Crop production in the USA is frequently limited by a lack of pollinators.

Most of the world's crops depend on pollinators, so declines in both managed and wild bees raise concerns about food security. However, the degree to which insect pollination is actually limiting current crop production is poorly understood, as is the role of wild species (as opposed to managed honeybees) in pollinating crops, particularly in intensive production areas. We established a nationwide study to assess the extent of pollinator limitation in seven crops at 131 locations situated across major crop-producing areas of the USA. We found that five out of seven crops showed evidence of pollinator limitation. Wild bees and honeybees provided comparable amounts of pollination for most crops, even in agriculturally intensive regions. We estimated the nationwide annual production value of wild pollinators to the seven crops we studied at over $1.5 billion; the value of wild bee pollination of all pollinator-dependent crops would be much greater. Our findings show that pollinator declines could translate directly into decreased yields or production for most of the crops studied, and that wild species contribute substantially to pollination of most study crops in major crop-producing regions.

The locus of sexual selection: moving sexual selection studies into the post-genomics era.

Sexual selection drives fundamental evolutionary processes such as trait elaboration and speciation. Despite this importance, there are surprisingly few examples of genes unequivocally responsible for variation in sexually selected phenotypes. This lack of information inhibits our ability to predict phenotypic change due to universal behaviours, such as fighting over mates and mate choice. Here, we discuss reasons for this apparent gap and provide recommendations for how it can be overcome by adopting contemporary genomic methods, exploiting underutilized taxa that may be ideal for detecting the effects of sexual selection and adopting appropriate experimental paradigms. Identifying genes that determine variation in sexually selected traits has the potential to improve theoretical models and reveal whether the genetic changes underlying phenotypic novelty utilize common or unique molecular mechanisms. Such a genomic approach to sexual selection will help answer questions in the evolution of sexually selected phenotypes that were first asked by Darwin and can furthermore serve as a model for the application of genomics in all areas of evolutionary biology.

Patient preferences for timing and access to radiation therapy.

PURPOSE: Patient preferences for radiation therapy (rt) access were investigated. METHODS: Patients completing a course of rt at 6 centres received a 17-item survey that rated preferences for time of day; day of week; actual, ideal, and reasonable travel times for rt; and actual, ideal, and reasonable times between referral and first oncologic consultation. Patients receiving single-fraction rt or brachytherapy alone were excluded. RESULTS: Of the respondents who returned surveys (n = 1053), 54% were women, and 74% had received more than 15 rt fractions. With respect to appointment times, 88% agreed or strongly agreed that rt between 08h00 and 16h30 was preferred; 14%-15% preferred 07h30-08h00 or 16h30-17h00; 10% preferred 17h00-18h00; and 6% or fewer preferred times before 07h30 or after 18h00. A preference not to receive rt before 07h30 or after 18h00 was expressed by 30% or more of the respondents. When days of the week were considered, 18% and 11% would have preferred to receive rt on a Saturday or Sunday respectively; 52% and 55% would have preferred not to receive rt on those days. A travel time of 1 hour or less for rt was reported by 82%, but 61% felt that a travel time of 1 hour or more was reasonable. A first consultation within 2 weeks of referral was felt to be ideal or reasonable by 88% and 73% of patients respectively. CONCLUSIONS: An rt service designed to meet patient preferences would make most capacity available between 08h00 and 16h30 on weekdays and provide 10%-20% of rt capacity on weekends and during 07h30-08h00 and 16h30-18h00 on weekdays. Approximately 80%, but not all, of the responding patients preferred a 2-week or shorter interval between referral and first oncologic consultation.

Interactive effects of competition and social environment on the expression of sexual dimorphism.

The expression of sexual dimorphism is expected to be influenced by the acquisition of resources available to allocate to trait growth, combined with sex-specific patterns of resource allocation. Resource acquisition in the wild may be mediated by a variety of ecological factors, such as the density of interspecific competitors. Allocation may in turn depend on social contexts, such as sex ratio, that alter the pay-off for investment in sexual traits. How these factors interact to promote or constrain the expression and evolution of sexual dimorphism is poorly understood. We manipulated sex ratio and interspecific resource competition over the growing season of red-spotted newts (Notophthalmus viridescens) in artificial ponds. Fish competitors had a stronger effect on female than male growth, which effectively eliminated the expression of sexual size dimorphism. In addition, newt sex ratio influenced fish growth, leading to reduction in fish mass with an increase in female newt frequency. Fish also reduced the expression of male tail height, a sexually selected trait, but only in tanks with a female-biased sex ratio. This suggests males alter their resource allocation pattern in response to the strength of sexual selection. Our results demonstrate that ecologically and socially mediated interactions between sex-specific resource acquisition and allocation can contribute to variation in the expression of sexual dimorphism.

A multivariate view of the evolution of sexual dimorphism.

Sexual differences are often dramatic and widespread across taxa. Their extravagance and ubiquity can be puzzling because the common underlying genome of males and females is expected to impede rather than foster phenotypic divergence. Widespread dimorphism, despite a shared genome, may be more readily explained by considering the multivariate, rather than univariate, framework governing the evolution of sexual dimorphism. In the univariate formulation, differences in genetic variances and a low intersexual genetic correlation (rMF) can facilitate the evolution of sexual dimorphism. However, studies that have analysed sex-specific differences in heritabilities or genetic variances do not always find significant differences. Furthermore, many of the reported estimates of rMF are very high and positive. When monomorphic heritabilities and a high rMF are present together, the evolution of sexual dimorphism on a trait-by-trait basis is severely constrained. By contrast, the multivariate formulation has greater generality and more flexibility. Although the number of multivariate sexual dimorphism studies is low, almost all support sex-specific differences in the G (variance-covariance) matrix; G matrices can differ with respect to size and/or orientation, affecting the response to selection differently between the sexes. Second, whereas positive values of the univariate quantity rMF only hinder positive changes in sexual dimorphism, positive covariances in the intersexual covariance B matrix can either help or hinder. Similarly, the handful of studies reporting B matrices indicate that it is often asymmetric, so that B can affect the evolution of single traits differently between the sexes. Multivariate approaches typically demonstrate that genetic covariances among traits can strongly constrain trait evolution when compared with univariate approaches. By contrast, in the evolution of sexual dimorphism, a multivariate view potentially reveals more opportunities for sexual dimorphism to evolve by considering the effect sex-specific selection has on sex-specific G matrices and an asymmetric B matrix.

Fecundity selection on ornamental plumage colour differs between ages and sexes and varies over small spatial scales.

Avian plumage colours are some of the most conspicuous sexual ornaments, and yet standardized selection gradients for plumage colour have rarely been quantified. We examined patterns of fecundity selection on plumage colour in blue tits (Cyanistes caeruleus L.). When not accounting for environmental heterogeneity, we detected relatively few cases of selection. We found significant disruptive selection on adult male crown colour and yearling female chest colour and marginally nonsignificant positive linear selection on adult female crown colour. We discovered no new significant selection gradients with canonical rotation of the matrix of nonlinear selection. Next, using a long-term data set, we identified territory-level environmental variables that predicted fecundity to determine whether these variables influenced patterns of plumage selection. The first of these variables, the density of oaks within 50 m of the nest, influenced selection gradients only for yearling males. The second variable, an inverse function of nesting density, interacted with a subset of plumage selection gradients for yearling males and adult females, although the strength and direction of selection did not vary predictably with population density across these analyses. Overall, fecundity selection on plumage colour in blue tits appeared rare and inconsistent among sexes and age classes.

Ontogenetic change in genetic variance in size depends on growth environment.

Within populations, the amount of environmental and genetic variation present may differ greatly among traits measured at multiple times over ontogeny. Brief periods of food deprivation are often followed by a period of accelerated (compensatory) growth. Early laboratory studies likewise reported a contraction of genetic variance in size as maturation approached. However, studies of wild populations often contradict these laboratory results. One possibility is that environmentally imposed stress is exposing genetic variance not seen in the laboratory. We tested the effect of rearing environment (high or low food) on genetic variance in size traits measured at two ages in the ladybird beetle Harmonia axyridis. A substantial amount of genetic variance was present in all combinations of rearing environment by ontogenetic stage among males. The pattern of change in male variance in mass over ontogeny was of opposite sign in the two food treatments, which may reflect cryptic genetic variance that is apparent only under stress. The proportion of overall variance that was due to additive genetic effects was much lower in females than in males, which suggests that the underlying genetics of female growth trajectories differs from that males. Our experimental design afforded an initial exploration of the genetics of compensatory growth.

U-type exchange is the most frequent mechanism for inverted duplication with terminal deletion rearrangements.

BACKGROUND: Chromosomal rearrangements resulting in an interstitial inverted duplication with concomitant terminal deletion were first described for the short arm of chromosome 8 in 1976. Since then, this type of alteration has been identified and characterised for most chromosome arms. Three mechanisms are commonly proposed to explain the origin of this type of rearrangement. All three mechanisms involve formation of a dicentric chromosome that then breaks in a subsequent meiotic division to produce a monocentric duplicated and deleted chromosome. However, the events leading to the formation of the dicentric chromosome differ between the mechanisms. In one mechanism, either parent carries a paracentric inversion. This results in formation of a loop during meiotic pairing with a recombination event occurring in the loop. In the second mechanism, inverted low copy repeats in the same chromosome arm allow partial folding of one homologue onto itself with a recombination event between the inverted repeats. The third mechanism involves a pre-meiotic double-strand break with subsequent fusion, or U-type exchange, between the sister chromatids. The first two mechanisms require a single copy region to exist between the duplicated and deleted regions on the derivative chromosome, and therefore high resolution analysis of the rearrangement can be used to distinguish between these mechanisms. METHODS AND RESULTS: Using G-banded chromosome analysis, fluorescence in situ hybridisation (FISH) and array comparative genomic hybridisation (CGH), we describe 17 new cases of inverted duplication with terminal deletion of 2q, 4p, 5p, 6q, 8p, 9p, 10q, 13q, 15q, 18p, 18q, and 22q. CONCLUSIONS: These new cases, combined with previously described cases, demonstrate that U-type exchange is the most frequent mechanism for this rearrangement and can be observed on most, or perhaps all, chromosome arms.

The addition of Valproic acid to concurrent radiation therapy and temozolomide improves patient outcome: a Correlative analysis of RTOG 0525, SEER and a Phase II NCI trial.

PURPOSE/OBJECTIVES: Valproic Acid (VPA) is an antiepileptic agent with HDACi (histone deacetylase inhibitor) activity shown to radiosensitize glioblastoma (GBM) cells. We evaluated the addition of VPA to standard radiation therapy (RT) and temozolomide (TMZ) in an open-label, phase II study (NCI-06-C-0112). The intent of the current study was to compare our patient outcomes with modern era standard of care data (RTOG 0525) and general population data (SEER 2006-2013). MATERIALS/METHODS: 37 patients with newly diagnosed GBM were treated in a phase II NCI trial with daily VPA (25 mg/kg) in addition to concurrent RT and TMZ (2006 - 2013) and 411 patients with newly diagnosed GBM were treated in the standard TMZ dose arm of RTOG 0525 (2006 - 2008). Using the SEER database, adult patients (age > 15) with diagnostic codes 9440-9443 (third edition (IDC-O-3) diagnosed between 2006 - 2013 were identified and 6083 were included in the analysis. Kaplan-Meier method was used to estimate OS and PFS. The effect of patient characteristics and clinical factors on OS and PFS was analyzed using univariate analysis and a Cox regression model. A landmark analysis was performed to correlate recurrence to OS and conditional probabilities of surviving an additional 12 months at diagnosis, 6, 12, 18, 24 and 30 months were calculated for both the trial data and the SEER data. RESULTS: Updated median OS in the NCI cohort was 30.9m (22.2- 65.6m), compared to RTOG 0525 18.9m (16.8-20.3m) (p= 0.007) and the SEER cohort of 11m. Median PFS in the NCI cohort was 11.1m (6.6 - 49.6m) compared to RTOG 0525 with a median PFS of 7.5m (6.9-8.2m) (p = 0.004). Younger age, class V RPA and MGMT status were significant for PFS in both the NCI cohort and the RTOG 0525 cohort, in addition KPS was also significant for OS. In comparison to RTOG 0525, the population in the NCI cohort had a more favorable KPS and RPA, and a higher proportion of patients receiving bevacizumab after protocol therapy however with the exception of RPA (V) (8% vs 18%) (0.026), the effects of these factors on PFS and OS were not significantly different between the two cohorts. CONCLUSION: Previously reported improvements in PFS and OS with the addition of VPA to concurrent RT and TMZ in the NCI phase II study were confirmed by comparison to both a trial population receiving standard of care (RTOG 0525) and a contemporary SEER cohort. These results provide further justification of a phase III trial of VPA/RT/TMZ.

Mars Extant Life: What's Next? Conference Report.

On November 5-8, 2019, the "Mars Extant Life: What's Next?" conference was convened in Carlsbad, New Mexico. The conference gathered a community of actively publishing experts in disciplines related to habitability and astrobiology. Primary conclusions are as follows: A significant subset of conference attendees concluded that there is a realistic possibility that Mars hosts indigenous microbial life. A powerful theme that permeated the conference is that the key to the search for martian extant life lies in identifying and exploring refugia ("oases"), where conditions are either permanently or episodically significantly more hospitable than average. Based on our existing knowledge of Mars, conference participants highlighted four potential martian refugium (not listed in priority order): Caves, Deep Subsurface, Ices, and Salts. The conference group did not attempt to reach a consensus prioritization of these candidate environments, but instead felt that a defensible prioritization would require a future competitive process. Within the context of these candidate environments, we identified a variety of geological search strategies that could narrow the search space. Additionally, we summarized a number of measurement techniques that could be used to detect evidence of extant life (if present). Again, it was not within the scope of the conference to prioritize these measurement techniques-that is best left for the competitive process. We specifically note that the number and sensitivity of detection methods that could be implemented if samples were returned to Earth greatly exceed the methodologies that could be used at Mars. Finally, important lessons to guide extant life search processes can be derived both from experiments carried out in terrestrial laboratories and analog field sites and from theoretical modeling.

Hair interior defect in AKR/J mice.

BACKGROUND: All AKR/J mice have a subtle defect that involves malformation of the central portion of hair fibres that is best visualized under white and polarized light microscopy. AIMS: This study sought to characterize the clinical and ultrastructural features of the hair interior defect (HID) phenotype and to determine the chromosomal localization of the hid mutant gene locus. METHODS: White and polarized light microscopy combined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the HID phenotype. Complementation testing and gene-linkage studies were performed to map the locus. RESULTS: Using SEM, the hair-fibre structure on the surface was found to be similar to hairs obtained from normal BALB/cByJ+/+and C57BL/6 J+/+mice. There were also no differences in sulphur content. TEM revealed degenerative changes in the medulla similar to that seen by light microscopy. This autosomal recessive mutation is called HID (locus symbol: hid). We mapped the hid locus to the distal end of mouse chromosome 1. No genes reported to cause skin or hair abnormalities are known to be within this interval except for the lamin B receptor (Lbr), which had been excluded previously as the cause of the hid phenotype in AKR/J mice. CONCLUSION: A potentially novel gene or known gene with a novel phenotype resides within this interval, which may shed light on human diseases with defects in the inner structure of the hair fibre.

Spectral tuning of photoproteins by partnering site-directed mutagenesis strategies with the incorporation of chromophore analogs.

Aequorin and obelin are photoproteins whose calcium controlled bioluminescent light emission is used for labeling in assays, for the determination of calcium concentrations in vivo, and as a reporter in cellular imaging. Both of these photoproteins emit blue light from a 2-hydroperoxycoelenterazine chromophore, which is non-covalently bound in the hydrophobic core of the proteins. In an effort to produce aequorin and obelin variants with improved analytical properties, such as alternative emission colors and altered decay kinetics, seven mutants of aequorin and obelin were prepared and combined with 10 different coelenterazine analogs. These semi-synthetic photoprotein mutants exhibited shifts in bioluminescent properties when compared with wild-type proteins. The bioluminescent parameters determined for these semi-synthetic photoprotein mutants included specific activity, emission spectra and decay half-life time. This spectral tuning strategy resulted in semi-synthetic photoprotein mutants that had significantly altered bioluminescent properties. The largest emission maxima shift obtained was 44 nm, and the largest decay half-life difference was 23.91 s.

Condition dependence of sexually dimorphic colouration and longevity in the ambush bug Phymata americana.

Sexually selected traits that are costly are predicted to be more condition dependent than nonsexually selected traits. Assuming resource limitation, increased allocation to a sexually selected trait may also come at a cost to other fitness components. To test these predictions, we varied adult food ration to manipulate condition in the colour dimorphic bug, Phymata americana. We compared the degree of condition dependence in a sexually selected trait expressed in males to a nonsexually selected trait expressed in males and females. We also evaluated the effects of condition on longevity of both sexes. We found that the expression of these colour pattern traits was strongly influenced by both diet and age. As expected, the strength of condition dependence was much more pronounced in the sexually selected, male-limited trait but the nonsexual trait also exhibited significant condition dependence in both sexes. The sexually selected male trait also exhibited a higher coefficient of phenotypic variation than the nonsexually selected trait in males and females. Diet had contrasting effects on male and female longevity; increased food availability had positive effects on female lifespan but these effects were not detected in males, suggesting that males allocated limited resources preferentially to sexually selected traits. These results are consistent with the expectation that optimal allocation to various fitness components differs between the sexes.

Role of procollagen mRNA levels in controlling the rate of procollagen synthesis.

Two factors must be present for primary avian tendon cells to commit 50% of their total protein production to procollagen: ascorbate and high cell density. Scorbutic primary avian tendon cells at high cell density (greater than 4 X 10(4) cells per cm2) responded to the addition of ascorbate by a sixfold increase in the rate of procollagen synthesis. The kinetics were biphasic, showing a slow increase during the first 12 h followed by a more rapid rise to a maximum after 36 to 48 h. In contrast, after ascorbate addition, the level of accumulated cytoplasmic procollagen mRNA (alpha 2) showed a 12-h lag followed by a slow linear increase requiring 60 to 72 h to reach full induction. At all stages of the induction process, the relative increase in the rate of procollagen synthesis over the uninduced state exceeded the relative increase in the accumulation of procollagen mRNA. A similar delay in mRNA induction was observed when the cells were grown in an ascorbate-containing medium but the cell density was allowed to increase. In all cases, the rate of procollagen synthesis peaked approximately 24 h before the maximum accumulation of procollagen mRNA. The kinetics for the increase in procollagen synthesis are not, therefore, in agreement with the simple model that mRNA levels are the rate-limiting factor in the collagen pathway. We propose that the primary control point is at a later step. Further support for this idea comes from inhibitor studies, using alpha, alpha'-dipyridyl to block ascorbate action. In the presence of 0.3 mM alpha, alpha'-dipyridyl there was a specific two- to threefold decrease in procollagen production after 4 h, but this was unaccompanied by a drop in procollagen mRNA levels. Therefore, inhibitor studies give further support to the idea that primary action of ascorbate is to release a post-translational block.

Transposition of yeast mating type genes from two translocations of the left arm of chromosome III.

In the yeast Saccharomyces cerevisiae, the HIS4C gene lies on the left arm of chromosome III. We analyzed two chromosomal rearrangements that have HIS4C translocated either to chromosome XII or to a new translocation chromosome. Using the cmt mutation that allows expression of the normally silent copies of mating type genes, we found that both of these translocations also carried HML alpha, more than 30 map units distal to HIS4C which normally lies on chromosome III. In the case of the translocation chromosome (designated T3), we also found an exchange event between HML alpha on the translocation chromosome and HMLa on chromosome III. In diploids containing two T3 chromosomes (one carrying HML alpha and the carrying HMLa), we found that HML was 32 centimorgans from HIS4C, which was 10 centimorgans from an unknown centromere. In homothallic strains carrying HMLa MATa HMRa on chromosome III, switching from MATa to MAT alpha could occur by using the HML alpha on the translocation as the sole donor of alpha information. Transposition from HML alpha on chromosome T3 was about 20 to 40% as efficient as transposition from intact chromosome III. In contrast, transposition from the HML alpha inserted into chromosome XII was reduced about 100-fold. This reduced efficiency did not appear to be caused by an alteration in the sequences immediately surrounding HML alpha in the translocation. The translocated HML alpha sequence was located in the same size (29-kilobase) SalI fragment as was found in chromosome III, and the same EcoRI, HindIII, and BglII restriction sites were also found. Furthermore, HML alpha was still under the control of the CMT gene, which maintains HML as a silent copy of mating type information. These results suggested that the position of the HML alpha sequence plays an important role in the efficiency of mating type switching.

Alteration of intracellular traffic by monensin; mechanism, specificity and relationship to toxicity.

Monensin, a monovalent ion-selective ionophore, facilitates the transmembrane exchange of principally sodium ions for protons. The outer surface of the ionophore-ion complex is composed largely of nonpolar hydrocarbon, which imparts a high solubility to the complexes in nonpolar solvents. In biological systems, these complexes are freely soluble in the lipid components of membranes and, presumably, diffuse or shuttle through the membranes from one aqueous membrane interface to the other. The net effect for monensin is a trans-membrane exchange of sodium ions for protons. However, the interaction of an ionophore with biological membranes, and its ionophoric expression, is highly dependent on the biochemical configuration of the membrane itself. One apparent consequence of this exchange is the neutralization of acidic intracellular compartments such as the trans Golgi apparatus cisternae and associated elements, lysosomes, and certain endosomes. This is accompanied by a disruption of trans Golgi apparatus cisternae and of lysosome and acidic endosome function. At the same time, Golgi apparatus cisternae appear to swell, presumably due to osmotic uptake of water resulting from the inward movement of ions. Monensin effects on Golgi apparatus are observed in cells from a wide range of plant and animal species. The action of monensin is most often exerted on the trans half of the stacked cisternae, often near the point of exit of secretory vesicles at the trans face of the stacked cisternae, or, especially at low monensin concentrations or short exposure times, near the middle of the stacked cisternae. The effects of monensin are quite rapid in both animal and plant cells; i.e., changes in Golgi apparatus may be observed after only 2-5 min of exposure. It is implicit in these observations that the uptake of osmotically active cations is accompanied by a concomitant efflux of H+ and that a net influx of protons would be required to sustain the ionic exchange long enough to account for the swelling of cisternae observed in electron micrographs. In the Golgi apparatus, late processing events such as terminal glycosylation and proteolytic cleavages are most susceptible to inhibition by monensin. Yet, many incompletely processed molecules may still be secreted via yet poorly understood mechanisms that appear to bypass the Golgi apparatus. In endocytosis, monensin does not prevent internalization. However, intracellular degradation of internalized ligands may be prevented.(ABSTRACT TRUNCATED AT 400 WORDS)

Spx1, a novel X-linked homeobox gene expressed during spermatogenesis.

Spx1, a novel mouse homeobox gene, encodes a homeodomain characteristic of the paired-like class of homeobox genes and has been mapped to the distal end of the X chromosome. Northern blot hybridization of adult tissues detected high levels of a single Spx1 transcript in the testis. Further analysis by in situ hybridization revealed predominant Spx1 expression within the spermatogonia/preleptotene spermatocytes and round spermatids of spermatogenic stages IV-VII. These expression data suggest SPX1 may play a role in the regulation of spermatogenesis.

Advantages of gradient vs. 5-fluorouracil enrichment of stem cells for retroviral-mediated gene transfer.

Retrovirally mediated gene transfer into murine totipotent hematopoietic stem cells (THSC) may be more efficient when the donor stem cells are enriched. We have used a rapid, nontoxic density gradient separation of mouse marrow to enrich stem cells. By characterizing the cell types in various fractions of the gradient, we found the majority of the THSC, spleen colony forming stem cells (CFU-S), erythroid burst forming cells (BFU-E) and dividing cells were in the same fraction. The gradient enrichment technique was then compared with one requiring 5-fluorouracil (5-FU) treatment of donor mice prior to marrow harvest. Cells enriched by both methods were tested for their ability to mediate retroviral gene transfer into normal mice. Gradient enrichment provided only one third as many nucleated cells as 5-FU treatment from the same number of donors. During the subsequent 4-day in vitro exposure to the retrovirus and growth factors, however, the number of gradient enriched cells increased 1.6-fold while the number of 5-FU treated cells decreased 3-fold. In lethally irradiated recipients, there was no difference between gradient and 5-FU enriched donor cells in the proportion of cells that generated CFU-S nor in the percentage of CFU-S that were infected. Secondary hosts did show differences. Gradient-enriched cells maintained more survivors for up to 6 months posttransplantation and more of the survivors were positive for the retrovirus. It is clear that the gradient method provides a rapid means to enrich CFU-S and THSC without exposure to the toxic effects of 5-FU.

The use of an enzyme-labelled assay as an aid to reading micro virus-neutralisation tests.

An indirect immunoperoxidase technique has been developed for the detection of virus-infected cells after completion of a micro virus-neutralisation test. This allows visual rather than microscopic reading of the plates, which is less time-consuming and does not require a technician skilled in distinguishing between specific viral cytopathic effect and non-specific cytotoxicity. The technique proved to be more sensitive than microscopic reading for the detection of low levels of antibody and could be of great use for other viruses which do not produce a marked cytopathic effect on cells or have a slow growth rate, making development of a standard virus-neutralisation test very difficult.