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Biomedical subjects

G Blanco

Publications and source records attributed to G Blanco.

At least 73 records · Page 4Linked to original sources
PubMed1997

Aggressive breast cancer leads to discrepant serum levels of the type I procollagen propeptides PINP and PICP.

The propeptides PICP and PINP are derived from the synthesis of type I collagen, a major matrix protein of bone and soft tissues. The aim of this cross-sectional study was to investigate their value as indicators of the aggressivity of breast cancer. Serum PINP, PICP, and total alkaline phosphatase were determined from 89 breast cancer patients. Forty had major bone and/or soft tissue metastases with an aggressive disease course: the progressive disease (PD) group. Forty-nine had either none or minor bone and/or soft tissue metastases with a stable clinical course: the stable disease group (SD). The mean value of PINP in the PD group was 7.2 times higher than that in the SD group (276 +/- 79 microg/l versus 38 +/- 3 microg/l, respectively; P = 0.005), whereas PICP mean value was only 1.7 times higher in the PD group (174 +/- 20 microg/l versus 100 +/- 5 microg/l; P = 0.001). The ratio of PICP to PINP was 1.02 +/- 0.07 in the PD group and 3.07 +/- 0.18 in the SD group (P < 0.001). The correlation between PICP and PINP was linear in the SD group and nonlinear in the PD group. The results indicate that high serum PICP and PINP concentrations and a low PICP:PINP ratio are associated with a highly aggressive nature of breast cancer. Determination of PINP, in particular, may be valuable when evaluating the clinical status of a breast cancer patient.

Alkaline Phosphatase↗
PubMed1997

Protective association and breeding advantages of choughs nesting in lesser kestrel colonies

Some bird species may breed close to aggressive predators to reduce predation risk by more dangerous, generalist predators. We tested this protective nesting association hypothesis by studying solitary choughs, Pyrrhocorax pyrrhocoraxbreeding within or outside lesser kestrel, Falco naumannicolonies in northern Spain (1993-1994). We found 27 potential predators of choughs and kestrels and confirmed predation on adults and nests of both species by at least eight common predators. We experimentally assessed the defence investment of choughs and kestrels towards a stuffed eagle owl, Bubo buboin 19 buildings shared by both species. Lesser kestrels were more efficient at detecting the predator, and defended more vigorously than choughs. Choughs clearly selected for breeding buildings where lesser kestrel colonies were installed. Breeding success of these choughs was much higher than that of choughs breeding alone, because of a lower percentage of nest failure. Benefits to choughs probably accrued from both the 'parasitism' of the kestrels' nest defence and the dilution of predation risk in the colonies. Since lesser kestrels do not prey on choughs, this could be a good example of protective nesting association in birds.

Journal Article↗
PubMed1997

Cloning, sequencing and transcriptional analysis of a Streptomyces coelicolor operon containing the rplM and rpsI genes encoding ribosomal proteins ScoL13 and ScoS9.

The N-terminal amino acid sequences of two peptides derived from a Streptomyces coelicolor ribosomal protein were determined and degenerate oligonucleotide primers derived from these sequences were used as probes for the screening of a chromosomal DNA library of S. coelicolor. Two positive clones were isolated and DNA sequencing of a 1740-bp region of these clones that hybridised with the probes revealed the presence of four genes, two of them incomplete. The deduced products of the two complete genes. rplM and rpsI, showed clear similarities to L13 and S9 ribosomal proteins from various organisms. Promoter-probe and primer extension experiments suggest that the two genes form a single transcriptional unit. The specific rate of synthesis of both proteins was high at early stages of growth but decreased later.

Amino Acid Sequence↗
PubMed1997

Folding of the polyketide chain is not dictated by minimal polyketide synthase in the biosynthesis of mithramycin and anthracycline.

BACKGROUND: Mithramycin, nogalamycin and aclacinomycins are aromatic polyketide antibiotics that exhibit antitumour activity. The precursors of these antibiotics are formed via a polyketide biosynthetic pathway in which acetate (for mithramycinone and nogalamycinone) or propionate (for aklavinone) is used as a starter unit and nine acetates are used as extender units. The assembly of building blocks is catalyzed by the minimal polyketide synthase (PKS). Further steps include regiospecific reductions (if any) and cyclization. In the biosynthesis of mithramycin, however, ketoreduction is omitted and the regiospecificity of the first cyclization differs from that of anthracycline antibiotics (e.g. nogalamycin and aclacinomycins). These significant differences provide a convenient means to analyze the determinants for the regiospecificity of the first cyclization step. RESULTS: In order to analyze a possible role of the minimal PKS in the regiospecificity of the first cyclization in polyketide biosynthesis, we expressed the mtm locus, which includes mithramycin minimal PKS genes, in Streptomyces galilaeus, which normally makes aclacinomycins, and the sno locus, which includes nogalamycin minimal PKS genes, in Streptomyces argillaceus, which normally makes mithramycin. The host strains are defective in the minimal PKS, but they express other antibiotic biosynthesis genes. Expression of the sno minimal PKS in the S. argillaceus polyketide-deficient strain generated mithramycin production. Auramycins, instead of aclacinomycins, accumulated in the recombinant S. galilaeus strains, suggesting that the mithramycin minimal PKS is responsible for the choice of starter unit. We also describe structural analysis of the compounds accumulated by a ketoreductase-deficient S. galilaeus mutant; spectroscopic studies on the major polyketide compound that accumulated revealed a first ring closure which is not typical of anthracyclines, suggesting an important role for the ketoreductase in the regiospecificity of the first cyclization. CONCLUSIONS: These experiments clearly support the involvement of ketoreductase and a cyclase in the regiospecific cyclization of the biosynthetic pathway for aromatic polyketides.

Aclarubicin↗
PubMed1997

Comparison of toremifene and tamoxifen in post-menopausal patients with advanced breast cancer: a randomized double-blind, the 'nordic' phase III study.

The study was planned to compare, in a prospective double-blind randomized trial, the efficacy and safety of toremifene (TOR) and tamoxifen (TAM) in post-menopausal patients with advanced breast cancer who have not had prior systemic therapy for advanced disease. Four hundred and fifteen post-menopausal patients with oestrogen receptor (ER)-positive or ER-unknown advanced breast cancer were randomly assigned to receive daily either 60 mg TOR or 40 mg TAM. The patients were stratified to measurable and non-measurable but evaluable groups. They were assessed for response to therapy, time to progression (TTP), time to treatment failure (TTF), response duration, overall survival and drug toxicity. Two hundred and fourteen patients were randomized into TOR and 201 into TAM treatment. The response rate (complete + partial) was 31.3% for TOR and 37.3% for TAM (P = 0.215). The 95% confidence interval (CI) for the 6% difference was -15.1% to 3.1%. The median TTP was 7.3 months for TOR and 10.2 months for TAM (P = 0.047). The 95% CI for the hazard ratio of 0.80 was 0.64-1.00. A percentage of the TOR patients (9.8%) and the TAM patients (18.9%) discontinued the treatment prematurely (P = 0.011) for various reasons. Consequently, the median TTF of 6.3 vs 8.5 months did not differ significantly (P = 0.271). The hazard ratio was 0.89 and the subsequent 95% CI 0.73-1.09. The median overall survival was 33.0 months for TOR and 38.7 months for TAM (P = 0.645). The hazard ratio was 0.94 with 95% CI of 0.73-1.22. The transient difference in TTP may be related to an imbalance in ER content of the tumours. When only patients with ER-positive tumours were considered (n = 238), no difference between two treatments was seen (P = 0.578). TAM was associated with an overall slightly higher frequency of adverse drug reactions than TOR (44.3 vs 39.3%) and a higher discontinuation rate due to these events (3.5% vs 0.9%). Treatment-emerged moderate dizziness (P = 0.026) and cataracts (P = 0.026) were more frequent among TAM than among TOR patients. In conclusion, TOR (60 mg day(-1)) and TAM (40 mg day(-1)) are equally effective and safe in the treatment of advanced post-menopausal ER-positive or ER-unknown breast cancer.

Adult↗
PubMed1997

Morphologic and immunocytochemical characterization of four human uveal cell lines (melanoma- and melanocytes-derived).

PURPOSE: To characterize three cell lines from human uveal melanomas and one ocular melanocyte cell line to study the specificity of several antigens in the malignant transformation of melanocytic uveal cells. METHODS: Light microscopy (LM), transmission electron microscopy (TEM), and immunocytochemical techniques were used in the characterization of OCM-1, SP 6.5, and MKT-BR human uveal melanoma cell lines and UW-1 normal melanocyte cell line from human uvea. Several monoclonal antibodies (MoAbs) S-100, HMB-45, MNF-116, PAL-M1, NK1/C-3, IND-1, and MAAMA were used. RESULTS: All cell lines showed an epithelioid/spindle morphology with occasional multinucleated cells, and nuclear pleomorphism. TEM showed intracytoplasmatic premelanosomes. Incubation with HMB-45 MoAb was positive in all cell lines. PAL-M2, NK1/C-3, MAAMA, and IND-1 MoAbs stainings were positive with variable intensity. MNF-116 MoAb showed negative staining in the four lines, and S-100 MoAb was also negative except for the UW-1 cell line. CONCLUSIONS: Human uveal melanoma cell lines OCM-1, SP 6.5, and MKT-BR and the ocular melanocyte cell line UW-1 exhibited maintenance of some structural and ultrastructural characteristics of melanocytic cells. All four MoAbs, PAL-M2, NK1/C3, IND-1, and MAAMA against cutaneous melanoma-associated antigens stained positively all melanoma cell lines as well as the melanocytic cell line, suggesting that in vitro proliferation of melanocytes could modify their antigenic expression.

Antibodies, Monoclonal↗
PubMed1997

Hematozoa in two populations of the threatened red-billed chough in Spain.

The prevalence of hematozoa in two populations of red-billed choughs (Pyrrhocorax pyrrhocorax) was sampled in 1992 and 1994 in Spain. Two blood parasites infected red-billed choughs. A species of Plasmodium, possibly Plasmodium relictum, and the piroplasm Babesia frugilegica, are described for the first time from this host. Low prevalence (1/178, < 1%) of hematozoa in these populations, was evidence for a lack of effects of blood parasites on the life history and conservation of this threatened species in at least the two populations studied.

Animals↗
PubMed1996

Refined mapping of the Usher syndrome type III locus on chromosome 3, exclusion of candidate genes, and identification of the putative mouse homologous region.

A locus for Usher syndrome type III (USH3; MIM No. 276902) was recently assigned to a 5-cM region on chromosome 3q. We constructed a yeast artificial chromosome contig that allowed us to position novel polymorphisms in the region. These were typed in a total of 32 pedigrees from a geographically isolated Finnish founder population in which a putative single ancestral USH3 mutation segregates. A multipoint linkage analysis assigned USH3 to a 4-cM region between D3S1555 and a novel marker D3S3625. By analysis of linkage disequilibrium and historical recombinations in 77 USH3 chromosomes, the location of the Finnish USH3 mutation could be narrowed to an approximately 1-cM interval between the markers D3S1299 and D3S3625. A gene for profilin-2 (PFN2) was mapped in the vicinity and excluded as a candidate for USH3 by sequencing. The putative mouse homolog of PFN2 was mapped to mouse chromosome 3, thus suggesting a localization for the mouse homolog of USH3.

Alleles↗
PubMed1996

Translational regulation of Na,K-ATPase alpha1 and beta1 polypeptide expression in epithelial cells.

To investigate the regulation of the Na,K-ATPase, we have studied the expression of the Na,K-ATPase polypeptides in several mammalian cell lines using the vaccinia virus/T7 RNA polymerase expression system. Infection of several fibroblast-like cell lines with viral recombinants containing the Na,K-ATPase alpha and beta isoforms, the glucose transporters, GLUT 1 and GLUT 4, or the capsid protein of the Sindbis virus all result in the production of the appropriate protein products. However, all epithelial cell lines tested fail to synthesize the Na,K-ATPase viral recombinants, yet they efficiently express the other virally directed polypeptides. While Madin-Darby canine kidney (MDCK) epithelial cells infected with the Na,K-ATPase alpha1 or beta1 recombinant viruses produce both mRNAs, the messages are inefficiently translated. Furthermore, the RNA from infected MDCK cells does not direct the in vitro synthesis of the beta1 polypeptide, whereas the message from infected fibroblast-like BSC 40 cells is efficiently translated both in vivo and in vitro. Moreover, the synthesis of the H,K-ATPase alpha subunit is also limited in MDCK cells, although the H,K-ATPase beta subunit is efficiently expressed. Expression of chimeras constructed between the Na+ pump beta1 isoform and the H,K-ATPase beta subunit indicates that sequences in the 5' coding region of the beta1 message have an inhibitory effect; however, the stringent translational regulation of the beta1 isoform in MDCK cells requires the 5' and 3' regions of the coding sequence. The ability of the polarized cell lines to limit the synthesis of the Na+ pump polypeptides while expressing other vaccinia recombinants at high levels suggests that the polarized cells possess a stringent mechanism for the specific translational regulation of a select set of messages.

Animals↗
PubMed1996

Characterization of Streptomyces argillaceus genes encoding a polyketide synthase involved in the biosynthesis of the antitumor mithramycin.

Mithramycin (Mtm) is an aromatic polyketide which shows antibacterial and antitumor activity. From a chromosomal cosmid library of Streptomyces argillaceus, a Mtm producer, a clone (cosAR7) was isolated by homology to the actI/III region of S. coelicolor and the strDEM genes of S. griseus. From this clone, a 5.3-kb DNA region was sequenced and found to encode six open reading frames (designated as mtmQXPKST1), five of them transcribed in the same direction. The deduced products of five of these genes resembled components of type-II polyketide synthases. The mtm genes would code for an aromatase (mtmQ), a polypeptide of unknown function (mtmX), a beta-ketoacylsynthase (mtmP) and a related 'chain length factor' (mtmK), an acyl carrier protein (mtmS) and a beta-ketoreductase (mtmT1). The involvement of this gene cluster in Mtm biosynthesis was demonstrated by the Mtm non-producing phenotype of mutants generated in two independent insertional inactivation experiments.

Amino Acid Sequence↗
PubMed1996

Substitutions of glutamate 781 in the Na,K-ATPase alpha subunit demonstrate reduced cation selectivity and an increased affinity for ATP.

The intramembrane Glu781 residue of the Na,K-ATPase alpha subunit has been postulated to have a role in the binding and/or occlusion of cations. To ascertain the role of Glu781, the residue was substituted with an aspartate, alanine, or lysine residue and the mutant Na,K-ATPases were coexpressed with the native beta 1 subunit in Sf9 insect cells using the baculovirus expression system. All alpha mutants are able to efficiently assemble with the beta 1 subunit and produce catalytically competent Na,K-ATPase molecules with hydrolytic activities comparable to that of the wild-type enzyme. Analysis of the kinetic properties of the mutated enzymes showed a decrease in apparent affinity for K+ compared to wild-type Na,K-ATPase, with the lysine and alanine substitutions displaying the greatest reduction. All Na,K-ATPase mutants demonstrated a significant increase in apparent affinity for ATP compared to wild-type Na,K-ATPase, while the sensitivity to the cardiotonic inhibitor, ouabain, was unchanged. The dependence on Na+, however, differs among the mutant enzymes with both the Glu781-->Asp and Glu781-->Ala mutants displaying a decrease in the apparent affinity for the cation, while the Glu781-->Lys mutant exhibits a modest increase. Furthermore, in the absence of K+, the Glu781-->Ala mutant displays a Na(+)-ATPase activity and a cellular Na+ influx suggesting that Na+ is substituting for K+ at the extracellular binding sites. The observation that trypsin digestion of the Glu781-->Ala mutant in Na+ medium produces a K(+)-stabilized tryptic fragment also intimates a decreased capacity of the mutant to discriminate between Na+ and K+ at the extracellular loading sites. All together, these data implicate Glu781 of the Na,K-ATPase alpha subunit as an important coordinate of cation selectivity and activation, although the modest effect of Glu781-->Lys substitution seemingly precludes direct involvement of the residue in the cation binding process. In addition, the fifth membrane segment is proposed to represent an important communicative link between the extramembraneous ATP binding domain and the cation transport regions of the Na,K-ATPase.

Adenosine Triphosphate↗
PubMed1996

Deciphering the biosynthetic origin of the aglycone of the aureolic acid group of anti-tumor agents.

BACKGROUND: Mithramycin, chromomycin, and olivomycin belong to the aureolic acid family of clinically important anti-tumor agents. These natural products share a common aromatic aglycone. Although isotope labeling studies have firmly established the polyketide origin of this aglycone, they do not distinguish between alternative biosynthetic models in which the aglycone is derived from one, two or three distinct polyketide moieties. We set out to determine the biosynthetic origin of this moiety using a recombinant approach in which the ketosynthase and chain-length factor proteins from the antibiotic-producer strain, which determine the chain length of a polyketide, are produced in a heterologous bacterial host. RESULTS: The ketosynthase and chain-length factor genes from the polyketide synthase gene cluster from the mithramycin producer, Streptomyces argillaceus ATCC 12956, and the acyl carrier protein and ketoreductase genes from the actinorhodin polyketide synthase were expressed in Streptomyces coelicolor CH999. The recombinant strain produced a 20-carbon polyketide, comprising the complete backbone of the aglycone of mithramycin. CONCLUSIONS: The aglycone moieties of mithramycin, chromomycin, and olivomycin are derived from a single polyketide backbone. The nascent polyketide backbone must undergo a series of regiospecific cyclizations to form a tetracenomycin-like tetracyclic intermediate. The final steps in the aglycone biosynthetic pathway presumably involve decarboxylation and oxidative cleavage between C-18 and C-19, followed by additional oxidation, reduction, and methylation reactions.

Antibiotics, Antineoplastic↗