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Biomedical subjects

M C Loonen

Publications and source records attributed to M C Loonen.

At least 37 records · Page 2Linked to original sources
PubMed1986

[A form of acquired childhood aphasia: Landau-Kleffner syndrome].

The Landau-Kleffner syndrome is a childhood disorder associating a loss of previous acquired speech with seizures and bilateral abnormalities on the EEG. The precise aetiology of this syndrome is unknown. Epilepsy is easily regulated by anticonvulsants. However, the aphasia is a more persistent defect and recovery is incomplete in 2/3 of the cases despite intensive speech therapy. A typical case is described in detail. Of five additional cases the most relevant data are presented.

Anticonvulsants↗
PubMed1985

Late-onset globoid cell leucodystrophy (Krabbe's disease). Clinical and genetic delineation of two forms and their relation to the early-infantile form.

A girl is described with a late-onset form of globoid cell leucodystrophy (GLD, Krabbe's disease). Data of this patient and seventeen reported patients with late-onset GLD and cerebroside-beta-galactosidase deficiency were compared with those of patients with classical early-infantile GLD. Three phenotypes of GLD are proposed, an early-infantile form, and two late-onset forms. Biochemical studies demonstrated residual activities of cerebroside-beta-galactocerebrosidase in the late-onset forms. The KM values were identical in the three GLD phenotypes. Autosomal recessive inheritance is likely for each of the subtypes. Complementation studies by somatic cell hybridization suggest that the mutations in early-infantile and late-onset GLD are allelic.

Cerebrosides↗
PubMed1984

Uptake and stability of human and bovine acid alpha-glucosidase in cultured fibroblasts and skeletal muscle cells from glycogenosis type II patients.

Acid alpha-glucosidase (EC 3.2.1.20) was purified from human placenta and bovine testis by affinity chromatography using concanavalin A (conA) and Sephadex G 200. When added to the culture medium of human fibroblasts, the enzyme purified from bovine testis is taken up with a 200-fold higher efficiency than the enzyme from human placenta. Uptake of acid alpha-glucosidase from bovine testis is mediated by the mannose-6-phosphate receptor, whereas only a minor fraction of placental enzyme appears to be equipped with the mannose-6-phosphate recognition marker. Once internalized, both human and bovine acid alpha-glucosidase demonstrate a half-life of about 10 days in fibroblasts from control individuals and patients with different clinical forms of glycogenosis type II (Pompe's disease, acid alpha-glucosidase deficiency). Evidence is presented that the mannose-6-phosphate receptor is also present on the plasma membrane of the clonal myogenic skeletal muscle cell lines G8-1 and L6J1 (respectively from mouse and rat origin) and on cultured human skeletal muscle cells derived from a muscle biopsy. Addition of bovine testis acid alpha-glucosidase to skeletal muscle cell cultures from an adult patient with glycogenosis type II leads to complete correction of the enzyme deficiency.

Animals↗
PubMed1984

Combined sialidase (neuraminidase) and beta-galactosidase deficiency. Clinical, morphological and enzymological observations in a patient.

A patient with combined deficiency of sialidase and beta-galactosidase is described. This now 39-year-old man, who is of Japanese origin, showed gradually progressive clinical features from the age of six years. Many of these features are commonly found in sialidosis type 2 or in GM1-gangliosidosis. Both sialidase and beta-galactosidase activities were deficient in leucocytes and cultured fibroblasts. Leucocytes of his mother showed activities of both enzymes in the lower limit of the control range. Morphologically, the pattern of storage products in a skin biopsy resembled in many respects that seen in GM1-gangliosidosis. Moreover, storage products which could be typical of sialidosis were also observed. Since the patient showed angiokeratomata, the morphological findings were compared with those specific to Fabry's disease, but no similarities were found. An enzymological diagnosis of the disease is most reliable on cultured fibroblasts, discriminating it from sialidosis type 2 and GM1-gangliosidosis. In view of recent findings, leucocytes seem to be less suitable for the establishment of the diagnosis galactosialidosis.

Adult↗
PubMed1983

Two genetically different MU-NANA neuraminidases in human leucocytes.

Human leucocytes contain two different MU-NANA neuraminidases, which can be distinguished by Concanavalin A binding. The Con A binding form is predominant in lymphocytes (more than 80%) and the non-binding form predominates in granulocytes. The pH optima of both these neuraminidases as well as their subcellular localization as determined by Percoll gradient centrifugation suggest that they are both lysosomal. Immunological studies indicate that the Con A binding form is present in a complex with beta-galactosidase whereas the non-binding form is not. Leucocytes from patients with sialidosis or galactosialidosis are deficient in the Con A binding neuraminidase, whereas the non-binding form is normal. In sialolipidosis both forms are normal. These results demonstrate that leucocytes contain at least two genetically different MU-NANA neuraminidases. Thus, the use of leucocytes should be avoided for the diagnosis of sialidosis and galactosialidosis, and isolated lymphocytes should be used to obtain reliable results.

Chromatography, Affinity↗
PubMed1981

Identification of heterozygotes for glycogenosis 2 (acid maltase deficiency).

In 21 obligate and 9 possible heterozygotes for acid maltase deficiency (AMD) (glycogenosis 2, Pompe's disease), different methods of identifying heterozygotes have been studied. Heterozygosity could not be demonstrated by physical examination, serum CPK assays, morphological examination of muscle biopsy (including light-microscopy, histochemistry and electron-microscopy), or by ultrastructural examination of a skin biopsy. Heterozygotes could be identified to a large, but still limited extent, by measuring the acid alpha-glucosidase activity in urine, cultivated fibroblasts, leucocytes, or skeletal muscle. Heterozygotes for the generalized from of AMD could not be distinguished from those for the muscular form. The limitations of heterozygote identification by means of enzyme assays are discussed, and some practical aspects for genetic counselling are mentioned.

Female↗
PubMed1981

A family with different clinical forms of acid maltase deficiency (glycogenosis type II): biochemical and genetic studies.

In the same family, the generalized or infantile form of acid maltase deficiency (glycogenosis type II, Pompe disease) and the muscular or adult-onset form affected different individuals. Autosomal-recessive inheritance for the two clinical forms was demonstrated in this family by assay of acid alpha-glucosidase in muscle, lymphocytes, cultured fibroblasts, and urine of asymptomatic relatives. Current biochemical techniques do not discriminate between persons heterozygous for the generalized form and those heterozygous for the muscular form. To explain the coexistence of both forms in the same family, the infant with the generalized form or her grandfather with the muscular form must have been a genetic compound of different mutant alleles for acid alpha-glucosidase.

Adult↗
PubMed1977

Ultrastructural study of the vacuoles in the peripheral lymphocytes in juvenile amaurotic idiocy. Juvenile form of generalized ceroid lipofuscinosis.

Lymphocytes of the peripheral blood of 31 patients with juvenile amaurotic idiocy (juvenile form of ceroid lipofuscinosis) were examined with the electron microscope. In all cases, intracytoplasmic clear vacuoles were present, containing round hollow, fingerprint and highly electron dense structures. The combination of these structures, not necessarily in one and the same vacuole, was considered to be highly indicative for the diagnosis of juvenile amaurotic idiocy. In addition to these three structures, parallel tubular inclusion bodies, rectilinear profiles and rod-shaped structures were found but in a number of the cases. The parallel tubular inclusion bodies were not regarded as having any diagnostic significance.

Adolescent↗
PubMed1977

Factors related to prognosis of acquired aphasia in children.

In a follow up study of 15 children with acquired aphasia, it was found that the persistent presence of concomitant neurological disorders was important for the final outcome. Prognosis seemed to be related to etiology, EEG disturbances and the severity of comprehension deficit at the onset of aphasia.

Age Factors↗
PubMed1976

beta-Galactosidase deficiency in an adult: a biochemical and somatic cell genetic study on a variant of GM1-gangliosidosis.

Biochemical data are presented of a 29-year-old male, who shows progressive psychomotor retardation and a beta-galactosidase deficiency in leucocytes and cultured skin fibroblasts. Somatic cell hybridization studies show that this variant of GM1-gangliosidosis is based on a different gene mutation than is present in types 1 and 2. No complementation is observed in fusion experiments with cells from type 3 variant.

Adult↗