RESUMEN

Routine post mortems of deceased penguins from Penguin Island, Western Australia, found that a temporal cluster of cases presented with characteristic gross and microscopic changes, namely birds in good body condition with hepatomegaly and splenomegaly, multifocal hepatic and splenic necrosis and numerous, 1-2 µm diameter protozoan parasites within the necrotic foci. Electron microscopy identified the protozoa as belonging to the phylum Apicomplexa. Molecular investigations by PCR gave inconsistent results. PCR performed by an external laboratory identified a novel Haemoproteus spp. organism in samples from 4 of 10 cases from this group, while PCR at Murdoch University identified Toxoplasma gondii in 12 of 13 cases (including 9 of the 10 assayed at the external laboratory). Immunohistochemistry of formalin fixed tissues also identified Toxoplasma in the hepatic and splenic lesions. The distinctive mortalities which were observed in this group of penguins are attributed to a fulminant toxoplasmosis, with a concurrent Haemoproteus infection in some cases. Though the clinical signs of infection are unknown, the gross and microscopic appearance at post mortem is sufficiently characteristic to allow a diagnosis to be made on these features. Definitive confirmation of Toxoplasma infection can be made by immunohistochemistry or PCR.

RESUMEN

The current study assessed the neuroprotective efficacy of magnesium using a FAST-Mag trial treatment protocol alone, and in combination with mild hypothermia, in Sprague Dawley rats subjected to permanent, middle cerebral artery occlusion (MCAO). Treatment with magnesium (MgSO4.7H2O) consisted of an intravenous loading dose (LD: 360 µmol/kg) and a 24 hour infusion (120 µmol/kg/h), while mild hypothermia at 35°C was maintained for 24 hours. Treatment groups consisted of animals receiving: i) saline; ii) magnesium LD/infusion at 1.5 h/2.5 h post-MCAO; iii) magnesium LD/infusion at 1.5 h/2.5 h post-MCAO and hypothermia commencing at 2.5 h post-MCAO; iv) magnesium LD and hypothermia at 1.5 h and magnesium infusion at 2.5 h post-MCAO; v) hypothermia commencing at 1.5 h post-MCAO and magnesium LD/infusion at 2.5 h post-MCAO; and vi/vii) hypothermia commencing at 1.5 h or 2.5 h post-MCAO. No treatment significantly reduced infarct volumes or improved adhesive tape removal time when measured 48 hours after MCAO. These findings indicate that FAST-Mag treatment alone or with mild hypothermia may not provide benefit after ischemic stroke, associated with permanent cerebral artery occlusion.

Asunto(s)

RESUMEN

In this study we compared the efficacy of mild (35°C) and moderate (33°C) hypothermia alone and when combined with magnesium in a transient focal cerebral ischaemia rat model. Spontaneously Hypertensive rats were subjected to 90min of transient intraluminal thread middle cerebral artery occlusion (MCAO). Thirty minutes after reperfusion animals were treated with mild (35°C/24h) or moderate (33°C/24h) hypothermia combined with either magnesium (intravenous MgSO4 infusion: 360µmol/kg, then 120µmol/kg/h for 24h) or a similar volume of saline. Control animals were maintained normothermic (37°C/24h) and received vehicle infusion (saline for 24h). Infarct volumes and functional assessment (bi-symmetrical adhesive tape removal) were measured 48h after MCAO induction. After transient MCAO, only moderate hypothermia and mild hypothermia combined with magnesium treatment significantly reduced infarct volumes by 32.9% (P=0.01) and by 24.8% (P=0.046), respectively. Mild hypothermia alone reduced infarct volume by 23.8%, but did not reach statistical significance (P=0.054), while moderate hypothermia combined with magnesium reduced infarct volume by 17.3% (P=0.17). No treatment improved adhesive tape removal time. In summary, moderate hypothermia and mild hypothermia with or without magnesium can reduce infarct volume, however magnesium may reduce the efficacy of moderate hypothermia. Given the potential advantages of mild hypothermia over moderate hypothermia in terms of side-effects and induction, and the potential beneficial effects of magnesium, these findings have important implications for the use of hypothermia for stroke.

Asunto(s)

RESUMEN

In this study, we have assessed the ability of two TAT-fused peptides PYC36D-TAT and JNKI-1D-TAT (JNKI-1 or XG-102), which respectively inhibit jun proto-oncogene (c-Jun) and c-Jun N-terminal kinase (JNK) activation, to reduce infarct volume and improve functional outcome (adhesive tape removal) after transient focal cerebral ischemia in Spontaneously Hypertensive (SH) rats. PYC36D-TAT and JNKI-1D-TAT peptide batches used for experiments were tested in vitro and protected cortical neurons against glutamate excitotoxicity. Rats were treated intravenously with three different doses of PYC36D-TAT (7.7, 76, or 255 nmol/kg), JNKI-1D-TAT (255 nmol/kg), D-TAT peptide (255 nmol/kg), or saline (vehicle control), 10 minutes after reperfusion after 90 minutes of middle cerebral artery occlusion (MCAO). Contrary to other stroke models, no treatment significantly reduced infarct volume or improved functional score measurements compared with vehicle-treated animals when assessed 48 hours after MCAO. Additionally, assessment of the JNKI-1D-TAT peptide, when administered 1 or 2 hours after reperfusion after 90 minutes of MCAO, also did not improve histological or functional outcomes at 48 hours after occlusion. This study is the first to evaluate the efficacy of PYC36D-TAT and JNKI-1D-TAT using the SH rat, which has recently been shown to be more sensitive to AMPA receptor activation rather than to NMDA receptor activation after cerebral ischemia, and which may have contributed to the negative findings.

Asunto(s)

RESUMEN

This study presents our findings on the extent of neuronal damage in the hippocampal CA1-4 subfields following global (forebrain) cerebral ischemia in rats when using different blood pressure levels (37 vs 45 mmHg) and bilateral carotid occlusion durations (8 vs 10 min) under isoflurane anesthesia. We observed that global ischemia induced at a blood pressure of 37 mmHg resulted in high-grade CA1 neuron injury (>90%) at either duration of carotid occlusion. In contrast, global ischemia induced at a blood pressure of 45 mmHg resulted in either high-grade CA1 neuronal loss or a neuronal loss of ≈50% or less. We also noted that a post-reperfusion EEG recovery time (return of burst suppression spikes) of >12 min was associated with an 85% rate of high-grade CA1 neuronal injury. Neuronal loss in the other hippocampal subfields did not differ significantly between any of the 4 different model parameters tested. In these subfields ≈55% neuronal loss occurred in the CA2 subfield, and ≈30% in the CA3 and CA4 subfields. These findings highlight the need to assess different model parameters in order to achieve consistent high-grade CA1 neuronal damage, which, among other experimental outcomes, will improve the ability to uncover therapeutic effects using the least possible animals when assessing a neuroprotective treatment.

Asunto(s)

RESUMEN

We first assessed the neuroprotective efficacy of mild hypothermia (35°C/24 hours) alone and in combination with magnesium (intravenous loading dose: 360 µmol/kg; 48 hours infusion: 120 µmol/kg/h) commencing 4 hours after global ischemia. Treatment with mild hypothermia alone (CA1 survival rate: 8.7%±0.9%) or with magnesium (9.0%±2.9%) did not significantly increase hippocampal CA1 neuronal survival compared with saline-treated controls (7.1%±0.7%). Next, we assessed mild hypothermia (35°C/24 hours) and moderate hypothermia (33°C/24 hours), alone or in combination with magnesium, when commenced 2 hours after global ischemia. At this time point, all treatments significantly increased CA1 neuronal survival compared with saline controls (CA1 survival rates: mild hypothermia: 13.6%±1.8%; mild hypothermia + magnesium: 19.4%±8.7%; moderate hypothermia: 15.9%±4.1%; moderate hypothermia + magnesium: 21.1%±11.2%; saline control: 6.7%±1.6%; p<0.001). Although a trend for increased neuroprotection was observed when hypothermia was combined with magnesium, it did not reach statistical significance. It also appears that when a 24-hour hypothermia treatment is commenced earlier (≤2 hours postischemia) there is no difference in efficacy between mild and moderate hypothermia.

RESUMEN

OBJECTIVE: To determine if remote ischemic preconditioning (RIPC) induced by transient limb ischemia is protective against delayed hippocampal neuronal death in rats undergoing transient global cerebral ischemia (GCI). METHOD: Animals were randomized into 3 groups: Group I (Control, n = 5) underwent sham procedure, namely, general anesthesia x 2, without cerebral ischemia; Group II (RIPC + GCI, n = 5) was subjected to RIPC, induced by transient left hind limb ischemia under general anesthesia prior to GCI; Group III (GCI only, n = 5) underwent sham procedure under general anesthesia prior to GCI. Twenty-four hours after the RIPC or sham procedure, a transient GCI was induced for 8 minutes in Groups II and III by means of bilateral common carotid artery occlusion and hypotension. Hippocampal CA1 neurons were histologically examined at 7 days after ischemia. RESULTS: There was no significant difference between the RIPC group and the ischemia only group. The number of neurons in the RIPC group were 0.90 (95% CI 0.20, 4.08) times the number in the ischemia group (p=0.89). The number of neurons in the RIPC group were 0.03 (95% CI 0.01, 0.10) times the number in the Control group (p=0.0001). CONCLUSION: Second window of the RIPC does not prevent hippocampal CA1 neuronal death at 7 days after transient global cerebral ischemia.

Asunto(s)

RESUMEN

BACKGROUND AND PURPOSE: Brain injury after stroke and other cerebral ischemic events is a leading cause of death and disability worldwide. Our purpose here is to argue in favor of combined mild hypothermia (35 degrees C) and magnesium as an acute neuroprotective treatment to minimize ischemic brain injury. METHODS: Drawing on our own experimental findings with mild hypothermia and magnesium, and in light of the moderate hypothermia trials in cardiac arrest/resuscitation and magnesium trials in ischemic stroke (IMAGES, FAST-Mag), we bring attention to the advantages of mild hypothermia compared with deeper levels of hypothermia, and highlight the existing evidence for its combination with magnesium to provide an effective, safe, economical, and widely applicable neuroprotective treatment after brain ischemia. With respect to effectiveness, our own laboratory has shown that combined mild hypothermia and magnesium treatment has synergistic neuroprotective effects and reduces brain injury when administered several hours after global and focal cerebral ischemia. CONCLUSIONS: Even when delayed, combined treatment with mild hypothermia and magnesium has broad therapeutic potential as a practical neuroprotective strategy. It warrants further experimental investigation and presents a good case for assessment in clinical trials in treating human patients after brain ischemia.

Asunto(s)

RESUMEN

Translational stroke research is a challenging task that needs long term team work of the stroke research community. Highly reproducible stroke models with excellent outcome consistence are essential for obtaining useful data from preclinical stroke trials as well as for improving inter-lab comparability. However, our review of literature shows that the infarct variation coefficient of commonly performed stroke models ranges from 5% to 200%. An overall improvement of the commonly used stroke models will further improve the quality for experimental stroke research as well as inter-lab comparability. Many factors play a significant role in causing outcome variation; however, they have not yet been adequately addressed in the Stroke Therapy Academic Industry Roundtable (STAIR) recommendations and the Good Laboratory Practice (GLP). These critical factors include selection of anesthetics, maintenance of animal physiological environment, stroke outcome observation, and model specific factors that affect success rate and variation. The authors have reviewed these major factors that have been reported to influence stroke model outcome, herewith, provide the first edition of stroke model guidelines so to initiate active discussion on this topic. We hope to reach a general agreement among stroke researchers in the near future with its successive updated versions.

RESUMEN

There is evidence from global cerebral ischemia experiments in the rat that the neuroprotection attributable to magnesium treatment depends on the concurrent presence of at least mild hypothermia. We set out to determine to what extent spontaneous hypothermia occurred after transient middle cerebral artery occlusion in the rat, and whether this hypothermia influenced the outcome of magnesium treatment. We found that rectal temperatures from 30 min to 3h after recovery from anaesthesia/surgery were 1 °C lower than in the period from 4 to 6h. Striatal infarcts were significantly reduced by 32% in animals treated with 360 µmol/kg MgSO(4) intravenously immediately prior to ischemia. A higher magnesium dose of 720 µmol/kg had not effect on infarct volume. Having previously established that these two doses of magnesium are ineffective in normothermic animals using this model, we conclude that the mild spontaneous hypothermia contributed to the observed neuroprotective effect of magnesium in this study, and that previous studies of magnesium in cerebral ischemia have likely been confounded in this way.

Asunto(s)

RESUMEN

BACKGROUND AND PURPOSE: Using transient focal and global cerebral ischemia models in the rat, we have previously shown that MgSO4 is not neuroprotective unless it is combined with mild hypothermia. This study establishes a therapeutic time window for combined MgSO4 and mild hypothermia treatment after permanent middle cerebral artery occlusion (MCAO). METHODS: Rats were subjected to permanent intraluminal thread MCAO and animals were treated 2, 4 or 6 h after ischemia with a MgSO4 infusion (360 micromol/kg, then 120 micromol/kg/h) and mild hypothermia (35 degrees C) or with vehicle for 24 h. At the 2 h time point, treatment with hypothermia alone and MgSO4 alone were also assessed. Infarct volumes were measured 48 h after MCAO induction. RESULTS: After permanent MCAO, combined MgSO4 and hypothermia treatment reduced infarct volumes by 54% at 2 h (P = 0.048) and by 39% at 4 h (P = 0.012), but there was no treatment effect detected at 6 h or in the hypothermia alone or MgSO4 alone groups. CONCLUSIONS: These findings support our earlier work highlighting the neuroprotective effect of MgSO4 when combined with mild hypothermia, even when treatment is delayed by several hours.

Asunto(s)

RESUMEN

Reptiles, particularly snakes, could serve as bioindicators of contamination because some are comparatively long-lived, exhibit different trophic levels, and are at the top of their food chains. We test the null hypothesis that there are no differences in the concentrations of heavy metals in the blood, muscle and liver of water snakes (Nerodia spp.) from rivers in New Jersey, Tennessee and South Carolina. While the former site is in an urban/suburban area, the latter two sites are relatively rural and are located on Department of Energy sites. For the snakes from New Jersey, there were significant differences in metal concentrations among tissues for all metals, the highest levels for arsenic and selenium were in liver and kidney, for cadmium were in the liver, for chromium and lead were in skin, and for mercury and manganese were in the muscle. Body length was not correlated with metal levels, and there were more significant correlations for skin with internal tissues than for blood with other tissues. There were more significant correlations for mercury than for other metals. In comparing metal levels among states, levels were generally higher for snakes collected from South Carolina. These data indicate that, since water snakes accumulate contaminants differentially as a function of location, they can be useful bioindicators of environmental exposure to contaminants. Moreover, because of their wide geographical distribution and use of varying trophic compartments, this genus can be useful for cross-site comparisons.

Asunto(s)

RESUMEN

We compared the levels of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in a small species of fish (Central stonerollers, Campostoma anomalum) collected from East Fork Poplar Creek (EFPC) and a reference site in eastern Tennessee. Stonerollers are minnows in the Cyprinidae family that serve as prey for many carnivores in aquatic systems. Fish were collected from East Fork Poplar Creek within the U.S. Department of Energy's Y-12 National Security Complex, part of the Oak Ridge Reservation, and from a reference stretch of the Little River in East Tennessee. Whole fish were homogenized for analysis. Concentrations of all metals (except arsenic) were significantly higher in stonerollers from EFPC compared to the reference site. Mercury levels in minnows from EFPC averaged 0.4 ppm (microg/g), four times higher than the average for fish in the U.S. in general. This was higher than levels in fish from the nearby Clinch River and higher than fillets of white bass (Morone chrysops) from the same creek. Most metal levels were inversely related to size and weight of the stonerollers, perhaps due to growth dilution.

Asunto(s)

RESUMEN

Comparatively little is known about heavy metal levels in reptiles, particularly for lizards. Yet lizards often are common predators that could serve as bioindicators of contamination on a small spatial scale. This study examined the differences in metal concentrations of adult brown anoles (Anolis sagrei) for arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in six locations in southern Florida, USA, from Lake Okeechobee (Pahokee) south to Key West. We predicted that levels of contaminants would be higher in the industrialized ports (Port Everglades, Port of Miami) and at a landfill (in Key West) compared to a campground, tropical garden, and marine laboratory. Males were significantly larger than females, as expected. Although there were significant locational differences in metal concentrations, they did not fit a consistent pattern, either among sites or between reference and study sites. However, the lowest levels were generally found at Everglades Marina and Campground (except for selenium) and at Fairchild Tropical Garden (except for manganese). For females, size was significantly correlated with cadmium, lead, and mercury levels, while for males, there were significant correlations between length and arsenic, chromium, and manganese concentrations. Where there were gender differences in metal levels, females had significantly higher levels than males even though they were smaller. We attribute these gender differences to differences in diet due to microhabitat differences in foraging locations. Females spend more time feeding near the ground and males spend more time feeding on tree trunks and branches where they consume more flying insects. This is the first study that examines concentrations of metals in lizards in the United States, and suggests that nonnative lizards may be useful in toxicological studies.

Asunto(s)

RESUMEN

Risks to humans and other organisms from consuming fish have become a national concern in the USA. In this paper, we examine the concentrations of 137Cs, arsenic, beryllium, cadmium, lead, mercury, and selenium in three species of fish from two river reaches adjacent to the US Department of Energy's Oak Ridge Reservation in Tennessee. We were interested in whether there were species and locational differences in radiocesium and metal concentrations and whether concentrations were sufficiently high to pose a potential health risk to humans or other receptors. Striped bass (Morone saxatilis) were significantly larger than white bass (M. chrysops), and crappie (Pomoxis spp.) were the smallest fish. Lead was significantly lower in striped bass, mercury was significantly higher in striped bass, and selenium was significantly higher in white bass compared to the other species. There were no other species differences in contaminants. White bass, the only species that was sufficiently abundant for a comparison, had significantly higher concentrations of cadmium, lead, and selenium in fillets from the Clinch River and significantly higher concentrations of mercury in fillets from Poplar Creek. The low concentrations of most contaminants in fish from the Clinch River do not appear to present a risk to humans or other consumers, although mercury concentrations in striped bass ranged as high as 0.79 ppm, well above the 0.5-ppm action level for human consumption of some US states.

Asunto(s)

RESUMEN

Catching and eating fish is usually viewed as a fun, healthy and safe activity. However, with continuing increases in fish consumption advisories due to the contamination of our environment, anglers have to decide whether or not to eat the fish they catch. The Clinch River arm of Watts Bar Reservoir is under a fish consumption advisory because of elevated PCB concentrations in striped bass (Morone saxatilis), catfish (Ictalurus spp.) and sauger (Stizostedion canadense) due in part from contaminants released from the US Department of Energy's (USDOE's) Oak Ridge Reservation (ORR) in East Tennessee. To obtain information about the demographics, fishing behavior, knowledge, fish consumption and risk perception of anglers, a survey was conducted of 202 people actively fishing either on land or by boat along the Clinch River arm of Watts Bar Reservoir adjacent to the ORR from Melton Hill Dam to the Poplar Creek confluence or on Poplar Creek within ORR boundaries from mid-March to early November 2001. Even though 81% of people interviewed knew about the fish consumption advisories for the study area, 48% of them thought the fish were safe to eat, while 38% ate the fish that they caught from the study area. Approximately 36% of anglers who had knowledge of the fish consumption warnings ate fish from the study area. Providing confirmation that people fish for many reasons, 35% of anglers interviewed did not eat fish at all. The majority of anglers interviewed knew about the fish consumption advisories because of the signs posted throughout the study area. However, few people knew the correct fish advisories. Significantly fewer blacks had knowledge of the fish consumption warnings than whites. Information resulting from this study could be used to design a program with the objective of reaching the people who may be most at risk from eating fish caught from the Clinch River arm of Watts Bar Reservoir.

Asunto(s)

RESUMEN

Reptiles, specifically lizards and snakes, usually are excluded from environmental contamination studies and ecological risk assessments. This brief summary of available lizard and snake environmental contaminant data is presented to assist in the development of priorities for lizard and snake ecotoxicology. Most contaminant studies were not conducted recently, list animals found dead or dying after pesticide application, report residue concentrations after pesticide exposure, compare contaminant concentrations in animals from different areas, compare residue concentrations found in different tissues and organs, or compare changes in concentrations over time. The biological significance of the contaminant concentrations is rarely studied. A few recent studies, especially those conducted on modern pesticides, link the contaminant effects with exposure concentrations. Nondestructive sampling techniques for determining organic and inorganic contaminant concentrations in lizards and snakes recently have been developed. Studies that relate exposure, concentration, and effects of all types of environmental contaminants on lizards and snakes are needed. Because most lizards eat insects, studies on the exposure, effects, and accumulation of insecticides in lizards, and their predators, should be a top priority. Because all snakes are upper-trophic-level carnivores, studies on the accumulation and effects of contaminants that are known to bioaccumulate or biomagnify up the food chain should be the top priority.

Asunto(s)