g/kg per day during 8 days. Twelve patients, aged 4-27 years, participated in the investigation. Protein restriction resulted in a significantly lower excretion of homogentisic acid in the urine of children younger than 12 years (p < 0.01), whereas this effect was less obvious for adolescent and adult patients. The results suggest that restriction of protein intake may have a beneficial effect on alkaptonuric children; but continuation of this regimen to older age seems questionable and not practical.

Adolescent↗
PubMed1998

Real-time quantitative PCR for the detection of minimal residual disease in acute lymphoblastic leukemia using junctional region specific TaqMan probes.

Analysis of minimal residual disease (MRD) can predict outcome in acute lymphoblastic leukemia (ALL). A large prospective study in childhood ALL has shown that MRD analysis using immunoglobulin (Ig) and T cell receptor (TCR) gene rearrangements as PCR targets can identify good and poor prognosis groups of substantial size that might profit from treatment adaptation. This MRD-based risk group assignment was based on the kinetics of tumor reduction. Consequently, the level of MRD has to be defined precisely in follow-up samples. However, current PCR methods do not allow easy and accurate quantification. We have tested 'real-time' quantitative PCR (RQ-PCR) using the TaqMan technology and compared its sensitivity with two conventional MRD-PCR methods, ie dot-blot and liquid hybridization of PCR amplified Ig/TCR gene rearrangements using clone-specific radioactive probes. In RQ-PCR the generated specific PCR product is measured at each cycle ('real-time') by cleavage of a fluorogenic intrinsic TaqMan probe. The junctional regions of rearranged Ig/TCR genes define the specificity and sensitivity of PCR-based MRD detection in ALL and are generally used to design a patient-specific probe. In the TaqMan technology we have chosen for the same approach with the design of patient-specific TaqMan probes at the position of the junctional regions. We developed primers/probe combinations for RQ-PCR analysis of a total of three IGH, two TCRD, two TCRG and three IGK gene rearrangements in four randomly chosen precursor-B-ALL. In one patient, 12 bone marrow follow-up samples were analyzed for the presence of MRD using an IGK PCR target. The sensitivity of the RQ-PCR technique appeared to be comparable to the dot-blot method, but less sensitive than liquid hybridization. Although it still is a relatively expensive method, RQ-PCR allows sensitive, reproducible and quantitative MRD detection with a high throughput of samples providing possibilities for semi-automation. We consider this novel technique as an important step forward towards routinely performed diagnostic MRD studies.

Adult↗
PubMed1995

Treatment of keratoconjunctivitis sicca in dogs with cyclosporine ophthalmic ointment: a European clinical field trial.

The results are reported of a six-week clinical trial of the efficacy of 0.2 per cent cyclosporine ophthalmic ointment for the treatment of chronic idiopathic keratoconjunctivitis sicca in dogs in the United Kingdom, Germany and France. The 87 dogs were referral cases with a history of chronic unresponsive keratoconjunctivitis sicca of which the aetiology was unknown, and they had to meet stringent criteria before being included in the trial. The clinical response to the therapy was monitored after seven, 21 and 42 days and the results for the right and left eyes were analysed separately. There was a statistically significant increase in lacrimal secretion throughout the study, with most of the increase occurring during the first week of treatment. The percentage of eyes with improved lacrimal secretion was higher in the dogs with initial Schirmer tear test values > or = 2 mm/min than in those with initial values of 0 or 1 mm/min. The observed steady improvement in conjunctival health was not always correlated with an improvement in lacrimal secretion. The incidence of blepharospasm, other signs of discomfort and corneal oedema decreased significantly during the study. No improvement in corneal vascularisation or pigmentation was observed during the six-week trial. Overall, 76 per cent of the left eyes and 87 per cent of the right eyes were considered to have improved at the end of the treatment period. No serious adverse reactions were observed and only mild irritation was noticed by the owners immediately after the application of the ointment. This irritation resulted in the recording of an adverse reaction at the scheduled observations in only three cases.

Animals↗
PubMed1989

Sodium and potassium currents recorded during an action potential.

A simple method was used to measure directly sodium and potassium currents underlying the action potential in single nerve fibres of Xenopus laevis. A short rectangular stimulus under current-clamp conditions elicited an action potential which was digitally stored and later used as command when voltage-clamping the same fibre. The currents thus obtained nearly reproduced the original rectangular stimulus. Adding first 100 nM TTX and subsequently 100 nM TTX plus 10 mM TEA to the extracellular Ringer solution revealed the sodium and the potassium currents during an action potential. They were converted to permeabilities by use of the constant-field equation and are in good agreement with the curves which had been calculated from conventional voltage-clamp data. Thus experimentally determined currents and permeabilities are shown as they are changing during an action potential.

Action Potentials↗