Hox2 Genes Are Required for Tonotopic Map Precision and Sound Discrimination in the Mouse Auditory Brainstem

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Geochemical baseline determination and pollution assessment of heavy metals in urban soils of Karachi,Pakistan

Karachi is one of the most populated urban agglomerations in the world. No categorical study has yet discussed the geochemical baseline concentrations of metals in the urban soil of Karachi. The main objectives of this study were to establish geochemical baseline values and to assess the pollution status of different heavy metals. Geochemical baseline concentrations of heavy metals were estimated using the cumulative frequency distribution (CDF) curves. The estimated baseline concentrations of Pb, Cr, Cu, Zn and Fe were 56.23, 12.9, 36.31, 123.03 and 11,776 mg kg⁻¹, respectively. The pollution status of heavy metals in urban soils was evaluated using different quantitative indices (enrichment factor–EF, Geo-accumulation Index–I_geo, and pollution index–PI). Enrichments factors of the selected heavy metals determined by using Fe as a normalizer showed that metal contamination was the product of anthropogenic activities. The urban soils of Karachi were found to have a moderate to moderately severe enrichment with Pb, whereas Cr and Cu has moderate and Zn has minor enrichment. I_geo results indicated moderate soil contamination by Pb at some of the sampling locations. PI for Pb, Cr, Cu and Zn was found in the range of 0.04–3.42, 0.19–1.55, 0.27–2.45 and 0.32–1.57, respectively. Large variations in PI values of Pb revealed that soil in those areas of the city which are influenced by intensive anthropogenic activities have exceptionally high concentrations of Pb. The findings of this study would contribute to the environmental database of the soil of the region and would also facilitate both at the local and the international scales, in a more accurate global environmental monitoring, which will eventually facilitate the development of management and remediation strategies for heavy metal contaminated urban soil.     

Modulation of spiking of neurons of the cat anterior hypothalamus induced by experimental shifts in the osmolarity of the blood plasma

We examined changes in the impulse activity (IA) generated by neurons of the anterior hypothalamus (including the preoptic region) resulting from infusions of hyper-and hypotonic NaCl solutions (3.0 and 0.2%, respectively; hyper-and hypoosmotic stimulations, respectively); the infused volumes did not exceed 200 μl. The effects of hyper-and hypoosmotic stimulations were studied in detail in 83 and 88 neurons, respectively. In 31.2% (26 cells) and 29.6% (26 cells) of the neurons of the above groups, these stimulations evoked changes in the IA frequency greater than +40 or −40% of the mean background IA frequency. In approximately 50% of the responding neurons in each group, such shifts in the IA frequency were observed in the course of infusions of test solutions (5 sec long) and within the subsequent 5 min after termination of the infusion. In another 50% of the neurons, changes in the IA frequency occurred within the afterperiod (30 sec long); these shifts could develop exclusively within the latter interval, or these changes accompanied an initial early reaction. In general, activating responses dominated (they were observed in 65% of the cases where test stimulations of both modalities were used). The possible aspects of the involvement of neurons of the anterior hypothalamus in the control of the water/salt balance in the organism are discussed. Neirofiziologiya/Neurophysiology, Vol. 38, No. 1, pp. 40–45, January–February, 2006.     

Radio frequency radiation causes no nonthermal damage in enzymes and living cells

The ability of radio frequency radiation (RFR) to exert irreversible nonthermal (i.e., not caused by accompanying heat) effects on biologics has been widely debated due to a relative paucity of comprehensive critical details in published reports dealing with this issue. In this study, we used rigorous control over experimental conditions to determine whether continuous RFR nonthermally affects commercially important enzymes and live bacterial and human cells using three most commonly used frequencies in current RF identification technology, namely 2.45 GHz, 915 MHz, and 13.56 MHz. Diverse biological samples were exposed to RFR under deliberately harsh conditions to increase the likelihood of observing such effects should they exist. Enzymatic activities of horseradish peroxidase and β‐galactosidase in aqueous solution exhibited no statistically discernable consequences of even very intense RFR. Likewise, with putative thermal effects excluded, the viabilities of bacteria (both gram‐positive and gram‐negative) and of human cells were not detectably compromised by such an RFR exposure. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Fatigue of the plantar intrinsic foot muscles increases navicular drop

Our purpose was to assess the effect of foot intrinsic muscle fatigue on pronation, as assessed with navicular drop, during static stance. Twenty-one healthy young adults participated. Navicular drop was measured before and after fatiguing exercise of the plantar foot intrinsic muscles. Surface electromyography of the abductor hallucis muscle was recorded during maximum voluntary isometric contractions (MVIC) in order to find the baseline median frequency (MedF). Subjects then performed sets of 75 repetitions of isotonic flexion contractions of the intrinsic foot muscles against a 4.55 kg weight on a custom pulley system. After each set an MVIC was performed to track shifts in MedF. After a MedF shift of at least 10%, navicular drop measurements were repeated. Subjects exhibited 10.0 ± 3.8 mm of navicular drop at baseline and 11.8 ± 3.8 mm after fatigue (p < 0.0005). The change in navicular drop was significantly correlated with change in MedF (r = .47, p = .03). The intrinsic foot muscles play a role in support of the medial longitudinal arch in static stance. Disrupting the function of these muscles through fatigue resulted in an increase in pronation as assessed by navicular drop.     

Effects of local density and flower colour polymorphism on pollination and reproduction in the rewardless orchid Dactylorhiza sambucina (L.) Soò

The rewardless orchid Dactylorhiza sambucina shows a stable flower colour polymorphism, with both yellow- and red-flowered morphs growing sympatrically. Pollination biology and breeding system were investigated to examine the effects of density of plants, colour polymorphism, inflorescence dimension, and flower position within inflorescence on male and female reproductive success in three natural populations of D. sambucina. There were significant differences among sites in the number of pollinia removed and in fruit set per inflorescence. Number of removed pollinia and capsule production in D. sambucina were independent from flower and inflorescence size or flower position. As a whole, the red morphs showed the highest number of capsules produced, while the yellow morphs had the greatest male success. The relative male and female reproductive success were independent from plant density but were significantly correlated with the yellow morph frequency at the population level. Overall, our findings show that the contribution to the total reproductive success deriving from the two colour morphs does not conform with the predictions of negative frequency-dependent selection.     

Water inputs across a tropical montane landscape in Veracruz,Mexico: synergistic effects of land cover,rain and fog seasonality,and interannual precipitation variability

Land‐cover change can alter the spatiotemporal distribution of water inputs to mountain ecosystems, an important control on land‐surface and land‐atmosphere hydrologic fluxes. In eastern Mexico, we examined the influence of three widespread land‐cover types, montane cloud forest, coffee agroforestry, and cleared areas, on total and net water inputs to soil. Stand structural characteristics, as well as rain, fog, stemflow, and throughfall (water that falls through the canopy) water fluxes were measured across 11 sites during wet and dry seasons from 2005 to 2008. Land‐cover type had a significant effect on annual and seasonal net throughfall (NTF <0=canopy water retention plus canopy evaporation; NTF >0=fog water deposition). Forest canopies retained and/or lost to evaporation (i.e. NTF<0) five‐ to 11‐fold more water than coffee agroforests. Moreover, stemflow was fourfold higher under coffee shade than forest trees. Precipitation seasonality and phenological patterns determined the magnitude of these land‐cover differences, as well as their implications for the hydrologic cycle. Significant negative relationships were found between NTF and tree leaf area index (R²=0.38, P<0.002), NTF and stand basal area (R²=0.664, P<0.002), and stemflow and epiphyte loading (R²=0.414, P<0.001). These findings indicate that leaf and epiphyte surface area reductions associated with forest conversion decrease canopy water retention/evaporation, thereby increasing throughfall and stemflow inputs to soil. Interannual precipitation variability also altered patterns of water redistribution across this landscape. Storms and hurricanes resulted in little difference in forest‐coffee wet season NTF, while El Niño Southern Oscillation was associated with a twofold increase in dry season rain and fog throughfall water deposition. In montane headwater regions, changes in water delivery to canopies and soils may affect infiltration, runoff, and evapotranspiration, with implications for provisioning (e.g. water supply) and regulating (e.g. flood mitigation) ecosystem services.     

Flowering Patterns in a Seasonal Tropical Lowland Forest in Western Amazonia

The phenological behavior of many tropical plant species is highly dependent on rainfall, but these plants may also respond to changes in photoperiod. Without a better knowledge of the proportion of species responding to different factors, it is difficult to predict how global climate change may affect natural ecosystem processes. The aim of this study was to describe flowering patterns for more than 100 species in Tinigua Park, Colombia, and to propose which factors may trigger flower production ( e.g. , rainfall, temperature, cloud cover, and photoperiod). Data gathered in 5.6 km of phenological transects during 4 yr and complementary information indicated that the vast majority of species showed intraspecific synchronization, and annual production was the most common pattern, followed by episodic frequency. The annual patterns were common in tree species, while episodic patterns were common in lianas. Simple and multiple regression analyses suggested several aspects of photoperiod as the most likely triggers for flowering in most species. However, the fact that many of these species produce flowers in different periods each year, suggests that the proportion of species responding to photoperiodic cues is less that 23 percent in this community. The flowering times of taxonomically related species seldom showed significantly staggered distributions; however they do not necessarily occur at the same time, suggesting that flowering patterns are not strongly constrained by phylogeny.