METRIC-EF: magnetic resonance enterography to predict disabling disease in newly diagnosed Crohn's disease-protocol for a multicentre, non-randomised, single-arm, prospective study

INTRODUCTION

Crohn's disease (CD) is characterised by discontinuous, relapsing enteric inflammation. Instituting advanced therapies at an early stage to suppress inflammation aims to prevent future complications such as stricturing or penetrating disease, and subsequent surgical resection. Therapeutics are effective but associated with certain side-effects and relatively expensive. There is therefore an urgent need for robust methods to predict which newly diagnosed patients will develop disabling disease, to identify patients who are most likely to benefit from early, advanced therapies. We aim to determine if magnetic resonance enterography (MRE) features at diagnosis improve prediction of disabling CD within 5 years of diagnosis.

METHODS AND ANALYSIS

We describe the protocol for a multicentre, non-randomised, single-arm, prospective study of adult patients with newly diagnosed CD. We will use patients already recruited to the METRIC study and extend their clinical follow-up, as well as a separate group of newly diagnosed patients who were not part of the METRIC trial (MRE within 3 months of diagnosis), to ensure an adequate sample size. Follow-up will extend for at least 4 years. The primary outcome is to evaluate the comparative predictive ability of prognostic models incorporating MRE severity scores (Magnetic resonance Enterography Global Score (MEGS), simplified MAgnetic Resonance Index of Activity (sMaRIA) and Lémann Index) versus models using standard characteristics alone to predict disabling CD (modified Beaugerie definition) within 5 years of new diagnosis.

ETHICS AND DISSEMINATION

This study protocol achieved National Health Service Research Ethics Committee (NHS REC), London-Hampstead Research Ethics Committee approval (IRAS 217422). Our findings will be disseminated via conference presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

ISRCTN76899103.

Mercaptopurine versus placebo to prevent recurrence of Crohn's disease after surgical resection (TOPPIC): a multicentre, double-blind, randomised controlled trial

BACKGROUND

Up to 60% of patients with Crohn's disease need intestinal resection within the first 10 years of diagnosis, and postoperative recurrence is common. We investigated whether mercaptopurine can prevent or delay postoperative clinical recurrence of Crohn's disease.

METHODS

We did a randomised, placebo-controlled, double-blind trial at 29 UK secondary and tertiary hospitals of patients (aged >16 years in Scotland or >18 years in England and Wales) who had a confirmed diagnosis of Crohn's disease and had undergone intestinal resection. Patients were randomly assigned (1:1) by a computer-generated web-based randomisation system to oral daily mercaptopurine at a dose of 1 mg/kg bodyweight rounded to the nearest 25 mg or placebo; patients with low thiopurine methyltransferase activity received half the normal dose. Patients and their carers and physicians were masked to the treatment allocation. Patients were followed up for 3 years. The primary endpoint was clinical recurrence of Crohn's disease (Crohn's Disease Activity Index >150 plus 100-point increase in score) and the need for anti-inflammatory rescue treatment or primary surgical intervention. Primary and safety analyses were by intention to treat. Subgroup analyses by smoking status, previous thiopurines, previous infliximab or methotrexate, previous surgery, duration of disease, or age at diagnosis were also done. This trial is registered with the International Standard Randomised Controlled Trial Register (ISRCTN89489788) and the European Clinical Trials Database (EudraCT number 2006-005800-15).

FINDINGS

Between June 6, 2008, and April 23, 2012, 240 patients with Crohn's disease were randomly assigned: 128 to mercaptopurine and 112 to placebo. All patients received at least one dose of study drug, and no randomly assigned patients were excluded from the analysis. 16 (13%) of patients in the mercaptopurine group versus 26 (23%) patients in the placebo group had a clinical recurrence of Crohn's disease and needed anti-inflammatory rescue treatment or primary surgical intervention (adjusted hazard ratio [HR] 0·54, 95% CI 0·27-1·06; p=0·07; unadjusted HR 0·53, 95% CI 0·28-0·99; p=0·046). In a subgroup analysis, three (10%) of 29 smokers in the mercaptopurine group and 12 (46%) of 26 in the placebo group had a clinical recurrence that needed treatment (HR 0·13, 95% CI 0·04-0·46), compared with 13 (13%) of 99 non-smokers in the mercaptopurine group and 14 (16%) of 86 in the placebo group (0·90, 0·42-1·94; pinteraction=0·018). The effect of mercaptopurine did not significantly differ from placebo for any of the other planned subgroup analyses (previous thiopurines, previous infliximab or methotrexate, previous surgery, duration of disease, or age at diagnosis). The incidence and types of adverse events were similar in the mercaptopurine and placebo groups. One patient on placebo died of ischaemic heart disease. Adverse events caused discontinuation of treatment in 39 (30%) of 128 patients in the mercaptopurine group versus 41 (37%) of 112 in the placebo group.

INTERPRETATION

Mercaptopurine is effective in preventing postoperative clinical recurrence of Crohn's disease, but only in patients who are smokers. Thus, in smokers, thiopurine treatment seems to be justified in the postoperative period, although smoking cessation should be strongly encouraged given that smoking increases the risk of recurrence.

FUNDING

Medical Research Council.

Relationship of Body Mass Index to Clinical Outcomes after Infliximab Therapy in Patients with Crohn's Disease

BACKGROUND & AIMS

There are conflicting data for the role of obesity in Crohn's disease (CD) and the effect on long-term clinical outcomes is poorly studied. Some evidence suggests obesity is associated with diminished responsiveness to biological agents, especially anti-tumour necrosis factor antibodies.

METHODS

We aimed to examine the influence of body mass index (BMI) on the response to infliximab in CD in a retrospective analysis. The outcomes of interest within 12 months were: (1) Composite loss of response (CD-related flare or surgery; LOR); (2) any CD-related surgery (CDRS); and (3) CD-related intestinal resectional surgery (CDRIS).

RESULTS

A total of 388 patients were included. The mean BMI was 24.2kg/m(2) [± standard deviation (SD) 5.1]. Of the 388 patients, 137 (35.4%) were overweight (BMI: 25-29.9kg/m(2)) or obese (BMI: ≥30kg/m(2))-160 (41.6%) patients had LOR during the 12 months follow-up; 121 (31.4%) required CDRS, and 109 (28.2%) required CDRIS. Multivariate analysis showed that increasing BMI (per unit, kg/m(2) increase) reduced the risk of LOR [odds ratio (OR): 0.98], CDRS (OR: 0.95), and CDRIS (OR: 0.95). Rates for all outcomes were higher, but not significantly so, in the extreme categories (underweight and obese) and lower in the underweight categories compared with normal BMI. Exclusion of the obese category of patients strengthened this relationship.

CONCLUSIONS

Body mass index at first infusion of infliximab has a non-linear relationship with outcomes at 12 months. The worst outcomes are at the extremes of weight (underweight and obese categories). Increasing BMI is associated with a modest reduction in risk of LOR, CDRS, and CDRIS within 12 months, increasing with the exclusion of the obese category.

Ipilimumab-induced colitis: experience from a tertiary referral center

BACKGROUND

Ipilimumab is an anticytotoxic T-lymphocyte antigen-4 (CTLA-4) monoclonal antibody used for the treatment of malignant melanoma. It can cause immune-mediated inflammatory adverse events, including diarrhoea and even intestinal perforation or death in clinical trials but there is a dearth of data on postmarketing outcomes.

METHODS

A total of 546 patients attending for treatment of metastatic melanoma between 1 January 2009 and 31 August 2015 were identified by interrogation of the oncology database. A total of 83 of these patients received ipilimumab. Clinical information was extracted from chart reviews, endoscopy and radiology reports, and prescription data.

RESULTS

A total of 83 patients received ipilimumab. Only 19.3% (n = 16) of patients developed a diarrhoeal illness not attributable to other causes. The median grade of diarrhoea among included patients was 2 (range 1-4). In two cases, diarrhoea settled spontaneously without any specific treatment. A total of 87.5% of patients received antidiarrhoeal agents such as loperamide or codeine. These resolved symptoms in all patients with grade 1 diarrhoea. For other treatment, 50% patients received systemic glucocorticosteroids and 31.3% required infliximab. Infliximab resolved symptoms in 100% of cases compared with 50% for systemic glucocorticosteroids.

CONCLUSIONS

The rate of diarrhoea related to ipilimumab in real-world practice is substantial, but below the range observed in data from RCTs. Grade 1 colitis can usually be managed symptomatically, without recourse to stopping ipilimumab. When diarrhoea was grade 2 or above, results from glucocorticosteroids use proved disappointing; but infliximab has been shown to work well. Further research is required into the earlier use of infliximab as an effective treatment for ipilimumab-induced diarrhoea.

METRIC (MREnterography or ulTRasound in Crohn's disease): a study protocol for a multicentre, non-randomised, single-arm, prospective comparison study of magnetic resonance enterography and small bowel ultrasound compared to a reference standard in those aged 16 and over

Background

Crohn’s disease (CD) is a lifelong, relapsing and remitting inflammatory condition of the intestine. Medical imaging is crucial for diagnosis, phenotyping, activity assessment and detecting complications. Diverse small bowel imaging tests are available but a standard algorithm for deployment is lacking. Many hospitals employ tests that impart ionising radiation, of particular concern to this young patient population. Magnetic resonance enterography (MRE) and small bowel ultrasound (USS) are attractive options, as they do not use ionising radiation. However, their comparative diagnostic accuracy has not been compared in large head to head trials. METRIC aims to compare the diagnostic efficacy, therapeutic impact and cost effectiveness of MRE and USS in newly diagnosed and relapsing CD.

Methods

METRIC (ISRCTN03982913) is a multicentre, non-randomised, single-arm, prospective comparison study. Two patient cohorts will be recruited; those newly diagnosed with CD, and those with suspected relapse. Both will undergo MRE and USS in addition to other imaging tests performed as part of clinical care. Strict blinding protocols will be enforced for those interpreting MRE and USS. The Harvey Bradshaw index, C-reactive protein and faecal calprotectin will be collected at recruitment and 3 months, and patient experience will be assessed via questionnaires. A multidisciplinary consensus panel will assess all available clinical and imaging data up to 6 months after recruitment of each patient and will define the standard of reference for the presence, localisation and activity of disease against which the diagnostic accuracy of MRE and USS will be judged. Diagnostic impact of MRE and USS will be evaluated and cost effectiveness will be assessed. The primary outcome measure is the difference in per patient sensitivity between MRE and USS for the correct identification and localisation of small bowel CD.

Discussion

The trial is open at 5 centres with 46 patients recruited. We highlight the importance of stringent blinding protocols in order to delineate the true diagnostic accuracy of both imaging tests and discuss the difficulties of diagnostic accuracy studies in the absence of a single standard of reference, describing our approach utilising a consensus panel whilst minimising incorporation bias.

Trial registration

METRIC - ISRCTN03982913 – 05.11.13.

The young patient with acute bloody diarrhoea

Acute bloody diarrhoea may be commonly encountered in the acute medical unit. Among young patients, the main differential diagnoses are acute infectious colitis, and first presentation of inflammatory bowel disease (IBD). A combination of clinical, laboratory, radiological, endoscopic and histological investigations are required to make the diagnosis. If inflammatory bowel disease is suspected, then the patient should be admitted to a specialist gastroenterology ward and receive input from the surgical team, IBD nurses and specialist stoma nurses. Intravenous steroid therapy for acute severe disease should be started before stool cultures are back unless there is a strong clinical suspicion of amoebiasis. All patients require thromboprophylaxis and close attention paid to fluid balance and nutritional requirements. Daily clinical review is required. The Travis criteria may be employed at day 3 to assess the likelihood of requiring surgery and plans for rescue therapy, medical or surgical should be made between day 3-7 if the patient is not responding adequately to initial medical therapy.

Efficacy, tolerability, and predictors of response to infliximab therapy for Crohn's disease: a large single centre experience

BACKGROUND

Infliximab is licenced for use in Crohn's disease (CD). Trial data demonstrate that infliximab is effective for inducing remission of active CD, healing fistulising CD, and preventing relapse once in remission. However, long-term data regarding efficacy, safety, and predictors of response are still emerging.

AIM

To examine these issues in a large cohort of patients who received infliximab for CD.

METHODS

A retrospective analysis of prospectively collected data was performed for 210 patients receiving infliximab for luminal or fistulising CD. Response to infliximab induction therapy, and sustained clinical benefit, were assessed by a decrease in Harvey-Bradshaw Index (HBI) of ≥ 2 points. Remission was defined as an HBI ≤ 4. Physician's global assessment was used where HBI could not be obtained. Demographic and disease factors that may predict response to therapy were analysed by Kaplan-Meier plots and univariate and multivariate analyses.

RESULTS

Overall, 173 (82.4%) patients responded to infliximab induction, with 114 (65.9%) achieving sustained clinical benefit. Almost 40% of the study cohort had an HBI ≤ 4, indicating remission, at last point of follow-up (median 24 months). Concomitant immunosuppression predicted sustained clinical benefit in the first 6 months of therapy (P=0.03). An inflammatory disease phenotype (P=0.04 univariate analysis, P=0.03 Kaplan Meier analysis) and male gender (P=0.03) also predicted sustained clinical benefit. Episodic therapy was associated with an increased likelihood of secondary non-response. Adverse events, including malignancies, were few.

CONCLUSION

In this single centre study, infliximab was efficacious and well-tolerated in CD.

The academic environment: the students' perspective

Dental education is regarded as a complex, demanding and often stressful pedagogical procedure. Undergraduates, while enrolled in programmes of 4-6 years duration, are required to attain a unique and diverse collection of competences. Despite the major differences in educational systems, philosophies, methods and resources available worldwide, dental students' views regarding their education appear to be relatively convergent. This paper summarizes dental students' standpoint of their studies, showcases their experiences in different educational settings and discusses the characteristics of a positive academic environment. It is a consensus opinion that the 'students' perspective' should be taken into consideration in all discussions and decisions regarding dental education. Moreover, it is suggested that the set of recommendations proposed can improve students' quality of life and well-being, enhance their total educational experience and positively influence their future careers as oral health physicians. The 'ideal' academic environment may be defined as one that best prepares students for their future professional life and contributes towards their personal development, psychosomatic and social well-being. A number of diverse factors significantly influence the way students perceive and experience their education. These range from 'class size', 'leisure time' and 'assessment procedures' to 'relations with peers and faculty', 'ethical climate' and 'extra-curricular opportunities'. Research has revealed that stress symptoms, including psychological and psychosomatic manifestations, are prevalent among dental students. Apparently some stressors are inherent in dental studies. Nevertheless, suggested strategies and preventive interventions can reduce or eliminate many sources of stress and appropriate support services should be readily available. A key point for the Working Group has been the discrimination between 'teaching' and 'learning'. It is suggested that the educational content should be made available to students through a variety of methods, because individual learning styles and preferences vary considerably. Regardless of the educational philosophy adopted, students should be placed at the centre of the process. Moreover, it is critical that they are encouraged to take responsibility for their own learning. Other improvements suggested include increased formative assessment and self-assessment opportunities, reflective portfolios, collaborative learning, familiarization with and increased implementation of information and communication technology applications, early clinical exposure, greater emphasis on qualitative criteria in clinical education, community placements, and other extracurricular experiences such as international exchanges and awareness of minority and global health issues. The establishment of a global network in dental education is firmly supported but to be effective it will need active student representation and involvement.

Quality assurance and benchmarking: an approach for European dental schools

This document was written by Task Force 3 of DentEd III, which is a European Union funded Thematic Network working under the auspices of the Association for Dental Education in Europe (ADEE). It provides a guide to assist in the harmonisation of Dental Education Quality Assurance (QA) systems across the European Higher Education Area (EHEA). There is reference to the work, thus far, of DentEd, DentEd Evolves, DentEd III and the ADEE as they strive to assist the convergence of standards in dental education; obviously QA and benchmarking has an important part to play in the European HE response to the Bologna Process. Definitions of Quality, Quality Assurance, Quality Management and Quality Improvement are given and put into the context of dental education. The possible process and framework for Quality Assurance are outlined and some basic guidelines/recommendations suggested. It is recognised that Quality Assurance in Dental Schools has to co-exist as part of established Quality Assurance systems within faculties and universities, and that Schools also may have to comply with existing local or national systems. Perhaps of greatest importance are the 14 'requirements' for the Quality Assurance of Dental Education in Europe. These, together with the document and its appendices, were unanimously supported by the ADEE at its General Assembly in 2006. As there must be more than one road to achieve a convergence or harmonisation standard, a number of appendices are made available on the ADEE website. These provide a series of 'toolkits' from which schools can 'pick and choose' to assist them in developing QA systems appropriate to their own environment. Validated contributions and examples continue to be most welcome from all members of the European dental community for inclusion at this website. It is realised that not all schools will be able to achieve all of these requirements immediately, by definition, successful harmonisation is a process that will take time. At the end of the DentEd III project, ADEE will continue to support the progress of all schools in Europe towards these aims.

Phase I trial involving the pharmacodynamic (PD) study of circulating tumour cells, of CP-751,871 (C), a monoclonal antibody against the insulin-like growth factor 1 receptor (IGF-1R), with docetaxel (D) in patients (p) with advanced cancer

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Background: C is the first specific, fully human, monoclonal antibody to target IGF-1R in clinical trials. It potently inhibits IGF-1R signaling, enhancing D antitumour activity. This trial investigated the safety, feasibility, dose limiting toxicity (DLT), PK and antitumor activity of D administered with C every 3 weeks. PD studies evaluated circulating tumor cell (CTC) IGF-1R expression and CTC counts pre- and post-treatment. Methods: The C doses tested were 0.1, 0.4, 0.8, 1.5, 3.0, 6.0 and 10 mg/kg in sequential cohorts of 3–6 p. D was fixed at 75mg/m2. P achieving disease control continued on C alone if experiencing D toxicity. Results: 21 p (20 male) have received 100 courses of C with D. 7 p received 8 or more courses of the combination. A further 21 courses of C alone have been administered. No toxicity has been attributed to C to date with the observed toxicities being attributable to D. Grade 3/4 toxicities were neutropenia (16/21 p) and neutropenic fever in 2/21 p. Grade 3 diarrhea was reported in 3 p, but this was easily controlled with antidiarrheals. Transient grade 1 hyperglycaemia was noted largely on day 1, following steroid premedication (14 p), but no significant C related hyperglycemia has been observed. An MTD has not been reached. Serial echocardiograms demonstrated no cardiac toxicity. Of 18 castration resistant prostate cancer (CRPC) p treated, 4 have had a confirmed PR, with 2 unconfirmed PR and 2 having disease stabilization for > 6 months (median number of courses: 10; range: 3–12). 5 p have maintained SD with C alone for 2–7 courses. CTC were detected in 16 of 18 p (CTC numbers ranged from 1 to 202 in 7.5ml of blood). IGF-1R expression was detected in 12 p. CTC IGF-1R was undetectable following treatment with C at doses above 3 mg/kg. Conclusions: This combination is safe and feasible with no toxicity attributed to C and encouraging antitumor activity in CRPC.

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Vaccination levels in Los Angeles public health centers: the contribution of missed opportunities to vaccinate and other factors

We abstracted 752 randomly selected records of 2-year-old children at 5 public health centers in Los Angeles. Only 27% of the children were up-to-date in their vaccinations by 2 years of age. Being up-to-date was strongly associated with the number of missed opportunities to vaccinate and number of well child visits. Missed opportunities to vaccinate occurred during 52% of all visits and were associated with minor illness diagnoses and inaccurate immunization status assessment by nurses. Frequent missed opportunities to vaccinate and inadequate numbers of well child visits may result in low immunization levels among children attending public health clinics.

Positive interaction between insulin and phorbol esters on the regulation of a specific messenger ribonucleic acid in rat hepatoma cells

With Northern blot analysis, we demonstrate that phorbol 12-myristate 13-acetate (PMA) stimulated P-33 messenger RNA (mRNA)-accumulation in rat hepatoma cells in a time- and concentration-dependent manner similar to insulin and plant lectins. No effect of PMA on P-33 mRNA half-life was detected when mRNA synthesis was inhibited with either actinomycin D or 5.6-dichloro-1-beta-D-ribofuranosyl benzimidazole. The effects of insulin and PMA were additive at submaximal concentrations and no additivity was observed under these conditions at maximal concentrations. Thus PMA has a marked insulin-like effect on the accumulation of P-33 mRNA in rat hepatoma cells.

Insulin-mimetic actions of wheat germ agglutinin and concanavalin A on specific mRNA levels

Insulin has pleiotropic effects on sensitive cells, including the regulation of specific mRNA accumulation initiated by the binding of insulin to its plasma membrane receptor. Lectins, such as wheat germ agglutinin (WGA) and concanavalin A (Con A), are known to be insulin mimetic. It is thought that WGA and Con A interact with the insulin receptor or associated membrane glycoproteins which, when activated, lead to insulin-mimetic responses. We attempted to determine whether WGA and Con A could induce the accumulation of a specific messenger RNA (p33-mRNA). Insulin treatment of H4IIE (H4) hepatoma cells increased the concentration of p33-mRNA within 30 min after addition, with a maximum effect of 10- to 15-fold. WGA and Con A also exhibited time- and dose-dependent stimulatory effects on p33-mRNA accumulation with maximal effects of 30- to 40-fold. The effect of insulin was maximal by 1 h and plateaued thereafter, whereas lectins had maximal effects at 2 h after addition to cell cultures. Insulin, WGA, and Con A did not significantly alter the stability (half-life) of p33-mRNA. The addition of RNA synthesis inhibitors blocked the ability of insulin, WGA, and Con A to induce the amount of p33-mRNA. These data suggest that lectins, as well as insulin, induce the synthesis of p33-mRNA in acutely treated H4 hepatoma cells.

Nerve fiber layer photography. A comparative study

Observation of the retinal nerve fiber layer with red-free light is an important means of evaluating optic nerve integrity. Many investigators have attempted to increase the usefulness of the technique by improving photographic procedures. Most reports comparing various parameters neither indicate the method of comparison nor give quantitative measure of the improvement gained with different films, filters, cameras, or processing procedures. We have compared in a masked fashion the parameters most recently recommended in the literature. Twelve trained observers compared 12 masked pairs of nerve fiber layer photos taken from the same eye in the same manner on two cameras and preferred those taken with a Canon CF-60Z camera 69% of the time and those taken with a Zeiss FF-111 17% of the time (this difference was statistically significant, P less than 0.01). Fourteen observers compared 14 pairs of photographs and judged Panatomic-X film to be superior to Plus-X film 51% of the time and both films to be of the same quality 25% of the time (this difference was also significant P less than 0.05). Fifteen observers compared 12 pairs and preferred the Standard SE-40 blue filter 2:1 over the green Spectrotech 540 filter. This difference was not statistically significant, and the preference was found to be dependent on fundus pigmentation and clarity of the media. The blue filter gave better contrast for the nerve fiber layer in patients with lightly pigmented fundi, and use of the green filter resulted in less light scatter in patients with ocular media opacities.

Effect of gamma rays at the dihydrofolate reductase locus: deletions and inversions

A series 11 gamma-ray-induced mutants at the dihydrofolate reductase (dhfr) locus in Chinese hamster ovary cells has been examined for the types of DNA sequence change brought about by this form of ionizing radiation. All 11 mutants were found to have suffered major structural changes affecting the dhfr gene. In eight of the mutants, all or part of the dhfr gene has been deleted. The extent of these deletions was examined in seven of these mutants and, for comparison, in two deletion mutants that were induced by UV irradiation. For this purpose, probes from an overlapping set of cosmids that span 210 kb of DNA in this region were used. Three of seven gamma-ray-induced mutants and one UV-induced mutant were shown to have deleted the entire 210-kb region. In the remaining mutants, endpoints ranging from within the dhfr gene to 100 kb downstream were observed. No upstream endpoints were detected, so that an upper limit on the size of these large deletions could not be assigned. Three of the 11 gamma-ray-induced mutants contained an interruption in the dhfr gene without any detectable loss of sequence. Restriction analysis of these interrupted mutants showed that at least 8-14 kb of "foreign" DNA sequence became joined to the gene at the point of disruption. Cytogenetic analysis of these mutants showed that in two cases an inversion of the banding pattern on chromosome Z-2 had taken place. The inverted dhfr mutants contain very low amounts of dhfr RNA sequences, and the 5' end of an inversion mutant gene exhibits the same pattern of DNA methylation and DNase I-hypersensitivity as the wild-type gene. Our results suggest that ionizing radiation causes primarily, if not exclusively, large deletions and inversions in mammalian cells.

The effects of insulin and concanavalin A on the accumulation of a specific mRNA in rat hepatoma cells

One of insulin's effects is to stimulate specific mRNA synthesis. Treatment of H4IIE hepatoma cells with 0.01-1.0 nM insulin results in a maximum 10-15 fold increase in the accumulation of a specific mRNA (p33-mRNA) as measured with a cloned cDNA. Concanavalin A, a lectin known to mimic many of insulin's effects, also stimulates the accumulation of p33-mRNA. The effects of both insulin and Con A were blocked by the addition of two RNA synthesis inhibitors, actinomycin D or 5,6 dichloro-1-beta-D-ribofuranosyl-benzimidazole. We therefore suggest that insulin and concanavalin A act to stimulate p33-mRNA synthesis.

Effects of insulin alone on the accumulation of a specific mRNA in rat hepatoma cells

Experiments were conducted to investigate the action of insulin alone on the induction of a specific mRNA referred to as p33. In 24-h serum-deprived rat liver hepatoma cells (H4) grown in monolayer cultures, insulin induced a 3-fold increase in the levels of p33 mRNA within 30 min, and a maximum 10-fold increase was observed by 1 h. The effects of insulin were evident at concentrations as low as 10(-12) M and were maximal at 0.5-1 X 10(-8) M. The effect of insulin was specific, since the level of mRNA for the histocompatibility complex, H2d, was unaffected by insulin. The increase in p33 mRNA was not due to an effect of insulin on the stabilization of mRNA, since insulin did not alter the half-life of this message. In addition, two different RNA synthesis inhibitors blocked the stimulation of p33 mRNA production by insulin. These data suggest that insulin may specifically stimulate the synthesis of p33 mRNA which results in an increased accumulation of total cellular p33 mRNA.

-Galactosidase: immunological activity of ribosome-bound, growing polypeptide chains

Ribosomes carrying nascent chains of beta-galactosidase were prepared by disruption of Escherichia coli in detergent-free buffer of high salt concentration, followed by purification on a discontinuous sucrose gradient. Assay by the method of immune hemolysis inhibition with anti-beta-galactosidase indicated that considerable amounts of antibody were bound by the growing chains. Much of the crossreacting material could be released from the ribosomes by treatment with puromycin. The ability to bind anti-beta-galactosidase was completely destroyed when ribosomes were heated at 60 degrees C. At very early times after induction, well before the appearance of active enzyme, crossreacting material could be demonstrated on ribosomes; this finding correlated with the appearance of an amino-terminal fragment of beta-galactosidase. Thus, growing chains of beta-galactosidase must begin to fold before their release from the ribosome.