Monitoring the results of Canada/U.S.A. acid rain control programs: some lake responses

Aquatic acidification by deposition of airborne pollutants emerged as an environmental issue in southeastern Canada during the 1970s. Drawing information from the extensive research and monitoring programs, a sequence of issue assessments demonstrated the necessity of reducing the anthropogenic emissions of acidifying pollutants, particularly sulphur dioxide (SO2). The 1991 Canada-U.S. Air Quality Agreement (AQA) was negotiated to reduce North American SO2 emissions by approximately 40% relative to 1980 levels by 2010, and at present, both countries have reduced emissions beyond their AQA commitment. In response to reduced SO2 emissions, atmospheric deposition of sulphate (SO4(2-)) and SO4(2-) concentrations in many lakes have declined, particularly in south-central Ontario and southern Québec. Sulphate deposition still exceeds aquatic critical loads throughout southeastern Canada however. Increasing pH or alkalinity (commonly deemed 'recovery') has been observed in only some lakes. Several biogeochemical factors have intervened to modify the lake chemistry response to reduced SO4(2-) input, notably release of stored SO4(2-) from wetlands following periods of drought and reduction in the export of base cations from terrestrial soils. Three examples from Ontario are presented to illustrate these responses. Significant increases in pH and alkalinity have been observed in many lakes in the Sudbury area of Ontario due to the large reductions in local SO2 emissions; 'early-stage' biological recovery is evident in these lakes. An integrated assessment model predicts that AQA emission reductions will not be sufficient to promote widespread chemical or biological recovery of Canadian lakes. Monitoring and modeling are mutually supporting assessment activities and both must continue.

Expression of CCAAT-binding factor antisense transcripts in reproductive tissues affects plant fertility

We have previously isolated a CCAAT-binding factor B subunit gene ( BnCBF-B) from Brassica napus that is widely expressed in different plant tissues and whose role is still unknown. To investigate the importance of this transcription factor subunit in plant reproductive tissues, we targeted antisense BnCBF-B transcripts to the tapetum of transgenic B. napus plants. Of the 24 independent transformants, 13 yielded reduced quantities of viable pollen, of which five were unable to produce the elongated siliques indicative of normal seed set. The decrease in pollen viability probably resulted from the precocious degeneration of the tapetal cell layer observed in these plants. Surprisingly, the male-sterile phenotype was also accompanied by a decrease in female fertility, which could be due to the expression of the antisense BnCBF-B transcripts in the female reproductive structures of the transgenic plants. These results suggest that the BnCBF-B gene plays a critical non-redundant role in plant reproductive tissues.

Performance of multidetector computed tomography colonography compared with conventional colonoscopy

BACKGROUND AND AIMS

This was a prospective blinded study to compare computed tomography (CT) colonography, performed with multidetector arrays CT scan (MDCT), with conventional colonoscopy for the detection of colorectal neoplasia.

METHODS

Fifty patients were examined by MDCT after standard bowel preparation and rectal air insufflation in the supine and prone positions. Data sets were examined by one radiologist and one gastroenterologist blinded to the patient's history and colonoscopy results. Patients subsequently underwent colonoscopy on the same day, which served as the gold standard.

RESULTS

Nine of 11 lesions >10 mm (82%), 5/15 lesions of 6-9 mm (33%), and 1/42 polyps <5 mm (3%) were detected by MDCT colonography. One false positive result for a structure larger than 10 mm was described. Nineteen of 21 patients who had no lesions during conventional colonoscopy were considered free of lesions by MDCT colonography, yielding a per patient specificity of 90%.

CONCLUSION

MDCT colonography provides good data quality and has good sensitivity and specificity for the detection of colonic lesions of 10 mm or more.

The homeobox gene BREVIPEDICELLUS is a key regulator of inflorescence architecture in Arabidopsis

Flowering plants display a remarkable range of inflorescence architecture, and pedicel characteristics are one of the key contributors to this diversity. However, very little is known about the genes or the pathways that regulate pedicel development. The brevipedicellus (bp) mutant of Arabidopsis thaliana displays a unique phenotype with defects in pedicel development causing downward-pointing flowers and a compact inflorescence architecture. Cloning and molecular analysis of two independent mutant alleles revealed that BP encodes the homeodomain protein KNAT1, a member of the KNOX family. bp-1 is a null allele with deletion of the entire locus, whereas bp-2 has a point mutation that is predicted to result in a truncated protein. In both bp alleles, the pedicels and internodes were compact because of fewer cell divisions; in addition, defects in epidermal and cortical cell differentiation and elongation were found in the affected regions. The downward-pointing pedicels were produced by an asymmetric effect of the bp mutation on the abaxial vs. adaxial sides. Cell differentiation, elongation, and growth were affected more severely on the abaxial than adaxial side, causing the change in the pedicel growth angle. In addition, bp plants displayed defects in cell differentiation and radial growth of the style. Our results show that BP plays a key regulatory role in defining important aspects of the growth and cell differentiation of the inflorescence stem, pedicel, and style in Arabidopsis.

RNA editing by base deamination: more enzymes, more targets, new mysteries

The posttranscriptional modification of messenger RNA precursors (pre-mRNAs) by base deamination can profoundly alter the physiological function of the encoded proteins. The recent identification of tRNA-specific adenosine deaminases (ADATs) has led to the suggestion that these enzymes, as well as the cytidine and adenosine deaminases acting on pre-mRNAs (CDARs and ADARs), belong to a superfamily of RNA-dependent deaminases. This superfamily might have evolved from an ancient cytidine deaminase. This article reviews the reactions catalysed by these enzymes and discusses their evolutionary relationships.

Eating disorders: a role for dipeptidyl peptidase IV in nutritional control

Dipeptidyl peptidase IV (DPP IV), a serine protease with broad tissue distribution and known activity in serum, has been postulated to modulate nutrition control by modification or inactivation of peptide hormones operating in the enteroinsular axis. We hypothesized that changes of DPP IV activity in serum are related to the nutrition status of patients with eating disorders. Serum DPP IV activity was measured in 52 patients (28 with anorexia nervosa and 24 with bulimia nervosa) in four consecutive weekly analyses. Simultaneously, the number of CD26 (DPP IV)-positive peripheral blood lymphocytes was counted. The same analyses were carried out in 28 healthy female volunteers. In week 1 and throughout the observation period, DPP IV activity in the sera of patients with anorexia nervosa and, to a lesser extent, those with bulimia nervosa was elevated in comparison to that of healthy controls (week 1: means = 92.8 U/L for anorexia-nervosa patients and 89.3 U/L for bulimia-nervosa patients versus 74.7 U/L for healthy control subjects, P = 0.014; weeks 1-4: 91.8 U/L for anorexia-nervosa patients and 86.2 U/L for bulimia-nervosa patients versus 77.6 U/L for healthy controls, P < 0.001). We assume that the increase in DPP IV serum activity will increase the turnover of distinct peptide hormones with known effects on nutrition control and susceptibility to degradation by DPP IV. The potential impact of an increase in DPP IV activity in serum on satiety and nutrition control contributes to previously reported implications for immune function.

[The effects of psychotherapy on Crohn's disease patients--results of a randomized multicenter study]

In a prospective multicenter study of Crohn disease patients, the influence of psychotherapy on the course of the disease and on psychosocial variables (anxiety, depression, life satisfaction and data of the PSKB) was studied. Psychodynamic oriented psychotherapy was provided in addition to a standardized medical treatment and took place during the first year of the two-year observation period. 108 of 488 patients were recruited and randomly assigned to the psychotherapy and the control group. 84 patients completed the somatic and 81 the psychosocial follow up. 23% of the control group and 30% of the psychotherapy group showed episode-free courses, 29% and 17% respectively underwent surgery (worst outcome group). The ranking and comparisons of the disease course showed no significant difference (p = 0.125) between psychotherapy and control group. The psychosocial variables also showed no differences between these groups. Subjectively, the patients report favourable effects to psychotherapy.

The yeast nucleoporin Nup53p specifically interacts with Nic96p and is directly involved in nuclear protein import

The bidirectional nucleocytoplasmic transport of macromolecules is mediated by the nuclear pore complex (NPC) which, in yeast, is composed of approximately 30 different proteins (nucleoporins). Pre-embedding immunogold-electron microscopy revealed that Nic96p, an essential yeast nucleoporin, is located about the cytoplasmic and the nuclear periphery of the central channel, and near or at the distal ring of the yeast NPC. Genetic approaches further implicated Nic96p in nuclear protein import. To more specifically explore the potential role of Nic96p in nuclear protein import, we performed a two-hybrid screen with NIC96 as the bait against a yeast genomic library to identify transport factors and/or nucleoporins involved in nuclear protein import interacting with Nic96p. By doing so, we identified the yeast nucleoporin Nup53p, which also exhibits multiple locations within the yeast NPC and colocalizes with Nic96p in all its locations. Whereas Nup53p is directly involved in NLS-mediated protein import by its interaction with the yeast nuclear import receptor Kap95p, it appears not to participate in NES-dependent nuclear export.

Human pre-mRNA cleavage factor II(m) contains homologs of yeast proteins and bridges two other cleavage factors

Six different protein factors are required in vitro for 3' end formation of mammalian pre-mRNAs by endonucleolytic cleavage and polyadenylation. Five of the factors have been purified and most of their components cloned, but cleavage factor II(m) (CF II(m)) remained uncharacterized. We have purified CF II(m) from HeLa cell nuclear extract by several chromatographic steps. During purification, CF II(m) activity separated into two components, one essential (CF IIA(m)) and one stimulatory (CF IIB(m)) for the cleavage reaction. CF IIA(m) fractions contain the human homologs of two yeast 3' end processing factors, Pcf11p and Clp1p, as well as cleavage factor I(m) (CF I(m)) and several splicing and transcription factors. We report the cloning of hClp1 and show that it is a genuine subunit of CF IIA(m). Antibodies directed against hClp1 deplete cleavage activity, but not polyadenylation activity from HeLa cell nuclear extract. hClp1 interacts with CF I(m) and the cleavage and polyadenylation specificity factor CPSF, suggesting that it bridges these two 3' end processing factors within the cleavage complex.