Biomedical subjects

A Motta

Publications and source records attributed to A Motta.

At least 19 recordsLinked to original sources

PubMed1999

In vitro evaluation of the inflammatory potential of the silk fibroin.

Silk fibroin membranes recently have been suggested as matrices for biomedical applications, such as guided tissue regeneration and burn wound dressings. The aim of this study was to evaluate the inflammatory potential of fibroin films and to compare the fibroin films with two model materials with completely different physico-chemical properties: poly(styrene) and poly(2-hydroxyethyl methacrylate). Fibroin bound lower levels of fibrinogen than did the two synthetic polymers while the same amounts of adsorbed human plasma complement fragment C3 and IgG were detected. Studies of the binding strength of C3 to fibroin, evaluated by a novel experimental procedure, indicated the occurrence of strong hydrophobic interactions at the interface. The activation of the mononuclear cells by fibroin, measured as interleukin 1beta production, was lower than the reference materials. Adhesion experiments showed the ability of the macrophages to adhere to fibroin by filopodia without a complete spreading of the cells. The results achieved in this study demonstrate that the interactions of fibroin with the humoral components of the inflammatory system were comparable with those of the two model surfaces while the degree of activation and adhesion of the immunocompetent cells appeared more limited.

Adsorption↗

PubMed1999

Synergistic effects of oxidative environments and mechanical stress on in vitro stability of polyetherurethanes and polycarbonateurethanes.

The in vitro structural stability of polyetherurethanes (PEUs) and polycarbonateurethanes (PCUs and PCUUs) was examined under strong oxidative conditions (0.5N HNO3, pH 0.3; and NaClO, 4% Cl2 available, pH approximately 13) and in the presence of a constant strain state. Solvent-cast dog-bone shaped specimens were strained at 100% uniaxial elongation over extension devices and completely immersed in the oxidative solutions at 50 degrees C for 15 days. Unstrained polyurethane (PU) samples were treated in the same way for comparison. The modification of the PU molecular structure was determined by DSC, GPC, ATR-FTIR, static contact angle, and surface roughness analyses. The incubation in nitric acid and sodium hypochlorite brought about a greater degradation of samples tested under the applied strain with the exception of PEU treated with nitric acid. PEU was the most affected material, showing bulk deterioration in NaClO and significant modifications in nitric acid, with the appearance of new IR bands, which were assigned to oxidation products. A higher phase separation between soft and hard domains occurred in PCUs upon incubation in nitric acid, the treatment with NaClO gave rise to new bands in the IR spectra, denoting the presence of oxidation products at the surface. The surface roughness greatly increased in strained PCUs with SEM evidence of deep cracks and holes or ragged and stretched fractures perpendicular to the direction of stress. PCUU underwent complex chemical modifications with a marked decrease of N-H and urea IR absorptions and showed a lower degradation than PEU and PCUs under mechanical constraint. From these results, sodium hypochlorite appears to be able to create an ESC-like degradation for PUs that are resistant to other aggressive chemical environments.

Microscopy, Electron, Scanning↗

PubMed1999

Forced adhesive growth of K562 leukemic cells that normally grow in suspension induces variations in membrane lipids and energy metabolism: a proton NMR study.

The mechanisms responsible for the adhesion of cells onto a material's surface and the effects that that adhesion may have on cell structure and function are fundamental questions in biomaterials research. We recently demonstrated that the erythroleukemic cell line K562, which normally grows in suspension, can be induced to grow attached to a polylysine-coated solid surface in an anchorage-dependent manner. In this study, the effects of the growth of K562 cells onto polylysine were further investigated utilizing 500 MHz 1H-NMR spectroscopy. The NMR results showed that when K562 cells are grown attached to a positively-charged polylysine surface, there are alterations in lipids and energy metabolism. In particular, there was a 31% increase in phosphatidylcholine and a 15% decrease in each of its two precursors, glycerophosphatidylcholine and choline, as well as a 20% increase in CH2 lipids and a 7% decrease in CH3 lipids in treated cells compared to the controls. These results suggest that adhesive growth can induce strong variations in membrane structure, including the membrane fluidity of K562 cells. In addition, in cells attached to polylysine there was about a 10% decrease in creatine (together with phosphocreatine), a 20% increase in gamma-glutamate, a 15% increase in beta-glutamate, and a 24% decrease in lactate. This second set of results, which is closely related to energy metabolism, indicates that not only does adhesive growth induce changes in K562 cell membrane structure, but also in the utilization of energy in these cells. The data are discussed in view of the possible role played by surface charge in affecting cell structure and function in cells that come into direct contact with charged biopolymers.

Cell Adhesion↗

PubMed1999

Effect of the urine conditioning film on ureteral stent encrustation and characterization of its protein composition.

The goal of this study was to characterize the protein composition of the conditioning film deposited onto the surface of ureteral stents during in vivo implantation and to relate its presence to the precipitation of calcium crystals. The protein pattern of the conditioning film of implanted nonencrusted and encrusted urological stents was assessed by SDS-PAGE and Western blot of the desorbed species. The results obtained highlighted different electrophoresis profiles between nonencrusted and encrusted stents. Western blot showed the ubiquitous presence of albumin, while Tamm-Horsfall Protein and alpha1-microglobulin adsorption was limited to nonencrusted devices. By an in vitro dynamic model in which artificial urine was flowed through the lumen of control and retrieved nonencrusted stents, we demonstrated that the organic layer remarkably enhanced crystal precipitation and aggregation events on the surface.

Adsorption↗

PubMed1999

Iopiperidol: nonionic iodinated contrast medium with promising anticoagulant and antiplatelet properties.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the anticoagulant and antiplatelet characteristics of iopiperidol, a nonionic, triiodinated contrast agent. MATERIALS AND METHODS: Anticoagulant effects of iopiperidol were assessed both in vitro and in vivo after single or repeated intravenous administrations to rats. To this aim, results of prothrombin time, activated partial thromboplastin time, thrombin time, and fibrinogen tests were evaluated. To define better the mechanism of action of iopiperidol and of the contrast media used for comparison, in vitro tests to study the effects on thrombin activity and on thrombin generation were performed. In addition, the effect of iopiperidol was studied on adenosine diphosphate- and collagen-induced platelet aggregation both in vitro and in vivo after single or repeated intravenous administrations in the rat. RESULTS: In vitro, iopiperidol showed anticoagulant properties similar or superior to those of the ionic ioxaglate. Iopiperidol also inhibited collagen-induced platelet aggregation statistically significantly more than iodixanol and ioxaglate (P < .05). In vivo, no significant differences between iopiperidol and ioxaglate were observed after single or repeated administrations. CONCLUSION: The in vitro anticoagulant effect of iopiperidol is similar or even superior to that of ioxaglate; the in vivo effect is similar to that of reference nonionic contrast media.

Animals↗

PubMed1999

Sapinofuranones A and B, two new 2(3H)-dihydrofuranones produced by sphaeropsis sapinea, a common pathogen of conifers

Two new 5-substituted dihydrofuranones, named sapinofuranones A and B (1 and 2), were isolated from liquid cultures of Sphaeropsis sapinea, a phytopathogenic fungus causing a wide range of disease symptoms on conifers. A fungal strain isolated from Cupressus macrocarpa produced both 1 and 2 at concentrations higher than those produced by the strain isolated from Cupressus sempervirens. Bioassay of 1 and 2 gave epinasty and brown discoloration on petioles of tomato leaves, sapwood stain on inner cortical tissues of the stem of cypress seedlings, and yellowing and needle blight on pine seedlings. Compounds 1 and 2 were characterized, using spectroscopic and chemical methods, as two new 4-[(2Z, 4E)-1-hydroxy-2,4-hexadienyl]butan-4-olides, which are epimers at C-1 of the side chain. The absolute stereochemistry of this chiral center, determined by application of the Mosher's method, proved to be S and R in 1 and 2, respectively.

Journal Article↗

PubMed1999

Conformational flexibility in calcitonin: the dynamic properties of human and salmon calcitonin in solution.

We have studied the dynamic properties of human (h) and salmon (s) calcitonin (CT) in solution. For both hormones, distance geometry in torsion-angle space has been used to generate three-dimensional structures consistent with NMR data obtained in sodium dodecyl sulfate micelles. For sCT and hCT we used, respectively, 356 and 275 interproton distances together with hydrogen-bonds as restraints. To better characterize their flexibility and dynamic properties two fully unrestrained 1100-ps molecular dynamics (MD) simulations in methanol were performed on the lowest-energy structures of both hormones. Statistical analyses of average geometric parameters and of their fluctuations performed in the last 1000 ps of the MD run show typical helical values for residues 9-19 of sCT during the whole trajectory. For hCT a shorter helix was observed involving residues 13-21, with a constant helical region in the range 13-19. Angular order parameters S(phi) and S(psi) indicate that hCT exhibits a higher flexibility, distributed along the whole chain, including the helix, while the only flexible amino acid residues in sCT connect three well-defined domains. Finally, our study shows that simulated annealing in torsion-angle space can efficiently be extended to NMR-based three-dimensional structure calculations of helical polypeptides. Furthermore, provided that a sufficient number of NMR restraints describes the system, the method allows the detection of equilibria in solution. This identification occurs through the generation of 'spurious' high-energy structures, which, for right-handed alpha-helices, are likely to be represented by left-handed alpha-helices.

Amino Acid Sequence↗

PubMed1999

Low chronic ethanol consumption affects ovulation and PGE synthesis by the cumulus cell masses in mice.

Central and gonadal function can be affected by chronic consumption of high and moderate doses of ethanol. Few studies have been conducted to determine the effect of ethanol intake at ovarian and gamete level. Previously, we showed that fertilization rates of low chronic ethanol treated female mice were diminished. Also, our recent results indicated that moderate chronic intake of ethanol by immature females could alter the ovulatory quantity and produce morphological alterations in the superovulated oocytes. Furthermore, PGE production by oocyte cumulus complexes (OCCs) was reduced in the females treated with 10% (w/v) ethanol. In the present investigation, we studied the effects of 5% ethanol treatment given to immature mice for 30 days on the quality and quantity of oocytes superovulated at 16 h posthuman chronic gonadotrophin. Treated females had impaired ovulation rates (P < 0.05) as compared to the controls. The percentage of activated and morphologically abnormal oocytes was elevated in the ethanol-treated females (P < 0.05). PGE synthesis by the OCCs was higher than in the controls (P < 0.01). In summary, the administration of long-term ethanol at a relatively low dose to immature females produces decreased ovulation rates, abnormal oocyte morphology with high spontaneous activation and altered levels of PGE production by the oocytes' cumulus complexes. The relationship between the oocyte quality and abnormal synthesis of PGE is discussed.

Animals↗

PubMed1998

Progesterone enhances prostaglandin E2 production via interaction with nitric oxide in the mouse acrosome reaction.

In the present study we evidenced that progesterone could directly stimulate sperm nitric oxide synthase (NOS) in capacitated mouse spermatozoa. This stimulation led to an increase in sperm prostaglandin E2 (PGE2) production and subsequent acrosomal exocytosis. However, cGMP levels were not modified during the progesterone-induced acrosome reaction under our experimental conditions. These results suggest a functional role for nitric oxide as an intracellular messenger through, at least, stimulation of PGE2 production during the acrosome reaction triggered by progesterone.

Acrosome Reaction↗

PubMed1998

Solution structure of human calcitonin in membrane-mimetic environment: the role of the amphipathic helix.

The 32 amino acid hormone human calcitonin was studied at pH 3.7 and 7.4 by multidimensional NMR spectroscopy in sodium dodecyl sulfate micelles at 310K. The secondary structure was obtained from nuclear Overhauser enhancement spectroscopy (NOESY), 3JHNalpha coupling constants, and slowly exchanging amide data. Three-dimensional structures consistent with NMR data were generated by using distance geometry calculations. A set of 265 interproton distances derived from NOESY experiments, hydrogen-bond constraints obtained from amide exchange, and coupling constants were used. From the initial random conformations, 30 distance geometry structures with minimal violations were selected for further refinement with restrained energy minimization. In micelles, at both pHs, the hormone assumes an amphipathic alpha-helix from Leu9 to Phel6, followed by a type-I beta-turn between residues Phel6 and Phel9. From His20 onward the molecule is extended and no interaction with the helix was observed. The relevance of the amphipathic helix for the structure-activity relationship, the possible mechanisms of interaction with the receptor, as well as the formation of fibrillar aggregates, is discussed.

Amino Acid Sequence↗

PubMed1998

Changes in serum conditioning profiles of glutaraldehyde-crosslinked collagen sponges after their treatment with calcification inhibitors.

The purpose of this study was to evaluate the effects of the calcification inhibitors FeCl3 and sodium dodecyl sulfate (SDS) on the morphology of glutaraldehyde-crosslinked type I collagen sponges and on their serum conditioning. Scanning electron microscopy (SEM) showed that the morphology of the sponges, already modified by glutaraldehyde crosslinking, underwent further changes after treatment of the hydrogels with inhibitors. Coral-like structures were found to branch from the bulk of the material especially in the case of SDS-treated samples. The composition and morphology of the conditioning layers was characterized after 48 h incubation in serum by SDS-polyacrylamide gel electrophoresis-immunoblot of the adsorbed proteins, by energy-dispersive X-ray analysis of the elements (EDX), and by SEM of the conditioned surfaces. All the samples showed the adsorption of proteins with molecular weights ranging from 10 to 203 kD. However, the peculiar adsorption of an approximately 10-kD band (complement C3 fragment) and of fibronectin were detected in the case of glutaraldehyde-crosslinked collagen. On the other hand, glutaraldehyde-crosslinked collagen treated with 0.1M FeCl3 showed the remarkable adsorption of a 29-kD band. The glutaraldehyde-crosslinked hydrogels showed the massive precipitation of crystals on their exposed surfaces, whereas a disordered network structure surrounding the collagen fibrils was found in the case of the samples pretreated with inhibitors. A predominant precipitation of sodium and chloride was detected in all the sponges, although the ratio between the peaks changed from from one hydrogel to another. The results reported in this article clearly indicate that the treatments with SDS and FeCl3 change the surface conditioning of collagen sponges, suggesting a possible role of deposited serum solutes in affecting mineralization processes on bioprosthesis.

Blood Physiological Phenomena↗

PubMed1998

Topology of the calmodulin-melittin complex.

The topology of the Ca2+-calmodulin-melittin ternary complex has been investigated by a combined strategy which integrates limited proteolysis and cross-linking experiments with mass spectrometric methodologies. The rationale behind the methods is that the interface regions of two interacting proteins are accessible to the solvent in the isolated molecules, whereas they become protected following the formation of the complex. Therefore, when limited proteolysis experiments are carried out on both the isolated proteins and the complex, differential peptide maps are obtained from which the interface regions can be inferred. Alternatively, cross-linking reactions performed under strictly controlled conditions lead to the identification of spatially closed amino acid residues in the complex. Mass spectrometry can be employed in both procedures for the definition of the cleavage sites and to identify covalently linked residues. Our results show that melittin interacts with calmodulin by adopting a parallel orientation, i.e. the N and C-terminal halves of the peptide are anchored to the amino and carboxy-terminal domains of the protein, respectively. This orientation is inverted with respect to all the peptide substrates examined so far. A model of the complex was designed and refined on the basis of the experimental results, supporting the above conclusions. This finding reveals a further dimension to the already remarkable capability of calmodulin in binding different protein substrates, providing this protein with the capability of regulating an even larger number of enzymes.

Amino Acid Sequence↗

PubMed1998

Effects of low chronic ethanol exposure on prostaglandin E synthesis by preimplantation mouse embryos.

Embryo prostaglandin (PG) synthesis plays a role in the modulation of embryo metabolism and viability, and in the beginning of the implantation. The effects of ethanol consumption seem to be mediated at least in part by PGs. Increased PG production of postimplantation embryos is associated with retardation and abnormalities in the gestational period. The aim of this study was to find out the effects of low chronic ethanol ingestion by mice, previous to pregnancy, on the PGE released by in vitro and in vivo derived embryos. Immature females or adult males were treated with 5% ethanol for 30 days. After fertilization and mating, two-cell embryos, morulae and blastocysts were collected. The PGE synthesis and release were measured by radioimmunoassay. PGE production by in vitro derived two-cell embryos from ethanol-treated females was lower than in the control group (P < 0.01). Also, PGE production was reduced when two-cell embryos came from ethanol-treated males (P < 0.01). There were no differences in PGE synthesis by in vitro derived morulae and blastocysts in these groups. Two-cell embryos derived from mating produced lower quantities of PGE when they came from ethanol-treated females mated with control males, as compared to the control group. PGE release by in vivo derived blastocysts from ethanol-treated females was reduced significantly, as compared to the control group (P < 0.01). We conclude that a low concentration of ethanol administered chronically to immature females reduces PGE synthesis and release by two-cell embryos from culture in vitro, and by embryos of days 2 and 4 from in vivo development.

Animals↗

PubMed1998

Relationship between mouse uterine contractility, nitric oxide and prostaglandin production in early pregnancy.

Despite the evidence for a functional role of nitric oxide (NO) in the regulation of uterine contractility in several species, there is little information about the effects of this gas on the mouse uterus. The aims of this study were to investigate if the NO relaxation pathway is present in mouse pregnant uterus and the relationship with the uterotonic prostaglandins (PGs E and F2alpha) production. We evaluated the effect of the treatment with a competitive nitric oxide synthase (NOs) inhibitor: N(G)-monomethyl-L-arginine on the spontaneous contractile activity and prostaglandin production on two different days of pregnancy: second day of pregnancy (preimplantation stage) and on the afternoon of the fifth day of pregnancy (postimplantation stage). We found that only on the fifth day of pregnancy did the inhibitor induce a highly significant isometric developed tension (IDT) and that this effect was maintained throughout the experiment. In order to evaluate if the generation of NO was also different between the two days of pregnancy, NOs activity was measured. Total NOs activity was significantly elevated during the postimplantation stage. We studied the interaction between the NO and cyclooxygenase (COX) pathways on the fifth day of pregnancy, and the data show no stimulation of PGs production by endogenous NO. In summary, we found that NO participates in the control of uterine contractility on the fifth day (a postimplantation stage) and that in this condition the NO was not able to elicit an increase in PGs production.

Animals↗

PubMed1998

Mouse oocyte quality and prostaglandin synthesis by cumulus oocyte complex after moderate chronic ethanol intake.

Chronic ingestion of ethanol produces a variety of effects on female reproductive function, depending on the dose and the exposure time but the mechanism of alcohol-induced ovarian failure has been little studied. Also the effects of chronic ethanol consumption on the oocyte quality in relation to morphological alterations and PGE synthesis by the oocyte cumulus complexes (OCCs) have not been described. In this study, immature female mice were treated with 10% ethanol in drinking water for 30 days. Then they were induced to superovulate, and at 14, 16 and 20 h post-hCG the quality of the ovarian and oviductal oocytes and PGE production by OCC was determined. At 14 h post-hCG, the percentage of oviductal immature oocytes was increased in the ethanol-treated females (P < 0.05). At 16 h post-hCG, the percent of oviductal activated oocytes was higher in the treated females (P < 0.05), and the ovarian immature oocytes were decreased as compared to the control females (P < 0.05). At 20 h post-hCG, the ethanol-treated females had higher percents of activated oocytes in the oviducts and in the ovaries (P < 0.05) with respect to the controls. PGE synthesis by OCCs, assessed by RIA, was decreased in the treated female mice (P < 0.001). In summary, moderate chronic ethanol treatment in immature female mice can produce morphologic abnormalities in the oocytes (high parthenogenetic activated rates) and altered PGE production in the OCCs.

Animals↗

PubMed1998

Effect of IL-1alpha on prostaglandin synthesis of oestrogenized rat uterus is mediated by nitric oxide.

We examined the possible relationship between cytokines, nitric oxide (NO) and prostaglandins in the oestrogenized rat uterus. Results indicate that: IL-1alpha but not IL-2 enhances the synthesis of prostaglandins in oestrogenized rat uteri; IL-1alpha but not IL-2 induced an augmention of NO production in this tissue; the effect of IL-1alpha on prostaglandin synthesis is abolished by NMMA, an NO antagonist; NS-398, a COX-2 inhibitor, prevents the augmention of prostaglandins produced by IL-1alpha. These results suggest that there is an interaction between IL-1alpha, NO and prostaglandins and that this interrelationship involves COX-2. This mechanism might be important during implantation and labor.

Animals↗

PubMed1998

Changes in the surface conditioning of calcium-salt crystals treated with physiological and alkaline urine.

OBJECTIVE: To study, using an in vitro model, the early phases of deposition of urinary components onto the surface of calcium-salt crystals treated with physiological and alkaline urine. MATERIALS AND METHODS: Calcium carbonate, oxalate and phosphate crystals were incubated in either freshly collected 'physiological' urine (pH 5.5) or with urine at pH 8.0. The surface conditioning was characterized using sodium-dodecyl sulphate-polyacrylamide gel electrophoresis immunoblot profiles of the adsorbed proteins and by Fourier transform infrared spectroscopy. Crystal morphology and aggregation were assessed using scanning electron microscopy. RESULTS: The patterns of protein adsorption from physiological urine showed the ubiquitous adsorption of bands within 51-86 kDa, while Tamm-Horsfall protein (THP) and alpha 1-microglobulin were found only in calcium oxalate crystals. Less aggregation was detected in calcium oxalate and phosphate crystals treated in urine at pH 5.5, while a new crystalline phase was deposited on calcium carbonate surfaces. Incubation in alkaline urine led to changes in the protein electrophoretic profiles, with a significant variation in the morphology of the inorganic phase only in calcium phosphate crystals. CONCLUSIONS: The binding of urinary proteins onto crystals depends on the chemistry of the surface and on the physicochemical composition of the urine. THP, albumin, alpha 1-microglobulin and a 20 kDa protein were able to bind calcium crystals under different circumstances. Except for THP, there was no clear relationship between the adsorption of proteins on crystals and the re-arrangement of the inorganic phase.

Blotting, Western↗

PubMed1998

High prevalence of antiphosphatidylinositol antibodies in young patients with cerebral ischemia of undetermined cause.

BACKGROUND AND PURPOSE: Anticardiolipin antibodies (aCL) are associated with thrombotic phenomena including cerebral ischemia in young adults. Although aCL are directed to a neoepitope formed by phospholipid and beta2-glycoprotein I (beta2-GPI), immunoassays based on cardiolipin as target antigen are widely used. We previously demonstrated that 47% of aCL-negative systemic lupus erythematosus (SLE) patients had antiphospholipid antibodies (aPL) to epitopes other than cardiolipin, and we found an association between aPL to noncardiolipin antigens and thrombosis. We now assess the prevalence and clinical significance of noncardiolipin aPL in young adults with cerebrovascular disease of undetermined etiology. METHODS: Seventy-seven non-SLE patients, aged <51 years, with cerebral ischemia were studied. Specificity of aPL were characterized by ELISAs using 7 different phospholipids: cardiolipin (CL), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylglycerol (PG), phosphatidic acid (PA), phosphatidylcholine, and phosphatidylethanolamine. RESULTS: Thirty-four patients (44.1%), had aPL to 1 or more of the following antigens: 23.4% to CL, 18.2% to PS, 15.6% to PG, 14.3% to PA, and 28.6% to PI. Fifty-nine patients (76.6%) were aCL negative. Of these subjects 23.4% showed aPL to noncardiolipin epitopes. PI was the specificity with highest prevalence in all subgroups, and in 6 patients anti-PI antibodies were the only detectable aPL. The binding of aPL to the different antigens was beta2-GPI dependent. CONCLUSIONS: Our data demonstrate a high prevalence of aPL in young adults with cerebral ischemia of undetermined cause. PI was the specificity with highest prevalence, suggesting that anti-PI antibodies may be an immunological marker in young patients with cerebrovascular disease.

Adult↗