Spin Relaxation Benchmarks and Individual Qubit Addressability for Holes in Quantum Dots

We investigate hole spin relaxation in the single- and multihole regime in a 2 × 2 germanium quantum dot array. We find spin relaxation times T₁ as high as 32 and 1.2 ms for quantum dots with single- and five-hole occupations, respectively, setting benchmarks for spin relaxation times for hole quantum dots. Furthermore, we investigate qubit addressability and electric field sensitivity by measuring resonance frequency dependence of each qubit on gate voltages. We can tune the resonance frequency over a large range for both single and multihole qubits, while simultaneously finding that the resonance frequencies are only weakly dependent on neighboring gates. In particular, the five-hole qubit resonance frequency is more than 20 times as sensitive to its corresponding plunger gate. Excellent individual qubit tunability and long spin relaxation times make holes in germanium promising for addressable and high-fidelity spin qubits in dense two-dimensional quantum dot arrays for large-scale quantum information.

Effects of mass loading on the viability of assessing the state of healing of a fixated fractured long bone

Introduction

This paper aims to evaluate the effects of mass loading on the healing assessment of an internally fixated femur by vibrational means. The presence of soft tissue surrounding a femur increases damping and mass of a system, and hence affects the vibrational response of a mechanical structure by obscuring the coherent modes. This may compromise vibration-based monitoring strategies in identifying modes associated with fracture healing.

Methods

This paper presents a series of experimental works to address this issue. Two osteotomised composite femurs were internally fixated using a plate-screw system and an intramedullary nail. Soft tissue is approximated by surrounding an artificial Sawbone femur with modelling clay. The femur is excited by an instrumented impact hammer and instrumented with two accelerometers to record bending and torsion modes between 0 and 600 Hz. A 30-min epoxy was applied to simulate the healing of the fractured femur in the osteotomised region. The resonant frequencies and its modes are monitored while union is being formed and a healing index is calculated at various times to quantify the degree of healing.

Results

The results demonstrate that the effect of modelling clay compressed the natural modes along the frequency axis. It is observed that frequency bandwidth in the vicinity of 150 Hz and 500 Hz is sensitive to the state of healing of the fixated femurs, which is due to the increase in stiffness of the osteotomised region. These findings were used to formulate the healing index which assists in identifying the initial, later and complete healing stages in conjunction with the index derivative.

Conclusion

In this study, a two-sensor measurement strategy to quantify fixated femur healing is investigated. It is shown that the mass loading effect did not affect this vibrational analysis method ability to assess the state of healing, and both coherent bending and twisting modes associated with healing were easily identified. The proposed healing index, its derivative, and the cross-spectra are a viable tool for quantitative healing assessment.

The 12C(n, 2n)11C cross section from threshold to 26.5 MeV

The ¹²C(n, 2n)¹¹C cross section was measured from just below threshold to 26.5 MeV using the Pelletron accelerator at Ohio University. Monoenergetic neutrons, produced via the ³H(d,n)⁴He reaction, were allowed to strike targets of polyethylene and graphite. Activation of both targets was measured by counting positron annihilations resulting from the β⁺ decay of ¹¹C. Annihilation gamma rays were detected, both in coincidence and singly, using back-to-back NaI detectors. The incident neutron flux was determined indirectly via ¹H(n,p) protons elastically scattered from the polyethylene target. Previous measurements fall into upper and lower bands; the results of the present measurement are consistent with the upper band.

Use of patient specific 3D printed neurovascular phantoms to evaluate the clinical utility of a high resolution x-ray imager

Modern 3D printing technology can fabricate vascular phantoms based on an actual human patient with a high degree of precision facilitating a realistic simulation environment for an intervention. We present two experimental setups using 3D printed patient-specific neurovasculature to simulate different disease anatomies. To simulate the human neurovasculature in the Circle of Willis, patient-based phantoms with aneurysms were 3D printed using a Objet Eden 260V printer. Anthropomorphic head phantoms and a human skull combined with acrylic plates simulated human head bone anatomy and x-ray attenuation. For dynamic studies the 3D printed phantom was connected to a pulsatile flow loop with the anthropomorphic phantom underneath. By combining different 3D printed phantoms and the anthropomorphic phantoms, different patient pathologies can be simulated. For static studies a 3D printed neurovascular phantom was embedded inside a human skull and used as a positional reference for treatment devices such as stents. To simulate tissue attenuation acrylic layers were added. Different combinations can simulate different patient treatment procedures. The Complementary-Metal-Oxide-Semiconductor (CMOS) based High Resolution Fluoroscope (HRF) with 75μm pixels offers an advantage over the state-of-the-art 200 μm pixel Flat Panel Detector (FPD) due to higher Nyquist frequency and better DQE performance. Whether this advantage is clinically useful during an actual clinical neurovascular intervention can be addressed by qualitatively evaluating images from a cohort of various cases performed using both detectors. The above-mentioned method can offer a realistic substitute for an actual clinical procedure. Also a large cohort of cases can be generated and used for a HRF clinical utility determination study.

Focal spot size reduction using asymmetric collimation to enable reduced anode angles with a conventional angiographic x-ray tube for use with high resolution detectors

The high-resolution requirements for neuro-endovascular image-guided interventions (EIGIs) necessitate the use of a small focal-spot size; however, the maximum tube output limits for such small focal-spot sizes may not enable sufficient x-ray fluence after attenuation through the human head to support the desired image quality. This may necessitate the use of a larger focal spot, thus contributing to the overall reduction in resolution. A method for creating a higher-output small effective focal spot based on the line-focus principle has been demonstrated and characterized. By tilting the C-arm gantry, the anode-side of the x-ray field-of-view is accessible using a detector placed off-axis. This tilted central axis diminishes the resultant focal spot size in the anode-cathode direction by the tangent of the effective anode angle, allowing a medium focal spot to be used in place of a small focal spot with minimal losses in resolution but with increased tube output. Images were acquired of two different objects at the central axis, and with the C-arm tilted away from the central axis at 1° increments from 0°-7°. With standard collimation settings, only 6° was accessible, but using asymmetric extended collimation a maximum of 7° was accessed for enhanced comparisons. All objects were positioned perpendicular to the anode-cathode direction and images were compared qualitatively. The increasing advantage of the off-axis focal spots was quantitatively evidenced at each subsequent angle using the Generalized Measured-Relative Object Detectability metric (GM-ROD). This anode-tilt method is a simple and robust way of increasing tube output for a small field-of-view detector without diminishing the overall apparent resolution for neuro-EIGIs.

A CMOS-based high resolution fluoroscope (HRF) detector prototype with 49.5 μm pixels for use in endovascular image guided interventions (EIGI)

X-ray detectors to meet the high-resolution requirements for endovascular image-guided interventions (EIGIs) are being developed and evaluated. A new 49.5-micron pixel prototype detector is being investigated and compared to the current suite of high-resolution fluoroscopic (HRF) detectors. This detector featuring a 300-micron thick CsI(Tl) scintillator, and low electronic noise CMOS readout is designated the HRF-CMOS₅₀. To compare the abilities of this detector with other existing high resolution detectors, a standard performance metric analysis was applied, including the determination of the modulation transfer function (MTF), noise power spectra (NPS), noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) for a range of energies and exposure levels. The advantage of the smaller pixel size and reduced blurring due to the thin phosphor was exemplified when the MTF of the HRF-CMOS₅₀ was compared to the other high resolution detectors, which utilize larger pixels, other optical designs or thicker scintillators. However, the thinner scintillator has the disadvantage of a lower quantum detective efficiency (QDE) for higher diagnostic x-ray energies. The performance of the detector as part of an imaging chain was examined by employing the generalized metrics GMTF, GNEQ, and GDQE, taking standard focal spot size and clinical imaging parameters into consideration. As expected, the disparaging effects of focal spot unsharpness, exacerbated by increasing magnification, degraded the higher-frequency performance of the HRF-CMOS₅₀, while increasing scatter fraction diminished low-frequency performance. Nevertheless, the HRF-CMOS₅₀ brings improved resolution capabilities for EIGIs, but would require increased sensitivity and dynamic range for future clinical application.

Quantitative comparison using Generalized Relative Object Detectability (G-ROD) metrics of an amorphous selenium detector with high resolution Microangiographic Fluoroscopes (MAF) and standard flat panel detectors (FPD)

A novel amorphous selenium (a-Se) direct detector with CMOS readout has been designed, and relative detector performance investigated. The detector features include a 25μm pixel pitch, and 1000μm thick a-Se layer operating at 10V/μm bias field. A simulated detector DQE was determined, and used in comparative calculations of the Relative Object Detectability (ROD) family of prewhitening matched-filter (PWMF) observer and non-prewhitening matched filter (NPWMF) observer model metrics to gauge a-Se detector performance against existing high resolution micro-angiographic fluoroscopic (MAF) detectors and a standard flat panel detector (FPD). The PWMF-ROD or ROD metric compares two x-ray imaging detectors in their relative abilities in imaging a given object by taking the integral over spatial frequencies of the Fourier transform of the detector DQE weighted by an object function, divided by the comparable integral for a different detector. The generalized-ROD (G-ROD) metric incorporates clinically relevant parameters (focal-spot size, magnification, and scatter) to show the degradation in imaging performance for detectors that are part of an imaging chain. Preliminary ROD calculations using simulated spheres as the object predicted superior imaging performance by the a-Se detector as compared to existing detectors. New PWMF-G-ROD and NPWMF-G-ROD results still indicate better performance by the a-Se detector in an imaging chain over all sphere sizes for various focal spot sizes and magnifications, although a-Se performance advantages were degraded by focal spot blurring. Nevertheless, the a-Se technology has great potential to provide breakthrough abilities such as visualization of fine details including of neuro-vascular perforator vessels and of small vascular devices.

Focal Spot Deblurring for High Resolution Direct Conversion X-ray Detectors

Small pixel high resolution direct x-ray detectors have the advantage of higher spatial sampling and decreased blurring characteristic. The limiting factors for such systems becomes the degradation due to the focal spot size. One solution is a smaller focal spot; however, this can limit the output of the x-ray tube. Here a software solution of deconvolving with an estimated focal spot blur is presented. To simulate images from a direct detector affected with focal-spot blur, first a set of high-resolution stent images (FRED from Microvention, Inc., Tustin, CA) were acquired using a 75μm pixel size Dexela-Perkin-Elmer detector and frame averaged to reduce quantum noise. Then the averaged image was blurred with a known Gaussian blur. To add noise to the blurred image a flat-field image was multiplied with the blurred image. Both the ideal and the noisy-blurred images were then deconvolved with the known Gaussian function using either threshold-based inverse filtering or Weiner deconvolution. The blur in the ideal image was removed and the details were recovered successfully. However, the inverse filtering deconvolution process is extremely susceptible to noise. The Weiner deconvolution process was able to recover more of the details of the stent from the noisy-blurred image, but for noisier images, stent details are still lost in the recovery process.

[Intra-aortic balloon pump (IABP) counterpulsation. Do we still need it and if so when?]

Intra-aortic balloon pump (IABP) counterpulsation was for a long time considered to be an indispensable standard for support of drug therapy for all forms of acute left-sided cardiac failure and especially in cardiogenic shock due to infarction. The advantages of the system seemed to be obvious; however, many of the postulated effects on the hemodynamics, microcirculation and coronary perfusion could not be confirmed later in prospective studies. It was found that IABP had no influence on microcirculation disorders in cardiogenic shock due to infarction. In a meta-analysis on the application for acute myocardial infarction without shock, no effect was found on mortality. The benefit as adjunct therapy for percutaneous coronary interventions (PCI) in cardiogenic shock due to infarction places a question mark over both IABP-SHOCK studies; however, in constellations without PCI the additional benefit of IABP cannot be excluded which is why the procedure could be an option in this situation.

Treatment Planning for Image-Guided Neuro-Vascular Interventions Using Patient-Specific 3D Printed Phantoms

Minimally invasive endovascular image-guided interventions (EIGIs) are the preferred procedures for treatment of a wide range of vascular disorders. Despite benefits including reduced trauma and recovery time, EIGIs have their own challenges. Remote catheter actuation and challenging anatomical morphology may lead to erroneous endovascular device selections, delays or even complications such as vessel injury. EIGI planning using 3D phantoms would allow interventionists to become familiarized with the patient vessel anatomy by first performing the planned treatment on a phantom under standard operating protocols. In this study the optimal workflow to obtain such phantoms from 3D data for interventionist to practice on prior to an actual procedure was investigated. Patient-specific phantoms and phantoms presenting a wide range of challenging geometries were created. Computed Tomographic Angiography (CTA) data was uploaded into a Vitrea 3D station which allows segmentation and resulting stereo-lithographic files to be exported. The files were uploaded using processing software where preloaded vessel structures were included to create a closed-flow vasculature having structural support. The final file was printed, cleaned, connected to a flow loop and placed in an angiographic room for EIGI practice. Various Circle of Willis and cardiac arterial geometries were used. The phantoms were tested for ischemic stroke treatment, distal catheter navigation, aneurysm stenting and cardiac imaging under angiographic guidance. This method should allow for adjustments to treatment plans to be made before the patient is actually in the procedure room and enabling reduced risk of peri-operative complications or delays.

New Family of Generalized Metrics for Comparative Imaging System Evaluation

A family of imaging task-specific metrics designated Relative Object Detectability (ROD) metrics was developed to enable objective, quantitative comparisons of different x-ray systems. Previously, ROD was defined as the integral over spatial frequencies of the Fourier Transform of the object function, weighted by the detector DQE for one detector, divided by the comparable integral for another detector. When effects of scatter and focal spot unsharpness are included, the generalized metric, GDQE, is substituted for the DQE, resulting in the G-ROD metric. The G-ROD was calculated for two different detectors with two focal spot sizes using various-sized simulated objects to quantify the improved performance of new high-resolution CMOS detector systems. When a measured image is used as the object, a Generalized Measured Relative Object Detectability (GM-ROD) value can be generated. A neuro-vascular stent (Wingspan) was imaged with the high-resolution Micro-Angiographic Fluoroscope (MAF) and a standard flat panel detector (FPD) for comparison using the GM-ROD calculation. As the lower integration bound increased from 0 toward the detector Nyquist frequency, increasingly superior performance of the MAF was evidenced. Another new metric, the R-ROD, enables comparing detectors to a reference detector of given imaging ability. R-RODs for the MAF, a new CMOS detector and an FPD will be presented. The ROD family of metrics can provide quantitative more understandable comparisons for different systems where the detector, focal spot, scatter, object, techniques or dose are varied and can be used to optimize system selection for given imaging tasks.

Inflammation and echocardiographic parameters of ventricular hypertrophy in a cohort with preserved cardiac function

OBJECTIVE

To investigate the association between inflammation and selective echocardiographic parameters (EP) characteristic for ventricular hypertrophy in cross-sectional and longitudinal population-based analyses.

METHODS

Baseline (711 men, 659 women: 45-83 years) and 4-year follow-up data (622 men, 540 women) of the prospective, population-based CARdio-vascular disease, Living and Ageing in Halle (CARLA)study after exclusion of participants with cardiacvascular diseases were analysed. Inflammation parameters: soluble tumour necrosis factor receptor 1 (sTNF-R1), high-sensitivity C reactive protein (hsCRP) and interleukin 6 (IL-6). EPs: left ventricular mass (LVM), left atrial systolic dimension (LADS), interventricular septum diameter (IVSD), posterior wall dimension (PWD), left ventricular diastolic diameter (LVDD), ejection fraction according to Teichholz (EF). For the longitudinal analyses baseline to follow-up differences were considered. Effect sizes were determined by using multiple linear regression and mixed models. Missing values were replaced by means of multiple imputations.

RESULTS

Men had higher sTNF-R1 levels; means of hsCRP and IL-6 were similar in men and women. In multiple regression models, sTNF-R1 was associated with LADS (1.4 mm/1000 pg/mL sTNF-R1, 95% CI 0.6 to 2.1) in men. Respecting confounder hsCRP was associated with LVM (5.2 g/10 mg/L hsCRP, 95% CI 1.6 to 8.8), IVSD (0.2 mm/10 mg/L hsCRP, 95% CI 0 to 0.3) and PWD (0.2 mm/10 mg/L hsCRP, 95% CI 0.1 to 0.3) in women, while there were no relevant effects in analysis of IL-6 in both sexes. The baseline to follow-up change in EPs was not relevantly associated with sTNF-R1, hsCRP or IL-6.

CONCLUSIONS

STNF-R1, hsCRP and IL-6 were inadequate predictors for structural changes of the heart at follow-up, while weak cross-sectional associations are restricted to certain EPs and depend on sex.

Levosimendan in the treatment of cardiogenic shock

Patients with cardiogenic shock (CS) are currently treated with acute coronary revascularization, mechanical support (i.e., IABP), and in addition with vasopressor and inotropic support. Among medical treatment dobutamine and norepinephrine are drugs of first choice. Nowadays, intravenous levosimendan, a new calcium sensitizer and K-ATP channel opener, has emerged as an alternative option of pharmacologic inotropic support in patients with cardiogenic shock. Recent reports on levosimendan's use in cardiogenic shock demonstrated more favorable effects when compared with conventional inotropic agents. Clearly, levosimendan is able to archieve profound increase of cardiac index and cardiac power index in combination with reduced systemic and pulmonary resistance reduction compared to conventional therapy. Further, levosimendan is able to improve hemodynamic parameters more rapidly compared to intraaortic ballon counter pulsation. Similar, in patients with low cardiac output syndrome upon cardiovascular surgery, levosimendan is able to improve cardiac performance when administered prior or after cardiac surgery. In the light of cardiogenic shock, the myocardial protective effects of levosimendan might be important to reduce reperfusion injury and myocardial stunning following ischemia and reperfusion. This review summarizes the evidence from current scientific literature including our recent trials regarding the mechanism of action, efficiency and the use of levosimendan in CS patients.

Anti-inflammatory actions of aprotinin provide dose-dependent cardioprotection from reperfusion injury

BACKGROUND AND PURPOSE

Myocardial injury following ischaemia and reperfusion has been attributed to activation and transmigration of polymorphonuclear leukocytes (PMNs) with release of mediators including oxygen-derived radicals and proteases causing damage.

EXPERIMENTAL APPROACH

We studied the serine protease inhibitor aprotinin in an in vivo rabbit model of 1 h of myocardial ischaemia followed by 3 h of reperfusion (MI+R). Aprotinin (10,000 Ukg(-1)) or its vehicle were injected 5 min prior to the start of reperfusion.

KEY RESULTS

Myocardial injury was significantly reduced with aprotinin treatment as indicated by a reduced necrotic area (11+/-2.7% necrosis as percentage of area at risk after aprotinin; 24+/-3.1% after vehicle; P<0.05) and plasma creatine kinase activity (12.2+/-1.5 and 17.3+/-2.3 IU g(-1) protein in aprotinin and vehicle groups, respectively, P<0.05). PMN infiltration (assessed by myeloperoxidase activity) was significantly decreased in aprotinin-treated animals compared to vehicle (P<0.01). Histological analysis also revealed a substantial increase in PMN infiltration following MI+R and this was significantly reduced by aprotinin therapy (44+/-15 vs 102+/-2 PMN mm2 in aprotinin vs vehicle-treated animals, P<0.05). In parallel in vitro experiments, aprotinin inhibited neutrophil-endothelium interaction by reducing PMN adhesion on isolated, activated aortic endothelium. Finally, immunohistochemical analysis illustrated aprotinin significantly reduced myocardial apoptosis following MI+R.

CONCLUSIONS AND IMPLICATIONS

Inhibition of serine proteases by aprotinin inhibits an inflammatory cascade initiated by MI+R. The cardioprotective effect appears to be at least partly due to reduced PMN adhesion and infiltration with subsequently reduced myocardial necrosis and apoptosis.

[New pharmacological treatment approaches to cardiogenic shock]

Cardiogenic shock after acute myocardial infarction continues to exhibit a high mortality rate. The prognosis can be improved with acute revascularization. Use of the intra-aortic balloon pump is also an established treatment concept. Administration of catecholamines should be limited as far as possible; monitoring hemodynamic parameters based on cardiac power output or cardiac power index can be very helpful. New treatment approaches such as the calcium sensitizer levosimendan, NO synthase inhibition, complement inhibition, or vasopressin therapy have not yet yielded convincing results. Future therapies will likely address the anti-inflammatory aspect of cardiogenic shock.

[Hematogenous osteomyelitis in adults]

Hematogenous osteomyelitis (HOM) in adults is a very rare event in industrialised countries. However, in tropical regions the morbidity of HOM is more important, primarily due to the impact of sickle cell disease, thalassemia, HIV-infection and tuberculosis. HOM is most commonly caused by pyogenic bacteria and mycobacteria, but infections by fungi, viruses and parasites must also be considered. In spite of modern diagnostic procedures such as nuclear and magnetic resonance imaging, the histopathologic and microbiologic examination of bone remains the gold standard for diagnosing OM. Other diagnoses should also be considered. Nonbacterial osteomyelitic lesions (plasmacellular OM, sclerosing OM, SAPHO syndrome) as well as acute leukemia, malignant bone tumors (i.e., Ewing's sarcoma, osteosarcoma) are conditions with similar presentations. Acute HOM is best managed by appropriate antibiotic therapy. In case of failure and in chronic HOM, surgical debridement is mandatory.

[Postoperative wound healing in wound-water contact]

The avoiding of water-contact to the freshly closed operation-wound is an unwritten law in surgery. In general, taking a bath or shower is not allowed before wound stitch removal under the idea that early water-contact may lead to a higher wound-infection rate. In a prospective trial 170 patients, operated in our short-stay surgery-unit, were allowed to take a shower 24 hours after surgery. Full water contact of the fresh uncovered wound was accepted. The wound-infection rate in this group was compared with the infection-rate of an historical group from our department (n = 956).

RESULTS

In the water-contact group no case of wound-infection was observed while we were observing a wound-infection-rate of 0.6% in the other group. The difference between the two groups wasn't statistically significant (p = 0.125).

CONCLUSION

Water-contact of the fresh operation wound 24 hours after surgery did not increase the post-operative wound infection risk in this study.

[Biosurgery - maggots, are they really the better surgeons?]

Between 1 October 1996 and 31 December 1998 123 patients (74 men, 43 women) suffering from acute (n = 17) and chronic (n = 21) infections and chronic wounds (n = 85) were treated with sterile maggots (Lucilia sericata). In most patients the indication for the use of maggots was a failure to respond to standard therapy. Healing occurred in all patients with acute infections, and chronic infections showed excellent short-term results. In chronic wounds disturbances of healing in diabetics responded best to maggot therapy, the etiologically inhomogeneous group of leg ulcers asked for a polypragmatic approach, and the worst results were seen in chronic arterial occlusive disease (stage 4). Our limited experience with "biosurgery", biased selection of patients, and lack of late results reduce the significance of our data; nevertheless, sterile maggots seem to be an astonishingly workable tool for solving problems in surgical wound treatment.

[The BMW (biosurgical mechanical wound treatment) in diabetic foot]

The BMW-concept (Biosurgical-Mechanical-Wound treatment) is a effective supplement of already existing options of wound treatment. Based on the established principles of septic surgery vacuum sealing, instillation vacuum sealing and the application of sterile maggots optimize the treatment of diabetic foot ulcers, reduce time of treatment and offers a high comfort to the patient.

Reduced activation and altered laterality in two neuroleptic-naive catatonic patients during a motor task in functional MRI

BACKGROUND

Catatonia, a symptom complex with motor, affective and cognitive symptoms seen in a variety of psychotic conditions and with organic disease, was examined using a motor task using functional magnetic resonance imaging (fMRI).

METHODS

Two acute catatonic patients and two age- and sex-matched healthy controls performed sequential finger opposition (SFO) after being medicated with 2 mg of lorazepam (i.v.). Functional magnetic resonance images were collected using a gradient echo pulse sequence (EPI).

RESULTS

Patients with catatonia showed reduced motor activation of the contralateral motor cortex during SFO of the right hand, ipsilateral activation was similar for patients and controls. There were no differences in the activation of the SMA. During left hand activation the right-handed catatonic patients showed more activation in the ipsilateral cortex, a reversal from the normal pattern of activation in which the contralateral side shows four to five times more activation than the ipsilateral side.

CONCLUSIONS

In catatonic patients there is a decreased activation in motor cortex during a motor task compared to matched medicated healthy controls. In addition activation of the non-dominant side, left-handed activity in right-handed patients, results in a total reversal of the normal pattern of lateral activation suggesting a disturbance in hemispheric localization of activity during a catatonic state.

[Vacuum sealing as carrier system for controlled local drug administration in wound infection]

Between 1.4.96 and 1.3.97 27 patients with acute infections of bone and soft tissues (n = 13), chronic osteomyelitis (n = 8), and chronic wounds (n = 6) were treated by using Instillation-Vacuum-Sealing. Polyvinylalcohol sponges with drainage tubes were used to cover the internal or external wound surfaces which resulted from surgical debridement. Having hermetically covered the wound with a transparent film dressing a vacuum source generated a partial vacuum in the sponge which was modified according to the type of wound between 20 and 80 kPa. Several times daily, the vacuum line was blocked and, in an alternating fashion, antiseptic or antibiotic solution instilled for 30 minutes. Then, the vacuum was reestablished and the fluids drained from the wound. Seven days later, intermittent drug instillation was stopped and there was either immediate or delayed wound closure by secondary suturing (n = 22), skin grafting (n = 3) or spontaneous epithelialization (n = 2). During a follow-up from the beginning of the instillation treatment of 4.2 (3-14) months there was one recurrency of infection in a patient with chronic osteomyelitis.

[Treatment of infection by vacuum sealing]

Between 1 January 1992 and 31 July 1995, 313 patients with acute and chronic infections were treated by vacuum sealing (VS). The average duration of VS treatment was 16.7 days, and there was an average of 3.1 changes in the VS system. In acute infections (n = 203) the wounds were closed by secondary suturing (65.5%), spontaneous epithelialization (17.2%), skin grafting (12.3%) and flap transfer (2%). Six patients died (3%). Infection recurred in 3.9% and was cured by another VS treatment. Unstable scar formations (1%) were treated by free flap transfers. When compared with standard open-wound treatment, the low-cost VS technique offers great advantages with regard to hospital hygiene, patient comfort and therapeutic results.

[Closure of defect wounds by combined vacuum sealing with instrumental skin expansion]

Between 1.6.1995 and 31.12.1995, 17 trauma defect wounds were closed by suturing in 12 patients with a median of age of 35 (11-65) years, a new type of instrument for skin stretching being used in combination with a vacuum sealing procedure. According to clinical experience, closure of the skin defect would have required skin grafting in all patients. After secondary suturing 15 wounds healed without problems, while in the case of 1 wound there was a small skin defect, which healed spontaneously. In another sutured wound a partial dehiscence occurred over the medial malleolus on the 10th postoperative day; this also healed spontaneously without further surgical measures. There were no wound infections or necroses of the wound edges. This procedure is recommended for the closure of defect wounds, as it reduces the risk of wound infections, shortens the period of treatment and avoids cosmetically and functionally inadequate skin grafts.

Effects of tumour necrosis factor alpha (TNF alpha) on glucose transport and lipid metabolism of newly-differentiated human fat cells in cell culture

Tumour necrosis factor alpha (TNF alpha) has been found to cause a delipidation of fat cells and a decrease of the adipose tissue mass. In the present study, we tried to elucidate some of the mechanisms responsible for this phenomenon by investigating the action of TNF alpha on specific pathways which are involved in lipid storage. Cultured stromal cells from human adipose tissue were induced to differentiate into adipose cells by exposure to adipogenic factors and subsequently used for studying the effects of TNF alpha on fat cell metabolism. Presence of 5 nmol/l TNF alpha for 24 h resulted in a complete loss of the stimulatory effect of insulin on 2-deoxy-glucose transport. This inhibitory action was paralleled by a decrease of GLUT4 protein and mRNA levels. The amount of cellular GLUT4 protein was reduced by 49 +/- 3% after a 24-h exposure and by 82 +/- 18% after a 72-h exposure to 5 nmol/l TNF alpha. GLUT4 mRNA was almost undetectable after a 24-h incubation with 5 nmol/l TNF alpha. In a similar time-dependent manner, TNF alpha dramatically reduced the lipoprotein lipase mRNA content of the cells. Furthermore, incubation of cultured human fat cells with TNF alpha resulted in a marked dose-dependent stimulation of lipolysis, assessed by glycerol release, by up to 400% above controls, which became apparent after a 6-h exposure at the earliest.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin action on cardiac glucose transport: studies on the role of protein kinase C

Isolated ventricular cardiomyocytes from adult rat have been used to elucidate a possible relationship between protein kinase C (PKC) and the stimulatory action of insulin on cardiac glucose transport. Cells were incubated in the presence of either insulin or phospholipase C from Clostridium perfringens (PLC-Cp) and intracellular sn-1,2-diacylglycerol (DAG) levels and initial rates of 3-O-methylglucose transport were determined. Insulin had no effect on the DAG mass level, whereas it was elevated by PLC-Cp to 200% of control. Under these conditions the hormone produced a 2.7-fold stimulation of glucose transport with no significant effect of PLC-Cp. Insulin was unable to produce a redistribution of PKC, whereas phorbol 12-myristate 13-acetate (PMA) increased membrane associated PKC twofold. The PKC inhibitors tamoxifen and staurosporine did not interfere with glucose transport stimulation by insulin. Furthermore, cells treated with PMA exhibited unaltered basal and maximally insulin stimulated rates of glucose transport. In contrast, at physiological concentrations of insulin the stimulatory action of the hormone was significantly reduced. We conclude from our data that PKC is not involved in insulin action on cardiac glucose transport. However, activation of this enzyme may lead to a modified insulin sensitivity of the cardiac cell.

G protein expression and adenylate cyclase regulation in ventricular cardiomyocytes from STZ-diabetic rats

Isolated adult ventricular cardiomyocytes have been used to study the effects of insulin-deficient diabetes on the expression of cardiac G protein alpha-subunits. Immunoblot analysis of plasma membranes revealed the presence of three different Gs proteins with molecular masses of 45, 47, and 52 kDa. Furthermore, cardiomyocytes were found to contain Gi-2 (41 kDa) and G(o) (39 kDa). Heart cells from streptozotocin-diabetic rats exhibited an unaltered expression of the Gs proteins, whereas Gi-2 and G(o) were reduced by 58 +/- 2 and 27 +/- 11%, respectively. In cells from diabetic rats, adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in response to isoproterenol decreased by approximately 30% at agonist concentrations of 10(-7) to 10(-5) M, with an unaltered maximum stimulation by forskolin. Treatment of cardiomyocytes with pertussis toxin resulted in an incremental increase of isoproterenol-stimulated cAMP formation, which was significantly lower in cardiac myocytes from streptozotocin-diabetic animals (19.2 +/- 1.7 vs. 11.5 +/- 2.4 pmol cAMP.5 x 10(4) cells-1 times 10 min-1). The inhibition of the isoproterenol-induced cAMP accumulation by carbachol in the intact cell was not altered in streptozotocin-diabetes. In conclusion, our data show that insulin-deficient diabetes is associated with a reduced expression and concomitant functional loss of Gi in ventricular cardiomyocytes. Receptor-mediated inhibition of adenylate cyclase remains unaffected by this process, whereas the beta-adrenergic stimulatory pathway involves an additional defect upstream of the adenylate cyclase/G protein system.

Photoaffinity labelling of cardiac membrane GTP-binding proteins in response to insulin

Plasma membranes from rat cardiac ventricular tissue and insulin receptors partially purified by wheat-germ-agglutinin chromatography were subjected to direct photoaffinity labelling with [alpha-32P]GTP in order to elucidate the presence of insulin-receptor-coupled GTP-binding proteins. In plasma membranes three proteins have been identified that exhibit an enhanced photolabelling with the nucleotide in response to insulin. The apparent molecular masses of these proteins were found to be 56, 60 and 74 kDa. Photolabelling of partially purified insulin receptors showed the copurification of the 60-kDa species, whereas the 56-kDa and 74-kDa proteins could not be detected. Furthermore, the 60-kDa G-protein was found to be specifically co-immunoprecipitated with the insulin receptor. Incubation of insulin receptors with insulin increased the labelling of the 60-kDa band to 205 +/- 27% (n = 5) of control. Immuno- and ligand-blotting experiments revealed the additional presence of a 39-kDa G(o)-like protein and two G-proteins with molecular masses of 24 and 26 kDa in the receptor preparation. Under basal conditions the insulin receptor and the 60-kDa G-protein exhibited an apparent inverse distribution between plasma and microsomal membranes with the G-protein being extensively labelled in the microsomal fraction. In conclusion, our data show that, in its native environment, the cardiac insulin receptor couples to at least three GTP-binding proteins. Out of these, a 60-kDa species of microsomal origin, copurifies with the insulin receptor. It is suggested that this G-protein is associated with the insulin receptor and may be involved in insulin receptor signalling in target cells.