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At least 523 records · Page 29Linked to original sources
PubMed1996

A salt-resistant plasma membrane carbonic anhydrase is induced by salt in Dunaliella salina.

The mechanisms allowing proliferation of the unicellular green alga Dunaliella salina in up to saturating NaCl concentrations are only partially understood at present. Previously, the level of a plasma membrane Mr 60,000 protein, p60, was found to increase with rising external salinities. Based on cDNA cloning and enzymatic assays, it is now shown that p60 is an internally duplicated carbonic anhydrase, with each repeat homologous to animal and Chlamydomonas reinhardtii carbonic anhydrases, but exceptional in the excess of acidic over basic residues. Increasing salinities, alkaline shift, or removal of bicarbonate induced in D. salina parallel increases in the levels of p60, its mRNA, and external carbonic anhydrase activity. Moreover, purified p60 exhibited carbonic anhydrase activity comparable to other carbonic anhydrases. A p60-enriched soluble preparation showed maximal carbonic anhydrase activity at approximately 1.0 M NaCl and retained considerable activity at higher salt concentrations. In contrast, a similar preparation from C. reinhardtii was approximately 90% inhibited in 0.6 M NaCl. These results identified p60 as a structurally novel carbonic anhydrase transcriptionally regulated by CO2 availability and exhibiting halophilic-like characteristics. This enzyme is potentially suited to optimize CO2 uptake by cells growing in hypersaline media.

Alkalies↗
PubMed1991

Sodium regulation in the affinity of renal alpha 2-adrenoceptors for epinephrine in Sabra salt-sensitive and salt-resistant rats.

Sodium ions markedly decreased in vitro renal alpha 2-adrenoceptor affinity for epinephrine in Sabra hypertensive (SBH) but not in normotensive (SBN) rats. Under these conditions, affinity of alpha 1-adrenoceptor for epinephrine was unchanged in SBH and SBN rats. If these data could be confirmed in vivo, the sodium ion, by acting as an inhibitor, could modify the effect of agonists on renal alpha 2-adrenoceptors in SBH rats. Conversely, the absence of sodium regulation in SBN rats might represent a genetically mediated change responsible for the resistance to the development of salt-induced hypertension.

Animals↗
PubMed1983

Characterization of DNA structures by Raman spectroscopy: high-salt and low-salt forms of double helical poly(dG-dC) in H2O and D2O solutions and application to B, Z and A-DNA.

Raman spectra of poly(dG-dC) . poly(dG-dC) in D2O solutions of high (4.0M NaCl) and low-salt (0.1M NaCl) exhibit differences due to different nucleotide conformations and secondary structures of Z and B-DNA. Characteristic carbonyl modes in the 1600-1700 cm-1 region also reflect differences in base pair hydrogen bonding of the respective GC complexes. Comparison with A-DNA confirms the uniqueness of C = O stretching frequencies in each of the three DNA secondary structures. Most useful for qualitative identification of B, Z and A-DNA structures are the intense Raman lines of the phosphodiester backbone in the 750-850 cm-1 region. A conformation-sensitive guanine mode, which yields Raman lines near 682, 668, or 625 cm-1 in B (C2'-endo, anti), A (C3'-endo, anti) or Z (C3'-endo, syn) structures, respectively, is the most useful for quantitative analysis. In D2O, the guanine line of Z-DNA is shifted to 615 cm-1, permitting its detection even in the presence of proteins.

DNA↗
PubMed2000

High DNA sequence variability at the alpha 1 Na/K-ATPase locus of Artemia franciscana (brine shrimp): polymorphism in a gene for salt-resistance in a salt-resistant organism.

We previously reported that the Na/K-ATPase alpha 1 subunit coding gene showed signs of being a very polymorphic locus in Artemia franciscana. This species is adapted to highly saline waters, and the Na/K-ATPase alpha 1 isoform presumably plays a key role in this adaptation. Therefore, we were interested in further study of the alpha 1 Na/K-ATPase polymorphisms to examine whether they might be due to an adaptation to salt resistance driven by natural selection. Using coding sequences from 10 genomic clones and 3 cDNAs, we observed that most substitutions are in synonymous positions (88.8%). The 12 nonsynonymous substitutions code for conservative amino acid replacements with an apparent scattered distribution across functional domains of the protein. Interspecific comparison between these sequences and two genomic clones from Artemia parthenogenetica containing 1,122 bp of the alpha 1 Na/K-ATPase locus coding sequence showed independence of the synonymous/nonsynonymous ratio in the comparison within A. franciscana and between A. franciscana and A. parthenogenetica, which fits the neutral model of evolution. Since there were no previous studies on DNA polymorphism for other A. franciscana genes, we also studied variability at the Actin 302 locus for comparison. Both loci were amplified by reverse transcription-polymerase chain reaction, and 20 sequences were obtained for each. This study shows that the amplified region of the alpha 1 Na/K-ATPase gene is 3.5 times as polymorphic as the Actin 302 gene and 2.9 times as heterozygotic. Interestingly, under a model of neutral evolution, the data observed would be expected with a probability of approximately 0.05, suggesting an excess of intraspecific variation of alpha 1 Na/K-ATPase with respect to Actin 302. Restriction fragment length polymorphism studies show similar patterns of polymorphism along the approximately 41-kb span of the alpha 1 Na/K-ATPase locus. Most of the nucleotide differences are linked in a few haplotypes, although recombination events are also inferred from the data. We propose a possible explanation for the high polymorphic levels at the alpha 1 Na/K-ATPase locus which invokes positive selection acting tightly to the locus in transiently isolated or semi-isolated subpopulations.

Actins↗
PubMed1994

Effects of NaCl on Flows of N and Mineral Ions and on NO3- Reduction Rate within Whole Plants of Salt-Sensitive Bean and Salt-Tolerant Cotton.

The effects of NaCl on the transport rates of cations, NO3-, and reduced N compounds between roots and shoot and on NO3- assimilation rate were examined on plants of two species differing in their sensitivity to salinity, bean (Phaseolus vulgare L. cv Gabriella) and cotton (Gossypium hirsutum L. cv Akala). Biomass production after 20 d in response to 50 and 100 mM NaCl decreased by 48 and 59% in bean, but only 6 and 14% in cotton. The comparison of the flow patterns obtained for control and NaCl-fed plants showed that salinity induced a general decrease in all the fluxes involved in partitioning of N and the various ions. This decrease was markedly higher in bean than in cotton. Within either species, the different flows (uptake, xylem flux, phloem flux) of a given element were affected by NaCl to the same extent with minor exceptions. No specific effect of salinity on any of the components of N partitioning were discerned. The greater sensitivity of nitrate reductase activity to NaCl in bean leaves compared to cotton leaves seems to be due to a decreased compartmentalization of ions rather than to a difference in salt tolerance of the enzyme itself. Overall, our data show that alteration of mineral nutrition is not solely the reflection of a decreased growth rate, but also is a general process that impairs uptake of all the minerals even at mild NaCl salinity.

Journal Article↗
PubMed1987

Salt tolerance in suspension cultures of sugar beet : induction of na/h antiport activity at the tonoplast by growth in salt.

Cell suspension cultures of sugar beet were grown at various salinities (0-200 millimolar NaCl). Their tolerance to Na(+) was comparable to that of the intact plant. Tonoplast vesicles were prepared by sucrose density gradient centrifugation of microsomal membranes and shown to be highly purified. The vesicles were subjected to a pH jump in the presence of acridine orange and the rate of recovery of fluorescence after addition of Na(+) was used as a measure of Na(+)-dependent H(+) efflux. In the presence of K(+) and valinomycin, the Na(+)/H(+) antiport showed saturation kinetics. Increasing Na(+) in the growth medium did not change the apparent K(m) for Na(+), but increased V(max) to about twice the control value, suggesting a specific induction of antiport synthesis by salt.

Journal Article↗
PubMed1996

Salt stress-induced proline transporters and salt stress-repressed broad specificity amino acid permeases identified by suppression of a yeast amino acid permease-targeting mutant.

A yeast mutant lacking SHR3, a protein specifically required for correct targeting of plasma membrane amino acid permeases, was used to study the targeting of plant transporters and as a tool to isolate new SHR3-independent amino acid transporters. For this purpose, an shr3 mutant was transformed with an Arabidopsis cDNA library. Thirty-four clones were capable of growth under selective conditions, but none showed homology with SHR3. However, genes encoding eight different amino acid transporters belonging to three different transporter families were isolated. Five of these are members of the general amino acid permease (AAP) gene family, one is a member of the NTR family, encoding an oligopeptide transporter, and two belong to a new class of transporter genes. A functional analysis of the latter two genes revealed that they encode specific proline transporters (ProT) that are distantly related to the AAP gene family. ProT1 was found to be expressed in all organs, but highest levels were found in roots, stems, and flowers. Expression in flowers was highest in the floral stalk phloem that enters the carpels and was downregulated after fertilization, indicating a specific role in supplying the ovules with proline. ProT2 transcripts were found ubiquitously throughout the plant, but expression was strongly induced under water or salt stress, implying that ProT2 plays an important role in nitrogen distribution during water stress, unlike members of the AAP gene family whose expression was repressed under the same conditions. These results corroborate the general finding that under water stress, amino acid export is impaired whereas proline export is increased.

Amino Acid Sequence↗
PubMed2000

Terephthalate salts: salts of monopositive cations

The crystal structures of dilithium, disodium and diammonium terephthalate (1,4-benzenedicarboxylate) have been solved ab initio using Monte Carlo simulated annealing techniques, and refined using synchrotron powder data. The structures of dipotassium terephthalate, potassium hydrogen terephthalate and ammonium hydrogen terephthalate have been refined using single-crystal techniques. Li2C8H4O4 crystallizes in P2(1)/c, with a = 8.35921 (5), b = 5.13208 (2), c = 8.48490 (5) A, beta = 93.1552 (4) degrees, V = 363.451 (3) A3, Z = 2. The Li anions are tetrahedrally coordinated and the packing of the terephthalate anions resembles the gamma-packing of aromatic hydrocarbons. Na2C8H4O4 crystallizes in Pbc2(1), with a = 3.54804 (5), b = 10.81604 (16), c = 18.99430 (20) A, V = 728.92 (2) A3, Z = 4. The coordination of the two independent Na is trigonal prismatic and the terephthalate packing resembles the beta packing of hydrocarbons. (NH4)2C8H4O4 also crystallizes in Pbc2(1), with a = 4.0053 (5), b = 11.8136 (21), c = 20.1857 (24) A, V = 955.1 (2) A3, Z = 4. The cations and planar anions are linked by hydrogen bonds and the packing is a looser version of the beta packing. K2C8H4O2 crystallizes in P2(1)/c, with a = 10.561 (4), b = 3.9440 (12), c = 11.535 (5) A, beta = 113.08 (3) degrees, V = 442.0 (3) A3, Z = 2. The K is trigonal prismatic and the packing is also beta. Both KHC8H4O4 and (NH4)HC8H4O4 crystallize in C2/c, with a = 18.825 (4) and 18.924 (4), b = 3.770 (2) and 3.7967 (9), c = 11.179 (2) and 11.481 (2) A, beta = 98.04 (3) and 94.56 (5) degrees, V = 816.8 (3) and 790.9 (3) A3, respectively, and Z = 4. The packing in the hydrogen-bonded acid salts is also beta. Electrostatic interactions among the terephthalate anions appear to be important in determining the crystal packing.

Journal Article↗
PubMed1984

Growth potential of halophilic bacteria isolated from solar salt environments: carbon sources and salt requirements.

Eighteen strains of extremely halophilic bacteria and three strains of moderately halophilic bacteria were isolated from four different solar salt environments. Growth tests on carbohydrates, low-molecular-weight carboxylic acids, and complex medium demonstrated that the moderate halophiles and strains of the extreme halophiles Haloarcula and Halococcus grew on most of the substrates tested. Among the Halobacterium isolates were several metabolic groups: strains that grew on a broad range of substrates and strains that were essentially confined to either amino acid (peptone) or carbohydrate oxidation. One strain (WS-4) only grew well on pyruvate and acetate. Most strains of extreme halophiles grew by anaerobic fermentation and possibly by nitrate reduction. Tests of growth potential in natural saltern brines demonstrated that none of the halobacteria grew well in brines which harbor the densest populations of these bacteria in solar salterns. All grew best in brines which were unsaturated with NaCl. The high concentrations of Na and Mg found in saltern crystallizer brines limited bacterial growth, but the concentrations of K found in these brines had little effect. MgSO(4) was relatively more inhibitory to the extreme halophiles than was MgCl(2), but the reverse was true for the moderate halophiles.

Journal Article↗
PubMedDate not supplied

Proteins binding to kallikrein and esterase A2 in the urine of salt-sensitive and salt-resistant rats.

Iodine-labeled ([125I]) rat urinary kallikrein and rat urinary TAME esterase A2 were used as probes to look for urinary and plasma proteins that bind to these enzymes. Such proteins are presumptive enzyme inhibitors. Complexes formed with labeled enzymes were identified by polyacrylamide gel electrophoresis followed by autoradiography. Urine from young (6 weeks old) Dahl salt-sensitive (S) rats showed no, or only traces, of protein binding to kallikrein. Concomitant with the slow development of hypertension and proteinuria in S rats fed normal rat chow, one of the six kallikrein-binding proteins demonstrable in plasma was readily found in S-rat urine. This kallikrein-binding protein was called "KBP-1." R rats showed either no or much less KBP-1 in the urine, compared to S rats up to 5 months of age. A partly purified preparation of KBP-1 was shown to inhibit the TAME esterase activity of rat urinary kallikrein in the radiometric TAME assay. Urine of proteinuric S rats also contained two TAME esterase-binding proteins, TEBP-1 and TEBP-2, detected with the [125I]-esterase A2 probe. As S rats aged from 3 to 8 months, free KBP-1 disappeared from the urine in spite of increased and marked proteinuria and the continued presence of KBP-1 in plasma. Concomitant with this age-related loss of urinary KBP-1 there was a marked shift in S urinary proteins binding to [125I]-esterase A2 from TEBP-1 to TEBP-2. It was speculated that KBP-1 and TEBP-1 were the same protein detectable with either labeled kallikrein or labeled esterase A2. The concomitant disappearance of free KBP-1 (TEBP-1) and the appearance of free TEBP-2 in the urine of old, hypertensive, proteinuric S rats suggests that: 1) most of the KBP-1 (TEBP-1) is bound to enzyme(s) in old rats; or 2) KBP-1 (TEBP-1) is largely converted to TEBP-2 in old rats; or 3) both are true and that binding of KBP-1 (TEBP-1) to enzymes is associated with the generation of TEBP-2.

Animals↗
PubMed1998

Comparative study of rice-based oral rehydration salt solution versus glucose-based oral rehydration salt solution (WHO) in children with acute dehydrating diarrhoea.

One hundred children with acute dehydrating diarrhoea were studied. They were divided into two groups: Group A (n = 50) were given rice-based oral rehydration salt (ORS) solution and group B (n = 50) were given glucose-based ORS solution (WHO). There was no significant decrease in mean stool output and percentage weight gain with rice-based ORS. Both the groups were comparable for volume of ORS solution consumed, time taken for initial rehydration, mean stool output and for correcting biochemical abnormalities.

Acute Disease↗
PubMedDate not supplied

[The effect of the table salt substitute sanasol on arterial pressure, water-salt metabolism and kidney functions in experimental pathology of circulatory homeostasis].

The potassium-containing salt substitute sanasol was examined for its effects on blood pressure and renal function in normo- and hypertensive rats, as well as on the edematous syndrome in circulatory insufficiency. The antihypertensive and occasional antiedematous effects of sanasol resulted in unfavorable changes in electrolyte balance. Sanasol was found to be ineffective in experimental renal failure.

Animals↗
PubMed1991

Swedish Aspirin Low-Dose Trial (SALT) of 75 mg aspirin as secondary prophylaxis after cerebrovascular ischaemic events. The SALT Collaborative Group.

The efficacy of aspirin in daily doses of 300 mg and more as secondary prophylaxis after cerebrovascular events is well established. Since much lower doses of aspirin can inhibit platelet function, and carry a lower risk of adverse effects, the Swedish Aspirin Low-dose Trial (SALT) was set up to study the efficacy of 75 mg aspirin daily in prevention of stroke and death after transient ischaemic attack (TIA) or minor stroke. 1360 patients entered the study 1-4 months after the qualifying event: 676 were randomly assigned to aspirin treatment and 684 to placebo treatment. The median duration of follow-up was 32 months. Compared with the placebo group, the aspirin group showed a reduction of 18% in the risk of primary outcome events (stroke or death; relative risk 0.82, 95% confidence interval 0.67-0.99; log-rank analysis p = 0.02), and reductions of 16-20% in the risks of secondary outcome events (stroke; stroke or two or more TIAs within a week of each other necessitating a change of treatment; or myocardial infarction). Adverse drug effects were reported by 147 aspirin-treated and 123 placebo-treated patients Gastrointestinal side-effects were only slightly more common in the aspirin-treated patients, but that group had a significant excess of bleeding episodes (p = 0.04). Thus, we have found that a low dose (75 mg/day) of aspirin significantly reduces the risk of stroke or death in patients with cerebrovascular ischaemic events.

Aspirin↗
PubMed1990

Fasting and 24-h urinary sodium/creatinine values in young and elderly women on low-salt and salt-supplemented regimens.

A high sodium intake is a risk factor for both hypertension and osteoporosis. High-salt diets cause calciuresis and may influence blood pressure (BP) by stimulating calcium-regulating hormones and augmenting intracellular calcium concentrations. Urinary calcium rises in parallel with urinary sodium. However, aging may influence the rate of excretion of a dietary sodium load. This study compares sodium/creatinine (Na/Cr) values in 2-h urines collected after an overnight fast (12 h) with values obtained in 24-h urines from normotensive women aged (a) 19-23 years (n = 6) and (b) 65-70 years (n = 9) who were consuming either 70 mmol of Na/day [low-sodium regimen (LSR)] or 170 mmol of Na/day [supplemental sodium regimen (SSR)]. Young and elderly women excreted similar amounts of sodium per 24-h period. The 24-h urinary sodium excretion matched dietary sodium input appropriately on LSR and SSR, and SSR raised calcium excretion by 30%. However, whereas in the young women Na/Cr values were similar in fasting and 24-h collections on both LSR and SSR, these values were higher in 24-h than in fasting urines on SSR in the elderly women. We attribute this response to temporal differences in urinary sodium excretion associated with aging. We conclude that assessing sodium excretion from fasting urinary sodium measurements may underestimate total sodium loss (and hence calcium loss) in subjects on a stable sodium intake, particularly in the elderly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[The results and tolerability of infusion cholegraphy using ioglycamide-85 (12.75 g meglumine salt in 75 ml) in comparison with the use of a hypotonic adipiodone solution (10 g meglumine salt in 100 ml)].

The quality of 96 infusion cholegraphies with isotonic Ioglycamide-85 solution and of 2,080 infusion cholegraphies with hypotonic adipiodone-50 gave equal images in 97% of the cases. Ioglycamide-85 caused side-effects in 15.6%, Adipiodone only in 1.5% of the cases. For improved compatibility of Ioglycamide and of new contrast media as Iotroxamide and Idoxamide the use of hypotonic solutions is recommended for infusion. Their concentration should be osmotically tolerated by the erythrocytes. For the prevention of liver necrosis by contrast media the amount of contrast medium should be limited to 10 g meglumine salt.

Adult↗
PubMed1986

Reduction of blood pressure in salt-fed Dahl salt-sensitive rats with diets rich in olive oil, safflower oil or calcium biphosphate but not with calcium carbonate.

Increased dietary calcium as CaCO3 had no effect in NaCl-induced hypertension in Dahl salt-sensitive (Dahl-S) rats, while the calcium supplementation as CaHPO4 did lower the blood pressure (BP). A diet rich in either monounsaturated or polyunsaturated fatty acids produced a significant lowering of blood pressure compared with the relatively saturated palm-oil diet in NaCl-induced hypertension in Dahl-S rats. The lower BP found with olive oil is probably not related to increased amounts of PGE2 and PGI2.

Animals↗
PubMed1985

Salt sensitivity in normotensives with and salt resistance in normotensives without heredity of hypertension.

We have studied blood pressure responses to moderate sodium restriction from 200 to 50 mmol/day over 2 weeks in 62 normotensive subjects with and without a family history of hypertension by continuous automatic blood pressure recording. Based on the average of the blood pressure of 1 hour continuous monitoring under basal conditions, we have been able to demonstrate a significant fall of blood pressure in 28 young subjects with a heredity of hypertension after moderate sodium restriction from 200 to 50 mmol over 2 weeks (fall in systolic blood pressure 5.4 +/- 1.1, diastolic 2.5 +/- 0.8, mean blood pressure 2.9 +/- 0.7 mmHg, mean +/- SEM), whereas blood pressure remained unchanged in a group of 34 subjects without heredity of hypertension after moderate sodium restriction (change in systolic blood pressure -1.0 +/- 0.6, diastolic blood pressure -0.6 +/- 0.7 and mean blood pressure -0.93 +/- 0.67 mmHg). 29 of the subjects were studied a third time 2 weeks after having returned to their usual high sodium diet and in those in whom a blood pressure fall was observed during sodium restriction it returned to pre-intervention values. This demonstrates that normotensives with a heredity of hypertension are salt sensitive and adds further evidence that a high sodium intake may be of critical importance for the initiation of essential hypertension.

Adult↗
PubMed1980

[Integration of mechanisms regulating water-salt equilibrium during increasing water, salt, and volume loading].

The mechanism of integration of osmo- and volume-regulating systems after intake of 3, 5, 7, and 10% of body weight water, salt, and volume loads, was studied in adult rats. The changes of diuretic and ionuretic renal functions depended on the character and quantity of shifts caused in organism. The volume shift is the starting mechanism for stabilization of disturbed balance while the osmotic factor secures the final regulation of watersalt homeostasis.

Animals↗