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Biomedical subjects

T A Duff

Publications and source records attributed to T A Duff.

36 records · Page 2Linked to original sources
PubMed1981

Effect of prophylactic methicillin on cerebrospinal fluid shunt infections in children.

This study retrospectively and prospectively analyzes uncomplicated, noninfected, primary ventriculoperitoneal shunting procedures and ventriculoperitoneal shunt revisions in children done at the University of Wisconsin Hospital from July 1973 to December 1979. We compared the infection rates between patients whose procedures were done without prophylactic antibiotics and those who received prophylactic single dose methicillin at the time of operation. Among 105 procedures done without prophylactic methicillin, there were 8 infections; 4 occurred after 73 primary shunt placements and 4 followed 32 shunt revisions. Among 66 procedures done with prophylactic methicillin, there were 3 infections; all followed primary shunt insertions. There was no infection after 32 shunt revisions in which prophylactic antibiotics were used.

Adolescent↗
PubMed1981

Nonsurgical management of spontaneous intracerebral hematoma.

This report describes our experience with the use of osmotic diuretics, governed by continuous monitoring of intracranial pressure (ICP), as the primary treatment for 12 consecutive patients suffering from an acute, supratentorial intracerebral hematoma. In all cases the hematoma, as shown by computed tomographic scan, had a long axis of greater than 4.0 cm. ICP and cerebral perfusion pressure were successfully maintained within the assigned limits in all patients, and in none was surgical evacuation required. There was one death during the 6-month follow-up period. With appropriate weighting to differences in admission status, statistical comparison of the patient outcome in the present series with that reported by McKissock et al. suggests that ICP monitoring can improve the outcome of conservatively (and perhaps surgically) treated patients.

Adolescent↗
PubMed1980

Topography of scalp recorded potentials evoked by stimulation of the digits.

The amplitude of the primary positive deflection, P24, was measured in each wave form recorded from a 36-channel scalp electrode array placed over sensorimotor cortex. Electrical stimulation of contralateral little, middle, index finger, or thumb produced wave forms possessing common features, but the location of peak P24 amplitude depended upon the digit stimulated. With thumb stimulation peak P24 amplitude was located approximately two-thirds the distance from midline to sylvian fissure, while stimulation of the other digits resulted in more medially located topographic peaks. These shifts correlate with previous descriptions of body-part representation in somatosensory cortex and suggest that at least certain wave form deflections recorded from the scalp provide accurate localization of their underlying neural generators.

Adult↗
PubMed1979

Electron microscopic evidence of a ventronasal to dorsotemporal variation in fiber size in pigeon optic nerve.

Using a uniform sampling method, electron-microscopic examination of pigeon optic nerve revealed a dorsotemporal to ventronasal gradient in mean fiber size. In the dorsotemporal region small, myelinated axons (mean diameter = 0.87 micrometer, S.D. = 0.27) were predominant. Also unique to this region were scattered clusters of fine, unmyelinated fibers. A wider, bimodal spectrum in fiber size (mean diameter = 1.50 micrometer, S.D. = 0.66) was found in the ventronasal region of the nerve. Axons located in the area between these regions possessed a mean diameter of 1.15 micrometer, S.D. = 0.43. This gradient, constant throughout the length of the nerve, resulted from a nasal-to-temporal diminution in size and frequency of large fibers superimposed upon a relatively uniform small fiber base. The total number of fibers within the nerve, excluding those comprising the unmyelinated clusters, was calculated to be approximately 2.3 x 10(6). The overall distribution in fiber size appeared to be unimodal with the peak at 0.75 micrometer and mean diameter = 1.04 micrometer, S.D. = 0.44. Although previous investigators have reported that cross-sectional analysis of pigeon optic nerve revealed a homogeneous distribution in fiber size, the findings of the present study may be more compatable with anatomical and physiological features of pigeon retinotectal organization. These features include visual field acuity gradients, ganglion cell population pattern, and density fields of tectal afferent terminations.

Animals↗
PubMed1979

Treatment of increased intracranial pressure: a comparison of different hyperosmotic agents and the use of thiopental.

Long term intracranial pressure (ICP) monitoring was carried out in over 200 patients with various intracranial abnormalities; a fiberoptic epidural intracranial pressure monitor was used. Ninety of these patients had significantly elevated ICP or exhibited pressure waves requiring therapy. Initial therapy consisted of hyperventilation with a respirator and administration of hyperosmotic agents. Comparison studies utilizing 30% urea, 20% mannitol, and furosemide intravenously and 30% urea and 10% glycerol orally were randomly done. In 45 patients two or more of these agents were used at different times in the same patient for comparison of effectiveness. When equimolar amounts of intravenous urea and mannitol were used, similar effects on increased ICP were obtained. There was no significant reduction of increased ICP with the use of furosemide alone. No rebound effect was observed with either mannitol or urea. Orally, urea was more effective than glycerol in equimolar amounts. Again no rebound was observed. In 14 patients who required doses of hyperosmotic agents more frequently than every 4 hours, continuous infusion of thiopental was used in conjunction with the hyperosmotic agents to control pressure. This regimen resulted in good ICP control in 12 patients. A rational protocol for the medical management of increased ICP utilizing hyperosmotic agents and, in refractory cases, hyperosmotic agents plus thiopental has resulted in effective control of ICP in 96% of our patients throughout their course without the need to resort to decompressive surgery. (Neurosurgery, 5: 570--575, 1979).

Brain Diseases↗
PubMed1977

Metrizamide--CSF contrast medium. Analysis of clinical application in 215 patients.

Two-hundred-fifteen patients were evaluated with metrizamide, a new water-soluble contrast agent for use in the subarachnoid spaces. Side effects were reported in 67% of these; 39% were moderate or severe. Cervical injections monitored by fluoroscopy provide the most precise positioning of the medium. The benefits of metrizamide use outweigh its risk.

Cerebrospinal Fluid↗
PubMed1975

Retinal afferents to the pigeon optic tectum: discharge characteristics in response to whole field illumination.

Responses of pigeon retinotectal afferents to changes in whole field illumination are quantitatively analyzed for 313 units recorded in the stratum opticum. One hundred per cent of these units were responsive in unanesthetized birds and 92.9 percent in urethane anesthetized preparations. Of the responsive units, 92.4 percent (anesthetized) and 100 percent (unanesthetized) gave on-responses whose discharge characteristics showed an orderly relationship to stimulus intensity. Following the on-response, discharge generally ceased during sustained illumination. At stimulus termination off-responses frequently occurred, their probability being a function of stimulus intensity and duration. This probability, as well as specific response characteristics, could be predicted to a large extent from on-response characteristics. Anesthesia and level of background illumination predictably affected these response characteristics quantitatively but did not alter them qualitatively. It is hypothesized that with respect to whole field illumination the pigeon's retinotectal afferents constitute a homogeneous population continuously distributed according to threshold for intensity change.

Animals↗
PubMed1973

Electrophysiological identification of a visual area in shark telencephalon.

Optic nerve stimulation in the shark evokes short-latency telencephalic field potentials localized to the ipsilateral, posterior central nucleus. Such a well-defined visual area in elasmobranch telencephalon further challenges classical formulations of forebrain evolution. Moreover, its ipsilateral representation confirms recent evidence for a crossed thalamotelencephalic visual projection.

Animals↗
PubMedDate not supplied

Optic glioma associated with Beckwith-Wiedemann syndrome.

A 6-year-old boy with decreased vision was found to have Beckwith-Wiedemann syndrome with an associated glioma involving the intracranial optic nerves, chiasm, and optic tracts. The association of this syndrome with visceral and central nervous system neoplasms is discussed.

Astrocytoma↗
PubMedDate not supplied

Does cerebral vasospasm result from denervation supersensitivity?

This study examined the role of denervation supersensitivity in the development of cerebral vasospasm. Adrenergic denervation of cat basilar artery was accomplished by resection of the superior cervical ganglia or by injection of 6-hydroxydopamine into the cisterna magna. In vivo dose-response characteristics were determined for normal and for denervated arteries, and no significant differences were found between topical applications of serotonin, norepinephrine, epinephrine, fresh blood, or incubated blood. In addition, analysis of cat blood incubated in vitro revealed that the levels of serotonin, norepinephrine, and epinephrine diminished over time, whereas levels of hemoglobin and methemoglobin increased up to Day 14. The results of this study indicate that adrenergic denervation is not the cause of cerebral vasospasm and that, whatever the mechanism, hemoglobin is far more likely to play a role than are the other agents.

Animals↗
PubMedDate not supplied

Intravenous video arteriography of the intracranial vasculature: early experience.

A computerized fluoroscopic apparatus developed by members of the University of Wisconsin Medical Physics Section was used for 12 months to perform intravenous video arteriography. In previous papers, the apparatus was described and its use was illustrated for performing time subtraction intravenous video arteriography of the extracranial carotid arteries, the arteries of the abdomen and extremities, as well as angiocardiography. In this report, the use and current limitations of this technique for evaluation of the intracranial vasculature are described and illustrated.

Aged↗