Structure determination by cryoEM at 100 keV

Electron cryomicroscopy can, in principle, determine the structures of most biological molecules but is currently limited by access, specimen preparation difficulties, and cost. We describe a purpose-built instrument operating at 100 keV-including advances in electron optics, detection, and processing-that makes structure determination fast and simple at a fraction of current costs. The instrument attains its theoretical performance limits, allowing atomic resolution imaging of gold test specimens and biological molecular structure determination in hours. We demonstrate its capabilities by determining the structures of eleven different specimens, ranging in size from 140 kDa to 2 MDa, using a fraction of the data normally required. CryoEM with a microscope designed specifically for high-efficiency, on-the-spot imaging of biological molecules will expand structural biology to a wide range of previously intractable problems.

The Einstein-de Haas effect in an Fe15cluster

Classical models of spin-lattice coupling are at present unable to accurately reproduce results for numerous properties of ferromagnetic materials, such as heat transport coefficients or the sudden collapse of the magnetic moment in hcp-Fe under pressure. This inability has been attributed to the absence of a proper treatment of effects that are inherently quantum mechanical in nature, notably spin-orbit coupling (SOC). This paper introduces a time-dependent, non-collinear tight binding model, complete with SOC and vector Stoner exchange terms, that is capable of simulating the Einstein-de Haas (EdH) effect in a ferromagnetic Fe15cluster. The tight binding model is used to investigate the adiabaticity timescales that determine the response of the orbital and spin angular momenta to a rotating, externally appliedBfield, and we show that the qualitative behaviors of our simulations can be extrapolated to realistic timescales by use of the adiabatic theorem. An analysis of the trends in the torque contributions with respect to the field strength demonstrates that SOC is necessary to observe a transfer of angular momentum from the electrons to the nuclei at experimentally realisticBfields. The simulations presented in this paper demonstrate the EdH effect from first principles using a Fe cluster.

Cohort profile: the ESC EURObservational Research Programme Non-ST-segment elevation myocardial infraction (NSTEMI) Registry

AIMS

The European Society of Cardiology (ESC) EURObservational Research Programme (EORP) Non-ST-segment elevation myocardial infarction (NSTEMI) Registry aims to identify international patterns in NSTEMI management in clinical practice and outcomes against the 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without ST-segment-elevation.

METHODS AND RESULTS

Consecutively hospitalised adult NSTEMI patients (n = 3620) were enrolled between 11 March 2019 and 6 March 2021, and individual patient data prospectively collected at 287 centres in 59 participating countries during a two-week enrolment period per centre. The registry collected data relating to baseline characteristics, major outcomes (in-hospital death, acute heart failure, cardiogenic shock, bleeding, stroke/transient ischaemic attack, and 30-day mortality) and guideline-recommended NSTEMI care interventions: electrocardiogram pre- or in-hospital, pre-hospitalization receipt of aspirin, echocardiography, coronary angiography, referral to cardiac rehabilitation, smoking cessation advice, dietary advice, and prescription on discharge of aspirin, P2Y12 inhibition, angiotensin converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB), beta-blocker, and statin.

CONCLUSION

The EORP NSTEMI Registry is an international, prospective registry of care and outcomes of patients treated for NSTEMI, which will provide unique insights into the contemporary management of hospitalised NSTEMI patients, compliance with ESC 2015 NSTEMI Guidelines, and identify potential barriers to optimal management of this common clinical presentation associated with significant morbidity and mortality.

Reducing IV-contaminated blood specimens in the clinical laboratory: A Quality Improvement Project

Introduction/Objective

Preanalytical errors constitute the most common errors in the laboratory, with improper specimen collection accounting for many errors. In our laboratory, we had a sentinel event related to repeated deletions of suspected IV-contaminated draws, and herein report our quality improvement project (QIP) to reduce deleted test results and IV-contaminated specimens.

Methods/Case Report

Our QIP initiated with creating a core-lab task force. Several interventions were launched: (A) policy/definition standardization, (B) nursing IV-line/cathedar in-services, (C) in-services on deleting test results and identifying IV-contamination, (D) policy updates to reflect no deletions without evidence of IV-contamination, and (E) mitigation steps requiring supervisory approval for result deletions. We measured: patient safety events (PSRs); RECOLLECTION comment usage and efficacy (disclaimer attached to results thought to be IV-contaminated, requesting recollection); and mitigation failures. Efficacy of the comment usage was measured by comparing subsequent collections to the original and determining likelihood of IV-contamination (contaminated, not contaminated, and unsure). Prior to the QIP, lab practice was to delete suspected IV-contaminated results and those requested by the care team.

Results (if a Case Study enter NA)

PSRs attributable to IV-contamination dropped from 47/mo. (time 0) to 18/mo. over an 11-month period (min-8/mo.; max-64/mo.), with the greatest decrement seen following intervention C. The RECOLLECTION comment was attached to 38 results (0.06% of total accessions) at the start and 73 results (0.12% of total accessions) at time 11 mos. and showed greatest increase in use immediately prior to interventions C and D (approximately 3-fold increase). At time 0, 54% of RECOLLECTION comments were deemed contaminated and 31% were not; at time 11mos., 74% (50/68) were contaminated and 24% (16/68) were not. Mitigation failures numbered 5/mo. initially and 1/mo. at time 11 mos.

Conclusion

With multiple educational and supervisory interventions, we demonstrate a reduction in PSRs attributable to IV-contamination collections at our hospital. Use of cautionary disclaimers was overall minimal and appropriately used.

Error Reduction in Specimen Processing of Irretrievable Body Fluids

Introduction/Objective

A lack of standardized processes for laboratory handling of irretrievable body fluid specimens, such as cerebrospinal fluid, serous fluids, synovial fluids, and aspirates, can result in failures that put the patient at risk by delaying testing results and/or requiring specimen recollection. We noted increased patient safety issues with irretrievable specimens in our laboratory and implemented a process improvement plan to mitigate patient harm.

Herein, we report our findings of this intervention.

Methods

A task force was organized with wide representation across the laboratory to design a new workflow for irretrievable specimens. Hospital Patient Safety Reporting data was used to identify flaws in the pre-analytical processes pre-intervention and to monitor effectiveness of process change, post-intervention. Our intervention consisted of developing a standardized pre-analytical process for both technical and non-technical staff that could be enforced through consistent and proper training, with well-defined responsibilities for each department involved including specimen processing, microbiology, hematology, and chemistry. Our process included a centralized sterile processing location within the Micro department as well as a standardized sample log in and sample distribution process that incorporated a chain of custody form.

Results

Pre-intervention, we had 23 patient safety reports during a 3-month period (5-10/month; average 8/month) on irretrievable specimens; post-intervention, we had 9 patient safety reports over a 5-month period (0-4/month; average 2/month). Pre-intervention, failures identified included inconsistent workflows and training among staff, the absence of established protocols, and inadequate communication. Post-intervention, failures were noted due to improper and inconsistent training (n=4) or deviation from the established procedure by staff members. These failures were investigated and addressed through retraining or corrective actions as needed.

Conclusion

Our data shows that the implementation of a standardized process within the laboratory significantly decreases patient safety events by improving testing turn-around-times and quality of results and by preventing the need for specimen recollections.

Differences in soil organic carbon and soil erosion for native pasture and minimum till agricultural management systems

There is considerable debate over how different agricultural management systems such as minimum tillage and grazing affect soil organic carbon (SOC), soil nitrogen (SN) concentrations and soil erosion over the long-term. In this study SOC, SN and erosion characteristics were compared over a ten year period for two neighbouring sites with longstanding but different land management strategies; one cropped under a minimum tillage (MT) regime and one used for grazing on largely native pasture. Both sites (Hunter Valley, New South Wales, Australia) shared the same soil type (Euchrozem) and climate. SOC and SN were both found to be ~50% higher at the grazing site while erosion was found to be significantly greater (an order of magnitude) at the cropping site despite the application of MT practices. No discernible link between erosion and either SOC, SN or C:N was evident. While both sites have temporally constant SOC, SN and C:N, the MT site offers scope for increased SOC sequestration.

Preclinical assessment of a new magnetic resonance-based technique for determining bone quality by characterization of trabecular microarchitecture

The utility of HR-CT to study longitudinal changes in bone microarchitecture is limited by subject radiation exposure. Although MR is not subject to this limitation, it is limited both by patient movement that occurs during prolonged scanning at distal sites, and by the signal-to-noise ratio that is achievable for high-resolution images in a reasonable scan time at proximal sites. Recently, a novel MR-based technique, fine structure analysis (FSA) (Chase et al. Localised one-dimensional magnetic resonance spatial frequency spectroscopy. PCT/US2012/068284 2012, James and Chase Magnetic field gradient structure characteristic assessment using one-dimensional (1D) spatial frequency distribution analysis. 7932720 B2, 2011) has been developed which provides both high-resolution and fast scan times, but which generates at a designated set of spatial positions (voxels) a one-dimensional signal of spatial frequencies. Appendix 1 provides a brief introduction to FSA. This article describes an initial exploration of FSA for the rapid, non-invasive characterization of trabecular microarchitecture in a preclinical setting. For L4 vertebrae of sham and ovariectomized (OVX) rats, we compared FSA-generated metrics with those from CT datasets and from CT-derived histomorphometry parameters, trabecular number (Tb.N), bone volume density (BV/TV), trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp). OVX caused a reduction of the higher frequency structures that correspond to a denser trabecular lattice, while increasing the preponderance of lower frequency structures, which correspond to a more open lattice. As one example measure, the centroid of the FSA spectrum (which we refer to as fSAcB) showed strong correlation in the same region with CT-derived histomorphometry values: Tb.Sp: r -0.63, p < 0.001; Tb.N: r 0.71, p < 0.001; BV/TV: r 0.64, p < 0.001, Tb.Th: r 0.44, p < 0.05. Furthermore, we found a 17.5% reduction in fSAcB in OVX rats (p < 0.0001). In a longitudinal study, FSA showed that the age-related increase in higher frequency structures was abolished in OVX rats, being replaced with a 78-194% increase in lower frequency structures (2.4-2.8 objects/mm range), indicating a more sparse trabecular lattice (p < 0.05). The MR-based fine structure analysis enables high-resolution, radiation-free, rapid quantification of bone structures in one dimension (the specific point and direction being chosen by the clinician) of the spine.

Stabilization of carbon nanotube field emitters

Carbon nanotubes (CNTs) have been determined to be field emitters of high quality, but CNTs produced by chemical vapour deposition can produce emission currents with high instability and noise. This work finds that adsorbates and amorphous carbon deposited during the growth process are the primary contributors to field emission instability, and shows that burning off the amorphous carbon in air at 450°C removes the amorphous carbon, resulting in stabilities of better than 3 per cent over 1 h. This work removes one of the major barriers to the use of CNTs in field emission devices.

Bamboo and herringbone shaped carbon nanotubes and carbon nanofibres synthesized in direct current-plasma enhanced chemical vapour deposition

Carbon nanotubes with different structures were catalytically synthesized on Ni coated SiO2/Si substrate in a Direct Current Plasma Enhanced Chemical Vapour Deposition system, in which C2H2 acted as the carbon source and NH3 as the etchant gas. A Scanning Electron Microscope study showed that carbon nanotubes were all vertically aligned with respect to the substrate, with diameters ranging from 10 nm to 200 nm. Different sizes of Ni catalyst particles were observed on the tips of carbon nanotubes. Transmission Electron Microscopy was used to study the morphology of the grown tubes and the results obtained show that the diameters and structures of these carbon nanotubes were closely correlated to the sizes and structures of the Ni nanoparticles. Two main structures namely bamboo shaped carbon nanotubes and herringbone shaped carbon nanofibres were found on the same sample. It is suggested that by controlling the pre-growth condition, desired structure of carbon nanotubes or carbon nanofibres could be produced for practical applications.

Does adiposity status influence femoral cortical strength in rodent models of growth hormone deficiency?

Growth hormone (GH)-deficiency is usually associated with elevated adiposity, hyperleptinemia, and increased fracture risk. Since leptin is thought to enhance cortical bone formation, we have investigated the contribution of elevated adiposity and hyperleptinemia on femoral strength in rodent models of GH deficiency. Quantification of the transpubertal development of femoral strength in the moderately GH-deficient/hyperleptinemic Tgr rat and the profoundly GH-deficient/hypoleptinemic dw/dw rat revealed that the mechanical properties of cortical bone in these two models were similarly compromised, a 25-30% reduction in failure load being entirely due to impairment of geometric variables. In contrast, murine models of partial (GH antagonist transgenic) and complete (GH receptor-null) loss of GH signaling and elevated adiposity showed an impairment of femoral cortical strength proportionate to the reduction of GH signaling. To determine whether impaired femoral strength is exacerbated by obesity/hyperleptinemia, femoral strength was assessed in dw/dw rats following two developmental manipulations that elevate abdominal adiposity and circulating leptin, neonatal monosodium glutamate (MSG) treatment, and maintenance on an elevated fat diet. The additional impairment of femoral strength following MSG treatment is likely to have resulted from a reduction in residual activity of the hypothalamo-pituitary-GH-IGF-I axis, but consumption of elevated dietary fat, which did not reduce circulating IGF-I, failed to exacerbate the compromised femoral strength in dw/dw rats. Taken together, our data indicate that the obesity and hyperleptinemia usually associated with GH deficiency do not exert a significant influence over the strength of cortical bone.

Clinical effectiveness of a brief educational intervention in Type 1 diabetes: results from the BITES (Brief Intervention in Type 1 diabetes, Education for Self-efficacy) trial

AIMS

Intensive 5-day educational interventions for people with Type 1 diabetes have shown improved outcomes in a number of European studies. The aim was to assess the effectiveness of a brief (2.5 days) psycho-educational intervention.

METHODS

Our randomized trial in a secondary-care setting had 54 and 60 participants allocated to intervention and control groups, respectively. Primary outcomes were HbA1c and severe hypoglycaemia. Secondary outcomes were blood pressure, weight, height, lipids and psychometric profile.

RESULTS

HbA1c showed no statistically significant change at 3 months [difference = 0.01, 95% confidence interval (CI) -0.23, 0.26, P = 0.92], 6 months (difference = -0.06, 95% CI -0.32, 0.20, P = 0.67) and 12 months (difference = 0.01, 95% CI -0.30, 0.32, P = 0.94). Incidence of severe hypoglycaemia (per patient per year) in the intervention group (0.41) and control group (0.48) was not statistically different. Treatment satisfaction improved at 3 months (difference = 9.4, 95% CI 5.2, 13.6, P = 0.0005), 6 months (difference = 10.4, 95% CI 6.0, 14.8, P = 0.0005) and 12 months (difference = 7.1, 95% CI 2.1, 12.1, P = 0.006). The 'Managing psychological aspects' and 'Setting and achieving goals' dimensions of the Diabetes Empowerment Scale also showed significant improvement at 3, 6 and 12 months. Diabetes Knowledge Test, Illness Perception Questionnaire, Hypoglycaemia Fear Scale and Short Form 36 showed no significant change.

CONCLUSIONS

This brief intervention had no significant impact on HbA(1c) or severe hypoglycaemia, but improved diabetes treatment satisfaction and patient empowerment. Current Controlled Trials ISRCTN75807800.

The pregnancy-induced increase in baseline circulating growth hormone in rats is not induced by ghrelin

The elevation in baseline circulating growth hormone (GH) that occurs in pregnant rats is thought to arise from increased pituitary GH secretion, but the underlying mechanism remains unclear. Distribution, Fourier and algorithmic analyses confirmed that the pregnancy-induced increase in circulating GH in 3-week pregnant rats was due to a 13-fold increase in baseline circulating GH (P < 0.01), without any significant alteration in the parameters of episodic secretion. Electron microscopy revealed that pregnancy resulted in a reduction in the proportion of mammosomatotrophs (P < 0.01) and an increase in type II lactotrophs (P < 0.05), without any significant change in the somatotroph population. However, the density of the secretory granules in somatotrophs from 3-week pregnant rats was reduced (P < 0.05), and their distribution markedly polarised; the granules being grouped nearest the vasculature. Pituitary GH content was not increased, but steady-state GH mRNA levels declined progressively during pregnancy (P < 0.05). In situ hybridisation revealed that pregnancy was accompanied by a suppression of GH-releasing hormone mRNA expression in the arcuate nuclei (P < 0.05) and enhanced somatostatin mRNA expression in the periventricular nuclei (P < 0.05), an expression pattern normally associated with increased GH feedback. Although gastric ghrelin mRNA expression was elevated by 50% in 3-week pregnant rats (P < 0.01), circulating ghrelin, GH-secretagogue receptor mRNA expression and the GH response to a bolus i.v. injection of exogenous ghrelin were all largely unaffected during pregnancy. Although trace amounts of 'pituitary' GH could be detected in the placenta with radioimmunoassay, significant GH-immunoreactivity could not be observed by immunohistochemistry, indicating that rat placenta itself does not produce 'pituitary' GH. Although not excluding the possibility that the pregnancy-associated elevation in baseline circulating GH could arise from alternative extra-pituitary sources (e.g. the ovary), our data indicate that this phenomenon is most likely to result from a direct alteration of somatotroph function.

Use of garden organic compost in vegetable production under contrasting soil P status

Little research has been carried out on the agronomic value of compost produced from garden organics for vegetable production. A field experiment was established in Camden, near Sydney, Australia, to (i) evaluate the effect of the compost on vegetable production and soil quality relative to conventional practice, (ii) compare vegetable production under high and low soil P status, and (iii) monitor the changes in soil P concentration under two compost treatments relative to conventional farmers’ practice. After three successive crops (broccoli, eggplant and cabbage), results indicate that compost (120 dry t/ha) and half-compost (60 dry t/ha supplemented by inorganic fertilisers) treatments can produce similar yield to the conventional practice of using a mixture of poultry manure and inorganic fertiliser. Furthermore, similar yields were achieved for three different crops grown under high and low P soil conditions, clearly demonstrating that the high extractable soil P concentrations currently found in the vegetable farms of Sydney are not necessary for maintaining productivity. The compost treatments also significantly increased soil organic carbon and soil quality including soil structural stability, exchangeable cations, and soil biological properties. Importantly, the compost treatment was effective in reducing the rate of accumulation of extractable soil P compared with the conventional vegetable farming practice. Our results highlight the potential for using compost produced from source separated garden organics in reversing the trend of soil degradation observed under current vegetable production, without sacrificing yield.

Egr-1-d2EGFP transgenic rats identify transient populations of neurons and glial cells during postnatal brain development

The inducible transcription factor Egr-1 has been extensively studied in the adult brain but potential roles during development are largely unexplored. Here we describe the analysis of a new transgenic rat model (egr-1 promoter driving a destabilized GFP molecule) that has provided novel information about the postnatal roles of Egr-1. We show that Egr-1 is more widely expressed in the neonatal brain than was previously appreciated, and is not restricted to neurons; it is expressed in glial cells in the postnatal neocortex and hippocampus. This pattern of expression has been revealed due to cellular filling by GFP, permitting co-localization with glial markers. The transgene/Egr-1 is also expressed in a novel population of cells associated with Cajal-Retzius-like neurons within the marginal zone of the postnatal neocortex. Both of these cellular populations are transient, being limited to the neonatal period, before Egr-1 expression becomes established in an adult-like pattern within neocortical neurons, CA1 hippocampus, and striatum. Another transient population of transgene/Egr-1 cells in the bed nucleus of the stria terminalis is maintained until pre-adolescence. The transient phenotype of these cells involves a low relative expression of the neuronal marker NeuN, perhaps indicating a failure to achieve full neuronal differentiation. Egr-1 is therefore present in a diverse range of cell-types during postnatal development. Transgenic expression of a destabilized fluorescent marker has permitted identification of these novel cell populations and will facilitate further analysis of the transcriptional mechanisms that underlie the specific functions and fate of these cells during postnatal brain development.

Reducing transfer times for coronary angiography in patients with acute coronary syndromes: one solution to a national problem

BACKGROUND

Patients with acute coronary syndrome (ACS) are at high risk of further cardiac events and benefit from early intervention, as reflected by international guidelines recommending early transfer to interventional centres. The current average waiting time of up to 21 days contravenes evidence based early intervention, creates geographical inequity of access, wastes bed days, and is unsatisfactory for patients.

METHODS

A regional transfer unit (RTU) was created to expatriate access of ACS patients referred from other centres to the revascularisation service. By redesigning the care pathway patients arriving on the RTU undergo angiography within 24 hours, and then leave the RTU the following day, allowing other ACS patients to be treated.

RESULTS

During the first six months of the RTU, the mean waiting time from referral to procedure decreased from 20 (SD 15) days (range 0-51) to 8 (SD 3) days (range 0-21) for 365 patients transferred from a district general hospital. Ninety seven per cent of patients underwent angiography within 24 hours, 61% having undergone percutaneous coronary intervention at the same sitting, and 78% were discharged home within 24 hours.

CONCLUSIONS

Delivering standards laid out in the National Service Framework, reducing inequalities of care across the region, and facilitating evidence based strategies of care represents a challenging and complex issue. For high risk patients suffering ACS who need early invasive investigation, a coordinated network wide approach together with the creation of an RTU resulted in a 62% reduction in waiting times for no extra resources. Further improvements can be expected through increased capacity of this verified strategy.

Hypothalamic expression of human growth hormone induces post-pubertal hypergonadotrophism in male transgenic growth retarded rats

Growth hormone (GH) is known to regulate peripheral components of the hypothalamo-pituitary gonadal (HPG) axis, but it remains unclear whether GH exerts a significant influence on the activity of the hypothalamo-pituitary components of the HPG axis. In this study, we investigated the development of HPG axis function in the male transgenic growth retarded (Tgr) rat, a model of moderate systemic GH deficiency caused by hypothalamic expression of human (h)GH. Impaired postnatal somatotroph expansion and moderate GH deficiency in male Tgr rats were accompanied by a two- to three-fold increase in pituitary gonadotrophin content, but without a significant change in the pituitary gonadotroph population. A three- to nine-fold elevation in basal circulating luteinising hormone concentration was seen in postpubertal Tgr rats, with a smaller increase in follicle-stimulating hormone. Despite this hypergonadotrophism, there was no corresponding increase in steroidogenic (circulating testosterone and seminal vesicle weights) or gametogenic (spermatozoa counts in seminiferous tubules) activity in the postpubertal Tgr testis. Following puberty, the plasma leptin concentration also became progressively elevated in Tgr males. Circulating gonadotrophin and leptin levels were normalised in Tgr rats by peripheral physiological replacement of rat GH, but plasma testosterone concentration was unaffected. These results confirm that hGH exerts a positive influence on the central control of gonadotrophin secretion in the Tgr rat, but the absence of a corresponding elevation in the steroidogenic or gametogenic function of the Tgr testis implies that the peripheral GH/insulin-like growth factor I axis may also exert a permissive influence on testicular function. The relative contribution of somatogenic and lactogenic mechanisms and the potential influence of elevated leptin and decreased sensitivity to androgen feedback to the development of postpubertal hypergonadotrophism in Tgr males remain to be determined.

Comparative analysis of the effects of ghrelin and unacylated ghrelin on luteinizing hormone secretion in male rats

Ghrelin, the endogenous ligand of GH secretagogue receptor type 1a, has emerged as pleiotropic modulator of diverse biological functions, including energy homeostasis and, recently, reproduction. Although inhibitory actions of ghrelin on LH secretion and puberty onset have been reported previously, the receptor mechanisms mediating these actions, and the potential gonadotropic effects of the unacylated isoform of ghrelin (UAG), remain unclear. In this work, the effects of single and repeated administration of ghrelin or UAG on LH secretion were compared in pubertal and adult male rats. In addition, the effects of ghrelin were assessed in models of transient or persistent hypergonadotropism. Daily injection of ghrelin or UAG throughout puberty similarly decreased LH levels and partially delayed balanopreputial separation. Likewise, chronic infusion of ghrelin or UAG to adult males resulted in significant decreases in circulating LH and FSH concentrations. Moreover, acute injection of ghrelin induced a transient reduction in LH levels in freely moving males, an effect that was fully mimicked by administration of UAG. Yet in contrast to ghrelin, UAG failed to modify GH secretion. Finally, injection of ghrelin moderately, but significantly, reduced the duration of LH secretory responses to the potent gonadotropin secretagogue kisspeptin-10, whereas ghrelin infusion in a model of chronic elevation of serum gonadotropin levels (the transgenic growth retarded male rat) evoked a significant reduction of LH concentrations. Altogether our present results further substantiate the inhibitory effect of ghrelin on basal and stimulated LH secretion in a wide array of experimental conditions. Moreover, our data are the first to demonstrate the ability of UAG, originally considered an inert form of the molecule, to mimic the actions of acylated ghrelin on LH release. These observations reinforce the contention that ghrelin, as putative signal for energy insufficiency, may operate as negative modifier of male puberty and LH secretion, an effect that might be, at least partially, conducted through a GH secretagogue receptor type 1a-independent mechanism.

Manipulating sorting signals to generate co-expression of somatostatin and eGFP in the regulated secretory pathway from a monocistronic construct

Targeted overexpression of biologically active peptides represents a powerful approach to the functional dissection of neuroendocrine systems. However, the requirement to generate separate, biologically active and reporter molecules necessitates the use of internal ribosome entry site (IRES) technology, which often results in preferential translation of the second cistron. We report here a novel approach in which the proteolytic processing machinery of the regulated secretory pathway (RSP) has been exploited to generate multiple mature proteins from a monocistronic construct that encodes a single precursor. This was achieved by duplication of the pre-pro cleavage sites in pre-prosomatostatin cDNA. The duplicated site included 10 flanking amino acids on either side of the Gly-Ala cleavage position. This enabled the incorporation of a foreign protein-coding sequence (in this case, enhanced green fluorescent protein (eGFP)) between these sites. The pre-eGFP-prosomatostatin (PEPS) construct generated co-localized expression of fully processed eGFP and somatostatin to the RSP of transiently transfected AtT20 cells. This approach represents an advance upon bicistronic and other extant approaches to the targeting of multiple, biologically active proteins to neuroendocrine systems, and, importantly, permits the co-expression of fluorescent markers with biologically active neuropeptides. In this study, our demonstration of the fusion of the first 10 amino acids of the prosomatostatin sequence to the N-terminus of eGFP shows that this putative sorting sequence is sufficient to direct expression to the RSP.

Morphological determinants of femoral strength in growth hormone-deficient transgenic growth-retarded (Tgr) rats

The extent to which childhood GHD affects adult fracture risk is unclear. We measured femoral strength in adult transgenic growth-retarded rats as a model of GHD. Long-term, moderate GHD was accompanied by endocrine and morphometric changes consistent with a significant reduction in femoral strength.

INTRODUCTION

Childhood growth hormone deficiency (GHD) is associated with osteopenia, but little is known about its effects on subsequent adult bone strength and fracture risk.

MATERIALS AND METHODS

We have therefore measured femoral strength (failure load measured by three-point bending) in a new model of moderate GHD, the transgenic growth-retarded (Tgr) rat at 15, 22-23, and 52 weeks of age, and have quantified potential morphological and endocrine determinants of bone strength.

RESULTS

Skeletal growth retardation in Tgr rats was accompanied by a sustained reduction in the anterior-posterior diameter of the femoral cortex, whereas mid-diaphyseal cortical wall thicknesses were largely unaltered. Total femoral strength was significantly impaired in Tgr rats (p < 0.01), and this impairment was more pronounced in males than females. Compromised bone strength in Tgr rats could not be accounted for by the reduction in mechanical load (body weight) and was not caused by impairment of the material properties of the calcified tissue (ultimate tensile stress), despite marked reductions in femoral mineral density (areal bone mineral density; p < 0.001). Microcomputerized tomographical analysis revealed significant modification of the architecture of trabecular bone in Tgr rats, with reductions in the number and thickness of trabeculae (p < 0.05) and in the degree of anisotropy (p < 0.01). The marked reduction in plasma insulin-like growth factor-1 in Tgr rats was accompanied by the development of high circulating leptin levels (p < 0.01).

CONCLUSION

These results show that the changes in endocrinology and bone morphology associated with long-term moderate GHD in Tgr rats are accompanied by changes consistent with a significant reduction in the threshold for femoral fracture.

Stimulus-specific induction of an Egr-1 transgene in rat brain

Regulated expression of Egr-1 (Zif268/NGFIA) in a variety of brain networks suggests a diversity of roles in neuronal plasticity. Here, we aimed to determine whether an egr-1 transgene would mediate transcriptional responses to different pharmacological and physiological stimuli in the brain of transgenic rats. Constitutive transgene expression was observed in the cortex, CA1 hippocampal area and pituitary, recapitulating expression of egr-1. Transgene induction was stimulus-specific. Metrazole induced widespread expression in the dentate gyrus, CA2 and CA3 areas, amygdala, and ventromedial nucleus. In contrast, induction following a light stimulus was restricted to the hypothalamic suprachiasmatic and periventricular nuclei. Our studies have provided novel insights into the differential regulation of egr-1, and facilitated approaches to the genetic manipulation of Egr-1-regulated neuronal systems.

The pharmacokinetics of enalapril in children and infants with hypertension

Forty children with hypertension between the age of 2 months and 15 years received 0.07 to 0.14 mg/kg of enalapril as a single daily dose. Enalapril was administered orally as a novel extemporaneous suspension in children younger than 6 years of age and as tablets in older children. First-dose and steady-state pharmacokinetics were estimated in children ages 1 to 24 months, 25 months to < 6 years, 6 to < 12 years, and 12 to < 16 years. Maximum serum concentrations for enalapril occurred approximately 1 hour after administration. Serum concentrations of enalaprilat, the active metabolite of enalapril, peaked between 4 and 6 hours after the first dose and 3 and 4 hours after multiple doses. The area under the concentration versus time curve (AUC), adjusted for body surface area, did not differ between age groups. Based on comparison of first-dose and steady-state AUCs, the accumulation of enalaprilat in children ranged from 1.13- to 1.45-fold. For children ages 2 to 15 years, mean urinary recovery of total enalaprilat ranged from 58.3% in children ages 6 to < 12 years to 71.4% in children ages 12 to < 16 years. Urinary recovery for children ages 2 to < 6 years was 66.8%. The mean percentage conversion of enalapril to enalaprilat ranged from 64.7% for children ages 1 to 24 months to 74.6% for children ages 6 to < 12 years. The median effective half-life for accumulation ranged from 14.6 hours in children ages 12 to < 16 years to 16.3 hours in children ages 6 to < 12 years. There were two serious adverse events, neither of which was attributed to enalapril or resulted in discontinuation of the study drug. The extemporaneous suspension used in this study was tolerated well. The pharmacokinetics of enalapril and enalaprilat in hypertensive children ages 2 months to 15 years with normal renal function appears to be similar to that previously observed in healthy adults.

Genetic engineering of neural function in transgenic rodents: towards a comprehensive strategy?

As mammalian genome projects move towards completion, the attention of molecular neuroscientists is currently moving away from gene identification towards both cell-specific gene expression patterns (neuronal transcriptions) and protein expression/interactions (neuronal proteomics). In the long term, attention will increasingly be directed towards experimental interventions which are able to question neuronal function in a sophisticated manner that is cognisant of both transcriptomic and proteomic organization. Central to this effort will be the application of a new generation of transgenic approaches which are now evolving towards an appropriate level of molecular, temporal and spatial resolution. In this review, we summarize recent developments in transgenesis, and show how they have been applied in the principal model species for neuroscience, namely rats and mice. Current concepts of transgene design are also considered together with an overview of new genetically-encoded tools including both cellular indicators such as fluorescent activity reporters, and cellular regulators such as dominant negative signalling factors. Application of these tools in a whole animal context can be used to question both basic concepts of brain function, and also current concepts of underlying dysfuction in neurological diseases.

Single nucleotide polymorphism markers for genetic mapping in Drosophila melanogaster

For nearly a century, genetic analysis in Drosophila melanogaster has been a powerful tool for analyzing gene function, yet Drosophila lacks the molecular genetic mapping tools that recently have revolutionized human, mouse, and plant genetics. Here, we describe the systematic characterization of a dense set of molecular markers in Drosophila by using a sequence tagged site-based physical map of the genome. We identify 474 biallelic markers in standard laboratory strains of Drosophila that span the genome. Most of these markers are single nucleotide polymorphisms and sequences for these variants are provided in an accessible format. The average density of the new markers is one per 225 kb on the autosomes and one per megabase on the X chromosome. We include in this survey a set of P-element strains that provide additional use for high-resolution mapping. We show one application of the new markers in a simple set of crosses to map a mutation in the hedgehog gene to an interval of <1 Mb. This new map resource significantly increases the efficiency and resolution of recombination mapping and will be of immediate value to the Drosophila research community.

Tissue-specific transgenic knockdown of Fos-related antigen 2 (Fra-2) expression mediated by dominant negative Fra-2

Fos-related antigen 2 (Fra-2) is a member of the Fos family of immediate-early genes, most of which are rapidly induced by second messengers. All members of this family act by binding to AP-1 sites as heterodimeric complexes with other proteins. However, each appears to have a distinct role. The role and biology of Fra-2 are less well understood than those of its relatives c-Fos, Fra-1, and FosB; moreover, Fra-2 target genes remain largely unknown, as does the basis of its selective effects on transcriptional activity. To pursue these issues, we created a transgenic rat line (NATDNF2) in which a dominant negative fra-2 (DNF2) gene is strongly expressed in the pineal gland; tissue selectivity was achieved by putting the DNF2 gene under the control of the rat arylalkylamine N-acetyltransferase (AANAT) regulatory region, which targets gene expression to a very restricted set of tissues (pineal gland >> retina). Expression of AANAT is normally turned on after the onset of darkness in the rat; as a result, pineal DNF2 expression occurs only at night. This was associated with marked suppression of the nocturnal increase in fra-2 mRNA and protein levels, indicating that DNF2 expression inhibits downstream effects of Fra-2, including the maintenance of high levels of fra-2 gene expression. Analysis of 1,190 genes in the NATDNF2 pineal gland, including the AANAT gene, identified two whose expression is strongly linked to fra-2 expression: the genes encoding type II iodothyronine deiodinase and nectadrin (CD24).

Skeletal growth acceleration with growth hormone secretagogues in transgenic growth retarded rats: pattern-dependent effects and mechanisms of desensitization

The transgenic growth retarded (Tgr) rat is the first genetic model of growth hormone (GH) deficiency whose growth can be accelerated with exogenous GH secretagogues (GHSs). In this study, we have demonstrated that GHS-receptor (GHS-R) mRNA expression in the arcuate nucleus of Tgr rats was not significantly different to that in wild-type littermates. We have confirmed that GHS-induced elevation in body weight gain was accompanied by acceleration of skeletal growth, and that the effects of the GHS, GHRP-6, were both dose- and pattern-dependent. The growth response with continuous infusion of GHRP-6 was transient, accompanied by suppression of GH and corticosterone responses to bolus injection of GHRP-6. This desensitization occurred without downregulation of arcuate GHS-R mRNA expression, but was accompanied by elevated periventricular somatostatin mRNA expression. In contrast, pulsatile (3-hourly) infusion of GHRP-6 produced sustained growth and GH responses, which were accompanied by suppression of corticosterone responses and elevated arcuate GH-releasing factor (GRF) mRNA expression. Skeletal growth was further accelerated by coinfusion of GRF, but significant depletion of pituitary GH stores suggested that this growth rate may not be sustainable. These experiments confirm the importance of the Tgr rat for investigating the growth promoting potential of the GHSs in the context of GH-deficient dwarfism, and suggest that elevated somatostatin expression may mediate the suppression of the GRF-GH and hypothalamo-pituitary-adrenal axes following continuous GHRP-6 treatment.

Congenital abdominal aortic aneurysm in the infant: case report and review of the literature

Congenital abdominal aortic aneurysms are a distinct entity from acquired aortic aneurysms. The authors present the case of a 6-week-old boy with a 6-cm aneurysm involving the abdominal aorta and common iliac arteries. Three other cases of congenital aortic aneurysms are reviewed, and an approach to these rare patients is discussed. J Pediatr Surg 36:657-658.

Anti-arrhythmic effects of levcromakalim in the ischaemic rat heart: a dual mechanism of action?

The action of pharmacological openers of K(ATP) channels depends on the availability and levels of various intracellular nucleotides. Since these are subject to change during myocardial ischaemia, K(ATP) channel openers may affect ischaemic and non-ischaemic tissue differentially. Using a recently developed dual coronary perfusion method, we investigated the effects on arrhythmias of the prototypical K(ATP) channel opener levcromakalim when applied selectively to ischaemic and/or non-ischaemic tissue. A novel perfusion cannula was used to independently perfuse the left and right coronary beds of hearts isolated from rats. Selective infusion of levcromakalim (3, 10 or 30 microM) into the left coronary bed in the absence of ischaemia did not induce ventricular arrhythmias. Regional zero-flow ischaemia was induced by cessation of flow to the left coronary bed and hearts received levcromakalim selectively into either the left, right, or both coronary beds. When applied selectively to the ischaemic left coronary bed, levcromakalim (3, 10 or 30 microM; n=10/group) delayed the onset of ventricular tachycardia in a dose-dependent manner (by 21*, 43* and 112%* at 3, 10 and 30 microM; *P<0.05 vs. control). When applied only to the non-ischaemic right coronary bed, levcromakalim reduced the incidence of ventricular tachycardia during later phases of ischaemia (from 100% in controls to 30%*). When present in both coronary beds, levcromakalim had a striking anti-arrhythmic effect--the overall incidence of ventricular tachycardia being reduced from 100% in controls to 20%*. We conclude that levcromakalim may have an anti-arrhythmic effect when applied either to ischaemic or non-ischaemic tissue but that the mechanisms may differ depending on the metabolic state of the heart.

CCR5 provides a signal for microbial induced production of IL-12 by CD8 alpha+ dendritic cells

The activation of dendritic cells (DC) to produce interleukin 12 (IL-12) is thought to be a key step in the initiation of cell-mediated immunity to intracellular pathogens. Here we show that ligation of the C-C chemokine receptor (CCR) 5 can provide a major signal for the induction of IL-12 synthesis by the CD8 alpha+ subset of DC and that this pathway is important in establishing interferon gamma-dependent resistance to the protozoan parasite Toxoplasma gondii. These findings support the concept that the early induction of chemokines by invading pathogens is a critical step not only for the recruitment of DC but also for the determination of their subsequent immunologic function.