Low Flow Areas Research Articles

Tissue engineering of blood vessel

Vascular grafts are in large demand for coronary and peripheral bypass surgeries. Although synthetic grafts have been developed, replacement of vessels with purely synthetic polymeric conduits often leads to the failure of such graft, especially in the grafts less than 6 mm in diameter or in the areas of low blood flow, mainly due to the early formation of thrombosis. Moreover, the commonly used materials lack growth potential, and long-term results have revealed several material-related failures, such as stenosis, thromboembolization, calcium deposition and infection. Tissue engineering has become a promising approach for generating a bio-compatible vessel graft with growth potential. Since the first success of constructing blood vessels with collagen and cultured vascular cells by Weinberg and Bell, there has been considerable progress in the area of vessel engineering. To date, tissue- engineered blood vessels (TEBVs) could be successfully constructed in vitro, and be used to repair the vascular defects in animal models. This review describes the major progress in the field, including the seeding cell sources, the biodegradable scaffolds, the construction technologies, as well as the encouraging achievements in clinical applications. The remaining challenges are also discussed.

Dispersal and colonisation of plants in lowland streams: success rates and bottlenecks

Plant dispersal and colonisation, including rates of dispersal, retention, colonisation and survival of dispersed propagules (shoots and seeds), were studied in a 300-m stream reach in a macrophyte-rich lowland stream during one growing season. Relationships between colonisation processes and simple flow parameters were tested. Each fortnight during a growing season, the number of dispersed plant propagules and the number of new and lost plant colonisations since the last sampling day were recorded. The retention of dispersing shoots was tested on two occasions during the growing season by releasing plant shoots and subsequently re-collecting the retained shoots in the study reach. The main bottleneck for plant colonisation in macrophyte-rich lowland streams is the primary colonisation (development of attached roots in the sediment from vegetative propagules or seedlings) of retained shoots and seeds, due in part to low retention success (1% of the dispersed shoots per 100-m reach) and to unsuccessful colonisation of retained shoots (3.4% of retained shoots colonised). The number of drifting shoots and seeds per day during the growing season were 650–6,950 and 2,970–62,780, respectively, and caused no constraint to colonisation. The survival rate of primary colonists was high with 80% surviving during the first growing season and about 50% surviving the first winter. There was no relationship between number of drifting shoots and flow, but the number of drifting seeds increased with flow. The number of colonisations between two consecutive sampling days correlated to the extent of low flow in the period. The loss rate of colonisations correlated to high flow events, but was low overall. My study strongly indicates that the number of propagules is not a constraint to colonisation in macrophyte-rich lowland streams. Rather, I conclude that primary colonisation is the main constraint to regaining vegetation in lowland streams in general and in vegetation-free rehabilitated streams in particular. Therefore, if plant colonisation is a target for stream rehabilitation, it is important to enhance retention and colonisation of propagules by creating areas of low flow and by providing physical obstacles to work as retention agents in the stream.

ALTERAçõES CAUSADAS POR AVULSÃO NO RIO TAQUARI, NO PANTANAL MATO-GROSSENSE

No leque aluvial do Rio Taquari, no Pantanal Mato-Grossense,registram-se processos de dinâmica fluvial, os quais ocasionamo fenômeno de avulsão, com a mudança de direção doRio Taquari, que altera o mosaico de paisagens e comprometea vida dos moradores residentes em colônias, a navegaçãoe as atividades econômicas. Os dados são provenientes deinformações extraídas de imagens de satélites e de trabalhode campo, e os resultados indicam que a avulsão é um processonatural, porém intensificado nos últimos anos por açõesantrópicas. Tem como exemplo socioambiental uma colôniade moradores, e as recomendações objetivam auxiliar osprogramas de planejamento para a área do baixo curso do RioTaquari, a qual apresenta riscos de novas mudanças do rio.

Spatial distribution of blood flow predicts metabolic phenotypes and electrophysiological properties in the heart

High resolution analysis (300 μl) reveals a temporally stable, patchy pattern of perfusion in the LV free wall. Low flow areas (LowF) receive <60% of the average flow and display decreased energy turnover and enhanced fatty acid content, while the mechanism of this spatial heterogeneity is unknown. Lipid profile analysis of canine LowF showed an elevated triglyceride content (+212%) when compared to High flow samples (HighF). In LowF, mRNA expression of PPARα was reduced to ¼ and the same was true for 5 key enzymes or transporters in lipid metabolism (p<0.05 – 0.001), suggesting preferential glycolysis in LowF. Potassium ion channel expression also displayed flow-related differences, with enhanced expression of ERG (3.5-fold, p<0.001) and KChIP2 (2.1-fold) in LowF, mediating resp. governing IKr and Ito. Model analysis predicted a shorter local APD in LowF, which was confirmed by epicardial mapping of local QT intervals. This revealed a patchy, temporally stable pattern and a QT prolongation upon ERG blockade predominantly in areas of short basal QT (p<0.01). In short QT areas, ERG expression was increased and basal perfusion decreased. Thus, within the apparently homogenous left ventricular wall, distinct metabolic and electrophysiological phenotypes exist. In LowF, both downregulation of fatty acid oxidation and APD shortening will reduce O2 consumption in these regions and may thus partially explain the spatial heterogeneity of perfusion. Supported by DFG.

산지유역에서의 최적용수공급방안에 관한 연구

In this study used tank model and specific discharge to calculate low-flow of mountain basin and supply data that need in water resources plan. Low-flow is calculated byspecific discharge and area ratio method as resulted that calculate storage of low-flow by tank model was construed that showd all similar aspect. In judged to help in water resources plan establishment calculating low-flow using model to supplement uncertainty of observed data in that calculate of low-flow ungaged mountain area. It shows by economical and realistic plan until 12 years after development that run parallel and use economic performance analysis result valley flow and groundwater. But wide area water services and Chungju dam since 12 years onward was expose that is economic.

Genetic differentiation in relation to marine landscape in a broadcast‐spawning bivalve mollusc (Placopecten magellanicus)

Marine bivalves are sessile or sedentary as adults but have planktonic larvae which can potentially disperse over large distances. Consequently larval transport is expected to play a prominent role in facilitating gene flow and determining population structure. The sea scallop (Placopecten magellanicus) is a dioecious species with high fecundity, broadcast spawning and a c. 30-day planktonic larval stage, yet it forms discrete populations or 'beds' which have significantly different dynamics and characteristics. We analysed variation at six microsatellite loci in 12 locations throughout the geographic range of the species from Newfoundland, Canada, to New Jersey, USA. Significant differentiation was present and the maximum pairwise theta value, between one of the Newfoundland samples in the north and a sample from the southern portion of the range, was high at 0.061. Other proximate pairs of samples had no detectable genetic differentiation. Mantel tests indicated a significant isolation by distance, but only when one of the populations was excluded. A landscape genetic approach was used to detect areas of low gene flow using a joint analysis of spatial and genetic information. The two major putative barriers inferred by Monmonier's algorithm were then used to define regions for an analysis of molecular variance (amova). That analysis showed a significant but low percentage (1.2%) of the variation to be partitioned among regions, negligible variation among populations within regions, and the majority of the variance distributed between individuals within populations. Prominent currents were concordant with the demarcation of the regions, while a novel approach of using particle tracking software to mimic scallop larval dispersal was employed to interpret within-region genetic patterns.

Upscaling and 3D Streamline Screening of Several Multimillion-Cell Earth Models for Flow Simulation

Summary Nine multimillion-cell geostatistical earth models of the Marrat reservoir in Magwa field, Kuwait, were upscaled for streamline (SL) screening and finite-difference (FD) flow simulation. The scaleup strategy consisted of (1) maintaining square areal blocks over the oil column, (2) upscaling to the largest areal-block size (200×200 m) compatible with 125-acre well spacing, (3) up-scaling to less than 1 million gridblocks for SL screening, and (4) upscaling to less than 250,000 gridblocks for FD flow simulation. Chevron's in-house scaleup software program, SCP, was used for scaleup. SCP employs a single-phase flow-based process for upscaling nonuniform 3D grids. Several iterations of scaleup were made to optimize the result. Sensitivity tests suggest that a uniform scaled-up grid overestimates breakthrough time compared to the fine model, and the post-breakthrough fractional flow also remains higher than in the fine model. However, preserving high-flow-rate layers in a nonuniform scaled-up model was key to matching the front-tracking behavior of the fine model. The scaled-up model was coarsened in areas of low average layer flow because less refinement is needed in these areas to still match the flow behavior of the fine model. The final ratio of pre- to post-scaleup grid sizes was 6:1 for SL and 21:1 for FD simulation. Several checks were made to verify the accuracy of scaleup. These include comparison of pre- and post-scaleup fractional-flow curves in terms of breakthrough time and post-breakthrough curve shape, cross-sectional permeabilities, global porosity histograms, porosity/permeability clouds, visual comparison of heterogeneity, and earth-model and scaled-up volumetrics. The scaled-up models were screened using the 3D SL technique. The results helped in bracketing the flow behavior of different earth models and evaluating the model that better tracks the historical performance data. By initiating the full-field history-matching process with the geologic model that most closely matched the field performance in the screening stage, the amount of history matching was minimized, and the time and effort required were reduced. The application of unrealistic changes to the geologic model to match production history was also avoided. The study suggests that single realizations of "best-guess" geo-statistical models are not guaranteed to offer the best history match and performance prediction. Multiple earth models must be built to capture the range of heterogeneity and assess its impact on reservoir flow behavior.

The Fluid Dynamical Properties of a Dilute Surfactant Solution around a Circular Cylinder

Influence of adding cationic surfactant (Ethoquard O12) with a consentration of 50 ppm on water flow around a cylinder in a range of Reynolds number Res between from 64 to 600 was investigated by using LDV and PIV. At Res =300, the flow with the surfactant formed a stagnant zone, which appeared periodically, in front of the cylinder expanding along the axial direction. The period of the appearance was about 120 [s]. The periodic flow structure was visualized by the measurements of velocity fluctuation. The development of the stagnant zone in front of the cylinder induced the expansion of a low speed flow area near the side of the cylinder.

Water flow influences oxygen transport and photosynthetic efficiency in corals

Recent studies indicate that the incidence and persistence of damage from coral reef bleaching are often highest in areas of restricted water motion, and that resistance to and recovery from bleaching is increased by enhanced water motion. We examined the hypothesis that water motion increases the efflux of oxygen from coral tissue thereby reducing oxidative stress on the photosynthetic apparatus of endosymbiotic zooxanthellae. We experimentally exposed colonies of Montastrea annularis and Agaricia agaricites to manipulations of water flow, light intensity, and oxygen concentration in the field using a novel mini-flume. We measured photosynthetic efficiency using a pulse amplitude modulated fluorometer to test the short-term response of corals to our manipulations. Under normal oxygen concentrations, A. agaricites showed a significant 8% increase in photosynthetic efficiency from 0.238 (± 0.032) in still water to 0.256 (± 0.037) in 15 cm s−1 flow, while M. annularis exhibited no detectable change. Under high-ambient oxygen concentrations, the observed effect of flow on A. agaricites was reversed: photosynthetic efficiencies showed a significant 11% decrease from 0.236 (± 0.056) in still water to 0.211 (± 0.048) in 15 cm s−1 flow. These results support the hypothesis that water motion helps to remove oxygen from coral tissues during periods of maximal photosynthesis. Flow mitigation of oxidative stress may at least partially explain the increased incidence and severity of coral bleaching in low flow areas and observations of enhanced recovery in high-flow areas.

Maternal Hemoglobin Concentration during Pregnancy and Risk of Infant Leukemia.

Little is known about the etiology of childhood leukemia. Elevated birth weight (> 4000 g) is gaining acceptance as a risk factor, particularly for children diagnosed < 2 years of age, but the underlying biological or physiological explanation for this association has yet to be defined. At least three recent studies have demonstrated a positive association with childhood leukemia and maternal anemia during pregnancy. Physiologic anemia of pregnancy, which results from normal plasma volume expansion, is thought to produce optimal blood viscosity for the low flow area of the placenta and is associated with the highest average birth weights in the offspring. We therefore hypothesized that maternal physiologic anemia of pregnancy would have a positive association with infant leukemia. To test this hypothesis, we utilized data from a case-control study conducted by the Children's Oncology Group (COG) that consisted of 240 incident cases of acute infant leukemia (< 12 months of age) diagnosed between 1996 and 2002 and 255 controls obtained by random digit dialing. Maternal blood counts were obtained by medical record abstraction. Information regarding the patients' diagnoses and cytogenetic/molecular abnormalities were obtained from COG institutions. Physiologic anemia of pregnancy was defined as a hemoglobin concentration of < 11 g/dL in the second or third trimester of pregnancy (WHO classification). Anemia earlier in pregnancy is more frequently due to nutritional deficiencies and can be associated with poor fetal outcomes and thus was excluded. Maternal hemoglobin values from the second or third trimester were available for 178 case and 180 control mothers. Data were analyzed using unconditional logistic regression. We found no evidence that physiologic anemia of pregnancy was associated with birth weight of > 4000 g (odds ratio (OR) 1.05, 95% confidence interval (CI)=0.55–1.99) Overall, the OR for physiologic anemia of pregnancy and risk of infant leukemia was 0.85 (95%CI=0.53–1.37). The association remained non-significant when cases were divided into acute myeloid leukemia (AML) (n=63) and acute lymphocytic leukemia (ALL) (n=115) with ORs of 0.64 (95%CI=0.32–1.30) and 0.98 (95%CI=0.58–1.66), respectively. The association was also not significant when cases were stratified by MLL gene abnormality status (OR=0.77; 95%CI=0.42–1.40 and OR=0.88; 95%CI=0.45–1.73, for cases with (n=92) and without (n=62) an MLL gene abnormality, respectively). These associations remained non-significant when the data were adjusted for birth weight, maternal race, and birth order. More stringent criteria for anemia also did not modify the results. We found no evidence for an increased risk of infant leukemia in the offspring of mothers with physiologic anemia of pregnancy. This work was supported by NIH R01 CA79940 and the Children's Cancer Research Fund.

MitoKATP-Channel Opener Protects against Neuronal Death in Rat Venous Ischemia

Mitochondrial adenosine triphosphate-dependent potassium (mitoKATP) channels are present in the brain, and several reports have shown their neuroprotective, preconditioning effect against an ischemic insult. The role of mitoKATP channels in the penumbra area has not been studied thoroughly. In a model of venous ischemia, widespread penumbra-like low flow areas are created, which are susceptible to cortical spreading depression. Thus, we studied effects of mitoKATP channels on infarct size in this model. Male Wistar rats were subjected to two-vein occlusion by photochemical thrombosis of two adjacent cortical veins combined with KCl-induced cortical spreading depression. The rats were assigned to four experimental groups pretreated intraventricularly 15 minutes before two-vein occlusion with 1) vehicle, 2) the mitoKATP channel opener diazoxide (2 mmol/L), 3) diazoxide (2 mmol/L) plus the selective mitoKATP channel blocker 5-hydroxydecanoate (5-HD; 100 mmol/L), or 4) 5-HD alone (100 mmol/L). Regional cerebral blood flow (laser Doppler scanning) and brain cell swelling (impedance) were monitored acutely. Infarct volume was assessed 7 days after ischemia. Pretreatment with diazoxide significantly reduced the infarct volume from 6.2 +/- 0.7 mm3 to 3.8 +/- 0.4 mm3, whereas regional cerebral blood flow in the vicinity of the two veins was comparable in both groups 70 minutes after two-vein occlusion. Effects of diazoxide were abolished by 5-HD, whereas 5-HD alone even increased infarct volume. These results suggest that the opening of mitoKATP channels plays a major role in brain protection under penumbra-like conditions, as shown in this venous occlusion model.

Radiological Terrorism

ABSTRACT We run the risk that terrorists will decide to detonate an explosive device laced with radioactive materials (a radiological dispersal device, or RDD). If such an attack occurs, it is unlikely that the affected population or emergency responders would be exposed to high levels of external radiation, although airborne radionuclides may present a health risk under some circumstances. However, the effects of radiation and radioactivity are not well known among the general population, emergency responders, or medical personnel. This could lead to unwarranted panic, refusal to respond to the incident, inappropriately delaying or denying treatment to injured victims, and other unfortunate reactions during the emergency phase of any response. During the recovery phase, current regulations may lead to costly and restrictive radiation safety requirements over very large areas, although there have been recent efforts to relax some of these regulations in the first year following a radiological attack. The wide spread of radioactive contamination can also lead to environmental contamination, particularly in low-flow areas and near storm sewer discharge points, but the total radiation dose to the environment should not be excessively high in most locations.

Analysis of Combined Treatment of Embolic Stroke in Rat with r-tPA and a GPIIb/IIIa Inhibitor

Suppression of platelet activation improves the efficacy of thrombolytic therapy for stroke. Thus, combination treatment with recombinant tissue plasminogen activator (r-tPA) and 7E3 F(ab')2, a GPIIb/IIIa inhibitor that binds the platelet to fibrin, may improve the efficacy of thrombolytic therapy in embolic stroke. Magnetic resonance imaging (MRI) was used to monitor treatment response in rats subjected to embolic middle cerebral artery (MCA) occlusion (MCAo). Animals were randomized into treated (n=12) and control (n=10) groups and received intravenous combination therapy or saline, respectively, 4 hours after MCAo. Magnetic resonance imaging (MRI) measurements performed 1 hour after MCAo showed no difference between groups. However, an increased incidence (50%) of MCA recanalization was found in the treated group at 24 hours compared with 20% in the control group. The area of low cerebral blood flow at 24 and 48 hours was significantly smaller in the combination treatment group, and the lesion size, as indicated from the T2 and T1 maps, differed significantly between groups. Fluorescence microscopy measurements of cerebral microvessels perfused with fluorescein isothiocyanate-dextran and measurements of infarct volume revealed that the combination treatment significantly increased microvascular patency and reduced infarct volume, respectively, compared with the control rats. The efficacy of combination treatment 4 hours after ischemia is reflected by MRI indices of tissue perfusion, MCA recanalization, and reduction of lesion volume. The treatment also reduced secondary microvascular perfusion deficits.

Irrigated-tip catheter ablation of intraatrial reentrant tachycardia in patients late after surgery of congenital heart disease

The aim of this study was to evaluate irrigated-tip catheter for ablation of intraatrial reentrant tachycardias late after surgical repair of congenital heart disease. In congenital heart disease patients, the right atrium can be markedly enlarged with areas of low blood flow. Radiofrequency (RF) lesion creation may be hampered by insufficient electrode cooling at sites with low blood flow. Thirty-six consecutive patients with intraatrial reentrant tachycardia refractory to antiarrhythmic therapy from two centers were included in the study. Entrainment pacing and electroanatomic mapping (CARTO) were used to delineate reentrant circuits and critical isthmus sites. RF ablation was performed using an irrigated-tip catheter (Navistar Thermocool). Fifty-two intraatrial reentrant tachycardia circuits were identified, and 48 were targeted with RF ablation. RF ablation was performed using a mean of 13 +/- 11 irrigated RF applications per tachycardia isthmus with a mean power of 36 +/- 8 W. In a historical control group of congenital heart disease patients managed with conventional catheter ablation, the number of lesions per isthmus was higher (23 +/- 11) and mean power was lower (27 +/- 14 W). Acute success was achieved in 45 intraatrial reentrant tachycardias (94% of targeted tachycardias and 87% of all tachycardias). After a mean follow-up of 17 +/- 7 months, 33 (92%) of 36 patients were free of recurrence. Five patients (14%) developed paroxysmal atrial fibrillation. The combination of modern techniques including electroanatomic mapping and catheter irrigation allows safe and highly effective ablation of intraatrial reentrant tachycardia in patients with surgically repaired congenital heart disease.

Erosion and sedimentation as processes controlling the BSR-derived heat flow on the Eastern Nankai margin

In 2000, a 3D MCS survey was carried out on the Eastern Nankai Trough. A strong and widespread bottom-simulating reflector (BSR) was observed and mapped after a preserved amplitude 3D prestack migration of the seismic data. We use this BSR to calculate a heat flow map over the 3D survey area. This map presents some high and low heat flow areas, that cannot be correlated to known active wedge faults and previously observed fluid venting sites. Since the heat flow anomalies are not correlated to known major faults or fluid venting sites, large fluid circulation is not likely to explain the varying BSR-derived heat flow distribution. In order to explain this heat flow distribution quantitatively, we calculate the rates of erosion and sedimentation that are necessary to create these anomalies. These rates are in good agreement with observations on seismic profiles, and are locally consistent with a sedimentation rate calculated from slope basin depth, and reflect the distribution of erosion, landsliding and deposition on the margin slope. We therefore propose that the observed BSR-derived heat flow anomalies are mainly due to active erosion and sedimentation, and that heat flow distribution on the margin section of the 3D survey is controlled by surface processes. Fluid migration could occur where a BSR is absent, but is probably episodic or limited where a BSR is present, and does not affect the BSR-derived heat flow in this part of the margin. These surface processes are the consequence of the tectonic and seismic activity of the wedge and are influenced by the subduction of a wide oceanic ridge below the Eastern Nankai margin.

Variation in blade morphology of the kelp Eisenia arborea: incipient speciation due to local water motion?

The southern sea palm kelp Eisenia arborea produces wide, bullate (bumpy) blades in low-flow areas, whereas in adjacent high-flow areas blades are flat and narrow. Here we determine if morphological differences in these 2 closely associated populations are correlated with physical factors in the environment, and whether this response is a genetically fixed or plastic trait. Both phenotypes were subjected to morphometric analysis, field and laboratory transplant experiments, and genetic analysis (M13 DNA fingerprinting). Physical variables (water motion, temperature, and light) were monitored simultaneously in the field. Results indicate that the 2 populations, separated by <10 m, are genetically distinct and transplants in the field and lab remained similar to individuals from the original collection location, regardless of the imposed flow environment. Water motion varied significantly between the 2 populations and was the single physical variable that correlated with morphology. Based on bump heights and water velocities in the field, bullate blades could increase turbulent transport of nutrients 4-fold that of flat blades. The thicker blades and large holdfasts of the flat morph may impart higher survivorship under high-flow conditions. This suggests water motion selects for 2 distinct morphotypes of E. arborea that represent adaptations to enhance fitness under different nutrient availability and drag force regimes. Thus, blade morphology is not a plastic response to the local environment but a genetically fixed trait and may be indicative of nascent speciation in the face of strong selection by water motion over spatial scales smaller than observed previously in kelps.

The influence of habitat on the distribution and abundance of metacercariae of Macravestibulum obtusicaudum (Pronocephalidae) in a small Indiana stream.

Snails (Elimia livescens) from a central Indiana stream were examined for encysted metacercariae of Macravestibulum obtusicaudum (Pronocephalide) to determine the distribution and abundance of this parasite on its second intermediate host. Five samples of snails were collected, with 2 samples being restricted to high-flow (riffle) or low-flow (pool) areas of the stream. Snails (n = 386) were measured for shell length; the shell and the inner and outer surfaces of the operculum (in most samples) were examined for metacercariae. Seventy-five percent of snails (overall) had encysted metacercariae (range, 52-97%), primarily on the opercula. A significantly lower proportion of snails from riffles were infected, and these snails had significantly fewer cysts as well. Snails collected from pools showed up to 10 times as many metacercariae than those from riffles, although there was no significant difference in the proportion of snails with intramolluscan infections of M. obtusicaudum. The inner opercular surface appeared to be the preferred site of encystment in both flow regimes. Differences in microhabitats, in terms of both snails in the stream and metacercariae on the snails, clearly must be considered when evaluating the infection patterns of this trematode.

Selective intracoronary injection of sestamibi to detect myocardial viability: prediction of perfusion and contractile recovery after percutaneous transluminal coronary angioplasty

Background The main limitation of myocardial single photon emission computed tomography (SPECT) in detecting hibernating myocardium is the poor delivery of radiotracers in hypoperfused areas supplied by severely stenotic coronary arteries. Increasing local availability of radiotracers by intracoronary injection might represent an attractive solution. The hypothesis that the intracoronary administration of sestamibi could improve myocardial SPECT accuracy in detecting hibernating myocardium was addressed in this pilot study. Methods and results Seven patients with prior myocardial infarction and severe stenosis of the infarct-related artery underwent myocardial SPECT after intracoronary injection of technetium 99m sestamibi immediately before percutaneous transluminal coronary angioplasty (PTCA). Wall motion and perfusion were evaluated, before and 1 month after PTCA, by 2-dimensional echocardiography and rest-redistribution thallium 201 SPECT. A “low-flow area” was identified on the pre-PTCA Tl-201 SPECT image as the area with less than 50% of maximum radiotracer uptake. Changes in wall motion and perfusion in the low-flow area were compared with results of intracoronary sestamibi imaging. On a pixel-by-pixel analysis, intracoronary sestamibi predicted perfusion recovery within the low-flow area with a 91% sensitivity, a 78% specificity, and an 82% overall accuracy. Only in the 5 patients with an extent of sestamibi uptake greater than one third of the low-flow area was an improved regional and global left ventricular wall motion observed after PTCA (wall motion score index decreased from 1.95 ± 0.28 to 1.60 ± 0.34, P = .007; left ventricular ejection fraction increased from 42% ± 7% to 49% ± 7%, P = .001; asynergic segments in the low-flow area decreased from 3.6 ± 0.9 to 1.8 ± 1.5, P = .021). Conclusions In patients with prior myocardial infarction and severe stenosis of the infarct-related artery, sestamibi uptake after intracoronary administration identified viable myocardium that was undetected after rest-redistribution thallium SPECT but capable of clinically significant contractile improvement after revascularization.

Habitat, growth and physiological ecology of a basaltic community of Ridgeia piscesae from the Juan de Fuca Ridge

The vestimentiferan tubeworm Ridgeia piscesae is an ecosystem-structuring organism in the hydrothermal vent environments of the Northeast Pacific. During this study, a single representative aggregation of the long-skinny morphotype of R. piscesae from the main endeavor segment was monitored for 3 yr before being collected in its entirety with a hydraulically actuated collection device manipulated in situ by a research vehicle. Vestimentiferan growth rates in this aggregation were determined by staining the exterior of the tubes and measuring newly deposited tube sections. The average growth rate of R. piscesae in this aggregation was very low in both years of the growth study (3.2 mm yr −1). Although the incidence of plume damage from partial predation was very high (>95%), mortality was very low (<4% yr −1). The distribution and the very tight clustering of recently recruited individuals indicated gregarious settlement behavior that is hypothesized to be partly due to biotic cues from settled larvae. Coupled measurements of vent fluid sulfide concentration and temperature were used to calculate the exposure of the vestimentiferans to sulfide from short- and long-term temperature monitoring. Plume-level temperature records indicate that most of the time individuals in this aggregation were exposed to extremely low levels of vent fluid, and therefore sulfide (<0.1 μM), while their posterior sections were consistently exposed to sulfide concentrations in the 100 μM range. A rootball-like structure formed the common base of the aggregation. In contrast to the anterior sections of the tubeworm tubes, the portions of the tubes within the “rootball” were freely permeable to sulfide. The results of this study show that R. piscesae, unlike vestimentiferans from the East Pacific Rise, can survive and grow in areas of low diffuse vent flow with very low plume-level exposure to sulfide. We propose that this morphotype of R. piscesae has the ability to acquire sulfide from sources near their posterior ends, similar to some species of cold seep vestimentiferans from the Gulf of Mexico. The ability of this single species of vestimentiferan to survive low exposure to vent flow with low mortality coupled with sulfide uptake across posterior tube sections may help explain the occurrence of a single vent vestimentiferan species in a wide variety of habitat conditions at hydrothermal vent sites in the Northeast Pacific.

Heterologous expression of human VEGF165 in rat brain: dose-dependent, heterogeneous effects on CBF in relation to vascular density and cross-sectional area.

Vascular endothelial growth factor (VEGF) induces increased vessel permeability and formation of abnormal vessels. To investigate cerebral blood flow (CBF) during local overexpression of VEGF recombinant adenoviruses carrying the human VEGF165 complementary DNA (2.3 to 23. 108 pfu/mL) were injected stereotactically into the caudate nucleus of anesthetized rats. Saline and adenoviruses carrying the beta-galactosidase gene served as controls. Eleven days later (1) size and density of vessels were assessed in hematoxylin-eosin-stained sections, (2) vascular permeability was measured by intravenous Evans blue injections, and (3) local CBF (lCBF) was quantified using the iodo-[14C]antipyrine technique. Dose-dependent increases were found in (1) vessel density and size (only vessels >43 microm could be quantified morphologically), (2) Evans blue extravasation and brain edema formation, and (3) lCBF (up to eightfold). At medium doses, hyperemic areas and smaller areas of decreased lCBF were found. In low flow areas, vascular cross-sectional areas were increased 223-fold and vessel density up to 10-fold. In high flow areas, these parameters were increased 32-fold and up to 15-fold, respectively. Adenovirus mediated VEGF overexpression results in (1) increased vessel size and density, (2) areas of increased and of decreased flow, and (3) more and smaller vessels in high flow than in low flow areas. These results indicate a diverging flow pattern of newly formed vessels.