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Biomedical subjects

E Barr

Publications and source records attributed to E Barr.

At least 37 records · Page 2Linked to original sources
PubMed1994

Stable delivery of physiologic levels of recombinant erythropoietin to the systemic circulation by intramuscular injection of replication-defective adenovirus.

A number of inherited and acquired serum protein deficiencies including hemophilias A and B, diabetes mellitus, and the erythropoietin-responsive anemias are currently treated with repeated subcutaneous or intravenous infusions of purified or recombinant proteins. The development of an in vivo gene-transfer approach to deliver physiologic levels of recombinant proteins to the systemic circulation would represent a significant advance in the treatment of these disorders. Here we describe the construction of a replication-defective adenovirus (AdEF1hEpo) containing the human erythropoietin (hEpo) cDNA under the transcriptional control of the cellular elongation factor 1 alpha (EF1 alpha) promoter and the 4F2 heavy chain (4F2HC) enhancer. Neonatal CD-1 and adult SCID mice injected once intramuscularly (i.m.) with 10(7) to 10(9) plaque-forming units (pfu) of this virus displayed significant dose-dependent elevations of serum hEpo levels and increased hematocrits, which were stable over the 4-month time course of these experiments. Adenovirus injected i.m. remained localized at the site of injection and there was no evidence of either systemic infection or a localized inflammatory response. These results suggest that i.m. injection of recombinant replication-defective adenovirus vectors may serve as a paradigm for the treatment of human serum protein deficiencies.

Adenoviridae↗
PubMed1994

Efficient catheter-mediated gene transfer into the heart using replication-defective adenovirus.

The ability to express recombinant genes in the coronary vasculature and the myocardium holds promise for the treatment of a number of acquired and inherited cardiovascular diseases. Previous in vivo gene transfer approaches in the heart have been limited by relatively low efficiencies of gene transduction. In this report, we demonstrate that catheter-mediated infusion of replication-defective adenovirus into the coronary arterial circulation in vivo represents a novel and efficient method for the induction of recombinant gene expression in both the coronary arteries and the myocardium. A single intracoronary infusion of 2 x 10(9) - 1 x 10(10) p.f.u. of adenovirus resulted in high level recombinant gene expression in both the coronary arteries and surrounding myocardium of adult rabbits for at least 2 weeks. No inflammatory response or myocardial necrosis was observed following the adenovirus infusions. The polymerase chain reaction (PCR) was used to assess the tissue distribution of infection following intracoronary infusion of adenovirus. Adenovirus DNA was detected by PCR in the livers, kidneys, lungs, brains and testes of animals 5 days after virus infusion. Percutaneous transluminal gene transfer (PTGT) into the heart by intracoronary infusion of replication-defective adenovirus represents a relatively non-invasive and efficient method of inducing recombinant gene expression both in the coronary arterial wall and in the surrounding myocardium.

Adenoviridae↗
PubMed1993

Skeletal troponin C reduces contractile sensitivity to acidosis in cardiac myocytes from transgenic mice.

Depressed contractile function plays a primary role in the pathophysiology of acute myocardial ischemia. Intracellular acidification is an important factor underlying the inhibition of force production in the ischemic myocardium. The effect of acidosis to depress contractility is markedly greater in cardiac as compared to skeletal muscle; however, the molecular basis of this difference in sensitivity to acidosis is not clearly understood. In this report, we describe transgenic mice that express the fast skeletal isoform of troponin C (sTnC) in cardiac muscle. In permeabilized single cardiac myocytes the shift in the midpoint of the tension-pCa relationship (i.e., pCa50, where pCa is -log[Ca2+]) due to lowering pH from 7.00 to 6.20 was 1.27 +/- 0.03 (n = 7) pCa units in control cardiac TnC (cTnC) expressing myocytes and 0.96 +/- 0.04 (n = 11) pCa unit in transgenic cardiac myocytes (P < 0.001). The effect of pH to alter maximum Ca(2+)-activated tension was unchanged by TnC isoforms in these cardiac myocytes. In a reciprocal experiment, contractile sensitivity to acidosis was increased in fast skeletal muscle fibers following extraction of endogenous sTnC and reconstitution with purified cTnC in vitro. Our findings demonstrate that TnC plays an important role in determining the profound sensitivity of cardiac muscle to acidosis and identify cTnC as a target for therapeutic interventions designed to modify ischemia-induced myocardial contractile dysfunction.

Acidosis↗
PubMed1992

Identification and characterization of a cardiac-specific transcriptional regulatory element in the slow/cardiac troponin C gene.

The slow/cardiac troponin C (cTnC) gene has been used as a model system for defining the molecular mechanisms that regulate cardiac and skeletal muscle-specific gene expression during mammalian development. cTnC is expressed continuously in both embryonic and adult cardiac myocytes but is expressed only transiently in embryonic fast skeletal myotubes. We have reported previously that cTnC gene expression in skeletal myotubes is controlled by a developmentally regulated, skeletal muscle-specific transcriptional enhancer located within the first intron of the gene (bp 997 to 1141). In this report, we show that cTnC gene expression in cardiac myocytes both in vitro and in vivo is regulated by a distinct and independent transcriptional promoter and enhancer located within the immediate 5' flanking region of the gene (bp -124 to +32). DNase I footprint and electrophoretic mobility shift assay analyses demonstrated that this cardiac-specific promoter/enhancer contains five nuclear protein binding sites (designated CEF1, CEF-2, and CPF1-3), four of which bind novel cardiac-specific nuclear protein complexes. Functional analysis of the cardiac-specific cTnC enhancer revealed that mutation of either the CEF-1 or CEF-2 nuclear protein binding site abolished the activity of the cTnC enhancer in cardiac myocytes. Taken together, these results define a novel mechanism for developmentally regulating a single gene in multiple muscle cell lineages. In addition, they identify previously undefined cardiac-specific transcriptional regulatory motifs and trans-acting factors. Finally, they demonstrate distinct transcriptional regulatory pathways in cardiac and skeletal muscle.

3T3 Cells↗
PubMed1991

Systemic delivery of recombinant proteins by genetically modified myoblasts.

The ability to stably deliver recombinant proteins to the systemic circulation would facilitate the treatment of a variety of acquired and inherited diseases. To explore the feasibility of the use of genetically engineered myoblasts as a recombinant protein delivery system, stable transfectants of the murine C2C12 myoblast cell line were produced that synthesize and secrete high levels of human growth hormone (hGH) in vitro. Mice injected with hGH-transfected myoblasts had significant levels of hGH in both muscle and serum that were stable for at least 3 weeks after injection. Histological examination of muscles injected with beta-galactosidase-expressing C2C12 myoblasts demonstrated that many of the injected cells had fused to form multinucleated myotubes. Thus, genetically engineered myoblasts can be used for the stable delivery of recombinant proteins into the circulation.

Animals↗
PubMed1988

Overlap of granulomatous vasculitis and sarcoidosis: presentation with uveitis, eosinophilia, leg ulcers, sinusitis, and past foot drop.

A 24-year-old black woman with a history of pulmonary and hepatic sarcoidosis followed by foot drop presented with uveitis, eosinophilia, leg ulcers, and sinus opacification. Biopsy of the leg ulcer and review of the past lung biopsy revealed numerous epithelioid noncaseating granulomas and granulomatous vasculitis. Although her clinical presentation raised the possibility of Wegener's granulomatosis, the many discrete granulomas and lack of necrosis on her biopsies were more in favor of sarcoidosis. Although granulomatous vasculitis has been reported as part of necrotizing sarcoid granulomatosis, our patient was unique in the extent and type of her extrapulmonary symptomatology.

Adult↗
PubMed1986

Sources of trophic factors that induce limb regeneration and prevent amputation-induced neuronal death.

Segments of 2-, 4-, 6- and 8-day neural tube, or of 15-day peripheral nerve were implanted longitudinally into limb stumps of 4-day chick embryos whose right-wing buds were amputated at the future elbow region. Stumps of amputated limbs (ALs) implanted with 7-day heart or without implant served as controls. Effects of progressively older neural tube implants (NTIs) upon ALs and host spinal cord neurons were analyzed by area measurements of the peripheral limb field (PLF) and NTI and by cell counts of the host lateral motor column (LMC). Nine days postamputation, 2- and 4-day NTIs contained many neurons and induced epimorphic regeneration in more than one-fourth of the embryos. Six-day NTIs contained few neurons and induced only tissue regeneration. Eight-day NTIs and peripheral nerve containing only non-neuronal cells were as ineffective as controls in stimulating regeneration, although peripheral nerve did cause a significant increase in the peripheral field. The NTIs of all ages and implants of peripheral nerve were equally effective in protecting LMC neurons from amputation-induced cell death in the host spinal cord. The results may indicate that neurons of the implant induce limb regeneration and non-neuronal cells of the implant protect against LMC neuronal death.

Age Factors↗
PubMed1985

Opioid peptides increase calcium uptake by synaptosomes from brain regions.

The fast-phase calcium uptake by depolarized hippocampal synaptosomes was increased significantly following treatment with 10 nM or 10 microM D-Ala2,D-Leu5-enkephalin (DADLE). No significant changes of calcium uptake by depolarized cortical or striatal synaptosomes were observed for 10 nM or 10 microM treatment with this enkephalin analog. Dynorphin 1-17 analog at 10 nM produces a significant increase in calcium uptake by depolarized striatal synaptosomes. beta-Endorphin and the dynorphin 1-13 fragment analog (10 nM) caused no significant change in the calcium uptake by depolarized synaptosomes from any of the three brain regions. However, calcium uptake by non-depolarized striatal and cortical synaptosomes was increased significantly in the presence of 10 nM beta-endorphin and DADLE. Opioid peptide action on neural calcium uptake is complex and appears to vary somewhat from one brain region to another.

Animals↗
PubMed1985

Responses of host motor and sensory neurons to a neural tube implant in amputated chick limbs.

The right wingbuds of stage 23-25 chick embryos were amputated at the future elbow region and a segment of 2-day neural tube was implanted longitudinally into the limb stump of experimental embryos to induce limb regeneration. Control embryos had no implant in the amputated limb stump. To analyze effects of the neural tube implant (NTI) upon the host nervous system, quantitative determinations were made of the peripheral limb field (PLF), dorsal root ganglia (DRG) and spinal cord lateral motor column (LMC) of the amputated side for comparison with similar determinations of the unamputated side in all embryos. The PLF was estimated by determining the area of the skeletal elements of the amputated and unamputated limb of each embryo. The size of the DRG was estimated by determining the sectional-profile area of a pair of ganglia; the LMC was determined by counting the neurons on both sides of a single spinal cord segment. The PLF was less on the amputated than on the unamputated side but was significantly greater in amputated limbs that received a NTI. The size of the DRG was positively correlated with the size of the PLF in all groups, indicating the DRG was not directly affected by the NTI but did respond to target structures. The number of neurons in the LMC was not positively correlated with the PLF and was not reduced by limb amputation in embryos with a NTI. The data suggest that the NTI may have protected host spinal cord cells from the induced-cell death expected to follow limb amputation; perhaps the implant produces a neuronal survival factor.

Animals↗
PubMed1983

Comparison of voltage-dependent 45Ca2+ uptake rates by synaptosomes isolated from rat brain regions.

45Ca2+ uptake by synaptosomes isolated from cerebral cortex, cerebellum, midbrain, and brain stem of male Sprague-Dawley rats was measured at 1-, 3-, 5-, 15-, 30-, and 60-s time periods. The fastest rate of depolarization-dependent calcium uptake occurred in each brain region between 0 and 1 s. Uptake rates dropped off quickly with 3-5-s rates at approximately 15-20% of those observed at 0-1 s in cerebral cortex, cerebellum, and midbrain. Uptake rates at the 1-3-s interval were maintained at a relatively high rate in these three brain regions suggesting mixed fast- and slow-phase processes. The magnitude and rate of 45Ca2+ uptake were similar in synaptosomes from cerebral cortex, cerebellum, and midbrain but were significantly less in brain stem synaptosomes. These results suggest a fast and a slow component to voltage-dependent 45Ca2+ uptake by presynaptic nerve terminals from various brain regions.

Animals↗
PubMed1983

Inhibition of fast- and slow-phase depolarization-dependent synaptosomal calcium uptake by ethanol.

Uptake of 45Ca++ by synaptosomes isolated from cerebral cortex, cerebellum, midbrain and brain stem of male, Sprague-Dawley rats was measured at 1-, 3-, 5-, 15-, 30- and 60-sec time periods. At 1 sec, the Ca++ uptake rate by cerebrocortical synaptosomes was 1.45 mumol/sec/g of protein, whereas the 60-sec rate was 0.03 mumol/sec/g of protein. In vitro addition of ethanol, 80 mM, inhibited depolarization-dependent (65 mM KCl) 45Ca++ uptake by synaptosomes but the time-response relationships varied depending upon the brain region studied. In cerebrocortical synaptosomes, ethanol significantly inhibited only the fast-phase component of 45Ca++ uptake (1 and 3 sec). Ethanol inhibited 45Ca++ uptake by midbrain synaptosomes at all measurement times studied (1, 3, 5 and 15 sec), whereas in cerebellum and brain stem ethanol inhibited 45Ca++ uptake at 3- and 5-sec time periods. Ethanol at concentrations of 25, 50, 100 and 150 mM inhibited 45Ca++ uptake by 9.0, 15.9, 24.8 and 30.7%, respectively, in cerebrocortical synaptosomes. In vitro ethanol, 80 mM, added to cerebrocortical synaptosomes isolated from rats fed a nutritionally adequate liquid ethanol diet did not significantly inhibit depolarization-dependent 45Ca++ uptake. The results of this study show that pharmacologically relevant ethanol concentrations inhibit voltage-dependent 45Ca++ uptake into synaptosomes. This inhibitory action may, at least in part, underlie some of the intoxicating effects of ethanol. In addition, chronic administration of ethanol resulted in an apparent adaptive response such that addition of ethanol no longer blocked 45Ca++ uptake. This adaptive response involving the calcium channel may represent a cellular mechanism for functional tolerance development.

Animals↗
PubMed1975

Growth rebound after termination of stimulant drugs.

To explore further the report of an accelerated weight gain following termination of treatment with a stimulant drug, 66 biannual growth measurements were obtained from 1970 to 1973 on hyperactive schoolchildren who were receiving medication. All received either dextroamphetamine or methylphenidate during the school year; some also received it during the summer. The data revealed that those whose stimulant medication was terminated at the start of summer subsequently grew in weight and height at a significantly greater rate than those who continued to receive medication from June to September. In fact, discontinuance of the medication resulted in a growth rebound for this period which was 15-68% above the age-expected increment.

Adolescent↗