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Biomedical subjects

A J Silver

Publications and source records attributed to A J Silver.

51 records · Page 3Linked to original sources
PubMed1983

Computed tomography of the brain stem with intrathecal metrizamide. Part II: lesions in and around the brain stem.

The practical usefulness of computed tomography with intrathecal metrizamide in imaging the brain stem is illustrated in six examples where the lesions were misdiagnosed on intravenously enhanced computed tomography, angiography, or air study. Focal and diffuse atrophic changes of the brain stem were demonstrated in symptomatic patients where none of the other radiographic or clinical investigations were conclusive. Metrizamide computed tomography is probably the most sensitive method for imaging lesions in and around the brain stem and cerebellopontine angle.

Adolescent↗
PubMed1982

Computed tomography of cerebellar hemangioblastomas.

Ten patients with proven cerebellar hemangioblastomas were studied by computed tomography (CT). Angiography was obtained in seven cases. Eight patients had a cyst and a nodule, one presented with a nodule only, and one with a cyst only. Some morphological features on CT were found particularly helpful in establishing the histological diagnosis of this tumor. All cysts in this series had either a nonenhancing wall or a thin, discontinuous enhancement rim. The remarkable thinness of the cyst is a helpful feature in differentiating between hemangioblastomas and ring enhancement due to metastases. All hemangioblastoma nodules are near the pia, particularly the tentorial surface or the occipital surface of the cerebellum. The nodules in this series were isodense with brain before and enhanced significantly after contrast medium injection, matching or exceeding the density of the straight sinus. In three cases, a large vessel leading to the nodule could be identified on CT. In only one of 10 cases was there a central lucency in the enhancing nodule. The CT density of the hemangioblastoma cyst correlated with the size of the nodule, i.e., the larger the nodule, the denser the cyst on precontrast studies. Compared to cerebellar astrocytomas, hemangioblastomas are not calcified and tend to have relatively small nodule associated with a large cyst. For a given size cyst, the nodule in an astrocytoma is usually larger.

Adult↗
PubMed1982

Computed tomography of tumors involving the atria of the lateral ventricles.

Computed tomograms, angiograms, and operative findings in 18 intra-atrial and 6 para-atrial lateral ventricle tumors were reviewed. Intra-atrial tumors were characteristically homogeneous, with an intraluminal mass effect. The benign types engulfed the choroid glomus; on angiography, the choroidal arteries were enlarged, with a definite tumor blush. Intra-atrial tumors without choroid involvement were usually gliomas. Para-atrial tumors had a low-density center on CT scans (in adults) with an extraluminal mass effect, displaced the glomus, and were avascular on angiography. They were low-grade gliomas in adults and ependymoblastomas in children. Forty non-atrial paraventricular and intraventricular masses were also reviewed. In general, an intraventricular, homogeneous mass which engulfs the choroid glomus on CT and has a significant choroidal artery supply on angiography is of choroidal origin and likely to be benign.

Cerebral Angiography↗
PubMedDate not supplied

Effect of gastrointestinal peptides on ingestion in old and young mice.

Early satiety may play a role in the anorexia of aging. The effects of the peripheral satiety agents cholecystokinin (CCK), bombesin, glucagon, and calcitonin were studied in 8 and 25 month old mice. During normal feeding behavior, the older mice consumed more than their younger counterparts, however, when food deprived, the younger consumed more. All peptides inhibited food intake over the first hour after administration in young and old mice. CCK, bombesin, and calcitonin suppressed feeding in 25 month old mice to a greater extent than in 8 month old mice. However, CCK demonstrated the greatest age-related suppression of food intake. CCK has a potential role to play in the pathogenesis of the anorexia of aging.

Aging↗
PubMedDate not supplied

Do peptide-induced changes in feeding occur because of changes in motivation to eat?

The usual paradigm in which peptides are tested for their effect on food intake involves measuring intake of readily available food. In the lever press apparatus, the subjects must "work" to get food. Such work has traditionally been used as a means of measuring motivation. Mice were trained to press a lever for milk reinforcement. After achieving a stable level of performance, we tested the effects of gastrin-related peptide (GRP), bombesin (BBS) and cholecystokinin octapeptide (CCK-8) on lever pressing. All three peptides suppressed lever pressing for milk reinforcement. Prefeeding mice with milk increased the suppression of lever pressing to a greater extent in peptide-treated mice than in saline-treated mice. As the duration of prefeeding increased, lever pressing decreased. When mice were required to make more lever presses to obtain milk, both saline- and CCK-8-treated mice increased their lever pressing. However, saline-treated mice pressed at a higher rate than CCK-8-treated mice. Unlike the results obtained with saline and CCK-8, administration of a known gustatory adversant, lithium chloride, suppressed lever pressing to the same degree in mice fed or not fed prior to training. The results are consistent with the hypothesis that these peptides act as satiety agents.

Analysis of Variance↗
PubMedDate not supplied

Angiotensin II and fluid ingestion in old rats.

Fluid ingestion was studied in Fischer 344/Brown Norway F1 rats aged 3, 12, 20, and 24 months of age. There was an age-related decrease in fluid ingestion when fluid intake was measured over 24 h. After water deprivation, 24- and 20-month-old rats drank less than 3- and 12-month-old rats. Twelve, 20-, and 24-month-old rats had less fluid intake associated with food deprivation than did 3-month-old rats. Three month old rats drank more fluid after angiotensin II than did 12-, 20-, and 24-month-old rats when expressed as fluid intake per kg body weight. These studies confirm that the rat is a reasonable model to study age-related hypodipsia.

Aging↗
PubMedDate not supplied

Anorexia in the elderly.

Weight loss and anorexia occur commonly in the elderly. While in many cases the anorexia can be attributed to associated disease processes, it does appear that a true anorexia of aging exists. Animal studies have suggested that older rodents have an excessive satiety effect of cholecystokinin and a decreased opioid feeding drive. Other older persons develop anorexia in association with depression. In these subjects, excess corticotropin-releasing factor may be the neurotransmitter involved in the pathogenesis of the anorexia. In Alzheimer's disease, decreases in norepinephrine and neuropeptide Y may be involved in the anorexia seen in the these patients.

Aged↗
PubMedDate not supplied

Computed tomography of primitive neuroectodermal tumors.

The primitive neuroectodermal tumor is a neoplasm of young individuals that occurs predominantly in the supratentorial compartment. It appears on computed tomography as a bulky mass, often with calcification with predominantly homogeneous enhancement but on occasion with cystic or necrotic areas. Cerebrospinal fluid seeding was observed in more than half the cases in our series. The patients had a short survival period (7-24 months). Despite surgery, radiation, and chemotherapy, further growth of this tumor has not been prevented.

Adolescent↗
PubMedDate not supplied

In vivo NMR imaging of tissue sodium in the intact cat before and after acute cerebral stroke.

The first in vivo nuclear magnetic resonance (NMR) images of tissue sodium in the intact animal are presented. The distribution of sodium in the normal cat's head is described. An experimental stroke was surgically induced. Sodium NMR imaging showed a pronounced focal increase in cerebral sodium concentration 9 hr after ligation of the middle cerebral artery. The method appears to be very sensitive for early detection of infarction. The measured increase in the regional sodium NMR signal probably reflects both a true increase in concentration of brain sodium and an increased NMR visibility of the sodium nucleus in the region of the infarction.

Animals↗
PubMedDate not supplied

Computed tomography of the anteverted internal auditory canal.

A symmetric variation in the course of the internal auditory canals, visualized best on axial computed tomographic views with thin sections, was observed in three of 75 patients examined mainly for hearing, vestibular, and facial nerve dysfunction. The incidence may be lower in an unselected population. In coronal section, with either pluridirectional or computed tomography, an anteverted internal auditory canal may mimic the normal configuration of "medial narrowing" because of the effect of partial sectioning of an angled cylinder with a thin beam. The pathologic significance of this finding is uncertain. In the three cases reported, it was associated with adult-onset uni- or bilateral hearing loss. Vestibular function may be compromised but may not be symptomatic. Facial nerve function was not impaired.

Adult↗
PubMedDate not supplied

Patterns of spinal cord atrophy by metrizamide CT.

Forty patients with cervical myelopathy underwent high-resolution computed tomography (CT) with intrathecal administration of metrizamide for evaluation of cervical spinal cord atrophy. Thirty of them showed evidence of either focal atrophic distortion or generalized accentuation of the anatomic surface features of the spinal cord. Patients with a Chiari malformation or syringomyelia were excluded. The characteristic features in cervical spondylosis and canal deformity include flattening of the ventral surface of the cord, central infolding, beaking of the lateral funiculi, and wasting of the dorsal surface of the cord. Patients with motor neuron disease showed a combination of anterolateral and posterolateral atrophy reflecting underlying degeneration of the anterior horn cells and/or corticospinal tracts, respectively. Those with monomelic motor neuron disease had a striking ipsilateral hemiatrophy of the spinal cord. Among those presenting with spastic paraparesis, seven with clinically definite multiple sclerosis showed diffuse atrophy or focal degeneration due to a localized plaque of demyelination. Two cases of cord neoplasm showed atrophy secondary to ascending or descending degeneration of the long tracts.

Atrophy↗
PubMedDate not supplied

Computed tomography of the cervical lymph nodes: use of intravenous contrast enhancement.

Intravenous contrast administration increases the sensitivity of computed tomographic scanning for enlarged cervical lymph nodes but requires a detailed knowledge of neck anatomy, especially in order to distinguish certain normal vessels from involved nodal groups. Along the collar chain, relations between the parotid and submandibular salivary glands and the posterior and anterior facial veins and facial artery are analyzed. The digastric muscle is defined as a transitional landmark between collar and deep cervical nodes. Along the deep cervical chain, emphasis is on the internal jugular vein, its variability in size, and its relations to the anterior scalene and omohyoid muscles.

Humans↗
PubMedDate not supplied

CT of subarachnoid hemorrhage due to ruptured aneurysm.

Computed tomographic scans in 81 consecutive patients wih subarachnoid hemorrhage due to ruptured aneurysm were analyzed for patterns of hemorrhage and lucency and correlated with the development of spasm and hydrocephalus. The circulation time was measured angiographically in representative cases of spasm. Hemorrhage corresponded in a general way to the fossa of aneurysm origin and, when there was parenchymal or ventricular hemorrhage, in more specific ways to anterior communicating, middle cerebral, and posterior inferior cerebellar artery aneurysms. Basal ganglionic hemorrhages due to aneurysm ruptures occurred in two cases and could not be distinguished by appearance from hypertensive hemorrhage. Regions of low attenuation (lucencies) were often persistent and had lateralizing value; they showed a high correlation with arterial spasm. Conversely, spasm, particularly of a distal type, showed a significant correlation with increased circulation time and the occurrence of brain lucency. In cases of multiple aneurysms arising from different vessels in which there was hemorrhage or lucency, CT scans correctly predicted the site of aneurysm in 77% of cases. Periventricular lucency was a weak predictor of progressive hydrocephalus, while an intraventricular hemorrhage was a strong predictor of moderate to severe hydrocephalus.

Humans↗