Search PubMed⌕ Search

Biomedical subjects

M Meyer

Publications and source records attributed to M Meyer.

At least 181 records · Page 10Linked to original sources
PubMed1999

Prevalence, predictors and patterns of postoperative polyuria and hyponatraemia in the immediate course after transsphenoidal surgery for pituitary adenomas.

OBJECTIVE: Disturbances of osmoregulation, leading to diabetes insipidus and hyponatraemia are well known complications after surgery in the sella region. This study was performed to examine the prevalence and predictors of polyuria and hyponatraemia after a complete and selective removal of pituitary adenomas was attempted via the transnasal-transsphenoidal approach. DESIGN: 1571 patients with pituitary adenomas (238 Cushing's disease, 405 acromegaly, 534 hormonally inactive adenomas, 358 prolactinoma, 23 Nelson's syndrome, and 13 thyrotropinoma) were daily examined within a 10-day postoperative inpatient observation period. Prevalence of patterns of polyuria (> 2500 ml) and oliguria/hyponatraemia (< 132 mmol/l) were surveyed as well as predictors of postoperative morbidity. RESULTS: 487 patients (31%) developed immediate postoperative hypotonic polyuria, 161 patients (10%) showed prolonged polyuria and 37 patients (2.4%) delayed hyponatraemia. A biphasic (polyuria-hyponatraemia) and triphasic (polyuria-hyponatraemia-polyuria) pattern was seen in 53 (3.4%) and 18 (1.1%) patients, respectively. Forty-one patients (2.6%) displayed immediate postoperative (day 1) hyponatraemia. Altogether, 8.4% of patients developed hyponatraemia at some time up to the 10th day postoperative, with symptomatic hyponatraemia in 32 patients (2.1%). Risk analysis showed that patients with Cushing's disease had a fourfold higher risk of polyuria than patients with acromegaly and a 2.8-fold higher risk for postoperative hyponatraemia. Younger age, male sex, and intrasellar expansion were associated with a higher risk of hypotonic polyuria, but this was not considered clinically relevant. CONCLUSIONS: The analysis illustrates that disturbances in osmoregulation resulting in polyuria and pertubations of serum sodium concentration are of very high prevalence and need observation even after selective transsphenoidal surgery for pituitary adenomas, especially in patients with Cushing's disease.

Acromegaly↗
PubMed1999

A new growth and in vitro sporulation medium for Clostridium perfringens.

Growth and in vitro sporulation capabilities of three related Clostridium perfringens strains (NCTC 8798, 8-6 and R3) were followed in a new sporulation medium (NSM), with notable changes from a maintenance medium originally designed for strictly anaerobic bacteria. Compared with thioglycollate (FTG) medium, the new sporulation medium promoted growth of Cl. perfringens with a shorter lag phase and a 20% higher biomass production. The age of inoculum did not change Cl. perfringens growth kinetics. When compared with reference conditions, in vitro spore production kinetics were different in the new sporulation medium, but both conditions led routinely to 100% sporulation and spore counts of approximately 10(8) ml-1. The ease of preparation of the NSM, and the use of the same culture medium for good growth, high sporulation yields and spore production, represent an attractive alternative to the complex media routinely used for in vitro studies of Cl. perfringens physiology.

Bacteriological Techniques↗
PubMed1999

The periplasmic domain of the histidine autokinase CitA functions as a highly specific citrate receptor.

The two-component regulatory system CitA/CitB is essential for induction of the citrate fermentation genes in Klebsiella pneumoniae. CitA represents a membrane-bound sensor kinase consisting of a periplasmic domain flanked by two transmembrane helices, a linker domain and the conserved kinase or transmitter domain. A fusion protein (MalE-CitAC) composed of the maltose-binding protein and the CitA kinase domain (amino acids 327-547) showed constitutive autokinase activity and transferred the gamma-phosphate group of ATP to its cognate response regulator CitB. The autokinase activity of CitA was abolished by an H350L exchange, and phosphorylation of CitB was inhibited by a D56N exchange, indicating that H-350 and D-56 represent the phosphorylation sites of CitA and CitB respectively. In the presence of ATP, CitB-D56N formed a stable complex with MalE-CitAC. To analyse the sensory properties of CitA, the periplasmic domain (amino acids 45-176) was overproduced as a soluble, cytoplasmic protein with a C-terminally attached histidine tag (CitAPHis). Purified CitAPHis bound citrate, but none of the other tri- and dicarboxylates tested, with high affinity (KD approximately 5 microM at pH 7) in a 1:1 stoichiometry. As shown by isothermal titration calorimetry, the binding reaction was driven by the enthalpy change (DeltaH = -76.3 kJ mol-1), whereas the entropy change was opposed (-TDeltaS = + 46.3 kJ mol-1). The pH dependency of the binding reaction indicated that the dianionic form H-citrate2- is the citrate species recognized by CitAPHis. In the presence of Mg2+ ions, the dissociation constant increased significantly, suggesting that the Mg-citrate complex is not bound by CitAPHis. This work defines the periplasmic domain of CitA as a highly specific citrate receptor and elucidates the binding characteristics of CitAPHis.

Bacterial Proteins↗
PubMed1999

A model for building collective capacity in community-based programs: the Elderly in Need Project.

As the focus of health promotion moves from individuals to organizations, communities and broader social policy, the models that guide public health program planning and development need reexamination. Public health nurses are gaining experience in strengthening and supporting the ability of communities to grow and change. This study aimed to illuminate the process. Data, gathered as part of an action research project to develop individual and community-based strategies to decrease isolation in frail older adults, provided a rich source of qualitative data. Analysis was directed toward identifying the factors and processes of capacity-building. The emerging model was clarified and partially validated with academics and practitioners from health promotion programs across the age span. Four stages of building collective capacity were identified: identifying common ground, working cooperatively, working in partnership, and working across the community. At each stage, processes of relationship building, project management and capacity-building resulted in stage specific products. A model of building collective capacity, grounded in community health practice and supported by the literature provides a base for developing practice indicators, and practice guidelines which will strengthen the ability to reach health goals.

Aged↗
PubMed1999

Structure and expression of the human small cytokine B subfamily member 11 (SCYB11/formerly SCYB9B, alias I-TAC) gene cloned from IFN-gamma-treated human monocytes (THP-1).

Among CXC chemokines, monokine induced by interferon-gamma (IFN-gamma) (MIG) and IGN-gamma-inducible protein, 10 kDa (INP10), constitute a distinct group because of their sequence and function. We studied genomic structure and expression of a third, recently identified member of this group named small inducible cytokine B subfamily member 11 (SCYB11, formerly SCYB9B) or IFN-inducible T cell alpha chemoattractant (I-TAC). The cDNA (1445 bp) for this 94 amino acid protein (Mr 10,364) was cloned from IFN-gamma-treated human myelomonocytic cells (THP-1). The reading frame of SCYB11 is distributed to 4 exons spanning 1197 bp of the genomic sequence. In vitro transcription/translation yielded a single protein of about 10 kDa, indicating that the deduced reading frame is translated by eukaryotic ribosomes. The recombinant 73 amino acid mature protein overexpressed in Escherichia coli was chemotactic for interleukin-2 (IL-2)-selected T memory cells. Studying various cytokines and lipopolysaccharide in THP-1 cells identified IFN-gamma as the major stimulus for SCYB11 mRNA expression, followed by IFN-alpha and IFN-beta, which were about 25 times less effective. Of a panel of different human cells tested, SCYB11 mRNA was also induced in umbilical vein endothelial cells, dermal fibroblasts, and tumor cell lines from various organs, whereas it was not found in T lymphocytes activated via anti-CD3 antibodies or via IL-2.

Amino Acid Sequence↗
PubMed1999

Role of glutathione and reactive oxygen intermediates in 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced immune suppression in C57Bl/6 mice.

Recent developments in basic immunology have revealed the importance of glutathione (GSH) and cellular redox balance in the generation of an immune response. In the liver, it has been shown that exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters cellular GSH and reactive oxygen intermediate (ROI) production. We have tested the hypothesis that TCDD mediates the suppression of the cytotoxic T lymphocyte (CTL) response to alloantigen by increasing oxidative stress. Total cellular GSH, GSSG, and GSH-protein adducts were analyzed by HPLC. Changes in intracellular GSH and ROI were simultaneously measured in isolated hepatocytes and individual subpopulations of spleen cells (CD4+, CD8+, B220+, and Mac-1+) following in vivo exposure to TCDD and antigenic challenge with P815 mastocytoma cells. Monochlorobimane was utilized to measure GSH levels, and two fluorescent probes were used to evaluate ROI levels: dichlorofluoroscein diacetate to monitor peroxides and dihydroethidine to assess superoxide anion. In hepatocytes, in vivo treatment with TCDD resulted in a transient, 2-fold increase in GSH, a 50% decrease in peroxide levels and a small (20-40%) decrease in superoxide anion levels. Although alloantigen challenge resulted in increased GSH and peroxide in spleen cells, in vivo exposure to TCDD had no effect on splenic ROI levels, nor did it consistently alter GSH levels in any subpopulation of spleen cells examined. Moreover, in vivo treatment with the antioxidant N-acetyl cysteine failed to affect the immune suppression caused by TCDD. These results suggest to us that although TCDD perturbs cellular redox balance in the liver, it does not exacerbate or diminish the normal increased GSH and ROI which occur in the spleen in response to antigenic challenge.

Animals↗
PubMed1999

Statistical properties of the volatility of price fluctuations.

We study the statistical properties of volatility, measured by locally averaging over a time window T, the absolute value of price changes over a short time interval deltat. We analyze the S&P 500 stock index for the 13-year period Jan. 1984 to Dec. 1996. We find that the cumulative distribution of the volatility is consistent with a power-law asymptotic behavior, characterized by an exponent mu approximately 3, similar to what is found for the distribution of price changes. The volatility distribution retains the same functional form for a range of values of T. Further, we study the volatility correlations by using the power spectrum analysis. Both methods support a power law decay of the correlation function and give consistent estimates of the relevant scaling exponents. Also, both methods show the presence of a crossover at approximately 1.5 days. In addition, we extend these results to the volatility of individual companies by analyzing a data base comprising all trades for the largest 500 U.S. companies over the two-year period Jan. 1994 to Dec. 1995.

Journal Article↗
PubMed1999

Scaling of the distribution of fluctuations of financial market indices.

We study the distribution of fluctuations of the S&P 500 index over a time scale deltat by analyzing three distinct databases. Database (i) contains approximately 1 200 000 records, sampled at 1-min intervals, for the 13-year period 1984-1996, database (ii) contains 8686 daily records for the 35-year period 1962-1996, and database (iii) contains 852 monthly records for the 71-year period 1926-1996. We compute the probability distributions of returns over a time scale deltat, where deltat varies approximately over a factor of 10(4)-from 1 min up to more than one month. We find that the distributions for deltat<or= 4 d (1560 min) are consistent with a power-law asymptotic behavior, characterized by an exponent alpha approximately 3, well outside the stable Lévy regime 0<alpha<2. To test the robustness of the S&P result, we perform a parallel analysis on two other financial market indices. Database (iv) contains 3560 daily records of the NIKKEI index for the 14-year period 1984-1997, and database (v) contains 4649 daily records of the Hang-Seng index for the 18-year period 1980-1997. We find estimates of alpha consistent with those describing the distribution of S&P 500 daily returns. One possible reason for the scaling of these distributions is the long persistence of the autocorrelation function of the volatility. For time scales longer than (deltat)x approximately 4 d, our results are consistent with a slow convergence to Gaussian behavior.

Journal Article↗
PubMed1999

Scaling of the distribution of price fluctuations of individual companies.

We present a phenomenological study of stock price fluctuations of individual companies. We systematically analyze two different databases covering securities from the three major U.S. stock markets: (a) the New York Stock Exchange, (b) the American Stock Exchange, and (c) the National Association of Securities Dealers Automated Quotation stock market. Specifically, we consider (i) the trades and quotes database, for which we analyze 40 million records for 1000 U.S. companies for the 2-yr period 1994-95; and (ii) the Center for Research and Security Prices database, for which we analyze 35 million daily records for approximately 16,000 companies in the 35-yr period 1962-96. We study the probability distribution of returns over varying time scales Delta t, where Delta t varies by a factor of approximately 10(5), from 5 min up to approximately 4 yr. For time scales from 5 min up to approximately 16 days, we find that the tails of the distributions can be well described by a power-law decay, characterized by an exponent 2.5 < proportional to < 4, well outside the stable Lévy regime 0 < alpha < 2. For time scales Delta t >> (Delta t)(x) approximately equal to 16 days, we observe results consistent with a slow convergence to Gaussian behavior. We also analyze the role of cross correlations between the returns of different companies and relate these correlations to the distribution of returns for market indices.

Journal Article↗
PubMed1999

Structural and phylogenetic characterization of human SLURP-1, the first secreted mammalian member of the Ly-6/uPAR protein superfamily.

Members of the Ly-6/uPAR protein family share one or several repeat units of the Ly-6/uPAR domain that is defined by a distinct disulfide bonding pattern between 8 or 10 cysteine residues. The Ly-6/uPAR protein family can be divided into two subfamilies. One comprises GPI-anchored glycoprotein receptors with 10 cysteine residues. The other subfamily includes the secreted single-domain snake and frog cytotoxins, and differs significantly in that its members generally possess only eight cysteines and no GPI-anchoring signal sequence. We report the purification and structural characterization of human SLURP-1 (secreted mammalian Ly-6/uPAR related protein 1) from blood and urine peptide libraries. SLURP-1 is encoded by the ARS (component B)-81/s locus, and appears to be the first mammalian member of the Ly-6/uPAR family lacking a GPI-anchoring signal sequence. A phylogenetic analysis based on the SLURP-1 primary protein structure revealed a closer relationship to the subfamily of cytotoxins. Since the SLURP-1 gene maps to the same chromosomal region as several members of the Ly-6/uPAR subfamily of glycoprotein receptors, it is suggested that both biologically distinct subfamilies might have co-evolved from local chromosomal duplication events.

Animals↗
PubMed1999

Empathy, expectations, and situational preferences: personality influences on the decision to participate in volunteer helping behaviors.

Although considerable evidence indicates that dispositional empathy is associated with the degree of help that observers will offer needy targets, little is known about the effect of empathy on one's initial willingness to enter situations in which such needy targets might be found. Three studies were conducted to evaluate two related propositions: (1) that dispositional empathy influences such situational preferences, and (2) that this influence is mediated by the expectancies one holds regarding the emotions likely to occur in those situations. Using hypothetical judgments, Study 1 found support for both propositions. Study 2, in which participants believed that their responses actually committed them to encountering needy targets, provided further support for the model, as did Study 3, which examined the experiences of actual community volunteers. The theoretical and practical implications of these findings are discussed.

Adult↗
PubMed1999

Structural characterization of the lactoferrin receptor from Neisseria meningitidis.

The meningococcal lactoferrin receptor is composed of the integral outer membrane protein LbpA and the peripheral lipoprotein LbpB. Homooligomeric complexes of LbpA and heterooligomers consisting of LbpA and LbpB were identified. Furthermore, five cell surface-exposed loops of LbpA were identified, which partially confirms a previously proposed topology model.

Amino Acid Sequence↗
PubMed1999

Phospholamban-to-SERCA2 ratio controls the force-frequency relationship.

The force-frequency relationship (FFR) describes the frequency-dependent potentiation of cardiac contractility. The interaction of the sarcoplasmic reticulum Ca2+-adenosinetriphosphatase (SERCA2) with its inhibitory protein phospholamban (PLB) might be involved in the control of the FFR. The FFR was analyzed in two systems in which the PLB-to-SERCA2 ratio was modulated. Adult rabbit cardiac myocytes were transduced with adenovirus encoding for SERCA2, PLB, and beta-galactosidase (control). After 3 days, the relative PLB/SERCA2 values were significantly different between groups (SERCA2, 0.5; control, 1.0; PLB, 4.5). SERCA2 overexpression shortened relaxation by 23% relative to control, whereas PLB prolonged relaxation by 39% and reduced contractility by 47% (0.1 Hz). When the stimulation frequency was increased to 1.5 Hz, myocyte contractility was increased by 30% in control myocytes. PLB-overexpressing myocytes showed an augmented positive FFR (+78%), whereas SERCA2-transduced myocytes displayed a negative FFR (-15%). A more negative FFR was also found in papillary muscles from SERCA2 transgenic mice. These findings demonstrate that the ratio of phospholamban to SERCA2 is an important component in the control of the FFR.

Animals↗
PubMed1999

Altered cardiac phenotype in transgenic mice carrying the delta337 threonine thyroid hormone receptor beta mutant derived from the S family.

The heart has been recognized as a major target of thyroid hormone action. Our study investigates both the regulation of cardiac-specific genes and contractile behavior of the heart in the presence of a mutant thyroid hormone receptor beta1 (T3Rbeta1-delta337T) derived from the S kindred. The mutant receptor was originally identified in a patient with generalized resistance to thyroid hormone. Cardiac expression of the mutant receptor was achieved by a transgenic approach in mice. As the genes for myosin heavy chains (MHC alpha and MHC beta) and the cardiac sarcoplasmic reticulum Ca2+ adenosine triphosphatase (SERCA2) are known to be regulated by T3, their cardiac expression was analyzed. The messenger RNA levels for MHC alpha and SERCA2 were markedly down-regulated, MHC beta messenger RNA was up-regulated. Although T3 levels were normal in these animals, this pattern of cardiac gene expression mimics a hypothyroid phenotype. Cardiac muscle contraction was significantly prolonged in papillary muscles from transgenic mice. The electrocardiogram of transgenic mice showed a substantial prolongation of the QRS interval. Changes in cardiac gene expression, cardiac muscle contractility, and electrocardiogram are compatible with a hypothyroid cardiac phenotype despite normal T3 levels, indicating a dominant negative effect of the T3Rbeta mutant.

Animals↗
PubMed1999

cGMP-dependent and -independent inhibition of a K+ conductance by natriuretic peptides: molecular and functional studies in human proximal tubule cells.

In immortalized human kidney epithelial (IHKE-1) cells derived from proximal tubules, two natriuretic peptide receptors (NPR) were identified. In addition to NPR-A, which is bound by atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and urodilatin (URO), a novel form of NPR-B that might be bound by C-type natriuretic peptide (CNP) was identified using PCR. This novel splice variant of NPR-B (NPR-Bi) was also found in human kidney. Whereas ANP, BNP, and URO increased intracellular cGMP levels in IHKE-1 cells in a concentration-dependent manner, CNP had no effect on cGMP levels. To determine the physiologic responses to these agonists in IHKE-1 cells, the membrane voltage (Vm) was monitored using the slow whole-cell patch-clamp technique. ANP (10 nM), BNP (10 nM), and URO (16 nM) depolarized these cells by 3 to 4 mV (n = 47, 7, and 16, respectively), an effect that could be mimicked by 0.1 mM 8-Br-cGMP (n = 15). The effects of ANP and 8-Br-cGMP were not additive (n = 4). CNP (10 nM) also depolarized these cells, by 3+/-1 mV (n = 28), despite the absence of an increase in cellular cGMP levels, indicating a cGMP-independent mechanism. In the presence of CNP, 8-Br-cGMP further depolarized Vm significantly, by 1.6+/-0.3 mV (n = 5). The depolarizations by ANP were completely abolished in the presence of Ba2+ (1 mM, n = 4) and thus can be related to inhibition of a K+ conductance in the luminal membrane of IHKE-1 cells. The depolarizations attributable to CNP were completely blocked when genistein (10 microM, n = 6), an inhibitor of tyrosine kinases, was present. These findings indicate that natriuretic peptides regulate electrogenic transport processes via cGMP-dependent and -independent pathways that influence the Vm of IHKE-1 cells.

Atrial Natriuretic Factor↗
PubMed1999

Therapeutic use of the natriuretic peptide ularitide in acute renal failure.

BACKGROUND: Ularitide is a member of the natriuretic peptide family. This hormone exhibits an N-terminal extension by four amino acids compared with atrial natriuretic peptide. Ularitide was shown to exert strong diuretic and natriuretic effects when infused intravenously. Its main action sites are the glomerulum, inducing preglomerular vasodilation and postglomerular vasoconstriction and thereby elevating the glomerular filtration rate, and the tubular system inhibiting Na(+)-reabsorption. In initial uncontrolled clinical trials, this peptide was shown to have beneficial effects in patients suffering from oliguric acute renal failure. METHODS: We conducted a double-blind, placebo-controlled, multicenter, dose-finding trial recruiting 176 patients randomized into 4 different Ularitide doses groups (U5, U20, U40, and U80 ng/kg/min) and a placebo group (U0). Ularitide/placebo infusion was performed for 5 days with half the originally infused dose on day 5. The primary objective of the study was to test various doses of Ularitide in patients suffering from oliguric acute renal failure to avoid mechanical renal replacement therapy during the first 12 hours. FINDINGS: The results indicate that Ularitide does not reduce the incidence of mechanical renal replacement therapy compared with placebo-treated patients during the first 12 h of treatment (U0: 36 (20), U5: 35 (11), U20: 36 (9), U40: 28 (8), U80: 41 (12), (% (n) (p = 0.87)). Diuresis increased in the Ularitide-treated groups and the placebo group after onset of infusion and did not show any significant difference in the first 12 h collection period (U0: 576, U5: 514, U20: 500, U40: 360, U80: 158 ML/12h (Median), (p = 0.16)). INTERPRETATION: In summary, the incidence of mechanical renal replacement therapy in critically ill patients suffering from oliguric acute renal failure could not be altered positively by Ularitide administration according to our protocol. Further prospective clinical trials are needed to answer the question whether a different patient collective or a prophylactic administration of Ularitide are more promising approaches in the clinical setting of oliguric acute renal failure.

Acute Kidney Injury↗