Franca Casagranda

Sequence of a Glycine-Rich Protein from Lizard Claw: Unusual Dilute Acid and Heptafluorobutyric Acid Cleavages

The hard keratins of mammals and birds have been extensively studied over recent years and a considerable body of knowledge is now available on the structure and composition of the constituent proteins and of their arrangement within the keratin structure1. Mammalian keratins have a very characteristic structure in which filaments of about 70A diameter are embedded in a non-filamentous matrix composed of sulfur-rich and glycine-tryosine-rich proteins. The filaments are responsible for the α-type X-ray pattern. In contrast avian keratins contain only one family of proteins arranged as small filaments of about 30A diameter which are responsible for a characteristic X-ray pattern, often referred to as the feather type. No sequence homology has been found between avian and mammalian keratin proteins and it is generally considered that they represent separate evolutionary developments.

Evaluation of a collagen-based biosynthetic material for the repair of abdominal wall defects

A collagen tissue polymer composite manufactured in sheep and prepared in two different forms (wet and dry) was compared to polypropylene mesh and to a control group for effectiveness in the repair of an abdominal wall defect in a rabbit model. The wet and dry patches were shown to differ significantly in their pore size. The wet material was shown to retain its natural porosity and promoted neovascularization, tissue integration, cellular infiltration, and neomatrix formation compared to the dry collagen-polymer patch. This material was superior to the polypropylene mesh implant, which was associated with significant adhesions. The appearance of type VI collagen was the earliest sign of new cell infiltration and neomatrix formation within the implant. New deposition of type VI collagen was apparent throughout the thickness of the implant within 4 weeks, followed by type III collagen accumulation. Decreased porosity of the collagen component in the dry patches resulted in a totally nonintegrated implant. This induced a foreign-body capsule with minimal cellular tissue infiltration and no deposition of collagen types VI and III within the implant.

Effects of mesh modification on the structure of a mandrel-grown biosynthetic vascular prosthesis

Mandrel-grown, mesh-reinforced vascular prostheses require adequate tissue coverage of the mesh for effective clinical function, particularly in low blood flow situations. Development of the ovine collagen-based Omniflowtrade mark vascular prosthesis has shown that the extent of this tissue cover is dependent on the interactions of the mandrel and the mesh with the sheep host. In the present study, the effects of chemical changes to the mesh have been examined. These data indicate that certain treatments of the mesh, particularly collagen or heparin, lead to increased tissue coverage while the number of sheep cells present and the ultrastructure of the resulting vessel remain unchanged.

C-terminal Sequencing: A New Look at the Schlack-Kumpf Thiocyanate Degradation Procedure

Application of the thiocyanate degradation procedure (Schlack and Kumpf 1926) to a peptide or protein (I) converts the C-terminal amino acid into a substituted thiohydantoin derivative (II) which can be subsequently cleaved to give a shortened (by one amino acid) peptide or protein (III) together with the C-terminal amino acid thiohydantoin (IV):

In vivo evaluation of modified mandrel-grown vascular prostheses

The Omniflowtrade mark Vascular Prosthesis (OVP) has been manufactured and extensively tested in animal and human trials. It has mechanical and biological qualities superior to synthetic and biological conduits, particularly in low flow conditions. For further development into the smaller diameter coronary prostheses, the inner luminal surface is of paramount importance. In a previous study this inner surface was modified to produce a more uniformly thicker nonundulating surface. In this study the mandrels of these modified OVPs were treated with either collagen or heparin; the OVPs were evaluated for patency, tissue integration and wound healing, and endothelialization using a dog model comparable to that used to evaluate the unmodified OVP. In all instances, each of the modified prostheses were fully patent and had no signs of any deleterious effects caused by these modifications; no thrombus or aneurysms were visible. The tissue response was rapid with excellent new host collagen deposition within the vessel wall and minimal inflammatory and foreign body giant cells. Endothelialization was noted at the earliest explant time point in central regions of the prostheses, albeit that the histological picture at this time point appeared to reflect a complex atypical intimal layer.

Stratigraphic evaluation of the collagen surrounding a biomaterial implant

Abstract A method that allows stratigraphic analysis of the collagen in the connective tissue which forms around a biomaterial implant is described. Collagen was analysed by densitometry of pepsin soluble a-chains and by hydroxyproline analysis. The tissue formed around a silicone tubing implant was used as a model system for quantitation of collagen types. The amount of collagen was lowest close to the material surface, while this same region had the highest content of type III compared to type I collagen. Type V collagen, which was the only other collagen detected, was present at low levels throughout. Immunohistological examination of the same tissue with highly specific monoclonal antibodies also showed types I and III collagens. The relative staining of these collagens indicated that even if the affinities of antibodies and their effectiveness in penetrating tissue could be taken into account, any quantitative estimates of collagens from immunohistology alone must be treated with great caution.