金属对金属人工髋关节的磨损预测

目的发展复杂动态载荷与瞬态运动条件下的球面共型接触硬对硬人工髋关节的磨损预测模型,并用于典型的金属对金属人工髋关节在复杂三维生理运动条件下的磨损预测研究。方法建立有限元模型用于接触力学问题求解,采用固定-跟踪法(fixed-tracked method)完成具有三维欧拉运动的人工髋关节双侧界面动态磨损几何再现及相应的接触与磨损问题模拟的数值交换。结果磨损预测表明,磨损导致金属对金属人工髋关节接触界面几何由球面向非球面过渡,接触区域随磨损周期而增大,接触压力变化趋于平缓、最大接触压力逐渐减小。结论本研究所发展的三维复杂动态、具有双侧界面几何磨损变化的人工髋关节磨损预测模型,能够很好地进行金属对金属髋关节磨损数值预测模拟实验,为认识人工髋关节磨损机理提供了新的方法。     

A machine learning approach for distinguishing age of infants using auditory evoked potentials

Objective

To develop a high performance machine learning (ML) approach for predicting the age and consequently the state of brain development of infants, based on their event related potentials (ERPs) in response to an auditory stimulus.

Methods

The ERP responses of twenty-nine 6-month-olds, nineteen 12-month-olds and 10 adults to an auditory stimulus were derived from electroencephalogram (EEG) recordings. The most relevant wavelet coefficients corresponding to the first- and second-order moment sequences of the ERP signals were then identified using a feature selection scheme that made no a priori assumptions about the features of interest. These features are then fed into a classifier for determination of age group.

Results

We verified that ERP data could yield features that discriminate the age group of individual subjects with high reliability. A low dimensional representation of the selected feature vectors show significant clustering behavior corresponding to the subject age group. The performance of the proposed age group prediction scheme was evaluated using the leave-one-out cross validation method and found to exceed 90% accuracy.

Conclusions

This study indicates that ERP responses to an acoustic stimulus can be used to predict the age and consequently the state of brain development of infants.

Significance

This study is of fundamental scientific significance in demonstrating that a machine classification algorithm with no a priori assumptions can classify ERP responses according to age and with further work, potentially provide useful clues in the understanding of the development of the human brain. A potential clinical use for the proposed methodology is the identification of developmental delay: an abnormal condition may be suspected if the age estimated by the proposed technique is significantly less than the chronological age of the subject.     

A new sulcus-corrected approach for assessing cerebellar volume in spinocerebellar ataxia

Precise volumetry of the cerebellum still remains challenging, due to thin sulci and gyri. We present a new fast and reliable sulcus-corrected approach for quantitative assessment of cerebellar atrophy, evaluated on patients with spinocerebellar ataxia (SCA). Thin-sliced T1-weighted magnetic resonance images (MPRAGE) were acquired in 11 genetically confirmed SCA6 patients and in a group of age-matched control subjects (n = 14). Post-processing involves a morphological image segmentation pipeline as a basis for a sulcus-corrected cerebellar volume measurement. Cerebellar volumes and intra-rater, inter-rater and scan-rescan reproducibility were quantified. Reliability of the measurements was validated using an anatomical preparation of the cerebellum. Repeatability coefficients (RC: intra-rater/inter-rater/scan-rescan) of the method were 1.07%/1.11%/1.35%. Absolute cerebellar volumes showed good agreement with the actual volume of the anatomical preparation. The cerebellar volume of the SCA 6 was 96.3 ± 12.1 ml (mean ± S.D.), which was significantly lower than the results of the corresponding control groups. The cerebellar volume correlated significantly to clinical dysfunction in SCA6. This is the first study to demonstrate the feasibility of a new sulcus-corrected approach to assess cerebellar volume. In contrast to currently used methods, this new approach may be more sensitive even to small atrophic changes affecting sulcal widening.     

Exposure to CSF from sporadic amyotrophic lateral sclerosis patients induces morphological transformation of astroglia and enhances GFAP and S100β expression

We have earlier shown that cerebrospinal fluid (CSF) of amyotrophic lateral sclerosis (ALS) patients’ produces selective degeneration of motor neurons, both in vitro as well as in vivo. The present study further evaluates the effect of ALS–CSF on the astrocytes in embryonic rat spinal cord cultures. We quantified the number of flat and process-bearing astrocytes in spinal cord cultures exposed to ALS–CSF and compared them against controls. In addition, GFAP and S100β expression were quantified by Western blot and measurement of immunofluorescence intensity respectively. We found higher number of process-bearing astrocytes in the cultures exposed to ALS–CSF. Both these proteins increased significantly in cultures exposed to ALS–CSF. Our results provide evidence that astroglia respond to toxic factor(s) present in ALS–CSF by undergoing morphological transformation from flat to process bearing which is further confirmed by elevated expression of GFAP and S100β. The above changes could possibly alter the microenvironment hastening the motor neuron degeneration.     

Genome‐wide transcriptome analyses reveal p53 inactivation mediated loss of miR‐34a expression in malignant peripheral nerve sheath tumours

Malignant peripheral nerve sheath tumours (MPNSTs) are aggressive soft tissue tumours that occur either sporadically or in patients with neurofibromatosis type 1. The malignant transformation of the benign neurofibroma to MPNST is incompletely understood at the molecular level. We have determined the gene expression signature for benign and malignant PNSTs and found that the major trend in malignant transformation from neurofibroma to MPNST consists of the loss of expression of a large number of genes, rather than widespread increase in gene expression. Relatively few genes are expressed at higher levels in MPNSTs and these include genes involved in cell proliferation and genes implicated in tumour metastasis. In addition, a gene expression signature indicating p53 inactivation is seen in the majority of MPNSTs. Subsequent microRNA profiling of benign and malignant PNSTs indicated a relative down‐regulation of miR‐34a in most MPNSTs compared to neurofibromas. In vitro studies using the cell lines MPNST‐14 (NF1 mutant) and MPNST‐724 (from a non‐NF1 individual) show that exogenous expression of p53 or miR‐34a promotes apoptotic cell death. In addition, exogenous expression of p53 in MPNST cells induces miR‐34a and other miRNAs. Our data show that p53 inactivation and subsequent loss of expression of miR‐34a may significantly contribute to the MPNST development. Collectively, our findings suggest that deregulation of miRNAs has a potential role in the malignant transformation process in peripheral nerve sheath tumours. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Chromophobe renal cell carcinoma with liposarcomatous dedifferentiation - report of a unique case

Sarcomatous transformation of chromophobe renal cell carcinoma (CRCC) is a well recognized phenomenon. Of the published cases with sarcomatous transformation of CRCC, none have shown liposarcomatous differentiation. Out of a cohort of 250 cases of CRCC, 19 (7.6%) showed sarcomatous differentiation. In one case (female, age 46 years), the sarcomatous component of the tumor displayed histological features of a pleomorphic liposar-coma. Light microscopic examination revealed a biphasic pattern with a chromophobe renal cell carcinoma(CRCC) and a high-grade sarcomatous component containing large pleomorphic lipoblasts. In several areas both components were intermingled. The conventional CRCC component showed classic histological features with calcifications, medium-sized polygonal cells arranged in solid-alveolar structures with raisinoid nuclei, pale-eosinophilic flocculent cytoplasm with perinuclear haloes. In addition, a microcystic-adenomatous component had luminal spaces filled with erythrocytes. The CRCC was positive with Hale''s colloidal iron-stain whereas the sarcomatous component was negative. The CRCC component was diffusely positive for cytokeratin 7, parvalbumin and racemase but negative for cy-tokeratin 20, vimentin, CD10, carboanhydrase IX and S100-protein. The pleomorphic liposarcomatous component displayed immunereactivity for CD10, vimentin, racemase and focally for carboanhydrase IX. The proliferative activity (Mib-1/Ki-67) was 5% in the CRCC and 30% in the pleomorphic liposarcomatous component. No immunereactivity for MDM2 or CDK4 was detected.This is the first reported case of a sarcomatoid CRCC where the sarcomatous component displayed features of a pleomorphic liposarcoma. The patient died from widespread metastatic disease 12 months after nephrectomy.     

Clear cell adenocarcinoma of the vagina in a patient with vaginal endometriosis

BACKGROUND: Malignant transformation of endometriosis is an infrequent complication of endometriosis. Extragonadal disease is uncommon. CASE: 55-year-old female presented with postmenopausal bleeding. Physical examination revealed a 2-cm polypoid lesion at the posterior vaginal apex, which was found to be a moderately differentiated invasive adenocarcinoma. Final pathology at the time of definitive surgery demonstrated a clear cell adenocarcinoma of the vagina arising in vaginal endometriosis. CONCLUSION: Vaginal endometriosis may lead to the development of cancer. Malignancy arising in endometriotic foci is rare, but most commonly occurs in the ovary. We report a case of clear cell malignancy arising in vaginal endometriosis, adding to only seven cases previously reported. Risk factors include unopposed estrogen and obesity, but it may occur in the absence of either.     

Detection of gastric dysrhythmia using WT and ANN in diabetic gastroparesis patients

Gastric myoelectrical activity can be measured by a noninvasive technique called electrogastrography where surface electrodes are placed on the epigastric area of the abdomen. The electrogastrogram (EGG) signal is by nature a nonstationary signal in terms of its frequency, amplitude and wave shape. Unlike the other methods discrete wavelet analysis (DWT) was designed for nonstationary signals. For automatic assessment of EGG, we used artificial neural networks (ANNs) that have been widely employed in pattern recognition due to their great potential of high performance, flexibility, robust fault tolerance, cost-effective functionality and capability for real-time applications. So we developed a new method for classification of EGG based on DWT and ANN.