Light availability determines susceptibility of reef building corals to ocean acidification

Elevated seawater pCO2, and in turn ocean acidification (OA), is now widely acknowledged to reduce calcification and growth of reef building corals. As with other environmental factors (e.g., temperature and nutrients), light availability fundamentally regulates calcification and is predicted to change for future reef environments alongside elevated pCO2 via altered physical processes (e.g., sea level rise and turbidity); however, any potential role of light in regulating the OA-induced reduction of calcification is still unknown. We employed a multifactorial growth experiment to determine how light intensity and pCO2 together modify calcification for model coral species from two key genera, Acropora horrida and Porites cylindrica, occupying similar ecological niches but with different physiologies. We show that elevated pCO2 (OA)-induced losses of calcification in the light (G L) but not darkness (G D) were greatest under low-light growth conditions, in particular for A. horrida. High-light growth conditions therefore dampened the impact of OA upon G L but not G D. Gross photosynthesis (P G) responded in a reciprocal manner to G L suggesting OA-relieved pCO2 limitation of P G under high-light growth conditions to effectively enhance G L. A multivariate analysis of past OA experiments was used to evaluate whether our test species responses were more widely applicable across their respective genera. Indeed, the light intensity for growth was identified as a significant factor influencing the OA-induced decline of calcification for species of Acropora but not Porites. Whereas low-light conditions can provide a refuge for hard corals from thermal and light stress, our study suggests that lower light availability will potentially increase the susceptibility of key coral species to OA.

Declining brain activity in cognitively normal apolipoprotein E ɛ4 heterozygotes: A foundation for using positron emission tomography to efficiently test treatments to prevent Alzheimer's disease

Cross-sectional positron emission tomography (PET) studies find that cognitively normal carriers of the apolipoprotein E (APOE) ɛ4 allele, a common Alzheimer's susceptibility gene, have abnormally low measurements of the cerebral metabolic rate for glucose (CMRgl) in the same regions as patients with Alzheimer's dementia. In this article, we characterize longitudinal CMRgl declines in cognitively normal ɛ4 heterozygotes, estimate the power of PET to test the efficacy of treatments to attenuate these declines in 2 years, and consider how this paradigm could be used to efficiently test the potential of candidate therapies for the prevention of Alzheimer's disease. We studied 10 cognitively normal ɛ4 heterozygotes and 15 ɛ4 noncarriers 50–63 years of age with a reported family history of Alzheimer's dementia before and after an interval of approximately 2 years. The ɛ4 heterozygotes had significant CMRgl declines in the vicinity of temporal, posterior cingulate, and prefrontal cortex, basal forebrain, parahippocampal gyrus, and thalamus, and these declines were significantly greater than those in the ɛ4 noncarriers. In testing candidate primary prevention therapies, we estimate that between 50 and 115 cognitively normal ɛ4 heterozygotes are needed per active and placebo treatment group to detect a 25% attenuation in these CMRgl declines with 80% power and P = 0.005 in 2 years. Assuming these CMRgl declines are related to the predisposition to Alzheimer's dementia, this study provides a paradigm for testing the potential of treatments to prevent the disorder without having to study thousands of research subjects or wait many years to determine whether or when treated individuals develop symptoms.

RNA virus error catastrophe: Direct molecular test by using ribavirin

RNA viruses evolve rapidly. One source of this ability to rapidly change is the apparently high mutation frequency in RNA virus populations. A high mutation frequency is a central tenet of the quasispecies theory. A corollary of the quasispecies theory postulates that, given their high mutation frequency, animal RNA viruses may be susceptible to error catastrophe, where they undergo a sharp drop in viability after a modest increase in mutation frequency. We recently showed that the important broad-spectrum antiviral drug ribavirin (currently used to treat hepatitis C virus infections, among others) is an RNA virus mutagen, and we proposed that ribavirin's antiviral effect is by forcing RNA viruses into error catastrophe. However, a direct demonstration of error catastrophe has not been made for ribavirin or any RNA virus mutagen. Here we describe a direct demonstration of error catastrophe by using ribavirin as the mutagen and poliovirus as a model RNA virus. We demonstrate that ribavirin's antiviral activity is exerted directly through lethal mutagenesis of the viral genetic material. A 99.3% loss in viral genome infectivity is observed after a single round of virus infection in ribavirin concentrations sufficient to cause a 9.7-fold increase in mutagenesis. Compiling data on both the mutation levels and the specific infectivities of poliovirus genomes produced in the presence of ribavirin, we have constructed a graph of error catastrophe showing that normal poliovirus indeed exists at the edge of viability. These data suggest that RNA virus mutagens may represent a promising new class of antiviral drugs.

Transferability of Regional Permafrost Disturbance Susceptibility Modelling Using Generalized Linear and Generalized Additive Models

To effectively assess and mitigate risk of permafrost disturbance, disturbance-p rone areas can be predicted through the application of susceptibility models. In this study we developed regional susceptibility models for permafrost disturbances using a field disturbance inventory to test the transferability of the model to a broader region in the Canadian High Arctic. Resulting maps of susceptibility were then used to explore the effect of terrain variables on the occurrence of disturbances within this region. To account for a large range of landscape charac- teristics, the model was calibrated using two locations: Sabine Peninsula, Melville Island, NU, and Fosheim Pen- insula, Ellesmere Island, NU. Spatial patterns of disturbance were predicted with a generalized linear model (GLM) and generalized additive model (GAM), each calibrated using disturbed and randomized undisturbed lo- cations from both locations and GIS-derived terrain predictor variables including slope, potential incoming solar radiation, wetness index, topographic position index, elevation, and distance to water. Each model was validated for the Sabine and Fosheim Peninsulas using independent data sets while the transferability of the model to an independent site was assessed at Cape Bounty, Melville Island, NU. The regional GLM and GAM validated well for both calibration sites (Sabine and Fosheim) with the area under the receiver operating curves (AUROC) N 0.79. Both models were applied directly to Cape Bounty without calibration and validated equally with AUROC's of 0.76; however, each model predicted disturbed and undisturbed samples differently. Addition- ally, the sensitivity of the transferred model was assessed using data sets with different sample sizes. Results in- dicated that models based on larger sample sizes transferred more consistently and captured the variability within the terrain attributes in the respective study areas. Terrain attributes associated with the initiation of dis- turbances were similar regardless of the location. Disturbances commonly occurred on slopes between 4 and 15°, below Holocene marine limit, and in areas with low potential incoming solar radiation

Test drivers in the Daimler-Benz driving simulator with drivers under diphenhydramine. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Evaluation of IDDM8 susceptibility locus in a Russian simplex family data set

Type 1 diabetes (TID) susceptibility locus, IDDM8, has been accurately mapped to 200 kilobases at the terminal end of chromosome 6q27. This is within the region which harbours a cluster of three genes encoding proteasome subunit beta 1 (PMSB1), TATA-box binding protein (TBP) and a homologue of mouse programming cell death activator 2 (PDCD2). In this study, we evaluated whether these genes contribute to TID susceptibility using the transmission disequilibrium test of the data set from 114 affected Russian simplex families. The A allele of the G/A1180 single nucleotide polymorphism (SNP) at the PDCD2 gene, which was significant in its preferential transfer from parents to diabetic children (75 transmissions vs. 47 non-transmissionS, x(2) = 12.85, P corrected = 0.0038), was found to be associated with T1D. G/A1180 dimorphism and two other SNPs, C/T771 TBP and G/T(-271) PDCD2, were shown to share three common haplotypes, two of which (A-T-G and A-T-T) have been associated with higher development risk of TID. The third haplotype (G-T-G) was related to having a lower risk of disease. These findings suggest that the PDCD2 gene is a likely susceptibility gene for TID within IDDM8. However, it was not possible to exclude the TBP gene from being another putative susceptibility gene in this region. (c) 2005 Elsevier Ltd. All rights reserved.

The v-MFG test: Investigating maternal, offspring and maternal-fetal genetic incompatibility effects on disease and viability

The MFG test is a family-based association test that detects genetic effects contributing to disease in offspring, including offspring allelic effects, maternal allelic effects and MFG incompatibility effects. Like many other family-based association tests, it assumes that the offspring survival and the offspring-parent genotypes are conditionally independent provided the offspring is affected. However, when the putative disease-increasing locus can affect another competing phenotype, for example, offspring viability, the conditional independence assumption fails and these tests could lead to incorrect conclusions regarding the role of the gene in disease. We propose the v-MFG test to adjust for the genetic effects on one phenotype, e.g., viability, when testing the effects of that locus on another phenotype, e.g., disease. Using genotype data from nuclear families containing parents and at least one affected offspring, the v-MFG test models the distribution of family genotypes conditional on offspring phenotypes. It simultaneously estimates genetic effects on two phenotypes, viability and disease. Simulations show that the v-MFG test produces accurate genetic effect estimates on disease as well as on viability under several different scenarios. It generates accurate type-I error rates and provides adequate power with moderate sample sizes to detect genetic effects on disease risk when viability is reduced. We demonstrate the v-MFG test with HLA-DRB1 data from study participants with rheumatoid arthritis (RA) and their parents, we show that the v-MFG test successfully detects an MFG incompatibility effect on RA while simultaneously adjusting for a possible viability loss.

Susceptibility to pattern glare following stroke

The aim of this work was to measure susceptibility to pattern glare within a stroke group, employing a direct method of assessment. Twenty stroke subjects, aged 38-85 years, were recruited, along with an age-matched control group (n = 20). Assessment of pattern glare susceptibility was undertaken using the pattern glare test. An abnormal degree of pattern glare is present when individuals score >1 on the mid-high spatial frequency difference variable, a relative score that allows for normalization of the subject, or >3 when viewing the mid spatial frequency grating. Stroke subjects demonstrate elevated levels of pattern glare compared to normative data values and a control population, as determined using the pattern glare test. This was most notable when considering the output measure for the mid-high difference variable. The mean score for the mid-high difference variable was 2.15 SD 1.27 for the stroke subjects versus 0.10 SD 1.12 for the control subjects. When considering the mid-high difference variable, 75% of the stroke group recorded an abnormal level of pattern glare compared to 5% in the control group. This study demonstrates an association between stroke subjects and elevated levels of pattern glare. Cortical hyperexcitability has been shown to present following stroke, and this has been proposed as a plausible explanation for the perceptual distortions experienced by individuals susceptible to pattern glare. Further work to assess the benefits of spectral filters in reducing perceptual distortions in stroke patients is currently underway.

Investigating the effects of antiepileptic drugs on the electrophysiology of vision

The principal aim of this work was to examine the effects of antiepileptic drugs (AEDs) on vision. Vigabatrin acts by increasing GABA at brain inhibitory synapses by irreversibly binding to GABA-transaminase. Remacemide is a novel non-competitive NMDA receptor antagonist and fast sodium channel inhibitor that results in the inhibition of the NMDA receptors located in the neuronal membrane calcium channels increasing glutamate in the brain. Vigabatrin has been shown to cause a specific pattern of visual field loss, as one in three adults taking vigabatrin have shown a bilateral concentric constriction. Remacemide has unknown effects on vision. The majority of studies of the effects of AEDs on vision have not included the paediatric population due to difficulties assessing visual field function using standard perimetry testing. Evidently an alternative test is required to establish and monitor visual field problems associated with AEDs both in children and in adults who cannot comply with perimetry. In order to test paediatric patients exposed to vigabatrin, a field-specific visual evoked potential was developed. Other tests performed on patients taking either vigabatrin or remacemide were electroretinograms, electro-oculograms, multifocal VEPs and perimetry. Comparing these tests to perimetry results from vigabatrin patients the field specific VEP was found to have a high sensitivity and specificity, as did the 30Hz flicker amplitude. The modified VEP was also found to provide useful results in vigabatrin patients. Remacemide did not produce a similar visual field loss to vigabatrin although macular vision was affected. The field specific VEP is a useful method for detecting vigabatrin associated visual field loss that is well tolerated by young children. This technique combined with the ERG under light adapted (30Hz flicker) condition is presently the superior method for detecting vigabatrin-attributed peripheral field defects present in children below the developmental age of 9. The effects of AEDs on vision should be monitored carefully and the use of multifocal stimulation allows for specific areas of the retina and visual pathway to be monitored.

Behavioural and neurochemical correlates of drugs acting at imidazoline and a2-adrenoceptor binding sites

A number of agents with differing selectivity profiles for the non-a2 adrenoceptor binding site (NAIBS), imidazoline preferring receptor (IPR) and a2-adrenoceptor were employed in a series of behavioural and neurochemical experiments to determine a functional role for the former two sites. The highly selective NAIBS ligand RX801 077 produced an increase in rat brain extracellular noradrenaline (NA) levels, as determined by the technique of in vivo microdialysis, which may underlie its ability to produce a discriminable cue in the same species. This increase in NA may be due to a suggested link between the NAIBS and the monoamine oxidase inhibitor (MAOI) activity of RX801 077. For instance, the RX801 077 cue was substituted for by the MAOI drugs pargyline and moclobemide, which themselves down regulate NAIBS when administered chronically. RX811 059 substituted for the RX801 077 cue which may be due its ability to stimulate NA release via its activity as a highly selective a2-adrenoceptor antagonist. An effect upon NA output may also explain the ability of RX801 077 to 'mimic' the anti-immobility effect of the antidepressant drug desmethylimipramine (DMJ) in the forced swimming test. Further studies are therefore required to examine a possible role for the NAIBS in the treatment of depression. Discriminable cues were also produced by RX811 059 and the a2- adrenoceptor agonist clonidine, probably as a consequence of their respective ability to stimulate and inhibit NA output via their opposing activity at a2-adrenoceptors. The IPR has been suggested to play a role in mediating the hypotensive effect of clonidine, although a precise role was unable to be established for this site in the present studies due to the unavailability of highly selective IPA agents.

Biological barriers to the nasal delivery of peptide drugs

The nasal absorption of larger peptide and protein drugs is generally low. The importance of the mucus layer and enzymic degradation in reducing absorption were investigated. Reversed-phase high-performance liquid chromatographic (HPLC) methods were developed to assay a variety of compounds. Pig gastric mucus (PGM) was selected to investigate the importance of the mucus layer. A method of treating and storing PGM was developed and evaluated which was representative of the gel in vivo. The nature of the mucus barrier was evaluated in vitro with three-compartment diffusion cells and a series of compounds with differing physicochemical properties. Mucus retarded the diffusion of all the compounds with molecular weight and charge exerting a marked effect. Binding to mucus was investigated by a centrifugation method. All of the compounds tested were found to bind to mucus with the exception of the negatively charged molecule benzoic acid. The small peptides did not demonstrate greater binding to mucus than any of the other compounds evaluated. The effect of some absorption enhancers upon the rate of diffusion of tryptophan through mucus was determined in vi tro. At the concentrations employed the enhancers EDTA, N-acetylcysteine and taurodeoxycholic acid exerted no effect, whilst taurocholic acid and cholic acid, were found to slightly reduce the rate of diffusion. The intracellular and luminal proteolytic activity of the nose was investigated in the sheep animal model with a nasal mucosal homogenate and a nasal wash preparation respectively and a series of chemically similar peptides. Hydrolysis was also investigated with the proteolytic enzymes carboxypeptidase A, cytosolic leucine aminopeptidase and microsomal leucine aminopeptidase. Sheep nasal mucosa possesses significant peptide hydrolase activity capable of degrading all the substrates tested. Considerable variation in susceptibility was observed. Degradation occurred excl us i ve ly at the pept ide bond between the aromatic amino ac id and glycine, indicating some specificity for aromatic amino acids. Hydrolysis profiles indicated the presence of both aminopeptidase and carboxypeptidase enzymes. The specific activity of the microsomal fraction was found to be greater than the cytosolic fraction. Hydrolysis in the nasal wash indicated the presence of either luminal or loosely-bound proteases, which can degrade peptide substrates. The same specificity for aromatic amino acids was observed and aminopeptidase activity demonstrated. The specific activity of the nasal wash was smaller than that of the homogenate.

A critical evaluation of contrast susceptibility as a predictor of driving accident involvement

Contrast susceptibility is defined as the difference in visual acuity recorded for high and low contrast optotypes. Other researchers refer to this parameter as "normalised low contrast acuity". Pilot surveys have revealed that contrast susceptibility deficits are more strongly related to driving accident involvement than are deficits in high contrast visual acuity. It has been hypothesised that driving situation avoidance is purely based upon high contrast visual acuity. Hence, the relationship between high contrast visual acuity and accidents is masked by situation avoidance whilst drivers with contrast susceptibility deficits remain prone to accidents in poor visibility conditions. A national survey carried out to test this hypothesis provided no support for either the link between contrast susceptibility deficits and accidents involvement or the proposed hypothesis. Further, systematically worse contrast susceptibility scores emerged from vision screeners compared to wall mounted test charts. This discrepancy was not due to variations in test luminance or instrument myopia. Instead, optical imperfections inherent in vision screeners were considered to be responsible. Although contrast susceptibility is unlikely to provide a useful means of screening drivers' vision, previous research does provide support for its ability to detect visual deficits that may influence everyday tasks. In this respect, individual contrast susceptibility variations were found to reflect variations in the contrast sensitivity function - a parameter that provides a global estimate of human contrast sensitivity.

Quality control of pharmaceutical ingredients:developing a caking test for industry

Objectives - Powdered and granulated particulate materials make up most of the ingredients of pharmaceuticals and are often at risk of undergoing unwanted agglomeration, or caking, during transport or storage. This is particularly acute when bulk powders are exposed to extreme swings in temperature and relative humidity, which is now common as drugs are produced and administered in increasingly hostile climates and are stored for longer periods of time prior to use. This study explores the possibility of using a uniaxial unconfined compression test to compare the strength of caked agglomerates exposed to different temperatures and relative humidities. This is part of a longer-term study to construct a protocol to predict the caking tendency of a new bulk material from individual particle properties. The main challenge is to develop techniques that provide repeatable results yet are presented simply enough to be useful to a wide range of industries. Methods - Powdered sucrose, a major pharmaceutical ingredient, was poured into a split die and exposed to high and low relative humidity cycles at room temperature. The typical ranges were 20–30% for the lower value and 70–80% for the higher value. The outer die casing was then removed and the resultant agglomerate was subjected to an unconfined compression test using a plunger fitted to a Zwick compression tester. The force against displacement was logged so that the dynamics of failure as well as the failure load of the sample could be recorded. The experimental matrix included varying the number of cycles, the amount between the maximum and minimum relative humidity, the height and diameters of the samples, the number of cycles and the particle size. Results - Trends showed that the tensile strength of the agglomerates increased with the number of cycles and also with the more extreme swings in relative humidity. This agrees with previous work on alternative methods of measuring the tensile strength of sugar agglomerates formed from humidity cycling (Leaper et al 2003). Conclusions - The results show that at the very least the uniaxial tester is a good comparative tester to examine the caking tendency of powdered materials, with a simple arrangement and operation that are compatible with the requirements of industry. However, further work is required to continue to optimize the height/ diameter ratio during tests.

The in vivo susceptibility of Leishmania donovani to sodium stibogluconate is drug specific and can be reversed by inhibiting glutathione biosynthesis

Resistance to pentavallent antimonial (Sb-v) agents such as sodium stibogluconate (SSG) is creating a major problem in the treatment of visceral leishmaniasis. In the present study the in vivo susceptibilities of Leishmania donovani strains, typed as SSG resistant (strain 200011) or SSG sensitive (strain 200016) on the basis of their responses to a single SSG dose of 300 mg of Sb-v/kg of body weight, to other antileishmanial drugs were determined. In addition, the role of glutathione in SSG resistance was investigated by determining the influence on SSG treatment of concomitant treatment with a nonionic surfactant vesicle formulation of buthionine sulfoximine (BSO), a specific inhibitor of the enzyme gamma-glutamylcysteine synthetase which is involved in glutathione biosynthesis, and SSG, on the efficacy of SSG treatment. L. donovani strains that were SSG resistant (strain 200011) and SSG sensitive (strain 200016) were equally susceptible to in vivo treatment with miltefosine, paromomycin and amphotericin B (Fungizone and AmBisome) formulations. Combined treatment with SSG and vesicular BSO significantly increased the in vivo efficacy of SSG against both the 200011 and the 200016 L. donovani strains. However, joint treatment that included high SSG doses was unexpectedly associated with toxicity. Measurement of glutathione levels in the spleens and livers of treated mice showed that the ability of the combined therapy to inhibit glutathione levels was also dependent on the SSG dose used and that the combined treatment exhibited organ-dependent effects. The SSG resistance exhibited by the L. donovani strains was not associated with cross-resistance to other classes of compounds and could be reversed by treatment with an inhibitor of glutathione biosynthesis, indicating that clinical resistance to antimonial drugs should not affect the antileishmanial efficacies of alternative drugs. In addition, it should be possible to identify a treatment regimen that could reverse antimony resistance.