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

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.

Bronchographic and angiologic observations in experimental autotransplantation of a lung or lung lobe.

Roentgenologic examinations were conducted after 260 experimental autotransplantations of a lung or its lobe in the course of a long-term dynamic observation (maximum follow-up 4 1/2 years). Accentuation and indistinctness of the pulmonary pattern were observed in combination with small focal shadows in the early post-transplant period (up to 15 days) in dogs with an uneventful course. Dynamic observations (maximum follow-up 4 1/2 years) revealed no changes in the pulmonary tissue and no anatomic or functional changes in the bronchial tree and vessels. In the late period after orthotopic and heterotopic autotransplantation of the lower lobe, the changes were due to impaired topographic interrelations of the thoracic organs: Removal of the upper lobe of the intact lung into the upper part of the left pleural cavity. This phenomenon, the so-called mediastinal hernia, is facilitated by the mobility of the cranial part of the mediastinal septum in dogs. Heterotopic autotransplantation of the lower lobe in place of the removed contralateral lung resulted in no shift of the mediastinum and no changes in the autotransplanted lobe in the late follow-up period. The signs of a mediastinalhernia were less distinct than after orthotopic autotransplantation of a lung lobe.

Function of lower lung lobe autograft in experimental animals.

The changes in ventilation, gas exchange, blood gases, and acid-base balance, as well as the compensatory capacity of the autotransplanted lung lobe, were studied in 30 dogs with an uncomplicated course following autotransplantation of the lower lobe of the left lung. The studies demonstrated that in the early postoperative period some deterioration in ventilation and gas exchange is noted in the autografted lobe which results in the development of arterial hypoxemia and metabolic acidosis. A normalization of the ventilation and gas exchange is observed in the beginning of the late postoperative period (3 months after surgery). As judged by the functional test with the exclusion of the right (intact) lung from respiration, the compensatory capacity of the autografter left lower lobe remained reduced for a long time after surgery. The author noted no restoration of the Hering-Breuer reflex on the side of the autografted lung lobe, the maximum follow-up period being 7 1/2 years.

Function of external respiration after experimental lung autotransplantation.

The function of external respiration was studied by way of a dynamic observation of 15 animals whose course was uneventful following autotransplantation of the left lung. The longest follow-up period was 4 years. The following studies were conducted: spirography, bronchospirography, functional tests with the right (intact) lung excluded from respiration, bronchopneumotachygraphy, electromyography of the intercostal muscles, and analyses of blood gases and acid-base balance. During the early hours and days after left lung autotransplantation, hyperventilation and gas exchange decrease were observed in the operated lung, along with arterial and venous hypoxemia and signs of metabolic acidosis. With the right (intact) lung excluded and only the autograft breathing, a considerable reduction of oxygen saturation of the peripheral arterial blood was observed, which indicated the low compensatory capacity of the autotransplanted lung. Restoration and normalization of ventilation and gas exchange, blood gases, and acid-base balance were noted within 8 days after left lung autotransplantation. The compensatory capacity of the lung autograft, as shown by the test with the right (intact) lung excluded, was restored within the first 2 months after surgery. Following lung autotransplantation, in the absence of the Hering-Breuer reflex, the adaptative reactions of the external respiration apparatus are provided by the reflexes from the proprioreceptors of the breathing muscles of the thoracic wall and by humoral factors that acquire a leading role in the regulation of respiratory mechanisms. After removal of the right (intact) lung in the late postoperative period, the left lung autograft supports normal vital functions of the body (with the longest follow-up being 3 1/4 years). This convincingly proves that the organ's function and structure have been restored.

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.

Domiciliary biting frequency and blood ingestion of the Chagas's disease vector Rhodnius prolixus Ståhl (Hemiptera: Reduviidae), in Venezuela.

Demolition of a rural house in the State of Cojedes, Venezuela, provided a collection of 7.934 Rhodnius prolixus of which a random sample of 1,415 was weighed within 48 hours. The field weights, coupled with laboratory information of weight loss (in %) with time, average blood ingestion and meal size sufficient to promote moulting, were used to estimate biting rate under domiciliary conditions. The results show that in this particularly highly infested house, the R. prolixus population bites, on the average, at a rate of 58 times/person/day, draining blood at a rate of about 100 cm3/person/month; this meant a total of 1.2 litres/month from the 11 people inhabiting the house. It was found that the more advanced R. prolixus is in its development, the more aggressive it is in securing its meal: 15, 25, 30, 59 and 77% of fed insects of instar 1 through 5, respectively, were able to achieve moulting with only one meal. Applying the estimated biting rate to R. prolixus collections of other 13 demolished houses, with more typical insect population densities, an average biting rate of 9 bites/person/day was obtained; this value was, however, extremely variable, ranging from 0.2 bites/person/day (once every five days) to 33 bites/person/day.

Effects of sublethal dose exposure to dieldrin on Rhodnius prolixus (Hemiptera: Reduviidae) under laboratory conditions.

The effects of a sublethal dose of Dieldrin (7.2 x 10(-5) g/day) were evaluated on oxygen consumption, survivorship, moulting and reproduction of Rhodnius prolixus. No difference was found in oxygen consumption between treated and control male insect. Survivorship proved to be very much affected by the sublethal exposure, but this was strongly dependent on the feeding stage of the individuals. Moulting times were prolonged by 2 to 3 days depending on the instar, but the number of individuals that succeeded in moulting was not affected. Total number of eggs laid by an average female was not affected, but the treated females layed fewer eggs in the first three weeks after feeding, and more eggs in the following weeks, than the untreated females. Possible physiological mechanisms that explain our results are related to the proteolytic activity of the midgut, to an interference with the hormonal system, to an insecticide hormoligasis effect, and to an interference with the ovarian follicles development. In terms of vector control these effects provide an alternative way of repopulating a sprayed house.

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.

[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.