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Biomedical subjects

B Christ

Publications and source records attributed to B Christ.

At least 145 records · Page 8Linked to original sources
PubMed1992

Comparison of the ECL-cell frequency in the stomachs of 3 different rat strains.

Three different rat strains, Sprague-Dawley, Wistar and Fischer 344, were treated for 3 months with 2 doses (0.8; 4 mg/kg) of the gastric acid suppressing ATPase inhibitor pantoprazole. The gastrin levels were determined, the height of the mucosa measured and the number of enterochromaffin-like (ECL) cells counted. Because these cells were stained according to the method of Grimelius they were designated as GPC (Grimelius positive cells). Under 4 mg/kg, the gastrin levels were increased 8 hours after administration, but fell again after 24 h. The Fischer rats showed the highest value. Also the height of the mucosa was increased under 4 mg/kg. A trend towards an increased mucosal height was noticeable even at 0.8 mg/kg. The number of GPC was determined in 2 ways: 1) without taking the mucosal height into account, 2) taking the height into account. An increase in GPC was observed at 4 mg/kg with both methods.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1992

A morphological study of the rabbit corneal assay.

We present a morphological study of the rabbit corneal assay. The effects of corneal pockets filled with methylcellulosis carriers with and without basic fibroblast growth factor (bFGF) were studied 4, 7, 11, 14 and 21 days following surgery. In the controls, strongly vacuolated keratocytes are present at the borders and especially at the bottom of the pocket. A large number of such cells can also be found in the region between the pocket and the epithelium. These cells obviously undergo necrosis. A few vacuolated keratocytes with poorly structured cytoplasm can even be found in the stroma between the pocket and the limbus. There are also changes in the epithelium. It is thinner than normal and the cells are longitudinally oriented. Construction of the pocket sometimes results in a fissure extending a variable distance from the bottom of the pocket to the limbus. Basic FGF induced blood-vessel growth from the limbus into the cornea. At least until day 7 this is accompanied by high vulnerability of the vessels, and changes in the pattern and structure of the extracellular matrix. Neutrophilic granulocytes, monocytes and a few mast cells migrate in front of the vessels. As in the controls, vacuolated and necrotic keratocytes are present within the stroma. From day 11 onward, many more vessels can be found in front of than behind the pocket, often located adjacent to vacuolated keratocytes. We suggest that an angiogenic substance placed in the corneal pocket is not the only angiogenic stimulus in the test, but acts together with many stimuli caused by the surgical manipulations.

Animals↗
PubMed1992

From somites to vertebral column.

We report on the development and differentiation of the somites with respect to vertebral column formation in avian and human embryos. The somites, which are made up of different compartments, establish a segmental pattern which becomes transferred to adjacent structures such as the peripheral nervous system and the vascular system. Each vertebra arises from three sclerotomic areas. The paired lateral ones give rise to the neural arches, the ribs and the pedicles of vertebrae, whereas the vertebral body and the intervening disc develop from the axially-located mesenchyme. The neural arches originate from the caudal half of one somite, whereas the vertebral body is made up of the adjacent parts of two somites. Interactions between notochord and axial mesenchyme are a prerequisite for the normal development of vertebral bodies and intervening discs. The neural arches form a frame for the neural tube and spinal ganglia. The boundary between head and vertebral column is located between the 5th and 6th somites. In the human embryo, proatlas, body of the atlas segment, and body of the axis fuse to form the axis.

Animals↗
PubMed1992

A comparative study of myogenic cell invasion of the avian wing and leg bud.

The borders of myogenic cell invasion of avian wing and leg buds were determined using the interspecific grafting technique between quail and chick embryos. Distal parts of quail limb buds were grafted ectopically into the coelomic cavity of chick embryos. The presence or absence of skeletal muscle was investigated in histological sections of the reincubated grafts. A comparison between the borders of myogenic cell invasion of the wing and leg buds showed that the differences in the position of the distal most muscles in the adult avian limbs could be a consequence of the cranio-caudal sequence of development.

Animals↗
PubMed1991

Interactions of nuclear protein from cultured rat hepatocytes with the cyclic AMP responsive elements and the NF1-CTF site in the promoter of the rat phosphoenolpyruvate carboxykinase gene.

Nuclear extracts from cultured rat hepatocytes were analyzed by gel mobility shift assay for protein binding to the cyclic AMP responsive elements CRE1 (-96/-77) and CRE2 (-152/-132) and the NF1-CTF binding site (-121/-99) of the phosphoenolpyruvate carboxykinase (PCK) promotor. Binding was very weak to the CRE2 and CRE1. The NF1-CTF site formed two complexes with nuclear protein. Protein binding was increased, when the NF1-CTF site was coupled to the CRE1, and further, when it was coupled to both the CRE1 and the CRE2. Complex formation was not altered by treatment of the hepatocytes with glucagon or with glucagon and insulin. Thus, protein binding was most efficient when all three elements were in context, which might be necessary for full transcriptional activation of the PCK gene.

Animals↗
PubMed1991

Binding of cytosolic protein from cultured rat hepatocytes to the 3'-end of phosphoenolpyruvate carboxykinase mRNA--significance for protein-mediated mRNA stabilization.

In vitro transcripts of the 3'-non-translated region of the phosphoenolpyruvate carboxykinase (PCK) gene both in "sense" and "antisense" orientation bound cytosolic protein from cultured rat hepatocytes as demonstrated by electrophoretic mobility shift assay. Binding of cytosolic protein was increased 3-fold and PCK mRNA was enhanced 10-fold by treatment of the hepatocytes with 10 nM glucagon. The similar time course of the glucagon-induced increase in protein binding to PCK mRNA 3'-end and in PCK mRNA suggests that protein binding might be involved in the stabilization of PCK mRNA.

Animals↗
PubMed1991

Modulation by oxygen of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase gene in rat hepatocyte cultures.

In liver phosphoenolpyruvate carboxykinase (PCK) activity, protein and mRNA are localized predominantly in the periportal zone. The activation of the PCK gene by glucagon was studied in primary rat hepatocyte cultures under physiological arterial and venous oxygen tensions [16% and 8% (by vol.)]. PCK gene expression was monitored on the level of transcription, mRNA abundance and enzyme activity as well as enzyme synthesis and degradation. 1. Transcription of the PCK gene was increased by 10 nM glucagon maximally after 0.5 h; it reached nearly basal levels again after 2 h. The increase in transcription was 45% lower under 8% oxygen than under 16% oxygen. 2. PCK mRNA was maximally increased after 2 h under 16% oxygen and after 4 h under 8% oxygen; it subsequently declined to twice the basal values after 8 h. The maximal increase after 2 h was 50% lower under 8% oxygen than under 16% oxygen. 3. PCK enzyme activity was maximally increased after 4-6 h. The maximal enhancement after 4 h was 50% lower under 8% oxygen than under 16% oxygen. 4. The increase in PCK enzyme activity was due to an enhanced synthesis rate of PCK protein. The rate increased after 3 h was 35% lower under 8% oxygen than under 16% oxygen. 5. The degradation of PCK protein was equal under both oxygen tensions. The results show that in cultured rat hepatocytes the induction of PCK gene expression is modulated by physiological concentrations of oxygen. The modulation occurred at the level of gene transcription, mRNA abundance, enzyme protein synthesis and enzyme activity. The periportal to perivenous oxygen gradient could be the major factor responsible for the predominant expression of the PCK gene in the periportal zone.

Animals↗
PubMed1991

Mechanism of the permissive action of dexamethasone on the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase gene in cultured rat hepatocytes.

Rat hepatocytes were cultured for 24 h in the presence or absence of 100 nM dexamethasone (DX). After a medium change, phosphoenolpyruvate carboxykinase (PCK) was induced by addition of glucagon at different concentrations, from physiological 0.1 nM to hyperphysiological 10 nM, again in the presence or absence of 100 nM dexamethasone. 1. With dexamethasone addition during the culture and induction phase (DX+/+), 10 nM glucagon increased PCK mRNA abundance (Northern blot analysis) and activity (in vitro translation) synchronously to the same extent with maxima after 2 h and PCK enzyme activity after a time lag with a maximum after 6 h. The total detectable PCK mRNA amount was apparently also translationally active. 10 microM N6,2'-O-dibutyryladenosine 3',5'-(cyclic)phosphate (Bt2cAMP) as the second messenger had essentially the same effect as 10 nM glucagon. 2. In the absence of dexamethasone during the preculture and the induction phase (DX-/-), 10 nM glucagon and 10 microM Bt2cAMP could enhance PCK mRNA only about half-maximally. Glucagon or dexamethasone added alone in physiological concentrations of 0.1 nM and 100 nM, respectively, were unable to increase PCK mRNA. However, treatment of the cells with dexamethasone also enabled 0.1 nM glucagon to enhance PCK mRNA to a maximum after 2 h, independent of the presence of dexamethasone during the induction period (DX+/+ and DX+/- cells). Thus, dexamethasone was a permissive agent in that it shifted the sensitivity of the cells towards glucagon into the physiological concentration range. 3. In the presence of dexamethasone during the culture and induction phase (DX+/+) 0.1 nM glucagon maximally enhanced the transcription of the PCK gene (nuclear run on) fourfold after 30 min; in the absence of dexamethasone during both phases (DX-/-) glucagon was without any effect. The overall transcriptional rate was not significantly different in cells with and without dexamethasone during the culture and induction phase (DX+/+ vs. DX-/-). Thus, dexamethasone acted permissively mainly on the transcription of the PCK gene. 4. With culture in the presence of dexamethasone over decreasing periods of time, 1 nM glucagon could induce submaximal PCK mRNA amounts already after 1-3 h steroid culture. This restitution by dexamethasone of the PCK mRNA inducibility by glucagon was inhibited by cycloheximide. This suggested that ongoing protein synthesis was required for the permissive action of dexamethasone on the expression of the PCK gene. The results allow the following conclusions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Two-phase in vitro culture of explanted chick embryos.

The present study describes a method of culturing chick embryos together with their surrounding area vasculosa on two different culture media in succession. Embryos in the 2nd day of incubation (stages 13, 14, 15 according to Hamburger and Hamilton, 1951) were explanted from the yolk with the aid of a ring of filter paper and transferred dorsal side up to a silicone culture dish containing the first culture medium (89.5% L-15, 10% fetal calf serum, 0.5% Antibiotics). The paper ring was clamped onto the wall of the culture dish by a steel ring so that the embryo was fixed for the culture period. After 4 +/- 1, 8 +/- 1, 12 +/- 1 hrs, the embryos were taken from the culture dishes and transferred to others containing a yolk-albumen mixture as culture medium; 81.2% of embryos survived the first phase of culture. On the second medium 50.3% of explanted embryos were still alive at stage 20 (HH), and 7.9% of them reached the 5th day of development (St 25 HH). The average length of survival in vitro was found to be influenced by both the length of the first culture phase and the stage at which embryos were explanted. This culture method may be useful for teratological tests, since in the first phase of culture, concentrations of test substances and the time of exposure can be exactly adjusted, and in the second phase, the embryo is allowed to develop quite normally, under conditions similar to those in ovo.

Animals↗
PubMed1991

A modified chorioallantoic membrane (CAM) assay for qualitative and quantitative study of growth factors. Studies on the effects of carriers, PBS, angiogenin, and bFGF.

The application of Thermanox tissue culture coverslips to the day 9 CAM of the chick causes constant effects beneath the carrier after 3 days, and these are associated with a change in the blood vessel pattern. Histological sections show enormous thickening of the CAM in the reactive areas. The stroma of the CAM shows fibrocyte proliferation, leucocyte infiltration, and clusters of dispersed ectodermal epithelial cells exhibiting signs of necrosis. The latter obviously cause a strong vascular response. The same effects are seen when the Thermanox discs are applied at day 11. Following application on day 12 a positive or negative response to the carrier is observed, whereas on day 13 no such carrier effects are seen. The only remaining effect is compression of the intra-ectodermal capillary plexus of the CAM. This can macroscopically be seen after peroxidase staining of the blood vessels. The effect of 5 microliters PBS dried on the Thermanox disc and applied to the day 13 CAM is to cause, after 3 days, hyperosmotic damage to the ectodermal epithelium, which becomes overgrown by fibrocytes. We found dose-dependent effects of salt-free human bFGF applied to the day 13 CAM. The first and main effect is fibrocyte proliferation (0.5 microgram). New capillaries appear with higher doses, but are not as frequent as would be expected for an angiogenic substance (1.25-2.5 micrograms). Also with higher doses additional hyperplasia of the endodermal (3.75 micrograms) and ectodermal (5 micrograms) epithelium can be seen. The latter might be a non-specific hyperosmotic effect. Leucocytes are regularly present within the reactive areas. When salt-free angiogenin is applied to the day 13 CAM, some effects appear with doses of 4.6 micrograms and more. The ectodermal epithelium of the reactive areas is discontinuous, exhibiting signs of necrosis. It is overgrown by parallel fibrocytes. Whether this is a non-specific hyperosmotic effect, or indicates enhancement of invasive growth, calls for further investigation.

Allantois↗
PubMed1991

Distribution and migration of angiogenic cells from grafted avascular intraembryonic mesoderm.

The hemangiogenic potencies of initially avascular intra-embryonic mesoderm were studied in chick and quail embryos and in chick-quail chimeras. The prechordal mesoderm, primitive streak and primitive node of quail embryos were heterospecifically grafted into limb buds of chick embryos. Hemangiopoietic quail cells in the host limb were detected by immunohistological staining with the monoclonal anti-MB-1 antibody after 3-6 days of re-incubation. The antibody is specifically directed against quail hemangiopoietic cells and their derivatives. Quail endothelial cells were found in pure quail and in chimeric vessels, inside as well as outside the graft. The main artery of the limb and the vessels inside the graft were connected by chimeric arteries. Proximal to the graft, quail endothelial cells were located predominantly within the lining of the main artery, while distally they were found mainly in the veins and the marginal sinus. The results show that, as early as stage 3 (according to Hamburger and Hamilton 1951, HH) all parts of the avascular intraembryonic mesoderm tested, give rise to endothelial cells. Both mechanisms, angiogenesis and vasculogenesis, contribute to the vascularization of the limb. Immunocytological and scanning electron microscopic studies indicate that centrifugal and centripetal migration of angiogenic cells occurs outside the vessels as well as on the inner surface of the endothelium.

Animals↗
PubMed1991

The role of fibronectin and laminin in development and migration of the avian Wolffian duct with reference to somitogenesis.

It has been suggested that matrix molecules like fibronectin and laminin influence the differentiation and migration of embryonic cells. We investigated the role of these two glycoproteins in somitogenesis as well as in the differentiation and migration of the avian Wolffian (pronephric and mesonephric) duct. At first, we described essential steps in the development of these two organ anlagen by light microscopy, SEM and TEM. To localize fibronectin and laminin more exactly in the actual stages, we used the indirect immunoperoxidase reaction at the light microscopic level and the peroxidase-antiperoxidase technique at the ultrastructural level. Fibronectin was found at the surface of the unsegmented paraxial mesoderm, increasing in the cranial direction, and in the basal laminae of somites and Wolffian duct. The mesenchymal tip of the duct contains a moderate amount of fibronectin. In the two investigated organ anlagen, laminin was found mainly in the basal laminae. The role of fibronectin and laminin was investigated further by using synthetic peptides that mimic the main cell binding domain of either fibronectin or laminin, and that competitively inhibit their cell surface receptors. Thus, the pentapeptides GRGDS, YIGSR, and for control, SHLVE were micro-injected under the ectoderm of 2-day-old embryos. After treatment with GRDS, the Wolffian duct and the segmental plate are more compact. The rounded cells exhibit only short processes and narrow intercellular spaces. At the side of injection the duct shows a delay in migration. After treatment with YIGSR the Wolffian duct migrated laterally over the somatopleure. The basal laminae seem to be incomplete. SHLVE had no effect. Our results suggest that fibronectin is a prerequisite for the migration of the Wolffian duct, and that laminin probably plays a role in guiding the duct. The epithelialization during somitogenesis and differentiation of the duct is a more complex process involving also fibronectin and laminin.

Animals↗
PubMed1991

Four triterpenoid saponins from dried roots of Gypsophila species.

Four new triterpenoid saponins were isolated from the roots of Gypsophila paniculata and G. arrostii. Their structures were elucidated using a combination of homo- and heteronuclear 2D NMR techniques, without having recourse to chemical degradation or modification. The saponins investigated are: 3-O-beta-D-galactopyranosyl-(1----2)-[beta-D-xylopyranosyl-(1----3)]-bet a-D- glucuronopyranosyl quillaic acid 28-O-beta-D-glucopyranosyl-(1----3)-[beta-D-xylopyranosyl-(1----4)]-alph a- L-rhamnopyranosyl-(1----2)-beta-D-fucopyranoside; 3-O-beta-D-galactopyranosyl-(1----2)-[beta-D-xylopyranosyl-(1----3)]-bet a- D-glucuronopyranosyl quillaic acid 28-O-beta-D-arabinopyranosyl-(1----4)-beta-D-arabinopyranosyl++ +-(1----3)-beta-D- xylopyranosyl-(1----4)-alpha-L-rhamnopyranosyl-(1----2)-beta-D-fucopyran oside; 3-O-beta-D-glucopyranosyl-(1----2)-beta-D-glucuronopyranosyl gypsogenin 28-O-beta-D-glucopyranosyl-(1----3)-[beta-D-xylopyranosyl-(1----4)]-alph a- L-rhamnopyranosyl-(1----2)-beta-D-fucopyranoside; 3-O-beta-D-xylopyranosyl-(1----3)-[beta-D-galactopyranosyl-(1----2)]-bet a- D-glucuronopyranosyl gypsogenin 28-O-beta-D-glucopyranosyl-(1----3)-[beta-D-xylopyranosyl-(1----4)-alpha -L- rhamnopyranosyl-(1----2)-beta-D-fucopyranoside.

Carbohydrate Sequence↗
PubMed1991

Differentiation of endothelial cells in avian embryos does not depend on gastrulation.

Unincubated quail eggs were treated with Cytochalasin B. By this means, gastrulation of the blastodiscs was inhibited. Fragments of these blastodiscs were grafted into wings buds of chick embryos, and the differentiation fate of graft-derived cells was studied. Results show that only endothelial cells differentiate from the grafts. They were even found outside the graft site in vessels made up of a chimeric endothelium. It can be concluded that determination, differentiation and migration of endothelial cells does not depend on gastrulation.

Animals↗
PubMed1990

Metabolic actions of insulin-like growth factor-I in cultured hepatocytes from adult rats.

Short-term and long-term regulation of hepatic carbohydrate metabolism by insulinlike growth factor-I was studied in primary cultures of adult rat hepatocytes and compared with the metabolic potency of insulin. Insulinlike growth factor-I stimulated the formation of [14C]lactate from [14C]glucose up to three-fold with a half-maximally effective concentration of approximately 50 nmol/L. Basal glycogenolysis was inhibited by about 20%, and glucagon-activated glycogenolysis was blocked completely by insulinlike growth factor-I with half-maximally effective concentrations of about 1.5 to 2 nmol/L. The activity of the key glycolytic enzymes glucokinase and pyruvate kinase were induced twofold. The glucagon-dependent induction of phosphoenolpyruvate carboxykinase--the key gluconeogenic enzyme--was antagonized with a half-maximally effective concentration of about 5 nmol/L. This inhibition of the glucagon-dependent induction of the enzyme was accompanied by a similar reduction of the increase in phosphoenolpyruvate carboxykinase-mRNA level as assessed by Northern blot analysis. The potency of insulinlike growth factor-I at half-maximally effective concentrations was approximately 2% to 4% that of insulin. Because binding studies demonstrated a comparably low affinity of insulinlike growth factor-I to the insulin receptor, it is suggested that in adult liver--in contrast to fetal and regenerating liver--insulinlike growth factor-I could exert short-term and long-term metabolic effects on parenchymal cells only through interaction with the insulin receptor.

Animals↗
PubMed1990

On the differentiation and origin of myoid cells in the avian thymus.

The avian thymus and its myoid cells were investigated paying special attention to the developmental and morphological differences between chick and quail. By means of light- and electron microscopy, and immunofluorescence technique using an anti-myosin antibody, the myoid cells were found to express characteristics corresponding to those of skeletal muscle cells. They change their appearance during embryonic development. In the chick the myoid cells become located singly and rounded, and their cross-striation disappears. In the quail they remain small, elongated, cross-striated, and become arranged in long cords. The origin of myoid cells was studied using the quail-chick marking technique: Cranial somites and the prechordal mesoderm were grafted from quail into chick embryos. After somite transplantation the host thymus does not contain graft-derived cells. The myoid cells are exclusively derived from the chick. After implantation of prechordal mesoderm, graft-derived quail cells are found in the central cores of all visceral arches and also within the early epithelial anlage of chimeric thymus. These findings indicate that the thymus myoid cells are derived from the axially located prechordal head mesoderm.

Animals↗
PubMed1990

Origin of spinal cord meninges, sheaths of peripheral nerves, and cutaneous receptors including Merkel cells. An experimental and ultrastructural study with avian chimeras.

The origin of cells covering the nervous system and the cutaneous receptors was studied using the quail-chick marking technique and light and electron microscopy. In the first experimental series the brachial neural tube of the quail was grafted in place of a corresponding neural tube segment of the chick embryo at HH-stages 10 to 14. In the second series the leg bud of quail embryos at HH-stages 18-20 was grafted in place of the leg bud of the chick embryos of the same stages and vice versa. It was found that all meningeal layers of the spinal cord, the perineurium and the endoneurium of peripheral nerves, as well as the capsular and inner space cells of Herbst sensory corpuscles, develop from the local mesenchymal cells. Schwann cells and cells of the inner core of sensory corpuscles are of neural crest origin. The precursors of Merkel cells migrate similarly to the Schwann cells into the limb bud where they later differentiate. This means that in addition to the Schwann cells and the melanocytes a further neural crest-derived subpopulation of cells enters the limb.

Animals↗