The specific nature of plant cell wall polysaccharides

Polysaccharide compositions of cell walls were assessed by quantitative analyses of the component sugars. Cell walls were hydrolyzed in 2 n trifluoroacetic acid and the liberated sugars reduced to their respective alditols. The alditols were acetylated and the resulting alditol acetates separated by gas chromatography. Quantitative assay of the alditol acetates was accomplished by electronically integrating the detector output of the gas chromatograph. Myo-inositol, introduced into the sample prior to hydrolysis, served as an internal standard.     

Sugar uptake and translocation in the castor bean seedling I. Characteristics of transfer in intact and excised seedlings

Changes in the dry weights of various parts of the castor bean seedling showed that the rates of transfer of material through the cotyledons to the embryonic axis exceeded 2 mg/hour after 5 to 6 days of germination. The sugar present in the endosperm was predominantly, and in the cotyledon almost exclusively, sucrose. Anatomical features were described which contribute to the efficiency of the cotyledons as organs of absorption and transmittal of sucrose to the embryonic axis, where hexoses are much more prevalent.The ability of the cotyledons to absorb sucrose survived removal of the endosperm from the seedling. A series of experiments is described in which the cotyledons of such excised seedlings were immersed in sucrose-(14)C and measurements made of uptake and of translocation to various parts of the seedling. Increasing rates of absorption were observed as the sucrose concentration was raised to 0.5 m and these rates were maintained for several hours. Removal of the embryonic axis (hypocotyl plus roots) drastically altered both the response to sucrose concentration and the time course of absorption by the cotyledons.More than 80% of the sugar normally entering the cotyledons from the endosperm is transmitted to the embryonic axis and this extensive turnover was seen also in pulse/chase experiments with excised seedlings. The cotyledons of excised seedlings absorbed sucrose against high apparent concentration gradients. The absorption was stimulated by phosphate and had a pH optimum at about pH 6.4. It was inhibited by arsenate, azide and 2,4-dinitrophenol.     

Biliary excretion in foreign compounds. Sulphonamide drugs in the rat

1. The extent of biliary excretion in the rat of 15 sulphonamide compounds was studied. 2. Most of the sulphonamides studied, with molecular weights from 172 (sulphanilamide) to 352 (N⁴-acetylsulphadimethoxine) are poorly excreted in the bile (0–4% of the dose), except sulphapyridine, sulphamethoxypyridazine and sulphadimethoxine. The last three are partly metabolized to glucuronides, whose molecular weights and polarities are such as to allow them to be excreted in the bile in appreciable amounts. 3. Succinylsulphathiazole and phthalylsulphathiazole are polar and have molecular weights (355 and 403) of an appropriate order, and are excreted unchanged in the bile in appreciable amounts. 4. Sulphadimethoxine N¹-glucuronide (mol.wt. 487) is extensively excreted in the bile unchanged. 5. The results are examined in the light of the hypotheses put forward in the preceding paper (Millburn, Smith & Williams, 1967).     

Biliary excretion of [C]succinylsulphathiazole in the rat and rabbit

1. After intravenous injection about 30% of the dose (20mg./kg.) of succinylsulphathiazole is excreted unchanged in the bile in 3hr. by the rat, whereas only about 1% is excreted by the rabbit. When the renal pedicles are ligated the biliary excretion of succinylsulphathiazole in the rat increases to about 80% of the dose, but in the rabbit under these conditions the biliary excretion is only 2% of the dose. 2. In the rat, the sulphonamide readily enters the liver and biliary excretion occurs against a concentration gradient from liver to bile; further, the excretory process can be saturated, and can be depressed by the simultaneous administration of phenolphthalein glucuronide or bile salts. 3. In the rabbit, these conditions have not been found; succinylsulphathiazole does not readily enter the liver from the plasma, there is no transfer of the drug from the liver cells to the bile against a concentration gradient, and no saturation or depression of the biliary excretion of succinylsulphathiazole is found. 4. It is suggested that two factors responsible, at least partly, for the low biliary excretion of succinylsulphathiazole in the rabbit are the poor entry of the sulphonamide into the liver in this species and a deficiency of the concentrative mechanism for its excretion in the bile.     

Effect of alloxan-diabetes on multiple forms of hexokinase in adipose tissue and lung

Comparison has been made of the effect of alloxan-diabetes on the multiple forms of hexokinase (EC 2.7.1.1) in adipose tissue and lung. Types I and II hexokinase were distinguished in adipose tissue by their different stabilities to heat treatment, which made it possible to determine the activity of each form spectrophotometrically; additional confirmatory evidence was obtained from starch-gel electrophoresis. Type II hexokinase was markedly depressed in adipose tissue from alloxan-diabetic rats. Lung contained types I, II and III hexokinase, type I predominating. There was no significant change in the pattern of these multiple forms of hexokinase in lung from alloxan-diabetic rats. These results are discussed in relation to current ideas that the insulin-sensitivity of a tissue may be correlated with the content of type II hexokinase.     

Canine reproduction: I. Reaction of animals to collection of semen and insemination procedures

Two methods of semen collection were attempted on ten untrained dogs of several breeds. Manual manipulation as described proved most reliable for untrained dogs. Electro-ejaculation was attempted unsucessfully with twelve additional dogs.Two methods of insemination were compared. Equipment found most satisfactory is described and a modification suggested.     

Influence of hormones on the nicotinamide nucleotide coenzymes of adipose tissue

The concentrations of the oxidized and reduced forms of the nicotinamide nucleotides were measured in the epididymal fat pads of normal, alloxan-diabetic and hypophysectomized rats. In both alloxan-diabetic rats and hypophysectomized rats the weight of the adipose tissue fell, as did the total content of NADH and NADPH; in addition, NAD⁺ was decreased in the alloxan-diabetic group. Of these changes the most marked was in NADPH and this was the only significant difference when the results were expressed as nicotinamide nucleotides/mg. of tissue protein. The concentration of NADPH in the hypophysectomized rats was not altered by treatment with growth hormone but was restored to normal by treatment with thyroxine. These results are discussed in relation to the known effect of these hormonal conditions on lipid synthesis in adipose tissue.