The Global Atmosphere-aerosol Model ICON-A-HAM2.3-Initial Model Evaluation and Effects of Radiation Balance Tuning on Aerosol Optical Thickness

The Hamburg Aerosol Module version 2.3 (HAM2.3) from the ECHAM6.3-HAM2.3 global atmosphere-aerosol model is coupled to the recently developed icosahedral nonhydrostatic ICON-A (icon-aes-1.3.00) global atmosphere model to yield the new ICON-A-HAM2.3 atmosphere-aerosol model. The ICON-A and ECHAM6.3 host models use different dynamical cores, parameterizations of vertical mixing due to sub-grid scale turbulence, and parameter settings for radiation balance tuning. Here, we study the role of the different host models for simulated aerosol optical thickness (AOT) and evaluate impacts of using HAM2.3 and the ECHAM6-HAM2.3 two-moment cloud microphysics scheme on several meteorological variables. Sensitivity runs show that a positive AOT bias over the subtropical oceans is remedied in ICON-A-HAM2.3 because of a different default setting of a parameter in the moist convection parameterization of the host models. The global mean AOT is biased low compared to MODIS satellite instrument retrievals in ICON-A-HAM2.3 and ECHAM6.3-HAM2.3, but the bias is larger in ICON-A-HAM2.3 because negative AOT biases over the Amazon, the African rain forest, and the northern Indian Ocean are no longer compensated by high biases over the sub-tropical oceans. ICON-A-HAM2.3 shows a moderate improvement with respect to AOT observations at AERONET sites. A multivariable bias score combining biases of several meteorological variables into a single number is larger in ICON-A-HAM2.3 compared to standard ICON-A and standard ECHAM6.3. In the tropics, this multivariable bias is of similar magnitude in ICON-A-HAM2.3 and in ECHAM6.3-HAM2.3. In the extra-tropics, a smaller multivariable bias is found for ICON-A-HAM2.3 than for ECHAM6.3-HAM2.3.

Orthotic treatment of idiopathic toe walking with a lower leg orthosis with circular subtalar blocking

BACKGROUND

There is no universally accepted treatment standard for idiopathic toe walking patients (ITW) in the current literature. None of the established methods provide homogenous satisfying results. In our department we treat ITW patients with lower leg orthoses with a circular foot unit for a total of 16 weeks. In this study we reviewed our database to evaluate the success of our treatment protocol for a 24 months follow up period.

RESULTS

Twenty-two patients were included in this study. Age at the beginning of treatment was 7.0 years +/- 2.9 (range 2.5-13.1). Percentage of ITW at the beginning of treatment according to the perception of the parents was 89% +/- 22.2 (range 50-100). Immediately after the treatment with our device, percentage of ITW dropped to 11% +/- 13.2 (range 0-50). After 12 months, 73% of the patients (16/22) walked completely normal or showed ITW less than 10% of the day. After 24 months, 64% of the patients kept a normal gait (14/22).

CONCLUSION

This study provides evidence that the treatment of idiopathic toe walking with lower leg orthoses with a circular foot unit results in satisfying long-term results in two thirds of the patients.

Is unilateral lower leg orthosis with a circular foot unit in the treatment of idiopathic clubfeet a reasonable bracing alternative in the Ponseti method? Five-year results of a supraregional paediatric-orthopaedic centre

Background

In the Ponseti treatment of idiopathic clubfoot, children are generally provided with a standard foot abduction orthosis (FAO). A significant proportion of these patients experience irresolvable problems with the FAO leading to therapeutic non-compliance and eventual relapse. Accordingly, these patients were equipped with a unilateral lower leg orthosis (LLO) developed in our institution. The goal of this retrospective study was to determine compliance with and the efficacy of the LLO as an alternative treatment measure. The minimum follow-up was 5 years.

Results

A total of 45 patients (75 ft) were retrospectively registered and included in the study. Compliance with the bracing protocol was 91% with the LLO and 46% with the FAO. The most common problems with the FAO were sleep disturbance (50%) and cutaneous problems (45%). Nine percent of patients experienced sleep disturbance, and no cutaneous problems occurred with the LLO. Thirteen percent of patients being treated with an FAO until the age of four (23 patients; 40 ft) underwent surgery because of relapse, defined by rigid recurrence of any of the components of a clubfoot. Fourteen percent of patients being treated with an LLO (22 patients; 35 ft), mostly following initial treatment with an FAO, experienced recurrence.

Conclusion

Changing from FAO to LLO at any point during treatment did not result in an increased rate of surgery and caused few problems.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2160-1) contains supplementary material, which is available to authorized users.

Androgen receptor dampens tissue factor expression via nuclear factor-κB and early growth response protein 1

Essentials Androgen deprivation increases the rate of venous thromboembolism in prostate cancer patients. We characterized androgen receptor-mediated tissue factor regulation in prostate epithelial cells. Androgen receptor is dampening tissue factor expression in prostate epithelial cells. Androgen deprivation could enhance tissue factor expression and raise venous thromboembolism rates.

SUMMARY

Background Prostate cancer is one of the leading causes of cancer death in men. Advanced prostate cancer is usually treated by androgen deprivation therapy (ADT), which is aimed at reducing circulating testosterone levels to reduce cancer growth. There is growing evidence that ADT can increase the rate of venous thromboembolism (VTE) in prostate cancer patients. The tissue factor (TF) gene is one of the most important mediators of coagulation and VTE, but, so far, there are limited data on androgen receptor (AR)-mediated TF gene expression. Objectives To characterize AR-mediated TF regulation in vitro and in vivo. Methods We used the androgen-dependent prostate cancer cell lines LNCaP and MyC-CaP to test whether TF expression is regulated by AR. Furthermore, we cloned the TF gene promoter into a luciferase reporter vector to identify the transcription factor-binding sites that mediate TF regulation downstream of AR. Finally, we used castration experiments in mice to characterize AR-mediated TF regulation in vivo. Results TF is directly regulated by AR. In LNCaP cells, nuclear factor-κB signaling and EGR1 mediate TF expression. By using castration experiments in mice, we could detect upregulation of TF and early growth response protein 1 mRNA and protein expression in prostate epithelial cells. Conclusion AR is crucial for dampening TF expression, which could be important for increased TF expression and TF-positive microvesicle release in androgen-deprived prostate cancer patients.

A novel method for automated assessment of megakaryocyte differentiation and proplatelet formation

Transfusion of platelet concentrates represents an important treatment for various bleeding complications. However, the short half-life and frequent contaminations with bacteria restrict the availability of platelet concentrates and raise a clear demand for platelets generated ex vivo. Therefore, in vitro platelet generation from megakaryocytes represents an important research topic. A vital step for this process represents accurate analysis of thrombopoiesis and proplatelet formation, which is usually conducted manually. We aimed to develop a novel method for automated classification and analysis of proplatelet-forming megakaryocytes in vitro. After fluorescent labelling of surface and nucleus, MKs were automatically categorized and analysed with a novel pipeline of the open source software CellProfiler. Our new workflow is able to detect and quantify four subtypes of megakaryocytes undergoing thrombopoiesis: proplatelet-forming, spreading, pseudopodia-forming and terminally differentiated, anucleated megakaryocytes. Furthermore, we were able to characterize the inhibitory effect of dasatinib on thrombopoiesis in more detail. Our new workflow enabled rapid, unbiased, quantitative and qualitative in-depth analysis of proplatelet formation based on morphological characteristics. Clinicians and basic researchers alike will benefit from this novel technique that allows reliable and unbiased quantification of proplatelet formation. It thereby provides a valuable tool for the development of methods to generate platelets ex vivo and to detect effects of drugs on megakaryocyte differentiation.

Myeloid PTEN deficiency impairs tumor-immune surveillance via immune-checkpoint inhibition

Tumor-host interaction is determined by constant immune surveillance, characterized by tumor infiltration of myeloid and lymphoid cells. A malfunctioning or diverted immune response promotes tumor growth and metastasis. Recent advances had been made, by treating of certain tumor types, such as melanoma, with T-cell checkpoint inhibitors. This highlights the importance of understanding the molecular mechanisms underlying the crosstalk between tumors and their environment, in particular myeloid and lymphoid cells. Our aim was to study the contribution of the myeloid PI3K/PTEN-signaling pathway in the regulation of tumor-immune surveillance in murine models of cancer. We made use of conditional PTEN-deficient mice, which exhibit sustained activation of the PI3K-signaling axis in a variety of myeloid cell subsets such as macrophages and dendritic cells (DCs). In colitis-associated colon cancer (CAC), mice deficient in myeloid PTEN showed a markedly higher tumor burden and decreased survival. We attributed this observation to the increased presence of immune-modulatory conventional CD8α(+) DCs in the spleen, whereas other relevant myeloid cell subsets were largely unaffected. Notably, we detected enhanced surface expression of PD-L1 and PD-L2 on these DCs. As a consequence, tumoricidal T-cell responses were hampered or redirected. Taken together, our findings indicated an unanticipated role for the PI3K/PTEN-signaling axis in the functional regulation of splenic antigen-presenting cells (APCs). Our data pointed at potential, indirect, tumoricidal effects of subclass-specific PI3K inhibitors, which are currently under clinical investigation for treatment of tumors, via myeloid cell activation.

[Spastic foot deformities in children: surgical management]

Although the neurological defects associated with cerebral palsy are not progressive, secondary musculoskeletal disorders due to growth and gravity are variable. In the clinical analysis of spastic foot deformities different mechanisms that produce a variety of deformities have to be analyzed. The goals of surgical treatment are correction of the deformity, reestablishment of stability of the foot and preservation of functionally important ranges of motion and muscle strength. The most common spastic foot deformities are equinus, planovalgus, equinovarus and calcaneus. For treatment soft tissue surgery, such as muscle lengthening and transfer together with bone surgery, such as osteotomy or arthrodesis are used and combinations of these methods are often required. Subsequently postoperative plasters are necessary followed by dynamic orthotic management.

[Determination of activity levels in patients with cerebral palsy]

AIM

The aim of this study is the determination of physical activity in everyday life of handicapped persons due to cerebral palsy using standardised testing procedures.

METHOD

The subjects were examined according to the Conconi test on a treadmill at increasing speeds for their fitness. We used a continuous heart rate monitoring, 3-axis acceleration sensors, lactate measurements and pedography.

RESULTS

Three groups of subjects could be differentiated. In one group, a rapid rise in heart rate even at lower walking speed was observed. In a second group of persons with poor motor coordination, the maximum walking speed was limited. Single subjects were not limited neither in their physical performance nor in their condition.

CONCLUSION

In the physical therapy for patients with cerebral palsy one should not lose sight of possible cardiovascular limitations additional to the physical disabilities.

[Primary malignant bone tumors]

Among human neoplasms, primary malignant bone tumors are fairly rare. They present an incidence rate of roughly 10 cases per 1 million inhabitants per year. During childhood (<15 years), the percentage of malignant bone tumors amounts to 6% of all infantile malignancies. Only leukemia and lymphoma show a higher incidence in adolescence. Of all primary malignant bone tumors, 60% affect patients younger than 45 years and the peak incidence of all bone tumors occurs between 15 and 19 years. The most common primary malignant bone tumors are osteosarcoma (35%), chondrosarcoma (25%), and Ewing's sarcoma (16%). Less frequently (≤ 5%) occurring tumors are chordoma, malignant fibrous histiocytoma of bone, and fibrosarcoma of bone. Vascular primary malignant tumors of bone and adamantinoma are very rare. Staging of the lesion is essential for systemic therapeutic decision-making and includes complete imaging and histo-pathological confirmation of the suspected entity. In most cases, this is established by open- or image-guided biopsy. Based on this information, an interdisciplinary tumor board will determine the individual therapeutic approach. Endoprosthetic or biological reconstruction following wide tumor resection is the most common surgical therapy for primary malignant bone tumors. There is vital importance in a thorough postoperative follow-up and continous after-care by a competent tumor center which is permanentely in charge of therapy.

CSF biomarkers in posterior cortical atrophy

OBJECTIVE

To describe CSF biomarker profiles in posterior cortical atrophy (PCA), which induces high-order visual deficits often associated with Alzheimer disease (AD) pathology, and relate these findings to clinical and neuropsychological assessment.

METHODS

This prospective observational study included 22 patients with PCA who underwent CSF biomarker analysis of total tau (t-tau), phosphorylated tau on amino acid 181 (p-tau181), and amyloid β (Aβ(42)). At group level, the CSF profiles of patients with PCA were compared to those of patients with typical AD and patients with other dementia (OD). Individually, the clinical presentation of patients with PCA was correlated to their CSF profile to assess the predictability of clinical features for diagnosis of underlying AD pathology.

RESULTS

At group level, the PCA biomarker profile was not different from that of the AD group, but very different from that of the OD group (p < 0.001). More than 90% of patients with PCA had CSF profiles consistent with AD. All patients with PCA with either isolated higher-order visual deficit (n = 8) or visual deficit associated with memory impairment (n = 11) had CSF profiles consistent with AD. Only one of the 3 patients with PCA with asymmetric motor signs fulfilled biological CSF criteria for AD.

CONCLUSIONS

PCA syndrome is usually associated with CSF biomarkers suggestive of AD, as shown by previous neuropathologic studies. This does not apply in case of motor signs suggesting associated corticobasal syndrome. CSF biomarkers help to discriminate AD from non-AD processes associated with this condition.

Quelle signification pour le taux de cholestérol après 75 ans?

Increasing comorbidity with aging reduces the predictive power of cardiovascular risk factors. From the age of 70 onward, total cholesterol levels decrease, perhaps associated with changes in the composition of some lipoprotein fractions. In subjects older than 75 years, being in the lowest quartile of cholesterol, insulinemia or serum albumin concentrations is associated with increased mortality. Cholesterol levels below 189 mg/dL in subjects older than 75 years should be considered an early sign of unidentified comorbidity or of rapid functional decline. HDL cholesterol levels, rather than total or LDL cholesterol, were inversely associated with increased mortality from ischemic coronary disease and stroke appears to rise as HDL cholesterol levels fall, rather than total or LDL cholesterol. On the other hand, LDL concentrations below 106 mg/dL and HDL concentrations below 36 mg/dL were associated with an increased risk of death from infectious disease. Stroke incidence, in particular, ischemic stroke, is highest in subjects older than 75 years. HDL cholesterol levels above 35 mg/dL appear to have a protective effect against ischemic stroke in subjects younger than 70 years. Two interventional drug studies investigating the effects of two statins (simvastatin and pravastatin) found that in subgroups of subjects older than 75 these drugs were associated with a reduction in all-cause mortality and cardiovascular morbidity, regardless of total cholesterol levels, but had no short-term effect on cognitive function.

Large-artery stroke in a young patient with Crohn's disease. Role of vitamin B6 deficiency-induced hyperhomocysteinemia

An increased incidence of ischemic stroke has been reported in patients with Crohn's disease. Cerebral infarcts are usually considered as a complication of the hypercoagulable state associated with this inflammatory bowel disease (IBD). The association between Crohn's disease, hyperhomocysteinemia and large-artery stroke of the young has rarely been reported. A 39-year-old woman, with prior medical history of Crohn's disease and hypertension, presented with an ischemic stroke of the left internal carotid artery (ICA) territory. Etiological workup disclosed bilateral high-grade ICA stenosis and atheroma of the subclavian and vertebral arteries. Exhaustive search for prothrombotic factors showed inflammation, with an increased level of fibrinogen and factor IX, and a marked hyperhomocysteinemia. Both vitamin B1 and vitamin B6 plasmatic levels were decreased. Heterozygous C677T methylene-tetrahydrofolate reductase gene mutation was present. This observation highlights the combined proatherogenic effect of vitamin B deficiency-induced hyperhomocysteinemia and inflammation leading to large-artery stroke of the young in the setting of Crohn's disease. Our case report stresses the importance of vitamin deficiency screening in patients with IBD in terms of stroke prevention.

Long-range transport and global fractionation of POPs: insights from multimedia modeling studies

The long-range transport of persistent organic pollutants (POPs) is investigated with two multimedia box models of the global system. ChemRange is a purely evaluative, one-dimensional steady-state (level III) model; CliMoChem is a two-dimensional model with different temperatures, land/water ratios and vegetation types in different latitudinal zones. Model results are presented for three case studies: (i) the effect of atmospheric aerosol particles on the long-range transport of POPs, (ii) the effect of oceanic deposition on the long-range transport of different PCB congeners, (iii) the global fractionation of different PCB congeners. The model results for these case studies show: (i) the low atmospheric half-lives estimated for several organochlorine pesticides are likely to be inconsistent with the observed long-range transport of these compounds; (ii) export to the deep sea reduces the potential for long-range transport of highly hydrophobic compounds (but does not remove these chemicals from the biosphere); (iii) there are different meanings of the term global fractionation that refer to different aspects of the fractionation process and need to be distinguished. The case-study results further indicate that the influences of varying environmental conditions on the physicochemical properties and the degradation rate constants of POPs need to be determined.

Haemolytic uraemic syndrome and mutations of the factor H gene: a registry-based study of German speaking countries

BACKGROUND

The aetiology of atypical haemolytic uraemic syndrome (aHUS) is, in contrast to classical, Shiga-like toxin induced HUS in children, largely unknown. Deficiency of human complement factor H and familial occurrence led to identification of the factor H gene (FH1) as the susceptibility gene, but the frequency and relevance of FH1 mutations are unknown.

METHODS

We established a German registry for aHUS and analysed in all patients and 100 controls the complete FH1 gene by single strand confirmational polymorphism and DNA sequencing. In addition, complement C3 and factor H serum levels were assayed. Demographic data at onset of aHUS and follow up were compared for the mutation positive and negative groups.

RESULTS

Of 111 patients with aHUS (68 female, 43 male, mean age 33 years) 14% had FH1 germline mutations, including two of eight patients with familial aHUS. For each of these eight patients, both parents were tested, and we were able to trace the mutation for five cases. In the other three cases (one with the mutation 3749 C/T, one with 3200 T/C, and one with 3566+1 G/A), we could not detect the mutation in either parent, although paternity was proven by genetic fingerprinting, suggesting that these subjects have new mutations. C3 was decreased in five mutation carriers but also in two non-carriers, and factor H was decreased in none of the carriers, but elevated in six carriers and 15 non-carriers. Clinical parameters including associated medications and diseases, and outcome of aHUS and of post-aHUS kidney transplantation were similar in the mutation positive and negative groups.

CONCLUSION

FH1 germline mutations occur with considerable frequency in patients with aHUS. Hypocomplementaemia is not regularly associated with a germline mutation, and factor H serum levels can even be elevated. Screening for FH1 mutations contributes to the classification of aHUS.

Sequence-specific NMR assignment of proteins by global fragment mapping with the program MAPPER

A new program, MAPPER, for semiautomatic sequence-specific NMR assignment in proteins is introduced. The program uses an input of short fragments of sequentially neighboring residues, which have been assembled based on sequential NMR connectivities and for which either the 13C(alpha) and 13C(beta) chemical shifts or data on the amino acid type from other sources are known. MAPPER then performs an exhaustive search for self-consistent simultaneous mappings of all these fragments onto the protein sequence. Compared to using only the individual mappings of the spectroscopically connected fragments, the global mapping adds a powerful new constraint, which results in resolving many otherwise intractable ambiguities. In an initial application, virtually complete sequence-specific assignments were obtained for a 110 kDa homooctameric protein, 7,8-dihydroneopterin aldolase from Staphylococcus aureus.

Sensitivity gain by simultaneous acquisition of two coherence pathways: the HNCA(+) experiment

In most multidimensional nuclear magnetic resonance experiments a single and distinct coherence transfer pathway is selected by phase cycling or by pulsed field gradients. It was shown that simultaneously exploiting more than one coherence transfer pathway could increase the overall sensitivity of NMR experiments. However, sensitivity enhancement schemes described to date introduce additional delays in the pulse schemes, resulting in considerable decrease of the expected sensitivity gain when applied to biomolecules due their fast transverse relaxation. A novel sensitivity enhancement principle which increases sensitivity of an experiment by simultaneously exploiting two completely independent coherence pathways in a single NMR pulse scheme is presented in this paper. As an example an improved HNCA experiment, the HNCA(+), is presented, which combines the "out-and-back" coherence transfer pathway used in HNCA with an "out-and-stay" experiment, analogous to HCANH, without adding any time periods compared to the conventional HNCA pulse sequence. The applicability of the HNCA(+) was theoretically evaluated with regard to different sizes of peptides or proteins, which showed that the experimental time can be reduced twofold in ideal cases. The application of this novel experiment to a 7-kDa protein showed a 20% sensitivity gain of HNCA(+) when compared to conventional HNCA.

Improved sensitivity and coherence selection for [15N,1H]-TROSY elements in triple resonance experiments

In experiments with proteins of molecular weights around 100 kDa the implementation of [15N,1H]-TROSY-elements in [15N]-constant-time triple resonance experiments yields sensitivity enhancements of one to two orders of magnitude. An additional gain of 10 to 20% may be obtained with the use of 'sensitivity enhancement elements'. This paper describes a novel sensitivity enhancement scheme which is based on concatenation of the 13C alpha-->15N magnetization transfer with the ST2-PT element, and which enables proper TROSY selection of the 15N multiplet components.

Transport and temperature effects on measurement of serum and plasma potassium

Transport of blood samples from general practice to a central laboratory can result in spuriously high or low potassium concentrations. The importance of this phenomenon was studied in a general practice serving a population of 15,000 patients, 27 km from the pathology laboratory that routinely measured serum potassium. The design involved comparison of potassium levels between control serum (plain gel-separation serum tubes centrifuged in the surgery), routine serum (plain gel-separation tubes centrifuged in the laboratory) and routine plasma samples (lithium-heparin tubes centrifuged in the laboratory). Complete triple sets of data were obtained for 371 samples. Altman and Bland plots for the control serum vs routine serum samples showed a mean difference of +0.1 mmol/L with limits of agreement (+/- 2SD) +0.6 mmol/L, -0.4 mmol/L and for control serum vs routine plasma a mean difference of +0.2 mmol/L with limits of agreement +0.8 mmol/L, -0.4 mmol/L. There was a negative association between mean weekly routine plasma potassium levels with mean weekly temperatures achieved. Regression analysis indicated that both maximum temperature achieved and time to centrifugation significantly contributed to differences observed in the routine plasma samples, but not with the routine serum samples. For plasma samples exposed to high temperatures a clinically significant lowering of potassium concentrations can arise. These results confirm that spurious lowering of potassium concentrations occurs in plasma samples collected in a primary care setting. The preferred method is to centrifuge samples soon after venepuncture. Where this is not possible, collection into plain gel-separation tubes (serum) ensures less variation due to temperature and time to centrifugation than does collection into lithium-heparin tubes (plasma).

[13C]-constant-time [15N,1H]-TROSY-HNCA for sequential assignments of large proteins

The greatly improved sensitivity resulting from the use of TROSY during 15N evolution and amide proton acquisition enables the recording of HNCA spectra of large proteins with constant-time 13C alpha evolution. In [13C]-ct-[15N,1H]-TROSY-HNCA experiments with a 2H/13C/15N-labeled 110 kDa protein, 7,8-dihydroneopterin aldolase from Staphylococcus aureus, nearly all correlation peaks seen in the [15N,1H]-TROSY-HNCA spectrum were also detected. The improved resolution in the 13C dimension then enabled a significant number of sequential assignments that could not be obtained with [15N,1H]-TROSY-HNCA without [13C]-constant-time period.

TROSY in triple-resonance experiments: new perspectives for sequential NMR assignment of large proteins

The NMR assignment of 13C, 15N-labeled proteins with the use of triple resonance experiments is limited to molecular weights below approximately 25,000 Daltons, mainly because of low sensitivity due to rapid transverse nuclear spin relaxation during the evolution and recording periods. For experiments that exclusively correlate the amide proton (1HN), the amide nitrogen (15N), and 13C atoms, this size limit has been previously extended by additional labeling with deuterium (2H). The present paper shows that the implementation of transverse relaxation-optimized spectroscopy ([15N,1H]-TROSY) into triple resonance experiments results in several-fold improved sensitivity for 2H/13C/15N-labeled proteins and approximately twofold sensitivity gain for 13C/15N-labeled proteins. Pulse schemes and spectra recorded with deuterated and protonated proteins are presented for the [15N, 1H]-TROSY-HNCA and [15N, 1H]-TROSY-HNCO experiments. A theoretical analysis of the HNCA experiment shows that the primary TROSY effect is on the transverse relaxation of 15N, which is only little affected by deuteration, and predicts sensitivity enhancements that are in close agreement with the experimental data.

Formation of TCR dimers/trimers as a crucial step for T cell activation

T cell activation involves specific interactions between the TCR and peptides presented by the MHC. This engagement leads to phosphorylation and subsequent internalization of the TCR complex. By analyzing the kinetics of the internalization of TCR, we found that the rate of TCR down-regulation was proportional to the square of the TCR density. Mathematical modeling of TCR interactions indicates that such a relation is only possible if TCR dimerize before internalization. By mathematical analysis, our data would also be compatible with trimer but not larger oligomer formation. Thus, minimal TCR oligomerization is an essential step for peptide-mediated T cell activation.

The role of T cell receptor dimerization for T cell antagonism and T cell specificity

T cell responses are highly specific and T cell receptors (TCRs) can recognise subtle differences in major histocompatibility complex (MHC)-peptide complexes. While nominal peptide antigens usually act as full agonists that trigger the whole spectrum of T cell responses, some peptides exhibiting mutations at the TCR-MHC/peptide contact site stimulate only a fraction of T cell responses (partial agonists) or may even inhibit T cell activation by full agonists (antagonist). The present study analyses mathematically the role of TCR-dimerization for T cell antagonism and T cell specificity in general. It demonstrates that T cell antagonists can effectively inhibit TCR-dimerization and that this mechanism can sufficiently explain all aspects of T cell antagonism. The kinetic model of T cell activation proposes that increasing the time required for effective TCR-signaling is the most effective mechanism to increase the discriminatory capacity of TCRs. Our results indicate that TCR-oligomerization is an alternative and efficient mechanism to ensure T cell specificity.

Estimation of maximal affinities between T-cell receptors and MHC/peptide complexes

Recognition of peptide/MHC complexes by T-cell receptors (TCRs) is a critical step for T-cell activation. We studied T-cell activation as a function of this interaction using a mathematical model. Unlike other models analysing TCR-MHC/peptide interactions, this study takes into account that both TCRs and MHC/peptide complexes are anchored in membranes and not in solution. The proposed model quantitatively predicts several essential features of antigen-specific T-cell activation, including the experimentally determined rate of TCR-downregulation during peptide-specific T-cell stimulation. In addition, the model offers an explanation as to why the affinity of the TCR for MHC/peptide complexes is low in general and it correctly predicts the on-rates of the TCR-MHC/peptide interaction observed in different model systems. Thus, the proposed model predicts key parameters of T-cell activation and offers an explanation for the surprisingly low affinity of the TCR for its antigen.

Fast-HMQC using Ernst angle pulses: An efficient tool for screening of ligand binding to target proteins

The application of Ernst angle pulses in multidimensional NMR spectroscopy is theoretically and experimentally investigated. Theory shows that only for a few pulse sequences employed at high repetition rate, a remarkable gain in sensitivity is possible using Ernst angle pulses. As an example, a new variant of the heteronuclear multiple quantum coherence (HMQC) experiment, the fast-((1)H,(15)N)-HMQC, is described. This sequence allows, with a 1 mM protein sample in H(2)O, the acquisition of a highly resolved two-dimensional ((1)H,(15)N) correlated spectrum within 37 s. The high efficiency of the fast-HMQC to detect ligand binding to a target protein is demonstrated.

[Postoperative benefit after laparoscopic cholecystectomy in acute cholecystitis]

Analysed were the results of all 48 patients with acute cholecystitis, who underwent laparoscopic cholecystectomy between 1991 and 1995 in the department of general surgery, AKH, University of Vienna. In 18 cases it was necessary to convert to laparotomy. In a second step the results of these two groups of patients were compared with results of patients without acute cholecystitis, who elective underwent laparoscopic cholecystectomy. In about 2/3 of the patients with acute cholecystitis laparoscopic cholecystectomy is possible. In these cases we found a mean postoperative hospital stay of 4.4 days, with a significant difference between those with drain (5.9 days) and those without (2.7 days). In cases of laparotomy the mean postoperative stay was 7.7 days, also significant longer. These patients consumed at the first postoperative day more than 1.5 times of opioid analgetics than those, who underwent laparoscopy with acute cholecystitis, laparoscopied patients without acute cholecystitis half of this. After the second postoperative day patients after laparotomy took 3 times of opioid analgetics than patients after laparoscopy, no matter if there was an acute cholecystitis or not. The rate of conversion to laparotomy sank with the increase of experience of a surgeon. Postoperative benefit of laparoscopic treatment, as less pain and shorter hospitalisation, can be saved even in cases of acute cholecystitis. So the management should primary be laparoscopic.

[Spontaneous spinal epidural hematoma: 2 cases]

The authors report on two cases of spontaneous spinal epidural hematomas with atypical subacute clinical presentation and good recovery after surgical treatment. Etiologies, physiopathology, early diagnosis and treatment are considered through a brief review of the literature.

Dural arteriovenous fistula of the posterior fossa draining into the spinal medullary veins--an unusual cause of myelopathy: case report

In a 31-year-old male patient suffering from progressive myelopathy, a right carotid angiography disclosed an intracranial tentorial arteriovenous fistula (AVF) draining intrathecally into the spinal medullary veins. An embolization via the afferent meningohypophyseal artery was not technically feasible, and a microsurgical excision of the AVF was accomplished via a suboccipital approach, resulting in the angiographic cure of the fistula and progressive relief of the myelopathy. Fourteen reported cases of intracranial dural AVF draining intrathecally are reviewed. In most patients, authors encountered diagnostic difficulties similar to those noted in this case. Surgical and/or endovascular therapeutic methods have provided disappointing results, likely attributable to a prolonged course of spinal cord dysfunction. Pathophysiologically, a mechanism of venous congestion of the cord seems to be involved, as acknowledged by several magnetic resonance and angiographic studies. In patients who appear to have a clinical and myelographic picture of "vascular" myelopathy and who exhibit negative spinal angiography, a four-vessel cerebral angiography should be undertaken, aiming at the recognition of an intracranial AVF.

A new point mutation in the prion protein gene at codon 210 in Creutzfeldt-Jakob disease

We screened 16 cases of sporadic Creutzfeldt-Jakob disease (CJD) and 28 healthy control subjects to detect possible polymorphisms in their prion protein gene (PRNP). The molecular analysis of the PRNP coding sequence was performed using denaturing gradient gel electrophoresis of polymerase chain reaction products and direct sequencing. We identified (1) a silent mutation at codon 177 in a healthy individual, (2) a codon 200 glutamate-to-lysine substitution in a 48-year-old CJD-affected Libyan Jew, and (3) a G-to-A point substitution at codon 210, leading a valine-to-isoleucine change, in a 63-year-old French CJD patient. This new mutation occurs in a highly conserved part of the PRNP coding sequence, close to the known CJD-associated codon 200 mutation, and might be linked to a symptomatologic and neuropathologic pattern of typical sporadic CJD. This mutation was also present in a sister of the patient who died at the age of 67 without neurologic symptomatology.

Korsakoff's syndrome as the initial presentation of multiple sclerosis

A 37-year-old man presented with an acute amnestic syndrome of Korsakoff's type and an upper brain-stem oculomotor syndrome. After a moderate improvement with steroid therapy, he developed progressive behavioural changes due to a frontal lobe syndrome, in addition to motor and visual impairment. Memory performance was investigated on several occasions during an 11-year follow-up. Diagnosis of laboratory-supported definite multiple sclerosis was established and magnetic resonance imaging showed disseminated white matter lesions, especially in both medial temporal lobes. No other cause than multiple sclerosis was found for the amnestic syndrome. Among the rare cases of Korsakoff's syndrome in the course of multiple sclerosis, this is to our knowledge the first case in which a memory deficit was the initial manifestation of the disease.

The methanoreductosome: a high-molecular-weight enzyme complex in the methanogenic bacterium strain Gö1 that contains components of the methylreductase system

The methanogenic bacterium strain Gö1 harbors a high-molecular-weight enzyme complex containing methyl coenzyme M methylreductase as revealed by immunoelectron microscopy. This complex consists of a spherelike, hollow head piece, in the wall of which a number of copies of the methyl coenzyme M methylreductase are located. It is named Rc (c indicates collector). Intimately bound to it is a group of additional subunits of unknown composition referred to as Rm (m indicates mediator). Electron microscopy of negatively stained samples indicated that Rm contains a functional pore or channel which connects the internal volume of Rc with the outside. The RcRm complex is named Rs (s indicates spherelike). This complex was often found detached from the inside of the cytoplasmic membrane when membrane vesicles were investigated. However, Rs was also seen attached to a third component of the complex located in the membrane, the attachment being mediated by Rm. This membrane part of the complex is designated Rt (t indicates translocator). It consists of subunits with unknown composition. When Rs is attached to the membrane, the pore in Rm appears to be plugged by Rt. This indicates that the internal volume in Rc is in contact, via the pore in Rm, with Rt. The RcRmRt complex is referred to as methanoreductosome. Functional implications of the structural organization of the methylreductase system are discussed in view of methane formation and the creation of a transmembrane proton gradient used by the cell for ATP synthesis.