technetium-tc-99m-exametazime and Body-Weight

Compared to lean subjects, obese men have less activation in the dorsolateral prefrontal cortex, a brain area implicated in the inhibition of inappropriate behavior, satiety, and meal termination. Whether this deficit precedes weight gain or is an acquired feature of obesity remains unknown. An adult animal model of obesity may provide insight to this question since brain imaging can be performed in lean vs. obese conditions in a controlled study. Seven diet-induced obese adult minipigs were compared to nine lean adult minipigs housed in the same conditions. Brain activation after an overnight fasting was mapped in lean and obese subjects by single photon emission computed tomography. Cerebral blood flow, a marker of brain activity, was measured in isoflurane-anesthetized animals after the intravenous injection of 99mTc-HMPAO (750 MBq). Statistical analysis was performed using statistical parametric mapping (SPM) software and cerebral blood flow differences were determined using co-registered T1 magnetic resonance imaging (MRI) and histological atlases. Deactivations were observed in the dorsolateral and anterior prefrontal cortices in obese compared to lean subjects. They were also observed in several other structures, including the ventral tegmental area, the nucleus accumbens, and nucleus pontis. On the contrary, activations were found in four different regions, including the ventral posterior nucleus of the thalamus and middle temporal gyrus. Moreover, the anterior and dorsolateral prefrontal cortices as well as the insular cortex activity was negatively associated with the body weight. We suggested that the reduced activation of prefrontal cortex observed in obese humans is probably an acquired feature of obesity since it is also found in minipigs with a diet-induced obesity.

Topics: Animals; Body Weight; Brain Mapping; Cerebrovascular Circulation; Diet; Fasting; Feeding Behavior; Magnetic Resonance Imaging; Male; Models, Animal; Obesity; Prefrontal Cortex; Satiation; Swine; Swine, Miniature; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

To evaluate the oxidative stress-related parameters and to determine their order of appearance in the brain aging process, radionuclide experiments were carried out on male DBF1 mice at 3, 12, 24 and 30 months of age. The content of nonprotein sulfhydryl compounds, mainly glutathione, was estimated with technetium-99m meso-hexamethyl propyleneamine oxime ([99mTc]meso-HMPAO) tissue sampling. Glucose transport and metabolism was examined with [1-14C]2-deoxy-D-glucose (2-DG) tissue sampling. Mitochondrial electron transport function was estimated with [15O]O2 gas-tissue ARG. [99mTc]Meso-HMPAO uptake in brain expressed as standardized uptake value (SUV), (radioactivity in brain tissue/tissue weight)/(total administered radioactivity/body weight), reached maximum at 12 months of age and decreased at 24 and 30 months of age in every region examined. The pattern of 2-DG, expressed as SUV, showed a tendency to increase rather than decrease with aging. [15O]O2 fixation in brain slices remained constant until 24 months, while it decreased significantly at 30 months of age. The results suggested the possibility of using imaging techniques in vivo for longitudinal evaluation of the aging process and indicated reduction of nonprotein sulfhydryl compounds including GSH at the early stages of aging may also accelerate the dysfunction of mitochondrial electron transport and neurodegeneration.

Topics: Aging; Analysis of Variance; Animals; Biological Transport; Body Weight; Brain; Deoxyglucose; Electron Transport; Glucose; Glutathione; Male; Mice; Mitochondria; Oxidative Stress; Radionuclide Imaging; Technetium Tc 99m Exametazime

Proposed radiopharmaceutical schedules based on readily measured parameters (age, height, weight, surface area) have been considered with respect to their applicability in nuclear medicine. Although schedules based on age are considered to be inappropriate, there are valid cases for schedules based on height, weight and surface area. For many radiopharmaceutical studies, the most appropriate schedules are based on weight or surface area. Examination of simple theoretical physical models, including the influence of attenuation, suggests that the optimum administered amounts of radiopharmaceuticals fall mainly within the region bounded by these two schedules. The results of recent clinical studies designed to test the validity of different schedules are summarized. In general, they support the predictions of theoretical models, but also show how simple models can be influenced significantly by the age dependency of radiopharmaceutical biodistribution. The schedule based on surface area (or height) is less likely than that based on weight to require the identification of minimum administered amounts of radiopharmaceutical to preserve image quality in small children. However, recent studies have shown that the most appropriate schedule for regional cerebral blood flow with 99Tcm-HMPAO is that based on weight, without the need for a minimum activity. Paediatric radiation dosimetry is briefly summarized to indicate some recent innovations in methodology. Effective doses per unit of administered radiopharmaceutical (mSv MBq-1) have been calculated using five paediatric phantoms for a number of radiopharmaceuticals commonly used in children. Values of total effective dose resulting from the application of the weight and surface area schedules are presented, based on the adult reference amounts of administered radiopharmaceutical proposed by the Paediatric Task Group of the European Association of Nuclear Medicine. Although some values of effective dose exceed 10 mSv for the surface area schedule, the majority of values are less than 5 mSv.

Topics: Body Height; Body Surface Area; Body Weight; Child; Child, Preschool; Dose-Response Relationship, Radiation; Humans; Infant; Infant, Newborn; Models, Biological; Phantoms, Imaging; Radiation Dosage; Radionuclide Imaging; Radiopharmaceuticals; Technetium Tc 99m Exametazime

Four methods of calculating the activity of 99Tcm-hexamethylpropyleneamine oxime to be administered in cerebral blood flow investigations of children were evaluated in patient studies. Three of the methods were based on the size of the child. We also constructed a theoretical dosage model based on physiological data and attenuation effects. The aim of the study was to find a dosage calculation method that gave the same image quality for children of all ages as well as for adults. The results showed that the dosage method based on body weight is the only one of the four methods that does not exhibit an age-dependent variation in image quality and therefore this method is recommended.

Topics: Adolescent; Adult; Body Height; Body Weight; Cardiac Output; Cerebrovascular Circulation; Child; Child, Preschool; Dose-Response Relationship, Drug; Humans; Infant; Infant, Newborn; Models, Theoretical; Organotechnetium Compounds; Oximes; Technetium Tc 99m Exametazime; Tissue Distribution; Tomography, Emission-Computed