Frontiers in the Application of RF Vacuum Electronics.

The application of radio frequency (RF) vacuum electronics for the betterment of the human condition began soon after the invention of the first vacuum tubes in the 1920s and has not stopped since. Today, microwave vacuum devices are powering important applications in health treatment, material and biological science, wireless communication-terrestrial and space, Earth environment remote sensing, and the promise of safe, reliable, and inexhaustible energy. This article highlights some of the exciting application frontiers of vacuum electronics.

Fibroblast growth factor 10 is a negative regulator of postnatal neurogenesis in the mouse hypothalamus.

New neurons are generated in the postnatal rodent hypothalamus, with a subset of tanycytes in the third ventricular (3V) wall serving as neural stem/progenitor cells. However, the precise stem cell niche organization, the intermediate steps and the endogenous regulators of postnatal hypothalamic neurogenesis remain elusive. Quantitative lineage-tracing in vivo revealed that conditional deletion of fibroblast growth factor 10 (Fgf10) from Fgf10-expressing ß-tanycytes at postnatal days (P)4-5 results in the generation of significantly more parenchymal cells by P28, composed mostly of ventromedial and dorsomedial neurons and some glial cells, which persist into adulthood. A closer scrutiny in vivo and ex vivo revealed that the 3V wall is not static and is amenable to cell movements. Furthermore, normally ß-tanycytes give rise to parenchymal cells via an intermediate population of α-tanycytes with transient amplifying cell characteristics. Loss of Fgf10 temporarily attenuates the amplification of ß-tanycytes but also appears to delay the exit of their α-tanycyte descendants from the germinal 3V wall. Our findings suggest that transience of cells through the α-tanycyte domain is a key feature, and Fgf10 is a negative regulator of postnatal hypothalamic neurogenesis.

Tissue localization of retinoic acid receptor (RAR) active drugs.

The retinoic acid (RA) signaling pathway is crucial for the control of embryonic development and also regulates function of several organ systems in the adult, including the central nervous system. The retinoic acid receptors (RARs) that mediate the majority of the functions of RA can promote proliferation, differentiation, morphogenesis and cell survival. Dysregulation of this signaling pathway has been considered in the pathophysiology of various diseases including neurodegenerative disorders such Alzheimer's disease and amyotrophic lateral sclerosis. Thus, drugs targeted to the RARs have been proposed as treatments for such diseases. Understanding how these drugs distribute in the body is essential to determine their potential effectiveness. However measuring tissue levels of what are often lipophilic drugs can be difficult. Here we describe an indirect measurement of RAR ligand tissue distribution after intraperitoneal injection into rodents that uses a sensitive RA reporter cell line.

Characterisation of endogenous players in fibroblast growth factor-regulated functions of hypothalamic tanycytes and energy-balance nuclei.

The mammalian hypothalamus regulates key homeostatic and neuroendocrine functions ranging from circadian rhythm and energy balance to growth and reproductive cycles via the hypothalamic-pituitary and hypothalamic-thyroid axes. In addition to its neurones, tanycytes are taking centre stage in the short- and long-term augmentation and integration of diverse hypothalamic functions, although the genetic regulators and mediators of their involvement are poorly understood. Exogenous interventions have implicated fibroblast growth factor (FGF) signalling, although the focal point of the action of FGF and any role for putative endogenous players also remains elusive. We carried out a comprehensive high-resolution screen of FGF signalling pathway mediators and modifiers using a combination of in situ hybridisation, immunolabelling and transgenic reporter mice, aiming to map their spatial distribution in the adult hypothalamus. Our findings suggest that ß-tanycytes are the likely focal point of exogenous and endogenous action of FGF in the third ventricular wall, utilising FGF receptor (FGFR)1 and FGFR2 IIIc isoforms, but not FGFR3. Key IIIc-activating endogenous ligands include FGF1, 2, 9 and 18, which are expressed by a subset of ependymal and parenchymal cells. In the parenchymal compartment, FGFR1-3 show divergent patterns, with FGFR1 being predominant in neuronal nuclei and expression of FGFR3 being associated with glial cell function. Intracrine FGFs are also present, suggestive of multiple modes of FGF function. Our findings provide a testable framework for understanding the complex role of FGFs with respect to regulating the metabolic endocrine and neurogenic functions of hypothalamus in vivo.

Magnetic Mechanoactivation of Wnt Signaling Augments Dopaminergic Differentiation of Neuronal Cells.

Wnt signaling is a key developmental pathway that regulates dopaminergic progenitor cell proliferation and differentiation during neuronal development. This makes Wnt signaling an important therapeutic target for neurodegenerative conditions such as Parkinson's disease. Wnt signaling can be modulated using peptides such as UM206, which bind to the Wnt receptor Frizzled. Previous work has demonstrated remote activation of the Wnt pathway through Frizzled using peptide-functionalized magnetic nanoparticles (MNPs) with magnetic field stimulation. Using this technology, Wnt signaling is remotely activated in the neuronal cell line SH-SY5Y, and the phenotypic response to stimulation is assessed. Results indicate ß-catenin translocalization and activation of TCF/LEF responsive transcription in response to MNP and magnetic fields, which result in dopaminergic marker expression when synergistically combined with differentiation factors retinoic acid and the phorbol ester phorbol 12-myristate 13-acetate. This approach is translated into ex vivo postnatal rat brain slices modeling the developing nigrostriatal pathway. Dopaminergic marker expression is maintained in MNP-labeled SH-SY5Y cells after injection and magnetic stimulation. These results demonstrate the translational value of remote control of signal transduction for controlling neuronal precursor cell behavior and highlight the potential applications for controlled cell differentiation as part of cell therapies for neurodegenerative disease.

The effect of aspirin on circulating netrin-1 levels in humans is dependent on the inflammatory status of the vascular endothelium.

In atherosclerotic animal models, the cyclo-oxygenase (COX)-inhibitor aspirin counteracts downregulation of endothelial-derived netrin-1, thus reducing arterial inflammation. We here explored the effect of aspirin on netrin-1 in healthy subjects undergoing influenza immunisation, which is an established experimental model of inflammation-related endothelial dysfunction. Our data showed that netrin-1 undergoes reduction (-29.25% from baseline; p=0.0017) in the presence of endothelial activation (VCAM-1 rose by 9.98% 2-days post-vaccination; p=0.0022). Aspirin counteracted vaccine-induced endothelial activation and reduction of netrin-1 in a dose-dependent manner (-3.06% and -17.03% from baseline at a dose of 300mg and 75mg respectively; p=0.0465 and p>0.05 vs untreated). Clopidogrel, which was used as a comparator due to its similar anti-platelet activity, also reduced endothelial activation but, unlike aspirin, enhanced netrin-1 levels (+20.96% from baseline; p=0.0033 vs untreated). A correlation analysis incorporating cytokines, hs-CRP, VCAM-1, TXB2 and PGE2, showed that changes in netrin-1 were directly related to PGE2 variations only (r=0.6103; p=0.0002). In a separate population of 40 healthy unimmunised volunteers, 28-day treatment with aspirin 300mg reduced netrin-1 (-18.76% from baseline; p=0.0012) without affecting endothelial markers or hs-CRP; as expected, aspirin suppressed TXB2 and PGE2. Netrin-1 and PGE2 levels were directly related (r=0.358; p=0.0015), but other parameters including TXB2, hs-CRP and endothelial markers, were not. In conclusion, aspirin counteracts downregulation of netrin-1 following endothelial dysfunction due to its anti-inflammatory effect on the activated endothelium. However, inhibition of COX-dependent prostanoids negatively modulates netrin-1 synthesis in healthy subjects, and this could give rise to aspirin-dependent reduction in netrin-1 under steady state conditions.

Interrogation of a lacrimo-auriculo-dento-digital syndrome protein reveals novel modes of fibroblast growth factor 10 (FGF10) function.

Heterozygous mutations in the gene encoding fibroblast growth factor 10 (FGF10) or its cognate receptor, FGF-receptor 2 IIIb result in two human syndromes - LADD (lacrimo-auriculo-dento-digital) and ALSG (aplasia of lacrimal and salivary glands). To date, the partial loss-of-FGF10 function in these patients has been attributed solely to perturbed paracrine signalling functions between FGF10-producing mesenchymal cells and FGF10-responsive epithelial cells. However, the functioning of a LADD-causing G138E FGF10 mutation, which falls outside its receptor interaction interface, has remained enigmatic. In the present study, we interrogated this mutation in the context of FGF10's protein sequence and three-dimensional structure, and followed the subcellular fate of tagged proteins containing this or other combinatorial FGF10 mutations, in vitro We report that FGF10 harbours two putative nuclear localization sequences (NLSs), termed NLS1 and NLS2, which individually or co-operatively promote nuclear translocation of FGF10. Furthermore, FGF10 localizes to a subset of dense fibrillar components of the nucleolus. G138E falls within NLS1 and abrogates FGF10's nuclear translocation whilst attenuating its progression along the secretory pathway. Our findings suggest that in addition to its paracrine roles, FGF10 may normally play intracrine role/s within FGF10-producing cells. Thus, G138E may disrupt both paracrine and intracrine function/s of FGF10 through attenuated secretion and nuclear translocation, respectively.

Expression of the retinoic acid catabolic enzyme CYP26B1 in the human brain to maintain signaling homeostasis.

Retinoic acid (RA) is a potent regulator of gene transcription via its activation of a set of nuclear receptors controlling transcriptional activation. Precise maintenance of where and when RA is generated is essential and achieved by local expression of synthetic and catabolic enzymes. The catabolic enzymes Cyp26a1 and Cyp26b1 have been studied in detail in the embryo, where they limit gradients of RA that form patterns of gene expression, crucial for morphogenesis. This paracrine role of RA has been assumed to occur in most tissues and that the RA synthetic enzymes release RA at a site distant from the catabolic enzymes. In contrast to the embryonic CNS, relatively little is known about RA metabolism in the adult brain. This study investigated the distribution of Cyp26a1 and Cyp26b1 transcripts in the rat brain, identifying several novel regions of expression, including the cerebral cortex for both enzymes and striatum for Cyp26b1. In vivo use of a new and potent inhibitor of the Cyp26 enzymes, ser 2-7, demonstrated a function for endogenous Cyp26 in the brain and that hippocampal RA levels can be raised by ser 2-7, altering the effect of RA on differential patterning of cell proliferation in the hippocampal region of neurogenesis, the subgranular zone. The expression of CYP26A1 and CYP26B1 was also investigated in the adult human brain and colocalization of CYP26A1 and the RA synthetic enzyme RALDH2 indicated a different, autocrine role for RA in human hippocampal neurons. Studies with the SH-SY5Y human neuroblastoma cell line implied that the co-expression of RA synthetic and catabolic enzymes maintains retinoid homeostasis within neurons. This presents a novel view of RA in human neurons as part of an autocrine, intracellular signaling system.

Hypothalamic tanycytes-masters and servants of metabolic, neuroendocrine, and neurogenic functions.

There is a resurgent interest in tanycytes, a radial glial-like cell population occupying the floor and ventro-lateral walls of the third ventricle (3V). Tanycytes reside in close proximity to hypothalamic neuronal nuclei that regulate appetite and energy expenditure, with a subset sending projections into these nuclei. Moreover, tanycytes are exposed to 3V cerebrospinal fluid and have privileged access to plasma metabolites and hormones, through fenestrated capillaries. Indeed, some tanycytes act as conduits for trafficking of these molecules into the brain parenchyma. Tanycytes can also act as neural stem/progenitor cells, supplying the postnatal and adult hypothalamus with new neurons. Collectively, these findings suggest that tanycytes regulate and integrate important trophic and metabolic processes and possibly endow functional malleability to neuronal circuits of the hypothalamus. Hence, manipulation of tanycyte biology could provide a valuable tool for modulating hypothalamic functions such as energy uptake and expenditure in order to tackle prevalent eating disorders such as obesity and anorexia.

Increased platelet expression of glycoprotein IIIa following aspirin treatment in aspirin-resistant but not aspirin-sensitive subjects.

AIMS: Aspirin is widely used as an anti-platelet agent for cardiovascular prophylaxis. Despite aspirin treatment, many patients experience recurrent thrombotic events, and aspirin resistance may contribute to this. We examined the prevalence of aspirin resistance in a healthy population, and investigated whether the platelet proteome differed in aspirin-resistant subjects. METHODS: Ninety-three healthy subjects received aspirin 300 mg daily for 28 days. Before and at the end of treatment, urine was taken to determine 11-dehydrothromboxane B2 , and blood was taken to measure arachidonic acid (AA)-induced aggregation of platelet-rich plasma and to interrogate the platelet proteome by mass spectrometric analysis with further confirmation of findings using Western blotting. RESULTS: In two of the 93 subjects, neither AA-induced aggregation nor urinary 11-dehydrothromboxane B2 was effectively suppressed by aspirin, despite measurable plasma salicylate concentrations, suggesting the presence of true aspirin resistance. Despite no detectable differences in the platelet proteome at baseline, following aspirin a marked increase was seen in platelet glycoprotein IIIa expression in the aspirin-resistant but not aspirin-sensitive subjects. An increase in platelet glycoprotein IIIa expression with aspirin resistance was confirmed in a separate cohort of 17 patients with stable coronary artery disease on long term aspirin treatment, four of whom exhibited aspirin resistance. CONCLUSIONS: In a healthy population, true aspirin resistance is uncommon but exists. Resistance is associated with an increase in platelet glycoprotein IIIa expression in response to aspirin. These data shed new light on the mechanism of aspirin resistance, and provide the potential to identify aspirin-resistant subjects using a novel biomarker.

Fgf10-expressing tanycytes add new neurons to the appetite/energy-balance regulating centers of the postnatal and adult hypothalamus.

Increasing evidence suggests that neurogenesis occurs in the postnatal and adult mammalian hypothalamus. However, the identity and location of the putative progenitor cells is under much debate, and little is known about the dynamics of neurogenesis in unchallenged brain. Previously, we postulated that Fibroblast growth factor 10-expressing (Fgf10(+)) tanycytes constitute a population of progenitor cells in the mouse hypothalamus. Here, we show that Fgf10(+) tanycytes express markers of neural stem/progenitor cells, divide late into postnatal life, and can generate both neurons and astrocytes in vivo. Stage-specific lineage-tracing of Fgf10(+) tanycytes using Fgf10-creERT2 mice, reveals robust neurogenesis at postnatal day 28 (P28), lasting as late as P60. Furthermore, we present evidence for amplification of Fgf10-lineage traced neural cells within the hypothalamic parenchyma itself. The neuronal descendants of Fgf10(+) tanycytes predominantly populate the arcuate nucleus, a subset of which express the orexigenic neuronal marker, Neuropeptide-Y, and respond to fasting and leptin-induced signaling. These studies provide direct evidence in support of hypothalamic neurogenesis during late postnatal and adult life, and identify Fgf10(+) tanycytes as a source of parenchymal neurons with putative roles in appetite and energy balance.

Patterning of retinoic acid signaling and cell proliferation in the hippocampus.

The nuclear receptor ligand retinoic acid (RA) has been identified as an endogenous regulatory factor in the hippocampus, acting on pyramidal neurons and granule neuron progenitors, but almost nothing is known about the distribution of RA itself in the hippocampus. This study describes the source of RA for the rodent hippocampus in the meninges via the key RA synthetic enzyme retinaldehyde dehydrogenase 2 (RALDH2). Diffusion of RA from the meninges potentially creates a gradient of RA across the infrapyramidal and suprapyramidal blades of the dentate gyrus, enhanced by the expression of the RA catabolic enzyme Cyp26B1 between the blades, and an infrapyramidal and suprapyramidal blade difference is evident in RA-regulated transcription. This asymmetry may contribute to some of the physiological and molecular differences between the blades, including a disparity in the rates of cell proliferation in the subgranular zone of the two blades through RA inhibition of cell proliferation. Such differences can be altered by either the application of excess RA, its effect dependent on the relative position along the septotemporal axis, or change in RA signaling through mutation of retinol binding protein, while the capacity of RA to inhibit proliferation of cells in the dentate gyrus is demonstrated using in vitro slice culture. Use of synthetic and catabolic enzymes in the hippocampus to create differing zones of RA concentration parallels the mechanisms used in the developing brain to generate patterns of RA-regulated transcription.

Photoperiod regulates vitamin A and Wnt/ß-catenin signaling in F344 rats.

In seasonal mammals, growth, energy balance, and reproductive status are regulated by the neuroendocrine effects of photoperiod. Thyroid hormone (TH) is a key player in this response in a number of species. A neuroendocrine role for the nutritional factor vitamin A has not been considered, although its metabolic product retinoic acid (RA) regulates transcription via the same nuclear receptor family as TH. We hypothesized that vitamin A/RA plays a role in the neuroendocrine hypothalamus alongside TH signaling. Using a reporter assay to measure RA activity, we demonstrate that RA activity levels in the hypothalamus of photoperiod-sensitive F344 rats are reduced in short-day relative to long-day conditions. These lower RA activity levels can be explained by reduced expression of a whole network of RA signaling genes in the ependymal cells around the third ventricle and in the arcuate nucleus of the hypothalamus. These include genes required for uptake (Ttr, Stra6, and Crbp1), synthesis (Raldh1), receptor response (RAR), and ligand clearance (Crapb1 and Cyp26B1). Using melatonin injections into long-day rats, we show that the probable trigger of the fall in RA is melatonin. Surprisingly we also found RPE65 expression in the mammalian hypothalamus for the first time. Similar to RA signaling genes, members of the Wnt/ß-catenin pathway and NMU and its receptor NMUR2 are also under photoperiodic control. Our data provide strong evidence for a novel endocrine axis, involving the nutrient vitamin A regulated by photoperiod and melatonin and suggest a role for several new players in the photoperiodic neuroendocrine response.

Retinoic acid influences neuronal migration from the ganglionic eminence to the cerebral cortex.

The ganglionic eminence contributes cells to several forebrain structures including the cerebral cortex, for which it provides GABAergic interneurons. Migration of neuronal precursors from the retinoic-acid rich embryonic ganglionic eminence to the cerebral cortex is known to be regulated by several factors, but retinoic acid has not been previously implicated. We found retinoic acid to potently inhibit cell migration in slice preparations of embryonic mouse forebrains, which was reversed by an antagonist of the dopamine-D(2) receptor, whose gene is transcriptionally regulated by retinoic acid. Histone-deacetylase inhibitors, which amplify nuclear receptor-mediated transcription, potentiated the inhibitory effect of retinoic acid. Surprisingly, when retinoic acid signalling was completely blocked with a pan-retinoic acid receptor antagonist, this also decreased cell migration into the cortex, implying that a minimal level of endogenous retinoic acid is necessary for tangential migration. Given these opposing effects of retinoic acid in vitro, the in vivo contribution of retinoic acid to migration was tested by counting GABAergic interneurons in cortices of adult mice with experimental reductions in retinoic acid signalling: a range of perturbations resulted in significant reductions in the numerical density of some GABAergic interneuron subpopulations. These observations suggest functions of retinoic acid in interneuron diversity and organization of cortical excitatory-inhibitory balance.

Photoperiodic regulation of retinoic acid signaling in the hypothalamus.

Both retinoic acid (RA) and thyroid hormone (TH) regulate transcription via specific nuclear receptors. TH regulates hypothalamic homeostasis and active T3 is generated by deiodinase enzymes in tanycytes surrounding the third ventricle. However, RA has not been previously considered in such a role. Data presented here highlights novel parallels between the TH and RA synthetic pathways in the hypothalamus implying that RA also acts to regulate hypothalamic gene expression and function. Key elements of the RA cellular signaling pathway were shown to be regulated in the rodent hypothalamus. Retinoid synthetic enzymes and the retinol transport protein Stra6 were located in the cells lining the third ventricle allowing synthesis of RA from retinol present in the CNS to act via RA receptors and retinoid X receptors in the hypothalamus. Photoperiod manipulation was shown to alter the expression of synthetic enzymes and receptors with lengthening of photoperiod leading to enhanced RA signaling. In vitro RA can regulate the hypothalamic neuroendocrine peptide adrenocorticotrophic hormone. This work presents the new concept of controlled RA synthesis by hypothalamic tanycytes giving rise to possible involvement of this system in endocrine, and possibly vitamin A, homeostasis.

High-throughput linkage analysis of Mutator insertion sites in maize.

Insertional mutagenesis is a cornerstone of functional genomics. High-copy transposable element systems such as Mutator (Mu) in maize (Zea mays) afford the advantage of high forward mutation rates but pose a challenge for identifying the particular element responsible for a given mutation. Several large mutant collections have been generated in Mu-active genetic stocks, but current methods limit the ability to rapidly identify the causal Mu insertions. Here we present a method to rapidly assay Mu insertions that are genetically linked to a mutation of interest. The method combines elements of MuTAIL (thermal asymmetrically interlaced) and amplification of insertion mutagenized sites (AIMS) protocols and is applicable to the analysis of single mutants or to high-throughput analyses of mutant collections. Briefly, genomic DNA is digested with a restriction enzyme and adapters are ligated. Polymerase chain reaction is performed with TAIL cycling parameters, using a fluorescently labeled Mu primer, which results in the preferential amplification and labeling of Mu-containing genomic fragments. Products from a segregating line are analyzed on a capillary sequencer. To recover a fragment of interest, PCR products are cloned and sequenced. Sequences with lengths matching the size of a band that co-segregates with the mutant phenotype represent candidate linked insertion sites, which are then confirmed by PCR. We demonstrate the utility of the method by identifying Mu insertion sites linked to seed-lethal mutations with a preliminary success rate of nearly 50%.

Handling technology of Mega-Watt millimeter-waves for optimized heating of fusion plasmas.

Millimeter-wave components were re-examined for high power (Mega-Watt) and steady-state (greater than one hour) operation. Some millimeter-wave components, including waveguide joints, vacuum pumping sections, power monitors, sliding waveguides, and injection windows, have been improved for high power CW (Continuous Waves) transmission. To improve transmission efficiency, information about the wave phase and mode content of high power millimeter-waves propagating in corrugated waveguides, which are difficult to measure directly, were obtained by a newly developed method based on retrieved phase information. To optimize the plasma heating efficiency, a proof-of-principle study of the injection polarization feedback control was performed in the low power test stand.

Pharmacogenetics of aspirin resistance: a comprehensive systematic review.

AIMS: The aim was to perform a systematic review of all candidate gene association studies in aspirin resistance. METHODS: Electronic databases were searched up until 1 December 2007 for all studies investigating any candidate gene for aspirin resistance in humans. Aspirin resistance was required to have been measured by a standardized laboratory technique to be included in the analysis. RESULTS: Within 31 studies, 50 polymorphisms in 11 genes were investigated in 2834 subjects. The PlA1/A2 polymorphism in the GPIIIa platelet receptor was the most frequently investigated, with 19 studies in 1389 subjects. The PlA1/A2 variant was significantly associated with aspirin resistance when measured in healthy subjects [odds ratio (OR) 2.36, 95% confidence interval (CI) 1.24, 4.49; P = 0.009]. Combining genetic data from all studies (comprising both healthy subjects and those with cardiovascular disease) reduced the observed effect size (OR 1.14, 95% CI 0.84, 1.54; P = 0.40). Moreover, the observed effect of PlA1/A2 genotype varied depending on the methodology used for determining aspirin sensitivity/resistance. No significant association was found with aspirin resistance in four other investigated polymorphisms in the COX-1, GPla, P2Y1 or P2Y12 genes. CONCLUSIONS: Our data support a genetic association between the PlA1/A2 molecular variant and aspirin resistance in healthy subjects, with the effect diminishing in the presence of cardiovascular disease. The laboratory methodology used influences the detection of aspirin resistance. However, as heterogeneity was significant and our results are based on a limited number of studies, further studies are required to confirm our findings.

The genetics of aspirin resistance.

Aspirin is widely used for the prophylaxis of cardiovascular events in patients with cardiovascular risk factors or established atherosclerotic disease. However, despite aspirin treatment, a substantial number of patients experience recurrent events. Such 'aspirin resistance' is generally defined as failure of aspirin to produce an expected biological response, for example inhibition of platelet aggregation or of thromboxane A2 synthesis. Whilst its aetiology is multifactorial, genetic factors are also likely to play their part. Here we review the evidence for and against such a genetic contribution, as well as the data suggesting the involvement of specific genes.

Is there a right to health?

This article challenges the widespread contention-promoted by the World Health Organization, the U.N. Human Rights Commission, and certain non-governmental organizations-that health care should be regarded as an individual human right. Like other "post-modern" rights, the asserted individual right to health care is a positive claim on the resources of others; it is unlimited by corresponding responsibilities; and it pertains exclusively to the individual. In fact, an individual human right to health, enforceable against either governments or corporations, does not currently exist in law. If established, such a right would portend a dramatic expansion of government control over health care, with negative consequences for efficiency and patient welfare. Voluntary efforts based on partnership, rather than the imposition of legal requirements, are the most productive means of expanding access to health care while preserving incentives for continued development of innovative health technologies.