Correction: The Relative Contribution of Metabolic and Structural Abnormalities to Diastolic Dysfunction in Obesity.

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The relative contribution of metabolic and structural abnormalities to diastolic dysfunction in obesity.

BACKGROUND: Obesity causes diastolic dysfunction, and is one of the leading causes of heart failure with preserved ejection fraction. Myocardial relaxation is determined by both active metabolic processes such as impaired energetic status and steatosis, as well as intrinsic myocardial remodelling. However, the relative contribution of each to diastolic dysfunction in obesity is currently unknown. METHODS: Eighty adult subjects (48 male) with no cardiovascular risk factors across a wide range of body mass indices (18.4-53.0 kg m-2) underwent magnetic resonance imaging for abdominal visceral fat, left ventricular geometry (LV mass:volume ratio) and diastolic function (peak diastolic strain rate), and magnetic resonance spectroscopy for PCr/ATP and myocardial triglyceride content. RESULTS: Increasing visceral obesity was related to diastolic dysfunction (peak diastolic strain rate, r=-0.46, P=0.001). Myocardial triglyceride content (ß=-0.2, P=0.008), PCr/ATP (ß=-0.22, P=0.04) and LV mass:volume ratio (ß=-0.61, P=0.04) all independently predicted peak diastolic strain rate (model R2 0.36, P<0.001). Moderated multiple regression confirmed the full mediating roles of PCr/ATP, myocardial triglyceride content and LV mass:volume ratio in the relationship between visceral fat and peak diastolic strain rate. Of the negative effect of visceral fat on diastolic function, 40% was explained by increased myocardial triglycerides, 39% by reduced PCr/ATP and 21% by LV concentric remodelling. CONCLUSIONS: Myocardial energetics and steatosis are more important in determining LV diastolic function than concentric hypertrophy, accounting for more of the negative effect of obesity on diastolic function than LV geometric remodelling. Targeting these metabolic processes is an attractive strategy to treat diastolic dysfunction in obesity.

Screening and risk assessment for coronary artery disease in HIV infection: an unmet need.

HIV infection is now considered a chronic, treatable disease, although treatment is associated with increased rates of coronary artery disease (CAD). Increased risk of CAD in HIV-infected patients has been associated with the inflammatory sequelae of the infection as well as the greater prevalence of cardiac risk factors in HIV-positive populations and the side effects of life-prolonging antiretroviral therapies. Patients with HIV infection now have a 1.5 to 2-fold greater risk of developing CAD compared with noninfected individuals, raising the independent risk of CAD in HIV infection to levels similar to those in diabetes. Despite this increased risk, screening and other adjuvant assessment tools are lacking. In this paper we explore the current climate of CAD in the contemporary HIV-infected population and look at the tools used in the assessment and management of patients as well as the limitations of these approaches for this at-risk population group.

Lower coronary plaque burden in patients with HIV presenting with acute coronary syndrome.

OBJECTIVE: Treated HIV infection is associated with a higher incidence of coronary artery disease and myocardial infarction, although the mechanisms remain unclear. We sought to characterise the burden of coronary artery disease in men with HIV using retrospective data from invasive coronary angiograms in patients presenting with acute coronary syndrome (ACS). METHODS: Demographic and coronary angiographic data were obtained from 160 men with ST elevation myocardial infarction, non-STEMI or high-risk chest pain; 73 HIV-infected cases and 87 age-matched controls. The burden of coronary disease was calculated using the Gensini Angiographic Scoring System by 2 independent cardiologists blinded to HIV status. RESULTS: The 2 groups were matched for age, sex and cardiac event subtype and there was no difference in rates of smoking or cholesterol levels. Compared with control participants, patients with HIV had higher usage of antihypertensives (46 (63%) vs 30 (35%), p<0.001) and statins (47 (64%) vs 29 (33%), p<0.001). There was no difference in plaque distribution between both groups; however, the Gensini score was 42% lower in cases with HIV than in controls (p<0.03). C reactive protein was higher in cases with HIV (13.4±15.4 vs 3.7±3.6). CONCLUSIONS: Men with HIV presenting with ACS paradoxically had a lower burden of coronary plaque than matched controls, despite more aggressive risk factor management, suggesting that plaque vulnerability, rather than total burden of atherosclerosis, may be important in the pathophysiology of coronary artery disease in men with HIV.

Cardiovascular disease in human immunodeficiency virus.

With widespread access to high-quality medical care as in Australia, human immunodeficiency virus (HIV) is now considered a chronic, treatable condition, with a good life expectancy. The use of combined highly active antiretroviral therapy has enabled effective suppression of the virus, but has also been associated with increased cardiac morbidity and mortality. Over representation of traditional cardiac risk factors, such as hyperlipidaemia and diabetes, as well as an increased incidence of ischaemic and non-ischaemic heart disease is now considered a major concern of treatment with antiretroviral therapy. Therefore, a contemporary management strategy for patients with HIV must include active prevention and treatment of cardiovascular risk. This review will outline the complex interplay between HIV infection, antiretroviral drug regimens and accelerated cardiovascular disease, with a particular focus on screening, prevention and treatment options in a contemporary Australian HIV population.

Details of left ventricular radial wall motion supporting the ventricular theory of the third heart sound obtained by cardiac MR.

OBJECTIVE: Obtaining new details of radial motion of left ventricular (LV) segments using velocity-encoding cardiac MRI. METHODS: Cardiac MR examinations were performed on 14 healthy volunteers aged between 19 and 26 years. Cine images for navigator-gated phase contrast velocity mapping were acquired using a black blood segmented κ-space spoiled gradient echo sequence with a temporal resolution of 13.8 ms. Peak systolic and diastolic radial velocities as well as radial velocity curves were obtained for 16 ventricular segments. RESULTS: Significant differences among peak radial velocities of basal and mid-ventricular segments have been recorded. Particular patterns of segmental radial velocity curves were also noted. An additional wave of outward radial movement during the phase of rapid ventricular filling, corresponding to the expected timing of the third heart sound, appeared of particular interest. CONCLUSION: The technique has allowed visualization of new details of LV radial wall motion. In particular, higher peak systolic radial velocities of anterior and inferior segments are suggestive of a relatively higher dynamics of anteroposterior vs lateral radial motion in systole. Specific patterns of radial motion of other LV segments may provide additional insights into LV mechanics. ADVANCES IN KNOWLEDGE: The outward radial movement of LV segments impacted by the blood flow during rapid ventricular filling provides a potential substrate for the third heart sound. A biphasic radial expansion of the basal anteroseptal segment in early diastole is likely to be related to the simultaneous longitudinal LV displacement by the stretched great vessels following repolarization and their close apposition to this segment.

Effects of ventricular insertion sites on rotational motion of left ventricular segments studied by cardiac MR.

OBJECTIVE: Obtaining new details for rotational motion of left ventricular (LV) segments using velocity encoding cardiac MR and correlating the regional motion patterns to LV insertion sites. METHODS: Cardiac MR examinations were performed on 14 healthy volunteers aged between 19 and 26 years. Peak rotational velocities and circumferential velocity curves were obtained for 16 ventricular segments. RESULTS: Reduced peak clockwise velocities of anteroseptal segments (i.e. Segments 2 and 8) and peak counterclockwise velocities of inferoseptal segments (i.e. Segments 3 and 9) were the most prominent findings. The observations can be attributed to the LV insertion sites into the right ventricle, limiting the clockwise rotation of anteroseptal LV segments and the counterclockwise rotation of inferoseptal segments as viewed from the apex. Relatively lower clockwise velocities of Segment 5 and counterclockwise velocities of Segment 6 were also noted, suggesting a cardiac fixation point between these two segments, which is in close proximity to the lateral LV wall. CONCLUSION: Apart from showing different rotational patterns of LV base, mid ventricle and apex, the study showed significant differences in the rotational velocities of individual LV segments. Correlating regional wall motion with known orientation of myocardial aggregates has also provided new insights into the mechanisms of LV rotational motions during a cardiac cycle. ADVANCES IN KNOWLEDGE: LV insertion into the right ventricle limits the clockwise rotation of anteroseptal LV segments and the counterclockwise rotation of inferoseptal segments adjacent to the ventricular insertion sites. The pattern should be differentiated from wall motion abnormalities in cardiac pathology.

Reproducibility of 31P cardiac magnetic resonance spectroscopy at 3 T.

The purpose of this work was to take advantage of the new clinical field strength of 3 T to implement and optimize a chemical shift imaging (CSI) acquisition protocol to produce spectra of high quality with high specificity to the myocardium within a clinically feasible scan time. Further, an analysis method was implemented dependent purely on anatomical location of spectra, and as such free from any potential user bias caused by inference from spectral information. Twenty healthy male subjects were scanned on two separate occasions using the optimized CSI protocol at 3 T. Data were analyzed for intra- and inter-subject variability, as well as intra- and inter-observer variability. The average phosphocreatine (PCr)/adenosine triphosphate (ATP) value for scan 1 was 2.07 +/- 0.38 and for scan 2 was 2.14 +/- 0.46, showing no significant difference between scans. Intra-subject variability was 0.43 +/- 0.35 (percentage difference 20%) and the inter-subject coefficient of variation was 18%. The intra-observer variability, assessed as the absolute difference between analyses of the data by a single observer, was 0.14 +/- 0.24 with no significant difference between analyses. The inter-observer variability showed no significant differences between the PCr/ATP value measured by four different observers as demonstrated by an intra-class correlation coefficient of 0.763. The increased signal available at 3 T has improved spatial resolution and thereby increased myocardial specificity without any significant decrease in reproducibility over previous studies at 1.5 T. We present an acquisition protocol that routinely provides high quality spectra and a robust analysis method that is free from potential user bias.

Applications of recombinant DNA technology in the production of glycosylated recombinant human granulocyte colony stimulating factor.

Lenograstim has been developed by recombinant DNA technology and is expressed in large-scale mammalian cell culture. It has been shown that lenograstim is indistinguishable in its physicochemical, structural and biological properties with respect to native granulocyte colony stimulating factor isolated from a human cell line. In particular, both the recombinant and natural proteins have identical amino acid sequences, contain the same intra-polypeptide chain disulphide bridges and exhibit the same posttranslational carbohydrate structures. Lenograstim is manufactured by expanding inoculum from vials of the Manufacturer's Working Cell Bank (from molecular cloning) followed by culture in a large bioreactor. Purification of lenograstim involves a four-step chromatographic process. The active ingredient is monitored by in-process controls at all stages of manufacture and routinely as purified bulk. The finished product is formulated into excipients reflecting conditions close to the natural environment of the protein with respect to pH, osmolarity and the presence of human serum albumin.

Mechanism of sulphate transfer from 4-nitrophenylsulphate to phenolic acceptors via liver cytosolic sulphotransferase.

Phenol sulphotransferase from cat and rabbit liver cytosol has been investigated using 4-nitrophenylsulphate as primary sulphate donor. The first stage of the reaction involves sulphation of cofactor adenosine 3',5'-diphosphate to adenosine 3'-phosphate 5'-phosphosulphate, which in turn acts as sulphate donor for other phenolic acceptors. Adenosine 3',5'-diphosphate is regenerated in this second stage, so that the overall reaction is a sulphate transfer from 4-nitrophenylsulphate to the phenolic acceptor. High acceptor concentrations lead to inhibition of the reaction; very low concentrations give deviation from Michaelis-Menten kinetics. From the kinetic data, a mechanism is suggested in which an enzyme-adenosine 3'-phosphate 5'-phosphosulphate complex is formed in situ, with which the acceptor then interacts to give the final sulphate transfer. The system employed here is useful for the study of phenol sulphotransferase in view of the difficulty in obtaining adequate amounts of adenosine 3'-phosphate 5'-phosphosulphate from commercial sources.

Hepatotoxic effects of sera from patients with fulminant hepatitis B on isolated rat hepatocytes in culture.

The hepatotoxicity of sera from patients with terminal fulminant hepatic failure has been investigated by cell culture techniques. It could be shown that both untreated and heat-treated sera are cytotoxic in nature. Compared with the action of sera from healthy individuals on liver cells in primary monolayer culture, the pathological sera exhibited significantly different behaviour with respect to morphological and biochemical parameters such as cell adhesion, growth and proliferation, and enzyme release.

Properties of agarose-encapsulated adsorbents. I. Adsorption of digoxin from human serum.

The elimination of the cardioactive steroid, digoxin, from human serum by a range of adsorbent phases has been investigated. In the native state, the uncharged resins of the Amberlite XAD-type proved more effective than the ion-exchange resins, Dowex 1X, or active charcoal. Of the materials tested, Amberlite XAD-8 is by far the best suited resin for haemoperfusion in cases of digoxin overdose, whereby the less efficient XAD-4 is more commonly employed at present in clinics. In order to improve the haemocompatibility of the adsorbent materials, the technique of encapsulation into large agarose beads has been employed. In contrast to the effects observed with many other classes of xenobiotics, encapsulation into agarose beads results in a considerable loss of adsorptive capacity of digoxin by Amberlite XAD-8. The poor performance of active charcoal in form of granules can be improved by an order-of-magnitude using charcoal powder encapsulated in agarose. Thus, the latter material, or uncoated XAD-8 resin should be considered as a better alternative to materials in current use for extracorporeal detoxification in cases of digoxin overdose.

Properties of agarose-encapsulated adsorbents. II. Elimination of endogenous and exogenous phenolic compounds from human serum.

Phenolic compounds derived from the amino acid tyrosine are endogenous toxins, which are believed to be involved in the pathogenesis of hepatic coma. There are also xenobiotic phenolic substances, such as p-hydroxy-acetanilide (paracetamol or acetaminophen), which can lead to serious complications if taken in an overdose. In both cases, a drastic therapeutic measure such as haemoperfusion may be indicated to eliminate the toxin from the blood. In the present work, human serum has been dosed with the phenolic compounds of immediate relevance in exogenous and endogenous intoxication, and the effectiveness of various adsorbent materials for the elimination of the toxins from the serum has been investigated. Resins and charcoal in the native state have been compared with those encapsulated into large agarose beads, a process which improves the haemocompatibility and thus the practicability of the adsorbents. A certain degree of specificity has been observed. Whereas phenolic acids are adsorbed quite effectively onto the strongly basic ion exchange resins of the Dowex 1X type, particularly 1X8 or 2X8, phenol or paracetamol are less effectively eliminated. In contrast to many other classes of toxin, the Amberlite XAD-type resins are ineffective for all the phenolic substances investigated. Charcoal is the most effective adsorber in most cases, particularly when encapsulated in powder form into agarose beads.

Gas chromatographic method for the quantitative assay of alkane thiol S-methyltransferase.

A method is described for the quantitative assay of the methylation of alkane-thiols from the methyl-donor S-adenosylmethionine, catalysed by the microsomal enzyme S-adenosyl-L-methionine:thiol S-methyltransferase (E.C. 2.1.1.9). The reaction is carried out in sealed vials, one fifth of whose volume is taken up by an aqueous phase containing the enzyme and reactants. The volatile substrates and products of the reaction, thiols and thioethers, respectively, are present in equilibrium both in the liquid and gas phases in the reaction vessels. Aliquots of the gas phase are removed at intervals in gas-tight syringes, and analysis is performed directly on a gas chromatograph fitted with a flame-ionization detector. The amounts of thiol and thioether detected are then related to the total amounts of substance in the reaction vessels from calibration measurements, so that the kinetics of the enzymatic process can be evaluated. This technique offers distinct advantages over previously reported methods, in that no radioactively labelled compounds are required. Furthermore, decreases in substrate and increases in product can be assayed simultaneously, and the methylation of a mixture of thiols can be monitored in a single set of analyses.

The capillary-isotachophoretic analysis of reactants and products of glucuronidation. A new method for the assay of UDPGlucuronosyltransferase.

UDPglucuronosyltransferase competes with a nucleotide pyrophosphatase for UDPglucuronate as a substrate. Both enzyme systems are located in the microsomal fraction of mammalian liver homogenates, and the pyrophosphatase is present in all but the purest preparations of UDP-glucuronosyltransferase, since solubilisation procedures yield both activities in the 100 000 x g supernatant. In glucuronidation studies, it is important to be able to ascertain the degree of hydrolysis of the substrate UDPglucuronate due to the pyrophosphatase activity. A new method is reported using analytical capillary isotachophoresis whereby reactants and products of both glucuronidation and hydrolysis can be assayed simultaneously. The example presented in this paper is the glucuronidation of paracetamol (4-acetamidophenol) an important phenolic drug of toxicological interest. Rabbit liver microsomes glucuronidate this substance much more slowly than other phenolic compounds, so that hydrolysis of the donor molecule UDPglucuronic acid becomes of primary importance. Furthermore, the ionic mobility of 4-acetamidophenyl glucuronoside is much less than the other constitutents of assay mixtures under the analytical conditions employed, so that a well-defined separation from other reaction species is afforded.

Large agarose beads for extracorporeal detoxification systems. Preparation and enzymatic properties of agarose-bound UDP-glucuronyltransferase.

UDP-glucuronlytransferase, E.C. 2.4.1.17, has been solubilised from the microsomal fraction of liver homogenate from phenobarbital pretreated rabbits by lipase or detergent treatments. A 110-fold purification of the enzyme with respect to the crude homogenate was achieved by precipitation and column separations. The cholate-detergent solubilised enzyme was far more stable than that prepared by the lipase method. The partially purified UDP-glucuronyltransferase has been covalently bound to cyanogen bromide-activated agarose in the form of large haemocompatible beads to the extent of 0.22 mg protein per mg agarose dryweight, equivalent to about 25 mg of swollen gel. The acceptors for glucuronidation employed were the non-physiological phenolic compounds p-nitrophenol and 1-naphthol, and an exogenous and endogenous substance of physiological importance, namely paracetamol and phenol respectively. The immobilised enzyme exhibited at least 80% of the original activity of the solubilised enzyme, and the catalytic function was preserved for a much longer period of time in the carrier-bound form. The system described in this publication could well be applied in an extracorporeal liver assist device for the replacement of glucuronidation function.

Agarose-encapsulated adsorbents.

A method is described for the encapsulation of ion-exchange and adsorbent resins of native particle diameter 0.2-1.0 mm into agarose spheres of diameter 5-10 mm. Plasma components diffuse rapidly through the agarose coating, but blood corpuscles have no direct access to the resins. At least 0.3 g of resin can be incorporated into 1 g of the agarose beads, so that the effective surface area with regard to erythrocytes, thrombocytes, and leucocytes is reduced by a factor of at least 5, and up to 20, depending on the native resin particle size. Pulverised active charcoal, or resins in powder form can also be encapsulated in this manner. The haemocompatibility of the agarose coating seems to be considerably more acceptable than that of the adsorbents in their native state.