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Biomedical subjects

E Unger

Publications and source records attributed to E Unger.

At least 109 records · Page 6Linked to original sources
PubMed1990

Effect of MAP 1, MAP 2, and tau-proteins on structural parameters of tubulin assemblies.

When temperature-dependent recycling procedures for purification were used, tubulin is usually accompanied by a mixture of microtubule-associated proteins (MAPs) primarily comprising MAP 1, MAP 2, and the tau-proteins. Formerly we reported that microtubules formed from tubulin in the presence of these MAPs have more protofilaments than those formed without MAPs. Furthermore, these MAPs suppress the formation of aberrant assemblies (Böhm et al., BBA 800, 119, 1984). Now, we report that each single MAP fraction is able to influence the protofilament number of microtubules and the ratio between aberrant assemblies and microtubules in the same manner as the MAP mixture. This implies that all the MAPs investigated play a certain role in lateral association of tubulin dimers.

Animals↗
PubMed1990

[SEM studies on IFN-receptor dynamics of cultured cells from mammals].

Visualization of rIFN-alpha 1 and -alpha 2 receptors on MDBK-cells was done by means of a two step method with gold-labelled monoclonal anti IFN-antibodies in the SEM. This binding showed a marked dependency from the temperature, concentration of the rHu-IFN, prefixation of the MDBK-cells, and time of incubation. This results are in agreement with findings of classical virological methods. By means of SEM was shown that the distribution and amount of the IFN-receptors on MDBK-cells depends strongly on the cell cycle and that not each was labelled. The results were discussed in connection with structural-functional alterations of the cytoskeleton.

Animals↗
PubMed1990

Nucleation of macrotubules on double-walled microtubule seeds.

It is known that histone H1 is able to cause the formation of double-walled microtubules from microtubule protein. Now, we demonstrate that in dependence on the mass ratio H1/microtubule protein upon addition of tubulin to short pieces of double-walled microtubules either their inner or their outer wall elongates resulting in normal microtubules or in macrotubules, respectively. Because of their genesis we suggest that macrotubules like double-walled microtubules (see Unger et al., Eur. J. Cell Biol. 46, 98-104 (1988)) expose those sides of tubulin dimers at their surface which usually form the lumen face of microtubules.

Animals↗
PubMed1989

Liposomal Gd-DTPA: preparation and characterization of relaxivity.

Gadolinium diethylenetriaminepentaacetic acid (DTPA) has not proved particularly useful for hepatosplenic magnetic resonance imaging. However, by entrapping the Gd-DTPA within lipid vesicles, one may exploit the ability of the reticuloendothelial system to endocytose particulates, permitting passive delivery of contrast agent to the liver and spleen while decreasing the rate of clearance of Gd-DTPA from the vasculature. Liposomes of 70-400 nm diameter containing Gd-DTPA were prepared by a freeze-thaw extrusion process. These exhibited high trapping efficiencies and excellent stability during storage. For all sizes of liposomes, the relaxivity of the entrapped Gd-DTPA was less than that of free Gd-DTPA. Relaxivity varied linearly with the surface-area-to-volume ratio of the liposomes; the smaller the liposomes, the greater the relaxivity. Liposomes containing cholesterol had a lower relaxivity than liposomes without cholesterol. The authors suggest this reflects the decrease in the water permeability coefficient caused by the presence of cholesterol in the liposome membrane.

Contrast Media↗
PubMed1988

Gadolinium-DTPA liposomes as a potential MRI contrast agent. Work in progress.

To evaluate the use of liposomes containing Gadolinium-DTPA (Gd-DTPA) as potential intravascular contrast agents, we synthesized and tested Gd-DTPA liposomes. A freeze-thaw extrusion process was used to synthesize neutral unilamellar vesicles. Using this technique, we prepared 0.4 micron vesicles with encapsulation efficiency as high as 39% for Gd-DTPA. In vitro dialysis showed that essentially 100% of the Gd-DTPA was retained with the liposomes after 72 hours of dialysis. MR imaging of in vitro samples showed concentration-dependent increase in signal intensity with Gd-DTPA liposomes. Imaging of rats after intravenous injection of Gd-DTPA liposomes showed sustained intravascular contrast enhancement of vascular structures and liver greater than free Gd-DTPA. There was no evidence of acute toxicity in rats during the imaging experiments or on follow-up of two months. Paramagnetic liposomes may be useful to enhance the vasculature, liver, and spleen.

Animals↗
PubMed1988

Diagnosis of osteomyelitis by MR imaging.

Bone scans are highly sensitive for the diagnosis of acute osteomyelitis, but the difficulty of separating bone-marrow processes from soft-tissue disease limits the specificity and accuracy. A diagnostic technique capable of distinguishing bone-marrow processes from soft-tissue disease would improve the diagnostic accuracy of osteomyelitis. To evaluate the use of MR in the diagnosis of osteomyelitis, MR examinations were performed in 35 patients with suspected acute osteomyelitis. Twelve of these were proved to have osteomyelitis either by surgery (nine patients) or by clinical follow-up (three patients). In the other 23, osteomyelitis was excluded by surgery (12 patients) or by the clinical course (11 patients). Evidence of osteomyelitis on MR consisted of abnormalities of the bone marrow with decreased signal intensity on the T1-weighted images and increased signal intensity on the T2-weighted or short-T1 inversion recovery (STIR) images. MR and bone scintigraphy were interpreted by two radiologists who were given no clinical information other than to rule out osteomyelitis. The sensitivities of MR and static bone scan were 100% for bone-marrow abnormality. Because bone-marrow abnormality in osteomyelitis associated with healing fractures was incorrectly diagnosed by MR (one case) and bone scintigraphy (two cases), the sensitivities of MR and scintigraphy for the diagnosis of osteomyelitis were 92% and 82%, respectively. The specificities of MR and scintigraphy were 96% and 65%, respectively (p less than .05). The overall accuracy for the diagnosis of osteomyelitis was 94% for MR and 71% for bone scan (p less than .05). Because of its ability to separate soft-tissue disease from underlying bone marrow, MR may be used to evaluate patients with positive bone scintigraphy to improve the specificity and accuracy of diagnosis for osteomyelitis.

Acute Disease↗
PubMed1988

Formation of double-walled microtubules and multilayered tubulin sheets by basic proteins.

Some basic proteins enable microtubule protein to form special assembly products in vitro, known as double-walled microtubules. Using histones (H1, core histones) as well as the human encephalitogenic protein to induce the formation of double-walled microtubules, we made the following electron microscopic observations: (1) Double-walled microtubules consist of an "inner" microtubule which is covered by electron-dense material, apparently formed from the basic protein, and by a second tubulin wall. (2) The tubulin of the second wall seems to be arranged as protofilaments, surrounding the inner microtubule in a helical or ring-like manner. (3) The surface of double-walled microtubules lacks the projections of microtubule-associated proteins, usually found on microtubules. (4) In the case of protofilament ribbons (incomplete microtubules), H1 binds exclusively to their convex sides that correspond to the surface of microtubules. Zn2+-induced tubulin sheets, consisting in contrast to microtubules of alternately arranged protofilaments, are covered by H1 on both surfaces. Furthermore, multilayered sheet aggregates appeared. The results indicate that the basic proteins used interact only with that protofilament side which represents the microtubule surface. In accordance with this general principle, models on the structure of double-walled microtubules and multilayered tubulin sheets were derived.

Animals↗
PubMed1987

Structural dynamics within mixed populations of microtubules and protofilament ribbons.

In the presence of glycerol, microtubule proteins reassemble into both microtubules and protofilament ribbons with C- and S-shaped cross-section profiles. By means of electron micrographs of cross-sectioned assemblies, we have demonstrated that, during the steady state, the percentage of ribbons, especially of C-shaped ones, decreases in favour of the formation of microtubules. The following conversion modes are discussed: A, closure of the protofilament wall by increasing its curvature; B, lateral association of C-ribbons; C, completion of C-ribbons to microtubules by lateral association of tubulin; D, disassembly of ribbons and elongation of microtubules. We conclude that ribbon disassembly proceeding in an end-wise fashion and microtubule elongation is the favoured mode of conversion. Microtubule-associated proteins were found to be required for the steady-state conversions of ribbons into microtubules. In the absence of microtubule-associated proteins, C-ribbons associate laterally, forming S-ribbons. It is shown that the protofilaments of the counter-curved parts of S-ribbons have the same polarity.

Alkaloids↗
PubMed1987

CT-guided laser therapy in resistant human tumors: phase I clinical trials.

Photodynamic therapy was performed on ten tumors in patients who did not respond to initial therapy and for whom no additional conventional therapy was available. A sensitizing agent (hematoporphyrin derivative [HpD]) was injected directly into each tumor under computed tomographic (CT) guidance to deliver high concentrations to the tumor and to minimize systemic toxicity. Three to 6 days after the injection, a clear Teflon sheath catheter was placed into the tumor under CT guidance. The tumor was exposed to red light (630-nm wavelength) through laser fiberoptics inserted in the sheath. The initial investigation confirmed the technical feasibility of CT-guided photodynamic therapy by means of intratumoral HpD injections and laser exposure through fiberoptics inserted in sheath catheters. The toxicity from a single treatment was minor, and the tumor response was encouraging.

Catheterization↗
PubMed1987

Histological examination of combined effects of chemotherapeutical agents and differently fractionated irradiations in transplanted solid Ehrlich carcinoma of mice. III. Observations after vincristine treatment.

Vincristine treatment alone does not evoke estimable histological damage in solid Ehrlich carcinoma. However, when combined with fractionated local X-irradiation it causes more severe damage than the irradiation alone, consequently vincristine has a synergistic effect in radiation therapy. Comparing the effects of irradiation of the same total dose fractionated differently and combined with vincristine, one cannot find any characteristic and consequent histological differences.

Animals↗
PubMed1987

Histological examination of combined effects of chemotherapeutic agents and differently fractionated irradiations in transplanted solid Ehrlich carcinoma of mice. II. Observations after dibromodulcitol treatment.

Dibromodulcitol treatment induced histological damages in solid Ehrlich carcinoma which increased on the effect of parallelly applied local fractionated X-irradiation. Comparing the effect of differently fractionated irradiations of the same total dose combined with dibromodulcitol treatment it can be stated that daily applied low radiation fractions cause more severe histologically demonstrable damage than relatively higher ones given in three to four day intervals.

Animals↗
PubMed1986

Ytterbium-DTPA. A potential intravascular contrast agent.

Ytterbium-DTPA was evaluated as a potential intravascular contrast agent. Ytterbium-DTPA was synthesized from ytterbium oxide and diethylene triamine penta-acetic acid (DTPA). CT scans of increasing concentrations of ytterbium and iodine showed that at 125 kVp, ytterbium was denser than an equal concentration of iodine. The LD50 of intravenous ytterbium-DTPA was 10 mM/kg (1.73 g ytterbium/kg) in rats. In enhanced CT scans and pulmonary angiography in dogs, ytterbium was visibly denser than iodine, and CT Hounsfield units showed greater enhancement of the aorta and inferior vena cava with ytterbium. The animals showed no sign of acute or delayed toxicity. Ytterbium-DTPA deserves further evaluation as a contrast agent for high kVp techniques.

Animals↗
PubMed1986

Factors regulating microtubule structure--a minireview.

The pathway of tubulin assembly is controlled by a lot of effectors. We summarize some of these effectors favouring the formation of microtubules or inducing several MT-aberrant, polymorphic structures. Both in vivo and in vitro, microtubules with different protofilament numbers were found. In vivo, microtubules are composed of 11-16 protofilaments. The protofilament number of microtubules formed in vitro varies from 8-17. We describe some effectors responsible for the diversity of the protofilament number in microtubules. Moreover, differences in the amino acid sequences of distinct tubulins should be taken into account, too. The protofilament number of an established microtubule can be still altered if activities of effectors or microenvironmental conditions are changed. Thus, the protofilament number of microtubules is a dynamic property based on the permanent tubulin exchange.

Amino Acid Sequence↗
PubMed1986

Histological examination of combined effects of chemotherapeutical agents and differently fractionated irradiations in transplanted solid Ehrlich carcinoma of mice. I. Observations after adriamycin treatment.

4 X 3 mg/kg body weight adriamycin treatment induced histological damages in solid Ehrlich carcinoma, which increased on the effect of the parallel applied 10 X 5 Gy dose local fractionated X-ray irradiation. Comparing the effect of differently fractionated irradiations of the same total dose combined with adriamycin treatment, it can be stated that daily given less radiation fractions induce more severe damage than relatively higher ones applied in three to four days interval.

Animals↗
PubMed1985

Heparan sulfate proteoglycans are concentrated on the sinusoidal plasmalemmal domain and in intracellular organelles of hepatocytes.

The distribution of cell surface heparan sulfate proteoglycans (HSPGs) was determined in rat liver by immunocytochemistry. A polyclonal antibody was raised against HSPGs purified from rat liver microsomes which specifically immunoprecipitated liver membrane HSPGs. It was shown to recognize both the heparin-releasable and membrane-intercalated form of membrane HSPGs and to recognize determinants on the core protein of these HSPGs. By immunocytochemistry membrane HSPGs were localized to hepatocytes. The distribution of HSPGs at the cell surface of the hepatocyte was restricted to the sinusoidal domain of the plasmalemma; there was little or no staining of the lateral or bile canalicular domains. Intracellularly, HSPGs were occasionally detected in cisternae of the rough endoplasmic reticulum and were regularly found in Golgi cisternae--usually distributed across the entire Golgi stack. HSPGs were also localized in some endosomes, lysosomes, and cytoplasmic vesicles of hepatocytes. We conclude that the HSPGs recognized by this antibody have a restricted distribution in rat liver: they are largely confined to the sinusoidal plasmalemmal domain and to biosynthetic and endocytic compartments of hepatocytes.

Animals↗