Tau interactome maps synaptic and mitochondrial processes associated with neurodegeneration

Tau (MAPT) drives neuronal dysfunction in Alzheimer disease (AD) and other tauopathies. To dissect the underlying mechanisms, we combined an engineered ascorbic acid peroxidase (APEX) approach with quantitative affinity purification mass spectrometry (AP-MS) followed by proximity ligation assay (PLA) to characterize Tau interactomes modified by neuronal activity and mutations that cause frontotemporal dementia (FTD) in human induced pluripotent stem cell (iPSC)-derived neurons. We established interactions of Tau with presynaptic vesicle proteins during activity-dependent Tau secretion and mapped the Tau-binding sites to the cytosolic domains of integral synaptic vesicle proteins. We showed that FTD mutations impair bioenergetics and markedly diminished Tau’s interaction with mitochondria proteins, which were downregulated in AD brains of multiple cohorts and correlated with disease severity. These multimodal and dynamic Tau interactomes with exquisite spatial resolution shed light on Tau’s role in neuronal function and disease and highlight potential therapeutic targets to block Tau-mediated pathogenesis.

By combining APEX and AP-MS proteomic approaches, Tau interactome mapping reveals that Tau interactors are modified by neuronal activity and FTD mutations in human iPSC-derived neurons.

Microtubules form by progressively faster tubulin accretion, not by nucleation-elongation

Microtubules are dynamic polymers that play fundamental roles in all eukaryotes. Despite their importance, how new microtubules form is poorly understood. Textbooks have focused on variations of a nucleation–elongation mechanism in which monomers rapidly equilibrate with an unstable oligomer (nucleus) that limits the rate of polymer formation; once formed, the polymer then elongates efficiently from this nucleus by monomer addition. Such models faithfully describe actin assembly, but they fail to account for how more complex polymers like hollow microtubules assemble. Here, we articulate a new model for microtubule formation that has three key features: (1) microtubules initiate via rectangular, sheet-like structures that grow faster the larger they become; (2) the dominant pathway proceeds via accretion, the stepwise addition of longitudinal or lateral layers; and (3) a “straightening penalty” to account for the energetic cost of tubulin’s curved-to-straight conformational transition. This model can quantitatively fit experimental assembly data, providing new insights into biochemical determinants and assembly pathways for microtubule nucleation.

CryoEM and AI reveal a structure of SARS-CoV-2 Nsp2, a multifunctional protein involved in key host processes

The SARS-CoV-2 protein Nsp2 has been implicated in a wide range of viral processes, but its exact functions, and the structural basis of those functions, remain unknown. Here, we report an atomic model for full-length Nsp2 obtained by combining cryo-electron microscopy with deep learning-based structure prediction from AlphaFold2. The resulting structure reveals a highly-conserved zinc ion-binding site, suggesting a role for Nsp2 in RNA binding. Mapping emerging mutations from variants of SARS-CoV-2 on the resulting structure shows potential host-Nsp2 interaction regions. Using structural analysis together with affinity tagged purification mass spectrometry experiments, we identify Nsp2 mutants that are unable to interact with the actin-nucleation-promoting WASH protein complex or with GIGYF2, an inhibitor of translation initiation and modulator of ribosome-associated quality control. Our work suggests a potential role of Nsp2 in linking viral transcription within the viral replication-transcription complexes (RTC) to the translation initiation of the viral message. Collectively, the structure reported here, combined with mutant interaction mapping, provides a foundation for functional studies of this evolutionary conserved coronavirus protein and may assist future drug design.

CryoEM and AI reveal a structure of SARS-CoV-2 Nsp2, a multifunctional protein involved in key host processes

The SARS-CoV-2 protein Nsp2 has been implicated in a wide range of viral processes, but its exact functions, and the structural basis of those functions, remain unknown. Here, we report an atomic model for full-length Nsp2 obtained by combining cryo-electron microscopy with deep learning-based structure prediction from AlphaFold2. The resulting structure reveals a highly-conserved zinc ion-binding site, suggesting a role for Nsp2 in RNA binding. Mapping emerging mutations from variants of SARS-CoV-2 on the resulting structure shows potential host-Nsp2 interaction regions. Using structural analysis together with affinity tagged purification mass spectrometry experiments, we identify Nsp2 mutants that are unable to interact with the actin-nucleation-promoting WASH protein complex or with GIGYF2, an inhibitor of translation initiation and modulator of ribosome-associated quality control. Our work suggests a potential role of Nsp2 in linking viral transcription within the viral replication-transcription complexes (RTC) to the translation initiation of the viral message. Collectively, the structure reported here, combined with mutant interaction mapping, provides a foundation for functional studies of this evolutionary conserved coronavirus protein and may assist future drug design.

Fragment binding to the Nsp3 macrodomain of SARS-CoV-2 identified through crystallographic screening and computational docking

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) macrodomain within the nonstructural protein 3 counteracts host-mediated antiviral adenosine diphosphate-ribosylation signaling. This enzyme is a promising antiviral target because catalytic mutations render viruses nonpathogenic. Here, we report a massive crystallographic screening and computational docking effort, identifying new chemical matter primarily targeting the active site of the macrodomain. Crystallographic screening of 2533 diverse fragments resulted in 214 unique macrodomain-binders. An additional 60 molecules were selected from docking more than 20 million fragments, of which 20 were crystallographically confirmed. X-ray data collection to ultra-high resolution and at physiological temperature enabled assessment of the conformational heterogeneity around the active site. Several fragment hits were confirmed by solution binding using three biophysical techniques (differential scanning fluorimetry, homogeneous time-resolved fluorescence, and isothermal titration calorimetry). The 234 fragment structures explore a wide range of chemotypes and provide starting points for development of potent SARS-CoV-2 macrodomain inhibitors.

Comparative host-coronavirus protein interaction networks reveal pan-viral disease mechanisms

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a grave threat to public health and the global economy. SARS-CoV-2 is closely related to the more lethal but less transmissible coronaviruses SARS-CoV-1 and Middle East respiratory syndrome coronavirus (MERS-CoV). Here, we have carried out comparative viral-human protein-protein interaction and viral protein localization analyses for all three viruses. Subsequent functional genetic screening identified host factors that functionally impinge on coronavirus proliferation, including Tom70, a mitochondrial chaperone protein that interacts with both SARS-CoV-1 and SARS-CoV-2 ORF9b, an interaction we structurally characterized using cryo-electron microscopy. Combining genetically validated host factors with both COVID-19 patient genetic data and medical billing records identified molecular mechanisms and potential drug treatments that merit further molecular and clinical study.

Fragment Binding to the Nsp3 Macrodomain of SARS-CoV-2 Identified Through Crystallographic Screening and Computational Docking

The SARS-CoV-2 macrodomain (Mac1) within the non-structural protein 3 (Nsp3) counteracts host-mediated antiviral ADP-ribosylation signalling. This enzyme is a promising antiviral target because catalytic mutations render viruses non-pathogenic. Here, we report a massive crystallographic screening and computational docking effort, identifying new chemical matter primarily targeting the active site of the macrodomain. Crystallographic screening of diverse fragment libraries resulted in 214 unique macrodomain-binding fragments, out of 2,683 screened. An additional 60 molecules were selected from docking over 20 million fragments, of which 20 were crystallographically confirmed. X-ray data collection to ultra-high resolution and at physiological temperature enabled assessment of the conformational heterogeneity around the active site. Several crystallographic and docking fragment hits were validated for solution binding using three biophysical techniques (DSF, HTRF, ITC). Overall, the 234 fragment structures presented explore a wide range of chemotypes and provide starting points for development of potent SARS-CoV-2 macrodomain inhibitors.

XMAP215 and γ-tubulin additively promote microtubule nucleation in purified solutions

Microtubule nucleation is spatiotemporally regulated in cells by several known molecules, including the template γ-tubulin and the polymerase XMAP215. The role of XMAP215 in nucleation is under debate, specifically whether it acts independently as a polymerase or acts dependently with γ-tubulin. We first confirm XMAP215 as a classically defined nucleator that reduces the nucleation lag seen in bulk tubulin assembly. Secondly, using deletion constructs, we probe the domain requirements for XMAP215 to promote microtubule nucleation. We show that its ability to nucleate microtubules in purified solutions correlates with its ability to elongate existing microtubules and does not depend on the number of tumor overexpressed gene (TOG) domains. Finally, we show that XMAP215 and γ-tubulin promote αβ-tubulin assembly in an additive, not synergistic, manner. Thus, their modes of action during microtubule nucleation are distinct. These findings suggest there are at least two independent processes in nucleation, one promoted by γ-tubulin and one promoted by XMAP215. We propose that XMAP215 accelerates the addition of subunits to existing nucleation intermediates formed either spontaneously or by oligomers of γ-tubulin. [Media: see text].

Pregnancy in Lung Transplant Recipients

Eight female lung transplant recipients, all of whom became pregnant after transplant, were reported to the National Transplantation Pregnancy Registry from US transplant centers. Outcomes of the 8 pregnancies were 4 live births, 3 therapeutic abortions, and 1 spontaneous abortion. Three of the 4 newborns were premature, with low birth weight (< 2500 grams). Rejection during pregnancy occurred in 3 pregnancies (38%). All 8 transplant recipients reported at least 1 complication during pregnancy, including shortness of breath, rejection, and infection. Two of the 4 deliveries were by cesarean section. At follow-up, all children were developing well with no residual problems. Female lung transplant recipients may face higher risks during pregnancy than other solid organ transplant recipients.

[Characterization of the seriously injured cyclist : An evaluation of the injury and treatment focus areas of 2817 patients]

BACKGROUND

Transport statistics classify bicyclists in a separate road user collective. For medical reasons, this differentiation is applied as well. Much literature is published in this field. Nevertheless there is a lack of literature regarding the overall injury patterns in a defined injury severity collective. Most literature is about isolated injured regions in combination with a heterogeneous injury severity. Further parameters, such as injury patterns, epidemiological aspects, treatment focal points and characteristic outcomes, have also been studied. The aim of the present study was to evaluate and characterize injury patterns in a standardized and representative collective of severely injured bicyclists. Methods We analysed data from the Traumaregister DGU® from 2002 to 2010. In total, 2817 severely injured (ISS ≥ 9 and additional intensive/intermediate care unit) bicyclists were included. The primary endpoint was evaluation of injury patterns and injury focal points. In addition to that we analysed parameters like epidemiological aspects, circumstances of accident, treatment focal points and outcome.

RESULTS

The mean age was 50.3 ± 20.9 years. Males accounted for 68.9 % (n = 1940). The mean ISS was 23.7 ± 12.6. The mean AIS regions were the head 71.9 % (n = 2025), the chest with 44.9 % (n = 1264) and the upper extremities 33.6 % (947). In 68.2 % of all cases an ISS ≥ 9 was achieved by a traumatic brain injury; 21.1 % of all cases were mono-injuries. A characteristic distribution of age and a characteristic prevalence of the accidents in relation to the weekday and the month could be shown.

CONCLUSION

The present study analysed the largest ever published collective of severely injured bicyclists. Traumatic brain injury could clearly be shown as the main injury in this collective. Moreover, one of five cases achieved the state "severely injured" due to mono-injury.

Higher-order oligomerization of Spc110p drives γ-tubulin ring complex assembly

Assembly of the microtubule-nucleating γ-tubulin ring complex (γTuRC) requires higher-order oligomerization of Spc110p, which connects γTuRC to the yeast spindle pole body (SPB). Because Spc110p is highly concentrated at the SPB, spatial regulation of microtubule nucleation is thus achieved by exclusive assembly of γTuRCs proximal to the SPB.

The microtubule (MT) cytoskeleton plays important roles in many cellular processes. In vivo, MT nucleation is controlled by the γ-tubulin ring complex (γTuRC), a 2.1-MDa complex composed of γ-tubulin small complex (γTuSC) subunits. The mechanisms underlying the assembly of γTuRC are largely unknown. In yeast, the conserved protein Spc110p both stimulates the assembly of the γTuRC and anchors the γTuRC to the spindle pole body. Using a quantitative in vitro FRET assay, we show that γTuRC assembly is critically dependent on the oligomerization state of Spc110p, with higher-order oligomers dramatically enhancing the stability of assembled γTuRCs. Our in vitro findings were confirmed with a novel in vivo γTuSC recruitment assay. We conclude that precise spatial control over MT nucleation is achieved by coupling localization and higher-order oligomerization of the receptor for γTuRC.

Serotype Diversity of Foot-and-Mouth-Disease Virus in Livestock without History of Vaccination in the Far North Region of Cameroon

Little information is available about the natural cycle of foot-and-mouth disease (FMD) in the absence of control measures such as vaccination. Cameroon presents a unique opportunity for epidemiological studies because FMD vaccination is not practiced. We carried out a prospective study including serological, antigenic and genetic aspects of FMD virus (FMDV) infections among different livestock production systems in the Far North of Cameroon to gain insight into the natural ecology of the virus. We found serological evidence of FMDV infection in over 75% of the animals sampled with no significant differences of prevalence observed among the sampled groups (i.e. market, sedentary, transboundary trade and mobile). We also found antibodies reactive to five of the seven FMDV serotypes (A, O, SAT1, SAT2 and SAT3) among the animals sampled. Finally, we were able to genetically characterize viruses obtained from clinical and subclinical FMD infections in Cameroon. Serotype O viruses grouped into two topotypes (West and East Africa). SAT2 viruses grouped with viruses from Central and Northern Africa, notably within the sublineage causing the large epidemic in Northern Africa in 2012, suggesting a common origin for these viruses. This research will guide future interventions for the control of FMD such as improved diagnostics, guidance for vaccine formulation and epidemiological understanding in support of the progressive control of FMD in Cameroon.

Data-Driven Models of Foot-and-Mouth Disease Dynamics: A Review

Foot-and-mouth disease virus (FMDV) threatens animal health and leads to considerable economic losses worldwide. Progress towards minimizing both veterinary and financial impact of the disease will be made with targeted disease control policies. To move towards targeted control, specific targets and detailed control strategies must be defined. One approach for identifying targets is to use mathematical and simulation models quantified with accurate and fine-scale data to design and evaluate alternative control policies. Nevertheless, published models of FMDV vary in modelling techniques and resolution of data incorporated. In order to determine which models and data sources contain enough detail to represent realistic control policy alternatives, we performed a systematic literature review of all FMDV dynamical models that use host data, disease data or both data types. For the purpose of evaluating modelling methodology, we classified models by control strategy represented, resolution of models and data, and location modelled. We found that modelling methodology has been well developed to the point where multiple methods are available to represent detailed and contact-specific transmission and targeted control. However, detailed host and disease data needed to quantify these models are only available from a few outbreaks. To address existing challenges in data collection, novel data sources should be considered and integrated into models of FMDV transmission and control. We suggest modelling multiple endemic areas to advance local control and global control and better understand FMDV transmission dynamics. With incorporation of additional data, models can assist with both the design of targeted control and identification of transmission drivers across geographic boundaries.

Interaction of CK1δ with γTuSC ensures proper microtubule assembly and spindle positioning

Casein kinase 1δ (CK1δ) family members associate with microtubule-organizing centers from yeast to humans. Budding yeast CK1δ, Hrr25, directly phosphorylated γTuSC proteins in vivo and in vitro, and this phosphorylation promoted δTuSC integrity and activity in biochemical assays.

Casein kinase 1δ (CK1δ) family members associate with microtubule-organizing centers (MTOCs) from yeast to humans, but their mitotic roles and targets have yet to be identified. We show here that budding yeast CK1δ, Hrr25, is a γ-tubulin small complex (γTuSC) binding factor. Moreover, Hrr25's association with γTuSC depends on its kinase activity and its noncatalytic central domain. Loss of Hrr25 kinase activity resulted in assembly of unusually long cytoplasmic microtubules and defects in spindle positioning, consistent with roles in regulation of γTuSC-mediated microtubule nucleation and the Kar9 spindle-positioning pathway, respectively. Hrr25 directly phosphorylated γTuSC proteins in vivo and in vitro, and this phosphorylation promoted γTuSC integrity and activity. Because CK1δ and γTuSC are highly conserved and present at MTOCs in diverse eukaryotes, similar regulatory mechanisms are expected to apply generally in eukaryotes.

Kinetic model of hydrogen generation by Rhodobacter sphaeroides in the presence of NH ions

AIMS

To examine the effects of ammonium ion concentration and illumination intensity on the effectivness of the hydrogen generation process of Rhodobacter sphaeroides.

METHODS AND RESULTS

In all experiments the amount of evolved hydrogen, biomass growth, concentration of ammonium ions, pH and chemical oxygen demand were measured. A nonstructural kinetic model was applied in description of biomass growth, the amount of evolved hydrogen and consumption of organic compounds and ammonium ions. An increase of ammonium ions concentration resulted in a decrease of maximal specific hydrogen potential production. At higher ammonium ion concentrations, no hydrogen evolution was observed. The efficiency of malic acid conversion into hydrogen and the PHB content in the biomass were the highest with lower concentrations of nitrogen compounds.

CONCLUSION

The presence of ammonium ions inhibits hydrogen photogeneration. A good agreement between the experimental data and model simulations were obtained. In all cases, hydrogen evolution started after an exhaustion of ammonium ions and the increase was proportional to the C/N ratio in the medium. The accumulation of PHB competes with the hydrogen evolution process while the conversion of acids into biomass was limited at higher levels of hydrogen generation.

SIGNIFICANCE AND IMPACT OF THE STUDY

Confirmation of the suitability of the selected model for kinetic studies of hydrogen photoevolution.

Low discomfort and pain associated with intensified insulin therapy in children and adolescents

OBJECTIVE

Discomfort during insulin injection and self-monitoring of blood glucose (SMBG) is a potential obstacle in diabetes therapy, but its prevalence and extent in relation to clinical variables is uncertain.

RESEARCH DESIGN AND METHODS

We prospectively assessed treatment-associated discomfort and pain in an unselected cohort of patients (60 boys and 52 girls; mean age 14.6+/-3.0 years, mean A1C 8.0+/-1.4%) with type 1 diabetes and multiple daily self-injections of insulin, using visual analogue/verbal rating scales (range, 0-10) and a six-item questionnaire.

RESULTS

Pain during insulin injection was absent to very low in 91.9% of patients, and its intensity was independent of age, gender, diabetes duration, current A1C, injection volume, or type of insulin. Injection was more unpleasant than SMBG in 64.2% of patients (mean difference of pain score, 1.0+/-1.7, p<0.0001). Injection into the upper arm was less painful than into the thigh and abdomen. Surprisingly, painlessness of injection and SMBG was not judged an important treatment goal by 22.0 and 32.9% of patients, respectively. Logistic difficulties (41.2% of responses) and time requirements (23.8%), but not pain (10.1%), were considered most relevant problems.

CONCLUSIONS

In young patients with access to optimized diabetes care, pain during insulin injection and SMBG is infrequent or mild, and not widely perceived as problematic, thus encouraging the use of multiple daily injection treatment.

[Management of accidental hypothermia]

Patients with hypothermia are frequently encountered in emergency medicine. Particularly trauma patients, but also other predisposed persons, can be expected to suffer from hypothermia at any time of the year. Therapy focuses not only on symptom-oriented intensive care to stabilize and secure vital functions, but also on rewarming. Even in cases of severe hypothermia with circulatory arrest, therapy can produce excellent results. This paper first gives a brief overview of the typical clinical symptoms of hypothermia, before giving a detailed description of the preclinical and in-hospital management of the hypothermia patient. The various rewarming strategies are the subject of special attention and critical evaluation.

Preparing cytoplasmic extracts from Drosophila embryos

INTRODUCTIONIn recent years, Drosophila has been an excellent source for biochemical quantities of proteins involved in a variety of cellular processes, such as cytoskeletal function and RNA binding. It is relatively simple to obtain a high-quality Drosophila embryonic cytoplasmic extract for protein purification or biochemistry, if population cages are used that produce at least 5 g of embryos during a 3-hour period. Smaller quantities of embryos can be used to produce extracts for in vitro biochemical assays. This protocol describes the collection and dechorionation of Drosophila embryos and the preparation of cytoplasmic extracts.

Aspirin and Clopidogrel Taken Until 2 Days Prior to Coronary Artery Bypass Graft Surgery Is Associated with Increased Postoperative Drainage Loss

OBJECTIVE

Platelet aggregation inhibitors, such as aspirin and clopidogrel, are associated with increased bleeding in patients undergoing cardiac surgery with cardiopulmonary bypass. We investigated the impact of time between the last intake of aspirin and clopidogrel before CABG surgery and drainage loss, transfusion requirements and rate of reoperation.

PATIENTS AND METHODS

The records of patients who had coronary artery bypass graft surgery (CABG) were reviewed for intake of aspirin and clopidogrel within 7 days prior to surgery. Drainage loss, transfusion requirements and rate of reoperation for bleeding within 5 days after the operation, were recorded.

RESULTS

Out of 261 analysed patients, 225 patients (86.2 %) had no anti-platelet medication and 36 patients (13.8 %) were on aspirin and clopidogrel. Aspirin and clopidogrel, taken all until 2 days prior to operation, were associated with a significantly higher postoperative blood loss (1840 mL [1230 - 3710] vs. 280 mL [185 - 765], p = 0.005 for one day and 850 mL [345 - 1725] vs. 277 mL [165 - 778], p = 0.026, for 2 days prior to surgery). The trend showed that patients in the study group received more platelet concentrates (PC: 5.3 % vs. 13.9 %, p = 0.067). The rate of reoperation for bleeding was not different ( p = 0.25).

CONCLUSION

Aspirin and clopidogrel up to 2 days prior to CABG were associated with a significantly higher postoperative drainage loss.

Safety and efficacy of living donor liver preservation with HTK solution

BACKGROUND

In living donor liver transplantation (LDLTx) organ procurement is usually well controlled, and allows to assess liver preservation and graft function under standardized conditions. Because publications on histidine-tryptophan-ketoglutarate (HTK) solution are limited, we prospectively studied its safety and efficacy in a consecutive series of LDLTx.

METHODS

Twenty-four patients received 22 right, 1 left, and 1 left lateral lobe graft. Liver preservation was done by gravity perfusion with HTK through portal vein, and hepatic artery, and flushing of bile ducts. Total ischemia time was 191 +/- 68 minutes.

RESULTS

There was no primary nonfunction, and all partial liver grafts showed good recovery: peak aspartate aminotransferase 577 U/L, total bilirubin 15.15 mg/dL, and partial thromboplastin time 49.37 seconds. One graft was lost from parenchymal fracture secondary to portal hyperperfusion after 6 days, and the patient was salvaged with retransplantation. Thirty-day mortality, including sudden cardiac death, pancreatitis, and hepatic artery rupture, was not related to graft dysfunction. Eight of 24 recipients developed early biliary leakage. There was no late ischemic type biliary lesion.

CONCLUSION

These results confirm that HTK solution is safe and effective when used in LDLTx. Potential advantages of HTK in comparison to other preservation solutions are low potassium concentration, low viscosity, no particles, in situ perfusion, no need to flush before reperfusion, improved biliary protection, better recovery of microcirculatory changes, ready to use, and lower costs. Because the risk-benefit ratio is of particular importance in LDLTx the use of HTK solution should be encouraged.

What Is the Best Immunosuppression in Living Donor Liver Transplantation?

INTRODUCTION

As we have learned, there are no golden rules of immunosuppression in solid organ transplantation, and every transplant program is using its own regimen to prevent or treat rejection. We have retrospectively analyzed the incidence and severity of acute rejection in a consecutive series of living donor liver transplants. The major objective during the whole study period was to ultimately avoid any steroids from the beginning.

METHODS

Twenty one adult patients and five children received 23 right, one left, and two left lateral lobe grafts from genetically or emotionally related living donors, including four ABO-incompatible pairs. The majority of patients had triple initial immunosuppression, based on tacrolimus, mycophenolate mofetil or sirolimus, and basiliximab or daclizumab. Except methylprednisolone administered before reperfusion in 13 patients, only seven had prednisolone after transplantation, and 12/26 had a completely steroid-free regimen.

RESULTS

The overall incidence of biopsy-proven acute rejection was 4/21 in adults (19%) and 4/5 in children (80%). Rejections were mild in five and moderate in three cases, respectively, and easily reversed with steroids in all patients. Different combinations of immunosuppressive drugs or ABO incompatibility did not seem to have an influence on the risk of rejection.

CONCLUSION

Despite the small number of patients in this series, completely steroid-free triple-drug immunosuppression with tacrolimus, mycophenolate mofetil, and basiliximab is safe and efficient to prevent acute rejection in adult recipients of living donor liver transplants. At least short-term administration of prednisolone should be considered in pediatric patients.

Simulect induction facilitates neoral-based steroid-free immunosuppression in primary kidney transplant recipients

This study compares outcomes of kidney transplantation with two distinct induction protocols Basiliximab (Simulect) versus Muromonab (OTK 3) in the setting of cyclosporine (Neoral)-based immunosuppression. Postinduction protocols included either total prednisone avoidance or prednisone sparing versus standard prednisone dosing. Two hundred forty five adult patients receiving kidney transplantation between 1995 and 2000 were included in the study. Treatment in group 1 was OKT 3 + Neoral + adjunct + standard prednisone; group 2, Simulect + Neoral + adjunct + steroid sparing; group 3, Simulect + Neoral + adjunct + no prednisone. The demographics between all groups were similar. The mean (+/- SD) trough cyclosporine levels at 1 month were 276 +/- 128 versus 291 +/- 180 versus 398 +/- 365 (P=.020); at 3 months were 261 +/- 120 versus 280 +/- 152 versus 399 +/- 408 (P=.32); at 12 month were 235 +/- 144 versus 245 +/- 154 versus 234 +/- 132 (P=.96). Creatinine clearance at 1 month was 59 +/- 24 versus 58 +/- 18 versus 47 +/- 23 mL/min (P=.004); at 3 months was 66 +/- 28 versus 62 +/- 22 versus 53 +/- 25 mL/min (P=.007); at 12 months was 68 +/- 38 versus 65 +/- 22 versus 64 +/- 29 mL/min (P=.556). Serum creatinine at 1 month was 1.8 +/- 0.9 versus 1.6 +/- 1.2 versus 2.8 +/- 2.21 mg/dL (P=.005); at 3 months was 1.7 +/- 0.6 versus 1.9 +/- 1.0 versus 2.3 +/- 1.3 mg/dL (P=.007); at 12 months was 1.9 +/- 1.3 versus 2.1 +/- 1.0 versus 2.3 +/- 1.7 mg/dL (P=.179). The incidence of acute rejection within 1 year in the respective groups were 28% versus 15% versus 16%. Therefore, we conclude that using Simulect in transplant recipients results in long-term patient and graft survival similar to those achieved with OKT 3. The use of Simulect resulted in significant reduction in clinical rejection incidence within the first year regardless of steroid use. Thus, the use of Simulect allows complete steroid avoidance in Neoral-based immunosuppression regimen.

GCP5 and GCP6: two new members of the human gamma-tubulin complex

The gamma-tubulin complex is a large multiprotein complex that is required for microtubule nucleation at the centrosome. Here we report the purification and characterization of the human gamma-tubulin complex and the identification of its subunits. The human gamma-tubulin complex is a ring of ~25 nm, has a subunit structure similar to that reported for gamma-tubulin complexes from other species, and is able to nucleate microtubule polymerization in vitro. Mass spectrometry analysis of the human gamma-tubulin complex components confirmed the presence of four previously identified components (gamma-tubulin and gamma-tubulin complex proteins [GCPs] 2, 3, and 4) and led to the identification of two new components, GCP5 and GCP6. Sequence analysis revealed that the GCPs share five regions of sequence similarity and define a novel protein superfamily that is conserved in metazoans. GCP5 and GCP6, like other components of the gamma-tubulin complex, localize to the centrosome and associate with microtubules, suggesting that the entire gamma-tubulin complex takes part in both of these interactions. Stoichiometry experiments revealed that there is a single copy of GCP5 and multiple copies of gamma-tubulin, GCP2, GCP3, and GCP4 within the gamma-tubulin complex. Thus, the gamma-tubulin complex is conserved in structure and function, suggesting that the mechanism of microtubule nucleation is conserved.

Impact of residual renal function in children on hemodialysis

Residual renal function (RRF) contributes to dialysis adequacy as well as lower mortality and morbidity in dialysis patients. Even very small changes in glomerular filtration rate (GFR) account for considerable improvements in complications of dialysis. The purpose of this cross-sectional study is to determine the possible contribution of RRF to hemodialysis clearance and to compare the biochemical markers of this patient group with anuric patients. Ten patients with RRF on chronic hemodialysis for more than 6 months were enrolled in the study. Duration of dialysis was not different between the two patient populations. Average GFR was 3.4+/-2.6 ml/min in the group with RRF. Cholesterol, albumin, and triglyceride levels were not different between the groups. Residual renal urea clearance enhanced mean Kt/V of patients from 1.29 to 1.52. However erythropoietin and renin levels were higher in the group with RRF (P=0.019, P=0.044, respectively). There was a positive correlation between erythropoietin, renin levels, and average GFR of all patients (r=0.69, P=0.002, r=0.60, P=0.014). We conclude that RRF plays a greater role in pediatric patients on hemodialysis than previously recognized, and knowledge about patients' RRF should assist in improved overall management.

Gamma-tubulin complexes and microtubule nucleation

Microtubules are dynamic cytoskeletal polymers that assemble from alpha/beta-tubulin and are vital for the establishment of cell polarity, vesicle trafficking and formation of the mitotic/meiotic spindle. gamma-Tubulin, a protein related to alpha/beta-tubulin, is required for initiating the polymerization of microtubules in vivo. gamma-Tubulin has been found in two main protein complexes: the gamma-tubulin ring complex and its subunit, the gamma-tubulin small complex. The latter is analogous to the yeast Tub4 complex. In the past year, important advances have been made in understanding the structure and function of the gamma-tubulin ring complex and how it interacts with microtubules.

Activating mineralocorticoid receptor mutation in hypertension exacerbated by pregnancy

Hypertension and pregnancy-related hypertension are major public health problems of largely unknown causes. We describe a mutation in the mineralocorticoid receptor (MR), S810L, that causes early-onset hypertension that is markedly exacerbated in pregnancy. This mutation results in constitutive MR activity and alters receptor specificity, with progesterone and other steroids lacking 21-hydroxyl groups, normally MR antagonists, becoming potent agonists. Structural and biochemical studies indicate that the mutation results in the gain of a van der Waals interaction between helix 5 and helix 3 that substitutes for interaction of the steroid 21-hydroxyl group with helix 3 in the wild-type receptor. This helix 5-helix 3 interaction is highly conserved among diverse nuclear hormone receptors, suggesting its general role in receptor activation.

Structure of the gamma-tubulin ring complex: a template for microtubule nucleation

The gamma-tubulin ring complex (gammaTuRC) is a protein complex of relative molecular mass approximately 2.2 x 10(6) that nucleates microtubules at the centrosome. Here we use electron-microscopic tomography and metal shadowing to examine the structure of isolated Drosophila gammaTuRCs and the ends of microtubules nucleated by gammaTuRCs and by centrosomes. We show that the gammaTuRC is a lockwasher-like structure made up of repeating subunits, topped asymmetrically with a cap. A similar capped ring is also visible at one end of microtubules grown from isolated gammaTuRCs and from centrosomes. Antibodies against gamma-tubulin label microtubule ends, but not walls, in centrosomes. These data are consistent with a template-mediated mechanism for microtubule nucleation by the gammaTuRC.

Pregnancy in lung transplant recipients

Eight female lung transplant recipients, all of whom became pregnant after transplant, were reported to the National Transplantation Pregnancy Registry from US transplant centers. Outcomes of the 8 pregnancies were 4 live births, 3 therapeutic abortions, and 1 spontaneous abortion. Three of the 4 newborns were premature, with low birth weight (< 2500 grams). Rejection during pregnancy occurred in 3 pregnancies (38%). All 8 transplant recipients reported at least 1 complication during pregnancy, including shortness of breath, rejection, and infection. Two of the 4 deliveries were by cesarean section. At follow-up, all children were developing well with no residual problems. Female lung transplant recipients may face higher risks during pregnancy than other solid organ transplant recipients.

Erythropoietin response to post-liver transplantation anemia

Anemia frequently accompanies end-stage liver disease. Erythropoietin has recently been shown to be of benefit in a number of diseases complicated by anemia. We studied erythropoietin levels before and after orthotopic liver transplantation (OLT) and correlated these with the degree of anemia. Twenty-seven patients with end-stage cirrhosis who underwent OLT had preoperative and weekly postoperative serum erythropoietin levels determined by a highly sensitive radioimmunoassay. The relation of erythropoietin level to the values for hematocrit, serum creatinine, and cyclosporine and other biochemical test results was evaluated. Before transplantation, 23 patients were anemic; erythropoietin levels were appropriately elevated (72.7 +/- 37 mU/mL; normal, 10 to 15 mU/mL) for the degree of anemia (hematocrit, 33.1% +/- 1%) in 16 patients (70%). A blunted erythropoietin response to anemia was found in 7 of the anemic patients with cirrhosis (30%). After OLT, the hematocrit decreased to 29.5% +/- 0.6% at 4 weeks, with a reciprocal increase in serum erythropoietin levels to 36 +/- 5 mU/mL. Erythropoietin response appeared appropriate to the degree of anemia in 82% of the liver transplant recipients and blunted in 18%. We conclude that the ability to secrete erythropoietin in response to anemia is defective in many patients with end-stage liver disease, and a normal response may be restored after OLT. The results suggest that exogenous erythropoietin administration may be beneficial in anemic patients with cirrhosis and liver transplant recipients who have inappropriately low serum erythropoietin levels.

Recruitment of the gamma-tubulin ring complex to Drosophila salt-stripped centrosome scaffolds

Extracting isolated Drosophila centrosomes with 2 M KI generates salt-resistant scaffolds that lack the centrosomal proteins CP190, CP60, centrosomin, and gamma-tubulin. To clarify the role of these proteins in microtubule nucleation by centrosomes and to identify additional centrosome components required for nucleation, we have developed an in vitro complementation assay for centrosome function. Centrosome aster formation is reconstituted when these inactive, salt-stripped centrosome scaffolds are supplemented with a soluble fraction of a Drosophila embryo extract. The CP60 and CP190 can be removed from this extract without effect, whereas removing the gamma-tubulin destroys the complementing activity. Consistent with these results, we find no evidence that these three proteins form a complex together. Instead, gamma-tubulin is found in two distinct protein complexes of 240,000 and approximately 3,000,000 D. The larger complex, which is analogous to the Xenopus gamma-tubulin ring complex (gammaTuRC) (Zheng, Y., M.L. Wong, B. Alberts, and T. Mitchison. 1995. Nature. 378:578-583), is necessary but not sufficient for complementation. An additional factor found in the extract is required. These results provide the first evidence that the gammaTuRC is required for microtubule nucleation at the centrosome.

Casted titanium for dental applications: an XPS and SEM study

Casted titanium for dental crowns has been investigated by means of X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The samples were prepared according to the Ohara process. XRD analysis revealed that the investment consisted essentially of SiO2, Mg2P2O7, SiO2 x H2O and Mg2SiO4. SEM experiments combined with EDX analysis revealed the following atomic concentrations Si (62.6%), Mg (19.7%), P (17.1%), and Ca (0.6%). After casting, the titanium samples exhibit a rough and irregular surface, and XRD analysis indicated that titanium contains essentially the alpha phase and traces of the beta phase. After demoulding titanium samples, the investment side which was in contact with titanium was black colored, proving the reaction between titanium and the investment. XPS analysis performed on this side of the investment indicated that the Si 2p peak presents a shoulder on the low binding energy side and thus suggest that SiO2 has been transformed into metallic Si.

[What is thought of the various surface treatments of biomaterials used in dental and maxillofacial implantology?]

The surface treatments for biomaterials have the following goals: to increase the biocompatibility and the tissue acceptation, to prevent infection to reduce the abrupt interfaces; to favour the biological integration and the long term in service behaviour. Advantages and inconveniences of these methods are analysed for the main biomaterials categories: metals, synthetic polymers, ceramics, materials of biological origin. In addition to appropriate physico-chemical and mechanical properties, the existence of biologically functional interfaces with the living cells is more and more wished. In the next 20 years, it appears likely that the design of prostheses or implants in actual clinical use will have to be totally or partly reconsidered.

Surface characterization of C/Ti-6Al-4V coating treated with ion beam

Surface of titanium alloy (Ti-6AI-4V) has been modified by ion beam mixing of thin C film. X-ray photoelectron spectroscopy analysis showed that after mixing, the surface film consists essentially of a Ti compound containing (Ti, O and C), TiO2, Ti and C contamination. The composition of the surface modified film determined by Rutherford backscattering spectrometry is approximately Ti0.5O0.3C0.2 and its thickness is about 200 nm. After three months immersion in a simulated body fluid, the growth of calcium phosphate species containing both HPO4- and H2PO4- (probably CaHPO4 and Ca(HPO4)2) have been observed. Titanium is found to be essentially composed of the Ti compound after immersion suggesting that both metallic Ti and TiO2 have dissolved.

Magnetic resonance of the disk of the temporomandibular joint. MR imaging protocol

Disk displacement can be well detected using proton density-weighted and T2*-weighted two-dimensional gradient-echo sequences. In uncertain cases, especially if the bilaminar zone is not sufficiently represented, a contrast-enhanced T1-weighted spin-echo sequence should also be performed. Also in patients with disk degeneration and osteoarthritis of the temporomandibular joint, proton density-weighted and T2*-weighted two-dimensional gradient-echo sequences are of great diagnostic value. In this collective, however, T1-weighted contrast-enhanced spin-echo sequences should be generally performed, to demonstrate inflammatory reaction of the synovia.

Microtubule nucleation by gamma-tubulin-containing rings in the centrosome

The microtubule cytoskeleton of animal cells does not assemble spontaneously, but instead requires the centrosome. This organelle consists of a pair of centrioles surrounded by a complex collection of proteins known as the pericentriolar material (PCM). The PCM is required for microtubule nucleation. The minus, or slow-growing, ends of microtubules are embedded in the PCM and the plus, or fast-growing, ends project outwards into the cytoplasm during interphase, or into the spindle apparatus during mitosis. gamma-Tubulin is the only component of the PCM that is so far implicated in microtubule nucleation. Here we use immuno-electron microscopic tomography to show that gamma-tubulin is localized in ring structures in the PCM of purified centrosomes without microtubules. When these centrosomes are used to nucleate microtubule growth, gamma-tubulin is localized at the minus ends of the microtubules. We conclude that microtubule-nucleating sites within the PCM are ring-shaped templates that contain multiple copies of gamma-tubulin.

Three-dimensional structural characterization of centrosomes from early Drosophila embryos

An understanding of the mechanism and structure of microtubule (MT)-nucleating sites within the pericentriolar material (PCM) of the centrosome has been elusive. This is partly due to the difficulty in obtaining large quantities of centrosomes for analysis, as well as to the problem of attaining interpretable structural data with conventional EM techniques. We describe a protocol for isolating a large quantity of functional centrosomes from early Drosophila embryos. Using automated electron tomography, we have begun a three-dimensional structural characterization of these intact centrosomes with and without regrown MTs. Reconstructions of the centrosomes to approximately 6-8 nm resolution revealed no large structures at the minus ends of MTs, suggesting that if MT-nucleating material physically contacts the MTs, it must conform closely to the shape of the minus end. While many MTs originate near the centrioles, MT minus ends were found throughout the PCM, and even close to its outer boundary. The MTs criss-crossed the PCM, suggesting that nucleating sites are oriented in many different directions. Reconstructions of centrosomes without MTs suggest that there is a reorganization of the PCM upon MT regrowth; moreover, ring-like structures that have a similar diameter as MTs are apparent in the PCM of centrosomes without MTs, and may be MT-nucleating sites.

Comparative study of results of electronic axiography with results of magnetic resonance imaging including MRI-assisted splint therapy

The most common temporomandibular joint disturbance is the internal derangement. Its prevalence has been shown to be as high as 28%. The purpose of this study was on one hand to compare the diagnostic efficiency of an electronic axiographic system with magnetic resonance imaging, and, on the other hand to evaluate the results of MRI-assisted treatment monitoring of occlusal splint therapy. The results of this survey clearly show that in evaluation of temporomandibular joint disorders, electronic axiography and magnetic resonance imaging should be used in conjunction with one another to increase the accuracy of positive and differentiated diagnoses. The medical concept of disc recapture involving the use of occlusal splints seems to be merely a clinical term which is not necessarily hinged on anatomical intraarticular changes.

Long-term results after primary restoration of the orbital floor

It has been possible to follow-up 74 (54%) of the 137 patients who were treated for orbital floor fractures in our clinic between 1988 and 1992. The minimum observation time was 12 months. The results of the orbital reconstruction were analysed on the basis of the postoperative findings and the advantages of access via a central lower lid incision and the use of allogenic dura mater, were evaluated on the basis of the functional results. The biocompatibility, stability and ready availability of allogenic dura mater all support its use in orbital floor restoration. Nevertheless, the potential problems of CJD transmission are discussed.

[Indications for and pertinence of 3D tomodensitometry in panfacial fractures]

Successful treatment of panfacial fractures is dependent on precise clinical and radiological examinations. However, the complexity of fracture lines accounts for the problems and inadequacies of plain films. Three-dimensional CT-reconstruction is recommended to help the maxillofacial surgeon to conceptualize the overall injury. Subsequently, a case involving complex panfacial fractures is presented and the potential value of three-dimensional computed tomography is discussed.