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Biomedical subjects

F D Brown

Publications and source records attributed to F D Brown.

At least 37 records · Page 2Linked to original sources
PubMed1984

Elevated beta-endorphin in cerebrospinal fluid after electrical brain stimulation: artifact of contrast infusion?

Beta-Endorphin-like immunoreactivity in cerebrospinal fluid was assayed in 11 patients receiving electrical stimulation of the brain for chronic pain. Immunoreactivity increased dramatically after contrast ventriculography prior to stimulation. No further elevations were observed after stimulation. The magnitude and time course of elevations were identical after placement of electrodes either in the thalamus or in the periventricular gray matter. These results suggest that previous findings of stimulation-induced elevation of beta-endorphin-like immunoreactivity in cerebrospinal fluid are attributable to an artifact of contrast ventriculography.

Adult↗
PubMed1984

Ultrasound-guided periventricular stereotaxis.

Intraoperative ultrasound can aid the biopsy of deep intracranial lesions. It is, perhaps, less clear whether ultrasound could be useful in functional neurosurgery, where the target is not abnormal in echogenicity. As an example, we chose to investigate in a dog model the periventricular gray target, which is frequently the choice for the placement of electrodes to control intractable pain. Autopsies showed the placement of our electrodes with less than 1 mm of error in four of five brains and a 1.5-mm error in the fifth brain. The largest error was seen to occur on the video screen and was due to our failure to tighten the guide properly. The potential advantages of this technique over conventional stereotaxis include the avoidance of: ventricular catheterization, the injection of contrast agent into the ventricles, the necessity for a stereotactic frame, and multiple x-ray exposures. Also, with real time scanning the surgeon has instant visual confirmation of electrode placement and can observe quickly any significant hematoma formation.

Animals↗
PubMed1984

beta-Endorphin-like immunoreactivity increases in human lumbar cerebrospinal fluid following routine metrizamide myelography.

Much interest has recently been focused on the possible role of the endogenous opiates in the perception of pain in humans. Several investigators have examined the levels of these substances in human cerebrospinal fluid (CSF) in attempts to identify the mechanisms by which electrical stimulation of the brain might induce analgesia. Most of these CSF samples were collected at the time of ventriculography or myelography. In the present study, the levels of beta-endorphin in the CSF of 22 patients undergoing myelography were examined before and after the injection of a contrast agent. beta-Endorphin increased an average of 356% (p less than 0.0005) 15 to 20 minutes following the injection of contrast material into the lumbar subarachnoid space. Thus, routine myelography may have a profound effect on the levels of beta-endorphin measured by radioimmunoassay in human CSF, and great care must be taken in interpreting the significance of changes seen in beta-endorphin levels in CSF collected from patients at the time of myelography or ventriculography. The effect of the injection of contrast material on beta-endorphin immunoreactivity must be distinguished from the postulated effects of any analgesia-inducing therapy.

Adult↗
PubMed1984

Changes in food intake with electrical stimulation of the ventromedial hypothalamus in dogs.

Six adult dogs were implanted stereotaxically with chronic indwelling Medtronic platinum-tipped electrodes in the left ventromedial hypothalamic area (VMH); two dogs with electrodes placed in the subcortical white matter served as controls. Following 24 hours of food deprivation, VMH-stimulated dogs delayed their next meal for a period ranging from 1 to 18 hours. When not stimulated, however, each dog ate immediately upon receiving its food and consumed greater than average daily intake (p less than 0.005). The two control dogs ate immediately upon receiving food regardless of whether they were stimulated or not. Dogs that received 1 hour of VMH stimulation every 12 hours for 3 consecutive days maintained an average daily food intake of 35% of normal baseline levels (range 13% to 51%), and water consumption averaged 50% of baseline intake (range 29% to 67%). Both of these results were statistically significant (p less than 0.01). After cessation of stimulation, food and water intake returned to normal within 6 to 9 days, with no observable "rebound hyperphagia." The two animals that received subcortical electrodes showed no change in food or water intake with stimulation. Blood pressure, pulse, respiration, temperature, and gross behavior were not altered during or after stimulation. These results suggest that the use of electrical stimulation of the VMH may be a useful modality for regulating food intake, and deserves further examination as a potential alternative therapy for human morbid obesity.

Animals↗
PubMed1984

Effect of contrast media on radioimmunoassay of beta-endorphin in cerebrospinal fluid.

An effect of metrizamide, a contrast medium, on results of beta-endorphin radioimmunoassay was examined. We found that 1, 5, and 10 microL of the medium added to 100 microL of standard containing 0 to 500 pg of beta-endorphin shifted the standard curve to the left in proportion to the metrizamide concentration. Three other contrast media showed a similar effect at low concentrations of beta-endorphin. This effect of contrast media artificially increased results in radioimmunoassay of beta-endorphin in cerebrospinal fluid, the mean overestimate being 121.9% (range, 0 to 435%). For plasma samples, this effect of contrast media resulted in an average 11.7% overestimate of beta-endorphin (range, -16% to 41%). These observations bring into question the validity of a previous suggestion that an increase in beta-endorphin in cerebrospinal fluid after intracerebral electrical stimulation is the mechanism for stimulation-produced analgesia.

Contrast Media↗
PubMed1984

Cerebral blood flow in sickle cell cerebrovascular disease.

Cerebral blood flow (CBF) has been studied by the xenon-133 (133Xe) inhalation method in 16 children with suspected sickle cell cerebrovascular disease. Abnormalities consisting of decreases in total, hemispheral, or regional CBF were found in 17 of 26 studies. Eleven studies performed immediately after stroke, transient ischemic attack, or depression of state of alertness showed abnormalities. In addition to confirming regional cerebrovascular insufficiency in children with stroke due to major cerebral artery occlusion, the method detected diffuse decrease in CBF in children with stupor, coma, and seizures who had normal angiographic findings. In contrast, six of seven studies obtained after exchange transfusion or during maintenance on hypertransfusion therapy showed normal findings. The difference between results in patients with acute neurologic disturbances and those receiving transfusion therapy was statistically significant (P less than .005). The data indicate that the 133Xe method reliably demonstrates cerebrovascular impairment in sickle cell disease. They also suggest that CBF changes in patients with sickle cell disease can be reversed by exchange transfusion and by hypertransfusion therapy. The 133Xe CBF method may be useful for following up children with sickle cell disease who are at high risk for recurrent stroke.

Adolescent↗
PubMed1983

In vivo characterization of vasocontractile activities in erythrocytes.

Partially purified protein from washed and artificially hemolyzed erythrocytes, known to cause significant contractions of isolated canine cerebral vessels in vitro, was injected into the cisterna magna of intact anesthetized dogs. Cerebral blood flow, measured by the xenon-133 washout technique, decreased from a control value of 49.5 +/- 1.17 ml/100 gm/min to an experimental value of 34.1 +/- 1.65 ml/100 gm/min at 2 hours. Cerebral vascular resistance rose from a control value of 2.05 +/- 0.17 PRU (peripheral resistance units) to an experimental value of 2.91 +/- 0.25 PRU at 2 hours. Mean arterial blood pressure, heart rate, intracranial pressure, and cerebral perfusion pressure remained stable. Cardiac output also fell significantly (in 2-hour control animals it was 2.89 +/- 0.37 liter/min, and in 2-hour experimental animals 1.43 +/- 0.13 liter/min) and peripheral vascular resistance rose. These changes were evident by 10 minutes after the cisternal injection of the hemolysate protein, and remained for the duration of the 2-hour monitoring period. Serial vertebrobasilar angiograms demonstrated marked narrowing of the intracranial basilar artery when compared to control values. The narrowing persisted for several days in most animals, and tended to increase with time. Relaxation occurred by the 10th through the 14th day. The authors conclude that this experimental preparation may be a useful model for both in vitro and in vivo investigation of chronic cerebral vasospasm.

Animals↗
PubMed1980

Dimethyl sulfoxide in experimental brain injury, with comparison to mannitol.

The effects of dimethyl sulfoxide therapy were studied in rhesus monkeys following a standardized occipitofrontal missile injury. This therapy resulted in substantially higher blood pressure, cerebral perfusion pressure, blood flow, and oxidative metabolism than those of a group of monkeys that had been treated similarly with mannitol, and than those of an untreated group.

Animals↗
PubMed1979

Detailed monitoring of the effects of mannitol following experimental head injury.

The experimental model of a cerebral missile injury developed by Crockard was used in three groups of Rhesus monkeys treated with mannitol. One group received mannitol 15 minutes after being injured with a BB pellet at 90 m/sec impact. Another group was wounded identically, but mannitol treatment was delayed until 1 hour after injury. The last group was wounded with the missile traveling at 180 m/sec, and mannitol was started 15 minutes after trauma. The data were contrasted with the results from the original model. After receiving mannitol, all groups showed marked improvement in mean blood pressure, cerebral perfusion pressure, cerebral blood flow, and cerebral metabolic rate of oxygen consumption out of proportion to the degree of reduction in intracranial pressure (ICP). The authors conclude that the therapeutic value of mannitol may, in some injuries, be directly related to its effects on blood flow and metabolism, as well as to its better known effects upon ICP.

Animals↗
PubMed1979

Hyperemic and ischemic problems of surgical treatment of arteriovenous malformations.

Three patients with arteriovenous malformations are described who showed signs of massive hyperemia in the vascular territory of the normal brain proximal to arterial ligation. One additional patient had evidence of ischemia of the brain in the territory distal to ligation (steal), and in another both mechanisms were considered as operative hazards.

Adolescent↗
PubMed1978

Treatment of aneurysmal hemiplegia with dopamine and mannitol.

Three patients with severe postoperative hemiplegia and one with hemiplegia following a subarachnoid hemorrhage are presented. None had hematomas. All were treated with dopamine-induced hypertension, mannitol, and large quantities of intravascular fluids. All showed a remarkable degree of clinical improvement, presumably secondary to an increase in cerebral blood flow.

Adult↗
PubMed1977

An experimental cerebral missile injury model in primates.

An experimental model of cerebal missile injury in rhesus monkey is described. The main objective was to create a "clean" wound devoid of bleeding from major vessels and complications due to bone fragments. There was a correlation between the wounding energy and the physiological signs, although we underestimated the actual energy level. After the right parietooccipital to right frontal injury, there was bradycardia, changes in blood pressure, and, in high-energy wounds, a marked alternation in resperation. This suggests that the missile's energy produces direct brain-stem damage, the extent of which can be related to the wounding energy.

Animals↗