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Biomedical subjects

G Karlström

Publications and source records attributed to G Karlström.

At least 19 recordsLinked to original sources
PubMed1992

Influence of the renal medulla and early treatment with enalapril upon the development of hypertension in young spontaneously hypertensive rats.

OBJECTIVE: To investigate the role of the renal medulla in early hypertension in spontaneously hypertensive rats (SHR), and to explore whether the attenuated increase of pressure induced by enalapril treatment is affected by chemical medullectomy. DESIGN: Forty-four male SHR were studied from 5 to 18 weeks of age: 22 remained intact; 22 were medullectomized at 5.5 weeks of age with 2-bromoethylamine hydrobromide; 11 of each of these two groups were treated with enalapril from 6 to 12 weeks of age. Blood pressure, heart rate and body weight were recorded intermittently, and at 18 weeks renal function was also analysed. RESULTS: The results indicate a protective effect of the renal medulla against severe pressure rises in SHR, although even when enalapril also lowered blood pressure in medullectomized SHR, persistent improvements of glomerular filtration rate and renal flow conductance occurred only in intact SHR. Furthermore, after enalapril treatment ended blood pressure rose to higher levels in medullectomized SHR, despite greater sodium-water losses. CONCLUSION: The renal medulla seems to exert a protective role both during and after enalapril treatment.

Animals↗
PubMed1992

Transpedicular bone grafts misplaced into the spinal canal.

After open reduction of a burst fracture of L1, transpedicular bone grafting of the fractured vertebral body was performed. Bone grafts accidentally slipped into the spinal canal through the damaged medial wall of the pedicle. No adverse effects were noted clinically, but this case illustrates that transpedicular bone grafting is a potentially dangerous procedure. Computed tomography after 1 year showed complete resorption of the intraspinal bone grafts.

Bone Transplantation↗
PubMed1992

Trophic effects of hypophyseal hormones on resistance vessels and the heart in normotensive and renal hypertensive rats.

UNLABELLED: Arterial pressure is an important determinant of cardiovascular structure and relates positively to it. The purpose of this study was to determine whether pituitary hormones influence the relation of pressure and structure. Male Sprague-Dawley rats, aged 5 weeks, were studied in three groups: the first underwent hypophysectomy; the second was hypophysectomized but received replacement therapy with growth hormone and thyroxine; the third served as controls. Four days later half of each group underwent unilateral renal artery clipping, the other half serving as normotensive controls. For 5 weeks estimates were made of systolic blood pressure, heart rate, body weight and plasma renin activity. Rats were then killed; left ventricular, kidney and adrenal weights were determined and, using hindquarter perfusion, estimates were made of resistance at maximal dilatation (reflecting inner radius), and of maximal pressor response (reflecting wall thickness). RESULTS: (1) Hypophysectomy in non-clipped rats reduced growth rate, systolic blood pressure and heart rate while plasma renin activity rose. As related to pressure and to body weight, resistance at maximal dilatation, maximal pressor response, left ventricular weight remained at the juvenile values of a 5-week-old rat. Hormone replacement restored values to those of control rats aged 11 weeks. (2) Clipping in the control group rats increased systolic blood pressure more than in hypophysectomized and growth hormone and thyroxine receiving hypophysectomized groups even though plasma renin activity remained higher in hypophysectomized than in control rats. Plasma renin activity was highest in hypophysectomized rats with highest pressure. (3) Systolic blood pressure related positively to left ventricle weight, resistance at maximal dilatation, maximal pressor response and calculated wall thickness to inner radius ratios in all groups. However, these regressions were all, like renal structural adaptation, considerably depressed in the hypophysectomized group. Hormone replacement restored the relation of structure and pressure towards that of control group rats. Thus, growth hormone and thyroxine influence maturation of the normal cardiovascular system and greatly enhance its structural upward resetting in hypertension.

Animals↗
PubMed1992

Posterior reduction of a pathologic spinal fracture. A case of indirect anterior dural decompression.

In a patient with paraparesis resulting from a pathologic fracture of Th9, which was due to a breast cancer metastasis, indirect anterior decompression via posterior reduction was performed. The rationale for the operation technique was the similarity between a pathologic fracture of the thoracolumbar spine and a traumatic burst fracture. The method, which uses a transpedicular reduction and fixation device, is substantially less invasive than a formal anterior decompression.

Adult↗
PubMed1992

Surgery for multiple myeloma of the spine. A retrospective analysis of 12 patients.

We report on 12 surgically treated patients with myeloma of the spine. Pain relief was obtained in all the patients. Paraparesis was present in 5 patients. All 12 patients subsequently became ambulatory. The average postoperative survival was 2.3 years. Eight patients, all without symptoms from the treated lesion, survived for more than 1 year. Our experience suggests that surgical treatment of multiple myeloma of the spine may be rewarding.

Aged↗
PubMed1991

Physiological effects of the humoral renomedullary antihypertensive system.

In experiments on rats, the physiological effects of the antihypertensive humoral system of the renal medulla were explored. We studied the parameters of blood pressure, heart rate, efferent sympathetic nervous activity to the splanchnic region, diuresis and natriuresis. The experimental situations included studies on normotensive rats, injected with extracted renomedullary lipids (medullipin), and normotensive rats extracorporally cross-perfusing an isolated kidney at increased pressure levels, to explore the release of renomedullary depressor substances. Spontaneously hyperactive rat (SHR) kidneys were also cross-perfused to study whether the renomedullary mechanism was reset upwards in this type of primary hypertension. Finally, the acute pressure reductions caused by angiotensin converting enzyme (ACE)-inhibitors were studied in intact and chemically medullectomized (2-bromo-ethylamine hydrobromide) rats to explore whether they were at least in part dependent on an intact renal medulla. In normal kidneys the renomedullary depressor system was initiated already at physiological pressure levels (at or above 100 mm Hg), causing the following humorally induced response pattern: the blood pressure fall was associated with decreases in both heart rate and sympathetic activity, while diuresis and natriuresis increased. In SHR kidneys, perfusion pressure had to be raised between 200 and 250 mm Hg before this depressor pattern was activated, revealing an "upward renomedullary resetting" well beyond the prevailing SHR blood pressure. The acute blood pressure decrease initiated in normotensive rats by an ACE-inhibitor (enalaprilat) was abolished in medullectomized rats, indicating an interaction between the renin-angiotensin and the renomedullary antihypertensive systems.

Animals↗
PubMed1991

Is the humoral renal antihypertensive activity of the spontaneously hypertensive rat (SHR) reset to the high blood pressure?

The kidneys have a humoral antihypertensive system, located in the renal medulla and presumably antagonizing the pro-hypertensive renin-angiotensin system. Medullipin I and II and maybe platelet activating factor (PAF), seem to be the mediators of this system, known to be activated after reversal of renovascular hypertension or when the perfusion pressure to a normotensive kidney is suddenly elevated. The present study was undertaken to investigate whether this system is functioning also in the spontaneously hypertensive rat (SHR), and if it is then reset in proportion to the increased mean arterial pressure (MAP). Isolated kidneys from spontaneously hypertensive rats and from Wistar Kyoto rats (WKY) were cross-perfused in vivo from anaesthetized intact Wistar Kyoto rat 'donors'. After 30 min of perfusion at 100 mmHg the perfusion pressure to the isolated kidneys were, for 60 min, either kept unaltered at 100 mmHg or, for the Wistar Kyoto rat kidneys, increased to 150-200 mmHg and, for the spontaneously hypertensive rat kidneys, raised to 200 or 250 mmHg. The results show that the humoral antihypertensive system is present also in spontaneously hypertensive rat kidneys, but is here reset upwards to or even beyond the elevated MAP level. Furthermore, all mean arterial pressure reductions caused by high-pressure perfusion of Wistar Kyoto and spontaneously hypertensive rat kidneys were accompanied by reductions in heart rate (HR) in the 'donors', in agreement with previous observations after reversing renal hypertension and after i.v. medullipin I injection. In fact, in spontaneously hypertensive rat kidneys, the 'incretory' depressor mechanism appears to be more markedly reset upwards than is the 'excretory' depressor mechanism inherent in pressure diuresis with consequent salt-volume elimination. In conclusion spontaneously hypertensive rats, like Wistar Kyoto rats and Wistar rats, have a humoral antihypertensive system in the kidneys, but it is reset upwards even beyond the elevated mean arterial pressure level in spontaneously hypertensive rats. The combination of a depressor response and reduced heart rate in the 'donors' renders further evidence that the medullipins are the principal, though probably not the only, humoral antihypertensive factors released from the cross-circulated kidneys.

Animals↗
PubMed1991

Myogenic responsiveness in rat hindquarter vessels during constant-flow and constant-pressure perfusion in vitro; effects of various potassium concentrations and of endothelial nitrous oxide blockade.

An in vitro constant-flow, alternatively constant-pressure, perfusion method for studying microvascular myogenic responsiveness in otherwise intact rat hindquarters was used to explore how three types of influences affect the pressure-flow induced enhancements of myogenic tone: (1) Changes of potassium concentration over the range 2-50 mmol; (2) Whether myogenic responsiveness, which is fairly weak during these conditions of high shear rates, is enhanced by blockade of endothelial prostacyclin and nitrous oxide formation; (3) Whether some of the drawbacks of the constant-flow technique, like rapid edema formation, is offset by a constant-pressure variant. The result can be summed up as follows. (1) Myogenic responsiveness is also during in vitro conditions markedly influenced by even modest potassium concentration changes around the physiological resting level, e.g. showing a fourfold difference between potassium concentrations of 2.5-4.5 mmol. It was entirely suppressed above 7-8 mmol potassium concentration but also when potassium concentration values above 20 mmol increasingly depolarize and constrict the resistance vessels. (2) While blockade of prostacyclin synthesis was without effect, suppression of endothelial nitrous oxide production could increase myogenic responsiveness up to fourfold, suggesting that shear-stress dependent release of this agent serves to suppress myogenic activity. These effects were, however, quite variable suggesting that also other endothelial inhibitory influences are involved. (3) The constant-pressure variant reduces some of the methodological drawbacks, particularly the oedema formation which can be further reduced by increasing perfusate colloid osmotic pressure. However, interferences by the mentioned, partly unknown endothelial mechanisms still tend to suppress myogenic responsiveness to a varying extent, which hampers quantitative analyses particularly of other inhibitory influences.

Animals↗
PubMed1991

Enzyme purification using temperature-induced phase formation.

A new type of aqueous two-phase system composed of an ethylene oxide and propylene oxide random co-polymer, UCON 50-HB-5100, as the upper phase polymer and either dextran or hydroxypropyl starch as the lower phase polymer has been characterized and used to purify 3-phosphoglycerate kinase (EC 2.7.2.3) and hexokinase (EC 2.7.1.1) from bakers' yeast. The UCON 50-HB-5100 polymer has a cloud point of 55 degrees C at which temperature it phase separates from water. This cloud point can be lowered to 40 degrees C by the addition of 0.2 M sodium sulfate salt. The low cloud point of this UCON polymer makes it possible to obtain the target enzymes in a water and buffer solution, and to recover and recycle the UCON 50-HB-5100 polymer. The phase diagrams for the systems UCON 50-HB-5100/Dextran T500 and UCON 50-HB-5100/hydroxypropyl starch have been determined. Yeast homogenate was first partitioned in a system composed of a top phase containing UCON 50-HB-5100 and a bottom phase containing either dextran or hydroxypropyl starch. The top phase containing the enzyme free of cell debris was removed and the temperature increased above the cloud point of the UCON until a new two phase system composed of water as the top phase and a concentrated liquid UCON 50-HB-5100 bottom phase was formed. The water phase containing the enzyme was removed and the bottom phase containing the UCON 50-HB-5100 could be recycled to perform a second extraction.

Hexokinase↗
PubMed1990

[Leg lengthening--historical review and current techniques].

The techniques earlier used for leg lengthening were notorious for their complications, and as late as the 1960s some authorities would not consider lengthening unless amputation was the alternative. The method introduced by Wagner in the 60s had the advantage of a stable external fixation, permitting the patients to be mobilized. The drawback was that at least three operations were needed: external fixation and osteotomy, bone grafting and internal fixation, and, finally, removal of the plate. With the Ilizarov technique, no bone grafting is needed and bone lengthening up to at least 15 cm is possible. The main problems in leg lengthening are related to joints and soft tissue. Every surgeon performing leg lengthenings should be familiar with the possible problems and complications. He must establish very good relations with the patient and be ready to spend a considerable amount of time with the patient during the process.

Bone Lengthening↗
PubMed1990

Do angiotensin converting enzyme inhibitors lower blood pressure in the rat partly via the humorally mediated antihypertensive system of the renal medulla?

It has been suggested that there is a negative-feedback interaction between the humoral renomedullary antihypertensive system and angiotensin II. If so, the acute blood pressure-lowering effects of angiotensin converting enzyme (ACE) inhibitors might be due, in part, to an increased secretion of renomedullary depressor substances. Groups of anaesthetized Wistar-Kyoto rats (WKY) with an intact or chemically destroyed renal medulla received either saline or the ACE inhibitor enalapril, and mean arterial pressure (MAP), heart rate and renal function were measured. MAP was clearly decreased after enalapril administration in the WKY controls with an intact renal medulla, but was not changed in the medullectomized group. In one WKY control group, where the prostaglandin and kallikrein-kinin systems had also been acutely blocked, the MAP reduction after enalapril was even more marked than in the intact controls. Thus, the acute blood pressure-lowering effect of enalapril is clearly dependent on an intact renal medulla, further suggesting that the renomedullary antihypertensive system is important to normal blood pressure homeostasis.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

Cervical spine fracture caused by high jump.

A case of disabling cervical spine arthrosis after a facet joint fracture sustained during a high jump is described. The condition was successfully treated by posterior fusion.

Adolescent↗
PubMed1990

Anterior stabilization of pathologic dens fractures.

By an anterior approach, six pathologic dens fractures were stabilized with screws and methyl methacrylate cement. All the patients had immediate pain relief and could be mobilized without external support. Using the anterior approach, the tumor can be removed and the instability neutralized at the site of the lesion.

Adult↗
PubMed1979

Open fractures of the shaft of the tibia: analysis of wound and fracture treatment.

Cooperation between orthopaedic and plastic surgeons is an important factor in the treatment of open fractures. In this article a report is made on a retrospective study of a 5-year series of open fractures of the shaft of the tibia treated at the University Hospital in Uppsala between 1972 and 1976. The study proves that the change to external fixation of these fractures and 'open' treatment of the wounds has meant that to a large extent the previous use of pedicle flaps to cover skin defects has been replaced by split skin grafts. The results in the reported series were good, with adequate function in most cases. The final results may, however, be less good than they appeared at this early review time.

Adolescent↗