On the Structure-Bounded Growth Processes in Plant Populations

If growing cells in plants are considered to be composed of increments (ICs) an extended version of the law of mass action can be formulated. It evidences that growth of plants runs optimal if the reaction–entropy term (entropy times the absolute temperature) matches the contact energy of ICs. Since these energies are small, thermal molecular movements facilitate via relaxation the removal of structure disturbances. Stem diameter distributions exhibit extra fluctuations likely to be caused by permanent constraints. Since the signal–response system enables in principle perfect optimization only within finite-sized cell ensembles, plants comprising relatively large cell numbers form a network of size-limited subsystems. The maximal number of these constituents depends both on genetic and environmental factors. Accounting for logistical structure–dynamics interrelations, equations can be formulated to describe the bimodal growth curves of very different plants. The reproduction of the S-bended growth curves verifies that the relaxation modes with a broad structure-controlled distribution freeze successively until finally growth is fully blocked thus bringing about “continuous solidification”.     

A catalogue of <Emphasis Type="Italic">Triticum monococcum</Emphasis> genes encoding toxic and immunogenic peptides for celiac disease patients

The celiac disease (CD) is an inflammatory condition characterized by injury to the lining of the small-intestine on exposure to the gluten of wheat, barley and rye. The involvement of gluten in the CD syndrome has been studied in detail in bread wheat, where a set of “toxic” and “immunogenic” peptides has been defined. For wheat diploid species, information on CD epitopes is poor. In the present paper, we have adopted a genomic approach in order to understand the potential CD danger represented by storage proteins in diploid wheat and sequenced a sufficiently large number of cDNA clones related to storage protein genes of Triticum monococcum. Four bona fide toxic peptides and 13 immunogenic peptides were found. All the classes of storage proteins were shown to contain harmful sequences. The major conclusion is that einkorn has the full potential to induce the CD syndrome, as already evident for polyploid wheats. In addition, a complete overview of the storage protein gene arsenal in T. monococcum is provided, including a full-length HMW x-type sequence and two partial HMW y-type sequences. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The role of visual field position in pattern-discrimination learning.

Invariance of object recognition to translation in the visual field is a fundamental property of human pattern vision. In three experiments we investigated this capability by training subjects to distinguish between random checkerboard stimuli. We show that the improvement of discrimination performance does not transfer across the visual field if learning is restricted to a particular location in the retinal image. Accuracy after retinal translation shows no sign of decay over time and remains at the same level it had at the beginning of the training. It is suggested that in two-dimensional translation invariance-as in three-dimensional rotation invariance-the human visual system is relying on memory-intensive rather than computation-intensive processes. Multiple position- and stimulus-specific learning events may be required before recognition is independent of retinal location.     

The role of GABA in dyskinesias induced by chemical stimulation of the striatum

The gamma aminobutyric acid (GABA) antagonists picrotoxin and bicuculline were injected into the striatum of rats via chronic cannulae. Dyskinesias were produced by these drugs which could be blocked by their injection combined with GABA. The intrastriatal (i.s.) injection of a cholinergic drug, carbachol, also produced dyskinesias which were blocked by GABA. The use of i.s. injection of GABA antagonists to produce an animal model of Huntington's chorea is discussed.     

Genetic relationships among the oral streptococci.

Genetic relationships and species limits among the oral streptococci were determined by an analysis of electrophoretically demonstrable variation in 16 metabolic enzymes. Fifty isolates represented 40 electrophoretic types, among which the mean genetic diversity per locus was 0.857. Mannitol-1-phosphate dehydrogenase was not detected in isolates of the sanguis species complex, and glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were absent in species of the mutans complex. Clustering from a matrix of Gower's coefficient of genetic similarity placed the 40 electrophoretic types in 10 well-defined groups corresponding to the Streptococcus species S. mutans, S. sobrinus, S. cricetus, S. rattus, S. ferus, S. oralis (mitior), two distinct assemblages of S. sanguis strains, and two subdivisions of "S. milleri." The assignments of isolates to these groups were the same as those indicated by DNA hybridization experiments, and the coefficient of correlation between genetic distance estimated by multilocus enzyme electrophoresis and genetic similarity indexed by DNA hybridization was -0.897 (P less than 0.001) for 50 pairwise combinations of isolates. S. ferus, which is widely believed to be a member of the mutans complex, was shown to be phylogenetically closer to species of the sanguis complex.     

Detergent solubilization of the interleukin 1 receptor

Interleukin 1 (IL 1) receptors were solubilized from membranes prepared from murine EL-4 thymoma cells with the zwitterionic detergent 3[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS). Binding of IL 1 to the solubilized receptor was detected by a polyethylene glycol (PEG) precipitation procedure. Concentrations of CHAPS from 4 to 8 mM were effective in solubilizing the IL 1 receptor. At 10 mM CHAPS, there was some loss in binding activity, whereas 2 mM CHAPS was completely ineffective in solubilizing the receptor. Detergent concentrations of 4 mM were routinely used. The solubilized receptor retains the ability to bind 125I-IL 1 in a specific and saturable manner. Scatchard analysis reveals a single type of high affinity binding site having an apparent dissociation constant (KD) of approximately 1.2 X 10(-10) M. Nearly identical KD values are observed for membrane fractions. There are approximately 400 to 500 fmol receptor/mg protein in the detergent extract, corresponding to a two- to threefold enrichment in the Bmax observed for membranes. There is no loss in receptor activity as determined by complete recovery of the total number of binding sites from membranes after solubilization. Binding kinetics show that apparent steady state for the solubilized receptor is reached after 60 min at 37 degrees C. The binding of 125I-IL 1 is essentially irreversible because relatively little bound ligand can be dissociated from the receptor on the addition of excess unlabeled IL 1 at 37 degrees C. Both human IL 1 alpha and IL 1 beta compete for binding of 125I-IL 1 to the soluble receptor, confirming that IL 1 alpha and IL 1 beta bind to the same receptor. Other recombinant proteins, including interferon-alpha A, interferon-gamma, and interleukin 2 have no inhibitory effect.     

Voltage gating in VDAC is markedly inhibited by micromolar quantities of aluminum

Summary The mitochondrial outer membrane contains voltagegated channels called VDAC that are responsible for the flux of metabolic substrates and metal ions across this membrane. The addition of micromolar quantities of aluminum chloride to phospholipid membranes containing VDAC channels greatly inhibits the voltage dependence of the channels' permeability. The channels remain in their high conducting (open) state even at high membrane potentials. An analysis of the change in the voltage-dependence parameters revealed that the steepness of the voltage dependence decreased while the voltage needed to close half the channels increased. The energy difference between the open and closed states in the absence of an applied potential did not change. Therefore, the results are consistent with aluminum neutralizing the voltage sensor of the channel. pH shift experiments showed that positively charged aluminum species in solution were not involved. The active form was identified as being either (or both) the aluminum hydroxide or the tetrahydroxoaluminate form. Both of these could reasonably be expected to neutralize a positively charged voltage sensor. Aluminum had no detectable effect of either single-channel conductance or selectivity, indicating that the sensor is probably not located in the channel proper and is distinct from the selectivity filter.     

Pseudocyphellaria dissimilis: a desiccation-sensitive,highly shade-adapted lichen from New Zealand

Summary Pseudocyphellaria dissimilis, a foliose, cyanobacterial lichen, is shown not to fit into the normal ecological concept of lichens. This species is both extremely shade-tolerant and also more intolerant to drying than aquatic lichens previously thought to be the most desiccation-sensitive of lichens. Samples of P. dissimilis from a humid rain-forest site in New Zealand were transported in a moist state to Germany. Photosynthesis response curves were generated. The effect of desiccation was measured by comparing CO₂ exchange before and after a standard 20-h drying routine. Lichen thalli could be equilibrated at 15° C to relative humidities (RH) from 5% to almost 100%. Photosynthesis was saturated at a photosynthetically active radiation (PAR) level of 20 mol m^-2 s^-1 (350 bar CO₂) and PAR compensation was a very low 1 mol m^-2 s^-1. Photosynthesis did not saturate until 1500 bar CO₂. Net photosynthesis was relatively unaffected by temperature between 10° C and 30° C with upper compensation at over 40° C. Temporary depression of photosynthesis occurred after a drying period of 20 h with equilibration at 45–65% relative humidity (RH). Sustained damage occurred at 15–25% RH and many samples died after equilibration at 5–16% RH. Microclimate studies of the lichen habitat below the evergreen, broadleaf forest canopy revealed consistently low PAR (normally below 10–20 mol m^-2 s^-1) and high humidities (over 80% RH even during the day time). The species shows many features of an extremely deep shade-adapted plant including low PAR saturation and compensation, low photosynthetic and respiratory rates and low dry weight per unit area.     

Lateral interactions among phosphatidylcholine and phosphatidylethanolamine head groups in phospholipid monolayers and bilayers

We develop theory for the lateral interactions among the zwitterionic head groups of phospholipids in monolayers and bilayers, particularly phosphatidylcholine (PC) and phosphatidylethanolamine (PE). With the P- end of the head group anchored at the water/hydrocarbon interface, a balance of two effects dictates the angle that the P--N+ dipole makes with respect to the plane of the bilayer: N+ is driven toward water due to the (Born) electrostatic free energy, but the hydrophobic effect drives the methyl and methylene groups around the N+ charge toward the hydrocarbon. The only adjustable parameter of the model is the average fluctuation of the oil/water interface or, alternatively, the dielectric constant of the hydrocarbon phase. The model predicts that at 5 degrees C the head group dipole should lie largely in the bilayer plane, in accord with X-ray, neutron diffraction, and NMR studies. The theory makes the novel prediction that the N+ end of the dipole becomes increasingly submerged in hydrocarbon with increasing temperature, leading to strongly enhanced lateral repulsion between PC head groups. This prediction is in good agreement with second and third viral coefficients of monolayer lateral pressures, and with the temperature dependence of the former. The theoretical model is consistent with head group fluctuations measured by neutron diffraction of PC and PE bilayers. Because PE has a smaller hydrophobic cluster near N+, its lateral repulsion should be much smaller and less temperature dependent than for PC, also in agreement with equation-of-state measurements. This suggests why at high density PE monolayers have higher melting temperatures than PC monolayers and more propensity for reversed curvature.     

31P nuclear magnetic resonance study of enzymatically phosphorylated glycophorin A

Glycophorin A was phosphorylated using protein kinases and the new protein was investigated using³¹P NMR spectroscopy. Most of these ～30 moles of phosphate were found to be attached to Ser and Thr. Some of these phosphate residues appear to be affected by the carbohydrate residues present. The phosphorylated protein appears to be in a severe state of aggregation, with the degree of aggregationpH-dependent.