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Biomedical subjects

M Castagnola

Publications and source records attributed to M Castagnola.

At least 55 records · Page 3Linked to original sources
PubMed1994

Structure-function relationship in the serotransferrin: the role of the pH on the conformational change and the metal ions release.

We report experimental evidence that the pH value of the micro-environment of the protein is the key for the conformational changes of transferrin, rather than the ligated for unligated state of the binding sites. The "open" and "closed" conformation of protein, suggested by X-ray crystallography in static condition, is triggered by the pH value and the effect is independent of the metal ion being transported. We propose a simple description of the structure-function relationship that allows this protein to deliver, in particular, iron or aluminum ions in the biological cycle.

Aluminum Compounds↗
PubMed1994

Cord blood mononuclear cell responsiveness to beta-lactoglobulin: T-cell activity in 'atopy-prone' and 'non-atopy-prone' newborns.

We have studied the T-cell-mediated response to the major allergen of cow's milk, in a group of newborns at risk of developing cow's milk allergy, and in a control group. Before any atopic status has developed, we observe beta-lactoglobulin-specific primary proliferation only in the group at risk for food-related allergies. In this group, the capability to proliferate is not due to placental transmission of 'factors' from allergic mothers. The recognition of the tested beta-lactoglobulin peptides does not show major differences between the responder and nonresponder populations. In the responder population, the response to p145-161 appears linked to a primary response to ovalbumin, another frequent food allergen. On the basis of our findings, we propose a model in which development of allergic diseases is linked to an alteration of T-cell activation through the engagement by the antigen; the HLA phenotype determines the allergen(s) involved, and other genetic or environmental factors dictate the clinical characteristics of the disease.

Epitopes↗
PubMed1994

[Surgical resection of exocrine neoplasms of the pancreatic head: indications and requirements].

Surgical resection is the only curative procedure for the treatment of the cancer of the pancreatic head: this paper describes the precise indications for surgery. These are: tumour size (diameter less than 4 cm), no metastases in the extra regional lymph nodes, no arterial invasion or involvement of the portal vein of more than 1.2 cm in length or its bilateral narrowing. The authors point out that only the complete removal of the retropancreatic tissue allows control of local recurrence and metastasis. They examine different resective procedures, concluding, on the basis of the literature and their own experience, that R2 subtotal pancreatoduodenectomy leads to a curative resection because of the removal of the foci of micrometastasis, a better control of local recurrence and, perhaps, a longer survival. They discuss the problem of the use of pyloro preserving pancreatic duodenectomy (PPDP) for exocrine tumours of the pancreas and conclude that it is correct to perform such an operation even for the treatment of these tumours if the local extension of the neoplasm allows it. Finally, the authors underline the need to use other adjuvant therapies to improve results: these however, are very often, quite limited.

Humans↗
PubMed1993

Physiological relevance of the overall delta H of oxygen binding to fetal human hemoglobin.

Human fetal hemoglobin is known to display, at 20 degrees C, a lower affinity than human adult hemoglobin for oxygen when both proteins are in the absence of organic phosphates. The physiologically important reverse situation is achieved at 37 degrees C upon addition of 2,3-bisphosphoglycerate (DPG), whose lower effect on fetal hemoglobin is related to some amino acid substitutions present in gamma-chains. However, the difference in oxygen affinity observed at 37 degrees C is not solely due to the different modulation power of DPG with respect to adult and fetal hemoglobins. In fact, the results presented here reveal new aspects linked to the interplay of temperature and organic phosphates. In particular, the lower effect of DPG on fetal hemoglobin renders almost identical the oxygen affinity of the two hemoglobins at 20 degrees C, abolishing the difference observed in the absence of the effector. Successively on going from 20 degrees C to 37 degrees C, by virtue of the lower overall heat of oxygenation (delta H) displayed by fetal hemoglobin when in the presence of DPG, adult hemoglobin shows a lower oxygen affinity, as it should if oxygen has to be transferred from maternal to fetal blood.

2,3-Diphosphoglycerate↗
PubMed1993

X-ray small angle scattering of the human transferrin protein aggregates. A fractal study.

X-ray small angle scattering experiments, using a pin hole SAXS camera with Synchrotron radiation source, have been performed to study the conformational changes of lyophilized samples of Apo-, Mono-, and Diferric- human transferrin. We report the experimental evidence that the analysis of the scattered intensity through the fractal theory may give information on the particle size and its variation upon iron binding.

Apoproteins↗
PubMed1993

Vertical root fractures in endodontically treated teeth: a clinical survey of 36 cases.

A clinical study was done on 36 original cases of vertical root fractures along with the data gathered from 32 cases published previously in the literature. Vertical root fractures most frequently occur in posterior teeth in patients between 45 and 60 yr of age. The average elapsed time between the endodontic treatment and the subsequent diagnosis of vertical fracture was found to be approximately 10 yr. The evidence and symptoms most often found are mild pain in the area of the fractured tooth often accompanied by swelling and fistula, along with a deep pocket in just one area of the attachment surrounding the tooth. The sign most often revealed by X-ray is a radiolucent periradicular band.

Age Factors↗
PubMed1992

Molecular basis of low-temperature sensitivity in pig hemoglobins.

It has been generally assumed that mammals have blood with a greater temperature sensitivity than ectothermic organisms. Recent results have shown that in some species of mammals, Hb displays a value of overall oxygenation enthalpy (delta H) much less exothermic than that observed for most mammalian hemoglobins, including human adult Hb. In this respect, a very interesting case is represented by porcine blood which shows a modest effect of temperature, the temperature coefficient of its oxygen-dissociation curve being significantly lower than that of human blood. Here we report a detailed functional characterization of pig Hb, which, interpreted on the basis of the amino acid sequence of the alpha and beta chains of the molecule, sheds some light on the molecular basis of the phenomenon.

Amino Acid Sequence↗
PubMed1992

Cooperative cyanide dissociation from ferrous hemoglobin.

Rapid reduction of cyano-met hemoglobin (Hb+CN-) leads to the formation of an intermediate species, the cyanide derivative of ferrous hemoglobin, which dissociates to unliganded hemoglobin because of the extremely low affinity of the ligand for the ferrous heme iron. The properties of the intermediate were studied by transient spectroscopy in human hemoglobin and its isolated alpha and beta chains, in the presence and absence of CO. When mixing with dithionite, the time courses of reduction of the heme iron and dissociation of cyanide overlap considerably; addition to the reaction mixture of the redox indicator methyl viologen considerably increases the rate of reduction and allows unequivocal determination of the spectroscopic and kinetic properties of the intermediate. The results show that (i) the dissociation of cyanide from the isolated alpha and beta chains (as well as the (alpha CO)2(beta + CN-)2 hybrid) is a simple process; (ii) the two chains display similar rate parameters, but show spectroscopic inequivalence, both in the Soret and the visible regions; (iii) cooperative effects are shown to control the rate of dissociation of cyanide from hemoglobin, similarly to what happens for oxygen; and (iv) allosteric effectors (typically inositol hexaphosphate) increase the overall rate of dissociation by stabilization of the T state. We have, therefore, shown for the first time that the dissociation of cyanide from ferrous hemoglobin is controlled by the quaternary state, thereby adding one more ligand to the analysis of the structure-function relationships in hemoglobin.

Cyanides↗
PubMed1992

Quantitative determination of methemoglobin by measuring the solvent-water proton-nuclear magnetic resonance relaxation rate.

We report a new method for the quantitative determination of human methemoglobin (metHb) based on the measurement of the solvent-water proton-nuclear magnetic resonance (NMR) relaxation rate R1 [normalized to 1 mmol/L hemoglobin (Hb) concentration]. MetHb (%) is estimated from the linear dependence of R1 on the metHb concentration, taking into account the simple relationship [MetHb] = [(R1 - R1HbO2)/(R1metHb - R1HbO2)].100, where R1HbO2 and R1metHb are values for the solvent-water relaxation rate of standard 1.0 mmol/L solutions of the oxygenated derivative of human hemoglobin (HbO2) and of metHb, respectively. The minimum metHb that may be determined from the analysis of the experimental data is 0.5 +/- 0.4%.

Cytochrome-B(5) Reductase↗
PubMed1991

Peptide mapping through the coupling of capillary electrophoresis and high-performance liquid chromatography: map prediction of the tryptic digest of myoglobin.

The tryptic map of horse myoglobin was analysed through capillary electrophoresis using capillaries modified by a monolayer of acrylamide. The results were reproducible and the map was obtained in less than 30 min from ca. 8 pmol of tryptic digest. The peptide identification was performed using peptides previously identified by high-performance liquid chromatography. The peak areas measured using the two techniques are closely related, and the comparison of elution and migration times shows that the two techniques provide different maps. Furthermore, using the semiempirical relationship suggested by Grossman et al. [Anal. Biochem., 179 (1989) 28], which links the electrophoretic mobility to the charge of the peptide and its number of amino acids, a good agreement between predicted and experimental mobilities was observed.

Amino Acids↗
PubMed1991

'Antibiobodies': antibiotic-like anti-idiotypic antibodies.

Pathogenic micro-organisms such as Candida albicans may be susceptible to the activity of antimicrobial products like yeast killer toxins due to the presence of specific cell wall receptors for these agents. Anti-idiotypic antibodies (anti-Ids) were produced that competed for these receptors with the yeast killer toxin of a strain of Pichia anomala. We report here that affinity chromatography purified anti-Ids may kill C. albicans cells in vitro which are susceptible to the activity of the yeast killer toxin, as well as P. anomala killer cells which are obviously immune to their own toxin despite possessing specific cell wall receptors which can be detected by indirect immunofluorescence with anti-Ids. We propose that these conceptually new antimicrobial immunoglobulins acting as antibiotics be called 'antibiobodies'.

Anti-Bacterial Agents↗
PubMed1991

Kinetic aspects of release of fibrinopeptides AP and AY by human alpha-thrombin.

The time-dependent release by human alpha-thrombin of the physiological variants of fibrinopeptide A, i.e. fibrinopeptide A-3-phosphate (FPAP) and des-Ala-fibrinopeptide A (FPAY), has been measured in order to study the kinetic pathway for their hydrolysis. The best-fit kinetic model for the release of FPAP and FPAY is consistent with a simple pseudo first-order reaction, as observed with FPA. These findings indicate that FPAP and FPAY are also released from intact fibrinogen before release of FPB. The values of the specificity constants, i.e. k(at)/Km, for the enzymatic reaction between thrombin and the various alpha-chains showed that AP alpha- and AY alpha-chain are hydrolyzed with a 0.2-and 0.4-fold higher specificity constant respectively than that of A alpha-chain. Such minor differences observed with the various chains suggest that the 1-3 NH2-terminal residues of the chain do not significantly contribute to the catalytic efficiency of thrombin toward the alpha-chains of fibrinogen.

Chromatography, High Pressure Liquid↗
PubMed1991

[Radiographic interpretation of experimentally produced osseous lesions in the human mandible].

Using rotary instruments drilled bony cavities which differed in diameter and depth into a human jaw. X-rays were taken and developed employing a very precise and accurate technique to obtain high definition radiograph. From a careful study of these x-rays it was found that localized lesions in cancellous bone alone are difficult to visualize on x-rays, whereas they are easily noticeable when the cortical bone is involved.

Humans↗
PubMed1991

[Access cavity for endodontic treatment of anterior teeth].

In this study the authors investigated a group of front teeth, extracted because of the periodontal problems, into which an access cavity have been drilled at the point shown on an x-ray between two straight lines which start at the apex and are tangent to the pulp chamber. These teeth were then horizontally sectioned at the cement-enamel junction to see how much dental substance remained compared to a control group into which a traditional opening had been made through the palatal surface. The result show a greater conservation of dentin when the direct method of opening discussed herein was used.

Dental Cavity Preparation↗
PubMed1991

[Pancreatoduodenectomy with preservation of the stomach and pylorus: technical and functional aspects].

Pancreatoduodenectomy is the most used resective operation in the treatment of cephalopancreatic pathology; nevertheless it is a severely demolitive operation, especially if performed according to the traditional technique. It can induce early as well as late complications in a high percentage of cases. A number of technical improvements have been proposed so far in order to reduce or avoid such complications; duodenopancreatectomy with gastric and pyloric preservation (PPDP) is the most representative one. The Authors analyze technical and functional features of PPDP in 22 patients operated on; results are compared with the traditional technique. In conclusion, among all the techniques proposed, PPDP assures the best improvement in the quality of life of these patients.

Ampulla of Vater↗
PubMed1990

Detection by immunofluorescent anti-idiotypic antibodies of yeast killer toxin cell wall receptors of Candida albicans.

Yeast killer toxin cell wall receptors of Candida albicans were observed by indirect immunofluorescence using an affinity purified rabbit anti-idiotypic antiserum. The antiserum had been raised against a monoclonal antibody neutralizing the in vitro activity of a killer toxin produced by a selected strain of Hansenula anomala UCSC 25F. This simple procedure permitted the location of killer toxin cell wall receptors in various morphological phases of the yeast cells. The use of the indirect immunofluorescence technique with anti-idiotypic antibodies may have potential value in determining the occurrence of killer toxin receptors in other microbial systems.

Antibodies, Anti-Idiotypic↗
PubMed1990

Effect of aromatic isothiocyanates on the functional properties of human hemoglobin. Role of the stereochemistry of the charged group.

The effect of chemical modification of hemoglobin with six derivatives of benzene isothiocyanate has been studied. The negatively charged reagents (isothiocyanates of benzoic and benzenesulfonic acids) markedly inhibit the interaction of hemoglobin with allosteric effectors such as H+, Cl- and organic phosphates; the affinity for heme ligands in the absence of effectors is reduced but cooperativity is maintained, making these modified hemoglobins suitable models for a possible 'blood substitute'. The only uncharged reagent tested (isothiocyanate of benzenesulfonamide) increases the oxygen affinity of hemoglobin and affects only slightly the interaction with heterotropic ligands; its potential use as an antisickling drug is under study.

Benzene Derivatives↗