Abstract: Early detection of infectious agents of human prion diseases such as CJD by using an animal model, etc. is needed in order to rapidly determine prion infections in pharmaceuticals such as blood products, foods, or cosmetics. This invention provides a screening method for infectious agents of human or non-human prion diseases in samples, which employs, as an indication, the deposition of the aberrant prion protein in the follicular dendritic cell (FDC) of a non-human animal.

Abstract: It is intended to provide a material for efficiently measuring the production of ?-amyloid which relates to the onset of Alzheimer's type dementia, and a method of efficiently screening a substance affecting the production of ?-amyloid by using the above material.

Abstract: Early detection of infectious agents of human prion diseases such as CJD by using an animal model, etc. is needed in order to rapidly determine prion infections in pharmaceuticals such as blood products, foods, or cosmetics. This invention provides a screening method for infectious agents of human or non-human prion diseases in samples, which employs, as an indication, the deposition of the aberrant prion protein in the follicular dendritic cell (FDC) of a non-human animal.

Abstract: A membrane filter of 0.025 to 0.05 .mu. in pore size is treated by passing the solution of a water-soluble high molecular substance such as albumin, dextran, polyvinylpyrrolidone, polysorbate 80, gelatin or the like through the membrane filter. Employing the filter thus treated, the solution of a physiologically active substance of human origin such as human growth hormone, kallikrein, trypsin inhibitor, epidermal growth factor, leucocyte interferon etc. is filtered at high recovery rate of the active substance avoiding the adsorption of the active substance onto the filter. By the filtration, harmful viruses such as Creutzfeldt-Jacob disease pathogen which may exist in the physiologically active substance can be removed.