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Biomedical subjects

E Silva

Publications and source records attributed to E Silva.

At least 145 records · Page 8Linked to original sources
PubMed1989

Randomized comparison of viral oncolysate plus radiation and radiation alone in uterine cervix carcinoma.

A randomized, controlled study was performed in patients with high-risk, untreated squamous cell carcinoma of the uterine cervix to evaluate the adjunctive use of viral oncolysate (VO) prepared from the SW756 cell line. Seventy-five patients were stratified by tumor volume and randomized to receive radiation therapy (RT) alone or RT plus intradermal immunization with VO. Fifty-one (68%) patients relapsed with a median survival (MS) of 29.1 months and a median progression-free interval (MPFI) of 18.0 months. No differences in MS or median PFI were observed by treatment arm or site of relapse, although a trend toward improved MS and median PFI in patients with small-volume primary lesions was suggested. Serum surface-binding antibody activity (greater than or equal to 1:8) to the SW756 cell line was detected in 14 of 41 unselected patients prior to therapy. Virus hemagglutination inhibitory activity (greater than or equal to 1:8) was detected in 37 of 41 patients before treatment. four-fold increases in titer were observed to the SW756 cell line in 83% and to influenza in 74% of patients tested after immunization. Preirradiation measurements of phytohemagglutinin-induced blastogenesis by the relative proliferation index (RPI) method in 39 patients revealed RPI values less than 0.58 in nine patients, eight of whom relapsed. At 3-6 months after the initiation of irradiation, 32 of 39 patients had values less than 0.58. Patients in the RT group with values less than 0.58 had significantly more relapses than those who received RT plus VO.

Adult↗
PubMed1989

Photointeraction of benzophenone triplet with lysozyme.

The quenching of the benzophenone triplet by lysozyme and its constituent amino acids in aqueous solutions have been studied. Native lysozyme quenches the benzophenone triplet with a high rate constant, 4 x 10(9) M-1 s-1. The quenching process takes place with production of significant amounts of free ketyl radicals, phi ketyl = 0.56, but with a very low benzophenone consumption yield (0.022). The consumption yield is considerably smaller than that observed for the free amino acids. This difference can be explained in terms of a dominant back hydrogen transfer to the protein in the disproportionation of the free radicals produced. Reduced and carboxymethylated lysozyme shows a higher quenching rate (7.8 x 10(9) M-1 s-1) and a larger benzophenone consumption yield (0.07). The deactivation of the benzophenone triplet by the native protein leads to its inactivation, with a quantum yield of 0.01. Tryptophan and arginine residues are destroyed with a quantum yield of 0.01. In the modified enzyme tyrosine and methionine groups are also consumed.

Amino Acids↗
PubMed1989

Amplification and rearrangement of c-erb B proto-oncogenes in cancer of human female genital tract.

There are two genes related to the v-erb B oncogene in the human genome. The c-erb B-1 gene encodes the epidermal growth factor receptor (EGF-r), and the c-erb B-2/neu gene encodes a receptor-like protein very similar to, but distinct from the EGF-r. Southern blot analysis of DNAs from 15 fresh human ovarian carcinomas showed that the c-erb B-2/neu gene was amplified in 3 tumors. The c-erb B-1/EGF-r gene was not amplified. However, in one case of adenocarcinoma of uterine endometrium, the c-erb B-1/EGF-r was found to be rearranged in the 5' region of this gene. The genomic structure of the rearranged c-erb B-1/EGF-r gene is similar to those found in the chicken v-erb B oncogene, which produces a truncated form of the EGF-r. The results suggest that amplification of the c-erb B-2/neu gene may play a role in the pathogenesis of ovarian carcinoma. Further, the human c-erb B-1/EGF-r gene in adenocarcinoma of uterine endometrium may be activated by a similar mechanism as that in the chicken v-erb B oncogene.

Adenocarcinoma↗
PubMed1988

Inadequacy of first and second order models to characterize the heart rate response induced by dynamic exercise.

Six normal subjects were submitted to dynamic exercise at workloads of 25, 50, 100 and 150 w for 4 min, intercalated by periods of rest, before and after an aerobic training period of 10 weeks. The heart rate response was fitted to 2 mathematical models, a 1st-order model and a 2nd-order model. The results indicate that these 2 models were not adequate to characterize the physiological response of heart rate induced by dynamic exercise.

Exercise Test↗
PubMed1988

Toxic effect of a photo-induced tryptophan-riboflavin adduct on F9 teratocarcinoma cells and preimplantation mouse embryos.

Solutions containing L-tryptophan and riboflavin exposed to visible light, under N2 atmosphere, yield a tryptophan-riboflavin adduct, able to inhibit the growth of cultured F9 teratocarcinoma cells. This same effect was found in the presence of a mixture of the tryptophan photooxidation products and the adduct, when using solutions previously irradiated with visible light in an O2 atmosphere. A cytotoxic effect was also observed with embryos incubated in the presence of a tryptophan-riboflavin adduct, in the latter case necrosis and embryo development arrest occurred.

Animals↗
PubMed1988

Riboflavin status and photo-induced riboflavin binding to the proteins of the rat ocular lens.

The presence of radioactivity in lenses of rats injected intraperitoneally with a solution of tryptophan and 14C-riboflavin, irradiated during 48 hours and under N2 atmosphere, was detected. The excitation fluorescence spectrum (lambda emission = 520 nm) of the soluble lens fraction corresponds to the riboflavin decomposition product of lumichrome type. When 14C-riboflavin enriched lenses were exposed to visible light, a photo-induced binding between riboflavin and a water insoluble protein fraction of the lenses was observed. This finding may help to clarify the lens modifications during aging and in cataractogenesis.

Animals↗
PubMed1987

Obtention of a photo-induced adduct between a vitamin and an essential aminoacid. Binding of riboflavin to tryptophan.

Studies in animals have suggested that the products of the irradiation of tryptophan in the presence of riboflavin may play a role in the development of hepatic dysfunction during parenteral nutrition. In this paper we describe the formation of an adduct between tryptophan and riboflavin obtained as a consequence of an anaerobic irradiation of these compounds. Through the use of molecular sieves and of an ion-exchange resin it was possible to separate the photo-adduct from the dimer riboflavin and other reaction products. The various fractions were characterized on the basis of their absorption and emission spectra. Also used were measures of anisotropy of fluorescence emission in order to characterize the derived adduct.

Light↗
PubMed1986

Exposure of tryptophanyl residues in alpha-lactalbumin and lysozyme. Quantitative determination by fluorescence quenching studies.

The effect of iodide ion on the tryptophyl fluorescence of the homologous proteins lysozyme and alpha-lactalbumin in their native form, as well as in their modified structures and in fragments from these proteins was studied. By assessing the contribution to the total fluorescence of the exposed and buried Trp residues, and of the respective fluorescence quantum yields, the quantification of the number of Trp exposed to the solvent for all the species studied was possible. Both native proteins show an important increase in the number of Trp residues exposed to the solvent when treated with denaturing agents. The peptides L-II (aa 13-105) and alpha-I (aa 1-90) from lysozyme and alpha-lactalbumin, respectively, showed Trp residues with different degree of exposure, whereas the smaller fragments, L-III (aa 106-129) and alpha-II (aa 91-123), had all their Trp residues exposed to the solvent.

Indicators and Reagents↗
PubMed1985

The riboflavin-sensitized photooxidation of horseradish apoperoxidase.

Native horseradish peroxidase, as well as its reduced and carboxymethylated form, and the apoenzyme, showed resistance to photodynamic action. Sensitivity to this action was detected only in reduced and carboxymethylated apoenzyme, when the photooxidation of its histidine residues was observed. When analyzing the bulk hydrophobic character (Hf) and the accessibility coefficients (Br) in those amino acid residues which can be subjected to photooxidation in horseradish peroxidase, it was found that all of them are situated in hydrophobic zones with low accessibility coefficients. This could justify the high resistance of this enzyme to photodynamic action. The only exception is tryptophan-117, which has low values of Hf and Br, and therefore its resistance to photodynamic action can only be explained in terms of its location and environment. Tryptophan-117 would be situated in a zone of antiparallel beta-structure, according to Chou and Fasman's predictive method for protein conformation.

Apoenzymes↗
PubMed1985

Study of a photo-induced lysozyme-riboflavin bond.

Irradiation of lysozyme in the presence of riboflavin results in the formation of a lysozyme-riboflavin adduct. Reduction and carboxymethylation of the four disulfide bonds as well as the chemical modification of the Tyr residues and the photochemical alteration of the His residue in lysozyme, do not affect the formation of the photo-induced lysozyme-riboflavin bond. When the lysozyme-riboflavin adduct was subjected to mild acid hydrolysis and ion exchange chromatography, the retention of a compound containing 14C-riboflavin was observed. Free 14C-riboflavin, on the contrary is not retained by the column. The photo-oxidation of free Trp in the presence of 14C-riboflavin, gave a compound which bound to the ion exchange resin like the above-mentioned derivative. The photo-oxidation of the Trp residues in lysozyme and in peptides obtained from lysozyme showed very high quantum yields, and these values were directly related to the incorporation of 14C-riboflavin in these samples.

Light↗
PubMed1985

Photochemical reactivity of the homologous proteins alpha-lactalbumin and lysozyme.

The fluorescent behaviour and the photodynamic effect was studied in native and structurally modified lysozyme and alpha-lactalbumin. The Tyr residues in lysozyme and alpha-lactalbumin show different sensitivities to the photodynamic effect. The effect is zero in the case of Tyr from native lysozyme. In contrast, the Tyr residues in alpha-lactalbumin are susceptible to photooxidation, which indicates a greater degree of exposure to the solvent. The three His residues of alpha-lactalbumin have different degrees of exposure and show two different kinetics of photooxidation whereas the His residue of lysozyme is photooxidized with a single kinetic. Two photooxidation kinetics were obtained for the Trp residues of both native proteins, an indication that in both cases there are Trp residues that are differently exposed to the solvent. The wavelengths of maximum fluorescent emission of the Trp residues were different for the two proteins, an effect which can also be explained in terms of a difference in the environment of these residues. The modified form of these proteins emit at wavelengths longer than those of the native forms. When modified the proteins photooxidize with noticeably greater quantum yields.

Lactalbumin↗
PubMed1984

Merkel cell carcinoma (endocrine carcinoma of the skin) of the head and neck.

Merkel cell carcinoma, also known as endocrine carcinoma of the skin, is a recently recognized and particularly aggressive form of skin cancer that exhibits histologic features similar to those of endocrine malignant neoplasms arising from other tissues. Forty-one patients with Merkel cell carcinoma arising from the cutaneous surfaces of the head and neck were seen at the University of Texas M. D. Anderson Hospital, Houston, between 1966 and 1983. Regional lymph node metastasis occur early and frequently, with a 79% overall incidence observed during the course of the disease. Treatment should consist of a wide resection of the primary tumor. A regional lymphadenectomy, when feasible, is successful in controlling nodal metastases. Postoperative radiation is recommended as an important adjuvant.

Adult↗
PubMed1984

Competitive inhibition by the D-isomer in racemic mixtures used as substrate in kinetic studies: a simple method for data treatment.

A set of equations was applied that allows the use of racemic mixtures for the estimation of kinetic parameters in systems where the L-isomer is substrate and the D-isomer a competitive inhibitor, displaying data as double reciprocal plots. A statistical treatment was introduced that renders compatible the output of presently available programs with the specific model requirements, with few additional calculations. An example is shown with beta-trypsin and its inhibition of benzozyl-D-arginine p-nitroanilide (Ki = 1.12 mM, pH 8,0, 37 degrees C).

Benzoylarginine Nitroanilide↗
PubMed1983

Residual paralytic poliomyelitis in a tropical region of Brazil, 1969-1977: prevalence surveys in different age groups as indicators of changing incidence.

The magnitude of the problem of paralytic poliomyelitis in recent years in the tropical Federal District of Brazil was estimated in 1980 by determining the prevalence of residual paralytic poliomyelitis in 10,007 schoolchildren born in 1969-1970 and in 10,794 schoolchildren born in 1973-1974. About 98% of these children attended school in the Federal District. The rate of residual paralytic poliomyelitis of 5.4 per 1000 children born in 1969-1970 was 2.3 times higher than the rate of 2.3 per 1000 born in 1973-1974, which may be related to increasing vaccination of children under one year of age. Paralysis appeared before four years of age in 96.5% of these children. These prevalence rates indicate a minimal average annual incidence of acute persisting paralytic poliomyelitis of 187 cases per million total population during the period 1969-1973 and of 80 per million total population during the period 1973-1977 compared with an average annual incidence of 135 reported persisting and non-persisting paralytic cases per million total population in the United States in the prevaccine era and of four persisting cases per 100 million during 1973-1978.

Age Factors↗
PubMed1983

Association of Streptococcus bovis bacteremia with bowel disease.

We reviewed the medical records of 19 patients who had Streptococcus bovis bacteremia. Eight patients had diverticulosis, four had benign adenomatous colonic polyps, and three had adenocarcinomas of the gastrointestinal tract. Laboratory workers and clinicians should be aware of the association of S. bovis bacteremia and gastrointestinal disease.

Gastrointestinal Diseases↗