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D Stambolian

Publications and source records attributed to D Stambolian.

30 records · Page 2Linked to original sources
PubMed1990

Mapping X-linked ophthalmic diseases. IV. Provisional assignment of the locus for X-linked congenital cataracts and microcornea (the Nance-Horan syndrome) to Xp22.2-p22.3.

The Nance-Horan syndrome (NHS) is an infrequent X-linked disorder typified by dense congenital central cataracts, microcornea, anteverted and simplex pinnae, brachymetacarpalia, and numerous dental anomalies. The regional location of the genetic mutation causing NHS is unknown. The authors applied the modern molecular techniques of analysis of restriction fragment length polymorphisms to five multigenerational kindreds in which NHS segregated. Provisional linkage is established to two DNA markers--DXS143 at Xp22.3-p22.2 and DXS43 at Xp22.2. Regional localization of NHS will provide potential antenatal diagnosis in families at risk for the disease and will enhance understanding of the multifaceted genetic defects.

Abnormalities, Multiple↗
PubMed1990

Ribosomal RNA gene sequences and hominoid phylogeny.

Sequences totaling 3,500 bases from the 28S rRNA gene and from one of the ribosomal internal transcribed spacers (ITS1) have been determined for human, chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and orangutan (Pongo pygmaeus). Analyses of the rRNA alignments show (1) a clustering of substitutions in the "variable regions" of the 28S gene, (2) a 1.5-3-fold increase in divergence in the transcribed spacer over that in the exon, and (3) that human and chimpanzee are the most closely related pair, in agreement with the results of Miyamoto et al., Sibley and Ahlquist, and Caccone and Powell.

Animals↗
PubMed1990

Nance-Horan syndrome: localization within the region Xp21.1-Xp22.3 by linkage analysis.

Nance-Horan Syndrome (NHS) or X-linked cataract-dental syndrome (MIM 302350) is a disease of unknown pathogenesis characterized by congenital cataracts and dental anomalies. We performed linkage analysis in three kindreds with NHS by using six RFLP markers between Xp11.3 and Xp22.3. Close linkage was found between NHS and polymorphic loci DXS43 (theta = 0 with lod score 2.89), DXS41 (theta = 0 with lod score 3.44), and DXS67 (theta = 0 with lod score 2.74), defined by probes pD2, p99-6, and pB24, respectively. Recombinations were found with the marker loci DXS84 (theta = .04 with lod score 4.13), DXS143 (theta = .06 with lod score 3.11) and DXS7 (theta = .09 with lod score 1.68). Multipoint linkage analysis determined the NHS locus to be linked completely to DXS41 (lod score = 7.07). Our linkage results, combined with analysis of Xp interstitial deletions, suggest that the NHS locus is located within or close to the Xp22.1-Xp22.2 region.

Abnormalities, Multiple↗
PubMed1986

Cataracts in patients heterozygous for galactokinase deficiency.

The role of heterozygous galactokinase deficiency in the development of presenile cataracts is presently undetermined. Erythrocyte galactokinase activity was measured from 95 normal Caucasian subjects and from 39 Caucasian patients who had developed idiopathic bilateral cataracts between ages 20 and 55. The diagnosis of heterozygous galactokinase deficiency was based on the following criteria: galactokinase activity more than 2.0 SD below the control population mean; when available, familial evidence for heterozygous galactokinase activity was used as additional evidence. Three of 39 patients (1/13) with cataracts were found to be carriers of the galactokinase deficiency allele (P less than 0.001). Two heterozygotes had high dietary galactose intake suggesting a possible relationship between a high galactose diet and cataract formation. Dietary information was unavailable for the third heterozygote. We conclude that there is a high prevalence of heterozygous galactokinase deficiency existing in patients less than 55 yr of age with cataracts, and recommend that adults at risk restrict their consumption of dairy products.

Adolescent↗
PubMed1985

Purification of human galactokinase and evidence for its existence as a monomer form.

A procedure for preparing a highly purified galactokinase (ATP:D-galactose 1-phosphotransferase, EC 2.7.1.6) from human erythrocytes and placenta is described, involving DEAE-Sephacel, ammonium sulfate fractionation, gel-filtration and a subsequent chromatography step on Blue Sepharose CL-6B. The final chromatography step yields a homogeneous preparation of high specific activity. The subunit molecular weight was determined to be 38 000 for both placental and erythrocyte galactokinases. Both active preparations of the native enzyme eluted from a gel filtration column gave a molecular weight of 37 000-38 000, thus suggesting the enzyme to be present in monomeric form. The isoelectric points for both crude and their respective purified enzymes was determined to be at pH 5.7. This method for purifying human galactokinase from placenta and erythrocytes represents a significant improvement over that previously reported and contradicts past evidence for the enzyme existing as a dimer.

Chromatography, Gel↗
PubMed1985

Macular deposits in galactokinase deficiency.

Deficiency of the enzyme, galactokinase, is a recognized cause of "juvenile" lens opacities; these opacities are felt to be its only clinical expression. The deficiency itself is inherited as an autosomal recessive and as such is expected to be clinically manifest in the homozygote. We have recently demonstrated cataracts and associated bilateral macular deposits in a white male who is heterozygous for the deficiency of the enzyme and whose dietary intake of milk and its products is extremely high. To our knowledge, intraretinal deposits have not previously been described in patients with galactokinase deficiency, and their clinical significance and biochemical makeup can only be speculative. Dietary restriction of galactose is recommended for all individuals proven to be deficient in this enzyme, whether homozygous or heterozygous.

Adult↗
PubMed1984

Isoelectric-focusing of galactokinase in lens and other tissues.

Thin-layer isoelectric focusing was used to investigate galactokinase in lenses from humans, cows, rats, rabbits and also in other tissues (red cells, liver, kidney, brain, placenta) from these species. In each case the enzyme activity was present as a single isozyme. The isoelectric point was the same in lens, red cell and other tissues of the same species, but differed from species to species. Post-translational modification due to deamidation was not detected in the lens or red cell from these species. Galactokinase activities in whole tissue extract were determined in different tissues of the various species. There were wide variations in activity. In the adult human lens, both normal and cataractous, it was low. The findings indicate that isoelectric focusing of RBC galactokinase combined with specific enzyme staining allows one to monitor lens galactokinase in patients with cataracts.

Adult↗
PubMedDate not supplied

Galactose and cataract.

Galactosemia is a disorder caused by a deficiency of any one of three possible enzymes involved in the metabolism of galactose: galactokinase, transferase or epimerase. Any single deficient enzyme can result in cataract through the accumulation of galactitol in the lens. The ophthalmologist may play an important role in this disease, since early recognition of cataract development followed by the initiation of a galactose-free diet may lead to clearing of lenticular opacities. The clinical and laboratory findings that distinguish the three enzyme deficiency disorders of galactosemia are discussed. The biochemical genetics of each enzyme also are reviewed, along with the recent evidence linking heterozygous galactokinase deficiency and presenile cataract.

Animals↗