Life Sciences Commons^™

Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

Photo- And Electropatterning Of Hydrogel-Encapsulated Living Cell Arrays, Dirk Albrecht, Valerie Tsang, Robert Sah, Sangeeta Bhatia

Dirk R. Albrecht

Living cells have the potential to serve as sensors, naturally integrating the response to stimuli to generate predictions about cell fate (e.g., differentiation, migration, proliferation, apoptosis). Miniaturized arrays of living cells further offer the capability to interrogate many cells in parallel and thereby enable high-throughput and/or combinatorial assays. However, the interface between living cells and synthetic chip platforms is a critical one wherein the cellular phenotype must be preserved to generate useful signals. While some cell types retain tissue-specific features on a flat (2-D) surface, it has become increasingly apparent that a 3-D physical environment will be required for others. …

Rhodobacter Capsulatus Porphobilinogen Synthase, A High Activity Metal Ion Independent Hexamer, David W. Bollivar, Cheryl Clauson, Rachel Lighthall, Siiri Forbes, Bashkim Kokona, Robert Fairman, Lenka Kundrat, Eileen K. Jaffe

David Bollivar

Background: The enzyme porphobilinogen synthase (PBGS), which is central to the biosynthesis of heme, chlorophyll and cobalamins, has long been known to use a variety of metal ions and has recently been shown able to exist in two very different quaternary forms that are related to metal ion usage. This paper reports new information on the metal ion independence and quaternary structure of PBGS from the photosynthetic bacterium Rhodobacter capsulatus. Results: The gene for R. capsulatus PBGS was amplified from genomic DNA and sequencing revealed errors in the sequence database. R. capsulatus PBGS was heterologously expressed in E. coli and …

Embryonic Expression Of Pre-Initiation Dna Replication Factors In Xenopus Laevis, Brian Walter, Jonathan Henry

Brian Walter

We examined the expression of various DNA replication factors, including: cdc45, the factors of the GINS heterotetramer (Sld5, Psf1, Psf2, Psf3), and PCNA, in Xenopus laevis during embryonic development via whole mount in situ hybridization. For the most part, these factors were expressed in similar patterns, with some subtle variations, throughout development within the anterior CNS, pharyngeal arches, and various placodes. More significant variations were also observed, including expression of only Psf1 and Psf2 in the pronephros and unique Psf2 expression in the somitic mesoderm. Overall, these results suggest that common regulatory mechanisms are involved in the transcriptional deployment of …

Thermal And Sodium Dodecylsulfate Induced Transitions Of Streptavidin, Mark Waner, Irina Navrotskaya, Amanda Bain, Edward Oldham, David Mascotti

David P. Mascotti

The strong specific binding of streptavidin (SA) to biotin is utilized in numerous biotechnological applications. The SA tetramer is also known to exhibit significant stability, even in the presence of sodium dodecylsulfate (SDS). Despite its importance, relatively little is known about the nature of the thermal denaturation pathway for SA. This work uses a homogeneous SA preparation to expand on the data of previous literature reports, leading to the proposal of a model for temperature induced structural changes in SA. Temperature dependent data were obtained by SDS and native polyacrylamide gel electrophoresis (PAGE), differential scanning calorimetry (DSC), and fluorescence and …

The Functions Of Animal Micrornas., Victor Ambros

Victor R. Ambros

MicroRNAs (miRNAs) are small RNAs that regulate the expression of complementary messenger RNAs. Hundreds of miRNA genes have been found in diverse animals, and many of these are phylogenetically conserved. With miRNA roles identified in developmental timing, cell death, cell proliferation, haematopoiesis and patterning of the nervous system, evidence is mounting that animal miRNAs are more numerous, and their regulatory impact more pervasive, than was previously suspected.

Receptivity For Probiotic Products Among Pre-Menopausal Female Students In An African University, Kingsley Anukam, Emmanuel Osazuwa, Gregor Reid, Melanie Katsivo

Kingsley C Anukam

OBJECTIVE: The objective of this study was to examine the receptivity for probiotic products among premenopausal female students in an African university. GOAL: The goal of this study was to determine the local knowledge in Nigeria of probiotics and the willingness of young women to use them should they be introduced. STUDY: Closed-ended questionnaires were administered to a sample of 280 participants and these addressed age, marital status, perceived risk of HIV infection for the next 3 years, and history of urogenital infections. The participants were also asked whether they would welcome a probiotic product in oral/vaginal form and in …

Two New Species Of Marsupial Frogs (Anura: Hylidae: Gastrotheca) From The Cordillera Oriental In Central Peru, Edgar Lehr, William E. Duellman, Daniel Rodriguez, Rudolf Von May

Edgar Lehr

A distinctive new species of Gastrotheca from the Rio Chanchamayo Valley in the Cordillera Oriental in Peru is the only known member of the genus that lacks a tympanum. Another new species from the Cordillera de Carpish is distinctive in having a pair of lateral brood pouches and only basal webbing on the foot.

Protein S-Glutathionylation In Retinal Pigment Epithelium Converts Heat Shock Protein 70 To An Active Chaperone., George Hoppe, Yuh-Cherng Chai, J. Crabb, Jonathan Sears

Yuh-Cherng Chai

A disulfide bond between key redox-sensitive cysteine residues and glutathione is one mechanism by which redox related allosteric effectors can regulate protein structure and function. Here we test the hypothesis that glutaredoxin-1 (Grx-1), a member of the oxidoreductase family of enzymes, may be a critical component of redox-sensitive molecular switches by mediating reversible protein S-glutathionylation and enzymatic catalysis of thiol/disulfide exchange. Deglutathionylation of a 70 kDa protein by Grx-1 was detected using a monoclonal antibody specific to protein S-glutathionylation. Heat shock cognate protein 70 (Hsc70) was identified as a substrate of Grx-1 through mass spectrometry. Recombinant Hsc70 was glutathionylated in …

Growth Rate Gradients And Extracellular Ph In Roots: How To Control An Explosion, Winfried S. Peters

Winfried S. Peters

The C. Elegans Heterochronic Gene Lin-46 Affects Developmental Timing At Two Larval Stages And Encodes A Relative Of The Scaffolding Protein Gephyrin., Anita Pepper, Jill Mccane, Kevin Kemper, Denise Yeung, Rosalind Lee, Victor Ambros, Eric Moss

Victor R. Ambros

The succession of developmental events in the C. elegans larva is governed by the heterochronic genes. When mutated, these genes cause either precocious or retarded developmental phenotypes, in which stage-specific patterns of cell division and differentiation are either skipped or reiterated, respectively. We identified a new heterochronic gene, lin-46, from mutations that suppress the precocious phenotypes caused by mutations in the heterochronic genes lin-14 and lin-28. lin-46 mutants on their own display retarded phenotypes in which cell division patterns are reiterated and differentiation is prevented in certain cell lineages. Our analysis indicates that lin-46 acts at a step immediately downstream …

Forisomes, A Novel Type Of Ca2+-Dependent Contractile Protein Motor [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

The Helicobacter Pylori Flaa1 And Wbpb Genes Control Lipopolysaccharide And Flagellum Synthesis And Function, Alexandra Merkx-Jacques, R. Obhi, G. Bethune, C. Creuzenet

Alexandra Merkx-Jacques

flaA1 and wbpB are conserved genes with unknown biological function in Helicobacter pylori. Since both genes are predicted to be involved in lipopolysaccharide (LPS) biosynthesis, flagellum assembly, or protein glycosylation, they could play an important role in the pathogenesis of H. pylori. To determine their biological role, both genes were disrupted in strain NCTC 11637. Both mutants exhibited altered LPS, with loss of most O-antigen and core modification, and increased sensitivity to sodium dodecyl sulfate compared to wild-type bacteria. These defects could be complemented in a gene-specific manner. Also, flaA1 could complement these defects in the wbpB mutant, suggesting a …

Molecular Profiling: Gene Expression Reveals Discrete Phases Of Lens Induction And Development In Xenopus Laevis, Brian Walter, Yimin Tian, Amy Garlisch, Maria Carinato, Matthew Elkins, Adam Wolfe, Jonathan Schaefer, Kimberly Perry, Jonathan Henry

Brian Walter

No abstract provided.

A Short History Of A Short Rna, Victor Ambros, Rosalind Lee, Rhonda Feinbaum

Victor R. Ambros

Comment on: The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14. [Cell. 1993]

Quantitative Nonisotopic Nitrocellulose Filter Binding Assays: Bacterial Manganese Superoxide Dismutase–Dna Interactions., Joshua Czerwinski, Stephanie Hovan, David Mascotti

David P. Mascotti

Nitrocellulose filter binding assays (NCFBAs) have been used for many years to qualitatively and quantitatively determine protein–nucleic acid affinities. While this technique can be robust thermodynamically and fairly simple to perform, the requirement of radiolabeled nucleic acids (typically 32P) has several major drawbacks. Some disadvantages are the short half-life of 32P, the inherent safety concerns, and the cost of working with radioisotopes. Another drawback is that over time the beta emissions cause fragmentation of the nucleic acids. We have modified standard NCFBAs by developing a quantitative nonisotopic chemiluminescent method using biotin-labeled DNA and a dual-filter format. The biotin tag is …

A Long Drink Of Water: How Xylem Changes With Depth, Gretchen North

Gretchen North

No abstract provided.

Darwinism, Design And Complex Systems Dynamics, David Depew, Bruce Weber

David J Depew

No abstract provided.

Aquaporins Account For Variations In Hydraulic Conductance For Metabolically Active Root Regions Of Agave Deserti In Wet, Dry, And Rewetted Soil, Gretchen North, P. Martre, P. Nobel

Gretchen North

The importance of aquaporins for root hydraulic conductance (LP) was investigated along roots of the desert succulent Agave deserti in wet, dry and rewetted soil. Water channel activity was inferred from HgCl2-induced reductions of LP that were reversible by 2-mercaptoethanol. Under wet conditions, HgCl2 reduced LP for the distal root region by 50% and for the root region near the shoot base by 36% but did not affect LP for the mid-root region. For all root regions, LP decreased by 30–60% during 10 d in drying soil and was not further reduced by HgCl2. After soil rewetting, LP increased to …

Cellular And Molecular Studies Of B Cells Exhibiting Reverse Somatic Mutation Throughout Life, Roberta Pollock, Takao Kodera, Dorel Radu, Tracy Mcgaha, Patty Zwolo, Cristina Stoica, Hilde Cheroute, Roberta Pollack, Constantin Bona

Roberta Pollock

Somatic mutation of immunoglobulin (Ig) genes plays an important role in generating antibody diversity. The frequency of somatic mutation appears to vary throughout life. However, this process has been difficult to study in vivo because the DNA in and around rearranged V genes undergoes random mutation, causing silent or replacement mutations. Therefore, we have developed a transgenic mouse model for studying the frequency of B cells exhibiting mutation in young and old mice. The system is based on a reporter transgene (HuG-X) that encodes a chimeric Ig heavy chain composed of a murine VDJ segment and a human IgG1 constant …

The Neural Bases Of Cognitive Conflict And Control In Moral Judgment., Joshua Greene, Leigh Nystrom, Andrew Engell, John Darley, Jon Cohen

Andrew Engell

Identification Of Micrornas And Other Tiny Noncoding Rnas By Cdna Cloning, Victor Ambros, Rosalind Lee

Victor R. Ambros

MicroRNAs (miRNAs) and other small RNAs can be identified by cloning and sequencing cDNAs prepared from the ∼22-nt fraction of total RNA. Methods are described for the construction of cDNA libraries from small noncoding RNAs through the use of T4 RNA ligase, reverse transcriptase, and polymerase chain reaction. cDNAs are cloned in λ or plasmid vectors, and the sequences are compared to annotated genomic sequence databases, and analyzed by RNA folding programs to distinguish miRNA sequences from other small RNAs of similar size. Northern blot hybridization is used to confirm the expression of small RNAs in vivo.

Species Specificity In Pollen-Pistil Interactions, Rob Swanson

Rob Swanson

For pollination to succeed, pollen must carry sperm through a variety of different floral tissues to access the ovules within the pistil. The pistil provides everything the pollen requires for success in this endeavor including distinct guidance cues and essential nutrients that allow the pollen tube to traverse enormous distances along a complex path to the unfertilized ovule. Although the pistil is a great facilitator of pollen function, it can also be viewed as an elaborate barrier that shields ovules from access from inappropriate pollen, such as pollen from other species. Each discrete step taken by pollen tubes en route …

Pollen And Stigma Structure And Function: The Role Of Diversity In Pollination, Rob Swanson

Rob Swanson

The ornate surfaces of male and female reproductive cells in flowering plants have long attracted attention for their variety and evolutionary significance. These structures, and the molecules involved in sexual interactions, remain among the most rapidly evolving and diverse characteristics known. As varied as they may be, each element takes part in performing the same functions, protecting pollen and stigma from the environment, delivering and capturing pollen, promoting pollen hydration and germination, allowing the entry of appropriate pollen tubes into the stigma, and guiding the tubes to the ovary (Figure 1 A). In this review, we (1) survey recent discoveries …