Biology Commons^™

Fc177, A Minor Dec-1 Proprotein, Is Necessary To Prevent Ectopic Aggregation Of The Endochorion During Eggshell Assembly In Drosophila, Debra Kay Mauzy-Melitz, Gail L. Waring

Biological Sciences Faculty Research and Publications

The Drosophila eggshell is a highly specialized extracellular matrix that forms between the oocyte and the surrounding epithelial follicle cells during late oogenesis. The dec-1 gene, which is required for proper eggshell assembly, produces three proproteins that are cleaved within the vitelline membrane layer to multiple derivatives. The different spatial distributions of the cleaved derivatives suggest that they play distinct roles in eggshell assembly. Using extant dec-1 mutations in conjunction with genetically engineered dec-1 transgenes, we show that, although all three dec-1 proproteins, fc106, fc125, and fc177, are required for female fertility, gross morphological abnormalities in the eggshell are observed …

Regulation Of Chloride Permeability By Endogenously Produced Tyramine In The Drosophila Malpighian Tubule, Edward M. Blumenthal

Biological Sciences Faculty Research and Publications

The Malpighian (renal) tubule of Drosophila melanogaster is a useful model for studying epithelial transport. The purpose of this study was to identify factors responsible for modulating transepithelial chloride conductance in isolated tubules. I have found that tyrosine and several of its metabolites cause an increase in chloride conductance. The most potent of these agonists is tyramine, which is active at low nanomolar concentrations; the pharmacology of this response matches that of the previously published cloned insect tyramine receptor. In addition, the tubule appears capable of synthesizing tyramine from applied tyrosine, as shown by direct measurement of tyrosine decarboxylase activity. …

Bacs: An Abundant Bacteroid Protein In Rhizobium Etli Whose Expression Ex Planta Requires Nifa, Olivia Jeanne Jahn, Guillermo Davila, David Romero, K. Dale Noel

Biological Sciences Faculty Research and Publications

Rhizobium etli CFN42 bacteroids from bean nodules possessed an abundant 16-kDa protein (BacS) that was found in the membrane pellet after cell disruption. This protein was not detected in bacteria cultured in tryptone-yeast extract. In minimal media, it was produced at low oxygen concentration but not in a mutant whose nifA was disrupted. N-terminal sequencing of the protein led to isolation of a bacS DNA fragment. DNA hybridization and nucleotide sequencing revealed three copies of the bacS gene, all residing on the main symbiotic plasmid of strain CFN42. A stretch of 304 nucleotides, exactly conserved upstream of all three bacS …

Rhoa Kinase And Protein Kinase C Participate In Regulation Of Rabbit Stomach Fundus Smooth Muscle Contraction, Paul H. Ratz, Joel T. Meehl, Thomas J. Eddinger

Biological Sciences Faculty Research and Publications

1. The degree to which the RhoA kinase (ROK) blockers, Y-27632 (1 µM) and HA-1077 (10 µM), and the PKC blocker, GF-109203X (1 µM), reduced force produced by carbachol, a muscarinic receptor agonist, and phenylephrine, an α-adrenoceptor agonist, was examined in rabbit stomach fundus smooth muscle.

2. When examining the effect on cumulative carbachol concentration-response curves (CRCs), ROK and PKC blockers shifted the potency (~EC50) to the right but did not reduce the maximum response.

3. In a single-dose carbachol protocol using moderate (~EC50) and maximum carbachol concentrations, Y-27632 and HA-1077 reduced peak force, but GF-109203X had no effect. By …

Asi1, A Gene Encoding A Novel Leucine Zipper Protein, Is Induced During Development Of The Macronucleus In Tetrahymena, Rupa A. Udani, Kathleen M. Karrer

Biological Sciences Faculty Research and Publications

Sexual reproduction in the ciliate Tetrahymena follows a complex developmental program involving the sequential regulation of dozens of genes. Genes that are up-regulated during post-zygotic development in Tetrahymena were isolated by subtractive hybridization. Anlagen stage induced gene 1 (ASI1) encodes a 2.8 kb transcript that contains a single intron and is induced during macronuclear development. ASI1 is a single copy gene in both the micronucleus and the macronucleus. It encodes a 95 kDa conceptual protein with a leucine zipper near the amino terminus

Insertion Of Proteins Into The Inner Membrane Of Mitochondria: The Role Of The Oxa1 Complex, Rosemary A. Stuart

Biological Sciences Faculty Research and Publications

The inner mitochondrial membrane harbors a large number of proteins that display a wide range of topological arrangements. The majority of these proteins are encoded in the cell's nucleus, but a few polytopic proteins, all subunits of respiratory chain complexes are encoded by the mitochondrial genome. A number of distinct sorting mechanisms exist to direct these proteins into the mitochondrial inner membrane. One of these pathways involves the export of proteins from the matrix into the inner membrane and is used by both proteins synthesized within the mitochondria, as well as by a subset of nuclear encoded proteins. Prior to …

Herbivore And Pathogen Damage On Grassland And Woodland Plants: A Test Of The Herbivore Uncertainty Principle, Stefan A. Schnitzer, Peter B. Reich, Belle Bergner, Walter P. Carson

Biological Sciences Faculty Research and Publications

Researchers can alter the behaviour and ecology of their study organisms by conducting such seemingly benign activities as non‐destructive measurements and observations. In plant communities, researcher visitation and measurement of plants may increase herbivore damage in some plant species while decreasing it in others. Simply measuring plants could change their competitive ability by altering the amount of herbivore damage that they suffer. Currently, however, there is only limited empirical evidence to support this `herbivore uncertainty principle' (HUP). We tested the HUP by quantifying the amount of herbivore and pathogen damage in 13 plant species (> 1400 individuals) at four different …

Unilateral Lower Limb Suspension Does Not Mimic Bed Rest Or Spaceflight Effects On Human Muscle Fiber Function, Jeffrey J. Widrick, S. W. Trappe, Janell Romatowski, Danny A. Riley, David Costill, Robert H. Fitts

Biological Sciences Faculty Research and Publications

We used Ca²⁺-activated skinned muscle fibers to test the hypothesis that unilateral lower leg suspension (ULLS) alters cross-bridge mechanisms of muscle contraction. Soleus and gastrocnemius biopsies were obtained from eight subjects before ULLS, immediately after 12 days of ULLS (post-0 h), and after 6 h of reambulation (post-6 h). Post-0 h soleus fibers expressing type I myosin heavy chain (MHC) showed significant reductions in diameter, absolute and specific peak Ca²⁺-activated force, unloaded shortening velocity, and absolute and normalized peak power. Fibers obtained from the gastrocnemius were less affected by ULLS, particularly fibers expressing fast MHC isoforms. …

A Novel Family Of Mobile Genetic Elements Is Limited To The Germline Genome In Tetrahymena Thermophila, Jeffrey D. Wuitschick, Jill A. Gershan, Andrew J. Lochowicz, Shuqiang Li, Kathleen M. Karrer

Biological Sciences Faculty Research and Publications

In the ciliated protozoan Tetrahymena thermophila, extensive DNA elimination is associated with differentiation of the somatic macronucleus from the germline micronucleus. This study describes the isolation and complete characterization of Tlr elements, a family of approximately 30 micronuclear DNA sequences that are efficiently eliminated from the developing macronucleus. The data indicate that Tlr elements are comprised of an ~22 kb internal region flanked by complex and variable termini. The Tlr internal region is highly conserved among family members and contains 15 open reading frames, some of which resemble genes encoded by transposons and viruses. The Tlr termini appear to …

The Ecology Of Lianas And Their Role In Forests, Stefan A. Schnitzer, Frans Bongers

Biological Sciences Faculty Research and Publications

Recent studies have demonstrated the increasingly important role of lianas (woody vines) in forest regeneration, species diversity and ecosystem-level processes, particularly in the tropics. Mechanisms responsible for the maintenance of liana species diversity could yield new insights into the maintenance of overall species diversity. Lianas contribute to forest regeneration and competition, not only by competing directly with trees, but also by differentially affecting tree species and thus changing how trees compete among themselves. In addition, they contribute considerably to ecosystem-level processes, such as whole-forest transpiration and carbon sequestration. As the rate of tropical forest disturbance increases, they are likely to …

Dual Requirement For Yeast Hnrnp Nab2p In Mrna Poly(A) Tail Length Control And Nuclear Export, Ronald E. Hector, Keith R. Nykamp, Sonia Dheur, James T. Anderson, Priscilla J. Non, Carl R. Urbinati, Scott M. Wilson, Lionel Minvielle‐Sebastia, Maurice S. Swanson

Biological Sciences Faculty Research and Publications

Recent studies of mRNA export factors have provided additional evidence for a mechanistic link between mRNA 3′‐end formation and nuclear export. Here, we identify Nab2p as a nuclear poly(A)‐binding protein required for both poly(A) tail length control and nuclear export of mRNA. Loss of NAB2 expression leads to hyperadenylation and nuclear accumulation of poly(A)⁺ RNA but, in contrast to mRNA export mutants, these defects can be uncoupled in a nab2 mutant strain. Previous studies have implicated the cytoplasmic poly(A) tail‐binding protein Pab1p in poly(A) tail length control during polyadenylation. Although cells are viable in the absence of NAB2 expression …

Smooth Muscle Myosin Heavy Chain Isoform Distribution In The Swine Stomach, Jonathan A. Parisi, Thomas J. Eddinger

Biological Sciences Faculty Research and Publications

To evaluate the distribution of smooth muscle myosin heavy chain isoforms (SMB, with head insert), we examined frozen sections from the various regions of swine stomachs using isoform-specific antibodies. We previously reported variable SMB myosin heavy chain (MHC) expression in stomach cells that correlates with unloaded shortening velocities. This is consistent with the generalization of tonic fundic muscle having low expression and phasic antral muscle having high expression of the SMB MHC isoform. Using immunohistochemistry (IHC), we show a progression of the SMB MHC from very low immunoreactivity in the fundus to very intense immunoreactivity in the antrum. In the …

Serotonin Modulates Oscillations Of The Membrane Potential In Isolated Spinal Neurons From Lampreys, I. V. Batueva, James T. Buchanan, N. P. Veselkin, E. I. Suderevskaya, E. A. Tsvetkov

Biological Sciences Faculty Research and Publications

Studies were performed on spinal neurons from lampreys isolated by an enzymatic/mechanical method using pronase. The effects of 100 µM serotonin (5-HT) on membrane potential oscillations induced by a variety of excitatory amino acids were studied. 5-HT was found to depolarize branched cells (presumptive motoneurons and interneurons) by 2–6 mV without inducing membrane potential oscillations. However, when oscillations were already present because of an excitatory amino acid, 5-HT changed the parameters of these oscillations, increasing the amplitudes of all types of oscillations, increasing the frequency of irregular oscillations, and increasing the duration of the depolarization plateaus accompanied by action potentials. …

Thin Filament Diversity And Physiological Properties Of Fast And Slow Fiber Types In Astronaut Leg Muscles, 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

Slow type I fibers in soleus and fast white (IIa/IIx, IIx), fast red (IIa), and slow red (I) fibers in gastrocnemius were examined electron microscopically and physiologically from pre- and postflight biopsies of four astronauts from the 17-day, Life and Microgravity Sciences Spacelab Shuttle Transport System-78 mission. At 2.5-µm sarcomere length, thick filament density is ~1,012 filaments/µm² in all fiber types and unchanged by spaceflight. In preflight aldehyde-fixed biopsies, gastrocnemius fibers possess higher percentages (~23%) of short thin filaments than soleus (9%). In type I fibers, spaceflight increases short, thin filament content from 9 to 24% in soleus and …

Shortening Velocity And Myosin Heavy- And Light-Chain Isoform Mrna In Rabbit Arterial Smooth Muscle Cells, Jennifer J. Sherwood, Thomas J. Eddinger

Biological Sciences Faculty Research and Publications

In smooth muscle cells (SMCs) isolated from rabbit carotid, femoral, and saphenous arteries, relative myosin isoform mRNA levels were measured in RT-PCR to test for correlations between myosin isoform expression and unloaded shortening velocity. Unloaded shortening velocity and percent smooth muscle myosin heavy chain 2 (SM2) and myosin light chain 17b (MLC_17b) mRNA levels were not significantly different in single SMCs isolated from the luminal and adluminal regions of the carotid media. Saphenous artery SMCs shortened significantly faster (P < 0.05) than femoral SMCs and had more SM2 mRNA (P < 0.05) than carotid SMCs and less MLC_17b mRNA (P < 0.001) and higher tissue levels of SMB mRNA (P < 0.05) than carotid and femoral SMCs. No correlations were found between percent SM2 and percent MLC_17b mRNA levels and unloaded shortening velocity in SMCs from these arteries. …

Spinal Cord Of Lamprey, James T. Buchanan

Biological Sciences Faculty Research and Publications

No abstract provided.

A Novel Family Of Mobile Genetic Elements Is Limited To The Germline Genome In Tetrahymena Thermophila, Jeffrey D. Wuitschick, Jill A. Gershan, Andrew J. Lochowicz, Shuqiang Li, Kathleen M. Karrer

Biological Sciences Faculty Research and Publications

In the ciliated protozoan Tetrahymena thermophila, extensive DNA elimination is associated with differentiation of the somatic macronucleus from the germline micronucleus. This study describes the isolation and complete characterization of Tlr elements, a family of approximately 30 micronuclear DNA sequences that are efficiently eliminated from the developing macronucleus. The data indicate that Tlr elements are comprised of an ∼22 kb internal region flanked by complex and variable termini. The Tlr internal region is highly conserved among family members and contains 15 open reading frames, some of which resemble genes encoded by transposons and viruses. The Tlr termini appear to …

Methylation Of Adenine In The Nuclear Dna Of "Tetrahymena" Is Internucleosomal And Independent Of Histone H1, Kathleen M. Karrer, Teresa Ann Van Nuland

Biological Sciences Faculty Research and Publications

There are about 50 copies of each chromosome in the somatic macronucleus of the ciliated protozoan Tetrahymena. Approximately 0.8% of the adenine residues in the macronuclear DNA of Tetrahymena are methylated to N⁶-methyladenine. The degree of methylation varies between sites from a very low percentage to >90%. In this study a correlation was found between nucleosome positioning and DNA methylation. Eight GATC sites with different levels of methylation were examined. There was a direct correlation between the degree of methylation and proximity to linker DNA at these sites. Although methylation occurs preferentially in linker DNA, the patterns …

The Effects Of Serotonin On Functionally Diverse Isolated Lamprey Spinal Cord Neurons, I. V. Batueva, James T. Buchanan, N. P. Veselkin, E. I. Suderevskaya, E. A. Tsvetkov

Biological Sciences Faculty Research and Publications

The experiments reported here showed that application of serotonin (5-hydroxytryptamine, 5-HT) (100 µ M) did not induce any significant current through the membranes of any of the spinal neurons studied (n = 62). At the same time, the membranes of most motoneurons and interneurons (15 of 18) underwent slight depolarization (2–6 mV) in the presence of 5-HT, which was not accompanied by any change in the input resistance of the cells. Depolarization to 10–20 mV occurred in some cells (3 of 18) of these functional groups, this being accompanied by 20–60% decreases in input resistance. The same concentration of 5-HT …

Genetic Locus Required For Antigenic Maturation Of Rhizobium Etli Ce3 Lipopolysaccharide, Dominik M. Duelli, Andrea Tobin, Jodie M. Box, V.S. Kumar Kolli, Russell W. Carlson, K. Dale Noel

Biological Sciences Faculty Research and Publications

Rhizobium etli modifies lipopolysaccharide (LPS) structure in response to environmental signals, such as low pH and anthocyanins. These LPS modifications result in the loss of reactivity with certain monoclonal antibodies. The same antibodies fail to recognize previously isolated R. etli mutant strain CE367, even in the absence of such environmental cues. Chemical analysis of the LPS in strain CE367 demonstrated that it lacked the terminal sugar of the wild-type O antigen, 2,3,4-tri-O-methylfucose. A 3-kb stretch of DNA, designated as lpe3, restored wild-type antigenicity when transferred into CE367. From the sequence of this DNA, five open reading frames …

Functional And Structural Adaptations Of Skeletal Muscle To Microgravity, Robert H. Fitts, Danny R. Riley, Jeffrey J. Widrick

Biological Sciences Faculty Research and Publications

Our purpose is to summarize the major effects of space travel on skeletal muscle with particular emphasis on factors that alter function. The primary deleterious changes are muscle atrophy and the associated decline in peak force and power. Studies on both rats and humans demonstrate a rapid loss of cell mass with microgravity. In rats, a reduction in muscle mass of up to 37% was observed within 1 week. For both species, the antigravity soleus muscle showed greater atrophy than the fast-twitch gastrocnemius. However, in the rat, the slow type I fibers atrophied more than the fast type II fibers, …

Characterization Of Transepithelial Potential Oscillations In The Drosophila Malpighian Tubule, Edward M. Blumenthal

Biological Sciences Faculty Research and Publications

The Malpighian tubule of Drosophila melanogaster is a useful model system for studying the regulation of epithelial ion transport. In acutely isolated tubules, the transepithelial potential (TEP) undergoes large oscillations in amplitude with a period of approximately 30s. The TEP oscillations are diminished by reductions in the peritubular chloride concentration in a manner consistent with their being caused by fluctuations in chloride conductance. The oscillations are eliminated by pretreating tubules with the calcium chelator BAPTA-AM, although removal of peritubular calcium has no effect, suggesting that the oscillations are a result of either the release of calcium from intracellular stores or …

Comparison Of A Space Shuttle Flight (Sts-78) And Bed Rest On Human Muscle Function, Scott W. Trappe, Todd A. Trappe, Gary A. Lee, Jeffrey J. Widrick, David L. Costill, Robert H. Fitts

Biological Sciences Faculty Research and Publications

The purpose of this investigation was to assess muscle fiber size, composition, and in vivo contractile characteristics of the calf muscle of four male crew members during a 17-day spaceflight (SF; Life and Microgravity Sciences Spacelab Shuttle Transport System-78 mission) and eight men during a 17-day bed rest (BR). The protocols and timelines of these two investigations were identical, therefore allowing for direct comparisons between SF and the BR. The subjects’ age, height, and weight were 43 +/- 2 yr, 183 +/- 4 cm, and 86 +/- 3 kg for SF and 43 +/- 2 yr, 182 +/- 3 cm, …

Functional Properties Of Slow And Fast Gastrocnemius Muscle Fibers After A 17-Day Spaceflight, Jeffrey J. Widrick, Janell Romatowski, Kris M. Norenberg, Shannon T. Knuth, James L. W. Bain, Danny A. Riley, S. W. Trappe, Todd A. Trappe, David Costill, Robert H. Fitts

Biological Sciences Faculty Research and Publications

The purpose of this investigation was to study the effects of a 17-day spaceflight on the contractile properties of individual fast- and slowtwitch fibers isolated from biopsies of the fast-twitch gastrocnemius muscle of four male astronauts. Single chemically skinned fibers were studied during maximal Ca²⁺-activated contractions with fiber myosin heavy chain (MHC) isoform expression subsequently determined by SDS gel electrophoresis. Spaceflight had no significant effect on the mean diameter or specific force of single fibers expressing type I, IIa, or IIa/IIx MHC, although a small reduction in average absolute force (P_o) was observed for the type …

Rna Levels And Activity Of Flowering Locus C Are Modified In Mixed Genetic Backgrounds Of Arabidopsis Thaliana, Michael Schläppi

Biological Sciences Faculty Research and Publications

Flowering time and FLOWERING LOCUS C (FLC) RNA levels were analyzed in different accessions of Arabidopsis thaliana and in mixed genetic backgrounds resulting from crosses between accessions. Dominant alleles of FRIGIDA (FRI) promote accumulation of FLC RNA, which in turn promotes late flowering. Although the coding regions of sequenced FLC alleles are identical, some accessions have genetically weak alleles that do not promote late flowering in the presence of FRI. In this study, a new weak allele of FLC with open reading frame identity to previously sequenced alleles was isolated from a Niederzenz (Nd) accession. …

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

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

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

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

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); …