Biotin-dextran: fast retrograde tracing of sciatic nerve motoneurons.

We present evidence that biotin-dextran (BD) provides good fast retrograde tracing in the rat sciatic nerve. Using BD injected distal to a crush injury of either tibial or common peroneal nerves, spinal cord motoneuron counts after 48 h compare favorably with counts obtained using horseradish peroxidase. Advantages of BD include fine staining of the soma and its branches, increasing the reliability of motoneuron counting, as well as good staining of sciatic nerve axons 30 mm away from the crush site. BD, already demonstrated to be a good anterograde tracer in the central nervous system, is shown to be a good retrograde tracer in a peripheral nervous system model.

Electric-field-induced reconnection of severed axons.

We report the first successful axon reconnection in the earthworm (Lumbricus terrestris) medial giant axon (MGA) by electric fields generated by electrical pulses of 10-100 microseconds duration and 80-200 V amplitude. Reconnection was documented by light and electron microscopy, and by transport of Lucifer yellow dye across the reconnected MGA segments. Direct repair of a severed nerve axon promises the advantages of preserving axon viability and distal connections.

Tanycytomas: a newly characterized hypothalamic-suprasellar and ventricular tumor.

We report five cases of tumors occurring in three children and in two adults. The tumors had unusual histomorphology and a mixture of ependymal and piloid-like astrocytic features and a myxoid stroma similar to myxopapillary ependymomas. MR imaging in three of the cases showed aggressive, intensely enhancing partially cystic hypothalamic-suprasellar masses near midline and near the floor of the third ventricle. In the three pediatric cases, the tumor encased the circle of Willis. This newly characterized tumor, the tanycytoma, has neoplastic cells with histomorphologic and ultrastructural characteristics similar to those of the tanycyte.

Action potentials pass severed earthworm MGA segments reconnected by laser and electric field pulses.

Active and passive electrical signals transmit across the earthworm (Lumbricus terrestris) medial giant axon (MGA) segment after reconnection induced by laser and electric field pulses. Laser pulses of 308 nm, 15 ns pulse duration, and pulse energy 5-50 microJ in the objective plane induced axon reconnection in 12 of 133 (9%) preparations. Electric field pulses of 200-800 V, 100 microseconds duration, induced axon reconnection in 15 of 188 (8%) preparations. Electrical continuity is possible after the reconnection of severed axons induced by laser and electric field pulses.

Endoscope-assisted craniotomy: approach to the rostral brain stem.

We describe a surgical technique to improve visualization of deep brain structures during craniotomy. The technique, developed in a cadaveric model, combines the use of an operating microscope and a solid-rod lens endoscope. Addition of the endoscope during craniotomy allows the operator to visualize structures that otherwise might not have been seen. An approach to the brain stem is demonstrated.

Endoscopic colloid cyst surgery.

OBJECTIVE: The purpose of this report is to discuss the technical aspects of operating on colloid cysts through a transventricular approach, with rigid endoscopes. METHODS: Twelve patients underwent 14 endoscopic operations in attempts to treat their colloid cysts. All patients were symptomatic, with headache being the most common complaint (8 of 12 patients). Six patients in this series exhibited enlarged ventricles associated with their colloid cysts. Using rigid endoscopes of < or =3.5-mm diameter, the cysts were inspected and fenestrated. Both hard and soft cyst contents were evacuated, and then the walls of the cysts were coagulated inside and outside. External ventriculostomy tubes were usually placed. Technical obstacles to successful completion of endoscopic colloid cyst surgery are discussed. RESULTS: For 11 of the 12 patients, the colloid cysts could be treated via an endoscopic approach. The mean follow-up time was 173 weeks, and the median follow-up time was 125 weeks. For the 12th patient, bilateral scarring of the foramina of Monro precluded direct surgery; therefore, a septostomy was performed and a ventriculoperitoneal shunt was placed. CONCLUSION: Endoscopic transventricular surgery should be considered for the treatment of colloid cysts.

Transnasal endoscopic surgery of the pituitary gland: technical note.

OBJECTIVE: An approach to transnasal transsphenoidal debulking of pituitary tumors using endoscopic guidance is presented. METHODS: Technical details of this approach using an endoscope inserted through one nostril and operating instruments inserted through a submucosal tunnel created via the other nostril are discussed. RESULTS: Ten patients who had operations are tabulated. Illustrative cases are presented. CONCLUSION: Endoscopic debulking of pituitary tumors can provide good results with minimal operative morbidity.

Antisense oligonucleotide-induced inhibition of adrenocorticotropic hormone release from cultured human corticotrophs.

OBJECT: Available therapies for Cushing's disease are often inadequate or involve the risk of significant morbidity. Accordingly, the need arises for the development of novel treatments, especially for cases caused by corticotroph hyperplasia, a condition difficult to treat using standard therapies. In this study, the authors investigated the use of phosphorothioate antisense oligonucleotides as a potential treatment for Cushing's disease. METHODS: Corticotrophs, obtained from a patient with Cushing's disease in whom pathological findings showed multifocal areas of corticotroph adenoma and hyperplasia, were grown in tissue culture. By assessing cell viability and using immunoradiometric assay techniques, it was determined that these cells grew autonomously and secreted adrenocorticotropic hormone (ACTH) in vitro. A fully phosphorothioated antisense oligonucleotide was constructed to be complementary to the first 25 bp of the region coding for ACTH in exon 3 of the proopiomelanocortin precursor. After incubation of the corticotrophs with liposome-coated phosphorothioate antisense oligonucleotides, a greater than 90% decrease in ACTH release was noted on Days 3 and 6, compared with nonsense-treated controls (p < 0.05). CONCLUSIONS: Antisense oligonucleotides may prove to be a useful adjunct in treating Cushing's disease by targeting one of its fundamental problems, ACTH hypersecretion.

Endoscopic removal of organized chronic subdural hematoma.

An endoscopic surgical approach to organized chronic subdural hematoma is described. Advantages of the endoscopic approach include access to virtually the entire hematoma cavity through a small craniectomy performed with local-standby anesthesia. Two illustrative cases are presented.

Diagnosis of sacral perineural cysts by nuclear magnetic resonance.

A case of sacral perineural ( Tarlov ) cyst is presented. The diagnostic advantages of nuclear magnetic resonance imaging in this uncommon entity are illustrated and explained.

Laser-induced reconnection of severed axons.

After their axons have been severed, nerve cells can achieve functional recovery either by regrowth of the injured cells or by direct repair of the injured cell at the site of injury. Direct repair of a severed axon promises the advantages of preserving the viability and existing connections of the axon distal to the injury. We report here the first successful axon reconnection in the earthworm (Lumbricus terrestris) medial giant axon (MGA) in vitro system (1) by the application of well-focused 15 nsec, 5 to 50 muJ/pulse, 308 nm laser pulses. Axon reconnection is documented by light and electron microscopy, as well as by transfer of the iontophoretically injected fluorescent dye, Lucifer Yellow, across the reconnected MGA segments.