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Biomedical subjects

K Norberg

Publications and source records attributed to K Norberg.

At least 19 recordsLinked to original sources
PubMed2006

Chimeric honeybees (Apis mellifera) produced by transplantation of embryonic cells into pre-gastrula stage embryos and detection of chimerism by use of microsatellite markers.

The production of chimeras, by use of cell transplantation, has proved to be highly valuable in studies of development by providing insights into cell fate, differentiation, and developmental potential. So far, chimeric honeybees have been created by nuclear transfer technologies. We have developed protocols to produce chimeric honeybees by use of cell transplantation. Embryonic cells were transplanted between pre-gastrula stage embryos (32-34 hr after oviposition) and hatched larvae were reared in vitro for 4 days. Chimeric individuals were detected by use of microsatellite analysis and a conservative estimation approach. 4.8% of embryos, posteriorly injected with embryonic cells, developed into chimeric honeybee larvae. By injection of cells pre-stained with fluorescent cell tracer dye, we studied the integration of transplanted cells in the developing embryos. Number of injected cells varied from 0 to 50 and cells remained and multiplied mainly in the area of injection.

Animals↗
PubMed2000

Salmon antithrombin has only three carbohydrate side chains, and shows functional similarities to human beta-antithrombin.

Antithrombin, a major coagulation inhibitor in mammals, has for the first time been cDNA cloned from a fish species. The predicted mature liver antithrombin of Atlantic salmon (Salmo salar) consists of 430 amino acids and shows about 67% sequence identity to mammalian and chicken antithrombins. Due to a single nucleotide replacement, Asn135 of the antithrombin in higher vertebrates is substituted by Asp in the salmon homolog. Hence, in contrast to the vertebrate antithrombins known so far, salmon antithrombin lacks the potential glycosylation site located close to the heparin binding site. The existence of only three N-linked side chains is evidenced by the sequential removal of three carbohydrate chains from salmon antithrombin during timed-digestion with N-glycosidase F. The high heparin binding affinity of the salmon inhibitor, Kd of 2.2 and 48 nM at I = 0.15 and 0.3, respectively, is very similar to that of the minor human isoform beta-antithrombin, which is not glycosylated at Asn135. Furthermore, the invariant third-position Ser137 at this glycosylation site of mammalian and chicken antithrombins is substituted by Thr in the salmon, a replacement that has been shown to induce full glycosylation in human antithrombin. Thus a rapidly reacting pool of antithrombin may have evolved in two different ways: absence of a glycosylation site in lower vertebrates vs. incomplete glycosylation of a part of the circulating antithrombin in higher vertebrates. Salmon antithrombin appears to have three complex oligosaccharide side chains containing sialic acid terminally linked alpha(2-3) to galactose, while trace amounts of Galbeta(1-4)GlcNAc suggest microheterogeneity due to partial loss of sialic acid.

Amino Acid Sequence↗
PubMed1996

Evidence of a protein C-like anticoagulant system in bony fish.

Evidence is presented, confirming the presence of an anticoagulant system in the plasma of Atlantic salmon (Salmo salar L) and rainbow trout (Oncorhynchus mykiss Walbaum) (Order: Teleostei, Family: Salmonidae) that bears striking similarities with the protein C anticoagulant system in mammals; its vitamin K-dependence was documented through a warfarin feeding trial. A potent activator of this system is the protein C activator from the venom of the Central American Moccasin, Agkistrodon bilineatus. When activated, the system splits the tripeptide substrate glu-pro-arg-pNa, which is the substrate preferred for the in vitro assay of human protein C. It also prolongates the plasma activated partial thromboplastin time, indicating that the system is of clinical relevance. A temperature dependence of the plasma protein C-like activity was evident, the mean activity being 5- to 10-fold higher, but also more variable, in both species in summer and early fall, than it was in winter. There was also a species difference, with rainbow trout having the higher levels. In man, subnormal values of protein C implies an increased risk of thrombosis. Whether this applies to fish is not known. It is, however, a fact that microvascular thromboses are prevalent in farmed Atlantic salmon in winter, whereas thrombotic disease is not a problem in rainbow trout; in the present study plasma protein C-like activity was 30% (of a human reference plasma) in salmon at 4 degrees C compared to a level of 60% in rainbow trout. A complicating factor for the assay of protein C-like activity in salmonid plasma, is the poor stability of the inhibitory system upon storage. Consequently, assays have to be done with freshly prepared citrated plasma.

Animals↗
PubMed1995

Some functional properties of teleost antithrombin.

Antithrombin from bony fish (Teleostei), represented by an ancient salmonid, Atlantic salmon (Salmo salar L.), and a more evolved species from the same family, rainbow trout (Oncorhynchus mykiss Walbaum), functions in vitro as does its human counterpart: it inactivates thrombin almost instantaneously in the presence of heparin and only slowly when heparin is absent. The inhibitory activity of salmonid antithrombin towards the homologous thrombin did not differ noticeably from its inactivating capacity in heterologous (teleost) systems, and enzyme-inhibitor reactions between reagents from fish and man proceeded just as efficiently. In all enzyme-inhibitor reactions with salmonid thrombin the inactivation by salmonid antithrombin or diluted fish plasma was maximal at pH 7.8-8.4. The inactivation was clearly dependent on heparin in all systems and maximal at concentrations between 1.5 and 6 U/ml. What particularly distinguishes the salmonid thrombin-antithrombin interaction from the human one is that the former has to function over a wide range of temperatures. And the thrombin inactivating capacity of purified antithrombin and diluted plasma in the presence of heparin was indeed present at temperatures down to 3 degrees C, a capacity that human antithrombin also has retained. Even more interesting was that the teleost enzyme-inhibitor reaction was nearly independent of temperature under the conditions studied.

Animals↗
PubMed1991

Effects of warfarin on vitamin K-dependent coagulation factors in Atlantic salmon and rainbow trout with special reference to factor X.

Plasma factor X (FX) was severely depleted in Atlantic salmon and rainbow trout after 18 days of oral warfarin administration; this response was further reflected in prolonged prothrombin time. Thus, both species require vitamin K for the maintenance of normal haemostasis. FX activity in controls of rainbow trout was 3- to 5-fold that of salmon. The FX of both species show several of the features of human FX: it is activated by RVV, inhibited by SBTI, inactivated in the presence of heparin, and adsorubs to insoluble barium precipitates. Rainbow trout sustained warfarin poisoning better than did salmon, with mortalities occurring 8 days later in trout. After 18 days all remaining fish had developed a severe haemorrhagic anaemia with anisocytosis, poikilocytosis, leucopenia, and thrombocytopenia.

Animals↗
PubMed1978

Amphetamine-induced increase in rat cerebral blood flow: apparent lack of catecholamine involvement.

The influence of D,L-amphetamine (5 mg/kg i.p.) on regional cerebral blood flow (CBF) in rats has been studied after surgically or pharmacologically induced depletion of brain catecholamines. (1) Bilateral removal of the superior cervical ganglion (one week before the experiment) did not prevent the amphetamine-induced augmentation of CBF present in intact animals to 2--4 times above the control value. Maximal changes occurred in the frontal and parietal cortex. (2) Destruction of the ascending noradrenergic pathways by uni- or bilateral injections of 6-hydroxydopamine, which decreased the noradrenaline (NA) level in the frontal cortex by 89%, was ineffective in abolishing the increase in CBF caused by the drug in the frontal cortex. (3) The involvement of other catecholaminergic systems was excluded by pretreatment of the rats with reserpine plus a-methyl-p-tyrosine which reduced the levels of NA, dopamine and adrenaline in the frontal cortex with 92, 97 and 99% respectively. Such treatment did not alter the effect of amphetamine on CBF in the frontal cortex. The results support the hypothesis that the action of amphetamine on CBF is not mainly mediated by catecholamines.

Adrenergic Fibers↗
PubMed1977

Mechanical, electrical, and biochemical effects of hypoxia and substrate removal on spontaneously active vascular smooth muscle.

Effects of hypoxia and glucose-free solution on the isolated rat portal vein were studied. Decrease of extracellular PO2 below 50 mm Hg caused graded inhibition of spontaneous mechanical activity; below 7 mm Hg, inhibition was complete in most preparations. Contracture force of depolarized portal vein was less sensitive to decreases in PO2. Responses to noradrenaline at all concentrations were markedly depressed at extreme hypoxia. Sucrose-gap experiments showed that hypoxia reduced the spontaneous electrical spike discharge. Mean tissue contents of PCr, ATP and glycogen (expressed as glucose) were 3.02, 2.47 and 5.07 micromol/g cell wt. in spontaneously active control muscles and 1.07, 1.65 and 1.83 after 20 min anoxia. Physiological variations in PO2 may influence myogenic activity of vascular smooth muscle largely through an action at the membrane level and this mechanism may participate in local blood flow control. Caculations indicated that the graded response to hypoxia in the present in vitro experiments was not due to diffusion limitation. Spontaneous mechanical activity was relatively well maintained even after prolonged exposure to glucose-free solution, whereas the responses to K+ and noradrenaline were markedly suppressed. Electrophysiological recordings during spontaneous activity indicated desynchronization and impaired conduction. PCr and ATP were maintained at control levels and glycogen reduced by 50 per cent after 2 h in glucose-free medium. Indications of the use of amino acids (glutamate) as substrate under these conditions were obtained.

Action Potentials↗
PubMed1976

Glucose consumption in rat cerbral cortex in normoxia, hypoxia and hypercapnia.

Glucose consumption was measured in the cerebral cortex of rats, anesthetized with 70% N20, under normoxic conditions, as well as in hypoxia (Pao2 about 25 mmHg) and hypercapnia (Paco2 80-85 mmHg). The method used was that Hawkins et al (1974), modified to allow studies of transients in glycolytic rate. Cortical glucose consumption in normoxia was 0.77 mumol-g(-1)-min(-1). It is concluded that whereas glucose consumption in the whole brain of unanesthetized rat may be close to 0.6 mumol-g(-1)-min(-1), that of the cerebral cortex is close to 0.8 mumol-g(-1)-min(-1). During the first 2 min of hypoxia, glucose consumption was increased to twice the normal, and during the fist 2 min of hypercapnia, the corresponding value was less thane third of the normal. After 15 min of hypoxia, the glucose consumption had returned towards control values. In "steady state" hypercapnia, the glycolytic flux was higher than in the inital phase although still below normocapnic values.

Animals↗
PubMed1976

Structure of some aliphatic dicarboxylic acids found in the urine of an infant with congenital lactic acidosis.

Gas chromatography/mass spectrometry was used to identify a series of acids in urine and serum from a child who died 26 h after birth in severe metabolic acidosis with high lactate excretion. cis-5-Decene-1, 10-dioic acid and cis-5-dodencene-1, 12-dioic acid were synthesized and used as references. The following acids were found: hexane-1,6-dioic acid, octane-1,8-dioic acid, decane-1,10-dioic acid, dodecane-1,12-dioic acid, cis-5-decene-1,10-dioic acid, cis-5-dodecen-1,12-dioic acid, cis-5-tetradecene-1,14-dioic acid, trans-3-decene-1,10-dioic acid, and trans-3-dodecene-1,12-dioic acid. The concentration of C6 to C14 acids in the patient's urine was 3.7 mol/mol of creatinine; it was less than 0.2 mol/mol of creatinine in eight normal newborns and approximately 0.1 mol/mol of creatinine in a case of fructose-1,6-biphosphatase deficiency with lactic acidosis. 5-cis-Dodecenedioic acid was present in highest concentration: 1 mol/mol of creatinine in urine and 61 mumol/liter in serum. We propose that impaired beta-oxidation, probably at the acyl-CoA-dehydrogenase step, resulted in the formation of the observed acids. The parents were consanguineous, and a sibling died with the same clinical picture, which suggests a genetic defect.

Acidosis↗
PubMed1975

Cerebral metabolism in hypoxic hypoxia. I. Pattern of activation of glycolysis: a re-evaluation.

In order to evaluate the pattern of activation of glycolysis in cerebral cortex during hypoxic hypoxia, lightly anesthetized rats were subjected to a lowering of arterial Po2 to about 25 mm Hg and brains were frozen in situ for metabolite analyses either 1, 2, 5, 15 or 30 min following the induction of hypoxia. The lactate and pyruvate concentrations increased progressively during the 30 min period of hypoxia. At 1 and 2 min there were decreases in G-6-P and F-6-P, and increases in FDP, DHAP and 3-PG, indicating activation of phosphofructokinase. At 5 min this pattern of changes was less pronounced and at 15 min it was absent in spite of the fact that the lactate and pyruvate concentrations were further increased. At 30 min F-6-P and F-6-P had further increased but the levels of DHAP, FDP and 3-PG were normal. Evidently, phosphofructokinase activation can only be detected in the early stages of hypoxia, i.e. when the maximal increase in glycolytic flux occurs and before there has been a corresponding activation of other rate-limiting enzymatic steps. Signs of activation of phosphofructokinase were observed in the absence of changes in tissue concentrations of ATP or AMP, with minimal elevation of NH4plus, and in spite of increased (or unchanged) levels of citrate. However, since there were small but significant increases in ADP at 1 and 2 min, and pH-independent decreases in phosphocreatine, the results indicate that hypoxia is accompanied by an initial imbalance between production and utilization of ATP. The metabolic consequences of this imbalance (decrease in phosphocreatine, increases in ADP and P1) may be at least partly responsible for activation of phosphofructokinase.

Adenosine Diphosphate↗