Paradoxical production of mouse thymocyte activating factor by ouabain-treated human mononuclear cells

At concentrations as low as 10(-7) M, the cardiotonic glycosteroid ouabain, a specific inhibitor of the membrane Na+, K+-ATPase, is known to inhibit in vitro human lymphocyte proliferation produced in mixed lymphocyte cultures or induced by various stimulating agents (PHA, Con A, PWM, soluble antigens), while mouse lymphocyte proliferation is unaffected at this concentration. Ouabain inhibits most of proliferative response parameters at all stages of the transformation. This observation prompted us to suggest that ouabain could also act through inhibition of interleukin production which is known to occur during the first hours after T-cell stimulation in the presence of monocytes. In order to check the possible influence of ouabain on interleukin production, conditioned media from stimulated human mononuclear cells, prepared in the presence or in the absence of inhibitor, were tested for their ability to promote a mouse thymocyte response to PHA. Instead of the expected inhibition, we found that ouabain, even at high concentrations (2 X 10(-6) M) enhanced the stimulatory effect and/or the production of murine thymocyte activating factor(s). Moreover conditioned media from serum-free cultures of unstimulated human mononuclear cells exposed for 24 hr to low ouabain concentrations (10(-8) to 10(-7) M) showed a high activating effect on the response of murine thymocytes to PHA. This soluble factor produced upon ouabain treatment is produced by adherent cells and appears to be functionally similar to interleukin 1.     

Intrinsic Bacterial Contamination of a Commercial Iodophor Solution: Investigation of the Implicated Manufacturing Plant

After an outbreak of peritoneal infections attributed to intrinsic contamination of a poloxamer-iodine solution with Pseudomonas aeruginosa, the manufacturer of the contaminated solution permitted investigation and sampling of materials within the plant. Pseudomonas spp. were recovered from two different unopened lots of solution and from numerous water samples obtained at the plant. The isolates from water identical to those of an isolate recovered from Prepodyne solution (West-Agro Chemical Co., Inc., Westwood, Kans., manufactured for AMSCO Medical Products Div., Erie, Pa.) manufactured 1 month earlier at the same plant. P. aeruginosa was not recovered from incoming city water. P. aeruginosa was recovered from sterile water and poloxamer-iodine after 48 h of incubation in a plant polyvinyl chloride pipe. Scanning electron micrographs of polyvinyl chloride pipe used in the plant showed massive concentrations of rod-shaped and coccobacillary cells apparently embedded in interior deposits of the pipe. Manufacturers of iodophors should be aware that pipes or other surfaces colonized with bacteria may be a source of contamination of their products.     

Analysis of the stomach content of the blue-eyed shag Phalacrocorax atriceps bransfieldensis at Nelson Island,South Shetland Islands

Stomach contents of 40 specimens of the blu0e-eyed shag Phalacrocorax atriceps bransfieldensis were sampled at Nelson Island, South Shetland Islands, in January 1994. The analysis of the diet showed that fish were by far the main component, followed by octopods, polychaetes and gammarids. Notothenia coriiceps predominated in frequency (58%) and in weight (65%), whereas Nototheniops nudifrons was the most important species by number (47%). The comparison with data published on pellet analysis of shags from the same colony gave similar results. However, although the methodology used in the present study requires more time in the field, it reduces the errors that arise from the examination of regurgitated casts, such as those due to erosion by digestion or loss of the otoliths through the gastrointestinal tract. The observation of 8 nests filmed continuously during 24 h showed that the members of the pairs alternate foraging and make 3–5 foraging trips per individual per day. The activity started as 0700 hours and finished at 2200 hours, and the mean duration of the trips was 73 min.     

Estimating intrinsic growth rates of arthropods from partial life tables using predatory mites as examples

The intrinsic rate of natural increase of a population (r_m) has been in focus as a key parameter in entomology and acarology. It is considered especially important in studies of predators that are potential biological control agents of fast-growing pests such as mites, whiteflies and thrips. Life-table experiments under controlled laboratory conditions are standard procedures to estimate r_m. However, such experiments are often time consuming and may critically depend on the precise assessment of the developmental time and the fecundity rate early in the reproductive phase. Using selected studies of predatory mites with suitable life-table data, we investigated whether and how measurements of growth rates can be simplified. We propose a new method for estimating r_m from partial life tables, in which the researcher can choose a level of precision based on a stand-in measure of relative error. Based on this choice, the procedure helps the researcher to decide when a life-table experiment can be terminated. Depending on the chosen precision, significant amounts of experimental time can be saved without seriously compromising the reliability of the estimated growth parameter.

     

Polyazetidine-based immobilization of redox proteins for electron-transfer-based biosensors

A highly stable functional composite film was prepared using polyazetidine prepolymer (PAP) with peroxidase from horseradish (HRP) and/or glucose oxidase (GOx). The good permeability of the PAP layer to classical electrochemical mediators, as evaluated by the determination of the diffusion coefficient of different redox molecules, is of great importance in view of the use of PAP as an immobilizing agent in second-generation biosensor development. Cyclic voltammetry of the HRP-PAP layer on a glassy carbon electrode (GCE) showed a pair of stable and quasi-reversible peaks for the HRP-Fe((III))/Fe((II)) redox couple at about -370 mV vs. Ag/AgCl electrode in pH 6.5 phosphate buffer. The electrochemical reaction of HRP entrapped in the PAP film exhibited a surface-controlled electrode process. This film and the successive modifications (HRP-PAP self-assembled monolayer (SAM) modified Au electrode) were used as a biological catalyst (hydrogen peroxide transducers) for glucose biosensors, after coupling to GOx. Both HRP/GOx-PAP and HRP/GOx-PAP SAM third generation biosensors were prepared and characterized. The use of PAP as immobilizing agent offers a biocompatible micro-environment for confining the enzyme and foreshadows the great potentiality of this immobilizing agent not only in theoretical studies on protein direct electron transfer but also from an applications point of view in the development of second- and third-generation biosensors.     

No mutations found in exon 2 of gene p16CDKN2A during rat tongue carcinogenesis induced by 4-nitroquinoline-1-oxide

The medium-term tongue carcinogenesis assay is a useful model for studying oral squamous cell carcinomas phase by phase. The present study aimed to investigate mutations in exon 2 of gene p16CDKN2A during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide (4NQO) using direct DNA-sequencing method. A total of 30 male Wistar rats were treated with 4-nitroquinoline 1-oxide (4NQO) in drinking water for 4, 12, and 20 weeks at 50 ppm dose. Ten animals were used as negative control. No histopathological changes in tongue epithelia were observed among controls or in the group treated for 4 weeks with 4NQO. Following 12-week treatment, hyperplasia and epithelial dysplasia were found in mild and moderate forms. At 20 weeks, the tongue presented moderate and/or severe oral dysplasia and squamous cell carcinoma, with squamous cell carcinoma in the majority of animals. No mutations were found in any experimental period evaluated that corresponded to normal oral mucosa, hyperplasia, dysplasia and squamous cell carcinomas. Taken together, our results suggest that p16CDKN2A mutations in exon 2 are not involved in the multistep tongue carcinogenesis of Wistar rats induced by 4NQO.     

Complementary retrieval of 16S rRNA gene sequences using broad-range primers with inosine at the 3'-terminus: implications for the study of microbial diversity

We evaluated the impact of the base analogue inosine substituted at the 3'-terminus of broad-range 16S rRNA gene primers on the recovery of microbial diversity using terminal restriction fragment length polymorphism and clonal analysis. Oral plaque biofilms from 10 individuals were tested with modified and unmodified primer pairs. Besides a core overlap of shared terminal restriction fragments (T-RFs), each primer system provided unique information on the occurrence of T-RFs, with a higher number generally displayed with inosine primers. All clones sequenced were at least 99% identical to publicly available full-length sequences. Analysis of the corresponding primer-binding sites showed that most sequence types were 100% complementary to the unmodified primers so that the characteristic of inosine to bind with all four nucleotides was not crucial for the observed increase in microbial richness. Instead, differences in community compositions were correlated with the identity of the nearest-neighbor 3' of the primer-targeting region. By influencing the thermal stability of primer hybridization, this position may play a previously unrecognized role in biased amplification of 16S rRNA gene sequences. In conclusion, the combined use of inosine and unmodified primers enables the complementary retrieval of 16S rRNA gene types, thereby expanding the observed diversity of complex microbial communities.     

Efficacy of chemical dosing methods for isolating nontuberculous mycobacteria from water supplies of dialysis centers

Investigations of nontuberculous mycobacterium (NTM) infections associated with various environmental sources have been hampered by the lack of adequate techniques for selective isolation of these organisms from environmental fluids. This study compared chemical dosing techniques for recovery of NTM from water samples collected from 115 randomly selected dialysis centers. Cell suspensions of NTM group II and IV isolates and gram-negative bacteria were exposed to solutions containing sodium hypochlorite (0.2 micrograms/ml of free available chlorine), formaldehyde (1, 0.75, or 0.5%), oxalic acid (1.25%), cetylpyridinium chloride (25 micrograms/ml), or cetyltrimethylammonium bromide (100 micrograms/ml). Results of standard membrane filtration assays with laboratory test strains and water samples from dialysis centers showed that 5 min of exposure to 1% formaldehyde effectively reduced gram-negative bacterial populations and allowed increased recovery of NTM in environmental fluids containing mixed microbial populations.