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Biomedical subjects

R G Lalonde

Publications and source records attributed to R G Lalonde.

16 recordsLinked to original sources
PubMed2006

Chaotic dynamics can select for long-term dormancy.

Extended dormancy in a population is evolutionarily costly unless some variance in season-to-season fitness (usually driven by variance in environmental quality) makes bet hedging useful. Consequently, dormancy in a population is usually accepted as evidence of environmental variance. Using a Ricker-type model with heritable variation in dormancy, we show that this need not be so. Intrinsic population dynamics can generate chaotic fluctuations in the absence of environmental variance. Chaotic dynamics increase the frequency of a range of dormant strategists under natural selection, even when mortality during dormancy is relatively high. The buffering effect of dormant individuals then eliminates chaotic dynamics or generates periodic orbits of relatively low amplitude. These stabilized populations harbor a high frequency of dormant individuals that express a range of propensities to enter dormancy.

Biological Evolution↗
PubMed2005

Influence of RANTES, SDF-1 and TGF-beta levels on the value of interleukin-7 as a predictor of virological response in HIV-1-infected patients receiving double boosted protease inhibitor-based therapy.

OBJECTIVES: Interleukin-7 (IL-7), RANTES (regulated on activation, normal T cell expressed and secreted), stromal cell-derived factor-1 (SDF-1) and transforming growth factor-beta (TGF-beta) appear to share certain biological properties in vitro and all are involved in HIV-1 disease progression. Our earlier observations indicated that IL-7 levels decrease upon CD4 T-cell recovery and represent a new, independent predictor of virological response. Here, we examine associations among circulating levels of IL-7, RANTES, SDF-1 and TGF-beta in hopes of gaining insight into their contribution to the predictive value of IL-7. METHODS: Levels of IL-7, RANTES, SDF-1 and TGF-beta, and immune and viral parameters were assessed in HIV-1-infected patients. RESULTS: Cross-sectional (n=148) and longitudinal (n=36) analyses showed that levels of IL-7, but not RANTES, SDF-1 or TGF-beta, were increased in HIV-1-infected adults compared with those of healthy controls. In the cross-sectional study, levels of IL-7 were correlated with RANTES (r=0.31, P=0.002) and TGF-beta (r=0.53, P<0.001) but not with SDF-1 (r=0.12, P=0.22), and these associations were more pronounced in patients with CD4 T-cell counts >200 cells/microL. In contrast to IL-7, levels of RANTES, SDF-1 and TGF-beta were not correlated with CD4 T-cell counts. Longitudinal analysis revealed a marked decline in IL-7 levels accompanied by an increase in CD4 T-cell count following antiretroviral therapy (ART), but no changes in RANTES, SDF-1 or TGF-beta levels. Multivariate regression analysis showed no influence of baseline RANTES, SDF-1 or TGF-beta levels on the value of IL-7 as a predictor of virological response at 48 weeks. CONCLUSIONS: Collectively, these results indicate that changes in IL-7 levels did not induce changes in RANTES, SDF-1 or TGF-beta. Furthermore, they indicate that RANTES, SDF-1 or TGF-beta levels do not explain the predictor value of IL-7 in patients receiving ART.

Adult↗
PubMed2003

Interleukin-7 levels may predict virological response in advanced HIV-1-infected patients receiving lopinavir/ritonavir-based therapy.

OBJECTIVES: To examine the relationship between levels of the T-cell regulatory cytokine interleukin-7 (IL-7) and CD4 cell counts during immune reconstitution and to assess its prognostic value in advanced HIV-1-infected patients receiving lopinavir/ritonavir-based therapy. METHODS: Thirty-six HIV-1-infected adults who completed 48 weeks of follow-up visits were included in this prospective study. Patients having failed two or more antiretroviral therapy regimens were treated with lopinavir/ritonavir-based therapy. An enzyme-linked immunosorbent assay was used to determine IL-7 plasma levels, flow cytometry was used to analyse cell surface antigens, and polymerase chain reaction was used to quantify plasma HIV-1. RESULTS: Pretreatment IL-7 levels were elevated in all patients (mean 11.0 pg/mL) and were negatively correlated with CD4 cell counts and age (r=-0.59, P<0.001 and r=-0.57, P<0.001, respectively). During the course of treatment, IL-7 levels decreased by 34% while CD4 cell numbers progressively increased by 88%. Multivariate regression analysis showed that only pretreatment IL-7 levels predicted viral load at 48 weeks when controlling for baseline CD4 cell counts, viral load and patient demographics. CONCLUSIONS: These findings are consistent with regulation of T-cell recovery by IL-7, and suggest that IL-7 measurements might be used to predict virological response.

Adult↗
PubMed2001

Prevalence of bronchial hyperresponsiveness among HIV-infected men.

HIV infection is associated with immune dysregulation primarily affecting T-cell function, whereas asthma is related to excessive T-cell activity. We compared the prevalence of asthma and related conditions among adult seropositive men with the prevalence among men of similar age drawn from the general population. Seropositive men had a significantly more frequent occurrence of wheezing (54.4 versus 21.2%), bronchial hyperresponsiveness (BHR) to methacholine (26.2 versus 14.4%), and an elevated total serum IgE (37.8 versus 25.7%). Differences in BHR were significant only among smokers. Among the seropositive men, FEV(1)/FVC and an elevated IgE were the principal determinants of BHR. Our results suggest that the frequency of asthma may be underestimated in HIV disease. Furthermore, the frequent occurrence of BHR in HIV-infected men who smoke (30.1%) suggests this group may be especially susceptible to the adverse effects of cigarette smoke.

Adult↗
PubMed1998

Does in vitro susceptibility to rifabutin and ethambutol predict the response to treatment of Mycobacterium avium complex bacteremia with rifabutin, ethambutol, and clarithromycin? Canadian HIV Trials Network Protocol 010 Study Group.

The in vitro susceptibilities of baseline Mycobacterium avium complex (MAC) blood isolates from 86 patients with AIDS who were treated with clarithromycin, ethambutol, and rifabutin were determined to examine whether these results predict bacteriologic response to treatment. No patient received prior prophylaxis with clarithromycin or azithromycin. Minimum inhibitory concentrations (MICs) of clarithromycin for all isolates were < or = 2 micrograms/mL. The median MIC of rifabutin was between 0.25 and 0.5 microgram/mL, and all isolates were susceptible to < or = 2 micrograms of rifabutin/mL. The median MIC of ethambutol was 4 micrograms/mL, and the MIC90 was 8 micrograms/mL. There was no correlation between ethambutol susceptibility and subsequent bacteriologic clearance. At all time points through week 12, bacteriologic clearance occurred more frequently in patients with isolates for which MICs of rifabutin were lower, but this difference was statistically significant only at week 2. Susceptibility testing for baseline MAC isolates from AIDS patients not previously treated with clarithromycin or azithromycin does not appear to be useful in guiding therapy.

AIDS-Related Opportunistic Infections↗
PubMed1996

A comparison of two regimens for the treatment of Mycobacterium avium complex bacteremia in AIDS: rifabutin, ethambutol, and clarithromycin versus rifampin, ethambutol, clofazimine, and ciprofloxacin. Canadian HIV Trials Network Protocol 010 Study Group.

BACKGROUND: Bacteremia with the Mycobacterium avium complex is common in patients with the acquired immunodeficiency syndrome (AIDS), but the most effective treatment for this infection remains unclear. METHODS: We randomly assigned 229 patients with AIDS and M. avium complex bacteremia to receive either rifampin (600 mg daily), ethambutol (approximately 15 mg per kilogram of body weight daily), clofazimine (100 mg daily), and ciprofloxacin (750 mg twice daily) (the four-drug group) or rifabutin (600 mg daily), ethambutol (as above), and clarithromycin (1000 mg twice daily) (the three-drug group). In the three-drug group the dose of rifabutin was reduced by half after 125 patients were randomized, because 24 of 63 patients had uveitis. RESULTS: Among 187 patients who could be evaluated, blood cultures became negative more often in the three-drug group than in the four-drug group (69 percent vs. 29 percent, P<0.001). Among patients treated for at least four weeks, the bacteremia resolved more frequently in the three-drug group (78 percent vs. 40 percent, P<0.001). In the three-drug group, bacteremia resolved more often with the 600-mg dose of rifabutin than with the 300-mg dose (P=0.025), but the latter regimen was more effective than the four-drug regimen (P<0.05). The median survival was 8.6 months in the three-drug group and 5.2 months in the four-drug group (P = 0.001). The median Karnofsky performance score was higher in the three-drug group than in the four-drug group from week 2 to week 16 (P<0.05). Mild uveitis developed in 3 of the 53 patients receiving the 300-mg dose of rifabutin, an incidence about one quarter that observed with the 600-mg dose (P<0.001). CONCLUSIONS: In patients with AIDS and M. avium complex bacteremia, treatment with the three-drug regimen of rifabutin, ethambutol, and clarithromycin leads to resolution of the bacteremia more frequently and more rapidly than treatment with rifampin, ethambutol, clofazimine, and ciprofloxacin, and survival rates are better.

AIDS-Related Opportunistic Infections↗
PubMed1996

Once-weekly intraocular injections of ganciclovir for maintenance therapy of cytomegalovirus retinitis: clinical and ocular outcome.

The clinical course and the outcome of treatment were studied in 40 patients with primary cytomegalovirus (CMV) retinitis in 57 eyes. All had received one 14-day course of intravenous ganciclovir and all were free of other end-organ CMV disease. All afficted eyes received weekly intravitreal injections of 400 micrograms of ganciclovir for maintenance therapy. Median survival of patients was at least 13 months. Fifteen patients had 19 new opportunistic infections during the observation period, but none developed new nonocular CMV disease. Active retinitis recurred in 68.4% of the eyes while receiving maintenance therapy, with a median time to progression of 14.7 weeks. CMV retinitis occurred in 30.4% of the previously uninvolved eyes (follow-up, 3.1 years). Bacterial endophthalmitis complicated treatment in 1 eye, and 5 eyes developed a retinal detachment. Thus, the long-term treatment of CMV retinitis with weekly intraocular injections of ganciclovir was associated with survival and ocular outcome similar to those reported with systemic ganciclovir.

AIDS-Related Opportunistic Infections↗
PubMed1990

Risk of occupational exposure to Herpesvirus simiae (B virus) in Quebec.

Herpesvirus simiae (B virus) causes a mild infection in macaques. Transmission to humans may result in life-threatening encephalomyelitis. To evaluate the risk of occupational exposure to B virus we surveyed the directors of 11 biomedical laboratories in Quebec that use monkeys. Information was obtained on the monkey population and on the use of infection control measures recommended by the US Centers for Disease Control (CDC), Atlanta. Of the 519 monkeys belonging to susceptible species the serologic status was positive in 264 (51%), all captured in the wilds, and it was unknown in 24 (5%). All of the monkeys were caged individually, and newly acquired ones were quarantined for 2 to 8 weeks. Of the 84 workers 52 (62%) handled monkeys whose serologic status was either positive or unknown. Only five laboratories (representing 61% of the workers) complied fully with the CDC guidelines. Nine of the laboratories had a wound management protocol, but only six had a designated specialist for consultation and prophylaxis. Although no cases of B virus infection have been reported from Quebec the severity of human illness necessitates strict adherence to infection control measures and expert management of occupational exposure to susceptible monkeys.

Animals↗
PubMed1985

Trypanosoma cruzi: regulation of mitogenic responses during infection in genetically resistant and susceptible inbred mouse strains.

The outcome of Trypanosoma cruzi infection in inbred strains of mice is under genetic control. The lymphocyte responses to T-cell mitogens and their regulation were investigated in strains of mice resistant or susceptible to T. cruzi. Six to eight days after the inoculation of T. cruzi, resistant and susceptible mice had depressed responses to T-cell mitogens. In resistant B6 mice, suppression was maximal 18 days after infection and it persisted for at least 320 days. The duration of immunosuppression correlated with the persistence of a subpatent parasitemia. In cell mixing experiments, it was determined that the concanavalin A (Con A) responses in the resistant B6 and B6C3F1 mouse strains were suppressed by highly active T-suppressor cells. In the susceptible C3H mice, intense suppression of the Con A responses was detected 14 days after inoculation of T. cruzi. Nevertheless, only weak suppressor cell activity was detected in the infected C3H mice, and suppression was not abrogated by passage through a nylon wool column nor by treatment with antitheta antibodies and complement. Thus, it was suggested that, during the course of infection with T. cruzi, splenic T cells from C3H mice acquired a block in the metabolic pathway for cellular activation by Con A. The influences of T. cruzi epimastigotes on the Con A responses of spleen cells from uninfected mice were then studied. The Con A responses of spleen cells from C3H mice were depressed in the presence of epimastigotes, whereas they were either unaffected or enhanced in spleen cells from B6 mice. Hence, the immunoregulatory events provoked by T. cruzi infection differed in genetically resistant and susceptible mice, and lymphocytes from C3H mice were predisposed to a parasite-induced block in the responses to Con A. Thus, the gene(s) determining the outcome of infection with T. cruzi may be phenotypically expressed through an influence on immunoregulatory events.

Animals↗
PubMed1984

Role of iron in intracellular growth of Trypanosoma cruzi.

Host hypoferremic responses occur during infection with Trypanosoma cruzi, presumably through the transfer of iron to the sites of intracellular parasite replication. Depletion of host intracellular iron stores reduces parasite pathogenicity. It has therefore been hypothesized that T. cruzi requires iron for optimal growth in host cells and that, unlike extracellular pathogens, T. cruzi may benefit from host hypoferremic responses. These hypotheses were examined by the in vitro infection of peritoneal macrophages with T. cruzi. Various doses of desferrioxamine or referrated desferrioxamine were added to the culture medium, and parasite growth was monitored. The influence of treatment on uninfected macrophage morphology, function, and iron content was also verified. Desferrioxamine reduced the rate of amastigote replication in a dose-dependent fashion, whereas referrated desferrioxamine did not. The iron content of desferrioxamine-treated macrophages was decreased by 55% without provoking significant morphological or functional changes. Thus, amastigotes used host cell iron stores for optimal growth, and desferrioxamine reduced growth by depleting host cell iron. Hence, it was suggested that depletion of host intracellular iron stores may protect against T. cruzi and, furthermore, that host responses which transfer iron to the intracellular sites of T. cruzi replication may enhance parasite pathogenicity.

Animals↗
PubMed1984

Role of iron in Trypanosoma cruzi infection of mice.

The role of iron in experimental infection of mice with Trypanosoma cruzi was investigated. B6 mice had a transient parasitemia and a transient anemia, both of maximal intensity 28 d after the inoculation of T. cruzi. There was a biphasic hypoferremic host response to infection with T. cruzi with the peak hypoferremia also occurring 28 d after inoculation of the parasite. The mortality rate from infection was increased from 23% in phosphate-buffered saline-treated B6 mice to 50% in a group of B6 mice receiving iron-dextran (P less than or equal to 0.025), whereas depletion of iron stores with the iron chelator desferrioxamine B and an iron-deficient diet provided complete protection of B6 mice (P less than or equal to 0.05). The mortality rate in the highly susceptible C3H strain was reduced from 100% in the control group to 45% (P less than or equal to 0.025) in the iron-depleted group. The tissue iron stores were altered in mice receiving either iron-dextran or desferrioxamine B and an iron-deficient diet. In vitro, T. cruzi was shown to require both a heme and a nonheme iron source for an optimal growth rate. The effects of iron excess or depletion on the outcome of infection with T. cruzi correlated both with the growth requirements of the parasite for iron and with the availability of intracellular iron. Thus, it was suggested that the hypoferremic response, by sequestering iron within intracellular stores, potentially enhanced the pathogenicity of the intracellular parasites. Furthermore, the in vivo effects of iron excess and depletion correlated with an effect of iron on the growth rate and pathogenicity of the parasite.

Anemia, Hypochromic↗
PubMedDate not supplied

Comparison of rosaramicin and erythromycin stearate for treatment of cervical infection with Chlamydia trachomatis.

The macrolide antibiotic rosaramicin inhibits in vitro growth of Chlamydia trachomatis. Rosaramicin (1 g daily given to 18 patients for seven days) and erythromycin stearate (2 g daily given to 19 patients for seven days) were compared in the treatment of chlamydial cervicitis. Cultures of cervical specimens obtained nine to 11 days and 24-32 days after commencement of therapy were negative for all rosaramicin-treated patients seen at follow-up. The first follow-up culture of one erythromycin recipient was positive. The extent of cervicitis decreased in all patients after treatment, but the only patients to achieve a completely normal cervical appearance were those with minimal-to-moderate lesions before treatment. Gastrointestinal side effects, including nausea, vomiting, and abdominal pain, occurred in ten of 19 patients given erythromycin and in 13 of 18 given rosaramicin. Minimally elevated levels of alanine aminotransferase in serum occurred in four (22.2%) of 18 rosaramicin recipients. It is concluded that rosaramicin and erythromycin stearate both eradicate C. trachomatis cervical infection but frequently cause adverse gastrointestinal effects.

Adolescent↗