PBDE-47 and PBDE mixture (DE-71) toxicities and liver transcriptomic changes at PND 22 after in utero/postnatal exposure in the rat.

Pentabromodiphenyl ethers (PBDE) are found in human tissue, in household dust, and in the environment, and a particular concern is the potential for the induction of cancer pathways from these fat-soluble persistent organic pollutants. Only one PBDE cancer study has been conducted and that was for a PBDE mixture (DE-71). Because it is not feasible to test all PBDE congeners in the environment for cancer potential, it is important to develop a set of biological endpoints that can be used in short-term toxicity studies to predict disease outcome after long-term exposures. In this study, PBDE-47 was selected as the test PBDE congener to evaluate and compare toxicity to that of the carcinogenic PBDE mixture. The toxicities of PBDE-47 and the PBDE mixture were evaluated at PND 22 in Wistar Han rat (Crl: WI (Han)) pups after in utero/postnatal exposure (0, 0.1, 15, or 50 mg/kg; dams, GD6-21; pups, PND 12-PND 21; oral gavage daily dosing). By PND 22, PBDE-47 caused centrilobular hypertrophy and fatty change in liver, and reduced serum thyroxin (T4) levels; similar effects were also observed after PBDE mixture exposure. Transcriptomic changes in the liver included induction of cytochrome p450 transcripts and up-regulation of Nrf2 antioxidant pathway transcripts and ABC membrane transport transcripts. Decreases in other transport transcripts (ABCG5 & 8) provided a plausible mechanism for lipid accumulation, characterized by a treatment-related liver fatty change after PBDE-47 and PBDE mixture exposure. The benchmark dose calculation based on liver transcriptomic data was generally lower for PBDE-47 than for the PBDE mixture. The up-regulation of the Nrf2 antioxidant pathway and changes in metabolic transcripts after PBDE-47 and PBDE mixture exposure suggest that PBDE-47, like the PBDE mixture (NTP 2016, TR 589), could be a liver toxin/carcinogen after long-term exposure.

First detection of Edwardsiella ictaluri (Proteobacteria: Enterobacteriaceae) in wild Australian catfish.

The bacterium Edwardsiella ictaluri is considered to be one of the most significant pathogens of farmed catfish in the United States of America and has also caused mortalities in farmed and wild fishes in many other parts of the world. E. ictaluri is not believed to be present in wild fish populations in Australia, although it has previously been detected in imported ornamental fishes held in quarantine facilities. In an attempt to confirm freedom from the bacterium in Australian native fishes, we undertook a risk-based survey of wild catfishes from 15 sites across northern Australia. E. ictaluri was detected by selective culturing, followed by DNA testing, in Wet Tropics tandan (Tandanus tropicanus) from the Tully River, at a prevalence of 0.40 (95% CI 0.21-0.61). The bacterium was not found in fishes sampled from any of the other 14 sites. This is the first report of E. ictaluri in wild fishes in Australia.

Immunohistochemical Characterization of Sarcomas in Trp53+/- Haploinsufficient Mice.

The use of immunohistochemical (IHC) staining in determining and/or confirming the cellular origin of poorly differentiated sarcomas was evaluated in this study. Sarcomatous neoplasms were evaluated in a research study conducted in 2 strains of p53+/- haploinsufficient mice. The most common neoplasms were undifferentiated sarcomas, followed by osteosarcomas and rhabdomyosarcomas (RMSs). The RMSs were poorly differentiated and appeared similar to the pleomorphic, or adult type, RMS of humans. All sarcomas stained positive by IHC for the mesenchymal cell intermediate filament vimentin. The RMSs were identified by positive IHC staining for myogenin, a transcription factor specific to skeletal muscle. Osteosarcomas were easily identifiable on hematoxylin and eosin-stained slides; no generally accepted IHC stain specific for bone is presently available. Some of the undifferentiated sarcomas contained numerous macrophages that stained positive for F4/80, a macrophage marker; the positive-staining cells were considered to be infiltrating macrophages. One-third of the neoplasms observed in this study were associated with subcutaneous implanted electronic microchips used for animal identification. Based upon histopathologic evaluation and IHC staining, it was not possible to distinguish neoplasms associated with subcutaneous microchips from neoplasms not associated with microchips.

Do they stay or do they go? Acoustic monitoring of whale sharks at Ningaloo Marine Park, Western Australia.

Whale sharks Rhincodon typus were monitored via acoustic transmitters at the northern end of Western Australia's Ningaloo Marine Park to establish the extent to which the species inhabits the region beyond the whale-shark ecotourism industry season, which usually extends from March to August in each year. Despite the vast majority (c. 98%) of photographic submissions of R. typus from Ningaloo Reef being between March and August, acoustic detections from the tagged R. typus at Ningaloo were recorded in all months of the year, but do not preclude the occurrence of extended absences. It is concluded that as a species, R. typus occurs year round at Ningaloo, where it generally remains in close proximity to the reef edge, but that some individuals move outside of the detection range of the array for extended periods.

Sawfishes stealth revealed using computational fluid dynamics.

Detailed computational fluid dynamics simulations for the rostrum of three species of sawfish (Pristidae) revealed that negligible turbulent flow is generated from all rostra during lateral swipe prey manipulation and swimming. These results suggest that sawfishes are effective stealth hunters that may not be detected by their teleost prey's lateral line sensory system during pursuits. Moreover, during lateral swipes, the rostra were found to induce little velocity into the surrounding fluid. Consistent with previous data of sawfish feeding behaviour, these data indicate that the rostrum is therefore unlikely to be used to stir up the bottom to uncover benthic prey. Whilst swimming with the rostrum inclined at a small angle to the horizontal, the coefficient of drag of the rostrum is relatively low and the coefficient of lift is zero.

Tetrabromobisphenol A activates the hepatic interferon pathway in rats.

Tetrabromobisphenol A (TBBPA) is a widely used flame retardant in printed circuit boards, paper, and textiles. In a two-year study, TBBPA showed evidence of uterine tumors in female Wistar-Han rats and liver and colon tumors in B6C3F1 mice. In order to gain further insight into early gene and pathway changes leading to cancer, we exposed female Wistar Han rats to TBBPA at 0, 25, 250, or 1000mg/kg (oral gavage in corn oil, 5×/week) for 13 weeks. Because at the end of the TBBPA exposure period, there were no treatment-related effects on body weights, liver or uterus lesions, and liver and uterine organ weights were within 10% of controls, only the high dose animals were analyzed. Analysis of the hepatic and uterine transcriptomes showed TBBPA-induced changes primarily in the liver (1000mg/kg), with 159 transcripts corresponding to 132 genes differentially expressed compared to controls (FDR=0.05). Pathway analysis showed activation of interferon (IFN) and metabolic networks. TBBPA induced few molecular changes in the uterus. Activation of the interferon pathway in the liver occurred after 13-weeks of TBBPA exposure, and with longer term TBBPA exposure this may lead to immunomodulatory changes that contribute to carcinogenic processes.

Rapid proliferation of an endemic galaxiid following eradication of an alien piscivore (Perca fluviatilis) from a reservoir.

Following the complete eradication of the alien piscivorous perch Perca fluviatilis from a potable reservoir, the abundance of the endemic western minnow Galaxias occidentalis, which was previously undetectable prior to the initial eradication event, increased dramatically. The study reveals the potential of reservoirs to act as ecological refuges and has implications for understanding the relative effects of alien fishes v. habitat alteration on native freshwater fishes.

Discovery of a pupping site and nursery for critically endangered green sawfish Pristis zijsron.

A pilot study targeting sawfishes in the southern Pilbara region of Western Australia, which is undergoing a major expansion in human activity, was conducted using gillnets during April and October 2011 in the Ashburton Estuary and adjacent mangrove creeks. Catch per unit effort was greatest in the Ashburton Estuary in October, due to an influx of green sawfish Pristis zijsron pups, and was orders of magnitude higher than previously reported for any Pristidae; the study sites contained P. zijsron up to almost 3 m total length. This study identified the first pupping site for P. zijsron in Western Australia, and the most southerly known nursery area for the species in Australian waters, and is potentially the most important globally.

Mass spectrometric analysis of rat cerebrospinal fluid proteins following exposure to the neurotoxicant carbonyl sulfide.

RATIONALE: Using a proteomic-based approach we have investigated possible altered expression of a range of cerebral spinal fluid (CSF) proteins following exposure to the neurotoxicant carbonyl sulfide (COS). CSF is ideal for the investigation of markers of brain injury or disease since it is secreted from several central nervous system structures and changes in the CSF composition may reflect brain insult and many pathological processes. METHODS: Animals were placed in exposure chambers and were exposed to 0 ppm or 500 ppm COS for 1, 2 or 3 days, 6 h per day. After the last inhalation exposure, 50-70 µL CSF sample was obtained by lumbar puncture. CSF samples were analyzed by electrospray ionization mass spectrometry (ESI-MS) on either a Premier quadrupole time-of-flight (QTOF) or an Agilent 6340 ion trap and by matrix-assisted laser desorption/ionization (MALDI)-MS on a 4800 MALDI-TOF/TOF analyzer. RESULTS: The dynamic range of abundance of the identified proteins spanned over more than three orders of magnitude. The four most abundant proteins identified (albumin, cystatin C, serotransferrin, transthyretin) are major proteins that are present in both CSF and blood at high levels but the fifth most abundant protein identified (prostaglandin H2D isomerase) is the second most abundant protein in human CSF and is secreted and synthesized in the rat central nervous system. No significant differences were observed between COS-treated CSF samples and the control CSF samples because of blood contamination. CONCLUSIONS: Quantitative MS protein analyses of rat CSF is limited by the low sample volumes that can practicably be obtained from rats and the low protein concentrations in rat CSF. Results of this work suggest a clear need for CSF collection that would minimize blood contamination. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA.

Using remote underwater video to estimate freshwater fish species richness.

Species richness records from replicated deployments of baited remote underwater video stations (BRUVS) and unbaited remote underwater video stations (UBRUVS) in shallow (<1 m) and deep (>1 m) water were compared with those obtained from using fyke nets, gillnets and beach seines. Maximum species richness (14 species) was achieved through a combination of conventional netting and camera-based techniques. Chanos chanos was the only species not recorded on camera, whereas Lutjanus argentimaculatus, Selenotoca multifasciata and Gerres filamentosus were recorded on camera in all three waterholes but were not detected by netting. BRUVSs and UBRUVSs provided versatile techniques that were effective at a range of depths and microhabitats. It is concluded that cameras warrant application in aquatic areas of high conservation value with high visibility. Non-extractive video methods are particularly desirable where threatened species are a focus of monitoring or might be encountered as by-catch in net meshes.

Trophic ecology of northern Australia's terapontids: ontogenetic dietary shifts and feeding classification.

The diets of 21 terapontid species from freshwater environments in northern Australia were investigated to determine the similarity and dissimilarity among species and the extent of any ontogenetic shifts. Distinct ontogenetic dietary shifts occurred in all species for which sufficient data were available, with many species passing through several discrete trophic categories during their life histories. Diets of all juvenile terapontids were similar, mainly comprising aquatic insects and zooplankton. Larger size classes of terapontids diverged into a broad spectrum of feeding groups comprising carnivorous dietary modes (including piscivory and lepidophagy), omnivory (including frugivory and consumption of allochthonous prey), herbivory and detritivory. The results indicate that the terapontids represent Australia's most trophically diverse freshwater fish family.

Parasites of native and exotic freshwater fishes in south-western Australia.

In this study, 1429 fishes of 18 different species (12 native and six exotic) were sampled from 29 localities to compare the levels of parasitism between native and exotic fish species and to examine the relationship between environmental degradation and parasite diversity. Forty-four putative species of parasites were found and most of these appear to be native parasites, which have not previously been described. Two parasite species, Lernaea cyprinacea and Ligula intestinalis, are probably introduced. Both were found on or in a range of native fish species, where they may cause severe disease. Levels of parasitism and parasite diversity were significantly greater in native fishes than in exotic species, and this may contribute to an enhanced demographic performance and competitive ability in invading exotics. Levels of parasitism and parasite diversity in native fishes were negatively related to habitat disturbance, in particular to a suite of factors that indicate increased human use of the river and surrounding environment. This was due principally to the absence in more disturbed habitats of a number of species of endoparasites with complex life cycles, involving transmission between different host species.

The shift in muscle's length-tension relation after exercise attributed to increased series compliance.

Eccentric exercise can produce damage to muscle fibres. Here damage indicators are measured in the medial gastrocnemius muscle of the anaesthetised cat after eccentric contractions on the descending limb of the muscle's length-tension relation, compared with eccentric contractions on the ascending limb and concentric contractions on the descending limb. One damage indicator is a shift of the optimum length for peak active tension, in the direction of longer muscle lengths. The shift has been attributed to an increase in muscle compliance. It is a corollary of a current theory for the mechanism of the damage. With the intention of seeking further support for the theory, in these experiments we test the idea that other damage indicators, specifically the fall in twitch:tetanus ratio and in muscle force are due, in part, to such an increase in compliance. This was tested in an undamaged muscle by insertion of a compliant spring (0.19 mm N(-1)) in series with the muscle. This led to a fall in tetanic tension by 17%, a shift in optimum length of 1.7 mm in the direction of longer muscle lengths and a fall in twitch tetanus ratio by 15%. The fall in tension is postulated to be due to development of non-uniform sarcomere lengths within muscle fibres. It is concluded that after a series of eccentric contractions of a muscle, the fall in force is the result of a number of interdependent factors, not all of which are a direct consequence of the damage process.

Force matching errors following eccentric exercise.

During eccentric exercise contracting muscles are forcibly lengthened, to act as a brake to control motion of the body. A consequence of eccentric exercise is damage to muscle fibres. It has been reported that following the damage there is disturbance to proprioception, in particular, the senses of force and limb position. Force sense was tested in an isometric force-matching task using the elbow flexor muscles of both arms before and after the muscles in one arm had performed 50 eccentric contractions at a strength of 30% of a maximum voluntary contraction (MVC). The exercise led to an immediate reduction of about 40%, in the force generated during an MVC followed by a slow recovery over the next four days, and to the development of delayed onset muscle soreness (DOMS) lasting about the same time. After the exercise, even though participants believed they were making an accurate match, they made large matching errors, in a direction where the exercised arm developed less force than the unexercised arm. This was true whichever arm was used to generate the reference forces, which were in a range of 5-30% of the reference arm's MVC, with visual feedback of the reference arm's force levels provided to the participant. The errors were correlated with the fall in MVC following the exercise, suggesting that participants were not matching force, but the subjective effort needed to generate the force: the same effort producing less force in a muscle weakened by eccentric exercise. The errors were, however, larger than predicted from the measured reduction in MVC, suggesting that factors other than effort might also be contributing. One factor may be DOMS. To test this idea, force matches were done in the presence of pain, induced in unexercised muscles by injection of hypertonic (5%) saline or by the application of noxious heat to the skin over the muscle. Both procedures led to errors in the same direction as those seen after eccentric exercise.

The influence of fatigue on damage from eccentric contractions in the gastrocnemius muscle of the cat.

Eccentric exercise is unique in that it can lead to muscle damage and soreness. Concentric exercise is not accompanied by evidence of damage. There are reports in the literature that muscle fatigue is a factor determining the amount of damage from eccentric exercise. Our theory for the damage process predicts that susceptibility for damage is independent of fatigue. Experiments were carried out to test this prediction as well as to seek other evidence in support of our theory. Comparisons were made between the effects of eccentric and concentric contractions. The nerve supply to the medial gastrocnemius muscle of the anaesthetized cat was divided into three equal portions in terms of the tension they generated. In the first experiment a muscle portion was fatigued by giving it 200 shortening contractions over 12 mm at a shortening speed of 50 mm s(-1). This led to a mean fall in isometric tension (37 +/- 4%) without a significant shift in the optimum length for peak active tension. Giving the fatigued muscle 10 eccentric contractions, active stretches over 6 mm at 50 mm s(-1), beginning from the muscle's optimum length led to a further fall in tension (11% +/- 7%) and a significant shift in optimum length (3.7 mm +/- 0.6 mm) in the direction of longer muscle lengths. The shift in optimum was taken as an indicator of muscle damage. This shift was not significantly different from that seen after eccentric contractions carried out on an unfatigued muscle. After a series of eccentric or concentric contractions, tension at the end of a ramp shortening of 6 mm at 10 mm s(-1) fell more than isometric tension, and by near equal amounts for the two kinds of contractions. In an unfatigued muscle, if tension was altered by changing the rate of stimulation, the fall in shortening tension was greater than after either concentric or eccentric contractions. These observations were seen to be consistent with predictions of the proposed mechanism for the damage process.

Identifying athletes at risk of hamstring strains and how to protect them.

1. One common soft-tissue injury in sports involving sprinting and kicking a ball is the hamstring strain. Strain injuries often occur while the contracting muscle is lengthened, an eccentric contraction. We have proposed that the microscopic damage to muscle fibres that routinely occurs after a period of unaccustomed eccentric exercise can lead to a more severe strain injury. 2. An indicator of susceptibility for the damage from eccentric exercise is the optimum angle for torque. When this is at a short muscle length, the muscle is more prone to eccentric damage. It is known that subjects most at risk of a hamstring strain have a previous history of hamstring strains. By means of isokinetic dynamometry, we have measured the optimum angle for torque for nine athletes with a history of unilateral hamstring strains. We also measured optimum angles for 18 athletes with no previous history of strain injuries. It was found that mean optimum angle in the previously injured muscles was at a significantly shorter length than for the uninjured muscles of the other leg and for muscles of both legs in the uninjured group. This result suggests that previously injured muscles are more prone to eccentric damage and, therefore, according to our hypothesis, more prone to strain injuries than uninjured muscles. 3. After a period of unaccustomed eccentric exercise, if the exercise is repeated 1 week later, there is much less evidence of damage because the muscle has undergone an adaptation process that protects it against further damage. We propose that for athletes considered at risk of a hamstring strain, as indicated by the optimum angle for torque, a regular programme of mild eccentric exercise should be undertaken. This approach seems to work because evidence from a group of athletes who have implemented such a programme shows a significant reduction in the incidence of hamstring strains.

Human forearm position sense after fatigue of elbow flexor muscles.

After a period of eccentric exercise of elbow flexor muscles of one arm in young, adult human subjects, muscles became fatigued and damaged. Damage indicators were a fall in force, change in resting elbow angle and delayed onset of soreness. After the exercise, subjects were asked to match the forearm angle of one arm, whose position was set by the experimenter, with their other arm. Subjects matched the position of the unsupported reference arm, when this was unexercised, with a significantly more flexed position in their exercised indicator arm. Errors were in the opposite direction when the reference arm was exercised. The size of the errors correlated with the drop in force. Less consistent errors were observed when the reference arm was supported. A similar pattern of errors was seen after concentric exercise, which does not produce muscle damage. The data suggested that subjects were using as a position cue the perceived effort required to maintain a given forearm angle against the force of gravity. The fall in force from fatigue after exercise meant more effort was required to maintain a given position. That led to matching errors between the exercised and unexercised arms. It was concluded that while a role for muscle spindles in kinaesthesia cannot be excluded, detailed information about static limb position can be derived from the effort required to support the limb against the force of gravity.

Fluoxetine exposures: are they safe for children?

Although it is generally believed that unintentional ingestions of fluoxetine by children are relatively safe, there are no large published studies supporting this concept. The goal of this retrospective study is to determine the signs and symptoms of these children. Inclusion criteria included fluoxetine exposures from six certified regional poison centers: <6 years old, known amount, single substance, 20 mg or more ingested, and follow up done to determine outcome. One hundred twenty cases met all inclusion criteria. Average age was 25 months +/- 12 months. Median amount ingested was 20 mg. Mild signs and symptoms were noted in 3.3%, and no major signs or symptoms were reported. In 48 cases, a milligram per kilogram dose was calculated, and the median dose ingested was 2.26 mg/kg. In 92% of the cases, the amount ingested was 60 mg or below. These children will have no adverse effects or only minimal effects and require no emergency treatment or gastric decontamination.

Low-frequency depression of tension in the cat gastrocnemius muscle after eccentric exercise.

Subjecting a muscle to a series of eccentric contractions in which the contracting muscle is lengthened results in a number of changes in its mechanical properties. These include a fall in isometric tension that is particularly pronounced during low-frequency stimulation, a phenomenon known as low-frequency depression (LFD). Reports of LFD have not taken into account the shift in optimum length for active tension generation to longer muscle lengths that takes place after eccentric contractions. Given the length dependence of the stimulation frequency-tension curve, we tested the hypothesis that the change in this relationship after eccentric exercise is due to the shift in optimum length. We measured LFD by recording tension in response to a linearly increasing rate of stimulation of the nerve to medial gastrocnemius of anesthetized cats, over the range 0-100 pulses per second. Tension responses were measured before and after 50 eccentric contractions consisting of 6-mm stretches starting at 3 mm below optimum length and finishing at 3 mm above it. An index of LFD was derived from the tension responses to ramp stimulation. It was found that LFD after the eccentric contractions was partly, but not entirely, due to changes in the muscle's optimum length. An additional factor was the effect of fatigue. These observations led to the conclusion that the muscle length dependence of LFD was reduced by eccentric contractions. All of this means that after eccentric exercise the tension deficit at low rates of muscle activation is likely to be less severe than first thought.