Pilonidal sinus with an anal canal fistula. Report of a case.

A rare case of a pilonidal cyst with the fistulous tract situated inside the anal canal is described. This is the sixth such case in the medical literature.

Resolution of human fibroblast interferon into two distinct classes by thiol exchange chromatography.

Chromatography of crude and purified human fibroblast interferon on activated thiol Sepharose 4B yielded two classes of material exhibiting different stability to inactivation by mechanical stress. Interferon which bound to the gel accounted for 20--30 per cent of recoverable activity, could be eluted with reducing agents and was unstable. Unbound material did not bind on subsequent rechromatography and was stable to shear forces.

Reagents which inhibit disulphide bond formation stabilize human fibroblast interferon.

Fibroblast interferon may be stabilized against many inactivating influences by the addition of certain simple sulphydryl reagents. The use of such easily removable and relatively non-toxic stabilizers should help in the preparation and purification of fibroblast interferon for clinical use.

The mechanism of the inactivation of human fibroblast interferon by mechanical stress.

Interferon derived from human fibroblasts is readily inactivated during agitation and filtration. This inactivation has been shown to be largely a product of mechanical stress, and has been studied in detail by subjecting interferon to controlled shear stress using a rotational viscometer. The possible mechanism of this phenomenon is discussed.