PubMed Health⌕ Search

Biomedical subjects

C Kirchner

Publications and source records attributed to C Kirchner.

At least 19 recordsLinked to original sources
PubMed2001

Proteolipid protein 2 mRNA is expressed in the rabbit embryo during gastrulation.

Differential display technology applied to rabbit blastocysts identified an mRNA that encodes a motif similar to that of the proteolipid protein PLP2/A4 of man, mouse and sheep. The open reading frame (456bp) has 88% amino acid identity to human PLP2/A4. The gene is maximally expressed at the beginning of gastrulation: in situ hybridizations exhibited a sickle-shaped area of labelling at the posterior pole of day 7 post-coitum embryos, which appeared at day 6.5 and decreased in size up to day 8. Weaker labelling was found in the extraembryonic mesoderm, in the anterior part of the primitive streak and in the trophoblast. Time and site of gene expression coincide with emerging morphogenetic activities at the posterior pole of the embryo at the beginning of gastrulation.

Amino Acid Sequence↗
PubMed2001

MADS-box genes are involved in floral development and evolution.

MADS-box genes encode transcription factors in all eukaryotic organisms thus far studied. Plant MADS-box proteins contain a DNA-binding (M), an intervening (I), a Keratin-like (K) and a C-terminal C-domain, thus plant MADS-box proteins are of the MIKC type. In higher plants most of the well-characterized genes are involved in floral development. They control the transition from vegetative to generative growth and determine inflorescence meristem identity. They specify floral organ identity as outlined in the ABC model of floral development. Moreover, in Antirrhinum majus the MADS-box gene products DEF/GLO and PLE control cell proliferation in the developing flower bud. In this species the DEF/GLO and the SQUA proteins form a ternary complex which determines the overall "Bauplan" of the flower. Phylogenetic reconstructions of MADS-box sequences obtained from ferns, gymnosperms and higher eudicots reveal that, although ferns possess already MIKC type genes, these are not orthologous to the well characterized MADS-box genes from gymnosperms or angiosperms. Putative orthologs of floral homeotic B- and C-function genes have been identified in different gymnosperms suggesting that these genes evolved some 300-400 million years ago. Both gymnosperms and angiosperms also contain a hitherto unknown sister clade of the B-genes, which we termed Bsister. A novel hypothesis will be described suggesting that B and Bsister might be involved in sex determination of male and female reproductive organs, respectively.

Evolution, Molecular↗
PubMed2000

Bias in proxies' reports of disability: data from the National Health Interview Survey on disability.

OBJECTIVES: These studies examined whether differences between self-reports and proxy reports of disabilities reflect proxy response biases or only respondent selection factors. METHODS: The data were from the National Health Interview Survey on Disability (1994-1995, phases 1 and 2). In study 1, reports of disabilities were regressed on respondent status, self vs proxy, and demographic factors. In study 2, the ratios of the proportions of self-reports and proxy reports of disabilities were regressed on independent lay ratings of observability of these disabilities and their "interactional" nature. In study 3, the disability reports for people who differed in respondent status in one phase but self-reported the same disability in the other phase were compared. RESULTS: In study 1, proxies under-reported disabilities for people aged 18 to 64 years but overreported for people 65 years or older. In study 2, the observability and interactional scores accounted for more than 60% of the variance of self and proxy differences in an inverse relationship, study 3 confirmed the basic findings of study 1. CONCLUSIONS: Use of proxies in representative surveys on disability introduces systematic biases, affecting national disability estimates.

Activities of Daily Living↗
PubMed1999

Suppression of food intake and growth by amino acids in Drosophila: the role of pumpless, a fat body expressed gene with homology to vertebrate glycine cleavage system.

We have isolated a Drosophila mutant, named pumpless, which is defective in food intake and growth at the larval stage. pumpless larvae can initially feed normally upon hatching. However, during late first instar stage, they fail to pump the food from the pharynx into the esophagus and concurrently begin moving away from the food source. Although pumpless larvae do not feed, they do not show the typical physiologic response of starving animals, such as upregulating genes involved in gluconeogenesis or lipid breakdown. The pumpless gene is expressed specifically in the fat body and encodes a protein with homology to a vertebrate enzyme involved in glycine catabolism. Feeding wild-type larvae high levels of amino acids could phenocopy the feeding and growth defects of pumpless mutants. Our data suggest the existence of an amino acid-dependent signal arising from the fat body that induces cessation of feeding in the larva. This signaling system may also mediate growth transition from larval to the pupal stage during Drosophila development.

Amino Acid Oxidoreductases↗
PubMed1996

Uterine fibroblast growth factor-2 and embryonic fibroblast growth factor receptor-1 at the beginning of gastrulation in the rabbit.

Fibroblast growth factor-2 (FGF-2) induces gastrulation of rabbit blastocysts in vitro and is present in the uterine secretion at day 6 after mating. The following study was made in order to show if changes in the uterine FGF-2 concentration or in the FGF receptor concentration of the embryonic tissues point to a regulation of this event. By the use of the ELISA technique and immunohistochemistry, FGF-2 concentration was determined in the endometrial tissue, uterine secretion and blastocyst between day 4 and day 8 of pregnancy, in the uterine secretion after induction of pseudopregnancy, in day 6 blastocysts after in vitro culture, and FGF immunoreactivity was localized in the endometrial tissue. FGF receptor-1 (FGFR-1) concentration was examined correspondingly in the blastocyst. Cross-linking experiments using 125I-FGF-2 were done to identify binding proteins in the blastocyst. In the uterine secretion, FGF-2 was constantly high up to day 6.5 but showed an increase thereafter. Similar values in pseudopregnant uterine secretions indicated that the growth factor was of uterine origin. It was probably synthesized by the uterine epithelium as shown by immunohistochemistry. Under culturing conditions, the blastocyst produced small amounts of FGF-2. In the blastocyst, FGFR-1 as well as binding of 125I-FGF-2 showed a dramatic increase from day 6.0 to day 6.5, coinciding with the onset of gastrulation. Receptor antigenicity was located in the embryonic disc at day 6.5 and day 7.0. Two binding proteins of about 200 and 130 kDa were found by cross-linking. The results indicate that a regulation of growth factor influence on embryonic differentiation is more probable via expression of the embryonic receptor than via differential release of the uterine growth factor.

Age Factors↗
PubMed1996

Influence of uterine growth factors on blastocyst expansion and trophoblast knob formation in the rabbit.

The effects of insulin-like growth factors (IGF-1 and IGF-2) on blastocyst expansion, and of basic fibroblast growth (FGF-2) on trophoblast knob formation were studied by in vitro culture of rabbit blastocysts. Both growth factors are present in the uterine secretions. Embryo culture was carried out in Ham's F10 supplemented with polyvinylpyrrolidone in the presence or absence of human recombinant growth factors in concentrations ranging from 1 to 100 ng/ml. IGF-1 stimulated expansion of late preimplantation blastocysts to levels found in vivo; after addition of 10 ng/ml, day-6.0 blastocysts increased their diameter within 24 h to 103% of that of day-7.0 blastocysts expanded in vivo (in comparison to 84% without growth factor), and day-7.0 blastocysts expanded to 108% (in comparison to 76% without growth factor). IGF-1 suppressed the synthesis of a pH 6.3/35-kDa protein. Addition of IGF-2 had no effects. FGF-2 effected formation of trophoblast knobs in day-7.0 blastocysts. After addition of 10 ng/ml, the trophoblast knobs appeared within 12 h of culture. The controls without FGF-2 were negative. The striking increase of FGF-2 concentration in the uterine secretion at day 7.0 is perhaps connected with the formation of trophoblast knobs in vivo. FGF receptor-1 was localized in the trophoblast knobs of day-7.5 blastocysts by the use of immunostaining.

Animals↗
PubMed1995

Promotion of gastrulation by maternal growth factor in cultured rabbit blastocysts.

Rabbit blastocysts of day 6 post coitus were cultured in a chemically defined, protein-free medium for 24 h. Although the trophoblast continued to grow, the embryonic disc degenerated. Addition of basic fibroblast growth factor (FGF-2, of human recombinant or bovine origin, 10 ng/ml) to the culture medium resulted in significant developmental progress. The embryonic disc became pear-shaped showing a round anterior edge and a posterior node. The primitive streak and Hensen's node indicated that gastrulation had begun. Mesoderm formation was confirmed from histological sections and by localization of the expression of T-gene transcripts in whole-mount preparations. FGF-2 mRNA was detected in both day-6 endometrium and day 6-blastocysts using in vitro translation followed by immunoprecipitation with a monoclonal antibody to FGF-2. In the uterine secretions of day-6 pregnant and pseudopregnant animals, several proteins exhibiting FGF-2 antigenicity were detected on Western blots following two-dimensional gel electrophoresis. As day-6 blastocysts required exogenous FGF-2 in vitro and as FGF-2 of uterine origin is present in the uterine secretion, the maternal growth factor can promote gastrulation in vivo.

Animals↗
PubMed1994

Chorionic gonadotropin-like proteins in the obplacental giant cells of the rabbit.

Obplacental giant cells are enlarged cells, found following implantation, in the antimesometrial region of the rabbit uterus. They probably originate from trophoblastic knobs that traverse the uterine epithelium during early implantation. Little is known about their function. In this study, trophoblast, placental, paraplacental and obplacental tissues at days 7-15 post-coitum, and enzyme-isolated giant cells at day 15 were studied by two-dimensional gel electrophoresis, followed by immunoblotting and light-microscopic immunohistochemistry, for the presence of human chorionic gonadotropin-like proteins. Immunostaining was performed by using anti-human chorionic gonadotropin antibodies. In gel electrophoresis of obplacental tissue and isolated giant cells, two proteins of human chorionic gonadotropin-like antigenicity at 26 kDa with pIs equivalent to pH 6.4 and 6.6 were found; they were absent in the placenta, paraplacenta, day-7 blastocyst and day-8 trophoblast. The onset of synthesis of these proteins could be observed when day-8 trophoblastic tissue was cultured in vitro for 24 h. In immunohistochemistry, only the obplacental giant cells showed a positive reaction, indicating that the production of chorionic gonadotropin occurs in this cell type.

Animals↗
PubMed1994

Effects of rilopirox on rabbit blastocysts in a protein-free in vitro culture under different culture conditions.

The effect of rilopirox (Hoe 351, CAS 104153-37-9) on rabbit blastocysts in vitro was studied. Blastocysts of day 6 post coitum were cultured in Ham's F 10 medium supplemented with polyvinylpyrrolidone using different concentrations of rilopirox with and without serum proteins. In culture conditions without serum proteins there were no differences in the growth rates of the blastocysts after 24 h of culture in the presence of 1 microgram/ml of rilopirox. However, 5 micrograms/ml of rilopirox resulted in a significant reduction of the mean growth rate as well as in a serious morphological damage of the treated blastocysts. Purified human serum albumin could partly prevent this toxic effect, while complete human serum and foetal calf serum did not show this characteristic. Analyses of the protein synthesis of the blastocysts treated with rilopirox by two-dimensional gel electrophoresis and subsequent fluorography did not show any differences in comparison to the untreated controls, despite of obvious morphological alterations.

Animals↗
PubMed1993

Glycogenolytic and antiglycogenolytic prostaglandin E2 actions in rat hepatocytes are mediated via different signalling pathways.

Prostaglandin E2 has been reported both to stimulate glycogen-phosphorylase activity (glycogenolytic effect) and to inhibit the glucagon-stimulated glycogen-phosphorylase activity (antiglycogenolytic effect) in rat hepatocytes. It was the purpose of this study to resolve this apparent contradiction and to characterize the signalling pathways and receptor subtypes involved in the opposing prostaglandin E2 actions. Prostaglandin E2 (10 microM) increased glucose output, glycogen-phosphorylase activity and inositol trisphosphate formation in hepatocyte cell culture and/or suspension. In the same systems, prostaglandin E2 decreased the glucagon-stimulated (1 nM) glycogen-phosphorylase activity and cAMP formation. The signalling pathway leading to the glycogenolytic effect of PGE2 was interrupted by incubation of the hepatocytes with 4 beta-phorbol 12-myristate 13-acetate (100 nM) for 10 min, while the antiglycogenolytic effect of prostaglandin E2 was not attenuated. The signalling pathway leading to the antiglycogenolytic effect of prostaglandin E2 was interrupted by an incubation of cultured hepatocytes with pertussis toxin (100 ng/ml) for 18 h, whereas the glycogenolytic effect of prostaglandin E2 was enhanced. The EP1/EP3 prostaglandin-E2-receptor-specific prostaglandin E2 analogue Sulproston had a stronger glycogenolytic potency than the EP3 prostaglandin-E2-receptor-specific prostaglandin E2 analogue Misoprostol. The antiglycogenolytic potency of both agonists was equal. It is concluded that the glycogenolytic and the antiglycogenolytic effects of prostaglandin E2 are mediated via different signalling pathways in hepatocytes possibly involving EP1 and EP3 prostaglandin E2 receptors, respectively.

Animals↗
PubMed1993

Placental lactogen-like proteins in the rabbit placenta.

Rabbit placentae and embryos at days 11 and 12 were analyzed by two-dimensional gel electrophoresis and by light microscopic histology for the presence of placental lactogen-like proteins. Immunoblotting and immunohistochemistry were performed by using a goat anti-human placental lactogen serum as well as a monoclonal mouse anti-human prolactin immunoglobulin; the results were similar. In the gel electrophoresis of placental tissue, three protein spots at pH 5.6 and 43, 39, and 35 kDa were immunostained; they were absent in the embryo. Immunoresponse was restricted to the cytotrophoblast. Immunofluorescent cells were mainly found on the proximal parts of the placental trabeculae.

Animals↗
PubMed1993

Fibroblast growth factor induces primitive streak formation in rabbit pre-implantation embryos in vitro.

Culturing of rabbit pre-implantation embryos was performed in Ham's F10 medium supplemented with polyvinylpyrrolidone. Under these culture conditions, day 6 post coitum blastocysts increased their diameter within 24 h to 80% of that of day 7 blastocysts grown in vivo. Despite this substained growth, the embryonic disc remained undifferentiated with clear signs of degeneration after 24 h of culture. Basic fibroblast growth factor (bFGF) was able to overcome this developmental block. After 12 h of culture, day 6 blastocysts showed pear-shaped embryonic discs, and after 24 h, the primitive streak with Hensen's node was visible. The bFGF had no comparable effects on day 5 and day 7 blastocysts. The embryonic discs of day 5 blastocysts degenerated, even in the presence of bFGF, whereas day 7 blastocysts were able to form their primitive streak, also in the absence of bFGF. TGF beta 1 did not promote embryonic development in vitro. The data indicate that the onset of mesoderm formation in the rabbit is controlled by a growth factor of the FGF-family.

Animals↗
PubMed1991

Uteroglobin in the developing rabbit conceptus in vivo and in vitro.

Uteroglobin (UGL) was measured in day-4 to day-10 rabbit conceptuses by a competitive ELISA. Levels in blastocyst fluid, tissues, coverings and in the early fetus were determined separately. The total amount of UGL increased from 18.4 ng to 6.8 micrograms per conceptus. The UGL content of individual day-6 blastocysts was studied in vitro. Culturing was carried out up to 60 h in Ham's F10 medium with polyvinylpyrrolidone as macromolecular component, with and without progesterone, and with progesterone plus estradiol. UGL was determined in the blastocyst fluids, tissues with coverings and in the culture media. After labelling with [35S]-methionine, protein patterns of total blastocysts and of culture media were analysed by two-dimensional gel electrophoresis and fluorography. The morphology of cultured blastocysts was examined by electron microscopy. During 60 h of culture, the blastocysts expanded in diameter by 84%, and released 19% of their initial UGL content into the medium, independent of the hormonal substitution. Neither de novo synthesis, nor degradation of UGL was found: the protein remained unlabelled in fluorography, and its total quantity was not significantly different from that of non-cultured controls. Trophoblast, endoderm and embryoblast cells showed well preserved cell organelles and intercellular junctions, while the morphological differentiation of the germ layer was inhibited.

Animals↗
PubMed1990

Ultrastructure, protein synthesis and secretion of day-6 rabbit blastocysts cultured in a chemically defined, protein-free medium.

Day-6 rabbit blastocysts were cultured in Ham's F10 medium supplemented with polyvinylpyrrolidone as a macromolecular component, for 4 to 12 h. The integrity of the blastocyst cells was demonstrated by electron microscopy. Expansion and biosynthesis of proteins and of DNA were studied after culturing in the presence of 35S-methionine and 3H-thymidine. Polyvinylpyrrolidone did not interfere with the subsequent protein analysis, which was performed by two dimensional gel electrophoresis followed by silver staining and fluorography. More than 600 labelled proteins were found in the blastocyst tissue, many of them were also present in the blastocyst fluid and in the blastocyst coverings. Several proteins seemed to be produced for incorporation into the blastocyst coverings; others, only detected in the culture medium, might have been synthesized for secretion into the environment.

Animals↗
PubMed1990

Uptake and accumulation of tritiated uteroglobin by day-6 rabbit blastocysts.

Uptake of uteroglobin (UGL) by day-6 rabbit blastocysts and the intracellular fate of this protein were studied by light- and electron-microscopic autoradiography, immunocytochemistry and acid-phosphatase cytochemistry. UGL, labelled with N-succinimidyl-(2-3-3H)-propionate, was administered to embryos in vitro for 25 min to 4 h. The kinetics, determined from light-microscopic autoradiographs, showed a continuous uptake of the labeled protein over a 4-h period of incubation. At the ultrastructural level, increasing numbers of silver grains and an intense UGL immunoreaction in protein vacuoles and crystalloid bodies of trophoblast cells indicated that 3H-UGL had accumulated in these organelles. The presence of crystalloid inclusions in protein vacuoles suggests their origin by a condensation of the protein content, including UGL. Lysosomes containing radioactivity were rarely found, suggesting a very low degradation rate of the 3H-UGL. Protein vacuoles and crystalloid bodies exhibited no acid phosphatase reaction. The enzyme was mainly found outside the basal and lateral cell membranes of trophoblast cells, and on the rough endoplasmic reticulum of endoderm cells.

Acid Phosphatase↗
PubMed1990

Uptake of tritiated uteroglobin by the endometrium of the rabbit during peri-implantation.

Uteroglobin, labelled with N-succinimidyl-(2-3-3H)-propionate, was applied in vivo for 3 h to pregnant rabbit uteri 7 and 9 days after mating. Light- and electron-microscopic autoradiographs showed that the endometrial epithelium, both ciliated and non-ciliated cells, is able to take up 3H-uteroglobin, however, with differing intensity. Large areas of labelling were found in the luminal epithelium, whereas the glandular epithelium contained fewer silver grains. Moreover, intensively labelled single cells or symplasms occurred in both luminal and glandular epithelium. They were identified as degenerating or dead cells. After internalization by pinocytosis or phagocytosis, the tritiated uteroglobin was observed in multivesicular bodies or in lysosomes with floccular content. Later, radioactivity was either found within residual bodies or distributed throughout the entire epithelium and the subepithelial stroma, i.e., the silver grains could no longer be assigned to specific cell organelles.

Animals↗