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Biomedical subjects

R J Rodrigues

Publications and source records attributed to R J Rodrigues.

18 recordsLinked to original sources
PubMed2005

Presynaptic kainate receptors are localized close to release sites in rat hippocampal synapses.

The subsynaptic distribution of kainate receptors is still a matter of much debate given its importance to understand the way they influence neuronal communication. Here, we show that, in synapses of the rat hippocampus, presynaptic kainate receptors are localized within the presynaptic active zone close to neurotransmitter release sites. The activation of these receptors with low concentrations of agonists induces the release of [(3)H]glutamate in the absence of a depolarizing stimulus. Furthermore, this modulation of [(3)H]glutamate release by kainate is more efficient when compared with a KCl-evoked depolarization that causes a more than two-fold increase in the intra-terminal calcium concentration but no apparent release of [(3)H]glutamate, suggesting a direct receptor-mediated process. Using a selective synaptic fractionation technique that allows for a highly efficient separation of presynaptic, postsynaptic and non-synaptic proteins we confirmed that, presynaptically, kainate receptors are mainly localized within the active zone of hippocampal synapses where they are expected to be in a privileged position to modulate synaptic phenomena.

Animals↗
PubMed2005

Adenosine A1 and A2A receptors are co-expressed in pyramidal neurons and co-localized in glutamatergic nerve terminals of the rat hippocampus.

Adenosine is a neuromodulator that controls neurotransmitter release through inhibitory A1 and facilitatory A2A receptors. Although both adenosine receptor-mediated inhibition and facilitation of glutamate release have been observed, it is not clear whether both A1 and A2A receptors are located in the same glutamatergic nerve terminal or whether they are located on different populations of these terminals. Thus, we have tested if single pyramidal glutamatergic neurons from the hippocampus simultaneously expressed A1 and A2A receptor mRNA and if A1 and A2A receptors were co-localized in hippocampal glutamatergic nerve terminals. Single cell PCR analysis of visually identified pyramidal neurons revealed the simultaneous presence of A1 and A2A receptor mRNA in four out 16 pyramidal cells possessing glutamatergic markers but not GABAergic or astrocytic markers. Also, A1 and A2A receptor immunoreactivities were co-localized in 26 +/- 4% of nerve terminals labeled with antibodies against vesicular glutamate transporters type 1 or 2, i.e. glutamatergic nerve terminals. This indicates that glutamatergic neurons in the hippocampus co-express A1 and A2A receptors and that these two receptors are co-localized in a subset of glutamatergic nerve terminals.

Animals↗
PubMed2003

Purinergic P2 receptors trigger adenosine release leading to adenosine A2A receptor activation and facilitation of long-term potentiation in rat hippocampal slices.

Electrophysiological recordings were used to investigate the effects of ATP analogues on theta-burst-induced long-term potentiation (LTP) in rat hippocampal slices. alpha,beta-Methylene ATP (alpha,beta-MeATP; 20 microM) decreased LTP from 36+/-9% to 17+/-5%, an effect prevented by adenosine A(1) receptor blockade in accordance with the localised catabolism of ATP analogues into adenosine, leading to adenosine A(1) receptor activation. Thus, to probe the role of extracellular ATP, all experiments were performed with the A(1) receptor selective antagonist, 1,3-dipropyl-8-cyclopentylxanthine (50 nM). In these conditions, alpha,beta-MeATP or 5'-adenylylimido-diphosphate (beta,gamma-ImATP; 20 microM) facilitated LTP by 120%, an effect prevented by the P2 receptor antagonists, pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS; 20 microM) or suramin (75 microM), as well as by the P2X(1/3)-selective antagonist 8-(benzamido)naphthalene-1,3,5-trisulfonate (10 microM). The facilitations of LTP by either alpha,beta-MeATP or beta,gamma-ImATP (20 microM) were also prevented by both 4-(2-[7-amino-2-(2-furyl(1,2,4)-triazolo(2,3a)-(1,3,5)triazin-5-yl-amino]ethyl)phenol (50 nM) or 7-2(-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c] pyrimidine (50 nM), antagonists of facilitatory adenosine A(2A) receptors, were occluded by the A(2A) receptor agonist, CGS 21680 (10 nM) and were prevented by the protein kinase C inhibitor, chelerythrine (6 microM) and unaffected by the protein kinase A inhibitor, H89 (1 microM). Furthermore, beta,gamma-ImATP (20 microM) enhanced [(3)H]adenosine outflow from rat hippocampal slices by nearly 150%, an effect prevented by PPADS (20 microM) or suramin (75 microM). The adenosine transport inhibitors, nitrobenzylthioinosine (5 microM) and dipyridamole (10 microM) also prevented beta,gamma-ImATP (20 microM)-induced [(3)H]adenosine outflow and facilitation of LTP. These results suggest that ATP analogues facilitate LTP through P2 receptor activation that mainly triggers adenosine release leading to the activation of adenosine A(2A) receptors.

Adenosine↗
PubMed2000

Information systems: the key to evidence-based health practice.

Increasing prominence is being given to the use of best current evidence in clinical practice and health services and programme management decision-making. The role of information in evidence-based practice (EBP) is discussed, together with questions of how advanced information systems and technology (IS&T) can contribute to the establishment of a broader perspective for EBP. The author examines the development, validation and use of a variety of sources of evidence and knowledge that go beyond the well-established paradigm of research, clinical trials, and systematic literature review. Opportunities and challenges in the implementation and use of IS&T and knowledge management tools are examined for six application areas: reference databases, contextual data, clinical data repositories, administrative data repositories, decision support software, and Internet-based interactive health information and communication. Computerized and telecommunications applications that support EBP follow a hierarchy in which systems, tasks and complexity range from reference retrieval and the processing of relatively routine transactions, to complex "data mining" and rule-driven decision support systems.

Decision Support Systems, Clinical↗
PubMed1995

Determination of the neutralizing potency of horse antivenom against bothropic and crotalic venoms by indirect enzyme immunoassay.

The use of ELISA to determine antisnake venom potency of horse immune sera should provide benefits of costs and reproducibility compared to in vivo assays. In the present investigation we evaluated the correlation between ELISA antibody levels and in vivo neutralization assays. For the indirect ELISA method, 0.016 micrograms/well of Bothrops jararaca or Crotalus durissus terrificus venom were used to coat the plates and 100 microliters/well of each sample of antibothropic or anticrotalic venom sera were used at 1:10,000 dilution. Sheep anti-horse IgG conjugated to peroxidase was added and the substrate H2O2/o-phenylenediamine produced the color that was read at 492 nm. A correlation coefficient of r = 0.97 was found for anticrotalic venom antibodies and no significant correlation was observed for antibothropic venom sera using 16 serum samples from immunized horses. However, when three antibothropic venom sera showing high in vivo neutralization potency and low absorbance in ELISA or high absorbance values and low in vivo protection were not included in the correlation analysis the coefficient value was r = 0.88. The correlation coefficient did not improve for all 16 antibothropic sera when a partially purified Bothrops jararaca venom fraction was used to coat the ELISA plates. The results indicate that ELISA could be used to determine the neutralizing potency of anticrotalic venom sera. For the antibothropic venom sera further studies are needed.

Animals↗
PubMed1974

Fungal septicemia in surgical patients.

Opportunistic systemic fungal infections are more frequent than generally realized. Increased awareness and a high index of suspicion of fungal super-infection in the presence of sepsis is required to bring about recognition and therapy. The intravenous catheter is an important portal of entry or may act as a foreign body favoring localization of a septic process. In its presence, fungemia must be guarded against. Whenever an intravenous catheter is removed, its tip should be cultured. Removal alone may be a critical item in therapy. In febrile patients, in whom the course of fever is not established, frequent blood cultures with attention directed specifically at fungi should be obtained. Fungi are not easily isolated and identified and only by requesting special attention from the microbiologist can the diagnosis be established in the average institutional laboratory in time to permit appropriate therapy. Since available therapeutic measures are strikingly effective when instituted early, awareness and alertness on the part of the clinician constitute the key to cure.

Adult↗
PubMedDate not supplied

[Information systems for the management of local health systems].

Owing to the diffusion of computers--personal as well as highly sophisticated models--and of modern data bank systems and more accessible programming methods that no longer require hiring professional programmers to develop a variety of applications, administrators are increasingly using this new technology as a basis for making more realistic decisions. Good information systems are of great importance in the management of local health systems; however, in order for them to be truly useful, data collection must be homogeneous so that the data may be subsequently consolidated and compared. In this connection the authors present a model consisting of four stages: strategic planning; analysis of needs; allocation of resources; and selection of alternatives for consideration by project teams and suppliers of equipment and programs.

Delivery of Health Care↗
PubMedDate not supplied

[Softening death].

Explore the source record for details and available documents.

Humans↗