bluuebunny/crossref_metadata_2025 huggingface dataset:
A NEW CLASS OF PATH EQUATIONS IN AP-GEOMETRY
Authors: WANAS M. I. , KAHIL M. E.
Published: December 2005

In the present work, it is shown that the application of the Bazanski approach to Lagrangians, written in AP-geometry and including the basic vector of the space, gives rise to a new class of path equations. The general equation representing this class contains four extra terms, when vanished reduces this equation to the geodesic one. If the basic vector of the AP-geometry is considered as playing the role of the electromagnetic potential, as done in a previous work, then the second term (of the extra terms) will represent Lorentz force while the fourth term gives a direct effect of the electromagnetic potential on the motion of the charged particle. This last term may give rise to an effect similar to the Aharanov–Bohm effect. It is to be considered that all extra terms will vanish if the spacetime used is torsion-less.
TURNAROUND STRATEGIES FOR DECLINING SMALL BUSINESS: THE EFFECTS OF PERFORMANCE AND RESOURCES
Authors: RASHEED HOWARD S.
Published: December 2005

This study explores the choice between growth and retrenchment as turnaround strategies for small business owners experiencing decline in performance. Current theory related to organizational failure describes deterministic and voluntaristic perspectives of strategic choice, but they have not been applied to small business decline. Using the voluntaristic perspective the proposed model suggests choice is contingent on the effects the owner/manager's perceptions of performance and resource availability during a period of decline. Survey data from small government contractors in the U.S. Small Business Administration database are used to test the model. The results indicate these contractors choose growth strategy when their perceptions of resource availability and past financial performance are both high and when both are low, indicating small business owner/managers remain aggressive when faced with adverse conditions.
NEAR-FIELD OPTICAL MICROSCOPY AND SPECTROSCOPY WITH POINTED PROBES
Authors: Novotny Lukas , Stranick Stephan J.
Published: December 2005

▪ Abstract  In recent years, developments in near-field techniques exploiting far-field illumination of a pointed, apertureless probe have demonstrated a newfound excitement. This is due in part to the advantages afforded by apertureless techniques that allow for the practical implementation of spectroscopic contrast mechanisms at length scales below 100 nm. These mechanisms include Raman and infrared absorption for chemical contrast, as well as materials contrast based on dielectric dispersion. In this review, we briefly describe the evolution of the field from the “classical” aperture-based approach toward the development of near-field optical microscopy with pointed probes. We highlight advances in state-of-the-art theory that describe the field distribution under an illuminated probe, as well as advances in the experimental implementation of scattering and excitation probe techniques.
ON THE NATURE OF IONS AT THE LIQUID WATER SURFACE
Authors: Petersen Poul B. , Saykally Richard J.
Published: December 2005

▪ Abstract  A qualitatively new understanding of the nature of ions at the liquid water surface is emerging. Traditionally, the characterization of liquid surfaces has been limited to macroscopic experimental techniques such as surface tension and electrostatic potential measurements, wherein the microscopic picture then has to be inferred by applying theoretical models. Because the surface tension of electrolyte solutions generally increases with ion concentration, all inorganic ions have been thought to be repelled from the air-water interface, leaving the outermost surface layer essentially devoid of ions. This oversimplified picture has recently been challenged: first by chemical kinetics measurements, then by theoretical molecular dynamics simulations using polarizable models, and most recently by new surface sensitive experimental observations. Here we present an overview of the nature of the interfacial structure of electrolyte solutions and give a detailed description of the new picture that is emerging.
Induced focal adhesion kinase expression suppresses apoptosis by activating NF-κB signaling in intestinal epithelial cells
Authors: Zhang Huifang M. , Keledjian Kaspar M. , Rao Jaladanki N. , Zou Tongtong , Liu Lan , Marasa Bernard S. , Wang Shelley R. , Ru Lisa , Strauch Eric D. , Wang Jian-Ying
Published: December 2005

Focal adhesion kinase (FAK) integrates various extracellular and intracellular signals and is implicated in a variety of biological functions, but its exact role and downstream targeting signals in the regulation of apoptosis in intestinal epithelial cells (IECs) remains unclear. The current study tested the hypothesis that FAK has an antiapoptotic role in the IEC-6 cell line by altering NF-κB signaling. Induced FAK expression by stable transfection with the wild-type (WT)-FAK gene increased FAK phosphorylation, which was associated with an increase in NF-κB activity. These stable WT-FAK-transfected IECs also exhibited increased resistance to apoptosis when they were exposed to TNF-α plus cycloheximide (TNF-α/CHX). Specific inhibition of NF-κB by the recombinant adenoviral vector containing the IκBα superrepressor prevented increased resistance to apoptosis in WT-FAK-transfected cells. In contrast, inactivation of FAK by ectopic expression of dominant-negative mutant of FAK (DNM-FAK) inhibited NF-κB activity and increased the sensitivity to TNF-α/CHX-induced apoptosis. Furthermore, induced expression of endogenous FAK by depletion of cellular polyamines increased NF-κB activity and resulted in increased resistance to TNF-α/CHX-induced apoptosis, both of which were prevented by overexpression of DNM-FAK. These results indicate that increased expression of FAK suppresses TNF-α/CHX-induced apoptosis, at least partially, through the activation of NF-κB signaling in IECs.
Modest dietary K+ restriction provokes insulin resistance of cellular K+ uptake and phosphorylation of renal outer medulla K+ channel without fall in plasma K+ concentration
Authors: Chen Pei , Guzman John P. , Leong Patrick K. K. , Yang Li E. , Perianayagam Anjana , Babilonia Elisa , Ho Jennifer S. , Youn Jang H. , Wang Wen Hui , McDonough Alicia A.
Published: December 2005

Extracellular K+ concentration ([K+]) is closely regulated by the concerted regulatory responses of kidney and muscle. In this study, we aimed to define the responses activated when dietary K+ was moderately reduced from a control diet (1.0% K+) to a 0.33% K+ diet for 15 days. Although body weight and baseline plasma [K+] (4.0 mM) were not reduced in the 0.33% K+ group, regulatory responses to conserve plasma [K+] were evident in both muscle and kidney. Insulin-stimulated clearance of K+ from the plasma was estimated in vivo in conscious rats with the use of tail venous and arterial cannulas. During infusion of insulin·(50 mU·kg−1·min−1), plasma [K+] level fell to 3.2 ± 0.1 mM in the 1.0% K+ diet group and to only 3.47 ± 0.07 mM in the 0.33% K+ diet group ( P < 0.01) with no reduction in urinary K+ excretion, which is evidence of insulin resistance to cellular K+ uptake. Insulin-stimulated cellular K+ uptake was quantitated by measuring the K+ infusion rate necessary to clamp plasma K+ at baseline (in μmol·kg−1·min−1) during 5 mU of insulin·kg−1·min−1 infusion: 9.7 ± 1.5 in 1% K+ diet was blunted to 5.2 ± 1.7 in the 0.33% K+ diet group ( P < 0.001). Muscle [K+] and Na+-K+-ATPase activity and abundance were unchanged during the 0.33% K+ diet. Renal excretion, which was measured overnight in metabolic cages, was reduced by 80%, from 117.6 ± 10.5 μmol/h/animal (1% K+ diet) to 24.2 ± 1.7 μmol/h/animal (0.33% K+ diet) ( P < 0.001). There was no significant change in total abundance of key renal K+ transporters, but 50% increases in both renal PTK cSrc abundance and ROMK phosphorylation in the 0.33% K+ vs. 1% K+ diet group, previously established to be associated with internalization of ROMK. These results indicate that plasma [K+] can be maintained during modest K+ restriction due to a decrease in insulin-stimulated cellular K+ uptake as well as renal K+ conservation mediated by inactivation of ROMK, both without a detectable change in plasma [K+]. The error signals inciting and maintaining these responses remain to be identified.
Effects of cholera toxin on the potential difference and motor responses induced by distension in the rat proximal small intestine in vivo
Authors: Kordasti Shirin , Sapnara Maria , Thomas Evan A. , Lindstrom Erik , Forsman Mikael , Bornstein Joel C. , Sjövall Henrik
Published: December 2005

Cholera toxin (CT) may induce uncontrolled firing in recurrent networks of secretomotor neurons in the submucous plexus. This hypothesis was tested in chloralose-anesthetized rats in vivo. The secretory reflex response to graded intestinal distension was measured with or without prior exposure to luminal CT. The transmural potential difference (PD) was used as a marker for electrogenic chloride secretion. In controls, distension increased PD, and this response was reduced by the neural blocker tetrodotoxin given serosally and the vasoactive intestinal peptide (VIP) receptor antagonist [4Cl-d-Phe6,Leu17]VIP (2 μg·min−1·kg−1 iv) but unaffected by the serotonin 5-HT3 receptor antagonist granisetron, by the nicotinic receptor antagonist hexamethonium, by the muscarinic receptor antagonist atropine, or by the cyclooxygenase inhibitor indomethacin. Basal PD increased significantly with time in CT-exposed segments, an effect blocked by granisetron, by indomethacin, and by [4Cl-d-Phe6,Leu17]VIP but not by hexamethonium or atropine. In contrast, once the increased basal PD produced by CT was established, [4Cl-d-Phe6,Leu17]VIP and indomethacin had no significant effect, whereas granisetron and hexamethonium markedly depressed basal PD. CT significantly reduced the increase in PD produced by distension, an effect reversed by granisetron, indomethacin, and atropine. CT also activated a specific motility response to distension, repeated cluster contractions, but only in animals pretreated with granisetron, indomethacin, or atropine. These data are compatible with the hypothesis that CT induces uncontrolled activity in submucous secretory networks. Development of this state depends on 5-HT3 receptors, VIP receptors, and prostaglandin synthesis, whereas its maintenance depends on 5-HT3 and nicotinic receptors but not VIP receptors. The motility effects of CT (probably reflecting myenteric activity) are partially suppressed via a mechanism involving 5-HT3 and muscarinic receptors and prostaglandin synthesis.
Localization of the sulfate/anion exchanger in the rat liver
Authors: Quondamatteo Fabio , Krick Wolfgang , Hagos Yohannes , Krüger Marie-Helen , Neubauer-Saile Katrin , Herken Rainer , Ramadori Giuliano , Burckhardt Gerhard , Burckhardt Birgitta C.
Published: December 2005

Although the sulfate/anion transporter (sat-1; SLC26A1) was isolated from a rat liver cDNA library by expression cloning, localization of sat-1 within the liver and its contribution to the transport of sulfate and organo sulfates have remained unresolved. In situ hybridization and immunohistochemical studies were undertaken to demonstrate the localization of sat-1 in liver tissue. RT-PCR studies on isolated hepatocytes and liver endothelial and stellate cells in culture were performed to test for the presence of sat-1 in these cells. In sulfate uptake and efflux experiments, the substrate specificity of sat-1 was evaluated. Sat-1 mRNA was found in hepatocytes and endothelial cells. Sat-1 protein was localized in sinusoidal membranes and along the borders of hepatocytes. The canalicular region and bile capillaries were not stained. Sulfate uptake was only slightly affected by sulfamoyl diuretics or organo sulfates. Sulfate efflux from sat-1-expressing oocytes was enhanced in the presence of bicarbonate, indicating sulfate/bicarbonate exchange. Estrone sulfate was not transported by sat-1. Sat-1 may be responsible for the uptake of inorganic sulfate from the blood into hepatocytes to enable sulfation reactions. In hepatocytes and endothelial cells, sat-1 may also supply sulfate for proteoglycan synthesis.
Corticotropin-releasing hormone in the lateral parabrachial nucleus inhibits sodium appetite in rats
Authors: De Castro e Silva Emilio , Fregoneze Josmara B. , Johnson Alan Kim
Published: December 2005

The present study investigated the role of corticotropin-releasing hormone (CRH) in the lateral parabrachial nucleus (LPBN) in the behavioral control of body fluid homeostasis by determining the effect of bilateral injections of the CRH receptor antagonist, α-helical corticotropin-releasing factor (CRF)9–41, and the CRH receptor agonist, CRH, on sodium chloride (salt appetite) and water (thirst) intake. Groups of adult, male Sprague-Dawley rats had stainless-steel cannulas implanted bilaterally into the LPBN and were sodium depleted or water deprived. Bilateral injections of α-helical CRF9–41 into the LPBN significantly potentiated water and salt intake in the sodium-depleted rats when access to fluids was restored. Bilateral injections of α-helical CRF9–41 into the LPBN (1.0 μg) also increased sodium appetite in water-deprived rats. Conversely, in sodium-depleted animals, bilateral injections of CRH inhibited sodium chloride intake. These results suggest that there is an endogenous CRH inhibitory mechanism operating in the LPBN to modulate the intake of sodium (salt appetite). This mechanism may contribute to the behavioral control of restoration of body fluid homeostasis in sodium-deficient states.
Ionic mechanisms of excitation-induced regulation of Na+-K+-ATPase mRNA expression in isolated rat EDL muscle
Authors: Murphy K. T. , Macdonald W. A. , McKenna M. J. , Clausen T.
Published: December 2005

This study investigated the effects of electrical stimulation on Na+-K+-ATPase isoform mRNA, with the aim to identify factors modulating Na+-K+-ATPase mRNA in isolated rat extensor digitorum longus (EDL) muscle. Interventions designed to mimic exercise-induced increases in intracellular Na+and Ca2+contents and membrane depolarization were examined. Muscles were mounted on force transducers and stimulated with 60-Hz 10-s pulse trains producing tetanic contractions three times at 10-min intervals. Ouabain (1.0 mM, 120 min), veratridine (0.1 mM, 30 min), and monensin (0.1 mM, 30 min) were used to increase intracellular Na+content. High extracellular K+(13 mM, 60 min) and the Ca2+ionophore A-23187 (0.02 mM, 30 min) were used to induce membrane depolarization and elevated intracellular Ca2+content, respectively. Muscles were analyzed for Na+-K+-ATPase α1–α3and β1–β3mRNA (real-time RT-PCR). Electrical stimulation had no immediate effect on Na+-K+-ATPase mRNA; however at 3 h after stimulation, it increased α1, α2, and α3mRNA by 223, 621, and 892%, respectively ( P = 0.010), without changing β mRNA. Ouabain, veratridine, and monensin increased intracellular Na+content by 769, 724, and 598%, respectively ( P = 0.001) but did not increase mRNA of any isoform. High intracellular K+concentration elevated α1mRNA by 160% ( P = 0.021), whereas A-23187 elevated α3mRNA by 123% ( P = 0.035) but reduced β1mRNA by 76% ( P = 0.001). In conclusion, electrical stimulation induced subunit-specific increases in Na+-K+-ATPase mRNA in isolated rat EDL muscle. Furthermore, Na+-K+-ATPase mRNA appears to be regulated by different stimuli, including cellular changes associated with membrane depolarization and increased intracellular Ca2+content but not increased intracellular Na+content.
Growth of the small airways and alveoli from childhood to the adult lung measured by aerosol-derived airway morphometry
Authors: Zeman Kirby L. , Bennett William D.
Published: December 2005

Understanding the human development of pulmonary air spaces is important for calculating the dose from exposure to inhaled materials as a function of age. We have measured, in vivo, the air space caliber of the small airways and alveoli at their natural full distension [total lung capacity (TLC)] by aerosol-derived airway morphometry in 53 children of age 6–22 yr and 59 adults of age 23–80 yr. Aerosol-derived airway morphometry utilizes the gravitational settling time of inhaled inert particles to infer the vertical distance necessary to produce the observed loss of particles to the airway surfaces at sequential depths into the lung. Previously, we identified anatomical features of the lung: the caliber of the transitional bronchioles [transitional effective air space dimension (EADtrans)]; the mean linear dimension of the alveoli (EADmin); and a measure of conducting airway volume [volumetric lung depth (VLDtrans)]. In the present study, we found that EADmin increased with age, from 184 μm at age 6 to 231 μm at age 22, generally accounting for the increase in TLC observed over this age range. EADtrans did not increase with TLC, averaging 572 μm, but increased with subject age and height when the entire age range of 6–80 yr is included {EADtrans (μm) = 0.012[height (cm)] × [age (yr)] + 508; P = 0.007}. VLDtrans scaled linearly with lung volume, but VLDtrans relative to TLC did not change with age, averaging 7.04 ± 1.55% of TLC. The data indicate that from childhood (age of 6 yr) to adulthood a constant number of respiratory units is maintained while both the smallest bronchioles and alveoli expand in size to produce the increased lung volume with increased age and height.
O-GlcNAc level variations are associated with the development of skeletal muscle atrophy
Authors: Cieniewski-Bernard Caroline , Mounier Yvonne , Michalski Jean-Claude , Bastide Bruno
Published: December 2005

O-linked N-acetylglucosaminylation ( O-GlcNAc) is a regulatory posttranslational modification of nucleocytoplasmic proteins, which consists of the attachment of N-acetylglucosamine to serine or threonine residues of a protein. This glycosylation is a ubiquitous posttranslational modification, which probably plays important roles in many aspects of protein function. Our laboratory has previously reported that, in skeletal muscle, proteins of the glycolytic pathway and energetic metabolism and contractile proteins were O-GlcNAc modified (Cieniewski-Bernard C, Bastide B, Lefebvre T, Lemoine J, Mounier Y, and Michalski JC. Mol Cell Proteomics 3: 577–585, 2004). O-GlcNAc has been recently demonstrated to play a role in modulating cellular function in response to nutrition and also in stress conditions. Therefore, we have investigated here the implication of the glycosylation/deglycosylation process in the development of atrophy in rat skeletal muscle after hindlimb unloading. The high O-GlcNAc level found in control soleus [compared with control extensor digitorum longus (EDL)] becomes lower in atrophied soleus. On the opposite side, the low rate of O-GlcNAc in control EDL reaches higher levels in EDL, not atrophied after hindlimb unloading. These variations in O-GlcNAc level are correlated with a variation of the O-GlcNAc process enzyme activities and could be associated with a differential expression of heat shock proteins. Our results suggest that O-GlcNAc variations could control the muscle protein homeostasis and be implicated in the regulation of muscular atrophy.
Role of astrocytes in cerebrovascular regulation
Authors: Koehler Raymond C. , Gebremedhin Debebe , Harder David R.
Published: December 2005

Astrocytes send processes to synapses and blood vessels, communicate with other astrocytes through gap junctions and by release of ATP, and thus are an integral component of the neurovascular unit. Electrical field stimulations in brain slices demonstrate an increase in intracellular calcium in astrocyte cell bodies transmitted to perivascular end-feet, followed by a decrease in vascular smooth muscle calcium oscillations and arteriolar dilation. The increase in astrocyte calcium after neuronal activation is mediated, in part, by activation of metabotropic glutamate receptors. Calcium signaling in vitro can also be influenced by adenosine acting on A2Breceptors and by epoxyeicosatrienoic acids (EETs) shown to be synthesized in astrocytes. Prostaglandins, EETs, arachidonic acid, and potassium ions are candidate mediators of communication between astrocyte end-feet and vascular smooth muscle. In vivo evidence supports a role for cyclooxygenase-2 metabolites, EETs, adenosine, and neuronally derived nitric oxide in the coupling of increased blood flow to increased neuronal activity. Combined inhibition of the EETs, nitric oxide, and adenosine pathways indicates that signaling is not by parallel, independent pathways. Indirect pharmacological results are consistent with astrocytes acting as intermediaries in neurovascular signaling within the neurovascular unit. For specific stimuli, astrocytes are also capable of transmitting signals to pial arterioles on the brain surface for ensuring adequate inflow pressure to parenchymal feeding arterioles. Therefore, evidence from brain slices and indirect evidence in vivo with pharmacological approaches suggest that astrocytes play a pivotal role in regulating the fundamental physiological response coupling dynamic changes in cerebral blood flow to neuronal synaptic activity. Future work using in vivo imaging and genetic manipulation will be required to provide more direct evidence for a role of astrocytes in neurovascular coupling.
Neurovascular coupling in the normal brain and in hypertension, stroke, and Alzheimer disease
Authors: Girouard Helene , Iadecola Costantino
Published: December 2005

The brain is critically dependent on a continuous supply of blood to function. Therefore, the cerebral vasculature is endowed with neurovascular control mechanisms that assure that the blood supply of the brain is commensurate to the energy needs of its cellular constituents. The regulation of cerebral blood flow (CBF) during brain activity involves the coordinated interaction of neurons, glia, and vascular cells. Thus, whereas neurons and glia generate the signals initiating the vasodilation, endothelial cells, pericytes, and smooth muscle cells act in concert to transduce these signals into carefully orchestrated vascular changes that lead to CBF increases focused to the activated area and temporally linked to the period of activation. Neurovascular coupling is disrupted in pathological conditions, such as hypertension, Alzheimer disease, and ischemic stroke. Consequently, CBF is no longer matched to the metabolic requirements of the tissue. This cerebrovascular dysregulation is mediated in large part by the deleterious action of reactive oxygen species on cerebral blood vessels. A major source of cerebral vascular radicals in models of hypertension and Alzheimer disease is the enzyme NADPH oxidase. These findings, collectively, highlight the importance of neurovascular coupling to the health of the normal brain and suggest a therapeutic target for improving brain function in pathologies associated with cerebrovascular dysfunction.
Chronic intermittent hypoxia alters NE reactivity and mechanics of skeletal muscle resistance arteries
Authors: Phillips Shane A. , Olson E. B. , Lombard Julian H. , Morgan Barbara J.
Published: December 2005

Although arterial dilator reactivity is severely impaired during exposure of animals to chronic intermittent hypoxia (CIH), few studies have characterized vasoconstrictor responsiveness in resistance arteries of this model of sleep-disordered breathing. Sprague-Dawley rats were exposed to CIH (10% inspired O2 fraction for 1 min at 4-min intervals; 12 h/day) for 14 days. Control rats were housed under normoxic conditions. Diameters of isolated gracilis muscle resistance arteries (GA; 120–150 μm) were measured by television microscopy before and during exposure to norepinephrine (NE) and angiotensin II (ANG II) and at various intraluminal pressures between 20 and 140 mmHg in normal and Ca2+-free physiological salt solution. There was no difference in the ability of GA to constrict in response to ANG II ( P = 0.42; not significant; 10−10–10−7 M). However, resting tone, myogenic activation, and vasoconstrictor responses to NE ( P < 0.001; 10−9–10−6 M) were reduced in CIH vs. controls. Treatment of rats with the superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (tempol; 1 mM) in the drinking water restored myogenic responses and NE-induced constrictions of CIH rats, suggesting that elevated superoxide production during exposure to CIH attenuates vasoconstrictor responsiveness to NE and myogenic activation in skeletal muscle resistance arteries. CIH also leads to an increased stiffness and reduced vessel wall distensibility that were not correctable with oral tempol treatment.
Nitric oxide regulation of microvascular oxygen exchange during hypoxia and hyperoxia
Authors: Cabrales Pedro , Tsai Amy G. , Intaglietta Marcos
Published: December 2005

The objective of this work was to test the hypothesis that the limitation of nitric oxide (NO) availability accentuates microvascular reactivity to oxygen. The awake hamster chamber window model was rendered hypoxic and hyperoxic by ventilation with 10 and 100% oxygen. Systemic and microvascular parameters were determined in the two conditions and compared with normoxia in a group receiving the NO scavenger nitronyl nitroxide and a control group receiving only the vehicle (saline). Mean arterial blood pressure did not change with different gas mixtures during infusion of the vehicle, but it increased significantly in the NO-depleted group. NO scavenging increased the reactivity of microvessels to the changed oxygen supply, causing the arteriolar wall to significantly increase oxygen consumption. Tissue Po2 was correspondingly significantly reduced during NO scavenger infusion. The present findings support the hypothesis that microvascular oxygen consumption is proportional to oxygen-induced vasoconstriction. The effect of oxygen on vascular tone is modulated by NO. As a consequence, NO acts as a regulator of the vessel wall oxygen consumption. The vessel wall consumes oxygen in proportion to the local Po2, and an impairment of NO availability renders the circulation more sensitive to changes in the oxygen supply.
Quantitative interrelationship between Gibbs-Donnan equilibrium, osmolality of body fluid compartments, and plasma water sodium concentration
Authors: Nguyen Minhtri K. , Kurtz Ira
Published: December 2005

The presence of negatively charged, impermeant proteins in the plasma space alters the distribution of diffusible ions in the plasma and interstitial fluid (ISF) compartments to preserve electroneutrality. We have derived a new mathematical model to define the quantitative interrelationship between the Gibbs-Donnan equilibrium, the osmolality of body fluid compartments, and the plasma water Na+ concentration ([Na+]pw) and validated the model using empirical data from the literature. The new model can account for the alterations in all ionic concentrations (Na+ and non-Na+ ions) between the plasma and ISF due to Gibbs-Donnan equilibrium. In addition to the effect of Gibbs-Donnan equilibrium on Na+ distribution between plasma and ISF, our model predicts that the altered distribution of osmotically active non-Na+ ions will also have a modulating effect on the [Na+]pw by affecting the distribution of H2O between the plasma and ISF. The new physiological insights provided by this model can for the first time provide a basis for understanding quantitatively how changes in the plasma protein concentration modulate the [Na+]pw. Moreover, this model defines all known physiological factors that may modulate the [Na+]pw and is especially helpful in conceptually understanding the pathophysiological basis of the dysnatremias.
Effect of a short-term diet and exercise intervention on oxidative stress, inflammation, MMP-9, and monocyte chemotactic activity in men with metabolic syndrome factors
Authors: Roberts Christian K. , Won Dean , Pruthi Sandeep , Kurtovic Silvia , Sindhu Ram K. , Vaziri Nosratola D. , Barnard R. James
Published: December 2005

The present study was designed to examine the effects of lifestyle modification on key contributing factors to atherogenesis, including oxidative stress, inflammation, chemotaxis, and cell adhesion. Obese men ( n = 31), 15 of whom had metabolic syndrome, were placed on a high-fiber, low-fat diet in a 3-wk residential program where food was provided ad libitum and daily aerobic exercise was performed. In each subject, pre- and postintervention fasting blood was drawn for circulating levels of serum lipids, glucose and insulin (for estimation of insulin sensitivity), oxidative stress-generating enzyme myeloperoxidase and marker 8-isoprostaglandin F2α, the inflammatory protein C-reactive protein, soluble ICAM-1 as an indicator of endothelial activation, sP-selectin as a marker of platelet activation, the chemokine macrophage inflammatory protein-1α, and total matrix metalloproteinase-9. Using subject sera and human aortic endothelial cell culture systems, we measured VCAM-1 cell surface abundance and monocyte chemotactic protein-1, nitric oxide, superoxide, and hydrogen peroxide production in vitro by fluorometric detection. Also determined in vitro was serum-induced, monocyte adhesion and monocyte chemotactic activity. After 3 wk, significant reductions ( P < 0.05) in body mass index, all serum lipids and lipid ratios, fasting glucose, insulin, homeostasis model assessment for insulin resistance, myeloperoxidase, 8-isoprostaglandin F2α, C-reactive protein, soluble ICAM-1, soluble P-selectin, macrophage inflammatory protein-1α, and matrix metalloproteinase-9 were noted. In vitro, serum-stimulated cellular VCAM-1 expression, monocyte chemotactic protein-1 production, and fluorometric detection of superoxide and hydrogen peroxide production decreased, whereas a concomitant increase in NO production was noted (all P < 0.01). Additionally, both monocyte adhesion ( P < 0.05) and MCA ( P < 0.01) decreased. Nine of 15 were no longer positive for metabolic syndrome postintervention. Intensive lifestyle modification may ameliorate novel coronary artery disease risk factors in men with metabolic syndrome factors before reversal of obesity.
Saturated, but not n-6 polyunsaturated, fatty acids induce insulin resistance: role of intramuscular accumulation of lipid metabolites
Authors: Lee Jong Sam , Pinnamaneni Srijan K. , Eo Su Ju , Cho In Ho , Pyo Jae Hwan , Kim Chang Keun , Sinclair Andrew J. , Febbraio Mark A. , Watt Matthew J.
Published: December 2005

Consumption of a Western diet rich in saturated fats is associated with obesity and insulin resistance. In some insulin-resistant phenotypes this is associated with accumulation of skeletal muscle fatty acids. We examined the effects of diets high in saturated fatty acids (Sat) or n-6 polyunsaturated fatty acids (PUFA) on skeletal muscle fatty acid metabolite accumulation and whole-body insulin sensitivity. Male Sprague-Dawley rats were fed a chow diet (16% calories from fat, Con) or a diet high (53%) in Sat or PUFA for 8 wk. Insulin sensitivity was assessed by fasting plasma glucose and insulin and glucose tolerance via an oral glucose tolerance test. Muscle ceramide and diacylglycerol (DAG) levels and triacylglycerol (TAG) fatty acids were also measured. Both high-fat diets increased plasma free fatty acid levels by 30%. Compared with Con, Sat-fed rats were insulin resistant, whereas PUFA-treated rats showed improved insulin sensitivity. Sat caused a 125% increase in muscle DAG and a small increase in TAG. Although PUFA also resulted in a small increase in DAG, the excess fatty acids were primarily directed toward TAG storage (105% above Con). Ceramide content was unaffected by either high-fat diet. To examine the effects of fatty acids on cellular lipid storage and glucose uptake in vitro, rat L6 myotubes were incubated for 5 h with saturated and polyunsaturated fatty acids. After treatment of L6 myotubes with palmitate (C16:0), the ceramide and DAG content were increased by two- and fivefold, respectively, concomitant with reduced insulin-stimulated glucose uptake. In contrast, treatment of these cells with linoleate (C18:2) did not alter DAG, ceramide levels, and glucose uptake compared with controls (no added fatty acids). Both 16:0 and 18:2 treatments increased myotube TAG levels (C18:2 vs. C16:0, P < 0.05). These results indicate that increasing dietary Sat induces insulin resistance with concomitant increases in muscle DAG. Diets rich in n-6 PUFA appear to prevent insulin resistance by directing fat into TAG, rather than other lipid metabolites.
Aberrant Transcription from an Unrelated Promoter Can Result in MDR-1 Expression following Drug Selection In vitro and in Relapsed Lymphoma Samples
Authors: Mickley Huff Lyn , Wang Zheng , Iglesias Angel , Fojo Tito , Lee Jong-Seok
Published: December 2005

The development of drug resistance in the treatment of cancer remains a major problem. The hallmark of multidrug resistance is cross-resistance to multiple structurally unrelated compounds. The MDR-1 gene encoding P-glycoprotein mediates one of the most extensively studied mechanisms of drug resistance. Previous studies led to the proposal that two promoters control expression of the MDR-1 gene, and these were designated the upstream and downstream promoters. In the present article, we provide evidence that transcripts originating from the putative upstream promoter of MDR-1 are in fact aberrant transcripts whose expression is regulated by nearby genomic sequences that include a human endogenous retroviral long terminal repeat (LTR). Expression of this LTR occurs in all cells. We show that following drug selection, especially in cases where gene amplification has occurred, MDR-1 transcripts can begin near this retroviral LTR with transcription proceeding in the direction opposite of the usual LTR transcription. Because expression of these aberrant MDR-1 transcripts (AMT) is found primarily in drug-resistant cell lines, we conclude that the development of drug resistance or the attendant drug exposure might have a role in the activation of this phenomenon or the selection of cells expressing AMTs. Demonstration of similar aberrant transcripts in tumor samples obtained from patients with relapsed lymphoma suggests that this phenomenon may also occur clinically. (Cancer Res 2005; 65(24): 11694-703)
Interleukin-13–regulated M2 Macrophages in Combination with Myeloid Suppressor Cells Block Immune Surveillance against Metastasis
Authors: Sinha Pratima , Clements Virginia K. , Ostrand-Rosenberg Suzanne
Published: December 2005

CD1-deficient mice reject established, disseminated 4T1 metastatic mammary cancer and survive indefinitely if their primary mammary tumors are surgically removed. This highly effective immune surveillance is due to three interacting mechanisms: (a) the generation of inducible nitric oxide synthase (iNOS)–producing M1 macrophages that are tumoricidal for 4T1 tumor cells; (b) a rapid decrease in myeloid-derived Gr1+CD11b+ suppressor cells that are elevated and down-regulate the CD3ζ chain when primary tumor is present and that suppress T cells by producing arginase; and (c) production of activated lymphocytes. Macrophages from wild-type BALB/c mice are polarized by interleukin-13 (IL-13) towards a tumor-promoting M2 phenotype, thereby inhibiting the generation of tumoricidal M1 macrophages. In contrast, CD1−/− mice, which are deficient for IL-13 because they lack IL-13–producting NKT cells, generate M1 macrophages that are cytotoxic for 4T1 via the production of nitric oxide. Although tumoricidal macrophages are a necessary component of immune surveillance in CD1−/− mice, they alone are not sufficient for tumor resistance because IL-4Rα−/− mice have M1 macrophages and retain high levels of myeloid suppressor cells after surgery; in addition, they are susceptible to 4T1 metastatic disease. These results show that effective immune surveillance against established metastatic disease is negatively regulated by IL-13 and requires the induction of tumoricidal M1 macrophages and lymphocytes combined with a reduction in tumor-induced myeloid suppressor cells. (Cancer Res 2005; 65(24): 11743-51)
Leukemogenic MLL Fusion Proteins Bind across a Broad Region of the Hox a9 Locus, Promoting Transcription and Multiple Histone Modifications
Authors: Milne Thomas A. , Martin Mary Ellen , Brock Hugh W. , Slany Robert K. , Hess Jay L.
Published: December 2005

Chromosome translocations involving the mixed lineage leukemia gene MLL are associated with aggressive acute leukemias in both children and adults. Leukemogenic MLL fusion proteins delete the MLL SET domain Lys4 methyltransferase activity and fuse MLL to 1 of >40 different translocation partners. Some MLL fusion proteins involve nuclear proteins that are transcriptional activators, whereas others have transcriptional activating activity but instead dimerize the truncated MLL molecule. Both types of MLL fusion proteins enforce persistent expression of Hox a9 and Meis1, which is pivotal for leukemogenesis through mechanisms that remain obscure. Here, we show that nuclear and dimerizable forms of MLL bind with a similar pattern to the Hox a9 locus that overlaps the distribution of wild-type MLL and deregulate transcription of three isoforms of Hox a9. Induction of MLL fusion protein activity is associated with increased levels of histone acetylation and Lys4 methylation at Hox target genes. In addition, the MLL-ENL-ER protein, but not dimerized MLL, also induces dimethylation of histone H3 at Lys79, suggesting alternative mechanisms for transcriptional activation. (Cancer Res 2005; 65(24): 11367-374)
Stepwise Neoplastic Transformation of a Telomerase Immortalized Fibroblast Cell Line
Authors: Zongaro Samantha , de Stanchina Elisa , Colombo Tina , D'Incalci Maurizio , Giulotto Elena , Mondello Chiara
Published: December 2005

We have described recently a human fibroblast cell line immortalized through ectopic telomerase expression (cen3tel), in which the extension of the life span was associated with the appearance of chromosomal aberrations and with the ability to grow in the absence of solid support. As reported in this article, on further propagation in culture, cen3tel cells became neoplastically transformed, being able to form tumors in nude mice. The analysis of the cells, during the gradual transition toward the tumorigenic phenotype, allowed us to trace cellular and molecular changes associated with different phases of transformation. At the stage in which they were able to grow in agar, cen3tel cells had lost contact growth inhibition but still retained the requirement of serum to proliferate and were not tumorigenic in immunocompromised mice. Moreover, they showed a down-regulation of the INK4A locus and were resistant to oncogenic Ras-induced senescence but still retained a functional p53. Subsequently, cen3tel cells became tumorigenic, lost p53 function because of a mutation in the DNA-binding motif, and overexpressed c-myc. Interestingly, tumorigenic cells did not carry activating mutations either in the ras proto-oncogenes (H-ras, N-ras, and K-ras) or in B-raf. Cen3tel cells gradually became hyperdiploid but did not display centrosome abnormalities. To our knowledge, cen3tel is the first telomerase immortalized fibroblast line, which became neoplastically transformed. In this system, we could associate a down-regulation of the INK4A locus with anchorage-independent growth and with resistance to Ras-induced senescence and link p53 mutations and c-myc overexpression with tumorigenicity. (Cancer Res 2005; 65(24): 11411-8)
γ-Aminobutyric Acid Inhibits Cholangiocarcinoma Growth by Cyclic AMP–Dependent Regulation of the Protein Kinase A/Extracellular Signal-Regulated Kinase 1/2 Pathway
Authors: Fava Giammarco , Marucci Luca , Glaser Shannon , Francis Heather , De Morrow Sharon , Benedetti Antonio , Alvaro Domenico , Venter Julie , Meininger Cynthia , Patel Tushar , Taffetani Silvia , Marzioni Marco , Summers Ryun , Reichenbach Ramona , Alpini Gianfranco
Published: December 2005

We studied the effect of the inhibitory neurotransmitter, γ-aminobutyric acid (GABA), in the regulation of cholangiocarcinoma growth. We determined the in vitro effect of GABA on the proliferation of the cholangiocarcinoma cell lines (Mz-ChA-1, HuH-28, and TFK-1) and evaluated the intracellular pathways involved. The effect of GABA on migration of Mz-ChA-1 cells was also evaluated. In vivo, Mz-ChA-1 cells were s.c. injected in athymic mice, and the effects of GABA on tumor size, tumor cell proliferation, apoptosis, collagen quantity, and the expression of vascular endothelial growth factor-A (VEGF-A) and VEGF-C (cancer growth regulators) were measured after 82 days. GABA decreased in vitro cholangiocarcinoma growth in a time-dependent and dose-dependent manner, by both cyclic AMP/protein kinase A– and d-myo-inositol-1,4,5-thriphosphate/Ca2+-dependent pathways, leading to down-regulation of extracellular signal-regulated kinase 1/2 phosphorylation. Blocking of GABAA, GABAB, and GABAC receptors prevented GABA inhibition of cholangiocarcinoma proliferation. GABA inhibited Mz-ChA-1 cell migration and, in vivo, significantly decreased tumor volume, tumor cell proliferation, and VEGF-A/C expression whereas increasing apoptosis compared with controls. An increase in collagen was evident in GABA-treated tumors. GABA decreases biliary cancer proliferation and reduces the metastatic potential of cholangiocarcinoma. GABA may represent a therapeutic agent for patients affected by malignancies of the biliary tract. (Cancer Res 2005; 65(24): 11437-46)
Cyclooxygenase-2 Inhibition Sensitizes Human Colon Carcinoma Cells to TRAIL-Induced Apoptosis through Clustering of DR5 and Concentrating Death-Inducing Signaling Complex Components into Ceramide-Enriched Caveolae
Authors: Martin Sophie , Phillips Darren C. , Szekely-Szucs Kinga , Elghazi Lynda , Desmots Fabienne , Houghton Janet A.
Published: December 2005

Cyclooxygenase-2 (COX-2) is up-regulated in human colon carcinomas, and its inhibition is associated with a reduction in tumorigenesis and a promotion of apoptosis. However, the mechanisms responsible for the antitumor effects of COX-2 inhibitors and how COX-2 modulates apoptotic signaling have not been clearly defined. We have shown that COX-2 inhibition sensitizes human colon carcinoma cells to tumor necrosis factor–related apoptosis-inducing ligand (TRAIL)–induced apoptosis by inducing clustering of the TRAIL receptor DR5 at the cell surface and the redistribution of the death-inducing signaling complex components (DR5, FADD, and procaspase-8) into cholesterol-rich and ceramide-rich domains known as caveolae. This process requires the accumulation of arachidonic acid and sequential activation of acid sphingomyelinase for the generation of ceramide within the plasma membrane outer leaflet. The current study highlights a novel mechanism to circumvent colorectal carcinoma cell resistance to TRAIL-mediated apoptosis using COX-2 inhibitors to manipulate the lipid metabolism within the plasma membrane. (Cancer Res 2005; 65(24): 11447-58)
A Putative Role for Psoriasin in Breast Tumor Progression
Authors: Krop Ian , März Annette , Carlsson Hanna , Li Xiaochun , Bloushtain-Qimron Noga , Hu Min , Gelman Rebecca , Sabel Michael S. , Schnitt Stuart , Ramaswamy Sridhar , Kleer Celina G. , Enerbäck Charlotta , Polyak Kornelia
Published: December 2005

Psoriasin (S100A7) was identifi`ed as a gene highly expressed in psoriatic keratinocytes and highly and more frequently expressed in ductal carcinoma in situ (DCIS) than in invasive breast carcinomas (IBC), suggesting a potential role in tumor progression. Psoriasin expression is associated with poor prognostic factors in both DCIS and IBC. Several putative functions have been proposed for psoriasin in various disease types, but none of these can fully explain its involvement in breast tumor progression. Here, we show that down-regulation of endogenous psoriasin expression via stable short hairpin RNAs in a human IBC cell line (MDA-MB-468) increases cell migration and invasion without influencing cell proliferation and survival in vitro but inhibits tumor growth in vivo. These seemingly paradoxical results are potentially explained by the dramatic up-regulation and down-regulation of matrix metalloproteinase-13 and vascular endothelial growth factor (VEGF), respectively, observed in cells with decreased psoriasin levels compared with controls. Correlating with this, high psoriasin expression in human IBC is associated with increased angiogenesis and worse clinical outcome, and psoriasin mRNA levels are coordinately regulated with VEGF and other genes related to hypoxia and mitochondrial reactive oxygen species (ROS). Based on these results, we propose that psoriasin may play a role in breast tumor progression by promoting angiogenesis and enhancing the selection for cells that overcome its anti-invasive function. This hypothesis may explain why psoriasin expression is highest in high-grade and/or estrogen receptor–negative tumors, as these are associated with increased hypoxia and ROS, a setting in which the angiogenic effects of psoriasin are most important. (Cancer Res 2005; 65(24): 11326-34)
Inducible IκB Kinase/IκB Kinase ε Expression Is Induced by CK2 and Promotes Aberrant Nuclear Factor-κB Activation in Breast Cancer Cells
Authors: Eddy Sean F. , Guo Shangqin , Demicco Elizabeth G. , Romieu-Mourez Raphaëlle , Landesman-Bollag Esther , Seldin David C. , Sonenshein Gail E.
Published: December 2005

Aberrant activation of nuclear factor-κB (NF-κB) transcription factors has been implicated in the pathogenesis of breast cancer. We previously showed elevated activity of IκB kinase α (IKKα), IKKβ, and protein kinase CK2 in primary human breast cancer specimens and cultured cells. A novel inducible IKK protein termed IKK-i/IKKε has been characterized as a potential NF-κB activator. Here, we provide evidence that implicates IKK-i/IKKε in the pathogenesis of breast cancer. We show IKK-i/IKKε expression in primary human breast cancer specimens and carcinogen-induced mouse mammary tumors. Multiple breast cancer cell lines showed higher levels of IKK-i/IKKε and kinase activity compared with untransformed MCF-10F breast epithelial cells. Interestingly, IKK-i/IKKε expression correlated with CK2α expression in mammary glands and breast tumors derived from MMTV-CK2α transgenic mice. Ectopic CK2 expression in untransformed cells led to increased IKK-i/IKKε mRNA and protein levels. Inhibition of CK2α via the pharmacologic inhibitor apigenin or upon transfection of a CK2 kinase-inactive subunit reduced IKK-i/IKKε levels. Expression of a kinase-inactive IKK-i/IKKε mutant in breast cancer cells reduced NF-κB activity as judged by transfection assays of reporters driven either by NF-κB elements or the promoters of two NF-κB target genes, cyclin D1 and relB. Importantly, the kinase-inactive IKK-i/IKKε mutant reduced the endogenous levels of these genes as well as the ability of breast cancer cells to grow in soft agar or form invasive colonies in Matrigel. Thus, CK2 induces functional IKK-i/IKKε, which is an important mediator of the activation of NF-κB that plays a critical role in the pathogenesis of breast cancer. (Cancer Res 2005; 65(24): 11375-83)