Sample efficient reinforcement learning with active learning for molecular design

Reinforcement learning (RL) is a powerful and flexible paradigm for searching for solutions in high-dimensional action spaces. However, bridging the gap between playing computer games with thousands of simulated episodes and solving real scientific problems with complex and involved environments (up to actual laboratory experiments) requires improvements in terms of sample efficiency to make the most of expensive information. The discovery of new drugs is a major commercial application of RL, motivated by the very large nature of the chemical space and the need to perform multiparameter optimization (MPO) across different properties. In silico methods, such as virtual library screening (VS) and de novo molecular generation with RL, show great promise in accelerating this search. However, incorporation of increasingly complex computational models in these workflows requires increasing sample efficiency. Here, we introduce an active learning system linked with an RL model (RL-AL) for molecular design, which aims to improve the sample-efficiency of the optimization process. We identity and characterize unique challenges combining RL and AL, investigate the interplay between the systems, and develop a novel AL approach to solve the MPO problem. Our approach greatly expedites the search for novel solutions relative to baseline-RL for simple ligand- and structure-based oracle functions, with a 5-66-fold increase in hits generated for a fixed oracle budget and a 4-64-fold reduction in computational time to find a specific number of hits. Furthermore, compounds discovered through RL-AL display substantial enrichment of a multi-parameter scoring objective, indicating superior efficacy in curating high-scoring compounds, without a reduction in output diversity. This significant acceleration improves the feasibility of oracle functions that have largely been overlooked in RL due to high computational costs, for example free energy perturbation methods, and in principle is applicable to any RL domain.

A tool for evaluating heterogeneity in avidity of polyclonal antibodies

Diversity in specificity of polyclonal antibody (pAb) responses is extensively investigated in vaccine efficacy or immunological evaluations, but the heterogeneity in antibody avidity is rarely probed as convenient tools are lacking. Here we have developed a polyclonal antibodies avidity resolution tool (PAART) for use with label-free techniques, such as surface plasmon resonance and biolayer interferometry, that can monitor pAb-antigen interactions in real time to measure dissociation rate constant (kd ) for defining avidity. PAART utilizes a sum of exponentials model to fit the dissociation time-courses of pAb-antigens interactions and resolve multiple kd contributing to the overall dissociation. Each kd value of pAb dissociation resolved by PAART corresponds to a group of antibodies with similar avidity. PAART is designed to identify the minimum number of exponentials required to explain the dissociation course and guards against overfitting of data by parsimony selection of best model using Akaike information criterion. Validation of PAART was performed using binary mixtures of monoclonal antibodies of same specificity but differing in kd of the interaction with their epitope. We applied PAART to examine the heterogeneity in avidities of pAb from malaria and typhoid vaccinees, and individuals living with HIV-1 that naturally control the viral load. In many cases, two to three kd were dissected indicating the heterogeneity of pAb avidities. We showcase examples of affinity maturation of vaccine induced pAb responses at component level and enhanced resolution of heterogeneity in avidity when antigen-binding fragments (Fab) are used instead of polyclonal IgG antibodies. The utility of PAART can be manifold in examining circulating pAb characteristics and could inform vaccine strategies aimed to guide the host humoral immune response.

Microglia regulate central nervous system myelin growth and integrity

Myelin is required for the function of neuronal axons in the central nervous system, but the mechanisms that support myelin health are unclear. Although macrophages in the central nervous system have been implicated in myelin health1, it is unknown which macrophage populations are involved and which aspects they influence. Here we show that resident microglia are crucial for the maintenance of myelin health in adulthood in both mice and humans. We demonstrate that microglia are dispensable for developmental myelin ensheathment. However, they are required for subsequent regulation of myelin growth and associated cognitive function, and for preservation of myelin integrity by preventing its degeneration. We show that loss of myelin health due to the absence of microglia is associated with the appearance of a myelinating oligodendrocyte state with altered lipid metabolism. Moreover, this mechanism is regulated through disruption of the TGFβ1-TGFβR1 axis. Our findings highlight microglia as promising therapeutic targets for conditions in which myelin growth and integrity are dysregulated, such as in ageing and neurodegenerative disease2,3.

Research Confirms Effectiveness of Oral Health Preventive Practices

Lack of insurance or funds for dental services, lack of access to dental offices, fear of dentists, and avoidance of dental offices during COVID can lead to oral health problems in older adults. Brushing, flossing, and drinking fluoridated water can protect teeth when dentists are unavailable. Limiting intake frequency of carbohydrates and chewing sugarfree gum after eating add protection. A recent systematic review and meta-analysis confirmed the effectiveness of sugarfree gum in reducing caries, in children and adults who chewed sugarfree gum compared with those who did not chew. Chewing sugarfree gum significantly reduced caries increment, with a prevented fraction of 28 percent, roughly equivalent to the prevented fractions for fluoride toothpastes and supplements. A follow-up systematic review provides further evidence that chewing sugarfree gum reduces the numbers of Streptococcus mutans in the oral cavity. Finally, chewing sugarfree gum could alleviate symptoms of xerostomia and may reduce caries.

Multimodal imaging of composite carbon fiber-based implants for orthopedic spinal fixation

OBJECTIVE

As cancer treatments continue to improve, the incidence of spinal metastases and the need for surgical management of these with fixation procedures are growing rapidly. Traditionally metallic implants, composed of titanium alloy, have been used in surgical fixation of unstable or symptomatic vertebral metastases or traumatic injuries. Metallic implants, however, cause significant artifact on post-operative imaging, degrading image quality and limiting interpretation, and can also impair the planning and delivery of radiotherapy. Composite carbon fiber-based materials, such as carbon fiber-reinforced polyetheretherketone (PEEK), have been developed to overcome these issues and are now available for spinal fixation procedures. We aimed to review the multimodal imaging features of these new implants.

MATERIALS AND METHODS

Current literature and a case example from our institution were used to describe the multimodal imaging characteristics and considerations of new carbon fiber-based spinal fixation implants.

RESULTS

New carbon fiber-based spinal implants allow far greater visualization of surrounding structures on post-operative cross-sectional imaging, significantly improving diagnostic accuracy and precision of radiotherapy planning, and do not significantly absorb or scatter X-ray photons during radiotherapy delivery. There are, however, important surgical and radiologic considerations associated with the use of carbon fiber-based implants which radiologists must be aware of, such as implications for surgical planning and intra-operative fluoroscopic and post-operative plain radiographic imaging.

CONCLUSION

The use of carbon fiber-based implants, rather than traditional metallic implants, for spinal fixation offers significant advantages for post-operative diagnostic imaging and radiotherapy planning and delivery.

Model-informed drug repurposing: A pharmacometric approach to novel pathogen preparedness, response and retrospection

During a pandemic caused by a novel pathogen (NP), drug repurposing offers the potential of a rapid treatment response via a repurposed drug (RD) while more targeted treatments are developed. Five steps of model‐informed drug repurposing (MIDR) are discussed: (i) utilize RD product label and in vitro NP data to determine initial proof of potential, (ii) optimize potential posology using clinical pharmacokinetics (PK) considering both efficacy and safety, (iii) link events in the viral life cycle to RD PK, (iv) link RD PK to clinical and virologic outcomes, and optimize clinical trial design, and (v) assess RD treatment effects from trials using model‐based meta‐analysis. Activities which fall under these five steps are categorized into three stages: what can be accomplished prior to an NP emergence (preparatory stage), during the NP pandemic (responsive stage) and once the crisis has subsided (retrospective stage). MIDR allows for extraction of a greater amount of information from emerging data and integration of disparate data into actionable insight.

Using in silico viral kinetic models to guide therapeutic strategies during a pandemic: An example in SARS-CoV-2

AIMS

We propose the use of in silico mathematical models to provide insights that optimize therapeutic interventions designed to effectively treat respiratory infection during a pandemic. A modelling and simulation framework is provided using SARS-CoV-2 as an example, considering applications for both treatment and prophylaxis.

METHODS

A target cell-limited model was used to quantify the viral infection dynamics of SARS-CoV-2 in a pooled population of 105 infected patients. Parameter estimates from the resulting model were used to simulate and compare the impact of various interventions against meaningful viral load endpoints.

RESULTS

Robust parameter estimates were obtained for the basic reproduction number, viral release rate and infected-cell mortality from the infection model. These estimates were informed by the largest dataset currently available for SARS-CoV-2 viral time course. The utility of this model was demonstrated using simulations, which hypothetically introduced inhibitory or stimulatory drug mechanisms at various target sites within the viral life-cycle. We show that early intervention is crucial to achieving therapeutic benefit when monotherapy is administered. In contrast, combination regimens of two or three drugs may provide improved outcomes if treatment is initiated late. The latter is relevant to SARS-CoV-2, where the period between infection and symptom onset is relatively long.

CONCLUSIONS

The use of in silico models can provide viral load predictions that can rationalize therapeutic strategies against an emerging viral pathogen.

Target-Mediated Drug Disposition Pharmacokinetic/Pharmacodynamic Model-Informed Dose Selection for the First-in-Human Study of AVB-S6-500

AVB-S6-500 neutralized growth arrest-specific 6 (GAS6) protein and effectively inhibited AXL signaling in preclinical cancer models. A target-mediated drug disposition (TMDD) pharmacokinetic/pharmacodynamic (PK/PD) model was used to select first-in-human (FIH) doses for AVB-S6-500 based on predicted target (GAS6) suppression in the clinic. The effect of TMDD on AVB-S6-500 clearance was incorporated into a standard two-compartment model, providing parallel linear and nonlinear clearance. Observed AVB-S6-500 and GAS6 concentration data in cynomolgus monkeys and relevant interspecies differences were used to predict the PK (serum concentration)/PD (GAS6 suppression) relationship in humans. Human exposure and GAS6 suppression were simulated for the proposed FIH doses of 1, 2.5, 5, and 10 mg/kg. A dose of 1 mg/kg was selected to target GAS6 suppression for 2 weeks in the initial healthy volunteer study. The cynomolgus monkey:human ratios for the highest proposed FIH dose were anticipated to yield more than a 10-fold margin to the nonclinical no observed adverse event level while maintaining > 90% GAS6 suppression. In human subjects, the first dose (1 mg/kg) model-projected and clinically observed maximal concentration (Cmax ) was within 10% of predicted; repeat dosing at 5 mg/kg was within 1% (Cmax ) and 45% (area under the serum concentration-time curve from time 0 to end of dosing interval) of predicted. Predicted GAS6 suppression duration of 14 days was accurate for the 1 mg/kg dose. A PK/PD model expedited clinical development of AVB-S6-500, minimized exposure of patients with cancer to subtherapeutic doses, and rationally guided the optimal dosing in patients.

Evaluation of the dual mTOR/PI3K inhibitors Gedatolisib (PF-05212384) and PF-04691502 against ovarian cancer xenograft models

This study investigated the antitumour effects of two dual mTOR/PI3K inhibitors, gedatolisib (WYE-129587/PKI-587/PF-05212384) and PF-04691502 against a panel of six human patient derived ovarian cancer xenograft models. Both dual mTOR/PI3K inhibitors demonstrated antitumour activity against all xenografts tested. The compounds produced tumour stasis during the treatment period and upon cessation of treatment, tumours re-grew. In several models, there was an initial rapid reduction of tumour volume over the first week of treatment before tumour stasis. No toxicity was observed during treatment. Biomarker studies were conducted in two xenograft models; phospho-S6 (Ser235/236) expression (as a readout of mTOR activity) was reduced over the treatment period in the responding xenograft but expression increased to control (no treatment) levels on cessation of treatment. Phospho-AKT (Ser473) expression (as a readout of PI3K) was inhibited by both drugs but less markedly so than phospho-S6 expression. Initial tumour volume reduction on treatment and regrowth rate after treatment cessation was associated with phospho-S6/total S6 expression ratio. Both drugs produced apoptosis but minimally influenced markers of proliferation (Ki67, phospho-histone H3). These results indicate that mTOR/PI3K inhibition can produce broad spectrum tumour growth stasis in ovarian cancer xenograft models during continuous chronic treatment and this is associated with apoptosis.

Resistance and resilience to experimental gingivitis: a systematic scoping review

Background

This systematic scoping review aimed to identify changes in biomarkers of microbiological, immunological and biochemical origin during experimental gingivitis (EG) studies that might indicate resistance and resilience.

Methods

The term ‘experimental gingivitis’ was run in PubMed from inception to April 11th, 2018. From the 411 studies retrieved, 22 studies were included for this review.

Results

Studies reporting data on biomarker changes during and after full mouth EG trial were included. Two studies reported findings on changes in biomarkers of microbiological, 12 on immunological and eight on biochemical origin. Changes were reported in the induction phase, and occasionally in the resolution phase. The microbiological composition of both supragingival and subgingival dental plaque changed over the course of EG to a more pathogenic direction, but showed a shift back to a more normal composition. This indicates resilience of the oral microbiome. For immunological biomarkers, it was challenging to retrieve a robust pattern of changes across multiple studies. IL-1β and IL-6 in saliva and in gingival crevicular fluid increased during induction phase and returned in the resolution phase below baseline values. The biochemical parameters cystatin-SN, cystatin-S and lactoferrin in saliva were increased at the end of induction phase, however also here no clear pattern emerged based on all available studies.

Conclusions

More research is needed to investigate which microbiological, immunological, and biochemical biomarkers can be useful for future investigations into the resistance and resilience of the oral cavity to experimental gingivitis.

Electronic supplementary material

The online version of this article (10.1186/s12903-019-0889-z) contains supplementary material, which is available to authorized users.

Operative Management of Perinatal Lumbar Disc Herniation and Cauda Equina Syndrome: A Case Series

Introduction Perinatal lumbar discectomy for lumbar disc herniation or cauda equina syndrome is a rare clinical scenario. This case series outlines the surgical management of this clinical scenario at a national tertiary referral centre over a 10-year period Methods A retrospective review of all females who underwent discectomy / decompression for lumbar disc herniation or cauda equina syndrome in the perinatal period at a national tertiary referral centre for spine surgery over a 10-year period between January 2008 to December 2017. Results 6 cases required surgical intervention. All patients were successfully managed with surgical decompressive procedures and recovered well in the postoperative period without complication. Conclusions The principles of management remain the same in the pregnant and non-pregnant populations, although treatment options are complicated by the desire to avoid risk to the developing foetus. Surgical intervention is safe to both mother and baby and if performed promptly is associated with an excellent functional outcome.

Magnolia officinalis L. Fortified Gum Improves Resistance of Oral Epithelial Cells Against Inflammation

Inflammatory diseases of the periodontal tissues are known health problems worldwide. Therefore, anti-inflammatory active compounds are used in oral care products to reduce long-term inflammation. In addition to inducing inflammation, pathogen attack leads to an increased production of reactive oxygen species (ROS), which may lead to oxidative damage of macromolecules. Magnolia officinalis L. bark extract (MBE) has been shown to possess antioxidant and anti-inflammatory potential in vitro. In the present study, the influence of MBE-fortified chewing gum on the resistance against lipopolysaccharide (LPS)-induced inflammation and oxidative stress of oral epithelial cells was investigated in a four-armed parallel designed human intervention trial with 40 healthy volunteers. Ex vivo stimulation of oral epithelial cells with LPS from Porphyromonas gingivalis for 6[Formula: see text]h increased the mRNA expression and release of the pro-inflammatory cytokines IL-1[Formula: see text], IL-[Formula: see text], IL-8, MIP-1[Formula: see text], and TNF[Formula: see text]. Chewing MBE-fortified gum for 10[Formula: see text]min reduced the ex vivo LPS-induced increase of IL-8 release by 43.8 [Formula: see text] 17.1% at the beginning of the intervention. In addition, after the two-week intervention with MBE-fortified chewing gum, LPS-stimulated TNF[Formula: see text] release was attenuated by 73.4 [Formula: see text] 12.0% compared to chewing regular control gum. This increased resistance against LPS-induced inflammation suggests that MBE possesses anti-inflammatory activity in vivo when added to chewing gum. In contrast, the conditions used to stimulate an immune response of oral epithelial cells failed to induce oxidative stress, measured by catalase activity, or oxidative DNA damage.

Molecular basis of Streptococcus mutans sortase A inhibition by the flavonoid natural product trans-chalcone

Sortase A (SrtA) from Gram positive pathogens is an attractive target for inhibitors due to its role in the attachment of surface proteins to the cell wall. We found that the plant natural product trans-chalcone inhibits Streptococcus mutans SrtA in vitro and also inhibited S. mutans biofilm formation. Mass spectrometry revealed that the trans-chalcone forms a Michael addition adduct with the active site cysteine. The X-ray crystal structure of the SrtA H139A mutant provided new insights into substrate recognition by the sortase family. Our study suggests that chalcone flavonoids have potential as sortase-specific oral biofilm inhibitors.

AMG 151 (ARRY-403), a novel glucokinase activator, decreases fasting and postprandial glycaemia in patients with type 2 diabetes

Phase I studies have shown that AMG 151 activates glucokinase, a key enzyme in glucose homeostasis. The present randomized, placebo-controlled phase IIa study evaluated the dose-effect relationship of the glucokinase activator AMG 151 relative to placebo on fasting plasma glucose (FPG) in 236 patients (33-35 patients per arm) with type 2 diabetes treated with metformin. Patients received oral AMG 151 at 50, 100 or 200 mg twice daily, AMG 151 at 100, 200 or 400 mg once daily or matching placebo for 28 days. A significant linear dose-effect trend was observed with the twice-daily regimen (p = 0.004) for change in FPG to day 28. No trend was observed with the once-daily regimen. A higher incidence of hypoglycaemia and hypertriglyceridaemia was observed with AMG 151 administration. AMG 151 significantly reduced FPG when administered twice daily but not when administered once daily in patients with type 2 diabetes treated with metformin.

Factors That Influence the Extensional Rheological Property of Saliva

The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste) salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva.

Crossover clinical investigation of a whitening chewing gum for inhibiting dental stain formation in conjunction with tooth brushing

OBJECTIVE

The purpose of this clinical investigation was to evaluate the effectiveness of a marketed whitening chewing gum compared to a no-gum control in preventing the formation of extrinsic stains on the teeth of stain-forming subjects when chewed over a 12-week period of regular unsupervised use in conjunction with daily tooth brushing.

METHODS

This was a single-center, examiner-blind, randomized, 12-week crossover clinical trial. Stain-forming (after smoking or drinking coffee or tea) adults, starting with a stain-free baseline, either chewed the test gum (Orbit White) unsupervised four times per day, 15 minutes/chew, or used no gum along with daily brushing with a commercially available toothbrush and dentifrice for 12 weeks. At the crossover, all procedures were repeated with subjects assigned the opposite treatment. Extrinsic stain was measured at six and 12 weeks by both the Lobene Stain Index (LSI) and the Modified Lobene Stain Index (MLSI) using separate experienced examiners.

RESULTS

After 12 weeks, LSI stain scores showed a significant 25% reduction (p = 0.0008) in new stain formation for subjects using the test chewing gum along with tooth brushing versus tooth brushing alone (no-gum control). The corresponding MLSI stain scores demonstrated a 36% reduction (p < 0.0001) in the formation of extrinsic stain on the teeth.

CONCLUSION

The overall findings of this clinical study demonstrated that regular use of Orbit White chewing gum, soon after smoking or drinking coffee or tea, will supplement daily tooth brushing in preventing unsightly stains from forming on the anterior teeth compared to brushing alone.

Defining the molecular response to trastuzumab, pertuzumab and combination therapy in ovarian cancer

BACKGROUND

Trastuzumab and pertuzumab target the Human Epidermal growth factor Receptor 2 (HER2). Combination therapy has been shown to provide enhanced antitumour activity; however, the downstream signalling to explain how these drugs mediate their response is not clearly understood.

METHODS

Transcriptome profiling was performed after 4 days of trastuzumab, pertuzumab and combination treatment in human ovarian cancer in vivo. Signalling pathways identified were validated and investigated in primary ovarian xenografts at the protein level and across a timeseries.

RESULTS

A greater number and variety of genes were differentially expressed by the combination of antibody therapies compared with either treatment alone. Protein levels of cyclin-dependent kinase inhibitors p21 and p27 were increased in response to both agents and further by the combination; pERK signalling was inhibited by all treatments; but only pertuzumab inhibited pAkt signalling. The expression of proliferation, apoptosis, cell division and cell-cycle markers was distinct in a panel of primary ovarian cancer xenografts, suggesting the heterogeneity of response in ovarian cancer and a need to establish predictive biomarkers.

CONCLUSION

This first comprehensive study of the molecular response to trastuzumab, pertuzumab and combined therapy in vivo highlights both common and distinct downstream effects to agents used alone or in combination, suggesting that complementary pathways may be involved.

Trastuzumab and pertuzumab produce changes in morphology and estrogen receptor signaling in ovarian cancer xenografts revealing new treatment strategies

PURPOSE

The aim of this study was to investigate the antitumor effects of HER2-directed combination therapy in ovarian cancer xenograft models to evaluate their potential. The combinations of trastuzumab and pertuzumab, and trastuzumab and aromatase inhibitor therapy were investigated.

EXPERIMENTAL DESIGN

The effects of trastuzumab, pertuzumab, and letrozole on growth response, apoptosis, morphology, and gene and protein expression were evaluated in the SKOV3 ovarian cancer cell line xenograft and a panel of five human ovarian xenografts derived directly from clinical specimens.

RESULTS

The combination of HER2-directed antibodies showed enhanced antitumor activity compared with single antibody therapy in the SKOV3 xenograft model. Apoptosis, morphology, and estrogen-regulated gene expression were modulated by these antibodies in both spatial and temporal manners. A panel of ovarian cancer xenografts showed differential growth responses to the combination of trastuzumab and pertuzumab. High HER2 expression and increasing HER3 protein expression on treatment were associated with growth response. In trastuzumab-treated SKOV3 tumors, there was a change in tumor morphology, with a reduction in frequency of estrogen receptor alpha (ERα)-negative clear cell areas. Trastuzumab, but not pertuzumab, increased expression of ERα in SKOV3 xenografts when analyzed by quantitative immunofluorescence. ERα and downstream signaling targets were modulated by trastuzumab alone and in combination. Trastuzumab enhanced the responsiveness of SKOV3 xenografts to letrozole when given in combination.

CONCLUSIONS

These data suggest that trastuzumab in combination with pertuzumab could be an effective approach in high HER2-expressing ovarian cancers and could also enhance sensitivity to endocrine therapy in ERα-positive ovarian cancer.

Naturally occurring phenolic antibacterial compounds show effectiveness against oral bacteria by a quantitative structure-activity relationship study

Natural and synthetic phenolic compounds were evaluated against oral bacteria. A quantitative structure-active relationship approach was applied to the germ-kill activity for a range of phenolic compounds. The lipophilicity and steric effects were found to be two key factors in determining germ-kill activity. The optimum lipophilicity, measured by the logarithm of the octanol/water partition coefficient, or log P, was found to be 5.5 for Fusobacterium nucleatum , a Gram-negative type of oral bacteria that causes bad breath. The optimum log P was found to be 7.9 for Streptococcus mutans , a Gram-positive type of oral bacteria that causes tooth decay. The steric effect of substituents ortho to the phenolic group was found to be critical in reducing antibacterial activity despite having increased lipid solubility approaching the optimum lipophilicity value. The antibacterial activity of phenolic compounds is likely exerted by multiple functions, primarily comes from its ability to act as a nonionic surface-active agent therefore disrupting the lipid-protein interface.

Gonadotropin-releasing hormone receptor levels and cell context affect tumor cell responses to agonist in vitro and in vivo

Activation of gonadotropin-releasing hormone (GnRH) receptors inhibits proliferation of transformed cells derived from reproductive tissues and in transfected cell lines. Hence, GnRH receptors represent a therapeutic target for direct action of GnRH analogues on certain proliferating cells. However, more cell biological data are required to develop this particular application of GnRH analogues. Therefore, we compared the effects of GnRH receptor activation in transfected HEK293 cells (HEK293([SCL60])) with transfected human ovarian cancer cell lines SKOV3 and EFO21, human hepatoblastoma HepG2 cells, and rat neuroblastoma B35 cells. Marked differences in receptor levels, magnitude of inositol phosphate generation, and dynamics of inositol phosphate turnover occurred in the different cells. Activation of GnRH receptors, expressed at high or moderate levels, inhibited the growth of HEK293([SCL60]) and B35 cells, respectively. Western blotting detected markers of apoptosis [cleaved poly(ADP-ribose) polymerase, caspase-9] in HEK293([SCL60]) and B35 following treatment with 100 nmol/L d-Trp(6)-GnRH-I. Cell growth inhibition was partially or completely rescued with inhibitor Q-VD-OPh or Ro32-0432. Low levels of GnRH receptor expression in transfected SKOV3, EFO21, or HepG2 activated intracellular signaling but did not induce apoptosis or significantly affect cell proliferation. Tumor xenografts prepared from HEK293([SCL60]) regressed during treatment with d-Trp(6)-GnRH-I and growth of xenografts derived from transfected B35 was slowed. SKOV3 xenografts were not growth inhibited. Therefore, differences in levels of GnRH receptor and signaling differentially affect the apoptotic machinery within cell lines and contribute to the cell type-specific effects of GnRH on growth. Further studies should exploit the growth-inhibitory potential of GnRH receptor activation in abnormal cells in diseased human tissues.

Anti-tumour activity in non-small cell lung cancer models and toxicity profiles for novel ruthenium(II) based organo-metallic compounds

Novel ruthenium(II) organo-metallic compounds are active in ovarian cancer models [Aird RE, Cummings J, Ritchie AA, Muir M, Morris RE, Chen H, et al. In vitro and in vivo activity and cross resistance profiles of novel ruthenium(II) organometallic arene complexes in human ovarian cancer. Br J Cancer 2002;86(10):1652-7]. [(eta6-C6H5C6H5)Ru(en)Cl]+ (as a PF6 salt, where en=ethylenediamine (RM175)) has been evaluated in a 13-cell line panel. Particular sensitivity (approximately 10-fold lower than mean IC50) was noted in breast cancer and non-small cell lung cancer cell lines. In addition, IC50 in the A549 was 2 microM and RM175 (25 mg kg-1, days 1 and 5, i.p.) caused a significant (p=0.004) growth delay in a xenograft model. HC11 [(eta6-tetrahydroanthracene)Ru(en)Cl]PF6 was more potent in the A549 cell line (IC50 0.5 microM). HC11 (25 mg kg-1, days 1, 8 and 15, i.p.) was also active in vivo. Following RM175 25 mg kg-1, days 1 and 5, and 15 mg kg-1, days 1-5, HC11 25 and 40 mg kg-1, day 1, elevated alanine transaminase levels were detected, suggesting hepatotoxicity. No changes were observed in kidney or haematological parameters. In liver sections, multi-focal hepatic necrosis was seen, becoming confluent at high doses of HC11. In vitro studies confirmed that HC11 was more toxic than RM175 to fresh human hepatocytes and equitoxic to mithramycin. Liver toxicity may be related to the arene ligand and modification may reduce the potential for hepatic toxicity, while maintaining the anti-tumour activity seen.

Normal variants in the paediatric orthopaedic population

Normal variations of lower limb development are a common source of parental concern and are commonly referred to paediatric orthopaedic clinics. To determine the proportion of children referred to a paediatric orthopaedic outpatients with potentially normal developmental variations, referral letters and case notes of children attending the paediatric orthopaedic clinic at our institution over three months were analysed and categorized according to the main reason for referral. The number with true orthopaedic pathology was documented. Variations of normal anatomy and physiology accounted for 53.1% of all new referrals seen at the clinic with intoeing and flexible flat feet being the commonest referrals in this category. The rate of true primary pathology was only 16.3%. Normal developmental variations form a significant proportion of all new referrals to paediatric orthopaedic clinics. These take time and resources to process. Strategies to minimise these referrals are needed.

Ethics committee reviews and mutual acceptance: a pilot study

AIMS

To develop a human research ethics committee (HREC) mutual acceptance (MA) model, based on the National Health and Medical Research Council's guidelines. The MA model aims to facilitate aspects of multicentre research and decrease the time taken to finalise the HREC review process.

METHODS

Four HREC (The Alfred Hospital, Austin Health, Peter MacCallum Cancer Centre and Melbourne Health) agreed to participate in a 13-month pilot project to evaluate the MA model. Evaluation included times from submission to approval and stakeholder surveys.

RESULTS

Seventeen consecutive studies were submitted to the MA pilot project. Stakeholders agreed that the MA model was efficient and effective and that submission and review processes had improved, with a demonstrable reduction in the levels of duplication. There was a 27% improvement in approval times for multicentre studies.

CONCLUSIONS

Our (MA) model resulted in clear improvements in HREC processes and timelines. Stakeholder acceptance was high. This model provides a framework for a broader program of MA.

Trust and confidence: towards mutual acceptance of ethics committee approval of multicentre studies

AIMS

To compare issues raised by Human Research Ethics Committees (HREC) during the ethics review process and to determine the length of time taken to gain HREC approval for multicentre research studies.

METHODS

Review and analysis of HREC documentation and correspondence for all multicentre research studies were conducted through three HREC under the auspices of Cancer Trials Australia, Melbourne, Victoria, Australia, between November 1997 and March 2001 to determine the variance of documentation, correspondence and recommendations across the three HREC and the time taken for study approval.

RESULTS

Thirty-one projects were submitted to any two of the HREC (16 studies) or all three HREC (15 studies). The median time for study approval at an individual HREC was 75 days, but it was 111 days for approval at all participating sites. There were 554 clarifications or comments made by the reviewing HREC, the majority of which had no significant bearing on the ethical or scientific calibre of the study. There was only one study in which a significant protocol change was requested by a HREC.

CONCLUSIONS

Multicentre study approvals are delayed when submitted to multiple HREC. The three HREC raised similar issues without substantive differences in their recommendations. A process for the mutual acceptance of HREC recommendations could facilitate multicentre research.

Salivary CA130 with and without unilateral autonomic parotid denervation of rats fed different diets

BACKGROUND

Tumor markers such as CA130 can be determined in human whole saliva. Saliva represents an attractive body fluid for longitudinal studies.

MATERIALS AND METHODS

CA130 was determined in parotid saliva from 8 rats fed different diets, with or without autonomic denervation.

RESULTS

CA130 could be determined in parotid saliva of rats, irrespective of diet and/or autonomic denervation. Whether the numerical decrease in CA130 observed after autonomic denervation is statistically significant requires further work.

CONCLUSIONS

Since salivary CA130 has been shown to decrease following treatment with anti-cancer drugs in humans, the ability to determine this tumor marker in rat saliva opens new opportunities for optimizing cancer chronotherapy in the experimental laboratory.

Antitumour activity and schedule dependency of 8-chloroadenosine-3',5'-monophosphate (8-ClcAMP) against human tumour xenografts

8-Chloroadenosine-3',5'-monophosphate (8-ClcAMP) is a novel antitumour agent currently undergoing phase I clinical trials in several European centres. In this study, its antitumour activity against human tumour xenografts and its dependence on schedule were investigated. When administered by continuous infusion at doses of 100 or 50 mg/kg/day to nude mice bearing human tumour xenografts, 8-ClcAMP inhibited the growth of the HT 29 colorectal, ZR-75-1 breast, HOX 60 and PE04 ovarian and PANC-1 pancreatic carcinoma xenografts. However, these infusion schedules produced hypercalcaemia and severe weight loss. In an attempt to optimise antitumour activity and minimise toxicity, several other schedules were studied. In comparison with continuous administration of 8-ClcAMP at 50 mg/kg/day for 14 days which, although producing complete growth inhibition in the HOX 60 model, was associated with a marked body weight loss, schedules in which the infusion was interrupted (infusion on either days 0-4; 7-11 or days 0-2; 6-8) produced minimal weight loss but also reduced antitumour activity. However, co-administration of salmon calcitonin with continuous infusion of 8-ClcAMP prevented both hypercalcaemia and body weight loss in 3/6 animals while still producing marked inhibition of tumour growth. These data indicate that 8-ClcAMP has broad-spectrum antitumour activity and the major side-effect of hypercalcaemia may at least in part be ameliorated by the use of salmon calcitonin.

Group Health Supervision Visits More Effective Than Individual Visits in Delivering Health Care Information

Preventive health care consumes a substantial amount of pediatricians' time and has been promoted as one of the most important medical functions physicians perform.1-4 The American Academy of Pediatrics (AAP) has emphasized the need for preventive health care. To assist in the delivery of child health supervision, the AAP Committee on Psychosocial Aspects of Child and Family Health has recently published guidelines recommending specific topics to be covered at each of the routine health maintenance visits.5

Despite the acceptance of recommendations for preventive child health care, the efficacy of office-based prevention strategies has not yet been proven.6 However, assessment of the literature addressing the effectiveness and costs of strategies for promoting and maintaining child health has been noted to be "more remarkable for its limitations than its findings."6

Regular exercise and reduction of breathlessness in patients with cystic fibrosis

The influence of regular exercise on breathlessness and its relationship to ventilation has not been studied previously. We have examined the effects of a training programme on eight patients (5 males, 3 females, mean age 20 years, range 17-27 years) with cystic fibrosis. Eleven minutes of exercise was undertaken each day for 2 months according to the Royal Canadian Air Force protocol. Daily diary cards were kept and the programme was supervised. Pulmonary function and responses to maximal exercise on bicycle ergometer were determined before and after completion of the training schedule. Breathlessness was assessed using visual analogue scales (VAS) and related to ventilation during submaximal exercise on two occasions prior to training, and at the end. Apart from a reduced RV (pre 1.90 +/- 1.11, post 1.20 +/- 0.28 P less than 0.05), all other indices of pulmonary function and exercise performance were unchanged. Before training the relationship of breathlessness to ventilation was highly reproducible for each patient. After training there was a statistically significant reduction in breathlessness but ventilation was unchanged. At a mean standardized ventilation of 31.6 litres/min the VAS scales were 26.7% pre- and 12.9% post-training (P less than 0.01). Breathlessness can be favourably influenced by exercise training independent of ventilation with a consequent improvement in submaximal exercise tolerance in patients with cystic fibrosis.

Iron deficiency and behavioral deficits

In an attempt to investigate the relationship of iron deficiency and mental status, cognitive development and attending behavior were assessed in nonanemic children aged 11 to 13 months who were severely or mildly iron deficient or were iron replete. Using two different approaches to the assessment of cognitive development and an habituation measure as an index of attending behavior, no statistically significant differences could be demonstrated in the overall level of performance between the iron-depleted and the iron-replete children. Isolated differences were demonstrated on a scale that measured fearfulness and on several of the scales that measured sensory areas of interest displayed.