bluuebunny/crossref_metadata_2025 huggingface dataset:
PROTEOMICS
Authors: de Hoog Carmen L. , Mann Matthias
Published: October 2004

▪ Abstract  The genome sequences of important model systems are available and the focus is now shifting to large-scale experiments enabled by this data. Following in the footsteps of genomics, we have functional genomics, proteomics, and even metabolomics, roughly paralleling the biological hierarchy of the transcription, translation, and production of small molecules. Proteomics is initially concerned with determining the structure, expression, localization, biochemical activity, interactions, and cellular roles of as many proteins as possible. There has been great progress owing to novel instrumentation, experimental strategies, and bioinformatics methods. The area of protein-protein interactions has been especially fruitful. First pass interaction maps of some model organisms exist, and the proteins in many important organelles are about to be determined. Researchers are also beginning to integrate large-scale data sets from various “omics” disciplines in targeted investigations of specific biomedical areas and in pursuit of a general framework for systems biology.
GENETIC SCREENING: Carriers and Affected Individuals
Authors: McCabe Linda L. , McCabe Edward R.B.
Published: October 2004

▪ Abstract  Genetic screening utilizes analytical approaches adapted for high throughput to identify carrier and affected individuals in a targeted population. Currently, genetic screening focuses on carrier screening, prenatal screening, and newborn screening. Newborn screening should serve as a model for all genetic screening, with more than forty years of experience and numerous lessons learned. As with all genetic screening, there are policy concerns in newborn screening regarding which disorders and technologies should be selected, and how centralized or decentralized the process to set policy should be. The need to share experiences and develop databases transcends all other policy considerations in genetic screening. The future will see population-based screening for adult-onset disorders. However, there needs to be extensive research to define predictive risk for various ethnocultural groups and to determine effective interventions. Ethical concerns regarding the timing of population screening, as well as the scope of use of information, will need to be resolved if genomic medicine will achieve its promise of a predictive, preventive, and personalized medicine.
NUTRITIONAL GENOMICS
Authors: Ordovas Jose M. , Corella Dolores
Published: October 2004

▪ Abstract  Nutritional genomics has tremendous potential to change the future of dietary guidelines and personal recommendations. Nutrigenetics will provide the basis for personalized dietary recommendations based on the individual's genetic make up. This approach has been used for decades for certain monogenic diseases; however, the challenge is to implement a similar concept for common multifactorial disorders and to develop tools to detect genetic predisposition and to prevent common disorders decades before their manifestation. The preliminary results involving gene-diet interactions for cardiovascular diseases and cancer are promising, but mostly inconclusive. Success in this area will require the integration of different disciplines and investigators working on large population studies designed to adequately investigate gene-environment interactions. Despite the current difficulties, preliminary evidence strongly suggests that the concept should work and that we will be able to harness the information contained in our genomes to achieve successful aging using behavioral changes; nutrition will be the cornerstone of this endeavor.
EPIGENETICS AND HUMAN DISEASE
Authors: Jiang Yong-hui , Bressler Jan , Beaudet Arthur L.
Published: October 2004

▪ Abstract  Epigenetics is comprised of the stable and heritable (or potentially heritable) changes in gene expression that do not entail a change in DNA sequence. The role of epigenetics in the etiology of human disease is increasingly recognized with the most obvious evidence found for genes subject to genomic imprinting. Mutations and epimutations in imprinted genes can give rise to genetic and epigenetic phenotypes, respectively; uniparental disomy and imprinting defects represent epigenetic disease phenotypes. There are also genetic disorders that affect chromatin structure and remodeling. These disorders can affect chromatin in trans or in cis, as well as expression of both imprinted and nonimprinted genes. Data from Angelman and Beckwith-Wiedemann syndromes and other disorders indicate that a monogenic or oligogenic phenotype can be caused by a mixed epigenetic and genetic and mixed de novo and inherited (MEGDI) model. The MEGDI model may apply to some complex disease traits and could explain negative results in genome-wide genetic scans.
PLANT GENOMICS: The Third Wave
Authors: Borevitz Justin O. , Ecker Joseph R.
Published: October 2004

▪ Abstract  Completing the primary genomic sequence of Arabidopsis thaliana was a major milestone, being the first plant genome and only the third high-quality finished eukaryotic genome sequence. Understanding how the genome sequence comprehensively encodes developmental programs and environmental responses is the next major challenge for all plant genome projects. This requires fully characterizing the genes, the regulatory sequences, and their functions. We discuss several functional genomics approaches to decode the linear sequence of the reference plant Arabidopsis thaliana, including full-length cDNA collections, microarrays, natural variation, knockout collections, and comparative sequence analysis. Genomics provides the essential tools to speed the work of the traditional molecular geneticist and is now a scientific discipline in its own right.
AFRICANS AND ASIANS ABROAD: Genetic Diversity in Europe
Authors: Barbujani Guido , Goldstein David B.
Published: October 2004

▪ Abstract  Besides its obvious intrinsic value, knowledge of population history, and of the demographic and evolutionary changes that accompany it, has proven fundamental to address applied research in human genetics. In this review we place current European genetic diversity in the context of the global human genome diversity and review the evidence supporting a recent African origin of the Europeans. We then discuss the results and the interpretation of genetic studies attempting to quantify the relative importance of various gene flow processes, both within Europe and from Asia into Europe, focusing especially on the initial, Paleolithic colonization of the continent, and on later, Paleolithic postglacial and Neolithic dispersals. Finally, we discuss how knowledge of the patterns of genetic diversity in Europe, and of their inferred generating processes, can be extremely useful in planning health care and in biomedical research.
COMPARATIVE PRIMATE GENOMICS
Authors: Enard Wolfgang , Pääbo Svante
Published: October 2004

▪ Abstract  With the completion of the human genome sequence and the advent of technologies to study functional aspects of genomes, molecular comparisons between humans and other primates have gained momentum. The comparison of the human genome to the genomes of species closely related to humans allows the identification of genomic features that set primates apart from other mammals and of features that set certain primates—notably humans—apart from other primates. In this article, we review recent progress in these areas with an emphasis on how comparative approaches may be used to identify functionally relevant features unique to the human genome.
FINDING PROSTATE CANCER SUSCEPTIBILITY GENES
Authors: Ostrander Elaine A. , Markianos Kyriacos , Stanford Janet L.
Published: October 2004

▪ Abstract  Prostate cancer is a heterogeneous disease with multiple loci contributing to susceptibility. Traditionally, genome-wide scans using high-risk families have utilized stratification by number of affected individuals, family history of other cancers, or family age at diagnosis to improve genetic homogeneity. In addition to locus heterogeneity, for later onset diseases such as prostate cancer, a major limitation to mapping efforts is that key parental DNA samples are rarely available. The lack of available samples from upper generations reduces inheritance information, and as a result, the standard 10-cM genome scan does not provide full power to detect linkage. To increase the ability to find disease-associated loci, much denser genome-wide scans must be undertaken in multiple ethnic groups. In addition, new ways of defining homogenous subsets of families need to be developed.
MOLECULAR NETWORKS IN MODEL SYSTEMS
Authors: Galitski Timothy
Published: October 2004

▪ Abstract  Model organisms, especially the budding yeast, are leading systems in the transformation of biology into an information science. With the availability of genome sequences and genome-scale data generation technologies, the extraction of biological insight from complex integrated molecular networks has become a major area of research. Here I examine key concepts and review research developments. I propose specific areas of research effort to drive network analysis in directions that will promote modeling with increasing predictive power.
COMPARATIVE GENOMICS
Authors: Miller Webb , Makova Kateryna D. , Nekrutenko Anton , Hardison Ross C.
Published: October 2004

▪ Abstract  The genomes from three mammals (human, mouse, and rat), two worms, and several yeasts have been sequenced, and more genomes will be completed in the near future for comparison with those of the major model organisms. Scientists have used various methods to align and compare the sequenced genomes to address critical issues in genome function and evolution. This review covers some of the major new insights about gene content, gene regulation, and the fraction of mammalian genomes that are under purifying selection and presumed functional. We review the evolutionary processes that shape genomes, with particular attention to variation in rates within genomes and along different lineages. Internet resources for accessing and analyzing the treasure trove of sequence alignments and annotations are reviewed, and we discuss critical problems to address in new bioinformatic developments in comparative genomics.
Endangered Antarctic Environments
Authors: Cowan Don A. , Tow Lemese Ah
Published: October 2004

▪ Abstract  The Antarctic continent harbors a range of specialized and sometimes highly localized microbial biotopes. These include biotopes associated with desiccated mineral soils, rich ornithogenic soils, glacial and sea ice, ice-covered lakes, translucent rocks, and geothermally heated soils. All are characterized by the imposition of one or more environmental extremes (including low temperature, wide temperature fluctuations, desiccation, hypersalinity, high periodic radiation fluxes, and low nutrient status). As our understanding of the true microbial diversity in these biotopes expands from the application of molecular phylogenetic methods, we come closer to the point where we can make an accurate assessment of the impacts of environmental change, human intervention, and other natural and unnatural impositions. At present, it is possible to make reasonable predictions about the physical effects of local climate change, but only general predictions on possible changes in microbial community structure. The consequences of some direct human impacts, such as physical disruption of microbial soil communities, are obvious if not yet quantitated. Others, such as the dissemination of nonindigenous microorganisms into indigenous microbial communities, are not yet understood.
Molecular Determinants ofListeria monocytogenesVirulence
Authors: Dussurget Olivier , Pizarro-Cerda Javier , Cossart Pascale
Published: October 2004

▪ Abstract  Listeria monocytogenes is the etiological agent of listeriosis, a severe human foodborne infection characterized by gastroenteritis, meningitis, encephalitis, abortions, and perinatal infections. This gram-positive bacterium is a facultative intracellular pathogen that induces its own uptake into nonphagocytic cells and spreads from cell to cell using an actin-based motility process. This review covers both well-established and recent advances in the characterization of L. monocytogenes virulence determinants and their role in the pathophysiology of listeriosis.
Anaerobic Microbial Dehalogenation
Authors: Smidt Hauke , de Vos Willem M.
Published: October 2004

▪ Abstract  The natural production and anthropogenic release of halogenated hydrocarbons into the environment has been the likely driving force for the evolution of an unexpectedly high microbial capacity to dehalogenate different classes of xenobiotic haloorganics. This contribution provides an update on the current knowledge on metabolic and phylogenetic diversity of anaerobic microorganisms that are capable of dehalogenating—or completely mineralizing—halogenated hydrocarbons by fermentative, oxidative, or reductive pathways. In particular, research of the past decade has focused on halorespiring anaerobes, which couple the dehalogenation by dedicated enzyme systems to the generation of energy by electron transport–driven phosphorylation. Significant advances in the biochemistry and molecular genetics of degradation pathways have revealed mechanistic and structural similarities between dehalogenating enzymes from phylogenetically distinct anaerobes. The availability of two almost complete genome sequences of halorespiring isolates recently enabled comparative and functional genomics approaches, setting the stage for the further exploitation of halorespiring and other anaerobic dehalogenating microbes as dedicated degraders in biological remediation processes.
The Vibrio shiloi/Oculina patagonica Model System of Coral Bleaching
Authors: Rosenberg Eugene , Falkovitz Leah
Published: October 2004

▪ Abstract  The scleractinian coral Oculina patagonica undergoes bleaching (loss of its endosymbiotic zooxanthellae) every summer in the eastern Mediterranean Sea when seawater temperatures rise. The causative agent of the disease is Vibrio shiloi. The pathogen adheres to a β-galactoside-containing receptor in the coral mucus, penetrates into epithelial cells, differentiates into a viable-but-not-culturable form, multiplies, and produces a proline-rich peptide toxin that inhibits photosynthesis of the zooxanthellae in the presence of ammonia. Several of the virulence factors, such as adhesin, toxin, and superoxide dismutase, are produced only at the elevated summer seawater temperatures. The fireworm Hermodice carunculata is a winter reservoir and spring/summer vector for V. shiloi. The generality of the bacterial hypothesis of coral bleaching is discussed.
Signaling in myxobacteria
Authors: Kaiser Dale
Published: October 2004

▪ Abstract  Myxobacteria use soluble and cell-contact signals during their starvation-induced formation of fruiting bodies. These signals coordinate developmental gene expression with the cell movements that build fruiting bodies. Early in development, the quorum-sensing A-signal in Myxococcus xanthus helps to assess starvation and induce the first stage of aggregation. Later, the morphogenetic C-signal helps to pattern cell movement and shape the fruiting body. C-signal is a 17-kDa cell surface protein that signals by contact between the ends of two cells. The number of C-signal molecules per cell rises 100-fold from the beginning of fruiting body development to the end, when spores are formed. Traveling waves, streams, and sporulation have increasing thresholds for C-signal activity, and this progression ensures that spores form inside fruiting bodies.
Molecular and Cellular Basis of Bartonella Pathogenesis
Authors: Dehio Christoph
Published: October 2004

▪ Abstract  The genus Bartonella comprises several important human pathogens that cause a wide range of clinical manifestations: cat-scratch disease, trench fever, Carrión's disease, bacteremia with fever, bacillary angiomatosis and peliosis, endocarditis, and neuroretinitis. Common features of bartonellae include transmission by blood-sucking arthropods and the specific interaction with endothelial cells and erythrocytes of their mammalian hosts. For each Bartonella species, the invasion and persistent intracellular colonization of erythrocytes are limited to a specific human or animal reservoir host. In contrast, endothelial cells are target host cells in probably all mammals, including humans. Bartonellae subvert multiple cellular functions of human endothelial cells, resulting in cell invasion, proinflammatory activation, suppression of apoptosis, and stimulation of proliferation, which may cumulate in vasoproliferative tumor growth. This review summarizes our understanding of Bartonella–host cell interactions and the molecular mechanisms of bacterial virulence and persistence. In addition, current controversies and unanswered questions in this area are highlighted.
Recent Advances in the Characterization of Ambient pH Regulation of Gene Expression in Filamentous Fungi and Yeasts
Authors: Peñalva Miguel A. , Arst, Jr. Herbert N.
Published: October 2004

▪ Abstract  All microorganisms must adapt to the pH of their environment. One aspect of this adaptation, particularly important for organisms that grow over a wide pH range, is the ability to express appropriately genes whose roles ultimately involve functions at the cell surface or in the environment. Genes encoding permeases, secreted enzymes, enzymes involved in synthesis of exported metabolites such as toxins and antibiotics, and probably enzymes modifying secreted proteins posttranslationally all fall into this category. Here we discuss the most recent findings on the transcriptional regulatory system in fungi that enables such genes to be expressed only when the ambient pH is conducive to their ultimate functions. The intriguing issue of how pH is sensed and how the resulting signal is transmitted to the transcription factor involves at least one late endosome component. Proper functioning of the regulatory system responding to ambient pH is essential for fungal pathogenicity of both animals and plants.
Johne's Disease, Inflammatory Bowel Disease, andMycobacterium paratuberculosis
Authors: Chacon Ofelia , Bermudez Luiz E. , Barletta Raúl G.
Published: October 2004

▪ Abstract  Johne's disease is a chronic diarrhea affecting all ruminants. Mycobacterium avium subsp. paratuberculosis (MAP), a slowly growing mycobacteria, is the etiologic agent. There is also a concern that MAP might be a causative agent of some cases of inflammatory bowel disease in humans, especially Crohn's disease. Food products including pasteurized bovine milk have been suggested as potential sources of human infection. This review addresses microbial factors that may contribute to its pathogenicity. In addition, the experimental evidence defining MAP as the cause of Johne's disease and the issues and controversies surrounding its potential pathogenic role in humans are discussed.
Circadian Rhythms in Microorganisms: New Complexities
Authors: Lakin-Thomas Patricia L. , Brody Stuart
Published: October 2004

▪ Abstract  Recent advances in understanding circadian (daily) rhythms in the genera Neurospora, Gonyaulax, and Synechococcus are reviewed and new complexities in their circadian systems are described. The previous model, consisting of a unidirectional flow of information from input to oscillator to output, has now expanded to include multiple input pathways, multiple oscillators, multiple outputs; and feedback from oscillator to input and output to oscillator. New posttranscriptional features of the frq/white-collar oscillator (FWC) of Neurospora are described, including protein phosphorylation and degradation, dimerization, and complex formation. Experimental evidence is presented for frq-less oscillator(s) (FLO) downstream of the FWC. Mathematical models of the Neurospora system are also discussed.
Stationary-Phase Physiology
Authors: Nyström Thomas
Published: October 2004

▪ Abstract  Bacteria enjoy an infinite capacity for reproduction as long as they reside in an environment supporting growth. However, their rapid growth and efficient metabolism ultimately results in depletion of growth-supporting substrates and the population of cells enters a phase defined as the stationary phase of growth. In this phase, their reproductive ability is gradually lost. The molecular mechanism underlying this cellular degeneration has not been fully deciphered. Still, recent analysis of the physiology and molecular biology of stationary-phase E. coli cells has revealed interesting similarities to the aging process of higher organisms. The similarities include increased oxidation of cellular constituents and its target specificity, the role of antioxidants and oxygen tension in determining life span, and an apparent trade-off between activities related to reproduction and survival.
The Small RNA Regulators ofEscherichia coli: Roles and Mechanisms
Authors: Gottesman Susan
Published: October 2004

▪ Abstract  Small noncoding RNAs have been found in all organisms, primarily as regulators of translation and message stability. The most exhaustive searches have taken place in E. coli, resulting in identification of more than 50 small RNAs, or 1%–2% of the number of protein-coding genes. One large class of these small RNAs uses the RNA chaperone Hfq; members of this class act by pairing to target messenger RNAs. Among the members of this class are DsrA and RprA, which positively regulate rpoS translation, OxyS, which negatively regulates rpoS translation and fhlA translation, RyhB, which reapportions iron use in the cell by downregulating translation of many genes that encode Fe-containing proteins, and Spot 42, which changes the polarity of translation in the gal operon. The promoters of these small RNAs are tightly regulated, frequently as part of well-understood regulons. Lessons learned from the study of small RNAs in E. coli can be applied to finding these important regulators in other organisms.
Abrogation of oxidative stress improves insulin sensitivity in the Ren-2 rat model of tissue angiotensin II overexpression
Authors: Blendea Mihaela C. , Jacobs David , Stump Craig S. , McFarlane Samy I. , Ogrin Cristina , Bahtyiar Gul , Stas Samir , Kumar Pawan , Sha Quan , Ferrario Carlos M. , Sowers James R.
Published: October 2004

To evaluate the role of renin-angiotensin system (RAS)-mediated oxidative stress in insulin resistance (IR), we compared the effects of the angiotensin II (ANG II) receptor blocker (ARB) valsartan and a superoxide dismutase (SOD) mimetic, tempol, on whole body glucose tolerance and soleus muscle insulin-stimulated glucose uptake in transgenic hypertensive TG(mREN-2)27 (Ren-2) rats. Ren-2 rats and Sprague-Dawley (SD) controls were given valsartan (30 mg/kg) or tempol (1 mmol/l) in their drinking water for 21 days. IR was measured by glucose tolerance testing (1 g/kg glucose ip). IR index (AUCglucose× AUCinsulin) was significantly higher in the Ren-2 animals compared with SD controls (30.5 ± 7.0 × 106arbitrary units in Ren-2 vs. 10.2 ± 2.4 × 106in SD, P < 0.01). Both valsartan and tempol treatment normalized Ren-2 IR index. Compared with SD controls (100%), there was a significant increase in superoxide anion production (measured by lucigenin-enhanced chemiluminescence) in soleus muscles of Ren-2 rats (133 ± 15%). However, superoxide production was reduced in both valsartan- and tempol-treated (85 ± 22% and 59 ± 12%, respectively) Ren-2 rats. Insulin (INS)-mediated 2-deoxyglucose (2-DG) uptake (%SD basal levels) was substantially lower in Ren-2 rat soleus muscle compared with SD (Ren-2 + INS = 110 ± 3% vs. SD + INS = 206 ± 12%, P < 0.05). However, Ren-2 rats treated with valsartan or tempol exhibited a significant increase in insulin-mediated 2-DG uptake compared with untreated transgenic animals. Improvements in skeletal muscle insulin-dependent glucose uptake and whole body IR in rats overexpressing ANG II by ARB or SOD mimetic indicate that oxidative stress plays an important role in ANG II-mediated insulin resistance.
Activation of PPARγ by curcumin inhibits Moser cell growth and mediates suppression of gene expression of cyclin D1 and EGFR
Authors: Chen Anping , Xu Jianye
Published: October 2004

Colorectal cancer is a leading cause of cancer-related morbidity and mortality in the United States. Curcumin, the yellow pigment in turmeric, possesses inhibitory effects on growth of a variety of tumor cells by reducing cell proliferation and inducing apoptosis. Effects of the peroxisome proliferator-activated receptor-γ (PPARγ) on stimulating cell differentiation and on inducing cell cycle arrest have attracted attention from the perspective of treatment and prevention of cancer. The aim of this study was to elucidate the mechanisms by which curcumin inhibits colon cancer cell growth. In the present report, we observed that curcumin, in a dose-dependent manner, inhibited the growth of Moser cells, a human colon cancer-derived cell line, and stimulated the trans-activating activity of PPARγ. Further studies demonstrated that activation of PPARγ was required for curcumin to inhibit Moser cell growth. Activation of PPARγ mediated curcumin suppression of the expression of cyclin D1, a critical protein in the cell cycle, in Moser cells. In addition, curcumin blocked EGF signaling by inhibiting EGF receptor (EGFR) tyrosine phosphorylation and suppressing the gene expression of EGFR mediated by activation of PPARγ. In addition to curcumin reduction of the level of phosphorylated PPARγ, inhibition of cyclin D1 expression played a major and significant role in curcumin stimulation of PPARγ activity in Moser cells. Taken together, our results demonstrated for the first time that curcumin activation of PPARγ inhibited Moser cell growth and mediated the suppression of the gene expression of cyclin D1 and EGFR. These results provided a novel insight into the roles and mechanisms of curcumin in inhibition of colon cancer cell growth and potential therapeutic strategies for treatment of colon cancer.
Role ofl-Ca2+channels in intestinal pacing in wild-type and W/WVmice
Authors: Boddy Geoffrey , Daniel E. E.
Published: October 2004

Rhythmic contractions generating transit in the digestive tract are paced by a network of cells called interstitial cells of Cajal (ICC) found in the myenteric plexus (MP). ICC generate cyclic depolarizations termed “slow waves” that are passively transmitted to the smooth muscle to initiate contractions. The opening of l-Ca2+channels are believed to be primarily responsible for the influx of calcium generating a contraction in smooth muscle. However, l-Ca2+channels are not thought to be important in generating the pacing current found in ICC. Using intact segments of circular (CM) and longitudinal (LM) muscle from wild-type mice and mice lacking c-kit kinase (W/WV), we found that l-Ca2+channel currents are required for pacing at normal frequencies to occur. Application of 1 μM nicardipine caused a significant decrease in contraction amplitude and frequency in LM and CM that was successfully blocked with BAY K 8644. Nicardipine also abolished the pacing gradient found throughout the intestines, resulting in a uniform contraction frequency of 30–40/minute. Stimulating l-Ca2+channels with BAY K 8644 neither removed nor recovered the pacing gradient. W/WVmice, which lack ICC-MP, also exhibited a pacing gradient in LM. Application of nicardipine to LM segments of W/WVmouse intestine did not reduce pacing frequency, and in jejunum, resulted in a slight increase. BAY K 8644 did not affect pacing frequency in W/WVtissue. In conclusion, we found that l-Ca2+channel activity was required for normal pacing frequencies and to maintain the pacing frequency gradient found throughout the intestines in wild-type but not in W/WVmouse intestine.
COOH-terminal 26-amino acid residues of progastrin are sufficient for stimulation of mitosis in murine colonic epithelium in vivo
Authors: Ottewell P. D. , Varro A. , Dockray G. J. , Kirton C. M. , Watson A. J. M. , Wang T. C. , Dimaline R. , Pritchard D. M.
Published: October 2004

Transgenic mice (hGAS) that overexpress human progastrin are more susceptible than wild-type mice (FVB/N) to the induction of colonic aberrant crypt foci (ACF) and adenomas by the chemical carcinogen azoxymethane. We have previously shown significantly increased levels of colonic mitosis in hGAS compared with FVB/N mice after γ-radiation. To investigate whether the effects of progastrin observed in hGAS colon require the presence of other forms of circulating gastrin, we have crossed hGAS (hg+/+) with gastrin knockout (G−/−) mice to generate mice that express progastrin and no murine gastrin (G−/−hg+/+). After azoxymethane, G−/−hg+/+mice developed significantly more ACF than control G−/−hg−/−mice (which do not express any forms of gastrin). G−/−hg+/+mice also exhibited significantly increased colonic mitosis both before and after exposure to 8 Gray Gy γ-radiation or 50 mg/kg azoxymethane compared with G−/−hg−/−. Treatment of G−/−hg−/−mice with synthetic progastrin (residues 21–101 of human preprogastrin) or G17 extended at its COOH terminus corresponding to the COOH-terminal 26-amino-acid residues of human preprogastrin (residues 76–101, G17-CFP) resulted in continued colonic epithelial mitosis after γ-radiation, whereas glycine-extended gastrin-17 and the COOH-terminal tryptic fragment of progastrin [human preprogastrin-(96–101)] had no effect. Immunoneutralization with an antibody against G17-CFP before γ-radiation significantly decreased colonic mitosis in G−/−hg+/+mice to levels similar to G−/−hg−/−. We conclude that progastrin does not require the presence of other forms of gastrin to exert proliferative effects on colonic epithelia and that the portion of the peptide responsible for these effects is contained within amino acid residues 76–101 of human preprogastrin.
Agonist-induced association of tropomyosin with protein kinase Cα in colonic smooth muscle
Authors: Somara Sita , Pang Haiyan , Bitar Khalil N.
Published: October 2004

Smooth muscle contraction regulated by myosin light chain phosphorylation is also regulated at the thin-filament level. Tropomyosin, a thin-filament regulatory protein, regulates contraction by modulating actin-myosin interactions. Present investigation shows that acetylcholine induces PKC-mediated and calcium-dependent phosphorylation of tropomyosin in colonic smooth muscle cells. Our data also shows that acetylcholine induces a significant and sustained increase in PKC-mediated association of tropomyosin with PKCα in the particulate fraction of colonic smooth muscle cells. Immunoblotting studies revealed that in colonic smooth muscle cells, there is no significant change in the amount of tropomyosin or actin in particulate fraction in response to acetylcholine, indicating that the increased association of tropomyosin with PKCα in the particulate fraction may be due to acetylcholine-induced translocation of PKCα to the particulate fraction. To investigate whether the association of PKCα with tropomyosin was due to a direct interaction, we performed in vitro direct binding assay. Tropomyosin cDNA amplified from colonic smooth muscle mRNA was expressed as GST-tropomyosin fusion protein. In vitro binding experiments using GST-tropomyosin and recombinant PKCα indicated direct interaction of tropomyosin with PKCα. PKC-mediated phosphorylation of tropomyosin and direct interaction of PKCα with tropomyosin suggest that tropomyosin could be a substrate for PKC. Phosphorylation of tropomyosin may aid in holding the slided tropomyosin away from myosin binding sites on actin, resulting in actomyosin interaction and sustained contraction.
Disruption of growth hormone secretion alters Ca2+current density and expression of Ca2+channel and insulin-like growth factor genes in rat atria
Authors: Larsen Janice K. , Chen Chien-Chang , Best Philip M.
Published: October 2004

The influence of the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis on expression of low-voltage-activated (LVA) Ca2+current in atrial tissue was investigated using spontaneous dwarf (SpDwf) rats, a mutant strain that lacks GH. Atrial myocytes from SpDwf rats express LVA and high-voltage-activated (HVA) Ca2+currents and the Ca2+channel α1-subunit genes CaV1.2, CaV2.3, CaV3.1, and CaV3.2. LVA current density decreases significantly beginning at, or shortly after, birth in normal animals; however, its density is maintained in SpDwf rats at 1 pA/pF for ≥12 wk after birth. The abundance of mRNAs encoding CaV2.3 and CaV3.2 declines with advancing age in normal atrial development, yet expression of CaV2.3 mRNA remains significantly elevated in older SpDwf animals. Quantitation of local transcript levels for mRNAs encoding IGF-I and IGF-I receptor (IGF-IR) also reveals significant differences in expression of these transcripts in atrial tissue of SpDwf animals compared with controls. In SpDwf rats, the abundance of IGF-IR mRNA remains elevated at many postnatal ages, whereas mRNA encoding IGF-I is maintained only in older animals. Physiological concentrations of IGF-I cause two- to threefold increases in LVA current density in primary cultures of atrial myocytes, and this effect is blocked by an antisense oligonucleotide targeting the IGF-IR. Thus disruption of GH production in SpDwf animals alters expression of atrial LVA Ca2+channel and IGF genes as well as postnatal regulation of LVA Ca2+current density, most likely acting through compensatory mechanisms via the local IGF-IR.
Engineering of fibrin-based functional and implantable small-diameter blood vessels
Authors: Swartz Daniel D. , Russell James A. , Andreadis Stelios T.
Published: October 2004

We engineered implantable small-diameter blood vessels based on ovine smooth muscle and endothelial cells embedded in fibrin gels. Cylindrical tissue constructs remodeled the fibrin matrix and exhibited considerable reactivity in response to receptor- and nonreceptor-mediated vasoconstrictors and dilators. Aprotinin, a protease inhibitor of fibrinolysis, was added at varying concentrations and affected the development and functionality of tissue-engineered blood vessels (TEVs) in a concentration-dependent manner. Interestingly, at moderate concentrations, aprotinin increased mechanical strength but decreased vascular reactivity, indicating a possible relationship between matrix degradation/remodeling, vasoreactivity, and mechanical properties. TEVs developed considerable mechanical strength to withstand interpositional implantation in jugular veins of lambs. Implanted TEVs integrated well with the native vessel and demonstrated patency and similar blood flow rates as the native vessels. At 15 wk postimplantation, TEVs exhibited remarkable matrix remodeling with production of collagen and elastin fibers and orientation of smooth muscle cells perpendicular to the direction of blood flow. Implanted vessels gained significant mechanical strength and reactivity that were comparable to those of native veins. Our work demonstrates that fibrin-based TEVs hold significant promise for treatment of vascular disease and as a biological model for studying vascular development and pathophysiology.
Regional timing of myocardial shortening is related to prestretch from atrial contraction: assessment by high temporal resolution MRI tagging in humans
Authors: Zwanenburg J. J. M. , Götte M. J. W. , Kuijer J. P. A. , Hofman M. B. M. , Knaapen P. , Heethaar R. M. , van Rossum A. C. , Marcus J. T.
Published: October 2004

Earlier studies have shown substantial nonuniformity in normal left ventricular (LV) myocardial function concerning both the degree of shortening and timing of shortening. We hypothesized that nonuniform LV function may be related to nonuniform prestretch induced by atrial contraction. Eleven healthy human subjects were studied using MRI myocardial tagging and strain analysis. The amount of circumferential prestretch was assessed in 30 LV segments. Prestretch was defined as the difference in strain between end diastole (at ECG R wave) and diastasis. Furthermore, both the degree of shortening (quantified as peak circumferential shortening, peak systolic shortening rate, and amount of postsystolic shortening) and timing of shortening (quantified as the onset time of shortening and time to peak shortening) were assessed. LV prestretch was found to be nonuniform, with the highest values in the lateral wall. The amount of segmental prestretch correlated significantly with peak shortening ( r = 0.79), peak shortening rate ( r = 0.50), amount of postsystolic shortening ( r = 0.67), onset time of shortening ( r = −0.57), and time to peak shortening ( r = 0.71) ( P < 0.001 for each of these relations). These relations may be explained by regional differences in wall stress or by a regional Frank-Starling effect. The correlation between timing of shortening and prestretch demonstrates that mechanical timing is not determined by electrical phenomena alone. In conclusion, regional variation in LV function correlates with the nonuniform prestretch from atrial contraction.
Regulation of atrial contraction by PKA and PKC during development and regression of eccentric cardiac hypertrophy
Authors: Haddad Georges E. , Coleman Bernell R. , Zhao Aiqiu , Blackwell Krista N.
Published: October 2004

ANG II plays a major role in development of cardiac hypertrophy through its AT1receptor subtype, whereas angiotensin-converting enzyme (ACE) inhibitors are effective in reversing effects of ANG II on the heart. The objective of this study was to investigate the role of PKA and PKC in the contractile response of atrial tissue during development and ACE inhibitor-induced regression of eccentric hypertrophy induced by aortocaval shunt. At 1 wk after surgery, sham and shunt rats were divided into captopril-treated and untreated groups for 2 wk. Then isometric contraction was assessed by electrical stimulation of isolated rat left atrial preparations superfused with Tyrode solution in the presence or absence of specific inhibitors KT-5720 (for PKA) and Ro-32-0432 (for PKC) and high Ca2+. Peak tension developed was greater in shunt than in sham hearts. However, when expressed relative to tissue mass, hypertrophied muscle showed weaker contraction than muscle from sham rats. In sham rats, peak tension developed was more affected by PKC than by PKA inhibition, whereas this differential effect was reduced in the hypertrophied heart. Treatment of shunt rats with captopril regressed left atrial hypertrophy by 67% and restored PKC-PKA differential responsiveness toward sham levels. In the hypertrophied left atria, there was an increase in the velocity of contraction and relaxation that was not evident when expressed in specific relative terms. Treatment with ACE inhibitor increased the specific velocity of contraction, as well as its PKC sensitivity, in shunt rats. We conclude that ACE inhibition during eccentric cardiac hypertrophy produces a negative trophic and a positive inotropic effect, mainly through a PKC-dependent mechanism.
Abnormal cardiac wall motion and early matrix metalloproteinase activity
Authors: García Ricardo A. , Brown Kristian L. , Pavelec Richard S. , Go Katrina V. , Covell James W. , Villarreal Francisco J.
Published: October 2004

Activation of matrix metalloproteinases (MMPs) in the heart is known to facilitate cardiac remodeling and progression to failure. We hypothesized that regional dyskinetic wall motion of the left ventricle would stimulate activation of MMPs. Abnormal wall motion at a target site on the anterior lateral wall of the left ventricle was induced by pacing atrial and ventricular sites of five open-chest anesthetized dogs. Changes in shortening at the left ventricular (LV) pacing site and at a remote site at the anterior base of the left ventricle were monitored with piezoelectric crystals. Simultaneous atrial and ventricular pacing resulted in abnormal motion at the LV pacing site, yielding early shortening and late systolic lengthening, whereas the shortening pattern at the remote site remained unaffected. Assessment of global myocardial MMP activity showed a sevenfold increase in substrate cleavage ( P < 0.02) at the LV pacing site relative to the remote site. Gelatin zymography revealed increases in 92-kDa MMP-9 activity and 86-kDa MMP-9 activity at the LV pacing site relative to the remote site, whereas MMP-2 activity was unaffected. Abnormal wall motion was associated with increases in collagen degradation (∼2-fold; P < 0.03), plasmin activity (∼1.5-fold; P < 0.05), nitrotyrosine levels (∼20-fold; P = 0.05), and inflammatory infiltrate (∼2-fold; P < 0.02) relative to the remote site. Results indicate that regional dyskinesis induced by epicardial activation is sufficient to stimulate significant MMP activity in the heart, suggesting that abnormal wall motion is a stimulus for MMP activation.
Hypoxia accelerates nitric oxide-dependent inhibition of mitochondrial complex I in activated macrophages
Authors: Frost Matthew T. , Wang Qi , Moncada Salvador , Singer Mervyn
Published: October 2004

Excess production of nitric oxide (NO) is implicated in the development of multiple organ failure, with a putative mechanism involving direct mitochondrial inhibition, predominantly affecting complex I. The persistent effects of NO on complex I may be mediated through S-nitrosylation and/or nitration. The temporal contribution of these chemical modifications to the inhibition of respiration and the influence of concurrent hypoxia have not been previously examined. We therefore addressed these questions using J774 macrophages activated by endotoxin and interferon-γ over a 24-h period, incubated at 21% and 1% oxygen. Oxygen consumption and complex I activity fell progressively over time in the activated cells. This was largely prevented by coincubation with the nonspecific NO synthase inhibitor l- N5-(1-iminoethyl)-ornithine. Addition of glutathione ethyl ester reversed the inhibition at initial time points, suggesting an early mechanism involving nitrosylation. Thereafter, the inhibition of complex I became more persistent, coinciding with a progressive increase in mitochondrial nitration. Hypoxia accelerated the persistent inhibition of complex I, despite a reduction in the total amount of NO generated. Our results suggest that hypoxia amplified the mitochondrial inhibition induced by NO generated during inflammatory disease states.
Parenteral iron compounds sensitize mice to injury-initiated TNF-α mRNA production and TNF-α release
Authors: Zager Richard A. , Johnson A. C. M. , Hanson S. Y. , Lund Steve
Published: October 2004

Intravenous Fe is widely used to treat anemia in renal disease patients. However, concerns of potential Fe toxicity exist. To more fully define its spectrum, this study tested Fe's impact on systemic inflammation following either endotoxemia or the induction of direct tissue damage (glycerol-mediated rhabdomyolysis). The inflammatory response was gauged by tissue TNF-α message expression and plasma TNF-α levels. CD-1 mice received either intravenous Fe sucrose, -gluconate, or -dextran (FeS, FeG, or FeD, respectively; 2 mg), followed by either endotoxin (LPS) or glycerol injection 0–48 h later. Plasma TNF-α was assessed by ELISA 2–3 h after the LPS or glycerol challenge. TNF-α mRNA expression (RT-PCR) was measured in the kidney, heart, liver, lung, and spleen with Fe ± LPS treatment. Finally, the relative impacts of intramuscular vs. intravenous Fe and of glutathione (GSH) on Fe/LPS- induced TNF-α generation were assessed. Each Fe preparation significantly enhanced LPS- or muscle injury-mediated TNF-α generation. This effect was observed for at least 48 h post-Fe injection, a time at which plasma iron levels were increased by levels insufficient to fully saturate transferrin. Fe did not independently increase plasma TNF-α or tissue mRNA. However, it potentiated postinjury-induced TNF-α mRNA increments and did so in an organ-specific fashion (kidney, heart, and lung; but not in liver or spleen). Intramuscular administration, but not GSH treatment, negated Fe's ability to synergize LPS-mediated TNF-α release. We conclude 1) intravenous Fe can enhance TNF-α generation during LPS- or glycerol-induced tissue damage; 2) increased TNF-α gene transcription in the kidney, heart, and lung may contribute to this result; and 3) intramuscular administration, but not GSH, might potentially mitigate some of Fe's systemic toxic effects.
Pulmonary artery smooth muscle activation attenuates arterial dysfunction during acute pulmonary hypertension
Authors: Santana Daniel Bia , Barra Juan Gabriel , Grignola Juan Carlos , Ginés Fernando Florencio , Armentano Ricardo Luis
Published: October 2004

Acute pulmonary hypertension (PH) may arise with or without an increase in vascular smooth muscle (VSM) tone. Our objective was to determine how VSM activation affects both the conduit (CF) and wall buffering (BF) functions of the pulmonary artery (PA) during acute PH states. PA instantaneous flow, pressure, and diameter of six sheep were recorded during normal pressure (CTL) and different states of acute PH: 1) passively induced by PA mechanical occlusion (PPH); 2) actively induced by intravenous administration of phenylephrine (APH); and 3) a combination of both (APPH). To evaluate the direct effect of VSM activation, isobaric (PPH vs. APH) and isometric (CTL vs. APPH) analyses were performed. We calculated the local BF from the elastic (EPD) and viscous (ηPD) indexes as ηPD/EPD and the characteristic impedance (ZC) from pressure and flow to evaluate CF as 1/ZC. We also calculated the absolute and normalized cross-sectional pulsatility (PCS and NPCS, respectively), the dynamic compliance (CDYN), the cross-sectional distensibility (DCS), and the pressure-strain elastic modulus (EP). The isobaric analysis showed increase of CF, BF, and ηPD ( P < 0.01) and decrease of EPD ( P < 0.05) during APH in respect to PPH (concomitant with isobaric VSM activation-induced vasoconstriction, P < 0.01). The isometric analysis showed increase of EPD and ηPD ( P < 0.01), nonsignificant difference in BF (even in the presence of a significant mean PA pressure rise, from 14 (SD 6) to 25 (SD 8) mmHg, P < 0.01), and decrease in CF ( P < 0.01) during APPH respect to CTL. Mechanical occlusions (PPH and APPH) reduced BF ( P < 0.01) and increased EPD ( P < 0.05) with regard to their previous steady states (CTL and APH). Nonsignificant differences were found in EPD between PPH and APPH. VSM activation (APH and APPH) increased ηPD ( P < 0.01) respect to their previous passive states (CTL and PPH), but no significant differences were found within similar levels of VSM activation. In conclusion, VSM plays a relevant role in main pulmonary artery function during acute pulmonary hypertension, because isobaric vasoconstriction induced by VSM activation improves both BF and CF, mainly due to the increase in ηPD concomitant with the arterial compliance. CDYN and DCS were the more pertinent clinical indexes of arterial elasticity. Additionally, the ηPD-mediated preservation of the BF could be evaluated by the geometric related indexes (PCS and NPCS), which appear to be qualitative markers of arterial wall viscosity status.