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M Zatz

Publications and source records attributed to M Zatz.

At least 127 records · Page 7Linked to original sources
PubMed1994

What does changing the temperature do to the melatonin rhythm in cultured chick pineal cells?

Chick pineal cells in static culture display a persistent, photosensitive circadian rhythm of melatonin production and release. We previously described the effects of light, the major physiological regulator of circadian rhythms, on the amplitude, period, and phase of the melatonin rhythm. Here we describe the effects of temperature, another physiological regulator of circadian rhythms, on the amplitude, period, and phase of this rhythm. Maintaining cells at 40.0-43.3 degrees C (104-110 degrees F) instead of 36.7 degrees C (98 degrees F) doubled the amplitude of the melatonin rhythm. In contrast, amplitude was reduced by about half at 33.3 degrees C (92 degrees F), and at 46.7 degrees C (116 degrees F) melatonin production was stopped within a few hours. Although temperatures of 40.0-43.3 degrees C raised melatonin output (unlike light, which suppresses it), they lengthened the period of the rhythm (as does constant light). Exposure of cells to 8-h pulses of these temperatures (40.0-43.3 degrees C) induced both phase delays and phase advances of the rhythm in subsequent cycles, with a phase dependence similar to that for the phase shifts induced by light pulses. Pulses of 40.0-43.3 degrees C were, however, weaker in their phase-shifting effects than light pulses. Pulses at still higher temperatures (46.7 degrees C) markedly inhibited melatonin output and delayed or disrupted the rhythm. The relationships (physiological and mechanistic) between the effects of temperature and light on the melatonin rhythm remain to be determined.

Animals↗
PubMed1994

[Myotonic dystrophy: study of clinico-genetic correlation in a pair of relatives (father-son)].

We report the case of a child with myotonic dystrophy (DM) with symptoms beginning at the age of seven, whose genetic study showed an additional DNA fragment, greater than of his father, an asymptomatic carrier. The clinical and molecular analysis of this parent-child pair are probably the first described in Brazil, since the recent discovery of genetic abnormality in DM by American and European researchers, that explained the long-debated phenomenon of "anticipation" in this disease. The main advances in molecular genetics in DM and its correlation with increasing severity and earlier onset of the symptoms in successive generations of a family are commented briefly.

Child↗
PubMed1993

Severe nonspecific X-linked mental retardation caused by a proximally Xp located gene: intragenic heterogeneity or a new form of X-linked mental retardation?

X-linked mental retardation (XLMR) can be subdivided into syndromic and nonsyndromic or nonspecific. Patients with non-syndromal XLMR show no characteristic manifestations, biochemical defects, or distinct fragile sites. Nevertheless, nonspecific XLMR seems to be heterogeneous. To determine the number and location of the genes responsible for XLMR, linkage studies in large pedigrees have to be performed. Here we report the data of linkage analysis in a large Brazilian family with 7 patients affected by a severe form of XLMR, with no other associated malformations. All the obligate carriers are normal. A close linkage without recombination (lod scores 1.95 and 3.25) was found between the disease locus and polymorphic DNA loci DXS255 (Xp11.22), DXS14 (Xp11.21). These results suggest that the gene responsible for the disease in this family maps in the Xp11-cent of the X chromosome. Positive lod scores in this region have also been reported for other XLMR genealogies, but with a much milder phenotype. The possibility of intragenic or locus heterogeneity is discussed.

Adolescent↗
PubMed1993

Intrafamilial variability in dystrophin abundance correlated with difference in the severity of the phenotype.

In Duchenne muscular dystrophy, the progression of the disease is always severe and predictable, while in Becker dystrophy there is a wide variability (intra and inter familial) in the severity of the phenotype. We report here a family in which the proband, who is currently 15 years old, is showing a severe DMD progression, while his affected maternal uncle, aged 29, has a more benign course, compatible with BMD. No DNA deletion was detected in both patients. Dystrophin analysis through immunofluorescence and western blotting showed a negative pattern in the youngest patient and a positive one in the oldest. Apparently, this is the first report on intrafamilial variability in dystrophin abundance correlated with a difference in the severity of the phenotype.

Adolescent↗
PubMed1993

Sarcolemmal distribution of abnormal dystrophin in Xp21 carriers.

Some Becker muscular dystrophy carriers, related to patients with specific DNA deletions, demonstrate both normal and abnormally sized dystrophin bands through qualitative Western blot analysis. The purpose of the present investigation was to assess the sarcolemmal distribution of the altered dystrophin in such carriers. Fibres expressing the normal or deleted dystrophin were identified using specific antibodies which reacted with epitopes from within the deleted region. No negative fibres or patchy immunostaining could be seen when sections from four carriers were labelled with either antibodies (C-terminal and corresponding to the deleted region), although a significant amount of abnormal dystrophin was present in their muscle (as seen on blots). Thus, we were able to confirm that in a proportion of the myonuclei, the defective allele was present on the active X chromosome. Our results suggest that the two types of nuclei were randomly distributed, resulting in normal and abnormal dystrophin molecules which were so intimately mixed that dystrophin-incompetent fibres could not be distinguished in the skeletal muscle from the Xp21 carriers.

Adult↗
PubMed1993

Is the maintainance of the C-terminus domain of dystrophin enough to ensure a milder Becker muscular dystrophy phenotype?

The severe Duchenne muscular dystrophy (DMD) and the more benign Becker type (BMD) are allelic conditions, controlled by a defective gene at Xp21, caused by the absence (DMD) or a defect in quantity or quality (BMD) of the protein dystrophin. It has been suggested that the C-terminus domain of dystrophin is fundamental to ensure the proper protein sub-cellular localization and function. We wish to report our dystrophin findings in 4 among 142 DMD patients studied for DNA deletions and dystrophin analysis. Although they have a severe clinical course, a positive dystrophin immunofluorescence pattern was seen using C-terminal antibody, and a dystrophin band of reduced molecular weight (corresponding to their DNA deletions), but which maintained the C-terminus was seen through Western blot (WB). Based on these findings, we suggest that in order to partially maintain its function, resulting in a milder phenotype, dystrophin may carry large internal deletions but in addition to the C-terminus, the region encompassing both the N-terminus and the proximal region of the rod domain cannot be absent. Therefore, the prognosis of a Becker phenotype in a young patient should be done with caution if based only on the presence or not of dystrophin.

Adolescent↗
PubMed1993

Genetic heterogeneity for Duchenne-like muscular dystrophy (DLMD) based on linkage and 50 DAG analysis.

Duchenne-like muscular dystrophy (DLMD) is an autosomal recessive (AR) muscular dystrophy which presents a clinical course indistinguishable from the Xp21 Duchenne muscular dystrophy or DMD. Recently, Othmane et al., based on a linkage study with 13q12 markers in 3 highly inbred DLMD families from Tunisia, suggested that the gene for this myopathy lies in the pericentromeric region of chromosome 13q. It is unknown if there is genetic heterogeneity causing the DLMD phenotype. Therefore, the aim of the present report is to describe the results of linkage analysis in 4 Brazilian DLMD families with 13q12 markers (D13S115 and D13S120), which were also tested for 50DAG. It was possible to exclude the 13q gene at theta = 0.10 as responsible for the DLMD phenotype in our families using both 13q12 markers, if the lod scores of each family were added up. Interestingly, 3 families were deficient for 50 DAG while one showed a positive pattern for this glycoprotein. Therefore, these results suggest: a) the DLMD phenotype is caused by more than one recessive gene; b) a gene, not located at 13q, causes deficiency of 50 DAG as a primary or secondary defect.

Brazil↗
PubMed1993

Cosegregation of schizophrenia with Becker muscular dystrophy: susceptibility locus for schizophrenia at Xp21 or an effect of the dystrophin gene in the brain?

A family is reported in which four of five adult patients with Becker muscular dystrophy (BMD) also have schizophrenia or related spectrum disorders. Although the estimated lod scores are not sufficient to conclude the existence of linkage between BMD and schizophrenia, it is suggested that there may be an association between these two disorders. Two alternative hypotheses are proposed to explain such an association: (1) the existence of a susceptibility locus for schizophrenia and spectrum disorders on the short arm of the X chromosome at Xp21; (2) that these psychiatric disorders may result from an abnormality in the expression of the dystrophin gene in the brain.

Adult↗
PubMed1993

Facioscapulohumeral muscular dystrophy: aspects of genetic counselling, acceptance of preclinical diagnosis, and fitness.

A questionnaire about the interest in and demand for preclinical diagnosis for facioscapulohumeral muscular dystrophy (FSH) was sent to 46 patients. Most stated that they would have liked to have known their diagnosis earlier in order to seek more efficient help, to avoid strenuous activities, to prepare themselves emotionally, or to choose an appropriate profession. Similar arguments were used to explain their interest in preclinical diagnosis for their children. Most patients also favoured prenatal diagnosis although only two stated they would abort a pregnancy in the case of an affected fetus. Genetic counselling had apparently little influence on family planning. According to this study, FSH does not seem to reduce reproductive performance in our population.

Adolescent↗
PubMed1993

The use of chromosome 5q markers for confirming the diagnosis of proximal spinal muscular atrophy.

1. Five Brazilian families referred to us with a probable diagnosis of chronic proximal spinal muscular atrophy (Kugelberg-Welander) were identified, and permanent (Epstein Barr virus transformed) cell lines were established from members of four of the families. 2. A genetic linkage study was carried out on 70 individuals using nine polymorphic DNA markers (eight RFLP and one microsatellite) from chromosome 5q11.2-13.3 which have been shown to flank the spinal muscular atrophy (SMA) gene. 3. The segregation of the markers in two of the five families was compatible with the disease-causing locus being located in this same region. In one family the pattern of segregation clearly excludes the causative gene from this region. In one of the remaining two families the analysis was inconclusive because the markers were not informative. In the fifth family the possibility of two concurrent neuromuscular diseases did not permit a definite conclusion. 4. These results further support the location of the major SMA gene at 5q11.2-13.3. 5. The possibility of non-allelic heterogeneity for the spinal muscular atrophy gene is discussed.

Adolescent↗
PubMed1992

Agents that affect calcium influx can change cyclic nucleotide levels in cultured chick pineal cells.

Previous experiments examined interactions among the effects of cyclic AMP and calcium-related agents on melatonin output by cultured chick pineal cells, and suggested that changes in calcium influx might act through cyclic AMP. Here, effects of calcium-related agents and manipulations on cyclic AMP (and cyclic GMP) levels are demonstrated directly. These effects support a role for cyclic AMP (but not cyclic GMP) in the effects of changes in calcium influx on melatonin production by these cells.

1-Methyl-3-isobutylxanthine↗
PubMed1992

A deletion including the brain promoter of the Duchenne muscular dystrophy gene is not associated with mental retardation.

A total of 161 unrelated Duchenne (DMD) and Becker muscular dystrophy (BMD) patients were screened for deletions in the brain promoter region of the dystrophin gene. Southern blot analysis using a probe for the brain promoter detected a deletion in this region in only one of the DMD families, in a patient with normal intelligence. This deletion also included the promoter of the muscle-type dystrophin and the exons encoding the actin-binding and part of the spectrin-like domains. Our data suggest that deletions in the brain promoter region are rare in DMD and are compatible with normal intelligence.

Adult↗
PubMed1992

Does the circadian pacemaker act through cyclic AMP to drive the melatonin rhythm in chick pineal cells?

Cyclic AMP is a key regulator of melatonin production in the chick pineal gland. Agents that raise cyclic AMP levels (such as forskolin), or cyclic AMP analogues (such as 8-bromocyclic AMP), increase melatonin synthesis and release, whereas agents that lower cyclic AMP levels (including light) decrease melatonin synthesis and release. A circadian oscillator in these cells also raises and lowers melatonin output. We have been investigating the relationships between cyclic AMP and the circadian pacemaker in the regulation of melatonin production. In the chick pineal (unlike certain neuronal systems), the weight of the evidence indicates that cyclic AMP is not on an entrainment pathway to the circadian pacemaker. Instead, cyclic AMP appears to act downstream from the pacemaker. The pacemaker might itself act directly through cyclic AMP, regulating melatonin content by raising and lowering cyclic AMP levels. If this were the case, and if the effects of cyclic AMP levels on melatonin output are saturable (as they must be), then, in the face of such saturating levels of cyclic AMP, the pacemaker should no longer raise or lower melatonin output. To test this prediction, maximally effective concentrations of forskolin and 8-bromocyclic AMP were determined. Both agents markedly increased melatonin output. After 36 hr, cells were refractory to additional stimulation of melatonin output by addition of both agents together, or by higher concentrations of forskolin (although cyclic AMP levels could still be raised further). Nonetheless, the circadian pacemaker continued to raise and lower melatonin output: The rhythm persisted in the face of saturating levels of cyclic AMP. It is therefore suggested that the circadian pacemaker in chick pineal cells acts with, not through, cyclic AMP to regulate melatonin synthesis. Cyclic AMP and the pacemaker act synergistically to regulate serotonin N-acetyltransferase activity and the melatonin rhythm, with cyclic AMP mediating acute effects and amplitude regulation.

8-Bromo Cyclic Adenosine Monophosphate↗