Cleavage of hemoglobin by hookworm cathespin D aspartic proteases and its potential contribution to host specificity

Hookworms routinely reach the gut of nonpermissive hosts but fail to successfully feed, develop, and reproduce. To investigate the effects of host-parasite coevolution on the ability of hookworms to feed in nonpermissive hosts, we cloned and expressed aspartic proteases from canine and human hookworms. We show here that a cathepsin D-like protease from the canine hookworm Ancylosotoma caninum (Ac-APR-1) and the orthologous protease from the human hookworm Necator americanus (Na-APR-1) are expressed in the gut and probably exert their proteolytic activity extracellularly. Both proteases were detected immunologically and enzymatically in somatic extracts of adult worms. The two proteases were expressed in baculovirus, and both cleaved human and dog hemoglobin (Hb) in vitro. Each protease digested Hb from its permissive host between twofold (whole molecule) and sixfold (synthetic peptides) more efficiently than Hb from the nonpermissive host, despite the two proteases' having identical residues lining their active site clefts. Furthermore, both proteases cleaved Hb at numerous distinct sites and showed different substrate preferences. The findings suggest that the paradigm of matching the molecular structure of the food source within a host to the molecular structure of the catabolic proteases of the parasite is an important contributing factor for host-parasite compatibility and host species range.

Mutations in the human ortholog of Aristaless cause X-linked mental retardation and epilepsy

Mental retardation and epilepsy often occur together. They are both heterogeneous conditions with acquired and genetic causes. Where causes are primarily genetic, major advances have been made in unraveling their molecular basis. The human X chromosome alone is estimated to harbor more than 100 genes that, when mutated, cause mental retardation(1). At least eight autosomal genes involved in idiopathic epilepsy have been identified(2), and many more have been implicated in conditions where epilepsy is a feature. We have identified mutations in an X chromosome-linked, Aristaless-related, homeobox gene (ARX), in nine families with mental retardation (syndromic and nonspecific), various forms of epilepsy, including infantile spasms and myoclonic seizures, and dystonia. Two recurrent mutations, present in seven families, result in expansion of polyalanine tracts of the ARX protein. These probably cause protein aggregation, similar to other polyalanine(3) and polyglutamine(4) disorders. In addition, we have identified a missense mutation within the ARX homeodomain and a truncation mutation. Thus, it would seem that mutation of ARX is a major contributor to X-linked mental retardation and epilepsy.

Immunity to malaria after administration of ultra-low doses of red cells infected with Plasmodium falciparum

Background The ability of T cells, acting independently of antibodies, to control malaria parasite growth in people has not been defined. If such cell-mediated immunity was shown to be effective, an additional vaccine strategy could be pursued. Our aim was to ascertain whether or not development of cell-mediated immunity to Plasmodium falciparum blood-stage infection could be induced in human beings by exposure to malaria parasites in very low density. Methods We enrolled five volunteers from the staff at our research institute who had never had malaria. We used a cryopreserved inoculum of red cells infected with P falciparum strain 3D7 to give them repeated subclinical infections of malaria that we then cured early with drugs, to induce cell-mediated immune responses. We tested for development of immunity by measurement of parasite concentrations in the blood of volunteers by PCR of the multicopy gene STEVOR and by following up the volunteers clinically, and by measuring antibody and cellular immune responses to the parasite. Findings After challenge and a extended period without drug cure, volunteers were protected against malaria as indicated by absence of parasites or parasite DNA in the blood, and absence of clinical symptoms. Immunity was characterised by absence of detectable antibodies that bind the parasite or infected red cells, but by the presence of a proliferative T-cell response, involving CD4+ and CD8+ T cells, a cytokine response, consisting of interferon gamma but not interleukin 4 or interleukin 10, induction of high concentrations of nitric oxide synthase activity in peripheral blood mononuclear cells, and a drop in the number of peripheral natural killer T cells. Interpretation People can be protected against the erythrocytic stage of malaria by a strong cell-mediated immune response, in the absence of detectable parasite-specific antibodies, suggesting an additional strategy for development of a malaria vaccine.

Postpartum issues' for expectant mothers and fathers

Objective: To investigate the postpartum psychosocial and infant care topics that women and men who attend preparation for parenthood classes have been thinking or worrying about during the pregnancy. Furthermore, to compare the rates of endorsement of such issues for women and men so that clinicians can use this information to help plan which topics to include in preparation for parenthood classes. Design: A survey of expectant parents attending preparation for parenthood classes at a local public hospital. Participants completed a 17- to 19-item postpartum issues checklist devised for the study. Setting: Preparation for parenthood classes conducted in a public hospital in South Western Sydney, Australia. Participants: People attending the session were in their 2nd to 3rd trimester, of low to middle socioeconomic status, and 95% were expecting their first child. Eighty-five percent of women were accompanied by their male partner at the session. Data are reported from 201 women and 182 men. Measure: A 17-item issues checklist was devised initially and later expanded to 19 items. The initial checklist covered three psychosocial issues: interpersonal, intrapersonal, and parental competency. The expanded checklist also included items on infant care issues. Participants rated each item as to the extent to which they had been thinking or worrying about it over the past few weeks. Results: More than half of the men and women had been thinking or worrying about their ability to cope as new parents; just less than half of both men and women endorsed the item regarding the effect having a baby would have on their relationship with their partner; approximately 40% of women had thought that they might get bored or lonely when at home with the baby, and an equal rate of men reported that their partner experiencing this sense of boredom or loneliness was an issue for them. There were few differences between the genders in the rate of endorsement on the issues checklist. Conclusion: That many of the issues on the checklist are prevalent in both women and men at this time in the pregnancy would suggest that these are topics that would be pertinent for inclusion at preparation for parenthood classes. Although the checklist is not exhaustive, the data reported give empirical justification for inclusion of these topics in such classes.

Prolonged retention after aggregation into secretory granules of human R183H-growth hormone (GH), a mutant that causes autosomal dominant GH deficiency type II

Human R183H-GH causes autosomal dominant GH deficiency type II. Because we show here that the mutant hormone is fully bioactive, we have sought to locate an impairment in its progress through the secretory pathway as assessed by pulse chase experiments. Newly synthesized wild-type and R183H-GH were stable when expressed transiently in AtT20 cells, and both formed equivalent amounts of Lubrol-insoluble aggregates within 40 min after synthesis. There was no evidence for intermolecular disulfide bond formation in aggregates of wild-type hormone or the R183H mutant. Both wildtype and R183H-GH were packaged into secretory granules, assessed by the ability of 1 mm BaCl2 to stimulate release and by immunocytochemistry. The mutant differed from wildtype hormone in its retention in the cells after packaging into secretory granules; 50% more R183H-GH than wild-type aggregates were retained in AtT20 cells 120 min after synthesis, and stimulated release of R183H-GH or a mixture of R183H-GH and wild-type that had been retained in the cell was reduced. The longer retention of R183H-GH aggregates indicates that a single point mutation in a protein contained in secretory granules affects the rate of secretory granule release.

Behavioural responses of two native Australian fish species (Melanotaenia duboulayi and Pseudomugil signifer) to introduced poeciliids (Gambusia holbrooki and Xiphophorus helleri) in controlled conditions

Experimental treatments to compare behavioural responses included native fish species only, natives plus one exotic species and natives plus both exotic species. The mosquitofish, Gambusia holbrooki frequently attacked both native species, but tended to nip Melanotaenia duboulayi (especially small individuals) and chase Pseudomugil signifer The frequency of attacks by G. holbrooki on M. duboulayi rose when all four fish species were present. When food was added, all four species showed a strong increase in aggression, especially in the four-species treatment, where there were significant increases in the frequency of attacks by the swordtail Xiphophorus helleri on M. duboulay and by M. duboulayi on G. holbrooki, and of conspecific attacks by M. duboulayi. Increased attack frequency was associated with aggregation closer to the water's surface, regardless of the presence of food. The results support the hypothesis that introduced poeciliids can have deleterious competitive effects on native species. However, while juvenile M. duboulayi were particularly vulnerable to the secondary, effects of fin-nipping, R signifer appeared to be more susceptible to physical displacement and reduced food capture success.

Role of complement C5 and T lymphocytes in pathogenesis of disseminated and mucosal candidiasis in susceptible DBA/2 mice

The aims of the study were to compare the pathogenesis of Candida albicans infection in various organs and anatomical regions of C5-deficient (DBA/2) and C5-sufficient (BALB/c) mice, and to evaluate the importance of complement C5 and T lymphocytes as factors that determine host susceptibility or resistance. The kidneys of DBA/2 mice showed higher colonisation and more severe tissue damage than those of BALB/c, but infection at other sites, including oral and vaginal mucosa, was generally similar in the two strains. Passive transfer of C5-sufficient serum into DBA/2 mice decreased the fungal burden in the kidney, and prolonged survival of the reconstituted animals. Depletion of CD4(+) and/or CD8(+) cells did not exacerbate either systemic or mucosal infection when compared to controls, and passive transfer of splenocytes from infected donors caused only a small and transient reduction in numbers of yeasts recovered from the kidney of sub-lethally infected recipients. It is concluded that the acute susceptibility of the kidneys in this mouse strain is due to C5 deficiency expressed on a susceptible genetic background. T lymphocytes, however, appear to have minimal influence on recovery from systemic infection with this isolate of C. albicans. (C) 2003 Elsevier Science Ltd. All rights reserved.

Exchange rate sensitivity of Australian international equity funds

This paper analyses the exchange rate exposure displayed by a sample of Australian international equity trusts (IET). Exchange rate exposure is also examined in the context of differing economic climates with particular emphasis on the Asian crisis in mid-1997. It is found that there is evidence of exchange rate exposure particularly in the context of a multiple exchange rate model. Exposure varies substantially between three alternative time periods with different exposure apparent subsequent to the Asian crisis than prior to this event.