Structure of the d-galactan isolated from aloe barbadensis miller

Hot-water extraction of the pulp obtained by dehydrating the jelly of the fleshy leaves of Aloe barbadensis furnished a mixture of polysaccharides containing mainly pectic acid, along with a d-galactan, a glucomannan, and an arabinan. The pectic acid was partly removed by treatment with calcium chloride, and the resulting, hexose-enriched, polysaccharide mixture was fractionated through a column of DEAE-cellulose to yield a d-galactan containing d-galactose (92.9% and d-galacturonic acid (3.8%). Hydrolysis of the permethylated d-galactan furnished 2,3,4,6-tetra-, 2,3,6-tri-, and 2,3-di-O-methylgalactose in the molar ratios of 1:26:1. On periodate oxidation, the d-galactan reduced 0.95 molar equivalent of the oxidant per hexosyl residue, and liberated one molar equivalent of formic acid per 26 galactosyl residues. Smith degradation of the d-galactan afforded mainly threitol. From these results, a structure has been assigned to the repeating unit of the d-galactan. The number-average, molecular weight of the peracetylated galactan has been found to be 3.74 x 10⁴.     

Effect of algal growth on the availability of phosphorus,iron and manganese in rice soils

Summary Laboratory experiments were conducted to study the effect of algal growth on the change of (I) pH, (II) available phosphorus and (III) solubility of iron and manganese content in five waterlogged alluvial rice soils of West Bengal, India. The results showed that the algal growth initially caused an increase in the soil pH, which later declined to the original value in some of the soils. The available phosphorus content decreased upto 90 days of their growth and began to increase towards the later period of incubation. The drastic fall of water soluble plus exchaneable manganese content of the soils due to algal growth was accompanied by similar increase in reducible manganese content. No appreciable change in water soluble plus exchangeable ferrous iron content was encountered but theN-NH₄OAC(pH 3) extractable iron due to algal growth progressively decreased with the progress of the incubation period.     

Radiation-induced inactivation of dihydroorotate dehydrogenase in dilute aqueous solution.

The inactivation of dihydroorotate dehydrogenase by gamma irradiation in dilute aqueous solution has been investigated. The activity of the enzyme decreased exponentially as a function of the absorbed dose under aerated and nitrous oxide-saturated conditions. The contributions of the individual radical species derived from water radiolysis were estimated from the inactivation results observed under aerated, argon-saturated, and nitrous oxide-saturated conditions. The hydrogen atom and hydroxyl radical were found to be important in enzyme inactivation. The effect of selected inorganic radical anions such as Br.2-, I.2-, and (SCN).2- on the enzyme activity was also studied, and the results implicate the possible involvement of cysteine and tyrosine residues in the catalytic activity of dihydroorotate dehydrogenase. Changes in the kinetic parameters (Michaelis-Menten constant, Km, and maximal velocity, Vmax) due to irradiation under the conditions investigated suggest that radiation-induced inactivation is due to modification of the substrate binding sites and that of the active site residues in the enzyme. Evidence for the reduction of iron-sulfur centers in the enzyme during the inactivation process has been put forward from the difference spectrum of the irradiated dihydroorotate dehydrogenase. It has also been shown by electrophoretic studies that radiation-induced inactivation was not due to any fragmentation of the protein structure or the formation of any intermolecular crosslinking.     

Membranes in the miotic apparatus of barley cells

Membranes in the mitotic apparatus have been investigated ultrastructually in dividing cells of barley (Hordeum vulgare). After osmium tetroxide- potassium ferricyanide or ferrocyanide postfixation (OsFeCN) of material that had been fixed in glutaraldehyde in the presence of Ca(++), the nuclear envolope (NE)-endoplasmic reticulum (ER) complex is selectively stained, permitting observations on the cellular pattern and structural ramifications of this membrane system that have not been previously recognized. Specifically, it is observed that membrane system that have not been previously recognized. Specifically, it is observed that during mitosis the NE-ER forms a continuous membrane system that ensheathes and isolates the mitotic apparatus (MA). Elements of ER progressively accumulate in the region of the spindle pole, becoming most concentrated by early anaphase. Within the MA itself, there are striking spindle- membrane associations; in particular, tubular elements of predominantly smooth NE-ER invade the spindle interior selectively along kinetochore microtubules. The membrane elements at the pole and surrounding the MA consist of tubular reticulum and fenestrated lamellae. Membranes of the MA thus resemble in considerable detail the tubular network and fenestrated elements of the sarcoplasmic reticulum of muscle. It is suggested that the NE-ER of the dividing barley cell may function in one or both of the following ways: (a) to control the concentration of free Ca(++) in the MA and (b) to serve as an anchor to chromosome motion.     

Campylobacter colitis.

Eleven consecutive patients with diarrhoea from whose stools campylobacter were isolated were investigated by sigmoidoscopy and rectal biopsy. Eight had definite proctitis, and in seven biopsy specimens were abnormal with histological changes ranging from non-specific colitis to gross colitis with goblet-cell depletion and crypt-abscess formation. Nine of the patients passed blood in their stools, and in all but one abdominal pain was a feature of the illness. Severe campylobacter colitis may be clinically, sigmoidoscopically, and histologically difficult to differentiate from ulcerative colitis and is a differential diagnosis in acute colitis.     

Heat-sensitive DNA-binding activity of thecI product of bacteriophage lambda

Summary The binding of genecI product to DNA was studied at temperatures from 0°C to 46° C. Binding activity of the products ofcIts mutants was higher at 22° C than at 0° C, 26° C or 30° C. BothcI⁺ andcIts products lost DNA-binding activity at 46° C, but after subsequent cooling to 22° C, they regained 50–100% of their activity.     

Augmentation of sickling process due to turbulent blood flow.

The purpose of this study was to determine if the fluid mechanical stresses associated with turbulent blood flow can contribute to the sickling process. Blood from seven patients with sickle cell disease was subjected to intermediate and high levels of turbulent flow in vitro. Turbulence was quantitated by hot film anemometry. Control samples showed 20 +/- 3% sickled cells. Cells subjected to intermediate levels of turbulent flow showed 26 +/- 4% sickling (P less than 0.01); and blood subjected to high intensities of turbulence showed 31 +/- 4% sickling (P less than 0.01). A quantitative count by electronmicroscopy, performed in one patient, showed polymerization of the hemoglobin indicative of sickling in more cells subjected to turbulence than in the control sample. A turbulence-reducing agent, polyethylene oxide, diminished the augmentation of the sickling process as it reduced turbulence at comparable Reynolds numbers. These results support the hypothesis that a deleterious effect upon hemoglobin SS erythrocytes may occur due to the mechanical stresses of turbulent flow. The agitation associated with turbulent flow presumably modifies the stabilizing factors of the intracellular colloidal solution of hemoglobin, thereby contributing to sol-gel transformation. Such hydrodynamic stresses may supplement the previously described factors which contribute to sickle cell crises.