Variation in fatty acid composition of apples in relation to soft scald

The distribution of fatty acids within individual fruits was uneven early in storage. When soft scald developed in the fruit, the affected tissue contained less linoleic acid than sound tissue. Differences in fatty acid composition were also found between freshly harvested fruit from different trees within an orchard. Apples that were stored at O° had a low linoleic acid content during the early weeks of storage when the fruit are susceptible to the disorder but the content then increased substantially during subsequent storage. It seems that a low linoleic acid content renders the fruit more susceptible to soft scald.     

Metabolism of added gibberellic acid in Malus pumilla in relation to cool storage breakdown

Gibberellic acid (GA₃) that was injected into the core of apples to reduce internal breakdown, was found to accumulate in the cortical tissue during cool storage only to a limited extent and never exceeded 0.5 % of the added dose. Limitations on the commercial use of GA₃ would appear to be associated with the low level of incorporation into susceptible tissue.     

Direct allowance for the effects of thermodynamic nonideality in the quantitative characterization of protein self-association by osmometry

A procedure is described for the direct analysis of osmotic pressure data for reversibly dimerizing proteins that makes allowance for effects of thermodynamic nonideality on the statistical–mechanical basis of the potential-of-mean-force between molecules. Detailed consideration is also given to calculation of the magnitudes of the required virial coefficients. After illustration of the approach with analysis of simulated osmotic pressure data, the method is used to obtain dimerization constants from published osmotic pressure data for soybean proteinase inhibitor, hemoglobin and α-chymotrypsin.     

On the multiplicity of platelet prostaglandin receptors. II. The use of N-0164 for distinguishing the loci of action for PGI2, PGD2, PGE2 and hydantoin analogs

The omega-chain variant analogs of prostacyclin (PGI2) and PGD2 in which n-amyl side-chain has been replaced by a cyclohexyl group have been prepared and their cardiovascular activities have been compared to those of BW-245C(Fig. 1) a potent anti-aggregatory vasodilator bearing a cyclohexyl-terminated side-chain on a hydantoin skeleton. The cyclohexyl group has little effect on PGI2, but converts PGD2 to a long lasting hypotensive agent and increases the platelet anti-aggregatory potency of PGD2 by a factor of 8. The prostaglandin antagonist N-0164 selectively blocks the anti-aggregatory actions of PGD2, cyclohexyl-PGD2, and BW-245C; with essentially no effect on PGI2, cyclohexyl-PGI2 and PGE2 at comparably effective doses. The latter observation is contrary to an earlier report by MacIntyre, but supports the view that the anti-aggregatory effect of high doses of PGE2 (EC50=50 microM) is mediated by the PGI2 receptor. The hydantoin acts at the platelet PGD2 receptor.     

Alterations in the transport and processing of Rous sarcoma virus envelope glycoproteins mutated in the signal and anchor regions

The env gene of Rous sarcoma virus codes for two glycoproteins which are located on the surface of infectious virions. Subcloning of these coding sequences in the place of the late region of SV40 DNA has allowed the expression of a normally glycosylated, functionally active glycoprotein complex on the surface of monkey cells. Through the use of site-directed mutagenesis, the role of specific amino acids in the signal peptide, signal peptidase cleavage site, and membrane anchor region have been investigated. Amino-terminal mutations have shown that deletion of the signal peptidase cleavage site along with one or two amino acids of the hydrophobic signal peptide results in the synthesis of an unglycosylated, uncleaved, and presumably cytoplasmically located precursor. Nevertheless, changing the signal peptidase cleavage site from ala/asp to ala/asn does not block the translocation of the glycoprotein across the membrane or the action of the peptidase. At the other end of the molecule, carboxy-terminal mutations have shown that the deletion of the hydrophobic membrane anchor region is not sufficient for the secretion of the truncated glycoprotein. Interpretations of these results based on recent models for protein transport and secretion are discussed.