Australasian Science: Australia's authority on science since 1938

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By Stephen Luntz

More than a dozen Browse articles for subscribers only.

Why Do Magpies Attack?
A study by Griffith University’s Suburban Wildlife Research Group has determined that magpie swooping behaviour is a form of brood defence designed to scare off predators coming after their young.

The finding, published in the journal Emu, was not unexpected although alternative theories have been raised. However, the research raises a new question – why do magpies only swoop in urban areas or where they have become habituated to humans?

Other theories to explain swooping include territorial defence and testosterone. Both may have arisen because almost all attacks come from the male magpie, although females have occasionally been observed joining in when their mate begins an attack.

However, A/Prof Jones found that testosterone levels peak prior to the laying of eggs, whereas virtually all attacks occur while the young are in the nest. Moreover, Jones compared the behaviour of magpies that had been reported to authorities as dangerous with those that had displayed no such aggression. He found no correlation with testosterone.

“Magpies are ridiculously territorial, defending their territory all year round, while other birds usually only do so during the mating season,” Jones says. However, he considers the fact that the attacks occur over such a short part of the year is a giveaway that the behaviour is designed to deter predators such as monitor lizards and barking owls.

It is not clear why transference of this behaviour to humans should take place. Jones says there is no cultural evidence of conflict between magpies and Aborigines, and magpies steer clear of humans in the wild.

Another mystery is why cyclists are a favourite target, often attacked at distances from the nest where pedestrians would be left in peace. A 12-year-old boy was killed by a car in 2010 trying to evade a magpie attack.

Jones warns that speeding up to avoid a magpie gives the attacker a sense of success, as the intruder has left his territory more rapidly. However, he acknowledges: “While getting people to stop their bike and get off works, it is so counter-intuitive I can’t persuade people to do it”. On the other hand, he says that tying cable ties to helmets appears to work in sufficient numbers.

Last year was unusual as a vastly extended breeding season due to wet weather led to attacks months after the normal September period.

Strawberry Sequenced
An international collaboration has made the woodland strawberry, Fragaria vesca, the latest species to have its genome sequenced.

Although several other fruit species have been sequenced, the woodland strawberry may prove particularly valuable because it is a relative of many other fruits but has an unusually small and easily navigated genome.

“The Rosaceae family is vital for modern horticulture, producing highly valuable fruits such as apple, peach, nectarine, almonds and berry fruits,” says Dr Roger Hellens, Science Leader of Genomics at New Zealand’s Plant & Food Research.

The woodland strawberry has just 206 million base pairs, the smallest plant species to be sequenced after Arabidopsis. Apples have a genome that is three times this size yet only a similar number of genes. As a result, pinpointing the location of genes in the apple genome can be hard. Hellens says: “Having the strawberry genome well annotated will help with annotation of related plants”.

Taste variations among the Rosaceae family are triggered by subtle genetic differences, so a better understanding of what causes these will be valuable for breeding new varieties.

The woodland strawberry is not grown commercially, but is one of the ancestors of the garden strawberry, which originated from cross-breeding 250 years ago. Hellens says the garden strawberry was not chosen as its genome is octoploid rather than diploid, making it far harder to unravel.

Depression Hits Men Harder
Depression and anxiety have a greater effect on the ability of men to fulfil their roles compared with women, a study published in the Journal of Affective Disorders has found. The finding contradicts previous research.

Dr Kate Scott of the University of Otago used a 20-point questionnaire to assess a random selection of the population’s ability to get around, take care of themselves and function socially and within what they consider their role – usually paid work or care of children. She found that women with mental health disorders were four times as likely as those without to report problems in social and role functioning in the last month. However, men in the same category were ten times as likely to report similar issues.

“Our research confirms that women are more likely than men to experience mood and anxiety disorders, but what is new is our finding that among men and women with those disorders, it is actually men who experience greater difficulties in role, social and cognitive functioning,” says Scott.

Scott says past studies showed the reverse, but these only looked at those who had sought treatment for mental health issues. “This is a very biased sample,” she notes. “More women seek treatment for mental health.”

Scott admits it is possible that the findings are partially because healthy men under-report incidences of role disability. However, she says that a regression analysis showed that gender was a significant factor in the relationship between depression and disability.

“One explanation for the difference may be that women are more willing to seek treatment than men. They also have greater intimate and emotional ties to family or friends, which may help to offset the impact that depression and anxiety have on social functioning,” Scott says.

Given that men visit doctors less frequently than women and are less likely to seek help for depression or anxiety, Scott believes that health professionals should pay more attention questioning men’s role and social functioning during consultations.

Childhood Mistreatment Leaves Its Mark
Children who have suffered abuse or neglect score lower marks for literacy, numeracy and abstract reasoning as adolescents, a University of Queensland study has found. While the headline result is unsurprising, the research turned up some unexpected details.

“These findings suggest that both abuse and neglect have independent and important adverse effects on a child’s cognitive development,” says Dr Ryan Mills of UQ’s School of Social Science. Mills says that most previous studies have not distinguished between different forms of mistreatment, but this research suggests the two have similar effects.

Adolescents who had been found by the Department of Families, Youth and Community Care to have been abused or neglected had IQ scores approximately three points lower than those who had never been reported as suffering abuse.

“For an individual child this would not be noticeable,” Mills says, “but across our population it was a larger effect than other factors known to influence cognitive skills, such as having been breastfed, mother’s education and parental income”. The study controlled for these factors and a range of others that might influence test scores.

Data were drawn from the Mater–University of Queensland Study of Pregnancy, in which 7000 children born at Mater Hospital from 1981–83 have been followed as they grow up. Of these children, 298 had been reported as victims of maltreatment.

Mills says the study found little difference among children whose abuse or neglect had been substantiated by the Department and those where it was not. “Many other studies rely on adult memories of abuse, which is problematic for many reasons, but in this case we have access to independent confirmation at the time,” Mills says.

There was no attempt to see if more serious or repeated abuse had a greater effect, as Mills says this would be difficult to measure. However, children who were both abused and neglected suffered a double impact.

Even the three IQ point figure is probably an under­estimate, since many cases of abuse would not be reported. “Any mis­classification will reduce the apparent effect,” Mills says.

Mills’ colleague Dr Lane Strathearn points out that abuse and neglect usually go hand-in-hand. “Seventy-four per cent of the children reported to the state as suspected cases of neglect also had been reported as suspected victims of abuse.”

Winter UV Warning
Construction workers need to be wary of zinc aluminium surfaces reflecting UV light at them, PhD student Joanna Turner has warned the Australian Institute of Physics Congress. Turner, of the University of Southern Queensland’s Centre for Rural and Remote Area Health, found that vertical zinc aluminium sheets, which are widely used in the construction industry, can increase UV exposure by 20–50% for workers nearby.

The problem is greatest in winter and autumn, when workers may feel they do not need to put on sunscreen. In summer, when the sun is higher in the sky, light is scattered in multiple directions but in winter the sunlight is reflected in one direction, putting workers in the wrong spot in danger.

“The message for construction workers is to take care to wear sunscreen all year round. Reflections in the construction environment may allow sunburn to sneak up on them when they least expect it,” Turner says.

Wear Sunscreen Every Day
Daily application of sunscreen drastically reduces the incidence of melanoma, according to researchers at the Queensland Institute of Medical Research.

Prof Adele Green enrolled 1621 residents of Nambour in southern Queensland in a study where half were encouraged to apply sunscreen every day while others kept to their usual routine. Although complete compliance could not be guaranteed, Green says that 755 people applied sunscreen more often than every second day, thanks in part to a dedicated team of nurses who met with the participants regularly to encourage them.

While the trial ran from 1992–96, it is possible that some participants continued to use sunscreen frequently due to habit after it was over. Ten years later the regular users had half the rate of melanomas of those in the control group. Green says there was also a reduction in some other forms of cancer, although not in basal cell carcinoma.

“This shows that while sun exposure in childhood is very important, it is not too late to prevent the final appearance of melanoma,” Green says. “Even if the conditions for melanoma are created in childhood, sunscreen can hold it back.”

Green believes that the winter sun in Queensland is strong enough that the application of sunscreen protection year-round is essential. However, she says that she wouldn’t be arguing for people to be applying sunscreen in high latitudes during winter.

“Even though people know the dangers of sun exposure thanks to regular sun awareness campaigns, many people still do not use sunscreen regularly. More behavioural research is needed to understand the barriers to regular sunscreen use. Our idea is that every bit of cumulative sun damage adds up, including the exposure people get every day.”

Willows Are Water Thieves
Willows with permanent access to water remove 5.5 ML of water per hectare of canopy each year, a CSIRO study has found. The average household uses 0.3 ML of water per year.

“So the evaporative loss of one hectare of willows is enough for about 17 households each year,” says project leader Tanya Doody. “A comparative study of native vegetation water use lining the same watercourse showed that willows could be replaced with native vegetation and the annual water savings would be maintained.”

The research was funded by Water for Rivers, a public company that has removed 220 hectares of in-stream willows in the Murray-Darling Basin. Wild for Rivers Project Director Phil Deamer notes that high security water in the Basin has an average market price of $2000 per ML.

Macular Degeneration Is a Vicious Immune Circle
Macular degeneration, Australia’s leading cause of vision loss, occurs when immune system cells trigger the pathway that is believed to cause the disease, according to Matt Rutar, a PhD student at the ARC Centre of Excellence for Vision Science.

“Inflammation has been proposed as the cause of macular degeneration for some time, and this has been more and more accepted,” Rutar says. While the cause of the inflammation has been more mysterious, Rutar and his colleagues have now found that white blood cells are to blame.

“Upon inflammation or damage to the eyes, the immune system kicks in and white blood cells, particularly macrophages, are recruited to clean up the debris or dead cells,” Rutar says. “Under healthy conditions, the white blood cells finish their task and leave the macula. However, in cases of MD, the macrophages call in other inflammatory proteins and combine with them. This then triggers a fresh cycle in which they attack healthy vision cells.”

The long-term damage resembles what is seen in Alzheimer’s disease and cerebral haemorrhaging.

Rutar’s research used albino rats as their eyes are easily damaged by light. Although Rutar acknowledges that any animal model may not perfectly reflect a human disease, he says that the rats “mimic many of the pathological features seen in humans,” and he is confident they form a good model for dry macular degeneration. “There is some evidence wet macular degeneration has the same pathway, but our model does not match this so we can’t be sure,” Rutar says.

Many treatments already focus on inhibiting the cellular pathway that forms part of the cycle, but Rutar says: “Having shown that macrophages target this pathway it may be possible to find a way to stop them triggering it.”

In the meantime he suggests minimising inflammation by wearing sunglasses in bright light, eating a diet high in omega-3 and exercising to keep blood pressure down.

Greenhouse Emissions Resume Rise
While emissions of greenhouse gases fell in 2009, this appears to have been a blip resulting from the Global Financial Crisis. CSIRO Marine and Atmospheric Research has found that 2010 emissions exceeded not only 2009 but the previous 2008 record. The conclusion was published in Nature Geoscience.

While 2010 figures are incomplete, Dr Pep Canadell of CSIRO says that “CO2 emissions from fossil fuels are projected to increase by more than 3% in 2010. Fortunately, we are seeing offsets to this in reduced tropical deforestation compared to the 1990s and increased forest regrowth in temperate regions.”

Global deforestation is down 25% from its peak, and accounts for approximately 10% of total emissions.

The carbon intensity of the economy (the amount of greenhouse gases emitted for each unit of global Gross Domestic Product) has been falling for many years, but co-author Dr Michael Raupach says the improvement has declined recently because the economies that are expanding most rapidly are heavy users of coal. “Both globally and for emerging economies, the fraction of fossil fuel emissions from coal continued to increase last year.”

Endometriosis Genetics Become Clearer
A little more has been revealed about the complex causes of endometriosis, a disease that affects 6–10% of women between puberty and menopause.

It is known that endometriosis is not caused by a single gene. Instead, a number of genetic, epigenetic and environmental factors play a role, but many of these have yet to be revealed.

“We have conducted the largest genome-wide association study to date comparing the DNA of 5586 women with endometriosis and 9331 people without,” says Prof Grant Montgomery of the Queensland Institute of Medical Research. This identified a region on chromosome 7 that appears to regulate nearby genes implicated in endometriosis. A weaker correlation was found with a DNA variant on chromosome 1.

“Ultimately, we hope these findings will lead to the development of less invasive methods of diagnosis, and more effective therapies, but we still have a long way to go,” Montgomery says.

“Previous studies have established that endometriosis is heritable, but have not examined the impact of genetics for different disease stages. Our study demonstrates a stronger genetic contribution to moderate-to-severe endometriosis, which has implications for how we research the condition in the future.”

Breast Cancer Protein Disappears
The protein inositol polyphophate 4-phospatase-II (INPP4B) disappears in the most serious forms of breast cancer. The discovery may assist diagnosis, and lead to methods to target the most aggressive cancers.

“We looked at a specific subtype of aggressive breast cancer and found that in about 90% of these types of almost untreatable tumours, INPP4B was gone,” says Dr Clare Fedele of Monash University. The discovery was made as part of Fedele’s PhD, with the findings published in the Proceedings of the National Academy of Sciences. Fedele emphasised the collaborative nature of the research, with contributions from the Alfred Hospital, Cancer Council of Victoria and Garvan Institute.

“In normal breast cells it appears INPP4B acts to control or regulate the proliferation of cells, so it acts as a tumour suppressant,” Fedele says. “We believe its loss in the most aggressive subclass of cancers contributes to their nature.”

The mechanism for removing INPP4B is unknown, but Fedele thinks that multiple pathways may be involved. “There’s some evidence to suggest the gene may be deleted,” she says. “The cell’s environment may be able to signal to the tumour cell to switch off expression of the protein.”

Although it is possible to generate replacement protein, Fedele says the delivery into cells is very difficult. Instead she says that “we are a step closer to identifying how drugs could be designed to specifically target the pathway that is controlled by INPP4B”.

The cancers that lack INPP4B do not usually respond to Tamoxifin, and Fedele says that alternative treatments are also lacking. However, she says that the ability to identify the most aggressive subclass of tumours will help the creation of more personalised treatments in future.

Fedele adds that there are indications the absence of INPP4B may be important in cancers of other parts of the body as well.

Glowing Sea Snails
The Australian sea snail Hinea brasiliana uses its shell as a lampshade to diffuse bioluminescent light, according to Dr Nerida Wilson of the Australian Museum.

“Bioluminescence is a common communication method in open water molluscs like squid, but is much rarer in marine snails that live on the bottom,” Wilson says. “One snail family has several members that can produce light; these are commonly known as ‘clusterwinks’ because they group together in crevices at low tide on the rocky shore.”

However, the discovery that clusterwinks use their shell to diffuse the light leaves many questions unanswered. The most obvious is what the bioluminescence is for. Many species use it to communicate to potential mates or scare of rivals. However, Wilson found that H. brasiliana seems no more inclined to glow when close to other members of their species than when on their own.

Instead she suspects that they use their light-generating abilities as a way of scaring off predators. “They only glow when they are jiggled or physically agitated in some way. It seems likely that this is a way of scaring off predators. If you think about a whole clump of these all suddenly glowing at once, that could be a frightening thing for a predator.” However, Wilson says we don’t even know what the clusterwinks’ predators are, and any conclusions will have to wait until we can consider their visual system.

Small patches of cells on the snail’s skin glow when they are shaken, but Wilson still does not understand how the light is diffused through the opaque yellowish shells. While such shells might be expected to block light, they seem to be uniquely capable of diffusing the green colour that the clusterwinks produce.

During daylight the glow is usually not bright enough to be noticed by humans, but at night on a low tide the snails become quite visible when disturbed.

Stem Cells Like to Stretch
The use of an elastic surface has more than doubled the number of blood-forming stem cells produced outside the body, offering great hope for improving the prospects of bone marrow and cord blood transplant patients.

“Haemopoietic stem cells, or blood-forming stem cells, play a critical role in creating the blood cells in our body,” says Prof John Rasko of the Centenary Institute. “In order to expand the number of these cells, researchers have attempted to reproduce the unique environment where stem cells live inside the body. In the past we have learnt how to use hormones and drugs to influence these niche environments, but less is known about the effect of physical forces.”

Rasko, along with Prof Tony Weiss and Dr Jeff Holst of the University of Sydney, experimented by placing HSCs on a layer of tropoelastin, a super-elastic protein that the body uses as a precursor of elastin, which gives arteries, lungs and ligaments their elasticity.

The results were dramatic. A tropo-elastin layer was as effective at getting stem cells to multiply as currently used hormone treatments. A paper published in Nature Biotechnology reveals that combining the two techniques produced two to three times the number of stem cells as either method on its own.“It became clear that cells sense the extensional ability of their environment, and are almost tricked into thinking they are in a stem cell niche within the body,” Weiss says.

Holst compares the cells to cats on sofas, finding comfort in pulling on what supports them. Tropoelastin is perfect for the purpose because a single molecule can be tugged to great lengths and then rebound as a perfect spring.

So far Weiss says that data are only available for HSCs, but the team is keen to see if other stem cells respond in a similar manner. “We’re the world leaders in tropoelastin research by far, so it’s an area where Australian science has an advantage.”

The University of Sydney has negotiated agreements to develop the research, but Weiss says he cannot talk about the details. However, he notes that “reagents don’t take as long to commercialise as things used for more complex purposes,” so he hopes to see the work put to use soon.