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Biomedical subjects

J B Simpson

Publications and source records attributed to J B Simpson.

At least 73 records · Page 4Linked to original sources
PubMed1984

Asthma management within North Canterbury general practice.

During 1980/81 a primary medical care survey comprising 4629 patient visits to North Canterbury general practitioner surgeries was undertaken. Given the current concern about asthma management information concerning asthma consultations was extracted from the survey. The diagnostic procedures undertaken, therapeutic services provided and follow-up arrangements are outlined for 96 patients with a primary diagnosis of asthma. Pharmaceuticals prescribed to 116 patients with either a primary or secondary diagnosis of asthma are described. Of those patients requiring medication 52% received only one item. Beta 2-agonists were the most commonly used antiasthmatic and were prescribed to 78% of the 116 patients. Theophylline was prescribed to 41% of cases, beclomethasone to 28%, oral corticosteroids to 22%, sodium cromoglycate to 12% and an antibiotic to 10% of cases. These results reflect pharmaceuticals prescribed at one point in time of on-going care.

Adolescent↗
PubMed1984

Advances in guidewire technology.

Since the introduction in 1979 of a movable guidewire system for PTCA, significant advances have been made in guidewire technology that have improved primary success rates and reduced complications with the use of this system. Coronary stenoses in distal sites or in branch vessels with abrupt angulations can now routinely be reached and crossed with newer-generation guidewires . This report concentrates on the evolution of advances in guidewire technology and outlines changes in guidewire design that have allowed for improved efficacy and safety with the movable wire system. Appropriate cases are presented to illustrate the advantages of available guidewires .

Angioplasty, Balloon↗
PubMed1984

Role for the subfornical organ in vasopressin release.

The effect of subfornical organ (SFO) lesions on plasma vasopressin and drinking was tested in rats given either of two stimuli: subcutaneous injection of hypertonic saline or injection of a single dose of angiotensin II (AII) into the dorsal third cerebral ventricle. Drinking in response to hypertonicity was significantly attenuated, whereas AII-induced drinking was unaffected by the lesions. In contrast, SFO lesions were associated with significantly reduced vasopressin responses following either of these potent stimuli to vasopressin secretion. Partial lesions that damaged structures adjoining the SFO (fornix or septum) had no significant effects. These results demonstrate that, in rats, the SFO is in some way necessary for vasopressin responses to both AII and hypertonicity.

Angiotensin II↗
PubMed1984

The anterior wall of the third cerebral ventricle and homeostatic responses to dehydration.

Within the anterior wall of the third cerebral ventricle, structures are found which have been implicated in the regulation of fluid and electrolyte balance. These structures include the subfornical organ (SFO), preoptic medianus nucleus (PMN) and the organum vasculosum of the lamina terminalis (OVLT). In sheep, the OVLT rises from the ventricular floor over the optic chiasma and occupies most of the midline ventricular wall up to the level of anterior commissure. It contains a plexus of blood vessels at its base which possess fenestrated endothelial cells, and appears to lack ependyma. The SFO of sheep bulges into the third ventricle above the anterior commissure and the PMN is situated between the SFO and OVLT, surrounding the rostral edge of the midline anterior commissure. Like most mammals, water deprivation in sheep results in hypertonicity of body fluids, thirst and graded increase in plasma concentration of vasopressin (AVP). Dehydration also causes a natriuresis in these animals. In sheep with combined ablation of OVLT/PMN tissue, the volume of water drunk, the increases in plasma vasopressin (AVP) level, and the natriuresis in response to dehydration were considerably attenuated, and extreme hypernatremia resulted. Additionally, ablation of OVLT/PMN tissue almost abolished water drinking and AVP secretion in response to systemic infusion of hypertonic NaCl, but did not diminish AVP secretion in response to haemorrhage. In other animals, the OVLT and PMN were individually ablated. While partial osmoregulatory deficits were observed in each case, these deficits were smaller than those observed with combined OVLT/PMN ablation. In contrast to these results, the homeostatic responses to dehydration were not diminished in sheep with combined SFO/PMN lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Arteriovenous fistula in arterial reconstruction of the ischemic limb.

The high flow associated with an arteriovenous fistula has been shown to help maintain patency in small arterial anastomoses. In 37 male patients we created common ostium arteriovenous fistula at the distal tibial or peroneal anastomosis as a part of their arterial reconstruction for threatened limb loss. Limb salvage was achieved in 28. Successful amputations at a lower level than would have been anticipated were performed in three. There was early graft failure in four patients resulting in below-the-knee amputations. This operative approach may be helpful in patients who have had previous revascularization procedures that have failed, who resist the idea of amputation, and who fulfill the angiographic criteria of extremely poor runoff with an absent or deficient pedal arch.

Adult↗
PubMed1983

Sodium retention and salt appetite following deoxycorticosterone in hamsters.

Previous research suggests that hamsters 1) fail to retain sodium after mineralocorticoid injections, 2) retain sodium after adrenalectomy equal to controls, and 3) do not develop salt appetite after mineralocorticoid or adrenalectomy. The present studies demonstrate sodium retention, body weight gain, hypernatremia, plasma volume expansion, and reduced fecal sodium excretion after daily injections of deoxycorticosterone acetate (DOCA). Salt appetite appeared after the 3rd and 4th days. Adrenalectomy caused reductions of sodium balance, plasma volume, and food intake, which were reversed by DOCA administration. Mineralocorticoids therefore represent one control of sodium metabolism in hamsters.

Adrenalectomy↗
PubMed1983

Drinking and pressor responses after acetylcholine injection into subfornical organ.

Mean arterial pressure and drinking were measured in rats before and after intracranial injection of acetylcholine (ACh) into the subfornical organ (SFO), the circumventricular organ of the dorsal third ventricle. Arterial pressure was recorded in unanesthetized unrestrained animals by means of an abdominal aortic catheter. Maximal increases in arterial pressure and drinking followed the application of ACh to SFO, while significantly smaller effects were obtained after ACh injections into near-SFO control sites. Inasmuch as the effects also occurred with the shortest latencies after SFO injections, the possibility of ACh diffusing to act at other than SFO sites seems unlikely. The pressor and drinking responses to ACh were blocked by SFO pretreatment with atropine, indicating muscarinic receptor involvement. The SFO-mediated pressor response to ACh was reduced after systemic injection of phentolamine, suggesting at least a partial role for the sympathetic nervous system in the response. The present experiments suggest that ACh acts at the SFO to generate not only drinking but also increases in arterial pressure.

Acetylcholine↗
PubMed1983

Deficits in drinking and vasopressin secretion after lesions of the nucleus medianus.

The effects of ablation of the nucleus medianus on drinking and vasopressin secretion were studied in male Long-Evans rats. The amount of water drunk in 1 h was assessed after subcutaneous injection of 5.8% NaCl (13.34 mosm/kg) or of angiotensin II (1.5 mg/kg). In a separate test with no water available, plasma vasopressin was measured 15 min after the above dose hypertonic saline. Ablation of the nucleus medianus, or the dorsal and anterior portions of the nucleus medianus, blocked drinking to hypertonic saline or angiotensin II and attenuated the vasopressin response to hyperosmolality. Animals with septal or diagonal band lesions showed responses comparable to sham-operated rats. These results indicate that a neural pathway important for fluid balance passes through, or terminates in, the nucleus medianus.

Angiotensin II↗
PubMed1982

A new catheter system for coronary angioplasty.

A new catheter system has been designed for percutaneous transluminal coronary angioplasty. An independently movable, flexible-tipped guide wire within the balloon dilation catheter facilitates selection of the involved vessel. This guide wire can be passed slowly and carefully beyond the coronary stenosis, permitting safe advancement of the balloon catheter. After testing in animal and cadaver hearts, this system was used in 53 patients (56 stenoses) with single vessel coronary artery disease, with an overall primary success rate of 64 percent. In the last 41 of these 56 cases, use of a balloon catheter with a smaller deflated diameter increased the success rate to 73 percent. In patients with lesions of the left anterior descending coronary artery, the success rate was 89 percent. Three (6 percent) of the 53 patients had complications during coronary arterial dilation that necessitated emergency coronary arterial bypass graft surgery. There were no procedure-related or late cardiac deaths. During the mean follow-up period of 8 months (range 1 to 21), there were one late death (of noncardiac causes) and no late myocardial infarctions. Clinical status was persistently improved in 31 of the 36 patients who had successful dilation. The remaining five patients experienced restenosis at the angioplasty site and return of angina pectoris within 3 months of dilation. Two of these patients had repeat coronary angioplasty with restoration of asymptomatic status, and three had elective coronary bypass graft surgery.

Angioplasty, Balloon↗
PubMed1982

Lesions of the subfornical organ block angiotensin-induced drinking in the dog.

The role of the subfornical organ (SFO) in drinking caused by cellular dehydration and angiotensin was examined in the dog. Drinking responses to intravenous administration of angiotensin and to hypertonic NaCl were compared before and after electrolytic ablation of the SFO. After destruction of the SFO, drinking in response to angiotensin was 0.5 +/- 0.3 ml/kg compared to 11.9 +/- 3.7 ml/kg prior to lesioning. Drinking in response to hypertonic NaCl was not affected by lesioning the SFO (12.6 +/- 6.6 ml/kg before vs. 13.4 +/- 5.4 ml/kg after the lesion). Lesions superior or lateral to the SFO did not affect drinking in response to either angiotensin or hypertonic NaCl. These data show that the SFO is essential for drinking in response to blood-borne angiotensin but not to the stimulus of cellular dehydration in the dog.

Angiotensin II↗
PubMed1981

The circumventricular organs and the central actions of angiotensin.

This review discusses the central nervous system actions of the circulating hormone, angiotensin II. Access of this peptide likely is limited to those central structures which lack the blood-brain barrier. Three of the circumventricular organs, the area postrema, the subfornical organ, and the organum vasculosum, have all been suggested to be sites of action for angiotensin within the brain. The area postrema is a site of pressor action of angiotensin in many species but not in the rat. The subfornical organ is a site where angiotensin provokes drinking, a pressor effect, and the secretion of vasopressin. The organum vasculosum and adjacent tissue has also been suggested to be a site for these three central effects of the peptide. Blood-borne angiotensin probably does not act at the same locus as does angiotensin applied to the brain via its ventricular system.

Angiotensin II↗
PubMed1980

Intracranial injection parameters which affect angiotensin II-induced drinking.

Three intracranial injection parameters, injectate concentration at equivalent doses, rupture or bypass of the lateral ventricle by cannula in reaching the site, and multiple injections per animal, were studied to assess their effects on the drinking behavior elicited by angiotensin II at the lateral preoptic area (LPOA). Half of the animals were implanted with 23 gauge cannulae which penetrated the lateral ventricle en route to the site. The remaining animals received cannulae that were angled laterally to bypass the ventricle. In ventricular animals, the more concentrated injectate increased the total water intake over a 30 min period and affected the pattern of drinking through time. Animals with cannulae that penetrated the ventricle en route to the LPOA drank significantly more than the animals whose cannulae missed the ventricle. In all cases, no significant difference in drinking response was found between the first and second injections received by each rat. These results indicate that standardized intracranial chemical injection methods are needed for comparison of experiments utilizing this technique.

Angiotensin II↗
PubMed1980

Subfornical organ: forebrain site of pressor and dipsogenic action of angiotensin II.

Intracranial injection of angiotensin II (AII) at three brain sites elicited near simultaneous dipsogenic and pressor effects in rats. Both effects were maximal, occurred with the shortest latencies, and at the lowest doses of AII when the cannula terminated precisely within the parenchyma of the subfornical organ (SFO). Pressor effects were produced by SFO injection of a dose of AII (0.1 pg) which approximates plasma AII concentrations at the high end of the physiological range. Both the drinking and pressor effects were blocked by saralasin. Injections of AII at sites immediately adjacent to SFO produced smaller effects with longer latencies. These results ruled out the possibility that SFO injections were effective via leakage to alternative sites. The pressor effect of AII at the SFO remained in animals under chloralose anesthesia, demonstrating that it is not an artifact of drinking behavior. These results indicate that the SFO is a site of AII pressor action, and confirm previous demonstrations that the structure is a site of AII drinking action.

Angiotensin II↗
PubMed1980

Subfornical organ lesions reduce the pressor effect of systemic angiotensin II.

The pressor effect of intravenous angiotensin II (AII) was compared in the unrestrained rat before and after electrolytic lesions of the subfornical organ (SFO), the circumventricular organ of the dorsal third cerebral ventricle. Abdominal aortic and venal caval catheters were used to measure arterial pressure and to infuse solutions, respectively. The pressor effect of AII was significantly reduced following complete SFO lesions but was unaffected by partial SFO lesions or by control lesions in adjacent tissue. The pressor effect of intravenous infusion of the alpha-adrenergic agonist, phenylephrine, was unaffected by any of these lesions. In agreement with experiments demonstrating that SFO injection of AII increases arterial pressure, the present results suggest that a significant portion of the pressor action of circulating AII is centrally mediated, and that the SFO participates in this mediation.

Angiotensin II↗