Bacteria for the nineties

Staphylococcus aureus and Enterococci have gained prominence as the causes of wound infections during this decade. Methicillin-resistant Staphylococcus aureus (MRSA) became commonplace in the United States during the 1980s. In Canada, infections with MRSA have been increasing in frequency since 1995. MRSA develops resistance by producing an altered penicillin-binding protein, PBP 2a, coded for by the mecA gene. Vancomycin is the usual drug of choice. Recently, strains with intermediate resistance to vancomycin (VISA) have been isolated from patients in Japan and the United States. Interim guidelines for their control have been developed by the Centers for Disease Control. Enterococci have developed a resistance to a variety of antimicrobials during the past three decades, including beta-lactams and aminoglycosides. Recently, strains resistant to vancomycin (VRE) have been found in the United States and Canada. They are particularly difficult to treat, although some success has been achieved with experimental drugs. These microorganisms have the ability to escape control by antimicrobials almost as soon as they are developed. Thus, we must practice good infection control and reserve antimicrobials only for clear cases of infection if we are to prevent or delay the emergence of resistance.     

Mammalian mitochondrial ribosomal proteins. N-terminal amino acid sequencing, characterization, and identification of corresponding gene sequences

The integrity of healthy mitochondria is supposed to depend largely on proper mitochondrial protein biosynthesis. Mitochondrial ribosomal proteins (MRPs) are directly involved in this process. To identify mammalian mitochondrial ribosomal proteins and their corresponding genes, we purified mature rat MRPs and determined 12 different N-terminal amino acid sequences. Using this peptide information, data banks were screened for corresponding DNA sequences to identify the genes or to establish consensus cDNAs and to characterize the deduced MRP open reading frames. Eight different groups of corresponding mammalian MRPs constituted from human, mouse, and rat origin were identified. Five of them show significant sequence similarities to bacterial and/or yeast mitochondrial ribosomal proteins. However, MRPs are much less conserved in respect to the amino acid sequence among species than cytoplasmic ribosomal proteins of eukaryotes and bacteria.     

Haemonchus contortus glycoproteins contain N-linked oligosaccharides with novel highly fucosylated core structures

Structural studies on the N-linked oligosaccharides of Haemonchus contortus, an economically important nematode that parasitizes domestic ruminants, have revealed core fucosylation of a type not previously observed in any eukaryotic glycoprotein. Mass spectrometric analyses were performed on detergent extracts of homogenized adult H. contortus and on purified H11, a glycoprotein isolated from intestinal brush borders which has been previously shown to be an effective vaccine antigen. The major N-linked glycans identified in the present study have up to three fucose residues attached to their chitobiose cores. The fucoses are found at the 3- and/or 6-positions of the proximal GlcNAc and at the 3-position of the distal GlcNAc. The latter substitution is unique in N-glycans. Most anti-H11 monoclonal antibodies are known to recognize carbohydrate epitopes, and it is possible that the newly discovered multifucosylated core structures are highly immunogenic in this glycoprotein.     

Perceptions of tonal changes in normal laryngeal, esophageal, and artificial laryngeal male Cantonese speakers

PURPOSE: Present radiobiological studies for different cell lines in vitro demonstrate the equivalence and efficacy of continuous low-dose-rate brachytherapy (LDR-BT) and pulsed dose rate brachytherapy (PDR-BT) when using small and frequent dose pulses. The aim of this study was to examine monolayer fibroblast cultures in vitro to examine the biological effects of different pulse doses and dose rates under clinically conditions. MATERIAL AND METHODS: B14 cells, Hy B14 FAF 28, peritoneal fibroblasts, were cultured in multi-well plates and exposed to a PDR radiation source at a distance of 9 mm. The following PDR-schemes were compared: dose per pulse: 1 Gy, 2.5 Gy and 5 Gy to a total dose of 5 Gy/5 h (overall time), 10 Gy/10 h, 20 Gy/20 h and 30 Gy/30 h. The pulse duration for the examination of dose rate effects was 20 min, 30 min or 52 min corresponding by dye pulse dose rate of 300 cGy/h, 200 cGy/h or 115 cGy/h. Treatment endpoints were cell measured by dye exclusion test and clonogenic cell survival. RESULTS: Cell survival decreased for pulse doses of 5 Gy compared to 2.5 Gy or 1 Gy per pulse (mean dose rate 200 to 300 cGy/h). No differences were observed with dose rates during irradiation of 300 cGy/h, 200 cGy/h or 115 cGy/h (20 Gy/1 Gy). CONCLUSION: Radiobiological effects of PDR-RT are dependent on the dose per pulse, with differences in biological effects only with a dose per pulse of more than 2.5 Gy, considering the described in-vitro conditions. More examinations with a more pronounced difference in dose rate will be continued for evaluation of dose rate effects.