bluuebunny/crossref_metadata_2025 huggingface dataset:
Insect herbivores and their frass affectQuercus rubraleaf quality and initial stages of subsequent litter decomposition
Authors: Frost Christopher J. , Hunter Mark D.
Published: September 2007

Defoliation‐induced changes in plant foliage are ubiquitous, though factors mediating induction and the extent of their influence on ecosystem processes such as leaf litter decomposition are poorly understood. Soil nitrogen (N) availability, which can be affected by insect herbivore frass (feces), influences phytochemical induction. We conducted experiments to test the hypotheses that insect frass deposition would (1) reduce phytochemical induction following herbivory and (2) increase the decomposition and nutrient release of the subsequent leaf litter. During the 2002 growing season, 80Quercus rubrasaplings were subjected to a factorial experiment with herbivore and frass manipulations. Leaf samples were collected throughout the growing season to measure the effects of frass deposition on phytochemical induction. In live foliage, herbivore damage increased tannin concentrations early, reduced foliar N concentrations throughout the growing season, and lowered lignin concentrations in the late season. Frass deposition apparently reduced leaf lignin concentrations, but otherwise did not influence leaf chemistry. Following natural senescence, litter samples from the treatment groups were decomposed in replicated litterbags for 18 months at the Coweeta Hydrologic Laboratory, NC. In the dead litter samples, initial tannin concentrations were lower in the herbivore damage group and higher in the frass addition group relative to their respective controls. Tannin and N release rates in the first nine months of decomposition were also affected by both damage and frass. However, decomposition rates did not differ among treatment groups. Thus, nutrient dynamics important for some ecosystem processes may be independent from the physical loss of litter mass. Overall, while lingering effects of damage and even frass deposition can therefore carry over and affect ecosystem processes during decomposition, their effects appear short lived relative to abiotic forces that tend to homogenize the decomposition process.
Dynamic spectral structure specifies vowels for children and adults
Authors: Nittrouer Susan
Published: September 2007

When it comes to making decisions regarding vowel quality, adults seem to weight dynamic syllable structure more strongly than static structure, although disagreement exists over the nature of the most relevant kind of dynamic structure: spectral change intrinsic to the vowel or structure arising from movements between consonant and vowel constrictions. Results have been even less clear regarding the signal components children use in making vowel judgments. In this experiment, listeners of four different ages (adults, and 3-, 5-, and 7-year-old children) were asked to label stimuli that sounded either like steady-state vowels or like CVC syllables which sometimes had middle sections masked by coughs. Four vowel contrasts were used, crossed for type (front/back or closed/open) and consonant context (strongly or only slightly constraining of vowel tongue position). All listeners recognized vowel quality with high levels of accuracy in all conditions, but children were disproportionately hampered by strong coarticulatory effects when only steady-state formants were available. Results clarified past studies, showing that dynamic structure is critical to vowel perception for all aged listeners, but particularly for young children, and that it is the dynamic structure arising from vocal-tract movement between consonant and vowel constrictions that is most important.
Transient evoked otoacoustic emission latency and cochlear tuning at different stimulus levels
Authors: Sisto Renata , Moleti Arturo
Published: September 2007

Cochlear latency has been evaluated in young adults by time-frequency analysis of transient evoked otoacoustic emissions recorded using the nonlinear acquisition mode at different levels of the click stimulus. Objective, even if model-dependent, estimates of cochlear tuning have been obtained from the otoacoustic latency estimates. Transmission-line cochlear models predict that the transient-evoked otoacoustic emission latency is dependent on the stimulus level, because the bandwidth of the cochlear filter (tuning) depends on the local cochlear excitation level due to nonlinear damping. The results of this study confirm the increase of tuning with increasing frequency and show clearly the decrease of latency and tuning with increasing stimulus level. This decrease is consistent with the expected relation between the slowing down of the traveling wave near the tonotopic place and the cochlear excitation amplitude predicted by cochlear models including nonlinear damping. More specifically, these results support the models in which nonlinear damping consists of a quadratic term and a constant positive term.
Modeling the cochlear nucleus: A site for monaural echo suppression?
Authors: Bürck Moritz , van Hemmen J. Leo
Published: September 2007

Echo suppression plays an important role in identifying and localizing auditory objects. One can distinguish between binaural and monaural echo suppression, although the former is the one commonly referred to. Based on biological findings we introduce and analyze a mathematical model for a neural implementation of monaural echo suppression in the cochlear nucleus. The model’s behavior has been verified by analytical calculations as well as by numerical simulations for several types of input signal. It shows that in the perception of a pair of clicks the leading click suppresses the lagging one and that suppression is maximal for an interclick interval of 2–3ms. Similarly, ongoing stimuli will be affected by the suppression mechanism primarily a couple of milliseconds after onset, resulting in a reduced perception of a sound shortly after its start. Both effects match experimental data.
A comparison of vocal tract perturbation patterns based on statistical and acoustic considerations
Authors: Story Brad H.
Published: September 2007

The purpose of this study was to investigate the relation between vocal tract deformation patterns obtained from statistical analyses of a set of area functions representative of a vowel repertoire, and the acoustic properties of a neutral vocal tract shape. Acoustic sensitivity functions were calculated for a mean area function based on seven different speakers. Specific linear combinations of the sensitivity functions corresponding to the first two formant frequencies were shown to possess essentially the same amplitude variation along the vocal tract length as the statistically derived deformation patterns reported in previous studies.
Physical mechanisms of phonation onset: A linear stability analysis of an aeroelastic continuum model of phonation
Authors: Zhang Zhaoyan , Neubauer Juergen , Berry David A.
Published: September 2007

In an investigation of phonation onset, a linear stability analysis was performed on a two-dimensional, aeroelastic, continuum model of phonation. The model consisted of a vocal fold-shaped constriction situated in a rigid pipe coupled to a potential flow which separated at the superior edge of the vocal fold. The vocal fold constriction was modeled as a plane-strain linear elastic layer. The dominant eigenvalues and eigenmodes of the fluid-structure-interaction system were investigated as a function of glottal airflow. To investigate specific aerodynamic mechanisms of phonation onset, individual components of the glottal airflow (e.g., flow-induced stiffness, inertia, and damping) were systematically added to the driving force. The investigations suggested that flow-induced stiffness was the primary mechanism of phonation onset, involving the synchroniza-tion of two structural eigenmodes. Only under conditions of negligible structural damping and a restricted set of vocal fold geometries did flow-induced damping become the primary mechanism of phonation onset. However, for moderate to high structural damping and a more generalized set of vocal fold geometries, flow-induced stiffness remained the primary mechanism of phonation onset.
Motion of a solid sphere in a viscoelastic medium in response to applied acoustic radiation force: Theoretical analysis and experimental verification
Authors: Aglyamov Salavat R. , Karpiouk Andrei B. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Emelianov Stanislav Y.
Published: September 2007

The motion of a rigid sphere in a viscoelastic medium in response to an acoustic radiation force of short duration was investigated. Theoretical and numerical studies were carried out first. To verify the developed model, experiments were performed using rigid spheres of various diameters and densities embedded into tissue-like, gel-based phantoms of varying mechanical properties. A 1.5MHz, single-element, focused transducer was used to apply the desired radiation force. Another single-element, focused transducer operating at 25MHz was used to track the displacements of the sphere. The results of this study demonstrate good agreement between theoretical predictions and experimental measurements. The developed theoretical model accurately describes the displacement of the solid spheres in a viscoelastic medium in response to the acoustic radiation force.
Hearing loss from interrupted, intermittent, and time varying non-Gaussian noise exposure: The applicability of the equal energy hypothesis
Authors: Hamernik Roger P. , Qiu Wei , Davis Bob
Published: September 2007

Sixteen groups of chinchillas (N=140) were exposed to various equivalent energy noise paradigms at 100dB(A) or 103dB(A) SPL. Eleven groups received an interrupted, intermittent, and time varying (IITV) non-Gaussian exposure quantified by the kurtosis statistic. The IITV exposures, which lasted for 8h∕day, 5days∕week for 3weeks, were designed to model some of the essential features of an industrial workweek. Five equivalent energy reference groups were exposed to either a Gaussian or non-Gaussian 5days, 24h∕day continuous noise. Evoked potentials were used to estimate hearing thresholds and surface preparations of the organ of Corti quantified the sensory cell population. For IITV exposures at an equivalent energy and kurtosis, the temporal variations in level did not alter trauma and in some cases the IITV exposures produced results similar to those found for the 5day continuous exposures. Any increase in kurtosis at a fixed energy was accompanied by an increase in noise-induced trauma. These results suggest that the equal energy hypothesis is an acceptable approach to evaluating noise exposures for hearing conservation purposes provided that the kurtosis of the amplitude distribution is taken into consideration. Temporal variations in noise levels seem to have little effect on trauma.
Sperm whale three-dimensional track, swim orientation, beam pattern, and click levels observed on bottom-mounted hydrophones
Authors: Nosal Eva-Marie , Frazer L. Neil
Published: September 2007

In an earlier paper [Nosal and Frazer Appl. Acoust. 61, 1187–1201 (2006)], a sperm whale was tracked in three-dimensions using direct and surface-reflected time differences (DRTD) of clicks recorded on five bottom-mounted hydrophones, a passive method that is robust to timing errors between hydrophones. This paper refines the DRTD method and combines it with a time of (direct) arrival method to improve the accuracy of the track. The position and origin time of each click having been estimated, pitch and yaw are then obtained by assuming the main axis of the whale is tangent to the track. Roll is then found by applying the bent horn model of sperm whale phonation, in which each click is composed of two pulses, p0 and p1, that exit the whale at different points. With instantaneous pitch, roll, and yaw estimated from time differences, amplitudes are then used to estimate the beam patterns of the p0 and p1 pulses. The resulting beam patterns independently confirm those obtained by Zimmer et al. [J. Acoust. Soc. Am. 117, 1473–1485 (2005); 118, 3337–3345 (2005)] with a very different experimental setup. A method for estimating relative click levels is presented and used to find that click levels decrease toward the end of a click series, prior to the “creak” associated with prey capture.
Searching for best exemplars in multidimensional stimulus spaces
Authors: Oglesbee Eric , de Jong Kenneth
Published: September 2007

Examining phonetic categorization in multidimensional stimulus spaces poses a number of practical problems. The traditional method of forced identification becomes prohibitive when the number and size of stimulus dimensions becomes increasingly large. In response, Evans and Iverson [J. Acoust. Soc. Am. 115, 352–361 (2004)] proposed an adaptive tracking algorithm for finding vowel best exemplars in a multidimensional space. This algorithm converged on best exemplars in a small number of trials; however, the search method was designed explicitly for vowel stimuli. In this paper, a more general multidimensional search algorithm is described, and results from simulations and experiments using the proposed algorithm are presented.
Fluorine in Pharmaceuticals: Looking Beyond Intuition
Authors: Müller Klaus , Faeh Christoph , Diederich François
Published: September 2007

Fluorine substituents have become a widespread and important drug component, their introduction facilitated by the development of safe and selective fluorinating agents. Organofluorine affects nearly all physical and adsorption, distribution, metabolism, and excretion properties of a lead compound. Its inductive effects are relatively well understood, enhancing bioavailability, for example, by reducing the basicity of neighboring amines. In contrast, exploration of the specific influence of carbon-fluorine single bonds on docking interactions, whether through direct contact with the protein or through stereoelectronic effects on molecular conformation of the drug, has only recently begun. Here, we review experimental progress in this vein and add complementary analysis based on comprehensive searches in the Cambridge Structural Database and the Protein Data Bank.
Transcranial Magnetic Stimulation Elicits Coupled Neural and Hemodynamic Consequences
Authors: Allen Elena A. , Pasley Brian N. , Duong Thang , Freeman Ralph D.
Published: September 2007

Transcranial magnetic stimulation (TMS) is an increasingly common technique used to selectively modify neural processing. However, application of TMS is limited by uncertainty concerning its physiological effects. We applied TMS to the cat visual cortex and evaluated the neural and hemodynamic consequences. Short TMS pulse trains elicited initial activation (∼1 minute) and prolonged suppression (5 to 10 minutes) of neural responses. Furthermore, TMS disrupted the temporal structure of activity by altering phase relationships between neural signals. Despite the complexity of this response, neural changes were faithfully reflected in hemodynamic signals; quantitative coupling was present over a range of stimulation parameters. These results demonstrate long-lasting neural responses to TMS and support the use of hemodynamic-based neuroimaging to effectively monitor these changes over time.
Stone Adze Compositions and the Extent of Ancient Polynesian Voyaging and Trade
Authors: Collerson Kenneth D. , Weisler Marshall I.
Published: September 2007

The last region on Earth settled by humans during prehistory was East Polynesia. Hawaiian oral histories mention voyaging from Hawai'i to Tahiti and back via the Tuamotus, an open ocean journey of several thousands of kilometers. The trace element and isotope chemistries of a stone adze recovered from the Tuamotu Archipelago are unlike those of sources in central Polynesia but are similar to the Kaho'olawe Island hawaiite, in the Hawaiian Islands, supporting the oral histories. Other adzes collected from the low coral islands of the northwest Tuamotus have sources in the Marquesas, Austral and Society Islands, and the Pitcairn Group, confirming that trade was widespread within East Polynesia.
Assessment of Mycobacterial Interspersed Repetitive Unit-QUB Markers To Further Discriminate the Beijing Genotype in a Population-Based Study of the Genetic Diversity of
Mycobacterium tuberculosis
Clinical Isolates from Okinawa, Ryukyu Islands, Japan
Authors: Millet Julie , Miyagi-Shiohira Chika , Yamane Nobuhisa , Sola Christophe , Rastogi Nalin
Published: September 2007

The present investigation focused on genetic diversity and drug resistance of 101
Mycobacterium tuberculosis
strains isolated between July 2003 and February 2005 in the Okinawa prefecture, Ryukyu Islands, Japan. A high rate of clustering (87%, eight clusters, 2 to 69 strains/cluster) was observed upon spoligotyping; most of it was due to the lower discriminatory power of this method for the Beijing lineage (
n
= 72; 71.3% of the isolates). The remaining diversity was limited to seven clusters (two to five isolates/cluster), with the following distribution of major lineages: ill-defined T (
n
= 13; 12.8%), ancestral East African-Indian (
n
= 6; 5.9%), Haarlem (
n
= 4; 4%), Latin American-Mediterranean (
n
= 2; 2%), X1 (
n
= 1; 1%), and a total absence of the central Asian clade. Three remaining strains could not be classified on the basis of their spoligotype pattern and were labeled “unknown.” Subtyping with mycobacterial interspersed repetitive units (MIRUs) in association with additional QUB minisatellites was performed to discriminate among the Beijing strains. Based on an “in-house” spoligotyping/MIRU database (
n
= 694 Beijing strains), eight highly discriminative MIRU loci for Beijing strains were selected (loci numbered 10, 16, 23, 26, 27, 31, 39, and 40). The highest discriminatory power (
h
) observed in our sample (
n
= 72; M-26, 0.385; M-10, 0.38; M-31, 0.255; M-16, 0.238) was too low, and 73.6% of the Beijing strains from Okinawa remained clustered. Typing of Beijing strains with additional QUB loci (with the exception of “one-copy” QUB-1451) resulted in higher discriminatory powers: QUB-11b, 0.68; QUB-11a, 0.656; QUB-26, 0.644; QUB-18, 0.553; QUB-4156, 0.5; and QUB-1895, 0.453. A definitive algorithm on the use of QUB markers to subtype Beijing isolates in expanded studies would shed light on their hypervariability, which may sometimes blur recognition between epidemiologically linked Beijing isolates. The total absence of multiple drug resistance among Beijing isolates from Okinawa, as well as the relatively older ages of the patients (majority above 60 years), shows that tuberculosis (TB) is a declining disease in Okinawa, and an adequate TB control program has successfully avoided both the emergence and the spread of multidrug-resistant TB in this insular setting.
Case of Pyomyositis Due to
Mycobacterium haemophilum
in a Renal Transplant Recipient
Authors: Jang Eun-Young , Lee Sang-Oh , Choi Seong-Ho , Sung Heungsup , Kim Mi-Na , Kim Bum-Joon , Choi Sang-Ho , Kim Yang Soo , Woo Jun Hee
Published: September 2007

We report a case of pyomyositis due to
Mycobacterium haemophilum
in a renal transplant recipient.
M. haemophilum
was identified by PCR-mediated sequence analysis of the heat shock protein gene in the DNA of the specimen. The patient was successfully treated with repeated surgical debridement and prolonged antimycobacterial therapy.
Utility of Human Immunodeficiency Virus Type 1 Envelope as a T-Cell Immunogen
Authors: Peut Viv , Kent Stephen J.
Published: September 2007

Human immunodeficiency virus (HIV)-specific CD8 T lymphocytes are important for the control of viremia, but the relative utility of responses to the various HIV proteins is controversial. Immune responses that force escape mutations that exact a significant fitness cost from the mutating virus would help slow progression to AIDS. The HIV envelope (Env) protein is subject to both humoral and cellular immune responses, suggesting that multiple rounds of mutation are needed to facilitate viral escape. The Gag protein, however, has recently been shown to elicit a more effective CD8 T-cell immune response in humans. We studied 30 pigtail macaques for their CD8 T-lymphocyte responses to HIV-1 Env and simian immunodeficiency virus (SIV) Gag following prime/boost vaccination and intrarectal challenge with simian-human immunodeficiency virus SHIV
mn229
. Eight CD8 Env-specific T-cell epitopes were identified and mapped in 10 animals. Animals that generated Env-specific CD8 T-cell responses had equivalent viral loads and only a modest advantage in retention of peripheral CD4 T lymphocytes compared to those animals without responses to Env. This contrasts with animals that generated CD8 T-cell responses to SIV Gag in the same trial, demonstrating superior control of viral load and a larger advantage in retention of peripheral CD4 T cells than Gag nonresponders. Mutational escape was common in Env but, in contrast to mutations in Gag, did not result in the rapid emergence of dominant escape motifs, suggesting modest selective pressure from Env-specific T cells. These results suggest that Env may have limited utility as a CD8 T-cell immunogen.
Synthesis, Characterization and Thermodynamics of Exchange Using Zirconium Titanium Phosphate Cation Exchanger
Authors: Thakkar Rakesh P. , Chudasama Uma V.
Published: September 2007

A mixed material of the class of tetravalent bimetallic acid (TBMA) salt - zirconium titanium phosphate (ZTP) - has been synthesized by the sol-gel technique. ZTP has been characterized by elemental analysis, thermal analysis (TGA, DTA), FTIR, X-ray diffraction and SEM. Ion exchange capacity (IEC) of the material has been determined and the effect of calcination (373-773 K) on IEC studied and chemical stability of the material in various media (acids, bases and organic solvents) assessed. Further, the equilibrium exchange of H in ZTP for Mg2+, Ca2+, Sr2+ and Ba2+ ions has been studied at 303, 313, 323 and 333 K at constant ionic strength. On the basis of the exchange isotherms, various thermodynamic parameters such as equilibrium constant (K), standard gibbs energy change (∆Go), entropy change (∆So) and enthalpy change (∆Ho) have been calculated. The parameters were correlated with the ion exchange characteristics of the material.
Diversity In guard cell plastids of the Orchidaceae: a structural and functional study
Authors: D'Amelio Elisa D'Antoni , Zeiger Eduardo
Published: September 2007

Guard cells of species representing 27 genera from the Orchidaceae were surveyed under fluorescence microscopy. With the exception of the genus Paphiopedilum, chlorophyll a fluorescence was observed in all species, indicating that, as in other families, chloroplasts are strongly conserved in the stomata of the Orchidaceae. The achlorophyllous stomata of Paphiopedilum therefore constitute a unique variation in that pattern, with its expression at the generic level pointing to an early, stable evolutionary event. Five of the orchid species, Vanilla aromaticum, Phragmipedium longifolium, Haemaria discolor, Paphiopedilum harrisianum, and Paphiopedilum insigne, were also studied ultrastructurally. There was a close correlation between plastid fluorescence intensity in guard cells and the presence of grana thylakoids in the organelles, with Vanilla showing an intense fluorescence and extensive grana stacking, while the Paphiopedilum stomata were completely devoid of both features. Phragmipedium stomata had an intermediate level of fluorescence and a reduced number of thylakoids, whereas Haemaria guard cells, which had no chlorophyll fluorescence in intact tissue but a weak fluorescence in cryostat sections, showed an unusual array of pleomorphic plastids with only a few exhibiting some thylakoids. Other ultrastructural features of orchid guard cells were also documented. These observations and a marked variation in fluorescence intensity and plastid number and size seen in the guard cells of the surveyed genera point to a broad structural diversity in the guard cell plastids of the Orchidaceae. This diversity could underlie specialized functional properties associated with stomatal adaptations to different growing habitats.
Permineralized fruits and Seeds from the Princeton chert (Middle Eocene) of British Columbia: Lythraceae
Authors: Cevallos-Ferriz Sergio R. S. , Stockey Ruth A.
Published: September 2007

Two types of lythraceous fruit and seed remains are described from the Middle Eocene, Allenby Formation of Princeton, British Columbia. Small globose, pedicellate fruits with persistent sepals, four to six locules, septa complete to the fruit apex, axial placentation, a palisade-like endocarp, and pyramidal seeds are referable to the genus Decodon Gmel. Numerous dispersed anatropous seeds of the same morphology show rounded or angular comers, lack lateral wings, and have a raphe that begins near the micropyle, passing through the middle integumentary layer on the dorsal face to the seed chalaza. Integuments are three zoned and seeds bear a ventral germination valve composed of radially elongated rectangular cells similar to the outer integumentary layer. Seeds show a prominent hypostase and dicotyledonous embryos with remains of a suspensor. These fruits and seeds are described as a new species of Decodon, D. allenibyensis Cevallos-Ferriz et Stockey sp.nov., which represents the oldest known species of the genus described to date. One fruit with several large, pyramidal lythraceous seeds is described. Seeds have three integumentary zones, the outer of which appears to have been mucilaginous. These remains most closely resemble the genus Lawsonia L., but additional specimens are needed to confirm this comparison. These lythraceous remains add to our knowledge of the Princeton angiosperm flora and further support the idea that these plants lived along a lake or marsh.
A fossil flower with in situ Pistillipollenites from the Eocene of British Columbia
Authors: Stockey Ruth A. , Manchester Steven R.
Published: September 2007

A single actinomorphic flower has been found in the Horsefly Mine Top Section (Middle Eocene) of British Columbia. The flower, 2.1 cm in diameter, has six sepals, probably a superior ovary, and six stamens, one opposite each sepal. The pollen is morphologically identical with that of the dispersed grain of Pistillipollenites macgregorii Rouse. Grains, 22 μm in diameter, have numerous gemmae supported by columellae and a finer ornamentation of nanoverrucae. The grains are triporate with gemmae around apertures. Spherical hollow Ubisch bodies indicative of a secretory tapetum underlie remains of tapetal membranes. The floral structure of this new taxon, Pistillipollianthus wilsonii gen. et sp. nov., is distinctly different from the only other Pistillipollenites-producing flower described from the Eocene of Texas. The current study indicates that Pistillipollenites grains identified in sediments from the Cretaceous to the Eocene probably represent pollen from different angiosperm families, and it adds to the evidence that this type of gemmate grain may have evolved several times through convergent evolution.
Étude de l'action d'un herbicide, le chlorthal, sur la prolifération cellulaire et la croissance de la tige du Cuscuta lupuliformis
Authors: Agaev R. , Lecocq F. M. , Fer A. , Hallet J. N.
Published: September 2007

The effects of a herbicide, chlorthal (2,3,5,6-tetrachloroterephthalic acid), on the growth and development of Cuscuta lupuliformis Krocker have been examined on seedlings 2 to 15 days old. In dodder, the shoot meristem is not restricted to the apex where rudimentary leaves are initiated but extends approximately 6 mm downwards, to the hook zone of the young stem. In this region, cell dimensions, values of the mitotic indices, and the distribution of the nuclear DNA contents measured by microspectrophotometry remain essentially unchanged. Beyond the hook zone, cell elongation gradually replaces cell division. A chlorthal treatment caused a reduction in the mitotic indices of the meristematic cells along with a temporary blocking of mitoses at metaphase. These effects were similar to those observed with colchicine treatments. The nuclei were then reconstituted with 4C DNA contents and, after several new cycles under which DNA was replicated normally, they became polyploid. After 15 days of herbicide application, the meristematic apex and the underlying zones exhibited numerous hypertrophied cells with nuclear DNA contents of 8, 16, 32, and 64C. There is evidence that chlorthal stops cellular division without inhibiting the other phases of the cell cycle; it induces a rapid arrest of the growth of the young dodder.
Distribution and species diversity of trichomycete gut fungi in aquatic insect larvae in two Rocky Mountain streams
Authors: Lichtwardt Robert W. , Williams Marvin C.
Published: September 2007

At least 20 species of Trichomycetes (Zygomycotina) were dissected from the hindguts and peritrophic membranes of larval Diptera (Simuliidae, Chironomidae), Ephemeroptera, and Plecoptera in two high-altitude streams, and the trichomycete species diversity in the two streams was compared. Periodic sampling of larvae over a 6-week summer period showed that some gut fungi are widely distributed in their respective host types, whereas other fungal species are more localized. Insect populations had infestations that varied from low to as high as 100% of the insects dissected, depending on the fungal species. There was no general increase over time, from early to late season, in fungal species diversity or percentage of larval infestation, nor were larvae in second- and third-order sites of one stream generally more infested than in a first-order site in that stream.
South American Gasteromycetes. II. The genus Vascellum
Authors: Homrich M. H. , Wright J. E.
Published: September 2007

In this second contribution to the Gasteromycetes of southern South America seven species of Vascellum Smarda found in that area are described. Of these, V. pampeanum (Speg.) Homrich is a new combination and V. cingulatum Homrich, V. cuzcoense Homrich, V. delicatum Homrich, and V. hyalinum Homrich are new species. Complete descriptions and illustrations of all features of the species are given, together with a key for their identification.
Growth and allocation patterns of Mikania micrantha in successional environments after slash and burn agriculture
Authors: Swamy P. S. , Ramakrishnan P. S.
Published: September 2007

The growth and allocation of biomass and nutrients in Mikania micrantha HBK., an exotic early successional perennial weed, was studied in seral stages after slash and burn agriculture. Peak vigour of the species was reached in a 3-year-old fallow, with decline in older fallows. In general, allocation of biomass and nutrients to the leaf component and for reproduction was low in a 12-year-old fallow. On the other hand, allocation to the rosette root, which is the perennating organ, increased in older fallows and is a strategy for survival and regeneration after a subsequent perturbation. Lower nutrient-uptake efficiency and higher nutrient-use efficiency in 6- and 12-year-old fallows are adaptations for survival in a nutrient-limiting competitive environment. This ruderal species has an exploitative growth strategy, with weed suppression occurring in older successional fallows dominated by shrubs and trees.
Isolation of angolide from Pithomyces atro-olivaceus and P. graminicola
Authors: Russell D. W.
Published: September 2007

Two additional Pithomyces species, P. atro-olivaceus and P. graminicola, produced the cyclotetradepsipeptide angolide, when grown in surface culture on a defined medium.
Morphometric analysis of reserve substances and ultrastructural changes during caulogenic determination and loss of competence of Eastern White pine (Pinus strobus) cotyledons in vitro
Authors: Flinn Barry S. , Webb David T. , Newcomb William
Published: September 2007

Lipid, starch, and protein reserves were monitored cytochemically and, along with certain ultrastructural changes, were quantified morphometrically during adventitious shoot determination or loss of competence in cotyledons from cultured Pinus strobus zygotic embryos. Initial expiants were rich in lipid, which declined during culture. There was more lipid retention in explants on cytokinin medium by day 5 than on basal medium. However, by day 7, five- and six-celled clusters showed greater lipid utilization than most other cells on cytokinin, which may have indicated a shift towards shoot determination in these cells. Except for an initially greater retention on cytokinin, a similar pattern for storage protein degradation was observed in both treatments. Starch levels increased during culture, but did not differ between treatments during the first 7 days. Vacuolation increased during culture and was greater on basal medium than on cytokinin. Relative nuclear size also increased, but was greater on cytokinin. Relative mitochondrial area increased during culture, except in noncluster cells on basal medium. While few differences were noted between cell types within each treatment, distinct differences in nuclear size, vacuolation, and lipid content existed between cells on cytokinin and basal medium. These coincided with the timing of caulogenic determination in cytokinin-treated expiants. The loss of lipid reserves, as well as ultrastructural changes associated with the maturation of cells on basal medium, was associated with the loss of competence.
Structure et variabilité des cires épicuticulaires chez le genre Typha (Typhaceae)
Authors: Djebrouni Mohamed
Published: September 2007

A scanning electron microscopic examination of epicuticular surfaces in four species of the genus Typha showed some interspecific uniformity. It revealed the presence of filaments and granules, which are basic elements of waxes. These elements are synthesized during the early development of shoots; their subsequent development is related to the age of individuals and to environmental conditions during growth. The formation of flat sheets and thin plates from the basic elements appears to be induced by climatic aridity and the effects of sea sprays. Key words: Typha, Typhaceae, epicuticular waxes, variability.
Morphological and anatomical development in the Vitaceae. III. Vegetative development in Parthenocissus inserta
Authors: Gerrath Jean M. , Posluszny U.
Published: September 2007

The vegetative shoot of Parthenocissus inserta (Kerner) Fritsch. was examined both histologically and three dimensionally. The shoot apex produces uncommitted primordia at two nodes of a three-node, five-primordium cycle. The primordia can be summarized as follows: (i) a leaf opposite a lower uncommitted primordium, arising above a leaf and low on the apical flank; (ii) a leaf either opposite an upper uncommitted primordium or without an uncommitted primordium opposite it, in both instances arising directly above an uncommitted primordium and high on the apical flank; (iii) a lower uncommitted primordium, arising above and opposite a leaf and high on the flank of the apex; (iv) an upper uncommitted primordium, arising above and opposite a leaf and low on the flank of the apex. The uncommitted primordium may develop into either an inflorescence or a tendril. Tendril growth is sympodial, usually with three orders of branching. Tendrils may, on occasion, develop adhesive discs at their tips, but most commonly the tips disintegrate. Axillary buds are present at the upper tendril node and the tendrilless node. Their initiation is more precocious at the tendrilless node. The pattern of development is the same for both, in that both form multiple orders of buds, each in the axil of the prophyll of the preceding one.
Effect of the triazine herbicides Goltix and Igran on cell wall degradation by some fungi
Authors: Ismail I. M. K. , Rahman Tahany M. A. Abdel , Elwy Esmat E. A. , Osman M. E.
Published: September 2007

Fifteen-day-old tomato and cotton hypocotyls were susceptible to degradation by the three fungi Aspergillus fumigatus, Fusarium oxysporum f.sp. lycopersici, and Fusarium oxysporum f.sp. vasinfectum. The last two fungi cause tomato and cotton wilts in Egypt. Addition of various concentrations (50–1200 ppm) of Goltix (4-amino-3-methyl-6-phenyl-1,2,4-triazine-5 (4H)-one(IUPAC)) inhibited the tomato cell wall degradation by the tested fungi except its pathogen, while the doses (50–1200 ppm) of Igran (4-ethylamino-2-tert-butylamino-6-methylthio-5-triazine) inhibited tomato cell wall degradation by the three fungi. On the other hand, the addition of various concentrations of Goltix to cotton cell wall culture increased the susceptibility of the cell wall to the degrading enzymes of the three fungi, while Igran inhibited the degradation by the two Fusarium species. The data also emphasized the presence of xylanase, arabanase, mannanase, galactanase, and cellulase enzymes in both tomato and cotton cell wall cultures of the tested fungi. Higher doses of either Goltix or Igran (800 and 1200 ppm) completely inhibited the activation of arabanase, xylanase, and mannanase, while cellulase and galactanase were less sensitive to the applied herbicide doses.
Influence des réserves azotées sur la formation des feuilles d’Alnus glutinosa et ses conséquences dans l'estimation de la fixation d'azote
Authors: Domenach A. M. , Kurdali F.
Published: September 2007

The influence of nitrogen reserves on leaf formation of 5- to 6-year-old plants of Alnus glutinosa (L.) Gaertn. was investigated using a 15N labelling method. Nitrogen reserves were derived essentially from the root system and along with N fixation by Frankia, supported the growth of the young leaves. The reserves represent 10% of the total nitrogen in the leaves at the end of the growing period under natural or environmentally controlled conditions. The percentage of fixed nitrogen in alder leaves was estimated to be 87% taking into account the nitrogen reserves and using the isotopic comparison with a nonfixing plant (Populus alba L.). Several conditions requiring the use of 15N methods to estimate the symbiotic nitrogen fixation by Frankia were formulated. The selection of samples for analysis must be from the most recently formed leaves at the end of the growing season to avoid the influence of nitrogenous reserves. Key words: nitrogen reserves, Alnus glutinosa, Populus alba, Frankia, 15N fixation.
Comparaison de quelques Loganiacées à l'aide des caractères quantitatifs et qualitatifs de l'anatomie du bois
Authors: Coulaud Joëlle
Published: September 2007

Seventy-three samples of wood, belonging to 11 genera of Loganiaceae and 2 genera of Rubiaceae are described. Fourteen quantitative characters are first studied by a discriminant multivariate analysis, and then all the characters are examined. The characters of wood anatomy show the unity as well as the subdivisions of the family Loganiaceae. The two genera Antonia and Bonyunia belong to an homogenous and individualized group. Potalia, Anthocleista, and Fagraea are also related and are opposite to Strychnos. Neuburgia is not near Strychnos, though it belongs to the same tribe. A new relation is discovered between Nuxia and Geniostoma, and the special feature of Buddlejeae (Nuxia, Buddleja) does not come into sight; these genera are also related to Strychnos and Peltanthera. The genera Gaertnera and Genipa can scarcely be distinguished from the family by a few qualitative characters. The necessity of standardization in the observations, in order to integrate wood characters in systematic studies, is noted.
Histological localization of furanocoumarins in Ruta graveolens shoots
Authors: Zobel Alicja M. , Brown Stewart A.
Published: September 2007

Three linear furanocoumarins, psoralen, xanthotoxin, and bergapten, were localized histologically in Ruta graveolens shoots. The highest amounts were present in the epidermis, lesser amounts in the parenchyma cells, and only traces in the glands. Scrapings and filter paper rubbings from leaf and stem surfaces gave qualitative indications of their presence. As determined by liquid chromatography, large amounts (up to at least 60% of the total in the plant) were extractable into boiling water after 2-s immersion, indicating their localization on the cuticle. Xanthotoxin was usually present in the highest concentrations on the surface, but in most cases amounts of psoralen were only slightly lower. In both the scanning electron microscope and the light microscope a layer covering the cuticle was observed; its crystal-like structure varied over the surface in the regions of the glands and other parts of the epidermis. It was thicker in younger leaves, and during leaf expansion it was stretched and sometimes broken. Localization of a substantial portion of these linear furanocoumarins on the surface is a factor in the propensity of this species to induce photophytodermatitis.
Fruiting body development in the mycetozoan Echinostelium bisporum
Authors: Spiegel Frederick W. , Feldman Joyce
Published: September 2007

Fruiting was followed from the prespore cell stage through the appearance of synaptonemal complexes in the spores in the simple mycetozoan Echinostelium bisporum. The prespore cell differentiates from a uninucleate amoeboflagellate that rounds up on the surface of the substrate. Centrioles are present in the prespore cell. As the prespore cell continues to differentiate it secretes a sheath and becomes nearly spherical. The prespore cell begins to lay down the stalk within an invagination, then rises as a sporogen at the tip of the stalk. By the sporogen stage the centrioles disappear and a spherical microtubule organizing center (MTOC) appears between the nucleus and the stalk apex. At the end of stalk elongation, the nucleus undergoes an apparently closed acentric mitosis and the sporogen cleaves into two hemispheres. Each daughter cell then rounds up and begins to produce a sculptured spore wall. The nuclei of the spores enter presumed meiotic prophase with synaptonemal complexes after the spore wall is complete. The spherical MTOC is present in all stages after the sporogen. These characters suggest that E. bisporum is a reduced myxomycete that has lost the free living plasmoidal stage of the life cycle.
Nonspecific responses in plant growth, yield, and root colonization of noncereal crop plants to inoculation with Azospirillum brasilense Cd
Authors: Bashan Y. , Ream Y. , Levanony Hanna , Sade A.
Published: September 2007

Inoculation of seven different crop plant species by Azospirillum brasilense Cd resulted in an increase in plant yield, as well as in changes in several other plant parameters, in tomato, eggplant, pepper, and cotton plants. Analysis of 56 different experiments revealed that the rate of success (positive plant response) ranged from 71 to 75 %. The dry weight of plants and yield responses ranged from significantly high yield increases to negligible or no response in similarly performed experiments. The average increases in yield in the positive response experiments were 30, 23, 18, and 16% for tomato, eggplant, pepper, and cotton, respectively. Significant earlier maturation was also detected in the four responding plant species. The response of other plant growth parameters varied between plant species. The level of root colonization by A. brasilense Cd was similar in all four plant species, i.e. root population size of 5 × 105 cfu/g fresh weight root. It is suggested that inoculation of noncereal crop plants by the cereal-root originate A. brasilense Cd is nonspecific with inconsistency in plant response to inoculation.
Cellularization of the female gametophyte in Ranunculus sceleratus
Authors: Bhandari N. N. , Chitralekha P.
Published: September 2007

Wall formation in Ranunculus sceleratus takes place simultaneously at the micropylar and chalazal poles of the embryo sac. During the last (third) mitotic division resulting in an eight-nucleate embryo sac, three distinct cell plates are formed at either pole. Of the three cell plates, CPI (horizontal), CPE (oblique), and CPIII (vertical), the first two are formed between the separating chromatin masses of the two dividing nuclei. CPIII (vertical cell plate) arises subsequently between the first two plates. CPI (horizontal cell plate) extends perpendicular to the long axis of the embryo sac to separate the central vacuole and one nucleus (polar) from the quartet of nuclei. The other two cell plates extend simultaneously between the three remaining nuclei; CPII (oblique plate) cuts off one of the nuclei while CPIII (vertical cell plate) separates the other two. Consequently, the egg apparatus, central cell with two polar nuclei, and three antipodal cells are formed.
Effects of amino acids on the development of spikelets in cultured tassels of Zea mays
Authors: Pareddy D. R. , Greyson R. I.
Published: September 2007

The effects of amino acids on spikelet development in in vitro cultured tassels of Zea mays inbred line Oh43 were studied. Single amino acids had differential effects on growth and differentiation of cultured tassels. While a few amino acids (arginine, lysine, valine, and proline) were stimulatory, most of the amino acids were either ineffective (serine, leucine, glycine, threonine, methionine, phenylalanine, histidine, aspartic acid, and tyrosine) or inhibitory (isoleucine, asparagine, tryptophan, glutamic acid, and alanine), at a concentration of 30 mg/L, to the development of "normal" spikelets and also to tassel growth. A mixture of the stimulatory amino acids at their optimal concentrations (arginine, 15 mg/L; lysine, 60 mg/L; valine, 120 mg/L; proline, 15 mg/L) produced the maximum number of "normal" spikelets, thereby duplicating the effect of an optimum concentration of casein hydrolysate.
A light and electron microscopic study of the developmental cycle in the basidiomycete Pachnocybe ferruginea
Authors: Kleven Nancy L. , McLaughlin David J.
Published: September 2007

The vegetative and basidial development of Pachnocybe ferruginea was studied by light and electron microscopy. Caffeine was used during fixation to improve cytoplasmic clarity, and a flat-embedding method incorporating Mylar as a release agent was used. Uninucleate basidiospores have ornamented walls and germinate by forming germ tubes. Within 72 h of germination, colonies produce singular conidia and coenocytic apical cells with synchronously dividing nuclei. Basidiospore germination, and hyphal and basidial branching involve breaking of the wall, but sterigma initiation does not. Simple septal pores contain densely staining, pulley-wheel shaped structures. Septal and lateral walls of the same isolate vary in thickness when grown in broth or agar. Basidial and reproductive hyphal walls have conical-shaped cavities containing cytoplasmic projections. Rod-shaped ladder-like connections not previously described join outer mitochondrial membranes and cisternae of endoplasmic reticulum in reproductive hyphae. At different stages in prophase I, the nucleus contains synaptonemal complexes and structures resembling the central element are located in nucleolar regions. Vacuole development follows a specific pattern in the basidium from nuclear fusion to spore release. The results of these observations are compared with developmental patterns observed in other organisms and the evolutionary, phylogenetic, and functional significance is discussed.