Gel formation on nodal root surfaces ofZea mays

Summary A gel forms profusely on the surface of nodal roots of corn. The nature and properties of the material was investigated with the purpose of understanding the mucilaginous layer which exists at the root-soil interface. Acid hydrolysis of the material revealed that it contained uronic acids, galactose, arabinose, xylose, and frucose in an approximate molecular ratio of (3:7:5:11). In addition to these sugars glucose and fructose were also present in the exudate of first or second stage nodal roots. The enzymes acid phosphatase and ATPase were present in the gel. ATPase was only slightly stimulated by K. The gel showed phosphatase activity over a broad range in pH. Contribution from the Department of Agronomy, Purdue University, Lafayette, Indiana, U.S.A. Journal Paper No. 3696 of the Purdue Agricultural Experiment Station.     

Some observations on the interaction of dopamine-beta-hydroxylase and its natural inhibitors in the rat brain.

The difficulty of assaying dopamine beta-hydroxylase (DbetaH) (EC 1.14.17.1) has been circumvented by including N-ethylmaleimide (5 X 10(-2) M) in the incubation mixture along with a small amount of Cu2+ (20-60 muM). Such a procedure ensures that the maximum DbetaH activity is assessed in all extracts. As a result, the absolute levels of DbetaH in various regions of the rat brain have been established. The DbetaH values obtained are higher by 40% in the hypothalamus and 20% in the cerebral cortex, spinal cord, and caudate nucleus than those previously reported. The mechanism of the synergic effect seen when N-ethylmaleimide and Cu2+ are combined is not presently understood.     

Contribution to the understanding of the mechanism of cytokinesis in plant cells: the action of deoxyguanosine on the kinetics of a root meristem cell population.

The kinetics of binucleate cells, formed by the action of deoxyguanosine, are studied using three methods: in a population synchronized with hydroxyurea, by autoradiography after pulse-labelling, and in a sample of a cell population morphologically located at the M--G1 limit. Deoxyguanosine induces a slowing down in S and G2, independent of the inhibition of cytokinesis. It is only when it takes effect during the G2 stage that deoxyguanosine brings about the formation of binucleate cells.     

Cytokinin action is coupled to ethylene in its effects on the inhibition of root and hypocotyl elongation in Arabidopsis thaliana seedlings.

Cytokinins have profound effects on seedling development in Arabidopsis thaliana. Benzyladenine (BA) inhibits root elongation in light- or dark-grown seedlings, and in dark-grown seedlings BA inhibits hypocotyl elongation and exaggerates the curvature of apical hooks. The latter are characteristic ethylene responses and, therefore, the possible involvement of ethylene in BA responses was examined in seedlings. It was found that the inhibitory effects of BA on root and hypocotyl elongation were partially blocked by the action of ethylene inhibitors or ethylene-resistant mutations (ein1-1 and ein2-1). Ethylene production was stimulated by submicromolar concentrations of BA and could account, in part, for the inhibition of root and hypocotyl elongation. It was demonstrated further that BA did not affect the sensitivity of seedlings to ethylene. Thus, the effect of cytokinin on root and hypocotyl elongation in Arabidopsis appears to be mediated largely by the production of ethylene. The coupling between cytokinin and ethylene responses is further supported by the discovery that the cytokinin-resistant mutant ckr1 is resistant to ethylene and is allelic to the ethylene-resistant mutant ein2.     

Effects of iodination of tyrosyl residues on the binding and action of glucagon at its receptor.

The binding and action of glucagon at its receptor in hepatic plasma membranes have been compared, as a function of pH, with that of glucagon containing iodotyrosyl residues. Iodinated glucagon, at pH 7.0 and below, binds to the receptor and activates adenylate cyclase with an affinity about threefold higher than that of native glucagon. At pH 8.5, the affinity of the receptor for native glucagon is the same as that seen at pH 7.0. However, iodinated glucagon binds with a lowered affinity with increasing pH. The decreased affinity of the iodinated hormone correlates with ionization of the iodotyrosyl phenoxy groups, which has a pKa of 8.2. It is suggested that the decreased affinity is actually due to the inability of the ionized iodoglucagon to bind to the receptor. The relative potency of native and iodoglucagon will depend, therefore, on the concentrations of ionized and un-ionized species of iodoglucagon, which in turn depend on the pH of the medium. We conclude that incorporation of iodine atoms in the tyrosyl residues of glucagon has two major effects: (i) the iodine atom increases hydrophobic interaction of the hormone with the receptor and (ii) ionization of the phenoxy groups results in the loss of biological activity possibly as the result of loss of hydrogen bonding capability. Thus, the tyrosyl residues in glucagon are critically involved in the function of the hormone.     

Reaction of the carp Cyprinus carpio L. at different periods of its ontogeny to the action of organophosphorus compounds

Effect of some organic phosphorous compounds on the carp Cyprinus carpio L. in consecutive stages of its development has been studied. The least and most vulnerable stages in carp's development under the action of these compounds have been identified. The gravity of disorders in fish organism on early stages and the degree of pathological changes induced by organic phosphorous compounds have been shown. Embryotoxic and gonadotoxic effect of these compounds has been found.     

The purification of human enterokinase by affinity chromatography and immunoadsorption. Some observations on its molecular characteristics and comparisons with the pig enzyme.

A method is described for the purification of human enterokinase from accumulated duodenal fluid by affinity chromatography using p-aminobenzamidine as the ligand. Resolution was greatest when glycylglycine was substituted as the spacer arm. Purification was not a one-step procedure, and some contamination, principally by the alpha-glucosidases, remained. Their removal was completed by immunoadsorption using antisera raised to enterokinase-free material containing these enzymes, prepared as a by-product of the purification procedure. The final preparation had an activity of 4260 nmol of trypsin/min per mg and was free of other enzymic activity tested. Amino acid and sugar analyses of the highly purified enzyme indicated an acidic glycoprotein containing 57% sugar (neutral sugars 47%, amino sugars 10%). The apparent mol.wts. and Stokes radii of human and pig enterokinase were 296 000 and 316 000, and 5.65 and 5.78 nm respectively. Two isoenzymes were identified for human enterokinase and three for the pig enzyme. Human enterokinase demonstrated a resistance to reduction of disulphide linkages and to sodium dodecyl sulphate binding, which may be related to the need for it to retain its integrity in the digestive environment of the upper small intestine. Antisera to highly purified pig and human enterokinases specifically inhibited enterokinase activity. Immuno-inhibition of intestinal aminopeptidase, maltase and glucoamylase by homologous antisera was not observed.     

Adsorption of apolipoprotein A-IV to phospholipid monolayers spread at the air/water interface. A model for its labile binding to high density lipoproteins.

The mechanisms that mediate the labile binding of apolipoprotein A-IV (apoA-IV) to high density lipoproteins (HDL) are not known. We therefore used a surface balance and surface radioactivity detector to investigate the adsorption of apoA-IV to egg phosphatidylcholine monolayers spread at the air/water interface. ApoA-IV bound rapidly and reversibly to phospholipid monolayers and generated a maximum increase in surface pressure of 19 millinewtons (mN)/m at a subphase concentration of 2 x 10(-5) g/dl. Binding decreased linearly with increasing initial surface pressure; at pressures greater than 28-29 mN/m, apoA-IV could no longer penetrate the lipid monolayer. The area occupied by the amino acid residues in apoA-IV reached an unusually low limiting molecular area of 10-12 A2/residue at surface saturation. The surface pressure of native HDL3 was calculated to be 33 mN/m, and it rapidly decreased with the action of lecithin:cholesterol acyltransferase on the particle surface. We conclude that the surface activity of apoA-IV is lower than that of any other human apolipoprotein; its binding and surface conformation are particularly sensitive to pressure; and at saturation, a significant portion of the molecule is excluded from the interface. The exclusion pressure of apoA-IV may be only slightly lower than the surface pressure of HDL; in vivo, the action of lecithin:cholesterol acyltransferase and lipid transfer proteins may cause the HDL3 surface pressure to oscillate about a narrow range that spans the exclusion pressure of apoA-IV. The resultant labile association of apoA-IV and HDL may be of central importance to its role in lipoprotein metabolism.     

Changes in the tail of Ambystoma maculatum at different stages of metamorphosis: observations on tissue remodeling and its relationship to hydrolytic enzymes.

A system for staging A. maculatum during growth and metamorphosis was devised, based on several parameters of body size; body length, tail length and tail width. Animals at various stages of metamorphosis were employed to study the relationship between specific biochemical and histological changes that occur in the tail of this urodele during metamorphosis. The specific and total activity of two hydrolytic enzymes, acid phosphatase and beta-N-acetyl-glucosaminidase, were measured in tail tissues at progressive stages of development. The activities of these enzymes increased in both the fins and muscular portion of the tail during metamorphosis. These activities can be correlated with resorption of the tail fins and the remodeling of tissues in the muscular portion of the tail.     

Vaccination against the nematode Trichostrongylus colubriformis. III. Some observations on factors influencing immunity to infection in vaccinated guinea-pigs

Rothwell T. L. W. 1978. Vaccination against the nematode Trichostrongylus colubriformis. III. Some observations on factors influencing immunity to infection in vaccinated guineapigs. International Journal for Parasitology8: 33–37. Guinea-pigs were protected against infection with T. colubriformis when soluble material extracted from fourth-stage larvae was administered by the subcutaneous, intradermal, intraperitoneal and intraduodenal but not oral routes. The level of immunity following vaccination by the various effective routes was similar. Mature animals were found to respond significantly better to vaccination than immature animals. Significant immunity was present 10 days after vaccination but higher levels were found after 20 and 40 days. A single dose of vaccine was as effective as three divided doses. Finally, it was found that the adjuvant aluminium hydroxide gel, but not B. pertussis vaccine or levamisole improved the level of immunity to infection which followed vaccination.     

Curvature effect on hemodynamic conditions at the inner bend of the carotid siphon and its relation to aneurysm formation

Although high-impact hemodynamic forces are thought to lead to cerebral aneurysmal change, little is known about the aneurysm formation on the inner aspect of vascular bends such as the internal carotid artery (ICA) siphon where wall shear stress (WSS) is expected to be low. This study evaluates the effect of vessel curvature and hemodynamics on aneurysm formation along the inner carotid siphon. Catheter 3D-rotational angiographic volumes of 35 ICA (10 aneurysms, 25 controls) were evaluated in 3D for radius of curvature and peak curvature of the siphon bend, followed by univariate statistical analysis. Computational fluid dynamic (CFD) simulations were performed on patient-derived models after aneurysm removal and on synthetic variants of increasing curvature. Peak focal siphon curvature was significantly higher in aneurysm bearing ICAs (0.36±0.045 vs. 0.30±0.048 mm⁻¹, p=0.003), with no difference in global radius of curvature (p=0.36). In CFD simulations, increasing parametric curvature tightness (from 5 to 3 mm radius) resulted in dramatic increase of WSS and WSS gradient magnitude (WSSG) on the inner wall of the bend. In patient-derived data, the location of aneurysms coincided with regions of low WSS (<4 Pa) flanked by high WSS and WSSG peaks. WSS peaks correlated with the aneurysm neck. In contrast, control siphon bends displayed low, almost constant, WSS and WSSG profiles with little spatial variation. High bend curvature induces dynamically fluctuating high proximal WSS and WSSG followed by regions of flow stasis and recirculation, leading to local conditions known to induce destructive vessel wall remodeling and aneurysmal initiation.