Past,present and future utilisation ofMyrica gale (Myricaceae)

The development ofM. gale oil as an insect repellent has created a requirement for cultivation of the plant. Botanical evidence indicates thatM. gale is likely to thrive on well—aerated acid peatland and could become a valuable crop on land of low agricultural value. Plant growth would be enhanced by the prevention of grazing and could be combined with softwood forestry since the trees would benefit from soil nitrogen enrichment thanks to the symbiotic association ofM. gale andFrankia. The economics of oil production would be improved if additional compounds of value such as pharmacologically active fiavonoids could be extracted from the by-products.     

The major colonic cell mitogen extractable from colonic mucosa is an N terminally extended form of basic fibroblast growth factor.

Colonic growth factors (CGFs) were extracted from porcine intestinal epithelium and mucosa. Under acidic conditions, very little mitogenic activity (as assayed using murine 3T3 fibroblasts and a human colonic cell line) was extractable. However, by extracting at neutral or slightly alkaline pH, significant mitogenic activity for both the murine fibroblasts and human colonic carcinoma cell line could be detected. CGFs are present throughout the intestine and cecum. The epithelial mucosa of the distal colorectal region appeared to contain mitogens which were more potent for the colonic cells than the 3T3 fibroblasts. Purification of CGFs from the colonic mucosa required removal of associated mucin by pH precipitation prior to chromatographic fractionation. It was then possible to develop a complete purification (390,000-fold) scheme for the major CGF, an 18-kDa protein which bound to heparin-Sepharose. N-terminal sequence analysis yielded a single sequence (Q)SPGGAMAAGSITTLPALP, i.e. an N-terminally extended form of basic fibroblast growth factor. Apart from the substitution of Gly in bovine basic fibroblast growth factor by a Ser in porcine CGF, the proteins are identical. A similar extraction procedure using purified human colonic crypt epithelial cells yielded a mitogen for the human colonic cell line with similar chromatographic properties.     

Determination of methotrexate in serum by high-performance liquid chromatography

A sensitive high-performance liquid chromatographic method with ultraviolet detection was developed to quantitate methotrexate in serum-based calibrators, controls and patient samples. Sample clean-up was achieved with C₁₈ Sep-Pak Classic cartridges. The chromatographic separation was accomplished on a 5-μm Ultrasphere ODS Beckman column. 8-Chlorotheophylline was used as an internal standard. The method was validated by recovery, linearity, accuracy and precision studies. Two standard curves were constructed to cover the high and the low ends of the calibrator range (0.05–1.0 μmol/l). Response was found linear over the whole range of the calibrator set with a correlation coefficient of 0.999 and 1.00 for the low-level and the high-level curves, respectively. Accuracy varied from 12% at the lowest level to 1.2% at the highest level. The precision study showed a C.V. of 14.4% at the lowest level and 3.3% at the highest level.     

Studies of Fe3+ transport across isolated intestinal brush-border membrane of the mouse

Mouse intestinal brush-border membrane vesicles take up iron from media containing 59Fe3 +-nitrilotriacetic acid. The iron uptake by the vesicles represents accumulation of iron which relates to an osmotically active space. Uptake is linearly related to vesicle protein concentration and is inhibited by low incubation temperature and low medium free Fe3+ concentrations. Experiments with the lipid soluble iron ligand 8-hydroxyquinoline and with Triton X-100 imply that the uptake is rate limited by membrane transport.     

The receptor for transferrin on murine myeloma cells: one-step purification based on its physiology, and partial amino acid sequence

The receptor for transferrin is one of the major surface proteins of proliferating lymphocytes and other cells. It binds ferrotransferrin from serum and endocytoses it into an acidic nonlysosomal intracellular compartment where iron is released, but in which apotransferrin remains tightly bound to its receptor. Recycling of the apotransferrin-receptor complex to the cell surface is associated with a return to neutral pH and concomitant loss of affinity of apotransferrin for its receptor. Apotransferrin is then free to leave the cell and initiate a new cycle. We have exploited this cycle in a novel method for the purification of the receptor for transferrin. Murine myeloma cells were lysed in nonionic detergent, and the lysate passed over a column of ferrotransferrin-agarose at pH 7.4. After washing with sodium acetate at pH 5.0, iron was removed with sodium citrate pH 5.0 and desferrioxamine. Upon returning the pH to neutrality, the receptor was eluted and found to be homogeneous by SDS-polyacrylamide gel electrophoresis under both reducing and nonreducing conditions. The degree of purification was estimated to be at least 3,000-fold, and the calculated yield was 10 to 20%. The purified receptor was capable of binding to transferrin. The receptor was digested with trypsin, and the resulting peptides were separated by reversed-phase high performance liquid chromatography in NH4HCO3. Selected peptides were rechromatographed in 0.1% trifluoroacetic acid, and their amino acid sequences were determined.     

The physiological basis of seed dormancy in Avena fatua. VIII. Action of malonic acid

Adkins, S. W., Symons, S. J. and Simpson, G. M. 1988. The physiological basis of seed dormancy in Avena fatua . VIII. Action of malonic acid - Physiol. Plant, 72: 477–482.
A low concentration of malonic acid (50 m M ) induced germination in four genetically pure dormant lines of Avena fatua L. Sensitivity to this treatment was poor immediately after harvest but increased markedly during after-ripening, indicating that the mode of action of malonic acid (50 m M ) was similar to that of another organic acid, citric acid. Over the concentration range (10–50 m M ) where malonic acid promoted germination, oxygen uptake was also stimulated, and this was before the first visible signs of germination. At higher concentrations (100–300 m M ) where there was no promotion of germination, malonic acid strongly inhibited oxygen uptake. These results show that malonic acid has a dual effect on oxygen uptake and subsequent germination. Low concentrations (10–50 m M ) act by stimulating the Krebs cycle and germination through an acidification reaction like citric acid, and high concentrations (100–300 m M ) act by inhibiting germination through enzymatic restraint of the Krebs cycle.
The stimulation of both oxygen uptake and germination by three established germination promoters (sodium nitrate, citric acid and ethanol) was inhibited by a high concentration of malonic acid (200 m M ) but unaffected by a low concentration (50 m M ). These results show that oxygen uptake, and hence the activity of the Krebs cycle, are important processes involved in the dormancy breaking mechanism of these three promotors.