Dose-response relationship of dicentric chromosomes in human lymphocytes obtained for the fission neutron therapy facility MEDAPP at the research reactor FRM II

The biological effectiveness of neutrons from the neutron therapy facility MEDAPP (mean neutron energy 1.9 MeV) at the new research reactor FRM II at Garching, Germany, has been analyzed, at different depths in a polyethylene phantom. Whole blood samples were exposed to the MEDAPP beam in special irradiation chambers to total doses of 0.14-3.52 Gy at 2-cm depth, and 0.18-3.04 Gy at 6-cm depth of the phantom. The neutron and gamma-ray absorbed dose rates were measured to be 0.55 Gy min(-1) and 0.27 Gy min(-1) at 2-cm depth, while they were 0.28 and 0.25 Gy min(-1) at 6-cm depth. Although the irradiation conditions at the MEDAPP beam and the RENT beam of the former FRM I research reactor were not identical, neutrons from both facilities gave a similar linear-quadratic dose-response relationship for dicentric chromosomes at a depth of 2 cm. Different dose-response curves for dicentrics were obtained for the MEDAPP beam at 2 and 6 cm depth, suggesting a significantly lower biological effectiveness of the radiation with increasing depth. No obvious differences in the dose-response curves for dicentric chromosomes estimated under interactive or additive prediction between neutrons or gamma-rays and the experimentally obtained dose-response curves could be determined. Relative to (60)Co gamma-rays, the values for the relative biological effectiveness at the MEDAPP beam decrease from 5.9 at 0.14 Gy to 1.6 at 3.52 Gy at 2-cm depth, and from 4.1 at 0.18 Gy to 1.5 at 3.04 Gy at 6-cm depth. Using the best possible conditions of consistency, i.e., using blood samples from the same donor and the same measurement techniques for about two decades, avoiding the inter-individual variations in sensitivity or the differences in methodology usually associated with inter-laboratory comparisons, a linear-quadratic dose-response relationship for the mixed neutron and gamma-ray MEDAPP field as well as for its fission neutron part was obtained. Therefore, the debate on whether the fission-neutron induced yield of dicentric chromosomes increases linearly with dose remains open.

Heart transplantation in a patient with multiple sclerosis and mitoxantrone-induced cardiomyopathy

We describe a 30-year-old man with end-stage heart failure after therapy with mitoxantrone for multiple sclerosis. A successful orthotopic heart transplantation was performed when intensified medical therapy failed to improve the patient's hemodynamics. In spite of the severe underlying disease he did well on dual immunosuppression with methylprednisone and cyclosporine. Neurologic symptoms remained stable throughout the procedure and, after 2 months, he resumed preoperative ambulatory status. Eight years after the operation, the patient is now in New York Heart Association (NYHA) Class I status. Using canes, he is able to walk short distances. Repeated urinary tract infections caused by Escherichia coli became a problem, but have been controlled by long-term oral antibiotic prophylaxis with trimethoprim.

Young Investigator's Prizewinner 2001. Direct visualization of the influence of normothermic as opposed to hypothermic cardiopulmonary bypass on the systemic microcirculation in neonatal piglets

The direct visualization of systemic microcirculation using intravitalmicroscopy permits the classification of proinflammatory and ischemic microvascular alterations during normothermic and hypothermic cardiopulmonary bypass in neonates. We used seven newborn piglets, on average aged 9 days, and weighing 3200g, as a control group. In addition, we studied nine piglets subjected to 60 minutes of constant nonpulsatile flow using hypothermic extracorporeal circulation at 28 degrees C, and five piglets using normothermic conditions at 37 degrees C. The microvascular network of the greater omentum and the subcutaneous tissue was directly visualized using intravitalmicroscopy. We analysed interactions between leukocytes and endothelial cells, microvascular morphology, and microrheological conditions, focussing on signs of ischemic and proinflammatory alterations. During normothermic cardiopulmonary bypass, the numbers of activated leukocytes were elevated compared to hypothermic cardiopulmonary bypass (p > 0.05). Arteriolar diameter decreased during hypothermia. Capillaries were markedly dilated during normothermia. Patterns of microvascular perfusion, for both types of cardiopulmonary bypass, showed signs of ischemic damage, revealed by a reduced functional capillary density. Perfusion dependent levels of lactate were higher during normothermic cardiopulmonary bypass (p > 0.05). This new experimental approach revealed that non-pulsatile cardiopulmonary bypass, independent of temperature, induces a proinflammatory and ischemic response compared to an unaltered control group. The markedly elevated numbers of activated adherent leukocytes, the reduced capillary density, and the high lactate levels in those undergoing bypass in normothermic conditions indicate a more pronounced inflammatory stimulus and tissue hypoperfusion compared to the possible protective effect of hypothermia for children undergoing cardiopulmonary bypass.

New telemetric system for daily pulmonary function surveillance of lung transplant recipients

BACKGROUND

Following lung transplantation, prompt diagnosis and therapy of acute pulmonary rejection and infection episodes relies primarily upon changes in pulmonary function and determines long-term outcome. We tested a new system that allows daily monitoring of the patient's pulmonary status even after discharge from the hospital.

METHODS

Seven lung transplant recipients from our center were equipped with a telemetric monitoring device consisting of a portable flowmeter and a special modem unit. The flowmeter measures forced vital capacity (FVC), forced expiratory volume per second (FEV1), and mid expiratory flows (MEFs), encodes information like fever, cough, and dyspnea in a binary code form, and stores all values in a 32 kB memory unit. After its use, the patient positions the flowmeter onto the modem unit which automatically connects to a central computer at our center to transfer all saved data. The whole set can be used via any regular phone jack. The patient's file in the computer can be checked every day.

RESULTS

All patients learned to use the unit during their postoperative stay or during later follow-up, and were able to apply the system at home. In a mean follow-up period of 10.3+/-2.2 months, 15 episodes of significant deterioration in home pulmonary function tests (PFTs) (>10%) were registered in 6 patients, which were all confirmed by in-hospital body plethysmography. They resulted in diagnoses of 4 episodes of acute rejection, 6 cases of beginning bacterial pneumonia, and 5 cases of, most likely, viral tracheobronchitis. Only 1 patient had to be admitted to the hospital. All patients PFTs returned to previous values after treatment.

CONCLUSIONS

Telemetric monitoring of graft function in lung transplant recipients allows reliable early diagnosis and treatment of infection or rejection, which might help to prevent exacerbation of the pathology and reduce quantity of amounting graft dysfunction.

Port Access surgery for congenital heart disease

OBJECTIVES

Minimally invasive surgical techniques have been introduced into cardiac surgery in order to avoid median sternotomy related complications. Surgical trauma to the patient can be significantly reduced without compromising the safety. In addition, a small lateral chest incision results in improved cosmesis, especially in female patients.

METHODS

Thirteen patients (median age 39 +/- 14 years, ranged from 17-61 years) with atrial septal defect were treated with a minimally invasive surgical method using a modified Port Access technique. In all patients access to the heart was achieved via a small (4-8 cm) right lateral chest incision in the 4th intercostal space. In these patients the selection of the Port Access system was used for cardiopulmonary bypass via the femoral vessel and for the application of cardioplegic solution.

RESULTS

No deaths or intraoperative complications were observed in any of the patients. The postoperative course was uneventful and only minor complications were observed postoperatively. The median hospital stay was 8.0 +/- 1 days (median +/- SEM).

CONCLUSION

This minimally invasive surgical technique for the treatment of atrial septal defects represent a safe alternative to conventional treatment of ASD using median sternotomy and standard cardiopulmonary bypass. The exposure of the right atrium via the 4th intercostal space is ideal and can be performed with excellent cosmetic results.

The Dresden approach for complete multivessel revascularization

BACKGROUND

In a prospective clinical trial, a group of patients receiving less invasive surgical procedure, including minithoracotomy in combination with cardiopulmonary bypass (group 1), was compared to a group of patients receiving conventional bypass surgery (group 2) for the treatment of coronary artery disease.

METHODS

Group 1 included 85 patients (71 men, 14 women, aged 39 to 82 years, median 61.1 +/- 9.0 years); group 2 included 53 patients (38 men, 15 women, aged 51 to 79 years, median 62.0 +/- 6.1 years).

RESULTS

There were no perioperative deaths in the whole series of patients. Time of operation was 256 +/- 43 minutes in group 1 and 150.0 +/- 53.6 minutes in group 2. Hospitalization was 6.0 +/- 1.4 days and intensive care unit stay 1 day for both groups. Back pain assessment on postoperative day 3 showed less pain in group 1. Three-month follow-up revealed ischemia in stress electrocardiogram in 2 patients (2.5%) in group 1 and in 2 patients (4.1%) in group 2. Coronary angiograms confirmed the stress-electrocardiogram findings.

CONCLUSIONS

Surgical results are equal for both techniques. Even though time of operation is longer in patients receiving less invasive procedures, intensive care unit stay and hospital stays are the same length. Early postoperative back pain is less in group 1 and combined with faster convalescence.

Oxygen tension in transplanted mouse osteosarcomas during fractionated high-LET- and low-LET radiotherapy--predictive aspects for choosing beam quality?

PURPOSE

The lower OER of high-LET radiations, compared to conventional (low-LET) radiations, has often been put forward as an argument for using high-LET radiotherapy in the management of hypoxic tumours. Among the different neutron beams used in therapy, the reactor fission neutrons have the lowest OER. The aim of the present study is to follow the variations of tumour oxygenation status during fractionated irradiation with different radiation qualities. Little information is available so far after fractionated high-LET irradiation. In addition, the RBE of reactor fission neutrons for effects on tumours and on normal tissues are compared.

MATERIAL AND METHODS

Murine OTS 64-osteosarcomas were transplanted in 102 balb-C mice and irradiated by 36 Gy of photons in fractions of 3 Gy five times a week (group P-36/3) or by 12 Gy of reactor fission neutrons in fractions of 2 Gy two times a week (group N-12/2). Irradiations started at a tumor volume of 500 to 600 mm3. A third group received no radiotherapy, but all investigations (group CG). Tumor volume and tumor oxygenation were measured once a week under therapy and during three weeks after therapy. For in vivo-evaluation of oxygen status a computerized polarographic needle electrode system (KIMOC pO2 histograph, Eppendorf) was used. The median pO2 and the hypoxic fraction (pO2 values < 5 mm Hg) of single tumors and of total groups were calculated from pooled histograms and from row data as well.

RESULTS

In correlation with the increase of tumor volume, from day 1 to day 42 of follow-up the median pO2 decreased from 20 mm to 8 mm Hg and the hypoxic fraction increased from 7% to 31%. After fractionated photon therapy a growth delay of three weeks was observed. Six weeks after beginning of the irradiation the median tumor volume had been doubled again. After fission neutron therapy growth delay continued until the end of the follow-up period. In both of the irradiated groups a significant decrease of median pO2 values and an increase of the hypoxic fraction were observed under radiotherapy. Hypoxia was more intensive after neutrons with a decrease of the median pO2 from 20 mm Hg to 1 mm Hg vs. 10 mm Hg after photon therapy and with an increase of the hypoxic fraction from 7% to 78% vs. 36% respectively. Two weeks after the end of therapy the median pO2 and the hypoxic fraction of both treated groups reached the levels prior to irradiation indicating a complete reoxygenation.

CONCLUSION

During fractionated irradiation of murine osteosarcomas with photons and reactor fission neutrons, a marked hypoxia was observed for both radiation qualities, but hypoxia was more intense during fractionated neutron irradiation. After irradiation, a complete reoxygenation occurred in both groups independently of the degree of hypoxia observed during the treatment. The RBE of reactor fission neutrons, after fractionated irradiation, was much higher for effects on murine osteosarcomas compared to their RBE observed for normal tissues in previous experiments. Present data are in agreement with our clinical observations on more than 300 patients treated with reactor fission neutrons for advanced and hypoxic tumours with various histologies.

New minimally invasive surgical technique using arterial T-grafts for treatment of double-vessel coronary artery disease: experimental study

Minimally invasive surgery has been used successfully in patients with single-vessel coronary artery disease (CAD), but there are no clinical reports of surgical techniques for the treatment of multivessel disease in this field using both internal mammary arteries (IMAs). Therefore a canine model has been established to demonstrate the feasibility of a minimally invasive surgical treatment of coronary artery double-vessel disease using both IMAs. Ten mongrel dogs underwent bilateral thoracoscopic preparation of both internal mammary arteries through small left lateral chest ports. Using the Port Access endovascular cardiopulmonary bypass system the right IMA (RIMA) was anastomosed as a free graft end-to-side to the left IMA (LIMA) as a T-graft. After induction of cardioplegic arrest the RIMA was anastomosed to the circumflex artery and the LIMA to the left anterior descending artery. All animals were weaned from cardiopulmonary bypass without inotropic support. The electrocardiogram showed sinus rhythm with no signs of ischemia. Intraoperative coronary angiography demonstrated patency of all anastomoses. The minimally invasive surgical treatment of double-vessel CAD using arterial T-grafts of both IMAs is thus feasible. Surgical trauma can be further reduced by harvesting the RIMA transmediastinally through the left lateral chest.