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G Blanco

Publications and source records attributed to G Blanco.

At least 109 records · Page 6Linked to original sources
PubMed1993

Refinement of regional loss of heterozygosity for chromosome 11p15.5 in human breast tumors.

The familial association of breast cancer with other tumors such as rhabdomyosarcoma that show loss of heterozygosity (LOH) for chromosome 11p15 as well as limited analyses showing LOH for chromosome 11p in breast tumors suggests the presence of a pleiotropic tumor suppressor gene in this region. In order to test this idea, we analyzed DNA samples for 50 matched normal and tumor tissues from unselected breast cancer patients for LOH at loci throughout the chromosome 11p15.5 region. We found that 12.5% of informative cases showed LOH at HRAS1, 26.8% at TH, and 33.3% at both D11S860 and HBB, providing genetic support for this hypothesis. In contrast to previous observations which excluded the involvement of 11p15.5 regions distal to the HBB cluster, our results indicate that the subregion between TH and HBB is a critical region in breast cancer. This region is identical to that identified for the clinically associated tumor, rhabdomyosarcoma, and thus warrants intensive molecular analysis.

Base Sequence↗
PubMed1993

Hybridization and DNA sequence analyses suggest an early evolutionary divergence of related biosynthetic gene sets encoding polyketide antibiotics and spore pigments in Streptomyces spp.

The whiE gene cluster of Streptomyces coelicolor, which is related to gene sets encoding the biosynthesis of polycyclic aromatic polyketide antibiotics, determines a spore pigment. Southern blotting using probes from three different parts of the whiE cluster revealed related gene sets in about half of a collection of diverse Streptomyces strains. A 5.2-kb segment of one such cluster, sch, previously shown to determine spore pigmentation in Streptomyces halstedii, was sequenced. Seven open reading frames (ORFs), two of them incomplete, were found. Six of the ORFs resemble the known part of the whiE cluster closely. The derived gene products include a ketosynthase (= condensing enzyme) pair, acyl carrier protein and cyclase, as well as two of unidentified function. The seventh ORF diverges from the main cluster and encodes a protein that resembles a dichlorophenol hydroxylase. Comparison with sequences of related gene sets for the biosynthesis of antibiotics suggests that gene clusters destined to specify pigment production diverged from those destined to specify antibiotics early in the evolution of the Streptomyces genus.

Amino Acid Sequence↗
PubMed1993

Functional expression of the alpha 2 and alpha 3 isoforms of the Na,K-ATPase in baculovirus-infected insect cells.

Multiple isoforms of both the alpha and beta subunits of Na,K-ATPase have been identified. Elucidating their roles has been complicated by the fact that most tissues express multiple isoforms and purification techniques specific for each isoform have not been achieved. The baculovirus expression system, which uses the baculovirus Autographica californica to infect insect cells, is an ideal system for studying the Na,K-ATPase isoforms since high amounts of foreign proteins can be produced and some insect cell lines have low levels of endogenous Na,K-ATPase. Recombinant baculoviruses containing the cDNAs for the alpha 2, alpha 3, and beta 1 isoforms of the rat Na,K-ATPase were prepared and used to infect Sf-9 cells, an insect cell line derived from the ovary of the fall armyworm Spodoptera frugiperda. By using this system, Na,K-ATPase alpha 2 and alpha 3 subunits that were antigenically and electrophoretically indistinguishable from the native subunits were produced. When each subunit is expressed independently in the Sf-9 cells, it is primarily delivered to the plasma membrane. Although the isolated expression of each Na,K-ATPase subunit did not render active Na,K-ATPase molecules, the coexpression of alpha 2 or alpha 3 with beta 1 resulted in catalytically active molecules. This activity could be measured as a ouabain-sensitive ATPase activity or directly demonstrated using either [gamma-32P]ATP or 32Pi to identify the phosphorylated intermediates of the alpha 2 and alpha 3 isoforms. [3H]Ouabain binding studies showed that both isoforms are capable of binding the cardiotonic steroid with high affinity, alpha 3 being more sensitive to ouabain. These results demonstrate that the baculovirus system is suitable for the expression of the Na,K-ATPase isoforms and should provide a useful method for the characterization of the enzymatic properties of each isoform.

Animals↗
PubMed1993

Identification of an operon involved in the assimilatory nitrate-reducing system of Azotobacter vinelandii.

A number of mutants lacking nitrate reductase (Nas-) or nitrite reductase (Nis-) activities have been isolated and characterized. An operon including two new genes (nasA and nasB) has been defined and cloned from an Azotobacter vinelandii gene bank. nasA encodes for nitrite reductase apoenzyme, whereas nasB is specific for nitrate reductase activity. Nitrate reductase exerts a regulatory effect on nasAB.

Amino Acid Sequence↗
PubMed1993

Sequence and molecular analysis of the nifL gene of Azotobacter vinelandii.

In both Klebsiella pneumoniae and Azotobacter vinelandii the nifL gene, which encodes a negative regulator of nitrogen fixation, lies immediately upstream of nifA. We have sequenced the A. vinelandii nifL gene and found that it is more homologous in its C-terminal domain to the histidine protein kinases (HPKs) than is K. pneumoniae NifL. In particular A. vinelandii NifL contains a conserved histidine at a position shown to be phosphorylated in other systems. Both NifL proteins are homologous in their N-termini to a part of the Halobacterium halobium bat gene product; Bat is involved in regulation of bacterio-opsin, the expression of which is oxygen sensitive. The same region showed homology to the haem-binding N-terminal domain of the Rhizobium meliloti fixL gene product, an oxygen-sensing protein. Like K. pneumoniae NifL, A. vinelandii NifL is shown here to prevent expression of nif genes in the presence of NH+4 or oxygen. The sequences found homologous in the C-terminal regions of NifL, FixL and Bat might therefore be involved in oxygen binding or sensing. An in-frame deletion mutation in the nifL coding region resulted in loss of repression by NH+4 and the mutant excreted high amounts of ammonia during nitrogen fixation, thus confirming a phenotype reported earlier for an insertion mutation. In addition, nifLA are cotranscribed in A. vinelandii as in K. pneumoniae, but expression from the A. vinelandii promoter requires neither RpoN nor NtrC.

Amino Acid Sequence↗
PubMed1993

A hydroxylase-like gene product contributes to synthesis of a polyketide spore pigment in Streptomyces halstedii.

A gene, schC, adjacent to the sch gene cluster encoding the biosynthesis of a polyketide spore pigment in Streptomyces halstedii was sequenced. Its deduced product resembled flavin adenine nucleotide-containing hydroxylases involved in the biosynthesis of polycyclic aromatic polyketide antibiotics and in catabolic pathways of aromatic compounds. When schC was disrupted, the normally green spores of S. halstedii became lilac. An schC-like gene was located in an equivalent position next to a large gene cluster (whiE) known to determine spore pigment in Streptomyces coelicolor A3(2).

Amino Acid Sequence↗
PubMed1993

Endometrial changes in postmenopausal breast cancer patients receiving tamoxifen.

OBJECTIVE: To assess the estrogenic effect of tamoxifen and associated pathologic changes of the endometrium in postmenopausal breast cancer patients. METHODS: The endometrium of 103 gynecologically asymptomatic postmenopausal breast cancer patients was examined. Fifty-one had been treated with tamoxifen and 52 had not received any hormonal treatment. The two groups were similar in age, parity, age at menopause, and body mass index. RESULTS: Compared with the control subjects, the tamoxifen patients had a thicker endometrium (mean +/- standard deviation 10.4 +/- 5.0 versus 4.2 +/- 2.7 mm; P = .0001) and larger uterine volume (45 +/- 27 versus 25 +/- 11 cm3; P = .001), as determined by transvaginal sonography. Hysteroscopy showed an atrophic endometrium in 28% of the patients in the tamoxifen group, as compared with 87% of the control patients (P = .0001). Endometrial polyps were more frequent in the tamoxifen group (36 versus 10%; P = .004), which included one patient with atypical hyperplasia, one with adenomatous hyperplasia, and one with endometrial adenocarcinoma; two controls had endometrial adenocarcinoma. CONCLUSION: The results provide evidence for an estrogenic effect of long-term tamoxifen treatment on the postmenopausal uterus and show it to be associated with an increased occurrence of polyps.

Aged↗
PubMed1992

Cloning and sequence of a gene encoding the L7/L12 ribosomal protein equivalent of Streptomyces antibioticus.

A 50S ribosomal(r) protein from the vegetative mycelium of Streptomyces antibioticus, that is absent or modified in the spore 50S r-subunit, was purified by HPLC. Determination of its N terminus and comparison with amino acid sequence data bases indicated a strong homology with the L7/L12 r-protein from Streptomyces griseus. Screening of a cosmid library of S. antibioticus chromosomal DNA with a 20-mer oligodeoxyribonucleotide probe, corresponding to an internal region of the N terminus, allowed the isolation of two hybridizing clones. A 0.90-kb HindIII-BamHI fragment from one of these clones was sequenced and found to contain a 387-bp open reading frame. The deduced gene product shows clear homology with L7/L12 r-protein equivalent from different bacteria.

Amino Acid Sequence↗
PubMed1992

Cloning and disruption of a fragment of Streptomyces halstedii DNA involved in the biosynthesis of a spore pigment.

A 5.2-kb BamHI fragment of Streptomyces halstedii was cloned by homology to the actI-carrying fragment which codes for part of the actinorhodin polyketide synthase of Streptomyces coelicolor A3(2). Gene disruption using the integrative plasmid vector, pGM160, and gene replacement experiments using a fragment mutated by introducing a cassette containing the gene encoding thiostrepton resistance, showed that the alteration of this region in the chromosome of S. halstedii caused sporulating colonies to remain white instead of taking on the typical green colour of sporulating wild-type colonies. This suggests that this fragment is involved in the biosynthesis of a spore pigment. In addition, the BamHI fragment complemented the whiE mutation of S. coelicolor C107 which confers to this mutant a white phenotype, indicating that both pigments could have a similar biosynthetic origin.

Blotting, Southern↗
PubMed1992

Influence of Epstein-Barr virus genomes on patient survival in Hodgkin's disease.

In previous studies, Epstein-Barr virus was considered a possible etiologic factor in Hodgkin's disease. Two hundred twenty-nine cases of Hodgkin's disease were investigated for the presence of Epstein-Barr virus DNA using the polymerase chain reaction technique on formalin-fixed, paraffin-embedded lymph node tissue to clarify the clinical importance of the incidence of this genome. In 42 cases (18.3%), genomic DNA was not amplifiable. The remaining 187 cases included the following subtypes: lymphocyte-predominant type (n = 13), nodular sclerosis type (n = 98), mixed cellularity type (n = 68), and lymphocyte-depleted type (n = 8). Sixty-six cases (35.2%) were positive for Epstein-Barr virus DNA. In the statistical analysis of available follow-up data from 130 patients, no influence of a positive Epstein-Barr virus DNA finding on length of survival time was revealed. This was true within the cohort of all patients and within the histologically defined subtypes of Hodgkin's disease. In this investigation, detection of Epstein-Barr virus DNA by polymerase chain reaction showed no prognostic relevance for patients with Hodgkin's disease.

Analysis of Variance↗
PubMed1992

Excretion of ammonium by a nifL mutant of Azotobacter vinelandii fixing nitrogen.

A mutation in the gene upstream of nifA in Azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. The resulting mutant, MV376, produced nitrogenase constitutively in the presence of 15 mM ammonium. When introduced into a nifH-lacZ fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. The gene upstream of nifA is therefore designated nifL because of its similarity to the Klebsiella pneumoniae nifL gene in proximity to nifA, in mutant phenotype, and in amino acid sequence of the gene product. The A. vinelandii nifL mutant MV376 excreted significant quantities of ammonium (approximately 10 mM) during diazotrophic growth. In contrast, ammonium excretion during diazotrophy was much lower in a K. pneumoniae nifL deletion mutant (maximum, 0.15 mM) but significantly higher than in NifL+ K. pneumoniae. The expression of the A. vinelandii nifA gene, unlike that of K. pneumoniae, was not repressed by ammonium.

Ammonia↗
PubMed1992

Genetic differentiation among natural European populations of Atlantic salmon, Salmo salar L., from drainages of the Atlantic Ocean.

Previously published allelic frequencies at four polymorphic protein coding loci were used as a basis for examining genetic relationships among 19 European populations of Atlantic salmon, Salmo salar L.--exclusive of Baltic drainages--from the Barents Sea to Spain. The data did not support a model of distinct ancestral (e.g. Boreal and Celtic) origins, but were consistent with all populations descending from a single ancestral group within this region with genetically diverged populations drawn together through limited local migrations.

Alleles↗
PubMed1991

Hepato-splenic distribution of 99Tcm-phytate and hepato-enteric distribution of 99Tcm-DISIDA in mice with carbon tetrachloride-induced acute liver damage.

The hepato-enteric distribution of 99Tcm-labelled DISIDA and the hepato-splenic distribution of 99Tcm-labelled phytate were studied in controls and in mice with carbon tetrachloride-induced acute liver damage. The test group animals showed a diminished excretion of DISIDA to intestine with retention of this tracer in the liver and an increased splenic uptake of phytate. No changes in the hepatic uptake of phytate were found. The joint evaluation of both tracers in the study of diffuse liver disease is discussed.

Animals↗
PubMed1991

The product of the nitrogen fixation regulatory gene nfrX of Azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnD in enteric bacteria.

We sequenced the nitrogen fixation regulatory gene nfrX from Azotobacter vinelandii, mutations in which cause a Nif- phenotype, and found that it encodes a 105-kDa protein (NfrX), the N terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnD in Escherichia coli. In vivo complementation experiments demonstrate that the glnD and nfrX products are functionally interchangeable. A vinelandii nfrX thus appears to encode a uridylyltransferase-uridylyl-removing enzyme, and in this paper we report the first sequence of such a protein. The Nif- phenotype of nfrX mutants can be suppressed by a second mutation in a recently identified nifL-like gene immediately upstream of nifA in A. vinelandii. NifL mediates nif regulation in response to the N status in A. vinelandii, presumably by inhibiting NifA activator function as occurs in Klebsiella pneumoniae; thus, one role of NfrX is to modify, either directly or indirectly, the activity of the nifL product.

Adenine↗
PubMed1990

Detection of a highly ouabain sensitive isoform of rat brainstem Na,K-ATPase.

The present work provides evidence for the existence in rat brainstem of a form of Na,K-ATPase catalytic subunit that displays a high affinity for ouabain (Kd about 10(-9) M). Its kinetic identification was made out from studies on dose response curves of ouabain inhibition of Na,K-ATPase activity, ouabain inhibition of Na(+)-dependent phosphorylation from ATP and ouabain stabilized phosphoenzyme formation from inorganic phosphate (Pi). In all these studies this isoform comprises around 11 percent of the total Na,K-ATPase enzyme. The PAGE electrophoretic mobility of its phosphoprotein obtained from Pi in the presence of ouabain is lower than that of the alpha-1 form but it cannot be distinguished from that of alpha-2. Whether this highly ouabain sensitive form corresponds to the alpha-3 isoenzyme or represents the translational product of one of the additional genes described for the large catalytic subunit remains at the moment an open question.

Animals↗
PubMed1990

Treatment of advanced breast cancer with 20 mg toremifene, a phase II study. Preliminary communication.

Fourteen postmenopausal women with estrogen-receptor positive advanced breast cancer and no prior cytostatic treatment received 20 mg toremifene daily as a single dose after a loading dose (120----60----60 mg) for the first 3 days. All were evaluable and had undergone at least 6 weeks' treatment. Results were: no complete remissions (CR), 3 partial remissions (PR), 8 no change (NC) and 3 cases of progressive disease (PD). Three patients had mild side effects: nausea, insomnia, sweating and arm pain.

Aged↗
PubMed1990

Safety and efficacy of toremifene in breast cancer patients. A phase II study.

46 postmenopausal women with estrogen receptor positive breast cancer entered a phase II study with a novel antiestrogen, toremifene. Patients had either recurrent or primarily inoperable advanced disease. No prior or concurrent cytostatic or hormonal treatment was allowed. Eight patients (17%) achieved complete response (CR), 17 (37%) partial response (PR) and 13 (28%) had stabilization of their disease at least for three months. The mean durations of responses were 52 +, 53 + and 27 + weeks, respectively, with 5 patients in CR, 6 in PR and 1 with no change (NC) still continuing the treatment. No significant differences could be seen in response rates according to the concentration of estrogen receptors or presence of progesteron receptors in this group of patients. Toxicity was not a problem, in general, the treatment was well tolerated. Two side effects (sweating and vertigo) were classified as severe and one patient after achieving PR interrupted the treatment because of tremor.

Aged↗