Theory of excitable membranes. I. A simple model for a three-state artificial membrane.

The effect of the thermal fluctuation on the orientation distribution pattern of globular protein molecules in a two-dimensional lattice was investigated by the method of computer simulation. A set of interaction parameters was assigned to interaction sites on each molecule and the interaction energy between two molecules was given by the product of the parameters of facing sites. Orientation fluctuation was assumed to take place with the probability proportional to the Boltzmann factor. Patterns having different degrees of order appeared with the change of temperature. The entropy and other thermodynamic quantities of these patterns were calculated, and gradual and transitional changes of the pattern were discussed in comparison with the case of simple atoms or molecules.     

The fine structure of the cysticercoid of Hymenolepis diminuta. III. The scolex.

Transmission electron microscopy of the scolex of the 8-day-old Hymenolepis diminuta cysticercoid demonstrates its resemblance to the scolex of the adult. A syncytial tegument composed of external and internal layers is connected by cytoplasmic extensions. Fully developed microtriches are present. Furthermore, a basement membrane, muscle layers, and medullary region containing flame cells, nerve tissue, and other cell bodies are observed. Of particular interest is the presence of discrete sensory endings whose function is discussed.     

Osteomalacia presenting as chorea.

A 16-year-old epileptic developed chorea. He had osteomalacia, hypocalcaemia, and hyperphosphataemia, which were due not to hypoparathyroidism but to vitamin D deficiency--itself secondary to longstanding dietary deficiency and anticonvulsant drug administration.     

Amphiphilicity is essential for mitochondrial presequence function.

We have shown earlier that a mitochondrial presequence peptide can form an amphiphilic helix. However, the importance of amphiphilicity for mitochondrial presequence function became doubtful when an artificial presequence, designed to be non-amphiphilic, proved to be active as a mitochondrial import signal. We now show experimentally that this 'non-amphiphilic' presequence peptide is, in fact, highly amphiphilic as measured by its ability to insert into phospholipid monolayers and to disrupt phospholipid vesicles. This result, and similar tests on three additional artificial presequences (two functionally active and one inactive), revealed that all active presequences were amphiphilic whereas the inactive presequence was non-amphiphilic. One of the active presequence peptides was non-helical in solution and in the presence of detergent micelles. We conclude that amphiphilicity is necessary for mitochondrial presequence function whereas a helical structure may not be essential.     

High water users can be drought tolerant: using physiological traits for green roof plant selection

Background and aims

Green roofs are often installed to reduce urban stormwater runoff. To optimally achieve this, green roof plants need to use water when available, but reduce transpiration when limited to ensure survival. Succulent species commonly planted on green roofs do not achieve this. Water availability on green roofs is analogous to natural shallow-soil habitats including rock outcrops. We aimed to determine whether granite outcrop species could improve green roof performance by evaluating water use strategies under contrasting water availability.

Methods

Physiological and morphological responses of 12 granite outcrop species with different life-forms (monocots, herbs and shrubs) and a common green roof succulent were compared in well watered (WW) and water deficit (WD) treatments.

Key results

Granite outcrop species showed a variety of water-use strategies. Unlike the green roof succulent all of the granite outcrop species showed plasticity in water use. Monocot and herb species showed high water use under WW but also high water status under WD. This was achieved by large reductions in transpiration under WD. Maintenance of water status was also related to high root mass fraction.

Conclusions

By developing a conceptual model using physiological traits we were able to select species suitable for green roofs. The ideal species for green roofs were high water users which were also drought tolerant.     

Comparison of pelagic food webs in lakes along a trophic gradient and with seasonal aspects: influence of resource and predation

Composition and seasonal dynamics of phytoplankton, bacteria,and zooplankton (including heterotrophic flagellates, ciliates,rotifers and crustaceans) were studied in 55 lakes in NorthernGermany with different trophic status, ranging from mesotrophicto hypertrophic. Mean abundance and biomass of all groups increasedsignificantly with trophic level of the lake, but bacteria andmetazooplankton showed only a weak correlation and a slightincrease with chlorophyll concentration. Composition of phytoplanktonshowed a dominance of cyanobacteria in hypertrophic lakes, whereasthe importance of chrysophytes and dinophytes decreased withan increase in trophic status. Protozoans (heterotrophic flagellatesand ciliates) made up 24% (mesotrophic lakes) to 42% (hypertrophiclakes) of total zooplankton biomass on average, and were dominatedby ciliates (62–80% of protozoan biomass). Seasonally,protozoans can build up to 60% of zooplankton biomass in spring,when heterotrophic flagellates can contribute     

DNA indels in coding regions reveal selective constraints on protein evolution in the human lineage

Background  

Insertions and deletions of DNA segments (indels) are together with substitutions the major mutational processes that generate genetic variation. Here we focus on recent DNA insertions and deletions in protein coding regions of the human genome to investigate selective constraints on indels in protein evolution.     

Shade light interaction with salicylic acid in regulating growth of sun (alpine) and shade (prairie) ecotypes of Stellaria longipes

Magnesium (Mg) deficiency in plants is a widespread problem, affecting productivity and quality in agriculture. The mechanism of Mg deficiency inducing antioxidant enzyme activities has not been elucidated in rice. We examined the relationship among abscisic acid (ABA), H₂O₂, and antioxidant enzymes in the leaves of rice seedlings grown under conditions of Mg deficiency. The expression of OsRab16A, an ABA responsive gene, was used to determine the content of ABA. Mg deficiency resulted in increased ABA content in leaves of rice seedlings. The production of H₂O₂ was examined by 3,3-diaminobenzidine staining and a colorimetric method. Mg deficiency also induced H₂O₂ production in leaves, which was blocked by dipehnyleneiodonium chloride (DPI), an NADPH oxidase inhibitor. Tungstate (Tu), an ABA biosynthesis inhibitor, was effective in reducing Mg deficiency-increased ABA content, as well as Mg deficiency-induced H₂O₂ production. Both Tu and DPI were effective in reducing Mg deficiency-induced activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, and catalase in the leaves. Mg deficiency-induced ABA accumulation may trigger increased production of H₂O₂, which may involve plasma-membrane NADPH oxidase, and, in turn, up-regulates the activities of antioxidant enzymes in leaves of rice seedlings.     

Water use by perennial plants in the transition zone between river oasis and desert in NW China

The study aimed at establishing the role of two possible water sources (inundation, ground water) for the water supply to the perennial plant species Alhagi sparsifolia, Calligonum caput-medusae, Populus euphratica and Tamarix ramosissima growing in the transition zone between a river oasis and the open desert at the southern fringe of the Taklamakan desert (Xinjiang province, NW China). The basic hypothesis was that inundations, which normally occur in summer when rivers from a nearby mountain range carry high water, contribute significantly to the plants’ water supply. When, in the first summer, inundations did not occur, four sites, each of which covered by a relatively dense stand of one species, were artificially flooded. Soil and plant water relations as well as meteorological variables were measured during two growing seasons. Water use efficiency of production (WUE_P) was calculated by relating biomass production, which was determined using allometric regressions, to water use.The effects of artificial flooding on the plant water relations were negligible. Water use was relatively high, especially in the A. sparsifolia and the P. euphratica stands and in a dense stand of T. ramosissima (up to approx. 500 kgH₂O m⁻² year⁻¹). Using the total above-ground biomass in the calculation, WUE_P was highest in C. caput-medusae and P. euphratica, and lowest, in A. sparsifolia. From soil and plant water relations, and against the background of the climate and the productivity of the vegetation, it is concluded that all perennial plants in the transition zone between oases and desert in that region must have sufficient access to ground water to ensure long-term survival. Management of ground water such that it remains continuously accessible to the perennial plants is a prerequisite for the conservation and sustainable use of the vegetation in the transition zone.