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Biomedical subjects

A Hammer

Publications and source records attributed to A Hammer.

At least 37 records · Page 2Linked to original sources
PubMed1999

Fas and Fas-ligand are expressed in the uteroplacental unit of first-trimester pregnancy.

PROBLEM: Fas and Fas-ligand (FasL) are thought to provide a strategy for reducing graft rejection in immunologically 'privileged' tissues by controlling injurious lymphocyte reactions. As the uteroplacental unit is often defined as an immune-privileged site, we investigated the expression of Fas and FasL in this tissue in the first trimester of pregnancy. METHOD OF STUDY: Western blotting, immunohistochemistry, and double immunofluorescence were used for this examination. RESULTS: Western blotting with purified first-trimester trophoblast cells revealed one specific band for FasL. The presence of FasL on different trophoblast populations could be confirmed by immunohistochemistry and double immunofluorescence. In the villous part of the placenta, FasL is mostly located on cytotrophoblast cells with no access to maternal blood flow, whereas in trophoblast-invaded uterine tissue, interstitial trophoblast cells, which are in close contact with maternal leukocytes, revealed a strong signal for FasL, but no staining for Fas on these cells. However, Fas was found on CD45+ maternal leukocytes. CONCLUSION: Based on our experimental findings, we speculate that the abundant presence of FasL on trophoblast cells within the maternal decidua may play an important role in the maintenance of immune privilege in the pregnant uterus by endowing fetal trophoblast cells with a defense mechanism against activated maternal leukocytes, whereas in the villous part of the placenta, the Fas FasL system seems to be involved in the regulation of placental growth.

Apoptosis↗
PubMed1999

Apoptotic nuclei within the uterine decidua of first trimester pregnancy arise from CD45 positive leukocytes.

PROBLEM: The Fas/Fas-ligand (FasL) system is discussed to be one of the main components responsible for the formation and maintenance of an immune privilege. As we were able to detect FasL on fetal trophoblast cells infiltrating the maternal uterine tissue and Fas on decidual leukocytes (Hammer et al., Am J Reprod Immunol, 1999; 41: 41-51), we investigated whether apoptosis occurs in the maternal decidua during the first trimester of pregnancy. METHOD OF STUDY: A TUNEL-assay was performed in combination with immunofluorescence to detect and characterize cells undergoing apoptosis. RESULTS: Apoptotic nuclei mainly arising from CD45+ leukocytes could be detected in the trophoblast-invaded decidua basalis as well as in the non-invaded decidua parietalis. However, while in the decidua parietalis the apoptotic leukocytes are scattered within the whole functional stroma, in the decidua basalis they are concentrated in the area around the so-called "necrotic foci" and especially in the primary feto-maternal contact zone. where trophoblast cells from the cell columns begin to invade the maternal tissue. CONCLUSION: Because of the irregular distribution of apoptotic CD45+ leukocytes in the decidua basalis we think that some of the maternal leukocytes are activated and killed by fetal trophoblast cells which express FasL.

Apoptosis↗
PubMed1998

HLA expression at the maternal-fetal interface.

Pregnancy in the human presents an "immunological paradox," because of the unexpected willingness of mothers to accept genetically disparate tissues. The fact that the fetus can develop unharmed for nine months shows that protective mechanisms must exist to permit its survival. The conditions that permit the genetically dissimilar human fetus to evade rejection by its mother's immune system have been the subject of intense interest for several decades. As the placental cells, which are in contact with maternal blood or tissue, are devoid of HLA class II antigens, interest has focused on the expression of HLA class I molecules. Recent developments in the constitutive, transcriptional, and translational expression of HLA class I molecules on anatomically and morphologically different subpopulations of trophoblast cells will form the basis of this short review.

Female↗
PubMed1997

Immunohistochemical examination of trophoblast populations in human first trimester and term placentae and of first trimester spiral arteries with the monoclonal antibody GZ 112.

This paper presents an immunohistochemical study with a monoclonal mouse antibody GZ 112, an IgG1 kappa, which is directed against an antigen expressed in first trimester placenta by all proliferative and invasive extravillous trophoblast populations including a population of Langhans cells that represent extravillous stem cells. Additionally, the GZ 112 antigen is associated with morphological changes of spiral arteries preceding local trophoblast invasion. In term placentae, GZ 112 also strongly reacts with all extravillous trophoblast populations, but additionally recognizes partly villous cytotrophoblast and syncytiotrophoblast too, displaying a heterogeneous staining pattern. GZ 112 is directed against a 42-KDa antigen. Intracytoplasmic network-like staining and cross-reactivity with various human surface and glandular epithelia indicate a cytokeratin intermediate filament or a cytokeratin intermediate filament associated molecule as antigen.

Animals↗
PubMed1997

Effect of oxidative stress by iron on 4-hydroxynonenal formation and proliferative activity in hepatomas of different degrees of differentiation.

It has been shown previously that oxidative stress by ferrous iron in vitro leads to an inhibition of proliferation of murine ascites tumour cells in vivo. This effect is associated with increased lipid peroxidation in terms of formation of the highly reactive aldehyde 4-hydroxynonenal (HNE), which has been shown to inhibit the proliferation of numerous tumours and to induce differentiation. It was the purpose of this article to study the occurrence and metabolism of HNE and its inducibility by oxidative stress in hepatomas of different degrees of differentiation to find further evidence for a possible role of HNE in proliferation and/or differentiation, because it is known that in hepatoma cells with a very low degree of differentiation basal lipid peroxidation is hardly detectable, while in normal hepatocytes the basal level of thiobarbituric acid reactive substances (TBArS) is rather high. MH1C1 hepatoma cells and Yoshida AH-130 hepatoma cells were chosen as highly differentiated and poorly differentiated tumour cells, respectively, and rat hepatocytes served as a control for normal liver phenotype. Ferrous histidinate (Fe/His) did not have a cytotoxic effect on Yoshida and MH1C1 cells, as measured by the LDH release test. In cell culture studies Fe/His revealed a dose dependent inhibition of the proliferation of Yoshida cells. The incorporation of 3H-thymidine into DNA of these cells was also inhibited by Fe/His in a dose-dependent manner, while the precursor uptake into the cytoplasm was unaffected. The basal levels of HNE were in the order: hepatocytes > MH1C1 cells > Yoshida cells. Both hepatocytes and Yoshida cells responded to the presence of Fe/His with increased formation of TBArS. Compared with hepatocytes the response of the Yoshida cells was greatly reduced. The response of cells to Fe/His with respect to HNE formation was decreased in the order: hepatocytes > MH1C1 cells > Yoshida cells, but in this case the differences were not very pronounced. The metabolic capacity of the cells to consume HNE was also decreased in the order: hepatocytes > MH1C1 cells > Yoshida cells. In this case the differences were very pronounced. These findings support the view that Yoshida cells with a low degree of differentiation and a low basal level of HNE are released from an inhibitory effect of HNE operative in hepatocytes and that HNE is causally involved in the iron induced inhibition of proliferation of poorly differentiated hepatoma cells.

Aldehydes↗
PubMed1997

Amnion epithelial cells, in contrast to trophoblast cells, express all classical HLA class I molecules together with HLA-G.

PROBLEM: The expression of the non-classical HLA-G gene has been shown at the protein level on trophoblast-derived embryonic tissue, like the extravillous cytotrophoblast. However, the presence of HLA-G on embryoblast-derived cells is currently controversial. The amnion epithelium is an embryoblast-derived cell layer covering the amnion cavity and is the main source for the amnion fluid. METHOD: The expression of HLA class I molecules was investigated by immunohistochemical, biochemical, and molecular biological methods in amnion membranes and amnion fluid. RESULTS: Immunohistochemically, HLA-C and occasionally also-B molecules as well as HLA-A and/or -G molecules have been identified on amnion epithelial cells. These results were extended by Western blotting with purified amnion epithelial cells where HLA-B and/or -C, HLA-A and HLA-G antigens have been detected. As expected HLA-G mRNA was detected in amino epithelial cells. Furthermore, classical HLA molecules as well as HLA-G were found in amnion fluid. CONCLUSION: These results show that the amnion epithelium frequently expresses classical HLA class I molecules as well as HLA-G. The expression of HLA-G antigens on amnion epithelial cells and their presence in the amnion fluid, which is continually ingested by the fetus, may be particularly relevant for the induction of peripheral tolerance.

Amnion↗
PubMed1997

HLA class I expression on the materno-fetal interface.

PROBLEM: The conditions that permit the genetically dissimilar (haplo-non-identical) human fetus to evade rejection by its mothers immune system have been the subject of intense interest for several years. As the placental cells, which are in contact with maternal blood or tissue, are devoid of HLA class II antigens, the interest has focused on the expression of HLA class I molecules. METHOD OF STUDY: Recent findings on the constitutive, transcriptional, and translational expression of HLA class I molecules on anatomically and morphologically different subpopulations of trophoblast cells will form the basis of this article. RESULTS: The expression of HLA class I molecules in the trophoblast cells, forming the materno-fetal junctional zone is inhomogeneous. It differs depending on the differentiation and location of trophoblast cells within the placenta and furthermore on the stage of gestation. On the transcriptional level HLA-A, -B, -C, -E, and -G could be detected on individual trophoblast populations, whereas only HLA-C and HLA-G seem to be translated to protein. CONCLUSIONS: The expression of HLA class I antigens by trophoblast cells is not simply suppressed. Instead, less polymorphic HLA-G and HLA-C antigens are carefully selected from the class I multigene family. This gives rise to the assumption that these two HLA class I molecules play an important role in the maintenance of pregnancy.

Female↗
PubMed1996

Degradation of 4-aminobenzenesulfonate by a two-species bacterial coculture. Physiological interactions between Hydrogenophaga palleronii S1 and Agrobacterium radiobacter S2.

The mutualistic interactions in a 4-aminobenzenesulfonate (sulfanilate) degrading mixed bacterial culture were studied. This coculture consisted of Hydrogenophaga palleronii strain S1 and Agrobacterium radiobacter strain S2. In this coculture only strain S1 desaminated sulfanilate to catechol-4-sulfonate, which did not accumulate in the medium but served as growth substrate for strain S2. During growth in batch culture with sulfanilate as sole source of carbon, energy, nitrogen and sulfur, the relative cell numbers (colony forming units) of both strains were almost constant. None of the strains reached a cell number which was more than threefold higher than the cell number of the second strain. A mineral medium with sulfanilate was inoculated with different relative cell numbers of both strains (relative number of colony forming units S1:S2 2200:1 to 1:500). In all cases, growth was found and the proportion of both strains moved towards an about equal value of about 3:1 (strain S1:strain S2). In contrast to the coculture, strain S1 did not grow in a mineral medium in axenic culture with 4-aminobenzenesulfonate or any other simple organic compound tested. A sterile culture supernatant from strain S2 enabled strain S1 to grow with 4-aminobenzenesulfonate. The same growth promoting effect was found after the addition of a combination of 4-aminobenzoate, biotin and vitamin B12. Strain S1 grew with 4-aminobenzenesulfonate plus the three vitamins with about the same growth rate as the mixed culture in a mineral medium. When (resting) cells of strain S1 were incubated in a pure mineral medium with sulfanilate, up to 30% of the oxidized sulfanilate accumulated as catechol-4-sulfonate in the culture medium. In contrast, only minor amounts of catechol-4-sulfonate accumulated when strain S1 was grown with 4ABS in the presence of the vitamins.

Benzenesulfonates↗
PubMed1996

Purification and characterization of a novel type of protocatechuate 3,4-dioxygenase with the ability to oxidize 4-sulfocatechol.

4-Aminobenzenesulfonate is degraded via 4-sulfocatechol by a mixed bacterial culture that consists of Hydrogenophaga palleronii strain S1 and Agrobacterium radiobacter strain S2. From the 4-sulfocatechol-degrading organism A. radiobacter strain S2, a dioxygenase that converted 4-sulfocatechol to 3-sulfomuconate was purified to homogeneity. The purified enzyme also converted protocatechuate with a similar catalytic activity to 3-carboxy-cis, cis-muconate. Furthermore, the purified enzyme oxidized 3, 4-dihydroxyphenylacetate, 3,4-dihydroxycinnamate, catechol, and 3- and 4-methylcatechol. The enzyme had a mol. wt. of about 97,400 as determined by gel filtration and consisted of two different types of subunits with mol. wt. of about 23,000 and 28,500. The NH2-terminal amino acid sequences of the two subunits were determined. An isofunctional dioxygenase was partially purified from H. palleronii strain S1. A. radiobacter strain S2 also induced, after growth with 4-sulfocatechol, an rising dbl quote, "ordinary" protocatechuate 3,4-dioxygenase that did not oxidize 4-sulfocatechol. This enzyme was also purified to homogeneity, and its catalytic and structural characteristics were compared to the "4-sulfocatechol-dioxygenase" from the same strain.

Amino Acid Sequence↗
PubMed1996

Expression of HLA class I molecules in human first trimester and term placenta trophoblast.

Expression of HLA class I molecules in trophoblast cells from various locations in normal human first trimester and term placenta was investigated by immunohistochemistry with a panel of monoclonal antibodies against the heavy chains or complete HLA class I molecules complexed with beta2-microglobulin. These reagents were also employed to distinguish between the products of different HLA class I loci. In addition to previously characterized reagents, a novel monoclonal antibody against HLA-A molecules (TU155) was used. Various choriocarcinoma and transfected cell lines served as controls for the specificities of the monoclonal antibodies. Cells in close contact with maternal cells, such as invading trophoblast cells and cells of the basal plate, expressed beta2-m micro globulin in association with HLA-G and HLA-C heavy chains. These class I heavy chains may also have been present as isolated molecules, although not in each of the cells. In contrast, cells of the chorion laeve exclusively expressed HLA-G, and not HLA-A, -B, or -C antigens. Our data support the often discussed immune protective function and the regulatory function of the HLA-G molecule, during invasion. In addition, by using monoclonal antibodies HCA2 (anti-HLA-A and -G), HC10 (anti-HLA-B and -C), TU149 (anti-HLA-B, -C, and some -A alleles), SFR8-B6 (anti-HLA-Bw6 and some -C), LA45 (some HLA-A and -B), TU48 (anti-HLA-Bw4 and some -A), and TU155 (anti-HLA-A), we show the presence of HLA-C molecules in all extravillous trophoblast cells of the cell columns and in the basal plate; the trophoblast cells of the chorion laeve lack this antigen. The function of this molecule is not clear, although a protective function against natural killer cell activity in the endometrium is postulated.

Blotting, Western↗
PubMed1996

The monoclonal antibody GZS-1 detects a maturation-associated antigen of human spermatozoa that is also present on the surface of human mononuclear blood cells.

A monoclonal antibody (GZS-1) has been generated by fusion of mouse myeloma cells with spleen cells from BALB/c mice immunised with human sperm cells. The antibody was determined to be an IgG1. The corresponding antigen is present on the whole surface of ejaculated human spermatozoa. It is not detectable on spermatozoa of other mammalian species (rabbit, cat, dog, sheep, boar, bull, horse). In human male genital organs, immunostaining with GZS-1 is observed on sperm cells in the epididymis and the ductus deferens together with the lining epithelium of those organs. No reactivity of sperm cells or germ cell precursors in the testis has been detected. Functional tests using the antibody show a strong inhibitory effect of human sperm in the hamster egg penetration assay. Furthermore, the GZS-1 antigen is detectable on the surface of human lymphocytes and monocytes by immunogold electron microscopy and FACS analysis. By Western blotting of human sperm and seminal plasma performed under reducing conditions immunostaining was detected at 21-25, 31, 51-54, and 62 kDa. The reaction with human lymphocytes shows one major band at 62 kDa and additional bands at 31 and 54 kDa. The results suggest that the monoclonal antibody GZS-1 may recognise an antigen which is secreted from the epithelial cells of the epididymis and binds to ejaculated spermatozoa as a sperm coating antigen. This component may be involved in the capacitation of the sperm and the acrosome reaction. Molecules that are expressed both on sperm and on immunocompetent cells may be relevant for the regulation of immunological processes or for the development of the related immunological tolerance of sperm in the female reproductive tract.

Antibodies, Monoclonal↗
PubMed1996

Differential phenotypic properties of human peripheral blood CD56dim+ and CD56bright+ natural killer cell subpopulations.

We investigated the presence of integrins and various other cell surface markers on the surface of freshly isolated CD56dim+ and CD56bright+ NK cells, the latter comprising a mean of 6.5% of total peripheral blood (PB) CD3-CD56+ NK cells. This small subpopulation stained more intensively for CD2, CD11c, CD15s, CD44, CD49e, CD55, CD62L, HLA-DR, and GZS-1, whereas there was no expression of CD49f in contrast to CD56dim+ cells. The myeloid antigen CDw65 was present on 11% of CD56bright+ cells, other myeloid markers were not found. 28% of CD56bright+ cells were positive for CD45R0. These results support the notion that CD56bright+ NK cells, based on their different marker profile, may possess different functional and biodistributional properties and--due to the signal-transducing capabilities of several adhesion molecules--differential patterns of stimulatability compared to the majority of PB-NK cells.

Adolescent↗
PubMed1995

Generation, characterization, and histochemical application of monoclonal antibodies selectively recognizing oxidatively modified apoB-containing serum lipoproteins.

To investigate either the role oxidized LDL plays in atherosclerosis or structural changes on the surface of oxidized LDL, monoclonal antibodies (mAbs) are an important tool. After immunizing mice with Cu(2+)-oxidized LDL (oxLDL) and fusion of splenocytes, hybridoma supernatants were screened and cloned. Two mAbs, OB/04 and OB/09 (IgG and IgM), were further characterized. In solid-phase fluorescence immunoassays and Western blot analysis both mAbs reacted with oxLDL, LDL oxidized by a free radical-generating azo compound, or oxVLDL but not with native LDL, acetylated LDL, oxHDL3, azo-oxidized HDL3, or HDL3 modified with malondialdehyde (MDA). In competitive immunoassays with LDL modified by oxidized fatty acid-derived aldehydes, mAb OB/09 strongly reacted with MDA-LDL or MDA-VLDL and LDL modified with 4-hydroxyhexenal followed by 4-hydroxynonenal but not with 4-hydroxyoctenal or hepta-2,4-dienal. mAb OB/04 had a weak affinity for LDL after modification with these aldehydes except for MDA-LDL. LDL modified with arachidonic acid oxidation products (AAOPs) was also recognized by this mAb. However, albumin modified either by the aldehydes applied or by AAOPs did not react with either mAb. Thus, the data indicate that each of the mAbs recognizes a different epitope that is expressed only on apoB-containing lipoproteins upon oxidative modification. An immunostaining with mAb OB/04 was obtained in areas rich in macrophages and in connective tissue of a human atherosclerotic lesion.

Amidines↗
PubMed1994

Crystal structure of chloromuconate cycloisomerase from Alcaligenes eutrophus JMP134 (pJP4) at 3 A resolution.

Chloromuconate cycloisomerase (E.C. 5.5.1.7) is an enzyme involved in the 2,4-dichlorophenoxyacetate degradation pathway of Alcaligenes eutrophus JMP134 (pJP4). The crystal structure of this protein was determined at 3 A resolution by molecular-replacement techniques using atomic coordinates from the reported crystal structure of the homologous muconate cycloisomerase (E.C. 5.5.1.1) from Pseudomonas putida as the search model (42% identical positions in the sequences). Structure refinement by simulated-annealing and restrained least-squares techniques converged at R = 0.195. In the crystals studied, space group I4, the protein is present as two octamers per unit cell with two subunits per asymmetric unit. Each subunit consists of two globular domains, one of which forms an alpha/beta-barrel. Comparison of this structure with that of muconate cycloisomerase reveals the reasons for the altered substrate specificity of chloromuconate cycloisomerase. Marked differences are observed in polarity, accessibility and hydrogen-bonding potential in the channel leading into the active site as well as in the active center itself.

Journal Article↗
PubMed1993

Crystallization and preliminary X-ray data of chloromuconate cycloisomerase from Alcaligenes eutrophus JMP134 (pJP4).

The pJP4-encoded chloromuconate cycloisomerase, an enzyme of the 2,4-dichlorophenoxy-acetate degradation pathway, was purified from cell-free extracts of Alcaligenes eutrophus JMP134 with a revised procedure. Tetragonal bipyramidal crystals were grown and characterized with respect to their X-ray diffraction properties. They were assigned to the space group I4, with cell dimensions of a = b = 111.9 A, c = 148.5 A. The crystals scattered to approximately 3 A resolution.

Alcaligenes↗
PubMed1993

[Oxidized lipoproteins and atherogenesis].

The assumption that the oxidation of lipoproteins plays an eminent role in the development of atherosclerosis is of increasing significance. Our examinations concerned the kinetics of lipid peroxidation of the poly-unsaturated fatty acids in lipoproteins and the existing protection mechanisms by antioxidants, such as vitamin E and carotenoids. Clinical studies proving a correlation of plasma levels and antioxidants, such as vitamin C and E and carotenoids in correlation with cardiovascular disease are cited and discussed. Certain aldehydes originating during lipid peroxidation in LDL modify the protein part of LDL. The consequence of the oxidative modification of LDL is a decreased recognition of LDL by the LDL-receptor and moreover the uptake by macrophages hereby changing to foam cells. Epitopes as developed in oxidatively modified LDL were also shown immunohistochemically in atherosclerotic plaques. Finally a hypothetic scheme is presented how LDL is oxidized in the vessel wall and how it initiates processes resulting in atherosclerosis.

Animals↗
PubMed1990

Post-critical period plasticity of callosal transfer to visual cortex cells of cats following early conditioning of monocular deprivation and late optic chiasm transection.

We studied whether plasticity-induced callosal transfer exists after the critical period for sensitivity of visual cortex cells in kittens postnatally monocularly deprived and in which interocular competition was cancelled by chiasm transection during adulthood. Callosal transfer was studied acutely (n = 3 cats) and chronically (n = 7) following the chiasm transection (OCAMD). For comparison, adult cats in which chiasm transection only was performed (OCA) were also studied acutely (n = 3) and chronically (n = 9). The results were also compared to cats in which monocular deprivation and chiasm transection were simultaneously performed (OCKMD) during development (n = 6) and to normal control cats (n = 18). Unit recording was extracellularly carried out in visual cortex areas 17 and 18 and their boundary region, where the corpus callosum is represented. When no interocular competition was allowed between the non-deprived and the deprived eye via the thalamocortical direct visual pathways on cortical cells, such as in the OCKMD cats, the absolute majority of the cells were ipsilaterally driven, regardless of which hemisphere was studied. Only a minor proportion (4.1%) of the cells had some contralateral input from the non-deprived eye in the hemisphere ipsilateral to the deprived eye, indicating almost no interhemispheric callosal transfer. A slight increase in the proportion of cells callosally driven from the non-deprived eye (9.8%), was found in this hemisphere in cats in which interocular competition was allowed via the direct visual pathways prior to its cancellation by chiasm transection (OCAMD), if studied acutely after the chiasm transection. A remarkable increase in callosal transfer was found in this hemisphere under chronic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗