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S Natelson

Publications and source records attributed to S Natelson.

At least 19 recordsLinked to original sources
PubMed1994

L-homoserine hydroxamic acid as an antitumor agent.

This report confirms the potent mutagenic and antitumor activity of L-homoserine hydroxamic acid in both in vitro and in vivo test systems. Its mutagenic potential is evident in the developing tadpoles of Xenopus laevis eggs exposed to the compound. Cytotoxic effects are demonstrated against human leukemia and melanoma cell lines proliferating in tissue culture and against xenografts of human breast cancer and sarcoma growing in nude mice. We propose that the mutagenic and antitumor activity are mediated through hydroxylamine, which is released from its stable carrier amino acid, homoserine, consequent to a reduction in pH occurring at the cellular level. The cytotoxic effects of L-homoserine hydroxamic acid are more intense than those of the D-isomer and are more evident in neoplastic than in normal cell lines.

Animals↗
PubMed1986

The lactam of alpha-guanidinoglutaric acid (1-amidino-2-pyrrolidone-5-carboxylic acid).

alpha-Guanidinoglutaric acid (alpha-GGA) has been reported to occur in the cerebral cortex after epileptic seizures. No physical characteristics of alpha-GGA have been given. A practical procedure for the preparation of alpha-GGA is reported here. alpha-GGA forms a lactam in aqueous solution at 80 degrees C. It is proposed to substitute this lactam, 1-amidino-2-pyrrolidone-5-carboxylic acid (pAGlu), for pyroglutamic acid (pGlu) at the N-terminal position in neuropeptides to modify their biological characteristics. L(+)-Glutamic acid was reacted with S-methylisothiourea (I) at pH 10 in aqueous solution to form L(-)-alpha-guanidinoglutaric acid: mp 165-168 degrees C, [alpha]22D = -22.7 (C = 4, 2 M HCl). alpha-GGA reacted promptly with excess reagent to form a salt, S-methylisothiourea-alpha-guanidinoglutarate: mp 209-210 degrees C, [alpha]22D = -13.0 (C = 4, 2 M HCl). I was removed from the salt with aqueous picric acid, since I readily formed an insoluble picrate, S-methylisothiourea picrate (mp 225-228 degrees C). Alternatively, the salt was added to a cation exchange column, and the alpha-GGA was eluted with molar ammonium acetate buffer, pH 9.5. Its lactam, 1-amidino-2-pyrrolidone-5-carboxylic acid, mp 248-249 degrees C, [alpha]22D = +2.1 (C = 4, 2 M HCl), formed a picrate (mp 196-199 degrees C).

Chemical Phenomena↗
PubMed1984

Metabolic relationship between urea and guanidino compounds as studied by automated fluorimetry of guanidino compounds in urine.

In this automated system for assaying guanidino compounds, the compounds are resolved on an ion-exchange (Dowex 50) column, then reacted with phenanthrenequinone in alkaline solution. This mixture is then acidified and the resulting fluorescence is measured (lambda ex, 305 nm; lambda em, 395 nm). I applied the system to the analysis of urine from control rats and rats given L-canavanine, L-canavaninosuccinic acid, L-guanidinosuccinic acid, L-arginine, or urea, intraperitoneally. The recorder tracings are compared with those obtained for urine from healthy and uremic humans. After urea administration some guanidinosuccinate is excreted, along with substantial quantities of another substance that elutes just before guanidinosuccinate and so may be mistaken for it. Urine from uremic humans also shows this unidentified peak, but not urine from untreated rats or healthy humans. L-Canavanine gives rise, mainly, to guanidine and homoserine, apparently by reduction. Similarly, canavaninosuccinate is reduced to homoserine and guanidinosuccinate. Arginine gives rise to small quantities of guanidinosuccinate. Guanidinosuccinate is excreted mainly unchanged. When the guanidinosuccinate concentration is increased, excretion of guanidinoacetic acid is suppressed.

Animals↗
PubMed1983

Effect of canavanine and 2,3-dimercapto-1-propanol (British antilewisite) on the proliferation of Novikoff hepatoma cells in the presence of concanavalin A.

The effect of canavanine and 2,3-dimercapto-1-propanol (British antilewisite, BAL) on the uptake of (3H)-thymidine by Novikoff hepatoma cells, as a measure of DNA formation, was measured in tissue culture in the absence and presence of the mitogen, concanavalin A (Con A). Canavanine and Con A stimulated cell proliferation at low concentrations, and inhibited at higher concentrations. BAL inhibited even at low concentrations. In the presence of a stimulating concentration of Con A, both canavanine and BAL inhibitory effects were amplified. In the presence of a high concentration of Con A and low concentration of BAL the combined effect was substantially greater than the sum of the individual effects. We describe the culture and harvest of Novikoff hepatoma cells, and changes in their morphology when acted upon by the toxic agents used.

Animals↗
PubMed1979

Clinical biochemistry of epilepsy. I. Nature of the disease and a review of the chemical findings in epilepsy.

In idiopathic or generalized epilepsy, serum glucose and cholesterol concentrations tend to be low, especially just before the seizure. Glucose tolerance curves are abnormal and variable. The electrolyte balance is disturbed, and epileptics tend to go readily into alkalosis. Serum [Na+] is usually unaffected, but [K+] is normal to low between attacks and increases during and after the seizure. Serum [Cl-] is usually high just before the seizure. Epileptics are generally mildly hypocalcemic, especially in the period before the seizure. Serum urea and nonprotein nitrogen values are low between paroxysms but increase after the seizure. Serum protein concentration is usually normal. Stress, which releases epinephrine and corticotropin, results in high serum citrate concentration, which probably contributes to decreased serum [Ca2+] just before a seizure. In the healthy individual, any increase in serum citrate is accompanied by increasing [Ca2+]. In the rabbit, convulsions can be induced with corticotropin, a result of increased serum citrate concentration coupled with a decrease in [Ca2+]. The net result is severe hypo-ionic-calcemia. A similar phenomenon has been reported in a few humans. Administration of insulin causes serum citrate concentrations to decrease. Apparently, the dynamic system that controls glucose and lipid metabolism, and thus electrolyte balance, through the hormones epinephrine, corticotropin, insulin, glucagon, calcitonin, and parathormone, is abnormal in the epileptic.

Adrenocorticotropic Hormone↗
PubMed1979

Clinical biochemistry of epilepsy. II. Observations on two types of epileptiform convulsions induced in rabbits with corticotropin.

We propose than an alarm mechanism is operative in animals, designed to regulate neuromuscular irritability by regulating [Ca2+]. Epinephrine or corticotropin (ACTH), injected intramuscularly into animals, causes a hypercitricemia, resulting in decreased [Ca2+]. This increases muscular excitability to facilitate escape. To avoid over reaction, [Cl-] is shifted into the plasma without a concomitant shift of Na+, thus generating an acidosis and an increase in ionization of Ca. Plasma pH, pCO2, total CO2, and [K+] decrease, and [Mg2+] increases. The acidosis, decrease in K+, and increase in [Mg2+] serve to counteract the effect of the decrease in [Ca2+], to protect against tetany. In the rabbit the hypercitricemia observed upon ACTH administration is accompained by a severe hypocalcemia and drop in blood pressure, resluting in tetanic convulsions. This seems to indicate calcitonin release, independent of the hypercitricemia. Thyroidectomized rabbits show only mild hypocalcemia when given ACTH, but develop a severe acidosis and typical grand mal epileptiform seizures. Administration of ACTH and then calcitonin to the goat, an animal resistant to the effects of ACTH alone, simulates the effect observed in the rabbit with respect to changes in blood components and blood pressure. Changes in the blood in the goat and rabbit resemble those in humans before an epileptic seizure. alpha-Melanotropin, containing a portion of the ACTH sequence, reacts in a manner similar to ACTH but more rapidly.

Adrenocorticotropic Hormone↗
PubMed1978

On the biosynthesis of guanidinosuccinate.

We report a study motivated by a report that guanidinosuccinate is formed by transamidination from arginine to aspartate by perfused liver [J. Clin. Invest 57, 807 (1976)]. We prepared viable liver cells and incubated them with [14C]arginine labeled at the guanidino carbon and aspartate labeled at the methylene groups with tritium. A diacetyl-reacting band, similar to that reported with the perfusate in the above reference, was obtained by column chromatography. This band did not give a Sakaguchi reaction and contained no measurable tritium or 14C. Thus it did not derive from aspartate or arginine. On electrophoresis at pH 5.0, the diacetyl-reacting material moves to the cathode, guanidinosuccinate to the anode. The absorption spectrum of the diacetyl-reacting band showed a double peak, with maxima at 539 and 432 nm; guanidinosuccinate has only one maximum, at 533 nm. The diacetyl reagent reacts with sulfhydryl compounds and polypyrroles (e.g., bilirubin) to produce blue colors with significant absorbance in the 432-nm range. We saw no evidence for guanidinosuccinate formation by transamidination in these experiments with viable liver cells.

Animals↗
PubMed1977

Canaline carbamoyltransferase in human liver as part of a metabolic cycle in which guanidino compounds are formed.

This and previous papers examine the reasons for the relationship between the concentrations of guanidino-succinate and guanidinoacetate in human urine. With the demonstration here that extracts of human liver-tissue can mediate ureidohomoserine formation from canaline [(2-amino-4-aminooxy)-butyric acid] and carbamoyl phosphate, all steps in a cycle proposed for the production of guanidinoacetate and guanidinosuccinate have been documented. This includes synthesis of canavaninosuccinate from aspartate and ureidohomoserine, reductive cleavage of canavaninosuccinate to form guanidinosuccinate and homoserine, or, alternatively, lytic action on canavaninosuccinate to form fumarate and canavanine, and transamidination to glycine to form guanidinoacetate, regenerating the canaline. We propose that canaline originates from aspartate, but the precise mechanism by which canaline is formed needs to be elucidated.

Aminobutyrates↗
PubMed1977

Improved staining characteristics of serum lipids after halogenation and esterification of thin-layer chromatograms.

We describe a procedure for treatment of thin-layer chromatographic serum lipid patterns so that they may be stained by dyes for evaluation by densitometry. After development of the chromatogram [Clin. Chem. 18, 384 (1972)] the plates are dried and sprayed with butyryl chloride. This esterifies the free cholesterol. After drying, the plate is treated with iodine monobromide, to add iodline to the double bonds. The triacylglycerols (triglycerides), cholesterol esters, free cholesterol, and phospholipids are now all in the form of esters with no unsaturated double bonds. The free fatty acids are also now saturated. The chromatogram is now stained with basic fuchsine in acetate buffer (0.1 mol/liter, pH 5.0). Excess stain is removed with a buffered solution of guanidine hydrochloride. Erythrosine B may also be used. With basic fuchsine the background will be a uniform pink. With erythrosine B the background is white, but the stain tends to be washed out of the free fatty acids. The chromatograms are evaluated by densitometry, with use of a 540-nm filter for basic fuchsine and a 520-nm filter for erythrosine B. The stained chromatograms and densitometric scans accurately represent the relative concentration of the various lipid fractions as compared to that of an internal standard, and correlate with the nature of the disease being explored.

Adult↗
PubMed1977

Automated system for infrared spectrometric analysis for total CO2 of plasma contained in capillary tubes.

We describe how to assay plasma total CO2 automatically, discretely, and highly specifically by infrared absorption spectrometry. Plasma, 50 mul, is sampled in disposable capillaries and inserted into a block wherein the specimens are protected from exposure to air. A sequencer advances the block and signals a dispenser to flush the sample into a reaction vessel with 2.6 ml fo 50 mmol/liter H2SO4. After 24 s of incubation, the evolved CO2 is swept into a 1-meter infrared gas cell by a stream of nitrogen. A recorder displays the resulting peak in absorbance units. Operation of all valves controlling gas and liquid flow is regulated by the sequencer. In the present version, the time required for analysis of one sample is 65 s. The sample size may be reduced by at least 10-fold and the time sequence accelerated to assay 70-80 specimens per hour.

Autoanalysis↗
PubMed1976

Screening for erros in galactose metabolism with the erythrocyte.

We propose determination of the ratio of the rate of galactose metabolism to glucose metabolism by erythrocytes as a screening test for abnormalities in glucose and galactose metabolism. Packed erythrocytes (20 mul) are incubated for 1 h at 37 degrees C in 0.42 ml of a solution comprising phosphate buffer (pH 7.4), 0.4 mg of glucose, 60 mg of methylene blue, and 50 nCi of either [1-14C]glucose or [1-14C]galactose. Metabolism is then stopped by injecting dilute H2SO4 through a rubber septum sealing the flasks. On incubating the acidified solution for 1 h, the evolved CO2 is trapped in a well containing ethanolamine, which is suspended from the septum. The radioactivity of the well and its contents is measured in a scintillator, and from these data CO2 is calculated. (The scintillation medium is preheated with ethanolamine to eliminate chemiluminescence.) For normal adults mean values for CO2 are 0.468 mumol/liter of erythrocytes per minute for galactose and 37.8 mumol/liter of erythrocytes per minute for glucose. Homozygous galactosemics exhibit no galactose metabolism but the rate for flucose metabolism is normal. Results for parents of homozymotes are described. We review various causes for galactosemia and point out that transfer of galactose through the cell wall and into the erythrocyte is markedly reduced in certain cats and, although unreported, may possibly be a cause for galactosemia in humans.

Adult↗
PubMed1975

Serum and erythocyte argininosuccinate lyase assay by NADH fluorescence generated from formed fumarate.

Measurement of argininosuccinase (I; EC 4.3.2.1) activity is useful in following the course of disease in hepatitis and in screening for the genetic defect, argininosuccinic aciduria. Methodology is proposed for a novel procedure for the determination of I in serum and erythrocytes. In the procedure, fumarate, generated in the reaction, is assayed by conversion to malate with fumarase, determining the malate enzymatically with malate dehydrogenase, and estimating the NADH formed spectrofluorometrically. By this procedure, the enzyme activity in serum from normal individuals is less than 11 mumol/liter of erthrocytes/per hour. The correlation coefficient between results by this method and by the colorimetric method, which measures the arginine generated in the reaction, is +0.97 for serum and +0.98 for erythrocytes. The proposed procedure has a relatively low initial blank, requires less serum, and is completed faster.

Animals↗
PubMed1975

Fluorometry of citrate in serum, with use of citrate (pro-3S)-lyase.

We describe a procedure for enzymatic assay of citrate in human serum. The citrate is degraded to acetate and oxaloacetate with citrate oxaloacetate-lyase (pro-3S-CH2-COO- yields acetate) (EC 4.1.3.6). Some oxaloacetate loses CO2 to form pyruvate. Addition of malate and lactate dehydrogenases (EC 1.1.1.37 and 1.1.1.27) permits determination of the oxaloacetate and pyruvate generated, and thus of the citrate concentration. The decrease in NADH concentration is measured fluorometrically. Results obtained for 30 consecutive human sera by this procedure were compared to the procedure in which the citrate is converted to pentabromoacetone. There was no statistically significant difference in values obtained by the two procedures. The range of values (mean plus or minus 2 SD) found for sera from 25 blood donors by this procedure was 12.8-27.2 mg/liter (mean, 19.0 mg/liter). Serum citrate as measured by both procedures during a glucose tolerance test was decreased from initial values under the influence of administered glucose (and endogenous insulin). Insulin concentrations were also measured during these glucose-tolerance tests. Citrate concentrations remain subnormal after the glucose and insulin concentrations return to their initial values. This accords with published reports.

Acetone↗
PubMed1975

Evidence supporting a proposed mechanism explaining the inverse relationship between guanidinoacetate and guanidinosuccinate in human urine.

A proposed mechanism [Clin. Chem. 19, 668 (1973)] for the inverse relationship between guanidinoacetate (I) and guanidinosuccinate (II) in human urine is explored. The mechanism proposes that canavaninosuccinate (III) may be reduced to form homoserine and II or, alternatively, that the III may be acted upon by a lyase to form canavanine and fumarate. The canavanine would then proceed to transamidinate to glycine to form I. This study demonstrates for the first time that lyase activity for converting III to canavanine and fumarate exists in human liver and kidney extracts. Transamidination from canavanine to glycine to form I is also readily accomplished with human tissue. Reductive cleavage of III to II and homoserine has been demonstrated before [Clin. Chem. 15, 397 (1969)]. The optimum pH for the lyase reaction is 6.5, for the reductive cleavage it is 8.7. In following the course of the lyase reaction, we developed a technique whereby the fumarate formed was hydrated with fumarase (EC 4.2.1.2) and then dehydrogenated with malate dehydrogenase (EC 1.1.1.37). The changes in absorbance of NADH formed in the reaction were then measured and used to determine the amount of fumarate formed, as a measure of lyase activity. Canavanino-succinate lyase activity follows pseudo-first-order reaction kinetics. The Michaelis constant of this lyase was 6.16 X 10-4 mol/liter, for argininosuccinate lyase 9.74 X 10-4 mol/liter. These data suggest that the binding affinity for III to the enzyme is greater than that for argininosuccinate. Glycine added to the reaction acts as an activator, probably because it removes the canavanine from the reaction mixture. On the other hand, arginine acts as an inhibitor of III-lyase. Other substances tested, such as canavanine, fumarate, and argininosuccinate had no effect on the reaction kinetics.

Acetates↗