Translational Pharmacokinetic-Pharmacodynamic Modeling and Simulation: Optimizing 5-Fluorouracil Dosing in Children With Pediatric Ependymoma

We previously investigated novel therapies for pediatric ependymoma and found 5‐fluorouracil (5‐FU) i.v. bolus increased survival in a representative mouse model. However, without a quantitative framework to derive clinical dosing recommendations, we devised a translational pharmacokinetic‐pharmacodynamic (PK‐PD) modeling and simulation approach. Results from our preclinical PK‐PD model suggested tumor concentrations exceeded the 1‐hour target exposure (in vitro IC₉₀), leading to tumor growth delay and increased survival. Using an adult population PK model, we scaled our preclinical PK‐PD model to children. To select a 5‐FU dosage for our clinical trial in children with ependymoma, we simulated various 5‐FU dosages for tumor exposures and tumor growth inhibition, as well as considering tolerability to bolus 5‐FU administration. We developed a pediatric population PK model of bolus 5‐FU and simulated tumor exposures for our patients. Simulations for tumor concentrations indicated that all patients would be above the 1‐hour target exposure for antitumor effect.

Activating the Wnt/β-Catenin Pathway for the Treatment of Melanoma--Application of LY2090314, a Novel Selective Inhibitor of Glycogen Synthase Kinase-3

It has previously been observed that a loss of β-catenin expression occurs with melanoma progression and that nuclear β-catenin levels are inversely proportional to cellular proliferation, suggesting that activation of the Wnt/β-catenin pathway may provide benefit for melanoma patients. In order to further probe this concept we tested LY2090314, a potent and selective small-molecule inhibitor with activity against GSK3α and GSK3β isoforms. In a panel of melanoma cell lines, nM concentrations of LY2090314 stimulated TCF/LEF TOPFlash reporter activity, stabilized β-catenin and elevated the expression of Axin2, a Wnt responsive gene and marker of pathway activation. Cytotoxicity assays revealed that melanoma cell lines are very sensitive to LY2090314 in vitro (IC50 ~10 nM after 72hr of treatment) in contrast to other solid tumor cell lines (IC50 >10 uM) as evidenced by caspase activation and PARP cleavage. Cell lines harboring mutant B-RAF or N-RAS were equally sensitive to LY2090314 as were those with acquired resistance to the BRAF inhibitor Vemurafenib. shRNA studies demonstrated that β-catenin stabilization is required for apoptosis following treatment with the GSK3 inhibitor since the sensitivity of melanoma cell lines to LY290314 could be overcome by β-catenin knockdown. We further demonstrate that in vivo, LY2090314 elevates Axin2 gene expression after a single dose and produces tumor growth delay in A375 melanoma xenografts with repeat dosing. The activity of LY2090314 in preclinical models suggests that the role of Wnt activators for the treatment of melanoma should be further explored.

Tumor-targeted prodrug ICT2588 demonstrates therapeutic activity against solid tumors and reduced potential for cardiovascular toxicity

Development of therapeutic strategies for tumor-selective delivery of therapeutics through exploitation of the proteolytic tumor phenotype has significant scope for improvement of cancer treatment. ICT2588 is a peptide-conjugated prodrug of the vascular disrupting agent (VDA) azademethylcolchicine developed to be selectively hydrolyzed by matrix metalloproteinase-14 (MMP-14) within the tumor. In this report, we extend our previous proof-of-concept studies and demonstrate the therapeutic potential of this agent against models of human colorectal, lung, breast, and prostate cancer. In all tumor types, ICT2588 was superior to azademethylcolchicine and was greater or comparable to standard clinically used agents for the respective tumor type. Prodrug activation in clinical human lung tumor homogenates relative to stability in human plasma and liver was observed, supporting clinical translation potential. A major limiting factor to the clinical value of VDAs is their inherent cardiovascular toxicity. No increase in plasma von Willebrand factor (vWF) levels, an indicator of systemic vascular dysfunction and acute cardiovascular toxicity, was detected with ICT2588, thereby supporting the tumor-selective activation and reduced potential of ICT2588 to cause cardiovascular toxicity. Our findings reinforce the improved therapeutic index and tumor-selective approach offered by ICT2588 and this nanotherapeutic approach.

Identification of risk factors associated with acute kidney injury in patients admitted to acute medical units

In 2009, the National Confidential Enquiry into Patient Outcome and Death (NCEPOD) report identified significant deficiencies in the management of acute kidney injury (AKI) in hospitals in the UK. Many errors arose from failure to recognise patients with AKI and those at risk of developing AKI. Currently, there is no universally accepted risk factor assessment for identifying such patients on admission to acute medical units (AMUs). A multicentre prospective observational study was performed in the AMUs of 10 hospitals in England and Scotland to define the risk factors associated with AKI and to assess quality of care. Data were collected on consecutive acute medical admissions over two separate 24-h periods. Acute kidney injury was present in 55/316 (17.7%) patients, with sepsis, hypovolaemia, chronic kidney disease (CKD) and diabetes mellitus identified as the major risk factors. Deficiencies in patient care were identified, reinforcing the continuing need to improve the management of AKI.

An inhibitor of thrombin activated fibrinolysis inhibitor (TAFI) can reduce extracellular matrix accumulation in an in vitro model of glucose induced ECM expansion

Chronic kidney disease (CKD) is characterised by the pathological accumulation of extracellular matrix (ECM) proteins leading to progressive kidney scarring via glomerular and tubular basement membrane expansion. Increased ECM synthesis and deposition, coupled with reduced ECM breakdown contribute to the elevated ECM level in CKD. Previous pre-clinical studies have demonstrated that increased plasmin activity has a beneficial effect in the protein overload model of CKD. As plasmin activation is downregulated by the action of the thrombin activated fibrinolytic inhibitor (TAFI), we tested the hypothesis that inhibition of TAFI might increase plasmin activity and reduce ECM accumulation in an in vitro model of glucose induced ECM expansion. Treatment of NRK52E tubular epithelial cells with increasing concentrations of glucose resulted in a 40% increase in TAFI activity, a 38% reduction in plasmin activity and a subsequent increase in ECM accumulation. In this model system, application of the previously reported TAFI inhibitor UK-396082 [(2S)-5-amino-2-[(1-n-propyl-1H-imidazol-4-yl)methyl]pentanoic acid] caused a reduction in TAFI activity, increased plasmin activity and induced a parallel decrease in ECM levels. In contrast, RNAi knockdown of plasmin resulted in an increase in ECM levels. The data presented here indicate that high glucose induces TAFI activity, inhibiting plasmin activation which results in elevated ECM levels in tubular epithelial cells. The results support the hypothesis that UK-396082 is able to reduce TAFI activity, normalising plasmin activity and preventing excess ECM accumulation suggesting that TAFI inhibition may have potential as an anti-scarring strategy in CKD.

An integrated in vitro and in vivo high-throughput screen identifies treatment leads for ependymoma

Using a mouse model of ependymoma-a chemoresistant brain tumor-we combined multicell high-throughput screening (HTS), kinome-wide binding assays, and in vivo efficacy studies, to identify potential treatments with predicted toxicity against neural stem cells (NSC). We identified kinases within the insulin signaling pathway and centrosome cycle as regulators of ependymoma cell proliferation, and their corresponding inhibitors as potential therapies. FDA approved drugs not currently used to treat ependymoma were also identified that posses selective toxicity against ependymoma cells relative to normal NSCs both in vitro and in vivo, e.g., 5-fluorouracil. Our comprehensive approach advances understanding of the biology and treatment of ependymoma including the discovery of several treatment leads for immediate clinical translation.

Development of a novel tumor-targeted vascular disrupting agent activated by membrane-type matrix metalloproteinases

Vascular disrupting agents (VDA) offer a strategy to starve solid tumors of nutrients and oxygen concomitant with tumor shrinkage. Several VDAs have progressed into early clinical trials, but their therapeutic value seems to be compromised by systemic toxicity. In this report, we describe the design and characterization of a novel VDA, ICT2588, that is nontoxic until activated specifically in the tumor by membrane-type 1 matrix metalloproteinase (MT1-MMP). HT1080 cancer cells expressing MT1-MMP were selectively chemosensitive to ICT2588, whereas MCF7 cells that did not express MT1-MMP were nonresponsive. Preferential hydrolysis of ICT2588 to its active metabolite (ICT2552) was observed in tumor homogenates of HT1080 relative to MCF7 homogenates, mouse plasma, and liver homogenate. ICT2588 activation was inhibited by the MMP inhibitor ilomastat. In HT1080 tumor-bearing mice, ICT2588 administration resulted in the formation of the active metabolite, diminution of tumor vasculature, and hemorrhagic necrosis of the tumor. The antitumor activity of ICT2588 was superior to its active metabolite, exhibiting reduced toxicity, improved therapeutic index, enhanced pharmacodynamic effect, and greater efficacy. Coadministration of ICT2588 with doxorubicin resulted in a significant antitumor response (22.6 d growth delay), which was superior to the administration of ICT2588 or doxorubicin as a single agent, including complete tumor regressions. Our findings support the clinical development of ICT2588, which achieves selective VDA targeting based on MT-MMP activation in the tumor microenvironment.

Management of acute ischaemic stroke in the acute medical unit

Ischaemic stroke is a major cause of death and disability which costs the NHS £2.8 billion/year. Acute stroke care is developing rapidly in line with an increasing evidence base. Intravenous thrombolysis is now recommended by NICE. For this guidance to be effectively implemented stroke must be viewed as a medical emergency by both the public and professionals. Emergency medical services must work in partnership with stroke services to establish systems and protocols which offer high quality acute stroke care. This provides challenges, both in systems design and delivery of clinical care.

Abstract A52: An interspecies genomics based high-throughput screen for novel treatments of ependymoma

Brain tumors are often chemoresistant and these diseases are heterogeneous complicating efforts to discover effective new therapies. We describe a powerful interspecies genomics approach that meticulously matches subgroup specific driver mutations with cellular compartments to model cancer subgroups for drug screening. First, we performed a comprehensive genomics analysis to identify disease subgroups among >200 ependymomas. Subgroup specific alterations included amplifications and homozygous deletions of genes not yet implicated in ependymoma. We then identified CNS cell compartments most likely to give rise to ependymoma subgroups by matching the transcriptomes of human tumors to those of distinct types of mouse neural stem cell (NSC). Remarkably, activation of oncogenes in appropriate NSCs generated ependymomas that modelled the histology and transcriptome of the human disease. Stem-like tumor cells isolated from these mouse ependymomas were then cultured under conditions that promote stem cell growth as neurospheres. These conditions were adapted for use in an automated high-throughput screening system. Control transduced NSCs were also included to identify ependymoma-selective agents. Tumor and control spheres were seeded in 384 well plates and drug treated using pin tool transfer 24 hours after plating. Cells were exposed to drug for 96 hours before compound cytotoxicity measured using the cell-titre glo luciferase based assay. We first performed replicate primary screens of a large ‘bioactive library’ including natural products, bioactive alkaloids and marketed drugs (5760 compounds [3460 unique in structure]) in a single concentration format (10uM). Active compound hit rate varied from 0.9% to 4.8% in spheres derived from mouse tumors and 3.1% in control NSCs. The primary screen was highly reproducible (263 and 261 hits in replicate assays, of which 226 of were common in an example tumor line). ROC analysis of primary screen data was used to assess predictive power of the screen. For all cells the ROC AUC was >0.89 (0.85–0.92 95% CI). We next performed secondary screens of all primary screen hits. These included full 10-point dose response assays that identified a total of 292 active agents with activity in at least one cell population. Following analysis of the ‘bioactive library, we screened a collection of 320 FDA approved active pharmaceutical ingredients representing all drug classes and all approved chemotherapy agents in a 10-point dose response format. The hit rate of this drug collection in all cell types was between 10.36% to 15.4% and hit compounds represented a variety of drug classes including chemotherapeutics, NSAIDs, antibiotics and dopamine-like agents. These compounds and the related families and structures will be described in detail as well as the results of ongoing in vivo activity against the originating ependymoma mouse models.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A52.

Tumour endoproteases: the cutting edge of cancer drug delivery?

Despite progression in anticancer drug development and improvements in the clinical utilization of therapies, current treatment regimes are still dependent upon the use of systemic antiproliferative cytotoxic agents. Although these agents are unquestionably potent, their efficacy is limited by toxicity towards 'normal' cells and a lack of tumour selective targeting, resulting in a therapeutic index which is modest at best. Consequently, the development of more tumour selective cancer treatments, with better discrimination between tumour and normal cells is unequivocally an important goal for cancer drug discovery. One such strategy is to exploit the tumour phenotype as a mechanism for tumour-selective delivery of potent therapeutics. An exciting approach in this area is to develop anticancer therapeutics as prodrugs, which are non-toxic until activated by enzymes localized specifically in the tumour. Enzymes suitable for tumour-activated prodrug development must have increased activity in the tumour relative to non-diseased tissue and an ability to activate the prodrug to its active form. One class of enzyme satisfying these criteria are the tumour endoproteases, particularly the serine- and metallo-proteases. These proteolytic enzymes are essential for tumour angiogenesis, invasion and metastasis, the major defining features of malignancy. This review describes the concept behind development of tumour-endoprotease activated prodrugs and discusses the various studies to date that have demonstrated the huge potential of this approach for improvement of cancer therapy.

Membrane type matrix metalloproteinases (MMPs) show differential expression in non-small cell lung cancer (NSCLC) compared to normal lung: correlation of MMP-14 mRNA expression and proteolytic activity

Improved understanding of the involvement of matrix metalloproteinases (MMPs), including membrane-type MMPs (MT-MMPs), in human tumours has potential diagnostic, prognostic and therapeutic implications. We assessed the relationship between MT-MMP expression and clinicopathological parameters in human non-small cell lung cancer (NSCLC) and histologically normal lung tissue by quantitative Real Time PCR (qRT-PCR). All MT-MMPs (MMPs 14-17, 24 and 25) were detected by qRT-PCR with significantly higher MMP-14, -15 and -17 expression observed in tumour relative to normal lung specimens. MMP-16 was undetectable in normal lung but expressed in 8% tumours. MMP-15 demonstrated significant overexpression in adenocarcinomas relative to squamous cell carcinomas and normal lung tissue. MMP-14 mRNA expression strongly correlated to MMP-14 proteolytic activity in preclinical tumour models, indicating that qRT-PCR may predict MMP-14 activity levels in NSCLC. These data suggest that MMP-14, -15 and -17 may be good markers of disease, or therapeutic targets for treatment of human NSCLC.

Randomised trial of personalised computer based information for patients with schizophrenia

OBJECTIVES

To compare use, effect, and cost of personalised computer education with community psychiatric nurse education for patients with schizophrenia.

DESIGN

Randomised trial of three interventions. Modelling of costs of alternatives.

PARTICIPANTS

112 patients with schizophrenia in contact with community services; 67 completed the intervention.

INTERVENTIONS

Three interventions of five educational sessions: (a) computer intervention combining information from patient's medical record with general information about schizophrenia; (b) sessions with a community psychiatric nurse; (c) "combination" (first and last sessions with nurse and remainder with computer).

MAIN OUTCOME MEASURES

Patients' attendance, opinions, change in knowledge, and psychological state; costs of interventions and patients' use of NHS community services; modelling of costs for these three, and alternative, interventions.

RESULTS

Rates of completion of intervention did not differ significantly (71% for combination intervention, 61% for computer only, 46% for nurse only). Computer sessions were shorter than sessions with nurse (14 minutes v 60 minutes). More patients given nurse based education thought the information relevant. Of 20 patients in combination group, 13 preferred the sessions with the nurse and seven preferred the computer. There were no significant differences between groups in psychological outcomes. Because of the need to transport patients to the computer for their sessions, there was no difference between interventions in costs, but computer sessions combined with other patient contacts would be substantially cheaper.

CONCLUSIONS

The computer based patient education offered no advantage over sessions with a community psychiatric nurse. Investigation of computer use combined with other health service contacts would be worth while.

Training nurses to support carers of relatives with schizophrenia

Carers have an enormous amount of responsibility for the welfare and management of people with a mental illness in Britain, and many require help if they are to continue caring. Mental health nurses may be in a key position to offer support, but they are often unclear of what is required and how it should be delivered. Existing UK nurse-led psychosocial interventions for families often focus on the needs of the patient rather than the carer. This article describes a needs-led support service that has been designed for carers whose relatives are diagnosed with schizophrenia. It recognizes the importance of a collaborative partnership between carers and nurses. In 2000, 10 mental health nurses were trained to deliver this support to carers. An evaluation is currently underway. This article outlines the principles of the training programme and how it might enable nurses to meet the carers' needs.

Randomised trial of personalised computer based information for cancer patients

OBJECTIVE

To compare the use and effect of a computer based information system for cancer patients that is personalised using each patient's medical record with a system providing only general information and with information provided in booklets.

DESIGN

Randomised trial with three groups. Data collected at start of radiotherapy, one week later (when information provided), three weeks later, and three months later.

PARTICIPANTS

525 patients started radical radiotherapy; 438 completed follow up.

INTERVENTIONS

Two groups were offered information via computer (personalised or general information, or both) with open access to computer thereafter; the third group was offered a selection of information booklets.

OUTCOMES

Patients' views and preferences, use of computer and information, and psychological status; doctors' perceptions; cost of interventions.

RESULTS

More patients offered the personalised information said that they had learnt something new, thought the information was relevant, used the computer again, and showed their computer printouts to others. There were no major differences in doctors' perceptions of patients. More of the general computer group were anxious at three months. With an electronic patient record system, in the long run the personalised information system would cost no more than the general system. Full access to booklets cost twice as much as the general system.

CONCLUSIONS

Patients preferred computer systems that provided information from their medical records to systems that just provided general information. This has implications for the design and implementation of electronic patient record systems and reliance on general sources of patient information.

The impact of education groups for people with schizophrenia on social functioning and quality of life

BACKGROUND

Education groups for people with schizophrenia have tended to concentrate on compliance with medication. This study examines impact on social behaviour and quality of life.

METHOD

A catchment-wide service was set up for community-based patients. Patients who indicated an interest in education groups were randomly allocated to either an education group or a waiting list control group. Those who attended groups were compared with the control group.

RESULTS

About one-quarter of community-based patients showed interest in attending education groups. Those who attended showed no change in mental state or compliance with medication (already high) but significant gains in quality of life, social functioning and social networks.

CONCLUSIONS

For patients who choose to attend education groups significant gains in social functioning and quality of life are possible without specific skills training.

Orthognathic surgery: patient expectations; psychological profile and satisfaction with outcome

61 orthognathic surgery patients were studied (39% male, 61% female). It confirms that the group of patients we see in the West of Scotland are well adjusted psychologically and that the majority seek orthognathic surgery for aesthetic reasons. The degree of satisfaction is high (87%). Dissatisfaction is not related to sex, age or procedure. Patients who were dissatisfied tend to have higher neuroticism scores on the Eysenck Personality Inventory and those patients who had had unreal expectations of post surgical pain, numbness and swelling, were likely to express dissatisfaction with the outcome in the early stages. Several patients initially expressed some dissatisfaction with the outcome after 3 months then went on to increase their score and by 12 months became satisfied with the procedure. The authors outline the importance of adequate patient preparation prior to surgery and the use of printed literature is recommended.

The patient as sufferer

The use of the term sufferer to replace patient has become increasingly common. This paper examines the varied meanings implicit in the word sufferer from the Judaeo-Christian perspective. This includes the biblical themes of suffering as human nature, as punishment, as a test, as atonement and as liberation and deliverance. The consequences of these themes for the sufferer's role are examined, particularly the sufferer as accepting and the sufferer as victim. It is argued that replacing the medical model, implied by 'patient' with a theological model, implied by 'sufferer' does not free the person from the constraints of a damaging label.

Intracellular calcium-mediated activation of hepatic Na+/H+ exchange by arginine vasopressin and phenylephrine

The effect of Ca++ mobilizing agonists arginine vasopressin and phenylephrine on Na+/H+ exchange was studied in freshly isolated hepatocytes and isolated perfused rat livers. The activity of Na+/H+ exchange was determined from the rate of H+ efflux, 22Na uptake and pHi recovery. Arginine vasopressin and phenylephrine stimulated H+ efflux and 22Na uptake in isolated rat hepatocytes and increased the rate of pHi recovery from acid-loaded hepatocytes. These effects were inhibited by amiloride. Arginine vasopressin- and phenylephrine-induced increases in H+ efflux were also dependent on extracellular Na+. Arginine vasopressin- and phenylephrine-induced increases in intracellular Ca++ concentration, H+ efflux, 22Na uptake and intracellular pH recovery were decreased in hepatocytes preloaded with the Ca(++)-buffering agent [bis-(2-amino-5-methylphenoxy)-ethane-N,N,N',N'-tetraacetic acid] (MAPTA). Na+/H+ exchange-dependent intracellular pH recovery from cytosolic acidification was stimulated by thapsigargin, which increases intracellular calcium concentration by inhibiting endoplasmic reticulum Ca++ ATPase. Arginine vasopressin- and phenylephrine-induced increases in intracellular pH recovery were not dependent on extracellular Ca++ and were inhibited by calmidazolium, a calmodulin inhibitor. Arginine vasopressin and phenylephrine also increased H+ efflux in the absence but not in the presence of amiloride in perfused rat livers without affecting biliary HCO3- excretion. These results indicate that arginine vasopressin and phenylephrine activate Na+/H+ exchange in rat hepatocytes, an effect mediated in part by intracellular Ca++ and calmodulin kinase. Furthermore, sinusoidal Na+/H+ exchange does not appear to be involved in biliary HCO3- excretion.

Mechanism of inhibition of hepatic bile acid uptake by amiloride and 4,4'-diisothiocyano-2,2'-disulfonic stilbene (DIDS)

The mechanisms by which amiloride and 4,4'-diisothiocyano-2,2'-disulfonic stilbene (DIDS) inhibit hepatic uptake of cholate and taurocholate (TC) were investigated in isolated rat hepatocytes. Amiloride inhibited Na(+)-dependent uptake of cholate and TC only when hepatocytes were preincubated with amiloride, indicating an indirect effect of amiloride. Time-dependent studies showed that the inhibition of bile acid uptake was associated with a parallel increase in intracellular Na+ concentration ([Na+]i). Although amiloride decreased intracellular pH, this decrease preceded amiloride-induced inhibition of bile acid uptake and increase in [Na+]i. Amiloride inhibited bile acid uptake, decreased membrane potential, and increased [Na+]i with comparable concentration dependency. DIDS inhibited Na(+)-dependent uptake of cholate and TC non-competitively. Neither DIDS nor amiloride inhibited Na(+)-independent uptake of cholate and TC. These results indicate that amiloride inhibits Na(+)-dependent cholate and TC uptake by decreasing the transmembrane Na(+)-gradient, and further support the hypothesis that two different transporters may be involved in hepatic bile acid uptake by Na(+)-dependent and Na(+)-independent mechanisms.

The prevention of dental disease: changing your patients' behaviour

This article aims to give practitioners a framework to help their patients establish lasting and healthy dental habits and eliminate harmful ones. The advice given is practical rather than theoretical in nature, and is intended to assist dentists in the development of the appropriate skills, so as to be able to persuade their patients to change their behaviour and thereby control dental disease.

Stress in dental practice

The life of a GDP is stressful, and the reasons why dentists may experience stress in their chosen profession are many and varied. This article discusses the causes of stress, and outlines some strategies for coping with it.

Advice for the dental team on coping with the nervous child

It is increasingly recognized that the provision of dental care should not be seen in isolation from the psychological make-up and social background of the patient. The General Dental Council has recently approved the report of its Working Party giving guidance on the teaching of the behavioural sciences (psychology and sociology) in the dental curriculum. One of the members of the Working Party was Professor Keith Millar. In this five-part series edited by Professor Millar we will cover the practical application of behavioural science in dentistry, covering communication with patients, ways to change your patients' behaviour, the management of anxious adult and child patients, and stress in dentistry. This first article offers some advice on coping with the nervous child.

Amiloride and taurine inhibit cholate-induced HCO3(-)-rich choleresis in perfused rat livers

Bile acid-induced HCO3(-)-rich choleresis may be due to primary activation of sinusoidal Na(+)-H+ exchange or to biliary reabsorption of unconjugated bile acid. To test these hypotheses, we studied the effect of cholate and taurocholate (TC) (infused at 10 mumol/min for 20 min) on net H+ efflux, biliary [HCO3-], and bile flow in perfused rat livers and on intracellular pH (pHi) in isolated hepatocytes. Cholate, but not TC, produced HCO3(-)-rich choleresis. Amiloride and taurine decreased cholate-induced choleresis and HCO3- excretion and biliary excretion of unconjugated cholate. Amiloride, but not taurine, decreased cholate-induced net H+ efflux. Both cholate and TC (200-750 microM) decreased pHi. Cholate was metabolized to a polar compound, most likely cholate glucuronide, in the presence of amiloride. These results are consistent with the hypothesis that the biliary reabsorption of unconjugated cholate may be involved in HCO3(-)-rich choleresis. Amiloride also inhibited net hepatic uptake and biliary excretion of cholate and TC without affecting hepatic content of bile acids. It is suggested that amiloride may decrease the maximal excretion rate of cholate and TC. Since cholate and TC induce amiloride-sensitive net H+ efflux and decrease pHi, it appears that cholate and TC activate Na(+)-H+ exchange indirectly by decreasing pHi.

Ursodeoxycholate-induced changes in hepatic Na+-H+ exchange and biliary HCO3- excretion

Ursodeoxycholate (UDC)-induced HCO3- -rich choleresis may be due to activation of sinusoidal Na+-H+ exchange followed by an increase in intracellular pH (pHi) and HCO3- excretion via canalicular Cl- -HCO3- exchange. To test this hypothesis, we studied the effect of UDC and tauroursodeoxycholate (TUDC) on net H+ efflux from perfused rat livers and pHi in isolated hepatocytes in the presence and absence of amiloride. UDC-induced increases in biliary HCO3- concentration and excretion were inhibited by amiloride. However, these increases were temporally associated with an initial decline in H+ efflux and pHi followed by a gradual recovery toward base line. The initial decline in H+ efflux was associated with a rapid uptake of UDC. Amiloride inhibited only the recovery phases of H+ efflux and pHi. TUDC increased amiloride-sensitive H+ efflux without affecting biliary [HCO3-] and decreased pHi in the presence but not in the absence of amiloride. Amiloride decreased TUDC-induced choleresis and HCO3- excretion most likely by decreasing TUDC excretion. TUDC decreased biliary [Cl-] and increased hepatic O2 uptake more than UDC. We conclude that a rapid influx of UDC in the protonated form decreases pHi and net H+ efflux initially. The recovery phase is due to Na+-H+ exchange activated by decreased pHi and possibly by UDC and increased cellular respiration. TUDC indirectly stimulates Na+-H+ exchange most likely by increasing cellular respiration. UDC-induced HCO3- -rich choleresis, which is observed at a time when both net H+ efflux and pHi are less than control values, is unlikely to be due to a direct activation of Na+-H+ exchange.

To tell or not to tell the diagnosis of schizophrenia

Some patients with schizophrenia are not told their diagnosis. The moral, clinical and practical issues involved in telling or not telling the patient are discussed. In some cases a relative is told the diagnosis but not the patient. The implications for the family and clinical outcome are outlined. A case history illustrating some of these issues is presented.

A low-cost community approach to weight control: initial results from an evaluated trial

This article describes a trial of a low-cost, readily disseminatable weight-control program ("Waistline") which uses behavioral, social support, and community strength-building principles. Participants meet for 12 weeks in small, lay-led groups in community settings, and use prepackaged materials designed specifically for those of modest education. Results from 407 participants are presented, showing a mean postcourse weight loss of 5.6 kg (12.3 lb) and a low attrition rate (9-12%). In a subsample followed up at 12 months (N = 96), 80% of this loss had been maintained. A comparison group ("Slimline," N = 26) lost 1.27 kg (2.8 lb) and had an attrition rate of 31-46%. The Waistline results are comparable to those obtained by more intensive and expensive behavioral programs, and demographic data show that those of relatively low educational attainment are well represented. The potential of this approach for cheap, noncommercial dissemination of weight-control programs on a population basis is noted.

Serratia: opportunistic pathogen of increasing clinical importance

Serratia marcescens can become a formidable nosocomial (hospital acquired) pathogen, and is reported increasingly in the world literature. However, it is only a recently recognized problem in Australia. Serratia can carry an antibiotic-resistance plasmid, and, after entry of the organism into very sick patients, it may be hard or impossible to eliminate. Initial experience of Serratia in 34 consecutive cases isolated in a three-months period is presented. Rapid increase in the number of Serratia infections occurred after the appearance of a resistant strain. Urinary infection was the commonest presentation (91% of cases). The presence of an indwelling urinary catheter in a debilitated patient was the major predisposing factor. Significant bacteraemia followed in four cases with one death. Contamination of burns (surfaces) and surgical wounds was found in four cases. Serratia strains were found to be highly resistant to most antimicrobial agents in routine sensitivity testing, 20% being fully resistant to all tested agents, and nalidixic acid being the most effective inhibitor in the remainder. With bacteriocin typing of Serratia, two types were found to be dominant. These two bacteriocin types were not identified among strains isolated from other sources such as soil, water and local hospitals. Pharyngeal carriage was found in only one case, but faecal excretion of Serratia was found in 11 cases and may be a significant portal of dissemination. Cross-infection from a hospital reservoir of resistant organisms is postulated. A model of cross-infection is also proposed, and methods of control are discussed. In view of the established danger of Serratia in the hospital setting, its isolation can no longer be ignored.

Acidaemia produced by spinal stimulation in the pithed rat

1. Electrical stimulation of the thoraco-lumbar spinal nervous outflow in the pithed rat preparation produces a fall in arterial blood pH.2. A component of the acidaemic response results from stimulation of skeletal muscle, since the acidaemic response is reduced when contractions of muscle are blocked with gallamine.3. The residual acidaemic response in gallamine-treated rats is reduced by adrenalectomy, suggesting that catecholamines liberated from the adrenal medulla may mediate part of the effect.4. Guanethidine reduces the acidaemic response remaining in adrenalectomized, gallamine-treated rats, suggesting that the effect of noradrenaline released from sympathetic nerve endings contributes to the fall in pH.5. Neither phenoxybenzamine nor propanolol alone significantly reduces the acidaemic response in gallamine-treated rats, but a combination of the two antagonists almost abolishes the effect. Hence the acidaemia is mediated through effects of catecholamines on both alpha- and beta-adreno-receptors.6. Since acidaemia affects responses to sympathetic nerve stimulation and sympathomimetic amines, the significance of these observations is discussed with reference to the use of the pithed rat preparation for assessment of drugs affecting adrenergic mechanisms.

The effect of directly and indirectly acting sympathomimetic amines on bronchospasm in the guinea-pig during CO2 inhalation

The bronchodilator effects of nine sympathomimetic amines were tested by reduction of histamine-induced bronchospasm in guinea-pigs. Their order of potency was: isoprenaline > adrenaline > noradrenaline > orciprenaline > ethylnoradrenaline > phenylephrine > amphetamine = tyramine > ephedrine. In guinea-pigs ventilated with 10% CO2 in air, there was a marked decrease in the bronchoconstrictor activity of histamine. Under these conditions, isoprenaline, adrenaline, noradrenaline and orciprenaline were as effective as bronchodilators as they had been in guinea-pigs ventilated with air, ethylnoradrenaline was less effective, phenylephrine, amphetamine and tyramine were completely inactive, and ephedrine potentiated the bronchoconstrictor action of histamine. After returning the guinea-pigs to ventilation with air, the bronchoconstrictor activity of histamine and the bronchodilator effects of the sympathomimetic amines were restored. The cardiovascular effects of histamine and of all the sympathomimetic amines used were diminished during ventilation with 10% CO2 in air and were restored after ventilation with air was resumed.

Mutal suppression of cardiovascular effects of some beta-adrenoreceptor agonists in the cat

Observations were made of the effects of adrenaline, isoprenaline and orciprenaline on the blood pressure, heart rate and configuration of the ECG in cats. The effects of single injections of these amines in producing a rise in heart rate and a fall in blood pressure were reduced during the intravenous infusion of any one of them: the pressor response to injected adrenaline was enhanced during an infusion. Combinations of these amines did not produce changes in the configuration of the ECG. These experiments were motivated by allegations of acute toxic effects on the cardiovascular system of large doses, or of combinations, of sympathomimetic bronchodilators in asthma. No evidence of deleterious effects of interactions was obtained.