Eight complete skeletons of prehistoric marsupial lions are among an astonishing menagerie of megafauna fossils discovered in a hidden cave in Australia鈥檚 outback desert. Only partial skeletons have been found before.

Among the creatures, all of which are now extinct, are extremely well-preserved partial skeletons of giant wombats (Phascolonus gigas) and a three metre-tall short-faced giant kangaroo (Procoptodon goliah). A smaller unidentified kangaroo with strange horn-like protrusions on its skull may well represent a new species.

John Long inspects the jaw of a giant marsupial lion (Photo: AFP)

John Long, a vertebrate palaeontologist at the Western Australian Museum in Perth told 快猫短视频: 鈥淚t鈥檚 truly a phenomenal find. This is a most unique site, because you usually find the bones scattered. These articulated skeletons are largely intact and in one place, sitting on the surface.鈥�

Three species of Sthenurus kangaroo and two Tasmanian tigers (Thylacine), were also found in the deep caves. These appear to have acted as death traps for passing animals over thousands of years.

The animals may have fallen in or been tempted by the smell of previous victims, and then been unable to escape. At the time, the region was much wetter than it is now, made up of a patchland of forest and savannah.

Extracted DNA

Precise dating has only just begun, but Long says the site easily fitted into the Pleistocene, between 1.75 million and 46,000 years ago.

Most of the fossils were uncovered in dry and dark conditions ideal for their preservation. In fact, so well preserved that Long was able to extract samples of DNA from the pulp cavity of one of the marsupial lions (Thylacoleo carnifex, as well as other soft tissue, hair and even blowfly remains, all of which have been sent to a laboratory in the UK for molecular analysis.

快猫短视频s hope the extracted DNA might help settle a debate about whether marsupial lions are descended from possums or from wombats 鈥� a hotly debated point in megafauna evolution.

Long, with colleague Gavin Prideaux of Adelaide鈥檚 Flinders University, has so far uncovered 20 skeletons in a three-week search of the large cave complex.

The find was made by caving enthusiasts in May. They uncovered the previously unknown network of caverns in the Nullarbor Plain, a featureless limestone plateau stretching 750 km across Australia鈥檚 southwest coast and bordered on the north by the Great Victoria Desert.

IF you鈥檝e ever wondered what colour the dinosaurs were, you won鈥檛 have much
longer to wait. Researchers in Australia have reconstructed the skin colours of
ancient fish from fossils and say the technique will help to inject a little
reality into reconstructions of other extinct animals.

鈥淐olour reconstructions of extinct animals, such as the dinosaurs in
Jurassic Park, are simply works of fiction,鈥� says Andrew Parker, a
biophysicist at the Australian Museum in Sydney.

Parker realised that the cell structures responsible for the iridescent sheen
of tiny marine crustaceans called ostracods鈥攁 group of animals that has
remained largely unchanged for the past 350 million years鈥攁re also present
in fossils. These structures, called diffraction gratings, are microscopic
patches of grooves, spaced so that they diffract light to give particular
colours. In fossil ostracods, the diffraction gratings were slightly more
primitive but served the same purpose.

This set Parker wondering whether the cellular structures responsible for
colour in other living animals could be found in their ancient
ancestors鈥攑erhaps allowing scientists to make a good guess at their
colours. When Parker looked at the well-preserved fossils of a number of marine
animals, ranging from worms to fish, he found the same tiny structures on their
spines and scales. He also identified other features responsible for colour:
cells called chromatophores, which contain coloured pigments.

To his surprise, Parker even found the remnants of pigment in some of the
better-preserved fossils. This allowed him to identify the chromatophores as
black (melanophores), red (erythrophores) and silvery (iridophores). Many of
these cells had survived in fossils because they were trapped within the bone as
new layers of tissue were laid down during the animal鈥檚 life.

In one ancient fish, a heavily armoured placoderm from the Devonian, some 370
million years ago, Parker and his colleagues found red pigment granules inside
the chromatophores on the upper part of the body. They also recognised
multilayered versions of the diffraction grating on the fish鈥檚 belly. In modern
fish, these diffract all wavelengths of light producing a silvery sheen. The
placoderm, then, was probably red above and silver below.

Once they could recognise these structures, the team had little trouble
reconstructing the colours of other extinct animals, says Parker. The
chromatophores had probably been overlooked before because they resemble
ordinary bone cells and are embedded in them. And the people who work on colour
don鈥檛 work on fossils, says Parker. If researchers know where to look and what
to look for, they will be able to work out the colours of other extinct animals,
including dinosaurs, he adds. 鈥淲e can finally accurately describe the colour of
animals from the past rather than simply speculate or extrapolate the colour by
comparing it to modern animals.鈥�

TRIALS of a type of gene therapy that slices through the genetic material of
HIV and prevents it from multiplying have begun in Australia. Within a few
months they should provide the first signs of whether the technique can halt the
progression of AIDS.

Existing treatments try to reduce the amount of HIV in the body with a
cocktail of anti-viral drugs. But researchers at Gene Shears, a biotechnology
company in Sydney, will try to discover whether an immune system already under
attack can be repaired from within.

Last week, Gene Shears announced that it had begun clinical trials of an
engineered 鈥渞ibozyme鈥濃�攁 molecule of RNA that behaves like an enzyme and
cuts through a vital part of HIV鈥檚 genetic material. In laboratory tests, the
ribozyme, called Rz2, halts replication of HIV inside CD4 cells. These are the
white blood cells, or lymphocytes, that the virus commandeers at the outset of
infection, converting them into factories turning out multiple copies of the
virus.

Six pairs of identical twins are taking part in the trials at St Vincent鈥檚
Hospital, Sydney. One twin in each pair is HIV-positive, the other is negative.
The team takes healthy lymphocytes from the uninfected twin, equips them with
the gene that makes the ribozyme and injects them into the HIV-positive twin.
The gene is carried into the lymphocytes on board a disarmed mouse leukaemia
virus. This inserts the anti-HIV gene into human DNA, allowing the lymphocyte to
create its own ribozyme.

Indications of how the armed cells are faring are expected in six months.
Their survival will be the first sign that gene therapy can halt the progress of
AIDS. 鈥淚鈥檓 very optimistic about it,鈥� says David Cooper, head of the Centre for
Immunology and HIV Medicine at St Vincent鈥檚. 鈥淎t worst we expect this technology
to be complementary to existing therapies.鈥�

BY GROWING heart cells in the laboratory, scientists have discovered clues to
how fish oils help prevent heart attacks. It seems that fatty acids in the oils
team up with the cells to keep the heart beating steadily.

Past clinical trials and epidemiological trials on human populations,
particularly Inuits, have suggested that some fatty acids鈥攅specially those
in fish oils such as eicosopentanoic acid and docosahexanoic acid鈥攁re
particularly useful in reducing the risk of heart attack. 鈥淲hat we wanted to do
was focus at the cellular level at what was happening with these fatty acids,鈥�
says Ted McMurchie of the Division of Human Nutrition at CSIRO, Australia鈥檚
national research organisation.

Along with his colleague Wayne Leifert, McMurchie developed a technique for
growing heart cells of adult mice in culture at their Adelaide labs. They
stimulated individual cells with a weak electrical current so that they were
beating regularly. By adding adrenaline, the team could make the cells beat out
of rhythm with the electrical pulses. This mimics 鈥渁rrhythmia鈥�, the irregular
beating that can bring on a heart attack.

McMurchie and Leifert then added food extracts, including fish oils, to the
cultures, and observed their effects on the cells through a microscope linked to
image enhancement systems.

It turned out that the fish oils could restore the beat to normal so that it
was in time with the electrical pulses. They seemed to do this because their
fatty acids become part of the membrane of each cell, which is itself made from
fatty materials called lipids and contains components which control the cell鈥檚
beating. 鈥淭hey get absorbed into the cell and work on the cell membrane,
influencing the signalling systems that control rhythmicity,鈥� says
McMurchie.

The researchers announced the results at last week鈥檚 4th International
Congress of Essential Fatty Acids and Eicosanoids in Edinburgh. McMurchie hopes
that the team鈥檚 techniques will allow researchers to find other food extracts
that have potential for preventing heart attacks.

The FAA鈥檚 data show that there are 14 000 medical emergencies each year on
the nine major US airlines, which carry 65 per cent of all passengers flown by
American carriers. Applied across all airlines in the US, this is equivalent to
15 emergencies a day鈥攁t least five times the number found in the last FAA
study, between 1986 and 1988, which revealed an average of two to three
emergencies a day on US airlines.

While each airline has its own definition of an emergency, most cases refer
to difficulties requiring a request for help from passengers with medical
expertise.

Overall, an estimated 350 passengers die each year on board planes operated
by American carriers. By comparison, an average of 118 passengers a year have
died in air crashes on US soil since 1978.

Data for carriers outside the US reveal a similar picture. In the year to
March, British Airways recorded one medical emergency for every 11 000
passengers. Australia鈥檚 Qantas Airways says that it has an average of three
emergencies a week. About five passengers a year suffer cardiac arrest and die
on Qantas鈥檚 international flights, a figure that translates into about one death
per million passengers.

Although the problem has increasingly been discussed by aviation
doctors鈥攐ften behind closed doors鈥攖he FAA study has forced the issue
into the open. Last month the aviation subcommittee of the US House of
Representatives began hearings into the adequacy of in-flight medical care in
the US, where aircraft generally carry fewer emergency medical supplies than in
many other countries.

Eric Donaldson, the outgoing president of the Airline Medical Directors
Association, an international professional body, and general manager of aviation
health services at Qantas, testified before the subcommittee on the importance
of carrying heart defibrillators. Not only do they save lives, they also reduce
the number of diversions in response to medical emergencies. Qantas carries
heart defibrillators on its long-haul flights, as well as medical kits with
a range of drugs and medical tools. Its 345 chief stewards are all trained to
operate defibrillators.

In the five years since they were introduced by Qantas, the defibrillators,
which send electric shocks into heart muscles that have stopped working, have
been used 109 times. On 24 occasions, passengers had their heart rhythm
restored.

鈥淒efibrillators will not save every victim of a heart attack, but they will
give them a chance that would not otherwise be available,鈥� Donaldson told
快猫短视频. 鈥淚f you are travelling at 30 000 feet and someone has a
heart attack, it would take at the very least 20 minutes to get back to the
gate. After 16 minutes, the chances of resuscitating someone who鈥檚 gone into
cardiac arrest are virtually nil.鈥� Donaldson and cardiologist Michael O鈥橰ourke
of the University of New South Wales in Sydney will publish their survey of the
use of defibrillators by Qantas in the journal Circulation later this
year.

The pressure on other airlines to carry similar equipment is growing. The
death last year of a 37-year-old businessman during a United Airlines flight
from Boston to Salt Lake City triggered a series of damning newspaper articles
on airline safety. The victim, an avid sportsman, died while being tended by
three doctors, a nurse and a paramedic. They could do little without the drugs
or the defibrillator that might have saved the patient鈥檚 life.

American Airlines, which carries some 80 million passengers a year, has
decided to introduce defibrillators and enhanced medical kits from 1 July. Some
2300 of its chief stewards have been trained to use the equipment. Later this
year, the International Civil Aviation Organization, the UN body that regulates
air safety standards worldwide, will begin its own study of in-flight
emergencies.

The British airline Virgin Atlantic and Air Zimbabwe already carry medical
defibrillators. Hong Kong鈥檚 Cathay Pacific has recently said that it intends to
introduce defibrillators, while British Airways and Scandinavian Airlines say
they are considering such a move.

While no one knows why the in-flight death rate has soared since 1988, there
are a number of theories: most of the deaths occur on long-haul flights, and the
number of passengers taking these has doubled in the past decade. Additionally,
more elderly people are now flying. Some doctors speculate that the exertion of
carrying heavy baggage before a flight, plus the excitement of holiday travel,
may increase the risk of heart failure.

DESPITE their solid appearance, modern aircraft are riddled with
holes鈥攅ach one a potential weak spot. Now a novel method for making holes,
invented by Australian defence scientists, could make planes stronger and extend
their working lives.

A Boeing 747 has more than half a million holes鈥攖iny ones for rivets
and large ones for doors. Landing and takeoff stresses generate micro-cracks
which radiate from the holes, eventually causing metal fatigue. If not repaired
this can lead to disaster. But checking each one is expensive and time
consuming, requiring planes to be grounded for long periods.

Now Albert Wong and Nik Rajic of the Defence Science and Technology
Organisation鈥檚 Aeronautical and Maritime Research Laboratory in Melbourne have
found a way to strengthen rivet holes and extend the life of a plane. The new
method replaces the drills and stamps used in conventional aerospace
manufacturing. Instead, clamps are placed on the top and bottom of a metal sheet
being pierced. Compression punches, or mandrels, press into the sheet from
opposite sides鈥攂ut stop before they meet. The bottom mandrel is withdrawn,
leaving the top one to finish the job.

The compression created by the bottom mandrel runs in the opposite direction
to that created by the perforating mandrel from above, forcing compressed metal
to 鈥渙oze鈥� sideways into the hole walls. 鈥淭he radial outward flow of the metal is
the trick,鈥� says Wong. 鈥淭he metal on the edge is highly compressed giving
improved fatigue resistance.鈥�

In tests on aluminium sheets the new holes lasted 2.5 times as long as
standard perforations. They also survived 50 per cent longer than holes
strengthened using a process known as cold expansion.

THE fangs of Australia鈥檚 feared funnel web spider could contain an environmentally friendly pesticide. Active compounds in the venom have been found to attack only the nervous systems of insects, leaving large animals鈥攁nd crops鈥攗nharmed.

The discovery was made by biochemist Glenn King and pharmacologist Merlin Howden, both at the University of Sydney. For the past two years the duo have been decoding the three-dimensional structure of the small protein fragments, or peptides, that are responsible for delivering the venom鈥檚 lethal neurotoxic effects. One of the world鈥檚 deadliest spiders, funnel webs killed one person every four years on average before an effective antivenin became widely available in Australia in 1980. Funnel web venom is only lethal to the insects that are its natural prey, and humans. Larger animals and amphibians are naturally immune.

Using nuclear magnetic resonance spectroscopy and X-ray crystallography, King and Howden have mapped all 45 active compounds in the venom. Laboratory tests on the peptides revealed one specific to insect brain cells. Others were found to target human nerve cells. 鈥淚t鈥檚 remarkable that parts of the venom affect humans and other parts are specific to insects,鈥� says King.

The insect-killing compound holds open tiny pores in the membranes of insects鈥� nerve cells. Usually ions cycle back and forth through these pores to carry message pulses along the nerve. But the protein jams them open, sending amino acids, sugars, sodium, potassium and other substances essential to proper brain function gushing into the cell. Neurological activity is severely disrupted鈥攚ith fatal consequences.

More recent work with student Xiuhong Wang has isolated the peptide fatal to humans. This works in a similar fashion to the insect-killing compound, but only affects human nerve cells.

Meanwhile, lab tests using brain cells from cockroaches and humans have confirmed that the insect-killing compound affects only insect pores and leaves human ones unaffected. King says that the venom has been shown to kill cotton bollworms, plague locusts, cockroaches and mealworms. 鈥淏ut it doesn鈥檛 kill any non-insect creatures it鈥檚 been tried on so far,鈥� he says. 鈥淭his could serve as a `natural鈥� pesticide.鈥�

The researchers hope any resulting pesticide will be effective against the cotton moth, Helicoverpa armigera, which has developed resistance to many pesticides. It has even overcome cotton crops that have been genetically engineered to withstand it.

King is using the detailed map of the whole peptide to make a design template to produce synthetic analogues suitable for crop spraying. The researchers have applied to patent insecticides based on their findings. A paper on the work will be published in the June edition of Nature Structural Biology.