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Background: The outreach emergency psychiatric service plays an important role in recognising, arranging interventions and preventing suicide and suicidal behaviour. However, little is known about the assessments that members of the emergency team make when faced with patients showing suicidal behaviour.
AIM: To describe the relationships that are revealed between patient characteristics, suicidal thoughts and attempted suicide during assessments made by the emergency psychiatric service in The Hague.
METHOD: The emergency service kept a detailed record of 14,705 consultations. We compared the characteristics of patients who had suicidal thoughts with those of patients who had no such thoughts and we also compared the characteristics of patients who had attempted to commit suicide with those of patients who had not. We drew these comparisons by using logistic regression models, adjusting for clustering.
RESULTS: 32.2% of the patients showed signs of suicidal behaviour and 9.2 % appeared likely to attempt suicide. Suicidal behaviour occurred most often in patients with depression. Suicidal patients were more often admitted to hospital than were non-suicidal patients and they were more likely to have been referred by a general practitioner or a general hospital. Medication was the most frequent means employed in attempts to commit suicide.
CONCLUSION: In about one third of the consultations of the outreach emergency psychiatric service, the patient showed suicidal behaviour. The actions and the policy of the emergency psychiatric service with regard to suicidal behaviour were diverse and dependent on factors that could change over the course of time.

Background: Randomised studies examining the effect on patients of training professionals in adherence to suicide guidelines are scarce., Aims: To assess whether patients benefited from the training of professionals in adherence to suicide guidelines., Method: In total 45 psychiatric departments were randomised (Dutch trial register: NTR3092). In the intervention condition, all staff in the departments were trained with an e-learning supported train-the-trainer programme. After the intervention, patients were assessed at admission and at 3-month follow-up. Primary outcome was change in suicide ideation, assessed with the Beck Scale for Suicide Ideation., Results: For the total group of 566 patients with a positive score on the Beck Scale for Suicide Ideation at baseline, intention-to-treat analysis showed no effects of the intervention on patient outcomes at 3-month follow-up. Patients who were suicidal with a DSM-IV diagnosis of depression (n = 154) showed a significant decrease in suicide ideation when treated in the intervention group. Patients in the intervention group more often reported that suicidality was discussed during treatment., Conclusions: Overall, no effect of our intervention on patients was found. However, we did find a beneficial effect of the training of professionals on patients with depression., (© The Royal College of Psychiatrists 2015.)

Background: Suffering from a psychiatric disorder is a well-known risk factor for suicide and suicidal behavior. Treatment of psychiatric disorders can reduce the risk of suicidal behavior and suicide. In the Netherlands, however, since 2012 the treatment costs of some psychiatric disorders have no longer been covered by health insurance.
AIM: To find out what proportion of suicides were committed by patients with a psychiatric disorder for which treatment costs are no longer covered by health insurance since the rules changed in 2012.
METHOD: We studied the files of 314 patients who were known to one of the large mental health hospitals in the Netherlands and who had committed suicide between 1 January 1999 and January 2012. We were able to determine the various psychiatric disorders from which the patients were suffering at the time they died.
RESULTS: About 6% of the patients who committed suicide between 1999 and 2012 suffered from a psychiatric disorder for which treatment costs are now no longer covered by health insurance.
CONCLUSION: Given the results of this study, the increased rates of suicide in the Netherlands and the importance of scientific research into the characteristics of suicide, we recommend that patients with suicidal behavior are not excluded from adequate treatment in the event they may or may not have met the criteria for a DSM-IV classification.

The number of confused people is increasing in Dutch society; the exact reason, however, is unknown. Recently, the government has formed a task force 'confused persons' to achieve more seamless care and support for people in great need. This comment describes, from a psychiatric care perspective, the changes that have occurred during the last few years which may have a causal relationship with the increase in incidence of confused people in the community.

Background: Admission at a closed acute psychiatric ward is a severe and possibly life changing experience for a patient. Sometimes admission is accompanied by coercive measures. Despite the impact that these measures may have on the patient, very little research has been published concerning this patient population., Aim: To obtain insight into the connection between the socio-demographic characteristics of patients admitted to a closed acute psychiatric ward and the coercive measures to which they were subjected., Method: For a year a database was compiled to give us information about the socio-demographic and clinical characteristics of patients admitted to a closed acute psychiatric ward in The Hague in the Netherlands. This record enables us to analyse the relation between these characteristics and coercive measures., Results: The majority of patients admitted were male, single, childless and were unemployed or not in education but were receiving some form of welfare payment. 33% of admissions were in fact re-admissions. 20% of the admissions/re-admissions were secluded during the admission procedure - for the following reasons: symptoms of a psychotic disorder, a manic episode and/or aggression. Secluded patients were younger and had more serious psychiatric problems; they functioned less well and had been in hospital longer than patients who had not been secluded upon admission. During the admission procedure 14% of patients received emergency medication., Conclusion: These results have given us more insight into the connection between the use of coercive measures in psychiatry and the socio-demographic characteristics and clinical characteristics of the patients involved. This information could serve as reference material for future research.

Background: Multidisciplinary evaluation of suicide cases effectively decreases the suicide rate in mental health care. A new suicide prevention tool (KEHR) can be used in this connection. KEHR has been developed on the basis of the Dutch multidisciplinary practice guideline on the assessment and treatment of suicidal behaviour. The guideline can serve as a frame of reference for the multidisciplinary evaluation of suicide cases. KEHR aims to provide professionals with a better method for preventing suicide., Aim: To describe and evaluate the recently developed KEHR strategy for reducing the number of suicide cases in mental health care., Method: Naturalistic and observational study. In the course of a year 22 out of 23 suicide cases that had occurred in the pilot institution were evaluated with the help of the KEHR system. Outcomes were discussed with members of multidisciplinary teams. Quantitative and qualitative methods were used in the evaluation process., Results: Professionals from the main disciplines involved were very willing to use the new tool and were prepared to reflect on their views on the outcomes. The professionals were ready to learn from the suicide cases. Data collected with the tool provided information that can be used to improve guideline adherence. However, the use of KEHR did not lead automatically to the formulation of adjustments and improvements relating to suicidal patients. A specific procedure for improving individual and team performance needs to be developed and tested thoroughly., Conclusion: KEHR is a promising strategy for improving and enhancing the guideline on the diagnosis and treatment of suicidal behaviour of patients in mental health care. Special procedures need to be developed and studied in order to implement the improvements deemed necessary as a result of the pilot study. The KEHR tool (in the Dutch language) is accessible to mental health care workers after online registration (www.mijnkehr.nl).

Background: There is a lack of information on the cost-effectiveness of suicide prevention interventions. The current study examines the cost-effectiveness of a multifaceted structured intervention aiming to improve adherence to the national suicide practice guideline in comparison with usual implementation., Methods: In the intervention condition, professionals of psychiatric departments were trained using an e-learning supported Train-the-Trainer program. Newly admitted suicidal patients were assessed as soon as their department was trained and at 3 months follow-up. The primary outcome was improvement in suicide ideation. Missing cost and effect data were imputed using multiple imputation. Cost-effectiveness planes were plotted, and cost-effectiveness acceptability curves were estimated., Results: For the total group of suicidal patients (n=566), no effect of the intervention on suicide ideation or costs was found. For a subgroup of depressed suicidal patients (n=154, intervention=75, control=79), mean level of suicide ideation decreased with 2.7 extra points in the intervention condition, but this was not statistically significant. For this subgroup, the intervention may be considered cost-effective in comparison with usual implementation if society is willing to pay≥€ 6100 per unit of effect on the suicide ideation scale extra., Limitations: Considering the cost outcomes, we had almost no cases that were complete, and heavily relied on statistical techniques to impute the missing data. Also, diagnoses were not derived from structured clinical interviews., Conclusions: We presented the first randomized trial (trial registration: The Netherlands Trial Register (NTR3092 www.trialregister.nl)) on cost-effectiveness of a suicide practice guideline implementation in mental health care. The intervention might be considered cost-effective for depressed suicidal patients if society is willing to make substantial investments., (Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Randomized studies examining the effect of training of mental health professionals in suicide prevention guidelines are scarce. We assessed whether professionals benefited from an e-learning supported Train-the-Trainer programme aimed at the application of the Dutch multidisciplinary suicide prevention guideline., Methods: 45 psychiatric departments from all over the Netherlands were clustered in pairs and randomized. In the experimental condition, all of the staff of psychiatric departments was trained by peers with an e-learning supported Train-the-Trainer programme. Guideline adherence of individual professionals was measured by means of the response to on-line video fragments. Multilevel analyses were used to establish whether variation between conditions was due to differences between individual professionals or departments., Results: Multilevel analysis showed that the intervention resulted in an improvement of individual professionals. At the 3 month follow-up, professionals who received the intervention showed greater guideline adherence, improved self-perceived knowledge and improved confidence as providers of care than professionals who were only exposed to traditional guideline dissemination. Subgroup analyses showed that improved guideline adherence was found among nurses but not among psychiatrists and psychologists. No significant effect of the intervention on team performance was found., Limitations: The ICT environment in departments was often technically inadequate when displaying the video clips clip of the survey. This may have caused considerable drop-out and possibly introduced selection bias, as professionals who were strongly affiliated to the theme of the study might have been more likely to finish the study., Conclusions: Our results support the idea that an e-learning supported Train-the-Trainer programme is an effective strategy for implementing clinical guidelines and improving care for suicidal patients., Trial Registration: Netherlands Trial Register (NTR3092 www.trialregister.nl)., (Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Copy number variations (CNVs) are subtle variations in our genetic material. In view of the scientific claim that schizophrenia depends for 40 to 80% on hereditary factors, we need to find out what role the cnvs play in this process., Aim: To provide an overview of what is currently known about CNVs and to summarise the implications of this information for the conceptualisation of 'schizophrenia' and for the diagnosis and treatment of psychoses., Method: We performed a literature search using PubMed., Results: The literature consulted contains discussions of 23 CNVs that are associated with an increased risk of psychosis. However, the relationship between the two variables is heterogeneous and pluriform in the sense that CNVs are often associated with several disorders or their penetrance varies considerably under the influence of gene modifiers and environmental factors., Conclusion: Research into CNVs demonstrates that the relationship between psychosis and heredity is of a even more subtle nature than the two pioneers Kraepelin and Rüdin had been able to foresee. It is to be expected that in the near future research will contribute to a deconstruction of the schizophrenia concept, to a blurring of the hitherto sharply defined boundaries between different (particularly severe) mental disorders and to the introduction of genetic counselling into regular psychiatric diagnostic procedures.

Background: To strengthen suicide prevention skills in mental health care in The Netherlands, multidisciplinary teams throughout the country are trained in the application of the new Dutch guideline on the assessment and treatment of suicidal behavior. Previous studies have shown beneficial effects of additional efforts for guideline implementation on professionals' attitude, knowledge, and skills. However, the effects on patients are equally important, but are rarely measured. The main objective of this study is to examine whether patients of multidisciplinary teams who are trained in guideline application show greater recovery from suicide ideation than patients of untrained teams., Methods/design: This is a multicentre cluster randomized controlled trial (RCT), in which multidisciplinary teams from mental health care institutions are matched in pairs, and randomly allocated to either the experimental or control condition. In the experimental condition, next to the usual dissemination of the guideline (internet, newsletter, books, publications, and congresses), teams will be trained in the application of the guideline via a 1-day small interactive group training program supported by e-learning modules. In the control condition, no additional actions next to usual dissemination of the guideline will be undertaken.Assessments at patient level will start when the experimental teams are trained. Assessments will take place upon admission and after 3 months, or earlier if the patient is discharged. The primary outcome is suicide ideation. Secondary outcomes are non-fatal suicide attempts, level of treatment satisfaction, and societal costs. Both a cost-effectiveness and cost-utility analysis will be performed. The effects of the intervention will be examined in multilevel models., Discussion: The strengths of this study are the size of the study, RCT design, training of complete multidisciplinary teams, and the willingness of both management and staff to participate., Trial Registration: Netherlands trial register: NTR3092.

We discuss the case history of a woman aged 49 years who displayed manic-psychotic symptoms as a clinical manifestation of hyperparathyroidism. Following resection of the parathyroid she developed severe depression. Primary hyperparathyroidism (PHPT) is characterised by an increase of the parathyroid hormone (PTH), which in turn leads to an increase in the plasma calcium. PHPT can be accompanied by various psychiatric symptoms ranging from personality changes and severe depression to obsessive-compulsive and paranoid symptoms.

This article describes Interpersonal and Social Rhythm Therapy (IPSRT) adapted for use in a group setting for patients with bipolar disorder. In a preliminary efficacy study, we studied the pre-post group treatment effect on affective symptoms. One-year pre-post findings in the IPSRT group indicated that this modality was effective in reducing depressive symptoms and might reduce the number of hospital admissions. Also, group IPSRT increased stability of the social rhythm, which is thought to be important in reducing recurrence of manic and depressive episodes. These findings suggest that group IPSRT could be an additional treatment option for patients with bipolar disorder who continue to have mood episodes despite adequate pharmacotherapy and psychoeducation.

Folie à famille is a rare psychiatric condition in which several family members develop similar psychotic symptoms. We describe the case of a family of four with a shared paranoid delusion, who all obtained complete remission after being treated with antipsychotics on different psychiatric wards.

Objective: We previously found psychotic depression (PSDEP) to have positively correlating plasma norepinephrine (NE) and vasopressin (AVP) concentrations. Since central noradrenergic activity and plasma NE concentration are highly correlated, this suggests an increased noradrenergic activation of the hypothalamus-pituitary-adrenal axis. We hypothesize the increased release of NE in PSDEP to be an associated mechanism., Methods: To test this hypothesis we analyzed the relation between plasma NE and PSDEP in a comparison with non-psychotically depressed patients. Potentially confounding variables were, among others, melancholia and two better validated subcategories in the field of melancholia and endogenous depression, three global dimensions of psychopathology - Emotional Dysregulation, Retardation and Anxiety - smoking habit, and different types of psychotropic and particularly antidepressant treatment. The data from nine patients with PSDEP and 69 patients with non-PSDEP were reanalysed., Results: Analysis of covariance controlling for the effects of tricyclic antidepressant treatment (≥100 mg) and smoking habit showed that PSDEP had an increased concentration of plasma NE. The previously found correlation between plasma NE and AVP was still present after correcting for the effects of confounding variables., Conclusions: The results suggest an increased activity of the sympathetic nervous system in PSDEP that may act as a specific mechanism for increased vasopressinergic activation. This supports the view of PSDEP as a distinct subcategory of major depression.

Background: Little is known about diagnostic procedures in acute psychiatry., Aim: To investigate the applicability of a structural diagnostic instrument in this setting and compare the results with clinical judgement., Method: The assessment was based on the mini International Neuropsychiatric Interview-plus., Results: There was poor agreement between the mini-plus diagnosis and clinical judgement and co-morbidity was under-reported., Conclusion: There is a need for a structural diagnostic instrument and more attention must be given to clinical diagnostic procedures in acute psychiatry.

Background. Support has been found for high harm avoidance as general vulnerability trait for depression and decreased self-directedness (SD) as central state-related personality change. Additional personality characteristics could be present in psychotic depression (PD). Increased noradrenergic activation in PD predicts the involvement of reward dependence (RD). Methods. The data during the acute episode and after full remission from the same subjects, that we used before, were reanalyzed. The dependence of the 7 dimensions of the Temperament and Character Inventory version 9 on PD, three other subcategories of depression, and a group of normal controls was tested by MANCOVA. Results. Low RD at both time points, and low Cooperativeness during the acute episode, were found as additional characteristics of PD. Conclusion. The combination of two premorbid temperaments, high HA and low RD, and the development of a state-related reduction of two character functions, SD and CO, may be the precondition for the development of combined depressive and psychotic psychopathology.

Background. Studies with the Temperament and Character Inventory (TCI) in depressive disorders have shown changes (Δ) of the character of Self-Directedness (SD) and the temperament of Harm Avoidance (HA). The central question of this study is which of these two changes is most proximally related to the production of depressive symptoms. Methods. The start and endpoint data from a two-year followup of 58 depressed patients were reanalyzed. We used the ΔHA and ΔSD scores as well as the Δ scores on three dimensions of psychopathology, called Emotional Dysregulation (ED), Retardation (RET), and Anxiety (ANX). The presence of the main relation between personality and psychopathology was tested in all patients and in four subcategories. The data were analyzed by MANCOVA and Structural Equation Modelling (SEM). Results. ΔHA and ΔSD correlated negatively, and only ΔSD was related (negatively) to ΔED. This pattern was found in all subcategories. SEM showed ΔHA and ΔSD had an ambiguous causal interrelationship, while ΔSD, ΔRET, and ΔANX had unidirectional effects on ΔED. Conclusion. The results correspond with a central pathogenetic role for a state-related deficit at the character level in depression. This may have important consequences for investigations of endophenotypes and clinical treatment.

The neuropeptide vasopressin is centrally involved in the regulation of social behaviour and response to stress. We previously found support for a subcategory of depression defined by above-normal plasma vasopressin (AVP) concentration. This subcategory is validated by a positive family history of depression and correlating plasma AVP and cortisol concentrations. The data support the validity of above-normal plasma AVP concentration as a genetically determined biological marker for a subcategory of depression. The aim of the present study was to test whether above-normal plasma AVP concentration in depression is related to personality characteristics reflecting a specific social behaviour style. The data of 78 patients from a previously investigated sample were reanalysed. Fifty-eight patients were available after 2 years, 15 of whom with initially above-normal plasma AVP. The dimensions of the Temperament and Character Inventory (TCI) were scored, with particular focus on the dimensions of Cooperativeness (CO) and Reward-dependence (RD). Normative subjects and other depressed subjects were used as controls. After full remission, patients with initially above-normal AVP had low CO compared with normal and patient controls. During depression, these patients had both low CO and low RD compared with normal controls and low RD compared with patient controls. Low CO is a presumably premorbid trait and reduced RD a state-dependent characteristic in depression with above-normal plasma AVP. The low CO further supports the validity of above-normal plasma AVP concentration as a genetically determined biological marker for a subcategory of depression.

Background: An anxious-retarded subtype of major depressive disorder, defined by high scores for both anxiety and retardation, has been derived from melancholia and appeared to have higher external validity in terms of poor outcome and vasopressinergic stress hormone regulation. A specific personality could enhance the validity of this subtype, and the association with melancholia suggested the absence of a personality disorder. As 2 character dimensions of the Temperament and Character Inventory (TCI), self-directedness (SD) and cooperativeness, parsimoniously predict the presence of a personality disorder, the primary aim was to test whether patients with the highly anxious-retarded subtype of depression have both normal SD and normal cooperativeness. A secondary aim was to optimally account for the general personality characteristics of patients with a major depressive disorder., Methods: Eighty-six patients with major depressive disorder and matched healthy controls were selected. Seventy patients were eventually recruited for a 2-year follow-up encompassing 5 assessments of personality (TCI) and psychopathology (Comprehensive Psychopathological Rating Scale). Full remission of depression was defined by the presence of less than 3 Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition items of depression during 2 weeks., Results: State-dependent changes of SD and harm avoidance (HA) scores were found in all depressed patients. Fully remitted patients had only high HA compared with healthy controls. Unexpectedly, fully remitted patients with the highly anxious-retarded subtype, in addition, had low SD., Conclusion: The temperament of high HA may be the predisposing TCI trait for major depressive disorder in general. Low SD may be a specific presumably premorbid character trait for the highly anxious-retarded subtype derived from melancholia.

Background: Anxious-retarded depression is a two-dimensionally defined subcategory of depression derived from DSM-IV melancholia. It is related to increased plasma vasopressin, correlative plasma vasopressin and cortisol levels, and a positive family history. We now explored its relation with outcome., Methods: Seventy depressed patients were included to follow-up for two years. Outcome was defined by time until full-remission. Cox regression analyses were used to compare anxious-retarded and non-anxious-retarded patients, as well as melancholic and non-melancholic patients., Results: Anxious-retarded depression had poor outcome., Limitations: The number of patients was relatively small., Conclusion: The poor outcome of anxious-retarded depression further supports its validity.

Anxious-retarded depression is a two-dimensionally defined subcategory of depression based on high scores for both anxiety and retardation. The anxious-retarded subcategory is related to melancholia as defined by DSM-IV. Patients with this diagnosis exhibit elevated plasma arginine vasopressin (AVP) and a high correlation between plasma vasopressin and cortisol, which suggests vasopressinergic overactivation of the hypothalamus-pituitary-adrenal (HPA) axis. In this report, we present the multidimensional derivation of the anxious-retarded subcategory from DSM-IV melancholia, and a second step in the validation of this anxious-retarded subcategory by exploring its relation to family history of depression. The patient sample comprised 89 patients with major depression and encompassed 66 patients investigated previously regarding plasma AVP and cortisol. All patients were rated for the following three dimensions of psychopathology: autonomic dysregulation (anxiety), motivational inhibition (retardation), and emotional dysregulation, as well as for family history of depression. The dependence of DSM-IV melancholia on the sum scores and the dichotomized scores on the three dimensions was investigated by multiple logistic regression. Thereafter, the dependence of the family history for depression on the same parameters was also investigated. The melancholic subcategory depended on the interaction between the sum scores, as well as on the interaction between the dichotomized scores for anxiety and retardation that constitute the anxious-retarded subcategory. Family history for depression depended only on the interaction of the dichotomized scores, and thus on the anxious-retarded subcategory., (Copyright 2004 Elsevier Ireland Ltd.)

Dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis is related to melancholic or endogenous depression; however, the strength of this relationship depends on the definition of the specific depression subcategory. A two-dimensionally defined subcategory, anxious-retarded depression, is related to melancholic depression. Since arginine vasopressin (AVP) activates the HPA axis, and both major depression and the melancholic subcategory are associated with elevated plasma AVP levels, we investigated whether the plasma AVP level is also elevated in anxious-retarded depression, melancholic depression and anxious-retarded melancholic depression, and whether plasma AVP and cortisol levels are correlated in these subcategories. A total of 66 patients with major depression not using oral contraception were investigated. Patients with anxious-retarded depression had a highly significant AVP-cortisol correlation, while no such correlation was found in patients with nonanxious-retarded depression. Log-transformed mean plasma AVP values were higher in patients with anxious-retarded depression than in patients with nonanxious-retarded depression. Patients with anxious-retarded melancholic depression also had a significantly elevated level of plasma AVP and a highly significant correlation between plasma AVP and cortisol levels. The correlation was low in patients with melancholic depression. Anxious-retarded depression may be a useful refinement of the melancholic subcategory with regard to dysregulation of the HPA axis and plasma AVP release.

S1 mapping of Xenopus laevis ribosomal RNA transcripts, both in oocyte microinjection experiments and in vivo, shows that all but 212 bp of the so-called "non-transcribed" spacer (NTS) of the ribosomal DNA repeat is transcribed as part of the primary ribosomal transcript. The 40S pre-ribosomal RNA (pre-rRNA) is therefore a processing intermediate. The primary ribosomal transcript co-terminates with the previously described spacer transcripts [Moss], at a site 213 bp upstream of the 40S pre-rRNA initiation site. This mode of transcription suggests a simple mechanism for the recently proposed phenomenon of "readthrough-enhancement", [Moss et al, Moss], where readthrough transcription from an upstream gene may enhance transcription of a gene immediately downstream in the tandem ribosomal repeat.

A procedure was devised for the identification and specific cloning of functionally rearranged variable region immunoglobulin (Ig) gene segments from genomic DNA of a murine hybridoma cell line which produces a high-affinity monoclonal antibody (MAb) directed against human carcinoembryonic antigen (CEA). The cloned, functionally-rearranged murine Ig H-chain and L-chain variable region gene segments were incorporated into plasmid vectors capable of directing the expression of a chimaeric mouse-human antibody molecule with human (gamma 4, kappa) constant region sequences. Expression plasmids were transfected into a mouse myeloma cell line by electroporation and transfectomas secreting functional chimaeric antibody selected. Chimaeric antibody generated by transfectomas was analysed and shown to compete effectively with its murine counterpart for binding to the CEA epitope, and to have an equivalent antigen-binding affinity. This anti-CEA recombinant antibody should find application in in vivo diagnosis by immunoscintigraphy of human colonic carcinoma, and possibly also in therapy of the disease, overcoming some of the difficulties associated with the repeated use of non-human immunoglobulins in human patients.

The X. laevis ribosomal DNA spacer contains duplicated RNA polymerase I "spacer promoters" and an array of repeated 60/81 bp promoter-related sequences. The latter have been shown to enhance transcription from a 40S preribosomal RNA promoter in cis. Here we present evidence that at least one spacer promoter is also necessary for efficient enhancement. Deletion of the spacer promoter sequences in a construct carrying only one such promoter reduces 40S RNA transcription to approximately 10% of wild type. This effect apparently is caused by inactivation of the spacer promoter, since mutants in which 4-177 bp of the spacer promoter and adjacent sequences are deleted are functionally equivalent. Spacer promoters and 60/80 bp arrays therefore probably act together to enhance 40S pre-RNA transcription in X. laevis.

The ribosomal DNA spacer in Xenopus laevis was shown in previous studies to be involved in regulating the expression of the ribosomal genes. Here transcription enhancement by this spacer has been studied in some detail, to fully identify the sequences involved and to determine their relative importance in this phenomenon. It is shown that the 60/81 base-pair (bp) repeats, which were reported to be enhancer elements, act as part of a mode of enhancement whose effect is amplified by the spacer promoters or Bam islands. The "Bam super repeat", a combination of spacer promoter and 60/81 bp elements, is the major enhancer unit. Within a Bam super repeat, a near linear correlation between the number of 60/81 bp elements and enhancer activity is observed. Thus, there is no significant co-operativity in the binding of transcription factors to an array of these elements. Multiple Bam super repeats do not act additively and may actually interfere with each others action. Surprisingly this effect is observed both in the presence and absence of active spacer promoters. Sequences between the 3' end of the 28 S coding region and the first spacer promoter may also be involved in enhancement but only in a very minor fashion. In confirmation of recent studies, the presence of the unique ribosomal termination sequence, 213 bp upstream from the pre-rRNA initiation site, is essential for efficient promotion, as deletion of this sequence virtually abolishes pre-rRNA- transcription. These data are discussed in terms of the possible mechanisms of transcription enhancement.