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Biomedical subjects

H Rivera

Publications and source records attributed to H Rivera.

At least 55 records · Page 3Linked to original sources
PubMed1997

A further microchromosome with centromeric association.

A 46,XY/47,XY,+mar karyotype was found in a 5-year-old boy with mental retardation and minor dysmorphisms. The marker was present in 68% of lymphocyte metaphases, was about the size of Yp, appeared pale with G- and C-bands and had a single pair of centromeric dots; it was never seen in two or more copies and appeared larger and clearly annular in a few cells. This microchromosome was associated (interchromosomal distance equal to or smaller than 18p) with any other chromosome(s) in 295/344 cells. Among a total of 457 associations, 240 (52%) were centromeric. Such a proportion as well as the mostly random distribution of centromeric associations was similar to 3 previous instances. The paucity of markers with centromeric association may reflect a relative unawareness on the subject but more probable indicates that such a phenomenon is confined to nonsatellited, monocentric and annular microchromosomes.

Abnormalities, Multiple↗
PubMed1996

T cell hyperreactivity to IL-6 in chronic nonviremic HBV carriers despite normal IL-6 receptor or gp130 expression.

We previously showed that T cells from chronic nonviremic HBsAg carriers activated with immobilized OKT3 MAb are hyperreactive to monocyte accessory signals, mainly to interleukin-6 (IL-6). We have further characterized this T cell hyperreactivity using phytohemagglutinin (PHA) as the primary activating signal. PHA-stimulated T cells from nonviremic patients had a significantly higher response to addition of monocytes, monocyte supernatants, and IL-6 alone or combined with IL-1 beta when compared to controls. We examined if these effects could be mediated by a differential expression of IL-6 receptor (p80) or gp130 on resting or PHA-stimulated T cells. We found that PHA, IL-6, IL-1 beta, or IL-2 induced only small changes of the dull p80 expression on T cells. In contrast, we found a significant increase of gp130 expression on PHA-activated T cells compared to unstimulated T cells, which was down-regulated by the presence of IL-6. However, no significant differences in p80 or gp130 expression were detected between patients and controls within all the culture conditions tested. Our results confirm that IL-6 is involved in the in vitro T cell hyperreactivity of nonviremic HBV carriers and indicate that this effect is not mediated by disturbances of IL-6 receptor expression.

Adult↗
PubMed1996

Alphoidless centromere of a familial unstable inverted Y chromosome.

We report on a 3-generation pedigree in which an inverted unstable Y chromosome had no phenotypical or reproductive repercussion despite a sizable proportion of secondary aneuploidies (mainly 45, X cells) in lymphocytes. This chromosome was metacentric and had a single Cd-positive primary constriction, but occasionally assumed a normal acrocentric aspect. FISH using the probe DYZ3 revealed a single strong signal; unexpectedly, the signal was outside the primary constriction and appeared to map in the middle of p, that is, at the usual centromeric localisation. Therefore, this chromosome should be regarded as a remarkable pseudodicentric because the major alphoid array was located at the inactive centromere but not at the active one. This chromosome may have resulted from a) a transcentric inversion with the 48 bp satellite array of proximal Yq being relocated next to the Yq heterochromatin, or b) an intrachromosomal insertion of nonalphoid centromeric sequences.

Adolescent↗
PubMed1995

Protection against daunorubicin cytotoxicity by expression of a cloned human carbonyl reductase cDNA in K562 leukemia cells.

Carbonyl reductase (CBR) catalyzes the reduction of daunorubicin (DN) to its corresponding alcohol, daunorubicinol (DNOL), and changes the pharmacological properties of this cancer chemotherapeutic drug. The DN reductase associated with CBR reduces the C13 methyl ketone group and does not metabolize the quinone ring of DN. Reports comparing DN and DNOL toxicity have resulted in various conclusions depending on the cells tested. Differences in toxicity could be due to variations in several enzymes involved in DN metabolism. In this report, the effects of CBR expression on DN metabolism and cell toxicity were determined by cloning and expressing a human CBR cDNA in DN reductase-deficient myeloid erythroleukemia K562 cells. CBR activity increased 83-fold in the K562-transfected cells and was associated with a 2-3-fold reduction in DN toxicity. Maximum protection occurred at 30 nM DN where 94% of the intracellular DN was converted to DNOL within 2 h. The reduced toxicity was specific for DN. Other CBR substrates such as menadione, phenanthrenequinone, and doxorubicin were equally toxic to both the CBR expresser cells and the control cells under the conditions tested. Our results suggest that high levels of CBR in tumor cells could contribute to drug resistance. The results also suggest that reduction of DN to DNOL protects against DN toxicity by altering interaction of the drug at one or more of the many target sites.

Alcohol Oxidoreductases↗
PubMed1995

Cloning and expression of the cDNA encoding rabbit liver carbonyl reductase.

Two cDNA sequences encoding rabbit carbonyl reductase (CBR) were cloned from a lambda gt10 rabbit liver cDNA library. The rabbit cDNAs coded for a protein with 84% identity to human CBR. Transient expression of the two rabbit cDNA sequences in COS7 cells increased both quinone reductase and aldo-keto reductase activities. These data demonstrate that CBR cDNAs from rabbit and human tissues code for similar proteins.

Alcohol Oxidoreductases↗
PubMed1995

A familial Xp+ chromosome, dup (Xq26.3-->qter).

A maternally transmitted Xp+ chromosome was associated with an abnormal phenotype, including developmental delay and short stature, in two male cousins and their 12 year old aunt. The respective mothers were not mentally impaired but had short stature. The G banding pattern identified the extra chromosome segment as a repeat of Xq26.3-->qter attached to an apparently intact Xp22.3 sub-band, so the Xp+ chromosome may be described as rea(X)(Xqter-->p22.3::Xq26.3-->Xqter). The rearranged chromosome was late replicating in 97 to 100% of the metaphases in the mothers but it was early replicating in 43% of the lymphocytes in the mentally defective female (n = 100 cells/subject). Fluorescence in situ hybridisation using X and Y chromosome paints, as well as cosmids A and 1A1 specific for loci within Xq28, confirmed both the identity of the extra segment and the entirety of the Xp pseudoautosomal region. Therefore, the phenotypic consequences in this family can be related to the Xq26.3-->qter functional disomy allowing for the effects of X inactivation in the female carriers.

Abnormalities, Multiple↗
PubMed1995

Telomeric translocations are uncommon.

Telomeric translocations are uncommon: Fluorescence in situ hybridisation with TTAGGG repeats as the probe was used to search for derivative chromosomes with telomeric repeats at the break-point junction in a sample of 16 translocations with at least one terminal breakpoint and ascertained through an aneuploid patient. There were 11 cases (8 autosomal and 3 X;Y translocations) with a de novo/unknown origin in the study group and 5 control familial rearrangements. At least 20 metaphases showing a clear telomeric signal on the relevant chromosomes(s) were analysed in each individual. All 16 translocations appeared to be reciprocal events as interstitial telomeric sequences were not found. The lack of telomeric translocations in this sample may be related, among other factors, to the relative absence of tertiary monosomies which are the most suitable candidates. These data and previously published information indicate that telomeric translocations are uncommon and differ from reciprocal exchanges in several relevant ways such as an exclusive unbalanced occurrence; a consistent de novo origin and therefore a non-significant recurrence risk; restricted malsegregations, namely 3:1 tertiary monosomy and adjacent-1; a yield of "pure" imbalances, and a proneness to exhibit a jumping behaviour.

Chromosome Aberrations↗
PubMed1994

Ultrastructure of systemic sclerosis inflammatory myopathy.

Muscle biopsies from 7 patients with systemic sclerosis (SS) and a slowly progressive proximal muscular weakness were studied ultrastructurally. In all cases an inflammatory myopathy was found exhibiting fibre atrophy, occasional fibre necrosis, connective tissue proliferation, filamentous bodies, concentric laminated bodies and a mononuclear cell infiltration formed by lymphocytes, macrophages and mast cells. Capillary abnormalities included alterations of endothelium, thickening and reduplication of basement membrane and the presence of cylindric confronting cisternae. The different associations between muscle diseases and SS are grouped. Our data suggest that SS inflammatory myopathy is a distinct clinical and pathological entity.

Biopsy↗
PubMed1993

Centromeric association of a microchromosome in a Turner syndrome patient with a pseudodicentric Y.

A 12-year-old patient with Turner syndrome was found to have a complex mosaicism for a microchromosome (MC) and a psu dic(Y)(q11). The MC was smaller than Yp, appeared pale in G, C and late replicating bands, had a pair of small centromeric dots, was associated with other chromosomes in most metaphases, and was rather stable both in size and during mitosis. The psu dic(Y) was Cd-positive only at the active centromere, had two pericentromeric heterochromatic regions, and lacked the Yq12 band. No cells with both abnormal chromosomes were found. To evaluate the association of the MC with all ordinary chromosomes, 857 G-banded cells with the marker were screened. The MC was considered as "associated" whenever the distance between it and other chromosome(s) was equal to, or smaller than, 18p. Out of 848 associations registered, 489 (57.7%) were centromeric, 202 (23.8%) telomeric, and 157 (18.5%) interstitial; i.e., centromeric associations were overrepresented (P < 0.001) and showed a random distribution, except for an excessive involvement of chromosome 8. This association pattern, also exhibited by two similar MCs in human beings, the minute Y of a marsupial and certain B chromosomes in plants, probably reflects the Rabl orientation of chromosomes in interphase.

Centromere↗
PubMed1993

Differential diagnosis of ovarian cancer with tumour markers CA 125, CA 15-3 and TAG 72.3.

OBJECTIVE: To determine the accuracy of tumour associated antigens CA 125, CA 15-3 and TAG 72.3 in the differential diagnosis of benign and malignant pelvic masses and to compare the results with a previously defined risk of malignancy index (RMI). DESIGN: Retrospective analysis of samples collected during a prospective observational study. SETTING: Department of Obstetrics and Gynaecology, the Royal London Hospital and Duke University Medical Center. SUBJECTS: One hundred and forty-three consecutive patients undergoing surgery for an adnexal mass. METHOD: Tumour marker levels were determined by radio-immunoassay in stored serum samples obtained from 143 study subjects. RESULTS: The highest diagnostic accuracy of the tumour marker panel was achieved by defining a positive result as elevation of any two of CA 125 (> 30 u/ml), CA 15-3 (> 30 u/ml) and TAG 72.3 (> 10 u/ml), (sensitivity 66.7%, specificity 93.1%). Similar diagnostic accuracy could be achieved by CA 125 alone using an upper limit of 50 u/ml (sensitivity 66.7%, specificity 94.1%). Inclusion of CA 15-3 or TAG 72.3 in stepwise logistic regression analysis did not improve the discriminative performance of the RMI. CONCLUSION: The risk of malignancy index incorporating CA 125, menopausal status and ultrasound is superior to the panel of three tumour markers for pre-operative differential diagnosis of the pelvic mass.

Antigens, Neoplasm↗