Hormonal regulation of human apolipoprotein E gene expression in HepG2 cells

• 1.1. Hormonal regulation of apolipoprotein E (apoE) gene expression by insulin and thyroid hormone was studied in a human hepatoma cell line, HepG2.
• 2.2. Changes at the mRNA level, mRNA translation, in vivo synthesis and secretion were monitored.
• 3.3. Both insulin and triiodothyronine were found to have no significant effect on apoE mRNA levels.
• 4.4. Insulin treatment caused an inhibition of: (a) the in vitro translation of endogenous apoE mRNA in a HepG2 cell-free system (25%), and (b) the incorporation of radioactivity into newly-synthesized apoE in an in vivo pulse-chase labeling experiment (32%).
• 5.5. Interestingly, apoE secretion rate was found to be significantly reduced with insulin (84%) suggesting that a major portion of newly-synthesized apoE may be shunted into a degradative pathway.
• 6.6. Using a similar experimental approach, triiodothyronine showed no significant effect on the rate of apoE synthesis or translation (6–15% decrease), however a slight reduction (20%) in secretion rate was shown.
• 7.7. Overall, apoE gene expression does not appear to be influenced by triiodothyronine significantly but is modulated by insulin at the translational and post-translational level.

     

Plasma lipid transport in the horse (Equus caballus)

• 1.1. Equine plasma contains lipoproteins corresponding to very low density (VLDL), low density (LDL) and high density lipoproteins (HDL).
• 2.2. HDL accounts for approximately 60% of plasma lipoprotein mass and consists of a single population of particles.
• 3.3. LDL is heterogeneous comprising three discrete subfractions.
• 4.4. Two proteins are found in the region of apolipoprotein (apo) B-100 in VLDL and LDL and a third similar to apo B-48 is in VLDL.
• 5.5. Lecithin:cholesterol acyl transferase is active in plasma and hepatic lipase and lipoprotein lipase are evident in post-heparin plasma.
• 6.6. There is no significant cholesteryl ester transfer protein activity.

     

Main serum protein of rainbow trout (Salmo gairdnerii): its biological properties and significance

• 1.1. Main serum α₁-protein (α₁P) of rainbow trout was purified and its biochemical and physico-pathological properties were studied.
• 2.2. α₁P was suggested to be a primitive protein having both properties of albumin and AFP in serum proteins of mammals according to the following results.
• 3.3. Molecular weight (75,000), two kinds of molecules (pI 4.55 and 5.05) and amino acid composition.
• 4.4. Dye- or ConA binding activity.
• 5.5. Estrogen binding activity and inhibitory effect on lymphoblastoid-forming activity.
• 6.6. Possible osmotic regulator.
• 7.7. Significant elevation of blood α₁P level in the course of hepatoma induction.

     

Distribution of canthaxanthin in immature rainbow trout Oncorhynchus mykiss serum

• 1.1. The present study was undertaken in order to define the distribution of canthaxanthin between the lipoprotein fractions in serum of immature rainbow trout fed a diet supplemented with synthetic canthaxanthin (80 mg/kg).
• 2.2. Lipoproteins were separated by density-gradient ultracentrifugation.
• 3.3. Canthaxanthin was found in all lipoprotein fractions, in different amounts according to the density of the lipoprotein fraction: VLDL, 13.9%; LDL, 15.2% or LDL, 29.1% since the density of the first fraction was 1.006 g/ml; HDL, 60.4% and VHDL, 10.5%.

     

Serum lipoproteins of sea bass (Dicentrarchus Labrax L.). Purification and partial characterization by density gradient ultracentrifugation and agarose column chromatography

• 1.1. Five classes of sea bass serum lipoproteins were purified by single vertical spin ultracentrifugation and agarose column chromatography
• 2.2. VLDL, beta migrating, are the larger and less dense lipoproteins.
• 3.3. LDL are the more heterogeneous in size, ranging from 11 × 10⁶ to 1 × 10⁶.
• 4.4. HDL represent the predominant class which, on the basis of density and electrophoresis migration, is differentiated in three subclasses.
• 5.5. VHDL float at a density > 1.22 mg/ml, which corresponds to the density of the other serum lipoproteins. This subclass, with an apparent molecular weight of 1.5 × 10⁵, resembles the albumin-like fatty acids binding proteins, shown in mammals and teleosts and absent in elasmobranchs.

     

Combined effect of adenosine,alpha adrenergic and adenosine antagonists on serum insulin and insulin secretion from rat pancreatic islets

• 1.1. The effect of adenosine separately or in combination with alpha-1 adrenergic antagonist prazosin and alpha-2 adrenergic antagonist yohimbine as well as adenosine antagonists 8-phenyltheophylline and xanthine amine conjugate on glucose-induced insulin secretion from isolated rat pancreatic islets was studied.
• 2.2. Their in vivo effects on serum glucose and insulin levels were also investigated. Adenosine at 10 and 100 μM inhibited significantly, insulin secretion from the isolated islets whereas at 10 mM slightly increased the secretion of insulin.
• 3.3. Prazosin used at 100 μM inhibited insulin secretion. When it combined with adenosine (10 μM) it augmented the inhibitory effect of adenosine.
• 4.4. In vivo prazosin (21 mg/kg bodywt) caused a hyperglycaemia which was accompanied by hypoinsulinaemia.
• 5.5. Concurrent administration of this drug with adenosine neither affect the hyperglycaemic nor the hypoinsulinaemic effects of adenosine.
• 6.6. On the other hand, yohimbine (100 μM) has no effect neither separately nor in combination with adenosine (10 μM) in modulating the inhibitory effect of adenosine on insulin secretion.
• 7.7. When Yohimbine administered at 19.5 mg/kg body wt it did not alter serum glucose but it markedly increased the serum insulin level. Its combined administration with adenosine reduced the hyperglycaemic effect of adenosine with a remarkable increase in serum insulin.
• 8.8. Both adenosine-antagonists were ineffective in alteration of insulin secretion.
• 9.9. However, combination of 8-phenyltheophylline with adenosine (10 μM) totally blocked the inhibitory effect of adenosine on insulin secretion while xanthine amine conjugate failed to prevent this effect of adenosine.
• 10.10. These results indicate that the inhibitory effect of adenosine on insulin secretion is neither mediated via alpha-1 nor alpha-2 adrenoceptors. It might be via activation of specific adenosine receptors on rat islets which are sensitive to blockade by 8-phenyltheophylline.

     

Effect of dietary coconut oil on lipoprotein composition of young chick (Gallus domesticus)

• 1.1. The composition of HDL, the major lipoprotein fraction from chick serum, drastically changed after 2 weeks of coconut oil feeding. Total cholesterol and triacylglycerols significantly increased following dietary 10 or 20% coconut oil supplementation.
• 2.2. Changes in LDL composition were less profound, cholesterol being the only component that increased by coconut oil supplementation (10 or 20%).
• 3.3. IDL proteins were the only components that increased following the same dietary treatment (20%).
• 4.4. VLDL cholesterol and proteins also increased after 1–2 weeks of 20% coconut oil supplementation to the diet.
• 5.5. Of total lipoproteins, the cholesterol content strongly increased after dietary treatment, while triacylglycerols did not change significantly.

     

Insulin-like growth-factor binding protein (IGFBP) serum levels and hepatic IGFBP-2 and -3 mRNA expression in diabetic and insulin-treated swine (Sus scrofa)

• 1.1. Diabetes had no significant effect on IGFBP-3 message and serum levels however, subsequent insulin treatment caused more than a two-fold increase in both hepatic IGFBP-3 mRNA and serum levels above controls (P < 0.05).
• 2.2. The induction of diabetes in pigs significantly increased the steady state levels of IGFBP-2 mRNA in the liver of young swine (P < 0.05).
• 3.3. Both liver message and serum IGFBP-2 were reduced to control levels with insulin therapy.
• 4.4. We report here that in addition to its affects on IGFBP-2, insulin is involved in the regulation of IGFBP-3 expression.

     

Conversion of the lipoprotein secreted by cultured eel hepatocytes to high density lipoprotein

• 1.1. The lipoprotein, a VLDL-like lipoprotein, secreted by cultured eel hepatocytes was incubated with whole eel serum, serum HDL, or serum VLDL. No change in the VLDL-like lipoprotein was found.
• 2.2. The secreted lipoprotein was incubated with five kinds of liposomes and a HDL-like particle was formed in the presence of BSA only when l-α-dimyristoyl lecithin liposome was used.
• 3.3. In the presence of 3% BSA, apo AI, proapo AI, apo AII and apo C of the secreted lipoprotein were transferred to the l-α-dimyristoyl lecithin liposome and a HDL-like particle was formed.
• 4.4. The secreted lipoprotein was hydrolyzed by lipoprotein lipase and a HDL-like particle formed after hydrolysis contained no triglyceride and had phospholipid as its main lipid.

     

A comparison of serum retinol concentration between human and different species of normo and hypercholesterolemic nonhuman primates fed semi-purified diets with defined amounts of vitamin A

• 1.1. Serum retinol and total cholesterol concentrations were determined in several species of nonhuman primates fed semipurified diets. Two species of Old World and three species of New World nonhuman primates were examined.
• 2.2. Retinol levels were significantly lower (up to four-fold) in the serum of the smaller New World than the larger Old World animals and the difference could not be explained by differences in dietary make-up.
• 3.3. Cholesterol levels were not different between the groups but differed within a species when type of dietary fat was altered.
• 4.4. Differences in circulating levels of retinol may reflect differences in levels of retinol binding protein between the groups.

     

Catalytic and inhibitory properties of a major molecular form of acetylcholinesterase isolated from Lygus hesperus knight (Hemiptera: Miridae)

• 1.1. The major form of acetylcholinesterase (AChE) from Lygus hesperus demonstrated a greater affinity to selected substrates than unresolved AChE.
• 2.2. The turnover numbers of the native AChE were 7000 min⁻¹ for acetylthiocoline, 4800 for acetyl-(β-methyl) thiocholine, 3000 for propionylthiocholine, and 390 for S-butyrylthiocholine.
• 3.3. Each molecule of the major form had two active sites and each subunit had one active site.
• 4.4. Paraoxon or dichlorvos had a higher affinity to the major AChE form than to the unresolved AChE, resulting in a higher potency for the inhibition.
• 5.5. Some references of comparison are also made with AChE from other animal species.

     

Mitochondrial and peroxisomal fractions derived from human white adipocytes

• 1.1. A procedure is described for the separation of intact peroxisomes from human white adipocytes using a linear metrizamide gradient (20–50% w/v).
• 2.2. Peroxisomes were found in the high density region of the gradient in an intact form.
• 3.3. Mitochondria were distributed in the high density and low density regions of the gradient.
• 4.4. Lysosomes separated well from the peroxisomes, occurring only in the low density region of the gradient.
• 5.5. Low levels of glyoxylate cycle enzyme activities (isocitrate lyase and malate synthase) were detected within the light and heavy mitochondrial pellet fractions.

     

D-d-lactoylglutathione accumulation in activated human platelets

• 1.1. S-d-Lactoylglutathione accumulates in human platelets activated by agonists. Among the tested inducers thrombin is the most active.
• 2.2. The effect is dose and time-dependent. S-d-Lactoylglutathione, corresponding to depleted pool of reduced glutathione, can also be detected in platelets incubated with exogenous methylglyoxal.
• 3.3. A further significant increase was observed in platelets stimulated with trombin in the presence of methylglyoxal.
• 4.4. No change in glyoxalase activities upon platelet stimulation with thrombin was shown.

     

Identification and characterization of a third form (D3) of cyclic 3'5'-nucleotide phosphodiesterase from rhizobwm fredii

• 1.1. A third form (D3) of cyclic nucleotide phosphodiesterase from Rhizobiumfrediiv/as detected and characterized for the first time.
• 2.2. The enzyme could hydrolyse both cyclic AMP and cyclic GMP with apparent K_m for cyclic AMP of approx. 0.2 μM.
• 3.3. D3 cyclic nucleotide phosphodiesterase had a pH optimum of about 6.0 when hydrolysing cyclic AMP.
• 4.4. The enzyme lost almost all its activity when heated to 60°C for 20 min.
• 5.5. Gel filtration with Sephadex G-100 gave a mol. wt of approx. 42.5 kD for the native enzyme.

     

Bovine serum sialic acid: Age-related changes in type and content

• 1.1. The sialic acid content of newborn calf serum (4.8 μmol/ml) is approx. 3-fold higher than that of mature animals (1.4 μmol/ml) and decreases to 2.4 μmol/ml at 20 days of age. Colostrum-fed and colostrum-deprived calves have similar levels of sialic acid from birth to 14 days of age.
• 2.2. The high level of sialic acid in newborn calf serum is due predominantly to N-acetylneuraminic acid, since this sialic acid accounts for 93% of the total and since <5% of the sialic acid is O-acetylated.
• 3.3. Comparison of day 0 and day 20 serum by gel filtration and by SDS polyacrylamide gel electrophoresis demonstrates that the increase in sialic acid is associated with increased production and/or sialylation of components with MW of 45–60 kDa.
• 4.4. A high percentage (64%) of the sialic acid in newborn calf serum is detected with the lipid-linked sialic acid assay, relative to 20 day old (25%) or mature (18%) animals.
• 5.5. This indicates that the glycoproteins of newborn calf serum are more efficiently extracted under the conditions of this assay than glycoproteins of mature serum.

     

Differentiation between carrier-bound forms of non-suppressible insulin-like activity (NSILA) in serum

• 1.1. Gel-permeation chromatography of serum on Sephacryl S-300 at pH 7.4 has shown that NSILA was detected over a range of MW 50,000–400,000 with a peak at about MW 200,000.
• 2.2. When fractions from the above chromatography were rechromatographed on Sephadex G-75 at pH 2.4 major amounts of acid-stable NSILA were found in a fraction of MW 200,000–600,000 (77% of the fraction NSILA or 28% of total serum NSILA).
• 3.3. Further evidence was obtained for the presence of an active acid-dissociable complex in serum. This was present in both the MW 100,000–200,000 and 35,000–100,000 fractions and corresponded to 37% of total serum NSILA.
• 4.4. Con-A Sepharose affinity chromatography of the serum fractions from Sephacryl S-300 chromatography, followed by Sephadex G-75 chromatography under acid conditions, showed that the acid-stable complex was consistently found in weakly bound materials. The active acid-dissociable complex was found in the bound fractions, especially in the Sephacryl S-300 pool of MW 35,000–100,000.
• 5.5. Low MW NSILA (<15,000) was also released on acid treatment from an otherwise inactive high MW complex(es) of MW 35,000–600,000. This complex was not bound by Con-A Sepharose.

     

Properties of enzymes hydrating epoxides in human epidermis and liver

• 1.1. Cytosolic and microsomal epoxide hydrolyzing enzymes of human skin and liver were compared and found to be different.
• 2.2. Epidermal and hepatic cytosolic epoxide hydrolases were different in terms of substrate selectivity, pI, inhibitor sensitivity and affinity Chromatographic properties.
• 3.3. Microsomal epoxide hydrolases had the same pIs but different substrate selectivities.
• 4.4. Cytosolic epoxide hydrolase from adults had higher specific activity than that from neonates or cultured epidermis, but lower activity than adult hepatic enzymes.
• 5.5. The sizes of cytosolic epoxide hydrolase from epidermis and liver were similar and lower than that from cultured fibroblasts.
• 6.6. Cytosolic epoxide hydrolase from all sources shared similar antigenic determinants.

     

Demonstration of highly specific and sensitive antibodies to a naturally occurring tetrahydroisoquinoline alkaloid,salsolidine

• 1.1. We report for the first time on the production and characterization of antibodies against a naturally occurring tetrahydroisoquinoline, namely salsolidine (6,7-dimethoxy-1-methyl-1,2,3,4-tetrahydroisoquinoline).
• 2.2. Immunogen synthesis was carried out by coupling the hapten salsolidine to bovine serum albumin (BSA) as carrier protein on the basis of reductive amination.
• 3.3. By immunization of rabbits with salsolidine-BSA conjugate antisalsolidine antibodies were produced.
• 4.4. At a final dilution of 1:1700 the highest-litre antiserum bound 35% of 0.21 pmol [³H] salsolidine. This antiserum was used to develop a radioimmunoassay for salsolidine.
• 5.5. Cross-reactivity studies revealed a high specificity of the antiserum to the hapten.
• 6.6. The antibodies had a high affinity to salsolidine (K_a = 1.5 × 10⁹ M⁻¹).
• 7.7. Standard curves covered a measuring range of 0.5–70 pmol/tube and the detection limit was found to be 0.27 pmol/tube.

     

Unfolding and release of heme from human hemoglobins A,S and F

• 1.1. Analysis of the Soret spectra of hemoglobins A, S and F has been used to determine the extent of heme exposure and release from these hemoglobins in the presence of several solvent perturbants.
• 2.2. Oxyhemoglobin S unfolding in the presence of either urea or propyl urea resulted in greater heme exposure and release than either oxyhemoglobins A or F.
• 3.3. Methemoglobin formation resulted in lower denaturation midpoints for each hemoglobin compared to the reduced oxyhemoglobin state; methemoglobin F had the lowest denaturation midpoint under isothermal denaturing conditions.
• 4.4. Rate of heme exposure was greater for oxyhemoglobin S than oxyhemoglobin A in the presence of 200 μM the anionic detergent sodium dodecyl sulfate.
• 5.5. Evidence for increased levels of heme release in hemoglobin S may be related to the greater tendency of sickled red cell membranes to undergo lipid oxidation.

     

Effects of milk fat,unhydrogenated and partially hydrogenated vegetable oils on serum lipoproteins in growing pigs

• 1.1. Crossbred Yorkshire (Yorkshire × Landrace) pigs were fed butter oil, cream, low erucic acid rapeseed oil, sunflower oil and partially hydrogenated sunflower oil in amounts representing 30% of energy for periods of up to 13 weeks.
• 2.2. After 13 wk of feeding serum total cholesterol levels of pigs fed milk fat were significantly higher than of pigs fed vegetable oils.
• 3.3. The difference in cholesterol was mainly due to an increase in the density range of 1.063–1.125 g/ml containing pig LDL₂ and some HDL.
• 4.4. A shift towards smaller LDL particle size was apparent in pigs fed milk fat.
• 5.5. The effects of dietary trans fatty acids did not differ from cis polyunsaturated or monounsaturated fatty acids.