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M De Wolf

Publications and source records attributed to M De Wolf.

10 recordsLinked to original sources
PubMed1979

Lipolytic enzymes in bovine thyroid tissue. III. Lysophospholipase activity.

Lysophospholipids are formed during phospholipid breakdown as a result of the action of phospholipases A. At certain concentrations these lysoderivatives destabilise biological membranes. Therefore, their concentration is of critical importance for membrane integrity. Prevention of lysophosphoglycerides accumulation may be the important role for lysophospholipases and is probably the explanation for their widespread occurrence in nature. Lysophospholipase activities were found in molds (Fairbairn, 1948), rice bran (Contardi & Ercoli, 1933), several microorganisms (Brockerhoff & Jensen, 1974), snake and bee venoms (Doery & Pearson, 1964; Mohamed et al., 1969; Shiloah et al., 1973), insects (Khan & Hodgson, 1967; Rao & Subrahmanyam, 1969), fish muscle (Yurkovski & Brockerhoff, 1965; Cohen et al., 1967) and in various animal tissues (Marples & Thompson, 1960). In mammalian tissue the enzyme was first described in beef pancreas (Shapiro, 1953). Relatively high levels were detected in intestine, lung, spleen, liver and pancreas, while lower levels were present in muscle, kidney, testes, brain and blood (Marples & Thompson, 1960). The presence of lysophospholipase activity in both supernatant and sediment of bovine thyroid was reported previously in relation to possible interference of this enzyme with the phospholipase A activity assay (De Wolf et al., 1976). The subcellular localization of bovine thyroid lysophospholipase and some properties of the membrane bound enzyme activity are discussed in this paper.

Animals↗
PubMed1978

Acid triacylglycerol lipase from bovine thyroid gland.

An acid lipase has been detected in bovine thyroid tissue using triolein as a substrate. The activity, probably associated with the lysosomes, displays a rather broad pH-optimum in the pH 4 to pH 6.5 range. The lipase activity can be partially purified by cosedimentation with lysosomes followed by solubilization through detergent and chromatography on Sephadex G-200 and carboxymethyl cellulose. The elution profile on Sephadex G-200 shows one peak (moleculare weight 67,000 +/- 2,000). In the final CM-cellulose step, two lipase peaks (lipase LA and lipase LB) are found. Sulhydryl reagents (iodoacetate, iodoacetamide, and N-ethylmaleimide) as well as mercuric ions markedly reduce both enzyme activities. Calcium ions, EDTA, and heparin have no effect. Sodium fluoride and diisopropylfluorophosphate are only slightly inhibitory. Sodium chloride causes a slight increase in both lipase activities. Anionic phospholipids such as cardiolipin and phosphatidylserine are not essential for enzyme activity.

Animals↗
PubMed1978

Lipolytic enzymes in bovine thyroid tissue. I. Subcellular localization, purification and characterization of acid phospholipase A1.

In mammalian cells the catabolism of membrane phosphoglycerides proceeds probably entirely through a deacylation pathway catalysed by phospholipase A and lysophospholipase (Wise & Elwyn, 1965). In the initial attack of diacylphosphoglycerides by phospholipase A two enzymatic activities with different positional specificities have been distinguished: phospholipase A1 (phosphatidate 1-acyl hydrolase EN 3.1.1.32) and phospholipase A2 (phosphatidate 2-acyl hydrolase EN 3.1.1.4) (Van Deenen & De Haas, 1966). Studies on these intracellular phospholipases were mainly concerned with their subcellular localization. Only occasionally more detailed enzymatic investigations have been conducted on them, in contrast to export phospholipases e.g. from snake venom, bee venom and porcine pancreas, which have been extensively investigated (Brockerhoff & Jensen 1974a). In a previous paper (De Wolf et al., 1976a), the presence of phospholipase A1 and phospholipase A2 activities in bovine thyroid was demonstrated, using 1-[9, 10-3H] stearoyl-2-[1-14C] linoleyl-sn-glycero-3-phosphocholine as a substrate. Optimal activity was observed in both instances at pH 4. Addition of the anionic detergent sodium taurocholate increased the A2 type activity and decreased the A1 type activity suggesting the presence of different enzymes. The lack of influence of Ca2+-ions and EDTA and the acid pH optima could suggest lysosomal localization. In this paper the subcellular distribution of both acid phospholipase activities is described as well as a purification scheme for phospholipase A1. Some characteristics of the purified enzyme preparation are discussed.

Animals↗
PubMed1978

Lipolytic enzymes in bovine thyroid tissue. II. Hydrolysis of [3H, 14C] phosphatidylethanolamine by neutral and alkaline phospholipase A activities.

Phospholipase and lysophospholipase activities are present in bovine thyroid (De Wolf et al., 1976). However, using exogenous [14C] phosphatidylcholine as substrate and subcellular fractions as enzyme source no activity could be detected at neutral and alkaline pH. Phospholipase A2 activity was found at neutral pH when [14C] phosphatidylethanolamine was substituted for [14C] phosphatidylcholine (De Wolf et al., 1976). In the present paper the occurrence of neutral and alkaline phospholipase A activities is clearly established. In addition their subcellular localization was investigated.

Animals↗
PubMed1976

[The transsexual enigma. Apropos of the work of Jan Morris "Enigma"].

The fixity of the therapeutic demand of the transsexual renders it refractory to psychotherapeutic analysis, which always tries to reveal an other demand behind the explicit demand. But the transsexual wants nothing else than to obtain from the medical wf his intime conviction to belong to the opposite sex despite his non equivoqual hormonal anatomic and genetic sex. As a consequence, he demands surgical correction of this mistake of nature. The author wants to draw from J. Morris's remarquable work, both on human and literary grounds, the essential axis of the deep problems of the transsexual: the precocious apparition of the conviction which becomes irreversible, the concern to have it accredited by scientists, a desexualised verbalisation with a rich claim for gender (psychological sex), the impact of the desire of the mother on the future of the subject, the necessary idealisation of the mother (virgin cult), the problem of castration, the link between identity and recognition by the other. The psychotherapeutic failure gives rise to an important theoretical lesson which is clearly illustrated in the transsexual: one can not conound penis and phallus (Lacan), because if the transexxual is ready to live without the former, it is to obtain (or become) the latest.

Diagnosis, Differential↗