Search PubMed⌕ Search

Biomedical subjects

R Keller

Publications and source records attributed to R Keller.

At least 235 records · Page 13Linked to original sources
PubMed1988

A heparin-binding protein involved in inhibition of smooth-muscle cell proliferation.

A heparin-binding protein was isolated from bovine uteri and purified to homogeneity. This protein appears as a double band of approx. 78 kDa in SDS/polyacrylamide-gel electrophoresis and has an isoelectric point of 5.2. The binding of heparin to this protein is saturable. No other glycosaminoglycan from mammalian tissue, such as hyaluronic acid, chondroitin sulphate, dermatan sulphate or keratan sulphate, binds to the 78 kDa protein. Dextran sulphate binds in a non-saturable fashion. Certain heparan sulphate polysaccharide structures are required for binding to the 78 kDa protein. Some proteoheparan sulphates, such as endothelial cell-surface proteoheparan sulphate, show only weak interaction with the 78 kDa protein in contrast with a basement-membrane proteoheparan sulphate from HR-9 cells. Antibodies against the 78 kDa protein inhibit binding of proteoheparan [35S]sulphate from basement membranes to smooth-muscle cells. Conventional antibodies, Fab fragments and some monoclonal antibodies, inhibit smooth-muscle cell proliferation in a similar range as that observed for heparin. The protein was detected in a variety of tissues and cells but not in blood cells. A possible role of this protein as a receptor for heparin or heparan sulphate and its function in the control of the arterial wall structure are discussed.

Amino Acids↗
PubMed1988

Localization of pigment-dispersing hormone (PDH) immunoreactivity in the central nervous system of Carcinus maenas and Orconectes limosus (Crustacea), with reference to FMRFamide immunoreactivity in O. limosus.

By use of antisera raised against synthetic pigment-dispersing hormone (PDH) of Uca pugilator and FMRFamide, the distribution of immunoreactive structures in the central nervous system (CNS) of Carcinus maenas and Orconectes limosus was studied by light microscopy. In both species, a total of 10-12 PDH-positive perikarya occur amongst the anterior medial, dorsal lateral and angular somata of the cerebral ganglion (CG). In C. maenas, one PDH-perikaryon was found in each commissural ganglion (COG) and several more in the thoracic ganglion. In O. limosus, only four immunopositive perikarya could be demonstrated in the ventral nerve cord, i.e., two somata in the anterior and two in the posterior region of the suboesophageal ganglion (SOG). PDH-immunoreactive tracts and fiber plexuses were present in all central ganglia of both species, and individual axons were observed in the connectives. FMRFamide-immunoreactivity was studied in O. limosus only. Neurons of different morphological types were found throughout the entire CNS, including numerous perikarya in the anterior medial, anterior olfactory, dorsal lateral and posterior cell groups of the CG. Four perikarya were found in the COG, six large and numerous smaller ones in the SOG, and up to eight cells in each of the thoracic and abdominal ganglia. In each ganglion, the perikarya form fiber plexuses. Axons from neurons belonging to the CG could be traced into the ventral nerve cord; nerve fibers arising from perikarya in the SOG appeared to project to the posterior ganglia. In none of the structures examined colocalization of PDH- and FMRF-amide-immunoreactivity was observed.

Animals↗
PubMed1988

Subdiaphragmatic bronchogenic cyst with gastric communication.

Upper gastrointestinal series and computed tomography of the abdomen in an elderly women demonstrated a large multiloculated mass in the left subphrenic space that communicated with the fundus. The resected specimen showed histopathological features of bronchopulmonary foregut malformation.

Bronchogenic Cyst↗
PubMed1988

Expression and enhanced secretion of proteochondroitin sulphate in a metastatic variant of a mouse lymphoma cell line.

Even though many studies suggest that proteoglycans with their structurally determinative polysaccharide chains, the glycosaminoglycans (GAGs), are important mediators of cellular interactions, little is known about expression and possible functions of these macromolecules expressed by tumour cells during the transition from low to highly metastatic behaviour. Therefore, we investigated the cellular expression and secretion of GAGs in a syngeneic tumour system of DBA/2 mice consisting of a methylcholanthrene-induced low metastatic T lymphoma (Eb), its highly metastatic spontaneous variant (ESb), and a low metastatic derivative of ESb (ESb-MP), selected by its adherent growth properties. The [35S]-sulphate-labelled GAGs were isolated from in vitro cultivated cells and further characterized by separation on Sepharose CL 6B, on Mono-Q ion exchange chromatography, and alkali- and enzymatic digestion. In contrast to Eb-cells which produce chondroitin/dermatan sulphate (CS/DS) and heparan sulphate (HS) (cellular extract: CS/DS 67%, HS 33%; culture medium: CS/DS 61%, HS 39%) ESb- and ESb-MP-cells only express and secrete CS/DS. For ESb cells the CS portions consisted of 42% chondroitin-4-sulphate (CS-4) and 58% chondroitin-6-sulphate (CS-6), for ESb-MP cells of 23% CS-4 and 77% CS-6, for Eb cells of 16% CS-4 and 84% CS-6. The cell surface GAGs of the adherent variant ESb-MP contained a significantly higher portion of DS (65%) compared to ESb cells (25%). GAGs of all tumour cell lines studied had a mol. wt ranging from 35-40 kD compared to GAG molecular weight standards. Ion exchange chromatography indicated that differences in charge density between GAGs of these cell lines were minimal. These findings suggest that the different biological behaviour of the cell lines cannot be attributed to altered size and charge density of their GAG chains. However, highly metastatic ESb-cells secreted significantly more GAG than low metastatic Eb- and ESb-MP-cells. The possible consequences of the enhanced secretion of CS/DS by ESb-cells are discussed in terms of the postulated role of CS/DS in cellular adhesion, growth regulation and interactions with the immune system.

Animals↗
PubMed1988

Studies in human lactation: milk volumes in lactating women during the onset of lactation and full lactation.

After validation of test-weighing procedures milk volumes produced by 13 multiparous Caucasian women were followed longitudinally through the first year of lactation. All practiced exclusive breast-feeding for at least 5 mo. Milk transfer to the infant was low on days 1 and 2 and increased rapidly to 498 +/- 129 g/d (means +/- SD) on day 5 and then more slowly to 753 +/- 89 g/d during months 3-5. There was a characteristic milk volume for each mother-infant pair that was significantly related neither to milk yield on days 4-6 nor to birth weight. It was, however, strongly related to infant weight at 1 mo, suggesting that infant and/or maternal factors coming into play during the first month of life are strong determinants of subsequent milk transfer to the infant.

Adult↗
PubMed1988

Modulation of major histocompatibility complex (MHC) expression by interferons and microbial agents. Independent regulation of MHC class II expression and induction of tumoricidal activity in bone marrow-derived mononuclear phagocytes.

In a pure population of rat bone marrow-derived mononuclear phagocytes (BMM phi), the expression of major histocompatibility complex (MHC) molecules and ability to manifest tumoricidal activity were simultaneously studied. Resting BMM phi, which express low levels of MHC class II molecules and do not manifest tumoricidal activity, become strongly MHC class II-positive, and evolve tumoricidal activity within 24 h when incubated with macrophage-activating lymphokines (MAF) or gamma interferon (IFN-gamma). In contrast, BMM phi which were interacted for 24 h with heat-killed microbial agents (Corynebacterium parvum, Listeria) evolve tumoricidal activity without parallel enhancement of MHC class II expression. IFN-alpha,beta neither induced tumoricidal activity nor enhanced MHC class II expression. Further experiments have shown that (a) the kinetics of MAF- and/or IFN-gamma-induced amplification of MHC class II expression and of tumoricidal activity are different; (b) enhancement of MHC class II expression by rIFN-gamma is not invariably paralleled by induction of tumoricidal activity; and (c) inhibitors of macrophage tumoricidal activity differ in their ability to affect MHC class II expression. It is concluded from these findings that in a population of pure BMM phi, i.e. in the complete absence of lymphocytes, the expression of MHC molecules and induction of tumoricidal activity are independently regulated phenomena; in particular, the enhanced expression of MHC class II molecules is not a prerequisite for induction and/or manifestation of tumoricidal activity by mononuclear phagocytes.

Adjuvants, Immunologic↗
PubMed1988

Regional expression, pattern and timing of convergence and extension during gastrulation of Xenopus laevis.

We show with time-lapse micrography that narrowing in the circumblastoporal dimension (convergence) and lengthening in the animal-vegetal dimension (extension) of the involuting marginal zone (IMZ) and the noninvoluting marginal zone (NIMZ) are the major tissue movements driving blastopore closure and involution of the IMZ during gastrulation in the South African clawed frog, Xenopus laevis. Analysis of blastopore closure shows that the degree of convergence is uniform from dorsal to ventral sides, whereas the degree of extension is greater on the dorsal side of the gastrula. Explants of the gastrula show simultaneous convergence and extension in the dorsal IMZ and NIMZ. In both regions, convergence and extension are most pronounced at their common boundary, and decrease in both animal and vegetal directions. Convergent extension is autonomous to the IMZ and begins at stage 10.5, after the IMZ has involuted. In contrast, expression of convergent extension in the NIMZ appears to be dependent on basal contact with chordamesoderm or with itself. The degree of extension decreases progressively in lateral and ventral sectors. Isolated ventral sectors show convergence without a corresponding degree of extension, perhaps reflecting the transient convergence and thickening that occurs in this region of the intact embryo. We present a detailed mechanism of how these processes are integrated with others to produce gastrulation. The significance of the regional expression of convergence and extension in Xenopus is discussed and compared to gastrulation in other amphibians.

Animals↗
PubMed1988

The behaviour and function of bottle cells during gastrulation of Xenopus laevis.

The behaviour of bottle cells in normal and microsurgically altered gastrulae and in cultured explants of Xenopus laevis was analysed, using time-lapse micrography, scanning electron microscopy (SEM) and cell tracing with fluorescein dextran amine (FDA). The results shed new light on the function of bottle cells. Bottle cells forming in vivo show a predominantly animal-vegetal apical contraction and a concurrent apical-basal elongation, whereas those forming in cultured explants show uniform apical contraction and remain rotund. Bottle cells forming in embryos with fewer subblastoporal cells contract more uniformly than those in normal embryos and release of normal bottle cells from supra- and subblastoporal cells results in immediate loss of the bottle shape. These results, and an analysis of the effects of bottle cell formation on the shapes and movements of surrounding tissues, show that unique shape of bottle cells and their probable function in development are not intrinsic properties but result from a modulation of the effect of a uniform and intrinsic apical contraction by the geometric and mechanical properties of the surrounding tissue. Mechanical simulations of bottle cell formation, using the finite element method, suggest how the site of bottle cell formation and the thickness and stiffness of adjacent tissues might change the effects of their formation. These results and FDA marking of prospective bottle cells and the adjacent deep mesodermal cells suggest that bottle cells function during their formation to initiate the involution of the prospective mesodermal mantle. Later they respread to deepen the archenteron and to form its peripheral wall.

Animals↗
PubMed1987

Constant and variable domains of different disaccharide structure in corneal keratan sulphate chains.

Four peptidokeratan sulphate fractions of different Mr and degree of sulphation were cut from the pig corneal keratan sulphate distribution spectrum. After exhaustive digestion with keratanase, the fragments were separated on DEAE-Sephacel and Bio-Gel P-10 and analysed for their Mr, degree of sulphation and amino sugar and neutral sugar content. It was found that every glycosaminoglycan chain is constructed of a constant domain of non-sulphated and monosulphated disaccharide units and a variable domain of disulphated disaccharide units. Total neuraminic acid of the four peptidokeratan sulphates was recovered from their isolated linkage-region oligosaccharides. In kinetic studies, the four peptidokeratan sulphates were investigated for Mr distribution after various incubation times with keratanase. There was a continuous shift towards lower Mr and no appearance of a distinct intermediate-sized product at any degradation time. The linkage-region oligosaccharide was already being liberated after a very short incubation period. From the results of these kinetic investigations in connection with the results of neuraminic acid analyses it is suggested that there exists only one disaccharide chain per peptidokeratan sulphate molecule. A model of corneal keratan sulphate is postulated. One of the alpha-mannose residues in the linkage region is bound to an oligosaccharide consisting of a lactosamine and a terminal sialic acid. The other alpha-mannose residue is attached to the disaccharide chain. This chain contains one or two non-sulphated disaccharide units at the reducing end, followed by 10-12 monosulphated disaccharide units. The disulphated disaccharide moiety of variable length is positioned at the non-reducing end of the chain.

Animals↗
PubMed1987

Proteoglycans from human umbilical vein endothelial cells.

Human umbilical vein endothelial cells were incubated with [35S]sulphate and investigated for their proteoglycan production. By gel chromatography, ion-exchange chromatography and CsCl density-gradient centrifugation we obtained preparative amounts of the endothelial proteoheparan sulphate HSI and of proteochondroitin sulphate from the conditioned medium of mass-cultured human umbilical vein endothelial cells. Approximately 90% of the 35S-labeled material in the endothelial cell conditioned medium was proteochondroitin sulphate. This molecule, with a molecular mass of 180-200 kDa, contains four side-chains of 35-40 kDa and a core protein of 35-40 kDa. Two proteoheparan sulphate forms (HSI and HSII) from the conditioned medium were distinguished by molecular mass and transport kinetics from the cell layer to the medium in pulse-chase experiments. One major form (HSI), with an approximate molecular mass of 160-200 kDa a core protein of 55-60 kDa and three to four polysaccharide side-chains of 35 kDa each, was found enriched in the cellular membrane pellet. Another proteoheparan sulphate (HSII), with polysaccharide moieties of 20 kDa, is enriched in the subendothelial matrix (substratum).

Amino Acids↗
PubMed1987

[Realities in the diagnosis of bronchial carcinoma in clinical and general practice].

In 100 patients with lung cancer the diagnostic procedure, results of clinical staging and therapeutic sequelae were analysed retrospectively and compared to a similar group of patients 10 years previously. During the 10 years' interval there was a remarkable shortening of the time between the onset of symptoms and the diagnosis, from 20 weeks to the present 10 weeks. Despite this acceleration the number of patients undergoing curative surgical resection increased only from 15 to 17%. Inoperability was still due to general condition in 14%, impaired lung function in 7%, advanced tumor stages with metastasis in 52% and local inoperability in 10%. Of the 77 patients with specific tumor related symptoms only 18 were in the prognostically favourable stage I, whereas in the asymptomatic group early stage I was observed in 13 out of 23 patients. We conclude that an improvement in early detection of lung cancer may be achieved by periodical screening of the high risk population, rather than by focusing on the onset of the first symptoms.

Combined Modality Therapy↗
PubMed1987

Induction, maintenance, and reinduction of tumoricidal activity in bone marrow-derived mononuclear phagocytes by Corynebacterium parvum. Evidence for the involvement of a T cell- and interferon-gamma-independent pathway of macrophage activation.

Rat bone marrow-derived mononuclear phagocytes, virtually homogeneous with respect to the cell lineage, do not exhibit spontaneous tumoricidal activity in the resting state. When incubated with macrophage-activating lymphokines, rat recombinant interferon-gamma (IFN), or heat-killed Corynebacterium parvum, bone marrow-derived mononuclear phagocytes readily evolve tumoricidal activity. Whereas tumoricidal activity induced by lymphokines and/or rat recombinant IFN-gamma is short-lived, that elicited by C. parvum is maintained for at least 2 wk, provided that the C. parvum organisms are continuously present in the culture. After washing off extracellular organisms, C. parvum-induced tumoricidal activity decays rapidly, suggesting that sustained extracellular stimulation is required for its maintenance. Induction of tumoricidal activity by macrophage-activating lymphokines and/or rat recombinant IFN-gamma is fully prevented by polyclonal and monoclonal anti-IFN-gamma antibodies; in contrast, induction by C. parvum is not affected by anti-IFN-gamma. Since induction of tumoricidal activity by C. parvum takes place irrespective of the presence of anti-Thy-1 antisera or cyclosporin A, T cells and/or their products appear not to be involved in this type of macrophage activation. Accordingly, present findings provide evidence for the existence of lymphokine-independent pathways of macrophage activation.

Animals↗