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MARSDEN FUND NEWSLETTERNO 20 June 2002ContentsProtein crosslinking - the chemistry of cataracts and croissants Using DNA to track dolphin and whale populations Bringing together museums and indigenous knowledge Marsden recognised in Queen's Birthday honours Protein crosslinking - the chemistry of cataracts and croissants
Marsden-funded research carried out by Dr Juliet Gerrard's team at Canterbury University has focused on a particular form of protein modification - protein crosslinking. Her specific interest is the reaction of proteins with sugars, a complex process known as the Maillard reaction. This reaction yields a multitude of products generally dubbed advanced glycation end products - AGEs. These accumulate in the body as we grow old and so are appropriately named. Proteins are generally surrounded by sugars in biological systems, and the consequences of protein crosslinking chemistry by the Maillard reaction can be enormous. These reactions have been implicated in many diseases, especially in diabetes where there is more sugar in the blood and, therefore, a higher chance of crosslinking taking place. Another condition in which crosslinking is implicated is Alzheimer's disease. Sufferers are often found to have tangles of protein in their brain, which alter neuronal pathways. Crosslinking in these protein aggregates makes the situation worse, as the body is unable to destroy the unwanted proteins. Another dramatic example of these chemical accidents is the formation of cataracts on the lens of the eye. Once again, crosslinking of the proteins of the eye lens has been found to play a role in the growth of cataracts, which can be simply formed in the laboratory by leaving an intact animal lens in a sugar solution. Cataracts are particularly common amongst diabetics, whose high blood sugar speeds up the rate of cataract formation. The fundamental aim of the Marsden research programme was to unravel the chemical
mechanisms of protein crosslinking, with the long term goal of determining methods
to control this process. A large amount of work has taken place around the world,
as well as in Dr Gerrard's laboratory. It is now well-established that the main
culprits are in fact breakdown products of sugars that form naturally in the
body, notably a small molecule called methylglyoxal. The Canterbury team has
made a substantial contribution to this advance in knowledge. In particular,
they have identified key structural features of molecules that are likely to
make them damaging, and shown that each of the molecules likely to be responsible
for the harmful reactions with proteins reacts in a unique way.
Dr Gerrard's group works closely with the Food and Biomaterials Innovation Team at Crop & Food Research, Lincoln, in a related research programme to explore the potential benefits of protein crosslinking in food. The Marsden Programme included a subcontract to Crop & Food Research, which investigated ways of manipulating the Maillard reaction during food processing. A basic understanding of the way in which proteins and sugar react may one day have huge benefits in both medicine and food science. Tuatara survivors
Tuatara are the only survivors of a line of reptiles that died out 200 million
years ago. They have survived continental drift, asteroid wipeouts and Ice Ages
to become one of the world's archetypal "living fossils". 430 tuatara hatchlings from Stephens Island are currently being reared in a
head start facility in Wellington. It is hoped that these animals will be released
in a few years' time on the Rangitotos - three islands in the Marlborough Sounds
recently cleared of predators. Some day, tuatara may also be released on Mana
Island, off Paremata, and in Wellington City's Karori Wildlife Sanctuary.
News from Marsden Cottageby Dr Valda McCann, Manager, Research FundingProgress of the assessment process
Personal news Using DNA to track dolphin and whale populations
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| Hector's Dolphin mother and calf Photograph: Steve Dawson |
You might remember that, back in 1993, Professor Baker was involved in identifying
species of whale meat in Tokyo shops. He had to do the DNA work in a Tokyo hotel
room as customs regulations prevented him from bringing samples back to New
Zealand to analyse. With the help of his former postdoctoral fellow, Dr. Gina
Lento, this molecular monitoring has been continued since 1993 and has identified
the specific origin of more than 1100 products from 26 species of whales, dolphins
and porpoises. This, despite the fact that species such as the humpback, gray,
sei, fin, and Bryde's whales have been protected for decades.
The ever-widening database is being put to many uses. Together with former Marsden
postdoctoral fellow Dr Luis Medrano (now at the University of Mexico) and Dr
Brad Congdon (now at James Cook University, Cairns), Professor Baker has described
the interchange of genes among humpback whales around the world. His former
student Dr Merel Dalebout, and colleagues at Museum of New Zealand (Te Papa)
and the Smithsonian Institution, have discovered a new species of beaked whale
from the North Pacific. They have also rediscovered a forgotten species of beaked
whale by using DNA to establish the genetic identity of a tooth and a jaw found
on the Chatham Islands in the 1870s and a skull cast up on White Island in the
1950s.
With his former student Dr Franz Pichler, his current student Kirsty Russell,
and colleagues from the University of Otago, Professor Baker has recently focused
on the genetic diversity of the world's rarest sea-going dolphin - Hector's
dolphin. These dolphins are divided into four populations - the South Island
west coast, south coast and east coast and the North Island west coast. Once,
dolphins from these populations exchanged genes through occasional migration
and interbreeding, but now the populations are isolated from each other. In
some places their numbers are falling as a result of accidental drowning in
fishnets. This is of grave concern as fewer than a hundred North Island dolphins
are left.
As a result of this study, Professor Baker and his team became interested in
the effects of population fragmentation on the dolphin's genetic diversity.
Using methods developed for 'ancient' samples, they extracted DNA from museum
specimens going back to 1870, and took samples from hundreds of living dolphins
(by approaching them in the open sea and gently scraping their skins with a
plastic pot cleaner). They examined the maternally inherited mitochondrial (mt)
DNA and the genes controlling the dolphins' immune system and compared their
diversity with populations of whales and land-going animals worldwide.
They found that populations of Hector's dolphins seem to have become more fragmented
and that their genetic diversity has declined along with their numbers in some
areas. Along the west coast of the North Island, the range of Hector's dolphins
has declined by nearly two thirds over the last 30 years. The small number of
dolphins remaining are found primarily off Auckland's west coast, between Raglan
and the Kaipara. The researchers warn us that, with such small numbers and the
loss of genetic diversity, the Auckland survivors are highly vulnerable to extinction.
Already, legislation is in the pipeline to limit the use of gill-nets off Auckland's
west coast. With such a fragmented species, the researchers suggest that it
might be possible to restore some genetic diversity by moving dolphins from
place to place. Although this strategy has been successfully used with endangered
birds, it has never been tried with dolphins before. Dolphin genetic restoration
is unknown territory.
| For further information, contact Associate Professor Scott Baker, School of Biological Sciences, The University of Auckland, P. O. Box 92019, Auckland - Tel: (09) 373 7599, ext. 7280 Email: cs.baker@auckland.ac.nz |
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Kumete, bowl, with figure supports on a dog, illustrating
the story located in Hawaiki of Tamatekapua and Whakaturia stealing the
bowl of Uenuku, helped by their dog. The carver was Wero Taroi of Ngati
Tarawhai from Lake Okataina, Rotorua. Wero was one of the most famous
carvers of the Te Arawa confederation of tribes whose carving career spanned
much of the nineteenth century and ranged from war canoes to storehouses,
early meeting houses, and the beginnings of tourist art in Rotorua.
Photo: Auckland Museum |
New Zealanders and visitors to this country have always realised that Maori
woodcarving is a very special art, unique to these islands. Although the Eastern
Polynesian origins of Maori art, language and culture are obvious, Maori woodcarving,
through its thousand-year history here, has developed its own regional, tribal
and individual styles that clearly mark it off from any other Pacific art forms.
Maori experience of culture contact and European influence through the nineteenth
century intensified these developments and set the scene for the present state
of Maori arts.
Some current Marsden-funded research carried out within the project "Bringing
Together Museums and Indigenous Knowledge", is demonstrating another aspect
of the special qualities of Maori woodcarving. Following on from his recently
published work on nineteenth century Rotorua carvers (Carved Histories: Rotorua
Ngati Tarawhai Woodcarving, Auckland University Press, 2001), Roger Neich,
Professor of Anthropology and Curator of Ethnology at Auckland Museum, has been
compiling records of all those nineteenth century Maori carvers whose works
can still be identified, in standing meeting houses, in museums, and in archival
photographs. So far, about 274 individual carvers, with their tribal affiliations
and their works, have been identified, but many unpublished sources are still
to be checked. Consultations with the descendants of these carvers are an important
source of new insights.
This situation is unique within the nineteenth century ethnic world. Among North-West
Coast American Indians about five Haida carvers, some Kwakiutl, and a few others
are known, along with their works. For nineteenth century African artists, the
record is limited to two or three from the Congo area. In the tropical Pacific,
only two from Melanesia and two from Polynesia can be identified.
This amazing wealth of information on Maori carvers can provide the basis for
a rich new art history of Maori woodcarving. Utilising these records and adding
to them from Maori oral traditions and family records, new insights are being
gained into the transmission of carving styles, the relationships between different
carving traditions, and the reasons for their survival or demise. Numerous projects
for future researchers are emerging from this preliminary study, with implications
for a better understanding of nineteenth century cultural and artistic change,
not only in New Zealand Maori art but also in other ethnic arts.
| For further information, Contact Professor Roger Neich Department of Anthropology, The University of Auckland, Private Bag 92019, Auckland - Tel: (09) 3737 999, ext. 4762 Email: r.neich@auckland.ac.nz |
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Hemideina maori, 7 cm long.
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The montane weta, Hemideina maori, is found throughout the South Island,
usually at high altitude beneath slabs of schist or in scree. A particularly
large variety is found above 4000 ft on the Rock and Pillar Range, about 50
miles north-west of Dunedin. In this environment the temperature may drop below
freezing at any time of the year and in winter, temperatures of -7 to -8°C
are not uncommon. Beneath the windswept rocks the insects may be exposed to
sub-zero temperatures for several days at a time. Associate Professor John Leader
and Professor Rob Smith of Otago University received a Marsden grant to see
how the weta can survive such conditions.
In the laboratory, Hemideina maori can be frozen to body temperatures
of -10°Cfor days. It is readily calculated that, at this temperature, 90%
of the body water is ice, and the tissues are then bathed in a saline solution
that is about as concentrated as the Dead Sea, which is 10 times that of normal
sea water. Metabolism, estimated from oxygen uptake, is reduced to unmeasurable
levels, and the principal chemical activity which occurs in the animal is the
regrowth of ice crystals and exchange, by diffusion, of potassium from inside
the cells with sodium in the concentrated fluids around them.
The frozen insects are quite rigid and brittle. In spite of this, when allowed
to rewarm, they thaw and rapidly become active again. Other insects, and indeed
some snakes and frogs, are known to tolerate some degree of ice formation within
their tissues, but the weta is by far the largest freezing-tolerant insect,
and the temperatures it tolerates are far in excess of those endured by vertebrates.
Weta lived through the Ice Ages in New Zealand and this particular species may
have survived this period by acquiring freezing tolerance. As this country has
warmed again and the glaciers have retreated, it has been pushed to the limits
of its range, surviving on high mountain tops. In scree slopes at the edge of
the Tasman Glacier, the weta can be found in a habitat much like those of earlier
times, freezing at night and becoming active by day.
An important feature of the freeze-tolerance of this insect lies in its blood
composition. Like most freeze-tolerant animals, the weta contains high concentrations
of the sugar trehalose and an amino acid, proline. In summer, trehalose concentrations
in the blood are similar to those of other insects, but in winter it may reach
as high as 100 grams per litre. Trehalose is a disaccharide, comprising two
molecules of glucose joined together. Possession of high concentrations of trehalose
is a common feature of a wide range of organisms exposed to water stress, either
as a result of dehydration or low temperature.
It is possible to mimic the processes which occur during freezing by using isolated
tissues of the weta. Recent experiments by the researchers suggest that trehalose
(and the amino acid proline) is acting in several ways. It helps to retain water
around the cellular machinery and prevents cell proteins from being put out
of shape by high salt concentrations. Also, concentrated trehalose solutions
tend to form a non-crystalline, amorphous glass when frozen, instead of physically
destructive ice crystals. The sugar binds to the water molecules and not only
prevents ice formation but traps the salts within the matrix, preventing damaging
diffusion.
Not all insects with trehalose in their blood are freeze-tolerant. In most insects,
trehalose doesn't readily pass through cell membranes, and when it does it is
rapidly metabolised. In the weta, however, trehalose can reach high concentrations
within cells and this may generate some surprising effects. Two recent reports
suggest that when trehalose is raised to high concentrations in mammalian cells
in tissue culture by artificial engineering, the cells become tolerant to both
freezing and drying. The team has not yet succeeded in demonstrating
dehydration tolerance in weta tissues, although the ability to remove almost
all the tissue water by freezing suggests that this may be possible. Current
experiments are aimed at determining how high intracellular concentrations of
trehalose are achieved, and to see if this can be duplicated in other, freezing-susceptible
insects.
| For further information, contact Associate Professor John Leader, Department of Physiology, University of Otago, P.O. Box 913, Dunedin- Tel: (03) 479 7322 Email: john.leader@stonebow.otago.ac.nz |
Marsden Update is published quarterly by the Marsden Fund and is available free on request. Editor: Glenda Lewis Email: glenda.lewis@rsnz.org
