Polymorphism at the Hor 1 locus of barley (Hordeum vulgare L.)

The Hor 1 locus of barley encodes a group of seed storage polypeptides called C hordein. Two-dimensional electrophoretic analysis of C-hordein fractions from six cultivars with different alleles at the Hor 1 locus showed extensive polymorphism. A total of 34 major polypeptides was mapped, with between 4 and 18 present in each cultivar. There was less variation among the same cultivars in the numbers (6 to 10) of restriction fragments of genomic DNA which hybridized to a cDNA clone related to C hordein. The total number of restriction fragments was also lower (22), and most pairs of cultivars had more restriction fragments than polypeptides in common. A total number of about 20–30 C-hordein genes per haploid genome was estimated. The results indicate that cultivars differ mainly in the extent of gene and polypeptide divergence, rather than in the degree of gene reiteration. They are consistent with the proposed origin of the multiple structural genes at the Hor 1 locus by the duplication and divergence of a single ancestral gene.NACB was supported by a grant from the Home Grown Cereals Authority.     

A portable silicon photodiode luminometer

A simple, inexpensive, battery-powered, portable luminometer which is based on a silicon photodiode is described. The instrument is intended to measure the light produced by chemiluminescent and bioluminescent reactions. The devic shows a good detection limit and, in a bioluminescent reaction for adenosine 5′-triphosphate (ATP), detected 0.5 pmol in 1ml of aqueous solution. The instrument measures irradiance from 10^?13 to 10?¹¹ W cm^?2 at the sensor, within the range 300 to 900nm.     

Photosynthetic characteristics of leaves developed at different irradiances and temperatures: an extension of the current hypothesis

Photosynthetic characteristics at high measurement irradiance were analyzed for single leaves of two C₃ and one C₄ species grown under twenty one combinations of irradiance level, irradiance duration, and air temperature in order to test the idea that photosynthetic characteristies developed by leaves in different environments are controlled by the daily amount of photosynthesis. Photosynthetic rates per unit area and mesophyll conductances at 25°C and air levels of CO₂ and O₂, and parameters for two photosynthesis models were used to characterize the photosynthetic properties of the leaves. Leaves with highest values of the photosynthetic parameters for each species were often developed in environments with irradiance levels below saturation for photosynthesis, and with only 12 hours of irradiance per day. Lower air temperature during growth increased the photosynthetic characteristics for a given irradiance regime. Photosynthetic characteristics had higher correlation coefficients with daily photosynthesis of mature leaves divided by 24-hour leaf elongation rates of young leaves, than with daily photosynthesis alone, indicating that photosynthetic characteristics may be related to a balance between photosynthesis and leaf expansion.     

ITE Merlewood Land Classification of Great Britain

Abstract. The Institute of Terrestrial Ecology (ITE) has classified the 1 km squares in Great Britain (GB) into thirty-two environmental strata, termed land classes, as a basis for ecological survey. The classes have been used in biogeographical studies of the distribution of individual species and species assemblages. The concept behind the technique is that there is an association between the environmental character of land and ecological parameters. The initial classification was based on a sample of squares drawn from a regular grid. The data for the 12121 km squares classified were drawn from published maps; the number of squares was limited by the available computing power. Subsequently the availability of more powerful computers and the need to improve geographical definition have led to the allocation of every 1 km square to its appropriate class. This paper has been written to summarise the principles involved in the development of the system and indicate the range of projects for which it has been used. The extension of the classification from a sample to the complete coverage of GB revealed the importance of the structure and style of data used to produce the classification. The significance of these conclusions for future work is discussed, with particular reference to automated methods of data capture.     

Light, temperature and nutrients as factors in photosynthetic adjustment to an elevated concentration of carbon dioxide

The short-term stimulation of the net rate of carbon dioxide exchange of leaves by elevated concentrations of CO₂ usually observed in C₃ plants sometimes does not persist. Experiments were conducted to test whether the patterns of response to the environment during growth were consistent with the hypotheses that photosynthetic adjustment to elevated CO₂ concentration is due to (1) feedback inhibition or (2) nutrient stress. Soybean [Glycine max (L.) Merr. cv. Williams] and sugar beet (Best vulgaris L. cv. Mono Hye-4) were grown from seed at 350 and 700 μl^? CO₂, at 20 and 25°C, at a photon flux density of 0.5 and 1.0 mmol m^?2 S^?1 and with three nutrient regimes until the third trifoliolate leaf of soybean or the sixth leaf of sugar beet had finished expanding. Net rates of CO₂ exchange of the most recently expanded leaves were then measured at both 350 and 700 μl 1^?1 CO₂. Plants grown at the elevated CO₂ concentration had net rates of leaf CO₂ exchange which were reduced by 33% in sugar beet and 23% in soybean when measured at 350 μl 1^?1 CO₂ and when averaged over all treatments. Negative photosynthetic adjustment to elevated CO₂ concentration was not greater at 20 than at 25°C, was not greater at a photon flux density of 1.0 than at 0.5 mmol m^?2 S^?1 and was not greater with limiting nutrients. Furthermore, in soybean, negative photosynthetic adjustment could be induced by a single night at elevated CO₂ concentration, with net rates of CO₂ exchange the next day equal to those of leaves of plants grown from seed at the elevated concentration of CO₂. These patterns do not support either the feedback-inhibition or the nutrient-stress hypothesis of photosynthetic adjustment to elevated concentrations of CO₂.     

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

The interactions between nucleic acids and polyamines. III. Microscopic protonation constants of spermidine

Changes in the NMR chemical shifts of protons adjacent to the nitrogen atoms of Spermidine which are undergoing protonation have been measured by two-dimensional heteronuclear coupled NMR. Data thus obtained measure the dependence of the state of protonation of individual nitrogens on the pH, and permit calculation of the microprotonation constants of Spermidine and the concentrations of all of the variously protonated Spermidine species present at any pH.     

The effect of sugars on (pro)insulin biosynthesis

Rates of incorporation of [4,5-(3)H]leucine into insulin plus proinsulin, designated ;(pro)insulin', and total protein in rat pancreatic islets were measured. Glucose stimulates rates of total protein and (pro)insulin biosynthesis, but (pro)insulin biosynthesis is stimulated preferentially. Mannose and N-acetylglucosamine also stimulate (pro)insulin and total protein biosynthesis; inosine and dihydroxyacetone stimulate (pro)insulin biosynthesis specifically. Fructose does not stimulate (pro)insulin biosynthesis when tested alone, but does so in the presence of low concentrations of glucose, mannose or N-acetylglucosamine. Many glucose analogues do not stimulate (pro)insulin biosynthesis. Mannoheptulose inhibits synthesis of (pro)insulin and total protein stimulated by glucose or mannose but not by dihydroxyacetone, inosine or N-acetylglucosamine; phloretin (9mum) inhibits N-acetylglucosamine-stimulated (pro)insulin biosynthesis preferentially. The data are in agreement with the view that the same glucose-sensor mechanism may control both insulin release and biosynthesis, and ;substrate-site' model is suggested. The threshold for stimulation of biosynthesis of (pro)insulin and total protein is lower than that found for glucose-stimulated insulin release; moreover the biosynthetic response to an elevation of glucose concentration is slower than that found for insulin release. The physiological implication of these findings is discussed. Caffeine and isobutylmethylxanthine, at concentrations known to increase islet 3':5'-cyclic AMP and potentiate glucose-induced insulin release, were without effect on rates of glucose-stimulated (pro)insulin biosynthesis.     

Control of cell volume in the J774 macrophage by microtubule disassembly and cyclic AMP

We have explored the possibilities that cell volume is regulated by the status of microtubule assembly and cyclic AMP metabolism and may be coordinated with shape change. Treatment of J774.2 mouse macrophages with colchicine caused rapid microtubule disassembly and was associated with a striking increase (from 15-20 to more than 90 percent) in the proportion of cells with a large protuberance at one pole. This provided a simple experimental system in which shape changes occurred in virtually an entire cell population in suspension. Parallel changes in cell volume could then be quantified by isotope dilution techniques. We found that the shape change caused by colchicine was accompanied by a decrease in cell volume of approximately 20 percent. Nocodozole, but not lumicolchicine, caused identical changes in both cell shape and cell volume. The volume loss was not due to cell lysis nor to inhibition of pinocytosis. The mechanism of volume loss was also examined. Colchicine induced a small but reproducible increase in activity of the ouabain-sensitive Na(+), K(+)-dependent ATPase. However, inhibition of this enzyme/transport system by ouabain did not change cell volume nor did it block the colchicines-induced decrease in volume. One the other hand, SITS (4’acetamido, 4-isothiocyano 2,2’ disulfonic acid stilbene), an inhibitor of anion transport, inhibited the effects of colchicines, thus suggesting a role for an anion transport system in cell volume regulation. Because colchicine is known to activate adenylate cyclase in several systems and because cell shape changes are often induced by hormones that elevate cyclic AMP, we also examined the effects of cyclic AMP on cell volume. Agents that act to increase syclic AMP (cholera toxin, which activates adenylate cyclase; IBMX, and inhibitor of phosphodiesterase; and dibutyryl cyclic AMP) all caused a volume decrease comparable to that of colchicine. To define the effective metabolic pathway, we studied two mutants of J774.2, one deficient in adenylate cyclase and the other exhibiting markedly reduced activity of cyclic AMP-dependent protein kinase. Cholera toxin did not produce a volume change in either mutant. Cyclic AMP produced a decrease in the cyclase-deficient line comparable to that in wild type, but did not cause a volume change in the kinase- deficient line. This analysis established separate roles for cyclic AMP and colchicine. The volume decrease induced by cyclic AMP requires the action of a cyclic AMP-dependent protein kinase. Colchicine, on the other hand, induced a comparable volume change in both mutants and wild type, and thus does not require the kinase.