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Biomedical subjects

S H Green

Publications and source records attributed to S H Green.

At least 37 records · Page 2Linked to original sources
PubMed1997

Regulation of rat cardiac myocyte growth by a neuronal factor secreted by PC12 cells.

Sympathetic innervation of cardiac myocytes in vitro induces growth independent of anatomic contact between the neurons and myocytes and is not mediated by alpha- or beta-adrenergic receptor stimulation. To establish a model system that will allow purification and identification of the neuronal factor(s) responsible for mediating this regulation, we have initiated studies utilizing conditioned medium from the PC12 cell line. PC12 cells acquire a cholinergic sympathetic neuronal phenotype when exposed to nerve growth factor. Culture medium conditioned by neuronal PC12 cells, but not nonneuronal PC12 cells, induces growth in newborn rat cardiac myocytes as measured by surface area and [35S]methionine incorporation into protein and increases expression of atrionatriuretic peptide, a marker for myocyte hypertrophy. The magnitude of the growth response is dose-dependent and mimics the response to sympathetic innervation. The myocyte response to conditioned medium is not detectable after 24 h of exposure; maximal rate of protein synthesis is obtained within 48 h. Neuronally differentiated PC12 cell-conditioned medium stimulation of growth could not be mimicked by alpha- or beta-adrenergic agonists or muscarinic agonists, nor inhibited by alpha- or beta-adrenergic antagonists, nor by muscarinic antagonists. Neuropeptide Y and somatostatin, peptides known to be present in PC12 cells and sympathetic neurons, were also ineffective at reproducing the effect of neuronally differentiated PC12 cell-conditioned medium. These data indicate that neuronal cells release a soluble factor, different from neurotransmitter, which stimulates myocyte growth. They further identify the PC12 cell line as providing a convenient and abundant supply of this molecule, thus facilitating its further characterization.

Animals↗
PubMed1995

A timetable of events during programmed cell death induced by trophic factor withdrawal from neuronal PC12 cells.

We describe a timetable of events during programmed cell death (PCD) in neuronal PC12 cells, specifically, Ras signaling, immediate-early gene (IEG) expression, DNA fragmentation and commitment to PCD. Commitment occurs over a period from 10-20 hr after NGF withdrawal. Ras signaling declines rapidly after NGF removal, reaching minimal levels within 2-4 hr, well before the onset of commitment. DNA fragmentation, detected by TUNEL reaction, begins about 24 hr after NGF withdrawal, well after all cells are committed, but coincident with the onset of cell dissolution previously determined by trypan blue exclusion (Mesner et al., 1992). Among the IEGs studied here, c-jun and TIS21 are expressed within 6 hr after NGF withdrawal. Expression of c-fos, egr-1, and TIS11 does not begin until 20 hr after NGF withdrawal. IEG expression generally ends by 24 hr after NGF withdrawal. The IEGs TIS7 and nur77 are not expressed during PCD, yielding a pattern distinct from that following other stimuli. An identical pattern of IEG expression occurs in non-neuronal PC12 cells deprived of serum, although expression begins at 10-14 hr after serum withdrawal. A similar IEG expression pattern was observed in Rat-1 fibroblasts, with various genes expressed 6-18 hr after serum withdrawal. In none of these cell types did expression of the stress-related gene Hsp70 change following trophic factor withdrawal. The distinctive pattern of IEG expression described here should facilitate identification of intracellular regulatory signals active during PCD.

Animals↗
PubMed1994

What is segmental neurofibromatosis?

Two unrelated children with von Recklinghausen's neurofibromatosis (NF1) had mothers with cutaneous NF1 lesions in a limited distribution. The cutaneous pattern in the mother of case 1 was clearly segmental, and probably represents mosaicism for the NF1 mutation which was passed on to the child. In the second case the distribution in the mother was less obviously segmental, but may still represent mosaicism. It is more difficult to diagnose mosaicism for NF1 in individuals with no affected offspring, or with more limited cutaneous manifestations. The difficulties in defining segmental NF and assigning a genetic risk are discussed.

Child↗
PubMed1993

Congenital livedo reticularis and recurrent stroke-like episodes.

Three children with pronounced livedo reticularis present since birth (cutis marmorata-telangiectasia congenita) have been followed to the ages of eight, 17 and 21 years. During childhood they developed frequent recurrent transient stroke-like hemipareses, affecting either side of the body, associated with ipsilateral pain, headache, visual symptoms, dysphasia, fits and confusion. Intellectual failure and, in one, progressive spasticity have followed. Attacks were more frequent in winter. Other problems have included abnormal peripheral vascular responses to temperature change, gastro-intestinal bleeding, glaucoma, local tissue hypertrophy and, in the two older patients, renal involvement with hypertension. Their condition represents a form of congenital vasculopathy. Anticonvulsants, anti-migraine agents, anti-platelet drugs and flunarizine have been ineffective. Nifedipine prevented further attacks in one patient and reduced attacks in another, but has not helped the third child. Adequate clothing and warmth may also be important.

Adult↗
PubMed1992

PC12 cell neuronal differentiation is associated with prolonged p21ras activity and consequent prolonged ERK activity.

Expression of oncogenic ras in PC12 cells causes neuronal differentiation and sustained protein tyrosine phosphorylation and activity of extracellular signal-regulated kinases (ERKs), p42erk2 and p44erk1. Oncogenic N-ras-induced neuronal differentiation is inhibited by compounds that block ERK protein tyrosine phosphorylation or ERK activity, indicating that ERKs are not only activated by p21ras but serve as the primary downstream effectors of p21ras. Treatment of PC12 cells with nerve growth factor or fibroblast growth factor results in neuronal differentiation and in a sustained elevation of p21ras activity, of ERK activity, and of ERK tyrosine phosphorylation. Epidermal growth factor, which does not cause neuronal differentiation, stimulates only transient (< 1 hr) activation of p21ras and ERKs. These data indicate that transient activation of p21ras and, consequently, ERKs is not sufficient for induction of neuronal differentiation. Prolonged ERK activity is required: a consequence of sustained activation of p21ras by the growth factor receptor protein tyrosine kinase.

Animals↗
PubMed1992

Nerve growth factor withdrawal-induced cell death in neuronal PC12 cells resembles that in sympathetic neurons.

Previous studies have shown that in neuronal cells the developmental phenomenon of programmed cell death is an active process, requiring synthesis of both RNA and protein. This presumably reflects a requirement for novel gene products to effect cell death. It is shown here that the death of nerve growth factor-deprived neuronal PC12 cells occurs at the same rate as that of rat sympathetic neurons and, like rat sympathetic neurons, involves new transcription and translation. In nerve growth factor-deprived neuronal PC12 cells, a decline in metabolic activity, assessed by uptake of [3H]2-deoxyglucose, precedes the decline in cell number, assessed by counts of trypan blue-excluding cells. Both declines are prevented by actinomycin D and anisomycin. In contrast, the death of nonneuronal (chromaffin-like) PC12 cells is not inhibited by transcription or translation inhibitors and thus does not require new protein synthesis. DNA fragmentation by internucleosomal cleavage does not appear to be a consistent or significant aspect of cell death in sympathetic neurons, neuronal PC12 cells, or nonneuronal PC12 cells, notwithstanding that the putative nuclease inhibitor aurintricarboxylic acid protects sympathetic neurons, as well as neuronal and nonneuronal PC12 cells, from death induced by trophic factor removal. Both phenotypic classes of PC12 cells respond to aurintricarboxylic acid with similar dose-response characteristics. Our results indicate that programmed cell death in neuronal PC12 cells, but not in nonneuronal PC12 cells, resembles programmed cell death in sympathetic neurons in significant mechanistic aspects: time course, role of new protein synthesis, and lack of a significant degree of DNA fragmentation.

Animals↗
PubMed1992

X-inactivation in girls with Rett syndrome.

Cytogenetic studies have been carried out on a series of nine girls with Rett syndrome, six of their mothers and nine normal female controls. No abnormality of the X-chromosome has been observed in any subject. X-inactivation studies using various methods of detecting the timing of individual band replication were performed. The overall pattern seen was essentially the same in all subjects, but in the patients with Rett syndrome there may be an alteration in the timing of the X-inactivation process in the region Xp11.3 or 4-->Xp21.

Adolescent↗
PubMed1992

Anal abnormalities in childhood myotonic dystrophy--a possible source of confusion in child sexual abuse.

Myopathic involvement of the perianal musculature is one of the less well recognised features of myotonic dystrophy in children and may present with physical signs suggestive of sexual abuse. Details of six children with myotonic dystrophy are presented to emphasise the importance of considering an underlying myopathic condition in the differential diagnosis of anal laxity.

Adolescent↗
PubMed1991

NGF and EGF rapidly activate p21ras in PC12 cells by distinct, convergent pathways involving tyrosine phosphorylation.

Activation of p21ras, demonstrated directly as an increase in p21ras-associated GTP, was induced rapidly but transiently by both nerve growth factor (NGF) and epidermal growth factor (EGF) in PC12 cells. The factors activate p21ras to equal extents and with virtually identical time courses. Growth factor-induced p21ras activation and tyrosine phosphorylation have similar time courses and sensitivities to genistein inhibition, indicating that p21ras activation is a result of tyrosine kinase activity. Furthermore, PC12 mutants lacking the Trk NGF receptor tyrosine kinase also lack NGF-inducible p21ras activation. The protein kinase inhibitor K252a and the methyltransferase inhibitor MTA abolish NGF-induced, but not EGF-induced, p21ras activation--effects correlated with inhibition only of NGF-induced tyrosine phosphorylation. In spite of differences in sensitivity to genistein, MTA, and K252a, EGF- and NGF-stimulated p21ras activation are not additive, implying that they do share at least one step in common.

Animals↗
PubMed1991

ras isoprenylation is required for ras-induced but not for NGF-induced neuronal differentiation of PC12 cells.

We have used compactin, an inhibitor of mevalonate biosynthesis, to block p21ras posttranslational modification and membrane association in PC12 cells. Previous studies have demonstrated a requirement for isoprenylation for mitogenic effects of activated p21ras in mammalian cells and for function of RAS gene products in yeast. Immunoprecipitation of [35S]methionine-labeled p21ras from PC12 cell homogenates confirmed that the processed p21ras species is missing from compactin-treated PC12 cells. Immunoprecipitation from particulate and cytosolic fractions of PC12 cells confirmed that compactin blocks p21ras membrane association: p21ras is confined to the cytosol fraction. Induction of neuronal differentiation and ornithine decarboxylase (ODCase) transcription by oncogenic p21N-ras does not occur in compactin-treated cells indicating that activity of oncogenic p21N-ras expressed in PC12 cells is abolished by compactin treatment. Thus, p21ras isoprenylation or association with the membrane appears to be required for early responses and neuronal differentiation attributable to p21ras activation. In contrast, blockade of p21ras isoprenylation and membrane association by compactin treatment did not significantly reduce PC12 cell responses to NGF. Responses examined included rapid phosphorylation of tyrosine hydroxylase, rapid induction of ODCase expression, survival in serum-free medium and neuronal differentiation. Compactin blocked growth factor-induced rapid changes in cell surface morphology but did so whether this response was induced by NGF or by EGF. These results indicate that functional p21ras is not necessary for responses to NGF which in turn implies that if a ras-dependent NGF signal transduction pathway exists, as has been previously suggested, at least one additional ras-independent pathway must also be present.

Animals↗
PubMed1990

Oncogene N-ras mediates selective inhibition of c-fos induction by nerve growth factor and basic fibroblast growth factor in a PC12 cell line.

A cell line was generated from U7 cells (a subline of PC12 rat pheochromocytoma cells) that contains a stably integrated transforming mouse N-ras (Lys-61) gene under the control of the long terminal repeat from mouse mammary tumor virus. Such cells, designated UR61, undergo neuronal differentiation upon exposure to nanomolar concentrations of dexamethasone, as a consequence of expression of the activated N-ras gene (I. Guerrero, A. Pellicer, and D.E. Burstein, Biochem, Biophys. Res. Commun. 150:1185-1192, 1988). Exposure of UR61 cells to either nerve growth factor (NGF) or basic fibroblast growth factor (bFGF) results in a marked induction of c-fos RNA, with kinetics paralleling those of NGF- or bFGF-induced expression of c-fos RNA in PC12 cells. Dexamethasone-induced expression of activated N-ras p21 results in blocking of c-fos RNA induction by NGF or bFGF in a time-dependent manner. Activated N-ras p21-mediated inhibition of c-fos RNA induction in UR61 cells is selective for NGF and bFGF and is not due to selective degradation of c-fos RNA. Normal and transforming N-ras can trans activate the chloramphenicol acetyltransferase gene linked to mouse c-fos regulatory sequences when transient expression assays are performed. Our observations suggest that N-ras p21 selectively interacts with pathways involved in induction of c-fos expression which initiate at the receptors for NGF and bFGF.

Adrenal Gland Neoplasms↗
PubMed1990

Optic nerve hypoplasia: associations and management.

Since its first description optic nerve hypoplasia has been identified with increasing frequency, and a range of associated problems have been described. The major neurological and endocrine associations are well established, but those factors that predispose to the development of optic nerve hypoplasia remain unclear. To understand the aetiology of these problems better, and to formulate a management regime, we studied a consecutive series of 40 patients who were divided into three groups. Group 1 (n = 24) had severe bilateral optic nerve hypoplasia; group 2 (n = 10) had mild, bilateral optic nerve hypoplasia; and group 3 (n = 6) had unilateral optic nerve hypoplasia. Previously described aetiological factors (for example, low maternal age or maternal alcohol or drug ingestion) were not present in any of the groups; this removes the need to screen a specific population. It is important that careful neurological and developmental assessments are carried out in children with optic nerve hypoplasia to identify potential disease. The role of imaging is discussed.

Child↗
PubMed1989

Neurological complications of heart disease in childhood.

A retrospective review was undertaken of 10 years experience in a Regional referral centre for cardiothoracic surgery identified 37 children with cardiovascular disease who developed chronic neurological handicap. In two-thirds of these, neurological lesions occurred in association with cardiovascular surgery, whilst in one-third they were unrelated to surgery. Motor handicap was found in the majority (94 per cent) of cases, with hemiplegia, tetraplegia and paraplegia being the most common patterns. In half the children, motor and intellectual function was severely impaired. Neurological complications of cardiovascular disease account for approximately two per cent of children with cerebral palsy in the area served by our hospital. One per cent of children undergoing cardiopulmonary bypass surgery risk chronic neurological handicap. Potentially avoidable factors could only be identified in a small proportion of cases.

Cardiac Surgical Procedures↗
PubMed1988

Expression of human nerve growth factor receptor on cells derived from all three germ layers.

Nerve growth factor (NGF) is a protein which promotes the survival and differentiation of neuronal cells in vitro and plays an important role in neuronal development. In this study, we have examined the expression of the receptor for NGF (NGFR) in human neuronal and nonneuronal cells, both in tissue culture and in vivo. In addition to cell lines derived from neuroblastoma, astrocytoma, and melanoma, all of which share a common neuroectodermal origin, NGFR was detected in a number of cultured cells of mesenchymal, epithelial, and hematopoietic derivation. Immunohistochemical analysis showed that NGFR is expressed in several nonneural human tissues, and the cell types in which NGFR was found include derivatives from all three germ layers. Thus, our findings demonstrate that NGFR is much more widely expressed in human cells and tissues than was previously thought.

Cell Differentiation↗