Centres of diversity quantified—A maximum variance approach to a biogeographic problem

Summary A quantitative method that optimizes the mapping of species diversity in phytogeographic studies is described. Diversity is computed on the basis of species number per unit area. The optimal size of unit area for which diversity is computed is held to be that which maximises the diversity difference between species-rich and species-poor regions. An example is given using Turkish Papaver. A very high correspondence is found between intuitive insights based on long study and the computer-generated diversity maps. Phytogeographic elements were also determined by computer after gridding Turkey at the scale discovered to be optimal for diversity and scoring the grid squares for presence-absence of each species. In this case, too, quite high correspondence was found between the computer and intuitive results.Nomenclature follows Cullen (1965).The authors express their thanks to Mr. K. Roberts, University of Western Ontario Computing Centre of writing the original maximum variance program and to the National Research Council of Canada for supporting the computing side of the project.     

Subsarcolemmal mitochondria and capillarization of soleus muscle fibers in young rats subjected to an endurance training

Summary Rats, 6 weeks old, were subjected to a program of endurance running for 3, 6 and 12 weeks. 0.5 to 0.8 m thick sections of Epon embedded soleus muscles were studied with morphometric methods.In cross-sections the area occupied by subsarcolemmal mitochondria was independent of the age, but was 53% higher after 12 weeks of training. The mean depth of the zones with subsarcolemmal mitochondria increased only 15% to about 0.9 m. Thus, the subsarcolemmal mitochondria showed a pronounced spreading at the muscle fiber surface in trained muscles. — The number of capillaries per fiber decreased slightly in controls and increased not significantly in trained muscles.It is concluded that the subsarcolemmal mitochondria supply the energy for the active transport of metabolites through the sarcolemma in oxidative muscle fibers, and that they are the limiting factor for endurance performance of the soleus muscle fibers because the changes in the capillarization were only small. It is suggested that the subsarcolemmal and the interfibrillar mitochondria have different functions and may therefore represent different types of mitochondria which can be distinguished by their morphology as well as by their biochemical properties.     

Studies on metabolic role of 5′-methylthioadenosine in Ochromonas malhamensis and other microorganisms

Several compounds containing a thiomethyl group were found to replace vitamin B₁₂ in a protozoan, Ochromonas malhamensis. The order of the effectiveness was as follows: 5-methylthioadenosine > S-adenosylmethionine > 5-methylthioribose > L-methionine. A similar order was obtained with respect to the permeability of these compounds into the protozoan cells, except for S-adenosylmethionine. 5-Methylthioadenosine and 5-methylthioribose as well as l-methionine markedly increased the intracellular content of l-methionine. The level of S-adenosylmethionine was also increased by them, but to a lesser degree. The thiomethyl group of the compounds was established to be incorporated into S-adenosylmethionine. The metabolic fate of the thiomethyl group of 5-methylthioadenosine cannot be distinguished from that of l-methionine. A high activity of 5-methylthioadenosine nucleosidase was detected in the cell-free extracts of the protozoan. These results strongly suggest that 5-methylthioadenosine would be metabolized to l-methionine via 5-methylthioribose and then the l-methionine would be converted to S-adenosylmethionine. Like l-methionine and vitamin B₁₂, 5-methylthioadenosine and 5-methylthioribose may play an important role in maintenance of the C-1 pool in Ochromonas malhamensis.Neither 5-methylthioadenosine nor 5-methylthioribose replaced vitamin B₁₂ in some vitamin B₁₂-requiring bacteria. This result is consistent with the fact that neither compounds was significantly taken up by these bacteria.Abbreviations MTA 5-methylthioadenosine - AdoMet S-adenosylmethionine - MTR 5-methylthioribose - TCA trichloroacetic acid Paper II in the series. The first paper of the series has been published (Sugimoto and Fukui, 1974)     

Effect of the pH of culture medium on the alkalophilicity of a species of Bacillus

The amino acid incorporation and -aminoisobutyric acid (AIB) uptake of an alkalophilic Bacillus grown at pH 8.2 (the pH 8-bacteria) were much less pH dependent (less alkalophilic) than those of the organisms grown at pH 10.0 (the pH 10-bacteria), respectively. The rate of AIB uptake of the pH 10-bacteria was almost the same as that of the pH 8-bacteria, while the rate of amino acid incorporation of the pH 10-bacteria was higher than that of the pH 8-bacteria in alkaline environments. The colloidal titration with clupein showed that the amount of negative charge on the pH 10-bacteria was greater than that of the pH 8-bacteria in alkaline environments. Considerable difference in protein composition was observed between the membranes of the pH 8-and 10-bacteria, while no difference was observed in phospholipid composition.Abbreviations AIB Amino-isobutyric acid     

The relationship between the ionic composition of the environment and the secretory activity of the endocrine cell types of stannius corpuscles in the teleost Gasterosteus aculeatus

Summary The corpuscles of Stannius of threespined sticklebacks contain two glandular cell types of presumed endocrine nature. To elucidate the function of both cell types the secretory activity of the cells was studied in fully adapted seawater and freshwater fishes and in specimens transferred from sea water to fresh water or adapted to media of various ionic composition. The secretory activity was established, in tissue sections and freeze-etch replicas, by estimating the volume of the nuclei, the density of the nuclear pores, and the frequency of exocytotic phenomena.The type-1 cells, ultrastructurally comparable to the predominant or only cell type described in many other teleosts, are more active in sea water than in fresh water. The activity of the type-2 cells, whose ultrastructural appearance is known only for salmonids and eels, is higher in fresh water. Transfer of seawater fishes to fresh water results in reduction of type-1 cells and activation of type-2 cells. The factors responsible for these changes were analyzed by exposure of fishes to solutions of various salts in fresh water and to artificial sea water with a reduced content of one of its components. The high activity of type-1 cells in sea water proved to be related to the high calcium content of this medium. These cells probably produce a substance comparable to hypocalcin, the endocrine factor isolated from the Stannius corpuscles of some other teleost species. The high activity of type-2 cells in fresh water appeared to be connected with the low sodium and potassium levels of this medium. Type-2 cells possibly produce a hitherto unknown hormone involved in the control of sodium and/or potassium metabolism.The technical assistance of Miss C. Mein and Mr. J. Zagers is gratefully acknowledged     

Regulation of amino acid transport in growing cells of Streptomyces hydrogenans

The uptake of various amino acids into Streptomyces hydrogenans grown in chemostatically and turbidostatically controlled steady state cultures has been investigated. A close correlation between transport capacity and the growth rates of the cells was found. As shown by kinetic analysis, the increased transport is due to elevated maximum uptake rates, the apparent Michaelis constants remaining unchanged. Analysis of the unidirectional fluxes of cycloleucine revealed that not only the influx is raised as the growth rate is increased but also the efflux. Hence, the conclusion is drawn that the growth-rate dependent modulation of transport capacity is, at least, partially due to the variation of the concentration of active transport components. Since the cells were grown in the absence of external amino acids the results suggest that amino acid transport into S. hydrogenans is under the control of endogenous effectors.List of Abbreviations AIB 2-aminoisobutyric acid - Cycloleucine 1-aminocyclopentane-1-carboxylic acid     

Structure and composition of intracytoplasmic membranes of Ectothiorhodospira mobilis

The lamellar membrane stacks of Ectothiorhodospira mobilis were isolated and purified by a combination of lysozyme and osmotic shock treatment, followed by differential and density gradient centrifugation. Preparations of lamellar membranes were enriched at least 2.4-fold in the ratio of bacteriochlorophyll a to protein.Thin-sectioning, negative staining, platinumcarbon shadowing and freeze-etching were used to study the architecture of the membrane units. Both platinum-carbon shadowing and freeze-etching showed the outer surfaces of the isolated lamellar membrane stacks to be relatively smooth. Particles averaging 7 nm in diameter were seen on several faces following freeze-ctching.Non-polar amino acids amounted to 60% of the total amino acid composition. Lipids constituted 32% of the membrane dry weight. Phosphatidyl ethanolamine and diphosphatidyl glycerol were the major phospholipids. Fatty acids of 10–15 carbons represented a small fraction of both membrane and whole cell fatty acids. Monoenes constituted 36% of the total membrane fatty acids and 38.4% of the total whole cell fatty acids. The major fatty acids of both whole cells and purified membranes were C16:0, C18:1 and cyclopropane C19:0.