Biomedical subjects

M G Ramos

Publications and source records attributed to M G Ramos.

6 recordsLinked to original sources

PubMed2004

Butyrate increases apoptosis induced by different antineoplastic drugs in monocytic leukemia cells.

BACKGROUND: Apoptosis is an essential form of cell death, the failure of which can lead to cancer development. Cancer including leukemia is usually treated with chemotherapeutic drugs that can be effective, but frequently problems are encountered that impair the success of the treatment. Butyrate is a short-chain fatty acid that can have many effects on different cells, including apoptosis. METHODS: The effect of a combination treatment with butyrate and antineoplastic agents Ara-C, etoposide and vincristine is evaluate on the leukemic cell line THP-1. RESULTS: We show that butyrate increased apoptosis induced by the three agents as seen by measurement of DNA content, annexin exposure and morphological characteristics. We also demonstrate that the process of apoptosis induced by butyrate and chemotherapeutic drugs involves the participation of caspases and induced activation of caspase-3, -8 and -9. CONCLUSIONS: We believe that butyrate could be a promising therapeutic agent for the treatment of leukemia in combination with other antineoplastic drugs.

Amino Acid Chloromethyl Ketones↗

PubMed2002

Butyrate induces apoptosis in murine macrophages via caspase-3, but independent of autocrine synthesis of tumor necrosis factor and nitric oxide.

We demonstrated that 4 mM butyrate induces apoptosis in murine peritoneal macrophages in a dose- and time-dependent manner as indicated by studies of cell viability, flow cytometric analysis of annexin-V binding, DNA ladder pattern and the determination of hypodiploid DNA content. The activity of caspase-3 was enhanced during macrophage apoptosis induced by butyrate and the caspase inhibitor z-VAD-FMK (100 microM) inhibited the butyrate effect, indicating the major role of the caspase cascade in the process. The levels of butyrate-induced apoptosis in macrophages were enhanced by co-treatment with 1 microg/ml bacterial lipopolysaccharide (LPS). However, our data indicate that apoptosis induced by butyrate and LPS involves different mechanisms. Thus, LPS-induced apoptosis was only observed when macrophages were primed with IFN-gamma and was partially dependent on iNOS, TNFR1 and IRF-1 functions as determined in experiments employing macrophages from various knockout mice. In contrast, butyrate-induced macrophage apoptosis was highly independent of IFN-gamma priming and of iNOS, TNFR1 and IRF-1 functions.

Amino Acid Chloromethyl Ketones↗

PubMed2001

Quantification of the contribution of biological nitrogen fixation to tropical green manure crops and the residual benefit to a subsequent maize crop using 15N-isotope techniques.

In this study the contribution of biological N2 fixation (BNF) to leguminous green manures was quantified in the field at different sites with different 15N methodologies. In the first experiment, conducted on a Terra Roxa soil in Cuba, the BNF contribution to three legumes (Crotalaria juncea, Mucuna aterrima and Canavalia ensiformis) was quantified by applying 15N-labelled ammonium sulphate to the soil. The second experiment was planted in a very low fertility sandy soil near Rio de Janeiro, and the 15N natural abundance technique was applied to quantify BNF in C. juncea, M. niveum and soybean. In both studies the advantages of using several non-N2-fixing reference plants was apparent and despite the much greater accumulation of the C. juncea in the experiment performed on the fertile soil of Cuba, the above ground contributions of BNF at both sites were similar (40-80 kg N x ha(-1)) and greater than for the other legumes. In a further experiment the possible contribution of root-derived N to the soil/plant system of two of the legumes was quantified using a 15N-leaf-labelling technique performed in pots. The results of this study suggested that total below-ground N could constitute as much as 39 to 49% of the total N accumulated by the legume crops.

Biochemistry↗

PubMed2001

Suprathreshold wavelet coefficient quantization in complex stimuli: psychophysical evaluation and analysis.

A psychophysical experiment is described that quantifies human sensitivities to suprathreshold distortions caused by wavelet coefficient quantization in natural images, and the resulting analysis is explained. The quantizer step sizes that cause the first three visible degradations relative to the original image are well predicted by exponential functions of subband standard deviation. The resulting root-mean-square (RMS) error in the image is constant for a spatial frequency and is independent of orientation. Contrast sensitivity calculations suggest a higher sensitivity to bands with higher energy, and threshold elevations for the second and third visible degradations are predicted well by the constant-RMS model. A quantization strategy based on the results is proposed for low-bit-rate applications.

Contrast Sensitivity↗

PubMed1999

Protection by short-chain fatty acids against 1-beta-D-arabinofuranosylcytosine-induced intestinal lesions in germfree mice.

In germfree mice, the administration of short-chain fatty acids (SCFA) protected the intestinal mucosa from damage produced by 1-beta-D-arabinofuranosylcytosine (Ara-C). Animals receiving SCFA and Ara-C had intestinal morphologies closer to normal than the control animals, which had severe intestinal lesions. We concluded that orally administrated SCFA reduce intestinal lesions, improving the mucosa pattern of the small intestine and colon.

Administration, Oral↗

PubMed1997

Oral administration of short-chain fatty acids reduces the intestinal mucositis caused by treatment with Ara-C in mice fed commercial or elemental diets.

Swiss mice fed commercial or elemental diets and an oral short-chain fatty acid (SCFA) solution or saline were treated with the cytostatic drug Ara-C (cytarabine, 3.6 mg/mouse/day) for two or four days. Histopathological examination revealed less damage (atrophy, inflammation, or necrosis) to the small intestine and colon caused by Ara-C when SCFA was administered. Accordingly, protein and nucleotide concentrations in the intestinal mucosa were higher in the group receiving SCFA than in the group receiving a placebo of the same pH and osmolarity. Improvement by SCFA treatment was correlated with an increase in the height of the intestinal villi, with no alterations of the crypts. Furthermore, the number of intraepithelial lymphocytes was similar to normal values in animals receiving SCFA and Ara-C. When large doses of SCFA were administered, xanthomized enterocytes appeared, suggesting an accumulation of fatty acids in these cells. We conclude that oral administration of SCFA at close to physiological proportions reduces the inflammation and necrosis caused by Ara-C administration, thus representing a potential factor for the improvement of patients with mucositis caused by cancer treatment.

Administration, Oral↗