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J M Alonso

Publications and source records attributed to J M Alonso.

At least 55 records · Page 3Linked to original sources
PubMed2000

Involvement of NRAMP1 from Arabidopsis thaliana in iron transport.

Nramp genes code for a widely distributed class of proteins involved in a variety of processes, ranging from the control of susceptibility to bacterial infection in mammalian cells and taste behaviour in Drosophila to manganese uptake in yeast. Some of the NRAMP proteins in mammals and in yeast are capable of transporting metal ions, including iron. In plants, iron transport was shown to require a reduction/Fe(II) transport system. In Arabidopsis thaliana this process involves the IRT1 and Fro2 genes. Here we report the sequence of five NRAMP proteins from A. thaliana. Sequence comparison suggests that there are two classes of NRAMP proteins in plants: A. thaliana (At) NRAMP1 and Oriza sativa (Os) NRAMP1 and 3 (two rice isologues) represent one class, and AtNRAMP2-5 and OsNRAMP2 the other. AtNramp1 and OsNramp1 are able to complement the fet3fet4 yeast mutant defective both in low- and high-affinity iron transports, whereas AtNramp2 and OsNramp2 fail to do so. In addition, AtNramp1 transcript, but not AtNramp2 transcript, accumulates in response to iron deficiency in roots but not in leaves. Finally, overexpression of AtNramp1 in transgenic A. thaliana plants leads to an increase in plant resistance to toxic iron concentration. Taken together, these results demonstrate that AtNramp1 participates in the control of iron homoeostasis in plants.

Amino Acid Sequence↗
PubMed2000

Changes of acetylcholinesterase activity in brain areas and liver of sucrose- and ethanol-fed rats.

The effects of chronic ethanol or sucrose administration to rats on acetylcholinesterase from brain and liver were investigated. Membrane-bound and soluble acetylcholinesterase activities were determined in fractions prepared by centrifugation. The thermal stability and the effects of temperature and different types of alcohols on acetylcholinesterase activity were also studied. Membrane-bound acetylcholinesterase activity increased (p < 0.01) in the liver after chronic ethanol administration, whereas no differences among groups in the encephalic areas, except in the brain stem soluble form, were found. Membrane-bound acetylcholinesterase from the ethanol- and sucrose-treated groups was more stable at the different temperatures assayed between 10 and 50 degrees C than that corresponding to the control group. Non-linear Arrhenius plots were obtained with preparations of membrane-bound acetylcholinesterase from rat liver, with discontinuities at 30 degrees C (control or sucrose groups) or 34-35 degrees C (alcohol group). Assays made with membrane-bound or soluble enzyme from brain showed linear Arrhenius plots in all groups studied. The inhibitory effects of increasing concentrations of ethanol, n-propanol and n-butanol on acetylcholinesterase preparations from forebrain, cerebellum, brain stem and liver of the three experimental groups (control, sucrose-fed and ethanol-fed) were very similar. However, n-butanol displayed a biphasic action on particulate or soluble preparations of rat forebrain. n-butanol inhibited (competitive inhibition) at higher concentrations (250-500 mM), while at lower concentrations (10-25 mM), the alcohol inhibited at low substrate concentrations but activated at high substrate concentration. These results suggest that the liver is more affected by ethanol than the brain. Moreover, the lipid composition of membranes is probably modified by ethanol or sucrose ingestion and this would affect membrane fluidity and consequently the behaviour of acetylcholinesterase.

1-Butanol↗
PubMed2000

O-glycans as a source of cross-reactivity in determinations of human serum antibodies to Anisakis simplex antigens.

BACKGROUND: Anisakis simplex is a seafood-borne parasite that may both infect humans and cause allergy. Serodiagnosis of anisakiasis and allergy caused by this nematode is difficult since most Anisakis antigens show cross-reactivity problems. OBJECTIVE: To analyse the possible role of sugar epitopes contained in Anisakis simplex antigens as causes of false-positive results in serodiagnostic assays. METHODS: The antigens UA2R and UA3R recognized by two anti-Anisakis monoclonal antibodies were used in this study. Capture ELISA techniques were used to compare the reactivities with native or O-deglycosylated antigens of sera from Anisakis-free children (most of them infected by several other parasites) and from Anisakis allergy patients. O-deglycosylation was done by mild alkali treatment with NaOH. SDS-PAGE and immunoblotting were used to characterize the effects of NaOH or N-glycanase F treatment on UA3R. RESULTS: Native UA2R was recognized by IgG1 and IgM antibodies in the sera of both Anisakis-free subjects and allergy patients. Native UA3R was recognized by most sera from allergy patients (92% considering immunoglobulin (Ig) G1, 100% considering IgE), but also by a significant proportion of sera from Anisakis-free subjects (36% considering IgG1, 14% considering IgE). O-deglycosylation of UA3R greatly improved specificity: none of the sera from Anisakis-free patients showed either IgG1 or IgE reactivity with O-deglycosylated UA3R, while the proportion of sera from allergy patients showing IgE reactivity with this antigen was practically unaffected. O-deglycosylation of UA2R did not improve the specificity of assays using this antigen. Our results also show that the protein core of glycoproteins may be altered by even very mild alkali treatment, depending on the nature of the protein. CONCLUSION: Native glycoproteins of A. simplex should not be used for diagnostic purposes. O-deglycosylated UA3R seems to be an excellent candidate for use as target antigen in the serodiagnosis of anisakiasis and A. simplex allergy.

Animals↗
PubMed2000

Ethylene captures a metal! Metal ions are involved in ethylene perception and signal transduction.

More than three decades ago, transition metal such as copper or zinc were postulated to be required for the ethylene perception. However, there was no direct evidence for this metal requirement until very recently. Two studies using Arabidopsis thaliana, one genetic and the other biochemical, have provided complementary evidence for the role of copper in ethylene perception, closing this argument. Additional evidence for the importance of the metal in the ethylene-signaling pathway came with the recent discovery that EIN2, a central signal transducer in the ethylene-signaling pathway, has significant homology to the Nramp divalent cation transporters. These studies suggest that metal metabolism may have a critical role not only in ethylene perception but also in ethylene signaling.

Arabidopsis↗
PubMed2000

ATP binding and ATPase activities associated with recombinant rabbit hemorrhagic disease virus 2C-like polypeptide.

The carboxy-terminal region of the rabbit hemorrhagic disease virus p37 polyprotein cleavage product has been expressed in Escherichia coli as a glutathione S-transferase (GST) fusion protein. The recombinant GST-Delta2C protein showed in vitro ATP-binding and ATPase activities. Site-directed mutagenesis studies of the conserved residues G(522) and T(529) in motif A, D(566) and E(567) in motif B, and K(600) in motif C were also performed. These results provide the first experimental characterization of a 2C-like ATPase activity in a member of the Caliciviridae.

Adenosine Triphosphatases↗
PubMed2000

Mutation analysis of the GDD sequence motif of a calicivirus RNA-dependent RNA polymerase.

The RNA-dependent RNA polymerase from rabbit hemorrhagic disease virus, a calicivirus, is known to have a conserved GDD amino acid motif and several additional regions of sequence homology with all types of polymerases. To test whether both aspartic acid residues are in fact involved in the catalytic activity and metal ion coordination of the enzyme, several defined mutations have been made in order to replace them by glutamate, asparagine, or glycine. All six mutant enzymes were produced in Escherichia coli, and their in vitro poly(U) polymerase activity was characterized. The results demonstrated that the first aspartate residue was absolutely required for enzyme function and that some flexibility existed with respect to the second, which could be replaced by glutamate.

Amino Acid Motifs↗
PubMed2000

[Value of antibiotype and bacteriocinotype for differentiating Shigella strains isolated in Argentina].

The aim of the present work was to analyse the phenotypical characteristics of Shigella strains in order to evaluate their possible utilisation as epidemiological markers. For one year, we studied 95 strains of Shigella obtained from stool specimens of patients with dysentery. Bacteria came from various health care centres in the states of Chaco and Corrientes (Argentina). Bacteria were identified by using classical biochemical methods. All strains were serotyped and susceptibility patterns were determined using thirteen antibiotics. Bacteriocin typing was determined by the sensitivity to piocins of Pseudomonas aeruginosa and to marcescins of Serratia marcescens. Colicin production in S. sonnei was also studied. Among all the strains examined, the most prevalent was Shigella flexneri (82%) followed by Shigella sonnei (18%). The most frequent serotype among S. flexneri was 2 (93%), followed by serotypes 6 (4%), 1 (1.5%), and 3 (1.5%). S. sonnei strains were classified in 7 antibiotypes, 6 piocin types, 3 marcescin types, and 4 colicin types. Strains of S. flexneri type 2 were divided among 14 antibiotypes, 4 piocin types and 2 marcescin types. Simpson's index of diversity was applied to evaluate the discriminatory power of studied typing methods, both alone and combined. Our results indicate that when taken independently, none of the evaluated typing methods had discriminative power, but when taken together, they may be successfully used for the epidemiological typing of Shigella strains.

Anti-Bacterial Agents↗
PubMed1999

EIN2, a bifunctional transducer of ethylene and stress responses in Arabidopsis.

Ethylene regulates plant growth, development, and responsiveness to a variety of stresses. Cloning of the Arabidopsis EIN2 gene identifies a central component of the ethylene signaling pathway. The amino-terminal integral membrane domain of EIN2 shows similarity to the disease-related Nramp family of metal-ion transporters. Expression of the EIN2 CEND is sufficient to constitutively activate ethylene responses and restores responsiveness to jasmonic acid and paraquat-induced oxygen radicals to mutant plants. EIN2 is thus recognized as a molecular link between previously distinct hormone response pathways. Plants may use a combinatorial mechanism for assessing various stresses by enlisting a common set of signaling molecules.

Amino Acid Sequence↗
PubMed1999

RESPONSIVE-TO-ANTAGONIST1, a Menkes/Wilson disease-related copper transporter, is required for ethylene signaling in Arabidopsis.

Ethylene is an important regulator of plant growth. We identified an Arabidopsis mutant, responsive-to-antagonist1 (ran1), that shows ethylene phenotypes in response to treatment with trans-cyclooctene, a potent receptor antagonist. Genetic epistasis studies revealed an early requirement for RAN1 in the ethylene pathway. RAN1 was cloned and found to encode a protein with similarity to copper-transporting P-type ATPases, including the human Menkes/Wilson proteins and yeast Ccc2p. Expression of RAN1 complemented the defects of a ccc2delta mutant, demonstrating its function as a copper transporter. Transgenic CaMV 35S::RAN1 plants showed constitutive expression of ethylene responses, due to cosuppression of RAN1. These results provide an in planta demonstration that ethylene signaling requires copper and reveal that RAN1 acts by delivering copper to create functional hormone receptors.

Alkenes↗
PubMed1999

Transjugular intrahepatic portosystemic shunt versus endoscopic sclerotherapy for the prevention of variceal rebleeding after recent variceal hemorrhage.

Variceal hemorrhage continues to be a major cause of morbidity and mortality in cirrhotic patients. Transjugular intrahepatic portosystemic shunt (TIPS) is gaining wide acceptance as a treatment for several complications of portal hypertension. The aim of the current randomized study was to compare the transjugular shunt and endoscopic sclerotherapy (ES) for the prevention of variceal rebleeding (VB) in cirrhotic patients. Forty-six consecutive cirrhotic patients with variceal bleeding were randomly allocated to receive either transjugular shunt (22 patients) or ES (24 patients) 24 hours after control of bleeding. VB (50% vs. 9%) and early (first 6 weeks) VB (33% vs. 5%) were significantly more frequent in sclerotherapy patients; the actuarial probability of being free of VB was higher in the shunt group (P <.002). Eight patients (33%) of the sclerotherapy group and 3 patients (15%) of the shunt group died; the actuarial probability of survival was higher for the shunted patients (P <.05); 6 patients in the sclerotherapy group and none in the shunt group died from VB (P <.05). No difference was found in the proportion of patients with clinically evident hepatic encephalopathy (HE). These results show that the transjugular shunt is more effective than sclerotherapy in the prevention of both early and long-term VB. Moreover, a significant improvement in survival was found in the shunt group.

Adolescent↗
PubMed1999

Mastitis caused by Mycoplasma mycoides subspecies mycoides (large colony type) in goat flocks in Spain.

We describe three different outbreaks of mastitis caused by M. mycoides subspecies mycoides LC type (Mmm LC) in three goat flocks from the Extremadura Region of south-west Spain. Thirty-two fast-growing isolates were obtained on Hayflick's and Friis's media with inhibitors from different specimens. All were identified as Mmm LC in spite of their cultural, biochemical and serological features.

Animals↗
PubMed1999

[Paracoccidioides brasiliensis infection in a subtropical region with important environmental changes].

Paracoccidioidomycosis is a systemic mycoses caused by Paracoccidioides brasiliensis, a dimorphic fungus that infects man through respiratory ducts. It has been accepted that its ecological niche is located in the soil and plants of subtropical forests of Latin America. The Province of Corrientes is located at the northeastern border of Argentina, in a subtropical area where important environmental modifications have been introduced in the last decade as consequence of damming the Paranà river at Yacyretà, one of the biggest hydroelectric dams in the world. Since there are no data on human infection provoqued by this fungal agent in Corrientes, the purpose of this study was to obtain information at present time about infection indexes and to assess if environmental changes introduced in the area could impact on the epidemiology of the disease. Skin tests with paracoccidioidin and histoplasmin were performed on 455 persons of both sexes, from 1 to 73 years of age, who live permanently in the area and voluntarily accepted to be included in the study. Both antigens were employed at the same time in order to evaluate crossed type reactions. Of the 455 persons, 52 (39 males-13 females) were reactive to paracoccidioidin (11.4%), with an increasing prevalence with age. According to previous data, these results would indicate an increase in the index of human infection by P. brasiliensis, and this may be related to the important changes in climatic and environmental conditions introduced in the area in the last years.

Adolescent↗
PubMed1999

[Ecological interactions among Yersinia in their common reservoir, the rodent].

Plague, due to Yersinia pestis, is still active in various foci in the Americas, in Africa and Asia, whereas it has been absent from Europe since the end of the 18th century, after having killed the two-thirds of the continent's inhabitants within four centuries. Various hypothesis have been proposed to attempt to explain the spontaneous "eradication" of plague from Europe, including the improvement of hygiene and habitat, changes in the rat population and cross-immunity induced by other infections, such as salmonellosis, leprosy and other yersiniosis. The only Yersinia currently isolated in Europe are the species genetically related to Y. pestis, Y. pseudotuberculosis and Y. enterocolitica, which are less virulent and mostly enteropathogenic. Y. pestis and Y. pseudotuberculosis have a DNA relatedness of 90%, whereas it is of only 60% with Y. enterocolitica. Y. pseudotuberculosis has been used as efficient vaccine against plague. Present world epidemiological data show that Y. enterocolitica is progressively replacing Y. pseudotuberculosis. Experimental infection by Y. enterocolitica, inducing a transitory and spontaneously cured infection in the immunocompetent host, only inducing opportunistic infections in the immunodeficient host, promotes efficient immunity against plague. Thus, it seems likely that the emergence of some variants of Yersinia, less virulent than Y. pestis, but able to induce a long-lasting protective immunity against plague, have contributed to its eradication by a silent enzootic infection among the wild reservoirs of rodents.

Animals↗
PubMed1998

Synaptic integration in striate cortical simple cells.

Simple cells in the visual cortex respond to the precise position of oriented contours (Hubel and Wiesel, 1962). This sensitivity reflects the structure of the simple receptive field, which exhibits two sorts of antagonism between on and off inputs. First, simple receptive fields are divided into adjacent on and off subregions; second, within each subregion, stimuli of the reverse contrast evoke responses of the opposite sign: push-pull (Hubel and Wiesel, 1962; Palmer and Davis, 1981; Jones and Palmer, 1987; Ferster, 1988). We have made whole-cell patch recordings from cat area 17 during visual stimulation to examine the generation and integration of excitation (push) and suppression (pull) in the simple receptive field. The temporal structure of the push reflected the pattern of thalamic inputs, as judged by comparing the intracellular cortical responses to extracellular recordings made in the lateral geniculate nucleus. Two mechanisms have been advanced to account for the pull-withdrawal of thalamic drive and active, intracortical inhibition (Hubel and Wiesel, 1962; Heggelund, 1968; Ferster, 1988). Our results suggest that intracortical inhibition is the dominant, and perhaps sole, mechanism of suppression. The inhibitory influences operated within a wide dynamic range. When inhibition was strong, the membrane conductance could be doubled or tripled. Furthermore, if a stimulus confined to one subregion was enlarged so that it extended into the next, the sign of response often changed from depolarizing to hyperpolarizing. In other instances, the inhibition modulated neuronal output subtly, by elevating spike threshold or altering firing rate at a given membrane voltage.

Action Potentials↗
PubMed1998

Ascending projections of simple and complex cells in layer 6 of the cat striate cortex.

Receptive field properties vary systematically across the different layers of the cat striate cortex. Understanding how these functional differences emerge requires a precise description of the interlaminar connections and the quality of information that they transmit. This study examines the contribution of the two physiological types of neuron in layer 6, simple and complex, to the cortical microcircuit. The approach was to make whole-cell recordings with dye-filled electrodes in vivo to correlate visual response property with intracortical projection pattern. The two simple cells we stained projected to layer 4, as previously reported (Gilbert and Wiesel, 1979; Martin and Whitteridge, 1984). Six of the eight complex cells that we labeled projected to the superficial layers, a pathway not previously described in the cat. The remaining two cells targeted the infragranular layers. Layer 4 is dominated by simple cells, whereas layers 5 and 2+3 are mainly composed of complex cells (Hubel and Wiesel, 1962; Gilbert, 1977). Hence, our results indicate that the ascending projections of simple cells in layer 6 target other simple cells. In parallel, the ascending projections of a population of complex cells in layer 6 favor other complex cells. Anatomical experiments in several species (Lund and Boothe,1975; Burkhalter,1989; Usrey and Fitzpatrick, 1996; Wiser and Callaway, 1996) had also demonstrated that layer 6 gives rise to two separate intracortical pathways. Pooling the results of these anatomical studies with our own suggests a common feature of the laminar organization: cells that project to different intracortical targets have distinct functional characteristics.

Action Potentials↗
PubMed1998

Genomic organization and promoter characterization of human CXCR4 gene.

CXCR4 is the receptor for the CXC chemokine SDF1 that has essential functions on embryo organogenesis, immunological functions and T lymphocyte trafficking. Recently, CXCR4 has drawn unexpected attention as it was recently identified as a co-factor required for entry of lymphotropic HIV isolates in CD4+ T lymphocytes. CXCR4 is the only SDF1 receptor identified so far. This suggests that CXCR4 expression is critical for the biological effects of SDF1. To investigate the mechanisms controlling both the constitutive and induced expression of CXCR4 receptors we have isolated and characterized the promoter region and determined the genomic structure of the human gene. The CXCR4 gene contains two exons separated by an intronic sequence. A 2.6 kb 5'-flanking region located upstream the CXCR4 open reading frame contains a TATA box and the transcription start site characteristic of a functional promoter. This region also contains putative consensus binding sequences for different transcription factors, some of them associated with the hemopoiesis and lymphocyte development.

Base Sequence↗