Two-year outcome of first-line antiretroviral therapy among HIV-1 vertically-infected children in Hanoi, Vietnam.

A retrospective analysis of 86 HIV-1 vertically-infected Vietnamese children with a follow-up period >24 months after initiating antiretroviral therapy (ART) was performed from 2008 to 2012, to assess the outcome of first-line ART in resource-limited settings. Of the 86 children, 68 (79.1%) were treated successfully (plasma HIV-1 viral load [VL] <1000 copies/ml), and 63 (73.3%) had full viral suppression (VL <400 copies/ml) after 24 months of ART. No significant difference between successfully treated patients and failure groups was observed in VL, CD4(+) T-cell count or clinical stage at baseline; age at ART start; or ART regimen. All 14 children with VL >5000 copies/ml, one of four children with VL 1000-5000 copies/ml and none with VL <1000 copies/ml developed reverse transcriptase inhibitor (RTI)-resistance mutations by 24 months of ART. Y181C and M184V/I were the most dominant non-nucleoside and nucleoside RTI-resistance mutations, respectively (13/15, 86.7%). These findings suggest that VL testing after 24 months of ART can be used to efficiently differentiate ART failures among HIV-1 vertically-infected children in resource-limited settings.

An examination of the factors affecting intestinal lymphatic transport of dietary lipids.

Lipophilic drugs are carried by chylomicrons secreted by the small intestine and transported in lymph. The intent of this review is to update the reader on the digestion, uptake, and transport of dietary lipids and how these processes impact the absorption of lipophilic drugs by the gut. The digestion of lipids in the gastric and intestinal lumen is discussed as well as the role of bile salts in the solubilization of lipid digestion products for uptake by the gut. Both passive and active uptake of lipid digestion products is reviewed. Also examined is how intestinal lipid transporters located at the brush border membrane may play a role in the uptake of lipids by the enterocytes. The intracellular trafficking and the resynthesis of complex lipids from lipid digestion products are explored. Finally, the formation and secretion of chylomicrons and their potential clinical disorders are described.

Intestinal lipid absorption and transport.

The purpose of this review is to update the reader on our current knowledge of the digestion, uptake, and transport of dietary lipid. In particular, it discusses how intestinal lipid transporters may play a role in the uptake of lipids by the enterocytes, and how chylomicrons are formed in the enterocytes and packaged for export into the lymphatic system through exocytosis. The classification and properties of lipids is first described followed by a discussion of structured lipids and their role in human nutrition. Digestion of triacylglycerols takes place in the stomach aided by the enzyme gastric lipase. The origin and properties of lingual and gastric lipase are reviewed. Most digestion of triacylglycerols by pancreatic lipase occurs in the intestinal lumen. Similarly, digestion of cholesteryl ester and phospholipids also takes place in the intestinal lumen. This review describes in considerable detail the uptake of lipid digestion products by the enterocytes, particularly the role of recently identified lipid transporters. The intracellular trafficking and the resynthesis of complex lipids from the lipid digestion products are talked about, particularly within the context of the recently generated knockout mouse that lacks the key lipid reesterification enzymes. Finally, the mechanisms of the formation and secretion of chylomicrons is described and clinical disorders discussed.

Plasma clearance of chylomicrons from butterfat is not dependent on saturation: studies with butterfat fractions and other fats containing triacylglycerols with low or high melting points.

BACKGROUND: Dietary fats influence plasma lipids, and changes in the clearance and metabolism of postprandial lipoproteins can affect atherosclerosis. Butterfat is considered hypercholesterolemic but contains a multitude of constituent fatty acids. OBJECTIVES: We determined triacylglycerol and cholesteryl ester clearances of lymph chylomicrons derived from butterfat, fractions of butterfat, and other dietary fats. METHODS: Radiolabeled lymph chylomicrons resulting from the intestinal absorption of different fats were reinjected into recipient rats to measure plasma clearance. Plasma clearance of [14C]triacylglycerol was used as an indicator of chylomicron lipolysis whereas clearance of [3H]cholesteryl ester was used as an indicator of chylomicron remnant removal. RESULTS: [3H]Cholesteryl ester clearance was slower from chylomicrons derived from a solid, high-saturated-butterfat fraction than from whole butterfat, but clearance of chylomicrons from other fractions did not correlate with the fractions' saturated fatty acid contents. Clearance of cholesteryl esters in chylomicrons derived from cocoa butter, palm oil, and butterfat was slower than clearance of cholesteryl esters in chylomicrons derived from safflower oil. Hepatic uptakes of cholesteryl esters were generally lower for chylomicrons from all butterfat fractions, cocoa butter, and palm oil. CONCLUSIONS: In contrast with minor effects on the lipolysis of chylomicron triacylglycerols, chylomicron remnant removal was strongly influenced by the type of dietary fat, with slower cholesteryl ester clearances for saturated fats with higher melting points. However, remnant removal and hepatic uptake of chylomicrons from whole butterfat and fractions of butterfat were not correlated with fat saturation. The mechanisms of this apparent paradox remain unknown but may be attributable to acyl arrangements in the lipid classes of chylomicrons that influence the association with apolipoproteins and receptors and hence remnant removal.

The diurnal rhythms of cholesterol metabolism and plasma clearance of model chylomicrons: comparison of normal and genetically hypercholesterolemic rats (RICO).

Previous studies showed a slower clearance of cholesterol-labeled lymph chylomicrons in genetically hypercholesterolemic rats (RICO) compared with normocholesterolemic rats. In this study, we compared rates of lipolysis and remnant clearance in RICO versus control normocholesterolemic rats of the same strain (RAIF) or with control Wistar rats, by injecting chylomicron-like lipid emulsions labeled with 14C-triolein to trace lipolysis, and 3H-cholesteryl ester to trace remnant clearance. Our findings showed slower clearance of chylomicron remnants in RICO compared with control RAIF or with control Wistar rats. During the light period, the clearance of lipids from chylomicron-like lipid emulsions injected intravenously was significantly slower in RICO rats compared with normocholesterolemic control rats of the same strain, RAIF. Within the RICO group, clearance of emulsion triolein (TO) was faster during the dark period compared with the light period. In contrast, however, the clearance of the emulsion remnants traced by cholesteryl oleate (CO) was slower during the dark period. This behaviour was not found within the Wistar group, where the clearances of TO and CO were similar in the light and dark period. Hepatic clearance of chylomicron remnants is mediated primarily by the low density lipoprotein (LDL) receptor, the expression of which shows diurnal variation. In both Wistar and RICO rats, the expression of LDL receptors was highest during the dark period. The LDL receptors in hepatic microsomal membranes from RICO rats migrated faster on SDS polyacrylamide gel electrophoresis when compared with normal Wistar and the RAIF. However in hepatic plasma membranes the LDL receptors from RICO and Wistar rats appeared identical after immunoblotting. Furthermore the LDL receptors from RICO and Wistar rats responded similarly to treatment with neuraminidase. An alteration in post-translational processing of the LDL receptor could possibly account for the slower clearance of chylomicron remnants in the RICO.

Vasoactive mediators affect the clearance of lipids from emulsion models of plasma lipoproteins in rats.

We wished to establish whether the haemodynamic changes accompanying alterations in blood pressure exert a direct effect on clearance of chylomicron-like emulsions. N-Nitro-L-arginine (NOLA) and endothelin-1 were used to increase the blood pressure of normotensive rats, sodium nitroprusside (NP) and calcitonin gene-related peptide (CGRP) were used to decrease the blood pressure of spontaneously hypertensive rats (SHR). The lipid emulsions contained radiolabeled triolein (TO) and cholesteryl oleate (CO) to trace plasma clearances. NP and CGRP enhanced TO clearance in the SHR but slowed the rate of CO clearance. NOLA in normotensive rats clearly slowed the rate of TO removal and also retarded CO clearance, whereas with endothelin-1 TO clearance remained unaffected and CO removal was markedly slowed. The effects on TO clearance are consistent with changes in arteriolar resistance regulating access of emulsion particles to lipoprotein lipase on the endothelial cells of capillaries in muscle and adipose tissue. The changes in CO removal rate are more difficult to interpret because factors determining hepatic blood flow are complex. The results suggest that haemodynamic changes potentially affect circulation times of various lipoprotein species in the plasma, with probable consequences in relation to atherogenesis.

Features of cholesterol structure that regulate the clearance of chylomicron-like lipid emulsions.

Cholesterol is an absolute requirement for the clearance from plasma of the remnants of triglyceride-rich lipoproteins. Our laboratory previously established that cholesterol was essential for the hepatic uptake of remnant particles after intravenous injection of chylomicron-like lipid emulsions (1). The aim of the present study was to determine the structural features of the cholesterol molecule that regulate the metabolism of chylomicrons. Chylomicron-like lipid emulsions, which reflect the size and composition and mimic the physiology of lymph chylomicrons, were prepared with tracer amounts of labeled triolein ([14C]TO) and cholesteryl oleate ([3H]CO) to follow the hydrolysis of triglyceride and the uptake of chylomicron remnant particles by the liver. Sterols selected as cholesterol congeners with functional group variations were incorporated into the emulsions in place of cholesterol and injected intravenously in rats. Control emulsions contained either no cholesterol or approximately 1% (by weight) cholesterol. The effects of the different sterol structures on lipolysis and hepatic remnant uptake were compared with controls to determine the significance of various functional groups. Clearance of emulsion CO was impaired when cholesterol was absent or replaced by cholesteryl chloride, cholesteryl formate, or 3-keto-cholesterol. Clearance of emulsions containing epicholesterol, where the OH group at the 3-position is in the alpha configuration, was similar to control emulsions containing cholesterol. Congeners with an additional hydroxyl group, viz. 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, or 25-hydroxycholesterol, reduced CO clearance. Androstenol, which lacks the side chain at the C17-position, also retarded CO clearance from plasma. In contrast, emulsions incorporating congeners with side chain variations such as campesterol, beta-sitosterol, stigmasterol, or saturated congeners of cholesterol such as cholestanol, coprostanol and its epimer, epicoprostanol, all were cleared similarly to emulsions containing cholesterol. In conclusion, for physiological clearance of a chylomicron-like emulsion, the presence of a hydroxyl (-OH) group at the 3-position and an alkyl side chain at the C17-position of cholesterol are essential, while the structure of the side chain and the saturation of the ring structure are not critical. The mechanism of the specificity of sterols on the metabolism of protein-free emulsions is unclear, but does not relate to changes in microfluidity of the surface lipids, nor to the amount or isoform of associated apolipoproteins.

Vitreous state in vitro culture: ethylene versus cytokinin.

The occurrence of a developmental anomaly i in vitro culture, named "vitreous plant", has been shown to be a deficiency in lignification. Several causes have been proposed, most recently the physical state of the culture medium and ethylene. Experiments, conducted to verify these suggestions, led toresults that did not confirm either the physical state or ethylene as causal agents. It rather appeared that cytokinins did induce the anomaly, probably by excessively promoting cell-divisions at the expense of cell-differentiation.

Analysis by reverse-phase high-pressure liquid chromatography of phenylisothiocyanate-derivatized 1-aminocyclopropane-1-carboxylic acid in apple extracts.

A rapid and sensitive method for the determination of 1-aminocyclopropane-1-carboxylic acid (ACC) in apple tissues is described. This method is based on the derivatization of ACC with phenylisothiocyanate, and the subsequent separation and quantification of the resulting phenylthiocarbamyl-ACC by reverse-phase high-pressure liquid chromatography. Phenylthiocarbamylation of ACC (and other amino acids) in apple extracts is complete within 20 min at room temperature. After removing solvents and reagent, the phenylthiocarbamyl derivatives are separated on an octadecyl reverse-phase column, eluted with a mixture of acetonitrile and sodium acetate buffer at pH 4.6, and monitored with a uv detector set at 254 nm. An analysis of apple extract can thus be achieved in 23 min and detect quantities as low as 1 pmol. Assays have been done to compare the efficiency of this method with that of a method using an ion-exchange amino acid analyzer and with that of Lizada and Yang's method [(1979), Anal. Biochem. 100, 140-145]. The latter method proved to yield markedly less accurate results than the other two, but the derivatization-HPLC method was preferred because of simplicity of operation and a better separation of ACC.

[Relationship between anatomical structure and metabolism of plant tissues. I. Differences between the qualitative and quantitative composition of phenolic substances of apple explants and that of callus and cells produced by the culture]. / Relation entre la structure anatomique et le métabolisme des tissue végétaux. I. Différences entre la composition qualitative et quantitative des substances phénoliques d'explantats de pomme, et celles de cals et de cellules qui en sont issus par culture.

Relationship between anatomical structure and metabolism of plant tissues. I. Differences between the qualitative and quantitative composition of phenolic substances of apple-fruit explants and that of calli and cells cultured from these explants. Phenolic compounds of intact apple-fruits (CV. Golden delicious), fruit fragments cultured on agar medium, newly formed calli and cell suspensions prepared from these calli, were studied quantitatively and qualitatively. The phenol content of the tissues decreased during the first days of culture, then recovered practically the initial level just before the initiating calli became visible. This content is very low in the calli and in the cultured cells. But the most remarkable result is that the qualitative compositions of the phenols extracted from the fruit tissues, the calli and the cells were different : p-coumaryglucose, which is abundant in the fruit, disappeared almost completely in the calli, in which three compounds were formed de novo, X1 which was tentatively identified as ferulylquinic acid, X2, a glycoside of p-coumaric acid different from p-coumarylglucose, and X3 not yet identified; the cells synthesized also X1 and X3 but not X2, and contained no p-coumaryglucose while feruylquinic acid was abundant. The study on the processes of induction or regulation of the enzymes implied in these metabolic modifications is under way.

Naturally-Occurring and Ethylene-Induced Phenolic Compounds in the Carrot Root.

Carrots accumulate phenols and often develop off-flavor and color after long periods of storage. To investigate probable causes for such physiological disorder, the effect of ethylene on various aspects of metabolism of carrot roots was studied. Ethylene, when applied at moderate level (100 ppm), caused an increase in total phenol content of the roots. It caused an increased accumulation of the phenols normally present in the tissue, especially isochlorogenic acid. Moreover, relatively longer exposure to a moderate level (100 ppm) and short exposure to high levels (2000 and 50,000 ppm) of ethylene induced formation of new compounds, viz, isocoumarin, eugenin, and two others yet unidentified. Studies with [1-14C]acetate, [2-14C]malonate and [3-14C]acetoacetate indicated that the newly synthesized compounds are probably synthesized via the acetate pathway. Ethylene stimulated the rate of O2 uptake and CO2 evolution by carrot slices, indicating probable relationship of glucose metabolism with de novo synthesis of "stress-metabolites". Studies with specifically labelled glucose showed that both the Embden-Meyerhof-Parnas (EMP) and the Pentose Phosphate (PP) pathways operate in carrots, and that ethylene preferentially stimulated the EMP pathway. Like ethylene, dinitrophenol (DNP) induced isocoumarin synthesis in carrots. Methylene blue, an electron acceptor often used for stimulating glucose catabolism via the PP pathway, also induced isocoumarin synthesis in carrots. The effect of cycloheximide, an inhibitor of protein synthesis, suggested that the de novo synthesis of enzyme protein(s) might be required for ethylene-induced isocoumarin synthesis in carrots. In conclusion, it appears that ethylene triggers changes in the metabolism of carrots during storage, which result in, among other things, synthesis of so-called "stress-metabolites," namely isocoumarin and eugenin and related compounds.

Damage by ozone to the mechanical integrity of the protoplast plasmalemma.

Ozone acts on the plasmalemma as to weaken its mechanical properties. This results in the bursting of protoplasts.

Studies on the biosynthesis of isocoumarins in carrot root tissues : induction by substances other than ethylene and effects of metabolic inhibitors.

Ethylene has been shown to induce carrot tissues to synthesize 8-hydroxy-6-methoxy-3-methyl-3,4-dihydroisocoumarin and 5-hydroxy-7-methoxy-2-methylchromone or eugenin. Our present data showed that the induction of isocoumarin formation could also be obtained by treating carrot slices with dinitrophenol and methylene blue. Methylene blue enhanced ethylene production, but dinitrophenol did not, therefore the action of the latter could not be mediated by ethylene. Arsenite inhibited isocoumarin synthesis, indicating the involvement of the glycolysis pathway. Assays on the pattern of derivation of isocoumarin from glucose lent support to the idea that isocoumarin is formed predominantly through the Embden-Meyerhof-Parnas pathway. Dinitrophenol-induced enhancement of both respiratory activity and isocoumarin formation indicates that the operation of the Krebs cycle and subsequently of the electron transport chain oxidations is required to provide acetate, the precursor of isocourmarin, as well as the energy necessary for the synthesizing process. The long initial lag phase as well as the mode of inhibition by cycloheximide seem to indicate that the ethylene-induced synthesis of isocoumarin is a sequential process.