Photodynamic antibacterial effect of graphene quantum dots

Synthesis of new antibacterial agents is becoming increasingly important in light of the emerging antibiotic resistance. In the present study we report that electrochemically produced graphene quantum dots (GQD), a new class of carbon nanoparticles, generate reactive oxygen species when photoexcited (470 nm, 1 W), and kill two strains of pathogenic bacteria, methicillin-resistant Staphylococcus aureus and Escherichia coli. Bacterial killing was demonstrated by the reduction in number of bacterial colonies in a standard plate count method, the increase in propidium iodide uptake confirming the cell membrane damage, as well as by morphological defects visualized by atomic force microscopy. The induction of oxidative stress in bacteria exposed to photoexcited GQD was confirmed by staining with a redox-sensitive fluorochrome dihydrorhodamine 123. Neither GQD nor light exposure alone were able to cause oxidative stress and reduce the viability of bacteria. Importantly, mouse spleen cells were markedly less sensitive in the same experimental conditions, thus indicating a fairly selective antibacterial photodynamic action of GQD.     

HLA-A, -B, -C, -DRB1 and -DQB1 allele and haplotype frequencies in the Serbian population

This study provides the first published detailed analysis of five loci polymorphisms as well as reports of two, three and five loci haplotype frequencies in the Serbian population in a sample of 1992 volunteer bone marrow donors recruited from different part of the country. Typing was performed by PCR SSO method combined with PCR SSP techniques to resolve ambiguities. In total, 16 HLA-A, 28 HLA-B, 14 HLA-C, 13 HLA-DRB1 and 5 HLA-DQB1 allelic groups were identified. The most frequent in allele groups are HLA-A^∗02 (29.5%), HLA-A^∗01 (14.2%), HLA-B^∗35 (13.1%), HLA-B^∗51 (12.8%), HLA-C^∗07 (24.8%), HLA-DRB1^∗11 (16.9%), HLA-DRB1^∗13 (13.2%), HLA-DQB1^∗03 (33.3%) and DQB1^∗05 (33.0%). The most frequent three- and five-loci haplotypes were A^∗01-B^∗08-DRB1^∗03 (5.9%) and A^∗02-B^∗18-DRB1^∗11 (1.9%), A^∗01-B^∗08-C^∗07-DRB1^∗03-DQB1^∗02 (6.6%) followed by A^∗02-B^∗18-C^∗07-DRB1^∗11-DQB1^∗03 (2.5%), then A^∗33-B^∗14-C^∗08-DRB1^∗01-DQB1^∗05 and A^∗02-B^∗35-C^∗04-DRB1^∗16-DQB1^∗05 (2.2% both), respectively. The results of cluster analysis showed that the Serbian population is closely related to the populations living in central Balkan and neighboring European regions. The level of allelic diversity found in this study are relevant to facilitate searching for unrelated matched donor and provide a healthy control population from our region that should be useful in the future disease association study.     

Distribution of BMP6 in the alveolar bone during mouse mandibular molar eruption

Eruption requires synchrony of the tooth with the surrounding tissues, particularly the bone. One important step during eruption is remodelling of the alveolar bone at the base of the tooth and along the roots. Expression of BMP6 was reported to be increased in the basal half of the dental follicle prior to eruption and inhibition of BMP6 affected bone formation at the base of the alveolar crypt. The aim of this study was to further investigate BMP6 protein in relation to tooth eruption and the corresponding bone remodelling using temporospatial correlations of BMP6 localization with morphogenetic events (proliferation, differentiation, apoptosis and bone apposition/resorption), other BMPs (BMP2 and BMP7) and three-dimensional images of tooth–bone development. BMP6 expression pattern was mapped in the mandibular molar teeth and related structures around eruption. Localization of BMP6 dominated in osteoblasts, in regions of bone formation within the alveolar crypt. These findings positively correlated with proliferation at the tooth base region, osteocalcin expression in the osteoblasts/osteocytes and BMP2 and BMP7 presence in the alveolar bone surrounding the tooth. Osteoclast activity and apoptotic elimination in the root region gradually decreased before eruption and totally ceased at eruption stages. Generally, BMP6 positively correlated with BMP2, BMP7 and osteocalcin-positive osteoblasts, and areas of bone remodelling. Moreover, BMP6 was found in the periodontium and cementoblasts. BMP6 expression in the alveolar bone accompanied tooth eruption. Notably, the expression pattern of BMP6 in the bone did not differ around individual molar teeth at the same stage of development. The expression of BMP6 in periodontal ligaments may contribute to interaction between the tooth and bone during the eruption and anchoring process.     

Long lasting near-obstruction stenosis of mesencephalic aqueduct without development of hydrocephalus – case report

The aim of this study is to present the five-year longitudinal magnetic resonance imaging (MRI) follow up of a patient with incidental finding of near-obstruction stenosis of the aqueduct of Sylvius due to a large pineal cyst. The patient was scanned 3 times on a 3T MR device using a set of standard structural sequences supplemented with high-resolution constructive interference of steady state (CISS) T2 sequence for precise delineation of the aqueduct of Sylvius and cardiac-gated phase-contrast sequences for the analysis of cerebrospinal fluid (CSF) movement. On all MR scans, the size of the pineal cyst and severity of near-obstruction aqueductal stenosis did not show any morphological changes. There was no significant ventricular enlargement although structural CISS sequence showed a near-obstruction stenosis and cardiac-gated phase-contrast sequences did not detect CSF movement through the aqueduct of Sylvius. Our findings are contradictory to the classic hypothesis of CSF physiology based on secretion, circulation, and absorption of CSF, which states that the impairment of CSF circulation through the aqueduct of Sylvius inevitably leads to a hypertensive hydrocephalus development involving the third and the lateral ventricle. Our research group previously proposed a new hypothesis of CSF physiology, which offers more suitable explanation for such clinical cases.Clinical practice has shown that an aqueduct of Sylvius obstruction or severe stenosis (tumoral compression, intrinsic non-tumoral pathology) could lead to a development of the triventricular hypertensive hydrocephalus (1). According to the classic hypothesis of CSF physiology, CSF is secreted inside the brain ventricles and flows unidirectionally along the subarachnoid space to be absorbed into the dural venous sinuses or into perineural lymphatic system (2,3). Therefore, a blockade of CSF flow from the third to the fourth lateral ventricle at the aqueduct of Sylvius level inevitably leads to the triventricular hypertensive hydrocephalus development. It is assumed that CSF is formed by an active secretion mainly by the choroid plexuses against hydrostatic pressure inside the CSF system, so any blockade between the site of secretion and the site of absorption will lead to CSF accumulation, CSF system enlargement, and subsequently to the development of hydrocephalus proximal to the obstruction site (1).The aqueduct of Sylvius is a narrow canal inside the mesencephalon that connects the third and the fourth lateral ventricle, thus, according to the classic hypothesis, its passability is of key importance for normal CSF physiology (2,3). An aqueduct of Sylvius stenosis sometimes leads to the compensatory changes of the CSF system that are known as “arrested hydrocephalus” (4). The compensatory mechanisms of this state are still unclear. We present a patient with long lasting near-obstruction stenosis without detectable CSF movement through the aqueduct of Sylvius, which has some similarities with the “arrested hydrocephalus” condition. Despite the functional blockade of CSF movement, no significant ventricular enlargement was observed during the follow up period of 5 years. Such findings are contradictory to the classic hypothesis of CSF hydrodynamics and classic circulatory hypothesis of hydrocephalus development. However, the new hypothesis of CSF physiology proposed by our team (Bulat, Orešković and Klarica hypothesis) (5-7) states that stenosis/blockade of aqueduct of Sylvius could favor but does not necessarily lead to the development of hydrocephalus (6,8). In this case report, we discuss pathophysiological mechanisms of hydrocephalus development from the perspective of both classic and new microcirculatory hypothesis of CSF physiology (5-7).     

The Level of Anxiety and Pain Perception of Endodontic Patients

Objectives

to compare the level of anxiety reported by patients and assessed by dentists. Also, the expected and actual pain during the treatment perceived by the patient and dentist were assessed.

Methods

sixty six endodontic patients filled in two questionnaires, prior to and after the treatment, so did their therapists. The first set of questions for patients was regarding demographics, the frequency of dental visits, the level of anxiety and expectations about the level of pain. Before the treatment, dentists estimated the level of patients'' anxiety and the expected intensity of pain. After the treatment, the patients evaluated the level of experienced pain and dentists'' empathy during the treatment, while dentists reassessed the intensity of patients'' pain.The data were statistically analysed by t-test for paired samples and by Spearmans''s Rho correlation coefficient at level of significance set at 0.05.

Results

Patients'' expectation of pain intensity was higher than the actual pain during the treatment (t-test=3.540, p=0.001). There was no difference in the level of pain which dentists expected and their perception of pain during the procedure. There was a statistically significant correlation between the patients'' level of anxiety and recognition of it by dentists (Spearman Rho=0.460, p<0.001). A higher level of anxiety increased the expected intensity of pain (Spearman Rho=0.401, p=0.001). Actual intensity of pain was not significantly associated with dental anxiety (Spearman Rho=0.080, p=0.524).

Conclusion

Since the level of dental anxiety was associated with the increased intensity of expected pain, a vicious cycle of pain and anxiety may be terminated by giving positive information to the patient before and during endodontic procedures.     

Qualitative and quantitative evaluation of human dental enamel after bracket debonding: a noncontact three-dimensional optical profilometry analysis

Objectives

The aim of this study was to undertake a qualitative and quantitative evaluation of changes on enamel surfaces after debonding of brackets followed by finishing procedures, using a high-resolution three-dimensional optical profiler and to investigate the accuracy of the technique.

Materials and methods

The labial surfaces of 36 extracted upper central incisors were examined. Before bonding, the enamel surfaces were subjected to profilometry, recording four amplitude parameters. Brackets were then bonded using two types of light-cured orthodontic adhesive: composite resin and resin-modified glass ionomer cement. Finishing was performed by three different methods: pumice on a rubber cup, fine and ultrafine aluminum oxide discs, and microfine diamond cups followed by silicon carbide brushes. The samples were subsequently re-analyzed by profilometry.

Results

Wilcoxon signed-rank test, Kruskal–Wallis test (p?U test with Bonferroni correction (p?Conclusions The 3D optical profilometry technique was able to provide accurate qualitative and quantitative assessment of changes on the enamel surface after debonding.

Clinical relevance

Morphological changes in the topography of dental surfaces, especially if related to enamel loss and roughness, are of considerable clinical importance. The quantitative evaluation method used herein enables a more comprehensive understanding of the effects of orthodontic bonding on teeth.     

Pavement Texture–Friction Relationship Establishment via Image Analysis Methods

Pavement surface texture is one of the prevailing factors for friction realization on pavement surfaces. In this paper, an overview of pavement texture properties related to the pavement frictional response is given. Image analysis methods used for pavement texture characterization are thoroughly analyzed together with their potential for the establishment of a pavement texture–friction relationship. Digital pavement surface models derived from photogrammetry or laser scanning methods enable the extraction of texture parameters comparable to the ones acquired by common pavement surface measuring techniques. This paper shows the results of a preliminary small-scale research study of the pavement texture–friction relationship. This research was performed in a laboratory which produced asphalt samples, primarily to analyze the potential of developing a methodology for the digital pavement texture model setup. Furthermore, the relationship between selected 2D texture parameters calculated from the digital texture model and measured friction coefficient expressed as SRT value was analyzed. A significant correlation was established for standard texture indicator mean profile depth (MPD) and SRT values (R = 0.81). Other texture parameters showed moderate correlation with the frictional response of the surface, with absolute values of correlation coefficients varying from 0.7 to 0.75. A further analysis of this relationship will be performed by inclusion of other texture parameters that can be determined from the digital texture model acquired by the established methodology.     

Vemurafenib and cobimetinib‐induced toxic epidermal necrolysis in a patient with metastatic melanoma

Combination therapy in the treatment of metastatic melanoma has been associated with more durable response rate compared to monotherapy. However, previous studies have shown that combined target therapy commonly causes a wide spectrum of adverse events. These adverse reactions are usually manageable, however, it is always necessary to compare drug efficacy with its potential adverse effects. Toxic epidermal necrolysis represents severe mucocutaneous reaction, usually triggered by medications and characterized by extensive necrosis and detachment of the epidermis. Here we present a first case of toxic epidermal necrolysis induced by combined target therapy (vemurafenib plus cobimetinib). The case was observed in a young patient with BRAF mutant melanoma who was started on first‐line metastatic immunotherapy with pembrolisumab.