Transduction of low-copy number plasmids by bacteriophage P22.

The generalized transducing bacteriophage of Salmonella typhimurium, P22, can transduce plasmids in addition to chromosomal markers. Previous studies have concentrated on transduction of pBR322 by P22 and P22HT, the high transducing mutant of P22. This study investigates the mechanism of P22HT transduction of low-copy number plasmids, namely pSC101 derivatives. We show that P22HT transduces pSC101 derivatives that share homology with the chromosome by two distinct mechanisms. In the first mechanism, the plasmid integrates into the chromosome of the donor by homologous recombination. This chromosomal fragment is then packaged in the transducing particle. The second mechanism is a size-dependent mechanism involving a putative plasmid multimer. We propose that this multimer is formed by interplasmidic recombination. In contrast, P22HT can efficiently transduce pBR322 by a third mechanism, which is independent of plasmid homology with the chromosome. It has been proposed that the phage packages a linear concatemer created during rolling circle replication of pBR322, similar in fashion to phage genome packaging. This study investigates the role of RecA, RecD, and RecF recombination proteins in plasmid/plasmid and plasmid/chromosome interactions that form packageable substrates in the donor. We also examine the resolution of various transduced plasmid species in the recipient and the roles of RecA and RecD in these processes.

Daily multivitamin supplementation and vitamin blood levels in the elderly: a randomized, double-blind, placebo-controlled trial.

Despite the many questions being raised about multivitamin use by the elderly, it has not been proven that consuming an oral multivitamin alters vitamin blood levels in the aged. To address this question, we performed a randomized, prospective, placebo-controlled study of daily multivitamin supplementation in 101 noninstitutionalized ambulatory elderly persons (median age, 64 years). Vitamin levels were assayed at baseline, and at two and four months of supplementation. At four months, those taking multivitamins had statistically significant increased levels of water soluble vitamins (C, B2, B12, plasma, and erythrocyte folate) that were greater than changes noted for the placebo group. This was not true for fat soluble vitamins A and E. Greater storage pools of fat soluble vitamins help explain this discrepancy. We conclude that in the ambulatory elderly, oral multivitamins can raise levels of water soluble vitamins but the effect on fat soluble vitamins remains uncertain.

Detection and imaging of nitrogen dioxide with the degenerate four-wave-mixing and laser-induced-fluorescence techniques.

The spectroscopic techniques of degenerate four-wave mixing (DFWM) and laser-induced fluorescence (LIP) have been applied to the detection of minor species for combustion diagnostics. We compare the results obtained when these techniques are used to detect NO(2). Previous results show that DFWM signals increase for NO(2) when buffer gas is added and that LIP signals are greatly reduced under the same circumstances. We make direct quantitative comparisons of these two techniques and discuss their suitability for making measurements of NO(2) in combustion environments.

Changing treatment of breast cancer in New Mexico from 1969 through 1985.

A review of information from the New Mexico Tumor Registry on women diagnosed as having primary breast cancer from 1969 through 1985 revealed temporal changes in the surgical treatment of this disease. After 1980 the percentage of women receiving breast-conserving surgery for local-stage disease increased from 6% to 25%. Most surgeons performing operations for breast cancer had not performed a breast-conserving operation before 1981 but had used this procedure at least once in the period from 1981 through 1985. Women younger than 50 years or older than 80 years were most likely to undergo this procedure. In that period, radiotherapy after breast-conserving surgery could not be documented for 26% of the women 65 years old or younger or for 56% of the women aged 65 years or older. Thus, there has been a marked shift in New Mexico in the surgical approach to local-stage breast cancer in the 1980s. This shift involved most surgeons treating the disease and included women of all age groups. The apparent lack of adjuvant radiotherapy in some women receiving conservative surgeries may prove to be a deleterious consequence of this change in surgical management.

Antibiotics with a selective aerobic or anaerobic spectrum have different therapeutic activities in various regions of the colon in interleukin 10 gene deficient mice.

BACKGROUND AND AIMS: Multiple rodent models implicate resident intestinal bacteria in the pathogenesis of chronic immune mediated intestinal inflammation. Specific pathogen free (SPF) interleukin 10 gene deficient (IL-10(-/-)) mice develop colitis, which does not occur in the germ free (GF) state. We investigated whether broad or narrow spectrum antibiotics affect onset and progression of disease in various regions of IL-10(-/-) mice. METHODS: Metronidazole, ciprofloxacin, vancomycin-imipenem (50 mg/kg/day), or water (control) was administered orally before (prevention) or two weeks after (treatment) colonisation of GF IL-10(-/-) mice with SPF bacteria. After four weeks, colonic histology scores and cytokine production by colonic explants were determined. Caecal and colonic contents were collected for quantitative bacterial analysis. RESULTS: In the prevention study, all antibiotics decreased inflammation in the caecum and colon. However, in the treatment study, ciprofloxacin and vancomycin-imipenem decreased caecal inflammation, and reduced Escherichia coli and Enterococcus faecalis concentrations, whereas only vancomycin-imipenem lowered direct microscopic bacterial counts. In contrast, metronidazole and vancomycin-imipenem reduced colonic injury and eliminated anaerobic bacteria, including Bacteroides spp. CONCLUSIONS: Both narrow and broad spectrum antibiotics can prevent disease but treatment of established colitis is more selective. Ciprofloxacin is most effective in the treatment of caecal inflammation, metronidazole preferentially treats the colon, whereas vancomycin-imipenem definitively treats both regions. These results suggest that subsets of aerobic or anaerobic bacteria show regional differences in their capacity to mediate experimental colitis in IL-10(-/-) mice.