[Improving the biocompatibility of silicone implants using spider silk coatings: immunohistochemical analysis of capsule formation]. / Verbesserung der Biokompatibilität von Silikonimplantaten durch Spinnenseidenbeschichtung: Immunhistochemische Untersuchungen zum Einfluss auf die Kapselbildung.

INTRODUCTION: Optimisation of the biocompatibility of silicone implants and reduction of capsule formation around the surface of such implants are in the focus of plastic surgical biomaterial research. In addition to its extraordinary physical and biochemical properties, spider silk shows high biocompatibility. Therefore, the coating of silicone implant surfaces with recombinant spider silk was analysed regarding foreign body reactions. MATERIALS AND METHODS: In the context of a preclinical study, miniaturised silicone implants were implanted in the back of 60 Sprague-Dawley rats. The animals were randomised; 30 animals received a texturised implant coated with the recombinant spider silk protein eADF4(C16) and 30 animals received uncoated implants. 3, 6 and 12 months after implantation, implants together with the surrounding capsules were removed and submitted to histological and immunohistochemical assessment. RESULTS: Coating of silicone implants with the recombinant spider silk protein eADF4(C16) resulted in a delayed and significantly decreased foreign body reaction and a reduced capsule manifestation. CONCLUSION: eADF4(C16) seems to be a promising candidate for the reduction of foreign body-associated capsule formation. Moreover, coating of other medical implants with this recombinant spider silk protein may improve their biocompatibility with little additional effort.

An Agrobacterium VirE2 channel for transferred-DNA transport into plant cells.

Transferred DNA (T-DNA) transfer from Agrobacterium tumefaciens into eukaryotic cells is the only known example of interkingdom DNA transfer. T-DNA is a single-stranded segment of Agrobacterium's tumor-inducing plasmid that enters the plant cell as a complex with the bacterial virulence proteins VirD2 and VirE2. The VirE2 protein is highly induced on contact of A. tumefaciens with a plant host and has been reported to act in late steps of transfer. One of its previously demonstrated functions is binding to the single-stranded (ss) T-DNA and protecting it from degradation. Recent experiments suggest other functions of the protein. A combination of planar lipid bilayer experiments, vesicle swelling assays, and DNA transport experiments demonstrated that VirE2 can insert itself into artificial membranes and form channels. These channels are voltage gated, anion selective, and single-stranded DNA-specific and can facilitate the efficient transport of single-stranded DNA through membranes. These experiments demonstrate a VirE2 function as a transmembrane DNA transporter, which could have applications in gene delivery systems.

Coupling site-directed mutagenesis with high-level expression: large scale production of mutant porins from E. coli.

Combination of an origin repair mutagenesis system with a new mutS host strain increased the efficiency of mutagenesis from 46% to 75% mutant clones. Overexpression with the T7 expression system afforded large quantities of proteins from mutant strains. A series of E. coli BE host strains devoid of major outer membrane proteins was constructed, facilitating the purification of mutant porins to homogeneity. This allowed preparation of 149 porin mutants in E. coli used in detailed explorations of the structure and function of this membrane protein to high resolution.

Serodiagnosis of toxoplasmosis by using a recombinant form of the 54-kilodalton rhoptry antigen expressed in Escherichia coli.

A 330-residue carboxy-terminal antigenic fragment of the Toxoplasma gondii 54-kDa rhoptry protein (ROP2) was expressed in Escherichia coli as a fusion polypeptide containing a 48-amino-acid sequence derived from phage lambda protein Cro and E. coli protein LacI followed by six consecutive histidyl residues. Metal chelate affinity chromatography provided an easy way to isolate the recombinant product in a highly purified form (> 95%). When this material was used to develop an immunoglobulin G (IgG) enzyme-linked immunosorbent assay for diagnosis of toxoplasmosis, the test reached a sensitivity of 89%. The sensitivity of the assay was similar whether the sera contained T. gondii-specific IgM or were devoid of such IgM. It was also found that ROP2 is a conserved antigen since antibodies against the recombinant antigen could be detected in mice experimentally infected with 11 independent T. gondii isolates originating from infected human tissues tested. Thus, the 54-kDa rhoptry antigen could advantageously complement other previously described T. gondii antigens for the development of more-sensitive and more-informative recombinant antigen-based tests for toxoplasmosis diagnosis.

"Tonight something special is happening in this neighbourhood." Report on experimental distribution of condoms to clients of prostitutes.

PIP: The incidence of sexually transmitted diseases (STDs) among prostitutes and their clients is relatively high in the Netherlands, although condoms have been known for a long time in prostitution. As part of the 1987 national condom campaign the STD Foundation developed public education activities targeting prostitutes, their partners, clients, and procurers trying to convince them about safer sexual contact to prevent STDs. Members of the working group Client and Prostitution (KLEP) offered their cooperation. A total of 18 condom distributions were carried out between January-November 1988. About 5000 clients of prostitutes were approached in the redlight districts of 9 towns and cities after members of the KLEP personally had informed prostitutes and procurers by means of leaflets in 5 languages about the purpose of the campaign and guidelines had been drawn up about distribution. Positive remarks were often heard, however, there were also those who ignored the distributors. Some of the positive results included the prostitutes' wish for safer sex and that the procurers frequently handed out condoms to clients in clubs and private houses. A follow-up project in preparation envisions reaching clients after contact with the prostitute, organization of local discussion evenings after condom distribution, and the provision of telephone numbers and addresses. The distribution of condoms frequently prompted prostitutes to inquire about STD/AIDS prevention, thus local and regional organizations might consider launching prevention activities. In November 1989 a report containing these recommendations was to be presented to representatives of local and regional organizations in localities where condom distribution had taken place.^ieng

Microvascular surgery and diseased vessels.

Hardly any data exist concerning the effects of arterial vessel disease on the results of microvascular surgery. As the scope of microvascular surgery expands, diseased vessels will surely be encountered more frequently. Therefore an experiment was performed in rabbits who were fed a cholesterol-enriched diet for 3 months. Then an anastomosis was made in both carotid and femoral arteries (total of 65 arteries) with microsurgical techniques. The diet was continued until the animals were killed at fixed times from 1 day to 4 months. The overall patency rate at the time of death was 91.8%. At the time of the operation two situations were present: hypercholesterolemia without any macroscopic changes and hypercholesterolemia with evident macroscopic atherosclerotic lesions. Atherosclerotic lesions in these small arteries present technical surgical difficulties, and direct results will depend on the skill and experience of the surgeon. Hypercholesterolemia without any macroscopic changes, in combination with the trauma of the operation, will lead to an accelerated formation of atherosclerotic changes. Lesions already present will progress in size. Both events lead to narrowing of the lumen at a later stage.

Healing of microvascular arterial anastomoses, as seen on corrosion casts by scanning electron microscopy.

We made 44 microsurgical anastomoses in the femoral artery in rats. The healing was studied from one day to 4 months, by making an acrylic cast of the lumen of the femoral artery and the surrounding vessels, and examining the cast by scanning electron microscopy. The method proved to be easy and relatively quick, and it limited the possibility of artifacts. The high depth of focus permitted simultaneous study of the main lumen and of the perivascular structures after microvascular anastomoses.