The cerebral ventricles: a computer-based interactive tutorial.

The computer-based tutorial, "The Cerebral Ventricles," enables the user to review the anatomy, imaging, and common pathologic conditions of the human cerebral ventricular system. The program runs on a workstation that includes a laser videodisk player and a videodisk with 21,000 still images plus motion sequences. By using a mouse to select specific portions of the anatomic diagram depicting the ventricles, the user can review different planes of normal gross anatomy, corresponding computed tomographic and magnetic resonance images of normal anatomy, images of gross specimens of different pathologic entities, and corresponding radiologic images. The motion sequences portion of the program shows reconstructed three-dimensional images of ventricular anatomy and helps the user gain a greater understanding of the complex anatomy as seen from all angles. Subprograms provide more detailed information about anatomic relationships, disease entities, and bibliographic references. "The Cerebral Ventricles" assists radiologists in gaining a greater understanding of the ventricles so that an appropriate differential diagnosis of an intraventricular lesion can be offered when such masses are encountered in clinical practice.

Animating the curriculum: integrating multimedia into teaching.

At many medical schools, the medical library assists faculty in finding and integrating new technology into the classroom, student laboratories, and lecture or small group sessions. Libraries also provide faculty with a place to do development. This paper recounts the author's experience creating software-based educational materials. In the process of creating the Slice of Life videodisc and developing and distributing other medical education software, techniques that do and do not work in producing multimedia for medical education became evident. Use of multimedia features and new modalities not possible with books, rather than development of electronic versions of texts and atlases, should be emphasized. Important human factors include collaboration, continuity, evaluation, and sharing of equipment, software, code, effort, expertise, and experiences. Distribution and technical support also are important activities in which medical libraries can participate.

A chronic intracortical electrode array: preliminary results.

Two sets of electrode arrays made of either 25- or 50-microns-diameter Teflon-insulated platinum-iridium wire and Teflon have been developed for chronic intracortical electrical stimulation. Cortical histological studies were performed following acute and chronic implantation in cats. While some neural damage resulted from the implantations of either array configuration, a unique set of problems was associated with each diameter wire. Arrays with 50-microns electrodes and lead wires tended to maintain interelectrode spacing upon implantation, but the percutaneous leads retained residual stress which made array implantation difficult. Arrays with 25-microns electrodes and lead wires suffered from changes in interelectrode spacing upon implantation, but were much easier to manipulate during surgery. Both array configurations demonstrated some movement after implantation. It is concluded that a chronic intracortical stimulating electrode array of this geometry should have the following properties: 1) the penetrating electrodes and supporting substrate must be stiff (to maintain interelectrode spacings upon implantation), and 2) the percutaneous leads must be extremely flexible (to avoid array movement after implantation).

Brain abscess of odontogenic origin: report of case.

Advanced dental infection rarely causes brain abscess resulting in death. Good dental hygiene and removing abscessed teeth are advised for prevention of any such occurrence. An intercranial infection is described in a 29-year-old male who also had a dental phobia.

Autoradiographic evidence of [3H]SCH 23390 binding sites in human prefrontal cortex (Brodmann's area 9).

The distribution of dopamine D-1 receptors has been determined in human prefrontal cortex (Brodmann's area 9) by an in vitro light microscopic autoradiographic method. Dopamine D-1 receptors were localized by using [3H]SCH 23390 as a ligand. Our results indicated that [3H]SCH 23390 binding to slide-mounted tissue sections of human brain is specific, saturable, and of high affinity. Lamina Va contained the highest density of D-1 receptors, with a Bmax value of 11.2 +/- 1.3 fmol/mg tissue. The KD values for [3H]SCH 23390 in all laminae ranged from 2.6 to 3.2 nM. Competition studies performed with [3H]SCH 23390 indicated a pharmacologic profile consistent with labeling of the D-1 receptor.

Intermittent exposure of rats to 2450 MHz microwaves at 2.5 mW cm2: behavioral and physiological effects.

Long-Evans male adult rats were intermittently exposed for 14 weeks to continuous wave (CW) 2450-MHz microwaves at an average power density of 2.5 mW/cm2. The mean specific absorption rate was 0.70 W/kg (+/- 0.02 SEM). The rats were exposed 7 h/day, 7 days/week in a radiation chamber with a monopole above ground, while housed in Plexiglas cages. Weekly measures of body mass and food intake did not indicate statistically significant effects of microwave irradiation. Assessments of threshold for electric-footshock detection revealed a significant difference between microwave and sham-exposed animals. Assessments of cholinesterase and sulfhydryl groups in blood and 17-ketosteroids in urine did not distinguish the two groups of rats. Behavioral measures made at the end of the 14-week exposure included an open-field test, shuttlebox avoidance performance, and schedule-controlled lever-pressing for food pellets. Statistically significant differences between microwave- and sham-exposed rats were observed for these measures. Examination of adrenal tissue, plasma electrolytes, and organ masses after 14 weeks of exposure revealed no difference between the two groups of rats.

Behavioral and physiological effects of chronic 2,450-MHz microwave irradiation of the rat at 0.5 mW/cm2.

Adult male Long-Evans rats were intermittently exposed to 2450 MHz CW microwaves at an average power density of 0.5 mW/cm2 for 90 days. The resulting SAR was 0.14 W/kg (range 0.11 to 0.18 W/kg). The animals were exposed 7 h/day, 7 days/wk, for a total of 630 h in a monopole-above-ground radiation chamber while housed in Plexiglas holding cages. Daily measures of body mass and food and water intake indicated no statistically significant effects of microwave exposure. Monthly assessment of reactivity to electric footshock, levels of cholinesterase and sulfhydryl groups in blood, and 17-ketosteroids in urine revealed no reliable differences between 14 sham-exposed and 14 microwave-exposed rats. After the 90 days of exposure, seven rats, randomly chosen from each group, were assessed for open-field behavior, shuttlebox performance, and schedule-controlled (IRT schedule) lever pressing for food pellets. Statistically significant differences between microwave-exposed and sham-exposed rats were observed in shuttlebox performances and lever pressing. Post mortem measures of mass of several organs and microscopic examination of adrenal tissue revealed no differences between the two groups of animals.

Histopathological evaluation of materials implanted in the cerebral cortex.

Histopathological changes of the cerebral cortex in response to small, penetrating metal and non-metal implants were analyzed by means of light and electron microscopy. The needle-shaped implants were left in place during all stages of histological preparation and embedded in plastic together with the cortex. Changes of the brain-implant boundary were classified as non-reactive, reactive, or toxic, according to the reactive cellular constituents. Among the non-reactive materials were several plastics and metals such as aluminum, gold, platinum, and tungsten. The boundary of these implants displayed little or no gliosis and normal neuropile with synapses within 5 micron of the implant's surface. The boundary of reactive materials such as tantalum or silicon dioxide was marked by multinucleate giant cells and a thin layer (10 micron)) of connective tissue. Toxic materials such as iron and copper were separated from the cortical neuropile by a capsule of cellular connective tissue and a zone of astrocytosis. Cobalt, a highly toxic material, produced more extensive changes in the zones of connective tissue and astrocytes. These results indicate that a variety of materials are well tolerated by the brain and could be used in the fabrication of neuroprosthetic devices.

The reaction of the cerebral cortex to chronically implanted plastic needles.

Plastic (araldite) needles were implanted in the cerebral cortex in order to evaluate changes produced by an indwelling and relatively inert foreign body. The implants were removed together with surrounding cortex after 4-723 days and the implant-CNS boundary analyzed by light and electron microscopy. Three border conditions were observed at the surface of the implant and were related to the degree of implantation trauma. Type I is characterized by little or no gliosis and synapses within 1-5mu of the implant; type II contains a pronounced zone of reactive astrocytes; and type III is typified by a zone of connective tissue near the implant surface. The type I border predominates, but all three conditions may exist around a single implant. The fact that the implant-CNS boundary is stable following an initial period of readjustment suggests that intracortical implants fabricated from inert materials would be well tolerated and could be used as part of neuro-prosthetic device. Multinucleated giant cells were observed at the boundary of some implants. Their cytology, intercellular relations, and similarity to foreign body giant cells are discussed.