Comparative study of the cellular replication kinetics of rat mammary epithelial cells in vivo and in vitro

Ts-131b, one of the temperature-sensitive (ts) mutants isolated from mouse FM3A cells, was found to be defective in DNA replication at a non-permissive temperature. After the cells were transferred to 39.5 °C, the cell number increased by only 10% and the rate of incorporation of precursors into cellular DNA decreased rapidly. Cell cycle analysis by a flow cytometric method with the cells incubated at 39.5 °C revealed that progression of the cells through the S phase was inhibited and most of the cells were arrested in the S phase. To study the defect in DNA replication of this ts-mutant at 39.5 °C, DNA-fiber autoradiography was performed to measure the rate of DNA-chain elongation. The results showed that the rate of DNA-chain elongation was decreased at 6 h after the temperature shift. However, since the decrease in the rate of DNA-chain elongation was not sufficient to account for the decrease in the rate of incorporation of the precursors, it was suggested that there was also a decrease in the rate of initiation of DNA replication at some of the replicon origins.     

Isolation of the origin of replication of the IncW-group plasmid pSa

The origin of replication of the IncW plasmid pSa has been cloned and the function of this origin in Escherichia coli examined. A 1.9-kb region of DNA is required for efficient autonomous replication, and a 0.47-kb fragment within this region can initiate replication only in the presence of an autonomously replicating derivative of pSa. An Mr 35,000 protein (repA) is encoded adjacent to the origin and is required for efficient initiation of replication. The derivatives examined provide information suggesting a direct role of partition factors in plasmid replication and incompatibility.     

Disruption of quorum sensing in seawater abolishes attraction of zoospores of the green alga Ulva to bacterial biofilms

Zoospores of the eukaryotic green seaweed Ulva respond to bacterial N-acylhomoserine lactone (AHL) quorum sensing signal molecules for the selection of surface sites for permanent attachment. In this study we have investigated the production and destruction of AHLs in biofilms of the AHL-producing marine bacterium, Vibrio anguillarum and their stability in seawater. While wild type V. anguillarum NB10 was a strong attractor of zoospores, inactivation of AHL production in this strain by either expressing the recombinant Bacillus lactonase coding gene aiiA, or by mutating the AHL biosynthetic genes, resulted in the abolition of zoospore attraction. In seawater, with a pH of 8.2, the degradation of AHL molecules was temperature-dependent, indicating that the AHLs produced by marine bacterial biofilms have short half-lives. The Ulva zoospores sensed a range of different AHL molecules and in particular more zoospores settled on surfaces releasing AHLs with longer (>six carbons) N-linked acyl chains. However, this finding is likely to be influenced by the differential diffusion rates of AHLs from the experimental surface matrix. Molecules with longer N-acyl chains, such as N-(3-oxodecanoyl)- L-homoserine lactone, diffused more slowly than those with shorter N-acyl chains such as N-(3-hydroxy-hexanoyl)- L-homoserine lactone. Image analysis using GFP-tagged V. anguillarum biofilms revealed that spores settle directly on bacterial cells and in particular on microcolonies which we show are sites of concentrated AHL production.     

Effect of parasympathetic denervation on acetylcholine levels in the rat parotid gland. Is there an extraneuronal pool of acetylcholine?

Parasympathetic denervation of the rat parotid gland by avulsion of the auriculotemporal nerve caused a marked and lasting decrease in gland weight. Parasympathectomy did not change the levels of choline in the gland but decreased by 60% the levels of acetylcholine (ACh) ten days after surgery and 65% at 28 days. It is puzzling that relatively high levels of ACh remained after parasympathetic denervation. The presence of additional cholinergic nerves that innervate the gland, or pass through it en route to other structures may account for some of the remaining ACh. Also, Schwann cells from denervated nerves might have contributed to some of the ACh. The existence of an extraneuronal source of ACh is considered.     

Adaptive governance of synthetic biology

As resistance to synthetic biology slowly coalesces, governments and scientists need to be proactive to avoid a repetition of the near moratorium on genetically modified crops in Europe.Synthetic biology has the potential to revolutionize the development of drugs, vaccines, biofuels and food crops, and to clean up environmental pollution, but the field is relatively young. It is too early to tell how it will deliver new fundamental understandings in the life sciences, how this understanding will create opportunities for innovation to satisfy human needs and the extent to which its applications might generate hazards to people or the environment.Synthetic biology is now being linked by NGOs to genetically modified (GM)crop development with potentially similar results for its future development [1]. An NGO advocacy coalition has published a report on synthetic biology that echoes the arguments made against GM crops in the late 1990s [2] with the intention to “… reign [sic] in these new technologies”, with an ideologically based framing of the technology as inherently hazardous, based on negative conjectures with little relationship to actual evidence.The prospect of another polarized public debate had already convinced policy-makers and scientists to pay early attention to the governance of synthetic biology.Reports from the US Presidential Commission for the Study of Bioethical Issues (PCSBI) and from the International Risk Governance Council (IRGC) [3,4] have attempted to develop principles of good governance that could be applied to synthetic biology, given the uncertainty about the nature of future developments. The reports recommend that policy-makers should aim for a governance approach that can adapt to changing innovation opportunities emerging from new scientific discoveries; encourage and promote innovation; minimize risk to humans and the environment; and balance the interests and values of all relevant stakeholders. The reports reject calls for a moratorium on synthetic biology until all risks are identified and mitigated, but also reject unfettered freedom for scientific investigation. The governance of synthetic biology should achieve an equitable balance between promoting innovation and imposing constraints to ensure safety. Dialogue with stakeholders should be conducted in a manner that welcomes the respectful exchange of opposing views and encourages mutual accommodation of differing opinions. Dialogues should contribute to decisions being taken on the basis of the best available evidence. Considering potential dual-use risks of synthetic biology, both reports note that undue restriction might be counterproductive to safety and security, by preventing the development of effective safeguards against, for example, terrorist threats.These principles of good governance are part of a long-term political and policy experiment that claims to use a lighter touch and be less top-down [5], but in effect has extended the regulatory process into areas that used to be left to market forces. It claims to be more democratic by involving a wider range of stakeholders in the decision-making process, but in effect has merely led to a shift in power away from industry and commerce towards advocacy groups with equally limited claims to represent ‘society''. The impact of implementing this governance agenda on innovation has so far been more marked and damaging in Europe than in the USA, but the recent criticism by Friends of the Earth and other advocacy groups might signal a change of emphasis and put the balanced approach to the governance of synthetic biology, that has so far been achieved, at risk.Indeed, the availability and quality of the scientific evidence used to support policy advice and decision-making, has been a major casualty of the new governance approach as applied in the EU to GM crops—as evidenced by the destruction of GM crop trials designed to evaluate the safety and efficacy of these crops. The role of neutral, impartial evidence in political decision-making has been diminished in favour of evidence that suits the agendas of particular advocacy groups. Politicians themselves helped to create this situation by shying away from making difficult, unpopular decisions on the basis of hard evidence, in favour of trying to accommodate all opinions, including ideologically driven agendas. Arthur Miller describes the sense of liberation experienced when eschewing the role of evidence in decision-making: “It was as though the absence of real evidence was a release from the burdens of this world; [….] Evidence, in contrast, is effort; leaping to conclusions is a wonderful pleasure…” [6].There is a need to reappraise both the role of scientific evidence in informing policy and political decision-making on new biotechnologies, and the legitimate context in which to accomodate value-based opinions as represented by NGOs.     

The DNA sequence of chromosome I of an African trypanosome: gene content,chromosome organisation,recombination and polymorphism

The African trypanosome, Trypanosoma brucei, causes sleeping sickness in humans in sub-Saharan Africa. Here we report the sequence and analysis of the 1.1 Mb chromosome I, which encodes approximately 400 predicted genes organised into directional clusters, of which more than 100 are located in the largest cluster of 250 kb. A 160-kb region consists primarily of three gene families of unknown function, one of which contains a hotspot for retroelement insertion. We also identify five novel gene families. Indeed, almost 20% of predicted genes are members of families. In some cases, tandemly arrayed genes are 99–100% identical, suggesting an active process of amplification and gene conversion. One end of the chromosome consists of a putative bloodstream-form variant surface glycoprotein (VSG) gene expression site that appears truncated and degenerate. The other chromosome end carries VSG and expression site-associated genes and pseudogenes over 50 kb of subtelomeric sequence where, unusually, the telomere-proximal VSG gene is oriented away from the telomere. Our analysis includes the cataloguing of minor genetic variations between the chromosome I homologues and an estimate of crossing-over frequency during genetic exchange. Genetic polymorphisms are exceptionally rare in sequences located within and around the strand-switches between several gene clusters.     

In vivo and in vitro effects of X-irradiation and histamine-PO4 on rat and bovine pineal HIOMT acitivty and melatonin synthesis

Localized irradiation to the heads of adult male rats with 450 R increased pineal gland HIOMT activity while the same amount of irradiation restricted to the body diminished the activity of the enzyme. Anesthesia had no effect on this enzyme. Extremely high doses of irradiation were required (3,870 R) to inhibit HIOMT activity of bovine enzyme preparations in vitro. Localized irradaition of the head of rats with 450 R increased melatonin biosynthesis from tryptophan-3-¹⁴C, but irradiation of the body only had no such an effect. Injections of histamine-PO₄ into rats or the addition of it to the incubation media of bovine enzyme preparations inhibited melatonin synthesis and bovine HIOMT activity, respectively.     

TRAIL receptor and CD95 signal to mitochondria via FADD,caspase-8/10, Bid,and Bax but differentially regulate events downstream from truncated Bid

The death receptor ligand TRAIL arouses much interest for clinical application. We found that TRAIL receptor could induce cytochrome c (Cyt c) release from mitochondria in cells that failed to respond to CD95. Therefore, we examined whether these two closely related death receptors use different intermediates to convey the apoptotic signal to mitochondria. Dominant negative FADD, FLIP(L), or a Bid mutant lacking cleavage sites for caspase-8/10 completely inhibited Cyt c release in response to either receptor. Depletion of Bid from TRAIL- or CD95-activated cytosols blocked their capacity to mediate Cyt c release from mitochondria in vitro, whereas Bax depletion reduced it. We conclude that FADD, caspase-8/10, and caspase-cleaved Bid are required for TRAIL receptor and CD95 signaling to mitochondria, whereas Bax is a common accessory. In vitro, caspase-8 treatment of cytosol from CD95-resistant cells permitted generation of truncated Bid and its association with mitochondria. However, this cytosol impaired the ability of truncated Bid to liberate Cyt c from exogenous mitochondria. We conclude that the TRAIL receptor can bypass or neutralize the activity of cytosolic factor that blocks truncated Bid function. This may benefit the capacity of TRAIL to break apoptosis resistance in tumor cells.