Waterborne pharmaceutical uptake and toxicity is modified by pH and dissolved organic carbon in zebrafish

Human and veterinary pharmaceuticals have been observed in natural aquatic environments around the world, and many have been shown to impact fish health. Presently, we examined the influence of pH, dissolved organic carbon (DOC) and Na⁺ or Ca²⁺ on the bioavailability and toxicity of waterborne pharmaceuticals in larval zebrafish. Drugs included sertraline (selective serotonin reuptake inhibitor; SSRI), fluoxetine (SSRI), diclofenac (nonsteroidal anti-inflammatory drug) and ethinyl estradiol (estrogen; EE₂). The 96 h-LC₅₀s for sertraline, fluoxetine and diclofenac were influenced by pH over an environmentally relevant range (pH 5.8-8.2). Toxicity was related to the predicted concentration of non-ionized compounds, which more readily cross cell membranes than ionized compounds. For example, sertraline was 4.1-fold more toxic (as measured by 96 h-LC₅₀s) at pH 8.2 compared to pH 5.8, while the predicted amount of non-ionized sertraline was also greater at pH 8.2 (based on previously reported pKa values). Experiments with radiolabelled drugs demonstrated that sertraline uptake was also 5.4-fold higher at pH 8.2 compared to pH 5.8. Terrigenous and autochthonous DOC samples (as low as 1 mg/L) protected against sertraline uptake and toxicity, although they were more effective at lower (environmentally relevant) drug concentrations. In contrast, the uptake of EE₂, which was principally non-ionized in all water chemistries tested, was not altered by pH or DOC. There was no change in sertraline toxicity with the addition of 12 mM Na⁺ or 3 mM Ca²⁺. In conclusion, the influence of pH and DOC on drug uptake and toxicity in fish appears to be predictable based on the physicochemical properties of the drug (e.g. pKa, polar surface area). The influence of water chemistry on drug bioavailability in fish is likely relevant to all aquatic life.

The effects of chronic acetaminophen exposure on the kidney, gill and liver in rainbow trout (Oncorhynchus mykiss)

In this study, we examined if rainbow trout chronically exposed to acetaminophen (10 and 30 μgL^-1) showed histological changes that coincided with functional changes in the kidney, gill and liver. Histological changes in the kidney included movement and loss of nuclei, non-uniform nuclei size, non-uniform cytoplasmic staining, and loss of tubule integrity. Histological effects were more severe at the higher concentration and coincided with concentration dependent increases in urine flow rate and increased urinary concentrations of sodium, chloride, potassium, calcium, urea, ammonia, glucose, and protein. Yet, glomerular filtration rate was not altered with acetaminophen exposure. In the gill, filament end swelling, whole filament swelling, and swelling of the lamellae were observed in exposed fish. Lamellar spacing decreased in both exposure groups, but lamellar area decreased only with 30 μgL^-1 exposure. At faster swimming speeds, oxygen consumption was limited in acetaminophen exposed fish, and critical swimming speed was also decreased in both exposure groups. The liver showed decreased perisinusoidal spaces at 10 and 30 μgL^-1 acetaminophen, and decreased cytoplasmic vacuolation with 30 μgL^-1 acetaminophen. A decrease in liver glycogen was also observed at 30 μgL^-1. There was no change in plasma concentrations of sodium, chloride, potassium, calcium, magnesium, and glucose with exposure, suggesting compensation for urinary loss. Indeed, an increase in Na⁺-K⁺-ATPase activity in the gills was found with 30 μgL^-1 acetaminophen exposure. Chronic exposure of rainbow trout to the environmentally relevant pharmaceutical acetaminophen, alters both histology and function of organs responsible for ion and nutrient homeostasis.

In Vitro Biotransformation of Two Human CYP3A Probe Substrates and Their Inhibition during Early Zebrafish Development

At present, the zebrafish embryo is increasingly used as an alternative animal model to screen for developmental toxicity after exposure to xenobiotics. Since zebrafish embryos depend on their own drug-metabolizing capacity, knowledge of their intrinsic biotransformation is pivotal in order to correctly interpret the outcome of teratogenicity assays. Therefore, the aim of this in vitro study was to assess the activity of cytochrome P450 (CYP)—a group of drug-metabolizing enzymes—in microsomes from whole zebrafish embryos (ZEM) of 5, 24, 48, 72, 96 and 120 h post-fertilization (hpf) by means of a mammalian CYP substrate, i.e., benzyloxy-methyl-resorufin (BOMR). The same CYP activity assays were performed in adult zebrafish liver microsomes (ZLM) to serve as a reference for the embryos. In addition, activity assays with the human CYP3A4-specific Luciferin isopropyl acetal (Luciferin-IPA) as well as inhibition studies with ketoconazole and CYP3cide were carried out to identify CYP activity in ZLM. In the present study, biotransformation of BOMR was detected at 72 and 96 hpf; however, metabolite formation was low compared with ZLM. Furthermore, Luciferin-IPA was not metabolized by the zebrafish. In conclusion, the capacity of intrinsic biotransformation in zebrafish embryos appears to be lacking during a major part of organogenesis.

Disinfection of human musculoskeletal allografts in tissue banking: a systematic review

Musculoskeletal allografts are typically disinfected using antibiotics, irradiation or chemical methods but protocols vary significantly between tissue banks. It is likely that different disinfection protocols will not have the same level of microorganism kill; they may also have varying effects on the structural integrity of the tissue, which could lead to significant differences in terms of clinical outcome in recipients. Ideally, a disinfection protocol should achieve the greatest bioburden reduction with the lowest possible impact on tissue integrity. A systematic review of three databases found 68 laboratory and clinical studies that analyzed the microbial bioburden or contamination rates of musculoskeletal allografts. The use of peracetic acid–ethanol or ionizing radiation was found to be most effective for disinfection of tissues. The use of irradiation is the most frequently published method for the terminal sterilization of musculoskeletal allografts; it is widely used and its efficacy is well documented in the literature. However, effective disinfection results were still observed using the BioCleanse™ Tissue Sterilization process, pulsatile lavage with antibiotics, ethylene oxide, and chlorhexidine. The variety of effective methods to reduce contamination rate or bioburden, in conjunction with limited high quality evidence provides little support for the recommendation of a single bioburden reduction method.

Interactions of waterborne and dietborne Pb in rainbow trout, Oncorhynchus mykiss: Bioaccumulation, physiological responses, and chronic toxicity

In Pb-contaminated environments, simultaneous exposure to both waterborne and dietborne Pb is likely to occur. This study examined the potential interactive effects of these two pathways in juvenile rainbow trout that were exposed to Pb in the water alone, in the diet alone, and in combination for 7 weeks. The highest waterborne Pb concentration tested (110μgL(-1)) was approximately equivalent to the 7-week LC20 (97μgL(-1)) measured in a separate trial, while the lowest was a concentration often measured in contaminated environments (8.5μgL(-1)). The live diet (10% daily ration on a wet mass basis) consisted of oligochaete worms (Lumbriculus variegatus) pre-exposed for 28days to the same waterborne Pb concentration, and the highest dietary dosing rate to the trout was 12.6μg Pb g fish(-1)day(-1). With waterborne exposure, whole body Pb burden increased to a greater extent in the worms than in the fish. Nonetheless, in trout waterborne exposure still resulted in 20-60-fold greater Pb accumulation compared to dietborne Pb exposure. However, combined exposure to both waterborne and dietborne Pb reduced the whole body accumulation extensively at waterborne Pb>50μgL(-1), with similar antagonistic interaction in liver and carcass (but not gill or gut) at a lower threshold of 20μgL(-1). Growth effects in trout were minimal with marginal reductions in the dietborne and combined exposures seen only at 110μgL(-1). Chronic Pb exposure reduced lipid and carbohydrates level in the worms by 50% and 80% respectively, while protein was unchanged, so growth effects in trout may have been of indirect origin. After 7 weeks, Ca(2+) homeostasis in the trout was unaffected, but there were impacts on Na(+). Blood Na(+) was reduced in waterborne and dietborne exposures, while gut Na(+)/K(+) ATPase activities were reduced in waterborne and combined exposures. This study is the first, to our knowledge to examine the interaction of waterborne and dietborne Pb exposure in fish. While physiological impacts of Pb were observed in both worms and fish, higher concentrations of dietborne Pb actually protected fish from waterborne Pb bioaccumulation and these effects. The impacts of metals on diet quality should not be neglected in future dietborne toxicity studies using live prey.

Reproductive impacts and physiological adaptations of zebrafish to elevated dietary nickel

Nickel (Ni) concentrations in the environment can rise due to human industrial activities. The toxicity of waterborne Ni to aquatic animals has been examined in a number of previous studies; however, little is known about the impacts of elevated dietary Ni. In the present study, zebrafish were chronically fed diets containing two concentrations of Ni [3.7 (control) and 116 μg Ni/g diet]. Ni-exposed males, but not females, were significantly smaller (26%) compared to controls at 80 days. In addition, total egg production was decreased by 65% in the Ni treatment at 75-78 days of the experiment. Ni was ubiquitously distributed in control animals (similar to previous studies), and concentrations varied between tissues by 15-fold. Ni exposure resulted in modest but significant Ni accumulation in some tissues (increases were highest in brain, vertebrae and gut; 44%, 34% and 25%, respectively), an effect observed only at 80 days. The limited Ni accumulation may be due to (1) the lack of an acidified stomach in zebrafish and/or (2) the efficient upregulation of Ni transport and excretion mechanisms, as indicated by the 4.5-fold increase in waterborne (63)Ni uptake by Ni-exposed fish. Eggs from Ni-exposed adults had Ni concentrations that were 5.2-fold higher than controls. However, by 4 days post fertilization, larvae had similar Ni concentrations as controls, demonstrating a capacity for rapid Ni depuration. Larvae from Ni-exposed adults were also more resistant to waterborne Ni (35% increase in the 96-h LC50 over controls). In conclusion, elevated dietary Ni significantly affected zebrafish reproduction despite only modest tissue Ni accumulation. There were also indications of adaptation, including increased Ni uptake rates and increased Ni tolerance of offspring from Ni-exposed adults. Ni concentrations were particularly elevated in the brain with exposure; possible relations to growth and reproductive impacts require further study.

Antifeedant action ofZ-dihydromatricaria acid from soldier beetles (Chauliognathus spp.)

The acetylenic acid,Z-dihydromatricaria acid (DHMA), previously isolated from the defensive secretion ofChauliognathus lecontei, and now shown to occur also inC. pennsylvanicus, is a potent feeding deterrent to jumping spiders (Phidippus spp.). A simple bioassay withPhidippus is described, which is generally applicable to studies dealing with the isolation and evaluation of feeding deterrency of natural products from insects. By use of this assay,Phidippus were shown to be sensitive to as little as 1 μg DHMA, an amount equivalent to less than 2% of the DHMA content ofC. pennsylvanicus.

Metal and pharmaceutical mixtures: is ion loss the mechanism underlying acute toxicity and widespread additive toxicity in zebrafish?

The acute toxicities and mechanisms of action of a variety of environmental contaminants were examined using zebrafish larvae (Danio rerio; 4-8 days post fertilization). Toxic interactions were observed between metals. For example, the addition of a sublethal level of nickel (15% of the LC50, one third of the LC01) to all copper treatments decreased the copper 96 h LC50 by 58%, while sublethal copper exposure (6% of the copper LC50, 13% of the LC01) decreased the cadmium 96 h LC50 by 47%. Two predictive models were assessed, the concentration addition (CA) model, which assumes similar mechanisms of action, and the independent action (IA) model, which assumes different mechanisms of action. Quantitative comparisons indicated the CA model performed better than the IA model; the latter tended to underestimate combined toxicity to a greater extent. The effects of mixtures with nickel or ammonia were typically additive, while mixtures with copper or cadmium were typically greater than additive. Larvae exposed to cadmium, copper or nickel experienced whole body ion loss. Decreases were greatest for Na(+) followed by K(+) (as high as 19% and 9%, respectively, in 24h). Additive toxicity between copper and other pharmaceutical compounds such as fluoxetine (Prozac™), β-naphthoflavone, estrogen and 17α-ethinylestradiol were also observed. Similar to metals, acutely toxic concentrations of fluoxetine, β-naphthoflavone and ammonia all decreased whole body Na(+) and K(+). Overall, whole body Na(+) loss showed the greatest correlation with mortality across a variety of toxicants. We theorize that a disruption of ion homeostasis may be a common mechanism underlying the acute additive toxicity of many contaminants in fish.

Effects of copper on the acute cortisol response and associated physiology in rainbow trout

The aim of this study was to determine the effects of chronic waterborne copper (Cu) exposure on the acute stress-induced cortisol response and associated physiological consequences in rainbow trout (Oncorhynchus mykiss). Trout were exposed to 30 μg Cu/L in moderately hard water (120 mg/L as CaCO(3)) for 40 days, following which time the acute cortisol response was examined with a series of stressors. At 40 days, a 65% increase in Cu was observed in the gill, but no accumulation was observed in the liver, brain or head kidney. Stressors such as air exposure or confinement did not elicit an increase in circulating cortisol levels for Cu-exposed fish, in contrast to controls. However, this inhibitory effect on the acute cortisol response appeared to have few implications on the ability of Cu-exposed fish to maintain ion and carbohydrate homeostasis. For example, plasma Na(+), Ca(2+) and glucose levels as well as hepatic glycogen levels were the same post-stress in control and Cu-exposed fish. Trout were also challenged with exposure to 50% seawater for 48 h, where Cu-exposed trout maintained plasma Na(+), glucose and hepatic glycogen levels. However, Cu-exposed fish experienced decreased plasma K(+) levels throughout the Cu exposure and stress tests. In conclusion, chronic Cu exposure resulted in the abolition of an acute cortisol response post-stress. There was no Cu accumulation in the hypothalamus-pituitary-interrenal axis (HPI axis) suggesting this was not a direct toxic effect of Cu on the cortisol regulatory pathway. However, the lack of an acute cortisol response in Cu-exposed fish did not impair the ability of the fish to maintain ion and carbohydrate homeostasis. This effect on cortisol may be a strategy to reduce costs during the chronic stress of Cu exposure, and not endocrine disruption as a result of toxic injury.

Metal uptake and acute toxicity in zebrafish: common mechanisms across multiple metals

Zebrafish larvae (Danio rerio) were used to examine the mechanisms of action and acute toxicities of metals. Larvae had similar physiological responses and sensitivities to waterborne metals as adults. While cadmium and zinc have previously been shown to reduce Ca(2+) uptake, copper and nickel also decreased Ca(2+) uptake, suggesting that the epithelial transport of all these metals is through Ca(2+) pathways. However, exposure to cadmium, copper or nickel for up to 48 h had little or no effect on total whole body Ca(2+) levels, indicating that the reduction of Ca(2+) uptake is not the acute toxic mechanism of these metals. Instead, mortalities were effectively related to whole body Na(+), which decreased up to 39% after 48 h exposures to different metals around their respective 96 h LC50s. Decreases in whole body K(+) were also observed, although they were not as pronounced or frequent as Na(+) losses. None of the metals tested inhibited Na(+) uptake in zebrafish (Na(+) uptake was in fact increased with exposure) and the observed losses of Na(+), K(+), Ca(2+) and Mg(2+) were proportional to the ionic gradients between the plasma and water, indicating diffusive ion loss with metal exposure. This study has shown that there is a common pathway for metal uptake and a common mechanism of acute toxicity across groups of metals in zebrafish. The disruption of ion uptake accompanying metal exposure does not appear to be responsible for the acute toxicity of metals, as has been previously suggested, but rather the toxicity is instead due to total ion loss (predominantly Na(+)).

Grizzly bear corticosteroid binding globulin: Cloning and serum protein expression

Serum corticosteroid levels are routinely measured as markers of stress in wild animals. However, corticosteroid levels rise rapidly in response to the acute stress of capture and restraint for sampling, limiting its use as an indicator of chronic stress. We hypothesized that serum corticosteroid binding globulin (CBG), the primary transport protein for corticosteroids in circulation, may be a better marker of the stress status prior to capture in grizzly bears (Ursus arctos). To test this, a full-length CBG cDNA was cloned and sequenced from grizzly bear testis and polyclonal antibodies were generated for detection of this protein in bear sera. The deduced nucleotide and protein sequences were 1218 bp and 405 amino acids, respectively. Multiple sequence alignments showed that grizzly bear CBG (gbCBG) was 90% and 83% identical to the dog CBG nucleotide and amino acid sequences, respectively. The affinity purified rabbit gbCBG antiserum detected grizzly bear but not human CBG. There were no sex differences in serum total cortisol concentration, while CBG expression was significantly higher in adult females compared to males. Serum cortisol levels were significantly higher in bears captured by leg-hold snare compared to those captured by remote drug delivery from helicopter. However, serum CBG expression between these two groups did not differ significantly. Overall, serum CBG levels may be a better marker of chronic stress, especially because this protein is not modulated by the stress of capture and restraint in grizzly bears.

Altered control of postural sway following cerebral infarction: a cross-sectional analysis

OBJECTIVE

Balance impairment is common following cerebral infarction. However, the effects of lesion hemisphere on postural control are largely unknown. We examined dependence upon vision and noninfarcted regional brain tissue volumes for postural control in individuals with right and left hemisphere middle cerebral artery (MCA) infarcts.

METHODS

Subjects with right MCA infarct (n = 17, age = 65 +/- 8 years, 7 +/- 6 years poststroke), left MCA infarct (n = 20, age = 65 +/- 8 years, 7 +/- 6 years poststroke), and controls (n = 55, age = 65 +/- 8 years) were studied. Postural control was defined by average velocity and the range and variability of mediolateral (ML) and anteroposterior (AP) sway during eyes-open and eyes-closed standing. Regional brain volumes were quantified using anatomic MRI at 3 Tesla.

RESULTS

Right and left hemisphere stroke groups had similar infarct volumes and outcomes. Subjects with right hemisphere infarcts demonstrated greater sway velocity, ML range, and ML variability with eyes closed compared to eyes open. In this group, smaller occipital lobe volumes were associated with greater eyes-open sway velocity (R = -0.64, p = 0.012) and ML range (R = -0.82, p = 0.001). Smaller cerebellar volumes were associated with greater eyes-closed sway velocity (R = -0.60, p = 0.015), ML range (R = -0.70, p = 0.007), and ML variability (R = -0.85, p < 0.001). These associations were not observed in left hemisphere infarct subjects or controls. AP sway was unaffected by infarct hemisphere or visual condition and did not correlate with regional brain volumes.

CONCLUSIONS

Right hemisphere middle cerebral artery infarcts are associated with increased dependence on vision and noninfarcted brain regions (i.e., occipital lobes, cerebellum) to control postural sway. Strategies emphasizing postural tasks under reduced visual conditions may enhance functional recovery in these individuals.

Structural integrity of corticospinal motor fibers predicts motor impairment in chronic stroke

OBJECTIVE

Motor impairment after stroke has been related to infarct size, infarct location, and integrity of motor tracts. To determine the value of diffusion tensor imaging (DTI) as a predictor of motor outcome and its role as a structural surrogate marker of impairment in chronic stroke, we tested correlations between motor impairment and DTI-derived measures of motor tract integrity.

METHODS

Thirty-five chronic stroke patients with varying degrees of recovery underwent DTI and motor impairment assessments. Fibers originating from the precentral gyrus were traced and separated into pyramidal tract (PT) and alternate motor fibers (aMF). Asymmetry indices of fiber number and regional fractional anisotropy (FA) values comparing lesional with nonlesional hemispheres were correlated with motor impairment scores and compared to an age-matched control group.

RESULTS

Fiber number and regional FA value asymmetry significantly differed between the groups with lower values in the patients' lesional hemispheres. Both measures significantly predicted motor impairment with stronger predictions when all motor tracts were combined as compared to predictions using only the PT. The pattern of motor tract damage (PT only vs PT and aMF) led to a classification of mild, moderate, or severe impairment with significant between-group differences in motor impairment scores.

CONCLUSIONS

Diffusion tensor imaging-derived measures are valid structural markers of motor impairment. The integrity of all descending motor tracts, not merely the pyramidal tract, appears to account for stroke recovery. A 3-tier, hierarchical classification of impairment categories based on the pattern of motor tract damage is proposed that might be helpful in predicting recovery potential.

Adrenocorticotropic hormone suppresses gonadotropin-stimulated estradiol release from zebrafish ovarian follicles

While stress is known to impact reproductive performance, the pathways involved are not entirely understood. Corticosteroid effects on the functioning of the hypothalamus-pituitary-gonadal axis are thought to be a key aspect of stress-mediated reproductive dysfunction. A vital component of the stress response is the pituitary secretion of adrenocorticotropic hormone (ACTH), which binds to the melanocortin 2 receptor (MC2R) in the adrenal glands and activates cortisol biosynthesis. We recently reported MC2R mRNA abundance in fish gonads leading to the hypothesis that ACTH may be directly involved in gonadal steroid modulation. Using zebrafish (Danio rerio) ovarian follicles, we tested the hypothesis that acute ACTH stimulation modulates cortisol and estradiol (E₂) secretion. ACTH neither affected cortisol nor unstimulated E₂ release from ovarian follicles. However, ACTH suppressed human chorionic gonadotropin (hCG)-stimulated E₂ secretion in a dose-related manner, with a maximum decrease of 62% observed at 1 I.U. ACTH mL⁻¹. This effect of ACTH on E₂ release was not observed in the presence of either 8-bromo-cAMP or forskolin, suggesting that the mechanism(s) involved in steroid attenuation was upstream of adenylyl cyclase activation. Overall, our results suggest that a stress-induced rise in plasma ACTH levels may initiate a rapid down-regulation of acute stimulated E₂ biosynthesis in the zebrafish ovary, underscoring a novel physiological role for this pituitary peptide in modulating reproductive activity.

The zebrafish stress axis: molecular fallout from the teleost-specific genome duplication event

The teleost-specific whole genome duplication event 350 million years ago resulted in a variety of duplicated genes that exist in fish today. In this review, we examine whether molecular components involved in the functioning of the hypothalamus-pituitary-interrenal (HPI) axis are present as single or duplicate genes. Specifically, we looked at corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and the glucocorticoid receptor (GR). The focus is on zebrafish but a variety of species are covered whenever data is available through literature or genomic database searches. Duplicate CRH genes are retained in the salmoniformes and cypriniformes, and the peptide sequences are very similar or identical. Zebrafish, along with the Acanthopterygii, are the exceptions as they have a single CRH gene. Also, two copies of the proopiomelanocortin (POMC) gene, which encodes for ACTH and other peptides, have been observed in all teleosts except tilapia and sea bass. In zebrafish, ACTH is derived from only one POMC gene, since the cleavage site is mutated in the other gene. All teleosts examined to date have two GRs, including the recent discoveries of duplicate GRs in two species of cyprinids (carp and fathead minnow). Zebrafish are the only known exception with one GR gene. The loss of duplicate genes is not a general feature of the zebrafish genome, but zebrafish have lost the duplicate CRH, ACTH and GR genes in the past 33 million years, after possessing two of each for the previous 300 million years. The evolutionary pressures underlying the rapid loss of these HPI axis genes, and the implications on the development and the functioning of the evolutionarily conserved cortisol stress response in zebrafish are currently unknown.

Molecular programming of the corticosteroid stress axis during zebrafish development

The functions of the hypothalamus-pituitary-interrenal (HPI) axis in teleosts have been studied primarily in juvenile and adult fish, whereas little is known about the molecular events leading to the onset of the stressor-induced cortisol response during development. Here we summarize a number of studies that have examined changes in the expression of genes encoding proteins critical for the functioning of the HPI axis, and the associated cortisol response in developing zebrafish embryos and larvae. The mRNA transcripts for some of these genes, including corticotropin releasing factor (CRF), proopiomelanocortin (POMC), melanocortin 2 receptor (MC2R), steroidogenic acute regulatory protein (StAR) and cytochrome P450 side chain cleavage (P450scc) have been detected during embryogenesis prior to hatch. The mRNA levels of MC2R, StAR and P450scc are up-regulated immediately prior to the dramatic rise in basal larval cortisol levels after hatch. Although all the components of the HPI axis are expressed and cortisol is synthesized at hatch, a stressor-induced cortisol response was not evident until 97 hpf. We hypothesize that this disconnect in the timing of the basal cortisol synthesis and stressor-induced cortisol synthesis is due to the delayed development of peripheral and central neural inputs relaying stressor stimuli to the hypothalamus. Overall, zebrafish appear to be an excellent model for elucidating the molecular mechanisms leading to the development of the corticoid stress axis in vertebrates.

The economic dimensions of integrating flood management and agri-environment through washland creation: a case from Somerset, England

In many river floodplains in the UK, there has been a long history of flood defence, land reclamation and water regime management for farming. In recent years, however, changing European and national policies with respect to farming, environment and flood management are encouraging a re-appraisal of land use in rural areas. In particular, there is scope to develop, through the use of appropriate promotional mechanisms, washland areas, which will simultaneously accommodate winter inundation, support extensive farming methods, deliver environmental benefits, and do this in a way which can underpin the rural economy. This paper explores the likely economic impacts of the development of flood storage and washland creation. In doing so, consideration is given to feasibility of this type of development, the environmental implications for a variety of habitats and species, and the financial and institutional mechanisms required to achieve implementation.

Retinoid requirements in the reproduction of zebrafish

This study examines whether retinoids are essential in the reproduction of zebrafish. Using RT-PCR, it was shown that the ovaries and testes express enzymes that synthesize and metabolize the hormone retinoic acid (RA) (raldh2 and cyp26a, respectively), and RA receptors (raraa, rarga, rxrba, rxrbb, rxrga but not rxrab). Three new isoforms of rxrba were also observed in a variety of tissues. In other experiments, zebrafish were exposed for 11 d to diethylaminobenzaldehyde (DEAB), an inhibitor of RA synthesis, or fed a retinoid deficient diet for 130 d in order to evaluate the functional requirements of retinoids in reproduction. DEAB altered cyp26a transcript numbers in the gonads, suggesting an impact on RA, and decreased the number of spawned eggs by 95%. The retinoid deficient diet decreased whole body retinoids (retinol and retinal) by 68% in females and 33% in males. Females fed the retinoid deficient diet also produced 73% fewer eggs that contained 78% less retinal than controls. Fertilization rates were not affected. These studies have shown that the RA receptors are expressed in zebrafish gonads, and RA is required for the spawning of eggs. Dietary retinoid content influences reproduction, while retinyl ester storage levels appear to be of little significance. Females were more susceptible to retinoid perturbation than males, likely due to the cost of retinal deposition in the eggs. Overall, these studies have shown retinoids play a fundamental role in the reproduction of zebrafish, and the lack of retinyl ester stores in controls that successfully spawned illustrates that we have only a limited understanding of the retinoid physiology and requirements of fish.

A structural basis for reading fluency: white matter defects in a genetic brain malformation

BACKGROUND

Multiple lines of evidence have suggested that developmental dyslexia may be associated with abnormalities of neuronal migration or axonal connectivity. In patients with periventricular nodular heterotopia--a rare genetic brain malformation characterized by misplaced nodules of gray matter along the lateral ventricles--a specific and unexpected reading disability is present, despite normal intelligence. We sought to investigate the cognitive and structural brain bases of this phenomenon.

METHODS

Ten adult subjects with heterotopia, 10 with dyslexia, and 10 normal controls were evaluated, using a battery of neuropsychometric measures. White matter integrity and fiber tract organization were examined in six heterotopia subjects, using diffusion tensor imaging methods.

RESULTS

Subjects with heterotopia and those with developmental dyslexia shared a common behavioral profile, with specific deficits in reading fluency. Individuals with dyslexia seemed to have a more prominent phonological impairment than heterotopia subjects. Periventricular nodular heterotopia was associated with specific, focal disruptions in white matter microstructure and organization in the vicinity of gray matter nodules. The degree of white matter integrity correlated with reading fluency in this population.

CONCLUSIONS

We demonstrate that a genetic disorder of gray matter heterotopia shares behavioral characteristics with developmental dyslexia, and that focal white matter defects in this disorder may serve as the structural brain basis of this phenomenon. Our findings represent a potential model for the use of developmental brain malformations in the investigation of abnormal cognitive function.

Development of the corticosteroid stress axis and receptor expression in zebrafish

Using zebrafish embryos and larvae, we examined the temporal patterns of cortisol and expression of genes involved in corticosteroid synthesis and signaling. Embryonic cortisol levels decreased approximately 70% from 1.5 h postfertilization (hpf) to hatch (approximately 42 hpf) and then increased 27-fold by 146 hpf. The mRNA abundances of steroidogenic acute regulatory protein, 11beta-hydroxylase and 11beta-hydroxysteroid dehydrogenase type 2, increased severalfold after hatch and preceded the rise of cortisol levels. In contrast to other teleosts that possess two glucocorticoid receptors (GRs) and one mineralocorticoid receptor (MR), only one GR and MR were identified in zebrafish, which were cloned and sequenced. GR mRNA abundance decreased from 1.5 to 25 hpf, rebounded, and then was stable from 49 to 146 hpf. MR transcripts increased continuously from 1.5 hpf and were 52-fold higher by 97 hpf. An acute cortisol response to a stressor was not detected until 97 hpf, whereas melanocortin type 2 receptor mRNA increased between 25 and 49 hpf. Collectively, the patterns of cortisol and the expression of cortisol biosynthetic genes and melanocortin type 2 receptor suggest that the corticoid stress axis in zebrafish is fully developed only after hatch. The temporal differences in GR, MR, and 11beta-hydroxysteroid dehydrogenase type 2 gene expression lead us to propose a key role for MR signaling by maternal cortisol during embryogenesis, whereas cortisol secretion after hatch may be regulating GR expression and signaling in zebrafish.

The effects of copper and benzo[a]pyrene on retinoids and reproduction in zebrafish

This study examines whether a link exists between toxicant exposure, retinoids and reproduction in fish. Zebrafish were fed a control diet (8.1 microg Cu/g diet, 0 microg benzo[a]pyrene/g diet) or diets containing elevated copper (100 microg, 500 microg and 1000 microg Cu/g diet) or benzo[a]pyrene (B[a]P; 30 and 150 microg B[a]P/g diet) for 260 days. Toxicant-supplemented diets did not affect growth or mortality rates. While whole body retinoid levels in control zebrafish decreased during the experiment, females exposed to Cu or B[a]P for 200 days or more experienced additional losses of retinyl esters (45-100% depleted) and retinal (45% depleted in B[a]P-fed fish). Despite the reduced retinoids, Cu and B[a]P did not effect reproduction with respect to the number of eggs spawned, fertilization rates or egg retinal content (retinal was instead increased 55-65% in eggs from B[a]P-fed fish). There were no apparent deformities observed in 36 h post fertilization embryos from any treatment. It appears that although internal retinoid stores were depleted in adults, dietary retinoids were sufficient to meet the daily requirement for retinal deposition in the eggs and retinoic acid synthesis. This study has shown that retinoid levels in female zebrafish are sensitive to Cu and B[a]P, and are a good indicator of long-term exposure. It also brings to light the resiliency of the retinoid system in fish and the importance of the diet on the toxicological response. Specifically that dietary retinoids appear to support normal reproduction in the absence of internal retinoid stores.

Sleep-dependent motor memory plasticity in the human brain

Growing evidence indicates a role for sleep in off-line memory processing, specifically in post-training consolidation. In humans, sleep has been shown to trigger overnight learning on a motor-sequence memory task, while equivalent waking periods produce no such improvement. But while the behavioral characteristics of sleep-dependent motor learning become increasingly well characterized, the underlying neural basis remains unknown. Here we present functional magnetic resonance imaging data demonstrating a change in the representation of a motor memory after a night of sleep. Subjects trained on a motor-skill memory and 12 hours later, after either sleep or wake, were retested during functional magnetic resonance imaging. Following sleep relative to wake, regions of increased activation were expressed in the right primary motor cortex, medial prefrontal lobe, hippocampus and left cerebellum; changes that can support faster motor output and more precise mapping of key-press movements. In contrast, signal decreases were identified in parietal cortices, the left insular cortex, temporal pole and fronto-polar region, reflecting a reduced need for conscious spatial monitoring and a decreased emotional task burden. This evidence of an overnight, systems-level change in the representation of a motor memory holds important implications for acquiring real-life skills and in clinical rehabilitation following brain trauma, such as stroke.

Constituents within pulp mill effluent deplete retinoid stores in white sucker and bind to rainbow trout retinoic acid receptors and retinoid X receptors

Wild female and male white sucker (Catostomus commersoni) inhabiting an area receiving pulp mill effluent had reduced hepatic levels of retinol, didehydroretinol, retinyl esters, and didehydroretinyl esters, while vitamin E levels were unaffected. This disruption of the retinoid system led us to test methanol and dichloromethane extracts from the effluent of 11 pulp mills from across Canada for their ability to bind to rainbow trout (Oncorhynchus mykiss) retinoic acid receptors (RARs) from the gill and retinoid X receptors (RXRs) from the liver. Concentrated extracts of the final effluent from 6 of the 11 pulp mills were able to displace greater than 25% of the receptor-bound [3H]all-trans retinoic acid (RA) or [3H]9-cis RA from trout RARs and RXRs, respectively. The ability of the extracts to displace retinoic acid did not appear to be linked to the pulping or treatment processes. Moreover, extracts with the greatest activity came from thermomechanical mills, suggesting the compounds may originate from the wood furnish. In addition, extracts prepared from wood furnish (wood chips: white spruce [50%], lodgepole pine [47%], and balsam fir [3%]) from one mill were able to displace [3H]RA from the RARs and RXRs. The 4-hydroxy RA, a metabolite of RA that has been shown to be generated in greater quantities in fish exposed to P450-inducing xenobiotics, was able to displace [3H]all-trans RA from trout RARs as effectively as unlabeled all-trans RA. These results suggest that pulp mill effluent may impact the retinoid system of fish at multiple sites, either by decreasing hepatic retinoid stores or through contributing additional ligands (from the wood furnish) that can bind to RA receptors.

Grammatical and resource components of sentence processing in Parkinson's disease: an fMRI study

BACKGROUND

Sentence comprehension requires linguistic processing as well as cognitive resources such as working memory (WM) and information-processing speed (IPS). The authors hypothesize that sentence comprehension difficulty in patients with mild PD is due to degradation of the large-scale neural network that supports cognitive resources during sentence processing.

OBJECTIVE

To understand the neural basis for sentence comprehension difficulty in PD.

METHOD

Regional brain activity with blood oxygenation level-dependent fMRI was monitored while seven PD patients and nine healthy seniors answered a simple probe about written sentences that vary in their grammatical and cognitive resource properties.

RESULTS

Healthy seniors recruited posterolateral temporal and ventral inferior frontal regions of the left hemisphere, brain regions associated with grammatical processing that were also activated by PD patients. Healthy seniors also recruited left dorsal inferior frontal, right posterolateral temporal, and striatal regions that are associated with cognitive resources during sentence processing. Direct contrasts showed that striatal, anteromedial prefrontal, and right temporal regions are recruited to a significantly lesser degree in PD, but these patients have increased activation of right inferior frontal and left posterolateral temporal-parietal areas during sentence comprehension.

CONCLUSION

These findings associate impaired sentence comprehension in PD with interruption of a large-scale network important for cognitive resources during sentence processing. These results also imply compensatory up-regulation of cortical activity that allows patients with mild PD to maintain sentence comprehension accuracy.

Cortisol effects on aerobic and anaerobic metabolism, nitrogen excretion, and whole-body composition in juvenile rainbow trout

The influence of chronic cortisol elevation on metabolism, body composition, and fuel use patterns was examined in juvenile rainbow trout (Oncorhynchus mykiss). Measurements were performed in a control group (day 0) and in two experimental groups at days 3, 10, and 30 after treatment with a cortisol implant or a sham implant. All fish were fed 1% daily ration. Measured plasma cortisol levels were highest at day 3 and returned close to normal values by day 30 in cortisol-implanted fish. No plasma cortisol elevation was observed in the sham group. Growth was depressed in the cortisol-treated fish. Cortisol elevation resulted in increased plasma glucose concentrations during the entire experimental period, elevated CO2 production at day 3 and 30, and an elevated respiratory quotient (RQ) exceeding 1.0 on these days. Nitrogen excretion, estimated as the sum of ammonia-N plus urea-N excretion, and the nitrogen quotient exhibited small decreases at day 30. Total-N excretion, measured with a nitrogen oxidizer, was approximately twice the sum of ammonia-N plus urea-N excretion but exhibited a similar trend. Aerobic metabolism (routine O2 consumption) was higher on day 10 compared to sham-implanted fish, although not relative to day 0 control levels. Anaerobic metabolism increased substantially, as evidenced by pronounced plasma lactate elevations at days 3 and 10, a small increase in whole-body lactate on day 10, and the elevated RQ on days 3 and 30. Body composition exhibited an increase in total carbohydrate at days 3 and 10, mainly reflecting increased glycogen levels. Protein concentration was stable, indicating, in accord with the respirometry data, that protein usage did not fuel the increased metabolism or carbohydrate elevation. Redirection of nutrient uptake from food and/or mobilization of lipid stores (which decreased relative to the control group but not relative to shams) are suggested as possible energy sources for these actions of cortisol.

Development of a retinoic acid receptor-binding assay with rainbow trout tissue: characterization of retinoic acid binding, receptor tissue distribution, and developmental changes

Retinoic acid (RA) regulates the transcription of various genes required for several essential functions in vertebrates through binding to two classes of nuclear receptors, the retinoic acid receptors (RAR) and retinoid X receptors (RXR). We investigated nuclear RA binding in tissues from rainbow trout using the radiolabeled all-trans and 9-cis isomers of RA. Specific binding (indicative of receptor binding) of both all-trans- and 9-cis-RA was found in all tissues tested, including the adult trout ovary, testis, gill, liver, kidney, blood, white muscle, and heart. The kinetics and absolute amount of RA binding were dependent on both the tissue and the isomer of RA used. All-trans-RA bound with high affinity (K(d) approximately 1.0-3.9 nM), and low capacity (B(max) approximately 75-484 fmol RA/mg protein), while 9-cis-RA bound with lower affinity (K(d) approximately 7-56 nM), but with a greater capacity (B(max) approximately 214-1076 fmol RA/mg protein). The B(max) results were used to estimate RAR and RXR levels and revealed that the gill possesses primarily RARs while the liver possesses primarily RXRs. The RAR-specific competitor TTNPB was able to effectively displace all-trans-[3H]RA in most tissues, and the RXR-specific competitor AGN 194204 was able to effectively displace 9-cis-[3H]RA. However, TTNPB and AGN 194204 could not displace all of the RA in the kidney and testis, suggesting the existence of another nuclear RA binding protein. Binding of all-trans- and 9-cis-RA was also found in developing trout embryos and fry. Kinetic analysis revealed that RAR levels predominated at the eyed-embryo stage, but decreased 87% by the swim-up fry stage, while RXR levels remained relatively constant over the same time period. These findings suggest that RA and its receptors may play a key role in early trout development. This study has provided a simple and rapid radioligand binding assay that can identify RAR and RXRs in trout tissues.

An fMRI study of sex differences in regional activation to a verbal and a spatial task

Sex differences in cognitive performance have been documented, women performing better on some phonological tasks and men on spatial tasks. An earlier fMRI study suggested sex differences in distributed brain activation during phonological processing, with bilateral activation seen in women while men showed primarily left-lateralized activation. This blood oxygen level-dependent fMRI study examined sex differences (14 men, 13 women) in activation for a spatial task (judgment of line orientation) compared to a verbal-reasoning task (analogies) that does not typically show sex differences. Task difficulty was manipulated. Hypothesized ROI-based analysis documented the expected left-lateralized changes for the verbal task in the inferior parietal and planum temporal regions in both men and women, but only men showed right-lateralized increase for the spatial task in these regions. Image-based analysis revealed a distributed network of cortical regions activated by the tasks, which consisted of the lateral frontal, medial frontal, mid-temporal, occipitoparietal, and occipital regions. The activation was more left lateralized for the verbal and more right for the spatial tasks, but men also showed some left activation for the spatial task, which was not seen in women. Increased task difficulty produced more distributed activation for the verbal and more circumscribed activation for the spatial task. The results suggest that failure to activate the appropriate hemisphere in regions directly involved in task performance may explain certain sex differences in performance. They also extend, for a spatial task, the principle that bilateral activation in a distributed cognitive system underlies sex differences in performance.

Immediate coma following inertial brain injury dependent on axonal damage in the brainstem

OBJECT

Immediate and prolonged coma following brain trauma has been shown to result from diffuse axonal injury (DAI). However, the relationship between the distribution of axonal damage and posttraumatic coma has not been examined. In the present study, the authors examine that relationship.

METHODS

To explore potential anatomical origins of posttraumatic coma, the authors used a model of inertial brain injury in the pig. Anesthetized miniature swine were subjected to a nonimpact-induced head rotational acceleration along either the coronal or axial plane (six pigs in each group). Immediate prolonged coma was consistently produced by head axial plane rotation, but not by head coronal plane rotation. Immunohistochemical examination of the injured brains revealed that DAI was produced by head rotation along both planes in all animals. However, extensive axonal damage in the brainstem was found in the pigs injured via head axial plane rotation. In these animals, the severity of coma was found to correlate with both the extent of axonal damage in the brainstem (p < 0.01) and the applied kinetic loading conditions (p < 0.001). No relationship was found between coma and the extent of axonal damage in other brain regions.

CONCLUSIONS

These results suggest that injury to axons in the brainstem plays a major role in induction of immediate posttraumatic coma and that DAI can occur without coma.

A respirometric analysis of fuel use during aerobic swimming at different temperatures in rainbow trout (Oncorhynchus mykiss)

Instantaneous fuel usage at 5 degreesC or 15 degreesC was assessed by measurement of rates of O2 consumption (O2), CO2 excretion (CO2) and nitrogenous waste excretion (nitrogen =ammonia-N + urea-N) in juvenile rainbow trout (Oncorhynchus mykiss) at rest and during swimming at 45 % and 75 % of aerobic capacity (Ucrit). After 2 weeks of training at approximately 1 body length s-1 (BL s-1), critical swimming speeds (approximately 3.0 BL s-1) and whole-body energy stores (total protein, lipids and carbohydrates) were identical in fish acclimated to 5 degreesC or 15 degreesC. O2 and CO2 increased with swimming speed at both temperatures and were higher at 15 degreesC than at 5 degreesC at all speeds, but the overall Q10 values (1.23-1.48) were low in these long-term (6 weeks) acclimated fish. The respiratory quotient (CO2/O2, approximately 0.85) was independent of both temperature and swimming speed. In contrast to O2 and CO2, the rate of ammonia excretion was independent of swimming speed, but more strongly influenced by temperature (Q10 1. 4-2.8). Urea excretion accounted for 15-20 % of nitrogen, was unaffected by swimming speed and showed a tendency (P&lt;0.07) to be positively influenced by temperature at one speed only (45 % Ucrit). Nitrogen quotients (NQ nitrogen/O2) were generally higher in warm-acclimated fish, remaining independent of swimming speed at 15 degreesC (0.08), but decreased from about 0.08 at rest to 0.04 during swimming at 5 degreesC. Instantaneous aerobic fuel use calculations based on standard respirometric theory showed that both acclimation temperature and swimming speed markedly influenced the relative and absolute use of carbohydrates, lipids and proteins by trout. At rest, cold-acclimated trout used similar proportions of carbohydrates and lipids and only 27 % protein. During swimming, protein use decreased to 15 % at both speeds while the relative contributions of both lipid and carbohydrate increased (to more than 40 %). On an absolute basis, carbohydrate was the most important fuel for fish swimming at 5 degreesC. In contrast, resting fish acclimated to 15 degreesC utilized 55 % lipid, 30 % protein and only 15 % carbohydrate. However, as swimming speed increased, the relative contribution of carbohydrate increased to 25 %, while the protein contribution remained unchanged at approximately 30 %, and lipid use decreased slightly (to 45 %). On an absolute basis, lipid remained the most important fuel in fish swimming at 15 degreesC. These results support the concept that lipids are a major fuel of aerobic exercise in fish, but demonstrate that the contribution of protein oxidation is much smaller than commonly believed, while that of carbohydrate oxidation is much larger, especially at higher swimming speeds and colder temperature.

The interactive effects of feeding and exercise on oxygen consumption, swimming performance and protein usage in juvenile rainbow trout (Oncorhynchus mykiss)

The impacts of feeding on the rate of O2 consumption (O2), aerobic swimming performance, nitrogenous waste excretion (ammonia-N and urea-N) and protein utilization as an aerobic fuel were investigated in juvenile rainbow trout. Feeding trout to satiation (in groups of 120) resulted in rapid growth and elevated routine O2 by 68% relative to fasted fish and by 30% relative to trout fed a maintenance ration of 1% of body mass daily. This in-tank O2 of satiation-fed trout was approximately 70% of the O2max observed at the critical swimming speed (UCrit) when trials were performed on individual trout in swimming respirometers. Feeding increased O2 at all swimming speeds; the absolute elevation (specific dynamic action or SDA effect) was dependent on ration but independent of swimming velocity. There was no difference in O2max at UCrit amongst different ration treatments, but UCrit was significantly reduced by 15% in satiation-fed fish relative to fasted fish. These results suggest that the irreducible SDA load reduces swimming performance and that O2max is limited by the capacity to take up O2 at the gills and/or to deliver O2 through the circulatory system rather than by the capacity to consume O2 at the tissues. Ammonia-N and urea-N excretion increased with protein intake, resulting in a 6.5-fold elevation in absolute protein use and a fourfold elevation in percentage use of protein as an aerobic fuel for routine metabolism in satiation-fed trout (50-70%) relative to fasted fish (15%). Urea-N excretion increased greatly with swimming speed in all treatments, but remained a minor component of overall nitrogen excretion. However, even in satiation-fed fish, ammonia-N excretion remained constant as swimming speed increased, and protein did not become more important as a fuel source during exercise. These results suggest that the reliance on protein as a fuel is greatly dependent on feeding quantity (protein intake) and that protein is not a primary fuel for exercise as suggested by some previous studies.

Functional magnetic resonance imaging of regional brain activity in patients with intracerebral arteriovenous malformations before surgical or endovascular therapy

Functional magnetic resonance (MR) imaging was performed in six patients harboring proven intracerebral arteriovenous malformations (AVMs) using a noninvasive blood oxygen level-dependent technique based on the documented discrepancy between regional increases in blood flow and oxygen utilization in response to regional brain activation. Statistical functional MR maps were generated and overlaid directly onto conventional MR images obtained at the same session. In the six patients studied, a total of 23 separate functional MR imaging activation studies were performed. Of these, two runs were discarded because of motion artifacts. All of the remaining 21 studies demonstrated activation in or near expected regions for the paradigm employed. Qualitatively reproducible regional localizations of functional activity in unexpected sites were also seen. The authors' findings indicating aberrant mapping of cortical function may be explained on the basis of the plasticity of brain function, in that the developing brain can take over function that would normally have been performed by regions of brain encompassed by the lesion. Preliminary results in this study's small number of cases also indicate that activity demonstrated within the confines of the apparent AVM nidus may help predict the development of a posttherapy deficit. The authors demonstrate that functional MR imaging can be successfully and reproducibly performed in patients with intracerebral AVMs. Notwithstanding the paucity of normative data using functional MR imaging, the author' findings support cortical reorganization associated with these congenital lesions. Blood oxygen level-dependent MR imaging is a noninvasive method used to localize areas of eloquent cortex in patients harboring AVMs; it may prove to be of value in treatment planning.

Functional magnetic resonance imaging of regional brain activity in patients with intracerebral gliomas: findings and implications for clinical management

Functional magnetic resonance imaging (fMRI) was performed in seven patients harboring intracerebral gliomas proven by histological analysis using a noninvasive blood oxygen level-dependent technique based on the documented discrepancy between regional increases in blood flow and oxygen use in response to regional brain activation. We combined fMRI with conventional magnetic resonance imaging (MRI) during motor or language task activation experiments to investigate the potential usefulness of mapping regional brain activity as part of treatment planning in patients with intracerebral gliomas, in whom preservation of areas of functioning brain tissue is critical. Statistical fMRI maps were generated and directly mapped onto conventional MRI scans obtained at the same session. Of the five patients cooperative enough to remain motionless for the study and perform the task, the location of activation in the primary sensorimotor cortex on the side of the tumor was clearly displaced compared with that in the normal contralateral hemisphere in four patients. Four of the five tumors in these patients showed fMRI activation within the periphery of (or immediately adjacent to) areas of presumed tumor based on spin-echo MRI. In some patients with neurological deficit, the extent of activation was reduced on the side of the tumor as compared with the normal hemisphere. The supplemental motor area and the ipsilateral primary motor cortex were also reproducibly activated during motor tasks. We conclude that blood oxygen level-dependent fMRI can localize areas of cortical function in patients undergoing treatment planning for gliomas so that therapy can be directed away from regions of residual function. Our preliminary data suggest that functioning cortex within or adjacent to tumor margins can be demonstrated, which may correspond to partial preservation of clinical function. Our preliminary data also suggest that there may be a quantifiable difference on fMRI between activation in tumor-bearing cortex and activation in corresponding normal cortex in the contralateral hemisphere. We postulate that the magnitude of this difference may relate to the severity of patient deficit.

Treatment of experimental intracranial murine melanoma with a neuroattenuated herpes simplex virus 1 mutant

Brain metastases occur commonly in the setting of a variety of human cancers. At present, such cases are invariably fatal and highlight a need for research on new therapies. We have developed a mouse brain tumor model utilizing the Harding-Passey melanoma cell line injected intracranially into C57Bl/6 mice. Tumors develop in 100% of the mice and can be detected by magnetic resonance imaging as early as 5 days post cell injection. Death from tumor progression occurs between 12 and 16 days post cell injection. Stereotactic injection of the neuroattenuated HSV-1 strain 1716 into brain tumors 5 or 10 days postinjection of the melanoma cells results in a statistically significant increase in the time to development of neurological symptoms and in complete tumor regression and the long-term survival of some treated animals. Moreover, viral titration studies and immunohistochemistry suggest that replication of this virus is restricted to tumor cells and does not occur in the surrounding brain tissue. These results suggest that HSV-1 mutant 1716 shows particular promise for use as a therapeutic agent for the treatment of brain tumors.

Preliminary results from the third flight of the Millimeter Anisotropy Experiment (MAX)

Preliminary results from the June 1991 flight of MAX are presented. Simultaneous observations were made in bands centered at 6, 9, and 12 cm-1 with a bolometric receiver operating at 300 mK. The experimental sensitivities are the highest reported at angular scales of 0.3 degrees to 1.0 degrees. Interstellar dust is observed to have an emissivity [symbol, see text] nu 1.4+/-0.3 and to correlate with the Infrared Astronomical Satellite (IRAS) 100- map. After removal of emission from interstellar dust, 1.3 hr of integration on a 6 degrees scan yields an upper limit of temperature difference Delta T/T < 2.6 x 10(-5) at a Gaussian autocorrelation function centered at 0.5 degrees. The experiment and data analysis are described.

Defensive steroids from a carrion beetle (Silpha americana)

The defensive anal effluent discharged by Silpha americana in response to disturbance contains a mixture of steroids stemming from a glandular annex of the rectum. The compounds have been characterized as 15 beta-hydroxyprogesterone (1, principal component), 5 beta-pregnan-15 beta-ol-3,20-dione (2), 5 beta-pregnan-3 alpha, 15 beta-diol-20-one (3), 5 beta-pregnan-7 beta, 15 beta-diol-3,20-dione (4), 5 beta-pregnan-3 alpha, 7 beta, 15 beta-triol-20-one (5), 5 beta-pregnan-16 alpha-ol-3,20-dione (6), and 5 beta-pregnan-3 alpha, 16 alpha-diol-20-one (7), none previously found in insects. Bioassays with jumping spiders showed compounds 1 and 6 to be feeding deterrents at the 1 microgram level.