Global longitudinal strain and plasma biomarkers for prognosis in heart failure complicated by diabetes: a prospective observational study

BACKGROUND

Heart failure (HF) and diabetes are associated with increased incidence and worse prognosis of each other. The prognostic value of global longitudinal strain (GLS) measured by cardiovascular magnetic resonance (CMR) has not been established in HF patients with diabetes.

METHODS

In this prospective, observational study, consecutive patients (n = 315) with HF underwent CMR at 3T, including GLS, late gadolinium enhancement (LGE), native T1, and extracellular volume fraction (ECV) mapping. Plasma biomarker concentrations were measured including: N-terminal pro B-type natriuretic peptide(NT-proBNP), high-sensitivity troponin T(hs-TnT), growth differentiation factor 15(GDF-15), soluble ST2(sST2), and galectin 3(Gal-3). The primary outcome was a composite of all-cause mortality or HF hospitalisation.

RESULTS

Compared to those without diabetes (n = 156), the diabetes group (n = 159) had a higher LGE prevalence (76 vs. 60%, p < 0.05), higher T1 (1285±42 vs. 1269±42ms, p < 0.001), and higher ECV (30.5±3.5 vs. 28.8±4.1%, p < 0.001). The diabetes group had higher NT-pro-BNP, hs-TnT, GDF-15, sST2, and Gal-3. Diabetes conferred worse prognosis (hazard ratio (HR) 2.33 [95% confidence interval (CI) 1.43-3.79], p < 0.001). In multivariable Cox regression analysis including clinical markers and plasma biomarkers, sST2 alone remained independently associated with the primary outcome (HR per 1 ng/mL 1.04 [95% CI 1.02-1.07], p = 0.001). In multivariable Cox regression models in the diabetes group, both GLS and sST2 remained prognostic (GLS: HR 1.12 [95% CI 1.03-1.21], p = 0.01; sST2: HR per 1 ng/mL 1.03 [95% CI 1.00-1.06], p = 0.02).

CONCLUSIONS

Compared to HF patients without diabetes, those with diabetes have worse plasma and CMR markers of fibrosis and a more adverse prognosis. GLS by CMR is a powerful and independent prognostic marker in HF patients with diabetes.

Strategies of nanoparticles integration in polymer fibers to achieve antibacterial effect and enhance cell proliferation with collagen production in tissue engineering scaffolds

Current design strategies for biomedical tissue scaffolds are focused on multifunctionality to provide beneficial microenvironments to support tissue growth. We have developed a simple yet effective approach to create core-shell fibers of poly(3-hydroxybuty-rate-co-3-hydroxyvalerate) (PHBV), which are homogenously covered with titanium dioxide (TiO2) nanoparticles. Unlike the blend process, co-axial electrospinning enabled the uniform distribution of nanoparticles without the formation of large aggregates. We observed 5 orders of magnitude reduction in Escherichia coli survival after contact with electrospun scaffolds compared to the non-material control. In addition, our hybrid cores-shell structure supported significantly higher osteoblast proliferation after 7 days of cell culture and profound generation of 3D networked collagen fibers after 14 days. The organic-inorganic composite scaffold produced in this study demonstrates a unique combination of antibacterial properties and increased bone regeneration properties. In summary, the multifunctionality of the presented core-shell cPHBV+sTiO2 scaffolds shows great promise for biomedical applications.

Sacubitril/valsartan versus valsartan in regressing myocardial fibrosis in hypertension: a prospective, randomized, open-label, blinded endpoint clinical trial protocol

Background

Diffuse interstitial myocardial fibrosis is a key common pathological manifestation in hypertensive heart disease (HHD) progressing to heart failure (HF). Angiotensin receptor-neprilysin inhibitors (ARNi), now a front-line treatment for HF, confer benefits independent of blood pressure, signifying a multifactorial mode of action beyond hemodynamic regulation. We aim to test the hypothesis that compared with angiotensin II receptor blockade (ARB) alone, ARNi is more effective in regressing diffuse interstitial myocardial fibrosis in HHD.

Methods

Role of ARNi in Ventricular Remodeling in Hypertensive LVH (REVERSE-LVH) is a prospective, randomized, open-label, blinded endpoint (PROBE) clinical trial. Adults with hypertension and left ventricular hypertrophy (LVH) according to Asian sex- and age-specific thresholds on cardiovascular magnetic resonance (CMR) imaging are randomized to treatment with either sacubitril/valsartan (an ARNi) or valsartan (an ARB) in 1:1 ratio for a duration of 52 weeks, at the end of which a repeat CMR is performed to assess differential changes from baseline between the two groups. The primary endpoint is the change in CMR-derived diffuse interstitial fibrosis volume. Secondary endpoints include changes in CMR-derived left ventricular mass, volumes, and functional parameters. Serum samples are collected and stored to assess the effects of ARNi, compared with ARB, on circulating biomarkers of cardiac remodeling. The endpoints will be analyzed with reference to the corresponding baseline parameters to evaluate the therapeutic effect of sacubitril/valsartan vs. valsartan.

Discussion

REVERSE-LVH will examine the anti-fibrotic potential of sacubitril/valsartan and will offer mechanistic insights into the clinical benefits of sacubitril/valsartan in hypertension in relation to cardiac remodeling. Advancing the knowledge of the pathophysiology of HHD will consolidate effective risk stratification and personalized treatment through a multimodal manner integrating complementary CMR and biomarkers into the conventional care approach.Clinical Trial Registration: ClinicalTrials.gov, identifier, NCT03553810.

Impact of Diabetes on Myocardial Fibrosis in Patients With Hypertension: The REMODEL Study

BACKGROUND

Compared with patients with hypertension only, those with hypertension and diabetes (HTN/DM) have worse prognosis. We aimed to characterize morphological differences between hypertension and HTN/DM using cardiovascular magnetic resonance; and compare differentially expressed proteins associated with myocardial fibrosis using high throughput multiplex assays.

METHODS

Asymptomatic patients underwent cardiovascular magnetic resonance: 438 patients with hypertension (60±8 years; 59% males) and 167 age- and sex-matched patients with HTN/DM (60±10 years; 64% males). Replacement myocardial fibrosis was defined as nonischemic late gadolinium enhancement on cardiovascular magnetic resonance. Extracellular volume fraction was used as a marker of diffuse myocardial fibrosis. A total of 184 serum proteins (Olink Target Cardiovascular Disease II and III panels) were measured to identify unique signatures associated with myocardial fibrosis in all patients.

RESULTS

Despite similar left ventricular mass (P=0.344) and systolic blood pressure (P=0.086), patients with HTN/DM had increased concentricity and worse multidirectional strain (P<0.001 for comparison of all strain measures) compared to hypertension only. Replacement myocardial fibrosis was present in 28% of patients with HTN/DM compared to 16% of those with hypertension (P<0.001). NT-proBNP (N-terminal pro-B-type natriuretic peptide) was the only protein differentially upregulated in hypertension patients with replacement myocardial fibrosis and independently associated with extracellular volume. In patients with HTN/DM, GDF-15 (growth differentiation factor 15) was independently associated with replacement myocardial fibrosis and extracellular volume. Ingenuity Pathway Analysis demonstrated a strong association between increased inflammatory response/immune cell trafficking and myocardial fibrosis in patients with HTN/DM.

CONCLUSIONS

Adverse cardiac remodeling was observed in patients with HTN/DM. The novel proteomic signatures and associated biological activities of increased immune and inflammatory response may partly explain these observations.

Markers of Focal and Diffuse Nonischemic Myocardial Fibrosis Are Associated With Adverse Cardiac Remodeling and Prognosis in Patients With Hypertension: The REMODEL Study

BACKGROUND

The prognostic significance of focal and diffuse myocardial fibrosis in patients with cardiovascular risk factors is unclear.

METHODS

REMODEL (Response of the Myocardium to Hypertrophic Conditions in the Adult Population) is an observational cohort of asymptomatic patients with essential hypertension. All participants underwent cardiovascular magnetic resonance to assess for myocardial fibrosis: nonischemic late gadolinium enhancement (LGE), native myocardial T1, postcontrast myocardial T1, extracellular volume fraction including/excluding LGE regions, interstitial volume (extracellular volume×myocardial volume), and interstitial/myocyte ratio. Primary outcome was a composite of first occurrence acute coronary syndrome, heart failure hospitalization, strokes, and cardiovascular mortality. Patients were recruited from February 2016 and followed until June 2021.

RESULTS

Of the 786 patients with hypertension (58±11 years; 39% women; systolic blood pressure, 130±14 mm Hg), 145 (18%) had nonischemic LGE. Patients with nonischemic LGE were more likely to be men, have diabetes, be current smokers, and have higher blood pressure (P<0.05 for all). Compared with those without LGE, patients with nonischemic LGE had greater left ventricular mass (66±22 versus 49±9 g/m²; P<0.001), worse multidirectional strain (P<0.001 for all measures), and elevated circulating markers of myocardial wall stress and myocardial injury, adjusted for potential confounders. Twenty-four patients had primary outcome over 39 (30-50) months of follow-up. Of all the cardiovascular magnetic resonance markers of myocardial fibrosis assessed, only nonischemic LGE (hazard ratio, 6.69 [95% CI, 2.54-17.60]; P<0.001) and indexed interstitial volume (hazard ratio, 1.11 [95% CI, 1.04-1.19]; P=0.002) demonstrated independent association with primary outcome.

CONCLUSIONS

In patients with hypertension, myocardial fibrosis on cardiovascular magnetic resonance is associated with adverse cardiac remodeling and outcomes.

Relationship of Quantitative Retinal Capillary Network and Myocardial Remodeling in Systemic Hypertension

Background

This study examined the associations between quantitative optical coherence tomography angiography (OCTA) parameters and myocardial abnormalities as documented on cardiovascular magnetic resonance imaging in patients with systemic hypertension.

Methods and Results

We conducted a cross‐sectional study of 118 adults with hypertension (197 eyes). Patients underwent cardiovascular magnetic resonance imaging and OCTA (PLEX Elite 9000, Carl Zeiss Meditec). Associations between OCTA parameters (superficial and deep retinal capillary density) and adverse cardiac remodeling (left ventricular mass, remodeling index, interstitial fibrosis, global longitudinal strain, and presence of left ventricular hypertrophy) were studied using multivariable linear regression analysis with generalized estimating equations. Of the 118 patients with hypertension enrolled (65% men; median [interquartile range] age, 59 [13] years), 29% had left ventricular hypertrophy. After adjusting for age, sex, systolic blood pressure, diabetes, and signal strength of OCTA scans, patients with lower superficial capillary density had significantly higher left ventricular mass (β=−0.150; 95% CI, −0.290 to −0.010), higher interstitial volume (β=−0.270; 95% CI, −0.535 to −0.0015), and worse global longitudinal strain (β=−0.109; 95% CI, −0.187 to −0.032). Lower superficial capillary density was found in patients with hypertension with replacement fibrosis versus no replacement fibrosis (16.53±0.64 mm ‐1 versus 16.96±0.64 mm ‐1 ; P =0.003).

Conclusions

We showed significant correlations between retinal capillary density and adverse cardiac remodeling markers in patients with hypertension, supporting the notion that the OCTA could provide a non‐invasive index of microcirculation alteration for vascular risk stratification in people with hypertension.

Echocardiographic Global Longitudinal Strain Is Associated With Myocardial Fibrosis and Predicts Outcomes in Aortic Stenosis

Aims: Left ventricular ejection fraction is the conventional measure used to guide heart failure management, regardless of underlying etiology. Left ventricular global longitudinal strain (LV-GLS) by speckle tracking echocardiography (STE) is a more sensitive measure of intrinsic myocardial function. We aim to establish LV-GLS as a marker of replacement myocardial fibrosis on cardiovascular magnetic resonance (CMR) and validate the prognostic value of LV-GLS thresholds associated with fibrosis.

Methods and results: LV-GLS thresholds of replacement fibrosis were established in the derivation cohort: 151 patients (57 ± 10 years; 58% males) with hypertension who underwent STE to measure LV-GLS and CMR. Prognostic value of the thresholds was validated in a separate outcome cohort: 261 patients with moderate-severe aortic stenosis (AS; 71 ± 12 years; 58% males; NYHA functional class I–II) and preserved LVEF ≥50%. Primary outcome was a composite of cardiovascular mortality, heart failure hospitalization, and myocardial infarction. In the derivation cohort, LV-GLS demonstrated good discrimination (c-statistics 0.74 [0.66–0.83]; P < 0.001) and calibration (Hosmer-Lemeshow χ² = 6.37; P = 0.605) for replacement fibrosis. In the outcome cohort, 47 events occurred over 16 [3.3, 42.2] months. Patients with LV-GLS > −15.0% (corresponding to 95% specificity to rule-in myocardial fibrosis) had the worst outcomes compared to patients with LV-GLS < −21.0% (corresponding to 95% sensitivity to rule-out myocardial fibrosis) and those between −21.0 and −15.0% (log-rank P < 0.001). LV-GLS offered independent prognostic value over clinical variables, AS severity and echocardiographic LV mass and E/e′.

Conclusion: LV-GLS thresholds associated with replacement myocardial fibrosis is a novel approach to risk-stratify patients with AS and preserved LVEF.

Multiparametric exercise stress cardiovascular magnetic resonance in the diagnosis of coronary artery disease: the EMPIRE trial

BACKGROUND

Stress cardiovascular magnetic resonance (CMR) offers assessment of ventricular function, myocardial perfusion and viability in a single examination to detect coronary artery disease (CAD). We developed an in-scanner exercise stress CMR (ExCMR) protocol using supine cycle ergometer and aimed to examine the diagnostic value of a multiparametric approach in patients with suspected CAD, compared with invasive fractional flow reserve (FFR) as the reference gold standard.

METHODS

In this single-centre prospective study, patients who had symptoms of angina and at least one cardiovascular disease risk factor underwent both ExCMR and invasive angiography with FFR. Rest-based left ventricular function (ejection fraction, regional wall motion abnormalities), tissue characteristics and exercise stress-derived (perfusion defects, inducible regional wall motion abnormalities and peak exercise cardiac index percentile-rank) CMR parameters were evaluated in the study.

RESULTS

In the 60 recruited patients with intermediate CAD risk, 50% had haemodynamically significant CAD based on FFR. Of all the CMR parameters assessed, the late gadolinium enhancement, stress-inducible regional wall motion abnormalities, perfusion defects and peak exercise cardiac index percentile-rank were independently associated with FFR-positive CAD. Indeed, this multiparametric approach offered the highest incremental diagnostic value compared to a clinical risk model (χ2 for the diagnosis of FFR-positive increased from 7.6 to 55.9; P < 0.001) and excellent performance [c-statistic area under the curve 0.97 (95% CI: 0.94-1.00)] in discriminating between FFR-normal and FFR-positive patients.

CONCLUSION

The study demonstrates the clinical potential of using in-scanner multiparametric ExCMR to accurately diagnose CAD.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03217227, Registered 11 July 2017-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03217227?id=NCT03217227&draw=2&rank=1&load=cart.

Paradoxical Higher Myocardial Wall Stress and Increased Cardiac Remodeling Despite Lower Mass in Females

Background

Increased left ventricular (LV) mass is characterized by increased myocardial wall thickness and/or ventricular dilatation that is associated with worse outcomes. We aim to comprehensively compare sex‐stratified associations between measures of LV remodeling and increasing LV mass in the general population.

Methods and Results

Participants were prospectively recruited in the National Heart Center Singapore Biobank to examine health and cardiovascular risk factors in the general population. Cardiovascular magnetic resonance was performed in all individuals. Participants with established cardiovascular diseases and abnormal cardiovascular magnetic resonance scan results were excluded. Global and regional measures of LV remodeling (geometry, function, interstitial volumes, and wall stress) were performed using conventional image analysis and novel 3‐dimensional machine learning phenotyping. Sex‐stratified analyses were performed in 1005 participants (57% males; 53±13 years). Age and prevalence of cardiovascular risk factors were well‐matched in both sexes (P>0.05 for all). Progressive increase in LV mass was associated with increased concentricity in either sex, but to a greater extent in females. Compared with males, females had higher wall stress (mean difference: 170 mm Hg, P<0.0001) despite smaller LV mass (42.4±8.2 versus 55.6±14.2 g/m², P<0.0001), lower blood pressures (P<0.0001), and higher LV ejection fraction (61.9±5.9% versus 58.6±6.4%, P<0.0001). The regions of increased concentric remodeling corresponded to regions of increased wall stress. Compared with males, females had increased extracellular volume fraction (27.1±2.4% versus 25.1±2.9%, P<0.0001).

Conclusions

Compared with males, females have lower LV mass, increased wall stress, and concentric remodeling. These findings provide mechanistic insights that females are susceptible to particular cardiovascular complications.

P1419 Sex-related differences in cardiac remodeling in health and hypertension

Funding Acknowledgements

National Medical Research Council

OnBehalf

National Heart Centre Singapore

BACKGROUND

Adverse cardiac remodelling is associated with worse cardiovascular outcomes. Development of left ventricular hypertrophy (defined as increased myocardial mass) is a complex process mediated by myocardial wall thickening and/or ventricular dilatation. Sex-related differences in the relationship between myocardial mass and wall thickening/ventricular dilatation have not been well-described.

PURPOSE

We examine differences in determinants and patterns of cardiac remodeling between males and females.

METHODS

Comprehensive cardiovascular magnetic resonance imaging was performed in 1006 participants: 316 healthy volunteers (50% males, 46 ± 14 years) and 690 asymptomatic hypertensive patients (60% males, 57 ± 11 years). Myocardial mass, ventricular volumes and maximal myocardial wall thickness (across 16 myocardial segments) were measured using standardized contouring techniques. Clinically relevant variables (age, weight, height, and adiposity) that demonstrated significant univariate association with myocardial mass (P &lt; 0.05) were selected in the multivariable linear regression model using the forward approach.

RESULTS

Increased body weight, lower body fat composition and higher systolic blood pressures were independently associated with increased myocardial mass in healthy volunteers (males and females) and hypertensive females. In hypertensive males, only increased body weight and elevated systolic blood pressure were independently associated with increased myocardial mass.

The association between myocardial mass and ventricular volumes was almost identical between males and females (P = 0.65 for interaction; Figure). Conversely, there was a significant gender-related difference in the association between wall thickness and myocardial mass after adjusting for potential confounders (P &lt; 0.001 for interaction). Concentric remodeling was initially more evident in males; but further with increase, myocardial mass was associated with greater concentric remodeling in females (Figure). Similar results were observed when analyses were performed separately in healthy volunteers and hypertensive patients.

CONCLUSION

There were sex-related differences in concentric remodeling at progressive stages of myocardial hypertrophy that may explain the higher prevalence of heart failure with preserved ejection fraction reported in females.

Abstract P1419 Figure

Platelet inhibition to target reperfusion injury trial: Rationale and study design

BACKGROUND

In ST-segment elevation myocardial infarction (STEMI) patients treated with primary percutaneous coronary intervention (PPCI), current oral P2Y12 platelet inhibitors do not provide maximal platelet inhibition at the time of reperfusion. Furthermore, administration of cangrelor prior to reperfusion has been shown in pre-clinical studies to reduce myocardial infarct (MI) size. Therefore, we hypothesize that cangrelor administered prior to reperfusion in STEMI patients will reduce the incidence of microvascular obstruction (MVO) and limit MI size in STEMI patients treated with PPCI.

METHODS

The platelet inhibition to target reperfusion injury (PITRI) trial, is a phase 2A, multi-center, double-blinded, randomized controlled trial, in which 210 STEMI patients will be randomized to receive either an intravenous (IV) bolus of cangrelor (30 μg/kg) followed by a 120-minute infusion (4 μg/kg/min) or matching saline placebo, initiated prior to reperfusion (NCT03102723).

RESULTS

The study started in October 2017 and the anticipated end date would be July 2020. The primary end-point will be MI size quantified by cardiovascular magnetic resonance (CMR) on day 3 post-PPCI. Secondary endpoints will include markers of reperfusion, incidence of MVO, MI size, and adverse left ventricular remodeling at 6 months, and major adverse cardiac and cerebrovascular events.

SUMMARY

The aim of the PITRI trial is to assess whether cangrelor administered prior to reperfusion would reduce acute MI size and MVO, as assessed by CMR.

Study of the scan uniformity from an i-CAT cone beam computed tomography dental imaging system

OBJECTIVES

As part of an ongoing programme to improve diagnosis and treatment planning relevant to implant placement, orthodontic treatment and dentomaxillofacial surgery, a study has been made of the spatial accuracy and density response of an i-CAT, a cone beam CT (CBCT) dental imaging system supplied by Imaging Sciences International Inc.

METHODS

Custom-made phantoms using acrylic sheet and water were used for measurements on spatial accuracy, density response and noise. The measurements were made over a period of several months on a clinical machine rather than on a machine dedicated to research.

RESULTS

Measurements on a precision grid showed the spatial accuracy to be universally within the tolerance of +/-1 pixel. The density response and the noise in the data were found to depend strongly on the mass in the slice being scanned.

CONCLUSIONS

The density response was subject to two effects. The first effect changes the whole slice uniformly and linearly depends on the total mass in the slice. The second effect exists when there is mass outside the field of view, dubbed the "exo-mass" effect. This effect lowers the measured CT number rapidly at the scan edge furthest from the exo-mass and raises it on the adjacent edge. The noise also depended quasi-linearly on the mass in the slice. Some general performance rules were drafted to describe these effects and a preliminary correction algorithm was constructed.

Presurgical, ultrasound-guided anchor-wire marking of impalpable cervical lymph nodes

This case illustrates the surgical use of wire localization, a well tried technique from a different field of surgery, in the removal of an ultrasound-detected, impalpable deep lower cervical lymph node in a high-risk patient. A localization needle with an echogenic tip was placed freehand under ultrasound guidance, immediately before surgery. The imaging and marking of the impalpable cervical lymph node resulted in a precise surgical dissection and a reduction in operating time whilst minimizing risks to the patient and staff.

Both chloroplastic and cytosolic phosphoglycerate kinase isozymes are present in the pea leaf nucleus

Phosphoglycerate kinase (EC 2.7.2.3) occurs in chloroplasts, cytosol, and nuclei in higher plants. Immunocytolocalization experiments with isozyme-specific antibodies indicate that both the chloroplastic and the cytosolic forms of the enzyme are present in the pea (Pisum sativum L.) leaf nucleus.

Online sales: profit without question

OBJECTIVES

To examine the ease with which underage smokers can purchase cigarettes online using money orders and to evaluate the effectiveness of internet filtering programs in blocking access to internet cigarette vendors (ICVs).

DESIGN

Four young people purchased 32 money orders using 32 different names to buy one carton of cigarettes for each named individual. Each money order was subsequently mailed to a different ICV in the USA. No age related information accompanied these online orders. Two internet filtering programs ("Bess" and filtertobacco.org) were tested for their relative efficacy in blocking access to ICV sites.

RESULTS

Of the 32 orders placed, four orders never reached the intended ICV. Of the remaining 28 orders, 20 (71%) were filled despite a lack of age verification. Only four (14%) of the orders received were rejected because they lacked proof of age. "Bess" blocked access to 84% and filtertobacco.org to 94% of the ICV sites.

CONCLUSIONS

Although underage smokers can easily purchase cigarettes online using money orders, access to these sites can be largely blocked if appropriate filtering devices are installed.

A comparison of radiographic foot measurements taken in two different positions

The purpose of this study was to ascertain if positioning of the feet for radiographic assessment produces significant variations in measured angles, and if measurements taken from radiographs taken on two separate occasions are reproducible. Weightbearing x-rays were taken of both feet of ten male healthy subjects in two standardized positions: 1) the angle and base of gait and 2) the feet together and straight-ahead positions. The radiographs were repeated 2 weeks later. The results failed to demonstrate significant differences of radiographic measurements between the two specific foot-positioning methods. No significant differences were found between radiographic measurements of normal feet taken on different occasions. A strong correlation of the repeated measures suggests that weightbearing foot radiographs can be reliably reproduced.

Origins and complexes: the initiation of DNA replication

Eukaryotic DNA is organized for replication as multiple replicons. DNA synthesis in each replicon is initiated at an origin of replication. In both budding yeast, Saccharomyces cerevisiae and fission yeast, Schizosaccharomyces pombe, origins contain specific sequences that are essential for initiation, although these differ significantly between the two yeasts with those of S. pombe being more complex then those of S. cerevisiae. However, it is not yet clear whether the replication origins of plants contain specific essential sequences or whether origin sites are determined by features of chromatin structure. In all eukaryotes there are several biochemical events that must take place before initiation can occur. These are the marking of the origins by the origin recognition complex (ORC), the loading onto the origins, in a series of steps, of origin activation factors including the MCM proteins, and the initial denaturation of the double helix to form a replication "bubble". Only then can the enzymes that actually initiate replication, primase and DNA polymerase-alpha, gain access to the template. In many cells this complex series of events occurs only once per cell cycle, ensuring that DNA is not re-replicated within one cycle. However, regulated re-replication of DNA within one cell cycle (DNA endoreduplication) is relatively common in plants, indicating that the "once-per-cycle" controls can be overridden.

A novel DNA-binding protein associated with DNA polymerase-alpha in pea stimulates polymerase activity on infrequently primed templates

A 42 kDa DNA-binding protein is associated with DNA polymerase-alpha-primase in pea (Pisum sativum). In a previous publication it was shown that the protein has strong preference for ds-ss junctions in DNA, including the cohesive termini generated by restriction endonucleases. In this paper it is shown that when the DNA-binding protein is added back to polymerase-primase, the protein stimulates the activity of the polymerase. The stimulation is particularly marked when M13 DNA, primed with a single sequencing primer or primed with oligoribonucleotides by the polymerase's associated primase activity, is used as a template. The stimulation of polymerase activity is not caused by an increase in processivity. These data lead to the suggestion that the 42 kDa DNA-binding protein is a primer-recognition protein.

High-field DNP and ENDOR with a novel multiple-frequency resonance structure

We describe a new triply tuned (e(-), (1)H, and (13)C) resonance structure operating at an electron Larmor frequency of 139.5 GHz for dynamic nuclear polarization (DNP) and electron nuclear double-resonance (ENDOR) experiments. In contrast to conventional double-resonance structures, the body of the microwave cavity simultaneously acts as a NMR coil, allowing for increased efficiency of radiofrequency irradiation while maintaining a high quality factor for microwave irradiation. The resonator design is ideal for low-gamma-nuclei ENDOR, where sensitivity is limited by the fact that electron spin relaxation times are on the order of the RF pulse lengths. The performance is demonstrated with (2)H ENDOR on a standard perdeuterated bis-diphenylene-phenyl-allyl stable radical. In DNP experiments, we show that the use of this resonator, combined with a low microwave power setup (17 mW), leads to significantly higher (1)H signal enhancement (epsilon approximately 400 +/- 50) than previously achieved at 5-T fields. The results emphasize the importance of optimizing the microwave B(1) field by improving either the quality factor of the microwave resonator or the microwave power level.

Pulsed electron-nuclear double resonance (ENDOR) at 140 GHz

We describe a spectrometer for pulsed ENDOR at 140 GHz, which is based on microwave IMPATT diode amplifiers and a probe consisting of a TE011 cavity with a high-quality resonance circuit for variable radiofrequency irradiation. For pulsed EPR we obtain an absolute sensitivity of 3x10(9) spins/Gauss at 20 K. The performance of the spectrometer is demonstrated with pulsed ENDOR spectra of a standard bis-diphenylene-phenyl-allyl (BDPA) doped into polystyrene and of the tyrosyl radical from E. coli ribonucleotide reductase (RNR). The EPR spectrum of the RNR tyrosyl radical displays substantial g-anisotropy at 5 T and is used to demonstrate orientation-selective Davies-ENDOR.

Novel DNA-binding characteristics of a protein associated with DNA polymerase-alpha in pea

DNA polymerase-alpha-primase may be isolated from pea shoot tip cells as a large (1.25 x 10(6) Da) multi-protein complex. The complex exhibits several enzyme activities and also binds to DNA. One of the DNA-binding activities has been purified as a 42 kDa polypeptide. The binding of this polypeptide to linear DNA fragments and to open circular plasmids has been studied by electron microscopy. The protein binds to restriction enzyme-generated cohesive ends of linear fragments and also exhibits some interstitial binding. Binding at the ends of linear molecules is very markedly reduced if the molecules are previously treated with S1 nuclease. The protein also binds to open circular plasmids; the number of binding sites is increased by exposing the plasmids to gamma-irradiation prior to the DNA-protein interaction. In these experiments, the number of protein units bound is directly related to the radiation dose. With both linear and open circular molecules, binding of the protein to the DNA leads to an apparent shortening of the DNA molecule. These observations, taken with the finding that the protein does not bind to completely single-stranded DNA, lead to the suggestion that the protein binds to double-stranded-single-stranded (ds-ss) junctions in DNA and that binding causes the DNA to wrap round the protein.

Effect of blood donation on the establishment of normal ranges of lymphocyte subsets

BACKGROUND

Absolute counts of CD4+ T-lymphocytes are used in the management of patients with human immunodeficiency virus infection. Low absolute counts of CD3+CD4+ cells have also been observed in healthy people--a phenomenon called idiopathic CD4 lymphocytopenia. It is common practice for normal ranges for lymphocyte subsets to be derived from samples taken from blood donors.

STUDY DESIGN AND METHODS

A sample of EDTA blood was taken through the donation line tubing, after donation from 565 blood donors in Sydney, Australia, who were selected from a range of age groups. An additional 12 donors provided a predonation sample as well as a postdonation sample. Hematologic assays were performed on two analyzers. Samples were stained for CD3, CD4, CD8, CD19, and CD56 and analyzed on a flow cytometer.

RESULTS

Three donors were found to have absolute CD3+CD4+ counts < 300 cells per microL. The percentage of CD3+CD4+ cells was found to increase with age. Both the percentage and the absolute count of CD3+CD8+ cells decreased with age, which resulted in an increased CD4:CD8 ratio with age. Men had consistently higher absolute counts of CD3-CD56+ cells than women. The 12 additional donors all had greater percentages of CD3+CD4+ cells and lower absolute counts for CD3+, CD3+CD4+, CD3+CD8+, CD19+ and CD3-CD56+ cells after donation than they had before donation (p < 0.001).

CONCLUSION

It is not satisfactory to base normal ranges for lymphocyte subsets on donor blood, from which the blood sample has been obtained after donation.

Coordinator's report on the flow cytometric analysis of the Rh antibodies

One hundred and four IgG monoclonal antibodies with specificity within the Rh Blood Group System were evaluated by flow cytometry as part of the Third International Workshop. Standardisation of data to permit interlaboratory comparison of antibody binding was achieved by adherence to a standard red blood cell staining protocol, defined control cells and a standard FITC-labelled antibody. In addition, calibration standards were provided to permit the calculation of Molecules of Equivalent Soluble Fluorochrome (MESF) values from the mean channel fluorescence. For the majority of anti-D antibodies mean MESF values obtained with D positive cells were far higher than with the negative controls (D negative cells), with D variants having intermediate although very varied MESFs. In general MESF values obtained with non anti-D antibodies were less than for the anti-D antibodies although some of the anti-E antibodies were very strong. The highest MESF values were obtained with an anti-CD antibody.

Protease-modified erythrocytes: CD55 and CD59 deficient PNH-like cells

The increased susceptibility to homologous complement in paroxysmal nocturnal haemoglobinuria (PNH) is known to be associated with the deficiency of the membrane complement inhibitors CD59 and CD55. Proteases have been used in this study to modify normal human RBC to complement sensitive PNH-like cells. To investigate the protective role of CD59 and CD55, the relationship between the content of CD59 and CD55 and the complement susceptibility of the PNH-like cells has been determined. The differential resistance of the enzyme-treated RBC to complement-mediated injury was measured by acidified serum lysis. Pronase-treated erythrocytes lacked both CD59 and CD55 and were very susceptible to complement-mediated lysis. Papain treatment of RBC reduced the CD55 content but did not affect CD59 and induced slight susceptibility to complement-mediated lysis. Trypsin treatment of RBC destroyed 80% of CD59, had little effect on CD55 (unless incubation was extended) and slightly increased susceptibility to lysis. Thus, partial CD55 and CD59 activity was sufficient to protect cells from complement-mediated lysis. In the reactive lysis assay, anti-CD55 and anti-CD59 induced haemolysis, anti-CD59 having the more pronounced effect. Lysis was enhanced when RBC were treated by both antibodies simultaneously.

Six monoclonal antibodies to the CD59 antigen

CD59 defines an N-glycosylated glycoprotein expressed on various hemopoietic cells. It is anchored to the cell membrane by a glycosylpbospbatidylinositol linkage and restricts the action of homologous complement. Monoclonal antibodies 2/24, 182, Fib75.1, BRIC 229, MEM-43, and YTH 53.1 were compared by immunoblotting against normal erythrocyte ghosts. All six stained a diffuse band of 17-25 kDa, but BRIC 229 also detected bands at 35 and 80 kDa. 2/24 reacts with all red blood cells (RBCs) tested, including Rhnull; Ob; ii; Ko; FY:-1,-2,-3; JK:-1,-2,-3; S-s-U-; p; CO:-1,-2; Yt(a-); Jr(a-); Vel-; At(a-); Cr(a-); GE:-2,-3; Wr(a+b+ MkMk; Jo(a-); and Lan-. 2-aminoethylisotbiouronium bromide treatment of erythrocytes destroyed blotting and serologic reactivity of all six antibodies. Pronase treatment reduced serologic reactivity and blotting ability of all antibodies except BRlC 229. Reactivity of all six antibodies was reduced with RBCs from paroxysmal nocturnal hemoglobinuria patients. Flow cytometric analysis was used to demonstrate that 182, Fib75.1, BRIC 229, YTH 53.1, and MEM-43 competitively inhibited the binding of 2/24 to RBCs, thus demonstrating that all six antibodies detect epitopes on the same molecule.

New monoclonal antibodies in CD59: use for the analysis of peripheral blood cells from paroxysmal nocturnal haemoglobinuria (PNH) patients and for the quantitation of CD59 on normal and decay accelerating factor (DAF)-deficient erythrocytes

CD59 is a widely expressed cell surface glycosylphosphatidylinositol (GPI)-linked glycoprotein which acts as an inhibitor of the assembly of the membrane attack complex of autologous complement. Four new monoclonal antibodies to CD59 (2/24, 1B2, BRIC 229, BRIC 257) are described. Competitive binding experiments using these antibodies, two known CD59 antibodies (MEM-43, YTH 53.1) and a previously described antibody LICR-LON-Fib75.1 demonstrated that all seven antibodies see related epitopes on human erythrocyte CD59. In common with other GPI-linked proteins, CD59 (as defined by antibody 2/24) was sensitive to treatment with phosphatidylinositol-specific phospholipase C (PI-PLC) on lymphocytes and monocytes but not on erythrocytes. Flow cytometric analysis using antibody 2/24 identified two populations (CD59 positive and CD59 deficient) of lymphocytes, monocytes and erythrocytes in peripheral blood from a patient with paroxysmal nocturnal haemoglobinuria (PNH). The abundance of CD59 on normal erythrocytes was determined as 21,000 copies/cell when radioiodinated BRIC 229 was used. Other CD59 antibodies gave values of 10,000 (IF5) and 15,000 (2/24) against the same target cells. Radioiodinated Fab fragments of BRIC 229 gave a value of 39,000 copies/cell. Erythrocytes from two individuals with a rare inherited deficiency of decay accelerating factor (DAF), known as the Inab phenotype, expressed normal levels of CD59.

Detection of CaMV gene I and gene VI protein products in vivo using antisera raised to COOH-terminal β-galactosidase fusion proteins

Specific antisera were prepared to the inclusion body protein (gene VI product) and the gene I product of cauliflower mosaic virus (CaMV). Translational fusions between the lacZ gene and gene VI or gene I were constructed by cloning the relevant DNA fragments into the expression vectors pUR290, pUR291 or pUR292. Large amounts of fusion protein were synthesized when the inserted DNA fragment was in frame with the lacZ gene of the expression vector. These fusion proteins were used to raise specific antisera to gene VI and gene I proteins of CaMV. Antiserum to the gene VI product detected a range of proteins in crude extracts and in a subcellular fraction enriched for virus inclusion bodies. This range of proteins was further shown to be related to gene VI by Staphylococcus aureus V8 partial proteolysis. Antiserum to the gene I product detected viral specific proteins of 46, 42 and 38 K in preparations of CaMV replication complexes from infected plants but not in any other subcellular fraction.

Hemifacial microsomia, ipsilateral facial palsy, and malformed auricle in two families: an autosomal dominant malformation

Hemifacial microsomia, ipsilateral facial palsy and anomalies of the auricle were observed in father and son in two families. This combination of anomalies is a causally heterogeneous developmental field defect which may occur rarely as an autosomal dominant trait.

Isolation of a fraction from cauliflower mosaic virus-infected protoplasts which is active in the synthesis of (+) and (-) strand viral DNA and reverse transcription of primed RNA templates

Sub-cellular fractions, isolated from cauliflower mosaic virus (CaMV)-infected turnip protoplasts, are capable of synthesising CaMV DNA in vitro on an endogenous template and of reverse transcribing oligo dT-primed cowpea mosaic virus RNA. The activity was not detected in mock-inoculated protoplasts. In vitro-labelled DNA hybridized to single-stranded M13 clones complementary to the putative origins of (-) and (+) strand CaMV DNA synthesis and to restriction endonuclease fragments encompassing more than 90% of the CaMV genome. The synthesis of (-) and (+) strand DNA appeared asymmetric. The template(s) for in vitro CaMV DNA synthesis are in a partially nuclease-resistant form. Fractions capable of in vitro CaMV DNA synthesis contained CaMV RNA both heterogeneous and as discrete species; they also contained a range of different sizes of CaMV DNA. Several lines of evidence indicate that this range of in vitro-labelled CaMV DNA, extending from 0.6kb to 8.0kb in length, represents elongating (-) strand DNA. These are discussed in relation to their role as possible replicative intermediates.