bluuebunny/crossref_metadata_2025 huggingface dataset:
THE DYNAMICS OF BILATERAL EXCHANGE AND DIVISION OF LABOR
Authors: HAUSKEN KJELL , MOXNES JOHN F.
Published: May 2005

The article presents a dynamic model of exchange, production, and consumption. In a dynamic world, complicated predictions often have to be made. Thus, in this article, the classical exchange model is expanded with a dynamic model specifying the intermediate states toward a static equilibrium, which may or may not be reached. A price mechanism was necessary to develop in order to describe these changes over time. The model is illustrated with two examples of the emergence of division of labor. The robustness of the dynamic model is tested with sensitivity analysis.
HOW SMART DOES AN AGENT NEED TO BE?
Authors: KIRKPATRICK SCOTT , SCHNEIDER JOHANNES J.
Published: May 2005

The classic distributed computation is done by atoms, molecules or spins in vast numbers, each equipped with nothing more than the knowledge of their immediate neighborhood and the rules of statistical mechanics. These agents, 1023 or more, are able to form liquids and solids from gases, realize extremely complex ordered states, such as liquid crystals, and even decode encrypted messages. We will describe a study done for a sensor-array "challenge problem" in which we have based our approach on old-fashioned simulated annealing to accomplish target acquisition and tracking under the rules of statistical mechanics. We believe the many additional constraints that occur in the real problem can be folded, step by step, into this stochastic approach. The results have applicability to other network management problems on scales where a distributed solution will be mandatory.
SCALING LAWS FOR THE LIFETIMES OF GOVERNMENTS IN THE SZNAJD DEMOCRACY
Authors: SCHNEIDER JOHANNES J. , HIRTREITER CHRISTIAN
Published: May 2005

We investigate the lifetimes of governments in the original and a randomized one-dimensional Sznajd model. We find various scaling laws for the lifetime of the democracy and for the reigning time of governments in this model, depending on the system size N.
NONLIFE INSURANCE PRICING: STATISTICAL MECHANICS VIEWPOINT
Authors: DAROONEH AMIR H.
Published: May 2005

We consider the insurance company as a physical system which is immersed in its environment (the financial market). The insurer company interacts with the market by exchanging the money through the payments for loss claims and receiving the premium. Here, in the equilibrium state, we obtain the premium by using the canonical ensemble theory, and compare it with the Esscher principle, the well-known formula in actuary for premium calculation. We simulate the case of car insurance for quantitative comparison.
FINAL STATE OF ECOSYSTEM CONTAINING GRASS, SHEEP AND WOLVES WITH AGING
Authors: HE MINGFENG , PAN QIU-HUI , WANG SHUANG
Published: May 2005

This paper describes a cellular automata model containing movable wolves, sheep and reproducible grass. Each wolf or sheep is characterized by Penna bitstrings. In addition, we introduce the energy rule and the predator–prey mechanism for wolf and sheep. With considering age-structured, genetic strings, minimum reproduction age, cycle of the reproduction, number of offspring, we get three possible states of a predator–prey system: the coexisting one with predators and prey, the absorbing one with prey only, and the empty one where no animal survived. In this paper, we mainly discuss the effect of the number of poor genes, the energy supply (food), the minimum reproduction age, the reproductive cycle and the birth rate on the above three possible final states.
Structural control of strontium concentrations in stream sediments: an example from major fault zones in central Norway
Authors: Sæther O.M. , Roberts D. , Reimann C.
Published: May 2005

A distinct linear Sr anomaly traceable over a distance of >120 km in central Norway can be linked directly to the ENE–WSW-trending Møre-Trøndelag Fault Complex. Another less prominent linear anomaly is associated with a major extensional detachment fault. Although the Sr values are not unusually high, those above the 90th percentile define a distinct subpopulation indicative of the effects of a secondary process. This is considered to relate to accessory and secondary mineral phases that precipated in dense vein networks (calcite, zeolites, epidote) within the hydrothermally and metasomatically altered cataclasites and breccias of this major, multiply reactivated, fault complex.

Along and adjacent to the Møre-Trøndelag Fault Complex and the detachment fault, a likely primary source of the enhanced Sr concentrations is that of Ordovician, calc-alkaline granitoid plutons with up to 1400 mg/kg Sr. In one area along the fault complex, an extensively exposed Ordovician limestone with high Sr contents (up to 950 mg/kg) may represent a second primary source. In a third area, Vikna, a more diffuse positive Sr anomaly may relate to the widespread occurrence of shell-rich marine deposits, but this area is also intensely faulted. Thus, although there are three likely primary sources for the Sr anomalies, the single unifying feature and underlying cause of the exceptional anomaly linearity has to be the intensely hydrothermally altered, multiply deformed, Møre-Trøndelag Fault Complex with its dense network of mineral veins and, to a slightly lesser extent, the major, extensional detachment fault. These observations stress the overall significance of structural control in defining these unusually prominent Sr anomalies.
CAJAL BODIES: A Long History of Discovery
Authors: Cioce Mario , Lamond Angus I.
Published: May 2005

This review surveys what is known about the structure and function of the subnuclear domains called Cajal bodies (CBs). The major focus is on CBs in mammalian cells but we provide an overview of homologous CB structures in other organisms. We discuss the protein and RNA components of CBs, including factors recently found to associate in a cell cycle-dependent fashion or under specific metabolic or stress conditions. We also consider the dynamic properties of both CBs and their molecular components, based largely on recent data obtained thanks to the advent of improved in vivo detection and imaging methods. We discuss how these data contribute to an understanding of CB functions and highlight major questions that remain to be answered. Finally, we consider the interesting links that have emerged between CBs and alterations in nuclear structure apparent in a range of human pathologies, including cancer and inherited neurodegenerative diseases. We speculate on the relationship between CB function and molecular disease.
MODIFIER GENETICS: Cystic Fibrosis
Authors: Cutting Garry R
Published: May 2005

▪ Abstract  Cystic fibrosis (CF) is the most common lethal autosomal recessive disorder in the Caucasian population, affecting about 30,000 individuals in the United States. The gene responsible for CF, the CF transmembrane conductance regulator (CFTR), was identified 15 years ago. Substantial variation in the many aspects of the CF phenotype among individuals with the same CFTR genotype demonstrates that factors independent of CFTR exert considerable influence on outcome in CF. To date, the majority of published studies investigating the cause of disease variability in CF report associations between candidate genes and some aspect of the CF phenotype. However, a definitive modifier gene for CF remains to be identified. Despite the challenges posed by searches for modifier effects, studies of affected twins and siblings indicate that genetic factors play a substantial role in intestinal manifestations. Identifying the factors contributing to variation in pulmonary disease, the primary cause of mortality, remains a challenge for CF research.
How to Tell Heart Rate From an ECG? (Learning Objects #769 and #878)
Authors: Prakash E. S. , Madanmohan
Published: May 2005

The APS Archive of Teaching Resources is a repository of case histories, simulations, figures, lectures and course syllabi, animations, and links to physiology teaching resources for use by APS members and other educators. The Archive is a searchable database that can be used by teachers at all levels (K-12, undergraduate, graduate, and medical school) to enhance and supplement their current teaching resources and is part of the National Science Digital Library Project and the BiosciEd Net collaborative ( http://www.biosciednet.org ). The APS Archive of Teaching Resources was established as an initiative of the APS Education Committee and APS Council with additional support from the National Science Foundation (DUE 0226185). Authors submitting materials to the Archive for review and inclusion have the option of developing an abstract for publication in Advances in Physiology Education. The following abstracts are from items that have been accepted into the Archive following peer review.
Exercise, nutrition and you: an off-campus course for grades 2–12
Authors: Snyder Ann C. , Mauzy-Melitz Debra K.
Published: May 2005

Since interest in science classes has declined recently and obesity, especially in youth, continues to increase, an exercise physiology-based course was taught in public parks to promote active-learning science and healthy living. The course emphasized and integrated exercise, nutrition, and health during a 3-h session. Following an introduction, five hands-on laboratory-based student modules were performed. Students performed respiratory, cardiovascular, temperature regulation, energy expenditure, oxygen uptake, and exercise modules. During most modules, the students made measurements at rest and during the performance of exercise at different intensities. The students were very involved and engaged in problem solving throughout the session. The program was given for 10 days to more than 500 students representing 18 classes from 10 different schools. Evaluations indicated that the program was a real-life science experience that gave the students a new understanding of how their bodies worked and the purpose of exercise. The students and teachers also experienced “school learning” put into action as the program fit well with their science curriculum.
CFTR in cystic fibrosis and cholera: from membrane transport to clinical practice
Authors: Goodman Barbara E. , Percy William H.
Published: May 2005

We have used a brief analysis of transport via cystic fibrosis (CF) transmembrane conductance regulators (CFTRs) in various organ systems to highlight the importance of basic membrane transport processes across epithelial cells for first-year medical students in physiology. Because CFTRs are involved in transport both physiologically and pathologically in various systems, we have used this clinical correlation to analyze how a defective gene leading to defective transport proteins can be directly involved in the symptoms of cholera and CF. This article is a “Staying Current” approach to transport via CFTRs including numerous helpful references with further information for a teaching faculty member. The article follows our normal presentation which begins with a discussion of the involvement of CFTR transport in the intestine and how cholera affects intestinal transport, extends to CFTR transport in various organ systems in CF, and concludes with the logic behind many of the treatments that improve CF. Student learning objectives are included to assist in assessment of student understanding of the basic concepts.
Valid and reliable authentic assessment of culminating student performance in the biomedical sciences
Authors: Oh Deborah M. , Kim Joshua M. , Garcia Raymond E. , Krilowicz Beverly L.
Published: May 2005

There is increasing pressure, both from institutions central to the national scientific mission and from regional and national accrediting agencies, on natural sciences faculty to move beyond course examinations as measures of student performance and to instead develop and use reliable and valid authentic assessment measures for both individual courses and for degree-granting programs. We report here on a capstone course developed by two natural sciences departments, Biological Sciences and Chemistry/Biochemistry, which engages students in an important culminating experience, requiring synthesis of skills and knowledge developed throughout the program while providing the departments with important assessment information for use in program improvement. The student work products produced in the course, a written grant proposal, and an oral summary of the proposal, provide a rich source of data regarding student performance on an authentic assessment task. The validity and reliability of the instruments and the resulting student performance data were demonstrated by collaborative review by content experts and a variety of statistical measures of interrater reliability, including percentage agreement, intraclass correlations, and generalizability coefficients. The high interrater reliability reported when the assessment instruments were used for the first time by a group of external evaluators suggests that the assessment process and instruments reported here will be easily adopted by other natural science faculty.
Student perspectives of assessment by TEMM model in physiology
Authors: Abraham Reem Rachel , Upadhya Subramanya , Torke Sharmila , Ramnarayan K.
Published: May 2005

Assessment is the process by which the teacher and the student gain knowledge about student progress. Assessment systems should aim at evaluating the desired learning outcomes. In Melaka Manipal Medical College, (Manipal Campus), Manipal, India, the TEMM model (consisting of 4 assessment methods: Triple Jump Test, essay incorporating critical thinking questions, Multistation Integrated Practical Examination, and multiple choice questions) was introduced to 30 refresher students in the fourth block of the academic year. At the end of the block, a questionnaire was distributed to ask the students to rank the different assessments in the order of their preference with respect to seven items. Analysis of the results showed that not a single type of assessment was ranked highest for all the seven items, proving the earlier observation that a single assessment does not fulfill all aspects of assessment and that there is a need for an evaluating system with multiple ways of assessment.
Teaching principles of cardiovascular function in a medical student laboratory
Authors: Gupta Sanjaya , Westfall Thomas C. , Lechner Andrew J. , Knuepfer Mark M.
Published: May 2005

We describe an animal laboratory using anesthetized swine to demonstrate the regulation of arterial blood pressure to second-year medical students at Saint Louis University School of Medicine (St. Louis, MO). The laboratory is designed to illustrate basic pharmacological and physiological concepts learned in the classroom. The specific learning objectives covered in this lab include maintenance of anesthesia, basic surgical technique including cannulation of blood vessels, understanding the measurement and significance of basic physiological parameters, premortem examination of in situ heart and lungs, direct cardiac massage and induction of ventricular fibrillation, understanding the fundamentals of the baroreceptor reflex, and cardiovascular responses to various pharmacological agents. Pharmacologic agents used include epinephrine, norepinephrine, isoproterenol, atropine, prazosin, propranolol, acetylcholine, nitroprusside, and angiotensin II. The laboratory demonstration has proven effective in reinforcing the fundamental principles of cardiovascular physiology and autonomic pharmacology. By the completion of this experiment, students are expected to be able to: 1) describe the basics of maintenance of anesthesia in a live animal; 2) describe basic surgical technique; 3) observe the procedure for proper cannulation of blood vessels; 4) describe the proper method of controlling hemorrhage from a bleeding source; 5) describe the measurement and recording of four physiological parameters: mean arterial pressure from a pressure transducer, heart rate from an ECG, hindquarters resistance from Doppler measurement of femoral arterial blood flow, and cardiac contractility by calculating dP/d t from left ventricular pressure measured with a Millar transducer; 6) perform a premortem exam of the heart and lungs and appreciate the in situ cardiothoracic anatomy of the living animal; 7) assist in the induction of ventricular fibrillation and perform direct cardiac massage; 8) characterize the autonomic responses activated by the baroreceptor reflex; 9) describe the effects of the adrenergic agonists epinephrine, norepinephrine, and isoproterenol on cardiovascular parameters and construct a dose response curve for each agent; 10) describe the effects of the adrenergic antagonists propranolol and prazosin on cardiovascular parameters and explain how they affect cardiovascular responses to adrenergic agonists; 11) describe the difference between endothelium-dependent and endothelium-independent vasodilation using acetylcholine, nitroprusside, and atropine; 12) observe the pressor response of angiotensin II and describe why this response is not blocked by pretreatment with prazosin; and 13) participate in the collection and analysis of experimental data and the presentation of results.
A new paradigm for graduate research and training in the biomedical sciences and engineering
Authors: Humphrey J. D. , Coté G. L. , Walton J. R. , Meininger G. A. , Laine G. A.
Published: May 2005

98Emphasis on the individual investigator has fostered discovery for centuries, yet it is now recognized that the complexity of problems in the biomedical sciences and engineering requires collaborative efforts from individuals having diverse training and expertise. Various approaches can facilitate interdisciplinary interactions, but we submit that there is a critical need for a new educational paradigm for the way that we train biomedical engineers, life scientists, and mathematicians. We cannot continue to train graduate students in isolation within single disciplines, nor can we ask any one individual to learn all the essentials of biology, engineering, and mathematics. We must transform how students are trained and incorporate how real-world research and development are done–in diverse, interdisciplinary teams. Our fundamental vision is to create an innovative paradigm for graduate research and training that yields a new generation of biomedical engineers, life scientists, and mathematicians that is more diverse and that embraces and actively pursues a truly interdisciplinary, team-based approach to research based on a known benefit and mutual respect. In this paper, we describe our attempt to accomplish this via focused training in biomechanics, biomedical optics, mathematics, mechanobiology, and physiology. The overall approach is applicable, however, to most areas of biomedical research.
Ethics and scientific publication
Authors: Benos Dale J. , Fabres Jorge , Farmer John , Gutierrez Jessica P. , Hennessy Kristin , Kosek David , Lee Joo Hyoung , Olteanu Dragos , Russell Tara , Shaikh Faheem , Wang Kai
Published: May 2005

This article summarizes the major categories of ethical violations encountered during submission, review, and publication of scientific articles. We discuss data fabrication and falsification, plagiarism, redundant and duplicate publication, conflict of interest, authorship, animal and human welfare, and reviewer responsibility. In each section, pertinent historical background and citation of relevant regulations and statutes are provided. Furthermore, a specific case(s) derived from actual situations is(are) presented. These cases were chosen to highlight the complexities that investigators and journals must face when dealing with ethical issues. A series of discussion questions follow each case. It is our hope that by increasing education and awareness of ethical matters relevant to scientific investigation and publication, deviations from appropriate conduct will be reduced.
Peer instruction enhanced meaningful learning: ability to solve novel problems
Authors: Cortright Ronald N. , Collins Heidi L. , DiCarlo Stephen E.
Published: May 2005

Students must be able to interpret, relate, and incorporate new information with existing knowledge and apply the new information to solve novel problems. Peer instruction is a cooperative learning technique that promotes critical thinking, problem solving, and decision-making skills. Therefore, we tested the hypothesis that peer instruction enhances meaningful learning or transfer, defined as the student’s ability to solve novel problems or the ability to extend what has been learned in one context to new contexts. To test this hypothesis, our undergraduate exercise physiology class of 38 students was randomly divided into two groups: group A ( n = 19) and group B ( n = 19). A randomized crossover design in which students either answered questions individually or during peer instruction was used to control for time and order effects. The first factor that influences meaningful learning is the degree of mastery of the original material. Importantly, peer instruction significantly enhanced mastery of the original material. Furthermore, the student’s ability to solve novel problems was significantly enhanced following peer instruction. Thus pausing two to three times during a 50-min class to allow peer instruction enhanced the mastery of the original material and enhanced meaningful learning, i.e., the student’s ability to solve novel problems.
Modulation of mitochondrial Ca2+ by nitric oxide in cultured bovine vascular endothelial cells
Authors: Dedkova Elena N. , Blatter Lothar A.
Published: May 2005

In the present study, we used laser scanning confocal microscopy in combination with fluorescent indicator dyes to investigate the effects of nitric oxide (NO) produced endogenously by stimulation of the mitochondria-specific NO synthase (mtNOS) or applied exogenously through a NO donor, on mitochondrial Ca2+ uptake, membrane potential, and gating of mitochondrial permeability transition pore (PTP) in permeabilized cultured calf pulmonary artery endothelial (CPAE) cells. Higher concentrations (100–500 μM) of the NO donor spermine NONOate (Sper/NO) significantly reduced mitochondrial Ca2+ uptake and Ca2+ extrusion rates, whereas low concentrations of Sper/NO (<100 μM) had no effect on mitochondrial Ca2+ levels ([Ca2+]mt). Stimulation of mitochondrial NO production by incubating cells with 1 mM l-arginine also decreased mitochondrial Ca2+ uptake, whereas inhibition of mtNOS with 10 μM l- N5-(1-iminoethyl)ornithine resulted in a significant increase of [Ca2+]mt. Sper/NO application caused a dose-dependent sustained mitochondrial depolarization as revealed with the voltage-sensitive dye tetramethylrhodamine ethyl ester (TMRE). Blocking mtNOS hyperpolarized basal mitochondrial membrane potential and partially prevented Ca2+-induced decrease in TMRE fluorescence. Higher concentrations of Sper/NO (100–500 μM) induced PTP opening, whereas lower concentrations (<100 μM) had no effect. The data demonstrate that in calf pulmonary artery endothelial cells, stimulation of mitochondrial Ca2+ uptake can activate NO production in mitochondria that in turn can modulate mitochondrial Ca2+ uptake and efflux, demonstrating a negative feedback regulation. This mechanism may be particularly important to protect against mitochondrial Ca2+ overload under pathological conditions where cellular [NO] can reach very high levels.
Differential susceptibility of subsarcolemmal and intermyofibrillar mitochondria to apoptotic stimuli
Authors: Adhihetty Peter J. , Ljubicic Vladimir , Menzies Keir J. , Hood David A.
Published: May 2005

Apoptosis can be evoked by reactive oxygen species (ROS)-induced mitochondrial release of the proapoptotic factors cytochrome c and apoptosis-inducing factor (AIF). Because skeletal muscle is composed of two mitochondrial subfractions that reside in distinct subcellular regions, we investigated the apoptotic susceptibility of subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria. SS and IMF mitochondria exhibited a dose-dependent release of protein in response to H2O2 (0, 25, 50, and 100 μM). However, IMF mitochondria were more sensitive to H2O2 and released a 2.5-fold and 10-fold greater amount of cytochrome c and AIF, respectively, compared with SS mitochondria. This finding coincided with a 44% ( P < 0.05) greater rate of opening (maximum rate of absorbance decrease, Vmax) of the protein release channel, the mitochondrial permeability transition pore (mtPTP), in IMF mitochondria. IMF mitochondria also exhibited a 47% ( P < 0.05) and 60% (0.05 < P < 0.1) greater expression of the key mtPTP component voltage-dependent anion channel and cyclophilin D, respectively, along with a threefold greater cytochrome c content, but similar levels of AIF compared with SS mitochondria. Despite a lower susceptibility to H2O2-induced release, SS mitochondria possessed a 10-fold greater Bax-to-Bcl-2 ratio ( P < 0.05), a 2.7-fold greater rate of ROS production, and an approximately twofold greater membrane potential compared with IMF mitochondria. The expression of the antioxidant enzyme Mn2+-superoxide dismutase was similar between subfractions. Thus the divergent protein composition and function of the mtPTP between SS and IMF mitochondria contributes to a differential release of cytochrome c and AIF in response to ROS. Given the relatively high proportion of IMF mitochondria within a muscle fiber, this subfraction is likely most important in inducing apoptosis when presented with apoptotic stimuli, ultimately leading to myonuclear decay and muscle fiber atrophy.
Novel lipid mediator aspirin-triggered lipoxin A4 induces heme oxygenase-1 in endothelial cells
Authors: Nascimento-Silva V. , Arruda M. A. , Barja-Fidalgo C. , Villela C. G. , Fierro I. M.
Published: May 2005

Lipoxins (LX) and aspirin-triggered LX (ATL) are eicosanoids generated during inflammation via transcellular biosynthetic routes that elicit distinct anti-inflammatory and proresolution bioactions, including inhibition of leukocyte-mediated injury, stimulation of macrophage clearance of apoptotic neutrophils, repression of proinflammatory cytokine production, and inhibition of cell proliferation and migration. Recently, it was reported that aspirin induces heme oxygenase-1 (HO-1) expression on endothelial cells (EC) in a COX-independent manner, what confers protection against prooxidant insults. However, the underlying mechanisms remain unclear. In this study, we investigated whether an aspirin-triggered lipoxin A4 stable analog, 15-epi-16-( para-fluoro)-phenoxy-lipoxin A4 (ATL-1) was able to induce endothelial HO-1. Western blot analysis showed that ATL-1 increased HO-1 protein expression associated with increased mRNA levels on EC in a time- and concentration-dependent fashion. This phenomenon appears to be mediated by the activation of the G protein-coupled LXA4 receptor because pertussis toxin and Boc-2, a receptor antagonist, significantly inhibited ATL-1-induced HO-1 expression. We demonstrate that treatment of EC with ATL-1 inhibited VCAM and E-selectin expression induced by TNF-α or IL-1β. This inhibitory effect of the analog is modulated by HO-1 because it was blocked by SnPPIX, a competitive inhibitor that blocks HO-1 activity. Our results establish that ATL-1 induces HO-1 in human EC, revealing an undescribed mechanism for the anti-inflammatory activity of these lipid mediators.
Stimulation of astrocyte Na+/H+ exchange activity in response to in vitro ischemia depends in part on activation of ERK1/2
Authors: Kintner Douglas B. , Look Andy , Shull Gary E. , Sun Dandan
Published: May 2005

We recently reported that Na+/H+ exchanger isoform 1 (NHE1) activity in astrocytes is stimulated and leads to intracellular Na+ loading after oxygen and glucose deprivation (OGD). However, the underlying mechanisms for this stimulation of NHE1 activity and its impact on astrocyte function are unknown. In the present study, we investigated the role of the ERK1/2 pathway in NHE1 activation. NHE1 activity was elevated by ∼75% in NHE1+/+ astrocytes after 2-h OGD and 1-h reoxygenation (REOX). The OGD/REOX-mediated stimulation of NHE1 was partially blocked by 30 μM PD-98059. Increased expression of phosphorylated ERK1/2 was detected in NHE1+/+ astrocytes after OGD/REOX. Moreover, stimulation of NHE1 activity disrupted not only Na+ but also Ca2+ homeostasis via reverse-mode operation of Na+/Ca2+ exchange. OGD/REOX led to a 103% increase in intracellular Ca2+ concentration ([Ca2+]i) in NHE1+/+ astrocytes in the presence of thapsigargin. Inhibition of NHE1 activity with the NHE1 inhibitor HOE-642 decreased OGD/REOX-induced elevation of [Ca2+]i by 73%. To further investigate changes of Ca2+ signaling, bradykinin-mediated Ca2+ release was evaluated. Bradykinin-mediated intracellular Ca2+ transient in NHE1+/+ astrocytes was increased by ∼84% after OGD/REOX. However, in NHE1−/− astrocytes or NHE1+/+ astrocytes treated with HOE-642, the bradykinin-induced Ca2+ release was increased by only ∼34%. Inhibition of the reverse mode of Na+/Ca2+ exchange abolished OGD/REOX-mediated Ca2+ rise. Together, our data suggest that ERK1/2 is involved in activation of NHE1 in astrocytes after in vitro ischemia. NHE1-mediated Na+ accumulation subsequently alters Ca2+ homeostasis via Na+/Ca2+ exchange.
Expression and membrane localization of MCT isoforms along the length of the human intestine
Authors: Gill Ravinder K. , Saksena Seema , Alrefai Waddah A. , Sarwar Zaheer , Goldstein Jay L. , Carroll Robert E. , Ramaswamy Krishnamurthy , Dudeja Pradeep K.
Published: May 2005

Recent studies from our laboratory and others have demonstrated the involvement of monocarboxylate transporter (MCT)1 in the luminal uptake of short-chain fatty acids (SCFAs) in the human intestine. Functional studies from our laboratory previously demonstrated kinetically distinct SCFA transporters on the apical and basolateral membranes of human colonocytes. Although apical SCFA uptake is mediated by the MCT1 isoform, the molecular identity of the basolateral membrane SCFA transporter(s) and whether this transporter is encoded by another MCT isoform is not known. The present studies were designed to assess the expression and membrane localization of different MCT isoforms in human small intestine and colon. Immunoblotting was performed with the purified apical and basolateral membranes from human intestinal mucosa obtained from organ donor intestine. Immunohistochemistry studies were done on paraffin-embedded sections of human colonic biopsy samples. Immunoblotting studies detected a protein band of ∼39 kDa for MCT1, predominantly in the apical membranes. The relative abundance of MCT1 mRNA and protein increased along the length of the human intestine. MCT4 (54 kDa) and MCT5 (54 kDa) isoforms showed basolateral localization and were highly expressed in the distal colon. Immunohistochemical studies confirmed that human MCT1 antibody labeling was confined to the apical membranes, whereas MCT5 antibody staining was restricted to the basolateral membranes of the colonocytes. We speculate that distinct MCT isoforms may be involved in SCFA transport across the apical or basolateral membranes in polarized colonic epithelial cells.
Impact on fatty acid metabolism and differential localization of FATP1 and FAT/CD36 proteins delivered in cultured human muscle cells
Authors: García-Martínez Cèlia , Marotta Mario , Moore-Carrasco Rodrigo , Guitart Maria , Camps Marta , Busquets Silvia , Montell Eulàlia , Gómez-Foix Anna M.
Published: May 2005

We compared the intracellular distribution and regulatory role of fatty acid transporter protein (FATP1) and fatty acid translocase (FAT/CD36) on muscle cell fatty acid metabolism. With the use of adenoviruses, FATP1 and FAT genes were delivered to primary cultured human muscle cells. FATP1 and FAT moderately enhanced palmitate and oleate transport evenly at concentrations of 0.05, 0.5, and 1 mM. Long-term (16 h) consumption of palmitate and oleate from the media, and particularly incorporation into triacylglyceride (TAG), was stimulated equivalently by FATP1 and FAT at all fatty acid concentrations tested. In contrast, long-term CO2 production was reduced by FATP1 and FAT at all doses of palmitate and at the lower concentrations of oleate. Neither FATP1 nor FAT markedly altered the production of acid-soluble metabolic intermediates from palmitate or oleate. The intracellular localization of fusion constructs of FATP1 and FAT with enhanced green fluorescent protein (EGFP) was examined. Independently of fatty acid treatment, FATPGFP was observed throughout the cytosol in a reticular pattern and concentrated in the perinuclear region, partly overlapping with the Golgi marker GM-130. FATGFP was found in the extracellular membrane and in cytosolic vesicles not coincident with GM-130. Neither FATP1 nor FAT proteins colocalized with lipid droplets in oleate-treated cells. We conclude that whereas FAT is localized on the extracellular membrane, FATP1 is active in the cytosol and imports fatty acids into myotubes. Overall, both FATP1 and FAT stimulated transport and consumption of palmitate and oleate, which they channeled away from complete oxidation and toward TAG synthesis.
Downregulation of the vasopressin type 2 receptor after vasopressin-induced internalization: involvement of a lysosomal degradation pathway
Authors: Bouley Richard , Lin Herbert Y. , Raychowdhury Malay K. , Marshansky Vladimir , Brown Dennis , Ausiello Dennis A.
Published: May 2005

Vasopressin (VP) increases urinary concentration by signaling through the vasopressin receptor (V2R) in collecting duct principal cells. After downregulation, V2R reappears at the cell surface via an unusually slow (several hours) “recycling” pathway. To examine this pathway, we expressed V2R-green fluorescent protein (GFP) in LLC-PK1a cells. V2R-GFP showed characteristics similar to those of wild-type V2R, including high affinity for VP and adenylyl cyclase stimulation. V2R-GFP was located mainly in the plasma membrane in unstimulated cells, but it colocalized with the lysosomal marker Lysotracker after VP-induced internalization. Western blot analysis of V2R-GFP showed a broad 57- to 68-kDa band and a doublet at 46 and 52 kDa before VP treatment. After 4-h VP exposure, the 57- to 68-kDa band lost 50% of its intensity, whereas the lower 46-kDa band increased by 200%. The lysosomal inhibitor chloroquine abolished this VP effect, whereas lactacystin, a proteasome inhibitor, had no effect. Incubating cells at 20°C to block trafficking from the trans-Golgi network reduced V2R membrane fluorescence, and a perinuclear patch developed. Cycloheximide reduced the intensity of this patch, showing that newly synthesized V2R-GFP contributed significantly to its appearance. Cycloheximide also inhibited the reappearance of cell surface V2R after downregulation. We conclude that after downregulation, V2R-GFP is delivered to lysosomes and degraded. Reappearance of V2R at the cell surface depends on new protein synthesis, partially explaining the long time lag needed to fully reestablish V2R at the cell surface after downregulation. This degradative pathway may be an adaptive response to allow receptor-ligand association in the hypertonic and acidic environment of the renal medulla.
iNOS initiates and sustains metabolic arrest in hypoxic lung adenocarcinoma cells: mechanism of cell survival in solid tumor core
Authors: Land S. C. , Rae C.
Published: May 2005

Nitric oxide (NO) modulates cellular metabolism by competitively inhibiting the reduction of O2 at respiratory complex IV. The aim of this study was to determine whether this effect could enhance cell survival in the hypoxic solid tumor core by inducing a state of metabolic arrest in cancer cells. Mitochondria from human alveolar type II-like adenocarcinoma (A549) cells showed a fourfold increase in NO-sensitive 4-amino-5-methylamino-2′,7′-difluorofluorescein (DAF-FM) fluorescence and sixfold increase in Ca2+-insensitive NO synthase (NOS) activity during equilibration from Po2s of 100→23 mmHg, which was abolished by Nω-nitro-l-arginine methyl ester-HCl (l-NAME) and the inducible NOS (iNOS) inhibitor, N6-(1-iminoethyl)-l-lysine dihydrochloride (l-NIL). Similarly, cytosolic and compartmented DAF-FM fluorescence increased in intact cells during a transition between ambient Po2 and 23 mmHg and was abolished by transfection with iNOS antisense oligonucleotides (AS-ODN). In parallel, mitochondrial membrane potential (ΔΨm), measured using 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolo-carbocyanine iodide (JC-1), decreased to a lower steady state in hypoxia without change in glycolytic rate, adenylate energy charge, or cell viability. However, l-NAME or iNOS AS-ODN treatment maintained ΔΨm at normoxic levels irrespective of hypoxia and caused a marked activation of glycolysis, destabilization energy charge, and cell death. Comparison with other cancer-derived (H441) or native tissue-derived (human bronchial epithelial; alveolar type II) lung epithelial cells revealed that the hypoxic suppression of ΔΨm was common to cells that expressed iNOS. The controlled dissipation of ΔΨm, absence of an overt glycolytic activation, and conservation of viability suggest that A549 cells enter a state of metabolic suppression in hypoxia, which inherently depends on the activation of iNOS as Po2 falls.
Attenuation of the colorectal tonic reflex in female patients with irritable bowel syndrome
Authors: Ng Clinton , Danta Mark , Kellow John , Badcock Caro-Anne , Hansen Ross , Malcolm Allison
Published: May 2005

Alterations in normal intestinointestinal reflexes may be important contributors to the pathophysiology of irritable bowel syndrome (IBS). Our aims were to compare the rectal tonic responses to colonic distension in female IBS patients with predominant constipation (IBS-C) and with predominant diarrhea (IBS-D) to those in healthy females, both fasting and postprandially. Using a dual barostat assembly, 2-min colonic phasic distensions were performed during fasting and postprandially. Rectal tone was recorded before, during, and after the phasic distension. Colonic compliance and colonic sensitivity in response to the distension were also evaluated fasting and postprandially. Eight IBS-C patients, 8 IBS-D patients, and 8 age- and sex-matched healthy subjects ( group N) participated. The fasting increments in rectal tone in response to colonic distension in both IBS-C (rectal balloon volume change −4.6 ± 6.1 ml) and IBS-D (−7.9 ± 4.9 ml) were significantly reduced compared with group N (−34 ± 9.7 ml, P = 0.01). Similar findings were observed postprandially ( P = 0.02). When adjusted for the colonic compliance of individual subjects, the degree of attenuation in the rectal tonic response in IBS compared with group N was maintained (fasting P = 0.007; postprandial P = 0.03). When adjusted for colonic sensitivity there was a trend for the attenuation in the rectal tonic response in IBS patients compared with group N to be maintained (fasting P = 0.07, postprandial P = 0.08). IBS patients display a definite attenuation of the normal increase in rectal tone in response to colonic distension (colorectal reflex), fasting and postprandially. Alterations in colonic compliance and sensitivity in IBS are not likely to contribute to such attenuation.
Catheter-based antegrade intracoronary viral gene delivery with coronary venous blockade
Authors: Hayase Motoya , del Monte Federica , Kawase Yoshiaki , MacNeill Briain D. , McGregor Jennifer , Yoneyama Ryuichi , Hoshino Kozo , Tsuji Tsuyoshi , De Grand Alec M. , Gwathmey Judith K. , Frangioni John V. , Hajjar Roger J.
Published: May 2005

The purpose of this study is to evaluate the feasibility of percutaneous antegrade myocardial gene transfer (PAMGT). A consistent and safe technique for in vivo gene transfer is required for clinical application of myocardial gene therapy. PAMGT with concomitant coronary venous blockade was performed in 12 swine. The myocardium was preconditioned with 1 min of occlusion of the left anterior descending and left circumflex arteries. The anterior interventricular vein was occluded during left anterior descending artery delivery, and the great cardiac vein at the entrance of the middle cardiac vein was occluded during left circumflex artery delivery. With arterial and venous balloons inflated (3 min) and after adenosine (25 μg) injection, PAMGT was performed by antegrade injection of an adenoviral solution (1 ml of 1011 plaque-forming units in each coronary artery) carrying β-galactosidase or saline through the center lumen of the angioplasty balloon. In one set of animals, PAMGT was performed with selective coronary vein blockade ( n = 9); in another set of animals, PAMGT was performed without coronary vein blockade ( n = 5). At 1 wk after gene delivery, the animals were killed. Quantitative β-galactosidase analysis was performed in the left and right ventricular walls. PAMGT was successfully performed in all animals with and without concomitant occlusion of the coronary veins. Quantitative β-galactosidase analysis showed that PAMGT with coronary blockade was superior to PAMGT without coronary blockade. β-Galactosidase activity increased significantly in the β-galactosidase group compared with the saline group: 1.34 ± 0.18 vs. 0.81 ± 0.1 ng ( P ≤ 0.01) in the left ventricular wall and 0.91 ± 0.1 vs. 0.66 ± 0.07 ng ( P ≤ 0.05) in the right ventricular wall. PAMGT with selective coronary venous blockade is feasible, reproducible, and safely achieved in a large-animal model.
Bone marrow stem cell transplantation for cardiac repair
Authors: Haider Husnain Kh , Ashraf Muhammad
Published: May 2005

Cardiomyocytes respond to physiological or pathological stress only by hypertrophy and not by an increase in the number of functioning cardiomyocytes. However, recent evidence suggests that adult cardiomyocytes have the ability, albeit limited, to divide to compensate for the cardiomyocyte loss in the event of myocardial injury. Similarly, the presence of stem cells in the myocardium is a good omen. Their activation to participate in the repair process is, however, hindered by some as-yet-undetermined biological impediments. The rationale behind the use of adult stem cell transplantation is to supplement the inadequacies of the intrinsic repair mechanism of the heart and compensate for the cardiomyocyte loss in the event of injury. Various cell types including embryonic, fetal, and adult cardiomyocytes, smooth muscle cells, and stable cell lines have been used to augment the declining cardiomyocyte number and cardiac function. More recently, the focus has been shifted to the use of autologous skeletal myoblasts and bone marrow-derived stem cells. This review is a synopsis of some interesting aspects of the fast-emerging field of bone marrow-derived stem cell therapy for cardiac repair.
CCK enhances response to gastric distension by acting on capsaicin-insensitive vagal afferents
Authors: van de Wall E. H. E. M. , Duffy P. , Ritter R. C.
Published: May 2005

Capsaicin treatment destroys vagal afferent C fibers and markedly attenuates reduction of food intake and induction of hindbrain Fos expression by CCK. However, both anatomical and electrophysiological data indicate that some gastric vagal afferents are not destroyed by capsaicin. Because CCK enhances behavioral and electrophysiological responses to gastric distension in rats and people, we hypothesized that CCK might enhance the vagal afferent response to gastric distension via an action on capsaicin-insensitive vagal afferents. To test this hypothesis, we quantified expression of Fos-like immunoreactivity (Fos) in the dorsal vagal complex (DVC) of capsaicin-treated (Cap) and control rats (Veh), following gastric balloon distension alone and in combination with CCK injection. In Veh rats, intraperitoneal CCK significantly increased DVC Fos, especially in nucleus of the solitary tract (NTS), whereas in Cap rats, CCK did not significantly increase DVC Fos. In contrast to CCK, gastric distension did significantly increase Fos expression in the NTS of both Veh and Cap rats, although distension-induced Fos was attenuated in Cap rats. When CCK was administered during gastric distension, it significantly enhanced NTS Fos expression in response to distension in Cap rats. Furthermore, CCK's enhancement of distension-induced Fos in Cap rats was reversed by the selective CCK-A receptor antagonist lorglumide. We conclude that CCK directly activates capsaicin-sensitive C-type vagal afferents. However, in capsaicin-resistant A-type afferents, CCK's principal action may be facilitation of responses to gastric distension.
BDNF-Induced Facilitation of Afferent-Evoked Responses in Lamina II Neurons Is Reduced After Neonatal Spinal Cord Contusion Injury
Authors: Garraway Sandra M. , Anderson Aileen J. , Mendell Lorne M.
Published: May 2005

We previously reported that brain-derived neurotrophic factor (BDNF), a pronociceptive neurotransmitter, induces synaptic facilitation of excitatory postsynaptic current (EPSC) in lamina II neurons of neonatal rats up to P14 in a N-methyl-d-aspartate (NMDA) receptor-dependent manner. Here we used the patch-clamp technique to study synaptic and NMDA-evoked responses in transverse spinal slices in the lumbar enlargement as well as the ability of BDNF to modify these responses from 1 day to 6 wk after neonatal contusion. In older uninjured animals (>P14), BDNF continued to evoke synaptic facilitation although superfusion of NMDA (in TTX) induced inward current of significantly smaller amplitude than that observed in younger rats. After contusion injury, BDNF was unable to facilitate dorsal root-evoked EPSCs in lamina II neurons despite the finding that NMDA-evoked currents were only slightly smaller than those observed in age-matched uninjured animals. These findings suggest that although BDNF-induced facilitation of the AMPA/kainate receptor-mediated response to dorsal root stimulation is maintained in the mature dorsal horn from intact rats, BDNF may no longer elicit these pronociceptive actions after neonatal contusion injury. The lack of change in NMDA-evoked currents in contused cords suggests that diminished NMDA receptor function is not the major cause of the decline in BDNF action after contusion. It seems more likely that diminished trkB expression and enhanced expression of truncated trkB receptors in the contused cord play a significant role in determining the reduced effect of BDNF under these conditions.
An Oscillatory Hierarchy Controlling Neuronal Excitability and Stimulus Processing in the Auditory Cortex
Authors: Lakatos Peter , Shah Ankoor S. , Knuth Kevin H. , Ulbert Istvan , Karmos George , Schroeder Charles E.
Published: May 2005

EEG oscillations are hypothesized to reflect cyclical variations in the neuronal excitability, with particular frequency bands reflecting differing spatial scales of brain operation. However, despite decades of clinical and scientific investigation, there is no unifying theory of EEG organization, and the role of ongoing activity in sensory processing remains controversial. This study analyzed laminar profiles of synaptic activity [current source density CSD] and multiunit activity (MUA), both spontaneous and stimulus-driven, in primary auditory cortex of awake macaque monkeys. Our results reveal that the EEG is hierarchically organized; delta (1–4 Hz) phase modulates theta (4–10 Hz) amplitude, and theta phase modulates gamma (30–50 Hz) amplitude. This oscillatory hierarchy controls baseline excitability and thus stimulus-related responses in a neuronal ensemble. We propose that the hierarchical organization of ambient oscillatory activity allows auditory cortex to structure its temporal activity pattern so as to optimize the processing of rhythmic inputs.