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Biomedical subjects

B Van Dijk

Publications and source records attributed to B Van Dijk.

7 recordsLinked to original sources
PubMed2004

Basic fitting and evaluation parameters of a newly designed cochlear implant electrode.

OBJECTIVE: To validate a newly designed cochlear implant electrode (TRACE) in the standard monopolar mode and compare it to a patient group implanted with a standard Nucleus Contour cochlear implant electrode. The electrode contacts of the TRACE electrode have the same active surface area for stimulation, but the position in the scala tympani is different from that of the Nucleus Contour electrode. MATERIAL AND METHODS: The following parameters, used in cochlear implant fitting and evaluation procedures, were determined: the threshold and comfort stimulation current levels; the electrode impedances; and the phoneme discrimination and speech recognition scores using the ACE speech algorithm. CONCLUSION: The new electrode does not differ significantly from the standard Nucleus Contour electrode in terms of the investigated parameters within the test group.

Acoustic Impedance Tests↗
PubMed1990

Allogeneic bone marrow transplantation for leukemia with marrow grafts depleted of lymphocytes by counterflow centrifugation.

Eighty consecutive patients were transplanted with human leukocyte antigen (HLA)-identical sibling marrow for acute myelogenous leukemia (AML, N = 29), acute lymphoid leukemia (ALL, N = 23), or chronic myelogenous leukemia (CML, N = 28). Donor marrow was depleted of lymphocytes using counterflow centrifugation. Median age of the recipients was 31 years. Pretransplant conditioning consisted of cyclophosphamide and fractionated total body irradiation (TBI) with a low (4.1 +/- 0.3 cGy/min) or high (13.1 +/- 1.6 cGy/min) midline average dose rate. In 43 patients, cytosine-arabinoside or anthracyclines were added to the conditioning regimen. Immunoprophylaxis posttransplant consisted of methotrexate (MTX) alone, cyclosporine A (CsA) in combination with MTX, or CsA alone; two patients received no immunoprophylaxis at all. Graft failure occurred in 4 of 77 evaluable patients (5%). The probability of acute graft-versus-host disease (GVHD) greater than or equal to grade 2 at day 100 after transplantation was 15%. The projected 3-year estimate of extensive chronic GVHD was 12%. Only three patients died of cytomegalovirus-interstitial pneumonitis. The projected 3-year probability of relapse was 30% (95% confidence interval [CI], range 8% to 53%) in transplants for AML in first complete remission (CR1), 35% (95% CI, 1% to 69%) after transplantation for ALL in CR1, and 38% (95% CI, 2% to 74%) after transplantation for CML in first chronic phase (CP1). The projected 3-year probability of leukemia-free survival (LFS) was 56% (95% CI, 35% to 77%) after transplantation for AML-CR1, 42% (95% CI, 16% to 69%) in patients transplanted for ALL-CR1, and 49% (95% CI, 18% to 80%) after transplantation for CML-CP1. After transplantation for AML-CR1, ALL-CR1, or CML-CP1, the median follow-up time for leukemia-free survivors was 31+, 30+, and 21+ months, respectively. Probabilities of relapse, survival, and LFS in AML-CR1 and ALL-CR1 transplants were comparable with those reported in recipients of untreated grafts. In patients transplanted for CML-CP1, probability of relapse was higher and probability of LFS was lower than in recipients of untreated grafts. In transplants for leukemia in CR1 and CP1, preparative regimen and immunoprophylaxis posttransplant were not associated significantly with the probability of acute GVHD greater than or equal to grade 2, extensive chronic GVHD, relapse, survival, or LFS. In bone marrow transplantation for leukemia, counterflow centrifugation is a useful technique for the prevention of GVHD.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

Mixed hematopoietic chimerism after allogeneic transplantation with lymphocyte-depleted bone marrow is not associated with a higher incidence of relapse.

Using red cell phenotyping, cytogenetic analysis of blood lymphocytes, chromosome studies of bone marrow cells, and restriction fragment length polymorphism (RFLP) studies of peripheral blood cells, we demonstrated a high number of mixed chimeras after allogeneic bone marrow transplantation (BMT). Donor marrow from HLA-A, -B, and -DR identical, mixed lymphocyte culture (MLC) nonreactive siblings was depleted of 98% of lymphocytes using counterflow centrifugation. Thirty-two of 48 recipients (67%) appeared to be mixed chimeras at 6 months after transplantation. The high number of mixed chimeras is probably a result of lymphocyte depletion of the marrow graft and the high sensitivity of red cell phenotyping for the demonstration of minor cell populations (at levels as low as 0.01%). The probability of relapse-free survival from 6 months to 4 years after BMT was 85% for the mixed chimeras and 65% for the complete donor chimeras. We conclude that in this study, mixed chimerism is not associated with a higher incidence of relapse.

Adolescent↗
PubMed1984

Pattern ERG of the cat.

Recent reports on pattern ERGs reopened the discussion of pattern or luminance origin of the ERG to pattern reversal stimulation. In this report cat ERGs to checkerboard stimuli were recorded. The stimulus parameters were manipulated in order to vary the strength of local luminance and contrast stimulation independently. Special care was taken to eliminate stray light effects. The results clearly show that pattern specific components in the cat ERG, if present at all, are no greater than the variance of the responses from local luminance nonlinearities. Thus a "Pattern ERG" can be recorded by luminance modulation.

Action Potentials↗
PubMedDate not supplied

Motion onset-offset VEPs in children.

We analysed motion onset-offset visually evoked potentials (VEPs), pattern appearance-disappearance VEPs and pattern reversal VEPs recorded in 23 adults and 37 children, ranging in age from 5 to 12 years. Motion-specific responses (i.e., responses that could not be attributed to the changes in contrast that are associated with the onset and offset of motion) were found in 25 children (67.6%) and in 19 (83%) adults. These percentages do not differ significantly. Also the age distributions of children with and without motion-specific VEPs do not differ significantly. For these reasons no development of motion VEPs with age could be established, in contrast with the well-known maturation of the pattern appearance VEPs.

Child↗