RESUMO
The different morphological characteristics of five bacterial pathogen strains were analyzed through transmission electron microscopy for addressing the particular relationship between optical density and colony-forming units for each strain. Generated linear equations will allow a reliable calculation of bacterial concentrations through simple optical density measurements.
Assuntos
Escherichia coli O157/isolamento & purificação , Microbiologia de Alimentos , Doenças Transmitidas por Alimentos/microbiologia , Listeria monocytogenes/isolamento & purificação , Microscopia Eletrônica de Transmissão/métodos , Salmonella typhimurium/isolamento & purificação , Staphylococcus aureus/isolamento & purificação , Contagem de Colônia Microbiana/métodos , Manipulação de Alimentos/métodosRESUMO
Acrobasis nuxvorella Neunzig (pecan nut casebearer) is a monophagous herbivore of Carya illinoinensis (Wang.) K. Koch (pecan); both are indigenous to North America, where Carya has evolved for ≈60 million years. We hypothesized that this close association may have resulted in a parallel evolution allowing casebearer to use pecan volatiles to synchronize seasonality. Casebearer overwinters in diapause as a first-instar larva in a hibernaculum attached to a dormant pecan bud. Larval emergence from this structure after diapause or postdiapause quiescence coincides with the onset of pecan bud growth in the spring, and this interaction was the subject of this study. Dormant pecan twigs with hibernacula-infested buds were exposed to a water control or pecan volatiles from 'Western Schley' cultivar, and monitored to observe larval response by using a microcalorimeter. Initial testing showed that metabolic heat produced by overwintering larvae remained low and unchanged when exposed to water vapor and significantly increased within a few hours after exposure to volatiles from new pecan foliage. This shows that these larvae in hibernacula are in a physiologically suppressed state of diapause or postdiapause quiescence, from which they detect and respond to these pecan volatiles. Further studies to quantify larval responses showed that 90 and 80% of the larvae became active and emerged from their hibernacula ≈6 d after exposure to Western Schley and 'Wichita' volatiles, respectively. Mixtures of 13 sesquiterpenes from those pecan volatiles were identified to induce physiological activity within larvae after hours of exposure, followed some days later by larval emergence from hibernacula. Host volatiles, to our knowledge, have not previously been reported to induce early instar larvae in hibernacula to rouse from a state of physiological arrest to resume normal growth and development. This also has potential for use in pest management.
Assuntos
Carya/metabolismo , Diapausa de Inseto , Mariposas/crescimento & desenvolvimento , Feromônios/metabolismo , Animais , Larva/crescimento & desenvolvimento , Controle Biológico de Vetores , Estações do AnoRESUMO
Angiotensin I-converting enzyme inhibitory (ACEI) activity was evaluated and compared in <3 KDa water-soluble extracts (WSE) isolated from milk fermented by wild and commercial starter culture Lactococcus lactis strains after 48 h of incubation. The highest ACEI activities were found in WSE from milk inoculated with wild L. lactis strains isolated from artisanal dairy products and commercial starter cultures. On the other hand, the lowest ACEI activities were found in WSE from milk inoculated with wild strains isolated from vegetables. Moreover, the IC(50) values (concentration that inhibits 50% activity) of WSE from artisanal dairy products were the lowest, indicating that these fractions were the most effective in inhibiting 50% of ACE activity. In fact, a strain isolated from artisanal cheese presented the lowest IC(50) (13 µg/mL). Thus, it appears that wild L. lactis strains isolated from artisanal dairy products and commercial starter cultures showed good potential for the production of fermented dairy products with ACEI properties.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/metabolismo , Microbiologia de Alimentos , Lactococcus lactis/metabolismo , Leite/microbiologia , Angiotensina I/metabolismo , Animais , Fermentação , Lactococcus lactis/classificaçãoRESUMO
The effect of exogenous polyamines on electrolyte leakage, chilling index, polygalacturonase activity (PG), ethylene production, and firmness in zucchini squash fruits stored for 12 days at 2 degrees C or 10 degrees C, 85-90% RH was evaluated. Fruits were infiltrated with putrescine (PUT) spermidine (SPD) and spermine (SPM) at 0.1, 0.25, 0.5, 2.0, and 4.0 mM. All polyamines exerted a protective effect on cell and organelle membranes. The most effective was SPD, which reduced electrolyte leakage between 62% and 82%, compared to control fruits stored at 2 degrees C. At 10 degrees C they did not exhibit chilling injury (CI) symptoms, while at 2 degrees C SPM (0.5 mM) and SPD (0.5 mM) diminished them 92% and 100%, respectively; which extended storage life for 8-10 days at 2 degrees C. High concentrations of polyamines (>2.0 mM) caused the appearance of CI symptoms. PG activity diminished proportionally to the concentration of polyamine except for the concentration at 4.0 mM. No significant changes were observed in ethylene production.
Assuntos
Temperatura Baixa , Cucurbita/efeitos dos fármacos , Poliaminas/farmacologia , Poligalacturonase/metabolismo , Cucurbita/enzimologia , Citoproteção , Relação Dose-Resposta a Droga , Transporte de Íons/efeitos dos fármacos , Putrescina/farmacologia , Espermidina/farmacologia , Espermina/farmacologiaRESUMO
Biological assays of Vitex trifolia L. organic extracts have shown relevant activities. Hexanic and dichloromethanic (DCM) extracts, when prepared from stems and foliage, have proved to be very toxic against several cancer cell lines in culture (SQC-1 UISO, OVCAR-5, HCT-15 COLADCAR, and KB). Also, an important antifeeding activity against the insect pest Spodoptera frugiperda (Lepidoptera: Noctuidae) was recorded. The hexanic extract from leaves completely inhibited the growth of the fungal plant pathogen Fusarium sp. within the first 2 days of the experiment, but dropped significantly at day 6 (15% inhibition). The potential of V. trifolia for several uses is discussed.