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M R Natowicz

Publications and source records attributed to M R Natowicz.

At least 37 records · Page 2Linked to original sources
PubMed1996

Human serum hyaluronidase: characterization of a clinical assay.

Hyaluronidase, a lysosomal endoglycosidase mediating hyaluronan (hyaluronic acid) turn-over, is thought to be important in many normal developmental and certain pathologic processes. Previous assays of serum hyaluronidase are limited with respect to their applicability for routine clinical chemistry or clinical biochemical genetics applications. We describe a new assay of human serum or plasma hyaluronidase activity based on the determination of released N-acetylglucosamine reducing termini that allows the analysis of the enzyme with small, easily obtained sample volumes. Using 10 microliters of serum or plasma, sodium formate buffer and human umbilical cord hyaluronan as substrate, we found a pH optimum of 3.9 and a K(m) and Vmax of 114 mg/l and 5102 mU/l, respectively. In addition, the assay has excellent linearity, precision and reproducibility.

Adult↗
PubMed1996

Heterozygote screening for Tay-Sachs disease: past successes and future challenges.

Tay-Sachs disease (TSD) is an autosomal recessive, neurodegenerative disorder caused by a deficiency of beta-hexosaminidase A activity. Mass screening for TSD heterozygotes has been routine in the Ashkenazi Jewish population since the early 1970s. Recent advances in the molecular genetics and epidemiology of TSD require a reevaluation of heterozygote screening practices. The use of DNA-based analyses for a panel of common mutations detects about 98% of TSD mutations found in the Ashkenazi Jews and about 50% of TSD mutations found in the general non-Jewish population; enzyme-based analysis has nearly 100% sensitivity for all populations. We recommend 1) that members of several ethnic groups and persons with a family history consistent with TSD be offered testing for TSD heterozygosity and 2) that assays of enzyme activity be used as the primary screening tool, with mutation analysis used as an adjunct tool in certain cases.

Gene Frequency↗
PubMed1996

Heterozygosity for Tay-Sachs disease in non-Jewish Americans with ancestry from Ireland or Great Britain.

We performed a genetic epidemiological analysis of American non-Jewish people with ancestry from Ireland or Great Britain with regard to heterozgosity for Tay-Sachs disease (TSD). This study was prompted by a recent report that the frequency of heterozygosity for TSD among Irish Americans was 1 in 8, a frequency much higher than that recognised for any other population group. We identified 19 of 576 (3.3%) people of Irish background as TSD heterozygotes by the standard thermolability assay for beta-hexosaminidase A (Hex A) activity. Three of 289 people of non-Irish British Isles background (1%) were also identified as heterozygotes by biochemical testing. Specimens from the biochemically identified Irish heterozygotes were analysed for seven different Hex A alpha subunit gene mutations; three (15.8%) had a lethal +1 IVS-9 G to A mutation, previously noted to be a common mutation among TSD heterozygotes of Irish ancestry. Eight of 19 (42.1%) had one of two benign or pseudodeficiency mutations, and no mutation was found in 42.1% of the heterozygotes analysed. These data indicate that non-Jewish Americans with Irish background have a significantly increased frequency of heterozygosity at the Hex A alpha subunit gene locus, but that approximately 42% of the biochemically ascertained heterozygotes have clinically benign mutations. A pseudodeficiency mutation was identified in one of the three TSD heterozygotes of non-Irish British Isles background; no mutations were found in the other two. The data allow for a frequency estimate of deleterious alleles for TSD among Irish Americans of 1 in 192 to 1 in 52. Non-Jewish Americans with ancestry from Great Britain have a minimal, if any, increase in rate of heterozygosity at the TSD gene locus relative to the general population.

Cohort Studies↗
PubMed1996

Urine sulfatides and the diagnosis of metachromatic leukodystrophy.

A deficiency of the lysosomal enzyme arylsulfatase A (ASA) causes the lysosomal storage disorder metachromatic leukodystrophy (MLD). The diagnosis of MLD is straightforward in cases with deficient leukocyte or fibroblast ASA activity and a typical clinical history. However, several atypical and late-onset forms of MLD have been described. The diagnosis is also complicated by the high frequency of presumably benign polymorphisms at the ASA gene locus that are associated with markedly diminished in vitro ASA activity. Additional diagnostic tools are needed in the clinically and (or) enzymatically atypical cases. Although analyses of urinary sulfatides have been reported to be helpful in the diagnosis of MLD, previously described methods are complex and incompletely characterized and validated. We developed an improved method for determining urinary sulfatides and applied it to a cohort of individuals with MLD. The sulfatides are extracted from urine, separated from glycerol-based lipids by alkaline hydrolysis, isolated by ion-exchange chromatography, and hydrolyzed to galactosylceramide, which is then perbenzoylated and quantified by HPLC. This assay provides excellent resolution of sulfatides from other lipids and good analytical precision. In addition, the urinary sulfatide concentrations of healthy controls (mean +offSD: 0.16 +/- 0.07 nmol/mg creatinine; range: 0.07-0.34; n = 18) are clearly distinguished from those of individuals with MLD (7.6 +/- 6.1 nmol/mg creatine; 1.2-24.2; n = 20).

Cerebroside-Sulfatase↗
PubMed1995

Tay-Sachs disease in persons of French-Canadian heritage in northern New England.

This study sought to determine whether persons of French-Canadian heritage in northern New England are at high risk for the lethal infantile form of Tay-Sachs disease. In order to accomplish this, death records and laboratory diagnostic records were surveyed to ascertain Tay-Sachs deaths in a cohort of 372,000 live births between 1977-1986. The proportion of the total population with French-Canadian or Jewish heritage was determined from census and birth records, and the ethnic background of Tay-Sachs cases was determined from the corresponding birth records. In 1,860 births, both parents were of Ashkenazi Jewish heritage. One of those children was diagnosed with Tay-Sachs disease. In 41,000 births, both parents were of French-Canadian heritage, and in an additional 93,000 births, one parent was of French-Canadian heritage. No cases of Tay-Sachs disease were identified in the offspring of those individuals. Approximately 14 cases (95% confidence interval 8-20) would be expected, if the gene frequency approximated that reported for individuals of Ashkenazi Jewish heritage. Based on the results of this study, routine testing for Tay-Sachs disease heterozygosity is not indicated for persons of French-Canadian heritage in northern New England. This conclusion may not necessarily be valid for persons of French-Canadian heritage residing in other states. Further studies of Tay-Sachs disease mutations and prevalence among persons of French-Canadian heritage will be important to determine possible regional variations in gene frequencies.

Child↗
PubMed1995

Marked heterogeneity in Niemann-Pick disease, type C. Clinical and ultrastructural findings.

Niemann-Pick disease type C (NP-C) is an autosomal recessive lysosomal lipid storage disorder of unknown etiology. Diagnosis of NP-C is based on characteristic clinical findings and reduced fibroblast esterification of LDL-derived cholesterol. We describe three patients who demonstrate the NP-C spectrum of clinical heterogeneity in age of onset, presenting signs, pattern of organ system involvement, and natural history. In addition, electron microscopic analysis of skin biopsy specimens from these patients revealed marked variability in the extent and cellular distribution of intralysosomal storage and was suggestive of the correct diagnosis in only one case. These cases demonstrate both the limitations of electron microscopy for diagnosis of NP-C and the marked clinical variability in patients with this disorder. Practical clinical guidelines for appropriate suspicion of NP-C are presented.

Adolescent↗
PubMed1995

Delayed myelination in infants and young children: radiographic and clinical correlates.

Magnetic resonance imaging (MRI) is the best method for assessing myelination in infants and young children. Although delayed myelination is a common neuroradiologic diagnosis, there are few or no data regarding the reliability of this diagnosis or radiographic and clinical findings in cohorts of such patients. We evaluated the cranial MRI scans of 109 patients from age 0 to 36 months, without knowledge of any patient's age or previous clinical or radiologic diagnosis. For each cranial MRI, seven neuroradiologic landmarks were evaluated and established criteria used to assess the state of myelination. We found that in 12 of 109 patients, delayed myelination was misdiagnosed, whereas the diagnosis of delayed myelination was missed in four other patients. Lack of familiarity with the myelination milestones of infancy was the most common reason for a misdiagnosis of delayed myelination. Failure to recognize delayed myelination was due to a failure to appreciate the forceps minor as a landmark. Overall, the diagnosis of delayed myelination was inaccurately applied or missed in 15% of the patients in this series. Of the 14 patients identified as having delayed myelination, 10 had other central nervous system structural abnormalities seen on MRI, most commonly cortical atrophy. Developmental delay was the most common clinical correlate of delayed myelination and was documented in 12 of the 14 patients. To increase the reliability of neuroradiologic assessments in young children, we propose that central nervous system myelin maturation be evaluated and expressed as a myelination age equivalent, analogous to the assessment of pediatric bone age using conventional radiographs.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrophy↗
PubMed1995

Mutational analyses of Tay-Sachs disease: studies on Tay-Sachs carriers of French Canadian background living in New England.

Tay-Sachs disease (TSD) results from mutations in HEXA that cause Hex A deficiency. Heterozygote-screening programs have been applied in groups with an increased TSD incidence, such as Ashkenazi Jews and French Canadians in Quebec. These programs are complicated by benign mutations that cause apparent Hex A deficiency but not TSD. Benign mutations account for only approximately 2% of Jewish and approximately 36% of non-Jewish enzyme-defined carriers. A carrier frequency of 1/53 (n = 1,434) was found in an ongoing prospective analysis of persons of French Canadian background living in New England by using an enzyme-based assay. DNA from enzyme-defined carriers from this population was analyzed to determine the molecular basis of Hex A deficiency. Samples (36) were tested for common mutations, and samples that were negative for these were screened for uncommon or novel mutations by using SSCP analysis. Exons showing mobility shifts were sequenced, and most mutations were confirmed by restriction enzyme digestion. Known disease-causing mutations were found in nine samples (four had a 7.6-kb deletion found in 80% of French Canadian TSD alleles), and known benign mutations were found in four samples. Seven novel changes were identified, including G748A in four samples. The molecular basis of Hex A deficiency in this carrier population differs from that of French Canadian TSD patients. Screening centers should be aware of the presence of benign mutations among U.S. French Canadians or Franco-Americans.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1994

Abnormal bile acids in the Smith-Lemli-Opitz syndrome.

The urinary bile acids from four patients with Smith-Lemli-Opitz (SLO) syndrome were analyzed by continuous flow fast atom bombardment mass spectrometry. Two types of abnormalities were noted: (1) a deficiency of normal bile acids (cholenoates) and (2) the presence of abnormal species postulated to be cholenoates and cholestenoates. The finding of abnormal urinary bile acids in children with SLO syndrome led to further investigation of the cholesterol metabolic pathway and to the delineation of a new inborn error of metabolism, deficient conversion of 7-dehydrocholesterol to cholesterol [Irons et al., 1993]. The abnormalities of urinary bile acids, if confirmed by further structural analyses and studies of additional patients, provide an explanation for various aspects of the gastro-intestinal abnormalities and growth retardation noted in SLO syndrome and suggest that exogenous bile acid replacement may play an important role in the therapy of patients with this syndrome.

Abnormalities, Multiple↗
PubMed1994

Genetic disorders that masquerade as multiple sclerosis.

There are many genetic disorders that have signs and symptoms suggestive of multiple sclerosis and that may easily be overlooked in the evaluation of both adult and pediatric multiple sclerosis patients. The recognition of a genetic disorder as the cause of a patient's "multiple sclerosis" phenotype has important implications not only for the patient, but often also for others in the patient's family who may be at risk for the same disease. We present here a review of single gene disorders that can masquerade as multiple sclerosis. For each disorder, the major clinical and biochemical characteristics are discussed, together with the appropriate testing to screen for and confirm the diagnosis. In addition, guidelines are presented for when to suspect an underlying genetic condition in a patient with a diagnosis of definite or probable multiple sclerosis. The great variety of genetic disorders that can masquerade as multiple sclerosis and the many implications of a genetic diagnosis underscore the importance of recognizing genocopies of multiple sclerosis.

Diagnosis, Differential↗
PubMed1994

Pelizaeus-Merzbacher disease presenting as spinal muscular atrophy: clinical and molecular studies.

Two brothers with profound neonatal hypotonia and hyporeflexia and electrodiagnostic testing consistent with lower motor neuron pathology were found to have a leukodystrophy. Using single-strand conformational polymorphism analysis and direct sequencing, a mutation within exon 3 of the gene encoding proteolipid protein (Gly73Arg substitution) was previously detected in both brothers and their mother, establishing the diagnosis of Pelizaeus-Merzbacher disease. Despite reported sparing of the peripheral nervous system in Pelizaeus-Merzbacher disease, we suggest that proteolipid protein gene products may influence the development of anterior horn cells or peripheral nervous system myelin and that some individuals affected with this disease may present with clinical and electromyographic features suggestive of neonatal spinal muscular atrophy.

Brain↗
PubMed1994

Genetic discrimination and screening for hemochromatosis.

Recent advances in tests for the genotype for hemochromatosis and suggestions that the tests be used in mass screening programs for the disease raise the possibility of a large increase in the incidence of discrimination against people who are found to be homozygous for hemochromatosis. This paper presents cases of genetic discrimination drawn from a study of discrimination against people with a variety of genetic conditions. The cases discussed here involve employment and several types of insurance discrimination against people diagnosed with hemochromatosis who either are currently asymptomatic or whose condition is controlled by means of phlebotomies. There is no justification for these types of discrimination since people with controlled hemochromatosis suffer no excess mortality or morbidity. Our study suggests that genetic discrimination is already a serious problem and that any proposed screening program for hemochromatosis or other genetic condition must consider and attempt to mitigate its effects.

Adult↗
PubMed1993

Screening techniques for the detection of inborn errors of bile acid metabolism by direct injection and micro-high performance liquid chromatography-continuous flow/fast atom bombardment mass spectrometry.

Two methods, direct injection-continuous flow fast atom bombardment (DI-CF/FAB) mass spectrometry and micro-high-performance liquid chromatography (mu HPLC)-CF/FAB) mass spectrometry were developed for the clinical analysis of urinary bile acids and their conjugates, specifically for the diagnosis of disorders of bile acid metabolism. The method based upon DI of urine extracts into the CF/FAB flow stream was developed for the rapid screening of large numbers of patient samples. It allows injections to be made at 4 min intervals for high sample throughput. Analyses of standard mixtures of bile salts demonstrate that linear response curves are obtained over more than a hundred-fold concentration range with a minimum detectable amount in the picogram range. Oxo bile salts are identified by reduction with sodium borodeuteride followed by reanalysis for detection of any reduction products. This methodology has been used for the analysis of over 1000 specimens. A reverse-phase mu HPLC-CF/FAB mass spectrometric method was also developed for use in the confirmation or further investigation of screening results. With no additional sample preparation this method permits the separation, identification and quantitation of urinary bile salt isomers within a 45 min analysis time.

Bile Acids and Salts↗
PubMed1993

On establishing the genetic basis of mental disease.

Many of the recent studies reporting genetic linkages for mental illnesses such as schizophrenia and manic depression have been retracted. The authors of this article argue that the fundamental reason for the difficulties in this research field lies in the strongly held preconceived belief that the primary cause of these illnesses is in fact genetic. All scientists hold preconceived ideas. However, such ideas are more likely to result in erroneous conclusions in the study of human behavior than in other more 'objective' research areas. Moreover, it is especially important that researchers studying human behavior be aware of their biases and learn to compensate for them because of the social consequences of their work.

Environment↗
PubMed1993

A second mutation associated with apparent beta-hexosaminidase A pseudodeficiency: identification and frequency estimation.

Deficient activity of beta-hexosaminidase A (Hex A), resulting from mutations in the HEXA gene, typically causes Tay-Sachs disease. However, healthy individuals lacking Hex A activity against synthetic substrates (i.e., individuals who are pseudodeficient) have been described. Recently, an apparently benign C739-to-T (Arg247Trp) mutation was found among individuals with Hex A levels indistinguishable from those of carriers of Tay-Sachs disease. This allele, when in compound heterozygosity with a second "disease-causing" allele, results in Hex A pseudodeficiency. We examined the HEXA gene of a healthy 42-year-old who was Hex A deficient but did not have the C739-to-T mutation. The HEXA exons were PCR amplified, and the products were analyzed for mutations by using restriction-enzyme digestion or single-strand gel electrophoresis. A G805-to-A (Gly269Ser) mutation associated with adult-onset GM2 gangliosidosis was found on one chromosome. A new mutation, C745-to-T (Arg249Trp), was identified on the second chromosome. This mutation was detected in an additional 4/63 (6%) non-Jewish and 0/218 Ashkenazi Jewish enzyme-defined carriers. Although the Arg249Trp change may result in a late-onset form of GM2 gangliosidosis, any phenotype must be very mild. This new mutation and the benign C739-to-T mutation together account for approximately 38% of non-Jewish enzyme-defined carriers. Because carriers of the C739-to-T and C745-to-T mutations cannot be differentiated from carriers of disease-causing alleles by using the classical biochemical screening approaches, DNA-based analyses for these mutations should be offered for non-Jewish enzyme-defined heterozygotes, before definitive counseling is provided.

Adult↗