Network Topology as a Driver of Bistability in the lac Operon

The lac operon in Escherichia coli has been studied extensively and is one of the earliest gene systems found to undergo both positive and negative control. The lac operon is known to exhibit bistability, in the sense that the operon is either induced or uninduced. Many dynamical models have been proposed to capture this phenomenon. While most are based on complex mathematical formulations, it has been suggested that for other gene systems network topology is sufficient to produce the desired dynamical behavior. We present a Boolean network as a discrete model for the lac operon. We include the two main glucose control mechanisms of catabolite repression and inducer exclusion in the model and show that it exhibits bistability. Further we present a reduced model which shows that lac mRNA and lactose form the core of the lac operon, and that this reduced model also exhibits the same dynamics. This work corroborates the claim that the key to dynamical properties is the topology of the network and signs of interactions.Comment: 15 pages, 13 figures, supplemental information include

Leishmania mexicana amazonensis isolated from a patient with fatal mucosal leishmaniasis

Faculdade de Medicina (FMD

Prader Willi Syndrome : Saliva quantification and culture in 10 patients

Prader Willi Syndrome (PWS) is a relatively rare neurogenetic illness. It is of interest to dentists for its clinical characteristics. The aim of this study was to evaluate the amount of saliva and the presence of Streptococcus mutans (S mutans) in patients with this syndrome. We measured saliva stimulated by chewing paraffin tablets for 5 minutes, and cultured saliva samples in order to determine the colony-forming units (CFUs) of S mutans. The study was conducted in a group of 10 children with PWS at the Hospital Sant Joan de Déu, Barcelona. Results showed that patients with PWS had lower saliva secretion than considered normal for a standard population and most cultures presented a high number of colony-forming units. We conclude that these patients are likely to present caries, and stress the need to place special emphasis on prevention

La Usina del Lenguaje: Teoría de la Poesía Neobarroca

La usina del lenguaje: Teoría de la poesía neobarroca examines one of the most relevant poetry tendencies of the last thirty years: the Neo-baroque. In this dissertation I have endeavored to analyze the works of a number of Hispano-American poets, such as: José Lezama Lima, José Kozer, Néstor Perlongher, Eduardo Espina, Roger Santiváñez, among others, in order to demonstrate that Neobaroque is a significant component of the cultural and aesthetic spirit of the contemporary Hispanic World. I also demonstrate and conclude that Neo-baroque appropriates the main discourses of Post modernity, while at the same time implying a critical revision of the poetic traditions to which it belongs, such as Baroque, Modernism, Vanguardism and Colloquialism. Additionally, this dissertation allows me to rethink the Spanish Baroque of the Golden Age looking for connections and ruptures between Baroque, Modernity and Neobaroque aesthetics. In order to establish a theoretical frame, on one level I adopt a structural approach along with a poetry analysis of the above-mentioned poets, and on another level, I explore the relationship between their works and other cultural endeavors, such as philosophical and theoretical thoughts, as well as appropriate political ideas

Human mucocutaneous leishmaniasis in Três Braços, Bahia - Brazil : an area of Leishmania braziliensis braziliensis transmission. II. Cutaneous disease. Presentation and evolution

Foram analisados os dados clínicos de 182 pacientes com leishmaniose cutânea, provavelmente causada por Leishmania braziliensis braziliensis. Sessenta e oito por cento apresentavam uma única lesão, usualmente uma úlcera, na terça parte inferior anterior da tíbia. Todos os grupos etários estavam representados e muitos apresentaram histórico de um a dois meses. Treze por cento apresentavam lesões fechadas de natureza verrucosa ou em placa. Após tratamento, a evolução destas lesões foi relacionada à regularidade da terapia por antimônio. Embora a cura usualmente ocorresse em três meses, o tempo de cicatrização, após o início de tratamento, foi variável e relativo ao tamanho da lesão (p < 0.01). Em geral a lesão fechava quando era dado suficiente antimônio como tratamento. Sete entre dez pacientes que apresentavam teste cutâneo negativo para leishmania tomavam positivos após o tratamento. Observou-se por fluorescência indireta, um declínio significante nos títulos de anticorpos em pacientes acompanhados durante e após a terapia. _________________________________________________________________________________ ABSTRACTThe clinical records of 182 patients with cutaneous leishmaniasis probably due to Leishmania braziliensis braziliensis are analysed. 68% had a single lesion which was usually an ulceron the lower anterior tibial third. Many had short histories of one to two months and all age groups were represented 13% had closed lesions of a verrucose or plaque like nature. Evolution of these skin lesions after treatment was related to the regularity of antimony therapy. Although healing usually occurred in three months, the time to scarring after commencing treatment was variable and related to the size ofthe lesion (p < 0.01). Usually if sufficient antimony treatment was given the lesion closed. Seven of the ten patients with initially negative leishmanin skin tests converted to positive after treatment. A significant decline of indirect fluorescent antibody titres occurred in patients followed, during and after therapy

Características epidemiológicas da leishmaniose tegumentar americana em uma região endêmica do Estado da Bahia : II leishmaniose canina

Um inquérito em cães realizado na região de Três Braços, Bahia, mostrou que 3,0% de 98 animais tinham amastigotas em lesões de pele. Parasitos não foram encontrados em pele normal da orelha. De uma amostra selecionada de 13 cães, portadores de lesão cutânea ativa, nove (69,2%) deles estavam comprovadamente infectados. Sete amostras de lesão produziram infecção em hamsters. O estudo biológico (crescimento em meio de cultura, evolução da lesão em hamster e desenvolvimento no tubo digestivo de Lutzomyia longipalpis) identificou o parasito como pertencente ao complexo L. braziliensis. A caracterização bioquímica (mobilidade eletroforética de enzimas em placas de acetato de celulose) e o estudo imunotaxonômico (anticorpos monoclonais) definiram as amostras como L. braziliensis braziliensis. O papel do cão como um possível reservatório de L. b. braziliensis na região de Três Braços é discutido. _______________________________________________________________________________ ABSTRACTDuring a survey of domestic and hunting dogs conducted in the Três Braços region, State of Bahia, 3,0% of 98 dogs had amastigotes in skin lesions. Parasites were not found in normal ear skin. In a nonrandomly selected sample of 13 dogs with active cutaneous lesions, infection was confirmed in nine (69,2%). Tissue biopsies from seven dog lesions produced infection in hamsters. The biological behaviour of the parasite (rate of growth in culture media, evolution of lesions in hamsters and development in the gut of Lutzomyia longipalpis,) identified it to the Leishmania braziliensis complex. Characterization by biochemical means (eletrophoretic mobility of enzymes in cellulose acetate plates) and immunotaxonomic studies (monoclonal antibodies) defined the strains as L. braziliensis braziliensis. The role of dogs as a possible reservoir host of L. b. braziliensis in Três Braços region is discussed

Energy Insecurity is a Major Threat to Child Health

With the recession and this winter's harsh weather, many families are facing a choice between eating and heating. Research by Children's HealthWatch shows that young children whose families struggle to pay their utility bills ('energy insecure' families) are more likely to suffer a host of problems including food insecurity, poor health, hospitalizations and developmental delays.The Low Income Home Energy Assistance Program (LIHEAP), which provides low-income households with assistance in paying their utility bills, is effective at shielding young children from the harmful effects of energy insecurity.According to research by Children's HealthWatch, young children whose families received LIHEAP were less likely to be at risk for growth problems and had healthier weights for their age.By appropriating the maximum authorized funding for LIHEAP and ensuring that climate change legislation buffers vulnerable families and children from the harmful effects of higher energy prices, Congress will be taking important steps to protect children's health