Polymers for biodegradable medical devices XI. Microencapsulation studies: characterization of hydrocortisone-loaded poly-hydroxybutyrate-hydroxyvalerate microspheres.

Hydrocortisone-loaded monolithic microspheres were prepared, using a single emulsion solvent evaporation process, from a range of poly-beta-hydroxybutyrate-hydroxyvalerate copolymers in which both molecular weight and hydroxyvalerate content were varied. Many similarities were observed in the effects of process parameters and co-polymer composition on the morphologies of the microspheres, and the morphologies of microcapsules prepared (and previously reported) by a double emulsion process. The yields of the single emulsion process were generally superior to those of the double emulsion process, although these were adversely affected by hydrocortisone incorporation as the molecular weight of the copolymer was reduced. The predominant effect of hydrocortisone incorporation was on polymer morphology, characterized by the appearance of small surface pores; an effect which increased with increasing drug loading. Changes in polymer molecular weight, copolymer composition and process temperature, together with the incorporation of polycaprolactone in the form of a solvent blend, enabled microspheres with a range of morphologies to be produced providing the potential for control of drug release.

Amine and tin fluoride inhibition of Streptococcus sanguis adhesion under continuous flow.

This study evaluated the ability of topically applied amine fluoride (AmF) and AmF-tin fluoride to inhibit the adhesion of Streptococcus sanguis within a parallel plate flow cell system. One of three AmF compounds and two tin fluoride preparations significantly reduced the net bacterial adhesion to conditioned glass over a 1-h period. Tin(IV) fluoride inhibited S. sanguis adhesion to the greatest extent, and this was shown to be dependent on the formation of the conditioning film prior to agent application.

Partial purification of a novel insect antidiuretic factor from the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), which acts on Malpighian tubules.

In this study, we report for the first time the presence of an antidiuretic factor in the head of the Colorado potato beetle (Leptinotarsa decemlineata (Say)) which acts directly on Malpighian tubules. Biologically active fractions were isolated from the head and separated using molecular weight filtration and high-performance liquid chromatography (HPLC). The resulting fractions were tested for their antidiuretic activity on single isolated Malpighian tubules. Antidiuretic activity was found in the 25% acetonitrile Sep-Pak fraction and the Cn-2 (3000-10,000 MW) and Cn-3 (<3000 MW) fractions, suggesting that the antidiuretic factor was probably a peptide of 25 to 50 amino acids. The antidiuretic factor was very potent, since after five successive fractionations on two different HPLC columns, a high level of inhibition (63%) of fluid secretion by Malpighian tubules could be observed at low dose (0.14 head-equivalent/microl). The antidiuretic factor isolated from the head of the Colorado potato beetle was not affected by repeated freezing and thawing but was sensitive to heat. The differences observed between the Colorado potato beetle antidiuretic factor and other insect diuretic and antidiuretic factors may indicate the possibility of a novel family of water regulation hormones in insects.

Human single-chain Fv fragments from a combinatorial library using the loxP-Cre recombination system.

A human scFv display library has been constructed from peripheral blood lymphocytes of a patient suffering from Hashimoto's thyroiditis. Upon induction of Cre recombinase, the amplified VH and VL genes were recombined via two loxP sites inserted in amplification primers to construct in vitro scFv genes. Either soluble scFvs or scFvs displayed on phage were screened for binding to human thyroglobulin after two pannings with this antigen. Three scFvs were obtained which showed very similar nucleotidic sequences. The VH genes expressed display 96.4% nucleotide sequence homology with the germline VH251 gene, one of the two functional members of the small VH5 family and are mutated in sites already described as "selectively neutral" mutations and the VL genes are close to the germline DPL8 gene. These scFvs bind not only to human thyroglobulin but also to other self and exogenous antigens.

Influence of growth mode and sucrose on susceptibility of Streptococcus sanguis to amine fluorides and amine fluoride-inorganic fluoride combinations.

This study evaluated the susceptibility to amine fluorides (AmFs) of planktonic and biofilm cultures of Streptococcus sanguis grown with and without sucrose. Cultures were incubated with AmFs (250 mg of fluoride liter-1) for 1 min. The susceptibility of biofilms was less than that of the planktonic form and was further decreased by growth in the presence of sucrose.

Methodology for selection of human antibodies to membrane proteins from a phage-display library.

We describe a simple antigen capture technique for the selection of a specific human antibody to p185erbB-2, a transmembrane glycoprotein, from a library of human Fab genes expressed on the surface of bacteriophage. Magnetic beads coated with the rat antibody ICR55 have been used to capture erbB-2 antigen from Triton X-100 extracts of SKOV3 cells. The antigen-coated beads have then been used to select bacteriophage displaying human Fab with affinity for p185erbB-2. After 4 rounds of selection, 65 phage clones were isolated which bound specifically to p185erbB-2 in a capture assay. Nine of the clones which gave the strongest reaction in an ELISA were selected for further development and the Fab genes were subcloned into the expression vector pUC119his6mycXba and electroporated into E. coli TG1. Colonies were grown, induced and the supernatants tested for the presence of secreted human Fab. Supernatants from two of the 9 clones contained human Fab and one of these bound specifically to erbB-2 in a capture assay, stained the membranes of the erbB-2 overexpressing cell lines BT474 and SKBR3 and immunoprecipitated a protein of molecular weight 185 000 kDa from SKOV3 cells. We conclude that a membrane antigen captured by specific monoclonal antibody can be used successfully to select phage displaying human antibodies specific for the antigen.

Polymers for biodegradable medical devices. X. Microencapsulation studies: control of poly-hydroxybutyrate-hydroxyvalerate microcapsules porosity via polycaprolactone blending.

Reservoir-type microcapsules were prepared using a double emulsion solvent evaporation process from a range of different poly-beta-hydroxybutyrate homopolymers and copolymers thereof with 3-hydroxyvalerate (P(HB-HV) polymers) blended with 20 per cent by weight of poly-epsilon-caprolactone (PCL). Microcapsules prepared from these P(HB-HV)/20 per cent PCL blends had very different typical surface morphologies from those prepared from the corresponding unblended P(HB-HV) polymers. At this blend ratio the effects of polymer blending on particle morphology were clearly dependent on the molecular weight of P(HB-HV) polymer and, to a reduced extent, the 3-hydroxyvalerate content. Microcapsules were also prepared from blends of a high molecular weight P(HB-HV) polymer with PCL in which the proportion of the latter was varied from 0 to 100 per cent at 10 per cent intervals. Increasing the proportion of PCL from 0 to 50 per cent produced a systematic and dramatic increase in microcapsule porosity; with only skeletal particles being generated from the even 50-50 blend. When the proportion of PCL in the blends was increased from 50 to 70 per cent the level of particle porosity diminished, and at 80 per cent or above the microcapsules were essentially smooth and non-porous.

Polymers for biodegradable medical devices. IX: Microencapsulation studies; effects of polymer composition and process parameters on poly-hydroxybutyrate-hydroxyvalerate microcapsule morphology.

Reservoir-type microcapsules were prepared using a double emulsion solvent evaporation technique from a series of nine different poly-beta-hydroxybutyrate (PHB)-based polymers in which both molecular weight and hydroxyvalerate content were varied. Particles prepared from a low molecular weight (MW 43,000) homopolymer had a shrivelled appearance, but were not porous. When the molecular weight of the fabricating homopolymer was increased to 540,000, however, these features disappeared and non-wrinkled particles with microporous surfaces were observed. Microcapsules prepared from a high molecular weight copolymer of PHB with 10.8 per cent hydroxyvalerate (HV) had a similar appearance, but particles prepared from a high molecular weight 20.1 per cent HV copolymer had much smoother and less porous surfaces. Lowering the molecular weight of the copolymer had the effect of producing particles that were generally distorted in shape and had highly irregular, macroporous, surface morphologies. Increasing the double emulsion temperature to 40 degrees C at 2 min after phase combination typically generated smoother and/or less porous particles and improved the batch yield. The numerous factors potentially responsible for the development of morphological characteristics of the products are discussed in the light of these observations.

Differential expression of the Lewis Y antigen defined by monoclonal antibody C14/1/46/10 in colonic polyps.

The expression of Le(y) (Lewis(y) Hapten), a difucosylated type 2 blood group-related antigen, in colorectal lesions was studied by using the monoclonal antibody C14. In normal colonic mucosa, strong staining has been observed in the terminal ileum, cecum, and ascending colon with minimal staining in the rest of the colon and rectum. Eighty-three percent of adenomas expressed Le(y), with 70% showing an increased expression of Le(y) compared with normal tissue. Only 25% of metaplastic (nonneoplastic) polyps showed an increased expression of Le(y). The expression of Le(y) in adenomas was correlated with both size and degree of epithelial dysplasia of the adenomas and also showed an association with histologic type. No correlation was found with the location and morphology of the adenomas. The most strongly related parameter was the degree of dysplasia. All adenomas with severe dysplasia showed increased expression of Le(y), with 83% showing marked expression. This finding was irrespective of their size or type. Adenomas which did not exhibit severe dysplasia showed increased expression in 66% of cases, but only 18% showed marked expression. These findings show that the expression of Le(y) in colorectal lesions is associated with features related to malignant potential. Le(y) expression may provide useful prognostic information in the assessment of colorectal polyps.

Evaluation of on-campus continuing medical education programs in Alberta.

Seven on-campus continuing medical education programs offered during the 1971-72 academic year were evaluated. A multiple-choice examination was taken by the participants before each course; the same examination was administered immediately after the course was completed, and a third examination was taken three to five months later. It was found that for each course there was a significant increase in knowledge at both post-testing periods. A questionnaire developed for the purpose of determining the effectiveness of the courses was also administered at the time of the third test, and exhibited reasonable degrees of reliability and validity. A large proportion of the participants indicated the content of their courses was relevant and necessary, and was being used in their medical practice. It was concluded that the effectiveness of these programs justified their continuation.