Biomedical subjects

R Moraes

Publications and source records attributed to R Moraes.

13 recordsLinked to original sources

PubMed2005

Toxicity of cadmium in Japanese quail: evaluation of body weight, hepatic and renal function, and cellular immune response.

Cadmium (Cd) is an environmental pollutant that is able to alter the immune function. Previous studies have shown that, in mammals, chronic exposure to Cd decreases the release of macrophagic cytokines such as IL1 and TN alpha and decreases phagocytosis activity. On the other hand contradictory results showed an increase in the humoral response. The cellular response could be decreased by exposure to Cd. These alterations were observed in mammals. The present study aimed to investigate some of the toxic effects of Cd exposure in birds. In particular, the main objective of this work was to elucidate the effects of exposure to this pollutant on the cellular immune function of the Japanese quail as a model for the study of toxicity in animals exposed in nature. The animals were exposed to the metal (100 ppm, per os) during development, i.e., from 1 to 28 days old. Body weight, biochemical parameters, and cellular immune response were measured during and at the end of treatment. The results showed that the exposure to Cd for 28 days significantly reduced the body weight and induced hepatic toxicity. The kidney function and cellular immune response were not affected by the Cd exposure.

Alanine Transaminase↗

PubMed2003

Measurement of gastric contraction activity in dogs by means of AC biosusceptometry.

The mechanical nature of gastric contraction activity (GCA) plays an important role in gastrointestinal motility. The aim of this study was to detect GCA in anaesthetized dogs, using simultaneously the techniques of AC biosusceptometry (ACB) and manometry, analysing the characteristics of frequency and amplitude (motility index) of GCA, modified by drugs such as prostigmine and N-butyl-scopolamine. The ACB method is based on a differential transformer of magnetic flux and the magnetic tracer works as a changeable external nucleus. This magnetic tracer causes a modification in the magnetic flux, which is detected by the coils. The results obtained from the ACB showed a performance comparable to the manometry in measuring the modifications in the frequency and amplitude of the GCA. We concluded that this ACB technique, non-invasive and free of ionizing radiation, is an option for evaluating GCA and can be employed in future clinical studies.

Anesthesia↗

PubMed2001

Short-term exposure to estrogen and progesterone induces partial protection against N-nitroso-N-methylurea-induced mammary tumorigenesis in Wistar--Furth rats.

The lifetime protective effect of a full term pregnancy for breast cancer is a reproducible and consistent finding in human beings and in rodent models. The duration of pregnancy necessary to confer protection has yielded contradictory results. As the administration of estrogen and progesterone mimics the full-term pregnancy effect on conferring protection, we examined whether short-term exposure to estrogen and progesterone confers protection against N-nitroso-N-methylurea-induced mammary carcinogenesis in Wistar--Furth rats. The results reported herein show that treatment of rats with estrogen or progesterone alone for 21 days does not confer protection, but a 10-day exposure to the same concentrations of estrogen and progesterone induced a partial protective effect. The significance of these results are discussed in terms of the contradictory results in the literature and the role of morphological differentiation in conferring the protective effect.

Adenocarcinoma↗

PubMed1999

Effects of methylselenocysteine on PKC activity, cdk2 phosphorylation and gadd gene expression in synchronized mouse mammary epithelial tumor cells.

Methylselenocysteine (MSC), an organic selenium compound is an effective chemopreventive agent against mammary cell growth both in vivo and in vitro but its mechanism of action is still not understood. We have previously demonstrated that MSC is able to inhibit growth in a synchronized TM6 mouse mammary epithelial tumor cell line at 16 h time point followed by apoptosis at 48 h. The decrease in cdk2 kinase activity was coincident with prolonged arrest of cells in S-phase. The present set of experiments showed that cdk2 phosphorylation was reduced by 72% in the MSC-treated cells at 16 h time point. Expression for gadd34, 45 and 153 was elevated 2.5 to 7 fold following MSC treatment only after 16 h time point. In order to investigate a possible upstream target for MSC, we analyzed protein kinase C (PKC) in this model. Total PKC activity was reduced in TM6 cells by MSC (50 microM) within 30 min of treatment, both in cytosolic (55.4 and 77.6%) and membrane (35.2 and 34.1%) fractions for calcium-dependent and independent PKCs, respectively. PMA significantly elevated the PKC activity in membrane fraction (P < 0.01) and MSC inhibited this activation by more than 57%. The effect of MSC was selenium specific as selenomethionine and sulfurmethyl-L-cysteine (SMC) did not alter PKC activity either in cytosolic or membrane fraction. Immunoblot analysis showed that PKC-alpha was translocated to the membrane by PMA and MSC did not alter this translocation. PKC-delta was faintly detectable in membrane fractions of control and MSC-treated cells. MSC treatment slightly reduced levels of PKC-e (in cytosolic and membrane fractions) and PKC-zeta (cytosolic fractions). The data presented herein suggest that PKC is a potential upstream target for MSC that may trigger one or all of the downstream effects; i.e. the decrease of cdk2 kinase activity, decreased DNA synthesis, elevation of gadd gene expression and finally apoptosis.

Animals↗

PubMed1996

Compensation for phase and amplitude imbalance in quadrature Doppler signals.

Quadrature phase detection is widely used in ultrasound Doppler systems to obtain directional information about flow velocities in blood vessels. The presence of phase and/or gain imbalance between the quadrature outputs produces crosstalk between the forward and reverse channels which may introduce errors into mean and maximum velocity estimates and hamper the interpretation of sonograms. This technical note describes the assessment of the crosstalk in a commercial pulsed-wave Doppler system, and suggests methods of compensation for the causative imbalance which can be implemented using digital signal processing techniques. Examples of applying these methods to the outputs of the commercial system are given.

Blood Flow Velocity↗

PubMed1995

Effects of nonuniform insonation by catheter-tipped Doppler transducers on velocity estimation.

Studies of the coronary arteries using intravascular Doppler catheters have frequently been performed to assess the local circulation in various clinical situations. The parameters which are correlated with clinical observations are usually calculated from the intensity weighted mean velocity (IWMV) or the maximum velocity extracted from the Doppler power spectrum. It is known that these estimates are affected by nonuniform insonation of the blood vessel by the ultrasonic beam. The sample volume of a commercially available Doppler catheter has been theoretically and experimentally studied, and the effects of the nonuniform sampling of the vessel by the ultrasound beam examined. The results show that the velocity estimates are dramatically affected by both the position of the catheter within the artery, and the blood velocity profile. It is concluded that the maximum velocity estimator is more reliable than the IWMV estimator, but that results obtained with this estimator must also be treated with extreme caution.

Blood Flow Velocity↗

PubMed1995

A microcomputer-based system for coronary artery Doppler studies.

Intra-vascular Doppler catheters are becoming popular as research tools for studies of the coronary circulation. Velocity estimates can be obtained from Doppler signals sampled with such catheters, and used to calculate various derived parameters which can then be correlated with the haemodynamic situation under investigation. This note discusses the requirements necessary for a system to perform the acquisition of the high-frequency Doppler signals obtained from catheter-tipped transducers, and a system developed to capture, process and store Doppler, ECG and pressure signals is described. Software used to calculate parameters from the stored waveforms is discussed and examples of the system outputs presented.

Coronary Vessels↗

PubMed1979