bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogenetic Relationships among Members of the Coregoninae Inferred from Direct Sequencing of PCR-Amplified Mitochondrial DNA
Authors: Lockwood S. Fournier , Dillinger Jr. Robert E. , Birt Tim P. , Green John M. , Snyder Thomas P.
Published: September 2008

We determined the DNA sequence of a portion of the mitochondrial cytochrome b gene for eight members of the Coregoninae (Salmonidae) from North America in an effort to elucidate phylogenetic relationships in the subfamily. DNA was prepared for sequencing by the polymerase chain reaction (PCR). Direct estimates of mitochondrial DNA (mtDNA) sequence divergence among taxa ranged from 0.0% between Arctic cisco (Coregonus autumnalis) from the Mackenzie River, Canada, and cisco (C. artedi) from the Laurentian Great Lakes to 5.8% between the inconnu (Stenodus leucichthys) and the round whitefish (Prosopium cylindraceum). As has been noted in other fish species and vertebrates in general, third position silent substitutions predominated over any other type of nucleotide change. No amino acid replacement substitutions were found among any of the eight taxa examined. Comparison of mtDNA sequence divergence estimates from this and other studies suggests that the radiation of the genera within the Coregoninae occurred relatively recently (2–6 million yr B.P.). Cladistic analysis of the mtDNA sequence data yields a hypothesis of relationships that supports previous genetic and morphological classifications of coregonines.
An Appraisal of the Size-Dependent Mortality Hypothesis for Larval Fish: Comparison of a Multispecies Study with an Empirical Review
Authors: Pepin Pierre
Published: September 2008

This study presents an assessment of the size-dependent mortality hypothesis for larval fish from a multispecies survey of Conception Bay, Newfoundland, Canada. Mortality rates are estimated using a length-based method (per millimetre). The results from this survey are consistent with previous studies which indicate that losses decrease with increasing size of fish. However, for each species within this survey, mortality rates are constant. Comparison of mortality rates within species among surveys indicates that as the range of size categories sampled increases, the estimated mortality rates decrease, despite evidence of adequate fit to the length-based model. The findings indicate that previous relationships between size or stage and mortality of larval fish should be reevaluated. Length-based methodology used to estimate mortality rates of larval fish appears to provide biased estimates of this vital characteristic. It is suggested that using size as a proxy for biological age (i.e., assuming a constant growth rate) may be an invalid assumption. Future surveys will need to provide accurate information about the age structure of larvae sampled in order to properly estimate mortality rates.
Patterns in Toxicity of Sublethal Mixtures of Metals and Organic Chemicals Determined by Microtox® and by DNA, RNA, and Protein Content of Fathead Minnows (Pimephales promelas)
Authors: Parrott Joanne L. , Sprague John B.
Published: September 2008

Combinations of copper (0–90 μg/1) and zinc (0–1200 μg/L) acted in an additive fashion when tested by Microtox®, decreasing the luminescence of the marine bacterium Photobacterium phosphoreum after a 30-min exposure. Acetophenone (0–18 mg/L) combined with diethylene glycof (0–40 g/L) had less-than-additive effects, as did acetophenone–zinc combinations. In contrast, less-than-additive action of copper (0–150 μg/L) and zinc (0–1500 μg/L) was apparent from DNA, RNA, and protein contents of newly hatched fathead minnows (Pimephales promelas) exposed for 4 d. The highest copper–zinc combinations caused dramatic decreases in DNA, RNA, and protein contents of fish to 35, 8, and 46% of control levels, respectively. Although most joint effects were less-than-additive, independent action and antagonism were observed for some combinations of toxicants, and the type of action usually changed as proportions of toxicants were altered. Isobole mapping of response surfaces gave a useful overall picture of joint action for all concentrations tested, was favoured as a method of illustrating the results, and provided the interpretations given above.
Influence of Parr Growth, Lake Morphology, and Freshwater Parasites on the Degree of Anadromy in Different Populations of Arctic Char (Salvelinus alpinus) in Northern Norway
Authors: Kristoffersen Knut , Halvorsen Morten , Jørgensen Lisbeth
Published: September 2008

Anadromy of nine lake populations of Arctic char (Salvelinus alpinus) in northern Norway was scored on the following criteria: prevalence of marine parasites, fish size, and size at maturity. In general, anadromy dominated in shallow lakes and residency dominated in deep lakes. The anadromy scores of the populations were significantly higher in lakes without a profundal zone compared with lakes with a profundal zone. There was also a significant negative correlation between the relative volume of the profundal zone (RPV) and the degree of anadromy and between RPV and mean parr length at ages 2+ and 3+. However, differences in parr growth could not explain all the observed variation in anadromy, and the correlation between mean parr length at ages 2+ and 3+ and the degree of anadromy in the different populations was not significant. In addition to the effect on parr growth, lake morphology seemed to influence the degree of anadromy through the relative size of different habitats, which in turn affects the number of available niches. The parr weight/length relationship and infection with the freshwater parasites Phyllodistomum umblae and Diphyllobothrium spp. did not affect the degree of anadromy.
Influence of Wind-produced Noise on Orientation in the Sole (Solea solea)
Authors: Lagardère J. P. , Bégout M. L. , Lafaye J. Y. , Villotte J. P.
Published: September 2008

Sole (Solea solea), telemetered in an enclosure using an acoustic positioning system, changed their swimming trajectories and orientation behaviour as a function of wind strength and direction. Monitoring of the spatial variation in both wind-generated currents and noise spectra in the enclosure indicates that these behavioural changes correspond to patterns in the spatial distribution of noise and to sound intensity. Thus, our observations indicate that sole perceives and reacts to horizontal variability in ambient noise levels. Such behaviour may be important in determining movements of fish populations at sea during poor weather conditions.
Lipids and Myelin Proteins in the Brains of Coelacanth (Latimeria chalumnae), lungfish (Lepidosiren paradoxaandProtopterus aetiopicus), bichir (Polypterus senegalus), and sturgeon (Acipenser ruthenus) (Osteichthyes): Phylogenetic Implications
Authors: Tamai Yoichi , Kojima Hisako , Takayama-Abe Kumiko , Suzuki Atsushi
Published: September 2008

The chemical components of nerve membranes of primitive bony fishes (coelacanth (Latimeria chalumnae), lungfish (Lepidosiren paradoxa and Protopterus aetiopicus), bichir (Polypterus senegalus), and sturgeon (Acipenser ruthenus)) were analyzed to investigate their phylogenetic relations. Representative myelin components such as cerebroside and myelin proteins and enzyme exhibited characteristic profiles in the different species. Coelacanth was characterized by an abundance of hydroxy components of cerebroside fatty acids and by the occurrence of a 28 000 molecular weight band (possibly P0-like protein) and proteolipid protein (PLP). Lungfish possessed glycosylated PLP, but lacked PLP; bichir and sturgeon showed the same protein compositions, PLP and P0-like protein being major components. The activity of 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP), a myelin marker enzyme, was detected in coelacanth myelin, but was almost negligible in the others. The ganglioside compositions were simple in coelacanth and lungfish compared with those in bichir and sturgeon, which were abundant in polysialo components. These findings suggest that coelacanth nerve membranes are the most developed in these species; thus, coelacanth may be more advanced phylogenetically than the others. Bichir and sturgeon were suggested to occupy unique phylogenetic positions, showing similar chemical compositions of nerve membranes which were distinct from those of coelacanth and lungfish.
Advection–Diffusion Modelling of Larval Capelin (Mallotus villosus) Dispersion in Conception Bay, Newfoundland
Authors: deYoung Brad , Anderson John , Greatbatch Richard J. , Fardy Paul
Published: September 2008

A numerical model was used to determine the residence time of capelin (Mallotus villosus) larvae in Conception Bay, Newfoundland. The larvae were observed in the surface mixed layer of the Bay following release from beaches in June–July in order to examine how they move outside the Bay and what physical factors influence their rate of transport. A diagnostic model of Conception Bay provides a fixed velocity field which drives an advection–diffusion model applied to capelin larval dispersal from the Bay. The model was run for different periods to explore dependence of the residence time on different conditions during the period 1989–90. Model results showed that the residence time depends on the release location of the larvae in the Bay. While the residence time of the larvae does vary, we estimate it to be roughly 30 d for larvae released from the head of the Bay. Residence times are much shorter for larvae near the mouth of the Bay.
Large-scale Analysis of Atlantic Nova Scotia American Lobster (Homarus americanus) Landings with Respect to Habitat, Temperature, and Wind Conditions
Authors: Hudon Christiane
Published: September 2008

American lobster (Homarus americanus) landings per unit of habitat, calculated for 25 statistical districts (SD) of Atlantic Nova Scotia (N.S.), were consistently higher in northern Cape Breton (SD 1–7) and southwestern N.S. (SD 32–34) than from the eastern (SD 15–18) and southern (SD 22–31) shores. Analyses suggest that changes in lobster populations of Atlantic N.S. take place over distances in the order of 100 km and over periods of about 5 yr and that lobster abundance is not limited by habitat availability. Five large homogeneous regions subject to similar historical landing trends could be identified on the basis of their thermal characteristics. Regions of lowest lobster landings (SD 8–31) are oriented in the axis of dominant southwest winds, which generate coastal upwelling, resulting in the lowest cumulative number of degree-days and a high year-to-year variability. Conversely, the high landings recorded in southwestern N.S. can be related to warm and stable temperature conditions, allowing lobsters to enhance yearly thermal gains via winter migrations into deep (> 100 m), warm Slope water. The definition of homogeneous regions characterized by common historical landing trends and thermal regime suggests that lobster abundance in Atlantic N.S. is ultimately controlled by large-scale oceanographic processes.
Association between the Regulatory LocusPGM-1r* and Life-history Types of Juvenile Atlantic Salmon (Salmo salar)
Authors: Pollard Susan M. , Danzmann Roy G. , Claytor Ross R.
Published: September 2008

We sampled three juvenile life-history types of Atlantic salmon (Salmo salar) from Western Arm Brook, Newfoundland, to test whether a regulatory gene variant PGM-1r*b is associated with accelerated life-history development. Seven nonmigratory parr populations from the Miramichi River, New Brunswick, and the Margaree River, Nova Scotia, were also sampled. Previous studies with rainbow trout (Oncorhynchus mykiss) indicate that the liver-specific regulatory gene variant PGM-1r*b is associated with faster embryonic and life-history development. We found no association between variation at PGM-1r* and body weight, fork length, gonadal development, and smolt age. However, the frequency of PGM-1r* was significantly higher in males than in females for combined life-history types from Western Arm Brook. These results suggest that PGM-1r* is sex linked or under strong sex-specific selection in this population. Furthermore, populations with higher frequencies of PGM-1r*b tended to have higher frequencies of precocious maturation in males.
Decline in Total Phosphorus in the Surface Waters of Lakes during Summer Stratification, and its Relationship to Size Distribution of Particles and Sedimentation
Authors: Guy Martha , Taylor William D. , Carter John C. H.
Published: September 2008

The decline in total phosphorus (TP) in the surface waters of 40 oligotrophy to mesotrophic lakes during stratification varied from 0 to 59.0%. Sediment traps were deployed in four of the lakes to examine the relationship between decline in TP and sedimentation. Declines in TP and sedimentation of P were similar in magnitude when summed over the stratified season, and a positive correlation between TP decline and sedimentation rate was observed. Lakes possessing larger particles exhibited larger declines in particulate phosphorus (PP) than lakes with smaller plankton. Declines in TP were not significantly related to particle size, possibly because of the influence of spring concentrations of dissolved P, which quickly declined in all lakes in which they were observed. These results support the contention that sedimentation plays a major role in the decline in TP during stratification and that sedimentation is influenced by plankton community structure.
pH, Hardness, and Humic Acid Influence Aluminum Toxicity to Rainbow Trout (Oncorhynchus mykiss) in Weakly Alkaline Waters
Authors: Gundersen Deke T. , Bustaman Sjahrul , Seim Wayne K. , Curtis Lawrence R.
Published: September 2008

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed for either 96 h (acute) or 16 d (subacute) to various combinations of aluminum and hardness concentrations or aluminum and humic acid concentrations between pH 7.14 and 8.58. Aluminum-induced mortality was higher at weakly alkaline pH (7.95–8.58) (attributed to up to 10-fold higher filterable aluminum concentrations) than near-neutral pH (7.14–7.64). Growth rates were higher in 16-d hardness tests at weakly alkaline pH (0.188–1.600% of initial weight∙d−1) than for fish exposed to similar aluminum concentrations at near-neutral pH (−0.535–0.756%∙d−1). This suggested that polymeric and colloidal forms of aluminum were more potent than soluble forms in restricting growth. Hardness and humic acid appeared most protective to trout against subacute aluminum toxicity. Cumulative mortality of trout exposed to 1.50 mg aluminum∙L−1at 103 or 20 mg∙L−1hardness as CaCO3was 10 and 45%, respectively. Hardness did not significantly protect against aluminum-induced growth inhibition. Trout exposed for 16 d to aluminum (0.53–2.56 mg∙L−1) and humic acid 4.31–5.23 mg∙L−1) had higher specific growth rates and decreased mortality than those exposed to aluminum and ho humic acid at any pH.
Interannual Mixed Function Oxidase (MFO) Activity in Winter Flounder (Pleuronectes americanus) from a Coal Tar Contaminated Estuary
Authors: Vignier V. , Vandermeulen J. H. , Singh J. , Mossman D.
Published: September 2008

7-Ethoxyresorufin-O-deethylase (EROD), benzo[a]pyrene hydroxylase (BaPH), and cytochromes P-450 (cyt-P450) and b5(cyt-b5) varied annually in winter flounder (Pleuronectes americanus) collected in August of 1987, 1988, and 1989 from a coal tar contaminated estuary (Sydney, Nova Scotia, Canada). For August 1989, with fish available from all estuary areas, these indices correlated strongly with a spatial (along estuary) gradient in PAH in bottom sediments (7.19 ± 6.59–191 ± 184 μg g dry weight−1). Mean EROD activities in flounder near the coal tar source were up to seven times those in other estuary areas and paralleled sediment PAH loadings; however, standard deviations were high. Correlations for all MFO indices and sediment PAH were obtained in female flounder (P < 0.01: EROD, cyt-b5, cyt-P450; P < 0.02: BaPH). For male flounder the trend was similar, but only cyt-P450 correlated with sediment PAH (P < 0.017). BaPH activity was highest near the coal tar source but was more variable and less sensitive to pollutant levels than EROD activity. Somatic indices in fish from Sydney estuary and St. George's Bay were similar. Winter flounder are vulnerable to PAH-induced MFO activities from coal tar contaminated sediments, but MFO induction does not occur equally in all fish; single-season or single-year data must be interpreted with caution.
Historical Status of Fish Populations in Canadian Rocky Mountain Lakes Inferred from Subfossil Chaoborus (Diptera: Chaoboridae) Mandibles
Authors: Lamontagne S. , Schindler D. W.
Published: September 2008

We used subfossil Chaoborus mandibles preserved in sediments of Cabin, Caledonia, and Celestine lakes, Alberta, to determine whether fish were present in the lakes (which now contain rainbow trout (Oncorhynchus mykiss) and lake chub (Couesius plumbeus)) prior to the first fish stockings early this century. We first tested whether Chaoborus were good indicators of the presence of fish in montane lakes in a survey of 43 lakes in jasper and Banff national parks. Chaoborus americanus was the only species inhabiting fishless lakes and was also found in three lakes with low fish density (co-occurring with C. flavicans in two of the three lakes). Other lakes containing fish had either C. flavicans or no Chaoborus species. Subfossils revealed that C. americanus was the predominant species prior to this century in Cabin and Celestine lakes, suggesting that these lakes were originally fishless; C. americanus (and C. trivittatus in Cabin Lake) were eliminated early this century, contemporarily with the first recorded fish stockings. Chaoborus flavicans was the only species recovered from Caledonia Lake, suggesting that the lake had fish prior to this century; while it is not possible to identify the species originally present, historical evidence suggests that rainbow trout is native to Caledonia Lake.
Environmental Effects on the Distributions of Groundfish in Hecate Strait, British Columbia
Authors: Perry R. Ian , Stocker Max , Fargo Jeff
Published: September 2008

Hecate Strait, British Columbia, is an area of variable topography with a variety of bottom habitats, which supports an important mixed-species groundfish fishery. A previous analysis identified three characteristic assemblages of groundfish species. In the present study, we identify relationships between the dominant species of these assemblages and environmental conditions in early summer 1989 and 1991: bottom type and depth (invariant conditions) and temperature (a variable condition). Three categories of species were identified: (i) those consistently associated with particular depths and temperatures between years, (ii) those with variable depth and temperature associations, and (iii) those with no apparent relationships to depth, temperature, or sediment type. Category (i) was dominated by flatfishes and could be further separated into groups associated with deep and cool, shallow and warm, and intermediate depth and temperature conditions. Category (ii) included roundfishes plus Pacific halibut (Hippoglossus stenolepis) and were widely distributed. At least one species (Pacific cod (Gadus macrocephalus)) tended to maintain a particular temperature range while changing its depth range between years. Identification of significant associations between fish species and habitat conditions is the first step towards incorporating environmental information into survey abundance indices and reducing by-catch problems.
Population Structure and Identification of North Pacific Ocean Chum Salmon (Oncorhynchus keta) Revealed by an Analysis of Minisateliite DNA Variation
Authors: Taylor Eric B. , Beacham Terry D. , Kaeriyama Masahide
Published: September 2008

We examined geographic variability in minisatellite DNA in chum salmon (Oncorhynchus keta) from 42 populations from the North Pacific Ocean to (1) determine the extent of regional population structure at minisatellite loci and (2) assess the ability of minisatellite variability to determine the geographic origin in individual chum salmon. Restriction fragments from 1.6 to 13.6 kilobase pairs in molecular weight were resolved with a minisatellite probe. The fragments were inherited from parent to offspring and appeared to represent segregation at two linked loci. Minisateliite DNA variability was negligible between annual samples from the same rivers, and chum salmon fell into three regional population groupings: (i) Japanese, (ii) Russian/Yukon River, and (iii) southeastern Alaska/British Columbia salmon. These regional groupings probably reflect historical patterns of postglacial dispersal of chum salmon from three distinct refugia in the North Pacific. We used restriction fragment counts as input to linear discriminant and neural network classification of independent test samples of salmon. Accuracies of 90–95, 81–86, and 72–80% were achieved when classifying fish as of either Japan/Russia/Yukon River versus southeastern Alaska/British Columbia origin, Japan versus Russia/Yukon River origin, or Russia versus Yukon River origin, respectively.
Quantitative Effects of Atyid Shrimp (Decapoda: Atyidae) on the Depositional Environment in a Tropical Stream: Use of Electricity for Experimental Exclusion
Authors: Pringle Catherine M. , Blake Gail A.
Published: September 2008

Effects of biotic (shrimp) and abiotic (discharge) factors on the depositional environment were quantified in a montane stream in Puerto Rico. Electricity was used experimentally to exclude large (approximately >1 cm in length) biota without artificially increasing sedimentation as in cage enclosure/exdosure experiments in stream systems. Shrimp (>1 cm in length) were excluded from rock substrata by semicircular fences hooked up to battery-powered fence chargers which emitted continuous pulses of electricity. Unelectrified control substrata had natural high densities of atyid shrimp. Significantly greater masses of total sediment, fine and large organic particles, and algal biovolume occurred in shrimp exclusion treatments relative to controls. Shrimp exclusion treatments experienced slow and steady accumulation of sediments under base flow conditions and a large stepwise increase in sediment weight following a storm. No measurable sediment accrued in the presence of natural densities of shrimp under base flow conditions. Shrimp rapidly removed sediments that accrued during the storm (440–620 g∙m2dry mass−1), decreasing sediment mass in control treatments to near prestorm levels (5–13 g∙m2dry mass−1) within 30 h. Atyid shrimp can significantly affect the accumulation of organic and inorganic materials on rock substrata in stream pools between high-discharge events.
Activation of Na+/H+ and K+/H+ exchange by calyculin A in Amphiuma tridactylum red blood cells: implications for the control of volume-induced ion flux activity
Authors: Ortiz-Acevedo Alejandro , Rigor Robert R. , Maldonado Hector M. , Cala Peter M.
Published: September 2008

Alteration in cell volume of vertebrates results in activation of volume-sensitive ion flux pathways. Fine control of the activity of these pathways enables cells to regulate volume following osmotic perturbation. Protein phosphorylation and dephosphorylation have been reported to play a crucial role in the control of volume-sensitive ion flux pathways. Exposing Amphiuma tridactylu red blood cells (RBCs) to phorbol esters in isotonic medium results in a simultaneous, dose-dependent activation of both Na+/H+ and K+/H+ exchangers. We tested the hypothesis that in Amphiuma RBCs, both shrinkage-induced Na+/H+ exchange and swelling-induced K+/H+ exchange are activated by phosphorylation-dependent reactions. To this end, we assessed the effect of calyculin A, a phosphatase inhibitor, on the activity of the aforementioned exchangers. We found that exposure of Amphiuma RBCs to calyculin-A in isotonic media results in simultaneous, 1–2 orders of magnitude increase in the activity of both K+/H+ and Na+/H+ exchangers. We also demonstrate that, in isotonic media, calyculin A-dependent increases in net Na+ uptake and K+ loss are a direct result of phosphatase inhibition and are not dependent on changes in cell volume. Whereas calyculin A exposure in the absence of volume changes results in stimulation of both the Na+/H+ and K+/H+ exchangers, superimposing cell swelling or shrinkage and calyculin A treatment results in selective activation of K+/H+ or Na+/H+ exchange, respectively. We conclude that kinase-dependent reactions are responsible for Na+/H+ and K+/H+ exchange activity, whereas undefined volume-dependent reactions confer specificity and coordinated control.
Type 1 inositol 1,4,5-trisphosphate receptors mediate UTP-induced cation currents, Ca2+signals, and vasoconstriction in cerebral arteries
Authors: Zhao Guiling , Adebiyi Adebowale , Blaskova Eva , Xi Qi , Jaggar Jonathan H.
Published: September 2008

Inositol 1,4,5-trisphosphate receptors (IP3Rs) regulate diverse physiological functions, including contraction and proliferation. There are three IP3R isoforms, but their functional significance in arterial smooth muscle cells is unclear. Here, we investigated relative expression and physiological functions of IP3R isoforms in cerebral artery smooth muscle cells. We show that 2-aminoethoxydiphenyl borate and xestospongin C, membrane-permeant IP3R blockers, reduced Ca2+wave activation and global intracellular Ca2+([Ca2+]i) elevation stimulated by UTP, a phospholipase C-coupled purinergic receptor agonist. Quantitative PCR, Western blotting, and immunofluorescence indicated that all three IP3R isoforms were expressed in acutely isolated cerebral artery smooth muscle cells, with IP3R1 being the most abundant isoform at 82% of total IP3R message. IP3R1 knockdown with short hairpin RNA (shRNA) did not alter baseline Ca2+wave frequency and global [Ca2+]ibut abolished UTP-induced Ca2+wave activation and reduced the UTP-induced global [Ca2+]ielevation by ∼61%. Antibodies targeting IP3R1 and IP3R1 knockdown reduced UTP-induced nonselective cation current ( Icat) activation. IP3R1 knockdown also reduced UTP-induced vasoconstriction in pressurized arteries with both intact and depleted sarcoplasmic reticulum (SR) Ca2+by ∼45%. These data indicate that IP3R1 is the predominant IP3R isoform expressed in rat cerebral artery smooth muscle cells. IP3R1 stimulation contributes to UTP-induced Icatactivation, Ca2+wave generation, global [Ca2+]ielevation, and vasoconstriction. In addition, IP3R1 activation constricts cerebral arteries in the absence of SR Ca2+release by stimulating plasma membrane Icat.
Spontaneous transient depolarizations in lymphatic vessels of the guinea pig mesentery: pharmacology and implication for spontaneous contractility
Authors: von der Weid Pierre-Yves , Rahman Mozibur , Imtiaz Mohammad S. , van Helden Dirk F.
Published: September 2008

Guinea pig mesenteric lymphatic vessels exhibit rhythmic constrictions induced by action potential (AP)-like spikes and initiated by entrainment of spontaneous transient depolarizations (STDs). To characterize STDs and the signaling mechanisms responsible for their occurrence, we used intracellular microelectrodes, Ca2+imaging, and pharmacological agents. In our investigation of the role of intracellular Ca2+released from Ca2+stores, we observed that intracellular Ca2+transients accompanied some STDs, although there were many exceptions where Ca2+transients occurred without accompanying STDs. STD frequency and amplitude were markedly affected by activators/inhibitors of inositol 1,4,5-trisphosphate receptors (IP3Rs) but not by treatments known to alter Ca2+release via ryanodine receptors. A role for Ca2+-activated Cl−(ClCa) channels was indicated, as STDs were dependent on the Cl−but not Na+concentration of the superfusing solution and were inhibited by the ClCachannel blockers niflumic acid (NFA), anthracene 9-carboxylic acid, and 5-nitro-2-(3-phenylpropylamino)benzoic acid but not by the volume-regulated Cl−blocker DIDS. Increases in STD frequency and amplitude induced by agonist stimulation were also inhibited by NFA. Nifedipine, the hyperpolarization-activated inward current blocker ZD-7288, and the nonselective cation/store-operated channel blockers SKF-96365, Gd3+, and Ni2+had no or marginal effects on STD activity. However, nifedipine, 2-aminoethoxydiphenyl borate, NFA, SKF-96365, Gd3+, and Ni2+altered the occurrence of spontaneous APs. Our findings support a role for Ca2+release through IP3Rs and a resultant opening of ClCachannels in STD generation and confirm the importance of these events in the initiation of lymphatic spontaneous APs and subsequent contractions. The abolition of spontaneous APs by blockers of other excitatory ion channels suggests a contribution of these conductances to lymphatic pacemaking.
Dissection of two Cx37-independent conducted vasodilator mechanisms by deletion of Cx40: electrotonic versus regenerative conduction
Authors: Figueroa Xavier F. , Duling Brian R.
Published: September 2008

Conduction of changes in diameter plays an important role in the coordination of peripheral vascular resistance and, thereby, in the control of arterial blood pressure. It is thought that conduction of vasomotor signals relies on the electrotonic spread of changes in membrane potential from a site of stimulation through gap junctions connecting the cells of the vessel wall. To explore this idea, we stimulated a short segment of mouse cremasteric arterioles with an application, via micropipette, of ACh, an endothelium-dependent vasodilator, or pinacidil, an ATP-sensitive K+channel opener. Vasodilations were evaluated at the stimulation site (local) and at 500, 1,000, and 2,000 μm upstream. The vasodilator response evoked by direct arteriolar hyperpolarization induced by pinacidil decayed rapidly with distance, as expected for the passive spread of an electrical signal. Deletion of the gap junction proteins connexin37 or connexin40 did not alter the conduction of pinacidil-induced vasodilation. In contrast to pinacidil, the vasodilator response activated by ACh spread along the entire vessel without decrement. Although the ACh-induced conducted vasodilation was similar in wild-type and connexin37 knockout mice, deletion of connexin40 converted the nondecremental conducted response activated by ACh into one similar to that of pinacidil, with a decline in magnitude along the vessel length. These results suggest that ACh activates a mechanism of regenerative conduction of vasodilator responses. Connexin40 is essential for the ACh-activated regenerative vasodilator mechanism. However, neither connexin40 nor connexin37 is indispensable for the electrotonic spread of hyperpolarizing signals.
Effects of rosuvastatin on cardiovascular morphology and function in an ApoE-knockout mouse model of atherosclerosis
Authors: Grönros J. , Wikström J. , Brandt-Eliasson U. , Forsberg G. B. , Behrendt M. , Hansson G. I. , Gan L. M.
Published: September 2008

This study investigated the effects of rosuvastatin on plaque progression and in vivo coronary artery function in apolipoprotein E-knockout (ApoE-KO) mice, using noninvasive high-resolution ultrasound techniques. Eight-week-old male ApoE-KO mice ( n = 20) were fed a high-fat diet with or without rosuvastatin (10 μmol·kg−1·day−1) for 16 wk. When compared with control, rosuvastatin reduced total cholesterol levels ( P < 0.05) and caused significant retardation of lesion progression in the brachiocephalic artery, as visualized in vivo using an ultrasound biomicroscope ( P < 0.05). Histological analysis confirmed the reduction of brachiocephalic atherosclerosis and also revealed an increase in collagen content in the statin-treated group ( P < 0.05). Coronary volumetric flow was measured by simultaneous recording of Doppler velocity signals and left coronary artery morphology before and during adenosine infusion. The hyperemic flow in response to adenosine was significantly greater in left coronary artery following 16 wk of rosuvastatin treatment ( P < 0.001), whereas the baseline flow was similar in both groups. In conclusion, rosuvastatin reduced brachiocephalic artery atherosclerotic plaques in ApoE-KO mice. Coronary artery function assessed using recently developed in vivo ultrasound-based protocols, also improved.
Ischemia-reperfusion injury in rats affects hydraulic conductivity in two phases that are temporally and mechanistically separate
Authors: Victorino Gregory P. , Ramirez René M. , Chong Terry J. , Curran Brian , Sadjadi Javid
Published: September 2008

Ischemia-reperfusion (IR) injury is a major insult to postcapillary venules. We hypothesized that IR increases postcapillary venular hydraulic conductivity and that IR-mediated changes in hydraulic conductivity result from temporally and mechanistically separate processes. A microcannulation technique was used to determine hydraulic conductivity (Lp) in rat mesenteric postcapillary venules serially throughout ischemia (45 min) and reperfusion (5 h) induced by superior mesenteric artery occlusion and release. Mesenteric IR resulted in a biphasic increase in Lp. White blood cell (WBC) adhesion slowly increased with maximal adhesion corresponding to the second peak ( P < 0.005). After IR, tissue was harvested for RT-PCR analysis of ICAM-1, E-selectin, and P-selectin mRNA. Intercellular adhesion molecule-1 (ICAM-1) mRNA in the gut showed the most significant upregulation. Quantitative real-time PCR revealed that ICAM-1 mRNA was upregulated 60-fold in the gut. An ICAM-1 antibody was therefore used to determine the effect of WBC adhesion on Lpduring IR. ICAM-1 inhibition attenuated Lpduring the first peak and completely blocked the second peak ( P < 0.005). When rats were fed a tungsten diet to inhibit xanthine oxidase and then underwent IR, Lpwas dramatically attenuated during the first peak and mildly decreased the second peak ( P < 0.005). Inhibition of xanthine oxidase by oxypurinol decreased Lpduring IR by over 60% ( P < 0.002). Tempol, a superoxide dismutase mimetic, decreased Lpduring IR by over 30% ( P < 0.01). We conclude that IR induces a biphasic increase in postcapillary hydraulic conductivity. Reactive oxygen species impact both the first transient peak and the sustained second peak. However, the second peak is also dependent on WBC-endothelial cell adhesion. These serial measurements of postcapillary hydraulic conductivity may lead the way for optimal timing of pharmaceutical therapies in IR injury.
Tricyclic antidepressant amitriptyline alters sarcoplasmic reticulum calcium handling in ventricular myocytes
Authors: Zima Aleksey V. , Qin Jia , Fill Michael , Blatter Lothar A.
Published: September 2008

Tricyclic antidepressants such as amitriptyline (AMT) have been reported to have adverse side effects on cardiac performance. AMT effects on Ca handling in ventricular myocytes, however, are not well understood. Therefore, we investigated AMT action on sarcoplasmic reticulum (SR) Ca release in ventricular myocytes, ryanodine receptor (RyR) activity, and Ca uptake by SR microsomes. In permeabilized myocytes, AMT transiently increased free luminal Ca concentration ([Ca]) followed by marked depletion. AMT (10 μM) caused a rapid and a transient increase of Ca spark frequency, followed by a significant suppression of spark activity. The latter was associated with a decrease of Ca spark amplitude and SR Ca load to 87 and 60%, respectively. AMT (10 μM) completely abolished propagation of spontaneous Ca waves. Higher concentrations of AMT (0.1–1 mM) evoked SR Ca release reminiscent of the effect of caffeine (20 mM) and caused almost complete depletion of SR Ca content. Studies on single calsequestrin-free RyR channels revealed that AMT increased the mean open time and open probability ( Po) in a dose-dependent fashion (dissociation constant = 4.2 μM). High concentrations of AMT (>25 μM) evoked frequent long openings with Poreaching very high levels (>0.70). In studies with cardiac SR microsomes, AMT slowed the rate of ATP-dependent Ca uptake. We conclude that AMT affects SR Ca handling in ventricular myocytes by multiple mechanisms, including direct stimulation of RyRs and inhibition of SR Ca uptake. These effects could contribute to AMT cardiotoxicity.
Impaired Ca2+ homeostasis is associated with atrial fibrillation in the α1D L-type Ca2+ channel KO mouse
Authors: Mancarella Salvatore , Yue Yuankun , Karnabi Eddy , Qu Yongxia , El-Sherif Nabil , Boutjdir Mohamed
Published: September 2008

The novel α1D Ca2+ channel together with α1C Ca2+ channel contribute to the L-type Ca2+ current ( ICa-L) in the mouse supraventricular tissue. However, its functional role in the heart is just emerging. We used the α1D gene knockout (KO) mouse to investigate the electrophysiological features, the relative contribution of the α1D Ca2+ channel to the global ICa-L, the intracellular Ca2+ transient, the Ca2+ handling by the sarcoplasmic reticulum (SR), and the inducibility of atrial fibrillation (AF). In vivo and ex vivo ECG recordings from α1D KO mice demonstrated significant sinus bradycardia, atrioventricular block, and vulnerability to AF. The wild-type mice showed no ECG abnormalities and no AF. Patch-clamp recordings from isolated α1D KO atrial myocytes revealed a significant reduction of ICa-L (24.5%; P < 0.05). However, there were no changes in other currents such as INa, ICa-T, IK, If, and Ito and no changes in α1C mRNA levels of α1D KO atria. Fura 2-loaded atrial myocytes showed reduced intracellular Ca2+ transient (∼40%; P < 0.05) and rapid caffeine application caused a 17% reduction of the SR Ca2+ content ( P < 0.05) and a 28% reduction ( P < 0.05) of fractional SR Ca2+ release in α1D KO atria. In conclusion, genetic deletion of α1D Ca2+ channel in mice results in atrial electrocardiographic abnormalities and AF vulnerability. The electrical abnormalities in the α1D KO mice were associated with a decrease in the total ICa-L density, a reduction in intracellular Ca2+ transient, and impaired intracellular Ca2+ handling. These findings provide new insights into the mechanism leading to atrial electrical dysfunction in the α1D KO mice.
Comparison of baroreceptive to other afferent synaptic transmission to the medial solitary tract nucleus
Authors: Andresen Michael C. , Peters James H.
Published: September 2008

Cranial nerve visceral afferents enter the brain stem to synapse on neurons within the solitary tract nucleus (NTS). The broad heterogeneity of both visceral afferents and NTS neurons makes understanding afferent synaptic transmission particularly challenging. To study a specific subgroup of second-order neurons in medial NTS, we anterogradely labeled arterial baroreceptor afferents of the aortic depressor nerve (ADN) with lipophilic fluorescent tracer (i.e., ADN+) and measured synaptic responses to solitary tract (ST) activation recorded from dye-identified neurons in medial NTS in horizontal brain stem slices. Every ADN+ NTS neuron received constant-latency ST-evoked excitatory postsynaptic currents (EPSCs) (jitter <192 μs, SD of latency). Stimulus-recruitment profiles showed single thresholds and no suprathreshold recruitment, findings consistent with EPSCs arising from a single, branched afferent axon. Frequency-dependent depression of ADN+ EPSCs averaged ∼70% for five shocks at 50 Hz, but single-shock failure rates did not exceed 4%. Whether adjacent ADN− or those from unlabeled animals, other second-order NTS neurons (jitters <200 μs) had ST transmission properties indistinguishable from ADN+. Capsaicin (CAP; 100 nM) blocked ST transmission in some neurons. CAP-sensitive ST-EPSCs were smaller and failed over five times more frequently than CAP-resistant responses, whether ADN+ or from unlabeled animals. Variance-mean analysis of ST-EPSCs suggested uniformly high probabilities for quantal glutamate release across second-order neurons. While amplitude differences may reflect different numbers of contacts, higher frequency-dependent failure rates in CAP-sensitive ST-EPSCs may arise from subtype-specific differences in afferent axon properties. Thus afferent transmission within medial NTS differed by axon class (e.g., CAP sensitive) but was indistinguishable by source of axon (e.g., baroreceptor vs. nonbaroreceptor).
Laminar shear stress inhibits lipid peroxidation induced by high glucose plus arachidonic acid in endothelial cells
Authors: Mun Gyeong In , An Sang Mi , Park Heonyong , Jo Hanjoong , Boo Yong Chool
Published: September 2008

Elevated blood glucose and free fatty acids induce oxidative stress associated with the incidence of cardiovascular disease. In contrast, laminar shear stress (LSS) plays a critical role in maintaining vascular health. The present study examined the mechanism for the antioxidant effect of LSS attenuating the oxidative stress induced by high glucose (HG) and arachidonic acid (AA) in human umbilical vein endothelial cells. HG and AA synergistically decreased cell viability and increased glutathione (GSH) oxidation and lipid peroxidation. The lipid peroxidation was markedly prevented by LSS as well as tetrahydrobiopterin (BH4) and GSH. LSS increased BH4 and GSH contents, and expression of GTP cyclohydrolase-1 and glutamylcysteine ligase (GCL) involved in their biosynthesis. Inhibition of GCL activity by DL-buthionine-(S,R)-sulfoximine and small-interfering RNA-mediated knockdown of GCL lessened the antioxidant effect of LSS. Therefore, it is suggested that LSS enhances antioxidant capacity of endothelial cells and thereby attenuates the oxidative stress caused by cardiovascular risk factors.
Role of EDHF in type 2 diabetes-induced endothelial dysfunction
Authors: Park Yoonjung , Capobianco Stefano , Gao Xue , Falck John R. , Dellsperger Kevin C. , Zhang Cuihua
Published: September 2008

Endothelium-derived hyperpolarizing factor (EDHF) plays a crucial role in modulating vasomotor tone, especially in microvessels when nitric oxide-dependent control is compromised such as in diabetes. Epoxyeicosatrienoic acids (EETs), potassium ions (K+), and hydrogen peroxide (H2O2) are proposed as EDHFs. However, the identity (or identities) of EDHF-dependent endothelial dilators has not been clearly elucidated in diabetes. We assessed the mechanisms of EDHF-induced vasodilation in wild-type (WT, normal), db/db (advanced type 2 diabetic) mice, and db/db mice null for TNF (dbTNF−/dbTNF−). In db/db mice, EDHF-induced vasodilation [ACh-induced vasodilation in the presence of NG-nitro-l-arginine methyl ester (l-NAME, 10 μmol/l) and prostaglandin synthase inhibitor indomethacin (Indo, 10 μmol/l)] was diminished after the administration of catalase (an enzyme that selectively dismutates H2O2to water and oxygen, 1,000 U/ml); administration of the combination of charybdotoxin (a nonselective blocker of intermediate-conductance Ca2+-activated K+channels, 10 μmol/l) and apamin (a selective blocker of small-conductance Ca2+-activated K+channels, 50 μmol/l) also attenuated EDHF-induced vasodilation, but the inhibition of EETs synthesis [14,15-epoxyeicosa-5(Z)-enoic acid; 10 μmol/l] did not alter EDHF-induced vasodilation. In WT controls, EDHF-dependent vasodilation was significantly diminished after an inhibition of K+channel, EETs synthesis, or H2O2production. Our molecular results indicate that mRNA and protein expression of interleukin-6 (IL-6) were greater in db/db versus WT and dbTNF−/dbTNF−mice, but neutralizing antibody to IL-6 (anti-IL-6; 0.28 mg·ml−1·kg−1ip for 3 days) attenuated IL-6 expression in db/db mice. The incubation of the microvessels with IL-6 (5 ng/ml) induced endothelial dysfunction in the presence of l-NAME and Indo in WT mice, but anti-IL-6 restored ACh-induced vasodilation in the presence of l-NAME and Indo in db/db mice. In dbTNF−/dbTNF−mice, EDHF-induced vasodilation was greater and comparable with controls, but IL-6 decreased EDHF-mediated vasodilation. Our results indicate that EDHF compensates for diminished NO-dependent dilation in IL-6-induced endothelial dysfunction by the activation of H2O2or a K+channel in type 2 diabetes.
Increased diastolic time fraction as beneficial adjunct of α1-adrenergic receptor blockade after percutaneous coronary intervention
Authors: Kolyva Christina , Verhoeff Bart-Jan , Spaan Jos A. E. , Piek Jan J. , Siebes Maria
Published: September 2008

The effect of α1-receptor blockade with urapidil on coronary blood flow and left ventricular function has been attributed to relief of diffuse coronary vasoconstriction following percutaneous coronary intervention (PCI). We hypothesized that an increase in diastolic time fraction (DTF) contributes to the beneficial action of urapidil. In eleven patients with a 63% (SD 13) diameter stenosis, ECG, aortic pressure (Pa) and distal intracoronary pressure (Pd), and blood flow velocity were recorded at baseline and throughout adenosine-induced hyperemia. Measurements were obtained before and after PCI and after subsequent α1-receptor blockade with urapidil (10 mg ic). DTF was determined from the ECG and the Pa waveform. Functional parameters such as coronary flow velocity reserve, fractional flow reserve, and an index of hyperemic microvascular resistance (HMR) were assessed. Urapidil administration after PCI induced an upward shift in the DTF-heart rate relationship, resulting in a 3.1% (SD 2.7) increase in hyperemic DTF at a constant heart rate ( P < 0.005) due to a shorter duration of systole. Hyperemic Pa and Pd decreased, respectively, by 6.1% (SD 6.6; P < 0.05) and 5.7% (SD 5.8; P < 0.01) after α1-blockade. Although epicardially measured functional parameters were on average not altered by α1-blockade due to concurrent changes in pressure and heart rate, HMR decreased by urapidil in those patients where coronary pressure remained constant. In conclusion, α1-receptor blockade after PCI produced a modest but significant prolongation of DTF at a given heart rate, thereby providing an adjunctive beneficial mechanism for improving subendocardial perfusion, which critically depends on DTF.
Tryptase activates calcium-independent phospholipase A2and releases PGE2in airway epithelial cells
Authors: Rastogi Prerna , Young Dawn M. , McHowat Jane
Published: September 2008

Human small airway epithelial cells (HSAEC) form the boundary between the external environmental allergens and the internal lung milieu. Mast cells are present in human lung tissue interspersed within the pulmonary epithelium and can secrete a host of pre- and newly formed mediators from their granules, which may propagate small airway inflammation. In this study, tryptase stimulation of HSAEC increased membrane-associated, calcium-independent phospholipase A2γ (iPLA2γ) activity, resulting in increased arachidonic acid and PGE2release. These responses were inhibited by pretreating HSAEC with the iPLA2-selective inhibitor bromoenol lactone. The tryptase-stimulated PGE2production was inhibited by treating HSAEC with the cyclooxygenase (COX)-1-selective inhibitor SC-560 and the nonselective COX inhibitor aspirin but not by the COX-2-selective inhibitor CAY10404 , indicating that the early release of arachidonic acid is metabolized by constitutive COX-1 to form PGE2in tryptase-stimulated HSAEC. Additionally, platelet-activating factor production and neutrophil adherence to tryptase-stimulated HSAEC was also increased. This complex response can set up a cascade of inflammatory mediator production in small airways. We speculate that selective inhibition of iPLA2γ-mediated phospholipid hydrolysis may prove beneficial in inflammatory airway diseases.