Behavior of human apolipoprotein A-I: phospholipid and apoHDL:phospholipid complexes in vitro and after injection into rabbits

Apolipoprotein A-I was purified from human high density lipoprotein and complexed with polyunsaturated phosphatidylcholine (PC) in deoxycholate (Lipostabil); the bile salt was removed subsequently by dialysis. The behavior of the resultant apoA-I/PC complexes was compared with that of Lipostabil in vitro and after injection into rabbits. In vivo apoA-I/PC complexes had the density of HDL throughout but had both alpha and pre beta electrophoretic mobility, the latter probably reflecting dissociation of apoA-I from PC. Lipostabil initially behaved like LDL but gradually acquired the density of HDL after incubation with plasma and in vivo. Both preparations increased plasma total phospholipids in normolipidemic rabbits to a similar extent, but, increments in HDL phospholipid were greater after apoA-I/PC complexes were injected. ApoHDL/PC complexes, prepared in a similar manner, appeared to promote efflux of cholesterol from perfused rabbit aortas in the presence of lecithin:cholesterol acyltransferase (LCAT) activity, consistent with a stimulatory effect on cholesterol mobilization. Injection of apoHDL/PC complexes into hyperlipidemic rabbits decreased plasma cholesterol but increased HDL cholesterol, whereas Lipostabil decreased both. These findings suggest that human apoA-I/PC complexes resemble HDL in their behavior more closely than does Lipostabil, and show that both types of liposome undergo modification upon interaction with plasma. It remains to be shown whether they possess any therapeutic potential.

High prevalence of hypertriglyceridaemia and apolipoprotein abnormalities in coronary artery disease

Serum lipids and apolipoproteins A-I and B were measured in 174 men aged less than 60 with angiographically confirmed coronary artery disease and in 572 healthy control men. Two thirds of the patients had raised age-corrected values of fasting serum cholesterol and/or triglyceride and/or a low high density lipoprotein (HDL) cholesterol compared with the controls. Eighteen (30%) of the 61 normolipidaemic patients had a concentration of serum apolipoprotein A-I below the 5th percentile of 233 controls. In normolipidaemic patients on beta blockers the relative prevalence of serum low density lipoprotein (LDL)-apolipoprotein B values above the 95th percentile of 339 controls was significantly increased. Discriminant function analysis showed that a raised concentration of serum triglyceride was the best discriminant between patients and controls, with raised LDL-apolipoprotein B and reduced apolipoprotein A-I coming second only to triglyceride in analyses where each was separately compared with all the lipid variables. These associations were highly significant and were independent of other influences, including beta blockade. These findings re-emphasise the importance of hypertriglyceridaemia as a risk factor and confirm that apolipoprotein abnormalities occur frequently in coronary disease, even in normolipidaemic patients.

Clinical consequences of hyperlipidaemia

Hyperlipidaemia is a common and important clinical entity which frequently has a genetic basis. The chief features of severe hypertriglyceridaemia are eruptive xanthomata and acute pancreatitis, whereas most forms of hypercholesterolaemia are associated with premature coronary heart disease. This applies especially to familial hypercholesterolaemia, which is also characterized by tendon xanthomata. Better recognition of hyperlipidaemia allied to recent improvements in treatment should help reduce the frequency of its disabling and sometimes fatal consequences.

Normal and pathological lipoprotein metabolism

Lipids are transported in plasma as lipoproteins, and an increase in 1 or more classes of lipoprotein underlies all forms of hyperlipidaemia. Physiological influences on lipoprotein metabolism are age, gender, bodyweight, diet and exercise. Pathological influences include genetic abnormalities, endocrine dysfunction, renal impairment and iatrogenic effects. Three inherited forms of hyperlipidaemia which predispose to atherosclerosis are familial hypercholesterolaemia (FH), type III hyperlipoproteinaemia and familial combined hyperlipidaemia (FCH), each of which has its own distinctive metabolism defect. In FH, deficiency of low density lipoprotein (LDL) receptors results in the accumulation in plasma of LDL-cholesterol because of a reduction in the receptor-mediated component of LDL catabolism. In type III hyperlipoproteinaemia, the presence of an abnormal apo E isoform (apo E2) in remnant particles leads to their accumulation in plasma, through nonrecognition by remnant receptors and a consequent reduced rate of hepatic uptake. In contrast, there is no primary catabolic defect in FCH, in which increased levels of very low density lipoprotein (VLDL) and LDL are largely the result of increased synthesis.

Plasma exchange and low density lipoprotein apheresis in Watanabe heritable hyperlipidemic rabbits

Comparison of the effects of plasma exchange using lipoprotein-deficient plasma with those of LDL apheresis using a dextran sulphate column was undertaken in two groups of Watanabe heritable hyperlipidemic rabbits pre-labelled with 3H-cholesterol. Total and HDL cholesterol were reduced more by plasma exchange but HDL cholesterol rebounded higher after LDL apheresis; rises in HDL cholesterol correlated with preceding decreases in both HDL and total cholesterol. An increase in the specific activity of HDL cholesterol occurred on the day after each procedure, being more marked after plasma exchange, and was accompanied by a decrease in the cholesterol/phospholipid ratio of HDL. These results suggest that an influx of extravascular HDL into plasma occurred after both procedures, resulting in mobilization of tissue cholesterol.

Treatment of severe accidental hypothermia using the Clinitron bed

Two cases of severe accidental hypothermia (core temperature less than 28 degrees C) rewarmed employing the Clinitron system are described. The physiological changes during hypothermia and rewarming are discussed and the current concepts of rewarming (active external versus internal) outlined. It is suggested that severely hypothermic patients can be successfully treated by rapid external rewarming using the Clinitron heated fluidised-bead bed. This method combines the advantages of rapid rewarming, minimal physiological disturbance and is non invasive.

Kinetics of LDL subfractions

After injecting 125I- or 131I-labeled lipoproteins, plasma was subjected to discontinuous density gradient centrifugation, which separates low-density lipoproteins (LDL) into three subfractions. Analysis of changes in apolipoprotein B-specific activity with time showed that light LDL is normally the product of intermediate-density lipoprotein and the precursor of heavy LDL, which is subsequently converted to heavier LDL. In hyperapobetalipoproteinemia these relationships are maintained but there is overproduction of light and heavy LDL secondary to increased synthesis of very low-density lipoprotein. In familial hypercholesterolemia, light LDL is produced normally but its conversion into heavy LDL is reduced and independent synthesis of the latter is apparent. These observations suggest that the LDL receptor normally plays a role in the conversion of light into heavy LDL. They also provide an explanation for previously documented differences in LDL composition between hyperapobetalipoproteinemia, in which there is a relative increase in cholesterol-depleted heavy and heavier subfractions, and familial hypercholesterolemia, in which there is a relative increase in the cholesterol-enriched light subfraction.

Paradoxical elevation of LDL apoprotein B levels in hypertriglyceridaemic patients and normal subjects ingesting fish oil

Twenty-three hypertriglyceridaemic patients treated with 15 g/day of a fish oil concentrate (Maxepa) showed the expected reduction in serum triglyceride concentration but levels of LDL apoprotein B (apoB), measured by radial immunodiffusion, increased significantly. Increases in LDL apoB did not correlate with lipoprotein phenotype or changes in serum triglyceride. Studies in eight normal volunteers demonstrated that the effect of fish oil on LDL apoB was not restricted to hypertriglyceridaemic subjects. In view of the evidence that LDL apoB may be a risk factor for coronary heart disease these findings raise questions regarding the use of fish oil in the treatment of hypertriglyceridaemia.

Efficacy of mevinolin as adjuvant therapy for refractory familial hypercholesterolaemia

Mevinolin, a potent inhibitor of cholesterol synthesis, was used as a therapeutic adjuvant in patients with refractory familial hypercholesterolaemia for an average period of 13 months. Sustained decreases in serum cholesterol of 23 and 31 per cent were achieved by doses of 20 mg and 40 mg/day respectively in 13 heterozygotes already on cholestyramine or after partial ileal bypass. Administration of 80 mg/day to three patients undergoing plasma exchange reduced peak serum cholesterol levels by 11.5 per cent in two homozygotes and by 17 per cent in a double heterozygote for familial hypercholesterolaemia and type III hyperlipoproteinaemia. The decrease in cholesterol was largely confined to low-density lipoprotein and no significant changes occurred in serum triglyceride or high-density lipoprotein cholesterol. Mevinolin was well-tolerated except in one patient who developed myositic symptoms; asymptomatic, transient elevations of serum enzymes were observed in five others. Short and long Synacthen tests showed no evidence that the drug impaired adrenocortical response to ACTH. These results indicate that mevinolin provides a safe and highly effective means of reducing LDL levels in patients with heterozygous familial hypercholesterolaemia refractory to conventional treatment but is less useful in homozygotes.

Binding and degradation of heavy and light subfractions of low density lipoprotein by cultured fibroblasts and macrophages

The heavy and light subfractions of low density lipoprotein (LDL) were bound to the same extent and with the same affinity by the LDL receptors of cultured human fibroblasts, both when assayed at 4 degrees C and when assayed at 37 degrees C. They were also degraded similarly by the low affinity, LDL-receptor-mediated pathway exhibited by normal human monocyte-derived macrophages maintained in medium containing whole serum. Neither of the subfractions was taken up by the 'scavenger' pathway in mouse peritoneal or human monocyte-derived macrophages. Assuming that the LDL particles were not altered during isolation, the results provide no evidence to suggest that the higher fractional catabolic rate of light LDL observed in vivo can be explained by any preferential catabolism through LDL-receptor-mediated pathways.

Metabolic basis of hyperapobetalipoproteinemia. Turnover of apolipoprotein B in low density lipoprotein and its precursors and subfractions compared with normal and familial hypercholesterolemia

The turnover of apolipoprotein B (apo B) in very low density, intermediate density, and low density lipoproteins (VLDL, IDL, and LDL) and in the light and heavy fractions of LDL was determined in seven patients with hyperapobetalipoproteinemia (hyperapo B), six normolipidemic subjects, and five patients with heterozygous familial hypercholesterolemia (FH). After receiving an injection of 125I-VLDL, hyperapo B patients were found to have a higher rate of synthesis of VLDL-apo B than controls (40.1 vs. 21.5 mg/kg per d, P less than 0.05) but a reduced fractional catabolic rate (FCR) (0.230 vs. 0.366/h, P less than 0.01). After receiving an injection of 131I-LDL, hyperapo B patients had higher rates of LDL-apo B synthesis than controls (23.1 vs. 13.0 mg/kg per d, P less than 0.001), as did FH patients (22.7 mg/kg per d). The FCR of LDL was similar in hyperapo B patients and controls (0.386 vs. 0.366/d) but was markedly decreased in FH patients (0.192/d). Most subjects exhibited precursor-product relationships between VLDL and IDL, and all did between IDL and light LDL; an analogous relationship between light and heavy LDL was evident in most hyperapo B patients and controls but not in FH patients. Simultaneous injection of differentially labeled LDL fractions and deconvolution analysis showed increased light LDL synthesis with normal conversion into heavy LDL in hyperapo B, whereas in FH conversion of light LDL was reduced and there was independent synthesis of heavy LDL. These data show that the increased concentration of LDL-apo B in hyperapo B is solely due to increased LDL synthesis, which is secondary to increased VLDL synthesis; in contrast, in FH there is both an increase in synthesis of LDL (which is partly VLDL-independent) and reduced catabolism.

Clinical judgments of depression

In an effort to reevaluate Gough's (1954) classic study of common misconceptions about neuroticism, an investigation was undertaken of the degree to which judges could simulate the Basic Personality Inventory (BPI) responses of a clinically depressed patient group. Judgments were recorded of the probability of responding to each of 240 BPI items by a total of 56 university student judges. Judges were assigned randomly to one of two information conditions, one that had only the label "clinical depression" and another that had, in addition, a more extensive definition. Judgmental profiles of depressed patients indicated very high reliabilities (.99) across information conditions, a high association with actual profiles of clinically depressed patients, and differentiation from other psychiatric patients and normal controls. Results were interpreted as supporting the accuracy of judgments of psychopathology, particularly when certain preconditions are met, namely, the use of a meaningful construct of psychopathology and the prediction of behavior relevant to that construct.

Improved survival of patients with homozygous familial hypercholesterolaemia treated with plasma exchange

Plasma exchange was undertaken in five patients with homozygous familial hypercholesterolaemia at intervals of two weeks for a mean of 8.4 years. These patients had survived an average of 5.5 years longer than their five respective homozygous siblings (p = 0.3), each of whom must have had a matching genetic defect but who died untreated. The 37% decrease in peak serum cholesterol concentrations maintained by plasma exchange presumably reduced progression of atherosclerosis in the treated patients and thus lessened their risk of premature death.

Triglyceride-lowering effect of marine polyunsaturates in patients with hypertriglyceridemia

Twenty male patients with primary hypertriglyceridemia were treated for 4 weeks with daily supplements (15 g) of oil, which provided approximately 6 g of polyunsaturated fatty acid (PUFA) either of fish or of vegetable origin. Total plasma cholesterol concentrations were unaffected, but both types of supplement increased high density lipoprotein-3 (HDL3) cholesterol concentrations. The fish, but not the vegetable, oil supplement led to a decrease in plasma triglyceride concentrations. Very low density lipoprotein (VLDL), fatty acid composition, and VLDL triglyceride kinetics were subsequently studied in five patients (four male, one female) before and after 4 weeks of therapy with 15 g of the same fish oil. The fish oil led to increases in the proportion of eicosapentaenoic acid in both the VLDL triglyceride and phospholipid fractions, but the increase was greater in the latter. In contrast, the proportion of docosahexanoic acid was increased only in the VLDL triglycerides. The decrease in plasma triglyceride concentrations that occurred with fish-oil therapy was accompanied by a reduction in the absolute catabolic rate of VLDL triglyceride, implying a concomitant change in synthetic rate; the fractional catabolic rate of VLDL triglyceride was unaltered. It is suggested that polyunsaturated fatty acids of marine origin may be therapeutically useful for hypertriglyceridemia.

Failure of experimental atherosclerosis to sensitize coronary arteries to spasm in hypercholesterolemic rabbits

Since hypercholesterolemia sensitizes isolated rabbit coronary arteries to vasoconstrictor stimuli, we assessed the possibility of reproducing occlusive coronary spasm both in vitro and in vivo in atherosclerotic rabbits. In Langendorff-perfused hearts from nine atherosclerotic rabbits (2% cholesterol diet for 18 weeks), despite a threefold increase of cholesterol concentration in the coronary wall compared with nine control rabbits, ergonovine and serotonin did not produce any increase of coronary vascular resistances; the increase produced by pitressin was significantly less in atherosclerotic than in normal hearts (56 +/- 13% vs 138 +/- 28%, p less than 0.05, respectively), whereas that produced by phenylephrine was similar (10.1 +/- 1.8% vs 8.5 +/- 2.4%, p = n.s.). In eight other unanesthetized rabbits we recorded the ECG during ergonovine administration (0.05 mg/kg) and during hypothalamic stimulation before and at regular intervals during the 2% cholesterol diet; rabbits survived for periods ranging from 1 to 22 weeks (mean 9.6 weeks). Only one animal had ST depression during episodes of marked tachycardia; no ischemic ECG changes were ever observed in the other rabbits despite the diffuse subintimal coronary deposition of cholesterol found postmortem. Thus, in atherosclerotic rabbits with chronic marked hypercholesterolemia, coronary arteries do not develop occlusive coronary spasm as observed in patients with variant angina.

Coronary artery disease and haemostatic variables in heterozygous familial hypercholesterolaemia

Haemostatic variables were measured in 61 patients with heterozygous familial hypercholesterolaemia, 32 of whom had evidence of coronary heart disease. Age adjusted mean concentrations of plasma fibrinogen and factor VIII were significantly higher in these patients than in the 29 patients without coronary heart disease, but there were no significant differences in serum lipid concentrations between the two groups. Comparisons in 30 patients taking and not taking lipid lowering drugs showed lower values for low density lipoprotein cholesterol, high density lipoprotein cholesterol and antithrombin III, and a higher high density lipoprotein ratio while receiving treatment. The results suggest that hypercoagulability may play a role in the pathogenesis of coronary heart disease in patients with familial hypercholesterolaemia.

Hyperlipidaemia and premature coronary artery disease associated with sex-change in a female

We describe the management of a genotypic female who developed hyperlipidaemia and premature coronary artery disease following bilateral oophorectomy and methyltestosterone administration, and present evidence to suggest that the therapeutic androgenization involved in the sex-change was responsible for the hyperlipidaemia.

Circulating human C-reactive protein binds very low density lipoproteins

Native human CRP in solution formed complexes with the abnormal lipoprotein beta-VLDL in serum of patients with type III hyperlipoproteinaemia. CRP also formed complexes in sera from individuals with type IV and type V hyperlipoproteinaemia. The binding was calcium-dependent and inhibitable by free phosphoryl choline. No complexes were demonstrable in sera containing high LDL levels from cases of type IIa hyperlipoproteinaemia. Addition of isolated beta-VLDL, but not of isolated LDL, to acute phase normolipoproteinaemic serum caused the appearance of soluble CRP-lipoprotein complexes. In contrast, addition of an excess of isolated normal VLDL to acute phase serum or to isolated CRP was followed by agglutination (creaming) of the lipoprotein particles. Rabbit CRP, on the other hand, formed soluble complexes both with normal human apoB containing lipoproteins and with the abnormal beta-VLDL. Human CRP complexed with rabbit beta-VLDL but not with normal rabbit serum lipoproteins. These interactions may be important for the role of CRP in health and disease.

Effects of starvation and plasma exchange on lecithin: cholesterol acyltransferase activity and cholesterol efflux in cholesterol-fed pigs

The effects of starvation and of plasma exchange with a cholesterol-free substitute on efflux of tissue cholesterol and on lecithin: cholesterol acyltransferase (LCAT) activity in plasma and peripheral lymph were investigated in two pigs fed a cholesterol diet for 3-4 months. The pigs were labelled with i.v. [14C]cholesterol before plasma exchange or starvation. The cholesterol diet increased plasma total cholesterol concentration and LCAT activity in plasma and lymph, but had little effect on the rate of esterification of cholesterol in plasma or lymph. During cholesterol feeding, and when the animals were fed a normal diet, cholesterol esterification rates in plasma and lymph were much lower than the maximum rates achieved when LCAT was saturated with substrate, suggesting that LCAT in normal pig plasma and lymph is not saturated with substrate. Plasma exchange, carried out when the specific activity of tissue cholesterol exceeded that of plasma cholesterol, was followed by a brief rise in the specific activity of plasma cholesterol to a maximum value between the specific activities of muscle and adipose-tissue cholesterol, reflecting the transfer of radioactive cholesterol from tissue to plasma. During the rise in plasma total cholesterol specific activity there were no differences between the specific activities of low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol in plasma or lymph. Starvation had no effect on the plasma-cholesterol specific-activity curve. From about day 14 after labelling, cholesterol-specific activity decreased in the order: tissues greater than lymph greater than plasma. This suggests that the transfer of cholesterol from tissues to plasma was mediated by lipoproteins in the interstitial fluid.

Effects of short term beta adrenoreceptor blockade on serum lipids and lipoproteins in patients with hypertension or coronary artery disease

The effects of beta adrenoceptor blockade with propranolol or pindolol on serum total cholesterol, low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), and its subfractions HDL2 and HDL3, serum triglyceride, and Intralipid clearance were studied in 17 normolipidaemic, non-diabetic patients with hypertension or angina pectoris. Both pindolol and propranolol had similar effects on fasting serum total and lipoprotein cholesterol concentrations. HDL2 cholesterol concentrations were reduced by 9 +/- 29% and HDL3 cholesterol increased by 11 +/- 16%, but there were no significant changes in total or LDL cholesterol in the combined groups after six weeks' treatment. After 12 weeks' treatment total cholesterol concentrations were reduced by 7 +/- 10% mainly owing to a reduction in the LDL fraction of 9 +/- 15%. Concentrations of HDL2 remained low, 8% less than control values. Serum triglyceride concentrations were increased by both drugs at six weeks but had returned to base values in the pindolol group by the twelfth week. Pindolol, but not propranolol, enhanced the rate of clearance of intravenous Intralipid.

Cinnamic aldehyde: a survey of consumer patch-test sensitization

The potential for cinnamic aldehyde, an important fragrance and flavour ingredient, to induce or to elicit delayed contact hypersensitivity reactions in man was evaluated by analysing patch-test data. Results of studies involving a total of 4117 patch tests on various consumer products and fragrance blends containing cinnamic aldehyde and on the material itself were collected from fragrance and formulator companies. The data indicate that cinnamic aldehyde contained in consumer products and fragrance blends at concentrations up to 6 X 10(-1)%, and patch-tested at concentrations up to 8 X 10(-3)%, has no detectable potential to induce hypersensitivity. Cinnamic aldehyde when tested alone induced a dose-related hypersensitivity response. According to published reports, cinnamic aldehyde elicited positive delayed hypersensitivity responses in dermatitic patients. However, results of the current survey show that when cinnamic aldehyde was tested alone or as part of a mixture in subjects in the general population, no pre-existing hypersensitivity reactions to the fragrance material were observed in any of the 4117 patch tests which constituted the survey. Cinnamic aldehyde at the concentrations contained in consumer products and fragrances, has a very low potential to induce hypersensitivity ('induced' reactions) or to elicit sensitization reactions ('elicited' reactions) in the general population.

Isoeugenol: a survey of consumer patch-test sensitization

The potential of isoeugenol, an important fragrance and flavour ingredient, to induce delayed contact hypersensitivity or to elicit pre-existing sensitization reactions in man was evaluated by analysing patch-test data from dermatitic and non-dermatitic subjects. Results from a total of 6512 patch tests (involving approximately 5850 subjects) on isoeugenol alone and on various consumer products and fragrance blends containing isoeugenol, were collected from fragrance and formulator companies. Hypersensitivity induced by isoeugenol was concentration dependent. All but two of the reactions occurring in this survey were at exposure concentrations greater than or equal to 0.8% isoeugenol. No induced reactions occurred in the 1004 patch tests reported at isoeugenol concentrations between 0.03 and 0.5%. One induced reaction in 32 patch tests was attributable to isoeugenol at a concentration of 0.02% while another induced reaction in 23 patch tests conducted at the same concentration was resolved to an isoeugenol-eugenol mixture. One elicited reaction at an isoeugenol concentration of 0.04% occurred in the 6512 patch tests reported in this survey. This single elicitation was resolved to an isoeugenol-eugenol mixture, but the specific causative agent was not identified. The results of this survey indicate that isoeugenol has a very low potential for either eliciting pre-existing sensitization reactions ('elicited' reactions) or inducing hypersensitivity ('induced' reactions) in subjects exposed to consumer products containing this ingredient.

Benzyl salicylate: a survey of consumer patch-test sensitization

The potential of benzyl salicylate, an important fragrance and flavour ingredient, to induce hypersensitivity or to elicit reactions to pre-existing hypersensitivity in the general population was evaluated by analysing patch-test data. Results obtained from fragrance and formulator companies for a total of 10,538 patch tests on benzyl salicylate alone, on a variety of household and personal care consumer products and on fragrance blends containing benzyl salicylate were analysed as part of this survey. No induced or elicited responses directly attributable to benzyl salicylate were observed in the 35 patch tests on benzyl salicylate alone, or in the 10,503 patch tests on consumer products or fragrance blends containing benzyl salicylate. The highest concentration of benzyl salicylate tested in the consumer-product tests was 2 X 10(-1)%, and benzyl salicylate alone was tested at 10% in ethanol. This study indicates that benzyl salicylate has a very low potential to induce hypersensitivity ('induced' reactions) or to elicit reactions presumably attributable to pre-existing sensitization ('elicited' reactions) and thus supports the safe use of benzyl salicylate in consumer products and fragrance blends.

Eugenol and clove leaf oil: a survey of consumer patch-test sensitization

The potential of eugenol and of clove leaf oil, which contains a high concentration of eugenol, to induce delayed skin hypersensitivity or to elicit reactions due to pre-existing skin sensitization in man was evaluated by analysing patch-test data. Results from a total of 11,632 patch tests on eugenol itself, on various consumer products containing eugenol and/or clove leaf oil, and on fragrance blends containing eugenol and/or clove leaf oil were collected from fragrance and formulation companies. One instance of induced hypersensitivity and one instance of pre-existing sensitization were observed at eugenol patch-test concentrations of 5 X 10(-2) and 9 X 10(-2)% respectively. In both cases, subsequent patch testing showed skin responses to mixtures of eugenol and isoeugenol, but no further attempt was made to define the causative agent. The survey indicates that, at the concentrations present in consumer products, eugenol alone or as part of clove leaf oil has a very low potential either to elicit pre-existing sensitization ('elicited' reactions) or to induce hypersensitivity ('induced' reactions).

Cross sectional echocardiographic assessment of the aortic root and coronary ostial stenosis in familial hypercholesterolaemia

Aortic root abnormalities (atherosclerotic thickening and obstruction) seen at necropsy may readily be detected by aortography in familial hypercholesterolaemia. We studied 35 patients with familial types IIa and IIb hyperlipoproteinaemia including three homozygotes and 32 heterozygotes. Two homozygotes showed abnormal bright echoes (atheroma) encircling the proximal aortic root, which interfered with full excursion of the aortic cusps. One homozygote showed the typical echocardiographic features of supravalvular aortic stenosis at the superior border of the sinus of Valsava with normal aortic cusps. Cardiac catheterisation showed valvular gradients of 15 and 80 mm Hg in two homozygotes and a supravalvular gradient of 40 mm Hg in the third. Left coronary artery ostial stenosis was identified by echocardiography in all three homozygotes. Echocardiographic measurements of the aortic root in the 32 heterozygotes were similar to the control group, but 10 patients showed abnormal bright echoes within the aortic cusps and four had supravalvular changes similar to, but less severe than, the homozygotes. In one severely heterozygote supravalvular atheroma prevented full aortic cusp excursion, and this finding was confirmed during coronary artery bypass surgery.

Composition and distribution of low density lipoprotein fractions in hyperapobetalipoproteinemia, normolipidemia, and familial hypercholesterolemia

Hyperapobetalipoproteinemia is defined as the combination of a normal low density lipoprotein (LDL) cholesterol in the face of an increased LDL apolipoprotein B (apoB) protein. To examine the physical basis for the apparent disproportion between LDL cholesterol and apoB characteristic of this syndrome, we used density gradient ultracentrifugation to isolate LDL fractions from 10 normal subjects, from 20 patients with hyperapobetalipoproteinemia (10 normotriglyceridemic and 10 hypertriglyceridemic), and from 7 patients with familial hypercholesterolemia. In familial hypercholesterolemia, more LDL was in fraction 1--"light" LDL--and this LDL was relatively enriched in cholesterol and poor in protein. By contrast, it was fraction 2--"heavy" LDL--that differed in hyperapobetalipoproteinemia, being denser, depleted of cholesterol (particularly cholesteryl ester), and relatively enriched in apoB. These findings were more pronounced in the hypertriglyceridemic patients than in the normotriglyceridemic patients with hyperapobetalipoproteinemia. Thus this study confirms that considerable heterogeneity exists between LDL subfractions within individuals but, in addition, indicates there are also marked--and apparently characteristic--differences in LDL composition amongst normal subjects and patients with hyperapobetalipoproteinemia or familial hypercholesterolemia.

Effects of vasoactive stimuli on coronary vascular resistance in isolated perfused rabbit hearts: no vasospastic response to ergonovine with or without atherogenic diet

The mechanism of ergonovine-provoked coronary vasospasm is poorly understood. We tested the effect of ergonovine in perfused hearts from normal and cholesterol-fed (18 weeks, 2% cholesterol diet) rabbits in a constant-flow Langendorff perfusion. Aortic perfusion pressure was monitored to measure coronary vascular resistance, and left ventricular pressure was measured with an isovolumetric balloon in the left ventricle. Control coronary vascular resistance was 1.12 +/- 0.11 mm Hg/ml/min in hearts from normal rabbits and 1.53 +/- 0.16 mm Hg/ml/min in hearts from cholesterol-fed rabbits (n = 9 each, mean +/- SEM, p less than 0.05). The cholesterol content of aortae from cholesterol-fed rabbits was markedly increased (432 +/- 85 mg/g protein vs. 14.9 +/- 8.2 in controls, p less than 0.001; for coronaries: 396 +/- 136 mg/g protein vs. 125 +/- 25, p less than 0.05). In both groups, increases in coronary vascular resistance were observed with vasopressin (40 IU/l) and phenylephrine (30 microM) and decreases with adenosine (10 microM), isoprenaline (0.1 microM) and 30 sec stop-flow (all p less than 0.05). Ergonovine maleate (10 microM) and serotonin (10 microM) did not increase coronary vascular resistance. Although in whole heart perfusion small changes in the caliber of epicardial vessels may not be detectable, changes severe enough to produce measurable changes in total coronary resistance were not found. Therefore the absence in our model of an increase in coronary vascular resistance after ergonovine is not compatible with a local direct mechanism in epicardial arterial wall, even when sensitized by a high cholesterol diet.

Normal adrenocortical response to adrenocorticotrophic hormone in patients with homozygous familial hypercholesterolaemia

1. Plasma cortisol concentration was measured in three subjects with homozygous familial hypercholesterolaemia immediately before, and 30 and 60 min after, an intramuscular injection of adrenocorticotrophic hormone. The baseline values and the values at 30 and 60 min were within the normal range. 2. We conclude that in the presence of a genetic deficiency of low-density lipoprotein receptors, the human adrenal cortex can respond to a single injection of adrenocorticotrophic hormone with a normal increase in corticosteroid production.

Collagen content of atherosclerotic arteries is higher in smokers than in non-smokers

The biochemical composition of coronary endarterectomy and aortic samples obtained during 52 coronary artery bypass graft operations was analysed. The content of cholesterol or collagen relative to protein in the aorta or endarterectomy specimens did not correlate with serum total cholesterol, triglyceride, or high-density-lipoprotein cholesterol, nor were there any significant differences between samples from normotensive and hypertensive patients. However, smokers had a significantly higher content of collagen in coronary endarterectomy specimens and the aorta and a higher content of cholesterol in the aorta than non-smokers.

Effect of partial ileal bypass on the gut hormone responses to food in man

The integrated response of the regulatory peptides of the gastrointestinal tract to a test meal was studied in six hypercholesterolaemic patients who had undergone partial ileal bypass (PIB) and compared with responses in ten age- and sex-matched controls. Plasma motilin was found to rise significantly whereas plasma pancreatic polypeptide release was impaired after PIB. Plasma cholecystokinin rose promptly in both controls and the partial ileal bypass patients, and the latter group showed marked further rises, at 60 and 120 minutes after the meal, which were significantly higher than controls. Basal and postprandial plasma gastrin, gastric inhibitory peptide, neurotensin, enteroglucagon, insulin and pancreatic glucagon were similar in the two groups.

Gold toxicity presenting as peripheral neuropathy

A patient with rheumatoid arthritis developed gold induced peripheral neuropathy after 255 mgs of aurothioglucose. This neuropathy is characterized by weakness and numbness of the hands and feet in association with hyperalgesia of the palmar surface of the hands. The absence of vasculitis permits differentiation of gold neuropathy from the neuritis associated with rheumatoid arthritis or systemic lupus erythematosus. Treatment consists in cessation of gold and possibly the use of dimercaprol; recovery is slow but generally complete.

X-linked spondyloepiphyseal dysplasia tarda: mucopolysaccharide excretion studies

Sex linked spondyloepiphyseal dysplasia tarda is described in a family with four affected members. The characteristic features of short trunk, hip disease, and flattening of the vertebrae with a posterior "hump" were present. Urinary mucopolysaccharides were characterized both quantitatively and qualitatively and were within normal values.

Difference in saturable binding of low density lipoprotein to liver membranes from normocholesterolemic subjects and patients with heterozygous familial hypercholesterolemia

To investigate the possible role of the low density lipoprotein (LDL) receptor in the catabolism of LDL by the human liver, the binding of 125I-labeled LDL to membrane fractions prepared from human liver biopsies was determined. Biopsy samples taken for routine histology were obtained from seven patients with heterozygous familial hypercholesterolemia, one with non-familial hypercholesterolemia, and seven normocholesterolemic subjects. LDL was bound by the membranes from normal subjects in a saturable manner that was inhibited by 56% in the presence of excess LDL. Binding of LDL was also inhibited by modification of the lipoproteins with 1,2-cyclohexanedione. The amount of 125I-labeled LDL bound to membranes from familial hypercholesterolemic livers that could be displaced with excess LDL was significantly less than that bound by normocholesterolemic membranes. These observations suggest that LDL receptors are expressed in normal human liver and are defective in the livers of familial hypercholesterolemic patients.

The effect of partial ileal bypass on receptor-mediated uptake and catabolism of low density lipoprotein in the rhesus monkey

The fractional rates of catabolism (FCR) of 125I-labelled low-density lipoprotein (LDL) and 131I-labelled LDL coupled with 1,2-cyclohexanedione (LDL-CHD) were determined before and 6 weeks after partial ileal bypass in three Rhesus monkeys. Receptor-mediated catabolism, determined as the difference between the FCRs of 125I-LDL and 131I-LDL-CHD, increased significantly after partial ileal bypass. Analysis of tissue distribution of radioactivity in one monkey, killed at the conclusion of a third turnover study 6 months after partial ileal bypass, suggested that the liver was the main tissue site of accumulation of LDL, and that uptake had occurred mainly via a receptor-mediated mechanism. It is concluded that partial ileal bypass stimulates receptor-mediated LDL catabolism in the Rhesus monkey as in man, and that this increase is probably mediated via hepatic LDL receptors.

The metabolism of very low density and intermediate density lipoproteins in patients with familial hypercholesterolaemia

The metabolism of apolipoprotein B (apoB) in very low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL) was studied in normal subjects and in patients with familial hypercholesterolaemia (FH) after an intravenous injection of autologous VLDL labelled with 125I. There were no significant differences in half life, pool size and turnover rate (mg/kg/h) of VLDL-apoB between the normal subjects, the FH heterozygotes and the FH homozygotes. IDL-apoB metabolism in the FH patients differed significantly from that in the normal subjects. In the FH patients, the rise to the maximum of the specific activity curve was slower, the half life of the descending limb of the specific-activity curve was longer, the fractional rate of turnover was lower and the plasma concentration was higher than in the normals. The effect of cholestyramine on IDL-apoB metabolism in the normal subjects did not differ from that in the FH heterozygotes and homozygotes, though cholestyramine is known to stimulate hepatic uptake of low density lipoprotein (LDL) by the LDL receptor. It is suggested that in normal human subjects the LDL receptor makes some contribution to the hepatic uptake of IDL-apoB derived from VLDL, but that IDL uptake is mediated partly by a separate receptor that recognizes apolipoprotein E but not apoB.

Receptor-mediated low-density lipoprotein catabolism

Low-density lipoprotein (LDL) receptors are demonstrable in cultured fibroblasts from normal subjects but are decreased or absent in cells from patients with heterozygous or homozygous familial hypercholesterolaemia. In vivo receptor-mediated LDL catabolism, determined as the difference between the turnover rates of 125I-LDL and 131I-LDL coupled with cyclohexanedione, is responsible for approximately one-third of the total catabolism of LDL in normal subjects, but less than one-fifth in heterozygotes and is totally absent in homozygotes. Receptor-mediated catabolism can be stimulated in normal subjects and in heterozygotes by measures that promote bile acid synthesis, namely, administration of anion-exchange resins or creating a partial ileal bypass. Studies in dogs have shown that such measures stimulate the high-affinity binding of LDL by liver cell membranes. Taken together, these observations suggest the existence of LDL receptors in human liver, the function of which is to maintain cholesterol homeostasis within the hepatocyte during periods of increased demand. Partial or complete absence of such hepatic receptors may play a major role in the pathogenesis of familial hypercholesterolaemia.

Contrasting patterns of coronary atherosclerosis in normocholesterolaemic smokers and patients with familial hypercholesterolaemia

An angiographic comparison was made of the extent and severity of coronary artery disease in 25 patients with heterozygous familial hypercholesterolaemia and 25 normocholesterolaemic patients with coronary artery disease in whom heavy cigarette consumption was the chief risk factor. The patients with familial hypercholesterolaemia were younger and included a much higher proportion of women than the smokers. Significantly more patients with familial hypercholesterolaemia had disease of the main stem of the left coronary artery (eight v none, p less than 0.05) and triple-vessel disease (18 v four, p less than 0.05). Disease affecting only distal vessels occurred in five smokers, whereas all the patients with familial hypercholesterolaemia showed a combination of proximal and distal lesions. These findings suggest that cigarette smoking and familial hypercholesterolaemia predispose to different patterns of coronary atheroma. Early coronary angiography with a view to coronary artery bypass surgery seems desirable in symptomatic patients with familial hypercholesterolaemia because of the common association of this disorder with life-threatening left main-stem disease.

Superiority of partial ileal bypass over cholestyramine reducing cholesterol in familial hypercholesterolaemia

Low density lipoprotein (LDL) turnover studies were conducted on three occasions in each of six patients with heterozygous familial hypercholesterolaemia (FH)-on diet, after 1 month on cholestyramine 16 g/day, and 2 months after partial ileal bypass. Partial ileal bypass lowered total and LDL cholesterol levels and increased the fractional catabolic rate of LDL to a greater extent than did cholestyramine; this difference presumably reflects the greater increase in bile acid excretion induced by the surgical procedure. Studies in two other heterozygotes showed that partial ileal bypass specifically enhanced receptor-mediated catabolism of LDL. The findings support the concept that therapeutic stimulation of bile acid synthesis increases the rate of receptor-mediated uptake and degradation of LDL by the liver.

Defects of receptor-mediated low density lipoprotein catabolism in homozygous familial hypercholesterolemia and hypothyroidism in vivo

The role of low density lipoprotein (LDL) receptors in the pathogenesis of hereditary and acquired forms of hypercholesterolemia has been investigated in vivo by simultaneously determining total and receptor-independent LDL catabolism with 125I-labeled LDL and 131I-labeled LDL coupled with cyclohexanedione. Receptor-mediated catabolism of LDL, determined as the difference between the turnover of 125I and 131I, was found to be virtually absent in two homozygotes with familial hypercholesterolemia and markedly reduced in a hypothyroid patient. Treatment of the latter with L-thyroxine markedly stimulated receptor-mediated catabolism and reduced LDL levels as did cholestyramine administration in a control subject. Reduction of LDL levels by plasma exchange in a control subject and homozygote had no such effect. These results demonstrate the existence of an intrinsic and almost total defect of receptor-mediated LDL catabolism in homozygous familial hypercholesterolemia and demontrate an analogous but reversible abnormality in hypothyroidism.

Cadiovascular complications of homozygous familial hypercholesterolaemia

Seven patients with homozygous familial hypercholesterolaemia, two female and five male, aged 12 to 25 years, underwent clinical and angiographic assessment to define the associated cardiovascular abnormalities. Four patients had angina, two of whom also had syncope on exertion. All had an ejection systolic murmur but no ejection click and a loud aortic second sound. All but one had a systolic gradient between the left ventricle and aorta, ranging from 20 to 80 mmHg at the time of presentation. Angiography showed a characteristic narrowing of the aortic root in all and five of the seven patients had coronary ostial stenosis. One patient died after an aortocoronary bypass and aortic valvotomy and two others underwent aortocoronary bypass and aortic valve replacement, one of whom also died after operation. The survivor and three other patients are now undergoing regular plasma exchange and remain well. The seventh patient died suddenly before the latter form of treatment could be started. These findings confirm that premature, severe atheroma of the aortic valve and root is a characteristic feature of homozygous familial hypercholesterolaemia and carries a high mortality.