Our Changing World
Thursday 27 November 2014, with Alison Ballance, Ruth Beran & Veronika Meduna
On This Programme
by Ruth Beran
Water treadmills are often used to help horses recover from injury, but Paul Macdermid from Massey University in Palmerston North has had one custom built for people.
“I believe there’s two [water treadmills] for human use in New Zealand, one down in Christchurch and this one, and there’s a number of horse water treadmills around the country,” says Paul.
Runners constantly hit the ground with 4 or 5 times their body weight through their legs, so they often suffer from overuse injuries. “So things like running in a microgravity climate like a water treadmill or a G-trainer like they have in Auckland could be quite beneficial for preserving athletes life span,” says Paul. Water treadmills can also be used by people who would otherwise have difficulty exercising on land, because they are overweight.
The water treadmill in Paul’s home was constructed by O'Leary Engineering and consists of a big, insulated stainless steel container, with a ladder at one end to climb in and out of. The treadmill belt is about 2 to 3 metres long, and the water sits at waist height.
“In total, with the water in, it’s about 3 tonnes in weight,” says Paul. “So without the water it’s about 800 kg.”
The water is set at 21.5˚C. “Which while colder than the average swimming pool, it’s good for exercising in,” says Paul.
Paul is studying how people run on a water treadmill compared with an ordinary treadmill and is recording stride frequency, ground contact time, and vertical oscillations, as well as using accelerometers to measure shock attenuation. “Which is the difference between the peak acceleration on impact, when the foot hits the floor, and at the same time, or very similar, the peak acceleration in the head,” he says.
The difference between the two indicates how hard the body has had to work to get rid of the energy to the head to protect the brain and the central nervous system. Paul says there’s an 80% reduction in the water treadmill as compared to running on land.
Trial participants also wear a gas mask connected to a portable metabolic gas analyser which analyses expired gas to estimate inspired gas. This enables an estimate to be made of the work that’s been done.
“You kind of look like Darth Vader. Everyone always thinks they’re the first one to come up with that comment, but we get that pretty much all the time,” says Matt Miller, from Massey University.
The study requires participants to run on a normal treadmill and the water treadmill for 15 minutes at 10.2km/hr with a five minute break in between. Some participants run on the water treadmill first while others run on the normal treadmill first. Participants are given no instructions, other than to run as normally as possible.
Kara Macdermid, a student at Awatapu College and cross country athlete says: “I like running on here,” she says. “As well as being without injury and stuff it also makes you feel better for the other training sessions I find.” She demonstrates how athletes run on the treadmill and is weighed beforehand. She is just over 50% lighter in the water.
From results so far, Paul is finding a 40 to 50% reduction in accelerations. “So it’s a very good method of allowing someone to run either while injured or to increase the amount of training that they can do safely without increasing the risk of an injury,” he says.
Secondly, oxygen consumption of the athletes is showing a difference of 15 to 20 ml oxygen/minute between the two treadmills. “Which is huge in terms of a percentage,” says Paul. “If you look at the gas analyser Kara’s here she’s at around 45 ml of oxygen per minute, on the normal treadmill she’s at around the 30 mark. So that’s a good reduction.”
Paul is also finding that athlete’s heart rate is higher on the water treadmill as compared with the normal treadmill. In Kara’s case there was a 25 beats per minute difference, indicating that it’s harder to run in the water treadmill than the ordinary treadmill when the water is at waist height. “That’s because of the hydrostatic resistance provided by the water as your moving your limbs through the water,” he says. “And the faster she tries to run the greater that resistance, so the greater the work that will have to be done.”
This means athletes don’t have to work as hard on the water treadmill to maintain fitness.
“The data shows that they can reduce the speed at which they run at but still get the cardiovascular adaptations that they would get if they were outside doing an easy run but without that risk of impact,” says Paul.
Mutant Petunias and Understanding Colour in Plants
By Alison Ballance
Petunias are a popular garden plant, and plant breeders have put a lot of effort into breeding 'mutant petunias' that boast spectacular colours and patterns. Such mutant plants interest Nick Albert, not as a gardener, but as a geneticist who is trying to unlock the genetic codes that underpin how pigmentation and colour patterns are expressed. Nick is quick to point out that the term mutant is a straight-forward genetic term that describes any variant of a plant that has been bred from an ancestral type.
Nick is interested in pigments known as anthocyanins, which are responsible for the reds, blues and purples in plant colour. They belong to a class of molecules called flavonoids. Yellows and oranges, on the other hand, are produced by carotenoid pigments, while chlorophylls produce greens.
Nick's interest in anythocyanins began during his PhD research at Massey University.
"We’re doing a lot of work understanding how the 15 genes that produce pigments]are turned on at the right time and place," says Nick. "And they’re regulated by a set of very special genes – these genes are the regulatory genes. And these proteins have partners, and they can only turn on their genes when their partner is present."
"A lot of previous work had been done on how genes are turned on. But I was really interested in the mechanisms that might allow the plant to turn off colour, or to put the brakes on so that excessive amounts of pigment aren’t produced at the wrong time. We’ve identified two different classes of genes that turn off these genes."
The two genes Nick has identified work in quite different ways. One essentially hijacks the activating part of those proteins and instead of allowing that complex to turn on the genes it turns the switch off – and it’s like the handbrake, it’s a very effective way of turning genes off. Then there’s another type of repression and this a small, interfering mechanism, more like damping on the pedal brake.
Nick says pigments are an important way for plants to respond to stress. “If conditions become unfavourable plants can’t move – and these systems allow the plant to respond very rapidly to changing conditions.”
David Lewis from Plant and Food Research says that understanding the genetic regulation of pigment production in petunias may be useful in breeding coloured fruits and vegetables, as pigments have recognised health benefits.
During a post-doctoral position at AgResearch Nick, who now works at Plant and Food Research, looked at how tannins, which are another group of flavonoids, were regulated in clover. Plants use tannins to deter insects from feeding on them. Tannin production in forage crops is important as it improves nitrogen use efficiency in the rumen of animals such as cows, and can help prevent bloat.
Nick was awarded the 2014 Roger Slack Award in Plant Biology by the New Zealand Society of Plant Biologists.
Tuatara in a Cold Climate
By Alison Ballance
The tuatara, Sphenodon punctatus, is the only living example of an ancient order of reptiles, the Rhynchocepahalia, which has been around for more than 250 million years. Once widespread throughout the North and South islands of New Zealand, tuatara numbers soon dropped after the arrival of Maori due to predation by both humans and the Pacific rat, or kiore, and habitat clearance. For the last couple of hundred years it’s been confined to 32 small islands in Cook Strait and northern New Zealand. The largest population of tuatara is found on Stephen’s Island or Takapourewa, in Cook Strait.
Tuatara have an interesting relationship with temperature. They are ectotherms (”cold blooded”) so their body temperature depends on the ambient temperature. They live in the forest, and are active at night, but spend sunny days basking at the entrance to their burrow. Tuatara don’t have sex chromosones, but instead, like other reptiles, sex is determined by the soil temperature during the long – up to 15 month – incubation. Temperatures below 21.2° Celsius during the first seven weeks of incubation produce females, while above 22° Celsius produces males. This pattern is the reverse of that seen in turtles, in which higher temperatures produce females.
Two years ago, a group of adult and juvenile tuatara from Takapourewa were moved to the Orokonui Ecosanctuary, north of Dunedin, which is surrouned by a predator-proof fence and is free of mammalian predators. This site is 500 kilometres further south, and therefore cooler than other known tuatara areas. Zoologist Alison Cree, from the Zoology Department at the University of Otago, and her students, including current PhD student Scott Jarvie and previous student Anne Besson, have been investigating how tuatara will cope with these cooler temperatures, for example the effect it has on growth rates of juvenile tuatara.
Some of the female tuatara that were transferred to Orokonui Ecosanctuary were gravid and several laid their eggs in a shared nest site, out in the open on a sunny gravel track. A third female was discovered outside the sanctuary, 1.5 kilometres from her home site, and she laid one egg which has also been added to the nest. This is the longest distance of travel known for a tuatara, and it is believed she may have been flushed out a culvert during a rain storm while she was wandering in search of a nest site.
These eggs at Orokonui were laid later and are taking longer to develop than eggs laid on Stephens Island/Takapourewa, which Alison Cree is not surprising given the cooler temperatures. One clutch of eggs has since been predated by a kiwi – although the event was not captured on remote cameras positioned at the nest there are distinctive probe holes in the ground and in the eggs.
“Some of the eggs were damaged, destroyed,” says Alison. “There were advanced embryos in some of them, so we know they can develop as embryos here, but we’re not going to see any evidence of hatching from that nest.
Alison is philosophical about the kiwi predation. “It’s not a predator-free situation. We’re trying to reconstruct part of what would have been a natural ecosystem, and it is natural for tuatara and kiwi to be in the same area – it just hasn’t happened that frequently recently, as tuatara have been restricted to offshore islands, most of which don’t have kiwi on.”
The remote cameras have collected photos of a kiwi walking past the tuatara nest site, and also shots of male tuatara that lives nearby, posturing and raising its spines in display. The kiwi in the sanctuary are rare Haast tokoeka.
The new book ‘Tuatara: biology and conservation of a venerable survivor’ is written by Alison Cree, and published by Canterbury University Press. The book, which is as venerable as the tuatara, and has taken Alison many years to write, is a comprehensive and scholarly account of tuatara aimed at biologists and people with a strong interest in the unusual reptile.