Life Sciences Commons^™

Control Of Developmental Timing In Caenorhabditis Elegans, Victor Ambros

Victor R. Ambros

Studies of the nematode Caenorhabditis elegans have identified genetic and molecular mechanisms controlling temporal patterns of developmental events. Mutations in genes of the C. elegans heterochronic pathway cause altered temporal patterns of larval development, in which cells at certain larval stages execute cell division patterns or differentiation programs normally specific for other stages. The products of the heterochronic genes include transcriptional and translational regulators and two different cases of novel small translational regulatory RNAs. Other genes of the pathway encode evolutionarily conserved proteins, including a homolog of the Drosophila Period circadian timing regulator, and a member of the nuclear receptor …

Precise, Highly Female-Biased Sex Ratios In A Social Spider, Leticia Avilés, John Mccormack, Asher Cutter, Todd Bukowski

John E. McCormack

It has been recognized for some time that the risk of producing maleless clutches should select for a lower than binomial variance in the sex ratio of organisms with female–biased sex ratios, small clutches and breeding groups containing the clutch of a single female. However, to date, precise sex ratios have only been reported for organisms with haplodiploid sex determination, a system which allows direct control of the sex of individual offspring. In contrast, under heterogametic sex determination chance is expected to play a crucial role in determining the sex composition of any one family, in particular when males are …

Regulation Of Cell Growth By Oxidized Ldl., Guy Chisolm, Yuh-Cherng Chai

Yuh-Cherng Chai

The first reports of the influences of oxidized LDL (oxLDL) on cell function pertained to negative effects on cell growth—growth arrest, injury, and toxicity. Since these studies, it has become apparent that sublethal levels of oxLDL cause some, but not all, cells to proliferate. This review highlights the growth-promoting effects of oxLDL rather than its inhibitory or injurious effects. Smooth muscle cells (SMCs) and monocyte-macrophages proliferate after exposure to oxLDL; endothelial cells do not. Scavenger receptors are involved in the proliferative effects on monocyte-macrophages, whereas the effects of oxLDL on SMCs appear to be receptor independent. Lysophosphatidylcholine (lysoPC), and structurally …

Nike’S Commercial Solution: Girls, Sneakers, And Salvation, Shelley Lucas

Shelley Lucas

In this article I critically examine the ways in which Nike has situated itself as an active participant in current cultural conversations about girls' and women's participation in sport through three television commercials: `If you let me play', `There's a girl being born in America', and `The Fun Police'. In these advertisements, Nike positions itself as helping girls get a chance to play sports, helping them lead healthier and happier lives, helping them learn the rules of the game, and helping them to have fun. However, I argue that Nike's suggestion that girls can be empowered through sport (and through …

The Mechanic State Of “Inner Tissue” In The Growing Zone Of Sunflower Hypocotyls And The Regulation Of Its Growth Rate Following Excision, Winfried Peters, A. Tomos

Winfried S. Peters

Elimination Of Sequestered Material From The Gills Of Decapod Crustaceans., Gary Martin, Michael Quintero, Michael Quigley, Hovhannes Khosrovian

Gary Martin

Ink particles injected into the hemolymph of the American lobster (Homarus americanus), spiny lobster (Panulirus interruptus), crayfish (Procambarus clarkii), and ridgeback prawn (Sicyonia ingentis) were rapidly removed from circulation, and most were sequestered within nodules in the gills. The morphology of the gills and the nodules were examined from the time of injection until the following molt. The process by which ink was cleared from the gills was the same in all four species. Nodules formed within 10 min after injection and were composed of hemocytes loosely attached to one another and binding small quantities of ink. Within one week, …

A Homeostatic Set Point For Branching In Neurospora Crassa, Michael Watters, Christine Humphries, Ingrid De Vries, Anthony Griffiths

Michael Watters

The mechanisms responsible for controlling hyphal extension and branching are still poorly understood. We have investigated these processes by studying their dependence on temperature and nutrient concentration. Tip growth is highly responsive to temperature change, increasing linearly from 4 to 37 °C. Over this range of temperatures the branching pattern shows virtually no response. Likewise, varying nutrient concentration does not affect branch distribution. Colonies subjected to rapid extreme temperature downshifts (for example from 25 to 4°) display a strong and highly predictable branching response. There are three stages to this response. First there is an initial lag phase of growth …

The Lin-41 Rbcc Gene Acts In The C. Elegans Heterochronic Pathway Between The Let-7 Regulatory Rna And The Lin-29 Transcription Factor, Frank Slack, Michael Basson, Zhongchi Liu, Victor Ambros, H. Horvitz, Gary Ruvkun

Victor R. Ambros

Null mutations in the C. elegans heterochronic gene lin-41 cause precocious expression of adult fates at larval stages. Increased lin-41 activity causes the opposite phenotype, reiteration of larval fates. let-7 mutations cause similar reiterated heterochronic phenotypes that are suppressed by lin-41 mutations, showing that lin-41 is negatively regulated by let-7. lin-41 negatively regulates the timing of LIN-29 adult specification transcription factor expression. lin-41 encodes an RBCC protein, and two elements in the lin-413'UTR are complementary to the 21 nucleotide let-7 regulatory RNA. A lin-41::GFP fusion gene is downregulated in the tissues affected by lin-41 at the time that the let-7 …

Xenopus Laevis Gelatinase B (Xmmp-9): Development, Regeneration, And Wound Healing, Brian Walter, Maria Carinato, Jonathan Henry

Brian Walter

It has been argued that matrix metalloproteinases play important roles in cellular differentiation and regeneration in certain systems. While studying changes in gene expression associated with the phenomena of cornea/lens transdifferentiation ("lens regeneration"), which takes place in the larva of Xenopus laevis, we identified the Xenopus gelatinase B gene. The open reading frame is homologous to other gelatinase B genes identified in other species and encodes all of the domains characteristic of this protein. Xenopus gelatinase B (Xmmp-9) is first expressed during early tail-bud stages in a subset of mesodermal cells scattered throughout the body. Expression is also seen in …

What Makes Plants Different? Principles Of Extracellular Matrix Function In 'Soft' Plant Tissues [Review Article], Winfried Peters, Wolfgang Hagemann, A. Tomos

Winfried S. Peters

Use Of Biotin-Labeled Nucleic Acids For Protein Purification And Agarose-Based Chemiluminescent Electromobility Shift Assays., Joseph Rodgers, Pinky Patel, Jason Hennes, Sara Bolognia, David Mascotti

David P. Mascotti

We have employed biotin-labeled RNA to serve two functions. In one, the biotin tethers the RNA to streptavidin–agarose beads, creating an affinity resin for protein purification. In the other, the biotin functions as a label for use in a modified chemiluminescent electromobility shift assay (EMSA), a technique used to detect the formation of protein–RNA complexes. The EMSA that we describe avoids the use not only of radioactivity but also of neurotoxic acrylamide by using agarose as the gel matrix in which the free nucleic acid is separated from protein–nucleic acid complexes. After separation of free from complexed RNA in agarose, …

Dependence Of The Extent Of Ion Association With Polynucleotides And Peptides As A Function Of Solution Dielectric., David Mascotti, A. Salwan

David P. Mascotti

No abstract provided.

The Baldwin Effect: An Archeology, David Depew

David J Depew

Abstract: “The Baldwin effect” stands for a wide variety of ways in which learn ing can be conceived as guiding adap tive evolution ary change. An analysis of the history of this notion reveals that it does not reliably refer either to a theory-neutral empirical phenomenon or to a single theoretical hypothesis. On the contrary, articulations of the general idea depend on distinctive, but in commensurable, theoretical backgrounds. In reconstructing the conceptual history of the Baldwin effect I hope to support contemporary explorations of idea by encouraging the articulation of new theoretical frameworks in which it might make sense. I …

Heterogeneity In Water Availability Alters Cellular Development And Hydraulic Conductivity Along Roots Of A Desert Succulent, Gretchen North, P. Nobel

Gretchen North

Plants of the desert succulent Agave deserti were grown in partitioned containers to determine whether heterogeneity in soil moisture leads to differences in cellular development and hydraulic conductivity along individual roots. Roots from containers with a dry distal compartment (furthest from the shoot), a wet middle compartment, and a dry proximal compartment had distal regions (including the root tips) that were more suberized and lignified in the endodermis and adjacent cell layers than were root regions from the wet middle compartment. Proximal root regions about 40 mm from the succulent shoot base were also relatively unsuberized, suggesting that both external …

Electrogenic Sodium–Sodium Exchange Carried Out By Na,K-Atpase Containing The Amino Acid Substitution Glu779ala, José Argüello, R.Daniel Peluffo, Jerry Lingrel, Joshua Berlin

José M. Argüello

Na,K-ATPase containing the amino acid substitution glutamate to alanine at position 779 of the a subunit (Glu779Ala) supports a high level of Na-ATPase and electrogenic Na1–Na1 exchange activityin the absence of K1. In microsomal preparations of Glu779Ala enzyme, the Na1 concentration for half maximal activation of Na-ATPase activity was 161 6 14 mM (n 5 3). Furthermore, enzyme activity with 800 mM Na1 was found to be similar in the presence and absence of 20 mM K1. These results showed that Na1, with low affinity, could stimulate enzyme turnover as effectively as K1. To gain further insight into the mechanism …

The Effects Of Drought In The Solidago Altissima - Eurosta Solidaginis - Natural Enemy Complex: Population Dynamics, Local Extirpations, And Measures Of Selection Intensity Of Gall Size, D Sumerford, Warren Abrahamson, A Weis

Warren G. Abrahamson, II

No abstract provided.

Adaptive Amplification, An Inducible Chromosomal Instability Mechanism, P. Hastings, H. Bull, Jennifer Kowalski, S. Rosenberg

Jennifer Kowalski

Adaptive mutation is an induced response to environmental stress in which mutation rates rise, producing permanent genetic changes that can adapt cells to stress. This contrasts with neo-Darwinian views of genetic change rates blind to environmental conditions. DNA amplification is a flexible, reversible genomic change that has long been postulated to be adaptive. We report the discovery of adaptive amplification at the lac operon in Escherichia coli. Additionally, we find that adaptive amplification is separate from, and does not lead to, adaptive point mutation. This contradicts a prevailing alternative hypothesis whereby adaptive mutation is normal mutability in amplified DNA. Instead, …

Review Of The Cynipid Gall Wasps Of The Genus Loxaulus (Hymenoptera Cynipidae) With Descriptions Of New Species, G. Melika, Warren Abrahamson

Warren G. Abrahamson, II

No abstract provided.

Clusterin Is An Atp-Independent Chaperone With Very Broad Substrate Specificity That Stabilizes Stressed Proteins In A Folding-Competent State, Stephen Poon, Simon Easterbrook-Smith, Mark Rybchyn, John Carver, Mark Wilson

Mark R Wilson

We recently reported that the ubiquitous, secreted protein clusterin has chaperone activity in vitro [Humphreys et al. (1999) J. Biol. Chem. 274, 6875−6881]. In this study, we demonstrate that clusterin (i) inhibits stress-induced precipitation of a very broad range of structurally divergent protein substrates, (ii) binds irreversibly via an ATP-independent mechanism to stressed proteins to form solubilized high molecular weight complexes, (iii) lacks detectable ATPase activity, (iv) when acting alone, does not effect refolding of stressed proteins in vitro, and (v) stabilizes stressed proteins in a state competent for refolding by heat shock protein 70 (HSP70). Furthermore, we show that, …

Exploring Adaptations To Famine: Rats Selectively Bred For Differential Intake Of Saccharin Differ On Deprivation-Induced Hyperactivity And Emotionality., Clinton Chapman, Jill Arnal, Dennis Vanderweele, Nancy Dess

Clinton D Chapman

In many mammals, including humans and rats, acute starvation increases locomotor activity. This seemingly paradoxical and potentially lethal behavior pattern may reflect an evolved, multisystem response to sudden threats to metabolic homeostasis. The present study provides a novel test of this idea. Occidental High- (HiS) and Low- (LoS) Saccharin-Consuming rats differ on the taste phenotype and also on some affective measures, on which LoS rats score higher. Wheel running was measured in HiS and LoS rats with food available freely vs for 1 hr daily. As predicted, restricted feeding stimulated significantly more running among LoS rats. Two independent tests of …

The Role Of Na,K-Atpase Alpha Subunit Serine 775 And Glutamate 779 In Determining The Extracellular K+ And Membrane Potential-Dependent Properties Of The Na,K-Pump, José Argüello, R.Daniel Peluffo, Joshua Berlin

José M. Argüello

The roles of Ser775 and Glu779, two amino acids in the putative fifth transmembrane segment of the Na,K-ATPase a subunit, in determining the voltage and extracellular K1 (K1o) dependence of enzyme-mediated ion transport, were examined in this study. HeLa cells expressing the a1 subunit of sheep Na,K-ATPase were voltage clamped via patch electrodes containing solutions with 115 mM Na1 (378C). Na,K-pump current produced by the ouabain-resistant control enzyme (RD), containing amino acid substitutions Gln111Arg and Asn122Asp, displayed a membrane potential and K1o dependence similar to wild-type Na,K-ATPase during superfusion with 0 and 148 mM Na1-containing salt solutions. Additional substitution of …

Historical Review And Current State Of The World Generic Classification Of Oak Galls (Hymenoptera: Cynipidae: Cynipini, Warren Abrahamson, G. Melika

Warren G. Abrahamson, II

No abstract provided.

Virulence Factors From Pseudomonas Aeruginosa Increase Lung Epithelial Permeability, Ali Azghani, E. J. Miller, Barry T. Peterson

Ali Azghani

A Viable Ubiquitin-Activating Enzyme Mutant For Evaluating Ubiquitin System Function In Saccharomyces Cerevisiae, Rob Swanson, Mark Hochstrasser

Rob Swanson

Ligation of proteins to ubiquitin requires activation of ubiquitin by E1, the ubiquitin-activating enzyme. Mutant alleles of E1 in mammalian cells have been crucial for dissecting the contribution of the ubiquitin system to cell function. Comparable mutants have been unavailable for Saccharomyces cerevisiae. Here we describe the isolation and characterization of a hypomorphic allele of S. cerevisiae E1. Protein modification by ubiquitin is strongly impaired in the mutant, inhibiting degradation of ubiquitin^proteasome pathway substrates as well as ubiquitin-dependent but proteasome-independent degradation of membrane receptors. This allele will be a useful tool for evaluating the ubiquitin-dependence of cellular processes in yeast, …