Consideration on the effects of pollution at community and population level

Summary The effects of pollution at population level are considered in relation to demographic characteristics and overall to the birthrate. The direct and indirect effects of pollution on community structure is discussed. The influence of pollution may vary according to the food-chain structure; (as a consequence, the hazard ceteris paribus will be greater in freshwater communities than in marine ones). Relations between diversity and stability are discussed. In addition, the advantages and difficulties in using diversity and biotic indices for monitoring polluted water are taken into account.     

Effect of air pollution on the leaf epidermis at the submicroscopic level

Summary Analysis of scanning electron micrographs of the leaf epidermis of 7 flowering plants shows that air pollution reduces the size of the stomatal pore and increases the trichome length on both surfaces of the leaf. Air pollution also increases trichome density and folding on subsidiary cells at the adaxial leaf surface.     

Presence in and effects of pineal indoleamines at very low level of phylogeny

The unicellular organism Tetrahymena contains serotonin and is able to take up the hormone from its mileiu. The serotonin content of the cell changes as a function of the presence of foreign exogenous hormones. This indicates a possible role of serotonin as a chemical mediator. Exogenous serotonin stimulates the RNA synthesis of Tetrahymena, and it was the only one among the hormones studied which kept the RNA level durably high. Serotonin stimulates phagocytosis and growth of Tetrahymena, and its precursors also stimulate growth. Serotonin can imprint Tetrahymena, and as a consequence of this the effect of the hormone increases in the case of further encounters. Treatment with serotonin-related molecules soon after imprinting can reduce the effect of imprinting. Melatonin can contract the pigment cells of Planaria; however, its precursors serotonin and tryptamine can do this more intensely. Both melatonin and serotonin can influenc the regeneration of Planaria, with effects which differ when different phenomena are studied. Evolutionary theories are discussed.     

Kuhn vs. Popper on criticism and dogmatism in science: a resolution at the group level

Popper repeatedly emphasised the significance of a critical attitude, and a related critical method, for scientists. Kuhn, however, thought that unquestioning adherence to the theories of the day is proper; at least for ‘normal scientists’. In short, the former thought that dominant theories should be attacked, whereas the latter thought that they should be developed and defended (for the vast majority of the time).Both seem to have missed a trick, however, due to their apparent insistence that each individual scientist should fulfil similar functions (at any given point in time). The trick is to consider science at the group level; and doing so shows how puzzle solving and ‘offensive’ critical activity can simultaneously have a legitimate place in science. This analysis shifts the focus of the debate. The crucial question becomes ‘How should the balance between functions be struck?’     

Chromosomal organization at the level of gene complexes

Metazoan genomes primarily consist of non-coding DNA in comparison to coding regions. Non-coding fraction of the genome contains cis-regulatory elements, which ensure that the genetic code is read properly at the right time and space during development. Regulatory elements and their target genes define functional landscapes within the genome, and some developmentally important genes evolve by keeping the genes involved in specification of common organs/tissues in clusters and are termed gene complex. The clustering of genes involved in a common function may help in robust spatio-temporal gene expression. Gene complexes are often found to be evolutionarily conserved, and the classic example is the hox complex. The evolutionary constraints seen among gene complexes provide an ideal model system to understand cis and trans-regulation of gene function. This review will discuss the various characteristics of gene regulatory modules found within gene complexes and how they can be characterized.     

Cardiac calcium currents at the level of single channels

Properties of cardiac Ca channels have come into sharper focus with the advent of single cell preparations and suction pipette recording methods. We briefly summarize our present picture of the gating and permeation properties of the conventional, dihydropyridine-sensitive type of Ca channel (L-type). Distinctive features of a second type of voltage-gated Ca channel (T-type) are discussed.     

A comparison of pyridoxal 5'-phosphate dependent decarboxylase and transaminase enzymes at a molecular level.

Pyridoxal 5'-phosphate is a coenzyme for a number of enzymes which catalyse reactions at C alpha of amino acid substrates including transaminases, decarboxylases and serine hydroxymethyltransferase. Using the X-ray coordinates for a transaminase, aspartate aminotransferase, and the results of stereochemical and mechanistic studies for decarboxylases and serine hydroxymethyltransferase, an active-site structure for the decarboxylase group is constructed. The structure of the active-site is further refined through active-site pyridoxyllysine peptide sequence comparison and a 3-D catalytic mechanism for the L-alpha-amino acid decarboxylases is proposed. The chemistry of serine hydroxymethyltransferase is re-examined in the light of the proposed decarboxylase mechanism.     

On the mechanism of radiosensitization by iodine compounds at the molecular level

Riassunto L'alcool deidrogenasi del lievito irradiata con raggi X in soluzioni contenenti ioduro di sodio, acido 3-iodopropionico o ioduro di metile, è inattivata con un rendimento più elevato che in assenza di tali sostanze. L'effetto sensibilizzante dello ioduro di sodio e dell'acido iodopropionico è proporzionale alla loro concentrazione nell'ambito di 0–16 molecole di essi per molecola di enzima. L'alcool deidrogenasi irradiata in presenza di ioduro di sodio marcato con I¹³¹ non rivela la presenza di iodio legato alla sua molecola.     

Analysis of nucleic acid derivatives at the subnanomolar level. II. Quantitative analysis of ribose derivatives by tritium labeling

Zusammenfassung Es wird eine Methode zur quantitativen Analyse von Ribosederivaten beschrieben, welche etwa fünftausendmal empfindlicher ist als die spektrophotometrischen Standardverfahren.

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This work was supported by grants-in-aid from the U.S. Atomic Energy Commission (No. AT(30-1)2643), the U.S. Public Health Service (No. CA 05018), and the American Cancer Society (No. E-51-J). This is publication No. 1325 of the Cancer Commission of Harvard University.

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The first paper of this series³ described a procedure for detecting subnanomolar quantities of mono- and oligonucleotides on PEI-cellulose thin layers.     

Herbicidal pollution. Pollen damage by the herbicide vapours

Zusammenfassung Herbiziddämpfe reduzieren die Pollenfertilität vonSolanum melongena Willd.     

Protein level in the haemolymph of the waspPolistes gallicus L. at the beginning of imaginal life and during overwintering. Action of the strepsiterian parasiteXenos vesparum rossi

Summary During the imaginal life of malePolistes wasps, the protein concentration in the haemolymph remained constant. In females, there were 2 groups; one in which this concentration was also stable and another in which it increased. No difference was detected between the haemolymphatic protein level of stylopized males and normal ones. All parasitized females exhibited low haemolymph protein levels similar to those of the low level group.