Crystal structure of bis(pentamethylcyclopentadienyl)difluorotitanium(IV), Ti[C5(CH3)5]2F2

C20H30F2Ti, monoclinic, P121/c1 (no. 14), a = 15.881(2) Å, b = 15.119(1) Å, c = 16.068(2) Å, β = 109.575(3)°, V = 3635.1 Å3, Z = 8, Rgt(F) = 0.054, wRref(F2) = 0.140, T = 100 K.

Crystal structure of (diethyl ether)-tetrachloro-dimethylamido-tantalum(V), TaCl4(C2H6N)(C4H10O)

C6H16Cl4NOTa, monoclinic, P121/c1 (no. 14), a = 13.975(2) Å, b = 12.494(2) Å, c = 15.318(2) Å, β = 91.717(3)°, V = 2673.4 Å3, Z = 8, Rgt(F) = 0.070, wRref(F2) = 0.171, T = 100 K.

[The organizational culture of ten Dutch veterinary practices. Based on the model of competitive value]

The aim of this study was to study the organizational culture of ten Dutch veterinary practices. In each practice, two veterinary nurses, two associates and two partners filled out the Organizational Culture Assessment Instrument for the current and preferred situation. Results showed that practice culture could be characterised best as the clan culture and, to a lesser extent, an adhocracy culture. The market culture was least prevalent. The family, adhocracy and hierarchy cultures were preferred above the market culture. The difference between current and preferred (i.e. the discrepancy) cultures was highest for the veterinary nurses, followed by the associates and smallest for the partners. Agreement between the three groups was stronger for the preferred situation than for the current situation.

The inhibition of tumor cell adhesion on human mesothelial cells (HOMC) by phospholipids in vitro

BACKGROUND AND AIMS

Intraperitoneal tumor cell adhesion to extracellular matrix and to mesothelial cells mediated by integrins is an important step in developing peritoneal carcinosis. In former animal studies, we could demonstrate that intraperitoneal treatment with a new phospholipid (PL) emulsion significantly reduces the amount of peritoneal carcinosis by adhesion prevention. This in vitro study tries to elucidate the influence of phospholipids on cells of the human gastric cancer cell line (NUGC-4) and the human rectal cancer cell line (HRT-18) adhering to mesothelial cells (HOMC) in a monolayer culture in vitro.

MATERIALS AND METHODS

HOMC cells were derived from omentum majus from patients undergoing elective abdominal surgery. Three passages of both cancer cell lines (NUGC-4 and HRT-18) were used. 1x10(5)/100 microl (HRT-18) or 1.2x10(5)/100 microl (NUGC-4) cells, according to forgoing dilution series, were pretreated with different concentrations of phospholipid emulsion (0.05, 0.1, 0.5, 0.75, 1% PL) stained with cell tracker chloromethyl-benzamidodialkylcarbocyanine (CM-DIL) and seeded into each well on the mesothelial monolayer. After 90 min, the number of adherent cells was counted by fluorescence microscopy at 530 and 620 nm. Additionally, flow cytometric analysis of integrin alpha3 and beta1 expression on the tumor cell surface after treatment with phospholipids was completed.

RESULTS

We found a dose dependent effect of phospholipids on both tumor cell lines causing a reduction of cell-cell adhesion. Already low concentrations of phospholipids (PL 0.5) had a significant influence. The mean cell count could be reduced from 234+/-12/mm2 in controls to 124+/-41/mm2 (PL 0.5; NUG-4) and from 295+/-49/mm2 to 169+/-29/mm2 (PL 0.5; HRT-18), respectively. Additionally, the integrin alpha3 and beta1 expression on both cell lines could be reduced.

CONCLUSION

Our results within the scope of published data indicate that adhesion prevention is capable to reduce peritoneal carcinosis.

CMPZ– an algorithm for the efficient comparison of periodic structures

The systematic comparison of the atomic structure of solid compounds has become an important task in crystallography, chemistry, physics and materials science, in particular in the context of structure prediction and structure determination of crystalline solids. In this work, an efficient and robust algorithm for the comparison of periodic structures is presented, which is based on the mapping of the point patterns of the two structures into each other. This algorithm has been implemented as the moduleCMPZin the structure visualization and analysis programKPLOT.

Verbesserungspotenzial des Medizinstudiums aus retrospektiver Sicht von Facharztprüflingen

BACKGROUND AND OBJECTIVE

As part of the new regulations for licensing doctors there have been numerous attempts at reform by many medical faculties to consider interdisciplinary linkage of the curriculum with emphasis on teaching of small groups of students. This study was undertaken to help answer the question of how much weight should be given to the various subjects and what resources are needed for any reformed curriculum and what key areas of competence need to be given greater importance.

METHODS

1029 candidates of specialist examinations of the Medical Council of North-Rhine in 2002 and 2003 filled in questionnaires to evaluate retrospectively the actual relevance of individual preclinical and clinical subjects, courses and areas of practical competence to their further medical education and related potentials for improvement in their studies. The participants were from 5 medical faculties in the North-Rhine area of Germany. They were also asked about methods of examination that were effective in aiding their learning behaviour.

RESULTS

Those answering the questionnaire considered especially chemistry and physics as well as environmental, occupational and forensic medicine, bio-mathematics, radiotherapy and nuclear medicine among the less relevant subjects. On the other hand, anatomy, physiology, internal medicine, pharmacology and surgery were considered especially relevant.

CONCLUSION

The greatest deficiencies in most of the medical curricula as taught in the North-Rhine medical courses are in the areas of competence in communication and practical clinical skills. Members of this group also pleaded for an increased use of standardized objective structured clinical examinations (OSCE).

Mucosal prolapse in the pathogenesis of Peutz-Jeghers polyposis

Germline mutations in LKB1 cause the rare cancer prone disorder Peutz-Jeghers syndrome (PJS). Gastrointestinal hamartomatous polyps constitute the major phenotypic trait in PJS. Hamartomatous polyps arising in PJS patients are generally considered to lack premalignant potential although rare neoplastic changes in these polyps and an increased gastrointestinal cancer risk in PJS are well documented. These conflicting observations are resolved in the current hypothesis by providing a unifying explanation for these contrasting features of PJS polyposis. We postulate that a genetic predisposition to epithelial prolapse underlies the formation of the polyps associated with PJS. Conventional sporadic adenomas arising in PJS patients will similarly show mucosal prolapse and carry the associated histological features.

Ab initio computation of low-temperature phase diagrams exhibiting miscibility gaps

A new methodology for the computation of the low-temperature part of phase diagrams without recourse to any experimental information is presented. A central element is a procedure for deciding whether formation of crystalline solid solution phases can take place in the chemical system. Via global exploration of the enthalpy landscapes for many different compositions in the system, candidates for ordered stoichiometric and crystalline solid solution phases are identified. Next, their free enthalpies are computed at ab initio level and a low-temperature phase diagram is derived. As examples, the low-temperature phase diagrams for the ternary alkali halides NaCl/LiCl NaBr/LiBr and NaCl/KCl are presented.

STRAD in Peutz-Jeghers syndrome and sporadic cancers

BACKGROUND/AIMS

LKB1 is a tumour suppressor gene that is associated with Peutz-Jeghers syndrome (PJS), a rare autosomal dominant cancer predisposition syndrome. However, germline mutations in the LKB1 gene are found in only about 60% of patients with PJS, suggesting the existence of a second PJS gene. The STRAD gene, encoding an LKB1 interacting protein that activates LKB1, which subsequently leads to polarisation of cells, is an interesting candidate for a second PJS gene and a potential tumour suppressor gene in sporadic carcinomas.

METHODS

The involvement of STRAD in 42 PJS associated tumours (sporadic lung, colon, gastric, and ovarian adenocarcinomas) was studied using loss of heterozygosity (LOH) analysis of eight microsatellite markers on chromosome 17, including TP53, BRCA1, and STRAD markers.

RESULTS

Loss of the marker near the STRAD locus was seen in 13 of 29 informative cases, including all gastric adenocarcinomas. Specific LOH of the STRAD marker was found in four of 29 informative cases. For these patients all exons and exon-intron boundaries of the STRAD gene were sequenced, but no somatic mutations were identified. Furthermore, no germline STRAD mutations were found in 10 patients with PJS and family members without LKB1 germline mutation.

CONCLUSIONS

Despite the frequent occurrence of LOH in the STRAD region, these results indicate that inactivation of the STRAD gene is not essential in the sporadic adenocarcinomas studied, although it is possible that STRAD may be inactivated in different ways. In addition, no evidence was found for the hypothesis that STRAD is a second PJS susceptibility gene.

Significance of sterol structural specificity. Desmosterol cannot replace cholesterol in lipid rafts

Desmosterol is an immediate precursor of cholesterol in the Bloch pathway of sterol synthesis and an abundant membrane lipid in specific cell types. The significance of the difference between the two sterols, an additional double bond at position C24 in the tail of desmosterol, is not known. Here, we provide evidence that the biophysical and functional characteristics of the two sterols differ and that this is because the double bond at C24 significantly weakens the sterol ordering potential. In model membranes, desmosterol was significantly weaker than cholesterol in promoting the formation or stability of ordered domains, and in mammalian cell membranes, desmosterol associated less avidly than cholesterol with detergent-resistant membranes. Atomic scale molecular dynamics simulations showed that the double bond gives rise to additional stress in the tail, creating a rigid structure between C24 and C27 and favoring tilting of desmosterol distinct from cholesterol. Functional effects of desmosterol in cell membranes were assessed upon acutely exchanging approximately 70% of cholesterol to desmosterol. This led to impaired raft-dependent signaling via the insulin receptor, whereas non-raft-dependent protein secretion was not affected. We suggest that the choice of cholesterol synthesis route may provide a physiological mechanism to modulate raft-dependent functions in cells.

Nonequilibrium Dynamics in Amorphous Si3B3N7

We present extensive numerical investigations of the structural relaxation dynamics of a realistic model of the amorphous high-temperature ceramic a-Si3B3N7, probing the mean-square displacement of the atoms, the bond survival probability, the average energy, the specific heat, and the two-point energy average. Combining the information from these different sources, we identify a transition temperature Tc approximately 2000 K below which the system is no longer ergodic and physical quantities observed over a time t(obs) show a systematic parametric dependence on the waiting time t(w), or age, elapsed after the quench. The aging dynamics "stiffens" as the system becomes older, which is similar to the behavior of highly idealized models such as Ising spin glasses and Lennard-Jones glasses.

Letrozole normalizes serum testosterone in severely obese men with hypogonadotropic hypogonadism

BACKGROUND

Morbid obesity is associated with increased estradiol production as a result of aromatase-dependent conversion of testosterone to estradiol. The elevated serum estradiol levels may inhibit pituitary LH secretion to such extent that hypogonadotropic hypogonadism can result. Normalization of the disturbed estradiol-testosterone balance may be beneficial to reverse the adverse effects of hypogonadism.

AIM

To examine whether aromatase inhibition with Letrozole can normalize serum testosterone levels in severely obese men with hypogonadotropic hypogonadism.

PATIENTS AND METHODS

Ten severely obese men, mean age 48.2 +/- 2.3 (s.e.) years and body mass index 42.1 +/- 2.6 kg/m(2), were treated with Letrozole for 6 weeks in doses ranging from 7.5 to 17.5 mg per week.

RESULTS

Six weeks of treatment decreased serum estradiol from 120 +/- 20 to 70 +/- 9 pmol/l (p = 0.006). None of the subjects developed an estradiol level of less than 40 pmol/l. LH increased from 4.5 +/- 0.8 to 14.8 +/- 2.3 U/l (p < 0.001). Total testosterone rose from 7.5 +/- 1.0 to 23.8 +/- 3.0 nmol/l (p < 0.001) without a concomitant change in sex hormone-binding globulin level. Those treated with Letrozole 17.5 mg per week had an excessive LH response.

CONCLUSION

Short-term Letrozole treatment normalized serum testosterone levels in all obese men. The clinical significance of this intervention remains to be established in controlled, long-term studies.

Diazoxide-mediated insulin suppression in obese men: a dose-response study

BACKGROUND

It has been suggested that diazoxide (DZX)-mediated insulin suppression may be useful to promote weight loss in obese subjects.

AIM

To assess the DZX-dose range that is safe to use in obese hyperinsulinaemic men.

METHODS

Assessment of DZX efficacy and safety was based on plasma glucose and insulin responses to a standardized 500-kcal breakfast, taken on the sixth day of treatment. Basic information regarding the potential efficacy of DZX treatment was first evaluated in an open-label study in five non-obese men. Subsequently, a double-blind, randomized, placebo-controlled study was performed in 12 obese but otherwise healthy men, comparing placebo treatment with DZX in doses of 50, 75 and 100 mg three times daily for 6 days.

RESULTS

In non-obese subjects, DZX 50 mg decreased peak insulin levels by +/-28% and raised peak glucose concentration from 7.1 +/- 0.6 to 7.8 +/- 0.6 mmol/l (p < 0.05). DZX 100 mg reduced peak insulin levels by 45% and caused a rise in peak glucose levels from 7.1 +/- 0.6 to 9.0 +/- 0.9 mmol/l (p < 0.05). In obese men, the 50 and 75 mg doses had no significant effects on glucose or insulin levels. DZX 100 mg reduced the peak insulin levels and insulin area under the curve by +/-20% (p < 0.05) but did not affect fasting or postprandial glucose levels. The relatively limited insulin-suppressive effects in obese subjects were attributed to the low plasma DZX levels that were achieved in this group. For comparable doses, plasma DZX levels were about 30% lower in obese than in non-obese men. Plasma DZX levels were highly dependent on dose (p < 0.001) and body weight (p < 0.001). Ninety-two percent of the total variability in DZX levels was explained by these two parameters.

CONCLUSION

DZX-mediated insulin suppression is dose dependent in normal and in obese men. However, the efficacy of DZX is much less in obese than in non-obese subjects. This is attributed to weight-dependent differences in distribution volume that lead to markedly lower plasma DZX levels in obese subjects. Weight-adjusted doses will be needed to achieve biologically effective plasma DZX levels. Extrapolation of the data suggests that effective insulin suppression in obese men will at least require a daily dose of 3.2-4.2 mg/kg.

Wigner crystallization in Na3Cu2O4 and Na8Cu5O10 chain compounds

We report the synthesis of novel edge-sharing chain systems Na(3)Cu(2)O(4) and Na(8)Cu(5)O(10), which form insulating states with commensurate charge order. We identify these systems as one-dimensional Wigner lattices, where the charge order is determined by long-range Coulomb interaction and the number of holes in the d shell of Cu. Our interpretation is supported by x-ray structure data as well as by an analysis of magnetic susceptibility and specific heat data. Remarkably, due to large second neighbor Cu-Cu hopping, these systems allow for a distinction between the (classical) Wigner lattice and the 4k(F) charge-density wave of quantum mechanical origin.

Surgical mesh as a scaffold for tissue regeneration in the esophagus

BACKGROUND

Textiles in the form of surgical meshes are widely used in hernia surgery. Their porous structure allows tissue infiltration to incorporate the fabric for complete healing and device stabilization. This study was aimed to reconstitute the esophageal wall and to investigate the functional and histological consequences of a new, non-absorbable polyvinylidene fluoride (PVDF) mesh and an absorbable polyglactin 910 (Vicryl((R))) mesh.

METHODS

Semicircular esophageal defects of 0.5 x 1 cm were created 2 cm proximal of the cardia in 10 rabbits. This gap was bridged using either polyglactin 910 or PVDF and additionally covered by omental wrapping. The clinical outcome was observed by clinical observation, regular esophagoscopies and X-ray contrast medium examinations. Local tissue regeneration was verified by light microscopy and immunohistochemistry.

RESULTS

After an observation period of 3 months we found no anastomotic strictures, complete mucosal regeneration, minimal inflammation reaction and initial regeneration of the muscle layer for the PVDF group. Within the polyglactin 910 group, three patch failures with consecutive anastomotic leakage occurred.

CONCLUSION

The results indicate that PVDF mesh structure gives the opportunity of local tissue regeneration in the esophagus. Though re-epithelialization and muscle cell ingrowth could be detected for absorbable polyglactin 910 mesh, this implant was accompanied by a high and early rate of anastomotic leakage.

Structure prediction of high-pressure phases for alkali metal sulfides

For a given chemical system we present a systematic approach to predict structures, which may exist at high pressure, by investigating the global enthalpy landscape. We combine global optimizations, based on empirical potential energy functions, and local optimizations (volume, cell shape, and atomic positions) on both Hartree-Fock and density functional theory level. We predict the existence of high-pressure phases for the alkali metal sulfides of the composition M2S (M = Li, Na, K, Rb, Cs), together with the transition pressures among these phases.

Prevention of weight gain in type 2 diabetes requiring insulin treatment

BACKGROUND

Patients with type 2 diabetes who are failing on oral agents will generally gain a large amount of body fat when switched to insulin treatment. This adverse effect may be related to chronic hyperinsulinism induced by long-acting insulin compounds.

AIM

To test the concept that regain of glycaemic control can be achieved without causing weight gain, using a regimen free of long-acting insulin.

METHODS

In a 3-month open-label pilot study including 25 patients with moderate overweight and secondary failure, we investigated whether nocturnal glycaemic control could be achieved with glimepiride administered at 20:00 hours. The starting dose was 1-2 mg, with subsequent titration up to a maximum of 6 mg. Rapid-acting insulin analogues were used three times daily to regain postprandial glucose control.

RESULTS

Glycaemic control at 3 months was established with glimepiride in a dose of 4.4 +/- 0.3 mg/day (mean +/- standard error of the mean), and a total daily insulin dose of 24.1 +/- 2.6 IU. Fasting glucose levels decreased from 12.7 +/- 0.6 mmol/l to 8.1 +/- 0.3 mmol/l (p < 0.001), and target levels were reached in 14 of 25 patients (56%). Mean HbA1c decreased from 10.5 +/- 0.4 to 7.7 +/- 0.2% (p < 0.001). Symptomatic nocturnal hypoglycaemia was not reported. Body weight did not change (85.7 +/- 3.6 kg vs. 85.7 +/- 3.3 kg, p = 0.99).

CONCLUSION

The data suggest that this new approach may be useful in about 50% of type 2 diabetes patients presenting with failure on maximal oral treatment.

A comparison of in vitro bioassays to determine cellular glucocorticoid sensitivity

An altered cellular glucocorticoid (GC) sensitivity is associated with several pathophysiological conditions such as asthma, diabetes, or rheumatoid arthritis. Several bioassays have been developed and employed to assess cellular GC sensitivity of peripheral blood mononuclear cells (PBMC), but correlations between these have rarely been investigated. We have compared four mitogen-based assays and an FK506 binding protein 51 (FKBP51) mRNA induction assay, using ten controls and a GC-resistant patient. The mitogen-based assays were performed using either diluted whole blood or isolated PBMC, and showed relatively large assay variations for the parameters maximal effect and half-maximal effect concentration. The FKBP51 assay showed smaller intra-assay and within-individual variation compared with the mitogen-based assays. The whole blood-based mitogen assays and the FKBP51 assay clearly discriminated the GC-resistant patient from the controls but, in contrast to expectations, both PBMC-based mitogen assays did not. The GC-induced FKBP51 mRNA increase in PBMC may be an alternative to determine an altered individual GC sensitivity with several advantages as compared with mitogen-based assays, such as the use of unstimulated PBMC, and a better intra- and inter-individual reproducibility.