PubMed Health⌕ Search

Biomedical subjects

P McKay

Publications and source records attributed to P McKay.

16 recordsLinked to original sources
PubMed2006

Development, application and validation of a Taqman real-time RT-PCR assay for the detection of infectious salmon anaemia virus (ISAV) in Atlantic salmon (Salmo salar).

Infectious salmon anaemia (ISA) is a disease of cultured Atlantic salmon (Salmo salar) which was successfully eradicated from Scotland following its emergence in 1998. The rapid deployment of sensitive diagnostic methods for the detection of ISA virus (ISAV) was fundamental to the swift eradication of ISA disease in Scotland and continues to be of crucial importance to surveillance of the aquaculture industry. This study reports the development, validation, application and interpretation of two independent, highly sensitive and specific semi-quantitative Taqman real-time RT-PCR (qRT-PCR) methods for the detection of ISAV. Such technology offers considerable advantages over conventional RT-PCR methods in current routine use for ISAV surveillance. These include an increased sensitivity, enhanced specificity, semi-quantification using endogenous controls, a lack of subjectivity in results interpretation, speed of processing and improved contamination control.

Animals↗
PubMed2003

Pupil dilatation does affect some aspects of daytime driving performance.

AIMS: To examine the effects of pupil dilatation on driving performance and determine whether this was related to changes in standard measures of visual function. METHODS: The driving and vision performance of 16 young, visually normal participants was measured with both normal and dilated pupils. Pupils were dilated with 1% tropicamide. Driving performance was measured under daytime conditions on a closed road circuit that was free of other vehicles and has been used in previous studies of driving performance. Measures included road sign detection and recognition, hazard detection and avoidance, gap perception and negotiation, driving reaction times and time to complete the circuit. Visual performance measures included high contrast visual acuity, Pelli-Robson letter contrast sensitivity, and glare sensitivity. RESULTS: Pupil dilatation significantly (p<0.05) decreased the ability of participants to recognise low contrast hazards and avoid them, decreased their visual acuity and contrast sensitivity and increased glare sensitivity. The decreases in vision performance were not, however, significantly related to the decrement in driving performance. CONCLUSION: Pupil dilatation can impair selected aspects of driving and vision performance and patients should be cautioned about these possible effects.

Adult↗
PubMed2001

Adapting pharmacokinetic properties of a humanized anti-interleukin-8 antibody for therapeutic applications using site-specific pegylation.

A neutralizing anti-interleukin-(IL-)8 monoclonal antibody was humanized by grafting the complementary determining regions onto the human IgG framework. Subsequent alanine scanning mutagenesis and phage display enabled the production of an affinity matured antibody with a >100-fold improvement in IL-8 binding. Antibody fragments can be efficiently produced in Escherichia coli but have the limitation of rapid clearance rates in vivo. The Fab' fragment of the antibody was therefore modified with polyethylene glycol (PEG) in order to obtain a more desirable pharmacokinetic profile. PEG (5-40 kDa) was site-specifically conjugated to the Fab' via the single free cysteine residue in the hinge region. In vitro binding and bioassays showed little or no loss of activity. The pharmacokinetic profiles of the 20 kDa, 30 kDa, 40 kDa, and 40 kDa branched PEG-Fab' molecules were evaluated in rabbits. Relative to the native Fab', the clearance rates of the PEGylated molecules were decreased by 44-175-fold. In a rabbit ear model of ischemia/reperfusion injury, all PEGylated Fab' molecules were as efficacious in reducing oedema as the original monoclonal antibody. These studies demonstrate that it is possible to customize the pharmacokinetic properties of a Fab' while retaining its antigen binding activity.

Alanine↗
PubMed2000

Adoption of alternative financing strategies to increase the diffusion of picture archiving and communication systems into the radiology marketplace.

The objective of the study was to evaluate current marketplace conditions and strategies employed by major picture archiving and communication systems (PACS) vendors in the creation of alternative financing strategies, to enhance the diffusion of filmless imaging. Data were collected from the major PACS vendors in the forms of survey questionnaires and review of existing leases. Topics evaluated in the survey included current financing options available, foreseeable changes in PACS financing, role of third-party financiers, and creation of risk-sharing arrangements. Generic leases were also reviewed evaluating the presence or absence of several key variables including technology obsolescence protection, hardware/software upgrades, end-of-term options, determination of fair market value, functionality/acceptance testing, uptime guarantees, and workflow management consulting. Eight of the 10 PACS vendors surveyed participated in the data collection. The vast majority of current PACS implementations (60% to 90%) occur through direct purchase, with conventional leasing (operating or capital) accounting for only 5% to 30% of PACS installations. The majority of respondents view fee-for-lease arrangements and other forms of risk sharing as increasing importance for future PACS financing. The specific targets for such risk-sharing arrangements consist of small hospital and privately owned imaging centers. Leases currently offered range in duration from 3 to 5 years and frequently offer technology obsolescence protection with upgrades, multiple end-of-term options, and some form of acceptance testing. A number of important variables frequently omitted from leases include uptime guarantees, flexibility in changing financing or vendors, and incorporation of expected productivity/operational efficiency gains. As vendors strive to increase the penetration of PACS into the radiology marketplace, there will be a shift from conventional financing (loan or purchase) to leasing. Fee-for-use leasing and other forms of risk sharing have the greatest potential in smaller hospitals, which do not have the financial resources to pursue conventional financing options. Potential PACS customers must be cautious when entering into these alternative financing strategies, to ensure that appropriate safeguards are incorporated, in order to minimize downside risk.

Cost Sharing↗
PubMed1999

Selection and analysis of an optimized anti-VEGF antibody: crystal structure of an affinity-matured Fab in complex with antigen.

The Fab portion of a humanized antibody (Fab-12; IgG form known as rhuMAb VEGF) to vascular endothelial growth factor (VEGF) has been affinity-matured through complementarity-determining region (CDR) mutation, followed by affinity selection using monovalent phage display. After stringent binding selections at 37 degrees C, with dissociation (off-rate) selection periods of several days, high affinity variants were isolated from CDR-H1, H2, and H3 libraries. Mutations were combined to obtain cumulatively tighter-binding variants. The final variant identified here, Y0317, contained six mutations from the parental antibody. In vitro cell-based assays show that four mutations yielded an improvement of about 100-fold in potency for inhibition of VEGF-dependent cell proliferation by this variant, consistent with the equilibrium binding constant determined from kinetics experiments at 37 degrees C. Using X-ray crystallography, we determined a high-resolution structure of the complex between VEGF and the affinity-matured Fab fragment. The overall features of the binding interface seen previously with wild-type are preserved, and many contact residues are maintained in precise alignment in the superimposed structures. However, locally, we see evidence for improved contacts between antibody and antigen, and two mutations result in increased van der Waals contact and improved hydrogen bonding. Site-directed mutants confirm that the most favorable improvements as judged by examination of the complex structure, in fact, have the greatest impact on free energy of binding. In general, the final antibody has improved affinity for several VEGF variants as compared with the parental antibody; however, some contact residues on VEGF differ in their contribution to the energetics of Fab binding. The results show that small changes even in a large protein-protein binding interface can have significant effects on the energetics of interaction.

Alanine↗
PubMed1997

Erythrocyte magnesium in elderly patients: not a reliable guide to magnesium status.

To assess body magnesium status in various illness states in older people by measurement of serum magnesium (S Mg) and erythrocyte magnesium (E Mg) and to explore the limitations of E Mg measurement. S Mg and E Mg were measured in 150 consecutive out-patients, mean age 77 years, and in 100 consecutive in-patient admissions, mean age 80 years. Results were analysed for different diagnostic groups S Mg was normally distributed for both in-patients and out-patients, mean values 0.79 mmol/l and 0.77 mmol/l respectively. In-patient E Mg concentrations were often higher but the distribution was considerably skewed, median 2.28 mmol/l, mean 2.35 mmol/l. Out-patient E Mg concentration followed a near normal distribution, median 2.32 mmol/l, mean 2.30 mmol/l. There was a significant correlation between E Mg and S Mg for out-patients, R = 0.29 (p < 0.001). In-patients with infections and pressure sores had significantly raised E Mg concentrations but normal or low S Mg. High E Mg concentrations in illness are likely to be due to alterations in characteristics of the erythrocytes themselves rather than an indication of body magnesium excess. E Mg concentrations in illness should be interpreted with caution.

Aged↗
PubMed1996

Recombinant human growth hormone (GH)-binding protein enhances the growth-promoting activity of human GH in the rat.

To address the role of the GH-binding protein (GHBP) in GH physiology, two forms of recombinant human GHBP (rhGHBP) were given alone or in combination with rhGH to hypophysectomized rats or GH-deficient dwarf rats. Hypophysectomized rats were given daily sc injections of excipient, hGH, rhGHBP, or rhGH plus rhGHBP (produced in Escherichia coli) for 7 days. Injections of rhGH induced dose-related body weight gain and bone growth that were increased by the coadministration of rhGHBP with rhGH; rhGHBP alone had no effect. Serum insulin-like growth factor increased 24 h later when rhGH was given together with rhGHBP (P < 0.01), but not when rhGH was given alone. E. coli-derived rhGHBP also enhanced the bioactivity of coadministered rhGH in the GH-deficient dwarf rat. In contrast, the glycosylated rhGHBP, made in human A293 cells, inhibited the growth-promoting activity of coadministered rhGH. The opposite effects of these two forms of rhGHBP could be explained by clearance studies that showed radiolabeled rhGH bound to A293 cell-derived rhGHBP to be cleared more rapidly from the blood than free rhGH. Natural rabbit GHBP and E. coli-derived rhGHBP both prolonged the presence of rhGH in blood. It is proposed that by slowing the clearance of GH, GHBP increased the bioactivity of GH. In summary, codelivery of rhGHBP and rhGH caused a dose-dependent enhancement of the activity of rhGH in two rat models of GH deficiency. This suggests that endogenous circulating GHBP may increase the activity of blood-borne GH in a similar manner.

Animals↗
PubMed1990

Preparation and properties of recombinant DNA derived tobacco mosaic virus coat protein.

Recombinant DNA derived tobacco mosaic virus (vulgare strain) coat protein (r-TMVP) was obtained by cloning and expression in Escherichia coli and was purified by column chromatography, self-assembly polymerization, and precipitation. SDS-PAGE, amino terminal sequencing, and immunoblotting with polyclonal antibodies raised against TMVP confirmed the identify and purity of the recombinant protein. Isoelectric focusing in 8 M urea and fast atom bombardment mass spectrometry demonstrated that the r-TMVP is not acetylated at the amino terminus, unlike the wild-type protein isolated from the tobacco plant derived virus. The characterization of r-TMVP with regard to its self-assembly properties revealed reversible endothermic polymerization as studied by analytical ultracentrifugation, circular dichroism, and electron microscopy. However, the details of the assembly process differed from those of the wild-type protein. At neutral pH, low ionic strength, and 20 degrees C, TMVP forms a 20S two-turn helical rod that acts as a nucleus for further assembly with RNA and additional TMVP to form TMV. Under more acidic conditions, this 20S structure also acts as a nucleus for protein self-assembly to form viruslike RNA-free rods. The r-TMVP that is not acetylated carries an extra positive charge at the amino terminus and does not appear to form the 20S nucleus. Instead, it forms a 28S four-layer structure, which resembles in size and structure the dimer of the bilayer disk formed by the wild-type protein at pH 8.0, high ionic strength, and 20 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylation↗
PubMed1990

Regulation of growth hormone (GH) bioactivity by a recombinant human GH-binding protein.

The in vitro biological effects of serum GH-binding protein (GHBP) were measured in the mouse 3T3-F442A preadipocyte adipogenesis assay during GH stimulation. Coincubation of increasing concentrations of human (h) GH (0.14-4.5 nM) with 4.2 nM recombinant hGHBP-(1-247) in serum-free medium shifted the hGH dose-response curve to the right over the range 0.14-0.9 nM. When the hGH concentration was fixed at 0.45 nM, a dose-dependent inhibition of GH bioactivity was seen over the range of 0.1-11.3 nM GHBP, with an ED50 of 3 nM. The presence of serum had no effect on the inhibitory properties of GHBP. When 2% pooled human serum was added to incubation medium containing 0.45 nM hGH and GHBP (0.6 nM-5.7 nM), the effect of GHBP was again inhibitory, with an ED50 of 1.2 nM. Two percent serum alone was adipogenic, but at this low serum concentration it is likely that some factor other than GH is responsible. In a homologous receptor assay, the binding of [125I]hGH to IM-9 lymphocytes was inhibited in a dose-dependent manner by increasing concentrations of hGHBP in the physiological range, providing further support for the idea that GHBP can regulate the bioactivity of GH by blocking the binding of free GH to target tissues in vivo. Our results suggest that one function of GHBP is to dampen the biological effects of pulsatile GH secretion by reducing free GH during secretory pulses. This effect combined with an increased half-life of circulating GH would have the effect of flattening the hormone secretory profile at the target tissue level.

Adipose Tissue↗
PubMed1989

Purification and characterization of recombinant human parathyroid hormone-related protein.

Full-length human parathyroid hormone-related protein (PTHrP-(1-141] as well as a carboxyl-terminal shortened form (PTHrP-(1-108] have been expressed from recombinant DNA-derived clones. These proteins were expressed in Escherichia coli as fusion proteins so that cyanogen bromide cleavage yields the desired product. Both proteins were purified and then characterized by sodium dodecyl sulfate gel electrophoresis, amino-terminal amino acid sequencing, peptide mapping, and mass spectral analysis. Recombinant PTHrP-(1-141), PTHrP-(1-108), synthetic PTHrP-(1-34), and naturally derived PTHrP are all equipotent in the stimulation of cyclic AMP levels in the osteoblast-like cell line UMR 106-01. However, PTHrP-(1-141) and -(1-108) are two to four times more active than PTHrP-(1-34) in the stimulation of plasminogen activator activity from this cell line. PTHrP-(1-141) reacts equipotently with PTHrP-(1-34) in a radioimmunoassay using an antiserum prepared against PTHrP-(1-34). PTHrP-(1-141), -(1-108), and -(1-84) were used as PTHrP-specific mobility standards on sodium dodecyl sulfate gel electrophoresis to determine the approximate length of two forms of naturally derived PTHrP. The data show that PTHrP purified from the lung tumor cell line BEN contains a major form of about 108 amino acids and another form of about 141 amino acids.

Amino Acid Sequence↗
PubMed1989

Morphine metabolism in children.

1. The metabolism of morphine was studied in 12 children and nine premature neonates on a continuous infusion of morphine (10-360 micrograms kg-1 h-1). 2. The mean plasma clearance of morphine was significantly higher in children than neonates (25.7 and 4.7 ml min-1 kg-1, respectively) (P less than 0.01). 3. All the neonates and children had detectable concentrations of morphine-3-glucuronide (M3G) in plasma. All the children and five neonates had detectable concentrations of morphine-6-glucuronide (M6G) in plasma or urine. 4. The M3G/morphine ratios in plasma and urine, and M6G/morphine ratios in urine were significantly higher in children than neonates (P less than 0.01), suggesting that morphine glucuronidation capacity is enhanced after the neonatal period. 5. There was no difference in the M3G/M6G ratio in children and neonates, indicating a parallel development of both glucuronidation pathways.

Adolescent↗
PubMed1982

Induction and augmentation of mitogen-induced immune interferon production in human peripheral blood lymphocytes by N alpha-desacetylthymosin alpha 1.

Treatment of human peripheral blood lymphocytes with cloned N alpha-desacetylthymosin alpha 1 induced interferon production. The kinetics is similar to that of mitogen-induced interferon induction. N alpha-desacetylthymosin alpha 1, in combination with mitogen, augments the amount of interferon produced. This interferon is immune interferon (IFN-gamma) as determined by sensitivity to pH 2, lack of neutralization by antibodies to IFN-alpha or IFN-beta and absence of activity of MDBK cells. Although the mechanism of induction of IFN-gamma by N alpha-desacetylthymosin alpha 1 is unclear, this compound is not mitogenic at concentrations causing IFN-gamma production. These results indicate that thymic factors may also participate in the regulation of IFN-gamma-production.

Cells, Cultured↗