RADIATION DOSE FROM DENTAL RADIOGRAPHY IN INDONESIA: A FIVE-YEAR SURVEY

Dose metrics on intraoral and panoramic dental radiography were analyzed to preliminarily indicate dose trend of dental radiology equipment in Indonesia. Measurements were performed in 71 healthcare institutions involving a total of 92 dental X-ray devices. Imaging modes are categorized into 'low dose' and 'high dose' based on the task. The 75th percentile for intraoral IAK was 2.8 and 4.3 mGy for 'low' and 'high' dose modes, respectively while for panoramic devices the 75th percentile of the KAP for 'low' and 'high' dose modes were 85.2 and 192.4 mGy cm2, respectively. Results compared with local regulatory recommendation for intraoral units indicated that 38.8 and 6.3% of measured dose modes on analogue and digital devices, respectively, were above the recommended range. The dose trend can be used as reference for local regulations concerning patient dose in dental radiography and preliminary value prior to the establishment of national diagnostic reference level.

Targeting inflammatory monocytes in sepsis-associated encephalopathy and long-term cognitive impairment

Sepsis-associated encephalopathy manifesting as delirium is a common problem in critical care medicine. In this study, patients that had delirium due to sepsis had significant cognitive impairments at 12-18 months after hospital discharge when compared with controls and Cambridge Neuropsychological Automated Test Battery-standardized scores in spatial recognition memory, pattern recognition memory, and delayed-matching-to-sample tests but not other cognitive functions. A mouse model of S. pneumoniae pneumonia-induced sepsis, which modeled numerous aspects of the human sepsis-associated multiorgan dysfunction, including encephalopathy, also revealed similar deficits in spatial memory but not new task learning. Both humans and mice had large increases in chemokines for myeloid cell recruitment. Intravital imaging of the brains of septic mice revealed increased neutrophil and CCR2+ inflammatory monocyte recruitment (the latter being far more robust), accompanied by subtle microglial activation. Prevention of CCR2+ inflammatory monocyte recruitment, but not neutrophil recruitment, reduced microglial activation and other signs of neuroinflammation and prevented all signs of cognitive impairment after infection. Therefore, therapeutically targeting CCR2+ inflammatory monocytes at the time of sepsis may provide a novel neuroprotective clinical intervention to prevent the development of persistent cognitive impairments.

Revisiting the cholinergic hypothesis in the development of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia affecting the elderly population today; however, there is currently no accurate description of the etiology of this devastating disorder. No single factor has been demonstrated as being causative; however, an alternative co-factors theory suggests that the interaction of multiple risk factors is responsible for AD. We have used this model, in combination with the original cholinergic hypothesis of AD to propose a "new" cholinergic hypothesis that we present in this review. This new version takes into account recent findings from the literature and our reports of removal of medial septum cholinergic projections to the hippocampus reduces both behavioural and anatomical plasticity, resulting in greater cognitive impairment in response to secondary insults (stress, injury, disease, etc.). We will first summarize the experimental results and discuss some potential mechanisms that could explain our results. We will then present our 'new' version of the cholinergic hypothesis and how it relates to the field of AD research today. Finally we will discuss some of the implications for treatment that arise from this model and present directions for future study.

The etiology of age-related dementia is more complicated than we think

Alzheimer's disease (AD) is the most common form of age-related dementia (ARD). Most research directed at understanding the causes of AD is focused on the genetic-based pathology associated with the familial form of this disorder. This is important work and significant progress has been made but 85% of all AD patients have the sporadic form of the disorder. This means that a complete understanding of these complex disorders will remain elusive unless alternative approaches are developed. In this paper we want to make two main points. First, we argue that the current diagnostic distinctions between AD and ARD do not accurately reflect the heterogeneity of these disorders. Second, we present an approach to understanding the etiology of these disorders by suggesting that multiple combinations of co-factors produce variants of the sporadic form of AD. Various proof of principle experiments are presented and the mechanistic and treatment implications of this view are discussed.

Enhanced cell death and learning deficits after a mini-stroke in aged hippocampus

One view of the etiology of age-related pathology is that a single genetic abnormality or some other single factor causes the disorder. An alternative view is that multiple combinations of factors produce variants of pathology. For example, the occurrence of stroke increases with age and has been linked to neurodegenerative disorders like Alzheimer's disease (AD). The current experiments test the hypothesis that a vascular insult and aging are co-factors that contribute to dementia by evaluating the neuronal and functional integrity of the hippocampus following small, localized strokes induced by the potent vasoconstrictor, endothelin-1 (ET-1) in the rat model of hippocampal aging. The neurotoxic effects of a low dose of ET-1 injected into the hippocampus measured by lesion size (volumetrics) and cell death (Fluorojade-B) were amplified in aged rats. The aged rats also showed hippocampal-dependent memory deficits that were not present in young rats. Overall, our pattern of results suggest that the aged hippocampus is more vulnerable to the same insult that has little or no effect on the young hippocampus.

NMDA-receptor blockade by CPP impairs post-training consolidation of a rapidly acquired spatial representation in rat hippocampus

Recent evidence suggests that N-methyl-D-aspartate (NMDA)-receptor mediated plasticity in hippocampus has a more subtle role in memory-based behaviours than originally thought. One idea is that NMDA-based plasticity is essential for the consolidation of post-training memory but not for the initial encoding or for short-term memory. To further test this idea we used a three-phase variant of the hidden goal water maze task. In the first phase, rats were pre-trained to an initial location. Next, intense, massed training was done in a 2-h interval to teach the rats to go to a new location after either an injection of the NMDA receptor antagonist (6)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) or of vehicle. Finally, under drug-free conditions 24 h after new location training, a competition test was done between the original and new locations. We find that N-methyl-D-aspartate (NMDA)-receptor blockade has little or no effect on new location training. In contrast, when tested 24 h later, the strength of the trace for the new location learned during NMDA-receptor blockade was much weaker compared with the trace for the new location learned after saline injection. Further experiments showed similar effects when NMDA-receptors were blocked immediately after the new location training, suggesting that this is a memory consolidation effect. Our results therefore reinforce the notion that hippocampal NMDA-receptors participate in post-training memory consolidation but are not essential for the processes necessary to learn or retain navigational information in the short term.