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PubMed1991

[Risk factors related with occupational and environmental exposure to organochlorine insecticides in the state of Bahia, Brazil, 1985].

In the cacao-growing region in the southern part of the state of Bahia, the organochlorine insecticides, mainly gamma-benzene hexachloride (BHC) and dichlorodiphenyltrichloroethane (DDT), have been used for about 40 years on cacao crops and in public health programs for control of the insect vectors of different diseases, especially malaria. This paper presents the results of tests performed on 127 persons, all males, between the ages of 15 and 52 years, divided into eight groups as follows: three groups consisted of persons occupationally exposed to 1.5% BHC, that is, technical hexachlorocyclohexane (HCH); two groups consisted of individuals who had had occasional contact with the products or worked in areas near those in which they were used; two groups were appliers of DDT, and the last group--the control group--consisted of 50 individuals who had had no history of occupational exposure to insecticides. All the participants underwent testing to determine the parameters of biochemistry, hematology, and organochlorine insecticide residues in the blood. It was found that improper handling of the products and failure to use individual protective equipment, together with longer time of exposure, significantly increased the rates of GOT and GPT in the appliers of DDT and technical HCH, and in the latter the rates of alkaline phosphatase, albumin, and cholesterol were also found to be higher. In view of the high morbidity among pesticide appliers in agriculture and public health campaigns, it is important to institute programs to teach these workers to avoid contamination of their persons and of the environment by developing good hygiene habits, using individual protective equipment, and correctly handling the products. Rural workers and public health authorities must become aware of the importance of protective equipment, periodic health examinations, and reduced environmental pollution in order to lessen occupational risks of field workers and promote improved conditions of life for the rural population at large.

Adolescent↗
PubMed2005

FMRFamide-like immunocytochemistry in the brain and subesophageal ganglion of Triatoma infestans (Insecta: Heteroptera). Coexpression with beta-pigment-dispersing hormone and small cardioactive peptide B.

The distribution of FMRFamide (FMRFa)-like immunoreactivity (LI) was studied in the brain and subesophageal ganglion of Triatoma infestans, the insect vector of Chagas' disease. The neuropeptide displayed a widespread distribution with immunostained somata in the optic lobe, in the anterior, lateral, and posterior soma rinds of the protocerebrum, and around the antennal sensory and mechanosensory and motor neuropils of the deutocerebrum. FMRFa-immunoreactive profiles of the subesophageal ganglion were seen in the mandibular, maxillary, and labial neuromeres. Immunostained neurites were detected in the medulla and lobula of the optic lobe, the lateral protocerebral neuropil, the median bundle, the calyces and the stalk of the mushroom bodies, and the central body. In the deutocerebrum, the sensory glomeruli showed a higher density of immunoreactive processes than the mechanosensory and motor neuropil, whereas the neuropils of each neuromere of the subesophageal ganglion displayed a moderate density of immunoreactive neurites. Colocalization of FMRFa-LI and crustacean pigment-dispersing hormone-LI was found in perikarya of the proximal optic lobe, the lobula, the sensory deutocerebrum, and the labial neuromere of the subesophageal ganglion. The distribution pattern of small cardioactive peptide B (SCP(B))-LI was also widespread, with immunolabeled somata surrounding every neuropil region of the brain and subesophageal ganglion, except for the optic lobe. FMRFa- and SCP(B)-LIs showed extensive colocalization in the brain of this triatomine species. The presence of immunolabeled perikarya displaying either FMRFa- or SCP(B)-LI confirmed that each antisera identified different peptide molecules. The distribution of FMRFa immunostaining in T. infestans raises the possibility that FMRFa plays a role in the regulation of circadian rhythmicity. The finding of immunolabeling in neurosecretory somata of the protocerebrum suggests that this neuropeptide may also act as a neurohormone.

Animals↗
PubMed1990

New viral diseases. A real and potential problem without boundaries.

Viruses are the most mutable and rapidly evolving human parasites. Therefore, it is not surprising that new virus diseases, such as the acquired immunodeficiency syndrome, are emerging. However, these new viruses are relatively few in number, which reflects the constraints placed on viral evolution by the requirement for maintenance of virus structure and function and virus adaptation to restricted ecologic sites. Most "new" viral diseases, such as the hemorrhagic fevers, result from environmental disruptions that increase human contact with animals or insect vectors of old viruses. However, truly novel viruses with lethal potential or capacity for global spread have emerged in animals as a consequence of single-point mutations or genetic recombination between viruses. Given the mutability of viruses and the inevitability of environmental change, we must be prepared for the evolution of new virus diseases.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Inactivation and reactivation of a variant-specific antigen gene in cyclically transmitted Trypanosoma brucei.

In Trypanosoma brucei, the activation of the variant-specific antigen gene AnTat 1.1 proceeds by the synthesis of an additional gene copy, the AnTat 1.1 ELC, which is transposed to a new location, the expression site, where it is transcribed. Using the AnTat 1.1 variant to infect flies, we investigated the fate of the AnTat 1.1 ELC during cyclic transmission of T. brucei. We show here that the AnTat 1.1 ELC is conserved in procyclic trypanosomes, obtained either from the midgut of infected Glossina or from cultures, and in metacyclic trypanosomes, although the AnTat 1.1 serotype is not detected among metacyclic antigen types. This same AnTat 1.1 ELC, which is thus silent as the parasite develops in the insect vector, can be reactivated without duplication during the first parasitemia wave following cyclical transmission. This re-expression of the conserved ELC accounts for the early appearance of the 'ingested' antigenic type after passage through the fly.

Animals↗
PubMed1986

The nucleotide sequence of an infectious clone of the geminivirus beet curly top virus.

A number of infectious clones of a Californian isolate of the leafhopper-transmitted geminivirus beet curly top virus (BCTV) have been constructed from virus-specific double-stranded DNA isolated from infected Beta vulgaris and used to demonstrate a single component genome. The nucleotide sequence of one infectious clone has been determined (2993 nucleotides). Comparison with other geminiviruses has shown that the organisation of the genome closely resembles DNA 1 of the whitefly-transmitted members. The four conserved coding regions of DNA 1 have highly homologous counterparts in BCTV with the exception of the putative coat protein which is more closely related to those of the leafhopper-transmitted geminiviruses suggesting a strong interrelationship between coat protein and insect vector. A BCTV component equivalent to DNA 2 is not required for virus infection or transmission and has not been isolated from infected plants.

Journal Article↗
PubMed1983

Pyrazolopyrimidine metabolism in Leishmania and trypanosomes: significant differences between host and parasite.

The pathogenic hemoflagellates of the genera Leishmania and Trypanosoma are major causes of human disease in the tropical and subtropical areas of the world. In general, the agents used to treat diseases caused by these organisms are toxic and not suitable for administration to the millions of people infected. Investigations over the past several years have shown that there are several major differences between man and these protozoans with respect to purine metabolism. The differences appear to offer promise for the development of effective chemotherapeutic compounds. These organisms do not synthesize purines de novo, as does man. They are able to concentrate pyrazolopyrimidines with the cell and metabolize them as purines through the salvage pathways, ultimately incorporating them into nucleic acids. This does not occur in mammals. The pyrazolopyrimidine base allopurinol, which has served as a prototype, is activated by a phosphoribosyltransferase to the ribonucleotide. The ribonucleotide is aminated to the 4-amino-pyrazolopyrimidine ribonucleotide and subsequently phosphorylated to the triphosphate form and incorporated into RNA. The pyrazolopyrimidine ribonucleosides formycin B and allopurinol ribonucleoside are activated through a nucleoside phosphotransferase. The resulting ribonucleotide is aminated and incorporated into RNA as described above. These metabolic peculiarities occur not only in the forms of these parasites which are found in the insect vectors but also in the intracellular forms which are pathogenic in man. The differences in the enzymology and metabolism of purines which exist in the genera Leishmania and Trypanosoma offer excellent opportunities for chemotherapeutic exploitation.

Adenine↗
PubMed1993

Rapid fixation and embedding method for immunocytochemical studies of tomato spotted wilt tospovirus (TSWV) in plant and insect tissues.

A new rapid fixation and embedding technique using microwave energy was evaluated for immunolabelling and examination of ultrastructure of plant and insect cells. Tissues in gluteraldehyde-paraformaldehyde were fixed for fifteen seconds in a microwave at 100% power, and dehydrated. Microwave energy was then used to polymerize the London Resin White (LR White) acrylic resin during the embedding process. Embedded specimens were then thin sectioned (90 nm) and treated with anti-tomato spotted wilt tospovirus (TSWV) antiserum followed by protein A-gold label, or antisera against a TSWV encoded nonstructural protein followed by goat anti-rabbit gold label. Using this technique, structural and nonstructural proteins of TSWV were readily detected and specifically labelled in cells of the insect vector, the western flower thrips, Frankliniella occidentalis (Pergande), and in infected cells of the plant species, Emilia sonchifolia L.

Animals↗
PubMed1989

Viruslike particles in liver in sporadic non-A, non-B fulminant hepatitis.

In a patient who followed the typical clinical course of fulminant hepatitis attributable to "sporadic" non-A,non-B (NANB) hepatitis and who finally received treatment by orthotopic liver grafting, three, apparently separate, virus-like agents (26, 45, and 80 nm) and cytoplasmic, reticular tubular structures (CTS) were identified in collapsed and regenerating areas of liver using electron microscopy. The 80-nm particles present within vacuoles, together with the finding of intranuclear rods in association with the smaller particles (26 nm), are similar to those found in the nuclei of cells infected with several different arboviruses. The third type of particle, existing as 45-nm spheres and rods, is similar in morphology only to some form of polyoma virus, which, hitherto, has not been reported as affecting the liver. Unlike typical polyoma virus, replication of the virus "cores" (25-26 nm) was extranuclear and appeared to be occurring in vacuoles. Although analysis for serological markers against a representative panel for arboviruses, flaviviruses, phleboviruses, arenavirus, and nairovirus was negative, an insect vector was implicated in the clinical history.

Adult↗
PubMed1989

Toga-like virus as a cause of fulminant hepatitis attributed to sporadic non-A, non-B.

Virus-like particles (60-70 nm) with spiked surfaces budding into cell vacuoles and rod-shaped inclusions were detected in nuclei of hepatocytes from a British patient transplanted for sporadic non-A, non-B fulminant hepatitis (NANB-FHF), probably contracted in Kenya. Identical particles were seen in two successive grafts (days 2 and 10) at regrafting for recurrent FHF. Ultrastructural features resembled those of the RNA-containing arbovirus, Rift Valley fever virus, but serological markers against a representative panel for arboviruses (Togaviruses) and transmission in mice proved negative. The particles shared features with the different arboviruses seen in the hepatectomy specimen of a second patient with NANB-FHF, and in both patients an insect vector was implicated in the clinical history. The particles were identical in size to those of a third patient with NANB-FHF, who had remained in the United Kingdom. These findings, together with the recent report of isolation of an RNA-containing virus resembling the Togaviridae, in parenteral NANB, suggest that several exotic virus-like agents resembling the arboviruses may be involved in the aetiology of NANB, including in the sporadic forms of FHF in the United Kingdom.

Adolescent↗
PubMed1996

Trypanosomatidae: a spliced-leader-derived probe specific for the genus Phytomonas.

We probed DNA from all trypanosomatid genera by slot blot hybridization with an oligonucleotide (SL3') complementary to a sequence of the Phytomonas spliced-leader or mini-exon RNA. The 19-nucleotide probe target site was previously shown to be highly conserved among a limited number of Phytomonas isolates, but diverges in other kinetoplastid genera. Our examination of 84 isolates of various genera of trypanosomatids showed hybridization of this probe exclusively with isolates from plants or insects which could, by morphological, biochemical, and molecular criteria, be considered to belong to the genus Phytomonas. In contrast, no hybridization was observed with flagellates of the genera Blastocrithidia, Crithidia, Endotrypanum, Herpetomonas, Leptomonas, Leishmania, and Trypanosoma. The method detected DNA quantities as low as 50 ng using either radioactive or nonradioactive probes, and was effective with as few as 10(4) intact flagellates. Together, these results suggest that this probe will serve as a convenient marker for taxonomic and epidemiological studies requiring reliable identification of Phytomonas spp. in plants or in putative insect vectors.

Animals↗
PubMed1997

Trypanosoma cruzi in the opossum Didelphis marsupialis: a study of the correlations and kinetics of the systemic and scent gland infections in naturally and experimentally infected animals.

The genus Didelphis (Marsupialia, Didelphidae) has the unique capacity of supporting both multiplication cycles of Trypanosoma cruzi simultaneously; besides the intracellular forms, the epimastigotes can be found multiplying and differentiating abundantly in the lumen of the scent glands. The biological significance of the life cycle of T. cruzi within the scent glands of Didelphis marsupialis, as well as its contribution to the epidemiology of the disease, is presently unclear. In order to clarify the mechanisms involved in the colonization of this singular habitat by T. cruzi, as well as to understand its biological role, we have carried out a serological and parasitological follow-up of both natural and experimental infections of young and adult opossums. Although all natural infections were stable and long lasting, no infected scent glands were found, indicating that the stability of the systemic infections does not depend on the presence of flagellates in the scent gland. In 84% of the experimentally infected animals the colonization of the scent glands was preceded by a period of patent parasitemia. Parasitism of the scent glands was essentially permanent and bilateral, and its maintenance was independent of circulating parasites. Moreover, the course of the infection differed depending on the source (scent glands versus axenic culture-derived) of the metacyclic forms. Our results suggest that parasitism of the SG of D. marsupialis is most likely a secondary acquisition, a step toward independence from the insect vector, similarly to what is accepted for Trypanosoma equiperdum.

Animals↗
PubMed2000

Killing of Trypanosoma brucei by concanavalin A: structural basis of resistance in glycosylation mutants.

Concanavalin A (Con A) kills procyclic (insect) forms of Trypanosoma brucei by binding to N-glycans on EP-procyclin, a major surface glycosyl phosphatidylinositol (GPI)-anchored protein which is rich in Glu-Pro repeats. We have previously isolated and studied two procyclic mutants (ConA 1-1 and ConA 4-1) that are more resistant than wild-type (WT) to Con A killing. Although both mutants express the same altered oligosaccharides compared to WT cells, ConA 4-1 is considerably more resistant to lectin killing than is ConA 1-1. Thus, we looked for other alterations to account for the differences in sensitivity. Using mass spectrometry, together with chemical and enzymatic treatments, we found that both mutants express types of EP-procyclin that are either poorly expressed or not found at all in WT cells. ConA 1-1 expresses mainly EP1-3, a novel procyclin that contains 18 EP repeats, is partially N-glycosylated, and bears hybrid-type glycans. On the other hand, ConA 4-1 cells express almost exclusively EP2-3, a novel non-glycosylated procyclin isoform with 23 EP repeats and no site for glycosylation. The predominance of EP2-3 in ConA 4-1 cells explains their high resistance to ConA killing. Thus, switching the procyclin repertoire, a process that could be relevant to parasite development in the insect vector, modulates the sensitivity of trypanosomes to cytotoxic lectins.

Amino Acid Sequence↗
PubMed1996

Normal replication of vesicular stomatitis virus without C proteins.

The expression of two small basic proteins (C and C') encoded by a second open reading frame of the New Jersey serotype of vesicular stomatitis virus (VSV) P gene was reported previously (Spiropoulou and Nichol, J. Virol., 67, 3103-3110, 1993). Here we found that the Indiana serotype virus also expressed C and C' proteins from this reading frame. We eliminated C and C' expression by making a single base change that introduced a stop codon in the C and C' coding sequence, but left the P-protein sequence unchanged. This mutated P gene supported normal replication and packaging of VSV minigenomes encoding G and M proteins. The mutated P gene was also recombined into an infectious clone of VSV that was used to recover virus. The mutant virus no longer expressed the C and C' proteins but showed growth kinetics identical to wild-type virus. The amounts of viral mRNAs and proteins synthesized were indistinguishable in mutant and wild-type virus infected cells as were the yields and composition of mutant and wild-type virus particles. The kinetics of host protein-synthesis shut-off were also identical for both viruses. Although the C and C' proteins were dispensable for VSV growth in tissue culture, they are known to be conserved in all vesiculoviruses, and thus perhaps play a role in viral pathogenesis or transmission by insect vectors.

Amino Acid Sequence↗
PubMed1997

Cucumber mosaic virus is restricted from entering minor veins in transgenic tobacco exhibiting replicase-mediated resistance.

Transgenic tobacco plants expressing an altered form of the 2a replicase gene from cucumber mosaic virus (CMV) strain Fny exhibited a suppression of viral replication and restricted viral movement when inoculated mechanically or by insect vectors. Resistant plants could be infected, however, through a graft-union with an infected nontransformed plant. The infectious entity moved quickly through intergrafts of resistant tissue, indicating that it could move without replicating in the vascular system. Viral replication continued to be suppressed in systemically infected transgenic portions of grafted plants, as demonstrated by the synthesis of lower levels of viral RNA than in systemically infected nontransformed portions of the same grafted plants. Cell-to-cell spread within this tissue also occurred much more slowly than in nontransformed tobacco. Young inoculated levels of transgenic-resistant plants exhibited limited cell-to-cell virus movement, revealed as chlorotic lesions, but no long-distance virus movement occurred. The results of in situ hybridization studies on these lesions indicated that CMV RNA does not traffic from bundle-sheath cells to vascular parenchyma or companion cells in chlorotic lesions on the inoculated leaves of transgenic-resistant tobacco plants. The inhibition of long-distance movement was a consequence of restricted entry of the infectious entity into the vascular system.

Cucumovirus↗
PubMed1999

Chitinases of human parasites and their implications as antiparasitic targets.

Pathogens causing a number of human and animal diseases use chitin and chitinases in their life cycles. Most of these diseases are caused by protozoan or metazoan pathogenic parasites. Some of these parasites contain chitin coats that protect them from the harsh conditions in the animal body or the environment. Some pathogens use chitinase to invade or exploit the chitin-containing structures of their host to establish successful infection or to be transmitted from one vertebrate to another via insect vectors. Recent studies indicate that each of these organisms has evolved to use chitin and chitinases differently and in a developmental stage-specific manner. Genes of many of these pathogenic parasites have been isolated, and the predicted amino acid sequences show a great deal of diversity. In this chapter we will discuss the roles chitin and chitinases play in several animal diseases, the strategies used to clone the chitinase genes from various parasites and the usefulness of chitinases as preventive or therapeutic agents.

Animals↗
PubMed1998

Future international management of African horse sickness vaccines.

Three types of African horse sickness (AHS) vaccine, namely adult mouse brain, modified live vaccine and inactivated viral vaccine (IVV) are reviewed. The results of efficacy trials carried out with each vaccine type highlight the advantages of the IVV. Vaccination with African horse sickness virus serotype 4 IVV, given as 2 separate doses, provided full protection against subsequent, homologous challenge. The absence of any detectable viraemia after challenge would also prevent infection of insect vectors. The advantages of establishing international vaccine banks for AHS are discussed.

African Horse Sickness↗
PubMed1991

Preliminary observations on the epidemiology of bovine ephemeral fever in China.

Bovine ephemeral fever (BEF) is a viral disease of cattle and water buffalo recognised for the first time in China in 1955. The disease has been endemic in south China with 13 epidemics since 1955, seven epidemics reaching central China and one extending into north-east China (40 degrees N). The outbreaks have been seasonal with all occurring in the warmer summer/autumn months of June to October when possible insect vectors are active. Reports of clinical disease were confirmed as BEF by the detection of virus-neutralising antibody. The economic impact of the disease includes loss of milk production, late-term abortions and the loss of draught animal power.

Animals↗
PubMed1985

Lipid analyses of isolated surface membranes of Leishmania donovani promastigotes.

Constituent lipids of surface membranes (SM) isolated from Leishmania donovani promastigotes were analyzed and compared with those obtained from whole cells and an isolated kinetoplast-mitochondrion fraction (KM). On a dry weight basis, the total extractable lipids constituted approximately 47%, 12% and 24% of the SM, cells and KM, respectively. The total lipids of SM, cells and KM all were composed of approximately 70% phospholipids (PL), 20-25% neutral lipids and 5-10% glycolipids. Sterols and diglycerides composed 60% and 30%, respectively, of the various neutral lipid fractions. Several mannose- and galactose-containing glycolipids were fractionated but not identified. The glycolipid fractions from cells and SM had demonstrable antigenic activities with rabbit anti-SM sera. Striking quantitative differences were apparent between the PL profiles of the 3 cellular components examined. The PL of SM, whole cells and KM, respectively, were composed of: 15%, 51% and 24% phosphatidylcholine; 37%, 13% and 11% phosphatidylethanolamine (PE); 18%, 10% and 14% phosphatidylinositol; 10%, 1% and 4% phosphatidylserine and traces of cardiolipin, phosphatidylglycerol and phosphatidic acid. An unknown PL containing sphingosine, choline and vicinal hydroxyl groups but no free amino moieties made up approximately 19% of the PL of SM and whole cells, but it constituted approximately 27% of the PL of KM. The PL side chain constituents of whole cells and SM were composed mainly of longchain fatty acids (C18-20). Further, over 50% of the PE of SM was in the alkyl and alK-1-enyl ether forms. These SM properties might contribute to the organism's resistance to digestion in the hydrolytic environs of both its insect vector and mammalian hosts.

Animals↗