Application of a photosystem II model for analysis of fluorescence induction curves in the 100 ns to 10 s time domain after excitation with a saturating light pulse

A mathematical model of photosystem II (PSII) events was used to analyze chlorophyll fluorescence transients in the time domain from 100 ns to 10 s after excitation with a saturating 10-ns flash, applied as a part of specialized illumination protocol, using preparations of a thermophilic strain of the unicellular green alga, Chlorella pyrenoidosa Chick (using both intact and diuron-treated cells). Analysis of simulation results has proven that particular attention should be given to flash-induced recombination processes, including nonradiative recombination in PSII, while subsequent charge transfer along the electron transport chain of thylakoid membrane can be adequately described by a single reaction of quinone reoxidation. The PSII model was extended by taking inhibition by diuron of the electron transport in the acceptor side of PSII into account, which allowed simulation of fluorescence induction curves observed in the presence of this inhibitor. The model parameters were determined (stromal pH, rate constants of nonradiative recombination, and the initial reduction state of the quinone pool) which provided adequate simulation of experimentally observed ratios of the maximal and initial fluorescence levels (F _m/F ₀).     

Purification of soluble guanylate cyclase enzyme from human platelets

Soluble guanylate cyclase enzyme was purified from human platelets. The soluble fraction of the lysed platelets was sequentially chromatographed over DEAE-sepharose, GTP-agarose and HPLC size-exclusion columns. About 0.1 mg of purified enzyme could be obtained from 2000 ml of platelet rich plasma. The purified enzyme had the specific activity of 205 nmoles cGMP/mg/min with Mn2+ as cofactor. The enzyme eluted at the 160,000 daltons position from the size-exclusion column. Electrophoresis in the presence of sodium dodecyl sulfate under reducing conditions revealed two subunits of 83,000 and 71,000 daltons respectively.     

Squamous cell carcinoma and lichen sclerosus et atrophicus of the prepuce.

Two cases of squamous cell carcinoma of the prepuce arising on balanitis xerotica obliterans are described. This event is unusual and not well known. The surgical treatment was a wide circumcision in which the prepuce and part of the shaft skin were removed, performing as well a decortication of the glans base. This technique seemed to be satisfactory in removing the carcinoma and obtaining a definite improvement in the clinical picture of balanitis xerotica obliterans as well.     

Reduced sensitivity of peripheral cells to glucocorticoids in hypercholesterolemia

It has been found that lymphocytes of hypercholesterolemic (HCh) subjects are characterized by a reduced number of glucocorticoid receptors (GcR) as compared with the cells of normolipidemics (N). Addition of HCh-sera or very low density lipoproteins, or low density lipoproteins isolated both from HCh-sera and N-sera to cultured human skin fibroblasts brought about a fall in the number of GcR in the cells. High density lipoproteins had no effect on GcR level. Dexamethasone was less effective in inhibiting cholesterol synthesis from [14C]acetate in the lymphocytes and fibroblasts with a reduced number of GcR. In the presence of dexamethasone (I x 10(-8)M) in fibroblast growth medium, reduced number of GcR (due to preincubation with very low density lipoproteins) led to a substantial increase in cholesterol synthesis. These findings indicate that the sensitivity of peripheral cells to glucocorticoids is decreased in HCh which might be one of the trigger mechanisms of atherogenesis.