bluuebunny/crossref_metadata_2025 huggingface dataset:
Population structure and history of southern African scrub hares, Lepus saxatilis
Authors: Kryger U. , Robinson T. J. , Bloomer P.
Published: May 2004

Genetic differentiation among populations of the South African scrub hare Lepus saxatilis was examined using hypervariable mitochondrial DNA control region I (CR‐I) sequences. Neighbour‐joining analysis revealed a pattern that did not correspond to the current subspecies delineations. The CR‐I sequence data delimit scrub hares into three major maternal lineages. The three phylogenetic assemblages exhibited different geographical distributions. AMOVA analyses and exact tests for population differentiation confirmed this phylogeographic partitioning. One lineage (SW) was confined to the south‐western Cape, the second lineage (N) was exclusively found in the northern part of South Africa and in the neighbouring countries, and the third lineage (C) was predominant in the central parts of South Africa. This spatial distribution did not coincide with the ranges of the 10 described subspecies covered by our sampling regime. The lineages C and N overlapped in an area including eastern parts of South Africa and southern Namibia. The presence of both lineages in that area of overlap was interpreted as the result of secondary contact due to recent range expansions after the two lineages had undergone a population restriction approximately 18 000 years ago. Analyses of contemporary gene flow disclosed an exchange of migrants between N and C, which was biased towards a movement from C to N. The SW group represents a very distinct evolutionary lineage that has been isolated for more than 45 000 years. It does not exchange female migrants with the other two groups. Mismatch distribution analyses indicated sudden population size expansions in the history of all three populations.
Is the highveld mole‐rat Cryptomys hottentotus pretoriae (Rodentia: Bathyergidae) an induced or spontaneous ovulator?
Authors: Malherbe G. P. , Schoeman A. S. , Bennett N. C.
Published: May 2004

The highveld mole‐rat Cryptomys hottentotus pretoriae is a social subterranean rodent that exhibits seasonal reproduction. Non‐reproductive females remain anovulatory whilst in the confines of the natal colony. However, during the southern hemisphere summer, dispersal of non‐reproductive females from the natal colony occurs with subsequent pairing with unrelated males. This study investigates whether the dispersing female highveld mole‐rat is an induced or spontaneous ovulator. Eight non‐reproductive females were removed from their natal colonies during the breeding season and housed individually for 5 weeks. Urine was collected every second day during the next 5 weeks of isolation. After this initial period, isolated females underwent one of three trials: two females were kept isolated without a male, three females were individually placed in chemical but not physical contact with unvasectomized males, while each of the remaining three females were allowed full contact with a vasectomized male. Urine was again collected every second day for a further 5 weeks, after which the females were killed. Both urinary progesterone profiles and histology of the ovaries revealed that the female highveld mole‐rat is an induced ovulator. Females in physical contact with vasectomized males exhibited a significant increase in urinary progesterone concentration as well as the presence of corpora lutea in their ovaries, both indicative of ovulation. The act of coitus is necessary for ovulation to take place even though the males were not capable of fertilization. This is the first time induced ovulation has been shown in bathyergid rodents.
Soil carbon CO2fertilization factor: The measure of an ecosystem's capacity to increase soil carbon storage in response to elevated CO2levels
Authors: Harrison Kevin G.
Published: May 2004

This research introduces the concept of a “CO2fertilization factor for soil carbon” (σCF). The σCFis a measure of an ecosystem's capacity to increase soil carbon storage in response to elevated carbon dioxide levels. This paper describes the mathematical derivation of σCFand illustrates how σCFcan be determined experimentally, using data from a white oak study. I have developed this concept to compare the results of carbon dioxide enrichment experiments having different soil carbon turnover times, different levels of CO2enrichment, and different lengths of exposure to elevated carbon dioxide levels. The σCFcan also be used to estimate increases in soil carbon uptake due to observed contemporary increases in atmospheric carbon dioxide levels. Although the approach used here may seem oversimplified, I present it as a simple way of estimating the extent to which elevated levels of CO2could increase soil carbon storage. I have determined a σCFof 1.18 for a white oak ecosystem using soil carbon and radiocarbon measurements. If major terrestrial ecosystems have similar σCFvalues, CO2fertilization may be transferring enough carbon from the atmosphere to soil to balance the global carbon budget.
Hyperstratification following glacial overturning events in the northern Arabian Sea
Authors: Reichart Gert‐Jan , Brinkhuis Henk , Huiskamp Frank , Zachariasse Willem Jan
Published: May 2004

Correlations between Arabian Sea organic carbon and GISP2 δ18O records indicate a pronounced oxygen minimum zone (OMZ) during interstadials, whereas well‐oxygenated conditions prevailed during stadials. Local deep winter mixing ventilated intermediate water during the coldest stadials, corresponding to North Atlantic Heinrich events. Here we show that in the Arabian Sea periods of climatic warming following Heinrich events H6–H4 and the Younger Dryas (YD) are characterized by dominant Polysphaeridium zoharyi (dinoflagellate) cysts. The finding of assemblages dominated by P. zoharyi in the open ocean is unusual because today similar assemblages are restricted to lagoonal settings. It is postulated that the highly saline mixed layer and the strong density gradient which characterized Arabian Sea hydrography after H6–H4 and the YD simulated a shallow seafloor, thereby enabling germination of cysts prior to sinking. The strong density gradient following cold stadials should have facilitated the rapid reestablishment of a pronounced OMZ during interstadials.
Presynaptic inhibition of spontaneous acetylcholine release induced by adenosine at the mouse neuromuscular junction
Authors: Lorenzo Silvana De , Veggetti Mariela , Muchnik Salomón , Losavio Adriana
Published: May 2004

At the mouse neuromuscular junction, adenosine (AD) and the A1 agonist 2‐chloro‐N6‐cyclopentyl‐adenosine (CCPA) induce presynaptic inhibition of spontaneous acetylcholine (ACh) release by activation of A1 AD receptors through a mechanism that is still unknown. To evaluate whether the inhibition is mediated by modulation of the voltage‐dependent calcium channels (VDCCs) associated with tonic secretion (L‐ and N‐type VDCCs), we measured the miniature end‐plate potential (mepp) frequency in mouse diaphragm muscles.

Blockade of VDCCs by Cd2+ prevented the effect of the CCPA. Nitrendipine (an L‐type VDCC antagonist) but not ω‐conotoxin GVIA (an N‐type VDCC antagonist) blocked the action of CCPA, suggesting that the decrease in spontaneous mepp frequency by CCPA is associated with an action on L‐type VDCCs only.

As A1 receptors are coupled to a Gi/o protein, we investigated whether the inhibition of PKA or the activation of PKC is involved in the presynaptic inhibition mechanism. Neither N‐(2[p‐bromocinnamylamino]‐ethyl)‐5‐isoquinolinesulfonamide (H‐89, a PKA inhibitor), nor 1‐(5‐isoquinolinesulfonyl)‐2‐methyl‐piperazine (H‐7, a PKC antagonist), nor phorbol 12‐myristate 13‐acetate (PHA, a PKC activator) modified CCPA‐induced presynaptic inhibition, suggesting that these second messenger pathways are not involved.

The effect of CCPA was eliminated by the calmodulin antagonist N‐(6‐aminohexil)‐5‐chloro‐1‐naphthalenesulfonamide hydrochloride (W‐7) and by ethylene glycol‐bis(β‐aminoethyl ether)‐N,N,N′,N′‐tetraacetic acid‐acetoxymethyl ester ɛ6TΔ‐BM, which suggests that the action of CCPA to modulate L‐type VDCCs may involve Ca2+‐calmodulin.

To investigate the action of CCPA on diverse degrees of nerve terminal depolarization, we studied its effect at different external K+ concentrations. The effect of CCPA on ACh secretion evoked by 10 mM K+ was prevented by the P/Q‐type VDCC antagonist ω‐agatoxin IVA.

CCPA failed to inhibit the increases in mepp frequency evoked by 15 and 20 mM K+. We demonstrated that, at high K+ concentrations, endogenous AD occupies A1 receptors, impairing the action of CCPA, since incubation with 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX, an A1 receptor antagonist) and adenosine deaminase (ADA), which degrades AD into the inactive metabolite inosine, increased mepp frequency compared with that obtained in 15 and 20 mM K+ in the absence of the drugs. Moreover, CCPA was able to induce presynaptic inhibition in the presence of ADA. It is concluded that, at high K+ concentrations, the activation of A1 receptors by endogenous AD prevents excessive neurotransmitter release.

British Journal of Pharmacology (2004) 142, 113–124. doi:10.1038/sj.bjp.0705656
EP1‐ and FP‐mediated cross‐desensitization of the alpha (α) and beta (β) isoforms of the human thromboxane A2 receptor
Authors: Kelley‐Hickie Leanne P , Kinsella B Therese
Published: May 2004

Heterologous desensitization or intermolecular cross‐talk plays a critical role in regulating intracellular signalling by diverse members of the G‐protein‐coupled receptor superfamily. We have previously established that the α and β isoforms of the human thromboxane A2 receptor (TP) undergo differential desensitization of signalling in response to 17 phenyl trinor prostaglandin (PG)E2, an agonist of the EP1 subtype of the PGE2 receptor (EP) family.

Herein, we investigated the molecular basis of TPα and TPβ desensitization in human embryonic kidney (HEK) 293 cells and in renal mesangial cells in response to 17 phenyl trinor PGE2 and in response to the PGF2α receptor (FP) agonist PGF2α, and sought to identify the target site(s) of those desensitizations.

Our results demonstrated that TPα and TPβ receptors are subject to desensitization in response to both EP1 and FP receptor activation and that these effects are mediated by direct protein kinase (PK)C phosphorylation of the individual TP isoforms within their unique carboxyl‐terminal (C)‐tail domains.

Moreover, deletion/site‐directed mutagenesis and metabolic labelling studies identified Thr337, within TPα, and Thr399, within TPβ, as the specific target residues for PKC phosphorylation and EP1‐ and FP‐mediated desensitization of TPα and TPβ signalling, respectively.

Hence, in conclusion, while the TPα and TPβ diverge within their C‐tail domains, they have evolved to share a similar mechanism of PKC‐induced phosphorylation and desensitization in response to EP1 and FP receptor activation, though it occurs at sites unique to the individual TP isoforms.

British Journal of Pharmacology (2004) 142, 203–221. doi:10.1038/sj.bjp.0705695
Peripheral PACAP inhibits gastric acid secretion through somatostatin release in mice
Authors: Piqueras Laura , Taché Yvette , Martínez Vicente
Published: May 2004

Studies in rats suggest that PACAP modulates gastric acid secretion through the release of both histamine and somatostatin.

We characterized the effects of exogenous PACAP on gastric acid secretion in urethane‐anesthetized mice implanted with a gastric cannula and in conscious 2‐h pylorus ligated mice, and determined the involvement of somatostatin and somatostatin receptor type 2 (SSTR2) by using somatostatin immunoneutralization, the SSTR2 antagonist, PRL‐2903, and SSTR2 knockout mice.

Urethane‐anesthetized wild‐type mice had low basal acid secretion (0.10±0.01 μmol (10 min)−1) compared with SSTR2 knockout mice (0.93±0.07 μmol (10 min)−1). Somatostatin antibody and PRL‐2903 increased basal secretion in wild‐type mice but not in SSTR2 knockout animals.

In wild‐type urethane‐anesthetized mice, PACAP‐38 (3–270 μg kg−1 h−1) did not affect the low basal acid secretion, but inhibited the acid response to pentagastrin, histamine, and bethanechol.

In wild‐type urethane‐anesthetized mice pretreated with somatostatin antibody or PRL‐2903 and in SSTR2 knockout mice, peripheral infusion of PACAP‐38 or somatostatin‐14 did not inhibit the increased basal gastric acid secretion.

In conscious wild‐type mice, but not in SSTR2 knockout mice, PACAP‐38 inhibited gastric acid secretion induced by 2‐h pylorus ligation. The antisecretory effect of PACAP‐38 was prevented by immunoneutralization of somatostatin.

These results indicate that, in mice, peripheral PACAP inhibits gastric acid secretion through the release of somatostatin and the activation of SSTR2 receptors. There is no evidence for stimulatory effects of PACAP on acid secretion in mice.

British Journal of Pharmacology (2004) 142, 67–78. doi:10.1038/sj.bjp.0705739
Reflectivity behavior of opals of gold nanoparticle coated spheres
Authors: Miclea P. T. , Susha A. S. , Liang Z. , Caruso F. , Sotomayor Torres C. M. , Romanov S. G.
Published: May 2004

The light reflectance in three-dimensional metallodielectric photonic crystals assembled from polyelectrolyte-coated latex spheres infiltrated with gold nanoparticles has been studied. Strong deviation of the optical reflectance of Au opals from bare opals has been observed, including flattening of the diffraction resonance dispersion and nondispersive surface plasmon bands.
In situ detection of faradaic current in probe oxidation using a dynamic force microscope
Authors: Kuramochi Hiromi , Ando Kazunori , Tokizaki Takashi , Yokoyama Hiroshi
Published: May 2004

A faradaic current on the order of a sub-pico-ampere was detected while fabricating two-dimensional oxide nanostructures on H-passivated Si(001) surfaces. The detected faradaic current has been shown to faithfully reflect the degree of probe oxidation with a clear dependence on the variation of voltage and the tip speed. The faradaic current in dynamic mode can serve as a sensitive monitor of the nano-oxidation reaction for implementing precise closed-loop control of the oxide growth.
Selectable-frequency and tunable-Q perfect transmissions of electromagnetic waves in dielectric heterostructures
Authors: Wang Z. , Peng R. W. , Qiu F. , Huang X. Q. , Wang Mu , Hu A. , Jiang S. S. , Feng D.
Published: May 2004

Multiple perfect transmissions of electromagnetic waves are found in the photonic band gap of the symmetric dielectric heterostructures (SDH) constructed as (AB)nBm(BA)n, where A and B stand for different dielectric materials, and m and n are the repeating numbers of the units. The photonic frequency and the mode number of resonant transmissions therein can be manipulated by varying m, and the quality factor Q of the perfect transmission peak increases exponentially with increasing n. These features are experimentally demonstrated in a SDH of TiO2/SiO2 for visible and near infrared light. The possible applications of SDH for the wavelength division multiplexing system are discussed.
Superconductivity in La-doped strontium titanate thin films
Authors: Olaya David , Pan Feng , Rogers Charles T. , Price Jonn C.
Published: May 2004

We report on the superconductivity of lanthanum-doped SrTiO3 thin films grown by off-axis laser ablation on LaAlO3, SrTiO3, and NdGaO3 substrates in oxygen partial pressures ranging from 10−8 T to 21 mTorr. The La/Sr doping ratio of the ablation target was 1%. The resulting films have carrier densities measured in the range of 6.5–30×1019 cm−3 independent of temperature from room temperature to 4 K and low-temperature mobilities as high as 130 cm2/V s. Critical temperatures range between 356 down to about 48 mK depending on oxygen partial pressure during growth. Measurements of superconductive transitions in a magnetic field suggest a value of the electronic effective mass around 4.5 times the free electron mass.
Initial growth of vertically aligned carbon nanofibers
Authors: Cui Hongtao , Yang Xiaojing , Simpson Michael L. , Lowndes Douglas H. , Varela Maria
Published: May 2004

Samples of vertically aligned carbon nanofibers (VACNFs) were viewed transverse to the growth direction and studied using both scanning and transmission electron microscopy. The VACNFs are composed of graphite layers nearly parallel to the substrate at their bottom end, gradually formed graphite “cups” in the main body, and a catalyst particle on the tip. The formation of such structure is due to the corresponding transformation of the shape of the catalyst particle during initial VACNF growth. A model for their initial growth is proposed.
The normal-state resistivity of grain boundaries in YBa2Cu3O7−δ
Authors: Ransley J. H. T. , Mennema S. H. , Sandeman K. G. , Burnell G. , Tarte E. J. , Evetts J. E. , Blamire M. G. , Kye J. I. , Oh B.
Published: May 2004

Using an optimized bridge geometry, we have been able to make accurate measurements of the properties of YBa2Cu3O7−δ grain boundaries above Tc. The results show a strong dependence of the change of resistance with temperature on grain boundary angle. Analysis of our results in the context of band bending at the boundary allows us to estimate the height of the potential barrier present at the grain boundary interface.
The Role of Hydrogen Bonding in the Intramolecular Cyclization of Carbenes
Authors: Jeffery David W. , Lister Troy , Prager Rolf H.
Published: May 2004

The cyclization products from the photolysis of 3-arylamino-4-ethoxycarbonyl-2-heteroarylisoxazol-5(2H)-ones are interpreted as arising from intramolecular cyclization of carbenes. The mode of cyclization appears to be controlled by hydrogen bonding of the 3-NH group with either the 2-heteroaryl group or the 4-ethoxycarbonyl group.
The Action of Vanadium Oxytrifluoride on N-Arylbenzylamines—a Route to Some Phenanthridines
Authors: Liepa Andris J. , Nearn Roland N. , Wright Denis M. J.
Published: May 2004

The action of four equivalents of vanadium oxytrifluoride upon electron-rich N-arylbenzylamines provides a convenient synthesis of phenanthridines. Excess of oxidant can lead to selective hydroxylation of a methyl substituent. Benzylamines with a phosphonate substituent on the methylene group lead to 6-substituted phenanthridines.
Corticotrophin Releasing Hormone: Chemistry and Recent Developments
Authors: Garner James , Keller Paul A. , McCluskey Adam
Published: May 2004

Corticotrophin Releasing Hormone [CRH; also known as Corticotrophin Releasing Factor (CRF)], a 41-amino-acid hormone, is one of the body’ major modulators of the stress response. CRH coordinates the endocrine, autonomic, and behavioural responses to stress through actions in both the brain and the periphery activating the ‘fight or flight’ response. CRH is also implicated in various neurological disorders including Alzheimer’s, Parkinson’s, and anorexia nervosa, and it has been described as a biological clock controlling the length of gestation in humans and other higher-order primates. In the past decade there has been an enormous effort expended in the design and development of new therapeutic agents targetting CRHs in the central nervous and peripheral systems. In this review, we examine the chemistry and recent developments in this exciting field.
Solute is imported to elongating root cells of barley as a pressure driven-flow of solution
Authors: Gould Nick , Thorpe Michael R. , Minchin Peter E. H. , Pritchard Jeremy , White Philip J.
Published: May 2004

This work relates solute import to elongating root cells in barley to the water relations of the symplastic pathway under conditions of varied plant K+ status. K+ is a major constituent of phloem sieve element (SE) sap, and as an osmoticum, it is believed to have a role in maintaining SE hydrostatic pressure and thus sap flow from source to sink tissue. The hypothesis that the solute import to elongating root cells is linked to pressure driven flow from the sieve tube is examined.Plants were grown in solutions containing either 0.05 mM (low K) or 2.05 mM (high K) K+ concentration. Solute import to the root elongation zone was estimated from biomass accumulation over time accounting for respiration and root elongation rate. SE sap K+ concentration was measured using X-ray microanalyses and osmotic pressure by picolitre osmometry. SE hydrostatic pressure was measured directly with a pressure probe glued onto an excised aphid stylet. Elongating root cell hydrostatic pressure was measured using a cell pressure probe.The low-K plants had lower SE K+ concentration and SE hydrostatic pressure compared to the high-K plants, but the elongating root cell hydrostatic pressure was similar in both treatments, thus the pressure difference between the SE and elongating root cells was less in the low-K plants compared to the high-K plants.The solute import rate to elongating root cells was lower in the low K plants and the reduction could be accounted for as a pressure driven solute flux, with a reduction both in the pressure difference between root sieve elements and elongating cells, and in the sap concentration.
Re-examination of the taxonomy of the Macrobrachium australiense Holthuis (Decapoda : Palaemonidae) species-complex: molecular evidence for a single species
Authors: Murphy Nicholas P. , Short John W. , Austin Christopher M.
Published: May 2004

The freshwater shrimp Macrobrachium australiense is distributed throughout the majority of inland, north-west, north-east and eastern drainages. Owing to the large amount of morphological divergence, both between and within catchments, this species has proven to be taxonomically difficult and, until recently, consisted of three separate species, each with subsequent subspecies. This study uses nucleotide sequences from the 16S rRNA mitochondrial gene region to investigate the genetic relationships between populations and confirm the taxonomic status of M. australiense. The results from sequencing an approximately 450-bp fragment from this gene region from M. australiense sampled from 12 locations across inland, eastern and northern Australia identified very little variation. The variation found between 16S M. australiense haplotypes is much less than that found between Macrobrachium species, indicating that it is in fact a single species. The results are concordant with a recent morphological revision of Australian species in which nominal taxa of the M. australiense complex were synonymised.
A systematic and phylogenetic revision of the family Elipsocidae (Insecta : Psocoptera), with the erection of two new families: Lesneiidae and Sabulopsocidae
Authors: New T. R. , Schmidt E. R.
Published: May 2004

The phylogeny of the Elipsocidae is reappraised to aid understanding of generic relationships within the family, leading to its clear definition as a monophyletic entity and clarification of its position within the infraorder Homilopsocidea. Examination of new material and generic-level revision results in descriptions of ten new elipsocid genera: Prionotodrilus, gen. nov. for P. parvus (Smithers & Thornton), comb. nov. and P. serratus (Schmidt & Thornton), comb. nov.; Ausysium, gen. nov. for A. joyceorum, sp. nov.; Diademadrilus, gen. nov. for D. annulatus (Smithers), comb. nov., for which a description of the female is given, and D. masseyi (New), comb. nov.; Euryphallus, gen. nov. for E. badonneli (New & Thornton), comb. nov., E. cinqueportsae (Thornton & New), comb. nov., E. cooki (Thornton & New), comb. nov., E. defoei (Thornton & New), comb. nov., E. selkirki (Thornton & New), comb. nov., E. skottsbergi (Thornton & New), comb. nov. and E. stigmaticus (Tillyard), comb. nov.; Gondwanapsocus, gen. nov. for G. australis, sp. nov.; Onychophallus, gen. nov. for O. diemenensis, sp. nov.; Psocophloea, gen. nov. for P. sarahae, sp. nov.; Telmopsocus, gen. nov. for T. waldheimensis, sp. nov.; Villopsocus, gen. nov. for V. tasmaniensis, sp. nov., and Weddellopsocus, gen. nov. for W. avius (Smithers), comb. nov., W. carrilloi (Thornton & Lyall), comb. nov., W. flavus (Thornton & Lyall), comb. nov., W. griseus (New & Thornton), comb. nov. and W. valdiviensis (Blanchard), comb. nov. A rediagnosis of Spilopsocus is given, the male of Sabulopsocus tractuosus Smithers is described and Nepiomorpha phragmitella Smithers is transferred to Clinopsocus New. We provide a phylogenetic analysis to assess the monophyly of Elipsocidae. Sixty-one characters are scored for 38 taxa, including the putative new genera and four outgroups. Monophyly of Elipsocidae is supported with the exclusion of four genera: Palmicola Mockford is transferred to Mesopsocidae; Sabulopsocus Smithers and Moapsocus, gen.�nov. for M. angelicus, sp. nov. are placed in the new family Sabulopsocidae; and Drymopsocus Smithers, which is the sister-taxon to Elipsocidae, is incertae sedis. Other taxa previously regarded as elipsocids are reassigned: Elipsocus impressus (Hagen), Elipsocus modestus Banks and Elipsocus boops (Hagen) are redescribed and respectively placed in Valenzuela Navás (Caeciliusidae), Dasydemella Enderlein (Dasydemellidae) and Mesopsocus Kolbe (Mesopsocidae). Lesneia Badonnel is placed in the new family Lesneiidae. The position of Eolachesilla Badonnel is discussed briefly. A key to genera and comment on characters diagnosing the family Elipsocidae is presented. We retain two subfamilies and discuss the merits of our proposed higher classification. A brief biogeographical interpretation suggests that the family has a southern origin and may be as old as the Mesozoic.
The first-instar larva of the genus Arthropterus (Coleoptera : Carabidae : Paussinae): implications for evolution of myrmecophily and phylogenetic relationships within the subfamily
Authors: Giulio Andrea Di , Moore Wendy
Published: May 2004

The first-instar larva of the genus Arthropterus W.S. MacLeay, 1838 is described and illustrated. This is the first description of a newly hatched (first-instar) larva in the myrmecophilous tribe Paussini and the first known larva from a basal paussine lineage. A phylogenetic analysis of the subfamily based on larval characters confirms the placement of the genus Arthropterus as a sister-group of the remaining Paussini and supports the hypothesis that Metriini is the sister-group of Ozaenini+Paussini, with 'Ozaenini' as a paraphyletic group. Within this phylogenetic framework, we reassess which larval characters are diagnostic of the tribes Paussini and Ozaenini. Several larval features of Arthropterus, such as the riddled sensilla S-VIII and the fused terminal disk, are interpreted as adaptations to myrmecophily. This interpretation supports the hypothesis that larvae have played an important role in the evolution of myrmecophily within the subfamily Paussinae.
Uncoupling conformational change from GTP hydrolysis in a heterotrimeric G protein α-subunit
Authors: Thomas Celestine J. , Du Xinlin , Li PiLong , Wang Ying , Ross Elliott M. , Sprang Stephen R.
Published: May 2004

Heterotrimeric G protein α (Gα) subunits possess intrinsic GTPase activity that leads to functional deactivation with a rate constant of ≈2 min
-1
at 30°C. GTP hydrolysis causes conformational changes in three regions of Gα, including Switch I and Switch II. Mutation of G202→A in Switch II of Gα
i1
accelerates the rates of both GTP hydrolysis and conformational change, which is measured by the loss of fluorescence from Trp-211 in Switch II. Mutation of K180→P in Switch I increases the rate of conformational change but decreases the GTPase rate, which causes transient but substantial accumulation of a low-fluorescence Gα
i1
·GTP species. Isothermal titration calorimetric analysis of the binding of (G202A)Gα
i1
and (K180P)Gα
i1
to the GTPase-activating protein RGS4 indicates that the G202A mutation stabilizes the pretransition state-like conformation of Gα
i1
that is mimicked by the complex of Gα
i1
with GDP and magnesium fluoroaluminate, whereas the K180P mutation destabilizes this state. The crystal structures of (K180P)Gα
i1
bound to a slowly hydrolyzable GTP analog, and the GDP·magnesium fluoroaluminate complex provide evidence that the Mg
2+
binding site is destabilized and that Switch I is torsionally restrained by the K180P mutation. The data are consistent with a catalytic mechanism for Gα in which major conformational transitions in Switch I and Switch II are obligate events that precede the bond-breaking step in GTP hydrolysis. In (K180P)Gα
i1
, the two events are decoupled kinetically, whereas in the native protein they are concerted.
Rational design and characterization of a Rac GTPase-specific small molecule inhibitor
Authors: Gao Yuan , Dickerson J. Bradley , Guo Fukun , Zheng Jie , Zheng Yi
Published: May 2004

The signaling pathways mediated by Rho family GTPases have been implicated in many aspects of cell biology. The specificity of the pathways is achieved in part by the selective interaction between Dbl family guanine nucleotide exchange factors (GEFs) and their Rho GTPase substrates. Here, we report a first-generation small-molecule inhibitor of Rac GTPase targeting Rac activation by GEF. The chemical compound NSC23766 was identified by a structure-based virtual screening of compounds that fit into a surface groove of Rac1 known to be critical for GEF specification.
In vitro
it could effectively inhibit Rac1 binding and activation by the Rac-specific GEF Trio or Tiam1 in a dose-dependent manner without interfering with the closely related Cdc42 or RhoA binding or activation by their respective GEFs or with Rac1 interaction with BcrGAP or effector PAK1. In cells, it potently blocked serum or platelet-derived growth factor-induced Rac1 activation and lamellipodia formation without affecting the activity of endogenous Cdc42 or RhoA. Moreover, this compound reduced Trio or Tiam1 but not Vav, Lbc, Intersectin, or a constitutively active Rac1 mutant-stimulated cell growth and suppressed Trio, Tiam1, or Ras-induced cell transformation. When applied to human prostate cancer PC-3 cells, it was able to inhibit the proliferation, anchorage-independent growth and invasion phenotypes that require the endogenous Rac1 activity. Thus, NSC23766 constitutes a Rac-specific small-molecule inhibitor that could be useful to study the role of Rac in various cellular functions and to reverse tumor cell phenotypes associated with Rac deregulation.
Genetic evidence that the human CYP2R1 enzyme is a key vitamin D 25-hydroxylase
Authors: Cheng Jeffrey B. , Levine Michael A. , Bell Norman H. , Mangelsdorf David J. , Russell David W.
Published: May 2004

The synthesis of bioactive vitamin D requires hydroxylation at the 1α and 25 positions by cytochrome P450 enzymes in the kidney and liver, respectively. The mitochondrial enzyme CYP27B1 catalyzes 1α-hydroxylation in the kidney but the identity of the hepatic 25-hydroxylase has remained unclear for >30 years. We previously identified the microsomal CYP2R1 protein as a potential candidate for the liver vitamin D 25-hydroxylase based on the enzyme's biochemical properties, conservation, and expression pattern. Here, we report a molecular analysis of a patient with low circulating levels of 25-hydroxyvitamin D and classic symptoms of vitamin D deficiency. This individual was found to be homozygous for a transition mutation in exon 2 of the CYP2R1 gene on chromosome 11p15.2. The inherited mutation caused the substitution of a proline for an evolutionarily conserved leucine at amino acid 99 in the CYP2R1 protein and eliminated vitamin D 25-hydroxylase enzyme activity. These data identify CYP2R1 as a biologically relevant vitamin D 25-hydroxylase and reveal the molecular basis of a human genetic disease, selective 25-hydroxyvitamin D deficiency.
Emphysema and Metalloelastase Expression in Mouse Lung Induced by Cigarette Smoke
Authors: Valença Samuel Santos , Da Hora Katia , Castro Paulo , Moraes Vera Gonçalves , Carvalho Laís , Cristó Vão De Moraes Sobrino Porto Luís
Published: May 2004

Cigarette smoke (CS) causes pulmonary emphysema in humans and elastin degradation plays a key role in its pathogenesis. Previous studies on CS-exposed animals have been equivocal and have not clearly demonstrated the progression of the disease. In this study, morphometry was used to assess lung modifications to alveolar septa, airspaces, elastic and collagen fibers, and alveolar macrophages. Male (n = 40) C57/BL6 mice were exposed 3 times/day, whole body, to CS from three cigarettes for 10, 20, 30, or 60 days. Control groups (n = 10) were sham-smoked or received no exposure (day 0, n = 10). Morphometry included measurements of volume fraction of alveolar septa and airspaces, elastic and collagen fibers, and surface fraction of elastic fibers and alveolar septa. Morphometrical differences in mice after 60 days of exposure were greater than those after 10, 20, or 30 days, suggesting a progression of the disease. Inflammatory lesions in the lungs of mice contained significantly more metalloelastase (MMP-12) in macrophages at 10, 20, and 30 days than in controls of mice exposed for 60 days. These results suggest that elastin degradation took place during development of pulmonary changes in mice exposed to CS, and activation of MMPs specific for elastin may be a determining factor for susceptibility to emphysema.
The Toxicity of SCH 351591, a Novel Phosphodiesterase-4 Inhibitor, in Cynomolgus Monkeys
Authors: Losco Patricia E. , Evans Ellen W. , Barat Stephen A. , Blackshear Pamela E. , Reyderman Larisa , Fine Jay S. , Bober Loretta A. , Anthes John C. , Mirro Elmer J. , Cuss Francis M.
Published: May 2004

SCH351591, a novel phosphodiesterase-4 inhibitor under investigation as a potential therapeutic for asthma and chronic obstructive pulmonary disease (COPD), was evaluated in a 3-month rising-dose study in Cynomolgus monkeys. Four groups, containing four monkeys/sex, received vehicle control or rising doses up to 12, 24, or 48 mg/kg of SCH351591 daily. Although initial exposure produced clinical signs of emesis, reduced food intake, and reduced body weight, tachyphylaxis to the emesis allowed dose escalation up to 48 mg/kg/day. Two monkeys died and 3 were sacrificed in moribund condition over the course of the study. Early mortality, involving monkeys dosed with 12 or 24 mg/kg, was attributed to sepsis (2 monkeys) or colon inflammation (3 monkeys). Leukocyte function assays on low- and mid-dose group survivors revealed an inhibition of T lymphocyte proliferation for 12 mg/kg group males and 24 mg/kg group monkeys of both sexes. Necropsy findings, unassociated with early mortality, included reduced size and weight of the thymus, depletion of body fat, red discoloration of the gastric mucosa, and perivascular hemorrhage of the stomach and heart. Stomach and heart gross findings were present in the high-dose group only. Histopathologic lesions, in addition to those attributed to concurrent bacterial infection, included thymic atrophy, serous atrophy of fat, myocardial degeneration and acute to chronic inflammation of small to medium-sized arteries in various organs and tissues including the heart, kidneys, stomach, salivary glands, pancreas, esophagus, gallbladder, and mesentery. The findings of this study demonstrate the potential of a PDE4 inhibitor to alter immunologic response as well as to produce arteriopathy in nonhuman primates.
Cardiac Damage in Rodents after Exposure to Bis(2-chloroethoxy)methane
Authors: Dunnick June K. , Lieuallen Warren , Moyer Carolyn , Orzech Denise , Nyska Abraham
Published: May 2004

We report that an environmental agent, bis(2-chloroethoxy)methane (CEM), caused cardiac toxicity in male and female F344 rats and B6C3F1 mice exposed to the chemical by dermal administration at doses of 0, 50, 100, 200, 400 or 600 mg/kg 5 days a week for up to 14 weeks. Treatment-related deaths occurred in 10/10 male and 10/10 female rats at 600 mg/kg, in 2/10 female rats at 400 mg/kg, and in 3/10 female mice at 600 mg/kg. The heart lesions were more severe in rats than mice, and more severe in females than males. In rats, the no-observed-adverse-effect level (NOAEL) for the heart lesions was 200 mg/kg for males and 100 mg/kg for females; in mice, it was more than 600 mg/kg for males and 200 mg/kg for females. Multifocal, widespread vacuolization of the myocytes comprised the main morphological feature of the lesions, and only in rats was it accompanied by mononuclear cell infiltration, myocytic necrosis and atrial thrombosis. Hearts from male rats were immunohistochemically stained for troponin T (cTnT) protein. Loss of cytoplasmic cTnT correlated with histopathological damage only in the 600 mg/kg animals. CEM is metabolized to thiodiglycolic acid, a chemical that causes mitochondrial dysfunction. It is hypothesized that mitochondrial damage leads to the heart toxicity from bis(2-chloroethoxy)methane.
Pathophysiological Effects of Chronic Toxicity with Synthetic Pyrethroid, Organophosphate and Chlorinated Pesticides on Bone Health of Broiler Chicks
Authors: Garg Umesh K. , Pal Asim K. , Jha Gautam J. , Jadhao Sanjay B.
Published: May 2004

This experiment evaluated effects following chronic toxicity with 20 ppm fenvalerate (synthetic pyrethroid), 2 ppm monocrotophos (organophosphate) and 2 ppm endosulfan (chlorinated hydrocarbon) on bone health of broiler chicks. A total of 120 chicks were divided equally into 4 groups and were fed poultry mash without (control) or mixed with different pesticides for 8 weeks. Body mass, serum calcium and phosphorus levels were unaffected due to pesticides treatment. However, an increase ( p < 0 .01) in serum alkaline phosphatase activity was noted and serum total protein decreased ( p < 0 .01) in all treated groups. Roentogenography revealed destructive changes in the upper part of the femur in the monocrotophos group. Endosulfan intoxicated chicks had increased numbers of trabeculae in the medullary cavity. Microscopic alterations of the costochondral junction in intoxicated chicks were similar. The zones of proliferating, maturing and degenerating, and calcifying cartilage cells were reduced in width and the metaphysis in treated birds showed a reduced number of cartilage cells and thinner trabeculae. Due to toxicity, the capillary scaffolding of the degenerating cartilage cells was reduced and a larger number of transverse trabeculae could be seen in the metaphysis. Appositional bone growth studied by the tetracyclicline labeling technique indicated decreased active osteons.
Epididymal and Systemic Phospholipidosis in Rats and Dogs Treated with the Dopamine D3 Selective Antagonist PNU-177864
Authors: Rudmann Daniel G. , Mcnerney Mary E. , Vandereide Stacey L. , Schemmer Joyce K. , Eversole Robert R. , Vonderfecht Steven L.
Published: May 2004

Repeat dose oral toxicity studies were conducted in rat and dog to assess the safety for human clinical testing of the potent dopamine D3 receptor antagonist, PNU-177864. Systemic phospholipidosis was the principal treatment-related change with epididymal epithelial cell phospholipidosis being the most prominent finding in rats and dogs. Epididymal epithelial cells had no histologic evidence of degeneration; sperm density and morphology were normal histologically in both species; and sperm concentration, morphology, and motility in the dog were comparable to dogs given vehicle. Other sites with phospholipidosis included lymphoid tissues (lymph nodes, Peyer's patches, and/or spleen), pulmonary alveolar macrophages, and peripheral blood lymphocytes in rats and dogs and adrenal cortex, liver, pituitary, hair follicles, bone marrow lymphocytes and plasma cells, and skeletal muscle in rats only. The phospholipidosis was resolved after a 6-week recovery period in all tissues but epididymis. There was no evidence of cell injury in tissues that had phospholipid accumulations except in rat skeletal muscle that had multifocal myofiber degeneration and necrosis. For clinical trials, serum AST and CK and peripheral blood lymphocyte vacuolation were considered potential safety biomarkers for skeletal muscle degeneration and phospholipidosis, respectively.
Characterization of Bronchiolar Metaplasia of the Alveolar Epithelium in Female Sprague—Dawley Rats Exposed to 3,3',4,4',5-Pentachlorobiphenyl (PCB126)
Authors: Brix Amy E. , Jokinen Michael P. , Walker Nigel J. , Sells Donald M. , Nyska Abraham
Published: May 2004

To test the dioxin toxic equivalency factor methodology, the National Toxicology Program conducted a series of 2-year rat bioassays of dioxin-like compounds. Following gavage exposure of female Harlan Sprague—Dawley rats to 2,3',4,4',5-pentachlorobiphenyl (PCB126), pulmonary alveolar epithelium at the junction of terminal bronchioles and along alveolar ducts was replaced by cuboidal to columnar ciliated cells. Scattered among these were cells exhibiting characteristics consistent with those of Clara cells; they lacked cilia and had a smooth apical surface that protruded into the alveolar space. This lesion was not typical of alveolar epithelial hyperplasia seen in rodent lungs; therefore, studies were done to characterize the lesion. Results of periodic acid-Schiff (PAS) staining, alcian blue (AB) staining, and GSTPi immunohistochemical staining of the lesions seen in treated rats were more similar to normal bronchiolar epithelium than normal alveolar epithelium or alveolar epithelial hyperplasia. These findings, along with the morphology of the cells, provide evidence that this lesion is closer in character to bronchiolar epithelium than alveolar type I or alveolar type II epithelium, and as a result, was called bronchiolar metaplasia.
Changes in Bronchoalveolar Lavage Cells after Intratracheal Instillation of Dimethyl Selenide in Mice
Authors: Cherdwongcharoensuk Duangrudee , Upatham Suchart , Oliveira José Carlos , Sousa Pereira António , Águas Artur P.
Published: May 2004

CD-1 mice were exposed to a single intratracheal instillation of either 0.025 or 0.075 mg Se/kg wt of dimethyl selenide (DMSe). They were studied over 4 weeks to define the cellular inflammatory response of the airways to DMSe. Bronchoalveolar (BAL) lavage was used to collect the DMSe-induced inflammatory exudates. The DMSe instillation resulted in phlogistic responses that had the neutrophil as the main leukocyte; they were present in BAL samples, mostly at days 1 and 7. Macrophages were also increased during DMSe-induced inflammation. The lower DMSe dose resulted in an inflammatory reaction lasting for 2 weeks. Mice treated with the higher DMSe dose still showed elevated numbers of neutrophils and macrophages 4 weeks after instillation. DMSe did not change the number of lymphocytes harvested from the airways. An early increase in total protein of BAL, and late enhancement in lactate dehydrogenase was observed in mice treated with the high DMSe dose. We conclude that inhalation of DMSe triggers a moderate and dose-dependent inflammatory reaction in the mouse airways, and that this phlogistic reaction is likely to participate in the damage of respiratory epithelia that occurs upon DMSe inhalation.
Specificity of Co-Promoting Effects of Caffeine on Thyroid Carcinogenesis in Rats Pretreated with N-Bis(2-hydroxypropyl)nitrosamine
Authors: Son Hwa-Young , Nishikawa Akiyoshi , Okazaki Kazushi , Kitamura Yasuki , Kanki Keita , Lee Kyong-Youl , Umemura Takashi , Hirose Masao
Published: May 2004

The specificity of copromotion effects of caffeine with known goitrogenic factors on thyroid carcinogenesis was examined in rats pretreated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). Male F344 rats were divided into 8 groups, each consisting of 10 animals, and received a single sc injection of 2,800 mg/kg DHPN. From one week after the DHPN initiation, they were given basal diet, iodine deficiency (ID) diet, 500 ppm phenobarbital (PB) solution or 1,000 ppm sulfadimethoxine (SDM) solution with or without 1,500 ppm caffeine feeding for 12 weeks. The caffeine, PB, SDM, and ID treatments significantly ( p < 0 .05 or 0.01) increased the relative thyroid weights, and the increases with PB or ID were further ( p < 0 .05 or 0.01) enhanced in combination with caffeine. SDM drastically promoted thyroid carcinogenesis in association with increased serum TSH levels regardless of the caffeine treatment. Thyroid follicular carcinomas and adenomas were more frequently observed in the additional caffeine groups than in the ID alone groups. The incidence and multiplicity of focal thyroid follicular hyperplasias in the ID-treated groups were significantly ( p < 0 .05 and 0.01) elevated in the case of combination with caffeine. Increases in serum TSH levels with PB or ID were also further enhanced in combination with caffeine. Serum thyroid hormone levels were significantly ( p < 0 .01) decreased by SDM but significantly ( p < 0 .05 or 0.01) increased by caffeine, PB or ID. Our results clearly indicate that dietary caffeine at a high dose of 1,500 ppm interacts with ID, but neither SDM nor PB, to promote rat thyroid carcinogenesis although the combined caffeine + PB treatment somewhat affected thyroid weights as well as thyroid hormone levels.
Functional analysis of the transcriptional activator XlnR from Aspergillus niger
Authors: Hasper Alinda A. , Trindade Luisa M. , van der Veen Douwe , van Ooyen Albert J. J. , de Graaff Leo H.
Published: May 2004

The transcriptional activator XlnR fromAspergillus nigeris a zinc binuclear cluster transcription factor that belongs to the GAL4 superfamily. Several putative structural domains in XlnR were predicted using database and protein sequence analysis. Thus far, only the functionality of the N-terminal DNA-binding domain has been determined experimentally. Deletion mutants of thexlnRgene were constructed to localize the functional regions of the protein. The results showed that a putative C-terminal coiled-coil region is involved in nuclear import of XlnR. After deletion of the C-terminus, including the coiled-coil region, XlnR was found in the cytoplasm, while deletion of the C-terminus downstream of the coiled-coil region resulted in nuclear import of XlnR. The latter mutant also showed increased xylanase activity, indicating the presence of a region with an inhibitory function in XlnR-controlled transcription. Previous findings had already shown that a mutation in the XlnR C-terminal region resulted in transcription of the structural genes under non-inducing conditions. A regulatory model of XlnR is presented in which the C-terminus responds to repressing signals, resulting in an inactive state of the protein.