A lamprey neural cell type atlas illuminates the origins of the vertebrate brain

The vertebrate brain emerged more than ~500 million years ago in common evolutionary ancestors. To systematically trace its cellular and molecular origins, we established a spatially resolved cell type atlas of the entire brain of the sea lamprey-a jawless species whose phylogenetic position affords the reconstruction of ancestral vertebrate traits-based on extensive single-cell RNA-seq and in situ sequencing data. Comparisons of this atlas to neural data from the mouse and other jawed vertebrates unveiled various shared features that enabled the reconstruction of cell types, tissue structures and gene expression programs of the ancestral vertebrate brain. However, our analyses also revealed key tissues and cell types that arose later in evolution. For example, the ancestral brain was probably devoid of cerebellar cell types and oligodendrocytes (myelinating cells); our data suggest that the latter emerged from astrocyte-like evolutionary precursors in the jawed vertebrate lineage. Altogether, our work illuminates the cellular and molecular architecture of the ancestral vertebrate brain and provides a foundation for exploring its diversification during evolution.

Evolution of a chordate-specific mechanism for myoblast fusion

Vertebrate myoblast fusion allows for multinucleated muscle fibers to compound the size and strength of mononucleated cells, but the evolution of this important process is unknown. We investigated the evolutionary origins and function of membrane-coalescing agents Myomaker and Myomixer in various groups of chordates. Here, we report that Myomaker likely arose through gene duplication in the last common ancestor of tunicates and vertebrates, while Myomixer appears to have evolved de novo in early vertebrates. Functional tests revealed a complex evolutionary history of myoblast fusion. A prevertebrate phase of muscle multinucleation driven by Myomaker was followed by the later emergence of Myomixer that enables the highly efficient fusion system of vertebrates. Evolutionary comparisons between vertebrate and nonvertebrate Myomaker revealed key structural and mechanistic insights into myoblast fusion. Thus, our findings suggest an evolutionary model of chordate fusogens and illustrate how new genes shape the emergence of novel morphogenetic traits and mechanisms.

Sex Differences in Internalizing Symptoms and Amygdala Functional Connectivity in Neurotypical Youth

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Internalizing symptoms in neurotypical youth relate to amygdala connectivity.

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Greater modulation is observed in females than in males.

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Connectivity might be a symptom of or a risk factor for disorders.

Amygdala resting-state functional connectivity (rsFC) is altered in adolescents with internalizing disorders, though the relationship between rsFC and subclinical symptomatology in neurotypical youth remains unclear. Here we examined whether amygdala rsFC varied across a continuum of internalizing symptoms in 110 typically-developing (TD) youths 8 to 17 years old using functional magnetic resonance imaging (fMRI). We assessed overall internalizing symptoms, as well as anxious-depressed, withdrawn-depressed, and somatic complaints. Given known sex differences in the prevalence of internalizing disorders, we compared connectivity between males and females. As compared to males, females with greater internalizing, anxious-depressed, and somatic symptoms displayed greater connectivity with the cingulate gyrus, insula, and somatosensory cortices. In contrast, males with greater anxious-depressed symptoms demonstrated weaker connectivity with the subcallosal prefrontal cortex. Sex differences in rsFC in relation to symptom severity were evident for the whole amygdala and for two of its subnuclei (centromedial and superficial amygdala). Overall, results suggest that, for females, higher internalizing symptoms are associated with greater rsFC between the amygdala and regions implicated in emotional and somatosensory processing, salience detection, and action selection. Future longitudinal investigations are needed to determine whether this hyperconnectivity may confer resilience to, or pose risk for, the development of internalizing disorders.

A genome-wide assessment of the ancestral neural crest gene regulatory network

The neural crest (NC) is an embryonic cell population that contributes to key vertebrate-specific features including the craniofacial skeleton and peripheral nervous system. Here we examine the transcriptional and epigenomic profiles of NC cells in the sea lamprey, in order to gain insight into the ancestral state of the NC gene regulatory network (GRN). Transcriptome analyses identify clusters of co-regulated genes during NC specification and migration that show high conservation across vertebrates but also identify transcription factors (TFs) and cell-adhesion molecules not previously implicated in NC migration. ATAC-seq analysis uncovers an ensemble of cis-regulatory elements, including enhancers of Tfap2B, SoxE1 and Hox-α2 validated in the embryo. Cross-species deployment of lamprey elements identifies the deep conservation of lamprey SoxE1 enhancer activity, mediating homologous expression in jawed vertebrates. Our data provide insight into the core GRN elements conserved to the base of the vertebrates and expose others that are unique to lampreys.

Barriers and facilitators to the successful development, implementation and evaluation of care bundles in acute care in hospital: a scoping review

Background

Care bundles are small sets of evidence-based recommendations, designed to support the implementation of evidence-based best clinical practice. However, there is variation in the design and implementation of care bundles, which may impact on the fidelity of delivery and subsequently their clinical effectiveness.

Methods

A scoping review was carried out using the Arksey and O’Malley framework to identify the literature reporting on the design, implementation and evaluation of care bundles. The Embase, CINAHL, Cochrane and Ovid MEDLINE databases were searched for manuscripts published between 2001 and November 2017; hand-searching of references and citations was also undertaken. Data were initially assessed using a quality assessment tool, the Downs and Black checklist, prior to further analysis and narrative synthesis. Implementation strategies were classified using the Expert Recommendations for Implementing Change (ERIC) criteria.

Results

Twenty-eight thousand six hundred ninety-two publications were screened and 348 articles retrieved in full text. Ninety-nine peer-reviewed quantitative publications were included for data extraction. These consisted of one randomised crossover trial, one randomised cluster trial, one case-control study, 20 prospective cohort studies and 76 non-parallel cohort studies. Twenty-three percent of studies were classified as poor based on Downs and Black checklist, and reporting of implementation strategies lacked structure.

Negative associations were found between the number of elements in a bundle and compliance (Spearman’s rho = − 0.47, non-parallel cohort and − 0.65, prospective cohort studies), and between the complexity of elements and compliance (p < 0.001, chi-squared = 23.05). Implementation strategies associated with improved compliance included evaluative and iterative approaches, development of stakeholder relationships and education and training strategies.

Conclusion

Care bundles with a small number of simple elements have better compliance rates. Standardised reporting of implementation strategies may help to implement care bundles into clinical practice with high fidelity.

Trial Registration

This review was registered on the PROSPERO database: CRD 42015029963 in December 2015.

Electronic supplementary material

The online version of this article (10.1186/s13012-019-0894-2) contains supplementary material, which is available to authorized users.

Single-dose fosaprepitant for the prevention of chemotherapy-induced nausea and vomiting associated with moderately emetogenic chemotherapy: results of a randomized, double-blind phase III trial

BACKGROUND

To establish the role of antiemetic therapy with neurokinin-1 (NK1) receptor antagonists (RAs) in nonanthracycline and cyclophosphamide (AC)-based moderately emetogenic chemotherapy (MEC) regimens, this study evaluated single-dose intravenous (i.v.) fosaprepitant for the prevention of chemotherapy-induced nausea and vomiting (CINV) associated with non-AC MEC.

PATIENTS AND METHODS

In this international, phase III, double-blind trial, adult cancer subjects scheduled to receive ≥1 non-AC MEC on day 1 were randomized to a regimen comprising single-dose i.v. fosaprepitant 150 mg or placebo along with ondansetron and dexamethasone on day 1; control regimen recipients received ondansetron on days 2 and 3. Primary end points were the proportion of subjects achieving a complete response (CR; no vomiting and no use of rescue medication) in the delayed phase (25-120 h after MEC initiation) and safety. Secondary end points included CR in the overall and acute phases (0-120 and 0-24 h after MEC initiation, respectively) and no vomiting in the overall phase. Nausea and the Functional Living Index-Emesis were assessed as exploratory end points.

RESULTS

The fosaprepitant regimen improved CR significantly in the delayed (78.9% versus 68.5%; P < 0.001) and overall (77.1% versus 66.9%; P < 0.001) phases, but not in the acute phase (93.2% versus 91.0%; P = 0.184), versus control. In the overall phase, the proportion of subjects with no vomiting (82.7% versus 72.9%; P < 0.001) and no significant nausea (83.2% versus 77.9%; P = 0.030) was also significantly improved with the fosaprepitant regimen. The fosaprepitant regimen was generally well tolerated.

CONCLUSION

Single-dose fosaprepitant added to a 5-HT3 RA and dexamethasone was well tolerated and demonstrated superior control of CINV (primary end point achieved) associated with non-AC MEC. This is the first study to evaluate NK1 RA therapy as an i.v. formulation in a well-defined non-AC MEC population.

CLINICALTRIALSGOV

NCT01594749 (https://clinicaltrials.gov/ct2/show/NCT01594749).

A retrospective analysis of the cost of hospitalizations for sickle cell disease with crisis in England, 2010/11

BACKGROUND

Sickle cell disease (SCD) is an inherited blood disorder which may result in a broad range of complications including recurring and severe episodes of pain--sickle 'crises'--which require frequent hospitalizations. We assessed the cost of hospitalizations associated with SCD with crisis in England.

METHODS

Hospital Episodes Statistics data for all hospital episodes in England between 2010 and 2011 recording Sickle Cell Anaemia with Crisis as primary diagnosis were used. The total cost of admissions and exceeded length of stay due to SCD were assessed using Healthcare Resource Groups tariffs. The impact of patients' characteristics on SCD admissions costs and the likelihood of incurring extra bed days were also examined.

RESULTS

In 2010-11, England had 6077 admissions associated with SCD with crisis as primary diagnosis. The total cost for these admissions for commissioners was £18,798 255. The cost of admissions increases with age (children admissions costs 50% less than adults). Patients between 10 and 19 years old are more likely to stay longer in hospital compared with others.

CONCLUSION

SCD represents a significant cost for commissioners and the NHS. Further work is required to assess how best to manage patients in the community, which could potentially lead to a reduction in hospital admissions and length of stay, and their associated costs.

The lamprey: a jawless vertebrate model system for examining origin of the neural crest and other vertebrate traits

Lampreys are a group of jawless fishes that serve as an important point of comparison for studies of vertebrate evolution. Lampreys and hagfishes are agnathan fishes, the cyclostomes, which sit at a crucial phylogenetic position as the only living sister group of the jawed vertebrates. Comparisons between cyclostomes and jawed vertebrates can help identify shared derived (i.e. synapomorphic) traits that might have been inherited from ancestral early vertebrates, if unlikely to have arisen convergently by chance. One example of a uniquely vertebrate trait is the neural crest, an embryonic tissue that produces many cell types crucial to vertebrate features, such as the craniofacial skeleton, pigmentation of the skin, and much of the peripheral nervous system (Gans and Northcutt, 1983). Invertebrate chordates arguably lack unambiguous neural crest homologs, yet have cells with some similarities, making comparisons with lampreys and jawed vertebrates essential for inferring characteristics of development in early vertebrates, and how they may have evolved from nonvertebrate chordates. Here we review recent research on cyclostome neural crest development, including research on lamprey gene regulatory networks and differentiated neural crest fates.

FGF signaling induces mesoderm in the hemichordate Saccoglossus kowalevskii

FGFs act in vertebrate mesoderm induction and also play key roles in early mesoderm formation in ascidians and amphioxus. However, in sea urchins initial characterizations of FGF function do not support a role in early mesoderm induction, making the ancestral roles of FGF signaling and mechanisms of mesoderm specification in deuterostomes unclear. In order to better characterize the evolution of mesoderm formation, we have examined the role of FGF signaling during mesoderm development in Saccoglossus kowalevskii, an experimentally tractable representative of hemichordates. We report the expression of an FGF ligand, fgf8/17/18, in ectoderm overlying sites of mesoderm specification within the archenteron endomesoderm. Embryological experiments demonstrate that mesoderm induction in the archenteron requires contact with ectoderm, and loss-of-function experiments indicate that both FGF ligand and receptor are necessary for mesoderm specification. fgf8/17/18 gain-of-function experiments establish that FGF8/17/18 is sufficient to induce mesoderm in adjacent endomesoderm. These experiments suggest that FGF signaling is necessary from the earliest stages of mesoderm specification and is required for all mesoderm development. Furthermore, they suggest that the archenteron is competent to form mesoderm or endoderm, and that FGF signaling from the ectoderm defines the location and amount of mesoderm. When considered in a comparative context, these data support a phylogenetically broad requirement for FGF8/17/18 signaling in mesoderm specification and suggest that FGF signaling played an ancestral role in deuterostome mesoderm formation.

Gene duplications and the early evolution of neural crest development

Neural crest cells are an important cell type present in all vertebrates, and elaboration of the neural crest is thought to have been a key factor in their evolutionary success. Genomic comparisons suggest there were two major genome duplications in early vertebrate evolution, raising the possibility that evolution of neural crest was facilitated by gene duplications. Here, we review the process of early neural crest formation and its underlying gene regulatory network (GRN) as well as the evolution of important neural crest derivatives. In this context, we assess the likelihood that gene and genome duplications capacitated neural crest evolution, particularly in light of novel data arising from invertebrate chordates.

Detection and separation of gas-phase carbon-centered radicals from cigarette smoke and diesel exhaust

Carbon-centered radicals were trapped from gas-phase cigarette smoke and diesel engine exhaust by reaction with a nitroxide, 3-amino-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (3AP). The resulting mixture of stable, diamagnetic adducts was derivatized with naphthalenedicarboxaldehyde (NDA) to produce highly fluorescent products. Derivatives were separated by high-performance liquid chromatography (HPLC), which revealed distinctly different suites of radicals present in the two systems. Integration of HPLC peaks gave approximately 22 ± 7 nmol of radicals per cigarette and 3 ± 1 nmol of radicals per liter of diesel engine exhaust. An estimated 8-10 different carbon-centered radical species are present in each system.

Diversification of the expression patterns and developmental functions of the dishevelled gene family during chordate evolution

Dishevelled (Dvl) proteins are key transducers of Wnt signaling encoded by members of a multi-gene family in vertebrates. We report here the divergent, tissue-specific expression patterns for all three Dvl genes in Xenopus embryos, which contrast dramatically with their expression patterns in mice. Moreover, we find that the expression patterns of Dvl genes in the chick diverge significantly from those of Xenopus. In addition, in hemichordates, an outgroup to chordates, we find that the one Dvl gene is dynamically expressed in a tissue-specific manner. Using knockdowns, we find that Dvl1 and Dvl2 are required for early neural crest specification and for somite segmentation in Xenopus. Most strikingly, we report a novel role for Dvl3 in the maintenance of gene expression in muscle and in the development of the Xenopus sclerotome. These data demonstrate that the expression patterns and developmental functions of specific Dvl genes have diverged significantly during chordate evolution.

An oral selective M3 cholinergic receptor antagonist in COPD

Cholinergic antagonists have been used since the early 1900s as bronchodilators for chronic obstructive pulmonary disease (COPD). The present study investigated whether an oral muscarinic M3-selective anticholinergic agent (OrM3) would provide an improved therapeutic advantage compared with an inhaled anticholinergic agent in patients with COPD. A 6-week, multicentre, randomised, placebo- and active-controlled, parallel-group study was performed at 56 sites in the USA. In total, 412 male and female patients (aged 35-86 yrs) with a clinical history consistent with COPD were randomised to receive OrM3 0.5, 2, 3 or 4 mg orally once daily, ipratropium bromide 36 mug by inhalation four times daily or placebo. OrM3 demonstrated a significant dose-related improvement in serial forced expiratory volume in one second and a trend for dose-related improvement in patient-reported symptoms compared with placebo. However, at a dose that provided efficacy less than that of ipratropium, the incidence of dose-related, mechanism-based side-effects for OrM3 exceeded those observed for ipratropium. In patients with chronic obstructive pulmonary disease, the oral M3-selective agent did not offer a therapeutic advantage over inhaled ipratropium. These results do not support the hypothesis that high selectivity for muscarinic M3 receptors over airway neuronal M2 receptors will represent a more effective therapy than current inhaled anticholinergics in obstructive airway disease.

Daily timed melatonin feedings mimic effects of short days on testis regression and cortisol in circulation in Siberian hamsters

This study tested the efficacy of timed oral administration of melatonin as an alternative both to invasive methods (daily injections, timed infusions) and to untimed oral administration in Siberian hamsters (Phodopus sungorus), an important model for the study of photoperiodism. Hamsters readily consumed a small piece of melatonin-treated apple immediately when presented and circulating melatonin was rapidly elevated with a half-life of approximately 3.5 h. Melatonin-treated apple was fed to hamsters for 3 weeks at 2 h before lights off to extend the duration of the nighttime rise in endogenous melatonin. Melatonin treatment induced testicular regression and elevated serum cortisol, effects comparable to those in hamsters exposed to short days. These findings support the hypothesis that timed oral administration of melatonin can mimic the effects of short days and provide a method by which melatonin can be delivered without the potentially confounding effects of handling and injection stress.

An ethical framework for psychiatry

Psychiatry has not reached a consensus hitherto concerning an optimal theoretical framework for ethical decision-making and corresponding action. Various theories have been considered, but found wanting. Moreover, classic theories may contradict one another, contribute to confusion and immobilise the clinician. We have examined major theories commonly applied in bioethics, conferred with moral philosophers and psychiatrists and striven to apply more recent insights drawn from moral philosophy. We report that instead of pursuing a single theoretical framework, we should garner the strengths of compatible approaches in a synergistic way. We propose a particular complementarity of principlism--with its pragmatic focus on respect for autonomy, beneficence, non-maleficence and justice--and care ethics, a variant of virtue theory, which highlights character traits pertinent to caring for vulnerable psychiatric patients.

The ethical commitments of academic faculty in psychiatric education

OBJECTIVE

This article explores the commitment of faculty to ethics training in psychiatric education. Although psychiatry has insufficiently addressed the profession's need for ethics training in education, program directors acknowledge its critical importance, and its positive impact has been demonstrated. Additionally, residents often seek ethics training as part of their instruction.

METHOD

The author suggests that academic faculty could respond to the profession's inadequate treatment of ethics training by helping trainees develop moral agency--the ability to recognize, assess, and respond to ethical dilemmas; decide what constitutes right or wrong care; and act accordingly. The author also describes how this objective could be met by promoting professionalism and offering didactic instruction that address substantive and process issues regarding psychiatric care.

CONCLUSION

Specific recommendations are provided.

Will insured citizens give up benefit coverage to include the uninsured?

OBJECTIVE

To describe the willingness of insured citizens to trade off their own health benefits to cover the uninsured.

DESIGN

Descriptive study of individual and group decisions and decision making using quantitative and qualitative methods.

SETTING AND PARTICIPANTS

Twenty-nine groups of citizens (N = 282) residing throughout Minnesota.

INTERVENTIONS

Groups participated in Choosing Healthplans All Together (CHAT), a simulation exercise in which participants choose whether and how extensively to cover health services in a hypothetical health plan constrained by limited resources. We describe individual and group decisions, and group dialogue concerning whether to allocate 2% of their premium to cover uninsured children in Minnesota, or 4% of their premium to cover uninsured children and adults.

MEASUREMENTS AND MAIN RESULTS

While discussing coverage for the uninsured, groups presented arguments about personal responsibility, community benefit, caring for the vulnerable, social impact, and perceptions of personal risk. All groups chose to insure children; 22 of 29 groups also insured adults. More individuals chose to cover the uninsured at the end of the exercise, after group deliberation, than before (66% vs 54%; P < .001). Individual selections differed from group selections more often for the uninsured category than any other. Nevertheless, 89% of participants were willing to abide by the health plan developed by their group.

CONCLUSION

In the context of tradeoffs with their own health insurance benefits, groups of Minnesotans presented value-based arguments about covering the uninsured. All 29 groups and two thirds of individuals chose to contribute a portion of their premium to insure all children and most groups chose also to insure uninsured adults.

Increase in urinary leukotriene LTE4 levels in acute asthma: correlation with airflow limitation

BACKGROUND

Leukotrienes play a key role in the pathophysiology of chronic asthma. Activation of leukotriene pathways is accompanied by rises in detectable urinary levels of leukotriene E4 (LTE4). The relationship between urinary LTE4 levels and factors associated with acute asthma has not been determined.

METHODS

Adults aged 15-54 years presenting with moderate to severe acute asthma were evaluated at emergency departments in 16 US sites. Forced expiratory volume in 1 second (FEV1) was measured during the first 60 minutes after arrival and at specified times until discharge or admission. Urine samples for measurement of LTE4 levels were obtained either on arrival at the study site and/or before discharge. Patients were seen 2 weeks later for follow up, at which time repeat FEV1 measurements and urine samples for LTE4 were obtained.

RESULTS

One hundred and eighty four patients were evaluated; LTE4 results from both the acute and follow up periods were available for analysis in 146. Urinary LTE4 levels were increased during asthma exacerbations compared with levels obtained 2 weeks later (geometric means 111.7 and 75.6 pg/mg creatinine, respectively, mean percentage change -32.3; 95% confidence interval (CI) for the mean percentage change -39.6 to -24.3, p<0.001). The correlation between improvement in FEV1 and decline in LTE4 over the 2 week interval was significant (p<0.001, r=0.43).

CONCLUSIONS

Activation of leukotriene pathways in acute asthma is correlated with the degree of airflow obstruction, and resolution of the asthma exacerbation is associated with a reduction in leukotriene levels.

Endosomal sorting of amyloid precursor protein-P-selectin chimeras influences secretase processing

Amyloid beta protein, the major component of the senile plaques in Alzheimer's disease, is generated by secretory and endocytic processing of amyloid precursor protein. Internalized amyloid precursor protein either recycles to the plasma membrane, where alpha-secretase resides, or moves to acidic compartment(s) for beta-secretase exposure. While the trans-Golgi network contains beta-secretase activity, recent examination of the subcellular distribution of this proteinase, called BACE, has led to the suggestion that beta-secretase activity might also reside at the plasma membrane and in endosomes. To examine the role of endocytic compartments in beta-secretase processing of amyloid precursor protein, the wild-type and endosomal sorting mutant P-selectin cytoplasmic domains were used to control movement of amyloid precursor protein through endosomes. Amyloid precursor protein/P-selectin, which is sorted from early to late endosomes, undergoes significantly less alpha-secretase cleavage, and more beta-secretase cleavage, than amyloid precursor protein/P-selectin768A, a mutant that recycles more efficiently to the cell surface. Our results demonstrate that endosomal sorting influences relative exposure of the amyloid precursor protein/P-selectin chimeras to alpha- and beta-secretase activities, and suggest that, because delivery to late endocytic compartments favors beta-secretase processing of amyloid precursor protein, there is likely limited beta-secretase activity in early endosomes or at the cell surface. We propose that the trans-Golgi network may be involved in both secretory and endocytic generation of amyloid beta protein.

Working in a flawed mental health care system: an ethical challenge

OBJECTIVE

Psychiatrists are under immense ethical pressure when practicing in circumstances that reasonable, informed colleagues would regard as not "good enough" in that they do not adequately meet the needs of patients and patients' families. This article is an examination of the ethical quandaries that ensue and options for response.

METHOD

The authors explore the ways in which mental health systems may become flawed and compare philosophical arguments that deal with the predicament of working in such systems.

RESULTS

The principle of fidelity to the patient is compromised in flawed systems, thus threatening professional integrity. Arguments for efficiency or the greater good in the provision of mental health care fail as remedies since they both lead to harms for particular clinical groups, as well as downgrading of a psychiatrist's integrity.

CONCLUSIONS

Psychiatrists should submit to the principle of fidelity in working with patients. Since flawed systems undermine fidelity, threatening the patient's interests, psychiatrists are morally responsible for working to improve such systems.

Comparison of gas-phase free-radical populations in tobacco smoke and model systems by HPLC

We used an improved method for trapping carbon-centered radicals (.R) from the gas-phase to compare radical suites trapped from various tobacco smoke and model smoke systems. Using a nitroxide trap, 3-amino-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (3AP), on solid support, we trapped radicals directly from the gas phase, washed them off the support, and analyzed them with HPLC. Separation of the trapped radicals showed that each tobacco type produced a unique radical suite of 4-10 distinct peaks. Gas mixtures used to model tobacco smoke consisted of nitric oxide, air, isoprene, and methanol. The model systems produced radical suites of four major and several minor peaks, two of which matched peaks in tobacco smoke chromatograms. Quantities of radicals trapped from tobacco smoke were: 54 +/- 2 nmol .R per Marlboro cigarette, 66 +/- 9 nmol .R per Djarum clove cigarette, and 185 +/- 9 nmol .R per Swisher Sweet cigar. In these experiments oxygen competes with the nitroxide trap for gas-phase radicals. A kinetic analysis of the O2 competition shows that actual radical concentrations in the smoke were approximately 100-fold higher than measured.

The Ile164 beta(2)-adrenoceptor polymorphism alters salmeterol exosite binding and conventional agonist coupling to G(s)

beta(2)-adrenoceptors (beta(2)AR) are polymorphic at amino acid 164 (Thr or Ile) of the fourth transmembrane domain. In transfected fibroblasts, six agonists commonly used in the treatment of bronchospasm were studied. Isoproterenol, albuterol, metaproterenol, terbutaline, formoterol, and salmeterol displayed decreased binding affinities (K(i)s were 1.2-3.0-fold higher) and a significant degree of impaired maximal stimulation of adenylyl cyclase ( approximately 40%), was observed with all agonists for the Ile164 receptor. The ratios of signal transduction efficiencies (Tau function, Ile164/Thr164) varied from a low of 0.17 for terbutaline to 0.49 for salmeterol. In addition, Ile164 bound salmeterol at the exosite, as delineated in perfusion washout studies, at a decreased level (31+/-4.8% vs. 49+/-4.4% retained salmeterol, respectively, P=0.02). In cAMP production studies under perfusion conditions, this decreased exosite binding caused a approximately 50% decrease in the duration of action of salmeterol at Ile164 (t(1/2)=21.0+/-3.6 vs. 46.8+/-4.1 min for Thr164, P=0.001). The durations of action for isoproterenol and formoterol under similar perfusion conditions were not different between the two receptors. These in vitro results indicate the Ile164 polymorphic receptor represents a pharmacogenetic locus for the most commonly utilized agonists in the treatment of asthma with a unique phenotype for salmeterol.

AP-3 adaptor functions in targeting P-selectin to secretory granules in endothelial cells

P-selectin, a cell adhesion protein participating in the early stages of inflammation, contains multiple sorting signals that regulate its cell surface expression. Targeting to secretory granules regulates delivery of P-selectin to the cell surface. Internalization followed by sorting from early to late endosomes mediates rapid removal of P-selectin from the surface. We show here that the P-selectin cytoplasmic domain bound AP-2 and AP-3 adaptor complexes in vitro. The amino acid substitution L768A, which abolishes endosomal sorting and impairs granule targeting of P-selectin, reduced binding of AP-3 adaptors but not AP-2 adaptors. Turnover of P-selectin was 2.4-fold faster than turnover of transferrin receptor in AP-3-deficient mocha fibroblasts, similar to turnover of these two proteins in AP-3-competent cells, demonstrating that AP-3 function is not required for endosomal sorting. However, sorting P-selectin to secretory granules was defective in endothelial cells from AP-3-deficient pearl mice, demonstrating a role for AP-3 adaptors in granule assembly in endothelial cells. P-selectin sorting to platelet alpha-granules was normal in pearl mice, consistent with earlier evidence that granule targeting of P-selectin is mechanistically distinct in endothelial cells and platelets. These observations establish that AP-3 adaptor functions in assembly of conventional secretory granules, in addition to lysosomes and the 'lysosome-like' secretory granules of platelets and melanocytes.

The evolution of medical technology: lessons from the Burgess Shale

Many forthcoming medical advances-growth factors, tissue engineering, gene therapy, attachable prosthetic limbs, and implantable computers--are so new that as yet there is no clinical experience with them. Each therapeutic technique will evolve in an environment containing few guideposts to help judge its efficacy and safety. Recent developments in evolution theory (based on an analysis of Cambrian fossils in Canada's Burgess Shale quarry) suggest that evolution passes, at times, through innovative cycles of progress--when diversification of design leads to perfection of form--with the concomitant production of many unsuccessful models. The evolution of the total knee replacement is a perfect example of the process, because many of the early devices have proven to be dismal failures. However, modern knee replacements would not have been developed without them. Because the risk of unforeseen complications associated with new medical products cannot be discerned in advance, each patient-consumer should have the opportunity to intelligently weigh an innovative product's risk potential against its possible benefit. The proposal made here, for a temporary New Product status for new drugs and devices after a product is cleared by the Food and Drug Administration for general marketing, provides a mechanism for making such decisions.

A third specificity-determining site in mu 2 adaptin for sequences upstream of Yxx phi sorting motifs

Internalization signals of the Yxx phi type (phi = bulky hydrophobic side chain) interact with the mu 2 chain of AP-2 adaptors. Internalization activity is intolerant of non-conservative substitution of either the tyrosine or the phi side chains, which bind to hydrophobic pockets in mu 2 adaptin in a conformation described as 'a two pinned plug into a socket'. P-selectin, a type I transmembrane protein, contains the Yxx phi-like sequence YGVF in its cytoplasmic domain, but substitution of either the tyrosine or phenylalanine with alanine in the full-length protein causes only small changes in the rate of endocytosis. It is shown here that the sequence YGVF contained within a peptide corresponding to the 17 COOH-terminal amino acids of P-selectin binds to mu 2 adaptin in the same fashion previously seen for other Yxx phi motifs. In addition, the P-selectin peptide binds to a third hydrophobic pocket in mu 2 adaptin through a leucine at position Y-3 in the peptide. This structure suggests that some sequences can function as a 'three pinned plug', in which internalization activity is not critically dependent on any one of the three interacting side chains.

The effects of ulnar axial malalignment on supination and pronation

BACKGROUND

Forearm fractures are common injuries in both adults and children. Despite efforts to obtain anatomical alignment, axial rotational malunions occur, resulting in a decreased range of motion and a poor appearance. The objective of this study was to quantify loss of forearm rotation after simulation of ulnar malunions in supination and pronation.

METHODS

Six fresh-frozen cadaveric upper extremities (mean age at the time of death, 79.4+/-2.8 years) were used to quantify loss of forearm rotation after simulation of axial rotational malunions of the ulna. First, maximum forearm rotation in supination and pronation was measured at torques of 6.8, 13.6, and 20.4 kilograms-centimeter applied with use of a custom jig. Following a midshaft ulnar osteotomy, a custom adjustable internal fixation plate was used to simulate axial rotational malunions of the ulna of 0, 15, 30, and 45 degrees in both directions. Measurements in supination and pronation were then repeated at the prespecified torques. Analysis of variance, with a p value of 0.05, was used for statistical analysis.

RESULTS

In all instances, a decrease in forearm rotation after simulation of the ulnar rotational malunion was accompanied by an increase in rotation in the opposite direction. Supination and pronation were significantly influenced, whereas the total arc of rotation was not affected by ulnar rotational malunion. At a torque of 20.4 kilograms-centimeter, pronation malunions of 15, 30, and 45 degrees resulted in a mean loss of supination (and standard error of the mean) of 5+/-1, 11+/-1, and 20+/-1 degrees, respectively, and supination malunions of 15, 30, and 45 degrees resulted in a mean loss of pronation of 4+/-1, 10+/-2, and 18+/-4 degrees, respectively. The ratio of the simulated rotational malunion to the loss of motion was larger than one.

CONCLUSIONS

Ulnar rotational malunions do not lead to a significant change in the total arc of forearm rotation. Instead, loss of motion in one direction is accompanied by increased motion in the opposite direction. Even with a 45-degree ulnar rotational malunion, forearm rotation decreases no more than 20 degrees.

Rapid transport of internalized P-selectin to late endosomes and the TGN: roles in regulating cell surface expression and recycling to secretory granules

Prior studies on receptor recycling through late endosomes and the TGN have suggested that such traffic may be largely limited to specialized proteins that reside in these organelles. We present evidence that efficient recycling along this pathway is functionally important for nonresident proteins. P-selectin, a transmembrane cell adhesion protein involved in inflammation, is sorted from recycling cell surface receptors (e.g., low density lipoprotein [LDL] receptor) in endosomes, and is transported from the cell surface to the TGN with a half-time of 20-25 min, six to seven times faster than LDL receptor. Native P-selectin colocalizes with LDL, which is efficiently transported to lysosomes, for 20 min after internalization, but a deletion mutant deficient in endosomal sorting activity rapidly separates from the LDL pathway. Thus, P-selectin is sorted from LDL receptor in early endosomes, driving P-selectin rapidly into late endosomes. P-selectin then recycles to the TGN as efficiently as other receptors. Thus, the primary effect of early endosomal sorting of P-selectin is its rapid delivery to the TGN, with rapid turnover in lysosomes a secondary effect of frequent passage through late endosomes. This endosomal sorting event provides a mechanism for efficiently recycling secretory granule membrane proteins and, more generally, for downregulating cell surface receptors.

An ethical argument for a right to mental health care

The author reviews moral arguments supporting a right to medical care, as well as empirical data concerning the effects of mental illness on society, and explores their relevance to a rights-based claim to mental health care. He concludes that there is ample ethical justification for a right to mental health care, given the obvious benefit it would convey to individuals and to society at large. He believes that this compelling moral claim should be translated into health policy.

Blocking P-selectin protects from ischemia/reperfusion-induced acute renal failure

Acute renal failure (ARF) in response to ischemia-reperfusion is thought to be associated with neutrophil infiltration. Neutrophil recruitment depends on adhesion molecules, including P-selectin. Our study sought to characterize the role of P-selectin in ischemia-reperfusion (I/R) -induced acute renal failure (ARF). In wild-type (wt) and P-selectin-deficient (P-/-) mice (both C57BL/6), ARF was induced by 32 min bilateral renal ischemia, followed by reperfusion (I/R). Wt showed a 12- and 20-fold increase in creatinine at 24 and 48 h after I/R, respectively. Similar changes were seen in blood urea nitrogen (BUN). By contrast, in P-/- creatinine and BUN increased only moderately (fourfold over sham). In wt, renal myeloperoxidase activity, indicating neutrophil infiltration, peaked after 24 h (19-fold over sham). This was significantly attenuated in P-/- (fivefold over sham). Western blot analysis revealed maximum P-selectin expression 12 h after I/R in wt. Immunostaining detected P-selectin in glomerular endothelium and in platelets adherent in glomerular and peritubular vessels. Postischemic injection of P-selectin antibody at 10 min after reperfusion, but not isotype control antibody, protected wt from ARF similar to the protection seen in P-/-. We conclude that blocking P-selectin even after onset of reperfusion protects mice from I/R-induced ARF, suggesting potential therapeutic strategies aimed at blocking P-selectin.

Arterial injury increases expression of inflammatory adhesion molecules in the carotid arteries of apolipoprotein-E-deficient mice

Recent studies demonstrate increased cellular adhesion molecule expression by neointimal endothelium overlying primary and restenotic atherosclerotic plaque. In this study, we developed an atherosclerotic mouse model of arterial injury and characterized adhesion molecule expression after injury. Sixteen apolipoprotein-E-(ApoE)-deficient mice fed a Western-type diet for 4 weeks underwent carotid artery wire denudation at week 2. For each segment, the extent of neointima formation and medial thickening, or adhesion molecule expression, were scored separately on a scale from 0 (no plaque/thickening or expression) to 3 (extensive plaque/thickening or expression) using Movat staining (n = 3) or immunohistochemical analysis (n = 13). Histology revealed significant medial thickening (1.8 +/- 0.9 vs. 0.3 +/- 0.5, p < 0. 001) versus controls and pronounced staining for monocytes/macrophages in the wall of injured vessels. Immunohistochemical analysis showed more robust expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on the luminal surface of injured arteries versus controls (2.2 +/- 0.6 vs. 1.4 +/- 0.7, p < 0.01, and 2.5 +/- 0.5 vs. 1.2 +/- 0.6, p < 0.001, respectively). Injury increased adventitial ICAM-1 expression (2.6 +/- 0.5 vs. 1.6 +/- 0.5, p < 0.002) and medial VCAM-1 expression (2.2 +/- 0.6 vs. 1.2 +/- 0. 7, p < 0.004). Thus, carotid injury results in significant medial thickening and increases adhesion molecule expression beyond that induced in ApoE-deficient mice fed a Western diet alone. The observation of macrophage infiltration into the media at sites of increased ICAM-1 and VCAM-1 expression suggests that these molecules may mediate monocyte/macrophage trafficking into the wall of injured arteries.

Is managed care ethical?

The author identifies ethical dilemmas inherent in fee-for-service medicine (grounded in patients' autonomous decision making) and managed care (grounded in the principle of efficiency). He argues that the moral legitimacy of the latter system of health care is more in question, and suggests a methodology for assessing its ethical status.

Orthopaedic surgeons. Inheritors of tradition

Bonesetting, a most ancient healing art, was absorbed into orthopaedic surgery approximately 120 years ago when Hugh Owen Thomas, a medical doctor specializing in pediatric deformities, assumed his father's nonmedical bonesetting practice. In many nonWestern nations, however, traditional bonesetters continue to treat large numbers of patients. Current market forces in the United States threaten to reduce the role of orthopaedic surgeons in the management of fractures not requiring surgery, leading to the possible reemergence of bonesetting as a separate and independent discipline.

Coupling of beta-adrenergic receptors to cardiac L-type Ca2+ channels: preferential coupling of the beta1 versus beta2 receptor subtype and evidence for PKA-independent activation of the channel

Beta1- and beta2-adrenergic receptors (beta-ARs) co-exist in mammalian heart, and it is generally accepted that both activate adenylyl cyclase (AC), resulting in increased levels of cAMP and subsequent activation of L-type Ca2+ channels (CaCh). To investigate the contribution of each beta-AR subtype in AC and CaCh coupling, we stably expressed cardiac CaCh alpha1 and beta2 subunits along with either beta1-AR or beta2-AR in CHW fibroblasts. Co-expression of either beta-AR with CaCh subunits conferred responsiveness of AC and CaCh to isoproterenol (ISO), which was not observed in non-transfected cells. ISO-promoted cAMP formation occurred at a lower EC50 through the beta2-AR than through the beta1-AR (0.13 +/- 0.01 vs. 0.6 +/- 0.14 nM). In contrast, activation of CaCh was more efficacious via the beta1-AR than the beta2-AR (EC50 for CaCh activation = 238 +/- 33 vs. 1057 +/- 113 nM). Pre-treatment with pertussis toxin (PTX) had no effect upon the responsiveness of either cAMP formation or CaCh activation through either receptor. We conclude (1) that beta1-ARs exhibit preferential coupling to CaCh activation, versus that observed for the beta2-AR; (2) that this preferential coupling cannot be explained solely by cAMP-dependent processes; and (3) that the relative attenuation of beta2-AR-promoted CaCh activation is not due to receptor coupling to PTX-sensitive G proteins. Thus, it is likely that other subtype-specific, cAMP-independent coupling of the beta-AR to CaCh is present.

A gain-of-function polymorphism in a G-protein coupling domain of the human beta1-adrenergic receptor

The beta1-adrenergic receptor (beta1AR) is a key cell surface signaling protein expressed in the heart and other organs that mediates the actions of catecholamines of the sympathetic nervous system. A polymorphism in the intracellular cytoplasmic tail near the seventh transmembrane-spanning segment of the human beta1AR has been identified in a cohort of normal individuals. At amino acid position 389, Gly or Arg can be found (allele frequencies 0.26 and 0. 74, respectively), the former previously considered as the human wild-type beta1AR. Using site-directed mutagenesis to mimic the two variants, CHW-1102 cells were permanently transfected to express the Gly-389 and Arg-389 receptors. In functional studies with matched expression, the Arg-389 receptors had slightly higher basal levels of adenylyl cyclase activities (10.7 +/- 1.2 versus 6.1 +/- 0.4 pmol/min/mg). However, maximal isoproterenol-stimulated levels were markedly higher for the Arg-389 as compared to the Gly-389 receptor (63.3 +/- 6.1 versus 20.9 +/- 2.0 pmol/min/mg). Agonist-promoted [35S]guanosine 5'-O-(thiotriphosphate) binding was also increased with the Arg-389 receptor consistent with enhanced coupling to Gs and increased adenylyl cyclase activation. In agonist competition studies carried out in the absence of guanosine 5'-(beta, gamma-imido)triphosphate, high affinity binding could not be resolved with the Gly-389 receptor, whereas Arg-389 displayed an accumulation of the agonist high affinity receptor complex (RH = 26%). Taken together, these data indicate that this polymorphic variation of the human beta1AR results in alterations of receptor-Gs interaction with functional signal transduction consequences, consistent with its localization in a putative G-protein binding domain. The genetic variation of beta1AR at this locus may be the basis of interindividual differences in pathophysiologic characteristics or in the response to therapeutic betaAR agonists and antagonists in cardiovascular and other diseases.

New cyclooxygenase-2/5-lipoxygenase inhibitors. 3. 7-tert-butyl-2, 3-dihydro-3,3-dimethylbenzofuran derivatives as gastrointestinal safe antiinflammatory and analgesic agents: variations at the 5 position

We report an expansion of the scope of our initial discovery that 5-keto-substituted 7-tert-butyl-2,3-dihydro-3,3-dimethylbenzofurans (DHDMBFs) are antiinflammatory and analgesic agents. Several other functional groups have been introduced at the 5 position: amides, amidines, ureas, guanidines, amines, heterocycles, heteroaromatics, and heteroaryl ethenyl substituents in the 5 position all provide active compounds. These compounds are dual cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) inhibitors. They inhibit both COX-1 and COX-2 with up to 33-fold selectivity for COX-2.

An atypical sorting determinant in the cytoplasmic domain of P-selectin mediates endosomal sorting

We previously identified the 11 amino acid C1 region of the cytoplasmic domain of P-selectin as essential for an endosomal sorting event that confers rapid turnover on P-selectin. The amino acid sequence of this region has no obvious similarity to other known sorting motifs. We have analyzed the sequence requirements for endosomal sorting by measuring the effects of site-specific mutations on the turnover of P-selectin and of the chimeric protein LLP, containing the lumenal and transmembrane domains of the low density lipoprotein receptor and the cytoplasmic domain of P-selectin. Endosomal sorting activity was remarkably tolerant of alanine substitutions within the C1 region. The activity was eliminated by alanine substitution of only one amino acid residue, leucine 768, where substitution with several other large side chains, hydrophobic and polar, maintained the sorting activity. The results indicate that the endosomal sorting determinant is not structurally related to previously reported sorting determinants. Rather, the results suggest that the structure of the sorting determinant is dependent on the tertiary structure of the cytoplasmic domain.

New cyclooxygenase-2/5-lipoxygenase inhibitors. 1. 7-tert-buty1-2,3-dihydro-3,3-dimethylbenzofuran derivatives as gastrointestinal safe antiinflammatory and analgesic agents: discovery and variation of the 5-keto substituent

A series of 5-keto-substituted 7-tert-buty1-2,3-dihydro-3,3- dimethylbenzofurans (DHDMBFs) were prepared and evaluated as potential nonsteroidal antiinflammatory and analgesic agents. Interest in this class of compounds arose when a DHDMBF was found to be an active metabolite of the di-tert-butylphenol antiinflammatory agent tebufelone. We have now found that a variety of 5-keto-substituted DHDMBFs have good in vivo antiinflammatory and analgesic activity after oral administration. These compounds inhibit both cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) in vitro. The cyclooxygenase inhibition was found to be selective for the cyclooxygenase-2 isoform, and this combination of COX-2/5-LOX inhibition may be responsible for the gastrointestinal safety of compounds such as 30.

New cyclooxygenase-2/5-lipoxygenase inhibitors. 2. 7-tert-butyl-2,3-dihydro-3,3-dimethylbenzofuran derivatives as gastrointestinal safe antiinflammatory and analgesic agents: variations of the dihydrobenzofuran ring

A series of 5-keto-substituted 7-tert-buty1-2,3-dihydro-3,3- dimethylbenzofurans (DHDMBFs) were found to be nonsteroidal antiinflammatory and analgesic agents. These compounds are inhibitors of 5-lipoxygenase (5-LOX) and cyclooxygenase (COX) with selectivity for the COX-2 isoform. A series of analogues were prepared to investigate the scope of this lead. Five ketone side chains from active DHDMBFs were used to investigate the effects of changes in the DHDMBF "core": the size and identity of the heterocycle and the substituent requirements of the heterocycle and phenyl ring. Biological testing showed that a variety of structural changes can be accommodated, but no structure was clearly superior to the DHDMBF structure.

Role of beta ARK in long-term agonist-promoted desensitisation of the beta 2-adrenergic receptor

Phosphorylation of the beta 2-adrenergic receptor (beta 2AR) is the initial event that underlies rapid agonist-promoted desensitisation. However, the role of phosphorylation in mediating long-term beta 2AR desensitisation is not known. To investigate this possibility, we performed intact cell phosphorylation studies with COS-7 cells transiently expressing an epitope tagged wild-type beta 2AR and found that receptor phosphorylation in cells treated with 1 microM isoproterenol for 24 h was approximately 4-fold over the basal state. This finding suggested that persistent phosphorylation of the receptor might contribute to functional long-term desensitisation which we further explored with mutated beta 2AR lacking the determinants of phosphorylation by the beta AR kinase (beta ARK), PKA or both. In CHW cells expressing the WT beta 2AR, pretreatment with 1 microM isoproterenol for 24 h reduced the isoproterenol-stimulated cAMP response by 82 +/- 5%. Substitution of the PKA sites with alanines had no effect on the extent of desensitisation (77 +/- 6%, P = NS compared to WT). In contrast, desensitisation was only 49 +/- 4% (P < 0.001 compared to WT) when the beta ARK sites were similarly substituted. Removal of both the beta ARK and PKA sites impaired desensitisation to the same extent as the beta ARK mutant. The extent of receptor loss (downregulation) was the same among all of the cell lines used and therefore could not account for the observed differences in desensitisation. Cellular beta ARK activity, assessed by a rhodopsin phosphorylation assay, was equivalent in all cell lines and was unaffected by agonist treatment. PKA activity, however, was dynamically regulated, increasing 4-fold over basal levels after 15 min of isoproterenol and returning to near basal levels after 24 h. The lower level of PKA activity after long-term agonist exposure may therefore have contributed to the apparent lack of effect of removing PKA sites. Nonetheless, long-term desensitisation was clearly attenuated with beta 2AR lacking beta ARK phosphorylation sites. These findings show that in addition to its role in regulating short-term desensitisation, beta ARK-mediated phosphorylation is an important mechanism underlying long-term desensitisation of the beta 2AR as well.

Four conductance levels of cloned cardiac L-type Ca2+ channel alpha1 and alpha1/beta subunits

Formation of single channel subconductance is one of the unique characteristics of the L-type Ca2+ channel. Although alpha1 subunit exhibits a primary function of the channel, it remains uncertain whether alpha1 subunit alone is able to produce subconductance. We tested this by studying single channel currents of cloned cardiac alpha1 subunit expressed in Chinese hamster fibroblast cells, with/without coexpression of cardiac beta subunit. The alpha1 subunit exhibited four distinct levels of conductance (22.7, 14.3, 6.2 and 3.2 pS). Coexpression of beta subunit significantly increased the number of openings in all four levels of conductance without changing the conductance values.

Modulation of cardiac Ca2+ channels by isoproterenol studied in transgenic mice with altered SR Ca2+ content

Phospholamban (PLB) ablation is associated with enhanced sarcoplasmic reticulum (SR) Ca2+ uptake and attenuation of the cardiac contractile responses to beta-adrenergic agonists. In the present study, we compared the effects of isoproterenol (Iso) on the Ca2+ currents (ICa) of ventricular myocytes isolated from wild-type (WT) and PLB knockout (PLB-KO) mice. Current density and voltage dependence of ICa were similar between WT and PLB-KO cells. However, ICa recorded from PLB-KO myocytes had significantly faster decay kinetics. Iso increased ICa amplitude in both groups in a dose-dependent manner (50% effective concentration, 57.1 nM). Iso did not alter the rate of ICa inactivation in WT cells but significantly prolonged the rate of inactivation in PLB-KO cells. When Ba2+ was used as the charge carrier, Iso slowed the decay of the current in both WT and PLB-KO cells. Depletion of SR Ca2+ by ryanodine also slowed the rate of inactivation of ICa, and subsequent application of Iso further reduced the inactivation rate of both groups. These results suggest that enhanced Ca2+ release from the SR offsets the slowing effects of beta-adrenergic receptor stimulation on the rate of inactivation of ICa.

cAMP-dependent regulation of cardiac L-type Ca2+ channels requires membrane targeting of PKA and phosphorylation of channel subunits

The cardiac L-type Ca2+ channel is a textbook example of an ion channel regulated by protein phosphorylation; however, the molecular events that underlie its regulation remain unknown. Here, we report that in transiently transfected HEK293 cells expressing L-type channels, elevations in cAMP resulted in phosphorylation of the alpha1C and beta2a channel subunits and increases in channel activity. Channel phosphorylation and regulation were facilitated by submembrane targeting of protein kinase A (PKA), through association with an A-kinase anchoring protein called AKAP79. In transfected cells expressing a mutant AKAP79 that is unable to bind PKA, phosphorylation of the alpha1C subunit and regulation of channel activity were not observed. Furthermore, we have demonstrated that the association of an AKAP with PKA was required for beta-adrenergic receptor-mediated regulation of L-type channels in native cardiac myocytes, illustrating that the events observed in the heterologous expression system reflect those occurring in the native system. Mutation of Ser1928 to alanine in the C-terminus of the alpha1C subunit resulted in a complete loss of cAMP-mediated phosphorylation and a loss of channel regulation. Thus, the PKA-mediated regulation of L-type Ca2+ channels is critically dependent on a functional AKAP and phosphorylation of the alpha1C subunit at Ser1928.