PubMed Health⌕ Search

Biomedical subjects

G Calderón

Publications and source records attributed to G Calderón.

18 recordsLinked to original sources
PubMed2001

Seasonal variation in prevalence of antibody to hantaviruses in rodents from southern Argentina.

We conducted a small mammal trapping study to investigate temporal variation in prevalence of infection in hantavirus reservoir populations in the Patagonian Andes mountain range, Rio Negro province, Argentina. Rodent blood samples collected in natural and periurban habitats and at the home of an hantavirus pulmonary syndrome (HPS) case patient were analysed by enzyme-linked immunosorbent assay. Organ tissue samples were tested by polymerase chain reaction (PCR) and nucleotide sequence analysis. Eight species of 1032 rodents were captured in 15 551 trap nights, giving an overall trap success of 6.6%. Hantavirus antibody was detected in 30 of 555 Oligoryzomys longicaudatus (reservoir of Andes virus), three of 411 Abrothrix longipilis, and one of 10 Loxodontomys micropus. Antibody prevalences in O. longicaudatus were 13.7% in spring 1996, 59.3% in summer 1996, 2.1% in autumn 1997, 12.4% in winter 1997 and 3.1% in spring 1997. A much higher antibody prevalence (33%) was found during trapping around the residence of an HPS case patient. Higher prevalences were found in older male O. longicaudatus. There was no apparent correlation of antibody prevalence with rodent population density, or of rodent population density or antibody prevalence with numbers of human cases. For an HPS case that occurred in our study area in 1997, we identified the probable rodent reservoir and likely site of exposure by matching the genetic sequences of virus obtained from a rodent and the HPS case patient.

Animals↗
PubMed2000

Genetic diversity of the Junin virus in Argentina: geographic and temporal patterns.

RNA was purified from 39 strains of cell-cultured Junin virus (JUN) from central Argentina, which included both human- and rodent-derived isolates (a total of 26 and 13, respectively), as well as from 2 laboratory JUN strains, XJ Cl3 and XJ #44. JUN-specific primers were used to amplify a 511-nucleotide (nt) fragment of the nucleocapsid protein gene and a 495-nt fragment of the glycoprotein 1 (GP1) gene. Genetic diversity among JUN strains studied was up to 13% at the nt level and up to 9% at the amino acid (aa) level for the GP1 gene and up to 9% (nt) and 4% (aa) for the NP gene. Phylogenetic analyses of both genes revealed three distinct clades. The first clade was composed of the JUN strains from the center of the endemic area and included the majority of JUN strains analyzed in the current study. The second clade contained 4 JUN strains isolated between 1963 and 1971 from Cordoba Province, the western-most edge of the known endemic area. The third clade contained 4 JUN strains that originated from Calomys musculinus trapped in Zarate, the northeastern edge of the known endemic area. Certain JUN sequences, which were obtained from GenBank and identified as XJ, XJ #44, and Candid #1 strains, appeared to form a separate clade. Over 400 nt of the GP1 and GP2 genes were additionally sequenced for 7 JUN strains derived from patients with different clinical presentations and outcomes of Argentine hemorrhagic fever. Analysis of the corresponding aa sequences did not allow us to attribute any particular genetic marker to the changing severity or clinical form of the human disease.

Animals↗
PubMed1999

Meiotic abnormalities and spermatogenic parameters in severe oligoasthenozoospermia.

The incidence of meiotic abnormalities and their relationship with different spermatogenic parameters was assessed in 103 male patients with presumably idiopathic severe oligoasthenozoospermia (motile sperm concentration < or = 1.5 x 10(6)/ml). Meiosis on testicular biopsies was independently evaluated by two observers. Meiotic patterns included normal meiosis and two meiotic abnormalities, i.e. severe arrest and synaptic anomalies. A normal pattern was found in 64 (62.1%), severe arrest in 21 (20.4%) and synaptic anomalies in 18 (17.5%). The overall rate of meiotic abnormalities was 37.9%. Most (66.7%) meiotic abnormalities occurred in patients with a sperm concentration < or = 1 x 10(6)/ml. In this group, total meiotic abnormalities were found in 57.8% of the patients; of these, 26.7% had synaptic anomalies. When the sperm concentration was < or = 0.5 x 10(6)/ml, synaptic anomalies were detected in 40% of the patients. In patients with increased follicle stimulating hormone (FSH) concentrations, total meiotic abnormalities occurred in 54.8% (synaptic anomalies in 22.6%). There were statistically significant differences among the three meiotic patterns in relation to sperm concentration (P < 0.001) and serum FSH concentration (P < 0.05). In the multivariate analysis, sperm concentration < or = 1 x 10(6)/ml and/or FSH concentration > 10 IU/l were the only predictors of meiotic abnormalities.

Adult↗
PubMed1997

Characterization of arenaviruses using a family-specific primer set for RT-PCR amplification and RFLP analysis. Its potential use for detection of uncharacterized arenaviruses.

Arenaviruses are enveloped viruses with a genome composed of two ssRNA species, designated L and S. The arenaviruses were divided in two major groups (Old World and New World), based on serological properties and genetic data, as well as geographic distribution. A sequence alignment analysis of all reported arenavirus S RNAs yielded 17 conserved regions in addition to a reported conserved region at the end of both RNAs. The consensus sequences of these regions were used to design generalized primers suitable for RT-PCR amplification of a set of overlapping nucleotide sequence fragments comprising the complete S RNA of any arenavirus. A restriction analysis (RFLP) was designed to rapidly typify the amplified fragments. This RT-PCR-RFLP approach was tested with Old World (LCM) and New World (Junin and Tacaribe) arenaviruses. Furthermore, using this procedure the whole S RNA of a novel arenavirus isolate obtained from a rodent trapped in central Argentina, was amplified and characterized. Partial nucleotide sequence data were used for phylogenetic analyses that showed the relationships between this arenavirus and the rest of the members of the family. This relatively simple methodology will be useful both in basic studies and epidemiological survey programs.

Animals↗
PubMed1997

Ureteral lesion secondary to vaginal ultrasound follicular puncture for oocyte recovery in in-vitro fertilization.

Techniques of oocyte retrieval have progressed from laparoscopy to transvaginal follicular aspiration under ultrasonographic control. This highly efficient method, routinely used nowadays, is not free of complications. We present a case of a ureteral lesion secondary to vaginal ultrasound follicular puncture for oocyte recovery in in-vitro fertilization. Despite the surgical procedure to reimplant the ureter, the patient achieved a twin pregnancy which is ongoing uneventfully.

Adult↗
PubMed1995

Evaluation of cytogenetic analysis for clinical preimplantation diagnosis.

OBJECTIVE: To evaluate the feasibility of using cytogenetic analysis in preimplantation diagnosis. DESIGN: Two different biopsy protocols (chemical drilling and zona cutting) and two fixation methods were tested in a mouse model. Afterwards, the efficiency of obtaining chromosome preparations from untransferable human embryos depending on the method used to obtain the blastomeres (embryos biopsy or removal of the zona pellucida and blastomere disaggregation) was determined. The chances of obtaining chromosome preparations depending on the type of embryo (haploid, diploid, triploid, and apparently unfertilized) were also evaluated. RESULTS: Results from the mouse model showed that chemical drilling yields better results than cutting in terms of metaphases per biopsied embryo and surviving rate after biopsy. In human embryos, biopsy of diploid embryos produced 46.6% chromosome preparations, while 29% were obtained after blastomere disaggregation and 20.4% when biopsying triploid embryos. CONCLUSIONS: These results suggest that the disaggregating procedure and triploid embryos cannot be considered as good models to assess the feasibility of cytogenetic analysis in preimplantation diagnosis. Poor chromosome quality and loss during fixation are the main problems to use cytogenetics in preimplantation diagnosis; a combination of cytogenetics and other techniques is suggested in cases of balanced translocations.

Animals↗
PubMed1994

Twin pregnancy after preimplantation diagnosis for sex selection.

A twin female pregnancy was obtained in a haemophilia carrier after two preimplantation diagnosis cycles. The embryonic sex of biopsied blastomeres was determined with the use of dual fluorescence in-situ hybridization with directly labelled DNA probes specific for the X and Y chromosome. A twin female pregnancy was confirmed by means of ultrasonography and amniocentesis at the 14th week of amenorrhoea. The patient delivered two healthy females by Caesarian section at the 37th week of pregnancy.

Adult↗
PubMed1993

Two years of assisted fertilization by partial zona dissection in male factor infertility patients.

OBJECTIVE: To assess partial zona dissection in our routine IVF-ET program over a 2-year period. DESIGN: Partial zona dissection before insemination on the day of oocyte collection or 24 hours after unsuccessful conventional IVF. In a subgroup of patients, oocytes were randomized to either partial zona dissection before insemination or IVF. SETTING: University infertility clinic. PATIENTS: Couples who suffered principally from male factor infertility or who had failed fertilization previously. INTERVENTIONS: Micromanipulation of oocytes with partial zona dissection. MAIN OUTCOME MEASURES: Comparison of fertilization rate, embryo morphology, and implantation rate between partial zona dissection inseminated oocytes and conventional IVF inseminated oocytes (controls). RESULTS: Five pregnancies were established in 199 patients. The incidence of polyspermy was significantly higher in the partial zona dissection group than in conventional IVF (4.8% versus 1.3%). There were no significant differences in the remaining parameters. The fertilization rate of partial zona dissection and reinsemination was significantly higher than conventional IVF insemination (13.6% versus 4.5%) but similar to the rate obtained when partial zona dissection was applied before insemination (13.6% versus 15.7%). CONCLUSIONS: Oocytes treated by partial zona dissection did not exhibit a greater fertilization rate than conventional IVF inseminated oocytes. Partial zona dissection may not be a useful technique for treating severe male factor infertility.

Adult↗
PubMed1993

Sephadex filtration and human serum albumin gradients do not select spermatozoa by sex chromosome: a fluorescent in-situ hybridization study.

Fluorescent in-situ hybridization (FISH) of decondensed sperm nuclei has been used directly to evaluate the enrichment efficiency of human sperm separation using Sephadex gel filtration and human serum albumin (HSA) gradients. Control and processed spermatozoa were fixed and their nuclei decondensed. In-situ hybridization was carried out with a Y-specific DNA probe (DYZ1). Sephadex filtration yielded 52.5% Y-chromosome-bearing spermatozoa, HSA separation resulted in 49.4% Y-chromosome-bearing spermatozoa and in the untreated control sample the percentage of Y spermatozoa was 49.3%. Statistical analysis revealed no significant differences between the selection methods employed and the controls, and no real enrichment for X- or Y-bearing spermatozoa was detected for any of the selection methods assayed. The usefulness of the protocols reported for selection of spermatozoa by sex chromosome in couples at risk for X-linked diseases is discussed.

Cell Separation↗
PubMed1992

Indications for oocyte donation.

Donated oocytes were transferred on 92 occasions to 87 women without gonadal function and 5 with functional ovaries. Twenty-three pregnancies were established (25% pregnancy rate), 9 after transfer of fresh embryos in 30 synchronous donor and recipient cycles and 14 after transfers of frozen-thawed embryos in 62 asynchronous donor and recipient cycles. Twenty-two pregnancies were obtained in agonadal patients (25.3% pregnancy rate) and 1 in a gonadal woman (20% pregnancy rate). Pregnant women were younger than those who did not become pregnant, but the difference was not significant. The pregnancy rate was higher when intra-Fallopian transfer was performed (46%) as compared with intrauterine transfer (21.5%) and when micronized progesterone was given intravaginally (pregnancy rate 30.3%) as compared to intramuscularly injected natural progesterone in oil (pregnancy rate 22%). Twenty healthy infants have been born including one set of twins; four pregnancies miscarried.

Adult↗
PubMed1992

Chromosome anomalies in mouse zygotes treated by growth hormone-releasing factor.

The incidence of chromosome anomalies was studied in fertilized oocytes in two groups of hybrid mice in which superovulation was induced by gonadotrophins and growth hormone-releasing factor (GRF) supplementation or gonadotrophins alone (controls). The rate of fertilization was significantly higher among GRF-treated females than among controls (74.1 versus 84.7%; P < 0.013). Cytogenetic data were obtained in 262 fertilized oocytes (89 from control females and 173 from GRF-treated females). The frequency of aneuploidy, calculated as twice the frequency of hyperhaploidy was 2.31% in GRF-treated females and 2.24% in controls (NS). The use of GRF to treat female mice did not adversely affect the maturation process of oocytes nor did it induce an increased frequency of aneuploidy.

Animals↗
PubMed1987

Chromosome studies in oocytes and zygotes from an IVF programme.

Chromosome studies have been carried out in 117 oocytes, 17 one-cell zygotes and four, two- to four-cell zygotes in our IVF programme. Three apparently unfertilized oocytes were, in fact, diploid zygotes. Two of 14 apparently polyspermic zygotes were also diploid. One zygote with four pronuclei was pentaploid. This indicates that pronuclei can either be confused with other cytoplasmic structures, like vacuoles, or be eliminated. Endoreduplication was observed in one tetraploid, apparently polyspermic zygote, and in one two-cell degenerated zygote. The incidence of aneuploidy in unfertilized oocytes, taken as twice the level of hyperhaploidy, was 15.4%. Five oocytes showed fragmented metaphase II chromosomes (4.3%). The incidence of unreduced oocytes, due to a lack of extrusion of the first polar body, was 6.8%. Thus the total number of potentially aneuploid, polyploid or non-viable zygotes due to chromosome aberrations in the oocyte was 26.5%.

Aneuploidy↗
PubMed1975

[Calorie deficiency in preschool children of the rural area of Costa Rica].

Diets of preschool children from two studies carried out in rural areas of Costa Rica were analyzed to determine the relationship between caloric and protein deficiencies. On the average, a clear caloric deficiency was observed in the diets of all age groups considered, but their protein content was adequate. The individual analysis of the diets indicate that when caloric intake is adequate, the amount of protein is enough to satisfy the needs of these children. It is concluded that the dietary problem of preschool children in Costa Rica depends upon the quantity and not the quality of the diet. Implications of the effect of nutrition intervention programs based on erroneous assumptions are discussed.

Child Nutritional Physiological Phenomena↗
PubMedDate not supplied

Hantavirus reservoir hosts associated with peridomestic habitats in Argentina.

Five species of sigmodontine rodents have been identified in Argentina as the putative reservoirs of six circulating hantavirus genotypes. Two species of Oligoryzomys are associated with the genotypes causing hantavirus pulmonary syndrome, Oligoryzomys flavescens for Lechiguanas and O. longicaudatus for Andes and Oran genotypes. Reports of human cases of hantavirus pulmonary syndrome prompted rodent trapping (2,299 rodents of 32 species during 27,780 trap nights) at potential exposure sites in three disease-endemic areas. Antibody reactive to Sin Nombre virus was found in six species, including the known hantavirus reservoir species. Risk for peridomestic exposure to host species that carry recognized human pathogens was high in all three major disease-endemic areas.

Animals↗