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At least 181 records · Page 10Linked to original sources
PubMed2006

Anti-ischemic effects of nimesulide, a cyclooxygenase-2 inhibitor on the ischemic model of rabbit induced by isoproterenol.

The objective was to devise an animal model of myocardial infarction (MI) against which cardioprotective drugs might be tested. We describe the effects of nimesulide, a COX experience with development and validation of such a model. The rabbit was chosen in preference to rodents because its heart and cardiac circulation more closely resemble those of human. Thus, the cardiovascular system of anaesthetized male rabbits, 1 to 1.5 kg (n=11), was stressed by a single bolus intravenous injection of isoprenaline (ISP), 65 mg/kg. The effects of the injection were followed for sixteen days and were evaluated in four ways: 1) measurements of creatinine kinase isozyme and troponin-I (TPI) in serum 2) Electrocardiographic (ECG) changes (ST elevation and Q wave development) 3) Cardiac histopathology observed in tissue sections of the isolated of the heart. The histopathological analysis showed that rabbit heart on 2nd day after ISP injection showed changes of coagulation necrosis. Day 4 total coagulation with the loss of nuclear and striation associated with heavy interstitial infiltrate of neutrophils was found. Day 8 after infarction showed collagen deposition with capillary channels in between the remaining islands of myocytes in the infarcted area. On the 16th day scarring was complete. Coronary perfusion rates (CPR) and heart rate (HR) of the infarcted and nimesulide (a COX-2 inhibitor) treated rabbits displayed significant improvement (n=11) on each corresponding day after infarction as compared to the infarcted and saline treated rabbits (P<0.05). All four indices revealed similarities with effects commonly associated with MI in humans.

Adrenergic beta-Agonists↗
PubMed2002

Fluorescence evidence that a phase transition causes the induction time in the reduction in dynamic tension during surfactant adsorption to a clean air/water interface and a kinetic-diffusive transport model for the phase-induced induction.

An aqueous soluble surfactant adsorbing from solution onto an initially clean air/water interface often exhibits an induction period in the surface tension relaxation in which, as the adsorption begins, the tension remains near the clean interface value for an extended period of time before decreasing rapidly to the equilibrium value. In this study, using a model nonionic soluble surfactant, C14E6(CH3(CH2)13-(OCH2CH2)6-OH), we present direct fluorescence evidence that this induction is due to a first-order phase transition from a gaseous (G) to a liquid expanded (LE) phase that the assembling monolayer undergoes at constant surface pressure. An open channel flow cell is initially filled with water, and onto its air/water interface is spread an insoluble amphiphilic dye that fluoresces upon irradiation in the LE phase and whose fluorescence is quenched in the G phase. An aqueous solution of C14E(6) is then allowed to flow through the channel. We observe the immediate appearance of bright islands of the LE phase growing in a dark (G) background, confirming the presence of the G/LE phase transition. These islands eventually occupy the entire surface, after which the interface remains uniformly bright. We correlate this phase transition to the induction period by simultaneously measuring the tension of the interface of the open channel, and verifying that as the islands grow the tension remains at the clean value until the bright LE phase occupies the entire surface, whereupon the tension rapidly decreases. We further develop a phase transition surfactant transport model for the induction period in which surfactant diffuses toward and kinetically adsorbs onto the surface, and then rapidly equilibrates between the G and LE phases. For our model surfactant C14E6, we independently measure the surface concentration of the nucleating LE phase, the LE phase surfactant equation of state, the kinetic rate constants for adsorption into the LE phase, and the bulk diffusion coefficient. Using these measurements, we predict induction times for adsorption onto a clean surface without convection. We also measure these induction times in tension relaxation for adsorption onto a pendant bubble using axisymmetric shape analysis, and demonstrate agreement with the simulations with no adjustable constants.

Journal Article↗
PubMed1994

Induction of vasculogenesis in quail blastodisc-derived embryoid bodies.

We have previously developed an in vitro culture system in which dissociated cells from unincubated quail blastodiscs formed in vivo-like blood islands consisting of blood and endothelial cells in response to fibroblast growth factors (FGFs). Here we demonstrate that the same quail blastodisc cells grown in suspension culture in the presence of basic FGF (bFGF) reaggregated and formed three-dimensional spherules (embryoid bodies, EBs) which underwent vasculogenesis and hematopoiesis within 3 days. In contrast to murine embryoid bodies, which undergo vasculogenesis spontaneously, the formation of vascular structures in quail blastodisc cultures was absolutely dependent on bFGF. While about 75% contained blood islands and about 50% formed capillaries in the presence of bFGF, only 0.2% of the embryoid bodies formed blood islands in control cultures without bFGF. Vascular channels were gradually encoated by primitive smooth muscle cells within 5 days. Ultrastructural examinations revealed capillary blood vessels and blood islands indistinguishable from their yolk sac counterparts. Mesodermal tissue was present in cultures both with and without bFGF, but consisted of an avascular undifferentiated mesenchyme in control cultures. Since the entire sequence of vasculogenesis from the formation of endothelial cells to their assembly into a vascular plexus is observed in response to the inducer bFGF, this culture system is a suitable model for studying the molecular events that initiate the emergence of endothelial cells and the formation of a vascular plexus during vasculogenesis.

Animals↗
PubMed1987

Intracisternal granules in the somatotrophs in the anterior pituitary of the mouse.

A detailed study of the anterior pituitaries of pregnant and lactating mice revealed changes occurring in the ultrastructure of the somatotrophs. The rough endoplasmic reticulum cisternae become greatly dilated forming channels that are continuous with the perivascular space. This occurrence expands the membrane surface available for the release of hormone. Individual granules and cytoplasmic islands containing numerous granules appear in these channels. This suggests an alternative mechanism for granule release which would facilitate a rapid response to increased hormone requirement.

Animals↗
PubMed1991

CpG island in the region of an autosomal dominant polycystic kidney disease locus defines the 5' end of a gene encoding a putative proton channel.

In an attempt to isolate candidate genes for autosomal dominant polycystic kidney disease, a number of CpG-rich islands have been identified from a region defined genetically as the site of disease mutations. Genomic fragments adjacent to one of these islands were used to isolate cDNAs from both HeLa cells and cultured cystic epithelium that encode a 155-amino acid peptide having four putative transmembrane domains. The corresponding transcript was found in all tissues tested but was most abundant in brain and kidney. Potential control response elements were identified in the genomic region 5' to the initiation codon. The deduced amino acid sequence has 93% similarity to the 16-kDa proteolipid component that is believed to be part of the proton channel of the vacuolar H(+)-ATPase. Possible roles for a mutated proton channel in the pathogenesis of cystic disease were considered. However, sequencing of cDNAs corresponding to both alleles of an affected individual revealed no differences in the deduced amino acid sequence. Moreover, transcript size and abundance were not altered in cystic kidney.

Amino Acid Sequence↗
PubMed1998

Cephalopods as a vector for the transfer of cadmium to top marine predators in the north-east Atlantic Ocean.

Three hundred and fifty individuals of 12 species of cephalopods which differed in their feeding habitats were sampled from the French Atlantic coast to the sub-Arctic region (Bay of Biscay, English Channel, west Irish coast and Faroe Islands) and analysed for their cadmium contents. Comparison of the Cd levels of the cephalopods showed that those from the sub-Arctic area contained very high Cd concentrations compared to those from lower latitudes such as along the French Atlantic coast. High Cd levels in cephalopods from the sub-Arctic zone correspond closely to the reported high Cd concentrations in the tissues of top vertebrate predators from the same area. Comparison of the weekly Cd intakes for the Faroe Island pilot whales with the 'Provisional Tolerable Weekly Intake' for humans recommended by the World Health Organisation, showed that top vertebrate predators are often subjected to Cd doses far in excess of those recommended for humans. Our limited survey results suggest that cephalopods constitute an important source of Cd for cephalopod predators, and that this bioaccumulation effect is most evident at high latitudes.

Animals↗
PubMedDate not supplied

[The use of the capture- recapture method in evaluating the epidemiological meningococcal disease monitoring system in Tenerife, Spain (1999-2000)].

BACKGROUND: Meningococcal Disease is mainly monitored passively on the Canary Islands, the regular Compulsory Disease Notification channels being used. The objective of this study includes describing the qualitative and quantitative aspects of this system and evaluating the exhaustiveness, by means of the capture-recapture system, of three information sources. METHODS: This study covers the 1999-2001 period in Tenerife. The information was gathered from three sources: the Compulsory Disease Notification System, the Microbiology Laboratories and the hospital Minimum Basic Data Set. The Evaluation Protocols of the Monitoring System of the Atlanta Centers of Disease Control and Prevention were used. A log-linear model was used for estimating the number of cases. The calculations of the exhaustiveness and the 95% confidence intervals were done in the SPSS10 statistics package. RESULTS: The system was found to have an 84.9% sensitivity, and an 80.4% positive predictive value. The delay in notification (timeliness) fell within the 0.5-13-day range, averaging 3 days. The system was found to have a 76.6% overall acceptability. The exhaustiveness value was 98.1%. CONCLUSIONS: This disease is being monitored well, with a degree of sensitivity which would be revealing of a good notification level, also confirmed by its exhaustiveness. Although the positive predictive value is high, this could be indicative of the expeditious starting of antibiotic treatment which would hinder microbiological confirmation. The system is timely, affording the possibility of measures being taken for fast intervention.

Adolescent↗
PubMed2005

Coral reefs of the Mascarenes, Western Indian Ocean.

The reefs of the Mascarenes differ in structure and stage of development. Mauritius is the oldest island, bound by a discontinuous fringing reef and small barrier reef, with large lagoon patch reefs. Rodrigues has nearly continuous fringing reefs bounding an extensive lagoon with deep channels and few patch reefs. Reunion, the youngest island, has short stretches of narrow fringing reefs along southwestern coasts. The islets of St Brandon are bound to the east by an extensive arc of fringing reef. Reef mapping of the Mascarenes using satellite imagery provides an estimate of 705 km2 of shallow reef habitats. These areas have been modified over geological time by changes in sea level, ocean-atmosphere disturbances and biological and chemical forcing. Further modification has resulted from historical changes in land-use patterns. Recent economic development has placed many of these reefs at risk from anthropogenic impact. The reefs of the Mascarenes have escaped mass mortality from bleaching to date, which increases their conservation significance within the wider Indian Ocean. The reefs are poorly protected. A case study shows how a geographic information system incorporating reef-habitat maps can help formulate and demonstrate Marine Protected Area boundaries.

Animals↗
PubMed2001

Decay characteristics of surface mounds with contrasting interlayer mass transport channels.

The decay characteristics of three-dimensional (3D) islands formed on surfaces are investigated theoretically considering two types of interlayer mass transport mechanisms. If an adatom on a given layer can easily descend from any site along the periphery of the layer, an optimal island slope and a constant terrace width will be selected during the decay. In contrast, if the adatom can descend primarily through selective (such as kinked) sites, the decay will be accompanied by a gradual increase in the island slope. These generic conclusions provide the basis for a microscopic understanding of the decay of nanostructures in fcc(111) and fcc(100) metal homoepitaxy and are applicable to other systems as well.

Journal Article↗
PubMed1989

Verapamil improves survival of rat hyperemic island skin flaps.

Inability to maintain cellular calcium homeostasis is a critical factor in the pathogenesis of cellular ischemic injury and may mediate oxygen radical release in the reperfusion period. We assessed the effect of the selective calcium channel blocker verapamil on the performance of rat hyperemic island skin flaps. Pretreatment with verapamil markedly improved survival of skin flaps after 6 hours of venous cross-clamping compared with animals receiving placebo only (99% vs 53.3%; p less than 0.01). Verapamil also prevented the formation of lipid peroxidation products and the depletion of the endogenous antioxidant glutathione, suggesting that the beneficial effect of verapamil is the result of protection against oxygen radical injury. After 12 hours of venous cross-clamping, verapamil did not improve survival of skin flaps despite protection against lipid peroxidation. Oxygen radical release is therefore a crucial event in the pathogenesis of skin flap necrosis after short-term ischemia but is of less significance in long-term ischemia.

Animals↗
PubMed2003

Cesium-137 concentrations in marine macroalgae from different biotopes in the Aegean Sea (Greece).

The commonest species of red, brown, and green macroalgae were sampled from a range of biotopes in the Aegean Sea during 1998 for their 137Cs content. Significant differences in 137Cs concentrations were found among different species growing under similar environmental conditions, suggesting that uptake does not follow physical levels but is influenced by allometric parameters and physiological mechanisms. 137Cs content in collected seaweeds were in the descending order: Ulva lactuca>Enteromorpha linza>Gracilaria verrucosa>Ceramium rubrum>Cystoseira barbata. A comparison of the stations studied indicated that the degree of accumulation is also dependent on the geomorphology of the specific area. The west side of Thermaikos Gulf, where the rivers Axios, Aliakmon, and Pinios flow, was highly contaminated as was the Strymonicos Gulf where the river Strymon flows. High cesium concentrations were also observed in algae from Lemnos Island near the mouth of the Dardanelles Channel, most likely due to the horizontal circulation of water masses from the Marmaras Sea to the Aegean Sea resulting in the discharge of 137Cs during the purification process in the Black Sea through the Dardanelles Straits. It is concluded that the general dispersion of 137Cs results from the water circulation regime within the Aegean Sea. Higher levels are present in the northern part of the basin due to current circulation originating from the Black Sea and from outflow of rivers. Levels decrease to the south and east, but increase again to the west of Crete where the Black Sea water mass can be periodically traced.

Cesium Radioisotopes↗
PubMed1996

Formation of the coronary vasculature: a brief review.

Myocardial vascularization is initiated after endothelial cell precursors from the region of the liver or septum transversarium migrate to the newly formed epicardium. Blood island-like structures appear and form vascular channels along the epicardium and into the myocardium. Prior to this time myocardial cells receive nutrition directly from the ventricular lumen, a process which is facilitated by the highly trabecular arrangement of the ventricles. A venous system is formed prior to any evidence of arteries or arterioles. The formation of a vascular plexus in the region of the outflow tract is followed by penetration of these microvessels into the wall of the aorta. These ingrowing vessels merge, acquire a muscular coat and form the left and then the right coronary vessels. These events occur during a short period of time, e.g., 2 weeks in humans, 4 days in rats. Maturation of the arterial tree occurs primarily after birth. Our knowledge of the regulation of coronary vascularization during development is very limited. Accordingly, future studies need to focus on the role of growth factors, chemotactic factors, extracellular matrix molecules, and mechanical events.

Animals↗
PubMed2003

Reef development at Inhaca Island, Mozambique: coral communities and impacts of the 1999/2000 Southern African floods.

Inhaca Island, southern Mozambique, is located towards the southerly latitudinal limits of coral reef growth. Reef development is restricted to the margins of channels which dissect intertidal flats on the Maputo Bay side of the island, and to depths of around 6 m. In contrast to lower latitude reefs, reef development is therefore both spatially and bathymetrically restricted (largely due to high turbidity levels). These natural stress levels were exacerbated, via increased freshwater and sediment discharge, during the severe floods of late 1999/early 2000. Flood impacts varied but were most significant on reefs on the inner (western) side of the island where live coral cover (LCC) decreased from 60.5% (1999) to 24.0% (2001). This is attributed to freshwater-induced bleaching. Dead in situ coral cover increased from 18.6% (1999) to 51.3% (2001). Reefs on the southern tip of the island, by contrast, were relatively unaffected. It is suggested that this largely reflects a closer proximity to the open Indian Ocean which mitigated the effects of freshwater dilution.

Animals↗
PubMed2005

Sub-20 nm short channel carbon nanotube transistors.

Carbon nanotube field-effect transistors with sub-20 nm long channels and on/off current ratios of >10(6) are demonstrated. Individual single-walled carbon nanotubes with diameters ranging from 0.7 to 1.1 nm grown from structured catalytic islands using chemical vapor deposition at 700 degrees C form the channels. Electron beam lithography and a combination of HSQ, calix[6]arene, and PMMA e-beam resists were used to structure the short channels and source and drain regions. The nanotube transistors display on-currents in excess of 15 microA for drain-source biases of only 0.4 V.

Journal Article↗
PubMed2004

The formation mechanisms of turbidity maximum in the Pearl River estuary, China.

The formation and dynamics of turbidity maxima (TM) in the Pearl River estuary (PRE) are not well understood but the existence of TM in the estuary have great potential engineering and environmental impacts. Based on the measurements of two large-scale field surveys conducted in the wet season of 1978 (July of 1978) and the dry season of 1979 (March of 1979), the existence and seasonal variations of TM in the PRE focusing on the two major natural navigation channels have been studied. The sediment transport fluxes over two consecutive tidal cycles have been analyzed in detail. The analysis results reveal that the formation mechanisms of TM in the estuary are rather complex. In general, gravitational circulation, tidal trapping, and sediment resuspension and deposition processes are the primary TM formation mechanisms in the PRE. The clockwise back flow pattern around Lingding Island also leads to the formation of TM in the West channel of the PRE. The occurrence of TM far upstream of the salt water wedge is the result of the complex hydrodynamic and sediment transport processes generated by the runoff of the major rivers.

China↗
PubMed2001

Growth and function of the embryonic heart depend upon the cardiac-specific L-type calcium channel alpha1 subunit.

The heart must function from the moment of its embryonic assembly, but the molecular underpinnings of the first heart beat are not known, nor whether function determines form at this early stage. Here, we find by positional cloning that the embryonic lethal island beat (isl) mutation in zebrafish disrupts the alpha1 C L-type calcium channel subunit (C-LTCC). The isl atrium is relatively normal in size, and individual cells contract chaotically, in a pattern resembling atrial fibrillation. The ventricle is completely silent. Unlike another mutation with a silent ventricle, isl fails to acquire the normal number of myocytes. Thus, calcium signaling via C-LTCC can regulate heart growth independently of contraction, and plays distinctive roles in fashioning both form and function of the two developing chambers.

Alleles↗
PubMed2002

Genomic analysis of the aromatic catabolic pathways from Pseudomonas putida KT2440.

Analysis of the catabolic potential of Pseudomonas putida KT2440 against a wide range of natural aromatic compounds and sequence comparisons with the entire genome of this microorganism predicted the existence of at least four main pathways for the catabolism of central aromatic intermediates, that is, the protocatechuate (pca genes) and catechol (cat genes) branches of the beta-ketoadipate pathway, the homogentisate pathway (hmg/fah/mai genes) and the phenylacetate pathway (pha genes). Two additional gene clusters that might be involved in the catabolism of N-heterocyclic aromatic compounds (nic cluster) and in a central meta-cleavage pathway (pcm genes) were also identified. Furthermore, the genes encoding the peripheral pathways for the catabolism of p-hydroxybenzoate (pob), benzoate (ben), quinate (qui), phenylpropenoid compounds (fcs, ech, vdh, cal, van, acd and acs), phenylalanine and tyrosine (phh, hpd) and n-phenylalkanoic acids (fad) were mapped in the chromosome of P. putida KT2440. Although a repetitive extragenic palindromic (REP) element is usually associated with the gene clusters, a supraoperonic clustering of catabolic genes that channel different aromatic compounds into a common central pathway (catabolic island) was not observed in P. putida KT2440. The global view on the mineralization of aromatic compounds by P. putida KT2440 will facilitate the rational manipulation of this strain for improving biodegradation/biotransformation processes, and reveals this bacterium as a useful model system for studying biochemical, genetic, evolutionary and ecological aspects of the catabolism of aromatic compounds.

Adipates↗
PubMed2005

Aharonov-Bohm superperiod in a Laughlin quasiparticle interferometer.

We report an Aharonov-Bohm superperiod of five magnetic flux quanta (5h/e) observed in a Laughlin quasiparticle interferometer, where an edge channel of the 1/3 fractional quantum Hall fluid encircles an island of the 2/5 fluid. This result does not violate the gauge invariance argument of the Byers-Yang theorem because the magnetic flux, in addition to affecting the Aharonov-Bohm phase of the encircling 1/3 quasiparticles, creates the 2/5 quasiparticles in the island. The superperiod is accordingly understood as imposed by the anyonic statistical interaction of Laughlin quasiparticles.

Journal Article↗