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Biomedical subjects

A Zanetti

Publications and source records attributed to A Zanetti.

At least 55 records · Page 3Linked to original sources
PubMed1991

Reduced activity of arylsulfatase A and predisposition to neurological disorders: analysis of 140 pediatric patients.

A sample of 140 children exhibiting neurologic disturbances (93 suffering from epilepsy and 47 with delayed psychomotor development or mental retardation) was tested for the activity of some lysosomal enzymes. A partial deficiency of arylsulfatase A (ASA) in leucocytes (activities lower than 60% of the control average) was detected in 36 patients (25.7%), whereas few ASA-deficient individuals (1.4%) were found in the control sample of 71 healthy children. Therefore, the frequency of ASA deficiency is abnormally high in our sample of pediatric patients. ASA activity levels were also assayed on fibroblasts from 12 of the 36 ASA-deficient patients; the mean activity in these cells was 20% of the control average. Excretion of urinary sulfatides was not increased in the tested ASA-deficient patients (10/36). Clinical symptoms of these ASA-deficient patients bore no resemblance to classical metachromatic leucodystrophy (MLD), but resemble literature cases labeled as atypical MLD or diagnostic puzzles. This result suggests that reduced ASA activity might be associated with an increased risk of developing neurologic or neuropsychiatric disturbances in children.

Adolescent↗
PubMed1991

Immunoassay external quality assessment in Italy: HBsAg and anti-HBs tests.

The mode of operation of the CNR/Tecnostandard external quality assessment scheme for HBsAg and anti-HBs assays is outlined, and the relevant results reported. Emphasis is given to the retrospective evaluation of data in an attempt to derive a picture of the state of the art in Italian laboratories. The approaches followed for this evaluation include analysis of the rate of correct results and inspection of the relationships between analyte concentration and either the percentage of positive classifications of samples or the numerical test responses. Information is given on the "average" performance of individual kits as actually used in participants' laboratories.

Evaluation Studies as Topic↗
PubMed1991

Suboptimal response to hepatitis B vaccine in drug users.

Fifty-five drug users institutionalized in a community for drug detoxification were vaccinated against hepatitis B virus (HBV) with a recombinant yeast-derived vaccine (Engerix B, Smith Kline Biologicals, Belgium). At 0, 1, and 6 months, 20 micrograms of vaccine was given in the deltoid to these patients, of whom 17 had no serum HBV markers, 15 had only the antibody to core antigen (anti-HBc), and 23 had anti-HBc and antibody to the surface antigen (anti-HBs) values lower than the allegedly "protective" value of 10 mIU/mL. Forty-one healthy controls were vaccinated in parallel. At month 7 (ie, 1 month after the third dose of vaccine), in 76% (13/17) of drug users with no HBV markers, 6% (1/15) of those with isolated anti-HBc, and 69% (16/23) of those with anti-HBc and nonprotective anti-HBs, protective anti-HBs titers (greater than or equal to 10 mIU/mL) developed, compared with 97% (40/41) of controls. At month 24, these rates fell to 43% for drug users with no HBV marker, 0% for those with anti-HBc, 31% for those with anti-HBc and anti-HBs, and 86% for controls. The drug users who did not respond to vaccination were more likely to be those with evidence of prior HBV infection and anergy to skin tests. This indicates that unresponsiveness to hepatitis B vaccine in drug users may be due to altered immunity.

Adult↗
PubMed1990

Modulation of vitronectin receptor binding by membrane lipid composition.

The vitronectin (Vn) receptor belongs to the integrin family of proteins and although its biochemical structure is fully characterized little is known about its binding affinity and specificity. We report here that Vn receptor binding to different matrix proteins is influenced by the surrounding lipid composition of the membrane. Human placenta affinity purified Vn receptor was inserted into liposomes of different composition: (i) phosphatidylcholine (PC); (ii) PC+phosphatidylethanolamine (PE); (iii) PC+PE+phosphatidylserine (PS) + phosphatidylinositol (PI) + cholesterol (chol). The amount of purified material that could be incorporated into the three lipid vesicle preparations was proportional to the efficiency of the vesicle formation that increased from PC (38%) to PC+PE and PC+PE+PS+PI+chol (about 50%) vesicles. Electron microscopy analysis showed that the homogeneity and size of the three liposome preparations were comparable (20-nm diameter) but their binding capacity to a series of substrates differed widely. Vn receptor inserted in PC liposomes bound only Vn, but when it was inserted in PC+PE and PC+PE+PS+PI+chol liposomes it also attached to von Willebrand factor (vWF) and fibronectin (Fn). Vn receptor had higher binding capacity for substrates when it was inserted in PC+PE+PS+PI+chol than PC+PE liposomes. Antibodies to Vn receptor blocked Vn receptor liposome binding to Vn, vWF, and Fn. The intrinsic emission fluorescence spectrum of the Vn receptor reconstituted in PC+PE+PS+PI+chol liposomes was blue-shifted in relation to PC liposomes, suggesting a conformational change of the receptor in the membranes. These data provide direct evidence that the Vn receptor is "promiscuous" and can associate with Vn, vWF and Fn. The nature of the membrane lipid composition surrounding the receptor could thus influence its binding affinity, possibly by changing its conformation or exposure or both.

Amino Acid Sequence↗
PubMed1990

High genomic variability in the pre-C region of hepatitis B virus in anti-HBe, HBV DNA-positive chronic hepatitis.

Some chronic HBV carriers have circulating HBV DNA despite the presence of anti-HBeAg antibodies. This observation has recently been related to the presence, in the HBV pre-C region, of a translational stop codon that prevents HBeAg synthesis. In the present study, we analyzed, at the nucleotide level, the pre-C/C region of HBV isolated from the sera of 11 anti-HBe, HBV DNA-positive chronic carriers. Nucleotide sequence analysis of 25 independent clones revealed that the pre-C sequence is highly variable, even among clones derived from the same serum sample. Moreover, our data show that HBeAg synthesis can also be prevented by as yet undescribed T-C substitution at position 1815 that eliminates the start codon of the pre-C transcript. These results suggest that the HBV genome contains segments of high variability that have probably been selected during evolution to favor the segregation of functionally advantaged mutants capable of avoiding host immunity.

Base Sequence↗
PubMed1989

Interaction of fibronectin with cultured human endothelial cells: characterization of the specific receptor.

In this study we provide a characterization of the fibronectin (FN) binding to endothelial cells (EC), and we identify the FN binding site on these cells. 125I-FN binding to EC in suspension was time dependent and reached a plateau at 4 h. Cold FN inhibited this interaction in a concentration-dependent way, but vitronectin, fibrinogen, and IgG were poorly effective. About 80% of the total FN associated to EC at the equilibrium was specifically bound; of this, 60% was reversibly bound, while 20% appeared to be internalized. The FN binding was saturable and an apparent dissociation constant of about 0.23 x 10(-6) mol/L and a maximal number of binding sites of about 9.8 x 10(5) was estimated from binding isotherms. Autoradiography data showed that EC-associated 125I-FN was all in high mol wt form that did not enter the gel. We then characterize the FN receptor (FNR) in EC. An antiserum to the FNR isolated from human placenta inhibited FN binding to EC by 89%, and using the immunoblotting technique, it recognized two bands in the EC detergent extract of mol wt 125/160 Kd. This antiserum also recognized the EC membrane protein complex eluted from the FN affinity column by an arg-gly-asp (RGD) peptide. When this complex was included into liposomes, it poorly bound to FN. However, the binding was strikingly increased by addition of Mn in the buffer and was specific for FN in respect to other substrata. These data define the FN binding site in EC and indicate that it is functionally and structurally related to that isolated from human placenta.

Antigens, Surface↗
PubMed1989

Fibrinogen-endothelial cell interaction in vitro: a pathway mediated by an Arg-Gly-Asp recognition specificity.

It has been previously shown that fibrinogen (FG) associates specifically with human umbilical vein and bovine aortic endothelial cells (EC) in culture and induces EC migration. In the present study, we have investigated whether the FG-EC interaction is mediated by an Arg-Gly-Asp (RGD) recognition specificity and whether EC membrane proteins related to platelet GPIIb-IIIa are involved. Highly purified radioiodinated human FG, containing no detectable fibronectin, interacted with cultured human and bovine EC in suspension in a time-dependent and specific manner. The binding was inhibited by EDTA. Two polyclonal antibodies to platelet GPIIb-IIIa, which immunoprecipitated a heterodimer molecule from EC, inhibited FG binding to EC. These same antibodies inhibited FG-induced EC migration in a dose-dependent manner as measured in a Boyden chamber. Preabsorption of the antibodies with purified platelet GPIIb-IIIa markedly reduced both inhibitory activities. A series of synthetic RGD-containing peptides inhibited FG binding to EC and FG-induced EC migration. Gly-Arg-Gly-Asp (GRGD) was the most active peptide tested in inhibiting FG binding and EC migration (ID50 of 30 microM), and conservative substitutions in the RGD sequence markedly reduced inhibitory activity (ID50 greater than 1,000 microM). These results indicate that FG binding and EC migration are events mediated by an RGD recognition specificity and that EC surface proteins immunologically related to the GPIIb-IIIa complex on platelets are involved in this recognition.

Antigens, Surface↗
PubMed1989

Pre-S proteins in hepatitis B.

Two reactive sequences of the pre-S regions of hepatitis B surface antigen were synthesized chemically and used in micro-ELISAs for the assay of pre-S1 and pre-S2 antigens in serum from patients with acute and chronic hepatitis B. Pre-S1 antigen correlated well with the presence of HBV-DNA and was no longer detectable on cessation of viral replication, after natural recovery and after successful treatment with alpha-interferon. Pre-S2 proteins were also lost after treatment with alpha-interferon. The results show that the assay of pre-S1 and pre-S2 proteins in serum provides additional useful markers for assessing patients with acute and chronic hepatitis B infection and for monitoring the response to treatment with interferon.

Amino Acid Sequence↗
PubMed1989

Dissociated antibody responses to the S and pre-S2 regions of the hepatitis B virus after vaccination in hemophiliacs.

The membranes of hepatocytes and the pre-S2 envelope protein of the hepatitis B virus (HBV) contain binding sites for polymerized human albumin, which is thought to act as a link between HBV and hepatocytes. Hence, anti-pre-S2 antibodies should prevent HBV uptake by the liver, and there is indeed preliminary evidence that they protect chimpanzees from HBV infection. To evaluate whether a plasma-derived vaccine containing the pre-S2 sequence induced an anti-pre-S2 response in 105 vaccinated hemophiliacs, anti-pre-S2 was measured in parallel with antibody to hepatitis B surface antigen (anti-HBs). Eighty-five percent of the hemophiliacs had both anti-pre-S2 and anti-HBs when vaccination was completed, 13% had anti-HBs alone, and 2% (two cases) had anti-pre-S2 alone. Eighty-seven percent of anti-pre-S2-positive hemophiliacs compared with only 50% of anti-pre-S2-negative hemophiliacs (P less than 0.001) developed high anti-HBs titers (greater than or equal to 1,000 mlU/ml). This study demonstrates, therefore, that the antibody responses to the S and pre-S2 regions of HBV may be dissociated after vaccination in hemophiliacs and that higher anti-HBs titers are attained in anti-pre-S2-positive hemophiliacs.

Adolescent↗
PubMed1988

Prostacyclin release in the coronary circulation during sustained stimulation in in vitro and in in vivo experimental systems.

Prostacyclin release from rat isolated perfused hearts and from dog coronary circulation was studied by measuring immunoreactive 6-keto-PGF1 alpha (6-keto-PGF1a) in heart perfusate and in plasma obtained from the great cardiac vein respectively. Continuous infusion of arachidonic acid at constant concentration in isolated perfused hearts induced an increased prostacyclin release. This release showed a rapid peak within 10 min and a subsequent decrease. Low-flow ischemia induced an increased perfusate concentration of 6-keto-PGF1a but, considering the decreased flow, prostacyclin release was actually reduced. During the whole period of ischemia (60 min) prostacyclin release was constant. In open-chest anesthetized dogs 6-keto-PGF1a concentration in the great cardiac vein was increased after ligation of the left anterior descending coronary artery. A prolonged period of coronary occlusion (4.5 hours) resulted in a progressive rise of prostacyclin release. 6-keto-PGF1a determinations in the femoral vein and in the aorta did not show relevant variations during the observation period.

Animals↗
PubMed1988

In vitro platelet adhesion to vascular subendothelium: studies in patients with polycythaemia vera.

In this work we studied platelet adhesion to subendothelial surfaces in 10 patients with polycythaemia vera and 10 healthy volunteers at 40% Hct (corresponding to the mean value of our control group) and 55% Hct (a value roughly corresponding to the mean Hct in polycythaemic patients). Platelet concentration was kept constant at 2.0-2.5 X 10(11)/l. The results indicate that there was a statistically significant increase in adhesion both in controls and in patients with Hct varying from 40% to 55%. The contribution of the higher Hct in promoting platelet adhesion was comparable in the two groups. When red blood cells (RBC) from the patients were tested with platelets from healthy volunteers in cross-over experiments, they promoted adhesion in the same way as control RBC. Similarly, when patients' platelets were mixed with control RBC, adhesion was the same as control platelets. These data indicate that platelet and RBC contribution to this parameter are not significantly modified in this group of polycythaemic patients, provided that platelet and RBC values are adjusted to control range.

Adult↗
PubMed1988

Biochemical and functional characteristics of fibrinogen interaction with endothelial cells.

Several observations indicate that endothelial cells interact with fibrinogen, fibrin, and their derivative products. The main biological function of fibrinogen on endothelial cells so far identified is its ability to promote adhesion, motility, and cytoskeletal organization of these cells. In other words, when fibrinogen is bound to a substratum, it behaves as a matrix protein like fibronectin, collagen, or vitronectin. Fibrinogen specifically binds to endothelial cells with low affinity and with a high number of binding sites. In addition, the putative fibrinogen receptor in endothelial cells appears to be related to the other extracellular matrix protein receptors.

Binding Sites↗
PubMed1987

At low extracellular calcium concentration platelet activating factor induces beta-thromboglobulin release from human platelets through thromboxane-endoperoxides formation.

The aim of this study was to investigate the mechanism involved in beta-thromboglobulin (BTG) release induced by platelet activating factor (PAF) in human platelet-rich plasma (PRP) and washed platelets (WP) during aggregation. PAF was used in PRP at increasing concentrations starting at its threshold concentration for irreversible aggregation (TAC: 90-150 nM). In citrated PRP, PAF induced release of BTG (80-95% of total content) and thromboxane B2 (TXB2) formation (30-40 pmol/ml). At low PAF concentrations aggregation and BTG release were blocked by apyrase (a scavenger of ADP), by ASA (an inhibitor of cyclooxygenase) and by BM 13177 (a thromboxane receptor antagonist). Higher concentrations of PAF overcame the effect of apyrase, but only induced reversible aggregation and minor release in the presence of ASA or BM 13177. In heparinized PRP, PAF induced full irreversible aggregation, but only very low BTG release (about 25% of total content) and thromboxane synthesis (2-3 pmol/ml). WP resuspended in the presence of 2 mmol/l Ca2+ seldom responded to PAF alone, as previously shown by others, but full aggregation could be induced by concomitant addition of subthreshold concentrations of PAF (25-50 nM) and epinephrine (1 microM). In these conditions average BTG release from WP was less than 20% of the amount releasable by thrombin. In contrast, when WP were resuspended in the absence of Ca2+, stimulation by PAF + EPI induced sustained BTG release (40-50% of total content) and TXB2 synthesis (15-20 pmol/ml). We conclude that at low Ca2+ concentration PAF induces BTG release mainly through thromboxane-endoperoxides formation. In contrast, when [Ca2+] is normal, PAF does not or weakly induces thromboxane formation and BTG release.

Blood Platelets↗
PubMed1987

Platelets express a membrane protein complex immunologically related to the fibroblast fibronectin receptor and distinct from GPIIb/IIIa.

We have previously identified and characterized a membrane glycoprotein complex (GP150/135) that functions as fibronectin receptor (FN-R) in fibroblast adhesion. Here we report that an immunologically related protein complex is expressed at the surface of human platelets. Antibodies monospecific for the smaller subunit (GP135) of the fibroblast FN-R in fact specifically stained the platelet surface, as determined by FACS analysis, and reacted with a component of molecular weight (mol wt) 138,000 as shown in western blots of platelet membranes. Moreover, the same antibodies precipitated the 138,000 component together with a 160,000 protein, suggesting that the two molecules are associated in a supramolecular complex. A comparative analysis indicated that this protein complex is distinct from the GPIIb/IIIa complex, known to function as a receptor of wide specificity for fibrinogen, fibronectin, and von Willebrand factor. Differential extraction experiments revealed that the platelet 138,000 component is an integral membrane protein.

Antibodies↗
PubMed1987

Immunogenicity of yeast-derived hepatitis B vaccines in young adults.

A study of the safety and immunogenicity of two different recombinant DNA yeast-derived hepatitis B vaccines was conducted in 90 young adults according to a 0-, 1-, and 6-month vaccination schedule. Preliminary results using the 20 micrograms SmithKline Biologicals or 10 micrograms Merck Sharp & Dohme recombinant yeast-derived hepatitis B vaccines indicate that both vaccines are clinically safe and immunogenic. Only minor side effects have thus far been reported. Seroconversion rates among vaccine recipients were 80% or greater after the first two injections with either vaccine, and 100% after the third dose of the SmithKline Biologicals recombinant DNA hepatitis B vaccine.

Adult↗