A narrow time-window for access to the brain by exogenous protein after immunological targeting of a blood-brain barrier antigen.

The endothelial barrier antigen (EBA) is a membrane protein expressed by endothelial cells of the rat blood-brain barrier (BBB). A previous short-term non-recovery study demonstrated that immunological targeting of EBA by intravenous administration of a monoclonal antibody (anti-EBA) led to acute opening of the BBB to exogenous and endogenous tracers. The aims of the present study were to determine whether opening of the BBB was reversible and compatible with survival, and whether a "therapeutic window" existed. A single intravenous injection of one of three doses (high, medium and low) of anti-EBA was used. Animals were allowed to survive for periods ranging from 17 min to 4 days. The tracer horseradish peroxidase (HRP) was administered intravenously 10 min before perfusion fixation, and its distribution was assessed in Vibratome sections of the brain and spinal cord. Leakage of HRP into the central nervous system was dose- and time-dependent. The medium dose produced incipient HRP leakage at 17 min and widespread pronounced leakage at 30 min. Progressive reduction in HRP permeability occurred from 45 min to 2 h, with barrier restoration by 3 h. At all subsequent time intervals (6 h-4 days) the BBB remained impermeable to HRP. The low and high doses produced less and greater HRP leakage, respectively, but restoration of the barrier still occurred at 3 h. The high dose, however, produced a number of deaths. Animals treated with an isotype control antibody showed no HRP leakage at comparable time intervals. The results indicated that (1) this model was compatible with survival, (2) opening of the BBB was monophasic and transient, occurring during a narrow "time-window", and (3) the barrier, once reconstituted, maintained its integrity.

Expression of a blood-brain barrier-specific antigen in the reproductive tract of the male rat.

The endothelial barrier antigen (EBA) is a protein expressed specifically by the endothelial cells of the rat brain barrier vessels. This antigen has been described as a 'barrier protein' and is used as a marker for the competent blood-brain barrier. A blood-testis barrier has also been described. However, unlike the blood-brain barrier, which is formed by endothelial cells, the blood-testis barrier is formed mainly by the Sertoli cells, which provide an isolated environment for spermatogenic cells within the seminiferous tubules. Testicular blood vessels express the erythroid glucose transporter protein and other markers, which are strongly expressed in brain blood vessels, and may contribute to the blood-testis barrier. This study was carried out to determine whether Sertoli cells or testicular blood vessels express EBA. Tissues of other organs were used as controls for EBA expression. EBA was expressed by the endothelial cells in most microvessels of the testis, and in a few vessels of the epididymis, seminal vesicle, prostate gland, vas deferens and bladder-neck region. Furthermore, EBA was strongly and consistently detected in epithelial cells of the rete testis and dorsolateral prostate gland, and in a few epithelial cells of the ventral prostate gland, the seminal vesicle and the coagulating gland. However, Sertoli cells, which are the main site of the blood-testis barrier, were negative for EBA. In conclusion, EBA may have a wider role in rat tissues than has been previously appreciated.

Immunological targeting of the endothelial barrier antigen (EBA) in vivo leads to opening of the blood-brain barrier.

The role of the endothelial barrier antigen (EBA) in the blood-brain barrier (BBB) of the rat is not fully understood. Pathological conditions which show BBB disruption and leakage of plasma proteins are associated with reduced EBA expression in brain endothelial cells (ECs). However, it is not known if the reduction in EBA is the primary event or is secondary to protein extravasation. We hypothesized that immunological targeting of EBA in vivo would lead to opening of the BBB. To test this hypothesis, a monoclonal antibody (anti-EBA) was intravenously injected in anaesthetized experimental rats. Control animals received intravenous injections of phosphate-buffered saline (PBS) or non-specific antibodies (anti-human cytokeratin, anti-Salmonella bacterial antigen, or anti-pan endothelial cell antigen). Two groups of rats were used, each included experimental and control animals. The first group was used for immunocytochemical detection of EBA in brain ECs and rat albumin in brain parenchyma. In the second group, the permeability of the BBB to horseradish peroxidase (HRP) was tested. Experimental animals, injected with anti-EBA antibody, showed extensive leakage of HRP and albumin in the grey and white matter of the brain. Immunocytochemistry of experimental brains showed that the intravenously injected anti-EBA became bound to ECs and was detected in tissue sections. Control animals did not show leakage of HRP or albumin, and EBA distribution was normal. This study demonstrated for the first time, that immunological 'neutralisation' of EBA leads to opening of the BBB, and provided direct evidence for the importance of EBA in maintaining the integrity of the BBB in the rat.

A study of the angle of inclination and facet curvature of superior lumbar zygapophyseal facets.

The angle of inclination and depth of curvature of L1-L5 of the superior articular facets of both sexes were measured in 112 lumbar spines. In addition to standard statistical methods data were also analyzed to show various degrees of departure from the "normal." The L3 vertebra showed the least variation and L5 and L1 showed the most. The angle and depth of L1 to L5 showed a small, albeit statistically significant, difference between the two sexes but no laterality differences were apparent. At L1 12.5% of males and 10.4% of females revealed an asymmetry of angle exceeding 20, and at L5 3.1% of males and 1.7% of females showed such tendency. An asymmetry of the depth of curvature of the articular facets exceeding 1.5 mm was recorded in 12.5% of males and 8.3% of females at L1 and 6.5% of males and 2.1% females at L5. The expected values of depth of curvature were lowest at L1 and highest at L3 and L4. It is suggested that a more quantitative approach to the study of the zygapophyseal joint would enhance precision and facilitate meaningful interlaboratory comparisons of published data.