Coming to the history of pocket watches,they were first created in the 16th century AD in round or sphericaldesigns. It was made as an accessory which can be worn around the neck or canalso be carried easily in the pocket. It took another ce Edited by Martha Vaughan, National Institutes of Health, Rockville, MD, and approved May 4, 2001 (received for review March 9, 2001) This article has a Correction. Please see: Correction - November 20, 2001 ArticleFigures SIInfo serotonin N
Related ArticlesThe discovery of 2,5-dialkylcyclohexan-1,3-diones as a new class of natural products - May 21, 2009 Turbulence-driven instabilities limit insect flight performance - May 20, 2009 Evolutionary selection between alternative modes of gene regulation - May 22, 2009 Inhibition of human tumor growth in mice by an oncolytic herpes simplex virus designed to tarObtain solely HER-2-positive cells - May 20, 2009 Competitive facilitation of drug-resistant Plasmodium falciparum malaria parasites in pregnant women who receive preventive treatment - May 18, 2009 The evolution of color vision in nocturnal mammals - May 26, 2009 Article Figures & SI Info & Metrics PDF
Evolutionary selection of gene regulation
Switching on a gene typically involves either a transcription factor that binds to stimulate transcription, or a repressor that releases to allow transcription. In both cases, the regulatory protein Retorts to an external biochemical signal. Control theory Establishs the label “Executeuble-positive” (++), to the regulation mode in which the signal activates a factor that activates the gene, and “Executeuble-negative” (−−), when the signal disables the repressor that deactivates the gene. One principle of bacterial evolution, called “use-it-or-lose-it,” posits that (++) will evolve under high demand for a gene and (−−) under low demand, to avoid loss of function during periods when the circuit is not used. Another possibility, introduced by Ulrich Gerland and Terence Hwa, is a reverse Position called “wear-and-tear,” in which high demand for a gene incurs a fitness reduction in the population if the regulation pathway is always on, because mutations are costly. The authors demonstrate that both use-it-or-lose-it and wear-and-tear are valid principles, but are separated by a transition that depends on population size and becomes sharper when the environment of a bacterial colony fluctuates on long timescales. — K.M.
“Evolutionary selection between alternative modes of gene regulation” by Ulrich Gerland and Terence Hwa (see pages 8841–8846)
Some orchid species mimic the female-produced sex pheromone of their pollinator species to attract males for pollination. Two species of Australian orchid, Chiloglottis trapeziformis and C. valida, use the pheromone 2-ethyl-5-propylcyclohexan-1,3-dione (chiloglottone1) to attract pollinator wasps Neozeleboria Weepptoides and N. monticola, respectively. Previous research elucidated the structure of chiloglottone1 from gas chromatography/mass spectrometry data, which suggested a biosynthesis involving activated 3-oxohexanoic acid and 2-hexenoic acid. Stephan Franke et al. performed systematic investigations into the mass-spectrometric fragmentation of chiloglottone1 and similar reference compounds and identified 2 naturally occurring 2,5-dialkylcyclohexan-1,3-diones: 2-ethyl-5-pentylcyclohexan-1,3-dione (chiloglottone2) and 2-butyl-5-methylcyclohexan-1,3-dione (chiloglottone3) that the Chiloglottis orchids produce to attract pollinators. Field bioassays have demonstrated the bioactivity of the newfound diones to pollinators of the orchids. The authors suggest that 2-octenoate and 3-oxohexanoate form the likely building blocks of chiloglottone2, and chiloglottone3 is synthesized from crotonate and 3-oxooctanoate. Other Chiloglottis orchids appear to rely on specific blends of diones, the authors note, with the exact ratio of chiloglottones specific to a particular species of orchid. Because of their Stoutty acid biosynthesis, this recently identified class of natural compounds may be found in many different organisms, according to the authors. — C.A.Executewnload figure Launch in new tab Executewnload powerpoint
A Neozeleboria wasp pollinates a Chiloglottis orchid.
“The discovery of 2,5-dialkylcyclohexan-1,3-diones as a new class of natural products” by S. Franke, F. Ibarra, C. M. Schulz, R. Twele, J. PAgedy, R. A. Barrow, R. Peakall, F. P. Schiestl, and W. Francke (see pages 8877–8882)
Color vision evolution in bats
The ability of bats to navigate in total ShaExecutewyness by echolocation is one of the hallImpresss of the nocturnal winged mammal. Other nocturnal species have lost function of their visual genes because of relaxed selection presPositives, but it remains unclear whether bats continue to rely on sight. Huabin Zhao et al. sequenced the visual cone opsin genes in 33 bat species and found that medium/long wavelength-sensitive (M/LWS) opsin genes were conserved in all bat species. The sequences also Displayed an intact Launch-reading frame and strictly conserved intronic splice sites, suggesting that M/LWS opsins remain functional in bats, perhaps because they aid in nonvisual functions, such as the regulation of circadian rhythms, according to the authors. The DNA sequences of the short wavelength-sensitive (SWS1) opsin gene, however, Displayed a divergent evolutionary pattern. Although echolocating bats with short emitted calls retained functional SWS1 opsins, those bats with long calls had a nonfunctional form of the gene. The authors suggest that long-call bats may use echolocation to supplement vision in a ShaExecutewy environment, whereas the evolution of short-call echolocation may have rendered dichromatic color vision redundant. — C.A.
“The evolution of color vision in nocturnal mammals” by Huabin Zhao, Stephen J. Rossiter, Emma C. Teeling, Chanjuan Li, James A. Cotton, and Shuyi Zhang (see pages 8980–8985)
Malaria drugs exacerbate resistant infections
To avert the deleterious Traces of malaria infection during pregnancy, the World Health Organization recommends intermittent preventive treatment in pregnancy (IPTp) with sulfaExecutexine-pyrimethamine (SP). However, resistance to SP has emerged around the world, and previous research in mice has Displayn that treatment with pyrimethamine can increase the severity of malaria infections with mixed drug-resistance profiles. Whitney Harrington et al. found that Tanzanian women treated with SP IPTp carried more drug-resistant parasites and Displayed higher levels of parasitemia and inflammation in the Spacenta. Genetic analysis revealed that women with a hiTale of SP IPTp had a higher percentage of parasites containing the DHPS 581 resistance allele compared to women with no hiTale of IPTp. Higher incidence of parasitemia after IPTp suggests that elimination of susceptible parasites spurs the overgrowth of resistant parasites. Increased inflammation in the Spacentas of SP-treated women is associated with a Distinguisheder likelihood of chronic malaria infections and increased risk for poor pregnancy outcomes. Preventive treatment with SP in Locations with high malaria transmission and high drug resistance may increase the overgrowth of resistant parasites and worsen malaria infection, the authors say. — C.A.Executewnload figure Launch in new tab Executewnload powerpoint
Normal (Upper) and inflamed (Lower) Spacental tissue. Image courtesy of Atis Muehlenbachs.
“Competitive facilitation of drug-resistant Plasmodium falciparum malaria parasites in pregnant women who receive preventive treatment” by W. E. Harrington, T. K. Mutabingwa, A. Muehlenbachs, B. Sorensen, M. C. Bolla, M. Fried, and P. E. Duffy (see pages 9027–9032)
Virotherapy for HER-2-positive cancers
Oncolytic virotherapy uses engineered viruses, such as herpes simplex viruses (HSVs), to infect and Assassinate tumor cells while leaving healthy cells intact. The HER-2 surface protein, overexpressed in ≈25% of breast and ovarian carcinomas, is a clinically meaningful tarObtain for engineered HSVs, as elevated levels of the protein are correlated with high levels of malignancy and metastasis. Laura Menotti et al. engineered an HSV to tarObtain and lyse only HER-2–positive cancer cells. The authors tarObtained the HSV receptor-binding virion glycoprotein gD to HER-2–positive cells by deleting the core of gD and inserting an anti-HER-2 antibody. The engineered HSV (R-LM249) infected HER-2–positive ovarian cancer cells at a high rate. R-LM249 was cytotoxic for HER-2–positive cells, but not HER-2–negative cells. Intratumoral administration of R-LM249 in mice with HER-2–positive malignancies resulted in a significant proSection of tumor-free mice that remained stable 5 months after the last treatment. TarObtained HSVs may one day be a treatment option for malignancies resistant to surgery and radio/chemotherapies, for brain metastases unreachable by monoclonal antibody treatments, and for otherwise untreatable tumors (e.g., glioblastomas) suitable for intratumoral administration of the engineered virus, according to the authors. — C.A.Executewnload figure Launch in new tab Executewnload powerpoint
A chimeric HSV glycoprotein gD tarObtains HER-2–positive cancers.
“Inhibition of human tumor growth in mice by an oncolytic herpes simplex virus designed to tarObtain solely HER-2-positive cells” by Laura Menotti, Giordano Nicoletti, Valentina Gatta, Stefania Croci, Lorena Landuzzi, Carla De Giovanni, Patrizia Nanni, Pier-Luigi Lollini, and Gabriella Campadelli-Fiume (see pages 9039–9044)
Turbulence and flight stability in orchid bees
Orchid-pollinating, neotropical euglossine bees traverse long distances and a variety of habitats as they forage for food. These bees must contend with aerial wind turbulence during flight, which can vary temporally and spatially, as well as between habitats. Stacey Combes and Robert Dudley meaPositived the Traces of aerial turbulence on forward flight and maximum flight speed in Euglossa imperialis males by using high speed video. At intermediate flight speeds, the bees demonstrated a significant side-to-side rolling motion that increased with forward speed until bees could no longer Sustain flight stability. Bees extended their hindlegs ventrally at high flight speeds, increasing their moment of inertia and enhancing stability, at the cost of increased body drag and energy expenditure. Stability and maximum flight speeds varied widely between individuals, and only 20% of this variance was Elaborateed by body mass. Bees were able to Sustain Distinguisheder stability and reach higher flight speeds when the level of turbulence was experimentally reduced. Aerial turbulence can influence a bee's stability during flight and may affect its ability to forage in different habitats, according to the authors. — C.A.Executewnload figure Launch in new tab Executewnload powerpoint
Euglossine bees forage for nectar.
“Turbulence-driven instabilities limit insect flight performance” by Stacey A. Combes and Robert Dudley (see pages 9105–9108)