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Biomedical subjects

R Hood

Publications and source records attributed to R Hood.

13 recordsLinked to original sources
PubMed2001

Functional expression of a GFP-tagged Kv1.5 alpha-subunit in mouse ventricle.

The experiments here were undertaken to determine the feasibility of increasing the cell surface expression of voltage-gated ion channels in cardiac cells in vivo and to explore the functional consequences of ectopic channel expression. Transgenic mice expressing a green fluorescent protein (GFP)-tagged, voltage-gated K+ (Kv) channel alpha-subunit, Kv1.5-GFP, driven by the cardiac-specific alpha-MHC promoter, were generated. In recent studies, Kv1.5 has been shown to encode the micromolar 4-aminopyridine (4-AP)-sensitive delayed rectifier K+ current (I(K,slow)) in mouse myocardium. Unexpectedly, Kv1.5-GFP expression is heterogeneous in the ventricles of these animals. Although no electrocardiographic abnormalities were evident, expression of Kv1.5-GFP results in marked decreases in action potential durations in GFP-positive ventricular myocytes. In voltage-clamp recordings from GFP-positive ventricular myocytes, peak outward K+ currents are significantly higher, and their waveforms are distinct from those recorded from wild-type cells. Pharmacological experiments revealed a selective increase in a micromolar 4-AP-sensitive current, similar to the 4-AP-sensitive component of I(K,slow) in wild-type cells. The inactivation rate of the "overexpressed" current, however, is significantly slower than the Kv1.5-encoded component of I(K,slow) in wild-type cells, suggesting differences in association with accessory subunits and/or posttranslational processing.

Action Potentials↗
PubMed1999

Human granulocytic ehrlichiosis in Northern California: two case descriptions with genetic analysis of the Ehrlichiae.

We report two cases of human granulocytic ehrlichiosis (HGE) that occurred in northern California in summer 1998. Patients had fever, malaise, and myalgia, reported tick bites, had moderate thrombocytopenia, and had normal or slightly elevated liver enzyme activities. Ehrlichial inclusions were observed in the blood of one patient, and HGE-agent DNA was amplified by PCR from both patients. Genetically, the strains resembled horse isolates from northern California. The close spatial and temporal proximity of the two new cases may be due to a nidus of infection in the area or heightened surveillance by local physicians.

Animals↗
PubMed1999

Genome-scale cloning and expression of individual open reading frames using topoisomerase I-mediated ligation.

The in vitro cloning of DNA molecules traditionally uses PCR amplification or site-specific restriction endonucleases to generate linear DNA inserts with defined termini and requires DNA ligase to covalently join those inserts to vectors with the corresponding ends. We have used the properties of Vaccinia DNA topoisomerase I to develop a ligase-free technology for the covalent joining of DNA fragments to suitable plasmid vectors. This system is much more efficient than cloning methods that require ligase because the rapid DNA rejoining activity of Vaccinia topoisomerase I allows ligation in only 5 min at room temperature, whereas the enzyme's high substrate specificity ensures a low rate of vector-alone transformants. We have used this topoisomerase I-mediated cloning technology to develop a process for accelerated cloning and expression of individual ORFs. Its suitability for genome-scale molecular cloning and expression is demonstrated in this report.

Animals↗
PubMed1993

Mechanics of the occlusive arm cuff and its application as a volume sensor.

Although a common medical instrument, the mechanical function of an occlusive arm cuff has not been fully described in an engineering sense. The occlusive arm cuff is examined here using a mathematical mechanics model and experimental measurements. Cuff stretch was modeled by a nonlinear pressure-volume function. Air compression was represented by Boyle's law. An apparatus was developed to measure pressure due to the air volume pumped into the cuff for fixed arm volume. Data were obtained for two different cuff designs, and reveal a nonlinear cuff pressure-volume relationship that could be represented accurately by the mathematical model. Calibration constants are provided for the two types of occlusive cuff. Thus, the cuff pressure was found to consist of a balance between that produced by stretch of the elastic cuff bladder and that of the compression of the air contained within the bladder. The use of the gas law alone was found to be inadequate to represent the cuff mechanics. When applying the cuff to measure change in arm volume, such as during plethysmography or oscillometry, it cannot be assumed that the cuff sensitivity is constant. More precisely, it was found that the occlusive cuff is a transducer with a volume sensitivity that increases with cuff pressure and volume until it becomes nearly constant at high levels of cuff pressure (150 mmHg). A hypothetical case of a linear elastic artery with constant pulse pressure was used as input to the cuff model to illustrate the change in cuff pressure oscillations that occurs while cuff pressure is released.(ABSTRACT TRUNCATED AT 250 WORDS)

Arm↗
PubMed1990

Health knowledge and beliefs as predictors of intended condom use among Zimbabwean adolescents in probation/remand homes.

The association of AIDS knowledge, perceived susceptibility to HIV, efficacy of preventive measures, severity of HIV infection, cues to action, barriers to action and alcohol/drug use with intended condom use was examined among Zimbabwean adolescents (mean age = 16.9) in probation/remand homes. Eighty-six percent of males and 83% of females were reportedly sexually experienced of whom 28% of males and 14% of females reported consistent condom use. Those who knew that babies can be born with AIDS, that there is no vaccine against HIV and that traditional healers cannot cure AIDS were 2.50, 2.32 and 1.97 times as likely to definitely intend to use condoms. Individuals who believed condoms seldom break or leak and are effective against HIV were 4.12 and 4.65 times as likely to definitely intend to use them. Those who believed parents and boyfriend/girlfriends thought condoms should be used were 2.27 and 2.13 times as likely to intend to use them. Respondents who had talked about AIDS with friends, with their boyfriend/girlfriend or a schoolteacher or seen a picture or film of a PWA were, in comparison to those who had not engaged in these actions, 3.70, 2.33, 2.43 and 2.50 times as likely to definitely intend to use condoms. Those who were embarrassed to get condoms from a clinic, thought persons who use condoms are loose and or that the pleasure of unprotected sex was worth the risk of HIV were 3.87, 3.42 and 3.40 times as likely to intend to use condoms. Logistic regression identified belief in efficacy of condoms as the principal predictor of intended condom use.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

New polyester arterial prostheses from Great Britain: an in vitro and in vivo evaluation.

Two models of knitted velour polyester prostheses have been developed in Great Britain, i.e. the VP1200K and the VP50K Triaxial. The evaluation of these new devices in vitro and in vivo in dogs has demonstrated that, while the first model has similar surgical, mechanical and healing characteristics in the short term to other commercial knitted velour prostheses, the second model has lower water permeability and superior strength and dimensional stability. On the basis of these results, clinical investigations can be undertaken.

Animals↗
PubMed1983

Epstein-Barr virus transcription in nasopharyngeal carcinoma.

Sequences which encode Epstein-Barr virus (EBV) RNA in nasopharyngeal carcinoma (NPC) tissue have been identified. We utilized human biopsy material directly as well as NPC grown in nude mice. Total RNA was extracted from the tumor material and separated into polyadenylated and nonpolyadenylated fractions by oligodeoxythymidylate-cellulose chromatography. This material was used as template to construct 32P-labeled cDNA. The labeled cDNAs were hybridized to Southern blots of recombinant EBV DNA fragments. Three of the biopsies, F, 49, and 55, contained polyadenylated RNA homologous to the EBV BamHI fragments V and K, and EcoRI-DIJhet. These same fragments encode the most abundant polyribosomal RNAs in latently infected lymphoblastoid cell lines. The sequences which encoded nonpolyadenylated RNA in NPC tumor 49 were more extensive and included BamHI fragments C, V, B, E, and K, and EcoRI fragments DIJhet, E, F, and G1, a result that indicates selective polyadenylation in EBV RNA processing. A fourth biopsy, NPC tumor 18, contained polyadenylated RNA homologous to the BamHI fragments H, B, K, Y, B1, I1, and A and EcoRI fragments F and G2. A similar pattern of transcription was identified in three tumor specimens from nude mice, 4, 5, and 8. Transformation of lymphocytes did not occur after cocultivation in vitro with explants from these nude mice tumors. This transcriptional pattern may represent an activated state of the EBV genome, formerly not detected in tumor tissue, which is analogous to the state of abortive infection identified in induced in vitro cell systems.

Animals↗
PubMed1978

Lower extremity amputation for ischemia.

Three hundred-twenty-four amputations of the lower extremity for ischemia at the University of Oregon Health Sciences Center over the past ten years are presented. Striking differences between the first and second five-year periods are noted in level of amputation. The primary healing rate of all patients in the two periods was similar. Diabetics tended to have more distal amputations but primary healing was lower than that of nondiabetics.

Amputation, Surgical↗
PubMedDate not supplied

Theory of the oscillometric maximum and the systolic and diastolic detection ratios.

It is proposed that the maximum in cuff pressure oscillations during oscillometry is due to the buckling of the brachial artery under a cuff. This theory is investigated by means of a mathematical model of oscillatometry that includes the mechanics of the occlusive arm cuff, the arterial pressure pulse waveform, and the mechanics of the brachial artery. A numerical solution is provided for the oscillations in cuff pressure for one cycle of cuff inflation and deflation. The buckling pressure is determined from actual arterial data and the von Mises buckling criteria. The buckling of an artery under a cuff occurs near -2 to 0 mm Hg transmural pressure. This effect corresponds with a maximum arterial compliance and maximum cuff pressure oscillations when cuff pressure is nearly equal to mean arterial pressure (MAP), in support of the suggested theory. The model was also found to demonstrate the basic characteristics of experimental oscillometry, such as an increasing and decreasing amplitude in oscillations as cuff pressure decreases, the oscillations that occur when cuff pressure is above systolic pressure, maximum oscillation amplitudes in the range of 1 to 4 mm Hg, and an oscillatory maximum at cuff pressure equal to MAP. These findings support the case that the model is representative of oscillometry. Finally, the model predicted values for the systolic and diastolic detection ratios of 0.593 and 0.717, respectively, similar to those found empirically. These ratios alter with blood pressure, but the tightness of the cuff wrap did not change their value.

Bias↗