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Biomedical subjects

J Chalmers

Publications and source records attributed to J Chalmers.

At least 163 records · Page 9Linked to original sources
PubMed1988

Automated non-invasive measurement of cardiac output: comparison of electrical bioimpedance and carbon dioxide rebreathing techniques.

Two commercial automated, non-invasive systems for estimation of cardiac output were evaluated. Values of cardiac output obtained by electrical bioimpedance cardiography (BoMed NCCOM3 machine) were compared with values derived from an indirect Fick technique that uses carbon dioxide rebreathing (Gould 9000 IV system) during 103 simultaneous measurements made at rest in 19 randomly selected subjects and on exercise in 11 subjects. Cardiac output values obtained with impedance cardiography were significantly correlated with those measured by the indirect Fick method, although there was a wide scatter with over 73% of the readings lying outside the limits defined by the line of identity +/- 20%. This correlation was greatly reduced when stroke volume index was used instead of cardiac output. Indirect Fick results were linearly related to oxygen uptake both at rest and on exercise, while impedance cardiography results did not correlate with oxygen uptake. Impedance cardiography gave consistently lower results for cardiac output than indirect Fick at all levels of exercise. Both machines were easy to use and produced acceptable mean (SE) coefficients of variation (BoMed NCCOM3 7.7 (1.0)%, Gould 9000 IV 10.6 (1.4)%). Further validation is required before either of these machines can be recommended as an alternative to invasive monitoring in clinical practice.

Adolescent↗
PubMed1988

Fractures of the femoral neck in elderly patients with hyperparathyroidism.

Five fractures of the femoral neck were observed in patients with primary or secondary hyperparathyroidism. In each case, the fracture line was vertically oriented near the base of the neck. The diagnosis was suggested by the patient's history and roentgenologic features and was confirmed by biochemical changes. None of the fractures healed despite internal fixation in four cases and appropriate treatment of the underlying disease. When such fractures occur in elderly patients, primary arthroplasty may be preferable to internal fixation.

Aged↗
PubMed1987

The use of microinjected colloidal gold and immunocytochemistry to localise pressor sites in the rostral medulla oblongata of the rat.

A new technique for localising the centre of sites of microinjection of drugs in the brain using the silver intensification of colloidal gold is described. The technique is compatible with immunocytochemistry and in this study was used in Wistar-Kyoto rats to investigate the relationship between the location of phenylethanolamine-N-methyltransferase-like immunoreactive (PNMT-LI) cell bodies in the medulla and the precise sites where microinjection of L-glutamate elicited pressor responses. Colloidal gold provided a simple technique for localising the centre of sites of microinjection with a high degree of spatial resolution and allowed pressor sites to be precisely localised in the region of ventrolateral medulla with the highest density of PNMT-LI cells.

Animals↗
PubMed1987

Plasma neuropeptide Y concentration is increased after hemorrhage in conscious rats: relative contributions of sympathetic nerves and the adrenal medulla.

Most peripheral noradrenergic nerves have been shown to contain the coexisting peptide, neuropeptide Y (NPY). The aim of this study was to determine whether NPY is released together with catecholamines during activation of the sympathoadrenal system by hemorrhagic stress in conscious rats. Plasma NPY rose from a baseline value of 7.7 +/- 1.2 to 14.4 +/- 2.7 and 14.9 +/- 2.3 ng/ml (mean +/- SEM, n = 8) 10 and 30 min after hemorrhage, respectively. Plasma norepinephrine (NE) and epinephrine concentrations rose immediately after hemorrhage and at 30 min were increased twofold and ninefold, respectively. To determine the source of the increase in circulating NPY after hemorrhage, rats were subjected to adrenalectomy or to chemical sympathectomy with intravenous (i.v.) 6-hydroxydopamine (6-OHDA). 6-OHDA-treated rats had no significant increase in plasma NPY after hemorrhage, whereas adrenalectomized rats had an enhanced NPY response to hemorrhage. These results suggest that the sympathetic nerves make the major contribution to the increase in plasma NPY concentrations after activation of the sympathoadrenal system by hemorrhagic stress.

Adrenal Medulla↗
PubMed1987

Complementary changes in plasma atrial natriuretic peptide and antidiuretic hormone concentrations in response to volume expansion and haemorrhage: studies in conscious normotensive and spontaneously hypertensive rats.

1. Plasma concentrations of atrial natriuretic peptide (ANP) and antidiuretic hormone (ADH) were measured in conscious stroke-prone spontaneously hypertensive (SPR), spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats before and after acute volume expansion or haemorrhage. 2. Plasma ANP concentration was reduced to one-third of resting values 30 min after a 1.5% haemorrhage (1.5 ml of blood per 100 g bodyweight). Plasma ADH concentration rose immediately 50-fold on haemorrhage and remained elevated at 30 min. 3. Plasma ANP concentration increased 2.5-fold relative to resting values 1 min after infusion of 2.0 ml per 100 g 5% dextrose; after 10 min plasma ANP remained elevated. Plasma ADH concentration tended to fall on volume expansion although no significant decrease was observed. 4. There was no difference in the basal levels of ANP and ADH, or in the changes produced by alterations in blood volume, in hypertensive SPR and SHR compared with normotensive WKY. 5. Thus, plasma ANP concentrations moved in opposite directions in response to two physiological stimuli: volume expansion and haemorrhage. Reciprocal changes were observed in plasma ADH.

Animals↗
PubMed1987

Are high blood sugar levels in the elderly ignored?

In a survey of 530 patients, aged 75 years and older, who were admitted to a general teaching hospital in Christchurch, 60 (11.3%) were known diabetics. One hundred and seventy-six other patients (33.2%) had a last measured laboratory blood glucose level of greater than 7.8 mmol/l, of whom 27 people (5.1% of all patients) had significant hyperglycemia (over 11 mmol/l). The Geriatric Assessment and Rehabilitation Unit (ARU) and acute general medical wards of the Princess Margaret Hospital made little use of the specialised Diabetes Services for help in managing known or newly diagnosed diabetics. The mean in-hospital laboratory blood glucose value for all diabetics was an unphysiological value of 12.2 mmol/l, compared with a community mean of 4.9 mmol/l and hyperglycemia persisted after resolution of acute medical problems. ARU diabetic patients had significantly lower blood glucose values than those achieved by physicians in acute medical wards. Prescribed medications such as steroids or diuretics contributing to insulin resistance were rarely modified. It is concluded that 16.4% of elderly patients had significant hyperglycemia or poorly managed diabetes mellitus, and that both general and geriatric physicians underestimated both the severity and consequences of elevated blood sugars in older patients in a regional New Zealand community with a 'high' diabetes profile.

Age Factors↗
PubMed1987

Do pressor neurons in the ventrolateral medulla release amines and neuropeptides?

Activation of neurons arising in the rostral ventrolateral medulla evokes a pressor response in the rat and the rabbit. This region of the medulla gives rise to bulbospinal neurons containing many different neurotransmitters, including amines such as adrenaline, noradrenaline and serotonin, and neuropeptides such as substance P and neuropeptide Y. Colocalization of amines and neuropeptides has been described in some neurons descending from the rostral ventrolateral medulla. In this paper we discuss the evidence that bulbospinal serotonin-containing neurons (B3) and adrenaline-containing neurons (C1) arising from this part of the medulla exert pressor effects by distinct central pathways and conclude that they do. We also consider the possibility that the pressor effects of activating these two groups of neurons are associated with release of neuropeptides and highlight evidence that substance P is released into the spinal cord by activation of descending serotonin-containing neurons, while neuropeptide Y may be released by activation of bulbospinal adrenaline-containing neurons.

Animals↗
PubMed1987

Rupture of the calcaneal tendon. The early and late management.

We have reviewed 106 patients after treatment for spontaneous rupture of the calcaneal tendon, and assessed the clinical results including the power of plantarflexion. In patients treated within 48 hours of injury the result was very similar in conservatively and in operatively treated patients. The incidence of major complications was higher after operation (17%) than in those treated conservatively (4%). Patients who were treated more than one week after injury, however, had an inferior result with respect to power of plantarflexion after conservative management. It is therefore recommended that calcaneal tendon rupture is treated conservatively with a plaster in full equinus when it is diagnosed within 48 hours of injury, and by operation when diagnosis has been delayed for more than one week.

Achilles Tendon↗
PubMed1987

Direct radioimmunoassay of human plasma atrial natriuretic peptide in various normal and pathophysiological states: increase in renal and cardiac failure during exercise.

We have used a sensitive direct radioimmunoassay to study the effects of exercise on plasma atrial natriuretic peptide (ANP) concentrations in man. Plasma ANP concentration increased three-fold in sixteen patients undergoing bicycle ergometer electrocardiographic tests for the investigation of chest pain. Resting ANP concentrations were higher in those patients in whom there was more evidence of heart disease, such as a positive exercise test, treatment with a beta blocker or history of myocardial infarction, although exercise resulted in increased ANP in both groups. We also confirm the increased plasma ANP concentration observed in patients with congestive cardiac failure and renal failure. In nine patients with renal failure routine haemodialysis was accompanied by a 30 per cent reduction in plasma ANP concentration. Plasma ANP concentrations were similar in treated hypertensive patients, untreated borderline hypertensive patients and normotensive subjects.

Adult↗
PubMed1987

Felodipine compared to prazosin as additional therapy to a beta-blocking drug.

Felodipine was compared with prazosin in patients with essential hypertension whose blood pressure was not controlled by a beta-blocking drug. One hundred patients with a supine diastolic blood pressure greater than or equal to mm Hg after 4 weeks or more on a beta-blocking drug and placebo were randomly assigned to felodipine or prazosin tablets. The drugs were titrated at 2-week intervals if diastolic BP was greater than or equal to 90 mm Hg. Titration steps of felodipine were 5, 10, 20 mg b.i.d. and of prazosin were 1, 2, 4 mg b.i.d. The fall in blood pressure with felodipine 32/21 mm Hg was greater than the fall with prazosin 16/12 mm Hg (p less than 0.001); 36 patients achieved a diastolic blood pressure of less than 90 mm Hg with felodipine, which was a significantly greater number than the 20 patients who obtained such a level with prazosin (p less than 0.01). Both drugs were well tolerated, but more patients complained of vascular type side effects (flushing, peripheral edema) with felodipine than with prazosin. There was significant weight gain with prazosin but not with felodipine. Felodipine was shown to be a well-tolerated, effective antihypertensive agent when used with a beta-blocking drug and to be suitable for people with hypertension who fail to be controlled with a beta-blocking drug.

Adrenergic beta-Antagonists↗
PubMed1986

Does substance P coexist with adrenaline in neurones of the rostral ventrolateral medulla in the rat?

Spinally projecting substance P- (SP) and adrenaline-containing neurones of the rostral ventrolateral medulla are believed to be important in the tonic and reflex control of blood pressure. In this paper we used dual immunofluorescence staining to investigate the degree of co-localisation of these two putative neurotransmitters in this region. In contrast to a recent report that SP and phenylethanolamine-N-methyltransferase (PNMT) are extensively co-localised, we report here that only a small number of neurones were found to be immunoreactive for both SP and PNMT.

Animals↗
PubMed1986

Relative importance of sympathetic nerves and of circulating adrenaline and vasopressin in mediating hypertension after lesions of the caudal ventrolateral medulla in the rat.

Electrolytic lesions of the A1 noradrenaline cells in the caudal ventrolateral medulla cause transient hypertension and bradycardia in the conscious rat, as previously described in the rabbit. The lesions produced 100-fold increases in plasma arginine vasopressin, 40-fold increases in plasma adrenaline and fourfold increases in plasma noradrenaline levels. Absence of circulating vasopressin [homozygous diabetes insipidus rats (DI)] or circulating adrenaline (adrenalectomized rats) did not affect A1 hypertension, but sympathectomy with systemic 6-hydroxydopamine (6-OHDA) significantly attenuated A1 hypertension. A factorial experiment was performed to assess the relative contributions of these three peripheral effector mechanisms in a quantitative manner, with combined deficiencies of any two or of all three of these effector systems. Results suggest A1 hypertension in the rat to be primarily mediated through increased sympatho-adrenal activity. The largest component of hypertension (66%) results from increased sympathetic vasoconstrictor nerve activity, and a smaller part (34%) reflects the action of circulating adrenaline. Increases in vasopressin levels do not contribute to A1 hypertension, although vasopressin makes a major contribution to A1 lesion bradycardia.

Adrenalectomy↗
PubMed1986

Osteosarcoma arising in relation to an enchondroma. A report of three cases.

Three cases are reported in which an osteosarcoma developed in relation to an enchondroma in a long bone. Two of the cases were in the proximal femur whilst one occurred in the proximal humerus, both recognised sites for old calcified enchondromas or "cartilage rests". The ages of the patients at presentation were 55, 63 and 84 years and all were women. Two patients died with pulmonary metastases within six months of the onset of clinical symptoms. Despite their intimate relationship to the enchondromas, none of the osteosarcomas could be shown histologically to have arisen from tumour cartilage. It appears probable that these are cases in which independently arising tumours have merged to form a so-called "collision" tumour, but the possibility that they could have been derived by dedifferentiation of a previously benign neoplasm cannot be discounted.

Aged↗
PubMed1986

The value of remanipulating Colles' fractures.

The value of remanipulating a Colles' fracture which has redisplaced after primary reduction was assessed in 50 patients. In those over 60 years old, remanipulation failed to achieve a lasting improvement in position, while the majority of those under 60 years maintained a significant improvement in dorsal angulation. It is concluded that the elderly patient does not benefit from this procedure.

Adult↗
PubMed1986

Australian National Health and Medical Research Council dietary salt study in mild hypertension.

Two-hundred-and-twelve untreated subjects (mean age 52.3 +/- 0.8 years; 181 males and 31 females) with a diastolic blood pressure between 90 and 100 mmHg were recruited to the study. Subjects were seen fortnightly and, after 4 pre-diet visits, were randomized into a normal diet group (A, 55 subjects), a high-potassium diet group (B, 52 subjects receiving greater than 100 mmol K+/day) a reduced-sodium diet group (C, 52 subjects receiving 50-75 mmol Na+/day) or a high-potassium and low-sodium diet group (D, 53 subjects receiving same Na+ and K+ as groups B and C). Two-hundred subjects completed the diet phase of 12 weeks. Urine sodium fell to 86 +/- 7 mmol/day in group C and 73 +/- 6 mmol/day in group D, while daily potassium excretion rose to 96 +/- 5 mmol in group B and 87 +/- 4 mmol in group C. Systolic and diastolic blood pressure fell by 3.8 +/- 1.0 and 1.6 +/- 0.6 mmHg respectively in the normal diet group. The falls in systolic and diastolic blood pressures (mmHg) in the diet phase were 7.7 +/- 1.1 and 4.7 +/- 0.7 (B), 8.9 +/- 1.0 and 5.8 +/- 0.6 (C) and 7.9 +/- 0.9 and 4.2 +/- 0.7 (D). These falls were all greater than those in the control group on an intention-to-treat analysis (P less than 0.005) but did not differ from each other. Factorial analysis confirmed that the falls in pressure attributable to the low-sodium diet and high-potassium diet were not additive.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1985

Renal sympathetic nerve responses to stimulation, inhibition and destruction of the ventrolateral medulla in the rabbit.

The role of the sympathetic nervous system in the cardiovascular responses to lesions of the caudal ventrolateral medulla of the rabbit was investigated by measurement of renal sympathetic nerve activity. In addition, the effect of chemical stimulation and inhibition on renal sympathetic nerve activity was assessed. The results show that lesions or chemical inhibition of the caudal ventrolateral medulla result in an increase in sympathetic nerve activity and blood pressure, whilst excitation results in a decrease in blood pressure and nerve activity. These findings contrast with chemical stimulation or inhibition of the rostral ventrolateral medulla in the region of the C1 cells where stimulation results in a rise in blood pressure and renal nerve activity, and inhibition, a fall in blood pressure and nerve activity.

Animals↗