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Biomedical subjects

F Pliquett

Publications and source records attributed to F Pliquett.

At least 19 recordsLinked to original sources
PubMed2000

Effects of glutathione peroxidase and catalase on hemolysis and methemoglobin modifications induced by photooxidized psoralen.

Psoralen photooxidation products (POP products) were obtained by UVA irradiation (365 nm, 180-640 W/m2) of an aqueous psoralen solution with fluences of 0-800 kJ/m2. Preincubation of POP products with glutathione peroxidase (GSHPer) or catalase, as well as presence of catalase during UVA irradiation of the aqueous psoralen solution did not influence their hemolytic activity. However, both GSHPer and catalase inhibited POP-induced conversion of methemoglobin. This indicates that hydrogen peroxide and psoralen peroxides destructible by GSHPer, which are being produced during psoralen photooxidation, do not possess hemolytic activity. Furthermore, hydrogen peroxide does not appear to serve as an intermediate in the process of hemolysin formation. Hydrogen peroxide generated during psoralen photooxidation is apparently the main POP product responsible for MetHb conversion.

Catalase↗
PubMed1999

Stress action on biological tissue and tissue models detected by the Py value.

The Py value, a fast measurable combination of the conductivity at the corner frequencies of the beta-dispersion, is a measure of the relative cell volume concentration in tissue. In many cases, if the biological object is stressed, for instance, by mechanical deformation, shortage of oxygen, electric field strength, temperature rise, or ischemia, Py increases. Depending on the object and the kind of stress, Py plateaus for minutes up to hours and then it decreases continuously. Values of passive electrical parameters of biological tissues are often given without information about the time following a stimulation or stress situation, for example, death, surgery, field application, etc. However, since the passive electrical properties change with time, information about their history, for example, time after death, should be given.

Electric Impedance↗
PubMed1996

Passive electrical properties of human stratum corneum in vitro depending on time after separation.

The passive electrical properties of human skin after separation from the body are predominated by the stratum corneum. Skin within a bath medium (150 mM phosphate buffered saline) at constant temperature (37 degrees C) exhibits a characteristic change of the passive electrical properties with time. Independent of the time the locus in the Z-plane is a depressed semicircular arc. The angle between the lines from the center of the arc to the points where the locus reaches the real axis remains unchanged. The difference between the high and low frequency resistivity (R0-Rx) increases over 10 h, reaches a plateau and decays after 20 h exponentially with a time constant of about 40 h. As model for the impedance we used a 5 element electrical circuit (R0, R1, R2, C1, C2), describing 3 pathways, (0) the dc path (appendages; R0), (1) tortuous pathways around the cell structures (R1, C1) and (2) direct pathways involving the corneocytes (R2, C2). There are characteristic changes with time in the elements of the equivalent circuit up to about 200 h after excision. Dramatic changes in C1 and R2 at about this time after separation strongly suggests destruction of the lipid structures. It will be suggested that the use of separated human stratum corneum as model for in vivo yields unreliable results after this time.

Electric Impedance↗
PubMed1992

Dielectric properties of biological tissue at low temperatures demonstrated on fatty tissue.

Dielectric behaviour of fatty tissue was investigated from T = 300 K to 4 K and f = 20 Hz to 1 MHz. Characteristic curves were obtained only at low frequencies. With decreasing temperature four important features were detected: the water-ice transition at T = 265 K, a relaxation process of the fat molecules (near 260 K) and one connected with the ice-part (210 K-170 K). The reason for the fourth relaxation at T = 140 K has not been fully understood yet: it may be caused by segmental rotation of the fatty acid molecules or the presence of multiple bonds. The epsilon"-maximum caused by the ice relaxation at T congruent to 200 K can be used to detect successful application of cryotherapy, i.e. the temperature fall below the minimum value of 233 K.

Adipose Tissue↗
PubMed1991

A measuring technique for the investigation of the dielectric behaviour of biological tissue at low temperatures.

The experimental technique described can be used to measure the complex dielectric constant of different kinds of samples in the temperature range T = 300 to 4K. The specially designed sample holder guarantees simple preparation and allows in-vitro measurements of biological tissues as well as investigations of related materials of interest including liquids. The results of fatty tissue chosen as a model substance will be shown and discussed in comparison to simple basic compounds in subsequent papers.

Electric Conductivity↗
PubMed1990

[The effect of the oxygen content of the air breathed in on the passive electrical properties of muscle tissue].

Due to a want of oxygen in the breathing air there appears a change of the volume of muscle cells, of ion concentrations inside and outside the cells as well as disturbances the structure and membrane potential. These changes are connected with changes of the passive electrical properties of the muscle tissue. Measuring the electrical impedance of the muscle it is possible to diagnose alterations as shock and disorder of microcirculation in an easy way continuously. Investigations with rats show that a decrease of the oxygen content in the inspiration air effects characteristic changes in muscle impedance. These changes are reversible in normoxia.

Animals↗
PubMed1989

[Changes in passive electric tissue properties of experimental tumors during carcinogenesis].

The DS-carcinosarcoma of rats changes its passive electrical properties during the development time. Using a pulse measurement method the pulse parameters h beta and h1 of cancer tissue from 10 rats were measured in vivo during a period of 13 days after the beginning of the tumour growth. These parameters depend on the intra- and extracellular conductivity, on the membrane capacity, and on the volume fraction of the structures surrounded by a membrane. The values of h beta and h1 decrease during the first 4 days of the cancerogenesis by more than 50%. These findings agree with measurements carried out in portiocarcinomas.

Animals↗
PubMed1988

[Passive electrical tissue parameters of normal and pathologically altered cervical epithelium].

Normal and pathologically changed tissues can be distinguished on the basis of passive electric measurements, if the concentrations of the membranes, the resistance of the membranes, the membrane capacity, or the conductivity in and outside of the cells are different for both tissues. The electrical parameters are immediately measurable without anesthesia under in vivo conditions by change of electrical pulses. 2043 measurements on 300 patients were carried out. A suitable combination of electrical parameters of the tissues revealed that there is a difference of 64.5 +/- 0.5% between normal and pathologically changed epithelium (cancer).

Electrodiagnosis↗
PubMed1984

PUVA-induced erythema and changes in mechanoelectrical properties of skin. Inhibition by tocopherols.

Influence of antioxidants on two phototoxic effects of 8-methoxypsoralen (8-MOP) was studied: erythema and changes in mechanoelectrical properties of skin. alpha-Tocopherol and its analogs with shortened lateral hydrocarbon chains at C2-atoms of chromane groups (chromanols) were used as antioxidants. alpha-Tocopherol and its analogs inhibited both phototoxic effects of 8-MOP. Inhibition was observed only if antioxidants were present in skin during irradiation. When applied after irradiation these antioxidants produce no inhibitory effect. The antioxidant antierythemal action depends greatly on their concentration. The protective effects is maximal at antioxidant concentrations 2.5 . 10(-10) - 5 . 10(-9) mol . cm-2 of skin, at concentrations higher than 5 . 10(-9) mol . cm-2 the protective action is decreased. The protective effect of antioxidants depends on the irradiation dose.

Animals↗
PubMed1984

[Changes in the passive electrical properties of the erythrocytes during hemosorption].

Passive electrical properties of erythrocytes were studied during hemosorption in vivo. It was shown that specific conduction and capacity of the erythrocyte plasma membrane were reduced after hemosorption. Incubation of erythrocyte suspension with free fatty acids resulted in an increase in specific conduction and capacity of the plasma membrane. That effect was eliminated after the passing of erythrocytes through a column with activated charcoal.

Animals↗
PubMed1983

Reticulocyte lipoxygenase changes the passive electrical properties of bovine heart submitochondrial particles.

Purified reticulocyte lipoxygenase oxygenates the polyunsaturated phospholipids of sonified submitochondrial particles from bovine heart as measured by a burst of oxygen uptake. Over the frequency range of 0.5 to 100 MHz, the complex impedance of the submitochondrial particles as a function of the frequency before and after lipoxygenase attack was measured. From these data, the membrane capacity, the conductivity of the membrane and the conductivity inside the particles were calculated. Lipoxygenase action causes a 4-fold increase in the membrane capacity and a 2-fold increase in the membrane conductivity. Using the method of deformation of electric pulses, kinetic measurements were performed. In parallel to the changes of the passive electric properties, a partial inhibition of NADH oxidase and succinate oxidase was caused by the lipoxygenase attack. Oxygen uptake, changes of the passive electric properties and the inhibition of respiratory enzymes were prevented by lipoxygenase inhibitors. Owing to the high oxygen consumption produced by the lipoxygenase reaction, anaerobiosis was reached within the first 30 s in the closed chamber. Therefore, it must be concluded that the changes in passive electric properties and the inhibition of the respiratory enzymes are due to secondary anaerobic processes such as the hydroperoxidase reaction catalyzed by the lipoxygenase or a slow redistribution of peroxidized membrane lipids. The results are discussed in relation to the breakdown of mitochondria during the maturation process of red cells.

Animals↗
PubMed1980

[Alpha-tocopherol inhibition of erythema in skin photosensitized by 8-methoxypsoralen].

Irradiation of the rabbit and human skin by near UV light (wave lengths greater than 320 nm) in the presence of 8-methoxypsoralen produced erythema, pigmentation and some changes in the mechanical and electric properties. All the photobiological effects mentioned were inhibited by alpha-tocopherol if it was applied before irradiation. When applied after exposure to irradiation alpha-tocopherol appeared to be ineffective.

Animals↗
PubMed1980

[Low temperature biopsy of biological tissues (author's transl)].

A method and an equipment are described to perform a low temperature biopsy. The advantages of this method are the immediate conservation and the excellent topical conjugation of tissue. Using the effect of adherence it is also possible to get a biopsy from tissues of a high rupture strength. We used this cryobiopsy method for histological diagnosis of colposcopically suspicious areas of the ectocervix uteri, where the representation of relations between epithelium and stroma is of practical importance.

Biopsy↗
PubMed1978

[Studies on the recognition of specific sensitization to tumor antigens by measuring passive electrical additive effects as against the electrophoretic mobility test].

Lymphocytes from cancer patients were incubated with different tumor antigens. In the medium in which the lymphocytes were suspended, passive electrical values could be measured in the Mc region. These values correlate with a specific sensibilization of tumor carriers. By comparison with the electrophoresis-mobility test (em-test) we found in 66 out of 74 supernatants, using CEA and KCl-extracts as antigens, a good conformity of the two reaction patterns.

Antigens, Neoplasm↗
PubMed1978

[Aging changes of passive electrical and mechanical properties of human skin (author's transl)].

Mechanical and electrical properties of human skin are definable by a apparatus, developed by Pliquett and Rollius (1975). Using this method was determined a value, correlate to the product of the elasticity and the electrical conductance on 90 healthy persons. This value depends in a characteristically way on age, with a maximum near 25 and 55 years. The amount of the maximum depends on sex and profession of the probands.

Adolescent↗
PubMed1977

[Passive electrical investigations on erythrocytes in dependence of age donars (author's transl)].

It was shown by passive electrical investigations, that the behavior of electrical relaxations of red cells depends on age. With increasing age of the human the relaxation time as well as man the exchange effect stability be increased. This results are due to the increasing of the volume and the contents of haemoglobin of the erythrocytes, and may be due to the changing of the charge of the membrane.

Adult↗