摘要:

The purified high molecular weight serogoup Y meningococcal polysaccharide contains equimolar proportions ofD-glucose andN-acetylneuraminic acid and is partiallyO-acetylated. Carbon-13 nuclear magnetic resonance (NMR) studies, together with other chemical data, have indicated that the polysaccharide is linked only at C-6 of theD-glucose and C-4 of the sialic acid residues, all the linkages being in the α-configuration. The13C NMR data also indicated that the Y polysaccharide is composed of an alternating sequence of these two different residues, and this was confirmed by its autohydrolysis where the major product was 4-O-α-D-glucopyranosyl-β-D-N-acetylneuraminic acid. The W-135 polysaccharide differs from that of Y only in the absence ofO-acetylation and in the configuration of one hydroxyl group of the disaccharide repeating unit. In this case autohydrolysis yielded 4-O-α-D-galactopyranosyl-β-D-N-acetylneuraminic acid as the major product. Structural evidence indicates that the BO and Y polysaccharides are identical.Methanolysis of the Y polysaccharide yielded in addition to the methyl glycosides of glucose and sialic acid, a 9-O-acetyl derivative of the latter. This derivative was formed during the re-N-acetylation process and its formation was mainly due to the presence of sodium ions in the original polysaccharide.

ISSN:0008-4018    

DOI:10.1139/o76-001

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Isolation of nucleolar proteins was obtained by dissociation in the presence of urea – guanidine hydrochloride, followed by high-speed centrifugation to remove nucleic acids. At least 31 fractions of nucleolar proteins were detected by isoelectrofocusing gel electrophoresis in the pH range 3.5–10. Following two-dimensional gel electrophoresis on sodium dodecyl sulfate – polyacrylamide slab gels, more than 100 components of nucleolar proteins were identified. Two-thirds of nucleolar proteins were located in the pH range 5–8 following isoelectrofocusing. The molecular weights of these classes of proteins were shown to be mostly 30 000 – 70 000 by sodium dodecyl sulfate – polyacrylamide gel electrophoresis.

ISSN:0008-4018    

DOI:10.1139/o76-002

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Biosynthesis of phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin was studied in liver endoplasmic reticulum obtained from newly hatched chicks which were made hypothyroid by feeding 0.2% propylthiouracil.In vitromeasurements were made of the specific activities of phosphorylcholine-glyceride (cholinephosphotransferase (EC 2.7.8.2)), phosphorylethanolamine-glyceride (ethanolamine-phosphotransferase (EC 2.7.8.1)), and phosphorylcholine-ceramide (ceramide cholinephosphotransferase (EC 2.7.8.3)) transferases in control and hypothyroid chick liver for a period of 40 days. The specific activity of all three transferases began to decline after the chicks were on the propylthiouracil-containing diet for 5 days and steadily declined, reaching levels 10–15% of the controls after 15 days. These low levels were maintained for as long as the chicks were on this diet.Administration ofL-thyroxine (15 μg/100 g of body weight) to the hypothyroid chicks caused a marked increase in the specific activities of all three transferases, reaching levels similar to those seen in the control chicks in 36–48 h. The specific activities then declined as the chicks were maintained on the diet of propylthiouracil, reaching the former low levels after 120 h.Administration of cycloheximide alone to the hypothyroid chicks caused a rise in the specific activities of the transferases after 24 h approximately equal to that caused by thyroxine alone, while thyroxine and cycloheximide together were no different than either alone.These studies indicate that in some manner circulating thyroxine controls the activities of enzymes involved in the biosynthesis of phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin in chick liver endoplasmic reticulum. There was no evidence that induction of hypothyroidism by propylthiouracil had any effect on the activities of these enzymes in the CNS.

ISSN:0008-4018    

DOI:10.1139/o76-003

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Phosphoenolpyruvate carboxykinase (ATP:oxaloacetate carboxy-lyase (transphosphorylating)) (EC 4.1.1.49) has been purified to homogeneity fromEscherichia coli. The enzyme shows the same molecular weight (ca. 65 000) either by sedimentation equilibrium under nondenaturing conditions or by polyacrylamide gel electrophoresis in the presence of detergent, indicating that the enzyme has a monomelic structure. We have confirmed the previous observation that NADH is an inhibitor of this enzyme, but we have failed to detect the previously reported appearance of homotropic cooperativity with respect to substrate binding in the presence of this inhibitor. Lack of such homotropic interactions is in harmony with our conclusion that the enzyme is a monomer. Replacement of Mg2+by Mn2+in the assay medium lowers theKmfor phosphoenolpyruvate by an order of magnitude, but does not affect the characteristics of inhibition by NADH.

ISSN:0008-4018    

DOI:10.1139/o76-004

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

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 Carneauxvs. 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.

ISSN:0008-4018    

DOI:10.1139/o76-005

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

A study of the enzymes of the orotate biosynthetic pathway in the kinetoplastid flagellateCrithidia fasciculatahas revealed a number of differences between them and those of other organisms, either prokaryotic or eukaryotic. Carbamyl phosphate synthesis could not be demonstrated in cell-free extracts. However, the incorporation of both CO2and the ureide carbon of citrulline into pyrimidines occurs in growing cells, the latter predominating over the former. The aspartate transcarbamylase of the flagellate has properties which are similar to those of this enzyme as it occurs in mammals rather than other microorganisms. Two enzymes, dihydroorotate synthetase and dihydroorotate hydrolase, are present, the former being responsible for the conversion of carbamylaspartate to dihydroorotate. Dihydroorotate hydroxylase, a soluble enzyme requiring a reduced pteridine as a cofactor, converts dihydroorotate to orotate. The hydroxylase is inhibited by orotate, but not by pyrimidine or purine ribonucleotides. Thus orotate serves to control its own biosynthesis.

ISSN:0008-4018    

DOI:10.1139/o76-006

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The carbohydrate composition of the apoprotein from low density lipoprotein (LDL) of normal (average LDL cholesterol, 122 mg/100 ml) and type II hyperlipoproteinemic (average LDL cholesterol, 236 mg/100 ml) males was studied using gas–liquid chromatographic analysis of the methyl glycoside derivatives. All samples containing detectable sinking pre-beta-lipoprotein were excluded from the study.The apo LDL from both groups of subjects contained mannose, galactose,N-acetylglucosamine, andN-acetylneuraminic acid. Glucose and fucose were not found while trace quantities of galactosamine were detected. Although the quantities of galactose andN-acetylglucosamine were the same in the two groups, lower quantities of mannoseandN-acetylneuraminic acidwere found in the type II patients as opposed to normal subjects.

ISSN:0008-4018    

DOI:10.1139/o76-007

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Specificin vitrobinding of [3H]testosterone (T), 5α-[3H]dihydrotestosterone (DHT), and [3H]estradiol (E2) was demonstrated in the 30 000 × gsupernatant (cytosol) of thigh muscles (TM) and of the levator ani – bulbocavernosus muscle complex (LA–BC) by gel filtration through Sephadex G-25 columns. In TM cytosol, T and E2[are bound with high affinity (Ka = 1.1 × 109 M−1and 2.3 × 109 M−1, respectively) whereas DHT binding is of lower affinity (Ka = 5.0 × 107 M−1).] In LA–BC cytosol, T, E2, and DHT are bound with high affinity (Ka = 1.9 × 109 M−1, 0.3 × 109 M−1and 0.5 × 109 M−1, respectively). Competition experiments suggest that the binding of the three hormones (T, E2, and DHT) is due to different proteins. In addition to TM and LA–BC, T and E2binding was found in other muscles of male and female rats, including gastrocnemius, the pectoralis, diaphragm, and heart.

ISSN:0008-4018    

DOI:10.1139/o76-008

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Histones were isolated from late spermatids and spermatozoa of the house cricketAcheta domesticus, and the individual histone fractions were separated by electrophoresis on polyacrylamide–urea gels. The stained gels were cut so as to isolate the different histone fractions, and the amino acid compositions were determined using the technique of Houston (Houston, L. L.:Anal.Biochem.44, 81–88 (1971)). Five of the histones had amino acid compositions resembling those for the histones of calf thymus and were thus identified as fractions F1, F3, F2a2, F2b, and F2a1. Another protein (SH) located exclusively in the late spermatids and spermatozoa was found to be basic and histone-like. It is a protein containing relatively high amounts of arginine (12.6%) and low amounts of lysine (7.6%), and, as a result, it has a low ratio of lysine–arginine (0.6). Other noteworthy features are its high contents of serine, glutamic acid, and glycine. It is an arginine rich histone and in this regard resembles other such proteins, but it does contain unique features which distinguish it from all previously described histones.

ISSN:0008-4018    

DOI:10.1139/o76-009

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

New methods for the determination ofL-asparagine and arginine are described. Solutions containingL-asparagine were pumped through an asparaginase tube, which catalyzed the hydrolysis ofL-asparagine toL-aspartic acid and ammonium ion. ForL-arginine determination, solutions containingL-arginine were pumped through an arginase–urease tube. This dual enzyme tube catalyzed the conversion ofL-arginine toL-ornithine, carbon dioxide, and ammonium ion. The ammonium ion concentrations in the effluent of the enzyme tubes were determined quantitatively by an ammonium-ion-selective electrode. The potentiometric response of the electrode was directly proportional to the logarithm of the concentration ofL-asparagine andL-arginine in the range of 0.1–50 mM. An equation relating the electrode response and the substrate concentration is derived.

ISSN:0008-4018    

DOI:10.1139/o76-010

出版商:NRC Research Press    

年代:1976

数据来源: NRC