Changes in activity and isoenzymes of invertase in cucumber leaves due to nitrogen status

When 20 ppm ammonium nitrogen was supplied to nitrogen starvedcucumbers, acid and alkaline invertase activities increased6 and 2 fold on a fresh weight basis, respectively. Two acidinvertase isozymes, I and II, were detected in cucumber leavesby DEAE cellulose chromatography and Sephadex G-100 gel filtration.Their activities were found to be reversed in nitrogen-starvedand -sufficient cucumber leaves, isozyme II being the majorisozyme in nitrogen sufficient plant. Isozyme II had nearlyhalf the Km value of I for sucrose, and hydrolyzed raffinoseless than half as much as I did, although they showed the nearlysame pH optimum at 5.0 and similar heat stability. These resultsare discussed in relation to the regulatory role of acid invertasein cucumber leaves under different nitrogen status. (Received March 26, 1976; )     

Is the peptidase activity of highly purified human plasma cholinesterase due to a specific cholinesterase isoenzyme or a contaminating dipeptidylaminopeptidase?

The peptidase site of human plasma cholinesterase (butyrylcholinesterase) is distinct from its esteratic site. We found that the number of peptidase sites on an enzyme highly purified from pooled plasma is less than 0.1, as compared with 4 esteratic sites, per tetramer. However, the subunits which carry the peptidase sites are electrophoretically indistinguishable from esteratic subunits. The atypical-silent enzyme (Ea1Es1) had a much higher absolute peptidase activity when substance P was used as the substrate, and we found that the number of peptidase and esteratic sites of this enzyme was roughly the same. This suggests that the mutated esteratic site of the silent possesses a peptidase activity. The esteratic site of the usual allozyme (Eu1Eu1) has no peptidase activity towards substance P. However, a small proportion of peptidase subunits are present in all preparations of enzymes purified from the plasmas of homozygote individuals. The peptidase activity of butyrylcholinesterase might therefore correspond to a specific isoenzyme produced by an epigenetic mechanism or produced by a gene distinct from genes E1 and E2 encoding for cholinesterase subunits. However, the possibility that highly purified cholinesterase contains traces of a dipeptidylaminopeptidase cannot be completely ruled out.     

Changes in breast volume during normal menstrual cycle and after oral contraceptives.

The volume of the left and right breasts was measured daily in four nulliparous women during normal menstrual cycles and after the use of oral contraceptives. Breast volume increased significantly in the second half of both normal and contraceptive-controlled cycles. The mean total change in volume throughout the cycle was 100 ml under natural conditions and 66 ml on oral contraceptives.     

Haemostasis and oral contraceptives

Selected hemostasis parameters were assayed in 131 women ingesting different kinds of oral contraceptives and 36 control women. No differences were noted in the plasma levels of fibrinogen, antithrombin III, prekallikrein, alpha 2 antiplasmin, fibrinopeptide A, platelet factor 4 and beta-thromboglobulin. Protein C and plasminogen levels were significantly higher in pill users (p less than 0.001, p less than 0.01) and fibronectin levels were lower (p less than 0.05). Canonical correlation, performed between clinical parameters and hemostasis data, revealed a negative correlation between antithrombin III levels and family history for thromboembolic diseases. A positive correlation was noted between fibrinogen and fibronectin levels in obese OC users. The data suggest that women taking OCs are not in a state of "hypercoagulability."     

Venous effects of oral contraceptives

In a five-year analysis of an oral contraceptive trial by the Council for the Investigation of Fertility Control venous effects were the third most troublesome group of side-effects with both combined and sequential therapy. Vein complaints, leg cramps, and thrombophlebitis were significantly more frequent with the combined preparations that contained a relatively low dose of progestogen and a high dose of oestrogen than with the other groups tested. No cases of thrombophlebitis occurred in women taking the strongly oestrogenic sequential groups.Histological examination of uterine curettings showed that most progestogenic combined preparations were associated with a high incidence of dilated endometrial sinusoids, while the oestrogenic sequential regimens and low-dose progestogen-only regimens had a low incidence. The incidence of stromal condensation round the sinusoids correlated with the incidence of leg cramps, and these effects appeared to be specific for each preparation tested.