Delay in Adélie penguin nest occupation restricts parental investment in nest construction and reduces reproductive output

Reproductive success is an important demographic parameter that can be driven by environmental and behavioural factors operating on various spatio-temporal scales. As seabirds breed on land and forage in the ocean, processes occurring in both environments can influence their reproductive success. At various locations around East Antarctica, Adélie penguins' (Pygoscelis adeliae) reproductive success has been negatively linked to extensive sea-ice. In contrast, our study site in the Windmill Islands has limited fast ice present during the breeding season, allowing us to examine drivers of reproductive success under vastly different marine environmental conditions. Here, we examined the reproductive success of 450 Adélie penguin nests over a 10-year period using images obtained from remotely operated cameras. We analysed nest survival in relation to marine and climatic factors, environmental conditions at the camera site and immediately around the nest, and behavioural attributes reflecting parental investment and phenological timing. Our key result was a strong positive association between nest structure and chick survival, particularly when ground moisture and snow cover around the nest were high. Earlier nesting birds were more likely to build bigger nests, although it is unclear whether this is due to more time available to build nests or whether early arrival and high-quality nests are complementary traits. This intrinsic activity is likely to become more important if future predictions of increased snowfall in this region manifest.

Mean reef fish body size decreases towards warmer waters

Aquatic ectotherms often attain smaller body sizes at higher temperatures. By analysing ~15,000 coastal-reef fish surveys across a 15°C spatial sea surface temperature (SST) gradient, we found that the mean length of fish in communities decreased by ~5% for each 1°C temperature increase across space, or 50% decrease in mean length from 14 to 29°C mean annual SST. Community mean body size change was driven by differential temperature responses within trophic groups and temperature-driven change in their relative abundance. Herbivores, invertivores and planktivores became smaller on average in warmer temperatures, but no trend was found in piscivores. Nearly 25% of the temperature-related community mean size trend was attributable to trophic composition at the warmest sites, but at colder temperatures, this was <1% due to trophic groups being similarly sized. Our findings suggest that small changes in temperature are associated with large changes in fish community composition and body sizes, with important ecological implications.

Modeling the effects of ration on individual growth of Oncorhynchus tshawytscha under controlled conditions

Fed aquaculture is one of the fastest-growing and most valuable food production industries in the world. The efficiency with which farmed fish convert feed into biomass influences both environmental impact and economic revenue. Salmonid species, such as king salmon (Oncorhynchus tshawytscha), exhibit high levels of plasticity in vital rates such as feed intake and growth rates. Accurate estimations of individual variability in vital rates are important for production management. The use of mean trait values to evaluate feeding and growth performance can mask individual-level differences that potentially contribute to inefficiencies. Here, the authors apply a cohort integral projection model (IPM) framework to investigate individual variation in growth performance of 1625 individually tagged king salmon fed one of three distinct rations of 60%, 80%, and 100% satiation and tracked over a duration of 276 days. To capture the observed sigmoidal growth of individuals, they compared a nonlinear mixed-effects (logistic) model to a linear model used within the IPM framework. Ration significantly influenced several aspects of growth, both at the individual and at the cohort level. Mean final body mass and mean growth rate increased with ration; however, variance in body mass and feed intake also increased significantly over time. Trends in mean body mass and individual body mass variation were captured by both logistic and linear models, suggesting the linear model to be suitable for use in the IPM. The authors also observed that higher rations resulted in a decreasing proportion of individuals reaching the cohort's mean body mass or larger by the end of the experiment. This suggests that, in the present experiment, feeding to satiation did not produce the desired effects of efficient, fast, and uniform growth in juvenile king salmon. Although monitoring individuals through time is challenging in commercial aquaculture settings, recent technological advances combined with an IPM approach could provide new scope for tracking growth performance in experimental and farmed populations. Using the IPM framework might allow the exploration of other size-dependent processes affecting vital rate functions, such as competition and mortality.

Scientific echosounder data provide a predator's view of Antarctic krill (Euphausia superba)

Raw acoustic data were collected in East Antarctica from the RSV Aurora Australis during two surveys: the Krill Availability, Community Trophodynamics and AMISOR Surveys (KACTAS) and the Krill Acoustics and Oceanography Survey (KAOS) in the East Antarctic (centre coordinate 66.5° S, 63° E). The KACTAS survey was conducted between 14th to 21st January and 2001, and the KAOS survey was conducted between 16 January and 1 February 2003. We examine the Antarctic krill (Euphausia superba) component of these surveys and provide scientific echosounder (EK500 and EK60) data collected at 38, 120 and 200 kHz, cold water (-1 °C) echosounder calibration parameters and accompanying krill length frequency distributions obtained from trawl data. We processed the acoustic data to apply calibration values and remove noise. The processed data were used to isolate echoes arising from swarms of krill and to estimate metrics for each krill swarm, including internal density and individual swarm biomass. The krill swarm data provide insights to a predators' views of krill distribution and density.

Potential for redistribution of post-moult habitat for Eudyptes penguins in the Southern Ocean under future climate conditions

Anthropogenic climate change is resulting in spatial redistributions of many species. We assessed the potential effects of climate change on an abundant and widely distributed group of diving birds, Eudyptes penguins, which are the main avian consumers in the Southern Ocean in terms of biomass consumption. Despite their abundance, several of these species have undergone population declines over the past century, potentially due to changing oceanography and prey availability over the important winter months. We used light-based geolocation tracking data for 485 individuals deployed between 2006 and 2020 across 10 of the major breeding locations for five taxa of Eudyptes penguins. We used boosted regression tree modelling to quantify post-moult habitat preference for southern rockhopper (E. chrysocome), eastern rockhopper (E. filholi), northern rockhopper (E. moseleyi) and macaroni/royal (E. chrysolophus and E. schlegeli) penguins. We then modelled their redistribution under two climate change scenarios, representative concentration pathways RCP4.5 and RCP8.5 (for the end of the century, 2071-2100). As climate forcings differ regionally, we quantified redistribution in the Atlantic, Central Indian, East Indian, West Pacific and East Pacific regions. We found sea surface temperature and sea surface height to be the most important predictors of current habitat for these penguins; physical features that are changing rapidly in the Southern Ocean. Our results indicated that the less severe RCP4.5 would lead to less habitat loss than the more severe RCP8.5. The five taxa of penguin may experience a general poleward redistribution of their preferred habitat, but with contrasting effects in the (i) change in total area of preferred habitat under climate change (ii) according to geographic region and (iii) the species (macaroni/royal vs. rockhopper populations). Our results provide further understanding on the regional impacts and vulnerability of species to climate change.

The role of allochrony in influencing interspecific differences in foraging distribution during the non-breeding season between two congeneric crested penguin species

Mechanisms promoting coexistence between closely related species are fundamental for maintaining species diversity. Mechanisms of niche differentiation include allochrony which offsets the peak timing of resource utilisation between species. Many studies focus on spatial and temporal niche partitioning during the breeding season, few have investigated the role allochrony plays in influencing interspecific segregation of foraging distribution and ecology between congeneric species during the non-breeding season. We investigated the non-breeding migrations of Snares (Eudyptes robustus) and Fiordland penguins (Eudyptes pachyrhynchus), closely related species breeding between 100-350 km apart whose migration phenology differs by two months. Using light geolocation tracking, we examined the degree of overlap given the observed allochrony and a hypothetical scenario where the species commence migration simultaneously. We found that Fiordland penguins migrated to the Sub-Antarctic Frontal Zone and Polar Frontal Zone in the austral autumn whereas Snares penguins disperse westwards staying north of the Sub-Tropical Front in the austral winter. Our results suggest that allochrony is likely to be at the root of segregation because the relative profitability of the different water masses that the penguins forage in changes seasonally which results in the two species utilising different areas over their core non-breeding periods. Furthermore, allochrony reduces relatively higher levels of spatiotemporal overlap during the departure and arrival periods, when the close proximity of the two species' colonies would cause the birds to congregate in similar areas, resulting in high interspecific competition just before the breeding season. Available evidence from other studies suggests that the shift in phenology between these species has arisen from adaptive radiation and phenological matching to the seasonality of local resource availability during the breeding season and reduced competitive overlap over the non-breeding season is likely to be an incidental outcome.

Horizontal-vertical movement relationships: Adélie penguins forage continuously throughout provisioning trips

BACKGROUND

Diving marine predators forage in a three-dimensional environment, adjusting their horizontal and vertical movement behaviour in response to environmental conditions and the spatial distribution of prey. Expectations regarding horizontal-vertical movements are derived from optimal foraging theories, however, inconsistent empirical findings across a range of taxa suggests these behavioural assumptions are not universally applicable.

METHODS

Here, we examined how changes in horizontal movement trajectories corresponded with diving behaviour and marine environmental conditions for a ubiquitous Southern Ocean predator, the Adélie penguin. Integrating extensive telemetry-based movement and environmental datasets for chick-rearing Adélie penguins at Béchervaise Island, we tested the relationships between horizontal move persistence (continuous scale indicating low ['resident'] to high ['directed'] movement autocorrelation), vertical dive effort and environmental variables.

RESULTS

Penguins dived continuously over the course of their foraging trips and lower horizontal move persistence corresponded with less intense foraging activity, likely indicative of resting behaviour. This challenges the traditional interpretation of horizontal-vertical movement relationships based on optimal foraging models, which assumes increased residency within an area translates to increased foraging activity. Movement was also influenced by different environmental conditions during the two stages of chick-rearing: guard and crèche. These differences highlight the strong seasonality of foraging habitat for chick-rearing Adélie penguins at Béchervaise Island.

CONCLUSIONS

Our findings advance our understanding of the foraging behaviour for this marine predator and demonstrates the importance of integrating spatial location and behavioural data before inferring habitat use.

Emerging evidence of resource limitation in an Antarctic seabird metapopulation after 6 decades of sustained population growth

The influence of resource limitation on spatio-temporal population dynamics is a fundamental theme in ecology and the concepts of carrying capacity, density dependence and population synchrony are central to this theme. The life history characteristics of seabirds, which include use of disjunct patches of breeding habitat, high coloniality during breeding, strong philopatry, and central-place foraging, make this group well suited to studying this paradigm. Here, we investigate whether density-dependent processes are starting to limit population growth in the Adélie penguin metapopulation breeding in the Windmill Islands, East Antarctica, after 6 decades of growth. Our finding that the regional growth rate has slowed in recent decades, and that growth is slowing differentially across local populations as availability of breeding habitat and possibly food resources decrease, supports the notion of density-dependent regulation. Our observation of the first new colonisation of a breeding patch in a half-century of population growth by this highly philopatric species is further evidence for this. Given these emerging patterns of spatio-temporal population dynamics, this metapopulation may be at a point where the rate of change in density-dependent processes and rare events such as colonisations accelerates into the future, potentially providing new insights into spatio-temporal metapopulation dynamics of a long-lived species over a short time-frame. Continued long-term study of populations experiencing these circumstances provides an opportunity to expedite advances in understanding metapopulation processes. Our study highlights the importance of spatial heterogeneity and the mosaic of abiotic and biotic features of landscapes and seascapes in shaping species' metapopulation dynamics.

Tracking of marine predators to protect Southern Ocean ecosystems

Southern Ocean ecosystems are under pressure from resource exploitation and climate change^1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.

The retrospective analysis of Antarctic tracking data project

The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for multiple species of Antarctic meso- and top-predators to identify Areas of Ecological Significance. These datasets and accompanying syntheses provide a greater understanding of fundamental ecosystem processes in the Southern Ocean, support modelling of predator distributions under future climate scenarios and create inputs that can be incorporated into decision making processes by management authorities. In this data paper, we present the compiled tracking data from research groups that have worked in the Antarctic since the 1990s. The data are publicly available through biodiversity.aq and the Ocean Biogeographic Information System. The archive includes tracking data from over 70 contributors across 12 national Antarctic programs, and includes data from 17 predator species, 4060 individual animals, and over 2.9 million observed locations.

Combining capture-recapture data and known ages allows estimation of age-dependent survival rates

In many animal populations, demographic parameters such as survival and recruitment vary markedly with age, as do parameters related to sampling, such as capture probability. Failing to account for such variation can result in biased estimates of population-level rates. However, estimating age-dependent survival rates can be challenging because ages of individuals are rarely known unless tagging is done at birth. For many species, it is possible to infer age based on size. In capture-recapture studies of such species, it is possible to use a growth model to infer the age at first capture of individuals. We show how to build estimates of age-dependent survival into a capture-mark-recapture model based on data obtained in a capture-recapture study. We first show how estimates of age based on length increments closely match those based on definitive aging methods. In simulated analyses, we show that both individual ages and age-dependent survival rates estimated from simulated data closely match true values. With our approach, we are able to estimate the age-specific apparent survival rates of Murray and trout cod in the Murray River, Australia. Our model structure provides a flexible framework within which to investigate various aspects of how survival varies with age and will have extensions within a wide range of ecological studies of animals where age can be estimated based on size.

Estimating drift of directional sonobuoys from acoustic bearings

A maximum likelihood method is presented for estimating drift direction and speed of a directional sonobuoy given the deployment location and a time series of acoustic bearings to a sound source at known position. The viability of this method is demonstrated by applying it to two real-world scenarios: (1) during a calibration trial where buoys were independently tracked via satellite, and (2) by applying the technique to sonobuoy recordings of a vocalising Antarctic blue whale that was simultaneously tracked by photogrammetric methods. In both test cases, correcting for sonobuoy drift substantially increased the accuracy of acoustic locations.

Decadal changes in habitat characteristics influence population trajectories of southern elephant seals

Understanding divergent biological responses to climate change is important for predicting ecosystem level consequences. We use species habitat models to predict the winter foraging habitats of female southern elephant seals and investigate how changes in environmental variables within these habitats may be related to observed decreases in the Macquarie Island population. There were three main groups of seals that specialized in different ocean realms (the sub-Antarctic, the Ross Sea and the Victoria Land Coast). The physical and climate attributes (e.g. wind strength, sea surface height, ocean current strength) varied amongst the realms and also displayed different temporal trends over the last two to four decades. Most notably, sea ice extent increased on average in the Victoria Land realm while it decreased overall in the Ross Sea realm. Using a species distribution model relating mean residence times (time spent in each 50 × 50 km grid cell) to 9 climate and physical co-variates, we developed spatial predictions of residence time to identify the core regions used by the seals across the Southern Ocean from 120°E to 120°W. Population size at Macquarie Island was negatively correlated with ice concentration within the core habitat of seals using the Victoria Land Coast and the Ross Sea. Sea ice extent and concentration is predicted to continue to change in the Southern Ocean, having unknown consequences for the biota of the region. The proportion of Macquarie Island females (40%) utilizing the relatively stable sub-Antarctic region, may buffer this population against longer-term regional changes in habitat quality, but the Macquarie Island population has persistently decreased (-1.45% per annum) over seven decades indicating that environmental changes in the Antarctic are acting on the remaining 60% of the population to impose a long-term population decline in a top Southern Ocean predator.

New insights into the cardiorespiratory physiology of weaned southern elephant seals (Mirounga leonina)

Southern elephant seal (Mirounga leonina) pups must strike a balance between conserving energy during their post-weaning fast and simultaneously developing diving abilities to attain nutritional independence. Little is known about environmental influences on cardiorespiratory patterns, hence energy use, throughout the 6 week fast. Continuous heart rates were recorded for free-ranging, newly weaned southern elephant seals using heart rate time-depth recorders for 5-9 days at Sub-Antarctic Macquarie Island, during October 1994 (n = 1), 1995 (n = 4) and 1996 (n = 1). Daytime observations of respiration and behaviour were made throughout. We present the first instance of synchronous heart rate traces recorded simultaneously for individual weaners. Generalized additive models revealed that a sinusoidal pattern of diurnal heart rate elevation and nocturnal depression was evident in all seals and, on at least one occasion, a conspicuous break in this pattern coincided with an extreme cold weather event. Seals in this study were capable of considerable cardiorespiratory control and regularly demonstrated bradycardia during periods of resting apnoea. Apnoeic duration ranged from 33 to 291 s (mean 134 s). Apnoeic heart rates (mean 67 ± 15 beats min(-1), range 40-114 beats min(-1)) were on average 19.7% lower than those exhibited during periods of eupnoea (mean 83 ± 15 beats min(-1), range 44-124 beats min(-1)). The early development of the cardiorespiratory response is characterized by arrhythmic heart and respiration rates. The strong temporal patterns observed are being driven by the opposing requirements of maximizing time spent fasting in order to develop diving capabilities and of maximizing departure mass. This pilot study has highlighted a potentially large effect of ambient weather conditions on newly weaned southern elephant seal cardiorespiratory activity. Given the increasing westerlies and more erratic and increasing storminess associated with the Southern Annular Mode predicted in the Southern Ocean, the patterns observed here warrant further investigation.

Testing paradigms of ecosystem change under climate warming in Antarctica

Antarctic marine ecosystems have undergone significant changes as a result of human activities in the past and are now responding in varied and often complicated ways to climate change impacts. Recent years have seen the emergence of large-scale mechanistic explanations–or “paradigms of change”–that attempt to synthesize our understanding of past and current changes. In many cases, these paradigms are based on observations that are spatially and temporally patchy. The West Antarctic Peninsula (WAP), one of Earth’s most rapidly changing regions, has been an area of particular research focus. A recently proposed mechanistic explanation for observed changes in the WAP region relates changes in penguin populations to variability in krill biomass and regional warming. While this scheme is attractive for its simplicity and chronology, it may not account for complex spatio-temporal processes that drive ecosystem dynamics in the region. It might also be difficult to apply to other Antarctic regions that are experiencing some, though not all, of the changes documented for the WAP. We use qualitative network models of differing levels of complexity to test paradigms of change for the WAP ecosystem. Importantly, our approach captures the emergent effects of feedback processes in complex ecological networks and provides a means to identify and incorporate uncertain linkages between network elements. Our findings highlight key areas of uncertainty in the drivers of documented trends, and suggest that a greater level of model complexity is needed in devising explanations for ecosystem change in the Southern Ocean. We suggest that our network approach to evaluating a recent and widely cited paradigm of change for the Antarctic region could be broadly applied in hypothesis testing for other regions and research fields.

Optimal scales to observe habitat dynamics: a coral reef example

A new technique to estimate the characteristic length scales (CLSs) of real ecological systems provides an objective means to identify the optimal scale(s) of observation to best detect underlying dynamical trends. Application of the technique to natural systems has focused on identifying appropriate scales to measure the dynamics of species as descriptors of community and ecosystem dynamics. However, ecosystem monitoring is often based not on assessing single species, but on species assemblages, functional groups, or habitat types. We asked whether the concept of CLSs based on dynamic interactions among species could be extended to examine interactions among habitat types and thus to identify optimal scales for observing habitat dynamics. A time series of three spatial maps of benthic habitats on a Caribbean coral reef was constructed from aerial photographs, Compact Airborne Spectrographic Imager (CASI) images, and IKONOS satellite images, providing the short time sequence required for this technique. We estimated the CLS based on the dynamics of three distinct habitat types: dense stands of seagrass, sparse stands of seagrass, and Montastrea patch reefs. Despite notable differences in the areal extent of and relative change in these habitats over the 21-year observation period, analyses based on each habitat type indicated a similar CLS of -300 m. We interpret the consistency of CLSs among habitats to indicate that the dynamics of the three habitat types are linked. The results are encouraging, and they indicate that CLS techniques can be used to identify the appropriate scale at which to monitor ecosystem trends on the basis of the dynamics of only one of a disparate suite of habitat types.

The behavioural response of lactating Weddell seals (Leptonychotes weddellii) to over-snow vehicles: a case study

Over-snow vehicles are used extensively at Antarctic scientific research stations. Adult female Weddell seals ( Leptonychotes weddellii (Lesson, 1826)) also utilise the fast-ice and are therefore often exposed to vehicular activity, with the potential of affecting their behaviour. Guidelines for vehicular travel have been developed to minimise disturbance to Antarctic wildlife; however, these guidelines have not yet been scientifically tested. To examine the efficiency and sensitivity of existing guidelines used within the Australian Antarctic Territory (AAT), we conducted drive-by experiments of two types of over-snow vehicles. The results of these experiments showed that the probability of a lactating Weddell seal looking at the vehicles and the duration of the seals’ looking at the vehicles were dependent on the distance between vehicles and seals, the position of the pups in relation to its mother, and the distance the adult female was from the water. Although the seals apparently perceived the vehicles to be a threat, no seals fled in response to vehicle activity. We propose that the existing guidelines used in the AAT could be amended to increase separation distances between vehicles and breeding Weddell seals if the goal of management is to ensure that Weddell seal behaviour is unaffected by vehicle travel.

AUSTRALIAN VASCULAR QUALITY OF LIFE INDEX (AUSVIQUOL): A PILOT STUDY OF A DISEASE-SPECIFIC QUALITY OF LIFE MEASURE

BACKGROUND

To develop and test a quality of life (QOL) index specific for patients with vascular disease and appropriate for patients with abdominal aortic aneurysm (AAA) in the clinical setting.

METHODS

The questions and domains of the Australian Vascular Quality of Life Index (AUSVIQUOL) were determined by examination of a prospective database for frequency of symptoms and an in-depth interview of a sample population. The validity of the AUSVIQUOL was tested by comparing it with the Medical Outcomes Short Form Health Survey (SF-36) in a study involving 60 patients who underwent endovascular AAA repair and 48 open AAA repair. A subpopulation of 22 patients representative of the two groups was then reassessed using the SF-36 and the AUSVIQUOL, to compare the reliability of the two indices.

RESULTS

Similar domains of the SF-36 and the AUSVIQUOL measured common QOL elements. The correlation between the two indices was moderate; the AUSVIQUOL measured additional disease-specific QOL factors. The AUSVIQUOL showed better reliability than the SF-36 in all domains and statistically better in the physical function domain (P < 0.05).

CONCLUSION

The AUSVIQUOL is an appropriate tool for the QOL assessment of patients with AAA in the clinical setting.

Mutant N-ras preferentially drives human CD34+ hematopoietic progenitor cells into myeloid differentiation and proliferation both in vitro and in the NOD/SCID mouse

OBJECTIVES

Ras oncogene mutations are the most frequently observed genetic abnormality (20-40% of patients) in acute myeloid leukemia (AML), and in the preleukemic conditions myelodysplastic syndrome (MDS) and myeloproliferative disorder (MPD). We have previously shown that mutant N-ras (N-rasm) can induce myeloproliferative disorders and apoptosis in a murine reconstitution system. In the present study we investigated the effect of N-rasm in human primary hematopoietic progenitor cells (HPC).

METHODS

Cord blood CD34+ hematopoietic progenitor cells (HPC) were transduced with retroviral vectors containing green fluorescence protein (GFP) alone, or in combination with N-rasm. Cells were then cultured in vitro with a cytokine supplement or cocultured with murine stroma MS-5 cells. The in vivo behavior of transduced cells was examined in the NOD/SCID mouse model.

RESULTS

N-rasm-transduced cells exhibited greater proliferative capacity; a higher frequency of granulocyte-macrophage colony-forming unit (CFU-GM); and an increase in myelomonocytic lineage cells with a concomitant decrease in lymphoid and erythroid cells. Analysis of transduced HPC in NOD/SCID mice revealed higher bone marrow engraftment by N-rasm HPC and increased numbers of myeloid lineage cells.

CONCLUSIONS

The results demonstrate that N-rasm in HPC induces myeloproliferation both in vitro and in the NOD/SCID mouse model as a primary event that does not appear to be dependent on cooperating transforming events.

Susceptibility of cell populations to transduction by retroviral vectors

Retroviral transduction efficiency is related to the multiplicity of infection and the physiological state of the target cells. It is generally not known what proportion of a cell population is susceptible to transduction. We used coinfection with two retroviral vectors containing the marker genes for green fluorescent protein and the truncated human nerve growth factor receptor. In the CD34+ cell line TF-1 or human primary CD34+ hematopoietic progenitor cells, it was found that cells transduced with one vector had a better than random chance of transduction by the other vector. A probability model was developed to estimate target cell susceptibility; susceptibility was calculated as the product of the proportions of transgene-positive cells divided by the proportion of double-positive cells. By using this relationship, it was found that susceptibility was related to the target cell type and culture conditions but not the retroviral titer or the retroviral packaging envelope protein used in this study. Cotransduction with two vectors is a relatively simple procedure that provides a means to assess the maximum transduction level possible in a given cell population.

Retrovirus vector production and transduction: modulation by the cell cycle

In this study, the cell cycle modulation of retrovirus vector production and transduction was analysed. Retrovirus vector expression was found to be similar in all phases of the cell cycle and, in contrast to some other virus promoters shown previously to be upregulated by G(2)/M arrest, Moloney murine leukaemia virus LTR-driven expression was upregulated neither by G(2)/M growth arrest nor by G(1)/S growth arrest. In contrast, cultures enriched for S phase cells produced more infectious virions, apparently by modulation of stages consequent to provirus expression. In terms of retrovirus transduction, limitations appear to be slow progression through the cell cycle and short half-life of the virus. Synchronization of cells prior to mitosis can increase transduction efficiency. Cell cycle modulation can be used to modify retrovirus vector production and transduction and can allow short transduction periods.

Patient factors affecting autologous and allogeneic blood transfusion rates in total hip arthroplasty

Factors that place patients undergoing total hip arthroplasty (THA) at increased risk of receiving an allogeneic or autologous blood transfusion may aid in determining which patients should predonate blood. The records of 354 consecutive patients undergoing THA were retrospectively reviewed to determine patient factors related to transfusion requirement. The risk of transfusion requirement was most strongly correlated with low preoperative hemoglobin level, but also with older age, higher American Society of Anesthesiologists physical status rating, female sex, cemented arthroplasty, and revision surgery. These patients were also least likely to predonate blood, likely because of their comorbid status.

Abdominal injury and the seat-belt sign

OBJECTIVE

To report on: 1. Prevalence of seat-belt sign in motor vehicle accident victims with abdominal injuries; 2. Prevalence of intestinal injuries in patients with seat-belt sign; and 3. Spectrum of abdominal injuries in a population with high usage of three-point restraints.

METHODS

A retrospective chart review was conducted in an adult tertiary-referral hospital from January 1992 to August 1998. Patients were identified from International Classification of Disease-9 codes for abdominal wall and intra-abdominal injuries.

RESULTS

The seat-belt sign was present in 60/99. The proportion of intestinal injuries in patients with and without seat-belt sign were 9/60 and 0/39, respectively (P = 0.01). In the 25 patients with intra-abdominal injuries, there were 10 hepatic, 8 splenic, 9 intestinal and 4 retroperitoneal injuries.

CONCLUSION

The seat-belt sign is indicative of an increased risk of intestinal injury, which is difficult to detect with no single test providing reliable diagnosis. Other intra-abdominal and retroperitoneal injuries may also occur, which are more readily diagnosed on computed tomography scan or focused abdominal utlrasound when available, but are no more frequent in patients with the seat-belt sign than those without.