Biomedical subjects

C Oliveira

Publications and source records attributed to C Oliveira.

At least 37 records · Page 2Linked to original sources

PubMed2004

Experimental vitrification of human compacted morulae and early blastocysts using fine diameter plastic micropipettes.

BACKGROUND: Vitrification of human blastocysts has been successfully applied using grids, straws and cryoloops. We assessed the survival rate of human compacted morulae and early blastocysts vitrified in pipette tips with a smaller inner diameter and solution volume than the previously described open pulled straw (OPS) method. METHODS: Excess day 5 human embryos (n = 63) were experimentally vitrified in vessels. Embryos were incubated at 37 degrees C with sperm preparation medium (SPM) for 1 min, SPM + 7.5% ethylene glycol (EG)/dimethylsulphoxide (DMSO) for 3 min, and SPM + 16.5% EG + 16.5% DMSO + 0.67 mol/l sucrose for 25 s. They were then aspirated (0.5 microl) into a plastic micropipette tip (0.36 mm inner diameter), exposed to liquid nitrogen (LN(2)) vapour for 2 min before being placed into a pre-cooled cryotube, which was then closed and plunged into LN(2). Embryos were warmed and diluted using 0.33 mol/l and 0.2 mol/l sucrose. RESULTS: The survival rate for compacted morulae was 73% (22/30) and 82% (27/33) for early blastocysts. CONCLUSIONS: The survival rates of human compacted morulae and early blastocysts after vitrification with this simple technique are similar to those reported in the literature achieved by slow cooling and other vitrification protocols.

Blastocyst↗

PubMed2004

A Monte Carlo multiple source model applied to radiosurgery narrow photon beams.

Monte Carlo (MC) methods are nowadays often used in the field of radiotherapy. Through successive steps, radiation fields are simulated, producing source Phase Space Data (PSD) that enable a dose calculation with good accuracy. Narrow photon beams used in radiosurgery can also be simulated by MC codes. However, the poor efficiency in simulating these narrow photon beams produces PSD whose quality prevents calculating dose with the required accuracy. To overcome this difficulty, a multiple source model was developed that enhances the quality of the reconstructed PSD, reducing also the time and storage capacities. This multiple source model was based on the full MC simulation, performed with the MC code MCNP4C, of the Siemens Mevatron KD2 (6 MV mode) linear accelerator head and additional collimators. The full simulation allowed the characterization of the particles coming from the accelerator head and from the additional collimators that shape the narrow photon beams used in radiosurgery treatments. Eight relevant photon virtual sources were identified from the full characterization analysis. Spatial and energy distributions were stored in histograms for the virtual sources representing the accelerator head components and the additional collimators. The photon directions were calculated for virtual sources representing the accelerator head components whereas, for the virtual sources representing the additional collimators, they were recorded into histograms. All these histograms were included in the MC code, DPM code and using a sampling procedure that reconstructed the PSDs, dose distributions were calculated in a water phantom divided in 20000 voxels of 1 x 1 x 5 mm3. The model accurately calculates dose distributions in the water phantom for all the additional collimators; for depth dose curves, associated errors at 2sigma were lower than 2.5% until a depth of 202.5 mm for all the additional collimators and for profiles at various depths, deviations between measured and calculated values were less than 2.5% or 1 mm.

Algorithms↗

PubMed2003

Carotenoid compounds in grapes and their relationship to plant water status.

The aim of this work was to study the relationship between carotenoid contents in grapevine berries and plant water status. For this purpose, a black grapevine variety, Vitis vinifera L. cv. Touriga Nacional, was studied. The experiments were carried out in the same Douro vineyards, with plants of the same age, in two different water retention soils. A higher water retention capacity soil, soil A, and a lower water retention capacity soil, soil B, were both in a 1.2 m deep silt-loam schist-derived soil. The training system was the double cordon trained and spur pruned. A first range was nonirrigated (NI) and a second one was irrigated (I), 60% of evapotranspiration (ET(0)). For soil B, a 30% of ET(0) treatment was also applied. The plant water status was estimated by predawn leaf water potential. The effects of plant water status on berry growth were studied by measurement of the berry weight and total soluble solids (degrees Brix). The carotenoid profile was quantitatively determined by high-performance liquid chromatography/diode array. Carotenoids determined were beta-carotene, lutein, neoxanthin, violaxanthin, and luteoxanthin. The comparison between irrigated and nonirrigated grapes was followed from 2 weeks before veraison until the ripe stage. Results showed that at harvest time, berries exposed to the NI had a lower weight than those exposed to the irrigated treatment (60% of ET(0)), 0.89 vs 1.36 g/berry and 0.94 vs 1.34 g/berry, for soils A and B, respectively. The irrigated treatment contributed to a higher sugar concentration in both soils. However, depending on the soil water retention capacity, the carotenoid contents were different in soils A and B. For soil A, the total carotenoid content was similar for both NI and I treatments. However, with regard to soil B, in irrigated treatment, levels of carotenoids were approximately 60% lower than those found for the NI. It seems to be possible to produce higher weight berries (with higher sugar levels) with similar carotenoid contents. On the other hand, soil characteristics had a larger influence than irrigation on the concentration of carotenoids in grapes, resulting in an important viticultural parameter to take into account in aroma precursor formation.

Agriculture↗

PubMed2003

Congenital chylothorax: a case report.

A case of unilateral congenital hydrothorax diagnosed at 21 weeks and treated with a pleuro-amniotic shunt at 23 weeks' gestation is presented. The rapid production of pleural fluid led to the development of polyhydramnios which was treated with a selective Cox inhibitor. Due to worsening of the hydrothorax, a third thoracocentesis was performed at 30 weeks' gestation prior to a Cesarean section. The neonate responded well to mechanical ventilation, a thoracic drainer that was inserted between days 5 and 14, fluid and protein replacement and gradual transition from parenteral to intestinal nutrition. Early diagnosis of chylothorax should be treated by thoraco-amniotic drainage to prevent fetal pulmonary hypoplasia and congestive cardiac failure. Polyhydramnios is a complication of this therapy and may require treatment with a Cox inhibitor.

Adult↗

PubMed2003

Spermiogenesis and sperm ultrastructure in Cichla intermedia with some considerations about Labroidei spermatozoa (Teleostei, Perciformes, Cichlidae).

Spermiogenesis and spermatozoal structure were studied in Cichla intermedia, a primitive species of Neotropical Cichlids. The analysis shows that spermiogenesis is characterized by chromatin compaction, flagellum development, nuclear rotation, nuclear fossa formation and residual cytoplasm elimination. In the spermatozoa, the head is round, the nucleus contains highly condensed filamentous clusters of chromatin and an acrosome is absent. The nuclear fossa is slightly eccentric and shows a projection that penetrates into the nuclear outline. The proximal centriole is located in the initial segment of the nuclear fossa. The midpiece and the cytoplasmic channel are long. The mitochondria, about 10 in number, are round or slightly elongated, disposed in two layers around the initial segment of the flagellum. The flagellum has a classical 9+2 axoneme and two lateral fins. The data available show that no characteristics of spermiogenesis or spermatozoa are exclusively found in members of the suborder Labroidei. However, three characteristics seem to be exclusively observed in Cichlidae: (1) compact filamentous clusters of chromatin; (2) slightly eccentric nuclear fossa; and, (3) number of mitochondria.

Animals↗

PubMed2003

Concurrent hypermethylation of gene promoters is associated with a MSI-H phenotype and diploidy in gastric carcinomas.

Changes in the pattern of DNA methylation are among the most common alterations observed in human cancers, such as gastric carcinomas. We analysed in a series of 51 sporadic gastric carcinomas the methylation status of the promoter regions of the hMLH1, CDH1, MGMT and COX2 genes. We aimed to determine the frequency of CpG island hypermethylation and to find out whether the occurrence of concurrent hypermethylation is related to the clinicopathological features of the gastric carcinomas. Using methylation-sensitive restriction analysis/polymerase chain reaction (PCR) and methylation-specific PCR (MSP) strategies, we searched for the presence of hypermethylation on the promoter region of the 4 selected genes. All showed hypermethylation of their promoter regions with frequencies of 37, 51, 61 and 29% for hMLH1, CDH1, MGMT and COX2, respectively. Concurrent hypermethylation was more frequently observed in MSI-H (P=0.0005) and diploid (P=0.029) tumours. Hypermethylation of hMLH1 was associated with MSI-H tumours (P=0.0001), whereas hypermethylation of MGMT was associated with MSI-H (p=0.021) and diploid tumours (p=0.012). Our results indicate that concurrent hypermethylation is a common event in gastric cancer, suggesting that global methylation changes play an important role in the development of sporadic gastric carcinoma. Moreover, inactivation of different gene promoters by hypermethylation is significantly associated with microsatellite instability (MSI-H) and diploidy: hMLH1 determines MSI-H and MGMT the diploid status of gastric carcinomas.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Basic dosimetry of radiosurgery narrow beams using Monte Carlo simulations: a detailed study of depth of maximum dose.

In radiosurgery narrow photon beams, the depth of maximum dose d(max), in the beam central axis increases as the size of the additional collimator increases. This behavior is the opposite of what is observed in radiotherapy conventional beams. To understand this effect, experimental depth dose curves of the additional collimators were obtained for a Siemens KD2 linear accelerator in 6 MV photon mode and the shift of d(max) varied from 11.0 +/- 0.6 mm for the 5 mm collimator to 14.5 +/- 0.6 mm for the 23 mm collimator. Monte Carlo simulations showed that the photons that had no interactions in the additional collimators, contributing more than 90% to the total dose in water, were responsible for the shift in d(max). Monte Carlo simulations also showed that electrons originated from these photons and contributing to the dose deposit in water in the beam central axis could be divided in two groups: those that deposit energy far away from their point of origin (the point of the first photon collision in water) and those that deposit energy locally (originated at more than one photon collision in water). Applying a simplified model based on the fact that the photons originating Compton electrons (at the first and subsequent collisions) have similar characteristics in air for all the additional collimators, it was shown that these electrons were also responsible for the shift of d(max) in the beam central axis. Finally, it was shown that the changes in the initial gradients of the depth dose curves of the additional collimators were mainly due to electrons originated from the first photon collision in water.

Algorithms↗

PubMed2002

Predictive value of testicular histology in secretory azoospermic subgroups and clinical outcome after microinjection of fresh and frozen-thawed sperm and spermatids.

BACKGROUND: A retrospective study was carried out on 159 treatment cycles in 148 secretory azoospermic patients to determine whether histopathological secretory azoospermic subgroups were predictive for gamete retrieval, and to evaluate outcome of microinjection using fresh or frozen-thawed testicular sperm and spermatids. METHODS: Sperm and spermatids were recovered by open testicular biopsy and microinjected into oocytes. Fertilization and pregnancy rates were assessed. RESULTS: In hypoplasia, 97.7% of the 44 patients had late spermatids/sperm recovered. In maturation-arrest (MA; 47 patients), 31.9% had complete MA, and 68.1% incomplete MA due to a focus of early (36.2%) or late (31.9%) spermiogenesis. Gamete retrieval was achieved in 53.3, 41.2 and 93.3% of the cases respectively. In Sertoli cell-only syndrome (SCOS; 57 patients), 61.4% were complete SCOS, whereas incomplete SCOS cases showed one focus of MA (5.3%), or of early (29.8%) and late (3.5%) spermiogenesis. Only 29.8% of the patients had a successful gamete retrieval, 2.9% in complete and 77.3% in incomplete SCOS cases. In total, there were 87 ICSI, 39 elongated spermatid injection (ELSI) and 33 round spermatid injection (ROSI) treatment cycles, with mean values of fertilization rate of 71.4, 53.6 and 17%, and clinical pregnancy rates of 31.7, 26.3 and 0% respectively. CONCLUSIONS: Histopathological subgroups were positively correlated with successful gamete retrieval. No major outcome differences were observed between testicular sperm and elongated spermatids, either fresh or frozen-thawed. However, injection of intact round-spermatids showed very low rates of fertilization and no pregnancies.

Cell Size↗

PubMed2002

Dynamics of 5S rDNA in the tilapia (Oreochromis niloticus) genome: repeat units, inverted sequences, pseudogenes and chromosome loci.

In higher eukaryotes, the 5S ribosomal DNA (5S rDNA) is organized in tandem arrays with repeat units composed of a coding region and a non-transcribed spacer sequence (NTS). These tandem arrays can be found on either one or more chromosome pairs. 5S rDNA copies from the tilapia fish, Oreochromis niloticus, were cloned and the nucleotide sequences of the coding region and of the non-transcribed spacer were determined. Moreover, the genomic organization of the 5S rDNA tandem repeats was investigated by fluorescence IN SITU hybridization (FISH) and Southern blot hybridization. Two 5S rDNA classes, one consisting of 1.4-kb repeats and another one with 0.5-kb repeats were identified and designated 5S rDNA type I and type II, respectively. An inverted 5S rRNA gene and a 5S rRNA putative pseudogene were also identified inside the tandem repeats of 5S rDNA type I. FISH permitted the visualization of the 5S rRNA genes at three chromosome loci, one of them consisting of arrays of the 5S rDNA type I, and the two others corresponding to arrays of the 5S rDNA type II. The two classes of the 5S rDNA, the presence of pseudogenes, and the inverted genes observed in the O. niloticus genome might be a consequence of the intense dynamics of the evolution of these tandem repeat elements.

Animals↗

PubMed2002

Temozolomide in second-line treatment after prior nitrosurea-based chemotherapy in glioblastoma multiforme: experience from a Portuguese institution.

Temozolomide is a new cytotoxic alkylating agent that has recently been approved in Portugal for the treatment of recurrent high-grade glioma. From September 1999 to March 2001, 16 patients with recurrent glioblastoma multiforme who had prior nitrosurea-based chemotherapy [procarbazine, carmustine, vincristine (PCV)] were given temozolomide 150-200 mg/m2/day for 5 days every 28-day cycle. The estimated 1-year survival rate was 16% and the median overall survival was 6.5 months. Despite the small sample size, the overall survival achieved with temozolomide was similar to that of other reports. These promising data suggest that randomized trials should be undertaken to assess its use in first-line therapy its inclusion in combined chemotherapy regimes and its effectiveness with concurrent radiotherapy.

Adult↗

PubMed2001

Diagnosis of HAM/TSP based on CSF proviral HTLV-I DNA and HTLV-I antibody index.

The contribution of human T-cell lymphotropic virus (HTLV-I) DNA by PCR in CSF and the intrathecal synthesis of antibodies to HTLV-I by the antibody index (AI) to the diagnosis of HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP) were evaluated. Cases of spastic paraparesis compatible with HAM/TSP had increased AI for HTLV-I (60/73) and HTLV-I proviral sequences in CSF (25/27). Among 27 patients with other neurologic diseases, three had increased AI and another three had positive HTLV-I DNA in CSF. Thus, the combination of PCR for proviral DNA and AI for HTLV-I in CSF provides consistent criteria for the diagnosis of HAM/TSP.

Chi-Square Distribution↗

PubMed2001

E-cadherin gene (CDH1) promoter methylation as the second hit in sporadic diffuse gastric carcinoma.

In diffuse gastric carcinoma, despite common E-cadherin gene (CDH1) mutations, tumors show absence of CDH1 loss of heterozigosity (LOH) in most cases. This observation challenges the classical two-hit model of tumor suppressor gene inactivation. In order to investigate whether or not CDH1 promoter methylation may function as the second hit we analysed a series of 23 sporadic gastric carcinomas for the presence of CDH1 mutations, CDH1 promoter methylation, LOH and E-cadherin expression. CDH1 mutations were detected in nine of the 16 (56.3%) diffuse gastric carcinomas and in none of the seven intestinal gastric carcinomas. In diffuse gastric carcinomas harboring CDH1 mutations, LOH was observed in a single case. Loss of plasma membrane E-cadherin expression was consistently found in all nine cases with CDH1 mutation, suggesting that tumors inactivated the remaining CDH1 allele via a different mechanism. CDH1 promoter methylation was observed in nine of the 16 (56.3%) diffuse-type gastric carcinoma cases, including six of the nine cases (66.7%) harboring CDH1 mutations. CDH1 promoter methylation was also seen in two (28.6%) intestinal-type cases. Our results show that CDH1 promoter methylation is the second hit in more than half of the sporadic diffuse gastric carcinoma cases harboring CDH1 mutations.

Adenocarcinoma↗

PubMed2001

On the osteology and myology of catfish pectoral girdle, with a reflection on catfish (Teleostei: Siluriformes) plesiomorphies.

The configuration of the pectoral girdle bones and muscles of numerous catfishes was studied in detail and compared with that of other siluriforms, as well as of other teleosts, described in the literature. The pectoral girdle of catfishes is composed of only three bones, which probably correspond to the posttemporo-supracleithrum (posttemporal + supracleithrum), scapulo-coracoid (scapula + coracoid), and cleithrum of other teleosts. These latter two bones constitute the place of origin of the pectoral girdle muscles. Two of these muscles are related to the movements of the pectoral fin. These two muscles correspond, very likely, to the abductor superficialis and to the adductor superficialis of other teleostean fishes. In relation to the pectoral spine (thickened first pectoral fin ray), it is usually moved by three well-developed muscles, which are probably homologous with the arrector ventralis, arrector dorsalis, and abductor profundus of nonsiluriform teleosts. The morphological diversity and the plesiomorphic configuration of these muscles, as well as of the other catfish pectoral girdle structures, are discussed.

Animals↗

PubMed2001

Amyloid beta-peptide promotes permeability transition pore in brain mitochondria.

In this work the effect of the neurotoxic amino acid sequence, Abeta25-35, on brain mitochondrial permeability transition pore (PTP) was studied. For the purpose, the mitochondrial transmembrane potential (deltapsim), mitochondrial respiration and the calcium fluxes were examined. It was observed that Abeta25-35, in the presence of Ca2+, decreased the deltapsim, the capacity of brain mitochondria to accumulate calcium and led to a complete uncoupling of the respiration. However, the reverse sequence of the peptide Abeta25-35 (Abeta35-25) did not promote the PTP. The alterations promoted by Abeta35-25 and/or Ca2+ could be reversed when Ca2 was removed by EGTA or when ADP plus oligomycin were present. The pretreatment with CsA or ADP plus oligomycin prevented the deltapsim drop and preserved the capacity of mitochondria to accumulate Ca2+. These results suggest that Abeta25-35 can promote the PTP induced by Ca2+.

Adenosine Diphosphate↗

PubMed2001

Interleukin 1B and interleukin 1RN polymorphisms are associated with increased risk of gastric carcinoma.

BACKGROUND & AIMS: Interleukin (IL)-1 gene cluster proinflammatory polymorphisms have been associated with development of gastric atrophy and with increased risk of gastric carcinoma. We aimed to determine the association between IL-1 loci polymorphisms and increased risk of gastric carcinoma in samples from a Portuguese population, and to find whether there was any relationship with the histologic types of gastric carcinoma. METHODS: In a case-control study including 220 controls and 152 patients with gastric carcinoma (intestinal, 76; diffuse, 37; and atypical, 39), both the IL-1B-511 biallelic polymorphism and the IL-1RN penta-allelic variable number of tandem repeats were genotyped. RESULTS: We found a significant association between the IL-1 polymorphisms and increased risk for tumor development in patients with intestinal-type gastric carcinoma. A trend towards an increased risk of tumor development was also observed in patients with diffuse-type gastric carcinoma. No significant relationship was observed in patients with atypical carcinoma. Carriers of IL-1B-511T and IL-1RN*2 homozygotes had increased risk for developing intestinal-type gastric carcinoma with odds ratios of 2.7 (95% confidence interval [CI], 1.5-4.9) and 3.1 (95% CI, 1.5-6.5), respectively. Statistical analysis showed an interaction between the 2 loci with the risk conferred by the IL-1B-511T allele substantially increased (odds ratio, 9.0; 95% CI, 3.5-23.0) in individuals homozygous for the IL-1RN*2 allele. CONCLUSIONS: Our results provide further support to the association between IL-1 gene cluster proinflammatory polymorphisms and increased risk of gastric carcinoma. Furthermore, we found evidence pointing to the existence of a synergistic interaction between the IL-1B and IL-1RN polymorphisms.

Adult↗

PubMed2001

Estrogens and epididymal function.

Estrogen is synthesized in the male reproductive system and is found in high concentrations in rete testis and seminal fluids. This luminal estrogen targets estrogen receptors (ER) along the male reproductive tract, and in particular the efferent ductules, where ERalpha is abundant. However, both ERalpha and ERbeta are found in various regions of the male reproductive tract. The transgenic ER knockout mice (alphaERKO and betaERKO) have been used to help define the role of ER in the male. In the alphaERKO animal model, the efferent ductules are dramatically altered, forming an epithelium in which fluid reabsorption is inhibited and epithelial cells have greatly reduced numbers of lysosomes and organelles associated with endocytosis. The betaERKO male reproductive tract appears normal. Because these animals are transgenic and lack ER throughout development, we developed animal models using pure antiestrogen ICI 182,780 treatments in adult males. The data show that ERalpha participates in the regulation of the apical cytoplasm of non-ciliated cells of the efferent ductules, narrow cells of initial segment epididymis and clear cells in the remaining segments of the epididymis. There appears to be no effect on vas deferens. The inhibition of ERalpha function in the male leads to decreases in sperm concentrations and eventually to infertility. The current literature leaves the mechanisms of estrogen action in the male reproductive tract unsettled and raises the question of androgen's contribution to the regulation of fluid transport, especially in the efferent ductules.

Animals↗

PubMed2001

In vitro effects of antiviral agents on human keratocytes.

PURPOSE: To study the effects of antiviral agents on human keratocytes in vitro. METHODS: Cultured human keratocytes were incubated with either ganciclovir, idoxuridine, trifluridine, or cidofovir at concentrations from 0.0001 to 10 mg/mL. Phase-contrast microscopy and XTT (sodium [2,3-bis [2-methoxy-4-nitro-5-sulphophenyl]-2h-tetrazolium-5-carboxanilide, inner salt) colorimetric assay were performed after 24, 48, and 72 hours of incubation. RESULTS: When adjustments were made for time of incubation and concentration, trifluridine reduced cell viability significantly more than ganciclovir, idoxuridine, and cidofovir (p<0.001, three-way analysis of variance). There was significant time-and dose-dependent reduction of cell viability (p<0.001) with trifluridine and cidofovir. After a 72-hour incubation with ganciclovir or idoxuridine, cell viability was reduced as compared with 24- and 48-hour incubation (p<0.001); only the effects of the highest concentration tested (1.0 mg/mL) were significantly different from those of the lower concentrations (p<0.002). At a concentration of 1.0 mg/mL, trifluridine and cidofovir produced moderate to severe signs of cytotoxicity, whereas ganciclovir and idoxuridine displayed much less severe morphologic signs. CONCLUSIONS: Our results indicate that antiviral agents may have both time- and concentration-related toxic effects on stromal keratocytes. These findings may impact the selection of the most appropriate antiviral drug when it is needed to treat infections involving the corneal stroma.

Antiviral Agents↗

PubMed2001

Synaptonemal complex analysis of the Holstein-Friesian, Piemontese and Simmental breeds of Bos taurus taurus.

The synaptonemal complex (SC) of specimens of Bos taurus taurus from the Holstein-Friesian, Piemontese, and Simmental breeds, was analysed. The analysis included quantification of the frequency of various types of abnormalities in the SC, and the frequency of cells with SC abnormalities. All animals had 29 autosomal bivalents and one sexual bivalent and the most frequently recorded abnormality was pairing failure. The number of cells with abnormalities in the Holstein-Friesian breed was 29.41%, in the Piemontese breed was 30.00% and in the Simmental breed it was 29.54%. The subspecies Bos taurus taurus had 29.63% of cells showing abnormalities with 57.33% of these abnormalities occurring in zygotene and 42.67% occurring in pachytene. Statistical analyses showed that there were no significant differences in the number of cells with SC abnormalities among the breeds studied. The frequency of cells with abnormalities, and the efect on the fertility of the Holstein-Friesian, Piemontese and Simmental breeds are discussed.

Animals↗