Search PubMed⌕ Search

Biomedical subjects

P Ward

Publications and source records attributed to P Ward.

At least 73 records · Page 4Linked to original sources
PubMed1997

Performance, survival, necropsy, and virological findings from calves persistently infected with the bovine viral diarrhea virus originating from a single Saskatchewan beef herd.

Fifty-one calves from 652 cows and heifers that calved on a Saskatchewan ranch in 1992 were identified as persistently infected with bovine viral diarrhea virus (BVDV), based on virological and necropsy findings. Herd records suggested a further 20 calves that died between birth and weaning were probably also persistently infected. Subsequent to weaning, all surviving persistently infected calves were transferred to one pen in a 10,000 head commercial feedlot, to mimic normal management practice in western Canadian beef herds. On average, when compared with healthy, BVDV-negative herdmates, persistently infected calves were "poor doers" and had poor survivability, with only 4 persistently infected calves surviving to 1 year of age. There was no difference (P > 0.05) in survival between male and female persistently infected calves. The clinical, pathological, and virological findings from these persistently infected calves varied over time. The majority of persistently infected calves had gross pathological lesions at necropsy, consistent with mucosal disease. However, approximately 25% of the persistently infected calves had gross pneumonic lesions at necropsy, with no or only mild lesions of mucosal disease. A wide variety of other lesions were also noted in persistently infected calves at necropsy. Therefore, the possibility that BVDV-induced lesions can be misdiagnosed is very real. The results of this study indicate that persistent infection with BVDV should always be considered in calves with chronic ill thrift, chronic enteritis, or respiratory disease.

Animals↗
PubMed1996

Site-specific integration by adeno-associated virus.

Adeno-associated virus (AAV) has attracted considerable interest as a potential vector for gene delivery. Wild-type virus is notable for the lack of association with any human disease and the ability to stably integrate its genome in a site-specific manner in a locus on human chromosome 19 (AAVS1). Use of a functional model system for AAV DNA integration into AAVS1 has allowed us to conclude that the recombination event is directed by cellular DNA sequences. Recombinant junctions isolated from our integration assay were analyzed and showed characteristics similar to those found in latently infected cell lines. The minimal DNA signals within AAVS1 required for targeted integration were identified and shown to contain functional motifs of the viral origin of replication. A replication mediated model of AAV DNA integration is proposed.

Base Sequence↗
PubMed1996

GR205171: a novel antagonist with high affinity for the tachykinin NK1 receptor, and potent broad-spectrum anti-emetic activity.

It has been demonstrated recently that antagonists of the tachykinin NK1 receptor, specifically CP-99,994 and GR203040, possess anti-emetic activity in a range of species. To optimise this activity, a series of analogues based around the structure of GR203040 have been synthesised and their affinity at the human tachykinin NK1 receptor determined. In addition, the potency of these analogues to inhibit emesis induced in the ferret by whole-body X-irradiation has been examined. A range of substitution at the C-1 position of the tetrazole moiety in GR203040 were explored in vitro and in vivo. The trifluoromethyl compound, GR205171, was the most potent antagonist with regard to the ability to inhibit emesis induced by X-irradiation. This compound was demonstrated to have a broad spectrum of anti-emetic activity, inhibiting emesis in the ferret induced by cisplatin, cyclophosphamide, morphine, ipecacuanha and copper sulphate. Furthermore, emesis was also inhibited in the house-musk shrew, Suncus murinus, when induced by either motion or cisplatin, and in the dog when induced by ipecacuanha. GR205171 has the most potent anti-emetic activity of any tachykinin NK1 receptor antagonist described to date. The compound is orally active in the ferret and dog, long-lasting, and warrants further investigation as a potential broad-spectrum anti-emetic agent.

Administration, Oral↗
PubMed1996

Differentiation of bifidobacteria by use of pulsed-field gel electrophoresis and polymerase chain reaction.

Several different genomic fingerprints can be obtained from various commercially-important species of Bifidobacterium using pulsed-field gel electrophoresis (PFGE) following digestion of DNA with XbaI and SpeI. Four different genomic finger printings were discernible for reference strains of Bifidobacterium animalis, five for B. bifidum, three for B. breve, five for B. infantis and three for B. longum. Standard commercially-available industrial strains of B. animalis are identical to the reference strain ATCC 27536, previously isolated from chicken feces. There was more genomic heterogeneity among industrial strains of B. longum, in that only one gave profiles similar to the type strain of this species (ATCC 15707). The other 14 commercially-available strains of B. longum (mainly isolated from Japanese commercial preparations) were divided into four new molecular types based on their PFGE patterns. The PFGE method indicated that only five distinct strains of B. longum and one strain of B. animalis are used in commercial preparations. Additionally, the use of polymerase chain reaction amplification of portions of 16S rDNA provides a highly specific technique to discriminate between the species B. breve, B. infantis and B. longum.

Adult↗
PubMed1996

Pilot study of the efficacy of atevirdine in the treatment of AIDS dementia complex.

OBJECTIVES: To determine the efficacy of the non-nucleoside reverse transcriptase inhibitor atevirdine in the treatment of AIDS dementia complex (ADC). DESIGN: Open label pilot study. METHODS: Ten patients with ADC (stage 1 or 2) who were intolerant to zidovudine or dideoxyinosine, or in whom the antiretrovirals had failed to prevent further decline in CD4 cell levels, were entered into the study. Atevirdine, 1800 mg daily in three divided doses, was given over a 12-week period. Patients were assessed neurologically and neuropsychologically every 4 weeks. Cerebrospinal fluid analysis was performed at entry and at weeks 4 and 12. Technetium-99 exametazine single photon emission computed tomographic cerebral perfusion scans and magnetic resonance imaging brain scans were performed at weeks 0 and 12. RESULTS: Five patients completed the 12 week protocol. Four of these five responded to atevirdine, as judged by quantified neurological and neuropsychological assessments. Atevirdine was well tolerated apart from the development of rash, anxiety, intermittent diarrhoea and fatigue. CONCLUSIONS: These preliminary results suggest that atevirdine is efficacious in the treatment of ADC. Larger blinded studies of this class of drug in the treatment of ADC are required.

AIDS Dementia Complex↗
PubMed1996

Safety, tolerance, and efficacy of atevirdine in asymptomatic human immunodeficiency virus-infected individuals.

Atevirdine is a nonnucleoside reverse transcriptase inhibitor of human immunodeficiency virus type 1 (HIV-1). In this study we investigated the effect of atevirdine in asymptomatic antiretroviral naive HIV-infected patients with CD4+ cell counts of between 200 and 750 cells per mm3. Patients were randomized to receive 600 mg of atevirdine (n = 15) or a placebo (n = 15) three times a day for 12 weeks. There was no statistically significant effect of atevirdine on viral loads (HIV p24 antigen and HIV-1 RNA levels by PCR) or CD4+ cell counts. The data do not support the use of atevirdine as a monotherapy in the treatment of HIV-infected patients.

Adult↗
PubMed1996

In vitro replication of adeno-associated virus DNA: enhancement by extracts from adenovirus-infected HeLa cells.

Previously we have described an in vitro assay for the replication of adeno-associated virus type 2 (AAV2) DNA. Addition of the AAV2 nonstructural protein Rep68 to an extract from uninfected cells supports the replication of linear duplex AAV DNA. In this report, we examine replication of linear duplex AAV DNA in extracts from either uninfected or adenovirus (Ad)-infected HeLa cells. The incorporation of radiolabeled nucleotides into full-length linear AAV DNA is 50-fold greater in extracts from Ad-infected cells than in extracts from uninfected cells. In addition, the majority of the labeled full-length AAV DNA molecules synthesized in the Ad-infected extract have two newly replicated strands, whereas the majority of labeled full-length AAV DNA molecules synthesized in the uninfected extract have only one newly replicated strand. The numbers of replication initiations on original templates in the two assays are approximately the same; however, replication in the case of the Ad-infected cell extract is much more likely to result in the synthesis of a full-length AAV DNA molecule. Most of the newly replicated molecules in the assay using uninfected cell extracts are in the form of stem-loop structures. We hypothesize that Ad infection provides a helper function related to elongation during replication by a single-strand displacement mechanism. In the assay using the uninfected HeLa cell extract, replication frequently stalls before reaching the end of the genome, causing the newly synthesized strand to be displaced from the template, with a consequent folding on itself and replication back through the inverted terminal repeat, using itself as a template. In support of this conjecture, replication in the uninfected cell extract of shorter substrate molecules is more efficient, as measured by incorporation of radiolabeled nucleotides into full-length substrate DNA. In addition, when shorter substrate molecules are used as the template in the uninfected HeLa cell assay, a greater proportion of the labeled full-length substrate molecules contain two newly replicated strands. Shorter substrate molecules have no replicative advantage over full-length substrate molecules in the assay using an extract from Ad-infected cells.

Cell Extracts↗
PubMed1996

Primary care in London: an evaluation of general practitioners working in an inner city accident and emergency department.

OBJECTIVE: To determine the characteristics of primary care attenders to St Mary's Hospital accident and emergency (A&E) department, evaluate the effects of the introduction of general practitioners (GPs) on patient care in A&E, and make recommendations for the provision of GPs in appropriate A&E departments. DESIGN: Prospective survey over a six week period. METHODS: Data collected from the attendances of 970 consecutive patients triaged with "minor" primary care problems, whether seen by A&E doctors or by GPs working in A&E, were analysed. RESULTS: During the study period 1078 patients (16.6%) were triaged as suitable for primary care. The A&E GPs saw 58.4% of these patients. The majority of primary care patients were young British residents, 71.1% of whom were registered with a GP. Sixty per cent of patients lived within St Mary's catchment area. Of those registered patients asked why they attended A&E, 27.1% thought their problem inappropriate for their GP. A&E doctors were more likely to investigate patients and arrange hospital follow up than GPs, who arranged community follow up in 80% of patients needing further care. CONCLUSIONS: The demand for primary care at St Mary's necessitates the provision of a primary care service, albeit for the first visit only. This can be provided by GPs in A&E. The features of the patients using the service suggests that discouraging first attendance is unrealistic, but using the visit to educate patients and return them to the care of the community is not.

Adolescent↗
PubMed1996

Towards understanding the aetiology and pathophysiology of the emetic reflex: novel approaches to antiemetic drugs.

The introduction of 5-HT3 antagonists, such as ondansetron, as antiemetic agents has transformed the management of patients receiving chemotherapy or radiation therapy. Studies in animal models with NK1 antagonists suggest that these represent a new class of antiemetic agents having a broader spectrum of activity than 5-HT3 antagonists. Compounds of this class may prove to be more effective in man against delayed emesis induced by cisplatin, post-operative nausea and vomiting and motion sickness. Thus, they have the potential to complement 5-HT3 antagonists and so provide a further advance in the management of nausea and vomiting.

Animals↗
PubMed1996

Pulmonary pharmacology of DT-TX 30 SE, a potent selective combined thromboxane synthetase inhibitor and receptor antagonist, in guinea pigs.

A novel chemical compound, DT-TX 30 SE (E-6-(4-2-(4-chlorobenzenesulphonylamino)-ethyl)phenyl)-6-(3-pyrid yl)- hex-5-enoic acid), was studied in various models of guinea pig pulmonary function. The compound was a potent inhibitor (ED50 0.019 mg/kg, i.v.) of bronchospasm induced by the thromboxane receptor agonist U-46619, indicating thromboxane receptor antagonism. At even lower doses (ED50 0.0036 mg/kg, i.v.), it blocked arachidonic acid-induced bronchospasm. Interpretation of the latter results as evidence for additional thromboxane synthetase inhibitory activity was supported by the inhibition of arachidonic acid- or bradykinin-induced thromboxane B2 production in an isolated lung preparation, although prostaglandin E2 and prostaglandin 6-oxo-F(1 alpha) production measured at the same time were not inhibited. The potency of DT-TX 30 SE was compared with thromboxane receptor antagonists and synthetase inhibitors described in the literature. As a receptor antagonist, DT-TX 30 SE was significantly more potent than BM 13505 and BM 13177 (assessed by antagonism of U-46619-induced bronchospasm), but less potent than SQ 29548, while as a thromboxane synthetase inhibitor, it was significantly more potent than OKY 046 and UK 37248 as assessed by antagonism of arachidonic acid-induced bronchospasm or (OKY 046) inhibition of thromboxane production in isolated lung. The compound was active by the oral route as shown by its ability, at 10 mg/kg, p.o., to significantly reduce the immediate allergic response of sensitized guinea pigs to an ovalbumin aerosol.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1995

Discovery of an orally bioavailable NK1 receptor antagonist, (2S,3S)-(2-methoxy-5-tetrazol-1-ylbenzyl)(2-phenylpiperidin-3-yl)amine (GR203040), with potent antiemetic activity.

The antiemetic, pharmacokinetic, and metabolic profile of CP-99,994, a potent NK1 receptor antagonist, has been carefully evaluated. As a result we began a medicinal chemistry program which initially identified a 3-furanyl analogue (6) with improved antiemetic potency and a methyl sulfone (5) with enhanced metabolic stability and oral bioavailability. The improved pharmacokinetic profile of methyl sulfone (5) was associated with its low lipophilicity, and a therefore a number of heterocyclic analogues with reduced log D were synthesized. Out of this program emerged 19 (GR203040), a tetrazolyl-substituted analogue. Tetrazole 19 inhibits radiation-induced emesis in the ferret with high potency when administered both subcutaneously and orally, has a long duration of action, and has high oral bioavailability in the dog. Tetrazole 19 is currently undergoing evaluation as a novel approach for the control of emesis associated with, for example, cancer chemotherapy.

Animals↗
PubMed1995

Minimum origin requirements for linear duplex AAV DNA replication in vitro.

We have investigated the minimal requirements for a functional origin of DNA replication in an in vitro assay which requires the adeno-associated virus (AAV) Rep 68/78 protein. When a linear duplex template was used, initiation of one round of DNA replication was achieved when nucleotides 1-56 of the AAV inverted terminal repeat (in the flop orientation) were present at the terminus of the template. A terminal resolution site was not required. Deletion of an additional 11 nucleotides from the terminal repeat blocked the reaction.

DNA Replication↗
PubMed1995

The pharmacology of GR203040, a novel, potent and selective non-peptide tachykinin NK1 receptor antagonist.

1. The in vitro and in vivo pharmacology of GR203040 ((2S, 3S)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), a novel, highly potent and selective non-peptide tachykinin NK1 receptor antagonist, was investigated in the present study. 2. GR203040 potently inhibited [3H]-substance P binding to human NK1 receptors expressed in Chinese hamster ovary (CHO) and U373 MG astrocytoma cells, and NK1 receptors in ferret and gerbil cortex (pKi values of 10.3, 10.5, 10.1 and 10.1 respectively). GR203040 had lower affinity at rat NK1 receptors (pKi = 8.6) and little affinity for human NK2 receptors (pKi < 5.0) in CHO cells and NK3 receptors in guinea-pig cortex (pKi < 6.0). With the exception of the histamine H1 receptor (pIC50 = 7.5). GR203040 had little affinity (pIC50 < 6.0) at all non-NK1 receptors and ion channels examined. Furthermore, GR203040 produced only weak inhibition of Na+ currents in SH-SY5Y neuroblastoma and superior cervical ganglion cells (pIC50 values < 4.0). GR203040 produced only weak antagonism of Ca(2+)-evoked contractions of rat isolated portal vein (pKn = 4.1). The enantiomer of GR203040, GR205608 (2R, 3R)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), had 10,000 fold lower affinity at the human NK1 receptor expressed in CHO cells (pKi = 6.3). 3. In gerbil ex vivo binding experiments, GR203040 produced a dose-dependent inhibition of the binding of [3H]-substance P to cerebral cortical membranes (ED50 = 15 micrograms kg-1 s.c. and 0.42 mg kg-1 p.o.). At 10 micrograms kg-1 s.c., the inhibition of [3H]-substance P binding was maintained for > 6 h. In the rat, GR203040 was less potent (ED50 = 15.4 mg kg-1 s.c.) probably reflecting, at least in part, its lower affinity at the rat NK1 receptor. 4. In guinea-pig isolated ileum and dog isolated middle cerebral and basilar arteries, GR203040 produced a rightward displacement of the concentration-effect curves to substance P methyl ester (SPOMe) with suppression of the maximum agonist response (apparent pKB values of 11.9, 11.2 and 11.1 respectively). 5. In anaesthetized rabbits, GR203040 antagonized reductions in carotid arterial vascular resistance evoked by SPOMe, injected via the lingual artery (DR10 (i.e. the dose producing a dose-ratio of 10) = 1.1 micrograms kg-1, i.v.). At a dose 20 fold greater than its DR10 value (i.e. 22 micrograms kg-1, i.v.), significant antagonism was evident more than 2 h after GR203040 administration. 6. In anaesthetized rats, GR203040 (3 and 10 mg kg-1, i.v.) produced a dose-dependent inhibition of plasma protein extravasation in dura mater, conjunctiva, eyelid and lip in response to electrical stimulation of the trigeminal ganglion. 7. It is concluded that GR203040 is one of the most potent and selective NK1 receptor antagonists yet described, and as such, has considerable potential as a pharmacological tool to characterize the physiological and pathological roles of substance P and NK1 receptors. GR203040 may also have potential as a novel therapeutic agent for the treatment of conditions such as migraine, emesis and pain.

Animals↗
PubMed1995

The broad-spectrum anti-emetic activity of the novel non-peptide tachykinin NK1 receptor antagonist GR203040.

1. Following our earlier observations that the tachykinin NK1 receptor antagonist CP-99,994 is an effective anti-emetic in ferrets, we have examined the anti-emetic effects of a more potent and novel NK1 receptor antagonist, GR203040, against various emetic stimuli in the ferret, dog and house musk shrew (Suncus murinus). 2. In ferrets, GR203040 (0.1 mg kg-1 s.c. or i.v.) is effective against emesis induced by radiation, cisplatin, cyclophosphamide, copper sulphate, ipecacuanha or morphine. 3. In animals in which emesis had been established with cisplatin, GR203040 (1 mg kg-1 s.c.) was fully effective as an interventional treatment. No further emesis was seen in animals treated with GR203040 whilst saline-treated animals continued to vomit. 4. GR203040 (0.1 mg kg-1 s.c.) retains anti-emetic efficacy in the ferret, even when given as a 6 h pretreatment, indicating that this compound has a long duration of action. The compound is also effective orally at the same dose, when given as a 90 min pretreatment. 5. GR203040 (0.1 mg kg-1 i.v.) is fully effective against ipecacuanha-induced emesis in the dog. 6. GR203040 is effective against motion- and cisplatin-induced emesis in Suncus murinus. These effects were seen at doses an order of magnitude greater than those shown to be effective against cisplatin in the ferret. 7. In conclusion, GR203040 is a novel anti-emetic agent, and the broad spectrum of anti-emetic activity, together with activity observed in three species, suggests that this compound is worthy of clinical investigation.

Animals↗
PubMed1995

Safety, tolerance, and pharmacokinetics of atevirdine mesylate (U-87201E) in asymptomatic human immunodeficiency virus-infected patients.

Atevirdine mesylate (U-87201E) is a new nonnucleoside (bisheteroarylpiperazine) inhibitor of human immunodeficiency virus type 1 reverse transcriptase. In a double-blind, escalating single-dose study the safety, tolerance, and pharmacokinetics of atevirdine mesylate were investigated in 24 asymptomatic human immunodeficiency virus-seropositive male patients. Each patient received one single oral dose of atevirdine mesylate and placebo separated by an interval of 1 to 3 weeks. For each dose level (400, 800, 1,200, and 1,600 mg) six patients received drug and placebo on separate occasions. Blood samples were collected before dosing and at intervals afterward for safety evaluation and estimation of atevirdine and metabolite levels. The concentrations of atevirdine and its principal metabolite (U-89255) in serum were determined by high-performance liquid chromatography. The results of the study showed that atevirdine mesylate is well tolerated at all dose levels. No clinically significant effects on vital signs, electrocardiograms, or laboratory tests were observed. Occasional headache and nausea were reported both in the drug group and in the placebo group. The times to peak values were relatively short (0.5 to 1.0 h), suggesting a rapid absorption. The maximum concentrations of drug in serum were 1.4 microM (400 mg), 4.2 microM (800 mg), 7.3 microM (1,200 mg), and 5.8 microM (1,600 mg). The values of the pharmacokinetic parameters for atevirdine were found to have relatively large intersubject variabilities, and consequently, the study had little power to detect dose-dependent changes in the values of the pharmacokinetic parameters. The oral clearance of atevirdine tended to increase by 90% as the atevirdine mesylate doses increased from 400 to 1,600 mg, but this change in oral clearance was not statistically significant. The values of the pharmacokinetic parameters determined in the study were similar to those found in a previous single-dose study in healthy volunteers.

Adult↗