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R Verna

Publications and source records attributed to R Verna.

At least 19 recordsLinked to original sources
PubMed1995

Age-related variations in plasma and liver lipids of Yoshida rats: a comparison with Wistar rats.

Lipoprotein and liver lipids of spontaneously hyperlipidemic Yoshida rats were compared with those of normolipidemic Wistar animals for studying their age- and strain-related differences. Both strains showed an age-related increase in the total plasma cholesterol concentration. However, the Yoshida strain had a higher content of cholesteryl esters and triglycerides than the Wistar strain in both young and adult animals (2- and 8-month-old animals, respectively). The free cholesterol content was also higher, but only in the 8-month-old animals. Both strains showed an age-related increase in the proportion of HDL1 and a symmetrical decrease in both the HDL2 and HDL3 subfractions, but the variations were more evident in the Yoshida strain. The study of strain-related differences suggested that the spontaneous hypertriglyceridemia of the Yoshida strain was not only related to the higher amount and proportion of the VLDL fraction, but also to the higher content of triglycerides in the LDL fraction. The livers of Yoshida rats accumulated more triglycerides (with an age-related progression) than those of Wistar rats. The major lipid classes in the liver of Yoshida rats contained a significantly higher proportion of monounsaturated fatty acyls. Furthermore, this proportion showed an age-related increase in all the lipid classes, but in cholesteryl esters. This suggested that liver desaturases had a relevant role in the development of hyperlipidemia, and of its age-related variations, in the Yoshida strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1992

Erythrocyte transmembrane Na and K fluxes in pseudohypoaldosteronism.

Pseudohypoaldosteronism (PHA) is a disease characterized by hyponatremia, hypotension, and dehydratation, despite the presence of hyperreninemic hyperaldosteronism. The membrane-bound Na,K ATPase activity and the transmembrane Na and K transport systems have been studied in vitro in red blood cells of two subjects, son and mother, affected by pseudohypoaldosteronism with different degrees of clinical involvement. Both parameters were significantly altered suggesting that the refractory response to mineralocorticoids is detectable, not only in kidneys and salivary and sweat glands, but also in red blood cells. Since pseudohypoaldosteronism, in its asymptomatic form, may be much more common than expected, we suggest the use of the tests described herein as a practical approach to the early diagnosis of pseudohypoaldosteronism in the investigation of sodium wasting syndromes.

Aldosterone↗
PubMed1989

Chronobiological evidence for an uncoupling of the Na,K-ATPase to aldosterone in normal renin hypertension.

The Na,K-ATPase activity of erythrocyte membranes is markedly increased in normal-renin essential hypertensives. A temporal shift of the chronobiology of the erythrocyte-membrane-bound Na,K-ATPase in these patients is described. The disorder causes a loss of synchronism between the circadian rhythms of aldosterone and Na,K-ATPase. Such uncoupling phenomenon may explain the inversion of the day/night sodium excretion ratio and other disturbances of sodium metabolism found in essential hypertensives.

Adolescent↗
PubMed1988

Enzymatic deglycosylation of human thyroglobulin: fluorescence studies.

The interaction between the carbohydrate and the amino acid residues in human thyroglobulin has been studied. Previous reports showed that the removal of the two terminal carbohydrates of the complex chains leads to an increase in thyroglobulin binding to thyroid membranes. In our study, after enzymatic release with glycosidases of the sugar moieties from thyroglobulin, a time-dependent decrease in tryptophan fluorescence has been observed. This decrease was also associated with a shift in the emission peak from 335 to 340 nm. The strong quenching of tryptophan emission was also accompanied by a decrease in the exposure of tryptophan residues, as shown by a Stern-Volmer analysis with the neutral quencher acrylamide. These data, together with the increase in fluorescence of the dansylated deglycosylated thyroglobulin, strongly suggest that a significant conformational change of thyroglobulin follows the deglycosylation of the protein.

Apoproteins↗
PubMed1988

Effect of ouabain binding on the fluorescent properties of the Na+/K+-ATPase.

The influence of occupancy by ouabain of its specific binding site on the stability and conformation of the Na+/K+-ATPase has been investigated. When native Na+/K+-ATPase is exposed to guanidinium chloride or diluted acid, tryptophanyl fluorescence falls to 50% of the initial value. If ouabain is bound, higher concentrations of GdmCl or acidity are needed to reach the same decrease in fluorescence. The rotational diffusion coefficient (relaxation time), shows higher values for the Na+/K+-ATPase (ouabain) complex compared to the enzyme alone, suggesting an increase in molecular asymmetry. This observation is confirmed by the Stern-Volmer analysis that shows an increase in the accessibility of the fluorophores in the Na+/K+-ATPase (ouabain) (KSV = 15.6 M-1) with respect to the native enzyme (KSV = 12.5 M-1). Iodine perturbation of the enzyme labelled with FITC, demonstrates a decrease in the accessibility of the fluorescein probe in the Na+/K+-ATPase(ouabain) (KSV = 4 M-1) compared to the Na+/K+-ATPase (KSV = 7 M-1) indicating that after ouabain binding this site of the enzyme is less exposed to the solvent. These data, in agreement with other reports, suggest an allosteric effect of ouabain binding on the Na+/K+-ATPase conformation.

Acrylamide↗
PubMed1987

Internal desynchronization between circadian rhythms of plasma aldosterone and erythrocyte membrane-bound Na/K-ATPase.

Normal-renin essential mesor hypertensives are characterized by a consistent increase in erythrocyte membrane-bound Na/K-ATPase activity. Low-renin essential hypertensives exhibit, in contrast, a lower activity in Na/K-ATPase of cell membranes. This study documents a third disorder characterized by a temporal shift in the rhythmic activity of the erythrocyte membrane-bound Na/K-ATPase in normal-renin hypertensives. The disorder causes the synchronism with the aldosterone circadian rhythm to be invariably lost. The uncoupling phenomenon could be invoked to explain the inversion in the day-night sodium excretion rate found in essential hypertensives. In addition, it suggests that the circadian rhythm in Na/K-ATPase is under the control of cycling factors other than aldosterone.

Adolescent↗
PubMed1987

[Fluorescent properties of (Na+/K+)ATPase].

1. The effect of ouabain on the molecular properties of (Na+/K+)-ATPase has been studied in purified preparations of the enzyme, isolated from the microsomal fraction of outer red medulla of porcine kidney, according to a modification of the method described by Jorgensen. 2. Ouabain, a specific inhibitor of (Na+/K+)-ATPase, binds at the potassium site of the enzyme, thus generating an increase in its stability towards the common denaturing agents, such as exposure to different concentration of guanidinium chloride (GdmC1) or to acidic solutions.

Animals↗
PubMed1986

Insulin effects on human red blood cells.

The effect of insulin on human red blood cells was investigated, both on intact cells and on isolated plasma membranes, testing the responsiveness of membrane-bound enzymes--such as (Na+-K+)-ATPase and 5'-nucleotidase--as well as the ouabain binding and ionic fluxes. It appears that insulin stimulates Na-pumping mechanisms increasing (Na+-K+)-ATPase activity through an enhanced availability of pumping sites, as can be inferred from the increased ouabain binding. The apparent unresponsiveness of fluorescence polarization parameters, following insulin treatment of isolated plasma membranes and intact cells, rules out--at present--an involvement of membrane lipid fluidity in the mechanism of action of insulin on human erythrocytes.

5'-Nucleotidase↗
PubMed1986

Prostaglandin-induced storage and secretion of esteroproteases in the mouse submaxillary gland.

The submaxillary glands of adult C3H mice which received intraperitoneal injections of prostaglandins F2 alpha and E2 (PGF2 alpha and PGE2) were examined biochemically and ultrastructurally. Results indicated that the specific activity of esteroprotease in an homogenate of submaxillary glands was significantly increased when mice were treated with PGF2 alpha (96 or 480 micrograms/kg), and decreased when they were treated with PGE2 (96 or 480 micrograms/kg). Ultrastructural findings were correlated with these biochemical data. Thus, it appeared that PGF2 alpha stimulated the secretion and synthesis of bioactive proteins, and that PGE2 stimulated only the secretion.

Animals↗
PubMed1985

Characterization of a cyclic AMP-resistant Chinese hamster ovary cell mutant containing both wild-type and mutant species of type I regulatory subunit of cyclic AMP-dependent protein kinase.

We have characterized a cyclic AMP-resistant Chinese hamster ovary (CHO) cell mutant in which one of two major species of type I regulatory subunit (RI) of cyclic AMP-dependent protein kinase is altered. Wild-type CHO cell extracts contain two cyclic AMP-dependent protein kinase activities. As shown by DEAE-cellulose chromatography, there is a peak of type I protein kinase activity in mutant extracts, but the type II protein kinase activity is considerably reduced even though free type II regulatory subunit (RII) is present. The type I kinase from the mutant has an altered RI (RI*) whose KD for the binding of 8-N3[32P] cAMP (KD = 1.3 X 10(-5) M) is increased by more than 200-fold compared to RI from the wild-type enzyme (KD = 5.5 X 10(-8) M). No differences were found between the catalytic subunits from the wild-type and mutant type I kinases. A large portion of RI in mutant and wild-type extracts is present in the free form. The RI* derived from mutant type I protein kinase shows altered labeling by 8-N3[32P]cAMP (KD = 1.3 X 10(-5) M) whereas the free RI from the mutant is labeled normally by the photoaffinity label (KD = 7.2 X 10(-8) M), suggesting that the RI* which binds to the catalytic subunit is functionally different from the free form of RI. The decreased amount of type II kinase activity in the mutant appears to be due to competition of RI* with RII for binding to the catalytic subunit. Translation of mRNA from wild-type CHO cells results in the synthesis of two different charge forms of RI, providing biochemical confirmation of two different species of RI in CHO cells. Additional biochemical evidence based on isoelectric focusing behavior of 8-N3[32P]cAMP-labeled RI species and [35S]methionine-labeled RI from mutant and wild-type extracts confirms the charge heterogeneity of RI species in CHO cells. These genetic and biochemical data taken together are consistent with the conclusion that there are at least two different species of RI present in CHO cells and that one of these species is altered in the mutant analyzed in this work.

Affinity Labels↗
PubMed1985

The effect of cyclic AMP on Na+ and K+ transport systems in mouse macrophages.

Exogenous cyclic AMP (cAMP) inhibits the Na+, K+-cotransport system and stimulates the Na+, K+-pump and Na+, Ca2+ exchange in mouse macrophages. These effects are enhanced by inhibition of phosphodiesterase with methylisobutylxanthine (MIX). MIX alone showed little or no effect. A similar response was observed after stimulation of endogenous production of cAMP by isoproterenol.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Na+/K+ ATPase and cell growth: effect of epidermal growth factor on the enzymatic activity in chick embryo epidermis during the embryonal development.

1. The behaviour of ATPase activity during embryonic development of chick embryo epidermis has been studied in the absence or presence of a single inoculation of EGF at the fifth day from fertilization (0-day). 2. EGF strongly decreases ATPase activity by affecting Na+/K+ ATPase. This effect occurs only if begun at 0-day. 3. This effect is due to the EGF induced decrease of -SH groups that are active part of Na+/K+ ATPase.

Animals↗
PubMed1983

Na+/K+ ATPase and cell growth--III: Enzymatic activity in cultured and EGF stimulated HeLa cells.

1. The behaviour of Na+/K+ ATPase during the growth of ectodermal tumoral cells (HeLa) has been investigated. 2. Besides spontaneously growing cells, also samples stimulated with EGF have been tested. 3. The content of--SH groups in the homogenates of both the untreated and the EGF stimulated samples has been tested. 4. Results show a decrease of enzymatic activity during the culture of neoplastic cells and an enhancement of this behaviour in the EGF stimulated cells due to the action of the hormone on--SH groups.

Cell Division↗