Receptor for Fc on the surfaces of schistosomes

Schistosoma mansoni masks its surface with adsorbed host proteins including erythrocyte antigens, immunoglobulins, major histocompatibility complex class I, and beta (2)-microglobulin (beta (2)m), presumably as a means of avoiding host immune responses, How this is accomplished has not been explained. To identify surface receptors for host proteins, we biotinylated the tegument of live S, mansoni adults and mechanically transformed schistosomula and then removed the parasite surface with detergent, Incubation of biotinylated schistosome surface extracts witt l human immunoglobulin G (IgG) Fc-Sepharose resulted in purification of a 97-kDa protein that was subsequently identified as paramyosin (Pmy), using antiserum specific for recombinant Pmy, Fc also bound recombinant S. mansoni Pmy and native S. japonicum Pmy, Antiserum to Pmy decreased the binding of Pmy to Fc-Sepharose, and no proteins bound after removal of Pmy from extracts. Fluoresceinated human Fe bound to the surface, vestigial penetration glands, and nascent oral cavity of mechanically transformed schistosomula, and rabbit anti-Pmy Fab fragments ablated the binding of Fc to the schistosome surface, Pmy coprecipitated with host IgG from parasite surface extracts, indicating that complexes formed on the parasite surface as well as in vitro. Binding of Pmy to Fe was not inhibited by soluble protein A, suggesting that Pmy does not bind to the region between the CH2 and CH3 domains used by many other Fc-binding proteins. beta (2)m did not bind to the schistosome Fc receptor (Pmy), a finding that contradicts reports from earlier workers but did bind to a heteromultimer of labeled schistosomula surface proteins, This is the first report of the molecular identity of a schistosome Fc receptor; moreover it demonstrates an additional aspect of the unusual and multifunctional properties of Pmy from schistosomes and other parasitic flatworms.

Structure-hepatic disposition relationships for cationic drugs in isolated perfused rat livers: Transmembrane exchange and cytoplasmic binding process

This work studied the structure-hepatic disposition relationships for cationic drugs of varying lipophilicity using a single-pass, in situ rat liver preparation. The lipophilicity among the cationic drugs studied in this work is in the following order: diltiazem. propranolol. labetalol. prazosin. antipyrine. atenolol. Parameters characterizing the hepatic distribution and elimination kinetics of the drugs were estimated using the multiple indicator dilution method. The kinetic model used to describe drug transport (the two-phase stochastic model) integrated cytoplasmic binding kinetics and belongs to the class of barrier-limited and space-distributed liver models. Hepatic extraction ratio (E) (0.30-0.92) increased with lipophilicity. The intracellular binding rate constant (k(on)) and the equilibrium amount ratios characterizing the slowly and rapidly equilibrating binding sites (K-S and K-R) increase with the lipophilicity of drug (k(on) : 0.05-0.35 s(-1); K-S : 0.61-16.67; K-R : 0.36-0.95), whereas the intracellular unbinding rate constant (k(off)) decreases with the lipophilicity of drug (0.081-0.021 s(-1)). The partition ratio of influx (k(in)) and efflux rate constant (k(out)), k(in)/k(out), increases with increasing pK(a) value of the drug [from 1.72 for antipyrine (pK(a) = 1.45) to 9.76 for propranolol (pK(a) = 9.45)], the differences in k(in/kout) for the different drugs mainly arising from ion trapping in the mitochondria and lysosomes. The value of intrinsic elimination clearance (CLint), permeation clearance (CLpT), and permeability-surface area product (PS) all increase with the lipophilicity of drug [CLint (ml . min(-1) . g(-1) of liver): 10.08-67.41; CLpT (ml . min(-1) . g(-1) of liver): 10.80-5.35; PS (ml . min(-1) . g(-1) of liver): 14.59-90.54]. It is concluded that cationic drug kinetics in the liver can be modeled using models that integrate the presence of cytoplasmic binding, a hepatocyte barrier, and a vascular transit density function.

Saturable dose-response relationships for melphalan in melanoma treatment by isolated limb infusion in the nude rat

Nude rats bearing melanomas on their hindlimbs were treated by isolated limb infusion (ILI) with increasing doses (7.5-400 mug/ml) of melphalan. The response of tumours to treatment at the end of the observation period was graded, according to diameter, as complete response (CR), partial response (PR), no change (NC) or progressive disease (PD). No linear relationship between the dose of melphalan and the tumour response was observed. All doses above a threshold of 15 mug/ml achieved a PR or CR. The achievement of CR was not related to increased dose. Two major implications arise from this work. Firstly, the typically two-to three-fold increase in cytotoxic drug concentration given in high dose chemotherapy compared with standard drug concentration may not be sufficient to produce the expected increase in tumour response and possibly survival, and the controversial results of high dose chemotherapy in different studies may thus be explained. Secondly, since an increase in melphalan dose above a certain threshold does not greatly increase tumour response, the use of combination therapies would seem to be more likely to be effective than increased chemotherapeutic drug doses in achieving better tumour responses.

Platyhelminth phylogenetics - a key to understanding parasitism?

The comparative method, the inference of biological processes from phylogenetic patterns, is founded on the reliability of the phylogenetic tree. In attempting to apply the comparative method to the understanding of the evolution of parasitism in the phylum Platyhelminthes, we have highlighted several points we consider to be of value along with many problems. We discuss four of these topics. Firstly, we view the group at a phylum level, in particular discussing the importance of establishing the sister taxon to the obligate parasite group, the Neodermata, for addressing such questions as the monophyly, parasitism or the endo or ectoparasitic nature of the early parasites. The variety of non-congruent phylogenetic trees presented so far, utilising either or both morphological and molecular data, gives rise to the suggestion that any evolutionary scenarios presented at this stage be treated as interesting hypotheses rather than well-supported theories. Our second point of discussion is the conflict between morphological and molecular estimates of monogenean evolution. The Monogenea presents several well-established morphological autapomorphies, such that morphology consistently estimates the group as monophyletic, whereas molecular sequence analyses indicate paraphyly, with different genes giving different topologies. We discuss the problem of reconciling gene and species trees. Thirdly, we use recent phylogenetic results on the tapeworms to interpret the evolution of strobilation, proglottization, segmentation and scolex structure. In relation to the latter, the results presented indicate that the higher cestodes are diphyletic, with one branch difossate and the other tetrafossate. Finally, we use a SSU rDNA phylogenetic tree of the Trematoda as a basis for the discussion of an aspect of the digenean life-cycle, namely the nature of the first intermediate host. Frequent episodes of host-switching, between gastropod and bivalve hosts or even into annelids, are indicated.

Tormopsolus attenuatus n. sp (Digenea : Acanthocolpidae) from Seriola hippos (Perciformes : Carangidae), Western Australia, with some observations on the relationships in the genus

A new acanthocolpid, Tormopsolus attenuatus n. sp., is described from the carangid Seriola hippos from waters off the coast of SW Australia. A cladistic analysis of the genus using 31 morphological and metrical characters indicates that the closest species is T. asiatica Parukhin, 1976 status amend. (previously T. orientalis asiatica). T. attenuatus differs from T. asiatica in its smaller overall dimensions, more attenuated outline, relatively shorter post-testicular region, vitelline interruption at the level of the ovary, papillae on the oral sucker and, possibly, much longer genital atrium. Other similar species, T. orientalis Yamaguti, 1934 and T. medius Reimer, 1983, differ in having interruptions of the vitelline fields at the level of both testes and at the level of the ovary.

Japanese encephalitis on Badu Island, Australia: the first isolation of Japanese encephalitis virus from Culex gelidus in the Australasian region and the role of mosquito host-feeding patterns in virus transmission cycles

During investigation of an outbreak of Japanese encephalitis (JE) in the Torres Strait, Australia, in 2000, mosquitoes were collected in Badu Island community and at a newly established communal piggery about 3 km from the community. A total of 94285 mosquitoes, comprising 91240 (96.8%) unengorged females, 1630 (1.7%) blood-engorged females and 1415 (1.5%) males, were processed for virus isolation. One isolate of JE virus was obtained from Culex gelidus, with a minimum infection rate of 12.4:1000. This is the first isolate of JE virus from Cx. gelidus in the Australasian region. No isolates were obtained from Cx. annulirostris, the primary implicated Australian JE vector. Analysis of mosquito host-feeding patterns, using gel diffusion, demonstrated that Cx. annulirostris and 5 other species fed predominately on mammals, Analysis of blood-fed mosquitoes collected within the community demonstrated that the proportion of Cx. annulirostris feeding on pigs in 2000 (2.3%) was significantly lower than that for the 1995-97 period (31.3%). The removal of the pigs from Badu Island community has limited the contact between potential amplifying hosts and mosquitoes, thus potentially reducing the risk of transmission of JE virus to the human population.

The Relationships between West Nile and Kunjin Viruses

Until recently, West Nile (WN) and Kunjin (KUN) viruses were classified as distinct types in the Flavivirus genus. However, genetic and antigenic studies on isolates of these two viruses indicate that the relationship between them is more complex. To better define this relationship, we performed sequence analyses on 32 isolates of KUN virus and 28 isolates of WN virus from different geographic areas, including a WN isolate from the recent outbreak in New York. Sequence comparisons showed that the KUN virus isolates from Australia were tightly grouped but that the WN virus isolates exhibited substantial divergence and could be differentiated into four district groups. KUN virus isolates from Australia were antigenically homologous and distinct from the WN isolates and a Malaysian KUN virus. Our results suggest that KUN and WN viruses comprise a group of closely related viruses that can be differentiated into subgroups on the basis of genetic and antigenic analyses.

Phylogenetic relationships of Trypanosoma chelodina and Trypanosoma binneyi from Australian tortoises and platypuses inferred from small subunit rRNA analyses

Trypanosome infections are often difficult to detect by conventional microscopy and their pleomorphy often confounds differential diagnosis. Molecular techniques are now being used to diagnose infections and to determine phylogenetic relationships between species. Complete small subunit rRNA gene sequences were determined for isolates of Trypanosoma chelodina from the Brisbane River tortoise (Emydura signata), the saw-shelled tortoise (Elseya latisternum), and the eastern snake-necked tortoise (Chelodina longicollis) from southeast Queensland, Australia. Partial sequence data were also obtained for T. binneyi from a platypus (Ornithorhynchus anatinus) from Tasmania. Phylogenetic relationships between T. chelodina, T. binneyi and other species were examined by maximum parsimony and likelihood methods. The Australian tortoise and platypus trypanosomes did not exhibit any close phylogenetic relationships with those of mammals, reptiles or amphibians, but were closely related to each other, and to fish trypanosomes. This contra-indicates their co-evolution with their vertebrate hosts but does not exclude co-evolution with different groups of invertebrate vectors, notably insects and leeches.

A revision of Benedenia Diesing, 1858 including a redescription of B-sciaenae (van Beneden, 1856) Odhner, 1905 and recognition of Menziesia Gibson, 1976 (Monogenea : Capsalidae)

Benedenia Diesing, 1858, a genus of capsalid (benedeniine) monogeneans, is redefined. The generic diagnosis is amended to include: the path of tendons in the haptor from extrinsic muscles in the body; presence and form of the marginal valve; a penis occupying a penis canal with weakly muscular wall; a weakly muscular accessory gland reservoir proximal to the penis and enclosed by a proximal extension of the wall of the penis canal; male and female genital apertures usually common, rarely separate; vagina with pore usually close to the common genital pore but may open in mid body between the germarium and the common genital pore, or anterior to the common genital pore. A conservative approach is adopted and the generic diagnosis is clarified and broadened to accommodate species that display some variation in reproductive anatomy, especially of the female system. We argue against potential alternative actions such as defining Benedenia strictly to contain species with separate male and female genital apertures and against recognition of a separate genus, Tareenia Hussey, 1986, for species with a vaginal pore anterior to the common genital pore. Under our conception, Benedenia comprises 21 species: B. sciaenae (van Beneden, 1856) Odhner, 1905 (type species); B. acanthopagri (Hussey, 1986) comb. nov.; B. anticavaginata Byrnes, 1986; B. bodiani Yamaguti, 1968; B. elongata (Yamaguti, 1968) Egorova, 1997; B. epinepheli (Yamaguti, 1937) Meserve, 1938; B. hawaiiensis Yamaguti, 1968; B. hendorffi(von Linstow, 1889) Odhner, 1905; B. hoshinai Ogawa, 1984; B. innobilitata Burhnheim Gomes and Varela, 1973: B. jaliscana Bravo-Hollis, 1952; B. lolo Yamaguti, 1968; B. lutjani Whittington and Kearn, 1993: B. monticellii (Parona and Perugia, 1895) Johnston, 1929; B. ovata (Goto, 1894) Johnston. 1929: B. pompatica Burhnheim, Gomes and Varela, 1973; B. rohdei Whittington, Kearn and Beverley-Burton, 1994; B. scari Yamaguti, 1968; B. sekii (Yamaguti, 1937) Meserve, 1938; B, seriolae (Yamaguti, 1934) Meserve, 1938; and B. synagris Yamaguti, 1953. The type species, B. sciaenae, is redescribed based on new material from Australia. No types for this taxon were designated and we have assigned a series of voucher specimens. Tareenia acanthopagri Hussey, 1986 becomes B. acanthopagri (Hussey, 1986) comb. nov. and T. anticavaginata (Byrnes, 1986) Egorova, 1997 and T. lutjani (Whittington and Kearn, 1993) Egorova, 1997 are returned to Benedenia as B. anticavaginata and B. lutjani Benedenia akaisaki Iwata, 1990 is considered a synonym of B. ovata and B. kintoki Iwata, 1990 is considered a synonym of B. elongata. Two species, B, madai Ishii and Sawada, 1938 and B. pagrosomi Ishii and Sawada, 1938, are considered species inquirendae. Based on the redefinition of Benedenia, the diagnosis for the Benedeniinae is amended. Tareenia is synonymized with Benedenia but Menziesia Gibson, 1976 is recognized and its generic diagnosis amended to include: anterior attachment organs tending to form a 'hooded' appearance; prominent anterior gland cells between the pharynx and the anterior margin of the body: long penis, tapering proximally, occupying a penis canal with weakly muscular wall: penis canal and penis describe a sigmoid; accessory gland reservoir dorsal and alongside, or posterior and lateral to, proximal end of the penis and enclosed by a proximal extension of the wall of the penis canal. Under this conception. Menziesia comprises: M. noblei (Menzies. 1946) Gibson, 1976 (type species); M. malaboni (Velasquez. 1982) comb. nov.: M. merinthe (Yamaguti, 1968) Gibson. 1976: M. ovalis (Yamaguti, 1968) Gibson, 1976: and M. sebastodis (Yamaguti, 1934) comb, nov. A key to valid species of Benedenia and Menziesia is provided and a list is presented of published records of undescribed or unattributed species of Benedenia. Some protocols are suggested for preparation of benedeniine material to enhance future taxonomic studies and comparisons. The host-specificity and geographic distribution of species in these revised genera are discussed. The composition of the Capsalidae is discussed and some difficulties in defining and distinguishing between its different subfamilies are considered.

Relationships between non-occupational cadmium exposure and expression of nine cytochrome P450 forms in human liver and kidney cortex samples

This study was undertaken to assess associations between age, gender, cigarette smoke and non-workplace cadmium exposure, and liver pathology and inter-individual variation in cytochrome P450 (CYP) expression in human tissues. Autopsy specimens of twenty-eight Queensland residents whose ages ranged from 3 to 89 years were analyzed for the presence of nine CYP protein isoforms by immunoblotting. All subjects were Caucasians and their liver cadmium contents ranged from 0.11 to 3.95 kg/g wet weight, while their kidney cadmium contents were in the range of 2 to 63 mug/g wet weight. CYP1A2, CYP2A6, CYP2D6, CYP3A4, and CYP3A5 were detected in liver but not in kidney, and CYP1A1 and CYP1B1 were not found in liver or kidney. Lowered liver CYP2C8/19 protein contents were found to be associated with liver pathology. Importantly, we show elevated levels of CYP2C9 protein to be associated with cadmium accumulation in liver. No mechanism that explains this association is apparent, but there are two possibilities that require further study. One is that variation in CYP2C9 protein levels may be, in part, attributed to an individual's non-workplace exposure to cadmium, or an individual's CYP2C9 genotype may be a risk factor for cadmium accumulation. A positive correlation was found between liver CYP3A4 protein and subject age. Levels of liver CYPIA2 protein, but not other CYP forms, were increased in people more exposed to cigarette smoke, but there was no association between CYPIA2 protein and cadmium. CYP2A6 protein was found in all liver samples and CYP2A6 gene typing indicated the absence of CYP2A6 null allele (CYP2A6(D)) in this sample group, confirming very low prevalence of homozygous CYP2A6(D) in Caucasians. CYP2A6 gene types W/W, WIC, and CIC were not associated with variations in liver microsomal CYP2A6 protein. CYP2D6 protein was absent in all twenty-five kidney samples tested but was detectable in liver samples of all but two subjects, indicating the prevalence of the CYP2D6 null allele (CYP2D6(D)) in this sample group to be about 7%, typical of Caucasian populations. (C) 2001 Elsevier Science Inc. All rights reserved.