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Biomedical subjects

L Oliver

Publications and source records attributed to L Oliver.

At least 55 records · Page 3Linked to original sources
PubMed1994

Up-regulation of aFGF expression in quiescent cells is related to cell survival.

Exogenously administrated acidic FGF modulates the proliferation of several cell types, controls cell differentiation, and promotes cell survival. Most cells that are sensitive to exogenous aFGF are also capable of expressing it at very low levels. Thus in order to establish the role of endogenous aFGF as a mitogenic, differentiation, or survival factor, we studied the regulation of aFGF expression by evaluating the level of mRNA by PCR amplification and the concentration of protein by Enzyme Immuno Assay (EIA). In the lens, the amount of aFGF transcripts in nondividing cells of the central epithelium and in the differentiated fiber cells located at the periphery of the lens is similar, suggesting that endogenous aFGF is not involved with lens differentiation. In cultures, depending on the growth conditions, the endogenous aFGF expressed by Bovine Epithelial Lens (BEL) cells is subject to modulation. Cells arrested either by contact inhibition or by serum deprivation express more aFGF transcripts and protein than in exponentially growing cells, implying that endogenous aFGF has no mitogenic role under these conditions. In serum-deprived cells, the addition of specific aFGF antisense primers inhibits endogenous aFGF expression and leads to the death of these cells. These results associated with the higher expression of aFGF in nondividing BEL cells, suggesting that, contrary to exogenous aFGF, endogenous aFGF is not a mitogenic factor but a survival factor.

Animals↗
PubMed1994

Effects of exogenous FGFs on growth, differentiation, and survival of chick neural retina cells.

Fibroblast growth factors (FGFs) are known to play important roles in various processes including development and differentiation. Chick embryo neural retina cells, capable of transdifferentiation into lentoid bodies and pigmented cells, were used in vitro to examine the effects of exogenous acidic (aFGF) and basic FGF (bFGF) on proliferation and protein accumulation. We demonstrate that both factors increase the proliferation of glial cells and modulate the survival of neurons without affecting protein accumulation within these cells. Moreover, FGFs stimulate the differentiation of the photoreceptors. The rate of proliferation varies over the period of culture, with a maximum occurring after 2 weeks, followed by a decrease concommitant with the appearance of lentoid bodies. The concentration of aFGF was measured using an enzyme immuno assay and showed an accumulation of this protein only in bFGF-treated cultures, suggesting that bFGF positively modulates aFGF synthesis in neural retina cell cultures.

Animals↗
PubMed1993

Acidic fibroblast growth factor is expressed abundantly by photoreceptors within the developing and mature rat retina.

In order to further understand the role(s) of fibroblast growth factors (FGFs) in the development, differentiation and function of the central nervous system, we analysed the expression of the mRNA, and the presence and tissue distribution of the translated product, of one member of the FGF family, acidic FGF (aFGF), within the mammalian retina. Firstly, the relative abundance of aFGF mRNA was assayed in embryonic (between 14 and 17 days of gestation), postnatal (between 1 and 17 days after birth) and adult rat retina by quantitative reverse transcription-coupled polymerase chain reaction amplification using specific aFGF oligonucleotides. The level of expression remained uniformly low throughout the embryonic period and until postnatal day 7. Therefore the quantity of aFGF mRNA increased rapidly, reaching 80% of adult levels by eye opening (postnatal day 13). Adult levels were three-fold higher than at early developmental times. In situ hybridization of adult rat retina using specific antisense aFGF riboprobes revealed labelling in all cellular layers. Antisera raised against recombinant human aFGF revealed very little labelling of 4-day postnatal retina, but by postnatal days 8 and 17 immunoreactive aFGF was localized mainly within the photoreceptor cell bodies. Western blots of retinal extracts derived from 17-day embryonic, 4-day postnatal and adult retina probed with the same antibody revealed a single immunoreactive band of the expected molecular weight (18 kDa) in all extracts. Thus aFGF is mostly transcribed and translated within the retina subsequent to the major steps of cell birth, migration and differentiation, and seems to be abundantly expressed by maturing photoreceptor cells.

Animals↗
PubMed1993

Caffeine and nicotine improve visual tracking by rats: a comparison with amphetamine, cocaine and apomorphine.

Psychomotor stimulant drugs such as caffeine, nicotine, amphetamine and cocaine, have been shown to improve vigilance in man under conditions of fatigue. Nicotine has also been shown to improve performance in some cognitive tests in patients with Alzheimer's disease. In rodents these drugs increase activity which may confound "performance enhancing effects" in rodent models. However, improvements have been found in a number of tests that do not seem to be directly dependent upon an enhancement of locomotor activation. In one example, Evenden and Robbins (1985) reported consistent improvements in a visual tracking test following amphetamine. The present study was undertaken to determine whether these performance enhancing effects of amphetamine could also be obtained with cocaine and apomorphine, which both have psychomotor stimulant effects through their actions as, respectively, indirect and direct dopamine agonists, and by caffeine and nicotine, which do not have a direct dopaminergic mechanism of action. The results of the study indicate that all five drugs improved tracking performance at one or more doses. The most consistent effects were obtained with amphetamine which, like cocaine and nicotine, improved tracking at a dose which did not produce other changes in behaviour. Taking into account previous studies (Evenden and Robbins 1983, 1985), these results were interpreted as indicating that psychomotor stimulant drugs produce a general activation of behaviour. At all but the highest doses of such drugs, the form of behaviour that is observed depends upon the environment.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamine↗
PubMed1993

Left ventricular false aneurysm complicating mitral valve repair.

Left ventricular false aneurysm is a rare complication of mitral valve replacement or myocardial infarction. A case of left ventricular false aneurysm complicating mitral valve repair is presented. The patient was clinically asymptomatic, and the diagnosis was made on postoperative transesophageal echocardiography. The patient subsequently underwent successful mitral valve replacement and false aneurysm repair.

Aged↗
PubMed1993

Developmental regulation of acidic fibroblast growth factor (aFGF) expression in bovine retina.

Acidic fibroblast growth factor (aFGF) is a signalling molecule implicated in a wide variety of biological processes such as cell growth, differentiation and survival. It has been purified from bovine retina. The present study was carried out to detect which cells in the bovine retina expressed aFGF at the different stages of embryonic and post-natal development. The specific aFGF mRNA and protein were detected by in situ hybridization employing riboprobes and immunocytochemistry using affinity purified polyclonal human recombinant aFGF antibodies respectively. No signal was detected by either technique until 4-5 months and then there was progressive expression of aFGF with terminal morphogenesis of the retina. By 8-9 months of embryonic development, nuclei of the 3 neuronal layers (ganglion cell layer, inner and outer nuclear layers) were all uniformly and intensely labeled. A slight labeling of the pigmented epithelium of the retina was also visible throughout development and maturation. These results showed a good correlation between message and protein expression in these cell types. In contrast, glial cells in the nerve fiber layer and vascular endothelial cells displayed a nuclear immunostaining for the protein in the absence of message. These data suggest that aFGF plays a role in the late steps of retinal differentiation by autocrine and paracrine mechanisms.

Animals↗
PubMed1992

Regulation of proteolytic activity in human bone marrow stromal cells by basic fibroblast growth factor, interleukin-1, and transforming growth factor beta.

Plasminogen activators (PAs) and/or plasmin may be involved in hematopoietic regulation. These enzymes release biologically relevant cytokines such as basic fibroblast growth factor (bFGF) from matrix and cell surfaces. In addition, transforming growth factor beta (TGF beta) and interleukin-1 beta (IL-1 beta) are converted from inactive to active forms by plasmin. Therefore, we studied the regulation of PAs and their specific inhibitors, PA inhibitor 1 (PAI-1) and PA inhibitor 2 (PAI-2), in human bone marrow stromal fibroblasts by IL-1 beta, bFGF, and TGF beta. All three cytokines stimulated PA secretion. IL-1 beta at 10(4) U/mL increased urokinase (u-PA) levels approximately 10-fold, bFGF at 0.2 ng/mL also increased production 10-fold, but increased predominantly tissue PA (t-PA) expression. TGF beta at 0.2 ng/mL increased u-PA production up to 300-fold. PAI-1 and PAI-2 are also regulated by these cytokines. IL-1 beta decreased PAI-1 levels by 50% and stimulated PAI-2 levels sixfold. bFGF had minimal effects on PAI-1 and TGF beta increased PAI-1 levels twofold. Neither of these agents had an effect on PAI-2 levels. Thus, three cytokines relevant to bone marrow physiology regulate PA and inhibitor production by human bone marrow stromal fibroblasts. In this manner PA and plasmin generation in specific microenvironments in the bone marrow may be one of the factors orchestrating the complex series of events, which results in an efficient exquisitely regulated hematopoietic process.

Bone Marrow↗
PubMed1992

Endogenous aFGF expression and cellular changes after a demyelinating lesion in the spinal cord of adult normal mice: immunohistochemical study.

Fibroblast growth factors (FGFs) are known to act on glial cells in vitro. At the present time, their involvement in the remyelinating process of the adult central nervous system (CNS) is still unknown. In the present study, using immunohistochemistry (IHC), we investigated the evolution in time and space of acidic FGF (aFGF) expression and CNS cell changes occurring after a chemically induced demyelinating lesion. In a first early period, aFGF immunostaining was shown to decrease around the demyelinated area. A dramatic increase was then observed and was accompanied by an increase of cell density around and inside the lesion. This was correlated with the beginning of remyelination. Late after demyelination, while remyelination was still in progress, aFGF immunostaining of the lesion and unlesioned spinal cord were comparable. A role of aFGF in remyelination is proposed.

Animals↗
PubMed1992

Acidic fibroblast growth factor (aFGF) in developing normal and dystrophic (mdx) mouse muscles. Distribution in degenerating and regenerating mdx myofibres.

Affinity purified polyclonal antibodies directed against human recombinant acidic FGF (aFGF), were used in immunofluorescence studies to localize this growth factor in several normal and dystrophic (mdx) mouse skeletal muscles. The expression of aFGF was detected throughout the life of both the control and mdx mice. In striated muscles, examined up to 3 weeks postnatal, aFGF was localized around the myofibres and this pattern was consistent in both mdx and the normal counterpart strain. However, the intensity of the signal was much stronger in the mdx strain. In mdx mouse skeletal muscles, examined during the acute phase of degeneration and regeneration (3-14 weeks) aFGF was localized around the myofibres, in approximately 60% of the nuclei of newly formed or regenerated myofibres and also in the pockets of necrosis which represented actively degenerating myofibres. In normal mouse skeletal muscles, studied over the same period, the antibodies localized aFGF mainly to the periphery of the muscle fibres. The augmentation of aFGF observed by immunofluorescence in mdx mouse muscles was confirmed by enzyme immunoassay (EIA) analysis of the same muscles over the same period of time. The data from the EIA indicated a 3.5-fold increase in aFGF in mdx as compared to normal muscles at 3 weeks, and an approximate 26-fold increase during the period of active degeneration-regeneration. This increased concentration of aFGF noted in the mdx muscles suggests that this endogenous aFGF may participate in the high level of regenerative activity observed in mdx mouse.

Animals↗
PubMed1992

Immunolocalization of acidic and basic fibroblast growth factors during mouse odontogenesis.

Acidic and basic fibroblast growth factors (aFGF and bFGF), are both known to bind to extracellular matrix components, particularly proteoheparin sulfates, and to regulate in vitro proliferation, differentiation and morphology of cells of neuroectodermal and mesodermal origins. Their patterns of distribution were studied during mouse odontogenesis by means of indirect immunofluorescence and immunoperoxidase histochemistry on frozen fixed sections and after Bouin's fixative and paraffin embedding. Localization of aFGF on frozen fixed sections was observed in the oral epithelium, dental lamina and oral mesenchyme (day-12 of gestation), the stellate reticulum and oral epithelium (day-14), the stratum intermedium and at the basal and apical poles of preameloblasts at bell stage. After birth aFGF epitopes were localized within the predentin-dentin area, the stratum intermedium and at the secretory pole of ameloblasts. There was no staining with anti-aFGF antibodies after Bouin's fixative and paraffin embedding. In contrast, using this protocol, intense stainings were found with anti-bFGF antibodies predominantly within dental and peridental basement membranes and mesenchyme: staining of the dental basement membranes was transient (bud and cap stage) and discontinuous; a preferential concentration of bFGF epitopes in the condensed dental mesenchyme of incisors (cap stage) and the dental papillae mesenchymal cells of molars (bell stage) was observed in the posterior and the cervical part of tooth germs. An intense immunostaining of the stellate reticulum with anti-bFGF antibodies was also found on paraffin sections from bud to bell stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Acidic fibroblast growth factor (aFGF) is expressed in the neuronal and glial spinal cord cells of adult mice.

Fibroblast growth factors (FGFs) are known to be synthesized in the central nervous system (CNS) and to act on CNS cells in vitro, but less is known about their synthesis, expression, and role in vivo. In this work, using specific anti-acidic fibroblast growth factor (aFGF) antibodies, we have shown for the first time, by immunohistochemistry, that aFGF is expressed in spinal cord cells of young adult normal mice. This expression is predominant in the cell nucleus. Using immunohistochemical double staining procedures, we identified the cell type expressing aFGF as neurons, astrocytes, and oligodendrocytes, but for each type, cells were not all positively immunostained.

Animals↗
PubMed1991

Hepatocyte growth factor in human placenta and trophoblastic disease.

The hepatocyte growth factor (HGF) is an acidic protein with a strong mitogenic effect on hepatocytes. Hepatocyte growth factor mRNA recently was cloned from a placental cDNA library. Here we demonstrate the purification of HGF from human placenta with heparin-agarose chromatography and TSK-heparin high-pressure liquid chromatography and describe the distribution of placental HGF by immunohistochemistry using a polyclonal antibody to HGF. The yield of HGF from the placenta was approximately 100 to 200 times greater than that previously obtained from human plasma. Placental HGF was expressed strongly in the villous syncytium, extravillous trophoblast, and amnionic epithelium, and, to a lesser degree in endothelial cells and villous mesenchyme. Hepatocyte growth factor also was identified in the trophoblast of complete hydatidiform moles, choriocarcinomas, and a case of blighted ovum. The presence of HGF in an organ characterized by rapid cell proliferation during gestation and in trophoblastic tumors strongly suggests that the growth-regulating effect of HGF is not limited to hepatocytes.

Abortion, Spontaneous↗
PubMed1990

Identification and partial characterization of receptor binding sites for HGF on rat hepatocytes.

Hepatocyte Growth Factor (HGF) (also known as Hepatopoietin A [HPTA] (1-9) is a heterodimeric heparin-binding polypeptide mitogen for hepatocytes distinct from other well-known growth factors. In this study, biologically active radioiodinated HGF was used to identify binding sites on intact hepatocytes in culture. The results show the presence of relatively low affinity binding sites due to the presence of heparin or heparin-like molecules and high affinity specific receptor binding sites on the cell surface of intact hepatocytes. Scatchard analysis of binding data indicates an apparent dissociation constant (Kd) of 3.5 nM with 120,000 sites per hepatocyte for the cell-surface receptor. Analysis of affinity cross-linked 125I-HGF-receptor complex by SDS-PAGE under non-reducing conditions reveals the presence of a distinct band with apparent Mr of 230,000. These data show that HGF exerts its biological effect on hepatocytes (stimulation of DNA synthesis) through a specific and unique cell-surface receptor.

Animals↗