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Biomedical subjects

R Alonso

Publications and source records attributed to R Alonso.

At least 145 records · Page 8Linked to original sources
PubMed1995

[Assessment of the sensitivity to antifungal agents of clinical isolates of Candida albicans serotype A and B by the ATB Fungus method].

BACKGROUND: Candida albicans is the most frequently species isolated in patients with candidiasis. This species may be antigenically divided in serotypes A and B, which have a different pathogenic behavior and antifungal susceptibility pattern. METHODS: The antifungal susceptibility of 443 clinical isolates from both serotypes of C. albicans to 5-fluorocytosine (5FC), amphotericin B, nystatin, econazole, miconazole and ketoconazole has been tested by means of the ATB Fungus method. RESULTS: Both serotypes showed a similar in vitro susceptibility to amphotericin B, nystatin, econazole, miconazole and ketoconazole. All the isolates were susceptible to amphotericin B and nystatin. A small number of in vitro resistant isolates were observed to azole compounds. However, serotype B was significantly more resistant than serotype A (p = 0.0001) to 5FC. CONCLUSIONS: C. albicans serotype B shows a lower susceptibility than serotype A to 5FC, an antifungal product not marketed in Spain. Serotyping of C. albicans does not offer additional information on antifungal susceptibility of clinical isolates from this species.

Antifungal Agents↗
PubMed1994

Tyrosine hydroxylase activity in peripherally denervated rat pineal gland.

The presence of tyrosine hydroxylase (TH) in the rat pineal gland was studied using a combination of immunochemical and biochemical methods. In superior cervical ganglionectomized (SCGx) animals and in isolated pineals incubated for 72 h, both TH immunoreactive (TH-IR) fibers and TH biochemical activity were still present but reduced. Conversely, in dispersed pinealocytes incubated for only 24 h we were unable to detect either TH activity or TH-positive cells. Since in the pineal gland of intact rats total 3-methoxy-4-hydroxy phenylglycol (MHPG) was undetectable, and only traces of norepinephrine (NE) were present in the pineal of ganglionectomized animals, the results suggest a central pinealopetal catecholaminergic pathway which could use dopamine as a neurotransmitter.

Animals↗
PubMed1994

Excitatory and inhibitory amino acids in the cerebral cortex of nucleus basalis magnocellularis lesioned rats.

It is well known that pathways arising from the nucleus basalis magnocellularis in the basal forebrain which terminate in the cerebral cortex are involved in cognitive function. The cholinergic system is generally thought to play a large part in these processes from lesion, pharmacological and transplantation studies. With increasing evidence suggesting the involvement of amino acid transmitters in learning and memory processes, it is of interest to also evaluate possible changes in the levels of amino acid transmitters in the cortex of nucleus basalis magnocellularis-lesioned rats. In the present study, 9 cortical amino acids were measured in rats with bilateral lesions of the nucleus basalis magnocellularis. We measured significant reductions in aspartate, alanine and gamma-aminobutyric acid; these were 80%, 75%, and 81%, respectively, of control brain values. These results suggest that changes in the amino acid content of the cerebral cortex following lesion of the nucleus basalis magnocellularis-lesioned rat should perhaps also be considered when evaluating behavioral effects in this model.

Amino Acids↗
PubMed1994

Statin, a marker of cell cycle arrest, is overexpressed during the early phase of delayed NMDA toxicity in hippocampal cell cultures.

Statin is a 57-kDa protein exclusively expressed in nuclei of nonproliferating mammalian cells. Recent studies have suggested that statin may play a role in the maintenance of growth arrest. Several lines of evidence also support the notion that a variety of genes and gene products are modulated during cell proliferation and cell death. The present study examined the possibility that statin expression could be modulated during neuronal injury using N-methyl-Daspartate (NMDA)-induced toxicity to rat embryonic hippocampal cultures as a model. Immunocytochemical studies using a monoclonal antibody to statin revealed a prominent nuclear localization of statin in cultured hippocampal cells. Western blot analysis showed that this antibody recognizes a 57-kDa protein band, indicative of the presence of statin in this preparation. Brief exposure of hippocampal neurons to NMDA (500 microM) produced severe neuronal degeneration over the subsequent hours. NMDA-treated neurons markedly overexpressed statin. Both NMDA-induced neuronal toxicity and statin overexpression were prevented by the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohept-5,10-imine hydrogen maleate (MK-801). Interestingly, time course studies indicate that the increased expression of statin observed following NMDA exposure clearly preceded the appearance of the first signs of neuronal death as determined by vital staining. In addition, exposure of hippocampal neurons to the Ca2+ ionophore, A23187, produced a marked increase in statin immunodetection, indicating that statin expression is likely regulated in a Ca(2+)-dependent manner. Thus, these results show that statin, which is expressed at low levels in embryonic rat cultured hippocampal neurons, is rapidly overexpressed following a toxic insult produced by the activation of the NMDA receptor. The observation that statin overexpression occurs prior to neuronal death raises the possibility that the up-regulation of statin could be used as an early index of neuronal injury.

Animals↗
PubMed1994

In vitro activity of biapenem against beta-lactamase producing Enterobacteriaceae.

The activity of biapenem was compared with that of imipenem and cefotaxime against 108 strains of beta-lactamase producing Enterobacteriaceae. Biapenem and imipenem were very active, inhibiting 90% of the strains at a concentration of 0.5 microgram/ml. Both carbapenems were very active against plasmidic beta-lactamase producers, with MIC90s below 1 microgram/ml. However, the MIC90 of biapenem for cephalosporinase producers was 1 microgram/ml. Against strains producing extended-spectrum beta-lactamases, biapenem exhibited better activity against TEM-type producers (MIC90 0.25 microgram/ml) than against SHV-type producers (MIC90 0.5 microgram/ml). Overall, the in vitro antibacterial activity of biapenem is similar to that of imipenem.

Cefotaxime↗
PubMed1994

Platelet-activating factor mediates pancreatic function derangement in caerulein-induced pancreatitis in rats.

1. We have assessed the role of platelet-activating factor in caerulein-induced acute pancreatitis (four subcutaneous injections of caerulein at a dose of 20 micrograms/kg) by measuring platelet-activating factor levels in portal blood, pancreatic tissue and peritoneal exudate in rats with and without pancreatitis. 2. We have also observed the effect of the platelet-activating factor antagonist, BN-52021, on the hyperamylasaemia and exocrine pancreatic secretion impairment associated with pancreatitis. 3. In rats with pancreatitis the basal pancreatic flow rate was increased (1.63 +/- 0.41 versus 0.25 +/- 0.03 microliters/min). Total protein output was similar in both untreated (5.98 +/- 1.93 micrograms/min) and caerulein-injected (6.5 +/- 2.0 micrograms/min) animals. Amylase output was lower in rats with pancreatitis (19.6 +/- 4.8 mu-units/min) than in controls (39.4 +/- 16.6 mu-units/min). 4. Caerulein-treated animals had significantly higher serum amylase levels than untreated animals. BN-52021 significantly reduced the caerulein-induced hyperamylasaemia. 5. Portal blood platelet-activating factor levels increased in rats with pancreatitis and in rats infused with cholecystokinin. Rats injected with caerulein and BN-52021 had portal blood levels of platelet-activating factor that were lower than those with pancreatitis. 6. Morphological derangements associated with pancreatitis (inflammatory infiltration and cell vacuolization) were also markedly reduced in BN-52021-treated animals. 7. The results of this study suggest that platelet-activating factor is involved in the development of caerulein-induced acute pancreatitis in rats.

Acute Disease↗
PubMed1994

In-vitro synergy between aminoglycosides deployed against Staphylococcus spp. harbouring a 6'-aminoglycoside acetyltransferase, 2"-aminoglycoside phosphotransferase enzyme.

In-vitro synergistic effects between commercial aminoglycosides are described for gentamicin resistant Staphylococcus strains harbouring 6'-aminoglycoside acetyltransferase activity. Seventy eight strains were studied using the double-disc test and synergy was observed with combinations in which at least one of the components has a garosamine-like 6'-aminosugar. These results were confirmed in chequerboard titrations (sigma FIC < or = 0.5) carried out on Staphylococcus epidermidis strains RYC13036 and RYC4904. Additionally, a clear reduction in tobramycin acetylating activity was observed in the presence of gentamicin or netilmicin in crude extracts of these strains. These experiments suggest that the observed synergy is due to inhibition of the aminoglycoside-modifying enzyme by aminoglycosides with a garosamine like 6'-aminosugar component.

Acetyltransferases↗
PubMed1994

Periovulatory LHRH, LH and FSH secretion in cyclic rats treated with RU486: effects of exogenous LHRH and LHRH antagonist on LH and FSH secretion at early oestrus.

The antiprogesterone RU486 injected on the morning of pro-oestrus blunts the preovulatory secretion of LH and FSH and abolishes the secondary secretion of FSH during oestrus without affecting ovulation in the rat. To ascertain whether the secretion of LHRH is involved in these effects, we studied the effects of RU486 (4 mg/0.2 ml oil), given s.c. at 0800 h on pro-oestrus, on LHRH secretion into the pituitary stalk blood vessels and on peripheral plasma concentrations of LH and FSH at 1800 h on pro-oestrus and 0200 h on oestrus. Furthermore, we determined the effects of an s.c. injection of 1 mg of an LHRH antagonist (LHRH-A; ORG30276) at 2000 h on pro-oestrus and those of an i.p. injection of 100 ng LHRH (Peninsula 7201) at 0100 h on oestrus on serum concentrations of LH, FSH and oestradiol at 0200 h on oestrus in oil- and RU486-treated rats. RU486 decreased LHRH secretion at 1800 h on pro-oestrus while this was increased at 0200 h on oestrus. While the reduction of preovulatory LHRH secretion in RU486-treated rats coincided with a reduction in both LH and FSH surges during the evening of pro-oestrus, the increased LHRH secretion during the early hours of oestrus was only accompanied by an increased concentration of LH. An injection of LHRH stimulated, while that of LHRH-A inhibited serum concentrations of LH at 0200 h on oestrus in both oil- and RU486-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Subtyping of Salmonella enteritidis using a new phage typing protocol].

BACKGROUND: Salmonella enteritidis isolates have increased since 1982 from 20% to more than 70% in 1992 in Spain. Currently available phenotypic subtyping methods have a low discriminatory power. In order to improve the phage-typing discriminatory power of Alonso's method, new bacteriophages have been developed. METHODS: Wild bacteriophages were isolated from different waste waters. Lysogenic bacteriophages were induced with mitomycin C. RESULTS: We selected 7 wild and 2 lysogenic bacteriophages, considering their stability, reproducibility and discriminatory power. Ten phage-types were also described. CONCLUSIONS: Using Simpson's index of diversity, the proposed scheme is more discriminatory power than Alonso's previously described one. It is necessary to compare it with other subtyping methods, like new molecular methods, before establishing its usefulness as a complementary marker.

Bacteriophage Typing↗
PubMed1993

Progesterone does not mediate the inhibition of pineal melatonin production during the rat proestrous night.

N-Acetyltransferase (NAT) activity and melatonin content were determined in pineal glands obtained during the proestrous stage of the rat estrous cycle. In control animals, both pineal NAT activity and melatonin levels were reduced during the first hours of proestrous night, as compared with day-time proestrous levels. The administration of antiprogestagen RU486, in a dose which blocked the preovulatory rise of serum luteinizing hormone and follicle-stimulating hormone levels, failed to prevent the reduction of pineal melatonin synthesis associated with the ovulatory events at proestrous night. These results suggest that estradiol, but not progesterone, might be the ovarian hormone responsible for the inhibition of pineal melatonin synthesis observed in the normal cycling female rat during proestrous night.

Acetyltransferases↗
PubMed1993

Muscarinic potentiation of excitatory amino acid-evoked dopamine release in mesencephalic cells: specificity for the NMDA response and role of intracellular messengers.

Of the five cloned muscarinic receptor subtypes, dopamine (DA) neurons in the substantia nigra and ventral tegmental areas have been shown to be selectively enriched with the mRNA for the m5 subtype, suggesting that muscarinic modulation of DA neurons may have a distinct pharmacology. In the present study we have used dissociated cell cultures of fetal rat ventral mesencephalon to characterize muscarinic modulation of DA neurons. [3H]DA release stimulated by activation of N-methyl-D-aspartate (NMDA) receptors was potentiated by carbachol, a mixed muscarinic-nicotinic agonist, and by oxotremorine-M, a muscarinic agonist. Neither carbachol nor oxotremorine-M had an effect on [3H]DA release evoked by the non-NMDA agonists, kainate or quisqualate. A nicotinic agonist, DMPP, had no effect on NMDA-stimulated release. Potentiation of NMDA-stimulated [3H]DA release by oxotremorine-M was inhibited by the broad spectrum muscarinic antagonist, QNB, and by low concentrations of a putative M1 antagonist, pirenzepine, while much higher concentrations of a purported M2 antagonist, AF-DX 384, were required to reverse the oxotremorine-M effect. The muscarinic antagonist, 4-DAMP, was active in a concentration range between that required for pirenzepine and AF-DX 384. Further experiments examined intracellular messenger mechanisms coupled to the muscarinic receptors modulating NMDA-stimulated [3H]DA release. In contrast to oxotremorine-M, two muscarinic agents with only weak partial agonism with respect to phosphoinositide turnover, pilocarpine and arecoline, had no effect on NMDA-stimulated [3H]DA release.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗
PubMed1993

Comparison of serotype, biotype and bacteriocin type with rDNA RFLP patterns for the type identification of Serratia marcescens.

Variations in rDNA gene loci in DNA digests of 209 clinical isolates of Serratia marcescens were determined with an Escherichia coli rRNA probe. Forty-one restriction fragment length polymorphism patterns (ribotypes) were identified, based on the size of 4-14 (mean 7.5) hybridization bands. The patterns differed by more than a single band in 98% of pair-wise comparisons. On a subset of 76 isolates, ribotyping proved to be marginally more discriminating than biotyping (discrimination index 0.92 v. 0.89) followed by serotyping (0.87) and bacteriocin typing (0.74). About one-third of isolates belonged to unique ribotypes and only two ribotypes exceeded 5% in frequency (23.0 and 6.4% respectively). A combination of serotype or biotype with ribotyping defined a similar number of strains, although none of the methods alone was sufficiently discriminatory to identify strains. We conclude that due to the accessibility of biotyping and the lack of commercially available antisera for S. marcescens, the biotype and ribotype together provide reliable markers of strain identity.

Bacterial Typing Techniques↗