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Biomedical subjects

R Hausmann

Publications and source records attributed to R Hausmann.

At least 55 records · Page 3Linked to original sources
PubMed1992

[MR angiography. Its use in pulmonary and mediastinal space-occupying lesions].

MR angiography (MRA) proved to be promising combined to MR imaging (MRI) in the assessment of intrathoracic masses. Sequential FLASH 2D angiograms were acquired in breath-hold technique using the following parameters: TR = 30 ms, TE = 10 ms, FA = 30 degrees. Section thickness was 5 mm with 1 mm overlap between sequential sections. Individual conditions of the examination were achieved by an automatized control procedure. Targeted MIP postprocessing resulted in 3D reconstructions illustrating vascular anatomy and avoiding superimposition. Presentation should be done by cine-mode for better spatial impression. This method was evaluated in a prospective study of 21 patients with malignant pulmonary and mediastinal masses in addition to spin-echo imaging. The diagnostic contribution concerning the relationship between the mass and the vasculature like displacement, stenosis, and poststenotic perfusion defect were assessed.

Adult↗
PubMed1992

[The evaluation of 2D- and 3D-"time of flight" magnetic resonance angiography (MRA) in the diagnosis of renal artery stenoses].

This study was carried out to evaluate time-of-flight RA in renal artery stenosis (RAS) in selected hypertensive patients (n = 41). In i.a. DSA studies, 10 unilateral, 8 bilateral RAS, and 4 unilateral RA occlusions were proven. MRA was done in coronal and axial 2D technique (FLASH), and in 3D technique (FISP) using GE-pulse sequences. DSA results were correlated with both 2D-individual slices, 2D- and 3D-MIP angiograms. Highest sensitivity and specificity was found for the axial 2D individual slice analysis (88%, 85% resp.), followed by the 3D-MIP MRA (78%, 80% resp.), and axial 2D-MIP MRA (73%, 79% resp.). MRA of renal arteries used in this study shows to be not adequate to DSA results due to many drawbacks. All MRA techniques, in particular the 3D-technique, tend to overestimate RAS occasionally pretending occlusions.

Adult↗
PubMed1992

Clinical features of an affected father and daughter with Ehlers-Danlos syndrome type VIIB.

The clinical features of a father and daughter with Ehlers-Danlos syndrome type VIIB are described. They included severe cutaneous fragility, generalized joint laxity, kyphoscoliosis and a slightly dysmorphic face in the adult, with generalized joint laxity and congenital hip dislocation, hyperextensible skin and easy bruising in the child. The dermis contained slightly distorted collagen fibrils when examined by electron microscopy. The disorder is caused by G to A point mutation in the first base of intervening sequence 6 with resultant mis-splicing.

Adult↗
PubMed1992

Absence of a gene dosage effect during bacteriophage T3- and T7-coded RNA polymerase synthesis.

The rates of synthesis of phage-coded RNA polymerase upon infection of Escherichia coli by bacteriophages T3 or T7 were measured at different MOIs under permissive and non-permissive conditions. At MOIs from 1 to 15, these rates did not vary appreciably, at MOIs of about 20 there was a slight depression in the synthesis rate. The reason for this absence of a positive gene dosage effect is unknown.

DNA-Directed RNA Polymerases↗
PubMed1992

[Magnetic resonance angiography: physical principles and clinical applications].

Within the last four years magnetic resonance angiography (MRA) developed very rapidly towards a well accepted screening technique for vascular examinations as a fast add on to conventional MR. This review describes the basic physical principles as well as the different methods like time-of-flight and phase-sensitive MRA for visualization of blood vessels. Different applications of 3D, 2D sequential and 3D multi-volume MRA are shown from various regions of the head and body. A short outlook to quantitative flow measurements is given in the last chapter including some interesting applications of these techniques which show the still expanding potential of magnetic resonance.

Blood Vessels↗
PubMed1991

T7 infection-dependent selective expression of cloned genes in P1-lysogenic Escherichia coli.

Expression systems based on the selective transcription of genes cloned behind a T7 promoter, by T7 RNA polymerase, display a non-negligible basal expression when the T7 RNA polymerase gene is present within the host organism before induction of the system. This is a problem, especially for cloning and controlled expression of genes toxic to the host organism. We have circumvented this problem by taking advantage of abortive T7 infection of E. coli (P1), in the course of which T7 RNA polymerase is synthesized but bacterial growth is not quantitatively impaired. We have tested this system with three reporter genes, the 6-phospho-beta-galactosidase gene of Staphylococcus aureus, the luciferase operon of Vibrio harveyi, and the rabbit beta-globin gene; we have found very low basal levels, while, upon T7 infection, transcription is at least as efficient as in other in vivo T7 RNA polymerase systems in use.

Animals↗
PubMed1991

Inhibition of anti-HLA-B7 alloreactive CTL by affinity-purified soluble HLA.

The objective of this study was to elucidate the interaction of naturally occurring soluble MHC class I molecules with alloreactive CTL and to discuss its possible relevance to graft acceptance. An anti-HLA-B7 specific CTL-line, BV.B7, was generated in vitro. On phenotyping the cells after 6 weeks, 80% were found to be CD8+, 14% CD4+ and 6% CD8+CD4+. CD4+ CTL were depleted using immunomagnetic beads precoated with an anti-CD4 antibody. Of the recovered CTL greater than 96% were CD8+. A total of 12 HLA-B7 target cell lines and PHA blasts tested were specifically lysed in a 51Cr-release assay. Soluble HLA class I molecules were isolated on affinity chromatography columns using the anti-HLA-B7 ME 1 and the anti-heavy chain W6/32 monoclonal antibodies. Antigen purity was confirmed by analysis on SDS-PAGE gels. CTL were preincubated with 0.1-1.8 micrograms/ml soluble HLA for 30 min at 37 degrees C and subsequently tested for cytotoxicity in the 51Cr-release assay; 1.1 micrograms/ml HLA-B7 molecules reduced CTL cytotoxicity by 50% whereas non-B7 HLA had no effect. Further, CTL cytotoxicity was reduced by preincubation with anti-CD8, anti-TcR, and anti-CD3 antibodies. We anticipate a possible down-regulatory role of soluble HLA on CTL in allogeneic transplantation.

Antibodies↗
PubMed1991

Three-dimensional time-of-flight MR angiography: applications in the abdomen and thorax.

The application of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiographic techniques to the vasculature of the abdomen and thorax has not, to the authors' knowledge, been previously reported; this is possibly due to the large amount of physiologic motion in these regions along with the anticipated sensitivity of the 3D acquisition scheme to image degradation caused by motion artifact. The authors describe an asymmetric short-echo velocity-compensated 3D TOF technique that minimized the effects of physiologic motion on image quality and provided rapid high-resolution 3D MR arteriograms of the abdomen and thorax. Contiguous 3D volumes were often combined to provide sufficient anatomic coverage. Benefits include high spatial resolution and minimization of signal loss; limitations include sensitivity to motion artifact and progressive spin saturation.

Abdomen↗
PubMed1990

The gene for Klebsiella bacteriophage K11 RNA polymerase: sequence and comparison with the homologous genes of phages T7, T3, and SP6.

We determined the nucleotide sequence of gene 1 of Klebsiella phage K11, which is a member of the T7 group of phages. The largest open reading frame corresponds to a polypeptide with 906 amino acids and a molecular weight of 100,383 daltons. The deduced amino acid sequence of this polypeptide shows 71% homology to the T7 RNA polymerase (the product of T7 gene 1), 72% homology to the T3 RNA polymerase and 27% homology to the SP6 RNA polymerase. Divergent evolution was clearly most pronounced in the amino-terminal portion.

Amino Acid Sequence↗
PubMed1988

Inhibition of gene expression of T7-related phages by prophage P1.

The gene expression of nine phages of the T7 group was compared after infection of Escherichia coli B(P1). With the exception of phage 13a which grew normally, all of them infected E. coli B(P1) abortively. Differences were found in the efficiency of host killing which ranged from 100% for phage 13a to 37% for phage A1122. Infection by T7 prevented colony formation by about 70% of the cells but they showed filamentous growth until about 2 h after infection. It was shown by SDS-polyacrylamide gel electrophoresis and autoradiography of [35S]methionine-labelled phage-coded proteins that all phages except for 13a showed measurable expression only of the early genes. No correlation was observed between killing capacity and the pattern of gene expression, and the ability to hydrolyse S-adenosyl-methionine (SAM, a cofactor for the P1 restriction endonuclease) by means of a phage-coded SAMase. Mixed infection of E. coli B(P1) with 13a and T7 yielded mixed progeny indistinguishable from that observed after mixed infection of the normal host E. coli B. Genetic crosses with amber mutants of 13a and T7 showed that the 13a marker opo+ (overcomes P one), required for growth on B(P1), is located in the early region, to the left of gene 1 (RNA polymerase gene).

Chromosome Mapping↗
PubMed1988

[Indirect blood pressure determination in the horse with the Dinamap 1255 research monitor].

In 26 horses measurings of blood pressure, using the Dinamap 1255 research monitor, were performed and compared for accuracy with blood pressure values obtained by direct measurement in the arteria carotis. It was found that oscillometrically ascertained initial blood values in standing horses have a sufficient correlation to initial blood pressure values obtained by direct measurement. But every blood pressure change is registered too late, when using the oscillometric blood pressure apparatus. This temporal delay becomes unacceptable, when a considerable increase in blood pressure occurs. A reliable oscillometric blood pressure measurement with uneven and irregular pulse waves is not possible at all.

Animals↗
PubMed1986

In vitro packaging of foreign DNA into heads of bacteriophage T1.

The isolation of a collection of 44 morphologically T1-like phages is described. It is shown that these phages share some similarity with T1 in terms of cross-inactivation with anti-T1 serum, particle proteins and DNA packaging in vitro by the headful process. Virion DNA extracted from these phages was treated with T1 in vitro packaging extracts and the reaction mixtures were tested for the formation of infectious phage particles. The packaging efficiencies observed varied from about 1 to 100% of that of virion T1 DNA. Phage lambda virion DNA was packaged with an efficiency of between 0.01 and 2% (5 X 10(1) to 3 X 10(3) p.f.u./micrograms DNA), the shorter deleted derivative lambda L47 being packaged more efficiently than normal length lambda C1857 DNA. Virion DNA from phages T3 and T7 was also packaged at an efficiency similar to that for lambda. The in vitro packaging of T1 DNA requires the presence of the pac sequence which initiates headful packaging from a concatemeric precursor. The high efficiency of packaging DNA from some of the T1-like phages may indicate the presence of similar packaging sequences. However, in the case of lambda L47, which is known not to contain such a sequence, the in vitro DNA packaging reaction must occur by a secondary pathway unrelated to the headful mechanism.

Bacteriophage lambda↗
PubMed1986

Two groups of capsule-specific coliphages coding for RNA polymerases with new promoter specificities.

Four bacteriophages (A16, CK235, phi 1.2 and K31) which specifically attack different encapsulated strains of Escherichia coli have been shown to be related to bacteriophage T7 (which is unable to grow on encapsulated hosts). The conclusion that phages A16 and CK235 are related to T7 is based on similarities in the pattern of expression of intracellular phage proteins, early appearance, in infected host cells, of a phage DNA-specific RNA polymerase and hybridization (albeit to a low extent) of A16 DNA and of CK235 DNA to T7 DNA. The first two criteria also apply to phages phi 1.2 and K31 but hybridization of their DNAs with T7 DNA could not be detected. The RNA polymerases of CK235 and A16 have similar template specificities and the same applies to the RNA polymerases of phi 1.2 and K31. None of the new RNA polymerases can use T7 DNA as template.

Coliphages↗
PubMed1985

On the evolution of the terminal redundancies of Klebsiella phage No. 11 and of coliphages T3 and T7.

The phylogenetic relationship between Klebsiella phage No. 11 and the classical coliphages T7 and T3, postulated in a previous study, was investigated at the nucleotide level by sequencing the termini of phage No. 11 DNA. This DNA was found to have a terminal redundancy of 181 base pairs. Comparison of the terminal sequences of T7, T3 and No. 11 DNA suggests that the terminal redundancies of the three phages contain different expansions and variations of the short 'founder sequence' 5' TTAACCTTGGG 3' of a common ancestor.

Bacteriophages↗
PubMed1982

Coliphage BA14: a new relative of phage T7.

Coliphage BA14 was isolated from sewage and shown to be related to phages T7 and T3. It is similar to T3 in that it directs the synthesis of an S-adenosyl-methionine-cleaving enzyme (SAMase) early upon infection. However, it differs from all other known T7-related coliphages by the inability of its RNA polymerase (gene 1 product) to transcribe T7 DNA or T3 DNA. BA14, T7 and T3 also show marked differences in autoradiographic patterns of their gel-electrophoretically separated 35S-labelled intracellular phage proteins, restriction endonuclease HpaI cleavage patterns of their DNAs, and serological specificities of their infectious particles. Other distinctive features became apparent upon simultaneous mixed infection with BA14 and T7 or T3: inability of BA14 to produce genetic recombinants with either T7 or T3; lack of functional complementation between amber mutants of BA14 and T7 or T3; mutual exclusion and depression of the burst size of the mixedly infected cells.

Antigens, Viral↗