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Biomedical subjects

A Haase

Publications and source records attributed to A Haase.

At least 181 records · Page 10Linked to original sources
PubMed1986

Nuclear magnetic resonance imaging of mummified corpses.

Clinical applications of nuclear magnetic resonance (NMR) imaging have demonstrated its great potential for noninvasive examinations of soft tissues. Here preliminary experiments are reported on mummified human tissue by means of NMR cross-sectional and transmission imaging. For this purpose the natural viscosity of the tissues has been lowered by rehydration with an aqueous solution of 20% acetone.

Acetone↗
PubMed1986

Rapid NMR imaging of dynamic processes using the FLASH technique.

FLASH (Fast Low-Angle SHot) imaging is a new method for rapid NMR imaging which has been demonstrated to provide abdominal images without artifacts due to respiratory or peristaltic motions. The sequence typically employs 15 degrees radiofrequency excitation pulses and acquires a free induction decay signal in the form of a gradient echo. Here FLASH images are recorded in the presence of dynamic processes with time constants even smaller than the measuring time of about 2 s for an image with a 128 X 128-pixel resolution. Experiments are carried out on flow phantoms and on rabbits yielding heart images without gating of the cardiac motion.

Animals↗
PubMed1986

Multipurpose NMR imaging using stimulated echoes.

STEAM (stimulated-echo acquisition mode) imaging techniques recently introduced by the authors are demonstrated to provide a versatile tool for improving the parametric specificity in NMR imaging. Stimulated echoes can be excited by a sequence of at least three rf pulses with flip angles of 90 degrees or less. The main characteristics of the STEAM method are based on the great functional flexibility of an imaging sequence comprising three rf pulses unequal to 180 degrees and three intervals prior to acquisition of the data. Major advantages are the easy access to contiguous multiplanar images, to CHESS (chemical-shift-selective) images, and to T1 information. Moreover, the rf power deposition is considerably reduced as compared to spin-echo NMR imaging sequences. Here first in vivo results on human extremities are presented including contiguous multislice images, multiple CHESS images, and spin-lattice relaxation time images calculated from a series of simultaneously recorded T1-weighted STEAM images.

Biophysical Phenomena↗
PubMed1986

Localization of unaffected spins in NMR imaging and spectroscopy (LOCUS spectroscopy).

A new method for the localization of NMR spectra in vivo is presented. Herein a series of selective 90 degrees pulses with different carrier frequencies in the presence of magnetic field gradients is saturating spins of unwanted regions. Only spins in the region of interest are left unaffected. The LOCUS (localization of unaffected spins) spectrum of this region is measured by a single 90 degrees excitation pulse. The FLASH imaging sequence combined with the LOCUS technique allows the identification of the region of interest.

Magnetic Resonance Spectroscopy↗
PubMed1986

Dynamic digital subtraction imaging using fast low-angle shot MR movie sequence.

High-quality magnetic resonance (MR) images can be recorded within seconds with the use of fast low-angle shot (FLASH) MR imaging. This technique also gives new access to the time evolution of both periodic functions, such as cardiac motion, and nonperiodic physiologic processes, such as flow within internal organs. The time course and regional distribution of dynamic processes detectable by FLASH MR movies are often demonstrated best within series of difference images obtained by digital subtraction of the original data, especially after the use of MR contrast agents. In addition, quantitative information is provided by the analysis of time-intensity profiles for selected regions of interest. Dynamic digital subtraction MR imaging was evaluated in rabbit brain and kidney using a 2.3-T, 40-cm-bore magnet. The time resolution was 1.5 seconds for brain studies and 28 seconds for kidney studies. The total examination times were 1.5 and 30 minutes, respectively.

Angiography↗
PubMed1986

MR imaging using stimulated echoes (STEAM).

The introduction of STEAM (stimulated echo acquisition mode) magnetic resonance (MR) sequences provides access to a variety of MR parameters. T1-weighted and calculated T1 proton MR images of the head of healthy volunteers and a patient with an astrocytoma are presented. MR examinations were performed with a 2.0-T whole-body system. The STEAM T1 method can be used to characterize multiexponential relaxation behavior, to evaluate T1 relaxation times, and to improve the T1 contrast within MR images. Both the measuring time and the spatial resolution are the same as for a conventional image.

Astrocytoma↗
PubMed1986

Multiple chemical shift selective (CHESS) MR imaging using stimulated echoes.

Recently, stimulated echo acquisition mode (STEAM) magnetic resonance (MR) imaging has been demonstrated as a new tool for multiparametric MR imaging studies. Applications of the chemical shift selective (CHESS) STEAM technique using a 2.0-T whole-body MR imaging system are reported in which a series of contiguous cross-sectional images of the head and the pelvis were acquired. Because selective excitation of the desired component is employed rather than elimination of the unwanted component, this method yields an improved degree of spectral resolution which is dependent only on the homogeneity of the static magnetic field. For routine medical applications, no sophisticated adjustment of the CHESS pulse is needed, as reported in previous methods.

Adipose Tissue↗
PubMed1986

Studies on the receptor profile of bisoprolol.

The in vitro binding affinity of (+/-)-1-[4-(2-isopropoxyethoxymethyl)-phenoxy]-3-isopropylamino-2- propranol hemifumarate (bisoprolol, EMD 33 512) to beta 1-, beta 2-, alpha 1-, alpha 2-, D1-, D2-, 5-HT2- and muscarinic cholinergic receptors of rat was compared with that of atenolol, betaxolol and propranolol. Bisoprolol showed a high specific binding affinity to beta 1-adrenoceptors (heart) and a low specific binding affinity to beta 2-adrenoceptors (lung). The beta 1-selectivity of bisoprolol (beta 2/beta 1 = 34.7) proved to be higher than that of atenolol (8.7) and betaxolol (12.5). Propranolol (0.59) was non-selective as expected. Bisoprolol and atenolol exhibited no remarkable binding affinity to alpha 1-, alpha 2-, D1-, D2-, 5-HT2- and muscarinic cholinergic receptors at concentrations up to 1 X 10(-4) mol/l. For betaxolol binding affinities for alpha 2-, D2- and 5-HT2-receptors were found with IC50 values ranging between 2 X 10(-5) and 7 X 10(-5) mol/l. For propranolol binding affinities for alpha 1-, alpha 2-, D1-, D2- and 5-HT2-receptors were found with IC50 values ranging between 2 X 10(-6) and 9 X 10(-5) mol/l.

Adrenergic beta-Antagonists↗
PubMed1985

Cloning of a gene whose expression is increased in scrapie and in senile plaques in human brain.

A complementary DNA library was constructed from messenger RNA's extracted from the brains of mice infected with the scrapie agent. The library was differentially screened with the objectives of finding clones that might be used as markers of infection and finding clones of genes whose increased expression might be correlated with the pathological changes common to scrapie and Alzheimer's disease. A gene was identified whose expression is increased in scrapie. The complementary DNA corresponding to this gene hybridized preferentially and focally to cells in the brains of scrapie-infected animals. The cloned DNA also hybridized to the neuritic plaques found with increased frequency in brains of patients with Alzheimer's disease.

Alzheimer Disease↗
PubMed1985

Chemical-shift-selective magnetic-resonance imaging of avascular necrosis of the femoral head.

Chemical-shift-selective (CHESS) nuclear-magnetic-resonance (NMR) imaging is a new method for separating "water" and "fat" (CH2) resonances in proton NMR imaging. Its major advantage over conventional composite NMR imaging is the contrast enhancement, which in particular allows the detection of small water-containing structures, such as vessels or joint surfaces, normally obscured by fat signals. First clinical findings in the femoral head with avascular necrosis are reported.

Adipose Tissue↗
PubMed1985

A Trojan Horse mechanism for the spread of visna virus in monocytes.

Visna virus is the prototype of the lentivirus subfamily of retroviruses that cause slow infections of sheep and goats. These viruses persist and can be isolated from blood and cerebrospinal fluid for years despite neutralizing antibody. In the studies reported here we have used quantitative in situ hybridization to analyze infected leukocytes. We show that (1) monocytes harbor the visna genome; and (2) virus gene expression is as constrained in this cell as it is in glial and epithelial cells. These results are in accord with a Trojan Horse mechanism of virus dissemination in an immunologically responsive host.

Animals↗
PubMed1985

Nucleotide sequence of the visna lentivirus: relationship to the AIDS virus.

We have determined the complete 9202 nucleotide sequence of the visna lentivirus. The deduced genetic organization most closely resembles that of the AIDS retrovirus in that there is a novel central region separating pol and env. Moreover, there is a close phylogenetic relationship between the conserved reverse transcriptase and endonuclease/integrase domains of the visna and AIDS viruses. These findings support the inclusion of the AIDS virus in the retroviral subfamily Lentivirinae.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Chemical shift selective MR imaging using a whole-body magnet.

We have applied a new method for separating water and fat resonances in proton magnetic resonance (MR) imaging to human studies using a whole-body MR imaging system at 2.0 T. Chemical shift selective (CHESS) MR imaging provides either a water or fat image in a single experimental run within the same time needed for a conventional composite image. Although the technique requires a spectral resolution of about 1 ppm over the entire imaging region, first images of the human head and hip indicated that CHESS MR imaging is extremely promising for use in clinical investigations. Moreover, CHESS MR imaging can be combined arbitrarily with other imaging modalities and is easy to implement in any high-field MR imaging system.

Adipose Tissue↗