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Biomedical subjects

R Roeder

Publications and source records attributed to R Roeder.

15 recordsLinked to original sources
PubMed2005

Ventricular fibrillation frequency.

BACKGROUND: Ventricular-fibrillation (VF) wave frequency is known to decrease with prolonged, untreated VF. VF wave frequency is used as an algorithm to identify VF in AEDs and ICDs; yet the nature of the frequency change is not appreciated. METHODS: In this study, anesthetized pigs were used and VF was induced electrically. VF wave frequency was measured each second during VF for periods up to 200 sec. Defibrillation was achieved with transchest electrodes. VF wave frequency was plotted for each second during VF. In 2 animals, CPR was applied and VF wave frequency was measured. RESULTS: In all cases VF wave frequency decreased with increasing duration of VF. At the onset of VF, the VF wave frequency ranged from 5 to 12/sec. A plot of the normalized ratio of VF wave frequency during fibrillation to the VF frequency at induction decreased to between 0.1 and 0.8 of the initial frequency. In one of the animals, VF was initiated, CPR was provided and the VF wave frequency was measured over a 200-second period. Then, the procedure was repeated without CPR. Beyond 130 seconds, the VF frequency with CPR was higher than that without CPR, indicating myocardial oxygenation. CONCLUSION: Those who use VF wave frequency to identify the presence of VF should be aware of the nature of the VF wave frequency decrease with the passage of time.

Animals↗
PubMed2001

Genes for human general transcription initiation factors TFIIIB, TFIIIB-associated proteins, TFIIIC2 and PTF/SNAPC: functional and positional candidates for tumour predisposition or inherited genetic diseases?

TFIIIB, TFIIIC2, and PTF/SNAPC are heteromultimeric general transcription factors (GTFs) needed for expression of genes encoding small cytoplasmic (scRNAs) and small nuclear RNAs (snRNAs). Their activity is stimulated by viral oncogenes, such as SV40 large T antigen and Adenovirus E1A, and is repressed by specific transcription factors (STFs) acting as anti-oncogenes, such as p53 and pRb. GTFs role as final targets of critical signal transduction pathways, that control cell proliferation and differentiation, and their involvement in gene expression regulation suggest that the genes encoding them are potential proto-oncogenes or anti-oncogenes or may be otherwise involved in the pathogenesis of inherited genetic diseases. To test our hypothesis through the positional candidate gene approach, we have determined the physical localization in the human genome of the 11 genes, encoding the subunits of these GTFs, and of three genes for proteins associated with TFIIIB (GTF3BAPs). Our data, obtained by chromosomal in situ hybridization, radiation hybrids and somatic cell hybrids analysis, demonstrate that these genes are present in the human genome as single copy sequences and that some cluster to the same cytogenetic band, alone or in combination with class II GTFs. Intriguingly, some of them are localized within chromosomal regions where recurrent, cytogenetically detectable mutations are seen in specific neoplasias, such as neuroblastoma, uterine leyomioma, mucoepidermoid carcinoma of the salivary glands and hemangiopericytoma, or where mutations causing inherited genetic diseases map, such as Peutz-Jeghers syndrome. Their molecular function and genomic position make these GTF genes interesting candidates for causal involvement in oncogenesis or in the pathogenesis of inherited genetic diseases.

Chromosome Mapping↗
PubMed2001

Measurement of the direct-current (Faradic) resistance of the electrode-electrolyte interface for commonly used electrode materials.

The direct-current (Faradic) resistance is important because it is the highest impedance that an electrode-electrolyte interface can attain. In this study, the Faradic resistance (Rf) of identical pairs of 0.5 cm2 electrodes of bare and chlorided silver, tin and chlorided tin, nickel-silver, copper, and carbon was measured in contact with 0.9% saline at room temperature. It was found that for positive and negative current flow, the data fit the expression Rf=Rf0 e(-alpha i) (with a high coefficient of determination), where Rf0 is the zero-current Faradic resistance and alpha is a constant that describes the manner in which Rf decreases with increasing current (i). It was found that chlorided silver exhibited the lowest Rf0; removing the chloride deposit increased Rf0 by more than sixfold. Likewise, chloriding tin reduced Rf0 by a factor of about 2. Electrolytically cleaning an electrode reduced Rf0. The highest value for Rf0 was for carbon. This paper concludes with a summary of the data for Rf0 scaled to 1 cm2 electrode area for the electrode materials measured in the present study and data from the published literature.

Biomedical Engineering↗
PubMed2000

Burst pressure of canine carotid arteries.

The burst pressure was measured on 40 freshly excised, unstretched carotid arteries derived from dogs ranging in weight from 20-25 kg. Each carotid artery specimen was tied to the nozzle of a high-pressure nitrogen tank and regulator. The pressure was slowly increased until the artery burst. The burst pressure ranged from 2400 to 6500 mmHg, a value well above typical mammalian systolic pressure.

Animals↗
PubMed1999

Compliance, elastic modulus, and burst pressure of small-intestine submucosa (SIS), small-diameter vascular grafts.

Small-intestine submucosa (SIS) is cell-free collagen, 100 mu thick, derived from the small intestine. It has been used as a vascular graft and has the highly desirable property of remodeling itself to become host tissue. To date there has been limited reporting on its preimplantation mechanical properties as a vascular graft. In this study, compliance, elastic modulus, and burst pressure have been measured on 5- and 8-mm SIS grafts. The compliance (percent of diameter increase for a pressure rise from 80 to 120 mmHg) was 4.6% av (range 2.9 to 8.6%) for the 5-mm grafts. For the 8-mm graft, the increase in diameter for the same pressure rise was 8.7% av (range 7.2 to 9.5%). The modulus of elasticity (E) increased exponentially with increasing pressure according to E = E(o)e(alphaP), where Eo is the zero-pressure modulus and alpha is the exponent that describes the rate of increase in E with pressure; the units for E, Eo, and P are g/cm2. The mean value for Eo was 4106 (g/cm2 range 1348-5601). The mean value for alpha was 0.0059 (range 0.0028-0.0125). At 100 mmHg, the mean value for E was 8.91 x 10(3) g/cm2 (range 1.02-8.80 x 10(3)). The mean burst pressure for 5.5-mm grafts was 3517 mm Hg (range 2069-4654). In terms of preimplant compliance, the small-diameter SIS graft is about (1/2) as compliant as the dog carotid artery, about four times more compliant than a typical vein graft, and more than an order of magnitude more compliant than synthetic vascular grafts.

Animals↗
PubMed1999

Specialty contact capitation.

Contact capitation is an emerging new payment method for risk contracts that aligns incentives among physicians, protects individual physicians from their colleagues' less efficient practice patterns, and allows physicians to share in the rewards of their own clinical effectiveness. Contact capitation is working in a variety of settings and developing a track record as a payment method to help ailing independent physician associations, physician-hospital organizations, health plans, and other risk-bearing entities.

Capitation Fee↗
PubMed1998

The hepatitis B virus X protein is a co-activator of activated transcription that modulates the transcription machinery and distal binding activators.

Hepatitis B virus X protein (HBx) transactivates viral and cellular genes through a wide variety of cis-elements, but the mechanism has not been well elucidated. Evidence for nuclear events in HBx transactivation has been reported. Here we examine the role of HBx in modulation of transcription with a transient transfection system and an in vitro transcription assay. Reporters bearing Gal4-binding sites were applied to avoid the effects of endogenous transcription factors with or without signaling processes. The Gal4-DNA binding domain fused form of HBx exhibited no effect on Gal4-responsive reporters. However, HBx augmented activated transcription by transcriptional activators, suggesting HBx retains a co-activator but not a transcriptional activator function. The functional domain for co-activation was the same as that for HBx transactivation, and the transcription factor IIB- and RNA polymerase II subunit 5-interacting sites of HBx, which were critical for HBx transactivation, were shown to be crucial for the co-activation function. Importantly, HBx stimulated transcription on templates bearing the X responsive elements in vitro with endogenous activators. These results imply that HBx acts as a co-activator that modulates transcriptional machinery and distal-binding activators, which may explain one of the mechanisms of transactivation by HBx when localized in nuclei.

DNA-Directed RNA Polymerases↗
PubMed1998

Genomics and transcription analysis of human TFIID.

TFIID, a multisubunit protein comprised of TBP (TATA box-binding protein) and TAF(II)s (TBP-associated factors), has a central role in transcription initiation at class II promoters. TAF(II)s role as mediators of regulatory transcription factors, such as pRb and p53, and their involvement in signal transduction pathways suggest that some may participate in the control of cell proliferation and differentiation: therefore, they could be considered potential protooncogenes or antioncogenes. With the aim of starting to analyse these potential roles, we have determined the genomic position of nine human TAF(II) genes (TAF[II]250, TAF[II]135, TAF[II]100, TAF[II]80, TAF[II]55, TAF[II]43, TAF[II]31, TAF[II]28, TAF[II]20/15) and of two previously unknown sequences related to TAF(II)250 and TAF(II)31, respectively. Except for those encoding TAF(II)250 and TAF(II)31, these genes are present in a single copy and, with the exclusion of those for TAF(II)43 and TAF(II)28 (both at 6p21), are localized in different segments of the genome. Indeed, six of them map to a chromosomal region commonly altered in specific neoplasias, which defines them as candidates for involvement in oncogenesis. Our experiments also demonstrate that TAF(II) transcripts are synthesized ubiquitously, mostly at low levels similar to those of TBP. Interestingly, the amount of the major mRNA species detected by TAF(II)20/15 cDNA is higher, which suggests that the polypeptide it encodes may also perform functions independently of TFIID. TAF(II) isoforms, indicated by additional bands on Northern blots, may play a role in modulation of TFIID function. These data will be useful for analysing variations of TAF(II) mRNA phenotype during cell proliferation, differentiation and development, both normal and pathological.

Animals↗
PubMed1996

Interaction of the human T-cell lymphotropic virus type 1 tax transactivator with transcription factor IIA.

The Tax protein of human T-cell lymphotropic virus type 1 (HTLV-1) is a 40-kDa transcriptional activator which is critical for HTLV-1 gene regulation and virus-induced cellular transformation. Tax is localized to the DNA through its interaction with the site-specific activators cyclic AMP-responsive element-binding protein, NF-kappaB, and serum response factor. It has been suggested that the recruitment of Tax to the DNA positions Tax for interaction with the basal transcriptional machinery. On the basis of several independent assays, we now report a physical and functional interaction between Tax and the transcription factor, TFIIA. First, Tax was found to interact with the 35-kDa (alpha) subunit of TFIIA in the yeast two-hybrid interaction system. Importantly, two previously characterized mutants with point mutations in Tax, M32 (Y196A, K197S) and M41 (H287A, P288S), which were shown to be defective in Tax-activated transcription were unable to interact with TFIIA in this assay. Second, a glutathione-S-transferase (GST) affinity-binding assay showed that the interaction of holo-TFIIA with GST-Tax was 20-fold higher than that observed with either the GST-Tax M32 activation mutant or the GST control. Third, a coimmunoprecipitation assay showed that in HTLV-1-infected human T lymphocytes, Tax and TFIIA were associated. Finally, TFIIA facilitates Tax transactivation in vitro and in vivo. In vitro transcription studies showed reduced levels of Tax-activated transcription in cell extracts depleted of TFIIA. In addition, transfection of human T lymphocytes with TFIIA expression vectors enhanced Tax-activated transcription of an HTLV-1 long terminal repeat-chloramphenicol acetyltransferase reporter construct. Our study suggests that the interaction of Tax with the transcription factor TFIIA may play a role in Tax-mediated transcriptional activation.

Amino Acid Sequence↗
PubMed1994

New compensation strategies support quality initiatives.

Three significant trends will dramatically affect human resources management within the healthcare industry in the next decade: changing workforce demographics, declining reimbursement revenues, and increasing demands for high quality services. These trends will require healthcare organizations to develop compensation programs that tie the effectiveness of their human resources to productivity measurements, total quality management initiatives, and individual employee empowerment.

Demography↗
PubMed1988

Cellular transcription factors and regulation of IL-2 receptor gene expression by HTLV-I tax gene product.

Expression of the interleukin-2 receptor (IL-2R alpha) gene is activated by the transcriptional activator protein, Tax (previously referred to as the tat gene product), encoded by the human T-cell leukemia virus (HTLV-I). Multiple protein binding sites for specific DNA-protein interactions were identified over the upstream IL-2R alpha transcriptional regulatory sequences. However, only one region, which includes the sequence motif GGGGAATCTCCC, was required for activation by both the tax gene product and mitogenic stimulation. Remarkably, this sequence also bound the nuclear factor NF kappa B, which is important for induction of kappa-immunoglobulin gene expression. A model is presented whereby regulation of cellular gene expression by the HTLV-I tax gene product occurs via an indirect mechanism that may involve a post-translational modification of preexistent cellular transcription factors.

Base Sequence↗
PubMed1987

Origin of intramuscular nerve action potential.

The origin of the intramuscular nerve action potential (INAP) was investigated using conventional surface recording electrodes. The appearance of the INAP was (1) associated with subjective paresthesias, (2) recorded only when the reference electrode (G2) was over an appropriate digital nerve, (3) increased in latency as G2 was placed more distally, (4) blocked by an orthodromic sensory nerve action potential arising from the thumb, and (5) abolished with an anaesthetic block in the digital nerve proximal to G2. The findings indicate that the INAP is recorded by the G2 electrode from the digital nerve.

Action Potentials↗
PubMed1983

Three organizations of human DNA.

Human DNA was denatured, annealed to low C0t, and fractionated by centrifugation to equilibrium on gradients of NaI. Three well-defined zones resulted. The topmost, least dense zone contained satellite DNA. The bottom zone contained molecules bearing infrequent sequences and short repeated DNA. The middle zone contained molecules bearing infrequent sequences, short repeated DNA, and long repeated DNA. The NaI pattern was independent of single-strand DNA chain length from 5 to 30 kilobases. Structural genes were found in the organization bearing long repeats.

Base Sequence↗
PubMedDate not supplied

Criteria for the selection of materials for implanted electrodes.

There are four criteria that must be considered when choosing material for an implanted electrode: (1) tissue response, (2) allergic response, (3) electrode-tissue impedance, and (4) radiographic visibility. This paper discusses these four criteria and identifies the materials that are the best candidates for such electrodes. For electrodes that make ohmic contact with tissues: gold, platinum, platinum-iridium, tungsten, and tantalum are good candidates. The preferred insulating materials are polyimide and glass. The characteristics of stimulator output circuits and the importance of the bidirectional waveform in relation to electrode decomposition are discussed. The paper concludes with an analysis, the design criteria, and the special properties and materials for capacitive recording and stimulating electrodes.

Biocompatible Materials↗