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Biomedical subjects

J E Pearson

Publications and source records attributed to J E Pearson.

At least 19 recordsLinked to original sources

Cu2O island shape transition during Cu-Au alloy oxidation.

In situ transmission electron microscopy observations of the oxidation of (001) Cu-Au alloys indicate that the Cu2O islands that form undergo a remarkable transformation from an initially compact morphology to a dendritic structure as growth proceeds. Correspondingly, the surface composition becomes nonuniform and the fractal dimension associated with the islands evolves from 2.0 to a stable value of 1.87, indicating a transition in the rate-limiting mechanism of oxidation from oxygen surface diffusion to diffusion of copper through the increasingly gold-rich regions adjacent to the islands.

Journal Article↗

Transportation of reagents, reference materials and samples: the international perspective.

The International Regulations for the transport of infectious substances, which could include reagents, reference material and samples, are based on the 13th revision of the United Nations Model Regulations and are the standard for transport of infectious substances by all means of transportation. The 13th revision, effective January 2005 and further amended in March and July 2005, made major improvements in these shipping regulations. They specifically exempt certain substances, including those that have been neutralized or inactivated to destroy any pathogens and samples from "normal" animals. Infectious substances are divided into Category A, which includes primarily cultures of the more pathogenic agents and Category B, which includes all other substances that do not meet the Category A criteria. Tissue specimens, submitted for diagnosis, are included in Category B. Category A shipments must have a Dangerous Goods Certificate and meet other requirements; Category B shipments do not. The National requirements, such as import permits, and certain airline restrictions must also be met.

Indicators and Reagents↗

International standards for the control of avian influenza.

The Office International des Epizooties (OIE) has developed international standards to reduce the risk of the spread of high-pathogenicity avian influenza though international trade. These standards include providing a definition of high-pathogenicity avian influenza (HPAI), procedures for prompt reporting of HPAI outbreaks, requirements that must be met for a country or zone to be defined as free of HPAI, requirements that should be met to import live birds and avian products into a HPAI-free country or zone, and the general provisions that countries should meet to reduce the risk of spread of HPAI through trade. The goal of these standards is to facilitate trade while minimizing the risk of the introduction of HPAI.

Animals↗

Cadaveric Tissue Supply to the Commercial Sector For Research: Collaboration between NHS Pathology and NBS Tissue Services in the U.K., Extending the Options for Donors.

The Peterborough Hospital Human Tissue Bank (PHHTB) and National Blood Service Tissue Services (London and South East Zone) (NBSTS) operate within the U.K. National Health Service (NHS) and have a system in place to retrieve cadaveric tissues for commercial sector research. The collaboration meets the aims of PHHTB and NBSTS and is legal, ethical and safe. This paper presents the results of the first 20 successful retrievals referred from NBSTS to PHHTB. Cadaveric retrieval of tissue for research extends the options for donors and their relatives. The research option is particularly welcomed in cases where clinical retrieval for tissue transplantation is contraindicated. We believe the system is applicable to other centres.

Journal Article↗

Experimental observation of disorder-driven hysteresis-loop criticality.

We have studied the effect of magnetic disorder on the magnetization reversal process in thin Co/CoO films. The antiferromagnetic CoO layer allows a reversible tuning of the magnetic disorder by simple temperature variation. For temperatures above a critical temperature T(c), we observe a discontinuous magnetization reversal, whereas smooth magnetization loops occur for T<T(c). Our measurements establish the existence of a disorder-driven critical point in the nonequilibrium phase diagram. In addition, we observe scaling behavior in the vicinity of the critical point and determine the critical exponents beta = 0.022+/-0.006 and betadelta = 0.30+/-0.03 for this two-dimensional system.

Journal Article↗

Fire-diffuse-fire model of dynamics of intracellular calcium waves.

When Ca2+ is released from internal stores in living cells, the resulting wave of increased concentration can travel without deformation (continuous propagation) or with burst-like behavior (saltatory propagation). We analyze the "fire-diffuse-fire" model in order to illuminate the differences between these two modes of propagation. We show that the Ca2+ release wave in immature Xenopus oocytes and cardiac myocytes is saltatory, whereas the fertilization wave in the mature oocyte is continuous.

Animals↗

A new solid-phase support for oligonucleotide synthesis.

An alternative solid support for oligonucleotide synthesis was developed by coupling a polymer colloid to a modified polyethylene filter disc. The functions on the polymer colloid not used for attachment to the surface were derivatized with a Jeffamine diamine and loaded with appropriate deoxynucleoside succinates. The performance of this support system was evaluated and compared to existing resins.

Mass Spectrometry↗

Surface plasmon resonance: a study of the effect of biotinylation on the selection of antibodies for use in immunoassays.

Surface plasmon resonance is a valuable optical phenomenon for monitoring biomolecular interactions in real time. In this project anti-mouse-Fc was coupled to the carboxymethyl dextran coating on the surface of a CM5 sensor chip (BIAcore) using amine coupling. Monoclonal antibodies (MAbs) to Luteinizing Hormone (LH) were then captured on this surface in the correct orientation for binding. LH (500 IU/l) was injected over the surface and the subsequent binding and dissociation events were monitored. The resulting optical response curves allowed fast analysis of the binding interactions of eight selected MAbs. It was possible to develop a two-site immunometric assay for LH using a pair of these MAbs. The effect of biotinylating the MAbs, using various biotin:antibody coupling ratios, on their subsequent binding to both LH and avidin conjugated alkaline phosphatase was also investigated. This approach has allowed rapid evaluation of the effect of changes in both reagent and reaction conditions on immunoassay performance and appears to be a valuable adjunct to immunosensor and immunoassay development.

Alkaline Phosphatase↗

Saltatory propagation of Ca2+ waves by Ca2+ sparks.

Punctate releases of Ca2+, called Ca2+ sparks, originate at the regular array of t-tubules in cardiac myocytes and skeletal muscle. During Ca2+ overload sparks serve as sites for the initiation and propagation of Ca2+ waves in myocytes. Computer simulations of spark-mediated waves are performed with model release sites that reproduce the adaptive Ca2+ release observed for the ryanodine receptor. The speed of these waves is proportional to the diffusion constant of Ca2+, D, rather than D, as is true for reaction-diffusion equations in a continuous excitable medium. A simplified "fire-diffuse-fire" model that mimics the properties of Ca2+-induced Ca2+ release (CICR) from isolated sites is used to explain this saltatory mode of wave propagation. Saltatory and continuous wave propagation can be differentiated by the temperature and Ca2+ buffer dependence of wave speed.

Animals↗

Central or national veterinary diagnostic laboratories.

Information on laboratory organisational structure and roles was gathered from twenty-four national veterinary diagnostic laboratories around the world. This information was used to develop an overview of the organisation and roles of the national veterinary diagnostic laboratory. In addition, the national diagnostic laboratory for the United States of America (the National Veterinary Services Laboratories) was used as an example to provide more information on the activities of such a laboratory. The survey revealed great variation in organisation and structure among the twenty-four laboratories. A few have only one facility, others function at multiple locations, and all have different supervisory reporting systems. However, these laboratories all form a significant part of the national veterinary infrastructure. All of the laboratories contacted in the survey report to (or are at least partially under the direction of) the Chief Veterinary Officer or another senior animal health official, and most report to the Ministry of Agriculture. The national veterinary diagnostic laboratories have similar roles, and are all responsible for foreign animal disease diagnosis and for providing support to national disease eradication or control programmes. Most also play an active role in import and export testing, either performing the tests themselves or developing a quality assurance programme for other laboratories that perform the testing. In addition, the national veterinary diagnostic laboratories usually undertake research and provide training, consultation, disease surveillance information and, in some cases, vaccine evaluation.

Animal Diseases↗

Comparison of Newcastle disease viruses isolated from cormorants in Canada and the USA in 1975, 1990 and 1992.

Seventeen Newcastle disease virus (NDV) isolates obtained from cormorants, turkeys, a pelican, and a gull in Canada and the USA collected in 1975, 1990 and 1992 were analyzed for relatedness by monoclonal antibody profiling. In addition, nucleotide sequence analysis was performed in two areas of the fusion (F) gene for 5 of the isolates. No difference in the antigenicity of these 17 viruses, as determined by monoclonal antibody binding patterns, was seen. The amino acid sequences obtained via nucleotide sequencing at the cleavage site of the F protein showed that all the isolates tested had two pairs of basic amino acids immediately upstream of the cleavage site, and a phenylalanine residue at the N-terminus of the F1 protein, which is consistent with velogenic NDV. The deduced amino acid sequence obtained at the cleavage site of the F protein from 6 of the isolates was virtually identical regardless of the species, year of isolation, or location. However, the 1975 cormorant isolate showed marked differences from the 1990-1992 isolates in the nucleotide and deduced amino acid sequence of the F gene signal region. These data indicate that the 1990 and 1992 outbreaks were caused by the same epizootic virus and further suggest that the population of NDV in these wild birds may be very stable. The belief that the velogenic NDV circulating in cormorants in 1992 was transmitted into the free-ranging turkey flocks located near the cormorants in North Dakota is supported by the present study in which no distinction could be made between the viruses isolated from turkeys or wild birds.

Amino Acid Sequence↗

Comparison of polymerase chain reaction and virus isolation for detection of epizootic hemorrhagic disease virus in clinical samples from naturally infected deer.

We compared our recently reported reverse transcriptase polymerase chain reaction (PCR)-based assay for detection of epizootic hemorrhagic disease virus (EHDV) in clinical samples with different virus isolation (VI) procedures. Thirty-six blood samples and 1 spleen sample from deer were assessed by the EHDV PCR assay and VI in baby hamster kidney (BHK)-21 cells and embryonated chicken eggs (ECE). The EHDV PCR assay detected EHDV RNA from 6 blood samples obtained from deer during 1988-1989 outbreaks of epizootic hemorrhagic disease and from the spleen and blood samples of a deer with clinical hemorrhagic disease in 1992. The 6 blood samples from the 1988-1989 outbreaks and the spleen sample from the 1992 case were VI positive on BHK-21 cell culture. The blood from the same deer with the PCR- and VI-positive spleen was VI negative in BHK-21 cells and ECE. All EHDV isolates were identified as EHDV serotype 2 by a plaque inhibition test. The results of this study indicate that the sensitivity of the previously described EHDV PCR assay is comparable to or greater than that of the VI method in BHK-21 cell culture or ECE. The EHDV PCR assays could provide a superior diagnostic alternative to the current cumbersome and time-consuming VI procedures.

Animals↗

Probable epizootic chlamydiosis in wild California (Larus californicus) and ring-billed (Larus delawarensis) gulls in North Dakota.

During the summer of 1986, more than 400 California gulls (Larus californicus) and ring-billed gulls (Larvus delawarensis), primarily fledglings, died on an island in Lake Sakakawea near New Town, North Dakota (USA). Mortality was attributed largely to chlamydiosis. Necropsy findings in nine carcasses included splenomegaly (n = 9), hepatomegaly (n = 4), and pericarditis (n = 1). Livers from three California gulls and two ring-billed gulls, and spleens from the same five birds plus a third ring-billed gull were positive for Chlamydia psittaci by the direct immunofluorescence test. Chlamydia psittaci was isolated from separate pools of liver and spleen from one California gull and one ring-billed gull. This is believed to be the first record of epizootic chlamydiosis in gulls and the second report of epizootic chlamydial mortality in wild birds in North America.

Animals↗