Circulation of cerebrospinal fluid in the bullfrog, Rana catesbiana.

In order to demonstrate features of the cerebrospinal fluid (CSF) path in the amphibian, 2--6 microliters of either Evans Blue-albumin (EBA) or ferrocyanide were injected into the ventricular system of anesthetized bullfrogs. The animals were sacrificed 1 to 135 minutes after injection by either quick freezing (EBA injections) or fixative perfusion (ferrocyanide injections). The contents of the cranial and vertebral cavities were then examined grossly and histologically for distribution of the tracers. In all animals, the tracers were seen throughout the ventricular cavity and in the subarachnoid space surrounding the caudal hindbrain. The site of communication between these two fluid spaces was the posterior tela of the hindbrain. Within this tela, "pores" were found between groups of pavement-like ependymal cells. In many animals, tracer was also observed in the vertebral subarachnoid and epidural spaces, adjacent to spinal nerve roots. In three EBA-injected animals, this tracer was also seen in the subcardinal lymph spaces. These findings suggest that the subarachnoid space in the bullfrog communicates functionally with the ventricular system by way of specialized "pores" in the posterior tela of the hindbrain. There is also indication of movement of fluid within the subarachnoid space which is predominately caudal in direction, with a primary absorptive path for CSF that consists of a perineural route to the lymphatic system.

The use of microelectrodes for measurement of local H+ activity in the cortical subarachnoidal space of cats.

pH microelectrodes with pointed tip (Hinke-type) were constructed for the continuous measurement of the local pH in the perivascular space of pial arteries in the feline cerebral cortex. The sensitive tip had a length of 20-60 mu and a base diameter of 10-25 mu. As reference electrode, a micropipette (tip diameter 2 mu), filled with 150 mM KCl was used. Calibration curves were linear and showed a sensitivity of 54.5-57.5 mV/pH unit at 38 degrees C. Advantages of such electrodes are the easy penetration of the subarachnoid membrane, the long life span, the quick response, and a minimal drift. The electrodes were tested in vivo during hyper- and hypoventilation and during local perivascular injection of mock spinal fluid at varying pH. A close correlation was observed between the change in perivascular pH and the corresponding change in pial arterial diameter.

Therapeutic irradiation of the central nervous system using intrathecal 90Y--DTA.

The erdication of established neuroleukaemia is often difficult, and with subsequent relapses even harder. The use of an intrathecally-injected beta emitting isotope has the advantage of preserving the bone-marrow of the vertebral column and cranium whislt irradiating the meninges. The value of intrathecal 90Y-DTPA(diethylene-triamine penta-acetic acid) has been investigated in nine patients with neuroleukaemia or CNS involvement in malignant lymphoma. Measurements of retention of the isotope in the whole body, spinal, and intracranial subarachnoid spaces have been made, together with blood levels, and are reported. The clinical results are presented. In three out of five evaluable patients 90Y-DTPA failed to maintain a chemotherapy-induced CNS remission and in two out of two evaluable patients malignant cells were not dispersed from the CNS with a single intrathecal injection of 90Y-DTA. It is concluded, therefore, that with this agent and the doses used no useful clinical result is gained.