Probing protein-peptide-protein molecular architecture by atomic force microscopy and surface plasmon resonance

We demonstrate the creation of a protein multilayer which utilises the high affinity interaction between streptavidin and biotin and incorporates a peptidic spacer. Surface plasmon resonance measurements enabled us to monitor the construction of the multilayer in real time. Atomic force microscopy was utilised to determine surface functionality at each stage of the multilayer construction, allowing us to investigate the associated mechanical properties. In this context we observed an increase in biomolecular stretching on the formation of the multilayer. We demonstrate, utilising circular dichroism, that variations in the solvent can affect the secondary structure of the peptide linker and hence its mechanical properties. Trifluoroethanol titrations on the assembled system indicate that the multilayer properties are also stimuli responsive with regard to solvent conditions. These results indicate that the multilayer stretch before cleavage is increased in the presence of trifluoroethanol. This was not expected from the study of the individual linker alone, indicating the need to study the system as a whole as opposed to the isolated components.

Improved efficacy of anodal biphasic defibrillation shocks following a failed defibrillation attempt

Although it is generally assumed that defibrillation becomes more difficult when the duration of VF is prolonged, after a failed defibrillation attempt, there is little information on the defibrillation efficacy of multiple shocks delivered at the same energy. The purpose of this study was to systematically examine the efficacy of a second shock delivered at the same or reversed polarity after a failed first shock. Defibrillation was attempted after 10 seconds of VF in 12 pigs (30-56 kg) using biphasic waveforms and a nonthoracotomy lead system. Shock energy was held constant for the first and second shocks at 50%-90% of the DFT. The second shock was delivered 10 seconds after a failed first shock. First and second shock polarity (first phase) was randomized to (+, +), (+, -), (-, -), (-, +). The incidence of successful defibrillation (for all polarities) was 12.3% for first and 49.1% for second shocks (P < 0.0001). Anodal first shocks had a 17.2% incidence of success as opposed to a 7.4% incidence of success with cathodal first shocks (P = 0.001). Anodal second shocks had a 55.5% incidence of success compared to a 42.7% incidence of success with cathodal second shocks (P = 0.008). There was no significant benefit from polarity reversal after a failed first shock (P = 0.29). In conclusion, less energy is required for successful defibrillation by a second shock after a failed first. The optimal configuration for first and second shocks is with the RV as anode. Polarity reversal of a second shock after a failed first does not affect the probability of second shock success.

Health outcomes as an organisation-wide quality initiative

Since the burgeoning of the 'health outcomes' movement there has been an ever-increasing body of literature on health outcomes policy debates, directions, frameworks and tools for implementing health outcome-directed initiatives. There is a significant gap in the literature, however, in regard to translating a comprehensive health outcomes policy into practice at a local level. This paper addresses that gap. It describes the local implementation of a comprehensive health outcomes approach which works across the continuum of care. It identifies those organisation-wide structures and processes that support successful progress, thereby providing a useful guide to other organisations wishing to institutionalise the health outcomes approach.

Antiphospholipid antibodies, proteins C and S, and coagulation changes in sickle cell disease

The significance, interactions, and sources of coagulation abnormalities and their relationship to clinical severity and painful episodes in sickle cell disease are not clear. To evaluate this, we have examined various measures of coagulation in 37 patients with sickle cell disease (20 patients with HbSS disease and 17 patients with HbSC disease). Measurements have included isotypes of antiphospholipid antibodies (IgG, IgM, IgA) to specific phospholipids; proteins C (activity, total antigen) and S (activity, total and free antigen); measures of coagulation activation (prothrombin fragment 1.2, thrombin-antithrombin, fibrinopeptide A, d-dimers); indicators of clinical severity; and studies obtained during steady states and painful episodes. Results in HbSS disease showed that antiphospholipid antibodies were increased, with IgG phosphatidylserine showing the highest and most frequently increased levels (37% of patients). Protein C (activity) and protein S (activity, total, free antigen) were decreased (P<.01), and all measures of coagulation activation were increased (P<.001). In HbSC disease, antiphospholipid antibodies were normal, protein C (activity) and protein S (free antigen) were decreased (P<.001), and all measures of coagulation activation were increased (P<.02). A strong correlation was observed in HbSS disease between IgG-PS and d-dimers. Moderate correlations occurred between protein C activity and thrombin-antithrombin and fibrinopeptide A, between protein S activity and prothrombin fragment 1.2 and d-dimers, and between protein C and protein S activity. In HbSC disease, moderate and fewer correlations occurred. Significant differences between HbSS disease and HbSC disease were observed in aPLs, proteins C and S, and measures of coagulation activation. Measurements during steady states and during painful episodes were not significantly different. We conclude that the antiphospholipid antibody IgG-PS may contribute to coagulation activation in HbSS disease and that IgG-PS, protein C, and protein S relate to each other and jointly to measures of coagulation activation. The increased level of IgG-PS in HbSS disease most likely reflects exposure of the procoagulant phosphatidylserine on the surfaces of red cell-shed vesicles and sickle red cells, which would further affect coagulation activation. The significant differences in coagulation measures between HbSS disease and HbSC disease are consistent with differences in clinical severity between the diseases. The development of painful episodes does not appear to be related to the coagulation changes.

A systematic evaluation of conventional and novel transvenous pathways for defibrillation

INTRODUCTION

Conventional implantable cardioverter defibrillators employ endocardial (shock) electrodes with a lead located in the right ventricular apex (RV) and a "hot-can" electrode located subcutaneously in the left pectoral region. In the event of a high defibrillation threshold (DFT) a third electrode is frequently employed in the superior vena cava (SVC). We report the comparison of conventional and novel locations of additional electrodes with the RV/Can configuration, in a porcine model.

METHOD

In 12 anesthetized pigs (30-45 kg), endocardial defibrillation electrodes were randomized to the following locations: RV/Can, RV/Can + SVC, RV/Can + main pulmonary artery (MPA) and RV/Can + left pulmonary artery wedge position (PAW), RV/Can + high inferior vena cava (HIVC), RV/Can + Low inferior vena cava (LIVC). Ventricular fibrillation (VF) was induced using 60 Hz alternating current. After 10 seconds VF a rectangular biphasic shock was delivered by the ARD9000 (Angeion Corp). The DFT was determined for each configuration using a modified four-reversal binary search. All configurations were compared using a repeated measures analysis of variance (ANOVA) statistical test and the five 3-electrode configurations were compared to the RV/Can position using a Dunnett test.

RESULTS

Mean DFTs: RV = 21.5 +/- 4.8 J, SVC = 16.8 +/- 4.7 J (p < 0.05 vs. RV), HIVC = 21.1 +/- 4.7 J (p <. 0.05), LIVC = 19.1 +/- 5.7 J (p <. 0.05 vs. RV), MPA = 16.0 +/- 5.8 J (p < 0.01), PAW = 17.5 +/- 4.6 J (p < 0.05 vs. RV).

CONCLUSIONS

Relative to the RV/can configuration the addition of a third electrode in the PA, PAW or SVC significantly reduces the DFT in the pig. The addition of an electrode to the IVC did not significantly reduce the DFT in our model.

Allelic variants of human beta-chemokine receptor 5 (CCR5) promoter: evolutionary relationships and predictable associations with HIV-1 disease progression

Variability in the natural history of HIV-1 infection has been repeatedly associated with genetic variants in the beta-chemokine receptor 5 (CCR5) locus. While CCR5 coding sequences have demonstrated relatively limited variation, sequences of its promoter appear polymorphic in all major populations. Our studies revealed five major CCR5 promoter alleles with distributions that differed widely among the four distinct ethnic groups from Kigali, Rwanda and Bronx, New York. In particular, promoter allele P*0103 (G59029-T59353-T59356-A59402-C59653) was largely restricted to black subjects. The promoter allele P*0202 (A59029-C59353-C59356-A59402-T59653) was tightly linked to the slightly less frequent CCR2b-641, a variant of the CCR2b gene, which is about 12.7 kbp upstream from the promoter region. Another closely related promoter allele P*0201 (A59029-C59353-C59356-A59402-C59653) exclusively carried the far less common CCR5-delta 32, a 32-bp deletion in the CCR5 coding sequence 2 kbp downstream from the promoter. The homozygous P*0201/*0201 genotype can be predicted as a risk factor for more rapid disease progression. Among human, chimpanzee, pig-tailed macaque, and sooty mangabey promoter allelic sequences, the apparent ancestral lineage of the promoter sequence (G59029-T59353-C59356-A59402-C59653 = human P*0102) was highly conserved across the primate species analyzed here while P*0201 and P*0202 arose more recently than the other three major alleles. Further effort to establish the mechanism by which CCR chemokine receptor polymorphisms govern the initiation and pathogenesis of primate lentivirus infection apparently requires fully detailed genotypic characterization of the affected populations.

A new cardiothoracic centre: 'how to do it?'

All cardiac surgical patients, emergency and routine, from the South West peninsula of England had to travel long distances until 19 months ago, a stressful if not dangerous situation. This paper describes the planning, commissioning and start-up of a brand new cardiac surgical facility. The lessons learnt may help similar projects as provision of specialist health care decentralizes.

Performance on WISC-III and WAIS-R NI vocabulary subtests assessed with event-related brain potentials: an innovative method of assessment

Assessment of intellectual functions is essential for rehabilitative interventions with traumatic brain injury and stroke patients. However, many of these patients are difficult or impossible to assess because of aphasia and physical disabilities that prevent their performance on traditionally administered tests of mental functioning. We present normative evidence obtained from healthy individuals for the efficacy of a new method of assessing such patients using standardized and validated tests formatted for computer presentation and using direct measures of brain activity (event-related brain potentials, ERP) as the measurable response instead of verbal or motor behavior.

The influence of epitope availability on atomic-force microscope studies of antigen-antibody interactions

The ability of the atomic-force microscope (AFM) to detect interaction forces between individual biological molecules has recently been demonstrated. In this study, force measurements have been obtained between AFM probes functionalized with the beta-subunit of human chorionic gonadotrophin (betahCG) and surfaces functionalized with anti-betahCG antibody. A comparison of the obtained results with previous anti-ferritin antibody-binding data identifies differences when the antigen molecule expresses only a single epitope (betahCG), rather than multiple epitopes (ferritin), for the monoclonal antibodies employed. Specifically, the probability of observing probe-sample adhesion is found to be higher when the antigen expresses multiple epitopes. However, the periodic force observed in the adhesive-force distribution, due to the rupture of single antigen-antibody interactions, is found to be larger and more clearly observed for the mono-epitopic system. Hence, these findings indicate the potential of the AFM to distinguish between multivalent and monovalent antibody-antigen interactions, and demonstrate the influence of the number of expressed epitopes upon such binding studies.

Typing of Leishmania lipophosphoglycans by electrospray mass spectrometry

A method has been developed to identify the repeating phosphosaccharide units of Leishmania lipophosphoglycans using electrospray mass-spectrometry (ES-MS). Cone voltage-induced fragmentation of intact lipophosphoglycan was found to be as effective as analysis of mild acid hydrolysates in identifying the degree of modification of the repeating units of lipophosphoglycans derived from Leishmania mexicana and Leishmania major. This finding was exploited in a 'rapid-analysis' method in which a crude organic extract of approximately 2 x 10(9) L. major promastigote cells was loaded onto a reverse-phase cartridge for immediate elution into the mass-spectrometer. Using this approach, it was possible to identify the repeating units by total ion scanning and scanning for parents of the m/z 79 (PO3-) fragment ion. This approach is suitable for quick-typing of lipophosphoglycan repeats and was shown to detect alterations in repeat side chains caused by: (1) culturing L. major promastigotes in the presence of L-fucose; and (2) in vitro metacyclogenesis of L. major promastigotes. It is anticipated that the method will be applicable to small samples of cultured field isolates or genetically-manipulated strains.

Dehydroepiandrosterone replacement in aging humans

Because so much medical and media attention has been drawn to the alleged benefits of dehydroepiandrosterone (DHEA) and its sulfate ester (DHEAS), it is important to evaluate the effects of replacement therapy objectively using double blind, cross-over, randomized research methodology. In this 9-month study, healthy older men (n = 39) received replacement dose DHEA. Lean body mass, blood hematology, chemistry and endocrine values, as well as urological and psychological data were measured. Data showed some mild and temporary, but significant, changes during oral use of 100 mg DHEA for 3 months compared with placebo taken for 3 months. Body composition did not change during the 6 months of treatment, nor did any urological parameters. Concomitant with the endocrine changes, some small but, significant, variations in blood values (blood urea nitrogen, creatinine, uric acid, alanine transaminase, cholesterol, high density lipoprotein, and potassium) were found. After cessation of DHEA and placebo, followed by 3 months of no treatment, all values previously found to be altered returned to entry baseline. Well publicized effects of the drug reported by others, such as a sense of well-being or improved sexual function, were not found in this study.

Catheter mounted coaxially moveable ablation electrode for the creation of linear transmural endocardial lesions

INTRODUCTION

Use of a novel ablation catheter for the creation of linear transmural endocardial lesions, which uses a coaxially moving ablation electrode mounted on the terminal portion of a catheter shaft and able to move axially for a distance of up to 4 cm, is reported.

METHODS AND RESULTS

The coaxially moving ablation electrode is moved by a sliding mechanism in the catheter handle. The distal portion of the catheter shaft is steerable. Bipolar or unipolar electrograms can be recorded from electrodes on the catheter tip and the coaxially moving ablation. Radiofrequency (RF) current is delivered to the coaxially moving ablation electrode with thermocouple temperature control. This ablation catheter was evaluated in five (30 to 65 kg) anesthetized pigs and introduced via the venous/arterial systems into the right and left atrium (1 lesion) (using the retrograde aortic approach). The catheter was maneuvered to bring the slide range into apposition with atrial endocardium. The coaxially moving ablation electrode was deployed to the terminal portion of the catheter's slide range and then withdrawn in 2-mm steps. RF current was delivered to the coaxially moving ablation electrode at each point (maximum temperature 70 degrees C). Postmortem examination of eight endocardial linear lesions (2.2 to 4.1 cm length) was made 1 to 3 hours after creation. Histopathologic examination confirmed transmural myocyte necrosis along the length of the lesion, that included the trabeculated right atrium.

CONCLUSION

We conclude that a catheter using a moveable electrode creates continuous linear transmural lesions and could find clinical application in the therapy of a variety of reentry tachycardia mechanisms.

Mechanisms of GDF-5 action during skeletal development

Mutations in GDF-5, a member of the TGF-beta superfamily, result in the autosomal recessive syndromes brachypod (bp) in mice and Hunter-Thompson and Grebe-type chondrodysplasias in humans. These syndromes are all characterised by the shortening of the appendicular skeleton and loss or abnormal development of some joints. To investigate how GDF-5 controls skeletogenesis, we overexpressed GDF-5 during chick limb development using the retrovirus, RCASBP. This resulted in up to a 37.5% increase in length of the skeletal elements, which was predominantly due to an increase in the number of chondrocytes. By injecting virus at different stages of development, we show that GDF-5 can increase both the size of the early cartilage condensation and the later developing skeletal element. Using in vitro micromass cultures as a model system to study the early steps of chondrogenesis, we show that GDF-5 increases chondrogenesis in a dose-dependent manner. We did not detect changes in proliferation. However, cell suspension cultures showed that GDF-5 might act at these stages by increasing cell adhesion, a critical determinant of early chondrogenesis. In contrast, pulse labelling experiments of GDF-5-infected limbs showed that at later stages of skeletal development GDF-5 can increase proliferation of chondrocytes. Thus, here we show two mechanisms of how GDF-5 may control different stages of skeletogenesis. Finally, our data show that levels of GDF-5 expression/activity are important in controlling the size of skeletal elements and provides a possible explanation for the variation in the severity of skeletal defects resulting from mutations in GDF-5.

HLA class I homozygosity accelerates disease progression in human immunodeficiency virus type 1 infection

Polymorphic products of HLA class I genes restrict cytotoxic T lymphocyte responses to the constantly evolving spectrum of HIV-1 antigens. Accordingly, homozygosity at class I loci can reduce the repertoire for such HLA-dependent interactions, leading to accelerated disease progression. To test this hypothesis we studied subjects from two distinct HIV/AIDS cohorts: 140 Dutch homosexual men and 202 Rwandan heterosexual women followed up to 13 years from HIV-1 seroconversion. We performed intermediate- and selective high-resolution molecular typing at HLA class I (A, B, and C) and high-resolution typing at HLA class II DRB1 and DQB1. Homozygosity at the HLA-A or -B locus or both was found at increasingly high frequency among individuals with successively more rapid progression to late-stage HIV-1-related conditions. In the combined cohorts (n = 342) the odds ratio (OR) due to HLA-A or -B antigen homozygosity in rapid versus slow progressors was 3.8 (p = 0.003); for Dutch men alone the OR was 3.5 (p = 0.102), and for Rwandan women the OR was 4.1 (p = 0.009). In contrast, homozygous genotypes at either HLA-C, DRB1, or DQB1 alone, or DRB1-DQB1 haplotypes, did not exert any deleterious effect on HIV-1 disease progression. These findings suggest strongly that diversity in addition to sequence specificity at HLA-A and -B loci can influence the rate of disease progression following HIV-1 infection.

Enhancing math competency of baccalaureate students

The result of a 4-year effort to study and institute changes in Baylor University School of Nursing's baccalaureate (BSN) students' math competencies was successful. The evolution of the current math competency process is detailed. By identifying at-risk, entry-level students through math examination in the junior I semester and each semester in the program, individual clinical faculty can customize the teaching-learning experience for students. Students who need more help than a clinical instructor has available, which is documented by semester examination failure, benefit from taking a 1-hour medication administration course before graduating from the BSN program. Insights and suggestions are offered for other schools encountering this problem.

Rural attitudes, opinions, and drug use

There are two primary purposes of this paper. The first is to summarize the results of a survey conducted in a rural area of Kentucky on attitudes and behaviors regarding substance use. The second purpose is to examine differences in drug attitudes and behaviors for higher and lower density rural areas. Participants for this study were contacted by telephone in March 1996. The sample was generated by random digit dialing for eight county telephone exchanges. The sample included 334 respondents from the eight counties who were grouped into respondents from higher density areas (n = 132) and lower density areas (n = 202). Results indicated that respondents from both higher density and lower density areas were similar on drug use and attitudes. However, lower density areas reported their county as a worse place to live and less safe than respondents from higher density areas. Respondents from lower density areas were also more likely to report there was more alcohol/drug use and more alcohol bootlegging in the past year, and that bootlegging alcohol is a serious problem in their county. Future research could include the examination of heterogeneity of rural areas using different indices.

Organizational characteristics associated with agency position in community care networks

This study examines how organizational characteristics affect agency participation and centrality in community service networks. We find that the network structure of agency relations varies for administrative and client-related activities among the 69 agencies studied, which include all but the most isolated agencies serving people with physical disabilities in a single community. In identifying structurally equivalent groups using network analysis, we find that all types of agencies except HMOs are found throughout community service networks. Analyses show that among the five types of relations, minimal intergroup activity occurs within funding and planning networks and that organizational size and ownership are the best organizational predictors of network location and centrality. Non-profits are the most central for planning and client referrals, and large agencies are the most central for funding. We explore the implications of these findings, particularly for sustaining cooperation within the service networks and for the role of non-profits and medical providers in the community.

Preliminary single center clinical experience of the use of a new implantable cardioverter defibrillator

We report a single center's preliminary clinical experience of the Sentinel (Angeion, Minneapolis, MN) implantable cardioverter defibrillator (ICD), which employs novel technologies that offer the potential for significant reduction in ICD size. Thirty-three patients have received Sentinel ICDs with a mean follow-up of 450 (range 150-1023) days. Device shock therapy has been used to defibrillate/cardiovert 43 spontaneous episodes of malignant ventricular arrhythmia and 510 episodes of hemodynamically well tolerated ventricular arrhythmia have been pace-terminated (pace-termination failed in 6 episodes with subsequent delivery of appropriate shock therapy). There has been no arrhythmic death in this patient population. There have been 9 inappropriate shocks in 6 patients (in 2 patients for atrial fibrillation which had satisfied the algorithm detection criteria for high zone ventricular arrhythmia, in 3 for sinus tachycardia [rate greater than 180 beats per min] and in 1 due to device capacitor malfunction). Device replacement has been required for component malfunction in 3 patients. There have been no other major complications. Follow-up time to date is short and longterm device efficacy and performance remain unproven. However, our early clinical experience suggests that the innovations used to manufacture the Sentinel ICD have facilitated reduction in ICD size without compromising therapeutic efficacy.

Expression of adhesion molecules by lp(a): a potential novel mechanism for its atherogenicity

Lp(a) is a major inherited risk factor for premature atherosclerosis. The mechanism of Lp(a) atherogenicity has not been elucidated, but likely involves both its ability to interfere with plasminogen activation and its atherogenic potential as a lipoprotein particle after receptor-mediated uptake. We demonstrate that Lp(a) stimulates production of vascular cell adhesion molecule 1 (VCAM-1) and E-selectin in cultured human coronary artery endothelial cells (HCAEC). This effect resulted from a rise in intracellular free calcium induced by Lp(a) and could be inhibited by the intracellular calcium chelator, BAPTA/AM. The involvement of the LDL and VLDL receptors in Lp(a) activation of HCAEC were ruled out since Lp(a) induction of adhesion molecules was not prevented by an antibody (IgGC7) to the LDL receptor or by receptor-activating protein, an antagonist of ligand binding to the VLDL receptor. Addition of alpha2-macroglobulin as well as treatment with heparinase, chondroitinase ABC, and sodium chlorate did not decrease levels of VCAM-1 and E-selectin stimulated by Lp(a), suggesting that neither the low density lipoprotein receptor-related protein nor cell-surface proteoglycans are involved in Lp(a)-induced adhesion molecule production. Neither does the binding site on HCAEC responsible for adhesion molecule production by Lp(a) appear to involve plasminogen receptors, as levels of VCAM-1 and E-selectin were not significantly decreased by the addition of glu-plasminogen, the lysine analog epsilon-aminocaproic acid, or by trans-4-(aminomethyl)-cyclohexanecarboxymethylic acid (tranexamic acid), which acts by binding to the lysine binding sites carried on the kringle structures in plasminogen. In contrast, recombinant apolipoprotein (a) [r-apo(a)] competed with Lp(a) and attenuated the expression of VCAM-1 and E-selectin. In summary, we have identified a calcium-dependent interaction of Lp(a) with HCAEC capable of inducing potent surface expression of VCAM-1 and E-selectin that does not appear to involve any of the known potential Lp(a) binding sites. Because leukocyte recruitment to the vessel wall appears to represent one of the important early events in atherogenesis, this newly described endothelial cell-activating effect of Lp(a) places it at a crucial juncture in the initiation of atherogenic disease and may lead to a better understanding of the role of Lp(a) in the vascular biology of atherosclerosis.

Ileostomy

Several different groups of patients may undergo an ileostomy, the two most common being those with ulcerative colitis and and Crohn's disease. Nurses have an important role in providing information, advice and support to such patients.

Lipid/vascular wall interaction

Atherosclerosis is an extremely complex process that involves the interaction of a large number of genes as well as environmental factors: a chronic inflammatory cascade that can be converted to an acute clinical event by the induction of plaque rupture, which, in turn, leads to thrombosis. What are the basic mechanisms that induce this sequence of events? For many years, atherosclerosis research concentrated on the role played by circulating lipids. Many clinical trials have demonstrated that interventions aimed at lowering lipid levels have beneficial effects in terms of reduction in the incidence of cardiac events and in mortality from coronary artery disease. To account for these clinical benefits that have been observed even with relatively short periods of intervention, several hypotheses, such as halting plaque progression and stabilizing rupture-prone lesions, have been suggested. The mechanisms responsible for these observations, however, remain poorly understood. This review focuses on 1) identifying the different lipid components that interact with the vessel wall, 2) defining the different endothelial lipoprotein receptors that bind and transfer the lipid into the cell, and 3) explaining the mechanisms of lipid atherogenicity.