N-terminal sequences of oat avenins compared to other cereal prolamins

Like the alcohol-soluble seed storage proteins (also called prolamins) of other cereals, avenins, the oat prolamins, are a series of polymorphic molecules belonging to a multigenic family stored within the protein bodies of the starchy endosperm. Nevertheless, they exhibit some pecularities: among the seed storage proteins, their proportion is low compared to prolamins from other cereal species; their net charge is higher; the amount of Gln + Pro only reaches 49 mol%; they are less polymorphic. We have isolated and purified several avenins and sequenced their N-terminal end. The microheterogeneity and the pecularity of avenins are revealed by the comparison of the N-terminal sequences. Like other prolamins, they exhibit tandem repeats; these repetitive peptides are slightly different from those of other prolamins of the Festucoideae, and the repetition begins earlier in the sequence. As for prolamins from other species, their predicted secondary structure reveals successive beta-turns which might be arranged in a pseudo-helix structure.     

Immunohistochemical localization of gamma-aminobutyric acid (GABA) in the rat pancreas

The localization of gamma-aminobutyric acid (GABA) in rat pancreas was investigated using antiserum raised against GABA conjugated to bovine serum albumin with glutaraldehyde. Immunoreactive cells were only found in the center of the pancreatic islets, and these cells were surrounded by nonimmunoreactive cells. When two serial sections of rat pancreas were consecutively stained with GABA antiserum and with antibodies against insulin, both antisera stained the same population of endocrine cells within the islets. In rats pretreated with streptozotocin, a B-cell toxin, we observed a marked decrease in the number of cells exhibiting GABA-like immunoreactivity. These observations indicate that GABA is present in the B cells of rat pancreatic islets.     

Common misinterpretations of the “linear,no-threshold” relationship used in radiation protection

Summary Absorbed doseD is shown to be a composite variable, the product of the fraction of cells hit (I _H ) and the mean dose (hit size)z to those cells.D is suitable for use with high level exposure (HLE) to radiation and its resulting acute organ effects because, sinceI _H = 1.0, it approximates closely enough the mean energy density in the cell as well as in the organ. However, with low level exposure (LLE) to radiation and its consequent probability of cancer induction from a single cell, stochastic delivery of energy to cells results in a wide distribution of hit sizesz, and the expected mean value,z, is constant with exposure. Thus, with LLE, onlyI _H varies withD so that the apparent proportionality between dose and the fraction of cells transformed is misleading. This proportionality therefore does not mean that any (cell) dose, no matter how small, can be lethal. Rather, it means that, in the exposure of a population of individual organisms consisting of the constituent relevant cells, there is a small probability of particle-cell interactions which transfer energy. The probability of a cell transforming and initiating a cancer can only be greater than zero if the hit size (dose) to the cell is large enough. Otherwise stated, if the dose is defined at the proper level of biological organization, namely, the cell and not the organ, only a large dosez to that cell is effective.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday     

Glycerol production in relation to the ATP pool and heat production rate of the yeasts Debaryomyces hansenii and Saccharomyces cerevisiae during salt stress

Changes in glycerol production and two parameters related to energy metabolism i. e. the heat production rate and the ATP pool, were assayed during growth of Saccharomyces cerevisiae and Debaryomyces hansenii in 4 mM and 1.35 M NaCl media. For both of the yeasts, the specific ATP pool changed during the growth cycle and reached maximum values around 10 nmol per mg dry weight in both types of media. The levels of glycerol were markedly enhanced by high salinity. In the presence of 1.35 M NaCl, D. hansenii retained most of its glycerol produced intracellularly, while S. cerevisiae extruded most of the glycerol to the environment. The intracellular glycerol level of S. cerevisiae equalled or exceeded that of D. hansenii, however, with values never lower than 3 mol per mg dry weight at all phases of growth. When D. hansenii was grown at this high salinity the intracellular level of glycerol was found to correlate with the specific heat production rate. No such correlation was found for S. cerevisiae. We concluded that during salt stress, D. hansenii possesses the capacity to regulate the metabolism of glycerol to optimize growth, while S. cerevisiae may not be able to regulate when exposed to different demands on the glycerol metabolism.     

Expression of a beta thalassemia gene with abnormal splicing.

Expression of a cloned human beta thalassemia gene with a single base change at position 5 of IVS 1 has been analyzed 48 hours after transfer of the gene into HeLa cells (transient expression). Little or no normal beta globin mRNA accumulates in the presence of the abnormal beta gene in contrast to significantly more normal beta mRNA produced with other mutations at this same position. By contrast, large amounts of an abnormal beta globin mRNA are present; this is due to the use of a cryptic 5' splice site in exon 1 rather than the normal 5' splice site of IVS 1. The results indicate the variability of the effect on RNA splicing of different single base defects within IVS.     

Silica and Ash in Native Plants of the Central and Southeastern Regions of the United States

Ash and silica contents and depositional patterns were determinedfor different tissues of 11 plants growing in the southeasternand central parts of the USA. Silica content was high in theleaves, sheaths and inflorescences of the grasses studied, especiallyso in the inflorescence of the C₃ grass, Stipa comata Trise.and Rupr. The ash content was especially high in leaves of Polymniauvedalia L., which are also high in calcium. Calcium depositionwas largely in trichomes and in veins of the leaf. Energy-dispersiveX-ray analysis showed that the distribution of the element siliconis closely related to certain epidermal structures such as ridges,cell walls, rows of irregularly-shaped structures lying lenghthwisealong the leaf, dumb-bell shaped structures and trichomes. Thesestructures also correspond to the phytoliths left behind afterdecay of the plant. The C₃ grasses differed from the C₄ in thatthey showed oval structures and produced correspondingly ovalphytoliths. Silicified trichomes (particularly in the C₃ grasses)and long, narrow, silica fibres were common in the inflorescencesof the grasses studied. These sharp particles could be irritatingto oesophageal and other tissues. Similar fibres in other grasseshave been implicated in certain cancers. High silicificationof the inflorescence structures might afford protection forthe seed, as reported for other grasses. C₃ and C₄ grasses, silica and ash content, scanning electron microscopy, energy-dispersive X-ray analysis, silicon distribution, spectra of elements in plants, trichomes, silica fibres, phytoliths