Trends of arbekacin-resistant MRSA strains in Japanese hospitals (1979 to 2000)

A total of 472 clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated in Japan between 1979 and 2000 were investigated for resistance to 8 aminoglycosides, 4 aminoglycoside-modifying enzyme gene profiles, and AluI-restriction fragment length polymorphism of the coagulase gene determined by polymerase chain reaction assay. The majority of MRSA strains tested belonged to 4 groups based on coa-RFLP: L21, L22, L31, and M22. About 90% of recent isolates belonged to type L21, indicating the spread of a specific type of MRSA in Japan. Of the type L21 strains, 41.9% included the aac(6')/aph(2") gene, which was one of the risk factors of arbekacin (ABK) resistance, but only 5.5% were resistant to ABK. In contrast, all of the type M22 strains carried aac(6')/aph(2") and 70.1% showed ABK resistance. Among the other types, less than 20% of strains showed ABK resistance. These results suggested that ABK has maintained potent activity. If the predominance of type L21 continues, there will be no progression to ABK resistance in MRSA. However, it may be necessary to monitor the trends in type M22 continuously.     

A cell-permeable NFAT inhibitor peptide prevents pressure-overload cardiac hypertrophy

The activation of the calcineurin-nuclear factor of activated T cells cascade during the development of pressure-overload cardiac hypertrophy has been previously reported in a number of studies. In addition, numerous pharmacological studies involving calcineurin inhibitors such as FK506 and cyclosporine A have now demonstrated that these agents can prevent such hypertrophic responses in the heart. However, little is known regarding the roles of the calcineurin downstream effector--nuclear factor of activated T cells. Our present study has further examined the roles of nuclear factor of activated T cells in pressure-overload cardiac hypertrophy by employing a recently developed cell-permeable nuclear factor of activated T cells inhibitor peptide. Rat hearts were subjected to pressure overload attributable by 4 weeks of aortic banding, and then treated with this cell-permeable nuclear factor of activated T cells inhibitor peptide and a control peptide. Treatment with the inhibitor was found to significantly decrease the heart weight/body weight ratio, the size of cardiac myocytes, and the serum brain natriuretic peptide and atrial natriuretic peptide levels. These results suggest that nuclear factor of activated T cells functions in a key role in the development of cardiac hypertrophy during pressure overload. Inhibition of nuclear factor of activated T cells by a specific inhibitor peptide is a suitable method for characterization of the molecular mechanisms underlying cardiac hypertrophy as well as in the search for new promising therapies for disease.     

Gastrointestinal transit and mucoadhesive characteristics of complexation hydrogels in rats

The aim of this study was to investigate the gastrointestinal (GI) transit and mucoadhesive properties of complexation hydrogels, poly(methacrylic acid-grafted-ethylene glycol). The fluorescent labeled complexation hydrogels containing different molar ratios of methacrylic acid/ethylene glycol and different particle diameters were synthesized by free radical solution polymerization. The GI transit profiles of microparticles after oral administration to rats were evaluated by determining the polymer remaining in the stomach and the small intestine. Moreover, the mucoadhesion to the duodenal mucosa was evaluated by an in situ perfusion method. The ethylene glycol content and particle size of the hydrogels influenced significantly the GI transit and mucoadhesive capacities. The microparticles composed of polymers prepared from 1:1 ratio of methacrylic acid/ethylene glycol and having diameters of <53 microm showed the strongest mucoadhesive capacity. These findings indicated that the hydrogels may be a promising tool for improving oral bioavailability of various drugs, which are poorly absorbed from the GI tract.     

Establishment of a highly tumorigenic LNCaP cell line having inflammatory cytokine resistance

Human androgen-dependent prostate cancer LNCaP cells are low tumorigenic even in immunodeficient mice and were killed by the synergistic effect of inflammatory cytokines, IL-beta and IL-6. To establish a highly tumorigenic LNCaP cell line, we isolated the cytokine-resistant LNCaP-CR cell line and examined the phenotypes. The parental LNCaP cells were induced to commit apoptosis by the addition of IL-1beta and IL-6, but LNCaP-CR cells showed strong resistance against the cytokine action. However, LNCaP-CR cells did not exhibit any resistance to various antitumor drugs investigated. While LNCaP cells formed only palpable tumors in SCID mice, LNCaP-CR cells readily made tumors and their growth was significantly higher than that of LNCaP cells. Moreover, LNCaP tumor-bearing mice gained the weight gradually, but LNCaP-CR tumor-bearing mice significantly lost their body weight. LNCaP-CR cells still responded to androgen action and expressed AR, erbB2, IL-1R, IL-6R, gp130, STAT3, p21, Bcl-2 and caspase-3 as well as LNCaP cells. These results indicate that LNCaP-CR cell line is a new type of tumorigenic LNCaP cell lines and should be useful for identifying responsible genes of tumorigenicity, cytokine resistance, and also cachexia.     

Novel Mucosal Insulin Delivery Systems Based on Fusogenic Liposomes

Purpose Fusogenic liposomes (FLs) are unique delivery vehicles capable of introducing their contents directly into the cytoplasm with the aid of envelope glycoproteins of Sendai virus (SeV). The objective of this study was to evaluate the potential of FL to improve the mucosal absorption of insulin from rat intestinal membranes. Method The FLs containing insulin were prepared by fusing insulin-loaded liposomes with inactivated SeV particles and were administered directly into the ileal, the colonic, and the rectal loops (10 IU/kg). Results The FL successfully enhanced the insulin absorption and induced a significant hypoglycemic effect following the colonic and the rectal administration without detectable mucosal damage. This enhancing effect of insulin absorption was further improved by increasing the amount of insulin loaded in the FL and by coencapsulating insulin-degrading enzyme inhibitor. In contrast, the insulin absorption was not increased by the ileal administration of FL because the mucous/glycocalyx layers overlaid on the ileal epithelium impede the fusion of FL to the intestinal mucosa. Conclusion Our results indicated that FL is a useful carrier for improving the absorption of poorly absorbable drugs, such as insulin, via the intestinal tract.     

Effect of temperature-increase rate on drug release characteristics of dextran microspheres prepared by emulsion solvent evaporation process

Microspheres containing theophylline (TH) were prepared from a hydrophobic dextran derivative by an emulsion solvent evaporation process using an acetone/liquid paraffin system. The effects of solvent evaporation rate on particle properties and drug release characteristic of the microspheres were evaluated. The solvent evaporation rate was controlled by the rate of increase in temperature of the water bath, ranging 7.5-30 degrees C/h. Drug release from the microspheres was examined using JPXIV 2nd fluid (pH 6.8) containing 0.1% Tween 80, and was found to be greatly affected by the solvent evaporation rate. The percentage of drug released until 8h varied; from 28% to 84% for 30 and 7.5 degrees C, respectively. Differential scanning calorimetry and powder X-ray diffraction studies revealed that TH partially interacted with the polymer and drug crystallinity was maintained intact in the microspheres. According to scanning electron microscopy observations, all microspheres showed a well-formed spherical particle with a solid interior. The appearances of the microspheres were, however, extremely different. Microspheres prepared at 30 degrees C/h had a very smooth surface, while those prepared at 7.5-15 degrees C/h had a rough surface with large craters. These findings demonstrated that the surface morphology and drug release characteristic were controlled by the rate of increase of temperature.     

Genetic analysis of mec A homologues in Staphylococcus sciuri strains derived from mastitis in dairy cattle

Methicillin-resistant Staphylococcus aureus (MRSA) is defined by the presence of the mec A gene, which is considered to have been transferred horizontally from unknown bacterial species to S. aureus. As a candidate of evolutionary precursor of the mec A, the mec A-like gene (mec A homologue), which is ubiquitously present in Staphylococcus sciuri has been proposed. In this study, sequences of the mec A homologue in four S. sciuri strains (SCBM 1-SCBM 4) derived from dairy cows were determined to analyze their genetic characteristics and relatedness to mec A and the mec A homologue reported so far. The mec A-like gene sequences of the four S. sciuri strains were identical with each other and were considered to encode a product comprising 665 amino acids that is one amino acid smaller in size than products of mec A-like gene reported previously for S. sciuri strains K1, K1 1, and K3 (mec A1). The mec A homologue of a representative strain SCBM 1 showed 79.3--79.8% sequence identity to MRSA mec A and 93.4--94.4% identity to mec A homologues reported for the three S. sciuri strains. Between S. sciuri strain SCBM 1 and strains K1, K1 1, or K3, amino acid sequence identities in transpeptidase domain of the mec A-like gene product (98.2--98.5%) were higher than those in the transglycosylase domain (92.1--94.3%). In addition, SCBM 1 showed extremely high sequence identities of hsp 60, sodA, and rpoB genes (more than 98.7%) to S. sciuri strains, while showing 70.3--94.2% identity of these genes to other staphylococcal species. These findings indicated that mec A homologues in S. sciuri may be genetically more divergent than mec A in MRSA and methicillin-resistant coagulase-negative staphylococci.