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Biomedical subjects

A Fernández

Publications and source records attributed to A Fernández.

At least 19 recordsLinked to original sources
PubMed1995

Inhibition and ADP-ribose pyrophosphatase-I by nitric-oxide-generating systems: a mechanism linking nitric oxide to processes dependent on free ADP-ribose.

Rat liver ADP-ribose pyrophosphatase-I (ADPRibase-I; EC 3.6.1.13) hydrolyzes ADP-ribose with high specificity and a low Km. Thus it can participate in the control of free ADP-ribose and nonenzymatic ADP-ribosylation of proteins. Here we show that ADPRibase-I was inactivated by acidified nitrite, whereas sodium nitroprusside (SNP) or 3-morpholinosydnonimine (SIN-1) at pH 7.5 produced a dose- and time-dependent Km increase from 0.5 microM to 2 microM. The effects of SNP and SIN-1 depended on the presence and concentration of dithiothreitol, pointing to S-nitrosylation of enzyme thiols. It is suggested that, by inhibiting ADPRibase-I, NO can stimulate nonenzymatic ADP-ribosylation of targets susceptible to micromolar free ADP-ribose. This is discussed in relation to apparently contradictory earlier reports on the role of NO in the ADP-ribosylation of actin.

Adenosine Diphosphate Ribose↗
PubMed1995

RNA helicase activity of the plum pox potyvirus CI protein expressed in Escherichia coli. Mapping of an RNA binding domain.

The plum pox potyvirus (PPV) cylindrical inclusion (CI) protein fused to the maltose binding protein (MBP) has been synthesized in Escherichia coli and purified by affinity chromatography in amylose resin. In the absence of any other viral factors, the fusion product had NTPase, RNA binding and RNA helicase activities. These in vitro activities were not affected by removal of the last 103 amino acids of the CI protein. However, other deletions in the C-terminal part of the protein, although leaving intact all the region conserved in RNA helicases, drastically impaired the ability to unwind dsRNA and to hydrolyze NTPs. A mutant protein lacking the last 225 residues retained the competence to interact with RNA. Further deletions mapped boundaries of the RNA binding domain within residues 350 and 402 of the PPV CI protein. This region includes the arginine-rich motif VI, the most carboxy terminal conserved domain of RNA helicases of the superfamily SF2. These results indicate that NTP hydrolysis is not an essential component for RNA binding of the PPV CI protein.

ATP-Binding Cassette Transporters↗
PubMed1995

Rat liver nucleoside diphosphosugar or diphosphoalcohol pyrophosphatases different from nucleotide pyrophosphatase or phosphodiesterase I: substrate specificities of Mg(2+)-and/or Mn(2+)-dependent hydrolases acting on ADP-ribose.

Three rat liver nucleotides(5') diphosphosugar (NDP-sugar) or nucleoside(5') diphosphoalcohol pyrophosphatases are described: two were previously identified in experiments measuring Mg(2+)-dependent ADP-ribose pyrophosphatase activity (Miró et al. (1989) FEBS Lett. 244, 123-126), and the other is a new, Mn(2+)-dependent ADP-ribose pyrophosphatase. They are resolved by ion-exchange chromatography, and differ by their substrate and cation specificities, KM values for ADP-ribose, pH-activity profiles, molecular weights and isoelectric points. The enzymes were tested for activity towards: reducing (ADP-ribose, IDP-ribose) and non-reducing NDP-sugars (ADP-glucose, ADP-mannose, GDP-mannose, UDP-mannose, UDP-glucose, UDP-xylose, CDP-glucose), CDP-alcohols (CDP-glycerol, CDP-ethanolamine, CDP-choline), dinucleotides (diadenosine pyrophosphate, NADH, NAD+, FAD), nucleoside(5') mono- and diphosphates (AMP, CMP, GMP, ADP, CDP) and dTMP p-nitrophenyl ester. Since the enzymes have not been purified to homogeneity, more than three pyrophosphatases may be present, but the co-purification of activities, thermal co-inactivation, and inhibition experiments give support to: (i) and ADP-ribose pyrophosphatase highly specific for ADP(IDP)-ribose in the presence of Mg2+, but active also on non-reducing ADP-hexoses and dinucleotides (not on NAD+) when Mg2+ was replaced with Mn2+; (ii) a Mn(2+)-dependent pyrophosphatase active on ADP(IDP)-ribose, dinucleotides and CDP-alcohols; (iii) a rather unspecific pyrophosphatase that, with Mg2+, was active on AMP(IMP)-containing NDP-sugars and dinucleotides (not on NAD+), and with Mn2+, was also active on non-adenine NDP-sugars and CDP-alcohols. The enzymes differ from nucleotide pyrophosphatase/phosphodiesterase-I (NPPase/PDEaseI) by their substrate specificities and by their cytosolic location and solubility in the absence of detergents. Although NPPase/PDEaseI is much more active in rat liver, its known location in the non-cytoplasmic sides of plasma and endoplasmic reticulum membranes, together with the known cytoplasmic synthesis of NDP-sugars and CDP-alcohols, permit the speculation that the pyrophosphatases studied in this work may have a cellular role.

Animals↗
PubMed1995

Changes in the prothrombin time, haematology and serum proteins during experimental aflatoxicosis in hens and broiler chickens.

Two groups of 32 laying hens and two groups of 32, 23-day-old broiler chickens were given 2.5 and 5 mg kg-1 of aflatoxin in their diet for four, eight, 16 and 32 days; 16 hens and 32 broiler chicks served as control groups. In the laying hens, aflatoxicosis was characterised mainly by an increase in prothrombin time, and decreases in total plasma proteins and albumin levels; there were increases in red blood cell (RBC) counts and haematocrit which were greater in the group fed 5 mg kg-1. There was a decrease in beta-globulins and an increase in gamma-globulins. In the broiler chickens, there was only a slight increase in prothrombin time and a decrease in RBC counts. This data proves the good sensitivity and utility of prothrombin time values as an indicator of aflatoxicosis in birds.

Aflatoxins↗
PubMed1995

Effect of ethanol treatment on rate and equilibrium constants for [3H] muscimol binding to rat brain membranes: alteration of two affinity states of the GABAA receptor.

Equilibrium binding curves were biphasic in control and ethanol-treated rats. [3H]Muscimol binds to sites of high (KDA of approximately 10 nM) and low (KDB of approximately 0.3-0.4 microM) affinity. Chronic ethanol treatment produced a decrease in BmaxA value, and the hyperbolic binding profiles were progressively affected by the chronic and in vitro ethanol treatments, with most of this effect corresponding to the high-affinity site. IC50 and Ki values were calculated for several competing ligands, using membranes from both control and ethanol-treated animals. The association and dissociation curves were also biphasic, using a radioligand concentration precluding a significant occupancy of the low-affinity sites, which suggests the existence of two forms or affinity states of the monoliganded receptor. Chronic ethanol treatment did not produce changes in the values of the dissociation rate constants (fast and slow phases). By contrast, we report for the first time a decrease in the values of the association rate constants, with this decrease being higher for the slow phase. Consequently, the dissociation equilibrium constants are two times higher in chronically ethanol-treated animals for both phases.

Animals↗
PubMed1995

[New etiopathogenic, diagnostic and therapeutic aspects in primary pulmonary hypertension].

Primary Pulmonary Hypertension (PPH) is a rare disease of unknown aetiology that is diagnosed only when the underlying causing factors are undetermined. Usually is discovered in its late stage, when pulmonary vascular resistances are severely compromised and the pathologic changes already well developed, resulting in right heart failure and death within several years of the onset of symptoms. The data published in the last years have provided new insights into the disease knowledge. In this article currents concepts about aetiology, pathogenesis and open lung biopsy value are reviewed; clinical manifestations and diagnostic methods are described; the usefulness of medical treatment to improve quality of life in these patients, mainly anticoagulation and vasodilator therapy with high-dose nifedipine, and how lung transplantation has increasingly become an option for selected patients with PPH, is also analysed.

Anticoagulants↗
PubMed1995

Changes in the coagulation profile of lambs intoxicated with aflatoxin in their feed.

Twenty-three male lambs were intoxicated with 2.5 ppm aflatoxins in their feed for a period of 3 weeks. Thirteen lambs were maintained as a control group (0 ppm aflatoxins in their feed). The coagulation profiles were determined from blood samples that were obtained at 0, 7, 14 and 21 d during the intoxication period and at 1, 2, 4 and 8 d of an 8-d clearance period. Aflatoxicosis in the animals was characterized by an increase in prothrombin time (P < 0.01) from d 14 of the intoxication period until the end of the experiment. An increase (P < 0.05) in fibrinogen concentration was detected beginning on d 21, instead of the expected decrease. This was probably due to the inflammation found in the lungs of the intoxicated animals. No difference in activated partial thromboplastin time was found between intoxicated and control animals. These results suggest that there was a significant change in some coagulation factors of the extrinsic pathway in the intoxicated lambs and that prothrombin time determination could be used as an indicator of aflatoxicosis in lambs.

Aflatoxins↗
PubMed1995

Synthesis and analgesic activity of 2-amino-5-tert-butyl-2-oxazoline.

2-Amino-5-tert-butyl-2-oxazoline (ATBO, 2) was synthetized from 3,3-dimethyl-2-iodobutyl isocyanate via N-(3,3-dimethyl-2-iodobutyl) urea (1). The structures of compounds 1 and 2 are based on analytical and spectroscopic data. Compound 2 induced in rats and mice a peripheral antinociceptive effect through both spinal and supraspinal mechanisms. ATBO did not impair motor coordination or activity of the experimental animals.

Acetates↗
PubMed1994

Polyarthritis in kids associated with Mycoplasma putrefaciens.

Fifteen two- to three-week-old kids, fed artificially with goats' milk from a dairy, were found to have polyarthritis. The most affected joints were the carpals, either unilaterally or bilaterally, and in some cases the tarsal joints. Mycoplasma putrefaciens was isolated from the joints which showed an acute fibrinopurulent arthritis. No clinical mastitis was detected in the dairy.

Animals↗
PubMed1994

Stress localization in the RNA backbone: a mechanical footprint for predicting base-backbone tertiary contacts.

A physico-chemical basis to understand the site-specificity of intramolecular nucleophilic attack in RNA self-splicing involves the identification of vulnerable backbone regions in addition to determining the proper placement of attacking groups. In preliminary relevant work we have introduced the decisive concept of structure-induced localized absorption of stress by backbone degrees of freedom. In this way we implemented a mechanical approach which incorporates the consensus structural information as a constraint and correctly identifies reactive sites as strain hot spots. In this work we turn this approach into a predictive tool to search for structural constraints which are necessary to localize strain at pre-determined splicing and cyclization sites. In particular, we identify tertiary base backbone contacts regarding them as appropriate constraints to the backbone mechanics. To implement our approach we introduce an effective Hamiltonian which governs the exploration of backbone conformation space by energetically penalizing structural distortions. We show how this Hamiltonian singles out specific regions of stress associated with reactive sites. As an illustration, we apply this working principle to a specific ribozyme, the cobI5 intron, for which the tertiary interactions predicted to be functional in 3' splicing have not been previously determined experimentally. To establish the predictive value of our approach, we identify the tertiary contacts that should be present in the cobI5 intron to serve as scaffolds stabilizing the conserved P10 secondary interaction and to introduce ribose conformational rigidity necessary to localize strain precisely at the 3' splicing site. Guided by our computations, the purported interactions are confirmed using deoxyribose substitution probes.

Animals↗
PubMed1994

Role of GABAA and GABAB receptors and peripheral cholinergic mechanisms in the antinociceptive action of taurine.

1. Gabaergic and cholinergic mediation in the antinociceptive effect of taurine has been investigated in mice (acetic acid test) and rats (tail-flick test). 2. Scopolamine sulfate and methylnitrate exhibit intrinsic antinociceptive activity and increase the effect of taurine in mice. 3. Baclofen also increases the antinociceptive effect of taurine in mice. 4. Anticholinergic agents and bicuculline but not CGP 35348 antagonize the effect of taurine in rats. 5. These results suggest that the antinociceptive effect of taurine may be partly mediated by spinal GABAA receptors and peripheral cholinergic mechanisms.

Analgesics↗
PubMed1994

Combined therapy for angioimmunoproliferative lesions.

43 patients with a diagnosis of angioimmunoproliferative lesions (AIL) entered onto a prospective clinical trial to evaluate the use of combined therapy as a primary therapeutic approach. Patients were treated initially with involved field radiotherapy 40-55 Gy (40 patients received 45 Gy) followed by six cycles of chemotherapy which consisted of CEOP-Bleo (cyclophosphamide, epirubin, vincristine, prednisone and bleomycin). Complete response was achieved in 41 cases (95%). At a median follow-up of 40 months, 40 patients (91%) remain in first complete remission. 2 patients died during radiotherapy secondary to sepsis and tumour progression. Treatment was well tolerated. The treatment of AIL remains controversial. Our results show that combined therapy appears to be the best therapeutic approach in patients with this type of malignant lymphoma. More studies are necessary to define the role of combined therapy in patients with AIL.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Measurement of the serum tumor marker neuron-specific enolase in patients with benign pulmonary diseases.

Serum concentrations of neuron-specific enolase (NSE) were measured in 135 patients with benign pulmonary diseases who also underwent a clinical, laboratory, and radiologic evaluation. Eleven percent of the patients as a whole and 27.3% of those who were tuberculous had abnormal serum levels of NSE. Significant differences in NSE levels were observed among the six diagnostic groups evaluated (p = 0.002). Males had higher levels than females (p = 0.003), and patients infected with the human immunodeficiency virus (HIV) had higher NSE levels than those not infected (p = 0.0026). Patients with alveolar infiltrates or an interstitial pattern on chest X-ray had higher NSE levels than those with normal radiographs (p = 0.003 and p = 0.01, respectively). In fact, only 3.6% of the patients with normal radiographs had above-normal levels of NSE. Direct damage to the neural or neuroendocrine lung cells or some degree of local hypoxia is likely to play a role in the increase in NSE in these patients. The small number and degree of abnormal values of NSE observed in this study make it unlikely that an underlying benign lung disease will substantially modify the interpretation of an increased NSE value in patients with lung cancer. However, care should be taken in interpreting a moderately abnormal NSE value in the cancer patient in the presence of lung infiltrates such as obstructive pneumonitis.

Acquired Immunodeficiency Syndrome↗