Separation of micro-organisms from meat and their rapid enumeration using a membrane filtration-epifluorescent microscopy technique

A new method of separating bacteria from beef mince has been developed, in which an alkaline protease, Alcalase 0.6 L, was used to degrade the meat proteins, leaving micro-organisms in suspension. The organisms were then counted, using a membrane filtration-epifluorescent microscopy technique. A correlation coefficient of 0.97 was obtained between this method and the standard plate count, indicating its suitability for use in quality control.     

Stabilization of glucose-6-phosphatase activity by a 21 000-dalton hepatic microsomal protein.

Hepatic microsomal glucose-6-phosphatase activity was rendered extremely unstable by a variety of techniques: (a) incubation at pH 5.0; (b) extraction of the microsomal fraction in the presence of 1% Lubrol; (c) various purification procedures. These techniques all result in the removal of a 21 kDa polypeptide from the fraction containing glucose-6-phosphatase activity. The 21 kDa protein was purified to apparent homogeneity by solubilization in the detergent Lubrol 12A-9 and chromatography on Fractogel TSK DEAE-650(S) and centrifugation at 105 000 g. The 21 kDa protein stabilizes glucose-6-phosphatase activity, whereas other purified hepatic microsomal proteins do not. The 21 kDa protein appears to be a potential regulator of glucose-6-phosphatase activity.     

Amplification of multicistronic plasmids in the human 293 cell line and secretion of correctly processed recombinant human protein C

We have constructed multicistronic vectors containing the cDNAs for murine dihydrofolate reductase (DHFR), hygromycin phosphotransferase (HyPR), and human protein C (HPC), an antithrombotic factor. Using a sequential selection protocol with hygromycin (Hy) and methotrexate (MTX), we demonstrate the selective amplification of the murine dhfr cDNA in the adenovirus-transformed human kidney cell line 293, and the coamplification of the cDNA for HPC. Such recombinant 293 cell lines secreted HPC at levels as high as 25 micrograms/10(6) cells/day. In addition, we found that the complex vitamin K-dependent posttranslational modification of gamma-carboxylation of glutamate was not limiting at these high secretion levels, although the proteolytic processing of the protein was slightly reduced. Further, the HPC secreted from the gene-amplified cell lines had full anticoagulant activity when compared to plasma-derived HPC.     

Consequences of herbivory in the mountain birch (Betula pubescens ssp tortuosa): importance of the functional organization of the tree

Summary Three types of experiments indicate that the functional organization of the mountain birch may influence the ways in which the tree responds to simulated or natural herbivory. The first experiment showed that herbivory to both short and long shoot leaves affects plant development but, because growth largely proceeds by resources of the previous year, is manifested only in the year following the damage. The second experiment showed that even partial damage to a single long shoot leaf caused the axillary bud of that leaf to produce a shorter shoot the next year. Therefore, the value of a leaf depends also on the organ which it is subtending. In the third experiment we manipulated the apical dominance of shoots in ramets and caused improvement to leaf quality in extant shoots. Ramets within a tree responded individually, probably mediated by disturbance of the hormonal control because removal of apical buds elicited the response although removal of the same number of basal buds did not. Induced amelioration is a different response to induced resistance. The two responses are triggered by different cues and may occur in the same plant. By altering hormonal balance of shoots it is potentially possible for herbivores to induce amelioration of food quality. The ways in which herbivory is simulated may explain variability of results obtained when herbivory-induced responses in plants have been studied.     

Caveat emptor: rank transform methods and interaction

When distributional assumptions for analysis of variance are suspect, and nonparametric methods are unavailable, ecologists frequently employ rank transformation (RT) methods. The technique replaces observations by their ranks, which are then analysed using standard parametric tests. RT methods are widely recommended in statistics texts and in manuals for packages like SAS and IMSL. They are robust and powerful for the analysis of additive factorial designs. Recently, however, RT methods have been found to be grossly inappropriate for use with non-additive models. This severe limitation remains largely unreported outside of the theoretical statistics literature. Our goal is to explain this shortcoming of RT methods.     

Variation in life history responses of Daphnia to toxic Microcystis aeruginosa

Three clones of Daphnia pulex and two clones of Daphnia longispinawere exposed to toxic Microcystis aeruginosa for 21 days ina lifetable experiment. The growth and reproduction of individualdaphnids were followed daily to study the long-term effectsof toxic Microcystis. Exposure to Microcystis increased mortality,decreased growth, delayed maturation and decreased offspringproduction, indicating nutritional deficiency and toxic effects.We found variation in life history responses between speciesand among clones. Our results suggest that toxic cyanobacteriamay act as a modifying agent in zooplankton communities at boththe species and clonal level.     

Nitrogen,phosphorus and Daphnia grazing in controlling phytoplankton biomass and composition – an experimental study

The role of nitrogen as a factor controllingphytoplankton biomass was studied in nutrientenrichment incubations in the laboratory using waterfrom pelagic region of two mesotrophic lakes ineastern Finland, Lake Kallavesi (in year 1994) andLake Juurusvesi (in year 1995). We used differentcombinations of phosphorus and nitrogen additions ina total of eight experiments. Furthermore, we includedDaphnia grazing treatment to the experimentaldesign in Lake Juurusvesi experiments. The nitrogentreatments did not increase chlorophyll aconcentration in any of the experiments compared withthe controls. Chlorophyll a content was highestin those nutrient treatments where phosphorus wasadded with or without nitrogen. Daphnia grazingdecreased chlorophyll a concentration comparedwith non-grazed treatments. In some cases grazing alsocaused higher ammonium concentrations. Theseexperiments, as well as the nutrient ratio of the lakewater used, suggest that phosphorus is likely tocontrol the amount of phytoplankton biomass. This revised version was published online in July 2006 with corrections to the Cover Date.