The inhibition of Crotalus adamanteus phospholipase A2 hydrolysis of L-dihexanoylphosphatidylcholine by D-dihexanoylphosphatidylcholine was investigated with inhibitor and substrate in the monomeric concentration range. The results showed that the D-enantiomer acts as a partial (not pure) competitive inhibitor of the enzyme. These results suggest that an ESI complex exists, in which hydrolysis of the substrate still occurs. Thus, binding of the D-enantiomer to the enzyme decreases the affinity for the substrate by a factor, alpha, while Vmax is unaffected. The value of alpha was determined to be 4.70 +/- 0.14. These findings complicate the use of D-phosphatidylcholines in mixed micelles with the L-enantiomer as a possible method to investigate the mechanism of interfacial activation of this enzyme.

Crotalid Venoms↗

PubMedDate not supplied

The use of decapitated insects to study lipid mobilization in adult Manduca sexta: effects of adipokinetic hormone and trehalose on fat body lipase activity.

In order to perform studies on lipid mobilization in adult M. sexta, it is necessary to overcome the effects of starvation and handling, which both provoke an increase in hemolymph lipid concentration. When trehalose was injected into intact insects, a 35% decrease in the content of the diacylglycerol (DG)-rich hemolymph lipoprotein, low density lipophorin (LDLp) was observed within 30 min, but the level of LDLp returned to control values after 1 h. Decapitated insects exhibited 60% reduction in LDLp concentration and the levels remained low for at least 24 h. In contrast to intact insects, injection of trehalose into decapitated animals did not alter the LDLp concentration. After decapitation, the response to adipokinetic hormone (AKH) and the ability of the fat body to release DG into the hemolymph was maintained for at least 24 h. In decapitated insects, 6 pmol of AKH-stimulated measurable lipid mobilization and a near maximum response was obtained with 100 pmol of the hormone. The action of trehalose and AKH on the fat body triacylglycerol (TG)-lipase activity in decapitated animals was studied. Fat body homogenates from trehalose-treated insects exhibited a TG-lipase activity 40% lower than the control insects. Activation of fat body triacylglycerol-lipase was observed after injection of AKH, with the extent of activation ranging between 97 and 380% ten min after AKH injection. A time course study showed that the activation of the fat body triacylglycerol lipase preceded the increase in hemolymph LDLp concentration, suggesting that activation of the lipase initiates lipid mobilization. It is concluded that decapitated insects injected with trehalose is a very useful system for investigating the hormonal regulation of lipid mobilization in adult M. sexta.

Animals↗

PubMedDate not supplied

The precursor protein of the structural apolipoproteins of lipophorin: cDNA and deduced amino acid sequence.

A 10 138 bp cDNA from the fat body of the tobacco hornworm, Manduca sexta, which encodes the precursor protein for apolipophorin aPOLP-1 and -II, the structural apolipoproteins of the insect lipoprotein, lipophorin, has been cloned and sequenced. The cDNA has a single 9915 bp open reading frame beginning at an initiating ATG at bp 59 and extending to a stop codon at position 9974. This open reading frame encodes a 3305 amino acid protein with a molecular mass of 366 812 Da. Signal peptide cleavage is predicted to occur after residue 23, leaving a 3,282 amino acid precursor protein. The precursor protein is arranged with apoLp-II at the amino terminal end and apoLp-I at the carboxy terminal end. At present, the site of cleavage of the precursor protein to generate apoLp-I and -II is unknown.

Amino Acid Sequence↗

PubMedDate not supplied

Inactivation and partition of human T-cell lymphotrophic virus, type III, during ethanol fractionation of plasma.

Because of concern about the safety of immune globulins prepared for injection, we studied the effects of ethanol fractionation of human plasma on human lymphotropic virus, type III, (HTLV-III) by spiking the products of various fractionation steps with HTLV-III. Tests of inactivation and removal indicated that the ratio of residual live virus in plasma fractions/live virus in starting plasma was about 1 X 10(-15) for precipitate II from which immune globulin for injection is manufactured. The results are reassuring regarding the potential safety of immune globulin.

Deltaretrovirus↗

PubMedDate not supplied

Inactivation of human T-cell lymphotropic virus, type III by heat, chemicals, and irradiation.

Infectivity of human T-cell lymphotropic virus, Type III (HTLV-III) was inactivated by heat more rapidly if in liquid medium than if lyophilized and more rapidly at 60 degrees than 56 degrees C. When HTLV-III was added to factor VIII suspension, then lyophilized and heated at 60 degrees C for 2 hours or longer there was elimination of 1 X 10(6) in vitro infectious units (IVIU) of virus. Much of the viral inactivation appeared to result from lyophilization. The application of water-saturated chloroform to the lyophilized material containing virus also resulted in elimination of infectivity. HTLV-III was efficiently inactivated by formalin, beta-propiolactone, ethyl ether, detergent, and ultraviolet light plus psoralen. The results are reassuring regarding the potential safety of various biological products.

Chloroform↗

PubMedDate not supplied

Diet, age and intestinal bile acids in pigs.

Total bile acid concentrations in gallbladder bile and duodenal juice of neonatal piglets receiving sow milk were compared to values from 10-wk-old pigs receiving either high-fat low-carbohydrate (HF/LC) or low-fat high-carbohydrate (LF/HC) diets. Ten-week-old pigs on either diet had higher bile acid concentrations in gallbladder bile than newborn pigs (108.6 +/- 2.5 and 109.3 +/- 1.4 vs. 50.0 +/- 10.0 mM, mean +/- SE for HF/LC, LF/HC, and newborn, respectively, p < 0.007; n = 8-10). Ten-week-old pigs in the LF/HC group had higher bile acid concentrations in duodenal juice than either the HF/LC or newborn animals (31.7 +/- 4.2 vs. 16.8 +/- 2.5 and 14.7 +/- 1.8 mM, respectively, p < 0.0001). These data demonstrate that like the human neonate, the newborn pig has decreased bile acid concentrations available for digestion compared with the adult and resembles the adult pig adapted to a high-fat diet.

Aging↗