Is L-Glutamate Toxic to Neurons and Thereby Contributes to Neuronal Loss and Neurodegeneration? A Systematic Review.

L-glutamate (L-Glu) is a nonessential amino acid, but an extensively utilised excitatory neurotransmitter with critical roles in normal brain function. Aberrant accumulation of L-Glu has been linked to neurotoxicity and neurodegeneration. To investigate this further, we systematically reviewed the literature to evaluate the effects of L-Glu on neuronal viability linked to the pathogenesis and/or progression of neurodegenerative diseases (NDDs). A search in PubMed, Medline, Embase, and Web of Science Core Collection was conducted to retrieve studies that investigated an association between L-Glu and pathology for five NDDs: Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). Together, 4060 studies were identified, of which 71 met eligibility criteria. Despite several inadequacies, including small sample size, employment of supraphysiological concentrations, and a range of administration routes, it was concluded that exposure to L-Glu in vitro or in vivo has multiple pathogenic mechanisms that influence neuronal viability. These mechanisms include oxidative stress, reduced antioxidant defence, neuroinflammation, altered neurotransmitter levels, protein accumulations, excitotoxicity, mitochondrial dysfunction, intracellular calcium level changes, and effects on neuronal histology, cognitive function, and animal behaviour. This implies that clinical and epidemiological studies are required to assess the potential neuronal harm arising from excessive intake of exogenous L-Glu.

A Descriptive Analysis of Clinical Articles Published in the Last 50 Years in the Dental Literature.

AIMS: This article describes the methodologies used in the dental literature and described how these approaches have changed over time. MATERIALS AND METHODS: Thirty-three ISI peer-reviewed journals were included in the analyses. Data were extracted independently by 11 investigators and in duplicate. Any differences in the results were resolved via discussion or by a third reviewer when necessary. Data were collected regarding the methodology used in the article, and dental specialty related to different study designs. In the case in which more than one study design or specialty was reported, reviewers were trained to identify the main methodology/specialty. RESULTS: The majority (36.96%) used a case report (CR) as the primary methodology, followed by a clinical trial (CT) (18.21%) or randomized CT (15.11%). The least used methodologies included a cohort (COH) study (6.07%) or a systematic review (SA)/meta-analysis (MA) (6.73%). Periodontology published the highest number of case controls (CCs) (46.8%), randomized CTs (RCTs) (29.9%), cross-sectional (CS) studies (26.0%), SRs/MAs (19.8%), and CTs (17.1%). Oral and maxillofacial surgery published the highest number of CRs/case series (54.5%) and COH studies (30.5%), whereas operative dentistry published the lowest number of CRs/case series (0.7%), CCs (2.9%), and SRs/MAs (2.3%). CRs/case series retain the highest number of publications across all time points in the dental literature overall. CONCLUSION: Our results indicate an improvement in the types of research and the pyramid of evidence, which will help in applying evidence-based dentistry (EBD) in clinical decision-making. CLINICAL SIGNIFICANCE: Types of studies used in the dental field are not yet investigated. Thus, little is known about the common study design types in dental literature. This can affect the decision made regarding technique, risk factors, prevention, or treatment.

First insight into the population structure of Mycobacterium tuberculosis in Saudi Arabia.

This study constitutes a first attempt to describe the genetic population structure and drug resistance of the tubercle bacilli circulating in Saudi Arabia. A total of 1,505 clinical isolates of M. tuberculosis, isolated between 2002 and 2005 from seven regions of Saudi Arabia, were studied. The sample studied showed a male-to-female sex ratio of 1.27, with half of the cases among foreign-born individuals and 47% within the 21- to 40-year-old age group; a total resistance rate of 19.7%; and multiple drug resistance of 4.5%. Upon spoligotyping, a total of 387 individual patterns were obtained (clustering rate, 86.4%; 182 clusters containing between 2 and 130 isolates per cluster). A total of 94% of the strains matched the spoligotype patterns in an international database. Nearly 81% of the isolates in this study belonged to established phylogeographic clades: Central Asian (CAS), 22.5%; ill-defined T clade, 19.5%; East African-Indian (EAI), 13.5%; Haarlem, 7.5%; Latin American-Mediterranean, 7.2%; Beijing, 4.4%; Manu, 2.7%; X, 0.9%; and Bovis, 0.9%. Two clonal complexes with unique spoligotyping signatures (octal codes 703777707770371 and 467777377413771) specific to Saudi Arabia were identified. These belonged to the CAS and EAI clades, respectively, as confirmed upon secondary typing using mycobacterial interspersed repetitive units (MIRUs). The results obtained underline the predominance of historic clones of principal genetic group 1, which are responsible for roughly 45% of all tuberculosis cases in Saudi Arabia. The high rate of clustering observed might be an indication of rapid ongoing transmission within certain communities and/or subpopulations in Saudi Arabia; nonetheless, spoligotyping is known to overestimate clustering, and only a systematic second-line typing, such as MIRUs, coupled with a better tuberculosis registry and epidemiological investigations would allow us to know the exact rate of ongoing transmission and associated risk factors in Saudi Arabia.