Replication fork reactivation downstream of a blocked nascent leading strand

Unrepaired lesions in the DNA template pose a threat to accurate replication. Several pathways exist in Escherichia coli to reactivate a blocked replication fork. The process of recombination-dependent restart of broken forks is well understood, but the consequence of replication through strand-specific lesions is less well known. Here we show that replication can be restarted and leading-strand synthesis re-initiated downstream of an unrepaired block to leading-strand progression, even when the 3'-OH of the nascent leading strand is unavailable. We demonstrate that the loading by a replication restart system of a single hexamer of the replication fork helicase, DnaB, on the lagging-strand template is sufficient to coordinate priming by the DnaG primase of both the leading and lagging strands. These observations provide a mechanism for damage bypass during fork reactivation, demonstrate how daughter-strand gaps are generated opposite leading-strand lesions during the replication of ultraviolet-light-irradiated DNA, and help to explain the remarkable speed at which even a heavily damaged DNA template is replicated.     

Distribution of a renin-like enzyme in the bovine adrenal gland

Résumé La glande surrénale bovine contient un enzyme qui réagit avec l'angiotensinogène pour former de l'angiotensine. L'enzyme est distribué dans toute la glande surrénale, en plus grande quantité dans la médullosurrénale et dans la veine centrale. Vu les effects bien connus de l'angiotensine sur la sécrétion de l'aldostérone et sur les catécholamines de la médullosurrénale, il est possible que l'enzyme «rénine-semblable» influence les fonctions spécifiques de la glande surrénale.     

Metabolism of diphenylamine in the rat and rabbit

Zusammenfassung Nach oraler Verabreichung von Diphenylamin wurde das Kaliumsalz des 4-Oxydiphenylaminsulfatesters aus dem Harn des Kaninchens isoliert. Die enzymatische Hydrolyse des Kaninchenharns ergab kleine Mengen von 2-Oxydiphenylamin, die mit Hilfe von Dünnschicht-Chromatographie identifiziert wurden. Bei der Ratte gelang nach intraperitonealer Verabreichung von Diphenylamin bei enzymatischer und saurer Hydrolyse des Harns der chromatographische Nachweis des 4-Oxydiphenylamins als Hauptprodukt der Umwandlung.

---

---

This work forms part of a programme supported by Grant EF.258 of the National Institute of Health, U.S. Public Health Service, the National Health and Medical Research Council of Australia and the Council of the Australian Food Technologists Association.     

Role for DNA methylation in the control of cell type specific maspin expression

The major histocompatibility complex (MHC) is a source of unique individual odors that influence individual recognition, mating preferences, nesting behavior and selective block of pregnancy in animals. Such phenomena have been difficult to study in humans, because the human leukocyte antigen (HLA, human MHC) loci are the most polymorphic loci in the human genome, with the potential to generate millions of unique combinations of genotypes. In addition, high variability in background odors, encoded by the rest of the genome and influenced by cultural practices, contribute to a low signal-to-noise ratio that could mask HLA-based olfactory cues. Here we show that women can detect differences of one HLA allele among male odor donors with different MHC genotypes. Notably, the mechanism for a woman's ability to discriminate and choose odors is based on HLA alleles inherited from her father but not her mother. The parents' HLA alleles that she does not inherit show no relationship with odor choice, despite exposure to these HLA-encoded odors throughout her life. Our data indicate that paternally inherited HLA-associated odors influence odor preference and may serve as social cues.     

Measuring intense rotation and dissipation in turbulent flows

Turbulent flows are highly intermittent--for example, they exhibit intense bursts of vorticity and strain. Kolmogorov theory describes such behaviour in the form of energy cascades from large to small spatial and temporal scales, where energy is dissipated as heat. But the causes of high intermittency in turbulence, which show non-gaussian statistics, are not well understood. Such intermittency can be important, for example, for enhancing the mixing of chemicals, by producing sharp drops in local pressure that can induce cavitation (damaging mechanical components and biological organisms), and by causing intense vortices in atmospheric flows. Here we present observations of the three components of velocity and all nine velocity gradients within a small volume, which allow us to determine simultaneously the dissipation (a measure of strain) and enstrophy (a measure of rotational energy) of a turbulent flow. Combining the statistics of all measurements and the evolution of individual bursts, we find that a typical sequence for intense events begins with rapid strain growth, followed by rising vorticity and a final sudden decline in stretching. We suggest two mechanisms which can produce these characteristics, depending whether they are due to the advection of coherent structures through our observed volume or caused locally.     

The effect of chronic heat stress on cortisol levels in the antarctic fishPagothenia borchgrevinki

Radioimmunoassay was used to determine levels of the stress-inducible glucocorticoid, cortisol, circulating in the plasma of the extremely stenothermal Antarctic fishPagothenia borchgrevinki at rest and after heat stress. Fish sampled immediately after capture (–1.9°C) had low cortisol levels (10.4±1.4 ng ml^–1, mean±SEM) as did fish which were laboratory rested for 3 days. Sudden exposure to 5°C (48h) resulted in a peak cortisol value after 3 h (69.9±6.8 ng ml^–1) whereas exposure to 8°C (6h) resulted in a peak value after 1 h (73.5±8.0 ng ml^–1). At both temperatures levels remained significantly elevated (p<0.05) for the entire period of exposure. Increased temperature also resulted in a significant change in haemoglobin, haematocrit and mean cell haemoglobin concentration (MCHC) (p<0.05). Plasma lactate was significantly elevated only after exposure to 8°C (p<0.05). Plasma cortisol levels fromP. borchgrevinki are reported here for the first time and show this cryopelagic Antarctic species to have an unusual hormonal stress profile.     

Impaired PtdIns(4,5)P2 synthesis in nerve terminals produces defects in synaptic vesicle trafficking

Phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) has an important function in cell regulation both as a precursor of second messenger molecules and by means of its direct interactions with cytosolic and membrane proteins. Biochemical studies have suggested a role for PtdIns(4,5)P2 in clathrin coat dynamics, and defects in its dephosphorylation at the synapse produce an accumulation of coated endocytic intermediates. However, the involvement of PtdIns(4,5)P2 in synaptic vesicle exocytosis remains unclear. Here, we show that decreased levels of PtdIns(4,5)P2 in the brain and an impairment of its depolarization-dependent synthesis in nerve terminals lead to early postnatal lethality and synaptic defects in mice. These include decreased frequency of miniature currents, enhanced synaptic depression, a smaller readily releasable pool of vesicles, delayed endocytosis and slower recycling kinetics. Our results demonstrate a critical role for PtdIns(4,5)P2 synthesis in the regulation of multiple steps of the synaptic vesicle cycle.