Contents Vol. 60(2002)

Volume Contents

Contents Vol. 60(2002)     

IMCO(++)--a Monte Carlo based IMRT system

The application of intensity modulated radiotherapy (IMRT) to dose escalation in the target volume sets particular demands in terms of accuracy of dose calculation. Dose calculation errors due to approximations are compensated by the optimization algorithm, a procedure that ultimately leads to incorrect fluence modulation. Such inaccuracies affect particularly the dose distribution in areas with secondary electron disequilibrium. In case tissues heterogeneity predominates, conventional dose calculation methods (such as Pencil Beam) can produce relative errors up to more than 10%. The accuracy can be significantly improved by the application of a Monte-Carlo (MC) algorithm. This paper describes a MC-based inverse treatment planning algorithm (IMCO++), based on a non-iterative approach with a feedback-controlling process. The convergence behavior of IMCO++ was investigated and the used MC dose-calculation codes MMms and XVMC were compared by means of a heterogeneous phantom. IMCO++ plans were optimized in various phantoms. All plans showed conformity in terms of dose distribution of the target volume and dose reduction in risk organs (according to the requirements of the target parameter), as well as a very fast convergence of the algorithm (in less than 10 optimization steps).     

Cell cycle retardation in monocytoid cells induced by aminopeptidase N (CD13)

Aminopeptidase N (APN, CD13) is highly expressed on human monocytes. Activation of leucocyte subpopulations, such as T-cells, can induce CD13 expression. However, little is known about the physiological role of CD13 expression on human leucocytes. It was suggested that CD13, similar to other peptidases, could be involved in control of cell growth. The hypothesis that CD13 influences proliferation of monocytoid cells by retarding the velocity of the cell cycle was tested. It was shown that CD13 expression was modulated within the cell cycle. Cells entering the S-phase of cell cycle decreased their CD13 surface expression. Occupation of the active center of CD13 with artificial ligands such as monoclonal antibodies (mab) or the low molecular weight inhibitor actinonin induced a prolongation of cell cycle and decreased the rate of cell growth. Additionally, after ligation of CD13 by mab the complex of CD13 and monoclonal antibody was actively internalized into the cell. We suggest that CD13 could have important functions for the proliferation of human monocytoid cells. Here we show for the first time that occupation of the CD13 active center by antibodies or inhibitors influences the cell cycle and thereby diminishes cell growth rate. Occupation of the active center by antibodies or inhibitors might prevent cleavage or binding and internalization of still unknown natural substrate(s) and could evoke a deceleration of the cell cycle and reduced cell growth rate.     

Accelerated radiochemotherapy in pancreatic cancer is not necessarily related to a pathologic pancreatic function decline in the early period

PURPOSE: To evaluate the functional effects of ionizing radiation in patients with unresectable pancreatic cancer in the early period after accelerated radiochemotherapy (ART). METHODS AND MATERIALS: To analyze the exocrine component, the amino acid consumption test and fecal elastase 1 were performed in 13 patients immediately before and 4-8 weeks after ART. Pancreatic duct morphology was evaluated before therapy. Weight loss and clinical steatorrhea were recorded. Endocrine parameters were examined according to standardized criteria. RESULTS: The relative change of the amino acid consumption test results and the median elastase concentration was 41.2% and 56.4%, respectively. Five patients still had normal test results after ART and 5 patients developed pathologic values. The median relative weight loss of the total body weight was 7.7% +/- 4.5%. No steatorrhea occurred. Of the 5 patients with normal values, 3 had a mean organ dose of <40 Gy. Of the 5 patients with pathologic values, 4 had a mean organ dose of >41 Gy. The endocrine function measurements remained unchanged. CONCLUSION: Although a nominal reduction of exocrine function parameters occurred in most patients, ART was not necessarily related to a pathologic level in the early period. Diabetes was not established. The functional impairment that was existent in the patient population presumably contributed to the weight loss. Pancreatic enzyme preparations may also play a role in maintaining an anabolic state during and after radiochemotherapy.     

Patients' Satisfaction with Psychiatric Treatment: Comparison Between an Open and a Closed Ward

The study compared patients' satisfaction with psychiatric inpatient treatment between an open and a closed ward. During a six-month period, all voluntarily participating patients on two wards of a psychiatric University hospital were investigated anonymously at admission and/or before discharge. A self-rating questionnaire (SATQ-98) was used to assess satisfaction with several domains of psychiatric inpatient treatment. In total, 135 questionnaires were received (retrieval rate 49%). The general level of satisfaction with treatment was high. General satisfaction, satisfaction with medication, ward equipment, visiting opportunities, and regulations for going out were significantly lower at discharge on the closed ward. Dissatisfaction with medication was related to low actual mood, and to low satisfaction with the frequency of psychotherapeutic interventions, visiting opportunities, and with the treating doctor. The results thus far strongly support the need for patients' satisfaction with treatment to be taken into account in order to improve psychiatric inpatient services, particularly on closed wards.     

Effect of reboxetine on depression in Parkinson's disease patients

BACKGROUND: Depression occurs frequently in patients with Parkinson's disease and appears to be associated with increased disability and reduced quality of life. Pharmacologic treatment with tricyclic antidepressants or serotonin reuptake inhibitors may produce adverse effects on cognition or motor functions in Parkinson's disease patients. The efficacy of reboxetine, a novel norepinephrine reuptake inhibitor, has been shown in major depressive disorder, with specific effects on motivation and negligible effects on psychomotor and cognitive function. METHOD: The effects of reboxetine on depression were investigated in 16 patients with idiopathic Parkinson's disease in an open, prospective study. Prior antidepressant medication was stopped because of lack of efficacy or intolerable side effects. Severity of depressive symptoms was assessed by the Hamilton Rating Scale for Depression, the Self-Rating Depression Scale, the Snaith-Hamilton Pleasure Scale, and the Social Adaptation Self-Evaluation Scale during the study period of 4 weeks. RESULTS: A significant improvement in depression scores was observed after 4 weeks (z = -3.31, p < .008). In 1 subject, reboxetine treatment was discontinued because of psychotic symptoms. Seven patients experienced transient side effects, including restlessness, insomnia, and increased sweating. There were no significant changes in parkinsonian motor symptoms or dosage of levodopa. CONCLUSION: Reboxetine appears to be effective and well tolerated in Parkinson's disease patients receiving 4 weeks of treatment of moderate-to-severe depression. There are good theoretical and clinical reasons, including pharmacologic specificity of effects and low incidence of side effects, to consider reboxetine for treatment of depression in Parkinson's disease.     

Experimental stereotactic gamma knife radiosurgery. Vascular contractility studies of the rat middle cerebral artery after chronic survival

In vitro isometric small vessel myograph experiments and pathological investigations were performed on rat middle cerebral arteries. Thirty-four animals provided 68 normal vessels, six further rats had the endothelial layer mechanically removed from their 12 arteries. Eighteen animals received gamma knife irradiation to the middle cerebral arteries. Fifteen of these received 50 Gray, and three 25 Gray dose to the 50% isodose and the contralateral vessels offered 20 Gray and 15 Gray irradiated specimens. Survival times varied from 12 weeks to 18 months. In the acute stage, abolition of potassium-induced relaxation occurred as early as 24 h after irradiation whilst in one year this reaction seemed to recover and remained active to 18 months. The contraction response to prostaglandin F2 alpha was diminished at six weeks in the 50 Gray-irradiated vessels. However, from one year further reduction was seen and by 18 months this response was totally abolished. We demonstrated reduction of contractile capability of the irradiated normal vessels while the vessels remained patent. When using low irradiation dose there were no pathological changes even at 18 months, but marked physiological changes could be demonstrated. Different vessel wall functions appear to have different radiosensitivity, time course and capability for regeneration.     

An implantable electrode design for both chronic in vivo nerve recording and axon stimulation in freely behaving crayfish

A chronically implantable electrode design permitting alternate extracellular nerve recording and axon stimulation in freely behaving crayfish was developed. The electrode consists of a double hook made from 20 microm thin platinum wire that can be fitted to various nerve diameters, and is easily implantable. A fast curing, flexible two-component silicone was used for insulation. The double hook was connected to plugs and fixed on the carapace of a crayfish allowing the animals to roam freely. The setup also allows for repeated dis- and re-connection of the crayfish for alternating recording and stimulation. Two channel recordings were used to determine directionality and to discriminate between afferent activity of the two stretch receptor neurons and efferent activity of several motor neurons. In addition, they were also used to determine the conduction velocity of the recorded efferent activity. Stable two-channel recordings could be obtained for up to 5 months and 15 days without apparent effects on the animal. In vivo stimulation could be performed for at least 3 1/2 weeks. The implantable double hook is suitable for widespread use in invertebrate neurobiology.