Detection of visual activation in the rat brain using 2-deoxy-2-[(18)F]fluoro-D: -glucose and statistical parametric mapping (SPM).

PURPOSE: This study was designed to assess changes in brain glucose metabolism in rats after visual stimulation. MATERIALS AND METHODS: We sought to determine whether visual activation in the rat brain could be detected using a small-animal positron emission tomography (PET) scanner and 2-deoxy-2-[(18)F]fluoro-D: -glucose (FDG). Eleven rats were divided into two groups: (a) five animals exposed to ambient light and (b) six animals stimulated by stroboscopic light (10 Hz) with one eye covered. Rats were injected with FDG and, after 45 min of visual stimulation, were sacrificed and scanned for 90 min in a dedicated PET tomograph. Images were reconstructed by a three-dimensional ordered subset expectation maximization algorithm (1.8 mm full width at half maximum). A region-of-interest (ROI) analysis was performed on 14 brain structures drawn on coronal sections. Statistical parametric mapping (SPM) adapted for small animals was also carried out. Additionally, the brains of three rats were sliced into 20-microm sections for autoradiography. RESULTS: Analysis of ROI data revealed significant differences between groups in the right superior colliculus, right thalamus, and brainstem (p < or = 0.05). SPM detected the same areas as the ROI approach. Autoradiographs confirmed the existence of hyperactivation in the left superior colliculus and auditory cortex. CONCLUSIONS: To our knowledge, this is the first report that uses FDG-PET and SPM analysis to show changes in rat brain glucose metabolism after a visual stimulus.

Rapid stimulation of diacylglycerol production in Xenopus oocytes by microinjection of H-ras p21.

The p21 products of ras proto-oncogenes are thought to be important components in pathways regulating normal cell proliferation and differentiation. These proteins acquire transforming properties as a result of activating lesions that convert ras genes to oncogenes in a wide array of malignancies. In Xenopus laevis oocytes, microinjection of transforming ras p21 is a potent inducer of maturation, whereas microinjection of a monoclonal antibody to ras p21 inhibits normal maturation induced by hormones. The phosphoinositide pathway is a ubiquitous system that appears to play a key role in diverse cellular functions. By use of the Xenopus oocyte system, it was possible to quantitate the effects of ras p21 microinjection on individual components of the phosphoinositide pathway. Within 20 minutes of microinjection, levels of phosphatidylinositol 4,5-bisphosphate, inositol 1-phosphate, and inositol bisphosphate increased 1.5- to 2-fold. The most striking effects were on diacylglycerol, which increased 5-fold under the same conditions. In contrast, the normal ras p21 protein induced no detectable alteration in any of the metabolites analyzed. The earliest effects of the transforming p21 on phosphoinositol turnover were observable within 2 minutes, implying a very rapid effect of ras p21 on the enzymes involved in phospholipid metabolism.

Extraction of the respiratory signal from small-animal CT projections for a retrospective gating method.

We propose a retrospective respiratory gating algorithm to generate dynamic CT studies. To this end, we compared three different methods of extracting the respiratory signal from the projections of small-animal cone-beam computed tomography (CBCT) scanners. Given a set of frames acquired from a certain axial angle, subtraction of their average image from each individual frame produces a set of difference images. Pixels in these images have positive or negative values (according to the respiratory phase) in those areas where there is lung movement. The respiratory signals were extracted by analysing the shape of the histogram of these difference images: we calculated the first four central and non-central moments. However, only odd-order moments produced the desired breathing signal, as the even-order moments lacked information about the phase. Each of these curves was compared to a reference signal recorded by means of a pneumatic pillow. Given the similar correlation coefficients yielded by all of them, we selected the mean to implement our retrospective protocol. Respiratory phase bins were separated, reconstructed independently and included in a dynamic sequence, suitable for cine playback. We validated our method in five adult rat studies by comparing profiles drawn across the diaphragm dome, with and without retrospective respiratory gating. Results showed a sharper transition in the gated reconstruction, with an average slope improvement of 60.7%.

[Research and surgery]. / Investigación y cirugía.

From the Second World War onwards an amazing development in science and clinical & surgery practice has taken place: antibiotics, blood storage, cardiac surgery, organ and tissue transplant, complete joint replacement, total intravenous nutrition or minimally invasive surgery. Paradoxically, during the last two decades of the XXth century, social popularity of doctors has decreased at the same time of some important changes: increases in costs of medical attention, trials against medical mistakes, some doubts on the real role of Academic Public Hospitals and rising in the importance of alternative medicine. Increasing complexity of biomedical research in the continuous changing age of molecular biology has promoted an increasing scepticism regarding clinics and surgeons are able to keep on contributing to medical advances. The study of the contemporaneous History of Medicine demonstrates that some of the more significant achievements have been accomplished by surgeons. Undoubtedly Science and Clinics must get adapted to these times of change and persist in generating important findings. Current Clinical and surgical practice is completely determined by yesterdays' scientific research; tomorrow won't be different.

[Design of experimental models in surgical investigation]. / Diseño de modelos experimentales en investigación quirúrgica.

INTRODUCTION: Research in Medicine is essentially based on three knowledge resources: diseased people (natural and primary), cadaveric bodies (Pathology primary resource) and experimental animals, whom constitutes physiopathologic knowledge resource. Experimental advances reached in the last century have determined the change of the concept "experimental animal" to a wider term: "experimental model". OBJECTIVES: This paper tryes to clarify this concept. To attain this goal, we must define previous considerations in the meaning of the concept "experimental models" and its two key-elements: statistics and design of experiments.

Peripheral leukocyte response to oncological radiotherapy: expression of heat shock proteins.

PURPOSE: To study Heat Shock Proteins (HSP) expression in patients subjected to radiotherapy and their potential use as biomarkers for radiation tolerance. An evaluation is also made of whether irradiated volume is critical to the outcome of normal tissue injury using polymorphonuclear neutrophils as biosensors, and whether HSP antibodies (Ab) may be involved in post-radiotherapy disease. MATERIAL AND METHODS: Twelve patients receiving the same total dose of radiotherapy, but in three different volumes, and four healthy volunteers used as controls were analysed. hsp27 and 70i mRNA were determined by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and Southern-blot, HSP by flow cytometry, and HSP-Ab by Enzyme-linked Immnoadsorbent Assay (ELISA). The clinical protocol included radiation related toxicity based on clinical and analytical scales. RESULTS: Radiotherapy caused hsp downregulation, maximum in patients with the largest irradiated volumes, and a decrease in intracellular HSP content. Patients with greatest intraleukocyte HSP levels before treatment suffered more severe radiation morbidity. Patients with endocrine neoplasms presented the highest HSP-Ab titers. CONCLUSIONS: Radiotherapy downregulates hsp27 and 70i, which would enhance radiosensitivity. HSP content prior to treatment is suggested as a prognostic biomarker for radiation tolerance, with circulating leukocytes as biosensors. HSP-Ab may be biomarkers of tumor disease, but do not seem to be involved in the morbidity of acute post-radiotherapy disease, which is closely related to the volumes irradiated.

Comparison between intra- and extracellular surfactant in respiratory distress induced by oleic acid.

The present study compares the phospholipid distribution and protein content in bronchoalveolar lavage, purified extracellular surfactant and lamellar bodies isolated from rabbits killed at intervals of 2.5, 12 and 24 h after oleic acid administration. The data suggest that the alteration of pulmonary surfactant could be partially due to the type II cell response to the injury.

Association of changes in lysophosphatidylcholine metabolism and in microsomal membrane lipid composition to the pulmonary injury induced by oleic acid.

Alterations in the lipid composition of lung microsomal membranes occur in oleic acid-induced respiratory distress. The marked decrease in the phosphatidylcholine/lysophosphatidylcholine molar ratio could be related with an altered metabolism of lysophosphatidylcholine in these membranes. Results revealed that the activity of phospholipase A increased whereas that of acyl-CoA:lysophosphatidylcholine acyltransferase decreased. Microsomal lysophospholipase activity remained unchanged. On the other hand, the microsomal enzyme system involved in the de novo synthesis of diacylglycerol was impaired, and cholinephosphotransferase activity was lowered. These changes in the activity of some membrane-bound enzymes were not caused by changes in the membrane lipid fluidity since lipid structural order parameter (SDPH) did not change and neither did the major factors on which the fluidity depends. The possible significance of microsomal lipid alterations in the pathogenesis of respiratory distress induced by oleic acid is discussed.

Cardiac beta-adrenoceptors, G-proteins and adenylate cyclase regulation during myocardial hypertrophy.

The role of the beta-adrenoceptor-G-protein-adenylate cyclase system in the pathogenesis of cardiac hypertrophy was studied. We have used a minipig model of pressure-overload cardiac hypertrophy secondary to aortic banding. Four groups of five animals were used: minipigs made hypertrophic were evaluated 2 months (CH2 group) and 9 months (CH9 group) later and compared to controls (C2 and C9 groups, respectively). A decrease in beta-adrenergic receptor density and an increase in antagonist affinity were shown in left ventricular membranes of hypertrophied animals compared with controls. In both groups, CH2 and CH9, an increase in EC50 for isoproterenol-stimulated adenylate cyclase activity, an increase in forskolin-stimulated adenylate cyclase activity and a diminished inhibition by carbachol of isoproterenol-stimulated adenylate cyclase were observed. In contrast, fluoride-stimulated adenylate cyclase activity was markedly increased only in the end stage of hypertrophy. alpha s-cholera toxin-catalysed ADP-ribosylation is increased in early hypertrophy and then decreases with late hypertrophy and a similar pattern is observed with alpha o pertussis toxin-catalysed ADP-ribosylation, whereas alpha i-ADP-ribosylation remains unchanged. Tissue content of Gs-, Gi- and Go-proteins, as assessed by specific antibodies, was found unchanged in CH9 and CH2 groups when compared with that in C9 and C2 control groups, respectively. Modifications in Gs functional activity in later hypertrophic stages, expressed as alterations in cholera toxin ADP-ribosylation and adenylate cyclase fluoride responsiveness, may be important in the pathogenesis of decompensation from compensated hypertrophy to cardiac failure.

Fluorescent and compositional changes in crystallin supramolecular structures in pig lens during development.

Water soluble proteins (WSPs) in Sus scrofa lenses from pigs in different developmental stages: (young (GI), young adult (GII), and middle-aged (GIII)) were separated using GF-HPLC, yielding fractions of different molecular weights. Non-tryptophan (345/420 nm) and tryptophan (280/345 nm) fluorescence was measured in these fractions. Relative non-tryptophan fluorescence increased with age at a rate directly correlated to the molecular weight of aggregates forming the different chromatographic fractions, while tryptophan fluorescence tended to decrease. The crystallins constituting each fraction were separated using 2D-electrophoresis and after development with Coomassie blue they were identified using MS-TOF. Also, the protein content of each spot was quantified by subsequent scanning and integration. The proportions of unchanged crystallins characteristically changed with age in chromatographic fractions of different molecular weights. Thus it was possible to relate these changes with those occurring in the fluorescent properties and molecular weight of supramolecular structures.

Levels and activity of brain protein kinase C alpha and zeta during the aging of the medfly.

Brain protein kinase C (PKC) activity, as well as PKC alpha and PKC zeta levels detected by immunoblotting, were monitored during the lifespan of the Mediterranean fruit-fly Ceratitis capitata. PKC activity increased in the particulate fraction during the last stages of the life of C. capitata. Immunoblotting studies with an anti-PKC alpha antibody also demonstrated increased enzyme levels in the particulate fraction. Cytosolic levels of PKC zeta decreased in the terminal phase of the lifespan of the fly, whereas levels of membrane-bound PKC zeta increased at that stage. Results thus indicate that during C. capitata final phase of life a translocation of PKC alpha and PKC zeta to the particulate fraction occurs, and therefore both kinases could be involved in the terminal process of this fruit-fly.

Hydrodynamic and biochemical effects of isolated hypothermic renal perfusion depending on the pump model and perfusion solution.

OBJECTIVES: To evaluate hydrodynamic, biochemical, and histological consequences of hypothermic isolated renal perfusion using a new computerized perfusion system. MATERIALS AND METHODS: The device that allowed us to obtain on renal hydrodynamics during perfusion included multiple parts. The organ was perfused at 4 degrees C with a constant flow either using a classic roller pump or a pump designed in our laboratory to employ vacuum or atmospheric pressure sequentially to achieve a truly pulsatile wave (vacuum-powered tubular pump). The study included 16 minipigs with Eurocollins or Belzer perfusion solutions sampled at predefined interval and histological studies of the organs performed. RESULTS: There was a significant difference in weight increase between the two types of pumps; those perfused with Eurocollins showed greater values than those with Belzer solution. Onset of nitric oxide (NO) in the perfusion solution increased inversely with the renal vascular resistance. The highest NO levels were observed with the Belzer solution and vacuum pump. CONCLUSIONS: Changes in renal hydrodynamics, as induced by perfusion wave form and solution type, may be recorded in real time using a computerized system. A vacuum pump with the Belzer solution achieved the best experimental results.

Simulated surgery on computed tomography and magnetic resonance images: an aid for intraoperative radiotherapy.

Intraoperative radiotherapy (IORT) is a relatively new technique in which irradiation with electrons is performed during an open surgery procedure. This approach poses significant problems in obtaining accurate dosimetry, since neither the pre- nor the postoperative patient images actually matches the irradiation field. Our objective was to implement a software tool able to provide an estimate of the dose distribution, overcoming the problem of the geometrical mismatch between the images and the surgical field during the irradiation. The program was developed in the C programming language, on a noncommercial version of a Philips EasyVision workstation. The application allows to create a new data set by manipulating the preoperative computed tomography and magnetic resonance images in order to simulate the final geometry of the surgical area during the IORT procedure. The exact dose distribution can then be calculated by transferring these new images to a standard radiotherapy planning system. Also an approximate dose distribution can be quickly displayed by superimposing isodose curves obtained from a water phantom. The proposed approach introduces a helpful tool for dosimetry and planning in IORT protocols, improving their accuracy and safety and allowing for more objective quality control and patient follow-up.

[Statistical parametric mapping (SPM) in nuclear medicine]. / Mapas de estadísticos paramétricos (SPM) en medicina nuclear.

In the scope of medical research, functional neuroimaging analysis permits the study of pathological or cognitive cerebral processes by using statistical quantification techniques. A tool of increasing use is the SPM (Statistical Parametric Mapping) software due to its wide availability and the variety of statistical studies that can be made. Nevertheless, being unaware of the theoretical background on which it is based may easily lead to inaccurate results and even to the reaching of erroneous conclusions. The present article summarizes these theoretical principles and discusses the main key points of the method without requiring advanced mathematical knowledge.

[Integration of multimodal medical images]. / Integración de imágenes médicas multimodalidad.

Multimodality analysis is becoming a required tool in medical practice due to the development of different image techniques and new imaging processing tools. This paper is a review of the basis of medical image integration, image fusion techniques, and their clinical applications, especially addressing our experience with brain tomographic studies in nuclear medicine and radiology.

Impact of ventricular enlargement on the measurement of metabolic activity in spatially normalized PET.

In pathologic brains with morphological alterations, the process of spatial normalization, as performed by SPM methods, may introduce a confounding effect in the measurement of metabolic activity data. To investigate the effect of the spatial normalization of PET images, we analyzed MRI and PET studies of 20 schizophrenic patients and 18 controls. Using a Talairach-based segmentation procedure and manual segmentation, we measured regional metabolic activity in the untransformed brains and after their spatial normalization. The effect of spatial normalization seems minimal for large ROIs like the main brain lobes, even in brains showing pronounced morphological abnormalities. However, the caudate nucleus shows a considerable change in metabolic activity values after normalization. This normalization effect is much larger in patients than in controls, and leads to artifactual differences between them. We obtained incorrect results (SPM analysis) regarding functional differences between patients and controls in the caudate due to this bias introduced by the spatial normalization. There was a significant correlation between the size of the lateral ventricles and the underestimation of metabolic activity of the caudate. Normalization bias seems to arise from a misalignment of the caudate in the normalized space, pixel overlap between the normalized caudate, and the caudate of the template being on average lower than 50% in both groups. Spatial normalization of the PET images of pathologic brains may introduce a potential source of error that should be taken into account in the analysis of functional data, in particular, in the study of small brain nuclei like the caudate.

Effects of MDMA on blood glucose levels and brain glucose metabolism.

PURPOSE: This study was designed to assess changes in glucose metabolism in rats administered single or repeated doses of MDMA. METHODS: Two different experiments were performed: (1) A single-dose study with four groups receiving 20 mg/kg, 40 mg/kg, saline or heat, and (2) a repeated-dose study with two groups receiving three doses, at intervals of 2 h, of 5 mg/kg or saline. Rats were imaged using a dedicated small-animal PET scanner 1 h after single-dose administration or 7 days after repeated doses. Glucose metabolism was measured in 12 cerebral regions of interest. Rectal temperature and blood glucose were monitored. RESULTS: Peak body temperature was reached 1 h after MDMA administration. Blood glucose levels decreased significantly after MDMA administration. In the single-dose experiment, brain glucose metabolism showed hyperactivation in cerebellum and hypo-activation in the hippocampus, amygdala and auditory cortex. In the repeated-dose experiment, brain glucose metabolism did not show any significant change at day 7. CONCLUSION: These results are the first to indicate that MDMA has the potential to produce significant hypoglycaemia. In addition, they show that MDMA alters glucose metabolism in components of the motor, limbic and somatosensory systems acutely but not on a long-term basis.