The interrelated process of becoming independent in user participation for young persons living with disabilities

PURPOSE

User participation is important in the delivery of health- and social services. Yet, our knowledge regarding how user participation is experienced from the perspective of those who use these services is limited. This study aims to develop knowledge regarding how young persons living with disabilities experience becoming independent in user participation.

MATERIALS AND METHODS

This qualitative study is inspired by Constructivist Grounded Theory. Nine young persons between 16 and 25 years of age and living with a disability, participated in the interviews.

RESULTS

The results revealed that user participation for young persons is a socially situated, relational, and skills-dependent process. User participation is characterized as a process, consisting of increasing skills, gradually reducing parental support, and responding to interactions with professionals. The three categories are strongly reciprocal and interrelated, forming the unifying core category of Striving towards independence in user participation.

CONCLUSION

We theorize about the Interrelated process of becoming independent in user participation for young persons with disabilities. This theory highlights the need to understand the interrelatedness of user participation, allowing for a recognition of the complexity of user participation, showing it as a process involving developing skills, and gradually becoming independent and skilled in user participation.Implications for rehabilitationYoung persons with disability rely on support from parents as well as professionals to become independent in user participationProfessionals should acknowledge that user participation is a learning process and allow for time and resources to aid this processFocusing on increasing health literacy alone is not sufficient to ensure user participation for young persons with disability.

Inaccessible Possibilities: experiences of using ICT to engage with services among young persons with disabilities

PURPOSE

The use of Information and communications technologies (ICT) in the public sector is widespread and on the increase. There is a need to develop knowledge regarding the end users experiences of using ICT to engage with services. This study aims to provide knowledge regarding young persons with disabilities or chronic disease experience using ICT to engage with health- and social care services.

MATERIALS AND METHODS

Nine young persons between 16 and 25, living with chronic disease or physical disability, participated in this study. The data was collected using semi-structured interviews. The interviews were recorded, transcribed verbatim and analysed using Constructivist Grounded Theory.

RESULTS

Three categories were identified that reflected the young persons' experiences with using ICT to engage with health and social care services. (1) Navigating in an information overflow, (2) Experiencing disparate dialogues, (3) Utilising the potential of ICT. The young persons experienced that ICT used for engaging with health and social care services did not necessarily fit their need, yet, they saw how ICT had potential to increase engagement with services, especially with an increased focus on dialogue. The findings can be subsumed by the core category Inaccessible Possibilities, illustrating both the potentials and the challenges ICT presented.

CONCLUSION

The study shows that although young persons are perceived as digitally native, they experienced challenges using ICT to engage with health- and social services. The poor fit of ICT combined with navigation- and accessibility issues, hinder engagement. However, ICT inhabit a potential to increase engagement, especially communication.IMPLICATIONS FOR REHABILITATIONYoung persons' experiences show that ICT can be useful for enhancing engagement with health and social care servicesICT provided by health and social services does not necessarily meet young persons need for dialogueAn increased focus on accessibility and design is necessary to ensure people with disabilities access to ICT used by health- and social care services.

How Implementation of Cognitive Assistive Technology in Home-Based Services for Young Adults with Intellectual Disabilities Influences Support Staff`s Professional Practice

The implementation of technology in home-based services takes place in contextualised socio-material practices negotiated through interactions between a diversity of actors. Prerequisites for succeeding in this process are time and competence, and that use of the technology is experienced as meaningful, for both the support staff and the resident. In this article, we investigate how implementation of cognitive assistive technology (CAT) in home-based services for young adults with intellectual disabilities influences the support staff`s professional practice. The participants are eight support staff members, five women and three men. Data were collected through two group interviews, the second one 8 months after the first one. The data were analysed according to a systematic text condensation (STC) approach. Implementation of CAT is a demanding process, revealing different perspectives on professionalism and changing power relations, and entails a new way of working for the support staff.

How using assistive technology for cognitive impairments improves the participation and self-determination of young adults with intellectual developmental disabilities

In Norway, where all citizens are entitled to live in their own homes in their local communities, people with intellectual disabilities receive community-based home care services that aim to promote their ability to live on their own. In our study, we investigated how using an assistive device for cognitive impairment - namely, a memo planner (MP) - in community-based home care services affected the everyday lives of people with intellectual developmental disabilities (IDD). Our sample consisted of seven young adults with IDD and their support staff. Data were collected during field observations and group interviews and analysed via systematic text condensation. The findings illuminate how using an MP can structure the daily lives of young adults with IDD and afford them opportunities to participate in everyday activities. In this article, we discuss how using an MP shapes interactions between people with IDD and their support staff.

"You have to argue the right way": user involvement in the service delivery process for assistive activity technology

PURPOSE

This article critically examines user-involvement in the service delivery process for assistive activity technology.

METHODOLOGY

Data were collected in semi-structured interviews with 44 end users of assistive activity technology and in focus group interviews with 11 professionals at Norway's Assistive Technology Centre. Data was analysed according to a stepwise deductive-inductive approach.

FINDINGS

Flawed organisational principles like division of responsibility, unclear regulations, and a lack of competence with assistive activity technology among service professionals have hindered user involvement in the service delivery process.

CONCLUSION

A missing knowledge of assistive activity technology among professionals and the current organisation of services creates barriers for a positive collaboration with users in the service delivery process of assistive activity technology.IMPLICATIONS FOR REHABILITATIONThe spread of information among users and courses for professionals should be expanded to ensure the necessary competence with assistive activity technology within the service delivery process.In developing the service delivery process for assistive activity technology, professionals should act less as guardians of traditional functional requirements and more as active providers of different technological solutions.The service delivery process for assistive activity technology should allow long-term testing to identify relevant social and physical factors affecting the use of this type of technology, before delivery.Guarantees and complaint systems should be established in the service delivery process for assistive activity technology.

Challenges and motivators to physical activity faced by retired men when ageing: a qualitative study

Background

Active ageing reflects the message from World Health Organisation about addressing the challenge faced by the rapidly ageing population. Knowledge about barriers and facilitators to an active lifestyle must be given more attention. In addition, men seem to participate less in cultural activities and less in fall-prevention groups than women do. When mostly women work with the elderly in primary care, one might question whether the activities offered to older men meet their activity preferences. The aim of this study is to provide new knowledge about challenges and motivators encountered by retired men in maintaining physical activity when ageing.

Methods

Nine retired men, aged between 66 and 83, wrote a Time Geographic Diary for 7 days each. Two focus group discussions with the men were held. A Systemic Text Condensation was used to analyse the data.

Results

The analyses identified three categories to describe challenges in being physical active: differences between men and women; meaningful physical activity; and environmental - especially socio-cultural - constraints. Motivating conditions were seen as: new activities to get younger friends, and more information about how to cope.

Conclusions

To achieve the aim of active ageing, service providers as well as local authorities need to have a better understanding of the challenges retired men encounter when ageing. This study highlights vital aspects of the challenges faced by retired men in maintaining their physical activity level.

Preload changes by positive pressure ventilation can be used for assessment of left ventricular systolic function

BACKGROUND

Assessment of preload independent left ventricular function with conductance volumetry is traditionally accomplished by inflating a balloon in the inferior caval vein. Our aim was to investigate if a similar change in preload could be achieved by positive pressure ventilation with large tidal volume.

METHODS

Conductance volumetry generating left ventricular pressure-volume loops was used in seven pentobarbital-anesthetized pigs. Changes in preload recruitable stroke work were studied, comparing the effects of inferior vena cava occlusion (IVCO) or large tidal volume (LTV). Cardiodepression was induced by halothane anesthesia and halothane + phenylephrine, and stimulation by epinephrine infusion.

RESULTS

Although the decreasis in left ventricular end diastolic volume was slightly less with LTV (16.5 +/- 1.7 ml, mean +/- SEM) than with IVCO (22.4 +/- 1.7 ml) (P < 0.0001) the PRSW-slopes showed a high degree of correlation (r=0.80, P < 0.0001). Although peak tracheal pressures increased significantly to 27.8 +/- 0.9 mmHg during LTV, esophageal pressures (used as an indicator of pericardial pressure) were unchanged.

CONCLUSIONS

Positive pressure ventilation with LTV is similar to IVCO in creating transient changes in preload, necessary for assessment of left ventricular systolic function. This observation was valid also during drug-induced cardiac depression and stimulation. The preload recruitable stroke work used for this validation was shown to be a reliable and stable method.

Interpretation of radial pulse contour during fentanyl/nitrous oxide anesthesia and mechanical ventilation

BACKGROUND

Peripheral arterial blood pressure is not a reliable substitute for proximal aortic pressure. Recognition of this phenomenon is important for correct appreciation of cardiac afterload. Our aim was to evaluate the utility of the radial pulse wave to better understand ventriculo-vascular coupling during anesthesia.

METHODS

We observed the differences between aortic systolic pressure (AoSAP, tipmanometry) and radial systolic pressure in 15 patients, (including two women) aged 53-78 years, before coronary artery bypass surgery. We studied the induction of anesthesia with fentanyl (20 microg kg-1), moderate volume loading, and thereafter the addition of 70% nitrous oxide. The circulatory effects of mechanical ventilation were studied by doubling the tidal volumes. Pulse wave contours were assessed by calculation of radical and aortic augmentation indices (AI), which measure the second systolic pressure peak.

RESULTS

Radial systolic pressure was higher than AoSAP in the control situation (8+/-2 mmHg), and this SAP gradient increased further with fentanyl (12+/-2 mmHg). The gradient persisted throughout the study, but was partially reduced by volume loading and nitrous oxide, respectively. Radial augmentation index was the only parameter remaining in a stepwise multivariate model to explain the variance in the SAP gradient (r2=0.48). Radial augmentation index also correlated with aortic pulse pressure (r2=0.71). Mechanical ventilation had significant and similar effects on pulse wave augmentation both in the aorta and in the radial artery, and did not affect the radial to aortic SAP gradient.

CONCLUSION

These elderly coronary patients had stiff vasculature (high aortic AI) and considerable pulse wave reflection, which was beneficially delayed by fentanyl. Changes in the radial pulse wave augmentation during mechanical ventilation were mainly a result of cyclic changes in the stroke volume, and were seldom associated with an increased systolic pressure gradient from the aorta to the radial artery.

Can a clinically useful aortic pressure wave be derived from a radial pressure wave?

BACKGROUND

The information contained in arterial pressure waveforms is probably underused by most clinicians who manage critically ill patients. It is not generally known that an aortic pressure wave can be synthesized by applying a generalized transfer function to the radial arterial pressure wave. We validated a commercially available system, SphygmoCo (PWV Medical, Sydney).

METHODS

Ascending aortic pressure waves were synthesized and comparisons were made between the synthesized aortic waveforms, the measured aortic and radial arterial waveforms. Ascending aortic pressure waves (catheter-tip manometer) and radial artery pressure waves (short fluid-filled catheter) were recorded simultaneously in 12 patients with angina pectoris (age 62-76 years) undergoing cardiac catheterization. Patients were studied at rest, following midazolam, sublingual nitroglycerin and during Valsalva manoeuvres.

RESULTS

Both midazolam and nitroglycerin lowered mean arterial pressure but nitroglycerin caused a more selective decrease in the measured and synthesized aortic systolic pressures than in the radial artery pressure. The synthesized aortic systolic pressure was less, by 6-8 mm Hg (SD 2-3) and the synthesized aortic diastolic pressure greater, by 4 mm Hg (SD 2). Despite these differences in pulse pressure, the synthesized waveform tracked the measured waveform before and during interventions.

CONCLUSIONS

By deriving an aortic waveform from the radial pulse, monitoring of left ventricular afterload can improve without more invasive means.

NGF, NT-3 and Trk C mRNAs, but not TrkA mRNA, are upregulated in the paraventricular structures in experimental hydrocephalus

OBJECTS

This study was designed to detect possible alterations in the expression of neurotrophins and trks in kaolin-induced hydrocephalus by in situ hybridization.

METHODS AND RESULTS

Sixteen rats were treated by injection of 25 mg kaolin suspended in 0.1 ml of physiological saline into the cisterna magna. Four rats were injected with saline and served as controls. The kaolin-treated rats were divided into two groups studied 1 and 4 weeks after treatment. Rats were anesthetized and killed, and their brains were rapidly dissected and frozen. DNA oligonucleotide probes for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and trkA, trkB, and C were labeled with [(35)S]dATP using terminal deoxyribonucleotidyl transferase for in situ hybridization. Hydrocephalic brains were also classified according to the degree of ventricular enlargement. The results observed were as follows. (1) The medial septal and striatal NGF mRNA levels increased with severity in animals. (2) Hippocampal trkB and BDNF mRNA levels increased with time in animals with moderate ventricular enlargement. (3) Expression of hippocampal trkB, trkC, and NT-3 mRNA increased in animals with moderate ventricular enlargement, while it apparently decreased in the large ventricular enlargement group reaching normal ranges. (4) In the corpus callosum there was an apparent increase in NGF, NT-3 and trkC mRNA, but not in trkA, in hydrocephalic animals. NT-3 EIA confirmed the presence of NT-3 protein increases in corpus callosum. It is therefore possible that simultaneous NGF, NT-3, and trkC receptor upregulation occurred in glial elements of the white matter.

CONCLUSIONS

These results demonstrate that neurotrophins and their receptors are overexpressed in many damaged structures of the severely hydrocephalic brain. There were discrepancies in the distribution of NGF and trkA mRNA, and we hypothesize that NGF mRNA in the damaged white matter structure might be due to the reduced availability of other receptors, such as the low-affinity NGF receptors.

External ventricular drainage catheters: effect of surface heparinization on bacterial colonization and infection

Surface heparinization of central venous catheters has earlier been shown to reduce the frequency of bacterial colonization and septicaemia. The present study was undertaken to investigate the benefit of surface heparinization of external ventricular drainage (EVD) catheters in relation to bacterial colonization, as measured by bacterial growth and examination by a 16S-rRNA PCR assay, of catheters and of samples of cerebrospinal fluid (CSF). Ninety-eight heparinized and one hundred unheparinized EVD catheters from the same batch of catheters were used. Twenty point five percent of the heparinized and 22.8% (p = 0.63) of the unheparinized EVD catheters were colonized with bacteria. Culture of CSF, which is the definition of clinical infection in this study, yielded growth in 10.3% of patients with heparinized and in 6.3% (p = 0.18) of those with unheparinized catheters. PCR examination yielded positive signal in 31.3% of patients with heparinized catheters and in 37.7% (p = 0.061) of patients without (CSF and catheters). In the subgroup of patients with subarachnoid haemorrhages, there was a tendency, though not statistically significant, towards a lowered frequency of colonization with 23.1% for heparinized and 33.3% (p = 0.31) for unheparinized catheters. PCR examination did not contribute any further to the diagnostic procedure in the patients concerned. The EVD catheters are skin-penetrating devices and contamination from the skin flora is common. Skin cultures, obtained after skin disinfection and insertion of catheters, showed growth of bacteria in 62% of the patients.

Mutual induction of TGFbeta1 and NGF after treatment with NGF or TGFbeta1 in grafted chromaffin cells of the adrenal medulla

Chromaffin cells have been recognized for their ability to transform into sympathetic ganglion-like cells in response to nerve growth factor (NGF) or to stimulation of other neurotrophic factors. Transforming growth factor beta (TGFbeta) family members have been shown to potentiate the effect of different trophic factors. The aim of this study was to investigate if TGFbeta may influence NGF-induced neuronal transformation and regulation of NGF, TGFbeta1, and their receptors in the adult rat chromaffin tissue after grafting. Intraocular transplantation of adult chromaffin tissue was employed and grafts were treated with TGFbeta1 and/or NGF. Graft survival time was 18 days after which the grafts were processed for TGFbeta luciferase detection assay, NGF enzyme immunoassay, or in situ hybridization. In grafts stimulated with NGF, increased levels of TGFbeta1 and TGFbeta1 mRNA were detected. When grafts instead were treated with TGFbeta1, enhanced levels of NGF protein were found. Furthermore, a positive mRNA signal corresponding to the transforming growth factor II receptor (TbetaRII) was found in the chromaffin cells of the normal adrenal medulla as well as after grafting. No increase of TbetaRII mRNA levels was detected after transplantation or after TGFbeta1 treatment. Instead a reduction of TbetaRII mRNA expression was noted after NGF treatment. NGF stimulation of grafts increased the message for NGF receptors p75 and trkA in the chromaffin transplants. Grafts processed for evaluations of neurite outgrowth were allowed to survive for 28 days and were injected weekly with NGF and/or TGFbeta1. NGF treatment resulted in a robust innervation of the host irides. TGFbeta1 had no additive effect on nerve fiber formation when combined with NGF. Combined treatment of NGF and anti-TGFbeta1 resulted in a significantly larger area of reinnervation. In conclusion, it was found that NGF and TGFbeta1 may regulate the expression of each other's protein in adult chromaffin grafts. Furthermore, TbetaRII mRNA was present in the adult rat chromaffin cells and became downregulated as a result of NGF stimulation. Although no synergistic effects of TGFbeta1 were found on NGF-induced neurite outgrowth, it was found that TGFbeta1 and NGF signaling are closely linked in the chromaffin cells of the adrenal medulla.

Changes in brain nerve growth factor levels and nerve growth factor receptors in rats exposed to environmental enrichment for one year

This study examined the effects of long-term differential rearing on levels of brain nerve growth factor, its receptors, and their relationships to cognitive function. Adult rats (two months old) were placed into either enriched or standard housing conditions where they remained for 12 months. Animals from the enriched condition group had significantly higher levels of nerve growth factor in hippocampus, visual and entorhinal cortices compared with animals housed in isolated condition. Immunohistochemical analysis of brain tissue from the medial septal area revealed higher staining intensity and fibre density with both the low-affinity and the high-affinity nerve growth factor receptors. Enriched rats performed better than isolated rats in acquisition of spatial learning and had lower locomotion scores in the open field. These results provide further evidence that experimental stimulation results in increased production of trophic factors and structural reorganization in specific brain regions known to be involved in cognitive function.

Aortic and radial pulse contour: different effects of nitroglycerin and prostacyclin

Through vasorelaxation, nitroglycerin is considered to reduce arterial wave reflection and to cause a more pronounced decrease in systolic pressure in the aorta (AoSAP) than in the radial artery (RaSAP). Our aim was to study how radial and aortic pulse wave configurations and the gradient (RaSAP-AoSAP) were affected by nitroglycerin and by prostacyclin, and how these changes correlated to stroke volume, vascular resistance/impedance, and wave reflection. Prostacyclin has not been studied in this context and was chosen because, in contrast to nitroglycerin, it does not reduce stroke volume and reduces afterload by arteriolar dilation. In 18 patients (53-81 yr old; heavily premedicated before coronary artery surgery), blood pressure was measured in both the radial artery and the ascending aorta (tipmanometry), and cardiac output was measured by thermodilution. Mean arterial pressure was reduced stepwise with each drug (mean total decrease 10-12 mm Hg). The initial RaSAP-AoSAP gradient (6 mm Hg) was increased 10 mm Hg by nitroglycerin and was not affected by prostacyclin. The nitroglycerin-induced increase in systolic gradient RaSAP-AoSAP correlated to decreases in stroke volume index, mean arterial pressure, and arterial elastance, but not to decrease in pulse wave augmentation. Thus, decreases in stroke volume index, not wave reflection, seem to be the main reason for an increased RaSAP-AoSAP when nitroglycerin is used in the elderly, hypertensive patient.

IMPLICATIONS

We studied ascending aortic and radial pulse contours in patients scheduled for coronary artery surgery. The radial pulse wave can be used for interpretation of central hemodynamic changes during nitroglycerin-, but not prostacyclin-, induced hypotension.

Effects of environmental enrichment on cognitive function and hippocampal NGF in the non-handled rats

In this study we examine whether exposure to differential housing after weaning would counteract the effects of postnatal handling (H) or nonhandling (NH) treatment by affecting learning and memory processes in young rats. In addition, we seek to determine if experience in enriched environment would alter hippocampal nerve growth factor (NGF) levels which is one of the factors known to be involved in the regulation of the survival and differentiation of developing basal forebrain neurones. Rats were either exposed to handling treatment, or left undisturbed starting day 1 after birth through day 21. After weaning on day 22, we exposed half of the H rats and half of the NH rats to environmental enrichment for 60 days. The other respective half of the rats was housed in isolated environmental condition (IC). Behavioural measures were taken in open field test, and spatial water maze test. Exposure to enriched environment following postnatal handling and nonhandling increased hippocampal NGF levels, and improved cognitive function in the both groups, with NH rats being more responsive to the effects of enrichment. Our results suggest that environmental enrichment has the potential to prevent or reduce the cognitive and neurochemical deficits in the adult animals associated with nonhandling.

Localized expression of BMP and GDF mRNA in the rodent brain

Expression of BMP- and GDF-related factors within the transforming growth factor-beta (TGF-beta) superfamily was examined in the rat and mouse brain by in situ hybridization. Strong signals were obtained in neurons for GDF-1 and GDF-10. GDF-1 is expressed at postnatal day 6 in the cerebral cortex, hippocampal CA1 through CA3 neurons, while only weakly expressed by cells in the dentate gyrus. Granule cells and neurons in the polymorph layer of the dentate gyrus are GDF-1-positive, as are the majority of neurons in the cortex. GDF-10 shows a distinct pattern of expression: At P6, strong labelling was seen in the superficial layers of cortex, notably in the posterior cingulate cortex, and in CA3 and dentate gyrus. From postnatal day 21, GDF-1 expression is strong in the hippocampus, cortex, and thalamic nuclei, while GDF-10 expression becomes restricted to the granule cell layer in the dentate gyrus. In contrast, OP-1 expression is restricted throughout development to cells of the medial habenular nucleus, choroid plexus, and leptomeninges. The markedly different expression patterns of these BMPs suggest they serve separate functions in the brain.

Aspects on the optimal photon beam energy for radiation therapy

The selection of optimal photon beam energy is investigated both for realistic clinical bremsstrahlung beams and for monoenergetic photon beams. The photon energies covered in this investigation range from 60Co to bremsstrahlung and monoenergetic beams with maximum energies up to 50 MeV. One head and neck tumor and an advanced cervix tumor are investigated and the influence of beam direction is considered. It is shown that the use of optimized intensity modulated photon beams significantly reduces the need of beam energy selection. The most suitable single accelerator potential will generally be in the range 6-15 MV for both superficially located and deep-seated targets, provided intensity-modulated dose delivery is employed. It is also shown that a narrow penumbra region of a photon beam ideally should contain low-energy photons (< or =4 MV), whereas the gross tumor volume, particularly when deep-seated targets are concerned, should be irradiated by high-energy photons. The regions where low photon energies are most beneficial are where organs at risk are laterally close to the target volume. The situation is completely changed when uniform or wedged beams are used. The selection of optimal beam energy then becomes a very important task in line with the experience from traditional treatment techniques. However, even with a large number of uniform beam portals, the treatment outcome is substantially lower than with a few optimized intensity-modulated beams.

Presence of vitronectin and activated complement factor C9 on ventriculoperitoneal shunts and temporary ventricular drainage catheters

OBJECT

The pathogenesis of cerebrospinal fluid (CSF) shunt infection is characterized by staphylococcal adhesion to the polymeric surface of the shunt catheter. Proteins from the CSF--fibronectin, vitronectin, and fibrinogen--are adsorbed to the surface of the catheter immediately after insertion. These proteins can interfere with the biological systems of the host and mediate staphylococcal adhesion to the surface of the catheter. In the present study, the presence of fibronectin, vitronectin, and fibrinogen on CSF shunts and temporary ventricular drainage catheters is shown. The presence of fragments of fibrinogen is also examined.

METHODS

The authors used the following methods: binding radiolabeled antibodies to the catheter surface, immunoblotting of catheter eluates, and scanning force microscopy of immunogold bound to the catheter surface. The immunoblot showed that vitronectin was adsorbed in its native form and that fibronectin was degraded into small fragments. Furthermore, the study demonstrated that the level of vitronectin in CSF increased in patients with an impaired CSF-blood barrier. To study complement activation, an antibody that recognizes the neoepitope of activated complement factor C9 was used. The presence of activated complement factor C9 was shown on both temporary catheters and shunts.

CONCLUSIONS

Activation of complement close to the surface of an inserted catheter could contribute to the pathogenesis of CSF shunt infection.

Optimal electron and combined electron and photon therapy in the phase space of complication-free cure

The possibility of using intensity-modulated high-energy electrons beams alone or in combination with photon beams to treat tumours located at depths from 5 cm to 25 cm has been investigated. A radiobiologically based optimization algorithm using the probability of complication-free tumour control has been used to calculate the optimal dose distributions. Two different target volumes have been used; one advanced cervical cancer with locally involved lymph nodes and one astrocytoma in the upper brain hemisphere. Treatments with only electron beams and also combinations between electron and photon beams have been investigated. The dependence of the expected treatment outcome on the beam energy and directions was investigated, and to some extent on the number of beam portals. It is shown that the beam direction intervals resulting in a high expected treatment outcome increase with increasing electron energy and also with some electron-photon combinations. For an eccentrically placed, not too deeply situated tumour surrounded by sensitive normal tissue it is shown that the expected treatment outcome can be improved by using electron beams in combination with photon beams compared with using two photon beams, and using two electron beams results in almost as high an expected treatment outcome. The possibility of improving the dose conformity from electron beams by adding photon fields parallel or orthogonal to the electron beams is demonstrated.

Potentiating interactions between morphogenetic protein and neurotrophic factors in developing neurons

mRNA for bone morphogenetic protein receptor type II (BMPR-II) was mapped to different neurons in peripheral ganglia and spinal cord of the chicken embryo. The expression of this serine/threonine kinase receptor partially overlaps with that of tyrosine kinase receptors Trk and Ret. Biological activities of osteogenic protein-1 (OP-1), a documented ligand for BMPR-II, were tested in explanted embryonic chicken ganglia and dissociated ganglionic neurons. OP-1 had only a limited stimulatory effect on neuronal survival. However, OP-1 combined with either neurotrophin-3 (NT-3, a relative of nerve growth factor) or glial cell line-derived neurotrophic factor (GDNF) potentiated neuronal survival three- to fourfold. We also show that OP-1 strongly potentiates nerve fiber outgrowth from ganglia stimulated with NT-3 or GDNF. Signaling by BMPR-II in neurons may potentiate the tyrosine kinase pathway activated by NT-3 and GDNF. The data suggest that morphogenetic proteins may modulate neurotrophic activities during neuronal development and plasticity.

A non-invasive system for delivering neural growth factors across the blood-brain barrier: a review

Intraventricular administration of nerve growth factor (NGF) in rats has been shown to reduce age-related atrophy of central cholinergic neurons and the accompanying memory impairment, as well as protect these neurons against a variety of perturbations. Since neurotrophins do not pass the blood-brain barrier (BBB) in significant amounts, a non-invasive delivery system for this group of therapeutic molecules needs to be developed. We have utilized a carrier system, consisting of NGF covalently linked to an anti-transferrin receptor antibody (OX-26), to transport biologically active NGF across the BBB. The biological activity of this carrier system was tested using in vitro bioassays and intraocular transplants; we were able to demonstrate that cholinergic markers in both developing and aged intraocular septal grafts were enhanced by intravenous delivery of the OX-26-NGF conjugate. In subsequent experiments, aged (24 months old) Fischer 344 rats received intravenous injections of the OX-26-NGF conjugate for 6 weeks, resulting in a significant improvement in spatial learning in previously impaired rats, but disrupting the learning ability of previously unimpaired rats. Neuroanatomical analyses showed that OX-26-NGF conjugate treatment resulted in a significant increase in cholinergic cell size as well as an upregulation of both low and high affinity NGF receptors in the medial septal region of rats initially impaired in spatial learning. Finally, OX-26-NGF was able to protect striatal cholinergic neurons against excitotoxicity and basal forebrain cholinergic neurons from degeneration associated with chemically-induced loss of target neurons. These results indicate the potential utility of the transferrin receptor antibody delivery system for treatment of neurodegenerative disorders with neurotrophic substances.

Overstimulation of nerve growth factors in postinfectious and autoimmune diseases

Nerve growth factor (NGF) in cerebrospinal fluid was measured by ELISA in ten children with postinfectious diseases and in five children with diseases suggested to be of autoimmune etiology. Three groups of patients were studied: (1) those with moderately elevated concentrations (50.67 +/- 17.02 pg/mL, mean and SEM), (2) those with high concentrations (mean 424.25 +/- 125.41 pg/mL, mean and SEM), and (3) those with enormously high concentrations (mean 2,745 +/- 1,819.46 pg/mL, mean and SEM). We suggest that CSF-NGF could be used as an immunologic marker of an ongoing CNS process. Uncontrolled signaling of NGF receptors may lead to long-term inflammatory and autoimmune responses, which in turn can lead to disease.

Bone morphogenetic proteins and their receptors: potential functions in the brain

Transforming growth factors-beta (TGF-betas), activins, and bone morphogenetic proteins (BMPs) comprise an evolutionarily well-conserved group of proteins controlling a number of cell differentiation, cell growth, and morphogentic processes during development. The superfamily of TGFbeta-related genes include over 25 members in mammals several of which are expressed in the growing nervous system and serve important functions in regionalizing the early CNS. Cultured nerve cells show different responses to these factors. Recent developments have revealed that TGFbetas, activins, and BMPs selectively signal to the responding cells via different hetero-oligomeric complexes of type I and type II serine/threonine kinase receptors. The adult brain exhibits specific expression patterns of some of these receptors suggesting neuronal functions not only during development but also in the mature brain. In particular, the brain is expressing high levels of bone morphogenetic protein receptor type II (BMPR-II), activin receptor type I (ActR-I), and activin receptor type IIA (ActR-II). This indicates that osteogenic protein-1 (OP-1/BMP-7), BMP-2, and BMP-4 as well as activins may serve functions for brain neurons. Expression of the receptors partially overlaps in populations of neurons and has been shown to be regulated by brain lesions. This suggests that brain neurons may use receptors BMPR-II and ActR-I to sense the presence of BMPs. This may form a system parallel to the neurotrophin Trk tyrosine kinase receptors regulating neuroplasticity and brain repair. The presence of BMPs in brain is not well studied, but preliminary in situ data indicate that the BMP relatives growth/differentiation factor (GDF)-1 and GDF-10 are distinctly but differentially expressed at high levels in neurons expressing BMPR-II and ActR-I. The receptors mediating responses to these two GDFs remain, however, to be defined. Finally, recent data show that the signal from the activated type I serine/threonine kinase receptor is directly transduced to the nucleus by Smad proteins that become incorporated into transcriptional complexes. Preliminary in situ hybridization observations demonstrate the existence of different Smad mRNAs. It is concluded that BMPs and their signaling systems may comprise a novel pathway for control of neural activity and offer means for pharmacological interventions rescuing brain neurons.

Prediction of excess risk of long-term cardiac mortality after radiotherapy of stage I breast cancer

BACKGROUND AND PURPOSE

Excess cardiac mortality has been reported in long-term follow up of breast cancer patients. Due to these findings it has been emphasized that radiotherapy techniques should be designed to minimize cardiac dose. The present study aims to provide risk figures of long-term excess cardiac mortality following radiotherapy for stage I breast cancer patients, using the relative seriality model. The impact of different modifications of the conventional irradiation technique on the calculated risk value is also analyzed.

MATERIAL AND METHODS

One hundred consecutive left-sided stage I breast cancer patients were selected. All patients were treated with post-operative radiotherapy, using tangential 6 MV photon beams. The dose planning of each patient was done by means of a three-dimensional dose planning system. The prescribed mean tumor dose was 50 Gy, 2 Gy/fraction, 5 days a week. For each dose plan the differential heart and myocardium dose-volume histogram (DVH) were calculated. The excess risk of late cardiac mortality was predicted for each patient with the relative seriality model, using a parameter set previously determined. Different methods to decrease the risk of excess cardiac mortality (conventional collimation vs. multileaf collimation (MLC), partial blocking of the target in order to spare the heart and finally a general fluence modulation method) were analyzed.

RESULTS AND CONCLUSIONS

The mean value of the calculated excess risk was 1.8%, having the heart as organ at risk, and 2.1% having the myocardium as organ at risk. However, a subgroup of patients where the risk increased up to about 9% (heart) and 12% (myocardium) was found. The risk could be substantially decreased either using an extended blocking of the target or applying the general fluence modulation method.

Forced air warming and intraoperative hypothermia

OBJECTIVES

To compare a forced air warming system with passive measures to avoid perioperative hypothermia.

DESIGN

Prospective open study.

SETTING

University hospital, Sweden.

SUBJECTS

28 Patients scheduled for extensive thoracoabdominal operations under standard combined general and regional anaesthesia.

MAIN OUTCOME MEASURES

Temperature measured before, repeatedly under anaesthesia and during the operation for up to three hours, and then up to eight hours postoperatively.

RESULTS

Three patients were excluded. In the 12 patients who had forced air warming, temperature was preserved, and ranged from a mean (SD) of 36.8 (0.7) degrees C, (95% confidence interval (CI) 36.4 to 37.2) at the start to 36.9 (0.8) degrees C, (95% CI 36.5 to 37.3) after 3 hours. In patients who had conservative passive heat preservation techniques the mean temperature fell significantly perioperatively, from 36.8 (0.6) degrees C (95% CI 36.5 to 37.1) at the start to 35.1 (0.5) degrees C, (95% CI 34.9 to 35.3), after three hours of anaesthesia and surgery. This was a significant fall compared with the temperature in the study group (p < 0.001).

CONCLUSION

Forced air warming intraoperatively can preserve normothermia during extensive thoracoabdominal operations.

Embryonic expression of the mRNA for the rat homologue of the fusin/CXCR-4 HIV-1 co-receptor

We have previously cloned a human receptor recently shown to be a cofactor for entry of T-tropic HIV-1 strains into CD4+ cells, now named fusin. Stromal derived factor-1 (SDF-1) is an endogenous ligand for fusin, also called CXCR-4. Here we show the distribution of fusin/CXCR-4 mRNA during ontogeny in the rat. The onset of mRNA expression is around embryonic day 9 and the mRNA expression is high in the thymus as well as proliferative areas of the brain during development. Our results suggest: (1) that fusin/CXCR-4 might have a dual role in both brain development and the immune system; (2) that SDF-1 has a role in brain development or that additional physiological ligands exist for this receptor; (3) co-expression of CD4 and fusin/CXCR-4 may make fetuses susceptible to HIV infection during development.

West syndrome: cerebrospinal fluid nerve growth factor and effect of ACTH

West syndrome is a strictly age-limited encephalopathy of early infancy with unknown pathogenesis. It is often progressive, leading to mental retardation. Neurotrophic factors are important for the regulation of neuronal survival and differentiation, and their expression is influenced by hormones. Levels of beta-nerve growth factor in the cerebrospinal fluid were examined by two-site enzyme-linked immunosorbent assay method. Human antigen was used as a standard. We present data on largely normal levels of nerve growth factor in the cerebrospinal fluid of infants with cryptogenic etiology, but low or negligible levels in infants with symptomatic etiology, and very high levels in infants with symptomatic postinfectious etiology. Treatment with ACTH led to a greater increase in patients with a good response than in those with a poor response. Low nerve growth factor in patients with symptomatic infantile spasms possibly reflects massive neuronal death. The regression seen in these infants and their poor response to ACTH therapy may be due in part to lack of growth factors supporting neuron survival. This study, previously only demonstrated in animal models, is the first to depict nerve growth factor gene activity in humans as modulated by steroids.

The influence of angular misalignment on fixed-portal intensity modulated radiation therapy

A method has been developed to estimate potential dose errors due to linear accelerator angular setting misalignments of Intensity Modulated Radiation Therapy (IMRT) treatments. A first-order approximation to the dose error at a point is modeled as the dot product of the dose gradient and the shift vector of the point due to the rotational error. The analysis method is applied to a previously published set of optimized fluences for a 50 MV IMRT pelvis irradiation. Three of the published cases exhibiting a wide range of modulation are presented; a rectangular open field, a field optimized for a static multileaf collimator defining the portal outline coupled with a single broad bremsstrahlung profile modulation, and a fully modulated field using a physical modulator. To examine the energy dependence of angle setting errors, the study is repeated using the same fluence distributions, but with a dose-spread kernel appropriate for a 6 MV photon beam. The collimator angle error is set to 2 degree, and the dose error determined with both a centrally located isocenter and an isocenter chosen to model a split-field geometry. The dose error due to a 2 degree gantry setting error is assessed at a plane 10 cm distal to the isocenter. The mathematical form of the dose error due to couch motion is similar to the other two errors, so the dose error resulting from a couch angle missetting is not presented. The magnitude of the errors is largest for the 6 MV beam, while the volume encompassed by the errors is greater for the 50 MV beam. The gantry error yields the largest dose error values, with the 6 MV modulated case presenting dose errors of greater than 40%.

Cloning of a new chicken trkC extracellular isoform and its mRNA expression in E9 sensory and autonomic ganglia

Neuronal development and maintenance are regulated by trophic interactions with the target tissues and the innervating nerve. The neurotrophin family of polypeptide growth factors, consisting of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5), are produced in limited amounts in target areas. They bind to tyrosine receptor kinases of the trk family, including trkA, trkB and trkC, which mediate intracellular signalling in the responding neurons. There are reports of different isoforms of trkA, trkB and trkC having different signalling capacities. This study reports a novel deletion of the first cysteine-rich domain in the extracellular part of chicken trkC. We describe the mRNA expression of this isoform compared to non-deleted forms in E9 peripheral ganglia studied by reversetranscriptase-polymerase chain reaction (RT-PCR) and in situ hybridization. We also compare the mRNA expression pattern of two existing signal peptide sequences and the distribution of trkC mRNA detected by the use of a kinase specific probe. The results show that the novel isoform is expressed in peripheral sensory and autonomic ganglia. Moreover both signal peptide forms are detected in these ganglia by RT-PCR. In addition, in situ hybridization results showed a weak mRNA expression of the novel isoform in the E9 dorsal root ganglion (DRG) but not in Remak's ganglion. The two existing signal peptides are equally expressed in the DRG and Remak's ganglion, at labelling densities comparable to those for the full-length catalytic form of trkC.

Effects of neonatal stimulation on later cognitive function and hippocampal nerve growth factor

This study examined the behavioural and physiological effects of chronic mild stress on neonatally handled and non-handled rats. Neonatally handled and non-handled rats were exposed to chronic mild stress from weaning time to 6 months of age. They were behaviourally tested at 6 months of age, and sacrificed for analysis of nerve growth factor (NGF) in the hippocampus and hypothalamus. In contrast to the reported deleterious effect of acute strong stress, mild stress appeared to stimulate production of NGF in the hippocampus and improve spatial learning in both handled and nonhandled rats. Because neonatal handling produces neuroanatomical changes in the rat hippocampus and enhances cognitive function throughout the rats life span, these results implicate hippocampal NGF in the neuroprotective effects of handling.

Expression of serine/threonine kinase receptors in traumatic brain injury

The aim of this study was to investigate the expression of serine/threonine kinase receptors in the brain following traumatic brain injury. We report here that, the recently cloned and characterized bone morphogenetic protein (BMP) receptor type II (BMPR-II) and the activin receptor type IA (ActR-1) Act: mRNAs were simultaneously up-regulated in neurones in the dentate gyrus 6 h after a mild cerebral contusion injury. This findings was specific for these receptors since other investigated genes (i.e. ActR-II, ActR-IB, trkB and c-fos) showed other temporal patterns. These data suggest that type I and type II receptors act together in signal transduction in vivo and that BMPs may be involved in neuronal plasticity after traumatic brain injury.

Effects of X-irradiation on nerve growth factor in the developing mouse brain

The involvement of neurotrophins after radiation injury during brain development were studied in pregnant mice (C 57/B1) exposed on gestation day 15 to X-ray doses of 0.02-2 Gy. Nerve growth factor protein (NGF) and different cholinergic markers were investigated on postnatal day 1 (P1) and day 21 (P21); in situ hybridization with brain-derived neurotrophic factor (BDNF) and trkC (receptor serving to bind neurotrophin-3) probes was investigated on P21 in cortex, hippocampus, septum and cerebellum. The level of NGF protein was increased in irradiated forebrain on P1 in a dose-related manner. However, on P21 the NGF protein dropped down below the control levels in irradiated hippocampus and cerebellum. The response of acetylcholine esterase (AChE) activity in cerebellum at P21 was correlated with the changes in the amount of NGF. The intensity of cell labelling with trkC probe decreased after irradiation in the region of the hippocampus at P21, especially in dentate gyrus. The expression of BDNF mRNA was increased at P21 by low doses of irradiation (0.02-1 Gy) but was decreased by a high dose (2 Gy) in the same area. Thus, the radiation induced an alteration of neurotrophins, and the changes varied depending on the dose or time after irradiation. Such alterations in the pattern of growth factor production may modulate the response of cells to radiation. Furthermore, NGF protein levels and the expression of BDNF and trkC mRNA were affected by radiation doses as low as 0.02 Gy, indicating that during development the neurotrophins and their receptors are very sensitive to radiation.

Expression of serine/threonine kinase receptors including the bone morphogenetic factor type II receptor in the developing and adult rat brain

The expression patterns of serine/threonine kinase receptors in the central nervous system of the developing and adult rat were studied by in situ hybridization. The recently cloned bone morphogenetic factor receptor type II (BMPR-II) was compared with the ActR-II and several type I receptors including ActR-I, ActR-IB, BMPR-IA, BMPR-IB and TbetaR-I. We found that these receptors are spatially and temporally regulated. As early as embryonic day 11 (E11), BMPR-II mRNA was expressed in the neuroepithelium in brain and spinal cord. At E15, the expression of ActR-II mRNA was stronger than that of BMPR-II in the spinal cord, followed in intensity by the expression of ActR-I, ActR-IB, BMPR-IA, BMPR-IB and TbetaR-I mRNA. The BMP type I receptors were expressed only in the ependymal epithelium and in the sympathetic ganglia at E15. Many of the examined receptor mRNAs were expressed at peak levels in the brain around birth. In the adult brain, mRNA for BMPR-II was expressed in different patterns together with ActR-II and ActR-I. Thus, BMPR-II mRNA was found in neurons of the cortex, dentate gyrus, hippocampus, habenula and substantia nigra. ActR-II, ActR-I, ActR-IB and, weakly, TbetaR-I were all expressed in the dentate gyrus. In contrast mRNA for BMPR-IA and BMPR-IB was not found in the adult brain. It is suggested that the expressed receptors may mediate actions of members of the TGFbeta superfamily, e.g. BMPs, controlling the development and plasticity in the nervous system.

Molecular cloning of the chicken trkA and its expression in early peripheral ganglia

The neurotrophin tyrosine kinase receptors trkA, trkB, and trkC have been isolated and sequenced from several mammalian species. Their cognate ligands nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-4 (NT-4), and neurotrophin-3 (NT-3) act as survival and trophic factors for neurons in the peripheral nervous system (PNS). In this study we have focused on the isolation and expression of the chicken trkA homologue. In addition to a near full-length cDNA sequence described, including an extracellular six amino-acid motif earlier found in neuronal TrkA in human and rat, a novel insert of 150 base pairs (bp) between subdomains IX and X in the otherwise well-conserved intracellular kinase domain is reported. Phylogenetic analysis showed the relationship between chicken trkA and the mammalian trkA receptors. Comparisons of the extracellular domains showed some amino-acid motifs of putative NGF binding function to be well conserved in chicken TrkA. The early expression of trkA mRNA, including the alternatively spliced insert form, was localized by in situ hybridization. As early as embryonal day 3 (E3), trkA mRNA is expressed in the condensing dorsal root ganglia, and at E4 distinct trkA mRNA expression appears in the primary sympathetic chain ganglia. Finally, using a reverse transcriptase-polymerase chain reaction (RT-PCR) approach, we found that among several tested growth factors only fibroblast growth factor-2 (FGF-2) upregulated trkA mRNA expression in E9 sympathetic ganglion explants. This upregulation of trkA was corroborated by subsequent NGF-stimulated fiber outgrowth.

Chronic infusion of nerve growth factor into rat striatum increases cholinergic markers and inhibits striatal neuronal discharge rate

New strategies have recently been developed where infusion of neurotrophic factors into the brain can rescue different populations of neurons. Infusion of nerve growth factor (NGF) has been used in combination with transplants of chromaffin tissue to the striatum in the rat model of Parkinson's disease as well as to patients suffering from Alzheimer's disease. In this study we have evaluated the distribution of recombinant human NGF (rhNGF) in different brain areas and evaluated morphological and electrophysiological effects after continuous infusion for 2 weeks of rhNGF (500 micrograms/ml) into the striatum of normal rats. One week after termination of rhNGF infusion, NGF levels in the infused striata were 10-fold increased while in contralateral striata normal levels were found. Extracellular recordings from striatal neurons revealed a significantly decreased spontaneous firing rate (0.76 +/- 0.07 Hz) in rats infused with rhNGF compared to vehicle-infused control animals (1.36 +/- 0.16 Hz). Local application of rhNGF during recordings showed no direct inhibitory effect of NGF on neuronal discharge rate. Immunohistochemistry, using antibodies against acetyl cholinesterase (AChE) and glial fibrillary acidic protein (GFAP), revealed a 38.7 +/- 7.0% increase in optical density of AChE immunoreactivity close to the NGF source and an increase in GFAP-positive profiles that was restricted close to the implanted dialysis fibre. In situ hybridization showed an increase in mRNAs for choline acetyltransferase, trkA, p75 and muscarinic m2 receptor in the large neurons of rhNGF-infused striatum. Messenger RNAs for m1 and m4 receptors in striatal neurons were not changed. Thus, chronic infusion of rhNGF into the striatum caused a cholinergic hyperinnervation and reduced spontaneous activity of striatal neurons.

Long-term functional recovery from age-induced spatial memory impairments by nerve growth factor gene transfer to the rat basal forebrain

Nerve growth factor (NGF) stimulates functional recovery from cognitive impairments associated with aging, either when administered as a purified protein or by means of gene transfer to the basal forebrain. Because gene transfer procedures need to be tested in long-term experimental paradigms to assess their in vivo efficiency, we have used ex vivo experimental gene therapy to provide local delivery of NGF to the aged rat brain over a period of 2.5 months by transplanting immortalized central nervous system-derived neural stem cells genetically engineered to secrete NGF. By grafting them at two independent locations in the basal forebrain, medial septum and nucleus basalis magnocellularis, we show that functional recovery as assessed in the Morris water maze can be achieved by neurotrophic stimulation of any of these cholinergic cell groups. Moreover, the cholinergic neurons in the grafted regions showed a hypertrophic response resulting in a reversal of the age-associated atrophy seen in the learning-impaired aged control rats. Long-term expression of the transgene lead to an increased NGF tissue content (as determined by NGF-ELISA) in the transplanted regions up to at least 10 weeks after grafting. We conclude that the gene transfer procedure used here is efficient to provide the brain with a long-lasting local supply of exogenous NGF, induces long-term functional recovery of cognitive functions, and that independent trophic stimulation of the medial septum or nucleus basalis magnocellularis has similar consequences at the behavioral level.

Expression of activin receptors type I and II only partially overlaps in the nervous system

In situ hybridization was used to localize mRNA encoding two cooperative serine/threonine kinase receptors. Activin receptor IIA mRNA in the adult rat brain is highly expressed in the dentate gyrus, in the pyramidal neurones of CA3 and CA1, in the entorhinal cortex, in the cortical amygdaloid nucleus and in the amygdalohippocampal area. In the E16 rat embryo, labelling was found in the dorsal root ganglion neurones and in the spinal cord. Activin type I receptor (ALK-2/R-1) labelling was also localized to the hippocampal formation but with an even distribution over the granular cells of the dentate gyrus, the CA3 and CA1 pyramidal neurones, while no labelling was found in the entorhinal or amygdaloid areas. In the E16 rat no neuronal labelling was found. The incomplete overlap of these two expression patterns suggests that these receptors may locally have other partners for forming signalling receptor complexes.

Which is the most suitable number of photon beam portals in coplanar radiation therapy?

PURPOSE

Computer-controlled milling machines for compensator manufacture, dynamic multileaf collimators, and narrow scanned electron or bremsstrahlung photon beams have opened up new possibilities to shape nonuniform fluence profiles and have thus, paved the road for truly three dimensional (3D) dose delivery. The present paper investigates the number of beam portals required to optimize coplanar radiation therapy using uniform and nonuniform dose delivery.

METHODS AND MATERIALS

A recently developed algorithm has been used for optimization of the dose delivery in such a way that the probability of achieving tumor control without causing severe reactions in healthy normal tissues becomes as high as possible. This method has been used to optimize the delivered dose distribution for an increasing number of beam portals to determine how many coplanar beam portals are desirable to safely achieve a good treatment outcome. Target volumes in the head and neck, thorax, and abdomen have been investigated.

RESULTS

Nonuniform dose delivery allows a considerable improvement in the treatment outcome compared to uniform dose delivery. This is evident both from the probability of achieving complication-free tumor control and the value of relevant properties of the dose distribution, such as the mean value and the standard deviation of the mean dose to target volume and organs at risk. The results also show a close relationship between the dose distribution parameters and the probability of achieving complication-free tumor control. The level of complication-free tumor control first increases rapidly when the number of beam portals is increased, but already reaches a level of saturation after three to five beam portals. When the saturation level has been reached, the standard deviation of the mean dose to the target volume is around 3%.

CONCLUSIONS

To achieve optimal expectation value of the treatment outcome, within an accuracy of a few percent as measured by the probability of achieving complication-free tumor control, it is generally sufficient to use three nonuniform beam portals. A very large number of coplanar beams may only raise the probability of achieving complication-free tumor control by 1 to 2%. However, good treatment outcome with three beam portals requires that the directions of incidence of the coplanar nonuniform beams are optimally selected. If, on the other hand, the treatment is performed using uniform beams, it is not possible, even with an infinite number of fields, to obtain as high a level of complication-free tumor control as with a few nonuniform beams. From an optimization point of view, it is sufficient to reach a relative standard deviation of the mean dose to the target volume of around 3%. Improved dose homogeneity beyond this level will, in general, not significantly improve the complication-free tumor control.

Monitoring release of neurotrophic activity in the brains of awake rats

Intracerebral microdialysis of awake rats was used to monitor the possible release of neurotrophic factors from brain cells in response to injury and excitation. Perfusates were tested with ganglia bioassays and enzyme immunoassay. Trophic activity was released after implantation of the microdialysis probe into the hippocampus but not into the striatum, as assessed by increased nerve fiber outgrowth from Remak's ganglion. Kainic acid treatment significantly increased the release of trophic activity from hippocampal sites. These findings suggest that the brain responds to mechanical injury as well as to certain excitatory stimuli by regional extracellular release of neurotrophic activity that is not identical to the actions of known neurotrophic factors.

The levels of neurotrophin-3 protein in the rat brain determined by enzyme immunoassay show a pattern distinct from nerve growth factor

Using the monoclonal antibody 3W3 a two-site enzyme immunoassay (EIA) for neurotrophin-3 (NT-3) was established. The assay was sensitive to levels of NT-3 below 10 pg/ml and does not recognize nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF). In the adult rat brain, highest levels of NT-3 (1-1.5 ng/g tissue) were found in hippocampus and piriform cortex. Also the cerebellum contained detectable NT-3 protein. In the postnatal (P1 and P5) rat brain very high levels of NT-3 (7-9 ng/g) were found in the cingulate cortex consistent with previous observations of a local, transient NT-3 mRNA expression. NT-3 was also found prenatally in hippocampus, telencephalon and cerebellum. The EIA shows that the pattern of NT-3 protein in brain tissues is distinct from that of NGF.

The effect of mercury vapour on cholinergic neurons in the fetal brain: studies on the expression of nerve growth factor and its low- and high-affinity receptors

The effects of mercury vapour on the production of nerve growth factor during development have been examined. Pregnant rats were exposed to two different concentrations of mercury vapour during either embryonic days E6-E11 (early) or E13-E18 (late) in pregnancy, increasing the postnatal concentration of mercury in the brain from 1 ng/g tissue to 4 ng/g tissue (low-dose group) or 11 ng/g (high-dose group). The effect of this exposure in offspring was determined by looking at the NGF concentration at postnatal days 21 and 60 and comparing these levels to age-matched controls from sham-treated mothers. Changes in the expression of mRNA encoding NGF, the low- and high-affinity receptors for NGF (p75 and p140 trk, respectively) and choline acetyltransferase (ChAT) were also determined. When rats were exposed to high levels of mercury vapour during early embryonic development there was a significant (62%) increase in hippocampal NGF levels at P21 accompanied by a 50% decrease of NGF in the basal forebrain. The expression of NGF mRNA was found to be unaltered in the dentate gyrus. The expression of p75 mRNA was significantly decreased to 39% of control levels in the diagonal band of Broca (DB) and to approximately 50% in the medial septal nucleus (MS) whereas no alterations in the level of trk mRNA expression were detectable in the basal forebrain. ChAT mRNA was slightly decreased in the DB and MS, significantly in the striatum. These findings suggest that low levels of prenatal mercury vapour exposure can alter the levels of the NGF and its receptors, indicating neuronal damage and disturbed trophic regulations during development.

Effects of transferrin receptor antibody-NGF conjugate on young and aged septal transplants in oculo

The purpose of this study was to investigate the effects of nerve growth factor (NGF) conjugated to a monoclonal transferrin receptor antibody (OX-26) on septal transplants in oculo. Three different doses of OX-26-NGF conjugate (0.3, 3, and 50 micrograms/injection) were injected into the tail vein of young adult hosts 2, 4, and 6 weeks following intraocular transplantation of fetal forebrain tissue containing septal nuclei. Intravenous injections of OX-26 alone, NGF alone, and saline served as controls. An increase in intraocular tissue growth, as well as an increase in the intensity of immunoreactivity for p75 receptors and acetylcholinesterase, was observed following peripheral OX-26-NGF administration at the two highest doses tested. In addition, aged host rats with 16-month-old intraocular septal grafts were injected intravenously with OX-26 or OX-26-NGF (10 micrograms NGF/injection) every 2 weeks until the transplants were 24 months old. The intensity of choline acetyltransferase-like (ChAT) staining appeared to be greater and the cell bodies were larger with more processes in aged transplants in hosts treated with the OX-26-NGF conjugate than in aged OX-26-treated subjects. The present results suggest that peripheral OX-26-NGF can deliver biologically active NGF across the blood-brain barrier and have dose-dependent positive effects on both aged and developing cholinergic neurons in septal transplants.

In vitro toxicity of methyl mercury: effects on nerve growth factor (NGF)-responsive neurons and on NGF synthesis in fibroblasts

The effect of methyl mercury chloride (MeHgCl) on the chick sympathetic and sensory dorsal root ganglia was studied in a biological in vitro assay. These cultures were not affected by the addition of MeHg up to a concentration of 2 microM. However, after an addition of 4-5 microM MeHg the capability of the neurons to respond to added nerve growth factor (NGF) was completely inhibited. The effect of MeHg was also examined in a fibroblast cell line, mouse 3T3 cells. After the addition of mercury to the culture medium at concentrations as low as 0.1 microM, an elevated production of the NGF protein was observed. However, NGF mRNA measured in the individual fibroblast cells by in situ hybridization was found to be reduced to about 80% of the control in the low level at day 2 of exposure. These results suggest that the release of NGF is actively enhanced from the 3T3 cells by addition of low levels of mercury. The results thus show that MeHg at low to moderate concentrations has adverse effects on NGF responses in cultured neurons and moreover alter levels of NGF production in cells, suggestive of mechanisms for mercury toxicity in the developing nervous system.