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Biomedical subjects

B Asfaw

Publications and source records attributed to B Asfaw.

At least 19 recordsLinked to original sources
PubMed2005

Lactosylceramide in lysosomal storage disorders: a comparative immunohistochemical and biochemical study.

Immunohistochemical studies of the presence of lactosylceramide (LacCer) in lysosomal storage disorders (LSDs) were done using anti-LacCer monoclonal antibody of the CDw 17 type (clone MG-2). No sign of an association between LacCer and the lysosomal system in normal cells was observed, except for histiocytes active in phagocytosis. A comparative study of a group of LSDs showed a general tendency for LacCer to increase in storage cells in Niemann-Pick disease type C (NPC), and types A and B, GM1 gangliosidosis, acid lipase deficiency, glycogen storage disease type II and mucopolysaccharidoses. LacCer accumulated in storage cells despite normal activity of relevant lysosomal degrading enzymes. The accumulation of LacCer displayed variability within storage cell populations, and was mostly expressed in neurons in NPC. An absence of the increase in LacCer in storage cells above control levels was seen in neuronal ceroid lipofuscinoses (neurons and cardiocytes) and in Fabry disease. Gaucher and Krabbe cells showed significantly lower levels, or even the absence, of LacCer compared with control macrophages. Results of immunohistochemistry were corroborated by semiquantitative lipid thin-layer chromatography (TLC). It is suggested that different associations of LacCer with the lysosomal storage process may reflect differences in glycosphingolipid turnover induced by the storage-compromised lysosomal/endosomal system.

Adult↗
PubMed2005

Acid sphingomyelinase deficiency. Phenotype variability with prevalence of intermediate phenotype in a series of twenty-five Czech and Slovak patients. A multi-approach study.

A multi-approach study in a series of 25 Czech and Slovak patients with acid sphingomyelinase deficiency revealed a broad phenotypic variability within Niemann-Pick disease types A and B. The clinical manifestation of only 9 patients fulfilled the historical classification: 5 with the rapidly progressive neurovisceral infantile type A and 4 with a slowly progressive visceral type B. Sixteen patients (64%) represented a hitherto scarcely documented 'intermediate type' (IT). Twelve patients showed a protracted neurovisceral course with overt or mild neurological symptoms, three a rapidly progressing fatal visceral affection with rudimentary neurological lesion. One patient died early from a severe visceral disease. The genotype in our patients was represented by 4 frameshift and 14 missense mutations. Six were novel (G166R, R228H, A241V, D251E, D278A, A595fsX601). The Q292K mutation (homoallelic, heteroallelic) was strongly associated with a protracted neurovisceral phenotype (10 of 12 cases). The sphingomyelin loading test in living fibroblasts resulted in total degradation from less than 2% in classical type A to 70-80% in classical type B. In the IT group it ranged from 5% to 49% in a 24 h chase. The liver storage showed three patterns: diffuse, zonal (centrolobular), and discrete submicroscopic. Our series showed a notable variability in both the neurological and visceral lesions as well as in their proportionality and synchrony, and demonstrates a continuum between the historical 'A' and 'B' phenotypes of ASM deficiency. This points to a broad phenotypic potential of ASM deficiency, suggesting the existence of still unknown factors independently controlling the storage level in the visceral and neuronal compartments. This report highlights the important position of the IT in the ASM deficiency phenotype classification. We define IT as a cluster of variants combining clinical features of both the classical types. The protracted neuronopathic variant with overt, borderline or subclinical neurology prevails and is important in view of future enzyme replacement therapy. It appears more common in central Europe. The visceral, rapidly progressing early fatal type has been recognized rarely so far.

Adolescent↗
PubMed2004

Hominid cranial remains from upper Pleistocene deposits at Aduma, Middle Awash, Ethiopia.

The Upper Pleistocene localities of Aduma and Bouri have yielded hominid fossils and extensive Middle Stone Age (MSA) archaeological assemblages. The vertebrate fossils recovered include parts of four hominid crania from Aduma and a complete right parietal from Bouri. Archaeological associations and radiometric techniques suggest an Upper Pleistocene age for these hominids. The more complete cranium from Aduma (ADU-VP-1/3) comprises most of the parietals, the occipital, and part of the frontal. This cranium is compared to late Middle and Upper Pleistocene hominid crania from Africa and the Middle East. The Aduma cranium shows a mosaic of cranial features shared with "premodern" and anatomically modern Homo sapiens. However, the posterior and lateral cranial dimensions, and most of its anatomy, are centered among modern humans and resemble specimens from Omo, Skhul, and Qafzeh. As a result, the Aduma and Bouri Upper Pleistocene hominids are assigned to anatomically modern Homo sapiens.

Animals↗
PubMed2001

Geology and palaeontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia.

The Middle Awash study area of Ethiopia's Afar rift has yielded abundant vertebrate fossils (approximately 10,000), including several hominid taxa. The study area contains a long sedimentary record spanning Late Miocene (5.3-11.2 Myr ago) to Holocene times. Exposed in a unique tectonic and volcanic transition zone between the main Ethiopian rift (MER) and the Afar rift, sediments along the western Afar rift margin in the Middle Awash provide a unique window on the Late Miocene of Ethiopia. These deposits have now yielded the earliest hominids, described in an accompanying paper and dated here to between 5.54 and 5.77 Myr. These geological and palaeobiological data from the Middle Awash provide fresh perspectives on hominid origins and early evolution. Here we show that these earliest hominids derive from relatively wet and wooded environments that were modulated by tectonic, volcanic, climatic and geomorphic processes. A similar wooded habitat also has been suggested for the 6.0 Myr hominoid fossils recently recovered from Lukeino, Kenya. These findings require fundamental reassessment of models that invoke a significant role for global climatic change and/or savannah habitat in the origin of hominids.

Animals↗
PubMed2000

Link between a novel human gammaD-crystallin allele and a unique cataract phenotype explained by protein crystallography.

We describe a 5-year-old boy with a unique congenital cataract caused by deposition of numerous birefringent, pleiochroic and macroscopically prismatic crystals. Crystal analysis with subsequent automatic Edman degradation and matrix-associated laser desorption ionization time-of-flight mass spectrometry have identified the crystal-forming protein as gammaD-crystallin (CRYGD) lacking the N-terminal methionine. Sequencing of the CRYGD gene has shown a heterozygous C-->A transversion in position 109 of the inferred cDNA (36R-->S transversion of the processed, N-terminal methionine-lacking CRYGD). The lens protein crystals were X-ray diffracting, and our crystal structure solution at 2.25 A suggests that mutant R36S CRYGD has an unaltered protein fold. In contrast, the observed crystal packing is possible only with the mutant protein molecules that lack the bulky Arg36 side chain. This is the first described case of human cataract caused by crystallization of a protein in the lens. It involves the third known mutation in the CRYGD gene but offers, for the first time, a causative explanation of the phenotype.

Alleles↗
PubMed2000

Jaws and teeth of Australopithecus afarensis from Maka, Middle Awash, Ethiopia.

The Maka locality in Ethiopia's Middle Awash area has yielded new craniodental remains dated to 3.4 million years (myr) in age. These remains are described and assessed functionally and systematically. The fossils are assigned to Australopithecus afarensis. Maka thus joins Hadar and Laetoli as the third major locality yielding this species. As with previous site samples, the Maka collection displays a wide range of size variation. The nearly complete and undistorted MAK-VP-1/12 adult mandible from Maka is an excellent match for Hadar and Laetoli counterparts, confirming the geographic and temporal distribution of A. afarensis. This specimen shows that this taxon is functionally and developmentally hominid in its incisor/canine/premolar complex. A postulated evolutionary trajectory through A. anamensis to A. afarensis would have involved postcanine megadontia and other adaptations to a more heavily masticated diet relative to the earlier Ardipithecus ramidus.

Adult↗
PubMed1999

Determination of urinary sulfatides and other lipids by combination of reversed-phase and thin-layer chromatographies.

A fast and simple method for determination of sulfatides in the urine of patients with metachromatic leukodystrophy (MLD, arylsulfatase A deficiency) has been developed. The procedure consists of two steps: extraction of total urinary lipids by reversed-phase chromatography and their HPTLC separation. Two types of sorbents based on different matrixes were compared, of which the hydroxyethyl methacrylate C-18 type sorbent was found to be superior. Twenty-milliliter aliquots of urine are sufficient for the analysis. The technique is appropriate for simultaneous qualitative identification and semiquantitative densitometric determination and is suitable for routine work. The amount of sulfatides is expressed in relation to sphingomyelin, which copurifies with sulfatides and better reflects the level of membrane lipids in urine than commonly used parameters (creatinine, urine volume, etc.). The ranges were found to be 0.15-0.68 nmol sulfatide/nmol sphingomyelin for control individuals and 3.5-27.2 nmol sulfatide/nmol sphingomyelin for MLD patients. The excretion of sulfatides is pathonognomic for true MLD (due to the accumulation in kidney) and therefore its analysis is important for evaluation of suspected MLD cases including clinically and enzymatically atypical cases. The method is also useful as a complementary analysis for other lipidoses with high excretion of sphingolipids in urine (e.g., Fabry disease).

Case-Control Studies↗
PubMed1999

Australopithecus garhi: a new species of early hominid from Ethiopia.

The lack of an adequate hominid fossil record in eastern Africa between 2 and 3 million years ago (Ma) has hampered investigations of early hominid phylogeny. Discovery of 2.5 Ma hominid cranial and dental remains from the Hata beds of Ethiopia's Middle Awash allows recognition of a new species of Australopithecus. This species is descended from Australopithecus afarensis and is a candidate ancestor for early Homo. Contemporary postcranial remains feature a derived humanlike humeral/femoral ratio and an apelike upper arm-to-lower arm ratio.

Animals↗
PubMed1998

4-Nitro-1-(trimethylsilylethynyl)benzene.

The title molecule, C11H13NO2Si, lies on a mirror plane, with only one methyl group lying out of plane. The C[symbol: see text]C triple bond has a length of 1.199 (4) A. Bond angles Si-C[symbol: see text]C and C[symbol: see text]C-C(Ar) are 177.9 (3) and 178.0 (3) degrees, respectively. The Si-Csp3 bond lengths are 1.831 (4) and 1.838 (3) A, while the Si-Csp distance is 1.839 (3) A.

Crystallography, X-Ray↗
PubMed1998

Degradation of blood group A glycolipid A-6-2 by normal and mutant human skin fibroblasts.

The degradation of blood group glycolipid A-6-2 (GalNAc(alpha1-->3)[Fuc alpha1-->2]Gal(beta1-->4)GlcNAc(beta1-->3)Gal(beta1-->4)Glc(beta1-->1')C er, IV2-alpha-fucosyl-IV3-alpha-N-acetylgalactosaminylneolact otetraosylceramide), tritium-labeled in its ceramide moiety, was studied in situ, in skin fibroblast cultures from normal controls, from patients with defects of lysosomal alpha-N-acetylgalactosaminidase, and from patients with other lysosomal storage diseases. Uptake of the glycolipid with apolipoprotein E-coated liposomes was linear with time and with the amount of glycolipid added. In normal cells, the expected array of less polar products and some lipids resulting from re-using the liberated sphingosine, mainly sphingomyelin and phosphatidylcholine, were formed. In alpha-N-acetylgalactosaminidase-deficient cells, the glycolipid was virtually not degraded; product formation was less than 2% of the normal control rate, suggesting that blood group A-active glycolipids contribute as storage compounds to the pathogenesis of this disease. The expected accumulation of degradation intermediates was seen in fucosidosis, and in Sandhoff, Gaucher, and Farber disease cells, whereas normal turnover rates were found in Tay-Sachs disease cells, G(M2) activator-deficient (variant AB of G(M2) gangliosidosis) and in sulfatide activator- (sap-B-) deficient cells. In G(M1) gangliosidosis and in sap precursor-deficient cells, the lysosomal glycolipid catabolism was found to be strongly retarded; accumulation of individual products could not be seen. Skin fibroblasts from patients with alpha-N-acetylgalactosaminidase deficiency (Schindler disease) cannot degrade the major blood group A glycolipid.

ABO Blood-Group System↗
PubMed1997

The first skull of Australopithecus boisei.

Australopithecus boisei was first described from a cranium recovered in 1959 from Olduvai Gorge, Tanzania. This and subsequent finds, mostly from Kenya's Turkana basin, resulted in its characterization as a specialized Australopithecus species with a hyper-robust masticatory apparatus. A distinct A. boisei facial morphology has been emphasized to differentiate robust Australopithecus lineages from East and South Africa. A preference for closed and/or wet habitats has been hypothesized. Here we report some new A. boisei specimens, including the taxon's first cranium and associated mandible, from Konso, Ethiopia. These fossils extend the known geographical range of A. boisei. They provide clear evidence for the coexistence of A. boisei and Homo erectus within a predominantly dry grassland environment. The A. boisei specimens from Konso demonstrate considerable morphological variation within the species. The unexpected combination of cranial and facial features of this skull cautions against the excessive taxonomic splitting of early hominids based on morphological detail documented in small and/or geographically restricted samples.

Animals↗
PubMed1997

A diiodo-substituted 9-anthracenone.

The central ring of the anthrone system in 1,8-diiodo-10-hydroxy-10-(3-methylbut-3-en-1-ynyl)anthrac en-9(10H)-one, C19H12I2O2, has a boat conformation and the two outer rings form a dihedral angle of 41.1 (2) degrees. The I-C bond lengths are 2.094 (4) and 2.083 (4) A. The hydroxyl and carbonyl groups form an intermolecular hydrogen bond having an O...O distance of 2.853 (4) A.

Anthracenes↗
PubMed1995

Benzenediazonium ion derived from Sudan I forms an 8-(phenylazo)guanine adduct in DNA.

1-(Phenylazo)-2-hydroxynaphthalene (Sudan I, Solvent Yellow 14) is a liver and urinary bladder carcinogen in mammals. Sudan I forms benzenediazonium ion during cytochrome P-450 catalyzed metabolism. Calf thymus DNA was reacted with Sudan I activated by microsomal enzymes or with benzenediazonium ion in vitro, and the adducts formed were analyzed by the 32P-postlabeling technique. Both enrichment procedures (1-butanol extraction and nuclease P1 digestion) of this technique were employed for detection and quantitation of the DNA adducts formed. Cochromatographic analyses of adduct spots obtained by reaction with DNA or homopolydeoxyribonucleotides showed that the major Sudan I-DNA adduct was formed with deoxyguanosine. This adduct was also found in DNA directly reacted with benzenediazonium ion. The major Sudan I-DNA adduct was characterized by UV/vis absorbance spectroscopy as well as by the chromatographic properties of the adduct on cellulose or poly(ethylenimine)--cellulose TLC and HPLC. The characteristics are identical to those of the adduct synthesized from benzenediazonium ion and guanine, identified by mass, UV/vis, and 1H-NMR spectroscopy as 8-(phenylazo)guanine. The results suggest strongly that benzenediazonium ion derived from Sudan I reacts with DNA in vitro to form the stable 8-(phenylazo)guanine adduct.

Adenine↗
PubMed1995

Peroxidase-activated carcinogenic azo dye Sudan I (Solvent Yellow 14) binds to guanosine in transfer ribonucleic acid.

Peroxidase in the presence of hydrogen peroxide catalyzes in vitro the activation of the carcinogenic azo dye Sudan I (1-phenylazo-2-hydroxynaphthalen) to tRNA-, homopolyribonucleotide- and 5'-monophosphate nucleoside-bound products. tRNA, poly G and guanosine 5'-monophosphate modified by activated Sudan I become colored and have an absorption maximum of approx. 480 nm. Cochromatographic analysis of adducts obtained by a reaction with tRNA and guanosine 5'-monophosphate on a thin layer of cellulose showed that the major Sudan I-tRNA adduct was formed by a reaction of activated Sudan I with guanosine in tRNA. The radical mechanism of the binding of the Sudan I molecule, containing the whole azo aromatic system, to nucleic acids is discussed.

Animals↗
PubMed1994

Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia.

Seventeen hominoid fossils recovered from Pliocene strata at Aramis, Middle Awash, Ethiopia make up a series comprising dental, cranial and postcranial specimens dated to around 4.4 million years ago. When compared with Australopithecus afarensis and with modern and fossil apes the Aramis fossil hominids are recognized as a new species of Australopithecus--A. ramidus sp. nov. The antiquity and primitive morphology of A. ramidus suggests that it represents a long-sought potential root species for the Hominidae.

Adult↗
PubMed1994

African Homo erectus: old radiometric ages and young Oldowan assemblages in the Middle Awash Valley, Ethiopia.

Fossils and artifacts recovered from the middle Awash Valley of Ethiopia's Afar depression sample the Middle Pleistocene transition from Homo erectus to Homo sapiens. Ar/Ar ages, biostratigraphy, and tephrachronology from this area indicate that the Pleistocene Bodo hominid cranium and newer specimens are approximately 0.6 million years old. Only Oldowan chopper and flake assemblages are present in the lower stratigraphic units, but Acheulean bifacial artifacts are consistently prevalent and widespread in directly overlying deposits. This technological transition is related to a shift in sedimentary regime, supporting the hypothesis that Middle Pleistocene Oldowan assemblages represent a behavioral facies of the Acheulean industrial complex.

Animals↗
PubMed1993

New discoveries of Australopithecus at Maka in Ethiopia.

The taxonomy of Australopithecus afarensis, the oldest known hominid species, has been a matter of debate since its description in 1978 (ref. 1). Some authorities regard all specimens assigned to A. afarensis as belonging to a single taxon whereas others regard the Tanzanian and Ethiopian specimens as each representing a different species. Further controversy surrounds the issues of sexual dimorphism and locomotion among these hominids. Resolution of these problems would shed light on hominid phylogeny in general and on the ancestry of later Australopithecus and Homo. Fossils discovered in the Afar of Ethiopia in 1990 constitute the first major addition to the 3-4 million year (Myr) hominid record since the 1970s. We report here the discovery of new fossils from Maka, dated to 3.4 Myr ago, which provide powerful support for the interpretation of A. afarensis as a single, ecologically diverse, sexually dimorphic, bipedal Pliocene primate species whose known range encompassed Ethiopia and Tanzania.

Animals↗