Operating parameters for glutamic acid crystallization in displacement ion exchange chromatography

Glutamic acid can be crystallized inside cation exchange column when displacer NaOH concentration is high enough to concentrate displaced glutamic acid beyond its solubility limit. Resulting crystal layer of glutamic acid was moved with liquid phase through the column, and thus could be eluted from the column and recovered in fraction collector. For the purpose of enhancing crystal recovery, effects of operating parameters on the crystal formation were investigated. The increase in the degree of crosslinking of resin favored crystal recovery because of its low degree of swelling. Higher concentration of displacer NaOH was advantageous. If NaOH concentration is too high, however, crystal recovery was lowered due to the solubility-enhancing effects of high pH and ionic strength. The decrease of mobile phase flow rate enhanced crystal recovery because enough time to attain local equilibrium could be provided, but film diffusion would control the overall crystal formation with extremely low flow rate. Lower temperature reduced solubility of glutamic acid and thus favored crystal formation unless the rate of ion exchange was severely reduced. The ion exchange operated by displacement mode coupled with crystallization was advantageous in reducing the burden of further purification steps and in preventing purity-loss resulted from overlapping between adjacent bands.     

Immunoenrichment of urinary S-phenylmercapturic acid

A carefully designed hapten-protein conjugate has enabled the generation of a monoclonal antibody reactive with S-phenylmercapturic acid (S-PMA). The immobilized antibody retains immunoreactivity and can be used to enrich S-PMA from the urine of workers exposed to benzene. The performance of the immunoaffinity column has been validated by comparison with data obtained by GC/MS analysis from the urine of benzene-exposed workers (range 12-168 μgl^-1, corr. coeff. 0.98, n = 23). Furthermore immunoaffinity chrom atography facilitates the quantitative determination of urinary S-PMA by reversed phase HPLC. Bioconcentration of S-PMA from the urine of benzeneexposed workers has perm itted the quantification of S-PMA by HPLC at 8 h TWA (time weighted average) exposures of around 1 ppm. The potential application of immunoaffinity enrichment in biomonitoring studies is discussed.     

Differences between attractive diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), sex pheromone lures are not determinable through analysis of emissions

1 Conjoint comparisons were made between trap captures of male diamondback moths, Plutella xylostella (L.), and gas chromatographic measures of sex pheromone emissions from grey and red rubber septa. The objective was to correlate trap captures with emissions. 2 Irrespective of their composition, all mixtures that were released from grey septa effected the capture of more males than the same mixtures released from red septa. There was no difference between captures by any of the mixtures when emitted from grey septa. However, when emitted from red septa, a nominal 50 : 50 ratio of (Z)-11-hexadecenal (Z11–16:Al) and (Z)-11-hexadecenyl acetate (Z11–16:Ac) effected the capture of more males than either nominal 70 : 30 or 67 : 23 ratios. Generally, the emitted ratios of Z11–16:Al and Z11–16:Ac from both types of septa were variable, ranging between 6 : 10 to about 40 : 10. 3 No statistical correlation was found between the emissions and trap captures by any single component, group or ratio of components. These results suggest that the environment substantially affects the emission of sex pheromone components from rubber septa. As a result, the demonstration of geographical biotypes of diamondback moths and other insects may be difficult.     

Effects of frost hardening on the composition of galactolipids and phospholipids occurring during isolation of chloroplast thylakoids from needles of scots pine

Frost hardening of seedlings of Scots pine (Pinus sylvestris) at a non-freezing temperature of 4°C resulted in a 2-fold increase of the acyl lipids of the needles. This was because of increases in phospholipids and triglycerides. The galactolipid content of the needles was almost the same in unhardened and frost-hardened seedlings. In unhardened seedlings the mol ratio of monogalactosyl diacylglycerol (MGDG) to digalactosyl diacylglycerol (DGDG) was 1.7 ± 0.3 and 0.9 ± 0.2 in needles and isolated thylakoids, respectively. Corresponding ratios for frost-hardened seedlings were 1.5 ± 0.2 and 0.3 ± 0.03. The lower ratios found in isolated thylakoids, particularly in thylakoids from frost-hardened seedlings, are suggested to depend on the enzyme galactolipid: galactolipid galactosyltransferase being active during the isolation procedure. This is deduced from the result that the content of MGDG decreased and that of DGDG and 1.2 diglycerides increased. Needles of Scots pine also contain phospholipidase D. This enzyme was active during thylakoid preparation, particularly after frost hardening, as judged from the large amount of phosphatidic acid found the in thylakoid fraction isolated from frost-hardening needles. The fatty acid composition of the acyl lipids showed no major changes due to hardening at non-freezing temperature.     

Comparison of prostanoid forming capacity of neuronal and astroglial cells in primary cultures

Prostaglandin (PG) and thromboxane (TX) biosynthesis in primary neuronal and astroglial cell cultures was studied. Cultures obtained from fetal (15–16 days old) and neonatal rat brain hemispheres were characterized by chemical and immunocytochemical staining techniques as predominantly neurons or mature and immature astrocytes, respectively. Six-day old neuronal cell cultures grown in the presence of cytosine arabinoside (2 μM) from the day 3 onwards were contaminated up to 10% with glioblasts. In astroglial cultures up to 3% of the cells were postively stained with a marker for oligodendroglial cells. Fibroblast contamination was below 1% in both cultures. Prostanoid formation (measured by specific radioimmunoassays) in 6-day old neuronal cell cultures was low (sum of the amount of PGs and TX formed: 1.16 ± 0.17 (ng/mg protein/15 min) as compared to 14-day old cultured astroglial cells: 21.27 ± 2.53 (ng/mg protein/15 min). Also the pattern of prostanoids formed was different in neuronal (PGD₂ ? PGF_2α > TXB₂ ? PGE₂) and astroglial cells (PGD₂ > TXB₂ ? PGF_2α ? PGE₂ ? 6-ketoPGF_1α). Preincubation with arachidonic acid (1 μg/ml) did not affect prostanoid formation in both cultures, whereas it was stimulated 4–6-fold by addition of the calcium ionophore A23187 (1 μM). These results, although found on cultured neuronal and glial cells of different stages of development, support the view that astroglial cells might play a crucial role in brain prostanoid synthesis.     

Potassium-Stimulated Taurine Release and Nitric Oxide Synthase Activity During Quinolinic Acid Lesion of the Rat Striatum

The microdialysis technique was used to study the effect of nitric oxide synthase (NOS) activity on taurine release. Taurine release was characterized in rat striatum that was excitotoxically lesioned compared to normal conditions. The basal taurine level of the dialysate decreased during quinolinate (QUIN) lesion in parallel to the cell degeneration process. The K⁺-stimulated taurine concentration also decreased during QUIN-lesion, but to an extent that was different from that of basal values. K⁺-stimulated taurine levels were further markedly lowered by coapplication of the NOS inhibitor L-NAME in control and in lesioned animals up to 30 days after QUIN-injection. Postdegenerative tissue did not show any NOS-dependency in K⁺-induced taurine release. We conclude that a substantial part of K⁺-induced taurine release depends on NOS-activity both in normal brain tissue and in excitotoxically induced neurodegeneration. The main source of K⁺-induced taurine release in control rats are neurons but in lesioned animals are activated astroglial cells.