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Biomedical subjects

A Klar

Publications and source records attributed to A Klar.

54 records · Page 3Linked to original sources
PubMed1989

Mapping replication units in animal cells.

A general approach for assaying the in vivo direction of replication for any DNA segment has been developed. This technique allows the scanning of genomic regions to detect bidirectional tail-to-tail replication, indicating the presence of a functional origin. By this criterion we identified the approximate positions of two origin sites downstream of the Chinese hamster DHFR gene. Further mapping revealed areas of head-to-head replication, signifying locations of replication termination and thus defining the landmarks of a complete animal cell replicon. Genetic proof for the existence of the DHFR origin was obtained by showing that this region serves as a bidirectional DNA synthesis initiation point following its integration into other sites in the genome by transfection. To show the general applicability of this methodology, we studied the APRT domain. Replication mapping together with the use of deletion mutants allowed the identification of an origin at a far-upstream locus.

Adenine Phosphoribosyltransferase↗
PubMed1988

Four mating-type genes control sexual differentiation in the fission yeast.

The mating-type region of fission yeast consists of three components, mat1, mat2-P and mat3-M, each separated by 15 kb. Cell-type is determined by the alternate allele present at mat1, either P in an h+ or M in an h- cell. mat2-P and mat3-M serve as donors of information that is transposed to mat1 during a switch of mating type. We have determined the nucleotide sequence of each component of mat. The P and M specific regions are 1104 and 1128 bp, respectively, and bounded by sequences common to each mating-type cassette (H1; 59 bp and H2; 135 bp). A third sequence is present at mat2-P and mat3-M but absent at mat1 (H3; 57 bp), and may be involved in transcriptional repression of these cassettes. mat1-P and mat1-M each encode two genes (Pc; 118 amino acids, Pi; 159 amino acids, Mc; 181 amino acids and Mi; 42 amino acids). Introduction of opal or frame-shift mutations into the open-reading-frame of each gene revealed that Pc and Mc are necessary and sufficient for mating and confer an h+ or h- mating type respectively. All four genes are required for meiotic competence in an h+/h- diploid. The transcription of each mat gene is strongly influenced by nutritional conditions and full induction was observed only in nitrogen-free medium. The predicted product of the Pi gene contains a region of homology with the homeobox sequence, suggesting that this gene encodes a DNA binding protein that directly regulates the expression of other genes.

Amino Acid Sequence↗
PubMed1987

Ultrastructural abnormalities of the liver in total lipodystrophy.

We present the results of light and electron microscopy studies of the liver in an 8-year-old girl with congenital total lipodystrophy. Liver histology revealed cirrhosis, and ultrastructural study showed mitochondrial abnormalities and an increase in the number of peroxisomes. A potential relationship between the high fatty acid concentration in the serum and the peroxisomal proliferation is considered.

Child↗
PubMed1985

Bilateral Bell's palsy due to Mycoplasma pneumoniae infection.

A 12-month-old infant developed bilateral facial paresis 4 weeks following a febrile illness associated with tonsillitis, bronchopneumonia and hepatosplenomegaly. Complement fixing antibody titer to Mycoplasma pneumoniae was 1:128, which subsequently dropped to 1:16. The clinical presentation in our patient was unusual in that he developed bilateral facial palsy at a very young age, and there was also a possible association of the palsy with Mycoplasma infection.

Electromyography↗
PubMed1984

A new locus in the phosphate specific transport (PST) region of Escherichia coli.

PhoS64 is a mutation in the Phosphate Specific Transport (PST) region on the E. coli chromosome which lacks the periplasmic phosphate binding protein. In contrast to other phoS mutations (which have the same phenotype) it complements the mutations in phoT and pstB. A detailed genetic map of the PST region constructed by three point transductional crosses has revealed that phoS64 is located distally from other phoS mutations. The genetic order obtained was phoS64-phoU35-pstB401-phoT-phoS-ilvC. The data indicate that phoS64 belongs to a different complementation unit in the PST region not known hitherto. We propose to name it phoV.

Bacterial Proteins↗
PubMed1984

Structure of the SAD mutation and the location of control sites at silent mating type genes in Saccharomyces cerevisiae.

The SAD mutation, an extra mating type cassette, has been shown to arise from an unequal mitotic crossover between the MAT and HMR loci, resulting in the formation of a hybrid cassette and a duplication of the MAT-HMR interval. The SAD cassette contains the "a" information and left-hand flanking regions from the parental HMRa cassette and the right-hand flanking sequences of the parental MAT cassette. This arrangement of flanking sequences causes a leaky but reproducible mating phenotype correlated with a low-level expression of the cassette as measured by RNA blotting. This weak expression is attributed to the loss of one flanking control site normally present at the silent HM storage loci.

Alleles↗
PubMed1984

Acetaminophen hypersensitivity resembling Kawasaki disease.

A 15-month-old girl initially suspected of having Kawasaki disease is presented. The diagnosis was based on the combination of prolonged fever, conjunctivitis, edema of hands and feet, exanthem and lymphadenopathy. A workup for infectious etiologies was negative. She was subsequently found to have acetaminophen hypersensitivity. To our knowledge this clinical presentation of acetaminophen hypersensitivity has not previously been described in medical literature in English.

Acetaminophen↗
PubMed1983

Activation of the c-mos oncogene in a mouse plasmacytoma by insertion of an endogenous intracisternal A-particle genome.

The activation of the cellular oncogene c-mos in mouse plasmacytoma XRPC24 was found to result from the insertion of a 4.7-kilobase-pair cellular DNA element, within the c-mos coding region. The element terminates on both sides with a direct repeat of around 335 nucleotides. The repeat as well as internal sequences of the element show strong homology to endogenous intracisternal A-particle (IAP) genes. The IAP genome integrated within c-mos in a head-to-head (5' to 5') configuration. This juxtapositioned the IAP 5' long terminal repeat next to the bulk of the oncogene's coding region and shifted c-mos 5' coding and flanking sequences to a position further upstream. The significance of several aspects of this activation and transposition event is discussed.

Animals↗
PubMedDate not supplied

Clinical-biochemical correlation in molecularly characterized patients with Niemann-Pick type C.

PURPOSE: Niemann-Pick disease type C (NP-C) is an autosomal recessive lipid storage disease manifested by an impairment in cellular cholesterol homeostasis. The clinical phenotype of NP-C is extremely variable, ranging from an acute neonatal form to an adult late-onset presentation. To facilitate phenotype-genotype studies, we have analyzed multiple Israeli NP-C families. METHODS: The severity of the disease was assessed by the age at onset, hepatic involvement, neurological deterioration, and cholesterol esterification studies. Screening of the entire NPC1 coding sequence allowed for molecular characterization and identification of disease causing mutations. RESULTS: A total of nine NP-C index cases with mainly neurovisceral involvement were characterized. We demonstrated a possible link between the severity of the clinical phenotype and the cholesterol esterification levels in fibroblast cultures following 24 hours of in vitro cholesterol loading. In addition, we identified eight novel mutations in the NPC1 gene. CONCLUSIONS: Our results further support the clinical and allelic heterogeneity of NP-C and point to possible association between the clinical and the biochemical phenotype in distinct affected Israeli families.

Age of Onset↗
PubMedDate not supplied

Perforated gastric ulcer complicating corticosteroid therapy in acute rheumatic fever.

We report an 11-year-old boy with acute rheumatic fever who presented with gastric perforation while treated with corticosteroids (CS). He had been treated initially with acetylsalicylic acid for 11 days, CS replaced the treatment with acetylsalicylic acid due to deterioration of carditis. The possible pathogenesis is discussed.

Adrenal Cortex Hormones↗