Health literacy among Medicare enrollees in a managed care organization

CONTEXT

Elderly patients may have limited ability to read and comprehend medical information pertinent to their health.

OBJECTIVE

To determine the prevalence of low functional health literacy among community-dwelling Medicare enrollees in a national managed care organization.

DESIGN

Cross-sectional survey.

SETTING

Four Prudential HealthCare plans (Cleveland, Ohio; Houston, Tex; south Florida; Tampa, Fla).

PARTICIPANTS

A total of 3260 new Medicare enrollees aged 65 years or older were interviewed in person between June and December 1997 (853 in Cleveland, 498 in Houston, 975 in south Florida, 934 in Tampa); 2956 spoke English and 304 spoke Spanish as their native language. MAIN OUTCOME MEASURE; Functional health literacy as measured by the Short Test of Functional Health Literacy in Adults.

RESULTS

Overall, 33.9% of English-speaking and 53.9% of Spanish-speaking respondents had inadequate or marginal health literacy. The prevalence of inadequate or marginal functional health literacy among English speakers ranged from 26.8% to 44.0%. In multivariate analysis, study location, race/language, age, years of school completed, occupation, and cognitive impairment were significantly associated with inadequate or marginal literacy. Reading ability declined dramatically with age, even after adjusting for years of school completed and cognitive impairment. The adjusted odds ratio for having inadequate or marginal health literacy was 8.62 (95% confidence interval, 5.55-13.38) for enrollees aged 85 years or older compared with individuals aged 65 to 69 years.

CONCLUSIONS

Elderly managed care enrollees may not have the literacy skills necessary to function adequately in the health care environment. Low health literacy may impair elderly patients' understanding of health messages and limit their ability to care for their medical problems.

High resolution structures of HIV-1 RT from four RT-inhibitor complexes

We have determined the structures of four complexes of HIV-1 reverse transcriptase with non-nucleoside inhibitors, three fully refined at high resolution. The highest resolution structure is of the RT-nevirapine complex which has an R-factor of 0.186 and a root-mean-square bond length deviation of 0.015 A for all data to 2.2 A. The structures reveal a common mode of binding for these chemically diverse compounds. The common features of binding are largely hydrophobic interactions and arise from induced shape complementarity achieved by conformational rearrangement of the enzyme and conformational/configurational rearrangement of the compounds.

Sequence and structural selectivity of nucleic acid binding ligands

The sequence and structural selectivity of 15 different DNA binding agents was explored using a novel, thermodynamically rigorous, competition dialysis procedure. In the competition dialysis method, 13 different nucleic acid structures were dialyzed against a common ligand solution. More ligand accumulated in the dialysis tube containing the structural form with the highest ligand binding affinity. DNA structural forms included in the assay ranged from single-stranded forms, through a variety of duplex forms, to multistranded triplex and tetraplex forms. Left-handed Z-DNA, RNA, and a DNA-RNA hybrid were also represented. Standard intercalators (ethidium, daunorubicin, and actinomycin D) served as control compounds and were found to show structural binding preferences fully consistent with their previously published behavior. Standard groove binding agents (DAPI, distamycin, and netropsin) showed a strong preference for AT-rich duplex DNA forms, along with apparently strong binding to the poly(dA)-[poly(dT)](2) triplex. Thermal denaturation studies revealed the apparent triplex binding to be complex, and perhaps to result from displacement of the third strand. Putative triplex (BePI, coralyne, and berberine) and tetraplex [H(2)TmPyP, 5,10,15, 20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine, and N-methyl mesoporphyrin IX] selective agents showed in many cases less dramatic binding selectivity than anticipated from published reports that compared their binding to only a few structural forms. Coralyne was found to bind strongly to single-stranded poly(dA), a novel and previously unreported interaction. Finally, three compounds (berenil, chromomycin A, and pyrenemethylamine) whose structural preferences are largely unknown were examined. Pyrenemethylamine exhibited an unexpected and unprecedented preference for duplex poly(dAdT).

Mechanism of inhibition of HIV-1 reverse transcriptase by non-nucleoside inhibitors

The structure of unliganded HIV-1 reverse transcriptase has been determined at 2.35 A resolution and refined to an R-factor of 0.219 (for all data) with good stereochemistry. The unliganded structure was produced by soaking out a weak binding non-nucleoside inhibitor, HEPT, from pregrown crystals. Comparison with the structures of four different RT and non-nucleoside inhibitor complexes reveals that only minor domain rearrangements occur, but there is a significant repositioning of a three-stranded beta-sheet in the p66 subunit (containing the catalytic aspartic acid residues 110, 185 and 186) with respect to the rest of the polymerase site. This suggests that NNIs inhibit RT by locking the polymerase active site in an inactive conformation, reminiscent of the conformation observed in the inactive p51 subunit.

Complexes of HIV-1 reverse transcriptase with inhibitors of the HEPT series reveal conformational changes relevant to the design of potent non-nucleoside inhibitors

Crystal structures of HIV-1 reverse transcriptase (RT) complexed with a range of chemically diverse non-nucleoside inhibitors (NNIs) have shown a single pocket in which the inhibitors bind and details of the inhibitor-protein interactions. To delineate the structural requirements for an effective inhibitor, we have determined the structures of three closely related NNIs which vary widely in their potencies. Crystal structures of HIV-1 RT complexed with two very potent inhibitors, MKC-442 and TNK-651, at 2.55 angstroms resolution complement our previous analysis of the complex with the less effective inhibitor, HEPT. These structures reveal conformational changes which correlate with changes in potency. We suggest that a major determinant of increased potency in the analogues of HEPT is an improved interaction between residue Tyr181 in the protein and the 6-benzyl ring of the inhibitors which stabilizes the structure of the complex. This arises through a conformational switching of the protein structure triggered by the steric bulk of the 5-substituent of the inhibitor pyrimidine ring.

Functional magnetic resonance imaging of reorganization in rat brain after stroke

Functional recovery after stroke has been associated with brain plasticity; however, the exact relationship is unknown. We performed behavioral tests, functional MRI, and histology in a rat stroke model to assess the correlation between temporal changes in sensorimotor function, brain activation patterns, cerebral ischemic damage, and cerebrovascular reactivity. Unilateral stroke induced a large ipsilateral infarct and acute dysfunction of the contralateral forelimb, which significantly recovered at later stages. Forelimb impairment was accompanied by loss of stimulus-induced activation in the ipsilesional sensorimotor cortex; however, local tissue and perfusion were only moderately affected and cerebrovascular reactivity was preserved in this area. At 3 days after stroke, extensive activation-induced responses were detected in the contralesional hemisphere. After 14 days, we found reduced involvement of the contralesional hemisphere, and significant responses in the infarction periphery. Our data suggest that limb dysfunction is related to loss of brain activation in the ipsilesional sensorimotor cortex and that restoration of function is associated with biphasic recruitment of peri- and contralesional functional fields in the brain.

Energetics of DNA intercalation reactions

Isothermal titration calorimetry has been used to determine the binding enthalpy and heat capacity change (DeltaC(p)()) for a series of DNA intercalators, including ethidium, propidium, daunorubicin, and adriamycin. Temperature-dependent binding enthalpies were measured directly for the ligands, from which DeltaC(p)() values of -140 to -160 cal mol(-)(1) K(-)(1) were calculated. Published van't Hoff plots were reanalyzed to obtain DeltaC(p)() values of -337 to -423 cal mol(-)(1) K(-)(1) for the binding of actinomycin D to several DNA oligonucleotide duplexes with defined sequences. Heat capacity changes for DNA intercalation were found to correlate with the alterations in solvent-accessible surface area calculated from available high-resolution structural data. Multiple linear regression was used to derive the relationship DeltaC(p)() = 0. 382(+/-0.026)DeltaA(np) - 0.121(+/-0.077)DeltaA(p) cal mol(-)(1) K(-)(1), where DeltaA(np) and DeltaA(p) are the binding-induced changes in nonpolar and polar solvent-accessible surface areas (in square angstroms), respectively. The DeltaC(p)() terms were used to estimate the hydrophobic contribution to intercalative binding free energies, yielding values that ranged from -11.2 (ethidium) to -30 kcal mol(-)(1) (actinomycin D). An attempt was made to parse the observed binding free energies of ethidium and propidium into five underlying contributions. Such analysis showed that the DNA binding behavior of these simple intercalators is driven almost equally by hydrophobic effects and van der Waals contacts within the intercalation site.

Structural origins of the selectivity of the trifunctional oxygenase clavaminic acid synthase

Clavaminate synthase (CAS), a remarkable Fe(II)/2-oxoglutarate oxygenase, catalyzes three separate oxidative reactions in the biosynthesis of clavulanic acid, a clinically used inhibitor of serine beta-lactamases. The first CAS-catalyzed step (hydroxylation) is separated from the latter two (oxidative cyclization/desaturation) by the action of an amidinohydrolase. Here, we describe crystal structures of CAS in complex with Fe(II), 2-oxoglutarate (2OG) and substrates (N-alpha-acetyl-L-arginine and proclavaminic acid). They reveal how CAS catalyzes formation of the clavam nucleus, via a process unprecedented in synthetic organic chemistry, and suggest how it discriminates between substrates and controls reaction of its highly reactive ferryl intermediate. The presence of an unpredicted jelly roll beta-barrel core in CAS implies divergent evolution within the family of 2OG and related oxygenases. Comparison with other non-heme oxidases/oxygenases reveals flexibility in the position which dioxygen ligates to the iron, in contrast to the analogous heme-using enzymes.

Insulin-like growth factor I as a cardiac hormone: physiological and pathophysiological implications in heart disease

Accumulating evidence has indicated that insulin-like growth factor-1 (IGF-1) plays a specific role in the intricate cascade of events of cardiovascular function, in addition to its well established growth-promoting and metabolic effects. IGF-1 is believed to mediate many effects of growth hormone (GH), IGF-1 promotes cardiac growth, improves cardiac contractility, cardiac output, stroke volume, and ejection fraction. In humans, IGF-1 improves cardiac function after myocardial infarction by stimulating contractility and promoting tissue remodeling. Furthermore, IGF-1 facilitates glucose metabolism, lowers insulin levels, increases insulin sensitivity, and improves the lipid profile. These data suggest an attractive therapeutic potential of IGF-1. Both clinically observed and experimentally induced impairments of cardiac function are also found to be associated with abnormal IGF-1 levels. IGF-1 and its binding proteins have been considered as markers for the presence of certain cardiac abnormalities, indicating that IGF-1 may be a risk factor for certain cardiac disorders. The present review will emphasize the role of IGF-1 in the regulation of cardiac growth and function, and the potential pathophysiological role of IGF-1 in cardiac function.

Leptin and hyperleptinemia - from friend to foe for cardiovascular function

The obese gene product, leptin, plays a central role in food intake and energy metabolism. The physiological roles of leptin in human bodily function have been broadened over the past decade since leptin was first discovered in 1994. Evidence has suggested that leptin plays a specific role in the intricate cascade of cardiovascular events, in addition to its well-established metabolic effects. Leptin, a hormone linking adiposity and central nervous circuits to reduce appetite and enhance energy expenditure, has been shown to increase overall sympathetic nerve activity, facilitate glucose utilization and improve insulin sensitivity. In addition, leptin is capable of regulating cardiac and vascular contractility through a local nitric oxide-dependent mechanism. However, elevated plasma leptin levels or hyperleptinemia, have been demonstrated to correlate with hyperphagia, insulin resistance and other markers of the metabolic syndrome including obesity, hyperlipidemia and hypertension, independent of total adiposity. Elevated plasma leptin levels may be an independent risk factor for the development of cardiovascular disease. Although mechanisms leading to hyperleptinemia have not been well described, factors such as increased food intake and insulin resistance have been shown to rapidly enhance plasma leptin levels and subsequently tissue leptin resistance. These findings have prompted the speculation that leptin in the physiological range may serve as a physiological regulator of cardiovascular function whereas elevated plasma leptin levels may act as a pathophysiological trigger and/or marker for cardiovascular diseases due to tissue leptin resistance.

The epidermal growth factor receptor regulates interaction of the human DF3/MUC1 carcinoma antigen with c-Src and beta-catenin

The DF3/MUC1 mucin-like, transmembrane glycoprotein is aberrantly overexpressed in most human carcinomas. The MUC1 cytoplasmic domain interacts with the c-Src tyrosine kinase and thereby increases binding of MUC1 and beta-catenin. In the present work, coimmunoprecipitation studies demonstrate that MUC1 associates constitutively with the epidermal growth factor receptor (EGF-R) in human ZR-75-1 breast carcinoma cells. Immunofluorescence studies show that EGF-R and MUC1 associate at the cell membrane. We also show that the activated EGF-R phosphorylates the MUC1 cytoplasmic tail on tyrosine at a YEKV motif that functions as a binding site for the c-Src SH2 domain. The results demonstrate that EGF-R-mediated phosphorylation of MUC1 induces binding of MUC1 to c-Src in cells. Moreover, in vitro and in vivo studies demonstrate that EGF-R increases binding of MUC1 and beta-catenin. These findings support a novel role for EGF-R in regulating interactions of MUC1 with c-Src and beta-catenin.

Structural basis for the resilience of efavirenz (DMP-266) to drug resistance mutations in HIV-1 reverse transcriptase

BACKGROUND

Efavirenz is a second-generation non-nucleoside inhibitor of HIV-1 reverse transcriptase (RT) that has recently been approved for use against HIV-1 infection. Compared with first-generation drugs such as nevirapine, efavirenz shows greater resilience to drug resistance mutations within HIV-1 RT. In order to understand the basis for this resilience at the molecular level and to help the design of further-improved anti-AIDS drugs, we have determined crystal structures of efavirenz and nevirapine with wild-type RT and the clinically important K103N mutant.

RESULTS

The relatively compact efavirenz molecule binds, as expected, within the non-nucleoside inhibitor binding pocket of RT. There are significant rearrangements of the drug binding site within the mutant RT compared with the wild-type enzyme. These changes, which lead to the repositioning of the inhibitor, are not seen in the interaction with the first-generation drug nevirapine.

CONCLUSIONS

The repositioning of efavirenz within the drug binding pocket of the mutant RT, together with conformational rearrangements in the protein, could represent a general mechanism whereby certain second-generation non-nucleoside inhibitors are able to reduce the effect of drug-resistance mutations on binding potency.

European guidelines for quality assurance in colorectal cancer screening and diagnosis: overview and introduction to the full supplement publication

Population-based screening for early detection and treatment of colorectal cancer (CRC) and precursor lesions, using evidence-based methods, can be effective in populations with a significant burden of the disease provided the services are of high quality. Multidisciplinary, evidence-based guidelines for quality assurance in CRC screening and diagnosis have been developed by experts in a project co-financed by the European Union. The 450-page guidelines were published in book format by the European Commission in 2010.  They include 10 chapters and over 250 recommendations, individually graded according to the strength of the recommendation and the supporting evidence. Adoption of the recommendations can improve and maintain the quality and effectiveness of an entire screening process, including identification and invitation of the target population, diagnosis and management of the disease and appropriate surveillance in people with detected lesions. To make the principles, recommendations and standards in the guidelines known to a wider professional and scientific community and to facilitate their use in the scientific literature, the original content is presented in journal format in an open-access Supplement of Endoscopy. The editors have prepared the present overview to inform readers of the comprehensive scope and content of the guidelines.

Esophagopharyngeal distribution of refluxed gastric acid in patients with reflux laryngitis

BACKGROUND & AIMS

A variety of otolaryngological abnormalities have been attributed to the contact of gastroesophageal refluxate with respective structures of the aerodigestive tract. The aim of this study was to determine and compare the pharyngoesophageal distribution of gastric acid refluxate between patients with proven laryngitis attributed clinically to gastroesophageal reflux and three control groups.

METHODS

An ambulatory 24-hour simultaneous three-site pharyngoesophageal pH monitoring technique was used to measure reflux parameters in the pharynx, proximal esophagus, and distal esophagus.

RESULTS

Between-group comparison showed no significant difference in the reflux parameters in the distal esophagus between the studied groups. A significantly higher percentage of distal reflux episodes reached the proximal esophagus in the laryngitis group than in the control groups (P < 0.01), and the number of pharyngeal reflux episodes and time of acid exposure were significantly higher in the laryngitis group than in the control groups (P < 0.001).

CONCLUSIONS

Compared with normal controls and patients with gastroesophageal reflux disease, pharyngeal reflux of gastric acid is significantly more prevalent and the ratio of proximal to distal esophageal acid reflux episodes is significantly increased in patients with posterior laryngitis. Simultaneous three-site ambulatory pharyngoesophageal pH monitoring may provide supporting evidence when the diagnosis of reflux-induced aerodigestive tract lesions is considered.

The c-Src tyrosine kinase regulates signaling of the human DF3/MUC1 carcinoma-associated antigen with GSK3 beta and beta-catenin

The DF3/MUC1 mucin-like glycoprotein is aberrantly overexpressed in most human carcinomas. The cytoplasmic domain of MUC1 interacts with glycogen synthase kinase 3 beta (GSK3 beta) and thereby decreases binding of MUC1 and beta-catenin. The present studies demonstrate that MUC1 associates with the c-Src tyrosine kinase. c-Src phosphorylates the MUC1 cytoplasmic domain at a YEKV motif located between sites involved in interactions with GSK3 beta and beta-catenin. The results demonstrate that the c-Src SH2 domain binds directly to pYEKV and inhibits the interaction between MUC1 and GSK3 beta. Moreover and in contrast to GSK3 beta, in vitro and in vivo studies demonstrate that c-Src-mediated phosphorylation of MUC1 increases binding of MUC1 and beta-catenin. The findings support a novel role for c-Src in regulating interactions of MUC1 with GSK3 beta and beta-catenin.

Unique features in the structure of the complex between HIV-1 reverse transcriptase and the bis(heteroaryl)piperazine (BHAP) U-90152 explain resistance mutations for this nonnucleoside inhibitor

The viral reverse transcriptase (RT) provides an attractive target in the search for anti-HIV therapies. The nonnucleoside inhibitors (NNIs) are a diverse set of compounds (usually HIV-1 specific) that function by distorting the polymerase active site upon binding in a nearby pocket. Despite being potent and of generally low toxicity, their clinical use has been limited by rapid selection for resistant viral populations. The 2.65-A resolution structure of the complex between HIV-1 RT and the bis(heteroaryl)piperazine (BHAP) NNI, 1-(5-methanesulfonamido-1H-indol-2-yl-carbonyl)-4- [3-(1-methyl-ethylamino) pyridinyl] piperazine (U-90152), reveals the inhibitor conformation and bound water molecules. The bulky U-90152 molecule occupies the same pocket as other NNIs, but the complex is stabilized quite differently, in particular by hydrogen bonding to the main chain of Lys-103 and extensive hydrophobic contacts with Pro-236. These interactions rationalize observed resistance mutations, notably Pro-236-Leu, which occurs characteristically for BHAPs. When bound, part of U-90152 protrudes into the solvent creating a channel between Pro-236 and the polypeptide segments 225-226 and 105-106, giving the first clear evidence of the entry mode for NNIs. The structure allows prediction of binding modes for related inhibitors [(altrylamino)piperidine-BHAPs] and suggests changes to U-90152, such as the addition of a 6 amino group to the pyridine ring, which may make binding more resilient to mutations in the RT. The observation of novel hydrogen bonding to the protein main chain may provide lessons for the improvement of quite different inhibitors.

Transmembrane orientation of hydrophobic alpha-helices is regulated both by the relationship of helix length to bilayer thickness and by the cholesterol concentration

A fluorescence-based approach to evaluate the regulation of transmembrane orientation of alpha-helices has been developed to examine the behavior of a membrane-inserted alpha-helical peptide with a 19 residue hydrophobic sequence. The emission lambdamax of a Trp residue in the helix was used to determine its location in the bilayer. To calibrate this method, Trp lambdamax and depth (determined by parallax analysis of fluorescence quenching) were measured for transmembrane peptides with Trp at different positions. Transmembrane orientation of the alpha-helix was found to be destabilized by differences between the width of the bilayer and the length of the hydrophobic sequence (i.e., hydrophobic mismatch). When bilayer width exceeded the length of the hydrophobic segment, mismatch induced formation of a nontransmembraneous orientation close to the polar/hydrocarbon interface. By manipulation of bilayer width in situ, it was found that the transmembrane and nontransmembrane orientations could interconvert. Cholesterol altered the transmembrane/nontransmembrane equilibrium to a degree consistent with its tendency to increase bilayer thickness. Evaluation of the energetics of transmembrane vs nontransmembrane insertion showed increased mismatch of a helix with bilayer width by the equivalent of just one hydrophobic residue can destabilize transmembrane orientation by roughly 0.5 kcal/mol. Inclusion of 30 mol % cholesterol in a bilayer can alter transmembrane insertion stability by 3-5 kcal/mol. Thus, physiologically relevant variations in both the hydrophobic helix length/membrane thickness ratio and the cholesterol levels influence transmembrane insertion significantly.

Structure of HIV-2 reverse transcriptase at 2.35-A resolution and the mechanism of resistance to non-nucleoside inhibitors

The HIV-2 serotype of HIV is a cause of disease in parts of the West African population, and there is evidence for its spread to Europe and Asia. HIV-2 reverse transcriptase (RT) demonstrates an intrinsic resistance to non-nucleoside RT inhibitors (NNRTIs), one of two classes of anti-AIDS drugs that target the viral RT. We report the crystal structure of HIV-2 RT to 2.35 A resolution, which reveals molecular details of the resistance to NNRTIs. HIV-2 RT has a similar overall fold to HIV-1 RT but has structural differences within the "NNRTI pocket" at both conserved and nonconserved residues. The structure points to the role of sequence differences that can give rise to unfavorable inhibitor contacts or destabilization of part of the binding pocket at positions 101, 106, 138, 181, 188, and 190. We also present evidence that the conformation of Ile-181 compared with the HIV-1 Tyr-181 could be a significant contributory factor to this inherent drug resistance of HIV-2 to NNRTIs. The availability of a refined structure of HIV-2 RT will provide a stimulus for the structure-based design of novel non-nucleoside inhibitors that could be used against HIV-2 infection.

The structure of HIV-1 reverse transcriptase complexed with 9-chloro-TIBO: lessons for inhibitor design

BACKGROUND

HIV reverse transcriptase (RT) is a key target of anti-AIDS therapies. Structural studies of HIV-1 RT, unliganded and complexed with different non-nucleoside inhibitors (NNIs), have pointed to a common mode of binding and inactivation through distortion of the polymerase catalytic site by NNIs containing two hinged rings. The mode of binding of the TIBO family of inhibitors is of interest because these compounds do not fit the two-hinged-ring model.

RESULTS

The structure of HIV-1 RT complexed with 9-chloro-TIBO (R82913) has been determined at 2.6 A resolution. As reported for the lower resolution analysis of another TIBO compound, this inhibitor binds at the same site as other NNIs, but our higher resolution study reveals the Cl-TIBO is distorted from the conformation seen in crystals of the inhibitor alone. This allows Cl-TIBO to mimic the binding of NNIs containing two hinged rings. Inhibitor-protein interactions are again predominantly hydrophobic and the protein conformation corresponds to that seen in complexes with other tight-binding NNIs.

CONCLUSIONS

Although Cl-TIBO is chemically very different from other NNIs, it achieves remarkable spatial equivalence and shape complementarity with other NNIs on binding to RT. Comparison of the different RT-NNI complexes suggests modifications to the TIBO group of inhibitors which might enhance their binding and hence, potentially, their therapeutic efficacy.

A family of insertion mutations between codons 67 and 70 of human immunodeficiency virus type 1 reverse transcriptase confer multinucleoside analog resistance

To investigate the occurrence of multinucleoside analog resistance during therapy failure, we surveyed the drug susceptibilities and genotypes of nearly 900 human immunodeficiency virus type 1 (HIV-1) samples. For 302 of these, the 50% inhibitory concentrations of at least four of the approved nucleoside analogs had fourfold-or-greater increases. Genotypic analysis of the reverse transcriptase (RT)-coding regions from these samples revealed complex mutational patterns, including the previously recognized codon 151 multidrug resistance cluster. Surprisingly, high-level multinucleoside resistance was associated with a diverse family of amino acid insertions in addition to "conventional" point mutations. These insertions were found between RT codons 67 and 70 and were commonly 69Ser-(Ser-Ser) or 69Ser-(Ser-Gly). Treatment history information showed that a common factor for the development of these variants was AZT (3'-azido-3'-deoxythymidine, zidovudine) therapy in combination with 2',3'-dideoxyinosine or 2',3'-dideoxycytidine, although treatment patterns varied considerably. Site-directed mutagenesis studies confirmed that 69Ser-(Ser-Ser) in an AZT resistance mutational background conferred simultaneous resistance to multiple nucleoside analogs. The insertions are located in the "fingers" domain of RT. Modelling the 69Ser-(Ser-Ser) insertion into the RT structure demonstrated the profound direct effect that this change is likely to have in the nucleoside triphosphate binding site of the enzyme. Our data highlight the increasing problem of HIV-1 multidrug resistance and underline the importance of continued resistance surveillance with appropriate, sufficiently versatile genotyping technology and phenotypic drug susceptibility analysis.

Cardiac contractile dysfunction in Lep/Lep obesity is accompanied by NADPH oxidase activation, oxidative modification of sarco(endo)plasmic reticulum Ca2+-ATPase and myosin heavy chain isozyme switch

AIMS/HYPOTHESIS

Obesity is an independent risk factor for heart diseases but the underlying mechanism is not clear. This study examined cardiac contraction, oxidative stress, oxidative modification of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and the myosin heavy chain (MHC) isoform switch in obese mice.

METHODS

Mechanical properties were evaluated in ventricular myocytes from C57BL/6J lean and Lep/Lep obese mice (formerly known as ob/ob mice), including peak shortening (PS), time to 50 or 90% PS, time to 50 or 90% relengthening (TR50, TR90), maximal velocity of shortening/relengthening (+/-dL/dt), intracellular Ca2+ and its decay (tau). Oxidative stress, lipid peroxidation, protein damage and SERCA activity were assessed by glutathione/glutathione disulfide, malondialdehyde, protein carbonyl and 45Ca2+ uptake, respectively. NADPH oxidase was determined by immunoblotting.

RESULTS

Myocytes from Lep/Lep mice displayed depressed PS and +/- dL/dt, prolonged TR50, TR90, elevated resting [Ca2+]i, prolonged tau, reduced contractile capacity at high stimulus frequencies and diminished responsiveness to extracellular Ca2+ compared with lean controls. Cardiac glutathione/glutathione disulfide was decreased whereas malondialdehyde, protein carbonyl, membrane p47(phox) and membrane gp91(phox) were increased in the Lep/Lep group. SERCA isoenzyme 2a was markedly modified by oxidation in Lep/Lep hearts and associated with decreased 45Ca2+ uptake. The MHC isozyme displayed a shift from the alpha to the beta isoform in Lep/Lep hearts. Short-term incubation of angiotensin II with myocytes mimicked the mechanical defects, SERCA oxidation and 45Ca2+ uptake seen in Lep/Lep myocytes. Incubation of the NADPH oxidase inhibitor apocynin with Lep/Lep myocytes alleviated contractile defects without reversing SERCA oxidation or activity.

CONCLUSIONS/INTERPRETATION

These data indicate that obesity-related cardiac defects may be related to NADPH oxidase activation, oxidative damage to SERCA and the MHC isozyme switch.

Effect of aging, position, and temperature on the threshold volume triggering pharyngeal swallows

BACKGROUND/AIMS

Swallows triggered by direct stimulation of pharyngeal structures may help to prevent aspiration by emptying the pharynx. The aims of this study were to compare the biomechanical events of the pharyngeal and primary swallow, determine the threshold volume of liquid required to trigger the pharyngeal swallows, and determine the effect of aging, position, and temperature on this threshold volume.

METHODS

Concurrent manometry, video fluoroscopy, and video endoscopy were used to study young and elderly healthy volunteers.

RESULTS

During pharyngeal swallows, in contrast to primary swallows, the free portion of the tongue did not make contact with the hard palate. In addition, pharyngeal swallows did not result in oral bolus clearance. All other biomechanical events, including deglutitive glottal function, were similar in both types of swallows. The threshold volume for pharyngeal swallows in young volunteers was significantly smaller than in the elderly (P < 0.01). Temperature and position did not have significant effects on threshold volume.

CONCLUSIONS

Swallowing is readily induced by water stimulation of the pharynx. Pharyngeal swallows do not induce lingual peristalsis or clearance of oral content. The threshold volume of the pharyngeal swallow is significantly higher in the elderly than in the young, but it is not affected by body position or bolus temperature.