Joint replacement and particulate wear debris.
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Foreign Bodies↗
Biomedical subjects
H Phillips
Publications and source records attributed to H Phillips.
Employing general practitioners in accident and emergency departments. All doctors should spend time in general practice to learn skills of GPs.
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Clinical Competence↗
Synchronous onset of NGF and TrkA survival dependence in developing dorsal root ganglia.
Determinations of dorsal root ganglion (DRG) neuron loss in nerve growth factor (NGF) and neurotrophin-3 (NT-3) null mutant mice have supported the concept that neurons can switch neurotrophin dependence by revealing that many neurons must require both of these factors acting either sequentially or simultaneously during development. The situation is complex, however, in that NT-3(-/-) mutant mice show far greater neuron loss than mice deficient in the NT-3 receptor TrkC, suggesting that NT-3 may support many DRG neurons via actions on the NGF receptor TrkA. To assess the possibility of ligand-receptor cross-talk as a developmental mechanism, we have compared the onset of survival dependence of lumbar DRG neurons on NT-3, TrkC, NGF, and TrkA signaling in mice deficient in these molecules as a result of gene targeting. At embryonic day 11.5 (E11.5), virtually all lumbar DRG cells express TrkC mRNA and many require NT-3 and TrkC signaling for survival. In contrast, although many lumbar DRG cells also express TrkA at E11.5, there is little survival dependence on TrkA signaling. By E13.5, most lumbar DRG cells have downregulated TrkC mRNA. The onset of survival dependence on NGF and TrkA-signaling is concurrent and of equal magnitude at E13.5, demonstrating that NT-3 alone does not support DRG neurons via TrkA, nor can NT-3 compensate for the loss of NGF. We conclude that many murine DRG cells require NT-3 activation of TrkA is unimportant to these early NT-3 survival-promoting actions. We suggest that the discrepancy in cell loss between NT-3(-/-) and trkC(-/-) mutants is attributable to the ability of NT-3 to support DRG neurons via TrkA in the artificial situation where TrkC is absent.
Animals↗
Renal and neuronal abnormalities in mice lacking GDNF.
Glial cell-line derived neurotrophic factor (GDNF) is a potent survival factor for embryonic midbrain dopaminergic, spinal motor, cranial sensory, sympathetic, and hindbrain noradrenergic neurons, and is available to these cells in vivo. It is therefore considered a physiological trophic factor and a potential therapeutic agent for Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. Here we show that at postnatal day 0 (P0), GDNF-deficient mice have deficits in dorsal root ganglion, sympathetic and nodose neurons, but not in hindbrain noradrenergic or midbrain dopaminergic neurons. These mice completely lack the enteric nervous system (ENS), ureters and kidneys. Thus GDNF is important for the development and/or survival of enteric, sympathetic and sensory neurons and the renal system, but is not essential for catecholaminergic neurons in the central nervous system (CNS).
Animals↗
Identification of Gas6 as a growth factor for human Schwann cells.
Schwann cells are one of the principal components of the peripheral nervous system. They play a crucial role in nerve regeneration and can be used clinically in the repair of injured nerves. We have established serum-free, defined culture conditions that rapidly expand adult human Schwann cells without fibroblast growth. We find that Gas6, a ligand for the Axl and Rse/Tyro3 receptor protein tyrosine kinase family, stimulates human Schwann cell growth, increasing both cell number and thymidine incorporation. Gas6 has synergistic effects with the other known human Schwann cell mitogens, heregulin/glial growth factor and forskolin. Addition of Gas6 causes phosphorylation of Axl and Rse/Tyro3 simultaneously and results in ERK-2 activation. A combination of Gas6 with heregulin and forskolin, on a defined background, supports maximal Schwann cell proliferation, while preserving the typical Schwann cell morphology and expression of the Schwann cell markers S-100, glial fibrillary acidic protein, and low-affinity nerve growth factor receptor. Gas6 mRNA is present in both spinal motor neurons and large neurons of the dorsal root ganglia, and neural injury has been reported to upregulate Rse/Axl in the schwann cell. This is the first demonstration of a potentially important biological role for the human Gas6/Rse-Axl system.
Animals↗
Complete analysis of the presenilin 1 gene in early onset Alzheimer's disease.
The presenilin 1 gene has recently been identified as the locus on chromosome 14 which is responsible for a large proportion of early onset, autosomal dominantly inherited Alzheimer's disease (AD). We have elucidated the intron/exon structure of the gene and designed intronic primers to enable direct sequencing of the entire coding region (10 exons) of the presenilin gene in a large number of families. This strategy has enabled us to find a further two novel mutations in the gene. We discuss the distribution of mutations and the proportions of autosomal dominant AD with a mean age of onset below 60 years caused by mutations in this gene.
Alzheimer Disease↗
A further presenilin 1 mutation in the exon 8 cluster in familial Alzheimer's disease.
Recent studies suggest that mutations in the presenilin 1 gene, which encodes a polypeptide predicted to be a multispanning membrane protein, are responsible for the majority of cases of early onset, autosomal dominant Alzheimer's disease. Here we describe a further mutation in the presenilin 1 gene (R269G) in a family with early onset Alzheimer's disease. This mutation is in exon 8 which appears to be a favoured region for pathogenic mutations. In the presenilin protein the region coded for by this exon is likely to comprise a domain located on the membrane surface. We discuss the likely effects of the exon 8 mutations on the structure of the exon and in the pathogenesis of the disease.
Alzheimer Disease↗
Nicotinamide pharmacokinetics in humans: effect of gastric acid inhibition, comparison of rectal vs oral administration and the use of saliva for drug monitoring.
The effect of inhibiting gastric acid secretion on nicotinamide pharmacokinetics was studied in five volunteers with the intent of reducing the large variations observed previously in the time to and magnitude of peak plasma concentrations. Plasma levels were determined using a standard high-performance liquid chromatography (HPLC) method after an oral dose of 3 g of nicotinamide either alone or preceded by pretreatment with omeprazole. Suppression of gastric acid production had no significant effect on the rate of uptake or on the peak levels achieved. To bypass gastric acidity, the rectal route was also assessed using a suppository in four volunteers and one patient undergoing radiotherapy. Absorption was slow and variable and much lower plasma levels were observed than after oral dosing. Thus, no improvement in the pharmacokinetics of nicotinamide was observed using either of these two approaches. Parallel estimations were made using a novel and non-invasive method for monitoring nicotinamide pharmacokinetics in saliva. A large and variable fraction of the total amount of nicotinamide-related material in saliva was found to be nicotinic acid, a metabolite not normally found in human plasma. This conversion was inhibited by the use of a chlorhexidine mouthwash, indicating that the oral flora was responsible for its production. The time to peak levels of nicotinamide or of nicotinamide plus nicotinic acid in saliva correlated well with that in plasma. However, peak concentrations for nicotinamide alone were significantly lower than in plasma, and very variable, whereas for nicotinamide plus nicotinic acid saliva levels were 20-30% higher, but more consistent. Although there are some practical difficulties in quantitatively handling saliva, the method is very useful for monitoring nicotinamide pharmacokinetics and for assessment of compliance with nicotinamide treatment.
Absorption↗
The bisindolylmaleimide GF 109203X, a selective inhibitor of protein kinase C, does not inhibit the potentiating effect of phorbol ester on ethanol-induced phospholipase C-mediated hydrolysis of phosphatidylethanolamine.
In fibroblasts, the protein kinase C (PKC) activator phorbol 12-myristate (PMA) either inhibits or stimulates phospholipase C-mediated hydrolysis of phosphatidylethanolamine in the absence or presence of ethanol, respectively. Here, we demonstrate that the specific PKC inhibitor bisindolylmaleimide GF 109203X prevents only the inhibitory, but not the stimulatory, PMA effect.
3T3 Cells↗
NGF receptor expression in sensory neurons develops normally in embryos lacking NGF.
Numerous in vivo and in vitro studies have shown that NGF increases the expression of its receptors, p75 and TrkA, in NGF-responsive cell lines and in NGF-responsive neurons of the developing and mature nervous system. To determine if endogenous NGF is required for the normal developmental increase in p75 and TrkA expression that occurs in sensory neurons shortly after they innervate their targets, we used quantitative RT/PCR to compare the levels of p75 and trkA mRNAs in the trigeminal ganglia of normal mouse embryos and embryos that are homozygous for a null mutation in the NGF gene. We show that the marked increase in p75 and trkA mRNA expression that occurs between E11 and E13 in normal embryos takes place on time and to the same extent in NGF-/- embryos. We also show that trigeminal neurons from E13 NGF+/+ and NGF-/- embryos have very similar dose responses for survival induced by NGF. These findings clearly show that the expression of both p75 and TrkA and the sensitivity of developing sensory neurons to NGF do not require and are not modulated by target-derived NGF during the early stages of target field innervation.
Animals↗
Radiological decompression of bowel gas and return of mediastinal shift in congenital diaphragmatic hernia: a signal for surgical repair?
The objective of this study was to document the pattern of bowel gas decompression and mediastinal shift in infants with congenital diaphragmatic hernia (CDH) before delayed surgical correction. The setting was the Neonatal Intensive Care Unit, Royal Alexandra Hospital, Edmonton. The design was a retrospective review of radiographs and charts of all infants with CDH between January 1990 and December 1993. Bowel gas in the upper and middle one third of the hemithorax was classified as grade III and grade II, respectively. Bowel gas in the lower one third of the hemithorax or absent bowel gas was classified as grade I. All the infants showed partial return of the contralateral shift in the mediastinum toward the midline when comparing the admission chest radiographs with the immediate preoperative films. Complete return of the mediastinum to normal (using the first postoperative radiograph as the gold standard) occurred in all but 1 of the 10 infants on extracorporeal membrane oxygenation (ECMO) (90%) and 7 of 13 (54%) of conventionally treated infants (P = .12). At the time of the first radiograph, a similar proportion of non-ECMO and ECMO infants (61% versus 70%, respectively) had either grade II or III bowel gas patterns. By 72 hours none of the non-ECMO-treated infants (who were paralyzed with muscle relaxants) had bowel gas in the middle and upper one third of the hemithorax. In contrast, 66% of infants on ECMO still had a grade II bowel gas pattern at 72 hours (P < .05), with 4 infants showing an actual increase in bowel gas after discontinuation of muscle relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)
Case-Control Studies↗
Total knee arthroplasty in the management of proximal tibial stress fractures.
Five patients with stress fractures of the proximal tibia adjacent to an arthritic knee joint were treated by resurfacing arthroplasty with intramedullary fixation of the fracture. All five fractures healed and limb realignment was achieved. The literature concerning proximal tibial stress fractures in relation to the arthritic knee and the management of this condition is reviewed.
Aged↗
Neurotrophin-4/5 is a survival factor for embryonic midbrain dopaminergic neurons in enriched cultures.
Parkinson's disease is a prevalent neurological disease characterized by profound and incapacitating movement disorders. A common pathology in Parkinson's patients is degeneration of substantia nigra dopaminergic neurons that innervate the striatum and a corresponding decrease in striatal dopamine content. We now report that NT-4/5 can prevent the death of rat embryonic substantia nigra dopaminergic neurons in low density, enriched, primary cultures. Furthermore, these neurons express messenger RNA encoding the trkB receptor for NT-4/5 and transcripts for NT-4/5 are present in their environment. In addition, we demonstrate that NT-4/5 protects embryonic dopaminergic neurons from the toxic effects of the neurotoxin MPP+. Thus, NT-4/5 could be a physiological survival factor for midbrain dopaminergic neurons and may be useful as a therapeutic agent for Parkinson's disease.
1-Methyl-4-phenylpyridinium↗
A cytokine receptor gene cluster in the X-Y pseudoautosomal region?
The receptors for interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) are heterodimers comprised of ligand specific alpha chains and a common beta chain. The genes encoding the IL-5 receptor alpha chain and the common beta chain reside on chromosome 3 and 22 respectively, while the GM-CSF receptor alpha chain gene (CSF2RA) has been mapped to the pseudoautosomal region (PAR) of the sex chromosomes, which is a 2.6-Mb stretch of homologous sequence at the tips of the short arms within which a single obligatory recombination occurs during male meiosis. We have mapped the gene encoding the IL-3 receptor alpha chain (IL3RA) to the sex chromosomes by polymerase chain reaction (PCR) analysis of human-mouse or human-chinese hamster cell hybrids, and to Yp13.3 and Xp22.3 using fluorescence in situ hybridization. To explore the possibility that IL3RA is located within the pseudoautosomal region we screened the Centre d'Etude du Polymorphisme Humain (CEPH) pedigrees for an informative-restriction fragment-length polymorphism (RFLP) that showed male meiotic recombination. Two informative CEPH pedigrees were identified that displayed this phenomenon, confirming the psuedoautosomal location of IL3RA. Using long-range restriction mapping we have found that IL3RA maps to the same 190-kb restriction fragment as CSF2RA, suggesting that a cytokine receptor gene cluster may reside in the PAR.
Base Sequence↗
Antitumor response to recombinant murine interferon gamma correlates with enhanced immune function of organ-associated, but not recirculating cytolytic T lymphocytes and macrophages.
The mechanism of therapeutic activity for recombinant murine interferon-gamma (rMu IFN gamma) in the treatment of metastatic disease was investigated by comparing effector cell augmentation with therapeutic activity in mice bearing experimental lung metastases (B16-BL6 melanoma). Effector cell functions in spleen, peripheral blood, and lung (the tumor-bearing organ) were tested after 1 week and 3 weeks of rMu IFN gamma administration (i.v. three times per week). Natural killer (NK), lymphokine-activated killer (LAK), cytolytic T lymphocyte (CTL) activities against specific and nonspecific targets, and macrophage tumoristatic activity were measured. rMu IFN gamma demonstrated immunomodulatory activity in most assays of immune function. The optimal therapeutic protocol of rMu IFN gamma (2.5 x 10(6) U/kg, three times per week) prolonged survival and decreased the number of pulmonary metastatic foci. This therapeutic activity was correlated with specific CTL activity from pulmonary parenchymal mononuclear cells (PPMC), but not from spleen or blood. Macrophage tumoristatic activity in PPMC also correlated with therapeutic activity, but activity in alveolar macrophages did not. However, therapeutic activity did not correlate with NK or LAK activity at any site. These results demonstrate that the optimal therapeutic protocol is the same as the optimal immunomodulatory dose for pulmonary CTL and macrophage activities. Furthermore, while immunological monitoring may help to optimize treatment protocols, current monitoring procedures that use readily accessible sites, particularly peripheral blood, may not accurately predict the therapeutic efficacy of biological response modifiers in clinical trials.
Animals↗
A comparison of cefpodoxime proxetil and cefaclor in the treatment of acute exacerbation of COPD in adults.
In this multicenter, observer-blinded study, 301 patients with signs and symptoms of acute bacterial exacerbation of COPD were randomized (2:1) to receive either cefpodoxime proxetil (200 mg, bid) or cefaclor (250 mg, tid) for 10 days. Clinical and microbiologic evaluations were performed before treatment, during therapy (study days 3 to 5), at the end of therapy (3 to 7 days posttreatment), and at long-term follow-up (4 weeks posttreatment). The most common pretreatment isolates were Haemophilus influenzae, Haemophilus parainfluenzae, and Streptococcus pneumoniae. Significantly (p < 0.001) more bacterial isolates were susceptible in vitro to cefpodoxime (233 of 256, 91 percent) than to cefaclor (215 of 255, 84 percent). There were no statistically significant differences between the two drug regimens in eradication of the initial pathogen (cefpodoxime, 116 of 128, 91 percent; cefaclor, 59 of 64, 92 percent) or end-of-therapy clinical response (cure + proved; cefpodoxime, 99 of 100, 99 percent; cefaclor, 45 of 49, 92 percent) rates for evaluable patients. Both drug treatments were well-tolerated, with a similar incidence of drug-related adverse events (cefpodoxime 11 percent, cefaclor 12 percent). Cefpodoxime (bid) was as safe and effective as cefaclor (tid) in the treatment of acute exacerbation of COPD. The less frequent dosing regimen of cefpodoxime may improve patient compliance compared to those antibiotics that require three or four daily doses.
Acute Disease↗
Effect of tumor burden and route of administration on the immunotherapeutic properties of polyinosinic-polycytidylic acid stabilized with poly-L-lysine in carboxymethyl cellulose [Poly(I,C)-LC].
We examined the immunomodulatory and therapeutic activities of poly(I,C)-LC. Mice received a subcutaneous (s.c.) injection of sufficient numbers of MBL-2 lymphoma cells to produce in 1 week either a high or low tumor burden. A week after tumor cell injection, poly(I,C)-LC treatment was initiated; the agent was administered intraperitoneally (i.p.) at 5 mg/kg twice a week or at 2.5 or 0.5 mg/kg every day or as an intravenous (i.v.) injection at 0.5, 0.05, or 0.005 mg/kg three times a week. Poly(I,C)-LC treatment significantly increased antitumor effector cell functions in a variety of organs (including spleen, lungs, and peritoneum), as shown by increased killing of MBL-2 cells in vitro and increased tumor cell killing by natural killer cells and macrophages. Furthermore, prolongation of survival correlated with peritoneal macrophage tumoricidal activity when poly(I,C)-LC was given i.p. and with pulmonary effector cell function (including natural killer, cytolytic T-lymphocyte and macrophage tumoricidal activity) when the agent was administered i.v.
Animals↗
Bone grafting in primary uncemented total knee arthroplasty.
Forty-two uncemented ICLH and Freeman Samuelson knee replacements that required bone grafting for tibial defects were studied before and after operation. The pattern of bone loss, the techniques of grafting, and the soft tissue releases required are described. Union of the graft was observed in 98% of cases, confirming the value of bone grafting in the reconstruction of the deformed, arthritic knee.
Aged↗