Production of cyclodextrins using moderately heat-treated cornstarch

Cyclodextrins are very useful compounds for the food, cosmetic, pharmaceutic, and plastic industries. We developed a process for the production of cyclodextrins from moderately heat-treated cornstarch. This method had many merits. First, the cyclodextrins were not degraded by cyclodextrin glucanotransferase, because low molecular weight maltodextrins were hardly produced. Second, it was possible to remove the residual cornstarch by a simple method such as filtration or centrifugation. Third, the amount of cyclodextrin glucanotransferase used for cyclodextrin production was less than that using the traditional method. Fourth, the pretreating method was simple. And fifth, the residual starch could be used as substrate for the production of other compounds. Cyclodextrins were produced at optimum conditions: heating temperature was 65°C; heating time was 1 h; concentration of substrate was 7.5%; amount of enzyme loaded was 48 U g⁻¹ of substrate. Using these conditions, the results were as follows: the content of cyclodextrins, 50%; the conversion yield of substrate, 25%; the productivity per enzyme unit, 5.22 mg of cyclodextrins.     

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.     

Functional Role of Amino-Terminal Serine16 and Serine27 of Gαz in Receptor and Effector Coupling

Abstract: The α subunit of G_z (α_z) harbors two N-terminal serine residues (at positions 16 and 27) that serve as protein kinase C-mediated phosphorylation sites. The cognate residues in the α subunit of G_t1 provide binding surfaces for the β₁ subunit. We used three serine-to-alanine mutants of α_z to investigate the functional importance of the two N-terminal serine residues. Wild-type or mutant α_z was transiently coexpressed with different receptors and adenylyl cyclase isozymes in human embryonic kidney 293 cells, and agonist-dependent regulation of cyclic AMP accumulation was examined in a setting where all endogenous α subunits of G_i were inactivated by pertussis toxin. Replacement of one or both serine residues by alanine did not alter the ability of α_z to interact with δ-opioid, dopamine D₂, or adenosine A₁ receptors. Its capacity to inhibit endogenous and type VI adenylyl cyclases was also unaffected. Functional release of βγ subunits from the mutant α_z subunits was not impaired because they transduced βγ-mediated stimulation of type II adenylyl cyclase. Constitutively active mutants of all four α_z subunits were constructed by the introduction of a Q205L mutation. The activated mutants showed differential abilities to inhibit human choriogonadotropin-mediated cyclic AMP accumulation in luteinizing hormone receptor-transfected cells. Loss of both serine residues, but not either one alone, impaired the receptor-independent inhibition of adenylyl cyclase by the GTPase-deficient mutant. Thus, replacement of the amino-terminal serine residues of α_z has no apparent effect on receptor-mediated responses, but these serine residues may be essential for ensuring transition of α_z into the active conformation.     

Regeneration of Medicago truncatula from protoplasts isolated from kanamycin-sensitive and kanamycin-resistant plants

Medicago truncatula (barrel medic) is an annual legume of agricultural and biological interest. In this report regeneration from isolated mesophyll protoplasts is described. A specifically developed, highly regenerable seed line is essential for regeneration. Other critical requirements for regeneration are the starting plant material, the use of agarose droplets incubated in a shallow layer of liquid medium, and protoplast density. Plants are grown in controlled environment conditions. Protoplasts are purified using a Percoll-based flotation procedure, then embedded in 100 l agarose droplets containing a basal medium plus 25 M NAA and 4 M BAP (the same medium as in the surrounding shallow liquid layer) to induce protoplast division. A protoplast density of 6–8×10⁵ ml^–1 is required for maximum colony formation. M. truncatula plants previously transformed for kanamycin resistance yielded embryogenic callus and also regenerated plants. Protoplasts from other annual Medicago (M.intertexta and M.scutellata) species readily form calli by the procedure we have described.Abbreviations BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid     

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.     

Sulphide as an inhibitor and electron donor for the cytochrome c oxidase system

Anomalies both kinetic and equilibrium in nature are described for the inhibition of cytochrome c oxidase activity by sulphide in the isolated enzyme and in submitochondrial particles. These anomalies are related to the involvement of more than 1 mol of sulphide in the blockage of one cytochrome aa3 centre. Sulphide reduces resting cytochrome a3, a reaction that results in oxygen uptake and the loss of a sulphide molecule. Sulphide can also reduce cytochromes c and a; in the former case, a part of the one-equivalent oxidation product, presumed to be the SH radical, reacts with oxygen. Such oxygen uptake is also seen under aerobic conditions when ferricyanide reacts with sulphide. Three phases are identified in the inhibitory interaction of sulphide with the cytochrome c oxidase enzyme itself: an initial rapid reaction involving sulphide oxidation, oxygen uptake, and conversion of cytochrome aa3 into the low-spin "oxyferri" form; a subsequent step in which sulphide reduces cytochrome a; and the final inhibitory step in which a third molecule of sulphide binds the a3 iron centre in the cytochrome a2+ a3 3+ (oxy) species to give cytochrome a2+ a3 3+ H2S. the initial events parallel some of the events in the interaction of the cytochrome c-cytochrome aa3 system with monothiols; the final inhibitory event resembles that with cyanide.