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Biomedical subjects

G Karlström

Publications and source records attributed to G Karlström.

At least 55 records · Page 3Linked to original sources
PubMed1989

Renal and circulatory effects of medullipin I, as studied in the in-vivo cross-circulated isolated kidney and intact Wistar-Kyoto (WKY) rat.

The renal medulla harbours powerful humoral antihypertensive mechanisms, as earlier explored in unclipping experiments on renal hypertensive rats or in normotensive isolated kidneys cross-circulated at increased perfusion pressures from 'donor rats', in which renal function also seemed to be affected. Injection of the renomedullary factor medullipin I (Med I; formerly ANRL) mimics these haemodynamic responses, and Med I seems to be one of the most important mediators of the depressor effects. The present study was performed to analyse further the haemodynamic and, particularly, the renal effects of Med I, using anaesthetized intact WKY rats and constant-pressure perfused (90 mmHg) isolated WKY kidneys, cross-circulated by these intact 'donor' rats. Mean arterial pressure (MAP), heart rate (HR) and renal function were followed for one 30-min period before and two 30-min periods after injection of 1 mg Med I (M; n = 7) or an equal volume of saline as control (C; n = 13). In the intact 'donor' WKY, MAP and HR remained largely constant in C during the three periods, being 126 +/- 5, 125 +/- 5, and 120 +/- 5 mmHg, while MAP fell in the M group after Med I, from 121 +/- 5 to 107 +/- 7 and 107 +/- 5 mmHg (P less than 0.05), and also HR tended to decrease in M. Renal resistance (RR) fell while renal plasma flow (RPF) and glomerular filtration rate (GFR) increased significantly (P less than 0.05) after Med I in the M donor rats despite their MAP reduction. However, in the constant-pressure perfused, cross-circulated kidneys the RR, RPF and GFR changes were clearly more pronounced (P less than 0.01) and also diuresis, natriuresis, osmolar excretion and osmolar clearance increased significantly after Med I (P less than 0.01). In conclusion, the present results support the view that Med I not only has important and long-lasting depressor effects but also affects renal function in important ways, inducing vasodilatation and increasing GFR, RPF, diuresis and sodium-osmolar excretion.

Animals↗
PubMed1988

The humoral renal antihypertensive system: nervous and hemodynamic effects in normotensive and unclipped renal hypertensive rats.

A series of studies of the humoral renal antihypertensive system in normotensive and 2K 1C-renal antihypertensive rats is outlined. The rapid structural upward resetting of the cardiovascular system in renal hypertensive rats was associated with a structural downward resetting in the vasculature of the hypotensive clipped kidney. Unclipping of this kidney caused a pronounced release of renomedullary depressor agents, explaining the rapid normalization of pressure seen after unclipping. This normalization of pressure masks a state of pronounced functional hypotension in a structurally still hypertensive cardiovascular system, characterized by marked splanchnic vasodilatation and a lack of neurogenic counter-regulation. Only when this state has lasted long enough to normalize the structural upward resettings, characteristic of hypertension does the cardiovascular system return to normal. Further, cross-circulation techniques have shown that the humoral antihypertensive agents suppress tonic sympathetic activity, thereby inhibiting normal reflex counter-regulation of their vasodilator effects. Presumably this occurs via both vagal cardiac afferents and central actions. Further, behavior and awareness become depressed during intense and prolonged renomedullary release. Finally, experiments for which a normotensive kidney is cross-circulated from a normotensive rat suggest that the humoral renomedullary antihypertensive system has its threshold of release set so low as to contribute to normal blood pressure regulation, presumably in reciprocal balance with the renocortical renin-angiotensin system. Stepwise pressure elevations increasingly enhance release of the depressor agents from the cross-perfused kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The importance of hypophyseal hormones for structural cardiovascular adaptation in hypertension.

The effect of renal artery clipping was tested in three groups of male Sprague-Dawley rats: (1) 30 control animals, (2) 30 hypophysectomized animals, and (3) 30 hypophysectomized animals treated with growth hormone and thyroxine. Fifteen rats in each group were clipped and 15 acted as controls. In the first group clipping raised arterial pressure and plasma renin activity. Thirty-five days after clipping, pair-perfused hindquarter preparations at maximal dilation and maximal pressor response were both increased, reflecting, respectively, decreased lumen diameters and increased media thickness in the resistance vessels. Clipping also increased left ventricular weight. Hypophysectomy eliminated the weight gain, and the maximal pressor response and maximal dilation were lower than in the control and treated groups. Hypophysectomy also considerably reduced the rise in blood pressure on clipping and, even more so, the associated structural cardiovascular changes. Replacement therapy with growth hormone and thyroxine almost restored the weight gain and also the structural responses of the heart and vessels to clipping. We conclude that pituitary hormones play an important, probably permissive, part in the development of normal vessel structure and in the adaptation of cardiovascular structure to chronic hypertension.

Animals↗
PubMed1988

Activation of the humoral antihypertensive system of the kidney increases diuresis.

Isolated kidneys taken from normotensive Wistar-Kyoto rats were cross-perfused extracorporeally by normotensive strain-matched donor rats. The extracorporeal perfusion circuit was arranged so that the perfusion pressure to the normotensive recipient kidney could be varied from 90 to 200 mm Hg without any change in total flow through this circuit. This setup avoided hemodynamic or mechanical interferences with reflexogenic circulatory control in the normotensive donor rat when the recipient kidney was manipulated. Diuresis and natriuresis were measured in the normotensive donor rat and the normotensive recipient kidney. A few minutes after normotensive recipient kidney perfusion pressure had been raised, mean arterial pressure (MAP) and heart rate started to decline rapidly in the normotensive donor rat, and circulatory collapse ensued within 15 to 100 minutes. During the control period at 90 mm Hg normotensive recipient kidney perfusion pressure, urinary flow, MAP and heart rate were stable in the normotensive donor rat and the normotensive recipient kidney. When perfusion pressure was raised to 200 mm Hg in the recipient kidney, the urinary flow in the donor rat increased 62% on average in the first 10 minutes over values recorded before the pressure rise (p less than 0.05) while MAP simultaneously fell by 16% and HR remained unchanged. During the subsequent period, the urinary flow of the donor rat declined together with MAP and heart rate. In the extracorporeally high-pressure perfused recipient kidneys, an eightfold to ninefold increase in diuresis and natriuresis occurred during the first 45 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Transpedicular segmental fixation: description of a new procedure.

The treatment of unstable fractures of thoracolumbar vertebrae is a controversial issue in the orthopedic community. The various methods employed for operative stabilization of these injuries have to date been found to have major disadvantages. A new therapeutic principle and a new device for stable internal fixation are presented.

Adult↗
PubMed1988

Transpedicular fixation of thoracolumbar vertebral fractures.

The most frequent surgical treatment of thoracolumbar fractures is still the Harrington rod system despite some adverse effects, the most serious being the locking of five to seven segments. The new pedicular fixation modifications suggested by Magerl and Dick lock only two segments and give far better stability of the fractures. Used internally, the system is convenient for the patient, permitting early mobilization, often without any external support. The instrument, called the "posterior segmental fixator" (PSF), is used both as a reduction device and as a fixation device. The injured vertebra is grafted through the pedicle, giving security against late collapse after device removal. Twenty patients treated with this method had an average follow-up period of ten months. The primary reduction attains 88% of the calculated height of the injured vertebra, with only a few percent loss during follow-up time. Clearance of fragments in the spinal canal, diagnosed with computed tomography scan in eight patients, was successfully accomplished in all but one, with only distraction or reduction of the fragment through a limited laminotomy. The instrumentation in these cases was lateral to the dura. Nine patients with neurologic deficits improved and could walk without support or with crutches within a few months. One patient with complete paraplegia remained unchanged.

Adolescent↗
PubMed1987

Phase equilibria in the phosphatidylcholine-cholesterol system.

A thermodynamic and a microscopic interaction model are proposed to describe the phase equilibria in the phosphatidylcholine-cholesterol system. The model calculations allow for a solid phase with conformationally ordered acyl chains and liquid phases with conformationally ordered as well as disordered chains. The resulting phase diagram is in excellent agreement with the experimental phase diagram for dipalmitoylphosphatidylcholine bilayers with cholesterol as determined by a recent NMR and calorimetry study. It is thus demonstrated that the phase behaviour of phosphatidylcholine-cholesterol mixtures can be rationalized using only a few basic assumptions: (i) Cholesterol interacts favourably with phosphatidylcholine chains in an extended conformation, (ii) the main transition of pure phosphatidylcholine bilayers takes place in terms of translational variables as well acyl-chain conformational variables, and (iii) cholesterol disturbs the translational order in the crystalline (gel) state of phosphatidylcholine. These results suggest that the occurrence of specific phosphatidylcholine-cholesterol complexes is not implied by the experimental thermodynamic data.

Chemical Phenomena↗
PubMed1987

Internal fixation of fractures and dislocations in the cervical spine.

The treatment of fractures of the cervical spine, like that of fractures of the extremities, has been considerably improved in the last decade. The aim of these changes has been to prevent and correct deformities and to achieve such a high degree of primary stability with the use of different internal fixation techniques that traditional external fixation can be avoided. Non-stable internal fixation and laminectomies, which invariably result in further loss of stability, have thus been completely eliminated from the therapeutic arsenal. The new system implies a considerably milder course of treatment for the patient. Confinement to bed is limited to a few days, even for tetraplegic patients. The duration of stay in the hospital is short and any necessary rehabilitation can be started at an extremely early stage. This article describes some of the new techniques and provides examples of indications for and methods of performing stable internal fixation.

Adolescent↗
PubMed1987

Intra- and post-operative blood loss and haemodynamics in total hip replacement when performed under lumbar epidural versus general anaesthesia.

The effects of lumbar epidural anaesthesia and two types of general anaesthesia on blood loss and haemodynamics during and after hip replacement were compared in three groups of patients. One group (n = 14) received continuous lumbar epidural anaesthesia, another group (n = 10) was given inhalational anaesthesia and spontaneous breathing after endotracheal intubation, and the third group (n = 14) received artificial ventilation after intubation and pancuronium and fentanyl intermittently i.v. Intra-operative blood loss in patients under epidural anaesthesia was 950 +/- 300 ml (mean +/- SD) and blood loss during the following 24 h-i.e. as long as the epidural anaesthesia was maintained-was 370 +/- 80 ml. These figures were significantly lower than the intra- and post-operative blood losses in patients under general anaesthesia with narcotics as post-operative pain treatment: 1140 +/- 200 ml (inhalational anaesthesia) followed by 480 +/- 70 ml and 1540 +/- 340 ml (artificial ventilation) followed by 500 +/- 110 ml. The intra-operative blood loss in the general anaesthesia group with spontaneous breathing was significantly smaller than the blood loss in the artificially ventilated group, whereas the post-operative blood loss in the two general anaesthetic groups was similar. Haemodynamic differences explain these differences in blood loss. Thus epidural anaesthesia induced hypotension on the arterial and venous sides. Intra-operatively, inhalational anaesthesia also induced hypotension on the arterial and venous sides compared with general anaesthesia using artificial ventilation. Post-operatively, the general anaesthesia groups behaved haemodynamically similarly and no differences in blood loss were seen. The reduction in blood loss, notably associated with lumbar epidural anaesthesia, is beneficial in decreasing the hazard and cost of blood transfusion.

Aged↗
PubMed1987

The humorally mediated antihypertensive system of the rat kidney: a physiological depressor mechanism?

The humoral renomedullary antihypertensive system, described by Muirhead [1], is known to be strongly activated upon unclipping renal hypertensive rats. The present study was designed to determine whether this system is tonically active in normotensive rat kidneys at normotensive pressure levels. Anaesthetized normotensive donor rats (NDR) were used to perfuse an isolated age-matched normotensive recipient (NRR) kidney, via an extracorporal circuit, set at different perfusion pressures, while the NDR mean arterial pressure and heart rate were measured continuously. The results showed non-significant alterations in the NDR heart rate and mean arterial pressure at 80 mmHg NRR kidney perfusion pressure, while at 100 and 150 mmHg there were significant, dose-dependent and gradual reductions in both the heart rate and mean arterial pressure in NDR. We conclude that the renal humoral antihypertensive system is active in normotensive kidneys already in the normotensive pressure range, but becomes further engaged in a dose-dependent way when renal perfusion pressure is raised.

Animals↗
PubMed1986

The influence of nylon cerclage on diaphyseal bone strength: an experimental evaluation of Partridge bands on rabbits.

Partridge-designed nylon bands which are used for the cerclage of fractured osteoporotic bones. These bands were given elevations on their inner surfaces to raise the band from the bone surface and thus minimize the negative effects on the periosteal blood circulation. It has previously been shown that the Partridge bands, when applied to a diaphyseal bone, cause a mechanical irritation to the periosteum resulting in an increased callus formation by comparison with the case when corresponding bands with no elevations are applied. It has been suggested that the increased amount of callus would result in increased strength. We have studied the effect of bands designed in accordance with Partridge, compared with corresponding bands having no elevations, in terms of torsion strength (maximum torque capacity), on intact rabbit femora. The results show an increased torsion strength in the femora to which Partridge bands had been applied for eight weeks, while the femora to which corresponding plain nylon bands had been applied had decreased in strength. The experimental study performed supports Partridge's recommendation to use the bands as cerclage in the internal fixation of fractured osteoporotic bones, preferably in combination with further internal fixation materials.

Animals↗
PubMed1986

Spontaneous effect of increased stability of the lower lumbar spine in cases of severe chronic back pain. The answer of an external transpeduncular fixation test.

Eighteen patients with severe low-back pain of long duration were externally stabilized over selected segments of the lumbar spine to evaluate the pain relieving effect of increased stability. Five millimeter Schantz screws were driven into the vertebral body transpeduncularly by a closed technique using an image intensifier. A modified Hoffmann fixation device with possibilities to compress and distract was used for external stabilization. The results were recorded by means of pain area sketches and pain lines. All but one patient experienced remarkable relief of low-back pain and often of pain radiating into the lower extremities. No serious complications were seen. Of eight patients with residual severe pain after fusions, five were considered healed using radiologic techniques and three were improved by external stabilization. This test could be used to identify candidates, select levels for lumbar fusion, and evaluate the stability of previous fusions.

Adult↗