Mercury enhances susceptibility to murine leishmaniasis.

The genetic background of mice infected with Leishmania major determines the response to infection, resulting in a resistant or susceptible phenotype. Susceptible mice develop a T-helper type 2 (Th2)-type immune response following infection distinguished by the development of interleukin (IL)-4 secreting T cells in the lymph node and spleen. In SJL mice, which normally heal L. major lesions, subtoxic doses of mercury induce an autoimmune syndrome characterized by an expansion of Th2 cells. In this study, we examined the effect of mercury administration on the outcome of L. major infection in SJL mice. We show that subtoxic doses of mercuric chloride (HgCl2) exacerbate disease outcome in SJL mice resulting in increased footpad swelling and increased parasite burdens. Furthermore, the effects of HgCl2 treatment on resistance to L. major are time-dependent. The nonhealing phenotype was observed only if mice had been treated with HgCl2 prior to L. major infection for at least 1 week, a timepoint at which mice treated with HgCl2 alone had increased splenocyte IL-4 production. HgCl2 treatment also increased production of serum immunoglobulin (Ig)E and IgG1, two IL-4 dependent isotypes. These results show that HgCl2 treatment enhances the susceptibility to L. major in SJL mice, consistent with the induction of host Th2 parameters. These findings have implications for the role of mercury contamination in areas of endemic leishmaniasis.

Regulation of GP63 mRNA stability in promastigotes of virulent and attenuated Leishmania chagasi.

GP63 is a 63-kDa glycoprotein that is abundantly expressed on the surface of all Leishmania species and is involved in several steps of promastigote infection of host cells. Leishmania chagasi has at least 18 haploid msp (major surface protease) genes encoding GP63 that are divided into three classes, mspS, mspL or mspC, according to their unique 3' UTR sequences and differential expression. All three msp classes are constitutively transcribed during virulent promastigote growth in vitro, although mspL mRNA is most abundant during logarithmic phase and mspS mRNA predominates in stationary phase. Thus, the steady state levels of the mspL and mspS mRNAs are post-transcriptionally regulated. Using Actinomycin D to arrest transcription, we found that in virulent promastigotes the half-life (t(1/2)) of mspL mRNA is coordinately modulated with growth phase, decreasing from a mean of 84 min during early logarithmic growth to a mean of 17 min at a stage intermediate between logarithmic and stationary phase. However, in attenuated promastigotes, the t(1/2) of mspL RNA remains the same throughout parasite growth. In contrast to mspL RNA, the t(1/2) of mspS and mspC RNA is constant throughout all growth phases of both virulent and attenuated promastigote growth. The presence of the translation inhibitor cycloheximide increases the t(1/2) of mspL RNA 4-6-fold in both virulent and attenuated promastigotes at all growth phases. These results indicate that the t(1/2) of mspL RNA is maintained by at least two distinct mechanisms - one activated during growth to stationary phase and the other dependent on a labile negative regulatory protein factor(s).

Services research outcomes study: overview of drug treatment population and outcomes.

The study examined a representative sample of the 1,060,000 individuals discharged from drug user treatment in the United States in the 12 months before September 1990, and compared self-reports of behavior 5 years before to 5 years after treatment. Self-reports about recent drug use were compared with urine samples, and the agreement between self-report and drug-test results was high. The key findings are that the number of alcohol and drug users declined markedly, ranging from one-seventh to more than one half; those who continued using drugs after treatment used them less frequently than before treatment; criminal behavior fell between one-quarter to one-half, and primary criminal support fell by one third; full-time employment did not change; homelessness, drug injection, and suicide attempts decreased by more than one-third.

Services research outcomes study: explanation of treatment effectiveness, using individual-level and programmatic variables.

This article examines the explanatory power of programmatic and individual-level variables, using the first nationally representative sample of both treatment facilities and clients. Multivariate statistical models accounted for almost half the variance in post-treatment heroin, marijuana, and any illicit drug use and about one-third the variance in crime. Use of any illicit drug during treatment, even after controlling for pretreatment use, was predictive of every type of drug use after treatment and three of the four major crimes analyzed. In addition, longer lengths of stay decreased the likelihood of alcohol/illicit drug use and criminal behavior after treatment. However, treatment variables added little explanatory power beyond the sociodemographic and pre-treatment variables.

Interaction of Leishmania gp63 with cellular receptors for fibronectin.

The most abundant protein on the surface of the promastigote form of the protozoan parasites Leishmania spp. is a 63-kDa molecule, designated gp63 or leishmanolysin. Because gp63 has been shown to possess fibronectin-like properties, we examined the interaction of gp63 with the cellular receptors for fibronectin. We measured the direct binding of Leishmania to human macrophages or to transfected mammalian cells expressing human fibronectin receptors. Leishmania expressing gp63 exhibited modest but reproducible adhesion to human macrophages and to transfected CHO cells expressing alpha4/beta1 fibronectin receptors. In both cases, this interaction depended on gp63 but occurred independently of the SRYD sequence of gp63, because parasites expressing gp63 with a mutated SRYD sequence bound to macrophages and alpha4/beta1 receptor-expressing cells as well as did wild-type parasites. The contribution of gp63 to parasite adhesion was more pronounced when the assays were performed in the presence of complement, suggesting that the receptors for complement and fibronectin may cooperate to mediate the efficient adhesion of parasites to macrophages. The interaction of gp63 with fibronectin receptors may also play an important role in parasite internalization by macrophages. Erythrocytes to which gp63 was cross-linked were efficiently phagocytized by macrophages, whereas control erythrocytes opsonized with complement alone bound to macrophages but remained peripherally attached to the outside of the cell. Similarly, parasites expressing wild-type gp63 were rapidly and efficiently phagocytized by resting macrophages, whereas parasites lacking gp63 were internalized more slowly. This rapid internalization of gp63-expressing parasites was dependent on the beta1 integrins, because pretreatment of macrophages with monoclonal antibodies to the beta1 integrins decreased the internalization of gp63-expressing parasites. These observations indicate that complement receptors are the primary mediators of parasite adhesion; however, maximal parasite adhesion and internalization may require the participation of the beta1 integrins, which recognize fibronectin-like molecules such as gp63 on the surface of the parasite.

Reports of smoking in a national survey: data from screening and detailed interviews, and from self- and interviewer-administered questions.

PURPOSE: This study compares responses to questions about smoking in a brief screening interview with those from a subsequent, more detailed interview; it also compares responses to self-administered questions and questions administered by interviewers. The data are from the 1994 National Household Survey on Drug Abuse (NHSDA). METHODS: About 22000 respondents completed the main questionnaire of the 1994 NHSDA. Earlier, a member of each sample household had been asked to provide screening information, including smoking status, for each person in the household. Then, one or more persons in the household were interviewed about their own smoking and drug use; for some respondents, the questions about smoking were self-administered and for others they were administered by an interviewer. We examined discrepancies between reports about smoking from the screening data and main interview data; we also compared the results across the two versions of the main interview smoking questions (self and interviewer-administered). RESULTS: The screening data produced lower estimated rates of smoking than did the main interview data, particularly when proxies provided the screening data. In the main interviews, self-administered questions produced higher estimates of the prevalence of smoking than interviewer-administered questions, but only for adolescents. CONCLUSIONS: Proxies can provide some information about smoking, although the data are likely to be biased for younger age groups and for infrequent smokers. For adolescents, self-administration appears to elicit more candid reports about smoking than interviewer administration. In addition, multiple items may help to capture smoking reports by persons who are reluctant to admit they have smoked recently or whose status as smokers is unclear.

Leishmania, macrophages and complement: a tale of subversion and exploitation.

Leishmania are intracellular protozoan parasites which reside primarily, if not exclusively, in host mononuclear phagocytes. Several studies have demonstrated that infectious promastigotes rapidly and efficiently fix complement when they encounter serum components during their transmission to the mammalian host. Activation of the complement system by a microorganism can have 3 distinct biological effects. First, fixation of the terminal complement components can result in complement-mediated lysis. Second, fixation of the 3rd component of complement can lead to opsonization of the organism for uptake by phagocytic cells. Finally, the elaboration of the complement anaphylotoxins, C3a and C5a, can lead to inflammation. In the present chapter, we discuss the interaction of leishmania promastigotes with the complement system. We show that infectious promastigotes avoid the lytic effects of complement and resist fixation of the terminal complement components. At the same time, however, these organisms depend on fixation of opsonic complement to invade host mononuclear phagocytes efficiently. We discuss the mechanisms which allow metacyclic leishmania promastigotes to exploit the opsonic properties of complement and the receptors on macrophages involved in leishmania recognition. The role of complement mediated inflammatory processes in the host response to leishmania infection is an area which requires additional study.

Exploitation of the complement system by Leishmania promastigotes.

Complement has long been acknowledged as an important component of host defense to extracellular pathogens. David Mosser and Andrew Brittingham here describe how Leishmania spp, intracellular pathogens of mononuclear phagocytes, exploit the opsonic and chemotactic effects of complement to initiate infection in the mammalian host.

Effect of amplification of the Cap b locus on complement-mediated bacteriolysis and opsonization of type b Haemophilus influenzae.

Amplification of the Cap b locus of Haemophilus influenzae occurs frequently in clinical isolates and has been proposed to be a mechanism by which this organism evades host defense. To determine if amplification of this locus affected complement fixation, in vitro studies to determine complement-mediated bacteriolysis and complement-mediated opsonization of an isogenic set of organisms containing 2, 3, and 4 copies of the Cap b locus were performed. Organisms containing 4 copies of the Cap b locus were significantly more resistant to antibody-dependent, classical complement pathway-directed bacteriolysis than were organisms containing 2 copies. Organisms containing 3 copies of this locus exhibited intermediate susceptibility to lysis. Complement-mediated opsonization of these organisms was assessed by determining the degree of binding of bacteria to murine or human macrophages or to nonphagocytic cells transfected with the genes for human Mac-1, the complement receptor type 3. In all three assay systems, organisms containing 4 copies of the Cap b locus bound less well than did organisms containing 2 copies of this locus. Consistent with their decreased susceptibility to lysis and opsonization, organisms with 4 copies of the Cap b locus fixed less C3 than did organisms containing 2 copies. These data demonstrate that amplification of the Cap b locus is associated with decreased susceptibility to complement-mediated lysis and decreased complement-mediated opsonization and suggest that amplification is used by these pathogens to increase their resistance to complement-dependent host defense mechanisms [correction of mecanisms].

Role of the Leishmania surface protease gp63 in complement fixation, cell adhesion, and resistance to complement-mediated lysis.

The Leishmania surface protease gp63 has been identified as a parasite virulence factor. To better define the role of gp63 in Leishmania infectivity, the interaction of recombinant gp63 with complement and complement receptors was examined. On Leishmania, gp63 was not necessary for complement fixation. Complement activation occurred on transfected organisms expressing varying amounts of gp63 and on organisms expressing a mutant form of gp63 devoid of proteolytic activity. However, organisms expressing wild-type gp63 on their surface fixed only small amounts of the terminal complement components and were dramatically more resistant to lysis by complement than were those lacking functional gp63. Organisms expressing wild-type gp63 more rapidly converted C3b on their surface to a form that exhibited the neoantigen of iC3b and interacted avidly with cells expressing Mac-1, the receptor for iC3b. Complement fixation by transfected mammalian cells expressing recombinant Leishmania gp63 on their surface was also examined. The presence of Leishmania gp63 on the surface of these cells converted them into efficient activators of complement. Cells expressing gp63 on their surface fixed complement and bound avidly to the human complement receptors. The proteolytic activity of this molecule was not necessary for complement activation or adhesion to complement receptors. Thus, gp63 may contribute to parasite virulence by exerting a novel type of control over complement fixation. Organisms expressing gp63 can exploit the opsonic properties of complement while avoiding its lytic effects.

Balanced reciprocal translocation mosaicism: how frequent?

We describe 2 cases of balanced reciprocal translocation (BRT) mosaicism. The frequency of this aberration in the population referred to our laboratory was determined and compared to those frequencies reported in the literature by other clinical cytogenetics laboratories. The extent of BRT mosaicism was also examined in surveys of parental populations, which are less likely to have a bias due to ascertainment on the basis of abnormal phenotype. the frequencies in the postnatal and prenatal populations examined in this study were calculated to be 5.7 x 10(-5) (95% confidence interval is 3.2-8.2 x 10(-5)) and 4.1 x 10(-5) (95% confidence interval is 2.0-6.2 x 10(-5)). However, in view of the extent of variation reported in the various studies, these estimates should be considered first approximations of the true frequency.