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Articles 631 - 660 of 750
Full-Text Articles in Biology
Treefall Gaps And The Maintenance Of Species Diversity In A Tropical Forest, Stefan A. Schnitzer, Walter P. Carson
Treefall Gaps And The Maintenance Of Species Diversity In A Tropical Forest, Stefan A. Schnitzer, Walter P. Carson
Biological Sciences Faculty Research and Publications
The maintenance of species diversity by treefall gaps is a long‐standing paradigm in forest ecology. Gaps are presumed to provide an environment in which tree species of differing competitive abilities partition heterogeneous resources. The empirical evidence to support this paradigm, however, remains scarce, and some recent studies even suggest that gaps do not maintain the diversity of shade‐tolerant species. Although there is evidence that gaps maintain the diversity of pioneer trees, most of this evidence comes from studies that did not make comparisons between gaps and intact forest sites (controls). Further, nearly all studies on the maintenance of diversity by …
Oxa1p Acts As A General Membrane Insertion Machinery For Proteins Encoded By Mitochondrial Dna, Kai Hell, Walter Neupert, Rosemary A. Stuart
Oxa1p Acts As A General Membrane Insertion Machinery For Proteins Encoded By Mitochondrial Dna, Kai Hell, Walter Neupert, Rosemary A. Stuart
Biological Sciences Faculty Research and Publications
Oxa1p is a member of the conserved Oxa1/YidC/Alb3 protein family involved in the membrane insertion of proteins. Oxa1p has been shown previously to directly facilitate the export of the N‐terminal domains of membrane proteins across the inner membrane to the intermembrane space of mitochondria. Here we report on a general role of Oxa1p in the membrane insertion of proteins. (i) The function of Oxa1p is not limited to the insertion of membrane proteins that undergo N‐terminal tail export; rather, it also extends to the insertion of other polytopic proteins such as the mitochondrially encoded Cox1p and Cox3p proteins. These are …
Fiber-Type Susceptibility To Eccentric Contraction-Induced Damage Of Hindlimb-Unloaded Rat Al Muscles, K. P. Vijayan, Joyce L. Thompson, Kris M. Norenberg, Robert H. Fitts, Danny A. Riley
Fiber-Type Susceptibility To Eccentric Contraction-Induced Damage Of Hindlimb-Unloaded Rat Al Muscles, K. P. Vijayan, Joyce L. Thompson, Kris M. Norenberg, Robert H. Fitts, Danny A. Riley
Biological Sciences Faculty Research and Publications
Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms …
Contributions Of Identifiable Neurons And Neuron Classes To Lamprey Vertebrate Neurobiology, James T. Buchanan
Contributions Of Identifiable Neurons And Neuron Classes To Lamprey Vertebrate Neurobiology, James T. Buchanan
Biological Sciences Faculty Research and Publications
Among the advantages offered by the lamprey brainstem and spinal cord for studies of the structure and function of the nervous system is the unique identifiability of several pairs of reticulospinal neurons in the brainstem. These neurons have been exploited in investigations of the patterns of sensory input to these cells and the patterns of their outputs to spinal neurons, but no doubt these cells could be used much more effectively in exploring their roles in descending control of the spinal cord. The variability of cell positions of neurons in the spinal cord has precluded the recognition of unique spinal …
Single Rabbit Stomach Smooth Muscle Cell Myosin Heavy Chain Smb Expression And Shortening Velocity, Thomas J. Eddinger, Daniel P. Meer
Single Rabbit Stomach Smooth Muscle Cell Myosin Heavy Chain Smb Expression And Shortening Velocity, Thomas J. Eddinger, Daniel P. Meer
Biological Sciences Faculty Research and Publications
Isolated single smooth muscle cells (SMCs) from different regions of the rabbit stomach were used to determine a possible correlation between unloaded shortening velocity and smooth muscle (SM) myosin heavy chain (MHC) S1 head isoform composition (SMA, no head insert; SMB, with head insert). α-Toxin-permeabilized isolated single cells were maximally activated to measure unloaded shortening velocity and subsequently used in an RT-PCR reaction to determine the SMA/SMB content of the same cell. SM MHC SMA and SMB isoforms are uniquely distributed in the stomach with cells from the fundic region expressing little SMB (38.1 ± 7.3% SMB; n = 16); …
Protransglutaminase (Factor Xiii) Mediated Crosslinking Of Fibrinogen And Fibrin, Kevin R. Siebenlist, David A. Meh, Michael W. Mosesson
Protransglutaminase (Factor Xiii) Mediated Crosslinking Of Fibrinogen And Fibrin, Kevin R. Siebenlist, David A. Meh, Michael W. Mosesson
Biological Sciences Faculty Research and Publications
No abstract provided.
Effects Of Depolarization And Low Intracellular Ph On Charge Movement Currents Of Frog Skeletal Muscle Fibers, Edward Michael Balog, Robert H. Fitts
Effects Of Depolarization And Low Intracellular Ph On Charge Movement Currents Of Frog Skeletal Muscle Fibers, Edward Michael Balog, Robert H. Fitts
Biological Sciences Faculty Research and Publications
The low intracellular pH and membrane depolarization associated with repeated skeletal muscle stimulation could impair the function of the transverse tubular (t tubule) voltage sensor and result in a decreased sarcoplasmic reticulum Ca2+ release and muscle fatigue. We therefore examined the effects of membrane depolarization and low intracellular pH on the t-tubular charge movement. Fibers were voltage clamped in a double Vaseline gap, at holding potential (HP) of 290 or 260 mV, and studied at an internal pH of 7.0 and 6.2. Decreasing intracellular pH did not significantly alter the maximum amount of charge moved, transition voltage, or steepness …
Biennialism And Vernalization-Promoted Flowering In Hyoscyamus Niger: A Comparison With Arabidopsis, Michael Schläppi, Monica Patel
Biennialism And Vernalization-Promoted Flowering In Hyoscyamus Niger: A Comparison With Arabidopsis, Michael Schläppi, Monica Patel
Biological Sciences Faculty Research and Publications
There are genetic similarities between the biennial growth habit of Hyoscyamus niger (H. niger) and winter annual ecotypes of Arabidopsis thaliana, including the response to demethylating agents. One focus of our research group at Marquette is to determine whether FLOWERING LOCUS C (FLC) homologs or FLC-related MADS-box genes are involved in biennialism of H. niger. This review also summarizes our initial characterization of expression profiles of 4 groups of H. niger MADS-box genes. Our results suggest that B-class floral homeotic gene homologs of H. niger are differentially expressed in flowers of annual and …
A Gene Expression Screen Identifies Earli1 As A Novel Vernalization-Responsive Gene In Arabidopsis Thaliana, Richard K. Wilkosz, Michael Schläppi
A Gene Expression Screen Identifies Earli1 As A Novel Vernalization-Responsive Gene In Arabidopsis Thaliana, Richard K. Wilkosz, Michael Schläppi
Biological Sciences Faculty Research and Publications
Vernalization promotes early flowering in late ecotypes of Arabidopsis thaliana. The mechanisms of vernalization are poorly understood. A subtractive hybridization approach was used to isolate vernalization-responsive genes from a late-flowering ecotype of Arabidopsis thaliana based on the premise that transcript levels of such genes would increase with cold treatment and remain high even after removal of the vernalization stimulus. EARLI1 is the first Arabidopsis gene shown to be stably activated by vernalization. The abundance of its RNA is progressively elevated by vernalization and remains high for at least 20 days at room temperature. The basal level of EARLI1 RNA …
Spaceflight Effects On Single Skeletal Muscle Fiber Function In The Rhesus Monkey, Robert H. Fitts, Dominique Desplanches, Janell Romatowski, Jeffrey J. Widrick
Spaceflight Effects On Single Skeletal Muscle Fiber Function In The Rhesus Monkey, Robert H. Fitts, Dominique Desplanches, Janell Romatowski, Jeffrey J. Widrick
Biological Sciences Faculty Research and Publications
The purpose of this investigation was to understand how 14 days of weightlessness alters the cellular properties of individual slow- and fast-twitch muscle fibers in the rhesus monkey. The diameter of the soleus (Sol) type I, medial gastrocnemius (MG) type I, and MG type II fibers from the vivarium controls averaged 60 ± 1, 46 ± 2, and 59 ± 2 µm, respectively. Both a control 1-G capsule sit (CS) and spaceflight (SF) significantly reduced the Sol type I fiber diameter (20 and 13%, respectively) and peak force, with the latter declining from 0.48 ± 0.01 to 0.31 ± 0.02 …
A Family Of Developmentally Excised Dna Elements In Tetrahymena Is Under Selective Pressure To Maintain An Open Reading Frame Encoding An Integrase-Like Protein, Jill A. Gershan, Kathleen M. Karrer
A Family Of Developmentally Excised Dna Elements In Tetrahymena Is Under Selective Pressure To Maintain An Open Reading Frame Encoding An Integrase-Like Protein, Jill A. Gershan, Kathleen M. Karrer
Biological Sciences Faculty Research and Publications
Tlr1 is a member of a family of ~20-30 DNA elements that undergo developmentally regulated excision during formation of the macronucleus in the ciliated protozoan Tetrahymena. Analysis of sequence internal to the right boundary of Tlr1 revealed the presence of a 2 kb open reading frame (ORF) encoding a deduced protein with similarity to retrotransposon integrases. The ORFs of five unique clones were sequenced. The ORFs have 98% sequence conservation and align without frameshifts, although one has an additional trinucleotide at codon 561. Nucleotide changes among the five clones are highly non-random with respect to the position in the …
Selection Of Alternative 5′ Splice Sites: Role Of U1 Snrnp And Models For The Antagonistic Effects Of Sf2/Asf And Hnrnp A1, Ian C. Eperon, Olga V. Makarova, Akila Mayeda, Stephen Munroe, Javier F. Cáceres, Daniel G. Hayward, Adrian R. Krainer
Selection Of Alternative 5′ Splice Sites: Role Of U1 Snrnp And Models For The Antagonistic Effects Of Sf2/Asf And Hnrnp A1, Ian C. Eperon, Olga V. Makarova, Akila Mayeda, Stephen Munroe, Javier F. Cáceres, Daniel G. Hayward, Adrian R. Krainer
Biological Sciences Faculty Research and Publications
The first component known to recognize and discriminate among potential 5′ splice sites (5′SSs) in pre-mRNA is the U1 snRNP. However, the relative levels of U1 snRNP binding to alternative 5′SSs do not necessarily determine the splicing outcome. Strikingly, SF2/ASF, one of the essential SR protein-splicing factors, causes a dose-dependent shift in splicing to a downstream (intron-proximal) site, and yet it increases U1 snRNP binding at upstream and downstream sites simultaneously. We show here that hnRNP A1, which shifts splicing towards an upstream 5′SS, causes reduced U1 snRNP binding at both sites. Nonetheless, the importance of U1 snRNP binding is …
Varying The Abundance Of O Antigen In Rhizobium Etli And Its Effect On Symbiosis With Phaseolus Vulgaris, K. Dale Noel, Lennart Scott Forsberg, Russell W. Carlson
Varying The Abundance Of O Antigen In Rhizobium Etli And Its Effect On Symbiosis With Phaseolus Vulgaris, K. Dale Noel, Lennart Scott Forsberg, Russell W. Carlson
Biological Sciences Faculty Research and Publications
Judged by migration of its lipopolysaccharide (LPS) in gel electrophoresis, the O antigen of Rhizobium etli mutant strain CE166 was apparently of normal size. However, its LPS sugar composition and staining of the LPS bands after electrophoresis indicated that the proportion of its LPS molecules that possessed O antigen was only 40% of the wild-type value. Its LPS also differed from the wild type by lacking quinovosamine (2-amino-2,6-dideoxyglucose). Both of these defects were due to a single genetic locus carrying a Tn5 insertion. The deficiency in O-antigen amount, but not the absence of quinovosamine, was suppressed by transferring into …
Have We Forgotten The Forest Because Of The Trees?, Stefan A. Schnitzer, Walter P. Carson
Have We Forgotten The Forest Because Of The Trees?, Stefan A. Schnitzer, Walter P. Carson
Biological Sciences Faculty Research and Publications
No abstract provided.
Uncharged Trna Activates Gcn2 By Displacing The Protein Kinase Moiety From A Bipartite Trna-Binding Domain, Jinsheng Dong, Hongfang Qiu, Minerva Garcia-Barrio, James T. Anderson, Alan G. Hinnebusch
Uncharged Trna Activates Gcn2 By Displacing The Protein Kinase Moiety From A Bipartite Trna-Binding Domain, Jinsheng Dong, Hongfang Qiu, Minerva Garcia-Barrio, James T. Anderson, Alan G. Hinnebusch
Biological Sciences Faculty Research and Publications
Protein kinase GCN2 regulates translation in amino acid–starved cells by phosphorylating eIF2. GCN2 contains a regulatory domain related to histidyl-tRNA synthetase (HisRS) postulated to bind multiple deacylated tRNAs as a general sensor of starvation. In accordance with this model, GCN2 bound several deacylated tRNAs with similar affinities, and aminoacylation of tRNAPhe weakened its interaction with GCN2. Unexpectedly, the C-terminal ribosome binding segment of GCN2 (C-term) was required in addition to the HisRS domain for strong tRNA binding. A combined HisRS+C-term segment bound to the isolated protein kinase (PK) domain in vitro, and tRNA impeded this interaction. An activating mutation …
Physiology Of A Microgravity Environment Invited Review: Microgravity And Skeletal Muscle, Robert H. Fitts, Danny R. Riley, Jeffrey J. Widrick
Physiology Of A Microgravity Environment Invited Review: Microgravity And Skeletal Muscle, Robert H. Fitts, Danny R. Riley, Jeffrey J. Widrick
Biological Sciences Faculty Research and Publications
Spaceflight (SF) has been shown to cause skeletal muscle atrophy; a loss in force and power; and, in the first few weeks, a preferential atrophy of extensors over flexors. The atrophy primarily results from a reduced protein synthesis that is likely triggered by the removal of the antigravity load. Contractile proteins are lost out of proportion to other cellular proteins, and the actin thin filament is lost disproportionately to the myosin thick filament. The decline in contractile protein explains the decrease in force per cross-sectional area, whereas the thin-filament loss may explain the observed postflight increase in the maximal velocity …
Physiology Of A Microgravity Environment Invited Review: Microgravity And Skeletal Muscle, Robert H. Fitts, Danny R. Riley, Jeffrey J. Widrick
Physiology Of A Microgravity Environment Invited Review: Microgravity And Skeletal Muscle, Robert H. Fitts, Danny R. Riley, Jeffrey J. Widrick
Biological Sciences Faculty Research and Publications
Spaceflight (SF) has been shown to cause skeletal muscle atrophy; a loss in force and power; and, in the first few weeks, a preferential atrophy of extensors over flexors. The atrophy primarily results from a reduced protein synthesis that is likely triggered by the removal of the antigravity load. Contractile proteins are lost out of proportion to other cellular proteins, and the actin thin filament is lost disproportionately to the myosin thick filament. The decline in contractile protein explains the decrease in force per cross-sectional area, whereas the thin-filament loss may explain the observed postflight increase in the maximal velocity …
The Impact Of Lianas On Tree Regeneration In Tropical Forest Canopy Gaps: Evidence For An Alternative Pathway Of Gap‐Phase Regeneration, Stefan A. Schnitzer, James W. Dalling, Walter P. Carson
The Impact Of Lianas On Tree Regeneration In Tropical Forest Canopy Gaps: Evidence For An Alternative Pathway Of Gap‐Phase Regeneration, Stefan A. Schnitzer, James W. Dalling, Walter P. Carson
Biological Sciences Faculty Research and Publications
1 Regeneration in forest canopy gaps is thought to lead invariably to the rapid recruitment and growth of trees and the redevelopment of the canopy. Our observations, however, suggest that an alternate successional pathway is also likely, whereby gap‐phase regeneration is dominated by lianas and stalled in a low‐canopy state for many years. We investigated gap‐phase regeneration in an old‐growth tropical forest on Barro Colorado Island (BCI) in Panama to test the following two hypotheses: (i) many gaps follow a pathway in which they remain at a low canopy height and are dominated by lianas and (ii) the paucity of …
Expression Of Smooth Muscle Myosin Light Chain 17 And Unloaded Shortening In Single Smooth Muscle Cells, Thomas J. Eddinger, A. A. Korwek, Daniel P. Meer, Jennifer J. Sherwood
Expression Of Smooth Muscle Myosin Light Chain 17 And Unloaded Shortening In Single Smooth Muscle Cells, Thomas J. Eddinger, A. A. Korwek, Daniel P. Meer, Jennifer J. Sherwood
Biological Sciences Faculty Research and Publications
These experiments were performed to test the hypotheses that myosin light chain 17 (MLC17) a and b isoform expression varies between individual vascular smooth muscle (SM) cells and that their expression correlates with cell unloaded shortening velocity. Single SM cells isolated from rabbit aorta and carotid arteries were used to measure unloaded shortening velocity and subsequently were analyzed via RT-PCR for MLC17 a and b mRNA ratio. The MLC17b/a mRNA and protein ratios from adjacent tissue sections correlate very well (R2 = 0.68), allowing use of the mRNA ratio to predict the protein ratio. …
A Developmentally Regulated Deletion Element With Long Terminal Repeats Has Cis-Acting Sequences In The Flanking Dna, Namrata S. Patil, Kathleen M. Karrer
A Developmentally Regulated Deletion Element With Long Terminal Repeats Has Cis-Acting Sequences In The Flanking Dna, Namrata S. Patil, Kathleen M. Karrer
Biological Sciences Faculty Research and Publications
Approximately 6000 specific DNA deletion events occur during development of the somatic macronucleus of the ciliate Tetrahymena. The eliminated Tlr1 element is 13 kb or more in length and has an 825 bp inverted repeat near the rearrangement junctions. A functional analysis of the cis-acting sequences required for Tlr1 rearrangement was performed. A construct consisting of the entire inverted repeat and several hundred base pairs of flanking DNA on each side was rearranged accurately in vivo and displayed junctional variability similar to the chromosomal Tlr1 rearrangement. Thus, 11 kb or more of internal element DNA is not required …
Substrate Profile In Rat Soleus Muscle Fibers After Hindlimb Unloading And Fatigue, Varvara P. Grichko, Anne R. Heywood-Cooksey, Kameha R. Kidd, Robert H. Fitts
Substrate Profile In Rat Soleus Muscle Fibers After Hindlimb Unloading And Fatigue, Varvara P. Grichko, Anne R. Heywood-Cooksey, Kameha R. Kidd, Robert H. Fitts
Biological Sciences Faculty Research and Publications
Limb muscles from rats flown in space and after hindlimb unloading (HU) show an increased fatigability, and spaceflight has been shown to result in a reduced ability to oxidize fatty acids. The purpose of this investigation was to determine the effects of HU on the substrate content in fast- and slow-twitch fibers and to assess the substrate utilization patterns in single slow type I fibers isolated from control and HU animals.Asecond objective was to assess whether HU altered the ability of the heart or limb muscle to oxidize pyruvate or palmitate. After 2 wk of HU, single fibers were isolated …
Decreased Thin Filament Density And Length In Human Atrophic Soleus Muscle Fibers After Spaceflight, Danny A. Riley, James L. W. Bain, Joyce L. Thompson, Robert H. Fitts, Jeffrey J. Widrick, Scott W. Trappe, Todd A. Trappe, David L. Costill
Decreased Thin Filament Density And Length In Human Atrophic Soleus Muscle Fibers After Spaceflight, Danny A. Riley, James L. W. Bain, Joyce L. Thompson, Robert H. Fitts, Jeffrey J. Widrick, Scott W. Trappe, Todd A. Trappe, David L. Costill
Biological Sciences Faculty Research and Publications
Soleus muscle fibers were examined electron microscopically from pre- and postflight biopsies of four astronauts orbited for 17 days during the Life and Microgravity Sciences Spacelab Mission (June 1996). Myofilament density and spacing were normalized to a 2.4-μm sarcomere length. Thick filament density (~1,062 filaments/μm2) and spacing (~32.5 nm) were unchanged by spaceflight. Preflight thin filament density (2,976/μm2) decreased significantly (P < 0.01) to 2,215/μm2 in the overlap A band region as a result of a 17% filament loss and a 9% increase in short filaments. Normal fibers had 13% short thin filaments. The 26% decrease in thin filaments …
Effect Of Spaceflight On The Maximal Shortening Velocity, Morphology, And Enzyme Profile Of Fast- And Slow-Twitch Skeletal Muscle Fibers In Rhesus Monkeys, Robert H. Fitts, Janell Romatowski, Lourdes De La Cruz, Jeffrey J. Widrick, Dominique Desplanches
Effect Of Spaceflight On The Maximal Shortening Velocity, Morphology, And Enzyme Profile Of Fast- And Slow-Twitch Skeletal Muscle Fibers In Rhesus Monkeys, Robert H. Fitts, Janell Romatowski, Lourdes De La Cruz, Jeffrey J. Widrick, Dominique Desplanches
Biological Sciences Faculty Research and Publications
No abstract provided.
Effect Of Spaceflight On The Isotonic Contractile Properties Of Single Skeletal Muscle Fibers In The Rhesus Monkey, Robert H. Fitts, Janell R. Romatowski, Cynthia A. Blaser, Lourdes J. De La Cruz, Gwen J. Gettelman, Jeffrey J. Widrick
Effect Of Spaceflight On The Isotonic Contractile Properties Of Single Skeletal Muscle Fibers In The Rhesus Monkey, Robert H. Fitts, Janell R. Romatowski, Cynthia A. Blaser, Lourdes J. De La Cruz, Gwen J. Gettelman, Jeffrey J. Widrick
Biological Sciences Faculty Research and Publications
No abstract provided.
Segmental Distribution Of Common Synaptic Inputs To Spinal Motoneurons During Fictive Swimming In The Lamprey, James T. Buchanan, Stefan Kasicki
Segmental Distribution Of Common Synaptic Inputs To Spinal Motoneurons During Fictive Swimming In The Lamprey, James T. Buchanan, Stefan Kasicki
Biological Sciences Faculty Research and Publications
These experiments were designed to measure the degree of shared synaptic inputs coming to pairs of myotomal motoneurons during swimming activity in the isolated spinal cord of the lamprey. In addition, the experiments measured the decrease in the degree of shared synaptic inputs with the distance between the motoneurons to assess the segmental distribution of these shared inputs. Intracellular microelectrode recordings of membrane potential were made simultaneously on pairs of myotomal motoneurons during swimming activity induced with an excitatory amino acid. The swim cycle oscillations of motoneuron membrane potentials were removed with a digital notch filter, thus leaving the fast …
Commissural Interneurons In Rhythm Generation And Intersegmental Coupling In The Lamprey Spinal Cord, James T. Buchanan
Commissural Interneurons In Rhythm Generation And Intersegmental Coupling In The Lamprey Spinal Cord, James T. Buchanan
Biological Sciences Faculty Research and Publications
Commissural interneurons in rhythm generation and intersegmental coupling in the lamprey spinal cord. To test the necessity of spinal commissural interneurons in the generation of the swim rhythm in lamprey, longitudinal midline cuts of the isolated spinal cord preparation were made. Fictive swimming was then induced by bath perfusion with an excitatory amino acid while recording ventral root activity. When the spinal cord preparation was cut completely along the midline into two lateral hemicords, the rhythmic activity of fictive swimming was lost, usually replaced with continuous ventral root spiking. The loss of the fictive swim rhythm was not due to …
Effect Of A 17 Day Spaceflight On Contractile Properties Of Human Soleus Muscle Fibres, Jeffrey J. Widrick, Shannon T. Knuth, Kris M. Norenberg, Janell A. Romatowski, James L. W. Bain, Danny A. Riley, M. Karhanek, S. W. Trappe, Todd A. Trappe, David Costill, Robert H. Fitts
Effect Of A 17 Day Spaceflight On Contractile Properties Of Human Soleus Muscle Fibres, Jeffrey J. Widrick, Shannon T. Knuth, Kris M. Norenberg, Janell A. Romatowski, James L. W. Bain, Danny A. Riley, M. Karhanek, S. W. Trappe, Todd A. Trappe, David Costill, Robert H. Fitts
Biological Sciences Faculty Research and Publications
1. Soleus biopsies were obtained from four male astronauts 45 days before and within 2 h after a 17 day spaceflight. 2. For all astronauts, single chemically skinned post-flight fibres expressing only type I myosin heavy chain (MHC) developed less average peak Ca¥ activated force (Pï) during fixed-end contractions (0·78 ± 0·02 vs. 0·99 ± 0·03 mN) and shortened at a greater mean velocity during unloaded contractions (Vï) (0·83 ± 0·02 vs. 0·64 ± 0·02 fibre lengths s¢) than preflight type I fibres. 3. The flight-induced decline in absolute Pï was attributed to reductions in fibre diameter and Ï or …
Physiological And Morphological Correlates Of Presynaptic Inhibition In Primary Afferents Of The Lamprey Spinal Cord, I. V. Batueva, E. A. Tsvetkov, A. K. Sagatelyan, James T. Buchanan, N. Vesselkin, V. Adanina, E. I. Suderevskaya, J. -P Rio, J. Repérant
Physiological And Morphological Correlates Of Presynaptic Inhibition In Primary Afferents Of The Lamprey Spinal Cord, I. V. Batueva, E. A. Tsvetkov, A. K. Sagatelyan, James T. Buchanan, N. Vesselkin, V. Adanina, E. I. Suderevskaya, J. -P Rio, J. Repérant
Biological Sciences Faculty Research and Publications
Patch-clamp recordings in a whole-cell mode were performed on dorsal sensory cells enzymatically isolated from the spinal cord of two lamprey species, Ichthyomyzon unicuspis and Lampetra fluviatilis. The voltage-activated currents through calcium channels were analysed. GABA and the specific GABAB receptor agonist baclofen reduced the peak amplitude of inward Ba2+ current, as a robust alternate charge carrier through voltage-dependent Ca2+ channels. These effects were dose-dependent and reversible. GABAB receptor antagonists, 2-hydroxysaclofen and δ-amino-n-valeric acid, blocked the reduction of Ba2+ currents by GABA and baclofen, while bicuculline, a GABAA receptor antagonist, had no blocking …
Developmental Changes In The Nicotinic Responses Of Ciliary Ganglion Neurons, Edward M. Blumenthal, Richard D. Shoop, Darwin K. Berg
Developmental Changes In The Nicotinic Responses Of Ciliary Ganglion Neurons, Edward M. Blumenthal, Richard D. Shoop, Darwin K. Berg
Biological Sciences Faculty Research and Publications
Developmental changes in the nicotinic responses of ciliary ganglion neurons. J. Neurophysiol. 81: 111–120, 1999. The accumulation of functional neurotransmitter receptors by neurons during development is an essential part of synapse formation. Chick ciliary ganglion neurons express two kinds of nicotinic receptors. One is abundant, contains the α7 gene product, rapidly desensitizes, and binds α-bungarotoxin. The other is less abundant, contains multiple gene products (α3, β4, α5, and β2 subunits), slowly desensitizes, and binds the monoclonal antibody mAb 35. Rapid application of agonist to freshly dissociated neurons elicits responses from both classes of receptors. Between embryonic days 8 and 15, …
Five Myofibrillar Lesion Types In Eccentrically Challenged, Unloaded Rat Adductor Longus Muscle—A Test Model, Joyce L. Thompson, Edward Michael Balog, Robert H. Fitts, Danny A. Riley
Five Myofibrillar Lesion Types In Eccentrically Challenged, Unloaded Rat Adductor Longus Muscle—A Test Model, Joyce L. Thompson, Edward Michael Balog, Robert H. Fitts, Danny A. Riley
Biological Sciences Faculty Research and Publications
Sarcomere disruptions are observed in the adductor longus (AL) muscles following voluntary reloading of spaceflown and hindlimb suspension unloaded (HSU) rat, which resemble lesions in eccentrically challenged muscle. We devised and tested an eccentric contraction (ECCON) test system for the 14-day HSU rat AL. Six to 7 hours following ECCON, ALs were fixed to allow immunostaining and electron microscopy (EM). Toluidine blue-stained histology semithin sections were screened for lesion density (#/mm2). Serial semithin sections from the ECCON group were characterized for myosin immunointensity of lesions. Five myofibrillar lesion types were identified in histological semithin sections: focal contractions; wide …