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R de la Vega

Publications and source records attributed to R de la Vega.

8 recordsLinked to original sources
PubMed2000

Thermal constant estimation in tropical horse tick, Anocentor nitens (Acari:Ixodidae).

Experience has demonstrated that the exclusive use of acaricides as a control method against cattle ticks causes several problems, and is not totally effective. Other methods need to be added in order to achieve better and more profitable control of these parasites. Groups of 12 to 15 engorged ticks, bred on bovines, were individually incubated at six temperatures (T = 24, 26, 28, 30, 32, and 34 degrees C) and four relatives humidities (RH = 100, 80, 75.5, and 70%), creating 24 variants. The onset of oviposition and eclosion (emergence of larvae from eggs) was observed in all ticks, and preeclosion times (PET) were determined. A linear regression equation for the velocity of development with temperature as a function of the inverse of PET was calculated for each RH value. For each RH the minimum thermal threshold (MTT) was obtained by extrapolation and the effective temperature summation (ETS) calculated from the equation (incubation temperature--MTT) x PET. The four MTT values obtained were not significantly different; the mean value of MTT was 15.25 degrees C. The thermal constants did not prove to be not statistically different over the range of RH values employed in the experiments, the mean being 354.04 degrees C-day.

Animals↗
PubMed2000

Larval survival of Anocentor nitens under simulated natural conditions.

Basic knowledge about the survival of free living stages of ticks is of great importance as a practical tool to improve control methods. For Anocentor nitens there is little information on this subject. Eighty-four engorged females were incubated at 30 degrees C and 100% relative humidity. After 17 days, groups of 5,500 eggs each were collected and isolated in vials. Age zero was defined as 10 days after eclosion had begun. At this time vials with larvae were attached to 40 Sorghum halepense plants sowed in clay pots, under outdoor conditions, and separated from one another by 30 cm in order to prevent the larvae from mixing. Four hours later vials were retired and the larvae remaining in the vials were counted. The next day four plants were sampled and this survival considered as 100%. Each week for eight weeks the same sampling procedure was performed. The remaining four plants were used to determine the maximum larval survival (MLS). Four repetitions of the procedure were performed, two in March 1989 and two in September 1989.

Animals↗
PubMed2000

Artificial feeding in Boophilus microplus (Acari:Ixodidae) through micropipettes.

Newly molted Boophilus microplus females obtained in a laboratory at 30 degrees C and environmental relative humidity (RH) were employed. An original device was used to hold ticks during feeding. Three groups of 15 ticks each were created: unfed, fed with heparinized blood, and fed with defibrinated blood. Ticks were weighed before and after feeding. Females were restricted by group in three isolators attached on the skin of a bovine. Ten sexually competent males were added to each isolator. Time of coupling, tick mortality, time of detachment, and weight of engorged ticks were determined. Engorged females were incubated at 30 degrees C and 100% RH. Periods of nonparasitic phase, laying efficiency, and fertility of eggs were noted. There were no statistical differences between the three groups. This means that feeding with micropipettes does not affect the non-parasitic phase of B. microplus, the differences between heparinized and defibrinated blood are not significant.

Animals↗
PubMed1996

Age and weight relationship in Boophilus microplus (Ixodoidea: Ixodidae) larvae.

The study of the age of free-living stages of ticks is not a frequent subject in acarology research. Baseline knowledge and some possible applications both in research and in tick control are to be considered. Sixty engorged females were incubated at 28 +/- 1 degrees C and 100% relative humidity. Age zero of larvae was established at 10 days after the beginning of eclosion. Larvae were weighted in paper envelopes in groups ranging from 150 to 400 each. Live weight means (LWM) and dry weight means (DWM) were obtained. All larvae have defecated at age zero. Maximum survival was 57 days. Larval age was also expressed as effective temperature summings (ETS). LWM declines slightly with age. DWM has a linear relationship to age from 0 to 504 degrees C-day with a determination coefficient of 0.95. Absolute water content increases from 0 to 504 degrees C-day; further water content diminishes. Dry matter weight declines just to 504 degrees C-day of age. It might be theoretically possible to estimate the age of larvae in pasture by weighing groups of them.

Aging↗
PubMedDate not supplied

[Affective disorders and solar activity].

INTRODUCTION: The present work discusses the link between solar activity and appearance of affective disorders. Solar activity is reflected by the Wolf number, which is given by the formula R = K (10 g + f), where g corresponds to the groups of sunspots and f is the total number of sunspots. METHODS: We examined 1,212 clinical files at the Clínica Psiquiátrica Universitaria, Santiago de Chile. Patients with major depressions and manic disorders, who were admitted to the clinic for the first time and had no previous treatment were considered. We examined the correlation between annual incidence of hospitalization and average Wolf numbers for those years, included in the period 1990-2000, which corresponds to a complete solar cycle of 11 years. RESULTS: An important number of hospitalizations of depressive patients occurred during years of low solar activity, and there was a slight increase in the number of manic patients during years of high solar activity. Depressive disorders showed a negative correlation with solar activity, the Pearson coefficient being equal to -0.72. Manic disorders showed a positive correlation, with coefficient equal to +0.334. CONCLUSIONS: Depressive disorders have an inverse correlation with solar activity, while manic disorders have a positive correlation.

Adolescent↗
PubMedDate not supplied

[Isolation of aspartic proteinases at different stages of development of Boophilus microplus tick].

The magnitud of tisular expression of aspartic proteinases at juvenile stages was analyzed in adult young Boophilus microplus ticks as well as the effect of one of the most widely used aspartic proteinase inhibitors (pepstatin A) on their development. The isolation and quantification of acid proteolytic activity was performed in samples of parasites with different stages of the digestive process where aspartic-proteinase activity was confirmed and a tendency to increased values of enzymatic activity per miligram of total weight was observed during the development of adults female ticks, with a lowering of this ratio just when they are full up. Adding pepstatin A to the ingesta at 14 and 70 mmol concentrations had no effect on the viability of young female ticks while they were kept in vitro for 24 h, so this rules out the immediate toxic effects of this compound. However, in those experiments where adult female ticks after receiving the various ingestas, are put together with sexually competent male ticks in isolators for 6-7 days, the viability showed different results (p< 0,01) at a 70 mmol concentration. The effect on the development of young adult female ticks was slight, but it indicates hat there might be a selective inhibitory action of pepstatin A on aspartic-dependent enzymes.

Animals↗