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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 91 records · Page 5Linked to original sources
PubMed2001

Comparison of phage pIII, pVIII and GST as carrier proteins for peptide immunisation in Balb/c mice.

Carrier proteins are important for improving the efficiency of synthetic peptide vaccines. Recently, genetically-based systems such as filamentous phage display or glutathione S-transferase (GST)-fusion proteins have been employed for immunisation. Whilst these carrier systems can facilitate the evaluation of a potential vaccine by reducing the time and cost of production, their relative efficacy and the kinetics of the immune response to each carrier has not been directly compared. In this study, we have displayed the epitopes of the anti-ErbB-2 Mabs N12 (C531-A586, EP531) and N28 (T216-C235, EP216) on phage minor coat protein pIII, major coat protein pVIII and GST. Balb/c H-2(d) mice were immunised with the constructs and the sera were tested after the initial, the 3rd, 5th and 6th immunisations for an anti-peptide, an anti-ErbB-2 and an anti-carrier response. The specificity of the antibody response was also mapped using synthetic peptides. It was found that GST was the best of the three carriers, both in terms of the magnitude and the kinetics of the induced anti-peptide and anti-ErbB-2 response. Multiple (five) administrations of the immunogens were necessary to obtain a high titre of antibodies specific for ErbB-2. It was further noted that whilst an anti-EP531 response was induced using all three carriers, EP216 was not immunogenic irrespective of the carrier used. The lack of immunogenicity of EP216 implies it does not contain a H-2(d) T cell recognition site. All three carriers provide a useful system for vaccination and consequently facilitate the identification of T-cell epitopes in Balb/c inbred mice.

Amino Acid Sequence↗
PubMed2001

Two crystal polymorphs of a flavonoid from Melicope ellyrana.

The crystal structure determinations of two crystalline components of the hexane extract of the fruit of the indigenous Australian tree Melicope ellyrana have shown them to be polymorphs of the same compound, namely the flavonoid 4',5-dihydroxy-3,3',8-trimethoxy-7-(3-methylbut-2-enyloxy)flavone [systematic name: 5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,8-dimethoxy-7-(3-methylbut-2-enyloxy)-4H-1-benzopyran-4-one], C(23)H(24)O(8). The two polymorphs, one monoclinic (polymorph A) and the other triclinic (polymorph B), show significant conformational differences, particularly in the enyloxy side chain, while only one (polymorph A) shows intermolecular hydrogen bonding.

Crystallography, X-Ray↗
PubMed2001

A TSM sensor investigation of low crystallinity cellulose films.

A thickness shear mode (TSM) quartz sensor has been used to characterize the substantivity, viscoelasticity, and mucoadhesive properties of low crystallinity cellulose (LCC) films. LCC is a novel pharmaceutical excipient that has been attributed with mucoadhesive properties. Thin films of LCC were deposited onto TSM sensors by a spin coating technique. The films were treated by passing water or 1.0% w/v mucin solution (pH 3.7 or 7.0) over the surface. Changes in the mass and viscosity of the film were observed by monitoring changes in the impedance spectra of the coated TSM sensors. Scanning electron micrographs (SEMs) of each film were used to assist the interpretation of the TSM sensor data. This study showed that LCC forms highly tenacious and viscoelastic films able to withstand prolonged (approximately 1 h) exposure to both water and mucin solution. Furthermore, these results indicate that the films may have mucoadhesive properties as LCC was found to bind significant (P<0.05) amounts of mucin in comparison with control measurements. Mucin binding to the LCC sensor was greater at pH 3.7 (P<0.05) than at pH 7.0, suggesting that the LCC formulation is mucoadhesive under these conditions.

Cellulose↗
PubMed2001

Measuring the quantum state of a large angular momentum.

We demonstrate a general method to measure the quantum state of an angular momentum of arbitrary magnitude. The (2F+1)x(2F+1) density matrix is completely determined from a set of Stern-Gerlach measurements with (4F+1) different orientations of the quantization axis. We implement the protocol for laser cooled Cesium atoms in the 6S(1/2)(F = 4) hyperfine ground state and apply it to a variety of test states prepared by optical pumping and Larmor precession. A comparison of input and measured states shows typical reconstruction fidelities F >/~0.95.

Journal Article↗
PubMed2001

Biofilm culture of Pseudomonas aeruginosa expressing lux genes as a model to study susceptibility to antimicrobials.

A simple in vitro model for culture of biofilm populations of self-bioluminescent Pseudomonas aeruginosa was used for real-time monitoring of the effects of ciprofloxacin. Biofilms of these organisms were established within Sorbarod filters, perfused with a chemically defined simple salts medium. The biofilm population was shown to achieve a pseudo-steady state which was reproducible and stable over several days. The viability of membrane-associated and eluted cells was assessed by spread plate viable counts and by monitoring bioluminescence as a measure of metabolic activity. Pseudo-steady state biofilms were exposed to 5x MIC ciprofloxacin (0.3 mg x l(-1)) in the perfusing medium for 1 h. Whilst both methods for viability assessment indicated an immediate reduction in viable cell numbers, the decline recorded with bioluminescence was greater. The use of bioluminescent bacteria proved to be a rapid and sensitive method for the measurement of real-time antibacterial effects on a bacterial biofilm.

Anti-Infective Agents↗
PubMed2001

Identification of epitope regions recognized by tumor inhibitory and stimulatory anti-ErbB-2 monoclonal antibodies: implications for vaccine design.

The self-oncoprotein ErbB-2 is overexpressed in a number of malignancies. The presence of endogenous anti-ErbB-2 Ab and T cell immune responses to this protein in cancer patients has made ErbB-2 an attractive target for active immunization. However, the finding that murine anti-ErbB-2 Abs can have stimulatory, inhibitory, or no effects on cancer cell growth suggests that an inappropriately induced immune response may have an adverse effect. To ensure the induction of a beneficial Ab response, it is important to identify the epitopes recognized by these Abs. In this study we have used phage-displayed ErbB-2 gene fragment libraries and synthetic peptides to epitope-map a panel of anti-ErbB-2 mAbs. The epitopes of three mAbs, N12, N28, and L87, were successfully located to C531-A586, T216-C235, and C220-C235 of ErbB-2, respectively. It was found that while N12 inhibited tumor cell proliferation, N28 stimulated the proliferation of a subset of breast cancer cell lines overexpressing ErbB-2. The peptide region recognized by N12, (C531-A586; EP531), was used as an immunogen to selectively induce an inhibitory immune response in mice. Mice immunized with the GST fusion peptide (GST-EP531) recognized the peptide region EP531 as well as native ErbB-2. More importantly, Igs purified from mouse sera were able to inhibit up to 85% of tumor cell proliferation. In conclusion, our study provides direct evidence of the function-epitope relationship of anti-ErbB-2 Abs and also emphasizes the value of inducing a potent tumor inhibitory polyclonal Ab response by rationally selecting regions of ErbB-2 used for immunization.

Amino Acid Sequence↗
PubMed2001

Preclinical and clinical pharmacology of Rosuvastatin, a new 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor.

Rosuvastatin (formerly ZD4522) is a new 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) with distinct pharmacologic properties. Compared with most other statins, it is relatively hydrophilic, similar in this respect to pravastatin. Rosuvastatin has been shown to be a comparatively potent inhibitor of HMG-CoA reductase activity in a purified preparation of the catalytic domain of the human enzyme, as well as in rat and human hepatic microsomes. In rat hepatocytes, rosuvastatin was found to have significantly higher potency as an inhibitor of cholesterol synthesis than 5 other statins. Rosuvastatin was approximately 1,000-fold more potent in rat hepatocytes than in rat fibroblasts. Further studies in rat hepatocytes demonstrated that rosuvastatin is taken up into these cells by a high-affinity active uptake process. Rosuvastatin was also taken up selectively into the liver after intravenous administration in rats. Potent and prolonged HMG-CoA reductase inhibitory activity has been demonstrated after oral administration to rats and dogs. Pharmacokinetic studies in humans using oral doses of 5 to 80 mg showed that maximum plasma concentrations and areas under the concentration-time curve are approximately linear with dose. The terminal half-life is approximately 20 hours. Studies with human hepatic microsomes and human hepatocytes have suggested little or no metabolism via the cytochrome P-450 3A4 isoenzyme. On the basis of these observations, it is suggested that rosuvastatin has the potential to exert a profound effect on atherogenic lipoproteins.

Animals↗
PubMed2001

The spherical aberration of the crystalline lens of the human eye.

The in vivo spherical aberration of the lenses of 26 subjects was estimated from the measured total aberration of the eye and that predicted from the measured shape of the anterior corneal surface. Since it was only possible to estimate the aberration contribution from the posterior corneal surface, its value led to an uncertainty in the final aberration level of the lens. For all the subjects and for a wide range of possible aberration levels at the posterior corneal surface, the spherical aberration of the relaxed lens was found to be negative.

Adult↗
PubMed2001

Effect of electrocardiographic left ventricular hypertrophy on left ventricular systolic function in systemic hypertension (The LIFE Study). Losartan Intervention For Endpoint.

Left ventricular (LV) ejection fraction is normal in most patients with uncomplicated hypertension, but the prevalence and correlates of decreased LV systolic chamber and myocardial function, as assessed by midwall mechanics, in hypertensive patients identified as being at high risk by the presence of LV hypertrophy on the electrocardiogram has not been established. Therefore echocardiograms were obtained in 913 patients with stage I to III hypertension and LV hypertrophy determined by electrocardiographic (Cornell voltage duration or Sokolow-Lyon voltage) criteria after 14 days' placebo treatment. The 913 patients' mean age was 66 years, and 42% were women. Fourteen percent had subnormal LV endocardial shortening, 24% had subnormal midwall shortening, and 13% had reduced stress-corrected midwall shortening. Nineteen percent had normal LV geometry, 11% had concentric remodeling, 47% had eccentric hypertrophy, and 23% had concentric hypertrophy. LV systolic performance evaluated by LV endocardial shortening and midwall shortening was impaired in 10% of patients with normal geometry, 20% with concentric remodeling, 27% with eccentric hypertrophy, and 42% with concentric hypertrophy. Relative wall thickness, an important independent correlate of LV chamber function, was related directly to endocardial shortening and negatively to midwall shortening and stress-corrected midwall shortening. LV mass was the strongest independent correlate of impaired endocardial shortening, midwall shortening, or both. In hypertensive patients with electrocardiographic LV hypertrophy, indexes of systolic performance are subnormal in 10% to 42% with different LV geometric patterns. Depressed endocardial shortening is most common in patients with eccentric LV hypertrophy, whereas impaired midwall shortening is most prevalent in patients with concentric remodeling or hypertrophy. Thus, in hypertensive patients with electrocardiographic LV hypertrophy, impaired LV performance occurs most often, and is associated with greater LV mass and relative wall thickness and may contribute to the high rate of cardiovascular events.

Aged↗
PubMed2001

Characterisation and comparison of novel ligands for the nociceptin/orphanin FQ receptor.

Studies of nociceptin/orphanin FQ (NC) have been hampered by the paucity of available ligands with activity at the nociceptin receptor (NCR). In this study we have compared the agonist profile of NC and a novel NCR agonist, Ro65-6570, in a series of radioligand binding studies and effects on forskolin-stimulated cAMP formation in Chinese hamster ovary (CHO) cells expressing the recombinant human NCR (CHOhNCR). In addition, we report the effects of three antagonists, [Nphe1]NC(1-13)NH2, J-113397 and III-BTD, on these responses. In radioligand binding studies Ro65-6570, [Nphe1]NC(1-13)NH2, J-113397 and III-BTD displaced [3H]NC with similar pKi values (8.4-8.8). This compares with a pK(D) of 10.2 for NC in a direct saturation experiment. [Nphe1]NC(1-13)NH2 and J-113397 showed at least 100-fold selectivity over classical opioid receptors. Both NC and Ro65-6570 produced a concentration-dependent inhibition of cAMP formation with pEC50 values of 9.56+/-0.06 and 8.68+/-0.04, respectively. Maximum inhibition achieved was 100%. [Nphe1]NC(1-13)NH2, J-113397 and III-BTD produced a parallel rightward shift in the concentration-response curves to both NC and Ro65-6570 with pK(B) values of approximately 6.5, approximately 7.5 and approximately 7.7, respectively. Importantly, all three antagonists were devoid of residual agonist activity. Collectively, these data indicate the value of Ro65-6570, [Nphe1]NC(1-13)NH2, J-113397 and III-BTD in studies of the physiological role played by NC. However, due to the relatively poor selectivity of Ro65-6570 and III-BTD caution should be exercised when using tissues that co-express micro-opioid receptors.

Animals↗
PubMed2001

Effectiveness of primary endoscopic incision of ureteroceles.

Endoscopic incision of a ureterocele (EIU) is simple when compared to an open procedure such as ureterocele excision with or without an upper-pole nephrectomy. It has, however, the potential to induce vesicoureteric reflux (VUR), which traditionally requires further surgical intervention. The natural history of the VUR that develops following EIU is not known. We have treated asymptomatic VUR that developed following EIU conservatively and have surgically intervened only in cases with recurrent urinary tract infections (UTI). This is a review from a single surgeon's practice involving 29 consecutive cases of ureterocele spread over a period of 4 years. The range of follow up was 4-54 months (median 32). Of the 24 children who underwent primary EIU, 6 required a second procedure, 3 a reincision and 3 an open procedure. Of the 3 who had a reincision, 2 required a further open procedure. The indication for reincision was failure of decompression of the upper tract and the indication for an open procedure was recurrent UTI following EIU. Thus, overall success was achieved in 19 of 24 cases of primary EIU (79.2%). VUR following EIU appeared in 10 cases (41%); UTI developed in only 5 (50%) of these 10 cases. Overall, UTI developed in 6 of the 24 (25%) cases of primary EIU. Eight children had an open procedure (3 as a primary procedure and 5 after EIU); 2 (25%) from this group had UTI following the procedure, and interestingly, neither had VUR. Ureterocele incision is thus a good alternative to upper-pole nephrectomy or excision of the ureterocele, especially in infancy. There is an inherent risk of producing VUR in the postincision period, however, the majority of cases can be managed conservatively. All patients need to be monitored for hypertension and UTI following EIU.

Child↗
PubMed2001

Increased contractility and calcium sensitivity in cardiac myocytes isolated from endurance trained rats.

OBJECTIVE: Regular exercise enhances cardiac function and modulates myocyte growth in healthy individuals. The purpose of the present study was to assess contractile function and expression of selected genes associated with intracellular Ca2+ regulation after intensity controlled aerobic endurance training in the rat. METHODS: Female Sprague-Dawley rats were randomly assigned to sedentary control (SED) or treadmill running (TR) 2 h per day, 5 days per week for 2, 4 or 13 weeks. Rats ran 8-min intervals at 85-90% of VO2max separated by 2 min at 50-60%. Myocyte length, intracellular Ca2+ (Fura-2), and intracellular pH (BCECF) were measured in dissociated cells in response to electrical stimulation at a range of stimulation rates. RESULTS: The increase in VO2max plateaued after 6-8 weeks, 60% above SED. After 13 weeks, left and right ventricular weights were 39 and 36% higher than in SED. Left ventricular myocytes were 13% longer, whereas width remained unchanged. After 4 weeks training, myocyte contractility was approximately 20% higher in TR. Peak systolic intracellular Ca2+ and time for the decay from systole were 20-35 and 12-17% lower, respectively. These results suggest that increased myofilament Ca2+ sensitivity is the dominant effect responsible for enhanced myocyte contractility in TR. Intracellular pH progressively decreased as stimulation frequency was increased in the SED group. This decrease was markedly attenuated in TR and the intracellular pH was significantly higher in the TR group at a stimulation rate of 5-10 Hz. This effect may contribute to the increased contractility observed at the higher stimulation frequencies in TR. A higher intrinsic myofilament Ca2+ sensitivity was observed in permeabilised myocytes from the TR group under conditions of constant pH and [Ca2+]. Western blot analysis indicated 21 and 46% higher myocardial SERCA-2 and phospholamban, but unaltered Na+/Ca(2+)-exchanger levels. Competitive RT-PCR revealed that TR significantly increased Na+/H(+)-exchanger mRNA. CONCLUSION: Intensity controlled interval training increases cardiomyocyte contractility. Higher myofilament Ca(2+)-sensitivity, and enhanced Ca(2+)-handling and pH-regulation are putative mechanisms. Our results suggest that physical exercise induces adaptive hypertrophy in cardiac myocytes with improved contractile function.

Animals↗
PubMed2001

Gradient refractive index of the crystalline lens of the Black Oreo Dory (Allocyttus Niger): comparison of magnetic resonance imaging (MRI) and laser ray-trace methods.

The gradient refractive index of the crystalline lens in the Black Oreo Dory (Allocyttus Niger) was determined using two methods; an optimisation program based on finite ray-tracing and the path of laser beams through the lens, and magnetic resonance imaging (MRI) and the linear relationship between refractive index and nuclear transverse relaxation rates. The methods showed good agreement in the cortical zone of the lens, but the lack of free water in the core of the lens made MRI measurement impossible in this region. The laser-optimisation method gave mean values of 1.368 and 1.543 for the surface and core refractive indices respectively, with a radial distribution for the gradient refractive index given by n(r)=1.543-0.121r2-0.033r4-0.021r6.

Animals↗
PubMed2001

PCR-based plasmid vector construction for generation of recombinant viruses.

A totally polymerase chain reaction (PCR)-based protocol for construction of plasmids for production of recombinant macropodid herpesvirus 1 (MaHV-1) is described. This protocol greatly simplifies traditional methods that use restriction enzyme-based cloning or a combination of restriction enzyme cloning and the PCR. PCR is used to amplify the vector backbone containing an origin of replication and selectable marker, and the inserts to be cloned (5' and 3' viral homologous recombination regions and the reporter gene green fluorescent protein (GFP)). The inserts are cloned in a sequential manner with the intermediate vectors then amplified to produce the next vector. At its most basic, this involves, after the initial PCR amplification of vector and inserts, two additional PCR amplifications and three ligation events. This protocol is however totally generic, and can be used not only for construction of plasmids for production of recombinant viruses, but also for any general cloning applications.

DNA, Viral↗
PubMed2001

Association of ErbB2 Ser1113 phosphorylation with epidermal growth factor receptor co-expression and poor prognosis in human breast cancer.

The carboxyterminal domain of the epidermal growth factor receptor (EGFR)--a putative binding site for the ubiquitin ligase Cbl--is the site of serine phosphorylation events which are essential for ligand-dependent EGFR desensitization and degradation. Using a monoclonal antibody (aPS1113) which selectively recognizes the homologous phosphorylated domain in the ErbB2 oncoprotein, we show here that wild-type ErbB2 becomes Ser1113-phosphorylated following treatment of 3T3 cells with growth factors or tyrosine phosphatase inhibitors. In EGFR-overexpressing A431 cells, ligand-inducible aPS1113 immunoreactivity declines more rapidly than other detectable phosphorylation events and is followed by EGFR downregulation. Analysis of 65 ErbB2-expressing primary breast cancers reveals a highly significant relationship between Ser1113 phosphorylation and EGFR overexpression (p < 0.0001) as well as an association with poor prognosis (p = 0.005). We submit that ErbB2 Ser1113 phosphorylation status represents a novel and informative biomarker of cancer cell biology and tumor behavior.

Animals↗