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Biomedical subjects

B Ibarra

Publications and source records attributed to B Ibarra.

At least 19 recordsLinked to original sources
PubMed2006

Y-linked haplotypes in Amerindian chromosomes from Mexican populations: genetic evidence to the dual origin of the Huichol tribe.

We studied six Y-linked short tandem repeats (Y-STRs) to describe the internal diversity of the Amerindian haplogroup Q-M3 in 129 males from eight Mexican populations. The low gene diversity in the Huichol tribe demonstrated the effects of genetic drift, attributable to geographic isolation and founder effect. The presence of two principal paternal lineages supported the historical and anthropometric records, which indicate that Huichols were formed by the fusion of two ancestral Mexican tribes. Moreover, genetic distances and close relationships of haplotypes between Huichols and Tarahumaras were in agreement with their linguistic affiliation. The high genetic diversity of the Purépechas and wide distribution of haplotypes along the constructed network-joining tree suggest that the present genetic composition was influenced by Purépecha dominance in western Mesoamerica. The Y-haplotypes shared between populations suggest that, among the Amerindian tribes studied herein, the paternal genetic pool of Nahuas could have contributed more importantly to the European-admixed population, the Mexican-Mestizos.

Chromosomes, Human, Y↗
PubMed2004

Bacteriophage capsids: tough nanoshells with complex elastic properties.

The shell of bacteriophages protects the viral DNA during host-to-host transfer and serves as a high-pressure container storing energy for DNA injection into a host bacterium. Here, we probe the mechanical properties of nanometer-sized bacteriophage phi 29 shells by applying point forces. We show that empty shells withstand nanonewton forces while being indented up to 30% of their height. The elastic response varies across the surface, reflecting the arrangement of shell proteins. The measured Young's modulus (approximately 1.8 GPa) is comparable with that of hard plastic. We also observe fatigue and breakage of capsids after probing them repetitively. These results illustrate the mechanoprotection that viral shells provide and also suggest design principles for nanotechnology.

Bacteriophages↗
PubMed2001

Purification and functional characterization of p16, the ATPase of the bacteriophage Phi29 packaging machinery.

Bacteriophage Phi29 codes for a protein (p16) that is required for viral DNA packaging both in vivo and in vitro. Co-expression of p16 with the chaperonins GroEL and GroES has allowed its purification in a soluble form. Purified p16 shows a weak ATPase activity that is stimulated by either DNA or RNA, irrespective of the presence of any other viral component. The stimulation of ATPase activity of p16, although induced under packaging conditions, is not dependent of the actual DNA packaging and in this respect the Phi29 enzyme is similar to other viral terminases. Protein p16 competes with DNA and RNA in the interaction with the viral prohead, which occurs through the N-terminal region of the connector protein (p10). In fact, p16 interacts in a nucleotide-dependent fashion with the viral Phi29-encoded RNA (pRNA) involved in DNA packaging, and this binding can be competed with DNA. Our results are consistent with a model for DNA translocation in which p16, bound and organized around the connector, acts as a power stroke to pump the DNA into the prohead, using the hydrolysis of ATP as an energy source.

Adenosine Triphosphatases↗
PubMed2001

Timing of spontaneous recanalization and risk of hemorrhagic transformation in acute cardioembolic stroke.

BACKGROUND AND PURPOSE: The relationship between reperfusion and hemorrhagic transformation (HT) remains uncertain. Therefore, we aimed to clarify the relationship between the time course of recanalization and the risk of HT in patients with cardioembolic stroke studied within 6 hours of symptom onset. METHODS: Fifty-three patients with atrial fibrillation and nonlacunar stroke in the middle cerebral artery (MCA) territory admitted within the first 6 hours after symptom onset were prospectively studied. Serial TCD examinations were performed on admission and at 6, 12, 24, and 48 hours. CT was performed within 6 hours after stroke onset and again at 36 to 48 hours. RESULTS: Proximal and distal MCA occlusions were detected in 32 patients (60.4%) and 18 patients (34%), respectively. Early spontaneous recanalization occurring within 6 hours was identified in 10 patients (18.8%). Delayed recanalization (>6 hours) occurred in 28 patients (52.8%). HT on CT scan was detected in 17 patients (32%) within the first 48 hours. Only large parenchymal hemorrhage (PH2) was significantly associated with an increase (P=0.038, Kruskal-Wallis test) in the National Institutes of Health Stroke Scale (NIHSS) score compared with the other subtypes of HT. Univariate analysis revealed that an NIHSS score of >14 on baseline (P=0.001), proximal MCA occlusion (P=0.004), hypodensity >33% of the MCA territory (P=0.012), and delayed recanalization occurring >6 hours of stroke onset (P=0.003) were significantly associated with HT. With a multiple logistic regression model, delayed recanalization (OR 8.9; 95% CI 2.1 to 33.3) emerged as independent predictor of HT. CONCLUSIONS: Delayed recanalization occurring >6 hours after acute cardioembolic stroke is an independent predictor of HT.

Adult↗
PubMed2000

Topology of the components of the DNA packaging machinery in the phage phi29 prohead.

Chromosome condensation inside dsDNA viral particles is a complex process requiring the coordinated action of several viral components. The similarity of the process in different viral systems has led to the suggestion that there is a common underlying mechanism for DNA packaging, in which the portal vertex or connector plays a key role. We have studied the topology of the packaging machinery using a number of antibodies directed against different domains of the connector. The charged amino-terminal, the carboxyl-terminal, and the RNA binding domain are accessible areas in the connector assembled into the prohead, while the domains corresponding to the 12 large appendages of the connector are buried inside the prohead. Furthermore, while the antibodies against the carboxyl and amino-terminal do not affect the packaging reaction, incubation of proheads with antibodies against the RNA binding domain abolishes the packaging activity. The comparison of the three-dimensional reconstructions of bacteriophage phi29 proheads with proheads devoid of their specific pRNA by RNase treatment shows that this treatment removes structural elements of the distal vertex of the portal structure, suggesting that the pRNA required for packaging is located at the open gate of the channel in the narrow side of the connector.

Antibodies, Viral↗
PubMed2000

Structural analysis of the bacteriophage T3 head-to-tail connector.

The connector protein of bacteriophage T3, p8, has been overexpressed in Escherichia coli. Purification of the oligomers built by several copies of p8 reveals a mixed population of dodecamers and tridecamers. The percentages of these two types of oligomers differ in every culture growth, indicating that assembly of this protein depends upon the conditions of the expression system. Those cultures that generated a majority of dodecamers allowed, after purification of the connectors, the two-dimensional crystallization of the dodecamers in a tetragonal arrangement, while the tridecamers did not form crystals. The processing and averaging of several images of frozen-hydrated crystals and their internal phase comparison shows that the crystals are arranged in a P42(1)2 space group, with cell unit dimensions of 165 x 165 A. The three-dimensional reconstruction generated with images of crystals ranging from 0 degrees to 60 degrees tilt reveals a wide domain surrounded by 12 protrusions and a narrow domain that serves to interact with the tail of the bacteriophage. A channel runs along the connector wide enough to allow the translocation of a double-stranded DNA molecule into the prohead. The general structure of the T3 connector is very similar to those obtained for other nonrelated bacteriophages and strongly suggests that the shape of this important viral structure is intimately related to its function.

Capsid↗
PubMed2000

Genetic variation among four Mexican populations (Huichol, Purepecha, Tarahumara, and Mestizo) revealed by two VNTRs and four STRs.

Allele distributions of two polymorphisms with variable number of tandem repeats (VNTR), D1S80 and APOB, and four polymorphisms with short tandem repeats (STR), VWA, TH01, CSF1PO, and HPRTB, were analyzed in three Mexican ethnic groups: Huichol, Purepecha, and Tarahumara. Genotype distribution was in agreement with Hardy-Weinberg expectations for each locus and ethnic group. Heterozygosity (H), power of discrimination, and probability of exclusion were estimated. The three groups presented some distinctive genetic features: (1) a diminished genetic diversity (H = 66.8% to 73.4%) and mean number of alleles by locus (5.8 to 6.3) in comparison with Mexican mestizos (H = 78.3%, 10.5 alleles/locus), and (2) uneven allele distributions as evidenced by "distinctive alleles" with high frequencies, especially in the Tarahumara and the Huichol. Genetic relatedness analysis included data from a previously typed mestizo population, the largest and most widely distributed population in Mexico. Allele distribution differentiation was observed among all four groups, except between mestizo and Purepecha (p > 0.05), which was interpreted as indicating a larger Spanish component in the Purepecha as a result of gene flow effects. Although intrapopulation inbreeding (FIS) was not significant, heterozygote deficiency in the total population (FIT) and divergence among populations (FST) were significant (p < 0.05). Genetic distances displayed a closer relationship among mestizos, Purepechas, and Huichols in relation to Tarahumaras. Correlation between the observed genetic features and the geographic isolation level points to genetic drift as the main cause of differentiation among these Mexican populations.

Consanguinity↗
PubMed1999

Hb D-Los Angeles associated with Hb S or beta-thalassemia in four Mexican Mestizo families.

Twenty-five individuals were studied from four unrelated Mexican Mestizo families with Hb D-Los Angeles. We observed five compound heterozygotes: four for Hb S and Hb D, and one for Hb D and beta-thalassemia (beta(0) 39 nonsense mutation); 16 heterozygotes: four for Hb S, seven for Hb D, and five for beta-thalassemia, while the remaining four were normal. The four Hb S/Hb D patients had severe hemolytic anemia, while in the Hb D/beta-thalassemia patient, the anemia was similar to that of a beta-thalassemia heterozygote; therefore, Hb D is clinically harmful when it is associated with Hb S. The beta(S) chromosomes were associated with the Benin haplotype in two families and Bantu in one family, while the beta(D) and beta(0) 39 mutations were associated with haplotype 1 [+ - - - - + +]. The Bantu and Benin haplotypes have been found with high frequency in Hb S individuals from the East Coast and Northwestern Mexico. The beta(D) chromosomes from Italy were also shown to be associated with haplotype 1, the most frequently observed haplotype in the world; there are no haplotype studies on beta(D) chromosomes from India or China where Hb D-Los Angeles is most common. Thus, the true origin of this mutation observed in these Mestizo families remains to be elucidated.

Adolescent↗
PubMed1998

[Arteriography using helicoidal computerized tomography in the study of complex aneurysms of the circle of Willis].

INTRODUCTION: Computed tomography angiography (CTA) can add information to digital subtraction angiography (DSA) in selected cases of aneurysms of the circle of Willis. CLINICAL CASES: 1. Patient with progressive visual loss and headache. CT and DSA showed an image of partially thrombosed suprasellar aneurysm. CTA better defined the relationship between the lesion and regional vessels. 2. Woman with subarachnoid hemorrhage (SAH). CTA defined the aneurysmal neck and its relationship to the clinoid process. 3. Man with SAH, CT and DSA showed an arteriovenous malformation and three arterial aneurysms one of which was in a tortuous vessel. CTA confirmed digital angiographic data. CONCLUSION: CTA is a new image technique that can either add or confirm DSA findings in complex aneurysms of the circle of Willis.

Adult↗
PubMed1997

Beta-thalassemia and beta[A] globin gene haplotypes in Mexican mestizos.

B-globin haplotypes of 20 beta-thalassemia (beta-thal) and 87 beta(A) Mexican mestizo chromosomes were analyzed to ascertain the origin of the beta-thal alleles and the frequencies and distribution of the beta(A) haplotypes among northwestern Mexican mestizos. Sixteen beta-thal chromosomes carried six Mediterranean alleles [five codon 39 C-->T; two IVS1:1 G-->A; two IVS1:5 G-->A; three IVS1:110 G(A; one codon 11 (-T) and three (deltabeta)zero-thal]; the remaining four were linked to three rare alleles (two -28 A-->C and one each: -87 C-->T and initiation codon ATG-->GTG). Among the 87 beta(A) chromosomes, 17 different 5' haplotypes with frequencies for 1, 3, 2 and 5 of 39.0%, 17. 2%, 9.2% and 6.9%, respectively, were observed. The beta-haplotype analysis showed that 13 out of 16 Mediterranean chromosomes could easily be explained by gene migration; however, one codon 39 associated with haplotype 4 (----+ +-), one IVS1:1 with haplotype 1(+----++) and one IVS1:5 G-->A, may represent separate mutational events. Analysis of the rare alleles showed that the -28 A-->C mutation was associated with the commonest beta(A) haplotype in Mexican mestizos, Mediterraneans and the total world population; therefore an independent origin cannot be ruled out. The -87 C-->T and initiation codon ATG-->GTG were found with beta-haplotypes different from the reported ones, suggesting an indigenous origin.

Alleles↗
PubMed1997

[Jugular megabulb as a cause of pulsatile tinnitus].

INTRODUCTION: Pulsatile tinnitus (AP), possibly of vascular origin, may be a sign of various vascular and non-vascular pathological processes. Arteriovenous fistulas and malformations are, perhaps, the commonest cause of AP. CLINICAL CASE: A 64 year-old woman presented with AP of the right ear for the past 14 years. It was continuous all day and could be observed externally by the examiner. The intensity of the tinnitus diminished on right later-cervical compression and on turning her head to the left. There was bilateral transmission deafness. Neurological examination was normal. Complementary explorations (MR, CT of the base of the skull and cerebral arteriography) showed the presence of a jugular megabulb of the right side. CONCLUSIONS: The presence of AP may be for many years the only sign of subjacent vascular pathology, such as a megabulb of the jugular vein.

Female↗
PubMed1996

Haplotype analysis of the Mexican frameshift Cd 11 (-T) and -28 A->C beta-thalassemia alleles.

The origins of the -28 A->C and frameshift Cd 11 - T(Fs CD 11-T)alleles were investigated by beta-globin cluster haplotype analysis. These alleles were found in a Mexican mestizo family with beta-thalassemia (beta-thal). The -28 A->C mutation was described previously in Kurdish Jews linked to the most common haplotype in the world(+----++),the same haplotype observed in this Mexican family. Therefore, it is not possible to assess a new origin of the -28 A->C mutation in our population. The Fs Cd 11 -T allele, not reported to date in any other populations, was linked to the -++--+-haplotype (sixth in frequency in the world). This haplotype has not been reported in association with any beta-thal mutant, suggesting a Mexican origin for the Cd 11 -T mutation.

Adolescent↗
PubMed1996

[Carotid cavernous fistula: endovascular therapy].

Abnormal communications between the carotidal artery and the cavernous sinus are known as carotid-cavernous fistulas. We can however distinguish between these fistulas two different evolutive and etiological entities: on the one hand there are the direct types with high flux and normally related to hard traumatisms and on the other hand there are the indirect types lacking clear etiological factors, with slower flux and which correspond to dural malformations with different arterial nutrition. In the last two years in our service we have treated eight carotid-cavernous fistulas, four direct and four indirect, using endovascular techniques with differing emboligenic materials according to the nature of the fistula, flux volume and origin. Complete closure was obtained in all patients with direct fistulas and in two whose fistulas were indirect. Closure was almost (greater than 75%) complete in the remaining two cases. In all cases symptomatology prior to intervention diminished completely a few weeks later with no relapse up until now. We discuss the classification and clinico-pathological characteristics of each fistula type, the comparative usefulness of different diagnostic methods and we review therapeutic symptoms with special emphasis on neuroradiological endovascular techniques, analyzing the usefulness of each emboligenic material type. The recent development of intervention techniques in neuroradiology makes low risk correct closure of carotid-cavernous fistulas a possibility. Endovascular is accepted as the treatment of choice today.

Adult↗
PubMed1993

Membrane-bound sorbitol dehydrogenase in human red blood cells. Studies in normal subjects and in enzyme-deficient subjects with congenital cataracts.

Membrane-bound and soluble forms of erythrocyte sorbitol dehydrogenase (SORD) activity are compared in normal individuals. Both isoenzymes showed similar properties. In a family with red cell SORD deficiency and congenital cataracts, Km values for sorbitol and NAD+ as well as the effect of the enzymatic deficiency on sorbitol accumulation in red cells incubated in high-glucose or high-fructose media were determined. In SORD-deficient patients, the enzymatic deficiency was observed in both crude haemolysate and SORD-M preparations with sorbitol, galactitol, xylitol or ribitol as substrates. The mutation responsible for SORD deficiency did not modify the Km for sorbitol and NAD+. Finally, SORD deficiency produced a significant increase of sorbitol accumulation in red cells incubated in high-concentration glucose media and a significant decrease when the cells were incubated in high-concentration fructose media.

Cataract↗
PubMed1993

[Fetal hemoglobin and the gamma G/gamma A chain ratio in children with acute lymphoblastic leukemia L1 and L2].

PURPOSE: To search in children with acute lymphoblastic leukaemia (ALL) for specific pattern of expression of foetal haemoglobin (HbF) and its G gamma/A gamma chain ratio. MATERIAL AND METHODS: 60 children with ALL were examined: 29 with ALL-L1, and 31 with ALL-L2, and 25 healthy children as control group, which were subdivided in three groups: A) 0-5, B) 6-10 and C) 11-18 years. We performed HbF and HbA2 quantification and Hb electrophoresis. G gamma and A gamma globin chain percentages were obtained with a new method based on the precipitation of the HbF eluate by Singer's method with sulphosalycilic acid, the globin chains were separated in polyacrylamide with Triton X-100 and quantified by densitometry. RESULTS: HbF showed similar levels in both ALL groups by the Betke and Singer's methods; (ALL-L1: 2.2 +/- 1.5%, ALL-L2: 2.0 +/- 1.2%; and ALL-L1: 2.0 +/- 1.2%, ALL-L2: 2.1 +/- 1.5% respectively), but there were statistically significant differences (p < 0.001) when compared with the control group (0.9 +/- 0.4%, and 1.0 +/- 0.6% for Betke and Singer's method). The G gamma/A gamma ratio showed to be different between the ALL-L1 and ALL-L2 (p < 0.001), with higher levels of G gamma in ALL-L1 (51.0%), the ALL-L2 and the control group showed similar G gamma values (37.5% and 42.1% respectively). CONCLUSION: The factors involved in the increase of HbF are similar for both ALL-L1 and ALL-L2. However there seems to be different factors affecting the expression of G gamma or A gamma.

Adolescent↗