Search PubMed⌕ Search

Biomedical subjects

P H Corran

Publications and source records attributed to P H Corran.

At least 19 recordsLinked to original sources
PubMed2005

Estimating medium- and long-term trends in malaria transmission by using serological markers of malaria exposure.

The implementation and evaluation of malaria control programs would be greatly facilitated by new tools for the rapid assessment of malaria transmission intensity. Because acquisition and maintenance of antimalarial antibodies depend on exposure to malaria infection, such antibodies might be used as proxy measures of transmission intensity. We have compared the prevalence of IgG antibodies with three Plasmodium falciparum asexual stage antigens in individuals of all ages living at varying altitudes encompassing a range of transmission intensities from hyper- to hypoendemic in northeastern Tanzania, with alternative measures of transmission intensity. The prevalence of antibodies to merozoite surface protein-1(19) was significantly more closely correlated with altitude than either point-prevalence malaria parasitemia or single measures of hemoglobin concentration. Analysis of age-specific seroprevalence rates enabled differentiation of recent (seasonal) changes in transmission intensity from longer-term transmission trends and, using a mathematical model of the annual rate of seroconversion, estimation of the longevity of the antibody response. Thus, serological tools allow us to detect variations in malaria transmission over time. Such tools will be invaluable for monitoring trends in malaria endemicity and the effectiveness of malaria control programs.

Adult↗
PubMed2003

Ammonia cleaves polypeptides at asparagine proline bonds.

Polypeptides that contain the sequence Asn-Pro undergo complete cleavage at this amide bond with ammonia. One cleavage product possesses Pro as the new amino terminus and the other Asn or isoAsn as the new C-terminus, the formation of the latter probably arising by way of a cyclic succinimide intermediate. Other Asn-X bonds where X = Tyr, Gln, Ile, Glu, Ala, Gly, Asn or Phe did not exhibit any peptide bond cleavage, whereas when X = Leu, Thr and Ser partial cleavage was observed. Asn residues not involved in chain-cleavage underwent deamidation to Asp as shown by MALDI-ToF mass spectrometry (MS) analysis. The partial conversion of in-chain Asp residues to isoAsp under the reaction conditions was inferred from RP-HPLC and MS analysis of reaction mixtures.

Amino Acid Sequence↗
PubMed2002

Application of an in vitro endopeptidase assay for detection of residual toxin activity in tetanus toxoids.

Tetanus vaccine is composed of chemically denatured tetanus toxin (TeNT), thus safety testing requires confirmation of freedom from residual and reversible toxicity. Currently, TeNT activity is estimated using in vivo assay models. Information that TeNT acts by selectively inactivating protein leading to the blocking of release of neurotransmitters has provided the opportunity to develop in vitro biochemical assay for toxin activity. In this study we describe development and use of an in vitro endopeptidase assay for detection of TeNT activity in toxoid vaccine formulations.

Animal Testing Alternatives↗
PubMed2001

Differences between neonates and adults in tissue-type-plasminogen activator (t-PA)-catalyzed plasminogen activation with various effectors and in carbohydrate sequences of fibrinogen chains.

Our study investigates the effect of fetal and adult soluble fibrin (SF), fetal and adult fibrinogen Aalpha- and gamma-chains, as well as adult CNBr-fibrinogen fragments on tissue-type plasminogen activator (t-PA)-catalyzed plasminogen activation of both fetal and adult Glu-plasminogen types 1 and 2. In addition, we determined carbohydrate sequences of fetal and adult Bbeta- and gamma-chains by mass spectrometric analysis. In the absence of an effector, no substantial differences in the rate of plasmin formation could be seen between the fetal and adult plasminogen types. In the presence of an effector, both fetal Glu-plasminogen types revealed lower values for k(cat app) than the respective adult types. No differences could be seen in the values for K(m app). The resulting differences in catalytic efficiencies between the fetal and adult plasminogen types were much less than previously reported. No differences could be seen between fetal and adult effectors in stimulating t-PA-catalyzed plasminogen activation. Detailed analyses of the activation kinetics revealed a longer initial phase of slow plasmin formation of both fetal Glu-plasminogen types compared to their respective adult types, indicating a slower plasmin-induced modification of CNBr-fibrinogen fragments or SF by fetal plasmin. Mass spectrometric analysis of the N-glycans present on adult and fetal Bbeta- and gamma-fibrinogen chains showed the presence of a major monosialylated biantennary structure with lesser amounts of the disialylated form. In contrast to previous data, we conclude that catalytic efficiency of t-PA-catalyzed plasminogen activation in neonates is only slightly lower than in adults.

Adult↗
PubMed1998

Recombinant human albumin as a stabilizer for biological materials and for the preparation of international reference reagents.

Recombinant human albumin expressed in Saccharomyces cerevisiae was compared with native human serum albumin in its physicochemical properties and in its use as a stabilizer in lyophilized preparations of thyroid-stimulating hormone (TSH), interleukin 15 (IL-15) and granulocyte colony-stimulating factor (G-CSF). Advantages of recombinant albumin include its lack of potential human contaminants and infectious agents. When used at concentrations of 0.1-0.2% (w/v), recombinant albumin was equivalent to native serum albumin in its capacity to protect immunological, biological and biochemical properties of TSH, IL-15 and G-CSF. Physicochemical characteristics of the two forms of albumin including their binding to fatty acids were also similar. The recombinant form of albumin used in this study should be considered as a suitable stabilizer in the preparation of lyophilized products and reference reagents.

Endotoxins↗
PubMed1995

Characterisation of the chains of human fibrinogen isolated by perfusion chromatography using fibrin specific monoclonal antibodies.

In order to study the epitopes on fibrin to which monoclonal antibodies are directed, we required pure individual polypeptide chains of human fibrinogen in milligram quantities. High purity chains of human fibrinogen were rapidly obtained, in under 3 minutes, by the novel procedure of reversed-phase perfusion chromatography and these chains were subjected to immunological characterisation using monoclonal antibodies specific to the individual chains. Cross-reactivity against these antibodies in both immunoblotting and enzyme linked immunospecific assay (ELISA) procedures showed that these isolated fibrinogen chains were of high purity and retained high immunoreactivity. These chains were employed to initiate studies to define the epitopes in fibrin to which four fibrin specific monoclonal antibodies, B10, A11, 5F3 and 1H10 are targeted. Two of these antibodies, B10 and A11, were shown to be directed to a linear sequence on the A alpha chain, although the binding profiles for the two antibodies suggested that different epitopes may be involved for each of these two antibodies. MAbs, 1H10 and 5F3, however, did not bind to any of the three fibrinogen chains, suggesting that conformational epitopes in fibrin are likely to be involved in the binding of these two antibodies to fibrin.

Antibodies, Monoclonal↗
PubMed1994

Ultra-rapid preparation of milligram quantities of the purified polypeptide chains of human fibrinogen.

In order to study the epitopes in fibrin towards which monoclonal antibodies are directed we needed the pure individual polypeptide chains of human fibrinogen in reasonable quantity. We report here a simplified, rapid method of separation of high-purity human fibrinogen chains. Following reduction and S-carboxymethylation of human fibrinogen, the sample was injected directly onto a column of the polymeric reversed-phase perfusion packing POROS 20-R2, and the chains were completely resolved in less than 3 min at a flow-rate of 10 ml/min. The capacity was equivalent to that of a similar sized conventional silica-based column. However the throughput was approximately five to ten times as high. The column was durable and robust in day-to-day use.

Chromatography↗
PubMed1994

Lysine vasopressin undergoes rapid glycation in the presence of reducing sugars.

Lysine vasopressin (LVP) readily reacts with reducing saccharides both in lyophilized preparations and in aqueous solution. Incubation of LVP with, for example, lactose over a pH range of 3.0-8.5 in phosphate buffer or simply in water, gives rise to a number of reaction products, some of which form rapidly (in a matter of hours) even in the frozen state. Reaction mixtures were analysed by reversed-phase HPLC and the structures of the products were deduced from the amino-acid composition of isolated components, by comparison with product profiles obtained with analogues under similar conditions and by FAB mass-spectral analysis of derivatives isolated after reduction with cyanoborohydride. The primary products arise from the formation of Schiff's bases at one or both of the two amino functions. The alpha-amino group of the N-terminal cystine is considerably more reactive than is the epsilon-amino group of lysine and it is the N-terminal adduct which rapidly forms even at -20 degrees C. It is concluded that caution must be shown in using reducing sugars in formulations containing peptides and proteins, particularly the vasopressins and oxytocin.

Amino Acid Sequence↗
PubMed1993

Identification of gonadorelin (LHRH) derivatives: comparison of reversed-phase high-performance liquid chromatography and micellar electrokinetic chromatography.

A number of reversed-phase (RP) HPLC systems for the separation of gonadorelin (gonadoliberin, LHRH) and five therapeutically important analogues have been systematically examined. The selectivity of RP-HPLC has been compared with several micellar electrokinetic chromatographic (MEKC) systems and free solution capillary electrophoresis. RP-HPLC exhibits greater selectivity towards structural differences, but complete separation of the peptides in one isocratic analytical run is tedious due to the large differences in retention. Gradient elution gives satisfactory separation in an acceptable time span. Of the micellar systems examined (sodium dodecyl sulphate, cetrimide, 3-[(cholamidopropyl)dimethylamino]-1-propanesulphonate and Triton X-100) only MEKC with cetrimide micelles gave a complete separation showing selectivity similar, but not identical, to RP-HPLC, and providing a complete separation of all six compounds as rapidly as gradient RP-HPLC.

Amino Acid Sequence↗
PubMed1993

Comparison of selectivities of reversed-phase high-performance liquid chromatography, capillary zone electrophoresis and micellar capillary electrophoresis in the separation of neurohypophyseal peptides and analogues.

A number of RP-HPLC systems, including those prescribed in several official monographs, have been evaluated for separating oxytocin, the vasopressins, some clinically important analogues and two additional neurohypophyseal nonapeptides. The separation has been compared with capillary zone electrophoresis and micellar electrophoresis in four micellar systems: cationic, anionic, zwitterionic and neutral. Complete separation was achieved by both RP-HPLC and micellar CE but the importance of charge as a major parameter of separation in CE confers a distinct and useful selectivity to micellar CE based separations.

Amino Acid Sequence↗
PubMed1990

Determination of L-thyroxine in reference serum preparations as the o-phthalaldehyde-N-acetylcysteine derivative by reversed-phase liquid chromatography with electrochemical detection.

A simple procedure for the assay of L-thyroxine in serum preparations with D-thyroxine as internal standard is described. The L-thyroxine is extracted with acetonitrile, fractionated on a reversed-phase silica cartridge and analysed by reversed-phase high-performance liquid chromatography of the o-phthalaldehyde-N-acetyl-L-cysteine derivative. This derivative is not fluorescent, but may be detected with suitable sensitivity and selectivity with an electrochemical detector.

Acetylcysteine↗
PubMed1990

International Standards for salmon calcitonin, eel calcitonin, and the Asu1-7 analogue of eel calcitonin: calibration by international collaborative study.

Regulatory specifications in most countries require that the potency of salmon calcitonin (sCT) clinical products be expressed in International Units (IU) defined by the World Health Organization (WHO) International Standard. The first ampouled standard was prepared in 1972 and has been distributed world-wide since then. A batch of ampoules to serve as the replacement standard is now required. Other piscine calcitonins, eel calcitonin (eCT) and an amino-suberic acid analogue of eCT (Asu1-7 eCT) are now clinical products in some countries and international standards are required for these peptides which are similar to, but not identical with, sCT. This paper describes the preparation of three new ampouled standards and their biological calibration by international collaborative study comprising 17 participants from 10 countries. Following the recommendations in the final report of the collaborative study, the 2nd International Standard (IS) for sCT, the 1st IS for eCT and the 1st IS for Asu1-7 eCT were recently established by WHO, each with an assigned potency in IU, and are now available for issue.

Animals↗
PubMed1982

The International Reference Preparation of Gonadorelin for Bioassay: a comparison with different preparations of synthetic luteinizing hormone releasing hormone using physicochemical methods of analysis, different bioassays and immunoassay.

The preparation and nature of the International Reference Preparation of Gonadorelin for Bioassay (IRP; coded 77/596) are described. The IRP was studied by four laboratories in four countries and compared, using physicochemical methods of analysis, various bioassay procedures and immunoassay, with preparations of synthetic luteinizing hormone releasing hormone (LH-RH) produced by different manufacturers. Analyses by thin-layer chromatography and by reverse-phase high-performance liquid chromatography (HPLC) indicated some heterogeneity of the peptide present in most of these preparations of synthetic LH-RH, including that of the IRP; the latter preparation appeared to be 88.3% (w/w) pure, judged by HPLC. The data from the collaborative study suggested that each ampoule of the IRP contains approximately 31 nmol LH-RH. The IRP appeared to be suitable to serve as an international reference preparation for bioassay since its behaviour was similar in different bioassays, so far as this could be examined, to that of the other preparations of LH-RH with which it was compared. Furthermore, the biological activities of different preparations of LH-RH, assessed in terms of the IRP, appeared to correlate with their degrees of purify assessed by physicochemical methods, suggesting that the peptides other than LH-RH present in the IRP did not contribute significantly to the biological activity of the preparation in these assay procedures. The limited data available suggested that the IRP might also be suitable as a reference preparation for immunoassay. The ampouled preparation, coded 77/596, was therefore established by the World Health Organization as the International Reference Preparation of Gonadorelin for Bioassay and assigned a unitage of 31 i.u./ampoule on the basis that the i.u. is represented by 1 nmole of LH-RH.

Chromatography, High Pressure Liquid↗
PubMed1981

Purification and assay of bovine parathyroid hormone by reversed-phase high performance liquid chromatography.

Reversed-phase high-performance liquid chromatography (HPLC) has been used to purify a crude extract of bovine parathyroid glands, in a single run on an analytical column, to give a high yield of homogeneous material with full bioactivity in in vivo bioassay. Bovine parathyroid hormone (bPTH) prepared and purified by conventional procedures has been rapidly and quantitatively separated from its oxidation and other degradation products, from hormone fragments and from non-hormonal contaminants. Recovery of bPTH, monitored by region-specific immunoassays, in vivo bioassay and re-chromatography on HPLC was greater than 93%. The detection limit of the HPLC system, using endogenous tryptophan fluorescence, was 20 ng bPTH.

Animals↗