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Biomedical subjects

U Cobet

Publications and source records attributed to U Cobet.

At least 19 recordsLinked to original sources
PubMed2000

Ultrasound enhancement of liposome-mediated cell transfection is caused by cavitation effects.

Cationic liposomes (CL) are widely used vectors for gene transfer. Recently, ultrasound (US) was reported to enhance liposome-mediated gene transfer to eucaryotic cells in culture. The present study was aimed at studying the effects of 2-MHz pulsed Doppler US on malignant brain tumor cells transfection by cationic liposome/plasmid-DNA complexes (lipoplexes). Cationic liposomes consisting of DOSPA/DOPE were complexed with a plasmid carrying the cDNA encoding green autofluorescent protein (EGFP). Rodent (9L) and canine (J3T) glioma cells were exposed to pulsed US in the presence of EGFP-lipoplexes. A diagnostic transcranial Doppler device (MultiDop L) was used for insonation for 30, 60, and 90 s at 2 MHz/0.5 W/cm(2). To eliminate US reflection and cavitation, a custom-made absorption chamber was designed, where US is applied through a water tank before interacting with the cells and is fully absorbed after passing through the cell layer. Expression of the marker gene EGFP was quantified by FACS analysis and intravital fluorescent microscopy. Cell viability was accessed by Trypan Blue staining. US treatment of tumor cells on microplates for 60 s yielded a significant increase in transfection rates without damaging the cells, but 90-s treatment killed most of the cells. In the absorption chamber, no significant effects of US on transfection were noted. Additional experiments employed US contrast agent (Levovist, Schering) which was able to significantly increase tumor cell transfection rate by enhancing cavitation effects, and also severely damaged most cells when applied at a concentration of 200 mg/mL. In conclusion, our results support the assumption that US effects on lipoplex transfection rates in brain tumor cells in culture are mediated by cavitation effects.

Animals↗
PubMed1998

[Equipment-independent ultrasound tissue characterization of testis and prostate].

The result of a B-scan ultrasound examination is strongly dependent on the type of the used B-system, the chosen system parameters and the experience and critical analysis of the clinical investigator. The estimation of quantitative acoustic parameters, independent of the type of the used B-system, is one way to overcome the subjective nature and the problems of the interpretation of B-scan images. A procedure was developed to determine acoustical tissue specific parameters (ultrasound attenuation, relative backscatter coefficient) in terms of the ultrasound spectroscopy and to correct the system effects. A requirement for the calculation of acoustical parameters is the availability of primary rf echo signals without any preprocessing. Up to now measurements of phantom materials and in-vivo investigations on human testis and prostate have been carried out. The effects of pathological changes in the tissue state on the acoustical parameters are demonstrated in some examples.

Artifacts↗
PubMed1998

[Duplex ultrasound examinations of retinal circulation after inhalation of various mixed respiratory gases].

BACKGROUND: Hyperoxic-hypercapnic inhalation is a therapeutic option in vascular disorders of the retina. The effect of hyperoxic and/or hypercapnic inhalation on the perfusion of the retina was examined. METHODS: Twenty-five young adults between 18 and 35 years were investigated in a prospective study. They inhaled one of three different mixtures of breathing gases: (1) 100% O2, (2) Carbogen 240 (95% O2 and 5% CO2), (3) 92% O2 with 8% CO2 and were examined by color Doppler imaging of the CRA and OA before and after inhalation. The resistance index (RI) was calculated. RESULTS: The majority of the subjects showed an Increase in the RI in both ophthalmic vessels after inhalation of pure O2, a decrease after breathing in 92% O2 and 8% CO2 and it remained almost constant with inhalation of 95% O2 and 5% CO2. CONCLUSIONS: Inhalation of 92% O2 and 8% CO2 is a possibility for decreasing the peripheral resistance of OA and CRA. No change in blood flow was observed with Carbogen 240.

Adolescent↗
PubMed1993

[Dietary management of phenylketonuria patients using a personal computer].

The communication between the responsible physician and the family of the phenylketonuric patient requires an extended period of time in the treatment centre. Computer software was developed for the centre to ensure individual treatment of all patients according to the dietary recommendations. The program is additionally able to document all clinical data and to handle the correspondence with the family of the patient.

Female↗
PubMed1992

Doppler sonographic pulse curve analysis for estimation of the haemodynamic function.

Experience with Doppler sonographic pulse curve analysis is given from 40 glaucoma patients (examination of the temporal posterior ciliary artery), and from premature babies (blood flow in the anterior cerebral artery). In the latter group the reaction to pain and stress connected with blood sampling was studied. In the glaucoma patients focus was on the influence of IOP level on vascular autoregulation, and the possible response to therapy with beta-blockers. Describing an averaging technique, methodological problems are discussed as relevant for the detection of changes in flow and velocity in small blood vessels.

Adrenergic beta-Antagonists↗
PubMed1992

[Modification of cerebral hemodynamics by invasive routine diagnostic procedures].

By means of cw-Doppler-ultrasonics pulsation curves of anterior cerebral arteries were recorded before, during and after a necessary capillary blood sampling in 12 premature newborns. Patients were stable and needed no oxygenation. Blood pressure and transcutaneous oxygen saturation have been recorded simultaneously. The most important hemorheological parameters were within normal range. Immediately following irritation pulsatility indices increased, partly diastolic reflux phenomena could be observed. Finishing irritation values went back to starting position very fast. It is supposed such strong changes of cerebral vascular resistance could be the reason of cerebrovascular damages in non sedated premature newborn babies.

Arousal↗
PubMed1991

[Electron probe microanalysis of fluorine content in deciduous and permanent teeth from an area with a fluoride-deficient (0,3% mg/I) water supply].

The content of fluorine in deciduous and permanent teeth of young people was determined by x-ray microanalysis. The purpose of this investigation was to determine the concentrations of F in teeth without any supplementation of fluorides and to elaborate basic dates as a standard of comparison. F was measured in microvolumes with a wavelength-dispersive spectrometer (Step-Scan 100 sec) after coating with about 300 A of Carbon. The highest values were established in the outermost surface of enamel with quantities between 300 and 600 micrograms/g. The lower concentrations were found in deciduouns teeth. In both dentitions the F-content increases at the surface following the permanent change between de- and remineralization. In subsurface areas the values are decreasing quickly. At a deep of 10 microns from surface layer the content is only 70 micrograms/g and than it declines to a minimum of 20-30 micrograms/g.

Child↗
PubMed1991

[Ultrasound cw Doppler studies of cerebral hemodynamics].

Using ultrasound-Doppler-system UBD 2 the pulsation curves of mean blood velocity and mean flow of anterior cerebral artery have been registered and examined. In 95 healthy newborns (mean age 36th to 41st gestational week) normal values and correlation for age have been determined for transit time as parameter independent from curve shape and pulsatility index and peripheral resistance index as parameters of curve form. Position test enables testing the autoregulative function of cerebral hemodynamic under physiologic conditions. This shows a postnatal ripening within the first five days of live.

Blood Flow Velocity↗
PubMed1986

[Hemodynamic studies of iloprost-conditioned ischemically stressed kidneys in animal experiments].

By means of computer-assisted Doppler signal analysis on the exposed renal artery of the pig the change of the haemodynamics under the influence of Iloprost is investigated in comparison to the electromagnetic flow measurement. The Doppler sonographic establishment of the speed of the blood flow and the relative volume of the blood flow allows additional informations about characteristic changes of the form of the pulse. During the measurement in situ on the renal artery the result was during the intraarterial application of Iloprost a distinct increase of the renal blood flow with simultaneous decrease of the renal resistance, which, issuing from the Doppler signal analysis, is characterized as change of the renal resistance index. The kidneys conditioned under influence of Iloprost were retransplanted after a warm ischaemia-time of 45 minutes with following machine preservation of 24 hours and showed a stable flow characteristics for the whole investigation period. The Doppler signals directly conducted via the renal parenchyma showed a stable pulsation also in the smaller arterial vessels.

Animals↗
PubMed1982

[Ultrasonic Doppler methods of blood flow studies of the arterial circulation from the aorta up to the kidney parenchyma in animals].

The Doppler method of ultrasonography was used in experimental investigations to examine the circulator behaviour at various points in the arterial system in the retroperitoneum as fast as the kidney in animals with normal circulation. This enabled reproducible Doppler curves to be determined. It remains to be seen to what extent characteristic curve patterns exist for e.g. partial or subtotal vascular occlusion. For the future it will be especially important to determine the flow curves in the cortical region of the renal parenchyma as an area of small and very small vessels, for this can give us important information on the circulation of blood in the individual segments of the kidney.

Animals↗
PubMed1978

[Characterization of heavy metal secretory granules in the islet tissue of adult white rats by means of the light and electron microscopy, including the high voltage electron miscroscopy and the electron microanalysis (author's transl)].

The metal secretory granules of Langerhans' islets of white rats were examined after histochemical detection by sulfide silver staining method as well as by conventional electron microscopy and high voltage electron microscopy. Zinc and calcium were determined with electron probe x-ray-microanalysis. The metals are located at the inside of cytoplasmatic vacuoles, a result, we discuss in connection with the release of pancreatic hormones.

Animals↗