bluuebunny/crossref_metadata_2025 huggingface dataset:
Action of the microbial metabolite and chitin synthesis inhibitor nikkomycin on the mite Tetranychus urticae; an electron microscope study
Authors: Mothes Ursula , Seitz Karl‐August
Published: November 2006

Chitinous structures of Tetranychus urticae K., after treatment with the microbial metabolite nikkomycin, were examined using an electron microscope. The results were compared with published information on the mechanisms of action of this antibiotic. Application of the drug resulted in an inhibition of moulting, due to a deficient or abnormal differentiation of the procuticle during ecdysis. Damage to the procuticle caused disorders in the muscle attachments, preventing the chrysalis stages leaving their exuviae after treatment with the metabolite. Application of nikkomycin to an adult female caused plug‐like accumulations below the procuticle of the prosoma and cranial opisthosoma, as well as inside the hypodermis. The egg shell was another site of action of nikkomycin; depending on when drug treatment began, an abnormally thickened or incomplete plaque‐like egg shell was produced. The deposition of affected eggs was strongly inhibited, if they were laid at all. The electron micrographs supported the suggestion that a competitive inhibition of chitin synthetase results in inhibition of cuticle synthesis. However, such a mechanism of action cannot explain the results on egg shell damage after nikkomycin treatment, which indicates some other influences of the antibiotic.
Gas‐liquid chromatographic determination of hydrazine in maleic hydrazide formulations and in samples stored at an elevated temperature
Authors: Bakker Henk , Martijn Albertus , Schreuder Rudolf H.
Published: November 2006

A method is described for the analysis of small amounts of hydrazine in maleic hydrazide formulations. Following derivative formation with pentafluorobenz‐aldehyde, the pentafluorobenzaldehyde azine was extracted with hexane and determined by gas‐liquid chromatography with electron‐capture detection. Recoveries of 72‐80% were obtained from samples fortified with 1 and 10 μg of hydrazine. The limit of detection was 0.05 mg kg−1. Fourteen commercial formulations with maleic hydrazide concentrations ranging from 180‐360 g litre−1 were investigated. The hydrazine content of the maleic hydrazide used in these formulations ranged from less than 0.05 to 53 mg kg−1. During the storage of two samples at 50°C for 10 weeks, the hydrazine contents increased from 2.2 to 124 and 0.4 to 54 mg litre−1, respectively.
Structure‐activity relationships in a series of new antifungal nitroalcohol derivatives
Authors: Lopata Antal , Darvas Ferenc , Valkó Klára , Mikite Gyula , Jakucs Erzsébet , Kis‐Tamás Attila
Published: November 2006

The structure‐antifungal activity correlations of 23 new nitroalcohol derivatives (1‐substituted‐2‐nitropropane‐1, 3‐diols, their ethers and esters) were investigated using a generalised quantitative structure‐activity relationships (QSAR) method, combining Golender and Rozenblit's logico‐structural approach and the Free‐Wilson and Hansch analyses. Based on results obtained from principal component analysis, the in‐vitro activities against Helminthosporium sativum, the inhibition of germination and of growth could be assumed to be governed by a common mechanism. It is suggested that the antifungal activity of the compounds studied is determined mainly by the presence or absence of an aromatic ring (unsubstituted, or bearing a hydrophobic group that is small in bulk and electron‐attracting) at position 1, of a (potential) double bond between carbon atoms 1 and 2, and of an acyloxy group at position 3. Among these factors, the double bond seems to be the most important, and the mechanism of the antifungal action is probably dependent on the reactivity of this bond towards thiol groups of endogenous substances.
The effect of drop speed, size and surfactant on the deposition of spray on barley and radish or mustard
Authors: Taylor William A. , Shaw Georgina B.
Published: November 2006

Sprays composed of uniformly‐sized drops were applied at different drop speeds to barley and either radish or mustard. Retention by the two broad‐leafed species showed no major response to changes in drop speed, nor to the presence or absence of a surfactant. In contrast, the barley retained less spray when there was no surfactant and when the drops possessed higher momenta. The application of spray dropsat higher speeds would therefore appear to provide a basis for the development of selective retention techniques.
Resistance in mutagen‐induced mutants of Ustilago maydis to fungicides which inhibit ergosterol biosynthesis
Authors: Barug Daniel , Kerkenaar Antonius
Published: November 2006

Resistance to a number of inhibitors of sterol C‐14 demethylation, (clotrimazole, imazalil, miconazole, fenarimol, nuarimol and triadimefon), as well as resistance to inhibitors of sterol C‐14(15) double bond reduction, (tridemorph and fenpropi‐morph), was readily induced in Ustilago maydis. Resistant mutants were obtained after mutagenic treatment by ultraviolet irradiation, or by treatment with 1‐methyl‐3‐nitro‐1‐nitrosoguanidine, of sporidia of the wild‐type strain, followed by selection in the presence of the toxicant. The level of resistance of these mutants varied appreciably. Although not always reciprocal, cross‐resistance to fungicides which inhibit ergosterol biosynthesis (EBIs) appeared to be present in most cases. Several of the U. maydis mutants which were resistant to inhibitors of sterol C‐14 demethylation lacked cross‐resistance to tridemorph and fenpropimorph, or displayed increased sensitivity to fenpropimorph (negatively correlated cross‐resistance). Cross‐resistance between EBIs and the antimicrobial agents climbazole and lombazole was also established. It is suggested that fungal mutants that possess a resistance mechanism based on a deficiency in sterol C‐14 demethylation or sterol C‐14(15) double bond reduction, have a greatly reduced chance of survival.
Lipoprotein composition and serum cholesterol ester fatty acids in nonwesternized melanesians
Authors: Lindeberg Staffan , Nilsson‐Ehle Peter , Vessby Bengt
Published: November 2006

In this study, the relationships between dietary fat [as measured by serum cholesterol ester fatty acids (CE‐FA)], age, smoking, body mass index, and serum lipids were analyzed in 151 subsistence horticulturalists, aged 20–86 yr, from Kitava, Trobriand Islands, Papua New Guinea. Their diet consists of tubers, fruit, coconut, fish, and vegetables with a negligible influence of western food and alcohol. Total fat intake is low [21% of energy (en%)], while saturated fat intake from coconuts is high (17 en%, mainly lauric and myristic acid). In multivariate analysis, 11–43% of the variation of the serum lipoprotein composition was explained by CE‐FA, age, and smoking habits. The proportion of CE20∶5n‐3 explained much of the variation of triglycerides (TG, negative relation) and high density lipoprotein‐cholesterol (HDL‐C, positive) in both sexes and serum apolipoprotein A1 (ApoA1, positive) in the males. CE16∶0 was positively related to TG and negatively related to HDL‐C and ApoA1 in both sexes, and in males it related negatively to total cholesterol (TC) and low density lipoprotein‐cholesterol (LDI‐C). In males, negative relationships were present between CE18∶2n‐6 and TC and between CE14∶0 and serum lipoprotein(a). Smoking was independently associated with lower ApoA1 in both sexes and with lower HDL‐C and higher TG, TC, LDL‐C, and apolipoprotein B in males. In conclusion, marine n‐3 fatty acids and linoleic acid showed the same potentially beneficial relationships with lipoproteins and apolipoproteins as in western populations. The relations of palmitic acid to serum lipids may be explained in terms of endogenous fat synthesis at a low‐fat intake, rather than reflecting its relative intake.
Specificity of two lipoxygenases from rice: Unusual regiospecificity of a lipoxygenase isoenzyme
Authors: Zhang Lian‐Ying , Hamberg Mats
Published: November 2006

The regio‐ and stereospecificity of two lipoxygenases from rice were investigated using arachidonic acid as the substrate. Rice seed lipoxygenase‐2 (RSL‐2) catalyzed oxygenation of arachidonic acid into a mixture of 5(S)‐hydroperoxy‐6,8,11,14‐eicosatetraenoic acid [5(S)‐HPETE] and 15(S)‐hydroperoxy‐5,8,11,13‐eicosatetraenoic acid [15(S)‐HPETE]. In addition, two double dioxygenase products, 5(S), 15(S)‐dihydroperoxy‐6,8,11,13‐eicosatetraenoic acid and 8(S), 15(S)‐dihydroperoxy‐5,9,11,13‐eicosatetraenoic acid, were obtained in a lower yield. The regiospecificity of the RSL‐2‐catalyzed oxygenation was pH‐dependent. Thus, incubation at pH 6.7 led to the formation of 5(S)‐HPETE and 15(S)‐HPETE in a ratio of 52∶48, and incubation at pH 9.8 strongly suppressed production of 5(S)‐HPETE and led to formation of 5(S)‐HPETE and 15(S)‐HPETE in a ratio of 3∶97. A pH‐dependent orientation of arachidonic acid at the active site is proposed to explain these findings. Rice leaf pathogen‐inducible lipoxygenase [Peng, Y.‐L., Shirano, Y., Ohta, H., Hibino, T., Tanaka, K., and Shibata, D. (1994)J. Biol. Chem. 269, 3755–3761] catalyzed oxygenation of arachidonic acid into a single hydroperoxide isomer of high optical purity, i.e., 15(S)‐HPETE (99.5%S).
Interaction of peroxidized cardiolipin with rat‐heart mitochondrial membranes: Induction of permeability transition and cytochrome c release
Authors: Petrosillo Giuseppe , Casanova Giacoma , Matera Mariagiuseppa , Ruggiero Francesca Maria , Paradies Giuseppe
Published: October 2006

Cardiolipin peroxidation plays a critical role in mitochondrial cytochrome c release and subsequent apoptotic process. Mitochondrial pore transition (MPT) is considered as an important step in this process. In this work, the effect of peroxidized cardiolipin on MPT induction and cytochrome c release in rat heart mitochondria was investigated. Treatment of mitochondria with micromolar concentrations of cardiolipin hydroperoxide (CLOOH) resulted in a dose‐dependent matrix swelling, ΔΨ collapse, release of preaccumulated Ca2+ and release of cytochrome c. All these events were inhibited by cyclosporin A and bongkrekic acid, indicating that peroxidized cardiolipin behaves as an inducer of MPT. Ca2+ accumulation by mitochondria was required for this effect. ANT (ADP/ATP translocator) appears to be involved in the CLOOH‐dependent MPT induction, as suggested by the modulation by ligands and inhibitors of adenine nucleotide translocator (ANT). Together, these results indicate that peroxidized cardiolipin lowers the threshold of Ca2+ for MPT induction and cytochrome c release. This synergistic effect of Ca2+ and peroxidized cardiolipin on MPT induction and cytochrome c release in mitochondria, might be important in regulating the initial phase of apoptosis and also may have important implications in those physiopathological situations, characterized by both Ca2+ and peroxidized cardiolipin accumulation in mitochondria, such as aging, ischemia/reperfusion and other degenerative diseases.
Catalytic competence of the Ras–GEF domain of hSos1 requires intra‐REM domain interactions mediated by Phenylalanine 577
Authors: Sacco Elena , Metalli David , Busti Stefano , Fantinato Sonia , D'Urzo Annalisa , Mapelli Valeria , Alberghina Lilia , Vanoni Marco
Published: October 2006

The Ras‐specific guanine nucleotide exchange region of hSos1 consists of two consecutive domains: the catalytic core (residues 742–1024) contains all residues binding to Ras, including the catalytic hairpin, and an upstream REM domain (residues 553–741), so called because it contains an evolutionary conserved Ras Exchange Motif (REM). We functionally define the boundaries of the REM domain through a combination of in vivo and in vitro assays. We show that an intra‐REM domain interaction, mediated by phenylalanine 577, is required to allow interaction of the REM domain with the catalytic core, constraining it in the active conformation.
Total and free tissue factor pathway inhibitor in pregnancy hypertension
Authors: Abdel Gader A.M. , Al‐Mishari A.A. , Awadalla S.A. , Buyuomi N.M. , Khashoggi T. , Al‐Hakeem M.
Published: October 2006

Abstract

Objective

To clarify the role played by tissue factor pathway inhibitor (TFPI) in pregnancy hypertension.

Methods

Using enzyme‐linked immunosorbent assays, hemostatic measurements were obtained for women with pre‐eclampsia (n = 51), nonproteinuric hypertension of pregnancy (n = 62), postpartum pre‐eclampsia 24 h after childbirth (n = 31), and no hypertension (healthy pregnant controls, n = 100).

Results

There was a significant increase in circulating free TFPI levels in women with pre‐eclampsia (9.7 ± 6.2 ng/mL) or nonproteinuric hypertension of pregnancy (8.3 ± 5.3 ng/mL) compared with healthy controls (5.3 ± 2.1 ng/mL). In women with pre‐eclampsia the levels remained elevated after placental delivery (10.6 ± 4.0 ng/mL). Free protein S levels were significantly higher in women with pre‐eclampsia (40.0% ± 10.7%), nonproteinuric hypertension of pregnancy (37.1% ± 12.5%), or postpartum pre‐eclampsia (39.3% ± 9.1%) than in healthy pregnant controls (32.2% ± 8.5%).

Conclusion

Increased levels of the physiologically active free forms of TFPI and free protein S, 2 coagulation inhibitors, may protect women with pregnancy‐induced hypertension from the risks of hemostatic activation.
Botulinum toxin: A potential alternative to current treatment of neurogenic and idiopathic urinary incontinence due to detrusor overactivity
Authors: Casanova N. , McGuire E. , Fenner D.E.
Published: October 2006

Objective: To analyze and report the current data on the treatment of both neurogenic and idiopathic detrusor overactivity with Botulinum toxin.

Methods: Literature review using Pub‐Med and Medline from 1990 until June 30, 2006.

Results: Case series of patients with neurogenic detrusor dysfunction (NDD) and idiopathic detrusor overactivity (IDO) range from 15 to 200 patients with follow up from 12 to 36 weeks post‐treatment. Significant improvements in cystometric bladder capacity, reflex volume at first urge to void, and bladder compliance are seen in nearly all patients. Approximately 50% of NDD patients achieved urinary continence and almost all had improvement in bladder control up to 36 weeks following treatment. Patients with IDO with urgency alone or with incontinence also had urodynamic as well as symptom improvement. Approximately 75% of patients with IDO and incontinence are dry at 12 weeks post‐treatment. Urgency disappears on average in two thirds of patients. Quality of life scores also shows significant improvement for all groups.

Conclusion: Botulinum toxin‐A has emerged as a promising option for the treatment of neurogenic and refractory idiopathic detrusor overactivity. Studies to date have shown that not only is this treatment effective at decreasing urinary symptoms and incontinence, as well as improving potentially dangerous urodynamic measures, but it is also minimally invasive, reversible and safe. Questions over proper dosing and dilution, number of injection sites, and re‐injection rates remain to be answered.
The relationship between oral malodor and volatile sulfur compound–producing bacteria
Authors: Krespi Yosef P. , Shrime Mark G. , Kacker Ashutosh
Published: October 2006

Halitosis can be a crippling social problem, and standard dental treatments and mouthwashes often provide only temporary relief. The mouth is home to hundreds of bacterial species that produce several fetid substances as a result of protein degradation. Volatile sulfur compound (VSC)‐producing bacteria colonizing the lingual dorsum have recently been implicated in the generation of halitosis. Detection of VSCs, such as methylmercaptan and hydrogen sulfite, via organoleptic and objective methods, can aid in the identification of their source. Following comprehensive evaluation for possible causes, most halitosis in patients seen in an ENT practice can be localized to the tongue. We review methods of diagnosis and treatment of oral malodor from the overgrowth of proteolytic, anaerobic, gram‐negative bacteria on the crevices of the lingual dorsum. Bacteriologic analysis of biofilm and scraped specimens obtained from the lingual dorsum and other oral sites, primarily gingival pockets and tonsillar crypts, can identify VSC‐producing bacteria. Porphyromonas, Prevotella, Actinobacillus, and Fusobacterium species are the most common organisms identified. Halitosis is an oral phenomenon, with almost no cases originating distal to the tonsils. Halitosis arising from the lingual dorsum secondary to overpopulated VSC‐producing bacteria can be successfully managed with a combination of mechanical cleansing using tongue brushes or scrapes and chemical solutions containing essential oils, zinc chloride, and cetylpyridinium chloride.
Bone graft necrosis of facial translocation: Comparison of 3 different techniques
Authors: Chen Chiang‐Wen , Hao Sheng‐Po , Pan Whei‐Lin
Published: October 2006

Objective

To compare the viability of translocated facial bone grafts among 3 different techniques of facial translocation: free bone graft (FBG), attached bone graft (ABG), and modified facial translocation (MFT).

Study Design

A total of 107 patients were divided into 3 groups: FBG group without reconstruction (N = 33), ABG group (N = 14), and FBG group with reconstruction using a flap (FBG[R +] and MFT) (N = 60). Data evaluated included the respective incidence of bone graft necrosis (BGN) and the impact of radiotherapy.

Results

The incidence of BGN significantly varied among the three different groups (P = 0.00003): FBG[R‐] (11/33[33.3%]), ABG (1/14[7.1%]) and FBG[R+] and MFT (1/60[1.67%]). Soft tissue reconstruction significantly decreased the incidence of BGN (P = 0.00003), even in patients with radiation therapy (P = 0.00001).

Conclusions

MFT significantly increases the viability of translocated facial bone grafts, which provides a good surgical approach to the anterior skull base.
The influence of epilarynx area on vocal fold dynamics
Authors: Döllinger Michael , Berry David A. , Montequin Douglas W.
Published: October 2006

Objective

This study investigated the influence of epilarynx area on an excised human vocal fold during phonation.

Study Design

A hemilarynx set‐up using an excised human larynx was used. An artificial vocal tract with an epilarynx tube of variable cross‐sectional area was attached. High‐speed imaging was performed and standard phonatory variables were measured.

Results

Glottal airflow, fundamental frequency, and sound level increased as a function of subglottal pressure. A decrease in epilarynx area decreased phonation threshold pressure, glottal airflow, and vocal fold displacements and velocities.

Conclusions

Preliminary experimental results confirm that narrowing the epilarynx area facilitates phonation by decreasing phonation threshold pressure, presumably through impedance matching of the glottal source and vocal tract.

Significance

As this phenomenon associated with epilarynx narrowing is further quantified and generalized, eventually new surgical alterations of the epilaryngeal structure may be suggested to facilitate phonation, in addition to standard phonosurgical procedures.
Glutathione ester protects against hydroxynonenal‐induced loss of auditory hair cells
Authors: Ruiz Jose W. , Guzman Jose , Polak Marek , Eshraghi Adrien A. , Balkany Thomas J. , Van De Water Thomas R.
Published: October 2006

OBJECTIVE

Test the ability of glutathione monoethy1 ester (GSHe) to protect auditory hair cells against the ototoxic effects of 4‐hydroxy‐2,3‐nonenal (HNE).

STUDY DESIGN AND SETTING

Organ of Corti explants were either untreated or treated with one of a series of four concentrations of GSHe for one day, then exposed to HNE. Counts of FITC‐phalloidin‐labeled hair cells determined both HNE ototoxicity and GSHe otoprotection.

RESULTS

HNE was toxic to hair cells at physiologically relevant levels, eg, 400 μm, and GSHe provided a significant level of protection against HNE ototoxicity (P < 0.05) at all levels tested, ie, 1.16 to 9.3 mM.

CONCLUSION

GSHe protects auditory hair cells from damage and loss initiated by a naturally occurring ototoxic molecule, ie, HNE (a by‐product of oxidative stress).

SIGNIFICANCE

Treatment with GSHe may be an effective therapy to protect the cochlea against the adverse effects of traumas (eg, electrode insertion) that generate oxidative stress.
Established prognostic variables in NO oral carcinoma
Authors: Clark Jonathan R. , Naranjo Natalie , Franklin Jason H. , de Almeida John , Gullane Patrick J.
Published: October 2006

OBJECTIVES

To examine the utility of established prognostic variables in patients with oral carcinoma and a clinically negative neck.

STUDY DESIGN

Retrospective cohort study.

METHODS

The distribution of occult metastases was assessed in 105 oral cancer patients with no clinical or radiological evidence of nodal disease. Predictors for nodal metastases, recurrence, and survival were examined.

RESULTS

Occult neck metastases occurred in 34 percent of patients. Tumor thickness was the only independent predictor of occult metastases, with thin (‡5 mm) and thick (>5 mm) tumors having a 10 percent and 46 percent incidence of regional disease, respectively (P = 0.001). Nodal metastases and perineural invasion were significant predictors of survival.

CONCLUSION

Patients with thick tumors are at high risk of nodal metastases and are likely to benefit from elective neck dissection. Comprehensive neck dissection should be considered in advanced primary disease.

SIGNIFICANCE

Tumor thickness is the most important predictor of occult regional metastases in oral cavity cancer.
Connexin expression and gap junctional intercellular communication in human squamous cell carcinoma of the head and neck
Authors: Frank Douglas K. , Szymkowiak Bozena , Hughes Cynthia A.
Published: October 2006

OBJECTIVE

Our laboratory is investigating the role that gap junction intercellular channels (composed of proteins called connexins) play in communicating apoptotic signals from therapeutically targeted squamous cell carcinoma of the head and neck (SCCHN) cells to adjacent, untreated, “bystander” cells (bystander effect). The nature of this research underscores the importance of delineating connexin expression patterns in SCCHN, and how this correlates with gap junctional intercellular communication (GJIC) and bystander effects.

STUDY DESIGN

The GJIC activity of a diverse panel of SCCHN cell lines, as well as normal oral epithelial (NOE) cell controls was determined in vitro. These data were correlated with connexin expression patterns determined through connexin 43 and connexin 26 immunofluorescence.

RESULTS

Cell lines with retained GJIC activity all expressed connexin 43 on the cell membrane. Cell lines that did not communicate microinjected lucifer yellow (lost GJIC activity) showed no connexin expression, either at the cell membrane or in the cytosol. Connexin 26 was not expressed in any of our SCCHN cell lines, whereas both connexin 43 and connexin 26 were expressed in the NOE cell controls. Furthermore, connexin 43 introduction into a GJIC (and connexin) deficient SCCHN cell line conferred no growth inhibitory effect.

CONCLUSION

Connexin 43 expression correlates with retained GJIC in SCCHN in vitro. Connexin 26 may have a role as a tumor suppressor in SCCHN.

SIGNIFICANCE

The data presented have relevance to our ongoing investigations of gap‐junction mediated bystander effects in SCCHN and are being expanded to investigations on actual SCCHN tumor specimens.
Holocene Climate and Cultural Evolution in Late Prehistoric–Early Historic West Asia
Authors: Staubwasser Michael , Weiss Harvey
Published: October 2006

The precipitation climatology and the underlying climate mechanisms of the eastern Mediterranean, West Asia, and the Indian subcontinent are reviewed, with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation. Holocene climate change of the region is summarized from proxy records. The Indian monsoon weakened during the Holocene over its northernmost region, the Ganges and Indus catchments and the western Arabian Sea. Southern regions, the Indian Peninsula, do not show a reduction, but an increase of summer monsoon rain across the Holocene. The long-term trend towards drier conditions in the eastern Mediterranean can be linked to a regionally complex monsoon evolution. Abrupt climate change events, such as the widespread droughts around 8200, 5200 and 4200 cal yr BP, are suggested to be the result of altered subtropical upper-level flow over the eastern Mediterranean and Asia.

The abrupt climate change events of the Holocene radically altered precipitation, fundamental for cereal agriculture, across the expanse of late prehistoric–early historic cultures known from the archaeological record in these regions. Social adaptations to reduced agro-production, in both dry-farming and irrigation agriculture regions, are visible in the archaeological record during each abrupt climate change event in West Asia. Chronological refinement, in both the paleoclimate and archaeological records, and transfer functions for both precipitation and agro-production are needed to understand precisely the evident causal linkages.
Facial palsy secondary to cholesteatoma: analysis of outcome following surgery
Authors: Siddiq M A , Hanu-Cernat L M , Irving R M
Published: November 2006

Facial palsy is a rare presenting feature of cholesteatoma. Prompt treatment usually results in a good outcome, but if treatment is delayed the prognosis can be difficult to predict. We retrospectively reviewed 326 consecutive patients who had undergone temporal bone surgery for cholesteatoma. Eleven patients had presented with facial palsy, of whom eight had petrous apex involvement and three had disease confined to the middle-ear cleft. All patients with middle-ear disease were operated upon within two months of presentation, and all showed some recovery in facial function. The diagnosis had been delayed in all eight cases of apical disease, with four cases having had a long-standing total weakness. One case treated after seven months' partial weakness achieved a full recovery. In three cases of long-standing partial weakness, pre-operative facial function was preserved by maintaining the facial nerve in its normal anatomical location.

Facial palsy associated with cholesteatoma should be treated as early as possible. Recovery can occur even if treatment is delayed for up to seven months. After this time, recovery is increasingly unlikely, but any residual function can be maintained and further deterioration prevented.
On the origin of unusual transport properties observed in densely packed polycrystalline CaAl2
Authors: Sergeenkov S. , Araujo-Moreira F. M.
Published: November 2006

A possible origin of unusual temperature behavior of transport coefficients observed in densely packed polycrystalline CaAl2 compound [M. Ausloos et al., J. Appl. Phys., 96, 7338 (2004)] is discussed, including a powerlike dependence of resistivity with ρ∝T−3∕4 and N-like form of the thermopower. All these features are found to be in good agreement with the Shklovskii-Efros localization scenario [Electronic Properties of Doped Semiconductors (Springer, Berlin, 1984)] assuming polaron-mediated hopping processes controlled by the Debye energy.
Effect of particle collisions on the expulsion of heavy particles from a vortex core
Authors: Marshall J. S.
Published: November 2006

A computational study has been performed on the effect of particle collisions as heavy particles are expelled from a vortex core. In the absence of collisions, particles collect in a band surrounding the vortex core, where the maximum particle concentration within this band increases indefinitely as the band of particles propagates radially outward. Particle collisions act to regulate the increase in concentration within this band by the enhanced spreading of the particles that occurs through the action of shear-induced migration. The presence of axial flow within the vortex core introduces a drift of the particles within the core toward the low-shear region at the core center, thus resisting the outward particle drift caused by centrifugal force. With increasing axial flow rates, the particles are retained in the vortex core for longer time periods. The role of various parameters on the particle expulsion is evaluated, including particle diameter, restitution coefficient, and initial concentration. The study also examines the effect of collisions on cases with two distinct particle sizes, in which the different outward expulsion rates act to separate particles of different size.
Valence-sensitive neurons exhibit divergent functional profiles in gregarious and asocial species
Authors: Goodson James L. , Wang Yiwei
Published: October 2006

The medial bed nucleus of the stria terminalis (BSTm) influences both social approach and social aversion, suggesting that this structure may play an important role in generating motivational and behavioral differences between gregarious and asocial species. However, no specific neurons have been identified within the BSTm that influence species-typical levels of sociality or that mediate approach and avoidance. Using five songbird species that differ selectively in their species-typical group sizes, we now demonstrate that vasotocin-immunoreactive (VT-ir) neurons of the BSTm exhibit very different immediate early gene responses to same-sex stimuli in gregarious and asocial species. Exposure to a same-sex conspecific increases VT-Fos colocalization in gregarious species while decreasing colocalization in relatively asocial species. We additionally demonstrate that these neurons are selectively activated by social stimuli that normally elicit affiliation (positively valenced social stimuli) but not by stimuli that elicit aversion (negatively valenced social stimuli). Constitutive Fos activity of the VT-ir neurons is also significantly greater in the gregarious species, and the two most social species express significantly more VT-ir neurons. These findings demonstrate that the properties of valence-sensitive neurons evolve in relation to sociality and indicate that gregarious species accentuate positive stimulus properties during social interactions.
Atherosclerosis-related molecular alteration of the human CaV1.2 calcium channel α1Csubunit
Authors: Tiwari Swasti , Zhang Yuwei , Heller Jennifer , Abernethy Darrell R. , Soldatov Nikolai M.
Published: October 2006

Atherosclerosis is an inflammatory process characterized by proliferation and dedifferentiation of vascular smooth muscle cells (VSMC). Cav1.2 calcium channels may have a role in atherosclerosis because they are essential for Ca2+-signal transduction in VSMC. The pore-forming Cav1.2α1 subunit of the channel is subject to alternative splicing. Here, we investigated whether the Cav1.2α1 splice variants are affected by atherosclerosis. VSMC were isolated by laser-capture microdissection from frozen sections of adjacent regions of arteries affected and not affected by atherosclerosis. In VSMC from nonatherosclerotic regions, RT-PCR analysis revealed an extended repertoire of Cav1.2α1 transcripts characterized by the presence of exons 21 and 41A. In VSMC affected by atherosclerosis, expression of the Cav1.2α1 transcript was reduced and the Cav1.2α1 splice variants were replaced with the unique exon-22 isoform lacking exon 41A. Molecular remodeling of the Cav1.2α1 subunits associated with atherosclerosis caused changes in electrophysiological properties of the channels, including the kinetics and voltage-dependence of inactivation, recovery from inactivation, and rundown of the Ca2+current. Consistent with the pathophysiological state of VSMC in atherosclerosis, cell culture data pointed to a potentially important association of the exon-22 isoform of Cav1.2α1 with proliferation of VSMC. Our findings are consistent with a hypothesis that localized changes in cytokine expression generated by inflammation in atherosclerosis affect alternative splicing of the Cav1.2α1 gene in the human artery that causes molecular and electrophysiological remodeling of Cav1.2 calcium channels and possibly affects VSMC proliferation.
Statistics of cellular signal transduction as a race to the nucleus by multiple random walkers in compartment/phosphorylation space
Authors: Lu Ting , Shen Tongye , Zong Chenghang , Hasty Jeff , Wolynes Peter G.
Published: October 2006

Cellular signal transduction often involves a reaction network of phosphorylation and transport events arranged with a ladder topology. If we keep track of the location of the phosphate groups describing an abstract state space, a simple model of signal transduction involving enzymes can be mapped on to a problem of how multiple biased random walkers compete to reach their target in the nucleus yielding a signal. Here, the first passage time probability and the survival probability for multiple walkers can be used to characterize the response of the network. The statistics of the first passage through the network has an asymmetric distribution with a long tail arising from the hierarchical structure of the network. This distribution implies a significant difference between the mean and the most probable signal transduction time. The response patterns for various external inputs generated by our model agree with recent experiments. In addition, the model predicts that there is an optimal phosphorylation enzyme concentration for rapid signal transduction.
A pathogen-inducible endogenous siRNA in plant immunity
Authors: Katiyar-Agarwal Surekha , Morgan Rebekah , Dahlbeck Douglas , Borsani Omar , Villegas Andy , Zhu Jian-Kang , Staskawicz Brian J. , Jin Hailing
Published: October 2006

RNA interference, mediated by small interfering RNAs (siRNAs), is a conserved regulatory process that has evolved as an antiviral defense mechanism in plants and animals. It is not known whether host cells also use siRNAs as an antibacterial defense mechanism in eukaryotes. Here, we report the discovery of an endogenous siRNA, nat-siRNAATGB2, that is specifically induced by the bacterial pathogen
Pseudomonas syringae
carrying effector
avrRpt2
. We demonstrate that the biogenesis of this siRNA requires DCL1, HYL1, HEN1, RDR6, NRPD1A, and SGS3. Its induction also depends on the cognate host disease resistance gene
RPS2
and the
NDR1
gene that is required for
RPS2
-specified resistance. This siRNA contributes to
RPS2
-mediated race-specific disease resistance by repressing PPRL, a putative negative regulator of the
RPS2
resistance pathway.
DNA Microarrays in Herbal Drug Research
Authors: Chavan Preeti , Joshi Kalpana , Patwardhan Bhushan
Published: October 2006

Natural products are gaining increased applications in drug discovery and development. Being chemically diverse they are able to modulate several targets simultaneously in a complex system. Analysis of gene expression becomes necessary for better understanding of molecular mechanisms. Conventional strategies for expression profiling are optimized for single gene analysis. DNA microarrays serve as suitable high throughput tool for simultaneous analysis of multiple genes. Major practical applicability of DNA microarrays remains in DNA mutation and polymorphism analysis. This review highlights applications of DNA microarrays in pharmacodynamics, pharmacogenomics, toxicogenomics and quality control of herbal drugs and extracts.
Arabidopsis Reversibly Glycosylated Polypeptides 1 and 2 Are Essential for Pollen Development
Authors: Drakakaki Georgia , Zabotina Olga , Delgado Ivan , Robert Stéphanie , Keegstra Kenneth , Raikhel Natasha
Published: October 2006

Reversibly glycosylated polypeptides (RGPs) have been implicated in polysaccharide biosynthesis. To date, to our knowledge, no direct evidence exists for the involvement of RGPs in a particular biochemical process. The Arabidopsis (Arabidopsis thaliana) genome contains five RGP genes out of which RGP1 and RGP2 share the highest sequence identity. We characterized the native expression pattern of Arabidopsis RGP1 and RGP2 and used reverse genetics to investigate their respective functions. Although both genes are ubiquitously expressed, the highest levels are observed in actively growing tissues and in mature pollen, in particular. RGPs showed cytoplasmic and transient association with Golgi. In addition, both proteins colocalized in the same compartments and coimmunoprecipitated from plant cell extracts. Single-gene disruptions did not show any obvious morphological defects under greenhouse conditions, whereas the double-insertion mutant could not be recovered. We present evidence that the double mutant is lethal and demonstrate the critical role of RGPs, particularly in pollen development. Detailed analysis demonstrated that mutant pollen development is associated with abnormally enlarged vacuoles and a poorly defined inner cell wall layer, which consequently results in disintegration of the pollen structure during pollen mitosis I. Taken together, our results indicate that RGP1 and RGP2 are required during microspore development and pollen mitosis, either affecting cell division and/or vacuolar integrity.
Variation of Enzyme Activities and Metabolite Levels in 24 Arabidopsis Accessions Growing in Carbon-Limited Conditions
Authors: Cross Joanna M. , von Korff Maria , Altmann Thomas , Bartzetko Linda , Sulpice Ronan , Gibon Yves , Palacios Natalia , Stitt Mark
Published: October 2006

Our understanding of the interaction of carbon (C) metabolism with nitrogen (N) metabolism and growth is based mainly on studies of responses to environmental treatments, and studies of mutants and transformants. Here, we investigate which metabolic parameters vary and which parameters change in a coordinated manner in 24 genetically diverse Arabidopsis (Arabidopsis thaliana) accessions, grown in C-limited conditions. The accessions were grown in short days, moderate light, and high nitrate, and analyzed for rosette biomass, levels of structural components (protein, chlorophyll), total phenols and major metabolic intermediates (sugars, starch, nitrate, amino acids), and the activities of seven representative enzymes from central C and N metabolism. The largest variation was found for plant weight, reducing sugars, starch at the end of the night, and several enzyme activities. High levels of one sugar correlated with high levels of other sugars and starch, and a trend to increased amino acids, slightly lower nitrate, and higher protein. The activities of enzymes at the interface of C and N metabolism correlated with each other, but were unrelated to carbohydrates, amino acid levels, and total protein. Rosette weight was unrelated or showed a weak negative trend to sugar and amino acid contents at the end of the day in most of the accessions, and was negatively correlated with starch at the end of the night. Rosette weight was positively correlated with several enzyme activities. We propose that growth is not related to the absolute levels of starch, sugars, and amino acids; instead, it is related to flux, which is indicated by the enzymatic capacity to use these central resources.
Ethylene Stimulates Nutations That Are Dependent on the ETR1 Receptor
Authors: Binder Brad M. , O'Malley Ronan C. , Wang Wuyi , Zutz Tobias C. , Bleecker Anthony B.
Published: October 2006

Ethylene influences a number of processes in Arabidopsis (Arabidopsis thaliana) through the action of five receptors. In this study, we used high-resolution, time-lapse imaging to examine the long-term effects of ethylene on growing, etiolated Arabidopsis seedlings. These measurements revealed that ethylene stimulates nutations of the hypocotyls with an average delay in onset of over 6 h. The nutation response was constitutive in ctr1-2 mutants maintained in air, whereas ein2-1 mutants failed to nutate when treated with ethylene. Ethylene-stimulated nutations were also eliminated in etr1-7 loss-of-function mutants. Transformation of the etr1-7 mutant with a wild-type genomic ETR1 transgene rescued the nutation phenotype, further supporting a requirement for ETR1. Loss-of-function mutations in the other receptor isoforms had no effect on ethylene-stimulated nutations. However, the double ers1-2 ers2-3 and triple etr2-3 ers2-3 ein4-4 loss-of-function mutants constitutively nutated in air. These results support a model where all the receptors are involved in ethylene-stimulated nutations, but the ETR1 receptor is required and has a contrasting role from the other receptor isoforms in this nutation phenotype. Naphthylphthalamic acid eliminated ethylene-stimulated nutations but had no effect on growth inhibition caused by ethylene, pointing to a role for auxin transport in the nutation phenotype.
Integrated Analysis of Metabolite and Transcript Levels Reveals the Metabolic Shifts That Underlie Tomato Fruit Development and Highlight Regulatory Aspects of Metabolic Network Behavior
Authors: Carrari Fernando , Baxter Charles , Usadel Björn , Urbanczyk-Wochniak Ewa , Zanor Maria-Ines , Nunes-Nesi Adriano , Nikiforova Victoria , Centero Danilo , Ratzka Antje , Pauly Markus , Sweetlove Lee J. , Fernie Alisdair R.
Published: October 2006

Tomato (Solanum lycopersicum) is a well-studied model of fleshy fruit development and ripening. Tomato fruit development is well understood from a hormonal-regulatory perspective, and developmental changes in pigment and cell wall metabolism are also well characterized. However, more general aspects of metabolic change during fruit development have not been studied despite the importance of metabolism in the context of final composition of the ripe fruit. In this study, we quantified the abundance of a broad range of metabolites by gas chromatography-mass spectrometry, analyzed a number of the principal metabolic fluxes, and in parallel analyzed transcriptomic changes during tomato fruit development. Metabolic profiling revealed pronounced shifts in the abundance of metabolites of both primary and secondary metabolism during development. The metabolite changes were reflected in the flux analysis that revealed a general decrease in metabolic activity during ripening. However, there were several distinct patterns of metabolite profile, and statistical analysis demonstrated that metabolites in the same (or closely related) pathways changed in abundance in a coordinated manner, indicating a tight regulation of metabolic activity. The metabolite data alone allowed investigations of likely routes through the metabolic network, and, as an example, we analyze the operational feasibility of different pathways of ascorbate synthesis. When combined with the transcriptomic data, several aspects of the regulation of metabolism during fruit ripening were revealed. First, it was apparent that transcript abundance was less strictly coordinated by functional group than metabolite abundance, suggesting that posttranslational mechanisms dominate metabolic regulation. Nevertheless, there were some correlations between specific transcripts and metabolites, and several novel associations were identified that could provide potential targets for manipulation of fruit compositional traits. Finally, there was a strong relationship between ripening-associated transcripts and specific metabolite groups, such as TCA-cycle organic acids and sugar phosphates, underlining the importance of the respective metabolic pathways during fruit development.
delayed flowering1Encodes a Basic Leucine Zipper Protein That Mediates Floral Inductive Signals at the Shoot Apex in Maize
Authors: Muszynski Michael G. , Dam Thao , Li Bailin , Shirbroun David M. , Hou Zhenglin , Bruggemann Edward , Archibald Rayeann , Ananiev Evgueni V. , Danilevskaya Olga N.
Published: October 2006

Separation of the life cycle of flowering plants into two distinct growth phases, vegetative and reproductive, is marked by the floral transition. The initial floral inductive signals are perceived in the leaves and transmitted to the shoot apex, where the vegetative shoot apical meristem is restructured into a reproductive meristem. In this study, we report cloning and characterization of the maize (Zea mays) flowering time gene delayed flowering1 (dlf1). Loss of dlf1 function results in late flowering, indicating dlf1 is required for timely promotion of the floral transition. dlf1 encodes a protein with a basic leucine zipper domain belonging to an evolutionarily conserved family. Three-dimensional protein modeling of a missense mutation within the basic domain suggests DLF1 protein functions through DNA binding. The spatial and temporal expression pattern of dlf1 indicates a threshold level of dlf1 is required in the shoot apex for proper timing of the floral transition. Double mutant analysis of dlf1 and indeterminate1 (id1), another late flowering mutation, places dlf1 downstream of id1 function and suggests dlf1 mediates floral inductive signals transmitted from leaves to the shoot apex. This study establishes an emergent framework for the genetic control of floral induction in maize and highlights the conserved topology of the floral transition network in flowering plants.
Lotus japonicusNodulation Requires Two GRAS Domain Regulators, One of Which Is Functionally Conserved in a Non-Legume
Authors: Heckmann Anne B. , Lombardo Fabien , Miwa Hiroki , Perry Jillian A. , Bunnewell Sue , Parniske Martin , Wang Trevor L. , Downie J. Allan
Published: October 2006

A new nodulation-defective mutant of Lotus japonicus does not initiate nodule cortical cell division in response to Mesorhizobium loti, but induces root hair deformation, Nod factor-induced calcium spiking, and mycorrhization. This phenotype, together with mapping data, suggested that the mutation could be in the ortholog of the Medicago truncatula NSP1 gene (MtNSP1). The sequence of the orthologous gene (LjNSP1) in the L. japonicus mutant (Ljnsp1-1) revealed a mutation causing a premature stop resulting in loss of the C-terminal 23 amino acids. We also sequenced the NSP2 gene from L. japonicus (LjNSP2). A mutant (Ljnsp2-3) with a premature stop codon was identified by TILLING showing a similar phenotype to Ljnsp1-1. Both LjNSP1 and LjNSP2 are predicted GRAS (GAI, RGA, SCR) domain transcriptional regulators. Transcript steady-state levels of LjNSP1 and LjNSP2 initially decreased and then increased following infection by M. loti. In hairy root transformations, LjNSP1 and MtNSP1 complemented both Mtnsp1-1 and Ljnsp1-1 mutants, demonstrating that these orthologous proteins have a conserved biochemical function. A Nicotiana benthamiana NSP1-like gene (NbNSP1) was shown to restore nodule formation in both Ljnsp1-1 and Mtnsp1-1 mutants, indicating that NSP1 regulators from legumes and non-legumes can propagate the Nod factor-induced signal, activating appropriate downstream targets. The L. japonicus nodules complemented with NbNSP1 contained some cells with abnormal bacteroids and could fix nitrogen. However, the NbNSP1-complemented M. truncatula nodules did not fix nitrogen and contained very few bacteria released from infection threads. These observations suggest that NSP1 is also involved in infection, bacterial release, and normal bacteroid formation in nodule cells.