Allografts of CNS tissue possess a blood-brain barrier. II. Angiogenesis in solid tissue and cell suspension grafts

Angiogenesis and patency of blood vessels were analyzed qualitatively in solid CNS and peripheral tissue syngeneic, allogeneic, and xenogeneic grafts and in individual cell suspension grafts of astrocytes, fibroblasts, PC12, and three additional tumor cell lines placed intracerebrally in adult host mice. Postgrafting survival times were 1 day through 4 weeks. The patency of graft vessels was determined in sections from immersion-fixed tissues incubated to reveal the endogenous peroxidase activity of host red cells trapped within the lumen of blood vessels. Additionally, horseradish peroxidase (HRP) was administered intravenously to live hosts; HRP labels host brain and graft vessels on the luminal surface and reveals the presence or absence of a blood-brain barrier (BBB) within the grafts. The origins of blood vessels supplying solid tissue xenografts were identified immunohistochemically with primary antibodies against host (athymic AKR mice) and donor (fetal Lewis rats) major histocompatibility complex (MHC) class I. Blood vessels supplying solid CNS grafts at 1-7 days post-transplantation were identified ultrastructurally and possessed interendothelial tight junctional complexes; however, they were not perfused with either host blood or blood-borne HRP prior to 8 days. Graft vessels at 10 days were outlined consistently by peroxidase-positive red cells in immersion-fixed material and labeled with blood-borne HRP. These vessels provided a BBB to the circulating HRP and exhibited interendothelial tight junctions. Evidence of angiogenesis within solid anterior pituitary grafts and the variety of cell suspension grafts was obtained prior to 3 days post-transplantation in immersion-fixed preparations; the vessels, with the notable exception of those supplying astrocyte cell suspensions, failed to present a BBB to blood-borne peroxidase. Endothelia in the solid pituitary allografts and the PC12 cell grafts were highly fenestrated and exhibited open interendothelial junctions; those in the tumor and fibroblast cell grafts, for the most part, appeared nonfenestrated, and many possessed open interendothelial junctional complexes. Immunostaining for host and donor MHC class I revealed that donor blood vessels predominate over host vessels in CNS xenografts and supply pituitary xenografts exclusively; in both preparations, donor vessels were not identified within the host CNS. Because cell suspension grafts were derived from endothelia-free preparations grown in culture, blood vessels supplying these grafts were necessarily of host CNS origin and manifested a morphological transformation from a BBB to a non-BBB endothelium. The data suggest that angiogenesis in solid CNS grafts placed into the adult host CNS, compared to similarly placed solid peripheral tissue/cell suspension grafts, is not rapid.(ABSTRACT TRUNCATED AT 400 WORDS)     

Experimental rabies in skunks and foxes. Pathogenesis of the spongiform lesions

The pathogenesis of rabies spongiform lesions in striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes) was studied by light and electron microscopy and peroxidase-antiperoxidase immunocytochemistry. Studies in skunks included use of several street virus variants (different antigenic profiles as tested by monoclonal antibodies) different routes of inoculation (intranasal, intracerebral and intramuscular), immunosuppression of infected skunks, different preparations of virus (brain and salivary gland suspensions and infective tissue culture fluids), and sequential development of the lesions. Foxes (Vulpes vulpes) were infected intramuscularly with a street virus isolate. Except for the group of immunosuppressed skunks, all animals that developed clinical signs of rabies had encephalitis characterized by varying degrees of mononuclear perivascular cuffing, focal gliosis, and Negri bodies. Spongiform change occurred in the neuropil of the grey matter (especially thalamus and cerebral cortex) in rabid animals from all groups, but not in controls or exposed animals that did not develop rabies. Rabies antigen (detected by peroxidase-antiperoxidase immunocytochemistry) occurred only in small amounts in many thalami; some vacuolated areas were devoid of antigen. Ultrastructurally, there was a gradation in lesions from small to large membrane-bound vacuoles in cellular processes (mainly dendrites, less frequently axons) and to large tissue spaces containing granular and/or membranous material. These studies indicate that rabies spongiform change occurs in skunks given street virus of several different antigenic profiles and challenge virus standard rabies virus and that the distribution of the lesions has remarkable similarities to those of the traditional spongiform encephalopathies. The occurrence of the lesion is not affected by the immune response, the route of inoculation of virus, the preparation (suspension of salivary gland or brain, or tissue culture fluid), or the incubation period. The paucity of antigen in many thalami suggests that incorporation of viral components into vacuolar membranes is not necessary for development of the spongiform change. The development of the lesions includes formation of small membrane-bound vacuoles in cellular processes, rapid enlargement (less than 3 days) with compression of adjacent neural tissue, and rupture resulting in the large tissue spaces readily visible by light microscopy.     

Lateral orientation, eye movements and dichotic listening.

Past studies have found that lateral orientation (eye or head turn) may influence hemispheric asymmetry on the dichotic listening task. The present work studied the effects of forced head and eye turn on a consonant-vowel dichotic test. Spontaneous conjugate lateral eye movements (CLEM) in response to questions were also measured. The subjects were 29 male and 25 female right-handed university students. The dichotic test was administered using a forced-attention method rather than free recall in order to control for attentional bias. As predicted, right lookers on the CLEM test, showed an enhanced right ear advantage while left lookers showed a diminished right ear advantage. This suggests that characteristic hemispheric arousal may enhance or inhibit asymmetry on perceptual laterality tests. No relationship was found between dichotic listening and forced head or eye turning. It was noted that past experiments may have failed to control for the attentional bias introduced by having the head or eyes turned to one direction.     

Effects of cadaver dissection on the attitudes of medical students

Summary: Summary. A study was conducted to determine whether the attitudes of medical students to death and caring changed during the 3 months following exposure to cadaver dissection. All first-year students were invited to complete a questionnaire immediately before their initial cadaver dissection experience, after 6 weeks, and after a further 3 months. The questionnaire reflected attitudes to death, violent death, death of someone known to the respondent and caring when someone known to the respondent is seriously injured. Ethnicity and previous exposure to dying has no effect on responses, but overall men students' reactions were significantly less than for women ( P < 0.001). The responses given on the final part of the questionnaire after 3 months were significantly lower than those to most questions in the first part of the questionnaire. The exceptions were those questions where the subject in the given scenario was known to the respondent, where reactions were rated significantly greater ( P < 0.001) in the follow-up questionnaire and can be explained on the basis that they were a personal referent.
Students rapidly develop a coping mechanism which enables them to view cadaver dissection as an occupation quite divorced from living human beings. During these early months of training solicitude decreases for those who die who are unknown to them, but concern for personal referents increases. Educators should be aware of the dramatic change of attitudes among students and the process of professionalization which might influence their caring of future patients.     

CD4-positive/heat-stable antigen-positive thymocytes cause graft-versus-host disease across non-major histocompatibility complex incompatibilities

Single-positive thymocytes are the immediate precursors of peripheral recent thymic emigrants (RTE) which develop into mature peripheral T cells. The functional ability of RTE is unclear but their state of differentiation may be relevant to the development of tolerance to peripheral “self” antigens. Since RTE are difficult to analyze, precursor CD4⁺/8⁻ thymocytes were assessed in a model in vivo to determine their functional capability and their susceptibility to tolerance induction. The ability of both heat-stable antigen-positive (HSA⁺) (immature) and HSA⁻ (mature) single-positive thymocytes to cause graft-versus-host disease (GVHD) across non-major histocompatibility complex differences was examined. Both HSA⁻ and HSA⁺ CD4⁺/8⁻ thymocytes from C3H mice caused lethal GVHD in AKR recipients as did CD4⁺ peripheral T cells in controls. Further, neonatal C3H thymocytes also caused lethal GVHD in AKR recipients. Since CD4⁺/8⁻ thymocytes are the precursors of RTE, these results suggest that RTE are not susceptible to tolerance induction to “minor” antigens and may have a normal immune function in vivo. This would suggest that peripheral tolerance may be dependent upon the manner of antigen presentation rather than T cell maturity.