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The pollen tube clear zone: Clues to the mechanism of polarized growth

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journal of Integrative Plant Biology 2015年第1期57卷 79-92页

作者： peter K.Hepler Lawrence j.Winship Biology Department University of Massachusetts School of Natural Science Hampshire College

Pollen tubes usually exhibit a prominent region at their apex called the ＂clear zone＂ because it lacks light refracting amyloplasts. A robust, long clear zone often associates with fast growing pollen tubes, and thus serves as an indicator of pollen tube health. Nevertheless we do not understand how it arises or how it is maintained. Here we review the structure of the clear zone, and attempt to explain the factors that contribute to its formation. While amyloplasts and vacuolar elements are excluded from the clear zone, virtually all other organelles are present including secretory vesicles, mitochondria, Golgi dictyosomes, and the endoplas-mic reticulum （ER）. Secretory vesicles aggregate into an inverted cone appressed against the apical plasma membrane. ER elements move nearly to the extreme apex, whereas mitochondria and Golgi dictyosomes move less far forward. The cortical actin fringe assumes a central position in the control of clear zone formation and maintenance, given its role in generating cytoplasmic streaming. Other likely factors include the tip-focused calcium gradient, the apical pH gradient, the influx of water, and a host of signaling factors （small G-proteins）. We think that the clear zone is an emergent property that depends on the interaction of several factors crucial for polarized growth.

关键词： Actin endoplasmic reticulum myosin polarized growth pollen tube

Dielectric confinement on exciton binding energy and nonlinear optical properties in a strained Zn_(1-x_(in))Mg_(x(in))Se/Zn_(1-x(out))Mg_(x(out))Se quantum well

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journal of Semiconductors 2012年第9期33卷 1-7页

作者： j.Abraham Hudson Mark A.john peter Department of Physics NPR Arts&Science CollegeNathamDindigul-624401India Department of Physics Government Arts CollegeMelur-625106MaduraiIndia

The band offsets for a Zn1-xin Mgxin Se/Zn1-xout Mgxout Se quantum well heterostructure are determined using the model solid theory. The heavy hole exciton binding energies are investigated with various Mg alloy contents. The effect of mismatch between the dielectric constants between the well and the barrier is taken into account. The dependence of the excitonic transition energies on the geometrical confinement and the Mg alloy is discussed. Non-linear optical properties are determined using the compact density matrix approach. The linear, third order non-linear optical absorption coefficient values and the refractive index changes of the exciton are calculated for different concentrations of magnesium. The results show that the occurred blue shifts of the resonant peak due to the Mg incorporation give the information about the variation of two energy levels in the quantum well width.

关键词： interband emission energy exciton binding energy quantum well

Association of Psb28 and Psb27 Proteins with PSII-PSI Supercomplexes upon Exposure of Synechocystis sp. PCC 6803 to High Light

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Molecular Plant 2017年第1期10卷 62-72页

作者： Martina Beckova Zdenko Gardian jianfeng Yu peter Konik peter j. Nixon josef Komenda Institute of Microbiology Center Algatech Opatovicky mlyn37981 Trebon Czech Republic Faculty of Science University of South Bohemia Branisovska 1760 37005 Ceske Budejovice Czech Republic Institute of Plant Molecular Biology Biology Centre Academy of Sciences Branisovska 3137005 Ceske Budejovice Czech Republic Sir Ernst Chain Building-Wolfson Laboratories Department of Life Sciences Imperial College London South Kensington Campus London SW7 2AZ UK

Formation of the multi-subunit oxygen-evolving photosystem II （PSII） complex involves a number of auxiliary protein factors. In this study we compared the localization and possible function of two homolo- gous PSU assembly factors, Psb28-1 and Psb28-2, from the cyanobacterium Synechocystis sp. PCC 6803. We demonstrate that FLAG-tagged Psb28-2 is present in both the monomeric PSII core complex and a PSII core complex lacking the inner antenna CP43 （RC47）, whereas Psb28-1 preferentially binds to RC47. When cells are exposed to increased irradiance, both tagged Psb28 proteins additionally associate with oligo- meric forms of PSII and with PSII-PSI supercomplexes composed of trimeric photosystem I （PSI） and two PSII monomers as deduced from electron microscopy. The presence of the Psb27 accessory protein in these complexes suggests the involvement of PSI in PSII biogenesis, possibly by photoprotecting PSII through energy spillover. Under standard culture conditions, the distribution of PSII complexes is similar in the wild type and in each of the single psb28 null mutants except for loss of RC47 in the absence of Psb28-1. In comparison with the wild type, growth of mutants lacking Psb28-1 and Psb27, but not Psb28-2, was retarded under high-light conditions and, especially, intermittent high-light/dark conditions, emphasizing the physiological importance of PSII assembly factors for light acclimation.

关键词： Psb28 proteins photosystem I and II Synechocystis

Deletion or underexpression of the Y-chromosome genes CDY2 and HSFY is associated with maturation arrest in American men with nonobstructive azoospermia

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Asian journal of Andrology 2012年第5期14卷 676-682页

作者： peter j Stahl Anna N Mielnik Christopher E Barbieri peter N Schlegel Darius A Paduch Department of Urology Weill Cornell Medical CollegeNew York Presbyterian HospitaI-CornellNew YorkNY 10065USA

Maturation arrest （MA） refers to failure of germ cell development leading to clinical nonobstructive azoospermia. Although the azoospermic factor （AZF） region of the human Y chromosome is clearly implicated in some cases, thus far very little is known about which individual Y-chromosome genes are important for complete male germ cell development. We sought to identify single genes on the Y chromosome that may be implicated in the pathogenesis of nonobstructive azoospermia associated with MA in the American population. Genotype-phenotype analysis of 132 men with Y-chromosome microdeletions was performed. Protein-coding genes associated with MA were identified by visual analysis of a genotype-phenotype map. Genes associated with MA were selected as those genes within a segment of the Y chromosome that, when completely or partially deleted, were always associated with MA and absence of retrievable testicular sperm. Expression of each identified gene transcript was then measured with quantitative RT-PCR in testicular tissue from separate cohorts of patients with idiopathic MA and obstructive azoospermia. Ten candidate genes for association with MA were identified within an 8.4-Mb segment of the Y chromosome overlapping the AZFb region. CDY2and HSFYwere the only identified genes for which differences in expression were observed between the MA and obstructive azoospermia cohorts. Men with obstructive azoospermia had 12-fold higher relative expression of CDY2transcript （1.33__.0.40 vs. 0.11＋_0.04; P=O.O003） and 16-fold higher expression of HSFYtranscript （0.78__.0.32 vs. 0.05_0.02; P=O.O005） compared to men with MA. CDY2 and HSFYwere also underexpressed in patients with Sertoli cell only syndrome. These data indicate that CDY2and HSFYare located within a segment of the Y chromosome that is important for sperm maturation, and are underexpressed in testicular tissue derived from men with MA. These observations suggest that impairments in CDY2 or HSFYexpression could be impli

关键词： CDY1 protein CDY2 protein genetics histology HSFY human make infertility nonobstructive azoospermia spermato-genesis sperm maturation

The Structure of Low Frequency Phenomena in the Tropics and Its Interaction with the Extratropics

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Advances in Atmospheric Sciences 1992年第1期9卷 1-16页

作者： peter j.Webster 董敏 Department of Meteorology The Pennsylvania Stale University PA 16802 USA Academy of Meteorological Science State Meteorological Administration Beijing 100081 PRChe structure of planetary scale low freonency phenomena in the tropics is studied and an attempt is made to determine its influence and interactions with phenomena at higher latitudes.In the tropics it is found that the majority of the variance in the zonal wind structure is made up in wave numbers I and 2. During warm events in the Pacific Ocean when the Southern Oscillation Index is negative almost all of the variance resides in the gravest mode which undergoes a 40° eastward phase shift. Meanwhile the second logitudinal mode almost disappears. On the other hand the meridional wind field possesses maximum amplitude at higher wave numbers. However near the equatorthe amplitude is small with extreme values occurring in the subtropics. The difference in scale and the location of cxtrcma of the meridional and zonal wind components indicate that the tropical atmosphere is responding to two different driving mechanisms.Correlation analyses between variations of the zonal wind at reference points along the equator with variations of component elsewhere show that there are strong logitudinal connections. The strongest correlations between the tropics and higher latitudes exist in the region of the equatorial westerlies. In fact stronger correlations occur between variations in U anywhere along the equator and the middle latitudes to the north and south of the equatorial westerlies than to the latitudes immediately to the north and south of the reference points. We interpret this "remote" correlation pattern as indicating a two-stage teleconnection process which emphasizes the importance of the equatorial tropical westerlies of the Pacific Ocean as a "corridor" of communication between the low and high latitudes. The regionality of the correlations confirms to some extent recent theoretical development regarding trapped equatorial modes. Finally

The structure of planetary scale low freonency phenomena in the tropics is studied, and an attempt is made to determine its influence and interactions with phenomena at higher *** the tropics, it is found that the majority of the variance in the zonal wind structure is made up in wave numbers I and 2. During warm events in the Pacific Ocean, when the Southern Oscillation Index is negative, almost all of the variance resides in the gravest mode which undergoes a 40° eastward phase shift. Meanwhile, the second logitudinal mode almost disappears. On the other hand, the meridional wind field possesses maximum amplitude at higher wave numbers. However, near the equator,the amplitude is small with extreme values occurring in the subtropics. The difference in scale and the location of cxtrcma of the meridional and zonal wind components indicate that the tropical atmosphere is responding to two different driving *** analyses between variations of the zonal wind at reference points along the equator with variations of component elsewhere show that there are strong logitudinal connections. The strongest correlations between the tropics and higher latitudes exist in the region of the equatorial westerlies. In fact, stronger correlations occur between variations in U anywhere along the equator and the middle latitudes to the north and south of the equatorial westerlies than to the latitudes immediately to the north and south of the reference points. We interpret this 'remote' correlation pattern as indicating a two-stage teleconnection process which emphasizes the importance of the equatorial tropical westerlies of the Pacific Ocean as a 'corridor' of communication between the low and high latitudes. The regionality of the correlations confirms, to some extent, recent theoretical development regarding trapped equatorial modes. Finally, time lagged correlations from plus and minus six months between variations of U and OLR indicate that the interactio

关键词： In The Structure of Low Frequency Phenomena in the Tropics and Its Interaction with the Extratropics

Claudin-11 and occludin are major contributors to Sertoli cell tight junction function, in vitro

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Asian journal of Andrology 2016年第4期18卷 620-626页

作者： Mark j McCabe Caroline FH Foo Marcel E Dinger peter M Smooker peter G Stanton Male Fertility Regulation Laboratory Hudson Institute of Medical Research Monash Medical Centre Clayton Victoria 3168 Australia School of Applied Sciences Royal Melbourne Institute of Technology University Bundoora Victoria 3088 Australia Kinghorn Centre for Clinical Genomics Garvan Institute of Medical Research Darlinghurst New South Wales 2010 Australia St Vincent's Clinical School UNSW Sydney New South Wales 2052 Australia.

The Sertoli cell tight junction （T j） is the key component of the blood-testis barrier, where it sequesters developing germ cells undergoing spermatogenesis within the seminiferous tubules. Hormonally regulated claudin-11 is a critical transmembrane protein involved in barrier function and its murine knockout results in infertility. We aimed to assess quantitatively the significance of the contribution of claudin-11 to Tj function, in vitro, using siRNA-mediated gene silencing. We also conducted an analysis of the contribution of occludin, another intrinsic transmembrane protein of the Tj. Silencing of claudin-11 and/or occludin was conducted using siRNA in an immature rat Sertoli cell culture model. Transepithelial electrical resistance was used to assess quantitatively Tj function throughout the culture. Two days after siRNA treatment, cells were fixed for immunocytochemical localization of junction proteins or lyzed for RT-PCR assessment of mRNA expression. Silencing of claudin-11, occludin, or both resulted in significant decreases in Tj function of 55% （P 〈 0.01）, 51% （P 〈 0.01）, and 62% （P 〈 0.01）, respectively. Data were concomitant with significant decreases in mRNA expression and marked reductions in the localization of targeted proteins to the Sertoli cell Tj. We provide quantitative evidence that claudin-11 contributes significantly （P 〈 0.01） to Sertoli cell Tj function in vitro. Interestingly, occludin, which is hormonally regulated but not implicated in infertility until late adulthood, is also a significant （P 〈 0.01） contributor to barrier function. Our data are consistent with in vivo studies that clearly demonstrate a role for these proteins in maintaining normal Tj barrier structure and function.

关键词： blood-testis barrier claudin-11 occludin Sertoli cell tight junction siRNA

Inhibition of kinesin-5 improves regeneration of injured axons by a novel microtubule-based mechanism

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Neural Regeneration Research 2015年第6期10卷 845-849页

作者： peter W.Baas Andrew j.Matamoros Department of Neurobiology and Anatomy Drexel University College of Medicine

Microtubules have been identified as a powerful target for augmenting regeneration of injured adult axons in the central nervous system. Drugs that stabilize microtubules have shown some promise, but there are concerns that abnormally stabilizing microtubules may have only limited benefits for regeneration, while at the same time may be detrimental to the normal work that microtubules perform for the axon. Kinesin-5 （also called kifl I or EgS）, a molecular motor protein best known for its crucial role in mitosis, acts as a brake on microtubule movements by other motor proteins in the axon. Drugs that inhibit kinesin-5, originally developed to treat cancer, result in greater mobility of microtubules in the axon and an overall shift in the forces on the microtubule array. As a result, the axon grows faster, retracts less, and more readily enters environments that are inhibitory to axonal regeneration. Thus, drugs that inhibit kinesin-5 offer a novel microtubule-based means to boost axonal regeneration without the concerns that accompany abnormal stabilization of the microtubule array. Even so, inhibiting kinesin-5 is not without its own caveats, such as potential problems with navigation of the regenerating axon to its target, as well as morphological effects on dendrites that could affect learning and memory if the drugs reach the brain.

关键词： microtubule axon kinesin-5 Eg5 regeneration monastrol molecular motor protein

Guest Editorial:Special Section on Active Distribution Networks:Markets,Operations,Planning,and Regulation

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journal of Modern Power Systems and Clean Energy 2023年第1期11卷 1-2页

作者： peter Palensky Qixin Chen Marcos j.Rider Delft University of Technology DelftNetherlands Tsinghua University BeijingChina University of Campinas Sao PauloBrazil

THE power system is in change,and the most fundamental changes are happening in the distribution *** passive consumers get active and smart,energy storage and distributed generation appears,and the“grid edge”is upgraded with Intenet of Things(IoT).Gone are the days where distribution infrastructure consisted of passive assets,dimensioned for the worst case of load.

关键词： passive IoT distribution

Algorithms for enumeration problem of linear congruence modulo m as sum of restricted partition numbers

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Frontiers of Mathematics in China 2015年第1期10卷 69-89页

作者： Tian-Xiao HE peter j. -S. SHIUE Department of Mathematics Illinois Wesleyan University Bloomington IL 61702 USA Department of Mathematical Sciences University of Nevada Las Vegas Las Vegas NV 89154-4020 USA

We consider the congruence x1＋ x2 ＋… ＋ xr - c （mod m）, wherem and r are positive integers and c ∈Zm ：= {0, 1, ..., m- 1} （m ≥ 2）. Recently,W.-S. thou, T. X. He,and peter j.-S. Shiue considered the enumerationproblems of this congruence, namely, the number of solutions with the restriction x1≤~ x2≤ ... ≤ xr, and got some properties and a neat formula ofthe solutions. Due to the lack of a simple computational method for calculating the number of the solution of the congruence, we provide an algebraic and a recursive algorithms for those numbers. The former one can also give a new and simple approach to derive some properties of solution numbers.

关键词： Congruence multiset congruence solution restricted integerpartition