Comparative study of the growth of Listeria monocytogenes in defined media and demonstration of growth in continuous culture

C.E. JONES, G. SHAMA, P.W. ANDREW, I.S. ROBERTS AND D.JONES. 1995 A basic requirement for physiological studies with Listeria monocytogenes is a chemically defined medium that supports growth of the bacterium in batch and continuous culture. A number of such media have been devised but comparative studies of their efficiency are few and none has been used in continuous culture. Six of the media were compared for their ability to sustain sequential growth of L. monocytogenes in static and aerated batch culture with glucose as sole carbon source. The most suitable, judged on the basis of ease of preparation, growth rate and yield, was that of Trivett and Meyer (1971). This medium was shown to support growth of L. monocytogenes NCTC 7973 in continuous culture in a chemostat. A lytic phenomenon, noted with the same strain under anaerobic conditions and in batch culture in the chemostat, is discussed.     

Growth of a lactate dehydrogenase deficient mutant of bacillus stearothermophilus in continuous culture

A lactate dehydrogenase deficient strain of B. stearothermophilus, lld-15, was outgrown by revertants to lactate production when cultivated in a chemostat at D = 0.25 h^?1 on a rich complex medium at a sucrose concentration of 2.5% (w/v) but was maintained without reversion at this dilution rate when the sucrose concentration was only 0.5% (w/v). In batch culture the revertant showed characteristics which distinguished it both from B. stearothermophilus strains lld-15 and NCA 1503.     

External thoracic scent efferent system of Scutelleridae (Hemiptera: Heteroptera)

The metathoracic scent glands in the Heteroptera produce defence secretions which are spread outside the body through and by using the thoracic external scent efferent system. That complex system was studied in 18 species from 11 genera of four subfamilies, Elvisurinae, Eurygastrinae, Hoteinae and Scutellerinae of the family Scutelleridae (Pentatomoidea). The results have been compared with published data. The pattern of that system is more consistent at the level of genus, mostly very similar in the congeneric species, but mostly variable within higher taxonomic levels, tribes and subfamilies. Five types of the external scent efferent system are recognized within the family Scutelleridae, basic two of them in studied species: (i) peritreme well developed, covering large part of metapleuron, evaporatorium small, developed only on metapleuron, (ii) evaporatorium large, more conspicuous than moderate-sized to small peritreme, extending to mesopleuron as large structure. The results do not support a hypothesis that the system of structures associated externally with metathoracic scent glands is in correlation with type of a habitat. However, these structures are well usable as diagnostic characters for scutellerid genera (e.g. Cantao, Hyperonchus, Scutellera and Solenosthedium).     

Nonlinear effects of temperature on body form and developmental canalization in the threespine stickleback

Theoretical models predict that nonlinear environmental effects on the phenotype also affect developmental canalization, which in turn can influence the tempo and course of organismal evolution. Here, we used an oceanic population of threespine stickleback (Gasterosteus aculeatus) to investigate temperature‐induced phenotypic plasticity of body size and shape using a paternal half‐sibling, split‐clutch experimental design and rearing offspring under three different temperature regimes (13, 17 and 21 °C). Body size and shape of 466 stickleback individuals were assessed by a set of 53 landmarks and analysed using geometric morphometric methods. At approximately 100 days, individuals differed significantly in both size and shape across the temperature groups. However, the temperature‐induced differences between 13 and 17 °C (mainly comprising relative head and eye size) deviated considerably from those between 17 and 21 °C (involving the relative size of the ectocoracoid, the operculum and the ventral process of the pelvic girdle). Body size was largest at 17 °C. For both size and shape, phenotypic variance was significantly smaller at 17 °C than at 13 and 21 °C, indicating that development is most stable at the intermediate temperature matching the conditions encountered in the wild. Higher additive genetic variance at 13 and 21 °C indicates that the plastic response to temperature had a heritable basis. Understanding nonlinear effects of temperature on development and the underlying genetics are important for modelling evolution and for predicting outcomes of global warming, which can lead not only to shifts in average morphology but also to destabilization of development.     

Neuroendocrine Signaling Via the Serotonin Transporter Regulates Clearance of Apoptotic Cells

Serotonin (5-hydroxytryptamine; 5-HT) is a CNS neurotransmitter increasingly recognized to exert immunomodulatory effects outside the CNS that contribute to the pathogenesis of autoimmune and chronic inflammatory diseases. 5-HT signals to activate the RhoA/Rho kinase (ROCK) pathway, a pathway known for its ability to regulate phagocytosis. The clearance of apoptotic cells (i.e. efferocytosis) is a key modulator of the immune response that is inhibited by the RhoA/ROCK pathway. Because efferocytosis is defective in many of the same illnesses where 5-HT has been implicated in disease pathogenesis, we hypothesized that 5-HT would suppress efferocytosis via activation of RhoA/ROCK. The effect of 5-HT on efferocytosis was examined in murine peritoneal and human alveolar macrophages, and its mechanisms were investigated using pharmacologic blockade and genetic deletion. 5-HT impaired efferocytosis by murine peritoneal macrophages and human alveolar macrophages. 5-HT increased phosphorylation of myosin phosphatase subunit 1 (Mypt-1), a known ROCK target, and inhibitors of RhoA and ROCK reversed the suppressive effect of 5-HT on efferocytosis. Peritoneal macrophages expressed the 5-HT transporter and 5-HT receptors (R) 2a, 2b, but not 2c. Inhibition of 5-HTR2a and 5-HTR2b had no effect on efferocytosis, but blockade of the 5-HT transporter prevented 5-HT-impaired efferocytosis. Genetic deletion of the 5-HT transporter inhibited 5-HT uptake into peritoneal macrophages, prevented 5-HT-induced phosphorylation of Mypt-1, reversed the inhibitory effect of 5-HT on efferocytosis, and decreased cellular peritoneal inflammation. These results suggest a novel mechanism by which 5-HT might disrupt efferocytosis and contribute to the pathogenesis of autoimmune and chronic inflammatory diseases.     

Endothelial Akt activation by hyperoxia: role in cell survival

High oxygen concentrations (hyperoxia), often required in the treatment of preterm infants and critically ill patients, cause lung injury, targeting especially the endothelium. Exposure of primary human lung microvascular endothelial cells (HLMVEC) to hyperoxia caused transient Akt activation after 60 min, as determined by Western blot analysis of phosphorylated Ser 473 of Akt. Akt phosphorylation was also increased after 24 h of hyperoxic exposure, which declined at 48 h. Adenoviral (Ad)-mediated expression of constitutively active myrAkt protected HLMVEC against hyperoxic injury. Cell death due to hyperoxia (95% O2, 8 days), which was primarily necrotic, was substantial in control and Ad-LacZ-transduced cells, but was diminished by almost half in myrAkt-transduced cells. Hyperoxia caused increased cellular glucose consumption, an effect that was amplified in cells transduced with myrAkt compared to the LacZ-transduced or the nontransduced controls. Increased glucose consumption in myrAkt-expressing cells was accompanied by increased phosphorylation of mTOR and p70 S6-kinase. Rapamycin treatment decreased glucose consumption in myrAkt-transduced cells to levels comparable to those in control and LacZ-transduced cells exposed to hyperoxia. Ultrastructural morphometric analyses demonstrated that mitochondria and endoplasmic reticulum were less swollen in myrAkt cells relative to controls exposed to hyperoxia. These studies demonstrate that early activation of Akt occurs in hyperoxia in HLMVEC. That this event is a beneficial response is suggested by the finding that constitutive activation of Akt protects against hyperoxic stress, at least in part, by maintaining mitochondrial integrity.     

Sodium nitroprusside enhances biomass and gymnemic acids production in cell suspension of Gymnema sylvestre (Retz.) R.Br. ex. Sm.

Plant Cell, Tissue and Organ Culture (PCTOC) - Gymnemic acids (a group of triterpenoid saponins) found in Gymnema sylvestre (Retz.) R.Br. ex Sm. works as the main hypoglycaemic active components....