Effects of cimetidine and ranitidine on plasma high-density lipoprotein subclasses in humans

The effects of cimetidine (400 mg b.d.) and ranitidine (150 mg b.d.) on high-density lipoprotein (HDL) subclasses and other plasma lipoproteins were studied in 18 men and 15 women with reflux oesophagitis and/or duodenitis. Serum testosterone and sex hormone binding globulin (SHBG) concentrations were also measured. Treatment with either drug was continued for 12 weeks. Ranitidine had no significant effect on any measured variable in either men or women. Cimetidine had no effect in men, but in women it raised the cholesterol concentration in the HDL2 subclass by 15% after 8 weeks, and by 48% after 12 weeks. In females, cimetidine also reduced the concentrations of SHBG (by 24% at 12 weeks) and of total testosterone (by 25% at 12 weeks). The significance of these latter changes is uncertain, however, as estimates of the biologically active free testosterone concentration were unchanged.

Sex, plasma lipoproteins, and atherosclerosis: prevailing assumptions and outstanding questions

We review the hypothesis that the incidence of coronary heart disease (CHD) is higher in men than in women due to differences in plasma lipoprotein risk factors between the sexes. Men and women appear to be equally susceptible to the effects of lipoprotein risk factors for CHD, and the difference between the sexes in lipoprotein risk factors for CHD appears to be consistent with their being, at least in part, responsible for the sex difference in CHD. This is apparent both when men and women of equal age are compared, and when age-related variations in the sex differences in plasma lipoproteins and CHD are considered. Differences between the sexes in lipoprotein concentrations are still present when sex differences in adiposity, cigarette smoking, physical activity, and diet are taken into account. Evidence relating these sex differences in CHD and lipoproteins to the effects of sex hormones is critically examined. It is commonly accepted that androgens induce changes in lipoprotein concentrations that would predispose towards CHD, whereas estrogens are held to have opposite effects. However, much of the evidence for this comes from studies of changes associated with administration of synthetic gonadal steroids or with changes in gonadal function. Studies of differences in lipoprotein metabolism in normal men and women are extremely limited. In males high-density lipoprotein (HDL) cholesterol levels fall at puberty, correlating with the rise in plasma testosterone concentrations. In females, HDL levels do not change at puberty, despite the rise in estrogen concentrations. Evidence for lipoprotein changes during the menopause, when estrogen levels decline, is equivocal. Similarly, the evidence for an increase in CHD incidence at the menopause is inconclusive. National mortality data indicate that the decreasing sex difference in CHD after 50 years of age is due to a declining rate of increase in men rather than to an acceleration in CHD incidence in women. In men the age-related increase in low-density lipoprotein (LDL) concentrations diminishes beyond 50 years of age, whereas in women the rate of increase remains unchanged. Studies of the effects of gonadectomy are of doubtful relevance in assessing the roles of sex hormones in CHD, and have not been performed with sufficient rigor to provide definitive conclusions.(ABSTRACT TRUNCATED AT 400 WORDS)

Mechanism-based inactivation of the major beta-naphthoflavone-inducible isozyme of rat liver cytochrome P-450 by the chloramphenicol analog N-(2-p-nitrophenethyl)dichloroacetamide

The effectiveness, selectivity, and mechanism of the inactivation of the major beta-naphthoflavone-inducible isozyme of rat liver cytochrome P-450 (BNF-B) by the chloramphenicol analog N-(2-p-nitrophenethyl)dichloroacetamide (pNO2DCA) have been investigated. Intraperitoneal administration of pNO2DCA to beta-naphthoflavone-treated rats at doses of 10 and 100 mg/kg resulted in 72 and 95% decreases, respectively, in the ethoxyresorufin deethylase activity of subsequently prepared liver microsomes. Similar decreases were observed in the warfarin R-6 and R-8 hydroxylase activities of the microsomes. At the lower dose of pNO2DCA, only those R-warfarin hydroxylase activities attributable to BNF-B were decreased, whereas, at the higher dose, inhibition of additional cytochromes P-450 was evident. In vitro, pNO2DCA was found to be a highly efficient inactivator of purified BNF-B in a reconstituted system. The maximal rate constant for inactivation and the apparent Km for the inhibitor were 0.52 min-1 and 2.7 microM, respectively. Inactivation of BNF-B by pNO2DCA appears to involve an impairment in electron transfer from NADPH-cytochrome P-450 reductase, as evidenced by a decrease in the NADPH- but not the iodosobenzene-supported metabolism of ethoxycoumarin by the modified enzyme. However, in the absence of substrate, there was no decrease in the NADPH oxidase activity or in the steady state level of ferrous carbonyl complex formed enzymatically. Likewise, the maximal level of isosafrole metabolite-P-450 complex formed by BNF-B was not decreased by modification with pNO2DCA, although the rate of complex formation was inhibited.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-blind trial of the long-term effects of acebutolol and propranolol on serum lipoproteins in patients with stable angina pectoris

In order to evaluate the long-term effects of propranolol and acebutolol on serum lipoprotein lipids, a double-blind clinical trial was carried out. Fifteen patients with stable angina pectoris, aged 32 to 79 years (mean = 53), were randomized to propranolol (80 to 160 mg/day) or acebutolol (400 mg/day) treatment groups, and followed for approximately 1 year (mean = 371 days). Blood was collected on the day treatment was begun, after approximately 5 months (mean = 158 days), and on completion of the trial. Very low-density lipoproteins (VLDL) (alpha less than 1.006), low-density lipoproteins (LDL) (1.006 to 1.063), and high-density lipoproteins (HDL) (1.063 to 1.125 [HDL2] and 1.125 to 1.21 [HDL3]) were isolated by sequential preparative ultracentrifugation, and their cholesterol and triglyceride quantified by enzymic procedures. After 1 year propranolol had raised the mean VLDL triglyceride concentration by 79% (p less than 0.005) and had lowered total HDL cholesterol by 24% (p less than 0.005). As LDL cholesterol was unchanged, the LDL cholesterol/HDL cholesterol ratio was increased by 26% (p less than 0.005). Mean values at 5 months were intermediate between those at baseline and those at 1 year. In contrast to these changes, acebutolol had no significant effect on any measured lipoprotein lipid.

On the associations of body cholesterol pool size with age, HDL cholesterol and plasma total cholesterol concentration in humans

Data from 17 subjects, in whom cholesterol kinetics had been measured by two-pool analysis of medium-term plasma cholesterol specific activity-time curves, were examined by multiple linear regression to explore the determinants of the size of the slowly exchanging cholesterol pool (MBmin) in humans. Pool size was independently and positively related to body weight (regression coefficient, 0.94 g per kg; P = 0.05) and age (1.77 g per year; P = 0.02). After allowance for these effects, MBmin retained a significant negative association with the plasma high density lipoprotein (HDL) cholesterol concentration (-0.56 g per mg/dl; P = 0.03), but was unrelated to plasma total cholesterol. This result is consistent with published data on the composition of those human tissues whose cholesterol is known to be largely a component of the slowly exchanging pool. It differs, however, from that of a recent study of cholesterol turnover [Blum et al, J. Lipid Res., 1985; 26: 1079-1088] in which pool size, measured by three-pool analysis of long-term decay curves, was unrelated to HDL and directly related to plasma total cholesterol. On the basis of other published data, it is considered that this discrepancy is unlikely to be a consequence of the difference between our respective studies in the duration and method of analysis of the specific activity decay curves. Differences in the variances of HDL cholesterol and plasma total cholesterol concentration that were examined, and in the biochemical-genetic factors underlying these variances, provide a more likely explanation. The overall weight of evidence favours the view that the pool of slowly exchangeable cholesterol in many human tissues expands during ageing at a rate which is increased in the presence of severe hypercholesterolemia, and which under some, but not all, circumstances also varies inversely with HDL cholesterol. The critical components of HDL metabolism which affect this process remain to be identified.

Effects of adrenoceptor-blocking drugs on plasma lipoprotein concentrations

Evidence from numerous clinical trials has indicated that beta-adrenoceptor blocking agents without intrinsic sympathomimetic activity increase plasma triglycerides and decrease high density lipoprotein cholesterol in patients with hypertension or coronary artery disease. There appears to be little or no difference between the nonselective and cardioselective drugs in this regard. In contrast, beta blockers with intrinsic sympathomimetic activity and alpha 1 blockers appear not to have these effects. The changes induced by adrenoceptor-blocking agents in lipid and lipoprotein metabolism and their possible significance in relation to the pathogenesis of coronary artery disease are discussed.

High-density lipoprotein: a major risk factor for coronary atherosclerosis

The high-density lipoproteins (HDL) are a polydisperse family of lipid--protein complexes whose principal functions in lipid transport are: (1) to act as a reservoir of C apoproteins required for triglyceride transport; (2) to act as a 'scavenger' of surplus cholesterol and phospholipid liberated from lipolysed triglyceride-rich lipoproteins; and (3) to transport surplus cholesterol from peripheral tissues to the liver for excretion and catabolism (reverse cholesterol transport), both directly and indirectly via other lipoproteins and the lipid transfer protein. The concentration of HDL cholesterol (mostly cholesteryl ester) has been found to be a strong risk factor for coronary atherosclerosis, and its clinical complications in most industrialized communities have been studied. The association with disease risk is independent of other lipoproteins and risk factors, has been found in both sexes, and persists following reduction of plasma lipids by diet and certain drugs. It is not yet clear whether or not certain HDL subclasses and/or apoproteins are better predictors of risk than HDL cholesterol. Indirect evidence from clinical studies and data from animal experiments suggests that certain pharmacologically induced increases in HDL cholesterol concentration are associated with a reduction of atherogenesis. However, the mechanism of the link between HDL and atherogenesis is not yet clear: although the original suggestion that it reflects the function of HDL in reverse cholesterol transport remains plausible, alternative mechanisms are possible. These include effects of HDL on platelet function and prostacyclin synthesis. Alternatively, the association might be indirect, reflecting an atherogenic effect of triglyceride-rich lipoproteins and/or their remnants, the plasma concentrations of which are correlated with HDL cholesterol.

Knowledge-based indexing of the medical literature: the Indexing Aid Project

This article describes the Indexing Aid Project for conducting research in the areas of knowledge representation and indexing for information retrieval in order to develop interactive knowledge-based systems for computer-assisted indexing of the periodical medical literature. The system uses an experimental frame-based knowledge representation language, FrameKit, implemented in Franz Lisp. The initial prototype is designed to interact with trained MEDLINE indexers who will be prompted to enter subject terms as slot values in filling in document-specific frame data structures that are derived from the knowledge-base frames. In addition, the automatic application of rules associated with the knowledge-base frames produces a set of Medical Subject Heading (MeSH) keyword indices to the document. Important features of the system are representation of explicit relationships through slots which express the relations; slot values, restrictions, and rules made available by inheritance through "is-a" hierarchies; slot values denoted by functions that retrieve values from other slots; and restrictions on slot values displayable during data entry.

Mental health services use by elderly adults in a primary care setting

This study examined the use of general health, mental health, and other medical specialty services by elderly persons 65 and older with mental disorders and compares them with adults 45 to 64 and 18 to 44. Data were collected at the Bunker Hill Health Center (BHHC), a Boston neighborhood health center providing a broad range of ambulatory medical and specialty mental health services. Results show that the 5-year rate of mental disorder diagnoses for elderly individuals is not significantly different from persons 45 to 64, although it is higher than the rate for young adults 18 to 44. Not only were elderly adults less likely to see a mental health specialist, but when they did, their use of mental health specialty services was usually lower.

Dichloromethyl compounds as mechanism-based inactivators of rat liver cytochromes P-450 in vitro

Twenty dichloromethyl compounds have been tested as potential mechanism-based inactivators of the major phenobarbital-inducible isozyme of rat liver cytochrome P-450 (PB-B) in a reconstituted system. With the exception of dichloromethane and dichloroacetamide, all the compounds decreased the ethoxycoumarin deethylase activity of the enzyme in a time- and NADPH-dependent manner. The inhibitory compounds could be divided into two classes according to whether the loss of monooxygenase activity was accompanied by a decrease in spectrally detectable cytochrome P-450. N-Monosubstituted dichloroacetamides in which the side-chain consisted of a phenyl or n-octyl group were able to mimic the action of chloramphenicol and inactivate the PB-B without destroying the heme moiety. In contrast, dichloroacetamides containing an n-hexyl, n-butyl, or methyl substituent caused a significant loss of heme, as did the five non-amides tested: 1,1,2,2-tetrachloroethane, 1,1-dichloroacetone, methyl dichloroacetate, alpha,alpha-dichlorotoluene, and alpha,alpha-dichloroacetophenone. Representative compounds were also examined as inactivators of the major beta-naphthoflavone-inducible isozyme of rat liver cytochrome P-450 (BNF-B), using a reconstituted system, as well as of constitutive cytochromes P-450, using intact liver microsomes from untreated rats. These studies suggested a marked difference in isozyme selectivity between certain of the compounds. For example, of the isozymes monitored, only the PB-B was affected by alpha,alpha-dichlorotoluene in an NADPH-dependent manner, whereas N-octyl dichloroacetamide inactivated not only the PB-B and BNF-B, but also certain constitutive cytochromes, as evidenced by decreases in microsomal S-warfarin hydroxylase activities. These studies help delineate the structural requirements for the use of dichloromethyl compounds as probes of cytochrome P-450 function and as potential isozyme-selective inhibitors.

Failure to replicate visceral learning in the acute curarized rat preparation

An attempt was made to replicate a series of experiments reported to demonstrate robust visceral learning (autonomic instrumental learning) in rats during acute (2-4 hr) pharmacological paralysis. The results of exploratory procedures involving more than 2,000 animals are described, and six complete experiments, representing systematic observations on an additional 500 animals, are presented. In the first three experiments, which closely followed the original procedures, the characteristics of the preparation were reproduced with the exception of initial heart rhythm and visceral learning. In the second three, the respiration procedure was modified to satisfactorily reproduce the heart rhythm, and the PaO2, PaCO2, and pH were verified to be within the range of freely moving, normally behaving animals; nevertheless, visceral learning was not observed in these experiments either. After more than 2,500 rats were studied, it is concluded that the original visceral learning experiments are not replicable and that the existence of visceral learning remains unproven; however, neither the original experiments nor the replication attempt included the necessary controls to support a general negative conclusion about visceral learning. Because continuing and extensive citation of the original experiments indicates their widely perceived significance, specific requirements for critically testing the visceral learning hypothesis are given, and the limited theoretical implications and practical value of neuromuscular blockade are discussed.

Association between dietary fat intake and plasma factor VII coagulant activity--a predictor of cardiovascular mortality

Repeated measurements were made in 8 adults of factor VII coagulant activity (VIIc) and fibrinogen concentration (two haemostatic variables associated with cardiovascular mortality), together with factor VII concentration, factor X, prothrombin, and serum cholesterol and triglyceride concentrations, while the usual diet was recorded by precise weighing over 12-14 days. In 6 subjects measurements were continued while low-fat and high-fat diets were taken for a further 2 and 3 weeks respectively. Plasma VIIc was related positively and independently to fat and protein intake, whereas factor VII concentration was associated only with protein consumption. In a second study, consumption of 50% extra energy for one day increased VIIc significantly when taken mainly as fat but not when taken mostly as carbohydrate. The character of the VIIc response to fat intake suggested an association with post-prandial lipaemia. A high fat intake may lead not only to coronary atheroma but also to fibrin deposition and thrombus formation through direct activation of the coagulation system.

Analogues of chloramphenicol as mechanism-based inactivators of rat liver cytochrome P-450: modifications of the propanediol side chain, the p-nitro group, and the dichloromethyl moiety

The importance of the p-nitro group, the propanediol side chain, and the dichloromethyl moiety of chloramphenicol in regulating its effectiveness and selectivity as a mechanism-based inactivator of rat liver cytochromes P-450 has been examined. 1-p-Nitrophenyl-2-dichloroacetamidoethane, 1-p-nitrophenyl-2-dibromoacetamidoethane, and 1-phenyl-2-dichloroacetamidoethane were as effective as chloramphenicol at inactivating the major phenobarbital-inducible isozyme of rat liver cytochrome P-450, whereas 1-p-nitrophenyl-2-difluoroacetamidoethane caused no enzyme inactivation. Unlike chloramphenicol, 1-p-nitrophenyl-2-dichloroacetamidoethane and 1-phenyl-2-dichloroacetamidoethane also inactivated the major beta-naphthoflavone-inducible isozyme of rat liver cytochrome P-450. Alkaline hydrolysis of the adducts formed upon in vitro incubation of liver microsomes from phenobarbital- and beta-naphthoflavone-induced rats with [14C]-1-p-nitrophenyl-2-dichloroacetamidoethane resulted in the release of 4-nitro-1-phenethyl-1,2-dicarboxylic acid amide and oxalic acid. Enzymatic digests of the radio-labeled protein produced by incubation of a reconstituted system containing the major isozymes induced by beta-naphthoflavone or phenobarbital with [14C]-1-p-nitrophenyl-2-dichloroacetamidoethane led to the release of 4-nitro-1-phenethyl-1,2-dicarboxylic acid amide and 4-nitro-1-phenethyl oxamyl lysine. These results suggest that a single oxamyl chloride intermediate is responsible for the covalent modification and, hence, inactivation of both isozymes by 1-p-nitrophenyl-2-dichloroacetamidoethane.

Failure to replicate visceral learning in the acute curarized rat preparation

An attempt was made to replicate a series of experiments reported to demonstrate robust visceral learning (autonomic instrumental learning) in rats during acute (2-4 hr) pharmacological paralysis. The results of exploratory procedures involving more than 2,000 animals are described, and six complete experiments, representing systematic observations on an additional 500 animals, are presented. In the first three experiments, which closely followed the original procedures, the characteristics of the preparation were reproduced with the exception of initial heart rhythm and visceral learning. In the second three, the respiration procedure was modified to satisfactorily reproduce the heart rhythm, and the PaO2, PaCO2, and pH were verified to be within the range of freely moving, normally behaving animals; nevertheless, visceral learning was not observed in these experiments either. After more than 2,500 rats were studied, it is concluded that the original visceral learning experiments are not replicable and that the existence of visceral learning remains unproven; however, neither the original experiments nor the replication attempt included the necessary controls to support a general negative conclusion about visceral learning. Because continuing and extensive citation of the original experiments indicates their widely perceived significance, specific requirements for critically testing the visceral learning hypothesis are given, and the limited theoretical implications and practical value of neuromuscular blockade are discussed.

Isozyme selectivity of the inhibition of rat liver cytochromes P-450 by chloramphenicol in vivo

The isozyme-selectivity of chloramphenicol as an inhibitor of rat liver cytochromes P-450 has been investigated. Untreated rats and rats treated with the inducers phenobarbital, beta-naphthoflavone, pregnenolone 16 alpha-carbonitrile, and clofibrate have been injected intraperitoneally with chloramphenicol, and inhibition of specific cytochrome P-450 isozymes has been assessed by monitoring the metabolism of warfarin, testosterone, isosafrole, or lauric acid in subsequently prepared hepatic microsomal preparations. Of eight major cytochrome P-450 isozymes which could be monitored in this fashion, three were inhibited by more than 50% by a dose of chloramphenicol of 300 mg/kg, whereas no evidence of inhibition of the remaining isozymes was obtained. P-450PB-C, an isozyme which is present in significant amounts in untreated rats and which is induced approximately 2-fold by phenobarbital, was the most susceptible cytochrome P-450 to inhibition by chloramphenicol both in vivo and in vitro. P-450PB-B, the major phenobarbital-inducible isozyme, and P-450UT-A, a male-specific testosterone 2 alpha- and 16 alpha-hydroxylase, were intermediate in their susceptibility to chloramphenicol. In contrast, the major isozymes induced by beta-naphthoflavone, pregnenolone 16 alpha-carbonitrile, and clofibrate, as well as a constitutive testosterone 7 alpha-hydroxylase, were not inhibited by chloramphenicol.

On the mechanism of the inactivation of the major phenobarbital-inducible isozyme of rat liver cytochrome P-450 by chloramphenicol

The mechanism of the inactivation of the major phenobarbital-inducible isozyme of rat liver cytochrome P-450 (P-450 PB-B2) by chloramphenicol has been investigated. Preparations of the enzyme from animals treated in vivo with chloramphenicol (CAP PB-B2) have been isolated, and their catalytic, spectral, and physical properties have been compared with those of the native PB-B2. The CAP PB-B2 exhibited: 1) a 60-70% loss in the rate of NADPH-supported monooxygenase activity with the substrates benzphetamine, 7-ethoxycoumarin, and p-nitroanisole; 2) a 60% decrease in the extent of enzymatic P-450 reduction catalyzed by NADPH-cytochrome P-450 reductase under both aerobic and anaerobic conditions; 3) a 60% decrease in the steady-state level of the ferrous dioxygen complex in the presence of substrates; 4) a 60% decrease in the magnitude of the type I spectral change induced by benzphetamine; and 5) a shift in the wavelength maximum for the chemically reduced ferrous-carbonyl complex from 450 to 451.5 nm. On the other hand, the ability of the CAP PB-B2 to catalyze the iodosobenzene-supported metabolism of 7-ethoxycoumarin and p-nitroanisole was unaltered. The results are consistent with a scheme whereby the binding of metabolites of chloramphenicol to amino acid residues in the PB-B2 close to the heme moiety blocks electron transport from NADPH-cytochrome P-450 reductase, thereby leading to a loss of monooxygenase activity.

Are plasma lipoprotein cholesteryl esters utilized for biliary cholesterol and bile acid production in man?

Studies were carried out to determine whether or not plasma lipoprotein cholesteryl esters are available to the liver for biliary cholesterol and bile acid production in humans with intact biliary tracts. Six healthy males were given intravenous infusions of autologous high-density (d, 1.063-1.21; n = 2), low-density (d, 1.019-1.063; n = 2) or intermediate-density (d, 1.006-1.019; n = 2) lipoproteins that had been labelled in vitro with radioactive cholesteryl linoleate (n = 5) or cholesteryl oleate (n = 1). Duodenal contents were continuously aspirated via the intermediate and distal ports of a triple-lumen tube (mean recovery, 64 per cent), through the proximal port of which was infused an amino-acid solution. During 5-6 hours only moderate fluctuations were observed in bile acid and cholesterol secretion rates, implying the existence of near steady-state conditions. In all subjects radioactivity rapidly appeared in both biliary cholesterol and bile acids, and continued to be secreted for the duration of the experiment. The total radioactivity recovered from cholesterol averaged 0.27 per cent of the administered dose; the corresponding figure for bile acids was 11.2 per cent. These results indicate that lipoprotein cholesteryl esters are readily available for biliary lipid production in humans.

High-density lipoprotein composition is altered by a common DNA polymorphism adjacent to apoprotein AII gene in man

25 of a group of 87 White men had Msp 1 restriction site polymorphism within an Alu sequence 3' to the human apo AII gene. Homozygosity for the polymorphism in 8 men was associated with a significant increase in serum apo AII levels (35.4 +/- 1.70 mg/dl, mean +/- SEM) and altered HDL composition, compared with heterozygotes (31.7 +/- 1.29; n = 17) and normal subjects (29.4 +/- 0.64; n = 62). This is the first account of a common variant of an HDL apoprotein gene that affects HDL composition. In view of its association with a high apo AII concentration homozygosity may protect against atherosclerosis.

Plasma apolipoprotein B metabolism in familial type III dysbetalipoproteinaemia

Lipoprotein metabolism was studied in eleven patients with Type III hyperlipoproteinaemia, one with normolipidaemic dysbetalipoproteinaemia and eight controls. Apolipoprotein B kinetics in very low density, intermediate density and low density lipoproteins (VLDL, IDL and LDL) was investigated. Fractional catabolic rates (FCRs) of VLDL-apo B and IDL-apo B were lower (P less than 0.005 and P less than 0.001) in the patients: 0.064 +/- 0.018 and 0.059 +/- 0.006 h-1 respectively, (mean +/- SEM), compared with 0.219 +/- 0.035 and 0.243 +/- 0.028 h-1. Synthetic rates (SRs) of IDL-apo B varied widely from 1.5 mg kg-1 day-1 in the subject with normolipidaemic dysbetalipoproteinaemia to 2.8-25.2 mg kg-1 day-1 in Type III. The mean time for conversion of IDL-apo B to LDL-apo B was prolonged, 18.7 h compared with 3.8 h in the controls (P less than 0.001). LDL-apo B pool size and SR were lower in the patients (P less than 0.05 for both). Two patients treated with gemfibrozil showed reduced hyperlipidaemia and decreased SR of VLDL-apo B and IDL-apo B. Dysbetalipoproteinaemia is associated with pronounced impairment of IDL and VLDL-remnant catabolism, lipoprotein levels reflecting an interaction between this defect and SR of these lipoproteins.

Behavioral method for the treatment of idiopathic scoliosis

Idiopathic scoliosis was treated by an automated portable posture-training device that incorporated precise behavioral principles and enabled therapeutic training to be given in the patients' normal environment throughout the entire day. Twenty-one patient-years of training were completed with a group of 12 adolescent girls selected as being imminently likely to require a brace because of the way their spinal curves had been progressing. As an alternative to conventional brace therapy, patients found the posture-training device considerably less physically restraining and more cosmetically acceptable. Most patients wore it 23 hr per day for at least 1 year and adapted well to the constant physical and psychological presence of the instrument. For 10 patients, the outcome was entirely successful; they were discharged from this pilot study as satisfactorily corrected. Progression of the scoliotic curve was arrested; in fact, there was an average slight improvement in the Cobb angle (a measure of spinal curvature) as measured by x-ray radiography.

Relationship between changes in plasma lipoprotein concentrations and fecal steroid excretion in man during consumption of four experimental diets

Limited information is available on the mechanism by which changes in nutrient intake influence plasma lipids. We compared the effects on plasma lipoprotein levels of 3 dietary modifications involving changes in total fat intake (27-40% of calories), cholesterol intake (100-250 mg/1000 kcal), the dietary polyunsaturated to saturated fatty acid ratio (0.3-1.0) and intake of vegetable-derived fiber and protein. On these 3 diets, plasma low density lipoprotein was reduced by 26-34%. Fecal bile acid excretion was similar on all diets (363-379 mg/day). There was no alteration in fecal bile acid output associated with an increase in polyunsaturated or total fat intake. Sterol balance became significantly more negative during consumption of only 1 of the 3 cholesterol-lowering diets. The observed reduction in plasma cholesterol levels was not associated with an increase in fecal bile acid output suggesting that diet-induced changes in circulating cholesterol are not maintained by an increase in sterol turnover but may reflect alterations in hepatic cholesterol and lipoprotein synthesis.

Direct evidence that reverse cholesterol transport is mediated by high-density lipoprotein in rabbit

Mammalian cells obtain cholesterol for membrane synthesis mostly via the receptor-mediated endocytosis of low-density lipoprotein (LDL). Macrophages and vascular endothelium additionally have receptors that recognize certain modified forms of LDL (for example, acetyl-LDL). The process by which cholesterol returns from peripheral cells to hepatocytes (reverse cholesterol transport) has not been established; although tissue culture studies have favoured high-density lipoprotein (HDL) as the principal vehicle, the in vivo evidence for this is meagre. When cholesterol-loaded macrophages are incubated in medium containing plasma, cholesterol moves from the cells to HDL and is then esterified by lecithin/cholesterol acyltransferase. The accumulation of cholesteryl esters in the particles increases their size and decreases their density; enrichment with apoprotein E (apo E) also occurs, producing a decrease in electrophoretic mobility. We now report that similar changes occur in the circulating HDL of rabbits, when their peripheral tissues are loaded with cholesterol by intravenous (i.v.) injection of acetylated or native human LDL. This result suggests that HDL is involved in reverse cholesterol transport in vivo.

Energy expenditure in patients with low-, mid-, or high-thoracic paraplegia using Scott-Craig knee-ankle-foot orthoses

Renewed interest in ambulation in patients with paraplegia prompted us to measure the energy expenditure (kcal/kg per min) during standing and ambulating with the Scott-Craig orthosis in nine patients who had low-, mid-, or high-thoracic paraplegia. Energy expenditure during standing and during ambulation with a walker was similar for patients with all levels of paraplegia. In patients with high-thoracic paraplegia, energy efficiency was significantly less (P less than 0.05) than that for patients with mid- or low-thoracic paraplegia, whose efficiency levels were similar. In patients with low-thoracic paraplegia, the only patients who could perform swing-through gait patterns, energy efficiency was increased because of increased velocity. Our data do not support the concept of denying, on the basis of the level of the lesion alone, young, otherwise healthy, well-motivated patients with thoracic paraplegia the opportunity of using Scott-Craig orthoses to supplement wheelchair mobility and activities of daily living.

Some professional and scientific problems and opportunities for biofeedback

This paper will deal with a variety of topics such as dangers and opportunities from the developing crisis in health care costs, a cooperative study of the cost-effectiveness of treatments for headaches, the need for a federation of related societies, exploiting remarkable electronic advances, the wide range of adaptive functions of visceral learning (including its role in homeostasis), why maladjustments occur and their implications for biofeedback, and the need for analytic experiments involving adequate amounts of training.

An alternative procedure for incorporating radiolabelled cholesteryl ester into human plasma lipoproteins in vitro

A simple method has been developed for labelling human plasma lipoproteins to high specific radioactivity with radioactive cholesteryl esters in vitro. After isolation by preparative ultracentrifugation, the selected lipoprotein was incubated for 30 min at 4 degrees C in human serum (d greater than 1.215) that had been prelabelled with [4-14C]cholesteryl oleate or [1,2-3H]cholesteryl linoleate, and was then re-isolated by ultracentrifugation. All major lipoprotein classes were labelled by the procedure. Specific radioactivities of up to 18 d.p.m. . pmol-1 (46 d.p.m. . ng-1) were achieved. When radiolabelled high-density lipoprotein was infused intravenously, the radioactive cholesteryl ester behaved in vivo indistinguishably from endogenous cholesteryl esters produced by the lecithin (phosphatidylcholine): cholesterol acyltransferase reaction.

Paraplegic energy expenditure during negotiation of architectural barriers

Long-leg braces are often used by persons with paraplegia to negotiate architectural barriers, and thereby increase their wheelchair mobility. Such barriers include ramps, stairways, and narrow corridors requiring multiple turns. This study was designed to measure the energy expenditure during such activities for two long-leg orthoses: standard braces without a dorsiflexion stop and Scott-Craig braces. Energy expenditure was measured in eight subjects by indirect spirometry using Douglas bag collection and Haldane analysis. Data obtained were used to calculate oxygen consumption per minute, volume of oxygen per turn, step, or meter, and calories per minute during each activity. Using Scott-Craig braces on one day and standard braces on another day, each subject negotiated five 90 degrees turns and two 180 degree turns, ten 15.24 cm steps, both up and down, and an 11.9 m ramp inclined 12 degrees, both up and down. Milliliters of oxygen consumed per kilogram of body weight per turn, step, or meter were recorded for Scott-Craig braces, standard braces, and normal walking. All of these activities required a high expenditure of energy. No significant difference was apparent between the standard and the Scott-Craig braces for any activity.

Studies of lipoprotein metabolism in a patient with fish-eye disease

In the rare familial disorder fish-eye disease, hypertriglyceridaemia is associated with elevated levels of very-low-density lipoprotein (VLDL) and enrichment of low-density lipoprotein (LDL) with triglyceride. The kinetic basis of the dyslipoproteinaemia was investigated by studying the metabolism of the apolipoprotein-B moeity of VLDL, intermediate-density lipoprotein (IDL) and LDL in a 68-year-old woman with this condition. The major kinetic abnormality was a pronounced reduction in the rate of fractional conversion of VLDL-B to IDL-B and of IDL-B to LDL-B, suggesting that the dyslipoproteinaemia represents accumulation in plasma of partly degraded products of VLDL metabolism. This kinetic disorder has features in common with type-III hyperlipoproteinaemia. In studies in vitro no defect in the enzyme, activator or substrate components of the lipoprotein lipase or hepatic lipase systems was observed.

Inhibition of cholesterol synthesis reduces low-density-lipoprotein apoprotein B production without decreasing very-low-density-lipoprotein apoprotein B synthesis in rabbits

The kinetics of the apoprotein B (apo B) of very-low-density (VLDL; d less than 1.006) and low-density (LDL; d 1.019-1.063) lipoproteins were studied in six rabbits by using radioiodinated homologous lipoproteins, before and during oral administration of mevinolin (5 mg/kg per day), a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (EC 1.1.1.34), to explore the mechanism by which the drug reduces LDL synthesis. Before treatment LDL-apo B production greatly exceeded VLDL-apo B production in all animals, indicating that a large proportion of plasma LDL was derived from a VLDL-independent pathway. Five animals responded to mevinolin with a fall in plasma cholesterol (mean change - 53%; P less than 0.01). This was associated with a 66% decrease in LDL-apo B synthesis (P less than 0.05). In contrast, VLDL-apo B synthesis was unaffected by mevinolin. Furthermore, in all but one animal the decrement in LDL-apo B synthesis was greater than the rate of VLDL-apo B synthesis before treatment, demonstrating that mevinolin had reduced the VLDL-independent production of LDL.

Energy expenditure of paraplegic patients standing and walking with two knee-ankle-foot orthoses

To determine which kind of knee-ankle-foot orthosis (KAFO) is more efficient, we measured energy expenditure in standing, walking with a walker, and walking with crutches by eight subjects using the Scott-Craig KAFO and a single-stopped long-leg KAFO. All subjects had complete motor paralysis below the level of their lesion and had been fully trained to use KAFOs. Every subject used both types of KAFO, and energy expenditure--per minute and per meter traveled--was measured by oxygen consumption. No significant difference in energy expenditure appeared during standing. During ambulation, however, mean energy expenditure was less with the Scott-Craig KAFO than with the single-stopped type: 31% less kcal/m with a walker and 25% less kcal/min with crutches. These results suggest that the Scott-Craig KAFO is more energy-efficient than the single-stopped long-leg KAFO.

A multifactorial diet in the management of hyperlipidaemia

To augment the effectiveness of conventional lipid-lowering treatment, a diet has been evolved combining modified fat content with an increase in vegetable-derived fibre and protein. This was evaluated in 37 hyperlipidaemic and normal ambulant subjects in whom plasma lipid and lipoprotein responses were measured for 4.7-11 months. Mean reductions in plasma cholesterol, triglyceride and low density lipoprotein cholesterol levels were 22, 24 and 25% respectively; there was no significant change in the cholesterol concentrations in high density lipoprotein or in its HDL2 subclass. The effectiveness of the diet in reducing hyperlipidaemia, its influence in optimizing the distribution of cholesterol between plasma lipoprotein classes, and its nutrient composition suggest that it is an advance on existing lipid-lowering dietary patterns.

Coronary heart disease in 'low risk' men

An attempt was made to explore the reasons why men develop coronary heart disease (CHD) despite being at low risk on the basis of established risk factors. A case control study was designed to take place after the end of a longitudinal study in which both low- and high-risk men who had developed CHD over the course of 5-6 years were compared with controls who had remained CHD-free, matched for initial risk characteristics. Low-risk men who had developed CHD had significantly lower levels of high density lipoprotein (HDL) cholesterol than their controls. This difference was not seen when high-risk men were compared with their controls. Apart from a suggestion that low risk cases had lower levels of free thyroxine (seen mainly when less severe categories of CHD were examined) there were no other significant differences between cases and controls (either low- or high-risk) in the other measured variables, which included levels of total testosterone and oestradiol in plasma, packed cell volume and heart rate. It is concluded that low levels of HDL cholesterol may partly explain why men who are otherwise at low risk develop CHD. This study design may be useful to test other hypotheses, particularly where it has not been possible to make the appropriate measurements at the start of a longitudinal study.

Relationship of high density lipoprotein cholesterol with total and free testosterone and sex hormone binding globulin

A cross-sectional study was performed to see if the previously described association between high density lipoprotein (HDL) cholesterol and plasma total testosterone concentration reflected a relationship with free testosterone or with sex hormone binding globulin (SHBG). In 295 employed middle-aged men, measurements were made of total testosterone and SHBG in serum and of testosterone in saliva, and also of plasma total and HDL cholesterol, plasma triglycerides and other factors which might influence HDL cholesterol levels such as body mass index, alcohol and smoking habits and thyroid hormone levels. In a multiple regression analysis using the GLIM package programme total testosterone concentrations had a persistent positive association with HDL cholesterol (t = 3.5, P less than 0.001) - this association was independent of SHBG (which had a negative association with HDL: t = -1.8, P less than 0.07. The association of HDL cholesterol with testosterone was independent of and stronger than the association of HDL cholesterol with body mass index, alcohol intake and cigarette smoking. Salivary testosterone (a measure of the circulating free hormone) also had a positive independent association with HDL cholesterol. The relationship between HDL cholesterol and testosterone thus appears to reflect an association with circulating hormone levels rather than with the hormone binding globulin.

Stress-induced suppression of immunity in adrenalectomized rats

Stress-induced suppression of lymphocyte stimulation by phytohemagglutinin was demonstrated in Isolated lymphocytes and in cultures of whole blood from adrenalectomized rats. The results demonstrate that corticosteroid independent mechanisms participate in the suppression of lymphocyte function by stressors. Stress-induced lymphopenia, however, was found to be adrenal dependent, indicating that the modulation of immunity by stress is complex and multidetermined.

Treatment of hyperlipidaemia retards progression of symptomatic femoral atherosclerosis. A randomised controlled trial

The effect of plasma lipid reduction on the progression of femoral atherosclerosis was studied in hyperlipidaemic patients with stable intermittent claudication. 24 patients were randomly assigned to treatment and usual-care groups, the former receiving dietary advice and cholestyramine, nicotinic acid, or clofibrate depending on their lipoprotein phenotype. Biplanar arteriography was performed when the study began and after a mean period of 19 months. Angiograms were assessed visually, with blinding, and by computerised image analysis. Therapy reduced mean plasma total cholesterol by 25%, mean low density lipoprotein (LDL) cholesterol by 28%, and mean plasma triglycerides by 45%. Significantly fewer arterial segments showed detectable progression of atherosclerosis in the treatment group. The mean increase in plaque area (mm2/segment/year) in the treatment group was only one third of that in the usual-care group. The mean increase in edge irregularity index (a measure of the severity of disease) in the treatment group was only 40% of that in the usual care group. Twice as many arterial segments showed improvement in the treatment group. In both groups changes in edge irregularity index were directly related to plasma LDL cholesterol concentration. This study, the first randomised controlled trial of its type, provides evidence that effective treatment of hyperlipidaemia favourably influences the natural history of symptomatic peripheral atherosclerosis.