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At least 163 records · Page 9Linked to original sources
PubMed1997

Simulation of large-scale tropical tuna movements in relation with daily remote sensing data: the artificial life approach.

Tunas are known to be able to travel long distances. The aim of this paper is to propose new ethological models which reproduce some tuna movements using the dynamics of their environment. We use sea surface temperature animations (from remote sensing data) to model the South West Indian Ocean, and French purse seiners data are used to estimate movements of fish. The objective of the models will be to find a northern movement from the Mozambique Channel to the Seychelles Islands at the appropriate time (May-July). The initial model uses our ecological knowledge of tunas, i.e. the search behavior for high concentrations of food commonly associated with thermal fronts. In some cases, this simple model creates some northern movements from the Mozambique Channel, but it cannot be used to reproduce large-scale movements between the Mozambique Channel and the Seychelles Islands. The next generation model is created where tuna behaviors are modeled by an artificial neural network, using a genetic algorithm to adjust the connection weights. The tuna school-network receives daily information from its local environment and chooses the best actions in order to be able to pass from the Mozambique Channel to the Seychelles Islands at the appropriate time. One neural network emerges and represents an adaptive behavior able to interpret daily sea surface temperatures to mimic large-scale tuna movements. This artificial behavior can be generalized to each possible departure position from the Mozambique Channel. This modelling represents a new tool to study large-scale movements of pelagic fish, and is a first step towards real-time management of fisheries.

Algorithms↗
PubMed1996

Erythropoiesis and vasculogenesis in embryoid bodies lacking visceral yolk sac endoderm.

During mouse embryogenesis the first hematopoietic and endothelial cells form in blood islands located between layers of visceral endoderm and mesoderm in the yolk sac. The role of visceral endoderm in primitive hematopoiesis and vasculogenesis is not well understood. We have assessed the consequences of a lack of visceral endoderm on blood cell and vessel formation using embryoid bodies derived from mouse embryonic stem (ES) cells deficient in GATA-4, a transcription factor expressed in yolk sac endoderm. When differentiated in vitro, these mutant embryoid bodies do not develop an external visceral endoderm layer. We found that Gata4-/- embryoid bodies, grown either in suspension culture or attached to a substratum, are defective in primitive hematopoiesis and vasculogenesis as evidenced by a lack of recognizable blood islands and vascular channels and a reduction in the expression of the primitive erythrocyte marker epsilon y-globin. Expression of the endothelial cell transcripts FIk-1, FIt-1, and platelet-endothelial cell adhesion molecule (PECAM) was not affected in the mutant embryoid bodies. Gata4-/- ES cells retained the capacity to differentiate into primitive erythroblasts and endothelial cells when cultured in methylcellulose or matrigel. Analysis of chimeric mice, generated by injecting Gata4-/- ES cells into 8-cell stage embryos of ROSA26 transgenic animals, showed that Gata4-/- ES cells can form blood islands and vessels when juxtaposed to visceral endoderm in vivo. We conclude that the visceral endoderm is not essential for the differentiation of primitive erythrocytes or endothelial cells, but this cell layer plays an important role in the formation and organization of yolk sac blood islands and vessels.

Animals↗
PubMed2006

Bioaccumulation of trace elements in pelagic fish from the Western Indian Ocean.

Trace elements were analyzed in fish of commercial interest to determine their importance in marine systems of the Western Indian Ocean and their bioaccumulation patterns. The results are equivalent or lower than levels reported in ichthyofauna worldwide. Certain values of muscular Cd, Hg, Pb and Zn were, however, above thresholds for human consumption. Levels varied among tissues, species and fish length, but were seldom influenced by the nutritional condition of the fish, its gender and its reproductive status. Correlations between hepatic Hg and Se levels in Swordfish (r2=0.747) and Yellowfin Tunas (r2=0.226), and among metallothionein linking metals imply the existence of detoxification processes in these species. Level differences between fish from the Mozambique Channel and Reunion Island reflect differences of diets rather than differences of elemental availability in both environments.

Animals↗
PubMed2005

Compressive stress in polycrystalline volmer-weber films.

The Volmer-Weber mode for growing polycrystalline films, which comprises island, network, and channel stages before the films become continuous, is well known for its complex stress behavior with compressive and tensile stress alternating in the initial three growth stages. Recently, two new mechanisms for the compressive stress have been proposed [Phys. Rev. Lett. 88, 156103 (2002); 89, 126103 (2002)], which account for the reversibility of stress generation and relaxation. We show that the two mechanisms play only minor roles for the development of compressive stress, which is confirmed to be due to capillarity effects in the precoalescence stage.

Journal Article↗
PubMed2001

First published record of the pathogenic monogenean parasite Neobenedenia melleni (Capsalidae) from Australia.

The monogenean Neobenedenia melleni (MacCallum, 1927) Yamaguti 1963 is a well-known and virulent pathogen in culture conditions recorded from the skin of many teleost fish species worldwide. Until now, N. melleni has not been reported from wild or cultured fish in Australian waters. This study documents a recent outbreak of N. melleni that occurred on Lates calcarifer (barramundi) cultivated in sea cages in Hinchinbrook Channel between Hinchinbrook Island and mainland Queensland, Australia, which resulted in the loss of 200,000 fish (50 tonnes). The origin of this outbreak is unclear because N. melleni has not been recorded from any wild host species in Australia and strict quarantine regulations exclude the possibility of its introduction on imported fish. We propose that N. melleni occurs naturally on wild populations of some teleost species in Australian waters and that the few surveys of wild fish conducted along the east coast have failed to report this species. The possibility that uncharacteristically low water temperatures led to the outbreak is discussed.

Animals↗
PubMed2000

Floodplain Formation and Cottonwood Colonization Patterns on the Willamette River, Oregon, USA.

/ Using a series of aerial photographs taken between 1936 and 1996, we trace coevolution of floodplain and riparian forest on the Willamette River. Within-channel barforms appear to be the predominant incipient floodplain landform and habitat for primary succession. Interlinked development of bar(s) and erosion of near banks, filling of channels, and establishment and growth of cottonwoods and willows results in coalescence with older floodplain. Sizeand internal structure of riparian forest patches reflect evolution of underlying barforms or channel beds. Floodplain matures as the active channel migrates away by repetition of the bar formation and near-bank erosion process, or is progressively abandoned by infilling and/or constriction with a bar. Other parts of the floodplain are recycled as eroding banks provide the coarse sediment and large woody debris for building new bars. A multichannel planform is maintained as building bars split flow; channels lengthen as bars and islands join into larger assemblages. Avulsion appears to cut new channels only short distances. Given the central role of bars and islands in building new floodplain habitat, we identify their area as a geomorphic indicator of river-floodplain integrity. We measure an 80% decline in bar and island area between 1910 and 1988 within a 22-km section. Dams, riprap, logging, and gravel mining may all be contributing to diminished bar formation rates. Removing obstacles to natural riparian forest creation mechanisms is necessary to regenerate the river-floodplain system and realize its productive potential.

Journal Article↗
PubMed1999

Inactivation of CACNA1G, a T-type calcium channel gene, by aberrant methylation of its 5' CpG island in human tumors.

Using a newly developed PCR-based technique called methylated CpG island amplification, we have identified several DNA fragments that are aberrantly methylated in a colon cancer cell line. One of the fragments, termed MINT31, mapped to human chromosome 17q21, where frequent loss of heterozygosity is detected in various human tumors. By characterizing the genomic sequence around this area, we identified a gene encoding a T-type calcium channel, CACNA1G, as a target for hypermethylation in human tumors. By reverse transcriptase-PCR we detected expression of CACNA1G in normal colon and bone marrow, but expression was absent in the five tumor cell lines in which methylation was found. After treatment with the methylation inhibitor 5-deoxyazacytidine, the expression of CACNA1G was restored in all five cell lines. Detailed methylation mapping of the 5' CpG island by bisulfite-PCR revealed that methylation of a region 300-800 bp upstream of the translation initiation site closely correlated with the inactivation of CACNA1G. This region contained the transcription start site, as determined by 5' rapid amplification of cDNA ends analysis. Aberrant methylation of CACNA1G was also examined in various human primary tumors and was detected in 17 of 49 (35%) colorectal cancers, 4 of 16 (25%) gastric cancers, and 3 of 23 (13%) acute myelogenous leukemia cases. Inactivation of CACNA1G may play a role in cancer development by modulating calcium signaling, which potentially affects cell proliferation and apoptosis.

Bone Marrow Cells↗
PubMed1990

The venous territories (venosomes) of the human body: experimental study and clinical implications.

The venous architecture of the integument and the underlying deep tissues was studied in six total-body human fresh cadavers and a series of isolated regional studies of the limbs and torso. A radiopaque lead oxide mixture was injected, and the integument and deep tissues were dissected and radiographed. The sites of the venous perforators were plotted and traced to their underlying parent veins that accompany the source (segmental) arteries. A series of cross-sectional studies were made in one subject to illustrate the course of the perforators between the integument and the deep tissues. The veins were dissected under magnification to identify the site and orientation of the valves. Results revealed a large number of valveless (oscillating) veins within the integument and deep tissues that link adjacent valved venous territories and allow equilibration of flow and pressure throughout the tissue. Where choke arteries define the arterial territories, they are matched by boundaries of oscillating veins in the venous studies. The venous architecture is a continuous network of arcades that follow the connective-tissue framework of the body. The veins converge from mobile to fixed areas, and they "hitchhike" with nerves. The venous drainage mirrors the arterial supply in the deep tissues and in most areas of the integument in the head, neck, and torso. In the limbs, the stellate pattern of the venous perforators is modified by longitudinal channels in the subdermal network. However, when an island flap is raised, these longitudinal channels are disconnected, and once again the arterial and venous patterns match. Our venous studies add strength to the angiosome concept. Where source arteries supply a composite block of tissue, we have demonstrated radiologically and by microdissection that the branches of these arteries are accompanied by veins that drain in the opposite direction and return to the same locus. Hence each angiosome consists of matching arteriosomes and venosomes. The clinical implications of these results are discussed with particular reference to the design of flaps, the delay phenomenon, venous free flaps, the pathogenesis of flap necrosis, the "muscle pump," varicose veins, and venous ulceration.

Aged↗
PubMed2001

Dynamical mechanisms of dc current generation in driven Hamiltonian systems.

Recent symmetry considerations [Flach et al., Phys. Rev. Lett. 84, 2358 (2000)] have shown that dc currents may be generated in the stochastic layer of a system describing the motion of a particle in a one-dimensional potential in the presence of an ac time-periodic drive. In this paper we explain the dynamical origin of this current. We show that the dc current is induced by the presence and desymmetrization of ballistic channels inside the stochastic layer. The existence of these channels is due to resonance islands with nonzero winding numbers. The characterization of the flight dynamics inside ballistic channels is described by distribution functions. We obtain these distribution functions numerically and find very good agreement with simulation data.

Journal Article↗
PubMed1994

[Results of one-stage hypospadias repair].

We reviewed 17 patients who had first undergone one-stage hypospadias repair. According to the criteria proposed by Keating and Duckett, the operative procedure performed was the MAGPI procedure in 2 patients, the pyramid procedure in 2, the Mathieu procedure in 1, the onlay island flap procedure in 6, the transverse preputial island flap and glans channel procedure (Duckett) in 4 and a combined method using the buccal and bladder mucosa graft in 2. The age of the patients ranged from 11 months to 22 years (median age 3.2 years). Postoperative follow-up ranged from 3 to 30 months (mean 7 months). Postoperative complications requiring revision occurred in 4 patients; urethrocutaneous fistula developed in 1 patient with the onlay island flap, urethral sticuture at the anastomosis and meatus in 1 patient with the transverse preputial island flap, meatal retraction in 1 patient with the mucosal graft, and urethral stricture at the distal anastomosis and bladder stone in the other patient with the mucosal graft. These complications were successfully revised by simple operations. Ventral skin tethering caused by scar contracture developed in 2 patients with the preputial island flap, and spontaneously improved with time in 1 patient. These results indicate that the criteria proposed by Keating and Duckett is proper to select an operative procedure for hypospadias.

Adolescent↗
PubMed2006

Processesof Tamarix invasion and floodplain development along the lower Green River, Utah.

Significant ecological, hydrologic, and geomorphic changes have occurred during the 20th century along many large floodplain rivers in the American Southwest. Native Populus forests have declined, while the exotic Eurasian shrub, Tamarix, has proliferated and now dominates most floodplain ecosystems. Photographs from late 19th and early 20th centuries illustrate wide river channels with largely bare in-channel landforms and shrubby higher channel margin floodplains. However, by the mid-20th century, floodplains supporting dense Tamarix stands had expanded, and river channels had narrowed. Along the lower Green River in eastern Utah, the causal mechanism of channel and floodplain changes remains ambiguous due to the confounding effects of climatically driven reductions in flood magnitude, river regulation by Flaming Gorge Dam, and Tamarix invasion. This study addressed whether Tamarix establishment and spread followed climate- or dam-induced reductions in annual peak flows or whether Tamarix was potentially a driver of floodplain changes. We aged 235 Tamarix and 57 Populus individuals, determined the hydrologic and geomorphic processes that controlled recruitment, identified the spatial relationships of germination sites within floodplain stratigraphic transects, and mapped woody riparian vegetation cohorts along three segments of the lower Green River. The oldest Tamarix established along several sampling reaches in 1938, and 1.50-2.25 m of alluvium has accreted above their germination surfaces. Nearly 90% of the Tamarix and Populus samples established during flood years that exceeded the 2.5-year recurrence interval. Recruitment was most common when large floods were followed by years with smaller peak flows. The majority of Tamarix establishment and Green River channel narrowing occurred long before river regulation by Flaming Gorge Dam. Tamarix initially colonized bare instream sand deposits (e.g., islands and bars), and most channel and floodplain changes followed the establishment of Tamarix. Our results suggest that Tamarix recruitment was triggered by large annual floods that were followed by years with lower peak flows, not by periods of low flow alone. Tamarix appears to have actively invaded floodplains, while Populus colonization has been limited. Thus, Tamarix invasion may have greatly influenced floodplain development and riparian vegetation composition along the lower Green River since the early 20th century.

Disasters↗
PubMed1977

Cutaneous leishmaniasis in the Libyan Arab Republic: preliminary ecological findings.

Preliminary results show cutaneous leishmaniasis in Libya to be, sometimes at least, a rural zoonotic infection. The parasites are transmitted, probably by Phlebotomus papatasi, between the rodents Psammomys obesus and Meriones libycus. The banks and 'islands' in the main channel of seasonal wadis provide the right combination of vegetation and permanence for the maintenance of an intense focus.

Animals↗
PubMed1992

Embryonic stem cell-derived cystic embryoid bodies form vascular channels: an in vitro model of blood vessel development.

Murine embryonic stem cells can differentiate in vitro to form cystic embryoid bodies (CEB) that contain different structures and cell types. The blood islands are one such structure that consist of immature hematopoietic cells surrounded by endothelial cells, the first identifiable vascular cells. CEBs differentiated in vitro developed blood islands initially, and subsequently these blood islands matured to form vascular channels containing hematopoietic cells. Phase contrast microscopy demonstrated the presence of channels in mature CEBs grown in suspension culture, and high resolution light and electron microscopy showed that the cells lining these channels were endothelial cells. The channels appeared less organized than the vasculature of the mature yolk sac. The hematopoietic cells were occasionally seen 'flowing' through the CEB channels, although their numbers were reduced relative to the yolk sac. Analysis of primary CEB cultures showed the presence of cells with two characteristics of endothelial cells: approximately 30% of the cells labelled with fluorescent acetylated low density lipoprotein and a small number of cells were positive for von Willebrand's factor by immunostaining. Thus we conclude that a primitive vasculature forms in CEBs differentiated in vitro, and that not only primary differentiation of endothelial cells but also some aspects of vascular maturation are intrinsic to this cell culture system. CEBs are therefore a useful model for the study of developmental blood vessel formation.

Animals↗
PubMed2001

Persistent organochlorine pollutants in eggs of colonial waterbirds from Galveston Bay and East Texas, USA.

Eggs of neotropic cormorants (Phalacrocorax brasilianus), black-crowned night herons (Nycticorax nycticorax), and great egrets (Ardea alba) nesting on several locations in Galveston Bay (TX, USA) and at two control sites outside the bay were collected during April-May 1996 and analyzed for chlorinated pesticides, PCBs, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans. Additionally, concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQs) were determined by use of relative potency factors (TEQs) or the H4IIE-luc bioassay TCDD-EQs. Concentrations of 1,1,-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) were greater in eggs of neotropic cormorants from Alexander Island (mean = 1,040 ng/g wet wt) in the Houston Ship Channel (Houston, TX, USA) and in those from Telfair Island (mean = 1,460 ng/g wet wt), a reference location outside the bay, than in most locations inside the bay (mean range = 119-453 ng/g wet wt). Mean PCB concentrations were greater in eggs of neotropic cormorants from Alexander Island (mean = 5,720 ng/g wet wt) than in eggs of cormorants from areas farther away from the ship channel, including two reference sites outside the bay (mean range = 404-3,140 ng/g wet wt). The TCDD was the main dioxin congener detected in eggs from all locations within Galveston Bay. Instrumental TEQs in eggs ranged from 67 pg/g wet weight at control sites to 452 pg/g wet weight at Alexander Island. Concentrations of TCDD-EQs determined in the H4IIE assay were correlated with instrumental TEQs and were greater in eggs of cormorants from islands within the bay, although these were farther away from the ship channel. Overall, concentrations of DDE, PCBs, TCDD, and TCDD-EQs were less than the threshold levels known to affect reproduction. However, some eggs contained concentrations of total PCBs or DDE greater than what would elicit adverse effects on birds. No identifiable deformities or abnormalities were detected in embryos collected from all sites.

Animals↗
PubMed1999

Topical and systemic calcium channel blockers in the prevention and treatment of microvascular spasm in a rat epigastric island skin flap model.

Vasospasm is a frustrating problem commonly encountered in microvascular surgery. Extreme arterial vasoconstriction usually occurs intraoperatively, shortly after release of the vascular clamps, but can be a problem for 48 to 72 hours postoperatively. Failure to alleviate vasospasm can have disastrous consequences in replanted and revascularized tissues, ultimately resulting in microsurgical failure. The authors investigated the efficacy of topical and systemic administration of two commonly prescribed calcium channel blockers-nifedipine and verapamil-in both the prevention and treatment of vasospasm in a rat epigastric island skin flap model. Superficial epigastric island skin flaps were elevated in 60 Sprague-Dawley rats. Femoral vessels were isolated from the inguinal ligament to a point 1 cm distal to the origin of the epigastric vessels, and the feeding vessels were ligated. The flap was returned to its natural anatomic bed and was sutured into place, leaving the femoral vessels exposed. The femoral artery and vein were transected, and anastomoses were performed under the operating microscope. A block of ice was then applied directly to the anastomotic site for 1 minute to induce additional vasospasm. Groups I through III received topical application of solutions of 0.5 ml of either 0.9% normal saline (control), verapamil (2.5 mg per milliliter), or nifedipine (5 mg per milliliter) directly to the anastomotic site immediately prior to release of the vascular clamps. Groups IV through VI received intraperitoneal injections of 1.0-ml solutions of either 0.9% normal saline (control), verapamil (2.5 mg per milliliter), or nifedipine (5 mg per milliliter) at 30 minutes prior to performing the anastomoses. Thermocouple temperature probes reflecting blood flow were placed at the center of the skin flap in a subcutaneous position, at the proximal femoral artery, and at the takeoff of the epigastric artery. Accurate, direct temperature measurements of the isolated skin flap and femoral vessels were recorded at 10, 20, and 30 minutes after release of the vascular clamps. Topical and systemic administration of verapamil and nifedipine moderated significantly the temperature declines observed at 10 minutes at the level of the femoral artery proximally and distally compared with controls. Following this decline, groups I through III (topical) demonstrated significant recovery of temperature toward baseline, with verapamil and nifedipine showing significantly better recovery of temperature than controls. Groups IV through VI (systemic) demonstrated a stabilization of temperature without any significant additional recovery of temperature toward baseline. Verapamil was more effective than nifedipine in its actions when administered topically or systemically. The authors' results suggest a potential role for topical and systemic administration of verapamil and nifedipine in preventing, or at least minimizing, the deleterious effects of vasospasm on flap survival, as demonstrated by its temporizing effect on temperature change across the anastomosis in their model.

Animals↗
PubMed2002

Beauty and the beast: results of the Rhode Island smokefree shop initiative.

Licensed hairdressing facilities are prevalent in communities nationwide and represent a unique and promising channel for delivering public health interventions. The Rhode Island Smokefree Shop Initiative tested the feasibility of using these facilities to deliver smoking policy interventions statewide. A statewide survey of hairdressing facilities was followed by interventions targeted to the readiness level (high/low) of respondents to adopt smoke-free policies.

Barbering↗