Enzyme deactivation

Enzyme deactivation kinetics is often first-order. Different examples of first-order deactivation kinetics exhibited by different enzymes under a wide variety of conditions are presented. Examples of both soluble and immobilized enzymes are presented. The influence of different parameters, chemical modification of specific residues, inhibitors, inactivators, protecting agents, induced conformational changes by external agents, enzyme concentration, and different substrates on the first-order inactivation kinetics of different enzymes is analyzed. The different examples presented from a variety of different areas provides a judicious framework and collection demonstrating the wide applicability of first-order deactivation kinetics. Examples of reversible first-order deactivation kinetics and deactivation-disguise kinetics are also presented.Different mechanisms are also presented to model complex enzyme deactivations. The non-series type mechanisms are emphasized and these involve the substrate and chemical modifiers. Substrate-dependent deactivation rate expressions that are of "separable" and "non-separable" type are presented. Rate expressions involving time-dependent rate constants along with their corresponding mechanisms are presented. Examples of enzymes that exhibit a deactivation-free grace period are also given. An interesting case of enzyme inactivation is the loss of activity in the presence of an auto-decaying reagent. The method is presented by which the intrinsic inactivation rate constants may be obtained. Examples of pH-dependent enzyme inactivation are presented that may be modelled by a five-step (or a simplified two-step) mechanism, and also by a single-step mechanism involving residual activity for the final state. Appropriate examples of enzyme inactivation are presented in each case to highlight the different mechanisms involved.     

冷害过程中黄瓜叶片SOD、CAT和POD活性的变化

实验选用3个耐冷力不同的黄瓜品种研究其叶片超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）等3种抗氧化酶活性在冷害过程中的变化。结果表明：低温胁迫期间的CAT和POD活性与黄瓜叶片的耐冷力表现一致,SOD活性则与其耐冷力表现相反。低温胁迫后,3个品种的所有3种抗氧化酶活性均降低,叶片表现出明显的冷害症状,但耐冷力较高的津优10号仍然具有相对较高的CAT活性。恢复期的SOD活性无显著性变化;耐冷力最弱的津研4号和耐冷力中等的津绿3号的CAT活性上升而津优10号的CAT活性降低;3个品种的POD活性都增高,但津研4号的上升幅度明显高于其它2个品种,可能与POD能催化活性氧（ROS）产生有关。     

Effects of visual flicker on subjective time in a temporal bisection task

This experiment investigated the effects of visual flicker on subjective time in humans using a temporal bisection task. A 200–800 ms duration range and 400–1600 ms duration range were presented. Each duration range was presented separately in three different conditions: (1) filled stimuli were presented in both the training and the testing phases, (2) flickering stimuli were presented in the training phase and filled stimuli were presented in the testing phase, and (3) filled stimuli were presented in the training phase and flickering stimuli were presented in the testing phase. Psychophysical functions displacements and bisection point values suggested that flicker increased the speed of the clock; however the direction of the displacement and bisection point changes depended on the phase of the task in which the flicker was presented. This result agrees with the specific storage in either working or reference memory components of Scalar Expectancy Theory of the increased number of pulses from the clock. Weber fractions and difference limens suggested that flicker did not affect subjects’ temporal sensitivity.     

Degenerate T-cell recognition of peptides on MHC molecules creates large holes in the T-cell repertoire

The cellular immune system screens peptides presented by host cells on MHC molecules to assess if the cells are infected. In this study we examined whether the presented peptides contain enough information for a proper self/nonself assessment by comparing the presented human (self) and bacterial or viral (nonself) peptides on a large number of MHC molecules. For all MHC molecules tested, only a small fraction of the presented nonself peptides from 174 species of bacteria and 1000 viral proteomes ([Formula: see text]0.2%) is shown to be identical to a presented self peptide. Next, we use available data on T-cell receptor-peptide-MHC interactions to estimate how well T-cells distinguish between similar peptides. The recognition of a peptide-MHC by the T-cell receptor is flexible, and as a result, about one-third of the presented nonself peptides is expected to be indistinguishable (by T-cells) from presented self peptides. This suggests that T-cells are expected to remain tolerant for a large fraction of the presented nonself peptides, which provides an explanation for the "holes in the T-cell repertoire" that are found for a large fraction of foreign epitopes. Additionally, this overlap with self increases the need for efficient self tolerance, as many self-similar nonself peptides could initiate an autoimmune response. Degenerate recognition of peptide-MHC-I complexes by T-cells thus creates large and potentially dangerous overlaps between self and nonself.     

Scapular hydatidosis with extraosseous involvement

A forty three-year-old female, born in a rural area of southern Chile, at the age of 30 presented pain and limitation of motility of the right shoulder. Later on, she presented an increasing of volume at the right scapular region. A radiography showed an osteolytic lesion of the scapula. In a biopsy an osseous hydatidosis was found and a hydatid cyst was extirpated from the soft tissues. Four years later, as she presented again pain and volume increasing in the same anatomical area, albendazole was given to her, and a CAT practiced revealed osteolytic lesions of the bone, several periosteal ruptures and multiple cysts in the muscles. She was submitted to surgery again in order to extirpate cysts. After two years the patient presented the same clinical manifestations and radiological and CAT images previously observed. In considering all these facts a radical surgery was decided.     

A single-fractal analysis of cellular analyte-receptor binding kinetics utilizing biosensors

A fractal analysis of a confirmative nature only is presented for cellular analyte-receptor binding kinetics utilizing biosensors. Data taken from the literature can be modeled by using a single-fractal analysis. Relationships are presented for the binding rate coefficient as a function of the fractal dimension and for the analyte concentration in solution. In general, the binding rate coefficient is rather sensitive to the degree of heterogeneity that exists on the biosensor surface. It is of interest to note that examples are presented where the binding coefficient, k exhibits an increase as the fractal dimension (D(f)) or the degree of heterogeneity increases on the surface. The predictive relationships presented provide further physical insights into the binding reactions occurring on the surface. These should assist in understanding the cellular binding reaction occurring on surfaces, even though the analysis presented is for the cases where the cellular "receptor" is actually immobilized on a biosensor or other surface. The analysis suggests possible modulations of cell surfaces in desired directions to help manipulate the binding rate coefficient (or affinity). In general, the technique presented is applicable for the most part to other reactions occurring on different types of biosensor or other surfaces.     

Building proteomic tool boxes to monitor MHC class I and class II peptides

Major histocompatibility complex Class I (MHCI) and Class II (MHCII) presented peptides powerfully modulate T cell immunity and play a vital role in generating effective anti‐tumor and anti‐viral immune responses in mammals. Characterizing these MHCI or MHCII presented peptides can help generate therapeutic treatments, afford information on T cell mediated biomarkers, provide insight into disease progression, and reduce adverse anti‐drug side effects from engineered biotherapeutics. Here, we explore the tools and techniques commonly employed to discover both MHCI‐ and MHCII‐presented peptides. We describe complementary strategies that enhance the characterization of these peptides and the informatics tools employed for both predicting and characterizing MHCI‐ and MHCII‐presented epitopes. The evolution of methodologies for isolating MHC‐presented peptides is discussed, as are the mass spectrometric workflows that can be employed for their characterization. We provide a perspective on where this field is headed, and how these tools may be applicable to the discovery and monitoring of epitopes in a variety of scenarios.     

Quantitation of immobilized proteins

A method for the quantitative determination of immobilized proteins based on the binding and subsequent elution of Coomassie Blue R is presented. Also presented is a method for the immobilization of proteins in solution by entrapment in polyacrylamide. These entrapped proteins are then available for use in the assay method presented. Other analytical procedures can also be performed on the entrapped proteins, either alone or in combination with the protein quantitation. The dye binding and elution method presented provides a sensitive and, in most applications, rapid method for the quantitative detection of immobilized proteins. Rather than immobilization being an obstacle to the assay method, this approach utilizes the advantages of immobilization for the removal of excess reagents. Application of this approach to several types of immobilized protein are presented.     

Anorexia dreaming: A case study.

A case study is presented focusing on a dream of a severely anorectic woman. The dream occurred at a point when the disorder had become life threatening. The dream is discussed in terms of its significance in the dreamer's experience, its implications for the use of dreams in psychotherapy, and its relevance for the broader literature on psychopathology and dreams. Archetypal psychology's aesthetic, and phenomenological approach to dreams is presented as a framework for understanding the ongoing significance of significant dreams such as the one presented here. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential left hemisphere activation during the voluntary control of skin resistance level

Sixteen dextral subjects were presented auditory feedback (FBK) in the form of clicks, the frequency of which was inversely proportional to the surn of the skin resistance levels (SRLs) of the two hands. The FBK was presented in a two-ear changeover paradigm: FBK was presented for 10 minutes to one ear while a white noise masking stimulus was presented to the other; the ears of FBK and masking stimulus presentation were then reversed. Subjects were instructed to decrease the frequency of the clicking. An increase in the SRL of each hand was used as a measure of the activation of the contralateral hemisphere. Significant increases in right-hand SRL (on the order of 40% of baseline) were seen following FBK and obtained regardless of the ear to which FBK was presented, the order of FBK presentation, or the sex of the subjects. Also seen were small-magnitude changes in left-hand SRL, which were not statistically significant. These findings indicate that the left hemisphere was differentially active during acquisition of inhibitory control of SRL in dextrals receiving auditory FBK. Clinical implications of this finding are discussed.     

Hemispheric differences in visual recognition of two Kanji characters

The purpose of the present study was to examine hemispheric differences in visual recognition of two kanji letters. Kanji phrases and nonsense kanji letters were presented unilaterally to the left or right visual hemifield in thirty normal right-handed men by a tachistoscope. The experiments were separated into three conditions; the mixing tasks (ten phrases and ten sets of nonsense letters are presented by mixture), the phase task (twenty phrases are presented), and the nonsense letters task (twenty sets of nonsense letters are presented). Under all conditions, significant right visual hemifield superiorities for the accuracy of recognition of phrase and nonsense letters were observed.     

Use of Multiple Genetic Markers in Prediction of Breeding Values

Genotypes at a marker locus give information on transmission of genes from parents to offspring and that information can be used in predicting the individuals' additive genetic value at a linked quantitative trait locus (MQTL). In this paper a recursive method is presented to build the gametic relationship matrix for an autosomal MQTL which requires knowledge on recombination rate between the marker locus and the MQTL linked to it. A method is also presented to obtain the inverse of the gametic relationship matrix. This information can be used in a mixed linear model for simultaneous evaluation of fixed effects, gametic effects at the MQTL and additive genetic effects due to quantitative trait loci unlinked to the marker locus (polygenes). An equivalent model can be written at the animal level using the numerator relationship matrix for the MQTL and a method for obtaining the inverse of this matrix is presented. Information on several unlinked marker loci, each of them linked to a different locus affecting the trait of interest, can be used by including an effect for each MQTL. The number of equations per animal in this case is 2m + 1 where m is the number of MQTL. A method is presented to reduce the number of equations per animal to one by combining information on all MQTL and polygenes into one numerator relationship matrix. It is illustrated how the method can accommodate individuals with partial or no marker information. Numerical examples are given to illustrate the methods presented. Opportunities to use the presented model in constructing genetic maps are discussed.     

Conditioned Sounds Enhance Visual Processing

This psychophysics study investigated whether prior auditory conditioning influences how a sound interacts with visual perception. In the conditioning phase, subjects were presented with three pure tones ( =  conditioned stimuli, CS) that were paired with positive, negative or neutral unconditioned stimuli. As unconditioned reinforcers we employed pictures (highly pleasant, unpleasant and neutral) or monetary outcomes (+50 euro cents, −50 cents, 0 cents). In the subsequent visual selective attention paradigm, subjects were presented with near-threshold Gabors displayed in their left or right hemifield. Critically, the Gabors were presented in synchrony with one of the conditioned sounds. Subjects discriminated whether the Gabors were presented in their left or right hemifields. Participants determined the location more accurately when the Gabors were presented in synchrony with positive relative to neutral sounds irrespective of reinforcer type. Thus, previously rewarded relative to neutral sounds increased the bottom-up salience of the visual Gabors. Our results are the first demonstration that prior auditory conditioning is a potent mechanism to modulate the effect of sounds on visual perception.     

Recognition of visual images by separate hemispheres in conditions of masked blocking of interhemispheric transmission

The subjects learned to recognize three figures presented in the left visual hemifield and three figures presented in the right visual hemifield. During presentation of a stimulus, the contralateral hemifield was overlapped by a mask. After the training, recognition of all six figures presented in the right and left visual hemifields, was compared. Each hemisphere recognizes figures which were learned in the corresponding visual hemifield, but the recognition of figures learned in the opposite visual hemifield was poor. Thus, the ability of the hemispheres to act separately in recognizing different sets of visual images, was established.     

MOUSE-III: Learning rules of conformational analysis from X-ray data

MOUSE-III is learning program that finds rules of conformational analysis from raw cristallographie data. The program perceives molecular features, finds conformational classes in the data and then learns rules that link features to classes. The rules that MOUSE learns are capable of correctly assigning conformations to ring systems that were not used for training with greater than 95% accuracy, when MOUSE was presented with sufficient data. The rules also show a compression of as much as 99% when compared to the raw data. This is accomplished through abstraction and generalization. The algorithm is presented along with a carefully worked example. An example of a learned rule is also presented and analyzed. Some conclusions about the scope and limitations of the learning process are presented.     

Feminization of chronic alcoholic men: a formulation.

A review of the factors historically thought to contribute to the feminization of men with Laennec''s cirrhosis is presented. Objective scientific data is presented both in support of and in rejection of such factors when available. Recent hypotheses about the significance of an altered estrogen to androgen (E/T) ratio as being important in the pathogenesis of feminization also are discussed. Finally, a hypothesis which incorporates the findings of hypogonadism and cirrhosis with portal-systemic shunting is presented as a pathogenic mechanism for the feminization of men with alcohol-induced Laennec''s cirrhosis.     

Opposite Distortions in Interval Timing Perception for Visual and Auditory Stimuli with Temporal Modulations

When an object is presented visually and moves or flickers, the perception of its duration tends to be overestimated. Such an overestimation is called time dilation. Perceived time can also be distorted when a stimulus is presented aurally as an auditory flutter, but the mechanisms and their relationship to visual processing remains unclear. In the present study, we measured interval timing perception while modulating the temporal characteristics of visual and auditory stimuli, and investigated whether the interval times of visually and aurally presented objects shared a common mechanism. In these experiments, participants compared the durations of flickering or fluttering stimuli to standard stimuli, which were presented continuously. Perceived durations for auditory flutters were underestimated, while perceived durations of visual flickers were overestimated. When auditory flutters and visual flickers were presented simultaneously, these distortion effects were cancelled out. When auditory flutters were presented with a constantly presented visual stimulus, the interval timing perception of the visual stimulus was affected by the auditory flutters. These results indicate that interval timing perception is governed by independent mechanisms for visual and auditory processing, and that there are some interactions between the two processing systems.     

Kinematic of animal locomotion under various gravitational fields.

A simple kinematic analysis of human locomotion under various gravitational fields is presented and a desirable way of locomotion is proposed. A comment on flight behaviors of insects in nongravity fields is also presented.     

Subitization and attentional engagement by transient stimuli

A series of experiments investigated the visual selection of moving and static items during enumeration. Small numbers of visual targets can be enumerated with little increase in reaction time and error with set size, a process referred to as 'subitization'. The number of items that can be subitized' is typically between one and four and known as the subitization range. This study looked for evidence of subitizing of subsets of items presented on a computer display. Fast and accurate enumeration was found for random configurations of moving targets even when presented among static distracters. This was not the case for static targets presented among moving or transient distracters. RTs to these targets were longer and showed a steady increase in RT with target number, even in the subitization range. However, when static targets and moving distracters were presented foveally, fast enumeration/subitization of the static targets was again possible. This was not due to reduced inter-item spacing, since linear effects of the number of targets still emerged when stimuli were presented peripherally but the size-spacing ratio was matched to the foveal presentations. There was indication that instead performance reflected perceived differences in movement speed for stimuli presented in parafoveal and more peripheral retinal regions. In support of this, subitization of static items improved as the movement speed of the distracters increased. The data suggest that the processes supporting subitization are highly sensitive to dynamic stimuli and depend on the ease of segmentation between static and moving arrays.     

Significant collections of Orchidaceae conserved in Herbarium Hamburgense (HBG)

An inventory of critical type material in the recently rediscovered Kraenzlin Orchid Herbarium is presented. In addition, a partial inventory of type material of Orchidaceae conserved in the general herbarium at Hamburg (HBG) is presented as a guide to the collections.