Proposal of a comprehensive definition of modified and other forms of mycotoxins including “masked” mycotoxins

As the term “masked mycotoxins” encompasses only conjugated mycotoxins generated by plants and no other possible forms of mycotoxins and their modifications, we hereby propose for all these forms a systematic definition consisting of four hierarchic levels. The highest level differentiates the free and unmodified forms of mycotoxins from those being matrix-associated and from those being modified in their chemical structure. The following lower levels further differentiate, in particular, “modified mycotoxins” into “biologically modified” and “chemically modified” with all variations of metabolites of the former and dividing the latter into “thermally formed” and “non-thermally formed” ones. To harmonize future scientific wording and subsequent legislation, we suggest that the term “modified mycotoxins” should be used in the future and the term “masked mycotoxins” to be kept for the fraction of biologically modified mycotoxins that were conjugated by plants.     

The mechanism of photodamage of eye structures. IV. Changes in the reactivity of crystalline SH-groups during UV irradiation

The kinetics of individual crystalline SH-group modification by DTNB were studied. According to the rates of their interaction with the modifier, the thiol groups in the native protein molecule can be classified as free, accessible, weakly modified and "masked" ones. Denaturation by the detergent (CTAB) caused an increase in the SH-group modification rate. In this case the SH-groups were modified as free and accessible ones. Illumination with UV-light resulted in a decrease in the number of SH-groups, opening of "masked" SH-groups in almost all crystallines except for alpha-crystalline, and essential changes in the SH-group modification rate.     

Solid-Phase Cross-Linking (SPCL): a new tool for protein structure studies

A wide range of chemical reagents are available to study the protein-protein interactions or protein structures. After reaction with such chemicals, covalently modified proteins are digested, resulting in shorter peptides that are analyzed by mass spectrometry (MS). Used especially when NMR of X-ray data are lacking, this methodology requires the identification of modified species carrying relevant information, among the unmodified peptides. To overcome the drawbacks of existing methods, we propose a more direct strategy relying on the synthesis of solid-supported cleavable monofunctional reagents and cross-linkers that react with proteins and that selectively release, after protein digestion and washings, the modified peptide fragments ready for MS analysis. Using this Solid-Phase Cross-Linking (SPCL) strategy, only modified sequences are analyzed and consistent data can be easily obtained since the signals of interest are not masked or suppressed by over-represented unmodified materials.     

Emotional Modulation of the Attentional Blink Is Awareness-Dependent

It is well known that emotion can modulate attentional processes. Previous studies have shown that even under restricted awareness, emotional facial expressions (especially threat-related) can guide the direction of spatial attention. However, it remains unclear whether emotional facial expressions under restricted awareness can affect temporal attention. To address this issue, we used a modified attentional blink (AB) paradigm in which masked (Experiment 1) or unmasked (Experiment 2) emotional faces (fearful or neutral) were presented before the AB sequence. We found that, in comparison with neutral faces, masked fearful faces significantly decreased the AB magnitude (Experiment 1), whereas unmasked fearful faces significantly increased the AB magnitude (Experiment 2). These results indicate that effects of emotional expression on the AB are modulated by the level of awareness.     

A versatile Solid Phase Method For the Synthesis of Masked 3′-Thiol Group Containing Oligonucleotides

Abstract

A new solid phase method for the introduction of masked thiol group on to the 3′-end of the oligonucleotide is reported. The modified oligonucleotides thus obtained can be better resolved by reverse phase column chromatography.     

Hormonotoxins. I. Strategy for synthesis of ovine luteinizing hormone--gelonin conjugate bearing the toxin in the beta-subunit

The amino groups in the beta-subunit of ovine luteinizing hormone (oLH) were modified by thiolation using N-succinimidyl-3-(2-pyridyldithio) propionate so that it may be coupled in a disulfide linkage to similarly modified ribosome inactivating protein, gelonin. The modified beta-subunit was able to hybridize with free LH alpha-subunit and the complex retained full biological activity. However, when gelonin was coupled to the beta-subunit, the resulting conformational changes masked or eliminated the sites necessary for intersubunit recognition of the free alpha-subunit. This has important implications for the design in the synthesis of gonadotropin-toxin/drug conjugates.     

果子狸研究现状

文献资料表明,有关果子狸的已有研究主要集中于人工饲养繁殖和疾病防治,区域性的动物学野外考察报告仅几篇涉及果子狸。目前,尚缺乏关于果子狸的基础生物学数据。鉴于果子狸曾被怀疑是SARS的疫源动物,故应立即开展果子狸的亚种及分布、野生种群与生境监测、繁殖交配制度与扩散行为等项研究。此外,还有必要研究果子狸的潜在疾病和预防,并开展人工养殖果子狸品系的选育工作。     

Inhibition of staphylococcal alpha-toxin by covalent modification of an arginine residue

The effects of 1,2-cyclohexanedione and phenylglyoxal on staphylococcal alpha-toxin were studied. Modification of one arginine residue in alpha-toxin was sufficient to render the toxin nonhemolytic with no conformational change. Modified alpha-toxin did not protect cells from hemolysis by native alpha-toxin. An arginine residue is therefore at or near the binding site of alpha-toxin. Trypsin digestion of modified alpha-toxin generated a 20 kDa fragment which was isolated using a boric acid gel column. Upon regeneration, this 20 kDa fragment was not recognized by a population of antibodies which prevented alpha-toxin binding. The fragment was recognized by antibodies directed against post-binding events. However, the antibinding antibodies recognized the intact modified toxin. This leads us to conclude that antibinding determinants are not found directly in the binding site or are conformationally masked.     

XII SYMPOSIUM OF THE INTERNATIONAL BIOACOUSTICS COUNCIL

ABSTRACT

Phonemic restoration, a form of temporal induction, occurs when the human brain compensates for masked or missing portions of speech by filling in obscured or nonexistent sounds. We tested for temporal induction and related abilities in females of the Gray Treefrog Hyla versicolor. The number of pulses in calls is used by females for assessment of males. Accordingly, an ability to “restore” or interpolate between masked or otherwise sonically degraded portions of calls could help females during mate choice in noisy choruses. In phonotaxis experiments, we employed unmodified calls and those that had a centrally placed gap, a region overlapped by a portion of another call or filtered noise, or replaced with filtered noise. When offered call alternatives with equivalent numbers of clear pulses, we found that females discriminated against calls with gaps two or more times greater than the natural 25 ms interpulse interval. When a gap was replaced with a zone of call overlap or noise (so, again the call durations of the alternatives were unequal), females discriminated either in favour (overlap) of the modified stimuli or failed to discriminate (noise). However, when the unmodified and modified stimuli were the same duration, females discriminated against the latter. Normal calls were also chosen when paired against calls with multiple noise sections. Pulses formed from noise bursts were attractive, but less so than normal pulses. In single speaker tests, standardized rates of movement did not differ between calls containing noise segments of different duration. Our results therefore do not indicate that females of the Gray Treefrog employ a form of temporal induction that is fully restorative. However, the data indicate that acoustically anomalous sections of calls can retain attractive potential provided acoustic energy and pulses are present.     

Spatial control of photomechanical movements in the lateral eye of the American horseshoe crab, Limulus polyphemus

This study asks whether photomechanical movements in the retinal cells of the lateral eye of the American horseshoe crab, Limulus polyphemus, are controlled locally within each ommatidium, or whether they are a retinal array property involving lateral communication between ommatidia. Three experiments were performed. A small spot, a vertical slit down the center, or the anterior third of an otherwise masked eye was illuminated. The contralateral eye was fully illuminated in each experiment and served as a light-adapted control. Morphometric analyses of aperture length and rhabdom dimensions were made from serial 1-microm plastic sections. The results suggest there is a different spatial threshold for photomechanical movement for aperture lengthening than for rhabdom lengthening. When only a few ommatidia are illuminated, the aperture does not change. When about 10% are illuminated, they lengthen, but the masked ommatidia do not. When about a third are illuminated, all the ommatidia in the eye lengthen together, including the two thirds that were masked. When either only a few ommatidia or about 10% of the ommatidia are illuminated, rhabdom shape is unchanged. When a third of the eye is illuminated, the illuminated rhabdoms lengthen, but the masked rhabdoms do not.     

A fast and symmetric DUST implementation to mask low-complexity DNA sequences.

The DUST module has been used within BLAST for many years to mask low-complexity sequences. In this paper, we present a new implementation of the DUST module that uses the same function to assign a complexity score to a sequence, but uses a different rule by which high-scoring sequences are masked. The new rule masks every nucleotide masked by the old rule and occasionally masks more. The new masking rule corrects two related deficiencies with the old rule. First, the new rule is symmetric with respect to reversing the sequence. Second, the new rule is not context sensitive; the decision to mask a subsequence does not depend on what sequences flank it. The new implementation is at least four times faster than the old on the human genome. We show that both the percentage of additional bases masked and the effect on MegaBLAST outputs are very small.     

Occupancy patterns of an apex avian predator across a forest landscape

Apex predators are integral parts of every ecosystem, having top‐down roles in food web maintenance. Understanding the environmental and habitat characteristics associated with predator occurrence is paramount to conservation efforts. However, detecting top order predators can be difficult due to small population sizes and cryptic behaviour. The endangered Tasmanian masked owl (Tyto novaehollandiae castanops) is a nocturnal predator with a distribution understood to be associated with high mature forest cover at broad scales. With the aim to gather monitoring data to inform future conservation effort, we trialled an occupancy survey design to model masked owl occurrence across ~800 km² in the Tasmanian Southern Forests. We conducted 662 visits to assess masked owl occupancy at 160 sites during July–September 2018. Masked owl site occupancy was 12%, and estimated detectability was 0.26 (±0.06 SE). Cumulative detection probability of masked owls over four visits was 0.7. Occupancy modelling suggested owls were more likely to be detected when mean prey count was higher. However, low detection rates hindered the development of confident occupancy predictions. To inform effective conservation of the endangered Tasmanian masked owl, there is a need to develop novel survey techniques that better account for the ecology of this rare, wide‐ranging and cryptic predator. We discuss the potential to combine novel census approaches that exploit different aspects of masked owl ecology to obtain more robust and detailed data.     

How different two almost identical action potentials can be: A model study on cardiac repolarization

Spatial heterogeneity in the properties of ion channels generates spatial dispersion of ventricular repolarization, which is modulated by gap junctional coupling. However, it is possible to simulate conditions in which local differences in excitation properties are electrophysiologically silent and only play a role in pathological states. We use a numerical procedure on the Luo-Rudy phase 1 model of the ventricular action potential (AP1) in order to find a modified set of model parameters which generates an action potential profile (AP2) almost identical to AP1. We show that, although the two waveforms elicited from resting conditions as a single AP are very similar and belong to membranes sharing similar passive electrical properties, the modified membrane generating AP2 is a weaker current source than the one generating AP1, has different sensitivity to up/down-regulation of ion channels and to extracellular potassium, and a different electrical restitution profile. We study electrotonic interaction of AP1- and AP2 - type membranes in cell pairs and in cable conduction, and find differences in source-sink properties which are masked in physiological conditions and become manifest during intercellular uncoupling or partial block of ion channels, leading to unidirectional block and spatial repolarization gradients. We provide contour plot representations that summarize differences and similarities. The present report characterizes an inverse problem in cardiac cells, and strengthen the recently emergent notion that a comprehensive characterization and validation of cell models and their components are necessary in order to correctly understand simulation results at higher levels of complexity.     

Four free cysteine residues found in human IgG1 of healthy donors

Modifications with different thiol reagents demonstrated that 28 of 32 cysteine residues of human IgG1 are involved in the formation of disulfide bonds, and four cysteines remain free. So IgG1 is a protein possessing both free SH-groups and disulfide bonds. Only one of the four SH-groups is accessible for silver or mercury ions and hydrophobic reagents, whereas the remaining three SH-groups are masked and can be revealed only after deep denaturation of the protein. Detection of the masked cysteine residues was shown to depend on the kinetics of intramolecular changes occurring during denaturation of the protein and on the method of the assay of the SH-groups.     

蛋白质的入核运送和它在基因表达中的调节作用

蛋白质进入细胞核是由蛋白质分子内部的核定位信号（nuclear localization signal, NLS）引导的.NLS蛋白首先与NLS受体结合,然后在多种胞浆因子及核孔复合物蛋白的作用下穿过核孔、转位入核.蛋白质上存在NLS并不一定总能够引导蛋白质入核.当NLS被修饰或遮掩时,它们便不能被核转运装置所识别.因而,NLS的遮掩被解除之前,蛋白质一直被扣留在胞浆中.以调节转录因子的入核运送来控制转录因子的活性是基因表达调节的一个新概念,也是细胞生长和分化的另一水平的调节.     

Masking the cryptodeterminant on the 54-kilodalton mouse sperm surface antigen.

Previously, we reported that the epitope of a 54-kDa sperm surface sialoglycoprotein on the flagellum is masked by sialic acid residues. The epitope is referred to as a hidden determinant or cryptodeterminant. This paper reports the manner in which the epitope is masked as evaluated qualitatively and quantitatively by means of SDS-PAGE/immunoblots (Western blot) and ELISA. Immunoblotting with four specific monoclonal antibodies to the 54-kDa sialoglycoprotein--T21 (IgM), MC71 (IgG1), MC81 (IgM), and MC91 (IgM)--demonstrated that not only IgM but also IgG antibody MC71 and the Fab fragment MC71 are masked. Quantitative evaluation with ELISA to compare the antibody titration curves of the masked and unmasked antigens on sialidase-treated and untreated sperm, respectively, indicated that sialidase caused the antibody-binding ability of the epitopes to increase to a different level for each antibody. There were 32-256-, 8-16-, 16-, and 2-4-fold increases in binding to T21, MC71, MC81, and MC91 antibodies, respectively. These results suggest that the antigen-masking through the cryptodeterminant does not depend upon the subtype or the molecular mass of the antibody, but upon the biochemical nature of the epitope region that is closely related to the sialic acid. The mechanism and physiological roles of the antigen-masking are discussed.     

青海海北地区艾虎的某些生态学特征及种群能量动态资料

艾虎,又名艾鼬(Mvstela eversmanni Lesson)在生态系统的牧食食物链(grazingfood chain)结构上,属二级消费者。其在能流和物质循环中起着重要作用。 有关艾虎生态学研究,报道甚少。Ванников(1954)和Новиков(1956)仅作过一般简单的综述,嗣后,Сысоев(1966),лалваниявов(1968)。Попов等(1968),Маръпп(1974)Bednarz(1964),Bardu(1971)亦均系简报之类。至于其能量的研究,涉及者甚少。国内有关艾虎生态学研究,尚乏报道。     

Specific modification of free lysine amino groups of histidine decarboxylase from Micrococcus sp. n. by trinitrobenzene sulfonic acid]

It has been found that 14 lysine residues are accessible for trinitrobenzene sulfonic acid (TNBS) in the molecule of histidine decarboxylase (HDC). The other 62 lysine residues in the molecule of native HDC are masked and inaccessible for TNBS. It is demonstrated that the SH- and alpha-amino groups of methionine are not modified by TNBS. A correlation between the decarboxylase activity of the enzyme and the degree of its trinitrophenylation has been studied. HDC, whose molecule contains 3--9 TNP groups, retains up to 90--97% of its initial activity. Trinitrophenylation of 14 lysine residues induces inactivation of HDC by 33--34%, which probably depends on conformational changes or steric hindrances, occurring in the catalytic site of the modified active centre of HDC. Using circular dichroism and fluorescence methods as well as disc-electrophoresis in polyacrylamide gel, it has been shown that trinitrophenylation does not cause any significant changes in the enzyme structure. The TNP groups have been found to be localized in the large and small subunits of the HDC molecule.     

Effect of conductivity changes on the stability of electric signal waveforms in dwarf stonebashers (Mormyridae; <Emphasis Type="Italic">Pollimyrus castelnaui</Emphasis>, <Emphasis Type="Italic">P. marianne</Emphasis>)

The dwarf stonebasher sibling species Pollimyrus castelnaui and P. marianne use differences in the electric organ discharges (EODs) for species recognition. As EOD waveforms are affected by water conductivity changes, the reliability of species recognition might be impeded due to natural variability in the environment. EODs of P. castelnaui (N = 8) and P. marianne (N = 8) under high (250 muS/cm) and low (25 muS/cm) conductivity were recorded and compared. Local peaks of the EODs of both species were significantly and predictably modified due to the conductivity change but species-specific differences were always recognizable. The duration of the EODs was not influenced by the conductivity change. Temperature alterations modified the duration in a linear relationship, allowing the determination of Q (10) values (1.6 for P. castelnaui's and 1.7 for P. marianne's EODs). As the species-specific differences are not masked by conductivity effects, EOD discrimination seems to be a reliable species recognition mechanism under natural circumstances.     

The Proximate Phonological Unit of Chinese-English Bilinguals: Proficiency Matters

An essential step to create phonology according to the language production model by Levelt, Roelofs and Meyer is to assemble phonemes into a metrical frame. However, recently, it has been proposed that different languages may rely on different grain sizes of phonological units to construct phonology. For instance, it has been proposed that, instead of phonemes, Mandarin Chinese uses syllables and Japanese uses moras to fill the metrical frame. In this study, we used a masked priming-naming task to investigate how bilinguals assemble their phonology for each language when the two languages differ in grain size. Highly proficient Mandarin Chinese-English bilinguals showed a significant masked onset priming effect in English (L2), and a significant masked syllabic priming effect in Mandarin Chinese (L1). These results suggest that their proximate unit is phonemic in L2 (English), and that bilinguals may use different phonological units depending on the language that is being processed. Additionally, under some conditions, a significant sub-syllabic priming effect was observed even in Mandarin Chinese, which indicates that L2 phonology exerts influences on L1 target processing as a consequence of having a good command of English.