Origin of the subepidermal tissue in Piper L. leaves.

Studies on the anatomy of Piper leaves demonstrate the presence of a subepidermal tissue distinct from the adjacent epidermis, which cells show thin walls and hyaline contents. Some authors consider such cells a hypodermal tissue, while others refer to them as components of a multiple epidermis. In this study, the nature of this subepidermal tissue was investigated through the analysis of leaf ontogeny in three Piper species. The analysis showed that the referred tissue originates from the ground meristem and, thus, should be considered a hypodermis. The studied species suggests that the role of the hypodermis would be to protect the photosynthetic apparatus from excess light, regulating the intensity of light reaching the chlorophyll parenchyma.

Origin of the subepidermal tissue in Piper L. leaves / Origem do tecido subepidérmico em folhas de Piper L.

Studies on the anatomy of Piper leaves demonstrate the presence of a subepidermal tissue distinct from the adjacent epidermis, which cells show thin walls and hyaline contents. Some authors consider such cells a hypodermal tissue, while others refer to them as components of a multiple epidermis. In this study, the nature of this subepidermal tissue was investigated through the analysis of leaf ontogeny in three Piper species. The analysis showed that the referred tissue originates from the ground meristem and, thus, should be considered a hypodermis. The studied species suggests that the role of the hypodermis would be to protect the photosynthetic apparatus from excess light, regulating the intensity of light reaching the chlorophyll parenchyma.

Os estudos de anatomia foliar de espécies de Piper revelam a presença de um tecido subepidérmico distinto da epiderme e cujas células apresentam paredes finas e conteúdo hialino. Estas células são referenciadas por alguns autores como um tecido hipodérmico e por outros, como sendo constituintes de uma epiderme múltipla. Nesse estudo verificou-se a natureza deste tecido subepidérmico a partir da análise da ontogênese foliar de três espécies de Piper. A análise revelou que o referido tecido tem origem do meristema fundamental e, portanto, deve ser denominado de hipoderme. Para as espécies avaliadas, sugere-se que a hipoderme teria função de, proteger o aparato fotossintético do excesso de luminosidade, regulando a intensidade luminosa que atinge o parênquima clorofiliano.

Germination response of Hylocereus setaceus (Salm-Dyck ex DC: ) Ralf Bauer (Cactaceae) seeds to temperature and reduced water potentials.

The germination response of Hylocereus setaceus seeds to isothermic incubation at different water potentials was analysed by using the thermal time and hydrotime models, aiming to describe some germination parameters of the population and to test the validity of the models to describe the response of the seeds to temperature and water potential. Hylocereus setaceus seeds germinated relatively well in a wide range of temperatures and the germination was rate limited from 11 to 20 degrees C interval and beyond 30 degrees C until 40 degrees C, in which the germination rate respectively shifts positively and negatively with temperature. The minimum or base temperature (T(b)) for the germination of H. setaceus was 7 degrees C, and the ceiling temperature varied nearly from 43.5 to 59 degrees C depending on the percent fraction, with median set on 49.8 degrees C. The number of degrees day necessary for 50% of the seeds to germinate in the infra-optimum temperature range was 39.3 degrees C day, whereas at the supra-optimum interval the value of theta = 77 was assumed to be constant throughout. Germination was sensitive to decreasing values of psi in the medium, and both the germinability and the germination rate shift negatively with the reduction of psi, but the rate of reduction changed with temperature. The values of base water potential (psi(b)) shift to zero with increasing temperatures and such variation reflects in the relatively greater effect of low psi on germination in supra optimum range of T. In general, the model described better the germination time courses at lower than at higher water potentials. The analysis also suggest that Tb may not be independent of psi and that psi(b(g)) may change as a function of temperature at the infra-otimum temperature range.

Germination response of Hylocereus setaceus (Salm-Dyck ex DC: ) Ralf Bauer (Cactaceae) seeds to temperature and reduced water potentials / Resposta de germinação das sementes de Hylocereus setaceus (Salm-Dyck ex DC: ) Ralf Bauer (Cactaceae) à temperatura e à redução do potencial de água

The germination response of Hylocereus setaceus seeds to isothermic incubation at different water potentials was analysed by using the thermal time and hydrotime models, aiming to describe some germination parameters of the population and to test the validity of the models to describe the response of the seeds to temperature and water potential. Hylocereus setaceus seeds germinated relatively well in a wide range of temperatures and the germination was rate limited from 11 to 20 °C interval and beyond 30 °C until 40 °C, in which the germination rate respectively shifts positively and negatively with temperature. The minimum or base temperature (Tb) for the germination of H. setaceus was 7 °C, and the ceiling temperature varied nearly from 43.5 to 59 °C depending on the percent fraction, with median set on 49.8 °C. The number of degrees day necessary for 50 percent of the seeds to germinate in the infra-optimum temperature range was 39.3 °C day, whereas at the supra-optimum interval the value of θ = 77 was assumed to be constant throughout. Germination was sensitive to decreasing values of ψ in the medium, and both the germinability and the germination rate shift negatively with the reduction of ψ, but the rate of reduction changed with temperature. The values of base water potential (ψb) shift to zero with increasing temperatures and such variation reflects in the relatively greater effect of low ψ on germination in supra optimum range of T. In general, the model described better the germination time courses at lower than at higher water potentials. The analysis also suggest that Tb may not be independent of ψ and that ψb(g) may change as a function of temperature at the infra-otimum temperature range.

As respostas de germinação de sementes de Hylocereus setaceus para incubações isotérmicas sob diferentes potenciais de água foram analisadas utilizando-se modelos de graus dia e psi dia, com o objetivo de descrever alguns parâmetros da população e para testar a viabilidade do modelo para descrever as respostas da semente a temperatura e potencial de água. Sementes de H. setaceus germinaram relativamente bem em uma ampla faixa de temperaturas e a germinação foi limitada pela velocidade nos intervalos de 11 a 20 °C, e de 30 até 40 °C, nos quais a velocidade de germinação aumenta e diminui, respectivamente, com a temperatura. A temperatura mínima ou base (Tb) para germinação de H. setaceus foi 7 °C, e a temperatura máxima variou de 43,5 a 59 °C dependendo da fração percentual, com média de 49,8 °C. O número de graus dia necessário para 50 por cento das sementes germinarem na faixa de temperatura infra-ótima foi de 39,3 °C dia, enquanto que, no intervalo supra-ótimo o valor de 77 °C dia foi assumido como constante para todo o intervalo. A germinação foi sensível à diminuição do ψ no meio, e tanto a germinabilidade como a velocidade de germinação mudaram negativamente com a redução do ψ, sendo que a taxa de redução mudou com a temperatura. Os potenciais base de água (ψb(g)) tendem a zero com o aumento da temperatura e essa variação se reflete no efeito relativamente maior do ψ sobre a germinação na faixa supra-ótima de temperatura. No geral, o modelo descreveu melhor as curvas de germinação em potenciais de água baixos do que em altos. As análises também sugerem que Tb pode não depender do ψ e que o ψb(g) pode mudar em função da temperatura na faixa infra-ótima de temperatura.

Qualitative modelling of regulated metabolic pathways: application to the tryptophan biosynthesis in E.coli.

MOTIVATION: The integrated dynamical modelling of mixed metabolic/genetic networks constitutes one of the challenges of systems biology. Furthermore, as most of available data about genetic and metabolic regulations are qualitative, there is a pressing need for rigorous qualitative mathematical approaches. RESULTS: On the basis of two established formalisms, the logical modelling of genetic regulatory networks and the Petri net modelling of metabolic networks, we propose a systematic approach for the modelling of regulated metabolic networks. This approach leans on previous work defining a systematic procedure to translate logical regulatory graphs into standard (discrete) Petri nets (PNs). This approach is illustrated by the qualitative modelling of the biosynthesis of tryptophan (Trp) in Escherichia coli, taking into account two types of regulatory feedbacks: the direct inhibition of the first enzyme of the pathway by the final product of the pathway, and the transcriptional inhibition of the Trp operon by the Trp-repressor complex. On the basis of this integrated PN model, we further indicate how available dynamical analysis tools can be applied to obtain significant insights in the behaviour of the system. AVAILABILITY: The software GINsim for the logical modelling of genetic regulatory networks together with the PN model of the regulated Trp biosynthesis pathway are available at: http://gin.univ-mrs.fr/GINsim.

Double blind trial on the effect of certain soluble cytoplasmic mycobacterial antigens on the late reactivity to lepromin.

Two hundred forty-four children between six months and 59 months of age from nursery schools and playgrounds in Ribeirão Preto, São Paulo, Brazil, were randomly allocated into five groups. These received: 1) intradermal BCG; 2) placebo; 3) antigen F, containing soluble cytoplasmic components of the mycobacteria Mycobacterium tuberculosis, M. aquae, and M. lepraemurium; 4) antigen G, containing soluble cytoplasmic components of M. piscium, and M. balnei, and 5) antigen H, containing soluble cytoplasmic components of M. leprae. BCG preinjected children had the highest proportion of positive late lepromin reactions. The injection of antigens F, G, or H had no effect on the late lepromin reactions. These findings contrasted with those observed in our earlier trial in which the injection of antigens X (containing soluble cytoplasmic components of the mycobacteria M. avium and M. gallinarum), Y (M. simiae, M. gallinarum, and M. avium), and Z (M. leprae, M. simiae, and M. borstelense) had caused significantly lower positive late lepromin reactions. By comparing the data of the present investigation with the findings of the first trial, it appears that the antigens obtained from M. borstelense and from either M. avium or M. gallinarum could have been instrumental in the impairment of lepromin activity observed in the first trial.

Epidemiology of Pseudomonas aeruginosa in a general hospital: a four-year study.

A retrospective study was done to determine the epidemiology of infection and/or colonization due to Pseudomonas aeruginosa in a Brazilian general hospital. In 1966, 1968, and 1969, there were only two instances where probable cross-contamination was shown; the remaining isolates were unrelated. In late 1971 the hospital experienced a marked increase in P. aeruginosa isolation. Contaminated dextrose solutions used in the infant feeding were the apparent cause of the problem which occurred in the premature and special care nurseries. A contaminated oxygen humidifying bottle was the source of a different outbreak in surgery. There was also evidence in four instances that cross-infection and/or contamination had occurred. Pyocin and serological typing revealed that many strains were involved and led to a clear understanding of the complex epidemiological relationships among all the strains.

Impairment of reactivity to lepromin by mycobacterial antigens related to, or identical with, Mycobacterium leprae.

Three hundred and twenty young children were injected with Bacillus Calmette-Guerin (BCG) saline, or with one of the mycobacterial cytoplasmic antigens related with Mycobacterium leprae. At an appropriate time thereafter they were tested for dermal hypersensitivity to the antigens and for reactions to lepromin. Whereas all the antigens induced cell-mediated immunity, the incidence and intensity of late response to lepromin were significantly reduced in children preinjected with the cytoplasmic mycobacterial antigens, as contrasted with increased lepromin reactivity in the BCG group and with the findings in saline-injected children.