BioUpdates for March, 2002

Getting to the Root of the Matter

Alternative Ways of Hearing Trees Fall in Forests

Small Dinosaur Equals Big Story

More to the Eye Than Meets It

Joint Discoveries

Getting to the Root of the Matter

Most of us have pulled a weed or two only to discover just how much of the plant resides beneath the surface. Biologists have theorized about the relationship between subsurface biomass and aboveground biomass, but they have been unable to establish any concrete rules. Now, after extensive analysis of data from many species of plants, researchers from Cornell University and the University of Arizona are confident that there is a consistent and predictable proportional relationship between the mass of a plant's stems and leaves above the surface and the mass of its root system below. Using a mathematical technique known as allometry to examine data from all varieties of seed plants, the researchers have concluded that no matter what the plant or habitat, the proportions of the biomass of leaves and stems remains constant to the biomass of the root system. By measuring the biomass of the stems and leaves of a plant, the researchers say it is possible to accurately estimate the biomass of the root system. One immediate application of this work concerns global climate modeling. One of the researchers, Karl J. Niklas, points out that now that this proportional relationship has been established, climatologists can more accurately estimate the total amount of carbon that is sequestered in the biosphere.

References:

Enquist, Brian J. and Niklas, Karl J. (2002). Global Allocation Rules for Patterns of Biomass Partitioning in Seed Plants. Science 295 (Feb. 22): 1,517.

Visit:

Science Magazine

http://www.sciencemag.org/cgi/content/abstract/295/5559/1517

Alternative Ways of Hearing Trees Fall in Forests

There are more ways to hear than with an ear. Thomas Hetherington of Ohio State University knows this and has been conducting experiments with lizards and salamanders to understand how these creatures detect sound, despite their lack of middle and external ears. Building on previous work that has demonstrated that certain earless frogs and toads detect sound vibrations through their lungs, Hetherington turned his attention to a number of species of lizards and salamanders. His experiments provide convincing evidence that these animals' lungs play an important role in the hearing process. Placing the animals in a soundproof chamber, lasers were used to measure skin movement on exposure to various sound frequencies. Peak motion was recorded in salamanders, whereas in lizards with middle ears the response was less but still present. In salamanders without lungs no response was detected. Subsequently, Hetherington repeated the process, this time filling the lungs of the animals with an oxygenated saline solution. He discovered that the skin vibrations declined by as much as 90 percent, indicating that the lungs are the key element in detecting sound. Once detected, the sound vibrations can be transmitted through air to the inner ear for processing. Hetherington believes his work demonstrates that using lungs to detect sound is especially prevalent in small animals where thin body walls permit the lungs to capture sound. He also hypothesizes that this method of sound detection could represent the type of auditory system employed by the first land animals.

References:

Hetherington, Thomas (2001). Laser vibrometric studies of sound-induced motion of the body walls and lungs of salamanders and lizards: implications for lung-based hearing. Journal of Comparative Physiology A 187: 499Ð507.

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Journal of Comparative Physiology A

http://link.springer.de/link/service/journals/00359/contents/
01/00220/s003590100220ch002.html

Abstract of above article.

Small Dinosaur Equals Big Story

A newly discovered dinosaur, Sinovenator changii, may provide the pieces of the puzzle that finally puts to rest the debate over whether birds evolved from dinosaurs. Found by a collaborative team from the USA's Field Museum and the Beijing Institute of Vertebrate Paleontology and Paleoanthropology, this almost complete fossil found in the Yixian Formation of Liaoning in China provides the evidence of the structural modifications needed in the evolution of birds from dinosaurs. Its age, more than 130 million years oldÑabout the same as the earliest known bird, ArchaeopteryxÑalso helps create a more acceptable timeline for the evolution of birds from dinosaurs. Sinovenator changii has been identified as the most primitive troodontid (a type of theropod) yet discovered. Often overshadowed by the larger, more spectacular dinosaurs, smaller examples such as this new species usually are more valuable sources of information for understanding the path of evolution, because in most cases they represent more primitive stages. This specimen was preserved in river deposits in a three-dimensional state, which has provided wonderful insight into the creature's structure. However, being preserved in such conditions has its downside. No physical evidence of feathers was present, although the researchers do believe that Sinovenator changii was feathered like other recently discovered Chinese fossils found in lakebed deposits.

References:

Malovicky, Peter J. et al (2002). A Basal Troodontid from the Early Cretaceous of China. Nature 415 (Feb. 14): 780.

Visit:

Nature

http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/
journal/v415/n6873/abs/415780a_fs.html

Abstract of above article.

Field Museum

http://www.fmnh.org/museum_info/press/press_sinovenator.htm

More to the Eye Than Meets It

Curious about the ability of the blind to adjust their internal biological rhythms to the night and day of the outside world, researchers at Brown University conducted experiments with rats to uncover some clues. Their investigations have revealed the eye to be more complex than previously understood. Injecting a fluorescent dye into the region of the rat's brain that governs the body's twenty-four-hour cycle, the researchers traced a neural pathway to a previously unknown type of photoreceptor located deep in the retina along with the rods and cones. Observations confirmed that these cells, temporarily called "intrinsically photosensitive ganglion cells," responded to light even when not connected to the retina or brain. Previously, the presence of ganglion cells had been known, but they had been recognized only as the output cells of the retina and not considered to be photoreceptors. The researchers believe that these cells participate in setting the circadian clock and also are most likely involved in other functions involving the brain's need to know how bright it is. So far these discoveries have been limited to rats, but it is entirely reasonable to assume that these cells also are present in other animals, including humans. It seems there is more to the retina and how the brain interacts with the eye than we have realized and that there is at least one other neural system working alongside the rods and cones.

References:

Berson, David M.; Dunn, Felice A.; and Takao, Motoharu (2002). Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock. Science 295 (Feb. 8): 1,070.

Hattar, S. et al (2002). Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity. Science 295 (Feb. 8): 1,065.

Barinaga, Marcia (2002). Circadian Clocks: How the Brain's Clock Gets Daily Enlightenment. Science (Feb. 8): 995.

Visit:

Science Magazine

http://www.sciencemag.org/cgi/contents/abstract/295/5557/1065

http://www.sciencemag.org/cgi/contents/abstract/295/5557/1070

http://www.sciencemag.org/cgi/contents/abstract/295/5557/995

Abstracts of the above articles.

Joint Discoveries

Two presentations at the recent Orthopedic Research Society 2002 annual meeting marked some significant developments in orthopedic surgery. They also may lead to developments in the broader surgical field, perhaps taking the controversy out of the current stem cell debate. A team from Duke University, using adult stem cells taken from a small fat deposit found behind the kneecap, has been able to "reprogram" the cells to develop into functioning cartilage, bone, and fat cells, which could be grown into replacement tissues. The team used adipose-derived stromal cells obtained during knee-joint replacement surgery. After a series of biochemical treatments and the use of a special three-dimensional matrix, the team was able to grow different cell types. The work may open up many avenues of surgical and therapeutic options, and it provides further optimism that adult stem cells can be used, thus bypassing the ethical issues associated with the use of embryonic stem cells. Moreover, if tissues can be grown from cells derived from a patient undergoing surgery, the problems of tissue rejection and compromised immunity might be solved. In a similar vein, researchers from Tufts University reported on their work developing tissues from adult stem cells. Propelled by the impact of anterior cruciate ligament (ACL) injuries in sports, the team is focusing on custom-built ACLs created from stem cells found in bone marrow. Given the amount of money involved in professional sports, it is not hard to envision professional athletes creating a backup supply of ACLs. Such replacement parts could potentially cut surgical problems and recovery time, without the rejection problems associated with artificial or donor parts. This is especially attractive in the world of sports, where saving and prolonging the careers of star performers has its obvious advantages.

References:

As yet, none of this work has been submitted for publication.

Visit:

Tufts Bioengineering Center

http://www.ase.tufts.edu/biotech

http://www.tufts.edu/communications/altman.htm

Science Daily

http://www.sciencedaily.com/releases/2002/02/020213075238.htm

http://www.sciencedaily.com/releases/2002/02/020211075619.htm