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Biomedical subjects

M Steinert

Publications and source records attributed to M Steinert.

At least 109 records · Page 6Linked to original sources
PubMed1980

Cloning and characterization of DNA sequences complementary to messenger ribonucleic acids coding for the synthesis of two surface antigens of Trypanosoma brucei.

Full length double-stranded complementary DNAs (ds cDNAs) could be synthesized on mRNAs enriched in sequences coding for the synthesis of the variant specific antigens (VSAs) AnTat 1.1 and AnTat 1.8 from Trypanosoma brucei brucei. The size of these ds cDNAs is about 1700 and 1850 base pairs for AnTat 1.1 and AnTat 1.8 respectively. The ds cDNAs were cloned in the plasmid pBR322; two clones harboring a copy of each coding sequence were selected. Both the hybrid-arrested translation and the positive hybridization elution methods confirmed that these recombinants contain VSA-specific inserts. A restriction map was constructed in each case. The two sequences seem to be inserted in a reversed 3'--5' orientation, respective to the plasmid polarity. The AnTat 1.8 cloned sequence is a palindrome probably due to a cloning artefact. Hybridization of the cloned DNAs with "Northern" blots of total or poly(A)+ RNA revealed in each case a single, specific band. The expression of these VSA genes appears thus to be regulated at the transcriptional level.

Antigens, Surface↗
PubMed1979

Characterization of long and short repetitive sequences in the sea urchin genome.

Long and short repetitive sequences were purified from the DNA of Paracentrotus lividus under conditions designed to optimize the yield of complete, end to end sequences. Double-stranded long repeat DNA prepared in this manner ranged in length from approximately 3000 to 15 000 nucleotide pairs with average sizes of approximately 6000 base pairs. In the electron microscope, long repeat DNA was observed to possess continuous sequences that often appeared to be terminated by one or more loops and/or fold backs. Long repeat DNA sequences, resheared to 300 base pairs, were found to have an average melting point identical to that for sheared native DNA. Thus, the reassociated duplexes of long repetitive DNA seem to possess very few mismatched base pairs. Reassociation kinetic analyses indicate that the majority of the long repeat sequences are reiterated only 4--7 times per haploid amount of DNA. Melt-reassociation analyses of short repetitive DNA, at several criteria, support the previously held concept that these sequences belong the sets or families of sequences which are inexact copies of one another. Our studies also support hypotheses suggesting that short repetitive sequences belong to families which may have arisen via distinct salttatory events. The relationships between long and short repetitive DNA sequences are considered with respect to widely held concepts of their sequence organization, evolution, and possible functions within eucaryotic genomes. A model for the possible organization of short repeats within long repetitive DNA sequences is also presented.

Animals↗
PubMed1979

Immunological purification and partial characterization of variant-specific surface antigen messenger RNA of Trypanosoma brucei brucei.

Polyadenylated RNA isolated from total polyribosomes of two variable antigen types (VATs) of T. brucei brucei were shown to program the synthesis, in mRNA-dependant reticulocyte lysates, of a wide variety of polypeptides. After immunoprecipitation of these cell-free products with an homologous antiserum raised against purified variant-specific surface antigen (VSSA), a major electrophoretic band was apparent on fluorography. It was confirmed that this band corresponds to the variable antigen since only an excess of purified homologous antigen will provoke competition. The apparent molecular weight of the in vitro synthesized antigen is about 63,000 daltons. The VSSA mRNA has been found in membrane-bound polyribosomes and a 15 fold immunological purification of this mRNA has been obtained, using partially purified anti-VSSA IgG in conjunction with inactivated Staphylococcus aureus.

Animals↗
PubMed1978

[Urinary bladder carcinoma in biopsies of the last 50 years. Changes in frequency and sex distribution (author's transl)].

Comparative investigations of 440 urinary bladder biopsies from 1927 to 1957 and 1634 bladder biopsies from 1972 to 1976 showed the following: Epithelial bladder tumors are today found much more frequently among old age groups than they used to be. Bladder carcinoma have also been noticed more frequently among women in recent years. The sex ratio of men to women has dropped from 3.4:1 to 2.6:1. In the past five years there has been a steady rise in the frequency of carcinoma; the number of biopsies has risen 67% over the established rates of 1972. The percentage of pure squamous cell carcinoma of bladder cancer found from 1927 to 1957 was 5.1%, almost double the rate of 1972 to 1976, which was 2.8%; 89.5% of all tumors from the first time interval and 93% from the second were transitional cell carcinomas. Highly differentiated epithelial bladder tumors are today more frequently diagnosed than before. The ratio of high- to low-differentiated bladder tumors is presently 1.7:1 in patients under the age of 50, and 1.3:1 in patients over 50.

Adult↗
PubMed1970

Electron microscopy of kinetoplastic DNA from Trypanosoma mega.

The electron microscopical aspect of kinetoplast DNA has been studied in preparations obtained by osmotic disruption of isolated organelles. A large amount of this DNA appears to be of large molecular size. This is apparently at variance with the observations, made by others using a different technical approach, of kinetoplast DNA consisting mainly of small circular molecules of constant size. As a homogeneous population of small circles (0.74 mum in contour length) could also be seen in our samples, the possibility that at least two different kinds of DNA exist in the kinetoplast is discussed.

Animals↗