PubMed Health⌕ Search

Biomedical subjects

J Benítez

Publications and source records attributed to J Benítez.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Genetic bases in Huntington disease].

Huntington disease is a neurodegenerative syndrome of late appearance in 80% of the cases. Its clinical course shows motor and cognitive disorders which lead to total incapacity of the individual 10 to 15 years after the appearance of the first syndromes. From a genetic point of view, this disease is of autosomic dominant inheritance with complete penetration. The gene (IT15) is localized in the short arm of chromosome 4 in the telemaric region 4p16.3 and it is known that the mutation is produced by an increase in the number of trinucleotides CAG (glutamine) localized in the 5' end of the gene, in the first exon. In the general population these are repeated in a number of less than 30 repetitions and in the disease population in a number greater than 36 and, in some cases, even greater than 100 repetitions. These sequences are unstable from one generation to another and this fact may explain the phenomenon of genetic anticipation shown in this disease since there is an inversely proportional correlation between the number of repetitions and the age of appearance of the first symptoms. The gene codifies for a protein known as "huntingtina" which is expressed not only in brain but also in different tissues. Although the function remains unknown, it is known that it is bound to other proteins related to the transmission of neuron signals and to the regulation of neuron death (apoptosis) among others. The defect is produced by a gain in function closely related to the number of repetitions. At present, presymptomatic and prenatal diagnosis of the disease may be achieved since the reliability of the studies is practically 100%. Nonetheless, the demand is lower than expected and this may be due to psychologic, social and legal problems, together with the lack of adequate infrastructure for completely guaranteeing the performance of these studies.

Chromosome Aberrations↗
PubMed1999

[MLL rearrangements in acute leukemias].

PURPOSE: In present study we have studied MLL rearrangements in a serie of acute myeloid, lymphoblastic and biphenotypic leukaemias. PATIENTS AND METHODS: We analyzed a total of 11 cases: 9 acute myeloid leukaemias (M4 and M5 subtypes in FAB classification), 1 lymphoid leukaemia, and 1 acute biphenotypic leukaemia. We studied bone marrow samples from all patients by using conventional cytogenetic techniques and fluorescence in situ hybridization (FISH) with an MLL probe. We also analyzed the correlation between clinical features and genetic results. RESULTS: Cells from 6 patients showed to contain MLL rearrangements and these arose in all types of leukaemias included in this study. Some MLL rearrangements were detected by FISH in kariotypically normal cases or without cytogenetic evidence of 11q23 aberration. MLL gene duplication has been observed in two cases with M4 and biphenotypic leukaemia, respectively. The presence of MLL gene rearrangements does not shape a group of patients with a common clinical pattern. CONCLUSIONS: MLL rearrangements occurs in a wide variety of leukemias. These rearrangements should be screened by FISH techniques, taking into account that gene duplications could arise in cases with normal karyotype. MLL rearrangements appear to have a considerable clinicopathologic heterogeneity.

Adult↗
PubMed1999

High prevalence of the C634Y mutation in the RET proto-oncogene in MEN 2A families in Spain.

The RET proto-oncogene encodes a receptor tyrosine kinase expressed in neural crest derived tissues. Germline mutations in the RET proto-oncogene are responsible for three different dominantly inherited cancer syndromes: multiple endocrine neoplasia type 2A (MEN 2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). MTC can also occur sporadically. Molecular characterisation of the RET proto-oncogene has been performed by PCR-SSCP analysis, direct DNA sequencing, and restriction enzyme analysis in 49 unrelated, Spanish, MEN 2 families: 30 MEN 2A families, six FMTC families, and 13 families classified as "other". Germline missense mutations in one of six cysteine codons (609, 611, 618, and 620 in exon 10, and codons 630 and 634 in exon 11), which encode part of the extracellular cysteine rich domain of RET, have been detected in the majority of these families: 100% of MEN 2A families, 67% of FMTC families, and 54% of families classified as "other". No RET mutations in exons 10, 11, 13, 14, 15, or 16 were detected in the remaining families. The most frequent RET mutation in MEN 2A Spanish families is C634Y, occurring in 73% of cases. Haplotype analysis does not exclude the possibility of founder effects in Spanish MEN 2A families with the C634Y mutation.

Chromosomes, Human, Pair 1↗
PubMed1998

Increased C-MYC oncogene copy number detected with combined modified comparative genomic hybridization and FISH analysis in a Richter syndrome case with complex karyotype.

Modified comparative genomic hybridization (mCGH) was performed in a Richter syndrome case with a complex karyotype to identify and map gains of DNA sequences with possible importance in the pathogenesis and progression of the tumor. The mCGH analysis revealed a more intense signal on part of the long arm of one pair of chromosomes belonging to group C. The G-banding study showed that the increased DNA-sequence copy number originated from the 8q22-->qter chromosomal region. This increase was confirmed by performing a fluorescence in situ hybridization analysis on tumor metaphases by first using a chromosome 8-specific library and subsequently a C-MYC probe, which revealed positive staining on six different regions located on six different chromosomes, each one bearing a single copy of the C-MYC oncogene. These results show the existence of C-MYC oncogene copy-number increases and confirm the usefulness of mCGH in the genetic analysis of malignancies.

Aged↗
PubMed1998

[The Pro347Leu mutation of the rhodopsin gene in a Spanish family with autosomal dominant pigmentary retinosis].

We present a Spanish family affected with autosomal dominant pigmentary retinosis in which we have identified the mutation responsible for the disease (Pro347Leu) within the rhodopsin (RHO) gene. Complete ophthalmological and electrophysiological studies were performed in 14 members of this family. The molecular study, performed by SSCP analysis of the 5 exon and the promotor region of the rhodopsin gene, direct sequentiation and restriction analysis with the enzyme Mspl, showed a C-->T change in the second base of 347 codon of RHO gene. This mutation predicts a change of proline by leucine at this position. Every patient with the mutation showed a phenotype of diffuse, early onset and severe pigmentary retinosis with a little intrafamiliar variation. The Pro347Leu mutation, that has been very frequently described among all the populations, has been identified as a cause of RP in an Spanish family.

Adolescent↗
PubMed1998

Molecular analysis of the six most recurrent mutations in the BRCA1 gene in 87 Spanish breast/ovarian cancer families.

BRCA1 accounts for nearly all families with multiple cases of both early onset breast and ovarian cancer and about 45% of families with breast cancer only. Although to date more than 200 distinct mutations have been described, several have been found to be recurrent in the gene. We have analyzed 87 Spanish breast/ovarian cancer families for the six most recurrent mutations in the BRCA1 gene. The analysis of the five exons where these mutations are located was made using the SSCP and sequenciation techniques. Four mutations were found in our families and only two carried one of the six mutations analyzed. In both cases the mutation identified was 185delAG. Our results suggest that these six mutations are not specially recurrent in the Spanish population and that differences in the geographical origin of the families can influence the type and proportion of mutations identified.

Adult↗
PubMed1998

Severity of cognitive impairment in juvenile and late-onset Huntington disease.

OBJECTIVES: To compare the severity of cognitive impairment among groups of patients with different age ranges at the onset of Huntington disease (HD) and to evaluate the variable influence of motor and cognitive deficits on functional disability across different ages at the onset of HD. DESIGN: Cross-sectional multidisciplinary evaluation of patients referred to our institution for care related to a possible diagnosis of HD. SETTING: The Huntington disease program in the Departments of Neurology and Genetics at the Fundación Jimenez Diaz, Madrid, Spain. PARTICIPANTS: Seventy-one patients with Huntington disease were classified into 3 groups depending on age at onset of motor symptoms: juvenile onset, 25 years of age or younger (group 1, n = 15); adult onset, from 26 to 50 years (group 2, n = 43); and late onset, 51 years or older (group 3, n = 13). Age- and education-matched controls (n=50) were included to compare cognitive performance with patients in groups 1 and 3. MEASURES: Cognitive evaluation encompassed a wide neuropsychological battery to assess global cognitive functioning and visuospatial, prefrontal, and memory functions. Clinical data included motor and functional variables measured by using the Unified Huntington's Disease Rating Scale. Genetic analysis determined the number of CAG trinucleotide repeats. RESULTS: Patients in group 1 scored 2.9 points and patients in group 3 scored 4.2 points below their respective controls on the Mini-Mental State Examination. Patients in groups 1 and 3 were similarly impaired in verbal memory. Visual function was much more impaired in patients in group 3, and prefrontal functions were slightly worse in patients in group 1. Cognitive scores were correlated only with time of evolution for patients in group 2. Functional scores were not significantly different among the 3 groups, but 11 (85%) of the patients in group 3 were in stage I or II vs 10 (67%) of the patients in group 1. Total functional capacity correlated better with the Mini-Mental State Examination score for patients in group 3 and with motor deficits (akinesia) and prefrontal dysfunction for patients in group 1. The mean+/-SD CAG repeat length decreased from 59.9+/-12.6 for patients in group 1 to 46.2+/-3.5 for patients in group 2 and 41.7+/-2.6 for patients in group 3. Longer CAG repeats in the HD study population correlated with akinetic features but not with cognitive performance. CONCLUSIONS: Despite the much greater genetic defect, cognitive status is slightly better preserved in patients with juvenile-onset HD. Cognitive impairment in patients with juvenile- and late-onset HD differs in the severity of visual and prefrontal deficits. Functional disability in patients with late-onset HD depends more on global cognitive status, while in patients with juvenile-onset HD, it is conditioned more by motor deficits and prefrontal dysfunction.

Adolescent↗
PubMed1998

Loss of p16/INK4A protein expression in non-Hodgkin's lymphomas is a frequent finding associated with tumor progression.

The CDKN2A gene located on chromosome region 9p21 encodes the cyclin-dependent kinase-4 inhibitor p16/INK4A, a negative cell cycle regulator. We analyzed p16/INK4A expression in different types of non-Hodgkin's lymphoma to determine whether the absence of this protein is involved in lymphomagenesis, while also trying to characterize the genetic events underlying this p16/INK4A loss. To this end, we investigated the levels of p16/INK4A protein using immunohistochemical techniques in 153 cases of non-Hodgkin's lymphoma, using as reference the levels found in reactive lymphoid tissue. The existence of gene mutation, CpG island methylation, and allelic loss were investigated in a subset of 26 cases, using single-strand conformational polymorphism and direct sequencing, Southern Blot, polymerase chain reaction, and microsatellite analysis, respectively. Loss of p16/INK4A expression was detected in 41 of the 112 non-Hodgkin's lymphomas studied (37%), all of which corresponded to high-grade tumors. This loss of p16/INK4A was found more frequently in cases showing tumor progression from mucosa-associated lymphoid tissue low-grade lymphomas (31 of 37) or follicular lymphomas (4 of 4) into diffuse large B-cell lymphomas. Analysis of the status of the p16/INK4A gene showed different genetic alterations (methylation of the 5'-CpG island of the p16/INK4A gene, 6 of 23 cases; allelic loss at 9p21, 3 of 16 cases; and nonsense mutation, 1 of 26 cases). In all cases, these events were associated with loss of the p16/INK4A protein. No case that preserved protein expression contained any genetic change. Our results demonstrate that p16/INK4A loss of expression contributes to tumor progression in lymphomas. The most frequent genetic alterations found were 5'-CpG island methylation and allelic loss.

Cells, Cultured↗
PubMed1998

Influence of genetic admixture on polymorphisms of drug-metabolizing enzymes: analyses of mutations on NAT2 and C gamma P2E1 genes in a mixed Hispanic population.

OBJECTIVES AND STUDY DESIGN: The genetic basis of two polymorphisms of drug- and carcinogen-metabolizing enzymes, NAT2 (arylamine N-acetyltransferase-2) and CYP2E1 (cytochrome P450 2E1), was studied in genomic deoxyribonucleic acid from 137 healthy, unrelated subjects from a mixed Nicaraguan population. RESULTS: Six point mutations were identified at the coding region of the NAT2 gene, including the most common alleles NAT2*4 (41.6%), NAT2*5B (31.4%), and NAT2*6A (16.8%). The percentage of carriers of two defective genes was 49.6%. The Nicaraguan population studied was in Hardy-Weinberg's disequilibrium for the NAT2 genotype (p < 0.01) and the allele frequencies were significantly different from those of other populations, being intermediate between those of pure Central American Indians and Spanish persons. The frequency of CYP2E1 alleles mutated at the RsaI site (c2 allele; 16.5%) was intermediate between that of Spanish white and Asian subjects. About 5% of the subjects were homozygous for the c2 allele. CONCLUSIONS: These findings indicate a high impact of genetic admixture of populations of Asian origin (Central American Indians) and white persons (Spaniards) on the genetic polymorphisms studied here and suggest that among mixed Hispanics a high heterogeneity of genotypes and phenotypes can be expected depending on the degree of genetic admixture of every subgroup. Therefore different subgroups of mixed Hispanic subjects can exhibit different results when treated with drugs that are inactivated through polymorphic enzymes.

Arylamine N-Acetyltransferase↗
PubMed1998

A recombinant protein based immunoassay for the combined detection of antibodies to HIV-1, HIV-2 and HTLV-I.

The aim of this study was to develop and evaluate a combined assay for the detection of antibodies to HIV-1, HIV-2 and HTLV-I (human T-cell leukemia virus type I). A mixture of recombinant proteins and synthetic peptides was fixed to the surface of microELISA wells and a protein A peroxidase conjugate was used as tracer. The combined assay was compared to specific HIV-1/2 and HTLV-I commercial ELISAs. The sensitivity was studied with a panel of 158 HIV-1, 82 HIV-2 and 48 HTLV-I positive sera, all of which were reactive in the combined assay. The analytical sensitivity was studied with a panel of serially diluted sera and was similar to that obtained for the specific ELISAs. The specificity of the test was 99.78% against a panel of 466 negative sera collected from voluntary donors that included HBsAg, HCV, and VDRL positive sera. The false positive serum was borderline in the HTLV-I specific ELISA. The new combined ELISA can be used as an efficient initial screening assay, avoiding the cost of individual tests for HIV and HTLV.

AIDS Serodiagnosis↗
PubMed1998

Expression in human prostate of drug- and carcinogen-metabolizing enzymes: association with prostate cancer risk.

The role of two common polymorphisms of enzymes involved in the metabolism of drugs and carcinogens was studied in relation to prostate cancer. The gene encoding one of these enzymes (NAT2) is located in an area where frequent allelic loss occurs in prostate cancer. Mutations at the genes CYP2D6 and NAT2 were analysed by allele-specific polymerase chain reaction and restriction mapping in DNA from 94 subjects with prostate cancer and 160 male healthy control subjects. Eleven prostate specimens were analysed for genotype and enzymatic activities NAT2, CYP2D6 and CYP3A by using the enzyme-specific substrates sulphamethazine and dextromethorphan. Enzyme activities with substrate specificities corresponding to NAT2, CYP2D6 and CYP3A are present in human prostate tissue, with mean +/-s.d. activities of 4.8+/-4.4 pmol min(-1) mg(-1) protein, 156+/-91 and 112+/-72 nmol min(-1) mg(-1) protein respectively. The Km values for the prostate CYP2D6 and CYP3A enzyme activities corresponded to that of liver CYP2D6 and CYP3A activities, and the CYP2D6 enzyme activity is related to the CYP2D6 genotype. The N-acetyltransferase, in contrast, had a higher Km than NAT2 and was independent of the NAT2 genotype. The CYP2D6 and CYP3A enzymes, and an N-acetyltransferase activity that is independent of the regulation of the NAT2 gene, are expressed in human prostate tissue. The presence of carcinogen-metabolizing enzymes in human prostate with a high interindividual variability may be involved in the regulation of local levels of carcinogens and mutagens and may underlie interindividual differences in cancer susceptibility.

Aged↗
PubMed1998

Effects of caffeine withdrawal from the diet on the metabolism of clozapine in schizophrenic patients.

Both clozapine (CLZ) and caffeine are CYP1A2 substrates. This study raises the hypothesis of whether caffeine withdrawal from the diet alters the metabolism and/or clinical status of patients receiving CLZ. Seven schizophrenic patients (six men and one woman) receiving monotherapy with CLZ at 271+/-102 mg/day (3.73+/-1.4 mg/kg) participated in the study. CLZ, norclozapine (NOR), and clozapine-N-oxide (NOX) were assayed in plasma by high-performance liquid chromatography at three different time points: A, with concomitant intake of caffeine from the diet; B, after caffeine withdrawal for 5 days; and C, after 2 weeks of rechallenge to habitual caffeine intake. The CYP1A2 activity was determined by means of a urinary caffeine test. After a caffeine-free diet for 5 days, CLZ concentrations relative to time point A decreased from 486 to 306 ng/mL (-47%) (p < 0.02), NOX levels decreased from 66 to 49 ng/mL (-31%) (p < 0.03), and the NOR/CLZ ratio significantly increased from 0.47 to 1.04 (185%) (p < 0.02). All parameters returned to initial figures at time point C. The NOR/CLZ ratio was significantly correlated to the CYP1A2 index (rs = 0.96, p < 0.0005). In conclusion, changes in the habitual caffeine intake alter the metabolism of CLZ in schizophrenic patients. Thus, patient intake of caffeine should be medically supervised, and the monitoring of CLZ and metabolite levels may be warranted. Furthermore, in those patients who receive therapy with CLZ, the NOR/CLZ ratio may provide an additional and valuable estimate of CYP1A2 activity.

Adult↗
PubMed1998

Molecular analysis of the BRCA2 gene in 16 breast/ovarian cancer Spanish families.

The recent isolated gene BRCA2 is responsible for about 45% of familial breast cancer and the majority of male breast cancer families. In order to evaluate the role of inherited BRCA2 mutations in Spanish families, the complete coding sequence of the gene was screened by SSCP/sequencing in 16 high-risk breast/ovarian cancer families. Four mutations were found that cause a premature termination codon. Two of them have been reported elsewhere and one is a novel mutation. In addition we have found seven polymorphisms, two of which have not been previously described. One of the mutations, 936delAAAC was found in two of our high-risk families. Because this mutation is considered as recurrent, we have tried to estimate its frequency in our breast cancer population. A total of 127 moderate- high-risk families were screened for this mutation and it was also found in another high-risk family. All the families carrying the 936delAAAC mutation harboured part of a common haplotype shared by other reported carriers, suggesting a possible founder effect for this mutation.

Adult↗
PubMed1998

Slow allotypic variants of the NAT2 gene and susceptibility to early-onset Parkinson's disease.

OBJECTIVE: To determine the frequency and the linkage distribution of seven mutations at the polymorphic gene coding for the arylamine N-acetyl transferase (NAT2; EC 2.3.1.5) in 121 unrelated patients with sporadic PD and in 121 unrelated healthy volunteers. METHODS: The study was performed with mutation-specific PCR using genomic DNA obtained from blood of the probands. RESULTS: Comparison of the NAT2 genotypes of the overall PD patients and control subjects did not indicate statistically significant differences. However, patients with early-onset PD (onset before the age of 50 years, n=37) showed a higher frequency of slow-acetylation genotypes (78.4% patients) compared with both healthy control subjects (55.4%) and with late-onset (onset after 51 years of age, n=84) PD patients (54.8%). Such a difference was statistically significant (p < 0.015) and was the result of a homogeneous increase in the frequency of slow-acetylation alleles. All subgroups analyzed in the study were in Hardy-Weinberg equilibrium for mutations at the NAT2 gene. CONCLUSIONS: Slow-acetylation-mutated alleles may be considered low-penetrance genes in early-onset PD pathogenesis, with a relative risk ratio for individuals with slow-acetylation genotype of 2.92 (95% CI, 1.26 to 6.78). This study provides evidence for the interaction of genetic and environmental factors in the etiology of sporadic PD.

Adult↗
PubMed1998

Modulation of CYP1A2 enzyme activity by indoleamines: inhibition by serotonin and tryptamine.

Recent evidence supports a role for the CYP2D6 enzyme in the metabolism of tryptamine. Because of the partial overlapping between substrate and inhibitor specificities that characterize some cytochrome P450 enzymes, these finding raise the possibility that other cytochrome P450 enzymes may be modulated by endogenous compounds. In the present study, the occurrence of modulatory effect of 17 neurotransmitters, precursors and metabolites on the cytochrome P450 1A2 (CYP1A2) enzyme activity was studied in human liver microsomes. Two indoleamines, serotonin and tryptamine, showed a competitive inhibitory effect on the high-affinity component of the phenacetin O-de-ethylase activity. Both substances induced an inhibition of 100% of the activity, with Ki values of 35 and 45 microns for serotonin and tryptamine, respectively. The inhibitors did not affect the microsomal NADPH-reductase activity. Other substances, which were either poor or partial inhibitors, were dopamine, L-tyrosine, tryptophol, 5-hydroxytryptophol, adrenaline, indole-3-acetaldehyde, 5-hydroxytryptophan, noradrenaline, vanillylmandelic acid, indole-3-acetic acid, dihydroxyphenylacetic acid, and homovanillic acid. L-tryptophan, dihydroxyphenylalanine and 5-hyroxyindole acetic acid induced very low or no inhibitory effect. Tryptamine and serotonin metabolism in human liver microsomes was studied after inhibition of monoamine oxidase activity with the unspecific MAO inhibitor pargyline. Both serotonin and tryptamine were metabolized in human liver microsomes. However, the metabolism of both indoleamines was not significantly inhibited with the CYP1A2-specific inhibitor furafylline, thus indicating that the inhibition of CYP1A2 was not related to metabolic activity of the CYP1A2 enzyme on serotonin or tryptamine. The CYP1A2 enzyme is expressed in brain and is involved in the metabolism of psychoactive drugs. Therefore, the fact that endogenous compounds could modulate the CYP1A2 activity suggests that local activity of brain CYP1A2 might be susceptible to local regulatory mechanisms. This may have important clinical implications, one of them being that CYP1A2 activity in brain tissue might correlate poorly with that of liver, as observed in vivo. In addition, the influence of indoleamines on CYP1A2 activity might be partly responsible for a number of associations of CYP1A2 activity with nutritional and environmental factors.

Brain↗
PubMed1998

[The ear of a boxer from Canary islands].

The canary fight is a sport with traditional character deeply-rooted in Spain. The pinna rubbing by bodies contact in hand-to-hand combat produce a typical deformity. We present this pathology not only due to its specific pathogenesis but also as part of the cultural patrimony of Canary Islands (Fortunate Islands).

Adult↗