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PubMed1992

Recognising faces: effects of lighting direction, inversion, and brightness reversal.

When information about three-dimensional shape obtained from shading and shadows is ambiguous, the visual system favours an interpretation of surface geometry which is consistent with illumination from above. If pictures of top-lit faces are rotated the resulting stimulus is both figurally inverted and illuminated from below. In this study the question of whether the effects of figural inversion and lighting orientation on face recognition are independent or interactive is addressed. Although there was a clear inversion effect for faces illuminated from the front and above, the inversion effect was found to be reduced or eliminated for faces illuminated from below. A strong inversion effect for photographic negatives was also found but in this case the effect was not dependent on the direction of illumination. These findings are interpreted as evidence to suggest that lighting faces from below disrupts the formation of surface-based representations of facial shape.

Adult↗
PubMed2003

Attending to faces: change detection, familiarization, and inversion effects.

We tested detection of changes to eye position, eye color (brightness), mouth position, and mouth color in frontal views of faces. Two faces were presented sequentially for 555 ms each, with a blank screen of 120 ms separating the two. Faces were presented either both upright or both inverted. Measures of detection (d') were calculated for several different degrees of change for each of the four dimensions of change. We first compared results to an earlier experiment that used an oddity design, in which subjects indicated which of three simultaneously viewed and otherwise identical faces had been altered on one of these four dimensions. Subjects in both of these experiments were partially cued, in that they knew the four possible types of changes that could occur on a given trial. The change-detection results correlated well with the oddity data. They confirmed that face inversion had little effect upon detection of changes in eye color, a moderate effect upon detection of eye-position or mouth-color changes, and caused a drastic reduction in the detection of mouth-position changes. An experiment in which uncued and fully cued subjects were compared showed that cueing significantly improved detection of feature color changes, but there was little difference between upright and inverted faces. Full cueing eliminated all effects of inversion. Compared to partial cueing, changes in mouth color were poorly detected by uncued subjects. Last, a change in the frequency of the base (unaltered) face in an experiment from 75% to 40% showed that increased short-term familiarity decreased the detection of eye changes and increased the detection of mouth changes, regardless of face orientation and the type of change made (color or position). We conclude that uncued subjects encode the spatial relations of features more than the colors of features, that mouth color in particular is not considered a relevant dimension for encoding, and that familiarization redistributes attention from more to less salient facial regions. Inversion effects are not simply an exaggeration of the salience effects revealed by withdrawing cueing, but represent an interaction of spatial encoding with salience, in that the greatest inversion effects occur for spatial shifts in less salient facial regions, and can be eliminated through the use of focused attention.

Adolescent↗
PubMed1982

Herpesvirus-dependent amplification and inversion of cell-associated viral thymidine kinase gene flanked by viral a sequences and linked to an origin of viral DNA replication.

The genome of herpes simplex virus 1 or 2 consists of two components, L and S, which invert relative to each other during infection. As a result, viral DNA consists of four equimolar populations of molecules differing solely in the relative orientations of the L and S components. Previous studies have shown that the a sequences, located in the same orientation at the genomic termini and in inverted orientation at the L-S junction, play a key role in the inversion of L and S components. In this report we describe a virus-dependent system designed to allow identification of the viral genes capable of acting in trans to invert DNA flanked by inverted copies of a sequences. In this system, cells are converted to the thymidine kinase-positive phenotype with a chimeric plasmid carrying the thymidine kinase gene flanked by inverted copies of the a sequence and linked to an origin of viral DNA replication derived from the S component. The DNA introduced into the cells is retained and propagated in its original sequence arrangement as head-to-tail concatemers. Infection of these cells with herpes simplex virus 1 or 2 results in as much as 100-fold amplification of the plasmid sequences and inversion of the DNA flanked by copies of the a sequence. In infected cells, the amplified resident DNA accumulates in head-to-tail concatemers and no rearrangement other than the inversions could be detected. These results suggest that the a sequence-dependent inversions required trans-acting viral gene products.

Animals↗
PubMed1988

Mechanochemical coupling in synthetic polypeptides by modulation of an inverse temperature transition.

For the polypentapeptide of elastin, (L-Val-L-Pro-Gly-L-Val-Gly)n, and appropriate analogs when suitably cross-linked, it has been previously demonstrated that development of elastomeric force at fixed length and length changes at fixed load occur as the result of an inverse temperature transition, with the temperature of the transition being inversely dependent on the hydrophobicity of the polypeptide. This suggests that at fixed temperature a chemical means of reversibly changing the hydrophobicity could be used for mechanochemical coupling. Evidence for this mechanism of mechanochemical coupling is given here with a 4%-Glu-polypentapeptide, in which the valine in position 4 is replaced in 1 out of 5 pentamers by a glutamic acid residue. Before cross-linking, the temperature for aggregation of 4%-Glu-polypentapeptide is remarkably sensitive to pH, shifting from 25 degrees C at pH 2 to 70 degrees C at pH 7.4 in phosphate-buffered saline (PBS). At 37 degrees C, the cross-linked 4%-Glu-polypentapeptide matrix in PBS undergoes a pH-modulated contraction and relaxation with a change from pH 4.3 to 3.3 and back. The mean distance between carboxylates at pH 4.3 in the elastomeric matrix is greater than 40 A, twice the mean distance between negatively charged species in PBS. Accordingly, charge-charge repulsion is expected to make little or no contribution to the coupling. Mechanochemical coupling is demonstrated at fixed load by monitoring pH dependence of length and at constant length by monitoring pH dependence of force. To our knowledge, this is the first demonstration of mechanochemical coupling in a synthetic polypeptide and the first system to provide a test of the recent proposal that chemical modulation of an inverse temperature transition can be a mechanism for mechanochemical coupling. It is suggested that phosphorylation and dephosphorylation may modulate structure and forces in proteins by locally shifting the temperatures of inverse temperature transitions.

Amino Acid Sequence↗
PubMed1999

Agonists and inverse agonists for the herpesvirus 8-encoded constitutively active seven-transmembrane oncogene product, ORF-74.

A number of CXC chemokines competed with similar, nanomolar affinity against 125I-interleukin-8 (IL-8) binding to ORF-74, a constitutively active seven-transmembrane receptor encoded by human herpesvirus 8. However, in competition against 125I-labeled growth-related oncogene (GRO)-alpha, the ORF-74 receptor was highly selective for GRO peptides, with IL-8 being 10,000-fold less potent. The constitutive stimulating activity of ORF-74 on phosphatidylinositol turnover was not influenced by, for example, IL-8 binding. In contrast, GRO peptides acted as potent agonists in stimulating ORF-74 signaling, whereas IP-10 and stromal cell-derived factor-1alpha surprisingly acted as inverse agonists. These peptides had similar pharmacological properties with regard to enhancing or inhibiting, respectively, the stimulatory effect of ORF-74 on NIH-3T3 cell proliferation. Construction of a high affinity zinc switch through introduction of two His residues at the extracellular end of transmembrane segment V enabled Zn2+ to act as a prototype non-peptide inverse agonist, which eliminated the constitutive signaling. It is concluded that ORF-74, which is believed to be causally involved in the formation of highly vascularized tumors, has been optimized for agonist and inverse agonist modulation by the endogenous angiogenic GRO peptides and angiostatic IP-10 and stromal cell-derived factor-1alpha, respectively. ORF-74 could serve as a target for the development of non-peptide inverse agonist drugs as demonstrated by the effect of Zn2+ on the metal ion site-engineered receptor.

3T3 Cells↗
PubMed2003

Zero-sized effect of nano-particles and inverse homogeneous nucleation. Principles of freezing and antifreeze.

It was found that freezing of water in terms of homogeneous nucleation of ice never occurs even in ultra-clean micro-sized water droplets under normal conditions. More surprisingly, at sufficiently low supercoolings, foreign nano-particles exert no effect on the nucleation barrier of ice; it is as if they physically "vanished." This effect, called hereafter the "zero-sized" effect of foreign particles (or nucleators), leads to the entry of a so-called inverse homogeneous-like nucleation domain, in which nucleation is effectively suppressed. The freezing temperature of water corresponds to the transition temperature from the inverse homogeneous-like nucleation regime to foreign particle-mediated heterogeneous nucleation. The freezing temperature of water is mainly determined by (i) the surface roughness of nucleators at large supercoolings, (ii) the interaction and structural match between nucleating ice and the substrate, and (iii) the size of the effective surface of nucleators at low supercoolings. Our experiments showed that the temperature of -40 degrees C, commonly regarded as the temperature of homogeneous nucleation-mediated freezing, is actually the transition temperature from the inverse homogeneous-like nucleation regime to foreign particle-mediated heterogeneous nucleation in ultra-clean water. Taking advantage of inverse homogeneous-like nucleation, the interfacial tensions between water and ice in very pure water and antifreeze aqueous solutions were measured at a very high precision for the first time. The principles of freezing promotion and antifreeze and the selection for the biological ice nucleation and antifreeze proteins are obtained. The results provide completely new insights into freezing and antifreeze phenomena and bear generic implications for all crystallization systems.

Antifreeze Proteins↗
PubMed2005

Inverse association between body mass and frequency of milk consumption in children.

Recent studies have shown an inverse association between the level of dietary Ca, particularly from dairy sources, and body weight in adults; there is, however, a paucity of data regarding this relationship in children. We therefore investigated this issue in 1087 children who underwent body weight and height measurement during a survey on childhood obesity. Lifestyle and dietary habits were investigated by a questionnaire. After excluding children who were following a dietary regimen for any reason, 884 children (M:F 451:433; age 7.5 (sd 2.1) years) were selected. Milk consumption was pooled into four frequency categories: poor (< or =1/week; n 125), moderate (>1 but < or =5-6/week; n 133), regular (1/d; n 408) and high (> or =2/d; n 218). The frequency of consumption of milk was inversely and significantly associated (t=-2.964, P=0.003) with age- and sex-specific BMI z-scores by linear regression analysis, controlling for sex, age, physical activity, birth weight and parental overweight and education. The statistical association remained significant (t=-2.831, P=0.005) after the inclusion of children consuming only skimmed milk (n 91). Milk consumption was still significantly and inversely associated with BMI z score (t=-2.791, P=0.005) in the whole-milk consumers when controlling for age and the frequency of consumption of various foods; this association was no longer significant (P=0.21) when children consuming skimmed milk were included in the analysis. This is the first report showing a significant inverse association between frequency of milk consumption and body mass in children. Regardless of the mechanisms involved, our results might encourage further research on this issue and might have important implications for the prevention of obesity.

Analysis of Variance↗
PubMed2006

Recognition of base pair inversions in duplex by chimeric (alpha,beta) triplex-forming oligonucleotides.

DNA recognition by triplex-forming oligonucleotides (TFOs) is usually limited by homopurine-homopyrimidine sequence in duplexes. Modifications of the third strand may overcome this limitation. Chimeric alpha-beta TFOs are expected to form triplex DNA upon binding to non-regular sequence duplexes. In the present study we describe binding properties of chimeric alpha-beta oligodeoxynucleotides in the respect to short DNA duplexes with one, three, and five base pair inversions. Non-natural chimeric TFO's contained alpha-thymidine residues inside (GT) or (GA) core sequences. Modified residues were addressed to AT/TA inversions in duplexes. It was found in the non-denaturing gel-electrophoresis experiments that single or five adjacent base pair inversions in duplexes may be recognized by chimeric alpha-beta TFO's at 10 degrees C and pH 7.8. Three dispersed base pair inversions in the double stranded DNA prevented triplex formation by either (GT) or (GA) chimeras. Estimation of thermal stability of chimeric alpha-beta triplexes showed decrease in T(m) values as compared with unmodified complexes.

Base Pairing↗
PubMed2000

Inverse dose-rate effects at the level of proteins observed in the presence of lipids.

PURPOSE: Radical-chain mechanisms such as lipid peroxidation are known to show an inverse dose-rate effect, i.e. the radiation effect increases with decreasing dose rate at identical doses applied. The present study was intended to investigate whether an inverse dose-rate effect can be transferred from the level of lipids to the level of proteins. METHOD: Functional inactivation or structural modification by 80kV X-rays of two classes of proteins was investigated: membrane proteins with a natural environment of lipids like the Ca-ATPase of the sarcoplasmic reticulum, succinate dehydrogenase and F0F1-ATPase from the inner mitochondrial membrane. The second class comprises the water-soluble proteins cytosolic creatine kinase (MM-CK) and bovine serum albumin (BSA). Their modification by free radicals of water radiolysis was investigated in the absence and presence of lipid vesicles. RESULTS: For all proteins investigated, an inverse dose-rate effect was observed in the presence of lipids. This also holds for the water-soluble proteins MM-CK and BSA. In the latter two cases, the dose-rate effect disappeared either in the absence of (unsaturated) lipids or in the presence of alpha-tocopherol. CONCLUSION: The largely identical results obtained for a variety of different proteins indicate that inverse dose-rate effects are a normal consequence of radiation induced protein damage in the presence of lipids. In view of the high amount of cellular lipids, this should also hold for the situation in vivo, although due to the comparatively high concentration of intracellular antioxidants the dose-rate dependence might be strongly reduced or even virtually abolished.

Animals↗
PubMed2004

A 3D generic inverse dynamic method using wrench notation and quaternion algebra.

In the literature, conventional 3D inverse dynamic models are limited in three aspects related to inverse dynamic notation, body segment parameters and kinematic formalism. First, conventional notation yields separate computations of the forces and moments with successive coordinate system transformations. Secondly, the way conventional body segment parameters are defined is based on the assumption that the inertia tensor is principal and the centre of mass is located between the proximal and distal ends. Thirdly, the conventional kinematic formalism uses Euler or Cardanic angles that are sequence-dependent and suffer from singularities. In order to overcome these limitations, this paper presents a new generic method for inverse dynamics. This generic method is based on wrench notation for inverse dynamics, a general definition of body segment parameters and quaternion algebra for the kinematic formalism.

Acceleration↗
PubMed1977

Cell shape changes and the mechanism of inversion in Volvox.

Inversion is a dominant aspect of morphogenesis in Volvox. In this process, the hollow, spheroidal Volvox embryo turns inside-out through a small opening called the phialopore to bring flagella from its inner to its outer surface. Analyses of intact, sectioned, and fragmented embryos by light, scanning electron, and transmission electron microscopy, suggest that shape changes preprogrammed into the cells cause inversion. First, cells throughout the embryo change from pear to spindle shape, which causes the embryo to contract and the phialopore to open. Then cells adjacent to the phialopore become flask-shaped, with long, thin stalks at their outer ends. Simultaneously, the cytoplasmic bridges joining all adjacent cells migrate from the midpoint of the cells to the stalk tips. Together, these changes cause the lips of cells at the phialopore margin to curl outward. Now cells progressively more distal to the phialopore become flask-shaped while the more proximal cells become columnar, causing the lips to curl progressively further over the surface of the embryo until the latter has turned completely inside-out. Fine structural analysis reveals a peripheral cytoskeleton of microtubules that is apparently involved in cellular elongation. Cell clusters isolated before inversion undergo a similar program of shape changes; this suggests that the changes in cellular shape are the cause rather than an effect of the inversion process.

Cell Division↗
PubMed1986

Kinetics of shoot inversion-induced ethylene production in Pharbitis nil.

Shoot inversion promotes a significant increase in ethylene production in the inverted part of the Pharbitis nil main shoot. The latent period for shoot inversion-induced ethylene production is ca. 2.75 h. Our results indicate that the shoot-inversion ethylene response is not persistent and can be terminated and rapidly reinitiated by appropriate alteration of the orientation of the main shoot regardless of prolonged previous exposures of the shoot to various orientations. The time course of the production of ACC (1-aminocyclopropane-1-carboxylic acid), the immediate precursor of ethylene, follows a pattern similar to that of ethylene during the various alterations of shoot orientation. Excised stem segments and intact stems are capable of induction, inhibition, and reinduction of ethylene evolution. Ethylene production reported here for shoot inversion does not result from segmenting (wounding) of the tissue.

Amino Acids↗
PubMed2002

Pre-clinical evaluation of an inverse planning module for segmental MLC based IMRT delivery.

Phantom tests are performed for pre-clinical evaluation of a commercial inverse planning system (HELAX TMS, V 6.0) for segmented multileaf collimator (MLC) intensity modulated radiotherapy (IMRT) delivery. The optimization module has available two optimization algorithms: the target primary feasibility and the weighted feasibility algorithm, only the latter allows the user to specify weights for structures. In the first series, single beam tests are performed to evaluate the outcome of inverse planning in terms of plausibility for the following situations: oblique incidence, presence of inhomogeneities, multiple targets at different depths and multiple targets with different desired doses. Additionally, for these tests a manual plan is made for comparison. In the absence of organs at risk, both the optimization algorithms are found to assign the highest priority to low dose constraints for targets. In the second series, tests resembling clinical relevant configurations (simultaneous boost and concave target with critical organ) are performed with multiple beam arrangements in order to determine the impact of the system's configuration on inverse planning. It is found that the definition of certain segment number and segment size limitations does not largely compromise treatment plans when using multiple beams. On the other hand, these limitations are important for delivery efficiency and dosimetry. For the number of iterations and voxels per volume of interest, standard values in the system's configuration are considered to be sufficient. Additionally, it is demonstrated that precautions must be taken to precisely define treatment goals when using computerized treatment optimization. Similar phantom tests could be used for a direct dosimetric verification of all steps from inverse treatment planning to IMRT delivery.

Algorithms↗
PubMed2003

AI-guided parameter optimization in inverse treatment planning.

An artificial intelligence (AI)-guided inverse planning system was developed to optimize the combination of parameters in the objective function for intensity-modulated radiation therapy (IMRT). In this system, the empirical knowledge of inverse planning was formulated with fuzzy if-then rules, which then guide the parameter modification based on the on-line calculated dose. Three kinds of parameters (weighting factor, dose specification, and dose prescription) were automatically modified using the fuzzy inference system (FIS). The performance of the AI-guided inverse planning system (AIGIPS) was examined using the simulated and clinical examples. Preliminary results indicate that the expected dose distribution was automatically achieved using the AI-guided inverse planning system, with the complicated compromising between different parameters accomplished by the fuzzy inference technique. The AIGIPS provides a highly promising method to replace the current trial-and-error approach.

Algorithms↗
PubMed2003

Inverse planning for intensity-modulated arc therapy using direct aperture optimization.

Intensity-modulated arc therapy (IMAT) is a radiation therapy delivery technique that combines gantry rotation with dynamic multi-leaf collimation (MLC). With IMAT, the benefits of rotational IMRT can be realized using a conventional linear accelerator and a conventional MLC. Thus far, the advantages of IMAT have gone largely unrealized due to the lack of robust automated planning tools capable of producing efficient IMAT treatment plans. This work describes an inverse treatment planning algorithm, called 'direct aperture optimization' (DAO) that can be used to generate inverse treatment plans for IMAT. In contrast to traditional inverse planning techniques where the relative weights of a series of pencil beams are optimized, DAO optimizes the leaf positions and weights of the apertures in the plan. This technique allows any delivery constraints to be enforced during the optimization, eliminating the need for a leaf-sequencing step. It is this feature that enables DAO to easily create inverse plans for IMAT. To illustrate the feasibility of DAO applied to IMAT, several cases are presented, including a cylindrical phantom, a head and neck patient and a prostate patient.

Algorithms↗
PubMed1999

An independent, inverse association of high-density-lipoprotein-cholesterol concentration with nonadipose body mass.

BACKGROUND: Increasing body mass index (BMI) is associated with progressively lower serum HDL-cholesterol concentrations, although the underlying body-composition compartment accounting for this unfavorable lipid change remains uncertain. OBJECTIVE: Because growing evidence favors a role of lean tissue in HDL homeostasis, the hypothesis was tested that non-adipose tissue components of body mass explain the inverse association of HDL cholesterol and BMI. DESIGN: Fasting serum lipid concentrations and body composition [total, subcutaneous, and visceral adipose tissue; adipose tissue-free mass (ATFM); and skeletal muscle by whole-body magnetic resonance imaging and body cell mass by 40K counting) were evaluated in healthy adults. Body-composition compartments were expressed as height2-normalized indexes. RESULTS: An inverse correlation was observed between serum HDL cholesterol and BMI in women (n = 68; R2 = 0.08, P = 0.023) and men (n = 61; R2 = 0.07, P = 0.046). Significant inverse correlations (P = 0.005-0.02) were also observed between HDL cholesterol and nonadipose components (ie, ATFM, skeletal muscle, and body cell mass) but not between HDL cholesterol and any adipose tissue component. The association between HDL cholesterol and ATFM remained significant after serum triacylglycerol was controlled for. When BMI was entered into the HDL cholesterol-ATFM regression model, BMI was not a significant independent variable. The strongest correlate of serum triacylglycerol was visceral adipose tissue (P = 0.002 for both women and men). CONCLUSIONS: Lean tissues and body cell mass appear to account in part for the long-observed inverse association of HDL cholesterol and BMI. These observations suggest a link between nonadipose tissue compartments and the greater cardiovascular risk associated with high BMI.

Adipose Tissue↗
PubMed2000

Inverse association of physical fitness with plasma fibrinogen level in children: the Columbia University BioMarkers Study.

Plasma fibrinogen has emerged as a risk factor for cardiovascular disease in adults, but relatively little is known about the correlates of plasma fibrinogen level in childhood. In the Columbia University BioMarkers Study (1994-1998), the authors evaluated the association between physical fitness and plasma fibrinogen level in 193 children 4-25 years old; 68% were Hispanic and 46% male. Fitness level assessed by treadmill testing was inversely associated with plasma fibrinogen (r = -0.24, p<0.001). Plasma fibrinogen levels showed a graded inverse relation with tertiles of fitness assessed by treadmill (p<0.001). In multivariate analyses, after adjustment for age, sex, race/ethnicity, body mass index, and presence of the A allele in the -455 position of the beta-fibrinogen promoter gene, the fitness level remained inversely associated with plasma fibrinogen level (beta = -1.3, 95% confidence interval (CI): -2.3, -0.34). Resting heart rate was also correlated with plasma fibrinogen level (r = 0.18, p<0.05). Fibrinogen levels (mg/dl) increased over tertiles of resting heart rate (p = 0.002) and were significantly associated with resting heart rate in multivariate analysis (beta = 0.82, 95% CI: 0.17, 1.5). These findings indicate that plasma fibrinogen is inversely associated with physical fitness in children independent of body mass index.

Adult↗
PubMed2001

Inverse correlation between alcohol consumption and lymphocyte levels of 8-hydroxydeoxyguanosine in humans.

In a cross-sectional study of 115 premenopausal non-smoking women, we examined the relationship between lymphocyte levels of 8-hydroxy-2'-deoxyguanosine (8-oxodGuo) and habitual alcohol consumption. The study was conducted in four different regions of Europe, including Potsdam (Germany), Turin (Italy), Malmö (Sweden) and Granada (Spain). Mean 8-oxodGuo levels differed significantly across study centres (P = 0.001), with the highest levels in Granada [2.17 8-oxodGuox10(-6) 2'-deoxyguanosine (95% confidence interval 1.27-4.40)] and lowest levels in Turin [1.19 (0.36-4.29)]. Mean levels of total alcohol intake and of types of alcoholic beverages consumed (wine, fortified wines, beer and cider) also differed across the study centres (P < 0.05), with the highest total alcohol consumption in Turin, and the lowest intake in GRANADA: When combining all the data, but adjusting for study centre, individual 8-oxodGuo level correlated inversely with alcohol intake. This inverse association remained unaltered after further adjustment for Quetelet Index, fruit and vegetable consumption, and plasma carotenoid levels. Furthermore, the inverse association was also observed for each of the study centres separately, and for different beverage types, with the exception of Granada, where the majority of women were non-drinkers and where alcohol intakes were also very low for the consumers. Finally, on a group level, mean levels of 8-oxodGuo and alcohol intake were also inversely associated between the four study centres. The finding of a relationship between alcohol consumption and 8-oxodGuo in lymphocytes was unexpected and not based on a prior hypothesis. This finding consequently requires confirmation from a randomized intervention study.

8-Hydroxy-2'-Deoxyguanosine↗