Conversion of the electrophoretic pattern of type IV hyperlipidaemia to type III by intravenous heparin

Heparin was given i.v. to subjects with type IV hyperlipoproteinaemia who had only ordinary pre-beta lipoproteins and no late pre-beta lipoproteins (LP-beta) in their very low density lipoproteins (VLDL, d less than 1.006) upon agarose gel lipoprotein electrophoresis. Within 15 min the electrophoretic pattern of VLDL had changed completely. The normal pre-beta lipoproteins had disappeared and a discrete LP-beta lipoprotein had appeared. This new electrophoretic pattern, induced 15 min after heparin, is similar to that diagnostic of type III hyperlipoproteinaemia. It is suggested that the LP-beta lipoproteins represent an end stage in the catabolism of VLDL.

Risk factors for ischaemic heart disease in men and women. Results of the 19-year follow-up of the Stockholm Prospective Study

In this 19-year follow-up of the Stockholm Prospective Study (SPS), 321 male and 55 female deaths from myocardial infarction (MI) had occurred. Fasting levels of plasma triglycerides acted as an independent risk factor for this cause of death in both sexes, which was the primary question asked when the SPS was designed. Other independent risk factors for MI were for men and women age, systolic blood pressure, smoking and for men only, plasma cholesterol, haemoglobin and erythrocyte sedimentation rate.

Decrease in alpha-lipoprotein cholesterol in men after cessation of exposure to chlorinate hydrocarbon pesticides

Eight men who in 1970 had been exposed to chlorinated pesticides and for whom the exposure had ceased in 1976, showed a significant fall in alpha-lipoprotein (HDL) cholesterol between these years. The cholesterol concentration of the other lipoprotein classes showed no significant trend. The data support our previous suggestion that exposure to chlorinated pesticides, mainly lindane, may raise the alpha-lipoprotein levels.

Effect of plasma free fatty acid lowering on exercise tolerance and ST segment depression in patients with angina pectoris

The effect of a single oral dose of a plasma FFA-lowering drug (5-(3-pyridyl) tetrazole), which does not act by conversion into nicotinic acid, on exercise tolerance and ECG reaction was studied on a double-blind basis in 15 men with stable angina pectoris. Exercise was performed on a bicycle ergometer in the sitting position with a load increase of 10 W/min. In addition to ECG, time to onset of chest pains and to termination of exercise because of strong chest pains was recorded. 5-(3-pyridyl) tetrazole decreased plasma FFA during exercise from 523 to 299 mumol/l. It reduced significantly the ST depression at corresponding work loads and permitted the patients to exercise 0.6 min longer, corresponding to a 7% higher work load, before the onset of chest pain. However, absolute exercise time was not significantly increased. The most probable explanation of the improved performance is a decreased lipid and increased carbohydrate oxidation by the ischemic heart, although a contribution may have come from hemodynamic effects of the drug, unrelated to effects on myocardial metabolism but perhaps involving heart rate and BP. The lack of a significant effect on performance time may have been due to general fatigue.

Serum lipid and lipoprotein concentrations in chronic uremia

The concentrations of triglycerides and cholesterol have been determined in total serum and in the three major serum lipoprotein classes--very low (VLDL), low (LDL) and high (HDL) density lipoproteins-after an overnight fast in 39 patients with chronic uremia of more than 2 years' duration and with serum creatinine above 350 mumol/l. The values were compared with data from healthy male and female controls. The findings were similar for male and female uremics. Hypertriglyceridemia was common while serum cholesterol tended to be normal or subnormal. With the conventional typing system for hyperlipidemia, types II A, III and IV were present in 6,9 and 30%,respectively. The tryglyceride and cholesterol concentrations in VLDL were increased, while their normal relation for this lipoprotein class was maintained. In LDL the concentration of tryglycerides was increased, while that of cholesterol was low. The LDL composition, therefore, was changed to be more triglyceride-rich than normal. The changes in concentration and composition of LDL indicated that the levels of LDL 1 were raised and of LDL 2 decreased in chronic uremia. Increased levels of LDL tryglycerides occurred more frequently (40%) than increased levels of VLDL triglycerides (33%). The most striking and consistent lipoprotein abnormality was a low HDL cholesterol, which was not related to high VLDL levels. The HDL tryglycerides, on the other hand, tended to be somewhat high. The importance of the raised levels of the triglyceride-rich VLDL and LDL 1 and the decreased levels of HLD cholesterol for the rapid development of atherosclerotic vascular diseases which occur in chronic uremia is discussed. It is of interest in this context that both total cholesterol and LDL cholesterol were low. The possible mechanisms underlying the lipoprotein abnormalities in chronic uremia are discussed and it is suggested that they are complex.

In vitro normalization of cholesteryl ester content and particle size of fish eye disease high density lipoproteins

Isolated high density lipoprotein (HDL) from the two living fish eye disease patients have been incubated in vitro with autologous lipoprotein depleted plasma or with lipoprotein depleted plasma from domestic pig (Sus domesticus), with and without the presence of LCAT inhibitor for 24 hours at 0 and 37 degrees C. The lecithin:cholesterol acyltransferase (LCAT) activity in lipoprotein depleted pig plasma increased the abnormally low cholesteryl ester content of the fish eye disease HDL particles from about 20 to 100% and increased their exceptionally small mean particle size, probably by particle fusion, to a range which is representative of normal HDL3. Both esterification and particle enlargement were totally blocked by the LCAT inhibitor. Incubation of concentrated fish eye disease HDL with autologous lipoprotein depleted plasma for 24 hours at 37 degrees C resulted in a small increase in its cholesteryl ester percentage to 37%, without affecting the apparent HDL particle size. This finding confirms a deficiency of HDL lecithin:cholesterol acyltransferase activity (alpha-LCAT) in fish eye disease. The observed normalization of both HDL cholesteryl ester percentage and particle size by lipoprotein depleted pig plasma which contains virtually no cholesteryl ester transfer activity indicates that the latter is not a requisite for esterification of the free cholesterol of fish eye disease HDL.

Restriction enzyme analysis of the apolipoprotein A-I gene in fish eye disease and Tangier disease

Restriction enzyme analysis of the apolipoprotein A-I (apo A-I) gene was performed in two patients with fish eye disease and one with Tangier disease. Despite the marked deficiency of high density lipoprotein and concomitantly of apo A-I in these two conditions, no evidence was found for major deletions or insertions in the apo A-I gene.

Studies on high density lipoproteins in fish eye disease

Serum high density lipoproteins (HDL) were isolated by preparative ultracentrifugation from two patients with fish eye disease (FED). Compared to HDL from control subjects the HDL particles of FED were characterized by their abnormally small size and a relative enrichment with polar lipids. No qualitative abnormalities of the HDL apolipoproteins were revealed upon polyacrylamide disc gel electrophoresis or isoelectric focusing. The plasma pool of apolipoprotein A was reduced by 90%.

Reduction of mortality in the Stockholm Ischaemic Heart Disease Secondary Prevention Study by combined treatment with clofibrate and nicotinic acid

Consecutive survivors of a myocardial infarction from the Southern Hospital, below 70 years of age, were randomized into a Control group (n = 276) and a Treatment group (n = 279). The latter was openly prescribed the combination of clofibrate and nicotinic acid for serum lipid lowering. Each patient should remain in the study for 5 years and be seen regularly every 4 months at a special IHD outpatient clinic within the hospital. The concentration of serum cholesterol and triglyceride was lowered by 13% and 19%, respectively, in the Treatment group compared to the Control group. Total mortality was 82 cases in the Control group and 61 in the Treatment group, a 26% reduction (p less than 0.05). For patients above 60 years of age in the Treatment group the reduction in mortality was 28% (p less than 0.05). IHD mortality was reduced by 36% (p less than 0.01) in the Treatment group compared to the Control group. The beneficial effect of the serum lipid lowering treatment was related to the serum triglyceride concentration in two ways. First, it only occurred in patients with a triglyceride level greater than 1.5 mmol/l (n = 216). Secondly, it was most pronounced in the 44% of the treated patients who had a lowering of the serum triglyceride by 30% or more, and in this subgroup the reduction of IHD mortality was 60% (p less than 0.01). For serum cholesterol there were no such relations. The difference between serum triglycerides and cholesterol concerning these relations to the treatment outcome may be due to the fact that hypertriglyceridaemia was the most common hyperlipidaemia among our patients, occurring in 50%, while hypercholesterolaemia only occurred in 13%. Caution should be exercised in the interpretation of the results as the trial was not blind. However, the fact that the decrease in IHD deaths was directly related to the degree of serum triglyceride lowering indicates that it was the drug effect on serum lipids that was responsible for the beneficial effect of the treatment.

Deficiency of hepatic lipase activity in post-heparin plasma in familial hyper-alpha-triglyceridemia

Hyper-alpha-triglyceridemia is a rare dyslipoproteinemia characterized by a pronounced increase in the concentration of triglycerides in the plasma high density lipoprotein (HDL) fraction. One case with this condition, an apparently healthy 61-year-old man, has been studied. Additional lipoprotein abnormalities were present, such as abnormally cholesterol-rich very low density lipoproteins (VLDL) with retarded electrophoretic mobility (beta-VLDL) and triglyceride enrichment of low density lipoproteins (LDL). The patient's plasma concentration of apolipoproteins A-I, A-II and B were normal and those of C-I, C-II, C-III and E were elevated. No abnormal forms of the soluble apolipoproteins of VLDL and high density lipoproteins (HDL) were found after analysis by isoelectric focusing. Lecithin:cholesterol acyltransferase activities, plasma cholesterol esterification rates and lipid transfer protein activities were normal. Post-heparin plasma activity of hepatic lipase was virtually absent and that of lipoprotein lipase was reduced by 50%. In plasma of this patient, HDL was almost exclusively present as large triglyceride-rich particles corresponding in size to particles of the HDL2 density fraction. The only brother of the patient also had hyper-alpha-triglyceridemia together with the other lipoprotein abnormalities described for the index case and deficiency of postheparin plasma activity of hepatic lipase. The findings presented below support the hypothesis that one primary function of hepatic lipase is associated with degradation of plasma HDL2. Deficiency of this enzyme activity thus causes accumulation of HDL2 in plasma leading to hyper-alpha-triglyceridemia. The results further suggest that the abnormal chemical and electrophoretic properties of VLDL and LDL in plasma from the patient, reminiscent of type III hyperlipoproteinemia, are secondary to the lack of the action of hepatic lipase on the HDL particles.

Paradoxical esterification of plasma cholesterol in fish eye disease

The activity of lecithin: cholesterol acyl transferase (LCAT), the enzyme which catalyses the esterification of human plasma cholesterol, has been measured by two independent methods in plasma from the two known living Swedish patients with fish eye disease. The enzyme activity was in both cases about 15% of that of normal plasma. Paradoxically, however, the percentage of plasma cholesterol which was esterified was almost normal in both patients. In addition, a normal spectrum of the fatty acids of the cholesteryl esters was present indicating a normal cholesterol esterification pathway in vivo. Incubation experiments in vitro of plasma from the two patients also yielded normal cholesterol esterification rates when measured by two different methods. These paradoxical results for cholesterol esterification are discussed on the basis of the present biochemical knowledge of fish eye disease and LCAT deficiency.

Evidence for deficiency of high density lipoprotein lecithin: cholesterol acyltransferase activity (alpha-LCAT) in fish eye disease

In a rare familial condition, fish eye disease, there is a low relative content of cholesteryl esters in the plasma high density lipoproteins (HDL) but a normal content of these lipids in the very low (VLDL) and low (LDL) density lipoproteins. Lecithin: cholesterol acyltransferase (LCAT) is the enzyme which mediates the esterification of free cholesterol in the plasma lipoproteins. In the present investigation, isolated HDL from our two fish eye disease patients were found to be excellent substrates during in vitro incubations with normal LCAT as present in lipoprotein depleted plasma from control subjects. Almost all free cholesterol of these HDL fractions became esterified and concomitantly the abnormally small fish eye disease HDL particles increased to a size in the range of that of normal HDL particles. Lipoprotein depleted plasma from fish eye disease, however, lacked the property of normal plasma to esterify the free cholesterol of HDL isolated from plasma of fish eye disease patients or control subjects. These results have led to the formulation of a new concept implying that two different LCAT activities exist in normal plasma. One of these activities, denoted alpha-LCAT, is specific for HDL (alpha-lipoproteins) and the other, beta-LCAT, is specific for VLDL-LDL (pre beta- and beta-lipoproteins). Fish eye disease according to this notion is classified as an alpha-LCAT deficiency in contrast to the classical LCAT deficiency which probably lacks both alpha- and beta-LCAT activities.

Serum apolipoproteins, lipoproteins and fatty acids in relation to ischaemic heart disease in northern and southern European males

Serum apolipoprotein and lipoprotein concentrations, fatty acid spectra of various lipids, dietary habits and common risk factors for ischaemic heart disease were studied in 73 and 77 randomly selected, 50-year-old healthy men in Naples and Stockholm, respectively. Mean serum cholesterol concentration was higher in Stockholm than in Naples men (6.23 vs. 5.47 mmol/l, p less than 0.001) as were low (LDL) (4.08 vs. 3.57 mmol/l, p less than 0.001) and high (HDL) (1.40 vs. 1.25 mmol/l, p less than 0.001) density lipoprotein fractions. Mean serum triglyceride concentrations did not differ. Mean apolipoprotein B and C-I concentrations were higher in Stockholm men (1,116 vs. 1,020 mg/l, p less than 0.05 and 96 vs. 79 mg/l, p less than 0.01, respectively). Stockholm men derived significantly more of their calories from fat (38 vs. 28%, p less than 0.001) and the dietary fat had significantly lower polyunsaturated-to-saturated fatty acid ratio (P/S-ratio 0.29 vs. 0.51, p less than 0.001), and less from carbohydrate (44 vs. 49%, p less than 0.001) than Naples men, respectively. Mean caloric intake and mean weight/height index did not differ. Stockholm men had higher blood pressures, but there were more smokers among Naples men. The higher fat intake in Stockholm men may offer an explanation of the differences seen in lipoprotein and apoprotein concentrations and compositions but other factors, such as genetic influences cannot be excluded. A greater cholesterol flux through the plasma compartment in Stockholm men may be one important factor contributing to the higher incidence of ischaemic heart disease in this population.

Plasma lipid transfer in fish-eye disease

Fish-eye disease is a familial condition characterized by corneal opacities and dyslipoproteinaemia with, i.a., pronounced enrichment of plasma low density lipoprotein (LDL) with triglycerides. Cholesterol ester and triglyceride transferase activities in lipoprotein-free plasma have been measured in two patients with fish-eye disease and found to be normal. This indicates that a deficiency of plasma lipid transfer protein is not involved in the abnormal composition of LDL in fish-eye disease.

Genetic and environmental determinants for lipoprotein concentrations in blood

Path and segregation analyses have been performed on cholesterol and triglyceride contents of serum as well as on very low, low and high density lipoproteins in 78 Swedish nuclear families. The effect of environmental variables like alcohol and smoking on the concentrations of the different lipoproteins has been studied. Genetic heritability was 0.16-0.68 for the cholesterol fractions and 0-0.56 for the triglyceride fractions. No major gene was evident for any of the variables studied.

Occurrence of acute myocardial infarction in Stockholm studied by two different methods

Two studies on the occurrence of acute myocardial infarction (AMI) in Stockholm have been made. In one, the study population consisted of patients who attended a health-control station; cases of AMI were detected retrospectively by a mail questionnaire and by the official cause-of-death register. In the other study, the population comprised the total population of Stockholm county; cases of AMI were detected from routine information on hospital care, and from the official cause-of-death register. The aims of the present study were to compare the two methods for detection of AMI cases and to compare the AMI morbidity of the two populations. The mail questionnaire method missed a small number of cases but, on the other hand, the register method included some cases in which the diagnostic criteria were not fulfilled. The AMI morbidity in the two populations did not differ significantly.

Different substrate specificities of plasma lecithin: cholesterol acyl transferase in fish eye disease and Tangier disease

Esterification of plasma free cholesterol is mediated by lecithin:cholesterol acyl transferase (LCAT). The free cholesterol of plasma high density lipoproteins (HDL) is considered to be the preferred substrate for LCAT. It therefore appeared as a paradox that plasma cholesterol esterification, both in vivo and in vitro, is normal in fish eye disease and Tangier disease, two familial conditions with extremely low plasma HDL levels. Fish eye disease plasma, however, was shown to have LCAT activity primarily acting on combined very low (VLDL) and low (LDL) density lipoproteins, denominated beta-LCAT, while it lacked LCAT activity esterifying HDL cholesterol (alpha-LCAT). Here we show that Tangier plasma, in contrast, has both alpha- and beta-LCAT. Thus, in both fish eye and Tangier diseases it is beta-LCAT that explains the apparent normal plasma cholesterol esterification. We also show that Tangier plasma, having alpha-LCAT activity, normalizes the low cholesteryl ester content as well as the abnormally small size of fish eye disease HDL particles during incubation.

Inhibitory effect of normal high density lipoproteins on lecithin:cholesterol acyltransferase activity in fish eye disease plasma

The lecithin:cholesterol acyltransferase (LCAT) activity of lipoprotein depleted normal and fish eye disease (FED) plasma was assayed in a modified Glomset-Wright incubation system where the enzyme was allowed to act on three different normal lipoprotein substrates consisting of an authentic mixture of very low (VLDL), low (LDL) and high (HDL) density lipoproteins to assay total LCAT activity, HDL to assay alpha-LCAT activity and combined VLDL and LDL to assay beta-LCAT activity, respectively. However, using normal plasma depleted of HDL, leaving its combined VLDL and LDL as enzyme substrate, resulted in a more than twofold increase in the LCAT activity of FED plasma from the two patients compared to the activity obtained with HDL present in the incubation mixture, indicating an inhibitory effect of HDL on the beta-LCAT activity present in FED plasma. This inhibitory effect of normal HDL could also be demonstrated by autoincubation of FED plasma mixed with isolated HDL2 or HDL3. Both these HDL subfractions had a pronounced inhibitory effect on the cholesteryl ester formation in FED plasma. The present study thus clearly demonstrates that normal HDL inhibits the beta-LCAT activity present in FED plasma, esterifying the free cholesterol of combined VLDL and LDL, derived from controls as well as from the two FED patients.

Substrate specificity of plasma lecithin: cholesterol acyltransferase in abetalipoproteinemia

The lecithin: cholesterol acyltransferase (LCAT) activity of lipoprotein-depleted plasma from a patient with abetalipoproteinemia has been assayed in a modified Glomset-Wright incubation system with three different normal lipoprotein substrates consisting of an authentic mixture of very low (VLDL), low (LDL) and high (HDL) density lipoproteins for the assay of total LCAT activity, HDL to assay alpha-LCAT activity and combined VLDL and LDL to assay beta-LCAT activity, respectively. Although reduced to about half the normal control values, both alpha- and beta-LCAT activities were present in the patient's plasma. It has been shown earlier that secretion of LCAT is linked to that of VLDL, but since patients with abetalipoproteinemia cannot form either chylomicrons or VLDL, our results suggest that a secretion of these triglyceride-rich lipoproteins do not seem to be a prerequisite for a basal secretion of beta-LCAT.

Serum lipids in alcoholics

Fasting serum lipid values (cholesterol, triglycerides and phospholipids) have been analysed in a group of 85 male and 10 female alcoholics of various ages in connection with an acute drinking bout and compared to the values of twice as many control subjects. The most prominent finding was an increase in the mean concentration of triglycerides and phospholipids, most marked in the younger age groups. The elevations, however, were moderate and most alcoholics had the same serum lipid values as the controls. Serum triglyceride values above 2 and 3 mmol/1, respectively, occurred in 23% and 4% in controls and in 28% and 13% in alcoholics. It is suggested that excessive intake of alcohol induces hypertriglyceridaemia only when other factors are present. One such factor may be a reduced i.v. fat tolerance.

Evidence for the presence in human plasma of lecithin: cholesterol acyltransferase activity (beta-LCAT) specifically esterifying free cholesterol of combined pre-beta- and beta-lipoproteins. Studies of fish eye disease patients and control subjects

The present study was undertaken to test our hypothesis that two different lecithin: cholesterol acyltransferase (LCAT) activities exist in normal human plasma, one denoted alpha-LCAT esterifying the free cholesterol of high density lipoproteins (HDL) and the other denoted beta-LCAT acting on the free cholesterol of very low (VLDL) and low (LDL) density lipoproteins. Plasmas depleted of HDL were obtained by means of preparative ultracentrifugation. Incubation at 37 degrees C of these plasma fractions from control subjects and patients with fish eye disease resulted in esterification of the remaining free cholesterol of combined VLDL and LDL (pre-beta- and beta-lipoproteins) in the HDL depleted plasmas. The shapes of the cholesterol esterification rate curves were similar for whole and HDL depleted plasmas from both control subjects and fish eye disease patients. In crosswise mixed incubation experiments with isolated combined VLD and LDL and total lipoprotein depleted plasma from a control subject and a patient with fish eye disease, respectively, esterification of free cholesterol occurred. Incubation of isolated total lipoproteins in plasma from a patient with LCAT deficiency mixed with total lipoprotein depleted plasma from a fish eye disease patient as a source of LCAT caused cholesterol esterification but did not result in normalization of the LCAT deficiency HDL particles, while the amount of normal-sized LDL particles increased. The present results support the hypothesis that a beta-LCAT exists in normal human plasma.

Serotonin syndrome caused by interaction between citalopram and fentanyl

OBJECTIVE

To report a case of serotonin syndrome associated with interaction between fentanyl and citalopram, as evidenced by medication history, clinical features and reversal following discontinuation of fentanyl.

CASE SUMMARY

A 65-year-old patient chronically treated with the selective serotonin reuptake inhibitor (SSRI) citalopram developed confusion, agitation, tachycardia, tremors, myoclonic jerks and unsteady gait, consistent with serotonin syndrome, following initiation of fentanyl, and all symptoms and signs resolved following discontinuation of fentanyl. Based on the Naranjo probability scale, serotonin syndrome was a probable adverse reaction associated with co-administration of citalopram and fentanyl.

DISCUSSION

Serotonin syndrome is a potentially lethal pharmacodynamic interaction between medications that increase serotonergic transmission at the synaptic junction. The development of new pharmacological agents with varied properties and actions has increased the risk of serotonin syndrome as a clinical diagnosis. SSRIs and fentanyl are commonly co-administered, especially in the setting of chronic or malignant pain, as underlying depression may contribute to the pathogenesis of pain.

CONCLUSION

Healthcare professionals should be aware of the possible development of serotonin syndrome as a complication of initiation of fentanyl and other phenylpiperidine opioids in patients treated with SSRIs.

Nicotinic acid: the broad-spectrum lipid drug. A 50th anniversary review

Nicotinic acid has, like the Roman God Janus, two faces. One is the vitamin. The other is the broad-spectrum lipid drug. The Canadian pathologist Rudolf Altschul discovered 50 years ago that nicotinic acid in gram doses lowered plasma levels of cholesterol. From the point of view of treatment of the dyslipidaemias that are risk factors for clinical atherosclerosis nicotinic acid is a miracle drug. It lowers the levels of all atherogenic lipoproteins--VLDL and LDL with subclasses as well as Lp(a)--and in addition it raises more than any other drug the levels of the protective HDL lipoproteins. Trials have shown that treatment with nicotinic acid reduces progression of atherosclerosis, and clinical events and mortality from coronary heart disease. The new combination treatment with statin-lowering LDL and nicotinic acid-raising HDL is reviewed. A basic effect of nicotinic acid is the inhibition of fat-mobilizing lipolysis in adipose tissue leading to a lowering of plasma free fatty acids, which has many metabolic implications which are reviewed. The very recent discovery of a nicotinic acid receptor and the finding that the drug stimulates the expression of the ABCA 1 membrane cholesterol transporter have paved the way for exciting and promising new 50 years in the history of nicotinic acid.

Niaspan, the prolonged release preparation of nicotinic acid (niacin), the broad-spectrum lipid drug

Niacin (nicotinic acid) is the broad-spectrum lipid drug, which lowers the concentration of all atherogenic plasma lipids/lipoproteins and at the same time raises the levels of the protective HDL (high-density lipoprotein). Niaspan is a prolonged release (PR) formulation of niacin, which has considerable advantages over both immediate release (IR) and slow release (SR) formulations of this drug. The major early side effect of IR niacin, the flush, is reduced with Niaspan. The hepatotoxic effects with SR niacin are not present with Niaspan. It is suitable for once daily prescription at bedtime. Niaspan is effective as monotherapy and in combination with other lipid-lowering drugs such as statins and fibrates. It is particularly useful for treatment of the dyslipidaemia of type 2 diabetes, where IR but not PR niacin may deteriorate the diabetic condition. Overall, niacin, now available as the well-tolerable drug formulation Niaspan, is the unique broad-spectrum lipid drug for the prevention and treatment of clinical atherosclerosis.

Grounding spatial language in perception: an empirical and computational investigation

The present paper grounds the linguistic cdategorization of space in aspects of visual perception; specifically, the structure of projective spatial terms such as above are grounded in the process of attention and in vector-sum coding of overall direction. This is formalized in the attentional vector-sum (AVS) model. This computational model accurately predicts linguistic acceptability judgments for spatial terms, under a variety of spatial configurations. In 7 experiments, the predictions of the AVS model are tested against those of 3 competing models. The results support the AVS model and disconfirm its competitors. The authors conclude that the structure of linguistic spatial categories can be partially explained in terms of independently motivated perceptual processes.

Angioplasty or stent placement in the proximal common iliac artery: is protection of the contralateral side necessary?

PURPOSE

To determine if protection of the contralateral common iliac artery is necessary when performing angioplasty or stent placement in a proximal common iliac artery.

MATERIALS AND METHODS

A retrospective review of all patients undergoing endovascular treatment for unilateral common iliac artery stenosis or occlusion from 1979 to 2000 was performed. All angiograms were reviewed independently by three experienced vascular interventional radiologists who evaluated both common iliac arteries before and after angioplasty or stent placement.

RESULTS

The medical records or angiograms of 514 patients were located. Of these, complete records and angiograms were found for 175 patients who underwent proximal (within 2 cm of its origin) common iliac artery angioplasty or stent placement without treatment or protection of the contralateral common iliac artery. Treatment of proximal common iliac stenosis in 160 patients resulted in luminal compromise of the contralateral common iliac in two patients (17% and 24% reduction in luminal diameter). No contralateral compromise was noted in 15 patients treated for iliac occlusion.

CONCLUSION

The data reported herein suggest that protection of the contralateral common iliac artery during angioplasty or stent placement in a proximal common iliac artery is not mandatory.

Using spatial terms to select an object

Our interactions with the world often involve selecting one object from a cluttered array of objects. One way to accomplish this is with language. For example, spatial terms, such as above, guide selection by specifying the position of one object (the located object) with respect to a second object (the reference object). Most of the work on the apprehension of spatial terms has examined displays that contain only these two objects. In the present paper, we examine how the presence of an extra object (a distractor) in the display impacts apprehension. Consistent effects of distractor presence were obtained across acceptability-rating and speeded sentence/picture verification tasks. Importantly, these effects were independent of the placement of the distractor. These results suggest that the distractor has its influence during processes that spatially index and identify the located and reference objects and that processes involved in computing the spatial term operate only on these objects.

Grounding spatial language in perception: an empirical and computational investigation

The present paper grounds the linguistic cdategorization of space in aspects of visual perception; specifically, the structure of projective spatial terms such as above are grounded in the process of attention and in vector-sum coding of overall direction. This is formalized in the attentional vector-sum (AVS) model. This computational model accurately predicts linguistic acceptability judgments for spatial terms, under a variety of spatial configurations. In 7 experiments, the predictions of the AVS model are tested against those of 3 competing models. The results support the AVS model and disconfirm its competitors. The authors conclude that the structure of linguistic spatial categories can be partially explained in terms of independently motivated perceptual processes.

Circulator boot therapy alters the natural history of ischemic limb ulceration

Despite numerous advances in interventional radiology and vascular surgery, the clinician continues to be confronted with inoperable vascular disease. Previous studies have shown that ulceration associated with a transcutaneous oxygen pressure (tcPO2) of <20 mmHg is refractory to all attempts at healing. External pneumatic compression for the treatment of peripheral vascular disease has been available for several years, although there is a relative paucity of data regarding its role in clinical practice as well as its efficacy. The objective of this study was to examine the experience with circulator boot therapy in the treatment of ischemic ulcers in the absence of osteomyelitis, and specifically to determine whether such therapy can be of benefit in ischemic limb ulceration associated with a tcPO2 of <20 mmHg. A retrospective chart review was undertaken of ail patients with a lower limb ulcer who, in the absence of osteomyelitis, underwent circulator boot therapy at the Gonda Vascular Center. A total of 98 patients was identified. Two patients died within 1 month of commencing therapy and were not included in further analysis. The tcPO2 data were unavailable in five patients. Outcome in the patient population was classified as favorable if (1)healing was achieved, (2)the ulcer decreased in size, or (3) the affected limb improved sufficiently to allow successful revascularization. An unfavorable outcome was one where a major amputation was performed or where the ulcer increased in size. Out of a total of 29 patients with a tcPO2 <20 mmHg at the area of ulceration, 19 had a favorable outcome following circulator boot therapy. Of the remaining 62 patients with a tcPO2 >20 mmHg, 54 had a favorable outcome. Circulator boot therapy is associated with improved outcomes in limb ulceration due to peripheral vascular disease. Complete ulcer healing as well as preservation of the affected limb can be achieved in most cases.

Stimulation of fecal steroid excretion after infusion of recombinant proapolipoprotein A-I. Potential reverse cholesterol transport in humans

BACKGROUND

Apolipoprotein (apo) A-I is the major protein component of HDL, a cholesterol transport particle that protects against atherosclerosis. Apo A-I is believed to promote reverse cholesterol transport, transferring cholesterol from peripheral cells to the liver for subsequent elimination. To test this hypothesis in humans, we measured fecal steroid excretion before and after the intravenous infusion of human proapo A-I (precursor of apo A-I) liposome complexes.

METHODS AND RESULTS

Four subjects with heterozygous familial hypercholesterolemia w re studied under standardized conditions. The fecal excretion of bile acids and neutral sterols was determined for 9 days before and 9 days after an intravenous infusion of recombinant human proapo A-I (4 g protein) liposome complexes. Plasma apoA-I and HDL cholesterol levels increased transiently (mean peak concentrations were 64% and 35% above baseline, respectively) during the first 24 hours. Mean lipoprotein lipid and apolipoprotein levels were not different during the 2 collecting periods, however. Serum lathosterol, a precursor of cholesterol whose concentration reflects the rate of cholesterol synthesis in vivo, was also unchanged. The fecal excretion of cholesterol (neutral sterols and bile acids) increased in all subjects (mean increase, +39% and +30%, respectively), corresponding to the removal of approximately 500 mg/d excess cholesterol after infusion. Control infusions with only liposomes in 2 of the patients did not influence lipoprotein pattern or cholesterol excretion.

CONCLUSIONS

Infusion of proapoA-I liposomes in humans promotes net cholesterol excretion from the body, implying a stimulation of reverse cholesterol transport. This mechanism may prove useful in the treatment of atherosclerosis.

Studies in hypertriglyceridaemia. VI: Serum lathosterol concentration is raised in hypertriglyceridaemic non-diabetic males with hyperinsulinaemia

OBJECTIVES

To assess the cholesterol synthesis rate in primary hypertriglyceridaemia using the serum unesterified lathosterol concentration as an indicator.

DESIGN

A cross-sectional, case-control study.

SETTING

The Karolinska Hospital, Stockholm.

SUBJECTS

Randomly selected hyper- (n = 53) and normotriglyceridaemic (n = 57) males, 40-50 years, with a fasting serum triglyceride concentration (mean +/- SD) of 3.81 +/- 1.65 and 1.28 +/- 0.53 mmol L-1, respectively. The exclusion criterion was diabetes mellitus, defined according to the World Health Organization (WHO) guidelines.

MAIN OUTCOME MEASURES

To compare the fasting serum concentration distributions of lathosterol, a cholesterol precursor, in hyper- and normotriglyceridaemic groups.

RESULTS

Thirty-six per cent of the hypertriglycerdaemic group had raised serum lathosterol concentrations, based on the 90th percentile of the lathosterol distribution of the normotriglyceridaemic group. In the hyper- but not in the normotriglyceridaemic group, lathosterol concentration was directly correlated with serum insulin responses to oral (r = 0.38; P = 0.007) and intravenous (r = 0.41; P = 0.005) glucose challenges.

CONCLUSIONS

One-third of a randomly selected non-diabetic hypertriglyceridaemic population had an increased serum lathosterol concentration and this might indicate an increased cholesterol synthesis rate compatible with increased production of VLDL particles, possibly as the result of chronic hyperinsulinaemia.

Nicotinic acid treatment shifts the fibrinolytic balance favourably and decreases plasma fibrinogen in hypertriglyceridaemic men

BACKGROUND

Nicotinic acid in gram doses decreases cholesterol and triglyceride concentrations in plasma, but the effect on haemostatic function is not known.

METHODS

Twenty-three men with hypertriglyceridaemia were treated with 4 g nicotinic acid daily for 6 weeks. Tests for haemostatic function and serum lipoproteins were performed before and at the end of the period of treatment.

RESULTS

Treatment with nicotinic acid had the expected effect on lipoprotein concentrations: it reduced the serum concentrations of triglyceride and the three major density fractions of triglyceride (very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL)). The VLDL cholesterol concentration was reduced, but that of HDL cholesterol was increased (all P<0.0001). The lipoprotein(a) (Lp(a)) concentration decreased significantly (P<0.01). The total fibrinolytic activity was increased by nicotinic acid treatment as indicated by decreases in plasminogen activator inhibitor-1 activity from 34.3 to 23.8 U/ml (P<0.01) and in alpha2-antiplasmin activity from 1.10 to 0.97 U/ml (P<0.01). The plasma fibrinogen concentration decreased from 3.55 to 3.01 U/ml (P<0.01). Multvariate analysis showed that the changes in alpha2-antiplasmin and Lp(a) concentrations could explain 53% of the change in plasma fibrinogen, suggesting that increased plasmin mobilization could be responsible for the decrease in plasma fibrinogen.

CONCLUSION

This study of hypertriglyceridaemic men has shown that long-term treatment with nicotinic acid not only corrects serum lipoprotein abnormalities, but also reduces the fibrinogen concentration in plasma and stimulates fibrinolysis.

In vitro reverse cholesterol transport from THP-1-derived macrophage-like cells with synthetic HDL particles consisting of proapolipoprotein A1 or apolipoprotein A1 and phosphatidylcholine

The human monocytic leukaemia cell line THP-1 was induced to differentiate to macrophage-like cells by the addition of phorbol myristoyl acetate (PMA). Subsequently, the cells were enriched in cholesterol and these cholesterol laden cells were used to study the capability of reconstituted discoidal complexes (RDCs), consisting of either human apolipoprotein A1 (apo A1) or recombinant human proapolipoprotein A1 (proapo A1) and phosphatidylcholine (PC), to promote cholesterol efflux. RDCs containing apo A1 and proapo A1 were both effective in the mobilization of intracellular cholesterol, whether this was measured by intracellular cholesterol mass or by the appearance of radiolabelled cholesterol in the supernatant. Using the radiolabelling technique, the activity was saturable and followed Michaelis-Menten kinetics. For both types of complexes and for native HDL the maximum rate of cholesterol removed was approximately 0.5 nmol h-1 per 10(6) cells. For RDCs of proapo A1 and apo A1 and for native HDL the Km values were 3.7, 2.9 and 64.8 micrograms ml-1 respectively. A significant in vitro cholesterol efflux could only be achieved with protein-lipid complexes; no significant export was observed with either free proapo A1 or multilamellar PC liposomes without apolipoprotein. Both RDCs were found to be more active in the mobilization of intracellular cholesterol than HDL isolated from human plasma. The combined results demonstrate that synthetic complexes consisting either of apo A1 or proapo A1 and PC are both active in the in vitro reverse transport of cholesterol.

Studies in hypertriglyceridaemia. 1. Serum triglyceride distribution and its correlates in randomly selected Swedish middle-aged men

OBJECTIVES

To obtain a randomly selected hypertriglyceridaemic population for detailed further characterization.

DESIGN

Study of randomly selected males.

SETTING

Subjects examined and blood sampled at Sollentuna Primary Health Care Centre.

SUBJECTS

Men aged 40-50 years (n = 1564), living in the Stockholm area, who were screened for hypertriglyceridaemia, January 1990-June 1992.

MAIN OUTCOME MEASURES

Fasting concentrations of serum triglycerides.

RESULTS

The serum triglyceride concentration distribution showed the expected skew distribution with the 90th and the 95th percentile at 2.51 and 3.05 mmol L-1, respectively. The mean serum triglyceride level compared well with several population values reported from this laboratory over the last 30 years, indicating stable triglyceride levels over time. There was no significant age-trend for the triglyceride concentration. Lower mean values for triglyceride, insulin and waist-to-hip (W/H) ratio were observed during the summer, whilst apolipoprotein A-I levels were higher. There was a linear relation between the number of cigarettes smoked and the serum triglyceride concentration. In stepwise multiple linear regression analysis with the triglyceride concentration as the dependent variable the following variables appeared as significant (P < 0.01) contributors: insulin, cholesterol, glucose, apolipoprotein A-I, number of cigarettes smoked, BMI, W/H ratio and diastolic blood pressure. The regression coefficient for apolipoprotein A-I was negative; all the others were positive. The multiple regression (R) was 0.68, suggesting that up to 47% of the variation of the serum triglyceride concentration could be predicted by these factors.

CONCLUSIONS

A group of randomly selected hypertriglyceridaemic men has been recruited for further clinical, metabolic and genetic studies. Basic characteristics of the population for their recruitment are described.

Efflux of cholesterol from cholesterol loaded macrophages by incubation with synthetic HDL-particles

Cells from the mouse monocyte/macrophage cell line J774A.1 were incubated with acetylated human low density lipoprotein for 2 days, resulting in an intracellular accumulation of mainly cholesteryl esters. These in vitro foam cell models were used to study the capability of synthetic HDL-particles to promote efflux of cholesterol. The synthetic HDL-particles were prepared from recombinant human pro-apolipoprotein A-I or human apolipoprotein A-I and phosphatidylcholine. Both types of reconstituted complexes were found to have a discoidal structure. A 24 h incubation of lipid loaded J774A.1 cells with these two types of discoidal complexes resulted in an equivalent and marked egress of cholesterol. The effect was the same whether the origin of phosphatidylcholine was egg yolk or soybean.

Serum lipoproteins and hemostatic function in intermittent claudication

Normoglucemic men with intermittent claudication (n = 41), mean age of 63 years, and sex-, age-, body mass index-, and smoking habit-matched controls (n = 75) were compared for plasma lipoprotein and hemostatic variables. The patients had significantly lower levels of large high-density lipoprotein (HDL) particles (HDL2b, HDL2a, and HDL3a) and elevated lipoprotein(a) [Lp(a)] concentrations than the control subjects. Of the hemostatic variables, plasminogen activator inhibitor-1 (PAI-1), plasma antiplasmin, plasma fibrinogen, and urine beta-thromboglobulin concentrations were significantly elevated in patients. In intermittent claudication patients Lp(a) correlated significantly with activation of the coagulation system, ie, with the levels of plasma fibrinogen and urine fibrinopeptide A. No correlations between the values for Lp(a) and PAI-1 or plasma alpha 2-antiplasmin were seen. The PAI-1 activity showed significant univariate correlations to the levels of HDL3b, HDL2b (inverse), and very-low-density lipoprotein triglycerides, of which the positive correlation to HDL3b persisted in multivariate analysis (r = .48, P < .001). Independent characteristics for intermittent claudication estimated by multiple regression analysis were PAI-1, plasma fibrinogen, and HDL3a, with a combined R2 of .36. The intermittent claudication subgroup that was being treated with beta-blockers/thiazides had a higher frequency of coronary heart disease compared with the other patients. In addition, the patients taking beta-blockers/thiazides had elevated triglyceride concentrations, lower HDL cholesterol with a size shift toward smaller particles, and a tendency toward raised PAI-1 and plasma alpha 2-antiplasmin levels compared with the patient group that did not take these medications.