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Biomedical subjects

A Campos

Publications and source records attributed to A Campos.

At least 55 records · Page 3Linked to original sources
PubMed2000

Contribution of artificial intelligence to the knowledge of prognostic factors in laryngeal carcinoma.

Many studies have investigated prognostic factors in laryngeal carcinoma, with sometimes conflicting results. Apart from the importance of environmental factors, the different statistical methods employed may have influenced such discrepancies. A program based on artificial intelligence techniques is designed to determine the prognostic factors in a series of 122 laryngeal carcinomas. The results obtained are compared with those derived from two classical statistical methods (Cox regression and mortality tables). Tumor location was found to be the most important prognostic factor by all methods. The proposed intelligent system is found to be a sound method capable of detecting exceptional cases.

Aged↗
PubMed2000

[Our management protocol and surgical technique in cerebrospinal fluid rhinorrhea treated with an endonasal approach].

Five patients with cerebrospinal fluid fistula (CFF) have been treated with intratecal fluoresceine, 2 cc at 2%, and endoscopic nasal surgery. In 3 patients CFF was postraumatic; one case spontaneous and another case iatrogenic. In all the cases CFF have been solved in the first time. Postoperatory follow-up vary from 8 to 14 months, and no recurrence was observed. Fluorescein must be managed adequately for prevent neural complications.

Adult↗
PubMed1999

Changes in elemental content during apoptotic cell death studied by electron probe X-ray microanalysis.

Recent data suggest that changes in ionic content, primarily potassium, play a pivotal role in the progression of apoptosis. However, the changes in total element content, i.e., sodium (Na), magnesium (Mg), phosphorous (P), chlorine (Cl), potassium (K), and calcium (Ca), during apoptosis have not been evaluated. Electron probe X-ray microanalysis (EPXMA) was used to measure total element content in U937 cells before and after the induction of apoptosis. As an experimental model we used U937 cells irradiated with ultraviolet (UV) light. Apoptosis was evaluated with phase-contrast microscopy, with scanning and transmission electron microscopy, and with the fluorescent dye bisbenzimide (Hoechst 33342). Plasma membrane permeability as a measure of cell death was determined by trypan blue dye exclusion. To investigate element content with EPXMA, cells were cryoprepared, i.e., cryofixed and freeze-dried, and analyzed as whole cells using a scanning electron microscope. We found that the UV irradiation induced rapid (within 2 h) morphological changes associated with apoptosis, such as plasma membrane blebbing, condensation of the chromatin, and the formation of membrane-bound apoptotic bodies. At this time, 95% of the apoptotic cells excluded trypan blue dye. EPXMA results demonstrated that UV light-irradiated apoptotic cells (cells with membrane-bound apoptotic bodies) had a lower Cl content (P < 0.001) and K content (P < 0.001) and a higher Na content (P < 0.001) in comparison with nonirradiated control cells. Also, P and Ca content was higher in apoptotic cells than in control cells, but this difference did not reach statistical significance. No differences were found in Mg. These data indicated that morphological changes characteristic of apoptotic cell death are related with significant changes in sodium, chlorine, and potassium content. In addition, we demonstrated that these changes in elemental composition were not associated with loss of cell membrane integrity.

Apoptosis↗
PubMed1999

The crystalline pattern of calcium in different topographical regions of the otoconial membrane. An electron probe and spectroscopic diffraction study.

Quantitative electron probe microanalysis and electron spectroscopic diffraction analysis was used to determine the gradient of distribution of calcium and its crystalline pattern at different levels (lower gelatinous membrane, upper gelatinous membrane and otoliths) in the otoconial membrane of adult OF1 mice. Our quantitative electron probe microanalytical data, obtained with scanning-transmission electron microscopy, indicated that there was a gradient in calcium concentration which increased from the vestibular surface towards the otoliths. Differences between the three regions of the otoconial membrane were statistically significant in both the utricle and saccule. Our results with electron spectroscopic diffraction revealed an increasing crystalline development from the lower gelatinous membrane towards the otoliths. Our findings with both techniques suggest that the gelatinous membrane is involved in the maturation and crystallization of the otoliths.

Animals↗
PubMed1999

Histomorphometric analyses of hydroxyapatite-coated and uncoated titanium dental implants in rabbit cortical bone.

In this article, we report the results of analyses of bone healing around four types of dental implants. Five implants of each type were inserted into the proximal tibia metaphysis of adult New Zealand rabbits and were analyzed using computerized histomorphometry 12 weeks after implantation. Hydroxyapatite-coated implants showed more direct bone contact and more lamellar bone in the threads than the titanium implants. There was a significant correlation between an increase in the percentage of mineralized tissue in the threads of metallic implants and cellular density around the implant, indicating less lamellar bone in contact with metallic implants.

Alveolar Process↗
PubMed1999

Capacity for mental imagery and its spontaneous use.

The aim of this study was to investigate whether the capacity to form mental images influences the frequency with which subjects use mental images. Two tests measuring capacity for mental imagery were given to 283 undergraduates, a self-assessment and a performance test. Frequency of spontaneous use of mental imagery was also measured. Subjects with high self-assessed ability to form images used mental imagery spontaneously more often than those with low self-assessed imaging ability.

Adult↗
PubMed1999

Emotionality of words as related to vividness of imagery and concreteness.

We investigated the association of the imagery and concreteness of words on their emotionality. Emotionality was evaluated on the basis of skin conductance. A total of 61 subjects (all university students) rated the vividness of imagery and concreteness of the words in a list of 25 word pairs. Each pair was comprised of one abstract word and one concrete word with a related meaning, e.g., "friendship" and "friend," thereby controlling meaning. The skin-conductance response of each word was measured subsequently from these same subjects. Our results show that both imagery and concreteness were significantly related to emotionality.

Adult↗
PubMed1999

Relationship between properties of words and elicitation of skin conductance response.

We investigated the association of subject-rated imagery, subject-rated concreteness, subject-rated emotionality, frequency, date of entry into the language, and word length with emotional imagery as measured by the skin conductance response elicited by that word. 50 words in a list of 25 word-pairs were rated by 96 university students; then their skin conductance response of each word was measured for each word. In each pair, one word was concrete and one was abstract but with related meaning, e.g., adolescent and adolescence. Stepwise multiple regression indicated that 30% of variance in the later skin conductance response was explained by imagery and subject-rated emotionality. Imagery alone explained 24% of variance.

Adult↗
PubMed1999

A procedure to prepare cultured cells in suspension for electron probe X-ray microanalysis: application to scanning and transmission electron microscopy.

We describe a simple procedure to prepare cultured cells in suspension to analyse elemental content at the cellular level by electron probe X-ray microanalysis. Cells cultured in suspension were deposited onto polycarbonate tissue, culture plate well inserts, centrifuged at low g, washed to remove the extracellular medium, cryofixed and freeze-dried, and analysed in the scanning mode of a scanning electron microscope. We tested the effect of different washing solutions (150 mM ammonium acetate, 300 mM sucrose, and distilled water) on the elemental content of cultured cells in suspension. The results demonstrated that distilled water was the best washing solution to prepare cultured cells. In addition, the low Na content, high K content and high K/Na ratio of the cells indicated that this procedure, based on the centrifugation at low g followed by cryopreparation, constitutes a satisfactory method to prepare cultured cells in suspension. We also investigated the effects of different accelerating voltages on X-ray signal collection. The results showed that moderate accelerating voltages, i.e. 10-11 kV, should be used to analyse whole cells in the scanning mode of the scanning electron microscope. We show that this method of preparation makes it possible to prepare cryosections of the cultured cells, thus permitting analysis of the elemental content at the subcellular level, i.e. nucleus, cytoplasm and mitochondria, using a scanning transmission electron microscope.

Cell Compartmentation↗
PubMed1998

Crystallization and preliminary X-ray analysis of FlhD from Escherichia coli.

The flhD gene from Escherichia coli codes for one of the transcriptional activators of flagellar genes and is a putative global regulator in the cell. FlhD together with FlhC forms a complex that positively regulates the expression of flagellar genes. However, FlhD is able to change its DNA binding specificity, probably by forming another complex with some unknown factor or by binding to other targets by itself. FlhD is a good model to study the DNA binding specificity by complex formation. The FlhD three-dimensional structure will certainly improve our understanding of this protein, which is the first case of combinatory specificity in prokaryotes. The flhD gene was over-expressed, and the resulting protein was purified to homogeneity. FlhD crystals were obtained from 15-25% PEG 5000, 0.05-0.1 M lithium sulfate, 0.1 M Tris, pH 8.5, or 20-30% PEG 5000, 0.05-0.2 M sodium acetate, and 0.1 M Tris-HCl, pH 8.5, as precipitant solutions, and belong to the space group I4 with unit cell parameters of a = b = 90 A, c = 42.6 A, and alpha = beta = gamma = 90 degrees and contain two molecules per asymmetric unit. A complete native data set has been collected to 2.3-A resolution.

Bacterial Proteins↗
PubMed1998

Phylogenetic relationships of platyhelminthes based on 18S ribosomal gene sequences.

Nucleotide sequences of 18S ribosomal RNA from 71 species of Platyhelminthes, the flatworms, were analyzed using maximum likelihood, and the resulting phylogenetic trees were compared with previous phylogenetic hypotheses. Analyses including 15 outgroup species belonging to eight other phyla show that Platyhelminthes are monophyletic with the exception of a sequence putatively from Acoela sp., Lecithoepitheliata, Polycladida, Tricladida, Trematoda (Aspidobothrii + Digenea), Monogenea, and Cestoda (Gyrocotylidea + Amphilinidea + Eucestoda) are monophyletic groups. Catenulids form the sister group to the rest of platyhelminths, whereas a complex clade formed by Acoela, Tricladida, "Dalyellioida", and perhaps "Typhloplanoida" is sister to Neodermata. "Typhloplanoida" does not appear to be monophyletic; Fecampiida does not appear to belong within "Dalyellioida," nor Kalyptorhynchia within "Typhloplanoida." Trematoda is the sister group to the rest of Neodermata, and Monogenea is sister group to Cestoda. Within Trematoda, Aspidobothrii is the sister group of Digenea and Heronimidae is the most basal family in Digenea. Our trees support the hypothesis that parasitism evolved at least twice in Platyhelminthes, once in the ancestor to Neodermata and again in the ancestor of Fecampiida, independently to the ancestor of putatively parasitic "Dalyellioida."

Animals↗
PubMed1998

An IS4 insertion at the glnA control region of Escherichia coli creates a new promoter by providing the -35 region of its 3'-end.

An insertion element (IS)4 insertion selected as suppressor of the rpoN73::Tn5 alelle was located inside the control region of the glnA gene in Escherichia coli. In the rpoN73::Tn5 background the IS4 insertion promotes glnA transcription at a low constitutive level sufficient to sustain glutamine-independent growth. The IS4 insertion mutation in either rpoN73::Tn5 or wild-type backgrounds promotes glnA transcription from a new start site located two bases downstream of the glnAp2 start site. Analysis of sequences flanking the insertion point showed a promoter sequence whose -35 region was located inside the IS4 sequence and the -10 region was inside the glnA control region. Site-directed mutagenesis of relevant nucleotide residues of the newly created promoter impaired transcription of a reporter gene. The results support our contention that IS4 carries a -35 promoter region that is able to create functional hybrid promoters. We propose that this mechanism could be one of the molecular reasons of the suppressor activity previously reported for IS4.

DNA Transposable Elements↗
PubMed1998

Primary vesicoureteral reflux: review of current concepts.

The well-known association between vesicoureteral reflux and urinary tract infection is the basis for pathophysiological and therapeutic implications which have dominated the literature on the subject for the last 2 decades. We critically review the following issues: (1) does urinary tract infection cause reflux? (2) does reflux predispose to infection? (3) does reflux predispose to pyelonephritis? (4) does reflux predispose to a renal parenchymal scar? (5) does long-term urinary antibiotic prophylaxis prevent renal damage in patients with reflux? We conclude that none of the reviewed issues have been rigorously proven or validated and that the role of vesicoureteral reflux in urinary tract infections needs to be redefined through well-designed, multicenter, prospective, randomized, controlled studies using state of the art renal imaging techniques.

Antibiotic Prophylaxis↗