The acidic polysaccharide from Palmaria decipiens (Palmariales,Rhodophyta)

Palmaria decipiens, one of the most abundant red seaweeds of the chilean Antarctic, was collected in King George Island. The hot water extract (26% yield) showed by acid hydrolysis to contain xylose, galactose and traces of glucose. Fractionation with cetrimide gave a soluble neutral xylan and an insoluble fraction. The insoluble fraction afforded an acidic polysaccharide that contained 4.8% of uronic acids, 2.8% of sulfate and 18.9% of protein. Polyacrylamide gel electrophoresis showed that it was homogeneous. The GLC and HPLC analysis of the total acidic hydrolysis products showed that the acidic polysaccharide was composed of the neutral sugars galactose and xylose in the molar ratio 8.2:1.0 and of galacturonic and glucuronic acid in the ratio 1.5:1.0. The second-derivative FT-IR spectrum showed the characteristic amide I, II and III bands of proteins. Alkaline cleavage with 0.1 M NaOH indicated the presence of a glycoprotein with O-glycosidic linkage.Results found in this work suggest that the acidic polysaccharide extracted from Palmaria decipiens is an acidic xylogalactan-protein complex.     

Gene integration in the Escherichia coli chromosome mediated by Tn21 integrase (Int21).

A replication-thermosensitive, pSC101-derived plasmid containing the int gene and RHS-2 from the integron in Tn21 and a kanamycin resistance marker has been constructed and used to obtain Tn21 integrase (Int21)-mediated plasmid integration in the Escherichia coli chromosome. Colonies carrying an integrated plasmid were obtained after growth at 42 degrees C. Southern hybridization and PCR experiments indicated that they contained the plasmid specifically integrated through the RHS into different positions in the E. coli chromosome. Nucleotide sequence determination of the plasmid-chromosome junctions showed that integration sites in the chromosome were pentanucleotides with the sequence described for Int21 secondary sites.     

Changes in extracellular levels of dopamine metabolites in somatosensory cortex after peripheral denervation

This study examined the effects of a nerve transection on monoamine release from primary somatosensory cortex. The technique of microdialysis was employed to sample extracellular levels of norepinephrine (NE), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HIAA) and homovanillic acid (HVA) in the barrel field of freely moving rats following the surgical transection of the contralateral infraorbital nerve. Microdialysates obtained 3, 4, and 5 days after deafferentation were analyzed using high-performance liquid chromatography with electrochemical detection. We found a significant increase in the release of the dopamine metabolites, DOPAC and HVA from the deafferented cortex. Three days after deafferentation the release of DOPAC was three-fold higher in the deafferented than in the control animals, and remained about 100% higher in the next two days in this group of animals. The release of HVA showed a gradual increase following the deafferentation procedure, since a 92% larger value on day 3 increased to a 338% difference on day 5. On the other hand, the release rate of NE and the levels of the serotonin metabolite 5-HIAA were not significantly affected by the deafferentation procedure. These results are discussed in the context of the possible participation of dopamine in the reorganization of the deafferented somatosensory cortex.     

Factors affecting transient gene expression in cultured radiata pine cotyledons following particle bombardment

Transfer and expression of the β–glucuronidase gene ( gusA ) in cultured cotyledons of radiata pine ( Pinus radiata D. Don ) were obtained by particle bombardment. Conditions for optimum transient expression were established by using plasmid pB[/12], delivered by gold particles, 1.6 μm in diameter, into 8-day-old cultured cotyledons. Helium pressure of 7.6 MPa, bombardment distance between the stopping screen and the target tissues of 6 cm, and 0.8 μg of plasmid DNA per bombardment proved to be the best parameters for transient expression; using these parameters 79% of bombarded cotyledons showed GUS activity, with 4.3 blue spots per cotyledon. This system was used for studying the expression of several gus-driven promoters the expression of the sunflower ubiquitin gene promoter was higher (99% of positive cotyledons, with 14.2 blue spots per cotyledon) than that of the CaMV 35S promoter, whereas the rice actin and the maize alcohol dehydrogenase gene promoters gave lower gusA expression, as determined histochemically. These results were confirmed by using the gus fluorometric assay. Use of the sunflower ubiquitin gene promoter resulted in gusA expression up to 20 days after bombardment, with a significant level of gus expressing loci per bombarded cotyledon, whereas with the CaMV 35S promoter gusA expression was lost 12 days after bombardment.     

Mixing power, external convection, and effectiveness in bioreactors

The phenomena of mixing and mass transfer of substrates to microorganisms greatly affect the biochemical reactions which take place in fermentation processes. The effect that agitation power has on the observable reaction kinetics involved in beer fermentation has been studied in different types of bioreactors, from laboratory to industrial scale. With this aim in mind, an effectiveness factor, eta, is introduced which is defined as the relation between the existing rate of reaction, whichever bioreactor is considered, and the reaction rate in the well-mixed, and therefore presumably homogeneous, bioreactor with no diffusional limits. The limitation to homogeneously supplying nutrient material to the cells produces a decrease in this effectiveness factor, which has been correlated to the energy dissipation rate with a similar slope to that which appears in an existing correlation in the literature between this energy and the mass transfer coefficient. Additionally, a dimensionless reaction-convection number, N(RC), which is a function of the power input per unit volume, is proposed, which has been appropriately employed in correlating the effectiveness factor for the types of processes in which convection may be the key resistance factor. (c) 1996 John Wiley & Sons, Inc.     

An extended x-ray absorption fine structure study of the high-affinity cation-binding site in the purple membrane.

The structure of the high-affinity cation-binding site of bacteriorhodopsin was studied using extended x-ray absorption fine structure techniques. The results obtained for Mn2+ in aqueous solution and for the complex BR-Mn2+ (1:1 molar ratio) show great similarities, suggesting that Mn2+, when bound to this site, is coordinated with six atoms of oxygen, forming an octahedral disposition. The interatomic distance between the atoms of oxygen and the Mn2+ was found to be 2.17 A for the complex BR-Mn2+, similar to Mn2+ in solution (2.15 A). In addition, the absence of any other peak at greater distances in the Fourier-transformed spectrum indicates that neither phosphorus nor sulphur atoms are present in the second coordination shell. This suggests that this binding site is located in the protein, discarding the proximity of lipid polar headgroups.     

A new species of Lupinus (Fabaceae: Lupininae) from southeastern Brazil

Lupinus rubriflorus Planchuelo, from Rio Grande do Sul, Brazil, is described and illustrated. This species is related toL. bracteolaris s.l. differing in pubescence, stipules, and floral characters.     

Conformation of 4-thio-l-lyxono-1,4-lactone in solution and in the crystalline state

The conformation in ²H₂O of 4-thio-l-lyxono-1,4-lactone (1) was studied by nuclear magnetic resonance spectroscopy, by means of homonuclear (J_1H,1H) and heteronuclear (J_1H,13C) coupling constants. The couplings were directly measured by a two-dimensional heteronucleus-coupled ω₁ hetero-half-filtered proton-proton correlation (HETLOC) experiment, which does not require ¹³C isotopic enrichment. In solution, the thiolactone ring of 1 adopts preferentially the E₃ conformation, and its hydroxymethyl group populates mainly the gt rotamer. The X-ray diffraction data of a single crystal of 1 indicates that also in the solid state the thiolactone ring adopts an E₃ conformation, with a puckering somewhat larger than that observed for aldono-1,4-lactones and furanose rings. The molecules are linked by hydrogen bonds, which form chains. Particularly, O-5 is fully engaged as donor and acceptor in hydrogen bonding and the rotameric conformation of the hydroxymethyl group of 1 is fixed in the tg form.     

Ontogeny of some endocrine cells of the digestive tract in sea bass (Dicentrarchus labrax): An immunocytochemical study

Serotonin- and ten peptide-immunoreactive (IR) cell types were identified in the digestive tract of sea bass (Dicentrarchus labrax L.) larvae of four morphofunctional phases ranging in age from hatching to 61 days. The sequence of appearance and location of endocrine cells during ontogenetic development of the larvae was determined. The differentiation of endocrine cells followed a distal-proximal gradient in the gut which paralleled the morphofunctional differentiation. Serotonin-IR cells were identified in the last portion of the digestive tract from phase I onwards and in the gastric region from phase III, before these regions were morphofunctionally differentiated; met-enkephalin-IR cells were identified from phase II onwards in both the differentiated rectum and the undifferentiated intestine; cholecystokinin (CCK)- and synthetic human gastrin-34-IR cells were located only in the intestine and first found in the undifferentiated intestine of phase II; human gastrin-17-, peptide YY (PYY)- and neuropeptide Y (NPY)-IR cells appeared in the intestine from phase II and in stomach in phase IV, when it showed gastric glands; pancreatic polypeptide (PP)- and glucagon-IR cells were observed in both intestine and stomach, but insulin- and somatostatin-IR cells only in stomach, from phase III, during which the intestine but not the stomach was differentiated. PP- and PYY-, PP- and glucagon-, and PYY- and glucagon-like immunoreactivities coexisted from their first appearance in some cells of the gut.