bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased repair of γ-induced DNA double-strand breaks at lower dose-rate in CHO cells
Authors: Boucher Didier , Hindo Joëlle , Averbeck Dietrich
Published: April 2004

DNA double-strand breaks (DSBs) are highly cell damaging. We asked whether for a given dose a longer irradiation time would be advantageous for the repair of DSBs. Varying the γ-irradiation dose and its delivery time (0.05 Gy/min low dose-rate (LDR) compared with 3.5 Gy/min high dose-rate), confluent Chinese hamster ovary cells (CHO-K1) and Ku80 mutant cells (xrs-6) deficient in nonhomologous end-joining (NHEJ) were irradiated in agarose plugs at room temperature using a cesium-137 γ-ray source. We used pulsed-field gel electrophoresis (PFGE) to measure DSBs in terms of the fraction of activity released (FAR). At LDR, one third of DSBs were repaired in CHO-K1 but not in xrs-6 cells, indicating the involvement of NHEJ in the repair of γ-induced DSBs at a prolonged irradiation incubation time. To improve DSB measurements, we introduced in our PFGE protocol an antioxidant at the cell lysis step, thus avoiding free-radical side reactions on DNA and spurious DSBs. Addition of the metal chelator deferoxamine (DFO) decreased more efficiently the basal DSB level than did reduced glutathione (GSH), showing that measuring DSBs in the absence of DFO reduces precision and underestimates the role of NHEJ in the dose-rate effect on DSB yield.Key words: γ-irradiation, Chinese hamster ovary cells (CHO), nonhomologous end-joining (NHEJ), low dose-rate, deferoxamine.
Tempol improves vascular function in the mesenteric vascular bed of senescent rats
Authors: Tatchum-Talom R , Martin D S
Published: April 2004

Ageing is associated with structural and functional alterations of the vasculature. The nature of age-related vascular disorders is not completely understood. Oxidative stress is hypothesized to play a crucial role in the pathophysiology of vascular complications. We investigated the effects of chronic treatment with the superoxide dismutase mimetic tempol (4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl) on vascular function in the mesenteric vasculature of aged rats. Young (3 weeks) and old (40 weeks) Sprague–Dawley rats were treated with tempol (1 mM in drinking water) or vehicle for 3 weeks. Arterial blood pressure was slightly, but significantly, higher in old than in young rats. Tempol had no effect on arterial blood pressure. The vasoconstrictor responses to norepinephrine (NE) and serotonin (5-HT) were exaggerated in the mesenteric vascular bed (MVB) removed from old rats. Vasodilator responses to acetylcholine (ACh), papaverine (PPV), and isoprenaline (ISO) were reduced in the MVB of old rats in comparison with young rats. Chronic treatment of old rats with tempol normalized their responses to NE and 5-HT. The dilator responses to ACh, PPV, and ISO were similar between old rats receiving tempol and young rats. The present findings suggest that oxidative stress contributes to vascular dysfunction in the mesentery of old rats. The vasculoprotective effects of tempol remain to be elucidated.Key words: ageing, oxidative stress, vascular reactivity.
Nest temperatures and sex-ratio estimates of loggerhead turtles at Patara beach on the southwestern coast of Turkey
Authors: Öz M , Erdoğan A , Kaska Y , Düşen S , Aslan A , Sert H , Yavuz M , Tunç M R
Published: April 2004

During the nesting period in 2000 and 2001 on Patara beach, total emergence and non-nesting emergence of loggerhead turtles (Caretta caretta), nest distribution, and nest distance from the sea were recorded . The main nesting seasons for sea turtles (family Cheloniidae) were during June and July. Loggerhead turtles comprised the majority of sea turtle emergence records; only two green turtle (Chelonia mydas) emergences were recorded. The small nesting population (52 and 53 nests in 2000 and 2001, respectively) of sea turtles on Patara beach was due to low hatching success resulting from a rise in seawater levels, owing to beach erosion, and the subsequent inundation of most nests. The temperatures of four nests and sand at different distances from the sea were measured with electronic temperature loggers, which recorded mean nest temperatures of 28.8–30.7 °C, with the mean temperature in the middle third of the incubation period from 28.5 to 31.0 °C. The mean temperatures, incubation periods, temperature during the middle third of the incubation period, and percentage of hatchling sexes were evaluated with respect to sand and nest temperatures. The results showed a female-dominated sex ratio, which was probably the result of predation of nests far from the sea and the seawater inundation of nests close to the sea, as the sand temperature was different at sites close and far from the sea.
Orientation and drifting behaviour of bumblebees (Hymenoptera: Apidae) in commercial tomato greenhouses
Authors: Birmingham Anna L , Winston Mark L
Published: April 2004

A novel environment lacking in directional cues may present orientation challenges to foraging bees. We examined orientation and drifting behaviour of Bombus occidentalis Greene and Bombus impatiens Cresson, the two major bumblebee pollinators of greenhouse tomatoes in British Columbia. Our objectives were to establish the extent and frequency of bee drift into foreign colonies and to examine the potential of nest entrance patterns and landmarks to reduce drift in commercial greenhouses. On average, 28% of marked bumblebees drifted into foreign hives, making up 0.3%–34.8% of the population in those colonies. Bees drifted towards the top position when hives were vertically stacked. The use of simple black and white patterns and large landmarks did not affect the number of drifting bees, suggesting that disorientation is not a major contributor to drift or to the substantial loss of adult bees from colonies during their first week in a greenhouse. Bees had decreased foraging times when landmarks were present in the greenhouse and showed a marginally but not significantly increased rate of pollen input to colonies. These studies contribute to understanding bumblebee behaviour in a novel environment and determining whether orientation cues are feasible management options to reduce drift and potential bee loss.
Effects of saline intake, sex, and season on Pekin duck osmoregulatory organ masses and comparison with wild Mallards
Authors: Hughes Maryanne R , Bennett Darin C
Published: April 2004

Osmoregulatory organ masses of freshwater Mallards (Anas platyrhynchos) do not differ between the sexes, but drinking saline induces changes that are sexually disparate in some organs. We examined relative size of organ masses of male and female Pekin ducks (that were domesticated from Mallards) and compared their responses to saline intake with those of Mallards. Organ masses of male and female Mallards do not differ in size. The liver and kidneys are heavier in female Pekin ducks and their digestive tract (except for the proventriculus and duodenum) is longer and heavier; male Pekin ducks have heavier salt glands. Mallards acclimated to saline drinking water have enlarged salt glands but not kidneys, adrenal glands, or Harderian glands, their proventriculus tends to be shorter and lighter, the jejunum longer in males, and the ileum longer and heavier in both sexes. In Pekin ducks that drink saline, the salt and Harderian glands are larger and their kidneys (but not adrenal glands) tend to be larger; the proventriculus is unaffected, but the small intestine is lighter, but not shorter, in females. Body, salt gland, Harderian gland, ventriculus, and duodenum masses vary seasonally in Pekin ducks. Discussion considers the effects of season and sex on relative organ masses and how saline-induced changes in them reflect domestication and may influence salt tolerance.
Visual health assessment of North Atlantic right whales (Eubalaena glacialis) using photographs
Authors: Pettis Heather M , Rolland Rosalind M , Hamilton Philip K , Brault Solange , Knowlton Amy R , Kraus Scott D
Published: April 2004

Although trends in reproduction, mortality, and entanglement events have been analyzed for the endangered North Atlantic right whale (Eubalaena glacialis) population, no method has been available to assess individual right whale health. Here, we describe a technique for assessing health based on evaluation of selected physical parameters from archived photographs of right whales. A scoring system was developed to assess body and skin condition, blowhole cyamids, and rake marks in over 200 000 photographs. Comparison of body condition scores of females during calving and noncalving years found that females were significantly thinner in calving years and in the year after calving compared with the year before calving, showing that changes in body condition known to occur during the reproductive cycle can be successfully evaluated from photographs. Comparison of scores for all parameters between living whales and whales with more than a 5-year gap in sighting history ("presumed dead") found that presumed dead whales received health assessment scores indicating compromised health with body condition emerging as a key visual indicator. This health assessment method provides a new tool to monitor health trends in right whales at individual and population levels and may provide a model for assessments of other well-photographed cetaceans.
Do female zebra finches (Taeniopygia guttata) copy each other's mate preferences?
Authors: Doucet Stéphanie M , Yezerinac Stephen M , Montgomerie Robert
Published: April 2004

We investigated whether female zebra finches (Taeniopygia guttata) would alter their mate preferences after observing the choices of other females. Experimental trials consisted of four 30-min stages: (A) acclimation, (B) observer female chooses between two males, (C) observer female watches a model female interact with her nonpreferred male from stage B, and (D) observer female again chooses between the two males. Control trials were identical except that there was no model female in stage C. Females in both experimental and control trials spent significantly more time with the nonpreferred male in stage D than they had in stage B; thus, our experiment appeared to reveal no evidence of mate choice copying. There was, however, a significant positive relationship between the increase in the time that an observer female in experimental trials spent with her nonpreferred male in stage D and the number of interactions that she had previously observed between the model female and that male in stage C. A second experiment of similar design, where observer females were prevented from observing the model female and nonpreferred male interact in stage B, demonstrated that the behaviour of the observer female in the first experiment was not simply a response to changes in male behaviour in stage D. While our experiment does not support the hypothesis that female zebra finches copy each other's mate preferences, our findings suggest that public information may influence the behaviour of female zebra finches toward potential mates.
Angiostrongylus vasorumandCrenosoma vulpisin red foxes (Vulpes vulpes) in Newfoundland, Canada
Authors: Jeffery Rebecca A , Lankester Murray W , McGrath Mike J , Whitney Hugh G
Published: April 2004

Angiostrongylus vasorum and Crenosoma vulpis infect the pulmonary arteries and airways, respectively, of red foxes (Vulpes vulpes). Both are widespread in Europe, but within North America, A. vasorum occurs only on the island of Newfoundland. During 2000–2002, 366 red fox carcasses were examined from six regions of Newfoundland for the purpose of determining the distribution of both parasites, effects on the condition of their host, and whether infection with one affects that of the other. Crenosoma vulpis occurred island-wide with a prevalence of 87% and mean (±SE) intensity of 230 ± 20.8. Young-of-the-year red foxes had more C. vulpis (260 ± 39.4) than yearlings (91 ± 31.2) or adults (78 ± 41.1) (χ2= 25.72, df = 2, p < 0.001), and numbers of adult worm were weakly related to fecal output of first-stage larvae (r2= 0.20, p < 0.001) but not to host sex or body-fat index. Angiostrongylus vasorum occurred only in southeast Newfoundland where prevalence was 56% and mean intensity was 72 ± 7.6. Its distribution may be limited by cold, as it was absent from areas with mean winter temperatures below –4 °C. Intensity of adult A. vasorum was not related to host age, sex, larval output, or measures of body condition. Although referred to as a heartworm, 88% of adult worms were actually found in the pulmonary arteries rather than in the right ventricle. Furthermore, there was no apparent association between infections with the two parasites (Gc[1]= 0.10) even though 40% of red foxes had dual infections.
Optical properties, mitochondria, and sutures of lenses of fishes: a comparative study of nine species
Authors: Bantseev V , Moran K L , Dixon D G , Trevithick J R , Sivak J G
Published: April 2004

This comparative study of lenses from nine fish species consisted of seven teleosts (oscar, Astronotus ocellatus; smallmouth bass, Micropterus dolomieu; orangespotted sunfish, Lepomis humilus; Arctic char, Salvelinus alpinus; common carp, Cyprinus carpio; rainbow trout, Oncorhynchus mykiss; American eel, Anguilla rostrata) and two species representing more primitive forms (brook lamprey, Lampetra lamotteni; lake sturgeon, Acipenser fulvescens). Lens optical properties were analysed using an automated scanning laser monitor. Lens suture anatomy and the morphology and distribution of mitochondria were analysed using a confocal laser scanning microscope. Lenses of Arctic char exhibited the sharpest focus, whereas American eel lenses exhibited the poorest ability to focus and the highest amount of spherical aberration. Metabolically active mitochondria are found in lens epithelial and superficial cortical fibre cells, as in mammals. The results of the detailed study of the lens sutures show that teleost lenses exhibit "line" sutures, whereas "Y" sutures are seen in lake sturgeon lenses. Line sutures are also seen in lenses of brook lamprey and American eel. These last results contrast with the common report of "point" sutures in fish lenses.
Seasonal and yearly changes in consumption of hypogeous fungi by northern flying squirrels and red squirrels in old-growth forest, New Brunswick
Authors: Vernes Karl , Blois Shauna , Bärlocher Felix
Published: April 2004

Seasonal consumption of mycorrhizal fungus by northern flying squirrels (Glaucomys sabrinus) and red squirrels (Tamiasciurus hudsonicus) was examined in old-growth mixedwood forest at Fundy National Park in southern New Brunswick between May 1999 and March 2001. Using faecal pellet analysis, we found that the amount of fungus in the diet of both species was dependent on season and year of study and ranged from 35% to 95%. Twenty fungal taxa, most of them hypogeous Ascomycetes and Basidiomycetes, were detected in diets. More taxa were detected in summer diets compared with all other seasons, but all seasonal samples contained several hypogeous taxa. Up to six taxa were identified in any one sample. Both squirrel species occurred at high densities throughout the study, and dietary overlap between them was great throughout this time in terms of both the amount of fungus and the proportions of different taxa that were consumed. Overall, our data suggest that both G. sabrinus and T. hudsonicus are abundant and important consumers of fungus in the region and that fungus may represent a key food resource, particularly during times when other foods are limited.
The relative importance of prey density and social dominance in determining energy intake by bears feeding on Pacific salmon
Authors: Gende S M , Quinn T P
Published: April 2004

We quantified foraging behavior of brown bears (Ursus arctos) feeding on adult chum (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha) at three small coastal streams in southeastern Alaska from streamside tree stands. These observations revealed that social dominance was much more important in determining intake rates among bears than salmon densities. Each small stream supported one large, socially dominant bear that directly displaced other bears in aggressive encounters or was avoided in "passive deferrals". Although the number of fish killed per foraging bout was positively correlated with salmon density, energy intake was determined primarily by foraging effort, as dominant bears visited the stream more often and foraged for longer periods than subdominant bears. Capture efficiency (fish captured per minute searching) was highly variable and increased only marginally with salmon density and among social ranks. Subdominant bears were more vigilant, used a smaller fraction of each stream, and carried salmon much farther into the forest prior to consumption, presumably to minimize interactions with other bears. Social dominance may play an important role in regulating reproductive success when salmon densities are low and may have important implications for managers in bear-viewing areas.
Microsatellite markers reveal multiple paternity and sperm storage in the Mediterranean spur-thighed tortoise, Testudo graeca
Authors: Roques S , Díaz-Paniagua C , Andreu A C
Published: April 2004

The spur-thighed tortoise (Testudo graeca) is a terrestrial species in which multiple mating is frequently observed. We assessed the probability of multiple paternity in clutches (n = 15) laid by eight females, including successive clutches. Paternity was determined by microsatellite analyses at three loci. A large number of alleles per locus (n = 15–22) provided high probabilities of detecting multiple paternity, particularly at all loci combined (P = 0.989). Multiple paternity was found in 20% of the clutches in which offspring displayed more than two paternal alleles. However, this frequency may have been underestimated, given the small clutch sizes and the few loci used. Also, T. graeca is able to store sperm from single or multiple matings and can use it to fertilize subsequent clutches of eggs, as indicated by the fact that the second clutch of a captive female was sired by a different male and that clutches of another female were multiply sired by the same males. These results confirm that multiple paternity exists in T. graeca and that sperm storage in this species may be an important reproductive strategy to fertilize multiple clutches per year.
ON THE TEMPERATURE INDEPENDENT RESISTIVITY OF IMPURITIES DILUTED IN NOBLE HOSTS
Authors: RAMUNNI V. P. , DE OLIVEIRA N. A. , TROPER A.
Published: March 2004

We discuss the temperature independent resistivity of s–p impurities and rare earth impurities diluted in noble hosts, using a T-matrix formulation. We take into account translational symmetry breaking and therefore a nonlocal charge potential is obtained. The effect of volume difference between impurity and host elements is also considered in the calculation. In the case of "magnetic" impurities (i.e. almost all rare earth impurities) we calculate the spin disorder resistivity, obtaining a charge potential renormalized De Gennes–Friedel spin disorder resistivity. Our numerical results describe the available experimental data quite well.
PROBABILITY DISTRIBUTION OF THE PHASE OF A BOSE–EINSTEIN CONDENSATE
Authors: LIU SHUJUAN , XIONG HONGWEI , WANG LEI
Published: March 2004

For temperatures far below the critical temperature, the probability distribution of the phase of a Bose–Einstein condensate is investigated for the phase diffusion process due to collective excitations spontaneously created from the condensate. Our results show that the phase diffusion decreases with the increasing of the particle number in the condensate.
KINETIC ANALYSIS OF PROTEIN FOLDING LATTICE MODELS
Authors: CHEN HU , ZHOU XIN , LIAW CHIH YOUNG , KOH CHAN GHEE
Published: March 2004

Based on two-dimensional square lattice models of proteins, the relation between folding time and temperature is studied by Monte Carlo simulation. The results can be represented by a kinetic model with three states — random coil, molten globule, and native state. The folding process is composed of nonspecific collapse and final searching for the native state. At high temperature, it is easy to escape from local traps in the folding process. With decreasing temperature, because of the trapping in local traps, the final searching speed decreases. Then the folding shows chevron rollover. Through the analysis of the fitted parameters of the kinetic model, it is found that the main difference between the energy landscapes of the HP model and the Go model is that the number of local minima of the Go model is less than that of the HP model.
ANALYSIS OF AN IRREGULAR SIERPINSKI TRIANGLE
Authors: PALAGALLO JUDITH , PALMER MATTHEW
Published: March 2004

An irregular Sierpinski triangle is a non-empty compact set F satisfying [Formula: see text] where each Ti is a contracting affine transformation. The irregular Sierpinski triangle is not generated with similarity transformations. Therefore, the calculation of its fractal dimension is not straightforward. We associate with each irregular Sierpinski triangle a self-similar regularization. The dimension of the regularization dictates the shape of the irregular Sierpinski triangle. We also describe properties of the regularizations and show their relationship to the classic Sierpinski triangle.
MELANOMA DETECTION WITH HYSTOPATHOLOGY IMAGE ENHANCEMENT USING LOCAL HURST EXPONENT
Authors: PASSONI LUCÍA ISABEL , ARIZMENDI C. M.
Published: March 2004

Malignant melanoma is nowadays one of the most frequent type of skin cancer among white-skinned populations and one of the most malignant tumors. In this work, we investigate fractal properties of color images of dermal tissue microscopic samples as a basis for detection of malignant melanoma lesions. The enhancement image process is applied to hematoxylin-eosin stained tissue samples microscopic images. A segmented image based on a color model attribute is processed with a local Hurst transformation added with edge detection algorithm. The result is used to modulate the intensity information of the original image in order to support the expert analysis essentially in low quality images. Our findings show that fractal measures such as the Hurst exponent can be used to detect regions with a high density of melanocytes nests included in dermal tissue allowing early diagnosis of malignant melanoma tumors.
SIMULATION METHODS FOR LINEAR FRACTIONAL STABLE MOTION AND FARIMA USING THE FAST FOURIER TRANSFORM
Authors: STOEV STILIAN , TAQQU MURAD S.
Published: March 2004

We present efficient methods for simulation, using the Fast Fourier Transform (FFT) algorithm, of two classes of processes with symmetric α-stable (SαS) distributions. Namely, (i) the linear fractional stable motion (LFSM) process and (ii) the fractional autoregressive moving average (FARIMA) time series with SαS innovations. These two types of heavy-tailed processes have infinite variances and long-range dependence and they can be used in modeling the traffic of modern computer telecommunication networks.

We generate paths of the LFSM process by using Riemann-sum approximations of its SαS stochastic integral representation and paths of the FARIMA time series by truncating their moving average representation. In both the LFSM and FARIMA cases, we compute the involved sums efficiently by using the Fast Fourier Transform algorithm and provide bounds and/or estimates of the approximation error.

We discuss different choices of the discretization and truncation parameters involved in our algorithms and illustrate our method. We include MATLAB implementations of these simulation algorithms and indicate how the practitioner can use them.
FRACTAL PROPERTIES OF A NEOGENE FAULT SYSTEM IN NORTHWESTERN SICILY, ITALY
Authors: GUARNIERI P. , VINCIGUERRA S. , VESUVIANO OSSERVATORIO
Published: March 2004

A Neogene transcurrent fault system affecting the Apenninic-Maghrebian thrust belt, located in northwestern Sicily, has been investigated using fractal analysis. The present-day structural setting of the sector between the Palermo and Madonie Mountains is the result of the superimposition, in space and time, of two distinct deformational events, a Miocene southeast-verging thrusting followed by Messinian to Pliocene strike-slip faulting, which cuts obliquely through the compressive fronts. The spatial distribution properties of the fault array were investigated by means of a fractal analysis. Fractal dimension was computed by adopting the correlation integral method. Fractal ranges have been evidenced between 350 and 3000 m. The fractal dimension obtained for the whole array is D=1.66. The scaling spatial distribution property of the fault array has been analyzed by calculating the fractal dimension with a moving window.
DISTRIBUTED ORDER FRACTIONAL SUB-DIFFUSION
Authors: NABER MARK
Published: March 2004

A distributed order fractional diffusion equation is considered. Distributed order derivatives are fractional derivatives that have been integrated over the order of the derivative within a given range. In this paper, sub-diffusive cases are considered. That is, the order of the time derivative ranges from zero to one. The equation is solved for Dirichlet, Neumann and Cauchy boundary conditions. The time dependence for each of the three cases is found to be a functional of the diffusion parameter. This functional is shown to have decay properties. Upper and lower bounds are computed for the functional. Examples are also worked out for comparative decay rates.
Nitric oxide decreases endothelin-1 secretion through the activation of soluble guanylate cyclase
Authors: Kelly Lisa K. , Wedgwood Stephen , Steinhorn Robin H. , Black Stephen M.
Published: April 2004

The use of exogenous nitric oxide (NO) has been shown to alter the regulation of other endothelially derived mediators of vascular tone, such as endothelin-1 (ET-1). However, the interaction between NO and ET-1 appears to be complex and remains incompletely understood. One of the major actions of NO is the activation of soluble guanylate cyclase (sGC) with the subsequent generation of cGMP. Therefore, we undertook this study to test the hypothesis that NO regulates ET-1 production via the activation of the sGC/cGMP pathway. The results obtained indicated that the exposure of primary cultures of 4-wk-old ovine pulmonary arterial endothelial cells (4-wk PAECs) to the long-acting NO donor DETA NONOate induced both a dose- and time-dependent decrease in secreted ET-1. This decrease in ET-1 secretion occurred in the absence of changes in endothelin-converting enzyme-1 or sGC expression but in conjunction with a decrease in prepro-ET-1 mRNA. The changes in ET-1 release were inversely proportional to the cellular cGMP content. Furthermore, the NO-independent activator of sGC, YC-1, or treatment with a cGMP analog also produced significant decreases in ET-1 secretion. Conversely, pretreatment with the sGC inhibitor ODQ blocked the NO-induced decrease in ET-1. Therefore, we conclude that exposure of 4-wk PAECs to exogenous NO decreases secreted ET-1 resulting from the activation of sGC and increased cGMP generation.
Hepatocyte growth factor inhibits the formation of the basement membrane of alveolar epithelial cells in vitro
Authors: Furuyama Akiko , Mochitate Katsumi
Published: April 2004

Hepatocyte growth factor (HGF) is a pulmotrophic factor for the regeneration of injured pulmonary tissue. We investigated the role of HGF in basement membrane formation during wound healing by immortalized alveolar type II epithelial cells that could form a continuous basement membrane when they were cultured on collagen fibrils in the presence of entactin-contaminated laminin-1. Cells cultured with 5.0 ng/ml HGF neither formed a continuous basement membrane on collagen fibrils nor maintained a continuous basement membrane architecture on a basement membrane substratum. The cells showed increased secretion of matrix metalloproteinase-9 and urokinase-type plasminogen activator, and the HGF-induced inhibition of basement membrane formation was attenuated by addition of 200 ng/ml tissue inhibitor of matrix metalloproteinase-1. Cells sequentially exposed to HGF and 1.0 ng/ml transforming growth factor-β1 had enhanced basement membrane formation compared with those receiving these reagents in the reverse order or concurrently. HGF simultaneously stimulated proliferation and migration of the cells so that it advanced wound closure on the basement membrane substratum. The present results indicate that the role of HGF in wound healing is the stimulation of reepithelization, but this factor may also contribute to the degradation of the basement membrane.
Molecular identity and function in transepithelial transport of KATP channels in alveolar epithelial cells
Authors: Leroy Claudie , Dagenais André , Berthiaume Yves , Brochiero Emmanuelle
Published: April 2004

K+ channels play a crucial role in epithelia by repolarizing cells and maintaining electrochemical gradient for Na+ absorption and Cl- secretion. In the airway epithelium, the most frequently studied K+ channels are KvLQT1 and KCa. A functional role for KATP channels has been also suggested in the lung, where KATP channel openers activate alveolar clearance and attenuate ischemia-reperfusion injury. However, the molecular identity of this channel is unknown in airway and alveolar epithelial cells (AEC). We adopted an RT-PCR strategy to identify, in AEC, cDNA transcripts for Kir channels (Kir6.1 or 6.2) and sulfonylurea receptors (SUR1, 2A, or 2B) forming KATP channels. Only Kir6.1 and SUR2B were detected in freshly isolated and cultured alveolar cells. To determine the physiological role of K+ channels in the transepithelial transport of alveolar monolayers, we studied the effect, on total short-circuit currents ( Isc), of basolateral application of glibenclamide, an inhibitor of KATP channels, as well as clofilium, charybdotoxin, clotrimazole, and iberiotoxin, inhibitors of KvLQT1 and KCa channels, respectively. Interestingly, activity of the three types of K+ channels was detected, since all tested inhibitors decreased Isc. Furthermore, these K+ channel inhibitors reduced amiloride-sensitive Na+ currents (mediated by ENaC) and completely abolished stimulation of Cl- currents by forskolin. Conversely, pinacidil, an activator of KATP channels, increased Na+ and Cl- transepithelial transport by 33–35%. These results suggest the presence, in AEC, of a KATP channel, formed from Kir6.1 and SUR2B subunits, which plays a physiological role, with KvLQT1 and KCa channels, in Na+ and Cl- transepithelial transport.
Store-operated Ca2+entry in porcine airway smooth muscle
Authors: Ay Binnaz , Prakash Y. S. , Pabelick Christina M. , Sieck Gary C.
Published: April 2004

Ca2+influx triggered by depletion of sarcoplasmic reticulum (SR) Ca2+stores [mediated via store-operated Ca2+channels (SOCC)] was characterized in enzymatically dissociated porcine airway smooth muscle (ASM) cells. When SR Ca2+was depleted by either 5 μM cyclopiazonic acid or 5 mM caffeine in the absence of extracellular Ca2+, subsequent introduction of extracellular Ca2+further elevated [Ca2+]i. SOCC was insensitive to 1 μM nifedipine- or KCl-induced changes in membrane potential. However, preexposure of cells to 100 nM–1 mM La3+or Ni2+inhibited SOCC. Exposure to ACh increased Ca2+influx both in the presence and absence of a depleted SR. Inhibition of inositol 1,4,5-trisphosphate (IP)-induced SR Ca2+release by 20 μM xestospongin D inhibited SOCC, whereas ACh-induced IP3production by 5 μM U-73122 had no effect. Inhibition of Ca2+release through ryanodine receptors (RyR) by 100 μM ryanodine also prevented Ca2+influx via SOCC. Qualitatively similar characteristics of SOCC-mediated Ca2+influx were observed with cyclopiazonic acid- vs. caffeine-induced SR Ca2+depletion. These data demonstrate that a Ni2+/La3+-sensitive Ca2+influx via SOCC in porcine ASM cells involves SR Ca2+release through both IP3and RyR channels. Additional regulation of Ca2+influx by agonist may be related to a receptor-operated, noncapacitative mechanism.
Toll-like receptors: function and roles in lung disease
Authors: Basu Subhendu , Fenton Matthew J.
Published: April 2004

Toll-like receptor (TLR) proteins have been shown to play a pivotal role in both innate and adaptive immune responses in higher vertebrates. TLR proteins enable the host to recognize a large number of pathogen-associated molecular patterns such as bacterial lipopolysaccharides, viral RNA, CpG-containing DNA, and flagellin, among others. Engagement of TLR proteins leads to the upregulation of costimulatory molecules and proinflammatory cytokines, as well as reactive nitrogen and oxygen products. The role of TLR proteins in lung-associated pathologies such as airway hyperreactivity, allergic asthma, and tuberculosis is being intensively studied. This review summarizes many of the findings made to date on the roles of TLR proteins in a variety of lung diseases. Generally, TLR proteins serve a protective role in infectious diseases, such as tuberculosis. The progression of chronic inflammatory lung diseases, such as allergic asthma, can also be influenced by TLR-dependent responses.
Calorie-related rapid onset of alveolar loss, regeneration, and changes in mouse lung gene expression
Authors: Massaro Donald , Massaro Gloria DeCarlo , Baras Alex , Hoffman Eric P. , Clerch Linda Biadasz
Published: April 2004

Calorie restriction, followed by ad libitum refeeding, results, respectively, in loss and regeneration of pulmonary alveoli. We now show 35% of alveoli are lost within 72 h of onset of calorie restriction (⅔ decreased daily chow intake), and an additional 12% of alveoli are lost over a subsequent 12 days of calorie restriction. Tissue necrosis was not seen. Within 72 h of refeeding, after 15 days of calorie restriction, the number of alveoli returns to precalorie restriction values. Microarray lung gene profiling, in conjunction with Western and RNase protection assay, demonstrate an increase of granzyme and caspase gene expression 2–3 h after onset of calorie restriction. By 12 h, granzyme and caspase expression is no longer increased, but tumor necrosis factor death receptor expression is elevated. At 336 h, Fas death receptor expression is increased. Because granzymes are found only in cytotoxic lymphocytes (CTLs) and natural killer (NK) cells, we suggest calorie restriction activates these cells, initiating a series of molecular events that results in alveolar destruction. The evidence of involvement of CTLs and NK cells and the absence of necrosis are similar to alveolar destruction in chronic obstructive pulmonary disease.
Regulation of macrophage cyclooxygenase-2 gene expression by modifications of histone H3
Authors: Park Gye Young , Joo Myungsoo , Pedchenko Tetyana , Blackwell Timothy S. , Christman John W.
Published: April 2004

Some transcription factors involved in the regulation of cyclooxygenase 2 (COX-2) expression in macrophage, including NF-κB, interact with p300, which contains histone acetyltransferase (HAT) enzyme complex. Chromatin structure is regulated by modifying enzymes, including HAT, and plays an important role in eukaryotic gene regulation through histone modification. We hypothesized that changes in chromatin structure related to phosphorylation and acetylation of histone H3 adjacent to key DNA binding sequence motif in the COX-2 promoter contribute to COX-2 gene activation in macrophages. Sodium butyrate (NaBT) is a short-chain fatty acid that possesses histone deacetyltransferase-inhibiting activity. Our data show that NaBT accentuates LPS-induced COX-2 gene expression at a transcriptional level, even though NaBT alone does not induce the COX-2 gene expression. Using a chromatin immunoprecipitation assay, we showed that costimulation of RAW 264.7 cells with NaBT and LPS synergistically increases COX-2 gene expression through both acetylation and phosphorylation of histone H3 at the promoter site. Our data show that NaBT accentuates LPS-induced COX-2 gene expression through MAP kinase-dependent increase of phosphorylation and acetylation of histone H3 at the COX-2 promoter site. These data indicate that posttranslational modification of histone H3 has a major effect on COX-2 gene expression by macrophages.
Tracing surfactant transformation from cellular release to insertion into an air-liquid interface
Authors: Haller T. , Dietl P. , Stockner H. , Frick M. , Mair N. , Tinhofer I. , Ritsch A. , Enhorning G. , Putz G.
Published: April 2004

Pulmonary surfactant is secreted by alveolar type II cells as lipid-rich, densely packed lamellar body-like particles (LBPs). The particulate nature of released LBPs might be the result of structural and/or thermodynamic forces. Thus mechanisms must exist that promote their transformation into functional units. To further define these mechanisms, we developed methods to follow LBPs from their release by cultured cells to insertion in an air-liquid interface. When released, LBPs underwent structural transformation, but did not disperse, and typically preserved a spherical appearance for days. Nevertheless, they were able to modify surface tension and exhibited high surface activity when measured with a capillary surfactometer. When LBPs inserted in an air-liquid interface were analyzed by fluorescence imaging microscopy, they showed remarkable structural transformations. These events were instantaneous but came to a halt when the interface was already occupied by previously transformed material or when surface tension was already low. These results suggest that the driving force for LBP transformation is determined by cohesive and tensile forces acting on these particles. They further suggest that transformation of LBPs is a self-regulated interfacial process that most likely does not require structural intermediates or enzymatic activation.
Reductions in the incidence of nitrofen-induced diaphragmatic hernia by vitamin A and retinoic acid
Authors: Babiuk Randal P. , Thébaud Bernard , Greer John J.
Published: April 2004

Congenital diaphragmatic hernia (CDH) is a serious medical condition in which the developing diaphragm forms incompletely, leaving a hole through which the abdominal contents can enter the thoracic space and interfere with lung growth. A perturbation of the retinoid system has been linked to the etiology of CDH. This includes findings that nitrofen, which induces CDH in rodents, inhibits the key enzyme for retinoic acid (RA) production, retinaldehyde dehydrogenase-2 (RALDH2) in vitro. Published studies indicate that antenatal vitamin A administration on gestational day (D) 12 in the nitrofen model of CDH reduced the severity and incidence of right-sided defects and lung hypoplasia. In this study, we administered nitrofen on D8, to include the induction of clinically more prevalent left-sided defects, and examined the efficacy of several vitamin A administration paradigms to gain insights into the developmental stage of susceptibility. Furthermore, we tested the hypothesis that administration of RA, the product of RALDH2 activity, is more potent than administering the substrate, vitamin A, in reducing the incidence of CDH. The incidence of CDH was reduced from ∼54% (nitrofen alone) to ∼32% with vitamin A treatment. The efficacy of RA treatment was very marked, with a reduction in the incidence of CDH to ∼15%. Administration of vitamin A or RA on ∼D10 was most effective. These data lend further support for the potential involvement of retinoid signaling pathways and the etiology of CDH and support data from in vitro studies demonstrating a nitrofen-induced suppression of RALDH2.
Functional diversity ofnotchfamily genes in fetal lung development
Authors: Kong Yanping , Glickman Jonathon , Subramaniam Meera , Shahsafaei Aliakbar , Allamneni K. P. , Aster Jon C. , Sklar Jeffrey , Sunday Mary E.
Published: April 2004

In Drosophila, developmental signaling via the transmembrane Notch receptor modulates branching morphogenesis and neuronal differentiation. To determine whether the notch gene family can regulate mammalian organogenesis, including neuroendocrine cell differentiation, we evaluated developing murine lung. After demonstrating gene expression for notch-1, notch-2, notch-3, and the Notch ligands jagged-1 and jagged-2 in embryonic mouse lung, we tested whether altering expression of these genes can modulate branching morphogenesis. Branching of embryonic day (E) 11.5 lung buds increased when they were treated with notch-1 antisense oligodeoxynucleotides in culture compared with the corresponding sense controls, whereas notch-2, notch-3, jagged-1, or jagged-2 antisense oligos had no significant effect. To assess cell differentiation, we immunostained lung bud cultures for the neural/neuroendocrine marker PGP9.5. Antisense to notch-1 or jagged-1 markedly increased numbers of PGP9.5-positive neuroendocrine cells alone without affecting neural tissue, whereas only neural tissue was promoted by notch-3 antisense in culture. There was no significant effect on cell proliferation or apoptosis in these antisense experiments. Cumulatively, these observations suggest that interactions between distinct Notch family members can have diverse tissue-specific regulatory functions during development, arguing against simple functional redundancy.
Effect of tyrosine kinase blockade on norepinephrine-induced cytosolic calcium response in rat afferent arterioles
Authors: Salomonsson Max , Arendshorst William J.
Published: March 2004

We used genistein (Gen) and tyrphostin 23 (Tyr-23) to evaluate the importance of tyrosine phosphorylation in norepinephrine (NE)-induced changes in intracellular free calcium concentration ([Ca2+]i) in rat afferent arterioles. [Ca2+]iwas measured in microdissected arterioles using ratiometric photometry of fura 2 fluorescence. The control [Ca2+]iresponse to NE (1 μM) consisted of a rapid initial peak followed by a plateau phase sustained above baseline. Pretreatment with the tyrosine kinase inhibitor Tyr-23 (50 μM, 10 min) caused a slow 40% increase in baseline [Ca2+]i. Tyr-23 attenuated peak and plateau responses to NE, both by ∼70%. In the absence of extracellular Ca2+(0 Ca), Tyr-23 reduced the immediate [Ca2+]iresponse to NE by ∼60%, indicative of mobilization of internal stores, and abolished the plateau phase. In other arterioles, the [Ca2+]iresponse to depolarization induced by KCl (50 mM) was not attenuated by Tyr-23, indicating no direct effect on L-type Ca+channels activated by depolarization. The Ca2+channel blocker nifedipine (1 μM) inhibited the NE response by ∼50%; the effects of nifedipine and Tyr-23 were not additive. Nifedipine had no inhibitory effect after Tyr-23 pretreatment, indicating Tyr-23 inhibition of Ca2+entry. Another tyrosine kinase inhibitor, Gen (5 and 50 μM), did not affect baseline [Ca2+]i. High-dose Gen inhibited the peak and plateau response to NE by 87 and 75%, respectively; low-dose Gen attenuated both responses by ∼20%. In 0 Ca, Gen (50 μM) abolished the immediate [Ca2+]imobilization response. Combined nifedipine and Gen (50 μM) inhibited the rapid NE response by ∼90% in the presence of extracellular Ca2+. Gen (50 μM) also inhibited by 60% the [Ca2+]iresponse to 50 mM KCl, indicating a direct interaction with voltage-sensitive, L-type Ca2+entry channels. These results indicate that tyrosine phosphorylation is an important link in the chain of events leading to α-adrenoceptor-induced Ca2+recruitment (both entry and release) in afferent arteriolar smooth muscle cells. Furthermore, different blockers of tyrosine kinase appear to have different modes of action in renal microvessels.
Phosphophloretin sensitivity of rabbit renal NaPi-IIa and NaPi-Ia
Authors: Peerce Brian E. , Peerce Brandon , Clarke Rebecca D.
Published: March 2004

The effect of phosphorylated phloretins on Na+-dependent phosphate uptake into rabbit renal brush-border membrane vesicles (BBMV) was examined. Na+-dependent phosphate uptake into isolated rabbit cortex BBMV was sensitive to 2′-phosphophloretin (2′-PP) and 2′-phospho-4′,4,6′-trimethoxy phloretin (PTMP) in a dose-dependent and pH-dependent manner. PTMP inhibition of Na+-dependent phosphate uptake was maximum at alkali pH, and 2′-PP inhibition of Na+-dependent phosphate uptake was maximum at acidic pH. Increasing Na+concentrations did not increase PTMP inhibition of renal cortex BBMV Na+-dependent phosphate uptake at pH 6. The effect of phosphophloretins on Na+-dependent phosphate uptake was examined in BBMV isolated from purified proximal tubules and distal tubules. 2′-PP and PTMP inhibition of Na+-dependent phosphate uptake into BBMV isolated from purified proximal tubules was similar to the inhibition seen with BBMV from renal cortex. 2′-PP, but not PTMP, inhibited Na+-dependent phosphate uptake into BBMV isolated from purified distal tubules. The pH dependence of inhibition, the absence of PTMP inhibition of Na+-dependent phosphate uptake into distal tubule BBMV, and the inhibition of Na+-dependent phosphate uptake into distal tubule BBMV suggest that NaPi-Ia is 2′-PP sensitive and NaPi-IIa is PTMP sensitive.
Permissive role of nitric oxide in macula densa control of renin secretion
Authors: Castrop Hayo , Schweda Frank , Mizel Diane , Huang Yuning , Briggs Josie , Kurtz Armin , Schnermann Jurgen
Published: March 2004

Experiments were performed in neuronal (nNOS)- and endothelial nitric oxide synthase (eNOS)-deficient mice to study the role of nitric oxide (NO) in macula densa control of renin secretion in vivo and in the isolated, perfused mouse kidney. Acute and chronic administration of loop diuretics was used as a method to stimulate macula densa-mediated renin secretion. Increases in plasma renin concentration (PRC) in response to a 3-day infusion of bumetanide (50 mg·kg-1·day-1) or an acute injection of furosemide (50 mg/kg ip) were not markedly altered in nNOS-/- mice. Responses to furosemide were also maintained in eNOS-/- mice, but the administration of Nω-nitro-l-arginine methyl ester (l-NAME) markedly attenuated the PRC response to furosemide in these mice. In the isolated kidney preparation, bumetanide caused similar relative increases in renin secretion in kidneys of wild-type, nNOS-/-, and eNOS-/- mice. Bumetanide only marginally increased renin secretion in l-NAME-treated kidneys, but the bumetanide effect was normalized by S-nitroso- N-acetyl-penicillamine. Basal PRC was significantly reduced in male nNOS-/- mice compared with nNOS+/+ (189 ± 28 vs. 355 ± 57 ng ANG I ·ml-1·h-1; P = 0.017). There was no significant difference in PRC between eNOS+/+ and eNOS-/- mice. Basal renin secretion rates in perfused kidneys isolated from nNOS-/- or eNOS-/- mice were markedly reduced compared with wild-type controls. Our data suggest that NO generated by macula densa nNOS does not play a specific mediator role in macula densa-dependent renin secretion. However, NO independent of its exact source permits the macula densa pathway of renin secretion to function normally.