Fas induces apoptosis in human coronary artery endothelial cells in vitro

Background  

Published work suggests that some types of endothelial cells undergo apoptosis in response to ligation of the receptor Fas (CD95, APO1) but other types are resistant. Because heterogeneity among endothelial cells from different tissues, has been demonstrated, the purpose of this study was to determine, if Fas ligation and/or activation by human Fas ligand induces apoptosis and caspase activities, in cultured human coronary artery endothelial cells, and the differences between TNF-a and FAS induced apoptosis in these cells.     

A new method for the adaptive determination of optimum pH and temperature

An adaptive control algorithm for the on-line determination of optimal temperature or pH for biomass production in a continuous fermentor is presented. The algorithm requires no prior information and uses a dynamic Hammerstein model to identify parameters and to estimate an optimal steady-state control value. A check of the estimated performance measure second derivative is included to ensure that the target extremum is an optimum. The process is driven towards this optimum with a variable step size that depends on the quality of the on-line identified model. Numerical simulations are performed on a dynamic chemostat model that incorporates a metabolic time delay. The algorithm successfully finds the optimum temperature or pH values and maintains the reactor at the optimum steady state.     

A simple model to describe transient differences between cell number and biomass growth rates of Escherichia coli

Information on the response of a microbial culture to dynamic environmental conditions is necessary for the design of transient operation processes. However, most attempts at modelling culture response have been directed at describing the steady-state behavior. Thus, there is a need for adequate dynamic models for process design. Simulations of nutrient shifts were completed using a "single-cell" model for Escherichia coli. It was discovered that the specific mass growth rate and the specific number of cells growth rate were different under transient conditions, whereas at steady state (balanced growth) these rates are equivalent. Using these observations, a simple delay model to describe the transient behavior of the two growth rates is formulated and tested. The model contains as state variables only the readily measurable macroscopic quantities (biomass, cell number, and limiting nutrient). This model agreed well with the predictions of the single-cell model.     

Periodic operation of a continuous culture of Baker's yeast

The possibility of enhancing the biomass productivity of a continuous culture of Saccharomyces cerevisiae growing on a glucose-limited medium is addressed. An unstructured Monod-type model is first identified using steady-state data. The culture is subjected to step changes in dilution rate, and it is seen that the Monod model is unable to predict even qualitatively the dynamic response of the culture. Incorporation of a time delay allows significant improvement in the transient fit. It is found that the culture has a time lag of about 3 h in adapting its growth rate. Cycling the dilution rate with a period of 3 h leads to substantial improvement in the average biomass productivity.     

A reinvestigation of the synthesis of arsonolipids (2,3-diacyloxypropylarsonic acids)

A reinvestigation of the reactions leading to arsonolipids (2,3-diacyloxypropylarsonic acids) has been carried out in order to understand why the yields of their preparation were only moderate, although they are better than those reported for 2,3-diacyloxypropylphosphonic acid (phosphotidic acid). Thus, the reaction of glycidol and of 3-chloro-1,2-propanediol with alkaline sodium arsenite, "Na3AsO3", gives the desired product, 2,3-dihydroxypropylarsonic acid, and approximately 10% of an arsenic-containing glycerol dimer which is removed during the preparation of these arsonolipids. The step which is mainly responsible for the diminished yields is due to the reaction of the -As(SPh)2 or -AsO3H- precursor with the activated acid chlorides or carboxylic acid anhydrides to give an intermediate which cyclizes with the primary hydroxy group of the 2,3-dihydroxypropyl moiety. This cyclization does not allow the primary hydroxy group to be acylated. Such cyclization could not be avoided with RCOCl/py, (RCO)2O/DMAP, or RCOOH/DCC/DMAP acylating systems.     

Periodic optimization of continuous microbial growth processes

Steady-state operation of continuous bioreactors is not necessarily the optimum type of operation. The method of pi-criterion is used in this work to determine whether periodic variation of the dilution rate can enhance the performance of continuous fermentation processes. It is found that the presence of time delay in the dynamic response of the chemostat renders a periodic operation of bioreactors, used for biomass production, superior to any steady-state operation. Also, employing Williams' structured model it is shown that cycling improves the average protein productivity.     

Adaptive steady-state optimization of biomass productivity in continuous fermentors

An adaptive steady-state optimization algorithm is presented and applied to the problem of optimizing the production of biomass in continuous fermentation processes. The algorithm requires no modeling information but is based on an on-line identified linear model, locates the optimum dilution rate, and maintains the chemostat at its optimum operating condition at all times. The behavior of the algorithm is tested against a dynamic model of a chemostat that incorporates metabolic time delay, and it is shown that large disturbances in the subtrate feed concentration and the specific growth rate, causing a shift in the optimum, are handled well. The developed algorithm is also used to drive a methylotroph single-cell production process to its optimum.     

Defining synchrony of cell cultures

A method was developed for the statistical analysis of growth data from synchronized growth experiments. The analysis provided a firm basis for the recognition of synchrony and the objective graphical presentation of the growth pattern of a synchronized culture. The latter could then supply reliably the parameters required for the calculation of a synchronization index, i.e. for the synchrony evaluation.     

Expert system for control of anaerobic digesters

Continuous anaerobic digesters are systems that present challenging control problems including the possibility that an unmeasured disturbance can change the sign of the steady-state process gain. An expert system is developed that recognizes changes in the sign of process gain and implements appropriate control laws. The sole on-line measured variable is the methane production rate, and the manipulated input is the dilution rate. The expert system changes the dilution rate according to one of four possible strategies: a constrained conventional set-point control law, a constant yield control law (CYCL) that is nearly optimal for the most common cause of change in the sign of the process gain, batch operation, or constant dilution rate. The algorithm uses a t test for determining when to switch to the CYCL and returns to the conventional set-point control law with bumpless transfer. The expert system has proved successful in several experimental tests: severe overload; mild, moderate, and severe underload; and addition of phenol in low and high levels. Phenol is an inhibitor that in high concentrations changes the sign of the process gain.     

Insects 'Down Under'– Diversity, endemism and evolution of the Australian insect fauna: examples from select orders

Abstract   The Australian insect fauna is highly endemic and characterised by numerous unique higher-level taxa. In addition, a number of groups are noticeably absent or depauperate on the continent. Many groups found in Australia show characteristic Gondwanan distribution patterns on the southern continents. There are extensive radiations on the plant families Myrtaceae and Mimosaceae, a specialised arid/semiarid fauna, and diverse taxa associated with rainforests and seasonally wet tropical regions. The fauna is also poorly studied, particularly when compared with the flora and vertebrate groups. However, studies in the last two decades have provided a more comprehensive picture of the size of the fauna, relationships, levels of endemism, origins and its evolution. Here we provide an overview of these and other aspects of Australian insect diversity, focusing on six groups, the Thysanoptera and the five megadiverse orders Hemiptera, Coleoptera, Diptera, Lepidoptera and Hymenoptera.