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H J Hilderson

Publications and source records attributed to H J Hilderson.

At least 37 records · Page 2Linked to original sources
PubMed1979

Occurrence and subcellular localization of glucose 6-phosphatase in bovine thyroid.

In bovine thyroid tissue the glucose 6-phosphatase activity is not entirely due to the presence of an unspecific acid phenylphosphatase nor to beta-glycerophosphatase. This glucose 6-phosphatase is very probably localized within endoplasmic reticulum membranes. It is not a good marker for distribution patterns obtained after differential pelleting. However it can be used as a marker for endoplasmic reticulum membranes after centrifugation in a zonal rotor.

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PubMed1978

Subcellular structure of bovine thyroid gland. The localization of the peroxidase activity in bovine thyroid.

1. After differential pelleting of bovine thyroid tissue the highest relative specific activities for plasma membrane markers are found in the L fraction whereas those for peroxidase activities (p-phenylenediamine, guaiacol and 3,3'-diaminobenizidine tetrachloride peroxidases) are found in the M fraction. 2. When M + L fractions were subjected to buoyant-density equilibration in a HS zonal rotor all peroxidases show different profiles. The guaiacol peroxidase activity always follows the distribution of glucose 6-phosphatase. 3. When a Sb fraction is subjected to Sepharose 2B chromatography three major peaks are obtained. The first, eluted at the void volume, consists of membranous material and contains most of the guaiacol peroxidase activity. Most of the protein (probably thyroglobulin) is eluted with the second peak. Solubilized enzymes are recovered in the third peak. 4. p-Phenylenediamine peroxidase activity penetrates into the gel on polyacrylamidegel electrophoresis, whereas guaiacol peroxidase activity remains at the sample zone. 5. DEAE-Sephadex A-50 chromatography resolves the peroxidase activities into two peaks, displaying different relative amounts of the different enzymic activities in each peak. 6. The peroxidase activities may be due to the presence of different proteins. A localization of guaiacol peroxidase in rough-endoplasmic-reticulum membranes (or in membranes related to them) seems very likely.

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PubMed1978

Structure of neutral glycolipids in bovine thyroid tissue.

Four asialo glycolipid fractions have been isolated from bovine thyroid glands. The structures were elucidated by partial hydrolysis, periodate oxidation, permethylation analysis and sequential enzymatic degradation studies. The following structures were identified: GL-1a glucosyl-beta-(1 leads to 1)ceramide; GL-1b galactosyl-beta-(1 leads to 1)ceramide: GL-2 galactosyl-beta-(1 leads to 4)glucosyl-beta-(1 leads to 1)ceramide: GL-3 galactosyl-alpha-(1 leads to 4)galactosyl-beta-(1 leads to 4)glucosyl-beta-(1 leads to 1)-ceramide; GL-4 N-acetylgalactosaminyl-beta-(1 leads to 3)galactosyl-alpha-(1 leads to 4)galactosyl-beta-(1 leads to 4)glucosyl-geta-(1 leads to 1)ceramide.

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↗
PubMed1978

Subcellular structure of bovine thyroid gland. VII. A study on the distribution of bovine thyroid plasma membranes by density gradient centrifugation in zonal rotors.

In order to obtain plasma membrane-rich fractions two methods were tried. Approach A was based on differential pelleting followed by discontinous gradient centrifugation in a B-XIV zonal rotor. In approach B homogeneization was performed in buffered water (NaHCO3, pH 7.4). The 73 300 X g pellet from this homogenate was subjected to buoyant density equilibrium in a HS zonal rotor (continuous sucrose gradient). Using approach A, the highest relative specific activity for plasma membrane markers was found at the 30-37% sucrose interphase. However, an increase for glucose 6-phosphatase (endoplasmic reticulum marker) was also found at that interphase. Using approach B marker profiles different from approach A were found. Approach B results in a subdivision of membrane material in four distinct regions. These regions do not contain completely pure membrane species, although region I seems to be essentially derived from plasma membranes. It is also concluded from approach A that plasma membranes from bovine thyroid tissue are heterogeneous.

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