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Biomedical subjects

B Drescher

Publications and source records attributed to B Drescher.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Age-dependent development of the long hollow bones in white New Zealand meat rabbits and chinchilla-hybrid laboratory rabbits].

The age dependent development of the long bones' diaphyses (humerus, os femoris and os tibiofibulare) was examined macroscopically, morphometrically and histologically using 15 White New Zealand Rabbits (WN) and 15 Chinchilla-Bastard-Experimental-Rabbits (Chbb) in 5 different age groups. The main growth of bone occurs in the first three months of life. The remodelling from juvenile to adult bone began in the period from the 4th-12th week. The different bones show various characteristic remodelling zones for each localization. Until the 12th week the resorption of juvenile bundled bone predominates. Afterwards an increasing bone formation by osteal bone can be observed. The bone growth is terminated between the 17th and 33rd week. The os tibiofibulare in both breeds represents the major part of the compact bone area on the whole cross-section area. Principally the bone-remodelling process proceeds equally in both breeds. Breed dependent differences in the adult bone are seen in the construction of the circumferential lamellae. These are formed considerably more irregularly by the Chbb-rabbits than by the WN-rabbits.

Aging↗
PubMed1992

Molecular variants of human papillomavirus type 16 from four continents suggest ancient pandemic spread of the virus and its coevolution with humankind.

We have amplified by the polymerase chain reaction, cloned, and sequenced genomic segments of 118 human papillomavirus type 16 (HPV-16) isolates from 76 cervical biopsy, 14 cervical smear, 3 vulval biopsy, 2 penile biopsy, 2 anal biopsy, and 1 vaginal biopsy sample and two cell lines. The specimens were taken from patients in four countries--Singapore, Brazil, Tanzania, and Germany. The sequence of a 364-bp fragment of the long control region of the virus revealed 38 variants, most of which differed by one or several point mutations. Phylogenetic trees were constructed by distance matrix methods and a transformation series approach. The trees based on the long control region were supported by another set based on the complete E5 protein-coding region. Both sets had two main branches. Nearly all of the variants from Tanzania were assigned to one (African) branch, and all of the German and most of the Singaporean variants were assigned to the other (Eurasian) branch. While some German and Singaporean variants were identical, each group also contained variants that formed unique branches. In contrast to the group-internal homogeneity of the Singaporean, German, and Tanzanian variants, the Brazilian variants were clearly divided between the two branches. Exceptions to this were the seven Singaporean isolates with mutational patterns typical of the Tanzanian isolates. The data suggest that HPV-16 evolved separately for a long period in Africa and Eurasia. Representatives of both branches may have been transferred to Brazil via past colonial immigration. The comparable efficiencies of transfer of the African and the Eurasian variants to the New World suggest pandemic spread of HPV-16 in past centuries. Representatives of the African branch were possibly transferred to the Far East along old Arab and Indonesian sailing routes. Our data also support the view that HPV-16 is a well-defined virus type, since the variants show only a maximal genomic divergence of about 5%. The small amount of divergence in any one geographic location and the lack of marked divergence between the Tanzanian and Brazilian African genome variants two centuries after their likely introduction into the New World suggest a very slow rate of viral evolution. The phylogenetic tree therefore probably represents a minimum of several centuries of evolution, if not an age equal to that of the respective human races.

Base Sequence↗
PubMed1992

[Behavioral studies of piglets and rabbits with special consideration of necessary supplies and avoidance of injury].

After introducing remarks on the meaning of the ethology of farm animals about the evaluation of housing systems the own examinations about piglets in the rearing period and about housing systems of rabbits held in groups respectively will be demonstrated. By these examinations choice experiments have proved true. For estimating and evaluating the ethological experimental results the concept of the meeting of requirements and avoidance of damage is an important point. The animals requirement can be found out in reference systems. Those investigated results are used as guiding-line for the evaluation of the dates found under practical conditions. The merits of Tschanz concerning the ethology of farm animals will be appreciated.

Animal Husbandry↗
PubMed1990

Nucleotide sequence analysis of the 3' half of the genome of bovine leukaemia virus grown in FLK cells.

The DNA sequence of the env and px (tat) regions of bovine leukaemia virus cloned from integrated proviral DNA of the virus producing FLK cell line was determined and compared with published sequences cloned from bovine leukaemia virus-induced tumours of cattle. The homology of 97% between a Belgian tumour clone and the FLK clone was significantly lower than that between a Japanese tumour clone and the FLK clone, where less than 1% nucleotide exchanges were observed. The sequences of cDNAs synthesized from purified virus RNA material which had been grown in different FLK sublines were found completely identical with one another as well as with the equivalent FLK proviral DNA sequences.

Base Sequence↗
PubMed1988

Expression of env sequences of the bovine leukemia virus (BLV) in the yeast Saccharomyces cerevisiae.

DNA sequences of the envelope (env) gene of the bovine leukemia virus (BLV) were expressed in the yeast Saccharomyces cerevisiae. Two yeast promoters, the repressible PHO5 promoter and the constitutive PGK promoter, were used to construct four expression plasmids comprising either a sequence of the surface antigen gp51 or a (gp51 + gp30) sequence. The expressed heterologous gene products were characterized by Western blot analysis and competitive radioimmunoassay. By means of Northern blot analysis the steady-state level of env-specific mRNA was analysed. The highest expression rate was obtained from recombinant plasmid YEpSG 94 comprising a gp51 sequence--a 630 base pair fragment containing 70% of the gp51 but lacking the N terminus--as well as the PHO5 promoter including PHO5 signal sequence and the PHO5 terminator. The recombinant gp51 was partially glycosylated but the PHO5 signal peptide did not seem to be cleaved off. No immunoreactive material could be found in the periplasm or in the culture medium. By means of monoclonal antibodies directed against eight different epitopes of viral gp51, all four sequential antigenic determinants were detected in the AH 216 (YEpSG 94) expression product.

Amino Acid Sequence↗
PubMed1987

Molecular cloning of an endogenous cat retroviral element (ECE 1)--a recombinant between RD-114 and FeLV-related sequences. Brief report.

A lambda L 47.1 clone library was constructed from BamHI digests of cellular cat DNA and was screened with cDNA probes specific for the 3'-terminus of the replication competent RD-114 virus. The first analysis of one clone (lambda-ECE 1) shows that it consists at least of a 3'-LTR and a 5' adjacent env gene. The LTR nucleotide sequences of the RD-114 cDNA clones and ECE 1 are identical within the R region and unrelated to FeLV. Otherwise, the region upstream from the 3'-LTR of ECE 1 shows homology to the transmembrane protein encoding gene of FeLV, but not to RD-114. These results imply that ECE 1 is a recombinant between an RD-114-like 3'-LTR and a FeLV-related env portion.

Amino Acid Sequence↗
PubMed1985

3'-Deoxy-3'-fluorothymidinetriphosphate: inhibitor and terminator of DNA synthesis catalysed by DNA polymerase beta, terminal deoxynucleotidyl transferase and DNA polymerase I.

3'-deoxy-3'-fluorothymidine-5'-triphosphate (dFTTP) was examined with respect to its capacity to inhibit and to terminate DNA-synthesis catalysed by DNA polymerases alpha and beta, terminal deoxynucleotidyl transferase (TdT) and E. coli DNA polymerase I (Klenow fragment). In analogy with 2', 3'-dideoxythymidine-5'-triphosphate (ddTTP) it was found that DNA polymerase beta was much more sensitive to dFTTP inhibition than DNA polymerase alpha. Moreover, the activity of TdT is strongly inhibited by both dFTTP and ddTTP, whereas the two compounds displayed a lower inhibitory potency on DNA polymerase I. Except for DNA polymerase alpha, the other investigated DNA polymerases are able to incorporate dFTTP into poly (dA).oligo (dT) and oligo (dG), respectively. The specific chain-terminating activity of dFTTP has proved for DNA sequencing to be at least equivalent to ddTTP.

Animals↗
PubMed1982

Detection of bovine leukaemia virus RNA sequences in non-cultivated peripheral lymphocytes by in situ hybridization with 3H-labelled viral cDNA.

Bovine leukaemia virus (BVL) in circulating lymphatic cells of the blood is repressed and has to be activated for its expression. After in situ hybridization of BLV-3HcDNA with a specific activity of 3.9 X 10 dpm/micrograms to noncultivated blood cells from 5 leukotic cattle, in 4 of these animals from 0.96% to 1.5% lymphocytes were found to contain BLV-specific RNA sequences. Non-hybridized lymphocytes as well as calf thymus cells, used as controls, gave only 0.47% and 0.39% labelled cells, respectively. After short-term cultivation of white blood cells from these leukotic animals the percentage of labelled cells increased. During the short-term cultivation the number of hybridizing cells from one and the same animal and from all animal, when compared with each other, varied to a high extent. The highest values of BLV-RNA sequences-containing cells from all 5 animals at different cultivation times were within the range of from 2.4 to 16.2%.

Animals↗
PubMed1982

Characterization of an RNA-directed DNA polymerase from mouse spleen infected with leukaemia virus activated during N-methyl-N-nitroso urea-induced leukaemogenesis.

An RNA-directed DNA polymerase was purified from mouse spleen infected with leukaemia virus activated during N-methyl-N-nitroso urea- (MNU-) induced leukaemogenesis. The enzyme was isolated from the microsomal fraction and purified by successive chromatography of Sephadex G-200 and phosphocellulose. Estimation of molecular weight from the sedimentation rate of the purified enzyme in a sucrose gradient gave a value of 70,000. The enzyme had a pH optimum of 7.4, a KC1 optimum of 50 mmol/l, an Mn2+ optimum of 0.2 mmol/l, and a temperature optimum of 25 degrees C, when (rA)n . (dT) 10 was used as the template-primer. It preferred (rA)n . (dT)10 as the template-primer and transcribed (rC)n . (dG) 12 and (OMeC)n . (dG)12. A comparison of the properties of this DNA polymerase with the enzyme purified from murine type C retroviruses showed that the MNU-activated virus enzyme was both biochemically and biophysically indistinguishable from murine leukaemia virus DNA polymerases.

Animals↗
PubMed1981

Demonstration of a syncarcinogenic effect of endogenous MuLV, rescued from MNU-induced leukemias, and suboptimal MNU doses in mice.

It was demonstrated that the combined action of activated endogenous MuLV isolated from MNU-induced leukemias and suboptimal doses of MNU yields a significantly high incidence of leukemias and tumors. Treatment with one agent alone shows low effects only. The findings were discussed in view of the mechanisms in which viruses and chemical carcinogens interact in a syncarcinogenic processes.

Animals↗
PubMed1980

Demonstration of C-type viruses in N-methyl-N-nitroso urea (MNU)-induced leukemia of mice by reverse transcriptase activity and XC assay.

A significantly higher MuLV expression was demonstrated in cells of MNU-induced leukemia of mice compared to corresponding cells of untreated control animals by reverse transcriptase activity and XC cell assay. These positive findings were verified by determination of indirect immunofluorescence test to look for intracytoplasmic MuLV p30. The problem is discussed whether these viruses play a role in chemical leukemogenesis.

Animals↗
PubMed1980

[Improved test for the detection of reverse transcriptase of bovine leukosis virus].

The revertase test with exogenous matrix, poly-(rA) . oligo-(dT), for the detection of bovine leukemia virus from crude virus sediments was standardised and miniaturised. An amount of 10 ml of cell culture supernatant of short-term cultured lymphocytes (5 . 10(6) cells/ml) is quite sufficient for testing one cattle sample. The lower sensitivity limit of the test was found to be 10(6) virus particles. The test is properly reproducible, within tolerance limits of +/- 20--30 per cent, provided that optimum lysis conditions be maintained (0.01 per cent triton X-100, 20 minutes, 0--4 degrees C incubation) and under the condition that the protein quantity in 100 microliter test solution does not exceed the threshold of 3--15 micrograms. The specificity of the test is based on the use of free viruses from cell culture supernatant, the optimum temperature of the revertase reaction at 25 degrees C, which actually deviates from that for cellular DNA polymerases, that is 37 degrees C, and magnesium ion concentration which has to be optimum for bovine leucosis virus revertase. Two-hundred heads of cattle, differing by haematological status, were examined, and 56 per cent of them were, clearly, virus producers, among them 95 per cent of all animals with positively established leucosis and 36 per cent of the haematologically intact animals. Examinations of individuals have shown that in repetitive checks, carried out in intervals between two months and one week, the revertase activities varied by something between 0.5 and two magnitudes.

Animals↗