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M Avila

Publications and source records attributed to M Avila.

At least 19 recordsLinked to original sources
PubMed2002

Mother-to-child HIV type 1 transmission in Argentina: BF recombinants have predominated in infected children since the mid-1980s.

The molecular epidemiology of HIV-1 in Argentina is more complex than was previously appreciated. One circulating recombinant form, CRF12_BF, and many related BF recombinant forms predominate in the capital city, Buenos Aires. This study of HIV-1 subtypes acquired perinatally between 1984 and 2000 has permitted, for the first time, a reconstruction of the history of BF recombination in Argentina. Sequencing of a partial genome region from the beginning of vpu to the beginning of env(gp120), which spans a breakpoint common in most contemporary Argentine BF recombinants, enabled samples to be rapidly screened. Among 23 children born between 1984 and 2000, 15 including 1 child born in 1986, harbored a BF recombinant. Thirteen of the 15 recombinants shared a common breakpoint at the 5' end of env(gp120). Full genome sequencing of two viruses, from 1986 and 1987, respectively, revealed them to be genetically related but not identical to CRF12_BF. Both contained more subtype B sequence than did CRF12_BF. BF recombinants related to CRF12_BF have been in circulation in Buenos Aires since 1986 and continue to predominate in perinatal transmissions.

Adolescent↗
PubMed2001

Diverse BF recombinants have spread widely since the introduction of HIV-1 into South America.

OBJECTIVE: To describe the genetic diversity of HIV-1 in South America by full genome sequencing and analysis. METHODS: Purified peripheral blood mononuclear cell DNA from HIV-infected individuals in Argentina, Uruguay and Bolivia was used to amplify full HIV-1 genomes. These were sequenced using the ABI 3100 automated sequencer and phylogenetically analysed. RESULTS: Twenty-one HIV-1 strains from three South American countries, 17 of which were pre-screened by envelope heteroduplex mobility assay (HMA), were studied. Ten out of 10 HMA subtype F and four out of seven HMA subtype B strains were actually BF recombinants upon full genome analysis. Two BF recombinants from Argentina and two from Uruguay had the same structure, representing a new circulating recombinant form termed CRF12_BF(ARMA159). Twelve other BF recombinants had structures related to CRF12 but with additional segments of subtype B; each was unique. BF recombinants were temporally and geographically widespread, found as early as 1986-1987 in vertically infected Argentinian children and in Argentina, Uruguay, and Bolivia.

Adult↗
PubMed2001

Genetic epidemiology and schizophrenia: a study of reproductive fitness.

Genetic epidemiological studies have demonstrated markedly reduced rates in reproduction among schizophrenic patients. According to evolutionary theory, behavioral and psychological phenotypes are selected based on ecological "fit". Where differential survival or reproductive success exists, genotype frequencies are altered in subsequent generations. In the case of schizophrenia, lower rates of reproduction constitute a negative selection factor that should reduce genes in the population associated with the expression of the disease--ultimately leading to decreases in prevalence. However, studies reveal a stable prevalence of about 1% over time. Attempts to explain the apparent contradiction between negative selection and stable prevalence have taken several forms. One explanation suggests that reproductive rates in relatives of schizophrenic patients are increased--compensating for reproductive loss in affected family members. Family data from schizophrenic patients at the Maryland Psychiatric Research Center were compared with those of healthy volunteers and volunteers with schizophrenia spectrum personality (SSP) disorders. Controlling for important socio-cultural and demographic variables, a multiple regression model revealed a significant increase in the number of siblings associated with schizophrenia. No differences in reproductive fitness were found among normal and SSP volunteers. This observed pattern in reproductive fitness provides one mechanism by which prevalence rates can remain stable despite lower reproductive rates among individuals with schizophrenia. Evidence of increased reproductive fitness in relatives suggests the need to consider the complex interactions of proximate and ultimate (evolutionary) mechanisms in the expression of schizophrenia.

Adult↗
PubMed2001

Reconstruction of ocular surface with heterologous limbal epithelium and amniotic membrane in a rabbit model.

PURPOSE: To report in vivo reconstruction of the ocular surface using amniotic membrane and heterologous transplants of epithelial limbal cells in rabbits with chemical burns. METHODS: After severe damage to the ocular surface with n-heptanol and keratectomy, 15 rabbits developed total limbal deficiency with conjunctival epithelialization, vascularization, and chronic inflammation. One month later, a complete keratectomy was performed in all eyes: 12 received additional transplantation of human amniotic membrane and heterologous limbal epithelial cells in a double amniotic membrane layer, 2 received amniotic membrane only, and 1 control eye received no procedure. RESULTS: After 1 month of follow-up, corneas in eight of the operated eyes presented minimal vascularization, without signs of rejection. Corneal surface reconstruction was demonstrated with the growth of new corneal-like epithelial phenotype and integration of amniotic membrane to the basal corneal surface. A superficial amniotic membrane (with the amnion side up as a dressing) peeled off after 7 to 10 days. The epithelialization with heterologous limbal epithelial cells was evident underneath. The other four operated eyes were followed for 6 months; the ocular surface was also stable with a corneal-like epithelial phenotype. CONCLUSION: Simultaneous transplantation of amniotic membrane and heterologous limbal epithelial cells in severe ocular surface disorders could restore ocular surface and may be useful in patients with severe bilateral limbal epithelial loss, giving new perspectives for the treatment of severe ocular surface disorders.

Amnion↗
PubMed2000

Nonsense mutations in the human beta-globin gene lead to unexpected levels of cytoplasmic mRNA accumulation.

Generally, nonsense codons 50 bp or more upstream of the 3'-most intron of the human beta-globin gene reduce mRNA abundance. In contrast, dominantly inherited beta-thalassemia is frequently associated with nonsense mutations in the last exon. In this work, murine erythroleukemia (MEL) cells were stably transfected with human beta-globin genes mutated within each of the 3 exons, namely at codons 15 (TGG-->TGA), 39 (C-->T), or 127 (C-->T). Primer extension analysis after erythroid differentiation induction showed codon 127 (C-->T) mRNA accumulated in the cytoplasm at approximately 20% of the normal mRNA level. Codon 39 (C-->T) mutation did not result in significant mRNA accumulation. Unexpectedly, codon 15 (TGG-->TGA) mRNA accumulated at approximately 90%. Concordant results were obtained when reticulocyte mRNA from 2 carriers for this mutation was studied. High mRNA accumulation of codon 15 nonsense-mutated gene was revealed to be independent of the type of nonsense mutation and the genomic background in which this mutation occurs. To investigate the effects of other nonsense mutations located in the first exon on the mRNA level, nonsense mutations at codons 5, 17, and 26 were also cloned and stably transfected into MEL cells. After erythroid differentiation induction, mRNAs with a mutation at codon 5 or 17 were detected at high levels, whereas the mutation at codon 26 led to low mRNA levels. These findings suggest that nonsense-mediated mRNA decay is not exclusively dependent on the localization of mutations relative to the 3'-most intron. Other factors may also contribute to determine the cytoplasmic nonsense-mutated mRNA level in erythroid cells. (Blood. 2000;96:2895-2901)

Animals↗
PubMed2000

Reverse flow in the umbilical vein in a case of trisomy 9.

This report describes a case of reverse flow in the umbilical vein and ductus venosus during atrial contraction of a fetus at 12 weeks of gestation with increased nuchal translucency (9.1 mm). In addition, Doppler velocimetry detected high retrograde flow in the inferior vena cava. Cytogenetic analysis of chorionic villi revealed trisomy 9. We suggest that these findings may be a first trimester sign of chromosomal and cardiac abnormalities in the fetus.

Adult↗
PubMed1998

Network analyses of Y-chromosomal types in Europe, northern Africa, and western Asia reveal specific patterns of geographic distribution.

In a study of 908 males from Europe, northern Africa, and western Asia, the variation of four Y-linked dinucleotide microsatellites was analyzed within three "frames" that are defined by mutations that are nonrecurrent, or nearly so. The rapid generation and extinction of new dinucleotide length variants causes the haplotypes within each lineage to diverge from one another. We constructed networks of "adjacent" haplotypes within each frame, by assuming changes of a single dinucleotide unit. Two small and six large networks were obtained, the latter including 94.9% of the sampled Y chromosomes. We show that the phenetic relationships among haplotypes, represented as a network, result largely from common descent and subsequent molecular radiation. The grouping of haplotypes of the same network thus fits an evolutionarily relevant criterion. Notably, this method allows the total diversity within a sample to be partitioned. Networks can be considered optimal markers for population studies, because reliable frequency estimates can be obtained in small samples. We present synthetic maps describing the incidence of different Y-chromosomal lineages in the extant human populations of the surveyed areas. Dinucleotide diversity also was used to infer time intervals for the coalescence of each network.

Africa, Northern↗
PubMed1998

The effects of RGD (Arg-Gly-Asp) peptides on glaucoma filtration surgery in rabbits.

BACKGROUND AND OBJECTIVE: Integrins are the main mediators of the interaction between fibroblasts and extracellular matrix (ECM) during scar formation. The adhesion motive RGD (Arg-Gly-Asp) is contained in the ECM and is recognized by the integrin receptor. Soluble peptides containing the RGD sequence can compete with -RGD- contained in the ECM for binding to the integrin receptor and thus prevent cell adhesion and scar formation. MATERIALS AND METHODS: The peptides RGD (p602), GRGDSP (p603), GRGDSPCA (p604), and GGRGDSPCA (p605) were used in 25 glaucoma filtering surgeries in rabbits (five eyes per peptide and five with saline). RESULTS: Postoperative subconjunctival injections of peptides were given at days 0, 4, 8, 12, and 16. Bleb size, bleb survival, and signs of toxicity were examined. The GRGDSPCA and GGRGDSPCA showed an increase in bleb formation, size, and survival with no clinical signs of toxicity compared with controls (P < .008). Histopathologic evaluation confirmed inhibitory effects in scar formation with bleb formation, and transmission electron microscopy demonstrated that there was no toxicity to the ciliary body. CONCLUSION: These peptides were effective in controlling scar formation in glaucoma filtering surgery.

Animals↗
PubMed1993

The effect of side chain substitution at positions 2 and 3 of the heterocyclic ring of N-acetylenic analogues of tryptamine as monoamine oxidase inhibitors.

N-Acetylenic analogues of tryptamine in which the side chain is located at position 2 of the indole ring are compared with those in which the side chain is located at position 3, in terms of their actions as inhibitors of monoamine oxidases A and B. IC50 values at 0 and 30 min of pre-incubation were determined. Time-dependence and irreversible inhibition confirmed that all of them behave as mechanism-based inhibitors. The kinetic constants of each inhibition step were determined for both monoamine oxidase forms and compared between them. In all cases the first-order rate constants for the covalent adduct formation were similar to inhibitor selectivity which is derived solely from differences in affinities for non-covalent binding to the A and B enzymes. Those compounds where the acetylenic side chain was substituted at position 2 of the heterocyclic ring and selective inhibitors of monoamine oxidase A were more potent than those with the side chain in position 3.

Acetylene↗
PubMed1993

Acute lower respiratory infection in Argentinian children: a 40 month clinical and epidemiological study.

In a total of 1,003 children (805 inpatients and 198 outpatients) with acute lower respiratory infections (ALRI), clinical, social, and environmental data were analyzed. The major clinical entities were bronchiolitis, pneumonia, bronchitis, and laryngitis. The first two of these predominated in inpatients; pneumonia and bronchitis were more common in older children, while bronchiolitis was observed in infants. Respiratory rates of > 50/min. were more common in younger children and in cases with bronchiolitis and bronchitis. Retractions showed markedly less age-dependent variations and were present in all severe cases with different clinical diagnoses. Retractions alone or associated with cyanosis were the best indicators for severity of ALRI. Among outpatients, fever and wheezing were more common; inpatients were younger, more frequently malnourished, and from a lower socioeconomic level; family history of chronic bronchitis, crowding, and parental smoking also prevailed in this group. Family asthma and exposure to domestic aerosols was more common among outpatients. Prematurity rate (17 and 15%) of all ALRI cases was twice that of the general pediatric population and a significant difference existed between in- and outpatients under 6 months of age when perinatal respiratory pathologies predominated among inpatients. It is suggested to consider the need for assessing personal, family, and environmental risk factors in addition to clinical signs and symptoms when severe cases of ALRI are evaluated.

Acute Disease↗
PubMed1992

Perinatal outcome of very low birthweight infants by mode of delivery.

In order to evaluate the influence of mode of delivery on perinatal morbidity and mortality in vertex infants weighing less than 1500 g (VLBW), we made a retrospective study of 152 singleton newborns, in vertex presentation, with a birthweight of less than 1500 g, delivered in the Cruces Hospital (Vizcaya, Spain), a major perinatal referral center, between 1 January 1987 and 31 December 1989. Twins and infants with lethal congenital anomalies or gross intrauterine growth deviations were excluded from the study (n = 71). Of the infants studied (n = 81), 37 were delivered by cesarean section (mean weight 1120 +/- 206 g, range: 680-1495 g) and 44 were delivered vaginally (mean weight 1029 +/- 283 g, range: 530-1475 g). The patients were divided into four groups: Group A: 500-749 g (n = 10); Group B: 750-999 g (n = 21); Group C: 1000-1249 g (n = 27); and Group D: 1250-1499 g (n = 23). The percentages of cesarean sections in each group were 10%, 42%, 66% and 39%, respectively. A comparison within each group of immediate perinatal outcome (Apgar score and umbilical vein cord pH), as well as mortality and sequelae up to 1 year of age did not yield any significant differences between cesarean and vaginal birth. We conclude that cesarean delivery does not appear to offer improved outcome over vaginal delivery in live births without congenital anomalies. For this reason, we believe that fetal weight should not be the only obstetrical variable considered when deciding whether or not to perform a cesarean section in these circumstances.

Adult↗
PubMed1990

Insulin-induced phospho-oligosaccharide stimulates amino acid transport in isolated rat hepatocytes.

The ability of the insulin-induced phospho-oligosaccharide to stimulate amino acid transport was studied in isolated rat hepatocytes. At low alpha-aminoisobutyric acid concentrations (0.1 mM), both 100 nM-insulin and 10 microM-phospho-oligosaccharide doubled amino acid uptake after 2 h of incubation. This stimulation was prevented by 0.1 mM-cycloheximide or 5 micrograms of actinomycin D/ml, indicating that the phospho-oligosaccharide, like insulin, was acting via the synthesis of a high-affinity transport component. The effects of the phospho-oligosaccharide and of insulin were blocked by Ins2P (2.5 mM), but not by myo-inositol, inositol hexaphosphoric acid or several monosaccharides such as mannose, glucosamine and galactose. Both the temporal effect on amino acid entry and the extent of stimulation of this process by the phospho-oligosaccharide indicate that this molecule mimics, and may mediate, some of the long-term actions of insulin. However, the effects of phospho-oligosaccharide and insulin were not exactly the same, since the effect of insulin, but not of the phospho-oligosaccharide, was additive with that of glucagon.

Amino Acids↗
PubMed1990

A phospho-oligosaccharide can reproduce the stimulatory effect of insulin on glycolytic flux in human fibroblasts.

It has been recently demonstrated that insulin promotes the hydrolysis of a glycosyl-phosphatidylinositol, stimulating the release of a phospho-oligosaccharide which displays several insulin-like effects. In the present study we have investigated whether the compound is able to mimic insulin action on glucose metabolism in human fibroblasts. Similarly to the hormone, the phospho-oligosaccharide elicited a dose dependent increase in lactate output and fructose 2,6-bisphosphate content. The effect of the compound was time dependent with a progressive increase starting from 2 hours of incubation. 1 microM phospho-oligosaccharide had half maximal effect on both parameters, increasing glycolytic flux by approximately 30% and fructose 2,6-bisphosphate content by 70%. Therefore the phospho-oligosaccharide appears to be able to strictly reproduce insulin action on glucose metabolism in human fibroblasts.

Cells, Cultured↗
PubMed1988

Anaphylaxis to amoxycillin but good tolerance for benzyl penicillin. In vivo and in vitro studies of specific IgE antibodies.

Three patients are reported on who suffered anaphylactic reactions after amoxycillin (AX) treatment and challenge but tolerated benzylpenicillin (BP) parenterally and orally. Two of the three patients had positive skin tests and RAST to AX reagents but negative responses to benzyl penicilloyl (BPO) specific skin tests and RAST and the minor determinant mixture (MDM) skin test reagent. The third case was negative to all skin tests and RAST. RAST and RAST inhibition on the two positive sera suggest that the response is related to the acyl side chain of AX.

Adult↗