bluuebunny/crossref_metadata_2025 huggingface dataset:
LATE TO MIDDLE JURASSIC SOURCE FACIES AND QUALITY VARIATIONS, SOUTH VIKING GRABEN, NORTH SEA
Authors: Justwan H. , Dahl B. , Isaksen G. H. , Meisingset I.
Published: March 2006

Source facies and quality of the Late to Middle Jurassic source rock system in the South Viking Graben between 58°N and 60°15'N are highly variable both regionally and stratigraphically. In order to assess the degree of variability and to create a model of source rock quality and potential, isochore maps of the syn‐ and post‐rift sections of the Upper Jurassic Draupne Formation and underlying Heather Formation were generated from seismic and well data, and maturity‐corrected Rock‐Eval data were used to generate quantitative maps of oil and gas potential. The thin post‐rift section at the top of the Draupne Formation is a rich oil‐prone source, while the up to 1,600 m thick syn‐rift section contains a mixture of Type III and Type II material with substantial amounts of gas‐prone and inert organic matter. The Heather Formation, which reaches modelled thicknesses of up to 930 m, is a lean source and is generally gas‐prone.

Detailed analyses and interpretations of biomarker and isotopic characteristics support this upward increase in oil‐prone Type II material. The analytical parameters include increasing relative amounts of C27 regular steranes; decreasing ratios of C30 moretane relative to C30 hopane; and an increasing predominance of short chain n‐alkanes and progressively lighter isotopic values for saturate and aromatic fractions of source rock extracts. In addition, increasing amounts of 17α(H),21β(H)‐28,30‐bisnorhopane and decreasing amounts of C34 homohopanes relative to C35 homohopanes, as well as decreasing Pr/Ph ratios, suggest a general decrease in oxygenation upwards. Maps of average Pr/Ph ratios for the syn‐ and post‐rift Draupne Formation and for the Heather Formation are consistent with permanent water column stratification and gradual ascent of the O2:H2S interface from the Callovian to the Ryazanian.

Interpretation of oil and gas potential maps, molecular parameters and estimates of sediment accumulation rates in combination suggest that the source facies of the upper, post‐rift Draupne Formation is controlled by widespread anoxia, reduced siliciclastic dilution and reduced input of gas‐prone organic and inert material; by contrast, the potential of the lower, syn‐rift Draupne Formation is strongly controlled by dilution by gas‐prone and inert organic matter resulting from mass flows and also by varying degrees of oxygenation. The oil and gas potential of the Heather Formation is mainly controlled by the degree of oxygenation and siliciclastic dilution.
THE STRUCTURAL STYLE OF SEDIMENTARY BASINS ON THE SHELVES OF THE LAPTEV SEA AND WESTERN EAST SIBERIAN SEA, SIBERIAN ARCTIC
Authors: Franke D. , Hinz K.
Published: March 2006

A total of 11,700 km of multichannel seismic reflection data were acquired during three recent reconnaissance surveys of the wide, shallow shelves of the Laptev and western East Siberian Seas in the Siberian Arctic Ocean. Three seismic marker horizons were defined and mapped in both shelf areas. Their nature and age were predicted on the basis of regional tectonic and palaeoenvironmental events and corroborated using onshore geology. To the north of the Laptev Sea, the Gakkel Ridge, an active mid‐ocean ridge which separates the North American and Eurasian Plates, abruptly meets the steep slope of the continental shelf which is curvilinear in plan view. Extension has affected the Laptev Shelf since at least the Early Tertiary and has resulted in the formation of three major, generally north‐south trending rift basins: the Ust’Lena Rift, the Anisin Basin and the New Siberian Basin.

The Ust’Lena Rift has a minimum east‐west width of 300km at latitude 75°N and a Cenozoic infill up to 6 s (twt) in thickness. Further to the NW of the Laptev Shelf, the downthrown and faulted basement is overlain by a sub‐parallel layered sedimentary succession with a thickness of 4 s (twt) that thins towards the west. Although this area was affected by extension as shown by the presence of numerous faults, it is not clear whether this depression on the NW Laptev Shelf is continuous with the Ust’Lena Rift.

The Anisin Basin is located in the northern part of the Laptev Shelf and has a Cenozoic sedimentary fill up to 5 s (twt) thick. The deepest part of the basin trends north‐south. To the west is a secondary, NW‐SE trending depression which is slightly shallower than the main depocentre. The overall structure of the basin is a half‐graben with the major bounding fault in the east.

The New Siberian Basin is up to 70 km wide and has a minimum NW‐SE extent of 300 km. The sedimentary fill is up to 4.5 s (twt) thick. Structurally, the basin is a half‐graben with the bounding fault in the east.

Our data indicate that the rift basins on the Laptev Shelf are not continuous with those on the East Siberian Shelf. The latter shelf can best be described as an epicontinental platform which has undergone continuous subsidence since the Late Cretaceous. The greatest subsidence occurred in the NE, as manifested by a major depocentre filled with inferred (?)Late Cretaceous to Tertiary sediments up to 5 s (twt) thick.
SOURCE ROCK CHARACTERIZATION BASED ON BIOLOGICAL MARKER DISTRIBUTIONS OF CRUDE OILS IN THE SOUTHERN GULF OF SUEZ, EGYPT
Authors: Younes M. A. , Philp R. P.
Published: March 2006

The depositional environment and maturity of source rocks in the southern Gulf of Suez were evaluated using biomarker and isotope data from crude oils derived from a variety of source rock types of different geological ages. Two oils families were identified and are referred to as types A and B. Type A oils are characterized by a predominance of oleanane and relatively low gammacerane concentrations, suggesting that they were derived from a terrigenous source rock with a significant input of angiosperm material inferred to occur within the marginally‐mature syn‐rift Lower Miocene Rudeis Shale. By contrast, type B oils are distinguished by a predominance of gammacerane and relatively low oleanane concentrations, suggesting that they were generated from mature marine carbonate source rocks inferred to occur within the Upper Cretaceous Brown Limestone and Middle Eocene Thebes Formation. Maturity parameters including the sterane isomerisation ratios C29αββ/(αββ+ααα), C29ααα20S/(S+R) and TAS/(TAS+MAS), together with aromatic sulphur compound ratios (4‐MDBT / I‐MDBT; 4,6‐ / 1,4‐DMDBT; 2,4–/ 1,4‐DMDBT; and DBT / phenanthrenes), support the higher thermal maturity of type B oils relative to type A oils.

The biomarker variablility reflects the occurrence of two distinct source rocks in the southern Gulf of Suez and suggests that two independent petroleum systems are present here. These appear to be confined to the pre‐rift (pre‐Miocene) and syn‐rift megasequences respectively.
HYDROCARBON SOURCE ROCKS AND GENERATION HISTORY IN THE LUNNAN OILFIELD AREA, NORTHERN TARIM BASIN (NW CHINA)
Authors: Xiao X. M. , Hu Z. L. , Jin Y B. , Song Z. G.
Published: March 2006

In this paper we report on source rocks and maturation history at the Lunnan oilfield, northern Tarim Basin (NW China), using a combination of organic petrographic and geochemical techniques. Three separate source rock intervals are present here: Cambrian mudstones and argillaceous limestones; Middle and Upper Ordovician argillaceous limestones; and Triassic mudstones. Reservoir rocks comprise Lower Ordovician carbonates, Carboniferous sandstones, and Triassic and Jurassic sandstones. Structural traps were formed principally during the Silurian and Jurassic.

The Lunnan field is located on a small‐scale palaeo uplift which developed during the Early Palaeozoic. Hydrocarbons migrated updip from source areas in surrounding palaeo‐lows along faults and unconformities. Major phases of hydrocarbon generation and migration occurred in the Early Silurian — Late Devonian, Cretaceous — Early Tertiary and Late Tertiary. Uplift and intense erosion at the end of the Devonian destroyed Early Palaeozoic oil and gas accumulations sourced from the Cambrian source rocks, but hydrocarbons generated by Middle and Upper Ordovician source rocks during the Mesozoic and Tertiary have been preserved. At the present day, accumulations are characterized by a range of crude oil compositions because source rocks from different source areas with different maturation histories are involved.
Do herbivores cause habitat degradation or vegetation state transition? Evidence from the tundra
Authors: Wal René van der
Published: March 2006

Range expansion and increasing densities of large herbivores are held responsible for large‐scale habitat degradation in a wide range of natural and semi‐natural ecosystems. Herbivore‐driven ecosystem changes frequently represent predictable transitions from one vegetation state to another. Whether such predictable changes justify the value judgement ‘habitat degradation’ may be debatable as this strongly depends on individual perspective.

To further the debate on herbivore‐driven habitat degradation, I apply the concept of alternative stable states to arctic tundra as a framework to capture predictable stepwise vegetation transitions in which the productivity and hence herbivore‐carrying capacity increases with grazing pressure. Specifically, evidence is provided that large parts of the tundra biome can be in either of three relatively discrete vegetation states and that changes in reindeer/caribou density are responsible for sudden, predictable but often reversible state transitions. From this, it appears that the relatively rapidly emerging vegetation changes do not necessarily equate to habitat degradation, but in many cases reflect predictable vegetation change. Acknowledgement of the existence of predictable state transitions in tundra ecosystems may help to evaluate the observed radical vegetation changes occurring throughout the reindeer/caribou range.
Predation risk effects on fitness related measures in a resident bird
Authors: Thomson Robert L. , Forsman Jukka T. , Mönkkönen Mikko , Hukkanen Markku , Koivula Kari , Rytkönen Seppo , Orell Markku
Published: March 2006

Predation risk is thought to be highly variable in space and time. However, breeding avian predators may create locally fixed and spatially fairly predictable predation risk determined by the distance to their nest. From the prey perspective, this creates predation risk gradients that potentially have an effect on fitness and behavioural decisions of prey. We studied how breeding avian predators affect habitat selection (nest location) and the resulting fitness consequences in a northern population of resident willow tit (Parus montanus). Data included 429 willow tit nests over a four year period in a landscape containing a total of 33 avian predator nests. Willow tit nests were located randomly in the landscape and no predator avoidance in habitat selection or emptying of territories in proximity to predators was observed. Nestling size, however, was positively associated with distance from predator nests (n=252). Nestling mass and wing length were about 4.5% smaller close to predator nests compared to nestlings raised far from predator nests. Tarsus length also exhibited a positive relationship with increasing distance from predator nest but this was limited to habitats of young forests and pine bogs or dense mixed forests (4% increase). It is likely that habitat structural complexity influenced the perception of predation risk in different habitats. Our results indicate that willow tits do not provide reliable cues of predator free habitats for settling migrants. Nonetheless, breeding avian predators may create predictable predation risk in the landscape which is an important factor affecting reproductive success and potentially the demography of prey populations.
Detritivory and the stoichiometry of nutrient cycling by a dominant fish species in lakes of varying productivity
Authors: A. Higgins Karen , J. Vanni Michael , J. González Maria
Published: March 2006

Little is known about the stoichiometry of nutrient cycling by detritivores. Therefore, we explored stoichiometric relationships in an omnivorous/detritivorous fish (gizzard shad, Dorosoma cepedianum) in three lakes that differed in productivity. Gizzard shad can feed on plankton and sediment detritus, but in all three lakes adult gizzard shad derived >98% of carbon (C) and phosphorus (P), and >90% of nitrogen (N) from sediment detritus, and the remainder from zooplankton.

Gizzard shad selectively consumed detritus with higher C, N and P concentrations than ambient lake sediments. Selective detritivory (i.e. the nutrient content of consumed detritus divided by the nutrient content of ambient detritus) was most pronounced in the lake with the lowest detrital nutrient concentrations. N and P cycling rates per fish were also consistently higher in this lake, in agreement with the prediction of stoichiometry theory that excretion rates should increase with food nutrient content. Among‐lake differences in nutrient cycling rates were unrelated to inter‐lake variation in fish body nutrient contents, which was minimal. The N:P ratio excreted was near Redfield (∼14:1) in all three lakes.

Stoichiometric analyses showed that the C:N and C:P ratios of sediment detritus were much higher (∼2.8×) than ratios of gizzard shad bodies, revealing substantial N and P imbalances between consumers and their food source. Gizzard shad alleviate N imbalance by selectively feeding on high N detritus (low C:N, high N:P), and apparently alleviate P imbalance by excreting nutrients at a higher N:P than that of their food or their bodies. Thus, this detritivore apparently regulates nutrient acquisition and allocation via both pre‐absorption processes (selective feeding) and post‐absorptive processes (differential N and P excretion).
Neutral theory in macroecology and population genetics
Authors: Hu Xin‐Sheng , He Fangliang , Hubbell Stephen P.
Published: March 2006

Current neutral theory in macroecology has many parallels with neutral theory in population genetics, but it also has many distinct features that arise because it focuses mainly on questions at the community level rather than at the population level. Here we highlight the similarities and differences between these two bodies of theories from the aspects of the operational units, definitions of neutrality, basic parameters, driving forces, spatial structure and community assembly rules. Compared with neutral theory in population genetics, whose development spans more than 40 years, neutral theory in ecology, which is only a few years old, is still immature and under‐developed. There are many opportunities for major theoretical contributions, some of which can be adopted directly from population genetics, while others will require new theoretical work. We critically discuss these opportunities and theoretical challenges in neutral macroecology, particularly in regard to effective community size, ecological drift, community differentiation and ecological dominance.
Human femoral artery and estimated muscle capillary blood flow kinetics following the onset of exercise
Authors: Harper Allison J. , Ferreira Leonardo F. , Lutjemeier Barbara J. , Townsend Dana K. , Barstow Thomas J.
Published: March 2006

The purpose of this study was to compare the kinetics of estimated capillary blood flow
to those of femoral artery blood flow
and estimated muscle oxygen uptake
. Nine healthy subjects performed a series of transitions from rest to moderate (below estimated lactate threshold, 6 min bouts) knee extension exercise. Pulmonary oxygen uptake
was measured breath by breath,
was measured continuously using Doppler ultrasound, and deoxyhaemoglobin ([HHb]) was estimated by near‐infrared spectroscopy over the rectus femoris throughout the tests. The time course of
was estimated by rearranging the Fick equation (i.e.
), (arterio – venous O2 difference) using the primary component of
to represent
and [HHb] as a surrogate for (a−v)O2. The overall kinetics of
(mean response time, MRT, 13.7 ± 7.0 s),
(τ, 27.8 ± 9.0 s) and
(MRT, 41.4 ± 19.0 s) were significantly (P < 0.05) different from each other. We conclude that for moderate intensity knee extension exercise, conduit artery blood flow
kinetics may not be a reasonable approximation of blood flow kinetics in the microcirculation
, the site of gas exchange. This temporal dissociation suggests that blood flow may be controlled differently at the conduit artery level than in the microcirculation.
The effect of sustained low‐intensity contractions on supraspinal fatigue in human elbow flexor muscles
Authors: Søgaard Karen , Gandevia Simon C. , Todd Gabrielle , Petersen Nicolas T. , Taylor Janet L.
Published: March 2006

Subjects quickly fatigue when they perform maximal voluntary contractions (MVCs). Much of the loss of force is from processes within muscle (peripheral fatigue) but some occurs because voluntary activation of the muscle declines (central fatigue). The role of central fatigue during submaximal contractions is not clear. This study investigated whether central fatigue developed during prolonged low‐force voluntary contractions. Subjects (n= 9) held isometric elbow flexions of 15% MVC for 43 min. Voluntary activation was measured during brief MVCs every 3 min. During each MVC, transcranial magnetic stimulation (TMS) was followed by stimulation of either brachial plexus or the motor nerve of biceps brachii. After nerve stimulation, a resting twitch was also evoked before subjects resumed the 15% MVC. Perceived effort, elbow flexion torque and surface EMG from biceps, brachioradialis and triceps were recorded. TMS was also given during the sustained 15% MVC. During the sustained contraction, perceived effort rose from ∼2 to ∼8 (out of 10) while ongoing biceps EMG increased from 6.9 ± 2.1% to 20.0 ± 7.8% of initial maximum. Torque in the brief MVCs and the resting twitch fell to 58.6 ± 14.5 and 58.2 ± 13.2% of control values, respectively. EMG in the MVCs also fell to 62.2 ± 15.3% of initial maximum, and twitches evoked by nerve stimulation and TMS grew progressively. Voluntary activation calculated from these twitches fell from ∼98% to 71.9 ± 38.9 and 76.9 ± 18.3%, respectively. The silent period following TMS lengthened both in the brief MVCs (by ∼40 ms) and in the sustained target contraction (by ∼18 ms). After the end of the sustained contraction, the silent period recovered immediately, voluntary activation and voluntary EMG recovered over several minutes while MVC torque only returned to ∼85% baseline. The resting twitch showed no recovery. Thus, as well as fatigue in the muscle, the prolonged low‐force contraction produced progressive central fatigue, and some of this impairment of the subjects' ability to drive the muscle maximally was due to suboptimal output from the motor cortex. Although caused by a low‐force contraction, both the peripheral and central fatigue impaired the production of maximal voluntary force. While central fatigue can only be demonstrated during MVCs, it may have contributed to the disproportionate increase in perceived effort reported during the prolonged low‐force contraction.
Discrimination between active and passive head movements by macaque ventral and medial intraparietal cortex neurons
Authors: Klam François , Graf Werner
Published: March 2006

An important prerequisite for effective motor action is the discrimination between active and passive body movements. Passive movements often require immediate reflexes, whereas active movements may demand suppression of the latter. The vestibular system maintains correct body and head posture in space through reflexes. Since vestibular inputs have been reported to be largely suppressed in the vestibular nuclei during active head movements, we investigated whether head movement‐related signals in the primate parietal cortex, a brain region involved in self‐motion perception, could support both reflex functions and self‐movement behaviour. We employed a paradigm that made available direct comparison of neuronal discharge under active and passive movement conditions. In this study, we demonstrate that a population of intraparietal (VIP (ventral) and MIP (medial)) cortex neurons change their preferred directions during horizontal head rotations depending on whether animals have performed active movements, or if they were moved passively. In other neurons no such change occurred. A combination of these signals would provide differential information about the active or passive nature of an ongoing movement. Moreover, some neurons' responses clearly anticipated the upcoming active head movement, providing a possible basis for vestibular‐related reflex suppression. Intraparietal vestibular neurons thus distinguish between active and passive head movements, and their responses differ substantially from those reported in brainstem vestibular neurons, regarding strength, timing, and direction selectivity. We suggest that the contextual firing characteristics of these neurons have far‐reaching implications for the suppression of reflex movements during active movement, and for the representation of space during self‐movement.
Renal vasoconstrictor responses to static exercise during orthostatic stress in humans: effects of the muscle mechano‐ and the baroreflexes
Authors: Momen Afsana , Thomas Karen , Blaha Cheryl , Gahremanpour Amir , Mansoor Ather , Leuenberger Urs A. , Sinoway Lawrence I.
Published: March 2006

Renal circulatory adjustments to stress contribute to blood pressure and volume regulation. Both handgrip (HG) and disengagement of baroreflexes with lower body negative pressure (LBNP) can engage the sympathetic nervous system (SNS). However, the effect of simultaneous HG and LBNP on the renal circulation in humans is not known. Eighteen young healthy volunteers were studied. Beat‐to‐beat changes in renal blood flow velocity (RBV; Duplex Ultrasound), mean arterial pressure (MAP; Finapres) and heart rate (ECG) were monitored during (a) 15 s HG at 30% maximum voluntary contraction (MVC); (b) LBNP at −10 and −30 mmHg (each level for 5 min); and (c) 15 s HG (at 30% MVC) during LBNP at both levels. Renal vascular resistance index (RVR units) was calculated by dividing MAP by RBV. The increases in RVR during HG alone (12 ± 6%) were not different from the responses noted during combined HG and LBNP (17 ± 6% at −10 mmHg and 25 ± 8% at −30 mmHg). These results suggest occlusion occurs between a neural circuit engaged during 15 s of HG (central command and/or the muscle mechanoreflex) and a circuit activated by LBNP. In additional experiments (n= 6), similar non‐algebraic summation of RVR was seen during 15 s involuntary biceps contractions (engages only muscle reflexes) and LBNP. With respect to RVR, neural occlusion occurs between baroreflexes and the muscle mechanoreflex. Muscle mechanoreflex mediated renal vasoconstriction during short bouts of HG is not influenced by baroreflex disengagement.
Effect of S5P α‐helix charge mutants on inactivation of hERG K+ channels
Authors: Clarke C. E. , Hill A. P. , Zhao J. , Kondo M. , Subbiah R. N. , Campbell T. J. , Vandenberg J. I.
Published: March 2006

The ether‐à‐go‐go (EAG) family of voltage‐gated K+ channels contains three subfamilies, EAG, ether‐à‐go‐go related (ERG) and ether‐à‐go‐go like (ELK). The human ether‐à‐go‐go related gene (hERG) K+ channel has been of significant interest because loss of function in the hERG channel is associated with a markedly increased risk of cardiac arrhythmias. The hERG channel has unusual kinetics with slow activation and deactivation but very rapid and voltage‐dependent inactivation. The outer pore region of the hERG K+ channel is predicted to be different from that of other members of the voltage‐gated K+ channel family. HERG has a much longer linker between the fifth transmembrane domain (SS) and the pore helix (S5P linker) compared to other families of voltage‐gated K+ channels (43 amino acids compared to 14–23 amino acids). Further, the S5P linker contains an amphipathic α‐helix that in hERG channels probably interacts with the mouth of the pore to modulate inactivation. The human EAG and rat ELK2 channels (hEAG and rELK2) show reduced or no inactivation in comparison to hERG channels, yet both channels are predicted to contain a similarly long S5P linker to that of hERG. In this study, we have constructed a series of chimaeric channels consisting of the S1–S6 of hERG but with the S5P α‐helical region of either hEAG or rELK2, and one consisting of the S1–S6 of rELK2 but with the S5P α‐helical region of hERG to investigate the role of the S5P linker in inactivation. Our studies show that charged residues on the α‐helix of the S5P linker contribute significantly to the differences in inactivation characteristics of the EAG family channels. Further, individually mutating each of the hydrophilic residues on the S5P α‐helix of hERG to a charged residue had significant effects on the voltage dependence of inactivation and the two residues with the greatest affect when mutated to a lysine, N588 and Q592, both lie on the same face of the S5P α ‐helix. We suggest that inactivation of hERG involves the interaction of this face of the S5P α‐helix with a charged residue on the remainder of the outer pore domain of the channel.
Lessons from
Drosophila
Models of DJ-1 Deficiency
Authors: Moore Darren J. , Dawson Valina L. , Dawson Ted M.
Published: March 2006

Mutations in the
DJ-1
gene are associated with rare forms of autosomal recessive early-onset Parkinson's disease (PD). Although the precise physiological function of DJ-1 remains obscure, accumulating evidence suggests that DJ-1 may normally function as a redox-sensitive molecular chaperone that can protect against the deleterious effects of oxidative stress, particularly in mitochondria. Recent studies in the fruit fly,
Drosophila melanogaster
, have shed further light on the biological role of DJ-1. DJ-1-deficient
Drosophila
models exhibit distinct phenotypes but collectively highlight a prominent neuroprotective role for DJ-1 against oxidative insult. However,
Drosophila
lacking DJ-1 do not consistently produce a useful PD-like phenotype (that is, they generally fail to exhibit degeneration of neurons that contain the neurotransmitter dopamine), which may reflect putative compensatory neuroprotective mechanisms. DJ-1-deficient fly models further highlight the utility of
Drosophila
as an important tool for elucidating protein function and for modeling neurodegenerative disease.
The Way of the Honeybee
Authors: Leslie Mitch
Published: March 2006

When it comes to aging, bees have flown away from other invertebrates, according to a new study. The work reveals that an egg protein that cuts survival in worms shields honeybees from destructive oxidants. The insects' social habits might have allowed them to divert the life-shortening protein to a beneficial function.
The Sour Side of Sweet
Authors: Leslie Mitch
Published: March 2006

Sugars tantalize our taste buds and fuel our cells, but we pay a price for relying on the sweet, energy-rich molecules. Glucose and its breakdown products--especially one called methylglyoxal--can gum up vital cellular components. In the last 10 to 15 years, methylglyoxal and its chemical cousins have grabbed the attention of experts studying diabetes, cancer, and other diseases. One new paper suggests that methylglyoxal undermines health in an unexpected way: by altering the activity of a gene that controls blood vessel growth, possibly triggering one complication of diabetes. Scientists suspect that methylglyoxal disrupts the activity of other genes as well.
When Good Cdk5 Turns Bad
Authors: Guo Qing
Published: March 2006

The cyclin-dependent kinase-5 (Cdk5) is critical to normal mammalian development and has been implicated in synaptic plasticity, learning, and memory in the adult brain. But Cdk-5 activity has also been linked to neurodegenerative diseases. Could a single protein have opposing effects? A new study shows that production of a neuronal protein capable of regulating Cdk-5 activity can turn Cdk-5 from "good" to "bad." The findings may have implications for the development and treatment of conditions like Alzheimer's disease.
Olfactory Loss in Aging
Authors: Rawson Nancy E.
Published: March 2006

Olfactory loss is a common age-related complaint that may be caused by changes in the anatomy of the structures required for olfaction (for example, loss of olfactory receptor cells) or in the environment surrounding the receptor cell (for example, altered nasal mucus composition). However, aging, as well as age-related diseases and medications, may also alter the distribution, density, or function of specific receptor proteins, ion channels, or signaling molecules that affect the ability of neural elements throughout the olfactory pathway to signal and process odorant information. Although a great deal has been learned about the prevalence and nature of age-related olfactory loss, we are just beginning to explore avenues to prevent or alleviate this sensory deficit. Some studies suggest that, rather than being a necessary outcome of aging, age-associated factors such as chronic diseases, medications, and dental and sinus problems are the primary culprits in causing olfactory impairment. This idea suggests optimism in that, as we address these other age-related health issues, the prevalence of olfactory loss will lessen as well.
Conservation of RET Regulatory Function from Human to Zebrafish Without Sequence Similarity
Authors: Fisher Shannon , Grice Elizabeth A. , Vinton Ryan M. , Bessling Seneca L. , McCallion Andrew S.
Published: March 2006

Evolutionary sequence conservation is an accepted criterion to identify noncoding regulatory sequences. We have used a transposon-based transgenic assay in zebrafish to evaluate noncoding sequences at the zebrafish
ret
locus, conserved among teleosts, and at the human
RET
locus, conserved among mammals. Most teleost sequences directed
ret
-specific reporter gene expression, with many displaying overlapping regulatory control. The majority of human
RET
noncoding sequences also directed
ret
-specific expression in zebrafish. Thus, vast amounts of functional sequence information may exist that would not be detected by sequence similarity approaches.
H5N1 Virus Attachment to Lower Respiratory Tract
Authors: van Riel Debby , Munster Vincent J. , de Wit Emmie , Rimmelzwaan Guus F. , Fouchier Ron A. M. , Osterhaus Ab D. M. E. , Kuiken Thijs
Published: March 2006

Highly pathogenic avian influenza virus (H5N1) may cause severe lower respiratory tract (LRT) disease in humans. However, the LRT cells to which the virus attaches are unknown for both humans and other mammals. We show here that H5N1 virus attached predominantly to type II pneumocytes, alveolar macrophages, and nonciliated bronchiolar cells in the human LRT, and this pattern was most closely mirrored in cat and ferret tissues. These findings may explain, at least in part, the localization and severity of H5N1 viral pneumonia in humans. They also identify the cat and the ferret as suitable experimental animals based on this criterion.
2005: Signaling Breakthroughs of the Year
Authors: Adler Elizabeth M. , Gough Nancy R. , Ray L. Bryan
Published: March 2006

2005 was particularly notable for the range and scope of exciting advances in cell signaling research. Nominations from leading scientists ranged from plant signaling, neurobiology, and immunology to systems biology and structural biology. In plant biology, a new piece added to a long-standing puzzle in auxin signaling was discovered. The exploitation and regulation of RNA in cell signaling was also in the limelight. Intriguing new twists were highlighted in relation to functional and dysfunctional signaling in the brain, calcium-mediated signals, and the innate immune response. Finally, mathematical and statistical analysis of biochemical networks provided new insights into the circuitry of cell signaling pathways.
DNA Damage and Tumor Surveillance: One Trigger for Two Pathways
Authors: Höglund Petter
Published: March 2006

Biological evolution ensures that several backup mechanisms always exist to prevent the failure of cellular processes of critical importance for life. This notion applies to processes aimed at preventing cancer development. Recent research suggests that the DNA damage response, activated in one of the earliest cellular responses to transformation, may elicit two independent tumor surveillance mechanisms. The first, and most well known, is activation of the proapoptotic molecule p53 and subsequent cellular suicide. The second, reported in a recent study, is induction of the expression of ligands for the activating immune receptor NKG2D. That DNA damage induces two independent tumor surveillance responses demonstrates how one tumor surveillance mechanism may be assisted by another to secure efficient protection against early tumorigenesis. The results also support the immunosurveillance theory of cancer and suggest that it may operate at very early stages of tumorigenesis.
Role of Docosahexaenoic Acid in Neuronal Plasma Membranes
Authors: Glomset John A.
Published: March 2006

The omega-3 fatty acid docosahexaenoic acid (DHA n-3) has long been known to be a major component of phosphoglycerides in the gray matter of mammalian brains. Furthermore, early studies of synaptosomes that had been isolated from gray matter showed that the plasma membranes of the synaptosomes contained DHA n-3 that was selectively esterified to phosphatidylethanolamine, plasmenylethanolamine (alkenylacyl-glycero-phosphorylethanolamine), and phosphatidylserine. In contrast, the phosphatidylcholine in these membranes contained esterified oleic acid, and the sphingomyelin and glycolipids in the membranes contained amide-linked stearic acid instead of a mixture of this acid with other, amide-linked fatty acids. The full implications of this unusual distribution of lipid head groups, esterified fatty acids, and amide-linked fatty acids are unclear, but the phosphoglycerides and sphingosine-containing lipids appear to be distributed asymmetrically between the two leaflets of the plasma membrane lipid bilayer and are likely to contribute to a dynamic lipid substructure. Because very few neuronal plasma membranes have been isolated and characterized to date, a major challenge for the future will be to investigate the composition of the lipid bilayers of different neuronal plasma membranes and identify effects of DHA n-3–containing phosphoglycerides on the ability of the plasma membranes to perform their many different functions. The aim of this Perspective is to stimulate further work in this important area by discussing recent evidence related to the role of neuronal plasma membrane phosphoglycerides in cell signaling.
Arabidopsis
Jasmonate Signaling Pathway
Authors: Gfeller Aurélie , Liechti Robin , Farmer Edward E.
Published: March 2006

Jasmonates control defense gene expression and male fertility in the model plant
Arabidopsis thaliana
. In both cases, the involvement of the jasmonate pathway is complex, involving large-scale transcriptional reprogramming. Additionally, jasmonate signaling is hard-wired into the auxin, ethylene, and salicylate signal networks, all of which are under intense investigation in
Arabidopsis
. In male fertility, jasmonic acid (JA) is the essential signal intervening both at the level of anther elongation and in pollen dehiscense. A number of genes potentially involved in jasmonate-dependent anther elongation have recently been discovered. In the case of defense, at least two jasmonates, JA and its precursor 12-oxo-phytodienoic acid (OPDA), are necessary for the fine-tuning of defense gene expression in response to various microbial pathogens and arthropod herbivores. However, only OPDA is required for full resistance to some insects and fungi. Other jasmonates probably affect yet more physiological responses. A series of breakthroughs have identified the SKP/CULLIN/F-BOX (SCF), CORONATINE INSENSITIVE (COI1) complex, acting together with the CONSTITUTIVE PHOTOMORPHOGENIC 9 (COP9) signalosome, as central regulatory components of jasmonate signaling in
Arabidopsis
. The studies, mostly involving mutational approaches, have paved the way for suppressor screens that are expected to further extend our knowledge of jasmonate signaling. When these and other new mutants affecting jasmonate signaling are characterized, new nodes will be added to the
Arabidopsis
Jasmonate Signaling Pathway Connections Map, and the lists of target genes regulated by jasmonates in
Arabidopsis
will be expanded.
How Sensitive Is a Nose?
Authors: Vogt Richard G.
Published: March 2006

Odor sensitivity may not be due to odor-receptor (OR) binding but rather may be due to emergent properties of transduction pathways and the anatomical convergence of olfactory neurons. A recent study suggests that odor-OR interactions are brief and infrequently activate heterotrimeric GTP-binding proteins (G proteins); in contrast, visual receptors have long-lasting activation states and activate many G proteins. These differences may reflect strategies that evolved to accommodate very different signals, and the mechanisms described might be applicable for receptors across phyla. However, whereas visual receptors (rhodopsin) appeared before protostome-deuterostome separation, ORs may be independently derived in different phyla. Alternatively, phylum-distinct ORs may share common ancestry but be influenced by diversifying selection. Phylum-distinct ORs may imply phylum-specific OR mechanisms, whereas common ancestry may imply common mechanisms. Nonetheless, most animals detect a similar repertoire of olfactory signals, and OR mechanisms may be convergent on those signals independent of receptor relatedness. Thus, recent insights into the molecular characteristics of odor perception in frogs may well be relevant to such processes as how mosquitoes detect host odors for a malaria-transmitting blood meal.
Retinoic Acid Signaling in the Functioning Brain
Authors: Dräger Ursula C.
Published: March 2006

Retinoic acid, an active form of vitamin A, regulates gene expression throughout the body, and many components of the signaling system through which it acts are present in the brain. Very little is known, however, about how retinoic acid functions in neurobiological systems. Several studies have provided evidence that retinoic acid plays a role in sleep, learning, and memory, but the precise mechanisms through which it influences these processes remain unclear. All of these processes involve local or long-range inhibition and synchronized neuronal activity between separate locations in the brain. A critical component in the generation of the synchronized firing of cortical neurons (cortical synchrony) is a network of inhibitory interneurons containing parvalbumin, a cell population affected by retinoid perturbations, such as exposure to a vitamin A overdose. An understanding of the role of retinoids in normal brain function would provide clues to the long-standing question of whether abnormalities in retinoic acid signaling contribute to the pathogenesis of some brain diseases with uncertain etiologies that involve both genetic and environmental factors.
Meeting Report: Barossa 2005—Signaling NetworksA report of the Signaling Networks meeting, Barossa Valley, South Australia, 16 to 19 November 2005.
Authors: Guthridge Mark A. , Goodall Gregory J. , Pitson Stuart M.
Published: March 2006

Cellular signal transduction involves an elaborate network of interrelated signaling pathways. Dissecting the components of these signaling pathways and the functional relationships between them is crucial to our understanding of biological processes. This was the central theme of the November 2005 Signaling Networks meeting held in the Barossa Valley, South Australia. The meeting highlighted recent exciting advances in this area, covering topics such as the initiation, integration, regulation, and architecture of signaling networks, and the importance of these pathways in normal physiological functions and pathophysiological processes.
Detecting Cryptic Epitopes Created by Nanoparticles
Authors: Lynch Iseult , Dawson Kenneth A. , Linse Sara
Published: March 2006

As potential applications of nanotechnology and nanoparticles increase, so too does the likelihood of human exposure to nanoparticles. Because of their small size, nanoparticles are easily taken up into cells (by receptor-mediated endocytosis), whereupon they have essentially free access to all cellular compartments. Similarly to macroscopic biomaterial surfaces (that is, implants), nanoparticles become coated with a layer of adsorbed proteins immediately upon contact with physiological solutions (unless special efforts are taken to prevent this). The process of adsorption often results in conformational changes of the adsorbed protein, which may be affected by the larger curvature of nanoparticles compared with implant surfaces. Protein adsorption may result in the exposure at the surface of amino acid residues that are normally buried in the core of the native protein, which are recognized by the cells as "cryptic epitopes." These cryptic epitopes may trigger inappropriate cellular signaling events (as opposed to being rejected by the cells as foreign bodies). However, identification of such surface-exposed epitopes is nontrivial, and the molecular nature of the adsorbed proteins should be investigated using biological and physical science methods in parallel with systems biology studies of the induced alterations in cell signaling.
Synthesis and Structures of (η3-Methallyl)palladium(II) Complexes with Phosphanylferrocenecarboxylic Ligands
Authors: Štěpnička Petr , Císařová Ivana
Published: March 2006

Di-μ-chlorobis{(η3-methallyl)palladium(II)} (1) reacts with two equivalents of 1'-(diphenylphosphanyl)ferrocene-1-carboxylic acid (Hdpf) and rac-[2-(diphenylphosphanyl)ferrocen-1-yl]acetic acid (rac-Hpfa) to give complexes with P-monodentate phosphanylcarboxylic ligands: [PdCl(η3-CH2C(Me)CH2)(L-κP)], L = Hdpf (2) and rac-Hpfa (4). Similar reactions with the corresponding carboxylate salts (Kdpf and Kpfa) afford, respectively, an ill-defined polymer formulated tentatively [{Pd(η3-CH2C(Me)CH2)(dpf)}n] (3) and the molecular chelate complex [Pd(η3-CH2C(Me)CH2)(pfa-κ2O,P)] (5), which crystallizes as a monohydrate. All compounds were studied by spectral methods (IR and NMR) and the solid-state structures of 2, 4, and 5·H2O were determined by single-crystal X-ray diffraction.
Rapid diagnosis ofPenicillium marneffeiinfection by fine needle aspiration cytology: Figure 1
Authors: Lim D , Lee Y-S , Chang A R
Published: March 2006

This report describes the use of fine needle aspiration (FNA) cytology to make a rapid diagnosis ofPenicillium marneffeiinfection in an HIV positive patient.Pmarneffeiis a thermally dimorphic fungus that is a mould at 25°C and a yeast at 37°C. It multiplies by fission. It can be easily mistaken for various other infections that are characterised by the presence of histiocytes with phagocytosed yeast cells. In smears the demonstration of yeast cells with a distinctive central septum confirms the diagnosis.
Eosinophil infiltration and degranulation in oesophageal mucosa from adult patients with eosinophilic oesophagitis: a retrospective and comparative study on pathological biopsy
Authors: Mueller S , Aigner T , Neureiter D , Stolte M
Published: March 2006

Aim:To examine eosinophil infiltration and degranulation in 50 oesophageal biopsy specimens from 30 patients (21 men, 9 women; mean 39 years) with eosinophilic oesophagitis, by haematoxylin and eosin staining and immunohistochemistry.

Methods:Immunohistochemistry was carried out using a monoclonal antibody for human eosinophilic major basic protein (MBP). Eosinophils were counted in three high power fields (×40) and degranulation, as quantified by extracellular MBP immunostaining, was scored on a scale of 1–4. Morphological changes (basal cell hyperplasia, elongation of papillae and dilatation of intercellular spaces) were scored on a 1–4 scale on sections stained with haematoxylin and eosin.

Results:Numbers of intraepithelial eosinophils were significantly higher with MBP immunostaining than with haematoxylin and eosin staining (mean 109.6v80.6; p<0.001), whereas numbers of eosinophils were considerably correlated (r = 0.794). Eosinophil degranulation was higher in the distal oesophagus. Additionally, basic morphological changes were markedly associated with eosinophil infiltration. Extracellular deposition of eosinophil-MBP and eosinophil infiltration in subepithelial connective tissue, present in the biopsy specimens, were detected by immunohistochemistry.

Conclusion:Numbers of eosinophils and degranulation are underestimated by haematoxylin and eosin staining. Immunohistochemistry detected up to two times more eosinophils than routine haematoxylin and eosin staining. Moreover, eosinophil-MBP immunoreactivity in extracellular regions indicates the release of toxic eosinophil granule proteins and gives further evidence for a causative role of eosinophils with regard to structural changes in eosinophilic oesophagitis. Immunohistochemistry may serve as a useful diagnostic tool to support the morphological differential diagnosis of eosinophilic oesophagitis and gastro-oesophageal reflux disease.
Furosemide reverses multidrug resistance status in bladder cancer cells in vitro
Authors: Speers A G , Lwaleed B A , Featherstone J M , Sallis B J , Cooper A J
Published: March 2006

Background:Multidrug resistance (MDR) has a potentially serious influence on cancer treatment and should be taken into consideration in the design and application of therapeutic regimens. It is mediated through the activity of cellular pumps.

Aim:To investigate whether furosemide, itself a pump-blocker, reverses MDR in an in vitro model.

Materials and methods:An MDR bladder cancer cell line (MGH-u 1R) and its parental (drug sensitive) clone were exposed to epirubicin and furosemide, with the concentration of one drug fixed and that of the other serially diluted in a 96-well plate format. Both drugs formed the variable component in separate experiments. After a 1-h exposure, the cells were washed and replenished with fresh medium. To examine the toxicity of epirubicin and furosemide separately and in combination, monotetrazolium-based assays were carried out. Intracellular epirubicin distribution was assessed by confocal microscopy as a second index of resistance status after in vitro exposure.

Results:MGH-u 1R cells incubated with furosemide showed distribution of drug similar to that in the parental cells (MGH-u 1 sensitive). Controls (without furosemide) continued to show a resistant pattern of fluorescence. In cytotoxicity assays furosemide appeared substantially non-toxic. Resistant cells in the toxicity titration experiments showed increased resistance to levels of furosemide over 500 μg/ml. Parental cells were made only marginally more sensitive against increased background toxicity.

Conclusion:Furosemide is effective in reversing MDR status in bladder cancer cell lines in vitro. It may also have an increment of intrinsic cytotoxicity, but only at higher concentrations. We propose a potential for further investigation of furosemide as an adjunct to chemotherapy for superficial bladder cancer.
A Cost Optimal Parallel Algorithm for Patience Sorting
Authors: NAKASHIMA TAKAAKI , FUJIWARA AKIHIRO
Published: March 2006

In this paper, we consider a parallel algorithm for the patience sorting. The problem is not known to be in the class NC or P-complete. We propose two algorithms for the patience sorting of n distinct integers. The first algorithm runs in [Formula: see text] time using p processors on the EREW PRAM, where m is the number of decreasing subsequences in a solution of the patience sorting. The second algorithm runs in [Formula: see text] time using p processors on the EREW PRAM. If [Formula: see text] is satisfied, the second algorithm becomes cost optimal.