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Purpose of review Multifetal pregnancy carries increased risk of preterm delivery, and consensus on management options to prevent early birth in this population has not been reached. This review serves to summarize the most contemporary findings on this controversial topic. Recent findings Examination-indicated cerclage is effective in reducing preterm birth in twin pregnancies, whereas cerclages for other indications are less convincing. Cervical pessary may be beneficial for patients with a short cervix and in those who have had threatened preterm labor. Progesterone supplementation for multifetal gestation alone is not beneficial, but it can be considered in those with a history of prior singleton preterm birth. Summary Interventions for preterm birth prevention in multiple gestations remain under investigation, and further data is required in order to reach consensus for this high-risk population.

Kicking powerfully and accurately is essential in soccer, and players who kick proficiently with both feet are highly sought after. Assessing performance in youth players is often confounded by more physically developed players outperforming their smaller peers. To alleviate such bias, we present a testing protocol and normative data developed with an elite Brazilian soccer academy that controls for players’ age and size to assess kick performance with both feet. We measured kick speed and kick accuracy of 178 players and recorded their age (10–20 years), height, and mass. Combining age, height, and mass into an age and size index (ASI), we developed equations describing the relationship between ASI and performance. To determine the underlying predictors of performance, we also measured sprint ability and soccer-specific motor control of each foot with ball dribbling tasks. Kicking speed with the dominant foot was predicted by ASI, sprint speed, and motor control of the nondominant foot, while kicking speed with the nondominant foot was predicted by ASI and motor control of the nondominant foot. Kick accuracy with each foot was predicted by ASI and motor control of the corresponding foot. To improve kicking performance, we suggest training programs focus on motor control.

The bag shelter moth, Ochrogaster lunifer Herrich-Schaffer, 1855 (Thaumetopoeinae), is abundant and widespread throughout Australia where its larvae have been reported to feed mostly on Acacia and eucalypts. The larvae, known as processionary caterpillars, build silken nests on their host plants either on the ground at the base of the plant (Acacia) or above ground on the trunk or among the canopy (Acacia and eucalypts). The caterpillars are medically important in that they shed tiny setae that can cause dermatitis and other health problems in humans and other mammals, including amnionitis and foetal loss in horses. Despite reports of behavioural, ecological and morphological differences between ground and canopy nesters, caterpillars of all nest types and hosts are currently considered to belong to one species. Here, we use DNA sequence data from the mitochondrial and nuclear genomes of caterpillars taken from different nest types in eastern Australia to determine whether there is evidence for there being more than one species. We find significant genetic divergence between caterpillars from different nest types despite occurrence in sympatry at multiple sites, indicative of a lack of gene flow and the presence of at least two reproductively isolated species. Given the range of hosts and nest locations within hosts throughout Australia, further sampling is needed to determine just how many species there are under the current concept of O. lunifer.

In many youth sports, selection into elite training academies is dominated by athletes born earlier in the year. Previous research suggests this is partly due to these athletes being more physically developed than their younger peers. How athletes born later in the year survive in elite academies is less understood. Here, we tested the hypothesis that players born later in the year are more technically skilled than their peers born earlier in the same year. Using 150 youth players (10–19 years of age) from an elite Brazilian soccer academy, we measured each player's date of birth, height, and mass; sprinting ability; dribbling ability; and kicking accuracy and speed. We found most players in this academy were born in the first half of the year, and those born earlier in the year (relatively older) tended to be taller and heavier than those born later in the same year (relatively younger). In addition, relatively older players were faster when sprinting and dribbling the ball in a straight line. Conversely, relatively younger players were more accurate when passing the ball with their nondominant foot, providing some evidence these players were more technically skilled than their older peers of the same age. We suggest skill tests with youth players need to consider relative age and physical size in order to best assess a player's potential.

Purpose of review The use of low dose aspirin (LDA) has become routine in prenatal care for a variety of diagnoses, most importantly in women with a history of preeclampsia and associated poor pregnancy outcomes. Although LDA is currently indicated in patients considered to be at risk for development of preeclampsia, optimal dosing, timing of treatment initiation, and persons of benefit are under investigation. Several studies have also looked at LDA treatment and its effect on other maternal and fetal outcomes. This review summarizes the current guidelines for the use of LDA, incorporating the most recent research findings, and offers possible future implications of LDA treatment. Recent findings Over 10 years ago, the American College of Obstetricians and Gynecologists, the World Health Organization, and the United States Preventive Service Task Force began publishing guidelines focused on the use of LDA in pregnancy. Since the release of these guidelines, several large studies have re-evaluated the use of LDA with a focus on initiation of treatment and dosing. The combined results of these studies suggest a decreased rate of preeclampsia at aspirin doses >100 mg when treatment is initiated prior to 16 weeks of gestation. Summary Overall, early initiation of LDA has been shown to decrease the development of preeclampsia in patients considered at increased risk. Current literature suggests increasing the recommended dose to >100 mg to optimize these risk reductions. Although LDA use seems promising for other outcomes like preterm delivery and intrauterine growth restriction, further studies to strengthen recommendations are warranted.

Interactions among selection, gene flow, and drift affect the trajectory of adaptive evolution. In natural populations, the direction and magnitude of these processes can be variable across different spatial, temporal, or ontogenetic scales. Consequently, variability in evolutionary processes affects the predictability or stochasticity of microevolutionary outcomes. We studied an intertidal fish, Bathygobius cocosensis (Bleeker, 1854), to understand how space, time, and life stage structure genetic and phenotypic variation in a species with potentially extensive dispersal and a complex life cycle (larval dispersal preceding benthic recruitment). We sampled juvenile and adult life stages, at three sites, over three years. Genome-wide SNPs uncovered a pattern of chaotic genetic patchiness, that is, weak-but-significant patchy spatial genetic structure that was variable through time and between life stages. Outlier locus analyses suggested that targets of spatially divergent selection were mostly temporally variable, though a significant number of spatial outlier loci were shared between life stages. Head shape, a putatively ecologically responsive (adaptive) phenotype in B. cocosensis also exhibited high temporal variability within sites. However, consistent spatial relationships between sites indicated that environmental similarities among sites may generate predictable phenotype distributions across space. Our study highlights the complex microevolutionary dynamics of marine systems, where consideration of multiple ecological dimensions can reveal both predictable and stochastic patterns in the distributions of genetic and phenotypic variation. Such considerations probably apply to species that possess short, complex life cycles, have large dispersal potential and fecundities, and that inhabit heterogeneous environments.

Aim: To test the influence of historical and contemporary environment in shaping the genetic diversity of freshwater fauna we contrast genetic structure in two co-distributed, but ecologically distinct, rainbowfish; a habitat generalist (Melanotaenia splendida) and a habitat specialist (M. trifasciata). Location: Fishes were sampled from far northern Australia (Queensland and Northern Territory). Methods: We used sequence data from one mitochondrial gene and one nuclear gene to investigate patterns of genetic diversity in M. splendida and M. trifasciata to determine how differences in habitat preference and historical changes in drainage boundaries affected patterns of connectivity. Results: Melanotaenia splendida showed high levels of genetic diversity and little population structure across its range. In contrast, M. trifasciata showed high levels of population structure. Whereas phylogeographic patterns differed, both species showed a strong relationship between geographical distance and genetic differentiation between populations. Melanotaenia splendida showed a shallower relationship with geographical distance, and genetic differentiation was best explained by stream length and a lower scaled ocean distance (11.98 times coast length). For M. trifasciata, genetic differentiation was best explained by overwater distance between catchments and ocean distance scaled at 1.16 × 10 times coast length. Main conclusions: Connectivity of freshwater populations inhabiting regions periodically interconnected during glacial periods appears to have been affected by ecological differences between species. Species-specific differences are epitomized here by the contrast between co-distributed congeners with different habitat requirements: for the habitat generalist, M. splendida, there was evidence for greater historical genetic connectivity with oceans as a weaker barrier to gene exchange in contrast with the habitat specialist, M. trifasciata.

Whereas the negative impact of human caused habitat degradation on community species richness is well established, less is known about its effect on within species genetic diversity. Here we investigate how different aspects of habitat degradation affects genetic diversity of an Australian native freshwater fish, Rhadinocentrus ornatus, and what impacts this may have on this species’ conservation status. We perform this investigation for R. ornatus across southeast Queensland. Based on mtDNA sequence data from 327 individuals and 20 populations, we identified three distinct genetic lineages that were allopatric at the stream level. Indicators of habitat degradation have large negative effects on measures of genetic diversity, with close proximity to urban development and alterations to waterways associated with drastically reduced measures of genetic diversity across three distinct mtDNA lineages (evolutionary significant units). Low effective population sizes and low standing genetic variation in degraded habitats may result in reduced adaptive potential in this already threatened narrow range endemic. The only surveyed populations with high genetic diversity are found in protected National Parks. Many historical populations of R. ornatus in the highly developed Greater Brisbane Region are already probably extinct, and without further study and management this may be the fate of presently genetically depauperate populations in urban areas.

A novel series of muscarinic receptor antagonists was developed, with the aim of identifying a compound with high M3 receptor potency and a reduced risk of dose-limiting side effects with potential for the treatment of COPD. Initial compound modifications led to a novel cycloheptyl series, which was improved by focusing on a quinuclidine sub-series. A wide range of N-substituents was evaluated to determine the optimal substituent providing a high M3 receptor potency, high intrinsic clearance and high human plasma protein binding. Compounds achieving in vitro study criteria were selected for in vivo evaluation. Pharmacokinetic half-lives, inhibition of bronchoconstriction and duration of action, as well as systemic side effects, induced by the compounds were assessed in guinea-pig models. Compounds with a long duration of action and good therapeutic index were identified and AZD8683 was selected for progression to the clinic.

Diversity in Australia’s freshwater fish fauna is relatively depauperate when compared toother landmasses. However the family Melanotaeniidae is one of Australia’s most widespread andspeciose groups of freshwater fishes. As such, they are an ideal group in which to examinefreshwater phylogeography within Australia, as they offer the opportunity to compare species withdifferent niches, but similar evolutionary history. This dissertation investigates patterns of geneticdiversity in three species of Australian freshwater rainbowfishes, two co-distributed species withdistinct niches in undisturbed habitat, and one species in an urban habitat, and explores thehistorical and contemporary processes that have influenced them.In my first chapter I used two co-distributed Melanotaenia species to test the hypothesis thata widespread habitat generalist will have lower levels of genetic diversity and population structurethan a closely related habitat specialist. I used sequence from one mitochondrial gene and onenuclear gene to investigate patterns of genetic diversity in M. splendida and M. trifasciata and todetermine how differences in habitat preference and historical changes in drainage boundaries haveaffected patterns of connectivity and isolation. M. splendida, a widespread species found in the vastmajority of freshwater habitats in northern Australia, showed high levels of genetic diversity, andvery little population structure across its range. Conversely, M. trifasciata, having a greatlycontracted distribution to the northernmost rivers of Queensland and the Northern Territory andhabitat preference for faster flowing, highly oxygenated upland streams, showed extremely highlevels of population structure. While phylogeographic patterns differed, both showed a strongrelationship between stream length and genetic distance. For M. trifasciata genetic distance wasbest explained by stream length within catchments, and an ocean distance at 100x coast length,likely reflecting infrequent dispersal between catchments at times of low sea level (r2 = 0.82). M.splendida had a much shallower relationship with geographic distance, and genetic distance wasbest explained by stream length and a weaker ocean distance (10x coast length), suggesting greaterrates of gene exchange. These results suggest that, although these species are co-distributed theyappear to have experienced different evolutionary histories, with differences in habitat preferencewithin waterways resulting in contrasting scales of genetic patterns.In chapter two I identified hybrid zones between co-distributed M. splendida and M.trifasciata at the periphery of M. trifasciata's distribution. I used morphological identification,mtDNA sequences and two nuclear single nucleotide polymorphism (SNP) diagnostic restrictionassays to characterize incidence, levels and directionality of gene flow between these tworeciprocally monophyletic taxa. Four populations were identified as having undergone extensivehybridization between M. splendida and M. trifasciata. Patterns of gene flow between the two taxawere different in different hybridizing populations with complete mitochondrial capture evident in two populations, uni-directional introgression in a third population, and a complete mixture ofmorphological hybrids and bi-directional gene exchange in the fourth population. This diversity inpatterns of hybridization between two species is unusual and could potentially be due to localenvironmental conditions, although further research is required to determine the processes that aredriving this pattern.In chapter four I investigated how different aspects of habitat degradation affect the geneticdiversity of an Australian native rainbowfish, Rhadinocentrus ornatus, distributed in a highlydeveloped region (southeast Queensland) and what impacts this may have on this species’conservation status. Based on mtDNA sequence data from 327 individuals and 20 populations, Iidentified three distinct genetic lineages that were allopatric at the stream level. Indicators of habitatdegradation had large negative effects on measures of genetic diversity, with close proximity tourban development and alterations to waterways associated with drastically reduced measures ofgenetic diversity across three distinct mtDNA lineages (evolutionary significant units). Loweffective population sizes and low standing genetic variation in degraded habitats may result inreduced adaptive potential in this already threatened narrow range endemic. The only surveyedpopulations with high genetic diversity were found in already protected national parks. Manyhistorical populations of R. ornatus in the highly developed Greater Brisbane Region are alreadyprobably extinct, and without further study and management this may be the fate of presentlygenetically depauperate populations in urban areas.This thesis represents the most comprehensive study to date of rainbowfish populationgenetics. Researching multiple species within the same genus, and sampling a large proportion ofeach species range has provided me with substantial power to infer the evolutionary andcontemporary processes that have shaped genetic diversity and connectivity in three species.Contrasting phylogeographic patterns from two co-distributed species with different environmentalniches occurring in relatively pristine habitats provided insight into long-term evolutionaryprocesses. Sampling large numbers of populations, both in pristine and developed habitats, providedinformation on ecologically relevant forces shaping fine scale connectivity. This work adds togrowing literature on population genetics of Australian freshwater fishes and specifically howhistorical changes in landscape connectivity, hybridization and urban development shape patterns ofgenetic diversity in Australian rainbowfishes.

Objective To identify factors influencing the time taken to either admit or discharge elderly patients from an emergency department. Design A cohort of patients aged 60 years and over was followed by an independent team of investigators until discharge from the emergency department. Setting The study took place over one week in the winter of 1995 in the St George Hospital Emergency Department, Sydney, a 600 bed teaching hospital. Main outcome measures The time spent waiting for medical attention, time taken to prepare the patient for admission or departure home and time spent waiting for transfer to a ward or home. Results The waiting times for less urgent cases did not meet the current NSW Health Department targets. Emergency department staff specialists and registrars took less time to prepare patients for admission compared with residents and interns (two hours vs three hours). While elderly patients generally had to wait long periods in the emergency department for a ward bed, there were significant differences in the waiting times for different specialties; average times were 4.8 hours for a surgical, 8.8 hours for a medical, and 27.2 hours for an aged care bed. Conclusion More medical staff may be required to reduce waiting times for less urgent cases. The time taken to ready patients for admission would be reduced if there were a higher proportion of senior medical staff. There is a need for improved availability of ward beds, particularly medical and aged care beds, for patients admitted through the emergency department.

A solid-phase, iridium-based ortho-exchange catalyst has been developed, with the aim of producing cleaner, more efficient, systems for tritium and deuterium labelling. The catalyst, which is a solvated polystyrene-bound triphenylphosphine complex of cyclooctadienyliridium(I) hexafluorophosphate, was evaluated with respect to more conventional catalysts such as CODIr(PPh 3 ) 2 PF 6 and the Crabtree catalyst using simple model compounds as substrates. Labelling of drug candidate molecules proceeds with high regioselectivity and, after a simple filtration step, affords products with high radiochemical purities directly from the exchange reaction. The solid-phase catalyst functioned well with a variety of traditional directing groups including nitro, amide, benzophenone and N-heterocycles.

A wide range of anilines, benzylamines and some N-heterocyclics can be ortho-deuterated at room temperature using deuterium gas and cycloocta-1,5-dienyliridium(I)-1,1,1,5,5,5-hexafluoropentan-2,4-dionate in DMF or DMA. The method is applicable to labelling with tritium. Copyright © 2004 John Wiley & Sons, Ltd.

“Synthesis & Application of Labelled Compounds 2002” Isotopes and Mass Spectrometry Carbon-13 Labelling to Aid the Development of the Catalytic Alkenation of Carbonyls Production and Applications of 124I for Positron Emission Tomography Organic Photochemistry: Synthetic Approaches to Alkaloids in a Reagentless Environment Fluorinaion for Positron Emission Tomography Synthetic Consequences of Kinetic Isotopes Effects: Synthesis of [13 C6]-SR31742A For Human Trail Purposes Tritio-Dehalogenation: New Variants on an Old Theme The Synthesis of BOC-L-Proline-[14C2] Benzyl Ester Peptide Labelling with Fluorine-18

The tenth annual symposium of the International Isotope Society's United Kingdom Group took place at the Alderley Park site of AstraZeneca plc. The symposium was attended by over 80 delegates from academia, the pharmaceutical and agrochemical industries, life science and fine chemical companies. Delegates were welcomed to the site by Dr Peter Warner of the Medicinal Chemistry Department. The scientific programme consisted of presentations on isotopic chemistry and applications of labelled compounds, or of chemistry with significant implications for isotopic synthesis. Both short-lived and long-lived isotopes were represented, as were stable isotopes. The programme was split into a morning and afternoon session chaired by Dr John Harding (AstraZeneca, who also organised the excellent domestic programme) and Dr Karl Cable (Glaxo Wellcome). The meeting ended with concluding remarks from Dr Ken Lawrie (SmithKline Beecham), chairman of the UK Group. This years symposium had a larger attendance from other European countries, an excellent level of sponsorship was achieved, and the symposium proved self-financing. The next UK group symposium is planned for early October 2001. Meeting Programme Paul Pringle [University of Bristol, UK] To what extent can Homogeneous Catalysts be Designed? Henrick Olsen [Novo Nordisk, Denmark] Mapping of Pharmaceutical Degradation Products in the Solid Dosage Form using Radiotracers. Marie-Claire Lasne [University of Caen, France] Synthesis of New Ligands of Cholinergic Receptors. Strategies for their Radiolabelling with Positron Emitters, Carbon-11 or Fluorine-18. Christopher Rayner [University of Leeds, UK] Catalysis in Supercritical Carbon Dioxide - What advantages does it have to Offer? Gunnar Antoni, [University of Uppsala, Sweden] Position Specific Labelling of Biomedically Interesting Compounds using Short-Lived Radionuclides. Hugh Wiltshire [Hoffmann-La Roche, UK] The Use of Stable-Labelled Isotopes in Bioequivalence Studies with the HIV-Protease inhibitor Saquinavir. Alison Hill [Kings College, UK] Elucidation of Soraphen A Biosynthesis using2H, 13C and18O-Labelled Precursors. Nick Shipley [Glaxo Wellcome, UK] Preparation of P450 Substrates for use in Drug-drug Interactions Andrew Mather [AstraZeneca, UK] Aspects of Isotopic Labelling by Parallel Chemistry. Helen Booth [Astra Zeneca, UK] Synthesis of14C-labelled forms of a series of Human Leukocyte Elastase Inhibitors.

A dissociation-enhanced lathanide fluorescence immunoassay (DELFIA) method has been developed for the determination of AR-C68397XX, a novel respiratory therapeutic agent, in human plasma. The method is a 'direct' immunoassay and provides an alternative to the solid phase extraction RIA described in a previous publication, which employs the same specific antiserum. The DELFIA method is suitable for the determination of the analyte at pg ml(-1) concentrations. The non-isotopic label was prepared by complexation of a DTPA derivative of AR-C68397XX with free europium cation (Eu3+). Plasma samples were diluted at least 5-fold prior to analysis to eliminate matrix interference. The calibration range is 10-2000 pg ml(-1), and the LOQ of the method is 50 pg ml(-1) using 50 microl of diluted human plasma sample.

The anti-epileptic agent remacemide hydrochloride has been prepared labelled with 14C, from [carbonyl-14C]acetophenone, and with 13C from [13C6]benzene, [1,2-13C]acetyl chloride and [1-13C]glycine. [2-3H]Glycine was utilised to prepare remacemide labelled with tritium at low specific activity. In addition other 2H- and high specific activity 3H-isotopomers of the drug, and of an active metabolite of the drug, were prepared by hydrogen isotope exchange methodology. The R-12C/S-14C and S-12C/R-14C pseudoracemic drugs were also prepared by a synthesis involving resolution of a 14C-labelled amine intermediate via fractional crystallisation of the dibenzoyltartrate salts. Copyright © 2000 John Wiley & Sons, Ltd.

Novel iridium-based catalysts which promote ortho -directed hydrogen isotope exchange between substituted aromatics and isotopic water have been identified via a combination of screening and subsequent ligand optimisation. The catalysts are more active, operate at lower temperature and are applicable to a wider variety of substrates than previously known systems.

A lead generation and optimization program delivered the highly selective and potent CatC inhibitor 10 as an in vivo tool compound and potential development candidate. Structural studies were undertaken to generate SAR understanding.

A wide range of aromatic compounds containing suitable directing groups can be labelled efficiently with deuterium using isotopic exchange catalysed by an easily prepared polystyrene based ortho-exchange catalyst. The labelling reactions can be carried out efficiently at ambient temperature by simple stirring of the substrate and catalyst under a deuterium atmosphere for a few hours. Isolation consists of a simple filtration and evaporation of the solvent. Deuterium is incorporated with ortho-regiospecificity.

A number of tumour cells, including Ehrlich ascites tumour cells (EATC), possess a polyamine uptake system which selectively accumulates endogenous polyamines and structurally related compounds by an active energy dependent system(s). We suggest that it may be possible to utilize this uptake system to target certain cytotoxic agents to those tumour cells possessing this system. In an initial attempt to determine the feasibility of this suggestion, we have synthesized a series of 2- and 5-nitroimidazoles linked to polyamines and determined their ability to utilize the polyamine uptake system. Within the limited series of compounds synthesized, 2-nitroimidazole-polyamine conjugates were more potent inhibitors of spermidine uptake into EATC than the 5-nitroimidazole conjugates. It has been assumed partly based on the competitive nature of this inhibition, that the ability of these compounds to inhibit spermidine uptake is also a measure of their ability to be accumulated by EATC. A greater than 700-fold variation was observed in the ability of different analogues to inhibit spermidine uptake. The most potent inhibitors retained certain structural characteristics similar to those of spermidine. Those compounds linked to polyamines were much more potent inhibitors of polyamine uptake than the parent nitroimidazoles i.e. metronidazole and misonidazole. The toxicity of the parent compounds and their polyamine conjugates in control and polyamine-depleted EATC was assessed by measuring inhibition of tritiated thymidine incorporation. Polyamine depletion, by prior exposure to difluoromethylornithine, results in a compensatory increase in the uptake of polyamines and related structures which may result in an increase in toxicity. Whilst many of the novel conjugates showed only little or moderate toxicity to control cells, the toxicity of several of the conjugates but not the parent nitroimidazoles increased in the polyamine-depleted cells. A clear distinction was also observed between the ability to inhibit spermidine uptake (and hence affinity for the uptake system) and toxicity, e.g. compound 430, a dinitroimidazole-polyamine conjugate, was the best inhibitor of spermidine uptake studied but showed no toxicity. These results support the hypothesis that linking polyamines to nitroimidazoles facilitates the entry of the latter into cells, such as EATC, which possess the polyamine uptake system and may therefore have therapeutic application in the delivery of polyamine-linked cytotoxics to certain tumours.

Despite growing evidence of rapid evolution in protein coding genes, the contribution of positive selection to intra- and interspecific differences in protein coding regions of the genome is unclear. We attempted to see if genes coding for secreted proteins and genes with narrow expression, specifically those preferentially expressed in the mammary gland, have diverged at a faster rate between domestic cattle (Bos taurus) and humans (Homo sapiens) than other genes and whether positive selection is responsible. Using a large data set, we identified groups of genes based on secretion and expression patterns and compared them for the rate of nonsynonymous (dN) and synonymous (dS) substitutions per site and the number of radical (Dr) and conservative (Dc) amino acid substitutions. We found evidence of rapid evolution in genes with narrow expression, especially for those expressed in the liver and mammary gland and for genes coding for secreted proteins. We compared common human polymorphism data with human-cattle divergence and found that genes with high evolutionary rates in human-cattle divergence also had a large number of common human polymorphisms. This argues against positive selection causing rapid divergence in these groups of genes. In most cases dN/dS ratios were lower in human-cattle divergence than in common human polymorphism presumably due to differences in the effectiveness of purifying selection between long-term divergence and short-term polymorphism.

An efficient synthesis of the chlorambucil–spermidine conjugate 4 has been achieved via N1,N8-bis-Boc-spermidine and 4 has been shown to crosslink DNA 104 times more efficiently than chlorambucil itself.

A radioimmunoassay has been developed for the determination of AR-C68397XX, a dual D 2 -receptor and β 2 -adrenoceptor agonist, in human plasma. The method incorporates solid phase sample extraction and is suitable for the determination of the analyte at pg ml −1 concentrations. The antiserum was raised in Suffolk cross sheep following primary and booster immunisations with an immunogen prepared by conjugating a carboxyphenylmethyl derivative of AR-C68397XX, to bovine serum albumin. The radioligand was prepared by the 125 I-labelled iodination of a derivative of AR-C68397XX. The solid phase extraction procedure, using octadecyl sorbent, was introduced to remove matrix interferences in the plasma and to enhance method sensitivity. The calibration range is 20–500 pg ml −1 , using 0.5 ml of undiluted human plasma sample.

Exposure of a range of DNA samples in various media to 60Co γ-rays at 77 K gives electron-capture centres characterized by an EPR doublet with A(1H) of ca. 16 G. Since the electron-adducts of C and T give very similar doublet EPR spectra in irradiated DNA, it is difficult to judge the proportions of C˙– and T˙– formation by inspection. The possibility, suggested by others, that computer fits can be used to give a quantitative measure of these species is discussed. However, in view of the variability of the features directly assignable to C˙– and T˙– units in different environments, we suggest that this approach has only qualitative significance.The alternative method involves annealing to convert T˙– into TH˙ radicals in which a hydrogen atom is added to C6, the resulting radical having a completely characteristic octet EPR spectrum. It is argued that the ejected electrons move through the stacked DNA bases, becoming trapped at C or T depending upon the relative rates at which C˙– and T˙– are protonated to give C˙–(H+)(protonated at N3) and T˙–(H+)(protonated on oxygen). If this is correct, interconversion between C˙– and T˙– on annealing is unlikely, and only T˙– can lead to TH˙ formation.This is also not accurate, since TH˙ decay sets in within the same temperature range as it is being formed. By generating TH˙ from frozen aqueous DNA with ultraviolet light, the pure decay annealing curve has been obtained, and using this we have been able to extrapolate the data for TH˙ from the γ-irradiated samples to give the real yields of TH˙. The results show that ca. 36% of the doublet must be due to T˙– centres, the remainder (64%) being assigned to C˙– centres.The ratio of C˙– to T˙– varies with the DNA source, and with the environment. We suggest that it is largely governed by the relative rates of protonation to give C˙–(H+) and T˙–(H+), and the factors controlling these rates are discussed. The use of lithium chloride glasses completely suppresses the formation of G˙+ centres, leaving well-defined radical-anion spectra, but on annealing, conversion to TH˙ is negligible despite the rapid, and complete, loss of the doublet species. This result is discussed in terms of reaction with Cl2˙– radicals formed in abundance in these glasses.Studies designed to detect any site-specificity in the DNA damage leading to strand breaks suggest that all possible sites are damaged. These results strongly support the postulate that yields of C˙– and T˙– are comparable. The possibility that some A˙+ cations are formed in addition to G˙+ cations is also considered in the light of these results.