Search PubMed⌕ Search

Biomedical subjects

P Arndt

Publications and source records attributed to P Arndt.

27 records · Page 2Linked to original sources
PubMed1995

Clinical significance of anti-At(a).

Ata is a high-frequency red blood cell (RBC) antigen. Anti-At(a) has been reported in rare At(a-) black subjects. We report two cases of anti-At(a). A clinically significant anti-At(a) was found in a 26-year-old black woman with systemic lupus erythematosus. The patient had a transfusion reaction with chills and nausea during a RBC survival study, and 95% of the radiolabeled At(a+) RBCs were destroyed within 3 h. A concurrently performed monocyte monolayer assay was strongly reactive. Anti-At(a) thus can cause rapid hemolysis of transfused RBCs, but At(a-) donor units are extremely scarce in rare donor registries. A second patient at our hospital had anti-At(a) which did not affect her newborn. She also had autoimmune disease, insulin-dependent diabetes mellitus.

Adult↗
PubMed1993

Combined electrical and acoustical stimulation using a bimodal prosthesis.

A new device incorporating a cochlear implant speech processor and a speech-processing hearing aid for the unimplanted ear has been designed and tested with four severely hearing-impaired patients. The aim of the device is to provide a more acceptable and effective combination of electrical and acoustic signals to the two ears. When used monaurally, and binaurally in conjunction with the cochlear implant, the speech-processing hearing aid mean scores for open-set sentences, words, and consonants were as good as or better than the mean scores for the patients' own conventional hearing aids. Some patients improved much more than did others. Although not conclusive, these results are encouraging, especially as they were achieved with a laboratory prototype that did not allow the patients to become accustomed to the processor in everyday situations.

Adult↗
PubMed1993

The effect of methyldopa and procainamide on suppressor cell activity in relation to red cell autoantibody production.

Kirtland et al (1980) suggested that methyldopa caused the production of red cell (RBC) autoantibodies by causing a persistent increase in lymphocyte cyclic AMP, which inhibited suppressor T cell function, leading to unregulated autoantibody production in some patients. They showed that significantly higher lymphocyte cyclic AMP concentrations were generated by lymphocytes from healthy donors after adding methyldopa, and by lymphocytes from patients who were receiving methyldopa compared to lymphocytes from healthy donors without methyldopa present. They also showed that methyldopa affected suppressor cell activity. We measured the effect of methyldopa and procainamide on suppressor cell activity, using a similar approach to Kirtland et al (1980). Suppressor cell activity was measured by measuring the amount of IgG, produced in vitro, by B cells following mitogen stimulation preceded by a 24 h incubation period. We found no significant increase in the amount of IgG generated by normal donor lymphocytes, when methyldopa or procainamide was present during the preincubation period. This is in contrast to the findings of Kirtland et al (1980). We also measured the amount of IgG generated in vitro by mitogen-stimulated lymphocytes from patients (with and without positive direct antiglobulin tests) taking methyldopa and compared this to the amount of IgG generated by lymphocytes from normal donors and patients (with and without positive direct antiglobulin tests). The results were similar for each group. This does not agree with the findings of Kirtland et al (1980) who found that lymphocytes from patients taking methyldopa produced more IgG in vitro than lymphocytes from normal donors. Our results do not support the hypothesis that methyldopa and procainamide induce autoantibodies by affecting suppressor cell function.

Autoantibodies↗
PubMed1991

Pediatric performance with the Nucleus 22-channel cochlear implant system.

Results from 80 pediatric subjects with 12 months of experience wearing the Nucleus multichannel cochlear implant are presented. The data suggest that children demonstrate statistically and clinically significant benefit across a broad spectrum of abilities with the implant. Significant postoperative improvement was demonstrated by 66 percent (51 of 77), 63 percent (45 of 72), and 46 percent (27 of 59) of subjects tested on suprasegmental (prosodic), closed-set and open-set tests, respectively. Forty-nine percent of subjects tested improved when lipreading was combined with sound from the implant, compared with lipreading alone. Children who were deaf at an early age or who had longer duration deafness tended to demonstrate poorer performance on the more difficult perceptual tasks after 12 months of implant experience. However, preliminary evidence suggests that continued improvements by congenital and prelinguistic subjects over longer periods of time may reduce performance differences between subjects with early and later onset deafness.

Adolescent↗
PubMedDate not supplied

Predicting the clinical significance of red cell alloantibodies using a monocyte monolayer assay.

Few data have been published that correlate in vitro monocyte monolayer assays (MMA) and red cell (RBC) survival in patients with alloantibodies of unknown significance. Over the past 6 years we gathered clinical correlations in 12 patients with the following antibodies: anti-Lan (three patients), -Ge (three patients), -Yta (five patients), and -Ytb (one patient). RBC survival was estimated using 51Cr studies in seven patients and follow-up of transfusion of incompatible blood in the other five. Six patients with no evidence of RBC destruction had negative MMA findings (anti-Lan [one patient], -Ge [two patients], and -Yta [three patients]). Five patients with evidence of in vivo RBC destruction had significant MMA results. The two clinically significant anti-Lans required fresh serum to give a meaningful MMA result. One patient (anti-Ytb) had an MMA result of borderline significance--normal 51Cr RBC survival at 1 hour--but a reduced T50Cr. The MMA we used appeared to predict the clinical outcome of transfusion in every patient with antibodies to high-frequency antigens whom we tested.

Erythrocyte Aging↗
PubMedDate not supplied

Evaluation of the optimal incubation temperature for detecting certain IgG antibodies with potential clinical significance.

It is commonly believed that IgG antibodies react optimally at 37 degrees C, but there are few published data supporting this. In this study, 140 antibodies from the Rh, Kell, Duffy, Kidd, and SsU blood groups were studied by a low-ionic-strength solution indirect antiglobulin technique at four different temperatures of incubation: 10, 22, 30, and 37 degrees C. Only titration score differences of greater than 10 were considered significant. None of the 140 antibodies sensitized red cells (RBC) significantly better at 10, 22, or 30 than at 37 degrees C. All antibodies, except one example of anti-c, sensitized RBCs as well at 30 as at 37 degrees C. At 22 degrees C, 100 percent of Kidd and SsU, 94 percent of Kell, and 82 percent of Duffy, but only 49 percent of Rh antibodies sensitized RBCs as well as they did at 37 degrees C. It is possible that these differences reflect the influence of antigenic structures and/or topography on the thermal dynamics of the antigen-antibody bond.

Autoanalysis↗
PubMedDate not supplied

Determination of zygosity using flow cytometric analysis of red cell antigen strength.

A flow cytometry method, developed in our laboratory to measure red cell (RBC)-bound IgG, was compared to the manual titration technique in the measurement of RBC antigen strength to determine zygosity. Parallel studies using antibodies to antigens in the Rh, Kell, Kidd, Ss, and Duffy systems were performed. The antisera (n = 20) were tested against five examples each of RBCs from apparent homozygotes and heterozygotes. The flow cytometry method was clearly superior, showing distinct differences, with no overlap of the ranges of results, between the reactions of RBCs from homozygotes and heterozygotes with 10 of 20 (50%) antisera. By the manual titration technique none of these sera clearly demonstrated dosage and 15 showed overlap of the ranges. It was obvious from the results that the commonly used manual titration technique for comparing the test RBCs with a single example of RBCs from a homozygote and heterozygote yielded inaccurate results.

Blood Group Antigens↗
PubMedDate not supplied

Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants.

A model of auditory performance and a model of ganglion cell survival in postlinguistically deafened adult cochlear implant users are suggested to describe the effects of aetiology, duration of deafness, age at implantation, age at onset of deafness, and duration of implant use. The models were compared with published data and a composite data set including 808 implant users. Qualitative agreement with the model of auditory performance was found. Duration of deafness had a strong negative effect on performance. Age at implantation had a slight negative effect on performance, increasing after age 60 years. Age at onset of deafness had little effect on performance up to age 60. Duration of implant use had a positive effect on performance. Aetiology had a relatively weak effect on performance.

Adolescent↗