PubMed Health⌕ Search

Biomedical subjects

U Montali

Publications and source records attributed to U Montali.

At least 37 records · Page 2Linked to original sources
PubMed1991

Purification of endogenous digitalis-like factor(s) from cord blood of neonate by immunoaffinity chromatography.

We have previously shown that antidigoxin antibodies may neutralize partially purified endogenous digitalis like factor(s) present in newborn (umbilical cord) plasma. We here report on the preparation of an immunoaffinity chromatographic system (high affinity digoxin-binding antibodies (Fab fragments) bound covalently to Sepharose) for the purification of endogenous digitalis like factor(s). Neonate plasma extract loses all its biological digitalis-like activity (erythrocyte 86Rb uptake inhibition) after absorption on Sepharose coupled to Fab fragments but not after absorption on uncoupled Sepharose. Endogenous digitalis like factor(s) absorbed to Sepharose coupled to Fab fragments can be eluted by methanol. Subsequent HPLC separation indicate that at least two molecular species with digitalis-like properties are retained by antibodies bound to Sepharose and can be recovered with methanol.

Antibodies↗
PubMed1991

Partial purification of endogenous digitalis-like compound(s) in cord blood.

Increasing evidence indicates the presence of endogenous digitalis-like compound(s) in human body fluids. In this preliminary report, we describe a study of the partial purification by HPLC of these compounds in the plasma of neonates (who have particularly high concentrations of this substance) and adults. Plasma samples from neonates (cord blood) and adults, lyophilized and extracted with methanol, were applied on a 300 x 3.9 mm C18 Nova Pak column and eluted with a mobile phase of acetonitrile/methanol/water (17/17/66 or 14/14/72 by vol) and, after 30 min, with 100% methanol. We assayed eluted fractions for inhibitory activity of 86Rb uptake and for digoxin-like immunoreactivity. The elution profile revealed a first peak of inhibitory activity of 86Rb uptake at the beginning of the chromatography; another peak was eluted with the 100% methanol. The two peaks also cross-reacted with antidigoxin antibodies. Because the second peak could possibly reflect the nonspecific interference of various lipophilic compounds, we focused our attention on the first peak. For these fractions dose-response curves for 86Rb uptake and for displacement of digoxin were parallel, respectively, to those of ouabain and digoxin, suggesting similarities of digoxin-like immunoreactive substance to cardiac glycosides. Similar chromatographic profiles were also obtained for plasma from adults, suggesting that the endogenous glycoside-like compound(s) in the neonate may be the same as those in the adult.

Adult↗
PubMed1989

Comparison between endogenous digoxin-like immunoreactivity and 86Rb uptake by erythrocytes in extracts of human plasma.

1. To investigate endogenous cardiac glycoside-like compounds in plasma and their ability to inhibit the sodium pump, digoxin-like immunoreactivity [digoxin-like immunoreactive substance(s), DLIS] and 86Rb uptake by erythrocytes were measured in plasma extracts from normal adults, hypertensive adults and neonates. 2. DLIS levels in neonate plasma extracts were significantly higher than those found for normotensive or hypertensive adults. No difference was observed between normotensive and hypertensive subjects. DLIS was significantly increased when boiled plasma was extracted. 3. Extracts of boiled neonate and adult plasma inhibited 86Rb uptake. Instead, when boiling was omitted, no detectable inhibition was found in extracts of plasma from normotensive or hypertensive adult subjects. When present, the inhibition resulted from a depression of the ouabain-sensitive (sodium-pump-mediated) component, and, for the boiled neonate plasma only, also of the ouabain-resistant component. When the data from the different groups were pooled, a statistically significant inverse relationship between DLIS and erythrocyte 86Rb uptake was observed. Furthermore, in a subgroup of samples in which determinations were made before and after boiling in the same samples, an inverse correlation was found between changes in DLIS and changes in ouabain-sensitive (but not ouabain-resistant) 86Rb uptake. 4. Plasma extracts incubated with albumin at a physiological concentration significantly decreased (by approximately 20%) the inhibition of 86Rb uptake observed. 5. These findings support the existence of one or more endogenous compounds which both bind to antidigoxin antibodies and inhibit transmembrane cation transport. Part of this inhibition may, however, not involve the sodium pump. Furthermore, this chemically unidentified substance(s) may be bound to plasma proteins which partly reduce its action in vivo.

Adult↗
PubMed1987

Characterization of the carrier protein of digoxin-like immunoreactive substance in plasma.

The presence of an endogenous digoxin-like immunoreactive substance(s) (DLIS) has been reported in the plasma and urine of experimental animals and humans. This substance might have a role in arterial hypertension. Although the chemical structure of DLIS is at present unknown, several studies indicate that DLIS has a low molecular weight and is reversibly bound in serum to carrier proteins. We have investigated the carrier protein of DLIS in chromatographic studies, using neonate plasma eluted on a Sephadex G200 column. The chromatographic profile of digoxin-like immunoreactivity showed a major peak with a molecular weight of approximately 60,000 daltons and a smaller peak eluted after the salt region. When the major peak was chromatographed on a Sephadex G100 column only one single peak was obtained, which closely coincided with the elution peak of albumin. Chromatographic separation of neonate plasma on a Sephadex G25 revealed a major post-salt immunoreactive peak. When these fractions were incubated with purified human albumin and separated again on the Sephadex G25, a large immunoreactive peak corresponding to albumin was again found while the immunoreactivity after salt completely disappeared. Our data therefore strongly suggest that the endogenous digitalis-like factor is carried in plasma by albumin.

Blood Proteins↗
PubMed1986

Correlation between endogenous digoxin-like immunoreactivity and 3H-ouabain displacement on erythrocyte membranes in extracts of human plasma.

The existence of endogenous cardiac glycoside-like compounds and their property of being recognized by anti-digoxin antibodies is still a matter of controversy. In order to investigate this problem, endogenous digoxin-like immunoreactivity (measured by RIA) and digitalis-like radioreceptor activity (measured by displacement of 3H-ouabain from erythrocyte membranes) were assessed in plasma extracts of normal adults, pregnant women and newborns. These three groups were chosen because of their known widely different levels of digoxin-like immunoreactivity. Compared to adults, newborns and pregnant women had significantly higher levels not only of immunoreactivity but also of displacement of 3H-ouabain binding, the latter being due, according to Scatchard analysis, to a decrease of the affinity of ouabain to its cellular receptor rather than to its maximal binding capacity. Furthermore, immunoreactivity and binding displacement correlated significantly. Our data indicate that one (or more) compounds with cardiac glycoside-like properties (both immunological and at the receptor level) are present in the plasma of newborns and pregnant women, and confirm the idea that radioimmunological methods may be useful in studying endogenous inhibitors of the sodium pump.

Adult↗
PubMed1985

Cardiotoxic effects of adriamycin and mitochondrial oxidation in rat cardiac tissue.

Rats were subjected to chronic treatment with adriamycin (ADR). Significant alterations of ECG tracings were induced, starting from the third week of treatment. These alterations were related to mitochondrial damage of the heart tissue. A decrease of respiration rate in phosphorylating conditions was observed in isolated organelles over a period of three weeks. Meanwhile, adriamycinol (ADRol) concentration in heart extracts increased during chronic treatment.

Animals↗
PubMed1984

beta 2-Microglobulin and other low molecular weight proteins in haemodiafiltrates and in haemofiltrates.

Uraemic patients underwent haemodialysis by cuprophan membrane, or haemodiafiltration by polyacrylonitrile membrane, or haemofiltration by acetate cellulose membrane. Plasma samples drawn before and after treatment with the dialyser were gel-filtered on Sephadex G-75. A comparison of the chromatograms showed that the treatment causes a removal of middle molecules, which is more consistent when haemodiafiltration and haemofiltration are used. Protein removal was examined in the fluids from the three dialysers. It was observed that proteins (300 +/- 45 mg and 410 +/- 60 mg respectively) were removed when polyacrylonitrile and acetate cellulose membranes were used, but not in the case of cuprophan membrane. beta 2-Microglobulin was the protein lost in the greatest amount.

Acrylic Resins↗
PubMed1984

Digoxin-like immunoreactivity in normal human plasma and urine, as detected by a solid-phase radioimmunoassay.

Reports on the presence of digoxin-like immunoreactive substance(s) (DLIS) in the plasma and urine of several animal species and a few human test subjects prompted us to undertake to confirm the presence of DLIS in plasma and urine of normal persons and to investigate some characteristics of this antibody-DLIS binding. For this purpose we used a modified radioimmunoassay kit involving antidigoxin antibody-coated test tubes and 125I-labeled digoxin to measure DLIS in urine and concentrated plasma of ostensibly healthy subjects. In 12 separate experiments with plasma the mean sensitivity was 5.12 (SD 1.11) pg per tube, expressed as digoxin. There was no significant cross reactivity with human serum albumin in concentrations up to 200 g/L. The mean DLIS value (in digoxin equivalents) for plasma from 24 normal subjects was 33.58 (SD 14.24) ng/L. Its mean concentration in urine from five subjects was 315.00 (SD 91.38) ng/L.

Adult↗
PubMed1981

Inactivation of rat muscle 5'-adenylate aminohydrolase by tyrosine nitration with tetranitromethane.

Reaction of rat muscle AMP deaminase with low molar excess of tetranitromethane results in a rapid loss of free thiol groups and a concomitant decrease in enzyme activity at high, but not at low, AMP concentration. This modification appears to be limited to the same non-essential thiol groups reactive towards specific reagents in non-denaturing conditions. On incubation with higher molar excess of tetranitromethane, a loss of enzyme activity is observed, which correlates with nitration of tyrosine residues. By amino acid analysis, approximately there tyrosine residues per subunit are estimated to be nitrated in the completely inactivated enzyme. The kinetic properties of the partially inactivated AMP deaminase reveal a negative co-operatively behaviour at approximately half saturation. This suggests that modification of tyrosine residues is also responsible for alteration of the binding properties of the hypothesized activating site of AMP deaminase.

AMP Deaminase↗
PubMed1978

Undersulfated urinary glycosaminoglycans in preterm newborns.

The glycosaminoglycans (GAG) isolated from pooled urine of preterm newborns were fractionated by stepwise elution from a Dowex 1-X2 column. Analytical reactions, cellulose acetate electrophoresis and enzymatic digestions with chondroitinases and testicular hyaluronidase were performed on each fraction. Chondroitin-4-sulfate and chondroitin-6-sulfate constitute about 60% of urinary GAG; heparan sulfate amounts to about 20%, while chondroitin represents 12% of total GAG; dermatan sulfate, hyaluronic acid and keratan sulfate are present in small traces. Approximately 30% of the total is constituted by nonsulfated GAG.

Chondroitinases and Chondroitin Lyases↗
PubMed1975

A general method of purification of adenosine deaminase by affinity chromatography.

Affinity chromatography has been used to purify adenosine deaminase from various sources: calf spleen, calf intestinal mucosa, chicken duodena and human erythrocytes. For this purpose a specific inhibitor, 9-(p-aminobenzyl) adenine, was synthesized and covalently joined to agarose. Adenosine deaminase is selectively retained by such an inhibitor-resin when highly impure solutions are chromatographed through it. After elution from the resin with guanylurea, a competitive inhibitor, the enzyme is homogeneous and can be recovered in yields of 80 percent or more and the same number of multiple forms of the enzyme is present in the purified preparation and in the crude extract.

Adenine↗
PubMed1975

Digestion of insulin derivatives with subtilisin: a kinetic study.

Native, denatured, performic acid-oxidized or S-sulfo insulin and S-sulfo or performic acid-oxidized A- and B-chains were digested with subtilisin type Carsberg. The proteolysis was followed by measuring the uptake of alkali through autotitration. The kinetic study shows the existence of 2 first-order reaction classes which differ markedly in rate constant. The number of bonds split with fast and with slow reactions has been calculated. Only one of a total of 12 cleavable bonds in native insulin is opened by fast reaction. In the denatured protein the number of bonds split by the fast reaction increases to 4 and in the oxidized and S-sulfo protein 3 bonds are cleaved, while the slow cleavable bonds number 2 and 7, respectively, The kinetic study of the proteolysis of S-sulfo A-chain and of oxidized or S-sulfo B-chain shows that two bonds are split in A-chain with the fast and slow reactions, while in B-chain only one of the six cleavable bonds is susceptible to fast attack.

Hydrogen Bonding↗
PubMedDate not supplied

Inhibition of rat Na+/K+-ATPase isoforms by endogenous digitalis extracts from neonatal human plasma.

An unique endogenous digitalis-like factor (EDLF) has been previously purified from human newborn cord plasma and its differential effects tested on the three well defined functional isoforms (alpha1, alpha2 and alpha3) of the alpha subunits of Na+/K+-ATPase in rat. EDLF specifically inhibits the enzymatic activity. It differs from ouabain by three criteria: a preincubation with the membranes is required for full activity, no effect on the rat cerebral alpha3 isoform and a steep dose-response curve with the same apparent potency for rat alpha2 and alpha1 isoforms of high (10(-7) M) and low affinity (3 x 10(-5) M) for ouabain. These results indicate that the Na+/K+-ATPase inhibitor involved in the regulation of sodium and body fluid volume and present in neonate and adult human plasmas is distinct from ouabain.

Animals↗