RESUMEN
Exocrine glands, e.g., salivary and pancreatic glands, play an important role in digestive enzyme secretion, while endocrine glands, e.g., pancreatic islets, secrete hormones that regulate blood glucose levels. The dysfunction of these secretory organs immediately leads to various diseases, such as diabetes or Sjögren's syndrome, by poorly understood mechanisms. Gland-related diseases have been studied by optical microscopy (OM), and at higher resolution by transmission electron microscopy (TEM) of Epon embedded samples, which necessitates hydrophobic sample pretreatment. Here, we report the direct observation of tissue in aqueous solution by atmospheric scanning electron microscopy (ASEM). Salivary glands, lacrimal glands, and pancreas were fixed, sectioned into slabs, stained with phosphotungstic acid (PTA), and inspected in radical scavenger d-glucose solution from below by an inverted scanning electron microscopy (SEM), guided by optical microscopy from above to target the tissue substructures. A 2- to 3-µm specimen thickness was visualized by the SEM. In secretory cells, cytoplasmic vesicles and other organelles were clearly imaged at high resolution, and the former could be classified according to the degree of PTA staining. In islets of Langerhans, the microvascular system used as an outlet by the secretory cells was also clearly observed. Microvascular system is also critically involved in the onset of diabetic complications and was clearly visible in subcutaneous tissue imaged by ASEM. The results suggest the use of in-solution ASEM for histology and to study vesicle secretion systems. Further, the high-throughput of ASEM makes it a potential tool for the diagnosis of exocrine and endocrine-related diseases.
Asunto(s)
Microscopía Electrónica de Rastreo/métodos , Páncreas , Glándulas Salivales , Animales , Femenino , Glándula de Harder/citología , Glándula de Harder/diagnóstico por imagen , Glándula de Harder/ultraestructura , Inmunohistoquímica , Ratones , Ratones Endogámicos ICR , Páncreas/citología , Páncreas/diagnóstico por imagen , Páncreas/ultraestructura , Glándulas Salivales/citología , Glándulas Salivales/diagnóstico por imagen , Glándulas Salivales/ultraestructura , Tejido Subcutáneo/irrigación sanguínea , Tejido Subcutáneo/diagnóstico por imagen , Tejido Subcutáneo/ultraestructuraRESUMEN
PURPOSE: Cerenkov-light imaging is a new molecular imaging technology that detects visible photons from high-speed electrons using a high sensitivity optical camera. However, the merit of Cerenkov-light imaging remains unclear. If a PET/Cerenkov-light hybrid imaging system were developed, the merit of Cerenkov-light imaging would be clarified by directly comparing these two imaging modalities. METHODS: The authors developed and tested a PET/Cerenkov-light hybrid imaging system that consists of a dual-head PET system, a reflection mirror located above the subject, and a high sensitivity charge coupled device (CCD) camera. The authors installed these systems inside a black box for imaging the Cerenkov-light. The dual-head PET system employed a 1.2×1.2×10 mm3 GSO arranged in a 33 × 33 matrix that was optically coupled to a position sensitive photomultiplier tube to form a GSO block detector. The authors arranged two GSO block detectors 10 cm apart and positioned the subject between them. The Cerenkov-light above the subject is reflected by the mirror and changes its direction to the side of the PET system and is imaged by the high sensitivity CCD camera. RESULTS: The dual-head PET system had a spatial resolution of â¼1.2 mm FWHM and sensitivity of â¼0.31% at the center of the FOV. The Cerenkov-light imaging system's spatial resolution was â¼275 µm for a 22Na point source. Using the combined PET/Cerenkov-light hybrid imaging system, the authors successfully obtained fused images from simultaneously acquired images. The image distributions are sometimes different due to the light transmission and absorption in the body of the subject in the Cerenkov-light images. In simultaneous imaging of rat, the authors found that 18F-FDG accumulation was observed mainly in the Harderian gland on the PET image, while the distribution of Cerenkov-light was observed in the eyes. CONCLUSIONS: The authors conclude that their developed PET/Cerenkov-light hybrid imaging system is useful to evaluate the merits and the limitations of Cerenkov-light imaging in molecular imaging research.
Asunto(s)
Imagen Molecular/instrumentación , Imagen Óptica/instrumentación , Tomografía de Emisión de Positrones/instrumentación , Animales , Encéfalo , Diseño de Equipo , Ojo/anatomía & histología , Ojo/diagnóstico por imagen , Fluorodesoxiglucosa F18 , Glándula de Harder/anatomía & histología , Glándula de Harder/diagnóstico por imagen , Modelos Biológicos , Imagen Molecular/métodos , Imagen Óptica/métodos , Fantasmas de Imagen , Tomografía de Emisión de Positrones/métodos , Radiofármacos , Ratas Desnudas , Relación Señal-RuidoRESUMEN
OBJECTIVE: To evaluate the Harderian gland in rabbits, guinea pigs, and chinchillas using B-mode ultrasound and to determine normal size and changes in size and/or location in normal and diseased eyes and orbits by ultrasonographic measurements. PROCEDURE: Normal Harderian glands were evaluated ultrasonographically in 20 rabbits, 10 guinea pigs, and eight chinchillas. The Harderian gland was measured ultrasonographically in horizontal and vertical planes. Normal Harderian gland sizes were then compared with sizes in 27 rabbits, 13 guinea pigs, and three chinchillas that had exophthalmos. RESULTS: Harderian glands in normal rabbits were 0.69 ± 0.07 cm (mean value ± SD) horizontally and 1.33 ± 0.14 cm vertically. Harderian glands in normal guinea pigs were 0.58 ± 0.05 cm horizontally and 0.61 ± 0.10 vertically. In normal chinchillas, the Harderian glands were 0.53 ± 0.04 cm horizontally and 0.53 ± 0.03 cm vertically. Harderian glands were significantly larger in the vertical plane in rabbits with exophthalmos (P = 0.001) and in the horizontal plane in guinea pigs with exophthalmos (P = 0.018). Harderian glands of rabbits with exophthalmos were significantly larger in both diseased and healthy glands in both planes compared with those of normal rabbits. Guinea pigs and chinchillas with exophthalmos had larger Harderian glands bilaterally in only the vertical plane. CONCLUSIONS: Ultrasonography is a valuable diagnostic imaging technique to evaluate the Harderian gland in the rabbit, guinea pig, and chinchilla. Retrobulbar pathologic processes cause enlargement of the Harderian gland, which may be attributable to inflammation or possible obstruction of the excretory ducts.
Asunto(s)
Chinchilla/anatomía & histología , Cobayas/anatomía & histología , Glándula de Harder/diagnóstico por imagen , Conejos/anatomía & histología , Animales , Femenino , Glándula de Harder/anatomía & histología , Masculino , Especificidad de la Especie , UltrasonografíaRESUMEN
Positron emission tomography (PET) using 2-deoxy-2-[(18)F] fluoro-D-glucose (FDG) as a radioactive tracer is a useful technique for in vivo brain imaging. However, the anatomical and physiological features of the Harderian gland limit the use of FDG-PET imaging in the mouse brain. The gland shows strong FDG uptake, which in turn results in distorted PET images of the frontal brain region. The purpose of this study was to determine if a simple surgical procedure to remove the Harderian gland prior to PET imaging of mouse brains could reduce or eliminate FDG uptake. Measurement of FDG uptake in unilaterally adenectomized mice showed that the radioactive signal emitted from the intact Harderian gland distorts frontal brain region images. Spatial parametric measurement analysis demonstrated that the presence of the Harderian gland could prevent accurate assessment of brain PET imaging. Bilateral Harderian adenectomy efficiently eliminated unwanted radioactive signal spillover into the frontal brain region beginning on postoperative Day 10. Harderian adenectomy did not cause any post-operative complications during the experimental period. These findings demonstrate the benefits of performing a Harderian adenectomy prior to PET imaging of mouse brains.
Asunto(s)
Encéfalo/metabolismo , Fluorodesoxiglucosa F18 , Glándula de Harder/cirugía , Neuroimagen/veterinaria , Tomografía de Emisión de Positrones/veterinaria , Radiofármacos , Animales , Encéfalo/diagnóstico por imagen , Lóbulo Frontal/diagnóstico por imagen , Lóbulo Frontal/metabolismo , Glándula de Harder/diagnóstico por imagen , Glándula de Harder/metabolismo , Ratones , Ratones Endogámicos BALB C , Neuroimagen/normasRESUMEN
The 18F isotope of fluoro-2-deoxy-D-glucose (FDG) is a radiotracer commonly used in positron emission tomography (PET) for determining regional metabolic activity in the brain. However, in rats and many other species with nictitating membranes, harderian glands located just behind the eyes aggressively incorporate 18F-FDG to the extent that PET images of the brain become obscured. This radioactive spillover, or 'partial volume error,' combined with the limited spatial resolution of microPET scanners (1.5 to 2 mm) may markedly reduce the ability to quantify neuronal activity in frontal brain structures. Theoretically, surgical removal of the harderian glands before 18F-FDG injection would eliminate the confounding uptake of the radioactive tracer and thereby permit visualization of glucose metabolism in the frontal brain. We conducted a pilot study of unilateral harderian gland adenectomy, leaving the contralateral gland intact for comparison. At 1 wk after surgery, each rat was injected intravenously with 18F-FDG, and 40 min later underwent brain microPET for 20 min. Review of the resulting images showed that the frontal cortex on the surgical side was defined more clearly, with only background 18F-FDG accumulation in the surgical bed. Activity in the frontal cortex on the intact side was obscured by intense accumulation of 18F-FDG in the harderian gland. By reducing partial volume error, this simple surgical procedure may become a valuable tool for visualization of the frontal cortex of rat brain by 18F-FDG microPET imaging.
Asunto(s)
Encéfalo/metabolismo , Fluorodesoxiglucosa F18 , Glándula de Harder/cirugía , Radiofármacos , Tomografía Computarizada de Emisión/veterinaria , Animales , Encéfalo/diagnóstico por imagen , Lóbulo Frontal/diagnóstico por imagen , Lóbulo Frontal/metabolismo , Glándula de Harder/diagnóstico por imagen , Glándula de Harder/metabolismo , Ratas , Ratas Sprague-Dawley , Tomografía Computarizada de Emisión/métodosRESUMEN
OBJECTIVE: This study investigated dopamine transporter blockade in the rat striatum after treatment with various doses of methylphenidate using a high-resolution small animal SPECT ('TierSPECT') and I-FP-CIT. METHODS: I-FP-CIT was administered intravenously 1 h after intraperitoneal injection of methylphenidate (3 mg.kg, 10 mg.kg) or vehicle. Rats underwent scanning 2 h after radioligand application. From the spatial resolution of the imaging system and the size of the rat striatum followed that 'true' radioactivity concentrations were underestimated by approximately 50%. From cerebellar and partial volume corrected striatal radioactivity concentrations, striatal equilibrium ratios (V3'') were computed as estimations of the binding potential. RESULTS: Vehicle-treated animals yielded striatal V3'' values of 3.5+/-0.9 (mean+/-SD). After pre-treatment with 3 mg.kg and 10 mg.kg methylphenidate, striatal V3'' values were reduced to 2.4+/-0.8 (independent t-test, two-tailed, P=0.026) and 1.7+/-0.6 (P<0.001), respectively. CONCLUSIONS: This first in-vivo study of rat dopamine transporter binding after pre-treatment with various doses of methylphenidate showed a dose-dependent reduction of striatal dopamine transporter binding. Results indicate that in-vivo quantification of dopamine transporter binding is feasible with I-FP-CIT and the TierSPECT method. This may be of future relevance for investigating in-vivo binding properties as well as pharmacological profiles of novel agents acting at the dopamine transporter binding site. Moreover, alterations of striatal transporter densities may be investigated in animal models of neurological and psychiatric diseases such as attention-deficit/hyperactivity disorder and Parkinson's disease.
Asunto(s)
Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/antagonistas & inhibidores , Neostriado/diagnóstico por imagen , Neostriado/metabolismo , Tomografía Computarizada de Emisión de Fotón Único/métodos , Algoritmos , Animales , Cerebelo/irrigación sanguínea , Cerebelo/diagnóstico por imagen , Circulación Cerebrovascular/fisiología , Interpretación Estadística de Datos , Inhibidores de Captación de Dopamina/farmacología , Relación Dosis-Respuesta a Droga , Glándula de Harder/diagnóstico por imagen , Masculino , Metilfenidato/farmacología , Cuello/irrigación sanguínea , Neostriado/efectos de los fármacos , Radiofármacos , Ratas , Ratas Wistar , Glándulas Salivales/diagnóstico por imagen , TropanosRESUMEN
To examine the reliability of quantitative positron emission tomography studies in the rat (Rat-PET), we assessed the influence of radioactivity accumulated in the Harderian glands on PET CMRglc determination. We measured CMRglc by PET and ex vivo dissection methods by using 2-[18F]fluoro-2-deoxy-D-glucose in rats with and without focal brain ischemia. The CMRglc values obtained by PET, after correcting with recovery coefficients, were higher than those measured by the ex vivo method at rostral slices, and reduction of the CMRglc in the ischemic brain was not demonstrated by PET in the frontal cortex. The radioactivity accumulated in the Harderian glands prevents the quantitative determination of CMRglc using Rat-PET.