Influence of Covid-19 disease on hemostasis dynamics during extracorporeal membrane oxygenation (ECMO)1

INTRODUCTION

COVID-19 causes a considerable degradation of pulmonary function to the point of an acute respiratory distress syndrome (ARDS). Over the course of the disease the gas exchange capability of the lung can get impaired to such an extent that extracorporeal membrane oxygenation (ECMO) is needed as a life-saving intervention. In patients COVID-19 as well as ECMO may cause severe coagulopathies which manifest themselves in micro and macro thrombosis. Previous studies established D-dimers as a marker for critical thrombosis of the ECMO system while on admission increased D-dimers are associated with a higher mortality in COIVD-19 patients. It is therefore crucial to determine if COVID-19 poses an increased risk of early thrombosis of the vital ECMO system.

METHODS

40 patients who required ECMO support were enrolled in a retrospective analysis and assigned into 2 groups. The COVID group consist of 20 COVID-19 patients who required ECMO support (n = 20), whereas 20 ECMO patients without COVID-19 were assigned to the control group. D-dimers, fibrinogen, antithrombin III (AT III), lactate dehydrogenase (LDH) and platelet count were analysed using locally weighted scatterplot smoothing and MANOVAs.

RESULTS

The analysis of both groups shows highly significant differences in the dynamics of hemostasis. The increase in D-dimers that is associated with thrombosis of the ECMO systems occurs in COVID-19 patients around 2 days earlier (p = 2,8115 10-11) while fibrinogen is consumed steadily. In the control group fibrinogen levels increase rapidly after ten days with a plateau phase of around five days (p = 1,407 10-3) . Both groups experience a rapid increase in AT III after start of support by ECMO (p = 5,96 10-15). In the COVID group platelet count decreased from 210 giga/l to 130 giga/l within eight days, while in the same time span in the control group platelets decreased from 180 giga/l to 105 giga/l (p = 1,1 10-15). In both groups a marked increase in LDH beyond 5000 U/l occurs (p = 3,0865 10-15).

CONCLUSION

The early increase in D-dimers and decrease in fibrinogen suggests that COVID-19 patients bear an increased risk of early thrombosis of the ECMO system compared to other diseases treated with ECMO. Additionally, the control group shows signs of severe inflammation 10 days after the start of ECMO which were absent in COVID-19 patients.

Relationship between nutritional goals and pressure injuries in critical care patients receiving enteral nutrition

OBJECTIVE

To examine the relationship between pressure injury (PI) development and achievement of nutritional goals (protein and caloric), as well as consider the clinical conditions, hospitalisation factors, and risk assessment for PI development in patients who are critically ill and receiving enteral nutrition (EN) in the intensive care unit (ICU).

METHOD

An observational cohort study was conducted in the ICU of the University Hospital in São Paulo, Brazil. Inclusion criteria were as follows: age ≥18 years; length of ICU stay ≥24 hours; without PI at ICU admission; and receiving EN exclusively during ICU stay. The development of PI was considered the dependent variable. The Chi-squared test was applied to compare categorical variables, and the Mann-Whitney U test was used to compare continuous variables between groups of patients with and without a PI. The analysis of the achievement of nutritional goals was performed using Fisher's exact test. A significance level of 5% (p-value<0.05) and a confidence interval (CI) of 95% was adopted in all statistical tests.

RESULTS

A total of 181 patients met the inclusion criteria, of whom 102 (56.4%) were male and 79 (43.6%) were female. Mean age was 55.1 years, and mean length of ICU stay was 17.5 days. PI development was associated with not achieving nutritional goals. There was a higher percentage (65.3%) of patients without a PI when both protein and caloric goals were achieved. In contrast, 45.6% of patients developed a PI when the goals were not achieved. The mean days for sedation, vasoactive drugs and mechanical ventilation were all significantly higher in patients who developed a PI (p<0.001).

CONCLUSION

There was a significant association between patients developing a PI and deficits in caloric and protein intake. Patients who did not develop PIs had a greater calorie and protein intake compared with those who developed a PI.

[Improved quality of stored packed red blood cells by mechanical rinsing]

BACKGROUND

The transfusion of packed red blood cells (PRBC) is associated with various side effects, including storage damage to PRBCs. The cells change their structure, releasing potassium as well as lactate. Mechanical rinsing, available in many hospitals, is able to remove toxic substances and possibly minimizes the negative side effects of transfusion.

OBJECTIVE

The primary aim of our study was to improve the quality of PRBCs before transfusion. The effects of different washing solutions on PRBC quality were analyzed.

MATERIAL AND METHODS

This in vitro study compares 30 mechanically washed PRBCs. They were either processed with standard normal saline 0.9% (n = 15, N group) or a hemofiltration solution containing 4 mmol/l potassium (n = 15, HF group) by a mechanical rinsing device (Xtra, LivaNova, Munich, Germany). A subgroup analysis was performed based on the storage duration of the processed PRBCs (7, 14, 37 days). Samples were taken before washing (EKprä), immediately after washing (EKpost) and 10 h later (EKpost10h), after storage in the "wash medium" at room temperature. Concentrations of ATP (probability of survival in transfused erythrocytes), lactate, citrate and electrolytes (potassium, sodium, chloride, calcium) were tested.

RESULTS AND CONCLUSION

Mechanical rinsing improves pretransfusion quality of PRBC. Washing with a hemofiltration solution results in a more physiological electrolyte composition. Even 10 h after mechanical rinsing with a hemofiltration solution, the quality of 37-day-old PRBC is comparable to young PRBC that have been stored for 7 days and have not been washed. Washing stored PRBC increases the ATP content, which subsequently leads to an increased probability of survival of red cells after transfusion.

Differences Between MR Brain Region Segmentation Methods: Impact on Single-Subject Analysis

For the segmentation of magnetic resonance brain images into anatomical regions, numerous fully automated methods have been proposed and compared to reference segmentations obtained manually. However, systematic differences might exist between the resulting segmentations, depending on the segmentation method and underlying brain atlas. This potentially results in sensitivity differences to disease and can further complicate the comparison of individual patients to normative data. In this study, we aim to answer two research questions: 1) to what extent are methods interchangeable, as long as the same method is being used for computing normative volume distributions and patient-specific volumes? and 2) can different methods be used for computing normative volume distributions and assessing patient-specific volumes? To answer these questions, we compared volumes of six brain regions calculated by five state-of-the-art segmentation methods: Erasmus MC (EMC), FreeSurfer (FS), geodesic information flows (GIF), multi-atlas label propagation with expectation–maximization (MALP-EM), and model-based brain segmentation (MBS). We applied the methods on 988 non-demented (ND) subjects and computed the correlation (PCC-v) and absolute agreement (ICC-v) on the volumes. For most regions, the PCC-v was good (>0.75), indicating that volume differences between methods in ND subjects are mainly due to systematic differences. The ICC-v was generally lower, especially for the smaller regions, indicating that it is essential that the same method is used to generate normative and patient data. To evaluate the impact on single-subject analysis, we also applied the methods to 42 patients with Alzheimer’s disease (AD). In the case where the normative distributions and the patient-specific volumes were calculated by the same method, the patient’s distance to the normative distribution was assessed with the z-score. We determined the diagnostic value of this z-score, which showed to be consistent across methods. The absolute agreement on the AD patients’ z-scores was high for regions of thalamus and putamen. This is encouraging as it indicates that the studied methods are interchangeable for these regions. For regions such as the hippocampus, amygdala, caudate nucleus and accumbens, and globus pallidus, not all method combinations showed a high ICC-z. Whether two methods are indeed interchangeable should be confirmed for the specific application and dataset of interest.

Is there a relationship between nutritional goal achievement and pressure injury risk in intensive care unit patients receiving enteral nutrition?

OBJECTIVES

To assess pressure injury risk and time until pressure injury development according to the achievement of nutritional goals, i.e. caloric and protein intake within the first 72 hours of the intensive care admission.

METHOD

Prospective observational cohort study conducted in two units at a public university hospital. The development of pressure injury was considered the dependent variable. Survival curves were prepared with the Kaplan Meier method. Univariate and multivariate Cox regression analysis was used to identify factors associated with the development of pressure injury.

RESULTS

The study sample included 181 patients, of which 56.4% were male and the average age was 55 years. Neurological pathologies were the most frequent cause of hospitalisation (44.8%). The average length of stay was 17.5 days and mortality 30.4%. With regards to nutritional goals, 105 patients (58.0%) achieved their caloric goal, 130 (71.8%) achieved protein goals, and 98 (54.1%) achieved both. The frequency of pressure injury occurrence was 31.5%. Caloric intake (hazard ratio [HR] 2.3, 95% confidence interval [CI] 1.24-4.36) and protein intake (HR 3.21, 95% CI 1.76-5.86), were identified as independently associated with pressure injury development. Higher Braden scores were identified as a protective factor (HR 0.65, 95% CI 0.56-0.77).

CONCLUSIONS

These results indicate that the time to pressure injury development in the group of patients who did not achieve nutritional goals was shorter compared to those who achieved nutritional goals. Further studies should be conducted to confirm these data and to study the relationships in greater detail.

Many-Body Physics of Single and Double Spin-Flip Excitations in NiO

Understanding many-body physics of elementary excitations has advanced our control over material properties. Here, we study spin-flip excitations in NiO using Ni L_{3}-edge resonant inelastic x-ray scattering (RIXS) and present a strikingly different resonant energy behavior between single and double spin-flip excitations. Comparing our results with single-site full-multiplet ligand field theory calculations we find that the spectral weight of the double-magnon excitations originates primarily from the double spin-flip transition of the quadrupolar RIXS process within a single magnetic site. Quadrupolar spin-flip processes are among the least studied excitations, despite being important for multiferroic or spin-nematic materials due to their difficult detection. We identify intermediate state multiplets and intra-atomic core-valence exchange interactions as the key many-body factors determining the fate of such excitations. RIXS resonant energy dependence can act as a convincing proof of existence of nondipolar higher-ranked magnetic orders in systems for which, only theoretical predictions are available.

Topical use of amitriptyline and linoleic acid to restore ceramide rheostat in atopic dermatitis lesions - a case report

Rebuilding, stabilizing and maintaining the dermal lipid barrier is an encouraging disease management concept (relief and care) in the treatment and prevention of atopic dermatitis. Prevention and topical treatment, however, lack a simple, safe, effective and modular approach. For decades, the mainstay of topical therapy of atopic dermatitis has been corticosteroids, with innovations being rare. Our case report demonstrates the struggle of a patient with little relief of itchy dermal lesions and the recurrence of skin lesions following current therapeutic guidelines which proved to be ineffective. Therefore we decided to try an advanced C₁₆-ceramide pathomechanism derived topical therapeutic measure since it offers hope of re-establishing skin and alleviating suffering. Amitriptyline in combination with linoleic acid offers a chance to release from dry and itchy skin, mild to moderate atopic dermatitis lesions without known serious adverse effects of topical corticosteroids, while preventing recurrence.

Biomechanical evaluation of two methods of fixation of a flexor hallucis longus tendon graft

Aims

The traditional transosseus flexor hallucis longus (FHL) tendon transfer for patients with Achilles tendinopathy requires two incisions to harvest a long tendon graft. The use of a bio-tenodesis screw enables a short graft to be used and is less invasive, but lacks supporting evidence about its biomechanical behaviour. We aimed, in this study, to compare the strength of the traditional transosseus tendon-to-tendon fixation with tendon-to-bone fixation using a tenodesis screw, in cyclical loading and ultimate load testing.

Materials and Methods

Tendon grafts were undertaken in 24 paired lower-leg specimens and randomly assigned in two groups using fixation with a transosseus suture (suture group) or a tenodesis screw (screw group). The biomechanical behaviour was evaluated using cyclical and ultimate loading tests. The Student’s t-test was performed to assess statistically significant differences in bone mineral density (BMD), displacement, the slope of the load-displacement curves, and load to failure.

Results

The screw group showed less displacement (loosening) during cyclical loading, which was significant during 300, 500, 600, 700, 800, 900, and 1000 cycles (p < 0.05: other cycles: 0.079 < p < 0.402). Compared with the suture group, the screw group had higher mean ultimate load values (133.6 N, sd 73.5 vs 110.1 N, sd 46.2; p = 0.416).

Conclusion

Fixation of the FHL tendon with a tenodesis screw enables a less invasive procedure to be undertaken and shows similar biomechanical behaviour and primary strength compared with fixation using a transosseus suture. Cite this article: Bone Joint J 2018;100-B:1175–81.

Motion artifacts in standard clinical setting obscure disease-specific differences in quantitative susceptibility mapping

As quantitative susceptibility mapping (QSM) is maturing, more clinical applications are being explored. With this comes the question whether QSM is sufficiently robust and reproducible to be directly used in a clinical setting where patients are possibly not cooperative and/or unable to suppress involuntary movements sufficiently. Twenty-nine patients with Alzheimer's disease, 31 patients with mild cognitive impairment and 41 healthy controls were scanned on a 3 T scanner, including a multi-echo gradient-echo sequence for QSM and an inversion-prepared segmented gradient-echo sequence (T1-TFE, MPRAGE). The severity of motion artifacts (excessive/strong/noticeable/invisible) was categorized via visual inspection by two independent raters. Quantitative susceptibility was reconstructed using 'joint background-field removal and segmentation-enhanced dipole inversion', based on segmented subcortical gray-matter regions, as well as using 'morphology enabled dipole inversion'. Statistical analysis of the susceptibility maps was performed per region. A large fraction of the data showed motion artifacts, visible in both magnitude images and susceptibility maps. No statistically significant susceptibility differences were found between groups including motion-affected data. Considering only subjects without visible motion, significant susceptibility differences were observed in caudate nucleus as well as in putamen. Motion-effects can obscure statistically significant differences in QSM between patients and controls. Additional measures to restrict and/or compensate for subject motion should be taken for QSM in standard clinical settings to avoid risk of false findings.

Radiographic contrast media alterate the localization of actin/band4.9 in the membrane cytoskeleton of human erythrocytes

Different radiographic contrast media (RCM) were shown to induce morphological changes of blood cells (e.g. erythrocytes or thrombocytes) and endothelial cells. The echinocytic shape change of erythrocytes, particularly, affords alterations of the membrane cytoskeleton. The cytoskeleton plays a crucial role for the shape and deformability of the red blood cell. Disruption of the interaction between components of the red blood cell membrane cytoskeleton may cause a loss of structural and functional integrity of the membrane. In this study band4.9 and actin as components of the cytoskeletal junctional complex were examined in human erythrocytes after suspension in autologous plasma or in plasma RCM mixtures (30% v/v Iodixanol-320 or Iopromide-370) followed by a successive double staining with TRITC-/FITC-coupled monoclonal antibodies. After adding Iopromide-370 to the plasma in practically none of the cells the rounded conformation of the membrane cytoskeleton - as it appeared in cells suspended in autologous plasma - was found. In addition, Iopromide-370 induced thin lines and coarse knob-like structures of band4.9 at the cell periphery while most cell centers were devoid of band4.9, and a box-like arrangement of bands of band4.9. A dissociation between colours red (actin) and green (band4.9) occurred as well. In contrast, erythrocytes suspended in a plasma/Iodixanol-320 mixture showed a membrane cytoskeleton comparable to cells suspended in autologous plasma, Similar results were found with respect to the distribution of actin. This study revealed for the first time RCM-dependent differences in band4.9 activities as possible pathophysiological mechanism for the chemotoxicity of radiographic contrast media.

Novel effects of adenosine receptors on pericellular hyaluronan matrix: implications for human smooth muscle cell phenotype and interactions with monocytes during atherosclerosis

Hyaluronan (HA) is responsive to pro-atherosclerotic growth factors and cytokines and is thought to contribute to neointimal hyperplasia and atherosclerosis. However, the specific function of the pericellular HA matrix is likely depend on the respective stimuli. Adenosine plays an important role in the phenotypic regulation of vascular smooth muscle cells (VSMC) and is thought to inhibit inflammatory responses during atherosclerosis. The aim of this study was to examine the regulation and function of HA matrix in response to adenosine in human coronary artery SMC (HCASMC). The adenosine receptor agonist NECA (10 μM) caused a strong induction of HA synthase (HAS)1 at 6 h and a weaker induction again after 24 h. Use of selective adenosine receptor antagonists revealed that adenosine A2(B) receptors (A2(B)R) mediate the early HAS1 induction, whereas late HAS1 induction was mediated via A2(A)R and A3R. The strong response after 6 h was mediated in part via phosphoinositide-3 kinase- and mitogen-activated protein kinase pathways and was inhibited by Epac. Functionally, NECA increased cell migration, which was abolished by shRNA-mediated knock down of HAS1. In addition to HA secretion, NECA also stimulated the formation of pronounced pericellular HA matrix in HCASMC and increased the adhesion of monocytes. The adenosine-induced monocyte adhesion was sensitive to hyaluronidase. In conclusion, the current data suggest that adenosine via adenosine A2(B)R and A2(A)R/A3R induces HAS1. In turn a HA-rich matrix is formed by HCASMC which likely supports the migratory HCASMC phenotype and traps monocytes/macrophages in the interstitial matrix.

Repeated intrauterine IgG infusions in foetal alloimmune thrombocytopenia do not increase foetal platelet counts

BACKGROUND AND OBJECTIVES

Foetal alloimmune thrombocytopenia (FNAIT) is often treated transplacentally with maternally administered i.v. immunoglobulins, but not all foetuses show a consistent platelet increase during such treatment.

MATERIALS AND METHODS

We retrospectively analysed data from a cohort of ten foetuses with FNAIT treated by direct foetal immunoglobulin infusion. Foetal treatment was begun between 17 and 25 weeks and continued until 36 weeks with weekly cordocenteses and foetal immunoglobulin infusions.

RESULTS

While foetal IgG levels increased steadily during weekly IgG infusions, foetal platelet counts remained unchanged.

CONCLUSION

Our retrospective study presents a unique analysis of a historical cohort, contributing to the ongoing debate about the treatment of choice for foetal alloimmune thrombocytopenia.

Deletion in Xp22.11: PTCHD1 is a candidate gene for X-linked intellectual disability with or without autism

Submicroscopic chromosomal anomalies play an important role in the aetiology of intellectual disability (ID) and have been shown to account for up to 10% of non-syndromic forms. We present a family with two affected boys compatible with X-linked inheritance of a phenotype of severe neurodevelopmental disorder co-segregating with a deletion in Xp22.11 exclusively containing the PTCHD1 gene. Although the exact function of this gene is unknown to date, the structural overlap of its encoded patched domain-containing protein 1, the transmembrane protein involved in the sonic hedgehog pathway, and its expression in human cortex and cerebellum as well as in mice and drosophila brain suggests a causative role of its nullisomy in the developmental phenotype of our family. Our findings support the recent notions that PTCHD1 may play a role in X-linked intellectual disability (XLID) and autism disorders.

Úlcera por pressão: risco e gravidade do paciente e carga de trabalho de enfermagem

OBJETIVOS: Verificar a associação entre ocorrência de úlcera por pressão (UP) em pacientes em estado crítico com escores da escala de Braden, gravidade do paciente e carga de trabalho de enfermagem e, identificar os fatores de risco para UP em pacientes de Unidade de Terapia Intensiva (UTI). MÉTODOS: trata-se de estudo transversal realizado em três UTIs de um hospital, cuja coleta prospectiva incluiu dados clínicos e de internação de 74 pcientes e a aplicação dos índices Simplified Acute Phisiology (SAPS II), Nursing Activities Score (NAS) e Escala de Braden. RESULTADOS: dos 74 pacientes estudados 31% apresentaram UP. As variáveis que se associaram a presença de UP foram: idade, tempo de internação, escores Braden e SAPSII. O NAS não se associou com ocorrência de UP. Escores SAPSII e NAS apresentaram correlação moderada com escores Braden e foram identificados como fatores de risco para UP. CONCLUSÃO: A ocorrência de UP associou-se à idade mais elevada, maior tempo de internação e gravidade do paciente. Identificaram-se como preditores de risco para UP a gravidade do paciente associada a carga de trabalho de enfermagem.

Methoden zur Messung der Azetylsalizylsäure- bzw. Clopidogrelresistenz

Basierend auf der Prämisse, wonach eine so genannte Resistenz gegenüber Thrombozytenfunktionshemmern vorliegt, wenn das Pharmakon den für die klinische Wirksamkeit entscheidenden pharmakodynamischen Effekt nicht ausübt, sollten zur Evaluation der Wirkung von Thrombozytenfunktionshemmern Laborteste eingesetzt werden, die den pharmakodynamischen Effekt möglichst direkt erfassen.

Für die Evaluation von Azetylsalizylsäurewirkungen scheint die Messung von Thromboxan B2 oder die der Arachidonsäure- induzierten Aggregation (Turbidimetrie oder Vollblutaggregometrie) angebracht. Für die Evaluation von Clopidogrelwirkungen scheint die Messung der VASP-Phosphorylierung (Durchflusszytometrie) oder die der ADPinduzierten Thrombozytenaggregation (Turbidimetrie oder Vollblutaggregometrie) sinnvoll.

[Methods to evaluate aspirin and clopidogrel resistance]

Based on the concept that the so-called resistance to anti-platelet drugs is meant to describe a phenomenon where the drug does not hit its direct pharmacodynamic target, assays, used to evaluated the effects of anti-platelet drugs, should as closely as possible measure the direct pharmacodynamic effect of a particular drug. Thus, for the detection of aspirin effects, thromboxane concentrations or arachidonic acid-induced responses (light aggregometry, whole-blood aggregometry) should be measured. For the detection of clopidogrel actions, VASP phosphorylation (flow cytometry) or ADP-induced responses (light aggregometry, whole blood aggregometry) should be analysed.

Different behaviour of soluble CD40L concentrations can be reflected by variations of preanalytical conditions

INTRODUCTION

Biomarkers reflecting an inflammatory or immunological response are increasingly offered to improve the risk stratification of patients. For example, current evidence suggests that soluble CD40 ligand (sCD40L) is elevated in patients with acute coronary syndrome. But only a few data are available to evaluate the influence of preanalytic conditions on sCD40L values.

METHODS

Blood samples of seven healthy blood donors were collected in tubes without additives and in EDTA- or citrate-filled tubes at various storage conditions. Platelet count was modified by serum dilution, and sCD40L was measured in platelet-rich-plasma and in whole blood. sCD40L levels were determined by an commercially available ELISA-Kit.

RESULTS

Immediately after blood sample assessment, sCD40L levels in serum samples were elevated (1258+/-820 pg/ml) compared to EDTA (64+/-32 pg/ml) and citrate (60+/-8.5 pg/ml) values. Additionally, sCD40L levels were dependent on storage duration. After platelet activation, sCD40L levels were significantly increased to 8278+/-2453 pg/ml and were significantly correlated to platelet count (r=0.96).

CONCLUSIONS

Soluble CD40L levels were clearly influenced by preanalytical conditions and were dependent on storage duration, sample technique and platelet count. These influences should be considered by the determination and evaluation of sCD40L concentrations.

Antikoagulation als onkologisches Therapieprinzip

The association of cancer with thromboembolic events has been established for more than hundred years. While the thrombophilic diathesis of tumor patients and the neoplastic thrombogenesis have been elucidated pathophysiologically, at least in part, there is growing experimental and clinical evidence that factors of plasmic hemostasis promote tumor growth, angiogenesis, and metastasis. Thus, the rationale for antithrombotic prophylaxis and therapy of tumor patients might not only be based on the prevention of thromboembolic complications but also on the potentially antineoplastic and antimetastatic effects of pharmacological anticoagulation. Encouraging results of clinical studies indicate that prophylactic and therapeutic anticoagulation might improve the survival of selected patients with cancer.

Cutaneous Microcirculation is not altered by a Weak 50 Hz Magnetic Field / Die Mikrozirkulation der Haut in schwachen 50-Hz-Magnetfeldern

Electromagnetic hypersensitivity (EH) is an increasing problem in modern industrial societies. As crawling sensations are frequently mentioned by EH patients alterations in cutaneous microcirculation possibly linked to exposure to magnetic fields might be involved in the development of such sensations and further dysesthesias. In seven healthy volunteers and in three persons convinced to suffer from EH the microcirculation of the right thumb was determined by laser-Doppler-flowmetry (LDF) during exposure to circularly polarized 50 Hz magnetic flux densities of 96 mT. During field exposure the LDF values remained constant. The LDF ratio "field on/field off" was found to be 1.03 +/- 0.03. In contrast, reactive hyperemia and hyperventilation caused significant changes in the LDF values of volunteers as well as of EH patients. Following arterial congestion of the forearm microcirculation of the thumb was clearly increased during reperfusion, and the LDF values were elevated up to 2.02 +/- 0.36. 10 deep breaths caused a significant decrease in the LDF values up to 0.63 +/- 0.18. In conclusion, reactive hyperemia and hyperventilation caused clear alterations of cutaneous microcirculation, whereas, 50 Hz magnetic fields had no influence on cutaneous microcirculation.

Hypoxia influences generation and propagation of electrical activity in embryonic cardiomyocyte clusters

The influence of tissue hypoxia on the generation and propagation of excitation was studied in spontaneously beating embryonic cardiomyocyte clusters grown in eight 9-12 days old embryoid bodies. Within the embryoid bodies one to three separately active clusters of cardiomyocytes were found, each having its own pacemaker cell. Lowering of tissue PO(2) caused bradycardia as well as arrhythmia in all embryoid bodies investigated. The mean frequency of the extracellularly recorded action potentials decreased under conditions of pronounced hypoxia from a mean of 1.4-1.8 Hz to below 0.8 Hz. In three embryoid bodies hypoxia-sensitive as well as hypoxia-tolerant cardiomyocyte clusters were found. The hypoxia-insensitive cardiomyocytes showed a low frequency of spontaneous activity. In addition to the observed changes in the generation of excitation, tissue hypoxia caused an approximately 60% reduction in the velocity of conduction within the cardiomyocyte clusters. Moreover, in at least one of the eight experiments propagation failure with an incomplete block in spread of excitation was observed. All hypoxia-induced effects on generation and propagation of embryonic cardiomyocyte excitation were completely reversible after reoxygenation.

Assessing the chromosome copy number in metaphase II oocytes by sequential fluorescence in situ hybridization

PURPOSE

Aneuploidy in oocytes is the main cause of failed embryo implantation and of miscarriage. At present, only limited data on the prevalence of aneuploidy in freshly collected human oocytes are available and all studies have been performed with conventional methods for karyotyping. In this feasibility study, multiple-hybridization fluorescence in situ hybridization (FISH) was evaluated as an alternative method to determine the number of chromosomes in oocytes.

METHODS

Fifty-two spare oocytes were collected from 23 patients treated with gonadotropins for intrauterine insemination or intracytoplasmic sperm injection. A conventional dual color FISH approach using mixtures of chromosome-specific standard alpha-satellite probes was applied consecutively to the chromosomes of the same metaphase II oocyte. Mixtures of three to six probes were designed in order to allow chromosome identification based on signal color and centromeric index.

RESULTS

One hybridization cycle was possible in 52 uninseminated metaphase II oocytes, two hybridizations in 43 oocytes (82.7%), three hybridizations in 30 oocytes (57.6%), four hybridizations in 27 oocytes (51.9%), and five hybridizations in 15 oocytes (28.8%). Altogether, 591 chromosomes could be marked (47.4% of the entire chromosome complement, 11.4 chromosomes per oocyte). The most important single factor contributing to technical failure was loss of the oocyte from the slide.

CONCLUSION

This feasibility study demonstrates that multiple-hybridization FISH can be used for the assessment of a larger proportion of the chromosome complement in oocyte as compared to previous studies based on FISH.

Non-invasive determination of metabolite concentrations in human transplanted kidney in vivo by 31P MR spectroscopy

PURPOSE

To investigate concentrations of phosphorus-containing metabolites in human transplanted kidney in vivo by quantitative 31P MR spectroscopy (MRS) using surface coils and to compare the obtained values with previous data.

MATERIAL AND METHODS

In 5 patients with well-functioning transplanted kidneys, 31P spectra were obtained with the three-dimensional localization image-selected in vivo spectroscopy technique applying a protocol for quantitative spectroscopy using surface coils. Relaxation corrected signal intensities determined by time domain fitting were used to derive absolute molar concentrations for phosphate-containing metabolites.

RESULTS

Little or no phosphocreatine in all spectra verified the absence of muscle contamination, confirming proper volume localization. The mean concentrations in the transplanted kidneys were as follows: ATP 1.60 +/- 0.26 mmol/ 1, PDE 2.14 +/- 0.91 mmol/l, Pi 0.66 +/- 0.25 mmol/l, PME 2.32+ /- 0.50 mmol/l. These values are consistent with previously reported values determined by other techniques.

CONCLUSION

The non-invasive determination of absolute metabolite concentrations in human kidney using MRS supplements the use of signal intensity ratios to detect pathologic changes in the energy metabolism of transplanted kidneys.

It takes more than money. Keys to success in leading and managing physician groups

Hospitals, health systems and physician practice management companies (PPMCs) that have acquired physician practices are losing millions of dollars a year on those practices. They wonder. "We're paying those physicians a lot of money. They should be highly motivated employees. Why aren't they?" Managing physicians with compensation is not enough. To manage physician groups well, all the interests and values of physicians must be addressed. Managing a physician group requires a management style that actively involves individual physicians. This article presents our insights into structuring the leadership and management of physician groups.

[Diagnostic procedure in cholecystolithiasis. Diagnostic approach, repeat examinations and (incidental) findings]

If non-surgical methods are to be taken into account in the therapeutic decision-making process in cholecystolithiasis, an expanded diagnostic work-up including not only stone parameters but also gallbladder function, is needed. In 2270 patients (1649 women, 621 men; age: 47.2 +/- 14 years) with (suspected) "cholecystolithiasis" attending the special gallstone outpatient clinic at a university medical department within a period of 5 years the diagnostic procedures most commonly used in both the doctor's office and hospital were abdominal ultrasonography (52%/78%), laboratory investigations (28%/39%) and plain films of the biliary tract (27%/39%). In the doctor's office gallbladder function testing took the form of an cholecystogram (17% of the patients); in the hospital ultrasonography to determine gallbladder contractility (38%). With decreasing frequency, the following additional procedures were carried out (office/hospital): CT 3%/19%, esophagogastroduodenoscopy 7%/3%, intravenous cholegram 6%/0.6%, abdominal X-ray 1%/0.4%, ERCP 1%/0.4%, chest X-ray 0.8%/1.6%. Duplicated examinations showed a relevant frequency only for ultrasonography (39% of the cases), laboratory investigations (18%) and plain films of the gallbladder (4%). Pathologic secondary findings were established in 22% of the cases.

[Changes in and acceptance of surgical and noninvasive therapy procedures in cholecystolithiasis]

BACKGROUND

The treatment of cholecystolithiasis has changed fundamentally in recent years due to the development of non-surgical techniques (extracorporeal shockwave lithotripsy [ESWL], oral litholysis) and the implementation of laparoscopic cholecystectomy.

PATIENTS AND RESULTS

Retrospective analysis of 2270 patients (1649 women, 621 men; age: 47.2 +/- 14 years) presenting with gallstone disorders in a university medical outpatients department between 1988 and 1992 in order to be instructed as to the most suitable therapy method bear witness to the rapid change in therapeutic procedure. Laparoscopic removal of the gallbladder has virtually supplanted conventional cholecystectomy, and within 5 years the proportionate role of ESWL has declined from 21 to 12%. Over the years, the proportion of patients requiring no therapeutic intervention remained constant (at about 20%). The therapeutic recommendations of the "experts" were implemented in almost 80% of cases. The majority of patients were satisfied with the chosen therapeutic approach (surgery: 93.0%, ESWL: 77.6%), although 44% of ESWL-patients and 36% of surgically managed patients reported complaints which persisted even after completion of therapy. Despite unsuccessful ESWL (residual fragments or recurrent stones) 58/95 (61%) of interviewed patients would again give preference to this non-invasive modality in the event of a renewed therapeutic decision.

CONCLUSION

Only a few years after its introduction, laparoscopic cholecystectomy has asserted itself as the predominant treatment option. But as far as acceptance and preference by the patient are concerned extracorporeal shockwave lithotripsy--as a non-invasive treatment modality--also enjoys high popularity and can be recommended as an alternative to surgery in suitable patients chosen according to the currently established stringent selection criteria.

[Volume selective 31P NMR spectroscopy for differentiation of graph rejection and acute tubular necrosis after kidney transplantation]

Volume-selective 31P-MR spectra were obtained from 37 patients using a whole-body MR scanner in combination with surface coils and a modified ISIS sequence. The quantitative evaluation took place by line fitting to the signal in the time domain using a non-linear procedure. The following signal intensities were determined: PME, PDE, Pi, gamma-, alpha-, beta-ATP and pH. 1024 excitations were averaged to achieve an adequate signal-to-noise ratio (10.0 +/- 3.3), measurements lasting 34 minutes on average. The mean measured volume was 174 +/- 52.4 ml. Contamination by muscle tissue could be excluded based on the absence of phosphocreatinine signal in the spectra. Contamination by fatty tissue was excluded by visualisation. A reduction in the value of the Pi/alpha-ATP ratio as a function of time was observed due to the regeneration process following reperfusion injury. In transplant rejection (n = 7) a significant rise in Pi/alpha-ATP ratio was seen compared to the control group (n = 20) (0.4 +/- 0.16 vs. 0.22 +/- 0.11, p < 0.01), the calculated difference in pH was significant as well. In cases of acute tubular necrosis a reduced value fore the PME/PDE ratio was observed (0.65 +/- 0.1 vs. 0.96 +/- 0.5, p < 0.04). Acute tubular necrosis could be differentiated from rejection by difference in pH (6.93 +/- 0.1 vs. 7.14 +/- 0.19, p < 0.04).

Localized 31P MR spectroscopy of the transplanted human kidney in situ shows altered metabolism in rejection and acute tubular necrosis

The purpose of this study was to investigate the function of transplant kidneys in situ, and to detect pathologic changes, using volume-selective phosphorous NMR spectroscopy (31P MRS). Localized 31P MR spectra were obtained from 37 patients using a whole-body MR scanner with a combination of surface coils, adiabatic excitation pulses, and a modified image-selected in vivo spectroscopy (ISIS) sequence. Seventeen patients with pathologic changes after renal transplant were compared with a control group of 20 patients with no evidence of transplant dysfunction. The transplant kidneys with rejection reaction showed higher ratios of inorganic phosphate (P2i) to adenosine triphosphate-alpha (ATP-alpha) than the normal control group (.4 +/- .16 compared with .22 +/- .11, P = .01) and reduced pH. The spectra of transplant kidneys with tubular necrosis had lower phosphomonoester (PME)/phosphodiester (PDE) ratios than the control group (.65 +/- .35 compared with .96 +/- .5, P = .04). The pathologies of rejection and tubular necrosis could be differentiated from each other by pH (6.93 +/- .1 in rejection versus 7.14 +/- .19 in tubular necrosis, P = .04). Preliminary results indicate that localized image-guided 31P MR spectroscopy of transplant kidneys in situ can detect rejection reactions and acute tubular necrosis noninvasively, providing an incentive for further research.

Methionine and serine formation in control and mutant human cultured fibroblasts: evidence for methyl trapping and characterization of remethylation defects

The conversion of labeled formate to methionine and serine, as a measure of remethylation of homocysteine to methionine and folate coenzyme cycling, has been studied in control and mutant human fibroblasts. Fibroblasts in monolayer culture were incubated with [14C]formate, and labeled methionine sulfone and serine were determined in hydrolysates of oxidized cell proteins. In control cells, methionine and serine were clearly measurable (n = 21, 1.7-5.5 and 2.4-9.7 nmol/mg protein/16 h, respectively). In contrast, methionine formation was reduced in cells from patients with methylenetetrahydrofolate reductase (MR) deficiency (MR mutant, n = 11, 0.05-0.44), combined methylmalonic aciduria/homocystinuria [cobalamin(cbl)C/D mutant, n = 12, 0.014-0.13), and methionine synthase deficiency (MS mutant, n = 3, 0.04-0.23). Furthermore, serine formation was low in cblC/D mutant (0.08-0.98) and MS mutant (0.17-0.94) cells, but normal or high in MR mutant cells (5.2-11.4). Growth of cblC/D mutant cells in medium supplemented with high concentrations of hydroxo-cbl resulted in significant increases of both methionine and serine formation. Taken together these findings provide clear evidence for the existence of the formate to serine pathway described by W. B. Strong and V. Schirch in cultured fibroblasts and indicate that disturbed MS function due to a specific genetic disorder is associated with reduced serine formation in vitro, which reflects availability of reduced folate coenzymes. The correction of this defect by vitamin B12 alone, in cblC/D mutant cell lines, correlates well with the clinical response in the patients and fits in well with the idea that reduced availability of folate coenzymes occurs in functional MS deficiency, in agreement with the methyl trap hypothesis.

Partially Molten Middle Crust Beneath Southern Tibet: Synthesis of Project INDEPTH Results

INDEPTH geophysical and geological observations imply that a partially molten midcrustal layer exists beneath southern Tibet. This partially molten layer has been produced by crustal thickening and behaves as a fluid on the time scale of Himalayan deformation. It is confined on the south by the structurally imbricated Indian crust underlying the Tethyan and High Himalaya and is underlain, apparently, by a stiff Indian mantle lid. The results suggest that during Neogene time the underthrusting Indian crust has acted as a plunger, displacing the molten middle crust to the north while at the same time contributing to this layer by melting and ductile flow. Viewed broadly, the Neogene evolution of the Himalaya is essentially a record of the southward extrusion of the partially molten middle crust underlying southern Tibet.