Biomedical subjects

D J King

Publications and source records attributed to D J King.

At least 37 records · Page 2Linked to original sources

PubMed2000

Newcastle disease virus phosphoprotein gene analysis and transcriptional editing in avian cells.

Nucleotide sequence was determined for the phosphoprotein (P) gene from 23 Newcastle disease virus (NDV) isolates representing all defined pathotypes with different chronological and geographic origins. Sequence variation, with synonymous substitutions dominating, occurred throughout the P gene. An exception was a conserved central region containing the transcriptional editing site. Four G nucleotide additions were detected in NDV P gene mRNA potentially creating alternative open reading frames. However, only one in-frame stop codon exists with a single G addition among all isolates that would allow for a potential V protein. A second potential stop codon does not exist in the P gene consensus sequence among all isolates with more than one G nucleotide addition at the editing site. This precludes a possible W protein in these isolates. A second potential alternative in-frame start site exists among all isolates that could encode a predicted X protein for NDV. Comparison of the P gene editing sites among the Paramyxovirinae and predicted P gene usage demonstrates that NDV more closely resembles the respiroviruses and morbilliviruses. Phylogenetic analysis of P gene sequences among NDV isolates demonstrates there are two clades of these viruses. One group includes viruses isolated in the US prior to 1970, while a second cluster includes virulent viruses circulating worldwide.

Amino Acid Sequence↗

PubMed2000

Molecular evolution of the Newcastle disease virus matrix protein gene and phylogenetic relationships among the paramyxoviridae.

Matrix (M) gene sequences for recent field isolates and older reference Newcastle disease viruses (NDV) were examined to determine phylogenetic relationships and population trends among these viruses. Overall, the M gene has a majority of synonymous nucleotide sequence substitutions occurring among NDV isolates. However, several predicted amino acid changes in the M protein of specific NDV isolates have occurred that correlate to phylogenetic relationships. Nucleotide substitutions in these codons have a greater number of nonsynonymous base changes. The NDV isolates arising since the 1970s belong to a population of viruses that expanded worldwide at an exponential rate. These viruses may have their origins in free-living birds, are present worldwide, and continue to circulate causing disease in poultry. A specific NDV lineage composed of virulent isolates obtained in the US prior to 1970 appears to no longer exists among free-living birds or commercial poultry. However, "vaccine-like" viruses are common in the US and continue to circulate among commercial poultry. Based on M protein amino acid sequences, NDV separates as a clade most closely related to morbilliviruses and not with their current designated category, the rubulaviruses among the Paramyxoviridae. Consequently, avian paramyxoviruses should have their own taxonomic subfamily among the Paramyxovirinae.

Animals↗

PubMed2000

Expression and characterization of truncated forms of humanized L243 IgG1. Architectural features can influence synthesis of its oligosaccharide chains and affect superoxide production triggered through human Fcgamma receptor I.

The properties of IgG and its subcomponents are being exploited to generate new therapeutics with selected biological activities. In this study, a series of truncated, humanized IgG1 antibodies was expressed in Chinese hamster ovary cells, to evaluate the contribution of structural components to glycosylation and function. The series includes L243 IgG1 (alpha-MHC Class II) lacking a CH3 domain pair (DeltaCH3-IgG1), single-chain Fv fusion proteins with Fc or a hinge-CH2 domain, Fc with/out a hinge, and a single CH2 domain. Glycosylation of IgG Fc is important for recognition by effector ligands such as Fcgamma receptors. HPLC analysis of released and pyridylaminated oligosaccharides indicates that intact IgG1 and scFvFc antibodies are galactosylated and sialylated to levels similar to those observed previously for normal human IgG1. The truncated forms express increased levels of digalactosylated (30-83%) or sialylated (9-21%) oligosaccharide chains with the highest levels observed for the single CH2 domain. These data show which architectural components influence IgG glycosylation processing and that the (CH3)2 pair is particularly influential. When MHC Class II bearing (JY) cells were sensitized with L243 DeltaCH3-IgG1, scFvFc, or scFvhCH2 they elicited superoxide production, from U937 cells, at levels of 35-45% relative to that obtained for intact L243 IgG1 (100%). Mild reduction and alkylation of the hinge disulphide bonds of scFvhCH2 greatly decreased its capacity to trigger superoxide production. Thus, the L243 scFvhCH2 homo-dimer constitutes the minimal truncated form that binds the MHC Class II antigen and triggers superoxide production through FcgammaRI.

Amino Acid Sequence↗

PubMed2000

Cholinergic agents and the McCollough effect.

The strength of the McCollough effect (ME), a pattern-contingent colour aftereffect, has been shown to be inversely related to acetylcholine, being significantly strengthened by (anticholinergic) scopolamine and weakened by (cholinergic) physostigmine delivered before adapting to the ME stimuli. The purpose of the present study was (i) to establish whether the effect of pre-adaptation scopolamine is linearly dose-dependent and (ii) to investigate the effects of scopolamine and physostigmine delivered between adaptation and testing. In experiment 1, ten healthy male volunteers who received placebo, or 0.6 mg, 1.2 mg, or 1.8 mg scopolamine before adapting to ME stimuli showed a significant linear dose-dependence over tests repeated from 10 to 70 min after adaptation. In experiment 2 twelve male volunteers adapted to ME stimuli and then received placebo, 1.2 mg oral scopolamine, or 0.75 mg subcutaneous physostigmine. On subsequent repeated testing, strength of the ME was increased by scopolamine and decreased by physostigmine relative to placebo. Both experiments were double-blind double-dummy repeated measures. These data support the view that the ME is a product of inhibitory mechanisms in the visual system rather than processes involved in associative learning.

Adult↗

PubMed2000

Antisaccade and smooth pursuit eye movements in healthy subjects receiving sertraline and lorazepam.

Patients suffering from some psychiatric and neurological disorders demonstrate abnormally high levels of saccadic distractibility when carrying out the antisaccade task. This has been particularly thoroughly demonstrated in patients with schizophrenia. A large body of evidence has been accumulated from studies of patients which suggests that such eye movement abnormalities may arise from frontal lobe dysfunction. The psychopharmacology of saccadic distractibility is less well understood, but is relevant both to interpreting patient studies and to establishing the neurological basis of their findings. Twenty healthy subjects received lorazepam 0.5 mg, 1 mg and 2 mg, sertraline 50 mg and placebo in a balanced, repeated measures study design. Antisaccade, no-saccade, visually guided saccade and smooth pursuit tasks were carried out and the effects of practice and drugs measured. Lorazepam increased direction errors in the antisaccade and no-saccade tasks in a dose-dependent manner. Sertraline had no effect on these measures. Correlation showed a statistically significant, but rather weak, association between direction errors and smooth pursuit measures. Practice was shown to have a powerful effect on antisaccade direction errors. This study supports our previous work by confirming that lorazepam reliably worsens saccadic distractibility, in contrast to other psychotropic drugs such as sertraline and chlorpromazine. Our results also suggest that other studies in this field, particularly those using parallel groups design, should take account of practice effects.

Adolescent↗

PubMed1999

'Naïve' and 'memory' CD4+ T-cells and T-cell receptor (TCR) V beta repertoire dynamics are independent of the levels of viremia following HIV seroconversion.

The progression of 'naive' and 'memory' T-cells and the T-cell receptor Vbeta (TCR Vbeta) repertoire dynamics within the peripheral CD4+ T-cell compartment were studied in individuals following HIV seroconversion. Profound TCR Vbeta repertoire perturbations were observed within the CD4+ T-cell pool in treatment-naive patients regardless of their levels of viremia during the first 6-8 months after seroconversion. The ratio of 'naive' to 'memory' CD4+ T-cells as well as the TCR Vbeta repertoire dynamics did not appear to correlate with absolute numbers of CD4 T-cells.

Adolescent↗

PubMed1999

Therapeutic antibody fragments with prolonged in vivo half-lives.

Antibody fragments can be isolated rapidly using techniques such as phage display and can be expressed to high levels in microbial systems. However, to date such antibody fragments have been of limited use for many therapeutic applications because they are rapidly cleared from the body. We present a strategy for the site-specific chemical modification of antibody fragments with polyethylene glycol, which results in the production of antibody fragments with long in vivo half-lives and full retention of antigen-binding properties. This technology should allow more rapid and economical production of therapeutic antibodies for chronic disease therapy.

Animals↗

PubMed1999

Dosimetric evaluation and radioimmunotherapy of anti-tumour multivalent Fab' fragments.

We have been investigating the use of cross-linked divalent (DFM) and trivalent (TFM) versions of the anti-carcinoembryonic antigen (CEA) monoclonal antibody A5B7 as possible alternatives to the parent forms (IgG and F(ab')2) which have been used previously in clinical radioimmunotherapy (RIT) studies in colorectal carcinoma. Comparative biodistribution studies of similar sized DFM and F(ab')2 and TFM and IgG, radiolabelled with both 131I and 90Y have been described previously using the human colorectal tumour LS174T nude mouse xenograft model (Casey et al (1996) Br J Cancer 74: 1397-1405). In this study quantitative estimates of radiation distribution and RIT in the xenograft model provided more insight into selecting the most suitable combination for future RIT. Radiation doses were significantly higher in all tissues when antibodies were labelled with 90Y. Major contributing organs were the kidneys, liver and spleen. The extremely high absorbed dose to the kidneys on injection of 90Y-labelled DFM and F(ab')2 as a result of accumulation of the radiometal would result in extremely high toxicity. These combinations are clearly unsuitable for RIT. Cumulative dose of 90Y-TFM to the kidney was 3 times lower than the divalent forms but still twice as high as for 90Y-IgG. TFM clears faster from the blood than IgG, producing higher tumour to blood ratios. Therefore when considering only the tumour to blood ratios of the total absorbed dose, the data suggests that TFM would be the most suitable candidate. However, when corrected for equitoxic blood levels, doses to normal tissues for TFM were approximately twice the level of IgG, producing a two-fold increase in the overall tumour to normal tissue ratio. In addition RIT revealed that for a similar level of toxicity and half the administered activity, 90Y-IgG produced a greater therapeutic response. This suggests that the most promising A5B7 antibody form with the radionuclide 90Y may be IgG. Dosimetry analysis revealed that the tumour to normal tissue ratios were greater for all 131I-labelled antibodies. This suggests that 131I may be a more suitable radionuclide for RIT, in terms of lower toxicity to normal tissues. The highest tumour to blood dose and tumour to normal tissue ratio at equitoxic blood levels was 131I-labelled DFM, suggesting that 131I-DFM may be best combination of antibody and radionuclide for A5B7. The dosimetry estimates were in agreement with RIT results in that twice the activity of 131I-DFM must be administered to produce a similar therapeutic effect as 131I-TFM. The toxicity in this therapy experiment was minimal and further experiments at higher doses are required to observe if there would be any advantage of a higher initial dose rate for 131I-DFM.

Animals↗

PubMed1999

Analysis of thiopurine methyltransferase variant alleles in childhood acute lymphoblastic leukaemia.

The role of 6-mercaptopurine (6MP) in the treatment of childhood acute lymphoblastic leukaemia (ALL) is well established. However, the efficacy of 6MP is significantly influenced by inactivation by the polymorphic enzyme thiopurine methyltransferase (TPMT). In the general population 89-94% have high TPMT activity, 6-11% have intermediate activity, and approximately 0.3% have low activity. Individuals with low-activity experience severe or fatal toxicity with standard 6MP doses. Prospective identification of this group of patients might prevent this problem. Recent identification of the molecular basis for low TPMT activity enabled rapid assessment of altered 6MP metabolism by PCR methods. This study evaluated the frequency of mutant TPMT alleles in 147 children with ALL. One patient was homozygous mutant (0.7%), and 16 patients were heterozygous for variant TPMT alleles (10.9%). The majority of mutant alleles were TPMT*3A. Both the allele frequency and the pattern of TPMT mutations were similar to that observed in an adult British population. The number of weeks when 6MP therapy was administered at full dose was determined in patients on MRC UKALL X and XI. The 94 patients spent a median 11% of the maintenance period receiving no therapy as a result of haematological toxicity. There was no significant difference in the number of weeks when no therapy could be administered among patients with a wild-type or heterozygous genotype. However, the one patient with a homozygous mutant genotype had severe haematological toxicity and no therapy could be administered for 53% of the maintenance period. This study demonstrates that 11.6% of the children had variant TPMT alleles. Prospective identification of TPMT genotype may be a promising tool for decreasing excessive haematological toxicity in individuals with low activity.

Adult↗

PubMed1999

Comparison of pathology-based techniques for detection of viscerotropic velogenic Newcastle disease virus in chickens.

Two pathology-based techniques, immunohistochemistry and riboprobe in-situ hybridization, were applied to formalin-fixed, paraffin wax-embedded tissues from chickens infected with three different isolates of velogenic viscerotropic Newcastle disease virus (VVNDV). With the immunohistochemical method, viral protein was consistently detectable in the spleen and caecum at the terminal phase of the infection. With in-situ hybridization, viral nucleic acid was consistently detected in the eyelid, spleen and caecum in both the acute and terminal phases. Hybridization with anti-sense probe to detect viral mRNA was often more intense than hybridization with sense probe to detect viral genomic RNA.

Animals↗

PubMed1999

Congenital rhabdomyosarcoma.

A congenital rhabdomyosarcoma presented as a partially necrotic mass on the left forearm on delivery at term. Ulceration and persistent bleeding were managed by primary curettage followed by local resection including partial excision of the muscles of the extensor compartment of the forearm. The defect was resurfaced with a split skin graft. The surgery was followed by chemotherapy according to the IVA regime. There was no recurrence at 2 years of age and the limb was fully functional. The presentation and management of rhabdomyosarcoma are discussed.

Female↗

PubMed1999

trans Fatty acids in human milk are inversely associated with concentrations of essential all-cis n-6 and n-3 fatty acids and determine trans, but not n-6 and n-3, fatty acids in plasma lipids of breast-fed infants.

BACKGROUND: Human milk fatty acids vary with maternal dietary fat composition. Hydrogenated dietary oils with trans fatty acids may displace cis n-6 and n-3 unsaturated fatty acids or have adverse effects on their metabolism. The effects of milk trans, n-6, and n-3 fatty acids in breast-fed infants are unclear, although n-6 and n-3 fatty acids are important in infant growth and development. OBJECTIVE: We sought to determine the relations between trans and cis unsaturated fatty acids in milk and plasma phospholipids and triacylglycerols of breast-fed infants, and to identify the major maternal dietary sources of trans fatty acids. DESIGN: We collected milk from 103 mothers with exclusively breast-fed 2-mo-old infants, blood from 62 infants, and 3-d dietary records from 21 mothers. RESULTS: Mean (+/-SEM) percentages of trans fatty acids were as follows: milk, 7.1 +/- 0.32%; infants' triacylglycerols, 6.5 +/- 0. 33%; and infants' phospholipids, 3.7 +/- 0.16%. Milk trans fatty acids, alpha-linolenic acid (18:3n-3), arachidonic acid (20:4n-6), docosahexaenoic acid (22:6n-3) (P < 0.001), and linoleic acid (18:2n-6) (P = 0.007) were each related to the same fatty acid in infant plasma phospholipids. Milk trans fatty acids were inversely related to milk 18:2n-6 and 18:3n-3, but not to milk or infant plasma 20:4n-6 or 22:6n-3. trans Fatty acids represented 7.7% of maternal total fat intake (2.5% of total energy); the major dietary sources were bakery products and breads (32%), snacks (14%), fast foods (11%), and margarines and shortenings (11%). CONCLUSIONS: There were comparable concentrations of trans fatty acids in the maternal diet, breast milk, and plasma triacylglycerols of breast-fed infants. Prepared foods were the major dietary source of trans fatty acids.

Breast Feeding↗

PubMed1999

Developing a patient care model for an integrated delivery system.

An integrated healthcare delivery system requires a consistent patient care delivery model. The authors describe the process used to define common elements of the patient care model. These elements include the roles of chief nurse executives, first-line managers, staff registered nurses, and unlicensed assistive personnel. In addition, the philosophy of nursing and support functions (staff education and nursing dashboard for quality measurement) in place across the system are discussed.

Chicago↗

PubMed1999

Pathogenesis of Newcastle disease in chickens experimentally infected with viruses of different virulence.

Groups of 4-week-old White Rock chickens were inoculated intraconjunctivally with nine isolates of Newcastle disease virus representing all pathotypes. Birds were monitored clinically and euthanatized sequentially, with collection of tissues for histopathologic examination and in situ hybridization using an anti-sense digoxigenin-labeled riboprobe corresponding to the sequence of the gene coding for the matrix protein. Disease was most severe with velogenic viscerotropic pathotypes and was characterized by acute systemic illness with extensive necrosis of lymphoid areas in the spleen and intestine. Viral nucleic acid was detected in multiple tissues but most prominently in macrophages associated with lymphoid tissue. Velogenic neurotropic isolates caused central nervous system disease despite minimal amounts of viral nucleic acid detected in neural tissue. Mesogenic and lentogenic pathotypes caused no overt disease; however, viral nucleic acid was present in myocardium and air sac epithelium following infection with these isolates. Compromise of air sac and myocardium may predispose mesogen- and lentogen-infected chickens to secondary infection and/or decreased meat and egg production.

Air Sacs↗

PubMed1998

Novel combinatorial selection of phosphorothioate oligonucleotide aptamers.

A novel combinatorial approach is described for construction and screening of enhanced nuclease-resistant phosphorothioate DNA "decoys" or "aptamers." Aptamers have been selected that bind tightly to the nuclear factor for human IL6 (NF-IL6), a basic leucine zipper transcription factor involved in the induction of acute-phase responsive and cytokine gene promotors in response to inflammation. Using a random combinatorial selection approach and dNTP(alphaS)'s in the PCR amplification, we can select specific thio-substituted agents which have the highest specificity in binding to target NF-IL6. Using a 22-nucleotide-long duplex random library, nanomolar binding, specific 22-mer thiophosphate backbone substitution sequences (at dA positions only) were selected. These show a different consensus sequence than normal phosphate backbone CCAAT/enhancer binding protein recognition sites for NF-IL6. Unlike the wild-type 10-mer sequences, which bind 1 protein dimer/duplex, these 22-mer thiophosphate aptamers bind with a stoichiometry of 2 dimers/duplex.

Base Sequence↗

PubMed1998

Effect of bradykinin-receptor blockade on the response to angiotensin-converting-enzyme inhibitor in normotensive and hypertensive subjects.

BACKGROUND: Angiotensin-converting-enzyme (ACE) inhibitors not only decrease the production of angiotensin II but also decrease the degradation of bradykinin. In this study, a specific bradykinin-receptor antagonist, icatibant acetate (HOE 140), was used to determine the contribution of bradykinin to the short-term effects of ACE inhibition on blood pressure and plasma renin activity in both normotensive and hypertensive subjects. METHODS: We compared the hemodynamic, renal, and endocrine effects of captopril alone (25 mg), captopril plus icatibant (100 microg per kilogram of body weight), the angiotensin II subtype 1-receptor antagonist losartan (75 mg), and placebo in 20 subjects with normal blood pressure and 7 subjects with hypertension. The subjects were studied while they were salt depleted (i.e., in balance on a diet in which they were allowed 10 mmol of sodium per day). The drugs were administered on four separate study days in a single-blind, randomized fashion. RESULTS: The coadministration of icatibant significantly attenuated the hypotensive effect of captopril (maximal decrease in mean arterial pressure for all subjects combined, 10.5+/-1.0 mm Hg, as compared with 14.0+/-1.0 mm Hg for captopril alone; P=0.001), in such a way that the decrease in blood pressure after the administration of captopril plus icatibant was similar to that after the administration of losartan (maximal decrease in mean arterial pressure, 11.0+/-1.7 mm Hg). Icatibant did not alter the renal hemodynamic response to captopril, but it significantly altered the change in plasma renin activity in response to ACE inhibition (-0.4+/-0.4 ng of angiotensin I per milliliter per hour, as compared with 2.0+/-0.7 ng per milliliter per hour for captopril alone; P=0.007). The magnitude of these effects was similar in both the normotensive and the hypertensive subjects, as well as in both the black subjects and the white subjects. CONCLUSIONS: These data confirm that bradykinin contributes to the short-term effects of ACE inhibition on blood pressure in normotensive and hypertensive persons and suggest that bradykinin also contributes to the short-term effects of ACE inhibition on the renin-angiotensin system.

Adrenergic beta-Antagonists↗

PubMed1998

The effects of chlorpromazine and lorazepam on abnormal antisaccade and no-saccade distractibility.

BACKGROUND: Abnormally high levels of saccadic distractibility have been demonstrated to occur in patients with schizophrenia. Converging evidence implicates frontal cortical dysfunction as a mechanism; however, much of the neuropharmacology of saccadic distractibility has not yet been established. METHODS: We measured antisaccade, no-saccade, and visually guided saccade components in healthy subjects following single doses of lorazepam 2 mg, chlorpromazine 50-100 mg, and placebo. Visual analogue rating scales (VARS) provided a subjective measure of sedation. RESULTS: Lorazepam, but not chlorpromazine, was shown to cause an increase in saccadic distractibility in both the antisaccade and no-saccade tasks. Peak visually guided saccade velocity was decreased by lorazepam and chlorpromazine in a dose-dependent manner, with corresponding changes seen in VARS. Lorazepam, unexpectedly, did not affect peak antisaccade velocity. The background level of antisaccade directional errors was 6.43%, which is relatively low compared to control groups in patient studies. CONCLUSIONS: These results support the view that abnormal saccadic distractibility in patients with schizophrenia is not due to an acute effect of antipsychotic medication. The use of benzodiazepines and the level of task practice are highlighted as possible confounding variables in patient studies. The implications of these results for the current neuropathological theories of abnormal saccadic distractibility are discussed.

Adult↗

PubMed1998

F(ab')2 molecules made from Escherichia coli produced Fab' with hinge sequences conferring increased serum survival in an animal model.

Fab's with hinges based on the human gamma1 sequence containing 1, 2, or 4 cysteines have been produced by high level Escherichia coli periplasmic secretion, and coupled in vitro by reduction/oxidation to form F(ab')2. We find that the F(ab')2 made with hinges containing 2 or 4 cysteines have a high level (approximately 70%) of multiple disulphide bonds. These F(ab')2 molecules have an increased pharmacokinetic stability as measured by area under the curve compared to those made by direct coupling through a single disulphide bond. One particular molecule containing 4 hinge cysteines has a greater pharmacokinetic stability than a F(ab')2 formed by chemical cross-linking. F(ab')2 made from the Fab' with 4 hinge cysteines is also relatively resistant to chemical reduction in vitro allowing partial reduction to expose reactive hinge thiols. These hinge sequences provide a simple method for producing robust F(ab')2 in vitro, obviating the need to use chemical cross-linkers, and provide a route to hinge specific chemical modification with thiol-reactive conjugates.

Amino Acid Sequence↗