Production and initial characterisation of the xylan-degrading system of Phanerochaete chrysosporium

We report the optimum conditions for the degradation of oat spelt arabinoxylan and a preliminary characterisation of the inducible xylan-degrading system of the lignin-degrading white-rot fungus Phanerochaete chrysosporium. Xylanase activity was optimal at pH 5.0 and 50°C; see attached sheet the maximum reaction velocity (V_max) of the system was 3.86 units (U) mg^–1 protein with arabinoxylan as substrate and the substrate concentration giving half V_max (S_0.5) was 0.52 mg ml^–1. At concentrations of arabinoxylan greater than 15 mg ml^–1 excess substrate inhibition was observed. Xylose at 0.9 mm inhibited activity to the extent of 50%. Xylanase activity increased as a function of the dilution of the enzyme preparation prior to assay. It was resolved into four peaks by using a DEAE-Biogel column; the material in these peaks differed with respect to xylan solubilisation and the formation of reducing sugars. Electrofocusing gels allowed visualisation of several bands of activity corresponding to each peak. The arabinoxylan degradation system of P. chrysosporium is therefore composed of multiple components. Correspondence to: P. Broda     

Cytological and molecular characterization of a chromosome interchange and addition lines in Cadet involving chromosome 5B of wheat and 6Ag of Lophopyrum ponticum

Efforts to transfer wheat curl mite (Eriophyes tulipae Keifer) resistance from Lophopyrum ponticum 10X (Podb.) Love to bread wheat (Triticum aestivum L.) have resulted in the production of a number of cytogenetic stocks, including an addition line of 6Ag, a ditelo addition line, and a wheat-Lophopyrum translocation line. Characterization of these lines with C-banding, in situ hybridization with a Lophopyrum species-specific repetitive DNA probe (pLeUCD2), and Southern blotting with pLeUCD2 and a 5S ribosomal DNA probe (pScT7) confirmed that the distal portion of the short arm of 6Ag was translocated onto the distal portion of 5BS (5BL. 5BS-6AgS). It was also determined that the ditelo addition was an acrocentric chromosome of 6AgS.     

Mechancial properties of bat wing membrane skin

The skin of the bat wing in functionally unique among mammals: it serves as a major locomotor organ in addition to its protective and regulatory functions. We used tensile testing to investigate the mechanical capabilities of wing membrane skin, and compared stiffness, strength, load at failure, and energy absorption among specific wing regions and among a variety of bat taxa. We related these characteristics to the highly architectural fibrous supporting network of the wing membrane. We found that all material properties showed a strong anisotropy. In particular, wing membrane skin shows maximum stiffness and stregth parallel to the wing skeleton, and greatest extensibility parallel to the wing's trailing edge. We also found significant variation among wing regions. The uropatagium (tail membrane) supported the greatest load at failure, and the plagiopatagium (proximal wing membrane between laterl body wall and hand skeleton) is the weakest and most extensible part of the wing. We believe that the increased load bearing ability of the uropatagium relats to its key role in capture of insect prey, and that the great extensibility of the plagiopatagium promotes development of camber near the wing's centre of lift. In interspecific comparisons, energy absorpion and load to failure were greatest in Artibeus jamaicensis , the largest bat in our sample and the species with the highest wing loading, suggesting that wing loading may play a role in dictating the fuctional design of wing membranes.     

Dextran production by Leuconostoc mesenteroides in the presence of a dextranase producing yeast, Lipomyces starkeyi

Summary A new process for the production of small size dextran is developed in which dextran is produced by cultures of Leuconostoc mesenteroides in the presence of a partially constitutive mutant of Lipomyces starkeyi producing dextranase. Mixed cultures were examined by scanning electron microscopy with ruthenium to show the effects of the mixed culture on low molecular weight dextran (M.W. of 5,000 – 100,000) formation. The presence of the size variation in dextran was confirmed by gel permeation chromatography.     

A scanning electron microscope study of Craspedella sp. from the branchial chamber of redclaw crayfish,Cherax quadricarinatus,from Queensland,Australia

Epidermal topography was examined, including papillate ridges, grooves and ciliated sensory papillae of Craspedella sp. from the branchial chamber of redclaw crayfish, Cherax quadricarinatus, from Queensland, Australia. Rhandites were observed to discharge from ducts opening mainly in a small distal region of the ventral epidermis of the three central (of five) tentacles. These regions, devoid of ciliated sensory papillae, serve to adhere the anterior end of the worms during locomotion. Secretions from glands associated with the posterior attachment organ were observed to discharge from pores on the outside region of the ventral surface of the disc.A comparison of various scanning electron microscopy (SEM) fixation techniques showed that (1) hot fixatives at 90 °C provide most information on the largest number of epidermal structures and (2) different fixation regimes highlight different epidermal features.     

Effects of cell swelling on fluid flow across alveolar epithelium

The effects of decreased temperature, metabolic inhibition, and hyposmolality on osmotically and hydrostatically driven water flux across bullfrog alveolar epithelium were studied. Lungs were isolated from double-pithed Rana catesbeiana and prepared as sacs. Either an osmotic (0.1 M raffinose) or hydrostatic (6.3-6.6 Torr) pressure gradient was imposed across the tissue. These gradients resulted in the volume flow of water from the alveolar to pleural bath. Control water flux and hydraulic conductivity were estimated from the rate of weight loss of the lung sac. Subsequently water flux and hydraulic conductivity were determined under one of the following conditions: 1) temperature of bathing solutions lowered to 2 degrees C; 2) 1 mM 2,4-dinitrophenol added to both alveolar and pleural baths, or 3) both baths changed to half-isosmotic Ringer solution. The control hydraulic conductivities for osmotic (Lpo) and hydrostatic (Lph) pressure gradients were 3.65(+/- 0.94) X 10(-12) and 2.14(+/- 0.63) X 10(-10) ml/dyn X s, respectively. Under conditions of metabolic inhibition, hyposmolality, and decreased temperature, Lph decreased by 77, 83, and 92%, and Lpo decreased by 56, 34, and 59%, respectively. These results are most consistent with the hypothesis that the decrements in hydraulic conductivity under our experimental conditions are due to epithelial cell swelling and perhaps to changes in the characteristics of the paracellular pathway.     

The nature of cells generating human myeloma colonies in vitro.

Freshly explanted human myeloma cells formed colonies of monoclonal plasma cells in soft agar in the presence of medium conditioned by the adherent spleen cells of mineral oil-primed BALB/c mice. The medium showed peak activity at a dilution of 1:4. 2-mercaptoethanol or monothioglycerol was necessary for colony formation. Other thiols tested were ineffective in promoting colony growth. Colony-forming cells adhered to nylon wool, but not glass beads or plastic dishes. The presence of E-rosetting cells was not required for myeloma colony formation. Antibody prepared against a human myeloma cell line, RPMI 8226, reduced colony formation. These studies demonstrate the usefulness of this bioassay for determining functional properties of the myeloma colony-forming cell.     

Bacillus subtilis alkaline phosphatases III and IV. Cloning, sequencing, and comparisons of deduced amino acid sequence with Escherichia coli alkaline phosphatase three-dimensional structure

Bacillus subtilis has an alkaline phosphatase multigene family. Two members of this gene family, phoAIII and phoAIV, were cloned, taking advantage of in vitro constructed strains containing a plasmid insertion within one or the other of the structural genes. The DNA sequences of the two genes showed approximately 64% identity at the DNA level and 63% identity in the deduced primary amino acid sequences. The phoAIII and phoAIV genes code for predicted proteins of 47,149 and 45,935 Da, respectively. Comparison of the deduced primary amino acid sequence of the mature proteins with other sequenced alkaline phosphatases from Escherichia coli, yeast, and humans shows 25-30% identity. Based on the refined crystal structure of E. coli alkaline phosphatase, it appears that the active site and the core of the structure are retained in both Bacillus alkaline phosphatases. However, both proteins are truncated at the amino terminus compared with other mature alkaline phosphatases, three sizable surface loops of E. coli are deleted, and a minidomain is replaced with a larger domain in the model. Neither Bacillus alkaline phosphatase sequenced contains any cysteine residues, an amino acid implicated in intrachain disulfide bond formation in other alkaline phosphatases.