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Biomedical subjects

D Schindler

Publications and source records attributed to D Schindler.

At least 55 records · Page 3Linked to original sources
PubMed1993

Increased amount and contour length distribution of small polydisperse circular DNA (spcDNA) in Fanconi anemia.

Small polydisperse circular DNA (spcDNA) in Fanconi anemia (FA) was analyzed from cultured fibroblast-like cells by electron microscopy. Application of the mica-press adsorption technique for the semi-quantitative determination of spcDNA amounts to three FA and three normal control skin-derived fibroblast strains revealed 85-fold increased levels of spcDNA in the FA cells. An even higher excess over controls was suggested when the FA fibroblasts were propagated for up to 11 serial in vitro passages, consistent with the short replicative life-span of primary FA cells and their rapid transition into a poorly dividing state, in which spcDNA reportedly further increases. In addition, contour length distributions of gradient-purified spcDNA preparations from five FA fibroblast strains were compared with those from five normal control strains. Mean spcDNA contour lengths were significantly greater in the FA than in the control cells. The reported findings of increased spcDNA amounts and sizes in FA coincide with a similar association of chromosome instability and abnormal spcDNA formation previously observed in cultured cells derived from angiofibromas in tuberous sclerosis. Circumstantial evidence from the present study in the paradigmatic chromosome breakage syndrome FA further supports the suggestion that a common mechanism underlies chromosome instability and the surplus generation of spcDNA. Notably, this apparent mechanism is functional in homonuclear primary cell strains with a distinct inherited basis of their chromosome instability, and is not restricted to heteroploid and neoplastoid cell lines.

Adolescent↗
PubMed1993

Physical mapping of the holoprosencephaly critical region on chromosome 7q36.

Holoprosencephaly (HPE) is a developmental field defect involving the brain and face. Cytogenetic deletions in patients with HPE have localized one of the HPE genes to chromosomal region 7q36. We have characterized the 7q deletions in thirteen HPE patients. The result is the construction of a high resolution physical map of 7q32-qter. As a first step towards cloning an HPE gene crucial for normal brain development, we have defined the HPE minimal critical region in 7q36 between D7S292 and D7S392.

Adult↗
PubMed1993

A variant of Noonan's syndrome: a case history.

The authors describe a variant of Noonan's syndrome hitherto undescribed. The special findings in this case were anomalous origin of the aortic arch vessels and focal glomerulonephritis.

Acute Kidney Injury↗
PubMed1992

Simultaneous measurement, using flow cytometry, of radiosensitivity and defective mitogen response in ataxia telangiectasia and related syndromes.

In a retrospective study, peripheral blood mononuclear cells from 13 patients with known ataxia telangiectasia (AT) (Louis Bar syndrome, McKusick #20890) were irradiated with different doses of X-rays prior to stimulation with phytohaemagglutinin. Mitogen response and cell cycle progression were assessed by two-parameter 5-bromo-2'-deoxyuridine/Hoechst--ethidium bromide flow cytometry. Compared to age-matched controls, AT cells show a severely defective mitogen response in both unirradiated and irradiated cells. Following irradiation with 1.5 Gy, AT cells exhibit significantly greater accumulations of cells in the G2 phase of the first cell cycle than controls. The ratio between the number of cells accumulated in the first cycle G2 phase and the growth fraction provides a clear distinction between AT and control cultures. In addition, two patients with microcephaly, normal intelligence, immunodeficiency, chromosomal instability and risk for lymphoreticular malignancies (Seemanová syndrome) and two patients with the Nijmegen breakage syndrome (both syndromes are listed as McKusick #25126) also exhibit very poor mitogen response and moderately increased G2 phase accumulations after X-irradiation. The simultaneous assessment of radiosensitivity and mitogen response in a single cell kinetic assay provides a speedy and accurate classification of cells of AT and AT-related syndromes.

Adolescent↗
PubMed1992

Cytogenetic studies of skin fibroblast cultures from a karyotypically normal female with dyskeratosis congenita.

Skin fibroblast cultures from a female patient with dyskeratosis congenita revealed markedly increased frequencies of chromosomal breaks, hypodiploidy, and premature centromere disjunction. The frequencies of mitotic disturbances, like ana- and telophase bridges, lagging chromosomes, and micronuclei were almost as dramatically elevated as in cultures from two severely affected patients with Fanconi anemia. Provided that our patient is representative for an autosomal form of dyskeratosis congenita, this type of the disease seems to be characterized by chromosomal instability with a characteristic pattern of cytogenetic abnormalities.

Adult↗
PubMed1992

An investigation into the glycolipid metabolism of alpha-N-acetylgalactosaminidase-deficient fibroblasts using native and artificial glycolipids.

Deficient activity of lysosomal alpha-N-acetylgalactosaminidase represents a recently recognized lysosomal disorder whose neurologic manifestation in infancy is infantile neuroaxonal dystrophy. The lysosomal enzyme defect, inherited as an autosomal recessive trait, was first identified in the two brothers, GD and BD. Metabolic modification of glycolipids with terminal alpha-GalNAc was studied in fibroblasts from these patients. [Ceramide-3H]Forssman-glycosphingolipid (GSL), the fluorescent C6-NBD-lyso-Forssman-glycolipid (GL) and a 14C-labelled neoglycolipid containing the blood group A trisaccharide were synthesized and used as probes in degradation studies with cell homogenates and with cells in culture. Assays of each of these substrates with fibroblast homogenates of the patients demonstrated the profound deficiency of alpha-N-acetylgalactosaminidase activity compared with controls. Residual activities in the patients' fibroblast homogenates were detected with all glycolipid substrates; those amounted to 6.3 +/- 3.7% (BD) and 12.8 +/- 6.3% (GD) of the mean activity in controls for [3H]Forssman-GSL, and to 2.2 +/- 0.8% (BD) and 3.6 +/- 1.8% (GD) for C6-NBD-lyso-Forssman GL, respectively. alpha-N-Acetylgalactosaminidase deficiency in intact cells was confirmed by TLC analyses, which showed impaired glycolipid modification in cell extracts obtained following addition of [3H]Forssman GSL and C6-NBD-lyso-Forssman GL to the culture media of fibroblasts from the patients.

Carbohydrate Sequence↗
PubMed1991

Chromosome instability and X-ray hypersensitivity in a microcephalic and growth-retarded child.

We report on a microcephalic, growth-retarded newborn girl without major anomalies who has chromosome instability in lymphocytes and fibroblasts. Frequent involvement of bands 7p13, 7q34, 14q11, and 14q32 suggested the diagnosis of ataxia telangiectasia (AT) or a related disorder. Supportive evidence was radioresistant DNA synthesis in fibroblasts and radiation hypersensitivity of short-term lymphocyte cultures. Follow-up for nearly 4 years showed largely normal development, and no signs of telangiectasia, ataxia, or immunodeficiency. Serum AFP levels turned from elevated at age 5 months to normal at age 2 years. We propose that our patient belongs to the expanding category of "AT-related" genetic disorders, probably to the Nijmegen breakage syndrome.

Cell Cycle↗
PubMed1991

Biosynthesis of human alpha-N-acetylgalactosaminidase: defective phosphorylation and maturation in infantile alpha-NAGA deficiency.

The biosynthesis of human alpha-N-acetylgalactosaminidase (alpha-NAGA) was studied in normal fibroblasts and in cells from patients with infantile alpha-NAGA deficiency. Normal alpha-NAGA is synthesized as a 52 kDa precursor which matures to a 49 kDa species through phosphorylation and carbohydrate triming. Fibroblasts from the patients synthesize normal amounts of a 52 kDa precursor, however phosphorylation does not occur and this precursor is subsequently degraded intracellularly.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1991

Medial forebrain bundle units in the rat: dependence of refractory period estimates on pulse duration.

The slope of some psychophysically-derived curves describing recovery from refractoriness in medial forebrain bundle (MFB) reward neurons decreases as the pulse duration is lengthened. This effect has been attributed to increased recruitment of small-diameter fibers by the long-duration pulses. Alternatively, this effect might be due to increases in the refractory periods of a fixed population of neurons. By means of extracellular recording, we measured the effect of increasing the pulse duration on recovery from refractoriness in 26 neurons antidromically activated by MFB stimulation. In all cases, recovery from refractoriness was delayed as the pulse duration was increased from 0.1 ms to 2.0 ms. The delay was more pronounced at near-threshold currents than at higher currents and was generally largest in neurons that recovered most rapidly from refractoriness when stimulated with brief pulses. These effects of long duration pulses on recovery of excitability in a fixed population of neurons may have contributed to the delay in recovery implied by the psychophysical data. Thus, delayed recovery does not necessarily imply preferential recruitment of small-diameter fibers by the long-duration pulses.

Animals↗
PubMed1991

Epidermal growth factor receptor gene expression in avian epiphyseal growth-plate cartilage cells: effect of serum, parathyroid hormone and atrial natriuretic peptide.

Avian chondrocytes and fibroblasts, derived from epiphyseal growth-plate and skin, respectively, were cultured in vitro. In chondrocytes, epidermal growth factor (EGF) caused a dose-dependent stimulation of proliferation. EGF receptor mRNA was not detected with the v-erb B probe in chondrocytes cultured in the presence of 5% fetal calf serum (FCS). In the absence of FCS in the medium, a time-dependent increase in the level of EGF receptor mRNA was observed. Parallel changes were also observed in the level of EGF receptor, as demonstrated by immunofluorescence using antibodies directed against avian EGF receptor. In avian fibroblasts, EGF receptor mRNA and EGF receptor levels were not affected by FCS. Furthermore, FCS did not affect the level of thyroid hormone receptor mRNA (using v-erb A as a probe) in either chondrocytes or fibroblasts. Parathyroid hormone (PTH), which acts as a mitogen in avian chondrocytes attenuated--whereas atrial natriuretic peptide (ANP), a suppressor of chondrocyte proliferation, enhanced--EGF receptor mRNA. The present results show that avian growth-plate chondrocytes respond to EGF and bear EGF receptors. The levels of EGF mRNA and EGF receptor are inversely related to cell proliferation. The results also support previous suggestions that PTH and ANP play important roles in chondrocyte proliferation, possibly through their effect on the synthesis of the EGF receptor.

Animals↗
PubMed1990

A method for the rapid detection of urinary glycopeptides in alpha-N-acetylgalactosaminidase deficiency and other lysosomal storage diseases.

A new method is described for the detection of abnormal urinary oligosaccharide and glycopeptide excretion by thin layer chromatography and differential visualization of oligosaccharides and glycopeptides. This method permits rapid screening and identification of disorders characterized by oligosacchariduria and glycopeptiduria including alpha-N-acetylgalactosaminidase deficiency, angiokeratoma corporis diffusum with glycopeptiduria, aspartylglucosaminuria, galactosialidosis, fucosidosis, GM1 gangliosidosis and sialidoses 1 and 2. Of note, the characterization of the glycopeptide excretion profiles in patients with alpha-N-acetylgalactosaminidase deficiency and angiokeratoma corporis diffusum with glycopeptiduria revealed essentially identical patterns, indicating the metabolic relatedness of these two phenotypically distinct conditions. Use of this improved thin layer chromatographic method should enhance routine screening of patients for lysosomal storage diseases as well as permit the identification of new disorders resulting from defective oligosaccharide and/or glycoprotein metabolism.

Adolescent↗
PubMed1990

Schindler disease: the molecular lesion in the alpha-N-acetylgalactosaminidase gene that causes an infantile neuroaxonal dystrophy.

Schindler disease is a recently recognized infantile neuroaxonal dystrophy resulting from the deficient activity of the lysosomal hydrolase, alpha-N-acetylgalctosaminidase (alpha-GalNAc). The recent isolation and expression of the full-length cDNA encoding alpha-GalNAc facilitated the identification of the molecular lesions in the affected brothers from family D, the first cases described with this autosomal recessive disease. Southern and Northern hybridization analyses of DNA and RNA from the affected homozygotes revealed a grossly normal alpha-GalNAc gene structure and normal transcript sizes and amounts. Therefore, the alpha-GalNAc transcript from an affected homozygote was reverse-transcribed, amplified by the polymerase chain reaction (PCR), and sequenced. A single G to A transition at nucleotide 973 was detected in multiple subclones containing the PCR products. This point mutation resulted in a glutamic acid to lysine substitution in residue 325 (E325K) of the alpha-GalNAc polypeptide. The base substitution was confirmed by dot blot hybridization analyses of PCR-amplified genomic DNA from family members with allele-specific oligonucleotides. Furthermore, transient expression of an alpha-GalNAc construct containing the E325K mutation resulted in the expression of an immunoreactive polypeptide which had no detectable alpha-GalNAc activity.

Base Sequence↗
PubMed1989

Forebrain neurons driven by rewarding stimulation of the medial forebrain bundle in the rat: comparison of psychophysical and electrophysiological estimates of refractory periods.

Psychophysically derived estimates of recovery from refractoriness were obtained at self-stimulation sites in the lateral hypothalamus and ventral tegmental area. The refractory periods of single units driven by the same stimulation electrodes and stimulation fields were then measured electrophysiologically. Antidromically driven units with refractory periods longer than those of the neurons responsible for the rewarding effect were concentrated in the septal complex. Units with refractory periods that overlapped the estimates for the reward-related neurons were found in this region as well but were also encountered in neighboring structures lateral, ventral, and/or caudal to the septal nuclei. It is argued that this latter class of units should be considered as possible constituents of the directly stimulated substrate for the rewarding effect because they are driven by rewarding stimulation, have refractory periods similar to those of the reward-related neurons and arise in or near regions in which lesions have been effective in decreasing the rewarding effect of stimulating the medial forebrain bundle.

Animals↗
PubMed1989

Continuous bromodeoxyuridine labeling and bivariate ethidium bromide/Hoechst flow cytometry in cell kinetics.

Most techniques of flow cytometric cell cycle analysis are not capable of distinguishing the number of rounds of DNA synthesis that a cell has undergone since the start of an experiment. Continuous labeling with 5-bromodeoxyuridine (BrdUrd) offers such a potential. We illustrate here that the bivariate analysis of non-BrdUrd-quenched ethidium bromide vs. BrdUrd-quenched Hoechst 33258 fluorescence offers a high degree of resolution that enhances the analytical power of the technique, and that this approach can be applied to the analysis of a broad range of human and murine primary cells and established cell lines.

Bisbenzimidazole↗