A model of microbial survival curves in water treated with a volatile disinfectant

AIM: To develop a method to calculate microbial survival parameters in water treated with a dissipating disinfectant and predict the inactivation patterns under different agent concentrations and decay rate regimes. METHODS AND RESULTS: It has been assumed that the survival curves of the organism, under (hypothetical) constant agent concentration conditions, follow the power law model log [N(t)/N0] = -btn with a concentration independent exponent, n. The concentration dependence of the 'rate parameter', b, has been assumed to obey a log logistic relationship. Under changing disinfectant concentration, the survival curve is constructed so that its local slope, i.e. momentary logarithmic inactivation rate of the organism, is the slope of the momentary 'constant concentration' curve at the momentary agent concentration, at the time which corresponds to the momentary survival ratio. The resulting differential equation was used to retrieve the survival parameters by numerical minimization procedures. Once these are calculated, the equation is solved numerically to produce the survival curve for almost any conceivable agent concentration history. The predictive ability of the method is demonstrated by using the survival parameters, calculated from published data obtained under one concentration profile, to predict survival curves under very different decay patterns. CONCLUSIONS: It is possible to calculate microbial survival parameters from data obtained in treatments where the unstable or volatile disinfectant progressively dissipates and use them to predict the outcome of different treatments. SIGNIFICANCE AND IMPACT OF THE STUDY: The proposed mathematical method will enable the prediction of microbial inactivation patterns in water treated with unstable and/or volatile chemical agents.     

Novel A-ring analogs of the hormone 1alpha,25-dihydroxyvitamin D3: synthesis and preliminary biological evaluation

Prepared from a commercial prostaglandin building block, novel vitamin D3 analogs with a contracted five-membered A-ring were designed and synthesized to mimic the A-ring diol structure of the natural hormone 1alpha,25-dihydroxyvitamin D3. Prepared from commercial 1,4-cyclohexanedione, a structurally simplified analog was designed and synthesized in which a suitably oriented primary allylic hydroxyl group at the C-2 position might be a surrogate for the biologically important 1alpha-OH in the natural hormone.     

Modelling biological processes using workflow and Petri Net models

MOTIVATION: Biological processes can be considered at many levels of detail, ranging from atomic mechanism to general processes such as cell division, cell adhesion or cell invasion. The experimental study of protein function and gene regulation typically provides information at many levels. The representation of hierarchical process knowledge in biology is therefore a major challenge for bioinformatics. To represent high-level processes in the context of their component functions, we have developed a graphical knowledge model for biological processes that supports methods for qualitative reasoning. RESULTS: We assessed eleven diverse models that were developed in the fields of software engineering, business, and biology, to evaluate their suitability for representing and simulating biological processes. Based on this assessment, we combined the best aspects of two models: Workflow/Petri Net and a biological concept model. The Workflow model can represent nesting and ordering of processes, the structural components that participate in the processes, and the roles that they play. It also maps to Petri Nets, which allow verification of formal properties and qualitative simulation. The biological concept model, TAMBIS, provides a framework for describing biological entities that can be mapped to the workflow model. We tested our model by representing malaria parasites invading host erythrocytes, and composed queries, in five general classes, to discover relationships among processes and structural components. We used reachability analysis to answer queries about the dynamic aspects of the model. AVAILABILITY: The model is available at http://smi.stanford.edu/projects/helix/pubs/process-model/.     

Metabolic stress with a high carbohydrate diet increases adiponectin levels.

BACKGROUND: Adiponectin is an adipose tissue-specific protein, which possesses anti-atherogenic and antidiabetic properties, yet its plasma levels are decreased in subjects with metabolic syndrome. Although high fat diet has been linked to hypoadiponectinemia, the effect of high-carbohydrate diet on adiponectin levels is not known. Therefore, we studied the effect of high-carbohydrate diet on adiponectin levels in the rat models of hypertension and insulin resistance. METHODS: Rats were randomly assigned to the high carbohydrate diet [Sprague-Dawley rats with fructose enriched diet (SDR-F) and spontaneously hypertensive rats with sucrose enriched diet (SHR-S model)] or chow diet (Control group). Rats were followed for 6 weeks (SDR-F model) and 8 weeks (SHR-S model). Body weight, systolic blood pressure, plasma levels of glucose, insulin, triglycerides and adiponectin, were recorded. RESULTS: Both models were associated with features of the metabolic syndrome, namely, high insulin levels, increased blood pressure and triglyceride levels. Plasma adiponectin levels did not change in the control groups. In contrast, adiponectin levels increased by 39 and 30% compared to baseline following four and six weeks of fructose enriched diet in SDR (from 3.3+/-0.2 to 4.5+/-0.4 and 4.3+/-0.2 microg/ml, respectively, p<0.05). Likewise, five and eight weeks of sucrose enriched diet in SHR, induced a 54 and 81% increase in adiponectin levels compared to baseline (from 4.2+/-0.3 to 6.3+/-0.3 and 7.3+/-0.5 microg/ml, respectively, p<0.01). CONCLUSION: Metabolic stress with a high-carbohydrate diet increases plasma levels of adiponectin. Further studies will elucidate whether this is a transitory compensatory mechanism or a sign of target organ resistance to adiponectin.     

The influence of acid on astringency of alum and phenolic compounds

Astringency of aqueous solutions of phenolic compounds (grape seed tannins, tannic acid, catechin and gallic acid) increased upon addition of citric acid, whereas the astringency of alum was reduced. Astringency of alum was decreased equivalently by addition of equi-sour levels of lactic acid, citric acid or hydrochloric acid. The difference between alum and the phenolic compounds is speculated to result from chemical modifications affecting binding of the astringents with oral proteins rather than cognitive differences. Chelation of the aluminum ion in alum by acids reduces its availability for interacting with salivary proteins or epithelial proteins. In contrast, the increased astringency produced upon acidification of phenolic compounds is speculated to result from the pH driven increase in the affinity of the phenols for binding with proteins. These results suggest that alum cannot be used interchangeably with phenolic astringents in psychophysical studies.      

Effect of the juvenoid Altosid on the development of three hymenopterous parasites

The juvenoid Altosid at concentrations of up to 0.1% a.i. had no adverse effect on the various developmental stages of 3 hymenopterous parasites:Aphytis holoxanthus DeBach,Coccophagus pulvinariae Comp. andTetrastichus ceroplastae (Girault); only among the pupae ofC. pulvinariae was some mortality observed. Considering its effectiveness in controlling soft scales, Altosid seems suitable for use in an integrated control program against citrus pests.     

Morphological control and mensuration of potato plantlets from tissue cultures for automated micropropagation

Automation in plant micropropagation can be greatly simplified if the propagated plantlets have some morphological properties that facilitate automatic chopping and subsequent inspection and classification of the pre-cut plantlet segments by machine vision as viable propagules. We were able to control the morphogenic pattern of in vitro-propagated potato plantlets by adding various concentrations of ancymidol to the nutrient solution. It was found that plantlets cultured in 0.25 mg l^–1 ancymidol best fit the requirements for automated mass micropropagation; the mean internode length was sufficiently large (9–10 mm), the color contrast between leaves and stems was significantly enhanced, the stem was thicker than in the control treatment and the number of axillary buds per plantlet was maximized. Microtuber formation on segments isolated from plants cultured in 0.25 and 0.5 mg l^–1 ancymidol media was enhanced shortly after transfer to tuber induction medium in vitro. On shoot segments from control plants, microtuber formation started after 24–28 days.Machine vision was used to evaluate the morphological and color changes in cultured potato plants. Geometrical and color features such as the number of buds, internode length and color contrast between leaf and stem were precisely measured and automatically logged. Features were measured that till now could only be observed qualitatively.Abbreviations F/W fresh weight - RGB red, green, blue principal color components - VTR video tape recorder