Ambient-temperature incubation for the field detection of Escherichia coli in drinking water

AIMS

 Escherichia coli is the pre-eminent microbiological indicator used to assess safety of drinking water globally. The cost and equipment requirements for processing samples by standard methods may limit the scale of water quality testing in technologically less developed countries and other resource-limited settings, however. We evaluate here the use of ambient-temperature incubation in detection of E. coli in drinking water samples as a potential cost-saving and convenience measure with applications in regions with high (>25°C) mean ambient temperatures.

METHODS AND RESULTS

  This study includes data from three separate water quality assessments: two in Cambodia and one in the Dominican Republic. Field samples of household drinking water were processed in duplicate by membrane filtration (Cambodia), Petrifilm™ (Cambodia) or Colilert® (Dominican Republic) on selective media at both standard incubation temperature (35–37°C) and ambient temperature, using up to three dilutions and three replicates at each dilution. Matched sample sets were well correlated with 80% of samples (n = 1037) within risk-based microbial count strata (E. coli CFU 100 ml−1 counts of <1, 1–10, 11–100, 101–1000, >1000), and a pooled coefficient of variation of 17% (95% CI 15–20%) for paired sample sets across all methods.

CONCLUSIONS

  These results suggest that ambient-temperature incubation of E. coli in at least some settings may yield sufficiently robust data for water safety monitoring where laboratory or incubator access is limited.

Basic fibroblast growth factor: the neurotrophic factor influencing the ingrowth of neural tissue into the anterior pituitary of alpha-T7 transgenic mice?

alpha-T7 mice are a transgenic line which carries a hybrid transgene composed of the 5' flanking region of the human glycoprotein hormone alpha-subunit gene (1.8 kb) linked to the coding region of the oncogene SV40 T-antigen. Large, hemorrhagic, pituitary tumors form in these mice and contain giant, transformed gonadotropes (immunopositive for T-antigen), in addition to normal-appearing gonadotropes (also immunopositive for T-antigen). An additional feature of these tumors is an abundance of neural tissue proliferating throughout the anterior pituitary, concentrated around the giant gonadotropes, and forming synaptoid contacts upon them. Continued study of these mice has demonstrated that the giant gonadotropes contain immunostainable basic fibroblast growth factor (FGF-2), and apparently release the FGF by focal cellular disruption and/or cytoplasmic blebbing. Normal gonadotropes, in control and transgenic mice, were strongly immunopositive for FGF, and appeared intact. In 8- to 13-month-old transgenic mice most of the giant cells were intact, and were surrounded by well-differentiated neural tissue. These giant cells were lightly immunopositive for FGF. Disrupted, giant gonadotropes were more frequent in 2- to 7-month-old transgenic mice, and also were surrounded by well-differentiated neural tissue with many synaptoid contacts. These cells generally were moderately immunopositive for FGF. In neonatal mice, 1-8 days old, precursors of the giant, transformed gonadotropes were identified, primarily, but not exclusively, near the periphery of the anterior pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)

GHF-1-promoter-targeted immortalization of a somatotropic progenitor cell results in dwarfism in transgenic mice

During pituitary development, the homeo domain protein GHF-1 is required for generation of somatotropes and lactotropes and for growth hormone (GH) and prolactin (PRL) gene expression. GHF-1 mRNA is detectable several days before the emergence of GH- or PRL-expressing cells, suggesting the existence of a somatotropic progenitor cell in which GHF-1 transcription is first activated. We have immortalized this cell type by using the GHF-1 regulatory region to target SV40 T-antigen (Tag) tumorigenesis in transgenic mice. The GHF-Tag transgene caused developmental entrapment of somatotropic progenitor cells that express GHF-1 but not GH or PRL, resulting in dwarfism. Immortalized cell lines derived from a transgenic pituitary tumor maintain the characteristics of the somato/lactotropic progenitor in that they express GHF-1 mRNA and protein yet fail to activate GH or PRL transcription. Using these cells, we identified an enhancer that activates GHF-1 transcription at this early stage of development yet is inactive in cells representing later developmental stages of the somatotropic lineage or in other cell types. These experiments not only demonstrate the potential for immortalization of developmental progenitor cells using the regulatory regions from cell type-specific transcription factor genes but illustrate the power of such model systems in the study of developmental control.

The 1990/91 Kentucky hospital smoking policy survey: a follow-up

We surveyed all Kentucky hospitals regarding smoking policies iin 1989, 1990, and 1991. There were statistically significant increases in the numbers of hospitals which developed smoking policies and became smoke free between 1990 and 1991. The sale of tobacco in hospitals declined significantly between 1989 and 1991, as did the number of institutions providing smoking areas within the hospital. Survey respondents indicated that the JCAHO mandate prompted changes in smoking policies. Kentucky hospitals are leading the way in developing smoke-free environments, but externally imposed regulations have played a major role in promoting this progress.

Neural tissue within anterior pituitary tumors generated by oncogene expression in transgenic mice

Pituitary tumorigenesis occurs in a transgenic line of mice, alpha-T7, which carries a hybrid transgene composed of the 5' flanking region of the human glycoprotein hormone alpha-subunit gene (1.8 kb) linked to the coding region of the SV40 T-antigen gene (alpha-Tag). Tumor foci were identified within the anterior pituitary of both male and female transgenic mice. In addition to a parenchyma with hypertrophied endocrine cells, mostly of the gonadotrope lineage, we here report the unexpected presence of neural tissue within the anterior pituitary, either as foci as large as 1.0 mm in diameter or greater, or in delicate bundles ramifying amongst the granulated parenchymal cells. Areas richest in neural tissue frequently were associated with tumor tissue composed of giant cells of three varieties, all with electron-lucent cytoplasm and similar organellar distribution including small secretory granules (80-160 nm diameter). In type I cells, the secretory granules were aligned at the plasma membrane; in type II cells, the secretory granules were distributed throughout the cytoplasm; type III cells formed colloid-filled follicles and their secretory granules rarely exceeded 100 nm diameter. These giant cells frequently had bizarre pleomorphic nuclei intensely immunopositive for T-antigen and cytoplasm which was lightly immunopositive for alpha-subunit, and immunopositive either for the LH-beta or TSH-beta subunits. Neural tissue contacted the normal granulated parenchymal cells directly, i.e., without a basal lamina or any connective tissue intervening, but only rarely formed synaptoid junctions with these granulated cells. Synaptoid junctions containing round, smooth vesicles, as well as dense core vesicles, were numerous between the neural processes themselves and between the neural tissue and the giant cells of the tumor tissue. These data suggest that in alpha-T7 transgenic mice the giant cells represent highly transformed gonadotropes or thyrotropes, and that a neurotrophic factor may be expressed by these transformed pituitary parenchymal cells.

Mutual cross-interference between glucocorticoid receptor and CREB inhibits transactivation in placental cells

Transcription of the glycoprotein hormone alpha-subunit gene in placental cells is repressed by glucocorticoids, an effect that is mediated through the glucocorticoid receptor (GR). Although the DNA-binding domain of GR has been shown to be important, mutation of the previously identified GR-binding sites in the alpha-subunit promoter fails to abolish repression. Furthermore, mutant receptors in which the DNA-binding specificity is converted to ERE binding or in which the first zinc finger is substituted with that from thyroid receptor remain fully inhibitory, indicating that specific DNA binding to the alpha-subunit gene is not important for repression. Inhibition by GR is only effective when the alpha-subunit promoter is activated by CREB, implicating CREB as the target for GR-mediated repression. Reciprocally, overexpression of CREB interferes with GR-mediated transcriptional activation of MMTV. This activity is not affected by the phosphorylation state of CREB. Despite the mutual cross-interference with activation of gene expression, GR and CREB do not appear to have a high-affinity protein:protein interaction in vitro. Nonetheless, GR and CREB may interact directly in vivo possibly through a third protein or, more likely, may sequester a mutually required target protein.

3' processing of pre-mRNA plays a major role in proliferation-dependent regulation of histone gene expression

A short histone-like fusion RNA, generated when the RNA 3' processing signal from a mouse histone H4 gene is inserted into a heterologous transcription unit, becomes correctly down-regulated in G1-arrested cells of a temperature-sensitive mouse mastocytoma cell cycle mutant (21-Tb; Stauber et al., EMBO J. 5, 3297-3303 [1986]), due to a specific deficiency in histone RNA processing (Lüscher and Schümperli, EMBO J. 6, 1721-1726 [1987]). In contrast, inhibitors of DNA synthesis, known to stimulate histone mRNA degradation, have little or no effect on the fusion RNA. This RNA can therefore be used to discriminate between regulation by RNA 3' processing and RNA stability, respectively. The fusion RNA is also faithfully regulated in 21-Tb cells arrested in G1 phase by the drug indomethacin or in C127 mouse fibroblasts during a serum starvation experiment. Moreover, nuclear extracts from serum-starved C127 cells show a specific deficiency in a heat-labile component of the histone RNA processing apparatus, similar to that previously observed for temperature-arrested 21-Tb cells. These results suggest that RNA 3' processing is a major determinant for the response of histone mRNA levels to changes in cell proliferation.

A signal regulating mouse histone H4 mRNA levels in a mammalian cell cycle mutant and sequences controlling RNA 3′ processing are both contained within the same 80-bp fragment

Fragments from the 3' end of a mouse histone H4 gene, when introduced into transcription units controlled by the SV40 early promoter, yield correctly processed RNA with histone-specific 3' ends, both in monkey and mouse cell lines. The processed RNA is regulated in parallel with endogenous H4 mRNAs in 21-Tb cells, a temperature-sensitive mouse mastocytoma cell cycle mutant that is specifically blocked in G1 phase at the non-permissive temperature. Mutational analyses of the H4 gene fragment indicate that the minimal sequences for this regulation and for RNA 3' processing are both contained within the same 80 bp. This fragment contains two histone-specific, highly conserved sequence elements that are located at the 3' end of histone mRNA and in the adjacent spacer region, respectively. Our data suggest that the observed cell cycle regulation is achieved either at RNA 3' processing or at some later step involving the conserved 3'-terminal sequence element of mature histone mRNA.

Faithful cell-cycle regulation of a recombinant mouse histone H4 gene is controlled by sequences in the 3'-terminal part of the gene

We have analyzed the expression of endogenous histone H4 genes and of a newly introduced H4 gene in 21-Tb cells, a mouse mastocytoma cell-cycle mutant. Endogenous H4 mRNAs were less abundant by a factor of 120-180 in G1-arrested than in exponentially multiplying cells. However, H4 transcription rates were only decreased by a factor of 3 under these conditions, as determined by in vitro elongation of nascent transcripts. This indicates that post-transcriptional control of histone mRNA levels is important, in accord with published data. We introduced a mouse H4 gene, modified by a 12-base-pair (bp) insertion in its coding sequence, into 21-Tb cells by DNA-mediated gene transfer. The levels of transcripts from this gene were regulated in parallel with those of the endogenous genes. Moreover, fusion of the simian virus 40 (SV40) early promoter to a 463-bp fragment containing the 3'-terminal half of the mouse H4 gene, including 230 bp of spacer sequences, led to the regulated expression of SV40/H4 fusion RNA. However, a small proportion of SV40-initiated transcripts were not processed to histone-specific 3' ends, but extended farther through the downstream Escherichia coli galactokinase gene to a SV40 polyadenylylation site. In contrast to the short SV40/H4 RNA, the levels of these longer transcripts were not reduced in G1-arrested cells. These results show that sequences in the 3'-terminal part of the H4 gene can regulate gene expression in the cell cycle, presumably at the post-transcriptional level, as long as they are not positioned much more distant from the terminus than normal.