Rotational phase transitions in antifluorite-type osmate and iridate compounds.

We present temperature-dependent single-crystal diffraction results on seven antifluorite-typeA2MeX6compounds withMe= Os or Ir: K2OsCl6,A2OsBr6withA= K, Rb, Cs and NH4, and K2IrX6withX= Cl and Br. The structural transitions in this family arise fromMeX6octahedron rotations that generate a rich variety of symmetries depending on the rotation axis and stacking schemes. In order to search for local distortions in the high-symmetry phase we perform refinements of anharmonic atomic displacement parameters with comprehensive data sets. Even at temperatures close to the onset of structural distortions, these refinements only yield a small improvement indicating only small anharmonic effects. The phase transitions in these antifluorites are essentially of displacive character. However, some harmonic displacement parameters are very large reflecting soft phonon modes with the softening covering large parts of the Brillouin zone. The occurrence of the rotational transitions in the antifluorite-type family can be remarkably well analyzed in terms of a tolerance factor of ionic radii.

Impact of the maximum ring difference on image quality and noise characteristics of a total-body PET/CT scanner.

The sensitivity of a PET system highly depends on the axial acceptance angle or maximum ring difference (MRD), which can be particularly high for total-body scanners due to their larger axial field of views (aFOVs). This study aims to evaluate the impact on image quality (IQ) and noise performance when MRD85 (18°), the current standard for clinical use, is increased to MRD322 (52°) for the Biograph Vision Quadra (Siemens Healthineers). METHODS: Studies with a cylindrical phantom covering the 106 cm aFOV and an IEC phantom filled with 18F, 68Ga and 89Zr were performed for acquisition times from 60 to 1800 s and activity concentrations from 0.4 to 3 kBq/ml to assess uniformity, contrast recovery coefficients (CRCs) and to characterize noise by coefficient of variation (CV). Spatial resolution was compared for both MRDs by sampling a quadrant of the FOV with a point source. Further IQ, CV, liver SUVmean and SUVmax were compared for a cohort of 5 patients scanned with [18F]FDG (3 MBq/kg, 1 h p.i.) from 30 to 300 s. RESULTS: CV was improved by a factor of up to 1.49 and is highest for short acquisition times, peaks at the center field of view and mitigates parabolic in axial direction with no difference to MRD85 beyond the central 80 cm. No substantial differences between the two evaluated MRDs in regards to uniformity, SUVmean or CRC for the different isotopes were observed. A degradation of the average spatial resolution of 0.9 ±â€¯0.2 mm in the central 40 cm FOV was determined with MRD322. Depending on the acquisition time MRD322 resulted in a decrease of SUVmax between 23.8% (30 s) and 9.0% (300 s). CONCLUSION: Patient and phantom studies revealed that scan time could be lowered by approximately a factor of two with MRD322 while maintaining similar noise performance. The moderate degradation in spatial resolution for MRD322 is worth to exploit the full potential of the Quadra by either shorten scan times or leverage noise performance in particular for low count scenarios such as ultra-late imaging or dynamic studies with high temporal resolution.

The value of peer support for self-management of diabetes among veterans in the Empowering Patients In Chronic care intervention.

AIM: To examine the value of peer support in the self-management of diabetes among veterans in an integrated health care system. METHODS: We conducted semi-structured in-depth interviews with veterans and clinicians 6 months after their participation in Empowering Patients in Chronic Care (EPIC), a group-based diabetes intervention with a peer-support component. Interviews elicited clinicians' narratives of how peer support unfolded in the groups and veterans' experiences of giving and receiving support from their peers. Data analysis was guided by principles of framework analysis using Heisler's peer-support model. RESULTS: Findings support Heisler's peer-support model and provide evidence supporting professional-led group visits with peer exchange. Clinicians and veterans endorsed informational and emotional support received in EPIC groups. Clinicians often referred to EPIC as an open forum or a support group where veterans could both give and receive help. Veterans noted the benefits of shared problem-solving and the support they received. Clinicians and veterans perceived the peer-support component of EPIC as facilitating increased empowerment in terms of self-efficacy, increased perceived social support and increased understanding of self-care. Ultimately, many veterans acknowledged that their participation in EPIC facilitated improved health-related quality of life, improved health behaviours and improved chronic disease control. CONCLUSIONS: Findings emphasize the value of peer support in managing chronic illness. Peer-support programmes may address veterans' unique challenges and have the potential to improve physical and mental health.

Variation in acoustic overstimulation changes tinnitus characteristics.

Tinnitus often occurs after exposure to loud noise. This raises the question of whether repeated exposure to noise increases the risk of developing tinnitus. We thus studied tinnitus development after repeated acoustic overstimulation using startle and auditory brainstem-response techniques applied to Mongolian gerbils. Noise with bandwidths ranging from 0.25 up to 0.5 oct were used for repeated acoustic overstimulation. Auditory brainstem response measurements revealed similar threshold shifts in both groups of up to about 30 dB directly after the acoustic overstimulation. We identified an upper limit in threshold values, which was independent of the baseline values before the noise exposure. Several weeks after the acoustic overstimulation, animals with the noise bandwidth of 0.25 oct showed a permanent threshold shift, while animals of the group with the 0.5-oct noise band featured only a temporary threshold shift. We thus conclude that the threshold shift directly after noise exposure cannot be used as an indicator for the upcoming threshold level several weeks later. By using behavioral measurements, we investigated the frequency-dependent development of tinnitus-related changes in both groups and one group with 1-oct noise bandwidth. The number of animals that show tinnitus-related changes was highest in animals that received noise with the bandwidth 0.5 oct. This number was, in contrast to the number of animals in the 0.25-oct bandwidth, not significantly increased after repeated overstimulation. The frequency distribution of tinnitus-related changes ranged from 4 to 20 kHz. In the group with the narrow-band noise (0.25 oct) changes center at one frequency range from 10 to 12 kHz. In the group with the broader noise band (0.5 oct), however, two peaks at 8-10 kHz and at 16-18 kHz were found, which suggests that different mechanisms underlie the tinnitus development.

Response of coliform populations in streambed sediment and water column to changes in nutrient concentrations in water.

As sediments increasingly become recognized as reservoirs of indicator and pathogen microorganisms, an understanding of the persistence of indicator organisms becomes important for assessment and predictions of microbial water quality. The objective of this work was to observe the response of water column and sediment coliform populations to the change in nutrient concentrations in the water column. Survival experiments were conducted in flow-through chambers containing sandy sediments. Bovine feces were collected fresh and introduced into sediment. Sixteen days later, the same fecal material was autoclaved and diluted to provide three levels - 1×, 0.5×, and 0.1× of nutrient concentrations - spike in water column. Total coliforms, Escherichia coli, and total aerobic heterotrophic bacterial concentrations were monitored in water and sediment. Bacteria responded to the nutrient spike with initial growth both in the water column and in sediment. The response of bacterial concentrations in water column was nonlinear, with no significant changes at 0.1 and .5× spikes, but a substantial change at 1× spike. Bacteria in sediment responded to the spikes at all added nutrient levels. Coliform inactivation rates both in sediment and in water after the initial growth occurred, were not significantly different from the inactivation rates before spike. These results indicate that introduction of nutrients into the water column results in nonlinear response of E. coli concentrations both in water and in sediments, followed by the inactivation with the same rate as before introduction of nutrients.

Persistence of Escherichia coli introduced into streambed sediments with goose, deer and bovine animal waste.

AIMS: The focus of this work was to compare the survival of Escherichia coli introduced into streambed sediments from goose, deer and bovine faeces vs indigenous E. coli. METHODS AND RESULTS: The survival experiments were conducted in flow-through chambers for 32days using two sediments (mineral and organic) obtained from a first-order creek in Maryland. Bovine, goose and deer faeces were collected fresh and diluted or enriched so that added E. coli and indigenous populations were equivalent. Escherichia coli and total coliforms were enumerated using the Colilert-18 Quanti-Tray system. Patterns of E. coli survival and inactivation rates were virtually identical for indigenous strains in both mineral and organic sediments. The addition of E. coli strains from bovine, goose or deer faeces had relatively little impact on final E. coli concentrations, with the exception of deer-borne E. coli populations in the organic sediment. CONCLUSION: These results indicate that indigenous sediment-borne E. coli strains are generally, or more, persistent than those deposited into sediments, including wildlife. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study on the survival of E. coli originating from wildlife faeces, in sediments, as opposed to bovine faeces or laboratory-cultured strains. As wildlife are likely to be the primary source of E. coli in most non agricultural watersheds, an understanding of the persistence of these strains is important to understanding microbial water quality.

Mechanism of action of 1-beta-D-2,6-diaminopurine dioxolane, a prodrug of the human immunodeficiency virus type 1 inhibitor 1-beta-D-dioxolane guanosine.

(-)-beta-D-2,6-Diaminopurine dioxolane (DAPD), is a nucleoside reverse transcriptase (RT) inhibitor with activity against human immunodeficiency virus type 1 (HIV-1). DAPD, which was designed as a water-soluble prodrug, is deaminated by adenosine deaminase to give (-)-beta-D-dioxolane guanine (DXG). By using calf adenosine deaminase a K(m) value of 15 +/- 0.7 microM was determined for DAPD, which was similar to the K(m) value for adenosine. However, the k(cat) for DAPD was 540-fold slower than the k(cat) for adenosine. In CEM cells and peripheral blood mononuclear cells exposed to DAPD or DXG, only the 5'-triphosphate of DXG (DXG-TP) was detected. DXG-TP is a potent alternative substrate inhibitor of HIV-1 RT. Rapid transient kinetic studies show the efficiency of incorporation for DXG-TP to be lower than that measured for the natural substrate, 2'-deoxyguanosine 5'-triphosphate. DXG-TP is a weak inhibitor of human DNA polymerases alpha and beta. Against the large subunit of human DNA polymerase gamma a K(i) value of 4.3 +/- 0.4 microM was determined for DXG-TP. DXG showed little or no cytotoxicity and no mitochondrial toxicity at the concentrations tested.

Survival advantage of combined chemoradiotherapy compared with resection as the initial treatment of patients with regional pancreatic carcinoma. An outcomes trial.

BACKGROUND: Resection of pancreatic carcinoma is resource-intensive with a limited impact on survival. Chemotherapy and/or radiotherapy (RT) have been shown to be effective palliation. To examine whether preoperative chemoradiotherapy as the initial treatment improves survival for patients with a regional pancreatic adenocarcinoma with a minimal chance of being resected successfully, an outcomes trial was conducted. METHODS: Patients with radiologically regional tumors were staged by laparotomy and/or computed tomography followed by endoscopic ultrasonography, angiography, and/or laparoscopy. Those with locally invasive, unresectable, regional pancreatic adenocarcinoma initially were treated with simultaneous split-course RT plus 5-fluorouracil, streptozotocin, and cisplatin (RT-FSP) followed by selective surgery (Group 1). Patients determined to have a resectable tumor initially underwent resection without preoperative chemoradiotherapy, with or without postoperative chemoradiotherapy (Group 2). RESULTS: Over 8 years 159 patients presenting with nonmetastatic pancreatic adenocarcinoma were administered RT-FSP or underwent surgery for resection. Group 1, comprised of 68 patients initially treated with RT-FSP, had a 0% mortality rate within 30 days of entry. In 20 of 30 patients undergoing surgery after RT-FSP, tumors were downstaged and resected. Group 2, comprised of 91 patients who initially underwent successful resection, had a 5% mortality rate within 30 days of entry. Postoperatively, 63 of these patients received chemotherapy with or without RT. The median survival for Group 1 was 23.6 months compared with 14.0 months for Group 2 (P = 0.006) despite more advanced disease cases in Group 1. Survival favored RT-FSP regardless of whether lymph nodes were malignant. The dominant prognostic factor of earlier stage pancreatic carcinoma having an expected survival advantage was reversed by the initial nonoperative treatment. CONCLUSIONS: Based on a reversal of the expected trend that patients with earlier stage resectable carcinoma (T1,2, N0,1, M0) who undergo removal of their tumors survive longer than patients with more advanced regional disease (T3, N0,1, M0), survival was found to improve significantly for patients reliably staged as having locally invasive, unresectable, nonmetastatic pancreatic adenocarcinoma when initially treated with RT-FSP.

Melanocortin receptor binding determinants in the agouti protein.

The agouti protein plays an important role in the development of diabetes and obesity in rodents and has been shown to be a potent antagonist of melanocortin receptors. For this reason alanine-scanning mutagenesis was performed on the agouti protein carboxyl terminus to locate residues important for melanocortin receptor binding inhibition. When agouti residues Arg116 and Phe118 are changed to alanine, very large decreases in agouti affinity for melanocortin receptor 1, 3, and 4 result. Mutation of Phe117 to alanine causes a similar increase in agouti KI app at melanocortin receptor 4. Substitution of agouti residue Asp108 with alanine results in large increases in KI app for all three melanocortin receptors examined. All of these residues are conserved in the agouti-related transcript, ART, whose expression is up-regulated in animal models of obesity. The three-dimensional structure of the agouti carboxyl terminus was modeled, and residues which decrease receptor binding by a factor of > or = 15 when mutated to alanine localize to one side of the structure. These agouti variants with altered receptor selectivity may be useful in determining the role of melanocortin receptors in diabetes and obesity.

[Effectiveness of psychoanalytically founded brief and dynamic psychotherapy]. / Zur Effektivität tiefenpsychologisch fundierter Kurz- und Psychotherapien.

OBJECTIVES: This study has been designed to investigate the effectivity of psychodynamic therapies. METHODS: In a naturalistic prospective longitudinal study, 117 patients are compared with 116 untreated probands. RESULTS: The improvement of the general psychosocial impairment of patients of clinical relevance and significance. The effective magnitude of change is high. Untreated patients show on the average no remission of impaired well-being and symptoms six months later. CONCLUSION: Analytically orientated short-term psychotherapy and dynamic psychotherapy are effective in the treatment of many dysthymic and anxiety disorders as well as in the treatment of a number of personality disorders.

Agouti regulation of intracellular calcium: role of melanocortin receptors.

Several dominant mutations at the murine agouti locus cause a syndrome of marked obesity and insulin resistance. We have recently reported that intracellular free Ca2+ concentration ([Ca2+]i) is elevated in viable yellow mice. Because [Ca2+]i has a key role in the pathogenesis of insulin resistance, obesity, and hypertension, the role of the purified agouti gene product in regulating [Ca2+]i was evaluated in a number of cell types. Purified murine agouti induced slow, sustained increases in [Ca2+]i in A7r5 vascular smooth muscle cells and 3T3-L1 adipocytes in a dose-dependent fashion. In L6 skeletal myocytes, agouti stimulated an increase in [Ca2+]i with an apparent concentration eliciting 50% of the maximal response (EC50) of 62 nM. This response was substantially inhibited by Ca2+ entry blockade with nitrendipine. To determine whether melanocortin receptors play a role in agouti regulation of [Ca2+]i, we examined the effect of melanocortin peptides and agouti in cells stably transfected with human melanocortin receptors. Human embryonic kidney cells (HEK-293 cells) transfected with either the human melanocortin 1 receptor (MC1R) or melanocortin 3 receptor responded to human agouti with slow, sustained increases in [Ca2+]i, whereas nontransfected HEK-293 cells with no melanocortin receptors did not respond to agouti. Dose-response curves in the MC1R line showed that agouti had an EC50 of 18 nM, which is comparable to that for agouti antagonism of (125)I-Nle,D-Phe-alpha-melanocyte-stimulating hormone binding in the same cell line. This direct effect of agouti on stimulating increases in [Ca2+]i suggests a potential mechanism for agouti-induced insulin resistance.

Mutations in the carboxyl terminus of the agouti protein decrease agouti inhibition of ligand binding to the melanocortin receptors.

Several mutations that cause ectopic expression of the agouti gene result in obesity, hyperinsulinemia, and yellow coat color. A candidate pathway for agouti induced obesity and hyperinsulinemia is through altered signaling by melanocortin receptors, as agouti normally regulates coat coloration through antagonism of melanocortin receptor 1. Furthermore, melanocortin peptides mediate functions including steroidogenesis, lipolysis, and thermoregulation. We report apparent inhibition dissociation constants for mouse and human agouti protein inhibition of ligand binding to the melanocortin receptors, to determine which of these receptors might be involved in agouti induced diabetes. The similarity in the apparent K(I) values for agouti inhibition of ligand binding to the brain melanocortin receptors 3 and 4 (mouse: K(I) app = 190 +/- 74 and 54 +/- 18 nM; human: K(I) app = 140 +/- 56 and 70 +/- 18 nM, respectively) suggests that the MC3-R is a potential candidate for a receptor mediating the effects of agouti protein overexpression. Agouti residues important for melanocortin receptor inhibition were identified through the analysis of deletion constructs and site-specific variants. Val83 is important for inhibition of binding to MC1-R (K(I) app for Val83Ala agouti increased 13-fold relative to wild-type protein). Arg85, Pro86, and Pro89 are important for selective inhibition of binding between MC1-R and MC3-R and MC4-R as their apparent K(I) values are essentially unchanged at MC1-R, while they have increased 6-10-fold relative to wild-type protein at MC3-R and MC4-R.

Reversal of the hydrogen bond to zinc ligand histidine-119 dramatically diminishes catalysis and enhances metal equilibration kinetics in carbonic anhydrase II.

Direct metal ligands to transition metals in metalloproteins exert a profound effect on protein-metal affinity and function. Indirect ligands, i.e., second-shell residues that hydrogen bond to direct metal ligands, typically exert more subtle effects on the chemical properties of the protein-metal complex. However, E117 of human carbonic anhydrase II (CAII), which is part of the E117-119-Zn(2+) triad, is a notable exception: E117-substituted CAIIs exhibit dramatically increased kinetics of zinc complexation, and the E117Q variant exhibits enormously diminished catalytic activity and sulfonamide affinity. The three-dimensional structures of zinc-bound and zinc-free E117Q CAII reveal no discrete structural changes in the active site that are responsible for enhanced zinc equilibration kinetics and decreased activity. Additionally, the structure of the acetazolamide complex is essentially identical to that of the wild-type enzyme despite the 10(4)-fold loss of enzyme-inhibitor affinity. We conclude, therefore, that the functional differences between E117Q and wild-type CAIIs arise from electrostatic and not structural differences in the active site. We propose that the E117Q substitution reverses the polarity of the residue 117-H119 hydrogen bond, thereby stabilizing H119 as a histidinate anion in the E117Q CAII holoenzyme. The additional negative charge in the first coordination sphere of the metal ion increases the pK(a) of the zinc-water ligand, destabilizes the transition state for CO(2) hydration, and facilitates the exchange of a zinc-histidine ligand with an additional water molecule by decreasing the stability of the tetrahedral zinc complex. These novel properties engineered into E117Q CAII facilitate the exploitation of CAII as a rapid and sensitive Zn(2+) biosensor.

Structure of His94-->Asp carbonic anhydrase II in a new crystalline form reveals a partially occupied zinc binding site.

The structure of histidine 94-->aspartate (H94D) carbonic anhydrase II (CAII) crystallized in an orthorhombic space group has been determined to 2.5 A resolution. This crystal form is not isomorphous with monoclinic wild-type enzyme crystals or with the monoclinic crystal form of H94D CAII reported earlier [Kiefer,L.L., Ippolito, J.A., Fierke, C.A. and Christianson, D.W. (1993) J. Am. Chem. Soc., 115, 12581-12582]. In monoclinic H94D CAII, a fully occupied zinc ion is tetrahedrally coordinated by D94, H96, H119 and a water molecule. In orthorhombic H94D CAII, a partially occupied zinc ion is coordinated by H96 and H119 and only weakly coordinated by a disordered D94 side chain. These differences are particularly surprising given that the two crystal forms co-precipitate in the same drop in the same experiment. Re-refinement of the orthorhombic crystal form of H94C CAII and comparison with its corresponding monoclinic crystal form yield similar results. It appears that partial-but not full-zinc dissociation accompanies the crystallization of CAII variants in the orthorhombic crystal form, and significant differences on the protein surface presumably affect the relative stability of each crystal lattice. These results underscore an unexpected ambiguity in this protein engineering experiment: which crystal structure of H94D CAII should be correlated with functional measurements made in solution?

Agouti structure and function: characterization of a potent alpha-melanocyte stimulating hormone receptor antagonist.

The murine agouti gene encodes for a novel 131 amino acid protein. The sequence includes a 22 residue putative secretion signal, an internal basic region, and a C-terminal domain containing 10 cysteines. Agouti has been found to antagonize the binding of certain pro-opiomelanocortin peptides, such as alpha-melanocyte stimulating hormone (alpha-MSH), to the murine melanocortin-1 receptor (MC1-R). We report the purification of a secreted murine agouti to homogeneity by a two-step procedure from baculovirus-infected Trichoplusia ni (T. ni). The protein is glycosylated and exhibits competitive, high-affinity antagonism (Ki = 0.8 nM) versus alpha-MSH in cell-based assays employing B16F10 cells. Association state analysis by analytical ultracentrifugation reveals that agouti exists in a monomer--dimer plus aggregate equilibrium at low micromolar concentrations. Data from secondary structure studies indicate that the protein is highly stable to thermal denaturation. Enzymatic digestion to probe disulfide bond arrangement yielded a discrete C-terminal (Val 83-Cys 131) domain. The isolated highly cysteine-rich C-terminal domain retains alpha-MSH antagonism equipotent with mature agouti. This bioactive domain contains all 10 cysteines which exhibit sequence homology when aligned with several conotoxins.

Functional characterization of human carbonic anhydrase II variants with altered zinc binding sites.

Carbonic anhydrase II (CAII) contains a conserved His3 zinc polyhedron which is essential for catalysis. Removal of any one of the His ligands by replacement with Ala decreases (approximately 10(5)-fold), but does not abolish, zinc binding and increases the rate constant for zinc dissociation. CAII variants with a His ligand substituted with Cys, Asp, or Glu bind zinc only approximately 10-fold better than a His2 zinc polyhedron in CAII. The large decrease in zinc affinity (approximately 5 kcal/mol) in these variants compared to the wild-type His3 site reflects mainly unfavorable compensatory protein structural rearrangements observed in the X-ray crystallographic structures of some of these CAII variants, described by Ippolito and Christianson (following paper in this issue). However, the zinc affinity of these sites is still higher than zinc polyhedra designed de novo. Substitution of the His zinc ligands with negatively charged amino acids both increases the pKa of the zinc-bound water by > or = 1.6 pH units, confirming that neutral ligands maintain the low zinc-water pKa, and decreases the pH-independent kcat/KM for ester hydrolysis (3-30-fold) and CO2 hydration (approximately 10(3)-10(5)-fold). Additionally, decreases in the dissociation constant (approximately approximately 10(2)-10(5)-fold) for the transition state analog acetazolamide correlate with the decreased catalytic efficiency and increased pKa of these CAII variants. These data indicate that the histidine ligands, although not essential for catalysis, are conserved to maximize electrostatic stabilization of both the ground-state zinc-hydroxide and the negatively charged transition state. These studies provide valuable insights into the functional consequences of engineering a catalytic zinc site in a metalloenzyme.

Endoscopic ultrasonographic criteria of vascular invasion by potentially resectable pancreatic tumors.

Endoscopic ultrasonography was used to examine 38 patients with a pancreatic neoplasm (mean size, 2.8 cm; range, 1 to 5 cm). Three EUS signs appear to be reliable criteria for the identification of tumor invasion of major veins forming the portal confluence: (1) peri-pancreatic venous collaterals in the area of a mass that obliterates the normal anatomic location of a major portal confluence vessel; (2) tumor within the vessel lumen; and (3) abnormal vessel contour with loss of the vessel-parenchymal sonographic interface. At least one of these signs was present in each of the 21 patients with vascular invasion; none of them was present in the 17 patients without vascular invasion. Findings were confirmed by laparotomy plus biopsy (33 patients), autopsy (1 patient), or angiography plus biopsy (4 patients). Arterial involvement was identified by alteration of vessel course and caliber. All 7 patients with arterial involvement also had venous involvement. These signs provide reliable criteria for endoscopic ultrasonographic definition of unresectable tumors in patients with a pancreatic neoplasm that appears to be resectable on standard radiologic tests.