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Biomedical subjects

R Lim

Publications and source records attributed to R Lim.

At least 91 records · Page 5Linked to original sources
PubMed1992

Expression of glial fibrillary acidic protein in human medulloblastoma cells treated with recombinant glia maturation factor-beta.

Medulloblastoma, a common pediatric brain tumor, is a primitive neuroectodermal tumor which often displays neuronal and/or glial characteristics. We have investigated the consequences of treating cell lines derived from a human medulloblastoma with glia maturation factor-beta (GMF-beta), a protein found in mammalian brain. GMF-beta promotes growth arrest and morphological alteration of cultured glioma and neuroblastoma cells. The proliferation of medulloblastoma cells was arrested 24-48 hr after exposure to human recombinant GMF-beta. During the same period, treated cells acquired a morphology similar to that of mature astrocytes. By 72 hr, all treated cells bound an antibody against glial fibrillary acidic protein (GFAP), a distinguishing biochemical feature of mature astrocytes. Immunoreactivity was accompanied by de novo expression of GFAP mRNA. Our observations are the first demonstration of the induction of morphological and biochemical characteristics of mature astrocytes in cultured medulloblastoma-derived cells by an exogenous factor.

Cell Division↗
PubMed1991

Glia maturation factor beta stimulates axon regeneration in transected rat sciatic nerve.

Rat sciatic nerves were bilaterally transected and repaired with an entubulation technique. The nerve interstump gap was filled with either collagen gel or collagen gel mixed with a putative neurotrophic factor (leupeptin, 4-aminopyridine, lipid angiogenic factor or glia maturation factor beta (GMF-beta]. Six weeks after nerve transection, the myelinated distal stump axons were quantified for each nerve. Only the nerves treated with GMF-beta had significantly more axons than the control side.

Animals↗
PubMed1991

Early prognosis after thrombolysis: value of exercise radionuclide ventriculography performed on anti-ischaemic medication.

We examined the prognostic value of exercise radionuclide ventriculography (RNV) performed on anti-ischaemic medication following thrombolysis. Within 3 months of thrombolysis for first myocardial infarction, 31 medically treated patients with revascularisable but non-critical and minimally symptomatic coronary disease had left ventricular ejection fraction (LVEF) measured by first-pass exercise RNV. This was first performed off treatment and then repeated within 4 weeks on patients' regular medication. Follow-up at 12 months post-thrombolysis showed that 5 patients (Group I) had suffered significant recurrent symptoms (worsening angina requiring revascularisation in 3, unstable angina in 1, reinfarction in 1), but 26 remained well (Group II). Both groups were similar in age, post-thrombolytic severity of coronary disease, exercise LVEF whether off (39% vs 43%) or on medication (43% vs 44%), and change in LVEF with exercise ([symbol: see text]LVEF) off medication (-11% vs - 3%). However, on medication, there was a significant difference in mean [symbol: see text]LVEF between Groups I and II (-11% vs + 5%, P = 0.0008, 99% confidence interval = 4 to 26%). Thus, following thrombolysis, an abnormal [symbol: see text]LVEF despite anti-ischaemic medication may identify patients at risk of significant early recurrent ischaemia. Post-thrombolysis prognostic testing by exercise RNV may therefore be of greater value when performed on rather than off medication.

Adult↗
PubMed1991

Molecular cloning and expression of biologically active human glia maturation factor-beta.

Glia maturation factor-beta, a protein found in the brains of all vertebrates thus far examined, appears to play a role in the differentiation, maintenance, and regeneration of the nervous system. Using oligonucleotide probes based on the sequences of three tryptic peptides derived from bovine glia maturation factor-beta, we screened a human brainstem cDNA library in lambda gt11. A 0.7-kb clone was isolated, sequenced in its entirety, and found to encode a polypeptide of 142 amino acids which contained regions identical to the three bovine peptides. This polypeptide, human recombinant glia maturation factor-beta, has been expressed in Escherichia coli and found to possess structural characteristics and biological activity indistinguishable from those of the native bovine protein.

Amino Acid Sequence↗
PubMed1991

Bradyarrhythmias in acute myocardial infarction: should thrombolysis lower the decision threshold for temporary pacing?

Both acute myocardial infarction and reperfusion therapy with thrombolytic agents may be associated with bradyarrhythmias, and there may be a case for 'prophylactic' insertion of a temporary pacing wire in selected patients. We describe 4 patients in whom clinical decisions had to be made concerning the appropriateness and timing of temporary pacing, and discuss the implications for modern guidelines on the indications for pacing in such a setting.

Bradycardia↗
PubMed1991

Bronchial reactivity in patients undergoing long-term haemodialysis for chronic renal failure.

Trapping of neutrophils within the lung occurs in patients undergoing haemodialysis and is also a possible mechanism in the pathogenesis of bronchial hyper-responsiveness. Falls in peak expiratory flow rate occur in most dialysis patients, and some develop overt asthmatic symptoms. To see whether these changes in airway function are secondary to increases in bronchial reactivity during haemodialysis, we therefore performed histamine challenge testing in 6 non-asthmatic patients before and after haemodialysis. No change in reactivity was observed, suggesting that haemodialysis does not commonly result in bronchial hyper-reactivity in non-asthmatic individuals.

Adult↗
PubMed1991

Do routine clinic visits prevent de-stabilization in patients awaiting coronary revascularization?

We examined retrospectively the usefulness of routine clinic visits in preventing adverse cardiac events in 115 patients awaiting coronary surgery or angioplasty. Mean waiting time from angiography to revascularization was 126 days. A total of 126 visits were made by 80 patients. No deaths occurred, but one patient, despite three visits, suffered myocardial infarction at 316 days post-angiography. Eight patients required admission for unstable angina, five having been on the waiting list for less than 5 weeks. The mean number of clinic visits, number of diseased vessels and proportion on triple anti-ischaemic therapy were similar in the patients suffering such events and those remaining stable. In conclusion, the inherent unpredictability of coronary disease greatly limits the role of interim clinic visits in the prevention of adverse cardiac events in patients awaiting revascularization.

Adult↗
PubMed1990

Disulfide isoforms of recombinant glia maturation factor beta.

Recombinant human glia maturation factor beta (r-hGMF-beta) is a single-chain polypeptide (141 amino acid residues) containing three cysteines, at positions 7, 86 and 95. Nascent r-hGMF-beta exists in the reduced state and has no biological activity. The protein can be activated through oxidative refolding by incubation with a mixture of reduced and oxidized glutathione. Reverse-phase HPLC analysis of the refolded r-hGMF-beta shows the presence of four peaks, corresponding to the reduced form plus three newly generated intrachain disulfide-containing isoforms predicted from the number of cysteine residues. Only one isoform shows biological activity when tested for growth suppression on C6 glioma cells. We infer from the HPLC elution pattern that the active form contains the disulfide bridge Cys86-Cys95.

Animals↗
PubMed1990

Identification of injury-induced mitotic cells in adult rat cerebral cortex by neuron-specific markers.

Adult rat brains were injured by partial decortication. Four days later, the brains were examined for mitotic cells that were immunostained for neuronal markers: the neuron-specific enolase (NSE) and neurofilaments (NF). Of the 30 rats stained for NSE, 15 were found to have NSE-positive cells containing mitotic figures; of the 25 rats stained for NF, 12 possessed NF-positive cells in mitosis. Most of the mitotic neurons were granule cells and small- and medium-size pyramidal cells and were located in cortical layer III within 500 microns from the wound margin. Although a rare phenomenon, mitosis of neurons in the neocortex of mature mammalian brains may reflect neuronal plasticity in response to injury.

Animals↗
PubMed1990

Glia maturation factor beta regulates the growth of N18 neuroblastoma cells.

Glia maturation factor beta (GMF-beta) is a 17-kDa growth regulating protein isolated from the brain. The effect of bovine GMF-beta on neurons was tested on the neuroblastoma line N18 and the pheochromocytoma line PC12. GMF-beta inhibited the proliferation of N18 cells and promoted their neurite outgrowth, with an increase in neurofilament protein, but had no effect on PC12 cells. This was in contrast to nerve growth factor (NGF) which regulated PC12 but not N18. Acidic fibroblast growth factor (FGF), on the other hand, had a weak effect on PC12 but none on N18. Antisera against GMF-beta and NGF neutralized the biological activity of the corresponding growth factors but showed no cross-neutralization. Fluorescence visualization revealed the binding of GMF-beta to N18 cells but not to PC12 cells; the opposite was true with NGF.

Adrenal Gland Neoplasms↗
PubMed1990

Factors influencing the compliance of patients using oxygen concentrators for long-term home oxygen therapy.

A previous study in the Liverpool district on patients receiving long term oxygen treatment using a domiciliary oxygen concentrator showed that only 55% were both using oxygen therapy correctly and had stopped smoking. To try and identify which factors influence patient behaviour, all 55 patients in this district receiving long-term oxygen therapy for hypoxaemic chronic airflow limitation were studied. We found that those with more symptoms were more likely to comply with this therapy. The prescription of a concentrator on the advice of a hospital physician did not improve on the compliance rates attained in those patients assessed by the general practitioner alone.

Adult↗