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At least 883 records · Page 49Linked to original sources
PubMed2006

Assessment of mangrove response to projected relative sea-level rise and recent historical reconstruction of shoreline position.

We predict the decadal change in position of three American Samoa mangroves from analysis of a time series of remotely sensed imagery, a geographic information system, tide gauge data, and projections for change in sea-level relative to the mangrove surface. Accurate predictions of changes to coastal ecosystem boundaries, including in response to projected relative sea-level rise, enable advanced planning to minimize and offset anticipated losses and minimize social disruption and cost of reducing threats to coastal development and human safety. The observed mean landward migration of three mangroves' seaward margins over four decades was 25, 64, and 72 mma(-1), 12 to 37 times the observed relative sea-level rise rate. Two of the sites had clear trends in reductions in mangrove area, where there was a highly significant correlation between the change in position of the seaward mangrove margin and change in relative sea-level. Here it can be inferred that the force of sea-level rise relative to the mangrove surface is causing landward migration. Shoreline movement was variable at a third site and not significantly correlated with changing sea-level, where it is likely that forces other than change in relative sea-level are predominant. Currently, 16.5%, 23.4%, and 68.0% of the three mangroves' landward margins are obstructed by coastal development from natural landward migration. The three mangroves could experience as high as a 50.0% reduction in area by the year 2100. A 12% reduction in mangrove area by the year 2100 is possible in the Pacific islands region.

American Samoa↗
PubMed2006

Environmental effects of dredging on sediment nutrients, carbon and granulometry in a tropical estuary.

This monitoring study encompassed a period prior to dredging, during dredging and post dredging between July 1999 to June 2000 in Ponggol estuary located along the northeastern coast of Singapore. Mean concentrations of sediment nutrients in mg x Kg(-1) (+/- standard error of means) prior to dredging, during dredging and post dredging were 9.75 +/- 4.24, 8.18 +/- 4.29 and 11.46 +/- 4.74 for ammonium, 0.08 +/- 0.05, 0.06 +/- 0.02 and 0.09 +/- 0.01 for nitrite, 0.04 +/- 0.04, 0.11 +/- 0.17 and 0.25 +/- 0.30 for nitrate, 4.83 +/- 3.48, 0.77 +/- 0.48 and 8.33 +/- 9.73 for phosphate respectively. Pre dredge, dredge and post dredge levels of total carbon (TC) were 18.5 +/- 3.7, 20.2 +/- 3.5 and 34.6 +/- 12.0, of total organic carbon (TOC) were 10.5 +/- 2.9, 19.5 +/- 3.6 and 34.6 +/- 12.0 and of total inorganic carbon (TIC) were 7.9 +/- 1.0, 0.7 +/- 0.4 and non detectable in the sediments, respectively. Both, sediment nutrients and carbon registered lower concentrations with onset of dredging, with the exception of nitrate and TOC. A shift in sedimentary carbon from inorganic carbon to organic carbon was also observed with the onset of the dredging activities when the organically enriched historically contaminated layer was exposed. Sediment granulometry showed that the sediments in the estuary were predominantly silt and clay prior to dredging, which changed to sand with onset of dredging. Silt load in the sediments was highest post-dredge. Sediment nutrients and sediment organic carbon were observed to associate with the finer fractions (silt and clay) of sediments. Finer fractions of sediments get resuspended during a dredging event and are dispersed spatially as the result of tides and water movements. Prior to this study, the potential for nutrient release and sediment granulometry due to dredging have been suggested, but there have been few studies of it, especially in the tropics. The baseline information gathered from this study could be used to work out effective management strategies to protect similar tropical ecosystems elsewhere, should there be no other alternative to dredging.

Carbon↗
PubMed2006

Assessment of the potential of the rock gunnel (Pholis gunnellus) along the Atlantic coast of Canada as a species for monitoring the reproductive impacts of contaminant exposures.

Evaluating the impacts of point source discharges on fish species in estuarine environments can be challenging because of a paucity of resident species. We evaluated the biology of rock gunnel (Pholis gunnellus) at three relatively uncontaminated sites in the Bay of Fundy, along the Atlantic coast of Canada. Rock gunnel are seasonally resident (April to November) in tide pools, but little was known about their life history in Atlantic Canada or their potential for use for monitoring environmental quality. Fish were collected between April and November, and ranged from 2.46 g-15.2g in weight and 97 mm-170 mm in length, with a maximum age of 7 years. Both males and females were similar in size, and both reached sexual maturity at a size of 5.5 g. Organ weights and condition indices of fish were stable from spring when they returned from offshore (April to May) until late summer (August to September), but fall fish (October to November) had slightly larger gonads, livers and condition indices. Rock gunnel may be a useful indicator to provide insight into local impacts of point sources over a short time period. However, they do not provide adequate information on reproductive development and performance since they are not exposed to onshore contaminants during the periods of gonadal development that have most commonly found to be sensitive to anthropogenic stressors.

Animals↗
PubMed2006

Identifying environmental determinants of diurnal distribution in marine birds and mammals.

Marine birds and mammals move between various habitats during the day as they engage in behaviors related to resting, sleeping, preening, feeding, and breeding. The per capita rates of movement between these habitats, and hence the habitat occupancy dynamics, often are functions of environmental variables such as tide height, solar elevation, wind speed, and temperature. If the system recovers rapidly after disturbance, differential equation models of occupancy dynamics can be reduced to algebraic equations on two time scales. Identification of environmental factors that influence movement between habitats requires time series census data collected in both the absence and presence of disturbance.

Algorithms↗
PubMed2006

Metabolic syndrome in children and adolescents.

Metabolic syndrome is a constellation of interrelated risk factors of metabolic origin that often accompany obesity and consist of atherogenic dyslipidemia, elevated blood pressure, impaired glucose tolerance, a prothrombotic state, and a proinflammatory state. Using a modification of the criteria by the National Cholesterol Education Program Adult Treatment Panel III, metabolic syndrome in children and adolescents can be clinically diagnosed when three or more of the following are present: body mass index > or = 2 z score, systolic or diastolic blood pressure greater than 95th percentile, triglyceride level greater than 95th percentile, and/or high-density lipoprotein cholesterol less than 5th percentile and impaired glucose tolerance (fasting glucose > 110 mg/dL ). The prevalence of the metabolic syndrome in adolescents has been shown to be 4% overall, but it is 30% to 50% in overweight adolescents. In the United States, 18% to 22% of children and adolescents are overweight; the prevalence of a metabolic syndrome phenotype among US adolescents has also been increasing significantly over the past decade. All of the features of metabolic syndrome are risk factors for atherosclerosis, and metabolic syndrome has been shown to constitute risk for atherosclerotic cardiovascular disease in adults. In children and adolescents with metabolic syndrome, biomarkers of an increased risk of adverse cardiovascular outcomes are already present. Therefore, there is need for prevention and treatment of metabolic syndrome in this population. The mainstay of the treatment is dietary intervention and promotion of active lifestyle to achieve and maintain optimum weight, normal blood pressure, and normal lipid profile for the height and age. The pharmaceutical intervention is usually not required and its long-term outcome has not been studied. There is need for large studies for the management and long-term outcomes of metabolic syndrome in children and adolescents if the future tides of cardiovascular and other associated complications of metabolic syndrome are to be turned around.

Journal Article↗
PubMed1985

Pathogenetic factors in erosive gastritis.

Under physiologic conditions, luminal acid and pepsin are absolute requirements in the development of erosive gastritis and ulceration. Even the injurious effects of most drugs are potentiated by acid and pepsin. Although the importance of luminal acid has long been recognized, only in the last 10 years has evidence accrued showing the detrimental effects of tissue acidosis in producing injury to the gastric mucosa. It now seems clear that by whatever means it is produced, e.g., through reduced mucosal blood flow, metabolic or respiratory acidosis, or inhibition of acid secretion with subsequent decreased "alkaline tide," tissue acidosis plays a profound role in the pathogenesis of erosive gastritis and ulceration. The gastric mucosal barrier is now recognized as the anatomic integrity of the surface epithelium, rather than as an ethereal physiologic barrier. This barrier is maintained as an intact layer under physiologic conditions by a newly described rapid repair process called restitution.

Acid-Base Imbalance↗
PubMed1977

Secretory state of gastric mucosa and resistance to injury by exogenous acid.

The capacity of the stomach to resist the effects of highly acid solutions was assessed by comparing the effects of such solutions on spontaneously secreting, stimulated, and inhibited gastric mucosae of rabbits in vivo and frogs in vitro. Exposure of unstimulated resting mucosa to HC1, 120 mM, for 60 minutes produced superficial erosions in all rabbits, whereas such lesions were observed in only one of ten animals stimulated with histamine. Metiamide obviated the protective effect of histamine against ulcerations even though it did not reduce H+ secretion to zero. Exposure of inhibited isolated frog fundic mucosa to HC1 resulted in significant deterioration of electrical parameters, suggesting impairment of active transport processes and increased tissue permeability. These data are consistent with the hypothesis that actively secreting gastric mucosae from two species resist injury to exogenous acid more effectively than do resting or inhibited tissues, perhaps in part as a result of a greater alkaline tide.

Animals↗
PubMed1984

Structure and function of hemoglobin from Urechis caupo.

The hemoglobin of the erythrocytes of Urechis caupo is tetrameric. Three chromatographic fractions have been isolated. Fractions F-I (the major fraction) and F-II are each composed of at least five electrophoretic components. Minor fractions F-III has an amino acid composition which is very different from those of fractions F-I and F-II. Amino acid analysis and peptide mapping suggests that fractions F-I and F-II are very similar, and may differ only in a few post-translational modifications. The major fraction, F-I, appears to consist of tetramers in which all subunits are almost identical. Oxygen binding is noncooperative, with a pressure of half-saturation (p50) of 12 mm Hg at 20 degrees C and pH 7.5 in Tris buffers. The oxygen equilibria of undialyzed lysate and of hemoglobin purified by chromatography on Sephadex G-100 are identical. This observation indicates that no allosteric modulator is present. The oxygen equilibrium is not significantly affected by ATP, Cl-, Ca2+, Mg2+, or CO2. The pH dependence of oxygen binding is extremely small: delta Log p50/delta pH is only +0.06 between pH 6 and 7.5. The p50 value changes by no more than 15% between 6.8 microM and 4.3 mM (heme). The apparent enthalpy of oxygenation, delta H, is -11 kcal/mol. Deoxygenation, oxidation, dilution, or pH changes have no significant effect on the state of aggregation. These oxygen-binding properties are consistent with the suggestion that the primary function of the hemoglobin is to store oxygen during the hypoxia which occurs in the burrows of the animal at low tide.

Amino Acid Sequence↗
PubMed1987

Tachykinin regulation of serotonin release: enhancement of [3H]serotonin release from rat cerebral cortex by neuromedin K and substance P acting at distinct receptor sites.

Neuromedin K and substance P (SP) enhanced the basal (5 mM K+) and potassium-evoked (40 mM K+) release of [3H]5-hydroxytryptamine ([3H]5-HT) from slices of the rat cerebral cortex. The effects of the two tachykinins were additive. The SP antagonist span-tide ([D-Arg1, D-Trp7.9, Leu11]-SP) (10(-6) M) inhibited the stimulatory effect of SP but not of neuromedin K on the release of [3H]5-HT. These findings suggest that the two tachykinins exhibit their effects on serotonin release at distinct receptor sites.

Animals↗
PubMed1977

The influence of Gomphosphaeria aponina on the growth of Gymnodinium breve and the effect of aponin on the ichthyotoxicity of Gymnodinium breve.

Cells of the marine blue-green alga Gomphosphaeria aponina survive in mixed culture with the marine dinoflagellate, Gymnodinium breve (the Florida red tide organism), but G. breve cells lysed within 4-7 days. It has been established that the cytolytic effect of G. aponina, not nutrient competition, is responsible for the decrease in number of cells. The material elaborated by G. aponina has been termed aponin and has been extracted from the cells. The effect of aponin on the ichthyotoxicity of G. breve cultures was measured using Poecilia sphenops, adapted to sea water, as the assay organism. Aponin is not ichthyotoxic toward P. sphenops, though this material, when incubated with G. breve cultures does destroy the cells and increases the ichthyotoxicity of the cultures. At certain concentrations of aponin, the ichthyotoxicity of G. breve cultures appeared to be mitigate d.

Animals↗
PubMed1983

Drinking induced by angiotensin II in fishes.

Among 20 species of freshwater fishes examined, Pseudorasbora parva, Rhodeus ocellatus, Cobitis anguillicaudatus, Carassius auratus, Oryzias latipes, Gambusia affinis, and Gyrinocheilus anymonieri were found to drink water like seawater fishes, while 13 remaining species did not drink. For fish species found exclusively in fresh water, angiotensin II (AII) treatment did not induce drinking. In contrast, those freshwater fishes which survive in estuarine brackish water (Leuciscus hakonensis, C. carassius, Parasilurus asotus, G. affinis, Chaenogobius annularis, Tridentiger obscurus, and G. anymonieri responded to AII by drinking. Furthermore, some freshwater fishes which survive either in hypertonic water (C. auratus) or in sea water (Anguilla japonica and O. latipes) also responded to AII by drinking. Of 17 seawater fishes examined, Eptatretus burgeri, Triakis scyllia, and Heterodontus japonicus failed to drink water, and for Trachurus japonicus, Platichthys bicoloratus, and Glossogobius giuris fasciatopunctatus, water intake was minor (similar to freshwater fishes). The 11 remaining seawater fishes drank water. AII did not induce drinking in fishes living exclusively in sea water. However, seawater fishes which survive either in tide pools (Chasmichthys dolichognathus gulosus) or in brackish water (Sillago japonica, Mugil cephalus, G. giuris fasciatopunctatus) responded to AII by drinking. P. bicoloratus, Acanthopagrus schlegeli, and Fugu niphobles were exceptional, in that they survive in brackish water, but did not respond to AII. Although some exceptions exist, it is generally concluded that a drinking response to AII is characteristic of fishes which encounter water more hypertonic than that in which they typically reside. Accordingly, a drinking mechanism induced by AII may be a compensatory emergency reaction to dehydration stress.

Angiotensin II↗
PubMed1988

Serum hormone levels associated with spawning activity in the mummichog, Fundulus heteroclitus.

Daily collections of the mummichog, Fundulus heteroclitus, from field populations during the first 45 days of the breeding season revealed a semilunar cycle in the sperm index. Peaks in the sperm index were preceded by 6 days with peaks in the serum testosterone concentration. Bihourly sampling of field populations during a 72-hr period at the new moon showed both diel cycling and an upward trend in serum progesterone levels in female mummichogs. Male mummichogs had 12-hr cycles in serum 17 beta-hydroxy-4-androstene-3,11-dione levels, the peaks of which preceded high tide by 4 hr. The physiological significance of these cycles are discussed.

Androgens↗
PubMed1989

The origin of the moon and the single-impact hypothesis III.

In previous papers in this series the smoothed particle hydrodynamics method (SPH) has been used to explore the conditions in which a major planetary collision may have been responsible for the formation of the Moon. In Paper II (W. Benz, W.L. Slattery, and A.G.W. Cameron 1987, Icarus 71, 30-45) it was found that the optimum conditions were obtained when the mass ratio of the impactor to the protoearth was 0.136. In the present paper we investigate the importance of the equation of state by running this optimum case several times and varying the equation of state and other related parameters. The two equations of state compared are the Tillotson (used in the previous papers) and the CHART D/CSQ ANEOS. Because of differences in these equations of state, including the fact that different types of rocks were used in association with each, it was not possible to prepare initial planetary models that were comparable in every respect, so several different simulations were necessary in which different planetary parameters were matched between the equations of state. We also used a new version of the SPH code. The results reaffirmed the previous principal conclusions: the collisions produced a disk of rocky material in orbit, with most of the material derived from the impacting object. These results indicate that the equation of state is not a critical factor in determining the amount of material thrown into orbit. This confirms the conclusions of Paper II that gravitational torques, and not pressure gradients, inject the orbiting mass. However, the way this mass is distributed in orbit is affected by the equation of state and the choice of rock material, the Tillotson equation for granite giving slightly larger mean orbital radius for the particles left in orbit than the ANEOS dunite for the same impact parameter. We also find, compared to Paper II, that in all subsequent cases the new SPH code leads to a slightly less extended prelunar accretion disk. We think this is due to the new shape adopted for the kernel. A few additional calculations were made to test the effects of increasing the impact parameter on the calculations, other parameters remaining unchanged. The motivation for this was that solar tides will have reduced the Earth-Moon angular momentum somewhat over the course of time. An increment of 6% in the angular momentum of the collision increases the amount of iron-free material in orbit and its mean orbital radius, but more than that leaves increasing amounts of iron in orbit (the iron has a small mean orbital radius). The debris from the destroyed impacting object tends to form a straight rotating bar which is very effective in transferring angular momentum. If the material near the end of the bar extends well beyond the Roche lobe, it may become unstable against gravitational clumping.

Astronomical Phenomena↗
PubMed1995

The role of synovial fluid filtration by cartilage in lubrication of synovial joints--IV. Squeeze-film lubrication: the central film thickness for normal and inflammatory synovial fluids for axial symmetry under high loading conditions.

The axially symmetric problem of synovial film filtration and synovial gel formation at normal approach of cartilage surfaces in the human hip joint loaded by a compressive force has been solved numerically in Part III of this paper [Hlavácek and Novák, J. Biomechanics 28, 1193-1198 (1995)] for the Newtonian viscous phase of the biphasic synovial fluid and for low loads only. Because of a high non-linearity of the problem the method used there breaks down for higher loads. On anticipating that for a high step loading the fluid pressure in the central part of the squeezed synovial film is close to the pressure in a dry frictionless contact, the synovial film filtration at the film centre is governed by two ordinary differential equations that are easy to solve. The central gel film thickness thus obtained, i.e. the film thickness at the moment, when the filtered fluid turns into a stable gel is about 1 micron for the normal synovial fluid (with a non-Newtonian viscous phase of the synovial fluid) and changes very little if the geometric, material and loading parameters of the problem vary within the physiological range. The inflammatory case (with a more or less Newtonian viscous phase) yields values by one order lower at least. The results of stress analysis in the cartilage for this mixture model suggest the reason for vertical cracking at the free cartilage surface and horizontal splitting at the tide mark observed in osteoarthritic joints.

Biomechanical Phenomena↗
PubMed1993

Post caesarean section delivery.

Recent clinical attention has focused upon the rising rate of caesarean sections being performed and whether patients with a previous caesarean section should be allowed a vaginal delivery. In this paper, the worldwide trend of caesarean section and the role of trial of scar following single and multiple caesarean surgery is reviewed. The role of oxytocin and regional epidural analgesia is evaluated as well as perinatal and maternal mortality. On the basis of the available data, there is no justification for the current clinical practice of almost 99% prevalence of elective repeat caesarean section in some hospitals in the North America. Oxytocin and epidural analgesia, when carefully monitored, are safe and reasonable in these patients. Watchful waiting has always been an essential virtue in obstetric management and should not be replaced by hopeful expectancy. This aspect of the art of obstetrics would appear to require rejuvenation if we are to stem the rising tide of caesarean sections.

Analgesia, Epidural↗
PubMed1986

Effect of salinity on the behavior and oxygen consumption of Mugil curema (Pisces, Mugilidae).

White mullet fingerlings (Mugil curema) occur together with freshwater species, of the Poeciliidae and Characidae, in a pond neighboring the beach at Pontal do Sul (Parana, Brasil). They tolerate changes in water quality during the year, brought about by the action of rains, waves and tides. When acclimating in the laboratory to various salinities, the highest survival rate for Mugil curema fingerlings (2.3 to 9.7 cm) is obtained at 8.5% salinity for temperatures between 13 and 30 degrees C. M. curema fingerlings do not survive in freshwater. The behavior of the individuals and of the group was related to the acclimation salinity in different temperature ranges. The most stressing condition, with highest oxygen consumption, was at 1.7% salinity; the equilibrium point between the internal and the external medium, with the lowest oxygen uptake, per gram fish, in one hour, was recorded at 8.5% salinity.

Adaptation, Physiological↗
PubMed1995

Intestine fullness influences feeding behaviour and crop filling in the domestic turkey.

Image-intensification radiology showed that artificial introduction of food slurry into the intestines of 6-12 wk-old turkey hens significantly increased the proportion of boli entering the crop during an evening meal, hence decreasing the proportion of boli travelling directly to the gizzard. Since bolus movement is directed by esophageal motility, esophageal motility may be partially mediated by stretch or chemoreceptors in the distal duodenum. Increased crop filling during afternoon meals lends support to the widely held belief that the crop increases gut storage capacity and helps "tide birds over" the nightly fast. Artificial filling of the distal duodenum paradoxically increased food intake in birds observed by radiology while eating a single meal (morning and evening), and in birds observed by eye over a 3 h period in the morning. This phenomenon is similar to that previously reported for rabbits and domestic chicken. Conversely, duodenal filing reduced food intake over a full day (11 h), more than compensating for the introduced food. Rapid filling of the small intestine (within 25 min. of the start of the meal) suggests a modification of the function of the domestic turkey duodenum to serve as a "mixing chamber," possibly enhancing digestive efficiency. The ways in which this modification affects digestion and absorption in the duodenum warrant investigation.

Animals↗
PubMed1985

A combination fluorescence assay and Folin-Ciocalteau phenol reagent assay for the detection of paralytic shellfish poisons.

Paralytic shellfish poison (PSP) profiles of crude shellfish extracts were determined by linear gradient elution from a Bio-Rad AG-50-X4 strong cation-exchange resin mini-column. STX, GTX2 and GTX3 were detected by fluorescence assay. NeoSTX and GTX1/GTX4 were detected with a Folin-Ciocalteau phenol reagent assay. The major toxicity associated with extracts of Mytilus edulis and Mya arenaria collected during a 1972 red tide off Hampton, New Hampshire, was due to the presence of GTX1/GTX4, with some activity associated with neoSTX, GTX2 and GTX3. STX was also present. Correlations to mouse toxicity are provided.

Amino Acids↗