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PubMed2002

Differences in pulse oximetry technology can affect detection of sleep-disorderd breathing in children.

UNLABELLED: Newer pulse oximeters have been developed to be motion resistant and thus have few false alarms. However, they have not yet been evaluated in a pediatric sleep laboratory setting. While evaluating new oximeters for use in our laboratory, we obtained simultaneous pulse oximetry data from two Masimo oximeters and from two Nellcor oximeters during nocturnal polysomnography in children referred for sleep-disordered breathing (SDB). In series 1, comprising 24 patients, comparisons were made between a Masimo oximeter with 4-second averaging time and the Nellcor N-200 oximeter set for 3 to 5 second averaging. A maximum of 20 events per patient were randomly selected for analysis, an "event" being a desaturation of > or = 4% registered by either oximeter. Interobserver agreement for event classification was 93%. Eighty-eight percent of 220 desaturation events occurring during wakefulness and 38% of 194 events occurring during sleep were classified as motion artifact on the Nellcor oximeter. Neither the Masimo oximeter nor the transcutaneous oxygen probe confirmed that the desaturation was real, in most of these cases. During sleep, there were 119 events detected by either or both oximeters: 113 (95%) by the Nellcor versus 82 (69%) by the Masimo. For these 119 events, the extent of desaturation was slightly less for the Masimo than the Nellcor oximeter, 4.5 +/- 2.4% versus 5.5 +/- 2.5%, respectively. In series 2, 22 patients were studied comparing a Masimo Radical oximeter with 2 second averaging to the Nellcor N-200 oximeter. The extent of desaturation was slightly greater for the Masimo oximeter. The Masimo oximeter detected more non-artifactual desaturation events occurring during sleep than the Nellcor oximeter, 90% versus 76% (chi2 = 9.9, p < 0.01). In series 3, comprising 128 events in 5 patients, a Nellcor N-395 oximeter detected fewer desaturations during non-movement, sleep periods and had more movement related "desaturation" events, compared to a Masimo Radical oximeter. CONCLUSIONS: The Masimo oximeters register many fewer false desaturations due to motion artifact. Using 4-second averaging, a Masimo oximeter detected significantly fewer SaO2 dips than the Nellcor N-200 oximeter but using 2-second averaging, the Masimo oximeter detected more SaO2 dips than the Nellcor N-200 oximeter. The sensitivity and motion artifact rejection characteristics of the Nellcor N-395 oximeter are not adequate for a pediatric sleep laboratory setting. These findings suggest that in a pediatric sleep laboratory, use of a Masimo oximeter with very short averaging time could significantly reduce workload and improve reliability of desaturation detection.

Adolescent↗
PubMed2002

Challenges with current technology for the detection, measurement and characterization of antibodies against biological therapeutics.

The primary concern with immunogenicity of biological products for manufacturers, regulatory agencies and clinicians is whether antibodies produced by patients receiving the product have clinical sequelae. However, the assessment of this concern is entirely dependent on the appropriate detection, measurement and characterisation of antibodies against biological therapeutics. The current assays for antibodies in biological fluids are prone to a wide range of technical difficulties in addition to scientific challenges in their interpretation. Problems such as matrix effects, selecting controls, antibody affinity, neutralizing capacity, antigen presentation and antigen/antibody complexes all require consideration in the design of antibody assays. Following the design of antibody assays, rigorous validation must be carried out to assure that the results they produce are meaningful. The relevance of quantitative measurement is particularly difficult to assess, as is the comparability of assay results between laboratories. Therefore considerable care is required in the design, execution, analysis and interpretation of antibody assays.

Antibodies↗
PubMed2003

New technologies for the detection of antibodies to therapeutic proteins.

The determination of antibody formation in response to a therapeutic product requires that a variety of data be evaluated. In addition to examining immuno-assay and bioassay results, it is important to determine any clinical relevance. By also examining pharmacokinetic data as well as other clinical results, an evaluation can be made as to whether any clinically relevant antibodies were generated. To help in this evaluation, it is important to fully characterize the antibodies that are generated. Both the BIAcore and IGEN platforms are powerful tools for determining if antibodies have been produced in a subject The BIAcore is also able to characterize these antibodies as to isotype, relative concentration, and relative affinity. The bioassay result can identify serum samples that contain an agent capable of inhibiting a biological effect of a drug. When combined with the results of an immuno-assay, it is possible to determine if the antibodies are capable of neutralizing the drug.

Antibodies↗
PubMed2000

Study of near infrared technology for intracranial hematoma detection.

Although intracranial hematoma detection only requires the continuous wave technique of near infrared spectroscopy (NIRS), previous studies have shown that there are still some problems in obtaining very accurate, reliable hematoma detection. Several of the most important limitations of NIR technology for hematoma detection such as the dynamic range of detection, hair absorption, optical contact, layered structure of the head, and depth of detection are reported in this article. A pulsed light source of variable intensity was designed and studied in order to overcome hair absorption and to increase the dynamic range and depth of detection. An adaptive elastic optical probe was made to improve the optical contact and decrease contact noise. A new microcontroller operated portable hematoma detector was developed. Due to the layered structure of the human head, simulation on a layered medium was analyzed experimentally. Model inhomogeneity tests and animal hematoma tests showed the effectiveness of the improved hematoma detector for intracranial hematoma detection.

Absorption↗
PubMed1994

The estrus detection problem: new concepts, technologies, and possibilities.

The single most important problem limiting high reproductive efficiency in the national dairy herd is poor detection of estrus. Failure to detect estrus or erroneous diagnosis of estrus results in an estimated annual loss of over $300 million to the dairy industry in the US. New technologies for the solution of this problem must be more effective than visual observation and aids currently used to detect estrus. Ideally, technologies that provide the solution for detection problems should provide the following: continuous (24 h/d) surveillance of the cow, accurate and automatic identification of cows in estrus, operation for the productive lifetime of the cow, minimized labor requirements, and high accuracy in identifying the appropriate physiologic or behavioral events that correlate highly with ovulation. New approaches are aimed at providing automation of detection of estrus using electronic technology. Pedometry, implantable impedance sensors, and surface-applied and implantable pressure sensors are in various stages of development and use.

Animals↗
PubMed2002

Critical evaluation of radiolabeled lymphocytes to detect acute renal transplant rejection in a large animal model.

BACKGROUND: Renal transplant rejection cannot be diagnosed with certainty by non-invasive techniques. These techniques lack the specificity to differentiate rejection from other causes of renal dysfunction such as ATN and calcineuria toxicity. Since rejection involves lymphocytes, which the other courses of dysfunction do not, radiolabeling lymphocytes is an attractive technique to diagnose rejection non-invasively. MATERIAL/METHODS: We report our experience with this technique in a pig model of renal transplantation. We studied two groups of pigs, one with renal autografts and the other with allografts. We optimized radiolabeling of lymphocytes and also the technology for detection of these lymphocytes. The uptake of the radiolabeled lymphocyte was compared between the two groups by surface detection and, at the end of the experiment, with scintigraphy of renal tissues. RESULTS: Despite adequate labeling and viability of lymphocytes, only 1-2% of injected lymphocytes 'homed' to the renal grafts. Furthermore, although the detection technology was optimized, a poor signal to noise ratio interfered with the detection of the labeled lymphocytes. Due to these problems rejection could not be differentiated from ATN in this model. CONCLUSIONS: We conclude that increasing the specific activity of the lymphocytes and improving the signal to noise ratio will enhance the specificity and sensitivity of this technique and facilitate non-invasive diagnosis of rejection.

Animals↗
PubMed2004

SNPWave: a flexible multiplexed SNP genotyping technology.

Scalable multiplexed amplification technologies are needed for cost-effective large-scale genotyping of genetic markers such as single nucleotide polymorphisms (SNPs). We present SNPWave, a novel SNP genotyping technology to detect various subsets of sequences in a flexible fashion in a fixed detection format. SNPWave is based on highly multiplexed ligation, followed by amplification of up to 20 ligated probes in a single PCR. Depending on the multiplexing level of the ligation reaction, the latter employs selective amplification using the amplified fragment length polymorphism (AFLP) technology. Detection of SNPWave reaction products is based on size separation on a sequencing instrument with multiple fluorescence labels and short run times. The SNPWave technique is illustrated by a 100-plex genotyping assay for Arabidopsis, a 40-plex assay for tomato and a 10-plex assay for Caenorhabditis elegans, detected on the MegaBACE 1000 capillary sequencer.

Alleles↗
PubMed2000

Rapid and reliable quantification of minimal residual disease in acute lymphoblastic leukemia using rearranged immunoglobulin and T-cell receptor loci by LightCycler technology.

The detection of minimal residual disease (MRD) using immunoglobulin and T-cell receptor (TCR) rearrangements as PCR targets provides important prognostic information on the in vivo effectiveness of treatment in acute lymphoblastic leukemia (ALL). Here we report on the real-time quantification of MRD in 25 ALL patients using LightCycler technology. We designed and adapted allele-specific oligonucleotide (ASO)-PCR protocols that enabled the detection of >90% of the IGH, IGK, TCRD, and TCRG rearrangements observed in ALL patients. In all patients, at least two suitable markers could be identified (average, 3.4 markers/patient). We applied ASO-PCR with 35 immunoglobulin and TCR rearrangements (11 IGH, 6 IGK, 12 TCRG, and 6 TCRD) and compared the sensitivity and practicability of the LightCycler strategy with conventional ASO-PCR on a block thermocycler followed by quantification with gel electrophoresis. The LightCycler measured leukemia-specific PCR products at each cycle (real-time) by staining the PCR product with the DNA-binding dye SYBR Green I. LightCycler technology showed a higher sensitivity than the conventional method in eight cases, whereas the sensitivity of the other markers matched exactly. The detection level varied between 10(-4) and 10(-6) leukemic cells. Furthermore, we determined the MRD status of 27 bone marrow follow-up samples from 15 ALL patients by both methods and revealed comparable results. However, the LightCycler also allowed accurate quantification in samples containing relatively high levels (>10(-3)) of residual leukemia cells. The conventional ASO-PCR technique comprises various laborious and time-consuming PCR experiments and post-PCR steps to determine the number of cycles with the optimal linearity and sensitivity of the PCR. Real-time quantification through LightCycler technology obviates these post-PCR steps, provides the highest sensitivity via software analysis, and therefore represents a rapid, reliable, sensitive, and cost-effective technique for the routine monitoring of MRD in ALL patients.

Adult↗
PubMed2007

Digital quantification of mutant DNA in cancer patients.

PURPOSE OF REVIEW: The accumulation of somatic mutations is the major driving force for tumorigenesis. These mutations uniquely differentiate tumor cells from their normal counterparts. Mutations within tumor cells and mutant DNA released by tumor cells into blood, lymph, stool, tissues and other bodily compartments can thereby be used for cancer detection. Here we discuss technologies available for the detection and quantification of mutant DNA in clinical samples and the value of such measurements for patient management. RECENT FINDINGS: Conventional mutation detection technologies are either qualitative or only roughly estimate the abundance of mutant DNA molecules. Recently-developed approaches, however, use single molecule counting to determine the genotype of each individual member of a DNA population, providing a more accurate and precise digital output. SUMMARY: In this review, we discuss the clinical utility of mutant DNA quantification in cancer patients in the context of recent technical advances made in digital mutation detection.

DNA Mutational Analysis↗
PubMed1981

Sequential transcription-translation of simian virus 40 by using mammalian cell extracts.

Ribonucleic acids (RNAs) transcribed in vitro by using the whole-cell extract system of Manley et al. (Proc. Natl. Acad. Sci. U.S.A. 77:3855-3859, 1980) were tested for their efficiency and fidelity in directing protein synthesis in reticulocyte lysates. Simian virus 40 deoxyribonucleic acid (DNA), cleaved by various restriction endonucleases, was used as the template. Successful translation of the small tumor antigen t, as well as the capsid proteins VP1, VP2, and VP3, was detected by immunoprecipitation analysis. Although no synthesis of large T antigen was detected, use of this technology allows detection of large T synthesis resulting from the correct splicing of as little as 0.2% of the in vitro RNA transcripts, making it ideal for use as an in vitro splicing assay. Transcripts synthesized in vitro were used as messages at least as efficiently as were viral messenger RNA's (mRNA's) synthesized in vivo; and in the case of small t, there was more efficient translation of small t mRNA synthesized in vitro than of small t mRNA synthesized in vivo. The transcripts that served as mRNA's for the various polypeptides were identified by using the following two criteria. (i) The sensitivity of synthesis of a given protein to digestion of the template DNA with restriction enzymes allowed the localization of the promoter and coding regions. (ii) Translation of size-fractionated RNA allowed confirmation of the transcript-mRNA assignments. With these techniques we found that VP2, VP3 and, in some cases, VP1 synthesis resulted from the initiation of translation at internal AUG codons. In fact, families of polypeptides were produced by initiation of translation at AUG codons within sequences coding for VP1 and T, presumably as a result of transcription initiation events that generated 5' ends immediately upstream from these AUGs. Application of this technology for the identification of coding regions within cloned DNA fragments is discussed.

Animals↗