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Biomedical subjects

A Herrmann

Publications and source records attributed to A Herrmann.

At least 181 records · Page 10Linked to original sources
PubMed1985

The effect of osmotic pressure of aqueous PEG solutions on red blood cells.

A drastic increase of the intracellular microviscosity of red blood cells in the presence of polyethylene glycol (PEG) was established by electron spin resonance using the small spin label molecule 2,2,6,6-tetramethyl-piperidine-N-oxyl-4-one (TEMPONE). The effective osmotic pressure of PEG solutions stressing the cells was estimated by comparison with those cytoplasmic rotational correlation times of TEMPONE measured in NaCl or sucrose containing media of known osmotic pressure.

Electron Spin Resonance Spectroscopy↗
PubMed1985

A new embedding and sectioning technique (macrovibratome) for macroscopic and morphometric examinations especially of the human brain.

The macrovibratome is a newly developed sectioning apparatus designed especially for the preparation of human brain material subject to macroscopic and morphometric examinations. The brain is embedded in an aqueous agar solution and cut into slices with a minimum thickness of 2 mm. Using a 20% or 40% gelatin solution as the embedding material results in an average shrinkage of the tissue blocks of 9.8 or 31.7% in volume, respectively. With a 3% agar solution the volume shrinkage lies on the average at 1.0% for smaller brain pieces and 4.5% for cerebra.

Agar↗
PubMed1984

The influence of Ca2+ on the lateral lipid distribution and phase transition in phosphatidylethanolamine/phosphatidylserine vesicles.

The lateral lipid distribution within dipalmitoylphosphatidylethanolamine (DPPE)/dipalmitoylphosphatidylserine (DPPS) vesicle membranes was investigated under the influence of Ca2+ using a lipid cross-linking method. To characterize the phase transition in DPPE/DPPS vesicles and to correlate the different phase states of the membrane lipids with the obtained lipid distribution ESR measurements using a fatty acid spin label were carried out. It is shown that Ca2+ has a significant influence on the lateral lipid distribution within the fluid phase of the membrane lipids; instead of a slight alternating lipid arrangement in absence of Ca2+ due to the electrostatic interaction between the DPPS headgroups after addition of Ca2+ a lateral cluster structure is characteristic of the fluid phase.

Calcium↗
PubMed1984

Effects of the antiandrogen, cyproterone acetate, on the induction of papillomas, DNA synthesis and ornithine decarboxylase activity in mouse skin.

The antiandrogen, cyproterone acetate (CPA), applied simultaneously with 12-O-tetradecanoylphorbol-13-acetate (TPA) to the dorsal skin of male and female SENCAR mice initiated with 7,12-dimethylbenz[a]anthracene inhibited the production of papillomas of the skin. Although 125 and 250 micrograms of CPA had no effect on the incidence of papillomas per mouse, 500 micrograms of CPA inhibited papilloma production by 95% and 91% in female mice after 20 and 37 weeks of promotion, respectively. Testosterone propionate only partially blocked the inhibitory effect of CPA. In male mice 500 micrograms and 1 mg of CPA inhibited papilloma production by 77% and 88%, respectively. In the two-stage promotion protocol 500 micrograms of CPA was ineffective as an inhibitor when it was applied with TPA during the 1st stage but inhibited papilloma production by 71% when it was applied with mezerein during the 2nd stage. CPA was also observed to inhibit TPA-stimulated epidermal DNA synthesis and inflammation but had no effect on TPA-induced epidermal ornithine decarboxylase activity.

Androgen Antagonists↗
PubMed1984

[Volume conduction in the electroneurographic study of arm and leg nerves].

Two arm and two leg nerves in each of a group of healthy subjects were stimulated electrically and the muscle action potentials were taken from the corresponding regions by surface electrodes. Volumetrically conducted potentials appeared in almost all cases, and other nerves were stimulated at the same time in many cases. The resultant errors in the calculation of the speed of pulse transmission are considerable. The use of a concentric needle electrode is recommended for recording evoked muscle action potentials.

Arm↗
PubMed1984

Interaction of fusogen substances with the erythrocyte membrane.

The influence of the fusogen substances poly-(ethylene glycol) (PEG) and linoleic acid on the dynamics and structure of the erythrocyte membrane was studied. Linoleic acid disturbs the lipid matrix and nonlamellar structures were formed. PEG affects the stability of membranes by changing the polarity of the aqueous medium and the hydration state of membrane lipids and proteins.

Cell Fusion↗
PubMed1983

Effect of poly(ethylene glycol) on the polarity of aqueous solutions and on the structure of vesicle membranes.

The partitioning of TEMPO into phosphatidylcholine vesicle membranes is reduced upon addition of poly(ethylene glycol). This is caused by reduced polarity of the aqueous phase as well as decreased membrane fluidity in the presence of poly(ethylene glycol). The isotropic hyperfine splitting of TEMPO in aqueous poly(ethylene glycol) solutions was used as a measure of solvent polarity. The alterations of the membrane fluidity were detected by means of two different fatty acid spin labels. The influences of physicochemical properties of an aqueous poly(ethylene glycol) phase on the membrane structure of cells and vesicles are discussed in the light of membrane fusion.

Cyclic N-Oxides↗
PubMed1983

Lateral lipid distribution and phase transition in phosphatidylethanolamine/phosphatidylserine vesicles. A cross-linking study.

To determine the nonideal mixing of two lipid components within the membrane, lipid cross-linking experiments were carried out on dipalmitoylphosphatidylethanolamine (DPPE) vesicles and on dipalmitoylphosphatidylethanolamine/dipalmitoylphosphatidylserine (DPPE/DPPS) vesicles. By comparison of the cross-linking reactions on both types of vesicle the mean neighbourhood relations within the binary lipid mixture can be obtained. To elucidate the relationship between cluster formation and phase transition, the temperature dependences of the lipid arrangement within the vesicle membrane and of the lipid order parameter describing the fluidity of the membrane were measured. Cluster size and phase transition correlate: during the phase transition of the lipid species with the lower phase-transition temperature (DPPS) the nonideality of the mixture increases by phase separation. Above the phase transition temperature of the second lipid species (DPPE) the clusters disappear and a slight alternating lipid arrangement is characteristic of the fluid phase.

Chemical Phenomena↗
PubMed1983

Influence of polyethylene glycol on the structure of the erythrocyte membrane: an ESR study.

Using a fatty acid spin label (I (10, 3)) it was found that the membrane fluidity of intact human erythrocytes is not influenced by polyethylene glycol (PEG) up to a concentration of 10 wt%. On the contrary a drastic effect of PEG on the spectrum of maleimide spin labeled membrane proteins of erythrocyte ghosts were detected. It is suggested that aggregation and/or conformational changes of membrane proteins were induced by PEG.

Blood Proteins↗
PubMed1982

Herpes simplex virus subunit vaccine: characterization of the virus strain used and testing of the vaccine.

Herpes simplex virus type 1 (HSV-1) used for vaccine production was isolated from a nasal recurrent infection and propagated over a limited number of passages in human diploid cells only. It was designated as HSV-1 BW3 and has been characterized by neutralizing antibodies as a typical HSV type 1 strain. In vitro transformation studies performed with this isolate in mouse or hamster cells revealed only very low, if any, transforming capacity. A preparation of HSV-1 BW3 which can be used as seed lot for vaccine production has been proven to be free of any adventitious agents such as bacteria, fungi mycoplasma or viruses other than HSV-1 BW3. An envelope antigen (EAG) preparation was obtained from purified HSV-1 particles. It was free of detectable viral DNA and could be proven to be efficacious in mouse models against challenge infections with either HSV-1 or HSV-2. The potency of the vaccine was greatly enhanced by the addition of poly-inosinic-poly-cytidylic acid complexed with poly L-lysine and carboxymethylcellulose (PICLC) as adjuvant. A single vaccine dose was sufficient to protect mice from morbidity and the fatal outcome of HSV infection, but not from the establishment of latency. Persistent ganglionic infections could be, however, significantly reduced by repeated administration of the vaccine before primary infection.

Adult↗
PubMed1982

Different volume changes of cerebral cortex and white matter during histological preparation.

In quantitative neuroanatomy and neuropathology, large neuronal systems are frequently analyzed on the basis of small tissue blocks thus assuming that the volume changes of the various compartments of the tissue block can be corrected by an overall factor. 228 blocks of cerebral cortex and white matter of the frontal lobe, thalamus, and striatum were prepared from 13 human brains and embedded in paraffin. The mean shrinkage in the paraffin sections was found to be 51% for the cerebral cortex and 42% for the white matter. Therefore, an overall correction factor tissue blocks both with cerebral cortex and white matter results in an underestimation of cerebral cortex and an overestimation of white matter.

Adult↗
PubMed1982

Structural transitions of the erythrocyte membrane: an ESR approach.

The effect of temperature and ionic strength on the ESR spectrum of the fatty acid spin label I (10,3) in membranes of freshly drawn human red blood cells has been investigated. The results suggest that the microviscosity of the membrane is not strongly influenced by the ionic strength. Discontinuities at various temperatures could be observed, which disappear after cholesterol treatment. The possible role of membrane lipids and proteins on the thermotropic membrane behaviour observed is discussed. It is assumed that the spectra are averaged signals from different regions of the membrane.

Blood Sedimentation↗
PubMed1981

Alterations in polyamine levels induced by phorbol diesters and other agents that promote differentiation in human promyelocytic leukemia cells.

Polyamine levels were evaluated in human HL-60 promyelocytic leukemia cells after treatment with inducers of terminal differentiation. Differentiation in these cells was determined by increases in the percentage of morphologically mature cells and in lysozyme activity. Treatment of the HL-60 cells with phorbol 12-myristate-13-acetate (PMA), phorbol 12,13-didecanoate or other inducers of terminal differentiation such as dimethylsulfoxide and retinoic acid resulted in increased levels of putrescine. However, no increase in putrescine could be detected after PMA treatment of a HL-60 cell variant that exhibited a decreased susceptibility to PMA-induced terminal differentiation. Similarly, no increase in putrescine was observed with two non-tumor-promoters (phorbol 12,13-diacetate and 4-O-methyl-PMA) or with anthralin, a non-phorbol tumor promoter. In addition to enhancing putrescine levels, PMA also increased the amount of spermidine and decreased the amount of spermine. The increase in putrescine and spermidine preceded the expression of the various differentiation markers. Unlike the changes observed in the polyamine levels after PMA treatment, the activities of ornithine and S-adenosylmethionine decarboxylases, which are polyamine biosynthetic enzymes, did not significantly change. alpha-Methylornithine and alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone), which are inhibitors of the polyamine biosynthetic enzymes, did not affect differentiation in control or PMA-treated cells. Because of these observations, we suggest that the change in polyamine levels involve biochemical pathways other than the known biosynthetic ones. By-products of these pathways may perhaps be the controlling factors involved in the induction of terminal differentiation in the HL-60 and other cell types as well.

Cell Differentiation↗
PubMed1981

The influence of procaine and cholesterol on the temperature dependent sedimentation behaviour of individual human erythrocytes.

Temperature dependent sedimentation measurements of individual human erythrocytes showed an anomaly near 20 degrees C in physiological medium at pH 7,4 [2,3]. Results of investigations on the influence of procaine and cholesterol on the sedimentation behaviour are presented. The results suggest a correlation to the thermotropic properties of membrane lipids.

Blood Sedimentation↗