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R Löwer

Publications and source records attributed to R Löwer.

31 records · Page 2Linked to original sources
PubMed1993

A general method for the identification of transcribed retrovirus sequences (R-U5 PCR) reveals the expression of the human endogenous retrovirus loci HERV-H and HERV-K in teratocarcinoma cells.

During the past decade, different types of endogenous retroviral sequences have been defined in the human genome usually by low stringency hybridization employing DNA probes of evolutionary conserved animal retrovirus genes. Although all human genomic loci sequenced were found to be defective or interspersed with stop codons, indirect evidence is accumulating that human endogenous retroviral loci are expressed at least in some instances. One example is the synthesis of retroviral particles in human teratocarcinoma cell lines observed by electron microscopy. To establish a link between virus expression and genomic loci we searched for retroviral RNA in human cellular mRNA populations using a generally applicable method. A tRNA-derived primer complementary to a putative retroviral primer binding site was extended by reverse transcription and this product was elongated with a homopolymeric stretch and amplified by PCR (R-U5 PCR). Cloning and sequencing of such products revealed that the endogenous retroviral loci HERV-H and HERV-K are expressed in those human teratocarcinoma cell lines which produce retroviral particles. The size distribution of four HERV-K mRNAs detected in Northern blots is reminiscent of the complex expression pattern seen with a number of exogenous retroviruses.

Animals↗
PubMed1993

Evidence that HERV-K is the endogenous retrovirus sequence that codes for the human teratocarcinoma-derived retrovirus HTDV.

Human teratocarcinoma-derived viruses (HTDV) are retrovirus-like particles that are regularly observed by electron microscopy at low frequency in cell lines established from human teratocarcinomas. Over the last years, one of our teratocarcinoma cell lines spontaneously began to produce high amounts of HTDV. This cell line is stained in immunofluorescence tests by an antiserum raised against recombinant gag protein of HERV-K, an expressed human endogenous retrovirus sequence. In immunoelectron microscopy of ultrathin frozen sections, this anti HERV-Kgag-specific antiserum reacts specifically with HTDV particles. In Western blots, the antiserum recognizes predominantly a protein with an apparent molecular weight of 30 kDa, presumably the major core protein of HTDV particles. Taken together, these results provide evidence that HERV-K codes for HTDV.

Fluorescent Antibody Technique↗
PubMed1987

[Retroviruses and the development of lymphoma].

Retroviruses are small, RNA-containing enveloped viruses which are widely distributed in nature. They exist in many animal species as well as in man. Exogenous virus strains are horizontally transmitted between individuals of a given species, like all other virus groups. Endogenous virus strains have managed some time during evolution to infect germ line cells like oocytes and spermatocytes and are thus transmitted vertically from parents to offspring. Several retrovirus strains possess oncogenes, i.e., acutely tumor-inducing genes. There are four human retrovirus strains so far. The initially discovered strain, HTLV-I, is accepted to be a co-factor in the development of an acute T-cell leukemia in adults. HTLV-II has repeatedly been isolated from cells of patients with hairy cell leukemia. Its etiological significance is unclear at present. HTLV-III/LAV-1, now designated HIV-1, is the causative agent of AIDS. HTLV-IV and LAV-2 are additional HIV-1 related strains and are supposed to cause AIDS as well. What is known about the pathogenicity of the human retrovirus strains will be discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Human teratocarcinomas cultured in vitro produce unique retrovirus-like viruses.

We have previously reported that among a series of human tumours investigated, only human teratocarcinoma cell lines derived from testicular tumours or pulmonary metastases of patients in Germany and the U.S.A. produced retrovirus-like particles spontaneously, albeit in low amounts. In a recent publication electron microscopical data suggested that the human teratocarcinoma-derived ( HTD ) particles were morphologically closely related, but not identical, to the type C retroviruses of animals. In this communication, the explantation of three human teratocarcinoma cell lines is briefly described. Evidence is presented that HTD particles (i) are synthesized only in a fraction of the epithelioid and differentiating cells; (ii) can be induced biochemically in a manner characteristic of retroviruses; (iii) either are not infectious or possess a peculiar host range; (iv) are immunologically unrelated to animal retrovirus strains; (v) possess an endogenous RNA-dependent DNA polymerase activity that can be banded at 1.16 g/ml in linear sucrose gradients. These results may be taken as suggestive evidence that HTD particles represent a novel group of unique retroviruses.

Antigens, Viral↗
PubMed1983

Structural organization of unique retrovirus-like particles budding from human teratocarcinoma cell lines.

Human teratocarcinoma cells cultured in vitro can be induced to produce retrovirus-like particles. The induction procedures are the same as those previously shown to induce the synthesis of animal retroviruses. Electron microscopical evidence is presented that the human teratocarcinoma-derived (HTD) particles are most closely related to the type C retrovirus strains. HTD particles can be banded at 1.16 g/ml in linear sucrose gradients, the characteristic density for retroviruses, and subsequently be used for negative staining and fine structure analysis.

Cell Line↗
PubMed1983

Retroviruses in human tumors.

Retroviruses received widespread attention in the past not only because they caused tumors in animals and, perhaps, in man, but also because they served as useful tools to elucidate molecular mechanisms involved in the control of eukaryotic gene expression. In this brief overview, evidences are presented that retrovirus-like particles can regularly be demonstrated in human teratocarcinomas cultured in vitro. These viruses are morphologically reminiscent of animal retrovirus strains but show also unique structural features. The viruses possess endogenous reverse transcriptase activity and can be banded at 1.16 g/ml in sucrose gradients, a density characteristic of retroviruses. They can clearly be distinguished from animal retrovirus strains on immunological grounds. We will also briefly summarize the data accumulating for the human T-cell lymphoma viruses (HTLV) which were recently discovered first by Gallo et al. and independently by Hinuma and Miyoshi. HTLV seem to play an etiological role in the establishment of human adult T-cell leukemia/lymphoma and thus represent the first pathogenic human retroviruses.

DNA, Neoplasm↗
PubMed1982

Synthesis of retrovirus-like particles in testicular teratocarcinomas.

Two lines of evidence led to the investigation of human teratocarcinoma cells in vitro for oncogenic retroviruses: the observation by electron microscopy of retrovirus-like particles budding from the syncytial trophoblasts of human placentas, and the demonstration that teratocarcinoma patients before treatment show a high serum antibody reactivity against envelope proteins of mammalian retroviruses. In all 5 teratocarcinoma cell lines studied so far, retrovirus-like particles have been detected by electron microscopy. The production of these human teratocarcinoma-derived (HTD)-particles is enhanced by induction procedures known to be effective in animal virus model systems. In parallel, virus induction also increases the level of chorionic gonadotropin in the culture supernatant, demonstrating syncytial trophoblast-like cells in the heterogeneous cell population of teratocarcinomas which could be responsible for HTD-particle production. The origin of these virus-like particles--endogenous or exogenous--as well as their role in the pathogenesis of teratocarcinomas is not known so far. The potential value of serum antibody reactivity in teratocarcinoma patients as a diagnostic marker is discussed.

Cell Line↗
PubMed1975

Diagnostic meaning of the urinary output of Nepsilon-methylated lysines. Investigation of healthy individuals and patients with malignant diseases, myopathies or renal failure.

In the urine of 36 healthy persons the excretion of the three Nepsilon-methylated lysines and some other basic amino acids was determined. The following average values, related to 1 g creatinine, were found: Lys(Me) 16.2 mumol, Lys(Me2) 31.2 mumol, Lys(Me3) 40.5 mumol. The 24-hour excretion in 6 adults related to 1 kg body weight, had the following average values: Lys(Me) 0.37 mumol, Lys(Me2) 0.88 mumol, Lys(Me3) 0.92 mumol. In patients with degenerative or inflammatory myopathies (6 cases) as well as with generalized tumors (7 cases) urinary output of methyllysines was not significantly altered. In a patient with extremely impaired renal function, it was found that the plasma level and the excretion pattern of the methylated lysines were unequivocally altered. Metabolic stability and renal excretion of 3H-labelled l-Lys(Me3) were investigated in man. During a 24 hour period 65 per cent of Lys(Me3) was excreted into the urine unmetabolized after intravenous injection but not more than 20 per cent after oral administration.

Adolescent↗