RESUMO
We have measured the expression levels of a range of distinct ion channel genes in the apex/ventricle region and sino-atrial node (SAN) sub-regions of heart under conditions in which conventional Northern hybridization or ribonuclease protection methods were too insensitive or non-quantitative. The abundance of six potassium channel mRNAs was determined in relation to a single synthetic competitor RNA template which was co-reverse transcribed and PCR-amplified. By these methods we have shown that coronary artery ligation procedures which induce anoxia and ischaemic scarring in the apical region reduce amplifiable message abundance in a time-dependent, but non-specific manner. There was no evidence for any selective reduction of individual mRNA levels during this process. Despite a high reproducibility of titration endpoints, competitive RNA template amplification assays did not provide a simple marker for ischaemic damage, since it was not possible to control for tissue sample heterogeneity. We have also applied these competitive nucleic acid titration techniques to demonstrate expression of cAMP- and cGMP-gated ion channel sequences in small pieces of tissue derived from the SAN sub-region of rabbit heart. Although the ion channels encoded by these sequences are obligately coupled to intracellular signalling agonists commonly found in cardiac cells, they have not been described in functional terms within SAN or any other cardiac subregion. For rapid determination of cDNA molecular numbers, we have devised single-gene, DNA template controls to measure absolute abundance of a cAMP-gated cDNA derived from heart tissue. Competitive titration procedures therefore provide an important technique for probing gene induction and/or repression accompanying pharmacological or surgical interventions, or in progression of disease states. For rare cDNAs, they can estimate the representativeness of a given preparation prior to library construction, screening and retrieval of clones, while eliminating 'false positive' or 'false negative' signals.
Assuntos
Canais Iônicos/genética , Isquemia Miocárdica/genética , Miocárdio/química , RNA Mensageiro/análise , RNA Mensageiro/genética , Animais , Sequência de Bases , Northern Blotting , Primers do DNA , Amplificação de Genes , Ventrículos do Coração/química , Ventrículos do Coração/metabolismo , Ativação do Canal Iônico/fisiologia , Canais Iônicos/metabolismo , Canais Iônicos/fisiologia , Masculino , Dados de Sequência Molecular , Isquemia Miocárdica/metabolismo , Miocárdio/metabolismo , Reação em Cadeia da Polimerase , Canais de Potássio/genética , Canais de Potássio/metabolismo , Canais de Potássio/fisiologia , RNA Mensageiro/metabolismo , Coelhos , Ratos , Ratos Sprague-Dawley , Nó Sinoatrial/química , Nó Sinoatrial/metabolismo , Titulometria , Transcrição GênicaRESUMO
A 55-yr-old man received a left supraclavicular brachial plexus block with 0.42% bupivacaine; he had profound motor and sensory block 26 h after injection; complete recovery occurred at 40 h.
Assuntos
Plexo Braquial , Bupivacaína/efeitos adversos , Bloqueio Nervoso/efeitos adversos , Período de Recuperação da Anestesia , Anestesia Geral , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de TempoRESUMO
The efficacy of pneumatic compression of the lower limbs using inflatable leg splints in prevention of hypotension during spinal anaesthesia was assessed in an open study of 46 patients undergoing elective caesarean section. All patients received 15 ml/kg of Hartmann's solution before spinal anaesthesia and were tilted to the left to minimise aortocaval compression. Splints were rapidly inflated to a pressure of 5.3 kPa immediately after institution of the block in treated patients. Blood pressure was measured by a cuff method at 1-min intervals until the commencement of surgery. Hypotension was less common (P less than 0.05) and less severe (P less than 0.05) in splint-treated patients, but the incidence was unacceptably high in both treated (48%) and control (83%) groups.
