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Biomedical subjects

M Zatz

Publications and source records attributed to M Zatz.

At least 217 records · Page 12Linked to original sources
PubMed1982

Biosynthesis of S-methyl-N-oleoylmercaptoethylamide from oleoyl coenzyme A and S-adenosylmethionine.

Addition of oleoyl-CoA to incubations containing rat lung membranes and S-adenosyl [methyl-3H]methionine resulted in the formation of a previously unidentified nonpolar methylated lipid. The product was formed enzymatically, with an apparent Km for S-adenosylmethionine (AdoMet) of about 0.3 microM and half-maximal activity using about 0.1 mM oleoyl-CoA. Activity was highest in microsomes but present in other membranous fractions, including plasma membranes from mature human erythrocytes. Intact red blood cells formed the nonpolar methylated lipid intracellularly upon incubation with [methyl-3H]methionine and oleoyl-CoA. Product formation differed among membranes from various tissues. The nonpolar methylated lipid was analyzed by TLC, high performance liquid chromatography, and gas chromatography with radiodetection. It was identified as S-methyl-N-oleoylmercaptoethylamide by gas chromatography-mass spectrometry. Products obtained from oleoyl-CoA or palmitoyl-CoA, incubated with nonradioactive or [methyl-14C]AdoMet, were compared using electron impact and/or chemical ionization mass spectrometry. Inferred structures were confirmed using authentic standards. The methylated product was apparently formed by tissue as follows: (a) cleavage of oleoyl-CoA by an amidase to form S-oleoylmercaptoethylamine; (b) spontaneous rearrangement to form N-oleoylmercaptoethylamide; and (c) enzymatic methylation of the free thiol by AdoMet. Participation of the amidase was suggested by the biosynthesis of the amide (free thiol) using [1-14C]oleoyl-CoA.

Acyl Coenzyme A↗
PubMed1982

Regulation of circadian rhythmicity.

Daily rhythms in many behavioral, physiological, and biochemical functions are generated by endogenous oscillators that function as internal 24-hour clocks. Under natural conditions, these oscillators are synchronized to the daily environmental cycle of light and darkness. Recent advances in locating circadian pacemakers in the brain and in establishing model systems promise to shed light on the cellular and biochemical mechanisms involved in the generation and regulation of circadian rhythms.

Animals↗
PubMed1982

Stimulation of fatty acid methylation in human red cell membranes by phospholipase A2 activation.

Nonpolar methylated products comprise approximately 50% of the radioactive material extractable into chloroform/methanol after incubation of human red cell membranes with S-[methyl-3H]adenosylmethionine. One of these nonpolar products is fatty acid methyl ester. The enzyme which synthesizes fatty acid methyl ester had an apparent Km for S-adenosylmethionine of about 0.6 micro M and a Vmax of about 0.6 pmol/mg protein per 30 min. Half-maximal activity was achieved upon addition of about 20 micro M sodium oleate. Of the fatty acids tested, sodium oleate increased activity most effectively (6-fold) and arachidonic acid was ineffective. Evidence indicated that fatty acid methylation takes place on the cytoplasmic side of the plasma membrane. The reaction was demonstrable in intact cells incubated with [methyl-3H]methionine, and increased upon addition of sodium oleate. Incubation of intact cells with melittin, a potent membrane phospholipase A2 activator from bee venom, increased fatty acid methylation several-fold. Fatty acid methylation appears to be one of the consequences of phospholipase A2 action in plasma membranes.

Dose-Response Relationship, Drug↗
PubMed1982

Nonpolar lipid methylation-identification of nonpolar methylated products synthesized by rat basophilic leukemia cells, retina and parotid.

Incorporation of radioactivity from [3H- or 14C-methyl] methionine into nonpolar lipids had been investigated in rat basophilic leukemia (RBL) cells, retina, and rat parotid gland. These nonpolar methylated lipids were extracted into heptane and characterized by thin-layer chromatography, high performance liquid chromatography, gas chromatography, and mass spectrometry. The major methylated nonpolar lipid product in the RBL cells themselves was ubiquinone-9, which accounted for about 90% of the nonpolar lipid and 20-30% of the total radioactive lipid formed. There was a modest increase in the methylation of nonpolar lipids upon stimulation of the RBL cells with IgE and anti-IgE, but the significance of this change is uncertain. In contrast to whole cells, RBL membrane fractions (incubated with [3H-methyl]-S-adenosylmethionine) incorporated radioactivity primarily into fatty acid methyl esters and not ubiquinone. A third product, 2-(methylthio)-benzothiazole, was formed by RBL cells, retina and minced parotid upon incubation in enriched media. This product was formed enzymatically, apparently by the known enzyme S-thiolmethyltransferase, using the thiol substrate which contaminates these media. Evidence suggest that the enzyme may reside, at least in part, on the surface of the cells.

Animals↗
PubMed1982

Pyruvate-kinase (PK) and creatine-kinase (CK) in normal pregnancy and its implication in genetic counseling of Duchenne muscular dystrophy (DMD).

The activities of pyruvate-kinase (PK) and creatine-kinase (CK) were measured in 50 normal pregnant women in both serum and amniotic fluid. Serum PK activity was found to be significantly higher in pregnant than in nonpregnant women, while serum CK did not differ significantly between the two population samples. In amniotic fluid, very little or no PK or CK activity was found. However, the mean PK activity in amniotic fluid obtained from women carrying male fetuses was significantly higher than in those carrying female fetuses. At the present time, it is concluded that if a woman at risk for having a son with Duchenne dystrophy is seeking genetic counseling when already pregnant her serum PK or CK should be compared with that of normal female pregnant controls. It is also suggested that determination of pyruvate-kinase in fetal blood might be used in addition to CK for prenatal diagnosis of Duchenne muscular dystrophy.

Adult↗
PubMed1981

Nonpolar lipid methylation. Biosynthesis of fatty acid methyl esters by rat lung membranes using S-adenosylmethionine.

Fatty acid methyl esters are the major radioactive lipid products obtained after incubation of rat lung membranes with [methyl-3H or 14C]S-adenosylmethionine. Evidence which suggests an enzymatic transmethylation includes: time and protein dependence, lack of reaction at 0 degrees C or with heat-denatured membranes, an apparent affinity for S-adenosylmethionine of about 1 microM, inhibition by S-adenosylhomocysteine, and lack of inhibition by 0.1% methanol. Activity was highest in microsomes but present in other membranous fractions. Endogenous activity was highest in membranes from parotid, lung, and pancreas. Products were analyzed by organic solvent extraction, thin layer chromatography, column chromatography, high performance liquid chromatography, and gas chromatography. Identification of methylpalmitate, methylstearate, methyloleate, and methyllinoleate was confirmed by mass spectrometry. Presence of the radioactive methyl group was demonstrated by the variation of isotopic ratios with specific activity. Addition of oleate to incubation mixture increased the rate of product formation and preincubation experiments suggested the absence of long lived intermediates. The data suggest an enzymatic transfer of methyl groups from S-adenosylmethionine to free fatty acids.

Animals↗
PubMed1981

Injection of alpha-bungarotoxin near the suprachiasmatic nucleus blocks the effects of light on nocturnal pineal enzyme activity.

Environmental lighting can prevent or quickly reverse the nocturnal elevation of serotonin N-acetyltransferase activity in the rat pineal gland. Intraventricular injections of carbachol, acting via a 'nicotonic' cholinergic receptor, mimic the acute effect of light. Injections of alpha-bungarotoxin near the suprachiasmatic nucleus of the hypothalamus prevent the effects of light. These results suggest that acetylcholine is involved in the effects of light on the rat pineal's circadian rhythm.

Acetyltransferases↗
PubMed1981

Translocation (X;6) in a female with Duchenne muscular dystrophy: implications for the localisation of the DMD locus.

A female with Duchenne muscular dystrophy who was a carrier of a balanced translocation t(X;6)(p21;q21) is reported. Four other previously described (X;A) translocations associated with DMD share with the present case a breakpoint at Xp21. The extremely low probability of five independent (X;A) translocations having a breakpoint at Xp21 points to a non-rand association of this site with the DMD phenotype. A DMD locus at Xp21 could be damaged by the translocation, giving rise to Duchenne muscular dystrophy. Alternatively, a pre-existing DMD gene could weaken the chromosome, favouring breaks at Xp21.

Child↗
PubMed1980

'Brain-specific' benzodiazepine receptors are localized in the inner plexiform layer of rat retina.

Saturable, high affinity binding sites for [3H] diazepam have recently been characterized in rat brain. A significant component of this binding was determined to occur to a population of receptors which is pharmacologically similar to receptors present in mammalian brain and spinal cord. Neonatal treatment of rats with monosodium glutamate (MSG), intraocular administration of kainic acid, and the use of pink-eyed, tan-hooded (PETH) rats with a genetic retinopathy (degeneration of photoreceptor cells) suggests that these 'brain-type' receptors are highly localized on neuronal elements of the inner plexiform layer and/or ganglion cells.

Animals↗
PubMed1980

Serum pyruvate-kinase (PK) and creatine-phosphokinase (CPK) in female relatives and patients with X-linked muscular dystrophies (Duchenne and Becker).

Determination of serum creatine phosphokinase (CPK) activity is often used in efforts to detect carriers of X-linked muscular dystrophies. We have recently demonstrated that another serum enzyme, pyruvate-kinase (PK) may also be of use in the diagnosis of patients affected with a variety of neuromuscular disorders. To evaluate the usefulness of this assay for carrier detection, a comparative study of serum PK and CPK activity was performed in 74 female relatives of patients affected with Duchenne (DMD) and Becker (BMD) muscular dystrophies. For obligate carriers of the DMD gene, 10 of 14 had elevated CPK's, 11 of 14 had elevated PK's and 12 of 14 had abnormal results for either of the two enzymes. Three of 16 mothers of isolated cases had increased serum CPK activity and 6 of 16 had increased PK activity (7 had elevation of at least one enzyme). These preliminary data suggest that the use of PK may enhance the capability to discriminate carriers for these X-linked recessive genes.

Adolescent↗
PubMed1980

Effect of age on the detection rate in Duchenne muscular dystrophy.

In order to estimate SCK (serum creatine kinase) variability with age in carriers of Duchenne dystrophy (DMD), repeated SCK determinations in 10 obligate and 19 possible carriers were performed over a period of several years. Although there was some variation in some individuals, the differences in SCK means and risks of heterozygosity were not statistically significant between the first and second determinations. The present investigation indicates that the relation between SCK and age in carriers of the Duchenne gene is still controversial.

Adolescent↗