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M R Natowicz

Publications and source records attributed to M R Natowicz.

51 records · Page 3Linked to original sources
PubMed1993

Genetic discrimination and the public entities and public accommodations Titles of the Americans with Disabilities Act.

The introduction of newly developed medical genetic diagnostic tests has been accompanied by social problems involving privacy issues and genetic discrimination. Previous studies of genetic discrimination have focused on the areas of employment and insurance. In this paper, we provide six hypothetical illustrative cases of genetic discrimination involving access to public entities and to private entities considered to be public accommodations. We argue that many of these forms of genetic discrimination that arise in both the public and private sectors should be prohibited by Titles II and III, respectively, of the Americans with Disabilities Act of 1990.

Persons with Disabilities↗
PubMed1993

Unusual thermolability properties of leukocyte beta-hexosaminidase: implications in screening for carriers of Tay-Sachs disease.

Tay-Sachs disease (TSD), an autosomal recessive neurodegenerative condition, is the result of a deficiency of beta-hexosaminidase A (hex A). Heterozygotic individuals are screened by analysis for hex A and hex B activities; the percent of hex A is the critical determinant of carrier vs noncarrier status. Most laboratories use a heat-inactivation assay that exploits the differential thermolability of the isoenzymes. However, we have found a reciprocal relation between the apparent leukocyte hex A activity and the amount of the sample used in the assay; i.e., a significant increase in the percent of hex A activity with decreasing amounts of sample. Three sets of data indicate that this phenomenon was caused by an effect on the hex B isoenzyme and not on hex A. This variation in hex A activity with sample amount was not observed when a hex A-specific substrate was used. This phenomenon was also not seen in assays of leukocytes from carriers for Sandhoff disease, a condition associated with a reduction in the amount of hex B. Finally, when leukocytes from a TSD homozygote, containing almost no hex A, were analyzed, marked increases in the percent of hex A were observed with decreasing sample concentrations. These data indicate that misdiagnoses could result from variations in sample concentrations used for TSD carrier testing and support the view that the leukocyte concentrations used for these assays should be standardized.

Genetic Carrier Screening↗
PubMed1992

A mutation common in non-Jewish Tay-Sachs disease: frequency and RNA studies.

Tay-Sachs disease (TSD) is an autosomal recessive genetic disorder resulting from mutation of the HEXA gene encoding the alpha-subunit of the lysosomal enzyme, beta-N-acetylhexosaminidase A (Hex A). We have discovered that a Tay-Sachs mutation, IVS-9 + 1 G-->A, first detected by Akli et al. (Genomics 11:124-134, 1991), is a common disease allele in non-Jewish Caucasians (10/58 alleles examined). A PCR-based diagnostic test, which detects an NlaIII site generated by the mutation, revealed a frequency among enzyme-defined carriers of 9/64 (14%). Most of those carrying the allele trace their origins to the United Kingdom, Ireland, or Western Europe. It was not identified among 12 Black American TSD alleles or in any of 18 Ashkenazi Jewish, enzyme-defined carriers who did not carry any of the mutations common to this population. No normally spliced RNA was detected in PCR products generated from reverse transcription of RNA carrying the IVS-9 mutation. Instead, the low levels of mRNA from this allele were comprised of aberrant species resulting from the use of either of two cryptic donor sites, one truncating exon 9 and the other within IVS-9, spliced to exon 10. Numerous additional splice products were detected, most involving skipping of one or more surrounding exons. Together with a recently identified allele responsible for Hex A pseudodeficiency (Triggs-Raine et al. Am J Hum Genet, 1992), these two alleles accounted for almost 50% (29/64) of TSD or carrier alleles ascertained by enzyme screening tests in non-Jewish Caucasians.

Alleles↗
PubMed1992

Adult onset lysosomal storage disease in a Tibetan terrier: clinical, morphological and biochemical studies.

We describe a novel late-onset lysosomal lipid storage disease affecting a Tibetan terrier. The principal clinical manifestations include visual loss, progressive cerebellar ataxia and dementia. A necropsy of an affected 10-year-old dog demonstrated cerebellar atrophy. Histological analysis revealed extensive loss of retinal ganglion cells and cerebellar Purkinje cells, and mild to moderate loss of neurons in the cerebrum, basal ganglia and spinal cord. There were generalized neuronal hypertrophy and multifocal neuronal necrosis associated with the presence of enlarged macrophages. Neurons and perineuronal macrophages contained cytoplasmic granules that stained with PAS, luxol fast blue and several lectins. The granules were sudanophilic and autofluorescent. Electron microscopic analysis revealed lysosomes laden with lamellated membrane structures in neurons, pancreatic ductal and centroacinar cells and in cultured fibroblasts. These findings indicate lysosomal storage of both lipid and carbohydrate. Biochemical analysis of brain lipids and numerous lysosomal enzyme assays of leukocytes and cultured fibroblasts were unsuccessful in elucidating the underlying enzyme defect, although a generalized increase of brain gangliosides was noted.

Animals↗
PubMed1992

Genetic discrimination and the law.

The use of genetic tests can lead to genetic discrimination, discrimination based solely on the nature of an individual's genotype. Instances of the discriminatory uses of genetic tests by employers and insurance companies have already been reported. The recently enacted Americans with Disabilities Act of 1990 (ADA), together with other federal and state laws, can be used to combat some forms of this discrimination. In this article we define and characterize genetic discrimination, discuss the applicability of the various relevant federal and state laws, including the ADA, in the areas of employment and insurance discrimination, explore the limitations of these laws, and, finally, suggest some means of overcoming these limitations.

Civil Rights↗
PubMed1992

Molecular diagnostics for myelin proteolipid protein gene mutations in Pelizaeus-Merzbacher disease.

Pelizaeus-Merzbacher disease (PMD) is a clinically heterogeneous, slowly progressive leukodystrophy. The recent detection of mutations in the myelin proteolipid protein (PLP) gene in several PMD patients offers the opportunity both to design DNA-based tests that would be useful in diagnosing a proportion of PMD cases and, in particular, to evaluate the diagnostic utility of single-strand conformation polymorphism (SSCP) analysis for this disease. A combination of SSCP analysis and direct sequencing of PCR-amplified DNA was used to screen for PLP mutations in 24 patients affected with leukodystrophies of unknown etiology. Two heretofore undescribed mutations in the PLP gene were identified, Asp202His in exon 4 and Gly73Arg in exon 3. The ease and efficiency of SSCP analysis in detecting new mutations support the utilization of this technique in screening for PLP mutations in patients with unexplained leukodystrophies.

Base Sequence↗
PubMed1992

A pseudodeficiency allele common in non-Jewish Tay-Sachs carriers: implications for carrier screening.

Deficiency of beta-hexosaminidase A (Hex A) activity typically results in Tay-Sachs disease. However, healthy subjects found to be deficient in Hex A activity (i.e., pseudodeficient) by means of in vitro biochemical tests have been described. We analyzed the HEXA gene of one pseudodeficient subject and identified both a C739-to-T substitution that changes Arg247----Trp on one allele and a previously identified Tay-Sachs disease mutation on the second allele. Six additional pseudodeficient subjects were found to have the C739-to-T mutation. This allele accounted for 32% (20/62) of non-Jewish enzyme-defined Tay-Sachs disease carriers but for none of 36 Jewish enzyme-defined carriers who did not have one of three known mutations common to this group. The C739-to-T allele, together with a "true" Tay-Sachs disease allele, causes Hex A pseudodeficiency. Given both the large proportion of non-Jewish carriers with this allele and that standard biochemical screening cannot differentiate between heterozygotes for the C739-to-T mutations and Tay-Sachs disease carriers, DNA testing for this mutation in at-risk couples is essential. This could prevent unnecessary or incorrect prenatal diagnoses.

Amino Acid Sequence↗
PubMed1992

Discrimination as a consequence of genetic testing.

Genetic discrimination refers to discrimination directed against an individual or family based solely on an apparent or perceived genetic variation from the "normal" human genotype. We describe here the results of a case history study designed to assess whether or not genetic discrimination exists. Using the above definition of genetic discrimination and applying stringent criteria for case selection, we find that genetic discrimination exists and is manifested in many social institutions, especially in the health and life insurance industries. Stigmatization, and denial of services or entitlements to individuals who have a genetic diagnosis but who are asymptomatic or who will never become significantly impaired, is noted. Follow-up comprehensive studies on the significance and varieties of genetic discrimination are needed. In order to avoid creating a new social underclass based on genetic discrimination (the "asymptomatic ill"), existing and future genetic testing or screening programs need review by medical, scientific, legal, and social policy experts, as well as the public, and may require modification.

Adult↗
PubMed1992

Diagnosis of alpha-mannosidosis by measuring alpha-mannosidase in plasma.

alpha-Mannosidosis is a lysosomal storage disease resulting from a deficiency of lysosomal alpha-mannosidase activity. Diagnosis of alpha-mannosidosis has traditionally been accomplished by demonstrating reduced alpha-mannosidase activity in leukocytes. We describe a new assay of alpha-mannosidase in serum or plasma that allows specific detection of the enzyme deficiency in alpha-mannosidosis with small, easily obtained sample volumes. The assay utilizes 40 microL of serum or plasma and a fluorescent substrate, 4-methylumbelliferyl-alpha-D-mannopyranoside in sodium acetate buffer, pH 4.0. The mean activity of a control population was 194 (SD 67) mU/L, whereas the activities obtained for four alpha-mannosidosis patients were 0, 17, 17, and 33 mU/L. Comparison with the standard leukocyte alpha-mannosidase assay showed this serum or plasma assay to be equally effective in diagnosing alpha-mannosidosis.

Humans↗
PubMed1991

Marked variation in blood beta-hexosaminidase in Gaucher disease.

Gaucher disease is due to a primary deficiency of acid beta-glucosidase activity and is associated with secondary elevations of several plasma/serum lysosomal enzyme activities, including beta-hexosaminidase. We analyzed plasma and serum beta-hexosaminidase A & B activities in 55 patients with enzyme-documented Gaucher disease. The mean beta-hexosaminidase activity was increased and the percent of the A isozyme decreased, consistent with earlier studies. Gaucher disease patients had 2,067 +/- 1,491 nmol ml-1 h-1 units of beta-hexosaminidase activity with 51.9 +/- 15.5% beta-hexosaminidase A compared to 1,086 +/- 260 nmol ml-1 h-1 and 67.8 +/- 4.0% beta-hexosaminidase A in normal controls and 965 +/- 261 nmol ml-1 h-1 and 43.6 +/- 5.5% beta-hexosaminidase A in Tay-Sachs disease heterozygotes. Contrary to previous reports, marked heterogeneity of both total plasma/serum enzyme activity and isozyme pattern was noted, as some patients had normal enzyme levels and others had severe reductions in the percent of hexosaminidase A. These data argue against the suggestions of recent studies that routine serum beta-hexosaminidase testing done in Tay-Sachs disease heterozygote detection programs can be effectively used to screen for patients with Gaucher disease.

Female↗
PubMed1991

Genetic screening: triumphs, problems, and controversies.

As genetic screening becomes more widespread, it becomes increasingly important to analyze the manifold implications of genetic screening programs. This paper characterizes the various types of programs and discusses some of the scientific, ethical, social, and economic issues that arise in evaluating any genetic screening program. Two examples of successful programs, newborn screening for phenylketonuria and carrier detection for Tay-Sachs disease, are presented. We then discuss three other screening programs that have not yet been fully implemented but which have already engendered a great deal of controversy: mass screening for heterozygosity for cystic fibrosis, DNA fingerprinting in the criminal justice system, and genetic screening in the workplace.

Cost-Benefit Analysis↗
PubMed1979

Enzymatic identification of mannose 6-phosphate on the recognition marker for receptor-mediated pinocytosis of beta-glucuronidase by human fibroblasts.

Human beta-glucuronidase (beta-D-glucuronide glucuronosohydrolase, EC 3.2.1.31), like many other glycoprotein lysosomal hydrolases, is subject to receptor-mediated endocytosis by fibroblasts. Prior work demonstrated charge heterogeneity in beta-glucuronidase and showed that high-uptake forms are more acidic than slowly internalized forms. Considerable indirect evidence implicated mannose 6-phosphate as an essential part of the recognition marker on high-uptake enzyme forms. Here we report the purification of beta-glucuronidase from human spleen and demonstrate enzymatically that mannose 6-phosphate is released on acid hydrolysis of pure enzyme varies directly with its susceptibility to pinocytosis by fibroblasts. Enzyme forms resolved by CM-Sephadex chromatography differed over an 18-fold range in uptake rate and in mannose 6-phosphate content. The most acidic forms had 4.4 mol of mannose 6-phosphate per mol of enzyme. The mannose 6-phosphate was released from the enzyme by treatment with endoglycosidase H with concomitant loss of susceptibility to adsorptive endocytosis. Thus, these studies provide direct evidence that mannose 6-phosphate is present on high-uptake enzyme forms, that it is present in the recognition marker for uptake, and that it is present on oligosaccharide that is released by endoglycosidase H.

Biological Transport, Active↗