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Biomedical subjects

W Seeger

Publications and source records attributed to W Seeger.

At least 361 records · Page 20Linked to original sources
PubMed1983

[Daily ultrasonic examinations of kidney transplants in the diagnosis of rejection].

The volume of transplanted kidneys was measured in 54 patients in the first 20 days post operation using short-term sonography. In non-rejecting patients it increased by 20% on average, by 35% in rejecting ones and by nearly 50% in rupturing patients. There were significant differences between the groups of rejecting and non-rejecting patients. Sonography is thus a suitable screening method for rejection diagnosis.

Graft Rejection↗
PubMed1983

Comparative influence of the Ca-ionophore A 23187, bradykinin, kallidin and eledoisin on the rabbit pulmonary vasculature with special reference to arachidonate metabolism.

In a model of isolated rabbit lungs, perfused with isoionic and isooncotic fluid in a recirculating system, the Ca-ionophore A 23187, bradykinin, (kallidin), and eledoisin all evoke a reversible and reproducible increase in pulmonary vascular resistance, partly with biphasic characteristics. Inhibition of thromboxane-synthetase (imidazole), cyclooxygenase (indomethacin) phospholipase activity (mepacrine), and interference with the Ca-calmodulin-complex (trifluoperazine) each suppresses the increase in resistance due to A 23187 or eledoisin completely and the increase due to bradykinin or kallidin to a great extent. Thus thromboxane A2 appears to be the mainly responsible mediator for the increase in vascular resistance after all three stimuli. Moreover, A 23187 and bradykinin cause an increase in vascular permeability that is augmented by indomethacin and diminished by additional lipoxygenase inhibition with BW 352C and which thus can, at least partly, be ascribed to lipoxygenase products of released arachidonic acid. In spite of the described similarities there are marked differences in the relative potencies of A 23187, bradykinin and eledoisin concerning the increase in vascular resistance and the increase in vascular permeability. Therefore, different stimulus transmission-pathways are suggested, having Ca-calmodulin-complex, phospholipase activity and arachidonic acid transformation via cyclooxygenase/thromboxane synthetase respectively via lipoxygenases as common characteristics.

Animals↗
PubMed1982

Increased pulmonary vascular resistance and permeability due to arachidonate metabolism in isolated rabbit lungs.

Liberation and metabolism of arachidonic acid may be the common final pathway of different stimuli on the pulmonary vascular bed. In a model of isolated, ventilated rabbit lungs, perfused with Krebs Henseleit albumin buffer in a recirculating system, changes of pulmonary vascular resistance and of vascular permeability are monitored continuously. The addition of free arachidonic acid or of the Ca-ionophore A 23187 to the perfusion fluid consistently evokes a biphasic increase in vascular resistance as well as an initially reversible increase in vascular permeability, followed by pulmonary edema. Both phases of increased vascular resistance are completely suppressed by inhibition of the cyclooxygenase, decreased to a large degree by inhibitors of thromboxane synthetase, and markedly augmented by short preincubation of arachidonic acid with ram seminal vesicular microsomes and by sulfhydryl reagents. The increased pulmonary vascular permeability is augmented by inhibition of cyclooxygenase and reduced by simultaneous lipoxygenase inhibition. Antagonists of histamine, serotonin and sympathic or parasympathic activity do not have any influence. PG F2alpha., TxB2, PG E2 and PG I2 alter the pulmonary vascular resistance, but do not increase vascular permeability. In conclusion, increased availability of free arachidonic acid evokes a rise in pulmonary vascular resistance, which can be ascribed to cyclooxygenase products, especially to thromboxane, and causes a rise in vascular permeability which can be ascribed to lipoxygenase products. The findings may be related to acute pulmonary lesions with increase in vascular resistance and with vascular leakage.

Animals↗
PubMed1982

Influence of tocopherol, its chromane compound, phytyl chains and superoxide dismutase on increased vascular resistance and permeability due to arachidonate metabolism in isolated rabbit lung.

In the model of isolated, ventilated rabbit lungs, perfused with isoionic and isooncotic fluid, the addition of arachidonic acid to the perfusion fluid or the liberation of arachidonic acid by the Ca-ionophore A 23187 result in an increase in pulmonary vascular resistance and permeability. The former can be ascribed to cyclooxygenase products, the latter to lipoxygenase products of arachidonic acid. The effect of alpha-tocopherol, its chromane compound, alpha-tocopherolquinone, phytol, 2-methyl-1,4-naphthoquinone, 2-methyl-3-phytyl-1,4-naphthoquinone and of superoxide dismutase (SOD) on the increase in pulmonary vascular resistance and permeability was investigated. A membrane effect of the phytyl side chain and an antioxidative effect of the chromane compound can be distinguished: phytol increase the arachidonate-induced rise of pulmonary vascular resistance and permeability, whereas the chromane compound decreases both to a large degree. Methyl-phytyl-naphthoquinone and methyl-naphthoquinone gave equivalent results. SOD decreases the enhanced vascular resistance and the vascular leakage. The possibility of antioxidative therapy in acute pulmonary lesions with vascular leakage and increased vascular resistance is discussed.

Animals↗
PubMed1982

[Dosimetry of a whole-body irradiation for bone marrow transplantation].

The authors present a method allowing to dose a whole-body irradiation in such a way that a nearly homogenous dose of 10 Gy is reached in the whole patient, with the exception of the lung which shall only receive 8 Gy. Particular attention is given to the increased dose in the head and neck region caused by the smaller thickness as compared to the trunk, which is compensated by shields. The measurements were taken in a plastic phantom for all possible patient's dimensions. All necessary basic data are stored in a program which calculates the monitor preselection for the individual fields after input of the patient's dimensions. Further controls are intended in the near future by in-vivo measurements. The time necessary for the described measurements is about for to six days, and the same time has to be appended for the evaluation and establishment of the program.

Bone Marrow Transplantation↗
PubMed1982

[Calcium metabolism before and during hemodialysis].

Calcium metabolism was studied in the serum of 10 patients before and during haemodialysis with the help of 47-Ca. The patients were in a stabilized condition within a chronic dialysis programme. The measured metabolic rate fell from 0.395 h-1 to 0.208 h-1 during dialysis. This corresponds to a reduction of metabolism by 0.43 mmol L-1 h-1. It is to be assumed that this alteration corresponds to the calcium inflow rate through the dialyser.

Calcium↗
PubMed1981

[Increase of pulmonary vascular resistance and permeability due to the metabolism of free arachidonic acid (author's transl)].

Release and metabolism of arachidonic acid are supposed to form the common final pathway of different stimuli on the pulmonary vascular endothelium. In a model of isolated, ventilated and perfused rabbit lungs we investigated the influence of increased availability of free arachidonic acid on pulmonary vascular resistance and permeability. Addition of arachidonic acid to the perfusion fluid or release of arachidonic acid by Ca-ionophore A 23187 regularly produces a characteristic biphasic increase of the pulmonary vascular resistance as well as a continuous increase in permeability, followed by pulmonary edema. Inhibition of cyclooxygenase by indomethacin prevents the augmentation of vascular resistance, the increase of vascular permeability however is enhanced. thus the raise in pulmonary vascular resistance can be ascribed to cyclooxygenase products, the increased pulmonary vascular permeability to lipoxygenase products of arachidonic acid.

Animals↗
PubMed1981

[The antioxidative chromane structure of alpha-tocopherol protects against the consequences of arachidonic acid release in the pulmonary vascular bed (author's transl)].

In the model of isolated, ventilated and perfused rabbit lungs release of arachidonic acid results in an increase of pulmonary vascular resistance and permeability. The former can be ascribed to cyclooxygenase products, the latter to lipoxygenase products of arachidonic acid. The effect of alpha-tocopherol on the increase of pulmonary vascular resistance and permeability either after the addition of arachidonic acid to the perfusion fluid or after stimulation of arachidonic acid liberation by Ca-ionophore A 23187 was investigated. It is possible to distinguish a membrane effect of the phytol side chain of alpha-tocopherol and an antioxidative effect of its chromane structure: Phytol augments the increase of pulmonary vascular resistance and permeability, whereas the chromane-structure decreases both to a large degree. The possibility of antioxidative therapy in disturbances of pulmonary vascular permeability is discussed.

Animals↗
PubMed1981

[Investigations on contrast values in mammography (author's transl)].

Measurements of the spectral distribution of x-rays using a Si(Li)-detector form the basis for an investigation into contrast values provided by molybdenum and tungsten tubes in mammography. In order to evaluate contrast, the intensity of the characteristic radiation and of the brems rays were related to anode kV and thickness of section; the spectral intensity was then calculated for small calcium inclusions in soft tissues. For average tissue thickness (4 cm.) and an anode working at 30 kV, the molybdenum tube with a molybdenum filter is significantly better than a tungsten tube. With increasing size of breast, hardening of the radiation also increases, until for practical purposes contrast is determined by the brems rays alone. At this stage there is only little difference between the molybdenum and tungsten spectrum, and in the resultant contrast.

Humans↗
PubMed1981

[Nuclear processes on operation of linear accelerators (author's transl)].

The primary nuclear reactions possibly occurring in accelerators operated on an energy level between 8 and 20 MeV are outlined, and their probability is estimated. Furthermore, the authors discuss which photoneutron rates par micron As are to be expected in case of different threshold energies in a tungsten sheet with a thickness of 6 mm and which secondary nuclear processes are induced by the photoneutrons.

Neutrons↗
PubMed1980

[Intraoperative doppler sonography of brain vessels (author's transl)].

Intraoperative Doppler-examination of brain vessels. The diagnostic possibilities of the intraoperative Doppler-examination are explained with a few selected cases. This method seems to be helpful for the following purposes: 1. the control of anastomoses, 2. the identification of arteries and veins and their blood flow direction in av-malformations. 3. the determination of the blood flow direction in cerebral veins and sinuses and the decision whether or not a sinus is patent (in parasagittal meningiomas).

Adolescent↗
PubMed1980

[A Cerenkov detector to determine the energy in electron accelerators (author's transl)].

The authors present a Cerenkov threshold value detector consisting of elements originating from the commercial vacuum industry. This detector allows to measure electron energies between 8 MeV and 20 MeV. By the comparison of the signals of two photo-multipliers, a considerable independence of external disturbing factors is achieved. It is demonstrated that the results achieved with normal propane are not worse than those of super-purified gas and, therefore, a cheap and simple method is available in order to control the electron energy of accelerators.

Electrons↗
PubMed1980

[Dosimetry on the linear accelerator. Second communication: moving field therapy with ultrahard X-radiation (author's transl)].

Further to the description of the stationary-field irradiation with ultra-hard X-radiation (first communication) the planning of a moving field therapy is now discussed. The authors give simple criteria how to choose as exactly as possible the dose distribution adequate to the clinical plan among the available isodose plots. The indication of the necessary equipment parameters in facilitated by an irradiation table containing the average length of the moving beam. Test measures taken since 1974 on the linear accelerator Philips SL 75/10 show how good the scanning of a certain sector is reproducible.

Humans↗