Search PubMed⌕ Search

Biomedical subjects

H Rivera

Publications and source records attributed to H Rivera.

At least 91 records · Page 5Linked to original sources
PubMed1991

Genomic sequence and expression of a cloned human carbonyl reductase gene with daunorubicin reductase activity.

Carbonyl reductase (NADPH: secondary-alcohol oxidoreductase; EC 1.1.1.184), a widely distributed NADPH-dependent enzyme considered as both an aldo-keto reductase and a quinone reductase, was cloned from a human liver genomic library and transiently expressed in COS7 cells. The gene contains 3142 bases comprising three exons and two introns. The absence of a CAAT and TATA box and the presence of a GC-rich island are characteristic of many "housekeeping" genes. Transient expression of the genomic gene in COS7 cells using an expression vector containing an SV40 origin of replication resulted in a greater than 50-fold increase in both menadione reductase activity and daunorubicin reductase activity, suggesting that both activities are derived from the same enzyme. Carbonyl reductase mRNA levels reflected enzyme activity levels in the transfected cells. Other parameters, such as pH profile, cofactor requirements, substrates, and inhibitors, were similar to those of carbonyl reductase purified by other investigators. Potential regulatory elements with consensus sequences for two GC boxes and the transcriptional activator protein AP-2 were present upstream of the transcriptional start site. Although the precise role of carbonyl reductase is unknown, the enzyme is involved in drug metabolism and in the reduction of activated carbonyl compounds. Its ability to act as a quinone reductase also implies a potential to modulate oxygen free radicals.

Alcohol Oxidoreductases↗
PubMed1991

Translocation (Y;19)(q12;q13) and azoospermia.

An azoospermic male with a 46,X,t(Y;19)(q12;q13) karyotype is described. The comparison with 12 similar cases reveals that the Y breakpoints are usually on the long arm whereas the autosomal ones seem to be at random. Since a premeiotic origin is inconsistent with the arrest at diakinesis seen in those cases with meiotic studies, we postulate that a balanced t(Y;A) arises either via a chromatid exchange in the meiotic interphase or through a chromosome exchange in spermiogenesis or at the one cell stage of the zygote.

Adult↗
PubMed1990

Nonreciprocal and jumping translocations of 15q1----qter in Prader-Willi syndrome.

We analyzed 33 cases of Prader-Willi syndrome (PWS) (including 2 personal observations) with translocations of 15q1----qter onto the terminals of different, apparently whole chromosomes. In all but one of the 23 informative cases the translocations was de novo. Thirty of the patients were unbalanced and 27 had a 45-chromosome constitution compatible with a 3:1 segregation. One balanced and 2 unbalanced translocations were jumping ones. The possible existence of actual non-reciprocal translocations in man is indicated by the following considerations about these and other PWS-associated rearrangements: 1) The observed excess of de novo translocations; 2) the relatively frequent familial occurrence of reciprocal 15q translocations; 3) the concurrence in 3 terminal translocation cases of an idic (15); 4) the visualization of jumping terminal translocations as simple transpositions rather than as successive reciprocal exchanges; 5) the predominance of true isodicentrics in PWS patients with extra inv dup(15) chromosomes; and 6) the rarity of extra derivatives resulting in 15q proximal tertiary trisomy. Additional findings in the present series were normal parental age in the de novo 45-chromosome cases, an apparently random distribution of telomeric breakpoints, and the occurrence of different breakpoints within the 15q1 region.

Adult↗
PubMed1990

Deletion of specific sequences or modification of centromeric chromatin are responsible for Y chromosome centromere inactivation.

Stable dicentric chromosomes behave as monocentrics because one of the centromeres is inactive. The cause of centromere inactivation is unknown; changes in centromere chromatin conformation and loss of centromeric DNA elements have been proposed as possible mechanisms. We studied the phenomenon of inactivation in two Y centromeres, having as a control genetically identical active Y centromeres. The two cases have the following karyotypes: 45, X/46,X,i(Y)(q12) and 46,XY/47,XY,+t(X;Y) (p22.3;p11.3). The analysis of the behavior of the active and inactive Y chromosome centromeres after Da-Dapi staining, CREST immunofluorescence, and in situ hybridization with centromeric probes leads us to conclude that, in the case of the isochromosome, a true deletion of centromeric chromatin is responsible for its stability, whereas in the second case, stability for its stability, whereas in the second case, stability of the dicentric (X;Y) is the result of centromere chromatin modification.

Adolescent↗
PubMed1990

A constitutional 5q23 deletion.

A 14 month old girl was found to have a deletion of the whole of band 5q23. By comparing 19 other cases monosomic for a part of the 5q13-q31 segment, the constitutional 5q interstitial deletions fall into two groups: adult patients with Gardner-like symptoms and mental retardation associated with deletion 5q21-q22, and patients (mostly children) with unspecific signs and symptoms and different deletions.

Chromosome Deletion↗
PubMed1990

Chromosome imbalance, normal phenotype, and imprinting.

A duplication of the sub-bands 1q42.11 and 1q42.12 was found in a boy and his mother. The proband has short stature (around the 10th centile) but a normal phenotype and psychomotor development. His mother is also asymptomatic. We found 30 published cases of normal subjects with an imbalance of autosomal euchromatic material. In these cases the imbalance involved either only one G positive band or a G positive and a G negative band. Thus the absence of a phenotypic effect cannot always be ascribed to the deficiency in the G positive bands of coding DNA. Moreover, in some cases, the method of transmission of the chromosome abnormality was such that an imprinting effect could be postulated.

Chromosome Aberrations↗
PubMed1990

Tandem duplication of proximal 5q.

A 3.5-year-old boy with a de novo tandem duplication 5q11.1----5q15 is reported. Since the physical stigmata of seven liveborn cases with 5q proximal duplications are variable and inconspicuous, a recognizable syndrome could not be delineated. On the contrary, the associated developmental delay seems to be severe in duplications extending into 5q22 and mild in duplications 5q11----q13.

Child, Preschool↗
PubMed1990

[11q distal trisomy due to a familial 11;18 translocation].

A seven-month-old boy with a distal trisomy 11q resulting from a maternal t(11;18)(q23;p11) is described. His main clinical features were microbrachycephaly, long philtrum, retracted lower lip, short neck, cardiac septal defect, and psychomotor retardation. It is concluded that the phenotype of the trisomy 11q is independent of the size of the duplication whenever the segment 11q23----qter is involved.

Abnormalities, Multiple↗
PubMed1990

CA 125 levels in menopausal women.

To assess the use of CA 125 as a potential screening test for ovarian cancer, it is necessary to understand how the test performs among cancer-free women, who would constitute the overwhelming majority of those being tested at any time. Two hundred fifty-eight menopausal volunteers who were not seeking gynecologic care had CA 125 measured on two occasions and also underwent transvaginal ultrasonography to measure ovarian volumes. Only one subject had a CA 125 level greater than 35 U/mL. The mean value for CA 125 was 5.6 +/- 3.5 U/mL. Within women, the correlation between two tests was very high (r = 0.82). Among women with apparently normal ovaries, CA 125 values were low, tightly distributed, and reproducible; these findings indicate that the test may prove to be useful and cost-effective in a screening program. The correlation between CA 125 values and ovarian volume determined by sonogram was low (r = 0.11). The independence of these two tests would also be desirable in any screening program. Other studies have found normal women to have higher levels of CA 125 with wider distributions than found here; further evaluation of test performance at these low levels is needed.

Adult↗
PubMed1989

Alternate centromere inactivation in a pseudodicentric (15;20)(pter;pter) associated with a progressive neurological disorder.

A 13 year old male with a severe progressive neurological disorder was found to have a pseudodicentric chromosome resulting from a telomeric fusion 15p;20p. In lymphocytes, the centromeric constriction of the abnormal chromosome was always that of the chromosome 20, while in fibroblasts both centromeres were alternately constricted. Cd staining was positive only at the active centromere, but a weak anticentromere immunofluorescence was present at the inactive one. We suggest that centromere inactivation results from a modified conformation of the functional DNA sequences preventing normal binding to centromere specific proteins. We also postulate that the patient's disorder, reminiscent of a spongy glioneuronal dystrophy as seen in Alper's and Creutzfeldt-Jakob diseases, may be secondary to the presence of the pathogenic isoform of the prion protein encoded by a gene mapped to 20p12----pter.

Adolescent↗
PubMed1989

[Karyotype-phenotype correlation in a child with an idic (Yp)].

An 8-year-old boy with hypospadias and a 45,X/46,X,idic(Yp) karyotype is described. This chromosome abnormality possibly originated in an early zygote. It is concluded that: a) phenotypic variability in patients with an idic(Yp) probably results from an unequal tissular distribution of the different clones, and (b) deletion of Yq in the present case was distal to the stature determinants.

Child↗
PubMed1988

A probably distinct autosomal recessive thoraco-limb dysplasia.

A Mexican mestizo family is reported in which two opposite sexed sibs, born to consanguineous parents, had a skeletal dysplasia. The salient features were a bell shaped thorax owing to short ribs, short limbed dwarfism, pelvic hypoplasia, dislocatable radial heads, elongated distal fibulae, and improvement with age. It is concluded that the present observation probably represents a distinct autosomal recessive thoraco-limb dysplasia identifiable at birth.

Bone Diseases, Developmental↗
PubMed1988

The 22q distal trisomy syndrome in a recombinant child.

A 4-month-old male infant with 22q distal trisomy and karyotype 46,XY,rec(22), dup q,inv(22)(q13q12)mat is reported. This and six previous similar instances are compared, and a distinct syndrome is delineated as follows: growth and psychomotor retardation, microcephaly or hydrocephaly, brain malformation, defective skull ossification, hypertelorism, narrow palpebral fissures, short broad nose, cleft palate with or without lip involvement, short neck, cardiac defect, renal and genital hypoplasia, osteoarticular abnormalities (mostly clubfoot), and poor survival. In addition, this syndrome is distinct from other duplications of chromosome 22, namely the complete trisomy, the proximal trisomy, and the cat-eye phenotype.

Abnormalities, Multiple↗