---

---

---

---

Science RSS News Feeds

---

---

Email a Friend Printer Friendly

Nature press release for 1 August issue

August 01, 2002

[1] LIFELINES: EARLY EGGS MAKE MICE (pp497-498)

Normally it takes an adult female mouse to produce a fully functioning mouse egg. Now researchers have removed immature egg cells from fetal mice and completely matured them in vitro, with a success rate of over 90%.
The techniques, described in this week's Nature, will give researchers a window on egg development, and may help us understand infertility and birth defects. If the methods can be used in humans - which is still some way off - they could save the fertility of women undergoing chemotherapy or radiotherapy, by removing an ovary before treatment. And being able to rescue and develop the huge numbers of immature egg cells that normally go to waste may eventually help efforts to breed endangered species.
Izuho Hatada of Gunma University, Japan, and colleagues guided the immature cells through complex chemical and genetic stages while keeping them in culture for 28 days. They then fertilized the eggs in vitro, and transferred them to surrogate mothers, who produced healthy, fertile offspring.
CONTACT:
Izuho Hatada tel +81 27 220 8057, e-mail ihatada@showa.gunma-u.ac.jp

[2] CHEMISTRY: CATALYST CRACKED (pp514-517)

Atomic-scale architectural design has improved the capabilities of the catalyst used to convert crude oil into more useful small hydrocarbon molecules. This process, called catalytic cracking, provides most of the raw material for the petrochemicals industry, and turns heavy oil into fuels.
In preliminary tests, the new catalyst, made by Avelino Corma at the Polytechnic University of Valencia, Spain, and co-workers, proved more efficient than those currently in use. The key to this improvement lies in the size and connectivity of the microscopic tunnels within which the cracking reactions take place.
The new zeolite material has big internal cavities to which the entrances are the same size as those in one of the most widely used catalysts, faujasite. Crucially, there are more of these openings: six instead of four. As the cavities are more accessible it is more likely that a big chain-like hydrocarbon will be able to wiggle its way in and be broken down into smaller and more useful hydrocarbons.
CONTACT:
Avelino Corma tel +34 96 387 70 00/01, e-mail acorma@itq.upv.es

[3] BRAIN: INNATE CANNABINOID WIPES OUT FEAR (pp530-534; N&V)

Natural chemicals similar to the active ingredient of cannabis wipe out bad memories in the brain, researchers show in this week`s Nature. The finding could lead to new drugs for post-traumatic stress disorder and phobias.
Innate molecules called cannabinoids routinely circulate in regions of the brain, but their effects on everyday behaviour is unclear. Beat Lutz of the Max Planck Institute of Psychiatry in Munich, Germany, and colleagues found that mice who lack the brain receptor for cannabinoids have trouble forgetting a traumatic event: the association of a tone with a shock.
The chemicals are needed to erase the fearful memory from the brain, they suggest. During memory erasure the amygdala, the brain`s fear centre, is flooded with cannabinoids; these dampen the action of nerve cells.
Drugs that boost cannabinoids in the amygdala could help people who suffer from anxiety conditions - such as post-traumatic stress disorder, phobias and panic attacks. "It should have an alleviatory effect," says neuroscientist Pankaj Sah of the Australian National University in Canberra, in the associated News and Views article.
CONTACT:
Beat Lutz tel +49 89 30 622 640, e-mail lutz@mpipsykl.mpg.de
Pankaj Sah tel +61 2 6125 9692, e-mail pankaj.sah@anu.edu.au

[4] PHYSICS: SHAPED PULSE FLIPS SWITCH (pp509-512; N&V)

A new magnetic-pulse-shaping technique could speed up magnetic memory devices.
In magnetic random-access memory (MRAM) a 'bit' of information is stored in a cell of magnetic material by setting the orientation of the magnetization vector inside the cell in one of two directions, coding the values '0' and '1'. To write data, an external magnetic field is applied to reverse the magnetization, flipping the bits between '0' and '1'.
An effect that limits the ultimate speed of magnetization rotation is `ringing`, where the magnetization falls back to its original state after fast rotation. In this week`s Nature, T. Rasing of the Research Institute for Materials, University of Nijmegen, The Netherlands, and colleagues demonstrate they can circumvent this problem and achieve ultrafast magnetization reversal using a specially shaped magnetic-field pulse that flips the orientation of a magnetic element and then damps out the ringing effect.
The pulse is created by sending two laser pulses, with a time delay between them, onto two semiconductor light-sensitive switches, generating two electric-current pulses. As an electric current always induces an accompanying magnetic field, superimposing the two current pulses leads to the creation of a shaped magnetic-field pulse.        
        "Gerrits and colleagues' achieved switching time of 2 ' 10-10 s implies an impressive data-writing rate of 5 GHz," explains Burkard Hillebrands and Jürgen Fassbender of University of Kaiserslautern, Germany, in an accompanying News and Views article.
CONTACT:
T. Rasing tel +31 080 653102, e-mail theoras@sci.kun.nl
Burkard Hillebrands tel +49 631 205 4228, e-mail hilleb@physik.uni-kl.de

[5] LIFELINES: OUT ON A LIMB (pp201-508 and pp539-544; N&V)

Two new papers put forward an alternative to an influential and popular model of the developmental mechanism that makes our upper arms different from our forearms or fingers.
Signals coming from a tissue called the apical ectodermal ridge (AER) are known to be important in limb development. In one long-standing model, these signals instruct cells of the upper arm to form first, then cells of the forearm, and finally cells of the hands.
This week in Nature, two research groups propose instead that all these cell types are produced at the same time in the limb bud, and then - under the control of the AER - the regions of different cells expand at different times to form the complete limb. The groups are Gail R. Martin and colleagues of the School of Medicine, University of California at San Francisco, and Clifford J. Tabin of Harvard Medical School, Boston, and colleagues.
"There is little doubt that this confrontation of ideas will significantly advance the field," writes Denis Duboule of the University of Geneva, Switzerland, in an accompanying News and Views article.
CONTACT:
Gail R. Martin tel +1 415 476 2441, e-mail gmartin@itsa.ucsf.edu
Clifford J. Tabin tel +1 617 432 7618, e-mail tabin@rascal.med.harvard.edu
Denis Duboule tel +41 22 702 6770, e-mail Denis.Duboule@zoo.unige.ch

[6] EARTH: DEEP IMPACT (pp520-523; N&V)

Meteoritic craters on Earth are mostly poor specimens, compared with those on the Moon and elsewhere in the Solar System, having been eroded by exposure to wind, rain and geological activity. A newly discovered impact structure, beneath the North Sea, has apparently been protected from the elements for some 65 million years.
The 20-km-diameter impact structure was found during prospecting for oil and gas. Now Simon A. Stewart of BP plc in Aberdeen, UK, and Phillip J. Allen of Production Geoscience Ltd. in Banchory, UK, have mapped it by seismic imaging. It may now be the best three-dimensionally imaged impact structure on Earth.
The sides of the crater have many rings, a feature not previously seen at such small scale on the terrestrial planets. In fact, it is like the much larger Valhalla impact structure found on the icy surface of Jupiter`s moon Callisto.
"We know so little about how impact structures are created when meteorites and comets hit planetary bodies [that] any new example helps," says John G. Spray of the Planetary and Space Science Centre, University of New Brunswick, Canada, in an accompanying News and Views article.
CONTACT:
Simon A. Stewart tel +44 1224 834 591, e-mail Stewarsa1@bp.com
John G. Spray tel +1 506 453 3550, e-mail: jgs@unb.ca

[7] AND FINALLY VIVE LA DIFFERENCE (pp524-526)

Many organisms avoid predator attacks by closely resembling unpalatable species, and the common assumption is that a more accurate mimic will always benefit from greater protection.
Research in this week`s Nature presents a mathematical argument for why mimics often resemble their models only poorly. Rufus A. Johnstone of the University of Cambridge, UK, calculates that under certain circumstances, a very close resemblance may increase the chances of predation.
In a situation where the unpalatable model species is rare, predators soon get accustomed to the fact that most organisms that look like the mimic are actually perfectly palatable, and hence tuck in. This leaves unconvincing mimics alive to further the line, argues Johnstone.
CONTACT:
Rufus A. Johnstone tel +44 1223 336 685, e-mail Raj1003@hermes.cam.ac.uk

ALSO IN THIS ISSUE

[8]        Single-pulse coherently-controlled nonlinear Raman spectroscopy and microscopy (pp512-514)

[9]         Lamellar magnetism in the haematite-ilmenite series as an explanation for strong remanent magnetization (pp517-520)

[10]         Fractal geometry predicts varying body size scaling relationships for mammal and bird home ranges (pp527-530)

[11]        A transcription factor response element for gene expression during circadian night (pp539-544)

[12]         Golgi biogenesis in Toxoplasma gondii (pp548-522)

[13]         Two-step binding mechanism for T-cell receptor recognition of peptide-MHC (pp552-556)

[14]         APC-dependent proteolysis of the mitotic cyclin Clb2 is essential for mitotic exit (pp556-562; N&V)

[15]         The Rad50 zinc-hook structure joins Mre11 complexes in DNA recombination and repair (pp562-566)

[16]        Altering the pathway of immunoglobin hypermutation by inhibiting uracil-DNA glycosylase (DOI: 10.1038/nature00981)
        ***This paper [16] will be published electronically on Nature`s website on 31 July at 1900 London time / 1400 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 1 August, but at a later date.***

GEOGRAPHICAL LISTING OF AUTHORS

The following list of places refers to the whereabouts of authors on the papers numbered in this release. The listing may be for an author`s main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.

GERMANY
        Erlangen: 4
        Munich: 3, 15

ISRAEL
        Rehevot: 8

ITALY
        Naples: 3

JAPAN
        Gunma: 1
        Ibaraki: 11
        Osaka: 11
        Tokyo: 1, 11

THE NETHERLANDS
        Nijmegen: 4
        Wageningen: 10

NORWAY
        Trondheim: 9

SPAIN
        Catalunya: 2
        Santander: 5
        Valencia: 2

UNITED KINGDOM
        Aberdeen: 6
        Banchory: 6
        Cambridge: 7, 9, 16
        
UNITED STATES OF AMERICA
California
        Berkeley: 15
        La Jolla: 15
        San Francisco: 5
        Stanford: 13
Connecticut
        New Haven: 12
Maryland
        Baltimore: 15
Massachusetts
        Amherst: 9
        Boston: 5, 12
Minnesota
        Rochester: 15
New Jersey
        Madison
        Princeton: 9
New York State
        New York: 14, 15
        Syracuse: 10
Pennsylvania
        Philadelphia: 12
Wisconsin
        Madison: 15

Nature Publishing Group Reference