Behavioural and chemical studies of discrimination processes in the leaf-cutting ant Acromyrmex laticeps nigrosetosus (Forel, 1908).

Leaf-cutting ants live in symbiosis with a basidiomycete fungus that is exploited as a source of nutrients for ant larvae. Tests of brood transport revealed that Acromyrmex laticeps nigrosetosus workers did not discriminate a concolonial brood from an alien brood. The same result was observed with tests of fungus transport. Adult workers showed no aggressive behaviour to workers from other alien colonies (non-nestmates). There was no qualitative variation in the chemical profiles of larvae, pupae and adult workers from the different colonies. However, quantitative differences were observed between the different colonies. Hypotheses about the lack of intraspecific aggression in this subspecies of ants are discussed.

Behavioural and chemical studies of discrimination processes in the leaf-cutting ant Acromyrmex laticeps nigrosetosus (Forel, 1908) / Estudos químico e comportamental dos processos discriminatórios na formiga cortadeira Acromyrmex laticeps nigrosetosus (Forel, 1908)

Leaf-cutting ants live in symbiosis with a basidiomycete fungus that is exploited as a source of nutrients for ant larvae. Tests of brood transport revealed that Acromyrmex laticeps nigrosetosus workers did not discriminate a concolonial brood from an alien brood. The same result was observed with tests of fungus transport. Adult workers showed no aggressive behaviour to workers from other alien colonies (non-nestmates). There was no qualitative variation in the chemical profiles of larvae, pupae and adult workers from the different colonies. However, quantitative differences were observed between the different colonies. Hypotheses about the lack of intraspecific aggression in this subspecies of ants are discussed.

As formigas cortadeiras vivem em simbiose com um fungo basidiomiceto que é utilizado como fonte de nutriente para suas larvas. Testes de transporte de prole revelaram que as operárias de Acromyrmex laticeps nigrosetosus não discriminaram a prole concolonial de prole estranha. O mesmo resultado foi verificado com testes de transporte do fungo. As operárias adultas não exibiram comportamento agressivo frente a operárias de outras colônias (não companheiras de ninho). Não houve variação qualitativa nos perfis químicos de larvas, pupas e operárias adultas de diferentes colônias. No entanto, diferenças quantitativas foram observadas entre as diferentes colônias. Hipóteses sobre a ausência de agressão intra-específica nesta subespécie de formiga são discutidas.

Queen influence on workers behavior of the leaf-cutting ant Atta sexdens rubropilosa (Forel, 1908).

In an ant colony, the queen is the single reproducer and can interact with her workers via pheromones and cuticular compounds. However, in most species queen importance is not restricted to reproduction: in the initial development of the colony, her presence might play a more important role. In this work, we studied the effects of queen absence on workers behavior displayed in the foraging arena. Ants mortality and refuse accumulation was also measured daily. The results showed that queen absence did not alter either workers behavior or foraging efficiency. However, we observed increased ant mortality accompanied by a decrease in refuse dumping outside the nest. These results corroborate the hypothesis that environmental factors are more important than intrinsical factors in the allocation of external tasks. Probably, the queen could only influence internal activities of the colony.

Queen influence on workers behavior of the leaf-cutting ant Atta sexdens rubropilosa (Forel, 1908)

Numa colônia de formiga, a rainha é a única que exerce a atividade de reprodução e sua interação com as operárias ocorre, principalmente, por meio de feromônios e compostos cuticulares. No entanto, em muitas espécies, a sua importância não está restrita à reprodução. Nos estágios iniciais do desenvolvimento da colônia, ela pode exercer um papel mais importante. Neste trabalho, foram estudados os efeitos da ausência da rainha no comportamento de operárias presentes na arena de forrageamento. A mortalidade de operárias e a acumulação de lixo também foi medida diariamente. Os resultados mostraram que a ausência da rainha não alterou o comportamento das operárias nem a eficiência de forrageamento. Entretanto, verificou-se o aumento da mortalidade diária acompanhado do decréscimo na deposição de lixo fora do ninho. Estes resultados corroboram a hipótese de que fatores ambientais são mais importantes do que fatores intrínsecos na alocação de tarefas externas. Provavelmente, a rainha atue apenas na influência de atividades internas da colônia.

Analysis of parenchymal density on mammograms in 1353 women 25-79 years old.

OBJECTIVE: This study was undertaken to determine the frequency and distribution of dense mammograms. Factors that may affect parenchymal density of breasts among the diverse age groups of women who undergo mammography were also studied. MATERIALS AND METHODS: Mammograms of 1353 women between 25 and 79 years old who were grouped in 5-year age cohorts were reviewed. Breast density and the presence of benign calcifications were analyzed. RESULTS: Parenchymal density on mammograms decreased progressively in the patient cohorts 25-29 years old through 75-79 years old (Spearman correlation, p < .01). In the cohort of 25- through 29-year-old patients, 38% had predominantly (> 50%) fatty breasts. In the cohort of 75- through 79-year-old patients, 76% had predominantly fatty breasts. Increased parenchymal density mammograms were more common in women who had smaller breasts, had had fewer than two pregnancies, and underwent hormone replacement (p < .01). Forty-nine percent of women 50-79 years old undergoing hormone replacement had predominantly dense breasts, a percentage similar to that (48%) of the patient cohort of women 40-44 years old. Prevalence of benign calcifications also increased with age, from 8% at ages 25-29 to 86% at ages 75-79 (p < .01). CONCLUSION: In our study, a significant percentage (38%) of women who were 25-39 years old had predominantly fatty breast tissue that should not impede selective mammographic screening or diagnostic efforts in this age group.

Detection of pelvic recurrence of colorectal carcinoma: prospective, blinded comparison of Tc-99m-IMMU-4 monoclonal antibody scanning and CT.

PURPOSE: To prospectively compare the accuracy of imaging with technetium-99m-labeled Fab' fragment of the anti-carcinoembryonic antigen antibody (CEA) IMMU-4 with that of computed tomography (CT) for the detection of pelvic recurrence of colorectal carcinoma. MATERIALS AND METHODS: In 61 patients, blinded interpretations of both modalities were correlated with surgical-pathologic (n = 23) or clinical and CT follow-up findings (n = 38). RESULTS: Sensitivity and specificity with antibody scanning alone and combined with CT (79% and 84% vs 83% and 81%, respectively) were not significantly different from those values for CT alone (66% and 97%, respectively). Sensitivity of antibody scanning was greater for recurrences larger than 2 cm (94% vs 55% [P = .02]), serum CEA more than 2.5 ng/mL (91% vs 40% [P = .03]), and combined planar and single photon emission CT antibody scanning compared with planar alone (79% vs 48% [P = .03]), without a significant decrease in specificity. CONCLUSION: Antibody scanning does not improve on findings at CT alone for recurrent colorectal carcinoma but can help differentiate recurrent tumor from fibrosis.

Strong binding of single-stranded DNA by stem-loop oligonucleotides.

We report that oligodeoxynucleotides which form stem-loop hairpin structures and which have pyrimidine-rich loops can form strong complexes with complementary single-stranded DNA sequences. Stem-loop oligonucleotides were constructed with a 25-nt T-rich loop and with variable Watson-Crick stems. The complexes of these oligomers with the sequence dA8 were studied by thermal denaturation. Evidence is presented that the complexes are one-to-one, bimolecular complexes in which the pyrimidine loop bases comprise the outer strands in a pyr.pur.pyr triplex, in effect chelating the purine strand in the center of the loop. Melting temperatures for the loop complexes are shown to be up to 29 degrees C higher than Watson-Crick duplex of the same length. It is shown that the presence of a stem increases stability of the triplex relative to an analogous oligomer without a stem. The effect of stem length on the stability of such a complex is examined. Such hairpin oligomers represent a new approach to the sequence-specific binding of single-stranded RNA and DNA. In addition, the finding raises the possibility that such a complex may exist in natural RNA folded sequences.