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Biomedical subjects

L E Larsson

Publications and source records attributed to L E Larsson.

At least 19 recordsLinked to original sources
PubMed1995

A stable late soleus EMG response elicited by cortical stimulation during voluntary ankle dorsiflexion.

Transcranial electrical or magnetic stimulation was performed in 47 experiments on 42 normal adult subjects. Surface compound muscle action potentials were recorded from the antagonistic tibialis anterior (TA) and soleus (SOL) muscles. A stable late response recorded from SOL during voluntary ankle dorsiflexion is described and called soleus MEP-80. Its origin has been studied with different experimental procedures. (1) It is only obtained during active voluntary dorsiflexion of the ankle within 70-100 msec (mean 86.9 +/- 6.4 msec) whereas passive dorsiflexion does not promote such a response. The size of SOL MEP-80 was always bigger than the primary SOL response. (2) A similar constant response has not been obtained during voluntary plantar flexion from SOL and TA muscles. (3) SOL MEP-80 is not changed significantly by the Jendrassik manoeuvre. (4) It is not obtained or is suppressed when the subject is sitting with the feet free in space. On the other hand, it is obtained when the subject is standing, especially when standing is made difficult. (5) SOL MEP-80 has not been obtained by brain-stem, spinal cord or root stimulation. (6) A later response of longer than 100 msec latency was sometimes obtained at rest but such an S100 soleus response was abolished or transformed to the SOL MEP-80 immediately during ankle dorsiflexion. (7) It is concluded that SOL MEP-80 is a polysynaptic extensor response related to postural mechanisms and originating through convergence of descending motor commands and peripheral sensory feedback.

Adult↗
PubMed1995

Effects of propranolol pretreatment on cerebral blood flow, oxygen uptake and catecholamines during metabolic acidosis following E. coli endotoxin in dogs.

After an intravenous injection of E. coli endotoxin in dogs a decrease in cerebral blood flow (CBF) and an increase in cerebral metabolic rate of oxygen (CMRo2) have been shown to occur. In metabolic acidosis following endotoxin CMRo2 increased with decreasing pH. A possible explanation for the increased CMRo2 after endotoxin and metabolic acidosis seems to be a damage of the blood-brain barrier (BBB) by endotoxin. This gives possibilities for a leakage of hydrogen ions and circulating monoamines from the blood to the brain, thus affecting the cerebral blood flow and metabolism. The effects of an E. coli endotoxin injection on CBF and CMRo2 during metabolic acidosis and beta-adrenoceptor blockade were studied in eight anaesthetized dogs. All the dogs were pretreated with propranolol (PPL), per os 12.5 mg.kg-1 twice a day for one week. Metabolic acidosis (pH 7.01-7.30) was achieved by an intravenous infusion of hydrochloric acid. Endotoxin E. coli lipopolysaccharide O 111:B 4 was given as an intravenous injection of 1 mg.kg-1 bodyweight over a 5 min period. Another five animals, published earlier, with the same experimental protocol but without PPL, constituted a control group. After endotoxin no increase in CMRo2 or CBF was observed with increasing acidosis in the PPL-group. In the control group, after endotoxin, both CBF and CMRo2 increased with decreasing pH. This resulted in a significant difference in both CBF and CMRo2 between the groups in the pH range 7.01-7.15. The present results indicate that the increase in CMRo2 and CBF with metabolic acidodis in endotoxinaemia is mediated via beta-adrenoceptors.

Acidosis↗
PubMed1995

Effects of arterial hypoxia and beta-adrenoceptor blockade on cerebral blood flow and oxygen uptake following E. coli endotoxin in dogs.

Earlier studies in normoxia have shown that an endotoxin injection in dogs leads to an increase in cerebral metabolic rate of oxygen (CMRo2), a decrease in cerebral blood flow (CBF) and increased concentrations of monoamines in blood and cerebrospinal fluid (CSF). In animals pretreated with propranolol (PPL) the CMRo2 increase was abolished and thus beta-adrenoceptor mediated. Arterial hypoxia normally increases CBF without any influence on CMRo2. The aim of this study was to investigate the effects of moderate arterial hypoxia on CBF, CMRo2 and catecholamine concentrations in blood and CSF after endotoxin with and without pretreatment with PPL. Three groups of dogs were studied. Group 1: Six animals were subjected to arterial hypoxia without any other intervention. Group 2: Six animals were given an endotoxin injection (E. coli lipopolysaccharide O 111: B 4), before the induction of hypoxia. Group 3: Eight animals were pretreated with PPL per os, 12.5 mg.kg-1 twice a day for one week before the experiments, and the effects of arterial hypoxia were studied both before and after an intravenous injection of endotoxin. Two levels of hypoxia were studied; oxygen saturation in arterial blood aiming at 75 and 50%. Endotoxin was given intravenously in a dose of 1 mg.kg-1 bodyweight over a 5 minute period. After an endotoxin injection, the response to arterial hypoxia was an increase in CMRo2, in contrast to the unchanged CMRo2 without endotoxin. After pretreatment with PPL the increase in CMRo2 after endotoxin was prevented. The CBF reaction to hypoxia was uniformly an increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effects of metabolic pH-alterations on cerebral blood flow and oxygen uptake following E. coli endotoxin in dogs.

The aim of the present study was to investigate if metabolic pH-alterations have an influence on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) after an injection of E. coli endotoxin. Following endotoxin in dogs with normal pH a decreased CBF and an increased CMRO2 have earlier been found. Thirteen anaesthetized dogs were subjected to metabolic pH-variations in blood by infusion of hydrochloric acid or sodium bicarbonate. Ten dogs received E. coli endotoxin in a dose of 1 mg.kg-1 bodyweight. CBF, CMRO2 and noradrenaline and adrenaline concentrations in blood and cerebrospinal fluid were measured repeatedly during normoxia and normocarbia. Measurements before endotoxin served as controls, together with three additional animals, where endotoxin was never given. In control measurements pH showed no influence on the variables studied. After endotoxin CBF, CMRO2 and noradrenaline in cerebrospinal fluid increased with decreasing arterial blood pH. The influence exerted by metabolic pH alterations in blood after endotoxin may be explained by hydrogen ions and monoamines passing over a blood-brain barrier (BBB), damaged by endotoxin, into the brain tissue causing vasodilation and neuronal activation.

Acidosis↗
PubMed1994

Early postoperative lipid administration after neonatal surgery.

The ability of neonates to eliminate and utilize lipid emulsions after surgery was investigated in 12 patients. All were subjected to major surgery within 29 h of birth. All neonates were given 10% glucose iv intraoperatively. Six patients continued with 10% glucose iv for 24 h postoperatively and 6 patients received a combination of 5% glucose and soy bean emulsion (Intralipid 20%). Both regimes provided equal amounts of fluid and energy. Blood glucose, lactate, triglycerides, free fatty acids, fractions of fatty acids in triglycerides, 3-hydroxybutyrate and arterial blood gases were measured at predetermined intervals throughout this period. Administration of a lipid emulsion early after neonatal surgery was well tolerated and utilized, with some latency. Concentrations of triglycerides, free fatty acids and 3-hydroxybutyrate were higher in the lipid group, but no accumulation of these substances was found. Palmitinic and linoleic acid were also higher in the lipid group.

Fat Emulsions, Intravenous↗
PubMed1993

The effects of prophylactic dixyrazine on postoperative vomiting after two different anaesthetic methods for squint surgery in children.

The incidence of postoperative vomiting after squint surgery was studied for two anaesthetic techniques with and without prophylactic dixyrazine. After induction, anaesthesia was maintained with either fentanyl/pancuronium/nitrous oxide or halothane/nitrous oxide in two randomly selected groups of 58 children each. Half of the children in each group were randomly allocated to receive dixyrazine 0.25 mg kg-1 i.v. after surgery had been completed but before reversal of muscle relaxants or termination of anaesthesia. With prophylactic dixyrazine the incidence of postoperative vomiting was significantly reduced from 69% (20/29) to 21% (6/29) in the fentanyl group and from 45% (13/29) to 10% (3/29) in the halothane group. Without prophylactic dixyrazine, 20 of 29 children in the fentanyl group vomited compared to 13 of 29 in the halothane group (n.s.). Thus, prophylactic dixyrazine reduced the incidence of vomiting in children given either opioid or halothane anaesthesia for squint surgery. In comparable groups avoidance of opioid anaesthetic technique and use of prophylactic dixyrazine resulted in a greatly reduced incidence of vomiting.

Adolescent↗
PubMed1993

Metabolic consequences of different perioperative fluid therapies in the neonatal period.

Carbohydrate and fat metabolism during and after anaesthesia and surgery was studied in 14 neonates with major congenital non-cardiac anomalies. They were either given a glucose solution until surgery or starved for at least 4 h before surgery. Ringer-acetate alone or Ringer-acetate plus 10% glucose was used for the intraoperative fluid therapy. After anaesthesia all neonates were given a 10% glucose solution. Concentrations of glucose, free fatty acids, triglycerides, lactate, pyruvate, alanine, glycerol and 3-hydroxybutyrate were measured at predetermined intervals pre-, intra- and postoperatively. Blood glucose concentrations rose during surgery both in neonates given glucose before and during surgery (n = 6) and in neonates not given glucose before and during surgery (n = 6). Increased intraoperative levels of free fatty acids and 3-hydroxybutyrate were found in neonates not given glucose before and during surgery. The triglyceride levels were equal in both groups. In two neonates given glucose before surgery and Ringer-acetate during surgery increased levels of 3-hydroxybutyrate were found, particularly in one patient who became hypoglycaemic. In conclusion, starved neonates without intraoperative glucose supply mobilized fat and maintained blood glucose concentrations.

3-Hydroxybutyric Acid↗
PubMed1993

Distribution of radioactive microspheres injected into the vertebral artery of the dog.

The aim of the present study was to evaluate the use of the vertebral artery for cerebral blood flow studies. In eight dogs a small catheter was introduced into an unligated a. vertebralis sin. Radioactive microspheres (141Cerium) were injected and detected with a gamma camera. The microspheres were distributed to all parts of the brain. The concentrations were highest in the cerebellum, pons and medulla oblongata, while the total activity was greatest in the cerebrum because of its higher weight. The activity in the extracerebral tissues in the head was found to be less than 5% of the brain activity.

Animals↗
PubMed1992

Transcranial cortical stimulation. Late excitability changes in the soleus and anterior tibial motoneurone pools.

The effect of conditioning magnetic transcranial cortical stimulation (TCCS) on the excitability levels of the soleus and anterior tibial motoneurone pools was studied by Hmax/2 technique 40-400 msec after the stimulus. The target muscles were relaxed throughout the tests. Two periods of facilitation (the first at 80-100 msec and the second at 180-200 msec) were found. They shared approximately the same latencies as the late responses (S100 and S > 150) that we have previously recorded following TCCS. A period of inhibition that started at 150 msec was also recorded. A period of facilitation could also be noted when the conditioning stimulus was applied either over the deltoid muscle or when the click that accompanied the magnetic pulse was used. This suggests that brain-stem areas related to those of the startle reaction play an important role for the appearance of the facilitatory changes. The necessary input probably comes from both peripheral and cortical sources.

Adolescent↗
PubMed1991

Prevention of endotoxin-induced increase of cerebral oxygen consumption in dogs by propranolol pretreatment.

Cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were studied in experimental endotoxic shock in dogs. Eight animals were pretreated with a beta-adrenoceptor blocking agent, propranolol (PPL), per os 12 mg/kg once a day for 7 days. Ten animals served as controls. After an intravenous injection of endotoxin, 1 mg/kg, CBF decreased in both groups, with no significant differences between the groups. CMRO2 increased in the control animals by about 18% from the baseline value both 1 and 2 h after the injection of endotoxin. CMRO2 in the PPL-pretreated animals was unchanged after endotoxin. The CMRO2-reactions to endotoxin in control and PPL animals were significantly different after both 1 and 2 h (P less than 0.05). The present results indicate that the increase in CMRO2 following intravenous endotoxin is mediated via beta-adrenoceptors.

Animals↗
PubMed1990

Examination of the descending pathway to the external anal sphincter and pelvic floor muscles by transcranial cortical stimulation.

In 26 neurologically normal patients and 9 healthy volunteers EMG responses after transcranial cortical stimulation (TCCS) were recorded from the external anal sphincter (EAS), the anterior tibial muscle (TA), the bulbocavernosus muscle (BC) and the rectus abdominis muscle (RA). Electrical TCCS was used in 29 subjects and magnetic TCCS in 6 subjects. Response patterns in the different muscles in relation to the strength of the stimulus were analyzed. It was found that the response patterns related to the strength of stimulation differed totally between the TA and the EAS. When the stimulus strength was increased stepwise, a response with a latency of 31.9 +/- 2.5 msec was first recorded in the TA, followed at higher strength by a secondary response with a latency of approximately 100 msec. In contrast, a response with a latency of 105.5 +/- 23.9 msec was first recorded in the EAS. The latency of this response gradually shortened with increasing stimulus strength until a response with a constant latency of 36.1 +/- 6.1 was obtained. In some subjects the response pattern in the BC was similar to that in the TA, and in others it was similar to that in the EAS. Responses in the TA, RA and EAS were all facilitated during voluntary contraction of the EAS. Both responses in the TA and in the EAS were facilitated by voluntary contraction of the TA. During voluntary contraction of the TA an inhibitory period was always recorded, while in the EAS no inhibitory periods were observed during either contraction or relaxation. The hypothesis that the fastest cortico-motoneuronal pathway to the EAS is polysynaptic is proposed.

Adult↗
PubMed1990

Late muscular responses to transcranial cortical stimulation in man.

Transcranial cortical stimulation was performed in healthy human subjects. Electrical and magnetic stimuli were applied over the motor areas of the hand and the leg. Surface EMGs were recorded from the antagonistic extensor and flexor carpi radialis and the anterior tibial and triceps surae muscles. Except for the well known early (primary) responses several secondary responses have been recorded. (1) A response with a latency of approximately 100 msec and with higher threshold than the primary response. It was found in approximately half of the muscles recorded from except for the anterior tibial where it was comparatively rare. It could appear both contra- and ipsilaterally and increased in amplitude with preactivation of the target muscle. It is probably not of startle origin but its appearance may be influenced by an approximately simultaneous startle effect from the scalp stimulus. (2) In some subjects a response with a latency of 50-60 msec was recorded. Sometimes it was easily separated from the primary response and from S 100 but sometimes the differentiation was difficult. (3) It was found that the known inhibitory period which follows the primary response was contralateral and increased in duration with increasing stimulus strength. The increase in duration may be due to inhibitory feedback from receptors activated by the simultaneously increasing primary muscle twitch. (4) In relaxed muscle we also observed a contralateral response with a latency exceeding 150 msec. The latency increased with increasing stimulus strength. This increase seems to be related to discontinuance of the inhibitory period.

Cerebral Cortex↗
PubMed1990

Influence of fluid regimens on perioperative blood-glucose concentrations in neonates.

Blood concentrations of glucose were measured during surgery and during the first 8 h after operation in 30 neonates undergoing major surgery during the first week of life. Fifteen of the neonates were given Ringer-acetate as the only crystalloid peroperative fluid; to the other 15, 10% glucose i.v. was administered during surgery. In the Ringer-acetate group, mean (SD) blood concentration of glucose increased from 3.1 (2.0) to 4.3 (2.4) mmol litre-1 during surgery. The corresponding increase in the glucose-supplemented group was 3.4 (1.5) to 6.3 (2.2) mmol litre-1. In the Ringer-acetate group, peroperative blood concentrations of glucose were found to be low if a preoperative glucose infusion was interrupted at the start of anaesthesia. Hypoglycaemia occurred in both groups, but more often in the group given Ringer-acetate only (3/15 vs 1/15). Hypoglycaemia was found only in neonates less than 48 h of age and during the first 1 h of anaesthesia only. Monitoring of blood concentrations of glucose and adjustment of the glucose infusion appears to be desirable during and after surgery in neonates.

Blood Glucose↗
PubMed1990

Parenteral nutrition in preterm neonates with and without carnitine supplementation.

The effects of carnitine supplementation on fat and glucose metabolism and carnitine balance were studied in 12 preterm neonates receiving full or partial parenteral nutrition (PN) for 5 to 21 days. The gestational age ranged from 27 to 32 weeks and the birth weight from 790 to 2090 g. The neonates were assigned at random to receive either L-carnitine 10 mg/kg (n = 6) or saline (n = 6). In the carnitine group, increased concentrations in plasma of total and free carnitine were observed. Less than 50% of the given dose was recovered in urine. In the placebo group no changes in the total plasma carnitine concentration were seen. In all neonates plasma triglycerides, free fatty acids, glycerol, alanine, 3-hydroxybutyrate (BOB), glucose and lactate were measured at predetermined intervals. The only significant difference between the groups was higher BOB-concentrations in the carnitine group 2 days after the start of parenteral nutrition. Elevated BOB concentrations are an indicator of improved fatty acid oxidation in the carnitine group. In this study, only a temporary effect of the carnitine supplementation was found.

Alanine↗
PubMed1990

Postanaesthetic nausea in children.

The incidence of emetic episodes during the first 24 h after anaesthesia was studied prospectively in 485 children aged 0-16 years in relation to age, premedication, type of induction, type and duration of anaesthesia, type of surgery and use of postoperative analgesics. The incidence of emetic episodes was 25% in the whole material. The majority of the emetic episodes were recorded after the immediate recovery period. In children under 2 years of age, vomiting was only recorded in 5%. Nausea and vomiting was most common after squint surgery (75%) and least common after endoscopies (17%). Neither premedication with diazepam nor the method of induction (thiopentone, i.v., thiopentone rectally, inhalation with halothane) influenced the incidence of nausea. For the same type of surgery, maintenance of anaesthesia with halothane resulted in a lower incidence of nausea than anaesthesia with fentanyl-pancuronium.

Adolescent↗
PubMed1989

Surface electromyography of pelvic floor muscles in healthy children. Methodological study.

Pelvic floor muscle activity was recorded in ten healthy children, aged six to ten years, by using surface electromyography and a polygraph writer. The electromyograms were recorded simultaneously from four electrode pairs on the perineum and three electrode pairs on adjacent muscle groups, i.e. hip and abdominis muscles. The children performed ten different manoeuvres. Necessary prerequisites for this investigatory method include good electrode application, adequate instruction of the child and the child's adjustment to the method. Using the described procedure, it was possible to record pelvic floor muscle activity without any appreciably detectable electrical influence from adjacent muscles. The method sometimes allows selective recording of electromyographic activity between the ventral urogenital and the dorsal anal regions. Therefore both anal and urethral electrode pairs should be used to achieve functional information about the pelvic floor muscles. The envisaged method should be useful as a tool for assessment of pelvic floor muscle exercises in children with voiding disorders.

Child↗
PubMed1989

A neurophysiological study of patients undergoing radical prostatectomy.

24 men suffering from localized prostatic cancer undergoing radical retropubic nerve-sparing prostatectomy were investigated by the following electrophysiological methods: Bulbocavernosus reflexes elicited from the penile skin or the posterior urethra, sensory thresholds in the posterior urethra, cerebral evoked potentials after stimulation of the pudendal nerve or the posterior urethra. 15 men were examined 4-33 months postoperatively only, 5 men were examined only preoperatively and 4 men were examined both pre- and postoperatively. 10 men suffering from minor problems due to benign prostatic hyperplasia served as controls. In patients with localized cancer of the prostate, the findings did not differ from those in the control group. In the operated group the findings were pathological in a large proportion of the patients, indicating injuries both to nervous pathways running through the pelvic nerve plexus and in the pudendal nerve. The conclusions were: Localized cancer of the prostate has minimal or no risk at all of impaired functioning in the pelvic nervous pathways. Radical retropubic prostatectomy may in some cases be undertaken without any objective evidence of injury to these nervous pathways, but is often followed by findings indicating such injury. The dorsal nerve of the penis may be affected by the operation. Transcranial stimulation of the motor cortex is a useful method in the evaluation of prolonged or absent bulbocavernosus reflexes.

Aged↗