Radiation protection - still necessary?

Knowledge about the effects of small doses of radiation on health is accumulating, and for example the maximum level of occupational exposure allowed for the lens of the eye will be lowered in the next radiation law. Radiographic examinations are carried out at various departments in a hospital. Although the numbers of examinations have decreased in Finland, the examinations are more complex, and more radiation than before as well as longer fluoroscopy times are utilized in them. The guidelines for radiation are consistent despite the fact that there is large variation in the radiologic studies and procedures performed at different departments.

Production of monocytic cells from bone marrow stem cells: therapeutic usage in Alzheimer's disease.

Accumulation of amyloid ß (Aß) is a major hallmark in Alzheimer's disease (AD). Bone marrow derived monocytic cells (BMM) have been shown to reduce Aß burden in mouse models of AD, alleviating the AD pathology. BMM have been shown to be more efficient phagocytes in AD than the endogenous brain microglia. Because BMM have a natural tendency to infiltrate into the injured area, they could be regarded as optimal candidates for cell-based therapy in AD. In this study, we describe a method to obtain monocytic cells from BM-derived haematopoietic stem cells (HSC). Mouse or human HSC were isolated and differentiated in the presence of macrophage colony stimulating factor (MCSF). The cells were characterized by assessing the expression profile of monocyte markers and cytokine response to inflammatory stimulus. The phagocytic capacity was determined with Aß uptake assay in vitro and Aß degradation assay of natively formed Aß deposits ex vivo and in a transgenic APdE9 mouse model of AD in vivo. HSC were lentivirally transduced with enhanced green fluorescent protein (eGFP) to determine the effect of gene modification on the potential of HSC-derived cells for therapeutic purposes. HSC-derived monocytic cells (HSCM) displayed inflammatory responses comparable to microglia and peripheral monocytes. We also show that HSCM contributed to Aß reduction and could be genetically modified without compromising their function. These monocytic cells could be obtained from human BM or mobilized peripheral blood HSC, indicating a potential therapeutic relevance for AD.

A new ultrasound method for determining the acoustic phase shifts caused by the skull bone.

A potential noninvasive means for obtaining the value of ultrasound (US) phase shifts caused by the skull is examined. Knowledge of these shifts could be used in new methods that restore the focus from an US array after transcranial propagation. In the present study, a pulsed signal was emitted from a single element of a therapeutic US transducer. The reflected signal was then recorded. The data were examined over the band width of the transducer, producing amplitude data as a function of frequency. A periodic appearance of local maxima and minima was observed in the data as a function of frequency. We hypothesize that the amplitude is primarily determined by the superposition of the reflections between the interfaces at the inner and outer surfaces of the skull and between the interior interfaces of trabecular and cortical bone. A homogeneous-layer model was used to predict the forward-propagated phase using the reflection data. Good correlation was found between the numeric calculation and phases measured after propagation through single-layer plastic plates. The method was used on curved three-layer plastic phantoms and four excised human skulls. The procedure could eventually be applied toward phasing multielement arrays. Such an application could have implications in both therapeutic and diagnostic brain procedures.

Multicenter evaluation of renography with an automated physical phantom.

PURPOSE: The diversity of the dynamic radionuclide renal imaging (renography) study protocols sets challenges for the overall study quality, therefore raising a need for national quality control. The aim of this study was to encourage the standardization of renography in Finland and to evaluate the development after a previous study performed in 1997. METHODS: The new Heikkinen phantom was imaged in each of the 20 participating nuclear medicine laboratories. The results were interpreted in the manner of a regular patient study, and reconstructions and printouts were made according to the clinical routines of each laboratory. Four quantitative parameters were calculated and compared between laboratories. The reports were also assessed in a blind test. RESULTS: The average error in T(max) values ranged from -5 to 7% (-29 to +18% in 1997), in T(1/2) from 0 to 35% (-43 to +66%), in RCA20 from -20 to +28% (-50 to +82%) and in relative uptake from -3 to 5%. The difference from average in relative uptake ranged from -4 to 5% (-21 to +36%). CONCLUSION: The results showed that the errors in T(max) and relative uptake were generally within quite acceptable margins, and the variation in quantitative parameters between laboratories was shown to be smaller than 14 years earlier. The reason might be the use of new software packages as well as increased efforts to improve the quality of the studies.

Silencing of either SR-A or CD36 reduces atherosclerosis in hyperlipidaemic mice and reveals reciprocal upregulation of these receptors.

AIMS: Macrophage scavenger receptor A (SR-A) and class B scavenger receptor CD36 (CD36) contribute to foam cell formation and atherogenesis via uptake of modified lipoproteins. So far, the role of these scavenger receptors has been studied mainly using knockout models totally lacking these receptors. We studied the role of SR-A and CD36 in foam cell formation and atherogenesis by RNA interference (RNAi)-mediated silencing, which is a clinically feasible method to down-regulate the expression of these receptors. METHODS AND RESULTS: We constructed lentivirus vectors encoding short hairpin RNAs (shRNAs) against mouse SR-A and CD36. Decreased SR-A but not CD36 expression led to reduced foam cell formation caused by acetylated low-density lipoprotein (LDL) in mouse macrophages, whereas the uptake of oxidized LDL was not altered. More importantly, silencing of SR-A upregulates CD36 and vice versa. In LDL receptor-deficient apolipoprotein B100 (LDLR(-/-)ApoB(100/100)) mice kept on a western diet, silencing of either SR-A or CD36 in bone marrow cells led to a marked decrease (37.4 and 34.2%, respectively) in cross-sectional lesion area, whereas simultaneous silencing of both receptors was not effective. CONCLUSION: Our results suggest that silencing of either SR-A or CD36 alone reduces atherogenesis in mice. However, due to reciprocal upregulation, silencing of both SR-A and CD36 is not effective.