Neurotoxic effects of water-soluble contrast agents on rat hippocampus

Electrical activity in cells directly exposed to water-soluble radiographic contrast agents was investigated by intracellular and extracellular recordings from neurons in in vitro rat hippocampus slices. Measurements included extracellular field potentials, intracellular resting membrane potential and membrane conductance, postsynaptic events, action potential configurations and spontaneous electrical activity. The neurons were exposed to test solutions of an ionic contrast agent, sodium diatrizoate, and a nonionic contrast agent, metrizamide, as well as control solutions. The ionic contrast agent produces bursts of action potentials having epileptogenic characteristics which is temporally followed by a depression of all electrical activity. The nonionic contrast agent produces minimal convulsive-like electrical bursts, but does produce a consistent depression of transmembrane electrical potentials, though in a lesser degree than the ionic contrast agents. The excitatory electrical events appear to be related to large depolarizing post-synaptic events while the later electrical depression is at least partially due to hyperpolarization. The depressing effects may be related to the hyperosmolality of the test solutions; however, no excitatory changes are related to hyperosmolality. These results provide the initial data on the neurotoxicity of water-soluble contrast agents at the intraneuronal level.

CT of laryngeal tumors

CT is the radiographic procedure of choice in evaluating laryngeal neoplasia. CT not only is easily tolerable and relatively noninvasive for the patient but also assesses deep and extralaryngeal pathology. It allows tumor staging and, therefore, treatment planning to be more intelligently performed.

Effect of nuclear magnetic resonance on chromosomes of mouse bone marrow cells

Three groups of six male Balb/c mice, subjected to 30 MHz continuous wave NMR exposure in a static magnetic field of 7.05 K Gauss for one hour, were each compared to another group of ten unexposed mice with respect to chromatid and chromosomal aberrations. The exposed groups were sacrificed at two hours, 24 hours and 48 hours following NMR exposure respectively. Control mice were sacrificed 24 hours after sham-exposure. All groups had approximately 0.02 apparent aberrations per cell. These apparent aberrations were in the form of metacentric chromosomes, possibly resulting from a union of chromosomes at their centromeres or possibly simply chromosomes in association. The results are consistent with earlier in vitro findings that NMR exposure causes no adverse cytogenetic effects.

Nuclear magnetic resonance diagnosis of an anaplastic astrocytoma

A patient presented with an 8-month history of a progressive left homonymous visual field deficit, left hemiparesis, and a left thalamocortical sensory deficit that was not detectable by repeated conventional neurodiagnostic evaluations. Proton nuclear magnetic resonance (NMR) imaging revealed a right parietal lesion characterized by a prolonged T2 (spin-spin relaxation time). At surgery, the mass proved to be an anaplastic astrocytoma. NMR appears to be more sensitive than x-ray computerized tomography scanning in some patients with malignant gliomas and offers the clinician an additional probe with which to evaluate these patients.

Nuclear magnetic resonance evaluation of stroke. A preliminary report

Nine patients who had acute and subacute stroke were examined by nuclear magnetic resonance (NMR) using a 6-MHz Bruker Instruments proton scanner. A modified Carr-Purcell-Meiboom-Gill pulse sequence was used for signal detection. The resultant string of spin-echoes was Fourier transformed into projections that were subsequently back-projected to a series of spin-echo images. From these images, spin density and T2 were calculated for each pixel. The NMR scans revealed stroke in each of the patients, while CT demonstrated only eight of the lesions. T2 was prolonged in all of the ischemic regions and is the most sensitive NMR parameter in detecting stroke. These preliminary results suggest that NMR scanning of patients who have acute stroke may be clinically useful, and that the T2 component of the NMR signal is most important.

Accurate T2 NMR images

We present a method for producing accurate calculated T2 nuclear magnetic resonance (NMR) images. A modified Carr-Purcell-Meiboom-Gill pulse sequence is used to obtain a series of images with progressive T2 dependence. This image series is then analyzed pixel by pixel to generate a T2 and initial signal strength image. Tests performed using four samples of known T2 indicate accuracies of better than 9%.

Effect of bromocriptine and pergolide on pituitary tumor size and serum prolactin

Forty-two patients with elevated serum prolactin were treated in a randomized, open-label trial with the conventional ergot bromocriptine, or a new ergot pergolide. Before treatment, the patients underwent thorough endocrine evaluation and computed tomographic scan. All patients had prolactin levels greater than 25 ng/ml, and 27 patients had a pituitary mass. Follow-up studies performed after 6 months of treatment showed both drugs effectively reduced prolactin levels to normal, though pergolide effects were more rapid. There was no change in the contents of the pituitary fossa in the 10 patients with hyperprolactinemia but without pituitary mass. Sixty percent of patients with pituitary mass had diminution of tumor size. Pergolide appears to be an effective medical treatment for hyperprolactinemia and pituitary tumor and offers a possible alternative to bromocriptine and surgical treatment.

NMR evaluation of stroke in the rat

Cortical stroke was produced in rats by cautery occlusion of the middle cerebral artery distal to the lenticulostriate origins. Brains were removed, and nuclear magnetic resonance (NMR) scans of whole fixed brains and in vitro measurements of small samples were obtained. Brain tissue was then processed for histology. Routine scans used a modified spin-echo technique. Spin-density and T2-dependent scans were also obtained. Infarcts were detectable in 6 hr due to diminution of the spin-echo intensity from T2 prolongation. NMR changes increased gradually over 48 hr and coincided anatomically with evidence from the neuropathologic sections. NMR imaging is a very sensitive method of evaluating acute cerebral infarction in this animal model.

Neuroangiography with iohexol

Iohexol is a new, nonionic water-soluble contrast agent undergoing early clinical trials in the United States. Using a double-blind, parallel format, iohexol was compared with meglumine iothalamate (60 patients) for selective cerebral angiography, and with sodium meglumine diatrizoate (40 patients) for arch aortography. Iohexol produced significantly less pain than meglumine iothalamate or sodium meglumine diatrizoate. There were no significant differences in terms of heart rate, blood pressure, or electrocardiogram (ECG) changes. Both produced a transient tachycardia and hypotension after arch aortography, but significantly less so with iohexol. No significant complications occurred. Film quality was comparable between contrast agents except for diminished motion artifacts with iohexol. Iohexol appears to be a superior neuroangiographic contrast agent to current ionic drugs.

Choroidal osteoma

Choroidal osteomas are benign, juxtapapillary, choroidal tumors that mandate no treatment. They occur predominantly in young (median age, 20 years) females (90%). While ophthalmoscopy and fluorescein angiography reveal suggestive ophthalmic findings, echography, plain radiography, and especially computed tomography (CT) are important in establishing the correct diagnosis. These lesions may be clinically confused with various dystrophic lesions, atypical or amelanotic malignant choroidal melanoma, metastatic carcinoma, leukemic or lymphomatous infiltrates, choroidal hemangioma, choroidal scars of the macula, and organized subretinal hemorrhage. The exclusion of the differential consideration of malignant melanoma is most important since radiation and enucleation are therapeutic possibilities. Review of the literature shows that all nine reported cases with CT scans had clearly demonstrable calcific densities in the posterior pole of the affected eye. Four other cases are reported here with a summary of the typical clinical, radiologic, and pathologic findings. The role of CT in the evaluation of choroidal osteoma and the distinctiveness of the CT findings are stressed.

Neurotoxicity of iohexol: a new nonionic contrast medium

The neurotoxicity of iohexol was evaluated and compared with the neurotoxicity of sodium diatrizoate, meglumine iothalamate, and metrizamide. Direct neurotoxicity was evaluated with in vitro rat hippocampal slices, and angiographic neurotoxicity was studied in a cat's spinal cord following thoracic aortography. In the experiments with the hippocampal slices, the ionic agents, sodium diatrizoate and meglumine iothalamate, and metrizamide caused early excitatory changes in electrical activity and later inhibition, but iohexol caused only inhibition. In the experiments with the cat's spinal cord, the ionic contrast materials produced an increase in the ventral root reflexes, and iohexol and metrizamide produced no significant effect. These results indicate that iohexol is less neurotoxic than metrizamide and the ionic contrast materials and may be a very useful angiographic and/or myelographic contrast agent.

Computed tomography of the major salivary glands

Forty-eight patients with proven disease of the salivary glands were evaluated by computed tomography (CT). Twenty-seven patients had salivary gland neoplasm and all were identified by CT. Fifteen benign tumors appeared as discrete, sharply marginated, high-density masses embedded in an otherwise normal gland. All 15 were correctly identified as benign by CT. There were 12 malignant tumors; 10 were invasive and presented as poorly defined, relatively dense lesions which obliterated and/or transgressed adjacent fat and fascial planes. Two malignant tumors presented as discrete masses and were incorrectly considered to be benign by CT. Twenty-one patients with inflammatory disease of the salivary glands were studied. A variety of patterns were noted, the most common a relatively diffuse, irregular area of increased density in an enlarged gland. Salivary duct calculi, diffuse sialectasis, and enlarged lymph nodes were well demonstrated. Differentiation between focal and inflammatory disease and malignant neoplasm was difficult. Computed tomography may be augmented by coincident sialography, although it is seldom necessary.

Neurotoxic effects of water-soluble contrast agents on rat hippocampus: extracellular recordings

Synaptically evoked extracellular field potentials were obtained from the pyramidal cell layer of the Cal field of rat hippocampus slices. Synaptic activity was evoked by Schaffer's collateral stimulation. The effects of the water-soluble contrast agents Na-diatrizoate and metrizamide, as well as control solutions of NaCl and sucrose, were studied. Test solutions were 300-345 mOsm and had iodine concentrations of 3-30 mg I/ml. The effects of test solutions are apparent within 10 minutes and reversible within 30-45 minutes. Control recordings have a small positive potential, followed by a large negative spike and a final slow positive wave. Contrast agents have two effects. The first is an epileptogenic property characterized by repetitive negative spikes arising from an extended slow positive field. The second effect is a depression characterized by a reduction in the amplitude of the synaptically evoked fields, particularly the negative spikes. Na-diatrizoate predominately produces the first effect, while metrizamide principally produces the second. Hyperosmolar solutions only produce depression. These results correlate well with the clinical setting where Na-diatrizoate is a potent convulsant, while metrizamide produces symptoms compatible with neuronal depression. These results indicate that contrast agent seizure activity is not due to hyperosmolarity but to a more direct chemical effect. The depression, however, may be related to a hyperosmolar effect.

Intra-arterial cisplatin treatment of adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is unique among salivary gland tumors in both its natural history and in its response to nonsurgical treatment methods (ie, radiation and chemotherapy). The chemotherapeutic agent, cisplatin, seems to be unique in its ability to affect ACC. It might be that ACCs of the minor salivary glands are especially vulnerable to the intra-arterial method of administering this drug, because there are accessible feeding vessels to most locations in which these tumors occur. We have treated four patients with advanced ACC with intra-arterial cisplatin. The responses suggest that this method may be a useful adjunct in the management of this tumor both as a preoperative and as a palliative measure.

Epileptogenic effects of radiographic contrast agents: experimental study

Electrical activity in cells directly exposed to water-soluble radiographic contrast agents was investigated by intracellular recordings from neurons of the abdominal ganglia of Aplysia. Measurements of membrane resting potential, membrane conductance, synaptic and action potential configuration, and spontaneous electrical activity were performed. Test solutions included sodium diatrizoate, meglumine iothalamate, metrizamide, and control solutions. Solutions (100 and 200 mOsm) of these agents did not significantly alter resting membrane potential, membrane conductance, action potential frequency or configuration, or excitatory postsynaptic potentials. Inhibitory postsynaptic potentials were suppressed by contrast agents. These results suggest that contrast agents affect at least some neurons by disinhibition.

Effects of radiographic contrast agents on spinal cord physiology

Segmental reflexes in the spinal cords of cats anesthetized with chloralose were used to evaluate the neurophysiologic effects of radiographic contrast agents. The exposed lumbar spinal cord was bathed with concentrations of ionic and nonionic agents including saline, sodium meglumine diatrizoate, meglumine iothalamate, meglumine iocarmate, and metrizamide. The following responses were evaluated: flexor and extensor monosynaptic reflex; polysynaptic flexion reflexes; spontaneous ventral root activity. Hypertonic solutions generally produced a transient decrease in all reflex activity for up to 1 hour. Isotonic solutions produced no significant changes in the monosynaptic responses, but an increase in amplitude of polysynaptic responses, and increased spontaneous activity. The usual facilitory effects of flexion reflex on the flexor monosynaptic reflex were unchanged, but the expected inhibitory effect of flexion reflex on the extensor monosynaptic reflex was changed to excitatory. The relative ability to produced these effects was sodium meglumine diatrizoate greater than meglumine iothalamate greater than meglumine iocarmate greater than metrizamide.

Radiographic staging of juvenile angiofibroma

A staging system for juvenile angiofibroma based on computerized tomographic findings is suggested. The need for such an endeavor has come about because of a lack of standardization of tumor data in both individual series and interinstitutional reports. The various stages reflect the number of anatomic sites occupied by a lesion rather than the actual tumor size. The "simpler" tumors are confined to the medial part of the skull base and are entirely extracranial. As a tumor extends laterally and/or intracranially, the staging designation, and therefore the treatment plan, changes accordingly. Presumably, with the application of consistent diagnostic tools and standardized stage designations, the analysis of both morbidity and treatment data will become more meaningful.

Radiographic management of juvenile angiofibromas

Juvenile angiofibromas are benign, vascular, locally aggressive neoplasms that are preferably treated by surgical resection, or irradiation if surgery is not possible. Adequate surgery in the past has been limited by incomplete knowledge of the anatomy of the tumor and technical difficulties related to the vascularity. To better define the tumor, 12 patients with juvenile angiofibroma have been studied by axial and coronal high resolution computed tomography (CT). The extent of the neoplasm was better demonstrated by CT than by other techniques. Based on the CT findings, we propose an anatomic classification that is helpful in determining treatment methods. Nine patients were considered operable, and eight of these underwent preoperative embolization with Silastic spheres and Gelfoam. The preoperative embolization significantly reduced operative difficulty and the necessity for blood transfusions. Based on these cases, we believe the current radiographic management of juvenile angiofibromas should consist of plain films, CT, angiography and, in surgical cases, preoperative embolization.

Role of hydration state and thiol-disulfide status in the control of thermal stability and protein synthesis in wheat embryo

Reduced (GSH), oxidized (GSSG), and protein-bound (PSSG) glutathione were determined in dry and hydrated wheat embryos. Dry embryos contained about 0.6 mumoles per gram dry weight each of GSSG and PSSG, and these levels declined 5- to 10-fold within minutes after the onset of imbibition. GSH declined from about 8 to 2 mumoles per gram over a period of 90 minutes. Similar changes occurred when embryos were hydrated by storage at 100% relative humidity. The decline in glutathione levels was not reversed upon redrying hydrated embryos. About 40% of the cysteine residues of embryo protein was found to be in the disulfide form in both dry and imbibed embryos. The ability of wheat embryos to withstand heat shock was shown to correlate with water content but not GSSG content. Incorporation of [(35)S]methionine into protein was studied using a system based upon wheat embryo extract (S23). Incorporation rate was found to be sensitive to the nature of thiol added to the system and to be decreased by GSSG. S23 exhibited a substantial capacity to reduce GSSG and preparation of S23 having a GSSG content comparable to dry embryos required addition of large amounts of GSSG to the extraction buffer S23 prepared in this fashion exhibited a marked decrease in ability to support protein synthesis. These results suggest that the early decrease in GSSG during germination is necessary for optimal protein synthesis in wheat embryo.

Evaluation of subarachnoid hemorrhage and cerebral vasospasm by computed tomography

The CT findings in patients with subarachnoid hemorrhage include visualization of the aneurysm (10% of the cases), subarachnoid, intraventricular, or intracerebral hemorrhage (87% of cases scanned within five days), "ischemic" lucency secondary to spasm (10%), and hydrocephalus (54%).

Premature craniosynostosis: A common complication of juvenile thyrotoxicosis

Cranial vault suture opacification (apparent closure) and bone age were evaluated roentgenographically in ten children with thyrotoxicosis. The bone age was advanced greater than 2 SD in only one. In comparison to 96 control children of similar age, craniosynostosis was present in each of the patients with thyrotoxicosis. Children with advanced bone age, nine due to virilizing adrenal hyperplasia and three with precocious puberty, had normal radiographic patterns of cranial suture closure. Thyrotoxic premature craniosynostosis did not interfere with continued head circumference growth nor did it result in clinical or radiographic evidence of increased intracranial pressure. We conclude that premature craniosynostosis appears to be a common feature of juvenile thyrotoxicosis. Investigation of the possible long-term adverse effects of this entity on central nervous system function is advocated.