Search PubMed⌕ Search

Biomedical subjects

M Nielsen

Publications and source records attributed to M Nielsen.

At least 55 records · Page 3Linked to original sources
PubMed2000

Ontogeny of oestrogen receptor alpha in gonads and sex ducts of fetal and newborn mice.

The distribution of nuclear oestrogen receptor alpha (ER-alpha) in the sex organs of fetal and newborn mice has been investigated immunohistochemically. There was no visible ER-alpha immunoreaction in the sexually undifferentiated gonads, whereas a faint immunoreaction was detected in a few cells surrounding the sex ducts, the Müllerian and Wolffian ducts. After sex differentiation, the immunoreaction of ER-alpha was observed in various cell types, with the exception of both the male and female germ cells. In the fetal ovary, immunoreaction was restricted to the surface epithelium and a few stroma cells without any preferential localization. In the testis, the number of ER-alpha-immunopositive cells, identified as Leydig and peritubular cells, increased with age. Immediately after sex differentiation, cells surrounding the sex ducts were ER-alpha-immunopositive, but no immunoreaction was detected in the epithelium in either sex. During development, the epithelium of the sex ducts attained a topographic difference in ER-alpha immunoreaction. In females, immunoreaction was detected in the epithelium of the oviduct, but not in the uterus. In males, the immunoreaction of ER-alpha was intense in the epithelium of the efferent ducts, weak in the epididymis and absent in the vas deferens. ER-alpha immunoreaction in the cells surrounding the sex duct differed between the sexes, being high in all these cells in females, but of varying intensity in males. ER-alpha may not play an important role in the development and function of ovarian cells, but may be involved in the development of Leydig and peritubular cells. Furthermore, substances that react with ER-alpha may influence the male germ cells indirectly through the ER-alpha-immunopositive peritubular cells. In addition, in both sexes, ER-alpha-immunopositive cells surrounding the sex ducts may be involved in the mediation of growth and functional differentiation of the ductal epithelium.

Animals↗
PubMed2000

Octylphenol does not mimic diethylstilbestrol-induced oestrogen receptor-alpha expression in the newborn mouse uterine epithelium after prenatal exposure.

This study examined whether the endocrine disruptor octylphenol (OP) mimics the synthetic oestrogen diethylstilbestrol (DES) in ability to induce oestrogen receptor-alpha (ER-alpha) expression in the newborn mouse uterine epithelium after prenatal exposure. Pregnant mice were given daily s.c. injections with DES (10 or 100 microgram DES/kg maternal wt) or OP (100 or 250 mg/kg maternal wt) or with vehicle alone from day 11.5 to 16.5 of pregnancy. ER-alpha expression was evaluated on histological sections by detecting ER-alpha mRNA with the in situ hybridization technique and ER-alpha protein using immunohistochemistry. The immunostaining was quantitated using a microspectrophotometer. Oestrogen-like activity of the DES and OP batches used for in vivo exposure was confirmed in an in vitro assay based on transient gene expression of an oestrogen-dependent reporter plasmid. In mice exposed prenatally to vehicle alone, the uterine epithelium did not express either ER-alpha mRNA or protein, while both were highly expressed in the stroma. Exposure to either DES dose induced the expression of both ER-alpha mRNA and protein in the epithelium, whereas it was unchanged in the stroma. In contrast, neither OP dose induced the expression of ER-alpha mRNA or protein in the epithelium and expression was unchanged in the stroma. Our data stress the importance of in vivo studies when investigating endocrine disruptors.

Animals↗
PubMed2000

Lck is involved in interleukin-2 induced proliferation but not cell survival in human T cells through a MAP kinase-independent pathway.

The role of Lck in IL-2-induced proliferation and cell survival is still controversial. Here, we show that the Src family kinase inhibitor, PP1, reduced the IL-2-induced proliferation of human T cells significantly without inhibiting the anti-apoptotic effect of IL-2. As Lck is the only Src family kinase activated upon IL-2 stimulation in T cells, this indicates that Lck is involved in IL-2-induced proliferation but not survival. IL-2-induced MAP kinase activation was only slightly inhibited by PP1, suggesting that Lck is not essential for IL-2-induced MAP kinase activation in human T cells. We found that an IL-2-sensitive, human mycosis fungoides-derived tumor T cell line is Lck negative, and that the IL-2-induced MAP kinase activation is comparable to non-cancerous T cells, although a little delayed in kinetics. An Lck expressing clone was established by transfecting Lck into mycosis fungoides tumor T cells, but Lck had no influence on the delayed kinetics of MAP kinase activation, indicating that Lck is not essential for MAP kinase activation in mycosis fungoides tumor T cells or in non-cancerous T cells. Taken together, this indicates that Lck is involved in IL-2-induced proliferation, but not cell survival, through a pathway not involving MAP kinase.

Base Sequence↗
PubMed1999

[Good quality of life after heart surgery. Comparable ratings by patients and their relatives].

In a series of 83 patients undergoing coronary artery bypass grafting for angina, perceived QOL (quality of life) was rated by the patients and their spouses, preoperatively and at two and 12 months postoperatively, using the SWED-QUAL instrument. One year after surgery, QOL had improved to a level which might be expected of a normal population comparable in age and gender distribution. Good correlation existed between patient and spouse ratings, especially on physical measures.

Angina Pectoris↗
PubMed1999

Neural representation of a rhythm depends on its interval ratio.

Rhythm is determined solely by the relationship between the time intervals of a series of events. Psychological studies have proposed two types of rhythm representation depending on the interval ratio of the rhythm: metrical and nonmetrical representation for rhythms formed with small integer ratios and noninteger ratios, respectively. We used functional magnetic resonance imaging to test whether there are two neural representations of rhythm depending on the interval ratio. The subjects performed a short-term memory task for a seven-tone rhythm sequence, which was formed with 1:2:4, 1:2:3, or 1:2.5:3.5 ratios. The brain activities during the memory delay period were measured and compared with those during the retention of a control tone sequence, which had constant intertone intervals. The results showed two patterns of brain activations; the left premotor and parietal areas and right cerebellar anterior lobe were active for 1:2:4 and 1:2:3 rhythms, whereas the right prefrontal, premotor, and parietal areas together with the bilateral cerebellar posterior lobe were active for 1:2.5:3.5 rhythm. Analysis on individual subjects revealed that these activation patterns depended on the ratio of the rhythms that were produced by the subjects rather than the ratio of the presented rhythms, suggesting that the observed activations reflected the internal representation of rhythm. These results suggested that there are two neural representations for rhythm depending on the interval ratio, which correspond to metrical and nonmetrical representations.

Adult↗
PubMed1999

Structure-activity relationships and molecular modeling analysis of flavonoids binding to the benzodiazepine site of the rat brain GABA(A) receptor complex.

The affinities for the benzodiazepine binding site of the GABA(A) receptor of 21 flavonoids have been studied using [(3)H]flumazenil binding to rat cortical membranes in vitro. We show that flavonoids with high affinity for the benzodiazepine receptor in vitro spanning the whole efficacy range from agonists (1q) to inverse agonists (1l) can be synthesized. The receptor binding properties of the flavonoids studied can successfully be rationalized in terms of a comprehensive pharmacophore model recently developed by Cook and co-workers (Drug Des. Dev. 1995, 12, 193-248), supporting the validity of this model. However, in contrast to the requirement by the model that an interaction with the hydrogen bond-accepting site A2 is necessary for compounds to display inverse agonistic activity, 6-methyl-3'-nitroflavone (1l), which cannot engage in such an interaction, nevertheless displays inverse agonism. The analysis of the binding affinities of 3'- and 4'-substituted flavones in terms of the pharmacophore model has yielded new information for the further development of the pharmacophore model.

Animals↗
PubMed1999

Inhibition of protein phosphatase 2A induces serine/threonine phosphorylation, subcellular redistribution, and functional inhibition of STAT3.

Signal transducers and activators of transcription (STATs) are rapidly phosphorylated on tyrosine residues in response to cytokine and growth factor stimulation of cell surface receptors. STATs hereafter are translocated to the nucleus where they act as transcription factors. Recent reports suggest that serine phosphorylation of STATs also is involved in the regulation of STAT-mediated gene transcription. Here, we studied the role of serine/threonine phosphatases in STAT3 signaling in human antigen-specific CD4(+) T cell lines and cutaneous T cell lymphoma lines, expressing a constitutively activated STAT3. We show that an inhibitor of protein phosphatases (PPs) PP1/PP2A, calyculin A, induces (i) phosphorylation of STAT3 on serine and threonine residues, (ii) inhibition of STAT3 tyrosine phosphorylation and DNA binding activity, and (iii) relocation of STAT3 from the nucleus to the cytoplasm. Similar results were obtained with other PP2A inhibitors (okadaic acid, endothall thioanhydride) but not with inhibitors of PP1 (tautomycin) or PP2B (cyclosporine A). Pretreatment with the broad serine/threonine kinase inhibitor staurosporine partly blocked the calyculin A-induced STAT3 phosphorylation, whereas inhibitors of serine/threonine kinases, such as mitogen-activated protein kinase-1 extracellular-regulated kinase-kinase, mitogen-activated protein p38 kinase, and phosphatidylinositol 3-kinase, did not. In conclusion, we provide evidence that PP2A plays a crucial role in the regulation of STAT3 phosphorylation and subcellular distribution in T cells. Moreover, our findings suggest that the level of STAT3 phosphorylation is balanced between a staurosporine-sensitive kinase(s) and PP2A.

CD4-Positive T-Lymphocytes↗
PubMed1999

Cutting edge: TCR stimulation by antibody and bacterial superantigen induces Stat3 activation in human T cells.

Recent data show that TCR/CD3 stimulation induces activation of Stat5 in murine T cells. Here, we show that CD3 ligation by mAb and Staphylococcal enterotoxin (SE) induce a rapid, gradually accumulating, long-lasting tyrosine, and serine phosphorylation of Stat3 (but not Stat5) in allogen-specific human CD4+ T cell lines. In contrast, IL-2 induces a rapid and transient tyrosine and serine phosphorylation of Stat3. Compared with IL-2, CD3 ligation induces a delayed Stat3 binding to oligonucleotide probes from the ICAM-1 and IL-2R alpha promoter. CD3-mediated activation of Stat3 is almost completely inhibited by a Src kinase inhibitor (PP1), whereas IL-2-induced Stat3 activation is unaffected. In conclusion, we show that CD3 ligation by mAb and SE triggers a rapid, PP1-sensitive tyrosine and serine phosphorylation of Stat3 in human CD4+ T cells. Moreover, we provide evidence that TCR/CD3 and IL-2 induce Stat3 activation via distinct signaling pathways.

Antibodies, Monoclonal↗
PubMed1999

Effects of isoflurane and hexafluorodiethyl ether on human recombinant GABA(A) receptors expressed in Sf9 cells.

Effects of volatile anesthetics and a volatile convulsant on human recombinant gamma-aminobutyric acid (GABA) type A receptor responses were studied using the whole cell configuration of the patch clamp technique. Sf9 cells were transfected with bacuroviruses carrying cDNAs of alpha1beta2, alpha1beta2gamma2s, alpha3beta2 and alpha3beta2gamma2s subunit combinations of the human GABA(A) receptor. Clinical concentrations of isoflurane (a volatile anesthetic) enhanced the GABA-induced current of the alpha1beta2gamma2s and alpha3beta2gamma2s GABA(A) subunit combinations. On the other hand, isoflurane suppressed the current of the alpha1beta2 and alpha3beta2 subunit combinations, indicating that the anesthetic effects depended upon the presence of gamma2s subunit. A high concentration (2 mM) of isoflurane generated a surge current following the washout of GABA and the anesthetic. Hexafluorodiethyl ether (a volatile convulsant) decreased the GABA-response of the both alpha3beta2gamma2s and alpha3beta2 constructs without generating a surge current. The results suggest that volatile agents affect the receptor-ionophore complex via direct interaction with proteins but not through a perturbation of the membrane lipid environment. A hypothetical sequential model for the anesthetic action is presented.

Anesthetics, Inhalation↗
PubMed1999

Arginine residue 120 of the human GABAA receptor alpha 1, subunit is essential for GABA binding and chloride ion current gating.

The effect of mutating the conserved amino acid residue arginine 120 to lysine in the GABAA receptor alpha 1 subunit was studied. In electrophysiological experiments, the arginine 120 lysine (R120K) mutation in the alpha 1 subunit, when co-expressed with beta 2 and gamma 2 subunits in Sf-9 insect cells, induces a 180-fold rightward shift of the GABA dose-response curve compared with wild type alpha 1 beta 2 gamma 2s GABAA receptors. The diazepam potentiation of GABA-gated chloride ion currents was not affected. The binding of the GABAA ligands [3H]muscimol and [3H]SR 95531 to alpha 1 (R120K) beta 2 gamma 2s GABAA receptors was abolished but the binding affinity of the benzodiazepine receptor ligand [3H]flunitrazepam was unchanged. These results suggest that the arginine residue 120 in the alpha 1 subtype of the GABAA receptor is essential for GABA binding.

Amino Acid Sequence↗
PubMed1999

Heat transfer in large-scale heavy-gas dispersion.

Heavy-gas dispersion of practical interest is usually cold gas dispersion with the enthalpy deficit as the main cause of the density effect. New analysis of existing field experiment data suggests that heat transfer from the ground sometimes reduces this thermally induced density effect considerably. The limited heat capacity of the ground implies that heat transfer to a gas plume must disappear eventually, and our interpretation of Desert Tortoise measurements indicates that the surface heat flux decreased by 38% during a 3-min long release period.

Gases↗
PubMed1999

Lipolysis in skeletal muscle is rapidly regulated by low physiological doses of insulin.

AIMS/HYPOTHESIS: Both patients with Type II (non-insulin-dependent) diabetes mellitus and normoglycaemic, insulin resistant subjects were shown to have an increased lipid content in skeletal muscle, which correlates negatively with insulin sensitivity. Recently, it was shown that during a hyperinsulinaemic euglycaemic clamp interstitial glycerol was reduced not only in adipose tissue but also in skeletal muscle. To assess whether lipolysis of muscular lipids is also regulated by low physiological concentrations of insulin, we used the microdialysis technique in combination with a 3-step hyperinsulinaemic glucose clamp. METHODS: Nineteen lean, healthy subjects (12 m/7 f) underwent a glucose clamp with various doses of insulin (GC I = 0.1, GC II = 0.25 and GC III = 1.0 mU x kg(-1) x min(-1)). Two double lumen microdialysis catheters each were inserted in the paraumbilical subcutaneous adipose tissue and in skeletal muscle (tibialis anterior) to measure interstitial glycerol concentration (index of lipolysis) and ethanol outflow (index of tissue flow). RESULTS: During the different steps of the glucose clamp, glycerol in adipose tissue was reduced to 81 +/- 7 % (GC I), 55 +/- 8 % (GC II) and 25 +/- 5 % (GC III), respectively, of basal. In contrast, glycerol in skeletal muscle declined to 73 +/- 5 % (GC I) and to 57 +/- 6 % (GC II) but was not further reduced at GC III. Tissue flow was higher in the skeletal muscle and remained unchanged in both compartments throughout the experiment. CONCLUSION/INTERPRETATION: This study confirms the presence of glycerol release in skeletal muscle. Lipolysis in skeletal muscle and adipose tissue are suppressed similarly by minute and physiological increases in insulin but differently by supraphysiological increases. Inadequate suppression of intramuscular lipolysis resulting in increased availability of non-esterified fatty acids, could represent a potential mechanism involved in the pathogenesis of impaired glucose disposal, i. e. insulin resistance, in muscle. [Diabetologia (1999) 42: 1171-1174]

Adipose Tissue↗
PubMed1999

Admission level of Gc-globulin predicts outcome after multiple trauma.

BACKGROUND: Actin is the dominating protein in mammalian cells. Release of excessive amounts of actin into the circulation may result in a condition resembling multiple organ failure. The purpose of this study was to determine if admission levels of Gc-globulin can predict survival after multiple trauma. Also, we wanted to compare the predictive ability of Gc-globulin with that of the TRISS-Like scoring system. METHODS: Fifty-seven patients with a median ISS 18 (16-75) were included. All patients had a blood sample taken median 42 min after the injury (19-110 min). Serum Gc-globulin was measured by rocket immunoelectrophoresis. RESULTS: On admission, all patients had significantly reduced levels of Gc-globulin compared with normal controls. Gc-globulin was significantly higher in the group of survivors (n = 41), compared with non-survivors (n = 16). Median 237 mg/l vs. 188 mg/l (P < 0.01). The predictive ability of Gc-globulin regarding death was similar to that of TRISS-Like with positive predictive values of 69%, a negative predictive value of 84%, a sensitivity of 56% and a specificity of 90%. CONCLUSIONS: The predictive value of Gc-globulin regarding survival was similar to that of an established scoring system. Gc-globulin, alone or in combination with other parameters, may serve as a routine tool for early identification of patients at risk after severe injury, increasing the possibility of early intervention.

Adolescent↗
PubMed1999

Prognosis after treatment for loco-regional recurrence after mastectomy or breast conserving therapy in two randomised trials (EORTC 10801 and DBCG-82TM). EORTC Breast Cancer Cooperative Group and the Danish Breast Cancer Cooperative Group.

The aim of this study was to investigate and compare the prognosis after treatment for loco-regional recurrences (LR) after (modified) radical mastectomy (MRM) or breast conserving therapy (BCT), in terms of overall survival and time to subsequent LR, in patients originally treated in two European randomised trials. In EORTC trial 10801 and DBCG trial 82-TM, 1,807 patients with stage I and II breast cancer were randomised to receive MRM or BCT from 1980 to 1989. All patients with a LR in these trials were analysed for survival and time to subsequent LR after salvage treatment. Of these, 133 patients had their LR as a first event, the majority within 5 years after initial treatment. The prognostic significance for survival and time to subsequent LR after salvage treatment was analysed in uni-, and multivariate analyses for a number of original tumour- and recurrence-related variables. After salvage treatment of LR after MRM or BCT, actuarial survival curves and the actuarial locoregional control curves were similar. The 5-year survival rates were 58% and 59% and the 5-year subsequent loco-regional control rates 62% and 63%, respectively. In a multivariate analysis, pN category (P = 0.03), pT category (P = 0.01) and vascular invasion (P = 0.02) of the primary tumour were the only independent prognostic factors for survival, whereas extensive LR (P < 0.001), interval < or = 2 years (P < 0.002) and pN+ at primary treatment (P = 0.004) were significant predictive factors for time to subsequent LR. The type of original treatment (MRM or BCT) did not have any prognostic impact. It is concluded that the survival and time to subsequent LR after treatment for an early loco-regional recurrence after MRM or BCT was similar in these two European randomised trials. This suggests that both after MRM and BCT an early LR is an indicator of a biologically aggressive tumour; early loco-regional relapse carries a poor prognosis and salvage treatment only cures a limited number of patients, whether treated by MRM or BCT originally.

Adult↗
PubMed1999

Honokiol and magnolol increase the number of [3H] muscimol binding sites three-fold in rat forebrain membranes in vitro using a filtration assay, by allosterically increasing the affinities of low-affinity sites.

1. The bark of the root and stem of various Magnolia species has been used in Traditional Chinese Medicine to treat a variety of disorders including anxiety and nervous disturbances. The biphenolic compounds honokiol (H) and magnolol (M), the main components of the Chinese medicinal plant Magnolia officinalis, interact with GABA(A) receptors in rat brain in vitro. We compared the effects of H and M on [3H]muscimol (MUS) and [3H]flunitrazepam (FNM) binding using EDTA/water dialyzed rat brain membranes in a buffer containing 150 mM NaCl plus 5 mM Tris-HCl, pH 7.5 as well as [35S]t-butylbicyclophosphorothionate (TBPS) in 200 mM KBr plus 5 mM Tris-HCl, pH 7.5. H and M had similar enhancing effects on [3H]MUS as well as on [3H]FNM binding to rat brain membrane preparations, but H was 2.5 to 5.2 times more potent than M. 2. [3H]FNM binding. GABA alone almost doubled [3H]FNM binding with EC50 = 450 nM and 200 nM using forebrain and cerebellar membranes, respectively. In the presence of 5 microM H or M the EC50 values for GABA were decreased to 79 and 89 nM, respectively, using forebrain, and 39 and 78 nM, using cerebellar membranes. H and M potently enhanced the potentiating effect of 200 nM GABA on [3H]FNM binding with EC50 values of 0.61 microM and 1.6 microM using forebrain membranes, with maximal enhancements of 33 and 47%, respectively. Using cerebellar membranes, the corresponding values were 0.25 and 1.1 microM, and 22 and 34%. 3. [3H]MUS binding. H and M increased [3H]MUS binding to whole forebrain membranes about 3-fold with EC50 values of 6.0 and 15 microM. Using cerebellar membranes, H and M increased [3H]MUS binding approximately 68% with EC50 values of 2.3 and 12 microM, respectively. Scatchard analysis revealed that the enhancements of [3H]MUS binding were due primarily to increases in the number of binding sites (Bmax values) with no effect on the high affinity binding constants (Kd values). The enhancing effect of H and M were not additive. 4. [35S]TBPS binding. H and M displaced [35S]TBPS binding from sites on whole rat forebrain membranes with IC50 values of 7.8 and 6.0 microM, respectively. Using cerebellar membranes, the corresponding IC50 values were 5.3 and 4.8 microM. These inhibitory effects were reversed by the potent GABA(A) receptor blocker R5135 (10 nM), suggesting that H and M allosterically increase the affinity of GABA(A) receptors for GABA and MUS by binding to sites in GABA(A) receptor complexes. 5. Two monophenols, the anesthetic propofol (2,6-diisopropylphenol, P) and the anti-inflammatory diflunisal (2',4'-difluoro-4-hydroxy-3-biphenyl carboxylic acid, D) also enhanced [3H]MUS binding, decreased the EC50 values for GABA in enhancing [3H]FNM binding and potentiated the enhancing effect of 200 nM GABA on [3H]FNM binding, although enhancements of [3H]MUS binding for these monophenols were smaller than those for H and M, using forebrain and cerebellar membranes. The enhancing effect of P and D on [3H]MUS binding were almost completely additive. 2,2'-biphenol was inactive on [3H]MUS and [3H]FNM binding. These, and other preliminary experiments, suggest that appropriate ortho (C2) and para (C4) substitution increases the GABA-potentiating activity of phenols. 6. The potentiation of GABAergic neurotransmission by H and M is probably involved in their previously reported anxiolytic and central depressant effects.

Allosteric Regulation↗
PubMed1999

Inhibition of constitutively activated Stat3 correlates with altered Bcl-2/Bax expression and induction of apoptosis in mycosis fungoides tumor cells.

The Jak/Stat signaling pathway transmits signals from many cytokine and growth factor receptors to target genes in the nucleus. Constitutive activation of Stat3 has recently been observed in many tumor cells and dysregulation of the Stat signaling pathway has been proposed to be implicated in malignant transformation. In a previous study, we found constitutively tyrosine phosphorylated Stat3 in mycosis fungoides tumor cells. Here, we show that the Jak kinase inhibitor, Ag490, inhibits the constitutive binding of Stat3 to an oligonucleotide representing the Stat-binding sequence from the ICAM promotor. The decreased ability of Stat3 to bind DNA precedes dynamic alterations in the expression of anti-apoptotic Bcl-2 and pro-apoptotic Bax proteins (decreased Bcl-2 expression and increased Bax expression) and induction of apoptosis. Thus, our data suggest that the involvement of Stat3 in oncogenic transformation could be mediated through regulation of survival signals.

Animals↗