Search PubMed⌕ Search

Biomedical subjects

B Carlsson

Publications and source records attributed to B Carlsson.

At least 109 records · Page 6Linked to original sources
PubMed1995

Beta-adrenergic receptor function in cultured AT-1 cardiomyocytes.

AT-1 cells are highly differentiated, contracting cardiomyocytes derived from atrial tumours in transgenic mice. The aim of this study was to characterize beta-adrenergic receptor function and associated intracellular calcium regulation in AT-1 cells. Equilibrium binding experiments with [3H]-CGP-12177 showed a Kd = 0.30 +/- 0.08nM and a Bmax = 2.25 +/- 0.47 fmol/10(5) cells. Competition binding experiments with CGP-20712A showed presence of predominantly beta 1-adrenoreceptors. S-(-)propranolol, atenolol and R-(+)propranolol showed a competitive inhibition of binding with successively lower affinity. Isoproterenol, 2 microM, for 48 hours down-regulated the number (p < 0.05) of beta-adrenergic receptors/cell by about 50%; 10 microM for one hour increased the cAMP concentration (p < 0.05) by about 100%. Cytosolic [Ca2+] was measured flourimetrically in spontaneously and synchronously beating AT-1 cells. The resting cytosolic concentration was 94 +/- 10 nM. The observed sinusoidal Ca2+ oscillation frequency increased after addition of 10 microM isoproterenol (p < 0.02). This effect was antagonized by 10 microM alprenolol (p < 0.01). In conclusion, AT-1 cells have functional beta-adrenoreceptor signalling pathways and constitute an important tool in cardiac biology.

Adrenergic beta-Antagonists↗
PubMed1995

Antibody titre and avidity in saliva and serum are not impaired in mildly to moderately undernourished children.

Avidities and titres of serum IgA, IgM, IgG, and salivary IgA antibodies for poliovirus type 3, beta-lactoglobulin and E. coli O antigens were analysed in well-nourished (n=58) and mildly to moderately undernourished (n = 18) 1-7-year-old children, living in slums in São Paulo, Brazil, with irregular water supply and no sewage system. The serum titres of antibodies in the undernourished children were not statistically different from the well-nourished ones, except for the IgA anti-beta-lactoglobulin titres which were lower in the youngest undernourished group. In respect to avidity of the serum antibodies, no statistical difference was observed, except that the youngest undernourished children presented avidities of serum IgA anti-E. coli O antigens higher than those of the well-nourished children of the same age range. With respect to salivary titres and avidities no difference was observed between well-nourished and undernourished children. The fact that the undernourished children were not deficient in antibody amount or quality, as measured in this study, suggests that in this respect their immune system was not impaired.

Antibodies, Bacterial↗
PubMed1995

Amiodarone is a dose-dependent noncompetitive and competitive inhibitor of T3 binding to thyroid hormone receptor subtype beta 1, whereas disopyramide, lignocaine, propafenone, metoprolol, dl-sotalol, and verapamil have no inhibitory effect.

The cardiovascular and electrophysiological effects of amiodarone resemble those of hypothyroidism. The drug has a structural resemblance to thyroid hormone (T3). Previous studies indicate that amiodarone exerts its major effect through antagonism of T3, probably as a result of inhibition of ligand binding to the thyroid hormone receptor (ThR). There are five subtypes of ThR, of which the beta 1 is the most prominent in the human heart. Our first aim was to investigate whether ThR is involved in a general antiarrhythmic mechanism for antiarrhythmic drugs or whether this action is specific for amiodarone. Therefore, we studied the affinity of one antiarrhythmic drug from every Vaughan-Williams group on T3 binding to human ThR beta 1 (hThR beta 1). Second, we wished to investigate whether amiodarone is a competitive or noncompetitive inhibitor. hThR beta 1, expressed in insect cells using a recombinant baculovirus, was used in regular binding competition assays. Disopyramide, lignocaine, propafenone, metoprolol, dl-sotalol, and verapamil had no effect on T3 binding to hThR beta 1. Amiodarone showed a noncompetitive binding pattern at low concentrations (0.25-2 microM) and a competitive binding at high concentrations (2-8 microM). Among the antiarrhythmics tested, only amiodarone had affinity for hThR beta 1. This may represent a novel type of antiarrhythmic mechanism. The finding that amiodarone, in concentrations corresponding to therapeutic range in plasma, shifts from a noncompetitive to a competitive inhibitor, is of clinical interest in comparisons of low- and high-dose treatment.

Amiodarone↗
PubMed1995

Scintillating microtitration plates as platform for determination of [3H]estradiol binding constants for hER-HBD.

A novel approach to direct determination of ligand binding constants for the human estrogen receptor hormone binding domain was developed. Recombinantly produced human receptor in yeast extracts was attached to scintillating microtitration plates. Radioligand binding to receptors was determined in a multi-detector scintillation counter designed for the microtitration plate format. The method was employed in equilibrium binding experiments, in binding competition tests and in determination of kinetic rate constants. The results obtained show that the methodology is valid in comparison to previously published data regarding hormone binding characteristics of estrogen receptors. Furthermore, the methodology offers several advantages over previous binding assays because the scintillating microtitration plates constitute both the binding reaction vial and the scintillant for the detection of bound radioactivity.

Binding Sites↗
PubMed1994

Prenatal diagnosis of glutathione synthase deficiency.

Prenatal diagnosis for glutathione synthase (EC 6.3.2.3) deficiency in two pregnancies of an at-risk couple was performed on amniotic fluid taken at 16 weeks' gestation. 5-Oxoproline (pyroglutamic acid) levels were 970 and 790 mumol/l compared with the normal mean value of 29 mumol/l (range 13-51 mumol/l). The pregnancies were terminated and the diagnosis in one case was subsequently confirmed by assay of glutathione synthase in cultured fetal fibroblasts. In the other, post-mortem tissue samples failed to grow.

Adult↗
PubMed1994

Equilibrium hormone binding to human estrogen receptors in highly diluted cell extracts is non-cooperative and has a Kd of approximately 10 pM.

It is generally accepted that the Kd for hormone binding to estrogen receptors in extracts ranges between 0.1-1 nM and that binding displays positive cooperativity due to formation of homodimers. After carefully optimizing assay procedures, to diminish ligand depletion phenomena and to fully control recoveries, we find a single class of non-interacting high affinity hormone binding sites with a Kd of approx. 10 pM. Ligand depletion was avoided by decreasing receptor concentrations to 5-8 pM. We were therefore obliged to employ radioiodinated estradiol as a probe as the specific radioactivity of tritiated estradiol was too low to maintain the accuracy of the binding assay. Human estrogen receptor extracted from the MCF7 cell line and recombinantly produced (in yeast) wild-type human receptor have identical equilibrium hormone binding characteristics.

Cell-Free System↗
PubMed1994

Reduced hepatic growth hormone (GH) receptor gene expression and increased plasma GH binding protein in experimental uremia.

In uremia, reduced longitudinal growth and decreased hepatic insulin-like growth factor-I (IGF-I) secretion despite elevated GH serum levels point to an insensitivity to the action of GH. The molecular basis that accounts for this insensitivity could comprise decreased GH receptor expression in the target organs for GH or binding of GH in the circulation to substances that compete with the receptor. To address this hypothesis, the abundance of hepatic GH receptor mRNA was measured by solution hybridization RNase protection assay in uremic female Sprague-Dawley rats, following two-stage 5/6 nephrectomy, and in pair-fed and in ad libitum-fed sham-operated controls; rat GH binding protein (GHBP) plasma concentration was measured by a sensitive direct RIA. Uremia was associated with a 50% decrease of hepatic GH receptor expression compared to pair-fed controls, which themselves showed a 25% reduction of hepatic GH receptor mRNA abundance when compared to ad libitum-fed controls. Plasma GHBP levels in uremia were markedly higher than in both control groups. Treatment with recombinant human GH (rhGH) (10 IU/kg body wt per day s.c. for 10 days) led to a comparable induction of IGF-I plasma levels and weight gain in uremia and pair-fed controls, indicating that the insensitivity to GH in uremia can be overcome by large rhGH doses. Subcutaneous rhGH injections did not significantly alter the hepatic GH receptor transcript abundance or plasma GHBP levels in any of the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Impaired synthesis of lipoxygenase products in glutathione synthetase deficiency.

Glutathione synthetase deficiency (GSD) is an inborn error of glutathione (GSH) metabolism leading to a generalized intracellular GSH deficiency. Because GSH is required for leukotriene C4 (LTC4) synthesis, we studied synthesis and metabolism of several lipoxygenase products in two patients with GSD by radio-HPLC, UV spectrophotometry, and enzyme immunoassays. In both patients, LTC4 synthesis was significantly decreased in calcium ionophore-stimulated neutrophils (up to 0.4 ng/10(6) cells; controls, 5.0 +/- 0.9) and monocytes (up to 3.6 ng/10(6) cells; controls, 30.2 +/- 3.3). LTB4 synthesis was about seven times higher in GSD cells compared with controls, whereas synthesis of other 5-, 12-, and 15-lipoxygenase products and prostaglandin E2 was not affected. Neutrophils and monocytes from both patients showed a marked reduction in capacity to form [3H]LTC4 from [3H]LTA4 (9-14% of control values). Urinary LTE4 was finally found to be 50-fold lower in GSD, reflecting a decreased synthesis of cysteinyl LT in vivo. GSD may serve as a unique model for the linkage between LT synthesis and GSH metabolism in vivo.

Calcimycin↗
PubMed1994

Estradiol regulation of mRNA expression of stimulatory G-protein alpha-subunit in white adipose tissue from female rats.

Adipose tissue has been recognized as a major peripheral metabolic target of estrogens. The present study was addressed to examine in female rats whether differences in the adipose tissue mRNA expression of alpha-subunit of stimulatory (Gs) and/or inhibitory (Gi) G-proteins exist between intact and ovariectomized rats, the latter with or without estradiol or testosterone treatment. The fat cell membrane protein amount of Gs and Gi alpha-subunit also was examined. All these parameters were evaluated in parametrial fat tissue samples obtained from 40 female Sprague-Dawley rats. A group of rats (N = 20) was investigated for evaluation of mRNA expression and another group (N = 20) for quantification of the protein amount of Gs and Gi alpha-subunit. Each group was represented by five control rats (sham-operated), five ovariectomized (OVX) rats, five ovariectomized rats treated with estradiol (OVXE) and five ovariectomized rats treated with testosterone (OVXT). Ribonucleic acid extracted from adipose tissue and analyzed by northern blot with G alpha s, G alpha i-3 cRNA probes revealed three major bands with estimated sizes of 1.9, 3.5 and 2.35 kb, respectively. Messenger RNA quantitative analysis, by a solution of hybridization RNAase protection assay on total nucleic acid samples, showed that the amount of G alpha i-1 and G alpha i-2 mRNA was similar within the different groups, whereas the G alpha s mRNA was significantly less abundant (p < 0.01) in OVX and OVXT rats than in control or OVXE rats. No difference in G alpha s mRNA content was found between control and OVXE rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1994

Endogenous hypercholecystokininemia, but not aspirin, reduces the gallstone incidence in the hamster model.

BACKGROUND: Studies in humans and rodents indicate that gallstone development may be prevented by inhibiting gallbladder mucus hypersecretion with non-steroidal anti-inflammatory drugs or by preventing stasis of gallbladder bile with administration of cholecystokinin. METHODS: The effect of oral aspirin and pancreaticobiliary diversion with endogenous hypercholecystokininemia on crystal and gallstone formation was studied in Syrian golden hamsters fed a lithogenic diet for 8 weeks. RESULTS: None of the control animals fed a normal diet developed gallstones or crystals in gallbladder bile. Gallstones developed in 67% of the animals fed a lithogenic diet only. The gallstone prevalence did not differ significantly in animals on a lithogenic diet and a daily aspirin dose of 6 mg/kg (gallstone prevalence, 60%) or 100 mg/kg (gallstone prevalence, 70%), whereas it was significantly lower in animals with endogenous hypercholecystokininemia on a lithogenic diet (gallstone prevalence, 29%). The prevalence of crystals in gallbladder bile did not differ significantly between any of the experimental groups. CONCLUSIONS: It is concluded that in hamsters on a lithogenic diet, aspirin does not prevent gallstone formation, whereas endogenous hypercholecystokininemia reduces the prevalence of stones without affecting the occurrence of crystals in gallbladder bile.

Animals↗
PubMed1994

Messenger RNA of G-proteins alpha-subunit in rat brown adipose tissue.

The present study was addressed to quantify the steady-state mRNA levels for the alpha subunit of stimulatory (Gs) and inhibitory (Gi-1 and Gi-2) G-proteins in brown (interscapular) male rat adipose tissue (n = 6 rats). The quantification of specific mRNA, estimated using a solution hybridization RNAse protection assay, showed that the amounts of G alpha i-1, G alpha i-2 and G alpha s mRNA were 0.88 +/- 0.28 amol/microgram DNA, 76 +/- 4 amol/micrograms DNA and 460 +/- 16 amol/micrograms DNA, respectively. When the amounts of G alpha i-1 and G alpha i-2 and G alpha s mRNA in brown adipose tissue were compared with those in epididymal white adipose tissue (obtained from the same rats), G alpha i-1 and G alpha i-2 mRNA levels were very similar between brown and white adipose tissue, whereas the level of G alpha s mRNA was significantly higher in brown than in white fat tissue (P < 0.001). In conclusion, the present study shows the steady-state levels of mRNA for the alpha subunit of Gs, Gi-1 and Gi-2 in rat brown fat and suggests that the quantity of G alpha s mRNA is higher in brown than in white adipose tissue. Further studies are needed to explain the possible physiological importance of these findings.

Adipose Tissue↗
PubMed1993

Prenatal analysis in two suspected cases of glutathione synthetase deficiency.

Prenatal diagnosis was performed in a family affected by generalized glutathione synthetase deficiency. The disorder is transmitted by autosomal recessive inheritance. The first child born in this family died of the disorder at 6 weeks of age. Prenatal diagnosis was performed in two subsequent pregnancies. Amniotic fluid samples were collected by amniocentesis in the 16th and 17th weeks of pregnancy, respectively. In the case of the second pregnancy the concentration of 5-oxoproline in the amniotic fluid was measured by stable isotope dilution, while both stable isotope dilution and glutathione synthetase activity measurements were employed in the prenatal analysis of the third pregnancy. The 5-oxoproline concentration in the second pregnancy was even lower than that of the controls and in the case of the third pregnancy the results fell within the control range. The second pregnancy resulted in the birth of a clinically healthy girl, and the outcome of 5-oxoproline concentration in a urine sample taken just after birth confirmed the unaffected state. The third pregnancy resulted in the birth of a healthy boy at term, and the 5-oxoproline concentration in his urine and the glutathione synthetase activity in haemolysates were determined. The results confirmed that this infant was also unaffected and he apparently had two normal alleles for the enzyme.

Amniotic Fluid↗
PubMed1993

Growth hormone-receptor messenger RNA in the rat ovary: regulation and localization.

The results of several reports indicate that GH can modulate ovarian function. In the present study, the expression of the growth hormone-receptor (GH-R) mRNA was studied in the rat ovary using an RNA probe corresponding to a part of the extracellular domain of the GH-R. The probe hybridized to two major transcripts with estimated sizes of 4.0 kb and 1.2 kb in RNA extracted from liver and ovary. Recently, these transcripts have been shown to encode the GH-R and the GH-binding protein (GH-BP). The ontogeny of the GH-R/GH-BP mRNA expression was studied using Northern blot analysis and a solution hybridization RNase protection assay. In the liver GH-R/GH-BP mRNA levels increased with age, while in the ovary, the levels decreased between 1 and 5 weeks of age. Hypophysectomy caused a decrease in GH-R/GH-BP gene expression in the ovary, an effect which could be partly reversed with a single injection of GH (2 mg/kg). No significant changes in the ovarian concentration of GH-R/GH-BP transcripts were seen during the estrus cycle. Using in situ hybridization GH-R/GH-BP transcripts were found to be most abundant in follicles. Northern blot analysis of RNA extracted from isolated granulosa cells and corpora lutea showed that both these compartments contained GH-R and GH-BP mRNA, although more abundant in granulosa cells. Immunoreactive GH-R was detected in granulosa cells of healthy follicles, corpus luteum, and in the germinal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗