Neuroimaging studies of alexithymia: physical,affective, and social perspectives

Alexithymia refers to difficulty in identifying and expressing one’s emotions, and it is related to disturbed emotional regulation. It was originally proposed as a personality trait that plays a central role in psychosomatic diseases. This review of neuroimaging studies on alexithymia suggests that alexithymia is associated with reduced neural responses to emotional stimuli from the external environment, as well as with reduced activity during imagery, in the limbic and paralimbic areas (i.e., amygdala, insula, anterior/posterior cingulate cortex). In contrast, alexithymia is also known to be associated with enhanced neural activity in somatosensory and sensorimotor regions, including the insula. Moreover, neural activity in the medial, prefrontal, and insula cortex was lowered when people with alexithymia were involved in social tasks. Because most neuroimaging studies have been based on sampling by self-reported questionnaires, the contrasted features of neural activities in response to internal and external emotional stimuli need to be elucidated. The social and emotional responses of people with alexithymia are discussed and recommendations for future research are presented.     

The zooplankton community structure in relation to its biological and physical environment on the Faroe shelf, 1989-1997

The Faroe shelf water is separated from the offshore water by a persistent tidal front, which surrounds the islands. This shelf water contains a neritic zooplankton community, which, regarding species composition, production, seasonal development and environmental conditions, is quite different from that in the surrounding ocean. While during spring and summer the zooplankton in the oceanic environment are dominated by the copepod Calanus finmarchicus, the zooplankton in the shelf water are largely dominated by neritic copepods, mainly Acartia longiremis and Temora longicornis. Calanus finmarchicus occurs in interannually highly variable abundance in the Faroe shelf ecosystem. Meroplanktonic larvae, mainly Balanus spp, and decapod larvae, are also common in the shelf water during spring and summer. During the period presented (1989-1997), the Faroe shelf ecosystem has undergone very large changes in abundance of different zooplankton species. The midsummer abundance of C.finmarchicus, which originally is advected into the shelf from the open ocean, fluctuated from 400 copepods m^-3 in 1989 to 25 copepods m^-3 in 1994, and at the same time the neritic zooplankton increased from 120 m^-3 in 1989 to 450 m^-3 in 1994. Consequently, the midsummer biomass in the shelf fluctuated by a factor of 10 during the same period. It is presumed that this variability between oceanic- and neritic-dominated zooplankton, their sizes and their biomass has greatly affected the entire pelagic ecosystem.      

The destruction of the agricultural environment in lower Silesia,Poland

The agricultural environment is affected by a series of internal and external factors which produce changes in the relations between the particular constituent parts of this environment as well as in their quality. The region of Lower Silesia has been taken as an example in an attempt at establishing the value of negative transformations by means of a synthetic index.     

Eradication and control of livestock ticks: biological, economic and social perspectives

Comparisons of successful and failed attempts to eradicate livestock ticks reveal that the social context of farming and management of the campaigns have greater influence than techniques of treatment. The biology of ticks is considered principally where it has contributed to control of ticks as practiced on farms. The timing of treatments by life cycle and season can be exploited to reduce numbers of treatments per year. Pastures can be managed to starve and desiccate vulnerable larvae questing on vegetation. Immunity to ticks acquired by hosts can be enhanced by livestock breeding. The aggregated distribution of ticks on hosts with poor immunity can be used to select animals for removal from the herd. Models of tick population dynamics required for predicting outcomes of control methods need better understanding of drivers of distribution, aggregation, stability, and density-dependent mortality. Changing social circumstances, especially of land-use, has an influence on exposure to tick-borne pathogens that can be exploited for disease control.     

Factors in the physical and biological environment affecting nodulation and nitrogen fixation by legumes

Summary The effects of root temperature on the four main stages of nodule formation and function are reviewed. Compared with results obtained under optimal conditions, lower root temperatures retard root hair infection more than they affect nodule initiation, nodule development (including bacteroid tissue development and degeneration), or nitrogen assimilation. Higher root temperatures upset the formation of bacteroid tissue and hasten its degeneration. Tropical and subtropical legumes have higher minimum temperatures for nodule formation than temperate species. Low and high shoot temperatures affect nodulation and nitrogen fixation, but the effect is less severe than that of similar root temperatures. Various approaches to minimise adverse environmental effects are considered. These include the selection of appropriate biological material (both host plants and bacterial strains) for the prevailing conditions, and the adoption of management practices designed to utilise the environment or to minimise its adverse effects. The importance of increase in bacteroid volume in relation to increase in rate of nitrogen fixation is considered, and the concept of compensation in nodule production and activity is examined. The limited information on defoliation effects on the nodulation of both temperate and tropical legumes is reviewed and aspects requiring examination are discussed.     

Vector strength after Goldberg, Brown, and von Mises: biological and mathematical perspectives

The vector strength, a number between 0 and 1, is a classical notion in biology. It was first used in neurobiology by Goldberg and Brown (J Neurophys 31:639–656, 1969) but dates back at least to von Mises (Phys Z 19:490–500, 1918). It is widely used as a means to measure the periodicity or lack of periodicity of a neuronal response to an outside periodic signal. Here, we provide a self-contained and simple treatment of a closely related notion, the synchrony vector, a complex number with the vector strength as its absolute value and with a definite phase that one can directly relate to a biophysical delay. The present analysis is essentially geometrical and based on convexity. As such it does two things. First, it maps a sequence of points, events such as spike times on the time axis, onto the unit circle in the complex plane so that for a perfectly periodic repetition, a single point on the unit circle appears. Second, events hardly ever occur periodically, so that we need a criterion of how to extract periodicity out of a set of real numbers. It is here where convex geometry comes in, and a geometrically intuitive picture results. We also quantify how the events cluster around a period as the vector strength goes to 1. A typical example from the auditory system is used to illustrate the general considerations. Furthermore, von Mises’ seminal contribution to the notion of vector strength is explained in detail. Finally, we generalize the synchrony vector to a function of angular frequency, not fixed on the input frequency at hand and indicate its potential as a “resonating” vector strength.     

Marker-assisted selection to improve drought adaptation in maize: the backcross approach, perspectives, limitations, and alternatives

A number of different marker-assisted selection (MAS) approaches do exist for the improvement of polygenic traits. Results of a marker-assisted backcross (MABC) selection experiment aimed at improving grain yield under drought conditions in tropical maize are presented and compared with alternative MAS strategies. The introgression of favourable alleles at five target regions involved in the expression of yield components and flowering traits increased grain yield and reduced the asynchrony between male and female flowering under water-limited conditions. Eighty-five per cent of the recurrent parent's genotype at non-target loci was recovered in only four generations of MABC by screening large segregating populations (2200 individuals) for three of the four generations. Selected MABC-derived BC(2)F(3) families were crossed with two testers and evaluated under different water regimes. Mean grain yield of MABC-derived hybrids was consistently higher than that of control hybrids (crosses from the recurrent parent to the same two testers as the MABC-derived families) under severe water stress conditions. Under those conditions, the best five MABC-derived hybrids yielded, on average, at least 50% more than control hybrids. Under mild water stress, defined as resulting in <50% yield reduction, no difference was observed between MABC-derived hybrids and the control plants, thus confirming that the genetic regulation for drought tolerance is dependent on stress intensity. MABC conversions involving several target regions are likely to result in partial rather than complete line conversion. Simulations were conducted to assess the utility of such partial conversions, i.e. containing favourable donor alleles at non-target regions, for subsequent phenotypic selection. The results clearly showed that selecting several genotypes (10-20) at each MABC cycle was most efficient. In the light of these results, alternative approaches to MABC are discussed, including recurrent selection, illustrated by an example of improving the adaptation of maize to low temperatures. Given the current approaches for MAS and the choices of marker technologies available now and potential for future developments, the use of MAS techniques in further improving grain yield under abiotic stresses in maize appears very promising.     

Perennially ice-covered Lake Hoare,Antarctica: physical environment,biology and sedimentation

Lake Hoare (77° 38 S, 162° 53 E) is a perennially ice-covered lake at the eastern end of Taylor Valley in southern Victoria Land, Antarctica. The environment of this lake is controlled by the relatively thick ice cover (3–5 m) which eliminates wind generated currents, restricts gas exchange and sediment deposition, and reduces light penetration. The ice cover is in turn largely controlled by the extreme seasonality of Antarctica and local climate. Lake Hoare and other dry valley lakes may be sensitive indicators of short term (< 100 yr) climatic and/or anthropogenic changes in the dry valleys since the onset of intensive exploration over 30 years ago. The time constants for turnover of the water column and lake ice are 50 and 10 years, respectively. The turnover time for atmospheric gases in the lake is 30–60 years. Therefore, the lake environment responds to changes on a 10–100 year timescale. Because the ice cover has a controlling influence on the lake (e.g. light penetration, gas content of water, and sediment deposition), it is probable that small changes in ice ablation, sediment loading on the ice cover, or glacial meltwater (or groundwater) inflow will affect ice cover dynamics and will have a major impact on the lake environment and biota.     

The physical chemistry of biological membranes

Physical chemistry explains the principles of self-organization of lipids into bilayers that form the matrix of biological membranes, and continuum theory of membrane energetics is successful in explaining many biological processes. With increasing sophistication of investigative tools, there is now a growing appreciation for lipid diversity and for the role of individual lipids and specific lipid-protein interactions in membrane structure and function.     

When quinones meet amino acids: chemical, physical and biological consequences

Summary. Quinones and amino acids are usually compartmentally separated in living systems, however there are several junctions in which they meet, react and influence. It occurs mainly in wounded, cut or crushed plant material during harvest, ensiling or disintegrating cells. Diffusing polyphenols are oxidized by polyphenol oxidases (PPOs) to quinonic compounds, which associate reversibly or irreversibly with amino acids and proteins. The reaction takes place with the free nucleophilic functional groups such as sulfhydryl, amine, amide, indole and imidazole substituents. It results in imine formation, in 1,4-Michael addition via nitrogen or sulphur and in Strecker degradation forming aldehydes. The formation and activity of quinone–amino acids conjugates influences the colour, taste, and aroma of foods. Physical and physiological phenomena such as browning of foods, discoloration of plants during processing, alteration of solubility and digestibility, formation of humic substances, germicidal activity, cytotoxicity and more occur when quinones from disintegrating cells meet amino acids. The mechanisms of toxicity and the pathways by which PCBs may be activated and act as a cancer initiator include oxidation to the corresponding quinones and reaction with amino acids or peptides. Sclerotization of insect cuticle is a biochemical process involving also the reaction between quinones and amino acid derivatives.     

The spatial structure of the physical environment

There is substantial environmental variance at small spatial scales (1 m or less) in both natural and disturbed environments. We have investigated the spatial structure of physical variables at larger scales (up to 10⁶ m). We analysed surveys of edaphic properties of Wisconsin forest soils, of the water chemistry of lakes in Ontario and Labrador, and of temperature and precipitation in northeastern North America. We found no clear indication that the variance among sites approaches some maximal value as the distance between them increases. We suggest instead that the variance of the physical environment tends to increase continually with distance. The slope of the log-log regression of variance on distance provides a means of comparing the heterogeneity of different environments with respect to a given factor, or of comparing different factors within a given environment. This slope provides a useful measure of environmental structure that can be related to the biodiversity or plasticity of native organisms.     

Potato pulp: microbiological characterization, physical modification, and application of this agricultural waste product

Potato pulp, one of the agricultural waste products obtained in high quantities during starch production, contains starch, cellulose, hemicelluloses, pectin, proteins, free amino acids and salts. It exhibits physical and physicochemical properties of a typical colloid. It is mainly used, in a dried and pelleted form, as cattle feed. Its autochthonic microbial flora (bacteria, fungi) was identified and studied with a view towards the degradative potential of the microorganisms and ways of conserving the pulp for subsequent technical applications; 33 isolates (28 bacteria, 4 fungi, 1 yeast), belonging to 15 genera were characterized. Biological conservation was possible at very low oxygen pressure, brought about by the autochthonic anaerobic microorganisms causing acidification. Chemical conservation was achieved with sorbic aicd. By treatment with hot water vapour under pressure (autoclaving), followed by a pressure release procedure, intact cells in the pulp (both potato cells and microorganisms, not spores) were destroyed, and their contents and wall fragments were set free. This process resulted in low drying costs and was a prerequisite for the production of a powder that can be used as glue or as animal feed. Received: 18 April 1997 / Received revision: 12 June 1997 / Accepted: 14 June 1997     

Catch bonds: physical models, structural bases, biological function and rheological relevance

Force can shorten the lifetimes of macromolecular complexes (e.g., receptor-ligand bonds) by accelerating their dissociation. Perhaps paradoxical at first glance, bond lifetimes can also be prolonged by force. This counterintuitive behavior was named catch bonds, which is in contrast to the ordinary slip bonds that describe the intuitive behavior of lifetimes being shortened by force. Fifteen years after their theoretical proposal, catch bonds have finally been observed. In this article we review recently published data that have demonstrated catch bonds in the selectin system and suggested catch bonds in other systems, the theoretical models for their explanations, possible structural bases, their relation to flow-enhanced adhesion, and the potential biorheological relevance.     

Group behaviour in physical,chemical and biological systems

Groups exhibit properties that either are not perceived to exist, or perhaps cannot exist, at the individual level. Such ‘emergent’ properties depend on how individuals interact, both among themselves and with their surroundings. The world of everyday objects consists of material entities. These are, ultimately, groups of elementary particles that organize themselves into atoms and molecules, occupy space, and so on. It turns out that an explanation of even the most commonplace features of this world requires relativistic quantum field theory and the fact that Planck’s constant is discrete, not zero. Groups of molecules in solution, in particular polymers (‘sols’), can form viscous clusters that behave like elastic solids (‘gels’). Sol-gel transitions are examples of cooperative phenomena. Their occurrence is explained by modelling the statistics of inter-unit interactions: the likelihood of either state varies sharply as a critical parameter crosses a threshold value. Group behaviour among cells or organisms is often heritable and therefore can evolve. This permits an additional, typically biological, explanation for it in terms of reproductive advantage, whether of the individual or of the group. There is no general agreement on the appropriate explanatory framework for understanding group-level phenomena in biology.     

Functional roles of melatonin in plants, and perspectives in nutritional and agricultural science

The presence of melatonin in plants is universal. Evidence has confirmed that a major portion of the melatonin is synthesized by plants themselves even though a homologue of the classic arylalkylamine N-acetyltransferase (AANAT) has not been identified as yet in plants. Thus, the serotonin N-acetylating enzyme in plants may differ greatly from the animal AANAT with regard to sequence and structure. This would imply multiple evolutionary origins of enzymes with these catalytic properties. A primary function of melatonin in plants is to serve as the first line of defence against internal and environmental oxidative stressors. The much higher melatonin levels in plants compared with those found in animals are thought to be a compensatory response by plants which lack means of mobility, unlike animals, as a means of coping with harsh environments. Importantly, remarkably high melatonin concentrations have been measured in popular beverages (coffee, tea, wine, and beer) and crops (corn, rice, wheat, barley, and oats). Billions of people worldwide consume these products daily. The beneficial effects of melatonin on human health derived from the consumption of these products must be considered. Evidence also indicates that melatonin has an ability to increase the production of crops. The mechanisms may involve the roles of melatonin in preservation of chlorophyll, promotion of photosynthesis, and stimulation of root development. Transgenic plants with enhanced melatonin content could probably lead to breakthroughs to increase crop production in agriculture and to improve the general health of humans.