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Biomedical subjects

A M Ambrosio

Publications and source records attributed to A M Ambrosio.

17 recordsLinked to original sources
PubMed2001

A novel amorphous calcium phosphate polymer ceramic for bone repair: I. Synthesis and characterization.

Traditional materials for bone repair or replacements such as autografts and allografts have a limited supply and other complications. Thus, alternative materials need to be explored. Three-dimensional, porous composites prepared from bioresorbable polymers and hydroxyapatite or other calcium phosphate ceramics are promising materials for the repair or replacement of diseased or damaged bone. However, in many cases the ceramic component of these composites is crystalline in nature, while bone apatite is made of a poorly crystalline, carbonated phosphate system. In this study, we synthesized a noncrystalline, carbonated calcium phosphate ceramic by carrying out the reaction within bioresorbable PLAGA microspheres using a modified emulsion/solvent evaporation technique, making each individual microsphere a composite. Sintering the composite microspheres together yielded a bioresorbable, porous, 3-dimensional scaffold that may be ideal for tissue ingrowth, making this composite scaffold potentially suitable for bone repair applications.

Bone Substitutes↗
PubMed2001

[Isolation of lymphocytic choriomeningitis virus from human individuals].

The activity of lymphocytic choriomeningitis virus (LCMv) in Argentina has been previously reported on the basis of serological evidence in rodents and humans and the isolation of only one strain of LCMv from a Mus domesticus captured in the province of Córdoba. The aim of this paper was to register patients with serological diagnosis of LCM, to isolate and to identify human strains of LCMv in Argentina. During the last 19 years, 15 cases were diagnosed as LCM by immunoflourescent indirect assay (IFI) and enzyme-linked immunosorbent assay (ELISA) but when neutralizing assay (NT) was incorporated, eight cases were classified as confirmed, three as probable and four as negative. The geographic distribution of the cases included three provinces: Córdoba, Buenos Aires and Santa Fe. Viral isolation was attempted in five patients classified as confirmed and only two resulted positive (P5226 and P8573). They were identified as LCMv by IFI and NT. The coexistence of LCMv with other arenaviruses, such as Junin and Oliveros viruses, in the same area, raises the probability of interactions between them, which could modify the virulence and/or pathogenicity for humans associated to genomic changes. Future studies of antigenic, genomic and virulence variability of different Argentine strains of LCMv, as well as the systematic search for human infection, will contribute to define the importance of this viral agent in our country and to implement control measures.

Animals↗
PubMed1999

Tissue engineering: orthopedic applications.

Because of an aging population and increased occurrence of sports-related injuries, musculoskeletal disorders have become one of the major health concerns in the United States. Current treatments, although fairly successful, do not provide the optimum therapy. These treatments typically rely on donor tissues obtained either from the patient or from another source. The former raises the issue of supply, whereas the latter poses the risk of rejection and disease transfer. This has prompted orthopedic surgeons and scientists to look for viable alternatives. In recent years, tissue engineering has gained increasing support as a method to treat orthopedic disorders. Because it uses principles of engineering, biology, and chemistry, tissue engineering may provide a more effective approach to the treatment of musculoskeletal disorders than traditional methods. This chapter presents a review of current methods and new tissue-engineering techniques for the treatment of disorders affecting bone, ligament, and cartilage.

Animals↗
PubMed1998

Protective efficacy of a live attenuated vaccine against Argentine hemorrhagic fever. AHF Study Group.

Argentine hemorrhagic fever (AHF), caused by the arenavirus Junin, is a major public health problem among agricultural workers in Argentina. A prospective, randomized, double-blind, placebo-controlled, efficacy trial of Candid 1, a live attenuated Junin virus vaccine, was conducted over two consecutive epidemic seasons among 6500 male agricultural workers in the AHF-endemic region. Twenty-three men developed laboratory-confirmed AHF during the study; 22 received placebo and 1 received vaccine (vaccine efficacy 95%; 95% confidence interval [CI], 82%-99%). Three additional subjects in each group developed laboratory-confirmed Junin virus infection associated with mild illnesses that did not fulfill the clinical case definition for AHF, yielding a protective efficacy for prevention of any illness associated with Junin virus infection of 84% (95% CI, 60%-94%). No serious adverse events were attributed to vaccination. Candid 1, the first vaccine for the prevention of illness caused by an arenavirus, is safe and highly efficacious.

Adolescent↗
PubMed1998

In vitro release of colchicine using poly(phosphazenes): the development of delivery systems for musculoskeletal use.

A colchicine release system utilizing biodegradable poly(phosphazenes) was investigated in vitro for intra-articular administration. Polymer degradation and drug release studies were performed on colchicine-loaded poly(phosphazenes) containing either imidazolyl (I-PPHOS) or ethyl glycinato (EG-PPHOS) side chain substituents over a 21-day period. To study the effects of an implantable colchicine-PPHOS delivery system on local musculoskeletal tissue in vitro, osteoblast-like cells were grown on the matrices. Colchicine release was 20% for I-PPHOS and 60% for EG-PPHOS over the 21-day period. Release appeared to proceed through a combination of diffusional and degradative mechanisms. Environmental scanning electron microscopy (ESEM) studies revealed large pores in the drug-depleted devices in contrast to the control matrices without drug, which may have contributed to the release seen, especially with ethyl glycinato-containing matrices. Cell growth on matrices containing colchicine was significantly (p < 0.05) inhibited in contrast to growth on tissue culture polystyrene (TCPS) and EG-PPHOS matrices without drug. The in vitro cell kinetic data suggest that designs for in vivo studies must take into account possible toxicity of colchicine and the polymer matrix on local tissue. Biodegradable PPHOS systems are promising candidates for use as intra-articular delivery vehicles for drugs with potential for systemic toxicity.

3T3 Cells↗
PubMed1997

Novel polyphosphazene/poly(lactide-co-glycolide) blends: miscibility and degradation studies.

A novel biodegradable polymer blend was developed for potential biomedical applications. A 50:50 poly(lactide-co-glycolide) (PLAGA) was blended in a 50:50 ratio with the followiing polyphosphazenes (PPHOS): poly[(25% ethyl glycinato)(75% p-methylphenoxy)phosphazene[, poly[(50% ethyl glycinato)(50% p-methylphenoxy)phosphazene], and poly[(75% ethyl glycinato)(25% p-methylphenoxy)phosphazene] to obtain Blends A, B, and C, respectively, using a mutual solvent technique. The miscibility of these blends was determined by measuring their glass transition temperature (Tg) using differential scanning calorimetry. After fabrication using a casting technique, the degradation of the matrices was examined. Differential scanning calorimetry showed one glass transition temperature for each blend which was between the Tg's of their respective parent polymers indicating miscibility of the blends. Surface analysis by scanning electron microscopy showed the matrices to have smooth uniform surfaces. Degradation studies showed near-zero order degradation kinetics for the blends with Blends A and B losing 10% of their mass after two weeks and Blend C degrading more rapidly (30% mass loss during the same period). These findings suggest that these novel biodegradable PLAGA/PPHOS blends may be useful for biomedical purposes.

Biocompatible Materials↗
PubMed1997

Molecular characterization of attenuated Junin virus strains.

The Junin virus strain Candid #1 was developed as a live attenuated vaccine for Argentine haemorrhagic fever. In this paper we report the nucleotide sequences of S RNA of Candid #1 and its more virulent ancestors XJ#44 and XJ (prototype). Their relationship to Junin virus wild-type MC2 strain and other closely and distantly related arenaviruses was also examined. Comparisons of the nucleotide and amino acid sequences of N and GPC genes from Candid #1 and its progenitor strains revealed some changes that are unique to the vaccine strain. These changes could be provisionally associated with the attenuated phenotype.

Amino Acid Sequence↗
PubMed1997

Evaluation of an enzyme immunosorbent assay for the diagnosis of Argentine haemorrhagic fever.

To elaborate a set of serological tests for the diagnosis of Argentine haemorrhagic fever (AHF), an enzyme-linked immunosorbent assay (ELISA) for detection of specific anti-Junin virus (JV) IgG is described, and its performance is compared with that of the plaque reduction neutralization test (PRNT). The reproducibility, sensitivity, specificity, and confidence limits for positive and negative results for ELISA were statistically analysed. The value of 800 was demonstrated as the lowest positive titer. Titers > or = 800 varied within one (two-fold) dilution in 95.6% of the tests, while the sensitivity and specificity were 99.2% and 98.8%, respectively. The assay yielded 1% of false positives and 0.05% of false negatives. A comparison of ELISA to PRNT in detecting the seroconversion for JV was studied by the chi square test (comparison of proportions in paired samples) and the K parameter for agreement proportion. Comparison of ELISA to PRNT showed no significant difference in the proportions of positive and negative results of these assays (P < 0.01), demonstrating an equivalent performance (K = 0.98) in the diagnosis of AHF. In addition, the simplicity and safety of the procedures involved make this ELISA the most suitable test to detect natural human JV infections.

Antibodies, Viral↗
PubMed1997

[Prevalence of hepatitis C antibodies in plasma donors for the treatment of Argentine hemorrhagic fever].

For Argentine Hemorrhagic Fever, a disease caused by Junin virus (JV), there is an effective treatment, consisting of the transfusion of immune plasma (IP). This plasma is obtained from individuals who have had the disease. Since Hepatitis C virus (HCV) is transmitted parenterally, this study was aimed to estimate the prevalence of anti-HCV in a population of IP donors. In this study, 376 donors (47 females and 329 males) were studied: 95 individuals (24 females and 71 males) who had had FHA but had not received treatment and 88 laboratory workers (57 females and 31 males) who were included as controls. Serum samples were tested by EIA (Abbott, Germany) for HCV, and later confirmed by LIATEK (Organon, Ireland). Antibodies to HCV were detected in 29/376 donors (7.7%), in only 1/95 (1.0%) untreated convalescents of AHF and in 1/ 88 (1.1%) of laboratory workers. Retrospective analysis of the seroconversion for HCV in these individuals demonstrated that in 16/24 donors (66.6%) the infection by HCV was probably associated with the IP transfusion. The data presented herein show how the infection with HCV was disseminated among donors of IP, stressing the risk associated to transfusional practices, and emphasizing the need of vaccination to prevent AHF and also the risk inherent to its treatment.

Adult↗
PubMed1996

Synthesis and characterization of pH-sensitive poly(organophosphazene) hydrogels.

A new class of pH-sensitive hydrogels has been designed and synthesized. These are novel polyphosphazenes that bear various ratios of sodium oxybenzoate and methoxyethoxyethoxy side groups. These water-soluble macromolecules were cross-linked by 60Co gamma irradiation and the products were allowed to absorb water to form hydrogels. The hydrogels had higher equilibrium degrees of swelling in basic than in acidic buffer solutions, and polymers with a higher loading of the ionic side group showed higher swellability than those with a lower loading of this side group. The effects of ionic strength, cation charge and radiation dose on the degree of swelling were also studied. A study of the diffusion of the dye Biebrich Scarlet from the hydrogels showed complete release of the dye in 4-12 h in pH 7.4 buffer solution but significantly lower release at pH 2 even after 48 h. The release rate also varied as the side-group ratios were changed. The prehydrogel polymers were synthesized via the macromolecular substitution reactions of poly(dichlorophosphazene) with sodium methoxyethoxyethoxide and the sodium salt of propyl 4-hydroxybenzoate, followed by ester hydrolysis to yield the sodium carboxylate. The hydrogels are of interest for possible use as pH-sensitive membranes and for a number of potential biomedical applications.

Azo Compounds↗
PubMed1994

Prevalence of lymphocytic choriomeningitis virus infection in a human population of Argentina.

The activity of lymphocytic choriomeningitis virus (LCMV) in the endemic area of Argentine hemorrhagic fever has been previously reported and represents the first evidence of the coexistence of two arenaviruses pathogenic for humans, Junin and LCMV, in the same geographic area. Data are presented on the prevalence of LCMV human infection in a 10,000-km2 area located in Santa Fe Province, Argentina. Study subjects were males, 15-65 years old, living and/or working in the rural area of 41 localities. One serum sample was obtained from each 7,227 volunteers from a total population of 21,340 individuals with the described features. Antibodies to LCMV were assessed by means of an indirect immunofluorescence assay. These antibodies were found in 172 serum samples, with titers ranging from 1:8 to 1:128 (geometric mean titer = 15.03), and a mean percentage of infection of 2.38%. A significantly different distribution of positive individuals was found between the eastern (1.54%) and western (3.07%) borders of the region studied (P < 0.0003). The higher percentage of infection on the western side was due to the existence of two clusters of counties with a mean percentage of 6.06% that was significantly different from the 1.67% obtained in the rest of the study area (P < 0.0003). These results provide new information on the LCMV activity in Argentina, and update the evidence on the coexistence of two arenaviruses in the same region of Argentina. This circumstance increases the probability of generation of viral reassortants with changes that could determine the need for new therapeutic and/or preventive strategies for arenaviral diseases.

Adolescent↗
PubMed1992

Peripheral blood leukocytes of patients with Argentine hemorrhagic fever as effectors of antibody-dependent cell-cytotoxicity.

Peripheral blood mononuclear cells (PBMC) and polymorphonuclear leukocytes (PMNL) of patients with Argentine hemorrhagic fever (AHF) were tested as effectors (E) of antibody-dependent cell cytotoxicity (ADCC). 51Cr labeled chicken red blood cells (CRBC) coated with anti-CRBC or normal rabbit serum were used as targets (T). Three ADCC assays were performed with both effectors from patients: on admission (I), 4 days after the transfusion of immune plasma (II), and 30 days after the clinical onset (III). The ADCC values obtained displayed high variation between individuals. From the linear portions in the curves representing specific 51Cr release vs. E:T ratio plots, extrapolations were made to determine lytic units (LU), defined here as effector concentrations required to lyse 50% of the targets. The results were expressed as LU in 10(6) effector cells. The killing activity ranges of patients' PMNL (I = 1.04 +/- 0.34; II = 2.22 +/- 0.66; and III = 2.08 +/- 1.18) were not significantly different from that of 21 normal controls (1.19 +/- 0.36), except for range II (P less than 0.01). ADCC activity ranges of patients' PBMC (I = 3.40 +/- 1.06; II = 3.16 +/- 1.60; and III = 1.93 +/- 0.42) were not significantly different from that determined in 12 healthy subjects (1.86 +/- 0.40). These results demonstrate that patients' PBMC and PMNL can perform ADCC with efficiency comparable to normal effector cells, during the acute period of AHF, and in early convalescence. Consequently, ADCC can be a relevant mechanism in the clearance of Junin virus-infected cells.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1989

Lymphocyte subsets alteration in patients with argentine hemorrhagic fever.

Peripheral blood lymphocyte subpopulations were studied in 15 patients with Argentine Hemorrhagic Fever (AHF), during the acute period of the disease and in early convalescence. Anti-human Ig antibodies were used to identify B cells and monoclonal antibodies to assess T4 and T8 subsets. During the acute period of the disease, significant alterations were found in B, T4, and T8 lymphocytes (P less than .001), as well as in T4/T8 ratios (P less than .001). These abnormalities disappeared in early convalescence, around 30 days after the clinical onset. Diminished numbers of T4 lymphocytes are interpreted as relevant to the immunodepression that characterizes the acute phase of AHF.

Hemorrhagic Fever, American↗
PubMed1986

Junin virus isolation from lympho-mononuclear cells of patients with Argentine hemorrhagic fever.

Detection of viremia was attempted by three different methods in 30 cases of Argentine hemorrhagic fever (AHF). Cocultivation of peripheral blood mononuclear cells (PBMC) with Vero cell monolayers was the most sensitive, detecting Junin virus (JV) in 96% of the cases. Inoculation of whole blood into suckling mice and on Vero cells rendered 53 and 46% of positive isolations, respectively. The results presented suggest that PBMC are infected with JV during the acute period of AHF. JV was isolated with decreasing frequency up to 3 days after treatment with immune plasma, but no virus was recovered from PBMC during early convalescence.

Animals↗
PubMedDate not supplied

Evaluation of an enzyme-linked immunosorbent assay for quantitation of antibodies to Junin virus in human sera.

An enzyme-linked immunosorbent assay (ELISA) was evaluated for the quantitation of anti-Junin virus (JV) antibodies, in 83 selected cases of Argentine haemorrhagic fever (AHF). Serum samples were studied in two groups to facilitate comparative analysis; the first group was ELISA with indirect immunofluorescence (IF) test, in the second ELISA with plaque reduction neutralization test (PRINT). From the results obtained by using ELISA and IF on the same serum samples, a clear tendency of ELISA to demonstrate seroconversion for JV earlier and at higher frequency than IF test was noted. Simultaneous titration of specific antibodies by ELISA and PRNT tests rendered significantly correlated titers (r = 0.81), both methods being equivalently specific (100%). The demonstration of specific antibodies by ELISA in two cases that were undetected by the PRNT test resulted in a higher sensitivity index for ELISA than for PRNT (100% vs 97%). It is concluded that ELISA could efficiently replace IF and PRNT tests for the diagnosis of AHF.

Antibodies, Viral↗
PubMedDate not supplied

[Neutralization test for lymphocytic choriomeningitis virus for distinguishing between two arenavirus infections in Argentina].

The active coexistence of two pathogenic arenaviruses, Junin (JUNV) and lymphocytic choriomeningitis (LCMV), in the same region of Argentina, has been known since the early 70's, and records of clinical and subclinical human infections by one and/or the other agent have been continuously produced for the last 25 years. Anti-LCMV antibody is currently searched only by indirect immunofluorescence, a test that shows cross reactions among a number of arenaviruses yielding, in the cases of LCMV and JUNV consecutive infections, a concomitant seroconversion for both viruses, as an inconclusive diagnostic result. In contrast, neutralization (NT) tests reveal arenavirus antibodies directed to unique epitopes on these virus envelopes, thus allowing to disclose the sequence in the cases of consecutive infections. In this paper, the characteristics of neutralization (NT) test for LCMV in cell cultures are described, as well as its performance in the field diagnosis of LCMV human infections. The native LCMV strain Cba An 13065 was inoculated on L-929 cell (ATCC CCL 1), and procedures were followed to perform a constant virus-variable serum NT test. Final points of sera titrations were expressed as the maximal serum dilution that yielded 75% of pfu inhibition. This NT test was assayed on paired serum samples of 36 patients with confirmed Argentine hemorrhagic fever (AHF) (a disease caused by JUNV), who had had a known previous contact with LCMV through IFI. The use of this one test led to confusing diagnosis of the disease due to concomitant seroconversion for JUNV and LCMV. By using NT test, it was shown that: some of them were possibly not infected by LCMV, and that 30/36 cases (83.3%) had a pre-existing level of LCMV antibody, with titers in the range of 5 to 640, remaining unchanged 60 days after the clinical AHF. This shows that NT antibodies to LCMV are not influenced by the outcome of the immune response to JUNV, thus confirming the efficiency of NT test as identificator among arenaviruses. To assess the performance of this NT test in individuals having only IFI antibodies to LCMV, 126 serum samples obtained through serological surveillance in a rural area of Argentina, were used. It was found that NT had improved coincidence with IFI as IFI titers increased. Interpretations were based on the pan-arenavirus antibody response obtained by using IFI as the only test. Results presented herein prove that the described NT test is a valuable tool for the detection of LCMV infections, particularly when a previous infection with LCMV has to be demonstrated during the acute phase of Argentine hemorrhagic fever.

Acute Disease↗