The suppression of star formation by powerful active galactic nuclei.

The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.

Submillimetre galaxies reside in dark matter haloes with masses greater than 3 × 10(11) solar masses.

The extragalactic background light at far-infrared wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared telescopes. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity variations. A previous attempt at measuring this power spectrum resulted in the suggestion that the clustering amplitude is below the level computed with a simple ansatz based on a halo model. Here we report excess clustering over the linear prediction at arcminute angular scales in the power spectrum of brightness fluctuations at 250, 350 and 500 µm. From this excess, we find that submillimetre galaxies are located in dark matter haloes with a minimum mass, M(min), such that log(10)[M(min)/M(⊙)] = 11.5(+0.7)(-0.2) at 350 µm, where M(⊙) is the solar mass. This minimum dark matter halo mass corresponds to the most efficient mass scale for star formation in the Universe, and is lower than that predicted by semi-analytical models for galaxy formation.

The detection of a population of submillimeter-bright, strongly lensed galaxies.

Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.

Service users and other stakeholders' evaluation of a liaison mental health service in an accident and emergency department and a general hospital setting.

Liaison mental health care has been an emerging specialism of mental health nursing in the UK since the early 1990s. Studies have so far looked only briefly at service user evaluation. A qualitative study involving 47 interviews with service user and professional stakeholders was undertaken to determine what is important to stakeholders in a liaison mental health-care service. The largest group of stakeholders interviewed were service users. Analysis of the data was undertaken using the service user interviews to guide the development of themes. The majority of the issues identified were raised by both service users and professionals. The three key themes were, the practicalities of the service including waiting time, the staffing profile and receiving the service, which included issues such as the opportunity to talk and outcomes. The findings provide new information regarding what service users and other stakeholders expect from a liaison mental health service and important areas to consider when offering a satisfactory service.

Evaluating the introduction of a pilot client attachment scheme in mental health nursing education.

Client attachment (CA) allows student nurses to gain clinical experience through forming therapeutic attachments with individual clients, rather than through a series of location-based placements. This paper describes a pilot project that evaluated CA with pre-registration student mental health nurses. Using semi-structured interviews, the researchers identified the students', their supervisor's, and their clients' experiences of CA. Most participants agreed that students were able to learn relevant and appropriate clinical skills, and to consolidate experience-increasing motivation, autonomy, organizational skills, and confidence.

A review of research on the structure, process and outcome of liaison mental health services.

Liaison mental health services (LMHS) developed originally to address the mental health needs of people with physical illnesses in general hospitals and more recently to work also with people with mental health problems presenting at non-mental health services. The purpose of the present paper was to review empirical research on the structure, process and outcome of liaison mental health services using systematic review methods. Following a comprehensive search strategy, the authors reviewed 48 papers published between 1975 and 2001. There is an extensive international literature on LMHS, much of which describes the structure and process of liaison work. Studies evaluating the outcomes of liaison mental health services are fewer, and handicapped by methodological flaws, some of which are serious enough to cast doubts on the reported results. Professionals and clients value LMHS. LMHS based in accident and emergency (A & E) departments appear to ease the burden of general A & E staff, help clients access mental health services and reduce re-admission rates of people with mental health problems. There is little evidence supporting one model of configuring LMHS over another.

Safety and security policies on psychiatric acute admission wards: results from a London-wide survey.

Very little research evidence is available regarding current safety and security procedures on acute psychiatric wards. This includes controversial areas such as the temporary removal of personal property, the searching of patients and visitors, the use of alarms and modern technology, and locking of entrances to regulate those entering and leaving. This is also despite widening dismay over increasing violence within a variety of hospital settings, the comparatively high risk of physical assault faced by mental health professionals and an abundance of literature and training in regards to violence management and prevention. To gain an understanding of current safety and security measures, a London-wide survey of acute admission wards was undertaken revealing a wide variety of measures and policies in operation. Over 100 NHS and private wards were sent questionnaires; there was a response rate of 70%. Results show that a significant proportion of acute admission wards are now locked at all times and a small proportion of units have 24-hour security/reception staff on-site and a low level of modern technology usage such as CCTV and electronic access systems. There is wide variation in items banned, restrictions placed on inpatients, and the searching of patients and visitors. Two independently varying emphases of ward security policies were identifiable, the first aimed at preventing harm to patients using door security, banning of item and restrictions on inpatients. The other is aimed at reducing risks to staff via searching of patients, use of security guards and sophisticated alarm systems. There is some preliminary evidence that these security policies are differentially associated with levels of absconding and violent incidents. Further research to guide practice is urgently required.

Characteristics of an Accident and Emergency liaison mental health service in East London.

AIM OF THE STUDY: To analyse the work of a liaison mental health service at the Accident and Emergency (A & E) department of a hospital in East London. BACKGROUND: The English National Service Frameworks (NSF) for Mental Health recommend that A & E departments provide liaison mental health services and this study reports how a service in East London is responding to this challenge. RESEARCH METHODS: Data were collected during a 14-month period using a specially designed audit form. RESULTS: The typical referral was aged 36, of either sex, United Kingdom (UK) non-White with a diagnosis of depression. The majority of referrals were in the afternoon and seen immediately. A slight majority were known to mental health services; many were new referrals. Older and male clients were more likely, and Bengali and other Asian clients were less likely, to be registered with a psychiatrist. There were seasonal variations in referral type. Emergency referrals tended to have a diagnosis of schizophrenia; urgent and non-urgent referrals were more likely to be depressed. The outcome for the majority of referrals was referral to appropriate community services. The majority of non-clinical referrals were for advice, information and support. DISCUSSION AND CONCLUSIONS: The service seems a useful resource for A & E staff, and clients with mental health problems. The service is a channel through which people access mental health services and appears to address the NSF for Mental Health.

Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase gene expression by sterols and nonsterols in rat liver.

The mechanisms by which sterols and nonsterols regulate hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase gene expression was investigated by measuring mRNA, protein, and enzyme activity in rats fed cholesterol or given drugs that deplete both endogenous sterols and nonsterols or that selectively deplete sterols. It was found that while dietary cholesterol had little effect on HMG-CoA reductase mRNA levels; immunoreactive protein was reduced to barely detectable levels, as was enzyme activity. Any possible effect on catalytic efficiency is thus ruled out. When rats were fed diets containing Lovastatin, a potent HMG-CoA reductase inhibitor which blocks synthesis of both nonsterols and sterols, similar 15- to 20-fold increases were observed for both HMG-CoA reductase mRNA and activity. However, HMG-CoA reductase immunoreactive protein was increased more than 200-fold. When endogenous sterols were selectively depleted by inhibiting squalene synthase with Zargozic acid A, the increase observed in reductase mRNA was similar to that seen in immunoreactive protein and enzyme activity. This is consistent with the concept that endogenous sterols exert their effects at the level of transcription while endogenous nonsterols act at the level of translation. The results suggest that in whole animals, sterols likely act at the level of mRNA while nonsterols exert their regulatory effects at the level of HMG-CoA reductase protein.

Specificity of a nucleolar 2'-O-methyltransferase for RNA substrates.

In this study we examined the specificity of a nucleolar 2'-O-methyltransferase isolated from nucleoli of Ehrlich ascites tumor cells. The nucleolar methyltransferase was capable of methylating each of the four nucleosides of RNA, however, the level of methylation at a particular nucleoside varied with the type of RNA. Both kinetic analysis and the stimulation of methylation by polyamines suggested that the structure of RNA was critical in influencing the discrimination and apparent specificity of nucleolar 2'-O-methyltransferase.

Isolation and characterization of a nucleolar 2'-O-methyltransferase from Ehrlich ascites tumor cells.

A 2'-O-methyltransferase that transfers the methyl group from S-adenosylmethionine to the 2'-hydroxyl group of ribose moieties of RNA has been purified from Ehrlich ascites tumor cell nucleoli. The partially purified enzyme is devoid of other RNA methylase activities and is free of ribonucleases. The enzyme has optimal activity in tris(hydroxymethyl)aminomethane buffer, pH 8.0, in the presence of 0.4 mM ethylenediaminetetraacetic acid, 2 mM dithiothreitol, and 50 mM KCl, and has an apparent Km for S-adenosylmethionine of 0.44 microM. Gel filtration studies of this enzyme gave a Stokes radius of 43 A. Sedimentation velocity measurements in glycerol gradients yield an S20,w of 8.0 S. From these values, a native molecular weight of 145,000 was calculated. The enzyme catalyzes the methylation of synthetic homoribopolymers as well as 18S and 28S rRNA; however, poly(C) is the preferred synthetic substrate, and preference for unmethylated sequences of rRNA was observed. For each RNA substrate examined, only methylation of the 2'-hydroxyl group of the ribose moieties was detected.

Activation of rat liver microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase by NADPH. Effects of dietary treatments.

The sigmoidal curves observed for rat liver microsomal 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase with NADPH as the varied substrate were markedly affected by feeding the animals diets containing colestipol, mevinolin and colestipol or cholesterol. Feeding of mevinolin and colestipol decreased the S0.5 for NADPH from 270 to 40 microM, while cholesterol feeding increased the value to 1.3 mM. Immuno-blotting analysis revealed that the Mr 100,000 form of HMG-CoA reductase predominated in cases where the S0.5 value was lowest, and the Mr 200,000 species was the major form where the S0.5 values were highest. Activation of HMG-CoA reductase by NADPH was not due to conversion of the Mr 200,000 form to the 100,000 form.

Purification and properties of a novel nucleolar exoribonuclease capable of degrading both single-stranded and double-stranded RNA.

A ribonuclease that hydrolyzes either linear duplex or single-stranded RNA in an exonucleolytic manner has been partially purified from Ehrlich ascites tumor cell nucleoli and is free from other ribonucleases. The enzyme will also degrade the RNA complement of an RNA X DNA duplex; however, no nuclease activity is observed on linear duplex or single-stranded DNA. The exonuclease acts on RNA nonprocessively from the 3' end releasing 5'-mononucleotides. The enzyme has a broad pH optimum around pH 8.0, requires Mg2+ or Mn2+ (0.06 mM) for optimum activity, and is sensitive to ethylenediaminetetraacetic acid and N-ethylmaleimide inhibition. Monovalent cations including K+, Na+, and NH4+ are inhibitory. Gel filtration studies of this enzyme gave a Stokes radius of 40 A. Sedimentation velocity measurements in glycerol gradients yield a S20,W of 6.0 S. From these values a native molecular weight of 100 000 was calculated. Copurification of the single- and double-stranded activities, identical reaction requirements, and identical heat-inactivation curves strongly suggest that both activities reside with the same enzyme.

The effect of RNA secondary structure on the action of a nucleolar endoribonuclease.

The effect of the folded macromolecular structure of RNA on the action of a purified single strand specific nucleolar ribonuclease was studied by comparing the limited hydrolysis of defined RNA substrates. The nucleolar RNase was shown to attack only single-stranded regions of the native 5.8 S rRNA, consistent with a computer-derived model for the secondary structure (Nazar, R. N., Stitz, T. O., and Busch, H. (1975) J. Biol. Chem. 250, 8591-8597). The single strand specific nucleolar RNase, unlike S1 nuclease, does not release the end-labeled nucleotide and therefore provides a more useful probe for structural analysis at or near 3'- or 5'-terminal ends of an RNA molecule. Although attacking only single strand regions of the native 5.8 S rRNA, the selectivity of the nucleolar RNase, when compared to S1 nuclease, is distinct and supports the suggestion that other factors besides the proposed secondary structure must also influence nuclease attack. The selective and limited attack of the nucleolar RNase on native RNA was similarly observed using mouse 45 S preribosomal RNA as a substrate and possibly suggests a role for this nucleolar RNase in ribosomal RNA processing.

Isolation and characterization of a single-stranded specific endoribonuclease from Ehrlich cell nucleoli.

An endoribonuclease which cleaves only single-stranded RNA has been purified from nucleoli of Ehrlich ascites tumor cells. The molecular weight of the ribonuclease is 50,000 to 52,000 as estimated from sedimentation in glycerol density gradients and by gel filtration on Sephadex G-100. The endoribonuclease requires Mg2+ or Mn2+ (0.2 mM) for optimum activity. Monovalent cations including K+, Na+, and NH+4 are inhibitory. The ribonuclease gave an apparent Km for single-stranded RNA of 30 microM. Using ribohomopolymers, we found that the enzyme could digest single-stranded, poly(C), poly(U), and poly(A) equally well, but would not degrade duplex poly(C) . poly(I) or poly(A) . poly(U). The lack of base specificity was further demonstrated using RNA sequence analysis of partial digest products of yeast 5.8 S RNA. The ribonuclease activity is sensitive to EDTA and N-ethylmaleimide, but is not inhibited by human placental RNase inhibitor. The enzyme makes endonucleolytic cleavages which generate 5'-phosphate-terminated oligonucleotides.