Herbert F. Janssen

Bilateral lesions of the fastigial nucleus prevent the recovery of blood pressure following hypotension induced by hemorrhage or administration of endotoxin

The present studies were undertaken to determine if bilateral lesions of the fastigial nuclei of the cerebellum would impair the recovery and maintenance of mean arterial blood pressure during hypotension caused by hemorrhage or administration of endotoxin. We had shown previously that cerebellectomy would produce such an impairment, and the fastigial nuclei were implicated as the specific area involved due to the known pressor response observed when they are stimulated electrically. Chloralose-anesthetized dogs were made hypotensive by administration of E. coli endotoxin or hemorrhage to 50 mm Hg and observed over the subsequent 3 h. Dogs with fastigial nucleus lesions had a significantly lower mean arterial pressure during both the recovery and maintenance phases when compared with intact animals under both hypotensive protocols. In the hemorrhage study, a significant number of lesioned animals died whereas none of the controls died. Lesion of the fastigial nuclei produced an impairment similar to that seen with cerebellectomy. It is concluded that the fastigial nuclei play an important role in the recovery of blood pressure following a hypotensive episode.

Cerebrovasculature permeability changes following experimental cerebral angiography: A light- and electron-microscopic study

Morphological alterations of the cerebral vasculature as related to the permeability of plasma proteins and angiographic contrast media following unilateral cerebral angiography were studied. Both Evans blue albumin and horseradish peroxidase were employed as protein tracers for light and electron microscopy investigation respectively. Grey matter regions of the cerebral cortex, cerebellum corpus striatum, hippocampus and midbrain showed the most extensive and consistent leakage of these protein tracers. The most extensive penetration of EBA was noted at 1 hr following cerebral angiography as compared to the 5 or 30 min sample times. Permeability changes were noted in small venules and arterioles as well as capillaries. The extent of permeability, however, was appreciably greater in the capillaires as evidences by rapid extravasation of HRP into the surrounding neuropil extracellular spaces. The glial basement membrane surrounding the perivascular spaces of small venules and arterioles precluded rapid penetration of HRP into the neuropil interstitium. Opening of the tight junctions between the endothelial cells was primarily responsible for the extravasation of HRP in all vessel types. Furthermore, it is out opinion that the hyperosmolar nature of the contrast medium is responsible for opening of these tight junctions.

Biomechanical and clinical evaluation of the expandable intramedullary fixation device

The use of an expandable intramedullary device for internal fixation of metacarpal or phalangeal bones is described. The device is applicable to transverse fractures, short oblique fractures, or transverse osteotomies. The device consists of a cylindrical apparatus made of titanium that allows collapse in the circumferential diameter. It is introduced into the medullary canal in its collapsed state, and on release expands to its normal diameter in the canal with the fracture reduced over it. A biomechanical evaluation compared the stability of this device with other commonly employed fixation methods. A retrospective review is presented of the first 43 patients in whom the device was implanted.

Cerebrovascular permeability changes induced by radiopaque contrast substances in various areas of rabbit brain

Abstract The cerebrovasculature is capable of excluding various large molecular weight substances from the neural tissue. It has been previously demonstrated that radiopaque substances can alter this blood-brain barrier (BBB). The purpose of this investigation was to determine if this response is variable between selected areas of the brain. It was found that intracarotid injections of radiopaque contrast agents produce small focal extravasations in the gray matter. The areas affected and the incidence of extravasation were: thalamus (75%), cerebral cortex (69%), caudate nucleus (64%), dorsal hippocampus (43%), hypothalamus (36%) and cerebellum (27%). It was also noted that the area of the brain affected depended upon the type of contrast agent used.