Egg-laying hormone peptides in the aplysiidae family.

The neuropeptidergic bag cells of the marine mollusc Aplysia californica are involved in the egg-laying behavior of the animal. These neurosecretory cells synthesize an egg-laying hormone (ELH) precursor protein, yielding multiple bioactive peptides, including ELH, several bag cell peptides (BCP) and acidic peptide (AP). While immunohistochemical studies have involved a number of species, homologous peptides have been biochemically characterized in relatively few Aplysiidae species. In this study, a combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) and electrospray ionization Fourier transform ion cyclotron resonance MS is used to characterize and compare the ELH peptides from related opisthobranch molluscs including Aplysia vaccaria and Phyllaplysia taylori. The peptide profiles of bag cells from these two Aplysiidae species are similar to that of A. californica bag cells. In an effort to characterize further several of these peptides, peptides from multiple groups of cells of each species were extracted, and microbore liquid chromatography was used to separate and isolate them. Several MS-based sequencing approaches are applied to obtain the primary structures of bag cell peptides and ELH. Our studies reveal that (&agr;)-BCPs are 100 % conserved across all species studied. In addition, the complete sequences of (&egr;)-BCP and ELH of A. vaccaria were determined. They show a high degree of homology to their counterparts in A. californica, with only a few amino acid residue substitutions.

Formation of N-pyroglutamyl peptides from N-Glu and N-Gln precursors in Aplysia neurons.

Matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry is used to examine the formation of N-pyroglutamate (pGlu) in single, identified neurons from Aplysia. Six pGlu peptides are identified in the R3-14 and the R15 neurons that result from in vivo processing of peptides containing either Glu or Gln at their respective N-termini. Moreover, we show that Glu-derived pGlu is not a sample collection or measurement artifact. The pGlu peptides are detected in isolated cell bodies, regenerated neurites in culture, interganglionic connective nerves, cell homogenates, and collected releasates. We also demonstrate that R3-14 cells readily convert a synthetic N-Glu peptide to its pGlu analogue, indicating the presence of novel enzymatic activity.

Management of diabetes mellitus in the Lovelace Health Systems' EPISODES OF CARE program.

OBJECTIVE: To design and implement the Lovelace Diabetes EPISODES OF CARE program in a managed care setting. This program is intended to address the complex needs of patients with type 2 diabetes mellitus by using specific physician-provider and patient interventions. DESIGN: Observational study. SETTING: Lovelace Health Systems, the second-largest and most fully integrated health care delivery system in New Mexico. The main facility is located in Albuquerque. PARTICIPANTS: Lovelace Health Plan members with type 2 diabetes. INTERVENTIONS: Physician-provider interventions included practice guidelines medical profile screens, and provider support reports. Patients interventions included diabetes education; improved access to care, with focused diabetes clinic visits and "Diabetes Days"; and reminder systems. MAIN OUTCOME MEASURES: Glycohemoglobin values, dilated eye examination rates, and access to education. RESULTS: Significant lowering of glycohemoglobin values, dilated eye examination rates exceeding benchmark measures, and increases in educational access rates have occurred since the Lovelace Diabetes EPISODES OF CARE program was implemented. CONCLUSIONS: An integrated health care delivery system with a comprehensive, diabetes disease management program can substantially improve outcomes.

Plasma apolipoprotein E, high density lipoprotein1 (HDL1) and urinary mevalonate excretion in pancreatectomized diabetic dogs: effects of insulin and lovastatin.

Hypercholesterolemia and increased concentrations of an apolipoprotein E (apoE)-containing HDL subclass, high density lipoprotein1 (HDL1) have been observed in streptozocin-alloxan diabetic dogs consuming normal amounts of dietary cholesterol. The aim of this study was to characterize the response of HDL1 and its targeting ligand, apoE, to insulin and HMG-CoA reductase inhibitor treatment in pancreatectomized diabetic dogs. Following induction of diabetes, plasma total cholesterol, HDL1, and apoE concentrations were all increased. Urinary mevalonate excretion, an index of cholesterol synthesis in humans, was 6-fold that of nondiabetic controls. Lipoprotein fractionation by Pevikon block electrophoresis and gel filtration chromatography showed that the increased cholesterol and apoE were associated with alpha 2-migrating particles corresponding to HDL1. Insulin treatment, resulting in near normal fasting blood glucose concentrations in the group as a whole (average 5.1 mM, 92 mg/dl), led to variable reductions in apoE, total plasma cholesterol, and HDL1. Uncorrected dyslipidemia during intensified insulin treatment appeared to be related to failure to achieve euglycemia. Despite unremitting hyperglycemia, treatment with lovastatin resulted in pronounced decreases in plasma cholesterol, HDL1 and apoE to concentrations below those observed in nondiabetic animals. Mevalonate excretion also fell, but remained twice normal. Thus neither modality corrected all of the abnormalities in canine diabetic dyslipidemia. Since apoE-containing HDL1 may mediate cholesterol traffic between the periphery and the liver (reverse cholesterol transport), the present observations suggest that increased cholesterol synthesis is accompanied by parallel abnormalities in cholesterol flux through the reverse transport pathway in the canine model.

Novel aspects of vitamin A metabolism in the dog: distribution of lipoprotein retinyl esters in vitamin A-deprived and cholesterol-fed animals.

Retinyl ester concentrations in plasma from fasting humans, rabbits and rats are usually negligible. In contrast, plasma from fasting dogs contains appreciable amounts of retinyl esters, associated almost entirely with the low-density lipoproteins. This study was undertaken to gather additional information about the nature and origin of canine retinyl ester-containing lipoproteins. We examined the metabolism of endogenous lipoprotein retinyl esters in adult mongrel dogs with moderate vitamin A deficiency. Four animals were fed a diet of oatmeal and tuna fish that provided only 4% of the vitamin A contained in their control rations (15 vs. 367% of the canine recommended daily intake). There was an initial rapid decline in plasma retinyl esters. However, measurable concentrations persisted in plasma for up to 1 year of restricted vitamin A intake. Total plasma retinyl ester concentrations after 6 months of vitamin A deprivation, extrapolated from best-fit monoexponential decay curves for each animal, ranged from 11 to 89% of control, suggesting that there was sustained secretion of retinyl esters from endogenous stores. Density gradient ultracentrifugation of plasma from fasting vitamin A-deprived dogs showed retinyl esters in the very-low- and low-density lipoproteins. After fat and vitamin A feeding retinyl esters appeared among the very-low-, intermediate- and low-density lipoproteins, consistent with the suggestion that chylomicron retinyl esters are first taken up by the liver, and then resecreted as density less than 1.006-1.063 g/ml lipoproteins. Maximal incorporation of dietary retinyl esters into low-density lipoproteins was not reached until 24-48 h. Intermediate-density and beta-migrating low-density lipoprotein retinyl esters were increased markedly in fasting animals maintained on cholesterol- and saturated fat-enriched diets. These observations provide further evidence for the proposal that the canine liver secretes retinyl ester-containing particles, in amounts governed by dietary composition and vitamin A content. What selective advantage this unusual transport pathway might provide is not apparent.

Effects of estrogen/progestin agents on plasma retinoids and chylomicron remnant metabolism.

Women using estrogen-progestin oral contraceptive agents have a marked decrease in the activity of hepatic triglyceride lipase, an enzyme believed to be involved in the catabolism of lipoprotein remnants. The hypothesis that women receiving these agents have defective remnant processing resulting in elevated chylomicron remnant concentrations in plasma was tested. Retinyl esters, which in humans are transported by intestinally-derived lipoproteins, were used to estimate chylomicron and chylomicron remnant concentrations. Women on a variety of oral contraceptive agents had increased plasma triglyceride concentrations, but only minimally increased fasting retinyl ester concentrations. Retinol and retinyl binding protein were elevated to about 150% of controls (p less than 0.001). Retinyl ester concentrations during active fat absorption were then measured in a second group of women taking a single preparation. Three-hour retinyl ester levels were lower in the treated group than control (p less than 0.05), but the difference had disappeared at six hours. Postheparin plasma hepatic triglyceride lipase was reduced by 46% in the treated group (p less than 0.05). Thus despite reduction in hepatic lipase activity, there was no accumulation of retinyl esters in the contraceptive-treated women to suggest impaired remnant processing.

PIP: Women using estrogen-progestin oral contraceptive agents have a marked decrease in the activity of hepatic triglyceride lipase, an enzyme believed to be involved in the catabolism of lipoprotein remnants. The hypothesis that women receiving these agents have defective remnant processing resulting in elevated chylomicron remnant concentrations in plasma was tested. Retinyl esters, which in humans are transported by intestinally-derived lipoproteins, were used to estimate chylomicron and chylomicron remnant concentrations. Women on a variety of oral contraceptive agents had increased plasma triglyceride concentrations, but only minimally increased fasting retinyl ester concentrations. Retinol and retinyl binding protein were elevated to about 150% of controls (cr 0.001). Retinyl ester concentrations during active fat absorption were than measured in a 2nd group of women taking a single preparation. 3 hour retinyl ester levels were lower in the treated group than control (p 0.05), but the difference had disappeared at 6 hours. Postheparin plasma hepatic triglyceride lipase was reduced by 46% in the treated group (p 0.05). Thus despite reduction in hepatic lipase activity, there was no accumulation of retinyl esters in the contraceptive-treated women to suggest impaired remnant processing.