Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Parasite Control”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,675 records · Page 93Linked to original sources
PubMed1994

Glucose metabolism in an insect Manduca sexta and effects of parasitism.

The metabolism of [1-13C]glucose was examined during the last larval stadium of an insect Manduca sexta (Lepidoptera: Sphingidae) parasitized by Cotesia congregata (Hymenoptera: Braconidae). Following injection, the isotopically substituted glucose was metabolized at a significantly lower rate by parasitized larvae than by normal, control insects. 13C enrichment was principally observed in [1-13C]trehalose in both groups. Randomization of the label at the triose phosphate step was evidenced by incorporation of 13C into C6 of trehalose. Parasitized and control larvae both synthesized [1,6-13C]glycogen but the relative amount of label observed in parasitized larvae was greater. The ratio of C6/C1 enrichment in trehalose and glycogen was significantly less in parasitized larvae. The rate of labelled trehalose and glycogen synthesis was relatively high when compared with the estimated rate of glycolytic glucose oxidation, and the difference in C6/C1 enrichment ratio between normal and parasitized insects was, therefore, not reflective of a difference in the rate of substrate cycling, but rather, was due to the increased synthesis of [1-13C]glycogen in parasitized larvae when compared with controls. Inhibition of glycolysis by administration of iodoacetate to normal larvae resulted in an increase in the incorporation of 13C into glycogen relative to glucose metabolized, suggesting that inhibition of glycolysis may be responsible for the higher level of glycogen synthesis observed in parasitized insects. In control larvae, significant 13C enrichment from [1-13C]glucose was observed in fat, but no evidence of lipogenesis was observed in parasitized insects. Iodoacetate had no observable effects on the relative amount of 13C incorporated into fat. Malonic acid and cyanide resulted in accumulation of 13C from [1-13C]glucose in several TCA cycle intermediates of normal larvae, but had little effect on the relative enrichments of trehalose, glycogen and fat.

Animals↗
PubMed1985

The population dynamics of competition between parasites.

A number of published studies of competition between parasite species are examined and compared. It is suggested that two general levels of interaction are discernible: these correspond to the two levels of competition recognized by workers studying free-living animals and plants: 'exploitation' and 'interference' competition. The former may be defined as the joint utilization of a host species by two or more parasite species, while the latter occurs when antagonistic mechanisms are utilized by one species either to reduce the survival or fecundity of a second species or to displace it from a preferred site of attachment. Data illustrating both levels of interaction are collated from a survey of the published literature and these suggest that interference competition invariably operates asymmetrically. The data are also used to estimate a number of population parameters which are important in determining the impact of competition at the population level. Theoretical models of host-parasite associations for both classes of competition are used to examine the expected patterns of population dynamics that will be exhibited by simple two-species communities of parasites that utilize the same host population. The analysis suggests that the most important factor allowing competing species of parasites to coexist is the statistical distribution of the parasites within the host population. A joint stable equilibrium should be possible if both species are aggregated in their distribution. The size of the parasite burdens at equilibrium is then determined by other life-history parameters such as pathogenicity, rates of resource utilization and antagonistic ability. Comparison of these theoretical expectations with a variety of sets of empirical data forms the basis for a discussion about the importance of competition in natural parasite populations. The models are used to assess quantitatively the potential for using competing parasite species as biological control agents for pathogens of economic or medical importance. The most important criterion for identifying a successful control agent is an ability to infect a high proportion of the host population. If such a parasite species also exhibits an intermediate level of pathology or an efficient ability to utilize shared common resources, antagonistic interactions between the parasite species contribute only secondarily to the success of the control. Competition in parasites is compared with competition in free-living animals and plants. The comparison suggests further experimental tests which may help to assess the importance of competition in determining the structure of more complex parasite-host communities.

Animals↗
PubMed2002

From "parasitic" association reactions toward the stoichiometry controlled gas phase synthesis of nanoparticles: a theoretically driven challenge for experimentalists.

In the present record a model for the gas-phase reactions during the chemical vapor deposition (CVD) processes of group 13-15 materials is presented, based on the results of extensive quantum-chemical modeling. Thermodynamic criteria have been introduced to evaluate the importance of a range of association reactions. For the organometallic and hydride derivatives, association processes are found to be favorable both thermodynamically and kinetically. Formation of high mass association products takes place under CVD conditions, including laser-assisted CVD. Structural and thermodynamic properties of the most important ring and cluster intermediates have been predicted. The stoichiometry-controlled synthesis of the 13-15 ternary alloys and nanoparticles using cluster compounds as single-source precursors is predicted to be viable. The association pathway described may be generalized to the CVD reactions of many binary materials (12-16, 13-16, 13-15, 14-15, 14-16).

Journal Article↗
PubMed1993

Experimental transmission of murine malaria by the oral route.

A total of 116 young male CD1 mice were orally inoculated with mouse blood; half of the animals received 0.2 ml of uninfected blood and the others were given 0.2 ml of Plasmodium berghei yoelii-infected blood in six experiments performed at different times. Almost 30% of the experimental mice acquired malaria as demonstrated by the observation of parasites in their blood. In no case were parasites found in the blood of control mice. Rodent malaria parasites may be transmitted to CD1 mice by the ingestion of mouse blood parasitized by P. b. yoelii. As far as we know, this study represents the first demonstration of oral transmission of murine malaria. Oral transmission studies in this mouse-Plasmodium model may produce very important information on the biology of the malaria parasites.

Administration, Oral↗
PubMed1984

Trypanosoma cruzi induces changes in the nucleic acids content of host Hela cells "in vitro".

The nucleic acid content of parasitized, non-parasitized Hela, cells, infected with metacyclic forms of Trypanosoma cruzi, was measured during 7 days of parasitization by means of histochemical techniques. Hela cells were first exposed to the parasite for 12 hrs. and then parasites were removed from the culture medium. Measurements of nuclear RNA + DNA content indicate that the three types of cells behave during 7 days of subsequent culture as three different populations. Similar results were obtained when only nuclear DNA was determined. DNA of parasitized cells increased dramatically compared to control and non-parasitized cells. This increase however was not observed in cells derived from non-parasitized cells, which were infected with trypomastigotes from the first parasitization cycle.

Animals↗
PubMed1996

Responses in milk production to control of gastrointestinal nematode and paramphistome parasites in dairy cattle.

OBJECTIVE: To determine the effect of treating naturally acquired gastrointestinal nematode and paramphistome infections on milk production in dairy cattle. DESIGN: A field trial. ANIMALS: One thousand two hundred and thirty nine dairy cows. PROCEDURE: Cows were either not treated or treated with 4.5 mg/kg oxfendazole, 16.6 mg/kg oxyclozanide or 4.5 mg/kg oxfendazole and 16.6 mg/kg oxyclozanide in March, May and August. RESULTS: A significant increase in milk production, averaging 0.4 L (SE 0.2) per day, was seen when dairy cows infected with gastrointestinal nematodes and paramphistomes were treated with oxfendazole or oxfendazole and oxyclozanide in March, May and August. Cows treated with oxyclozanide alone at these times produced no more milk than untreated cows. Faecal egg counts confirmed that oxyclozanide treatment reduced paramphistome populations and oxfendazole treatment reduced nematode populations in cows over the 7-month monitoring period. CONCLUSION: When dairy cows infested with gastrointestinal nematodes and paramphistomes were treated with oxfendazole alone or oxfendazole and oxyclozanide in March, May and August milk production increased.

Animals↗
PubMed2001

Infiltration of a Hawaiian community by introduced biological control agents.

To examine the community-wide effects of introduced biocontrol agents on Kauai Island, Hawaii, we constructed quantitative food webs showing interactions among plants, moths, and moth parasitoids in a native forest. Eighty-three percent of parasitoids reared from native moths were biological control agents, 14% were accidental immigrants, and 3% were native species. Although parasitism by biological control agents reached 28% in some species of moth, all biocontrol agents reared had been released before 1945. This study highlights the importance of considering the potential damage caused by an introduced control agent, in addition to that caused by the target alien species.

Animals↗
PubMed1982

Failure of bacterial lipopolysaccharide to elicit a cytostatic effect on Plasmodium vinckei petteri in C3H/HeJ mice.

Malarial parasites, Plasmodium vinckei petteri, taken from lipopolysaccharide (LPS) high-responder (C3H/HeJGiFWeHi) mice which had been injected 7 to 8 h previously with either Escherichia coli LPS B or LPS W incorporated the purine nucleotide precursor hypoxanthine more slowly in an in vitro assay than parasites taken from saline-injected controls. In contrast, malarial parasites taken from LPS low-responder C3H/HeJ mice after injection of either LPS B or LPS W did not show reduced levels of hypoxanthine incorporation. These differing results with LPS high- and low-responder mouse strains demonstrated that the cytostatic effect on the parasites seen in the high-responder strain was not due to the direct action of LPS and implied that the cytostasis was mediated via host lymphoreticular cells. Furthermore, the failure of LPS B, a lipid A-associated protein-containing LPS preparation, to elicit a cytostatic effect on P. vinckei petteri in C3H/HeJ mice suggested that the LPS-induced effector mechanisms acting against malarial parasites may be similar to those reported against bacteria and tumors.

Animals↗
PubMed1992

Identification and characterization of a parasite antigen in the circulating immune complexes of Onchocerca volvulus infected patients.

A PEG-ELISA was used to demonstrate parasite specific immune complexes in a significant proportion (25/26) of Onchocerca volvulus infection sera from Sierra Leone. The parasite antigen was detected using a peroxidase-conjugated rabbit serum raised to the bovine parasite O. gibsoni. Controls including European control serum, endemic control serum and Rh+ sera gave consistently low readings. Characterization of the parasite component in the immune complexes by Western blotting demonstrated a heat stable antigen of M(r) 46,000. This antigen was not present in the circulating immune complexes (CIC) prepared from patients with Wuchereria bancrofti infection, but a cross-reactive molecule of the same size was weakly recognized in the CIC of Loa loa and Mansonella perstans infected patients. No association between the level of parasite specific CIC and clinical disease was observed in the O. volvulus patients.

Animals↗
PubMed1992

[Advances in molecular parasitology].

Recent studies on molecular biology of parasites revealed novel mechanisms for the control of expression of parasitic genes. In trypanosomatid protozoa, unusual characteristics of gene regulation, including polycistronic transcription, trans-RNA splicing and RNA editing have been discovered. This review describes the recent progress of RNA editing in trypanosomes, and trans-splicing in both trypanosomes and nematodes. Studies of the editing of mRNAs in trypanosomatid mitochondria indicate the involvement of small guide RNA molecules, which are encoded in the minicircles and/or maxicircles of kinetoplast DNA. A proposed transesterification model for RNA editing suggests an analogous reaction between RNA editing and RNA splicing. In addition, the development of stable transfection system and success of homologous gene targeting in Trypanosoma and Leishmania are reported.

Animals↗