Highly efficient dehydrogenation of formic acid in aqueous solution catalysed by an easily available water-soluble iridium(iii) dihydride.

The new water-soluble cis-mer-[IrH2Cl(mtppms)3] (mtppms = monosulfonated triphenylphosphine) was employed as a catalyst for selective decomposition of formic acid to H2 + CO2 in aqueous solution at T = 30-100 °C. The easily synthesized compound showed high catalytic activity (TOF up to 298 000 h(-1)) and could be reused several times with no loss of activity (total TON = 67 650). A sharp maximum in the reaction rate was observed at pH = 3.75; its coincidence with the pKa of formic acid shows that both H(+) or HCOOH and HCOO(-) play important roles in the reaction mechanism.

CYP24A1 splice variants--implications for the antitumorigenic actions of 1,25-(OH)2D3 in colorectal cancer.

25-hydroxyvitamin D3 24-hydroxylase (CYP24A1), the catabolizing enzyme of the active vitamin D3, is often overexpressed in solid tumors. The unbalanced high levels of CYP24A1 seem to be a determinant of vitamin D resistance in tumors. Splice variants of CYP450 enzymes are common. Existence of CYP24A1 isoforms has been reported recently. We have investigated the presence of CYP24A1 splicing variants (SV) in human colon cancer cell lines and tissue samples. Using a set of primer combination we have screened the entire coding sequence of CYP24A1 and identified three splice variants in colon cancer cell lines. The presence of these SVs in human colon tissue samples showed a correlation with histological type of the tissue and gender of patients. The sequencing of the alternatively spliced fragments showed that two have lost the mitochondrial target domain, while the third lacks the heme-binding domain. All SVs retained their sterol binding domain. Translation of these variants would lead to a dysfunctional enzyme without catalytic activity that still binds its substrates therefore they might compete for substrate with the synthesizing and catabolizing enzymes of vitamin D.

LCT 13910 C/T polymorphism, serum calcium, and bone mineral density in postmenopausal women.

SUMMARY: LCT 13910 CC genotype is associated with lactose intolerance, a condition often resulting in reduced milk intake. Women with the CC genotype were found to have decreased serum calcium and reduced bone mineral density. INTRODUCTION: The CC genotype of the 13910 C/T polymorphism of the LCT gene is linked to lactose intolerance and low calcium intake. METHODS: We studied 595 postmenopausal women, including 267 osteoporotic, 200 osteopenic, and 128 healthy subjects. Genotyping, osteodensitometry, and laboratory measurements were carried out. RESULTS: Frequency of aversion to milk consumption was 20% for CC genotype and 10% for TT + TC genotypes (p = 0.03). The albumin-adjusted serum calcium was 2.325 +/- 0.09 mmol/L for CC genotype and 2.360 +/- 0.16 mmol/L for TT + TC genotypes (p = 0.031). Bone mineral density (BMD; Z score) was lower in the CC than TT + TC genotypes, respectively, at the radius (0.105 +/- 1.42 vs 0.406 +/- 1.32; p = 0.038), at the total hip (-0.471 +/- 1.08 vs -0.170 +/- 1.09; p = 0.041), and at the Ward's triangle (-0.334 +/- 0.87 vs -0.123 +/- 0.82; p = 0.044). CONCLUSION: LCT 13910 C/T polymorphism is associated with decreased serum calcium level and lower BMD in postmenopausal women.

Microchimerism in bone marrow-derived CD34(+) cells of patients after liver transplantation.

Lymphoid and dendritic cells of donor origin can be detected in the recipient several years after a solid organ transplantation. This phenomenon is termed microchimerism and could play a role in the induction of tolerance. The fate of other hematopoietic cells transferred by liver transplantation, in particular of stem and progenitor cells, is unknown. For this reason, we studied peripheral blood and bone marrow samples of 12 patients who had received a liver transplant from an HLA-DR mismatched donor. Eight patients were long-term survivors between 2.8 and 10.1 years after allografting. CD34(+) cells from bone marrow were highly enriched with the use of a 2-step method, and a nested polymerase chain reaction was applied to detect donor cells on the basis of allelic differences of the HLA-DRB1 gene. Rigorous controls with DRB1 specificities equal to the donor and host were included. In 5 of 8 long-term liver recipients, donor-specific CD34(+) cells could be detected in bone marrow. Microchimerism in the CD34(+) cell fraction did not correlate to the chimeric status in peripheral blood. In conclusion, our results demonstrate a frequent microchimerism among bone marrow-derived CD34(+) cells after liver transplantation. The functional role of this phenomenon still needs to be defined. (Blood. 2000;96:763-767)

The production of recombinant proteins in transgenic barley grains.

The grain of the self-pollinating diploid barley species offers two modes of producing recombinant enzymes or other proteins. One uses the promoters of genes with aleurone-specific expression during germination and the signal peptide code for export of the protein into the endosperm. The other uses promoters of the structural genes for storage proteins deposited in the developing endosperm. Production of a protein-engineered thermotolerant (1, 3-1, 4)-beta-glucanase with the D hordein gene (Hor3-1) promoter during endosperm development was analyzed in transgenic plants with four different constructs. High expression of the enzyme and its activity in the endosperm of the mature grain required codon optimization to a C+G content of 63% and synthesis as a precursor with a signal peptide for transport through the endoplasmic reticulum and targeting into the storage vacuoles. Synthesis of the recombinant enzyme in the aleurone of germinating transgenic grain with an alpha-amylase promoter and the code for the export signal peptide yielded approximately 1 microgram small middle dotmg(-1) soluble protein, whereas 54 microgram small middle dotmg(-1) soluble protein was produced on average in the maturing grain of 10 transgenic lines with the vector containing the gene for the (1, 3-1, 4)-beta-glucanase under the control of the Hor3-1 promoter.

Trends in alkanes and PAHs in airborne particulate matter from Oporto and Vienna: identification and comparison.

A total of 56 weekly samples from Oporto and 40 from Vienna were collected and analysed, for 23 n-alkanes and 16 polycyclic aromatic hydrocarbons (PAH), by GC-MS after extraction with a toluene/methanol mixture. Total and elemental carbon were in the same range of values for both sampling sites. Although parts of the spectrum of species in both sampling sites were constant over the sampling period there is no evidence for suggesting a universal tracer for alkanes. For both Oporto and Vienna, Principal Component Analysis (PCA) identified two PCs and in both cases the first PC contained only PAHs while the second contained only alkanes. This separation between alkanes and PAHs and the observation of an alternating pattern with higher concentrations of odd carbon numbered from C27 to C30 (natural emissions from biological origin) is believed to result from a separation between anthropogenic and biological contributions associated with the first and second PC, respectively.

The function of CreA, the carbon catabolite repressor of Aspergillus nidulans, is regulated at the transcriptional and post-transcriptional level.

The creA gene of A. nidulans encodes a wide-domain regulatory protein mediating carbon catabolite repression. Northern blot analysis of creA mRNA revealed a complex expression profile: the addition of monosaccharides to a carbon-starved culture of A. nidulans provoked a strong transient stimulation of creA transcript formation within a few minutes. In the case of repressing carbon sources, creA mRNA levels were subsequently downregulated, whereas the high creA mRNA levels were maintained in a creA mutant strain and in the presence of derepressing monosaccharides. A high creA transcript level is essential to achieve carbon catabolite repression and is dependent on glucose transport and, at least partially, on the creB gene product. Subsequent downregulation of creA mRNA levels, on the other hand, is typical of carbon catabolite repression and requires a functional CreA recognition site in the creA promoter (and thus involves autoregulation) and formation of glucose-6-phosphate. Despite the presence of continuing high transcript levels of creA in the presence of derepressing carbohydrates, EMSA demonstrated the presence of only low levels of a CreA-DNA complex in respective cell-free extracts. Upon transfer of carbon catabolite derepressed mycelia to catabolite-repressing conditions, a CreA-DNA complex is formed, and this process is dependent on de novo protein synthesis.

Temporal and spatial variations of the Vienna aerosol.

For several intensive sampling periods the mass concentration, light extinction, light scattering and light absorption coefficients, and the mass size distribution of the aerosol have been determined at up to eleven location in the non-industrial town of Vienna. Obviously, large variations of the measured values have been found. The following factors influenced the aerosol markedly: wind speed, wind direction, increased aerosol production such as by space heating or traffic and resuspension. Most of the variations in aerosol were found to be caused by these factors. A comparison of the mass concentration and light absorption of the aerosol upwind and downwind of Vienna permitted the estimation of locally produced aerosols: about 50% of the mass of the aerosol and 75% of the light-absorbing aerosol appears to be produced locally.

Influence of nonuniform ground reflectance on horizontal visibility.

One of the assumptions made in calculating the horizontal visibility of black targets is that every volume element of the atmosphere or medium is illuminated by the same amount of light. This assumption has always been interpreted as a homogeneous illumination, without considering the importance of the reflectance properties of the ground extending between observer and horizon along the path of sight. This paper is a theoretical and experimental study of the effect of ground, with varying reflectance properties, on the horizontal visibility. The laboratory simulation shows that, if that part of the ground extending between observer and target has a higher reflectance than the one extending between target and horizon, the visibility may decrease by up to 15%. In the opposite case, the visibility increases.

[Teratogenic action of an inhibitor of cholesterol synthesis in Wistar and Sprague-Dawley rats]. / Action tératogène d'un inhibiteur de la synthèse du cholestérol chez les rats Wistar et Sprague-Dawley.

Sprague-Dawley rats are sensitive to the teratogenic action of AY 9944, an inhibitor of cholesterol synthesis, but the dose of inhibitor necessary to induce the same rate of characteristic malformations is twice as large for Sprague-Dawley as for Wistar rats. This variation is probably related to differences in levels of blood cholesterol in the strains and demonstrates a relationship between teratogenicity and metabolic disturbances.