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R Meier

Publications and source records attributed to R Meier.

At least 73 records · Page 4Linked to original sources
PubMed1997

Role of translocation in the activation and function of protein kinase B.

We have investigated the role of subcellular localization in the regulation of protein kinase B (PKB) activation. The myristoylation/palmitylation motif from the Lck tyrosine kinase was attached to the N terminus of protein kinase B to alter its subcellular location. Myristoylated/palmitylated (m/p)-PKBalpha was associated with the plasma membrane of transfected cells, whereas the wild-type kinase was mostly cytosolic. The activity of m/p-PKBalpha was 60-fold higher compared with the unstimulated wild-type enzyme, and could not be stimulated further by growth factors or phosphatase inhibitors. In vivo 32P labeling and mutagenesis demonstrated that m/p-PKBalpha activity was due to phosphorylation on Thr308 and Ser473, that are normally induced on PKB following stimulation of the cells with insulin or insulin-like growth factor-1 (IGF-1). A dominant negative form of phosphoinositide 3-kinase (PI3-K) did not affect m/p-PKBalpha activity. The pleckstrin homology (PH) domain of m/p-PKBalpha was not required for its activation or phosphorylation on Thr308 and Ser473, suggesting that this domain may serve as a membrane-targeting module. Consistent with this view, PKBalpha was translocated to the plasma membrane within minutes after stimulation with IGF-1. This translocation required the PH domain and was sensitive to wortmannin. Our results indicate that PI3-K activity is required for translocation of PKB to the plasma membrane, where its activation occurs through phosphorylation of the same sites that are induced by insulin or IGF-1. Following activation the kinase detached from the membrane and translocated to the nucleus.

Amino Acid Substitution↗
PubMed1997

Mitogenic activation, phosphorylation, and nuclear translocation of protein kinase Bbeta.

Protein kinase B (PKB) is a member of the second messenger-dependent family of serine/threonine kinases that has been implicated in signaling pathways downstream of growth factor receptor tyrosine kinases and phosphatidylinositol 3-kinase. Here we report the characterization of the human beta-isoform of PKB (PKBbeta). PKBbeta is ubiquitously expressed in a number of human tissues, with mRNA and protein levels elevated in heart, liver, skeletal muscle, and kidney. After transfection into HEK-293 or COS-1 cells, PKBbeta is activated 2- to 12-fold by mitogens and survival factors. Activation was due to phosphorylation on Thr-309 and Ser-474, which correspond to Thr-308 and Ser-473 implicated in the regulation of PKBalpha. Both phosphorylation and activation were prevented by the phosphatidylinositol 3-kinase inhibitor wortmannin. Moreover, membrane-targeted PKBbeta was constitutively activated when overexpressed in HEK-293 cells. Although the specific activity of PKBbeta was lower than that of PKBalpha toward Crosstide as a substrate (23 nmol/min/mg compared with 178 nmol/min/mg for PKBalpha), both enzymes showed similar substrate specificities. Using confocal microscopy, we show that activation of PKBbeta results in its nuclear translocation within 20 to 30 min after stimulation. These observations provide evidence that PKBbeta undergoes nuclear translocation upon mitogenic activation and support a role for PKB in signaling from receptor tyrosine kinases to the nucleus through phosphatidylinositol 3-kinase.

Amino Acid Sequence↗
PubMed1997

Measurements of 12C/13C, 14N/15N, and 32S/34S ratios in comet Hale-Bopp (C/1995 O1).

The 12C/13C, 14N/15N, and 32S/34S isotope ratios in comet Hale-Bopp (C/1995 O1) were determined through observations taken with the James Clerk Maxwell Telescope. Measurements of rare isotopes in HCN and CS revealed isotope ratios of H12CN/H13CN = 111 +/- 12, HC14N/HC15N = 323 +/- 46, and C32S/C34S = 27 +/- 3. Within the measurement uncertainties, the isotopic ratios are consistent with solar system values. The cometary volatiles thus have an origin in the solar system and show no evidence for an interstellar component.

Carbon↗
PubMed1997

Clinical pharmacodynamics of SDZ HTF 919, a new 5-HT4 receptor agonist, in a model of slow colonic transit.

OBJECTIVES: To explore the pharmacodynamic effects of the new promotile agent SDZ HTF 919, a selective partial 5-HT4 receptor agonist, in healthy subjects. METHODS: A pharmacodynamic model was applied to prolong colonic transit by dietary means. Subsequently, the effects of twice-daily multiple doses of SDZ HTF 919 (1, 5, 25, and 100 mg) were investigated in a randomized, double-blind, placebo-controlled parallel-group study with 12 subjects per dose level. The sequential design with three study periods of 7 days each included intake of a self-selected diet, a liquid formula diet with soluble fiber supplementation, and a fiber-supplemented diet together with either SDZ HTF 919 or placebo administration. Stool characteristics (frequency and consistency) and total colonic transit times (with use of radiopaque markers) were recorded in each study period. RESULTS: SDZ HTF 919 was well tolerated at all dose levels. The frequency of loose stool and headache increased with higher doses. After a fiber-supplemented diet intake, the median stool frequency decreased from 8 1/2-9 to 5-7 defecations per study period. SDZ HTF 919 in doses of 25 and 100 mg twice a day increased the stool frequency (p < 0.05). Stool consistency was softened by all but the lowest SDZ HTF 919 dose. A fiber-supplemented diet prolonged total colonic transit time in all groups by 45 hours on average. Twice-a-day administration of SDZ HTF 919 for 6 days in addition to a fiber-supplemented diet significantly shortened the total colonic transit time only at the 5 mg dose. The lack of effect at lower and higher SDZ HTF 919 doses suggests a biphasic dose-response relationship for total colonic transit time. CONCLUSIONS: The suitability of total colonic transit time measurements in healthy subjects as a surrogate marker should be confirmed by patient studies.

Adult↗
PubMed1997

Differential phosphorylation of lamin B2 in normal and leukemic cells.

Lamins constitute the nuclear lamina, which underlie the inner membrane of the cell nucleus. Phosphorylation of lamins is a key factor in the regulation of nuclear structure during the cell cycle and of gene transcription. Since an uncontrolled cell cycle and altered gene transcription are major characteristics of neoplasms, we looked for differences in lamin B2 phosphorylation between PBMC, ALL and AML cells. Using different lamin B2-specific antibodies, we detected two different lamin B2 species termed lamin B2 and B2A. Although phosphorylation of lamin B2 in leukemic cells was reminiscent of resting cells, the majority of ALL and AML samples showed significantly higher and more altered lamin B2A phosphorylation compared to PBMC. It remains to be elucidated which mechanism leads to these alterations and whether it could explain the extended G1-phase frequently observed in ALL cells.

Acute Disease↗
PubMed1997

Comparison between esophageal Wallstent and Ultraflex stents in the treatment of malignant stenoses of the esophagus and cardia.

BACKGROUND AND STUDY AIMS: Several published studies have examined various self-expanding metal esophageal stents for use in the palliative treatment of esophageal or cardiac neoplasia, but few have compared different self-expanding metal stents. The aim of this study was to evaluate non-covered Wallstent and Ultraflex prostheses in the treatment of malignancies in the esophagus and the cardiac region. MATERIALS AND METHODS: In a retrospective study, the effectiveness of non-covered Wallstents (46 patients) and Ultraflex stents (36 patients) was compared in the treatment of malignancies in the esophageal and cardiac regions. RESULTS: Reintervention procedures were necessary in 16 of the 46 Wallstent patients (six patients during an early phase) and in 22 of the 36 Ultraflex patients (13 during an early phase) (overall P = 0.022; early P = 0.018). The major complication in the Wallstent group was tumor ingrowth (12 of 35 complications), while in the Ultraflex group, it was incomplete deployment (18 of 49 complications). Incomplete stent deployment occurred more often in patients treated with Ultraflex (P = 0.01), and food impaction was more often observed in the Wallstent group (P = 0.001). In addition, in patients with Ultraflex stents, more complex reinterventions were necessary than those required with Wallstents (four vs. 13 complex reinterventions, P = 0.0046). Wallstents tended to improve dysphagia better than Ultraflex stents. CONCLUSION: Compared to Ultraflex stents, Wallstents have several significant short-term and long-term advantages in the palliative treatment of malignancy of the esophagus and cardia.

Adult↗
PubMed1997

[Symptomatic therapy of severe diarrhea in eosinophilic gastroenteritis with the somatostatin analog octreotide (Sandostatin)].

We describe a patient with eosinophilic gastroenteritis whose symptoms included severe watery diarrhea (1.5 l/d), abdominal cramps, and weight loss. Biopsies revealed massive eosinophilic inflammation of the entire gastrointestinal tract. The total plasma eosinophilic count was elevated by up to 30%. Infectious etiologies and chronic inflammatory bowel disease had been ruled out. By use of the somatostatin analogue octreotide the diarrhea decreased immediately in a dose-dependent fashion and the patient recovered within twelve days. In this case octreotide was helpful in controlling severe diarrhea and limiting the subsequent necessary i.v. fluid replacement.

Adult↗
PubMed1997

[Irritable colon].

Irritable Bowel Syndrome (IBS) is a common functional gastrointestinal disorder, defined as a variable combination of chronic or recurrent gastrointestinal symptoms not explained by structural or biochemical abnormalities. It is attributable to the intestine with symptoms of abdominal pain, altered bowel habits and bloating. The diagnosis is primarily based on typical symptoms and prudent use of investigations to exclude organic disorders. The initial positive diagnosis is accurate and on a longterm follow-up its revision rarely required. A change in its clinical manifestation may imply the superimposition of another disorder. Treatment primarily rely on the confidence in the diagnosis and a strong physician-patient relationship. High fiber diets and bulking agents may be effective in alleviating symptoms. Though antispasmodic, antidiarrheal and psychotropic drugs are repeatedly used in patients with moderate to severe symptoms their effects remain uncertain. Psychotherapy, hypnosis and biofeedback may relief symptoms and may be considered for motivated patients with moderate to severe symptoms.

Colonic Diseases, Functional↗
PubMed1996

Purification and cDNA cloning of SAPKK3, the major activator of RK/p38 in stress- and cytokine-stimulated monocytes and epithelial cells.

Two chromatographically distinct stress-activated protein kinase kinases (SAPKKs) have been identified in several mammalian cells, termed SAPKK2 and SAPKK3, which activate the MAP kinase family member RK/p38 but not JNK/SAPK in vitro. Here we demonstrate that SAPKK2 is identical or very closely related to the MAP kinase kinase family member MKK3. However, under our assay conditions, SAPKK3 was the major activator of RK/p38 detected in extracts prepared from stress- or interleukin-1-stimulated epithelial (KB) cells, from bacterial lipopolysaccharide and tumour necrosis factor alpha-stimulated THP1 monocytes or from rabbit skeletal muscle. The activated form of SAPKK3 was purified from muscle to near homogeneity, and tryptic peptide sequences were used to clone human and murine cDNAs encoding this enzyme. Human SAPKK3 comprised 334 amino acids and was 78% identical to MKK3. The murine and human SAPKK3 were 97% identical in their amino acid sequences. We also cloned a different murine cDNA that appears to encode a SAPKK3 protein truncated at the N-terminus. SAPKK3 is identical to the recently cloned MKK6.

Amino Acid Sequence↗
PubMed1996

Cellular stresses and cytokines activate multiple mitogen-activated-protein kinase kinase homologues in PC12 and KB cells.

The identities of the upstream activators of the mitogen-activated protein (MAP) kinase homologues termed stress-activated-protein (SAP) kinase-1 (also known as JNK or SAPK) and SAP kinase-2 (also known as p38, RK and CSBP) were investigated in rat PC12 cells and human KB cells after exposure to cellular stresses and cytokines. In PC12 cells, the same two upstream activators, SAP kinase kinase-1 (SAPKK-1) and SAPKK-2 were activated after exposure to osmotic shock, ultraviolet irradiation or the protein synthesis inhibitor anisomycin, and more weakly in response to sodium arsenite. SAPKK-1 was capable of activating both SAP kinase-1 and SAP kinase-2 and was similar, if not identical, to the previously described MAP kinase kinase homologue MKK4, as judged by immunological criteria and by its ability to be activated by MEK kinase in vitro. In contrast, SAPKK-2 activated SAP kinase-2, but not SAP kinase-1 in vitro. In KB cells, five distinct upstream activators of SAP kinase-1 and SAP kinase-2 were induced, namely SAPKK-1, SAPKK-2, SAPKK-3, SAPKK-4 and SAPKK-5, whose appearance depended on the nature of the stimulus. SAPKK-3, which was strongly induced by every stimulus tested (osmotic shock, ultraviolet irradiation, anisomycin or IL-1), accounted for about 95% of the SAP kinase-2 activator activity in these cells, did not activate SAP kinase-1 and eluted from Mono S at a lower salt concentration than SAPKK-2. SAPKK-4 and SAPKK-5 were also eluted from Mono S at higher NaC1 concentrations than SAPKK-3 and these enzymes activated SAP kinase-1 but not SAP kinase-2. SAPKK-4 was the only SAP kinase-1 activator induced by interleukin-1 or ultraviolet irradiation, while two SAP kinase-1 activators, SAPKK-1 and SAPKK-5, were induced by osmotic shock or anisomycin. SAPKK-2, SAPKK-3, SAPKK-4 and SAPKK-5, were not activated by MEK kinase in vitro, were separable from the major activator(s) of p42 MAP kinase, and were not recognised by anti-MKK4 antibodies. At least two of these enzymes are likely to be novel MAP kinase kinase homologues. Our results demonstrate unexpected complexity in the upstream regulation of stress and cytokine-stimulated kinase cascades and indicate that the selection of the appropriate SAPKK varies with both the stimulus and the cell type.

Amino Acid Sequence↗
PubMed1996

[Anesthesiologic problems in patients with fibrodysplasia ossificans progressiva].

Fibrodysplasia ossificans progressiva (FOP) is a rare, congenital disease of the striated muscular system, ligaments and fascia; it leads to complete ossification in adult life. The disease usually begins in the first decade of life and is accompanied by abnormalities of the hands and feet that have already begun to occur at birth. There is no effective therapy. Although some of these patients have to undergo an operation, there is very little information available on anaesthetic procedures. CASE REPORT. A 49-year-old-woman came to the anaesthetic ward for amputation of her left foot with the diagnosis of fibrodysplasia ossificans progressive (FOP) and an infection resistant to any antibiotic treatment. Except for her left elbow, she could not move any of her extremities. Her back and neck were stiff (Figs. 1, 2), she could not open her mouth more than 2.5 cm, and her teeth were full of cavities and loose (Fig. 3). Aspiration of gastric content some time ago was known. Lung function showed a restrictive pattern. She suffered from kyphoscoliosis and needed chronic nasal administration of O2. With this therapy the arterial blood gas analysis was normal. Right bundle-branch block on the electrocardiogram was found. She was in a wheelchair and was completely dependent on the help of others. She was taking no medicine at the time of admission. A second operation was necessary because of reactive bone proliferation with a danger of skin perforation. DISCUSSION. This rare and congenital disease was first described in 1648 by G. Patin [14] and again in 1736 by J. Freke [10]. Since then, the progressive ossification of striated muscles, ligaments and facia has been described more than 600 times. Despite this fact, descriptions of anaesthetic procedures are rare. Because of the neck stiffness, the small mouth opening, the poor teeth and the recently observed history of aspiration, fiberoptic nasal intubation when the patient is awake was found to be the best choice. The possibility of atlanto-axial subluxation in such cases [2, 4] favored this procedure. Other authors have used blind nasal intubation [11], ketamine without intubation [18], or even local anaesthesia for a cesarean section [21]. Newer publications [13, 20] promote fiberoptic intubation and general anaesthesia with or without muscle relaxation. In this case propofol/fentanyl/ N2O/O2 without muscle relaxation was used for the first operation and etomidate/fentanyl/ethran/ N2O/O2 without muscle relaxation for the second procedure. During both anaesthesias important hypotension with good response to a generous volume supply was seen. The patient recovered well. Unfortunately, she died a few weeks later from suicide. The goal of this case report is to emphasize the value of the fibrobronchoscope in patients with FOP.

Adult↗