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Articles 751 - 780 of 1010

Full-Text Articles in Biology

Myosin Heavy Chain Isoforms And Dynamic Contractile Properties: Skeletal Versus Smooth Muscle, Thomas J. Eddinger Mar 1998

Myosin Heavy Chain Isoforms And Dynamic Contractile Properties: Skeletal Versus Smooth Muscle, Thomas J. Eddinger

Biological Sciences Faculty Research and Publications

Myosin, one of the primary contractile muscle proteins, displays molecular, enzymatic, structural, functional and regulatory variability. This variability has been shown to account for a significant amount of the functional uniqueness of skeletal and smooth muscle. However, the universal generation of force and/or shortening by these two muscle types belies the ever-increasing number of known distinct differences that bring this about. Thus, the notion that the functional roles of skeletal and smooth muscle, their development and regulation, all appear to be uniquely applicable for their physiological purpose no longer appears heretical. This manuscript presents a cursory overview of the numerous …

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Effect Of 17 Days Of Bed Rest On Peak Isometric Force And Unloaded Shortening Velocity Of Human Soleus Fibers, Jeffrey J. Widrick, Janell Romatowski, James L. W. Bain, Scott W. Trappe, Todd A. Trappe, Joyce L. Thompson, David L. Costill, Danny A. Riley, Robert H. Fitts Nov 1997

Effect Of 17 Days Of Bed Rest On Peak Isometric Force And Unloaded Shortening Velocity Of Human Soleus Fibers, Jeffrey J. Widrick, Janell Romatowski, James L. W. Bain, Scott W. Trappe, Todd A. Trappe, Joyce L. Thompson, David L. Costill, Danny A. Riley, Robert H. Fitts

Biological Sciences Faculty Research and Publications

The purpose of this study was to examine the effect of prolonged bed rest (BR) on the peak isometric force (Po) and unloaded shortening velocity (Vo) of single Ca2+-activated muscle fibers. Soleus muscle biopsies were obtained from eight adult males before and after 17 days of 6° head-down BR. Chemically permeabilized single fiber segments were mounted between a force transducer and position motor, activated with saturating levels of Ca2+, and subjected to slack length steps. Vo was determined by plotting the time for force redevelopment vs. the slack step distance. …

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Expression Of The Thyroid Hormone Receptor Gene, Erbaα, In B Lymphocytes: Alternative Mrna Processing Is Independent Of Differentiation But Correlates With Antisense Rna Levels, Michelle Laura Hastings, Christine Milcarek, Kathlee Martincic, Martha L. Peterson, Stephen H. Munroe Nov 1997

Expression Of The Thyroid Hormone Receptor Gene, Erbaα, In B Lymphocytes: Alternative Mrna Processing Is Independent Of Differentiation But Correlates With Antisense Rna Levels, Michelle Laura Hastings, Christine Milcarek, Kathlee Martincic, Martha L. Peterson, Stephen H. Munroe

Biological Sciences Faculty Research and Publications

The erbAα gene encodes two α-thyroid hormone receptor isoforms, TRα1 and TRα2, which arise from alternatively processed mRNAs, erbAα1 (α1) and erb α2 (α2). The splicing and alternative polyadenylation patterns of these mRNAs resemble that of mRNAs encoding different forms of immunoglobulin heavy chains, which are regulated at the level of alternative processing during B cell differentiation. This study examines the levels of erbAα mRNA in eight B cell lines representing four stages of differentiation in order to determine whether regulation of the alternatively processed α1 and α2 mRNAs parallels the processing of immunoglobulin heavy chain mRNAs. Results show that …

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Expression Of Smooth Muscle Myosin Heavy Chains And Unloaded Shortening In Single Smooth Muscle Cells, Daniel P. Meer, Thomas J. Eddinger Oct 1997

Expression Of Smooth Muscle Myosin Heavy Chains And Unloaded Shortening In Single Smooth Muscle Cells, Daniel P. Meer, Thomas J. Eddinger

Biological Sciences Faculty Research and Publications

The functional significance of the variable expression of the smooth muscle myosin heavy chain (SM-MHC) tail isoforms, SM1 and SM2, was examined at the mRNA level (which correlates with the protein level) in individual permeabilized rabbit arterial smooth muscle cells (SMCs). The length of untethered single permeabilized SMCs was monitored during unloaded shortening in response to increased Ca2+ (pCa 6.0), histamine (1 μM), and phenylephrine (1 μM). Subsequent to contraction, the relative expression of SM1 and SM2 mRNAs from the same individual SMCs was determined by reverse transcription-polymerase chain reaction amplification and densitometric analysis. Correlational analyses between the SM2-to-SM1 …

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Compounds Exuded By Phaseolus Vulgaris That Induce A Modification Of Rhizobium Etli Lipopolysaccharide, Dominik M. Duelli, K. Dale Noel Sep 1997

Compounds Exuded By Phaseolus Vulgaris That Induce A Modification Of Rhizobium Etli Lipopolysaccharide, Dominik M. Duelli, K. Dale Noel

Biological Sciences Faculty Research and Publications

Exudates released from germinating seeds and roots of a black-seeded bean (Phaseolus vulgaris cv. Midnight Black Turtle Soup) induce an antigenic change in the lipopolysaccharide (LPS) of Rhizobium etli CE3. By spectroscopic analyses and chromatographic comparisons with derived standards, the chemical structures of the aglycone portions of the major inducing molecules from seed exudate were deduced, and they were identified as delphinidin, cyanidin, petunidin, and malvidin. These anthocyanidins were present in seed exudate mainly as glycosides, the chief inducer being delphinidin 3-glucoside. Also present were 3-glucosides of petunidin and malvidin and glycosides of cyanidin and delphinidin. Seed exudate from …

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Detection Of Functional Nicotinic Receptors Blocked By Α-Bungarotoxin On Pc12 Cells And Dependence Of Their Expression On Post-Translational Events, Edward M. Blumenthal, William G. Conroy, Suzanne J. Romano, Paul D. Kassner, Darwin K. Berg Aug 1997

Detection Of Functional Nicotinic Receptors Blocked By Α-Bungarotoxin On Pc12 Cells And Dependence Of Their Expression On Post-Translational Events, Edward M. Blumenthal, William G. Conroy, Suzanne J. Romano, Paul D. Kassner, Darwin K. Berg

Biological Sciences Faculty Research and Publications

A major class of nicotinic receptors in the nervous system is one that binds α-bungarotoxin and contains the α7 gene product. PC12 cells, frequently used to study nicotinic receptors, express the α7 gene and have binding sites for the toxin, but previous attempts to elicit currents from the putative receptors have failed. Using whole-cell patch-clamp recording techniques and rapid application of agonist, we find a rapidly desensitizing acetylcholine-induced current in the cells that can be blocked by α-bungarotoxin. The current amplitude varies dramatically among three populations of PC12 cells but correlates well with the number of toxin-binding receptors. In contrast, …

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Properties And Regulation Of The Mink Potassium Channel Protein, Leonard K. Kaczmarek, Edward M. Blumenthal Jul 1997

Properties And Regulation Of The Mink Potassium Channel Protein, Leonard K. Kaczmarek, Edward M. Blumenthal

Biological Sciences Faculty Research and Publications

The minK gene encodes a protein of 130 amino acids that has a single transmembrane segment and is expressed in many tissues including heart, uterus, and kidney. When Xenopus oocytes are injected with minK mRNA, a very slowly activating voltage-dependent potassium current is induced in these cells. The induced channels appear to result from the interaction of the minK protein with other channel-forming subunits such as the KvLQT1 channel. The minK protein is intimately associated with the structure of the resultant channels, and mutations in minK can alter ion selectivity and modulation by second messengers. Strong candidates for native currents …

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Effect Of Intermittent Weight Bearing On Soleus Fiber Force-Velocity-Power And Force-Pca Relationships, J. J. Bangart, Jeffrey J. Widrick, Robert H. Fitts Jun 1997

Effect Of Intermittent Weight Bearing On Soleus Fiber Force-Velocity-Power And Force-Pca Relationships, J. J. Bangart, Jeffrey J. Widrick, Robert H. Fitts

Biological Sciences Faculty Research and Publications

Rat permeabilized type I soleus fibers displayed a 33% reduction in peak power output and a 36% increase in the free Ca2+ concentration required for one-half maximal activation after 14 days of hindlimb non-weight bearing (NWB). We examined the effectiveness of intermittent weight bearing (IWB; consisting of four 10-min periods of weight bearing/day) as a countermeasure to these functional changes. At peak power output, type I fibers from NWB animals produced 54% less force and shortened at a 56% greater velocity than did type I fibers from control weight-bearing animals while type I fibers from the IWB rats produced …

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Myosin Isoform Heterogeneity In Single Smooth Muscle Cells, Thomas J. Eddinger, Daniel P. Meer May 1997

Myosin Isoform Heterogeneity In Single Smooth Muscle Cells, Thomas J. Eddinger, Daniel P. Meer

Biological Sciences Faculty Research and Publications

We review the current understanding of the myosin heavy chain (MHC) isoforms and show that the mRNA levels of smooth muscle (SM)1 and SM2 mimic the expressed levels of SM1 and SM2 protein. The reverse transcriptase-polymerase chain reaction technique has been shown to be sufficiently sensitive to examine SM-MHC expression at the single cell level. Most single smooth muscle cells isolated from adult rabbit carotid express both SM1 and SM2. However, expression of these SM-MHC isoforms at the cellular level is nonuniform and highly variable. This work provides a foundation for future investigations as to the possible unique functional characteristics …

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Αa-Adrenoceptor Activation Induces Rhythmic Contractile Activity In Carotid Arteries From Young, Not Adult, Rats, Thomas J. Eddinger, Paul H. Ratz Feb 1997

Αa-Adrenoceptor Activation Induces Rhythmic Contractile Activity In Carotid Arteries From Young, Not Adult, Rats, Thomas J. Eddinger, Paul H. Ratz

Biological Sciences Faculty Research and Publications

Rhythmic contractions are produced by small arteries, arterioles and veins in several vascular beds, but they are often absent in large arteries. However, under certain conditions, and in certain disease states, large arteries may produce rhythmic contractions. For this reason, the present study was undertaken to test the hypothesis that rhythmic contractions may be a ‘normal’ response in large arteries at some stage in development. We investigated this hypothesis by examining contractions of carotid arteries in male and female rats aged 15, 25 and 30 days, and in adult rats. Rhythmic contractions were produced by exposure to, or during washout …

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Contractile Properties Of Rat, Rhesus Monkey, And Human Type I Muscle Fibers, Jeffrey J. Widrick, Janell Romatowski, M. Karhanek, Robert H. Fitts Jan 1997

Contractile Properties Of Rat, Rhesus Monkey, And Human Type I Muscle Fibers, Jeffrey J. Widrick, Janell Romatowski, M. Karhanek, Robert H. Fitts

Biological Sciences Faculty Research and Publications

It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle …

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Peak Force And Maximal Shortening Velocity Of Soleus Fibers After Non-Weight-Bearing And Resistance Exercise, Jeffrey J. Widrick, Robert H. Fitts Jan 1997

Peak Force And Maximal Shortening Velocity Of Soleus Fibers After Non-Weight-Bearing And Resistance Exercise, Jeffrey J. Widrick, Robert H. Fitts

Biological Sciences Faculty Research and Publications

Widrick, Jeffrey J., and Robert H. Fitts. Peak force and maximal shortening velocity of soleus fibers after non-weight-bearing and resistance exercise. J. Appl. Physiol. 82(1): 189–195, 1997.—This study examined the effectiveness of resistance exercise as a countermeasure to non-weight-bearing-induced alterations in the absolute peak force, normalized peak force (force/fiber cross-sectional area), peak stiffness, and maximal shortening velocity (V o) of single permeabilized type I soleus muscle fibers. Adult rats were subjected to one of the following treatments: normal weight bearing (WB), non-weight bearing (NWB), or NWB with exercise treatments (NWB+Ex). The hindlimbs of the NWB and NWB+Ex rats were …

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A Highly Sensitive Plant Hybrid Protein Assay System Based On The Spm Promoter And Tnpa Protein For Detection And Analysis Of Transcription Activation Domains, Michael Schläppi, Ramesh Raina, Nina V. Fedoroff Nov 1996

A Highly Sensitive Plant Hybrid Protein Assay System Based On The Spm Promoter And Tnpa Protein For Detection And Analysis Of Transcription Activation Domains, Michael Schläppi, Ramesh Raina, Nina V. Fedoroff

Biological Sciences Faculty Research and Publications

TnpA is a multifunctional DNA binding protein encoded by the maize Suppressor-mutator (Spm) transposable element. TnpA is required for transposition and is a repressor of the unmethylated Spm promoter. While analyzing protein domains using a yeast GAL4-based hybrid system in transiently transformed tobacco cells, we found that TnpA represses the >10-fold transcriptional activation observed when the GAL4 DNA-binding domain is used alone. By contrast, compared to the backgroundless TnpA DNA-binding domain alone, 33- to 45-fold activation of the Spm promoter was observed when the VP16 activation domain was fused to it. TnpA-binding sites, but no TATA box, …

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Effects Of Fatiguing Stimulation On Intracellular Na+ And K+ In Frog Skeletal Muscle, Edward Michael Balog, Robert H. Fitts Aug 1996

Effects Of Fatiguing Stimulation On Intracellular Na+ And K+ In Frog Skeletal Muscle, Edward Michael Balog, Robert H. Fitts

Biological Sciences Faculty Research and Publications

The purpose of this study was to describe the alterations in the intracellular concentrations of sodium ([Na+]i) and potassium ([K+]i) and the membrane potential (Em) as a result of fatiguing stimulation of the frog semitendinosus muscle and to relate these changes to the alterations in the sarcolemma action potential and force-generating ability of the muscle. [Na+]i and [K+]i were measured by using ion-selective microelectrodes. Before stimulation (100-ms trains at 150 Hz, 1 stimulus/s for 5 min), [Na+]i, [K+] …

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Effect Of Intracellular And Extracellular Ion Changes On E–C Coupling And Skeletal Muscle Fatigue, Robert H. Fitts, Edward Michael Balog Mar 1996

Effect Of Intracellular And Extracellular Ion Changes On E–C Coupling And Skeletal Muscle Fatigue, Robert H. Fitts, Edward Michael Balog

Biological Sciences Faculty Research and Publications

The causative factors in muscle fatigue are multiple, and vary depending on the intensity and duration of the exercise, the fibre type composition of the muscle, and the individual's degree of fitness. Regardless of the aetiology, fatigue is characterized by the inability to maintain the required power output, and the decline in power can be attributed to a reduced force and velocity. Following high-intensity exercise, peak force has been shown to recover biphasically with an initial rapid (2 min) recovery followed by a slower (50 min) return to the pre-fatigued condition. The resting membrane potential depolarizes by 10–15 mV, while …

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Soleus Fiber Force And Maximal Shortening Velocity After Non-Weight Bearing With Intermittent Activity, Jeffrey J. Widrick, J. J. Bangart, M. Karhanek, Robert H. Fitts Mar 1996

Soleus Fiber Force And Maximal Shortening Velocity After Non-Weight Bearing With Intermittent Activity, Jeffrey J. Widrick, J. J. Bangart, M. Karhanek, Robert H. Fitts

Biological Sciences Faculty Research and Publications

This study examined the effectiveness of intermittent weight bearing (IWB) as a countermeasure to non-weight-bearing (NWB)-induced alterations in soleus type I fiber force (in mN), tension (Po; force per fiber cross-sectional area in kN/m-2), and maximal unloaded shortening velocity (Vo, in fiber lengths/s). Adult rats were assigned to one of the following groups: normal weight bearing (WB), 14 days of hindlimb NWB (NWB group), and 14 days of hindlimb NWB with IWB treatments (IWB group). The IWB treatment consisted of four 10-min periods of standing WB each day. Single, chemically permeabilized soleus fiber segments …

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Effect Of Hindlimb Unloading On Rat Soleus Fiber Force, Stiffness, And Calcium Sensitivity, Kerry S Mcdonald, Robert H. Fitts Nov 1995

Effect Of Hindlimb Unloading On Rat Soleus Fiber Force, Stiffness, And Calcium Sensitivity, Kerry S Mcdonald, Robert H. Fitts

Biological Sciences Faculty Research and Publications

The purpose of this study was to examine the time course of change in soleus muscle fiber peak force (N), tension (Po, kN/m2), elastic modulus (Eo), and force-pCa and stiffness-pCa relationships. After 1, 2, or 3 wk of hindlimb unloading (HU), single fibers were isolated and placed between a motor arm and a transducer, and fiber diameter, peak absolute force, Po, Eo, and force-pCa and stiffness-pCa relationships were characterized. One week of HU resulted in a significant reduction in fiber diameter (68 +/- 2 vs 57 +/- 1 microns), force …

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Lipopolysaccharide Core Structures In Rhizobium Etli And Mutants Deficient In O-Antigen, Russell W. Carlson, Bradley Reuhs, Tong-Bin Chen, U. Ramadas Bhat, K. Dale Noel May 1995

Lipopolysaccharide Core Structures In Rhizobium Etli And Mutants Deficient In O-Antigen, Russell W. Carlson, Bradley Reuhs, Tong-Bin Chen, U. Ramadas Bhat, K. Dale Noel

Biological Sciences Faculty Research and Publications

Lipopolysaccharide (LPS) is a major component of the bacterial outer membrane, and for Rhizobium spp. has been shown to play a critical role in the establishment of an effective nitrogen-fixing symbiosis with a legume host. Many genes required for O-chain polysaccharide synthesis are in the lps α region of the CE3 genome; this region may also carry lps genes required for core oligosaccharide synthesis. The LPSs from several strains mutated in the α region were isolated, and their mild acid released oligosaccharides, purified by high performance anion-exchange chromatography, were characterized by electrospray- and fast atom bombardment-mass spectrometry, NMR, and …

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Arachidonic Acid As A Possible Negative Feedback Inhibitor Of Nicotinic Acetylcholine Receptors On Neurons, Sukumar Vijayaraghavan, Bo Huang, Edward M. Blumenthal, Darwin K. Berg May 1995

Arachidonic Acid As A Possible Negative Feedback Inhibitor Of Nicotinic Acetylcholine Receptors On Neurons, Sukumar Vijayaraghavan, Bo Huang, Edward M. Blumenthal, Darwin K. Berg

Biological Sciences Faculty Research and Publications

Neuronal acetylcholine receptors, being highly permeable to calcium, are likely to regulate calcium-dependent events in neurons. Arachidonic acid is a membrane-permeant second messenger that can be released from membrane phospholipids by phospholipases in a calcium-dependent manner. We show here that activation of neuronal acetylcholine receptors triggers release of 3H-arachidonic acid in a calcium-dependent manner from neurons preloaded with the fatty acid. Moreover, low concentrations of arachidonic acid reversibly inhibit the receptors and act most efficiently on receptors likely to have the highest permeability to calcium, namely receptors containing α7 subunits. Low concentrations of arachidonic acid also reversibly inhibit α7- …

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Quantitative Analysis Of Electrotonic Structure And Membrane Properties Of Nmda-Activated Lamprey Spinal Neurons, C. R. Murphey, L. E. Moore, James T. Buchanan May 1995

Quantitative Analysis Of Electrotonic Structure And Membrane Properties Of Nmda-Activated Lamprey Spinal Neurons, C. R. Murphey, L. E. Moore, James T. Buchanan

Biological Sciences Faculty Research and Publications

Parameter optimization methods were used to quantitatively analyze frequency-domain-voltage-clamp data of NMDA-activated lamprey spinal neurons simultaneously over a wide range of membrane potentials. A neuronal cable model was used to explicitly take into account receptors located on the dendritic trees. The driving point membrane admittance was measured from the cell soma in response to a Fourier synthesized point voltage clamp stimulus. The data were fitted to an equivalent cable model consisting of a single lumped soma compartment coupled resistively to a series of equal dendritic compartments. The model contains voltage-dependent NMDA sensitive (INMDA), slow potassium (IK …

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Localization And Interaction Of N-Methyl-D-Aspartate And Non-N-Methyl-D-Aspartate Receptors Of Lamprey Spinal Neurons, L. E. Moore, James T. Buchanan, C. R. Murphey Jan 1995

Localization And Interaction Of N-Methyl-D-Aspartate And Non-N-Methyl-D-Aspartate Receptors Of Lamprey Spinal Neurons, L. E. Moore, James T. Buchanan, C. R. Murphey

Biological Sciences Faculty Research and Publications

Small volumes of N-Methyl-D-Aspartate (NMDA) and non-NMDA excitatory amino acid receptor agonists were applied to localized regions of the dendritic trees of lamprey spinal neurons along their medial-lateral axis to obtain a spatial map of glutamate receptor distribution. Voltage clamp and frequency domain methods were used to obtain quantitative kinetic data of the voltage dependent ionic channels located both on the soma and on highly branched dendritic membranes. Pressure pulses of NMDA applied to the most peripheral regions of the dendritic tree elicited large somatic impedance increases, indicating that the most peripheral dendrites are well supplied with NMDA receptors. Experiments …

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Activities Of Spinal Neurons During Brain Stem-Dependent Fictive Swimming In Lamprey, James T. Buchanan, Stefan Kasicki Jan 1995

Activities Of Spinal Neurons During Brain Stem-Dependent Fictive Swimming In Lamprey, James T. Buchanan, Stefan Kasicki

Biological Sciences Faculty Research and Publications

1. We made intracellular microelectrode recordings of membrane potential from spinal neurons during fictive swimming elicited by brief electrical shocks to the spinal cord in a brain stem-spinal cord preparation of the adult silver lamprey (Ichthyomyzon unicuspis). 2. We characterized membrane potential activities recorded during brain stem-dependent fictive swimming in five spinal cell types: myotomal motoneurons, lateral interneurons (inhibitory neurons with ipsilateral descending axons), CC interneurons (neurons with contralateral and caudal projecting axons), edge cells (intraspinal stretch receptors), and dorsal cells (primary mechanosensory neurons with cell bodies in the spinal cord). The membrane potential activities were compared with data from …

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Nitrous Oxide: Mechanism Of Its Antinociceptive Action, Raymond M. Quock, Linda K. Vaughn Jan 1995

Nitrous Oxide: Mechanism Of Its Antinociceptive Action, Raymond M. Quock, Linda K. Vaughn

Biological Sciences Faculty Research and Publications

Nitrous oxide (N2O) is an anesthetic gas known to produce an analgesic effect at sub-anesthetic concentrations. This analgesic property of N2O can be clinically exploited in a broad range of conditions where pain relief is indicated. The mechanism of this analgesic effect was long thought to be nonspecific in nature, but a landmark study by Berkowitz and others in 1976 first implicated an opioid mechanism of action, possibly via N2O-stimulated neuronal release of endogenous opioid peptides to activate opioid receptors. N2O-induced release of opioid peptide has been demonstrated in both in vivo …

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Force-Velocity And Power Characteristics Of Rat Soleus Muscle Fibers After Hindlimb Suspension, Kerry S. Mcdonald, C. A. Blaser, Robert H. Fitts Oct 1994

Force-Velocity And Power Characteristics Of Rat Soleus Muscle Fibers After Hindlimb Suspension, Kerry S. Mcdonald, C. A. Blaser, Robert H. Fitts

Biological Sciences Faculty Research and Publications

The effects of 1, 2, and 3 wk of hindlimb suspension (HS) on force-velocity and power characteristics of single rat soleus fibers were determined. After 1, 2, or 3 wk of HS, small fiber bundles were isolated, placed in skinning solution, and stored at -20 degrees C until studied. Single fibers were isolated and placed between a motor arm and force transducer, functional properties were studied, and fiber protein content was subsequently analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Additional fibers were isolated from soleus of control and after 1 and 3 wk of HS, and fiber type distribution …

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A Small Family Of Elements With Long Inverted Repeats Is Located Near Sites Of Developmentally Regulated Dna Rearrangement In Tetrahymena Thermophila, John M. Wells, Jay Lee Edward Ellingson, Diana M. Catt, Patricia J. Berger, Kathleen M. Karrer Sep 1994

A Small Family Of Elements With Long Inverted Repeats Is Located Near Sites Of Developmentally Regulated Dna Rearrangement In Tetrahymena Thermophila, John M. Wells, Jay Lee Edward Ellingson, Diana M. Catt, Patricia J. Berger, Kathleen M. Karrer

Biological Sciences Faculty Research and Publications

Extensive DNA rearrangement occurs during the development of the somatic macronucleus from the germ line micronucleus in ciliated protozoans. The micronuclear junctions and the macronuclear product of a developmentally regulated DNA rearrangement in Tetrahymena thermophila, Tlr1, have been cloned. The intrachromosomal rearrangement joins sequences that are separated by more than 13 kb in the micronucleus with the elimination of moderately repeated micronucleus-specific DNA sequences. There is a long, 825-bp, inverted repeat near the micronuclear junctions. The inverted repeat contains two different 19-bp tandem repeats. The 19-bp repeats are associated with each other and with DNA rearrangements at seven locations …

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Role Of Sarcolemma Action Potentials And Excitability In Muscle Fatigue, Edward Michael Balog, Ladora Vaughan Thompson, Robert H. Fitts May 1994

Role Of Sarcolemma Action Potentials And Excitability In Muscle Fatigue, Edward Michael Balog, Ladora Vaughan Thompson, Robert H. Fitts

Biological Sciences Faculty Research and Publications

The purposes of this study were to characterize the alterations in the sarcolemma action potential (AP) waveform and sarcolemma excitability as a result of fatiguing stimulation of the frog semitendinosus muscle and to relate these changes to the decrease in the force-generating ability of the muscle. Trains of APs were recorded before and after stimulation (100-ms trains, 150 Hz, 1/s for 5 min). The resting membrane potential (RMP), AP overshoot (OS), and duration at 50% of peak magnitude (DUR) were -84.3 +/- 2.0 mV, 19.5 +/- 1.9 mV, and 1.3 +/- 0.1 ms, respectively, before stimulation. The stimulation protocol caused …

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The Mink Potassium Channel Exists In Functional And Nonfunctional Forms When Expressed In The Plasma Membrane Of Xenopus Oocytes, Edward M. Blumenthal, Leonard K. Kaczmarek May 1994

The Mink Potassium Channel Exists In Functional And Nonfunctional Forms When Expressed In The Plasma Membrane Of Xenopus Oocytes, Edward M. Blumenthal, Leonard K. Kaczmarek

Biological Sciences Faculty Research and Publications

The minK protein induces a slowly activating voltage-dependent potassium current when expressed in Xenopus oocytes. In order to measure the levels of minK protein in the plasma membrane, we have modified the minK gene by inserting a 9 amino acid epitope into the N- terminal domain of the protein sequence. When intact live oocytes are injected with the modified minK RNA and subsequently incubated with an antibody to this epitope, specific binding is detected, indicating that the N-terminal domain is extracellular. We found that when oocytes are injected with amounts of minK mRNA up to 50 ng, the levels of …

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Molecular Analysis Of Ovary Specific Cdnas From Galleria Mellonella, Veeraramini S. Rajaratnam Apr 1994

Molecular Analysis Of Ovary Specific Cdnas From Galleria Mellonella, Veeraramini S. Rajaratnam

Dissertations (1934 -)

To study the regulation of sex-specific gene expression during oogenesis, a vitellogenic ovariole cDNA library was constructed and differentially screened with ovary and male pharate pupal total cDNAs. Six classes of ovary specific clones were isolated. Clones, F11, F20 and N23 represent 1.1, 2.0 and 2.3 kb ovary specific transcripts. In situ hybridization and developmental Northern analysis showed that F11 and F20 transcripts are limited to vitellogenic follicle cells. N23 transcripts are present in the pre-vitellogenic and vitellogenic nurse cells, and they persist in choriogenic follicles and early embryos suggesting that N23 may represent a maternal message. The 0.95 kb …

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Cellular Mechanisms Of Muscle Fatigue, Robert H. Fitts Jan 1994

Cellular Mechanisms Of Muscle Fatigue, Robert H. Fitts

Biological Sciences Faculty Research and Publications

Fatigue, defined as the failure to maintain the required or expected power output, is a complex problem, since multiple factors are clearly involved, with the relative importance of each dependent on the fiber type composition of the contracting muscles(s), and the intensity, type, and duration of the contractile activity. The primary sites of fatigue appear to be within the muscle cell itself and for the most part do not involve the central nervous system or the neuromuscular junction. The major hypotheses of fatigue center on disturbances in the surface membrane, E-C coupling, or metabolic events. The cell sites most frequently …

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Electrophysiological Properties Of Identified Classes Of Lamprey Spinal Neurons, James T. Buchanan Dec 1993

Electrophysiological Properties Of Identified Classes Of Lamprey Spinal Neurons, James T. Buchanan

Biological Sciences Faculty Research and Publications

1. As part of a continuing analysis of the mechanisms of the central pattern generator underlying fictive swimming in lamprey, a systematic survey of electrophysiological properties of lamprey neurons was made in the in vitro spinal cord preparation with the use of intracellular current-clamp recordings. A total of 70 neurons was included in the study, representing 6 classes of spinal neurons. The classes were myotomal motoneurons, three classes of interneurons involved in fictive swimming [lateral interneurons, nerve cells with contralateral and caudal projecting axons (CC interneurons), and excitatory interneurons], and two classes of interneurons involved in sensory processes (edge cells …

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