Biological control of the stink bug Nezara viridula (Heteroptera: Pentatomidae) by two parasitoids and their interaction in non-crop habitats: a simulation model.

Non-cultivated areas are resting, overwintering, feeding, and/or reproducing habitats for insects, and also places from where crop areas are colonized; thus, they are essential for understanding the biological control programs in agroecosystems. We developed a simulation model for a non-cultivated area of Buenos Aires province (Argentina), and we analyzed the control of Nezara viridula achieved by the action of two parasitoids: the oophagous Trissolcus basalis and the tachinid Trichopoda giacomellii, which attack older nymphs and adults. The model is a discrete time, deterministic, phenomenological, spatially homogeneous with a 1-week time interval simulation model, based on the age-structure and/or stage-structure of N. viridula and its two parasitoids. The host-parasitoid interactions were combined with a degree-day model affecting development times of T. giacomellii pupae and T. basalis pre-imaginal stages. The simultaneous attack of both parasitoid species enables the persistence of the system at low host densities, mediated by the functional response of the parasitoids, identified as population regulation factors. However, if only one parasitoid exists (i.e., only T. basalis or only T. giacomellii) the interaction N. viridula-parasitoid persisted but at higher density of N. viridula. These results explain the successful biological control of N. viridula after the introduction of T. basalis in the 1980s, when T. giacomellii was the only parasitoid present, unable to control N. viridula. Our model shows an indirect competition when both parasitoids are present: the attack of one of them diminished the potential number of hosts available to the other parasitoid species. In the field this interaction is obscured by the hibernation period which acted as a reset mechanism affecting the density and age/stage structure of all three populations. Our model was supported by field observations, and never exhibited the extinction of any of the parasitoids from the interaction.

The functional and numerical responses of Trissolcus basalis (Hymenoptera: Platygastridae) parasitizing Nezara viridula (Hemiptera: Pentatomidae) eggs in the field.

Trissolcus basalis has been used as a biological control agent of its main host, Nezara viridula, in many countries. However, estimations of its functional and numerical responses in the field are lacking. We estimated the density of N. viridula eggs, the proportion of parasitized N. viridula eggs, and the number of T. basalis adults/trap in the field. We transformed relative parasitoid density to an absolute density, and estimated the parasitoid's attack rate, a, and the mutual interference parameter, m, in two ways: following Arditi & Akçakaya (1990) and using the Holling-Hassell-Varley model with two iterative techniques. The attack rate estimated by both methods were a=1.097 and a=0.767, respectively. Parameter m varied less between methods: m=0.563 and m=0.586, respectively, and when used to calculate the number of parasitized N. viridula eggs per m2, differences with the observed values were not significant. The numerical response of T. basalis was affected by the sex allocation of their progeny and the proportion of adult parasitoids trapped decreased with field parasitoid population density. Theoretical models show that 0

[Multiple synchronous urinary tract tumors in a hemodialysis patient]. / Multiple synchrone urologische Tumore bei einem dialysepflichtigen Patienten.

We report the case of a 67-year-old patient on hemodialysis with asymptomatic gross hematuria and increased PSA levels who was diagnosed with invasive bladder cancer. The postoperative histological studies revealed a bilateral renal cell carcinoma, right ureter and renal pelvis carcinoma in situ and prostate cancer. We believe this to be the first case of such a combination of synchronous urinary tract tumors. When treating urological cancer patients on hemodialysis, one should be aware of a possible combination of multiple synchronous urinary tract tumors.

Variations in sex ratio, feeding, and fecundity of Triatoma dimidiata (Hemiptera: Reduviidae) among habitats in the Yucatan Peninsula, Mexico.

Chagas' disease is a major public health concern in most Latin American countries and its prevention is based on insect vector control. Previous work showed that in the Yucatan peninsula of Mexico, houses are transiently infested by adult Triatoma dimidiata, which then fail to establish sustained colonies. The present study was designed to evaluate the seasonality and possible causes of the dispersal of sylvatic T. dimidiata toward the houses and the subsequent failure of colonization. Dispersal was highly seasonal and correlated with temperature, pressure, and wind speed. Analysis of sex ratio, feeding status, and fecundity of sylvatic populations of T. dimidiata indicated a rather low feeding status and low potential fecundity, suggesting that seasonal dispersal may be associated with foraging for better conditions. Also, feeding status and potential fecundity tended to improve in the domestic habitat but remained largely suboptimal, suggesting that these factors may contribute to the ineffective colonization of this habitat.

Probability of Trypanosoma cruzi transmission by Triatoma infestans (Hemiptera: Reduviidae) to the opossum Didelphis albiventris (Marsupialia: Didelphidae).

The probability of Trypanosoma cruzi transmission to opossums by independent events of predation and fecal contamination during feeding ("biting") with positive Triatoma infestans was estimated. Negative female opossums were challenged for 23 hr with 10 infected third and fourth instars of T. infestans, and tests for positivity for T. cruzi by xenodiagnosis were performed at 30, 60, and 90 days. From these data, seven probability parameters were estimated by maximum likelihood, and likelihood ratio statistics confidence intervals were calculated. Simultaneous estimation of p1 (probability that a "bite" will infect an opossum), p3 (probability that a bug that has been eaten by an opossum will infect it), and p6 (probability that the opossum will become infected if faced with an infected triatomine), resulted in p1 = 0.06, p3 = 0.075, and p6 = 0.059. On average, each opossum should be exposed to an average of 700 encounters with bugs during its life, resulting in about eight potentially infective contacts, to produce the 35% opossum prevalence found in the field.

El desafío de la sexualidad

Contiene: La sexualidad como construcción social. Familias. El cuerpo, la identidad y los sentimientos. Infancia. Pubertad y adolescencia. Sexualidad, reproducción y no reproducción. Las enfermedades de transmisión sexual y SIDA. Sexualidad y violencia. Erótica, pornografía y prostitución. . Varones y mujeres ¿como se perciben a sí mismos?

El desafío de la sexualidad

Contiene: La sexualidad como construcción social. Familias. El cuerpo, la identidad y los sentimientos. Infancia. Pubertad y adolescencia. Sexualidad, reproducción y no reproducción. Las enfermedades de transmisión sexual y SIDA. Sexualidad y violencia. Erótica, pornografía y prostitución. . Varones y mujeres ¿como se perciben a sí mismos?

Abundance of Lutzomyia ovallesi but not Lu. gomezi (Diptera: Psychodidae) correlated with cutaneous leishmaniasis incidence in north-central Venezuela.

In north-central Venezuela Lutzomyia gomezi and Lu. ovallesi are the main endophilic/anthropophilic species of phlebotomine sandflies implicated as vectors of cutaneous leishmaniasis (CL). Lutzomyia ovallesi has been found infected with Leishmania braziliensis (1.2%) and less often with Le. mexicana (0.07%), while Le. braziliensis infections have also been found in Lu. gomezi (0.47%). We investigated population densities of these sandflies using two sampling methods with four series of collections between January 1991 and March 1995 at El Ingenio, Miranda State. All-night outdoor collections from a Shannon trap were correlated with indoor collections from CDC light-traps by linear regression, which proved to be statistically significant for both species. Estimated numbers of female sandflies per house per night were found to be proportional to monthly precipitation (i.e. rainfall), with a lag time of seven months for Lu. ovallesi and of six months for Lu. gomezi. Predominance of Lu. ovallesi over Lu. gomezi (c. 10:1) was observed throughout the year, with the number of infected females estimated as 0.043+/-0.047 Lu. ovallesi and 0.0085+/-0.0124 Lu. gomezi per CDC trap per house per night (ratio approximately 5:1). The mean rate of new CL cases per house per year and sandfly abundance were correlated by linear regression, showing a statistically significant relationship for Lu. ovallesi but not for Lu. gomezi. The negative intercept indicated that, on average, the CDC trap density exceeds 800 Lu. ovallesi females/house/year before new CL cases occur at El Ingenio.

Spatial distribution of Triatoma guasayana (Hemiptera:Reduviidae) in hardwood forest biotopes in Santiago del Estero, Argentina.

In the study area Triatoma guasayana Wygodzinsky & Abalos is the only wild triatomine found sympatric with Triatoma infestans (Klug) in peridomestic premises. The Trypanosoma cruzi Chagas wild cycle is centered around the same biotopes occupied by T. guasayana, which are also visited mainly by opossums with annual prevalences of 29-50%. Twelve hectares were sampled for 4 consecutive years during all seasons. During that time, 420 T. Guasayana individuals were collected in 11.3% of 1,188 biotopes of 4 types, which included quimiles (the cactus Opuntia quimilo), chaguares (several species of bromeliads), trees, and logs. Quimiles had the highest percentage of positive biotopes (31.5%) followed by chaguares (22.3%), whereas 5% of the logs were found infested. During all seasons, 9.6-15.2% of biotopes were found infested. Distance to artificial biotopes was not statistically significant when comparing the frequency of triatomine numbers per biotope in all biotope-season combinations. With the exception of quimiles in the fall, the mean number of triatomines was higher in chaguares during all seasons. Triatomine abundance by biotope and season strata showed a clumped distribution, except for the quimiles biotope during the summer. When pooling by seasons, the mean number of triatomines in chaguares and quimiles biotope was higher than in logs and trees, with all biotopes showing a strong clumped distribution. When pooling by biotopes, the mean number of T. guasayana was relatively similar for all seasons, with a strong clumped distribution. The strong contagious distribution of T. guasayana in the hardwood forest biotopes may explain the maintenance of the wild cycle of T. cruzi, despite the low number and the low prevalences of the insect vector.

Biochemistry of proteins that bind and metabolize juvenile hormones.

A diverse group of proteins has evolved to bind and metabolize insect juvenile hormones (JHs). Synthetic radiolabeled JHs and their photoaffinity analogs have enabled us to isolate and characterize JH binding proteins (JHBPs), a putative nuclear JH receptor, JH esterases (JHEs), JH epoxide hydrolases (JHEHs), and methyl farnesoate binding proteins (MFBPs). Highlights of recent progress on structural characterization of JHBPs and JHEHs of two lepidopterans will be described. Efforts to identify MFBPs of penaeid shrimp will be discussed, and the discovery of a possible vertebrate JHBP will be presented.

Density estimates of the domestic vector of Chagas disease, Rhodnius prolixus Stål (Hemiptera: Reduviidae), in rural houses in Venezuela.

We reported the use of the timed manual method, routinely employed as an indicator to the relative abundance of domestic triatomine bugs, to estimate their absolute density in houses. A team of six people collected Rhodnius prolixus Stål bugs from the walls and roofs of 14 typical palm-leaf rural houses located in Cojedes, Venezuela, spending 40 minutes searching in each house. One day after these manual collections, all the houses were demolished and the number of triatomine bugs were identified by instar and counted. Linear regression analyses of the number of R. prolixus collected over 4 man-hours and the census counts obtained by house demolition indicated that the fit of the data by instar (stage II--adult) and place of capture (roof versus palm walls versus mud walls) was satisfactory. The slopes of the regressions were interpreted as a measure of "catchability" (probability of capture). Catchability increased with developmental stage (ranging from 11.2% in stage II to 38.7% in adults), probably reflecting the increasing size and visibility of bugs as they evolved. The catchability on palm wall was higher than that for roofs or mud walls, increasing form 1.3% and 3.0% in stage II to 13.4% and 14.0% in adults, respectively. We reported, also, regression equations for converting field estimates of timed manual collections of R. prolixus into absolute density estimates.

Distribution of alternatively spliced chicken c-myb exon 9A among hematopoietic tissues.

The role of the c-myb proto-oncogene in cellular differentiation may be regulated in part by alternative splicing of its mRNAs. Previously, two forms of alternative splicing of the chicken c-myb gene between exons 9 and 10 were described: one form utilizes the entire 360 base pair (bp) exon 9A while a second form utilizes exon 9A' which consists of the 3' 150 bp of exon 9A. In this study the distribution among chicken hematopoietic tissues of these two forms of alternative splicing was determined by Northern blot analysis using a probe specific for exon 9A. RNA species of 4.2 kilobases (kb) and 4.4 kb which contain exon 9A' or exon 9A, respectively, were detected in each tissue tested. Quantitative analysis of the major 4.0 kb c-myb species and the c-myb species containing exon 9A and exon 9A' revealed that cells from yolk sac contained both the highest absolute and the highest relative levels of alternatively spliced c-myb mRNA, presumably because of the preponderance of immature erythroid cells in these preparations.

Alternative splicing of the chicken c-myb exon 9A.

The c-myb gene products are thought to be regulators of cellular replication and of differentiation and heterogeneity may underlie their multiple functions. To investigate the possible existence of heterogeneity we have examined the chicken c-myb mRNAs by Northern blot analysis and polymerase chain reaction amplification of cDNAs (RT-PCR). Northern blot analysis with the c-myb cDNA clone pSG3, which contains the entire open reading frame (ORF) plus 500 base pairs of 3' untranslated sequences (Gerondakis & Bishop, 1986), and genomic probes revealed c-myb RNA species of 4.3 kb in addition to the major 4.0 kb species. The 4.3 kb c-myb RNA contained the alternatively spliced exon 9A which is highly conserved and has also been detected in a minor 4.3 kb alternatively spliced c-myb mRNA in murine and human cells. Sequencing of the avian exon 9A revealed 360 bp exon homologous to that found in murine and human mRNAs, which contains three highly conserved sequence regions shared by all three species. RT-PCR demonstrated usage of exon 9A in five hematopoietic tissues and revealed an additional splicing variant which used the 3' portion of exon 9A. Northern blot analysis using splice site-specific oligonucleotide probes spanning the two splice junctions between exon 9 and 9A revealed four additional c-myb RNAs of 4.4 kb, 2.2 kb, 2.0 kb and 1.4 kb.

Probability of transmission of Chagas disease by Triatoma infestans (Hemiptera: Reduviidae) in an endemic area of Santiago del Estero, Argentina.

The daily probability (P) of transmission of Trypanosoma cruzi to a noninfected human host by an infected Triatoma infestans bug was estimated using field data from a 2-year longitudinal study carried out in a rural settlement of 20 households in Amamá, Santiago del Estero, Argentina. The following information was used for this purpose: the bug density and the proportion of infected bugs; the bug biting rate and the distribution of bites between humans and animals; the age-specific seropositivity to T. cruzi of the human population; and the actual number of new cases of human infection. The 2-year accumulated number of infective contacts per house estimated using a binomial model shows a statistically significant logistic correlation with the observed proportion of new cases per house. An average house where new cases of human infection were registered in the 2-year period had a P value of 0.0012, while an average general house (i.e., with and without new cases) had a P value of 0.0009. The observed range of P is discussed in terms of the chain of factors that affects the individual human risk of acquiring the infection and the possible entomological sampling errors.

Carcinoma del hepatico izquierdo intraparenquimatoso. / Left intraparenchymatous hepatic cardinoma

Se presenta un caso de colangiocarcinoma originado en la via biliar intraparenquimatosa, de hallazgo casual en el curso de una intervencion por litiasis biliar. Se hacen consideraciones generales sobre los tumores hepaticos y sobre las dificultades diagnosticas en esta localizacion. Se enumeran las condiciones para el tratamiento quirurgico, asi como las vias de abordage, tacticas y tecnicas operatorias y se comentan las posibilidades terapeuticas coadyuvantes

Carcinoma del hepatico izquierdo intraparenquimatoso. / Left intraparenchymatous hepatic cardinoma

Se presenta un caso de colangiocarcinoma originado en la via biliar intraparenquimatosa, de hallazgo casual en el curso de una intervencion por litiasis biliar. Se hacen consideraciones generales sobre los tumores hepaticos y sobre las dificultades diagnosticas en esta localizacion. Se enumeran las condiciones para el tratamiento quirurgico, asi como las vias de abordage, tacticas y tecnicas operatorias y se comentan las posibilidades terapeuticas coadyuvantes