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C Luz

Publications and source records attributed to C Luz.

11 recordsLinked to original sources
PubMed2005

Potential of oil-based formulations of Beauveria bassiana to control Triatoma infestans.

The in vitro development of Beauveria bassiana conidia was monitored when immersed in six concentrations of seven non-ionic (MP 6400, MP 600, Renex 60, Renex 95, Span 80, Tween 20 and Tween 80) and three anionic (DOS 75, Hostapaval BVQ 9 and Surfax 220) surfactants and 11 vegetable oils (linseed, soybean, groundnut, rapeseed, thistle, sunflower, olive, sesame, corn, castor, and babassu). The influence of the oils on the settling behavior of Triatoma infestans nymphs and the activity of an oil-water formulation of the fungus against this vector under laboratory and simulated field conditions were also determined. With exception of DOS 75 and Surfax 220 germination of conidia on complete medium was >98% at 24 h after exposure to surfactants up to 10%. Elevated rates of germination (>25%) were observed in 10% corn, thistle and linseed oil 8 days after incubation. Pure oils had a significant repellent effect to T. infestans. Repellency decreased generally at 10% of the oil and some oils showed some attractiveness for nymphs when tested at 1%. Nymphs were highly susceptible to oil-water formulated conidia, even at unfavorable moisture for extra-tegumental development of the fungus on the insect cuticle.

Animals↗
PubMed2000

Effects of fluctuating moisture and temperature regimes on the infection potential of Beauveria bassiana for Rhodnius prolixus.

The effect of both moisture and temperature on the infective potential of Beauveria bassiana to the Chagas' disease vector, Rhodnius prolixus, was studied under fluctuating regimes. At constant 25 degrees C, contaminated first-instar nymphs exposed to increasing daily periods of initial exposure to 97% RH, followed by transfer to reduced humidity (43, 53, 75, and 86% RH), showed a significant reduction in mortality when the 97% RH exposure time declined from 12 to 8 h per day. The duration of disease incubation depended on the daily 97% RH exposure time. Under fluctuating regimes of both humidity (97% RH versus 75% RH) and temperature (15/28, 20/25, 25/28, and 25/35 degrees C), first-instar mortality was affected by weather conditions, daily 97% RH exposure time (8, 12, and 16 h per day), and number of temperature and humidity fluctuations before transferring tested insects to constant unfavorable conditions. In most cases, at 12/12 h alternating cycles, high and rapid mortality required five cycles. Under these fluctuating regimes, fungus-induced mortality and mortality time were similarly affected in third- and fifth-instar nymphs by the daily 97% RH exposure time. Despite a lower susceptibility of older larval stages, mortality rates in insects exposed for at least 12 h per day at 97% RH remained very high except at 15 degrees C. Moisture and temperature regimes at 12/12 h cycling significantly affected the dose-mortality response in first-instar nymphs. The most favorable conditions consisted of 97%-20 degrees C combined with either 75%-25 degrees C or 43%-25 degrees C. Under less favorable alternating conditions (lower and higher temperatures) the amounts of inoculum required for killing 50% of first-instar nymphs were 10 or 20 times higher. From a vector control standpoint, daily high humidity appears to be the most crucial climatic constraint. B. bassiana has the potential to control R. prolixus populations with applications made during the rainy seasons when humidity is high.

Animals↗
PubMed1999

Dependence of the entomopathogenic fungus, Beauveria bassiana, on high humidity for infection of Rhodnius prolixus.

The impact of relative humidity (RH) on the infective potential of the isolate Bb INRA 297 of Beauveria bassiana (Bals.) Vuillemin (Deuteromycotina: Hyphomycetes) against first instar nymphs of Rhodnius prolixus Stål. (Hemiptera: Reduviidae) was determined. Fungus-treated insects were exposed to RHs ranged from 75 to 100% at 25 degrees C. Results clearly showed a threshold of humidity at ca. 96% for high and rapid mortality. After initial exposure to increasing periods of 97% (4, 8, 16, 24, 36 and 48 h) and subsequent transfer to constant lower RHs (43, 53, 75 and 86%) at a constant 25 degrees C, an incubation of at least 48 h at 97% RH was necessary to kill all insects. On changing RHs of 97/75% and different regimes of temperature (15/28 degrees C, 20/25 degrees C, 25/28 degrees C, and 25/35 degrees C), at least 72 h of initial exposure at 97% RH for the 15/28 degrees C regime, 48 h for the 20 degrees/25 degrees C and 25/28 degrees C regimes and 36 h for 25/35 degrees C were needed to kill all insects over a 6-day incubation time. Delayed exposure to favorable moisture condition (97% RH), significantly affected infection for up to a 3-day delay within the various temperature-humidity regimes tested.

Animals↗
PubMed1998

Factors affecting conidial production of Beauveria bassiana from fungus-killed cadavers of Rhodnius prolixus.

The epizootic potential of Beauveria bassiana for control of the triatomine vectors of Chagas' disease was investigated by studying the effects of both biotic and abiotic factors on the recycling of a highly virulent fungal isolate from fungus-killed cadavers of Rhodnius prolixus. The conidial production of B. bassiana from mummified cadavers of R. prolixus required high RH levels of at least 96.5% RH. At 97% RH and 25 degrees C, the amount of conidia per insect ranged from 5.3 x 10(6) (on first-instar larval cadavers) to 1.7 x 10(8) (on adult cadavers) depending on the size of the different stages of development of the host. Under optimal conditions, B. bassiana sporulation from R. prolixus cadavers took place in 4 to 5 days after death. At a high humidity level (97% RH) the intensity of the conidial production from Rhodnius cadavers was little affected by temperature over a range from 15 to 25 degrees C, but it declined at 28-30 degrees C and was null at 35 degrees C. There was only a weak influence of the blood meal of nymphs and its timing on the conidial production from B. bassiana-killed cadavers. The recycling capacity of different B. bassiana isolates, selected for their pathogenic activity to R. prolixus, did not differ. From a vector control standpoint, high humidity appears to be the most crucial climatic constraint. The recycling ability of B. bassiana on fungus-killed R. prolixus might contribute to the regulation of triatomine vectors only after applications during the rainy seasons.

Animals↗
PubMed1998

Beauveria bassiana (Hyphomycetes) as a possible agent for biological control of Chagas disease vectors.

Beauveria bassiana (Balsamo) Vuillemin (isolate CG306) was tested on 3rd instars of 9 Triatoma spp., 4 Rhodnius spp., 2 Panstrongylus spp. and Dipetalogaster maxima (Uhler) at 25 degrees C and 50% RH. Quantitative sporulation of the fungus on cadavers was studied at 25 degrees C and 97% RH. Mortality, estimates of survival time, and conidial production on cadavers differed significantly among the genera and species tested. Panstrongylus herreri Wygodzinsky, Dipetalogaster maxima, Triatoma picturata Usinger, Rhodnius robustus Larrousse, Rhodnius prolixus Stål, Triatoma infestans (Klug), and Triatoma brasiliensis Neiva were most susceptible to fungal infection. Most conidia per cadaver were produced on Triatoma williami Galvão, Souza & Lima and Triatoma lecticularia (Stål). Results indicate that B. bassiana (CG306) might be a candidate for control of important or potential vectors of Trypanosoma cruzi using the fungus as a bioinsecticide.

Animals↗
PubMed1997

Temperature and moisture requirements for conidial germination of an isolate of Beauveria bassiana, pathogenic to Rhodnius prolixus.

The effects of temperature, relative humidity and water activity on germination of conidia of an isolate of Beauveria bassiana (Bals.) Vuill. pathogenic to the triatomine vector of Chagas' disease, Rhodnius prolixus Stål., were investigated in vitro. Germination occurred at temperatures between 15 degrees C and 35 degrees C under saturated atmosphere and the optima ranged from 25 degrees C to 30 degrees C. At the extreme temperatures tested (15 degrees C and 35 degrees C) the germination process was delayed, but germination rates reached more than 95%. Germination of B. bassiana conidia was strongly affected by moisture conditions. The availability of water, in both atmospheric and liquid conditions, caused changes in germination times as well as in germination rates. For example, at 25 degrees C + 0.5 degrees C, germination took place within 20 h at 95.5% RH, whereas it needed 72 h of incubation at 90% RH. Germination times increased as the water activity declined from 0.96 a(w) to 0.92 a(w). Below 0.92 a(w), no germination was observed after a 72 h incubation time.

Journal Article↗
PubMed1995

Evaluation of immune parameters in depressed patients.

The association between depression and altered immunological activities has repeatedly been suggested, but experimental data show contradictory results. In this work, cellular and humoral immunological activities were evaluated in patients presenting major depression, unipolar subtype. Natural killer cell activity (NKCA) was significantly reduced in patients as compared to healthy controls (p < 0.001). However, lymphocyte mitogenic responses and immunoglobulin titers (IgG, IgM, and IgA) were similar for all samples. Hematological, hormonal, and nutritional variables presented normal values in patients and in controls. A familial history of depression was related to lower NKCA and higher phytohemagglutinin responses (p < 0.01). These data suggest possible differential inhibition of cellular immune responses in depressed patients.

Adult↗
PubMedDate not supplied

Selection of Beauveria bassiana and Metarhizium anisopliae isolates to control Triatoma infestans.

Twenty three isolates of Beauveria bassiana and 13 isolates of Metarhizium anisopliae were tested on third instar nymphs of Triatoma infestans, a serious vector of Chagas disease. Pathogenicity tests at saturated humidity showed that this insect is very susceptible to fungal infection. At lower relative humidity (50%), conditions expected in the vector microhabitat, virulence was significantly different among isolates. Cumulative mortality 15 days after treatment varied from 17.5 to 97.5%, and estimates of 50% survival time varied from 6 to 11 days. Maintaining lower relative humidity, four B. bassiana and two M. anisopliae isolates were selected for analysis of virulence at different conidial concentrations and temperatures. Lethal concentrations sufficient to kill 50% of insects (LC50) varied from 7.1 x 10(5) to 4.3 x 10(6) conidia/ml, for a B. bassiana isolate (CG 14) and a M. anisopliae isolate (CG 491) respectively. Most isolates, particularly B. bassiana isolates CG 24 and CG 306, proved to be more virulent at 25 and 30 degrees C, compared to 15 and 20 degrees C. The differential virulence at 50% humidity observed among some B. bassiana isolates was not correlated to phenetic groups in cluster analysis of RAPD markers. In fact, the B. bassiana isolates analyzed presented a high homogeneity (> 73% similarity).

Animals↗
PubMedDate not supplied

Development of Rhodnius prolixus (Hemiptera: Reduviidae) under constant and cyclic conditions of temperature and humidity.

Development of Rhodnius prolixus after eclosion until the adult stage was studied at constant temperatures (T), 15, 20, 25, 28, 35 C, and relative humidities (RH), 75, 86 and 97%, and fluctuating (16/8 hr) temperatures, T I/II, 15/28 C, 20/25 C, 25/28 C and 25/35 C, and relative humidities, RH I/II, 86/75% and 97/75%. Eclosion or molting were not observed at 15 C and 86 or 97% RH, respectively. At 35 C and 75% RH only few insects molted. By alternating T I/II, 15/28 C and 25/35 C, insects developed at high frequency. Cumulating the average lengths of the interphases within independent groups for each instar, R. prolixus reached the adult stage most rapidly (86.7 days) and at highest frequency per instar (mean: 91.8%) at 28 C and 75% RH. Under fluctuating T I/II, development was completed within 100 days or less at 25/28 C and 25/35 C with high rates of hatch and molting. Development was slowest at fluctuating TI/II, 15/28 C and 20/25 C (>185 days), and at constant 20 C (>300 days). Mortality was higher at constant 97% RH or fluctuating RH I, 97%, than at constant or fluctuating 86% RH. Refeeding was minimal at optimal conditions of T and RH for development. The most refeeding was observed at a constant 35 C.

Animals↗