Synthesis of ribonucleic acid in baby-hamster kidney cells in the presence of actinomycin D

1. RNA molecules with sedimentation values in sucrose gradients of 12-20s are synthesized in baby-hamster kidney cells even after prolonged incubation in medium containing 1mug. of actinomycin D/ml. 2. The rate of formation of this RNA is dependent on the age of the cultures and is greatest during the exponential phase of growth. 3. Growth of cells on nutritionally poor medium causes degradation and inhibits the synthesis of these RNA fractions. 4. Replacement of the nutritionally poor medium with a rich medium stimulates the synthesis of actinomycin-resistant RNA. This stimulation is blocked by cycloheximide. 5. The base composition of this RNA is characterized by low cytidine and high guanosine values.

A solution concentration dependent transition from self-stratification to lateral phase separation in spin-cast PS:d-PMMA thin films

Thin films with a rich variety of different nano-scale morphologies have been produced by spin casting solutions of various concentrations of PS:d-PMMA blends from toluene solutions. During the spin casting process specular reflectivity and off-specular scattering data were recorded and ex situ optical and atomic force microscopy, neutron reflectivity and ellipsometry have all been used to characterise the film morphologies. We show that it is possible to selectively control the film morphology by altering the solution concentration used. Low polymer concentration solutions favour the formation of flat in-plane phase-separated bi-layers, with a d-PMMA-rich layer underneath a PS-rich layer. At intermediate concentrations the films formed consist of an in-plane phase-separated bi-layer with an undulating interface and also have some secondary phase-separated pockets rich in d-PMMA in the PS-rich layer and vice versa. Using high concentration solutions results in laterally phase-separated regions with sharp interfaces. As with the intermediate concentrations, secondary phase separation was also observed, especially at the top surface.

Granzymes in cancer and immunity

Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells are indispensable factors in the body's ongoing defence against viral infection and tumor development. CTL/NK cells recognize and kill infected or aberrant target cells by two major pathways: either through introduction of a battery of proteases - called granzymes - to the target cell cytosol, or through TNF superfamily-dependent killing. During granzyme-dependent killing, target cell death is quick and efficient and is mediated by multiple granzymes, acting via redundant cell death pathways. Although granzyme-mediated cell death has been intensively studied, recent work has also hinted at an alternative, proinflammatory role for these enzymes. Thus, in addition to their well-established role as intracellular effectors of target cell death, recent data suggest that granzymes may have an extracellular role in the propagation of immune signals. In this study, we discuss the role of granzymes as central factors in antitumor immunity, as well possible roles for these proteases as instigators of inflammation.

Multi-level selection for hygienic behaviour in honeybees

Disease is one of the main factors driving both natural and artificial selection. It is a particularly important and increasing threat to the managed honeybee colonies, which are vital in crop pollination. Artificial selection for disease-resistant honeybee genotypes has previously only been carried out at the colony-level, that is, by using queens or males reared from colonies that show resistance. However, honeybee queens mate with many males and so each colony consists of multiple patrilines that will vary in heritable traits, such as disease resistance. Here, we investigate whether response to artificial selection for a key resistance mechanism, hygienic behaviour, can be improved using multi-level selection, that is, by selecting not only among colonies as normal but also among patrilines within colonies. Highly hygienic colonies were identified (between-colony selection), and the specific patrilines within them responsible for most hygienic behaviour were determined using observation hives. Queens reared from these hygienic patrilines (within-colony selection) were identified using DNA microsatellite analysis of a wing-tip tissue sample and then mated to drones from a third highly hygienic colony. The resulting colonies headed by queens from hygienic patrilines showed approximately double the level of hygienic behaviour of colonies headed by sister queens from non-hygienic patrilines. The results show that multi-level selection can significantly improve the success of honeybee breeding programs.

Regulation of caspase activation in apoptosis: implications for transformation and drug resistance

Recent developments in the apoptosis field have uncovered a family of cysteine proteases, the Caspases, that act as signalling components as well as effectors of the cell death machinery. Caspases are constitutively present as inactive precursors within most cells and undergo proteolytic processing in response to diverse death-inducing stimuli to initiate the death programme. Active caspases can process other caspases of the same type as well as process caspases further downstream in the pathway that ultimately leads to collapse of the cell. This cellular collapse is thought to occur as a consequence of caspase-mediated cleavage of a diverse array of cellular substrates. Regulation of entry into the death programme is controlled at a number of levels by members of the Bcl-2 family, as well as by other cell death regulatory proteins. Recent data has shed light upon the mechanism of action of these regulatory molecules and suggests that the point of caspase activation is a major checkpoint in the cell death programme. Because many transformed cell populations possess derangements in cell death-regulatory genes, such as bcl-2, such cells frequently exhibit elevated resistance to cytotoxic chemotherapy. Thus, a deeper understanding of how apoptosis is normally regulated has therapeutic implications for disease states where the normal controls on the cell death machinery have been subverted.

The CASBAH: a searchable database of caspase substrates

Apoptosis is coordinated by members of the caspase family of aspartic acid-specific proteases. Other members of this protease family also play essential roles in inflammation where they participate in the maturation of pro-inflammatory cytokines. To date, almost 400 substrates for the apoptosis-associated caspases have been reported and there are likely to be hundreds more yet to be discovered. Thus, the fraction of the proteome that is degraded (the degradome) by caspases during the demolition phase of apoptosis appears to be quite substantial. Despite this, we still know surprisingly little concerning how caspases provoke some of the signature events in apoptosis, such as membrane phosphatidylserine externalization, cellular retraction, chromatin condensation and apoptotic body production. The inflammatory caspases appear to be much more specific proteases than those involved in apoptosis and only two confirmed substrates for these proteases have been described to date. Here, we have compiled a comprehensive list of caspase substrates and describe a searchable web resource (The Casbah; www.casbah.ie) which contains information pertaining to all currently known caspase substrates. We also discuss some of the unresolved issues relating to caspase-dependent events in apoptosis and inflammation.

The rodent hippocampus and spatial memory: from synapses to systems

Although its operations are not limited to the spatial domain, there is a near consensus that the hippocampus plays a critical role in memory for place. This review aims to explore this role, with a particular emphasis on the functions performed by distinct hippocampal subregions. The use of innovative lesioning techniques, localized pharmacological treatments, and molecular genetic interventions is offering increasingly precise brain-regional specificity and temporal control. Together with the electrophysiological recording of neuronal activity, these techniques are beginning to shed light on the functioning of specific components of the hippocampal circuitry in the different phases of memory - encoding, storage, consolidation, and retrieval. In view of these developments, we examine the involvement of the hippocampus in the encoding versus retrieval of spatial memory, before turning to the issue of long-term information storage and the role of 'cellular' and 'systems' consolidation processes in the formation of lasting memories.

The pH-induced swelling and collapse of a polybase brush synthesized by atom transfer radical polymerization

We have used neutron reflectometry to characterize the swelling behaviour of brushes of poly[2-(diethyl amino)ethyl methacrylate], a polybase, as a function of pH. The brushes, synthesized by the "" method of atom transfer radical polymerization, were observed to approximately double their thickness in low pH solutions, although the p is shifted to a lower pH than in dilute solution. The composition-depth profile obtained from the reflectometry experiments for the swollen brushes reveals a region depleted in polymer between the substrate and the extended part of the brush.

Downregulation of Bcr-Abl in K562 cells restores susceptibility to apoptosis: characterization of the apoptotic death

We examined the susceptibility of a variety of human leukemic cell lines to the induction of apoptosis. K562, a chronic myelogenous leukemic cell line which expresses the bcr-abl fusion gene, was found to be extremely resistant to apoptosis, irrespective of the inducing agent. This resistance can be attributed to the deregulated Abl kinase activity of bcr-abl, as downregulation of its expression using antisense oligodeoxynucleotides targeted to the beginning of the abl sequence in this chimeric gene rendered these cells susceptible to cytotoxic drug-induced apoptosis. Examination of the morphological and biochemical features of apoptosis in K562 cells revealed the typical membrane blebbing and chromatin condensation associated with this form of cell death. In situ TdT-mediated end labeling of the DNA revealed the presence of strand breaks in the treated cells and field inversion gel electrophoresis revealed the presence of large 10-50 kb fragments. However there was an absence of oligonucleosomal DNA fragmentation, whether or not Bcr-Abl was expressed. Thus, while inhibition of expression of Bcr-Abl renders K562 cells susceptible to apoptosis, the absence of oligonucleosomal DNA fragmentation in these cells is independent of the function of this molecule.

Responsive brushes and gels as components of soft nanotechnology

Progress in the development of generic molecular devices based on responsive polymers is discussed. Characterisation of specially synthesised polyelectrolyte gels, "grafted from" brushes and triblock copolymers is reported. A Landolt pH-oscillator, based on bromate/ sulfite/ferrocyanide, with a room temperature period of 20 min and a range of 3.1 < pH < 7.0, has been used to drive periodic oscillations in volume in a pH responsive hydrogel. The gel is coupled to the reaction and changes volume by a factor of at least 6. A continuously stirred, constant volume, tank reactor was set-up on an optical microscope and the reaction pH and gel size monitored. The cyclic force generation of this system has been measured directly in a modified JKR experiment. The responsive nature of polyelectrolyte brushes, grown by surface initiated ATRP, have been characterised by scanning force microscopy, neutron reflectometry and single molecule force measurements. Triblock copolymers, based on hydrophobic end-blocks and either polyacid or polybase mid-block, have been used to produce polymer gels where the deformation of the molecules can be followed directly by SAXS and a correlation between molecular shape change and macroscopic deformation has been established. The three systems studied allow both the macroscopic and a molecular response to be investigated independently for the crosslinked gels and the brushes. The triblock copolymers demonstrate that the individual response of the polyelectrolyte molecules scale-up to give the macroscopic response of the system in an oscillating chemical reaction.

In vitro selectivity, in vivo biodistribution and tumour uptake of annexin V radiolabelled with a positron emitting radioisotope

The availability of a noninvasive method to detect and quantify apoptosis in tumours will enable tumour response to several cancer therapies to be assessed. We have synthesised two radiotracers, annexin V and the N-succinimidyl-3-iodobenzoic acid (SIB) derivative of annexin V, labelled with radio-iodine (¹²⁴I and ¹²⁵I) and provided proof of the concept by assessing specific binding and biodistribution of these probes to apoptotic cells and tumours. We have also assessed the tumour uptake of [¹²⁴I]annexin V in a mouse model of apoptosis. RIF-1 cells induced to undergo apoptosis in vitro showed a drug concentration-dependent increased binding of [¹²⁵I]annexin V and [¹²⁵I]SIB–annexin V. In the same model system, there was an increase in terminal deoxynucleotidyl transferase-mediated nick end labelling (TUNEL)-positive cells and a decrease in clonogenic survival. Radiotracer binding was completely inhibited by preincubation with unlabelled annexin V. In RIF-1 tumour-bearing mice, rapid distribution of [¹²⁵I]SIB–annexin V-derived radioactivity to kidneys was observed and the radiotracer accumulated in urine. The binding of [¹²⁵I]SIB–annexin V to RIF-1 tumours increased by 2.3-fold at 48 h after a single intraperitoneal injection of 5-fluorouracil (165 mg kg⁻¹ body weight), compared to a 4.4-fold increase in TUNEL-positive cells measured by immunostaining. Positron emission tomography images with both radiotracers demonstrated intense localisation in the kidneys and bladder. Unlike [¹²⁴I]SIB–annexin V, [¹²⁴I]annexin V also showed localisation in the thyroid region presumably due to deiodination of the radiolabel. [¹²⁴I]SIB–annexin V is an attractive candidate for in vivo imaging of apoptosis by PET.

Elements of a neurobiological theory of the hippocampus: the role of activity-dependent synaptic plasticity in memory

The hypothesis that synaptic plasticity is a critical component of the neural mechanisms underlying learning and memory is now widely accepted. In this article, we begin by outlining four criteria for evaluating the 'synaptic plasticity and memory (SPM)' hypothesis. We then attempt to lay the foundations for a specific neurobiological theory of hippocampal (HPC) function in which activity-dependent synaptic plasticity, such as long-term potentiation (LTP), plays a key part in the forms of memory mediated by this brain structure. HPC memory can, like other forms of memory, be divided into four processes: encoding, storage, consolidation and retrieval. We argue that synaptic plasticity is critical for the encoding and intermediate storage of memory traces that are automatically recorded in the hippocampus. These traces decay, but are sometimes retained by a process of cellular consolidation. However, we also argue that HPC synaptic plasticity is not involved in memory retrieval, and is unlikely to be involved in systems-level consolidation that depends on HPC-neocortical interactions, although neocortical synaptic plasticity does play a part. The information that has emerged from the worldwide focus on the mechanisms of induction and expression of plasticity at individual synapses has been very valuable in functional studies. Progress towards a comprehensive understanding of memory processing will also depend on the analysis of these synaptic changes within the context of a wider range of systems-level and cellular mechanisms of neuronal transmission and plasticity.

New life in an old idea: the synaptic plasticity and memory hypothesis revisited

The notion that changes in synaptic efficacy underlie learning and memory processes is now widely accepted, although definitive proof of the synaptic plasticity and memory hypothesis is still lacking. This article reviews recent evidence relevant to the hypothesis, with particular emphasis on studies of experience-dependent plasticity in the neocortex and hippocampus. In our view, there is now compelling evidence that changes in synaptic strength occur as a consequence of certain forms of learning. A major challenge will be to determine whether such changes constitute the memory trace itself or play a less specific supporting role in the information processing that accompanies memory formation.

The role of mitochondrial factors in apoptosis: a Russian roulette with more than one bullet

Mitochondria are 'life-essential' organelles for the production of metabolic energy in the form of ATP. Paradoxically mitochondria also play a key role in controlling the pathways that lead to cell death. This latter role of mitochondria is more than just a 'loss of function' resulting in an energy deficit but is an active process involving different mitochondrial proteins. Cytochrome c was the first characterised mitochondrial factor shown to be released from the mitochondrial intermembrane space and to be actively implicated in apoptotic cell death. Since then, other mitochondrial proteins, such as AIF, Smac/DIABLO, endonuclease G and Omi/HtrA2, were found to undergo release during apoptosis and have been implicated in various aspects of the cell death process. Members of the Bcl-2 protein family control the integrity and response of mitochondria to apoptotic signals. The molecular mechanism by which mitochondrial intermembrane space proteins are released and the regulation of mitochondrial homeostasis by Bcl-2 proteins is still elusive. This review summarises and evaluates the current knowledge concerning the complex role of released mitochondrial proteins in the apoptotic process.

A new precursor for the radiosynthesis of [18F]FLT

In order to improve the [18F]FLT production for nuclear medical purposes, the syntheses and labeling results obtained with six new thymidine derivatives involving an alternative protection group strategy are described. The syntheses of the FLT-labeling precursors were performed using the following protection groups at the 5'-O-position: trityl (Tr) and 4,4'-dimethoxytrityl (DMTr). Formation of an electrophilic center at the 3'-carbon was achieved with methylsulfonyl, p-toluenesulfonyl and 4-nitrobenzenesulfonyl groups. The major difference to previous accomplishments rested upon the 3-N-Boc-protection of the FLT-labeling precursors avoiding the deprotection with ceric ammonium nitrate (CAN). With CAN, a precipitate was formed which was found to interact unfavourably with synthesis automation. Here, deprotection resulted in homogeneous solutions which could immediately be loaded on HPLC. The radiosyntheses were performed with high doses of [18F]fluoride to obtain realistic results for routine production of the clinically interesting radiopharmaceutical, [18F]FLT. It was shown that the nosylated precursors were more favorable for radiofluorination than the mesylated or tosylated derivatives. A positive effect on the radiochemical yield was found with DMTr in comparison to Tr. Best results were obtained using 3-N-Boc-1-[5-O-(4,4'-dimethoxytrityl)-3-O-nosyl-2-deoxy-beta-D-lyxofuranosyl]thymine yielding 1.7 GBq (19.8% EOB) whithin 85 minutes.

CARDINAL, a novel caspase recruitment domain protein, is an inhibitor of multiple NF-kappa B activation pathways

Proteins possessing the caspase recruitment domain (CARD) motif have been implicated in pathways leading to activation of caspases or NF-kappaB in the context of apoptosis or inflammation, respectively. Here we report the identification of a novel protein, CARDINAL, that contains a CARD motif and also exhibits a high degree of homology to the C terminus of DEFCAP/NAC, a recently described member of the Apaf-1/Nod-1 family. In contrast with the majority of CARD proteins described to date, CARDINAL failed to promote apoptosis or NF-kappaB activation. Rather, CARDINAL potently suppressed NF-kappaB activation associated with overexpression of TRAIL-R1, TRAIL-R2, RIP, RICK, Bcl10, and TRADD, or through ligand-induced stimulation of the interleukin-1 or tumor necrosis factor receptors. Co-immunoprecipitation experiments revealed that CARDINAL interacts with the regulatory subunit of the IkappaB kinase (IKK) complex, IKKgamma (NEMO), providing a molecular basis for CARDINAL function. Thus, CARDINAL is a novel regulator of NF-kappaB activation in the context of pro-inflammatory signals.

Caspases: cellular demolition experts

Apoptosis is co-ordinated by a family of cysteine proteases, the caspases, that dismantle the cell by targeting a panoply of proteins for limited proteolysis. The mammalian caspase family contains 14 members, a subset of which participates in apoptosis, with the remainder likely to be involved in the processing of pro-inflammatory cytokines. Apical caspase activation events are typically initiated by adaptor molecules that promote caspase aggregation and facilitate caspase autoactivation. In contrast, distal caspase activation events are controlled by caspases activated earlier in the cascade. Many cellular stresses provoke apoptosis by damaging mitochondria which results in the release of factors [such as cytochrome c and SMAC (second mitochondrial-derived activator of caspase)/Diablo] that trigger caspase activation and cell death. Here, we discuss the hierarchical nature of the caspase cascade that is triggered upon the release of mitochondrial cytochrome c into the cytoplasm, and the role of specific caspases within this cascade in targeting proteins for degradation. Finally, feedback amplification loops and important control points within the caspase cascade will be discussed.