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P Robles

Publications and source records attributed to P Robles.

At least 19 recordsLinked to original sources
PubMed2006

Human fetal ovarian culture permits meiotic progression and chromosome pairing process.

BACKGROUND: The female meiotic process seems to be crucial for aneuploidy in humans. The first stages of mammalian female meiosis take place during the fetal period. Therefore, only little is known about female meiosis. The goal of this study was to develop a culture technique that permits human oocytes to progress through meiotic prophase, to provide a system to study human female meiosis. METHOD: Fetal ovaries from four cases were cultured up to 35 days in alpha-minimal essential medium, 2% human serum albumin, 5 microg/ml insulin, 5 microg/ml transferrin, 5 ng/ml selenium and 100 IU/ml penicillin-100 microg/ml streptomycin. RESULTS AND CONCLUSIONS: Although ovarian response to culture conditions varied, human oocytes survived in vitro up to 5 weeks. In three cases, we observed significant variation in stages of meiosis among the cultures. The homologous chromosome pairing process was studied for the first time in cultured oocytes, and the results suggested that the pairing process was completed following the same features described previously for euploid oocytes, as followed by the chromosome-13 pairing process and synaptonemal complex formation. Although a higher proportion of degenerated oocytes were observed as culture time increased, we also observed oogonial entrance to meiotic prophase.

Cell Cycle↗
PubMed2005

Evolution of the meiotic prophase and of the chromosome pairing process during human fetal ovarian development.

BACKGROUND: Studies on human oocytes in prophase I are limited due to the difficulty in obtaining the sample. However, a complete study of meiotic prophase evolution and the homologue pairing process is necessary to try to understand the implication of oogenesis in the origin of human aneuploidy. METHODS: A complete analysis of meiotic prophase progression comprising the long developmental time period during which meiotic prophase takes place, based on the analysis of a total of 8603 oocytes in prophase I from 15 different cases is presented. The pairing process of chromosomes 13 and 18 is also described. RESULTS: The findings significantly relate for the first time the evolution of meiotic prophase to fetal development. Although for both chromosomes 13 and 18 a high pairing efficiency is found, pairing failure at the pachytene stage has been observed in 0.1% of oocytes. However, errors at the diplotene stage are substantially increased, suggesting that complete, premature disjunction of the homologues commonly occurs. Moreover, pre-meiotic errors are also described. CONCLUSIONS: Our findings show that homologous chromosomes pair very efficiently, but the high frequency of complete, premature homologue separation found at diplotene suggests that mechanisms other than the pairing process could be more likely to lead to the high aneuploidy rate observed in human oocytes.

Aneuploidy↗
PubMed2005

Pleuropulmonary infections caused by Mycobacterium bovis: a re-emerging disease.

Between 1980 and 2003, 13 patients (0.95% of all cases of tuberculosis) at a 600-bed university hospital in Madrid, Spain, were diagnosed with Mycobacterium bovis infection. All 13 cases occurred between 1994 and 1999; the mean age of the patients was 50 years (range 23-83 years), and 77% were males. Four (30%) patients were also positive for human immunodeficiency virus (HIV). The most frequent localisation of the disease was the lung (ten patients; 77%). Seven patients, including four HIV-positive patients who died, had multidrug-resistant M. bovis infection. No other patient died, including two HIV-negative patients with multidrug-resistant disease.

AIDS-Related Opportunistic Infections↗
PubMed2005

Chromosome 18 pairing behavior in human trisomic oocytes. Presence of an extra chromosome extends bouquet stage.

Little is known about the first meiotic prophase stages in the human female because these occur during fetal life, and only a few studies have addressed aneuploid human oocytes. In this paper, the synaptic process in the meiotic prophase in three 47, XX+18 cases is analyzed. A complete study of the dynamics of centromeres and telomeres, cohesin core and synapsis development in aneuploid female meiosis was performed. Investigation of chromosome dynamics in prophase of trisomy 18 oocytes show that these events follow the major patterns seen earlier in euploid oocytes. However, there is a significant delay in the resolution of bouquet topology which could relate to the presence of a surplus chromosome 18 axial element in zygotene oocytes. Pachytene oocytes displayed normal synapsis among the three chromosome 18s. However, in some oocytes the surplus chromosome 18 core was aligned to the bivalent 18. As ataxia telangiectasia and Rad3 related kinase (ATR) has been described as a marker for late-pairing chromosomes in mice, ATR distribution was analyzed in human meiocytes--spermatocytes, euploid oocytes and trisomic oocytes. In contrast to the observations made in mice, no preferential staining for late-pairing chromosomes was observed in humans. In the cases studied, bivalent synapses progressed as in a normal ovary, contrasting with the hypothesis that a surplus chromosome can modify pairing of other chromosomes.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2002

Optical absorption for parallel cylinder arrays.

We study the long-wavelength electromagnetic resonances of interacting cylinder arrays. By using a normal-modes expansion where the effects of geometry and material are separated, it is shown that two parallel cylinders with different radii have electromagnetic modes distributed symmetrically about depolarization factor 1 / 2. Both sets couple to longitudinal and transverse components of the external field, but amplitudes of symmetric depolarization factors become exchanged when considering longitudinal or transverse polarization. We also find that amplitudes satisfy sum rules that depend on the ratio of the cylinders radii. The main effect of the difference in radii is a spectral shift towards the isolated cylinder resonance as this difference increases.

Journal Article↗
PubMed2001

Genome-wide linkage analysis of Arabidopsis genes required for leaf development.

In most crop species, primary productivity depends mainly on the leaf. However, the genes that contribute to the making of plant leaves remain largely unknown. With a view to identifying the genes involved in leaf development in Arabidopsis thaliana, we previously isolated EMS-induced mutants with abnormally shaped leaves and demonstrated that they fall into 94 complementation groups. We present here the map positions of 76 of these genes, which have been obtained using a high-throughput genetic mapping method, based on the simultaneous coamplification by PCR of 21 polymorphic microsatellites and the semiautomated fluorescent detection of the products. The map positions and F2 mapping populations obtained in this work will be instrumental in the positional cloning of these genes, which are essential for leaf development.

Alleles↗
PubMed2000

Genetic analysis of incurvata mutants reveals three independent genetic operations at work in Arabidopsis leaf morphogenesis.

In an attempt to identify genes involved in the control of leaf morphogenesis, we have studied 13 Arabidopsis thaliana mutants with curled, involute leaves, a phenotype herein referred to as Incurvata (Icu), which were isolated by G. Röbbelen and belong to the Arabidopsis Information Service Form Mutants collection. The Icu phenotype was inherited as a single recessive trait in 10 mutants, with semidominance in 2 mutants and with complete dominance in the remaining 1. Complementation analyses indicated that the studied mutations correspond to five genes, representative alleles of which were mapped relative to polymorphic microsatellites. Although most double-mutant combinations displayed additivity of the Icu phenotypes, those of icu1 icu2 and icu3 icu4 double mutants were interpreted as synergistic, which suggests that the five genes studied represent three independent genetic operations that are at work for the leaf to acquire its final form at full expansion. We have shown that icu1 mutations are alleles of the Polycomb group gene CURLY LEAF (CLF) and that the leaf phenotype of the icu2 mutant is suppressed in an agamous background, as is known for clf mutants. In addition, we have tested by means of multiplex RT-PCR the transcription of several floral genes in Icu leaves. Ectopic expression of AGAMOUS and APETALA3 was observed in clf and icu2, but not in icu3, icu4, and icu5 mutants. Taken together, these results suggest that CLF and ICU2 play related roles, the latter being a candidate to belong to the Polycomb group of regulatory genes. We propose that, as flowers evolved, a new major class of genes, including CLF and ICU2, may have been recruited to prevent the expression of floral homeotic genes in the leaves.

Arabidopsis↗
PubMed2000

[Validity of the Cognitive Mini-Exam of Lobo et al. for the detection of dementia-associated cognitive deterioration] .

BACKGROUND AND OBJECTIVES: The Mini-Examination Cognitive (MEC) of Lobo et al is widely used as a screening tool for dementia in epidemiological studies and in clinical context for the rapid evaluation of cases in whom there is a suspicion of cognitive deterioriation due to dementia. Nevertheless, the validity analysis in old people have not been accomplished. The objective of this study has been to validate the use of this instrument to detect cognitive deterioration associated with dementia in elderly people. PATIENTS AND METHODS: Ninety-five old people have participated, one group of patients of a Neurology Service and another group of healthy old people. All of them have been evaluated through a neuropsychological exploration protocol and the MEC. RESULTS: The results show a high validity of this test for the evaluation of the cognitive deterioration in this population, as in the correlation with the neurological tests used as in the ANOVA intergroups (with and without deterioration) executed; they also reflect the influence on the puntuations of variables such as the age and the educational level. CONCLUSIONS: The utility of this procedure for the Spanish population with a low cultural level and the necessity of working with different criteria depending on the age and the educational level of the patients evaluated is shown here.

Aged↗
PubMed1999

Genetic analysis of leaf form mutants from the Arabidopsis Information Service collection.

Although a vast inventory of morphological mutants of Arabidopsis thaliana is available, only some have been used for genetic studies of leaf development. Such is the case with the Arabidopsis Information Service (AIS) Form Mutants collection, assembled by A. R. Kranz and currently stored at the Nottingham Arabidopsis Stock Centre, which includes a large number of mutant lines, most of which have been little studied. With the aim of contributing to the genetic dissection of leaf ontogeny, we have subjected 57 mutant lines isolated by others to genetic analysis; 47 of which were from the AIS collection. These are characterized by vegetative leaves of abnormal shape or size, and were chosen as candidates for mutations in genes required for leaf morphogenesis. The mutant phenotypes studied were shown to be inherited as single recessive Mendelian traits and were classified into 10 phenotypic classes. These mutant strains were found to fall into 37 complementation groups, 7 of which corresponded to known genes. Results of the phenotypic analysis and data on the genetic interactions of these mutants are presented, and their possible developmental defects discussed.

Arabidopsis↗
PubMed1999

High-throughput genetic mapping in Arabidopsis thaliana.

To facilitate rapid determination of the chromosomal location of novel mutations, we have improved current approaches to gene mapping using microsatellite length polymorphisms. The high-throughput linkage analysis method described here allows a novel gene to be tested for linkage against the whole genome of a multicellular eukaryote, Arabidopsis thaliana, in a single polyacrylamide gel. The procedure is based on the simultaneous co-amplification of 21 microsatellites in a single tube, using a multiplex PCR mix containing 21 primer pairs, each including one oligonucleotide labeled with one of three fluorescent dyes that have different emission wavelengths. The amplification products, which range in number from 21 to 42, depending on the genotype of the individual being tested, are electrophoresed in a single lane on a polyacrylamide gel. The use of an automated fragment analyzer makes it possible to perform linkage analysis on a one gel-one gene basis using DNA samples from 19 F2 individuals obtained from an outcross involving a mutant and a wild-type that is genetically polymorphic with respect to the ecotype in which the mutant was generated. Discrimination of the amplification products is facilitated not only by labeling with different fluorochromes, but also by prior testing of different sequences for the ability to prime the amplification of each microsatellite, in order to ensure that multiplex PCR yields compatible amplification products of non-overlapping size. The method is particularly useful in large-scale mutagenesis projects, as well as for routine mapping of single mutants, since it reveals the map position of a gene less than 24 h after the F2 individuals to be analyzed have become available. The concepts employed here can easily be extended to other biological systems.

Arabidopsis↗
PubMed1999

A mutational analysis of leaf morphogenesis in Arabidopsis thaliana.

As a contribution to a better understanding of the developmental processes that are specific to plants, we have begun a genetic analysis of leaf ontogeny in the model system Arabidopsis thaliana by performing a large-scale screening for mutants with abnormal leaves. After screening 46,159 M2 individuals, arising from 5770 M1 parental seeds exposed to EMS, we isolated 1926 M2 putative leaf mutants, 853 of which yielded viable M3 inbred progeny. Mutant phenotypes were transmitted with complete penetrance and small variations in expressivity in 255 lines. Most of them were inherited as recessive monogenic traits, belonging to 94 complementation groups, which suggests that we did not reach saturation of the genome. We discuss the nature of the processes presumably perturbed in the phenotypic classes defined among our mutants.

Alleles↗
PubMed1997

[Prosthetic endocarditis and splenic abscess caused by Clostridium clostridiformis].

We report the first case of Clostridium clostridiformis endocarditis in a 71 year old man with an aortic prosthetic valve. He was febrile with left upper quadrant pain and left lower lobe infiltrate in chest X ray. The diagnosis was made by gram-positive bacilli grown from three blood cultures. Transthoracic and transesophageal echocardiogram showed a paraaortic abscess. A computed tomographic scan of the abdomen revealed a large splenic abscess. He received penicillin G 4 million units every 4 hours intravenously. A successful percutaneous drainage guided computed tomographic scan was performed. The patient remained febrile and a new computed tomographic scan of the abdomen revealed residual splenic abscess. A splenectomy was performed. The patient defervesced on the second day of surgery and remained afebrile during the remainder of his hospitalization. He has returned for medical follow-up and two years later the patient is asymptomatic.

Abscess↗