The cytoarchitecture, cytology, and synaptic organization of the basilar pontine nuclei in the rat. I. Nissl and Golgi studies.
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Animals↗
Biomedical subjects
C B McArdle
Publications and source records attributed to C B McArdle.
The cytoarchitecture, cytology, and synaptic organization of the basilar pontine nuclei in the rat. II. Electron microscopic studies.
The basilar pontine gray in adult rats was subjected to electron microscopic examination in order to characterize: 1) certain general cytologic features, 2) the principle categories of presynaptic profiles, and 3) the postsynaptic targets of the various categories of presynaptic boutons. General cytologic features included the presence of neuronal somata exhibiting either a smooth contoured nucleus and central nucleolus or an irregularly contoured nucleus with numerous invaginations and an eccentric nucleolus. In addition, dendritic protrusions with variable morphology were apparent as well as a class of dendrites and somata with a curious dense, granular matrix. Four general types of presynaptic profiles were distinguished and were classified as: round vesicle boutons, elongate vesicle, pleomorphic vesicle, and dense core vesicle boutons. The category of round vesicle boutons formed asymmetric synaptic contacts and included three subtypes. One group contained vesicles with diameters of 25-35 nm, a second group contained larger (40-60 nm) round vesicles, and a third group of much larger boutons (2.5-6.8 microns) exhibited the smaller round vesicles. Another general category of presynaptic profile contained distinctly elongated synaptic vesicles, formed symmetrical active sites, and ranged in size from 0.4-1.7 microns. A third category of synaptic end-structures was distinguished by the presence of pleomorphic synaptic vesicles and microtubules and exhibited a distinctive pale or lucent matrix, while the fourth type was characterized by a mixed population of clear and dense core vesicles. Analysis of the distribution of such bouton types over the surface of pontine neurons revealed that: somata and proximal dendrites were contacted by round, elongate, and dense core vesicle boutons; intermediate and distal dendrites received synapses from all categories of boutons including the large endings with smaller round vesicles, while dendritic spines were contacted by round vesicle boutons (large and small), the large boutons, and elongate vesicle boutons. Synapses were also observed to occur between two vesicle-containing profiles. In such situations, pleomorphic vesicle boutons were found to be postsynaptic to either elongate vesicle boutons or small boutons with round vesicles and at the same time were presynaptic to a dendritic profile.
Animals↗
Development of outer segments and synapses in the rabbit retina.
The peripheral retina of rabbits aged 0 to 60 days was studied by electron microscopy. Ribbon and conventional synaptogenesis was studied with serial sections, and the density of synapses of the inner plexiform layer was measured on large (1,500 micrometer 2) montages. Photoreceptor and bipolar ribbon synapses seem to develop similarly in that processes of the prospective dyad or triad contact the presynaptic ribbon-containing terminal one at a time. No statistically significant difference in the lengths of ribbon lamellae was found at 11 and 30 days. Conventional synapses appear to result from the aggregation of synaptic vesicles on one side of junctions that first existed as symmetrical membrane densities without vesicles. The length of the synaptic membrane specialization constant between 0 and 30 days. The density of inner plexiform layer conventional synapses remains at a low and roughly constant level from 0 to 9 days, after which there is an abrupt increase to a plateau at about 20 days. After nine days the density of ribbon synapses also increases, with an initially steep time course similar to that of conventional synapses. All subcategories of synapse studied (amacrine-to-amacrine, amacrine-to-bipolar, serial, and reciprocal) participate in the general increase between 9 and 20 days. Functional circuits of the inner plexiform layer thus seem to be assembled primarily during the second and third weeks of life.
Age Factors↗
Cervical spine MR imaging using multislice gradient echo imaging: comparison with cardiac gated spin echo.
Forty-one patients with suspected cervical spine disorders were studied using multislice gradient echo imaging (GE) technique, with a 1.5-T system. The images were compared to cardiac-gated spin echo (CGSE) images in the diagnosis of suspected cord and spinal disorders. Images were graded for ability to detect cord lesion, cord-CSF contrast, CSF-bone contrast and contrast between CSF and extradural abnormality. The signal-to-noise ratio and contrast-to-noise ratio were used to compare images. There was 44% decrease in contrast between cord lesion and normal cord on GE when compared to CGSE, except for spinal cord hemorrhage. There was a 40% improvement between bone and CSF contrast on GE compared to CGSE. GE images were significantly better qualitatively as well as quantitatively in the detection of extradural lesions. This effect was more marked in axial plane where CGSE images are extremely suboptimal. CGSE images are better than GE for spinal cord lesions, while GE are superior in the diagnosis of degenerative disease in the cervical spine.
Cerebrospinal Fluid↗
MR imaging of orbital blow-out fractures.
We report on a case of orbital blow-out fractures involving the medial and inferior walls. In this case conventional multiplanar 8 mm thick sections with magnetic resonance (MR) imaging proved to be more helpful than 1.5 mm axial thin sections with CT in demonstrating the extent of orbital floor herniation of fat. Entrapment of muscle was excluded. Oblique sagittal views were most helpful in evaluating the orbital floor, since the full course of the inferior rectus muscle is seen. Additionally, the optic nerve is seen along its entire length. Masking of intraorbital contents by isodense hemorrhage on CT studies apparently is not a problem with MR imaging if hemorrhage is small or nonacute.
Adult↗
Benign pleomorphic adenomas of the salivary glands: surface coil MR imaging versus CT.
High resolution magnetic resonance (MR) imaging of three salivary gland tumors was performed at 1.5 T and compared with CT. Two of the three tumors were well seen on CT. However, one required CT sialography to separate tumor from the remaining parotid parenchyma, and, in the other, soft tissue invasion could not be excluded on the basis of CT. Magnetic resonance imaging demonstrated sharp tumor margins with no evidence of invasion. All three tumors were pathologically proven benign pleomorphic adenomas confirming the MR findings. On T2 weighted images, the two large adenomas demonstrated inhomogeneity that was not observed on CT.
Adenoma, Pleomorphic↗
MR imaging of transverse/sigmoid dural sinus and jugular vein thrombosis.
Magnetic resonance (MR) imaging was performed on six patients with thrombosis involving the transverse/sigmoid sinus and jugular bulb/vein. Venographic confirmation was obtained in five cases. Thrombi were characterized by increased intraluminal signal on all planes of section and pulse sequences. The change in signal intensity from first to second echo for thrombi was qualitatively less than that found with slow flow. Partial thrombosis in one case was seen as a ring pattern of central intermediate intensity corresponding to the thrombus, surrounded by a peripheral ring of signal void related to flowing blood. The MR findings closely correlated with venography in predicting thrombosis. Evidence of thrombi was not available from CT. Magnetic resonance is well suited for the diagnosis of occlusive disease of the dural venous sinus and jugular bulb.
Aged↗
MR imaging of hyperacute intracranial hemorrhage in the cat.
Hyperacute intracerebral hematomas were successfully created in five cats by injecting a prepared blood sample in which the oxygen (O2) saturation ranged from 0-80%. T1- and T2-weighted spin-echo sequences and T2-weighted gradient refocused scans were obtained 2.5-10 hr after injection on a 1.5-T imaging system. Detailed histology or electron microscopy was performed on each brain to confirm the presence of intact red blood cells in a retracted clot matrix. Areas of the hematoma were hypointense relative to brain in all five cats on the gradient refocused scans. The hematoma was isointense relative to brain on the T1- and T2-weighted spin-echo scans in all cats except one, which suffered a seizure/respiratory arrest and died during the scanning procedure. Portions of the hematoma in this animal had a hypointense T2-weighted signal and a hyperintense T1-weighted signal, which corresponded to the predicted MR properties of intracellular methemoglobin. We hypothesize that acute (less than 10 hr old) hematomas that contain virtually 100% intracellular deoxyhemoglobin may not appear hypointense relative to brain on T2-weighted scan sequences at 1.5 T unless surrounding tissue hypoxia and/or anoxia promote additional changes, one of which may be the formation of intracellular methemoglobin.
Acute Disease↗
Surface coil MR of spinal trauma: preliminary experience.
Nineteen fractured vertebral bodies involving the spine from C1 to L2 in 14 patients were imaged with a 0.6-T magnet using prototypical surface coils. Ten of these patients were studied within the first week of trauma. CT and plain films are superior to MR in detecting fractures and identifying the origin of displaced fragments in cases of extensive comminution. However, all body fractures and most posterior element fractures in the thoracolumbar spine were visible on MR. Fractures involving the cervical neural arch were difficult to detect on transverse section without CT correlation. Our results indicate that MR can probably replace CT in the thoracolumbar region. MR is superior to CT in demonstrating ligamentous injury and trauma to the disk. Unlike CT, MR shows the relation of the thecal sac and spinal cord to retropulsed fragments and epidural hematoma. MR also visualizes cord parenchyma; two cases of cord hemorrhage were not seen on CT. Even at this early stage of development, surface coil MR promises to become important in the evaluation of spinal trauma, not only in assessing the integrity of the spinal canal and cord, but in separating stable from unstable fractures on the basis of disruption of the posterior ligaments and elements. Additionally, the demonstration of rupture of specific ligaments may have an impact on surgical management.
Adolescent↗
1.5-T MR imaging of pituitary microadenomas: technical considerations and CT correlation.
Thirty-seven patients with suspected pituitary tumors were evaluated prospectively with MR imaging at 1.5 T. MR detected a microadenoma at its correct location in all eight patients who underwent transsphenoidal surgery, while CT showed a focal abnormality in the correct location in only four of the eight patients. In patients who were clinically and endocrinologically considered to harbor a microadenoma, MR detected a focal pituitary signal abnormality in 83% and CT demonstrated a focal density abnormality in 42%. Infundibular displacement, focal gland convexity, and sellar-floor abnormality were seen equally well with CT and MR. MR imaging protocol included sagittal T1-weighted spin-echo, coronal inversion-recovery, and coronal spin-echo or cardiac-gated spin-echo images. Although inversion-recovery images were superior in detecting focal pituitary lesions, some microadenomas were better seen on T2-weighted images. Cardiac-gated spin-echo images showed focal pituitary lesions better than ungated images did. Our technique demonstrates MR's superior sensitivity to CT in detecting a pituitary microadenoma.
Adenoma↗
High-resolution MR imaging of juxtasellar meningiomas with CT and angiographic correlation.
The purpose of this study was to compare the relative merits of MR imaging, CT, and angiography in the preoperative evaluation and postoperative follow-up of patients with juxtasellar meningiomas. High-resolution MR studies in nine patients with juxtasellar meningiomas were evaluated and compared with CT and angiography. The techniques were compared for the evaluation of suprasellar, parasellar, and intrasellar extension, as well as for vascular displacement or encasement, postoperative recurrence or residual calcification, and bone changes. MR provided additional information considered significant by the neurosurgeon when compared with CT, and MR was considered superior to CT in the juxtasellar area. Although MR does not obviate angiography, in many cases angiographic findings were predictable by MR.
Cerebral Angiography↗