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Biomedical subjects

J M Taveras

Publications and source records attributed to J M Taveras.

104 records · Page 6Linked to original sources
PubMedDate not supplied

High-flow angiopathy: cerebral blood vessel changes in experimental chronic arteriovenous fistula.

Profound vascular damage secondary to high-flow extracranial states has been well characterized. However, changes in cerebral vasculature secondary to high-flow states have not been studied. To determine changes related to high-flow states in cerebral vessels, a rabbit model was developed in which torrential flow was created in the vertebrals, carotids, basilar, and vessels of the circle of Willis by means of a carotid-jugular shunt after ligation of the proximal carotid. The clinical, angiographic, and histologic changes noted in the animal model include: abrupt clinical deterioration after a variable interval with some animals developing ptosis, afferent vessel dilatation and the development of prominent anastomotic channels, variable cerebral vessel histopathology--related to duration and relative proximity to the shunt--affecting all three vessel layers, plump, irregular, and clumped endothelium, denuded with adherent platelets, irregular, duplicated, and thinned internal elastic membrane, frayed with invasion of the intima by mesenchymal cells, vacuolization and necrosis of the media muscle, and invasion of adventitia by foreign cells and small blood vessels. The high-flow angiopathy seen in this model may help explain vascular changes associated with high-flow cerebral vascular lesions, as well as other types of vascular damage.

Animals↗
PubMedDate not supplied

CT of neonatal herpes encephalitis.

Seven neonates with proven herpes (HSV type 2) encephalitis exhibited a characteristic sequence of findings on cranial computed tomography (CT). The initial CT abnormalities in all infants were fingerlike areas of cortical increased attenuation noted on unenhanced scans obtained 2-30 days after presentation. These usually were accentuated by increased white-matter lucency. Subsequently (more than 30 days after presentation), extensive cerebral destruction, multicystic encephalomalacia, and calcification were seen on follow-up CT scans obtained in five infants.

Brain↗
PubMedDate not supplied

Selective arteriography of glomus tympanicum and jugulare tumors: techniques, normal and pathologic arterial anatomy.

Glomus tympanicum and jugulare tumors arise within the middle ear and jugular fossa, respectively, but often extend into the adjacent areas of the skull base and posterior fossa. Multiple branches of the external carotid, internal carotid, and vertebral arteries may contribute to the vascular supply of these lesions. The arteriograms of 15 patients with glomus tumors were correlated with the surgical findings to determine if selective arteriography could define precisely the involvement within the middle ear, jugular fossa, and mastoid. The arteriographic mapping correlated well with the surgical findings in nine of 13 cases that had surgery, but a few important limitations were found. Therefore, a new arteriographic projection, called a transcanalicular view, is proposed that separates the middle ear from the jugular fossa, allowing for better visualization and assessment of the tumor blush.

Angiography↗
PubMedDate not supplied

Cholinergic actions of metrizamide.

In a study of the possible mechanisms of the clinical side effects of metrizamide, it was applied to several in vitro model preparations. It was shown that, although high metrizamide concentrations are without noticeable effect on many basic neuronal functions, metrizamide does interfere with cholinergic mechanisms. At concentrations equivalent to, or significantly lower than, those probably achieved during clinical procedures, metrizamide is both an inhibitor of the enzyme acetylcholinesterase and an antagonist of cholinergic transmission. These data suggest the possibility that some of the side effects resulting from clinical procedures employing metrizamide may be explained by its actions on cholinergic synapses.

Acetylcholine↗
PubMedDate not supplied

Complementary roles of a noninvasive test battery and DSA in evaluating carotid artery disease.

Initial comparisons of the results of digital subtraction angiography (DSA) and a battery of tests for noninvasive diagnosis of carotid artery disease indicate the two techniques are complementary, rather than competitive. DSA provides important morphologic information at the carotid bifurcation and siphon, but the images are sometimes difficult to interpret with precision. Noninvasive testing gives discrete physiologic information related to hemodynamics, but the findings are less specific for the level of the lesion in the carotid/ophthalmic system. Noninvasive tests may be more useful than DSA for determining if a lesion is hemodynamically significant and whether advanced disease shows evidence of progression on sequential studies. The noninvasive tests are not definitive procedures, but are useful in selecting patients for a contrast study. They are the initial procedure of choice for the patient with asymptomatic bruit. Depending on the clinical situation and quality of the study, DSA can sometimes be a definitive procedure, but in some situations correlative noninvasive test results are necessary to assess whether the patient is a candidate for arteriography and/or surgery.

Carotid Artery Diseases↗
PubMedDate not supplied

MR imaging of pituitary adenomas using a prototype resistive magnet: preliminary assessment.

Magnetic resonance (MR) images were obtained with a prototype resistive magnet system in 10 patients, all of whom had been shown to have pituitary tumors by enhanced high-resolution computed tomography (CT). Histologic verification was obtained in eight cases. Inversion-recovery (IR) T1-weighted images revealed the tumor in six of nine cases; saturation-recovery (SR) images with less T1 weighting identified seven of nine tumors; Carr-Purcell-Meiboom-Gill (CPMG) spin-echo T2-weighted images revealed two of four tumors. MR images failed to demonstrate three microadenomas: 5 X 5 X 8 mm, 6 X 6 X 6 mm, and one less than 5 mm in estimated size. In the last pretreatment study, CT had demonstrated a 13 mm maximum diameter adenoma. Repeat CT at the time of MR imaging also showed a partially empty sella and did not resolve the residual adenoma. The larger adenomas were identified readily by MR imaging, which, unlike CT, suggested old tumor hemorrhage in two cases, which was confirmed at surgery and histologic examination. MR and CT images were also compared for relative effectiveness in identifying important perisellar structures.

Adenoma↗
PubMedDate not supplied

Experimental in vivo imaging of the cranial perineural lymphatic pathway.

After intraventricular injection of 99mTc antimony sulfide in rabbits (n = 12) and cats (n = 14), radiolabeled colloid was imaged passing into the nasal mucosa and subsequently into the cervical lymph nodes. The cervical lymph nodes accounted for about 12% of the injected dose in rabbits sacrificed at 22-24 hr after injection and about 5% of the injected dose in cats sacrificed at 5-6 hr after injection. In both animals this represented at least one-third of the cerebrospinal fluid colloid clearance. This technique is applicable to in vivo imaging studies of the perineural lymphatic pathway for cerebrospinal fluid absorption in primates and, with modifications, in human subjects.

Animals↗