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K Harzer

Publications and source records attributed to K Harzer.

At least 55 records · Page 3Linked to original sources
PubMed1994

Sphingolipid activator protein D (sap-D) stimulates the lysosomal degradation of ceramide in vivo.

Glycosphingolipids of cultured fibroblasts from patients with total sphingolipid activator proteins (SAPs) deficiency (Schnabel et al. J. Biol. Chem. 267:3312-3315, 1992) were labeled biosynthetically with [14C]serine. After a chase period of 120h the patients' fibroblasts showed increased labeling of ceramide, glucosylceramide, lactosylceramide and ganglioside GM3 in comparison to normal control cells. Addition of sap-D to the chase-media of the patients' fibroblasts led to the degradation of the accumulated ceramide down to nearly normal levels, whereas the levels of other labeled sphingolipids remained unaffected. In contrast, addition of sap-B to the chase-media of the patients' fibroblasts did not reduce the increased ceramide levels but resulted, as expected from in vitro experiments, in a specific decrease of levels of lactosylceramide and ganglioside GM3. Therefore, we conclude that sap-D stimulates in vivo the lysosomal degradation of ceramide.

Cells, Cultured↗
PubMed1994

Leptomeningeal lipid storage patterns in Fabry disease.

We found two patterns of leptomeningeal storage that reflect two basic visceral storage patterns in Fabry disease. (i) A generalized-type leptomeningeal storage pattern, affecting all main leptomeningeal cell types (external arachnoideal epithelium, fibroblasts, vessel wall elements), was a consistent finding in three cases of classical generalized visceral phenotype. (ii) A localized leptomeningeal storage pattern was expressed, to a high degree, solely in the external arachnoidal epithelium; this pattern was found in one case with the variant visceral-restricted-type storage (confined to the cardiocytes). Thus, the external arachnoidal epithelium may be particularly susceptible to Fabry lipid storage, probably caused by a distinctly larger sustained lysosomal lipid load as compared to other cell types.

Aged↗
PubMed1994

Bone marrow cytological storage phenomena in lipidoses.

The bone marrow cytological storage phenomena in generalized lysosomal lipid storage disorders (Gaucher disease, Niemann-Pick disease, GM1-gangliosidosis, cholesterol ester storage diseases) are reviewed. The value of bone marrow cytology as a pre-screening method in the diagnostic strategy for the different diseases depends on the disease type suspected and the availability of biochemical screening methods. While cytological screening is not necessary in certain patients with typical clinical pictures, it may prove undispensable in others.

Bone Marrow Cells↗
PubMed1994

Further evidence that human lysosomal sialidase is not derived from prosaposin. Prosaposin biosynthesis and ganglioside sialidase studies in prosaposin- and sialidase-deficient fibroblast lines.

Human lysosomal sialidase has been considered by Potier et al. (Potier M., Lamontagne S., Michaud L., Tranchemontagne J. (1990) Biochem Biophys Res Commun 173, 449-456) to be a processing product of prosaposin, the common precursor of the saposin proteins A, B, C, and D that function as activators in the lysosomal degradation of sphingolipids. We tested this hypothesis on cultured fibroblasts of patients with prosaposin deficiency, a neurolipidosis caused by a complete lack of synthesis of the prosaposin protein, by determining their lysosomal and, for comparison, their plasma membrane sialidase activities. Using both the natural substrate ganglioside GM3 and the synthetic compound 4-methylumbelliferyl neuraminate, we found the lysosomal sialidase activity in the prosaposin-deficient cells to be in the normal control range; normal values were also found for the plasma membrane sialidase. In fibroblasts from patients with a genetic deficiency of the lysosomal sialidase (sialidosis), on the other hand, biosynthesis and processing of prosaposin were unimpaired. Our findings therefore show no precursor/product relationship between prosaposin and the lysosomal or the plasma membrane sialidase.

Cell Line↗
PubMed1993

Prosaposin deficiency: further characterization of the sphingolipid activator protein-deficient sibs. Multiple glycolipid elevations (including lactosylceramidosis), partial enzyme deficiencies and ultrastructure of the skin in this generalized sphingolipid storage disease.

Sphingolipid activator protein (SAP) deficiency, previously described in two sibs and shown to be caused by the absence of the common saposin precursor (prosaposin), was further characterized by biochemical lipid and enzyme studies and by ultrastructural analysis. The 20-week-old fetal sib had increased concentrations of neutral glycolipids, including mono-, di-, tri- and tetrahexosylceramide, in liver, kidney and cultured skin fibroblasts compared with the controls. Glucosylceramide and lactosylceramide were particularly elevated. The kidney of the affected fetus showed additional increases in the concentration of sulphatide, galactosylceramide and digalactosylceramide. Free ceramide was stored in the liver and kidney, and GM3 and GM2 gangliosides were elevated in the liver, but not the brain, of the fetus. Phospholipids, however, were normal in the affected fetus. In the liver biopsy of the propositus, who later died at 16 weeks of age, only a few lipids could be studied. Glucosylceramide, dihexosylceramide and ceramide were elevated in agreement with our previous study. Enzyme studies were undertaken using detergent-free liposomal substrate preparations and fibroblast extracts. The sibs' beta-glucocerebrosidase and beta-galactocerebrosidase activities were clearly reduced, but their sphingomyelinase activities were normal. The normal activity of the latter enzyme and the almost normal tissue concentration of sphingomyelin in prosaposin deficiency suggest that the prosaposin-derived SAPs are not required for sphingomyelinase activity in vivo. In keeping with the biochemical findings, skin biopsies from the sibs showed massive lysosomal storage with a vesicular and membranous ultrastructure. The function of SAPs in sphingolipid degradation and the role of SAPs for enzyme activity in vitro are discussed. In addition, the similarity in neutral glycolipid accumulations in Niemann-Pick disease type C and in prosaposin deficiency are noted. The phenotype of the prosaposin deficient sibs resembled acute neuronopathic (type 2) Gaucher disease more than Farber disease in several aspects, but their genotype was unique.

Brain Chemistry↗
PubMed1993

Unusual orthochromatic leukodystrophy with epitheloid cells (Norman-Gullotta): increase of very long chain fatty acids in brain discloses a peroxisomal disorder.

Very long chain fatty acids (VLCFA) were found to be markedly increased and phytanic acid was borderline above normal in formalin-fixed brain white matter of case with an unusual type of familial leukodystrophy with epitheloid cells as described previously by Gullotta et al. [Neuropädiatrie (1970) 2: 173-186]. Increased VLCFA in brain clearly demonstrate that the patient had suffered from a peroxisomal disease. This diagnosis is corroborated by ultrastructural findings in brain showing typical lamellar inclusions. The particular type of peroxisomal disorder present in case (heterozygote of X-linked adrenoleukodystrophy?) remains speculative.

Adrenoleukodystrophy↗
PubMed1993

Ultrastructural pathology of eccrine sweat gland epithelial cells in globoid cell leukodystrophy.

Three of four children were recognized by deficient beta-galactocerebrosidase activities as having globoid cell leukodystrophy inclusions in sweat gland epithelial cells, similar in ultrastructure to those seen in Schwann cells. This observation in globoid cell leukodystrophy emphasizes the need to include sweat gland epithelial cells in examinations of skin in globoid cell leukodystrophy, as well as in any neurometabolic disorder.

Biopsy↗
PubMed1992

Additional biochemical findings in a patient and fetal sibling with a genetic defect in the sphingolipid activator protein (SAP) precursor, prosaposin. Evidence for a deficiency in SAP-1 and for a normal lysosomal neuraminidase.

It has been shown that sphingolipid activator proteins (SAPs) 1 and 2 are encoded on the same gene along with two other putative activator proteins [Fürst, Machleidt & Sandhoff (1988) Biol. Chem. Hoppe-Seyler 369, 317-328 and O'Brien, Kretz, Dewji, Wenger, Esch & Fluharty (1988) Science 241, 1098-1101]. We have undertaken further biochemical investigations on a patient and fetal sibling, who were previously shown to have a unique sphingolipid storage disorder associated with an SAP-2 deficiency [Harzer, Paton, Poulos, Kustermann-Kuhn, Roggendorf, Grisar & Popp (1989) Eur. J. Pediatr. 149, 31-39]. The severity of their disorder suggested that other products of the SAP precursor or prosaposin gene may also be deficient. The turnover of cerebroside sulphate and globotriaosylceramide were investigated and were both impaired in fibroblasts from the patient and fetus. However, the activities of cerebroside sulphate sulphatase and globotriaosylceramide alpha-galactosidase in vitro were normal in cells from the fetus and patient respectively. In addition, there was an increase in cerebroside sulphate concentration in the kidney of the affected fetus. These results indicate that, in addition to the SAP-2 deficiency, there was a defect in SAP-1 function in this disorder. Additional increases in the concentration of monohexosyl- and dihexosyl-ceramide in the fetal kidney probably reflect the deficiency of SAP-2 in the case of monohexosylceramides, and the combined activator deficiency in the case of dihexosylceramides. Lactosylceramide-loading studies confirmed that there was a defect in the turnover of this lipid in fibroblasts from the affected patient and fetus but not from a patient with an isolated SAP-1 deficiency, or from patients with Krabbe disease, GM1 gangliosidosis or galactosialidosis. It has been suggested [Potier, Lamontagne, Michaud & Tranchemontagne (1990) Biochem. Biophys. Res. Commun. 173, 449-456] that the prosaposin gene also codes for lysosomal neuroaminidase. However, we found normal neuraminidase activity in fibroblasts from our patient, using assay conditions which are diagnostic for sialidosis patients. The role of prosaposin gene products in sphingolipid metabolism is discussed in view of our biochemical findings in this genetic disorder.

Cells, Cultured↗
PubMed1992

Simultaneous deficiency of sphingolipid activator proteins 1 and 2 is caused by a mutation in the initiation codon of their common gene.

Sphingolipid activator proteins (SAPs) are small, nonenzymic glycoproteins that stimulate lysosomal degradation of various sphingolipids. SAP-1, SAP-2, and two additional potential activator proteins are derived from a common precursor by proteolytic processing. A severe case of sphingolipid storage disease that led to death within 16 weeks was attributed to a possible total deficiency of the SAPs generated by this gene (Harzer, K., Paton, B. C., Poulos, A., Kustermann-Kuhn, B., Roggendorf, W., Grisar, T., and Popp, M. (1989) Eur. J. Pediatr. 149, 31-39). Analysis of the SAP precursor cDNA from the patient and his fetal sibling showed an A to T transversion in the initiation codon. Allele-specific oligonucleotide hybridization revealed that both parents are heterozygous carriers for this mutation. In pulse-chase experiments using antisera raised against SAP-1 or SAP-2, no cross-reacting material could be detected in the patients' fibroblasts.

Alleles↗
PubMed1992

Metabolism of GM1 ganglioside in cultured skin fibroblasts: anomalies in gangliosidoses, sialidoses, and sphingolipid activator protein (SAP, saposin) 1 and prosaposin deficient disorders.

Cultured skin fibroblasts from controls and patients with lysosomal storage diseases were loaded with GM1 ganglioside that had been labelled with tritium in its ceramide moiety. After a 65-h or 240-h incubation, a large percentage of this ganglioside remained undegraded in GM1 gangliosidoses, whereas in the other storage diseases studied, one of its metabolites accumulated by 2-4 fold relative to controls. Labelled GM2 ganglioside accumulated in 4 variants of GM2 gangliosidosis, whereas labelled GM3 ganglioside accumulated in sialidosis, galactosialidoses and sphingolipid activator protein 1 (SAP-1, saposin B) and prosaposin (saposin A, B, C and D) deficient lipidoses. The reduced degradation of GM3 ganglioside in the SAP-1 and prosaposin deficiencies was attributed to the deficient function of SAP-1. The prosaposin deficient cells also showed a reduced re-utilization of radioactive metabolites from GM1 ganglioside (i.e. sphingosine and fatty acid) for phospholipid biosynthesis compared with fibroblasts from the SAP-1 deficient patient or normal controls. This anomaly was ascribed to the previously shown defect in ceramide degradation in prosaposin deficiency.

Child, Preschool↗
PubMed1992

[Response criteria for enzyme substitution in Gaucher disease].

Recently the intravenous enzyme replacement therapy with modified beta-glucocerebrosidase has become available for patients with M. Gaucher. We report here the considerable improvement of activity and vigor in a 5 year old girl with type 1 M. Gaucher administering 60 IU/kg every two weeks for 6 months. The platelet count increased from 82-96/nl to more than 150/nl and hemoglobin from 10.8 to more than 12 g/dl. Serum acid phosphatase decreased from 14.6 U/l to 5.9. U/l and angiotensin-converting enzyme from 327 to 102 U/l. The estimation of splenic volume by MRT showed a decrease by 40%, while liver size was not reduced within 6 months of therapy. MRT proved to be useful to demonstrate the bone marrow infiltration by Gaucher cells. The enzyme replacement therapy resulted in an objective response. No side effects have been observed so far. The extreme high treatment costs enforce a considerable dose reduction for maintenance therapy.

Acid Phosphatase↗
PubMed1991

Sulfatide activator protein. Alternative splicing that generates three mRNAs and a newly found mutation responsible for a clinical disease.

The sulfatide activator protein, also known as SAP-1, is derived from a gene that generates an mRNA coding for four homologous proteins. Its physiological function is to stimulate hydrolysis of sulfatide by arylsulfatase A in vivo. A genetic defect in the sulfatide activator results in a metabolic disorder similar to classical metachromatic leukodystrophy, which is itself caused by a genetic defect in arylsulfatase A. In a patient with sulfatide activator deficiency, a nucleotide transversion G722----C (counted from A of the initiation codon ATG) was found in the mRNA of the sulfatide activator precursor, resulting in the substitution of serine for Cys241 in the mature sulfatide activator. The remainder of the coding sequence was completely normal except for a polymorphism C to T in position 1389, which does not change the amino acid sequence. The patient produces at least three different forms of mRNA for the precursor. Two of them include a stretch of an additional 9 and 6 bases, respectively, within the sulfatide activator coding region. In normal individuals this stretch of additional bases has also been observed. This could be explained by the presence of a small 9-base pair exon which can be introduced, or not, by alternative splicing as a stretch of 9 or 6 bases into the mature mRNA. The shortest form of the mRNA yields an active sulfatide activator (Fürst, W., Schubert, J., Machleidt, W., Meier, H. E., and Sandhoff, K. (1990) Eur. J. Biochem. 192, 709-714).

Base Sequence↗
PubMed1991

Sphingolipid activator protein 1 deficiency in metachromatic leucodystrophy with normal arylsulphatase A activity. A clinical, morphological, biochemical, and immunological study.

A 7-year-old boy had clinical features of metachromatic leucodystrophy (MLD), however, an increased urinary sulphatide excretion was found in the presence of normal arylsulphatase A (and alpha-galactosidase A) activity. A rectal biopsy showed metachromatically staining storage macrophages as well as nonmetachromatic, but PAS-positive, submucosal neurons filled with membranous cytoplasmic bodies. These two types of storage material led to testing for a sphingolipid activator protein (SAP) deficiency. Loading tests with sulphatide and globotriaosylceramide showed deficient turnover of both sphingolipids in cultured fibroblasts. Using the Ouchterlony method, there was no reactivity between a described anti-SAP 1 antiserum and the patient's fibroblast extracts. This new case of SAP-1 deficient MLD was compared with the four cases of this variant known from the literature. Our results indicate that rectal biopsy morphology and lipid loading biochemistry should prove useful for the screening of SAP defects.

Biopsy↗
PubMed1991

Type C Niemann-Pick disease: biochemical aspects and phenotypic heterogeneity.

Within Niemann-Pick diseases, type C has now been demonstrated to be a nosological entity totally distinct from types A and B, and is best characterized at present by unique abnormalities of intracellular translocation of exogenous cholesterol, which are briefly reviewed. Although the primary defect is still unknown in type C Niemann-Pick disease, this discovery has had immediate medical applications, by providing the first strategy for reliable prenatal detection of the disorder and easy diagnosis of patients. From our personal experience of 134 cases, diagnosis is best reached by the combined demonstration of a deficient induction of esterification and of an intravesicular cholesterol storage by cytochemistry after filipin staining. The prevalence of the various clinical forms observed is given, together with a brief report of 6 adult-onset cases. The spectrum of phenotypic heterogeneity in relation to abnormal LDL processing has been defined, resulting in the delineation of three biochemical groups, classical (86%), variant (7%) and intermediate (7%). Correlations between clinical and biochemical phenotypes have been studied. To get further insight into genetic heterogeneity, complementation studies were performed. Preliminary results have yet given no evidence of several complementation groups within type C Niemann-Pick disease. The recognition of the three biochemical phenotypes is however critical for diagnosis and genetic counselling.

Adolescent↗
PubMed1990

[Fabry's disease with isolated disease of the cardiac muscle, manifesting as hypertrophic cardiomyopathy].

A case is presented of Fabry's disease manifesting in an adult (aged 64) as hypertrophic nonobstructive cardiomyopathy caused by massive ceramidtrihexoside storage confined exclusively to the cardiocytes. There was no storage detectable in capillaries or in any other structure of the organs examined (liver, pancreas, brain, aorta, pulmonary artery, coronary arteries, heart valves). The clinical picture was dominated by heart failure slowly progressing during the last fifteen years of the patient's life terminated by pulmonary thromboembolism. There were no clinical signs of ocular, renal or skin affection. Since no unfixed tissues were available for enzyme analysis diagnosis had to be done using formaldehyde fixed tissues. The isolated stored lipid was characterized by TLC and by proton magnetic resonance analysis as globotriaosyl ceramide (Gal alpha 1-4 Gal beta 1-4 Glc beta 1-1' Cer) and was proved to be cleaved by control cell homogenates but left intact by those prepared from Fabry mutant cells (leukocytes, cultured fibroblasts). alpha galactosidase activity in each of his four daughters was in heterozygous range (peripheral leukocytes were used for analysis). The existing variants of cardiological syndromes in Fabry's disease are reviewed together with problems of diagnosis of atypical cases.

Cardiomyopathy, Hypertrophic↗