Chirality of reverse micelles

Four chiral analogues of the surfactant Aerosol-OT (AOT) have been synthesized and characterized. All of them form reverse micelles in apolar solvents in the w₀ range 0–30 (w₀ = [water]/[tenside]). Reverse micellar solutions have been investigated by UV absorption and circular dichroism spectroscopies with the aim of clarifying whether the formation of the macromolecular micellar structure induces the appearance of new chromophoric bands or perturbs the existing ones. Methanolic solutions of the surfactants, in which no micellar aggregates are formed, were taken as references. One of the products 1(S),1′(S)-dimethylbisheptylsulphosuccinate sodium salt (MH-AOT) was capable of forming reverse micelles of relatively high water content (w₀ up to 40) and this process was accompanied by a specific increase in the intensity of the circular dichroism band associated with the ester absorbance of the molecule. As no concomitant changes were seen in the UV absorbance spectrum, it was concluded that this observation reflected conformational events occurring within the surfactant rather than chromophoric perturbation. These results are qualitatively similar to those found recently for lecithin reverse micelles which, however, form gels at sufficiently high water contents. The chiroptical properties of these supramolecular aggregates are compared with those of covalent macromolecular systems such as polypeptides.     

Biochemical and morphological modifications in rabbit Achilles tendon during maturation and ageing.

1. The plasma clearance of intravenously injected 125I-labelled mitochondrial malate dehydrogenase (half-life 7 min) was not influenced by previous injection of suramin and/or leupeptin (inhibitors of intralysosomal proteolysis). 2. Pretreatment with both inhibitors considerably delayed degradation of endocytosed enzyme in liver, spleen, bone marrow and kidneys. 3. The tissue distribution of radioactivity was determined at 30 min after injection, when only 3% of the dose was left in plasma. All injected radioactivity was still present in the carcass. The major part of the injected dose was found in liver (49%), spleen (5%), kidneys (13%) and bone, including marrow (11%). 4. Liver cells were isolated 15 min after injection of labelled enzyme. We found that Kupffer cells and parenchymal cells had endocytosed the enzyme at rates corresponding to 9530 and 156 ml of plasma/day per g of cell protein respectively. Endothelial cells do not significantly contribute to uptake of the enzyme. 5. Uptake by Kupffer cells was saturable, whereas uptake by parenchymal cells was not. This suggests that these cell types endocytose the enzyme via different receptors. 6. Previous injection of carbon particles greatly decreased uptake of the enzyme by liver, spleen and bone marrow.     

Calcitroic acid: biological activity and tissue distribution studies

Calcitroic acid was recently identified as a major metabolite of 1,25-dihydroxyvitamin D₃ (Esvelt, Schnoes, and DeLuca, Biochemistry 18, 3977, 1979). The metabolite was found to have little, although significant, activity in healing rickets, and causing bone mineral mobilization but elicited no significant elevation in intestinal calcium transport. The compound showed little affinity for either the serum 25-hydroxyvitamin D binding protein or the intestinal cytosol receptor for 1,25-dihydroxyvitamin D₃. Various tissues of the rat were examined for the presence of calcitroic acid following a 120-ng dose of 1,25-dihydroxy-[3α-³H]vitamin D₃. The metabolite was detected in liver, intestinal mucosa, kidneys, and blood with livers and mucosa containing the highest concentrations. In each of these tissues the calcitroic acid content increased during the period between 4 and 12 h after the dose. The presence of calcitroic acid in femurs was indicated but could not be confirmed. Bile duct cannulation reduced but did not abolish the intestinal calcitroic acid content. In addition to calcitroic acid, other polar metabolites of 1,25-dihydroxyvitamin D₃ were detected in these experiments.     

Inhibition of the biosynthesis of thyroglobulin with propranolol in the rat

Thyroglobulin biosynthesis was studied in thyroid glands of rats treated during 30 days with a daily dose of propranolol, a non-selective beta-adrenergic blocking drug. Studies were carried out by extraction of soluble proteins from homogenates after incubation of the glands in presence of [3H]-4,5-L-leucine and [3H]-D-1-galactose. Thyroglobulin 19S, 12S and 4-8S soluble proteins were separated and identified by ultracentrifugation in a saccharose gradient. The glands of rats treated with propranolol showed a decreased amount of soluble proteins as well as a decreased incorporation of [3H] labeled markers. 19S thyroglobulin is poorly represented, but very large amounts of the 12S monomer are present; this suggests an impairment in the dimerization of the 12S subunit, absent in normal controls. This impairment could be due to a structure modification. Propranolol reduces the biosynthesis of thyroglobulin in thyroid gland as well as the formation of T3 from T4 in peripheral tissues; its therapeutical use against thyrotoxicosis is thus justified. The study of its action on the dimerisation of the 12S subunit could be of interest to clear the mechanism of thyroglobulin biosynthesis.     

Characterization and kinetics of isoenzymes of pyruvate kinase from developing castor bean endosperm

Isozymes of pyruvate kinase (PK) have been isolated from developing castor bean endosperm. One isozyme, PK_c, is localized in the cytosol, and the other, PK_p, is in the plastid. Both isozymes need monovalent and divalent cations for activity, requirements which can be filled by K⁺ and Mg²⁺. Both isozymes are inhibited by citrate, pyruvate, and ATP. PK_c has a much broader pH profile than PK_p and is also more stable. Both have the same K_m (0.05 millimolar) for PEP, but PK_p has a 10-fold higher K_m (0.3 millimolar) for ADP than PK_c (0.03 millimolar). PK_c also has a higher affinity for alternate nucleotide substrates than PK_p. The two isozymes have different kinetic mechanisms. Both have an ordered sequential mechanism and bind phosphoenolpyruvate before ADP. However, the plastid isozyme releases ATP first, whereas pyruvate is the first product released from the cytosolic enzyme. The properties of the two isozymes are similar to those of their counterparts in green tissue.     

Production of the mosquito-parasitic fungus,Coelomomyces dodgei,through synchronized infection and growth of the intermediate copepod host,Cyclops vernalis

High yields of the copepodCyclops vernalis infected with the mosquito-parasitic fungusCoelomomyces dodgei Couch & Dodge were obtained by infecting nauplii in large synchronously developing populations. Exposure of 2000 48 or 72 h old nauplii to 6×10³ sporangia at the time of meiospore release yielded ca. 1500 infected copepods. Based on yields of infected copepods, susceptibility ofC. vernalis toC. dodgei decreased as copepods developed. Infection rates were 75% for copepods exposed as 48 or 72 h old nauplii but declined to 32 and 9.6%, respectively, for those exposed as copepodids or adults. The relevance of these results for domestication of other species ofCoelomomyces and studies on non-target organisms is discussed, and improved procedures for routine production ofC. dodgei are described.     

NADH-coupled spectrophotometric assay of tyrosine aminotransferase

A rapid spectrophotometric method for estimation of tyrosine aminotransferase activity (TAT) is described, based on a coupled reaction with NADH-dependent aromatic ketoacid reductase. 3-iodo-L-tyrosine, upon TAT action, is transformed into 3-iodo-4-hydroxyphenylpyruvate which quickly reacts with NADH in the presence of aromatic ketoacid reductase; oxidation rates at 340 nm are linear with protein concentration over the whole range of purification steps of TAT. This new method, for its sensitivity, easy performance and possibility of a continuous monitoring of TAT reaction, may be considered comparable to the more diffuse spectrophotometric standard method, and also as an alternative, advantageous procedure in some instances. The method for purification of the coupled aromatic ketoacid reductase is also described.     

Isolation of an iridovirus from two terrestrial isopods,the pill bug, Armadillidium vulgare, and the sow bug, Porcellio dilatatus

An iridovirus was isolated from two terrestrial isopods (class Crustacea, order Isopoda), the pill bug, Armadillidium vulgare, and the sow bug, Porcellio dilatatus, collected in southern California. The isolates have been designated Type 31 (from A. vulgare) and Type 32 (from P. dilatatus). Diseased isopods were recognized by a characteristic blue discoloration of the normally gray cuticle. Based on the relative number of virions observed in diseased cells, viral replication was most extensive in epidermal, muscle, and adipose tissue. Additionally, small clusters of midgut epithelial cells were heavily infected in many specimens, although replication throughout this tissue was never observed. Nerve and reproductive tissues were lightly infected. Infection was not observed in hemocytes or the hepatopancreatic caeca. Virions of both isolates measured ca. 125 nm in diameter in ultrathin sections and 141 nm in negatively stained preparations, and formed paracrystalline arrays in heavily infected cells. The isolation of a typical iridovirus from isopods further demonstrates that the natural host range of this virus group extends beyond the class Insecta.