Psychosocial correlates of physical activity in healthy children.

Background: Understanding the determinants of physical activity in children is critical for the treatment and prevention of childhood obesity. Social-cognitive theory has been used to understand behavioral patterns in children.

Objectives: To explore the relationship between health beliefs, self-efficacy, social support, and sedentary activities and physical activity levels in children and to examine the relationship between physical activity and children's self-esteem.

Induction of heme oxygenase 1 in radiation nephropathy: role of angiotensin II.

Datta, P. K., Moulder, J.

The cap-to-tail guide to mRNA turnover.

The levels of cellular messenger RNA transcripts can be regulated by controlling the rate at which the mRNA decays. Because decay rates affect the expression of specific genes, they provide a cell with flexibility in effecting rapid change. Moreover, many clinically relevant mRNAs--including several encoding cytokines, growth factors and proto-oncogenes--are regulated by differential RNA stability.

Attenuation of malonate toxicity in primary mesencephalic cultures using the GABA transport blocker, NO-711.

Cultured rat mesencephalic neurons were used to assess the effects of gamma-aminobutyric acid (GABA) transport blockers on toxicity caused by malonate, a reversible, competitive inhibitor of succinate dehydrogenase. Previous studies utilizing an ex vivo chick retinal preparation have shown that GABA release and cell swelling are early consequences of acute energy impairment and that GABA transport blockers attenuate this toxicity. The present results demonstrate that the nonsubstrate GABA transport blocker, NO-711 (1 nM-1 microM), dose-dependently protected cultured mesencephalic dopamine (DA) and GABA neurons from malonate-induced toxicity.

Folding pathway mediated by an intramolecular chaperone: the structural and functional characterization of the aqualysin I propeptide.

Aqualysin I, a thermostable homologue of subtilisin, requires its propeptide (ProA) to function as an intramolecular chaperone (IMC). To decipher the mechanisms through which propeptides can initiate protein folding, we characterized ProA in terms of its sequence, structure and function. Our results show that, in contrast to ProS (propeptide of subtilisin), ProA can fold spontaneously, reversibly and cooperatively into a stable monomeric alpha-beta conformation, even when isolated from its cognate protease-domain.

Tumor hypoxia and anemia: impact on the efficacy of radiation therapy.

The adverse effects of tumor hypoxia and anemia on the efficacy of radiation therapy have been increasingly recognized. In vitro data indicate that radiation therapy under hypoxic conditions is approximately one third as effective as that under normoxic conditions. There is accumulating clinical evidence of significantly reduced local-regional tumor control and overall survival in anemic patients receiving radiotherapy for head and neck, respiratory tract, pelvic, or genitourinary cancers.

The DNA repair protein rad23 is a negative regulator of multi-ubiquitin chain assembly.

Rad23 is a nucleotide-excision repair protein with a previously unknown biochemical function. We determined that yeast and human Rad23 inhibited multi-ubiquitin (Ub) chain formation and the degradation of proteolytic substrates. Significantly, Rad23 could be co-precipitated with a substrate that contained a short multi-Ub chain.

Evidence for an interaction between ubiquitin-conjugating enzymes and the 26S proteasome.

The targeting of proteolytic substrates is accomplished by a family of ubiquitin-conjugating (E2) enzymes and a diverse set of substrate recognition (E3) factors. The ligation of a multiubiquitin chain to a substrate can promote its degradation by the proteasome. However, the mechanism that facilitates the translocation of a substrate to the proteasome in vivo is poorly understood.

Expression patterns of two putative odorant-binding proteins in the olfactory organs of Drosophila melanogaster have different implications for their functions.

The aqueous medium bathing the dendrites of olfactory neurons contains high concentrations of odorant-binding proteins (OBPs) whose role is still unclear. OBPs may facilitate interactions between odorants and their membrane-bound receptors, perhaps by increasing the water solubility of hydrophobic molecules. Alternatively, OBPs may be involved in the inactivation of odorants and other volatile molecules, preventing desensitization and/or protecting olfactory neurons from toxic chemicals.

Type XV collagen in human colonic adenocarcinomas has a different distribution than other basement membrane zone proteins.

In situ carcinomas must penetrate their own basement membrane to be classified as invasive, and subsequently infiltrate surrounding connective tissue and cross vascular basement membranes to metastasize hematogenously. Accordingly, in many studies, integral basement membrane components, including type IV collagen, laminin, and heparan sulfate proteoglycan, have been localized in a spectrum of tumors to gain insight into their role in neoplasia. A number of recently identified extracellular matrix molecules and isoforms of the aforementioned proteins have been localized to the basement membrane zone, illustrating another level of biochemical heterogeneity in these structures.

Evaluation of the clinical usefulness of C. difficile toxin testing in hospitalized patients with diarrhea.

Although numerous studies have evaluated the sensitivity and specificity of different assays for Clostridium difficile toxin, none has evaluated how physicians utilize these tests or respond to test results. Therefore, we assessed patient characteristics, clinical findings, and physician responses to positive and negative assay results at two university-affiliated hospitals, one of which used a cell cytotoxicity assay to test for C. difficile toxin and the other of which used an enzyme immunoassay.

Introduction of protein kinase recognition sites into proteins: a review of their preparation, advantages, and applications.

Labeled proteins are used in a variety of applications. This review focuses on methods that utilize genetic engineering to introduce protein kinase recognition sites into proteins. Many protein kinase recognition sites can be introduced into proteins and serve as useful tags for a variety of purposes.

Pleiotropic defects caused by loss of the proteasome-interacting factors Rad23 and Rpn10 of Saccharomyces cerevisiae.

Rad23 is a member of a novel class of proteins that contain unprocessed ubiquitin-like (UbL) domains. We showed recently that a small fraction of Rad23 can form an interaction with the 26S proteasome. Similarly, a small fraction of Rpn10 is a component of the proteasome.

Characterization of a temperature-sensitive mutant of a ubiquitin-conjugating enzyme and its use as a heat-inducible degradation signal.

The ubiquitin/proteasome pathway is a highly conserved mechanism of proteolysis in all eukaryotes. Ubiquitin (Ub) is conjugated to proteolytic substrates through the sequential action of ubiquitin-activating (E1/Uba) and ubiquitin-conjugating (E2/Ubc) enzymes. The mechanism of substrate recognition and ubiquitination is an area of active investigation, and we have begun a site-directed mutagenesis approach to define the biochemical and biophysical properties of ubiquitin-conjugating enzymes.

Proximity of a Tat peptide to the HIV-1 TAR RNA loop region determined by site-specific photo-cross-linking.

Transcriptional regulation in human immunodeficiency virus type 1 (HIV-1) requires specific interactions of Tat protein with the trans-activation responsive region (TAR) RNA, a 59-base stem-loop structure located at the 5'-ends of all HIV-1 mRNAs. We have used a site-specific cross-linking method based on 4-thio-uracil (4-thioU) photochemistry to determine the interactions of a Tat peptide, Tat(38-72), with the loop region of TAR RNA under physiological conditions. A TAR RNA construct with a single 4-thioU residue at positions U31 in the loop sequence was synthesized by chemical methods.

The surveillance complex interacts with the translation release factors to enhance termination and degrade aberrant mRNAs.

The nonsense-mediated mRNA decay pathway is an example of an evolutionarily conserved surveillance pathway that rids the cell of transcripts that contain nonsense mutations. The product of the UPF1 gene is a necessary component of the putative surveillance complex that recognizes and degrades aberrant mRNAs. Recent results indicate that the Upf1p also enhances translation termination at a nonsense codon.

Identifying the right stop: determining how the surveillance complex recognizes and degrades an aberrant mRNA.

The nonsense-mediated mRNA decay (NMD) pathway functions by checking whether translation termination has occurred prematurely and subsequently degrading the aberrant mRNAs. In Saccharomyces cerevisiae, it has been proposed that a surveillance complex scans 3' of the premature termination codon and searches for the downstream element (DSE), whose recognition by the complex identifies the transcript as aberrant and promotes its rapid decay. The results presented here suggest that translation termination is important for assembly of the surveillance complex.

Bovine type I interferon receptor protein BoIFNAR-1 has high-affinity and broad specificity for human type I interferons.

The type I interferon receptor (IFNAR) is composed of two transmembrane polypeptides, IFNAR-1 and IFNAR-2. Human IFNAR-1 has low intrinsic affinity for IFNs, but enhances the affinity for IFNs of the complex over that of HuIFNAR-2 alone, and modulates the ligand specificity. Bovine cells respond to human alpha interferons.

Expression and potential role of the extracellular matrix in hepatic ontogenesis: a review.

Studies from a number of laboratories have provided information on the temporal and spatial expression of a variety of extracellular matrix (ECM) components in the developing liver and insight into their potential roles in hepatogenesis. Collagen type IV and laminin are present in the basement membranes of the capsular mesothelium, vascular structures of the portal and hepatic vein branches, and the ductular elements of the developing liver. The mesothelial, vascular, and ductular epithelial cells synthesize laminin and type IV collagen.

Protein memory through altered folding mediated by intramolecular chaperones.

The 77-residue propeptide of subtilisin acts as an intramolecular chaperone that organizes the correct folding of its own protease domain. Similar folding mechanisms are used by several prokaryotic and eukaryotic proteins, including prohormone-convertases. Here we show that the intramolecular chaperone of subtilisin facilitates folding by acting as a template for its protease domain, although it does not form part of that domain.

Dynamics of RNA-protein interactions in the HIV-1 Rev-RRE complex visualized by 6-thioguanosine-mediated photocrosslinking.

Expression of the structural proteins of human immunodeficiency virus type 1 (HIV-1) requires the direct interaction of multiple copies of the viral protein Rev with its target RNA, the Rev response element (RRE). RRE is a complex 351-nt RNA that is highly structured and located within the viral env gene. During initial Rev-RRE recognition, Rev binds with high affinity to a bubble structure located within the RRE RNA stem-loop II.

Signaling pathways that regulate specification of neurons in developing cerebral cortex.

The expression of the limbic system-associated membrane protein (LAMP), a marker of specific functional regions of the cerebral cortex, has been used to determine the environmental signals that regulate cortical regionalization. Transplant and cell culture studies have shown previously that the fate of precursor cells, based on LAMP expression, is amenable to regulation by exposure to novel environmental stimuli. This has been demonstrated in vitro to be dependent upon exposure to transforming factor-alpha and collagen type IV.

Incorporation of an artificial protease and nuclease at the HIV-1 Tat binding site of trans-activation responsive RNA.

The synthesis of a C-5 modified uridine phosphoramidite which contains a primary amino group protected with Fmoc is described. During cleavage and deprotection of chemically synthesized RNA, the Fmoc protecting group is removed to yield a free amino group at a predetermined position in the RNA sequence that can be covalently modified with any reporter group, small structural probes, and biological molecules. This modified uridine phosphoramidite was used to incorporate a reactive primary amino group at position 24 in the HIV-1 Tat binding site of a trans-activation responsive (TAR) RNA sequence during chemical syntheses.

Complementary distribution of collagen type IV and the epidermal growth factor receptor in the rat embryonic telencephalon.

We previously identified an interaction between collagen type IV and the EGF receptor that regulates the differentiation of a limbic cortical phenotype in vitro (Ferri and Levitt, 1995). In the present study, we map the expression of the EGF receptor and collagen type IV in the embryonic telencephalon of the rat. At embryonic day (E) II, the earliest age examined, both proteins are coexpressed throughout the ventricular zone in the cerebral wall; this zone remains immunoreactive throughout corticogenesis (E14-E19).