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Biomedical subjects

J S McLean

Publications and source records attributed to J S McLean.

14 recordsLinked to original sources
PubMed2005

Detection of integrins in human cataract lens epithelial cells and two mammalian lens epithelial cell lines.

AIM: To compare the incidence of various integrin subunits in human cataract anterior lens epithelial cells (A-LEC) and in two mammalian LEC lines. METHODS: Circular sections of anterior capsules with attached LEC were obtained during cataract surgery. Integrin subunits were immunolocalised in these anterior LEC and in a human and rabbit LEC line, using four monoclonal antibodies specific for subunits alpha2, alpha3, and alpha5, and beta subunit 2. RESULTS: All of these subunits were found in at least a proportion A-LEC samples as follows: alpha2 71%, alpha3 92%, alpha5 62%, and beta2 24%. The human LEC line was immunoreactive for alpha2 and alpha3 only. The rabbit lens epithelial cell line was immunoreactive for alpha5 but there was no staining for alpha2, alpha3, or beta2. CONCLUSION: The A-LEC and mammalian LEC lines showed a similarity in their pattern of integrin expression. As these integrins are receptors for extracellular matrix (ECM) components, they are likely to be associated with the attachment and migration of LECs that precedes capsular opacification. Therefore these cell lines may be useful in the elucidation of mechanisms involved the pathogenesis of capsule opacification.

Animals↗
PubMed2004

Divergent roles of nitrergic and prostanoid pathways in chronic joint inflammation.

BACKGROUND: Nitrergic and prostanoid pathways have both been implicated in inflammatory processes. OBJECTIVE: To investigate their respective contributions in a rat model of chronic arthritis. METHODS: Male Wistar rats (n = 4-6/group) received either an intra-articular injection of 2% carrageenan/4% kaolin (C/K) or intra- and periarticular injections of Freund's complete adjuvant (FCA; 10 mg/ml M tuberculosis). Joint diameter, urinary nitric oxide metabolites (NO(x)), and prostaglandin E(2) (PGE(2)) levels were measured as indices of the inflammatory process. A prophylactic and therapeutic (day 5) dose ranging study of an inducible nitric oxide synthase inhibitor, L-N-(1-iminoethyl)-lysine (L-NIL), and a cyclo-oxygenase-2 (COX-2) inhibitor, SC-236, was performed with the drugs given subcutaneously. Submaximal doses were identified and used for combination studies. Appropriate vehicle controls were included. RESULTS: L-NIL and SC-236 dose dependently inhibited C/K induced acute joint swelling, the magnitude being greatest when they were given in combination. Both prophylactic and therapeutic administration of SC-236 in the FCA induced model of chronic arthritis produced a dose dependent reduction in all the measures assessed. However, although L-NIL demonstrated similar dose dependent inhibition of urinary NO(x) and PGE(2) levels, joint swelling was significantly exacerbated in this model. Co-administration of the inhibitors nullified the benefits of SC-236. CONCLUSION: Whereas COX-2 derived prostaglandins are proinflammatory in both acute and chronic joint inflammation, NO seems to have divergent roles, being anti-inflammatory in chronic and proinflammatory in acute joint inflammation.

Acute Disease↗
PubMed2001

Expression of constitutive but not inducible cyclooxygenase maintains articular perfusion in the rat knee.

Experiments were performed in the normal rat knee joint to investigate the role of different isoforms of cyclooxygenase (COX) in the regulation of basal joint blood flow. Laser Doppler imaging (LDI) was used to measure articular perfusion, and reverse transcriptase polymerase chain reaction (RT-PCR) for the detection of COX-1 and COX-2 mRNA in joint tissue. Intravenous infusion of indomethacin (a non-selective inhibitor of COX; 0.34 nmol min(-1)) over 40 min produced a time dependent increase in articular vascular resistance (maximum 22.5 % at 40 min; P < 0.0001, one-way ANOVA) whereas vehicle over a similar time period had no effect in a control group. An equimolar concentration of a highly selective inhibitor for COX-2, SC-236, was administered in a further group of rats but this did not increase articular vascular resistance. While there was no significant difference between the response to vehicle and SC-236 (two-way ANOVA; P = 0.686, n = 6) the response to indomethacin was significantly greater than vehicle or SC-236 (two-way Anova; P < 0.0001, n = 6). COX-1, but not COX-2, was detectable by RT-PCR in all joint tissue samples examined (n = 4). The results of this study indicate that prostaglandins (PGs) play an important role in the maintenance of basal perfusion in the rat knee joint, with COX-1 being the physiologically relevant isoform. Experimental Physiology (2001) 86.2, 191-197.

Animals↗
PubMed2000

Isolation and characterization of a chromium-reducing bacterium from a chromated copper arsenate-contaminated site.

A Gram-negative bacterium (CRB5) was isolated from a chromium-contaminated site that was capable of reducing hexavalent chromium to an insoluble precipitate, thereby removing this toxic chromium species from solution. Analysis of the 16S rRNA from the isolate revealed that it was a pseudomonad with high similarity to Pseudomaonas synxantha. CRB5 was tolerant to high concentrations of chromate (500 mg l(-1)) and can reduce Cr(VI) under aerobic and anaerobic conditions. It also exhibited a broad range of reduction efficiencies under minimal nutrient conditions at temperatures between 4 degrees C and 37 degrees C and at pH levels from 4 to 9. As reduction increased, so did total cellular protein, indicating that cell growth was a requirement for reduction. Under low nutrient conditions with CRB5 or when using non-sterile contaminated groundwater from the site, reduction of Cr(VI) was followed by a increase in solution turbidity as a result of the formation of fine-grained Cr(III) precipitates, most probably chromium hydroxide mineral phases such as Cr(OH)3. Chromium adsorption and precipitation, as observed by transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM/EDS), revealed that the surfaces of the cells were uniformly stained with bound Cr(III) and amorphous precipitates (as determined by selected area electron diffraction; SAED). A mass balance of chromium in a batch bioreactor revealed that up to 30% of the total Cr was as settable precipitates or bound to cells.

Arsenates↗
PubMed2000

Umbilical cord endothelial cells expressing large T antigen: comparison with primary cultures and effect of cell age.

A number of human endothelial cell lines from umbilical cord cells (HUVECs) have been generated by transfection with SV40 large T and small t antigen sequences. Comparison of these lines with primary cultures of HUVECs has been carried out by monitoring the expression of a number of endothelial cell markers with specific regard to cell age. The secreted levels of the protein plasminogen activator inhibitor (PAI) was found to be significantly reduced in SV40-transfected cells when compared to untransfected controls. Tissue plasminogen activator (tPA) and urokinase (uPA) levels were unchanged. As cells entered crisis, there was a rapid and significant increase in the levels of tPA, uPA, and PAl and this was observed for all clones screened. The endothelial cell marker von Willebrand Factor (vWF) was found intracellularly and was also secreted into the medium. The levels were not altered between transfected and untransfected cells. Angiotensin converting enzyme (ACE) activity was maintained in cell lines at levels found in nonimmortalized HUVECs. Both isoforms (alpha and beta) of IL-1 (interleukin-1) increased as cells approached crisis, and the presence of these cytokines may be responsible for the increased levels of tPA, PAI, and uPA. With one exception, the ability of the transfected cells to produce prostacyclin (PGI2) was lost by all clones.

Antigens, Polyomavirus Transforming↗
PubMed1995

Activation of phospholipase A2 by the human endothelin receptor in Chinese hamster ovary cells involves Gi protein-mediated calcium influx.

The signalling pathways used by the human endothelin A receptor to activate phospholipase A2 in Chinese hamster ovary cells were investigated. Pertussis toxin caused a partial but significant reduction in endothelin-1-induced arachidonic acid release although cAMP-dependent kinase inhibitors did not mimic its action. Extracellular calcium and its entry into the cell was essential for activation of phospholipase A2 as its removal from media or incubation with an intracellular calcium chelator-reduced activation. Nifedipine had no effect on endothelin-1-induced arachidonic acid release while divalent cations caused a significant reduction indicating the possible role of CRAC. Thapsigargin caused an increase in arachidonic acid release which was completely inhibited by pertussis toxin treatment. This further supports the involvement of CRAC in calcium influx and activation of phospholipase A2 by the human endothelin A receptor.

Animals↗
PubMed1995

Cell-based assay for functional screening of compounds active at the human endothelin A receptor.

We have developed a cell based assay for the functional screening of chemical libraries for novel chemical entities active at the human endothelin A (ET(A)) receptor. The assay is relatively inexpensive, suitable for dealing with large number of samples, and simple to operate; it generates results quickly. We achieved this by expressing the cDNA for the receptor in mammalian cell lines and determining whether coupling to pIA(A) occurred through the quantification of released radiolabeled arachidonic acid (AA) into the culture medium. Significant coupling was observed only when the receptor was expressed in the Chinese hamster ovary (CHO) line DG44. The assay could distinguish between ET(A)r agonists and antagonists, and the IC50 (the concentration that inhibits maximum response by 50%) values obtained were similar to those from other sources of receptor. The ET(B) receptor-selective agonist BQ3020 did not stimulate AA release, indicating that the assay can also discriminate between receptor subtypes.

Animals↗
PubMed1994

Production of immortal human endothelial cell lines by strontium phosphate transfection and electroporation of SV40 sequences.

Eleven human endothelial cell lines have been produced by introducing sequences from the DNA tumor virus SV40 into human umbilical vein endothelial cells either by strontium phosphate coprecipitation or electroporation. The resultant lines were confirmed as being endothelial in origin by their production of endothelial-specific von Willebrand factor. The growth characteristics of the different lines in normal and reduced levels of serum was determined, as was their cellular response to endothelial cell growth supplement in combination with heparin, basic fibroblast growth factor, transforming growth factor-alpha, and epidermal growth factor.

Antigens, Polyomavirus Transforming↗
PubMed1993

Improved techniques for immortalizing animal cells.

The use of cultured mammalian cells for assessing potential new drugs and for basic biological research is increasing, since it facilitates the large-scale screening of candidate drugs and reduces the need for animal experimentation. In this review, the technology and tools required for producing cell lines of interest are described, and possible areas of research that will enhance the application of this rapidly expanding area of biotechnology are discussed.

Animals↗
PubMedDate not supplied

Combined inhibition of nitrergic and prostanoid pathways in J774 macrophages.

OBJECTIVES: Nitric oxide and prostaglandins are both implicated in the pathogenesis of inflammatory conditions such as rheumatoid arthritis (RA). The hypothesis that simultaneous inhibition of nitric oxide synthase (NOS) and cyclooxygenase (COX) was more effective than inhibition of either enzyme alone was tested. METHODS: J774 macrophages were pre-incubated with L-NAME and/or indomethacin, prior to activation with LPS (10 micrograms/ml). RESULTS: LPS significantly increased NO2-; PGE2 and TNF-alpha levels by 24 h. Quantitative real-time PCR demonstrated a dose-dependent reduction in the expression of COX-2 in the presence of increasing doses of L-NAME. NO2- and PGE2 production were inhibited in a dose-dependent manner by either indomethacin or L-NAME. Combined administration of L-NAME and indomethacin produced a significantly greater inhibition of NO2- and PGE2 than either inhibitor alone. CONCLUSION: The data supports the therapeutic potential of combined inhibition of the prostanoid and nitrergic systems as an anti-inflammatory treatment strategy and supports the progression of this work into models of arthritis.

Cells, Cultured↗
PubMedDate not supplied

Phenotypic modification of human glioma and non-small cell lung carcinoma by glucocorticoids and other agents.

Glucocorticoids are cytostatic for human glioma grown at a high cell density in cell culture. The effect is not cytotoxic, appears to involve a modification of the cell surface, and has been detected with methyl prednisolone, dexamethasone, and beta-methasone. Glucocorticoids were also found to reduce malignancy-associated properties (plasminogen activator and endothelial mitogenesis) and enhance differentiation (glutamyl synthetase activity and high affinity GABA uptake). Cytostasis was also seen at high cell densities in non-small cell lung carcinoma with a concomitant reduction in plasminogen activator activity and endothelial mitogenesis. Preliminary data on surfactant production in A549 cells suggests that the repression of malignancy-associated properties is accompanied by an increase in cell differentiation. Treatment of the WIL adenocarcinoma gown as a xenograft in nude mice caused total cessation of growth and massive central necrosis in the tumor.

Astrocytoma↗