Plasma tumor gene conversions after one cycle abiraterone acetate for metastatic castration-resistant prostate cancer: a biomarker analysis of a multicenter international trial.

BACKGROUND: Plasma tumor DNA fraction is prognostic in metastatic cancers. This could improve risk stratification before commencing a new treatment. We hypothesized that a second sample collected after one cycle of treatment could refine outcome prediction of patients identified as poor prognosis based on plasma DNA collected pre-treatment. PATIENTS AND METHODS: Plasma DNA [128 pre-treatment, 134 cycle 2 day 1 (C2D1), and 49 progression] from 151 chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC) patients in a phase II study of abiraterone acetate (NCT01867710) were subjected to custom targeted next-generation sequencing covering exons of these genes: TP53, AR, RB1, PTEN, PIK3CA, BRCA1, BRCA2, ATM, CDK12, CHEK2, FANCA HDAC2 and PALB2. We also captured 1500 pan-genome regions enriched for single nucleotide polymorphisms to allow detection of tumor DNA using the rolling B-allele method. We tested associations with overall survival (OS) and progression-free survival (PFS). RESULTS: Plasma tumor DNA detection was associated with shorter OS [hazard ratio (HR): 2.89, 95% confidence intervals (CI): 1.77-4.73, P ≤ 0.0001] and PFS (HR: 2.05; 95% CI: 1.36-3.11, P < 0.001). Using a multivariable model including plasma tumor DNA, patients who had a TP53, RB1 or PTEN gene alteration pre-treatment and at C2D1 had a significantly shorter OS than patients with no alteration at either time point (TP53: HR 7.13, 95% CI 2.37-21.47, P < 0.001; RB1: HR 6.24, 95% CI 1.97-19.73, P = 0.002; PTEN: HR 11.9, 95% CI 3.6-39.34, P < 0.001). Patients who were positive pre-treatment and converted to undetectable had no evidence of a difference in survival compared with those who were undetectable pre-treatment (P = 0.48, P = 0.43, P = 0.5, respectively). Progression samples harbored AR gain in all patients who had gain pre-treatment (9/49) and de novo AR somatic point mutations were detected in 8/49 patients. CONCLUSIONS: Plasma gene testing after one cycle treatment refines prognostication and could provide an early indication of treatment benefit.

PDGF-simvastatin delivery stimulates osteogenesis in heat-induced osteonecrosis.

Heat generated during implant osteotomy might lead to osteonecrosis and delayed bone repair, thus resulting in impaired early osseointegration and fixation of bone-anchoring devices. In this study, we proposed to overcome heat-induced injury to bone by fabricating core-shell polymeric biodegradable microspheres encapsulating a mitogenic factor, platelet-derived growth factor (PDGF), and a differentiation factor, simvastatin, in a simultaneous or sequential release profile. Microspheres encapsulating bovine serum albumin (BSA), PDGF, simvastatin, PDGF-in-core with simvastatin-in-shell, and simvastatin-in-core with PDGF-in-shell were delivered to fill standardized osteotomy sites on edentulous ridges of rat maxillae under irrigated or non-irrigated conditions. In the absence of irrigation, significant reduction of cell viability and increase in inflammation and sequestrum formation without evidence of osteogenesis were observed. Both PDGF and simvastatin deliveries facilitated cell viability and reduced osteonecrosis. Localized osteogenesis was seen under simvastatin treatment, while generalized but primitive osteogenesis was noted in PDGF-treated osteotomy sites. In addition, sequential PDGF-simvastatin delivery further augmented osteogenesis and promoted bone maturation. The results suggested that sequential PDGF-simvastatin delivery was an effective modality to prevent heat-induced complications and facilitate bone apposition after implant osteotomy, potentially favoring the early fixation of bone-anchoring devices and oral implant osseointegration.

Relationship between markers of metabolic control and inflammation on severity of periodontal disease in patients with diabetes mellitus.

AIM: The aim of this study was to investigate the relationship between markers of metabolic control and inflammation and periodontal disease parameters in patients with diabetes. MATERIAL & METHODS: One hundred and eighty one adult patients with diabetes attending treatment at two diabetes centres were invited to participate in the study. Periodontal examination included full-mouth assessment for probing depths and bleeding on probing (BOP). Blood analyses were carried out for glycated haemoglobin, (HbA1c), high-sensitivity C reactive protein, (hsCRP) and lipid profile comprising total cholesterol, low-density lipoprotein cholesterol (LDL chol), high-density lipoprotein cholesterol (HDL chol) and triglycerides. RESULTS: Upon multivariate analysis, periodontal disease severity in terms of increased percentage of BOP and mean percentage of sites with probing depths > or = 5 mm were found to be associated with inadequate glycaemic control as measured by HbA1c (p<0.01). HsCRP was also found to be a significant predictor for mean percentage of sites with probing depths > or = 5 mm (p<0.05). After controlling for age, gender, smoking habits and number of teeth, positive correlations were found between HbA1c and percentage sites with probing depths > or = 5 mm, percentage sites BOP, total cholesterol, LDL chol and triglycerides (p<0.05). Using the adjusted differences, subjects with acceptable glycaemic control (HbA1c < 8%) showed a lower percentage of sites with BOP and probing depths > or = 5 mm (p<0.05) when compared with those having inadequate glycaemic control. There was also a trend towards lower blood cholesterol in the well-controlled group. CONCLUSION: The level of glycaemic control as measured by HbA1c emerged as the most consistent risk factor associated with the extent and severity of periodontal disease in this study cohort.

Periodontal disease -- the emergence of a risk for systemic conditions: pre-term low birth weight.

This paper addresses the problem of adverse pregnancy outcome in relation to periodontal disease. There is compelling evidence that a link exists between pre-term low birth weight (PLBW) and periodontitis. Although 25% to 50% of PLBW deliveries occur without any known aetiology, there is increasing evidence that infection may play a significant role in pre-term delivery. A model explaining the plausible relationship is proposed based upon the concept of infection leading to a cascade of inflammatory reactions associated with pre-term labour and periodontal disease. Current evidence has pointed to an interest in dental intervention studies to control periodontal disease as one of the potential strategies to reduce pre-term labour. This paper reviews the potential association between periodontal infection and adverse pregnancy outcomes.

Stressful life events of dental students and salivary immunoglobulin A.

To study the perceived sources of stressful events in dental students and the relationship between their self-perceived stress levels and salivary IgA. Undergraduates as well as postgraduates at the Faculty of Dentistry, National University of Singapore were surveyed one month after the new term. A 38-item dental environmental stress (DES) questionnaire, with subscales of academic work (AW), clinical factors (CF), faculty and administration factors (FA) and personal factors (PF), was used to identify the potential stressors in the dental environment. A 4-point perceived stress scale was used to rank their self-perceived stress levels. Enzyme linked immunosorbent assay method was used to determine the salivary IgA level. One hundred and thirty students (81.3%--valid response rate) participated in the study. Overall, students ranked AW with the highest score (mean 2.76), followed by CF (2.67), FA (2.24) and PF (2.16). Among the 38 items of DES questionnaire, 1st year students perceived "fear of being unable to catch up if behind" as the most stressful event (mean 3.30). For 2nd and 3rd year students, examination and grades had the highest scores (mean 3.28, 3.19, respectively). Completing graduation requirements was the most important stressor for 4th year students (mean 3.89). Post graduates perceived atmosphere created by clinical faculty was most stressful to them (mean 3.05). The mean total perceived stress scores were highest (22.1) in 1st year students and lowest (21.0) in postgraduates, however, no significant different among various classes. First year students had had the lowest IgA secretion rates (geometric mean [GM] 46.8 microg/min), significantly lower (p<0.05) than postgraduates (GM 79.4 microg/min). An inverse correlation was noted between perceived stress scale and log IgA secretion rates (r= -0.20, p= 0.002). AW was also significantly inversely correlated with salivary IgA (r= -0.18, p= 0.04). Dental students in different academic years perceived different important stressors. Salivary IgA secretion rate correlated inversely with self perceived stress.

Paediatric extracranial germ cell tumours: a retrospective review.

INTRODUCTION: Germ cell tumours (GCTs) are rare, constituting 3% of all childhood malignancies. The aim of this study was to analyse the epidemiology and outcome of these patients. MATERIALS AND METHODS: A retrospective, cohort study was conducted on 38 paediatric patients presenting with extracranial GCTs, treated at the Singapore General Hospital, Tan Tock Seng Hospital and Kandang Kerbau Women's and Children's Hospital from 1 January 1989 to 30 June 1999. The median age at diagnosis was 1.7 years (0 to 13 years). RESULTS: There was no sex or racial preponderance. Eighteen patients (47.3%) had teratomas, 16 (42.1%) had yolk sac tumours, 1 (2.6%) had dysgerminoma and 3 (7.9%) had mixed GCTs. Thirty-four patients (89.5%) had Stage I disease, 1 (2.6%) had Stage II disease, 1 (2.6%) had Stage III disease and 2 (5.3%) had metastatic disease. Complete tumour resection was achieved in 36 of the 38 patients (95%). Cisplatin-based combination chemotherapy was given to 11 patients (28.9%). None of the patients received radiotherapy. Complications from chemotherapy included anaemia requiring packed red cell transfusion (n = 3), Port-a-cath sepsis requiring removal (n = 1), febrile neutropenia (n = 1) and nephropathy (n = 1). CONCLUSION: Using the Kaplan-Meier life tables, the overall and event-free survivals at 10 years for the patients with malignant GCTs were 96% and 88%, respectively, with a mean follow-up period of 5.1 years (0.7 to 10 years). The majority of the patients presented with early Stage I disease and this contributed to our high survival rate.

An abundant class of tiny RNAs with probable regulatory roles in Caenorhabditis elegans.

Two small temporal RNAs (stRNAs), lin-4 and let-7, control developmental timing in Caenorhabditis elegans. We find that these two regulatory RNAs are members of a large class of 21- to 24-nucleotide noncoding RNAs, called microRNAs (miRNAs). We report on 55 previously unknown miRNAs in C. elegans. The miRNAs have diverse expression patterns during development: a let-7 paralog is temporally coexpressed with let-7; miRNAs encoded in a single genomic cluster are coexpressed during embryogenesis; and still other miRNAs are expressed constitutively throughout development. Potential orthologs of several of these miRNA genes were identified in Drosophila and human genomes. The abundance of these tiny RNAs, their expression patterns, and their evolutionary conservation imply that, as a class, miRNAs have broad regulatory functions in animals.

A computational analysis of sequence features involved in recognition of short introns.

Splicing of short introns by the nuclear pre-mRNA splicing machinery is thought to proceed via an "intron definition" mechanism, in which the 5' and 3' splice sites (5'ss, 3'ss, respectively) are initially recognized and paired across the intron. Here, we describe a computational analysis of sequence features involved in recognition of short introns by using available transcript data from five eukaryotes with complete or nearly complete genomic sequences. The information content of five different transcript features was measured by using methods from information theory, and Monte Carlo simulations were used to determine the amount of information required for accurate recognition of short introns in each organism. We conclude: (i) that short introns in Drosophila melanogaster and Caenorhabditis elegans contain essentially all of the information for their recognition by the splicing machinery, and computer programs that simulate splicing specificity can predict the exact boundaries of approximately 95% of short introns in both organisms; (ii) that in yeast, the 5'ss, branch signal, and 3'ss can accurately identify intron locations but do not precisely determine the location of 3' cleavage in every intron; and (iii) that the 5'ss, branch signal, and 3'ss are not sufficient to accurately identify short introns in plant and human transcripts, but that specific subsets of candidate intronic enhancer motifs can be identified in both human and Arabidopsis that contribute dramatically to the accuracy of splicing simulators.

Dental trauma management awareness of Singapore pre-school teachers.

The purpose of this study was to assess the awareness of pre-school teachers concerning the management of traumatized teeth. A questionnaire survey of teachers' backgrounds, attitudes/practices and knowledge was distributed to all teachers who attended a dental education program organized by the Singapore Dental Health Foundation. Of a total of 291 teachers surveyed, 29% had received tertiary education, while the rest (71%) had received secondary education. The mean teaching experience was 6.8 +/- 6.9 years. About a quarter had previous experience in handling dental trauma. Sixty-three percent admitted having no knowledge of dental trauma; 79% were unsatisfied with their level of knowledge in this area; 95% were keen to have further education in dental trauma; 65% thought dental trauma emergency should be dealt with as soon as possible. Concerning knowledge, during-office hour emergency services were more familiar (84%) than after-office hour emergency services (15%), as was the concept of management of avulsed teeth (71%) compared to that of fractured teeth (51%). Knowledge about optimal storage media for avulsed permanent teeth was especially poor--being as low as 15%. Using multiple logistic regression analysis, it was found that teaching experience significantly influenced the respondents' self-assessed knowledge and their level of satisfaction with their knowledge (P = 0.012). Teachers with more teaching experience had better knowledge about the replantation of permanent teeth (P = 0.003). It is recommended that public education targeted at teachers should be carried out to increase dental trauma management awareness.

Computational inference of homologous gene structures in the human genome.

With the human genome sequence approaching completion, a major challenge is to identify the locations and encoded protein sequences of all human genes. To address this problem we have developed a new gene identification algorithm, GenomeScan, which combines exon-intron and splice signal models with similarity to known protein sequences in an integrated model. Extensive testing shows that GenomeScan can accurately identify the exon-intron structures of genes in finished or draft human genome sequence with a low rate of false-positives. Application of GenomeScan to 2.7 billion bases of human genomic DNA identified at least 20,000-25,000 human genes out of an estimated 30,000-40,000 present in the genome. The results show an accurate and efficient automated approach for identifying genes in higher eukaryotic genomes and provide a first-level annotation of the draft human genome.

Survey of dental fees charged by dentists in Singapore.

A survey on dental fees was conducted among all private dental clinics registered with the Medical Audit and Accreditation Unit of the Ministry of Health in Singapore. Replies were received from 74 dental clinics. Analysis of results showed that there was a general increase in the median of fees charged in 1998 compared to the fees listed in the Minimum Fee Schedule issued by the Singapore Dental Association in 1994. 93% of the respondents indicated that there is a need to revise the Minimum Fee Schedule.

Patient and parental awareness of the importance of immediate management of traumatised teeth.

The purpose of this study was to assess patient and parental awareness of the importance of immediate management of traumatised teeth. A three-part questionnaire comprising questions on demographic data, attitude and knowledge was distributed to patients or accompanying parents who presented to the principal author for treatment in an 8-week period. One hundred and fifty-seven respondents with a mean age of 31.1 years participated in the study. Only 30% of the respondents recalled having had previous experience of dental trauma. The majority of the respondents, especially those with a higher educational background, had a positive attitude, expressing enthusiasm for public education on emergency management of dental trauma (85%). The availability of an emergency service during office hours was known by 71% of the respondents while only 26% were aware of the after-office-hour emergency service. Participants generally had a better concept of management of avulsed teeth (63%) compared to that of fractured teeth (35%). Knowledge on some critical aspects of the handling of avulsed teeth was poor (6%). Using multiple logistic regression analysis, it was found that the respondents' attitude tended to be influenced by their educational background (P = 0.08). In addition, subjects with higher education were more knowledgeable regarding the emergency service available during office hours (P = 0.05) and the concept of management of fractured teeth (P = 0.02). Educational background appeared to influence the level of awareness of the importance of immediate management of traumatised teeth.

Challenges and relevance of problem-based learning in dental education.

The rôle of PBL as an innovative approach in medical education has been well documented. There has been an emerging trend of incorporating PBL into the dental curriculum. The potential advantages of PBL as a mode of learning encompass the enhancement of an integrated approach in solving dental-treatment-related problems, the development of critical thinking and problem solving skills and the encouragement of independent life-long learning. PBL was introduced into the dental curriculum as a pilot project in the Faculty of Dentistry, National University of Singapore in summer 1996. An example of a case-based study was illustrated and the learning objectives of the study were highlighted. Initial feedback from students indicated a positive attitude to this mode of learning in terms of cognitive, affective and psychomotor skills. Strategies to enhance learning in the PBL environment include time allocation for self-study, availability of resource materials and use of appropriate assessment methods. Problems that remain to be resolved include the choice of appropriate outcome assessment measures to evaluate the effectiveness of PBL as a mode of learning in undergraduate dental education.

Alternative splicing of the fibronectin EIIIB exon depends on specific TGCATG repeats.

The fibronectin EIIIB exon is alternatively spliced in a cell-type-specific manner, and TGCATG repeats in the intron downstream of EIIIB have been implicated in this regulation. Analysis of the intron sequence from several vertebrates shows that the pattern of repeats in the 3' half of the intron is evolutionarily conserved. Point mutations in certain highly conserved repeats greatly reduce EIIIB inclusion, suggesting that a multicomponent complex may recognize the repeats. Expression of the SR protein SRp40, SRp20, or ASF/SF2 stimulates EIIIB inclusion. Studies of the interplay between mutations in the repeats and SRp40-stimulated inclusion suggest that the repeats are recognized in many, if not all, cell types, and that EIIIB inclusion may be regulated by quantitative changes in multiple factors.

Comparison of modes of oral hygiene instruction in improving gingival health.

195 Hong Kong Chinese employees from a single company participated in a 10-month longitudinal study on the effects of various modes of delivery of oral hygiene messages on their gingival health. Subjects were allocated to one of the following modes of oral hygiene education: (1) personal instruction; (2) self-education manual; (3) video; (4) a combination of 2 or more of these modes of instruction. Scaling or any other form of periodontal treatment was not given throughout the study period. Full mouth clinical examinations were carried out using a Williams Periodontal probe to examine for the presence or absence of plaque and bleeding on probing from the gingival sulcus. At 2 weeks, 4 months and 10 months, results showed significant reductions in the mean % of plaque and bleeding when compared with baseline. No significant differences were found between the groups given the various modes of oral hygiene education. The study does confirm the effectiveness of oral hygiene alone in improving gingival health, but the lack of difference in the outcome of various oral hygiene education approaches indicates that the mode of instruction is not crucially important to the end result. However, it has to be acknowledged that improvement in oral hygiene may be related to factors other than the oral hygiene programme itself. The findings have significant implications in oral health promotion programmes to improve the periodontal status of the local community.

Comparison of various modalities of "simple" periodontal therapy on oral cleanliness and bleeding.

550 Chinese employees of both sexes aged 25-44 from an industrial organisation participated in a 16-month longitudinal study. Subjects were divided into 4 groups: an oral hygiene group (group A), a scaling group (group B), an oral hygiene + scaling group (group C) and a control (group D). The experimental subjects were examined at baseline, 2 weeks, 4 months, 10 months and 16 months. After 10 months, group A received scaling while group B was given oral hygiene instruction for the 1st time. The control group did not receive any treatment until completion of the programme. At 16 months, all 3 experimental groups had significantly lower plaque and bleeding scores than the control. The plaque and bleeding levels of the experimental groups were lower at all review appointments when compared with baseline. Some variations in the clinical parameters were found between groups at 2 weeks, 4 months and 10 months. The scaling + oral hygiene group showed the best response. Although a proportion of subjects showed a substantial improvement in bleeding scores following scaling, the significant resource implications in providing such treatment has to be considered in planning community health programmes to promote periodontal health, wherein oral hygiene education must still have the highest priority.