bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipogenesis in biotin deficiency
Authors: Dakshinamurti K. , Desjardins P. R.
Published: December 2009

The effect of biotin deficiency on the lipid composition of rat liver, epididymal fat pad, and carcass was investigated. The incorporation of acetate-1-14C into liver lipids, the concentration of liver acetyl-CoA, and the in vitro activities of mitochondrial and supernatant pathways were also studied in biotin-deficient and pair-weighed controls.Biotin-deficient rats had higher levels of carcass cholesterol, though there was no significant difference in liver cholesterol levels between deficient and control rats. These results indicate that the malonyl-CoA pathway proposed for cholesterol synthesis may not be the major route for cholesterogenesis.The reduction in esterified fatty acids of adipose tissue and carcass of biotin-deficient rats was greater than that of liver suggesting that biotin deficiency might have a more marked effect on the metabolism of the adipose tissue than of liver.
Phospholipids. XVIII. Synthesis of ethylene glycolphosphonic acid analogues of cephalins
Authors: Baer Erich , Basu Hemendra
Published: December 2009

The synthesis of ethylene glycolphosphonic acid analogues of cephalins is reported. Two methods for the preparation of several typical members of the new type of phosphonolipids, viz. myristoyl, palmitoyl, and stearoyl ethylene glycol-(2-aminoethyl)phosphonate are described in detail The compounds were obtained by phosphonylation of monoacyl ethylene glycols in the presence of triethylamine with either (2-phthalimidoethyl)phosphonic acid monochloride or (2-N,N-dibenzylaminoethyl)phosphonic acid monochloride (hydrochloride), and freeing the reaction products from their protective groups by hydrazinolysis or hydrogenolysis, respectively. The glycolphosphonocephalins with long-chain fatty acid substituents, in contrast to the corresponding glycolphosphonolecithins, are water-insoluble, show no hemolytic activity, and are not hydrolyzed by lecithinase C to any significant degree. They are hydrolyzed, however, by lecithinase C in the presence of sphingomyelin.
Detection of multiple forms of proteolytic enzymes by starch gel electrophoresis
Authors: kaminski E. , Bushuk W.
Published: December 2009

A rapid and sensitive method for the direct detection of multiple forms of proteolytic enzymes by starch gel electrophoresis is described. The location of the enzyme components is identified by the degradation of hemoglobin which is included in the starch gel. This method was used to identify the enzyme components of the 10 commercial proteolytic enzymes bromelain, chymotrypsin, ficin, papain, pepsin, pronase B, protease, proteinase, and two preparations of trypsin. The effects of urea concentration and the ionic strength of aluminium lactate buffer were also examined. The best results were obtained with 3 M urea and with an ionic strength of 0.1 for the lactate buffer. It was observed that the number of enzyme components decreased with increasing concentrations of urea or increasing ionic strength of lactate buffer. The number of enzyme components did not always correspond to the number of protein bands. Self-digestion occurred in some of the protein bands in the starch gel after electrophoretic separation of the proteolytic enzymes.
The utilization of glucose by tissue slices of liver and other organs of the domestic fowl
Authors: Duncan H. J.
Published: December 2009

The utilizations of glucose-1-14C, glucose-6-14C, and glucose-U-14C by liver slices from the immature and the laying domestic fowl have been evaluated. The relative degrees of incorporation of C-1 and C-6 into CO2, total lipid, fatty acids, and glyceride-glycerol resulted in C-1/C-6 quotients that approximated unity for both groups of fowl. The amounts of incorporation of the two specifically labelled carbon atoms into glycogen were significantly different for liver from the immature bird, but not for that from the laying fowl. These results indicate that the commencement of egg production is not accompanied by activation of the phosphogluconate oxidative pathway.When compared on a DNA basis, the amounts of isotope from glucose-U-14C incorporated into CO2, total lipid, fatty acids, glyceride-glycerol, and glycogen by liver slices from the immature fowl were almost equal to the degrees of incorporation observed following incubation of liver obtained from laying birds. The results with glucose-U-14C suggest that little or no modification of carbohydrate metabolism occurred when sexual maturity was reached.Yields of 14CO2 from the oxidation of glucose-1-14C and glucose-6-14C by various fowl tissues other than the liver are also reported. The observed C-1/C-6 ratios were in general lower than values reported in the literature for corresponding mammalian tissues, except that the quotients for fowl heart and ovary were higher than those reported for rat heart and ovary.
Incorporation of serine-U-14C into β-cyanoalanine and γ-glutamyl-β-cyanoalanine in Vicia sativa
Authors: Nigam S. N. , McConnell W. B.
Published: December 2009

Administration of serine-U-14C to Vicia sativa plants at the time of seed maturation resulted in extensive labeling of both the free β-cyanoalanine and its glutamyl peptide. Since an exogenous source of cyanide was not required for the incorporation of serine, it is concluded that under natural conditions this is the stage in the life of Vicia sativa plants during which synthesis of β-cyanoalanine occurs.
Oxidative metabolism of bovine spermatozoa
Authors: Masken J. F. , Hopwood M. L.
Published: December 2009

Suspensions of washed bovine sperm (phosphate buffer, pH 7.4) were incubated at 37 °C for 1 h with pyruvate-3-14C and in some cases, with oxaloacetate. Oxygen consumption and 14CO2 evolution were measured. Radioactive citrate, malate, fumarate, α-ketoglutarate, and oxaloacetate were found following incubation. The latter two compounds were positively identified by melting-point and specific-activity determinations of their 2,4-dinitrophenylhydrazone derivatives. The results indicate citric acid cycle activity in bull sperm. Oxygen consumption and the evolution of 14CO2 from pyruvate-3-14C tended to decline when oxaloacetate was added to the sperm suspensions.
Egg proteins of pacific salmons genus Oncorhynchus: proteins in the soluble fraction
Authors: Markert J. R. , Vanstone W. E.
Published: December 2009

The soluble fraction of eggs from pacific salmon contained three major protein components which were precipitated as a lipovitellin–phosvitin complex by distilled water. Two of these components were identified provisionally as lipovitellin and phosvitin, while the third, a simple protein, appeared to be a unique component of teleostean eggs. Livetins, present in only trace amounts, were composed of several electrophoreticaily distinct proteins which differed in number, relative mobility, and concentration between species.
The oxidized forms of cytochrome oxidase
Authors: Williams G. R. , Lemberg R. , Cutler M. E.
Published: December 2009

Ferric cytochrome oxidase (Soret max. 418 mμ) and "oxygenated" cytochrome oxidase (Soret max. 428 mμ) carry the same number of oxidizing equivalents (two per heme a) available for the oxidation of ferrous cytochrome c. "Oxygenated" oxidase can be formed by the aerobic oxidation of a3+ + a32+CO and therefore the difference from ferric cytochrome oxidase resides in the a3 moiety of the enzyme. When reductant is added to ferric oxidase aerobically, a transient formation of a2+a33+ occurs but at later times the dominant species in the steady state is "oxygenated" oxidase. It is suggested that the reason for the inhibition of electron flow between a2+ and a33+ may be either in conformational restraints or in the redox state of the associated copper. No such block is apparent in the reduction of "oxygenated" oxidase.
Reaction of N-methyl-N′-nitro-N-nitrosoguanidine with protein: formation of nitroguanido derivatives
Authors: McCalla D. R. , Reuvers Antoon
Published: December 2009

When serum albumin is exposed to N-methyl-N′-nitro-N-nitrosoguanidine (NG) one of the main reactions is conversion of ε-amino groups of lysine to nitroguanido groups. This conversion results in a large increase in the extinction coefficient of the protein as well as an increase in electrophoretic mobility (toward the positive pole). The lysine content of the protein is reduced. Enzymatic hydrolysis of NG-treated protein liberates an ultraviolet-absorbing, ninhydrin positive compound with chromographic properties which are identical with those of nitrohomoarginine. The concentration of NG required to form at least one nitroguanido group in a significant fraction of protein molecules is very much greater than that required to inactivate transforming DNA in vitro or to kill various microorganisms.Further evidence for the formation of nitroguanido derivatives is provided by the observation that glycine reacts with NG to form nitroguanidoacetic acid.
The Influence of tumor–host relationships on plasma phosphate levels and phospholipid labelling
Authors: Aleyassine H. , Scholefield P. G.
Published: December 2009

A decrease occurs in the plasma phosphate level of mice transplanted with the Ehrlich ascites tumor. When 32Pi is injected into such animals the plasma acid soluble radioactivity per unit of inorganic phosphate and hence the specific activity of the liver phospholipids are correspondingly increased.
Influence of N-cyclohexyl linoleamide on cholesterol synthesis by rat liver slices
Authors: Kritchevsky David , Tepper Shirley A.
Published: December 2009

The addition of N-cyclohexyl linoleamide in dimethyl sulfoxide to suitably fortified rat liver slices had no significant effect upon synthesis of cholesterol from sodium acetate-1-14C. The test compound was added at concentrations of 10−3, 4 × 10−3, and 5.5 × 10−3 M (1.8, 7.2, and 10 mg, respectively). Ethanol (0.1 ml) inhibited cholesterogenesis by rat liver slices, but dimethyl sulfoxide and propylene glycol had no effect. The latter two compounds are useful solvents for substances being tested for in vitro effects on cholesterogenesis.
Studies of the uptake of macromolecules by cells. II. Metabolic aspects of protein uptake by cells of the Ehrlich–Lettré ascites carcinoma
Authors: Choi Y. C. , Kay E. R. M.
Published: December 2009

The close interrelationship between cellular metabolism and the process involved in the uptake of protein by cells was studied. The activation energy in this process suggests that the rate-determining step for the overall process is driven by an enzymatic reaction. The driving force was found to be derived from various pathways in glucose metabolism. The uptake of protein under aerobic conditions is higher than that under anaerobic conditions. Inhibitors which were studied, such as iodoacetate, sodium fluoride, sodium azide, and oligomycin caused an inhibition in the uptake of protein. It is probable that the energy present in ATP is involved in driving the process of protein uptake and that the control mechanism for the process is bioenergetic in character. The major modification of cellular metabolism coincident with the uptake of protein was found to be in an enhanced nuclear RNA turnover. The significance of a metabolic involvement was further clarified by using actinomycin D and puromycin. Both inhibitors brought about an inhibition in the process of protein uptake.
The kinetics of fluoride binding by lactoperoxidase
Authors: Segal Raymond , Dunford H. Brian , Morrison Martin
Published: December 2009

The kinetics of the reversible binding of fluoride by ferric lactoperoxidase has been studied over the pH range 3.8–5.4 by means of a stopped-flow apparatus. Because of small absorbance changes upon the binding of fluoride by lactoperoxidase, the reaction was driven to completion by addition of a large excess of fluoride. Under these conditions the binding reaction obeys pseudo-first-order kinetics and an accurate analysis of the dissociation rate data is not possible. The results are consistent with a mechanism in which HF binds to the active site which contains no groups capable of ionization in the pH range of the present study. The specific rate constant for the binding reaction of HF to lactoperoxidase is (9.7 ± 0.4) × 102 M−1s−1.
Comparative mitochondrial function in two strains of Aspergillus niger
Authors: Higgins Edwin S. , Friend Wilson H.
Published: December 2009

A relatively simple procedure for isolation of mitochondria from Aspergillus niger was described. The organelles satisfied standard criteria for structural and functional integrity and were characterized by a somewhat higher degree of respiratory control than that associated with mitochondria from fungi reported by others. Mitochondria from a nitroaryl-resistant strain respired more vigorously and had higher respiratory control ratios than mitochondria from the parent wild strain. These observations may explain previous demonstrations that the former strain had high citrate cycle activity and no measurable direct oxidative pathway, whereas the wild strain metabolized glucose predominantly via gluconate and had very little citrate cycle capability. The respiratory chains in A. niger for NADH and for succinate were similar to those in mitochondria from higher organisms, although NADH was freely permeable to the organelles and was oxidized the most vigorously of all externally supplied substrates.
The detection of imidazoles including histidine and some of its derivatives in biological fluids
Authors: Pasieka Arthur E. , Thomas M. E.
Published: December 2009

A staining method for the detection of imidazoles including histidine and histidine-containing compounds is described. It is based on the treatment of developed high-voltage paper electrograms or paper chromatograms with bromophenol blue. The electrogram or chromatogram after drying is fixed in n-butanol, complexed with mercuric chloride, and subsequently stained with 0.2% bromophenol blue in 95% ethanol. The electrogram or chromatogram is washed while still damp with tap water until the background is clear. None of the other 20 known amino acids including tyrosine, such as are found in the synthetic mixture M150, reacted in the above staining procedure. Purines also react with the described reagent due to their imidazole configuration.
Effect of feeding ethionine on the distribution and metabolism of 1-14C-linoleic acid in the rat
Authors: Lyman R. L. , Giotas C. , Fosmire M. A. , Miljanich P.
Published: December 2009

Male rats fed a 9% casein-purified diet for 14 days were compared with a similar group of rats whose diet contained 0.25% DL-ethionine. At the end of the feeding period, the animals were tube fed their respective diets plus 1-14C-linoleic acid, and control and experimental rats randomly chosen were then killed 18 h and 30 h thereafter. Composition and radioactivity were determined in carcass and liver lipids. Total amounts of carcass and liver lipids did not differ among the groups, nor were there any differences in the distribution or specific activity of the carcass linoleate. Liver triglyceride of rats fed ethionine, while being no higher in concentration than that of control animals, did, however, have a higher proportion of radioactivity and more linoleic acid with a higher specific activity than did the controls. The differences were greatest at the 18-h post-feeding period. Ethionine also increased the proportion of linoleic acid and decreased that of arachidonic acid in the liver phospholipids as compared with controls. Analysis of the phosphatidylethanolamines and phosphatidylcholines showed that by the 18-h post-feeding period, the proportions of radioactivity and specific activity of arachidonic acid in both phospholipid fractions were reduced far below control values, whereas the specific activity of linoleic acid was high and similar for all groups. However, by 30 h after administration of the labeled linoleic acid, specific activities, but not the distribution of the label, had returned to normal ranges. From the results it was concluded that the liver phospholipid fatty acid patterns seen in rats fed ethionine were a consequence of an impairment by the analogue in the normal utilization and conversion of linoleic acid to arachidonic acid.
Formation of ring-D-hydroxylated estrogens from C19 precursors administered to the fetus in utero
Authors: YoungLai E. V. , Bowman J. M. , Solomon S.
Published: December 2009

Two studies were performed on the origin of ring-D-hydroxylated estrogens during late pregnancy using an experimental design in which the labeled substrates were introduced into the fetus during transfusion in utero for erythroblastosis fetalis. Maternal urine was then collected for 5 days and estriol, 15α-hydroxyestradiol, and 15α-hydroxyestriol were isolated following Glusulase hydrolysis of the urinary conjugates. From the radioactivity present in each urinary metabolite expressed as a percentage of that excreted, it was possible to conclude that a large amount of dehydroisoandrosterone sulfate was converted to estriol and smaller amounts to 15α-hydroxyestradiol and 15α-hydroxyestriol. In addition, 15α-hydroxyandrostenedione was converted to 15α-hydroxyestriol in better yields than to 15α-hydroxyestrad-iol. These findings suggest that 15α-hydroxylated estrogens found in late pregnancy urine can be derived from neutral precursors in the fetus. It was also apparent that a sequence of hydroxylation, 15α followed by 16α, occurs in the formation of 15α-hydroxyestriol but it is uncertain whether 16α hydroxylation occurs prior to, or after, aromatization.
Urinary conversion products of injected progesterone-4-14C in the domestic fowl
Authors: Chen P. H. , Common R. H.
Published: December 2009

Progesterone-4-14C was administered intramuscularly to hens. The urine subsequently excreted contained radioactive 5β-pregnane-3α,20β-diol and 5β-pregnan-3α-ol-20-one, the identities being established by thin-layer chromatographic mobilities of the isolated materials and derivatives thereof, and by crystallization of the alcohols and their acetates to constant specific activity with reference carrier materials. Radioactive progesterone was not detected in the urine, neither did the results provide any evidence for the presence of radioactive 5α-pregnane derivatives.
Hypoxanthine–guanine phosphoribosyltransferase: further evidence for the identity of the binding sites for hypoxanthine and guanine
Authors: Henderson J. Frank
Published: December 2009

Isotope exchange between hypoxanthine and both inosinate and guanylate, and between guanine and the same two ribonucleotides, support the view that hypoxanthine and guanine bind to the same site on hypoxanthine-guanine phosphoribosyltransferase.
Refutation of alleged differences in the energy contents of optical isomers
Authors: Baer Erich , Flehmig Hans-Helmut
Published: December 2009

The heats of combustion of the optical isomers of α-monostearin and of glyceraldehyde reported by D. Buchnea to differ by 62 and 64 kcal/g-mole, respectively, were redetermined. Our experimental values for these, and for the optical isomers of several related compounds, are in accord with the generally accepted view that the heats of combustion of optical isomers are identical. They refute not only Buchnea's concept of different energy contents for optical isomers, but also the claim that they are responsible for the different rates of reaction observed by him for L-, D-, and DL-α-monostearin in ethereal suspensions containing gaseous hydrogen chloride.
Inhibition of respiration in submitochondrial particles by N,N′-dicyclohexylcarbodiimide: the effect of sodium, potassium, and antibiotics which alter membrane permeability
Authors: Beyer Robert E. , Brinker Karl R. , Crankshaw Daune L.
Published: December 2009

NADH oxidation catalyzed by submitochondrial particles produced by sonic treatment (ETPH) is inhibited by N,N′-dicyclohexylcarbodiimide. The inhibition of electron-transfer activity is released by uncouplers of oxidative phosphorylation, but not by ADP nor by potassium or sodium ions, either in the presence or absence of valinomycin or tyrocidin. Low concentrations of potassium or sodium (0–30 mM) either in the presence or absence of valinomycin or tyrocidin do not significantly increase the rate of NADH oxidation by ETPH. High concentrations of sodium or potassium ions (30–120 mM) cause a significant increase in the rate of NADH oxidation by ETPH. It is suggested that the metal ion transport system is a property of the oriented inner mitochondrial membrane, and that high concentrations of metal ion are required to overcome the low permeability of the ETPH membrane in the inward direction in order to transport the metal ion actively in the outward direction.
Studies on heme proteins using the n.m.r. halide-ion probe technique
Authors: Ellis William D. , Dunford H. Brian , Martin John S.
Published: December 2009

The n.m.r. halide probe technique is shown to be a sensitive method for detecting the binding of Cl− and Hg2+ to proteins. The direct binding of chloride ions to proteins has been demonstrated for the first time by this technique. There appears to be only a small amount of chloride binding to horseradish peroxidase and to its apoprotein in basic aqueous solutions, but the binding increases markedly as the pH is lowered, indicating that the chloride is binding nonspecifically to positively charged regions on the protein. HgCl2 was found to bind to sperm whale myoglobin in increasing amounts as the pH was raised above 7, indicating that it may be binding to regions of negative charge on the protein. Use of the halide-ion probe technique as a means of detection of reactive sulfhydryl groups by HgCl2 titration led to the finding that there is one reactive sulfhydryl group in peroxidase, and that the rotational correlation time for the peroxidase–HgCl2 complex may be caused by rotation of the segment of the protein containing the sulfhydryl group rather than rotation of the entire protein. One sulfhydryl group was detected in bovine hemoglobin and possibly a second sulfhydryl group of lower activity.
Physical and chemical studies of Mengo virus variants. II. Chromatographic behavior and chemical composition
Authors: Scraba D. G. , Hostvedt P. , Colter J. S.
Published: December 2009

The preparation of highly purified L, M, and S plaque-type variants of Mengo virus is described, and data are presented to show that the purification procedure eliminates at least 99.92% of cellular proteins and nucleates. The nucleotide compositions of the ribonucleates and the amino acid compositions of the proteins isolated from the three virions are strikingly similar. However, surface (charge) differences between the variants do exist, as evidenced by differences in elution profiles obtained from chromatography on hydroxylapatite, and it has been shown that these differences can be exploited to separate L-Mengo from either of the other two variants.
Action of α-methyl-DL-tryptophan in vivo on catabolism of amino acids and their conversion to liver glycogen
Authors: Oravec M. , Sourkes T. L.
Published: December 2009

AMTP (α-methyl-DL-tryptophan) stimulates the incorporation of (labeled) alanine, glutamate, leucine, isoleucine, histidine, threonine, tryptophan, pyruvate, and acetate into hepatic glycogen. Accompanying this phenomenon is an enhanced rate of oxidation of these substances to carbon dioxide, except for acetate whose oxidation is not influenced by AMTP. AMTP also causes an increased excretion of urea and a rise in body temperature. Presence of the adrenal glands is necessary for the stimulatory action of AMTP on the oxidation of alanine, glutamate, isoleucine, and pyruvate. AMTP-stimulated oxidation of leucine and threonine is only partially dependent upon the adrenal gland. The oxidation of histidine is increased to the same extent by AMTP in both intact and adrenalectomized rats. The ability of AMTP to increase the level of tryptophan pyrrolase activity and, thereby, to create an imbalance of the proportion of amino acids in the rat is implicated in the mechanism responsible for its glyconeogenic property and ability to increase catabolism of amino acids.
Mode of action of choline. II. The fate of intravenously administered labelled fatty acids in choline-deficient rats
Authors: Chalvardjian A.
Published: December 2009

Two groups of rats (200 g, male) were fed, respectively, a choline-deficient and a choline-supplemented diet for 3 days. On the 3rd day each rat was injected intravenously with rat serum containing 9,10-3H-palmitate and 18-14C-stearate. The fate of the labelled fatty acids was followed in the triglycerides and phospholipids of liver and serum for time periods ranging from 1 min to 6 h. When compared to the choline-supplemented controls, the livers in the choline-deficient rats were fatty and were characterized by: (1) an increased hepatic triglyceride pool, (2) a decrease in turnover of hepatic triglycerides with sequestration of fatty acids and decrease in their recycling, (3) an increase in the hepatic free fatty acid pool and total phospholipid pool, the latter reflecting the net result of synthesis and transport, (4) a decrease in the early and rapid turnover of the phosphatidylcholine pool, (5) a decrease in turnover of the phosphatidylethanolamine pool, (6) a decrease in transport of triglycerides and phospholipids from liver to serum, and consequently, (7) a decrease in triglyceride and phospholipid pools in serum. These results confirm previous observations that, although an impairment of transport of both triglycerides and phospholipids from liver to serum exists in choline-deficient rats, the hepatic accumulation of triglycerides is far greater than that of phospholipids. This effect is due to the presence of a potential triglyceride pool in liver that can accommodate large amounts of triglyceride within a short period of time.
Effect of growth hormone and hydrocortisone on the synthesis of rapidly labeled, high molecular weight, nuclear RNA in rat liver
Authors: Brossard Maurice , Nicole Louis
Published: December 2009

The effects of growth hormone and hydrocortisone on the synthesis of rat liver RNA have been studied. Administration of growth hormone stimulated the incorporation of 14C-orotic acid into 45 S preribosomal nucleolar RNA, and had no effect on the 6–50 S polydisperse nuclear RNA of extra-nucleolar origin. On the other hand, hydrocortisone stimulated the synthesis of all types of nuclear RNA, but mainly that of the 18 S class of 6–50 S polydisperse nuclear RNA.
An investigation of factors influencing mitotic G2 delay in synchronous cultures of human kidney cells after X-irradiation
Authors: Scaife J. F. , Brohée H.
Published: December 2009

Factors affecting mitosis have been studied in human kidney T-cells synchronized by two exposures to 7.5 mM thymidine. Biochemical measurements were correlated with the position of the cells in the cell cycle from S to mitosis. Anaerobic conditions during S, although not inhibition of respiration, prevented cells from progressing to mitosis. ATP production is largely anaerobic and glycolytic metabolism is sufficient for a cell to complete mitosis once it has entered G2 or prophase. Both RNA and protein synthesis are required in G2 for the initiation of cell division, while treatment with carbon monoxide or thiol blocking agents also prevents mitosis.Postirradiation mitotic delay is greater for cells irradiated in G2 than for cells irradiated in S. This G2 delay is reversible if the cells are blocked in S by addition of excess thymidine. Pretreatment with 5–15 mM cysteamine largely protected irradiated cells from mitotic delay. Cysteine at a concentration of 20 mM and AET at 10 mM were only weakly protective, while 20 mM mercaptoethanol was ineffective. All these compounds added after irradiation were ineffective. Anoxia during irradiation had a slight protective effect. Mitotic delay was enhanced by lowered concentrations but not reduced by elevated concentrations of calcium, while agmatine before or after irradiation was without protective effect.The protein thiol content of cells increases from S to a maximum at metaphase, while the nonprotein thiol content is unchanged. X-irradiation of up to 500 R has no effect on the protein or nonprotein thiol content of the cell up to mitosis. The intracellular ATP content is maximal for cells in G2, then falls subsequently to mitosis. Irradiation slows this premitotic accumulation of ATP. The respiration rate per cell is constant up to mitosis then drops sharply following division. Irradiation has no effect on respiration. Decreased specific activities of DNA from cells irradiated in S and incorporating 3H-TdR post-irradiation over a 2-h period suggest a pool effect as the mechanism of reduced thymidine incorporation. No evidence could be obtained for any significant breakdown of DNA following irradiation. Prolonged DNA synthesis following irradiation is not considered to be the primary reason for mitotic delay. The radiation block is located less than 30 min before the onset of prophase and is possibly correlated with a condensation mechanism of the chromatin strands.
The effect of age and cold acclimation on the metabolism of brown adipose tissue in cold-exposed rats
Authors: Himms-Hagen Jean
Published: December 2009

The effect of exposure to cold (4°) on the incorporation of glucose carbon into total lipids of interscapular brown adipose tissue was studied in warm-acclimated and cold-acclimated rats of different ages. Exposure to cold had little effect on the very low incorporation in warm-acclimated rats regardless of their ages. Incorporation was always greater in cold-acclimated rats in the cold than in warm-acclimated rats in the cold, but the increase due to cold exposure was smaller in young cold-acclimated rats than in older cold-acclimated rats. The concentration of glucose in the blood was highest in the youngest rats and was increased further after exposure to cold; older rats did not become hyperglycemic in the cold. The relation between brown adipose tissue metabolism and nonshivering thermogenesis is discussed.
Liver phospholipids of rats deprived of dietary choline
Authors: Beare-Rogers Joyce L.
Published: December 2009

The effect of choline deprivation on the fatty acid composition of liver phospholipids was determined in male rats fed the test diet for 3 weeks in one experiment and for 2 weeks in another experiment.Phospholipids from total lipid extracts were precipitated in acetone saturated with MgCl2, and their acyl groups examined by gas chromatography. The concentration of arachidonic acid in the total phospholipids was inversely related to the total amount of lipid accumulated in the liver. Analyses of fatty acids released by snake venom also demonstrated the reduced proportion of arachidonic acid in the fatty livers of choline-deprived rats. In deficient livers having relatively low lipid deposits, there were increased concentrations of docosapentaenoic and docosahexaenoic acids. Choline deprivation appeared not to alter the fatty acid composition of phosphatidylcholine, but less of this phospholipid was synthesized. The most striking effect of the deficiency was the decreased concentration of arachidonic acid compensated by more unsaturated acids in liver phosphatidylethanolamine.
Kinetic properties of the α-lytic protease of Sorangium sp., a bacterial homologue of the pancreatopeptidases
Authors: Kaplan H. , Whitaker D. R.
Published: December 2009

The kinetics under consideration are those of a bacterial serine protease with the same "active serine" sequence as chymotrypsin, trypsin, and elastase, and with a single histidine residue in a sequence which closely matches the sequences around histidine-57 of chymotrypsin and the analogous histidine residues of trypsin and elastase. In agreement with previous evidence of an elastase-like specificity, esters of N-substituted, neutral, aliphatic L-amino acids proved to be good to excellent substrates for the α-enzyme; esters of arginine, tyrosine, and tryptophan were not hydrolyzed. The enzyme has a much higher activity than the pancreatopeptidases towards p-nitrophenyl acetate and p-nitrophenyl trimethyl acetate; the catalytic rate coefficient kc for the latter substrate is about fivefold greater than that of elastase.The catalytic properties match those of the pancreatopeptidases in the following respects. As demonstrated with N-acetyl-L-valine methyl ester as substrate, kc is dependent on an ionization with a pKa of 6.7 in water and 7.3 in H22O; Δ log (kc/Km)/ΔpH for this ionization is equal to 1.0; kc is reduced 50% when H2O is replaced by H22O. These findings are consistent with a requirement for a single unprotonated histidine residue and general basic catalysis by that residue. The burst of p-nitrophenol in hydrolyses of p-nitrophenyl trimethyl acetate is proportional to [E]0; the magnitude of the proportionality factor and the rate of attainment of a steady state are consistent with the condition [Formula: see text], as in chymotrypsin kinetics. Thus the purely catalytic properties of the α-enzyme match those of chymotrypsin very closely. These findings do not support reaction mechanisms which require two catalytically functional histidine residues for such catalysis. The substrate-binding properties of the α-enzyme differ from those of chymotrypsin in that substrate binding does not depend on ionization of an N-terminal α-amino group; Km for the hydrolysis of N-acetyl-L-valine methyl ester is constant from pH 5 to pH 10 and enzymatic activity is unaffected by acetylation of the enzyme's α- and ε-amino groups. Ks for the hydrolysis of p-nitrophenyl trimethyl acetate is appreciably greater than the Ks of elastase for this substrate.The chloromethyl ketones of glycine and valine did not inhibit the enzyme or alkylate its histidine residue.
Oxidation of catechol in higher plants. I. Enzymic conversion of catechol to 3,4,3′,4′-tetrahydroxydiphenyl
Authors: Kandaswami C. , Rao P. V. Subba , Nair P. M. , Vaidyanathan C. S.
Published: December 2009

Acetone-dried powders prepared from the leaves of Tecoma stans oxidized catechol to 3,4,3′,4′-tetra-hydroxydiphenyl and diphenylenedioxide-2,3-quinone. Extracts of acetone powder when fractionated with acetone and adsorbed onto and eluted from alumina Cγ gave preparations which catalyzed the stoichiometric formation of 1 mole of 3,4,3′,4′-tetrahydroxydiphenyl from 2 moles of catechol
Protective factors in the detoxication of hydrogen peroxide in erythrocytes
Authors: Paniker N. V. , Iyer G. Y. N.
Published: December 2009

The scope of catalase and of glutathione as factors protecting the hemoglobin of erythrocytes of several animal species against oxidation by hydrogen peroxide has been studied. In catalase-rich cells, catalase by itself can largely protect the hemoglobin even if glutathione is immobilized with iodoacetamide. The protective effect of added glucose was studied in erythrocytes exposed to hydrogen peroxide in the presence of the catalase inhibitors 3-amino-1,2,4-triazole and sodium azide. Except in the cow erythrocytes, glucose is uniformly effective in protecting hemoglobin and also in maintaining glutathione in the presence of aminotriazole. Lactate is generally ineffective in protecting hemoglobin or maintaining glutathione. Inhibition of catalase by azide makes the hemoglobin of monkey erythrocytes quite vulnerable to oxidation by hydrogen peroxide even in the presence of added glucose, but rabbit hemoglobin is effectively protected under the same conditions. However, glutathione levels are maintained in both. Iodoacetamide causes increased methemoglobin formation in glutathione-free hemolysates exposed to hydrogen peroxide in the presence of azide. The effect is largest in the rabbit and guinea pig hemolysates, while it is least in the monkey hemolysate. Cysteine and glutathione can reverse this effect. It would appear that besides catalase and glutathione, a nonglutathione sulfhydryl compound(s) might have a role in the protection of hemoglobin.
Differential determination of D-isoascorbic acid and L-ascorbic acid in guinea pig organs
Authors: Pelletier Omer
Published: December 2009

To test the theory that D-isoascorbic acid (IAA) was not retained by the organs of animals, guinea pigs were fed a synthetic diet containing ascorbic acid (AA) plus IAA. The incorporation of IAA and AA was determined by making use of the different rates of osazone formation of oxidized AA and IAA with 2,4-dinitrophenylhydrazine. It was found that the organs of the guinea pigs retained a significant quantity of IAA which replaced a corresponding quantity of AA. The incorporated IAA could, in turn, be replaced by AA when only AA was subsequently given in the diet.
Proton magnetic resonance studies at 220 MHz of alanine transfer RNA
Authors: Smith Ian C. P. , Yamane Tetsuo , Shulman R. G.
Published: December 2009

Proton magnetic resonance spectra at 220 MHz of alanine transfer RNA do not permit assignments of individual peaks due to each of the common bases; only a peak attributable to protons at position eight in adenine can be assigned with certainty. Measurements of the relative areas of proton magnetic resonance peaks due to the base and ribose-1′ protons indicate that the ribose moieties of tRNA are not involved in bonds stronger than those experienced by the bases. Proton magnetic resonance peaks attributable to the methyl and dihydro protons of the rare bases can be distinguished in the 220 MHz spectra; the variation of their line widths and chemical shifts with increasing temperature indicates that the rare bases are located in regions of the alanine transfer RNA molecule which are more highly organized than indicated by an open cloverleaf model.
Fructose diphosphate aldolase of yeast: studies on the sulfhydryl groups
Authors: Ingram J. M.
Published: December 2009

Yeast fructose 1,6-diphosphate aldolase is inhibited by mercury ion and p-hydroxymercuribenzoate. The respective inhibitions are freely reversed upon the addition of thiol. Incubation of the enzyme at values as low as pH 4.5 inhibited activity, and the inactivated enzyme was reactivated by Cleland's reagent. The results suggested that this mode of inhibition proceeded initially via disulfide bond formation.Quantitative –SH group titrations of the native enzyme indicate that approximately six residues are available for reaction. The addition of 6 M urea increased the available –SH groups to between eight and nine. This latter value approaches the number of half-cystine residues determined following amino acid analysis of the native enzyme. Quantitative –SH group titrations with 5,5′-dithiobis(2-nitrobenzoic acid) also indicated four to five available residues, while in the presence of 6 M urea an additional four residues were released. Chelate inhibitors of the enzyme, EDTA and o-phenanthroline, behaved in a manner similar to 6 M urea in that additional –SH groups were released for reaction. Qualitative rate studies showed that the first group of four –SH residues reacted at least 100 times more rapidly than the second group. The significance of these two classes of –SH residues to catalysis and structure is discussed.
ADP-dependent palmitoykarnitine sensitivity of mitochondria isolated from the perfused rabbit heart
Authors: Kako K. J.
Published: December 2009

The function of mitochondria as influenced by the depletion of oxidizable substances in the myocardium was examined during perfusion of the isolated rabbit heart. Mitochondria were isolated using proteinase and KCl–albumin medium, and their respiration was measured polarographically at 25 °C.(i) Mitochondria of nonperfused hearts (control) responded to repeated additions of ADP with repeated and reproducible "state 4 to state 3 transitions" in the presence of a variety of oxidizable substrates (glutamate, oxoglutarate, acetate, pyruvate, β-hydroxybutyrate, succinate, and palmitoyicamitine).(ii) The heart of a fed animal was perfused almost to exhaustion in a substrate-free medium and mitochondria were isolated and tested. The following findings were obtained (iii–viii).(iii) The respiratory control was gradually lost in a response to repeated additions of ADP, when palmitoylcamitine was used as the substrate. A larger quantity of mitochondria in a given assay partially counteracted this gradual loss of the respiratory control.(iv) The respiratory control and P/O ratios of mitochondria obtained from these hearts were slightly depressed as compared to those of the control, when measured using glutamate or oxoglutarate. Malate addition was required for pyruvate oxidation by mitochondria from perfused hearts.(v) The state 3 respiratory rate of the mitochondria obtained from an exhausted heart was about one-quarter that of the control mitochondria regardless of substrates used. The values were independent of the amount of mitochondria present in the assay system.(vi) With paimitoyicamitine as the substrate, the respiratory control ratio calculated from the first state 3 to state 4 transition was influenced by the amount of mitochondria present. The ratio was depressed at low concentrations of mitochondria.(vii) The rate of exogenous NADH oxidation in the absence of cytochrome c and the optical density of the mitochondrial suspension at 520 mμ, were similar with mitochondria prepared from nonperfused and perfused hearts. An addition of cytochrome c accelerated the rate of NADH oxidation by the latter more than the control.(viii) Unstimulated ATPase activity was high in mitochondria of the perfused heart; the enzyme was stimulated by DNP to a lesser degree and by a smaller quantity of paimitoyicarnitine than the control.(ix) The mitochondria prepared from the perfused heart of a fasted animal and from the fed rabbit's heart perfused in the presence of glucose, albumin, or 30 mM KCl (cardiac arrest) showed a normal respiratory function.(x) The mitochondria of the heart in anoxic arrest showed uncoupling of oxidative phosphorylation and a low respiratory rate regardless of the hydrogen donors used.(xi) It is concluded that a prolonged lack of hydrogen sources in perfused exhausted rabbit hearts results in the mitochondrial dysfunction.
Ultraviolet circular dichroism studies on synthetic polynucleotides
Authors: Wolfe Fred H. , Oikawa Kimio , Kay Cyril M.
Published: December 2009

The ultraviolet circular dichroism spectra of polyadenylic acid, polyguanylic acid, polycytidylic acid, polyinosinic acid, and polyuridylic acid have been examined at neutral and acidic pH values, and at moderate and low ionic strengths, over the wavelength range 300–185 mμ. Increased resolution of spectra below 225 mμ has revealed heretofore unexamined ellipticity bands in the low wavelength region, which are sensitive to conformational alterations for those polynucleotides which exhibit both single and multistranded secondary structures. It is concluded that these ellipticity bands, in view of their extreme sensitivity to conformation, will be of significance in increasing the usefulness of the homopolynucleotides as model compounds in conformational studies of naturally occurring RNAs.
Nitrogen metabolism of Picea glauca. IV. Metabolism of uniformly labelled 14C-L-arginine, [carbamyl-14C]-L-citrulline, and [l,2,3,4-14C]-γ-guanidinobutyric acid during diurnal changes in the soluble and protein nitrogen associated with the onset of expansion of spruce buds
Authors: Durzan D. J.
Published: December 2009

In spring as white spruce buds started to expand, seasonal levels of proline were high and pool sizes of most free amino acids were maximal at sunset and sunrise. Uniformly labelled 14C-L-arginine, applied to buds at sunrise, was converted to citrulline via ornithine. [Carbamyl-14C]-L-citrulline was metabolized to argininosuccinate, arginine, and urea. These reactions indicated the presence at low levels of the Krebs–Henseleit or ornithine cycle. No convincing urease activity could be extracted or detected histochemically. Urease, added to extracts of buds exposed to radioactive L-arginine or L-citrulline, released 14CO2 confirming the presence of 14C-urea. L-Arginine was converted readily to ornithine, Δ1-pyrroline-5-carboxylic acid, and proline. The appearance of 14C in monosubstituted guanidines, e.g. γ-guanidinobutyric acid and others, which remained unidentified but proven not to be homoarginine, agmatine, argininic acid, nor γ-guanidinobutyramide, accounted more readily for the metabolism of arginine than did the ornithine cycle alone. L-Citrulline was metabolized via arginine to γ-guanidinobutyric acid and to several unidentified compounds that were not amino acids or related to monosubstituted guanidines. 14C-γ-Aminobutyric acid, a product of arginine degradation, was also derived from [l,2,3,4-14C]-γ-guanidinobutyric acid suggesting the presence of a heteroarginase. γ-Guanidinobutyric acid was translocated down the shoot with little distribution of 14C into other compounds.14C from arginine and citrulline and to a much lesser extent from γ-guanidinobutyric acid was recovered in the protein fraction mainly as arginine, glutamic acid, and proline. Maximal incorporation of 14C into protein was reached at or near midnight, then rapidly fell to noon of the following day. Incorporation of 14C into bud protein was out of phase with levels of total protein N and in phase with an increase of radioactivity in compounds of the anionic and neutral fraction, reflecting dramatically the complexity of the nitrogen metabolism of buds awakening from winter dormancy.
Regulation of lysosomal enzymes. I. Adaptive changes in enzyme activities during starvation and refeeding
Authors: Desai I. D.
Published: December 2009

The changes in the activity of five representative lysosomal enzymes of rat liver and kidney, namely acid phosphatase, β-glucuronidase, β-galactosidase, arylsulfatase, and cathepsin D, during starvation and refeeding have been studied. When rats were fasted for periods of up to 120 h, both free and total activities of hepatic lysosomal enzymes progressively increased reaching levels two to seven times higher than those of fed controls. On resuming feeding at the end of a starvation period, enzyme activities rapidly returned to normal. There was a close relationship between increased lysosomal enzymes during starvation and loss in liver and body weights of the animal. These findings, taken together, suggest a specific role for lysosomal enzymes in adaptive processes requiring turnover of body tissues for maintenance and survival of the animal without doing itself irreparable damage during starvation.
The isolation of estrone sulfate and estradiol-17β sulfate from stallion testes
Authors: Raeside James I.
Published: December 2009

A method is described for the extraction and purification of estrogen sulfates from testicular tissues. By use of this method estrone 3-sulfate and estradiol-17β 3-sulfate were isolated from stallion testes and identified by infrared spectroscopy. Further characterization was effected by the use of estrone-4-14C and estrone-6,7-3H 3-sulfate as standards for chromatographic comparison. Preliminary results indicated that the amounts of the estrogens present as sulfates were greatly in excess of the amounts present as free steroid. Estradiol-17α could not be detected.
Preparation of myelin using the L-4 zonal ultraceatrifuge
Authors: Murdock D. D. , Katona E. , Moscarello M. A.
Published: December 2009

A method for the isolation of large amounts of myelin from human white matter has been developed, using the zonal ultracentrifuge. The myelin prepared by this method compares favorably with the method previously used for smaller amounts of myelin. The composition of the isolated myelin was 8–12 μg P/mg, 18–22% protein, 0.072–0.128% RNA, 0.05–0.07% DNA, and was 95% soluble in chloroform–methanol 2:1 v/v.