Functional magnetic resonance imaging (fMRI) studies of the human brain have suggested that low-frequency fluctuations in resting fMRI data collected using blood oxygen level dependent (BOLD) contrast correspond to functionally relevant resting state networks (RSNs). Whether the fluctuations of resting fMRI signal in RSNs are a direct consequence of neocortical neuronal activity or are low-frequency artifacts due to other physiological processes (e.g., autonomically driven fluctuations in cerebral blood flow) is uncertain. In order to investigate further these fluctuations, we have characterized their spatial and temporal properties using probabilistic independent component analysis (PICA), a robust approach to RSN identification. Here, we provide evidence that: i. RSNs are not caused by signal artifacts due to low sampling rate (aliasing); ii. they are localized primarily to the cerebral cortex; iii. similar RSNs also can be identified in perfusion fMRI data; and iv. at least 5 distinct RSN patterns are reproducible across different subjects. The RSNs appear to reflect "default" interactions related to functional networks related to those recruited by specific types of cognitive processes. RSNs are a major source of non-modeled signal in BOLD fMRI data, so a full understanding of their dynamics will improve the interpretation of functional brain imaging studies more generally. Because RSNs reflect interactions in cognitively relevant functional networks, they offer a new approach to the characterization of state changes with pathology and the effects of drugs.

We analyzed prospectively 1213 adults with de novo acute myeloid leukemia (AML) to ascertain the prognostic impact of cytogenetic abnormalities on complete remission (CR) rate, 5-year cumulative incidence of relapse (CIR), and 5-year overall survival (OS). All patients received similar induction therapy. Median follow-up for surviving patients was 8.3 years. Nonprioritized cytogenetics distinguished t(8;21) and inv(16)/t(16;16) as conferring a significantly better prognosis than normal karyotype. Prognostic impact of many abnormalities could not be determined independently because of their association with complex karyotype. Neither complex karyotype nor secondary aberrations affected outcome of patients with t(8;21), inv(16)/t(16;16), or t(9;11). Among other patients, those with complex karyotypes had significantly worse outcomes than cytogenetically normal patients. Based on outcome for specific cytogenetic abnormalities and karyotype complexity, patients were divided into 3 risk groups: favorable (CR 88%, CIR 54%, OS 55%), intermediate (CR 67%, CIR 67%, OS 24%), and adverse (CR 32%, CIR 92%, OS 5%). Multivariate analyses confirmed the major contribution of cytogenetics to the probability of attaining CR, CIR, and OS. For the adverse-risk group, the probability of achieving CR was 4.0 and 11.9 times lower, the probability of relapse 3.0 and 4.4 times higher, and the risk of death 2.1 and 4.3 times higher than those for the intermediate and favorable groups, respectively. We conclude that although the prognostic impact of many recurring abnormalities has not been ascertained independently of complex karyotype, cytogenetics is among the most useful factors predicting attainment of CR, CIR, and long-term survival in adult AML.

Although optical absorption is strongly associated with the physiological status of biological tissue, existing high-resolution optical imaging modalities, including confocal microscopy, two-photon microscopy and optical coherence tomography, do not sense optical absorption directly. Furthermore, optical scattering prevents these methods from imaging deeper than approximately 1 mm below the tissue surface. Here we report functional photoacoustic microscopy (fPAM), which provides multiwavelength imaging of optical absorption and permits high spatial resolution beyond this depth limit with a ratio of maximum imaging depth to depth resolution greater than 100. Reflection mode, rather than orthogonal or transmission mode, is adopted because it is applicable to more anatomical sites than the others. fPAM is demonstrated with in vivo imaging of angiogenesis, melanoma, hemoglobin oxygen saturation (sO2) of single vessels in animals and total hemoglobin concentration in humans.

BACKGROUND

The worldwide increase in type 2 diabetes mellitus is becoming a major health concern. We aimed to assess the effect of acarbose in preventing or delaying conversion of impaired glucose tolerance to type 2 diabetes.

METHODS

In a multicentre, placebo-controlled randomised trial, we randomly allocated patients with impaired glucose tolerance to 100 mg acarbose or placebo three times daily. The primary endpoint was development of diabetes on the basis of a yearly oral glucose tolerance test (OGTT). Analyses were by intention to treat.

RESULTS

We randomly allocated 714 patients with impaired glucose tolerance to acarbose and 715 to placebo. We excluded 61 (4%) patients because they did not have impaired glucose tolerance or had no postrandomisation data. 211 (31%) of 682 patients in the acarbose group and 130 (19%) of 686 on placebo discontinued treatment early. 221 (32%) patients randomised to acarbose and 285 (42%) randomised to placebo developed diabetes (relative hazard 0.75 [95% CI 0.63-0.90]; p=0.0015). Furthermore, acarbose significantly increased reversion of impaired glucose tolerance to normal glucose tolerance (p<0.0001). At the end of the study, treatment with placebo for 3 months was associated with an increase in conversion of impaired glucose tolerance to diabetes. The most frequent side-effects to acarbose treatment were flatulence and diarrhoea.

CONCLUSIONS

Acarbose could be used, either as an alternative or in addition to changes in lifestyle, to delay development of type 2 diabetes in patients with impaired glucose tolerance.

Antiretroviral therapy fails to cure HIV-1 infection because latent proviruses persist in resting CD4(+) T cells. T cell activation reverses latency, but <1% of proviruses are induced to release infectious virus after maximum in vitro activation. The noninduced proviruses are generally considered defective but have not been characterized. Analysis of 213 noninduced proviral clones from treated patients showed 88.3% with identifiable defects but 11.7% with intact genomes and normal long terminal repeat (LTR) function. Using direct sequencing and genome synthesis, we reconstructed full-length intact noninduced proviral clones and demonstrated growth kinetics comparable to reconstructed induced proviruses from the same patients. Noninduced proviruses have unmethylated promoters and are integrated into active transcription units. Thus, it cannot be excluded that they may become activated in vivo. The identification of replication-competent noninduced proviruses indicates that the size of the latent reservoir-and, hence, the barrier to cure-may be up to 60-fold greater than previously estimated.

Endothelins are a newly described peptide family consisting of three peptides (ET-1, ET-2 and ET-3) which are the most potent vasoconstrictive peptides known. They are crucial in the regulation of vascular smooth muscle tone. The diverse functions of endothelins are thought to be mediated by interaction with many different receptors coupled to the inositol phosphate/calcium ion messenger pathway. However, because of the structural resemblance of the three peptides, the presence and nature of multiple endothelin receptors remain to be elucidated. We report here the cloning of a complementary DNA encoding a bovine endothelin receptor, which has a transmembrane topology similar to that of other G protein-coupled receptors and shows specific binding, with the highest selectivity to ET-1 in animal cells transfected with the cloned cDNA. This receptor messenger RNA is widely distributed in the central nervous system and peripheral tissues, particularly in the heart and lung. Our results support the view that there are other receptor subtypes.

Regulatory guidance specifies the need to establish cardiovascular safety of new diabetes therapies in patients with type 2 diabetes in order to rule out excess cardiovascular risk. The cardiovascular effects of semaglutide, a glucagon-like peptide 1 analogue with an extended half-life of approximately 1 week, in type 2 diabetes are unknown.

We randomly assigned 3297 patients with type 2 diabetes who were on a standard-care regimen to receive once-weekly semaglutide (0.5 mg or 1.0 mg) or placebo for 104 weeks. The primary composite outcome was the first occurrence of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. We hypothesized that semaglutide would be noninferior to placebo for the primary outcome. The noninferiority margin was 1.8 for the upper boundary of the 95% confidence interval of the hazard ratio.

At baseline, 2735 of the patients (83.0%) had established cardiovascular disease, chronic kidney disease, or both. The primary outcome occurred in 108 of 1648 patients (6.6%) in the semaglutide group and in 146 of 1649 patients (8.9%) in the placebo group (hazard ratio, 0.74; 95% confidence interval [CI], 0.58 to 0.95; P<0.001 for noninferiority). Nonfatal myocardial infarction occurred in 2.9% of the patients receiving semaglutide and in 3.9% of those receiving placebo (hazard ratio, 0.74; 95% CI, 0.51 to 1.08; P=0.12); nonfatal stroke occurred in 1.6% and 2.7%, respectively (hazard ratio, 0.61; 95% CI, 0.38 to 0.99; P=0.04). Rates of death from cardiovascular causes were similar in the two groups. Rates of new or worsening nephropathy were lower in the semaglutide group, but rates of retinopathy complications (vitreous hemorrhage, blindness, or conditions requiring treatment with an intravitreal agent or photocoagulation) were significantly higher (hazard ratio, 1.76; 95% CI, 1.11 to 2.78; P=0.02). Fewer serious adverse events occurred in the semaglutide group, although more patients discontinued treatment because of adverse events, mainly gastrointestinal.

In patients with type 2 diabetes who were at high cardiovascular risk, the rate of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke was significantly lower among patients receiving semaglutide than among those receiving placebo, an outcome that confirmed the noninferiority of semaglutide. (Funded by Novo Nordisk; SUSTAIN-6 ClinicalTrials.gov number, NCT01720446 .).

Mesenchymal stem cells (MSCs) have been recently shown to inhibit T-cell proliferation to polyclonal stimuli. We characterized the effect of MSCs of bone marrow origin on the T-cell response of naive and memory T cells to their cognate antigenic epitopes. The immune response to murine male transplantation antigens, HY, was selected because the peptide identity and major histocompatibility complex (MHC) restriction of the immunodominant epitopes are known. C57BL/6 female mice immunized with male cells were the source of memory T cells, whereas C6 mice transgenic for HY-specific T-cell receptor provided naive T cells. Responder cells were stimulated in vitro with male spleen cells or HY peptides in the presence or absence of MSCs. MSCs inhibited HY-specific naive and memory T cells in a dose-dependent fashion and affected cell proliferation, cytotoxicity, and the number of interferon gamma (IFN-gamma)-producing HY peptide-specific T cells. However, the MSC inhibitory effect did not selectively target antigen-reactive T cells. When MSCs were added to the T-cell cultures in a Transwell system or MSCs were replaced by MSC culture supernatant, the inhibitory activity was abrogated. T-cell reactivity was also restored if MSCs were removed from the cultures. The expression of MHC molecules and the presence in culture of antigen-presenting cells (APCs) or of CD4(+)/CD25(+) regulatory T cells were not required for MSCs to inhibit. We conclude that MSCs inhibit naive and memory T-cell responses to their cognate antigens. Overall our data suggest that MSCs physically hinder T cells from the contact with APCs in a noncognate fashion.

BACKGROUND

Tuberous Sclerosis Complex (TSC) is a genetic disorder that occurs through the loss of heterozygosity of either TSC1 or TSC2, which encode Hamartin or Tuberin, respectively. Tuberin and Hamartin form a tumor suppressor heterodimer that inhibits the mammalian target of rapamycin (mTOR) nutrient signaling input, but how this occurs is unclear.

RESULTS

We show that the small G protein Rheb (Ras homolog enriched in brain) is a molecular target of TSC1/TSC2 that regulates mTOR signaling. Overexpression of Rheb activates 40S ribosomal protein S6 kinase 1 (S6K1) but not p90 ribosomal S6 kinase 1 (RSK1) or Akt. Furthermore, Rheb induces phosphorylation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1) and causes 4E-BP1 to dissociate from eIF4E. This dissociation is completely sensitive to rapamycin (an mTOR inhibitor) but not wortmannin (a phosphoinositide 3-kinase [PI3K] inhibitor). Rheb also activates S6K1 during amino acid insufficiency via a rapamycin-sensitive mechanism, suggesting that Rheb participates in nutrient signaling through mTOR. Moreover, Rheb does not activate a S6K1 mutant that is unresponsive to mTOR-mediated signals, confirming that Rheb functions upstream of mTOR. Overexpression of the Tuberin-Hamartin heterodimer inhibits Rheb-mediated S6K1 activation, suggesting that Tuberin functions as a Rheb GTPase activating protein (GAP). Supporting this notion, TSC patient-derived Tuberin GAP domain mutants were unable to inactivate Rheb in vivo. Moreover, in vitro studies reveal that Tuberin, when associated with Hamartin, acts as a Rheb GTPase-activating protein. Finally, we show that membrane localization of Rheb is important for its biological activity because a farnesylation-defective mutant of Rheb stimulated S6K1 activation less efficiently.

CONCLUSIONS

We show that Rheb acts as a novel mediator of the nutrient signaling input to mTOR and is the molecular target of TSC1 and TSC2 within mammalian cells.

The ability of drugs of abuse to increase dopamine in nucleus accumbens underlies their reinforcing effects. However, preclinical studies have shown that with repeated drug exposure neutral stimuli paired with the drug (conditioned stimuli) start to increase dopamine by themselves, which is an effect that could underlie drug-seeking behavior. Here we test whether dopamine increases occur to conditioned stimuli in human subjects addicted to cocaine and whether this is associated with drug craving. We tested eighteen cocaine-addicted subjects using positron emission tomography and [11C]raclopride (dopamine D2 receptor radioligand sensitive to competition with endogenous dopamine). We measured changes in dopamine by comparing the specific binding of [11C]raclopride when subjects watched a neutral video (nature scenes) versus when they watched a cocaine-cue video (scenes of subjects smoking cocaine). The specific binding of [11C]raclopride in dorsal (caudate and putamen) but not in ventral striatum (in which nucleus accumbens is located) was significantly reduced in the cocaine-cue condition and the magnitude of this reduction correlated with self-reports of craving. Moreover, subjects with the highest scores on measures of withdrawal symptoms and of addiction severity that have been shown to predict treatment outcomes, had the largest dopamine changes in dorsal striatum. This provides evidence that dopamine in the dorsal striatum (region implicated in habit learning and in action initiation) is involved with craving and is a fundamental component of addiction. Because craving is a key contributor to relapse, strategies aimed at inhibiting dopamine increases from conditioned responses are likely to be therapeutically beneficial in cocaine addiction.

The occurrence of ventricular premature depolarizations in survivors of myocardial infarction is a risk factor for subsequent sudden death, but whether antiarrhythmic therapy reduces the risk is not known. The Cardiac Arrhythmia Suppression Trial (CAST) is evaluating the effect of antiarrhythmic therapy (encainide, flecainide, or moricizine) in patients with asymptomatic or mildly symptomatic ventricular arrhythmia (six or more ventricular premature beats per hour) after myocardial infarction. As of March 30, 1989, 2309 patients had been recruited for the initial drug-titration phase of the study: 1727 (75 percent) had initial suppression of their arrhythmia (as assessed by Holter recording) through the use of one of the three study drugs and had been randomly assigned to receive active drug or placebo. During an average of 10 months of follow-up, the patients treated with active drug had a higher rate of death from arrhythmia than the patients assigned to placebo. Encainide and flecainide accounted for the excess of deaths from arrhythmia and nonfatal cardiac arrests (33 of 730 patients taking encainide or flecainide [4.5 percent]; 9 of 725 taking placebo [1.2 percent]; relative risk, 3.6; 95 percent confidence interval, 1.7 to 8.5). They also accounted for the higher total mortality (56 of 730 [7.7 percent] and 22 of 725 [3.0 percent], respectively; relative risk, 2.5; 95 percent confidence interval, 1.6 to 4.5). Because of these results, the part of the trial involving encainide and flecainide has been discontinued. We conclude that neither encainide nor flecainide should be used in the treatment of patients with asymptomatic or minimally symptomatic ventricular arrhythmia after myocardial infarction, even though these drugs may be effective initially in suppressing ventricular arrhythmia. Whether these results apply to other patients who might be candidates for antiarrhythmic therapy is unknown.

There are currently about 10000 drug-like compounds. These are sparsely, rather than uniformly, distributed through chemistry space. True diversity does not exist in experimental combinatorial chemistry screening libraries. Absorption, distribution, metabolism, and excretion (ADME) and chemical reactivity-related toxicity is low, while biological receptor activity is higher dimensional in chemistry space, and this is partly explainable by evolutionary pressures on ADME to deal with endobiotics and exobiotics. ADME is hard to predict for large data sets because current ADME experimental screens are multi-mechanisms, and predictions get worse as more data accumulates. Currently, screening for biological receptor activity precedes or is concurrent with screening for properties related to "drugability." In the future, "drugability" screening may precede biological receptor activity screening. The level of permeability or solubility needed for oral absorption is related to potency. The relative importance of poor solubility and poor permeability towards the problem of poor oral absorption depends on the research approach used for lead generation. A "rational drug design" approach as exemplified by Merck advanced clinical candidates leads to time-dependent higher molecular weight, higher H-bonding properties, unchanged lipophilicity, and, hence, poorer permeability. A high throughput screening (HTS)-based approach as exemplified by unpublished data on Pfizer (Groton, CT) early candidates leads to higher molecular weight, unchanged H-bonding properties, higher lipophilicity, and, hence, poorer aqueous solubility.

OBJECTIVE

To determine whether a nutritional supplement of selenium will decrease the incidence of cancer.

METHODS

A multicenter, double-blind, randomized, placebo-controlled cancer prevention trial.

METHODS

Seven dermatology clinics in the eastern United States.

METHODS

A total of 1312 patients (mean age, 63 years; range, 18-80 years) with a history of basal cell or squamous cell carcinomas of the skin were randomized from 1983 through 1991. Patients were treated for a mean (SD) of 4.5 (2.8) years and had a total follow-up of 6.4 (2.0) years.

METHODS

Oral administration of 200 microg of selenium per day or placebo.

METHODS

The primary end points for the trial were the incidences of basal and squamous cell carcinomas of the skin. The secondary end points, established in 1990, were all-cause mortality and total cancer mortality, total cancer incidence, and the incidences of lung, prostate, and colorectal cancers.

RESULTS

After a total follow-up of 8271 person-years, selenium treatment did not significantly affect the incidence of basal cell or squamous cell skin cancer. There were 377 new cases of basal cell skin cancer among patients in the selenium group and 350 cases among the control group (relative risk [RR], 1.10; 95% confidence interval [CI], 0.95-1.28), and 218 new squamous cell skin cancers in the selenium group and 190 cases among the controls (RR, 1.14; 95% CI, 0.93-1.39). Analysis of secondary end points revealed that, compared with controls, patients treated with selenium had a nonsignificant reduction in all-cause mortality (108 deaths in the selenium group and 129 deaths in the control group [RR; 0.83; 95% CI, 0.63-1.08]) and significant reductions in total cancer mortality (29 deaths in the selenium treatment group and 57 deaths in controls [RR, 0.50; 95% CI, 0.31-0.80]), total cancer incidence (77 cancers in the selenium group and 119 in controls [RR, 0.63; 95% CI, 0.47-0.85]), and incidences of lung, colorectal, and prostate cancers. Primarily because of the apparent reductions in total cancer mortality and total cancer incidence in the selenium group, the blinded phase of the trial was stopped early. No cases of selenium toxicity occurred.

CONCLUSIONS

Selenium treatment did not protect against development of basal or squamous cell carcinomas of the skin. However, results from secondary end-point analyses support the hypothesis that supplemental selenium may reduce the incidence of, and mortality from, carcinomas of several sites. These effects of selenium require confirmation in an independent trial of appropriate design before new public health recommendations regarding selenium supplementation can be made

MicroRNAs are well suited to regulate tumor metastasis because of their capacity to coordinately repress numerous target genes, thereby potentially enabling their intervention at multiple steps of the invasion-metastasis cascade. We identify a microRNA exemplifying these attributes, miR-31, whose expression correlates inversely with metastasis in human breast cancer patients. Overexpression of miR-31 in otherwise-aggressive breast tumor cells suppresses metastasis. We deploy a stable microRNA sponge strategy to inhibit miR-31 in vivo; this allows otherwise-nonaggressive breast cancer cells to metastasize. These phenotypes do not involve confounding influences on primary tumor development and are specifically attributable to miR-31-mediated inhibition of several steps of metastasis, including local invasion, extravasation or initial survival at a distant site, and metastatic colonization. Such pleiotropy is achieved via coordinate repression of a cohort of metastasis-promoting genes, including RhoA. Indeed, RhoA re-expression partially reverses miR-31-imposed metastasis suppression. These findings indicate that miR-31 uses multiple mechanisms to oppose metastasis.

The discovery of long-lived epithelial stem cells in the bulge region of the hair follicle led to the hypothesis that epidermal renewal and epidermal repair after wounding both depend on these cells. To determine whether bulge cells are necessary for epidermal renewal, here we have ablated these cells by targeting them with a suicide gene encoding herpes simplex virus thymidine kinase (HSV-TK) using a Keratin 1-15 (Krt1-15) promoter. We show that ablation leads to complete loss of hair follicles but survival of the epidermis. Through fate-mapping experiments, we find that stem cells in the hair follicle bulge do not normally contribute cells to the epidermis which is organized into epidermal proliferative units, as previously predicted. After epidermal injury, however, cells from the bulge are recruited into the epidermis and migrate in a linear manner toward the center of the wound, ultimately forming a marked radial pattern. Notably, although the bulge-derived cells acquire an epidermal phenotype, most are eliminated from the epidermis over several weeks, indicating that bulge stem cells respond rapidly to epidermal wounding by generating short-lived 'transient amplifying' cells responsible for acute wound repair. Our findings have implications for both gene therapy and developing treatments for wounds because it will be necessary to consider epidermal and hair follicle stem cells as distinct populations.

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory condition of the central nervous system with similarities to multiple sclerosis. In both diseases, circulating leukocytes penetrate the blood-brain barrier and damage myelin, resulting in impaired nerve conduction and paralysis. We sought to identify the adhesion receptors that mediate the attachment of circulating leukocytes to inflamed brain endothelium in EAE, because this interaction is the first step in leukocyte entry into the central nervous system. Using an in vitro adhesion assay on tissue sections, we found that lymphocytes and monocytes bound selectively to inflamed EAE brain vessels. Binding was inhibited by antibodies against the integrin molecule alpha 4 beta 1, but not by antibodies against numerous other adhesion receptors. When tested in vivo, anti-alpha 4 integrin effectively prevented the accumulation of leukocytes in the central nervous system and the development of EAE. Thus, therapies designed to interfere with alpha 4 beta 1 integrin may be useful in treating inflammatory diseases of the central nervous system, such as multiple sclerosis.

It is generally accepted that human bipedal upright stance is achieved by feedback mechanisms that generate an appropriate corrective torque based on body-sway motion detected primarily by visual, vestibular, and proprioceptive sensory systems. Because orientation information from the various senses is not always available (eyes closed) or accurate (compliant support surface), the postural control system must somehow adjust to maintain stance in a wide variety of environmental conditions. This is the sensorimotor integration problem that we investigated by evoking anterior-posterior (AP) body sway using pseudorandom rotation of the visual surround and/or support surface (amplitudes 0.5-8 degrees ) in both normal subjects and subjects with severe bilateral vestibular loss (VL). AP rotation of body center-of-mass (COM) was measured in response to six conditions offering different combinations of available sensory information. Stimulus-response data were analyzed using spectral analysis to compute transfer functions and coherence functions over a frequency range from 0.017 to 2.23 Hz. Stimulus-response data were quite linear for any given condition and amplitude. However, overall behavior in normal subjects was nonlinear because gain decreased and phase functions sometimes changed with increasing stimulus amplitude. "Sensory channel reweighting" could account for this nonlinear behavior with subjects showing increasing reliance on vestibular cues as stimulus amplitudes increased. VL subjects could not perform this reweighting, and their stimulus-response behavior remained quite linear. Transfer function curve fits based on a simple feedback control model provided estimates of postural stiffness, damping, and feedback time delay. There were only small changes in these parameters with increasing visual stimulus amplitude. However, stiffness increased as much as 60% with increasing support surface amplitude. To maintain postural stability and avoid resonant behavior, an increase in stiffness should be accompanied by a corresponding increase in damping. Increased damping was achieved primarily by decreasing the apparent time delay of feedback control rather than by changing the damping coefficient (i.e., corrective torque related to body-sway velocity). In normal subjects, stiffness and damping were highly correlated with body mass and moment of inertia, with stiffness always about 1/3 larger than necessary to resist the destabilizing torque due to gravity. The stiffness parameter in some VL subjects was larger compared with normal subjects, suggesting that they may use increased stiffness to help compensate for their loss. Overall results show that the simple act of standing quietly depends on a remarkably complex sensorimotor control system.

The COVID-19 pandemic represents a massive global health crisis. Because the crisis requires large-scale behaviour change and places significant psychological burdens on individuals, insights from the social and behavioural sciences can be used to help align human behaviour with the recommendations of epidemiologists and public health experts. Here we discuss evidence from a selection of research topics relevant to pandemics, including work on navigating threats, social and cultural influences on behaviour, science communication, moral decision-making, leadership, and stress and coping. In each section, we note the nature and quality of prior research, including uncertainty and unsettled issues. We identify several insights for effective response to the COVID-19 pandemic and highlight important gaps researchers should move quickly to fill in the coming weeks and months.

A general strategy for selecting insertion mutations in mice has been devised. Constructs lacking a promoter and including a beta-galactosidase gene, or a reporter gene encoding a protein with both beta-galactosidase and neomycin phosphotransferase activity, were designed so that activation of the reporter gene depends on its insertion within an active transcription unit. Such insertion events create a mutation in the tagged gene and allow its expression to be followed by beta-galactosidase activity. Introduction of promoter trap constructs into embryonic stem (ES) cells by electroporation or retroviral infection has led to the derivation of transgenic lines that show a variety of beta-galactosidase expression patterns. Intercrossing of heterozygotes from 24 strains that express beta-galactosidase identified 9 strains in which homozygosity leads to an embryonic lethality. Because no overt phenotype was detected in the remaining strains, these results suggest that a substantial proportion of mammalian genes identified by this approach are not essential for development.

Interaction of spherical particles with cells and within animals has been studied extensively, but the effects of shape have received little attention. Here we use highly stable, polymer micelle assemblies known as filomicelles to compare the transport and trafficking of flexible filaments with spheres of similar chemistry. In rodents, filomicelles persisted in the circulation up to one week after intravenous injection. This is about ten times longer than their spherical counterparts and is more persistent than any known synthetic nanoparticle. Under fluid flow conditions, spheres and short filomicelles are taken up by cells more readily than longer filaments because the latter are extended by the flow. Preliminary results further demonstrate that filomicelles can effectively deliver the anticancer drug paclitaxel and shrink human-derived tumours in mice. Although these findings show that long-circulating vehicles need not be nanospheres, they also lend insight into possible shape effects of natural filamentous viruses.

BACKGROUND

Beta-blocking agents reduce the risk of hospitalization and death in patients with mild-to-moderate heart failure, but little is known about their effects in severe heart failure.

METHODS

We evaluated 2289 patients who had symptoms of heart failure at rest or on minimal exertion, who were clinically euvolemic, and who had an ejection fraction of less than 25 percent. In a double-blind fashion, we randomly assigned 1133 patients to placebo and 1156 patients to treatment with carvedilol for a mean period of 10.4 months, during which standard therapy for heart failure was continued. Patients who required intensive care, had marked fluid retention, or were receiving intravenous vasodilators or positive inotropic drugs were excluded.

RESULTS

There were 190 deaths in the placebo group and 130 deaths in the carvedilol group. This difference reflected a 35 percent decrease in the risk of death with carvedilol (95 percent confidence interval, 19 to 48 percent; P=0.00013, unadjusted; P=0.0014, adjusted for interim analyses). A total of 507 patients died or were hospitalized in the placebo group, as compared with 425 in the carvedilol group. This difference reflected a 24 percent decrease in the combined risk of death or hospitalization with carvedilol (95 percent confidence interval, 13 to 33 percent; P<0.001). The favorable effects on both end points were seen consistently in all the subgroups we examined, including patients with a history of recent or recurrent cardiac decompensation. Fewer patients in the carvedilol group than in the placebo group withdrew because of adverse effects or for other reasons (P=0.02).

CONCLUSIONS

The previously reported benefits of carvedilol with regard to morbidity and mortality in patients with mild-to-moderate heart failure were also apparent in the patients with severe heart failure who were evaluated in this trial.

We employed a whole body magnetic resonance imaging protocol to examine the influence of age, gender, body weight, and height on skeletal muscle (SM) mass and distribution in a large and heterogeneous sample of 468 men and women. Men had significantly (P < 0.001) more SM in comparison to women in both absolute terms (33.0 vs. 21.0 kg) and relative to body mass (38.4 vs. 30.6%). The gender differences were greater in the upper (40%) than lower (33%) body (P < 0.01). We observed a reduction in relative SM mass starting in the third decade; however, a noticeable decrease in absolute SM mass was not observed until the end of the fifth decade. This decrease was primarily attributed to a decrease in lower body SM. Weight and height explained approximately 50% of the variance in SM mass in men and women. Although a linear relationship existed between SM and height, the relationship between SM and body weight was curvilinear because the contribution of SM to weight gain decreased with increasing body weight. These findings indicate that men have more SM than women and that these gender differences are greater in the upper body. Independent of gender, aging is associated with a decrease in SM mass that is explained, in large measure, by a decrease in lower body SM occurring after the fifth decade.

In this study we report on the 1H, 13C and 15N NMR chemical shifts for the random coil state and nearest-neighbor sequence effects measured from the protected linear hexapeptide Gly-Gly-X-Y-Gly-Gly (where X and Y are any of the 20 common amino acids). We present data for a set of 40 peptides (of the possible 400) including Gly-Gly-X-Ala-Gly-Gly and Gly-Gly-X-Pro-Gly-Gly, measured under identical aqueous conditions. Because all spectra were collected under identical experimental conditions, the data from the Gly-Gly-X-Ala-Gly-Gly series provide a complete and internally consistent set of 1H, 13C and 15N random coil chemical shifts for all 20 common amino acids. In addition, studies were also conducted into nearest-neighbor effects on the random coil shift arising from a variety of X and Y positional substitutions. Comparisons between the chemical shift measurements obtained from Gly-Gly-X-Ala-Gly-Gly and Gly-Gly-X-Pro-Gly-Gly reveal significant systematic shift differences arising from the presence of proline in the peptide sequence. Similarly, measurements of the chemical shift changes occurring for both alanine and proline (i.e., the residues in the Y position) are found to depend strongly on the type of amino acid substituted into the X position. These data lend support to the hypothesis that sequence effects play a significant role in determining peptide and protein chemical shifts.

Cystic fibrosis transmembrane conductance regulator (CFTR) is a plasma membrane Cl- channel regulated by cyclic AMP-dependent phosphorylation and by intracellular ATP. Mutations in CFTR cause cystic fibrosis partly through loss of cAMP-regulated Cl- permeability from the plasma membrane of affected epithelia. The most common mutation in cystic fibrosis is deletion of phenylalanine at residue 508 (CFTR delta F508) (ref. 10). Studies on the biosynthesis and localization of CFTR delta F508 indicate that the mutant protein is not processed correctly and, as a result, is not delivered to the plasma membrane. These conclusions are consistent with earlier functional studies which failed to detect cAMP-stimulated Cl- channels in cells expressing CFTR delta F508 (refs 16, 17). Chloride channel activity was detected, however, when CFTR delta F508 was expressed in Xenopus oocytes, Vero cells and Sf9 insect cells. Because oocytes and Sf9 cells are typically maintained at lower temperatures than mammalian cells, and because processing of nascent proteins can be sensitive to temperature, we tested the effect of temperature on the processing of CFTR delta F508. Here we show that the processing of CFTR delta F508 reverts towards that of wild-type as the incubation temperature is reduced. When the processing defect is corrected, cAMP-regulated Cl- channels appear in the plasma membrane. These results reconcile previous contradictory observations and suggest that the mutant most commonly associated with cystic fibrosis is temperature-sensitive.