bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular mechanism of the voltage‐dependent change in slow potentials generated in circular smooth muscle of the guinea‐pig gastric corpus
Authors: Hirst G. D. S. , Hashitani H. , Suzuki H.
Published: September 2008

The cellular mechanism of the voltage‐dependent properties of slow potentials were investigated in single bundles of circular smooth muscle isolated from the gastric corpus of guinea‐pig using conventional microelectrode recordings. Hyperpolarization of the membrane by current injection decreased the frequency and increased the amplitude of slow potentials linearly. At potentials negative of −80 mV, slow potential generation was abolished and a periodic generation of clustered unitary potentials was evident. Application of cyclopiazonic acid (CPA, 20 μm) or thapsigargin (1 μm; inhibitors of Ca2+‐ATPase), carbonyl cyanide m‐chlorophenyl hydrazone (CCCP, 0.1 μm; mitochondrial protonophore) or 2‐aminoethoxydiphenyl borate (2‐APB, 20 μm; inhibitor of IP3 receptor‐mediated Ca2+ release) depolarized the membrane and reduced or inhibited the amplitude and frequency of slow potentials: repolarization of the membrane to the resting level by current injection resulted in a recovery of the amplitude of slow potentials in the presence of CPA or CCCP, but not 2‐APB. The slow potentials abolished by thapsigargin did not recover upon membrane repolarization. The altered frequency of slow potentials by 2‐APB, CPA or CCCP was not reversed by membrane repolarization to control potentials. Depolarization of the membrane by about 10 mV with high‐potassium solution also reduced the amplitude and increased the frequency of slow potentials in a manner restored by repolarization to control potentials upon current injection, suggesting that membrane depolarization did not affect the voltage dependency of pacemaker activity. The results indicate that in corpus circular muscles the voltage dependency of the frequency and amplitude of slow potentials requires a functional Ca2+ store and mitochondria.
Assembling Materials with DNA as the Guide
Authors: Aldaye Faisal A. , Palmer Alison L. , Sleiman Hanadi F.
Published: September 2008

DNA's remarkable molecular recognition properties and structural features make it one of the most promising templates to pattern materials with nanoscale precision. The emerging field of DNA nanotechnology strips this molecule from any preconceived biological role and exploits its simple code to generate addressable nanostructures in one, two, and three dimensions. These structures have been used to precisely position proteins, nanoparticles, transition metals, and other functional components into deliberately designed patterns. They can also act as templates for the growth of nanowires, aid in the structural determination of proteins, and provide new platforms for genomics applications. The field of DNA nanotechnology is growing in a number of directions, carrying with it the promise to substantially affect materials science and biology.
The Coevolution of Cultural Groups and Ingroup Favoritism
Authors: Efferson Charles , Lalive Rafael , Fehr Ernst
Published: September 2008

Cultural boundaries have often been the basis for discrimination, nationalism, religious wars, and genocide. Little is known, however, about how cultural groups form or the evolutionary forces behind group affiliation and ingroup favoritism. Hence, we examine these forces experimentally and show that arbitrary symbolic markers, though initially meaningless, evolve to play a key role in cultural group formation and ingroup favoritism because they enable a population of heterogeneous individuals to solve important coordination problems. This process requires that individuals differ in some critical but unobservable way and that their markers be freely and flexibly chosen. If these conditions are met, markers become accurate predictors of behavior. The resulting social environment includes strong incentives to bias interactions toward others with the same marker, and subjects accordingly show strong ingroup favoritism. When markers do not acquire meaning as accurate predictors of behavior, players show a markedly reduced taste for ingroup favoritism. Our results support the prominent evolutionary hypothesis that cultural processes can reshape the selective pressures facing individuals and so favor the evolution of behavioral traits not previously advantaged.
Mars' Paleomagnetic Field as the Result of a Single-Hemisphere Dynamo
Authors: Stanley Sabine , Elkins-Tanton Linda , Zuber Maria T. , Parmentier E. Marc
Published: September 2008

Mars' crustal magnetic field was most likely generated by dynamo action in the planet's early history. Unexplained characteristics of the field include its strength, concentration in the southern hemisphere, and lack of correlation with any surface features except for the hemispheric crustal dichotomy. We used numerical dynamo modeling to demonstrate that the mechanisms proposed to explain crustal dichotomy formation can result in a single-hemisphere dynamo. This dynamo produces strong magnetic fields in only the southern hemisphere. This magnetic field morphology can explain why Mars' crustal magnetic field intensities are substantially stronger in the southern hemisphere without relying on any postdynamo mechanisms.
Complete Characterization of Quantum-Optical Processes
Authors: Lobino Mirko , Korystov Dmitry , Kupchak Connor , Figueroa Eden , Sanders Barry C. , Lvovsky A. I.
Published: September 2008

The technologies of quantum information and quantum control are rapidly improving, but full exploitation of their capabilities requires complete characterization and assessment of processes that occur within quantum devices. We present a method for characterizing, with arbitrarily high accuracy, any quantum optical process. Our protocol recovers complete knowledge of the process by studying, via homodyne tomography, its effect on a set of coherent states, that is, classical fields produced by common laser sources. We demonstrate the capability of our protocol by evaluating and experimentally verifying the effect of a test process on squeezed vacuum.
Synthesis and Solid-State NMR Structural Characterization of
13
C-Labeled Graphite Oxide
Authors: Cai Weiwei , Piner Richard D. , Stadermann Frank J. , Park Sungjin , Shaibat Medhat A. , Ishii Yoshitaka , Yang Dongxing , Velamakanni Aruna , An Sung Jin , Stoller Meryl , An Jinho , Chen Dongmin , Ruoff Rodney S.
Published: September 2008

The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (
13
C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance
13
C have poor signal-to-noise ratios. Approximately 100%
13
C-labeled graphite was made and converted to
13
C-labeled GO, and
13
C SSNMR was used to reveal details of the chemical bonding network, including the chemical groups and their connections. Carbon-13–labeled graphite can be used to prepare chemically modified graphenes for
13
C SSNMR analysis with enhanced sensitivity and for fundamental studies of
13
C-labeled graphite and graphene.
Disruption of the
CFTR
Gene Produces a Model of Cystic Fibrosis in Newborn Pigs
Authors: Rogers Christopher S. , Stoltz David A. , Meyerholz David K. , Ostedgaard Lynda S. , Rokhlina Tatiana , Taft Peter J. , Rogan Mark P. , Pezzulo Alejandro A. , Karp Philip H. , Itani Omar A. , Kabel Amanda C. , Wohlford-Lenane Christine L. , Davis Greg J. , Hanfland Robert A. , Smith Tony L. , Samuel Melissa , Wax David , Murphy Clifton N. , Rieke August , Whitworth Kristin , Uc Aliye , Starner Timothy D. , Brogden Kim A. , Shilyansky Joel , McCray Paul B. , Zabner Joseph , Prather Randall S. , Welsh Michael J.
Published: September 2008

Almost two decades after
CFTR
was identified as the gene responsible for cystic fibrosis (CF), we still lack answers to many questions about the pathogenesis of the disease, and it remains incurable. Mice with a disrupted
CFTR
gene have greatly facilitated CF studies, but the mutant mice do not develop the characteristic manifestations of human CF, including abnormalities of the pancreas, lung, intestine, liver, and other organs. Because pigs share many anatomical and physiological features with humans, we generated pigs with a targeted disruption of both
CFTR
alleles. Newborn pigs lacking CFTR exhibited defective chloride transport and developed meconium ileus, exocrine pancreatic destruction, and focal biliary cirrhosis, replicating abnormalities seen in newborn humans with CF. The pig model may provide opportunities to address persistent questions about CF pathogenesis and accelerate discovery of strategies for prevention and treatment.
Equine Infectious Anemia Virus Resists the Antiretroviral Activity of Equine APOBEC3 Proteins through a Packaging-Independent Mechanism
Authors: Bogerd Hal P. , Tallmadge Rebecca L. , Oaks J. Lindsay , Carpenter Susan , Cullen Bryan R.
Published: September 2008

Equine infectious anemia virus (EIAV), uniquely among lentiviruses, does not encode a
vif
gene product. Other lentiviruses, including human immunodeficiency virus type 1 (HIV-1), use Vif to neutralize members of the APOBEC3 (A3) family of intrinsic immunity factors that would otherwise inhibit viral infectivity. This suggests either that equine cells infected by EIAV in vivo do not express active A3 proteins or that EIAV has developed a novel mechanism to avoid inhibition by equine A3 (eA3). Here, we demonstrate that horses encode six distinct A3 proteins, four of which contain a single copy of the cytidine deaminase (CDA) consensus active site and two of which contain two CDA motifs. This represents a level of complexity previously seen only in primates. Phylogenetic analysis of equine single-CDA A3 proteins revealed two proteins related to human A3A (hA3A), one related to hA3C, and one related to hA3H. Both equine double-CDA proteins are similar to hA3F and were named eA3F1 and eA3F2. Analysis of eA3F1 and eA3F2 expression in vivo shows that the mRNAs encoding these proteins are widely expressed, including in cells that are natural EIAV targets. Both eA3F1 and eA3F2 inhibit retrotransposon mobility, while eA3F1 is a potent inhibitor of a Vif-deficient HIV-1 mutant and induces extensive editing of HIV-1 reverse transcripts. However, both eA3F1 and eA3F2 are weak inhibitors of EIAV. Surprisingly, eA3F1 and eA3F2 were packaged into EIAV and HIV-1 virions as effectively as hA3G, although only the latter inhibited EIAV infectivity. Moreover, all three proteins bound both the HIV-1 and EIAV nucleocapsid protein specifically in vitro. It therefore appears that EIAV has evolved a novel mechanism to specifically neutralize the biological activities of the cognate eA3F1 and eA3F2 proteins at a step subsequent to virion incorporation.
Systematic Assembly of a Full-Length Infectious Clone of Human Coronavirus NL63
Authors: Donaldson Eric F. , Yount Boyd , Sims Amy C. , Burkett Susan , Pickles Raymond J. , Baric Ralph S.
Published: September 2008

Historically, coronaviruses were predominantly associated with mild upper respiratory disease in humans. More recently, three novel coronaviruses associated with severe human respiratory disease were found, including (i) the severe acute respiratory syndrome coronavirus, associated with a significant atypical pneumonia and 10% mortality; (ii) HKU-1, associated with chronic pulmonary disease; and (iii) NL63, associated with both upper and lower respiratory tract disease in children and adults worldwide. These discoveries establish coronaviruses as important human pathogens and underscore the need for continued research toward the development of platforms that will enable genetic manipulation of the viral genome, allowing for rapid and rational development and testing of candidate vaccines, vaccine vectors, and therapeutics. In this report, we describe a reverse genetics system for NL63, whereby five contiguous cDNAs that span the entire genome were used to generate a full-length cDNA. Recombinant NL63 viruses which contained the expected marker mutations replicated as efficiently as the wild-type NL63 virus. In addition, we engineered the heterologous green fluorescent protein gene in place of open reading frame 3 (ORF3) of the NL63 clone, simultaneously creating a unique marker for NL63 infection and demonstrating that the ORF3 protein product is nonessential for the replication of NL63 in cell culture. The availability of the NL63 and NL63gfp clones and recombinant viruses provides powerful tools that will help advance our understanding of this important human pathogen.
Mesothelial reaction in longstanding Crohn’s ileitis simulating papillary mesothelioma
Authors: Wilkinson L , De P , Bloxham C
Published: September 2008

Intestinal and extraintestinal complications of Crohn’s disease are well documented. Changes in the connective tissue within the intestinal wall and surrounding tissue including mesenteric fat are characteristically seen in resected and autopsy specimens. A rare and unusually florid mesothelial reaction in the surrounding small bowel serosa of a patient with a 2-year history of Crohn’s ileitis is described. The peritoneal surface of the ileal resection specimen displayed exuberant tubulo-papillary formations of the mesothelium, with superficial invasion of the underlying stroma. The case demonstrates the well-recognised difficult differential diagnosis between a benign mesothelial proliferation and malignant mesothelioma in a novel clinical setting, and the diversity of the extramural manifestations of Crohn's disease.
Morphological quality and nucleic acid preservation in cytopathology
Authors: Gazziero A , Guzzardo V , Aldighieri E , Fassina A
Published: September 2008

Background:

Fixation is a chemical or physical procedure to prevent the degradation of proteins and tissue morphology. To optimise molecular analysis of archival tissues, it is essential that fixation preserves morphology along with protein epitopes and DNA/RNA integrity.

Methods:

A new formalin-free alcoholic-based fixative, FineFIX, was used to fix 15 serous effusions and 38 fine-needle aspirates, and cellular morphology and nucleic acid quality were evaluated.

Results:

The cytomorphology of the effusions and fine-needle aspirates obtained with FineFIX fixation was similar to that obtained with formalin-fixed counterparts. Immunocytochemistry showed comparable results with the traditional fixative, but FineFIX preserved higher-molecular-mass DNA and RNA, as demonstrated by successful PCR of large amplification products of >2000 bp.

Conclusions:

The formalin-free fixative produced not only satisfactory results for immunocytochemistry on cytological smears and cell blocks, but also excellent preservation of DNA and RNA, which can also be efficiently used for sophisticated molecular techniques.
The gross appearances of fine needle aspiration cytology samples: Figure 1
Authors: Mayall F G , Cormack A , McAnulty K , Darlington A
Published: September 2008

Aims:

This study set out to photograph and describe the gross appearances of fine needle aspiration (FNA) cytology samples of commonly encountered lesions.

Methods:

During a 2 year period, a cytopathologist photographed the gross appearances of near patient FNA samples, concentrating on commonly encountered lesions.

Results:

The gross appearances are described, accompanied by photographic illustrations.

Conclusions:

This paper describes and illustrates the gross appearances of FNA cytology samples of some commonly encountered lesions.
Floral initiation in wheat, sunflower, and sorghum under carbon dioxide enrichment
Authors: Marc Jan , Gifford Roger M.
Published: September 2008

Wheat cv. Timgalen and cv. Gabo, sunflower cv. HA 124, and sorghum cv. RS 610 plants were grown at normal atmospheric or an elevated CO2 concentration (atmospheric + 500 μmol CO2 mol air−1). Enrichment with CO2 advanced floral initiation by 1 – 3 days in wheat and sunflower but had no such effect in sorghum. The rate of differentiation of the primordial inflorescence was unaffected in sunflower but was reduced slightly in wheat and significantly in sorghum. Exposing plants to a brief CO2 enrichment in series during the vegetative phase showed that the sensitive period for stimulation of floral initiation in wheat commenced within 10 days before the formation of double ridges. The sensitive period for retardation of inflorescence differentiation in sorghum commenced within 6 days before floral initiation. For sunflower the sensitive period was short, with peak stimulation occurring 7 days before floral initiation. It is concluded that the flowering response to CO2 enrichment was not due solely to a general growth response; rather, direct morphogenic effects were involved.
Breeding systems and relationships among species of Boykinia and related genera (Saxifragaceae)
Authors: Gornall Richard J. , Bohm Baruce A.
Published: September 2008

Self- and cross-pollinations were made within and between selected species belonging to Boykinia, Peltoboykinia, Bolandra, Suksdorfia, Sullivantia, and Jepsonia (Saxifragaceae). Self-incompatibility is reported for the first time in Boykinia. No intergeneric hybrids were produced, supporting the separate integrities of the genera involved, particularly the segregation of Peltoboykinia. Intrageneric hybrids were made in Boykinia and Peltoboykinia. In the case of Boykinia, this supports the retention within it of the often segregated Telesonix. Crosses between the two North American Suksdorfia species failed, but for various reasons, this was taken to reflect the existence of two "biological species" rather than two separate genera.
Buried viable seed in a ponderosa pine community
Authors: Pratt David W. , Black R. Alan , Zamora B. A.
Published: September 2008

The seed bank of a Pinus ponderosa – Symphoricarpos albus stand in east-central Washington was examined with respect to species composition, depth distribution, and germination responses to heat and shade treatments. Seeds of 57 species were present in the seed bank to a depth of 10 cm. Twenty-one of these species were not found in the aboveground vegetation of the study area. Estimated viable seed densities in spring and autumn collections were 13 052 ± 1481 and 14 463 ± 1356 seeds m−2, respectively. Stellaria media and Poa pratensis, both alien species, accounted for 50% of the buried viable seed. Seed density was highest in litter samples. Total seed density decreased with soil depth, although seeds of some pioneer species were more abundant in the mineral soil than in the litter. Species dominating the seed bank were generally unimportant in the aboveground vegetation. Woody species, which dominated the aboveground vegetation, accounted for only 1% of the seed bank. Annual forbs dominated the seed bank (45% of total buried viable seed) but were not dominant in the vegetation. Seeds of several species survived prestratification heat treatments. Poststratification heat treatments inhibited germination or destroyed seed of nearly all species. As shading increased, germination of most species decreased. However, shade did not inhibit germination of species characteristic of mature successional stages.
Growth and development at cold-hardening temperatures. Chloroplast ultrastructure, pigment content, and composition
Authors: Huner Norman P. A. , Elfman B. , Krol M. , McIntosh A.
Published: September 2008

Chloroplast ultrastructure, pigment content, and composition were investigated during growth of 'Puma' rye at warm and cold-hardening temperatures. Cytological characteristics of leaf mesophyll cells were altered upon growth at cold-hardening temperatures as indicated by an apparent increase in the amount of cytoplasm. Univacuolate and multivacuolate mesophyll cells were found in leaves from cold-hardened plants, but only univacuolate mesophyll cells were found in leaves from warm-grown plants. Chloroplast ultrastructure was affected by growth at low temperature as indicated by a higher frequency of smaller granal stacks. However, there was no significant difference in the number of grana per chloroplast in mesophyll cells from either warm- or cold-grown plants. Chlorophyll per plastid increased by a factor of 1.67 upon growth at cold-hardening temperatures, as did β-carotene and the xanthophylls. However, there was no significant difference in photosynthetic unit size based on P700 measurements between chloroplasts from warm- or cold-grown tissue. Analysis of freeze-fractured thylakoid membranes indicated a loss in the bimodal nature of particle size distribution on the exoplasmic fracture face and a general increase in particle size on the protoplasmic fracture face upon growth and development at cold temperatures. However, particle densities on the exoplasmic and protoplasmic fracture faces were not significantly different in thylakoids from plastids developed at either warm or cold temperatures. It is concluded that chloroplast ultrastructure and pigment content but not composition are altered upon growth and development at cold-hardening temperatures.
Influence of choline derivatives on the sterol composition of Chlorella vulgaris grown in continuous culture
Authors: Orcutt D. M. , Davis G. A. , Moore L. D.
Published: September 2008

Three choline derivatives, (2-chloroethyl)trimethylammonium chloride (CCC), (2-hydroxyethyl)trimethylammonium chloride (CC), and (2-hydroxyethyl)trimethylammonium chloride phosphate (PCC) were found to decrease ergosterol as a percentage of total sterol extracted from Chlorella vulgaris cells grown in continuous culture. Each compound was tested sequentially at concentrations of 10−6, 10−5, and 10−4 M. The greatest reduction in the relative percentage of ergosterol occurred with 10−4 M CC. CCC and PCC treatment resulted in an increase in the relative percentage of 22-dihydroergosterol, yet no accumulation of 22-dihydroergosterol was observed with the CC treatments. All three chemicals increased the relative amounts of C27 sterols. Absolute concentrations of total sterols were significantly reduced by CC at 10−6 and 10−4M. CC at 10−5 M significantly stimulated absolute concentrations of total sterols as did PCC at 10−6 and 10−5 M.
Ultrastructure of susceptible, host resistant, and nonhost resistant interactions of alfalfa with Phytophthora megasperma
Authors: Miller Sally A. , Maxwell Douglas P.
Published: September 2008

Zoospores of Phytophthora megasperma Drechs. f. sp. medicaginis (Pmm), an alfalfa (Medicago sativa L.) pathogen, and P. megasperma f. sp. glycinea (Pmg), a pathogen of soybean (Glycine max (L.) Merr.), were used to inoculate alfalfa seedlings from the Pmm-susceptible cultivar 'Vernal' and the Pmm-resistant breeding line M193. The susceptible interaction ('Vernal'–Pmm) was characterized by rapid disruption of host mitochondria in cells adjacent to intercellular hyphae, dissolution of host cell walls, and death of host cells 12–24 h after inoculation. Colonization of roots was extensive, and hyphae usually appeared healthy. Both host resistant (M193–Pmm) and nonhost resistant (M193 or 'Vernal' – Pmg) interactions were characterized by hyphal growth inhibition, production of cell wall appositions in root cells in contact with hyphae, and rapid necrosis of root cells. Wall appositions were more numerous in root cells in contact with Pmg than with Pmm, and rapid cell necrosis was more extensive in the nonhost resistant interaction than in the host resistant interaction. Numerous abnormalities were observed in Pmg hyphae. Nonhost resistance was expressed more rapidly and appeared to be more effective than host resistance in limiting hyphal growth. An examination of a compatible interaction of Pmg with soybean indicated that its mode of pathogenesis may be fundamentally different from that of Pmm in alfalfa.
Variation in substrate chemistry along microtopographical and water-chemistry gradients in peatlands
Authors: Karlin E. F. , Bliss L. C.
Published: September 2008

A broad range of water chemistry (pH 3.5–8.2; Ca, 2–120 mg L−1) and substrate chemistry (pH 3.3–7.8; Ca, 4–138 mequiv. 100 g−1) exists among peatlands present in central Alberta. The six peatlands comprising the main study sites included strongly minerotrophic, moderately minerotrophic, and weakly minerotrophic systems. Variation in substrate chemistry along the hollow to hummock gradient in strongly and moderately minerotrophic peatlands was high (ranging from highly minerotrophic peats to ombrotrophic peats), while variation in substrate chemistry in weakly minerotrophic peatlands was slight (weakly minerotrophic peats to ombrotrophic peats) along the same gradient. Substrate chemistry and plant community composition of hollow and low-hummock communities varied considerably along the strongly minerotrophic to weakly minerotrophic peatland gradient. In contrast, the chemistry of the upper peat layers of the hummocks and hummock plant community composition were similar in all of the peatlands studied. Distributional patterns of plant species in weakly minerotrophic peatlands are not primarily in response to gradients in substrate chemistry but arise from gradients in substrate moisture and biotic interactions. This is not the case for strongly and moderately minerotrophic systems, where gradients in substrate chemistry may also strongly influence plant species distribution. The increase in complexity of the substrate environment in peatlands along the weakly minerotrophic to strongly minerotrophic gradient is reflected by a parallel increase in plant species diversity.
Altitudinal variation in freezing resistance of Saghalien fir (Abies sachalinensis)
Authors: Eiga S. , Sakai A.
Published: September 2008

Altitudinal variation in freezing resistance of Abies sachalinensis in central mountainous areas in Hokkaido was investigated. Freezing resistance of winter buds of the open-pollinated progenies from 51 mother trees and ramets from 80 clones, growing at different altitudes, was assessed. Freezing resistance increased with increasing altitude from about 300 to 1200 m. The increase in freezing resistance was always accompanied by a decrease in the variance. These results suggest that natural selection has operated under influence of winter temperature gradients to bring about the hardiness related to altitudinal occurrence.
Mesophyll resistance to photosynthetic carbon dioxide uptake in leaves: dependence upon stomatal aperture
Authors: Parkhurst David F.
Published: September 2008

A model for carbon dioxide uptake by plant leaves, based on the partial differential equation for diffusion with chemical reaction, is used to simulate photosynthesis for various stomatal openings. The results show that not only the "stomatal resistance" but also the commonly calculated "mesophyll resistance" varies when nothing but stomatal aperture is changed. Simplistic uses of the resistance concept (or related conductances) may be more misleading than useful for modelling photosynthesis, because the various resistance components are neither independent nor additive.
Response of source–sink relationship in soybean to temperature
Authors: Hofstra G.
Published: September 2008

The need for carefully defined conditions to demonstrate sink-source interaction was investigated using 'Biloxi' soybean grown under defined growth conditions. When the source area was reduced in seedlings by removal of the cotyledons and one primary leaf, the CO2 uptake in the remaining leaf was increased at 24 °C but not at 27 °C. The 17% increase in the rate of CO2 uptake at 24 °C was accompanied by an increase of assimilate export of about 5% over 24 h. The effects on CO2 uptake at 21 and 30 °C were smaller than at 24 °C but larger than at 27 °C. The percentage of assimilated 14C that was translocated was also increased at 27 °C, but there was no accompanying stimulation of CO2 uptake. Fruiting plants at 24 °C had close to double the CO2 uptake rates of barren plants; whereas at 27 °C the rates were the same. Removing the pods reduced the CO2 uptake at 24 °C to close to that of barren plants. Sink activity appeared to limit CO2 uptake over a very narrow temperature range below optimum temperatures for growth, whereas at optimum temperatures CO2 uptake appeared to limit growth.
Transmission of nopaline crown gall tumour markers through meiosis in regenerated whole plants of Bidens alba
Authors: Norton Robert A. , Towers G. H. N.
Published: September 2008

Results show the feasibility of regenerating rooting Bidens alba plants from nopaline-type crown galls incited by Agrobacterium tumefaciens containing pTi-T37. Transmission of the tumour marker nopaline synthesis is demonstrated into the fourth generation but decreases in level of expression or loss of the trait occurs. Nopaline synthesis and auxin autotrophy, as markers, can also be differentially lost, making it difficult to demonstrate Mendelian inheritance. Formation of octopine-type tumours on nopaline positive plants occurs in a high percentage of inoculations. Transformed plants show several morphological traits which distinguish them from normal plants: they are smaller, have decreased apical dominance, show hypertrophy of the hypocotyl region, lower nodes, and petiole bases, and frequently form an extra spur of tissue in ray flowers.
Shoot development in Betula papyrifera. IV. Comparisons between growth characteristics and expression of vegetative long and short shoots
Authors: Caesar J. Cartey , Macdonald Alastair D.
Published: September 2008

Postflush observations on shoots of Betula papyrifera Marsh. indicated that long and short shoots differ in a range of morphological characteristics. Long shoots developed from distal axillary buds and short shoots developed from proximal axillary buds on the previous year's long shoots. Consequently, the potential of a bud to develop into a long shoot decreased basipetally. Potential long-shoot buds had higher bud-relative growth rates, stem-relative growth rates, leaf-relative growth rates, and stem dry weights during the course of postflush growth. Changes in leaf thickness, expressed in terms of specific leaf area and specific leaf weight, indicated that long shoots temporarily had thinner leaves than did short shoots a few weeks after flushing. Net assimilate requirements in long shoots for late leaf and internodal expansion may explain these observations. Nearing maturity, long-shoot early leaves became thicker, possibly owing to greater shoot vigour and (or) higher photosynthetic efficiency. Consequently, mature long-shoot early leaves possessed larger and thicker laminae, longer petioles, more side nerve pairs, and tended to grow more in length than width than short-shoot leaves on shoots of comparable age. Leaves of older short shoots, 2–10 years old, attained a greater size and had longer petioles than those of 1-year-old short shoots. Stem elongation and the development and expression of leaves in long shoots seemed to have a correlative influence on the overall vigour of long shoots.
Chromosome numbers and the taxonomy of North American Agalinis (Scrophulariaceae)
Authors: Canne Judith M.
Published: September 2008

Chromosome counts are provided for 25 populations representing 18 species of Agalinis Raf. Chromosome numbers are reported for the first time for A. pinetorum, A. laxa, A. acuta, A. gattingeri, and A. skinneriana. The base chromosome number for section Linifoliae, section Heterophyllae, section Purpureae subsections Purpureae and Setaceae, and section Tenuifoliae is established at x = 14. Section Erectae and section Purpureae subsection Pedunculares have a base number of x = 13.
Bud development in mountain hemlock (Tsuga mertensiana). I. Vegetative bud and shoot development
Authors: Owens John N.
Published: September 2008

Vegetative buds of mature Tsuga mertensiana (Bong) Carr. (mountain hemlock) were studied throughout the annual growth cycle. Cell divisions began in vegetative buds in mid-April and shoots and leaves elongated within the bud scales causing the buds to burst in late June. Lateral shoots completed elongation by the end of July. Vegetative terminal apices from lateral branches began bud-scale initiation when bud dormancy ended. All bud scales were initiated by the end of July. Leaf primordial initiation occurred from that time until mid-October when vegetative buds again became dormant. Axillary buds were initiated on the elongating shoots in early June then followed the same phenology as vegetative terminal buds. Vegetative bud and shoot development are compared with that of western hemlock and certain other members of the Pinaceae. The relationship of bud development to shoot development is discussed for mountain hemlock and other conifers having a similar pattern of vegetative bud development.
Differential responses of sunflower (Helianthus annuus cv. Modern) towards high and low concentrations of dikegulac sodium
Authors: Bhattacharjee A. , Gupta K.
Published: September 2008

In pot experiments, foliar application of dikegulac sodium (2,3:4-6-di-O-isopropylidene-α-L-xylo-2-hexalofuranosate) at 500 and 750 μg/mL inhibited plant growth and decreased growth and dry matter production of the treated leaves of sunflower (Helianthus annuus L. cv. Modern). A concentration of 100 μg/mL, however, increased leaf area and anabolic activities of treated leaves. Increased cambial activity was noted at all concentrations of dikegulac, which resulted in formation of secondary tissues. At 500 and 750 μg/mL RNase and protease activities increased appreciably, while catalase activity was drastically suppressed. The inhibitory effect of dikegulac was also found in newly expanding leaves which developed after treatment. Beneficial effects of dikegulac at low concentration were also reflected in field experiments where increased yield was noted, while high concentrations were distinctly inhibitory. The importance of dikegulac as an agronomically promising chemical for sunflower is discussed.
Alterations in internal partitioning of carbon in soybean plants in response to nitrogen stress
Authors: Rufty Jr. Thomas W. , Raper Jr. C. David , Huber Steven C.
Published: September 2008

Alterations in internal partitioning of carbon were evaluated in plants exposed to limited nitrogen supply. Vegetative, nonnodulated soybean plants (Glycine max (L.) Merrill, ‘Ransom’) were grown for 21 days with 1.0 mM[Formula: see text] and then exposed to solutions containing 1.0, 0.1, or 0.0 mM[Formula: see text] for a 25-day treatment period. In nitrogen-limited plants, there were decreases in emergence of new leaves and in the expansion rate and final area at full expansion of individual leaves. As indicated by alterations in accumulation of dry weight, a larger proportion of available carbon in the plant was partitioned to the roots with decreased availability of nitrogen. Partitioning of reduced nitrogen to the root also was increased and, in plants devoid of an external nitrogen supply, considerable redistribution of reduced nitrogen from leaves to the root occurred. The general decrease in growth potential and sink strength for nutrients in leaves of nitrogen-limited plants suggested that factors other than simply availability of nitrogen likely were involved in the restriction of growth in the leaf canopy and the associated increase in carbon allocation to the roots.
Growth and mycorrhizal development of potted white ash and black walnut fertilized by two methods
Authors: Ponder Jr. Felix
Published: September 2008

White ash (Fraxinus americana L.) and black walnut (Juglans nigra L.) seedlings were grown for 20 weeks in fumigated soil that was either infested with Glomus fasciculatus or noninoculated; they were fertilized with N, P, and N–P by soil or foliar application methods. Neither the method of fertilization nor fertilizers significantly affected the number of mycorrhizal infected root segments for either species grown in infested soil. Nitrate nitrogen was significantly higher in noninoculated soil than in inoculated soil; the reverse was true for foliar N. Though not statistically significant, phosphorus was lower in inoculated soil and higher in inoculated plants in comparison with noninoculated soil and plants. Both inoculation and foliar fertilization increased root mass and overall growth of seedlings. White ash appears to benefit more from mycorrhizal inoculation than black walnut does. The greater root mass of foliar-fertilized inoculated plants could be an important factor in increasing growth and survival of outplanted seedlings.
Mycorrhizae in a southern California desert: ecological implications
Authors: Bethlenfalvay G. J. , Dakessian S. , Pacovsky R. S.
Published: September 2008

Perennial plants of 19 families were surveyed for colonization by vesicular–arbuscular mycorrhizal (VAM) fungi at four sites in the Anza–Borrego Desert State Park, California, an area characterized as arid to extremely arid. Soils at all sites were very low in phosphorus and nitrogen and had a coarse sandy texture. The sites were distinct in the floristic composition of their vegetation. All plants (38 species) were colonized by VAM fungi (six species). The distribution of the VAM mycoflora was not random. Site preference by VAM-fungal species was ascribed to an interaction of factors pertaining to the host plants and to edaphic and climatic conditions.
Identification of planktonic Mallomonadaceae and other Chrysophyceae from selected lakes in the lower Fraser Valley, British Columbia (Canada)
Authors: Donaldson Deborah A. , Stein Janet R.
Published: September 2008

Identification of the Mallomonadaceae of selected lakes in British Columbia reveals 20 species of the genera Chromophysomonas, Chrysosphaerella, Mallomonas, Mallomonopsis, Paraphysomonas, and Synura. The following eight taxa in the family are new records for British Columbia (* indicates those new to North America): Mallomonas asmundiae, M. doignonii var. tenuicostis, M. papillosa, M. transsylvanica, Mallomonopsis ouradion*, Paraphysomonas vestita, Synura glabra, S. splendida*. Thirteen additional Chrysophyceae were also present, with the most diversity observed being in the three lakes studied extensively (Whonock, Como, Munday).
Influence of the mycangial fungi of the western pine beetle on water conduction through ponderosa pine seedlings
Authors: Paine T. D.
Published: September 2008

The mycangial fungi Ceratocystis nigracarpa Davidson and a basidiomycete associated with western pine beetle reduce water conduction through seedling ponderosa pine. Only after the trees had been severely water stressed was the water tension in control treated trees not significantly different from that of a fungus treatment. There were no differences in the lengths of the lesions produced in a hypersensitive response to inoculated fungi or in the controls. This suggests that the reduction in water movement is a result of some factor other than destruction of conductive tissue.
Detection of pathogenesis-related proteins (PR or b) and of other proteins in the intercellular fluid of hypersensitive plants infected with tobacco mosaic virus
Authors: Parent Jean-Guy , Asselin Alain
Published: September 2008

In tobacco mosaic virus infected hypersensitive Nicotiana species, the pathogenesis-related (PR) or b proteins were found with other proteins in the intercellular fluid of leaf tissue. Analysis of leaves from mock-inoculated plants did not reveal the presence of detectable amounts of proteins in the intercellular fluid. The presence of proteins in the intercellular fluid seems to be widespread since 10 proteins were detected in tobacco mosaic virus infected Chenopodium quinoa Willd. These proteins were found not only in inoculated tissue but also in the intercellular fluid of uninoculated upper leaves. A two-dimensional gel electrophoretic analysis of intercellular fluid proteins from N. tabacum L. cv. Xanthi-nc infected leaves showed that the relative molecular weight of protein b2 is larger (14 700) than the one of b1 and b3 (14 200). Other proteins, ranging in molecular weights from 12 500 to 36 300, could also be detected. We postulate that the presence of rather large amounts of proteins, including the well-characterized b proteins, in the intercellular fluid of infected hypersensitive leaves reflects overall changes in cell-to-cell interactions and in the cell wall metabolism.
Cell wall protuberances in the resin-pocket callus of Pinus nigra
Authors: Donaldson L. A. , Singh A. P.
Published: September 2008

Cell wall protuberances are found on the outer surface of parenchyma cells in callus tissue lining resin pockets in the wood of Pinus nigra Arn. The protuberances occur in a variety of forms ranging from bumps to distinctly stalked structures. They have a distinctive internal structure consisting of areas of fibrillar material of various densities and textures. The adjacent middle lamella often appears to be continuous with regions within the protuberance. No direct connection between the primary wall and the protuberance is observed, although staining at the light-microscope level indicates a similarity between areas of the protuberance and the primary wall. Protuberances are found only on parenchyma cells which have not developed secondary walls.
Chromosome pairing affinities between Old and New World species of Bromus section Pnigma
Authors: Armstrong K. C.
Published: September 2008

A low frequency of allosyndetic chromosome pairing occurred in interspecific hybrids between species having large chromosomes (Bromus benekenii (Lange) Trimen, 2n = 4x = 28; B. ramosus Huds., 2n = 4x = 28; B. pacificus Shear, 2n = 4x = 28) and species having small chromosomes (B. erectus Huds., 2n = 4x = 28; B. inermis Leyss, 2n = 4x = 28; B. pumpellianus Scribn., 2n = 4x = 28; B. riparius Rehm, 2n = 10x = 70; and B. variegatus, 2n = 2x = 14). These results are consistent with the suggestion that the large (predominantly Eurasion) and small (predominantly American) chromosome species of section Pnigma have followed different evolutionary pathways. Chromosome pairing in interspecific hybrids revealed low affinities between the chromosomes of the Eurasian species B. ramosus and the North American species B. pacificus. Thus there was no evidence that B. ramosus contained a form of the L genome found in American species. However genetic factors suppressing homoeologous pairing could be present in the allotetraploid parents.
The effect of atmospheric humidity on stomatal control of gas exchange in two tropical coniferous species
Authors: Meinzer Frederick , Goldstein Guillermo , Jaimes Marisol
Published: September 2008

Stomatal response to changes in leaf to air vapor pressure difference (VPD) and its influence on total gas exchange were measured for leaves of Podocarpus oleifolius and Podocarpus rospigliosii in an open gas exchange system. Stomatal conductance (g) of both species declined as VPD increased. Once a critical VPD was attained, the decrease in g was sufficient to decrease transpiration rate in spite of increasing VPD. This response pattern suggested "feedforward" control of stomatal response to humidity rather than negative feedback control based on changes in leaf water status. Coupling between CO2 assimilation and g and inherent water-use efficiency were greater in P. oleifolius. Stomatal response to humidity in P. oleifolius was consistent with a recent hypothesis that stomata optimize CO2 assimilation with respect to a given level of water loss by maintaining constant the ratio of the sensitivities of transpiration rate (E) and assimilation rate (A) to changes in g (∂E/∂g/∂A/∂g). This gain ratio did not remain constant in P. rospigliosii as VPD was varied. The possible ecological basis for these differences in gas exchange behavior is discussed.
Ultrastructural characterization of a pigment mutant of the red alga Palmaria palmata
Authors: Pueschel C. M. , Meer J. P. van der
Published: September 2008

Ultrastructural examination of a green-pigmented mutant of the red alga Palmaria palmata (L.) O. Kuntze revealed unusual features of the chloroplasts. Encircling peripheral thylakoids, characteristic of the wild-type plastids and florideophyte plastids generally, were lacking. Parallel evenly spaced thylakoids occurred in groups, leaving large volumes of thylakoid-free stroma. Irregularly shaped, electron-dense inclusions with an amorphous substructure and diameters up to 3 μm occurred in some plastids. Cells of the sporeling holdfasts contained structures resembling prolamellar bodies. Attempts to induce formation of prolamellar bodies in blades by dark treatment for 5 weeks were unsuccessful. However, some plastids did develop highly corrugated thylakoids with the crests of one thylakoid apposed to the troughs of the adjacent thylakoid. Thylakoid morphology of the wild-type control was not altered by the absence of light.
Acidification, growth promoter, and red light effects on germination of skotodormant lettuce seeds (Lactuca sativa)
Authors: Hsiao Andrew I. , Vidaver William , Quick William A.
Published: September 2008

Increasing the period of dark storage (DS) within a uniform seed lot of lettuce (Lactuca sativa L. cv. Grand Rapids) increased the degree of secondary dormancy (skotodormancy) induced, as evidenced by a loss of sensitivity to red light (R) and growth promoters such as gibberellin A3 (GA3), kinetin, thiourea, and ethylene. Differential degrees of skotodormancy were induced in lettuce seeds from three different sources (lot I < lot II < lot III). Either R or GA3 significantly increased the germination of skotodormant seeds if seeds were first immersed in strongly acidic solutions (pH ≤ 3.0) and then rinsed with water. The critical factor was found to be pH, not ionic strength. Promotion of germination by R or GA3 was positively related to increasing acidity, and also to the duration of DS. Sensitivity of the germination response to acid immersion varied with the seed lots, as little as 1 s being effective with some seeds. Acid treatment thus enables skotodormant seeds to recover much of their responsiveness to R and GA3. Extended DS (21 days) produced such pronounced skotodormancy (seed lot III) that acid immersion followed by usual R and GA3 produced only 10% germination. Continuous R or a seed-piercing treatment produced complete germination in otherwise skotodormant seeds. Responsiveness of germination to thiourea, kinetin, and ethylene, however, was not regained by treatment with acid. The action of these three chemicals on skotodormant seeds thus seems to be dependent on an active phytochrome and GA3-sensitive system. Acid-immersion treatments appear primarily to weaken membrane barriers of the endosperm cells, with resulting increased sensitivity of seeds to R treatment and GA3 penetration.
Formation de Weddellite (CaC2O4∙2H2O) extracellulaire en culture in vitro par Paxillus involutus; signification de cette production pour la symbiose ecto- mycorhizienne
Authors: Lapeyrie F. , Perrin Monique , Pepin R. , Bruchet G.
Published: September 2008

Several forms of extracellular crystals have been observed in vitro on a semisynthetic culture medium. The conditions for their formation have not been determined. Their morphology and their localisation on the hyphal surface and in the culture medium have been investigated by means of scanning electron microscopy. These crystals have been identified as dehydrated calcium oxalate (Weddellite) using x-ray diffraction methods. Their high calcium content has been demonstrated with the scanning electron microprobe, by detecting the x-ray emission of calcium. The significance of calcium oxalate production by an ectomycorrhizal fungus is discussed.