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K Svensson

Publications and source records attributed to K Svensson.

At least 19 recordsLinked to original sources
PubMed1998

The paternal allele of the H19 gene is progressively silenced during early mouse development: the acetylation status of histones may be involved in the generation of variegated expression patterns.

Transcriptional silencing can reflect heritable, epigenetic inactivation of genes, either singly or in groups, during the life-time of an organism. This phenomenon is exemplified by parent-of-origin-specific inactivation events (genomic imprinting) for a subset of mammalian autosomal genes, such as H19. Very little is known, however, about the timing and mechanism(s) of silencing of the paternal H19 allele during mouse development. Using a novel in situ approach, we present evidence that the silencing of the paternal H19 allele is progressive in the trophectodermal lineage during early mouse development and generates variegated expression patterns. The silencing process apparently involves recruitment of histone deacetylases since the mosaic paternal-specific H19 expression reappears in trichostatin A-treated mouse conceptuses, undergoing in vitro organogenesis. Moreover, the paternal H19 alleles of PatDup.d7 placentas, in which a region encompassing the H19 locus of chromosome 7 is bipaternally derived, partially escape the silencing process and are expressed in a variegated manner. We suggest that allele-specific silencing of H19 share some common features with chromatin-mediated silencing in position-effect variegation.

Acetylation↗
PubMed1996

Binding of H-2Kb-specific peptides to TAP and major histocompatibility complex class I in microsomes from wild-type, TAP1, and beta2-microglobulin mutant mice.

Major histocompatibility complex (MHC) class I molecules are trimolecular complexes consisting of a heavy chain (HC), beta2-microglobulin (beta2m), and a short peptide. Assembly of MHC class I molecules is thought to take place early during biosynthesis. Deficiency in either beta2m or the transporter associated with antigen processing (TAP) results in accumulation of class I molecules in the endoplasmic reticulum (ER). In this study, we have assessed peptide binding to TAP and MHC class I in purified microsomes derived from wild-type, TAP1(-/-), beta2m-/-, and TAP1/beta2m-/- mice using a cross-linkable H-2Kb-binding peptide. This enabled us to study the influence of an intact TAP complex and beta2m on peptide binding to MHC class I and to analyze the stepwise interaction of peptide with TAP and MHC class I molecules. Peptide bound both immature and mature (terminally glycosylated) class I molecules in intact as well as permeabilized microsomes from wild-type mice. Efficient peptide binding to immature class I molecules was also detected in permeabilized microsomes from TAP1(-/-) mice. In contrast, no peptide binding to beta2m-free HC was detected in permeabilized microsomes from beta2m-/- and TAP1/beta2m-/- mice. However, the addition of exogenous beta2m allowed peptide binding to class I in permeabilized beta2m-/- and TAP1/beta2m-/- microsomes. These results demonstrate that a preformed class I HC middle dotbeta2m heterodimer is necessary for efficient peptide binding under physiological conditions. The observed peptide binding to class I in permeabilized TAP1(-/-) microsomes further suggests that TAP1 is not required for peptide binding to class I in the ER. Finally, kinetic studies allowed the demonstration of a stepwise binding of peptide to TAP, subsequent translocation across the ER membrane, a step that required ATP hydrolysis, and binding of peptide to preformed class I HC.beta2m heterodimers.

Adenosine Triphosphate↗
PubMed1996

Different patterns of oxytocin, prolactin but not cortisol release during breastfeeding in women delivered by caesarean section or by the vaginal route.

The aim of this study was to find out whether the hormonal patterns of oxytocin, prolactin and cortisol differed between women delivered by emergency section or by the vaginal route and if these patterns show any relation to the duration of breastfeeding. Seventeen mothers with emergency section (C.S.) and 20 mothers with normal vaginal deliver (V.D.) were blood sampled in connection with breastfeeding on day 2 post partum for oxytocin, prolactin and cortisol. The number of oxytocin pulses as calculated with the PULSAR program occurring during the first 10 min of the breastfeeding session varied between 0 and 5. The V.D. mothers had significantly more pulses than the C.S. ones. Furthermore the C.S. women lacked a significant rise in prolactin levels at 20-30 min after the onset of breastfeeding. Logistic regression analysis revealed mode of delivery and infant's age at first breastfeed to be the most important, independent variables showing a relation to the release pattern of oxytocin on day 2. Correlations between oxytocin pulsatility on day 2 and the duration of the exclusive breastfeeding period in the V.D. group suggest that development of an early pulsatile oxytocin pattern is of importance for breastfeeding.

Adult↗
PubMed1996

High glucose concentration inhibits migration of rat cranial neural crest cells in vitro.

Cranial neural crest cells give rise to a large part of the facial structures, and disturbed development of these cells may therefore cause congenital malformations affecting the head and face. We studied the effects of increased glucose concentration on the migration and development of cranial neural crest cells, maintained in vitro for 48 h. Pre-migratory cranial neural crest cells were removed from embryos of normal and diabetic rats on gestational day 9. After 24 h in 10 mmol/l glucose the cells were exposed to glucose concentrations of 10, 30, or 50 mmol/l for another 24 h. The cultures were photographed at 24 h and 48 h in a phase-contrast microscope to evaluate cell morphology, cell number, and cell migration. Exposure to 50 mmol/l glucose reduced the total number of neural crest cells, their mean migratory distance and migratory area expansion compared to cells cultured in 10 mmol/l glucose. To investigate the effect of antioxidant agents, high glucose cultures were studied after addition of N-acetylcysteine (NAC), or superoxide dismutase (SOD). Addition of NAC diminished the inhibitory effect of high glucose, whereas SOD did not offer any improvement in cell development. Neural crest cell culture from embryos of diabetic rats showed reduced cell migration in vitro at all glucose concentrations compared to normal cells. In addition, the cells from embryos of diabetic rats showed reduced migratory area expansion after culture in the basal 10 mmol/l glucose concentration, indicating that maternal diabetes permanently influences the future development of premigratory cranial neural crest cells. These findings indicate that high glucose concentration inhibits cranial neural crest development in vitro, and that antioxidant therapy may diminish this inhibition. Free radical oxygen species may be involved in the induction of malformations and antioxidants may therefore have a role in future attempts to block the teratogenic effects of diabetic pregnancy.

Animals↗
PubMed1996

Effects on locomotor activity after local application of (+)-UH232 in discrete areas of the rat brain.

The preferential dopamine autoreceptor, and slightly D3 preferring, antagonist (+)-UH232 (cis-(+)-(1S,2R)-5-methoxy-1-methyl-2-(n-dipropylamino) tetralin) increases locomotor activity and synaptic dopamine release in the nucleus accumbens and striatum after systemic administration to the rat. As shown in this study, (+)-UH232, was unable to produce an increase in locomotor activity measured for 60 minutes after local administration into the terminal or somato-dendritic regions of the mesolimbic dopamine pathways or into the lateral ventricle. Instead, a dose dependent decrease of spontaneous locomotor activity after local application (0.05-50.0 nmol/side) of (+)-UH232 into the nucleus accumbens, was seen. A similar reduction in locomotor activity was produced by the classical dopamine antagonist raclopride. Analysis of the dose*time interactions on locomotor activity did, however, indicate that there is a significant dose*time interaction after local application of (+)-UH232 into the lateral ventricle and VTA. Raclopride, on the other hand, produced only a weak time dependent effect in the VTA. The potential problem of Leao's spreading depression in micro-injection experiments were considered, however, spreading depression does not seem to influence the effects of (+)-UH232 locally applied into the nucleus accumbens. In conclusion, both (+)-UH232 and raclopride produced a dose dependent decrease in spontaneous locomotor activity when examined as the total activity count over 60 minutes after local application into the N Acc.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

Expression of a novel member of estrogen response element-binding nuclear receptors is restricted to the early stages of chorion formation during mouse embryogenesis.

Members of the nuclear hormone receptor gene family of transcription factors have been shown to be expressed in characteristic patterns during mouse organogenesis and postnatal development. Using an RT-PCR based screening assay, we have identified nuclear receptors expressed in embryonal carcinoma stem cells. One of the cDNAs characterized, mERR-2, was found to be expressed exclusively during a narrow developmental window in trophoblast progenitor cells between days 6.5 and 7.5 post coitum (p.c.). From 8.5 days p.c. and onwards, the mERR-2 gene activity evaded detection as analysed by in situ hybridization. We also show that the mERR-2 gene product and the estrogen receptor share a common target DNA-sequence recognition specificity unique among members of the gene family. Furthermore, efficient homodimerization and DNA-binding of the orphan receptor mERR-2 was found to be dependent on interaction with the heat shock protein 90, a molecular chaperone hitherto recognized to interact only with the steroid hormone receptor subgroup of nuclear receptors. Based on our results we suggest that the mouse orphan receptor mERR-2 has the potential to regulate overlapping gene networks with the estrogen receptor and may participate in signal transduction pathways during a short developmental period coinciding with the formation of the chorion.

Amino Acid Sequence↗
PubMed1996

Proteasomes generate in vitro a natural peptide of influenza-A nucleoprotein functional in HLA-B27 antigen assembly.

We have studied the degradation of a set of long peptides (9-30 amino acids) from the nucleoprotein of influenza A. In common for all these peptides is the core sequence NH2-Ser-Arg-Tyr-Trp-Ala-Ile-Arg-Thr-Arg-COOH, NP383-391, known as an antigenic peptide specific for the HLA-B27 class I antigen. We show that this peptide is generated by enriched cytosolic proteasomes of two sizes, 20S and 12S. The 12S proteasome is the precursor, the preproteasome, to the 20S mature proteasome as shown by pulse-chase experiment and is most likely responsible for the proteolytic activity in the 12S region. Cleavage at the N-terminus is distinct and restricted to residue 383, independent of the N-terminal extension of the peptide. The C-terminus is generated via cleavage at three sites. Intermediate and final peptide products were identified by mass spectrometry. Finally, we show that the NP383-391 peptide generated by proteasomes in vitro is functional inasmuch as it possesses the ability to stimulate assembly of in vitro translated HLA-B27 antigens.

Amino Acid Sequence↗
PubMed1996

Effects of extracellular matrix molecules on subepidermal neural crest cell migration in wild type and white mutant (dd) axolotl embryos.

Migration of neural crest (NC) derived pigment cells is restricted in the white mutant (dd) axolotl embryo (Ambystoma mexicanum). Transplantations between mutant and wild type embryos show that the extracellular matrix (ECM) of the white mutant is unable to support the migration of prospective pigment cells in wild type embryos (Löfberg et al., 1989, Dev. Biol. 131:168-181). In the present study, we test the effects of various purified ECM molecules on NC cell migration in the subepidermal migratory pathway of wild type (D/-) and white mutant (dd) axolotl embryos. We adsorbed the ECM molecules onto membrane microcarriers, which were then implanted under the epidermis. Fibronectin (FN), tenascin (TN), collagens I and VI, and a chick aggrecan stimulated migration in both types of embryos. Laminin-nidogen, rat chondrosarcoma aggrecan, and shark aggrecan stimulated migration in dd embryos but did not affect migration in D/- embryos. Collagen III, fibromodulin and bovine aggrecan had no effect on migration in either type of embryo. NC cells did not migrate on control microcarriers, which lacked ECM molecules. Some cells observed contacting, and presumably migrating on, coated microcarriers could be identified as pigment cells by their ultrastructure. Enzymatic digestion in vivo with chondroitinase ABC had no effect on NC cell migration. The neutral or stimulatory effect of the aggrecans is surprising; when tested in vitro they inhibited NC cell migration. The effect of three-dimensionality and other molecules present either in the embryonic ECM or in solution may overcome the inhibitory effect of aggrecans.

Ambystoma↗
PubMed1995

Structure-activity relationships in the 8-amino-6,7,8,9-tetrahydro-3H-benz[e]indole ring system. 1. Effects of substituents in the aromatic system on serotonin and dopamine receptor subtypes.

A series of 1-, 3-, and 4-substituted analogs to the potent 5-HT1A against 8-(dipropylamino)-6,7,8,9-tetrahydro-3H-benz[e]indole-1-carbaldehyde (5) were prepared and tested in vitro at 5-HT1A, 5-HT1D alpha, 5-HT1D beta, D2, and D3 receptors and in vivo for agonist activity in the 5-HTP and DOPA accumulation assays in reserpine-pretreated rats. Some of the compounds were resolved. The substituents used in the 1-position were chosen from a principal component analysis (PCA) plot constructed from both tabulated variables and variables calculated by semiempirical methods (PM3) and molecular mechanics software (MMX). Among the analogs prepared, some, e.g., compound 21, were equipotent to compound 5 with respect to 5-HT1A effects. All compounds were more or less selective for the 5-HT1A receptor, but many of the compounds displayed higher affinities for 5-HT1D alpha than for 5-HT1D beta receptors.

Animals↗
PubMed1995

Structure-activity relationships in the 8-amino-6,7,8,9-tetrahydro-3H-benz[e]indole ring system. 2. Effects of 8-amino nitrogen substitution on serotonin receptor binding and pharmacology.

A series of analogs of the potent and selective 5-HT1A agonist 8-(di-n-propylamino)-6,7,8,9-tetrahydro-3H-benz[e]indole-1-carbaldehyde (2b) (OSU191) was prepared in which the dipropylamino group was modified to bear a variety of substituents. These compounds were evaluated for both in vitro and in vivo effects, including the establishment of a receptor binding profile for these analogs at the 5-HT1A, dopamine D-2, dopamine D-3, 5-HT1D alpha, and 5-HT1D beta sites. Several of the analogs were evaluated for their biochemical effects in reserpinized rats, specifically with regard to in vivo changes in brain levels of 5-HTP and DOPA. Nearly all of the compounds prepared for this study were exceedingly potent at the 5-HT1A receptor, although most also displayed significant affinity for the dopamine D-2 receptor. A strong preference for the 5-HT1D alpha over the 5-HT1D beta receptor was also apparent. An analog bearing a butylglutarimide side chain, S-7k, was extremely selective for the 5-HT1A receptor. Although this compound possessed a Ki of 0.6 nM, it elicited only modest changes in 5-HTP brain levels. However, this compound did not appear as an antagonist when tested in a cyclic-AMP-based intrinsic activity assay.

Animals↗
PubMed1995

Synthesis and evaluation of pharmacological and pharmacokinetic properties of monopropyl analogs of 5-, 7-, and 8-[[(trifluoromethyl)sulfonyl]oxy]-2-aminotetralins: central dopamine and serotonin receptor activity.

In order to explore further the structure-activity relationships of serotonergic and dopaminergic ligands, a series of enantiopure 5-, 7-, or 8-triflate (-OTf)-substituted 2-(monopropylamino)-tetralins have been synthesized and evaluated in in vitro binding and in vivo biochemical and behavioral assays in rats. Consequently, the 8-OTf-substituted compound R-(+)-6 was found to be a potent and selective 5-HT1A (5-hydroxytryptamine) receptor agonist inducing a full-blown 5-HT syndrome in normal rats, while the corresponding 5-OTf-substituted compound S-(-)-12 was found to be a preferential dopamine (DA) autoreceptor agonist. A partial 5-HT syndrome was also observed for S-(-)-12, while the corresponding R-(+)-12 was found to be inactive at the DA and 5-HT receptors both in vitro and in vivo. Compounds 6 and 12 were found to be major urinary metabolites following oral administration of their dipropyl analogs (2 and 13, respectively). Thus 6 was proposed to be the metabolite responsible for the full-blown 5-HT syndrome seen after oral (but not subcutaneous) administration of 2. Similarly, 12 was proposed to be the metabolite responsible for the partial 5-HT syndrome seen after oral (but not subcutaneous) administration of 13. The bioavailability of R-(+)-6 (7.6 +/- 1.1%) appeared to be slightly lower than that of 2 (11.2 +/- 5.2%), although the in vitro metabolism of R-(+)-6 appeared to be slower than that of 2. Therefore first-pass metabolism was not thought to be the reason for the lower bioavailability of R-(+)-6, as compared to 2.

Animals↗
PubMed1995

Dosimetry of styrene 7,8-oxide in styrene- and styrene oxide-exposed mice and rats by quantification of haemoglobin adducts.

Rats (Sprague Dawley) and mice (NMRI) were administered nonlabelled or labelled styrene and styrene oxide by i.p. injection. Blood samples were collected 6 and 24 h after treatment for studies of dose-response and 6 h to 32 days after treatment for studies of adduct stability. Haemoglobin (Hb) and plasma protein adduct levels were determined by radioactivity measurements or, in the case of adducts to N-terminal valine in Hb, by the so-called N-alkyl Edman procedure. Adducts to N-terminal valine were found to be chemically stable during the life-span of the erythrocytes, whereas adducts to carboxylic acid residues showed a reduced stability. The Hb-adduct levels found after styrene oxide treatment were compatible with a linear dose-response at low doses (< or = 0.4 mmol/kg body weight). At higher doses the detoxification of styrene oxide was overloaded resulting in a higher than proportional increase in adduct levels. Saturation of detoxification of styrene oxide could also explain the non-linear dose-response relationship observed in the mouse following treatment with styrene. Styrene oxide gave 4-7 times higher adduct levels than styrene when administered to the animals at equimolar low concentration. For both compounds, the levels of adducts to N-terminal valine were 2-3 times higher in the mouse than in the rat. A comparison of Hb-adduct levels in the styrene-exposed animals with adduct levels in styrene-exposed reinforced plastics workers (Christakopoulos et al., Scand. J. Work Environ. Health, 19(4) (1993) 255-263) suggests that styrene is less effective in humans than in mice and rats.

Animals↗
PubMed1995

Effects of the dopamine autoreceptor antagonist (-)-DS121 on the discriminative stimulus properties of d-amphetamine and cocaine.

(-)-DS121 [S-(-)-3-(3-cyanophenyl)-N-n-propyl piperidine) is a recently synthesised phenylpiperidine derivative suggested to be a dopamine receptor antagonist acting preferentially at dopamine autoreceptors. The drug exerts 'agonist-like' behavioural effects by enhancing dopamine release, but also shares properties in common with neuroleptics. The ability of (-)-DS121 to both generalise to and antagonise the stimulus effects of psychostimulants was determined in rats trained to discriminate d-amphetamine (0.5 mg/kg) or cocaine (5.0 mg/kg) from saline in a two-lever, food-reinforced, drug discrimination task. (-)-DS121 (3.5-14.0 mg/kg) produced small, but significant, increases in drug lever-appropriate responding in both d-amphetamine and cocaine-trained rats. However, there was no indication of a dose-dependent effect in either case. On the other hand, (-)-DS121 dose-dependently reduced response rate. Caffeine produced a higher level of drug lever-appropriate responding than (-)-DS121 in d-amphetamine-trained rats. (-)-DS121 (7.0-14.0 mg/kg) also weakly antagonised the cueing properties of both d-amphetamine and cocaine. A marked response disruption with the drug combination precluded testing of higher doses of (-)-DS121. A combination of subthreshold doses of (-)-DS121 (3.5 mg/kg) and d-amphetamine (0.0625 mg/kg) produced a significant degree of drug lever-appropriate responding, suggesting a synergistic interaction between these drugs. However, such an interaction was not noted with a higher dose of (-)-DS121, or when this drug was administered with a low dose of cocaine (0.25 mg/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamine↗
PubMed1995

C-9 and N-substituted analogs of cis-(3aR)-(-)-2,3,3a,4,5,9b-hexahydro-3- propyl-1H-benz[e]indole-9-carboxamide: 5-HT1A receptor agonists with various degrees of metabolic stability.

Closely related analogs of the 5-HT1A receptor agonist cis-(3aR)-(-)-2,3,3a,4,5,9b-hexahydro-3-propyl-1H-benz[e]indole-9- carboxamide (1, U93385) were synthesized and pharmacologically evaluated. 9-Carboxamide analogs with varied nitrogen substitution (R2) were synthesized, and their serotonergic activity was evaluated in vitro and in vivo. Many of these compounds were incubated in the presence of rat hepatocytes, and the metabolic stability in vitro was compared to that of compound 1. Only the N-methyl and N-ethyl analogs ((-)-5a and (-)-5b) were more stable than compound 1, indicating that N-dealkylation is a major route of metabolism in this series. In addition, these analogs were found to be partial 5-HT1A receptor agonists in vivo. Modifications were also made to the carboxamide functionality of compound 1 (R1 in 2) to yield substituted amides or ketones. Among these analogs, the methyl ketone (-)-15a was found to be a 5-HT1A agonist with full intrinsic activity in vivo and was approximately 20 times more potent than compound 1 and 5 times more potent than 8-OH-DPAT.

Animals↗
PubMed1995

Effects of dopamine D3 preferring compounds on conditioned place preference and intracranial self-stimulation in the rat.

Compounds showing an in vitro binding preference for the dopamine D3 receptor were tested in two models designed to assess positive reinforcement in the rat: intracranial self-stimulation (ICSS) and conditioned place preference (CPP). R-(+)-7-OH-DPAT, a D3 preferring agonist, inhibited ICSS behaviour over a wide dose range. At higher doses, a facilitation of ICSS was seen. In the CPP model, 7-OH-DPAT was inactive except at the highest dose where a significant change in preference was seen. A dose of R-(+)-7-OH-DPAT, that significantly inhibited ICSS behaviour, was combined with a dose of d-amphetamine, that significantly facilitated ICSS behaviour. Surprisingly, this resulted in a significant synergistic facilitation of the amphetamine response. The putative D3 antagonist, U99194A was inactive in the ICSS model but induced significant place preference. The present results suggest that the dopamine D3 receptor, in contrast to the D2 receptor, has an inhibitory influence on reward mechanisms.

Animals↗
PubMed1995

Effects on locomotor activity after local application of D3 preferring compounds in discrete areas of the rat brain.

Compounds showing an in vitro binding preference for the dopamine D3 vs. D2 receptors were tested for effects on locomotor activity after local application in the nucleus accumbens (N Acc) and the ventral tegmental area (VTA) of the rat brain. R-(+)-7-OH-DPAT, a dopamine D3 preferring agonist, inhibited spontaneous locomotor activity over a wide dose range after injection into the N Acc. A decrease in activity over a wide dose range was also seen after local application into the VTA of both R-(+)-7-OH-DPAT and the dopamine D2 preferring agonist (+)-3-PPP. Furthermore, (+)-3-PPP produced a dose dependent increase in activity after local application into the N Acc. The putative D3 antagonist, U99194A, with a 30 fold preference for the dopamine D3 vs. D2 receptor, produced an increase in activity when injected into the N Acc. A similar pattern were seen after infusion into the lateral ventricle. Local application into the VTA did, however, not produce any significant effects. The present results support the hypothesis that dopamine D3 receptors (in contrast to the D2 receptors) are mainly postsynaptically located where they display an inhibitory action on locomotor activity.

Animals↗
PubMed1995

H19 is imprinted in the choroid plexus and leptomeninges of the mouse foetus.

It has been proposed that either the Igf-2 gene or the H19 gene--but not both--can be expressed from a given chromosome. Igf-2 is known to be biallelically expressed in the choroid plexus and leptomeninges, however, raising the question of whether H19 is down-regulated or absent there. We found by in situ hybridization that H19 is indeed expressed in the choroid plexus and leptomeninges of the developing mouse foetus. Comparison with the expression pattern of Igf-2 showed that the genes are coexpressed in all areas, with the exception of the choroid plexus epithelium. To evaluate whether H19 is also biallelically expressed in these tissues, we microdissected embryos from interspecific crosses and performed RNAse protection analysis on the isolated RNA. This revealed that H19 maintains its imprint in the choroid plexus/leptomeninges, being transcribed from the maternal allele at a level comparable to that in normal liver. We discuss the significance of these results for current models of Igf-2 and H19 imprinting.

Alleles↗