Biomedical subjects

C Vicente

Publications and source records attributed to C Vicente.

At least 37 records · Page 2Linked to original sources

PubMed1999

Free and conjugated polyamines and phenols in raw and alkaline-clarified sugarcane juices.

Sugarcane juice contains a lot of sucrose associated with several monosaccharides, defined as low molecular mass carbohydrates (LMMC), as well as some polysaccharides and glycoproteins, which are defined as mid and high molecular mass carbohydrates (MMMC and HMMC, respectively). These three categories of carbohydrates can be separated by size-exclusion chromatography through Sephadex G-10 and Sephadex G-50 columns, but elution profiles change drastically after juice clarification performed by adjusting the pH value of the juice to 8.0. In addition, polyamines and some phenolics are currently associated with carbohydrate preparations, and the distribution pattern of these conjugates also changes after clarification. Polyamine levels generally decrease after juice clarification. Cadaverine is completely removed from the different carbohydrate preparations, whereas spermidine is the main polyamine occurring in association with sugarcane carbohydrates, as free or acid-soluble form in LMMC preparation or as acid-soluble and -insoluble forms in both MMMC and HMMC preparations. Polyamines, presumably spermidine, conjugate to p-hydroxybenzoic acid in LMMC, mostly to caffeic acid in MMMC, and to syringic acid in HMMC preparations. HMMC-associated polyamines appear in both acid-soluble and -insoluble fractions. Syringic acid also occurs in the LMMC preparation, but juice clarification changes it from acid-soluble to free form, and it coelutes with sucrose.

Food Handling↗

PubMed1998

Secreted, glycosylated arginase from Xanthoria parietina thallus induces loss of cytoplasmic material from Xanthoria photobionts.

A secreted, glycosylated arginase (lectin) from Xanthoria parietina thallus binds to the cell wall of Xanthoria photobiont when cell wall urease has previously been induced. The uptake of this secreted arginase by the algal cell without cell wall ligand for the lectin increases the concentration of algal putrescine and it is followed by an apparent loss of chlorophyll. However, neither chlorophyllase activity has been detected nor chlorophyllide concentration increases after loading the cells with putrescine. The loss of chlorophyll can be explained by the loss of algal protoplast resulting from the action of a putrescine-activated glucanase and the split of their membrane in an hypoosmotic medium. The loss and split of protoplasts have been shown by light and transmission electron microscopy.

Arginase↗

PubMed1997

Relative impact of HLA phenotype and CD4-CD8 ratios on the clinical expression of hemochromatosis.

Hemochromatosis is a hereditary iron-overload disease linked to HLA. The clinical expression of hemochromatosis is influenced by sex and age. However, other factors must account for the notorious heterogeneity of expression of the disease independent of sex, age, and HLA phenotype. The present study attempts to clarify some of these additional factors based on exhaustive statistical analysis of data collected from 43 selected patients with hemochromatosis. The statistical analysis focused on three groups of variables: the first group included variables reflecting the clinical expression of the disease; the second group represented the biochemical and hematological values at the time of diagnosis; and the third group consisted of the independent variables sex, age, HLA phenotype, and T-cell subset profile, i.e., the percentages and total numbers of CD4+ and CD8+ cells and the CD4-CD8 ratios. The results show that the relative expansion of the two main T-cell subsets, in the context of the HLA phenotype, correlates significantly with the clinical expression of hemochromatosis and the severity of iron overload. The present findings substantiate further the postulate that T cells have a role in the regulation of iron metabolism.

Adult↗

PubMed1994

Ionic adsorption of catalase on bioskin: kinetic and ultrastructural studies.

Bioskin is a natural polymer produced by Acetobacter xylinum and several yeasts in culture. It contains glucosamine and N-acetyl galactosamine which promote ionic adsorption of catalase at the adequate pH value. High values of ionic strength are required to enzyme desorption. Adsorption of catalase on bioskin fibers has been visualized by scanning electron microscopy associated to a dispersion X-ray analyzer. At low enzyme density, the affinity of the immobilized catalase for hydrogen peroxide was 30% lower than that of the free enzyme. This affinity decreased dramatically at higher density of immobilized enzyme and could not be increased by agitation of the enzyme reaction mixture. Immobilized catalase retains about 70% of its initial activity after 16 d storage, whereas soluble enzyme is completely inactivated after 3 d at room temperature. The haeme group of catalase is not protected after immobilization since it is accessible to both EDTA and phloroglucinol, chelating agents which inactivate catalase by removing the iron atom from the haeme group.

Acetobacter↗

PubMed1994

Haemochromatosis as a window into the study of the immunological system: a novel correlation between CD8+ lymphocytes and iron overload.

In the present study we report a serial investigation of the numbers of the peripheral blood cells--erythrocytes, polymorphonuclear neutrophils, total lymphocytes, T-lymphocyte subpopulations (CD2, CD4, CD8), B lymphocytes and monocytes--in a group of 21 patients with haemochromatosis during the time of intensive phlebotomy treatment, i.e., from iron overload until the onset of iron deficiency. A remarkable individual stability of all blood cell populations studied was found in all patients. Patients differed in their relative proportions of CD4+ and CD8+. Each individual's CD4/CD8 ratio, as well as the absolute numbers, remained unaffected with time, confirming the existence of a strict homeostatic regulation of the relative numbers of the two major peripheral T lymphocytes. A significant positive correlation between CD4/CD8 ratios and the amount of iron mobilised by phlebotomy was found during this study. A novel correlation between the relative proportions of CD4+ and CD8+ cells and iron overload is confirmed by the follow-up of iron re-entry in the serum transferrin pool in the treated patients.

Adult↗

PubMed1994

Analysis of Usnea fasciata crude extracts with antineoplastic activity.

Different fractions, isolated from the lichen Usnea fasciata, were analyzed by PC, TLC, and RP-HPLC. Analysis of the organic phases, mainly containing phenolics, revealed that usnic acid is the main product from secondary metabolites, whereas the polysaccharides isolichenin and raffinose are the most abundant water-soluble carbohydrates. Fractions containing usnic acid, as well as those containing isolichenin, showed moderate activity against sarcoma 180 and Ehrlich tumor cells. High antitumoral activity, near 90% inhibition, was found associated with the fraction containing raffinose.

Animals↗

PubMed1992

Importance of establishing appropriate local reference values for the screening of hemochromatosis: a study of three different control populations and 136 hemochromatosis family members. Hemochromatosis Clinical and Research Group.

Hemochromatosis is a human leukocyte antigen-linked (HLA-linked), potentially lethal disorder of iron metabolism with a high prevalence in white populations albeit an autosomal recessive mode of transmission. The diagnosis and treatment at early stages of the disease are critical to the prevention of the morbidity and mortality caused by the iron overload. After the identification of the first cases of hemochromatosis in Portugal, a screening program was started with a systematic search for the disease among family members of the patients, as well as in subjects from the normal population. In this study we analyze the results obtained with a total of 136 family members from 15 different families and 353 control subjects from three different villages, two in the north and one in the south of Portugal. We establish reference values for the biochemical tests used in the screening for iron overload and analyze the factors that affect those results. Besides sex-related differences, factors that were found to influence biochemical parameters most significantly included age and levels of daily alcohol intake. In addition, differences in iron status were identified between the populations from the regions in the north and the south of the country. We estimate, by HLA typing and family studies, a gene frequency for hemochromatosis of 0.14 that corresponds to a frequency of homozygotes and heterozygotes of 0.019 and 0.24, respectively.

Adolescent↗

PubMed1990

Purification and Partial Characterization of a Fructanase which Hydrolyzes Natural Polysaccharides from Sugarcane Juice.

A new sugarcane (Saccharum officinarum L.) fructanase which hydrolyzes both high molecular weight polysaccharides mid R:Fructose(4):Galactitol(5)mid R:(n) (SP) and moderate-sized carbohydrates mid R:Fructose(2):Galactitol(3)3mid R:(n) (MMWC) has been purified from sugarcane juice. The K(m) value has been estimated to be 33.7 micrograms per milliliter and 20 micrograms per milliliter for SP and MMWC, respectively. The optimal pH and temperature values are 6.0 and 30 degrees C, respectively. Purified protein has a pl value of 6.35 and a molecular weight of 13.2 kilodaltons. Fructanase activity appears to be Mn(2+)-dependent.

Journal Article↗

PubMed1990

Method for establishing serum ferritin reference values depending on sex and age.

A method is described for the establishment of reference values for serum ferritin depending on sex and age. The results obtained in a stratified random sample of 353 healthy individuals from the Portuguese population revealed that 23% of the variation observed on serum ferritin values was related to sex differences and 6% of the variation was explained by age differences. Furthermore, the effect of age was different in both sexes: serum ferritin values increase with age in females over 40 years and in males under 40. The minimum and maximum reference values were established for the different subgroups of subjects as follows: for females under 40 years and males over 40, reference values were considered as the 2.5 and 97.5 percentiles from the adjusted lognormal distribution; for females over 40 years and males under 40, reference values were considered as the exponential transformation of the upper and lower limits of the 95% prediction intervals for the log of serum ferritin for each particular age point.

Adolescent↗

PubMed1989

Algal partner regulates fungal urease in the lichen Evernia prunastri by producing a protein which inhibits urease synthesis.

Occurrence of a protein controlling urease synthesis (PIUS) at the transcriptional level in the lichen Evernia prunastri has been previously reported (Perez-Urria & Vicente, Physiol Plant 65: 433-438, 1985; id. Endocyt C Res 3: 311-316, 1986). In this work it was found that 0.1 mM cycloheximide seems to inhibit PIUS synthesis when lichen thalli are incubated on PIUS inducer, L-arginine. PIUS has been purified and characterized by PAGE, electrofocusing and amino acid analysis. It is a glycoprotein containing a homopolymer of fructose bound to the protein. PIUS has been located in whole thallus and lichenized mycobiont but remains undetectable in cultured fungi. PIUS is only detected in photobiont cells when they are axenically cultured on arginine. Thus, it is postulated that PIUS could be synthesized by lichenized photobionts from which it moves to mycobionts where it inhibits the production of fungal urease.

Amino Acids↗

PubMed1987

Equivalence between Pfr and Cyclic AMP in the Induction of d-Usnic Acid Dehydrogenase in the Lichen Evernia prunastri.

d-Usnic acid dehydrogenase is induced in Evernia prunastri thalli by a supply of exogenous d-usnic acid in light. This effect is enhanced by red light pulses through a two step way: a very rapid increase of activity after the first 10 minutes of red light, which is not reversed by far-red light, and a slow enhancement following successive red light pulses at the beginning of each hour of incubation. The last response is completely reversed by far-red following red light. Although induction of the enzyme is not achieved in the dark, 0.1 and 0.5 millimolar cyclic AMP, or 0.1 millimolar dibutyryl cyclic AMP substitutes light action and, then, the enzyme is produced. In addition, phytochrome-far red-absorbing form-increases the amount of endogenously produced cyclic AMP and this effect is shown to be photoreversible when ethylenediaminetetraacetic acid is inhibiting adenylate cyclase.

Journal Article↗

PubMed1986

Extracranial internal carotid artery aneurysms.

Two cases of extracranial internal carotid artery aneurysms are presented. In each case the cranial end of the aneurysm was in contact with the base of the skull. Ligation of the internal carotid artery was performed in the first case. Temporary occlusion of the distal internal carotid artery by means of a Fogarty catheter allowed resection with end-to-end anastomosis in the second case.

Aneurysm↗

PubMed1983

Endogenous Inactivators of Arginase, l-Arginine Decarboxylase, and Agmatine Amidinohydrolase in Evernia prunastri Thallus.

Arginase (EC 3.5.3.1), l-arginine decarboxylase (EC 4.1.1.19), and agmatine amidinohydrolase (EC 3.5.3.11) activities spontaneously decay in Evernia prunastri thalli incubated on 40 millimolar l-arginine used as inducer of the three enzymes if dithiothreitol is not added to the media. Lichen thalli accumulate both chloroatranorin and evernic acid in parallel to the loss of activity. These substances behave as inactivators of the enzymes at a range of concentrations between 2 and 20 micromolar, whereas several concentrations of dithiothreitol reverse, to some extent, the in vitro inactivation.

Journal Article↗

PubMed1982