bluuebunny/crossref_metadata_2025 huggingface dataset:
Conserved roles for Oct4 homologues in maintaining multipotency during early vertebrate development
Authors: Morrison Gillian M. , Brickman Joshua M.
Published: May 2006

All vertebrate embryos have multipotent cells until gastrulation but, to date, derivation of embryonic stem (ES) cell lines has been achieved only for mouse and primates. ES cells are derived from mammalian inner cell mass (ICM)tissue that express the Class V POU domain (PouV) protein Oct4. Loss of Oct4 in mice results in a failure to maintain ICM and consequently an inability to derive ES cells. Here, we show that Oct4 homologues also function in early amphibian development where they act as suppressors of commitment during germ layer specification. Antisense morpholino mediated PouV knockdown in Xenopus embryos resulted in severe posterior truncations and anterior neural defects. Gastrulation stage embryos showed reduced expression of genes associated with uncommitted marginal zone cells, while the expression of markers associated with more mature cell states was expanded. Importantly, we have tested PouV proteins from a number of vertebrate species for the ability to substitute Oct4 in mouse ES cells. PouV domain proteins from both Xenopus and axolotl could support murine ES cell self-renewal but the only identified zebrafish protein in this family could not. Moreover, we found that PouV proteins regulated similar genes in ES cells and Xenopusembryos, and that PouV proteins capable of supporting ES cell self-renewal could also rescue the Xenopus PouV knockdown phenotype. We conclude that the unique ability of Oct4 to maintain ES cell pluripotency is derived from an ancestral function of this class of proteins to maintain multipotency.
Roadkill attenuates Hedgehog responses through degradation of Cubitus interruptus
Authors: Kent David , Bush Erik W. , Hooper Joan E.
Published: May 2006

The final step in Hedgehog (Hh) signal transduction is post-translational regulation of the transcription factor, Cubitus interruptus (Ci). Ci resides in the cytoplasm in a latent form, where Hh regulates its processing into a transcriptional repressor or its nuclear access as a transcriptional activator. Levels of latent Ci are controlled by degradation, with different pathways activated in response to different levels of Hh. Here, we describe the roadkill (rdx) gene, which is expressed in response to Hh. The Rdx protein belongs to a conserved family of proteins that serve as substrate adaptors for Cullin3-mediated ubiquitylation. Overexpression of rdx reduced Ci levels and decreased both transcriptional activation and repression mediated by Ci. Loss of rdx allowed excessive accumulation of Ci. rdx manipulation in the eye revealed a novel role for Hh in the organization and survival of pigment and cone cells. These studies identify rdx as a limiting factor in a feedback loop that attenuates Hh responses through reducing levels of Ci. The existence of human orthologs for Rdx raises the possibility that this novel feedback loop also modulates Hh responses in humans.
When bad things happen to good fish: the loss of hemoglobin and myoglobin expression in Antarctic icefishes
Authors: Sidell Bruce D. , O'Brien Kristin M.
Published: May 2006

The Antarctic icefishes (Family Channichthyidae) provide excellent examples of unique traits that can arise in a chronically cold and isolated environment. Their loss of hemoglobin (Hb) expression, and in some cases, loss of myoglobin (Mb) expression, has taught us much about the function of these proteins. Although absences of the proteins are fixed traits in icefishes, the losses do not appear to be of adaptive value. Contrary to some suggestions,loss of Hb has led to higher energetic costs for circulating blood, and losses of Mb have reduced cardiac performance. Moreover, losses of Hb and Mb have resulted in extensive modifications to the cardiovascular system to ensure adequate oxygen delivery to working muscles. Recent studies suggest that losses of Hb and Mb, and their associated nitric oxide (NO)-oxygenase activities, may have accelerated the development and evolution of these cardiovascular modifications. The high levels of NO that should occur in the absence of Hb and Mb have been shown in other animal groups to lead to an increase in tissue vascularization, an increase in the lumenal diameter of blood vessels, and an increase in mitochondrial densities. These characteristics are all hallmark traits of Antarctic icefishes. Homeostatic feedback mechanisms thus may have accelerated evolution of the pronounced cardiovascular traits of Antarctic icefishes.
Evolution of pharyngeal behaviors and neuronal functions in free-living soil nematodes
Authors: Chiang Jing-Tzyh Alan , Steciuk Mark , Shtonda Boris , Avery Leon
Published: May 2006

To explore the use of Caenorhabditis elegans and related nematodes for studying behavioral evolution, we conducted a comparative study of pharyngeal behaviors and neuronal regulation in free-living soil nematodes. The pharynx is divided into three parts: corpus, isthmus and terminal bulb,and pharyngeal behaviors consist of stereotyped patterns of two motions:pumping and peristalsis. Based on an outgroup species, Teratocephalus lirellus, the ancestral pattern of pharyngeal behaviors consisted of corpus pumping, isthmus peristalsis and terminal bulb pumping, each occurring independently. Whereas corpus pumping remained largely conserved, isthmus and terminal bulb behaviors evolved extensively from the ancestral pattern in the four major free-living soil nematode families. In the Rhabditidae family,which includes Caenorhabditis elegans, the anterior isthmus switched from peristalsis to pumping, and anterior isthmus and terminal bulb pumping became coupled to corpus pumping. In the Diplogasteridae family, the terminal bulb switched from pumping to peristalsis, and isthmus and terminal bulb became coupled for peristalsis. In the Cephalobidae family, isthmus peristalsis and terminal bulb pumping became coupled. And in the Panagrolaimidae family, the posterior isthmus switched from peristalsis to pumping. Along with these behavioral changes, we also found differences in the neuronal regulation of isthmus and terminal bulb behaviors. M2, a neuron that has no detectable function in C. elegans, stimulated anterior isthmus peristalsis in the Panagrolaimidae. Further, M4 was an important excitatory neuron in each family, but its exact downstream function varied between stimulation of posterior isthmus peristalsis in the Rhabditidae,isthmus/terminal bulb peristalsis in the Diplogasteridae, isthmus peristalsis and terminal bulb pumping in the Cephalobidae, and posterior isthmus/terminal bulb pumping in the Panagrolaimidae. In the Rhabditidae family, although M4 normally has no effect on the terminal bulb, we found that M4 can stimulate the terminal bulb in C. elegans if the Ca2+-activated K+ channel SLO-1 is inactivated. C. elegans slo-1 mutants have generally increased neurotransmission, and in slo-1 mutants we found novel electropharyngeogram signals and increased pumping rates that suggested activation of M4-terminal bulb synapses. Thus, we suggest that the lack of M4-terminal bulb stimulations in C. elegans and the Rhabditidae family evolved by changes in synaptic transmission. Altogether, we found behavioral and neuronal differences in the isthmus and terminal bulb of free-living soil nematodes, and we examined potential underlying mechanisms of one aspect of M4 evolution. Our results suggest the utility of Caenorhabditis elegans and related nematodes for studying behavioral evolution.
Characterization of a branchial epithelial calcium channel (ECaC) in freshwater rainbow trout (Oncorhynchus mykiss)
Authors: Shahsavarani A. , McNeill B. , Galvez F. , Wood C. M. , Goss G. G. , Hwang P.-P. , Perry S. F.
Published: May 2006

The entry of calcium (Ca2+) through an apical membrane epithelial calcium channel (ECaC) is thought to a key step in piscine branchial Ca2+ uptake. In mammals, ECaC is a member of the transient receptor potential (TRP) gene family of which two sub-families have been identified, TRPV5 and TPRV6. In the present study we have identified a single rainbow trout (Oncorhynchus mykiss) ECaC (rtECaC) that is similar to the mammalian TRPV5 and TRPV6. Phylogenetic analysis of the protein sequence suggests that an ancestral form of the mammalian genes diverged from those in the lower vertebrates prior to the gene duplication event that gave rise to TRPV5 and TRPV6.

The putative model for Ca2+ uptake in fish proposes that the mitochondria-rich cell (also termed ionocyte or chloride cell) is the predominant or exclusive site of transcellular Ca2+ movements owing to preferential localisation of ECaC to the apical membrane of these cells. However, the results of real-time PCR performed on enriched gill cell populations as well as immunocytochemistry and in situ hybridisation analysis of enriched cells, cell cultures and whole gill sections strongly suggest that ECaC is not exclusive to mitochondria-rich cells but that it is also found in pavement cells. Not only was ECaC protein localized to areas of the gill normally having few mitochondria-rich cells, but there was also no consistent co-localization of ECaC- and Na+/K+-ATPase-positive (a marker of mitochondria rich cells) cells. Taken together, the results of the present study suggest that although ECaC (mRNA and protein) does exist in trout gill, its cellular distribution is more extensive than previously thought, thus suggesting that Ca2+ uptake may not be restricted to mitochondria-rich cells as was proposed in previous models.
Immunolocalisation of theD. melanogaster NramphomologueMalvolioto gut and Malpighian tubules provides evidence thatMalvolioandNramp2are orthologous
Authors: Folwell James L. , Barton C. Howard , Shepherd David
Published: May 2006

Nramp (Slc11a1) genes in mammals are associated with the transport of iron and other divalent cations; Nramp1 in macrophages involved in the innate immune response against intracellular pathogens, and Nramp2 with duodenal iron uptake and the transferrin–transferrin-receptor pathway of iron assimilation. The Drosophila melanogaster Nramp-related gene is known as Malvolio. The localisation of Malvolio protein was inferred from the enhancer trap line initially used to isolate Malvolio in a screen for mutants with defects in taste perception. Here we describe the generation of a Malvolio-reactive polyclonal antibody and apply it to evaluate Malvolio localisation during stages of D. melanogaster development,and compare the results with the localisation of the enhancer trap line identified with beta-galactosidase. All immunolocalisation studies have been confirmed to be specific with Malvolio-blocking peptides. Our results demonstrated expression within Malpighian tubules, testis, brain, the amnioserosa of embryos, the larval and adult alimentary canal. Expression within the gut was of significant interest, as mammalian Nramp2 in the gut plays a primary role in the acquisition of dietary iron. We confirm expression within the central nervous system and in cells of the haematopoietic system. By immunohistochemistry we showed that expression within cells was either punctuate, diffuse cytoplasmic or plasma membrane associated, or both. The staining within the gut indicates a degree of conservation of components for iron acquisition between flies and mammals, suggesting that a comparable mechanism has been retained during evolution.
Flight and echolocation behaviour of whiskered bats commuting along a hedgerow: range-dependent sonar signal design, Doppler tolerance and evidence for `acoustic focussing'
Authors: Holderied Marc W. , Jones Gareth , von Helversen Otto
Published: May 2006

Echolocating bats obtain three-dimensional images of their surroundings in complete darkness by emitting sonar signals and evaluating returning echoes. When flying close to objects, bats risk collision and therefore depend on the accuracy of images – particularly in the perceived distance of obstacles, which is coded by the time delay between call and echo. Yet, during flight, such accuracy is perturbed first because bats call and receive echoes at different positions and second because echoes are modified by Doppler shifts. Certain call designs avoid both sources of ranging error, but only for a limited range of distances [the `distance of focus' (DOF)]. Here, we show that whiskered bats (Myotis mystacinus) using broadband echolocation calls adjust call design in a range-dependent manner so that nearby obstacles are localised accurately. Such behaviour is adaptive because it reduces collision risk. The bats also reduced call duration to some extent as they approached obstacles so that most returning echoes arrived after they finished calling. This reduction in call duration during the approach to obstacles was neither the only nor the main factor that influenced DOF. Indeed, both duration and bandwidth of calls influenced DOF independently, with lower bandwidths and longer durations giving greater DOF. Our findings give a new perspective on the adaptive significance of echolocation call design in nature and have implications for sonar engineering.
A new set of laboratory-selected Drosophila melanogaster lines for the analysis of desiccation resistance: response to selection, physiology and correlated responses
Authors: Telonis-Scott Marina , Guthridge Kathryn M. , Hoffmann Ary A.
Published: May 2006

Artificial selection experiments provide insights into the evolutionary factors that can shape adaptive responses and have previously been utilized to examine the physiological adaptations that can improve survival to desiccation in Drosophila melanogaster. While such studies demonstrate that multiple resistance mechanisms may arise via different base populations and selection regimes, water retention emerges as a key mechanism for desiccation survival. Here, we present the physiological, correlated response and life history data for a new set of selection lines designed for the genetic dissection of desiccation resistance. After 26 generations of selection for desiccation resistance, female survival increased twofold. In contrast to previous studies, the altered resistance was associated primarily with enhanced dehydration tolerance and increased mass and less consistently with decreased rates of water loss. Life history tradeoffs and correlated selection responses were examined and overlap with previously published data. We crossed the resistant selected lines to desiccation-sensitive lines from the same control background to examine how each heterozygous resistant chromosome (excluding four) may improve desiccation resistance and observed that most of the resistance was due to genes on the third and first chromosomes, although interaction effects with the second chromosome were also detected. Results are compared to other selection responses and highlight the multiple evolutionary solutions that can arise when organisms are faced with a common selection pressure, although water loss rate remains a common mechanism in all studies.
Transcriptional regulation of neuropeptide and peptide hormone expression by theDrosophila dimmedandcryptocephalgenes
Authors: Gauthier Sebastien A. , Hewes Randall S.
Published: May 2006

The regulation of neuropeptide and peptide hormone gene expression is essential for the development and function of neuroendocrine cells in integrated physiological networks. In insects, a decline in circulating ecdysteroids triggers the activation of a neuroendocrine system to stimulate ecdysis, the behaviors used to shed the old cuticle at the culmination of each molt. Here we show that two evolutionarily conserved transcription factor genes, the basic helix-loop-helix (bHLH) gene dimmed (dimm)and the basic-leucine zipper (bZIP) gene cryptocephal (crc),control expression of diverse neuropeptides and peptide hormones in Drosophila. Central nervous system expression of three neuropeptide genes, Dromyosuppressin, FMRFamide-related and Leucokinin, is activated by dimm. Expression of Ecdysis triggering hormone (ETH) in the endocrine Inka cells requires crc; homozygous crc mutant larvae display markedly reduced ETH levels and corresponding defects in ecdysis. crcactivates ETH expression though a 382 bp enhancer, which completely recapitulates the ETH expression pattern. The enhancer contains two evolutionarily conserved regions, and both are imperfect matches to recognition elements for activating transcription factor-4 (ATF-4), the vertebrate ortholog of the CRC protein and an important intermediate in cellular responses to endoplasmic reticulum stress. These regions also contain a putative ecdysteroid response element and a predicted binding site for the products of the E74 ecdysone response gene. These results suggest that convergence between ATF-related signaling and an important intracellular steroid response pathway may contribute to the neuroendocrine regulation of insect molting.
Water dynamics in the digestive tract of the freshwater rainbow trout during the processing of a single meal
Authors: Bucking Carol , Wood Chris M.
Published: May 2006

The temporal effects of feeding and digestion on chyme composition,specifically water and solid content, and net fluxes across the gastrointestinal tract, as well as plasma parameters, were examined in freshwater rainbow trout. A single meal of commercial dry pellets,incorporating ballotini beads as inert reference markers, was employed. Plasma Na+ levels increased by 15–20% at 2 h post-feeding, where Cl– levels did not change. Plasma osmolality was well regulated despite an initial chyme osmolality (775 mOsm) 2.8-fold higher than that in the blood plasma. Chyme osmolality throughout the gastrointestinal tract remained significantly higher than plasma osmolality for the duration of the 72 h period. Solid material was absorbed along the entire intestinal tract, although not in the stomach, necessitating the incorporation of an inert marker. A similar temporal pattern of transit between the ballotini beads (solid phase marker) and 3[H]-PEG 4000 (fluid phase marker),provided support for the use of ballotini beads. Large additions of water to the chyme were seen in the stomach, the largest occurring within 2 h following feeding (7.1±1.4 ml kg–1), and amounted to ∼16 ml kg–1 over the first 12 h. As the chyme entered the anterior intestine, a further large water secretion (3.5±0.5 ml kg–1) was seen. Thereafter the water fluxes into the chyme of the anterior intestine decreased steadily over time, but remained positive,whereas the mid-intestine exhibited net absorption of water at all time points, and the posterior intestine demonstrated little water handling at any time. The endogenous water that was secreted into the anterior intestine was absorbed along the tract, which showed a net water flux close to zero. However, assuming that the water secreted into the stomach was endogenous in nature, the processing of a single meal resulted in net loss of endogenous water (0.24 ml kg–1 h–1) to the environment,a beneficial consequence of the osmotic challenge offered by the food for a freshwater hyperosmotic regulator.
Vomeronasal sensory neurons fromSternotherus odoratus(stinkpot/musk turtle) respond to chemosignalsviathe phospholipase C system
Authors: Brann Jessica H. , Fadool Debra A.
Published: May 2006

The mammalian signal transduction apparatus utilized by vomeronasal sensory neurons (VSNs) in the vomeronasal organ (VNO) has been richly explored, while that of reptiles, and in particular, the stinkpot or musk turtle Sternotherus odoratus, is less understood. Given that the turtle's well-known reproductive and mating behaviors are governed by chemical communication, 247 patch-clamp recordings were made from male and female S. odoratus VSNs to study the chemosignal-activated properties as well as the second-messenger system underlying the receptor potential. Of the total neurons tested, 88 (35%) were responsive to at least one of five complex natural chemicals, some of which demonstrated a degree of sexual dimorphism in response selectivity. Most notably, male VSNs responded to male urine with solely outward currents. Ruthenium Red, an IP3 receptor(IP3R) antagonist, failed to block chemosignal-activated currents,while the phospholipase C (PLC) inhibitor, U73122, abolished the chemosignal-activated current within 2 min, implicating the PLC system in the generation of a receptor potential in the VNO of musk turtles. Dialysis of several second messengers or their analogues failed to elicit currents in the whole-cell patch-clamp configuration, negating a direct gating of the transduction channel by cyclic adenosine monophosphate (cAMP), inositol 1,4,5-trisphosphate (IP3), arachidonic acid (AA), or diacylglycerol(DAG). Reversal potential analysis of chemosignal-evoked currents demonstrated that inward currents reversed at –5.7±7.8 mV (mean ±s.e.m.; N=10), while outward currents reversed at–28.2±2.4 mV (N=30). Measurements of conductance changes associated with outward currents indicated that the outward current represents a reduction of a steady state inward current by the closure of an ion channel when the VSN is exposed to a chemical stimulus such as male urine. Chemosignal-activated currents were significantly reduced when a peptide mimicking a domain on canonical transient receptor potential 2 (TRPC2), to which type 3 IP3 receptor (IP3R3) binds, was included in the recording pipette. Collectively these data suggest that there are multiple transduction cascades operational in the VSNs of S. odoratus, one of which may be mediated by a non-selective cation conductance that is not gated by IP3 but may be modulated by the interaction of its receptor with the TRPC2 channel.
Electrochemical gradients for Na+, K+,Cl– and H+ across the apical membrane in Malpighian (renal) tubule cells ofRhodnius prolixus
Authors: Ianowski Juan P. , O'Donnell Michael J.
Published: May 2006

Measurements of intracellular and luminal ion activities as well as membrane potential were used to calculate electrochemical gradients for Cl–, Na+, K+ and H+ across the apical membrane during fluid secretion by Malpighian tubules of Rhodnius prolixus. The results show that the contribution of Na+/H+ and/or K+/H+ exchangers to fluid secretion is feasible both in unstimulated and serotonin-stimulated tubules. Similarly, the electrochemical potential for Cl– is consistent with the passive movement of Cl– from cell to lumen through Cl– channels. The contribution of apical K+:Cl– cotransport and/or paracellular Cl– movement to net transepithelial ion transport is thermodynamically unfeasible. pH in the lumen (pH 6.08±0.1, N=6) was more acid than in the bath (pH 7.25±0.01, N=26) and serotonin stimulation produced a significant increase in lumen pH to 6.32±0.04 (N=5). Intracellular pH was 6.97±0.01 and 6.82±0.04 in unstimulated and serotonin-stimulated tubules, respectively. Lumen pH was altered whereas intracellular pH was tightly regulated during serotonin and bumetanide treatment. Furthermore, DIDS or amiloride treatment did not affect intracellular pH. However, intracellular pH shifted 0.25 pH units more acid in Na+-free saline, suggesting that a Na+-dependent pH regulatory mechanism is at play in steady state pH regulation during fluid secretion by Malpighian tubules of Rhodnius prolixus. The data are consistent with a role for a basolateral Na+/H+ exchanger in intracellular pH regulation during fluid secretion.
Partial coherence and other optical delicacies of lepidopteran superposition eyes
Authors: Stavenga D. G.
Published: May 2006

Superposition eyes are generally thought to function ideally when the eye is spherical and with rhabdom tips in the focal plane of the imaging optics of facet lenses and crystalline cones. Anatomical data as well as direct optical measurements demonstrate that the superposition eyes of moths and skippers often deviate severely from the expected ideal case. Part of the deviation has been attributed to diffraction at the single facet lens, which was taken to be an essential limit to spatial resolution, because light traveling through different facet lenses was assumed to be incoherent. By considering the two-dimensional facet lens lattice, it is here demonstrated that many facets within a superposition aperture transmit coherent light, allowing a much sharper image than possible with single facet lens diffraction. Partial coherence therefore is an important aspect of superposition imaging. It is argued that broadening of the photoreceptor acceptance angles occurs because of optical errors in the facet lens-crystalline cone system other than diffraction. The transmittance of the superposition aperture of moths and skippers is improved by the corneal nipple arrays of the facet lenses, but quantitative assessment shows that the effect is minor.
The effects of temperature on peripheral neuronal function in eurythermal and stenothermal crustaceans
Authors: Young John S. , Peck Lloyd S. , Matheson Thomas
Published: May 2006

To determine whether neuronal function in Antarctic crustaceans is adapted to the low and narrow range of temperatures at which these animals live, we have compared conduction velocities in the peripheral nervous systems of two temperate species, the decapod Carcinus maenas and the isopod Ligia oceanica, and two Antarctic species, the isopod Glyptonotus antarcticus and the amphipod Paraceradocus gibber.

Neuronal conduction velocity differs among the species in the order C. maenas > G. antarcticus > P. gibber > L. oceanica. When measured at the normal environmental temperatures characteristic of each species, conduction velocity of the Antarctic peracarid P. gibber is greater than that of its similar sized temperate relativeL. oceanica, demonstrating complete thermal compensation.

The temperate decapod C. maenas has a higher thermal dependence of neuronal conduction velocity than either of the Antarctic species, G. antarcticus and P. gibber, but the temperate L. oceanica does not. These data, when collated with published values,indicate that peracarid crustaceans (L. oceanica, G. antarcticus and P. gibber) have lower neuronal conduction velocities and a lower thermal dependence of neuronal conduction velocity than do other arthropods, irrespective of habitat. There is a linear dependence of conduction velocity on temperature down to –1.8°C in all three species. Our data extend by more than 10° the lower range of temperatures at which conduction velocities have been tested systematically in previous studies.

The upper thermal block of neuronal conduction is similar in C. maenas, G. antarcticus, P. gibber and L. oceanica at 24.5, 19.5, 21.5 and 19.5°C, respectively. This suggests that failure to conduct action potentials is not what determines the mortality of Antarctic invertebrates at approximately 10°C.

The excitability of axons in the leg nerve of G. antarcticus is not affected by temperatures ranging from –1.8 to +18°C. The responses of sensory neurones activated by movements of spines on the leg,however, are strongly modulated by temperature, with maximal responses at 5–10°C; well above the normal environmental temperature range for the species. The responses fail at 20–22°C.

The number of large diameter axons (which produce the fast action potentials recorded in this study) is the same in L. oceanica and G. antarcticus, but the median axon diameter is greater in L. oceanica than G. antarcticus. In G. antarcticus,however, there are glial wrappings around some large (>5 μm diameter)axons that may increase their conduction velocity. Such wrappings are not found in L. oceanica.
The hydrodynamic effects of shape and size change during reconfiguration of a flexible macroalga
Authors: Boller Michael L. , Carrington Emily
Published: May 2006

Rocky intertidal organisms experience large hydrodynamic forces due to high water velocities created by breaking waves. Flexible organisms, like macroalgae, often experience lower drag than rigid organisms because their shape and size change as velocity increases. This phenomenon, known as reconfiguration, has been previously quantified as Vogel's E, a measure of the relationship between velocity and drag. While this method is very useful for comparing reconfiguration among organisms it does not address the mechanisms of reconfiguration, and its application to predicting drag is problematic. The purpose of this study was twofold: (1) to examine the mechanisms of reconfiguration by quantifying the change in shape and size of a macroalga in flow and (2) to build a mechanistic model of drag for reconfiguring organisms. Drag, frontal area and shape of the intertidal alga Chondrus crispus were measured simultaneously in a recirculating flume at water velocities from 0 to ∼2 m s–1. Reconfiguration was due to two separate mechanisms: whole-alga realignment(deflection of the stipe) at low velocities (<0.2 m s–1)and compaction of the crown (reduction in frontal area and change in shape) at higher velocities. Change in frontal area contributed more to drag reduction than change in drag coefficient. Drag coefficient and frontal area both decrease exponentially with increasing water velocity, and a mechanistic model of drag was developed with explicit functions to describe these changes. The model not only provides mechanistic parameters with which to compare reconfiguration among individuals and species, but also allows for more reliable predictions of drag at high, ecologically relevant water velocities.
The role of the sarcoplasmic reticulum in the generation of high heart rates and blood pressures in reptiles
Authors: Galli Gina L. J. , Gesser Hans , Taylor Edwin W. , Shiels Holly A. , Wang Tobias
Published: May 2006

The functional significance of the sarcoplasmic reticulum (SR) in the generation of high heart rates and blood pressures was investigated in four species of reptile; the turtle, Trachemys scripta; the python, Python regius, the tegu lizard, Tupinanvis merianae, and the varanid lizard, Varanus exanthematicus. Force-frequency trials and imposed pauses were performed on ventricular and atrial tissue from each species with and without the SR inhibitor ryanodine, and in the absence and presence of adrenaline. In all species, an imposed pause of 1 or 5 min caused a post-rest decay of force, and a negative force-frequency response was observed in all species within their in vivo frequency range of heart rates. These relationships were not affected by either ryanodine or adrenaline. In ventricular strips from varanid lizards and pythons, ryanodine caused significant reductions in twitch force within their physiologically relevant frequency range. In atrial tissue from the tegu and varanid lizards,SR inhibition reduced twitch force across the whole of their physiological frequency range. In contrast, in the more sedentary species, the turtle and the python, SR inhibition only decreased twitch force at stimulation frequencies above maximal in vivo heart rates. Adrenaline caused an increase in twitch force in all species studied. In ventricular tissue, this positive inotropic effect was sufficient to overcome the negative effects of ryanodine. In atrial tissue however, adrenaline could only ameliorate the negative effects of ryanodine at the lower pacing frequencies. Our results indicate that reptiles recruit Ca2+ from the SR for force development in a frequency and tissue dependent manner. This is discussed in the context of the development of high reptilian heart rates and blood pressures.
Seasonal variation in mussel byssal thread mechanics
Authors: Moeser Gretchen M. , Carrington Emily
Published: May 2006

The blue mussel, Mytilus edulis, attaches itself to the substrate by producing a radially arranged complex of collagenous byssal threads. The strength of byssal attachment, or tenacity, has been shown to vary seasonally on Rhode Island shores, increasing twofold in spring in comparison with fall. It was previously assumed that this seasonality was due to increased thread production following periods of increased wave action; however, recent findings do not support this view. As an alternate hypothesis, this study evaluates the contribution of seasonal changes in the material properties of byssal threads to an annual cycle in mussel attachment strength. Tensile mechanical tests were performed seasonally, on both newly produced threads and on threads outplanted in the field for up to nine weeks. Threads produced in spring were over 60% stronger and 83% more extensible than threads produced in all other seasons. The mechanical integrity of byssal threads also deteriorated over time in spring and summer. These results suggest that reduced attachment strength in fall reflects the production of inferior quality threads following a period of increased decay. Here, we propose a new scheme where variation in byssal thread material properties, rather than quantity, explains the seasonal pattern in attachment strength observed on Rhode Island shores.
The Operating Temperature Lowering for CO2 Gas Sensor with a Lithium Conducting Solid Electrolyte
Authors: Imanaka Nobuhito , Murata Toshihide , Kawasato Takeshi , Adachi Gin-ya
Published: May 2006

The lowering of the operating temperature for the CO2 gas sensor with the lithium conducting solid electrolyte was examined by applying a ductile solid of a Li2CO3 + Li2O mixture or a Li2CO3-K2CO3-Na2CO3 eutectic. In the case of the eutectic solid, the CO2 sensor can detect the gas content precisely from 100 ppm to 1% at as low a temperature as 350 °C. The ductilities of the solid greatly enhanced the reactivity between Li2CO3 in the eutectic and the CO2 gas in the atmosphere.
A Lipase Mediated Asymmetric Hydrolysis of 3-Acyloxy-1-octynes and 3-(E)-Acyloxy-1-octenes
Authors: Shimizu Makoto , Kawanami Hiroshi , Fujisawa Tamotsu
Published: May 2006

Optical resolution of 3-propionyloxy-1-trimethylsilyl-1-octyne or 3-(E)-propionyloxy-1-octene via lipase-mediated hydrolysis gave optically pure (S)-1-trimethylsilyl-1-octyn-3-ol and (R)-(E)-1-iodo-1-octen-3-ol, respectively, in which a reversal of enantio-selectivity for hydrolysis was observed between 3-propionyloxy-1-octyn and its 1-trimethylsilylated derivative, and the effect of the acyl groups on the enantio-discrimination was also investigated.
Fe(CO)5/Sulfur-Catalyzed Coal Liquefaction Using H2O-CO as a Hydrogen Source
Authors: Watanabe Yoshihisa , Yamada Hiro-aki , Kawasaki Nori-aki , Wada Kenji , Mitsudo Take-aki
Published: May 2006

Catalytic activity of Fe/sulfur in coal liquefaction using H2O-CO as a hydrogen source was investigated. Fe(CO)5/sulfur was found to be an excellent catalyst precursor. In the two-staged heating reaction (375 °C-60 min and 425 °C-60 min) of Yallourn coal, both high coal conversion (92.9 d.a.f.%) and high oil yield (55.8 d.a.f.%) were achieved by the Fe(CO)5/sulfur catalyst.
Metal Instability of (DMe-DCNQI)2Cu Induced by Uniaxial Stress and Enhancement of Electron Mass
Authors: Miyamoto Akihito , Kobayashi Hayao , Kato Reizo , Kobayashi Akiko , Nishio Yutaka , Kajita Koji , Sasaki Wataru
Published: May 2006

The metal instability of (DMe-DCNQI)2Cu was induced by applying uniaxial stress or coating the crystal with Apiezon L grease. The quadratic temperature dependence of the resistivity gave an indication of the large enhancement of the effective mass of the conduction electrons.
Superconducting Transition Temperature of the Organic Alloy System. κ-[(BEDT-TTF)1−x(BEDT-STF)x]2Cu[N(CN)2]Br
Authors: Naito Toshio , Miyamoto Akihito , Kobayashi Hayao , Kato Reizo , Kobayashi1 Akiko
Published: May 2006

The superconducting transition temperature (Tc) was investigated by alloying (BEDT-TTF)2Cu[N(CN)2]Br with (BEDT-STF)2Cu[N(CN)2]Br. The Tc of the former rapidly decreased with doping the latter. The relation between stoichiometry and structure is also discussed.
Model Study of Hepatocyte Targeting Polymeric Super Molecular Assembly as Drug Carrier
Authors: Goto Mitsuaki , Kobayashi Akira , Kobayashi Kazukiyo , Saito Kazuhiro , Akaike Toshihiro
Published: May 2006

The drug binding properties of lactose carrying polystyrene (PVLA), which could be endocytosed into hepatocytes due to its interaction with receptors of asialoglycoprotein, were examined by UV and NMR spectroscopies. The results obtained with a hydrophilic drug model, 8-anilino-naphthalene-1-sulphonate (ANS), and with a hydrophobic drug model, 1,6-diphenyl-hexatriene (DPH), indicated the PVLA can be used as a hepatocyte targeting drug carrier.
New Cembranolide Diterpenes with a Dimethylamino Group from the Okinawan Soft Coral (Sinularia sp.)
Authors: Iguchi Kazuo , Nishimura Kunihiko , Yamazaki Kei , Iwashima Makoto , Yamada Yasuji
Published: May 2006

Three new cembranolide diterpenes each possessing a dimethylamino group were isolated from the Okinawan soft coral Sinularia sp. Their structures were determined based on data from spectroscopic analysis and chemical transformation.
Reactions of Phosphonate Carbanions with Selenium or Sulfur in the Presence of Amines. Synthesis of Seleno- and Thioamides
Authors: Okuma Kentaro , Ikari Koumei , Ohta Hiroshi
Published: May 2006

The reaction of phosphonate carbanions with elemental selenium in the presence of amines afforded the corresponding selenoamides in moderate yields. The reaction of these anions with sulfur also gave thioamides. These reactions might proceed through thio- or selenoaldehyde intermediates.
Mixed Valence State of Cerium in Bis(phthalocyaninato)cerium Complex
Authors: Isago Hiroaki , Shimoda Masahiko
Published: May 2006

Spectroscopic properties of the titled complex are reported compared to the other radical bis(phthalocyaninato)lanthanoid(III) complexes. Electronic, infrared, and Ce 3d XPS spectra show that the cerium in the titled complex is neither tri- nor tetravalent and Ce 4f electron delocalizes in a phthalocyanine π orbital.
Synthesis of a New Tellurium Heterocycle, 5H,7H-Dibenzo[b,g][1,5]tellurathiocin, and Isolation and Reactivity of Its Tellurathia Dication Salt
Authors: Fujihara Hisashi , Takaguchi Yutaka , Chiu Jer-Jye , Erata Tomoki , Furukawa Naomichi
Published: May 2006

A new heterocycle containing tellurium and sulfur atoms, 5H,7H-dibenzo[b,g][1,5]tellurathiocin (1), has been synthesized. The transannular bond formation between tellurium and sulfur atoms was found in the reaction of 1 with coned H2SO4 by 1H, 13C, and 125Te NMR spectroscopy. Two-electron oxidation of 1 with 2 equiv. of NOPF6 gave the tellurathia dication salt 3 ( > Te+–S+ < 2PF6−) which acts as an oxidizing agent.
Litophynins I and J, Two New Biologically Active Diterpenoids from the Soft Coral Litophyton sp.
Authors: Ochi Masamitsu , Yamada Koji , Kataoka Kumi , Kotsuki Hiyoshizo , Shibata Kozo
Published: May 2006

Two new diterpenoids, litophynins I and J, which exhibit molluscicidal and repellent activities against the muricid gastropod Drupella fragum, have been isolated from the soft coral Litophyton sp. Their structures were fully characterized by extensive 2D-NMR studies.
A New Fragmentation Reaction of γ-Oxosulfonium Methylides
Authors: Watanabe Yoshihiko , Takeda Toyonori , Anbo Keiji , Ueno Yoshio , Toru Takeshi
Published: May 2006

Reactions of sulfonium methylides attached to a 5- or 6-membered cycloalkanone undergo the ring-fission as a major reaction course to give α-methylene-ω-(phenylthio)carboxylates, whereas sulfonium methylides attached to a larger ring give α-methylenecycloalkanones predominantly. Reactions of the acyclic compounds are also examined.
Persicanidine A, a Novel Cerveratrum Alkaloid from the Bulbs of Fritillaria persica
Authors: Ori Kazutomo , Mimaki Yoshihiro , Sashida Yutaka , Nikaido Tamotsu , Ohmoto Taichi , Masuko Akiyoshi
Published: May 2006

Persicanidine A, a novel cerveratrum alkaloid was isolated from the fresh bulbs of Fritillaria persica together with a known alkaloid, delavine. The structure was elucidated by spectroscopic data and X-ray crystallographic analysis. Persicanidine A is unique in structure having the D/E trans (H-13α/H-17β) and E/F cis (cis-quinolizidine) ring fusions. Persicanidine A and delavine were active as a cyclic AMP phosphodiesterase inhibitor.
Total Synthesis of (+)-Bicyclohumulenone
Authors: Fukuyama Yoshiyasu , Hirono Motoko , Kodama Mitsuaki
Published: May 2006

(+)-Bicyclohumulenone, a bicyclic sesquiterpene isolated from liverworts, was synthesized using stereoselective Simmons-Smith cyclopropanation and intramolecular alkylation of α-sulfenyl carbanion as key steps.
New Types of Photochemical Switching Phenomena in Langmuir-Blodgett Films
Authors: Tachibana Hiroaki , Azumi Reiko , Nakamura Takayoshi , Matsumoto Mutsuyoshi , Kawabata Yasujiro
Published: May 2006

Three types of photochemical switching phenomena in LB films were observed using amphiphilic molecules consisting of azobenzene, alkyl chain, and pyridinium(TCNQ)2. For two types the conductivity of the LB film changed reversibly with photoisomerization of azobenzene. The third type showed phenomena which are compared to the learning process.
Experimental and Theoretical (AM1) Studies on Photoaddition Reactions of 3-Nitro-2-enopyranoside Derivatives
Authors: Sakakibara Tohru , Matuo Ichiro , Takaide Aya , Nakamura Takanori , Seta Akinori
Published: May 2006

Irradiation of 3-nitro-α- and β-d-erythro-hex-2-enopyranoside derivatives in methanol, ethanol, and isopropanol with high pressure Hg lamp gave the adducts in moderate yields. The stereoselectivities calculated by AM1 calculation by the use of model compounds with 1,3-dioxolan-2-yl radical are not conflict with those observed in similar photoreaction in 1,3-dioxolane as well as the present results.
A Novel Method for the Preparation of Optically Active Dipeptide. Chemo- and Stereoselective Reduction of 2-Hydroxyimino Amides with Samarium Diiodide
Authors: Mukaiyama Teruaki , Yorozu Kiyotaka , Kato Koji , Yamada Tohru
Published: May 2006

Various α,β-unsaturated amides derived from α-amino acids are converted to the corresponding 2-hydroxyimino amides of α-amino acids by the reaction with butyl nitrite and silane, which are directly reduced with samarium diiodide to the optically active dipeptides in good yields under mild conditions with high chemo- and stereoselectivities.
Rational Preparation and Characterization of Tandem Tetrametal Clusters. Crystal Structure of Tetrakis(6-diphenylphosphino-2-pyridonato)dimolybdenum
Authors: Mashima Kazushi , Nakano Hiroshi , Mori Takehiko , Takaya Hidemasa , Nakamura Akira
Published: May 2006

Dinuclear molybdenum complex Mo2(pyphos)4, pyphos = 6-diphenylphosphino-2-pyridonato, was treated with transition metal complexes such as Mo(CO)3(CH3CN)3, PdCl2(PhCN)2, and PtBr2(cod) to form one-dimensional tetranuclear cluster complexes Mo2(pyphos)4(MLn)2 (3) (a: MLn = Mo(CO)3, b: MLn = PdCl2, and c: MLn = PdBr2). Iodine–doped material of 3a showed semi-conducting property.
Platinum-Catalyzed Novel Reactions of Nitriles and an Azirine with o-Bis(dimethylsilyl)benzene
Authors: Reddy N Prabhakar , Uchimaru Yuko , Lautenschlager Hans-Jürgen , Tanaka Masato
Published: May 2006

Nitriles and 2-phenylazirine underwent dehydrogenative double silylation with o-bis(dimethylsilyl)benzene in the presence of (ethylene)bis(triphenylphosphine)platinum catalyst to give silyl enamines and imines in excellent yields.
Facile Syntheses of (S,S)-2,3-Diaminobutyric Acid and the Acid Containing N-Terminal Tripeptide of Antrimycins
Authors: Nakamura Yutaka , Shin Chung-gi
Published: May 2006

The stereoselective synthesis of (S,S)-2,3-diaminobutyric acid (Dab), which is one of the four uncommon α-amino acid residues of antrimycins (1a) and cirratiomycins (1b), was accomplished. Furthermore, N-terminal tripeptide segment of 1 containing Dab residue was also synthesized.
Photochemistry of o-Nitrophenylazide in Matrices. The First Direct Spectroscopic Observation of o-Dinitrosobenzene
Authors: Murata Shigeru , Tomioka Hideo
Published: May 2006

Photolysis of o-nitrophenylazide in an Ar matrix at 12 K produced the mixture of benzofuroxan and a new species, which could be identified as o-dinitrosobenzene on the basis of its IR and UV spectra.
Chemiexcitation of Naphthacenequinone Derivative via the Thermal Cycloreversion of the Corresponding hemi-Dewar-naphthacenequinone
Authors: Miki Sadao , Kobayashi Osamu , Kagawa Hiroyuki , Yoshida Zen-ichi , Nakatsuji Hiroshi
Published: May 2006

7,8,9-Tri-t-butyl-1,4-Dewar-5,12-naphthacenequinone (1) was synthesized. Upon thermolysis of 1 the formation of the detectable amount of naphthacenequinovalene (3) was observed. Singlet excited state of 7,8,9-tri-t-butyl-5,12-naphthacenequinone produced via the thermal cycloreversion of 1 is responsible for the formation of 3.
New Ruthenium-Molybdenum and -Tungsten Heterodinuclear Complexes with trans-Styryl Ligand
Authors: Fukuoka Atsushi , Ohashi Nobutoshi , Komiya Sanshiro
Published: May 2006

New styryl ruthenium-molybdenum and -tungsten complexes Cp(CO)3M-Ru (trans-styryl)(CO)(PPh3)2 [M = Mo (2), W (3)] have been prepared by the metathetical reactions of Ru(trans-styryl)Cl(CO)(PPh3)2 with Na[MCp(CO)3]. The reactions of 2 with CO and with PMe3 give Cp(CO)3Mo-Ru(trans-styryl)(CO)2(PPh3)2 (4) and Cp(CO)3Mo-Ru(trans-styryl)(CO)(PMe3)2 (5), respectively. The complexes of 2, 3, 4, and 5 have been characterized by IR, 1H NMR, 31P{1H} NMR spectroscopy, and elemental analysis.
2-Aminobenzoyl-peptide-2,4-dinitroanilinoethylamides. Facile Fluorescent Detection System for Sequence Specific Proteases
Authors: Nishino Norikazu , Makinose Yuichi , Fujimoto Tsutomu
Published: May 2006

New fluorogenic peptides with efficient quenching group were synthesized and subjected to the action of thermolysin and trypsin. The hydrolysis of the peptide bond resulted in the increase in fluorescence intensity by 50-200-fold of the quenched peptides.
The Catalytic Pinacol Rearrangement of 1,2-Diols Using an Antimony(V) Salt
Authors: Harada Tsunehiro , Mukaiyama Teruaki
Published: May 2006

In the presence of a catalytic amount of antimony(V) chloride or antimony(V) salt generated from antimony(V) chloride and silver hexafluoroantimonate, the pinacol rearrangement of several 1,2-diols or their trimethylsilyl ethers proceeds smoothly to give the corresponding ketones in good yields.
Efficient Optical Resolution of 4-Hydroxy-2-cyclopentenone Derivatives by HPLC on 1-Phenylethylcarbamates of Cellulose and Amylose
Authors: Kaida Yuriko , Okamoto Yoshio
Published: May 2006

Esters and silyl ethers of 4-hydroxy-2-cyclopentenone which are important building blocks for the synthesis of prostagrangins have been efficiently resolved into optically active isomers by HPLC on amylose tris(1-phenylethylcarbamate)s.
Novel Branching of a Ketose Promoted by the Nickel(II) – Diamine Complex. The Isomerization of D-Fructose into D-Hamamelose
Authors: Yanagihara Ryoji , Osanai Shuichi , Yoshikawa Sadao
Published: May 2006

D-Fructose was converted into 2-C-(hydroxymethyl)-D-ribose in a methanolic solution containing a nickel(II) – N,N′-diethylethylenediamine complex.
Radical Polymerization of 5-(4-Acrylamido)-phenyl-10,15,20-triphenylporphyrin
Authors: Kajiwara Atsushi , Aramata Kaoru , Nomura Shigeki , Morishima Yotaro , Kamachi Mikiharu
Published: May 2006

Polyacrylamide having tetraphenylporphyrin rings in its side chain was prepared by radical polymerization of 5-(4-acrylamido)-phenyl-10,15,20-triphenylporphyrin (AATPP) by using AIBN at 60 °C in benzonitrile.
Stereoselective C-Alkynylation, Allenylation, and Prop-2-ynylation Leading to Sugar Glycosides
Authors: Saeeng Rungnapha , Isobe Minoru
Published: May 2006

Carbohydrates have been recognized and utilized for a long time as the starting materials for target-oriented syntheses toward optically active compounds. C-Glycosides are often employed for this purpose because they have much potential for the introduction of new stereogenic centers to the side chain. We describe herein various methods for the introduction of carbon chains to the sugar rings under acidic conditions, particularly in the form of alkynyl, allenyl, or prop-2-ynyl group at the anomeric position with high stereoselectivity.
Facile Synthesis of Cu2O Polyhedral Micro/Nanocrystals in Aqueous Solution of an Amphiphilic Polyvinylacetone
Authors: Wu Wei-Tai , Shi Lei , Zhu Qingren , Wang Yusong , Xu Guoyong , Pang Wenmin , Lu Fei
Published: May 2006

Cu2O polyhedral micro/nanocrystals were synthesized in aqueous solution of amphiphilic polyvinylacetone (PVKA) (ketalization degree DH = 0.549) under ambient conditions (20–23 °C), via natural oxidation of copper metal by naturally dissolved oxygen in water.