Effects of Local Melatonin Application on Implant Osseointegration

Purpose: The aim of this study was to assess the effect of local melatonin administration on bone osseointegration around implants in rabbit tibiae. Material and Methods: Ten female, 6‐month‐old New Zealand rabbits were randomly divided into two groups: the experimental group, where five rabbits were treated with local application of melatonin (3 mg) to implant sites when placed into the rabbit tibia, and the control group, those who where without additive materials. Four weeks later, animals were sacrificed; tibiae were dissected from soft tissues and fixed in buffered formaldehyde, and then included in methacrylate. Histological sections were performed to be studied under light microscopy and analyzed morphometrically to evaluate the amount of bone to implant contact (BIC), trabecular area density, and cortical area density. One‐way analysis of variance test was used for statistical evaluation. p < .05 was considered to be significant. Results: Histological evaluation showed more trabecular reaction in the melatonin group. Morphometrical analysis showed a statistically significant increase in trabecular BIC in the melatonin group when compared with the control group (24.61% ± 2.87 vs 13.62% ± 1.44; p < .01). Cortical BIC was decreased in the melatonin group, without statistical significance (71.08 ± 3.63 vs 76.28 ± 2.57; p = 0.31). Trabecular area density was increased significantly in the melatonin group (8.68 ± 1.61 vs 4.02 ± 0.36; p < .05). Cortical area density was decreased significantly in the melatonin group (91.31 ± 1.6 vs 95.7 ± 0.5; p < .05). Conclusion: Within the limitation of this animal study, local melatonin application at the time of implant placement might induce more trabecular bone at implant contact and higher trabecular area density.     

过敏性哮喘患者外周血CD4+T细胞中miR-155的表达及临床意义

目的:探讨过敏性哮喘患者外周血CD4+T细胞中miR-155及其前体基因BIC的表达及临床意义.方法:应用实时荧光定量聚合酶链反应检测不同严重程度哮喘患者50例及健康对照20例外周血CD4+T细胞中BIC及miR-155的表达水平,并且与哮喘患者临床指标进行相关性分析;运用过表达或抑制,探讨miR-155在CD4+T细胞体外分化中的作用.结果:哮喘患者组BIC及miR-155的表达较对照组显著降低(P＜0.01),中、重度哮喘患者的BIC表达均低于对照组(P＜0.05),轻、中、重度哮喘患者的miR-155表达显著低于对照组(P＜0.01);组间比较发现,轻、中、重度哮喘患者的BIC表达无统计学意义,而重度哮喘患者miR-155的表达较轻度哮喘组有明显下降(P ＜0.05);miR-155的表达与用力呼气第1秒量之间呈正相关(P＜0.01);miR-155过表达促进CD4+T细胞向Th1分化,而抑制miR-155的表达则促进CD4+T细胞向Th2分化.结论:过敏性哮喘患者外周血CD4+T细胞中miR-155表达下调,其表达水平与哮喘严重程度相关,提示miR-155调控CD4+T细胞分化在哮喘中发挥重要作用.     

Laminar analysis of initiation and spread of epileptiform discharges in three in vitro models

Overexcitation of neuronal networks in some forebrain structures and pathological synchronization of neuronal activity play crucial role in epileptic seizures. Seizure activity can be elicited experimentally by different convulsants. Because of various distribution of excitatory and inhibitory connections in the neocortex there might be laminar differences in seizure sensitivity. Current source density (CSD) analysis or immunocytochemical c-Fos localization offer suitable tools to localize increased activation of neurons during seizure. In the present experiments, interictal epileptiform activity elicited by 4-aminopiridine, bicuculline or Mg(2+)-free solution was recorded with a 16-channel multielectrode assembly in different layers of the somatosensory cortex, and CSDs were calculated. Parallel c-Fos immunocytochemistry was applied. Each convulsant elicited characteristic activation pattern. 4-aminopiridine induced relatively short discharges, which were associated with a huge sink in layer V, the sink and source pattern was relatively simple. Mg(2+)-free solution elicited the longest discharges, sinks appeared typically in the supragranular layers II and III than quickly distributed toward layers V and VI. Bicuculline induced rather similar seizure pattern as Mg(2+)-free solution, but the amplitudes of field potentials were larger, while the durations shorter. The peak of c-Fos activation, however, was not parallel with the largest electrical activation. Larger amount of stained cells appeared in layers II and III in 4-aminopiridine and bicuculline, respectively. In Mg(2+)-free solution the highest c-Fos activity was detected in upper layer VI. Long-lasting cellular effects do not always correspond to the largest electrical responses, which are primarily determined by the activation of asymmetrical pyramidal neurons. Interneurons, which possess more symmetric process arborisation, play less important role in the generation of field potentials, although they may be intensively activated during seizure.     

Selecting a Measurement Model for the Analysis of the National Institutes of Health Stroke Scale

To select the most appropriate model for the analysis of data from the National Institutes of Health Stroke Scale (NIHSS), the graded-response, Rasch partial credit, and generalized partial credit models were used to analyze NIH stroke data of 1,191 acute ischemic stroke patients. Based on Akaike's Information Criterion (AIC) and Bayesian Information Criterion (BIC), the generalized partial credit model has the most generalizable parameters. Items on the NIHSS have different discriminating powers. The generalized partial credit model, which allows varying slopes of item response functions, is the most appropriate model for the analysis of the NIHSS.     

Injections of picrotoxin and bicuculline into the amygdaloid complex of the rat: an electroencephalographic, behavioural and morphological analysis

Bicuculline methiodide (0.5-3 nmol) and picrotoxin (0.5-4 nmol) were injected uni- or bilaterally into the rat amygdala and the resulting behavioural, electroencephalographic and morphological alterations were studied. In rats treated unilaterally with lowest doses of either bicuculline or picrotoxin (0.5 and 1 nmol) increase in the locomotor activity, occasional myoclonus of the hindlimbs and wet dog shakes were observed. At doses of 2-3 nmol, both gamma-aminobutyrate antagonists produced a sequence of repetitively occurring behavioural alterations including limbic gustatory automatisms, tremor and myoclonus of the forelimbs, head nodding and rearing, that developed over 15-30 min and built up progressively into the recurrent motor limbic seizures lasting for 1-6 h. In animals injected bilaterally with either bicuculline (0.5-3 nmol) or picrotoxin (0.5-3 nmol) motor limbic seizures rapidly developed into the status epilepticus lasting for several hours. Bicuculline and picrotoxin produced both ictal and interictal epileptiform activity in the electroencephalogram. A spectrum of electroencephalographic changes consisted of high voltage fast activity, slow and fast voltage spiking, paraoxysmal bursts and periods of postictal depression. The earliest electrographic alterations appeared in the amygdala and then rapidly spread to cortical areas. Electrographic seizures started 1-10 min after unilateral injections of large doses of bicuculline and pictrotoxin (2-4 nmol). Ictal periods lasted for 1-2 min, recurred every 5-10 min and were followed by periods of depression of the electrographic activity. Bilateral injections of large doses of both gamma-aminobutyrate antagonists (2-3 nmol) resulted in the status epilepticus. Morphological examination of frontal forebrain sections with light microscopy revealed a widespread damage to the amygdala, olfactory cortex, substantia nigra, thalamus, hippocampus and neocortex. Pretreatment of animals with diazepam prevented the build-up of convulsive activity and brain damage produced by bicuculline or picrotoxin. Muscimol retarded the appearance and shortened the duration of convulsive activity, but did not alter the sequence and intensity of seizures. The results indicate that gamma-aminobutyrate antagonists, bicuculline and picrotoxin when directly applied to the amygdala can elicit in rats motor limbic seizures, epileptic changes in the electroencephalogram indicative of repetitive limbic seizures, and status epilepticus accompanied by seizure-related brain damage.(ABSTRACT TRUNCATED AT 400 WORDS)     

Negative masking and the units problem in audition

Masking functions constructed from pedestal levels bracketing absolute threshold may exhibit negative masking, particularly when stimuli are defined in terms of amplitude (pressure). Three experimental conditions using 10-ms 1000-Hz tones in quiet, 1000-Hz tones embedded in continuous noise, and 6500-Hz tones in quiet, yielded negative masking when amplitudes were used to define the stimulus, with the greatest amount of negative masking occurring with 6500-Hz tones. Two models were applied to the data: the transduction model, which assumes direct coupling, and the sensory analytical model, which assumes differential coupling. Maximum likelihood estimates were derived to indicate goodness-of-fit, and the Akaike information criterion and Bayesian information criterion were utilised to adjust for model complexity. Overall, both models effectively accounted for the data, though the sensory analytic model provided the best fits to the data and has the added quality of being based on underlying physiological processes.     

Osseointegration of zirconia dental implants in animal investigations: A systematic review and meta-analysis

Objective

To determine the osseointegration rate of zirconium dioxide (ZrO₂) dental implants in preclinical investigations.