bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of potassium and calcium deficiencies on stomatal functioning in intact leaves of Vicia faba
Authors: Ridolfi Michèle , Garrec Jean Pierre , Louguet Philippe , Lafray Daniel
Published: December 2007

The effects of potassium or calcium deficiency on stomatal functioning were investigated in Vicia faba L. plants grown hydroponically. In the leaves of plants grown with 1 mM K+, stomatal opening occurred in light with either normal or CO2-free air; K+ and C1− accumulations in guard cells were similar to those of the control plants grown with 5 mM K+. With the zero K+ treatment, stomatal apertures were not affected, while K+ and Cl− guard cell concentrations fell to 30% of the control values. These results may indicate that other solutes contribute to the lowering of osmotic potential during opening. Stomata of calcium-deficient plants remained fully open in darkness, whereas abscisic acid (ABA) supply induced a partial stomatal closing movement. Therefore, calcium deficiency inhibited the process(es) linked with the perception of darkness and stomatal closure. On the other hand, stomatal sensitivity to ABA was only partially affected. Key words: stomatal aperture, potassium, calcium, X-ray microanalysis.
La phénologie des arbres caducifoliés en forêt guyanaise (5° de latitude nord) : illustration d'un déterminisme à composantes endogène et exogène
Authors: Loubry Denis
Published: December 2007

The French Guianan forest is an evergreen rain forest that contains approximately 100 deciduous tree species. The taxonomical distribution of the deciduous character is widely spread, and its presence or absence among some taxa, as well as its ancient origin, are arguments in favour of an endogenous origin. Leaf-fall periodicity was studied on a sample of 500 trees during a 2-year period. Periodicity is annual and seasonal. It is not correlated to rainfall and not linked to the occurrence of a dry season. It seems closely correlated to photoperiodical variations, even though those variations are weak (35 min at latitude 5°30′N). However, each tree has its own periodicity for leaves shedding. Therefore, there is a paradox between seasonality and individual periodicity of leaf fall. The existence of this paradox leads us to consider the hypothesis of an integration of endogenous and exogenous components in the determination of leaf-fall periodicity. Key words: deciduousness, French Guiana, phenology, photoperiodism, tree, tropical rain forest.
GENERIC ENZYMATIC RATE EQUATION UNDER LIVING CONDITIONS
Authors: LEE L. W. , YIN L. , ZHU X. M. , AO P.
Published: December 2007

Based on our experience in kinetic modeling of coupled multiple metabolic pathways, we propose a generic rate equation for the dynamical modeling of metabolic kinetics. It is symmetric for forward and backward reactions. Its Michaelis-Menten-King-Altman form makes the kinetic parameters (or functions) easy to relate to experimental values in the database and to use in computation. In addition, such a uniform form is ready to arbitrary number of substrates and products with different stiochiometry. We explicitly show how to obtain such rate equations rigorously for three well-known binding mechanisms. Hence, the proposed rate equation is formally exact under the quasi-steady state condition. Various features of this generic rate equation are discussed. In particular, for irreversible reactions, the product inhibition which directly arises from enzymatic reaction is eliminated in a natural way. We also discuss how to include the effects of modifiers and cooperativity.
A MATHEMATICAL MODEL FOR THE EFFECT OF TOXICANT ON THE IMMUNE SYSTEM
Authors: DUBEY UMA S. , DUBEY BALRAM
Published: December 2007

In this paper, a nonlinear mathematical model is proposed and analyzed to study the effect of environmental toxicant on the immune response of the body. Criteria for local stability, instability and global stability are obtained. It is shown that the immune response of the body decreases as the concentration of environmental toxicant increases, and certain criteria are obtained under which it settles down at its equilibrium level. In the absence of toxicant, an oscillatory behavior of immune system and pathogenic growth is observed. However, in the presence of toxicant, oscillatory behavior is not observed. These studies show that the toxicant may have a grave effect on our body's defense mechanism.
THREE TYPES OF SIMPLE DDE'S DESCRIBING TUMOR GROWTH
Authors: BODNAR MAREK , FORYŚ URSZULA
Published: December 2007

In this paper, we compare three types of dynamical systems used to describe tumor growth. These systems are defined as solutions to three delay differential equations: the logistic, the Gompertz and the Greenspan types. We present analysis of these systems and compare with experimental data for Ehrlich Ascites tumor in mice.
AN IMPROVEMENT OF THE HOLLING TYPE III FUNCTIONAL RESPONSE IN ENTOMOPHAGOUS SPECIES MODEL
Authors: CABELLO T. , GÁMEZ M. , VARGA Z.
Published: December 2007

In this study, we analyze the functional response for a parasitoid-host and a predator-prey system, as a tool of biological control of pests to evaluate the potential of bio-control agents. A possible biological interpretation was given to the adjustment coefficients of type I and II functional response by Hassell.1Based on this, we propose new expressions for type III in terms of a new parameter that we call entomophagous potential (parasitoid or predator), providing examples using actual data from trials carried out previously for parasitoid species Chelonus blackburni Cameron (Hym.: Braconidae) and predator species Joppeicus paradoxus Puton (Het.: Joppeicidae). The novelty of the paper consists in the fact that these new expressions for Holling type III functional response have a biological interpretation, and result in a better fit to data than Hassel's model.
AN UNSUPERVISED PATTERN (SYNDROME IN TRADITIONAL CHINESE MEDICINE) DISCOVERY ALGORITHM BASED ON ASSOCIATION DELINEATED BY REVISED MUTUAL INFORMATION IN CHRONIC RENAL FAILURE DATA
Authors: CHEN JIANXIN , XI GUANGCHENG , CHEN JING , ZHEN YISONG , XING YANWEI , WANG JIE , WANG WEI
Published: December 2007

The syndrome is the basic pathological unit and the key concept in traditional Chinese medicine (TCM), and the herbal remedy is prescribed according to the syndrome a patient catches. Nevertheless, few studies are dedicated to investigate the number of syndromes in chronic renal failure (CRF) patients and what these syndromes are. In this paper, we carry out a clinical epidemiology survey and obtain 601 CRF cases, including 72 symptoms in each report. Based on association delineated by mutual information, we propose a novel pattern discovery algorithm to discover syndromes, which probably have overlapped symptoms in TCM. A revised version of mutual information is presented here to discriminate positive and negative association. The algorithm self-organizedly discovers 16 effective patterns, each of which is verified manually by TCM physicians to recognize the syndrome it belongs to. The super-additivity of cluster by mutual information is proved and n-class association concept is introduced in our model to reduce computational complexity. Validation of the algorithm is performed by using the syndrome data and consolidated clinically to have 16 patterns. The results indicate that the algorithm achieves a high sensitivity with 96.48% and each classified pattern is of clinical significance. Therefore, we conclude that the algorithm provides an excellent solution to chronic renal failure problem in the context of traditional Chinese medicine.
APPLICATION OF AUTO REGRESSIVE MODELS OF WAVELET SUB-BANDS FOR CLASSIFYING TERAHERTZ PULSE MEASUREMENTS
Authors: YIN XIAOXIA , NG BRIAN W.-H. , ABBOTT DEREK , FERGUSON BRADLEY , HADJILOUCAS SILLAS
Published: December 2007

This paper presents an approach for automatic classification of pulsed Terahertz (THz), or T-ray, signals highlighting their potential in biomedical, pharmaceutical and security applications. T-ray classification systems supply a wealth of information about test samples and make possible the discrimination of heterogeneous layers within an object. In this paper, a novel technique involving the use of Auto Regressive (AR) and Auto Regressive Moving Average (ARMA) models on the wavelet transforms of measured T-ray pulse data is presented. Two example applications are examined — the classification of normal human bone (NHB) osteoblasts against human osteosarcoma (HOS) cells and the identification of six different powder samples. A variety of model types and orders are used to generate descriptive features for subsequent classification. Wavelet-based de-noising with soft threshold shrinkage is applied to the measured T-ray signals prior to modeling. For classification, a simple Mahalanobis distance classifier is used. After feature extraction, classification accuracy for cancerous and normal cell types is 93%, whereas for powders, it is 98%.
The In-Medium \barK NInteraction within a Chiral Unitary Approach
Authors: Tolós Laura , Ramos Angels , Oset Eulogio
Published: December 2007

The s- and p-wave contributions to the \barK N interaction in dense nuclear matter are obtained using a chiral unitary approach. We perform a self-consistent calculation of the \barK self-energy including Pauli blocking effects, meson self-energies modified by short-range correlations and baryon binding potentials. We find that the on-shell factorization cannot be applied to evaluate the in-medium corrections to p-wave amplitudes. Furthermore, the Λ and Σ develop a mass shift of -30 MeV at saturation density while the Σ* width increases to 80 MeV. We conclude that no deep and narrow \barK bound states could be observed.
Regge Pole Model and Hadron Physics
Authors: Hara Yasuo
Published: December 2007

The Regge pole model of hadron physics is surveyed. Kinematical properties of helicity amplitudes (symmetry properties, crossing relations and analyticity properties), Reggeization of helicity amplitudes, the MacDowell symmetry and the factorization of Regge residues are discussed. We also study the Pomeron, the vector- and tensor-trajectories and the pseudoscalar trajectories. Inclusive reactions in the Regge pole model are briefly discussed.
Asymmetry of Beta-Ray Angular Distribution in Polarized 12B and 12N and Second-Class Current
Authors: Morita Masato , Nishimura Mitiaki , Shimizu Asao , Ohtsubo Hisao , Kubodera Kuniharu
Published: December 2007

An explicit formula for beta-ray angular distribution in the decay of polarized nuclei is given by taking into account the radiative corrections, Coulomb corrections of the finite-size nucleus, weak magnetisim, induced pseudoscalar, second-class induced tensor, and contributions of the d-wave leptons. Generally speaking, the radiative corrections are almost the same for P0 (cosθ) and P1 (cosθ) terms. In particular, the logarithmic divergence disappears for the asymmetry factor in the case of the Gamow-Teller transitions. And the effect of the induced pseudoscalar current is extremely small. Experimental data on the beta decays of polarized 12B and 12N are carefully investigated, and it is shown that these data are in favor of the existence of the second-class induced tensor current. Contributions of the ∫(σ·r)r and ∫σr2 terms, which are evaluated with available nuclear models, are found to be negligible. The effect of the exchange currents is also discussed in connection with the elementary particle treatment of the nuclear beta decay.
Insights in the Neoproterozoic–Early Cambrian transition of NW Argentina: facies, environments and fossils in the proto-margin of western Gondwana
Authors: Aceñolaza G. , Aceñolaza F.
Published: December 2007

In NW Argentina, over 3000 metres of highly tectonized and metamorphosed siliciclastics of the Puncoviscana Formation underlie the more fossiliferous Cambro–Ordovician strata of the Mesón and Santa Victoria groups. Historically regarded as the non-fossiliferous ‘basal Precambrian shield’ of the region, its age was later found to be in part Phanerozoic, with the discovery of Early Cambrian trace fossils, and more recently refined with geochronological data. Widespread siliciclastic deposits characterize this sequence. A review of trace fossils in the Puncoviscana Formation has added new taxa. Trace fossil assemblages denote? geographical belts, indicating shallower marine conditions to the east (
Nereites
association) and deeper to the west (
Oldhamia
association). Such assemblages related to the palaeomorphology of the basin also represent different temporal levels, and in so doing reflect the overall evolution of the Puncoviscana Sea through time. The use of taxa that characterize Siberian stages in order to date parts of the Puncoviscana Formation should be abandoned as Siberian stages are defined by a specific set of fossils that are absent in the strata of NW Argentina. Thus, careful systematic studies and re-evaluation of the strata and fauna in the Puncoviscana Basin are the only way to improve understanding of the Neoproterozoic–Cambrian transition in the Andean margin of South America.
First Early Cambrian Radiolaria
Authors: Braun A. , Chen J. , Waloszek D. , Maas A.
Published: December 2007

Radiolarian skeletons are known from a limestone concretion collected from a black shale succession and from black cherts of the Yangtze Platform, China. Both occurrences are of earliest Cambrian age. The findings, reported in this paper, represent the oldest known fossil Radiolaria. Their spherical skeletons display a morphology typical of spherical radiolarians from Ordovician and younger faunas. This occurrence of radiolarians with radial symmetry and, most probably, a planktonic lifestyle can now be traced back into the earliest Cambrian. Thus, radiolarians have been part of the early oceanic plankton and likely played a significant role in the silica cycle of the oceans along with siliceous sponges.
Ventogyrus
, a possible siphonophore-like trilobozoan coelenterate from the Vendian Sequence (late Neoproterozoic), northern Russia
Authors: Fedonkin M. A. , Ivantsov A. Y.
Published: December 2007

Complex internal anatomy is documented for the first time in a Neoproterozoic soft-bodied invertebrate. New data suggests that
Ventogyru
s, originally described as a sessile, boat-shaped form belonging to the enigmatic Neoproterozoic group Petalonamae, is actually composed of three, identical modules, arranged around an axial rod. Each module has one longitudinal and numerous transverse septa, which delimit chambers of decreasing size from one end to the other. Three distinct longitudinal channels with alternating lateral branches make up an internal network, perhaps a circulatory system.
Ventogyrus
is a most unusual form, particularly in the quality of its three dimensional preservation of a complex internal structure and a three-fold symmetry, a symmetry shared by many Ediacarans.
Morphology and taphonomy of an Ediacaran frond:
Charnia
from the Avalon Peninsula of Newfoundland
Authors: Laflamme M. , Narbonne G. M. , Greentree C. , Anderson M. M.
Published: December 2007

The Ediacaran frond
Charnia
, known mainly from fragmentary leaf-like fronds from around the world, is represented by completely preserved specimens with holdfasts in the Mistaken Point biota of Newfoundland. Previous reconstructions of
Charnia
from two-dimensional impressions were significantly oversimplified, resulting in three-dimensional reconstructions which highlighted a sheet-like morphology. Overlapping relationships and internal structures are rarely (if ever) preserved, and only through detailed photography together with both landmark and traditional morphometric analyses of numerous complete
Charnia
specimens can the preservational biases be removed.
Charnia
is reinterpreted here as having a series of individual overlapping primary branches attached to an internal central stalk, and with individual branches constrained by an internal, organic skeleton and/or attachments between adjacent branches. Three species,
C. masoni
Ford 1958
,
C. wardi
Narbonne & Gehling 2003
, and
C. antecedens
sp. nov. can be distinguished on the basis of length/width ratios and the degree of attachment of adjacent branches. Morphological, taphonomical, and ecological studies at Mistaken Point imply that
Charnia
was a sessile, epibenthic frond that fed from suspension in this deep-water volcaniclastic setting. Evolution of more rigorous connections between the primary branches allowed
Charnia
to migrate into more turbulent, shallower-water habitats by the late Ediacaran.
Comparative taphonomy of Vendian genera
Beltanelloides
and
Nemiana
: taxonomy and lifestyle
Authors: Leonov M. V.
Published: December 2007

Taphonomic analysis of new material from Vendian sequences of the White Sea and southwestern Ukraine provides data for a better definition of both the widely distributed fossil taxa of
Beltanelloides
and
Nemiana.
A new type of
Beltanelloides
preservation is described, so it is now possible to attribute some sandstone imprints to this taxon.
Nemiana simplex
seems to have a lifestyle and level of body organization comparable with that of sponges. The narrow range of facies in which
Nemiana
occurs, when compared to the much broader range of
Beltanelloides
, is compelling evidence for a benthic lifestyle of
Nemiana
.
Vendian
Hiemalora
from Arctic Siberia reinterpreted as holdfasts of benthic organisms
Authors: Serezhnikova E. A.
Published: December 2007

Hiemalora
Fedonkin, 1982 is based on cosmopolitan fossils of the late Vendian (Ediacaran) Neoproterozoic sequences. There is no consensus on the nature and systematic position of these organisms. Taphonomic and morphological observations of extensive collections of
Hiemalora pleiomorphus
from Khatyspyt Formation (Arctic Siberia) indicate that this fossil is just a part of an unknown organism. Most probably
Hiemalora
represents a form with a thick-walled body, possessing a cone-like attachment bearing radial processes that resemble sponge root offshoots or algal rhizoids. Originally these structures penetrated the soft sediment and served as anchors as well as a source of symbiotic nutrition. Various imprints of
Hiemalora
could represent different sections of conic-shaped bodies. Probably, there were several organisms referred to as
Hiemalora
that had a similar substrate attachment organ.
A new reconstruction of
Protolyellia
(Early Cambrian psammocoral)
Authors: Savazzi E.
Published: December 2007

A new reconstruction of
Protolyellia
(psammocoral) from the Mickwitzia sandstone, Early Cambrian of south-central Sweden, is proposed. Observations, conceptual analysis and physical modelling indicate that the distinctive honeycomb or (less frequently) ridge sculpture of the upper side of the sand-button was a wrinkle pattern in a flexible epithelium. Wrinkling was caused by contraction of a subepithelial muscle layer joined to the epithelium by connective tissue. Fine-grained sand particles adhering on, or embedded within, the epithelium preserved its surface relief after the soft parts decomposed. The sand-bearing epithelium covered a subcylindrical structure attached around the periphery of the sand-button and extending upwards. This structure is occasionally preserved felled horizontally near a sand-button, but is more commonly found as isolated shreds. Sudden burial caused the lower portion of this structure to contract and wrinkle against the tissues containing the sand-button. After the soft parts decomposed, sediment compaction pasted the wrinkled layer onto the sand-button, thus producing the typical preservation mode. The wrinkle pattern of
Protolyellia
differs from those of Recent cnidarians, and suggests that
Protolyellia
did not possess mesenteries.
Protolyellia
may be more distantly related to modern cnidarians than previously assumed. In addition, alternative affinities with Ediacaran frond-bearing forms cannot be excluded.
Poriferan paraphyly and its implications for Precambrian palaeobiology
Authors: Sperling E. A. , Pisani D. , Peterson K. J.
Published: December 2007

Well-supported molecular phylogenies, combined with knowledge of modern biology, can lead to new inferences about the sequence of character acquisition in early animal evolution, the taxonomic affinity of enigmatic Precambrian and Cambrian fossils, and the Proterozoic Earth system in general. In this paper we demonstrate, in accordance with previous molecular studies, that sponges are paraphyletic, and that calcisponges are more closely related to eumetazoans than they are to demosponges. In addition, our Bayesian analysis finds the Homoscleromorpha, previously grouped with the demosponges, to be even more closely related to eumetazoans than are the calcisponges. Hence there may be at least three separate extant ‘poriferan’ lineages, each with their own unique skeleton. Because spiculation is convergent within ‘Porifera’, differences between skeletonization processes in enigmatic Cambrian taxa such as
Chancelloria
and modern sponges does not mean that these Problematica are not organized around a poriferan body plan, namely a benthic, sessile microsuspension feeding organism. The shift from the anoxic and sulphidic deep ocean that characterized the mid-Proterozoic to the well-ventilated Phanerozoic ocean occurs before the evolution of macrozooplanton and nekton, and thus cannot have been caused by the advent of faecal pellets. However, the evolution and ecological dominance of sponges during this time interval provides both a mechanism for the long-term generation of isotopically-light CO
2
that would be recorded in carbon isotopic excusions such as the ‘Shuram’ event, and an alternative mechanism for the drawdown and sequestration of dissolved organic carbon within the sediment.
Towards a morphospace for the Ediacara biota
Authors: Antcliffe J. B. , Brasier M. D.
Published: December 2007

The Ediacara biota of the late Neoproterozoic is justly famous as a biological puzzle. Studies of Ediacaran biology have commonly used analogy with living organisms as a cipher for the decoding of biological affinity, and consequently the life mode and habit. Here, we discuss the problems of using such analogous reasoning and put forward our alternative approach, that of using Morphospace Analysis for the study of growth, form and phylogeny. This tool, we suggest, has the potential to be used for testing the unity of an evolutionary clade, such as ‘rangeomorphs’ and ‘dickinsoniomorphs’. Preliminary data from the members of the Ediacara biota do indeed show such a unity within our preliminary morphospace model (all
k
values are low). This method reveals no clear relationships, between these forms and more recent biological groups such as the sea pens or the Foraminifera.
The nature of vendobionts
Authors: Seilacher A.
Published: December 2007

The notion that the majority of Ediacaran fossils do not represent stem groups to modern metazoan phyla is now increasingly accepted. Nevertheless, the further claim of the vendobiont hypothesis needs to be elaborated: that these large and seemingly complex organisms were not truly multicellular. Arguments for interpreting vendobionts as an extinct class of rhizopodan Protozoa are: (1) negative allometry of the quilts; (2) presence of a loosely englutinated, but sandy fill skeleton similar to the xenophyophorian stercomare; (3) a disparity of designs and lifestyles that would be incompatible with metazoan bauplans and feeding strategies; (4) unusual patterns of regeneration; (5) resting traces of some mobile, epibenthic species.
Theoretical morphology of quilt structures in Ediacaran fossils
Authors: Tojo B. , Saito R. , Kawakami S. , Ohno T.
Published: December 2007

Vendobiont type fossils are characterized by possessing ‘gliding symmetry’, in which quilts of the different vanes consisting the body of the Vendobionta meet along the seam with small offset. Because two, three or more vanes are joined along this seam and the quilts of different vanes can be variously offset along the seam, a variety of gliding symmetry exists among Vendobionta. Our theoretical consideration here predicts that the number of possible gliding symmetry is one, two and three for organisms having two, three and four vanes, respectively. We also predict that a special combination of morphological types appear alternatively during the growth of the Vendobionta with two vanes. Further, we were able to identify the existence of two types in gliding symmetry predicted by us for
Pteridinium
specimens with three vanes. Detailed examination of the gliding symmetry of other Vendobionta, therefore, may give important clues in solving riddles veiling the vendobiont relationships.
The Verdun Syndrome: simultaneous origin of protective armour and infaunal shelters at the Precambrian–Cambrian transition
Authors: Dzik J.
Published: December 2007

All of the structurally identifiable latest Ediacaran and earliest Cambrian infaunal trace fossils represent shelters of animals feeding above the sediment surface. It is the case with the most complete and oldest radiometrically dated Precambrian–Cambrian transition strata along the Khorbusuonka River in northern Siberia, in the basal Cambrian succession at Meishucun in southern China, richest in small shelly fossils, as well as in the type succession of the Vendian in Podolia, Ukraine. The oldest traces of feeding within the mud are known from no earlier than the late Tommotian of Siberia, Mongolia, Sweden, and Poland. This suggests that the invention of hydraulic mechanisms of sediment penetration was enforced by predation, not by trophic needs. Various ways to protect the body by secretion of a mineral skeleton or building tubes by collected mineral grains were developed by other animals at the same time. Predation may thus appear to be the triggering mechanism for the ‘Cambrian explosion’. Subsequent increase in the depth of bioturbation resulted in a profound change of taphonomic conditions, artificially enhancing the effects of evolution.
The Cambrian ‘basement’ of gastropod evolution
Authors: Parkhaev P. Y.
Published: December 2007

The oldest gastropods are known from the uppermost Nemakit-Daldynian to lowermost Tommotian deposits. However, to trace ancestry before this time, when most metazoans did not possess shells, is difficult. Study of the oldest gastropods, diagnosed and discussed here, sheds some light on the earliest stages of evolution of major gastropod branches. It appears that the subclass Archaeobranchia served as the base for this early radiation.
Fleshing out the Ediacaran period
Authors: Gehling J. G.
Published: December 2007

The Flinders Ranges Ediacaran succession preserves an apparently primary palaeomagnetic record, distinctive stratigraphic events such as the Acraman ejecta layer, and fossils of the Ediacara biota at three well-separated levels. The fossil assemblage of the Ediacara Member includes both trace fossils and body fossils, and shares at least 65% of its taxa with the White Sea assemblages in northern Russia, suggesting they were coeval. Globally, Ediacaran successions are diverse in their lithostratigraphy but share many characteristics of biota, isotope signatures and events which can be calibrated with radiometric dating. Available radiometric dating of Ediacaran successions supports the concept of distinct Avalon (575 Ma–565 Ma), White Sea (558 Ma–555 Ma) and Nama (549 Ma–543 Ma) associations as a temporal succession rather than being controlled by environment or palaeobiogeography. The challenge to document the tempo and pattern of evolution of early animals and the associated changes in global climate make the subdivision and calibration of the Ediacaran a vital task for the next decade.
Microstratigraphy of the Late Ediacaran to the Ordovician in NW Iran (Takab area)
Authors: Jafari S. M. , Shemirani A. , Hamdi B.
Published: December 2007

Platform sediments of Iran span the Late Ediacaran and extend into the Palaeozoic. They are primarily clastic and carbonaceous in nature, deposited in coastal and lagoonal settings. They crop out in the Takab area, as the Soltanieh Formation (Late Proterozoic to Atdabanian), the Barut Formation (Early Bottomian), the Zaigun Formation (Middle Bottomian), the Lalun Formation (Late Bottomian) and the Mila Formation (Middle Cambrian to Early Ordovician). A Precambrian–Cambrian assemblage has been identified at the base of Member 3 and the top of Member 2 in the Soltanieh Formation. The Soltanieh Formation consists of shallow marine sediments. Vertical microfacies variation reflects two regressive sequences, the earliest Cambrian System being a regressive cycle. The presence of
Chuaria
and
Vendotaenia
in the Soltanieh Formation allows correlation of Iranian sequences to those elsewhere in the world, indicating a late Neoproterozoic age. Detailed facies analyses of the Soltanieh, Barut, Zaigun, Lalun, and Mila formations allow refined palaeoenvironmental reconstructions to be made for the Ediacaran–Cambrian/Ordovician in Iran.
Sprigg, Glaessner and Wade and the discovery and international recognition of the Ediacaran fauna
Authors: Turner S. , Vickers-Rich P.
Published: December 2007

Reg Sprigg was a young geologist when he found Ediacaran fossils in the hills of the western Flinders Ranges of South Australia. At first not taken seriously by his mentors, the reality of his fossils and the true age of his finds were recognized by the late 1940s.

Research on these oldest known metazoans of the time was then carried out by Martin Glaessner and his student, Mary Wade, who first studied Foraminifera. Sprigg was not included in this research but took a different path pursuing a career as an economic geologist and founding Santos. Wade and Glaessner interpreted their Ediacaran fossils as worms and jellyfish, but more recent interpretations have led to very different conclusions.
Saline giants, cold cradles and global playgrounds of Neoproterozoic Earth: the origin of the Animalia
Authors: Rich P. Vickers
Published: December 2007

It is still an enigma of just what triggered the development of multicellular animals, the metazoans. The rise of oxygen has commonly been suggested as the cause, which probably had a marked effect. But why do the metazoans seem to appear in the fossil record, with some diversity, in the late Neoproterozoic around 575–580 million years ago? Perhaps the sudden appearance is related to a rapid expansion of metazoans into global oceans as they became markedly less saline with the deposit of saline giants in the Neoproterozoic. Metazoans may well have developed first in ‘cold cradles’ in deltaic and estuarine conditions earlier, when seas were more saline, and with the removal of salts from the global oceans, the seas became their ‘global playgrounds’ and with this invasion the fossil record improved significantly. Such an idea can only be tested with more precise dating of the saline giants themselves.
Ediacaran rocks from the Cadomian basement of the Saxo-Thuringian Zone (NE Bohemian Massif, Germany): age constraints, geotectonic setting and basin development
Authors: Linnemann U.
Published: December 2007

This paper is focused on a compilation of known data from the low-grade metamorphosed rocks of the Ediacaran period in the German part of the Saxo-Thuringian Zone at the northeastern margin of the Bohemian Massif. The geotectonic setting during the formation of Ediacaran rock units is characterized by Cadomian orogenic processes from
c.
650–540 Ma at the periphery of the West African Craton. The basin development during that time is characterized by the formation of a Cadomian backarc basin with a passive margin, and the outboard sitting Cadomian magmatic arc originated at
c.
570–560 Ma. This arc-marginal basin system was formed on stretched continental crust in a strike-slip regime and reflects an active-margin setting in a style similar to the recent West Pacific. The backarc basin was closed between
c.
560–540 Ma by the collision of the Cadomian magmatic arc with the cratonic hinterland: this resulted in the closure of the backarc basin and the formation of a Cadomian retroarc basin. Collision of an oceanic ridge with the Cadomian Orogenic Belt led to a slab break-off of the subducted oceanic plate resulting in an extreme heat flow, and a magmatic and anatectic event culminating at
c.
540 Ma that was responsible for the intrusion of voluminous granitoid plutons.
Siliciclastic prelude to Elatina–Nuccaleena deglaciation: lithostratigraphy and rock magnetism of the base of the Ediacaran system
Authors: Raub T. D. , Evans D. A. D. , Smirnov A. V.
Published: December 2007

The basal Ediacaran global boundary stratotype section and point (GSSP) horizon beneath Nuccaleena Formation cap dolostone in South Australia's central Flinders Ranges South Australia coincides with an interpreted unconformity preceding deglacial transgression. Detailed lithostratigraphy of three sections across the base of the Ediacaran System at its type area reveals contrasting character of the Elatina Formation—Nuccaleena Formation transition across
c
. 9 km of exposure, changing the interpretive context of the GSSP.

We suggest that a locally pervasive, incisive flaser-bedded sandstone exposed between Elatina diamictites and Nuccaleena cap dolostone lies above an unconformity that correlates with the defined base of Wilpena Group, reflecting onset of terminal Elatina ‘Snowball Earth’ deglaciation and dynamic interplay between eustatic sea level change and isostatic rebound. Nuccaleena cap dolostone is sedimentologically mixed and conformable with underlying siliciclastics at Elatina Creek; hence the recently defined Ediacaran GSSP horizon, at the base of solid cap carbonate at Enorama Creek, lies in continuous section and not at an unconformity.

Nuccaleena Formation cap dolostone contains pervasive terrigenous debris, including apparently detrital hematite. While magnetite and/or maghemite is produced in abundance upon heating of the cap carbonate above
c
. 400°C, and we cannot exclude secondary origin of any Nuccaleena magnetite, Nuccaleena Formation cap dolostone should preserve primary magnetization.
The rise and decline of the Ediacaran biota: palaeobiological and stable isotopic evidence from the NW and NE Lesser Himalaya, India
Authors: Tewari V. C.
Published: December 2007

Sediments of Ediacaran age have recently been recognized in the Krol Belt (NW Lesser Himalaya, India) with the discovery of pre-Ediacaran and Ediacaran biotas, carbon isotopic excursions matching the global curve and evidence for one Neoproterozoic glacial event. Other data include evidence for termination of the Krol algal-stromatolitic carbonate cycle in Late Proterozoic and deposition of phosphorite, phosphatic stromatolites similar to Tommotian taxa, and diversification of Small Shelly Fossils (SSF) of Tommotian/Meischucunian Zone 1 in Lower Tal Formation. Recently, Riphean–Ediacaran organic-walled microfossils, stromatolites and sponge spicules (monaxon) have been recovered. The link between the decrease in microbial-induced carbonate sedimentation and the decline of large Riphean stromatolites is recorded in the inner sedimentary belt (Deoban–Gangolihat). The first appearance of complex organic-walled microfossils and acanthomorphic acritarchs is recorded in the Blaini–Infrakrol sediments along with possible Ediacaran soft-bodied metazoans and metaphytes in the Krol Formation. In India, the Late Proterozoic base occurs at the bottom of a pink, microbial limestone in the Blaini Formation, and the Precambrian–Cambrian boundary occurs somewhere in the Lower Tal Formation. Ediacaran metazoans occur above glacial deposits assigned to the Varangian/Marinoan/Blainian and below the first occurrence of SSF (Meischucunian zone I), in the lowermost Cambrian.
Calcite–dolomite cycles in the Neoproterozoic Cap carbonates, Otavi Group, Namibia
Authors: Tojo B. , Katsuta N. , Takano M. , Kawakami S. , Ohno T.
Published: December 2007

The lower cap carbonate (Rasthof Formation) overlies Neoproterozoic glacial deposits (Chuos Formation) and is exposed in the Khowarib-Warmquelle area in Northern Namibia. The basal 14.2 m part of the Rasthof Formation (total about 220 m) consists of the carbonate rhythmite. The rhythmite part of the Rasthof Formation contains 1 m cycles of dark- and light-coloured rhythmites. Alizarin-red staining of thin sections and elemental mapping of polished samples indicate that the dark-coloured parts are rich in calcite, whereas the light-coloured parts are dolomite-rich. On a 1 cm scale, a reddish clay layer is intercalated in each calcite rich dark-coloured rhythmite part. These cycles of reddish clays as well as some associated major turbidites can be well correlated between columns up to about 20 km distance. Furthermore, at one locality (K4), rip-up clasts occur in a turbidite bed. Their lithology consists of dark- and light-coloured rhythmite and a reddish clay layer and can be judged to have been derived from underlying horizons. Because the clasts are elastically deformed, it is strongly suggested that the difference in lithology observed within the basal part of the Rasthof Formation existed when clasts were ripped-up shortly after sedimentation. This suggests that the cycle involving dolomite is synsedimentary, and not a diagenetic feature. Direct precipitation of dolomite does not occur in present day open marine seawater. Hurtgen
et al.
(2002) suggest that seawater was depleted in sulphate after Neoproterozoic glaciation. It is proposed here that some possible depositional models of cycles that consist of calcite-rich and dolomite-rich parts as well as reddish clay beds in rhythmites of the Rasthof cap carbonate.
Correlating the Ediacaran of Australia
Authors: Grey K. , Calver C. R.
Published: December 2007

Now that a Global Stratotype Section and Point (GSSP) has been ratified and a new system defined for the terminal Proterozoic era, the Ediacaran, the next step is to develop global correlations and to further subdivide this system. Means of correlating and subdividing older parts of the Proterozoic era are also needed. This is not a simple task. Phanerozoic correlations depend on biostratigraphic zonation made possible by biodiversity, supported by geochronology. Proterozoic biotas are more restricted, geochronological data is often sparse, and although rapid and significant carbon isotope excursions are present through some time intervals, the curve is essentially quiescent and of limited utility at other times. Nevertheless, a foundation for Ediacaran acritarch biostratigraphy has now been established in Australia and linked to the carbon-isotope curve using sample splits. In conjunction with other correlation techniques, this has allowed the development of a continent-wide correlation scheme. The Australian Ediacaran experience suggests that an integrated approach offers the best way forward for Proterozoic subdivision. However, it raises issues about some aspects of Neoproterozoic correlation; in particular, it indicates that reliance on a two-main-glaciations model may be over simplistic.
Protein Translocation Across the Bacterial Cytoplasmic Membrane
Authors: Driessen Arnold J.M. , Nouwen Nico
Published: December 2007

About 25% to 30% of the bacterial proteins function in the cell envelope or outside of the cell. These proteins are synthesized in the cytosol, and the vast majority is recognized as a ribosome-bound nascent chain by the signal recognition particle (SRP) or by the secretion-dedicated chaperone SecB. Subsequently, they are targeted to the Sec translocase in the cytoplasmic membrane, a multimeric membrane protein complex composed of a highly conserved protein-conducting channel, SecYEG, and a peripherally bound ribosome or ATP-dependent motor protein SecA. The Sec translocase mediates the translocation of proteins across the membrane and the insertion of membrane proteins into the cytoplasmic membrane. Translocation requires the energy sources of ATP and the proton motive force (PMF) while the membrane protein insertion is coupled to polypeptide chain elongation at the ribosome. This review summarizes the present knowledge of the mechanism and structure of the Sec translocase, with a special emphasis on unresolved questions and topics of current research.
Phosphorylation of GRK2 by PKA augments GRK2-mediated phosphorylation, internalization, and desensitization of VPAC2 receptors in smooth muscle
Authors: Murthy Karnam S. , Mahavadi Sunila , Huang Jiean , Zhou Huiping , Sriwai Wimolpak
Published: December 2007

The smooth muscle of the gut expresses mainly Gs protein-coupled vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase-activating peptide receptors (VPAC2 receptors), which belong to the secretin family of G protein-coupled receptors. The extent to which PKA and G protein-coupled receptor kinases (GRKs) participate in homologous desensitization varies greatly among the secretin family of receptors. The present study identified the novel role of PKA in homologous desensitization of VPAC2 receptors via the phosphorylation of GRK2 at Ser685. VIP induced phosphorylation of GRK2 in a concentration-dependent fashion, and the phosphorylation was abolished by blockade of PKA with cell-permeable myristoylated protein kinase inhibitor (PKI) or in cells expressing PKA phosphorylation-site deficient GRK2(S685A). Phosphorylation of GRK2 increased its activity and binding to Gβγ. VIP-induced phosphorylation of VPAC2 receptors was abolished in muscle cells expressing kinase-deficient GRK2(K220R) and attenuated in cells expressing GRK2(S685A) or by PKI. VPAC2 receptor internalization (determined from residual 125I-labeled VIP binding and receptor biotinylation after a 30-min exposure to VIP) was blocked in cells expressing GRK2(K220R) and attenuated in cells expressing GRK2(S685A) or by PKI. Finally, VPAC2 receptor degradation (determined from residual 125I-labeled VIP binding and receptor expression after a prolonged exposure to VIP) and functional VPAC2 receptor desensitization (determined from the decrease in adenylyl cyclase activity and cAMP formation after a 30-min exposure to VIP) were abolished in cells expressing GRK2(K220R) and attenuated in cells expressing GRK2(S685A). These results demonstrate that in gastric smooth muscle VPAC2 receptor phosphorylation is mediated by GRK2. Phosphorylation of GRK2 by PKA enhances GRK2 activity and its ability to induce VPAC2 receptor phosphorylation, internalization, desensitization, and degradation.
Antibody-independent localization of the electroneutral Na+-HCO3− cotransporter NBCn1 (slc4a7) in mice
Authors: Boedtkjer Ebbe , Praetorius Jeppe , Füchtbauer Ernst-Martin , Aalkjaer Christian
Published: December 2007

The expression pattern of the electroneutral Na+-HCO3−cotransporter NBCn1 (slc4a7) was investigated by β-galactosidase staining of mice with a LacZ insertion into the NBCn1 gene. This method is of particular value because it is independent of immunoreactivity. We find that the NBCn1 promoter is active in a number of tissues where NBCn1 has previously been functionally or immunohistochemically identified, including a broad range of blood vessels (vascular smooth muscle cells and endothelial cells), kidney thick ascending limb and medullary collecting duct epithelial cells, the epithelial lining of the kidney pelvis, duodenal enterocytes, choroid plexus epithelial cells, hippocampus, and retina. Kidney corpuscles, colonic mucosa, and nonvascular smooth muscle cells (from the urinary bladder, trachea, gastrointestinal wall, and uterus) were novel areas of promoter activity. Atrial but not ventricular cardiomyocytes were stained. In the brain, distinct layers of the cerebral cortex and cerebellar Purkinje cells were stained as was the dentate nucleus. No staining of skeletal muscle or cortical collecting ducts was observed. RT-PCR analyses confirmed the expression of NBCn1 and β-galactosidase in selected tissues. Disruption of the NBCn1 gene resulted in reduced NBCn1 expression, and in bladder smooth muscle cells, reduced amiloride-insensitive Na+-dependent HCO3− influx was observed. Furthermore, disruption of the NBCn1 gene resulted in a lower intracellular steady-state pH of bladder smooth muscle cells in the presence of CO2/HCO3− but not in its nominal absence. We conclude that NBCn1 has a broad expression profile, supporting previous findings based on immunoreactivity, and suggest several new tissues where NBCn1 may be important.
ClC-3 is required for LPA-activated Cl− current activity and fibroblast-to-myofibroblast differentiation
Authors: Yin Zhaohong , Tong Yiai , Zhu Haiqing , Watsky Mitchell A.
Published: December 2007

To determine the effects of chloride channel 3 (ClC-3) knockdown and overexpression on lysophosphatidic acid (LPA)- and volume-regulated anion channel Cl− currents ( ICl,LPA and ICl,VRAC, respectively), cell differentiation, and cell volume regulation, a short hairpin RNA (shRNA) expression system based on a mouse U6 promoter was used to knock down ClC-3 in human corneal keratocytes and human fetal lung fibroblasts. ClC-3 overexpression was achieved by electroporating full-length ClC-3, within a pcDNA3.1 vector, into these two cell lines. RT-PCR and Western blot analysis were used to detect ClC-3 mRNA and protein levels. Whole cell perforated patch-clamp recording was used to measure ICl,LPA and ICl,VRAC currents, and fluorescence-activated cell sorting analysis was used to measure cell volume regulation. ClC-3 knockdown significantly decreased ICl,LPA and ICl,VRAC activity in the presence of transforming growth factor-β1 (TGF-β1) compared with controls, whereas ClC-3 overexpression resulted in increased ICl,LPA activity in the absence of TGF-β1. ClC-3 knockdown also resulted in a reduction of α-smooth muscle actin (α-SMA) protein levels in the presence of TGF-β1, whereas ClC-3 overexpression increased α-SMA protein expression in the absence of TGF-β1. In addition, keratocytes transfected with ClC-3 shRNA had a significantly blunted regulatory volume decrease response following hyposmotic stimulation compared with controls. These data confirm that ClC-3 is important in VRAC function and cell volume regulation, is associated with the ICl,LPA current activity, and participates in the fibroblast-to-myofibroblast transition.
Mitochondrial DNA damage triggers mitochondrial-superoxide generation and apoptosis
Authors: Ricci Craig , Pastukh Viktor , Leonard Josh , Turrens Julio , Wilson Glenn , Schaffer David , Schaffer Stephen W.
Published: December 2007

Recently, it has become apparent that mitochondrial DNA (mtDNA) damage can rapidly initiate apoptosis independent of mutations, although the mechanism involved remains unclear. To elucidate this mechanism, angiotensin II-mediated apoptosis was studied in cells that were transduced with a lentiviral vector to overexpress the DNA repair enzyme 8-oxoguanine glycosylase or were treated with inhibitors known to block angiotensin II-induced mtDNA damage. Cells exhibiting angiotensin II-induced mtDNA damage showed two phases of superoxide generation, the first derived from NAD(P)H oxidase and the second of mitochondrial origin, whereas cells prevented from experiencing mtDNA damage importantly exhibited only the first phase. Furthermore, cells with mtDNA damage demonstrated impairments in mitochondrial protein expression, cellular respiration, and complex 1 activity before the onset of the second phase of oxidation. After the second phase, the mitochondrial membrane potential collapsed, cytochrome c was released, and the cells underwent apoptosis, all of which were prevented by disrupting mtDNA damage. Collectively, these data reveal a novel mechanism of apoptosis that is initiated when mtDNA damage triggers mitochondrial superoxide generation and ultimately the activation of the mitochondrial permeability transition. This novel mechanism may play an important pathological role.