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Biomedical subjects

R Braun

Publications and source records attributed to R Braun.

At least 127 records · Page 7Linked to original sources
PubMed1988

Homology of the HSV-2 "a-sequence" to cellular sequences.

Bgl-II fragments of the genome of Herpes simplex virus type 2 (HSV-2) HG-52 were cloned into the vector p-Neo and were used to screen the complete HSV-2 genome for regions cross-hybridizing with the genome of HEL cells. Most extensive cross-hybridizing activity was observed with a 530 bp SstII subfragment of the viral BamHI G DNA-fragment (contained in Bgl II F), which spans the joint and the viral a-sequence. From a lambda-L47 library, a cellular 15 kb HindIII DNA fragment was subcloned in pBR 322 which contained a 1920 bp SstII subfragment having strong cross-hybridizing activity with the 530 bp Sst II fragment of HSV-2 BamHI G. Within this 1920 bp Sst II fragment the cross-hybridizing activity was confined to a 230 bp Bgl I/Hpa II subfragment. This 230 bp fragment (including the flanking sequences) was analyzed in comparison to the viral a-sequence. Sequence data revealed a (G + C) content of 66% in the cellular and 81% in the viral DNA fragment, which is mainly determined by an extremely (G + C) rich 16-fold direct repeat (DR2) at the 5'-end. The homology between both DNA-fragments varies between 56% and 79% within the L-S inversion region. Both sequences, furthermore, show homology to the human c-myc protooncogene.

Animals↗
PubMed1988

Serological evidence for expression of the polymerase gene of human hepatitis B virus in vivo.

Human sera were examined by immunoblotting for antibodies against the polymerase (reverse transcriptase) believed to be encoded in the P open reading frame (ORF) of human hepatitis B virus (HBV). Sera from patients with self-limited and chronic hepatitis reacted specifically with fusion proteins containing different domains of the P ORF. The results indicate that this ORF is expressed, and that the corresponding proteins contain at least two immunogenic domains. In contrast to human immunodeficiency virus, induction of antibodies against reverse transcriptase appears to be less common for HBV, and may depend on long persistence of infection.

Acute Disease↗
PubMed1987

Structure of the extrachromosomal ribosomal RNA chromatin of Physarum polycephalum.

Isolated nucleoli from exponentially growing microplasmodia of Physarum polycephalum were digested with micrococcal nuclease or DNAase I, or were photoreacted with trimethyl psoralen. In the coding region for the precursor of the ribosomal RNA, micrococcal nuclease and DNAase I digestions show predominantly a smear, and treatment with psoralen leads to a fairly continuous crosslinking of the DNA. All three assays are compatible with the absence of a typical nucleosomal array in most of the gene copies. In contrast, in the central non-transcribed spacer, except in the immediate 5'-flanking region, micrococcal nuclease and DNAase I digestions yield fragments that are multiples of a basic repeat, compatible with a nucleosomal packing of this region. The crosslinking pattern with psoralen confirms this conclusion. In addition, there are three sites over 400 base-pairs long that are inaccessible for psoralen crosslinking. Two of these sites have been mapped to the putative origins of replication. In the terminal non-transcribed spacer, except in the immediate 3'-flanking region, digestions with micrococcal nuclease and DNAase I give a smeared repeat. The crosslinking pattern after treatment with psoralen suggests that this region is packed in nucleosomes, except for about 900 base-pairs constituting the telomere regions of the linear extrachromosomal palindromic rDNA. Micrococcal nuclease digestion of the immediate 5'-flanking region shows a complete absence of any nucleosomal repeat, but digestion with DNAase I leads to a faint ten base-pair repeat. In contrast, in the 3'-flanking regions both nuclease assays indicate a chromatin structure similar to the coding region. Both flanking regions are unusual with respect to psoralen crosslinking, in that crosslinking is reduced both in chromatin and deproteinized DNA. On the basis of the known sequence-dependent psoralen crosslinking and the established sequences in these regions, crosslinking should be expected to occur. However, it does not and we therefore propose the presence of an unusual DNA conformation in these regions.

Chromatin↗
PubMed1987

A double-blind clinical trial of prophylactic cloxacillin in open fractures.

In 100 patients with first-, second-, and third-degree open fractures, a randomized, double-blind study was carried out to compare prophylactic cloxacillin and placebo. Prophylaxis was started preoperatively and continued for 10 days. The standard fracture treatment consisted of operative stabilization, mostly by means of plates or external fixators. In the cloxacillin group two infections were observed as compared to 12 in the control group. This difference was significant.

Adolescent↗
PubMed1987

Distinct replication-independent and -dependent phases of histone gene expression during the Physarum cell cycle.

During the S phase of the cell cycle, histone gene expression and DNA replication are tightly coupled. In mitotically synchronous plasmodia of the myxomycete Physarum polycephalum, which has no G1 phase, histone mRNA synthesis begins in mid-G2 phase. Although histone gene transcription is activated in the absence of significant DNA synthesis, our data demonstrate that histone gene expression became tightly coupled to DNA replication once the S phase began. There was a transition from the replication-independent phase to the replication-dependent phase of histone gene expression. During the first phase, histone mRNA synthesis appears to be under direct cell cycle control; it was not coupled to DNA replication. This allowed a pool of histone mRNA to accumulate in late G2 phase, in anticipation of future demand. The second phase began at the end of mitosis, when the S phase began, and expression became homeostatically coupled to DNA replication. This homeostatic control required continuing protein synthesis, since cycloheximide uncoupled transcription from DNA synthesis. Nuclear run-on assays suggest that in P. polycephalum this coupling occurs at the level of transcription. While histone gene transcription appears to be directly switched on in mid-G2 phase and off at the end of the S phase by cell cycle regulators, only during the S phase was the level of transcription balanced with the rate of DNA synthesis.

Actins↗
PubMed1986

Processing in the external transcribed spacer of ribosomal RNA from Physarum polycephalum.

The rDNA of the myxomycete Physarum polycephalum is transcribed to give a 13.3 kb precursor of ribosomal RNA. At 1.7 kb downstream of the primary initiation site there is a processing site or a second initiation site. This site was studied by S1-mapping, DNA sequencing and electron microscopy. None of these methods could conclusively distinguish between the two formal possibilities. However, capping experiments indicate that rapid processing is taking place at this site rather than reinitiation. In addition, primary transcripts and processed molecules were assayed throughout the synchronous mitotic cycle. During all interphase stages newly initiated transcripts of rDNA and products of the first processing step are present in similar amounts, indicating control of initiation and not of maturation as being the main regulatory step for the accumulation of mature rRNAs. During the brief period of mitosis the level of newly initiated rRNA precursors is lowered.

Base Sequence↗
PubMed1986

Tubulin mRNAs of Trypanosoma brucei.

The tubulin genes of Trypanosoma brucei are located in a single, tightly packed cluster of ten tandemly arranged alternating alpha and beta-genes. No tubulin genes are detected outside the clustered array. Therefore, the cluster can be assumed to be the locus of tubulin gene expression. Single bands of alpha and beta-tubulin mRNAs are observed in cultured procyclic as well as in bloodstream trypanosomes. Both alpha and beta-tubulin mRNAs have distinct 5' termini, which carry a 35-nucleotide mini-exon sequence. The 3' termini of both mRNA populations are heterogeneous.

Animals↗
PubMed1986

Transplacental genetic and cytogenetic effects of alkylating agents in the mouse. II. Induction of chromosomal aberrations.

Six monofunctional alkylating agents, trenimon, cyclophosphamide, and isoniazid were proven for transplacental cytogenetic activity in mouse embryos at day 10 of gestational age under the same conditions as used in the mammalian spot test. With the exception of isoniazid, all compounds led to an increase in the aberration frequencies in embryonal cells. The results were statistically not significant in the case of EMS, while all other chemicals showed a dose-dependent clastogenic activity. After treatment with monofunctional alkylants, chromatid breaks were dominating, while polyfunctional compounds also produced chromatid exchanges, especially in the case of trenimon. ENU and DMS showed a very early aberration maximum 6 hr after injection. For both compounds, very similar dose-response curves were found for induction of chromatid breaks in the dose range 10-75 mg/kg. There is no correlation between the Swain-Scott factors of monofunctional alkylants and their ability to induce chromosomal damage when compared in terms of pharmacological doses. A quantitative comparison of data found in the cytogenetic test in embryonal cells with those obtained in the mammalian spot test led to the conclusion that chromosomal mutations are of minor relevancy for the expression of recessive alleles in heterozygous mouse embryos. With this respect, the mammalian spot test must be considered as an in vivo test for the detection of gene mutations in somatic cells of the mouse.

Alkylating Agents↗
PubMed1986

Human cytomegalovirus replicates in primary human bone marrow cells.

As an attempt to elucidate further the pathogenesis of human cytomegalovirus (HCMV) infection the replication of HCMV in primary human bone marrow cells (BMC) has been investigated. It was found that BMC held in culture in general were susceptible to HCMV infection. Compared to human embryonic lung cells, however, the replicative cycle of HCMV AD169 in BMC as determined by the analysis of viral protein and DNA synthesis was delayed and productive virus infection was restricted to a subset of BMC not exceeding 21% of the total cell population. Both of these phenomena may explain the short-term persistence of HCMV in BMC cultures which was observed over 3 months. By experiments with specifically enriched and depleted cell populations and by indirect double immunofluorescence experiments we found that both bone marrow fibroblasts and a subset of bone marrow stem cells supported productive virus infection. The finding that HCMV replicates in early stem cells of the human bone marrow may explain important aspects of the pathogenesis of HCMV infection including the presence of HCMV in peripheral blood leukocytes.

Bone Marrow↗
PubMed1986

[Autologous spongiosa as an antibiotic carrier in the treatment of osteitis].

The treatment of osteomyelitis essentially depends on a bactericidal concentration of antibiotic in bone tissue with an appropriate spectrum. Ciprofloxacin is effective against the main organisms causing osteomyelitis (staphylococcus aureus, pseudomonas aeruginosa) at low MIC. We investigated the concentration of ciprofloxacin in human bone. After a single dose (200 mg ciprofloxacin i.v., preoperatively) the concentration in cortical bone was 6.9 +/- 0.8 mcg/g and 9.7 +/- 0.8 mcg/g in cancellous bone. In any case the concentration of ciprofloxacin exceeded the MIC for staph. aureus and pseudomonas aeruginosa. For the treatment of osteomyelitis we transferred the antibiotic bound to autologous cancellous bone grafts to the site of inflammation after surgical debridement. First clinical results are documented.

Administration, Topical↗
PubMed1985

A whole-blood lymphoproliferation assay for measuring cellular immunity against herpes viruses.

A whole blood test system was established to study cell-mediated immunity to cytomegalovirus (CMV) and herpes simplex virus (HSV) in a large number of healthy blood donors. Cellular immunity was measured by the in vitro proliferative response (LP) of peripheral lymphocytes. These responded vigorously to several mitogens. Lymphocytes of most individuals responded to HSV, but only a limited number were reactive towards CMV. In parallel, antibodies against CMV and HSV were measured by an ELISA technique. For HSV, good correlation was observed between serological and lymphocyte proliferation results. For CMV, no clear correlation was obtained, only 21 of 40 donors positive in the antibody test being positive in the LP test. The majority of seronegatives were negative in the LP test. Use of virions purified by sucrose gradient centrifugation, or an additional strain of CMV (strain Davis) did not increase the number of donors positive in the LP test. One explanation might be that individuals possessing antibodies against CMV as measured by ELISA but no capacity to react in the LP test had suffered from a CMV infection a long time before, and now showed waning cellular immunity, but antibody still detectable. Use of the whole blood technique on 108 individuals showed that this very simple test works well with various mitogens and at least some antigens.

Antigens, Viral↗