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Biomedical subjects

I Rubio

Publications and source records attributed to I Rubio.

At least 37 records · Page 2Linked to original sources
PubMed1999

Farnesylation of Ras is important for the interaction with phosphoinositide 3-kinase gamma.

The correct functioning of Ras proteins requires post-translational modification of the GTP hydrolases (GTPases). These modifications provide hydrophobic moieties that lead to the attachment of Ras to the inner side of the plasma membrane. In this study we investigated the role of Ras processing in the interaction with various putative Ras-effector proteins. We describe a specific, GTP-independent interaction between post-translationally modified Ha- and Ki-Ras4B and the G-protein responsive phosphoinositide 3-kinase p110gamma. Our data demonstrate that post-translational processing increases markedly the binding of Ras to p110gamma in vitro and in Sf9 cells, whereas the interaction with p110alpha is unaffected under the same conditions. Using in vitro farnesylated Ras, we show that farnesylation of Ras is sufficient to produce this effect. The complex of p110gamma and farnesylated RasGTP exhibits a reduced dissociation rate leading to the efficient shielding of the GTPase from GTPase activating protein (GAP) action. Moreover, Ras processing affects the dissociation rate of the RasGTP complex with the Ras binding domain (RBD) of Raf-1, indicating that processing induces alterations in the conformation of RasGTP. The results suggest a direct interaction between a moiety present only on fully processed or farnesylated Ras and the putative target protein p110gamma.

Animals↗
PubMed1999

Acute and nongenomic effects of testosterone on isolated and perfused rat heart.

Gonadal steroid hormones influence vascular tone and the development of hypertension. There are sex differences in the incidence of cardiovascular diseases, and great attention has been placed on the study of estrogen cardiovascular effects. However, there are only a few reports on the effects of testosterone on the vasculature. It is commonly accepted that the mechanism of the action of steroid hormones on target tissues is mediated through the binding of hormones to cytoplasmic or nuclear receptors. However, some studies indicate that steroid action can be extremely rapid and therefore unlikely to be through a genomic mechanism. The purpose of this study was to assess the effect of intravascularly confined testosterone on an isolated rat heart to demonstrate acute and possibly nongenomic effects of the steroid. Our results show that testosterone blocked the adenosine vasodilator effect and increased vascular resistance, even when its presence was restricted to the coronary vascular lumen. These effects were exerted rapidly and possibly through nongenomic mechanisms.

Adenosine↗
PubMed1999

Differential regulation of lipid and protein kinase activities of phosphoinositide 3-kinase gamma in vitro.

G protein sensitive phosphoinositide 3-kinase gamma (PI3Kgamma) has been characterised as a pleiotropic signalling protein expressing lipid kinase and protein kinase activities. Whereas the regulation of the lipid kinase activity has been investigated in detail, the regulatory features of PI3Kgamma protein kinase activity are unknown. Here we report that Gbetagamma subunits of heterotrimeric G proteins induce a biphasic response of PI3Kgamma autophosphorylation in vitro, which contrasts the regulatory effects of the G proteins on PI3Kgamma lipid kinase activity. In addition to autophosphorylation PI3Kgamma is able to catalyse transphosphorylation of the adapter protein p101 and the protein kinase MEK-1. In the presence of the p101, Gbetagamma affects PI3Kgamma protein kinase activities in a complex manner. In summary, the differential regulatory effects of heterotrimeric G proteins on PI3Kgamma lipid and protein kinase activities in vitro reflect the functional diversity of the enzyme observed in vivo.

GTP-Binding Protein beta Subunits↗
PubMed1998

Bifurcation of lipid and protein kinase signals of PI3Kgamma to the protein kinases PKB and MAPK.

Phosphoinositide 3-kinases (PI3Ks) activate protein kinase PKB (also termed Akt), and PI3Kgamma activated by heterotrimeric guanosine triphosphate-binding protein can stimulate mitogen-activated protein kinase (MAPK). Exchange of a putative lipid substrate-binding site generated PI3Kgamma proteins with altered or aborted lipid but retained protein kinase activity. Transiently expressed, PI3Kgamma hybrids exhibited wortmannin-sensitive activation of MAPK, whereas a catalytically inactive PI3Kgamma did not. Membrane-targeted PI3Kgamma constitutively produced phosphatidylinositol 3,4, 3,4,5-trisphosphate and activated PKB but not MAPK. Moreover, stimulation of MAPK in response to lysophosphatidic acid was blocked by catalytically inactive PI3Kgamma but not by hybrid PI3Kgammas. Thus, two major signals emerge from PI3Kgamma: phosphoinositides that target PKB and protein phosphorylation that activates MAPK.

Amino Acid Sequence↗
PubMed1997

Interaction of Ras with phosphoinositide 3-kinase gamma.

Phosphoinositide 3-kinase gamma (PI3Kgamma) can be activated in vitro by both alpha and betagamma subunits of heterotrimeric G-proteins and does not interact with p85, the regulatory subunit of PI3Kalpha. Here we demonstrate the binding of Ras to PI3Kgamma in vitro. An N-terminal region of PI3Kgamma was identified as a binding site for Ras. After co-expression with PI3Kgamma in COS-7 cells, Ras induced only a modest increase in PI3K activity compared with the stimulation of PI3Kalpha by Ras in the same cells.

Animals↗
PubMed1997

Synchronization of estrus and ovulation and associated endocrine changes in Bos indicus cows.

The effects of 4 estrus synchronization treatments on intervals to and synchrony of estrus and ovulation, on timing of the preovulatory LH surge and associated changes in plasma progesterone, LH, FSH, and 17beta-estradiol (E(2)) were investigated in 48 Bos indicus cows. Treatment 1 consisted of 2 injections of PGF(2alpha) 14 d apart (n = 12); Treatment 2 of a subcutaneous 3-mg norgestomet implant and an intramuscular injection of 3 mg of norgestomet and 5 mg estradiol valerate, with the implant removed 10 d later (n = 12; norgestomet-estradiol); Treatment 3 of norgestomet-estradiol, with a subcutaneous injection of PMSG given at time of implant removal (Day 10; n = 12); and Treatment 4 of norgestomet implant (as for Treatments 2 and 3) inserted for 10 d, with an intramuscular injection of PGF(2alpha) given at the time of implant removal (n = 12). The experiment was conducted in 2 replicates (24 cows/replicate, 6 cows/group). Estrus, ovulation and timing of the preovulatory surge of LH varied less in cows treated with norgestomet-estradiol and PMSG than in cows in Treatments 1 and 4 (P < 0.008). Treatment with PMSG reduced variation in ovulation times and timing of the LH surge in cows treated with norgestomet-estradiol (P < 0.02). Concentrations of E(2) were higher in cows in Treatments 2 and 3 on the final day of treatment and at about 6 h post ovulation compared with cows in Treatments 1 and 4 (P < 0.05). Different methods for synchronizing estrus did not alter sequential endocrine and behavioral changes in relation to the timing of the LH peak, and the results were consistent with current recommendations for insemination times in Bos taurus cattle.

Journal Article↗
PubMed1996

Predictive value of palpation per rectum for detection of the CL in Zebu cattle as evaluated by progesterone concentrations and ultrasonography.

The main objective of this study was to calculate the predictive value of the positive and negative diagnosis of the presence of a corpus luteum by palpation per rectum in Zebu cattle. Gyr breed (n = 16) heifers were palpated by a veterinarian every 3 d during March and April, and every 5 days during May. The presence or absence of a CL was recorded for 442 examinations. A blood sample was obtained after each examination, and a functional CL was considered to be present if plasma progesterone concentrations were above 1 ng/ml. Progesterone results were used as the reference to calculate the sensitivity and specificity of palpation per rectum for the diagnosis of a functional CL on different months. Predictive values for the positive and negative diagnoses were calculated using different hypothetical rates of the prevalence of CL. To evaluate the morphological basis of an erroneous diagnosis, ultrasonographic scanning of the ovaries was performed in 264 cases and the physical presence or absence of a CL was registered. The calculations were repeated using the ultrasonographic findings as the reference to evaluate the sensitivity and specificity of the diagnosis of a structural CL by per rectum palpation. Several heifers were not cyclic in March but began to cycle during the study. Thus, the prevalence of both functional and structural CL increased with time. As a result, the proportion of palpation diagnoses classified as true positives increased in May, while the proportion of true negatives decreased. Although the values of sensitivity and specificity remained constant from month to month, the predictive values changed markedly in May, when the predictive value of the positive test increased while the predictive value of the negative test decreased. These changes were due to differences in the prevalence of a CL and not to differences in the palpable characteristics of CLs in different months. The prevalence of a structural CL was always higher than that of a functional CL. The Cohen's Kappa test for concordance revealed better correspondence between palpation per rectum and ultrasound (k = 0.82) than between progesterone and either ultrasound (k = 0.68) or palpation (k = 0.66). These results show that a large proportion of the errors imputed to deficient palpation when progesterone concentrations are used as a reference are in fact the result of lack of correspondence between the physical and functional presence of a CL.

Journal Article↗
PubMed1996

Cerebral amyloid angiopathies.

The cerebral amyloid angiopathies comprise a heterogeneous group of disorders that are characterized clinically by ischaemic and/or haemorrhagic strokes, and histologically by deposition of amyloid in the wall of leptomeningeal and cerebral cortical blood vessels. On the basis of the molecular composition of the amyloid, two forms can be distinguished. Cystatin C amyloid angiopathy is a rare autosomal dominant disorder confined to several families from Iceland. beta-amyloid cerebral amyloid angiopathies may be hereditary or sporadic, and share clinical, pathological and biochemical features with Alzheimer's disease. Both types of vascular amyloid derive from precursor proteins synthesized in situ by astrocytes (cystatin C) or smooth muscle cells (beta-amyloid), and induce progressive degeneration of smooth muscle cells, blood vessel rupture and haemodynamic changes. In recent years, it has been reported that mutations underlying both types of hereditary cerebral amyloid angiopathy directly involve the gene encoding the precursor protein. These findings have increased our understanding of the amyloidogenic mechanisms and allowed preclinical diagnosis. Nevertheless, the aetiopathogenetic factors involved in the more frequent sporadic form of amyloid angiopathy remain unknown.

Animals↗
PubMed1995

Cloning and characterization of a G protein-activated human phosphoinositide-3 kinase.

Phosphoinositide-3 kinase activity is implicated in diverse cellular responses triggered by mammalian cell surface receptors and in the regulation of protein sorting in yeast. Receptors with intrinsic and associated tyrosine kinase activity recruit heterodimeric phosphoinositide-3 kinases that consist of p110 catalytic subunits and p85 adaptor molecules containing Src homology 2 (SH2) domains. A phosphoinositide-3 kinase isotype, p110 gamma, was cloned and characterized. The p110 gamma enzyme was activated in vitro by both the alpha and beta gamma subunits of heterotrimeric guanosine triphosphate (GTP)-binding proteins (G proteins) and did not interact with p85. A potential pleckstrin homology domain is located near its amino terminus. The p110 gamma isotype may link signaling through G protein-coupled receptors to the generation of phosphoinositide second messengers phosphorylated in the D-3 position.

Amino Acid Sequence↗
PubMed1994

Effects of neutron-gamma irradiation on striatal D1 and D2 receptor distribution.

The early effects of neutron irradiation on the striatal D1 and D2 dopaminergic receptor distribution were investigated by quantitative receptor autoradiography. One hour after exposure at the dose of 8.4 Gy, an increase of D1 (+21%) and D2 (+25%) receptor density was observed in the striatum, located at the most anterior levels, containing the richest plexus of dopaminergic fibers afferent from the substantia nigra. Regional differences in changes of D1 and D2 receptor density were observed. This up-regulation could contribute to the development of early radio-induced neuro-vegetative syndrome.

Animals↗
PubMed1993

Early and transient effects of neutron irradiation on dopamine receptors in the adult rat brain.

The early neurochemical effects of neutron-gamma radiation exposures were studied through ligand dopamine D1, D2 receptors binding experiments. The parameters of binding were investigated on crude preparations from striatum at different delays (from 2 to 72 hours) after irradiation. An early and transient increase in the total number of sites was seen after exposure, even at infra-lethal dose. This 'radiosensitivity' was higher for D1 than for D2 receptor. It is assumed that these modifications could participate in the early neuro-vegetative syndrome observed in irradiated persons.

Animals↗
PubMed1993

The cellular pathology associated with Alzheimer beta-amyloid deposits in non-demented aged individuals.

In this study, we have compared the cellular pathology associated with beta-amyloid (beta A) deposits which characterize Alzheimer's disease (AD) in demented patients with pathologically confirmed AD, with that in non-demented aged individuals. Brain sections from two severely demented AD cases, six non-demented individuals with beta A deposits, and six age-matched controls devoid of beta A deposits were double-immunostained with antibodies against beta A, and antibody markers for neurofibrillary tangles (NFT), astrocytes and microglial cells. We found that the severely demented patients displayed numerous plaques of variable morphology, most of which were associated with NFT, hypertrophied astrocytes and reactive microglial cells. In contrast, non-demented patients showed fewer plaques, few or not NFT and less astroglial and microglial reaction. The number of plaques with associated abnormal cellular elements were much lower in non-demented than in demented cases. Furthermore, classical plaques were more likely to be associated with abnormal cellular elements than diffuse plaques, which were most often devoid of any associated cellular change. These findings suggest that: (i) beta A plaques in non-demented individuals may represent an early stage of AD; (ii) beta A deposition is the first recognizable pathological abnormality of AD; and (iii) NFT, and astro- and microglial proliferation are later features, possibly secondary to the known dystrophic effects of the beta A peptide and other fragments of its precursor protein.

Aged↗
PubMed1993

[Variables associated with pathologic heart murmurs in primary care consultations].

OBJECTIVE: To assess the existence of variables associated to pathological murmurs in infancy. DESIGN: Retrospective crossover study. SETTING: Paediatrics clinic at Carrus Health Centre, Elche. PARTICIPANTS: 109 cases of children with a cardiac murmur recorded between 1987 and 1991 were studied. MEASUREMENTS AND MAIN RESULTS: The percentage of children with pathological cardiac murmurs was 10.1. An association of pathology to younger age at diagnosis (p = 0.006) and to the intensity of the murmurs (p = 0.001) was found. CONCLUSIONS: The frequency of pathological murmurs in our study is similar to that in other series consulted. The age of diagnosis and the intensity of the murmur appear to be variables associated to pathology in children, which should be borne in mind in Primary Care clinics.

Child↗