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Biomedical subjects

J Carretero

Publications and source records attributed to J Carretero.

At least 19 recordsLinked to original sources
PubMed2006

Dysfunctional AMPK activity, signalling through mTOR and survival in response to energetic stress in LKB1-deficient lung cancer.

LKB1, mutated in Peutz-Jeghers and in sporadic lung tumours, phosphorylates a group of protein kinases named AMP-activated protein kinase (AMPK)-related kinases. Among them is included the AMPK, a sensor of cellular energy status. To investigate the relevance of LKB1 in lung carcinogenesis, we study several lung cancer cells with and without LKB1-inactivating mutations. We report that LKB1-mutant cells are deficient for AMPK activity and refractory to mTOR inhibition upon glucose depletion but not growth-factor deprivation. The requirement for wild-type LKB1 to properly activate AMPK is further demonstrated in genetically modified cancer cells. In addition, LKB1-deficient lung primary tumours had diminished AMPK activity, assessed by complete absence or low level of phosphorylation of its critical substrate, acetyl-CoA carboxylase. We also demonstrate that LKB1 wild-type cells are more resistant to cell death upon glucose withdrawal than their mutant counterparts. Finally, modulation of AMPK activity did not affect PI3K/AKT signalling, an advantage for the potential use of AMPK as a target for cancer therapy in LKB1 wild-type tumours. Thus, sustained abrogation of cell energetic checkpoint control, through alterations at key genes, appear to be an obligatory step in the development of some lung tumours.

AMP-Activated Protein Kinase Kinases↗
PubMed2005

Stochastic model to forecast ground-level ozone concentration at urban and rural areas.

Stochastic models that estimate the ground-level ozone concentrations in air at an urban and rural sampling points in South-eastern Spain have been developed. Studies of temporal series of data, spectral analyses of temporal series and ARIMA models have been used. The ARIMA model (1,0,0) x (1,0,1)24 satisfactorily predicts hourly ozone concentrations in the urban area. The ARIMA (2,1,1) x (0,1,1)24 has been developed for the rural area. In both sampling points, predictions of hourly ozone concentrations agree reasonably well with measured values. However, the prediction of hourly ozone concentrations in the rural point appears to be better than that of the urban point. The performance of ARIMA models suggests that this kind of modelling can be suitable for ozone concentrations forecasting.

Cities↗
PubMed2005

Contrast media: future aspects.

In spite of the dramatic development in CT, there was no major breakthrough in the iodinated contrast media development. New agents based on hybrid between MRI and CT compounds may be a new innovative alternative. This new approach may also open new indications such as radiotherapy.

Contrast Media↗
PubMed2004

Analyses of ozone in urban and rural sites in Málaga (Spain).

Ozone concentrations were measured at two (urban and a rural) sites near the city of Málaga (Spain). The aim of this study was to determine the daily, monthly and seasonal variation patterns of ozone concentrations at both sites and to study the possible regional influences. The daily variations mostly have the usual features with the afternoon maximum and the night minimum being more pronounced in the urban area. The average monthly concentrations throughout the year start to increase in March reaching their maximum values in July for the urban site. However, in the rural area, the monthly variations are smaller reaching their maximum value in June. The hourly evolution of the ozone concentrations in both sampling sites is well defined in spring and summer and not so well defined in autumn and winter. Taking into account the four seasons, the rural concentrations are higher than the urban ones. Summer is the season when there are similar concentrations at both sampling sites. Average hourly summer afternoon ozone for the hours 12:00-20:00 LST exceeded the 110 microg m(-3) European Union guidelines for human health for 8 h ozone exposure at the urban and rural sites.

Air Pollutants↗
PubMed2003

Dopaminergic modulation of nNOS expression in the pituitary gland of male rat.

Nitric oxide is an unconventional transmitter since it is not transported and released by exocytosis. In the pituitary gland, nitric oxide is locally synthesised by gonadotroph and folliculo-stellate cells. Dopamine, the principal central inhibitory signal in prolactin release, may exert its inhibitory effects by stimulation of nitric oxide production. However, the effects of dopaminergic modulation on nitric oxide-producing pituitary cells have not been analysed. Therefore, we examined the effects of intraventricular administration of the dopamine antagonist haloperidol (40 microg) on the pituitary expression of neuronal nitric oxide synthase (nNOS) in male adult rats. In untreated and control animals, nNOS-positive cells were very similar. Two types of nNOS-positive cells appeared in the pars distalis: round or polygonal cells and stellate cells. Although some isolated cells were found, the nNOS-positive cells commonly appeared grouped in clusters close to blood vessels. nNOS immunoreactivity appeared as a uniform staining throughout the cytoplasm, including cell prolongations. The number and size of nNOS-expressing cells in the pituitary gland decreased significantly after treatment with haloperidol (p<0.01). To evaluate the potential direct effect of dopamine on pituitary cells, pituitary monolayer cultures were treated with dopamine during a time-course of 12 h. Our in vitro studies revealed that dopamine increases the percentage of nNOS-positive cells and augments cellular area (p<0.05). These results demonstrate that: (1) treatment of rats in vivo with a dopamine antagonist significantly decreases expression of nNOS in the pituitary and (2) in vitro dopamine exerts a direct effect on pituitary cultures by increasing nNOS-positive cells. Thus, these findings suggest that dopamine may function as a physiological stimulator of nNOS expression in the rat pituitary gland.

Animals↗
PubMed2003

Postnatal differentiation of the immunohistochemical expression of aromatase P450 in the rat pituitary gland.

At our laboratory, we have recently demonstrated the immunohistochemical expression of aromatase P450 in the pituitary glands of adult rats; this expression was seen to be sex-dependent. In order to determine whether the changes in the expression of the enzyme are related to changes in the gonadal sphere and whether the expression of the enzyme is related to the postnatal differentiation of hypophyseal cytology, in the present work we performed an immunohistochemical study in the rat pituitary gland from birth to old age. The immunohistochemical reaction to aromatase was evident and very generalized at 7 days after birth, with no large differences between the male and female animals. At 14 days the immunohistochemical reaction was decreased in the females, with no changes in the males. At 17 days, aromatase immunoreactivity in the pituitary glands of female rats was very weak whereas the males showed large numbers of reactive cells. These observations were further pronounced at 21 days and 2 months of life. At 24 months, the immunoreactivity found in the pituitary glands of the male rats had almost completely disappeared. Our results show that a postnatal differentiation in the immunohistochemical expression of aromatase occurs; this is tightly linked to sexual activity and is lost in old age. This suggests that hypophyseal aromatase would be related to the mechanisms of action of gonadal steroids on hypophyseal differentiation and secretion.

Animals↗
PubMed2002

Assessment of ozone variations and meteorological effects in an urban area in the Mediterranean Coast.

Ozone concentrations are valuable indicators of possible health and environmental impacts. However, they are also used to monitor changes and trends in the sources of both ozone and its precursors. For this purpose, the influence of meteorological variables is a confusing factor. This study presents an analysis of a year of ozone concentrations measured in a coastal Spanish city. Firstly, the aim of this study was to perceive the daily, monthly and seasonal variation patterns of ozone concentrations. Diurnal cycles are presented by season and the fit of the data to a normal distribution is tested. In order to assess ozone behaviour under temperate weather conditions, local meteorological variables (wind direction and speed, temperature, relative humidity, pressure and rainfall) were monitored together with ozone concentrations. The main relationships we could observe in these analyses were then used to obtain a regression equation linking diurnal ozone concentrations in summer with meteorological parameters.

Cities↗
PubMed2001

Glutamine potentiates TNF-alpha-induced tumor cytotoxicity.

L-glutamine (Gln) sensitizes tumor cells to tumor necrosis factor (TNF)-alpha-induced cytotoxicity. The type and mechanism of cell death induced by TNF-alpha was studied in Ehrlich ascites tumor (EAT)-bearing mice fed a Gln-enriched diet (GED; where 30% of the total dietary nitrogen was from Gln). A high rate of Gln oxidation promotes a selective depletion of mitochondrial glutathione (mtGSH) content to approximately 58% of the level found in tumor mitochondria of mice fed a nutritionally complete elemental diet (standard diet, SD). The mechanism of mtGSH depletion involves a glutamate-induced inhibition of GSH transport from the cytosol into mitochondria. The increase in reactive oxygen intermediates (ROIs) production induced by TNF-alpha further depletes mtGSH to approximately 35% of control values, which associates with a decrease in the mitochondrial transmembrane potential (MMP), and elicits mitochondrial membrane permeabilization and release of cytochrome c. Mitochondrial membrane permeabilization was also found in intact tumor cells cultured with a Gln-enriched medium under conditions of buthionine sulfoximine (BSO)-induced selective GSH synthesis inhibition. Enforced expression of the bcl-2 gene in tumor cells could not avoid the glutamine- and TNF-alpha-induced cell death under conditions of mtGSH depletion. However, addition of GSH ester, which delivers free intracellular GSH and increases mtGSH levels, preserved cell viability. These findings show that glutamine oxidation and TNF-alpha, by causing a change in the glutathione redox status within tumor mitochondria, activates the molecular mechanism of apoptotic cell death.

Adenosine Triphosphate↗
PubMed2001

Tumoricidal activity of endothelial cells. Inhibition of endothelial nitric oxide production abrogates tumor cytotoxicity induced by hepatic sinusoidal endothelium in response to B16 melanoma adhesion in vitro.

The mechanism of NO- and H(2)O(2)-induced tumor cytotoxicity was examined during B16 melanoma (B16M) adhesion to the hepatic sinusoidal endothelium (HSE) in vitro. We used endothelial nitric-oxide synthetase gene disruption and N(G)-nitro-l-arginine methyl ester-induced inhibition of nitric-oxide synthetase activity to study the effect of HSE-derived NO on B16M cell viability. Extracellular H(2)O(2) was removed by exogenous catalase. H(2)O(2) was not cytotoxic in the absence of NO. However, NO-induced tumor cytotoxicity was increased by H(2)O(2) due to the formation of potent oxidants, likely ( small middle dot)OH and (-)OONO radicals, via a trace metal-dependent process. B16M cells cultured to low density (LD cells), with high GSH content, were more resistant to NO and H(2)O(2) than B16M cells cultured to high density (HD cells; with approximately 25% of the GSH content found in LD cells). Resistance of LD cells decreased using buthionine sulfoximine, a specific GSH synthesis inhibitor, whereas resistance increased in HD cells using GSH ester, which delivers free intracellular GSH. Because NO and H(2)O(2) were particularly cytotoxic in HD cells, we investigated the enzyme activities that degrade H(2)O(2). NO and H(2)O(2) caused an approximately 75% (LD cells) and a 60% (HD cells) decrease in catalase activity without affecting the GSH peroxidase/GSH reductase system. Therefore, B16M resistance to the HSE-induced cytotoxicity appears highly dependent on GSH and GSH peroxidase, which are both required to eliminate H(2)O(2). In agreement with this fact, ebselen, a GSH peroxidase mimic, abrogated the increase in NO toxicity induced by H(2)O(2).

Cell Communication↗
PubMed2001

Gross-alpha and gross-beta activities in airborne particulate samples. Analysis and prediction models.

Measurements of gross-alpha and gross-beta activities were made every week during the years 1992-1997 for airborne particulate samples collected using air filters at a clear site. The data are sufficiently numerous to allow the examination of variations in time and by these measurements to establish several features that should be important in understanding any trends of atmospheric radioactivity. Two models were used to predict the gross-alpha and gross-beta activities. A good agreement between the results of these models and the measurements was highlighted.

Air↗
PubMed2001

Characterization of GFAP expression and cell proliferation in the rat median eminence following hypophysectomy.

To analyze whether the reorganization of the rat median eminence after hypophysectomy might be related to changes in glial fibrillary acidic protein (GFAP)- and cellular proliferation, the distribution of cells immunoreactive for GFAP and the proliferation rate of such cells were analyzed at 20, 40 and 60 days posthypophysectomy. For this study, four rostro-caudal regions of the median eminence were differentiated: the retrochiasmatic, preinfundibular, infundibular and postinfundibular regions. In each of these regions, three layers were studied: the ependymal, the internal and the external. At 20 and 40 days after hypophysectomy, significant increases in cellular proliferation affecting all three layers studied in the preinfundibular and infundibular regions were found. At the same time points, increases in GFAP expression were also observed. However, after 60 days, GFAP and proliferative cellular nuclear antigen (PCNA) expression decreased. Although variations of PCNA and GFAP levels were evident, no colocalisation of PCNA and GFAP was found in the cells of the median eminence in untreated or hypophysectomized rats when sections were analyzed by double immunohistochemical staining. Our results suggest that reorganization of median eminence involves alterations (or modulation) of GFAP-immunoreactive cells together with a proliferation of cells that are not GFAP-immunoreactive. This study also demonstrates that this reorganization is completed within the first two months after hypophysectomy.

Animals↗
PubMed2001

Possible mechanisms for tumour cell sensitivity to TNF-alpha and potential therapeutic applications.

TNF is a macrophage/monocyte-derived cytokine with cytostatic and cytotoxic anti-tumour activity. TNF-alpha can cause haemorrhagic necrosis and regression of experimental tumours. Nevertheless, the TNF-alpha doses required to cure tumour-bearing mice lead to injury of normal tissues and, eventually, may cause a lethal shock syndrome. This toxicity implies severe limitations for the therapeutic use of TNF-alpha. Reactive oxygen intermediates (ROls) are involved in TNF-alpha-induced cell killing. Different studies are consistent with the hypothesis that tumour cell sensitivity to TNF-alpha is related to its capacity to buffer oxidative attack. Recently, we have demonstrated that the sensitivity of Ehrlich ascites tumor (EAT) cells to TNF depends on their glutathione (GSH, the most prevalent nonprotein thiol in mammalian cells) content and their rate of proliferation. This is important because tumour cell populations under active proliferative states may show higher GSH levels, and drug- and/or radiation-resistant tumours have increased cellular levels of GSH. TNF-alpha induces a shift towards oxidation in the mitochondrial glutathione (mtGSH) status, a fact that is consistent with the hypothesis that mtGSH plays a key role in scavenging TNF-induced ROIs. GSH, which is not synthesized within mitochondria but is neccessary for their normal function, needs to be taken up from the cytosol through a high affinity multicomponent transport system. In consequence, different approaches that lead to depletion of mtGSH may improve the anticancer efficacy of TNF-alpha both in vitro and in vivo. As an example, EAT-bearing mice fed a glutamine-enriched diet (GED) show a selective increase of glutamate content witihin the tumour cells. Glutamate inhibits GSH uptake by tumour mitochondria and leads to a selective depletion of mtGSH content (not found in mitochondria of normal cells) to approx. 57% of the level found in tumour mitochondria of mice fed a standard diet (SD). Administration of rhTNF-alpha, which increases generation of mitochondrial ROIs, to EAT-bearing mice fed a SD does not affect significantly the rate of tumour growth. However, when tumour-bearing mice fed a GED where treated with rhTNF-alpha the number of viable tumour cells was decreased to approx. 38% of controls.

Animals↗
PubMed2000

Mitochondrial glutathione depletion by glutamine in growing tumor cells.

The effect of L-glutamine (Gln) on mitochondrial glutathione (mtGSH) levels in tumor cells was studied in vivo in Ehrlich ascites tumor (EAT)-bearing mice. Tumor growth was similar in mice fed a Gln-enriched diet (GED; where 30% of the total dietary nitrogen was from Gln) or a nutritionally complete elemental diet (SD). As compared with non-tumor-bearing mice, tumor growth caused a decrease of blood Gln levels in mice fed an SD but not in those fed a GED. Tumor cells in mice fed a GED showed higher glutaminase and lower Gln synthetase activities than did cells isolated from mice fed an SD. Cytosolic glutamate concentration was 2-fold higher in tumor cells from mice fed a GED ( approximately 4 mM) than in those fed an SD. This increase in glutamate content inhibited GSH uptake by tumor mitochondria and led to a selective depletion of mitochondrial GSH (mtGSH) content (not found in mitochondria of normal cells such as lymphocytes or hepatocytes) to approximately 57% of the level found in tumor mitochondria of mice fed an SD. In tumor cells of mice fed a GED, 6-diazo-5-norleucine- or L-glutamate-gamma-hydrazine-induced inhibition of glutaminase activity decreased cytosolic glutamate content and restored GSH uptake by mitochondria to the rate found in EAT cells of mice fed an SD. The partial loss of mtGSH elicited by Gln did not affect generation of reactive oxygen intermediates (ROIs) or mitochondrial functions (e.g., intracellular peroxide levels, O(2)(-)(*) generation, mitochondrial membrane potential, mitochondrial size, adenosine triphosphate and adenosine diphosphate contents, and oxygen consumption were found similar in tumor cells isolated from mice fed an SD or a GED); however, mitochondrial production ROIs upon TNF-alpha stimulation was increased. Our results demonstrate that glutamate derived from glutamine promotes an inhibition of GSH transport into mitochondria, which may render tumor cells more susceptible to oxidative stress-induced mediators.

Adenosine Triphosphate↗
PubMed2000

[Death caused by designer drugs].

OBJECTIVE: To draw pediatrician's attention to the risks of the use of designer drugs among adolescents and to review the problem. MATERIAL AND METHODS: We report the case of a 15-year-old girl admitted for seizures, who rapidly developed acute liver failure and died. Clinical and pathological details are reviewed. COMMENT: The use of designer drugs has increased considerably amongst Spanish adolescents and has been related to deaths in young adults with a variety of symptoms. Differential diagnosis should be made with the adverse effects of recreational drugs when clinical symptoms are confusing and in any unexplained deaths. Information on the effects of designer drugs should be disseminated among the population.

Acute Disease↗
PubMed1999

Swim stress enhances the NADPH-diaphorase histochemical staining in the paraventricular nucleus of the hypothalamus.

Regulatory control of the hypothalamic-pituitary-adrenocortical axis (HPA) originates principally from the paraventricular nucleus (PVN), which contains an important population of nitric oxide synthesizing (NOS) neurons. In the present study, the effect of swim stress upon these neurons was investigated by means of the NADPH-diaphorase (ND) histochemical technique. A significant increase in the number of ND-neurons was observed following forced swim, especially after 30 min. These data confirm the involvement of NOS-neurons of the PVN in the response to different types of acute stressors.

Animals↗
PubMed1999

Immunohistochemical evidence of the presence of aromatase P450 in the rat hypophysis.

In order to analyze whether aromatase is present in the hypophysis of adult rats, we have performed an immunohistochemical study in young adult male and female rats. Our study has revealed that the hypophysis of adult rats contains aromatase, although marked differences are found between the sexes. The hypophyses of male rats have cells immunoreactive for the enzyme, 34.40% of these hypophyseal cells showing reaction. By contrast, cells from female rats show very little reaction, only 0.84% of them being reactive. No significant differences in the percentage of immunoreactive cells between one phase and another are observed during the estrous cycle. Our results point to the immunohistochemical expression of aromatase in the hypophysis of adult rats and at the same time suggest that its expression is sex-dependent. The enzyme may therefore be involved in the regulation of adenohypophyseal cytology by androgens.

Amino Acid Sequence↗
PubMed1999

Changes in glutathione status and the antioxidant system in blood and in cancer cells associate with tumour growth in vivo.

The relationship among cancer growth, the glutathione redox cycle and the antioxidant system was studied in blood and in tumour cells. During cancer growth, the glutathione redox status (GSH/GSSG) decreases in blood of Ehrlich ascites tumour-bearing mice. This effect is mainly due to an increase in GSSG levels. Two reasons may explain the increase in blood GSSG: (a) the increase in peroxide production by the tumour that, in addition to changes affecting the glutathione-related and the antioxidant enzyme activities, can lead to GSH oxidation within the red blood cells; and (b) an increase of GSSG release from different tissues into the blood. GSH and peroxide levels are higher in the tumour cells when they proliferate actively, however GSSG levels remain constant during tumour growth in mice. These changes associate with low levels of lipid peroxidation in plasma, blood and the tumour cells. The GSH/GSSG ratio in blood also decreases in patients bearing breast or colon cancers and, as it occurs in tumour-bearing mice, this change associates with higher GSSG levels, especially in advanced stages of cancer progression. Our results indicate that determination of glutathione status and oxidative stress-related parameters in blood may help to orientate cancer therapy in humans.

Animals↗