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Biomedical subjects

F Seifert

Publications and source records attributed to F Seifert.

26 records · Page 2Linked to original sources
PubMed1990

[Cryopreservation of bovine embryos].

The method of cryopreservation of embryos aged seven days, proposed for embryo transfer with cattle by Niemann (1985), was tested under production conditions on three cattle breeding farms and three experimental animal units. The number of donors was 128, and 467 intact embryos were obtained from them and were cryopreserved in semen straw. Following thawing, 455 were recovered, and 439 (96.5 percent) of these were suitable for transfer. A pregnancy rate of 49.0 percent was recorded from 412 transfers. This rate was differentiated by oestric cycle conditions of heifer recipients, which gave percentages of 46.0 among recipients of seven-day old embryos, 45.7 for eight-day recipients, and 65.8 for six-day recipients. Related to pregnancy results recorded on the same units from transfer of freshly collected seven-day embryos, the efficiency coefficient was 0.69 (550 fresh transfers = 65.4 percent and 222 cryopreserved transfers = 48.2 percent). The method is recommended for general field practice.

Animals↗
PubMed1988

Effect of coronary artery bypass grafting on left ventricular diastolic function.

Because left ventricular (LV) diastolic function is abnormal in patients with coronary artery disease (CAD), pulsed Doppler echocardiography was used to evaluate LV filling before and after coronary artery bypass grafting (CABG). Filling was evaluated by Doppler in 2 studies: (1) in a group of 41 unpaired patients (11 with angiographically normal coronary arteries, 14 with CAD but without CABG and 16 at 1 week after CABG) and (2) in a group of 12 patients with CAD before and 1 week after CABG. Doppler sampling at the level of the mitral anulus was analyzed for the deceleration half-time and for the ratio of peak late (A) to peak early (E) filling velocity, measures reflecting early ventricular filling and the relative contribution of atrial contraction to ventricular filling. In the first study the deceleration half-time was significantly prolonged in both CAD and CABG groups. The late to early peak transmitral velocity ratio, however, was significantly prolonged only in the nonrevascularized CAD patients. In the second group of CAD patients studied before and 1 week after surgical revascularization, both the late to early peak transmitral velocity ratio and the deceleration half-time showed significant postoperative improvement. Thus, patients with CAD showed impairment in early LV filling and a compensatory increase in the proportion of filling with active atrial contraction. Successful CABG appears to result in normalization of early filling and decreased reliance on active atrial transport.

Coronary Angiography↗
PubMed1988

Sensing aberration by the automatic implantable cardioverter defibrillator during intraoperative testing.

A 50-year-old man underwent replacement of his automatic implantable cardioverter defibrillator (AICD) because a magnet test revealed severe battery depletion. He had had his unit implanted 18 months previously after an episode of sudden cardiac death. He had documented torsades de pointes and inducible ventricular tachycardia, confirmed by electrophysiologic study. Before a new unit was implanted thresholds were measured by an external cardioverter defibrillator. Ventricular fibrillation (VF) was induced by alternating current through a standard, line-operated battery charger with stimulation delivered to the epicardium via rate-sensing electrodes. VF was allowed to continue for 10 seconds before shock was delivered. Termination of VF required 15 joules, which was higher than that required at initial implantation 18 months earlier. The new pulse generator was activated for testing and VF was again induced. The AICD discharged after 12.3 seconds. Prior to wound closing, the AICD was deactivated by magnet. Instead of R-wave synchronous beeping tones during deactivation, double beeping tones were heard. Electrogram recordings revealed abnormalities of the T-wave and ST segment of the rate-sensing electrodes, which were the cause of the tone irregularities. Stabilization of the T-wave and ST segment occurred within 8 minutes and the tones became normal. The procedure was then completed.

Electric Countershock↗
PubMed1978

Intravital microscopy of the microcirculation in man during and after experimentally controlled ischemia.

In man, using a skin tube chamber technique, microvascular reactions during and after complete experimental ischemia was studied by intravital microscopy. During 1 and 2 hour ischemia the trapped blood cells did not adhere to each other or to the vascular walls except for RBCs which formed rouleaux. Reflow after 1 and 2 hour ischemia was rapid with a hyperemic reaction and a transient increase in WBC stickiness. Thus, a mild and reversible inflammatory reaction was provoked by the short ischemic insult. During 6 hour ischemia most of the blood cells maintained their integrity. However, in a few vessels the RCSs formed homogeneous masses indicating hemolysis of some of the RBCs. There was also marked diapedesis of RBCs and increased WBC stickiness, but the platelets did not react to form thrombi. After the 6 hour ischemia reflow occurred in all vessels and the homogeneous masses seemed to cause only a temporary hindrance to reflow. The final outcome of the 6 hour ischemic insult was uncertain since in one of the two experiments there was a complete circulatory standstill 24 hours after the ischemia while in the other there was an almost normal blood flow.

Adult↗
PubMed1977

Pressure-induced ischemia. I. An experimental model for intravital microscopic studies in hamster cheek pouch.

A model to study pressure-induced ischemia by intravital microscopy is presented. A hamster cheek pouch is prepared to get a single layer of epithelium, together with vessels and connective tissue. Pressure, which can be varied, is transmitted to the tissue by a pressure chamber with a rubber membrane. Microcirculatory reactions may be studied while the pressure is applied, when the pressure is released and as the tissue is regaining circulation. The local environment is controlled by irrigating the test tissue with a solution approximating the composition of interstitial fluid. Local oxygen and carbon dioxide tensions are controlled. There is a marked difference in restoration of blood flow to the tissue after 2- and 4-hour ischemia. After 2-hour ischemia the tissue regained circulation rapidly. Microbleedings developed during the postpressure observation time. After 4-hour ischemia, on the other hand, the tissue regained circulation slowly and only in one third of the microvessels. Extensive white blood cells sticking to the vessel walls were seen indicating endothelial damage. In the 4-hour experiments there were very few microbleedings compared to the 2-hour experiments.

Animals↗
PubMedDate not supplied

The Protein Crystallization Facility (PCF) for EURECA.

Research on the structure of molecules by X-ray diffraction analysis requires large single crystals. However, the dynamic behavior of proteins caused by their high molecular weight prevents the growth of large single crystals if this process is disturbed by thermal convection. For example, protein single crystals grown under terrestrial (1 g) conditions are limited to dimensions in the order of 0.1 mm, whereas the size of crystals, grown under (quasi) space conditions has been 5 times larger (pilot experiment CRYOSTAT, Spacelab). Under EURECA conditions (e.g. no microgravity disturbances), the result in regularity of crystal growth and size is expected to be much better. In this paper an overview is given of the protein crystallization facility which includes Experiment-, Service- and Secondary Cooling Module, and its interfaces to the EURECA Carrier. At the end, there will be presented a short mission profile concerning cooling-, power- and data exchange requirements.

Convection↗
PubMedDate not supplied

Performance and use of current sheet antennae for RF-hyperthermia of a phantom monitored by 3 tesla MR-thermography.

Several MR-compatible current sheet antennae (CSA) of different height (h) (16 cm (l) x 8 cm (w) x 1-5 cm (h)) were built for simulated RF (96 MHz) hyperthermia of a medium-sized (12l) tissue-equivalent phantom inside a 3 tesla whole body tomograph. Prior to use, efficiencies of the CSA were determined by network analysis and by calorimetry. Depending on the height h of the CSA and on the thickness d(bolus) of the water bolus used for RF-coupling of the CSA to the lossy medium, their efficiency varied between 20-70% and the CSA with h = 3 cm was selected for simulated RF hyperthermia. During heating, spatial temperature distributions (20-42 degrees C) of five slices (voxel size 2 x 2 x 10mm(3)) were recorded intermittently within 4 s/slice by measuring the temperature dependent shift of the (1)H resonance frequency (125.32 MHz). A phased array consisting of two identical CSA produced distinctly different spatial temperature distributions at 0 and 180 degrees phase difference between both RF channels feeding the antennae. Within a one-dimensional heat diffusion model, the specific absorption rate (SAR) of the electromagnetic wave generated by a single antenna was deduced from the experimental data resulting in a penetration depth (1/e(2)) of approximately 4 cm.

Biophysical Phenomena↗