Synthesis, characterization and differentiation of the structural isomers of valine and tert-leucine derived synthetic cannabinoids

The identification of the synthetic cannabinoids receptor agonists (SCRAs) has always posed a great challenge to drug testing laboratories with slight structural modifications aimed at evading drug legislation. In addition, the most prevalent synthetic cannabinoids have valine and tert-leucine amino acid moieties where re-arrangement of the carbon chains can result in structural isomers that are very similar to the parent synthetic cannabinoids. This makes their analysis and identification challenging, and the problem is compounded with the difficulty in purchasing reference standards quickly and a lack of literature for comparison. Therefore, in this investigation, four series of synthetic cannabinoids (AB-PINACA, AB-CHMINACA, MMB-FUBINACA and 5-fluoro-MDMB-PINACA) and their alkyl chain structural isomers at the amino acid moieties were synthesized and characterized using various analytical techniques-gas chromatography-mass spectrometry (GC-MS), gas chromatography-infrared detection (GC-IRD) and nuclear magnetic resonance (NMR) spectroscopy to evaluate the ability of each analytical technique to differentiate the respective isomers for their identification. A total of 12 isomers were synthesized and analysed together with the four parent synthetic cannabinoids. NMR was able to differentiate between all the compounds, whereas GC-IRD was able to discern between most of the synthetic cannabinoids and their isomers. GC-MS had the least discriminating power and was not able to differentiate some of the compounds that has very similar mass spectra. The results from this work will be useful to other drug testing laboratories that are facing the identification of related synthetic cannabinoids.

Refractive errors in medical students in Singapore

INTRODUCTION

Refractive errors are becoming more of a problem in many societies, with prevalence rates of myopia in many Asian urban countries reaching epidemic proportions. This study aims to determine the prevalence rates of various refractive errors in Singapore medical students.

METHODS

157 second year medical students (aged 19-23 years) in Singapore were examined. Refractive error measurements were determined using a stand-alone autorefractor. Additional demographical data was obtained via questionnaires filled in by the students.

RESULTS

The prevalence rate of myopia in Singapore medical students was 89.8 percent (Spherical equivalence (SE) at least -0.50 D). Hyperopia was present in 1.3 percent (SE more than +0.50 D) of the participants and the overall astigmatism prevalence rate was 82.2 percent (Cylinder at least 0.50 D).

CONCLUSION

Prevalence rates of myopia and astigmatism in second year Singapore medical students are one of the highest in the world.

Post-laryngospasm pulmonary oedema in oral & maxillofacial surgery

Laryngospasm in oral & maxillofacial surgery may occur due to irritants in the form of surgical debris washed towards the oropharynx. In the two cases reported, pulmonary oedema ensued after the laryngospasm was relieved. The mechanism and causative factors of this phenomena is explained and preventive measures discussed. As the surgical area of the Oral & Maxillofacial (OMF) surgeons are closely related to that of the anaesthetist, it is imperative that OMF surgeons understand and recognize this condition.

Allelic variants of acidic proline-rich proteins observed in Japanese, Chinese, and Malays

Three new variants of acidic proline-rich proteins (At, Au, Aw) were found in human parotid saliva by isoelectric focusing and basic gel electrophoresis. Electrophoretic comparison of the purified proteins and their tryptic peptides suggested minor charge and size differences from other acidic PRPs. Genetic and biochemical studies indicate that the At and Aw proteins are allelic products of the PRH1 locus. Gene frequencies of the At productive allele (PRH1(6)) in Japanese, Chinese, and Malays were 0.008, 0.012, and 0.004, respectively. The Au protein was also found in Japanese (2 in 746 samples), Chinese (1 in 215 samples), and Malays (1 in 220 samples), however, the Aw protein was found only in one Japanese (n = 746). These three proteins were not found in 106 Indian subjects.

Salivary proline-rich protein polymorphisms in Chinese, Malays and Indians in Singapore

Salivary proline-rich protein (PRP) polymorphism, PRH1, PRH2, Ps, Pm (PmF), PmS and Gl, were investigated in three ethnic groups in Singapore: Chinese, Malays and Indians. The phenotype and gene frequencies were presented and comparison with other ethnic groups was made. The As protein, which was recently found in Japanese but not in Caucasians as a new allelic product of the PRH1 locus, was also observed in Chinese and Malays but not in Indians. Another allelic product (Ps4) of Ps protein polymorphism was found in Malays but not in Chinese and Indians. The results indicate the usefulness of salivary PRP polymorphism as markers in population genetic studies.

Government dental service in Singapore

The mission of the Singapore Government Dental Service is to prevent dental diseases and promote dental health, and to develop excellence in dentistry. The history and organisation of the Dental Service are recounted together with the development of the Hospital Dental Service, School Dental Service, Community Dental Service, Training Department and Dental Health Education. Information on the development of a new dental centre with the objective of achieving dental excellence is provided.

Dental caries status of children and youth in Singapore

Dental health surveys on Singapore children and youths are reviewed. The survey data showed that Singapore youths had a reduction in DMFT of approximately 55% from 1954 to 1968 while the 1979 survey results showed a small increase in DMFT when compared with 1968 data. In the case of school children the DMFT had dropped from 2.98 in 1970 and 2.61 in 1979 to 1.97 in 1984 for the whole group. The decline in caries incidence could be attributed to water fluoridation, the school dental health programme and dental health education.