Biomedical subjects

John P Miller

Publications and source records attributed to John P Miller.

6 recordsLinked to original sources

PubMed2004

Phased-array processing for spike discrimination.

We present a novel approach for the detection, discrimination, and identification of superimposed neuronal action potentials from multineuronal, multichannel extracellular nerve recordings with low signal-to-noise ratios. The approach uses phased-array processing techniques to identify the spikes from different neurons on the basis of their unique propagation velocities. We evaluated this new approach using simulated electrophysiological data, under conditions that are known to limit the effectiveness of existing spike discrimination techniques. This approach enabled discrimination of simulated spikes from multiple simultaneously active neurons with a high degree of reliability and robustness within the expected range of experimental recording conditions, even in situations where there was a high degree of spike waveform superposition on the recording channels. Moreover, the technique enables the reliable detection and discrimination of spikes recorded with signal-to-noise ratios less than 1.

Action Potentials↗

PubMed2004

Racial diversity with high nucleated cell counts and CD34 counts achieved in a national network of cord blood banks.

Banked, unrelated, partially HLA-matched, umbilical cord blood is an alternative stem cell source for patients in need of transplantation therapy who lack traditionally matched donors. A presumed advantage of cord blood is the ability to increase recruitment of donors of minority ethnic backgrounds. The American Red Cross Cord Blood Program was established in 1999 with 6 banks and 10 collection sites throughout the country. Cord blood donors self-report racial designations on questionnaires, and donor race was collected from each site. Postprocessing nucleated cell counts and CD34(+) counts were obtained on the cord blood units, and results from each racial group (white, black, Asian, Hispanic, and Native American) were compared in the natural logarithmic scale by using analysis of variance. A total of 18878 donors consented: 64% white, 16% black, 12% Hispanic, 4% Asian, 1% Native American, and 3% other. The Detroit area consented the highest percentage of black donors (87%), San Diego consented the highest percentage of Hispanic donors (59%), and Oakland consented the highest percentage of Asian donors (15%). Seven thousand eight hundred sixty-six cord blood units have been banked for transplantation. The mean preprocessing nucleated cell count was 1220 x 10(6) (range, 327-7300 x 10(6)). There was no difference among racial groups when controlled for site (P =.395). The mean CD34(+) count was 3.28 x 10(6). Blacks had a significantly lower CD34(+) count than the other racial/ethnic groups in the Midwest, Northwest, and North Carolina collection sites. A racially diverse cord blood bank can be achieved. Nucleated cell counts were similar among the different racial/ethnic groups. CD34(+) counts were lower for blacks in some collection sites.

Antigens, CD34↗

PubMed2004

Evidence that Hy- RBCs express weak Joa antigen.

BACKGROUND: RBCs of the Hy- phenotype have, in the past, been typed as Gy(a+w), Hy-, Jo(a-), and RBCs with the Jo(a-) phenotype type Gy(a+), Hy+w, and Jo(a-). Anti-Hy and anti-Joa are difficult to identify mainly because appropriate reagent RBCs are poorly characterized. Historically, anti-Joa has not reacted with RBCs with either phenotype. This report describes a case of an anti-Joa that shows Hy- RBCs express some Joa antigen, albeit weakly. CASE REPORT: Anti-Joa was identified in a serum sample of a 71-year-old woman. The antibody reacted 1+ to 2+ by the IAT with all untreated and ficin-treated panel RBCs and did not react with Gy(a-) RBCs and Jo(a-) RBCs. Unexpectedly, the serum sample reacted weakly with six of eight RBC samples with the Hy- phenotype. The anti-Joa was adsorbed onto and eluted from Hy- RBCs, indicating the presence of weak Joa antigen. The patient's RBCs typed Gy(a+), Hy+, Jo(a-). DNA studies using PCR-RFLP analysis showed the patient to be homozygous for the JO allele, which is consistent with the serologically determined Jo(a-) status. CONCLUSION: The DNA and serologic evidence of this case show that Hy- RBCs may express low levels of Joa antigen, which contradicts previously published data concerning the Joa type of Hy- RBCs.

Aged↗

PubMed2003

Perfluorooctanesulfonate and other fluorochemicals in the serum of American Red Cross adult blood donors.

Perfluorooctanesulfonyl fluoride-based products have included surfactants, paper and packaging treatments, and surface protectants (e.g., for carpet, upholstery, textile). Depending on the specific functional derivatization or degree of polymerization, such products may degrade or metabolize, to an undetermined degree, to perfluorooctanesulfonate (PFOS), a stable and persistent end product that has the potential to bioaccumulate. In this investigation, a total of 645 adult donor serum samples from six American Red Cross blood collection centers were analyzed for PFOS and six other fluorochemicals using HPLC-electrospray tandem mass spectrometry. PFOS concentrations ranged from the lower limit of quantitation of 4.1 ppb to 1656.0 ppb with a geometric mean of 34.9 ppb [95% confidence interval (CI), 33.3-36.5]. The geometric mean was higher among males (37.8 ppb; 95% CI, 35.5-40.3) than among females (31.3 ppb; 95% CI, 30.0-34.3). No substantial difference was observed with age. The estimate of the 95% tolerance limit of PFOS was 88.5 ppb (upper limit of 95% CI, 100.0 ppb). The measures of central tendency for the other fluorochemicals (N-ethyl perfluorooctanesulfonamidoacetate, N-methyl perfluorooctanesulfonamidoacetate, perfluorooctanesulfonamidoacetate, perfluorooctanesulfonamide, perfluorooctanoate, and perfluorohexanesulfonate) were approximately an order of magnitude lower than PFOS. Because serum PFOS concentrations correlate with cumulative human exposure, this information can be useful for risk characterization.

Adult↗

PubMed2003

Analysis of neural coding through quantization with an information-based distortion measure.

We discuss an analytical approach through which the neural symbols and corresponding stimulus space of a neuron or neural ensemble can be discovered simultaneously and quantitatively, making few assumptions about the nature of the code or relevant features. The basis for this approach is to conceptualize a neural coding scheme as a collection of stimulus-response classes akin to a dictionary or 'codebook', with each class corresponding to a spike pattern 'codeword' and its corresponding stimulus feature in the codebook. The neural codebook is derived by quantizing the neural responses into a small reproduction set, and optimizing the quantization to minimize an information-based distortion function. We apply this approach to the analysis of coding in sensory interneurons of a simple invertebrate sensory system. For a simple sensory characteristic (tuning curve), we demonstrate a case for which the classical definition of tuning does not describe adequately the performance of the cell studied. Considering a more involved sensory operation (sensory discrimination), we also show that, for some cells in this system, a significant amount of information is encoded in patterns of spikes that would not be discovered through analyses based on linear stimulus-response measures.

Air↗

PubMed2002

In utero or ex utero cord blood collection: which is better?

BACKGROUND: The relative nucleated cell count of umbilical cord blood (CB) correlates with improved engraftment and survival. This study compares two collection methods to assess CB content, including cell numbers. STUDY DESIGN AND METHODS: The Massachusetts CB bank used trained obstetricians and midwives to collect CB in utero before the delivery of the placenta. The banks in California, Ohio, Oregon, and Minnesota used trained American Red Cross (ARC) personnel who collected CB ex utero after the delivery of the placenta. All banks processed CB by RBC sedimentation and volume reduction. RESULTS: The volume and total nucleated cell count of collected CB before processing, as well as after processing CFU-GM and CD34+ cells, showed no advantage of either method. In utero collections resulted in more rejections of collected units (due to labeling problems, bacterial contamination, clotting, and delay between collection and processing) than ex utero collections. There were fewer medical exclusions after in utero collection. CONCLUSION: CB can be collected successfully using either the in utero or ex utero methods; both methods produce comparable nucleated cell, MNC, CD34+, and CFU-GM numbers. Bacterial contamination, low volume, clotting, and delay until processing are generally higher with in utero collection.

Adult↗