| subsidiary atrial pacemaker | Secondary source for rhythmic control of the heart, available for controlling cardiac activity if the sinoatrial pacemaker fails; located within the crista terminalis and atrial free wall near the inferior vena cava. (05 Mar 2000) |
|---|---|
| demand pacemaker | A form of artificial pacemaker usually implanted into cardiac tissue because its output of electrical stimuli can be inhibited by endogenous cardiac electrical activity. (05 Mar 2000) |
| diaphragmatic pacemaker | A device that paces the diaphragm, used in patients with chronic ventilatory insufficiency resulting from malfunction of the respiratory control centre on certain types of phrenic nerve malfunction. (05 Mar 2000) |
| ectopic pacemaker | Any pacemaker other than the sinus node. (05 Mar 2000) |
| electric cardiac pacemaker | An electric device that can substitute for the normal cardiac pacemaker, controlling the heart's rhythm by artificial electric discharges. Synonym: electronic pacemaker. (05 Mar 2000) |
| electronic pacemaker | An electric device that can substitute for the normal cardiac pacemaker, controlling the heart's rhythm by artificial electric discharges. Synonym: electronic pacemaker. (05 Mar 2000) |
| electronic pacemaker load | The impedance to the output, the standard load being 500 ohms resistance ± 1%. (05 Mar 2000) |
| transthoracic pacemaker | Artificial pacemaker delivering stimuli through the chest wall usually applied as a temporizing measure in patients with atrioventricular block. (05 Mar 2000) |
| external pacemaker | An artificial cardiac pacemaker whose electrodes for delivering rhythmical electrical stimuli to the heart are placed on the chest wall. (05 Mar 2000) |
| fixed-rate pacemaker | An artificial pacemaker that emits electrical stimuli at a constant frequency. (05 Mar 2000) |
| receptors, cytoplasmic and nuclear | Proteins in the cytoplasm or nucleus that specifically bind signalling molecules and trigger changes which influence the behaviour of cells. The major groups are the steroid hormone receptors, which usually are found in the cytoplasm, and the thyroid hormone receptors, which usually are found in the nucleus. Receptors, unlike enzymes, generally do not catalyze chemical changes in their ligands. (12 Dec 1998) |
| Remak's nuclear division | <cell biology> An unusual form of nuclear division, in which the nucleus simply constricts, rather like a cell without chromosome condensation or spindle formation. Partitioning of daughter chromosomes is haphazard. Observed in some Protozoa. (18 Nov 1997) |
| Pelger-Huet nuclear anomaly | Congenital inhibition of lobulation in the nuclei of neutrophilic leukocytes; most cells present band or bilobulate appearance, and only an occasional cell is trilobed; it is not associated with disease, but may be confused with leukocyte "shift to left"; autosomal dominant inheritance. (05 Mar 2000) |
| ribonucleoproteins, small nuclear | Highly conserved nuclear RNA-protein complexes that function in RNA processing in the nucleus, including pre-mRNA splicing and pre-mRNA 3'-end processing in the nucleoplasm. The u3 snrnp is localised in the nucleolus, where it aligns into base pairs with the 28s rrna precursor in a still unidentified region and functions in pre-rrna processing. The u7 snrnp aligns into base pairs with a conserved sequence in the 3'-end of histone pre-mRNA and is an essential cofactor for the cleavage that creates the mature nonadenylated 3'-end. (12 Dec 1998) |
| RNA, heterogeneous nuclear | Nuclear nonribosomal RNA larger than about 1000 nucleotides, the mass of which is rapidly synthesised and degraded within the cell nucleus. Some heterogeneous nuclear RNA may be a precursor to mRNA. However, the great bulk of total hnrna hybridises with nuclear DNA rather than with mRNA. (12 Dec 1998) |