Efficiency-corrected PCR quantification for identification of prevalence and load of respiratory disease-causing agents in feedlot cattle.

Bovine respiratory disease (BRD) is the most prevalent disease in feedlot cattle worldwide with Bovine alphaherpesvirus 1 (BoAHV1), Histophilus somni, Mannheimia haemolytica, Mycoplasma bovis, Pasteurella multocida and Trueperella pyogenes accepted to be common etiological agents associated with BRD. Although these agents are common in the upper and lower airways in clinical BRD cases, some also exist as normal flora suggesting their presence in the upper airways alone is not necessarily informative with respect to disease status or risk. To determine the relationship between presence, load and disease status, we investigated the relationship between load in the upper airways at induction and active BRD cases in feedlot cattle using efficiency-corrected PCR quantification. By this approach, we were able to accurately determine the prevalence and load of the key BRD agents in the upper respiratory tract showing that cattle in the hospital pen had a higher prevalence, and load, of these agents both singly and in combination compared to cattle sampled at feedlot induction. A combination of agents was the most accurate indicator of BRD risk with cattle with four or more agents detected in the upper airway more likely to be undergoing treatment for BRD than non-BRD ailments. In addition, M. bovis was rarely detected at feedlot induction but was identified at high prevalence in cattle in the hospital pen. These findings present a potential new technological approach for the investigation, analysis and identification of BRD-associated viral and bacterial agents for Australian feedlot systems as well as for BRD disease management and treatment.

The impact of rising sea temperatures on an Arctic top predator, the narwhal.

Arctic top predators are expected to be impacted by increasing temperatures associated with climate change, but the relationship between increasing sea temperatures and population dynamics of Arctic cetaceans remains largely unexplored. Narwhals (Monodon monoceros) are considered to be among the most sensitive of Arctic endemic marine mammals to climate change due to their limited prey selection, strict migratory patterns and high site fidelity. In the context of climate change, we assume that the population dynamics of narwhals are partly influenced by changes in environmental conditions, with warm areas of increasing sea temperatures having lower abundance of narwhals. Using a unique large dataset of 144 satellite tracked narwhals, sea surface temperature (SST) data spanning 25 years (1993-2018) and narwhal abundance estimates from 17 localities, we (1) assessed the thermal exposure of this species, (2) investigated the SST trends at the summer foraging grounds, and (3) assessed the relationship between SST and abundance of narwhals. We showed a sharp SST increase in Northwest, Mideast and Southeast Greenland, whereas no change could be detected in the Canadian Arctic Archipelago (CAA) and in the Greenland Sea. The rising sea temperatures were correlated with the smallest narwhal abundance observed in the Mideast and Southeast Greenland (< 2000 individuals), where the mean summer sea temperatures were the highest (6.3 °C) compared to the cold waters of the CAA (0.7 °C) that were associated with the largest narwhal populations (> 40,000 individuals). These results support the hypothesis that warming ocean waters will restrict the habitat range of the narwhal, further suggesting that narwhals from Mideast and Southeast Greenland may be under pressure to abandon their traditional habitats due to ocean warming, and consequently either migrate further North or locally go extinct.

Surgery with and without adjuvant radiotherapy is associated with similar survival in T4 colon cancer.

AIM: There is little evidence regarding the role of adjuvant radiotherapy for colon cancer. Despite this, national consensus guidelines recommend consideration of radiation for patients with T4 colon cancer. Large comparative studies may be beneficial in clarifying the potential benefit of postoperative radiation for this cohort. METHOD: We compared the overall survival between patients treated with surgery with and without adjuvant radiation using the National Cancer Database (NCDB) and the Surveillance, Epidemiology, and End Results Program (SEER), as well as disease-specific survival using SEER. Cox proportional hazards models and propensity score matching were used to adjust for relevant confounders. RESULTS: There were a total of 18 776 patients in the NCDB cohort and 9926 patients in the SEER cohort. After propensity score matching, there was no statistically significant difference in overall mortality between surgery with and without radiation in the NCDB [hazard ratio (HR) 1.11; 95% CI 0.93-1.31; P = 0.25] or in SEER (HR 1.20; 95% CI 0.84-1.72; P = 0.32). Additionally, using SEER, we found no statistically significant difference in disease-specific mortality between these two groups (HR 1.13; 95% CI 0.76-1.67; P = 0.54). CONCLUSION: Using the NCDB and SEER, we found no statistically significant difference in overall survival or disease-specific survival between patients treated with and without adjuvant radiation. Further studies should evaluate the impact of adjuvant radiotherapy on local control and prevention of recurrence-related morbidity in patients with T4 colon cancer.

High-energy, high-fat lifestyle challenges an Arctic apex predator, the polar bear.

Regional declines in polar bear (Ursus maritimus) populations have been attributed to changing sea ice conditions, but with limited information on the causative mechanisms. By simultaneously measuring field metabolic rates, daily activity patterns, body condition, and foraging success of polar bears moving on the spring sea ice, we found that high metabolic rates (1.6 times greater than previously assumed) coupled with low intake of fat-rich marine mammal prey resulted in an energy deficit for more than half of the bears examined. Activity and movement on the sea ice strongly influenced metabolic demands. Consequently, increases in mobility resulting from ongoing and forecasted declines in and fragmentation of sea ice are likely to increase energy demands and may be an important factor explaining observed declines in body condition and survival.

The paradoxical psychological effects of lysergic acid diethylamide (LSD).

BACKGROUND: Lysergic acid diethylamide (LSD) is a potent serotonergic hallucinogen or psychedelic that modulates consciousness in a marked and novel way. This study sought to examine the acute and mid-term psychological effects of LSD in a controlled study. METHOD: A total of 20 healthy volunteers participated in this within-subjects study. Participants received LSD (75 µg, intravenously) on one occasion and placebo (saline, intravenously) on another, in a balanced order, with at least 2 weeks separating sessions. Acute subjective effects were measured using the Altered States of Consciousness questionnaire and the Psychotomimetic States Inventory (PSI). A measure of optimism (the Revised Life Orientation Test), the Revised NEO Personality Inventory, and the Peter's Delusions Inventory were issued at baseline and 2 weeks after each session. RESULTS: LSD produced robust psychological effects; including heightened mood but also high scores on the PSI, an index of psychosis-like symptoms. Increased optimism and trait openness were observed 2 weeks after LSD (and not placebo) and there were no changes in delusional thinking. CONCLUSIONS: The present findings reinforce the view that psychedelics elicit psychosis-like symptoms acutely yet improve psychological wellbeing in the mid to long term. It is proposed that acute alterations in mood are secondary to a more fundamental modulation in the quality of cognition, and that increased cognitive flexibility subsequent to serotonin 2A receptor (5-HT2AR) stimulation promotes emotional lability during intoxication and leaves a residue of 'loosened cognition' in the mid to long term that is conducive to improved psychological wellbeing.

Summing the strokes: energy economy in northern elephant seals during large-scale foraging migrations.

BACKGROUND: The energy requirements of free-ranging marine mammals are challenging to measure due to cryptic and far-ranging feeding habits, but are important to quantify given the potential impacts of high-level predators on ecosystems. Given their large body size and carnivorous lifestyle, we would predict that northern elephant seals (Mirounga angustirostris) have elevated field metabolic rates (FMRs) that require high prey intake rates, especially during pregnancy. Disturbance associated with climate change or human activity is predicted to further elevate energy requirements due to an increase in locomotor costs required to accommodate a reduction in prey or time available to forage. In this study, we determined the FMRs, total energy requirements, and energy budgets of adult, female northern elephant seals. We also examined the impact of increased locomotor costs on foraging success in this species. RESULTS: Body size, time spent at sea and reproductive status strongly influenced FMR. During the short foraging migration, FMR averaged 90.1 (SE = 1.7) kJ kg(-1)d(-1) - only 36 % greater than predicted basal metabolic rate. During the long migration, when seals were pregnant, FMRs averaged 69.4 (±3.0) kJ kg(-1)d(-1) - values approaching those predicted to be necessary to support basal metabolism in mammals of this size. Low FMRs in pregnant seals were driven by hypometabolism coupled with a positive feedback loop between improving body condition and reduced flipper stroking frequency. In contrast, three additional seals carrying large, non-streamlined instrumentation saw a four-fold increase in energy partitioned toward locomotion, resulting in elevated FMRs and only half the mass gain of normally-swimming study animals. CONCLUSIONS: These results highlight the importance of keeping locomotion costs low for successful foraging in this species. In preparation for lactation and two fasting periods with high demands on energy reserves, migrating elephant seals utilize an economical foraging strategy whereby energy savings from reduced locomotion costs are shuttled towards somatic growth and fetal gestation. Remarkably, the energy requirements of this species, particularly during pregnancy, are 70-80 % lower than expected for mammalian carnivores, approaching or even falling below values predicted to be necessary to support basal metabolism in mammals of this size.

Energetic demands of immature sea otters from birth to weaning: implications for maternal costs, reproductive behavior and population-level trends.

Sea otters (Enhydra lutris) have the highest mass-specific metabolic rate of any marine mammal, which is superimposed on the inherently high costs of reproduction and lactation in adult females. These combined energetic demands have been implicated in the poor body condition and increased mortality of female sea otters nearing the end of lactation along the central California coast. However, the cost of lactation is unknown and currently cannot be directly measured for this marine species in the wild. Here, we quantified the energetic demands of immature sea otters across five developmental stages as a means of assessing the underlying energetic challenges associated with pup rearing that may contribute to poor maternal condition. Activity-specific metabolic rates, daily activity budgets and field metabolic rates (FMR) were determined for each developmental stage. Mean FMR of pre-molt pups was 2.29 ± 0.81 MJ day(-1) and increased to 6.16 ± 2.46 and 7.41 ± 3.17 MJ day(-1) in post-molt pups and dependent immature animals, respectively. Consequently, daily energy demands of adult females increase 17% by 3 weeks postpartum and continue increasing to 96% above pre-pregnancy levels by the average age of weaning. Our results suggest that the energetics of pup rearing superimposed on small body size, marine living and limited on-board energetic reserves conspire to make female sea otters exceptionally vulnerable to energetic shortfalls. By controlling individual fitness, maternal behavior and pup provisioning strategies, this underlying metabolic challenge appears to be a major factor influencing current population trends in southern sea otters (Enhydra lutris nereis).

The effect of acutely administered MDMA on subjective and BOLD-fMRI responses to favourite and worst autobiographical memories.

3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine-releaser that is widely used as a recreational drug. Preliminary work has supported the potential of MDMA in psychotherapy for post-traumatic stress disorder (PTSD). The neurobiological mechanisms underlying its putative efficacy are, however, poorly understood. Psychotherapy for PTSD usually requires that patients revisit traumatic memories, and it has been argued that this is easier to do under MDMA. Functional magnetic resonance imaging (fMRI) was used to investigate the effect of MDMA on recollection of favourite and worst autobiographical memories (AMs). Nineteen participants (five females) with previous experience with MDMA performed a blocked AM recollection (AMR) paradigm after ingestion of 100 mg of MDMA-HCl or ascorbic acid (placebo) in a double-blind, repeated-measures design. Memory cues describing participants' AMs were read by them in the scanner. Favourite memories were rated as significantly more vivid, emotionally intense and positive after MDMA than placebo and worst memories were rated as less negative. Functional MRI data from 17 participants showed robust activations to AMs in regions known to be involved in AMR. There was also a significant effect of memory valence: hippocampal regions showed preferential activations to favourite memories and executive regions to worst memories. MDMA augmented activations to favourite memories in the bilateral fusiform gyrus and somatosensory cortex and attenuated activations to worst memories in the left anterior temporal cortex. These findings are consistent with a positive emotional-bias likely mediated by MDMA's pro-monoaminergic pharmacology.

Implications for psychedelic-assisted psychotherapy: functional magnetic resonance imaging study with psilocybin.

BACKGROUND: Psilocybin is a classic psychedelic drug that has a history of use in psychotherapy. One of the rationales for its use was that it aids emotional insight by lowering psychological defences. AIMS: To test the hypothesis that psilocybin facilitates access to personal memories and emotions by comparing subjective and neural responses to positive autobiographical memories under psilocybin and placebo. METHOD: Ten healthy participants received two functional magnetic resonance imaging scans (2 mg intravenous psilocybin v. intravenous saline), separated by approximately 7 days, during which they viewed two different sets of 15 positive autobiographical memory cues. Participants viewed each cue for 6 s and then closed their eyes for 16 s and imagined re-experiencing the event. Activations during this recollection period were compared with an equivalent period of eyes-closed rest. We split the recollection period into an early phase (first 8 s) and a late phase (last 8 s) for analysis. RESULTS: Robust activations to the memories were seen in limbic and striatal regions in the early phase and the medial prefrontal cortex in the late phase in both conditions (P<0.001, whole brain cluster correction), but there were additional visual and other sensory cortical activations in the late phase under psilocybin that were absent under placebo. Ratings of memory vividness and visual imagery were significantly higher after psilocybin (P<0.05) and there was a significant positive correlation between vividness and subjective well-being at follow-up (P<0.01). CONCLUSIONS: Evidence that psilocybin enhances autobiographical recollection implies that it may be useful in psychotherapy either as a tool to facilitate the recall of salient memories or to reverse negative cognitive biases.

Changes in partial pressures of respiratory gases during submerged voluntary breath hold across odontocetes: is body mass important?

Odontocetes have an exceptional range in body mass spanning 10(3) kg across species. Because, size influences oxygen utilization and carbon dioxide production rates in mammals, this lineage likely displays an extraordinary variation in oxygen store management compared to other marine mammal groups. To examine this, we measured changes in the partial pressures of respiratory gases ([Formula: see text], [Formula: see text]), pH, and lactate in the blood during voluntary, quiescent, submerged breath holds in Pacific white-sided dolphins (Lagenorhynchus obliquidens), bottlenose dolphins (Tursiops truncatus), and a killer whale (Orcinus orca) representing a mass range of 96-3,850 kg. These measurements provided an empirical determination of the effect of body size on the variability in blood biochemistry during breath hold and experimentally determined aerobic dive limits (ADL) within one taxonomic group (odontocetes). For the species in this study, maximum voluntary breath-hold duration was positively correlated with body mass, ranging from 3.5 min in white-sided dolphins to 13.3 min for the killer whale. Variation in breath-hold duration was associated with differences in the rate of change for [Formula: see text] throughout breath hold; [Formula: see text] decreased twice as fast for the two smaller species (-0.6 mmHg O(2) min(-1)) compared to the largest species (-0.3 mmHg O(2) min(-1)). In contrast, the rate of increase in [Formula: see text] during breath hold was similar across species. These results demonstrate that large body size in odontocetes facilitates increased aerobic breath-hold capacity as mediated by decreased mass-specific metabolic rates (rates of change in [Formula: see text] served as a proxy for oxygen utilization). Indeed the experimentally determined 5 min ADL for bottlenose dolphins was surpassed by the 13.3 min maximum breath hold of the killer whale, which did not end in a rise in lactate. Rather, breath hold ended voluntarily as respiratory gases and pH fell within a narrow range for both large and small species, likely providing cues for ventilation.

Deadly diving? Physiological and behavioural management of decompression stress in diving mammals.

Decompression sickness (DCS; 'the bends') is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers. Breath-hold diving marine mammals were thought to be relatively immune to DCS owing to multiple anatomical, physiological and behavioural adaptations that reduce nitrogen gas (N(2)) loading during dives. However, recent observations have shown that gas bubbles may form and tissue injury may occur in marine mammals under certain circumstances. Gas kinetic models based on measured time-depth profiles further suggest the potential occurrence of high blood and tissue N(2) tensions. We review evidence for gas-bubble incidence in marine mammal tissues and discuss the theory behind gas loading and bubble formation. We suggest that diving mammals vary their physiological responses according to multiple stressors, and that the perspective on marine mammal diving physiology should change from simply minimizing N(2) loading to management of the N(2) load. This suggests several avenues for further study, ranging from the effects of gas bubbles at molecular, cellular and organ function levels, to comparative studies relating the presence/absence of gas bubbles to diving behaviour. Technological advances in imaging and remote instrumentation are likely to advance this field in coming years.

The effects of water temperature on the energetic costs of juvenile and adult California sea lions (Zalophus californianus): the importance of skeletal muscle thermogenesis for thermal balance.

As highly mobile marine predators, many pinniped species routinely encounter a wide range of water temperatures during foraging and in association with seasonal, geographical and climatic changes. To determine how such variation in environmental temperature may impact energetic costs in otariids, we determined the thermal neutral zone of adult and juvenile California sea lions (Zalophus californianus) by measuring resting metabolic rate using open-flow respirometry. Five adult female (body mass range =82.2-107.2 kg) and four juvenile (body mass=26.2-36.5 kg) sea lions were examined over experimental water temperatures ranging from 0 to 20 degrees C (adults) or 5 to 20 degrees C (juveniles). The metabolic rate of adult sea lions averaged 6.4+/-0.64 ml O(2) kg(-1) min(-1) when resting within the thermal neutral zone. The lower critical temperature of adults was 6.4+/-2.2 degrees C, approximately 4 degrees C lower than sea surface temperatures routinely encountered off coastal California. In comparison, juvenile sea lions did not demonstrate thermal neutrality within the range of water temperatures examined. Resting metabolic rate of the younger animals, 6.3+/-0.53 ml O(2) kg(-1) min(-1), increased as water temperature approached 12 degrees C, and suggested a potential thermal limitation in the wild. To determine whether muscle thermogenesis during activity could mitigate this limitation, we measured the active metabolic rate of juveniles swimming at water temperature (T(water))=5, 12 and 20 degrees C. No significant difference (F=0.377, P=0.583) in swimming metabolic rate was found among water temperatures, suggesting that thermal disadvantages due to small body size in juvenile sea lions may be circumvented by recycling endogenous heat during locomotor activity.

Causes and consequences of marine mammal population declines in southwest Alaska: a food-web perspective.

Populations of sea otters, seals and sea lions have collapsed across much of southwest Alaska over the past several decades. The sea otter decline set off a trophic cascade in which the coastal marine ecosystem underwent a phase shift from kelp forests to deforested sea urchin barrens. This interaction in turn affected the distribution, abundance and productivity of numerous other species. Ecological consequences of the pinniped declines are largely unknown. Increased predation by transient (marine mammal-eating) killer whales probably caused the sea otter declines and may have caused the pinniped declines as well. Springer et al. proposed that killer whales, which purportedly fed extensively on great whales, expanded their diets to include a higher percentage of sea otters and pinnipeds following a sharp reduction in great whale numbers from post World War II industrial whaling. Critics of this hypothesis claim that great whales are not now and probably never were an important nutritional resource for killer whales. We used demographic/energetic analyses to evaluate whether or not a predator-prey system involving killer whales and the smaller marine mammals would be sustainable without some nutritional contribution from the great whales. Our results indicate that while such a system is possible, it could only exist under a narrow range of extreme conditions and is therefore highly unlikely.

The ontogeny of aerobic and diving capacity in the skeletal muscles of Weddell seals.

Our objective was to determine the ontogenetic changes in the skeletal muscles of Weddell seals that transform a non-diving pup into an elite diving adult. Muscle biopsies were collected from pups, juveniles and adults and analyzed for changes in fiber type, mitochondrial density, myoglobin concentrations and aerobic, lipolytic and anaerobic enzyme activities. The fiber type results demonstrated a decrease in slow-twitch oxidative (Type I) fibers and a significant increase in fast-twitch oxidative (Type IIA) fibers as the animals mature. In addition, the volume density of mitochondria and the activity of lipolytic enzymes significantly decreased as the seals matured. To our knowledge, this is the first quantitative account describing a decrease in aerobic fibers shifting towards an increase in fast-twitch oxidative fibers with a significant decrease in mitochondrial density as animals mature. These differences in the muscle physiology of Weddell seals are potentially due to their three very distinct stages of life history: non-diving pup, novice diving juvenile, and elite deep diving adult. During the first few weeks of life, pups are a non-diving terrestrial mammal that must rely on lanugo (natal fur) for thermoregulation in the harsh conditions of Antarctica. The increased aerobic capacity of pups, associated with increased mitochondrial volumes, acts to provide additional thermogenesis. As these future elite divers mature, their skeletal muscles transform to a more sedentary state in order to maintain the low levels of aerobic metabolism associated with long-duration diving.

Strategies and technical challenges in allele level Class II typing in 2578 bone marrow transplantation donor-recipient pairs.

Human leukocyte antigen typing of 2578 donor-recipient pairs whose transplantation was facilitated by the National Marrow Donor Program allowed for an in-depth analysis of the accuracy of high-volume allele level testing data. The methods employed provided allele level typing at DRB1/3/5, DQA1, DQB1, DPA1, and DPB1 using sequence-specific oligonucleotide probe hybridization (SSOPH), polymerase chain reaction (PCR) restriction fragment length polymorphism analysis, sequence specific PCR, and direct sequence-based typing (SBT). Each typing was independently tested by two laboratories in Phase 1, and in subsequent phases targeted samples were typed in duplicate by SBT to monitor typing quality. Comparison with prior transplant center typing was also evaluated. SSOPH detected discrepancies ranged from 0.6% at DPB1 to 5.1% at DQB1 in Phase 1. The majority of discrepancies, 62%, resulted from human error such as sample handling, result interpretation, or clerical errors. Alleles that are frequently discrepant have been identified in this predominantly white population.

Allelic diversity within the high frequency Mamu-A2*05/Mane-A2*05 (Mane-A*06)/Mafa-A2*05 family of macaque MHC-A loci.

Macaque species serve as important animal models of human infection and immunity. To more fully scrutinize their potential in both the analysis of disease pathogenesis and vaccine development, it is necessary to characterize the major histocompatibility complex (MHC) class I loci of Macaca mulatta (Mamu), Macaca nemestrina (Mane), and Macaca fascicularis (Mafa) at the genomic level. The oligomorphic Mamu-A2*05/Mane-A2*05 (previously known as Mane-A*06) family of macaque MHC-A alleles has recently been shown to be present at high frequency in both Indian rhesus and pig-tailed macaque populations. Using a locus-specific amplification and direct DNA typing methodology, we have additionally found that the locus encoding this family is very prevalent (75%) among a sampling of 182 Chinese rhesus macaques and has a high prevalence (80%) within a larger, independent cohort of 309 pig-tailed macaques. Interestingly, among the Chinese rhesus macaques, only six alleles previously identified in Indian-origin animals were observed, while three recently identified in Chinese-origin animals and 25 new alleles were characterized. Among the pig-tailed macaques, we observed 1 previously known (Mane-A*06) and 19 new alleles. Examination of the orthologous locus in a preliminary sampling of 30 cynomolgus macaques showed an even higher presence (87%) of Mafa-A2*05 family alleles, with 5 previously identified and 15 new alleles characterized. The continued discovery of novel alleles and thus further diversity within the Mamu-A2*05/Mane-A2*05/Mafa-A2*05 family indicates that this MHC-A locus, although highly conserved across the three species of macaques, has remained a dynamic entity during evolution.

Growth of aligned ZnO nanorods.

Growth of high-density and aligned ZnO nanorods on ZnO film substrate has been demonstrated using vapor-transport of thermally evaporated Zn metal powders followed by condensation. Morphological studies show that the nanorods grow preferentially from a hexagonal ZnO base with a uniform hexagonal structure following three-dimensional island-like growth mechanism. Structural and spectroscopic properties clearly indicate that the nanorods are relatively good and defect-free in quality. These nanorods have potential for technological implications.

Susceptibility of Escherichia coli to L-selenaproline and other L-proline analogues in laboratory culture media and normal human urine.

AIMS: The aims of this study were to identify analogues of L-proline which inhibit the growth of Escherichia coli in both laboratory culture media and normal human urine and to study their mechanisms of uptake. METHODS AND RESULTS: The susceptibility of E. coli to L-proline analogues was studied by radial streak assays on agar plates and by minimal inhibitory concentration determinations in liquid media. Only L-selenaproline (SCA) inhibited growth in Mueller-Hinton medium and human urine as well as in glucose minimal medium. L-Proline did not prevent the inhibition of growth by SCA and strains defective in L-proline transport were as susceptible to SCA as wild-type strains. However, E. coli was resistant to SCA in the presence of L-cysteine and L-cystine. Spontaneous mutants selected for resistance to SCA or L-selenocystine were resistant to the other compound and had reduced growth in minimal medium containing L-cysteine or L-cystine as the sole sulfur source. CONCLUSIONS: L-selenaproline inhibited the growth of E. coli under conditions that may occur in the urinary tract and appeared to be taken up by the L-cystine transport system. SIGNIFICANCE AND IMPACT OF THE STUDY: Although urinary tract infections caused by E. coli can be treated with sulfamethoxazole/trimethoprim and quinolones, resistance to these antibiotics has been increasing. These results suggest that L-selenaproline may represent a new class of compounds that could be used to treat these infections.

The development of diving bradycardia in bottlenose dolphins (Tursiops truncatus).

Bradycardia is an important component of the dive response, yet little is known about this response in immature marine mammals. To determine if diving bradycardia improves with age, cardiac patterns from trained immature and mature bottlenose dolphins ( Tursiops truncatus) were recorded during three conditions (stationary respiration, voluntary breath-hold, and shallow diving). Maximum (mean: 117+/-1 beats.min(-1)) and resting (mean: 101+/-5 beats.min(-1)) heart rate (HR) at the water surface were similar regardless of age. All dolphins lowered HR in response to apnea; mean steady state breath-hold HR was not correlated with age. However, the ability to reduce HR while diving improved with age. Minimum and mean steady state HR during diving were highest for calves. For example, 1.5-3.5-year-old calves had significantly higher mean steady state diving HR (51+/-1 beats.min(-1)) than 3.5-5.5-year-old juveniles (44+/-1 beats.min(-1)). As a result, older dolphins demonstrated greater overall reductions in HR during diving. Longitudinal studies concur; the ability to reduce HR improved as individual calves matured. Thus, although newly weaned calves as young as 1.7 years exhibit elements of cardiac control, the capacity to reduce HR while diving improves with maturation up to 3.5 years postpartum. Limited ability for bradycardia may partially explain the short dive durations observed for immature marine mammals.

Sequential megafaunal collapse in the North Pacific Ocean: an ongoing legacy of industrial whaling?

Populations of seals, sea lions, and sea otters have sequentially collapsed over large areas of the northern North Pacific Ocean and southern Bering Sea during the last several decades. A bottom-up nutritional limitation mechanism induced by physical oceanographic change or competition with fisheries was long thought to be largely responsible for these declines. The current weight of evidence is more consistent with top-down forcing. Increased predation by killer whales probably drove the sea otter collapse and may have been responsible for the earlier pinniped declines as well. We propose that decimation of the great whales by post-World War II industrial whaling caused the great whales' foremost natural predators, killer whales, to begin feeding more intensively on the smaller marine mammals, thus "fishing-down" this element of the marine food web. The timing of these events, information on the abundance, diet, and foraging behavior of both predators and prey, and feasibility analyses based on demographic and energetic modeling are all consistent with this hypothesis.