The localisation of 2-carboxy-D-arabinitol 1-phosphate and inhibition of Rubisco in leaves of Phaseolus vulgaris L. (1/944)

A recent controversial report suggests that the nocturnal inhibitor of Rubisco, 2-carboxy-D-arabinitol 1-phosphate (CAIP), does not bind to Rubisco in vivo and therefore that CA1P has no physiological relevance to photosynthetic regulation. It is now proved that a direct rapid assay can be used to distinguish between Rubisco-bound and free CA1P, as postulated in the controversial report. Application of this direct assay demonstrates that CA1P is bound to Rubisco in vivo in dark-adapted leaves. Furthermore, CA1P is shown to be in the chloroplasts of mesophyll cells. Thus, CA1P does play a physiological role in the regulation of Rubisco.  (+info)

Preparation of isolated intestinal villi useful for studying hydrolysis rates of penicillin and cephalosporin esters. (2/944)

A method for the preparation of freeze-dried intestinal villi from hamsters and mice is described. The villi, consisting largely of epithelial cells rich in esterase activity, are useful for hydrolysis studies of penicillin and cephalosporin esters.  (+info)

Effect of diluent temperature on creatine kinase values found for lyophilized controls and reference sera. (3/944)

We report the effect of temperature of diluent on creatine kinase activity in several lyophilized controls. Creatine kinase activity was significantly greater when the lyophilized control was reconstituted with diluent at 4 degrees C as compared to 25 degrees C. This is an additional source of variation in creatine kinase controls.  (+info)

The frog neuromuscular junction revisited after quick-freezing-freeze-drying: ultrastructure, immunogold labelling and high resolution calcium mapping. (4/944)

Until now, most ultrastructural studies on the neuromuscular junction have been carried out on samples first exposed to chemical treatments--with fixatives and/or dehydration agents--that are known to induce, or to be inadequate to prevent, artefactual changes of the native state. We report here on the potential of a physical approach to the preparation of samples that combines quick-freezing and freeze-drying (with or without exposure to OsO4 vapours) followed by direct embedding of the samples in various resins. Thin sections from physically processed frog neuromuscular junctions, when compared to their chemically fixed counterparts, exhibit an overall excellent preservation, with the organelles retaining their native density and shape. These preparations were also investigated by electron spectroscopic imaging and electron energy loss spectroscopy, obtaining high resolution maps of native total calcium distribution within the nerve terminal. Finally, thin sections from analogously processed, however unfixed, preparations embedded in Lowicryl, were immunogold labelled before exposure to OsO4. Nerve-muscle preparations treated this way exhibited adequate preservation of ultrastructure and revealed the distribution of synaptophysin with high sensitivity and resolution. In conclusion, we provide an overview of the potential of the quick-freezing-freeze-drying approach in the study of the neuromuscular junction function.  (+info)

Cell surface analysis techniques: What do cell preparation protocols do to cell surface properties? (5/944)

Cell surface analysis often requires manipulation of cells prior to examination. The most commonly employed procedures are centrifugation at different speeds, changes of media during washing or final resuspension, desiccation (either air drying for contact angle measurements or freeze-drying for sensitive spectroscopic analysis, such as X-ray photoelectron spectroscopy), and contact with hydrocarbon (hydrophobicity assays). The effects of these procedures on electrophoretic mobility, adhesion to solid substrata, affinity to a number of Sepharose columns, structural integrity, and cell viability were systematically investigated for a range of model organisms, including carbon- and nitrogen-limited Psychrobacter sp. strain SW8 (glycocalyx-bearing cells), Escherichia coli (gram-negative cells without a glycocalyx), and Staphylococcus epidermidis (gram-positive cells without a glycocalyx). All of the cell manipulation procedures severely modified the physicochemical properties of cells, but with each procedure some organisms were more susceptible than others. Considerable disruption of cell surfaces occurred when organisms were placed in contact with a hydrocarbon (hexadecane). The majority of cells became nonculturable after air drying and freeze-drying. Centrifugation at a high speed (15,000 x g) modified many cell surface parameters significantly, although cell viability was considerably affected only in E. coli. The type of washing or resuspension medium had a strong influence on the values of cell surface parameters, particularly when high-salt solutions were compared with low-salt buffers. The values for parameters obtained with different methods that allegedly measure similar cell surface properties did not correlate for most cells. These results demonstrate that the methods used to prepare cells for cell surface analysis need to be critically investigated for each microorganism so that the final results obtained reflect the nature of the in situ microbial cell surface as closely as possible. There is an urgent need for new, reliable, nondestructive, minimally manipulative cell surface analysis techniques that can be used in situ.  (+info)

The influence of packing on free radical yields in solid-state DNA: film compared to lyophilized frozen solution. (6/944)

Radiation-induced free radical damage in solid-state DNA arises from direct-type damage mechanisms. In the present study, free radical yields in film and lyophilized Na DNA model systems are compared. The free radical yields in lyophilized samples are significantly greater than those in films. Since DNA conformation cannot account for the differences in free radical yields between different DNA preparations, it is proposed that the intermolecular spacing of DNA is a critical variable. The differences in the hydration dependence of free radical yields between the film and lyophilized DNA model systems are consistent with this thesis. The relatively large free radical yields observed in lyophilized DNA emphasize the fact that DNA is an extremely effective electron and hole scavenger, more so than previously thought.  (+info)

99mTc-ENS: a new radiopharmaceutical for aerosol lung scintigraphy. Comparison between different freeze-dried formulations. (7/944)

Exogenous natural surfactant (ENS) labeled with 99mTc(99mTc-ENS) is a new radiopharmaceutical for pulmonary aerosol scintigraphy. In this study, different freeze-dried formulations were evaluated to develop a suitable and long-storage method for the ENS, the nonradioactive precursor of this radiopharmaceutical. METHODS: Two freeze-dried formulations were evaluated: the sterile ENS suspension-stannous chloride altogether lyophilized (chlorlioENS) and the lyophilized sterile ENS suspension with the addition of stannous chloride as a solid drug (lioENS). These precursors were stored at room temperature for 3 mo and then labeled with 99mTc. For comparative purposes, the sterile ENS suspension with the addition of stannous chloride labeled with 99mTc(99mTc-chlorENS) was also studied. The quality controls for each radiopharmaceutical were performed by an ascending paper chromatography to determine the labeling yield percentages. The study was performed in 30 female Sprague Dawley rats, which inhaled each radiopharmaceutical by nebulization. Twenty-five minutes after the aerosol inhalation, the animals were killed to extract their organs and measure their activity in a gamma spectrometer. The data are given as the percentage of activity concentration (C%) for each organ. RESULTS: The physicochemical properties of lioENS were adequate for a freeze-dried product. The labeling yields for 99mTc-lioENS and for 99mTc-chlorENS were always greater than 95% even after nebulization. The results of the biologic distribution studies showed that the activity concentration found in lungs for these radiopharmaceuticals were 95.7% +/- 2.6% and 96.7% +/- 2.6% respectively, results that do not differ statistically. On the other hand, the activity concentration found in lungs for the 99mTc-chlorlioENS (31.3% +/- 11.1%) and its labeling yield percentages (<10%) are statistically different (P < 0.05) from the results obtained with the two radiopharmaceuticals mentioned above. CONCLUSION: Taking into account the lioENS physicochemical properties, its long shelf life and that 99mTc-lioENS shows the same radiochemical and radiopharmacological behavior of the 99mTc-chlorENS, it can be concluded that the 99mTc-lioENS can be used for aerosol lung scintigraphy.  (+info)

Preparation and characterization of microencapsulated proteinase inhibitor aprotinin. (8/944)

Preparation of microcapsules through interfacial cross-linking of soluble starch/hydroxyethyl starch and bovine serum albumin (BSA) with terephthaloyl chloride is described. The proteinase inhibitor aprotinin, either native or active site protected, was microencapsulated, being incorporated in the aqueous phase. The influence of aqueous phase pH, BSA, and terephthaloyl chloride concentrations as well as stirring rate on microcapsule morphology and size was studied. The polycondensation pH was shown to be the determining factor for tough microcapsule production with a high encapsulation yield. The size of the microcapsules ranged between 10-30 and 50-100 microm at stirring speed 1500 and 500 rpm, respectively. Fourier transform infrared spectroscopic studies were performed on microcapsules prepared under various conditions. A correlation was established between spectral changes and microcapsule morphology and size. The optimal conditions for microcapsule degradation by alpha-amylase were found. Active site-protected aprotinin was shown to fully retain its activity after microencapsulation.  (+info)