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At least 19 recordsLinked to original sources
PubMed1992

Antigenic differences between the life cycle stages of Cooperia oncophora.

The antigenic differences among the life cycle stages of Cooperia oncophora were studied by SDS-gel electrophoresis and Western blotting. Sodium dodecylsulphate polyacrylamide gel electrophoresis of the different life cycle stages of C oncophora revealed a complex protein pattern with a decreasing number of protein bands towards the adult stages. Several bands of the fourth stage larvae were in common with both the third stage and the adult nematode. Western blotting with sera from C oncophora monoinfected calves showed that the antigens of the fourth stage larvae were recognised predominantly and the presence of stage specific antigens in all stages. Strong cross reactivity was demonstrated when serum from Ostertagia ostertagi infected calves was used.

Animals↗
PubMed1992

Guide RNAs for transcripts with developmentally regulated RNA editing are present in both life cycle stages of Trypanosoma brucei.

RNA editing of several mitochondrial transcripts in Trypanosoma brucei is developmentally regulated. The cytochrome b and cytochrome oxidase II mRNAs are edited in procyclic-form parasites but are primarily unedited in bloodstream forms. The latter forms lack the mitochondrial respiratory system present in procyclic forms. Editing of the NADH dehydrogenase 7 (ND7) and ND8 transcripts is also developmentally regulated but occurs preferentially in bloodstream forms. Other transcripts, cytochrome oxidase III and ATPase 6, are edited in both life forms. We have identified many minicircle-encoded guide RNAs (gRNAs) for ATPase 6, ND7, and ND8. The characteristics of these gRNAs reveal how extensively edited RNA can be edited in the 3'-to-5' direction. Northern (RNA) blot and primer extension analyses indicate that gRNAs for transcripts whose editing is developmentally regulated are present in both procyclic and bloodstream form parasites. These results suggest that the developmental regulation of editing in these transcripts is not controlled by the presence or absence of gRNAs.

Aging↗
PubMed1992

Effect of quassin on the metabolism of catecholamines in different life cycle stages of Culex quinquefasciatus.

Quassin, a mosquito larvicide isolated from Quassia amara, inhibits tyrosinase activity in the larvae of Culex quinquefasciatus. Since tyrosinase is directly involved in sclerotisation of the cuticle, it is suggested that quassin, as a larvicide, inhibits development of the cuticle. In presence of quassin phenylalanine, tyrosine and L-dopa levels were increased in larvae. In the larval stages, mosquitoes have a high concentration of phenylalanine and tyrosine with the level of the latter being very high just before pupation and then declines sharply. Monoamine oxidase (MAO), an enzyme directly involved in the metabolism of catecholamines, remained unaffected by quassin, in fact the level of adrenaline also remained unchanged in larvae during quassin poisoning. MAO showed high variation in its activity between synthetic and natural substrates. Tyramine is not a substrate for MAO. Tyrosinase activity was high in developing stages and negligibly low in adults and showed specificity to L-dopa. Phenylalanine and tyramine are unaffected by tyrosinase. Blood feeding did not influence the activity of both these enzymes.

Animals↗
PubMed1976

Immunity to coccidiosis: stages of the life-cycle of Eimeria maxima which induce, and are affected by, the response of the host.

An attempt was made to determine the relative importance of the different life-cycle stages of Eimeria maxima in the induction of immunity and also those stages most affected by the immune response of the host. In one experiment the life-cycle was controlled by chemotherapy but in all other experiments partial life-cycles were induced by transfers of infected mucosa between hosts. The results indicated that the second generation schizont stage is probably that most concerned in the induction of protective immunity and that sexual stages are most susceptible to immune inhibition. After initial inhibition in the immune host the earlier asexual stages were able to resume development when transferred to a susceptible host. The longer the period of exposure to the immune environment, the less able was the parasite to recover.

Animals↗
PubMed1978

[Cytochemical study of various stages of life cycle of Toxoplasma gondii. 10. Phosphatases in the parasites during developmental stages in cat's intestines].

Several methods of acid and alkaline phosphatese and ATPase detection using both natural and artificial substrates were applied to the intestinal stages of Toxoplasma gondii with negative results to reveal enzymatic activity in all the stages except the microgametocyte. Possible explanation of this unexpected phenomenon is discussed taking into account host-parasite relationships with intestinal stages of Toxoplasma and with coccidia in general.

Acid Phosphatase↗
PubMed1978

[Cytochemical study of various stages of life cycle of Toxoplasma gondii. 11. oxidation-reduction enzymes in the parasites during developmental stages in cat's intestines].

Dehydrogenases of glycolysis, Krebs' cycle and pentose phosphate shunt were investigated in the intestinal stages of T. gondii. The "oval stages" appeared to display the activity of all the enzymes studied differing in this from merozoites and macrogametocytes. The macrogametocytes displayed very low, if any, activity of the enzymes studied, even the mature parasites. Immediately after fertilization, sharp shifts were observed in the oxidative metabolism of the zygote: from very low or negative it became moderate to strong. This may be suggestive of the changes in metabolic requirements of the zygote which is no longer an intracellular parasite. In this respect macrogametocytes and zygotes of Toxoplasma resemble the corresponding stages of chicken and rabbit intestinal coccidia of the genus Eimeria.

Animals↗
PubMed1992

Host stadium specificity in the gregarine assemblage parasitizing Tenebrio molitor.

Reciprocal cross-stadia experimental infections were used to demonstrate stadium specificity within the gregarine assemblage parasitizing Tenebrio molitor, the yellow mealworm. Gregarina cuneata, Gregarina polymorpha, and Gregarina steini are characteristic parasites of larval T. molitor. Gregarina niphandrodes is a characteristic parasite of adult T. molitor. Experimental infections were produced in all homologous host-parasite combinations. No infection was produced in heterologous or cross-stadia combinations. This study introduces the concept of separate, distinct parasite niches corresponding to separate life cycle stages and established by known, predictable life cycle events within a single host species.

Animals↗
PubMed1992

A developmentally regulated cysteine proteinase gene of Leishmania mexicana.

We have isolated a gene encoding a previously unreported class of trypanosomatid cysteine proteinase (CP) from the protozoan parasite Leishmania mexicana. The single-copy gene (lmcpa) [corrected]. has several unusual features that distinguish it from CP genes cloned from the related species Trypanosoma brucei and Trypanosoma cruzi. These include a shorter C-terminal extension of only 10 amino acids and a three-amino-acid insertion, GlyValMet, close to the predicted N-terminus of the mature protein. Northern blot analysis showed that the gene is expressed in all life-cycle stages but at higher levels in the amastigote stage in the mammal and in stationary phase promastigote cultures which contain the infective metacyclic form of the parasite. A precursor protein of 38 kDa was detected in amastigotes and stationary phase promastigotes with antisera specific to the LmCPa pro-region, but was barely detectable in early log-phase promastigotes. Anti-central domain antisera recognized the 38 kDa precursor and 24 and 27 kDa proteins. The major CPs of L. mexicana amastigotes, previously designated types A, B and C, were not detected with the antisera, suggesting that the gene codes for a previously uncharacterized CP in L. mexicana. The 24 kDa protein detected by the antiserum has no activity towards gelatin but apparently hydrolyses the peptide substrate BzPheValArgAMC. The relative levels of the 24 and 27 kDa proteins vary between the different life-cycle stages. The results indicate that expression of this CP is regulated at both the RNA and protein level.

Amino Acid Sequence↗
PubMed1975

Structure and ultrastructure of the pituitary gland in the sea lamprey, Petromyzon marinus at different stages in its life cycle.

The structure and fine structure of the pituitary gland in the sea lamprey, Petromyzon marinus L., are described at all major stages in the life cycle. Synthetically active adenohypophysial cells are evident in even the smallest ammocoetes examined (body length 2.5 cm). An attempt is made to correlate changes in the activity of pituitary cell types with biological events. In the neurohypophysis a single fibre type was discriminated in electron micrographs. This contained electron-dense cytoplasmic granules 800 to 1600 A in diameter.

Age Factors↗
PubMed1992

Age and depression.

In this study, the relationship between age and depression is analyzed, looking for effects of maturity, decline, life-cycle stage, survival, and historical trend. The data are from a 1990 sample of 2,031 U.S. adults and a 1985 sample of 809 Illinois adults. The results show that depression reaches its lowest level in the middle aged, at about age 45. The fall of depression in early adulthood and rise in late life mostly reflects life-cycle gains and losses in marriage, employment, and economic well-being. Depression reaches its highest level in adults 80 years old or older, because physical dysfunction and low personal control add to personal and status losses. Malaise from poor health does not create a spurious rise of measured depression in late adulthood. However, some of the differences among age groups in depression reflect higher education in younger generations, and some reflect different rates of survival across demographic groups that also vary in their levels of depression.

Activities of Daily Living↗
PubMed2026

Genome-Guided Discovery of Antimalarial 4-Amino-2,4-Pentadienoate-Containing Cyclolipodepsipeptides.

4-Amino-2,4-pentadienoate-containing cyclolipodepsipeptides (APD-CLDs) represent a structurally distinctive family of natural products known for their selective activity against hypoxic cancer cells. To explore the structural diversity of APD-CLDs, we have identified and prioritized cryptic APD-CLD biosynthetic gene clusters (BGCs) for compound discovery. Using a combination of genetic and chemical methods, we successfully activated three dormant BGCs, leading to the discovery of 12 new APD-CLDs. These newly discovered metabolites significantly expanded the diversity of the APD-CLD family, with chloromalamides and arabimalamides representing the first halogenated and glycosylated members, respectively. Unexpectedly, chloromalamides and arabimalamides exhibited potent antiplasmodial activity, with IC50 values in the 25-161 nM range against drug-sensitive and multidrug-resistant Plasmodium falciparum strains. Phenotypic studies revealed arabimalamide B halted parasite development during the asexual blood stage life cycle, resulting in enlarged digestive vacuoles, dispersed hemozoin, and ultimately reduced reinvasion efficiency. These phenotypes are reminiscent of the effect of chloroquine and other 4-aminoquinoline drugs, suggesting that arabimalamides may disrupt the parasite's heme detoxification mechanism. Biosynthetic studies identified key scaffold-forming and modifying enzymes, including a rare membrane glycosyltransferase in arabimalamide biosynthesis. Together, these findings unveil APD-CLDs as new antimalarial lead scaffolds and set the stage for structural diversification and optimization.

Antimalarials↗
PubMed1977

[Cytochemical study of the different stages in the life cycle of Toxoplasma gondii. IX. The polysaccharides and lipids in the parasites at developmental stages from the cat intestine].

Amylopectin was detected in all the stages examined. In the oval stages the minute granules of PAS-positive material were seen in the cytoplasm when examined on fresh-frozen sections. In merozoites, amylopectin was more conspicuous with maturation. The residual body of microgametocytes contain large amounts of amylopectin; no polysaccharide was visualized in microgamete bodies. Amylopectin was most abundant in macrogametocytes and zygotes. However, no peripheral position of PAS-positive "plastic granules" (wall-forming bodies), so characteristic of other coccidia and revealed by the electron microscopy for T. gondii macrogametocytes, was seen. Acid mucopolysaccharides in the macrogametocyte were detected in the central zone, leaving the periphery of the cell unstained. Very small, if any, amounts of lipids were detected in asexual stages of T. gondii. Unlike, large accumulation of lipid droplets were seen in growing macrogametocytes suggesting the involvement of lipids along with amylopectin in the metabolism of oocysts later discharged from the host body.

Amylopectin↗
PubMed1992

Isolation and characterization of a cysteine proteinase gene of Plasmodium falciparum.

We have previously identified a 28-kDa cysteine proteinase of Plasmodium falciparum trophozoites that appears to be an essential malarial hemoglobinase and a potential target for antimalarial chemotherapy. The trophozoite cysteine proteinase (TCP) shares a number of biochemical properties with the lysosomal cysteine proteinase cathepsin L. To isolate the gene encoding TCP, we synthesized degenerate oligonucleotides based on two amino acid sequences of cathepsin L that are well conserved among papain-family cysteine proteinases, and used the oligonucleotides to prime the polymerase chain reaction (PCR) with P. falciparum genomic DNA. A 549-bp DNA fragment was amplified by PCR. This fragment was used as a hybridization probe to screen a lambda gt11 library of P. falciparum genomic DNA and isolate a 1.8-kb genomic clone (C1.8) that encoded an intact malarial cysteine proteinase gene. The sequence of C1.8 predicted a 67-kDa protein containing a typical signal sequence, a large pro sequence, and a 26.8-kDa mature proteinase with 37% amino acid identity to cathepsin L. Antisera directed against a peptide encoded by C1.8 recognized a 28-kDa trophozoite protein on immunoblots. In a Northern analysis, C1.8 hybridized predominantly with RNA from rings, the life-cycle stage immediately preceding the trophozoite stage. Taken together, these results strongly suggest that the P. falciparum cysteine proteinase gene we have isolated and characterized encodes TCP.

Amino Acid Sequence↗
PubMed1992

Immunology of Giardia and Cryptosporidium infections.

Giardiasis and cryptosporidiosis occur in immunocompetent persons, and as opportunistic infections in immunocompromised individuals. The causative organisms of giardiasis (Giardia lamblia) and cryptosporidiosis (Cryptosporidium parvum) have markedly different life cycles, but currently available evidence suggests that intestinal antibody plays a major part in host protection against both parasites. In the case of G. lamblia, the evidence points to a role for intestinal antitrophozoite antibody in blocking adherence of trophozoites to intestinal epithelium, with consequent removal of trophozoites from the intestine by peristalsis. Similarly, recent work supports the view that C. parvum infection can be prevented or interrupted by antibody that binds to Cryptosporidium life cycle stages present in the intestinal lumen (sporozoites and merozoites). Molecular characterization of G. lamblia and C. parvum immunodominant antigens would facilitate future studies aimed at determining whether vaccination against giardiasis or cryptosporidiosis is feasible.

Animals↗
PubMed1975

Protein uptake and digestion in bloodstream and culture forms of Trypanosoma brucei.

The mechanisms of ferritin uptake and digestion differ in bloodstream and culture forms of Trypanosoma brucei. Ferritin enters bloodstream forms from the flagellar pocket by pinocytosis in large spiny-coated vesicles. These vesicles become continuous with straight tubular extensions of a complex, mostly tubular, collecting membrane membrane system where ferritin is concentrated. From the collecting membrane system the tracer enters large digestive vacuoles. Small spiny-coated vesicles, which never contain ferritin, are found in the Golgi region, fusing with the collecting membrane system, and around the flagellar pocket. Acid phosphatase activity is present in some small spiny-coated vesicles which may represent primary lysosomes. This enzymic activity is also found in the flagellar pocket, pinocytotic vesicles, the collecting membrane system, the Golgi (mature face), and digestive vacuoles of bloodstream forms. About 50 percent of the acid phosphatase activity of blood forms is latent. The remaining nonlatent activity is firmly cell-associated and probably represents activity in the flagellar pocket. The structures involved in ferritin uptake and digestion are larger and more active in the short stumpy than in the long slender bloodstream forms. The short stumpy forms also have more autophagic vacuoles. No pinocytotic large, spiny-coated vesicles or Golgi-derived, small spiny-coated vesicles are seen in culture forms. Ferritin leaves the flagellar pocket of these forms and enters small smooth cisternae located just beneath bulges in the pocket membrane. The tracer then passes through a cisternal collecting membrane network, where it is concentrated, and then into multivesicular bodies. In the culture forms, acid phosphatase activity is localized in the cisternal system, multivesicular bodies, the Golgi (mature face), and small vesicles in the Golgi and cisternal regions. The flagellar pocket has no acid phosphatase activity, and almost all the acitvity is latent in these forms. The culture forms do not release acid phosphatase into culture medium during 4 days growth. Uptake of ferritin by all forms is almost completely inhibited by low temperature. These differences among the long slender and short stumpy bloodstream forms and culture forms are undoubtedly adaptive and reflect different needs of the parasite in different life cycle stages.

Acid Phosphatase↗
PubMed1975

Epizootic and enzootic aspects of Minchinia nelsoni (Haplosporida) disease in Maryland oysters.

Minichinia nelsoni disease in oysters (Crassostrea virginica) from Marumsco Bar, Pocomoke Sound, Maryland (an estuarine tributary of Chesapeake Bay) was studied for 8 years (1961-68) to determine epizootiologic relationships concerning life cycle of the parasite, pathologic effects on the host, and effects of physical factors on population density and recruitment of the host and parasite. The study period covered pre-epizootic, epizootic, and post-epizootic disease conditions. Data on the native oyster population as well as annual introductions of previously unexposed, susceptible populations of juvenile oysters from 1965-68 were included. Salinity, water temperature, mortality, prevalence, incidence, life cycle stages, gross pathology, and histopathologic relationships were observed. Mortality was high (45-55% per year) during the first 3 years of the study; however, M. nelsoni prevalences were low (less than 25%) and did not clearly imply a cause and effect relationship. Drought conditions that began in the summer of 1963 and continued through 1967 caused higher salinities, and apparently initiated epizootic disease in the native oyster populations. The epizootic peaked in May 1965 with a diagnosed prevalence in native oysters of 70%. Enzootic levels of annual mortality (40% in 1966, 30% in 1967, and 2% in 1968) and fall prevalence (16%, 24%, and 4%) developed after that time. Introduced populations had a typical epizootiologic pattern in 1965 55% annual mortality, 82% incidence) and 1966 (55% annual mortality, 66% incidence) which declined in 1967 (30% annual mortality, 44% incidence) followed by a disappearance of the disease in 1968. Epizootiologic differences noted between native oysters (adult and juvenile) and the introduced juvenile populations were also evident from the stages of the disease. Infections in native animals tended to be less serious, and in many cases were delayed or attentuated, while infections in introduced oysters progressed to advanced or terminal phases. Occult manifestations (mantle recession thought to be due to M. nelsoni in oysters not showing histologic evidence of infection) were absent in introduced populations and common in the native population. These differences are interpreted as evidence of resistance in surviving native oysters and their progency, and may indicate genetic resistance developed by natural selection and manifested by an increased ability to survive and overcome infection.

Animal Diseases↗