Biomedical subjects
Publications and source records attributed to D C Gray.
A new labelling system for use on medical equipment dispensers is tested. This system uses one of the objects stored in each unit of the dispenser as the 'label', by attaching it to the front of the dispenser with tape. The new system was compared to conventional written labelling by timing subjects asked to select items from two dispensers. The new system was 27% quicker than the conventional system.
Isolated salivary glands of the cockroach Nauphoeta cinerea Olivier secrete fluid in response to nerve stimulation or application of dopamine, the acinar cells undergoing a hyperpolarization during secretion. The aim of the present work was to examine whether cyclic AMP acts as a second messenger in the acinar cells to cause the secretory and electrical responses to the transmitter dopamine. Cyclic AMP (10-500 microM) in the bathing solution of isolated glands caused a dose-dependent secretory response but no change in the membrane potential of acinar cells. The time courses and magnitudes of the secretory responses to cyclic AMP resembled those features of responses to dopamine. Forskolin, an adenylate cyclase activator, caused fluid secretion but the responses were small and irregular. The phosphodiesterase inhibitor, 3-isobutyl-l-methylxanthine (IBMX)(1-1000 microM) produced fluid secretion in a dose-dependent manner, the maximal response being equal to that of dopamine. Maintained responses to cyclic AMP or IBMX required the presence of extracellular calcium ions. An inhibitor (MDL 12,330A) of adenylate cyclase suppressed the secretory responses to dopamine, cyclic AMP, IBMX, the ionophore A23817 or the readmission of calcium ions to the bathing solution; this inhibitor did not block the acinar hyperpolarization caused by nerve stimulation. Cyclic AMP stimulation of glands, bathed in chloride-free solution to prevent fluid secretion, produced a change in the gland cells which outlasted the period of exogenous cyclic AMP stimulation and expressed itself as a transient secretion upon return of the normal bathing solution. It was concluded that stimulus-secretion coupling in this gland involves a calcium-dependent second messenger system and that cyclic AMP is probably the second messenger. The evidence did not support the idea that cyclic AMP is also a second messenger for the acinar cell hyperpolarization evoked by nerve stimulation.
The fluorescent compound chlorotetracycline (CTC) enters the cells of the cockroach salivary gland. The acinar peripheral cells and the non-secretory duct cells become preferentially labelled by CTC. Microscopic examination of the intracellular distribution of CTC indicates that this compound labels the highly folded apical plasma membranes of the peripheral cells and the deep infolds of the basal plasma membranes of the non-secretory duct cells. Lanthanum blocks the entry of CTC into all of the gland cells and in this condition the CTC labels the basal surfaces of the acini and ducts. The results of this investigation support the idea that CTC labels calcium ions in the vicinity of plasma membranes.
When cockroach salivary glands are bathed in calcium-free medium the basal rate of fluid secretion increases from about 1 nl/min to about 10 nl/min; maintained dopamine stimulation elicits a further rise in secretory rate which gradually declines. Evidence is presented which indicates that magnesium is unable to substitute for calcium in this system. When calcium is returned to the bathing solution after a period of calcium deprivation there is a transient increase in secretory rate. Stimulation of the glands in certain conditions which inhibit the secretory response leads to some kind of calcium-dependent active state in the secretory cells which can outlast the interaction of the agonist with its receptors. It is concluded that stimulus-secretion coupling in this gland involves a calcium-dependent second messenger system.
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