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M Zatz

Publications and source records attributed to M Zatz.

At least 145 records · Page 8Linked to original sources
PubMed1992

Different mosaicism frequencies for proximal and distal Duchenne muscular dystrophy (DMD) mutations indicate difference in etiology and recurrence risk.

In about 65% of the cases of Duchenne muscular dystrophy (DMD) a partial gene deletion or duplication in the dystrophin gene can be detected. These mutations are clustered at two hot spots: 30% at the hot spot in the proximal part of the gene and about 70% at a more distal hot spot. Unexpectedly we observed a higher frequency of proximal gene rearrangements among proved "germ line" mosaic cases. Of the 24 mosaic cases we are aware of, 19 (79%) have a proximal mutation, while only 5 (21%) have a distal mutation. This finding indicates that the mutations at the two hot spots in the dystrophin gene differ in origin. Independent support for the different mosaicism frequency was found by comparing the mutation spectra observed in isolated cases of DMD and familial cases of DMD. In a large two-center study of 473 patients from Brazil and the Netherlands, we detected a significant difference in the deletion distribution of isolated (proximal:distal ratio 1:3) and familial cases (ratio 1:1). We conclude from these data that proximal deletions most likely occur early in embryonic development, causing them to have a higher chance of becoming familial, while distal deletions occur later and have a higher chance of causing only isolated cases. Finally, our findings have important consequences for the calculation of recurrence-risk estimates according to the site of the deletion: a "proximal" new mutant has an increased recurrence risk of approximately 30%, and a "distal" new mutant has a decreased recurrence risk of approximately 4%.

Blotting, Southern↗
PubMed1992

A model to estimate the expression of the dystrophin gene in muscle from female Becker muscular dystrophy carriers.

The purpose of the present investigation was to assess the possibility of building a model to estimate, through dystrophin western blotting analysis, the expression of the DMD/BMD gene in muscle from heterozygotes. Dystrophin was analysed by mixing in increasing proportions (from 0% to 100%) aliquots of solubilised muscle from BMD patients with a qualitatively abnormal dystrophin and a normal male control. The intensity of the abnormal bands, which could be detected starting with 20% of muscle from the BMD patient, increased progressively according to the affected muscle concentration. In five obligate BMD carriers, two dystrophin bands were observed (corresponding to the products from the X bearing the normal and the BMD alleles), even among those with normal serum enzyme activities. Surprisingly, in the four obligate BMD carriers related to patients in whom an additional dystrophin fragment of 250 kd was present (two of them with raised serum enzymes), this band could not be seen, suggesting that the stability or the mechanism responsible for the synthesis of abnormal dystrophin products differs in heterozygotes compared to affected patients.

Adult↗
PubMed1991

Apparent association of mental retardation and specific patterns of deletions screened with probes cf56a and cf23a in Duchenne muscular dystrophy.

A total of 162 Duchenne (DMD) patients and two girls with a DMD phenotype were analysed for deletions in the central region of the dystrophin gene in order to determine if there was a correlation between mental retardation (MR) and the pattern of deletion. Approximately 43% of the patients studied had deletions with two dystrophin cDNAs, cf23a and cf56a, and among 148 patients who were mentally assessed, 50% were mentally retarded. The average IQ in the group of patients with DNA deletions did not differ significantly from those patients with no detectable deletions. However, six unrelated DMD boys with MR showed an identical pattern of deletion. Our observations in the group of patients who had detected DNA deletions suggest that exon 52 of the dystrophin gene may be functionally significant in the manifestation of MR: 70% (19/27) of patients with a deletion of this exon were mentally retarded, whereas only 38% (15/39) of MR patients had deletions not involving exon 52. This difference was statistically significant.

Chromosome Deletion↗
PubMed1991

Screening of male patients with autosomal recessive Duchenne dystrophy through dystrophin and DNA studies.

Previously we estimated that about 2.5-4% of isolated male patients diagnosed as Duchenne dystrophy (DMD) may have the autosomal recessive form (AR-DMD). Such cases can be distinguished from X-linked DMD through the analysis of dystrophin. Fifty DMD patients from 47 families were investigated for dystrophin and DNA deletions. Based on our results, we estimate that the frequency of AR-DMD may be about 8-12% among male patients diagnosed as DMD in whom X-linked inheritance could not be confirmed through pedigree data, serum enzymes in female relatives or DNA studies. Such an estimate must be confirmed in a larger sample; however, it shows the importance of assessing dystrophin in all patients diagnosed as DMD in whom X-linked inheritance cannot be proved, since the distinction between these 2 forms has implications for genetic counseling.

Consanguinity↗
PubMed1991

Familial occurrence of Duchenne dystrophy through paternal lines in four families.

In a survey of 454 families with patients affected with Duchenne muscular dystrophy (DMD) we have found 4 genealogies with 2 or more affected patients who were related through paternal lines. In 1 of these families, 2 affected cousins showed different DNA deletions suggesting 2 independent mutations; in the other 2, in which only the propositus could be studied DNA deletions were also detected in the dystrophin gene. In the last one, with 3 affected patients, no DNA deletions were detected but immunohistochemical study of muscle biopsies showed a negative dystrophin pattern typical of DMD. Although one of these families might have occurred by chance, the probability of finding the other 3 in our sample of families with DMD patients constitutes a rare event. It is suggested that other mechanisms, such as the presence of transposable elements in other sites of the genome, could be responsible in some families, for a greater predisposition for the occurrence of pathogenic deletions, duplications or mutations.

Child↗
PubMed1991

Linkage analysis in families with autosomal recessive limb-girdle muscular dystrophy (LGMD) and 6q probes flanking the dystrophin-related sequence.

The clinical similarity with the X-linked muscular dystrophies and the uniqueness of the homology between the DMD-like and the 1.8 kb sequences at the carboxyterminal domain of the dystrophin gene led to the suggestion that this 6q sequence might be a strong candidate for one of the autosomal recessive muscular dystrophies. Thus, we tested, through linkage analysis, if 6q probes flanking the dystrophin-homologous sequence are linked to the gene responsible for limb-girdle dystrophy (LGMD). A total of 226 individuals (57 patients and 169 unaffected relatives) from 19 large unrelated Brazilian families was studied. Results of two-point analysis excluded linkage with MYB (6q22-23) and ESR (6q24-q27) at 8 = 0.10 and with TCP1 (6q25-q27) at 0 = 0.05, indicating that the LGMD gene is not in the 6q23-q27 region. Therefore, the dystrophin-homologue sequence is not the gene responsible for LGMD.

Chromosome Mapping↗
PubMed1991

Immunofluorescence dystrophin study in Duchenne dystrophy through the concomitant use of two antibodies directed against the carboxy-terminal and the amino-terminal region of the protein.

Dystrophin immunohistochemical studies in muscle from Duchenne patients (DMD) have shown a population of fibers with partial labelling. In order to determine whether this is related to a cross reaction or to the presence of dystrophin. 22 DMD patients were studied immunohistochemically, through the concomitant use of antibodies from the N-terminal and the C-terminal regions of the protein. In 2, the reaction was negative while in 2 others 17 and 25% of fibers were positive with both antibodies. In the remainder, a population of partially stained fibers was seen: 11 were positive with both antibodies and in 7 only with the N-terminal one. Apparently, there is no correlation between the proportion of positive fibers and clinical progression, or the presence and pattern of DNA deletions in the central part of the gene. These observations led us to suggest that some truncated protein, intermediate synthesis or degradation products of dystrophin are present in muscle from Duchenne patients.

Antibodies↗
PubMed1991

Serum creatine-kinase (CK) and pyruvate-kinase (PK) activities in Duchenne (DMD) as compared with Becker (BMD) muscular dystrophy.

Serum creatine-kinase (CK) activities were determined in 536 patients affected with X-linked muscular dystrophy (456 with Duchenne or DMD and 80 with Becker or BMD) and serum pyruvate-kinase (PK) in 360 among them (309 DMD and 51 BMD). The aim of this investigation was to assess the variability and rate of decrease in serum activity in DMD as compared with BMD as a function of age and in DMD as a function of Vignos scale as well. In DMD, maximum CK and PK activities were found around 1-6 years old and the average rate of decline according to age was estimated as 0.18 per year and 0.27-0.29 for both enzymes as a function of Vignos scale (assessed in 291 cases). For BMD, maximum serum enzyme levels were found around 10-15 years old and the rate of decline of serum activity per year was 0.06 for CK and 0.07 for PK. If maximum levels of serum enzyme reflect active muscle degeneration and the rate of decline per year to progressive loss of muscle mass (responsible for the release of muscle enzymes to the blood stream) our observations suggest: (a) active muscle degeneration occurs, on average, 5 years later in the group of outliers and 10 years later in BMD as compared with severe DMD; (b) the rate in which muscle mass is lost is significantly greater in DMD than in BMD and therefore serum enzyme determinations may represent an important test for evaluation of therapeutic trials; (c) serum enzymes determination may represent an important preliminary test to discriminate in a proportion of young patients if they will develop a severe or milder phenotype.

Adolescent↗
PubMed1991

Exclusion of the gene responsible for facioscapulohumeral muscular dystrophy (FSH) at 6q23-q27.

Facioscapulohumeral muscular dystrophy (FSH) is an autosomal dominant condition with variable expressivity and age dependent penetrance. Linkage studies still did not exclude regions 11, 2q, 6q, 7p, 8p, 10q, 12p and 14p as possible locations for the FSH gene. In the present study we have analysed 80 individuals (36 patients and 44 normals) belonging to 8 unrelated Brazilian families with 3 probes located on the long arm of chromosome 6:MHB(6q22-q23), ESR(6q24-q27) and TCP1(6q25-q27). Results of linkage analysis suggest that the gene responsible for FSH muscular dystrophy is not in the region 6q23-q27.

Chromosomes, Human, Pair 6↗
PubMed1991

Limb-girdle syndrome: a genetic study of 22 large Brazilian families. Comparison with X-linked Duchenne and Becker dystrophies.

The differential clinical diagnosis between the X-linked muscular dystrophies (DMD and BMD) and autosomal recessive limb-girdle muscular dystrophy (LGMD), which is extremely important for genetic counseling, may be very difficult. The aim of the present report is to describe clinical and laboratory findings in patients from large families, with AR inheritance, in an attempt to characterize better cases which have been diagnosed as LGMD compared with the X-linked forms. The main features analysed are: age of onset and of confinement to a wheelchair, reproductive performance, serum enzymes (CK and PK) and dystrophin assessment (through immunohistochemistry and Western blot). Twenty-two families, with 62 affected patients diagnosed as limb-girdle muscular dystrophy, were included in this report. In 19 families, the patients had a milder clinical course, while in the remaining 3, the progression of the disease was continuous and clinically similar to X-linked DMD ("DMD-like"). A high consanguinity rate was observed among the parents of the affected patients (77%). No major clinical difference was observed between the X-linked and the AR forms. However, muscle dystrophin was found qualitatively and quantitatively normal in the autosomal forms but absent or abnormal in the X-linked ones. The reproductive performance was significantly higher for male than female patients. In addition, a surprising finding was the significantly greater fitness estimated for male LGMD cases as compared with Becker patients of comparable age studied in our center. The implications of such findings are discussed.

Adolescent↗
PubMed1991

Dystrophin immunofluorescence pattern in manifesting and asymptomatic carriers of Duchenne's and Becker muscular dystrophies of different ages.

In order to investigate if the same apparent decrease in dystrophin negative fibers with aging observed in mouse mdx female heterozygotes also occurs in carriers of the DMD and BMD gene, we have studied the muscle of 29 DMD carriers (19 adults and 10 young daughters of obligate carriers, including 3 manifesting carriers) and 5 adult asymptomatic heterozygotes for Becker dystrophy (BMD). All young DMD possible carriers and 11 of 24 adult DMB/BMD heterozygotes had increased serum enzymes activities. A population of dystrophin negative fibers, more evident with the use of the C-terminal antibody, was seen in the three manifesting and in a 9-yr-old possible DMD carrier. In the remaining females, a positive immunohistochemical pattern of dystrophin, which did not differ from normal controls, was observed. Our results suggest that: (1) the increased population of dystrophin negative fibers reported in young mdx female heterozygotes was not seen in young DMD carriers, aged 6-17 yr; and (2) abnormalities in dystrophin immunostaining are not easily observed and are more frequent in manifesting carriers, when the muscle is grossly altered.

Adolescent↗
PubMed1991

Estimates of genetic and environmental components of serum isocitrate dehydrogenase (ICDH) in normal twins.

Environmental (b2) and genetic heritability (h2) of serum isocitrate dehydrogenase (ICDH) were estimated in 96 pairs of healthy twins according to a path analysis model. The results showed significant heritability (0.42) and a very low environmental component (based on obesity and level of habitual physical activity), suggesting that these factors do not influence ICDH serum activity.

Adult↗
PubMed1991

High salt mimics effects of light pulses on circadian pacemaker in cultured chick pineal cells.

Chick pineal cells in static culture display a persistent photosensitive circadian rhythm of melatonin production and release. Pulses of white light or darkness, in otherwise constant red light, induce phase shifts in subsequent cycles whose magnitude and direction depend on the phase at which the pusle is given. Such "phase-dependent phase shifts" are mediated by effects on the underlying pacemaker. We reported previously that inhibiting the Na+-K+-adenosinetriphosphatase with ouabain evokes phase shifts with the same phase dependence as those induced by pulses of darkness. Two of the consequences of inhibiting the Na+ pump are membrane depolarization and cell swelling. To test the relevance of these effects and to distinguish between them, we exposed chick pineal cells to pulses of high concentrations of added KCl, which should cause both membrane depolarization and cell shrinkage. We also compared the effects of added NaCl, sodium gluconate, and mannitol, which should cause cell shrinkage without comparable depolarization. Each of these hypertonic solutions induced phase shifts in the melatonin rhythm with the same phase dependence as those caused by pulses of light rather than those caused by ouabain or darkness. These results argue strongly against a dominant role for changes in membrane potential in phase shifting the melatonin rhythm. Rather, they suggest that cell swelling may mediate the darklike effects of ouabain on the circadian pacemaker in chick pineal cells and indicate that cell shrinkage mimics the effects of light.

Animals↗
PubMed1991

Low salt mimics effects of dark pulses on circadian pacemaker in cultured chick pineal cells.

Chick pineal cells in static culture display a persistent photosensitive circadian rhythm of melatonin production and release. Pulses of white light or darkness, in otherwise constant red light, induce phase shifts in subsequent cycles whose magnitude and direction depend on the phase at which the pulse is given. Such "phase-dependent phase shifts" are mediated by effects on the underlying pacemaker. We reported previously that inhibiting the Na-K-ATPase with ouabain or salt solutions lacking potassium evokes phase shifts with the same phase dependence as those induced by pulses of darkness. One of the consequences of inhibiting the sodium pump is cell swelling. To test the relevance of this effect, we exposed chick pineal cells to pulses of medium containing reduced concentrations of NaCl, which should cause cell swelling. These hypotonic solutions induced phase shifts in the melatonin rhythm with the same phase dependence as those caused by pulses of ouabain or darkness. The size of the phase shifts varied with degree of dilution, and phase shifting was prevented by replacement of NaCl. In view of previous results showing that hypertonic media mimicked the phase-shifting effects of light, these results suggest that cell swelling may mediate the darklike effects of ouabain on the circadian pacemaker in chick pineal cells.

Animals↗
PubMed1991

Estimate of the intrafamilial correlation for serum creatine kinase and pyruvate kinase in females at risk for Duchenne and Becker muscular dystrophies.

In order to verify the possibility of nonrandom X-inactivation in females heterozygous for Duchenne (DMD) and Becker (BMD) muscular dystrophies, intrafamilial correlations and the heritabilities for serum creatine kinase (CK) and pyruvate kinase (PK) were estimated in a large sample of females belonging to families with affected patients. The results of the present investigation suggest that the apparent intrafamilial correlations for serum CK reported in previous studies in DMD families are not related with the presence of the DMD/BMD gene. Our data do not seem to support the hypothesis of a gene leading to a preferential inactivation of the X-chromosome in females at risk for the dystrophin gene.

Adolescent↗
PubMed1991

Light and norepinephrine similarly prevent damping of the melatonin rhythm in cultured chick pineal cells: regulation of coupling between the pacemaker and overt rhythms?

The circadian rhythm of melatonin output displayed by chick pineal cells in static culture damps rapidly in constant red light (RR). This can be seen in the first cycle following a switch from a cycle of 12 hr white light (L) and 12 hr red light (R) to RR. Melatonin output is higher during the "day" in R than it is in L, but higher that next night (in R) after daytime L than after daytime R. This effect might be due entirely to the entraining effect of L. Alternatively, the higher nocturnal output after daytime L could be related to the acute suppression caused by L; it might be a "rebound" phenomenon. These alternative hypotheses differ in their predictions for the effects of norepinephrine (NE) and pertussis toxin (PT). Previous results dissociated the acute and entraining effects of L: PT blocks the acute effect but not the entraining effect of L. NE mimics the acute effect of L (and is blocked by PT), but not the entraining effect. If L prevents damping entirely by entrainment, then NE should not mimic and PT should not block this same-cycle effect of daytime L on nocturnal melatonin output. However, the present research found that NE did mimic and PT did block this effect, indicating that the ability of L to prevent damping is mediated by a same-cycle "rebound" following L's acute inhibition of melatonin production. Furthermore, NE enhanced the "rebound" effect of daytime L, and cycles substituting NE for L were effective in driving the melatonin rhythm. Lowering extracellular potassium did not induce a "rebound," and adding exogenous melatonin did not prevent one. The difference between nocturnal melatonin synthesis after daytime R and that after daytime L or NE implies regulation of coupling between the output of the circadian pacemaker and melatonin production. These results also suggest a role for NE in regulating and maintaining the expression of the melatonin rhythm.

Animals↗
PubMed1991

Short stature in Duchenne muscular dystrophy.

Growth rate was assessed in 187 boys affected with Duchenne muscular dystrophy (DMD) and bone age in 127 among them. Patients' heights were compared with their normal sibs, with expected stature according to midparents' stature and with normal Brazilian children of comparable age. The results showed that DMD boys have a normal length and weight at birth, but a delayed growth starting during the first years of life with a mean approximate decrease of -6.00 cm according to the expected height of the normal Brazilian population. The proportion of DMD patients with short stature (below the 3rd centile) was similar in younger boys (up to 7 years) to that in the older group (more than 7 years) of affected boys. Bone maturation in DMD boys did not differ from their normal sibs. Weight was also decreased in DMD patients as compared with normal sibs of comparable age.

Adolescent↗