No abstract

We measured choline influx and phosphorylation, ATP concentration ([ATP]), choline kinase activity and lens swelling during formation and partial reversal of sugar cataracts in rat lenses incubated with xylose or galactose and in lenses of galactosemic rats. [ATP] and phosphocholine (P-Cho) synthesis decreased about 60 and 40% after 4 h in normal rat lenses incubated up to 24 h in medium containing 30 mM xylose and partially recovered when the lenses were then removed from the xylose. Incubation with the somewhat less cataractogenic sugar galactose decreased P-Cho synthesis but had little effect on [ATP]. P-Cho synthesis decreased rapidly in the lenses of rats fed a 50% galactose diet, but began recovery by the third day on this diet. [ATP] decreased for at least 10 days during the galactose diet and did not recover, even with resumption of the control diet (50% starch) after 4 or 7 days. The results of in vitro and in vivo sugar cataractogenesis differed from each other in several respects, including effects on choline influx and the degree to which the changes were reversible. The in vitro and in vivo sugar cataracts, however, could both produce swelling and opacification of the lens and decreased P-Cho synthesis and [ATP]. Neither model caused a substantial change in the choline kinase activity (as measured in cell-free assays). The data did not generally support the hypothesis that decreased [ATP] causes decreased P-Cho synthesis.

Matrix metalloproteinase (MMP), a protease enzyme, participates in proteolytic cleavage of extracellular matrix proteins from Drosophila and mammals. But, recent studies have revealed other physiologically important roles of MMP in Drosophila. MMP contributes to cardioblast movement and distribution of collagen proteins during cardiogenesis in developing Drosophila. Tissue remodeling, especially tracheal development is also maintained by MMP. MMP regulates certain immunological functions in Drosophila such as wound repairing, plasmatocyte assemblage at the injured site of the basement membrane and glial response to axon degeneration in Drosophila nervous system. But, the contribution of MMP to tumor formation and metastasis in Drosophila has made it an interesting topic among researchers. Ovulation and egg laying are also found to be affected positively by MMP in Drosophila.

We investigated the effects of cataractogenesis on phospholipid (P-lipid) synthesis in sugar cataracts from galactosemic rats and in hereditary cataracts from 13/N guinea pigs. Cataractous lenses from rats fed a 50% galactose diet for 7 days were incubated 24 h with radiolabeled choline or ethanolamine and the P-lipids were extracted. The galactosemic cataracts synthesized twice as much phosphatidylcholine (PtdCho) as control rat lenses, and phosphatidylethanolamine synthesis also was increased. Similar analysis of cataractous lenses from 3-week-old 13/N guinea pigs showed a 3-fold increase in PtdCho synthesis compared with control lenses. In all cases, the P-lipid precursor pool was lower in cataracts than in control lenses. The increased P-lipid synthesis in these cataracts may represent a membrane repair response to cataractogenic stress.

Acetylcholinesterase (AChE), an esterase enzyme, terminates synaptic transmission by hydrolyzing the neurotransmitter acetylcholine into acetate and choline. Found in membrane-bound form, AChE has also been reported to be secreted in soluble form by numerous enteric helminth parasites. Secretory AChE is considered to be an immunomodulator that may promote the survival of parasites against the host’s immune response. Our aim was to investigate the immunomodulation and survival strategy of helminth parasites Ascaridia galli inside the host Gallus gallus domesticus through analysis of AChE activity. The parasites, host intestinal tissue and post-secretory parasites were subjected to centrifugation, followed by AChE activity determination. The AChE activities among intestinal tissue, fresh parasites, excretory/secretory (E/S) product and post-secretory parasites were even compared. An inverse relationship between the reduced enzyme activity of the host’s intestinal tissue and the increased enzyme activity in the parasite was observed. Our study indicates that the increased AChE activities in fresh parasites, postsecretory parasites and E/S product are their survival strategy as well as a part of their adaptive features vis-à-vis the hostile environment of the host’sintestine.