The effect of vascular endothelial growth factor (VEGF165) on the chorioallantoic membrane (CAM) of 13-day-old chick embryos was studied. The factor was applied in doses of 0.5-4 micrograms for a period of up to 4 days. Macroscopical, histological and immunohistological studies were carried out. The localization of the factor was examined with an anti-VEGF antibody. The mitogenicity of VEGF165 and basic fibroblast growth factor (bFGF) were studied by means of the BrdU-anti-BrdU method. Furthermore, the effect of heparin alone and in combination with VEGF165 was investigated. VEGF165 specifically induces angiogenesis in doses of 0.5 microgram and more. A brush-like formation of blood vessels can be seen in the region of the precapillary vessels. Angiogenesis also takes place in the region of the capillaries and the venules. Histologically we found indications of sprouting as well as of intussusceptive capillary growth. The presence of the factor in the application area could be demonstrated with the anti-VEGF antibody for a period of 3 days. The factor is located in the chorionic epithelium and the intraepithelial capillaries. The BrdU-studies show that VEGF165 induces strong endothelial cell proliferation, whereas bFGF elicits fibrocyte proliferation and minor endothelial cell proliferation. Heparin induces squamous metaplasia of the chorionic and allantoic epithelium in combination with an aggregation of fibrocytes. We could not detect any enhancement of VEGF165 by heparin.

The application of Thermanox tissue culture coverslips to the day 9 CAM of the chick causes constant effects beneath the carrier after 3 days, and these are associated with a change in the blood vessel pattern. Histological sections show enormous thickening of the CAM in the reactive areas. The stroma of the CAM shows fibrocyte proliferation, leucocyte infiltration, and clusters of dispersed ectodermal epithelial cells exhibiting signs of necrosis. The latter obviously cause a strong vascular response. The same effects are seen when the Thermanox discs are applied at day 11. Following application on day 12 a positive or negative response to the carrier is observed, whereas on day 13 no such carrier effects are seen. The only remaining effect is compression of the intra-ectodermal capillary plexus of the CAM. This can macroscopically be seen after peroxidase staining of the blood vessels. The effect of 5 microliters PBS dried on the Thermanox disc and applied to the day 13 CAM is to cause, after 3 days, hyperosmotic damage to the ectodermal epithelium, which becomes overgrown by fibrocytes. We found dose-dependent effects of salt-free human bFGF applied to the day 13 CAM. The first and main effect is fibrocyte proliferation (0.5 microgram). New capillaries appear with higher doses, but are not as frequent as would be expected for an angiogenic substance (1.25-2.5 micrograms). Also with higher doses additional hyperplasia of the endodermal (3.75 micrograms) and ectodermal (5 micrograms) epithelium can be seen. The latter might be a non-specific hyperosmotic effect. Leucocytes are regularly present within the reactive areas. When salt-free angiogenin is applied to the day 13 CAM, some effects appear with doses of 4.6 micrograms and more. The ectodermal epithelium of the reactive areas is discontinuous, exhibiting signs of necrosis. It is overgrown by parallel fibrocytes. Whether this is a non-specific hyperosmotic effect, or indicates enhancement of invasive growth, calls for further investigation.

The case studies of three patients are presented and discussed (patient 1 with coenaesthetic schizophrenia, patient 2 with coenesthesia in the course of a delusional (paranoid) disorder; patient 3 with coenesthesia caused by carcinomatous meningitis).