Mechanisms of energy balance in obesity.

Maintains that the proper understanding of obesity requires a multifaceted approach and that behavioral considerations of eating and activity patterns do not account for the large between- and within-Ss variance associated with the energy-balance equation. Sources of adaptive and dispositional variance in metabolic rates are suggested to be a likely source of importance for the proper conceptualization and intervention of obesity. Five proposed mechanisms of metabolic variation are reviewed with consideration of the supporting evidence for each mechanism. The generalizability of some of the proposed mechanisms is considered to be limited because of the scope of past research. However, the roles of lipoprotein lipase in fat storage and brown adipose tissue in thermogenesis are possibilities for future research with humans. (103 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Season of birth in schizophrenia: A review of evidence, methodology, and etiology.

Reviews research examining the association between season of birth and later onset of schizophrenia. Methodological issues in studies comparing seasonal birth rates of schizophrenics to those of controls are discussed. After summarizing a critique by M. S. Lewis and T. A. Griffin (see record 1981-21450-001) of the season of birth literature and the responses to that critique, it is concluded that seasonal birth rates of schizophrenics do in fact differ from those of the general population. Four hypotheses (harmful effects, genetic-fitness procreational habits, and amplified deviation) proposed to account for this observation are evaluated. Empirical support for each hypothesis is judged to be insufficient, although infectious agents and obstetric complications appear to be the most promising explanations. Recommendations for further research are offered, and the need for a systemic conceptualization of this problem is emphasized. (103 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The simulating social mind: The role of the mirror neuron system and simulation in the social and communicative deficits of autism spectrum disorders.

The mechanism by which humans perceive others differs greatly from how humans perceive inanimate objects. Unlike inanimate objects, humans have the distinct property of being "like me" in the eyes of the observer. This allows us to use the same systems that process knowledge about self-performed actions, self-conceived thoughts, and self-experienced emotions to understand actions, thoughts, and emotions in others. The authors propose that internal simulation mechanisms, such as the mirror neuron system, are necessary for normal development of recognition, imitation, theory of mind, empathy, and language. Additionally, the authors suggest that dysfunctional simulation mechanisms may underlie the social and communicative deficits seen in individuals with autism spectrum disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrogen use and cancer risk: a review

The role of estrogens as carcinogens, cocarcinogens or tumor promoters, as well as their mechanism(s) of action on cancer cells, are thoroughly reviewed. Although there is ample evidence that estrogens (natural and synthetic) can induce multiple benign and malignant tumors in animals, and most of these tumors are histologically similar to that in humans, there is no direct evidence that natural estrogens (estradiol-17 beta, estrone) are carcinogenic in humans. Recent evidence in cellular and molecular oncology revealed that estrogens act by genetic and epigenetic mechanisms on cancer cells, and a close relationship between estrogens, growth factors, and oncogenes is important for human cancer. Long-term exposure to estrogens should always be regarded as increased cancer risk. Estrogen replacement therapy (ERT) by unopposed estrogens in postmenopausal women with high familial cancer risk or existent premalignant lesions should be avoided, since estrogens may act as tumor promoters. Combination of estrogens with progesterone (or other progestins) cyclically or sequentially, significantly reduce and prevent the cancer risk.     

Speed dependence of crutch force and oxygen uptake: implications for design of comparative trials on orthoses for people with paraplegia

The major defence mechanism in frogs in via the secretion of toxins from their skin. In humans, intoxication may occur when part of the amphibian integument is ingested, as in the form of herbal medicines. Two groups of South African frogs have skin secretions that are potentially lethal to humans and animals. Toads (Bufo and Schismaderma species), the amphibians with which man and his pets most frequently have contact, secrete potent toxins with cardiac glycoside activity. Topical and systemic intoxication, while seen in humans, remains predominantly a veterinary problem. Intoxication by the red-banded rubber frog, which secretes an unidentified cardiotoxin, is far less common. The probable mechanisms of intoxication and management of a poisoned patient are discussed.     

钢铁行业二噁英的形成机理及降解方法研究现状

雾霾天气的日益严重使得国家环保部门更加关注大气污染问题,而造成雾霾天气的大气污染物也越来越被熟知并分类治理.在中国二氧化硫和氮氧化物已经进入治理末端阶段,二噁英的治理还处于一个萌芽阶段.二噁英是迄今为止科研领域发现的无意识副产品中毒性最强的化合物之一,对人体的毒性主要体现在伤害的不可逆.介绍了二噁英的形成机理和降解方法...     

High-resolution transmission electron microscopy investigation of the face-centered cubic/hexagonal close-packed martensite transformation in Co-31.8 wt pct Ni alloy: Part 2. Plate intersections,extended defects,and nucleation mechanisms

The face-centered cubic/hexagonal close-packed (fcc/hcp) martensite phase transformation in a Co-31.8 wt pct Ni alloy was studied by high-resolution transmission electron microscopy (HRTEM). The HRTEM was used to study the structure and properties of intersections between martensite plates and other defects observed in the alloy such as stacking fault tetrahedra (SFT) and Z-type defects. The HRTEM was also used to attempt to determine if various proposed mechanisms for the fcc/hcp martensite transformation were operating. There is evidence to suggest that the reflection mechanism proposed by Bollmann and the dipole mechanism proposed by Hirth are active in the fcc/hcp martensitic transformation, although the evidence is not completely certain in either case. Growth of the hcp phase by a four- or six-plane mechanism as proposed by Mahajanet al. is possible in theory but was not observed in this study. Transformation by previously proposed pole mechanisms was also not observed in this study, although evidence for a new type of pole mechanism was found. The formation of SFT along the fcc/hcp martensite interface was observed to occur by the cross-slip of Shockley partial dislocations out of the fcc/hcp interface onto conjugate fcc matrix planes, followed by further cross-slip to form the SFT, as previously observed for grain boundaries in fcc alloys.     

Role of serotonin in the paradoxical calming effect of psychostimulants on hyperactivity

The mechanism by which psychostimulants act as calming agents in humans with attention-deficit hyperactivity disorder (ADHD) or hyperkinetic disorder is currently unknown. Mice lacking the gene encoding the plasma membrane dopamine transporter (DAT) have elevated dopaminergic tone and are hyperactive. This activity was exacerbated by exposure to a novel environment. Additionally, these mice were impaired in spatial cognitive function, and they showed a decrease in locomotion in response to psychostimulants. This paradoxical calming effect of psychostimulants depended on serotonergic neurotransmission. The parallels between the DAT knockout mice and individuals with ADHD suggest that common mechanisms may underlie some of their behaviors and responses to psychostimulants.     

Of mice (Mus musculus) and toddlers (Homo sapiens): Evidence for species-general spatial reorientation.

There is ongoing debate in spatial cognition about the mechanisms by which organisms are able to reorient, or reestablish a position, in the world after losing their bearing. The traditional view is that there is an encapsulated reorientation module that can only process environmental geometry such as distances or angles (Cheng, 1986). Recently, this view has been challenged on the grounds that the reorientation mechanism is only able to accept geometric information and may instead depend on a more general ability to use relative cues. J. Huttenlocher and S. F. Lourenco (2007) demonstrated that toddlers are successfully able to reorient with continuous cues but show remarkable deficits using categorical cues that are similar in perceptual complexity for reorientation. Here, the authors show the same pattern of results with mice (Mus musculus). These findings provide evidence that there is a homologous reorientation mechanism between mice and humans. Thus, future researchers can examine the genetic basis of this important cognitive ability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Systemic aluminum toxicity: effects on bone, hematopoietic tissue, and kidney

Although the full mechanisms are not yet elucidated, research into the mechanism of toxicity of aluminum (Al) on bone formation and remodeling and on hematopoietic tissue is ongoing. In contrast little information exists on the interactive effects of systemic Al and the kidney. In bone, both clinically and experimentally, high doses of Al inhibit remodeling, slowing both osteoblast and osteoclast activities and producing osteomalacia and adynamic bone disease. In contrast, while very low levels of Al are mitogenic in bones of experimental animals, the effect of low levels of Al in humans is unknown. Aluminum has been shown to have its mitogenic action at the osteoblast, but whether the effect on resorption is viz osteoblast-directed changes in osteoclast activity has not yet been determined. Parathyroid hormone (PTH) levels are disrupted by Al in humans and animals. Whether altered PTH levels play a major or even a minor role in Al-dependent osteotoxicity requires clarification. In hematopoietic tissue, Al causes a microcytic anemia, not reversible by iron. Friend leukemia cells treated with Al have been reported to accumulate excess iron, without incorporating it into ferritin or heme. It is not yet known which steps in iron metabolism are disrupted by Al, if they involve a single mechanism of action, or even if this disruption in iron metabolism accounts for the anemia seen in Al toxicosis. In kidney, research is needed to evaluate Al nephrotoxicity; there are almost no studies in this area. Furthermore, research is needed to evaluate mechanisms of renal Al excretion, presently shown by one study to occur at the distal tubule. Such studies might well throw light on whether Al plays a role in aggravating renal insufficiency, or whether the role of the kidney in Al toxicosis is limited to the causative effect of renal compromise on Al accumulation. In summary, while a number of mechanisms have been proposed for the toxic action of Al, no single mechanism emerges to explain these diverse effects of systemic Al. Recommendations for future research are presented and summarized in Table 1.     

Parental licensure.

Most of the 1,400,000 men currently locked up in American prisons would have become tax-paying neighbors had they been switched in the hospital nursery and sent home with a mature, self-supporting, married couple. The parent with whom they did go home would in most instances not have been fit to adopt someone else's baby. It is argued that perhaps the only effective way to reduce crime and the other pathologies of the growing American underclass-apart from building still more prisons-would be to require from persons wishing to birth and rear a child of their own those same minimal criteria usually expected in adoptive parents. For evolutionary reasons, human beings are reluctant to interfere with the procreational rights of any person, no matter how immature, incompetent, or unsocialized he or she might be. In consequence, human beings tend not to think about the right of the child to a reasonable opportunity for life, liberty, and the pursuit of happiness. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Body size and feeding specificity: macrolepidoptera in Britain

Within a geographic assemblage, large-bodied species of macrolepidopteran moths tend, on average, to be less host-specific than small-bodied. Five possible explanations for this pattern are identified, based respectively on (i) phylogenetic relationships between species, (ii) latitudinal gradients in body size and feeding specificity, (iii) the relationship between range size and body size, (iv) larger body size as a buffer from environmental variation, and (v) the relationship between endophagous host associations and small body size. These mechanisms are tested using data for British macrolepidoptera and also evaluated using evidence from the literature at large. Although some of their assumptions are found to be justified, there is no significant support for any single mechanism. This lack of evidence for previously proposed mechanisms is discussed in the light of a recently proposed alternative explanation which combines theories of host quality and host defence mechanisms.Copyright 1998 The Linnean Society of London     

The effect of a carbonated beverage on the wear of human enamel and dental ceramics

Ochratoxins, of which ochratoxin A (OA) is the most prevalent, are secondary fungal metabolites of some toxigenic species of Aspergillus and Penicillium. OA has been shown to be nephrotoxic, hepatotoxic, teratogenic, carcinogenic and immunosuppressive. The natural occurrence of OA in food and feed stuffs is widespread, especially in temperate areas such as Canada, Denmark, Germany, Sweden and the United Kingdom, and detectable amounts were even found in randomly collected human milk samples in Germany, Sweden and Italy. Of greatest concern in humans is its implicated role in an irreversible and fatal kidney disease referred to as Balkan Endemic Nephropathy. The mean dietary intake for humans in the European Union was found to be in the range of 1 to 2 ng/kg bw/day. Compared with the Provisional Tolerable Daily Intake (PTDI) proposed by the WHO of 16 ng OA/kg bw/day for humans, the average OA intake in Europe seems to be rather low. The main contributor to the OA intake in humans are cereals and cereal products, other possible contributors are coffee, beer, pork, products containing pig blood/plasma, pulses and spices. Only very few countries have regulations for OA in food and feed products. Based on the current literature, the mechanisms involved in the toxicity of OA indicate three major effects: (1) inhibition of mitochondrial respiration correlated with a depletion of ATP; (2) inhibition of tRNA-synthetase accompanied by a reduced protein synthesis; and (3) enhanced lipid peroxidation. Generation of free radicals and lipid peroxidation as an important mode of action of OA in vitro and in vivo is discussed in detail, as well as counteracting effects of dietary antioxidants.     

Patterns of drug-induced cardiovascular pathology in the beagle dog: relevance for humans

In toxicity studies, the examination of tissue sections for pathological changes is the principle method for the identification of organ toxicity and characterisation of the hazard of novel drugs for humans. Study of the patterns of pathological alterations also represents an important means of developing an understanding of the mechanism of toxicity. However as pathological change frequently represents a final common expression of diverse processes, additional functional information is often required for a clear understanding of the mechanisms of toxicity. This is exemplified in the evaluation of the effects of drugs on the beagle dog cardiovascular system where an understanding of mechanisms is crucial in the assessment of human risk. Particular patterns of drug-induced structural change in the myocardium or blood vessels are frequently linked to specific mechanisms of toxicity. However, assessment based on the interpretation of patterns of cardiovascular pathology alone may be misleading. Quite different changes in cardiac and vascular function or direct cellular toxicity may also be manifest by pathological features in common. Therefore, a clear understanding of mechanism frequently requires additional in vivo or in vitro physiological, pharmacological, biochemical or other mechanistic information. The beagle dog remains an important model for the study of cardiovascular toxicity because in this species, haemodynamic changes and pathological alterations can be related in a way that provides the basis for the safe study in humans of novel drugs with cardiovascular activity.     

Cognitive function in mammals: the evolutionary perspective

The work of behavioural pharmacologists has concentrated on small animals, such as rodents and pigeons. The validity of extrapolation of their findings to humans depends upon the existence of parallels in both physiology and psychology between these animals and humans. This paper considers the question whether there are in fact substantial cognitive parallels between, first, different non-human groups of vertebrates and, second, non-humans and humans. Behavioural data from 'simple' tasks, such as habituation and conditioning, do not point to species differences among vertebrates. Using examples that concentrate on the performance of rodents and birds, it is argued that, similarly, data from more complex tasks (learning-set formation, transitive inference, and spatial memory serve as examples) reveal few if any cognitive differences amongst non-human vertebrates. This conclusion supports the notion that association formation may be the critical problem-solving process available to non-human animals; associative mechanisms are assumed to have evolved to detect causal links between events, and would therefore be relevant in all ecological niches. In agreement with this view, recent advances in comparative neurology show striking parallels in functional organisation of mammalian and avian telencephalon. Finally, it is argued that although the peculiarly human capacity for language marks a large cognitive contrast between humans and non-humans, there is good evidence-in particular, from work on implicit learning--that the learning mechanisms available to non--humans are present and do play an important role in human cognition.     

Learned industriousness.

Extensive research with animals and humans indicates that rewarded effort contributes to durable individual differences in industriousness. It is proposed that reinforcement for increased physical or cognitive performance, or for the toleration of aversive stimulation, conditions rewards value to the sensation of high effort and thereby reduces effort's aversiveness. The conditioning of secondary reward value to the sensation of effort provides a dynamic mechanism by which reinforced high performance generalizes across behaviors. Applications to self-control, moral development, and education are described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms of directed attention in the human extrastriate cortex as revealed by functional MRI

A typical scene contains many different objects, but the capacity of the visual system to process multiple stimuli at a given time is limited. Thus, attentional mechanisms are required to select relevant objects from among the many objects competing for visual processing. Evidence from functional magnetic resonance imaging (MRI) in humans showed that when multiple stimuli are present simultaneously in the visual field, their cortical representations within the object recognition pathway interact in a competitive, suppressive fashion. Directing attention to one of the stimuli counteracts the suppressive influence of nearby stimuli. This mechanism may serve to filter out irrelevant information in cluttered visual scenes.     

Estimating frequency of occurrence.

Various models have been proposed that attribute judgments of frequency of occurrence either to the direct coding of frequency information or to the estimation of frequency from characteristics of memory traces that are not direct frequency codes. We present three experiments that replicate and further explore a phenomenon that is significant in the distinction between direct and indirect models of frequency coding. The phenomenon is that deeper processing of stimulus material results in superior judgments of frequency for that material than does shallower processing. This effect is at least partly attributable to the number of associations that are generated by deep analysis. The results of the present experiments thereby implicate an indirect coding mechanism underlying frequency judgments. However, we also show that there is ample reason to suppose a contribution of a direct coding mechanism as well. The most reasonable view, therefore, is that multiple mechanisms are involved in the registration of frequency of occurrence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A longitudinal study of the role of negative affectivity on the work stressor–strain process.

A significant proportion of previous research in the occupational stress area has tended to treat the personality variable negative affectivity (NA) as a nuisance variable. This perspective has led researchers to routinely control for the effects of NA. However, P. E. Spector, D. Zapf, P. Y. Chen, and M. Frese (2000) have proposed a number of different mechanisms by which NA could have substantive effects. The current research used a longitudinal framework to test several competing mechanisms proposed by Spector et al. (specifically, the perception, hyperresponsivity, and causality mechanisms) on the relationship between work stressors and psychological well-being. Customs workers and dentists constituted the longitudinal sample (N = 345). Results provided strong support for the perception mechanism, indicating that the effects of NA on psychological health were partially mediated by work stressors. The authors discuss the theoretical and practical relevance of the perception mechanism to occupational health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)