Organic matter and nutrient cycling within an endemic birch stand in the Etna massif (Sicily):Betula aetnensis Rafin

At altitudes between 1300 m to 2100 m in the Etna massif (Sicily), an endemic species of theBetula genus,Betula aetnensis Rafin, grows in a well-defined microclimatical context. Aboveground biomass and nutrient content studies within one stand revealed no significant differences from the otherBetula species, normally found in colder more temperate climate regions.Throughout the studied sites, biomass production, nutrient cycling and various structural or physiological characteristics (leaf area index) varied very little.Other researches indicate that the originality ofBetula aetnensis lies more in the histological or anatomical characteristics of its water conducting system which enables the species to adapt to Mediterranean-climate summer droughts in the Etna massif.

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Riassunto Sull'Etna, tra 1300 e 2100 m d'altitudine, in una zona microclimaticamente ben definita del versante nordorientale, si rinviene laBetula aetnensis Rafin.Dallo studio della fitomassa e della mineralomassa aerea del bosco di Monte Baracca, è emerso che non vi sono differenze notevoli con le altre specie indagate del genereBetula, più caratteristiche dei climi temperati e freddi.La produzione di biomassa, cosi come la gestione degli elementi nutritivi, è molto simile ai diversi popolamenti già indagati, cosi come certe caratteistiche strutturali e fisiologiche (leaf area index).L'originalità dellaBetula aetnensis è da ricercarsi nel vantaggio che ne ricava, a livello endogeno, sfruttando le caratteristiche istologiche ed anatomiche del suo apparato conduttore, che le consentono un efficace ed eccellente adattamento alle condizioni di siccità estive particolari del clima mediterraneo del vulcano.

     

Oxyprenylated secondary metabolites: a survey of their innovative extraction methodologies

Phytochemistry Reviews - Oxyprenylated secondary metabolites of plant, fungal, and microbial origin have emerged as biologically active natural compounds with a great potential for the next future....     

Circadian Rhythm of Cardiac Output, Peripheral Vascular Resistance, and Related Variables by a Beat-to-Beat Monitoring

This study aimed to explore the 24-h patterns of stroke volume, cardiac output, and peripheral vascular resistance along with other correlated variables, such as left ventricular ejection time, ejection velocity index, thoracic fluid index, heart rate, and blood pressure. The study was performed on 12 clinically healthy subjects by means of a noninvasive beat-to-beat monitoring using the thoracic electric bioimpedance technique associated with the automated sphygmomano-metric recording. Time data series were analyzed by means of chronobiological procedures. The results documented the occurrence of a circadian rhythm for all the variables investigated, giving relevance to the beat-to-beat bioperiodicity of cardiac output and peripheral vascular resistance. Temporal quantification of the investigated variables may be useful for a better insight of the chronophysiology of the cardiovascular apparatus.     

Submicroscopic structure of the membranous labyrinth

Summary Investigations were performed by light and electron microscope on the basilar membrane, limbus spiralis and spiral ligament.These different parts continue one into the other and make up a single morphological and functional structure which may be called the supporting structure of Corti's organ (s.s.C.o.).It is formed by a tissue the components of which are the cells and an intercellular substance in which are arranged the capillary vessels.The cells can be classed in two groups, the first consisting of the cells proper (basilar membrane, limbus spiralis and spiral ligament cells) which present structural changes parallel with the growth mechanism of the intercellular substance; the second of the cochlear duct covering cells (Corti's organ cells, inner and outer spiral sulcus cells, interdental cells, stria vascularis cells).The intercellular substance is organised in laminae, fibrolaminae, bundles and microscopic fibers composed of filaments with an intervening ground substance.The filaments have a diameter ranging from 85 to 105 Å. Topochemical tests with polarised light microscope, enzymatic tests, diffractographic and chemical analyses suggest that these filaments unquestionably consist of protein material which have nothing to do with collagen or elastic fibers. Perhaps it may be classed in the K.E.M.F. group.The ground substance generally appear anhistous and transparent but in some parts of the basilar membrane it presents a cottony appearance.The possible different hypotheses about the classification of the s.s.C.o. tissue are discussed.The quantity and architecture of the cells and the intercellular substance vary appreciably in the basilar membrane, limbus spiralis and spiral ligament, which are examined in detail one by one.The demonstration that the s.s.C.o. is formed of a tissue possessing an intercellular substance containing filamentous scleroproteins clearly corroborates the theory that is performs supporting activity in respect of Corti's organ. The term supporting structure of Corti's organ is based on this interpretation.Research financed by C.N.R. grant.     

Biosynthesis of Leishmania lipophosphoglycan: solubilization and partial characterization of the initiating mannosyiphosphoryltransferase

Lipophosphoglycan (LPG) is the predominant surface glycoconjugateof Leishmania promastigotes and consists of a capped polymerof Gal(ß1,4)Man(     

Malic acid production and consumption by selected of Saccharomyces cerevisiae under anaerobic and aerobic conditions

Summary Fermentation tests in clearly defined laboratory conditions were carried out with eight functionally selected strains of Saccharomyces cerevisiae. Analysis of the data showed that there were no significant differences in malic acid production between the strains when the acid was initially present. When it was initially absent, however, significant differences were observed two strains (Nos. 1141 and 1083) showing marked productive superiority. With malic acid as the sole C source, two strains (Nos. 1109 and 1141) showed less acid consumption.