A preliminary study of serum beta-glucuronidase enzyme activity in progressive muscular dystrophies.
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Adult↗
Biomedical subjects
M Zatz
Publications and source records attributed to M Zatz.
Serum CK-MB activity in progressive muscular dystrophy: is it of nosologic value?
Serum creatine-kinase (CK) isoenzyme MB was measured in 53 patients affected by different types of myopathies (20 with Duchenne muscular dystrophy (DMD), eight with the Becker form (BMD), ten with the limb-girdle form (LGMD), six with the facioscapulohumeral form (FSH), and nine affected by polymyositis and in 21 normal control subjects). The aim of this study was to compare each group with the control individuals and to assess the nosologic value of CK-MB activity among some clinically similar dystrophies, which may have an important application for genetic counseling. A statistically significant increased CK-MB activity was found only in the Duchenne and Becker patients when compared with control persons (p less than 0.05). When the different groups of patients were compared among themselves, no significant difference was found between DMD and BMD or LGMD and polymyositis. However, a significant difference was found between BMD and LGMD. Based on these data, it is possible, through discriminant analysis, to estimate the relative biochemical probability of an isolated male patient belonging to either group.
Adult↗
Creatine-kinase and pyruvate-kinase activities in normal children: implications in Duchenne muscular dystrophy carrier detection.
Serum creatine-kinase (CK) and pyruvate-kinase (PK) levels were determined in 201 boys and girls less than 15 years old to establish values and to investigate a possible correlation between enzyme activity, sex, and age. It was observed that the mean CK activity in boys was significantly higher than in females (of all ages), whereas it did not differ statistically between girls and women. A slight but significant correlation between CK activity and age was found only in females. The mean PK activity in children was significantly greater than in adult women and it decreased significantly with age in children of both sexes. Furthermore, a slight correlation between CK and PK was observed only in girls. Based on these results, we suggest that the results of CK and PK determinations of females at risk for Duchenne muscular dystrophy should be compared with controls of comparable age and sex.
Adolescent↗
Definitive localization of Becker muscular dystrophy in Xp by linkage to a cluster of DNA polymorphisms (DXS43 and DXS9).
A study of linkage between Becker muscular dystrophy and four X chromosome-specific DNA polymorphisms in 17 kindreds has indicated that this gene is located in Xp, as already anticipated by single pedigree analysis. In particular the DXS43 and DXS9 loci, identified by probes D2 and RC8, respectively, are closely linked to each other and are both located at approximately 15 cM from the Becker locus. These linkage data, together with the previously established linkage between Becker and the DXS7 locus identified by probe L 1.28, indicate that the Becker gene is located in the same region where Duchenne has been mapped and also yield information about relative genetic distances among different DNA polymorphisms of the X chromosome.
Alleles↗
Lithium induces corticotropin secretion and desensitization in cultured anterior pituitary cells.
Lithium stimulated corticotropin (ACTH) secretion by mouse pituitary tumor cells (AtT-20/D16-16) and by normal rat anterior pituitary cells in primary culture. Effects were observed at less than 2 mM LiCl. ACTH secretion was comparable in magnitude to that induced by other secretagogues, was calcium dependent, and was inhibited by somatostatin. Lithium also induced changes in [3H]inositide metabolism; these changes accompanied and were correlated with changes in ACTH secretion. The most prominent and reliable effect was to increase [3H]inositol monophosphate. Other secretagogues had no effect on [3H]inositides in the presence or absence of lithium. Pretreatment with lithium for 3 hr desensitized the cells to the effects of subsequent exposure to lithium. The cells were not desensitized to lithium by pretreatment with other secretagogues, nor were they desensitized by lithium to the effects of corticotropin-releasing factor, high potassium, or forskolin. However, pretreatment with lithium did desensitize the cells to stimulation by phorbol esters. The interaction between lithium and phorbol esters suggests the involvement of inositide metabolism and protein kinase C in the regulation of ACTH secretion and possibly of other hormones or neurotransmitters. It also suggests new avenues of research into the basis of lithium's psychopharmacological effects.
Adrenocorticotropic Hormone↗
Phorbol esters mimic alpha-Adrenergic potentiation of serotonin N-acetyltransferase induction in the rat pineal.
alpha-Adrenergic stimulation of the rat pineal gland is known to stimulate phosphatidylinositol turnover and to potentiate the induction of serotonin N-acetyltransferase (SNAT) activity evoked by submaximal beta-adrenergic stimulation. In some (other) systems tumor-promoting phorbol esters are known to mimic physiologic stimulation and to enhance specifically the activity of protein kinase C. Here it is shown that phorbol esters specifically mimic the potentiating effect of alpha-adrenergic stimulation on SNAT activity in the rat pineal. These effects contribute to the argument for a role for phosphatidylinositol turnover and protein kinase C in mediating alpha-adrenergic stimulation.
Acetyltransferases↗
Denervation supersensitivity of the rat pineal to norepinephrine-stimulated [3H]inositide turnover revealed by lithium and a convenient procedure.
A convenient procedure for the assay of myo-[2-3H(N)]inositol ([3H]inositol) metabolites in cells or small amounts of tissue was developed. The procedure is a composite of modifications of published methods. After preincubation with [3H]inositol, rat pineal glands were disrupted in an acidified organic solvent mixture. Lipids were separated from the hydrophilic products and precursor using Sephadex G-25 columns and further analyzed by TLC. Hydrophilic products were further analyzed by anion-exchange column chromatography using Dowex AG1-X8 (formate form). In the presence of lithium, increases in inositol phosphates consequent to stimulation of the glands by norepinephrine were apparent within 10 min. The response in denervated glands was considerably greater than in intact pineals.
Animals↗
Metabolism of pantethine in cystinosis.
D-Pantethine is a conjugate of the vitamin pantothenic acid and the low-molecular-weight aminothiol cysteamine. Pantethine is an experimental hypolipemic agent and has been suggested as a source of cysteamine in the treatment of nephropathic cystinosis. We treated four cystinotic children with 70-1,000 mg/kg per d oral D-pantethine and studied its metabolism. Pantethine was rapidly hydrolyzed to pantothenic acid and cysteamine; we could not detect pantethine in plasma after oral administration. The responsible enzyme, "pantetheinase," was highly active in homogenates of small intestinal mucosa and plasma. The Michaelis constant of the rat intestinal enzyme was 4.6 microM and its pH profile showed a broad plateau between 4 and 9. Pantothenate pharmacokinetics after orally administered pantethine followed an open two-compartment model with slow vitamin elimination (t1/2 = 28 h). Peak plasma pantothenate occurred at 2.5 h and levels over 250 microM were seen at 300 times normal. Apparent total body storage of pantothenate was significant (25 mg/kg), and plasma levels were elevated threefold for months after pantethine therapy. Plasma cysteamine concentrations after pantethine were similar to those reported after equivalent doses of cysteamine. However, at best only 80% white blood cell cystine depletion occurred. We conclude that pantethine is probably less effective than cysteamine in the treatment of nephropathic cystinosis and should only be considered in cases of cysteamine intolerance. Serum cholesterol was decreased an average of 14%, which supports the potential clinical significance of pantethine as a hypolipemic agent. Rapid in vivo hydrolysis of pantethine suggests that pantothenate or cysteamine may be the effectors of its hypolipemic action.
Adolescent↗
Acylation of bovine rhodopsin by [3H]palmitic acid.
Bovine retinas or preparations of rod outer segments incorporate [3H]palmitic acid into rhodopsin. The incorporation is both time- and temperature-dependent. The major product retains the chromatographic and electrophoretic properties of rhodopsin and remains photosensitive as demonstrated by alteration of its chromatographic behavior upon exposure to light. The incorporated radioactivity resists extraction with organic solvents and is not dissociated from the protein by detergents or under the denaturing conditions of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Radioactive free fatty acid can, however, be released by alkaline hydrolysis. Hydroxylamine treatment yields a mixture of the free fatty acid and the fatty acyl hydroxamate. These results demonstrate the formation of an ester bond between [3H]palmitic acid and rhodopsin. Cycloheximide fails to inhibit the incorporation. This finding along with the ability of rod outer segments to support the incorporation point to the acylation of rhodopsin as a late post-translational event.
Acylation↗
Pantethine and cystamine deplete cystine from cystinotic fibroblasts via efflux of cysteamine-cysteine mixed disulfide.
Children suffering from cystinosis, a genetic disease characterized by high levels of lysosomal cystine, are currently being treated with cysteamine to lower the cystine levels in their cells. In fibroblasts from these patients, cysteamine and its disulfide, cystamine, are equally effective in lowering cystine levels. We recently reported that pantethine, a dietary precursor of coenzyme A, depletes cystine from cultured, cystinotic fibroblasts as effectively as cystamine. To determine the mechanism of action of pantethine, and of cystamine, we have compared the fate of [35S]cystine-derived metabolites in the presence and absence of these agents. The results indicate that the ability of pantethine to deplete cystine resides in its being a metabolic precursor of cysteamine. Furthermore, both pantethine and cystamine act by generating the mixed disulfide of cysteamine and cysteine in the lysosomes, which is then rapidly excreted from the cells. The fall in intracellular [35S]cystine caused by these agents was not accompanied by a comparable increase in any intracellular metabolite; rather, it could be accounted for by the appearance of mixed disulfide in the medium. There was no accumulation of mixed disulfide in the cells. Radioactivity in cytoplasmic glutathione was, however, increased by cystamine or pantethine. Thus, cysteamine (formed intracellularly in these experiments) undergoes thiol-disulfide exchange with cystine in the lysosomes, producing cysteamine-cysteine mixed disulfide and free cysteine, which enter the cytoplasm. The free cysteine is available to several pathways, including oxidation to the disulfide or the mixed disulfide, and synthesis of glutathione. The mixed disulfide is excreted from the cell, which ultimately depletes the cell of its excess cystine.
Cells, Cultured↗
Cyclic guanosine 3':5'-monophosphate mimics the effects of light on a circadian pacemaker in the eye of aplysia.
Environmental light regulates the phase of a circadian oscillator in the eye of Aplysia. We are attempting to define the events involved in transmitting light information from the environment to the circadian pacemaking mechanism in the eye. In this paper, we present several lines of evidence that cyclic guanosine 3':5'-monophosphate (cGMP) is involved in the photic entrainment pathway. Light increases the level of cGMP in eyes without having detectable effects on cyclic adenosine 3':5'-monophosphate (cAMP). An analogue of cGMP, 8-bromoguanosine 3':5'-cyclic monophosphate (cGMP), can shift the phase of the circadian rhythm from the eye; the phase response curves for light and for 8-bromo cGMP are indistinguishable. Neither 8-bromo cAMP nor 8-bromo 5'-GMP mimics the effect of light or of 8-bromo cGMP on the rhythm. Light and 8-bromo cGMP appear to use convergent mechanisms for entrainment since the effects of these two treatments are nonadditive. Also, low Na+ solutions antagonize the effects of both treatments. Finally, the kinetics of phase shifting by 8-bromo cGMP are similar to the kinetics of phase shifting by light. In addition to perturbing the circadian rhythm, 8-bromo cGMP increases the frequency of spontaneous optic nerve impulses. The pattern of nerve impulses during 8-bromo cGMP treatment is the same as the pattern of impulses produced by light. The excitatory effect of 8-bromo cGMP, the low Na+ blockade of the effects of 8-bromo cGMP, and the involvement of membrane depolarization in phase shifting by light suggest that depolarization mediates the effect of 8-bromo cGMP on the rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Results of blind testing a method to detect carriers of the Duchenne muscular dystrophy gene.
We blind-tested a method that in earlier studies had shown increased leucine uptake in muscle fibers of biopsy specimens from three obligate carriers and seven of 11 putative carriers of the gene for Duchenne muscular dystrophy. Here, muscle samples obtained at biopsy in seven obligate carriers and nine control subjects from Brazil were examined in Canada without knowledge of the carrier status or serum enzyme concentrations. Leucine uptake was increased in four controls and within normal range in four carriers, a rate of false-positives and -negatives that underscores the need for blind-testing methods for detecting carriers of this disease.
Adult↗
Novel formation of S-methylacylthioester from oleoyl coenzyme A and S-adenosylmethionine in the presence of FeSO4.
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Acyl Coenzyme A↗
Identification of ubiquinone-50 as the major methylated nonpolar lipid in human monocytes. Regulation of its biosynthesis via methionine-dependent pathways and relationship to superoxide production.
Human blood monocytes incorporated the methyl group from methionine into their neutral lipids. The major methylated product was identified as ubiquinone-50 in monocytes, lymphocytes, and a variety of human tumor cell lines by several analytical procedures including TLC or high performance liquid chromatography and as ubiquinone-45 in a mouse tumor cell line. Up to three methyl groups were shown to be derived from methionine by mass spectrometry. The rate of synthesis of ubiquinone-50 by monocytes as assessed by measuring labeled methyl group incorporation was shown to be linear over a 3-h period. Degradation of ubiquinone proceeded slowly; 80% of the labeled compound persisted after 18 h. The dependence of ubiquinone-50 synthesis upon methionine concentration was established in monocytes, with an estimated apparent Km for methionine of about 20 microM. The tumor promoter, tetradecanoate phorbol acetate, a potent stimulator of superoxide anion (O2-) production in phagocytic cells, inhibited ubiquinone-50 synthesis at nanomolar concentrations in monocytes, but not in lymphocytes, under conditions where oxidation of methionine takes place. Degradation of the labeled ubiquinone was unaffected. Formylmethionylleucyl-phenylalanine, a chemoattractant peptide which stimulates O2- production in phagocytic cells, also inhibited ubiquinone-50 synthesis. The degree of inhibition by either stimulus was increased when the methionine concentration in the medium was low. These findings demonstrate that in human monocytes ubiquinone-50 biosynthesis is regulable and that methionine concentration modulates both its rate of synthesis and the inhibitory effects of two stimuli of O2- production.
Animals↗
Serum pyruvate-kinase (PK) activity during pregnancy in potential carriers for Duchenne muscular dystrophy.
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Creatine Kinase↗
Effects of genetic counseling on Duchenne muscular dystrophy families in Brazil.
We report the preliminary results of a follow-up study of 574 females at-risk for Duchenne dystrophy, recontacted 3 to 13 yr after genetic counseling (GC). Among them, 290 are younger than 18 yr or still unmarried. The effectiveness of GC (reproductive performance) in the remaining group is analyzed in terms of procreation, rate of sterilization, and mean number of children. The observed data suggest that females at-risk involved in GC had about 169 children less than their normal, nonaffected brothers. In terms of prevention this would correspond roughly to 42 Duchenne affected boys and 42 carrier girls.
Amniocentesis↗
Creatine-kinase (CK) and pyruvate-kinase (PK) activities in cord blood of normal newborn infants: application to Duchenne muscular dystrophy screening programs.
Creatine-kinase (CK) and pyruvate-kinase (PK) were determined in cord blood samples from 125 normal newborn infants in order 1) to investigate the correlation between CK and PK, 2) to evaluate a possible influence of the mode of delivery (cesarean section versus vaginal delivery) and birth weight on enzyme activity, 3) to establish normal values for both sexes. In the present investigation, the enzyme activities of cord blood were significantly higher than in the normal adult, and no correlation was observed between enzyme activity and mode of delivery or birthweight. Although there was an apparent and significant correlation (r = 0.5) between CK and PK levels in cord blood samples, in no case did we find both high CK and PK values, something that would suggest preclinical DMD or a false-positive result. These results have led us to suggest determination of serum PK activity in male newborn screening programs. This would allow an early discrimination between false-positives and clinical cases already in the neonatal period. Furthermore, the concomitant use of PK and CK in boys not walking by 18 months could be a useful test for diagnosing preclinical DMD boys.
Birth Weight↗
Pantethine depletes cystinotic fibroblasts of cystine.
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Cells, Cultured↗