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Biomedical subjects

F Aguilar

Publications and source records attributed to F Aguilar.

At least 55 records · Page 3Linked to original sources
PubMed1993

Aflatoxin B1 induces the transversion of G-->T in codon 249 of the p53 tumor suppressor gene in human hepatocytes.

Approximately half of hepatocellular carcinoma (HCC) from regions in the world with high contamination of food with the mycotoxin aflatoxin B1 (AFB1) contain a mutation in codon 249 of the p53 tumor suppressor gene. The mutation almost exclusively consists of a G-->T transversion in the third position of this codon, resulting in the insertion of serine at position 249 in the mutant protein. To gain insight into the mechanism of formation of this striking mutational hot spot in hepatocarcinogenesis, we studied the mutagenesis of codons 247-250 of p53 by rat liver microsome-activated AFB1 in human HCC cells HepG2 by restriction fragment length polymorphism/polymerase chain reaction genotypic analysis. AFB1 preferentially induced the transversion of G-->T in the third position of codon 249. However, AFB1 also induced G-->T and C-->A transversions into adjacent codons, albeit at lower frequencies. Since the latter mutations are not observed in HCC it follows that both mutability on the DNA level and altered function of the mutant serine 249 p53 protein are responsible for the observed mutational hot spot in p53 in HCC from AFB1-contaminated areas. Our results are in agreement with an etiological role of AFB1 in hepatocarcinogenesis in regions of the world with AFB1-contaminated food.

Aflatoxin B1↗
PubMed1993

Screening for TP53 mutations in osteosarcomas using constant denaturant gel electrophoresis (CDGE).

We have previously developed conditions to screen for TP53 point mutations inside the conserved domains II-V of the gene by using constant denaturant gel electrophoresis (CDGE). The present study reports conditions for screening more of the codons in the frequently mutated region exon 5-8 and for detecting mutations in sequences encoding functional domains in the N- and C-terminal part of the protein. The ability of the CDGE technique to detect mutations was studied using controls with known sequence deviations. The resolution power of the technique to separate different types of mutations was tested by using seven different single base pair mutants all residing in a stretch of four base pairs. All mutants were separated from the wild type. The established CDGE screening strategy was then used to look for mutations in DNA from 28 osteosarcomas. Six (21.5%) of the samples were shown to have a TP53 mutation, and the exact characterization was performed by direct sequencing. All of these were within the frequently reported mutated region exon 5-8.

Adolescent↗
PubMed1992

Biosynthesis of active spinach-chloroplast thioredoxin f in transformed E. coli.

The recently cloned gene for spinach chloroplast thioredoxin f was subcloned in a modified pKK233-2 expression vector and used for transformation of Escherichia coli cells containing the Iq plasmid. After induction with IPTG (isopropyl-beta-D-thiogalactoside) the transformed cells produce the chloroplast protein in large amounts as insoluble deposit within the cell. The protein has been solubilized, purified and analysed for activity. It shows no difference in catalytic activity from native spinach chloroplast thioredoxin f. Its electrophoretic behaviour suggests that the native thioredoxin f may have a different N-terminus than was assumed on the basis of the protein sequencing results.

Amino Acid Sequence↗
PubMed1991

Two genes encoding the soybean translation elongation factor eEF-1 alpha are transcribed in seedling leaves.

A cDNA and a genomic DNA library from soybean (Glycine max L.) were used to identify and sequence two genes coding for the alpha-subunit of the translation elongation factor eEF-1. Within the coding part, the two genes (tefS1 and tefS2) diverge in 80 wobble positions thus yielding an identical protein composed of 447 amino acids. The soybean protein has about 95% similarity with eEF-1 alpha proteins of Arabidopsis thaliana and tomato. Both genes S1 and S2 contain, within the coding part at a site seemingly unique to higher plants, a single short intron of 86 and 116 nucleotides, respectively. The untranslated leader part of both genes is interrupted by a large intron (partially sequenced). Genes S1 and S2 are transcribed in young leaves. cDNA and gene-specific oligonucleotide probes interact with a unique transcript of close to 1.9 kb. Northern hybridization studies using RNAs from dark- and light-grown seedlings show that light sharply increases the level of stable transcripts (1.9 kb). A peak value is measured after about 3 h of illumination, afterwards the transcript concentration drops to about 10% of the peak value. Genes S1 and S2 follow a similar transcription pattern in developing seedling leaves, which is distinct from that of the rbcS genes measured in parallel experiments. According to northern results, S1 transcripts are more abundant in leaves at all measured stages of development than S2 transcripts.

Amino Acid Sequence↗
PubMed1989

Primary structure of spinach-chloroplast thioredoxin f. Protein sequencing and analysis of complete cDNA clones for spinach-chloroplast thioredoxin f.

The primary structure of thioredoxin f from spinach chloroplasts was determined by standard amino acid sequencing and furthermore by sequencing the corresponding nuclear genome region. The protein, with a calculated molecular mass of 12,564 Da and a molar absorption coefficient at 280 nm of 17,700 M-1 cm-1, consists of 113 residues and exhibits 24% residue identities with spinach chloroplast thioredoxin mb or Escherichia coli thioredoxin. A monospecific antibody elicited against thioredoxin f has been used to select recombinant phage from spinach cDNA libraries in lambda gt11. The inserts of positive clones were sequenced. They code for a polypeptide of 190 amino acids, composed of the thioredoxin f sequence (113 residues) and an upstream element (77 residues) which most probably constitutes the N-terminal transit peptide that directs the polypeptide into chloroplasts. In vitro transcription and translation of this construct generates a polypeptide of approximately 21 kDa, which is imported by isolated spinach chloroplasts and processed to the mature 12.5-kDa protein.

Amino Acid Sequence↗
PubMed1986

Biocompression external fixation. Sliding external osteosynthesis.

Biocompression is a term applied to the stresses that have their origin in the elastic deformation of a diaphyseal bone, under the loads of functional activities. Its significance is the osteogenic response that biocompression stress induces in the cells of the healthy bone. The Biocompression Theory assumes that biocompression is as essential as osteogenic factors in the repair of a fracture. Thus, fracture healing requires not only stability, which is not osteogenic in itself, but physiologic biocompression. An external fixator that provides good stability and enables local biocompression has been used in the tibia of 127 patients, and healing with callus formation has been achieved in all.

Adolescent↗
PubMedDate not supplied

Role of tryptase, eosinophil cationic protein and histamine in immediate allergic reactions to drugs.

20 subjects (8 men, 12 women) with anaphylactic or urticarial reactions after drug intake were evaluated. Tryptase (TRY) and eosinophil cationic protein (ECP) were determined in serum 2 and 24 h after the allergic episode. Histamine was determined in three sequential urine samples. Results indicated that in the group of subjects evaluated, TRY and histamine were elevated, although in not all cases for both markers. With ECP, no clear association was found either at 2 or 24 h after the allergic episode. These results suggested that mast cells participated in the adverse reactions, but a role for eosinophils could not be established. Further studies need to be undertaken to establish the participation of these cells in immediate reactions to drugs.

Adult↗
PubMedDate not supplied

Diagnosis of reversible versus irreversible cerebral ischemia by the intravenous administration of naloxone.

Naloxone was given as an I.V. bolus of 0.8 mgs to four groups of patients with stroke: 1) 20 patients with C.T. proven cerebral infarcts of longer than 7 days duration; 2) 20 patients with acute cerebral ischemia of less than 24 hours; 3) 5 patients with C.T. proven intracerebral hemorrhage of less than 24 hours, and; 4) 3 patients with hyperacute cerebral ischemia which occurred during the performance of a cerebral angiogram. The patients with established cerebral infarctions of more than 7 days duration and the patients with intracerebral hematomas had no response to intravenous naloxone. Of 20 patients with acute cerebral ischemia of less than 24 hours duration, 7 had prompt, complete and long-lasting recovery. These patients had no subsequent evidence of cerebral infarct by C.T. scanner 48 hours after the onset of the cerebral ischemia and were asymptomatic when discharged. The 3 patients with hyperacute cerebral ischemia secondary to cerebral angiography had a dramatic response to the injection of naloxone. These findings suggest that intravenous naloxone may differentiate reversible versus irreversible cerebral ischemia.

Aged↗
PubMedDate not supplied

Interaction of penicillin G with the human erythrocyte membrane and models.

Penicillin G (PEN) is a widely used antibiotic whose mechanism of action is related to the interference with the synthesis of bacteria cell wall. In order to evaluate its perturbing effect upon human cell membranes PEN was made to interact with human erythrocytes, isolated resealed human erythrocyte membranes and molecular models. The latter were multibilayers of the phospholipids dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) as well as DMPC large unilamellar vesicles. These studies were performed by scanning electron microscopy, fluorescence spectroscopy and X-ray diffraction methods. The observed results coincide in that PEN did not exert any significant effect upon the structures of the red cell membrane neither on its molecular models. This is in agreement with its reported lack of major toxicity and hematological reactions.

Dimyristoylphosphatidylcholine↗
PubMedDate not supplied

Interaction of the organochlorine pesticide dieldrin with phospholipid bilayers.

Dieldrin is an organochlorine insecticide highly toxic for human beings. Although its exact mechanism of action is not well known, there is evidence that it acts at the cell membrane level. In fact, the lipophilicity of the pesticide as well as that of the phospholipid bilayer present in biological membranes makes the latter a most likely target for the interaction of dieldrin with living organisms. In order to evaluate its perturbing effect upon cell membranes the pesticide was made to interact with human erythrocytes and molecular models. These studies were performed by scanning electron microscopy on erythrocytes, fluorescence spectroscopy on dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles and X-ray diffraction on multilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE). It was observed that dieldrin particularly interacted with DMPC liposomes and multilayers perturbing its molecular arrangements. However, no effect was noticed on erythrocytes, which might be due to its high cholesterol content.

Cell Membrane↗
PubMedDate not supplied

Interaction of the anticancer drug tamoxifen with the human erythrocyte membrane and molecular models.

Tamoxifen is a non steroidal antiestrogen drug extensively used in the prevention and treatment of hormone-dependent breast cancer. To evaluate its perturbing effect upon cell membranes it was made to interact with human erythrocytes and molecular models. These consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and of dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipids classes located in the outer and inner leaflets of the erythrocyte membrane, respectively. Experiments by fluorescence spectroscopy showed that tamoxifen interacted with DMPC vesicles fluidizing both its polar head and acyl chain regions. These results were confirmed by X-ray diffraction which indicated that tamoxifen perturbed the same regions of the lipid. However, it did not cause any significant structural perturbation to DMPE bilayers. The examination by electron microscopy of human erythrocytes incubated with tamoxifen revealed that they changed their normal discoid shape to stomatocytes. According to the bilayer couple hypothesis, this result means that the drug is inserted in the inner leaflet of the erythrocyte membrane. Given the fact that tamoxifen did not interact with DMPE, it is concluded that it interacted with a protein located in the cytoplasmic moiety of the erythrocyte membrane.

Antineoplastic Agents, Hormonal↗
PubMedDate not supplied

The anticancer drug adriamycin interacts with the human erythrocyte membrane.

Adriamycin is an aminoglycosidic anthracycline antibiotic widely used in the treatment of cancer. Increasing reports point to the involvement of cell membranes in its mechanism of action. The interaction of adriamycin with human erythrocytes was investigated in order to determine the membrane binding sites and the resultant structural perturbation. Electron microscopy revealed that red cells incubated with the therapeutical concentration of the drug in human plasma changed their discoid shape to both stomatocytes and echinocytes. According to the bilayer couple hypothesis, this means that adriamycin was incorporated into either the inner or outer leaflets of the erythrocyte membrane. To explain this unusual result, the drug was incubated with molecular models. One of them consisted of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) multilayers, representative of phospholipid classes located in the outer and inner leaflets of the erythrocyte membrane, respectively. X-ray diffraction showed that adriamycin interaction perturbed the polar head and acyl chain regions of both lipids. Fluorescence spectroscopy on another model, consisting of DMPC large unilamellar vesicles (LUV), confirmed the X-ray results in that adriamycin fluidized its hydrophobic moiety. It is concluded that adriamycin incorporates into both erythrocyte leaflets affecting its membrane structure.

Adult↗
PubMedDate not supplied

Determination of inflammatory markers in allergic reactions to drugs.

Serum tryptase (Tryp) and eosinophil cationic protein (ECP) and urine N-methylhistamine (N-MH) were quantitated in a group of 13 subjects who had experienced immediate allergic reactions to different drugs. Results indicated that both Tryp and N-MH were involved and the levels were related to the severity of the reaction. Results of serum ECP levels failed to provide relevant information concerning the participation of eosinophils in immediate reactions to drugs.

Adolescent↗
PubMedDate not supplied

[Psammomatoid ossifying fibroma. Apropos a case].

A 41-year-old woman had a left palatal tumor diagnosed as psammomatoid ossifying fibroma. This tumor is a rare subtype of benign fibro-osseous craniofacial lesion that occurs mainly in women, younger age groups, and the sinonasal tract. It has distinctive histomorphological features. The tumor is slow-growing but tends to be locally aggressive and to destroy adjacent anatomic structures. Surgical excision with broad margins is the treatment of choice.

Adult↗
PubMedDate not supplied

[Otoneurological manifestations of Lyme's disease].

Infection with Borrelia burgdorferi is responsible for Lyme disease, an uncommon disorder in our country. It should be stressed that any of the neurologic manifestations of this disease may occur alone and may be the presenting manifestation of the illness. Several reports suggest that 1/4 of idiopathic Bell's palsies can be associated with this infection and in Europe is the most common cause of childhood facial nerve paresis. The same disease has been related to sudden deafness and vertigo cases. For its important therapeutic and prognostic implications the diagnosis of a Lyme disease must be taken into account in every case of peripheral facial nerve palsy, specially in children, in bilateral or recurrent cases and in those cases associated to other cranial neuritis or general manifestations.

Adult↗