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J Carlsen

Publications and source records attributed to J Carlsen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Impact of immediate and delayed myocardial scintigraphy on therapeutic decisions in suspected acute myocardial infarction.

Early myocardial scintigraphic imaging has become technically feasible in patients admitted to hospital with suspected acute myocardial infarction. After prompt injection of 99mTc-sestamibi, subsequent scintigraphic imaging of perfused myocardium can be performed. During a 5-month period, 237 patients were admitted to the coronary care unit of a district hospital on suspicion of acute ischaemic syndrome, and injection of 99mTc-sestamibi for the performance of myocardial scintigraphy was carried out in 134 patients, on average 2 h after onset of symptoms. The investigation was repeated in 126 patients, on average 18 h after the injection. Three planar views were taken in the coronary care unit with a mobile gamma camera. The prevalence of acute myocardial infarction was 53%. The predictive value at the first scintigraphic imaging for a positive or negative test for myocardial infarction 54% and 56%, respectively. Even exclusion of patients with a previous infarction did not increase the diagnostic validity. The predictive value of a negative test, 77%, at the second scintigraphy was still insufficient to make immediate therapeutic decisions. Myocardial scintigraphy performed early, on suspicion of acute myocardial infarction, cannot therefore be used routinely as a diagnostic test prior to intervention in unselected patients because some 90% of this patient group have myocardial perfusion defects.

Aged↗
PubMed1994

CMP-N-acetylneuraminic acid hydroxylase from mouse liver and pig submandibular glands. Interaction with membrane-bound and soluble cytochrome b5-dependent electron transport chains.

In this report, the nature of the protein components involved in the functioning of cytidine-5'-monophosphate-N-acetylneuraminic acid (CMP-Neu5 Ac) hydroxylase in high-speed supernatants of mouse liver has been investigated. Fractionation and reconstitution experiments showed that this enzyme system consists of NADH-cytochrome b5 reductase, cytochrome b5 and a 56-kDa terminal electron acceptor having the CMP-Neu5 Ac hydroxylase activity. This enzyme system is extracted in a soluble protein fraction; however, the amphipathic, usually membrane-associated, forms of cytochrome b5 and the reductase were found to predominate and are presumably the forms which support the turnover of the hydroxylase in vivo. Although the majority of cellular cytochrome b5 and cytochrome b5 reductase is membrane-bound, the addition of intact microsomes elicited no significant increase in the hydroxylase activity of supernatants. Detergent-solubilised microsomes, however, potently activated the hydroxylase, probably due to the greater accessibility of the cytochrome b5. Accordingly, in reconstitution experiments, pure hydrophilic cytochrome b5 interacts more effectively with the hydroxylase than isolated amphipathic cytochrome b5. Studies on the CMP-Neu5 Ac hydroxylase system in fractionated porcine submandibular glands and bovine liver suggest that the composition of this enzyme system is conserved in all mammals possessing sialoglycoconjugates containing N-glycolylneuraminic acid.

Animals↗
PubMed1994

Membrane topology of insulin receptors reconstituted into lipid vesicles.

Insulin receptors were incorporated into liposomes by two different procedures, one using dialysis and one using detergent removal by Bio-Beads. Receptor incorporation was analyzed by gradient centrifugation and electron microscopy. Reconstituted receptors projected up to 12 nm above the membrane and exhibited a T-shaped structure compatible with that previously described for the solubilized receptor. Insulin binding and autophosphorylation experiments indicated that approx. 50% of the receptors were incorporated right-side out. Such random orientation was confirmed by immunogold labeling of the alpha- and the beta-subunit of the receptor. Immunogold labeling of the C-terminus of the beta-subunit indicates that it resides about 6 nm off the membrane, while two alpha-subunit epitopes were labeled at about twice this distance, confirming that the alpha-subunit is harbored in the cross-bar of the T-structure.

Humans↗
PubMed1994

An echocardiographic method for selecting high risk patients shortly after acute myocardial infarction, for inclusion in multi-centre studies (as used in the TRACE study). TRAndolapril Cardiac Evaluation.

The aim of our study was to examine if echocardiography can reproducibly be used in a multicentre study to select high risk patients with reduced left ventricular function early after an acute myocardial infarction (MI). In the TRAndolapril Cardiac Evaluation Study (TRACE) patients with reduced left ventricular systolic function were randomized 3-7 days post MI to receive either the ACE inhibitor trandolapril, or placebo. Twenty-seven Danish centres participated and 7001 consecutive MI patients were screened for entry. Local doctors and technicians who had received a brief but thorough training course recorded a two-dimensional echocardiographic examination on videotape 2-6 days after MI. Within 24 h, wall motion index (WMI) was visually assessed by one of two cardiologists (examiners) with considerable experience in echocardiography. A WMI of < or = 1.2 (corresponding to a left ventricular ejection fraction (LVEF) < or = 0.35) meant that the patient was eligible for randomization in the TRACE study. Two other experienced cardiologists with substantial experience in echocardiography (controllers) performed blind reassessment of 155 randomly chosen videotapes. We showed that 93% of the 7001 screened MIs had an assessable echocardiogram. WMI was < or = 1.2 in 37% of patients. The one-year mortality was inversely related to WMI, being 60%, 30%, 14% and 11% in patients with a WMI < 0.8, 0.8-1.2, 1.3-1.6 and > 1.6, respectively. In the random sample of 155 videorecordings that were reevaluated, 97% were found to be technically adequate for analysis both by the examiners and the controllers.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Mouse liver cytidine-5'-monophosphate-N-acetylneuraminic acid hydroxylase. Catalytic function and regulation.

In this paper, we present the results of an investigation into the catalytic properties of CMP-Neu5Ac hydroxylase (Neu5Ac: N-acetylneuraminic acid) in high-speed supernatants of mouse liver. The enzyme was most active in Hepes/NaOH pH 7.4 and was markedly inhibited by relatively small increases in ionic strength, though the inhibition was abolished by desalting procedures. Several nonionic detergents could activate the hydroxylase to various degrees in a concentration-dependent manner. Ionic detergents and a number of phospholipids were, however, generally inert or inhibitory. The lack of inhibitory influence of a wide range of nucleotides revealed that CMP-Neu5Ac hydroxylase binds its sugar-nucleotide substrate with a high degree of specificity. Thus, even millimolar concentrations of several cytidine nucleotides elicited virtually negligible inhibition, though the reaction product, CMP-Neu5Gc (Neu5Gc: N-glycoloylneuraminic acid), was a weak inhibitor. The results also indicate that the enzyme is not regulated by any nucleotides or sugar-nucleotides. Dilution of high-speed supernatants with buffer gave rise to a decrease in the specific activity of the hydroxylase, implicating the involvement of more than one component in catalysis. Activity could be restored by the addition of a heat extract of the supernatant. The active principle in this extract was found to be a heat-stable protein with a molecular mass of about 17 kDa. Immunochemical studies allowed this protein to be identified as cytochrome b5 and it was shown that this electron carrier is essential for the activity of CMP-Neu5Ac hydroxylase. Inhibition studies using iron ligands and activation by exogenous iron salts suggest the involvement of a non-haem iron cofactor in the catalytic cycle of this hydroxylase. Cytochrome b5 may thus serve as an electron donor for this postulated cofactor.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗
PubMed1992

Insertion of isolated insulin receptors into placental membrane vesicles.

Purified human insulin receptors were inserted into placental plasma-membrane vesicles by fusion of membranes with receptor-lysophosphatidylcholine micelles. Scatchard analysis of insulin binding showed that about 10-15% of the added receptors became inserted into the membrane. The receptor number could be increased about 3-fold, corresponding to approx. 5 pmol of receptor/mg of membrane protein. The receptors became firmly bound to the membrane, as they could not be removed by extensive wash. The insertion of exogenous receptors could be demonstrated by immunoblotting. The inserted insulin receptor had the same insulin-binding affinity as the isolated receptor and the endogenous receptor of the membrane. Insulin binding in the presence or absence of Triton X-100 revealed that more than 80% of the exogenous receptors had a right-side-out orientation. Function of the inserted receptors, as observed by insulin-stimulated autophosphorylation, could be demonstrated. About 80% of the added lysophospholipid, corresponding to approx. 160 nmol of lysophospholipid/mg of membrane protein, became integrated into the membrane and was partly metabolized to phospholipid and to non-esterified fatty acid. The method of insertion of isolated insulin receptors using the natural detergent, lysophospholipid, may be a method for insertion of receptors into intact cells, where the lysophospholipid, as in the plasma-membrane vesicles, will be acylated to phospholipid.

Cell Membrane↗
PubMed1992

Myocardial perfusion at fatal infarction: location and size of scintigraphic defects.

In a consecutive study of myocardial scintigraphy in acute ischemic syndrome, four patients had 99mTc-hexamibi injected intravenously before they developed fatal cardiogenic shock. Planar scintigraphy was performed after death. Slices of the hearts after autopsy were analyzed for scintigraphic and pathoanatomic abnormalities. Location of perfusion defects in planar views of the heart was in good agreement with the scintigraphied, sliced sections. The extent of infarction judged from inspection and formasan staining was much smaller (7%-40% and 6%-43% of the total slice area) than found at scintigraphy, where 83%-92% of the myocardium showed ischemia as defined by a 99mTc-hexamibi uptake below an arbitrary limit on half maximum uptake. Myocardial hypoperfusion might thus aggravate the functional impairment at myocardial infarction and lead to cardiogenic shock.

Aged↗
PubMed1991

A model for the quaternary structure of human placental insulin receptor deduced from electron microscopy.

Electrophoretically pure and functionally intact human placental insulin receptor was studied by electron microscopy with negative-staining techniques. The quaternary structure of the detergent-solubilized receptor was determined. The receptor had the shape of a letter T approximately 24 nm in height and 18 nm in width with a thickness of the stem and the crossbar of 3-4 nm. No consistent change in ultrastructure of the receptor could be detected after the addition of insulin alone or insulin and Mn2+/Mg2+/ATP. After partial reduction of the alpha 2 beta 2 heterotetrameric receptor into alpha beta heterodimers, the electron micrographs showed a clear reduction in average size of the molecule with disappearance of the T profiles characteristic of the alpha 2 beta 2 heterotetramers. By incubation of the heterodimers in a phosphorylation medium containing insulin, a reassociation to molecules with molecular weights of the alpha 2 beta 2 heterotetramer took place judged from SDS/PAGE. Electron microscopy showed that the molecule formed larger aggregates, and only a few solitary T-shaped copies were seen.

Chromatography, Affinity↗
PubMed1989

Determinants of visual evoked potentials in preterm infants.

The latency and amplitude of N1, the first negative peak of single flash visual evoked cortical potentials (VEP) were evaluated in 86 preterm infants (25-34 weeks of gestation), investigated during the first day of life. All infants were regarded stable at the time of investigation and none had experienced severe asphyxia. Both the VEP latency and amplitude were inversely related to gestational age. When latency was corrected for age it was longer in boys than in girls. Age corrected VEP amplitude was inversely related to head circumference, umbilical cord pH and EEG activity. There was no difference between VEP parameters in asymmetrically growth retardated infants compared to those with normal growth. Administration of dexamethasone to the mother before delivery, mode of delivery, presence of hyaline membrane disease, mode of assisted ventilation or imminent development of periintraventricular haemorrhage did not affect the VEP.

Evoked Potentials, Visual↗
PubMed1989

New perspectives on the functional anatomical organization of the basolateral amygdala.

We have examined the functional anatomical organization of the basolateral amygdaloid nucleus (BL) in the rat and guinea pig using combined light and electron microscopic methods. Afferent and efferent connections as well as the internal organization of the BL have been studied with combined tracing, immunohistochemical, and Golgi techniques. We have found that the BL receives an intense cholinergic innervation from the ventral forebrain cholinergic system and, for the first time, described a group of intrinsic cholinergic neurons in the BL. The innervation from the primary olfactory cortex and the thalamus, as well as the GABAergic innervation of the amygdalostriatal projection neurons, is also described. Electron microscopic analyses have shown that the cholinergic system as well as the thalamic afferents primarily innervate the distal dendritic arbor of the projection neurons in the BL, whereas the GABAergic fibers are directed primarily towards their soma and proximal dendrites. Correlated light and electron microscopic studies have revealed that the projection neurons in the BL share many features with pyramidal and spiny stellate cells in the cerebral cortex. The ultrastructural characteristics of the afferent fiber systems and of the non-projection neurons in the BL are also reminiscent of the situation in the cerebral cortex. The observations reported in this study lend further support to the concept of a cortical-like organization of the BL. The anatomical observations of the BL are discussed particularly in relation to three major forebrain systems: 1. the ventral striatopallidal system, 2. the continuum formed by the centromedial amygdala, the substantia innominata and the bed nucleus of the stria terminalis, and 3. the cholinergic ventral forebrain system. The clinical implications of the results obtained in this series of experimental studies are discussed in relation to Alzheimer's disease and complex partial seizures. The cholinergic system, in particular, has attracted much interest in relation to senile dementia of Alzheimer's type (SDAT), which often seems to be characterized by disruption of the ventral forebrain cholinergic projection system. We have found that the cholinergic innervation of the BL is often significantly reduced in SDAT, but interestingly enough, the areas of the basolateral amygdala with the highest content of cholinergic markers contain the smallest numbers of senile plaques.

Afferent Pathways↗
PubMed1988

Rat hepatic microsomal cytochrome b5. A simple large-scale purification procedure and antibody production by antigen-containing liposomes.

Cytochrome b5 from rat liver microsomes (microsomal fractions) was purified in its native form. The procedure described has great capacity, is fast, and the final product is pure as judged from SDS/polyacrylamide-gel electrophoresis. Antibodies to cytochrome b5 are obtained after administration of the antigen inserted into small unilamellar lipid vesicles.

Animals↗
PubMed1988

Immunocytochemical localization of glutamate decarboxylase in the rat basolateral amygdaloid nucleus, with special reference to GABAergic innervation of amygdalostriatal projection neurons.

Glutamate decarboxylase (GAD) immunohistochemistry was employed at the light and electron microscopic levels to localize GABAergic structures in the basolateral amygdaloid nucleus (BL). The GAD-immunoreactive (GAD-IR) staining pattern consisted of punctate structures and a morphologically diverse group of GAD-IR neurons. At the electron microscopic level many of these punctate structures were found to make symmetrical synaptic contacts with cell bodies as well as distal parts of unlabeled, presumably projection and nonprojection, neurons. In addition, GAD-immunoreactive neurons were identified in the BL, and they had the ultrastructural characteristics of local circuit or intrinsic neurons and were not retrogradely labeled with HRP following ventral striatal injections. Some of these GAD-immunoreactive neurons were contacted by GABAergic boutons, forming symmetrical synaptic contacts. GABAergic innervation of amygdaloid projection neurons in the BL was identified by combining GAD immunohistochemistry with Golgi impregnation and retrograde tracing of horseradish peroxidase (HRP) following injections of the tracer in the olfactory-tubercle-related parts of the ventral striatum. Amygdalostriatal projection neurons in the BL were observed to be in continuity with neurons in the piriform cortex which project to the ventral striatum. The results provide direct evidence for the presence of GAD-IR boutons in the BL making synaptic contacts with identified amygdalostriatal projection neurons. The present study provides direct anatomical evidence for the physiological observation that GABA exhibits a powerful regulation of the amygdaloid projection neurons in the BL and lends further support to the concept of a corticallike functional organization of the basolateral amygdala.

Amygdala↗
PubMed1988

The basolateral amygdaloid complex as a cortical-like structure.

The thalamic innervation of the rat basolateral amygdaloid complex was studied with a combination of light- and electron microscopic techniques using anterogradely transported Phaseolus vulgaris-leucoagglutinin (PHA-L) as well as combined degeneration and single-section Golgi impregnation for the identification of thalamo-amygdaloid synaptic relations. The results indicated that the basolateral amygdaloid nucleus corresponds in several features to a cortical structure. Like all cortical areas, the basolateral amygdaloid nucleus is reciprocally related to other cortical regions as well as to the thalamus.

Amygdala↗
PubMed1988

The distribution of neuritic plaques and acetylcholinesterase staining in the amygdala in Alzheimer's disease.

The relationship between neuritic plaque formation in Alzheimer's disease and cholinergic innervation of brain regions is unclear. Many neuritic plaques are found in the amygdala, which also receives dense cholinergic innervation from the ventral forebrain, predominantly to the basolateral complex. To determine whether the regional distribution of neuritic plaques is related to the pattern of cholinergic innervation, we studied serial sections through the amygdala of four patients with Alzheimer's disease and four neurologically normal patients. We compared acetylcholinesterase reactivity, neuritic plaques stained with thioflavine S, and cytoarchitectural features in adjacent sections. Neuritic plaque counts were high in most amygdaloid nuclei but were significantly lower in the most acetylcholinesterase-positive region, the lateral portion of the basal nucleus of the amygdala. Acetylcholinesterase reactivity was reduced in the Alzheimer's cases, but the basal nucleus was easily recognized by the characteristic large neurons. The morphology of neuritic plaques also differed in the various regions. These results show that neuritic plaques occur to varying degrees in all nuclei of the amygdala, but are significantly less frequent in the region that receives the most prominent innervation from the cholinergic ventral forebrain.

Acetylcholinesterase↗
PubMed1987

Randomised comparison of early versus late induction of labour in post-term pregnancy.

In a prospective randomised study of mothers referred for prolonged pregnancy (around the 42nd week) 214 (group 1) were submitted to attempted induction of labour and 195 (group 2) assigned to continue for a further week without intervention. Strict selection criteria were used for the certainty of term. Mothers in group 2 were given regular non-stress tests to ensure fetal wellbeing, as were those in group 1 in whom induction failed. In group 1, 48 (23%) out of 210 first attempted inductions failed. In group 2, 135 (69%) of the births started spontaneously as compared with 38 (18%) in group 1. The mean duration of labour was 7.5 hours in each group. There was no significant difference in incidence of operative delivery, use of analgesics, or signs of perinatal asphyxia. Significantly more children in group 1 needed phototherapy for hyperbilirubinaemia. There was a clustering of births in the late afternoon and evening, which was most pronounced in group 1. A policy of vigilant non-intervention up to the 44th completed week of pregnancy does not appear to jeopardize mother or fetus.

Anthropometry↗
PubMed1986

Incorporation of cytochrome b5 into endoplasmic reticulum vesicles as protein-lysophospholipid micelles.

Cytochrome b5 is incorporated into vesicles of the endoplasmic reticulum as protein-lysophosphatidylcholine micelles. Cytochrome b5 becomes firmly bound to the membrane and at the same time lysophosphatidylcholine is acylated by acyltransferases of the endoplasmic reticulum and converted into the membrane component phosphatidylcholine. The possibility of an insertion of cytochrome b5 into the endoplasmic reticulum in vivo by this mechanism is discussed.

Carboxypeptidases↗