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Biomedical subjects

U Borst

Publications and source records attributed to U Borst.

10 recordsLinked to original sources
PubMed1992

A new motion responsive pacemaker: first clinical experience with an acceleration sensor pacemaker.

A new accelerometer-based adaptive rate pacemaker (EXCEL VR) was evaluated to investigate its behavior at nominal settings during treadmill exercise testing and postural changes. Eight patients with sinus rhythm were selected to compare intrinsic heart rate to sensor mediated rate. Throughout exercise treadmill testing, changes in the sensor mediated rate closely paralleled actual physiological changes. The Pearson product moment correlation of pacing rate with sinus frequency, calculated for all patients, was r = 0.82 (P = 0.001). Change in the patient's physical position resulted in immediate change in sensor rate, which corresponded appropriately to the type of position change and activity level. Average (+/- SD) pacing rate was 62.4 +/- 2.7 beats/min supine; 67 +/- 3.8 beats/min sitting; 69.8 +/- 6.4 beats/min standing; 81.6 +/- 8.7 beats/min slow walking; and 96.8 +/- 1.3 beats/min fast walking. After 4 minutes of recovery, the average pacing rate dropped to 65 +/- 3 beats/min. The interaction between the accelerometer and the pulse generator at nominal settings was accurate and infrequently required the use of its many programming options. The accelerometer sensor and pulse generator algorithm in this device during postural change and exercise resulted in physiological-like changes in sensor mediated heart rate.

Acceleration↗
PubMed1992

[Indium-111 or Tc-99m-HMPAO marked granulocytes as specific markers of florid stage endocarditis--results comparing clinical, histological and scintigraphic findings in 30 patients with suspected endocarditis].

Thirty patients with clinically suspected infective endocarditis were scanned with Indium-111- or Tc-99m-HM-PAO-labeled granulocytes. The scans were correlated with the clinical course, and in 20 cases with the results from histologic examination of the valves. In six cases the scintigraphic examination gave correct positive results, in three cases false negative, in one case a false positive, and in 20 cases correct negative results. If we limit the analysis to only the histologically proven cases, our data suggest a specificity of the method of 86% and a sensitivity of about 67%.

Abscess↗
PubMed1989

Tc-99m-HMPAO labelled human platelets: in vitro and in vivo results.

The lipophilic 99mTc-HMPAO complex can be used for labelling platelets as well as granulocytes. Platelets were isolated according to standard isolation procedures for the evaluation of the optimal labelling parameters. The labelling efficiency (%) depends on incubation temperature (22 degrees C: 40%: 37 degrees C: 50%), incubation time (3 min: 20%, 25 min: 55%) and the incubation medium (plasma: 40%; saline 50%). The 60 min 99mTc elution out of the platelets ranged around 8%. The platelet recovery used as a quality control parameter is around 25% +/- 4% and is stable for at least 240 min. The high elution rate out of the platelets leads to renal excretion of the label and hence to significant kidney and bladder activity. Intestinal excretion of the label can also be frequently demonstrated. Fresh thrombotic lesions can normally be detected 4 h after reinjection of the labelled platelets, and in some patients as early as 1 h after reinjection. In conclusion, 99mTc-HMPAO seems to be a promising platelet label for imaging thrombotic lesions but not for platelet survival studies, because of the short physical half life of 99mTc.

Blood Platelets↗
PubMed1989

Kinetic data of in-vivo labeled granulocytes in humans with a murine Tc-99m-labelled monoclonal antibody.

Twenty-five patients were examined in vivo with 99mTc labelled monoclonal antibodies; 15 with suspected infections with an antigranulocyte antibody (BW 250/183), 10 with suspected recurrence of a colorectal carcinoma with an anti CEA antibody (BW 431/26). Both antibodies were IgG1 isotypes. In the patients with suspected infections no change of the peripheral leukocyte count could be observed after the antibody injection (1 mg, n = 9; 0.5 mg, n = 1; 0.25 mg, n = 6). In 2 patients examined with the anti CEA antibody (2 mg), a significant decrease of the peripheral leukocyte count could be observed. The recovery rate of the 99mTc antibody labelled granulocytes was calculated to be about 10%. The increase of the antibody-antigen binding was calculated to be 0.2%/min. In vivo the organ distribution curves demonstrated an increase of 99mTc activity over spleen and bone marrow of 1.1%/min, which was interpreted as antigen-antibody reactivity. The organ distribution curves of the anti granulocyte antibody over spleen and bone marrow showed typical binding characteristics to the local granulocyte epitopes. The curves over other organs showed a simple perfusion pattern. The curves of the anti CEA antibody showed a perfusion pattern over all the examined organs. A sham dialysis model in one patient with renal insufficiency undergoing regular dialysis treatment demonstrated the viability of 99mTc antibody labelled granulocytes in vivo. The kinetic patterns of the 99mTc antibody in patients with Crohn's disease were interpreted as CEA binding of the antibody in the bowel wall.

Animals↗
PubMed1989

Effect of bisoprolol on cardiac performance in coronary heart disease.

The effects of 5 and 10 mg bisoprolol once daily for 7 days on exercise ECG, myocardial perfusion and left ventricular function in 25 patients with stable coronary heart disease have been assessed in a double-blind, randomized, parallel group trial design. ST-segment depression during exercise was reduced by 56% by 5 mg bisoprolol and by 64% after 10 mg; the difference between the dose levels was significant. Heart rate, systolic and diastolic blood pressure and the rate-pressure product were reduced to similar extent both at rest and during exercise by both doses. Left ventricular thallium-201 scintigrams indicated a significant reduction in myocardial perfusion defects after 10 mg bisoprolol compared to baseline; however, the difference between the two active treatments was not significant. Left atrial and left ventricular diameters obtained by one-dimensional echocardiography, and the calculated shortening fraction, remained unchanged after bisoprolol, and so gave no evidence of a negative inotropic action. It is concluded that 5 mg bisoprolol was effective in once-a-day treatment of angina pectoris due to coronary heart disease, and a further improvement can be expected on increasing the dose to 10 mg.

Adrenergic beta-Antagonists↗
PubMed1989

Filling the preparatory interval with temporal information or visual noise: crossover effect in schizophrenics and controls.

Three variants of a simple reaction time task with regular and irregular series of different preparatory intervals (PIs) were presented to schizophrenics and a control group of alcoholics and normals: the visual warning signal (WS) either (1) remained fixed, (2) shrank at a constant rate, or (3) changed in size erratically. Time information provided by shrinking WSs reduced the average reaction time in all groups and attenuated the crossover effect (COE) of schizophrenics, although even here more schizophrenics than controls had COE-scores greater than or equal to 25 msec. Erratically changing WSs introduced the COE in controls. Within groups the COE was not related to general response speed, age, duration of hospitalization, or medication. Results are interpreted as indicating that schizophrenics eschew controlled anticipatory processes on the basis of WS- and PI-information which are crucial for motor preparation when PIs are too long to allow an automatic perceptual grouping of warning and imperative stimulus. This may also occur in controls when time estimation is impeded by distraction.

Adult↗
PubMed1988

99Tcm hexamethylpropyleneamineoxime (HMPAO) as a platelet label: evaluation of labelling parameters and first in vivo results.

The lipophilic 99Tcm hexamethylpropyleneamineoxime (HMPAO) complex can be used for labelling platelets as well as granulocytes. For the evaluation of optimal labelling parameters, platelets were isolated according to standard isolation procedures. The labelling efficiency (%) depends on incubation temperature (22 degrees C: 40%; 37 degrees C: 50%), incubation time (3 min: 20%; 25 min: 55%) and the incubation medium (plasma: 40%; saline: 50%). The 60 min 99Tcm elution from the platelets is around 8%. The platelet recovery, used as a quality parameter, is around 25 +/- 4% and is stable for at least 240 min. The high elution rate from the platelets leads to renal excretion of the label and so to significant kidney and bladder activity. Intestinal excretion of the label can also be frequently demonstrated. Fresh thrombotic lesions can usually be detected 4 h after reinjection of the labelled platelets, and in some patients as early as 1 h after reinjection of the platelets. In conclusion, 99Tcm HMPAO seems to be a promising platelet label for imaging thrombotic lesions but not for platelet-survival studies because of the short physical half-life of 99Tcm.

Blood Platelets↗
PubMed1987

Impact of time estimation on the crossover effect in schizophrenia.

To test the role of time estimation in the crossover effect (COE), reaction times (RTs) of schizophrenic, alcoholic, and normal subjects were collected in two conditions: a standard visual RT task with different preparatory intervals in regular or irregular series, and a time information condition with the intervals filled by a visual countdown analogue. In the standard condition, the COE was found not only for schizophrenics but also for alcoholics. Time information reduced RTs in all groups, but not the average COE in schizophrenics. The relationship between RTs and simultaneously collected event-related potentials was examined.

Adult↗