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Biomedical subjects

W Peters

Publications and source records attributed to W Peters.

At least 217 records · Page 12Linked to original sources
PubMed1985

The metabolism of leukotrienes in blood plasma studied by high-performance liquid chromatography.

The metabolism of leukotrienes (B4, C4, D4, and E4) within human plasma was studied and a simple sample preparation is presented. It was demonstrated that leukotriene E4 and leukotriene B4 were stable during incubation at 37 degrees C using the in vitro system. In contrast, leukotriene C4 was metabolized by gamma-glutamyl transpeptidase activities into leukotriene D4 which was further metabolized by dipeptidase activities of plasma into leukotriene E4. The transition state inhibitor of gamma-glutamyl transpeptidase L-serine-borate decreased the metabolism of leukotriene C4 in plasma. Dilution of plasma demonstrated that the dipeptidase was more active compared to the gamma-glutamyl transpeptidase. The metabolizing activities of plasma were functionally characterized by fractionating the plasma proteins.

Blood Proteins↗
PubMed1985

Leishmania infecting man and wild animals in Saudi Arabia. 1. General survey.

Using up to 13 enzymes, biochemical characterization of 75 isolates of Leishmania made from man, wild animals and sandflies from a wide variety of localities in the Kingdom of Saudi Arabia has revealed the presence of L. major (two similar zymodemes), L. tropica (two zymodemes) and a parasite of the L. donovani-L. infantum complex. Zymodeme LON-4 of L. major has been found in 52 of 53 isolates so far characterized from man, from one specimen of Phlebotomus papatasi, from 15 Psammomys obesus, from one Meriones libycus and from one dog. One isolate from man has been identified as a new variant of L. major. This variant, zymodeme LON-65, varies from zymodeme LON-4 in a single enzyme. While this is the only example of zymodeme LON-65 identified so far, zymodeme LON-4 has also been obtained from Kuwait and Iraq. These are the first reports of L. major in Meriones libycus from Saudi Arabia and the first proven isolate from the dog in any country. L. tropica was identified from only two foci, whereas L. major appears to be widely distributed in the Kingdom. Two infants with kala-azar were found to be infected with a parasite apparently identical to zymodeme LON-42 of L. donovani (sensu lato) which also occurs in the highlands of Ethiopia.

Animals↗
PubMed1985

Zoonotic cutaneous leishmaniasis in Saudi Arabia: the incrimination of Phlebotomus papatasi as the vector in the Al-Hassa oasis.

Surveys of the phlebotomine fauna in a focus of zoonotic cutaneous leishmaniasis (ZCL) in the Al-Hassa oasis, Eastern Province, Saudi Arabia, revealed only one species of Phlebotomus (P. papatasi) and three of Sergentomyia (S. antennata, S. clydei and S. fallax). 11 specimens of P. papatasi from six sites in the oasis were found with promastigotes in the midgut. An isolate from one of the sandflies was typed by the examination of isoenzymes and identified as Leishmania major, zymodeme LON-4 (= Montpellier zymodeme 26), the principal zymodeme of L. major isolated from patients with ZCL in the oasis. Three isolates from leishmanial lesions at sites of the bites of wild caught specimens of P. papatasi were also identified as the same zymodeme of L. major as the isolate from the sandfly. The findings show that P. papatasi is the vector of ZCL in the Al-Hassa oasis and probably in other ecologically similar foci in the Kingdom.

Animals↗
PubMed1985

Zoonotic cutaneous leishmaniasis in Saudi Arabia: lesions healing naturally in man followed by a second infection with the same zymodeme of Leishmania major.

A patient with a previous history of an infection with Leishmania b. braziliensis contracted zoonotic cutaneous leishmaniasis (ZCL) in the Al-Hassa oasis, Eastern Province, Saudi Arabia. Five lesions healed spontaneously over a period of 40 weeks without treatment. A year after acquiring ZCL he became infected again in the same focus. Isolates of parasites at both episodes were identified as L. major, zymodeme LON-4. Compared with the first infection of ZCL, parasites were fewer in the lesions on the second occasion, the lesions were smaller and healing was quicker (10 weeks). This work and a previous report of patients with active lesions and leishmanial scars suggest that second infections of L. major are not uncommon in the oasis where no autochthonous infections of other species of Leishmania have yet been recorded in man and only one species of Phlebotomus (P. papatasi) is known.

Adult↗
PubMed1985

The problem of drug resistance in malaria.

The resistance in human malaria is mainly of practical importance in relation to Plasmodium falciparum. Strains resistant not only to chloroquine but also to dihydrofolate reductase inhibitors, and even to potentiating combinations of these with sulphonamides or sulphones, are appearing in an ever increasing geographical area which now includes tropical Africa and India. Few new drugs are available or foreseen for the near future, mefloquine and artemisinine being the leading contenders. It is vital that all measures possible should be taken to protect such new compounds, their deployment in the form of judiciously selected combinations with other antimalarials being an essential procedure that should be followed. Drugs in new chemical classes and with different modes of action are still urgently needed. Reliance should not be placed on drugs alone to control malaria on a community basis.

Africa↗
PubMed1985

An improved technique for the cultivation of Plasmodium falciparum in vitro without daily medium change.

A simple method is described allowing growth of Plasmodium falciparum in suspension cultures with 1% outdated human erythrocytes without the need for medium change for three to four days. Depending on the initial parasitaemia, final parasitaemias of from 10% to 30% can be obtained. Growth is exponential and asynchronous with a mean multiplication rate of 7.7 +/- 1.0 (n = 5) -fold per 48-hour cycle. The method is suitable for cultivation of a wide range of laboratory strains of P. falciparum, as well as for primary isolations of clinical material.

Animals↗
PubMed1985

Corticosteroid stimulation of the growth of Plasmodium falciparum gametocytes in vitro.

Corticosteroids were found to enhance gametocyte production in vitro in two gametocyte-producing chloroquine-resistant strains of Plasmodium falciparum. No significant enhancement was observed in two chloroquine-sensitive strains. Gametocytes were not induced by corticosteroids in a fifth strain which had lost the ability to produce gametocytes.

Adrenal Cortex Hormones↗
PubMed1985

A practical heparin reduction algorithm: execution and operational characteristics.

A limited pilot study has been made of a newly devised heparin reduction algorithm (HRA). This formulation is a derivative of the alternative surveillance plan known as the activated partial thromboplastin time after heparin removal (aPTT/HR) scheme. Unlike the traditional plan, the HRA is the first approach to provide information about the individual and collective pharmacological effects of heparin and coumarins when the drugs are administered simultaneously. In this feasibility study the HRA was used without incident in six patients every 24 h to calculate the trend of the evolving anticoagulant effect of coumarin. The computations provided by a laboratory based data management group permitted the clinician to titrate precisely the withdrawal of heparin in response to the daily fluctuations in coumarin effect. In this way, the activated partial thromboplastin time could always be maintained within the desired therapeutic interval. Three divergent patient experiences are presented to demonstrate the operational characteristics and responsiveness of the new HRA plan.

Adult↗
PubMed1985

The chemotherapy of rodent malaria, XXXIX. Ultrastructural changes following treatment with artemisinine of Plasmodium berghei infection in mice, with observations of the localization of [3H]-dihydroartemisinine in P. falciparum in vitro.

Ultrastructural changes were followed in Plasmodium berghei after the treatment of the mouse host with a single 10 mg kg-1 dose of artemisinine (qinghaosu). After 30 minutes, changes in the limiting and other membranes of the parasite were seen, together with alterations in ribosomal organization and endoplasmic reticulum. No changes were noted in digestive vacuoles or pigment, but nuclear membrane blebbing developed after one hour and segregation of the nucleoplasm after three hours. Further degenerative changes with disorganization and death occurred from eight hours onwards. The morphological changes in ribosomes and endoplasmic reticulum correlate in time with the depression in protein synthesis observed in P. falciparum in vitro. Similarly, the onset of nucleoplasmic segregation correlates with the development of nucleic acid synthesis inhibition. Tritiated reduced drug was shown to be localized in parasite membranes, indicating that changes in membrane integrity might precede the early depression of protein synthesis. Membrane association of artemisinine may be related to its amphipathic characteristics and similarity in some respects to a sterol.

Animals↗
PubMed1985

[Cultivation of exo-erythrocytic schizonts of rodent Plasmodium in hepatocytes: a new experimental model for chemotherapy of malaria].

An in vitro experimental model using primary cultures of laboratory bred Thamnomys gazellae's hepatocytes and Plasmodium yoelii yoelii' sporozoites was set up for chemotherapeutic studies. The surface of the culture was reduced (0.5 cm) and allowed the rapid performance and analysis of schizonticide activity tests, with a reduced biological material (Rodents, Anopheles, sporozoites). Fifteen compounds were tested. When activity of molecules is known in vivo, both results in vivo and in vitro are parallel.

Animals↗