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Biomedical subjects

I Uerlings

Publications and source records attributed to I Uerlings.

At least 19 recordsLinked to original sources
PubMed1992

Primary phase of hepatocytic autophagocytosis under ischaemic conditions.

Increased autophagocytosis in hepatocytes was found in response to conditions of ischaemia/hypoxia. Initial stages proved to be recordable. These were found to become manifest through the formation of phospholipid membrane structures, approximately 5 nm in width, coalescing in circular formations with vesicular extensions. They may further develop to form multilayer myelin structures. Enveloped cytoplasmic regions and organelles were unchanged, at the beginning, and subsequently coalesced typically into autophagolysosomes and autophagic vacuoles. Verification will be necessary to find out if these initial stages occur only in response to hypoxia or constitute a phenomenon of general validity.

Animals↗
PubMed1992

[Ultrastructure of amitosis and mitosis of the liver].

Thousands of liver cells of several ultrastructural investigation programs of our laboratory have been evaluated in respect to amitosis and mitosis. Multiplication of hepatocytes by amitosis and mitosis often leads to bi-, tri- and multinucleated cells. No striking ultrastructural changes have been observed in the hepatocytes of human and animal livers. There are no indications of enhanced autophagocytosis or other signs of dedifferentiation. However, non-hepatocytes suffer ultrastructural changes during mitosis: endothelial cells reduce their organelles in number, round up their shape and form microvilli reaching between the microvilli of hepatocytic sinusoidal membrane. Mitotic Kupffer cells contain only small phagosomes and are separated from hepatocytes by endothelial cell processes.

Animals↗
PubMed1992

[Nuclear ultrastructure of binuclear and trinuclear hepatocytes].

Binucleated and less frequently trinucleated hepatocytes appear in human and animal livers under normal conditions as well as in pathological cases. To provide further ultrastructural data hepatocyte nuclei were investigated in different pathological states. Important results of this study are: Size of the nuclei and structure of the karyoplasm as well as size and localization of the nucleolus are obviously, same in most of the binucleated hepatocytes. In a small percentage of hepatocytes the following findings have been made: One of the nuclei will be light microscopically overlooked due to its small size pretending mononucleated cells. The disappearance of one of the nuclei results in an increase of the number of mononucleated cells and should therefore be evaluated like a decrease of binucleated hepatocytes: a pathological incident. Functional differences between both nuclei become morphologically obvious during virus replication, e.g. HBc-particle production is restricted to one of the nuclei. These results seem to consist rather with amitotic than mitotic cell division.

Cell Nucleus↗
PubMed1991

Electron microscopy of liver in patients with chronic haemodialysis.

Liver biopsies were performed on 18 haemodialysis patients with clinically as well as clinico-chemically altered liver values and partially positive HBV marker serology, with the view to comparing these values with ultrastructural findings in correlation with histological and immunohistological results. The following characteristic combination of findings was recorded at ultrastructural level: hypertrophy and hyperplasia of agranular endoplasmic reticulum of hepatocytes, haemosiderin deposits in Kupffer cells and hepatocytes, invasion of lymphocytes into Disse and intercellular spaces; megamitochondria in hepatocytes and perisinusoidal fibrosis established in some cases. The same findings proved to be recordable in histological diagnosis of hepatitis or toxico-metabolic liver damage. The study shows that inflammatory lesions are not all the only causes for haemodialysis-related changes in clinico-chemical values, so that liver biopsies together with ultrastructural investigations are indicated for differential diagnosis.

Adult↗
PubMed1989

[Ultrastructure of intralobular lymphocyte migration in the liver of hemodialysis patients].

Presence of predominantly small lymphocytes in sinusoids and their immigration into the Disse space as well as into intercellular spaces between hepatocytes were recorded by electron microscopy from liver biopsies of 11 in 18 haemodialysis patients. No degenerative alterations were recordable from adjacent hepatocytes. These findings were obtained from patients with acute hepatitis (one case), minimal or chronic persistent hepatitis (two cases), reactive hepatitis (three cases), lobular and portal hepatitis (one case) as well as from the cases of metabolic-toxic alterations and one case of chronic blood congestion. HBV antigens were serologically identified in six cases. A HBcAg-free HBsAg type was immunohistologically diagnosed in one case only. No correlation was found to exist between the morphological results, on the one hand, and cellular immune pattern in peripheral blood, on the other. The above findings differed from most investigations of hepatitis B cases, in that no evidence could be found to cytotoxic action of lymphocytes upon adjacent hepatocytes. More investigations will be required for interpretation of the above findings, primarily immuno-electron microscopic studies.

Cell Movement↗
PubMed1989

Changes in the nucleotide metabolism of Ehrlich ascites tumour cells during their growth in vivo.

During the transition of Ehrlich mouse ascites tumour cells from the proliferating into the resting phase of growth a tremendous loss of purine and pyrimidine compounds was quantitated by ion-pair reversed-phase high performance liquid chromatography. This change is accompanied by a distinct decline in the incorporation rates of adenine, hypoxanthine, and adenosine. Inorganic phosphate stimulates the low rate of hypoxanthine incorporation of cells in the plateau phase, but lacks any effect on the high rate during proliferation. The mitochondria suffer structural deteriorations and decrease in their cellular content in the course of the plateau phase; however, other changes were not seen by morphometric analysis. The interrelations between nucleotide metabolism, mitochondrial content and the rates of formation and consumption of ATP are discussed.

Adenine↗
PubMed1988

Pathology of hepatic peroxisomes in chronic hepatitis B and immunosuppression.

After kidney transplantation and immunosuppressive therapy patients with chronic hepatitis B show not only peroxisome proliferation in hepatocytes but also additional alterations of these organelles: lysis and occasional complete loss of peroxisomes in HBsAg areas as well as lysis and/or autophagocytic degradation of peroxisomes in hepatocytes which contained hepatitis-B virus particles. Two mechanisms are suggested as being significant for the numerical decrease of peroxisomes in HBsAg areas: Reduced neogenesis, but typical lytic degradation; Direct toxic action of immunosuppressive substances. For elucidation further studies have to be undertaken.

Autophagy↗
PubMed1987

The perisinusoidal functional unit in amyloidosis.

The close morphological and functional relations between the various components of the perisinusoidal functional unit may be demonstrated by combination of ultrastructural results with the latest findings in the context of intra-hepatic synthesis and transformation of amyloid. The precursors of amyloid, synthesised in hepatocytes in the region of the endoplasmic reticulum, lysosomes, and plasma membrane of the vascular pole, are moved into the vascular system together with high-density lipoproteins which are probably identical with lipoprotein vesicles close to plasma membranes and in Disse space, and in the vascular system they are transformed to Serum Amyloid A (SAA). A certain role is probably played by Kupffer cells in polymerisation of amyloid A to fibrils. Growing accumulation of fibrils causes ligature and melt-off of peripheral parts from the vascular pole of hepatocytes, with its volume being substantively reduced, so that the spacing between plasma membrane and nucleus may reduce from something between 10 and 12 micron to below 1 micron. There is neither any compression of cytoplasm nor translocation of organelles. Hence, the process can be interpreted as a specific form of atrophy.

Amyloid↗
PubMed1986

Preservation damage in liver transplantation. Influence of rapid cooling.

Liver preservation and transplantation was performed in pigs. For flush perfusion cold (2 degrees C) and warm (15 degrees C) lactated Ringer's solution were compared. Administration of cold Ringer's resulted in a severe endothelial damage of sinusoids that was aggravated after recirculation, as shown by electron microscopic examination. Using warm Ringer's solution this alteration was limited. Liver parenchymal cells are impaired mainly during reflow as a consequence of microcirculatory disturbance. After cold flushing animals died within a few hours, whereas after flushing with warm Ringer's solution pigs survived definitively.

Animals↗
PubMed1986

[The sinusoid wall of the liver in viral infections].

The elements of the "peri-sinusoidal functional complex" (i.e. non-hepatocytes, space of Disse, vascular pole of hepatocytes) can react to the presence of virus in the sinusoidal blood stream by retaining viruses, sometimes followed by viral proliferation, by reactive proliferation, or by degenerative changes in the cells which may culminate in cell death. Immune processes may be also activated or alternatively, there may be no response whatever to the viremia. In hepatitis B infection the principal changes are in the Kupffer cells and in the vascular pole of the hepatocytes. Along with immunologic responses there are proliferative and degenerative events in the Kupffer cells, which may deleteriously affect the sinusoidal cell membrane of the hepatocytes. These factors, as well as the receptor structure of these cell membranes, are regarded as responsible for the uptake of virus in the hepatocyte. Cytotoxic T-cells which have migrated to the region also play a role in the overall process. The point should be made, however, that these concepts are largely hypothetical and that hepatitis B virus particles have yet to be demonstrated in the peri-sinusoidal complex.

Animals↗
PubMed1985

Alteration of the ultrastructure of the pig liver after a continuous perfusion of six hours in vitro.

Livers of mini LEWE pigs were perfused continuously for 6 h on a novel perfusion system through the portal vein (laminar flow from 200 to 300 ml/min, pressure 270 Pa) and through the A. hepatica (pulsating flow from 100 to 200 ml/min, pressure: 10.6/5.5 kPa). The following perfusion media were used for determining the best conservation conditions at 10 to 12 degrees C: Pig blood/Krebs-Henseleit bicarbonate buffer 1:1; Pig blood/Ringer lactate solution 1:1; Pig plasma; Collins C 2 perfusion solution. After perfusion with Collins C 2 solution the hepatocytes show swelling and dilation of the granular endoplasmic reticulum; after perfusion with the other solutions the changes of the hepatocytes are negligible. The alterations of the sinusoidal wall cells depend on the perfusion pressure and flow and the composition of the solution. After continuous perfusion the sinusoidal walls are characterized by vesicles of endothelial cells, dilatation of the Disse space and fragmentation of hepatic microvilli.

Animals↗
PubMed1983

Quantitative ultrastructure of the rat liver by immersion and perfusion fixations.

Morphometric and qualitative investigations of rat liver with immersion fixation (I) and perfusion fixation (P) have not produced any statistically significant differences in the volume densities and numbers per area of elements of hepatocytes: Vv mitochondria: 0.194 (I), 0.189 (P); peroxisomes 0.011 (I), 0.012 (P); glycogen 0.196 (I), 0.183 (P); agranular endoplasmic reticulum 0.144 (I), 0.183 (P); granular endoplasmic reticulum and groundplasm 0.455 (I), 0.437 (P). The numbers per unit area (micrometers 2) for the mitochondria are 0.492 (I) and 0.496 (P), and for the peroxisomes 0.048 (I) and 0.044 (P), respectively. From the results, the following conclusions can be drawn: -- There are no differences in qualitative and quantitative findings as to the preservation of the hepatocytes by immersion and perfusion fixation. Immersion fixation can be applied as analogous and equivalent methods in routine investigations of human excision and bioptic tissues and also of very large and very small organs. -- Ischemic autolytic alterations of the cells, especially in the mitochondria occur: with immersion fixation in the surface zone and the central zone of the specimen (the intermediate zone is well preserved), with perfusion fixation in different areas. -- Alterations in the sinusoidal wall affect the width of the lumen and the openings of the endothelial cells which show better conditions at optimum pressure and flow rate of the perfusion fluid. -- Pronounced alterations in the endothelial cells, partially the total destruction and detachment are caused by non-optimal pressure and flow rates of the perfusion. They may appear, however, as secondary results caused by the composition of the fluid or circumscribed constrictions of the vascular system of the liver. -- With regard to the transplantology of the liver the studies on the perfusion fixation demonstrate the importance of pressure, flow rate and composition of the perfusion fluid for preserving the tissue, especially the sinusoidal wall.

Animals↗
PubMed1981

Electron microscopic evidence of circular molecules in 9-S globin mRNA from rabbit reticulocytes.

9S globin mRNA prepared by the proteinase K method from polysomes of rabbit reticulocytes consists of 40% circular molecules as revealed by electron microscopy, if spreading of the molecules is performed from a solution of 50% formamide, 0.5 M NaCl, 25 mM Tris, 10 mM EDTA, pH 8, after 16 h incubation at 42 degrees C. We assume a noncovalent nature of the circularization because of the fact that a total transformation into the well known linear form occurs if strong denaturing conditions for spreading were used. The biological significance of the circular globin mRNA molecules is unknown.

Animals↗
PubMed1979

[Electron microscopic preparation of DNA on uncharged carbon films (author's transl)].

DNA is adsorbed with densities sufficient for electron microscopy on thin uncharged carbon films. Superhelical SV 40 DNA remains superhelical on the supporting film on the contrary to the relaxation of DNA on films treated with alky dimethylbenzyl ammonium chloride (BAC). The number of superhelical turns increases to the two- or threefold of the value in solution. Investigations with a structural resolution below 1nm are possible with this preparation method.

Animals↗
PubMed1977

[Chacterization of human reticulocytes: respiration, Pasteur effect, and electron microscopic findings on mitochondria].

On 5 blood samples of newborns, whose reticulocytes had been enriched by density gradient centrifugation, and on 25 blood samples of different reticulocytoses of man were determined: the extent of intra- and extramitochondrial respiration, coupling of the electron transfer with the oxidative phosphorylation and the electronmicroscopic appearance, and the number of mitochondria. The reticulocytes occurring in the flowing human blood are in general relatively stiff and are characterized by the following properties:--low respiration--low capacity of the respiratory chain enzymes--weakened Pasteur effect --varying proportion of intramitochondrial respiration and total respiration--decoupling of a major part of the intramitochondrial respiration--low number of mitochondria--qualitative changes of mitochondria. However, there are situations of erythropoiesis where immature reticulocytes are discharged in man (similar to the socalled "stress reticulocytes" of rabbits). On the other hand, it could be shown that the reticulocytes of rabbits are mature in the normal state.

Animals↗