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At least 145 records · Page 8Linked to original sources
PubMed1984

Myocardial monovalent cation transport during the quinidine-digoxin interaction in dogs.

To study the relationship of the serum digoxin concentration to the digoxin effect on monovalent cation transport during the quinidine-digoxin interaction, we used radiolabeled rubidium to measure monovalent cation active transport in myocardial biopsy samples from dogs. In a preliminary study, we showed that quinidine did not affect rubidium uptake by myocardial samples from intact dogs. Then, we studied four groups, each consisting of 13 dogs, which received either saline, low dose digoxin, high dose digoxin, or low dose digoxin plus quinidine treatment. In these groups of dogs, the following steady state serum digoxin concentrations were achieved: saline-treated, 0 ng/ml; low dose digoxin, 1.2 +/- 0.2 ng/ml (mean +/- SD); high dose digoxin, 2.4 +/- 0.4 ng/ml; and low-dose digoxin plus quinidine treated, 2.3 +/- 1.1 ng/ml. Compared to control values, rubidium uptake was decreased by 17% in dogs treated with low dose digoxin (P less than 0.05) and by 38% in dogs treated with high dose digoxin (P less than 0.01 vs. saline-treated, P less than 0.01 vs. low dose digoxin). Although low dose digoxin plus quinidine-treated dogs had the same mean serum digoxin concentration as the high dose digoxin-treated dogs, rubidium uptake in low dose digoxin plus quinidine-treated dogs was decreased by only 17% compared to control (P less than 0.05 vs. saline-treated, (P less than 0.01 vs. high dose digoxin). During the quinidine-digoxin interaction in the intact dog, the reduction in myocardial rubidium uptake is less than expected from the increase in serum digoxin concentration.

Animals↗
PubMed1998

Bacterial milking: A novel bioprocess for production of compatible solutes.

A novel biotechnological process called "bacterial milking" has been established for the production of compatible solutes using the Gram-negative bacterium Halomonas elongata. Following a high-cell-density fermentation which provided biomass up to 48 g cell dry weight per liter, we applied alternating osmotic shocks in combination with crossflow filtration techniques to harvest the compatible solutes ectoine and hydroxyectoine. H. elongata, like other halophilic or halotolerant microorganisms, produces compatible solutes in response to the salinity of the medium. When transferred to a low salinity medium (osmotic downshock), H. elongata cells rapidly released their solutes to achieve osmotic equilibrium. Subsequent reincubation in a medium of higher salt concentration resulted in resynthesis of these compatible solutes and-after a defined regeneration time-the procedure could be repeated. By repeatedly performing this "bacterial milking" process (at least nine times) we were able to produce large amounts of ectoines with a biomass productivity of 155 mg of ectoine per cycle per gram cell dry weight. Further purification of the products was achieved by a simple two-step procedure based on cation exchange chromatography and crystallization. The principles described in this article may also be useful for the production of other low-molecular-weight compounds.

Amino Acids, Diamino↗
PubMed2000

A fluctuating salinity regime mitigates the negative effects of reduced salinity on the estuarine macroalga, Enteromorpha intestinalis (L.) link.

We tested the response of Enteromorpha intestinalis to fluctuating reduced salinity regimes which may occur in coastal estuaries due to both natural and anthropogenic influences. In a fully crossed two factor experiment, we subjected E. intestinalis to 0, 5, 15 and 25 psu water enriched with nutrients for 1-, 5-, 11- and 23-day periods. Each period was followed by 24 h of exposure to 25 psu (ambient) water that was not nutrient enriched. Following 24 h in ambient salinity water, algae were returned to reduced salinity conditions for the appropriate period and the cycle continued over the 24 days for which all treatments were maintained. Exposure to 0 psu for 5 days or longer resulted in loss of pigmentation, decreased wet and dry biomass, increased wet wt:dry wt ratios, decreased removal of nitrogen (N) and phosphorus (P) from the water column and an accumulation of NH(4) in the water column. More frequent exposure to ambient salinity in the 1-day treatment mitigated these effects. Across all salinity levels tested, biomass increased as frequency of exposure to ambient salinity increased. At all durations of exposure to low salinity tested, biomass increased as salinity level increased. We conclude that growth of E. intestinalis is decreased by reduced salinity. E. intestinalis is able to withstand exposure to 0 psu but there is a temporal limit to this tolerance that is somewhere between 1 and 5 days. Populations of E. intestinalis in coastal estuaries may suffer from freshwater inputs if salinity conditions are persistently reduced.

Journal Article↗
PubMed2001

Spiniferites cruciformis: a fresh water dinoflagellate cyst?

Palynological studies of cored lacustrine sediments from the late Quaternary of Lake Kastoria, northern Greece, revealed a Late Glacial interval with abundant dinoflagellate cysts. Cyst assemblages include two identifiable species, Spiniferites cruciformis and Gonyaulax apiculata. The presence of the fresh water species G. apiculata is consistent with the lacustrine setting of these deposits, but that of S. cruciformis is anomalous. Previously, this species has only been recorded in abundance from presumed brackish marine sediments from the Black Sea and Marmara Sea sediments where geochemical data clearly record brackish salinities. Therefore, it has been regarded as a low salinity cyst type with a wide range of morphological variation that some workers have suggested to reflect salinity fluctuations. Specimens from Greece display only part of the range of morphological variability previously described from these (brackish) marine settings. Encountered morphological variation includes ellipsoidal/pentameral and cruciform endocyst shapes with rare intermediate shapes, and highly variable septa development. Specimens characterized by extremely reduced ornamentation known from (brackish) marine environments have not been recorded. Our records of S. cruciformis indicate that: (1) it could thrive in fresh water conditions; and (2) that apparently most of the strong morphological variations of the cysts are an intrinsic phenomenon for this taxon, and may only partly be linked to salinity variations as suggested earlier. We suggest that S. cruciformis essentially is a fresh water taxon, and that its records in (brackish) marine environments, with the exception of specimens with strongly reduced ornamentation, may be due to transportation, to short-lived fresh water surface conditions in such environments, or to tolerance of the species to brackish conditions.

Journal Article↗
PubMed1996

Differentially transcribed regions of Haloferax volcanii genome depending on the medium salinity.

To identify genomic regions involved in osmoregulation in the extremely halophilic archaeon Haloferax volcanii, we used a technique which involves hybridization of cDNAs obtained at different salinities against a cosmid library of the organism. Both low and high salt concentrations trigger differential expression; however, adaptation to low salinities seems to elicit a wider response. The presence of a large domain within the largest of the megaplasmids with a strong response to low salt concentrations is noteworthy.

Blotting, Northern↗
PubMed1990

Entrainment of bimodal circatidal rhythms in the shore crab Carcinus maenas.

Individuals of the shore crab Carcinus maenas were exposed to artificial cycles, applied in tidal antiphase, of pairs of the three major environmental variables that entrain circatidal rhythmicity in this species: salinity, temperature, and hydrostatic pressure. During entrainment, the observed locomotor activity patterns were dominated by exogenous responses to high pressure, low temperature, or low salinity. In subsequent constant conditions, many of the crabs showed bimodal circatidal rhythms, with peaks phased to the times of expected high-tide characteristics of high pressure, low temperature, or high salinity. Similar bimodal rhythms were induced by exposing freshly captured crabs, with free-running circatidal rhythms, to tidal antiphase cycles of each of the three environmental variables applied individually. The hypothesis that circatidal rhythmicity in this species is controlled by at least two separate circatidal oscillators, with differential sensitivities to specific cyclical environmental variables, is discussed.

Animals↗
PubMed2001

Physical, chemical, and microbiological characteristics of microbial mats (kopara) in the South Pacific atolls of French Polynesia.

Microbial mats that develop in shallow brackish and hyposaline ponds in the rims of two French polynesian atolls (Rangiroa and Tetiaroa) were intensively investigated during the past three years. Comparative assessment of these mats (called kopara in polynesian language) showed remarkable similarities in their composition and structure. Due to the lack of iron, the color of the cyanobacterial pigments produced remained visible through the entire depth of the mats (20-40 cm depth), with alternate green, purple, and pink layers. Profiles of oxygen, sulfide, pH, and redox showed the anoxia of all mats from a depth of 2-3 mm. Analyses of bacterial pigments and bacterial lipids showed that all mats consisted of stratified layers of cyanobacteria (mainly Phormidium, Schizothrix, Scytonema) and purple and green phototrophic bacteria. The purple and green phototrophic bacteria cohabit with sulfate reducers (Desulfovibrio and Desulfobacter) and other heterotrophic bacteria. The microscopic bacterial determination emphasized the influence of salinity on the bacterial diversity, with higher diversity at low salinity, mainly for purple nonsulfur bacteria. Analyses of organic material and of exopolymers were also undertaken. Difference and similarities between mats from geomorphological, microbiological, and chemical points of view are discussed to provide multicriteria of classification of mats.

Bacteria↗
PubMed1997

Numerical dominance of a group of marine bacteria in the alpha-subclass of the class Proteobacteria in coastal seawater.

A cluster of marine bacteria within the alpha-3 subclass of the class Proteobacteria accounted for up to 28% of the 16S ribosomal DNA (rDNA) sequences in seawater samples from the coast of the southeastern United States. Two independent oligonucleotide probes targeting 16S rDNA of this "marine alpha" cluster indicate that the group dominates bacterioplankton communities in estuarine and nearshore regions of the southeastern U.S. coast. Marine alpha bacteria decline predictably in abundance with decreasing salinity along estuarine transsects and are not detectable in low-salinity (5%) or freshwater samples. Sequences of 16S rDNA obtained from seawater by PCR with one group-specific oligonucleotide as a primer confirm that the oligonucleotide targets only members of this phylogenetic cluster. Likewise, sequences of 16S rDNA obtained from seawater by PCR with several different pairs of nonspecific primers show an unusually high abundance of marine alpha sequences (52 to 84%) among the clones, which possibly indicates a PCR bias toward the group. Members of the marine alpha group were readily cultured from coastal seawater, accounting for 40% of the colonies isolated on low-nutrient marine agar, based on hybridizations with the group-specific 16S rDNA probe and on sequence analysis. This is the first description of a numerically dominant cluster of coastal bacteria, identified by molecular techniques, that can be readily cultured and studied in the laboratory.

Bacteria↗
PubMed1988

Salinity Effects on Photosynthesis, Carbon Allocation, and Nitrogen Assimilation in the Red Alga, Gelidium coulteri.

The long-term effects of altered salinities on the physiology of the intertidal red alga Gelidium coulteri Harv. were assessed. Plants were transfered from 30 grams per liter salinity to media with salinities from 0 to 50 grams per liter. Growth rate, agar, photosynthesis, respiration, and various metabolites were quantified after 5 days and 5 weeks adaptation. After 5 days, growth rates were lower for plants at all altered salinities. Growth rates recovered from these values with 5 weeks adaptation, except for salinities of 10 grams per liter and below, where tissues bleached and died. Photosynthetic O(2) evolution was lower than control values at both higher and lower salinities after 5 days and did not change over time. Carbon fixation at the altered salinities was unchanged after 5 days, but decreased below 25 grams per liter and above 40 grams per liter after 5 weeks. Respiration increased at lower salinities. Phycobili-protein and chlorophyll were lower for all altered salinities after 5 days. These decreases continued at lower salinities, then were stable after 5 weeks. Chlorophyll recovered over time at higher salinities. Decreases in protein at lower salinities were quantitatively attributable to phycobili-protein loss. Total N levels and C:N ratios were nearly constant across all salinities tested. Carbon flow into glutamate and aspartate decreased with both decreasing and increasing salinities. Glycine, serine, and glycolate levels increased with both increasing and decreasing salinity, indicating a stimulation of photorespiration. The cell wall component agar increased with decreasing salinity, although biosynthesis was inhibited at both higher and lower salinities. The storage compound floridoside increased with increasing salinity. The evidence suggests stress responses to altered salinities that directly affected photosynthesis, respiration, and nitrogen assimilation and indirectly affected photosynthate flow. At low salinities, respiration and photorespiration exceeded photosynthesis with lethal results. At higher salinities, although photosynthesis was inhibited, respiration was low and carbon fixation adequate to offset increased photorespiration.

Journal Article↗
PubMed2006

Removal of chromium ions from [corrected] aqueous solutions by adsorption on activated carbon and char.

Adsorption isotherms of chromium ions in aqueous solution have been experimentally measured on a granular activated carbon (GAC) and on a char of South African coal (CSAC). Experimental results show that the adsorption capacity for the GAC strongly depends on solution pH and salinity, with maximum values around 7mg/g at neutral pH and low salinity levels. On the contrary, the CSAC shows a smaller adsorption capacity, near 0.3mg/g, which slightly decreases by increasing pH and salinity levels. Chromium adsorption mainly depends on the availability of chromium ions in solution and on the occurrence of redox reactions between the surface groups and the Cr(VI) which lead to the formation of Cr(III). The reduction of Cr(VI) and the following sorption of Cr(III) cations appears as the leading mechanism for chromium uptake on the CSAC. A similar behaviour can be observed for the GAC at pH below 3. On the contrary, at pH>7, the multicomponent competitive adsorption of Cr(VI), OH(-) and Cl(-) has to be considered.

Adsorption↗
PubMed2003

Misidentification of Aeromonas veronii biovar sobria as Vibrio alginolyticus by the Vitek system.

AIMS: To find the cause of misidentification of aeromonads when using the Vitek system. METHODS AND RESULTS: Two Aeromonas veronii biovar sobria isolates were misidentified as Vibrio alginolyticus by the Vitek system. Both strains' identification was confirmed by biochemical testing, API 20E/20NE kits and/or 16S RFLP analysis. Thirty-one known Aeromonas species were tested by the Vitek system using 0.45 and 0.85% saline in the suspension medium. It was not clear whether low salinity causes misidentification of Aeromonas species more frequently. CONCLUSIONS: The specified reaction time may be inappropriately short for some critical biochemical tests of some strains. An ingenious reading strategy regarding incubation time is necessary to improve identification of Aeromonas species by the Vitek system. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report of misidentification of A. veronii biovar sobria as V. alginolyticus in the Vitek system.

Aeromonas↗
PubMed1976

Incidence of Salmonella spp., Clostridium botulinum, and Vibrio parahaemolyticus in an estuary.

A study of the incidence of Salmonella spp., Vibrio parahaemolyticus-like organisms, and clostridium botulinum in samples collected at five stations located in the Upper Chesapeake Bay, a major estuary on the Atlantic Coast of the United States, was conducted in December 1973 through December 1974. C. botulinum types B and E were detected in 12.3% of the total sediment samples examined. V. parahaemolyticus was recovered from 10.4% of a total of 86 water, sediment, and suspended sediment samples. Of 131 samples examined for the presence of Salmonella spp., approximately 3% were found to be positive for serologically confirmed Salmonella isolates. Shellfish examined during the investigation were also found to be free of enteric pathogens. The low frequency of occurrence of V. parahaemolyticus was attributed to the low salinities encountered at the sites included in the study. A low incidence of Salmonella spp. in the Upper Chesapeake Bay samples was found, whereas the distribution of C. botulinum appeared to be both random and autochthonous. A strong relationship between presence of potential pathogens and other generally accepted microbiological indicators of pollution was not observed.

Animals↗
PubMed2003

[Impact of salt stress on peroxidase activity in Populus deltoides cambium and its consequence].

Studies on the impact of salt stress on the peroxidase (POD) activity in Populus deltoides cambium and on the anatomic characteristics of its secondary xylem indicated that the changes of POD activity caused by soil salinity stress behaved differently in dormant and growing period. In low salinity soil, the POD activity of dormant Populus deltoides showed the trend of increasing first, and then, decreasing as the soil salinity was rising gradually. Namely, with the rising of soil salinity in the range of 0.024-->0.094-->0.145%, the POD activity varied in the range of 83.7-->132.1-->63.2 units.min-1.g-1FW accordingly. However, in growing season, with the gradual increase of soil salinity from 0.036 to 0.289%, the POD activity decreased gradually from 405.2 to 107.2 units.min-1.g-1FW. There were regular changes in wood anatomic characteristics of Populus deltoides. Namely, with the increase of soil salinity 0.036-->0.125-->0.289%, the vessel diameters (VD) of both early wood and late wood varied accordingly in the range of 41.8-->56.6-->43.4 microns, and 29.1-->33.1-->33.1 microns, respectively. The vessel frequencies (VF) were 141.8-->113.8-->144.2 and 160.0-->134.8-->206.7 entries mm-2, respectively. Along with the gradual increase of soil salinity from 0.036 to 0.289%, the fiber length gradually decreased from 693.8 to 570.4 microns, and the fiber width decreased from 14.9 to 13.5 microns.

Ecology↗
PubMed2003

Environment affects stress in exercised turbot.

We investigated the interaction of water temperature (10, 18 and 22 degrees C) and salinity (33.5 and 15 per thousand ) on the stress response of juvenile turbot. At each temperature/salinity combination, fish were subjected to 10 min enforced exercise. This induced a moderate stress response, which differed at the various temperature and salinity combinations. High temperatures caused more rapid increases in plasma cortisol and glucose, larger and more rapid increases in plasma lactate levels, which were also influenced by body weight, and a faster recovery in plasma Na(+) and Cl(-). Low salinity ameliorated cortisol responses at low but not at high temperatures. The magnitude of ionic disturbance was reduced at 15 per thousand. Plasma K(+) did not change at any temperature or salinity. The stress response involved activation of the brain-pituitary-interrenal axis, as indicated by the cortisol elevations. The low magnitude of glucose responses, the mild Na(+) and Cl(-) disturbances, and the lacking K(+)-responses indicated mild activation of the brain-sympathetic-chromaffin cell axis, and hence a low release of catecholamines, which seemed though to occur to a higher extent at higher temperatures. The relatively low catecholaminergic response of turbot may be linked to their inactive sedentary lifestyle. The higher responsiveness at higher water temperatures may reflect a higher overall adaptive capacity.

Animals↗
PubMed2003

Arbuscular mycorrhizal fungal propagules in a salt marsh.

The tolerance of indigenous arbuscular mycorrhizal fungi (AMF) to stressful soil conditions and the relative contribution of spores of these fungi to plant colonization were examined in a Portuguese salt marsh. Glomus geosporum is dominant in this salt marsh. Using tetrazolium as a vital stain, a high proportion of field-collected spores were found to be metabolically active at all sampling dates. Spore germination tests showed that salt marsh spores were not affected by increasing levels of salinity, in contrast to two non-marsh spore isolates, and had a significantly higher ability to germinate under increased levels of salinity (20 per thousand) than in the absence of or at low salinity (10 per thousand). Germination of salt marsh spores was not affected by soil water levels above field capacity, in contrast to one of the two non-marsh spore isolates. For the evaluation of infectivity, a bioassay was established with undisturbed soil cores (containing all types of AM fungal propagules) and soil cores containing only spores as AM fungal propagules. Different types of propagules were able to initiate and to expand the root colonization of a native plant species, but spores were slower than mycelium and/or root fragments in colonizing host roots. The AM fungal adaptation shown by this study may explain the maintenance of AMF in salt marshes.

Ecosystem↗
PubMed2004

Transport of the harmful bloom alga Aureococcus anophagefferens by oceangoing ships and coastal boats.

It is well established that cyst-forming phytoplankton species are transported in ships' ballast tanks. However, there is increasing evidence that other phytoplankton species which do not encyst are also capable of surviving ballast transit. These species have alternative modes of nutrition (hetero- or mixotrophy) and/or are able to survive long-term darkness. In our studies of no-ballast-on-board vessels arriving in the Great Lakes, we tested for the presence of the harmful algal bloom species Aureococcus anophagefferens (brown tide) in residual (i.e., unpumpable) ballast water using methods based on the PCR. During 2001, the brown tide organism was detected in 7 of 18 ballast water tanks in commercial ships following transit from foreign ports. Furthermore, it was detected after 10 days of ballast tank confinement during a vessel transit in the Great Lakes, a significant result given the large disparity between the salinity tolerance for active growth of Aureococcus (>22 ppt) and the low salinity of the residual ballast water (approximately 2 ppt). We also investigated the potential for smaller, recreational vessels to transport and distribute Aureococcus. During the summer of 2002, 11 trailered boats from the inland bays of Delaware and coastal bays of Maryland were sampled. Brown tide was detected in the bilge water in the bottoms of eight boats, as well as in one live-well sample. Commercial ships and small recreational boats are therefore implicated as potential vectors for long-distance transport and local-scale dispersal of Aureococcus.

DNA, Ribosomal↗
PubMed1993

Energy flux and osmoregulation of Saccharomyces cerevisiae grown in chemostats under NaCl stress.

The energetics and accumulation of solutes in Saccharomyces cerevisiae were investigated for cells grown aerobically in a chemostat under NaCl stress and glucose limitation. Changed energy requirements in relation to external salinity were examined by energy balance determinations performed by substrate and product analyses, with the latter including heat measurements by microcalorimetry. In both 0 and 0.9 M NaCl cultures, the catabolism was entirely respiratory at the lowest dilution rates tested but shifted to a mixed respiratory-fermentative metabolism at higher dilution rates. This shift occurred at a considerably lower dilution rate for salt-grown cells. The intracellular solute concentrations, as calculated on the basis of intracellular soluble space determinations, showed that the internal Na+ concentration increased from about 0.02 molal in basal medium to about 0.18 molal in 0.9 M NaCl medium, while intracellular K+ was maintained around 0.29 molal despite the variation in external salinity. The intracellular glycerol concentration increased from below 0.05 molal at low salinity to about 1.2 molal at 0.9 M NaCl. The concentrations of the internal solutes, however, changed insignificantly with growth rate and energy metabolism. The additional maintenance energy expenditure for growth at 0.9 M NaCl was, depending on the growth rate, 14 to 31% of the total energy requirement for growth at 0 M NaCl. Including the energy conserved in glycerol, the total additional energy demand for growth at 0.9 M NaCl corresponded to 28 to 51% of the energy required for growth at 0 M NaCl.

Adenosine Triphosphate↗
PubMed2003

Osmotic, sodium, carbon dioxide and acid-base state of the Port Jackson shark, Heterodontus portusjacksoni, in response to lowered salinity.

In marine elasmobranch fish the consequences for CO2 and acid-base state of moving into low salinity water are not well described. Sub-adult Port Jackson sharks, Heterodontus portusjacksoni, occasionally enter brackish water and survive in 50% seawater (SW). The unidirectional Na efflux and content, plasma volume, glomerular filtration rate (GFR), body mass, as well as CO2 and acid-base state in H. portusjacksoni were investigated following transfer from 100% SW to 75% SW and then to 50% SW. A rapid water influx resulted in a doubling of the plasma volume within 24 h in sharks in 75% SW and an 11% increase in body weight. Osmotic water influx was only partially offset by a doubling of the GFR. There was a approximately 40% decrease in plasma [Na] through a transiently elevated Na clearance and haemodilution. The result was a decrease in the inward gradient for Na+ together with reductions of nearly 50% in CO2 and buffer capacity. The sharks remained hypo-natric to 50% SW by partially conforming to the decrease in external osmotic pressure and avoided the need for active Na+ uptake. The gradient for Na+ efflux would by extrapolation approach zero at approximately 27% SW which may of itself prove a lethal internal dilution. In sharks transferred to 75% SW, a small transient hypercapnia and a later temporary metabolic alkalosis were all largely explained through anaemia promoting loss of CO2 and buffer capacity. In sharks transferred to 50% SW the metabolic alkalosis persisted until the end of the 1-week trial. Within the erythrocytes, increased pH was consequent on the large decrease in haemoglobin content exhibited by the sharks, which caused a large reduction in intracellular buffer. In water as dilute as 50% SW there was no evidence of specific effects on the mechanisms of management of CO2 or H+ excretion but rather significant and indirect effects of the severe haemodilution.

Acclimatization↗