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Biomedical subjects

M Guerrini

Publications and source records attributed to M Guerrini.

At least 19 recordsLinked to original sources
PubMed1995

Conformational analysis of heparin epoxide in aqueous solution. An NMR relaxation study.

1H and 13C NMR relaxation measurements at various magnetic fields have been used to characterize the nature of overall and internal motions in heparin epoxide in aqueous solution. A two-dimensional homonuclear NOESY experiment showed a considerable number of cross-relaxing protons in the molecule. The inter-proton distances calculated from NOE data were compared with those obtained by molecular mechanics calculations. Several discrepancies between the experimental and the theoretical inter-proton distances as well as the variations in 13C spin-lattice relaxation times, measured at two magnetic fields, indicated that the polysaccharide tumbles anisotropically in solution. The rates of overall and internal motions as well as the order parameters have been calculated using a model-free spectral density function. The numerical values indicate that the correlation times which characterize overall molecular motion are outside the extreme narrowing limit (tau parallel = 8 x 10(-10) s and tau perpendicular = 4.2 x 10(-8) s) and that internal motion correlation time is on a picosecond timescale.

Carbohydrate Conformation↗
PubMed1995

Magnetic bead protamine-linked microtiter assay for detection of heparin using iodinated low-molecular-mass heparin-tyramine.

We have developed a competitive heparin binding assay employing protamine-coated magnetic beads for detection and measurement of heparin. The assay utilizes 125-iodine specifically bound to newly synthesized low-molecular-mass (LMM) heparin-tyramine. The tracer was stable over a period of 3 weeks, as demonstrated by gel filtration chromatography. The protamine-coated beads were found to be stable over at least two months. The heparin-tyramine bead assay had in buffer a lower detection limit of 0.04 microgram/ml and in plasma of 0.23 microgram heparin/ml. 50% binding was obtained at 0.7 microgram/ml and 20% binding at 4 micrograms/ml in plasma. The within assay coefficient of variation ranged from 9 to 28% for unfractionated, high molecular mass (HMM) heparin and from 12 to 15% for LMM-heparins in buffer system and in plasma. Various heparin fractions displaced the tracer from the protamine-coated magnetic beads to different extents. The validity of the assay was proven after intravenous administration of unfractionated and LMM-heparin in man. The elimination rate was similar using the heparin-tyramine bead assay compared with the anti-factor Xa coagulation assay. After intravenous dosing of LMM-heparin the maximal concentration was lower using the heparin-tyramine bead assay compared with the anti-factor Xa coagulation assay. The bead assay was found to be reproducible, valid, and rapid for measurement of the concentration of heparin preparations in purified systems and for HMM-heparin in plasma. Measurement of the concentration of LMM-heparin in plasma has a high coefficient of variation using the binding assay.

Binding, Competitive↗
PubMed1995

[An epidemiological study on blood viscosity and intraerythrocytic calcium in a group of high-school students selected according to their family histories].

An epidemiological study was performed in a group of secondary school students selected according to their family history to assess whether changes exist in blood viscosity and intraerythrocytic calcium levels in young healthy subjects with positive family histories of arterial hypertension or cerebral and cardiac ischemic vasculopathies, compared to a control group with a negative family history of these disorders. A population of 130 secondary school students without any pathologies were subdivided into 4 groups: 1) with a positive family history of ischemic cardiopathy (ICP); with a positive family history of cerebral ictus; 3) with a family history of arterial hypertension; 4) a negative family history of these diseases. Total blood viscosity, hematocrit, plasma fibrinogen and intraerythrocytic calcium was evaluated in all groups. The results show that these parameters were within the normal range, as was to be expected in healthy subjects. Blood viscosity was also normal in all groups; intraerythrocytic calcium levels were slightly higher in groups with histories of cardiovascular disease and in particular there was an increased percentage of cases with values above the threshold level. Higher fibrinogen levels were also recorded, but always within the normal range, in the group with a positive history of ICP. The epidemiological study is important to assess whether a family pattern of cardiovascular disease can also influence such independent risk parameters as blood viscosity and intraerythrocyte calcium, owing to the possible greater frequency of development of cardiovascular disease.

Adolescent↗
PubMed1995

[Plasma Lp(a) levels: a comparison between diabetic and nondiabetic patients with the nephrotic syndrome and control subjects].

The aim of this study was to evaluate Lp(a), total, HDL and LDL cholesterol, triglycerides, Apo A and Apo B100 plasmatic concentrations in patients affected by nephrotic syndrome that is known able to increase the ratio of the risk of cerebral and cardiovascular events, in comparison with a group of healthy patients homologous for sex and age. In the group of patients with nephrotic syndrome we have compared the variables between diabetic mellitus type I patients and non diabetic patients. All the variables, in exception of HDL cholesterol, were significantly increased in the group of patients with nephrotic syndrome compared with the control group. HDL-cholesterol concentration was significantly higher in controls than in nephrotic patients. Diabetic and nephrotic patients showed increased levels of Lp(a) concentration than non diabetic patients and the difference was statistically confirmed. These data suggest that Lp(a) acts really like a risk factor for atherosclerotic disease, being elevated in patients characterized for increased risk for cerebral and cardiovascular events because of the presence of nephrotic syndrome. Moreover we can suppose that elevated plasmatic Lp(a) levels in nephrotic patients could be linked to increased synthesis of proteins in the liver as physiological reaction to severe proteinuria.

Aged↗
PubMed1994

Quantitation of dermatan sulfate active site for heparin cofactor II by 1H nuclear magnetic resonance spectroscopy.

The sequence (IdoA2SO3-GalNAc4SO3)n contributes to the HCII-mediated inhibition of thrombin by dermatan sulfate (DS). This sequence clearly results from the 13C NMR spectrum and can be quantified by the signal C1-H of IdoA2SO3 in the 1H NMR spectrum. A linear correlation has been found between the content in the disulfated disaccharide delta Di-2,4diS obtained by enzymatic demolition with ABC lyase, the percentage content in IdoA2SO3 quantified by 1H NMR, and the HCII-mediated activity of dermatan sulfates from beef mucosa and pig skin. DSs have been obtained also from pig mucosa and contain an amount, not negligible, of delta Di-4, 6diS. This disulfate disaccharide contributes to the activity expressed by the IdoA2SO3-GalNAc4SO3 sequence. The analytical techniques HPLC and 1H NMR, applied to the currently performed analyses of DS, are described and discussed.

Binding Sites↗
PubMed1994

Heparin-like compounds prepared by chemical modification of capsular polysaccharide from E. coli K5.

O-Sulfation of sulfaminoheparosan SAH, a glycosaminoglucuronan with the structure-->4)-beta-D-GlcA(1-->4)-beta-D-GlcNSO3(-)-(1-->, obtained by N-deacetylation and N-sulfation of the capsular polysaccharide from E. coli K5, was investigated in order to characterize the sulfation pattern eliciting heparin-like activities. SAH was reacted (as the tributylammonium salt in N,N-dimethylformamide) with pyridine-sulfur trioxide under systematically different experimental conditions. The structure of O-sulfated products (SAHS), as determined by mono- and two-dimensional 1H and 13C NMR, varied with variation of reaction parameters. Sulfation of SAH preferentially occurred at O-6 of the GlcNSO3- residues. Further sulfation occurred either at O-3 or at O-2 of the GlcA residues, depending on the experimental conditions. Products with significantly high affinity for antithrombin and antifactor Xa activity were obtained under well-defined conditions. These products contained the trisulfated aminosugar GlcNSO3-3,6SO3-, which is a marker component of the pentasaccharide sequence through which heparin binds to antithrombin.

Carbohydrate Conformation↗
PubMed1994

Synthesis of a N'-alkylamine anticoagulant active low-molecular-mass heparin for radioactive and fluorescent labeling.

Heparin plays an important role in anticoagulation and several other biological processes. Cleavage of heparin by nitrous acid results in a reactive 2,5-anhydromannose (Am) which can be used to selectively insert primary and secondary amines by reductive amination. Low-molecular-mass heparin (LMMH) was bound to 4-(2-aminoethylphenol) as shown by nuclear magnetic resonance spectroscopy (NMR), high-performance size-exclusion chromatography (HPSEC), polyacrylamide gel electrophoresis (PAGE), and ultraviolet/visible (uv/vis) spectroscopy. 1H NMR spectra revealed an average sequence of (IdoA2SO3-GlcNSO36SO3)9-IdoA2SO3-Am-tyramine and a 50% binding rate of tyramine to LMMH. LMMH-Tyr had an anticoagulant activity of 108 antifactor Xa activity (aXa) U/mg and 42 antifactor IIa activity (aIIa) U/mg. The compound was neutralized by protamine. The N-alkylamine derivative was adopted to label LMMH with iodine-125 by oxidation with chloramine T. Fluorescein-5-isothiocyanate (Fitc) was used to label LMMH-Tyr with fluorescence. NMR, HPSEC, PAGE, and uv/vis spectroscopy demonstrated the binding of Fitc to LMMH-Tyr. 1H NMR spectra indicated that about 80% of the LMMH-Tyr was labeled at the secondary amino group. The fluorescent compound exhibited 70 aXa and 5 aIIa U/mg and was neutralized by protamine. The selectively bound labeled heparin derivatives are "endpoint attached" and have intact anticoagulant activity.

Anticoagulants↗
PubMed1994

Semisynthesis and analysis of lipophilically modified unfractionated and low molecular mass heparins.

Unfractionated heparin and LMMH were substituted with different lipophilic organic compounds. Specifically endpoint attached (LMMH-tyramine and LMMH-tyramine-FITC) and nonspecifically substituted heparins (acylated heparins, and LMMH-biotin and LMMH-cholesterol hemisuccinate) were obtained. The lipophilically substituted heparins were analysed by HPSEC and showed different retention times, high peak purity, different UV/VIS absorbances, and areas under the absorbance time curve. The determination of the average molecular mass Mn, Mm, and Mz and the polydispersity P was performed by PAGE. The substituted heparins showed an increase in their molecular mass Mm, ranging from 2.9 to 129.7% unfractionated heparin and 3.9 to 224.0% (LMMH) compared with the parent compounds (unfractionated heparin and LMMH). The anticoagulant activity was measured by anti-Factor Xa. Lipophilically modified heparin had an aXa activity ranging from 52 to 168 U/mg (unfractionated) and 60 to 108 U/mg (LMMH) and antithrombin activity ranging from 31 to 270 U/mg (unfractionated) and 5 to 15 U/mg (LMMH). The thrombin generation inhibition assay demonstrated an effective anticoagulant potency of the modified compounds. They were neutralized by different amounts (1.1 to 4.1, w/w) of protamin. 1H NMR spectroscopy revealed the specific endpoint attachment of tyramine to LMMH and FITC to LMMH-tyramine. The lipophilically modified heparins showed intact anticoagulant properties and are now used for pharmacokinetic investigations.

Acylation↗
PubMed1994

[Lp(a) and lipid order in a group of secondary school students selected according to their family anamnesis].

In this study we evaluated the several risk-factors, Lp(a) and lipids order, related to the family history for ischaemic cardiovascular disease (CHD) atherosclerotic cerebrovasculopathy and arterious hypertension, in a healthy adolescent group, to stress possible early and significant alteration of the lipids order and Lp(a); we also considered which of these parameters may be considered the risk factor most closely related to family history. We studies 130 healty high school students, mean age 16.5 +/- 5.5 years, selected in four groups related to the family history: the first one composed of 34 subjects with positive family history for CHD; the second one of 32 subjects with positive family history for cerebral infarction (CI); the third by 32 subjects with family history for arterial hypertension and the last group by 30 control subjects. Mean value of all variables considered was in the normality range. Lp(a) resulted in the normality range with the exception of the group with positive family history for CHD. Also the traditional risk factors (Total-Col., LDL/Col. and Triglycerides) were increased in this group. Besides the differences between the mean of Lp(a) and Total/Col. in the group with positive family history for CHD and in the control group were statistically significant. The results showed that Lp(a), even if it cannot replace the family history in the screening of coronary atherosclerotic disease, might be considered a risk marker of early atherosclerotic disease.

Adolescent↗
PubMed1993

Structure and contribution to the heparin cofactor II-mediated inhibition of thrombin of naturally oversulphated sequences of dermatan sulphate.

Dermatan sulphate (DS) obtained from bovine and pig mucosa and pig skin, and charge-enriched fractions of a selected DS preparation, were characterized in terms of charge density, M(r) and disaccharide composition of chondroitin ABC lyase digests, and by 13C-n.m.r. spectroscopy. Besides the major IdoA-GalNAc4SO3 sequences, all DS preparations contain about 10% disulphated disaccharide sequences (mostly IdoA2SO3-GalNAc4SO3, with minor amounts of IdoA-GalNAc4,6SO3). DS fragments (prepared by radical-catalysed depolymerization of DS and retaining the internal structure of the parent polysaccharide) as well as Smith degraded fragments [SD-DS, obtained by controlled degradation of periodate-oxidized and borohydride-reduced DS (RO-DS)] with the general structure GalNAc4SO3(IdoA2SO3-GalNAc4SO3)n-R (where R is the remnant of a glycol-split uronic acid, and n = 2-3 and 3-4) were characterized by one- and two-dimensional 1H-n.m.r., 13C-n.m.r. and disaccharide composition analysis. In accordance with previous findings [Maimone and Tollefsen (1990) J. Biol. Chem. 265, 18263-18271], only fragments with n > or = 3 significantly enhance the heparin cofactor II-mediated inhibition of thrombin. In natural DS preparations and their fractions, this activity (as well as the antithrombotic activity in an animal model) appears to require IdoA2SO3-containing sequences. The heparin cofactor II activity of DS, RO-DS and SD-DS fragments decreases with decreasing M(r). However, RO-DS fragments are more active than DS fragments of similar M(r), probably because of the extra flexibility endowed by glycol-split IdoA residues.

Animals↗
PubMed1993

Free ADP-ribose in human erythrocytes: pathways of intra-erythrocytic conversion and non-enzymic binding to membrane proteins.

We have previously identified free ADP-ribose (ADPR) as a normal metabolite in mature human erythrocytes. In this study the metabolic transformations of ADPR were investigated in both supernatants from erythrocyte lysates and intact erythrocytes, loaded with ADPR by means of a procedure involving hypotonic haemolysis and isotonic resealing. In both experimental systems, the main pathway was a dinucleotide pyrophosphatase-catalysed hydrolysis to yield AMP, which was readily converted into the adenylic and inosinic nucleotide pools. To a lesser extent, ADPR underwent conversion into a compound that was identified as ADP-ribulose (ADPRu), on the basis of m.s., n.m.r. spectroscopy and enzymic analysis. ADPRu was also susceptible to degradation by the dinucleotide pyrophosphatase, which was partially purified from erythrocyte lysates and characterized with respect to its substrate specificity. Isomerization of ADPR to ADPRu was markedly enhanced by ATP. Incubation of unsealed haemoglobin-free erythrocyte membranes with labelled ADPR did not cause any transformation of this nucleotide and resulted in its trichloroacetic acid- and formic acid-resistant binding to a number of membrane cytoskeletal proteins. These proteins include spectrin, glyceraldehyde 3-phosphate dehydrogenase (Ga3PDH), three proteins of molecular masses 98, 79 and 72 kDa, which apparently comigrate with bands 3, 4.1 and 4.2 respectively, and two additional proteins of molecular masses 58 and 41 kDa. Acid-resistant binding of ADPR, as well as of NAD+, to Ga3PDH was confirmed for the enzyme purified from human erythrocytes.

Adenine Nucleotides↗
PubMed1990

[Calcium dobesilate in the treatment of primary venous insufficiency of the lower limbs. A controlled clinical study].

Fourty patients with lower limb chronic venous insufficiency entered a randomised placebo controlled study with calcium dobesilate for one month. Clinical symptoms and plethysmographic parameters were evaluated before and after therapy in all patients. In the group of patients treated with calcium dobesilate we observed an improvement of clinical and instrumental parameters; no changes were found in the placebo group. We observed good tolerance to the drug and no side effects required withdrawal of treatment.

Aged↗
PubMed1989

[Use of a new preparation of flunarizine in patients with peripheral obliterating arteriopathy at the second stage. Controlled clinical study].

The authors report a randomised double-blind clinical study on the efficacy and tolerability of flunarizine. Two groups of patients with obliterating peripheral arterial disease (stage II) were treated for 3 months either with 10 mg flunarizine or with placebo and were examined monthly as to subjective symptoms, laboratory and instrumental parameters. Findings were evaluated by analysis of variance and Student's t-test. After three months, the flunarizine group had a greater increase of the distance walked before the onset of claudication and of maximum post-ischemic blood flow. No changes were observed in laboratory tests and central hemodynamics. The score of subjective symptoms was improved in the flunarizine treated group. Tolerance was good, side effects requiring withdrawal of treatment were not observed.

Aged↗
PubMed1989

[Calcium dobesilate, hemorheology, fibrinolysis and endothelium. New perspectives on the prevention of diabetic microangiopathy. Clinical pharmacological study].

The authors report the results of a double-blind cross-over study on calcium dobesilate in which two groups of eight recent-onset type-II diabetics were treated either p.o. (1 g once daily) or i.v. (500 mg in 100 ml of physiological saline) with calcium dobesilate or with placebo. During oral administration of the drug, blood rheology and total fibrinolytic capacity were assessed by calculating euglobulin lysis time. In view of the evidence for a viscosity-lowering action of the drug (which had already been found in "long-term" studies) and of potentiation of fibrinolytic activity, intravenous treatment was started with the object of elucidating the possible mechanisms of action, evaluating at the same time other parameters concerning the functional fibrinolytic pathways. It has thus been possible to ascertain that the drug has "rheologic" activity, interferes with the function of endothelial cells by stimulating the release of tissue plasminogen activator and thus increases fibrinolytic activity while not interfering with the clotting function and not altering platelet beta-thromboglobulin secretion. These findings appear to confirm the possibilities for therapeutic use of calcium dobesilate which is thought to act on a variety of pathogenetic mechanisms involved in diabetic microangiopathy.

Administration, Oral↗
PubMed1987

Primary and secondary blood hyperviscosity syndromes, and syndromes associated with blood hyperviscosity.

Despite the methodological difficulties of evaluating the role of a single rheological component, some clinical situations characterised by an increase of blood viscosity can be identified. These are classified as 'blood hyperviscosity syndromes' and can be divided into 2 groups. The first includes pathophysiological conditions in which a primary blood abnormality causes a decrease of blood flow, as occurs in polycythaemic, sclerocythaemic and seric hyperviscosity syndromes, and may be referred to as 'primary blood hyperviscosity syndromes'. The second group includes pathological conditions in which a primary reduction of blood supply to tissue provokes tissue ischaemia, and an impairment of rheological properties of blood can be observed at microcirculatory level. Thus, these situations have been described as 'secondary blood hyperviscosity syndromes'. Patients with peripheral obliterative arterial disease, ischaemic cardiopathies and cerebrovascular insufficiencies show a diminution in blood fluidity during spontaneous or provoked ischaemic conditions which disappears after reperfusion of the tissue. The pathogenesis of this rheological damage is unclear, but may arise from the complex relationship among blood cells (red cells, leucocytes, platelets), endothelium and plasma components. In addition to these 2 groups of blood hyperviscosity syndromes, several pathological states such as diabetes, shock, surgery, and rheumatic disease have been described in which an increase of blood viscosity can be observed. For these situations, which require much further investigation, the term 'syndromes associated with blood hyperviscosity' could be proposed.

Blood Viscosity↗
PubMed1985

Hemorheological factors in the pathophysiology of acute and chronic cerebrovascular disease.

The hemorheologic changes in three groups of patients suffering from acute and chronic cerebrovascular diseases were studied. Firstly, a horizontal study on 57 patients with definite stroke and on 49 patients with TIA was made. Plasma viscosity, whole blood filtration rate, fibrinogen concentration and hematocrit were evaluated as markers of the rheological property of blood. Blood samples were drawn within 6 h from the onset of vascular syndrome. The findings were compared with values obtained in 112 as controls. At the same time, washed red cell filtration rate, together with lactoferrin, betaglucuronidase and beta-thromboglobulin plasma level were assayed. In both groups the onset of the vascular storm was associated with a marked increase of plasma fibrinogen and of blood and plasma viscosity and a significant decrease of whole blood filterability. Lactoferrin, betaglucuronidase and beta-thromboglobulin levels were also significantly increased. Following this, a longitudinal study was performed on 27 patients with definite stroke and 32 patients with TIA. The clinical regression of acute stroke was associated with the progressive reduction of rheological abnormalities. Finally, 81 patients with clinical diagnosis of cerebrovascular disease due to previous stroke or repeated TIA were studied together. An increase of blood viscosity, of fibrinogen concentration and of hematocrit and a decrease of blood filtration rate together with higher levels of beta-thromboglobulin were registered. These results confirm the existence of an association between CVD and hemorheological alterations and suggest more in depth research directed towards identifying the significance of these alterations in the pathogenesis of tissue ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗