Authentic Living Fossils From The Jurassic And Cretaceous Periods

Jordi López of the Barcelona Botanical Institute has joined local researchers in a study to locate and define "havens and museums of flora" in China – areas where vegetation resisted the glaciations of the Quaternary Period.

At the eastern edge of the Tibetan Plateau in the south-west of China, near the Burmese border, are Hengduan mountains. According to Jordi López Pujol, researcher at the Botanical Institute of Barcelona, "they are possibly the most rugged and steepest mountains on Earth." The study of this region, and others in China, consists of the search for areas where flora has remained intact for millions of years due to their privileged position.

This is a Ginkgo biloba leaf.

Credit: Jordi Lopez

Along with a team of four scientists from the Botanic Institute (belonging to the Chinese Academy of Sciences) López Pujol both literally and bibliographically went deep into one of the most biologically diverse regions on the planet, far beyond where China's three major rivers (the Yang-Tse, the Mekong and the Salween) pass through deep parallel valleys creating places such the Tiger Leaping Gorge or the Jade Dragon Snow Mountain.

Leading to two articles published in the Mountain Research and Development Journal and Journal of Biogeography, the study was designed to bridge the gap in China's floristic knowledge "mainly from a flora evolution point of view" adds López Pujol. It is based on the hypothesis that the great floristic abundance of China, the third country in the world in the number of plant species, is mostly due to its numerous flora refuges at the end of Tertiary Period and throughout the Quaternary Period. During this era, the world's climate dramatically cooled and switched between glacial and interglacial periods.

"A range of evidence is available that points to the existence of these refuges," says the Catalan botanist. In China, an enormous amount of ancient flora still exists. This is called boreotropical flora. The lineage of these plants appeared millions of years ago which means that they are "authentic living fossils that date back to the Cretaceous and even the Jurassic Periods like the famous Ginkgo biloba," according to López Pujol.

In keeping with the results of the study, some 15 million years ago this abundance of species was common across the entire northern hemisphere. However, the harshening of the climate at the end of the Tertiary and Quaternary Period brought about the extinction of the lineages, with the exception of the refuges in the subtropical mountains of southern China.

The methodology of the study consisted of defining the endemic areas of flora as an indirect marker of the refuges of the Quaternary Period. For this purpose, a database of endemic species was compiled and their distribution was mapped," states López Pujol. The most innovative aspect of this study was that the researchers made an effort to differentiate between ancient endemic species (paleoendemic) and those that originated in the last millions years (neo-endemic).

The botanist says that the "areas with the greatest number of endemisms in general could only be found in the main mountain chains of central and southern China." These mountain regions remained on the edge of the great ice caps that covered most of Europe and North America which meant that they probably enjoyed relatively mild climatic conditions during the glacial periods.

Unhindered by geographical barriers, "these species were able to survive through altitudinal and latitudinal movement. Furthermore, the rugged topography of these mountains not only allowed the survival of various ancient lineages but created differentiation and speciation phenomena" mainly due to geography isolation.

For López, these refuges "can be seen as havens and museums for plants" but despite the fact that they were home to both paleoendemic and neo-endemic species, clear differences were evident between refuges. In this way the botanist points out that "the species that have formed in recent times are mostly located in the Hengduan mountains whereas the ancient species (or relicts) can be mainly found in the mountains of central, southern central and southeast China."

The researchers put this clear tendency down to the ages in which China's different mountain chains were formed. The mountains of the east of the Tibetan plateau are a lot older than the elevation of the plateau itself (which took place during the Pliocene and Pleistocene Periods). López Pujol says that "like in the case of the Hengduan mountains, the orogenesis of the Tibetan plateau and its adjacent mountain systems created a broad range of new habitats which stimulated speciation phenomena."

For the Catalan botanist, the Hengduan mountains "constitute the main evolutionary front in the temperate areas of the northern hemisphere given that the areas further to the east enjoyed relative tectonic stability – something that favours the conservation of relic flora."


Contacts and sources:
SINC
FECYT - Spanish Foundation for Science and Technology

References:

Jordi López Pujol, Fu-Min Zhang, Hai-Qin Sun, Tsun-Shen Ying, Song Ge. Centres of plant endemism in China: places for survival or for speciation? Journal of Biogeography, 38, 1267-1280. 2011.

Jordi López Pujol, Fu-Min Zhang, Hai-Qin Sun, Tsun-Shen Ying, Song Ge. Mountains of Southern China as "Plant Museums" and "Plant Cradles": Evolutionary and Conservation Insights. Mountain Research and Development, 31(3), 261-269. 2011.

Yale Researchers Develop A Way To Monitor Engineered Blood Vessels As They Grow In Patients

New research in the FASEB Journal suggests magnetic resonance imaging allows researchers to study and monitor how new vessels perform while they are 'under construction' in patients

 Using magnetic resonance imaging (MRI) and nanoparticle technology, researchers from Yale have devised a way to monitor the growth of laboratory-engineered blood vessels after they have been implanted in patients. This advance represents an important step toward ensuring that blood vessels, and possibly other tissues engineered from a patient's own biological material, are taking hold and working as expected. Until now, there has been no way to monitor the growth and progress of engineered tissues once they were implanted. This research was published in the December 2011 issue of the FASEB Journal (http://www.fasebj.org).

"We hope that the important findings from our study will serve as a valuable tool for physicians and scientists working to better understand the biological mechanisms involved in tissue engineering," said Christopher K. Breuer, M.D., co-author of the study from the Interdepartmental Program in Vascular Biology and Therapeutics at Yale University School of Medicine in New Haven, CT. "Resulting advances will hopefully usher in a new era of personalized medical treatments where replacement vessels are specifically designed for each patient suffering from cardiac anomalies and disease."

To make this advance, scientists used two different groups of cells to make tissue-engineered blood vessels. In the first group, the cells were labeled with the MRI contrast agent. In the second group, the cells were normal and did not have an MRI label. Cells from each group were then used to create separate laboratory-engineered blood vessels, which were implanted into mice. The purpose was to see whether the laboratory-engineered blood vessels made from cells that were labeled with the contrast agent would indeed be visible on MRI and to make sure that the addition of the contrast agent did not negatively affect the cells or the function of the laboratory-engineered vessels. Researchers imaged the mice with MRI and found that it was possible to track the cells labeled with contrast agent, but not possible to track the cells that were not labeled. This suggests that using MRI and cellular contrast agents to study cellular changes in the tissue-engineered blood vessels after they are implanted is an effective way to monitor these types of vessels.

"This is great news for patients with congenital heart defects, who have to undergo tissue grafting, but that's only the tip of the scalpel," said Gerald Weissmann, M.D., Editor-in-Chief of the FASEB Journal. "As we progress toward an era of personalized medicine—where patients' own tissues and cells will be re-engineered into replacement organs and treatments—we will need noninvasive ways to monitor what happens inside the body in real time. This technique fulfills another promise of nanobiology."

Contacts and sources:
Cody Mooneyhan
Federation of American Societies for Experimental Biology

Scientists Use Laser Imaging To Assess Safety Of Zinc Oxide Nanoparticles In Sunscreen

Ultra-tiny zinc oxide (ZnO) particles with dimensions less than one-ten-millionth of a meter are among the ingredients list of some commercially available sunscreen products, raising concerns about whether the particles may be absorbed beneath the outer layer of skin. 

Overlay of the confocal/multiphoton image of the excised human skin. Yellow color represents skin autofluorescence excited by 405 nm; Purple color represents zinc oxide nanoparticle distribution in skin (stratum corneum) excited by 770 nm, with collagen-induced faint SHG signals in the dermal layer.

Credit: Biomedical Optics Express

To help answer these safety questions, an international team of scientists from Australia and Switzerland have developed a way to optically test the concentration of ZnO nanoparticles at different skin depths. They found that the nanoparticles did not penetrate beneath the outermost layer of cells when applied to patches of excised skin. The results, which were published this month in the Optical Society's (OSA) open-access journal Biomedical Optics Express, lay the groundwork for future studies in live patients.

The high optical absorption of ZnO nanoparticles in the UVA and UVB range, along with their transparency in the visible spectrum when mixed into lotions, makes them appealing candidates for inclusion in sunscreen cosmetics. However, the particles have been shown to be toxic to certain types of cells within the body, making it important to study the nanoparticles' fate after being applied to the skin. By characterizing the optical properties of ZnO nanoparticles, the Australian and Swiss research team found a way to quantitatively assess how far the nanoparticles might migrate into skin.


Zinc oxide (ZnO) nanoparticle distribution in excised human skin. The black line represents the surface of the skin (top), blue represents ZnO nanoparticle distribution in the skin (stratum corneum), and pink represents skin.

Credit: Timothy Kelf, Macquarie University

The team used a technique called nonlinear optical microscopy, which illuminates the sample with short pulses of laser light and measures a return signal. Initial results show that ZnO nanoparticles from a formulation that had been rubbed into skin patches for 5 minutes, incubated at body temperature for 8 hours, and then washed off, did not penetrate beneath the stratum corneum, or topmost layer of the skin. The new optical characterization should be a useful tool for future non-invasive in vivo studies, the researchers write.


Contacts and sources:
Angela Stark
Optical Society of America

Paper: "Characterization of optical properties of ZnO nanoparticles for quantitative imaging of transdermal transport," Biomedical Optics Express, Vol. 2, Issue 12, pp. 3321-3333 (2011).