Bromodeoxyuridine induction of deoxycytidine deaminase activity in a hamster cell line

The Syrian hamster cell line, RPMI 3460, was found to express barely detectable levels of the enzyme deoxycytidine deaminase. In contrast, the cell lines B4 and HAB, which are derived from 3460 cells and have approx. 60 and 100% bromodeoxyuridine substitution in DNA, respectively, show an approx. 50-fold higher enzyme activity. Deoxycytidine deaminase activity can be "induced" in 3460 cells by growth in 10(-5) M bromodeoxyuridine, as well as by the other halogenated pyrimidines, iododeoxyuridine and chlorodeoxy-uridine. The time required for maximal enzyme activity to accrue (approx. 8 days) suggests that new genetic expression is required for enhanced deoxycytidine deaminase activity and inhibition of induction in the presence of Ara. C shows that bromodeoxyuridine must be incorporated into DNA. In addition, the extent of enhanced deoxycytidine deaminase activity is directly related to the level of bromodeoxyuridine substitution in DNA. Another hamster cell line, BHK21/C13, which shows no detectable deoxycytidine deaminase activity, cannot be induced by bromodeoxyuridine. These results are discussed with respect to a mechanism by which bromodeoxyuridine may alter gene expression due to an altered binding of both positive and negative regulatory proteins to DNA.     

Determination of 5′-bromodeoxyuridine in DNA by buoyant density

Cesium chloride buoyant density analysis shows the density difference between the double-stranded alternating copolymers of dT and dA, poly(dAT·dAT) and of dA and BrdU, (dABU·dABU), to be 0.1730 g/cm³. A mammalian DNA fully substituted with 5′-bromodeoxyuridine (BrdU) increases in density over control, unsubstituted, DNA by a value within 1% of that predicted from analysis of the copolymers. A simple relationship is presented for the accurate determination of the extent of BrdU substitution in a DNA of heterogeneous base composition.     

A quantitative method for distinguishing BrdUTP and dTTP in soluble pools

5-Bromodeoxyuridine (BrdU) has the well-known property of inhibiting differentiated cell functions in a variety of biological systems, and considerable attention has been focused on elucidating its mechanism of action [see Ref. (1) for review]. While most studies are consistent with a DNA-mediated mode of action, it is becoming clear that most experiments to date are insufficient to exclude other levels of action. Therefore, it is becoming increasingly relevant to examine aspects of BrdU metabolism in addition to its incorporation into DNA, including its uptake and equilibration into nucleotide pools.     

The analysis of small-and mesoscale dispersion patterns ofMarenzelleria viridis (Polychaeta: Spionidae) in a coastal water area of the southern Baltic

The horizontal mesoscale distribution ofMarenzelleria viridis (Verrill, 1873), a spionid polychaete introduced from North American coastal waters during the 1980s, was studied in shallow water in the southern Baltic (German coast). The polychaete achieved an individual dominance of 80% and abundances up to around 8500 ind./m². Samples taken from a small (1.2 m×1.2 m, 6×6 samples, depth 0–35 cm) and a large station grid (5.5 m×5.5 m, 11×11 samples, depth 0–35 cm) were used to calculate dispersion indices for subpopulations of adult and juvenileM. viridis and subdominant chironimids (theChironomus plumosus andCh. halophilus complexes). The distribution patterns were significantly patchy. The patch sizes were estimated with the help of the dispersion indices and by analysing the correlograms in which spatial autocorrelations such as Moran's I and Geary's c values were plotted versus the field distance k. The patch sizes were heterogenous. The smallest patches found were 0.04 m². The largest sizes observed were 9 m². It is conceivable that smaller patches merge to form larger aggregations. Calculation of the abundance and rank correlations between subpopulations revealed significant positive relationships. These indicate principal suspension feeding. Sediment structure, substrate preference, feeding mode and biotic or abiotic attraction centres are considered to be the main causes of aggregation and the positive correlations.     

Stability and fine structure of eukaryotic DNA rings in formamide

Folded rings formed from Drosophila and Necturus DNA fragments were examined by electron microscopy in increasing concentrations of formamide, in an effort to identify regions of non-homology within the closure region. Unusual closure regions of this type were not found, in spite of an extensive search. If such regions exist, they must be too short to be detectable (<50 nucleotides), or longer than 1000 nucleotides. In this latter case, they could not be contained within the overlap region of the ring. A study of the thermal (formamide) stability of these rings in relation to the observed closure lengths suggests that extensive (>2 to 3%) mismatching is not possible. At higher formamide concentrations, some rings will partly denature, yet remain circular because the closure region remains intact.     

The effects of CGRP on calcium transients of dedifferentiating cultured adult rat cardiomyocytes compared to non-cultured adult cardiomyocytes: possible protective and deleterious results in cardiac function

CGRP has potent cardiovascular effects but its role in heart failure is unclear. Effects of CGRP on calcium concentrations in fresh adult rat cardiomyocytes, cultured adult cardiomyocytes and neonatal cardiomyocytes were determined by real time fluorescence spectrophotometry. Treatment of cultured adult cardiomyocytes with CGRP resulted in a rapid cessation of beating and a reduction in intracellular calcium. Similar results were obtained in cultured neonatal myocytes. However, rod-shaped adult cardiomyocytes revealed a number of responses; (a) non-beating cells began to beat with increased intracellular calcium; (b) spontaneously beating cells exhibited increased intracellular calcium content and a faster beating rate or (c), myocytes increased their beating rate and became arrhythmic, suggesting that CGRP action on cultured dedifferentiated adult and neonatal myocytes depletes intracellular calcium, whereas in the rod-shaped mature myocytes calcium is retained, pointing to a different mode of action for CGRP on developing and dedifferentiating cardiomyocytes, compared to fully developed cardiomyocytes.     

How to Switch Off a Histidine Kinase: Crystal Structure of Geobacillus stearothermophilus KinB with the inhibitor Sda

Entry to sporulation in bacilli is governed by a histidine kinase phosphorelay, a variation of the predominant signal transduction mechanism in prokaryotes. Sda directly inhibits sporulation histidine kinases in response to DNA damage and replication defects. We determined a 2.0-Å-resolution X-ray crystal structure of the intact cytoplasmic catalytic core [comprising the dimerization and histidine phosphotransfer domain (DHp domain), connected to the ATP binding catalytic domain] of the Geobacillus stearothermophilus sporulation kinase KinB complexed with Sda. Structural and biochemical analyses reveal that Sda binds to the base of the DHp domain and prevents molecular transactions with the DHp domain to which it is bound by acting as a simple molecular barricade. Sda acts to sterically block communication between the catalytic domain and the DHp domain, which is required for autophosphorylation, as well as to sterically block communication between the response regulator Spo0F and the DHp domain, which is required for phosphotransfer and phosphatase activities.