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Biomedical subjects

M Portolés

Publications and source records attributed to M Portolés.

At least 19 recordsLinked to original sources
PubMed2002

Ethanol impairs monosaccharide uptake and glycosylation in cultured rat astrocytes.

Astrocyte and glial-neuron interactions have a critical role in brain development, which is partially mediated by glycoproteins, including adhesion molecules and growth factors. Ethanol affects the synthesis, intracellular transport, subcellular distribution and secretion of these glycoproteins, suggesting alterations in glycosylation. We analyzed the effect of long-term exposure to low doses of ethanol (30 mm) on glycosylation process in growing cultured astrocytes in vitro. Cells were incubated for short (5 min) and long (90 min) periods with several radioactively labeled carbohydrate precursors. The uptake, kinetics and metabolism of these precursors, as well as the radioactivity distribution in protein gels were analyzed. The levels of GLUT1 and mannosidase II were also determined. Ethanol increased the uptake of monosaccharides and the protein levels of GLUT1 but decreased those of mannosidase II. It altered the carbohydrate moiety of proteins and increased cell surface glycoproteins containing terminal non-reduced mannose. These results indicate that ethanol impairs glycosylation in rat astrocytes, thus disrupting brain development.

Animals↗
PubMed2001

[Troponine T as possible myocardial injury marker. Its application in myocardial stunning and silent ischemia].

INTRODUCTION AND OBJECTIVES: The need for more specific, more sensitive and earlier biochemical markers of acute myocardial infarction, has led to the development of alternative methods to CK-MB). The aim of this work is to assess the usefulness of TnT measurement, in comparison with other markers for detecting transitory ischemic processes without necrosis in some experimental models. METHODS: The plasma levels of Troponine T, CK, CK-MB and adenosine were assessed as markers of ischemic myocardial injury. Two protocols were used: in Series I and II very brief (2 min ischemia with 3-min reperfusion) repeated (20 episodes) ischemias were induced, while Series III involved a single 15-min ischemia with a 60-min reperfusion. In Series I the coronary occlusor was placed close to the anterior descending coronary artery (AD); in Series II and III it was placed distally in the AD. Blood samples were taken from the peripheral vein (PVB) and corresponding coronary segment vein; in a basal situation, during ischemia, upon reperfusion, after 24 hours, and after 5 and 10 days. The plasma levels of adenosine, troponine T, CK and CK-MB as well as general and regional function parameters were measured. RESULTS: In Series I we observed hypokinesis that lasted 10 days, reaching its maximum on days 4-5. In Series II and III regional function was restored by 24 hours. CK and CK-MB showed similar behaviour; they rose significantly when the chest was opened (p < 0.05) reaching the highest value at 24 hours in all the series. Adenosine rose significantly only during reperfusion (p < 0.05). Troponine T increased after ischemia but not before, remained high for 5 days in all series (PVB). CONCLUSIONS: Troponine T rises in absence of necrosis, preferably when the ischemia is longer.

Adenosine↗
PubMed2001

Staphylococcus aureus Cap5O has UDP-ManNAc dehydrogenase activity and is essential for capsule expression.

The Staphylococcus aureus serotype 5 capsular polysaccharide (CP5) has a repeating unit composed of (-->4)-3-O-acetyl-beta-D-ManNAcA-(1-->4)-alpha-L-FucNAc (1-->3)-beta-D-FucNAc-(1-->)(n). Sixteen chromosomal genes (cap5A through cap5P) are involved in the synthesis of CP5. We recently demonstrated that Cap5P, a 2-epimerase, catalyzes the conversion of UDP-N-acetyl glucosamine (UDP-GlcNAc) to UDP-N-acetylmannosamine (UDP-ManNAc). In this study, we show that UDP-ManNAc is oxidized to UDP-N-acetylmannosaminuronic acid (UDP-ManNAcA) by a UDP-ManNAc dehydrogenase encoded by S. aureus cap5O. We expressed Cap5O in Escherichia coli and purified the recombinant protein. The UDP-ManNAc dehydrogenase activity of purified Cap5O was assessed by incubating Cap5P and UDP-GlcNAc (to produce UDP-ManNAc), together with Cap5O, NAD(+), and a reducing agent. Enzymatic activity was quantitated indirectly by measuring the increase in absorbance at 340 nm resulting from NADH formation. The product of the reaction was confirmed as UDP-ManNAcA by gas chromatography-mass spectroscopy. A cap5O mutation, created by deletion of 727 bp in the 5' end of the gene, was introduced by allelic replacement into S. aureus Reynolds, rendering it CP5 negative. Mice inoculated intravenously or subcutaneously with the wild-type strain Reynolds had greater numbers of S. aureus recovered from their kidneys (P = 0.019) or their subcutaneous abscesses (P = 0.0018), respectively, than did animals inoculated with the cap5O mutant. The results of this study indicate that S. aureus cap5O is essential for capsule production and that capsule promotes staphylococcal virulence in mouse models of abscess formation.

Animals↗
PubMed1995

Effect of poloxamer 407 on the adherence of Pseudomonas aeruginosa to corneal epithelial cells.

The effect of poloxamer 407 on Pseudomonas aeruginosa adherence to cultured epithelial cells from rabbit corneas was investigated. Three methods of bacterial quantification were used to assess P. aeruginosa adherence: scanning electron microscopy (SEM) counts, radioactivity counts, and viable bacteria counts. Confluent monolayers of rabbit corneal epithelial cells were incubated in agitation for 30 min at room temperature with H3-labeled or nonradiolabeled P. aeruginosa (10(10) bacteria/ml) in a solution of poloxamer 407 [2% or 4% in phosphate-buffered saline (PBS)] or PBS as control. Cell monolayers were washed to remove nonadherent bacteria and fixed with 2.5% glutaraldehyde and processed for SEM or processed for radioactivity counting or for culture on agar plates. The results showed that both solutions of poloxamer 407 inhibited approximately 75% of the bacterial adherence to epithelial cells (p < 0.05). Similar percentages of bacterial inhibition were obtained using the three methods of bacterial quantification. The use of an antiadherent agent such as poloxamer 407 in eye drops could possibly be a prophylactic approach to P. aeruginosa keratitis.

Animals↗
PubMed1994

Poloxamer 407 as a bacterial adhesive for hydrogel contact lenses.

Bacterial adherence and colonization of biomedical prosthetic implants is one of the main causes for implant withdrawal. The abhesive (anti-adhesive) effect of poloxamer 407 on several Gram-positive and Gram-negative strains and the site of action of its effect have been investigated. Poloxamer 407 significantly inhibited 92-99% of Pseudomonas aeruginosa adherence to hydrophilic contact lenses (P < .05). This adherence inhibition was concentration-dependent. A reduction of about 50-60% was obtained for Staphylococcus strains, and 50-70% for Gram-negative strains other than Pseudomonas. The poloxamer seems to act on the bacteria surface, but not on the contact lens surface. Poloxamer 407 could potentially prevent implant-related infections and keratitis associated with contact lens wear, by inhibiting bacterial adherence onto the implant or contact lens surface.

Bacterial Adhesion↗
PubMed1994

Nuclear calmodulin/62 kDa calmodulin-binding protein complexes in interphasic and mitotic cells.

We report here that a 62 kDa calmodulin-binding protein (p62), recently identified in the nucleus of rat hepatocytes, neurons and glial cells, consists of four polypeptides showing pI values between 5.9 and 6.1. By using a DNA-binding overlay assay we found that the two most basic of the p62 polypeptides bind both single- and double-stranded DNA. The intranuclear distribution of calmodulin and p62 was analysed in hepatocytes and astrocyte precursor cells, and in proliferating and differentiated astrocytes in primary cultures by immunogold-labeling methods. In non-dividing cells nuclear calmodulin was mostly localized in heterochromatin although it was also present in euchromatin and nucleoli. A similar pattern was observed for p62, with the difference that it was not located in nucleoli. p62/calmodulin complexes, mainly located over heterochromatin domains were also observed in interphasic cells. These complexes remained associated with the nuclear matrix after in situ sequential extraction with nucleases and high-salt containing buffers. In dividing cells, both calmodulin and p62 were found distributed over all the mitotic chromosomes but the p62/calmodulin aggregates were disrupted. These results suggest a role for calmodulin and p62 in the condensation of the chromatin.

Animals↗
PubMed1993

Reduced bacterial adhesion to heparin-surface-modified intraocular lenses.

Bacterial adherence to intraocular lenses (IOLs) could be the cause of endophthalmitis following cataract surgery and lens implantation. There are previous reports that heparin bound to the surface of poly(methyl methacrylate) (PMMA) IOLs reduces cell adhesion. In this study, the in vitro adherence of Staphylococcus epidermidis, Staphylococcus aureus, and Pseudomonas aeruginosa to regular PMMA IOLs and to heparin-surface-modified (HSM) PMMA IOLs was investigated. The three bacterial strains attached in significantly lower numbers to HSM-PMMA IOLs than to PMMA IOLs (P < .01). Heparin in solution also inhibited attachment of Staphylococcus epidermidis to regular PMMA IOLs. Heparin may reduce adherence by placing a highly hydrated layer between the bacteria and the IOL surface. Therefore, the use of HSM-PMMA IOLs could diminish the incidence of endophthalmitis.

Bacterial Adhesion↗
PubMed1990

In vitro toxicity of lomefloxacin in rabbit corneal epithelial cell cultures.

Lomefloxacin (NY-198) is a chemotherapic agent from the new 4-quinolone group, acting on DNA gyrase system. Lomefloxacin (LFLX), as some other new 4-quinolone compounds are antimicrobials of potential use for ophthalmic application. A first approach on the oculotoxicity of LFLX is the main purpose of this study. Four concentrations of LFLX (10, 30, 100 and 300 micrograms/ml) were tested on the first subculture of pigmented rabbit corneal epithelial cells. Cell number, protein contents, neutral red stain and wound healing were evaluated. The results showed that the lower concentrations (10 & 30 micrograms/ml) had no effect while the highest one had a remarkable cytotoxic effect. Pharmacokinetic data show that peak values achieved in the cornea and other ocular structures are lower than 40 micrograms/g (0.3% topical application) and, on another hand, MIC values range from less than or equal to 0.05 to 16 micrograms/ml. So, these "critical" concentrations have no cytotoxic effects according to our results. Then, it is concluded that Lomefloxacin could be a useful drug for topical ophthalmic development.

4-Quinolones↗
PubMed1989

Effect of caffeine on urea biosynthesis and some related processes, ketone bodies, ATP and liver amino acids.

An increase in urea synthesis has been found in rats administered large doses of caffeine. A parallel increase in urea biosynthesis was also found in hepatocytes isolated from caffeine-treated rats, which confirms a greater capacity for urea synthesis induced by caffeine. This increase appeared only after some days of caffeine treatment; during the first days there was no increase in serum urea levels or in in vitro studies of urea synthesis in isolated hepatocytes. However, no appreciable changes were found in either cytosolic or mitochondrial redox states, or in ATP levels in in vivo and in vitro studies. A parallelism was observed between the decreased amino acid levels in caffeine-treated rats and in isolated hepatocytes incubated with different concentrations of caffeine. Several possible mechanisms to explain these findings are considered in the discussion.

Adenosine Triphosphate↗
PubMed1989

Free amino acids in preterm and term milk from mothers delivering appropriate- or small-for-gestational-age infants.

Free amino acids were quantitated in human milk collected during the first month postpartum from mothers of appropriate preterm (26-32 and 33-36 wk gestation) and term (small or appropriate-for-gestational-age) infants. Glutamic acid and taurine were the most abundant amino acids in all four groups at all stages of lactation. The ratio of essential to nonessential amino acids was higher in colostrum than in mature milk although the total amino acid level of mature milk was double that of the colostrum. Nonprotein amino acids amount to approximately 40% of the free-amino acid pool in colostrum. Differences in the content and changes in free-amino acid levels during lactation among the groups were observed.

Adult↗
PubMed1988

Effect of streptozotocin-diabetes on rat liver mitochondrial adenosine triphosphatase turnover.

The apparent turnover rates of some mitochondrial enzymes can be modified in diabetes. We studied the effect of streptozotocin-diabetes on the half-life of a protein tightly bound to the inner membrane, ATPase. The half-life (t 1/2), measured by the double-isotope technique, decreased by approx. 20% in diabetes (from approximately equal to 2.56 days in controls to approximately equal to 2.06 days in diabetic rats). These results suggest that diabetes produces an increase in degradation of ATPase by a mechanism which is not yet clear, possibly influenced by alterations induced by diabetes in hepatic lysosomes that are associated with hepatic autophagy.

Adenosine Triphosphatases↗
PubMed1988

Effects of inhibition of ornithine aminotransferase or of general aminotransferases on urea and citrulline synthesis and on the levels of acetylglutamate in isolated rat hepatocytes.

Canaline and gabaculine, inhibitors of gamma-aminotransferases and thus of ornithine aminotransferase (E.C. 2.6.1.13), decreased the flow through ornithine carbamoyl transferase (E.C. 2.1.3.3) in isolated rat hepatocytes incubated with 10 mM NH4Cl and ornithine. The levels of acetylglutamate, an essential activator of carbamoyl phosphate synthetase (ammonia) (E.C. 6.3.4.16), were also decreased, suggesting that the inhibitors had also caused a decrease in the rate of carbamoyl phosphate synthesis. Under these conditions, ornithine appears to be a precursor of acetylglutamate, via ornithine aminotransferase, possibly as a consequence of glutamate synthesis. The influence of aminooxyacetate, an aminotransferase inhibitor, has also been examined.

Aminobutyrates↗
PubMed1988

Long-term high-protein diet induces biochemical and ultrastructural changes in rat liver mitochondria.

We have shown in previous work that long-term high-protein diet treatment (420 days) induces important biochemical and stereological changes in rat liver mitochondria. In this paper we have studied the time course for these changes in rats fed a high-protein diet for 30, 90, 180, and 420 days. The liver carbamoyl-phosphate synthetase I (ammonia), which represents 15-20% of the mitochondrial protein, increased ca. 2.5-fold in 30 days, with no further significant changes during the treatment. This increase was accompanied by an increment in the serum urea levels and a diminution in the half-life of blood urea, which could be interpreted as compensatory mechanisms for detoxification of blood and for maintaining osmotic pressure. The stereological study indicates that there is an enlargement of individual mitochondria in rats fed the high-protein diet, and that the maximum enlargement occurred at 90 days of treatment. The analysis of data shows, however, that the increase in mitochondrial volume density was due mainly to proliferation of normal mitochondria. These mitochondria were functionally normal as demonstrated by the unaltered P:O ratio during treatment. The total content of liver amino acids was increased, and the taurine/glycine ratio (which has been related to metabolic stress) was greatly increased. The possible correlation between the increases of both liver taurine levels and cell volume is discussed.

Amino Acids↗
PubMed1988

In vitro effect of caffeine on some aspects of nitrogen metabolism in isolated rat hepatocytes.

Long-term exposure to high doses of caffeine affects several aspects of nitrogen metabolism, such as purine, pyrimidine and urea synthesis. However, little is known about the mechanisms of these changes and if they occur at shorter term. We have studied in isolated hepatocytes: 1) the in vitro effect of high doses of caffeine on amino acid levels, 2) the main destination of ammonia and carbon chains from amino acid catabolism, and 3) the cytosolic and mitochondrial redox states. We have found that, whereas it has a small effect on urea synthesis and on the levels of the cofactors and intermediates, it decreases the levels of several amino acids, the gluconeogenesis and the redox state. Our results suggest that a longer exposure to caffeine is necessary to affect the normal functions of some metabolic pathways.

Amino Acids↗
PubMed1988

Thyroid hormone levels in rats exposed to alcohol during development.

Maternal ingestion of alcohol appears to cause a pattern of congenital anomalies with a reduction of pre- and postnatal growth in the offspring. In order to study the possible implication of thyroid function in the effects of pre- and/or postnatal exposure to alcohol, we have studied serum thyroxine (T4) and triiodothyronine (T3) levels in rats from alcohol-fed mothers during the postnatal period (0-50 days). Blood alcohol levels of ethanol-treated pregnant rats were approximately equal to 20-25 mM and their serum T4 levels were decreased, compared with the pair-fed controls, at 15 and 21 days of gestation. No significant changes were observed in T3 levels. Prenatal alcohol exposure was associated with a decrease in both T4 and T3 levels in pups at birth. Although T4 levels continued reduced in the 40-50 days of the postnatal period, no clear effects were observed on T3 levels during this time. Moreover, the more marked alterations were obtained when the offspring were postnatally and pre + postnatally exposed to alcohol. Significant decreases were found in both T4 and T3 levels following postnatal exposure, except at the 20-25th day when a marked but transient increase in T4 levels was observed. These results indicate that alcohol exposure disturbs the hypothalamo-pituitary-thyroid axis, as measured by T3 and T4 hormone levels, mainly when the rats are exposed during the postnatal period.

Aging↗
PubMed1988

A Golgi and electron microscope study of the ventral septum in the reptile, Podarcis hispánica.

The ventral septum of the reptile Podarcis hispánica has been studied using cytoarchitectonical and Golgi methods as well as electron microscopy techniques. The ventral septum is located in the medial wall of the telencephalon, just ventral to the dorsal septum. 2 different cell masses or nuclei can be easily appreciated in this structure: the Ventro-lateral Nucleus, located close to the ventricle, and the Ventro-medial Nucleus, located close to the medial hemispheric wall. Using Golgi methods, 3 classes of neurons have been distinguished: Big Polymorphic (BP) neurons, Small Polymorphic (SP) neurons and Horizontal (H) neurons. BP neurons are located within Ventro-medial Nucleus and they are characterized by a large dendritic 3 with numerous dendritic spines (50 spines per 100 microns). SP neurons are located within Ventro-lateral Nucleus and they are characterized by a small dendritic tree which is covered by numerous dendritic spines (48 spines per 100 microns). H neurons are located around both nuclei and they are characterized by a linear dendritic tree and a low number of dendritic spines. Using E.M. techniques 3 classes of neuronal cell bodies can be distinguished: big neuronal somata, small neuronal somata and spindle-like neuronal somata Big somata are located within Ventro-medial Nucleus. Small somata are located within Ventro-lateral Nucleus. Spindle-like somata are located either close to the lateral ventricle or close to the medial hemispheric wall. We have identified 4 different types of synaptic endings in the neuropil, depending on the vesicle morphology: A) endings with slightly pleomorphic vesicles; B) endings with big round vesicles; C) endings with dense core vesicles and D) endings with small round vesicles.

Animals↗