TB Use Research Articles

Comparison of microbial markers (15N and purine bases) and bacterial isolates for the estimation of rumen microbial protein synthesis

AbstractThe first objective of this experiment was to investigate the effect of using different bacterial isolates on the estimation of microbial protein production in semi-continuous fermenters (RUSITEC) given four diets, and to test whether a ‘mixed’ bacterial pellet was representative of the whole bacterial population in the fermenters. A second objective was to compare two different microbial markers (nitrogen-fifteen (15N) and purine bases (PB)). Diets consisted of neutral-detergent fibre from grass hay (10 g/day) and sugar-beet pulp (2 g/day) and 280 mg/day of one of four N forms (isolated soya-bean protein, soya-bean peptides, amino acids blended to profile soya-bean protein and NH4Cl). Two 14-day incubation runs were carried out and in each run each of the four different diets were given to two vessels. On days 12 and 13, total digesta (effluent plus nylon bags residues) was collected for analyses of non-ammonia N,15N enrichment and PB concentration, and for isolation of total mixed bacterial pellets (TB). On the last day of each incubation run, the system was stopped for isolation of liquid- (LAB) and solid-associated (SAB) bacteria. Microbial N flow was estimated from the15N enrichment and PB concentration in both total digesta and in the three different bacterial pellets (TB, LAB, and SAB). For all diets, LAB presented a greater (P < 005)15N enrichment and PB: N ratio than SAB, with TB having an intermediate value. For both markers, the use of LAB produced the lowest (P < 005) estimates of microbial N flow and the use of SAB produced the greatest (P < 005) estimates. The use of TB produced intermediate values with all diets, suggesting that TB consisted of SAB and LAB. For all bacterial pellets, PB produced greater (P 005) values of microbial N flow than15N. However, there was a positive relationship (r = 0·883; P 0001; no. = 15) between the values of microbial N flow determined with the two markers when TB were used as reference.

IAU resolutions on reference systems and time scales in practice

To be consistent with IAU/IUGG (1991) resolutions ICRS and ITRS should be treated as four-dimensional reference systems with TCB and TCG time scales, respectively, interrelated by a four-dimensional general relativistic transformation. This two-way transformation is given in the form adapted for actual application. The use of TB and TT instead of TCB and TCG, respectively, involves scaling factors complicating the use of this transformation in practice. New IAU B1 (2000) resolution is commented taking in mind some points of possible confusion in its practical application. The problem of the relationship of the theory of reference systems with the parameters of common relevance to astronomy, geodesy and geodynamics is briefly outlined.

Tb 3+ f–d absorption as indicator of the effect of covalency on the Judd–Ofelt Ω2 parameter in glasses

The two effects, covalency and asymmetry, on the Judd–Ofelt Ω 2 parameter have been separated by use of Tb 3+ 4f–5d absorption peak wavelength as a measure of covalency. According to the Judd–Ofelt theory, Ω 2 increases with increasing reciprocal energy difference between the 4f N and 4f N−1 5d 1 configurations. In fact, a linear correlation between Ω 2 of Eu 3+ and the peak wavelength of the Tb 3+ 4f 8 → 4f 75d 1 absorption band has been found for the fluoride, fluoride phosphate and phosphate glasses investigated. The differences in the peak wavelengths are caused by differences in the polarizability of the ligands, leading to differences in the covalency of the rare earth sites. This behavior is responsible for the sensitivity of Ω 2 to the covalency of the bond between rare earth ions and their ligands. The deviation of the ultraphosphate glass investigated from the correlation between Ω 2 and the Tb 3+ 4f–5d peak wavelength is attributed to a higher degree of asymmetry of the local crystal fields around the rare earth ions.

Silent travelers: germs, genes, and the "immigrant menace"

Amid concerns over use of TB and AIDS to exclude immigrants, this book looks at how earlier generations grappled with such problems, from the Irish immigrants of New York wrongly blamed for the cholera epidemic in 1832 to San Francisco's Chinese labourers vilified for causing the bubonic plague in 1900, to Miami's Haitian refugees stigmatized as AIDS carriers in the 1980s. The book describes these and many other episodes of medicalized prejudice, and analyzes their impact on public health policy. Alan M. Kraut is the author of Huddled Masses: The Immigrant in American Society, 1880-1920.

Fluorescence of phosphotyrosine — Terbium(III) complexes

Phosphotyrosine, a biologically important protein residue, was investigated for the ability to enhance terbium (Tb 3+) fluorescence. Spectroscopic analysis of the Tb 3+: phosphotyrosine interaction indicated the development of a new excitation peak at 275 nm and strong Tb + fluoresence enhancement at 488 and 540 nm that was linear over a range from 0.5 to 100 μM amino acid. Subsequent experiments comparing the ability of phosphotyrosine, phosphothreonine, phosphoserine and 20 other common non-phosphorylated amino acids showed that only phosphotyrosine produced significant Tb 3+ fluoresence enhancement. Analysis of various phospho-sugars and nucleotides showed (with the expected exception of GMP) that they produced little or no significant fluoresence enhancement, indicating a further selectiveness for the phosphotyrosine: Tb 3+ fluoresence enhancement event. These results establish a basis for the future use of Tb 3+ fluoresence enhancement as a unique probe for the investigation of phosphotyrosine residues.

Investigation of Ion-Binding Properties of Synthetic Polyelectrolytes with The Tb[III] Luminescence Probe

Abstract The binding properties of trivalent metal ions to polyelectrolytes were investigated through the use of Tb(III) luminescence studies. The condensation of Tb(III) with the homopolymers poly(acrylic acid) and poly(methacrylic acid) was studied in detail. In addition, the 1 : 1 copolymers of maleic acid with ethylene, isobutene, and 2,4,4-trimethyl-1-pentene were also examined. The emission intensity of the 305 nm Tb(III) hypersensitive excitation band was found to correlate with the size of the alkyl group on the polymer chains. Tb(III) luminescence lifetime studies indicated that the metal ion binding site was equivalent over a wide range of Tb(III)/polymer ratios. The number of solvent molecules coordinated by Tb(III) in the various polymer complexes was determined and found to range between 3.5 and 4 molecules of water of hydration.

Use of terbium fluorescence enhancement as a new probe for assessing the single-strand content of DNA

Since a previous study showed that the guanosine monophosphate moieties resident in RNA gave markedly greater enhancement of terbium (III) (Tb 3+) fluorescence than those resident in an equal amount of DNA, we investigated the possibility that only the guanosine monophosphate moieties residing in single-strand regions of nucleic acids participated in the enhancement of Tb 3+ fluorescence. When native versus thermally denatured DNAs from rat liver were compared, we observed that thermal denaturation of DNA increased its ability to enhance Tb 3+ fluorescence by more than 10-fold. Furthermore, over a range of increasing temperatures (therefore increased thermal denaturation) a positive correlation was demonstrated for increases in Tb 3+ fluorescence enhancement and susceptibility to hydrolysis by the single strand-specific S 1 nuclease. Comparison of changes in Tb 3+ and ethidium bromide fluorescence for native versus thermally denatured DNA indicated that Tb 3+ was five times more sensitive in measuring increases in single-strand content. It is concluded that only those dGuo-5′-P moieties in single-strand DNA are capable of enhancing Tb 3+ fluorescence and, therefore, Tb 3+ fluorescence enhancement can be used to assess the single-strand content of DNA. Standard conditions are described for the use of Tb 3+ fluorescence in the measurement of DNA single strandedness.