Life Sciences
First sex-specific gene linked to Alzheimer's
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January 12 2009 at 06:35AM
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A gene found on the X chromosome harbours the first sex-specific genetic variant linked to a greater susceptibility to Alzheimer's, according to a new study.
Researchers at the Mayo Clinic in Jacksonville, Florida and Rochester, Minnesota showed that women who inherited the same variant of the gene, known as PCDH11X, from both parents were far more likely to develop the disease.
Among Alzheimer's patients evaluated for the study, "the odds a women had two copies of the PCDH11X variant as opposed to no copies was nearly twice as high as for the control group," the lead researcher, Steven Younkin, told AFP.
Both men and women with only a single copy were also slightly more likely to have Alzheimer's. But only women have two X chromosomes, making them uniquely vulnerable to the impact of the double variant.
Men have one Y chromosome, and one X chromosome.
Alzheimer's is a degenerative disorder of the brain characterised by forgetfulness, agitation and dementia. There is no known cure.
While many gene variants, or alleles, have been implicated in the onset of the disease, only one other - APOE 4 - has been shown to be a higher risk factor.
The findings, published in the journal Nature Genetics, do not necessarily mean that women as a whole are more prone to getting Alzheimer's.
"There may be male-specific risk factors - genetic or environmental - that balance the increased risk in women from PCDH11X variant," Younkin explained.
The researchers discovered the wayward string of DNA by scanning the entire genome of 844 patients and 1,255 healthy persons, looking for telltale markers that might point to a genetic culprit.
After identifying PCDH11X, they confirmed the "highly significant association" by repeating the gene tests on an even larger group of 1,547 patients, and a slightly smaller number of controls.
Follow up studies will investigate the exact mechanism by which the variant affects the nervous system in order to help diagnose the disease early on and develop suitable drugs, Younkin said.
Alzheimer's is caused by a massive loss of cells in several regions of the brain, driven by a buildup of plaques of amyloid protein. The disease occurs most frequently in old age.
An estimated 37 million people worldwide live with dementia, with Alzheimer's disease causing the majority of cases, according to the World Health Organisation (WHO).
With the ageing of populations, this figure is projected to increase rapidly over the next 20 years.
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Scientists find gene that makes cancer spread
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IOL NEWS January 06 2009 at 10:22AM
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By Julie Steenhuysen
Chicago - A single gene appears to play a crucial role in deadly breast cancers, increasing the chances the cancer will spread and making it resistant to chemotherapy, US researchers said on Monday.
They found people with aggressive breast cancers have abnormal genetic alterations in a gene called MTDH, and drugs that block the gene could keep local tumours from metastasising or spreading, increasing a woman's chances for survival.
"Not only has a new metastasis gene been identified, but this also is one of a few such genes for which the exact mode of action has been elucidated," said Dr Michael Reiss of The Cancer Institute of New Jersey in New Brunswick, whose study appears in the journal Cancer Cell.
"That gives us a real shot at developing a drug that will inhibit metastasis," he said in a statement.
Stopping cancer's spread is important - while more than 98 percent of patients with breast cancer that has not spread live five years or more, only 27 percent of patients whose cancer has spread to other organs survive.
Reiss and Yibin Kang of Princeton University used several different research approaches to find the gene, which helps tumour cells stick to blood vessels in distant organs.
To get them in the right general area, they used big computer databases of breast tumours and found that a small segment of human chromosome 8 was repeated many times in people with aggressive breast tumours.
While most normal DNA sequences contain only two copies of a gene, they found some breast tumours had as many as eight copies of this gene segment.
The team then turned to human breast tumour samples taken from 250 patients to look for these genetic abnormalities and found the gene MTDH was overly active or expressed in aggressive tumours.
"This gene exists in every one of our cells," Kang said in a telephone interview. "Somehow the tumour gains extra copies and over-expresses them.
"We saw 30 to 40 percent of them over-expressed this gene."
The researchers then injected lab mice with tumour cells from patients who had this genetic alteration and found the mice formed tumours that were more likely to spread.
They also were more likely to resist treatment with traditional chemotherapy drugs, such as paclitaxel.
But when they genetically altered these tumours, inhibiting the MTDH gene, the tumour cells were less able to spread and were more vulnerable to chemotherapy.
Kang said he is hopeful the finding will lead to drugs that not only keep breast cancer from spreading, but also make it more responsive to treatment.
"If we have a drug to inhibit this type of gene, one stone hits two birds," Kang said.
He said MTDH may also play a role in other types of cancers, including prostate cancer. "It's likely to be a broad influence gene," he said.
Kang said he thinks it would be possible to develop an antibody to neutralise the activity of the gene.
Already, it has gained the attention of drugmakers. Kang said he plans to meet with Johnson & Johnson next week.
"I'm quite optimistic we will try to develop a drug as quickly as possible," he said. (Editing by Maggie Fox and David Wiessler) - Reuters
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Yebo Gogga Yebo AmaBlomo - Free exhibition of live insects, plants, and animals aimed at learners and the public which form an interactive framework round the theme of uMuthi / Medicine.
Exhibitors: Spider Club, Lepidopterists Soc, WitsBird Club, Transvaal Museum, GDACE, Tree Soc, Walter Sisulu Botanical Gardens, Medical Entomology and Biodiversity Systematics division of Plant Protection Research Institute etc.
4 - 8 October 09:00 - 16:00 Weekdays / 10:00 - 16:00 Weekend
Life Sciences Museum, School of Animal, Plant & Environmental Sciences, University of Witwatersrand
School Bookings Tennyson (011) 717-1188
IEB BIOLOGY TEACHERS have their own free easy to use e-service. The service enables the sharing of information, ideas and opinions. Files too can be shared e.g. tests and exams. In order to sign up, send an email to Robert Mckay at Bridge House (robmck@bridgehouse.org.za) with your name and email address and school name in the subject line.
Learn to juggle - it's good for your brain (from IOL News)
January 21 2004 at 07:30PM
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London - It's a great party trick and useful for circus performers but scientists said on Wednesday that learning to juggle can cause changes in areas of the adult brain.
Mastering the skill increases the amount of grey matter in areas of the brain that process and store visual information, proving what was not thought possible - that new stimuli can alter the brain's structure.
A comparison of brain-imaging scans of non-jugglers and other volunteers before they learned to juggle and three months later, revealed an increase in grey matter in certain areas of the newly trained jugglers' brains.
"Our results challenge our view of the human central nervous system. Human brains probably must be viewed as dynamic, changing with development and normal learning," said Arne May, of the University of Regensburg in Germany, who headed the research team.
Grey matter refers to parts of the brain and spinal cord that are comprised of the tightly packed nuclei of nerve cells. In the brain it is mainly found in the outer layers of the cerebrum which is responsible for advanced mental functions.
In a report in the science journal Nature, May and his colleagues said brain scans done three months after the new jugglers had stopped juggling showed the increase in grey matter had been reduced.
"I believe the challenge we face is to be able to adapt and modulate this knowledge into disease management," May added in an interview.
Indigenous Plant of the Week: FOREST ELDER (Nuxia floribunda)
The Forest Elder is an indigenous evergreen tree that is found along the eastern and southern portions of South Africa, from the Western Cape to the Soutpansberg Mountains in Limpopo Province. Its main habitat is coastal, riverine and mountain forest, where it can reach a height of 15-20 metres, but smaller specimens do appear in dense woodland in Kwa-Zulu Natal, Mpumalanga and Limpopo.
It is generally a tree of moist sub-tropical environments and it enjoys a lot of water, good soil and full sun, although it grows well in shade or semi-shade as an under-storey tree. In the garden, the Forest Elder is frost tender and needs to be protected for the first few years of its life. It makes a good container plant, having a non-aggressive root system. The tree makes a beautiful specimen plant, with masses of white pom-pom flowers occurring in winter and spring, and glossy green foliage. The tree attracts many fruit and nectar eating birds, as well as butterflies and other insects.
'Umlulama', as it is called in Zulu, is popular in traditional medicine. A mixture is made with the bark and is used by a widow to wash her body when the man of the house has passed away.
The wood of the Forest Elder was very popular for furniture making during the late 1800's and early 1900's. Large specimens occurred in the Knysna Forests, and they were chopped down and made into tables, chairs, doors and other items of luxury furniture. Together with the Yellowwoods, Stinkwoods, White Pear and Hard Pear, the Forest Elder was one of the popular trees to be targeted for harvesting. The wood is superficially similar to Yellowwood, but is heavier.
The Forest Elder is a beautiful indigenous tree and needs to be planted and conserved. The remaining large specimens that still occur in our indigenous forests are precious trees and are part of our natural heritage. The furniture that has been made from these indigenous hardwoods and softwoods should be a reminder that our resources need to be harvested in a respectful and sustainable way.
Ref: Making the Most of Indigenous Trees, Fanie and Julye-Ann Venter.
Copyright May 2004 Paul Lawrence 0724656421
Indigenous Plant of the Week - THE BUSH LILY (Clivia species)
The Bush Lily, or more commonly called by its botanical name, the Clivia, is an evergreen plant that is found in the forests of South Africa's warmer, sub-tropical eastern regions.
The plant consists of dark green strap-shaped leaves that reach an average length of about 300mm to 500mm when mature, thick fleshy roots that anchor the plant in the mulch of the moist forest floors, and the beautiful orange flower head which appears from late summer, late winter and spring, depending on the species. When Clivias are growing in ideal conditions, i.e. moist soil, lots of organic material, summer rain, full shade and warm temperatures, they send out thick rhizomes or underground stems, from which new plants shoot off. In this way, Clivias spread and colonise their habitat. Clivias need preferably full shade in order to thrive and in these conditions the flowers will be at their best.
Clivia miniata is found in central and coastal Kwa-Zulu Natal, in the shade of the evergreen forests and thick bush. It is the only species that has flowers that open up and face outwards and is the only one that is common in cultivation. All the other Clivias have more closed, pendulous flowers, but are no less beautiful.
There are five different Clivias in South Africa, all occuring in the eastern regions except for the recently discovered Clivia mirabilis. This Clivia was found to occur in only one valley in the Western Cape in the region of Nieuwoudtville, and was discovered only a few years go. It is protected and extremely endangered due to its limited distribution, and is truly a botanical treasure. Botanists believe that about 4-5 million years ago the whole sub-continent was covered in sub-tropical forest, and due to environmental changes, (climatic cycles, sea currents and rainfall patterns etc) the forest began to recede in an easterly direction, and was slowly replaced with Fynbos in the southern regions, and succullent semi-desert / Karoo in the interior. Interestingly, the Karoo is still moving eastwards today, and is beginning to invade the Free State grasslands. This process has, however, been artificially sped up by the detrimental results of sheep farming and agriculture. The Botanists believe that this one valley was protected and the conditions remained stable over the eons of change, and Clivia mirabilis is a relic of this ancient forest ecosystem. It has truly been a botanical wonder to discover a Clivia growing in a dry semi desert environment where they naturally occur in moist sub-tropical forests.
Clivia caulescens is found in the forests of eastern Mpumalanga and Limpopo. The pendulous flowers are a deep red, and the leaves tend to be more rounded at the ends. It is not common in gardens at all, but is very common at traditional medicine markets in Gauteng. Many people believe that only C. miniata and C. nobilis (Eastern Cape Clivia) are used as traditional 'muti', but C. caulescens is also widely used. Traditional culture has a number of medicinal uses for Clivias, decoctions of the rhizomes being used to ease labour during childbirth, and given to the baby to ensure strength and good health. Only an experienced 'Nyanga' should prepare the medicine as the Clivia or 'umayime' as it is known in Zulu, contains toxic alkaloids, being part of the Amaryllis family.
The Eastern Cape Clivia (C nobilis) is a slower growing species, with dark green leaves that are duller than the other Clivias. It is more of a collectors plant in the nursery trade, mature plants being expensive and more difficult to obtain. The flowers are somewhat less attractive than the other species, having less individual pendulous blooms. Finally, Clivia gardeni, is an attractive plant that is found naturally in the midlands and northern interior of Kwa-Zulu Natal. Large orange pendulous flowers appear in late summer, and also again in spring on mature plants. Good news for plant lovers is that this Clivia is becoming more and more available in the nursery trade. However, the rapid rate at which mature plants are appearing in nurseries indicates that many are not being cultivated, but are being dug out from their natural environment. It is important that when buying plants it is always from a reputable source.
The greatest threat to our Clivias is habitat destruction. When the forest canopy is destroyed, Clivias can no longer survive. Illegal collecting for the nursery trade and mass indiscriminate collecting for the traditional medicine market also take their toll, and populations of Clivias, as well as other valuable indigenous plants, are rapidly disappearing. The issue is one of a socio-economic vs environment struggle, and a balance has to be achieved in the near future to ensure the survival of our natural heritage.
Copyright April 2004 Paul Lawrence 0724656421
Indigenous Plant of the Week SMALL KNOBWOOD (Zanthoxylum capense)
The Small Knobwood is a small to medium sized deciduous tree that is widespread in the eastern parts of our country, including parts of the milder Highveld and Bushveld regions, such as Gauteng and North-West Province.
It occurs in many habitats, from dry Bushveld to rocky exposed slopes, dense woodland and even the edge of forests. In ideal conditions, the Small Knobwood can reach about 12 - 15 metres, but around Gauteng and in it's Bushveld range, it can usually be seen as a small, attractive, upright tree of about 4m in height. The tree usually occurs as a single-stemmed plant, but occasionaly the trunk branches quite low to the ground. Thorny bosses or knobs occur all over the trunk and the branches are full of small, dark prickly thorns. The flowers appear in small yellowish-white clusters in mid-summer and are followed by the small brownish-red fruit which ripens red and later splits to release a black seed. The fruits attract many birds such as Rameron Pigeons, as well as monkeys and Baboons, and the seeds are eaten by a variety of indigenous birds.
It is the leaves, however, that truly characterize the Small Knobwood as an attractive, useful garden plant. Being a member of the family Rutaceae or the Citrus family, the leaves have a strong citrus smell when crushed. They are glossy green, slightly toothed and occur as compound leaves consisting of about 6 - 8 leaflets and a terminal leaflet. The Small Knobwood is the larval food plant of the Citrus Swallowtail Butterfly (Papilio demodicus), and in summer many of these impressive indigenous butterflies can be seen around this tree.
In the garden, the Small Knobwood is a beautiful specimen plant, being hardy, fast growing and ideal for attracting many types of wildlife. It does not have an aggressive root system and does well in containers, where it forms a small, neatly shaped plant. However, it is very difficult to obtain from nurseries, and is also difficult to grow from seed. the easiest way the cultivate the Small Knobwood is from root cuttings.
It is popular in traditional medicine, being used to treat a wide range of ailments from toothache to stomach problems and fever. Some people use the crushed seeds and leaves as a perfume, because of the attractive citrus smell.
(For all your Indigenous plant requirements, visit Berga Nursery at Smut's House in Irene, 0834595115)
Copyright April 2004 Paul Lawrence 0724656421
Indigenous Plant of the Week: PARSLEY TREE (Heteromorpha arborescens)
This medium sized tree is common in the southern and eastern parts of South Africa from the Western Cape to the Karoo, along the coastal regions and the Lowveld to the high altitude grasslands and kloofs around Gauteng. It is a member of the carrot family, Apiaceae, with a characterisistic long taproot and fine, carrot-like flowers. The stem of the tree is the most striking aspect, being rusty brown in colour with thin papery bark peeling off horizontally. The tree is single-stemmed and sometimes multi-stemmed and is deciduous. It is hardy and tolerates cold winds and frost, being ideal for a Highveld garden. It is fairly common on rocky outcrops and in shaded kloofs in the Bronkhorstspruit area, as well as Suikerbosrand.
The Parsley tree is also common in Kwa-Zulu Natal, where it is known as 'uMbangandlala' in Zulu. It is popular as a medicinal plant, being used as an aphrodisiac. The stems and branches are boiled in water and the mixture is combined with milk and then drunk. Small pieces of the stem are also kept on a key-ring as a lucky charm and a decoction of the stem is taken to detoxify the internal organs.
In the garden the Parsley tree makes a beautiful specimen plant, attracting birds and insects to the garden. It deserves to be planted and cultivated and recognised as a valuable part of our natural heritage.
Copyright June 2004 Paul Lawrence 0724656421
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"Acts of creation are ordinarily reserved for gods and poets, but humbler folk may circumvent this restriction if they know how. To plant a pine, for example, one need be neither god nor poet; one need only own a good shovel. By virtue of this curious loophole in the rules, any clodhopper may say: Let there be a tree--and there will be one."
Aldo Leopold, conservationist (1887-1948).
Education linked to lower dementia risk 