Allocating resources for child welfare services: the effect of a caseload-driven approach

The authors examine the unintended effects of a funding mechanism based on historical caseload statistics on the number of recorded investigated child abuse and neglect reports in seven California counties from January 1985 to December 1992. Forecasting results show that in five out of the seven counties, in the presence of an allocation methodology based solely on caseload statistics, the number of recorded investigated reports was approximately three to thirty-five percent higher than it would have been had only population measures been used. The findings suggest that a funding mechanism based solely on population measures may eliminate the unintended effects of increasing child welfare caseloads.

Substrate specificity of a CoA-dependent stearoyl transacylase from bovine testis membranes

We identified a CoA-dependent stearoyl transacylase activity in bovine testis membranes, then examined the enzyme's specificity in mixed micelle systems containing the neutral detergent Triton X-100. The enzyme transferred stearoyl groups from a variety of phospholipids to sn-2-arachidonoyl lysophosphatidic acid (lysoPA), but showed very little palmitoyl transacylase activity. Its ability to transfer stearoyl groups was both donor- and acceptor-dependent. For example, it used weakly acidic phospholipids, such as sn-1-stearoyl-2-acyl species of phosphatidylinositol (PI), as donors, but did not use phosphatidylinositol-4,5-bisphosphate or sn-1-stearoyl-2-arachidonoyl phosphatidylcholine. Moreover, it used sn-2-acyl species of lysoPA and sn-2-arachidonoyl lysoPI as acceptors but did not use sn-2-arachidonoyl species of lysophosphatidylserine, lysophosphatidylethanolamine, or lysophosphatidylcholine. When taken together, our results raise the possibility that sn-1-stearoyl-2-acyl species of PI may be the primary acyl donors in the transacylase reaction in vivo, while sn-2-acyl species of lysoPA may be the primary acyl acceptors. Available evidence suggests that the PA that is formed may subsequently be converted into PI, but the metabolic fate of the other reaction product, sn-2-acyl lysoPI, remains to be determined.

Differential low density lipoprotein receptor-dependent formation of eicosanoids in human blood-derived monocytes

We studied the ability of low density lipoproteins (LDLs) to provide arachidonic acid (AA) for eicosanoid biosynthesis in human blood-derived monocytes. When incubated in the presence of reconstituted LDL that contained cholesteryl [1-14C]arachidonate (recLDL-[14C]AA-CE), resting monocytes formed three labeled products of the prostaglandin (PG) H synthase pathway: 6-keto-PGF1 alpha, thromboxane B2, and PGE2. The amounts of these eicosanoids in response to recLDL-[14C]AA-CE were comparable to or exceeded those that were produced in response to the addition of 10 microM unesterified [1-14C]AA. By contrast, resting monocytes formed only small amounts of products of the 5-lipoxygenase pathway, leukotriene (LT) B4 and LTC4 from either recLDL-[14C]AA-CE or [14C]AA, indicating preferential utilization of AA in the PGH synthase reaction. However, they converted LDL-derived [14C]AA efficiently into LTB4 and LTC4, when they were first incubated with recLDL-[14C]AA-CE and subsequently stimulated with the chemotactic peptide N-formylmethionylleucylphenylalanine or the Ca2+ ionophore A23187. The classical LDL receptor pathway mediated the synthesis of all of the above eicosanoids from LDL but not from unesterified AA. These results demonstrate that the LDL receptor pathway preferentially promotes the synthesis of PGH synthase products in resting human blood-derived monocytes and that an additional mechanism is required to promote effective synthesis of 5-lipoxygenase pathway products from AA that originates in LDL cholesteryl esters.

Swiss 3T3 cells preferentially incorporate sn-2-arachidonoyl monoacylglycerol into sn-1-stearoyl-2-arachidonoyl phosphatidylinositol

The sn-1-stearoyl-2-arachidonoyl phospholipids of animal cells appear to be formed by special mechanisms. To determine whether monoacylglycerol (MG) incorporation pathways are involved we incubated quiescent Swiss 3T3 cells with [3H]glycerol-labeled sn-2-arachidonoyl MG, then analyzed the radioactive cell lipids that accumulated. We also examined cell homogenates to identify enzyme activities that might promote the incorporation of sn-2-arachidonoyl MG into other cell lipids. The cell incubation experiments demonstrated rapid labeling of several lipids, including diacylglycerol, lysophosphatidic acid, phosphatidic acid, and phosphatidylinositol. They also demonstrated selective labeling of sn-1-stearoyl-2-arachidonoyl species of phosphatidylinositol, phosphatidylethanolamine, and phosphatidylserine. The cell homogenate experiments identified an sn-2-acyl MG acyltransferase activity, an MG kinase activity that phosphorylates sn-2-arachidonoyl MG in preference to sn-2-oleoyl MG, and a stearoyl-specific acyl transferase activity that converts sn-2-arachidonoyl lysophosphatidic acid into sn-1-stearoyl-2-arachidonoyl phosphatidic acid. The results also showed that this stearoyl transferase could act with other enzymes to convert sn-2-arachidonoyl lysophosphatidic acid into sn-1-stearoyl-2-arachidonoyl phosphatidylinositol. The combined results indicate that Swiss 3T3 cells incorporate sn-2-arachidonoyl MG into phospholipids by at least two different pathways, including one that specifically forms sn-1-stearoyl-2-arachidonoyl phosphatidylinositol.

The LDL receptor pathway delivers arachidonic acid for eicosanoid formation in cells stimulated by platelet-derived growth factor

Animal cells can convert 20-carbon polyunsaturated fatty acids into prostaglandins (PGs) and leukotrienes. These locally produced mediators of inflammatory and immunological reactions act in an autocrine or paracrine fashion. Arachidonic acid (AA), the precursor of most PGs and leukotrienes, is present in the form of lipid esters within plasma lipoproteins and cannot be synthesised de novo by animal cells. Therefore, AA or its plant-derived precursor, linoleic acid, must be provided to cells if PGs or leukotrienes are to be formed. Because several classes of lipoproteins, including low-density lipoproteins (LDL), very-low-density lipoproteins, and chylomicron remnants, are taken up by means of the LDL receptor, and because LDL and very-low-density lipoproteins, but not high-density lipoproteins, stimulate PG synthesis, we have suggested previously that PG formation is directly linked to the LDL pathway. Using fibroblasts with the receptor-negative phenotype of familial hypercholesterolaemia and anti-LDL receptor antibodies, we show here that LDL deliver AA for PG production and that an LDL receptor-dependent feedback mechanism inhibits the activity of PGH synthase, the rate-limiting enzyme of PG synthesis. These results indicate that the LDL pathway has a regulatory role in PG synthesis, in addition to its well-known role in the maintenance of cellular cholesterol homeostasis.

Distribution of distinct arachidonoyl-specific and non-specific isoenzymes of diacylglycerol kinase in baboon (Papio cynocephalus) tissues

We investigated the diacyglycerol kinase species present in several baboon tissues using the substrates sn-1-stearoyl-2-arachidonoyl diacylglycerol and sn-1,2-didecanoyl diacylglycerol. Chromatography of octyl glucoside extracts of the baboon (Papio cynocephalus papio) tissues on hydroxyapatite columns revealed the presence of three diacylglycerol kinase species with different substrate preferences. One species markedly 'preferred' the substrate sn-1-stearoyl-2-arachidonoylglycerol, the two other species preferred sn-1,2-didecanoylglycerol. Measurement of the activity of the baboon brain diacylglycerol kinases toward diacylglycerols with a range of different fatty acid chains revealed a strict preference of the arachidonoyl diacylglycerol kinase for sn-1-acyl-2-arachidonoyl diacylglycerol, whereas the other enzymes showed no preference toward several long-chain-fatty-acid-containing diacylglycerols. The arachidonoyl diacylglycerol kinase was particularly abundant in brain and testis, whereas liver was practically devoid of this enzyme. The arachidonoyl diacylglycerol kinase from baboon brain was found to be predominantly associated with the particulate fraction and exhibited an apparent molecular mass of 130 kDa.

A membrane-bound diacylglycerol kinase that selectively phosphorylates arachidonoyl-diacylglycerol. Distinction from cytosolic diacylglycerol kinase and comparison with the membrane-bound enzyme from Escherichia coli

The membrane-bound diacylglycerol kinase from Swiss 3T3 cells (M-DG kinase) was characterized with a mixed micellar assay system, and compared with the cytosolic diacylglycerol kinase from 3T3 cells and with the membrane-bound diacylglycerol kinase from Escherichia coli. M-DG kinase selectively phosphorylated arachidonoyl-diacylglycerols, at a rate 2- to 8-fold higher than that for other naturally occurring long-chain diacylglycerols. In contrast, the cytosolic 3T3 enzyme exhibited little or no selectivity among long-chain diacylglycerols but had higher activity with more soluble substrates such as 1,2-didecanoylglycerol. Comparison of the properties of M-DG kinase with those of the bacterial membrane-bound enzyme revealed that selectivity for arachidonoyl-diacylglycerol was unique to the mammalian enzyme. All three kinases were activated by phosphatidylserine, but activation did not alter the arachidonoyl selectivity of M-DG kinase. Phosphatidylserine activated M-DG kinase by increasing Vm and decreasing the apparent Km for diacylglycerol. High concentrations of diacylglycerol reduced the Ka for phosphatidylserine, but did not abolish the phosphatidylserine requirement for maximum activity. Examination of the thermal lability of M-DG kinase revealed that this enzyme was rapidly and selectively inactivated by preincubation with its preferred substrate. This novel effect may have obscured previous attempts to discern substrate selectivity. Taken together, the results provide evidence that M-DG kinase is an arachidonoyl-diacylglycerol kinase that may participate in the formation of arachidonoyl-enriched species of phosphatidylinositol.

A study of the small spherical high density lipoproteins of patients afflicted with familial lecithin: cholesterol acyltransferase deficiency

We studied the effects of the lecithin:cholesterol acyltransferase reaction on the size and composition of the small spherical high density lipoproteins of patients afflicted with familial lecithin:cholesterol acyltransferase deficiency. We isolated these lipoproteins by preparative ultracentrifugation and rate zonal ultracentrifugation, determined their diameter by gradient gel electrophoresis, and then calculated their composition by relating measurements of their lipid and apolipoprotein content to particle volume. Our results revealed lipoprotein particles 6.0-6.2 nm in diameter that contained approximately 2 molecules of apolipoprotein A-I, 37-38 molecules of phospholipid, 3-9 molecules of unesterified cholesterol, 1-2 molecules of cholesteryl ester, and 1-2 molecules of triacylglycerol. Upon being incubated with lecithin:cholesterol acyltransferase and a source of additional unesterified cholesterol, these lipoproteins increased in content of total cholesterol and in particle size to form discrete lipoprotein products 6.6-8.6 nm in diameter. The increase in size occurred despite a net decrease in product unesterified cholesterol and phospholipid and though the net change in total lipid volume was small. Moreover, specific product lipoproteins, isolated by rate zonal ultracentrifugation, contained an increased amount of apolipoprotein A-I. These results seem best explained by a process involving lecithin:cholesterol acyltransferase-induced particle rearrangement reactions. The possibility that a similar process normally occurs in vivo deserves to be explored.

Early changes in phosphatidylinositol and arachidonic acid metabolism in quiescent swiss 3T3 cells stimulated to divide by platelet-derived growth factor

We added platelet-derived growth factor to cultures of quiescent Swiss 3T3 cells to investigate early changes in lipid metabolism related to initiation of cell cycle traverse. In a series of experiments that focused on lipid degradation we added the growth factor to cells that had been prelabeled with myoinositol, glycerol, or arachidonic acid. We observed the following mitogen-dependent effects: a decline of radioactivity in cell phosphatidylinositol within 2 to 5 min that progressed to 25 to 50% during the 1st h, a transient rise of radioactivity in cell diacylglycerol that peaked at 10 min, a gradual increase of radioactivity in monoacylglycerol in the medium, and a concomitant increase of radioactivity in medium-free fatty acid. In experiments that focused on lipid biosynthesis, we added the growth factor to cells and pulse-labeled them with radioactive precursors. We observed increased incorporation within 60 min of myoinositol into phosphatidylinositol, arachidonic acid into phosphatidylinositol, diacylglycerol, and phosphatidylethanolamine, and choline into phosphatidylcholine. These results support the possibility that action of platelet-derived growth factor on Swiss 3T3 cells leads to release of diacylglycerol from phosphatidylinositol, that some of the released diacylglycerol is hydrolyzed to monoacylglycerol and arachidonic acid, and that these lipid products are in part reconverted to phosphatidylinositol and other lipids.

Abnormalities in lipoproteins of d < 1.006 g/ml in familial lecithin:cholesterol acyltransferase deficiency

Studies of different sized lipoproteins of d < 1.006 g/ml from patients with familial lecithin:cholesterol acyltransferase deficiency have yielded new evidence of abnormalities in this lipoprotein class. Lipoproteins of all sizes contain high amounts of unesterified cholesterol, low amounts of total protein, and particularly low amounts of apolipoproteins C-II and C-III. Lipoproteins 60 nm in diameter or larger include particles that show a notched appearance upon electron microscopy, and contain a) a high combined volume of phospholipid, unesterified cholesterol, and protein; b) high amounts of cholesteryl ester and apolipoproteins C-I and E, and c) two major tetramethylurea-insoluble proteins that can be separated by electrophoresis in the presence of sodium dodecylsulfate. In contrast, lipoproteins that are 40 nm in diameter or less appear to contain low amounts of cholesteryl ester, normal amounts of apolipoproteins C-I and E, and a single tetramethylurea-insoluble protein the size of that in control lipoproteins. Since these abnormalities occur in the lipoproteins of four different patients from four different families, they are probably effects of the enzyme deficiency. Most, however, appear to arise indirectly because in vitro experiments published earlier indicate that few are reversed by incubation in the presence of the enzyme and patient high density lipoproteins.

Characterization of apolipoprotein E-rich high density lipoproteins in familial lecithin:cholesterol acyltransferase deficiency

We have isolated and charachterized a subfraction of high density lipoproteins, rich in apolipoprotein E, from the plasma of patients afflicted with familial lecithin:cholesterol acyltransferase deficiency. Prepared by successive ultracentrifugal flotation, affinity chromatography on heparin-agarose, and affinity chromatography on conconavalin A-agarose, the subfraction contained disc-shaped lipoproteins that measured 14--40 nm in diameter and 4.4--4.5 nm in thickness. The major components were apolipoprotein E, phosphatidylcholine, and unesterified cholesterol, though other apolipoproteins and lipids were present in small amounts. A second subfraction of high density lipoproteins, isolated during the chromatography, contained apolipoproteins A-I and A-II, but no apolipoprotein E. This subfraction included disc-shaped lipoproteins, 13--24 nm in diameter, as well as small round particles, 5.7 nm in diameter. Both subfractions contained similar proportions of total protein relative to lipid, similar amounts of unesterified cholesterol relative to phosphatidylcholine, and a similar distribution of phosphatidylcholine fatty acid.

In vitro effects of lecithin:cholesterol acyltransferase on apolipoprotein distribution in familial lecithin:cholesterol acyltransferase deficiency

Action of LCAT on the plasma of patients afflicted with familial LCAT deficiency shifts the distribution of C apolipoproteins from lipoproteins of d less than 1.019 g/ml to lipoproteins of d greater than 1.109 g/ml, and causes an opposite shift in the distribution of apolipoprotein E. The altered distribution of apolipoprotein E appears to depend primarily on enzyme-related effects on HDL. Loss of apolipoprotein E from HDL occurs as cholesteryl esters are formed and transfer to other lipoproteins; disc-shaped HDL, rich in apolipoprotein E, are converted into spherical particles; and the population of HDL as a whole is converted first into particles the size of HDL2 and HDL3 and then into intermediate-sized particles. Transfer of apolipoprotein E to artificially prepared triglyceride-rich particles occurs at a nearly linear rate that is slow than the rates of formation and transfer of cholesteryl esters or the rate of formation of "HDL2" and "HDL3." Transfer of apolipoprotein E is faster, however, when the patients' disc-shaped HDL are incubated with triglyceride-rich particles in the presence of normal plasma lipoproteins of d greater than 1.063 g/ml. Since the disc-shaped HDL, rich in apolipoprotein E, resemble particles reported to be released from perfused rat livers, they may be nascent lipoproteins of hepatic origin. If so, it appears that action of LCAT on these lipoproteins may be one of the factors that regulates the content of apolipoprotein E in VLDL.

Survival of Vibrio parahaemolyticus in oyster shellstock at two different storage temperatures

In oyster shellstock harvested from Maryland waters Vibrio parahaemolyticus was found to be present, to survive storage for at least 3 weeks at 4 C, and to multiply after being held for 2 to 3 days at 35 C.