bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of Newly Formed Fatty Acids Among Glycerolipids of Isolated Perfused Rat Liver
Authors: Kuksis A. , Myher J. J. , Marai L. , Yeung S. K. F. , Steiman I. , Mookerjea S.
Published: December 2009

Livers of chow fed rats were perfused 1–3 h with buffer, glucose, albumin, and red blood cells, made up in 100% D2O. Glycerolipids were isolated and the deuterated fatty acids determined by gas chromatography with mass spectrometry on Silar 5 CP. Percentage of replacement by deuterated acids ranged from 1 to 14, of which palmitate was 87%. Differences were found in total lipid class and in subcellular distribution of the newly synthesized acids. Microsomes had 37% more deuterated acids than the total or floating fat. At 3 h the highest replacement was found in diacylglycerols (17%) and free fatty acids (11%). Of the palmitate in hepatic choline and ethanolamine phosphatides, 6.9% and 4.7%, respectively, contained dueterium. The serine and inositol phosphatides had a higher proportion of deuterated palmitate (7.7%) than other phosphatides. The data support the hypothesis that palmitate is incorporated into glycerolipids largely via de novo synthesis while stearate enters them by deacylation – acyl transfer replacement.
Carboxylesterases (EC 3.1.1). Purification and Titration of Chicken, Sheep, and Horse Liver Carboxylesterases
Authors: Inkerman Peter A. , Scott Keith , Runnegar Maria T. C. , Hamilton Susan E. , Bennett Ernest A. , Zerner Burt
Published: December 2009

Chicken, sheep, and horse liver carboxylesterases have been purified by procedures involving ammonium sulfate fractionation, ion-exchange chromatography and gel filtration on Sephadex. The actual yields of the procedures described were as follows: chicken, 1 g from 2 kg of liver powder (chloroform–acetone); sheep, 200 mg from 400 g of powder (chloroform–acetone); horse, 230 mg from 800 g of powder (acetone). The purified enzymes are free of non-carboxylesterase protein as shown by gel electrophoresis, although they do contain electrophoretic variants. The equivalent weight of the chicken enzyme is 67 000 based on titration with p-nitrophenyl diethyl phosphate or bis(p-nitrophenyl) phosphate, whereas those of the sheep and horse enzymes are ~69 500 and ~70 000, respectively, based on titration with p-nitrophenyl dimethylcarbamate.
The Effect of Temperature on the Rate of Conversion of p,p′-DDT to p,p′-DDE in Brook Trout (Salvelinus fontinalis)
Authors: Zinck M. E. , Addison R. F.
Published: December 2009

Brook trout (Salvelinus fontinalis) were maintained in flowing fresh water at 2, 10, and 18 °C and injected intramuscularly with p,p′-[14C]DDT. Fish were killed at intervals up to 16 weeks after injection, and analyzed by a combination of thin-layer chromatography, gas-liquid chromatography, and liquid-scintillation counting. Only one labelled metabolite, p,p′-DDE, was detected during the experimental period. Its rate of production varied with temperature; after 16 weeks, about 9, 13, and 19% of the original p,p′-DDT in fish maintained at 2, 10, and 18 °C, respectively, had been converted.
DNA from Eukaryotic Cells Contains Unusually Long Pyrimidine Sequences
Authors: Birnboim H. C. , Straus N. A.
Published: December 2009

Analysis of DNA samples from several different organisms revealed the presence of unexpectedly long pyrimidine tracts (polypyrimidines), ranging in size from about 25 to 200 nucleotides in length. This fraction of the DNA accounted for 0.07–0.8% of the total thymidine residues. Pyrimidine clusters of this length and amount would not be expected on a random basis, suggesting they may have been conserved during evolution because they are required for a specialized function(s).
Citrate Transport in Guinea Pig Heart Mitochondria
Authors: Robinson B. H. , Oei J.
Published: December 2009

Guinea pig heart mitochondria loaded with [14C]citrate show exchanges of radioactivity at 30 °C with added citrate, L-malate and phosphoenolpyruvate. These exchanges are inhibited by benzene-1,2,3-tricarboxylate.Measurements of rates of citrate transport indicate that the activity of this transporting system is low in heart mitochondria compared to that observed in liver mitochondria. The Km values obtained indicate a similarity to those obtained in liver. Citrate oxidation by coupled mitochondria was also found to be slow at 30 °C but was inhibited by benzene-1,2,3-tricarboxylate. The role of mitochondrial citrate transport in control of glycolytic flux in the heart is discussed.
The Effect of Polychlorinated Biphenyl on Steroidogenesis and Reproduction in the Brook Trout (Salvelinus fontinalis)
Authors: Freeman H. C. , Idler D. R.
Published: December 2009

Livers from brook trout (Salvelinus fontinalis) held in water containing 3.8 p.p.m. (mg/1) Corexit and in water containing 3.8 p.p.m. Corexit + 0.2 p.p.m. polychlorinated biphenyl (PCB) were firmer in texture than livers taken from control trout held in fresh water. The testes from the PCB-treated trout were darker in color, smaller in size, contained less spermatic fluid, and appeared to be regressed when compared with testes from the control fish.Only 72% of the eggs from PCB-treated trout hatched compared to 92% for control eggs when eggs were incubated in fresh water. Fertilized eggs incubated in water containing 0.2 p.p.m. PCB + 3.8 p.p.m. Corexit resulted in less than 1% of the eggs from the untreated fish and none of the eggs from PCB-treated fish being hatched. The young fish from the control group lived only a few days in the water containing PCB.PCB greatly stimulated the in vitro 11β-hydroxylation of testosterone by trout testicular tissue. There was no significant change in 11-ketotestosterone blood levels in maturing brook trout after treatment with 3.8 p.p.m. Corexit or 3.8 p.p.m. Corexit + 0.2 p.p.m. PCB for 21 days during the final stages of maturation. It is thought that sublethal levels of PCB can interfere with the reproduction process in this species.
An Incubation Medium for the Elevation of Adenosine Triphosphate and 2,3-Diphosphoglycerate in Fresh and Long-Preserved Human Erythrocytes
Authors: Rubinstein David , Warrendorf Elizabeth
Published: December 2009

The levels of adenosine triphosphate (ATP) and 2,3-diphosphoglycerate in freshly drawn human erythrocytes can be tripled by a 2 h incubation at 37 °C in a medium containing 21 mM glucose, 1.8 mM adenine, 5 mM pyruvate, 10 mM inosine, and 96 mM phosphate. Similar incubation conditions will restore the levels of ATP and 2,3-diphosphoglycerate in erythrocytes from blood preserved for 12 and 15 weeks, respectively, to those of fresh cells. Omission of pyruvate from the incubation medium further increases the level of ATP slightly, but there is little elevation of 2,3-diphosphoglycerate. Under these conditions labelled pyruvate and lactate production from [14C]glucose or [14C]inosine is not diminished, but labelled fructose 1,6-di-phosphate, rather than 2,3-diphosphoglycerate, accumulates. In addition, omission of pyruvate from the incubation medium, with a concomitant decrease in accumulation of 2,3-diphosphoglycerate, diminishes the concentration of inorganic phosphate required for optimal ATP elevation.A 5 h incubation in the glucose–adenine–pyruvate–inosine–phosphate medium elevates the levels of ATP and 2,3-diphosphoglycerate in erythrocytes from blood preserved in the cold for 15 weeks to twice that of fresh cells, indicating that the cells retain their metabolic potential even after prolonged storage at 2 °C. The medium may provide a method of rejuvenating 10–12 week cold-preserved erythrocytes for transfusion purposes, by a 1 h incubation at 37 °C.
Effect of Modifiers on the Hydrolysis of Basic and Neutral Peptides by Carboxypeptidase B
Authors: Moore Graham J. , Benoiton N. Leo
Published: December 2009

The initial rates of hydrolysis of Bz-Gly-Lys and Bz-Gly-Phe by carboxypeptidase B (CPB) are increased in the presence of the modifiers β-phenylpropionic acid, cyclohexanol, Bz-Gly, and Bz-Gly-Gly. The hydrolysis of the tripeptide Bz-Gly-Gly-Phe is also activated by Bz-Gly and Bz-Gly-Gly, but none of these modifiers activate the hydrolysis of Bz-Gly-Gly-Lys, Z-Leu-Ala-Phe, or Bz-Gly-phenyllactic acid by CPB. All modifiers except cyclohexanol display inhibitory modes of binding when present in high concentration.Examination of Lineweaver–Burk plots in the presence of fixed concentrations of Bz-Gly has shown that activation of the hydrolysis of neutral and basic peptides by CPB, as reflected in the values of the extrapolated parameters, Km(app) and keat, occurs by different mechanisms. For Bz-Gly-Gly-Phe, activation occurs because the enzyme–modifier complex has a higher affinity than the free enzyme for the substrate, whereas activation of the hydrolysis of Bz-Gly-Lys derives from an increase in the rate of breakdown of the enzyme–substrate complex to give products.Cyclohexanol differs from Bz-Gly and Bz-Gly-Gly in that it displays no inhibitory mode of binding with any of the substrates examined, activates only the hydrolysis of dipeptides by CPB, and has a greater effect on the hydrolysis of the basic dipeptide than on the neutral dipeptide. Moreover, when Bz-Gly-Lys is the substrate, cyclohexanol activates its hydrolysis by CPB by increasing both the enzyme–substrate binding affinity and the rate of the catalytic step, an effect different from that observed when Bz-Gly is the modifier.The anomalous kinetic behavior of CPB is remarkably similar to that of carboxypeptidase A, and is a good indication that both enzymes have very similar structures in and around their respective active sites. A binding site for activator molecules down the cleft of the active site is proposed for CPB to explain the observed kinetic behavior.
A Rapid and Sensitive Auxin Binding System for Detecting N6-Substituted Adenines, and Some Urea and Thiourea Derivatives, that Show Cytokinin Activity in Cell Division Tests
Authors: LéJohn H. B.
Published: December 2009

A selective, sensitive and rapid (2 min or less) method for detecting compounds with potential for cytokinin activity is described. The method does not measure cytokinesis; instead, it determines the ability of cytokinin-active agents to (i) activate the intake of either L-tryptophan or indoleacetic acid by germinated spores of the water-mould Achlya, while inhibiting the energy-dependent transport of all L-amino acids usually found in proteins; (ii) inhibit the energy-dependent transport of nucleosides and sugars by the same organism. The compounds with cytokinin activity generally activate auxin (tryptophan) intake at 10−8 M or greater and inhibit at 10−6 M or greater. The most effective activating compounds were N6-(Δ2-isopentenyI)adenine, N6-benzyladenine, N6-furfuryladenine, and N6-(trans-hydroxy-3-methyl-but-2-enyl)adenine. These compounds are classed generally as cytokinins in plant growth studies.A cell membrane - localized glycopeptide of molecular weight 6000 was isolated from this organism and shown to be the site at which cytokinins, auxin, and tryptophan bind. An earlier study had also established that calcium ions bind to this entity as well. Tryptophan binding to the glycopeptide was enhanced by cytokinins, suggesting that this may be the way in which whole cells display enhanced tryptophan binding in the bioassay. On the other hand, calcium binding was antagonized by cytokinin.The results suggest that this may be an important experimental system for use in studying one possible way in which cytokinin may regulate plant growth.
Biosynthesis of Mitochondrial Phospholipids Using Endogenously Generated Diglycerides
Authors: McMurray W. C.
Published: December 2009

When isolated mitochondria or microsomes from rat liver were treated with phospholipase C, the incorporation of radioactive phospholipid precursors was markedly enhanced, presumably as a result of production of diglycerides by hydrolysis of endogenous phospholipids. Incorporation of CDP[14C]choline into lecithin in rat liver or BHK-21 mitochondria could be attributed to residual contamination from elements of the endoplasmic reticulum, with added diglycerides or with endogenous diglycerides produced by the phospholipase C treatment. A similar stimulation of [γ32P]ATP incorporation into phospholipids was observed with exogenous or endogenous diglycerides, but the mitochondrial diglyceride kinase in either case was also related to the degree of microsomal contaminants. It was concluded that previous studies showing negligible capacity of mitochondria for lecithin biosynthesis de novo were not explainable on the basis of limited accessibility of added diglycerides, and that formation of phosphatidic acid by diglyceride kinase was not of significance in rat liver mitochondria.
Nutritional Control of Differentiation (Sclerotization) of the Myxomycete Physarum flavicomum
Authors: Henney Jr. Henry R. , Maxey Glenna
Published: December 2009

During differentiation (sclerotization) of the Myxomycete Physarum flavicomum, the acellular Plasmodium converts into numerous dormant cells surrounded by cell walls. This work establishes that a condition of nutrient imbalance triggers the differentiation process. Specifically, the unavailability of an adequate spectrum of amino acids in the medium initiates the metabolic and morphological alterations characteristic of the sclerotizing Plasmodium.In the absence of extracellular amino acids, the cellular pool of amino acids and cellular protein were catabolized as differentiation proceeded. The pattern of amino acids in the cellular pool also changed during differentiation, as the content of pool amino acids was reduced at least 75%. The decrease in protein content was negligible after 12 h incubation but was about 40% at 48 h when differentiation was complete. However, in the presence of extracellular amino acids, protein degradation, amino acid pool depletion, and differentiation were all inhibited. Ammonium ions (12.4 mM) similarly delayed differentiation.Differentiation, amino acid pool depletion, and the degradation of cellular protein readily occurred in the presence of an extracellular supply of dextrose, which stimulated cell wall formation. The effect of dimethyl sulfoxide, cyclic 3′,5′-adenosine monophosphate, glutathione, diamide, and other compounds on the differentiation process are reported also.
The Tris-Catalyzed Isomerization of Potassium D-Glucose 6-O-sulfate
Authors: Fitzgerald John W.
Published: December 2009

Potassium D-glucose 6-O-[35S]sulfate was partially converted by Tris (≥25 mM, pH 7.5) to 35SO42−, fructose, and a 35S-labelled compound which was tentatively identified as fructose 6-O-sulfate. The isomerization reaction was also catalyzed by ethanolamine and 2-dimethylaminoethanol but not by glycine, triethanolamine, or pentaerythritol. The significance of these findings in relation to kinetic studies of the enzyme glycosulfatase is discussed.
The Isolation and Characterization of the Plasma Membrane of Cultured Chinese Hamster Ovary Cells
Authors: Juliano R. L. , Gagalang E.
Published: December 2009

Plasma membranes were prepared from cultured Chinese hamster ovary cells utilizing a two-phase polymer system and were characterized by enzymatic and chemical assay, and by electron microscopy. The usual degree of purification of presumptive membrane markers such as Na+–K+ ATPase (ATP phosphohydrolase, EC 3.6.1.3) ranged from three-to eightfold. Gel electrophoresis in SDS revealed several polypeptides and two glycopeptides which were enriched in the plasma membrane fraction.
The Preparation of Some Biochemically Important Aldehydes
Authors: Duncan R. Julian S.
Published: December 2009

Methods for the preparation of 3,4-dihydroxyphenylacetaldehyde, 4-hydroxy-3-methoxyphenylacetaldehyde, and 3,4-dihydroxyphenylglycolaldehyde are described. Michaelis constants and maximal velocities for the reduction of a number of biologically important aldehydes by horse liver alcohol dehydrogenase and NADH are tabulated.
Comparison of the Effect of Various Methods of Dissociation on the Protein Composition of Rat Liver Ribosomal Subunits
Authors: Hanna Nabil , Godin Claude
Published: December 2009

Rat liver ribosomes were dissociated into subunits using EDTA, sodium pyrophosphate, high concentrations of KCl, as well as by incubation with puromycin in presence of 0.5 M KCl. The subunits obtained were analyzed using the density gradient centrifugation technique and their ribosomal proteins were separated by means of two-dimensional polyacrylamide gel electrophoresis. The ribosomal protein patterns of the two subunits isolated using each of the dissociating method were compared to the protein patterns of monosomes prepared by puromycin treatment alone. Our results revealed that the use of chelating agents to dissociate the ribosomes resulted in the loss of some ribosomal proteins from the small subunit. On the other hand, the use of KCl in high concentrations to dissociate the ribsosomes did not appear to cause any major loss of proteins from the ribosomes except for some acidic proteins.
Inhibition of Phosphatidylethanolamine Biosynthesis in Baby Hamster Kidney-21 Cells Infected with Semliki Forest Virus
Authors: Vance Dennis E. , Dahlke Rita M.
Published: December 2009

Semliki Forest virus inhibits phosphatidylethanolamine biosynthesis in baby hamster kidney-21 cells 6 h after infection. Viral infection reduced the incorporation of [1,2-14C]-ethanolamine into intact cells by approximately 50%. A similar reduction in the activity of the ethanolaminephosphotransferase (EC 2.7.8.1) was also observed. The apparent Km for CDPethanolamine was 60 μM for the microsomal enzymes from infected or mock-infected cells. In addition, exogenous diglyceride only stimulated by 1.5-fold the ethanolaminephosphotransferase from virus- or mock-infected cells, whereas the same diglyceride preparations stimulated the cholinephosphotransferase (EC 2.7.8.2) from baby hamster kidney cells by sixfold. Generation of endogenous diglyceride by pretreatment of the microsomes with phospholipase C (EC 3.1.4.3) stimulated the activity of the cholinephosphotransferase but not the ethanolaminephosphotransferase. Semliki Forest virus does not inhibit all microsomal enzymes, since the activities of NADH- K3Fe(CN)6 reductase and NADH dehydrogenase (EC 1.6.99.3) were not affected. The ethanolaminephosphotransferase from virus- and mock-infected cells showed similar profiles of activity as a function of temperature; this result and other studies suggest that that membranous environment of the ethanolaminephosphotransferase was not significantly modified by the virus.
Purification and Characterization of a Trypsin Inhibitor from Solanum tuberosum
Authors: Rouleau Maurice , Lamy François
Published: December 2009

A trypsin inhibitor isolated from a potato acetone powder has been purified by affinity chromatography. This protein inhibits trypsin mole per mole. To a lesser extent it combines also with chymotrypsin and elastase. For trypsin, Ki = 8 × 10−7 M. The inhibitor has a single polypeptide chain of 207 amino acid residues. It contains no sugar or free sulfhydryl groups. Its extinction coefficient E2801% = 10.3 and its isoelectric point is 6.9. Its molecular weight is of the order of 21 000–22 000, as determined by sedimentation equilibrium, by inhibition experiment or from its amino acid composition. These same techniques, taken together with the single band observed at different pH on polyacrylamide gel electrophoresis, indicate that the protein purified is monodisperse. However, the finding of two N-terminal amino acid residues, leucine and aspartic acid, and the different stoichiometry observed during the interaction of the inhibitor, either with trypsin or with chymotrypsin and elastase, raises the possibility that our preparation is contaminated by a polyvalent inhibitor not detectable by physicochemical methods.
Liver Cell Plasma Membrane Lipids and the Origin of Biliary Phospholipid
Authors: Yousef I. M. , Bloxam D. L. , Phillips M. J. , Fisher M. M.
Published: December 2009

The liver cell plasma membranes of fed male Wistar rats were separated into a fraction rich in bile canaliculi and the remainder of the plasma membrane. Electron-microscopically, the bile canalicular fraction consisted almost exclusively of intact bile canaliculi with their contiguous membranes. The remaining plasma membrane fraction consisted primarily of vesicles and sheets of membranes essentially free from bile canaliculi. The bile canalicular membrane fraction contained relatively more total lipid, cholesterol, and phospholipid, and relatively less protein. Although the phospholipid composition of the two fractions was the same, the specific activity of the bile canalicular membrane phospholipids, up to 12 h following in vivo administration of [2-3H]glycerol, was always significantly greater than that of the remaining plasma membranes, and showed a biphasic response not found in the latter. The specific activity of the phosphatidylcholine, phosphatidylethanolamine and lysophosphatidylcholine of the bile canalicular membranes rose to a peak within 40 min after administration of the label, fell sharply and then rose to a second peak after 120 min. The specific activity of the sphingomyelin and phosphatidylserine plus phosphatidylinositol of the bile canalicular membranes and of all the phospholipids of the remaining plasma membranes did not show the biphasic pattern but increased steadily to reach a maximum at 120 min. The specific activity of biliary phosphatidylcholine followed a pattern identical to that of the phosphatidylcholine, phosphatidylethanolamine and lysophosphatidylcholine of the bile canalicular membrane fraction. These results show that the average rate of turnover of phospholipid in the bile canalicular membranes is considerably greater than that in the remaining plasma membrane and other cell membrane fractions; they indicate that the phospholipid of the bile canalicular membranes exists in two or more pools, turning over at different rates; and they support the concept that biliary phospholipid is derived from the bile canalicular membrane. The results also suggest that bile canalicular phospholipid may be derived from two different sources, in contrast to the remaining plasma membrane.
Studies of the Metabolism of Asialotransferrins: the Metabolic Heterogeneity of Human Asialotransferrin
Authors: Regoeczi E. , Wong K.-L. , Hatton M. W. C.
Published: December 2009

Catabolism of human transferrin and human asialotransferrin was simultaneously studied in guinea pigs by means of total body radioactivity measurements. Total body activity representing transferrin decreased at a constant rate with an average half-life of 88 h. Decrease of the total body activity representing asialotransferrin exhibited at least two rates; the half-life of the fast initial component averaged at 25 h, whereas the half-life of the slower component averaged at 55 h. Transition occurred between the 50th and 80th hours of the experiments.The complex character of the elimination curves could not be explained by differences in the iron content of asialotransferrin, by the presence of transferrin variants or of denatured protein in the injected material, by residual sialic acid in the preparations, by accumulation of radioactive terminal catabolic products in the body, by an association of asialotransferrin with any other macromolecular plasma constituent, by changing conditions for mass action, or by a continuing return of labeled protein from the extravascular space. Injection of bovine asialotransferrin into guinea pigs did not result in complex total body curves. Analyses of guinea pig tissues demonstrated that human asialotransferrin had marked affinity for the liver and none for the kidney, lung, or spleen.These observations are consistent with the hypothesis that the glycopeptides in human transferrin are hetegrogeneous in that removal of the sialyl residues exposes structures with different affinities for the hepatic asialoglycoprotein receptor. The precise chemical basis for the metabolic heterogeneity is unknown.
Properties of a Free and a Solubilized Form of Bound α,α-Trehalase Purified from Honey Bee Thorax
Authors: Talbot B. G. , Muir J. G. , Huber R. E.
Published: December 2009

The free and bound forms of α,α-trehalase (EC 3.2.1.28) of the honey bee thorax were separated and the bound enzyme was solubilized by raising the pH to 8.0 for 10 h. Both enzymes were purified. They were homogeneous as determined by several electrophoretic criteria. It was found that the two enzymes had very similar Km's (each about 0.89 mM), Vm's (53.2 and 54.3 U/mg for free and solubilized, respectively), inhibition characteristics, specificities (both only hydrolyzed α,α-trehalose), pH maxima (each had maxima at about 3.5 and 6.5), molecular weights (65 000), isoelectric points (5.1), reactivities to sulfhydryl reagents, electrophoretic mobilities, activation energies (about 12.8 kcal/mol), and similar stabilities to heat, pH, and urea. Some significant differences between the two enzymes were, however, found: the solubilized α,α-trehalase floated at 70% saturation of ammonium sulfate while the free α,α-trehalase did not; the solubilized α,α-trehalase did not dissociate into subunits as readily as did the free one; and the solubilized α,α-trehalase was found to bind more readily to a hydrophobic grouping than the free enzyme. In addition to these comparisons, three new findings relating to thorax α,α-trehalases are reported. (1) Thorax α,α-trehalases are strongly inhibited by β-glucosides (Ki values of about 8 × 10−4 M); (2) under certain conditions thorax α,α-trehalases from honey bees dissociated into subunits of one-half the normal molecular weight; (3) honey bee thorax α,α-trehalases have unusual biphasic pH activity profiles.
Studies on Adenylate Cyclase – Cyclic AMP System of the Myopathic Hamster (UM-X7.1) Skeletal and Cardiac Muscles
Authors: Harrow J. A. C. , Singh J. N. , Jasmin G. , Dhalla N. S.
Published: December 2009

Cyclic AMP content, adenylate cyclase (EC 4.6.1.1) activity and phosphodiesterase I (EC 3.1.4.1) activity of the hind leg skeletal muscle and cardiac muscle in 60- and 150-day-old normal and myopathic (UM-X7.1) hamsters were examined. In 60-day-old myopathic animals, cardiac cyclic AMP levels were higher and phosphodiesterase I activity was lower, without any changes in the basal adenylate cyclase activity, whereas in 150-day-old myopathic hamsters, cardiac cyclic AMP and basal adenylate cyclase activity were lower, without any changes in the homogenate phosphodiesterase I activity. On the other hand, basal adenylate cyclase and phosphodiesterase I activities in the skeletal muscle homogenate from 60- and 150-day-old myopathic animals were not different from the normal values but the skeletal muscle cyclic AMP levels were significantly less in 60-day-old myopathic hamsters only. The plasma cyclic AMP levels in 60-day-old myopathic hamsters, unlike 150-day-old myopathic animals, were higher than the normal. Although these results reveal differences in myopathic cardiac and skeletal muscles, it is concluded that changes in adenylate cyclase – cyclic AMP system in myopathy are dependent upon the degree of disease.
Piperonyl Butoxide, a Potent Inhibitor of Potato Spindle Tuber Viroid in Scopolia sinensis
Authors: Singh R. P. , Michniewicz J. J. , Narang S. A.
Published: December 2009

Piperonyl butoxide has been found to act as potent inhibitor for potato spindle tuber viroid in Scopolia sinensis Hemsl plant.
Evidence for 16α-Hydroxylation of Estrone 3-Sulphate by Guinea Pig Liver Slices
Authors: Hobkirk R. , Nilsen Mona , Jennings Barbara
Published: December 2009

[6,7-3H, 35S]Estrone 3-sulfate (E13S) of 3H/35S = 3.57 was incubated with female guinea pig liver slices. Small amounts of free steroid and estrone-3-glucuronide, each containing 3H, were found. In addition, E13S, 17β-estradiol 3-sulfate, and a 'disulfate' fraction, with 3H/35S = 4.4, 4.3, and 4.7, respectively, were also isolated from the incubated tissue. The latter fraction was a major metabolite and about 45% of it consisted of 'disulfates' of 16α-hydroxyestrone and estriol, thus providing strong evidence for 16α-hydroxylation in guinea pig liver slices.
An Endogalactosaminidase from Streptomyces griseus
Authors: Reissig Jose L. , Lai Wei-Hsien , Glasgow James E.
Published: December 2009

An endogalactosaminidase has been purified 34-fold from the culture filtrate of Streptomyces griseus. This enzyme cleaves GalN–GalN linkages in oligogalactosaminoglycan, a galactosamine-rich oligosaccharide isolated from the culture filtrate of a Neurospora mutant. Since some or all of the GalN–GalN bonds in this molecule link positions 1 and 4, and are in the α-configuration, we are probably dealing with an endo-α-(1 → 4)-galactosaminidase, but this characterization is only tentative because the few bonds cleaved by the enzyme could have a different structure. The enzyme is inactive towards N-acetyl-oligogalactosaminoglycan and chitosan.The endogalactosaminidase preparations also cleave high molecular weight galactosaminoglycan (obtained from Neurospora) into fragments [Formula: see text] daltons in molecular weight, and catalyze the release of Neurospora sporelings from the glass surfaces to which they are anchored. Galactosaminoglycan-cleaving and sporeling-releasing activities elute jointly from DEAE-cellulose columns. This observation provides further support for an earlier proposal that the sporelings are anchored to the glass by means of galactosaminoglycan molecules.
Quantitative Effects of Unsaturated Fatty Acids in Microbial Mutants. IV. Lipid Composition of Saccharomyces cerevisiae When Growth is Limited by Unsaturated Fatty Acid Supply
Authors: Holub Bruce J. , Lands William E. M.
Published: December 2009

The Saccharomyces cerevisiae mutant KD46 (ole 2), which is unable to synthesize unsaturated fatty acids, was grown on limiting amounts of different added unsaturated fatty acids. The acyl chain composition of the cellular lipid classes was determined in these cultures at different stages of growth. During growth on added oleic acid, there was no marked change in the mole percentage of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, or phosphatidylserine among the total phospholipids.Cells grown on palmitoleic, oleic, or linoleic acid showed a steady decrease in their total phospholipid levels per cell concomitant with a decrease in growth rate approaching minimal levels at stationary phase. Furthermore, the mole percentage of the supplemented unsaturated fatty acid in the cellular phospholipids also decreased during growth and attained minimal values when growth ceased.At stationary phase the total phospholipid content per cell was similar for cells grown on a wide range of fatty acids or mixtures thereof, whereas the composition of the fatty acids in the cellular phospholipids were strikingly different. The differences in efficiencies for supporting growth of most of the unsaturated fatty acids tested did not seem due to the extent of their incorporation into cellular phospholipids, but rather to differences in the ability of the derived membrane phospholipids to support cellular functions.Palmitoleate, oleate, linoleate, linolenate, arachidonate, eicosapentaenoate, and docosahexaenoate all appeared to contribute to the functionality of cellular membranes in an additive linear manner. Thus, the contribution of these acids to cellular growth can be characterized by a functionality factor that seems independent of the mixtures of acids supporting growth. Use of the functionality concept allows the cumulative influence of many different acids to be summarized quantitatively by a single number rather than resorting to qualitative descriptions of the degree of unsaturation or 'fitness' of the membrane phospholipids.
Differences in Chemical Composition Between the Epithelial Glycoproteins of the Upper and Lower Halves of Rat Colon
Authors: Reid P. E. , Culling C. F. A. , Dunn W. L. , Ramey C. W. , Clay M. G.
Published: December 2009

Analysis of the apparently homogeneous sulfated sialoglycoproteins isolated from the epithelial cells of the upper (proximal to the ileum) and lower (proximal to the rectum) halves of Wistar rat colon showed that whereas they were similar in overall carbohydrate and amino acid composition, they differed significantly in the O-acetyl substitution pattern of their constituent sialic acids.The glycoprotein from the upper half of the colon was found to contain a larger percentage of sialic acid substituted at C7 and/or C8, as well as at C4 and C7 and/or C8; it contained less sialic acid which was unsubstituted as well as less substituted at C4 alone.It has been shown that differences in substitution at C7 and/or C8 can be detected by analysis of the 105 000 g supernatants prepared from homogenates of isolated epithelial cells or fresh or formol calcium fixed whole colonic tissue.
17-Oxidoreduction of 17β-Estradiol, Estrone and Their 3-Sulfates by Kidney Slices from Guinea Pig and Human
Authors: Hobkirk R. , Nilsen Mona , Jennings Barbara
Published: December 2009

Slices of whole kidney and kidney cortex from the female guinea pig catalyzed a marked reduction of estrone 3-sulfate (E13S) and estrone (E1) to 17β-estradiol 3-sulfate (E23S) and 17β-estradiol (E2), respectively, as well as the reverse (dehydrogenation) reactions. Slices of medulla did not appear active in E23S–E13S interconversion but did possess the ability to interconvert E2 and E1, besides possessing considerable sulfatase activity. The use of [3H-35S]E13S and [3H-35S]E23S as substrates, together with a demonstrated lack of estrogen sulfate synthesis by the tissue slices, provided ample evidence that the intact sulfates were involved in direct oxidoreduction. Slices of human kidney cortex catalyzed the reduction of E13S to a very limited extent. Slices of whole kidney and of cortex from guinea pig formed small amounts of estrogen glucuronide(s).
Inhibition of Lymphocyte Transformation: Effect of Soy Bean Trypsin Inhibitor and Synthetic Anti-Proteases
Authors: Moreau Pierre , Dornand Jacques , Kaplan J. G.
Published: December 2009

Soybean trypsin inhibitor (SBI) was found to inhibit transformation of human lymphocytes induced by mitogens (leucoagglutinin, concanavalin A, NaIO4) or in mixed lymphocyte reaction (MLR). SBI covalently cross-linked to Sepharose beads inhibited the MLR and mitogen stimulation virtually completely. We have confirmed the work of others which showed that the synthetic anti-proteases e-aminocaproic acid and tosyl-L-lysyl-chloromethane (TLCK) also inhibited mitogen-induced blastogenesis and we have shown that phenylmethylsulfonylfluoride was effective also; all of these agents were found to inhibit the MLR as well. SBI and TLCK were most inhibitory when added along with mitogen or when mixing allogeneic cells in a MLR; significant decrease in inhibition was noted when TLCK was added 1 h after mitogen. These data support the hypothesis that protease action at a cell surface is an essential early event common to all types of lymphocyte transformation.
Hormonal Stimulation of Ribosomal RNA Synthesis in Achlya ambisexualis
Authors: Horgen Paul A. , Smith Robin , Silver Julie C. , Craig Gary
Published: December 2009

The experiments reported show that one of the early effects of the steroid sex hormone antheridiol is on the synthesis of rRNA and ribosomes. This is demonstrated in hormone treated cultures of Achlya ambisexualis (strain E87) by an enhancement of the incorporation of [3H]uridine into 26S and 18S rRNA and by an increase in measurable amounts of ribosomes per milligram dry weight of mycelium. Furthermore, since the hormone does not significantly alter the pool size or the specific activity of uridine triphosphate, this effect appears to represent an increased rate of RNA synthesis.
The Probable 'Capping' of Wheat Leaf Messenger Ribonucleates by 7-Methylguanosine
Authors: Kennedy T. D. , Lane B. G.
Published: December 2009

Experiments have been designed to test the possibility that, as with messenger RNA from animal cells, 7-methylguanosine may be bonded through a pyrophosphate bridge to the 5′-termini of messenger RNA molecules from the cells of a higher-plant organism. It is concluded that 7-methylguanosine is probably bonded through a pyrophosphate bridge to the 5′-termini of messenger RNA molecules from wheat leaves.
Plasma lipoprotein profile and composition in White Carneau and Show Racer breeds of pigeons
Authors: Langelier M. , Connelly P. , Subbiah M. T. R.
Published: December 2009

Plasma lipoprotein profile and composition in atherosclerosis-susceptible White Carneau and atherosclerosis-resistant Show Racer pigeons were investigated while consuming a regular pigeon chow diet free of cholesterol. Plasma was studied by analytical and preparative ultracentrifugation and paper electrophoresis. Lipid composition of each lipoprotein was determined by combined TLC–GLC techniques. The major plasma lipoprotein of both breeds was high density lipoprotein (HDL) with some low density lipoprotein (LDL) and no very low density lipoprotein (VLDL). Cholesterol was mainly found in the HDL in both breeds (71.7%), and no difference was noticed in the total cholesterol content of whole plasma or in various lipoproteins. The LDL fraction in White Carneaux showed a significantly lower (P < 0.05) percentage of cholesterol esters compared with Show Racers (58.63 ± 4.9 in White Carneaux vs. 72.12 ± 2.1 in Show Racers). In LDL, the percentage of the triglyceride concentration in White Carneaux was significantly lower (P < 0.01) than that of Show Racers while the percentage of protein content in White Carneaux was higher than in Show Racers. No significant differences were observed in fatty acid composition of steryl esters, phospholipids, and triglycerides in the lipoprotein fractions of the two breeds. These studies show important differences in the cholesterol esters, protein, and triglyceride content of LDL in the atherosclerosis-susceptible breed of pigeons.
Synthesis of hemopexin with and without hormonal supplementation in rat hepatocyte suspensions: comparison with that of albumin and of fibrinogen
Authors: Jeejeebhoy Khursheed N. , Bruce-Robertson Alan , Ho Joseph , Kida Setsuko , Muller-Eberhard Ursula
Published: December 2009

The rate of hemopexin synthesis in adult rat hepatocyte suspensions (0.17 ± 0.019 (6)) (mean ± SEM (n)) mg/g hepatocytes per hour) was found to be linear for 48 h. By contrast, the rate of synthesis of albumin and fibrinogen was close to linear for only 12 h after which it continued at a diminished rate. Supplementation of the incubation medium with insulin, cortisol, glucagon, triiodothyronine, and growth hormone effected no significant increase in the synthesis rate of hemopexin but by contrast did do so in that of albumin (22%) and of fibrinogen (123%) (although not to the point of causing these last to become linear). The pattern of hemopexin synthesis and its response to hormones is clearly different from that observed with other plasma proteins studied in this hepatocyte system. Hemopexin synthesis appeared to be at its maximum and to be independent of hormone supplementation, and it was continuing linearly at a time when the synthesis of other plasma proteins was falling.
The influence of lighting conditions upon the level and course of increase in specific activity of serotonin N-acetyltransferase in the developing chick pineal gland
Authors: Fraser I. H. , Wainwright S. D.
Published: December 2009

A diurnal cycle in level of serotonin acetyltransferase (acetyl-CoA: arylamine N-acetyltransferase (EC 2.3.1.5)) activity was found in the pineal gland of chicks aged 16 to 20 days maintained under diurnal lighting conditions. Diurnal variation in levels of activity was markedly reduced in the pineal gland of birds kept in constant darkness, and suppressed in the gland of chicks under constant illumination. High levels of activity attained during the dark phase of the normal cycle rapidly declined when the birds were transferred to the light. The light phase level of serotonin acetyltransferase of the pineal increased progressively from the 11th day of incubation to about 1 week post-hatch. This course of increase in enzyme activity was largely unaffected by lighting conditions. Under conditions for assay of serotonin acetyltransferase activity in the chick pineal gland and brain, radioactive serotonin gave rise to N-acetylserotonin, 5-hydroxyindoleacetic acid and a further unidentified metabolite, which was quantitatively the major product.
Acid proteases from species of Mucor. III. Interaction with concanavalin A and concanavalin A Sepharose
Authors: Rickert W. S. , McBride-Warren P. A.
Published: December 2009

The reaction of Mucor miehei protease with concanavalin A was followed by a turbidimetric assay in the pH range 5–8. At pH 4.0, no turbidity developed but binding of the enzyme to concanavalin A could be demonstrated by gel filtration. Two fractions of apparent molecular weight 65 000 and 52 000 were isolated, the 65 000 molecular weight species apparently representing a protomer of concanavalin A (24 000) bound to the enzyme. An analysis of the circular dichroism spectrum of this complex suggested that protomer binding results in a conformational change in the enzyme which is associated with a 30% increase in proteolytic activity.At pH 6.0, the enzyme was strongly bound to columns of concanavalin A Sepharose but could be removed by including α-methyl D-glucoside and NaCl in the elution buffer. Some column degradation occurred at room temperature but was not detectable at 4 °C where rapid elution of the enzyme resulted in a greater than 90% yield of highly active protein. Periodate-oxidized Mucor miehei protease and Mucor rennin did not react with concanavalin A and were not bound to the affinity column.
Physical, chemical, and enzymatic studies on the major sucrase of honey bees (Apis mellifera)
Authors: Huber R. E. , Mathison R. D.
Published: December 2009

A sucrase from honey bees (Apis mellifera) which precipitates between ammonium sulfate saturations of 50 and 70% (5 mg protein per millilitre) and which makes up the major portion of the sucrases of honey bees was purified to homogeneity as shown by several criteria. A large part of the sucrase was found in the head while most of the rest was in the abdomen (a small amount was in the thorax). The enzyme precipitated between the same values of ammonium sulfate saturation as did the sucrase in honey and honey sucrase exhibited kinetics very similar to those of this enzyme. The enzyme was found to be a relatively nonspecific α-glucosidase and was shown to have transglucosidase activity. The production of glucose from sucrose was rectilinear when plotted by the Hofstee method at low substrate concentrations but decreased at high sucrose concentrations. The production of fructose was rectilinear throughout the concentration range used. The production of both glucose and p-nitrophenol when p-nitrophenyl α-D-glucoside was the substrate was linear by the Hofstee plot. These effects were found to be due to transglucolysis and a mechanism of action is proposed. Amino acid and amino sugar analyses indicated that the sucrase was a glycoprotein. The molecular weight was found to be between 51 000 and 82 000 by three different methods and an s020,W value of 4.0 S was obtained. There was no evidence for subunit structure. Tests of the enzyme under various denaturation conditions did not reveal any unusual stabilities. The sucrase bound very tightly to a hydrophobic column. Iodoacetic acid decreased the activity of the sucrase but a large concentration was needed to bring about a 50% activity loss. Reducing agents caused some activity declines. Diethyl pyrocarbonate activated the enzyme.
Pyrimidine reducing enzymes of rat liver
Authors: Hallock Ronald O. , Yamada Esther W.
Published: December 2009

Dihydrouracil dehydrogenase (NADP+) (EC 1.3.1.2) was partially purified from the cytosol fraction of rat liver and fractionated by disc gel electrophoresis. A major and minor band were visualized by staining for enzyme activity. The substrate specificity of these bands was investigated. It was found that both bands were two to three times more active with dihydrothymine as substrate than with dihydrouracil in the presence of NADP+ and the optimum pH of 7.4.Mitochondrial fractions containing most of the NADH-dependent uracil reductase of rat liver cells were fractionated by centrifugation in sucrose density gradients. Two procedures involving linear or discontinuous gradients were used. By both, good separation of NADH- and NADPH-dependent reductases was achieved. Marker enzyme studies supported the view that the NADH-dependent enzyme is located principally in mitochondria whereas the NADPH-dependent enzyme is mainly in plasma and endoplasmic reticulum membranes. For the NADH-dependent reductase the apparent Km for thymine at pH 7.4 was 1.39 times that found for uracil whereas for the NADPH-dependent enzyme the apparent Km values were similar for the two substrates at this pH.Dihydrouracil was the principal product isolated by paper chromatography from the reaction mixture containing a partially purified fraction of mitochondria, uracil and NADH at pH 7.4. This fraction also catalyzed the formation of radioactive carbon dioxide from [2-14C]uracil. The proportion of CO2 formed by the mitochondria was about 10% of that formed by the original homogenate.
The specific activity of aldolase in the livers of old and young rats
Authors: Anderson Peter J.
Published: December 2009

The catalytic activity of liver fructose-biphosphate aldolase (EC 4.1.2.13) of young and old rats in units per manomole sequence has been calculated. No evidence of the accumulation with age of altered enzyme molecules of low catalytic activity was obtained. This is contrary to results obtained using mice and rabbits and indicates that the accumulation of altered enzymes may not always be associated with aging. The possibility that altered proteins are formed, but do not accumulate, cannot be ruled out.
The influence of hydrocortisone on the synthesis and turnover of microvillous membrane glycoproteins in suckling rat intestine
Authors: Forstner G. , Galand G.
Published: December 2009

Synthesis and degradation of intestinal mucosal and microvillous membrane glycoproteins were studied in control suckling rats, and suckling rats given cortisol acetate by intraperitoneal injection for 3 days. Cortisol acetate had no effect on total uptake of radioactive glucosamine by the protein free compartment of rat intestine. Early incorporation of [1-14C]glucosamine by intestinal glycoproteins was enhanced by cortisol, but stimulation was the same in membrane and homogenate fractions. Polyacrylamide gel electrophoresis of membrane proteins solubilized with 2% sodium dodecyl sulphate demonstrated a cortisol dependent change, characterized by loss of faster travelling glycoproteins, and a corresponding shift in maximum labelling at 3 h from these glycoproteins to more slowly migrating glycoproteins. Degradation was studied qualitatively with a double isotope technique. Glycoprotein degradative rates appeared to be stimulated by cortisol, but similarly in membrane and total homogenate fractions. On polyacrylamide gels, the areas occupied by glycoproteins with the highest apparent degradative rates, corresponded closely with the areas of most active labelling at 3 h. The rate of degradation in the most actively labelled zone appeared to be higher after cortisol than in the controls. The results indicate that cortisol does not alter membrane composition by inhibiting degradation of selected glycoproteins, and are consistent with a model in which cortisol stimulates the synthesis of specific membrane glycoproteins in suckling rats, while inhibiting synthesis of other glycoproteins.