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Biomedical subjects

G Wolf

Publications and source records attributed to G Wolf.

At least 883 records · Page 49Linked to original sources
PubMedDate not supplied

MRI evaluation of thermal ablation of tumors with focused ultrasound.

MRI was used to target and evaluate the tissue effects of focused ultrasound ablation on tumors implanted in the skeletal muscle of rabbits in vivo. First, MRI was used to localize the tumors and plan the ultrasound therapy. Second, temperature-sensitive phase-difference images were acquired to monitor the location of the ultrasound focus and to estimate the effects of temperature rise. After the treatment, the spatial and temporal temperature profiles for defining boundaries of tissue coagulation were calculated. Finally, these boundaries were compared to T2-weighted and contrast-enhanced T1-weighted images obtained immediately after therapy. The results indicate that using MRI for planning and evaluating focused ultrasound surgery is feasible. We showed a linear relationship between applied power and shifts in the proton resonant frequency. Fluctuations in the location of the focus about the target location were on the order of the resolution of the MR images. The temperature rise and lesion size varied significantly. Regions of tissue coagulation calculated from MR data correlated well with post-therapy imaging.

Animals↗
PubMedDate not supplied

Incorporation of labeled glucosamine into glycoproteins by organ cultures of hamster trachea: adverse effects of HEPES buffer.

Hamster tracheas were cultured in serum-free CMRL 1066 medium buffered with either NaHCO3 alone or HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid) plus NaHCO3 in an atmosphere of 95% O2 and 5% CO2. Afther 2 days in culture, tracheas maintained in HEPES plus NaHCO3-buffered medium showed an altered surface morphology. Histiological examination after 6 days of culture with HEPES plus NaHCO3 showed the presence of only scattered clumps of cilia. Incorporation of [14C]-glucosamine into intracellular glycoproteins was reduced by 75% and into secreted glycoproteins by 54% in cultures buffered with HEPES plus NaHCO3, compared to NaHCO3-buffered cultures. Incorporation of [H]fucose into intracellular glycoproteins was also reduced, although no effect was observed on secreted glycoproteins.

Animals↗
PubMedDate not supplied

Angiotensin II induces alpha3(IV) collagen expression in cultured murine proximal tubular cells.

Angiotensin II (ANG II) induces cellular hypertrophy of cultured proximal tubular cells from various species. This hypertrophic response is associated with an increase in synthesis of basement membrane-associated collagen type IV. Previous investigations by our group have shown that ANG II stimulates mRNA and protein expression of the "classic" alpha1 and alpha2(IV) chains in cultured murine proximal tubular cells (murine cortical tubules [MCT cells]). Since it is clearer today that kidney basement membranes also contain heterotrimers of novel type IV collagens, the aim of the present study was to evaluate whether ANG II may influence the expression of alpha3 and alpha5(IV) collagen chains in MCT cells. A single dose of 10-8-10-6 M ANG II stimulated mRNA expression of alpha3(IV), but not of alpha5(IV), in MCT cells cultured in serum-free media. This response was mediated through AT1-receptors because losartan, but not an AT2-receptor antagonist, abolished the ANG II-induced expression of alpha3(IV) transcripts. Transient transfection of MCT cells with transforming growth factor-beta1 (TGF-beta1) antisense phosphorothioate-modified oligonucleotides partly abolished the ANG II-induced alpha3(IV) mRNA expression. Furthermore, Western blots of cellular lysates incubated with polyclonal antibodies generated against the recombinant collagen chains revealed that ANG II stimulated alpha3(IV) but not alpha5(IV) protein expression. This stimulation was partly prevented by co-incubation with a neutralizing anti-TGF-beta1-3 antibody. In summary, our data indicate that ANG II stimulates expression of the alpha3(IV) collagen chain in cultured MCT cells, due in part to TGF-beta1 activation.

Angiotensin II↗
PubMedDate not supplied

[Josefilaria mackerrasae gen. et sp. nov. (Nematoda: Filarioidea) a parasite of the ghost bat Macroderma gigas Dobson (author's transl)].

Josefilaria mackerrasae n. gen., n. sp., a filarial of the ghost bat Macroderma gigas in Australia is described. This filarioid has affinities with the genus Litomosa, but it can be separated by a variety of both more highly evolved characters (buccal capsule reduced to a pre-oesophageal ring; external lateral papillae absent) and primitive characters ("caudal alae" of the male, long and divided oesophagus, vulva not far from the nerve ring, numerous caudal mucrons of the female).

Animals↗
PubMedDate not supplied

Prepregnancy genetic testing for age-related aneuploidies by polar body analysis.

Current practice for prevention of chromosomal aneuploidies involves prenatal screening and termination of pregnancy, a procedure that is not universally acceptable. We introduced prepregnancy genetic testing by sampling and fluorescence in situ hybridization (FISH) analysis of the first and second polar body (PB), to avoid fertilization and transfer of embryos resulting from aneuploid oocytes. In 395 in vitro fertilization (IVF) patients of advanced maternal age, the first and second PBs were removed following their extrusion from oocytes and studied by FISH, using probes specific for chromosomes 13, 18, and 21, to detect and avoid the transfer of oocytes with common aneuploidies. Overall, 3,651 oocytes obtained from 598 IVF cycles were available for FISH analysis, with 2,952 showing interpretable FISH results (80.9%). The analysis revealed 1,271 (43.1%) oocytes with aneuploidy, which were excluded from transfer and subjected to follow-up FISH analysis to confirm PB diagnosis in the cleavage or blastocyst stage embryos. Only embryos originating from 1,681 aneuploidy-free oocytes were transferred back to patients, resulting in 119 pregnancies overall, from which 78 healthy children have already been born, 35 were spontaneously aborted, and 16 are ongoing, after confirming PB diagnosis by prenatal diagnosis. The results demonstrate that PB-based preimplantation diagnosis may be used for prepregnancy screening in women with age-related risk for common aneuploidies.

Aneuploidy↗
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Slow response induced in canine Purkinje fiber by contrast medium.

Cardiac toxicity of angiographic contrast medium has been documented at the cellular level by using the methods of micro-electrode electrophysiology. Canine Purkinje fibers exposed to contrast medium exhibit a "slow response." The increased automaticity and slowed conduction inherent in this "slow response" may cause the serious arrhythmias and other adverse effects recorded by electrocardiograms during coronary angiography. Hyperosmolarity plays only a minor role in the observed cellular toxicity. The unphysiologic concentrations of sodium, potassium, and calcium in the tested contrast medium were not responsible for the changes observed. Toxicity is probably an inherent chemical property of iodinated diatrizoate or meglumine ions.

Angiocardiography↗
PubMedDate not supplied

The effect of pulmonary edema on proton nuclear magnetic resonance relaxation times.

This study was done to determine the effect of permeability pulmonary edema on proton nuclear magnetic resonance (NMR) relaxation times. Permeability edema was induced in rats by the intravenous injection of alloxan in saline. Control animals received only saline. The rats were ventilated through a tracheostomy; and after a time sufficient for the edema to become uniform, they were sacrificed. T1, and T2 and extravascular lung water were measured on lung samples. A linear relationship was found between the relaxation times and the extravascular lung water. Any diffuse alveolar process including pulmonary edema can increase proton density as well. The T1 and T2 relaxation times may be used to distinguish among different causes of increased proton density in the lung.

Alloxan↗
PubMedDate not supplied

AT1-receptor antagonists abolish glomerular MCP-1 expression in a model of mesangial proliferative glomerulonephritis.

BACKGROUND: Glomerular accumulation of macrophages/monocytes (M/M) is a typical early feature in the course of anti-thymocyte serum (ATS)-induced nephritis. We have previously shown that glomerular synthesis and expression of monocyte-chemoattractant protein-1 (MCP-1) occurs before influx of M/M and a neutralizing anti-MCP-1 antibody reduced this cell infiltrate by one third. The present study was undertaken to test the effect of two angiotensin II type 1 (AT1) receptor antagonists, losartan and irbesartan, on ATS-stimulated MCP-1 expression as well as glomerular influx of M/M. METHODS: Treatment of rats with either losartan or irbesartan was started 24 h before administration of ATS. After 24 h, MCP-1 mRNA expression was evaluated by RT-PCR and Northern blots. MCP-1 protein was determined by Western blots and chemotactic factors released from isolated glomeruli were measured by chemotactic assay. Kidney sections were stained for rabbit IgG, complement C3, and M/M (ED1 antigen). RESULTS: Both AT1-receptor antagonists caused a significant, but not total reduction in MCP-1 mRNA and protein expression 24 h after injection of ATS. Treatment with losartan or irbesartan also reduced the chemotactic activity of isolated glomeruli from nephritic animals. Quantification of ED1-positive cells revealed that losartan as well as irbesartan reduced glomerular M/M invagination in nephritic rats by approximately 30-50%. However, treatment with AT1-receptor antagonists did not influence binding of ATS to mesangial cells and subsequent complement activation indicating that the attenuated MCP-1 expression is not due to differences in delivery and binding of ATS to mesangial cells. CONCLUSION: Our data indicate that short-term antagonism of AT1 receptors abolished the early glomerular MCP-1 expression and M/M influx. These results indicate that angiotensin II may exert immunomodulatory effects in vivo and adds a new mechanism showing how this vasopeptide may be involved in the pathogenesis of renal diseases.

Angiotensin Receptor Antagonists↗
PubMedDate not supplied

Headaches and sinus disease: the endoscopic approach.

Headaches can be of sinugenic origin even if this cause may not be suspected from the case history. Endoscopy of the lateral nasal wall with rigid cold light endoscopes in combination with polytomography or computed tomography usually will reveal the underlying causes hidden from the unaided eye, the operating microscope, and standard x-ray examination. Small lesions in the lesser cells of the ethmoid complex may give rise to headaches, especially when located in the key areas of the ethmoid infundibulum or frontal recess. Many anatomic variations of the structures in the middle meatus can narrow the stenotic clefts even more and thus predispose to more or less intense contact of opposing mucosal surfaces. This may impede or block ventilation and drainage of the ethmoid and surrounding larger sinuses and thus affect those as well. After identification of these underlying causes, functional endoscopic sinus surgery with usually minimal operations often can provide dramatic relief of symptoms that may have been present for months or even years. The neuropeptides recently were newly identified as a group of mediators besides the neurotransmitters noradrenalin and acetylcholine. Substance P (SP) is one of the most important neuropeptides that we can identify in the human nasal mucosa. It mediates pain impulses to the cortex via afferent C fibers. Simultaneously from polymodal receptors in the nasal mucosa, local reflexes are mediated by SP via an axon reflex, causing vasodilatation, plasma extravasation ("neurogenic edema"), and hypersecretion. The receptors can be stimulated by chemical and caloric irritants and also mechanical irritants such as pressure. The pressure exerted on nasal mucosa by polyps or mucosal swelling due to other reasons in the ethmoid clefts, cells, and narrow spaces apparently can be enough to trigger an SP-mediated pain sensation via afferent C fibers. Over the axon reflex an initially small lesion may lead in a vicious circle to quite significant symptoms. The model of "referred pain" explains why the pain is not necessarily felt at its origin, but may be projected onto corresponding dermatomes. The pain-mediating function of SP can be blocked selectively by capsaicin, the pungent component of red pepper, which leads to desensitization of the receptors and degeneration of the afferent C fibers without affecting other sensory qualities. In patients with vasomotor rhinitis we were able to block all the patients' symptoms including headaches by topical administration of capsaicin. After identification of underlying causes with endoscopy and CT, lesions and contact areas should be operated upon if medical treatment fails.(ABSTRACT TRUNCATED AT 400 WORDS)

Capsaicin↗
PubMedDate not supplied

[Detection of border disease virus in a sheep flock in Saxony].

A pestivirus has been isolated from brain samples of two lambs suffering from clinical signs of border disease. The two identical isolates were allocated to the "true" border disease virus group concerning their reaction pattern with monoclonal antibodies and the 5'UTR sequence data. Nevertheless, alterations of phenotype and genotype in comparison with references of both BDV-subgroups have been shown. The existence of an infection with border disease virus in the flock has been confirmed by serological studies.

Animals↗
PubMedDate not supplied

Anatomy of the brainstem: correlation of in vitro MR images with histologic sections.

MR imaging was performed on three formaldehyde-fixed brainstem specimens that were sectioned in the axial plane and myelin stained. The histologic sections were used to identify and label the structures demonstrated on short TR/TE axial MR images. Fiber tracts and nuclei that cannot be resolved on in vivo scans were well delineated by in vitro MR. Improved gray-white differentiation may be due to much greater T1 shortening of gray matter relative to white matter after fixation. The excellent anatomic detail provided by these scans should facilitate comparison of clinical scans with histologic sections.

Brain Stem↗
PubMedDate not supplied

Model-driven visualization of coronary arteries.

In a joint project between the Department of Computer and Information Sciences and the Department of Radiology, we are applying techniques of artificial intelligence to improve clinical performance in coronary arteries. Specifically, we are investigating how images from intravenous digital subtraction angiography (DSA) can be enhanced so that their efficacy for lesion detection and quantitation becomes comparable with that of the more dangerous procedure of selective coronary arteriography. The enhancement techniques (which include algorithms for 3-dimensional vessel detection, reconstruction and display, as well as for accurate lumen-size estimation) are based on models of (i) the 3-dimensional topological structure of the coronary arterial tree, (ii) myocardial dynamics, and (iii) the X-ray imaging process involved in producing digital subtraction angiograms. The evaluation of these model-driven visualization techniques is done by the standard psychophysical method of Receiver Operating Characteristic (ROC) analysis applied to observer performance tests on images from an animal coronary atherosclerosis model.

Analog-Digital Conversion↗