The dynamic relationship between cerebellar Purkinje cell simple spikes and the spikelet number of complex spikes

Key points

Purkinje cells are the sole output of the cerebellar cortex and fire two distinct types of action potential: simple spikes and complex spikes.

Previous studies have mainly considered complex spikes as unitary events, even though the waveform is composed of varying numbers of spikelets.

The extent to which differences in spikelet number affect simple spike activity (and vice versa) remains unclear.

We found that complex spikes with greater numbers of spikelets are preceded by higher simple spike firing rates but, following the complex spike, simple spikes are reduced in a manner that is graded with spikelet number.

This dynamic interaction has important implications for cerebellar information processing, and suggests that complex spike spikelet number may maintain Purkinje cells within their operational range.

Abstract

Purkinje cells are central to cerebellar function because they form the sole output of the cerebellar cortex. They exhibit two distinct types of action potential: simple spikes and complex spikes. It is widely accepted that interaction between these two types of impulse is central to cerebellar cortical information processing. Previous investigations of the interactions between simple spikes and complex spikes have mainly considered complex spikes as unitary events. However, complex spikes are composed of an initial large spike followed by a number of secondary components, termed spikelets. The number of spikelets within individual complex spikes is highly variable and the extent to which differences in complex spike spikelet number affects simple spike activity (and vice versa) remains poorly understood. In anaesthetized adult rats, we have found that Purkinje cells recorded from the posterior lobe vermis and hemisphere have high simple spike firing frequencies that precede complex spikes with greater numbers of spikelets. This finding was also evident in a small sample of Purkinje cells recorded from the posterior lobe hemisphere in awake cats. In addition, complex spikes with a greater number of spikelets were associated with a subsequent reduction in simple spike firing rate. We therefore suggest that one important function of spikelets is the modulation of Purkinje cell simple spike firing frequency, which has implications for controlling cerebellar cortical output and motor learning.

Purkinje cells are the sole output of the cerebellar cortex and fire two distinct types of action potential: simple spikes and complex spikes.

Previous studies have mainly considered complex spikes as unitary events, even though the waveform is composed of varying numbers of spikelets.

The extent to which differences in spikelet number affect simple spike activity (and vice versa) remains unclear.

We found that complex spikes with greater numbers of spikelets are preceded by higher simple spike firing rates but, following the complex spike, simple spikes are reduced in a manner that is graded with spikelet number.

This dynamic interaction has important implications for cerebellar information processing, and suggests that complex spike spikelet number may maintain Purkinje cells within their operational range.

Postoperative care after varicose vein surgery: patient-based questionnaire

Objective: Practical advice given postoperatively to varicose vein patients remains subjective. They are encouraged to walk in their stockings or bandages as much as possible. The aim of this study was to investigate if this is a realistic request.

Methods: A postal questionnaire was given to all patients undergoing varicose vein surgery from July 2003. The questionnaire referred to the following issues: pain scores, walking ability, stairs, driving, return to work, dressings and stockings.

Results: A total of 93 patients replied, of which 55 (59%) were women and the mean age was 52 years (range 23–83). Of the patients who replied, 66 (71%) had a unilateral procedure and 13 (14%) had recurrent varicose veins. A total of 65 (70%) underwent a high tie, strip and avulsions, 16 (17%) underwent a short saphenous tie, nine (10%) underwent ligation of both saphenous systems and three (3%) underwent avulsions alone. Pain scores were low (3/10), resolving completely after nine days on average. Despite this, 89% of patients could only walk around the garden or block in the first week. After two weeks, normal activities were possible but most patients remained off work for three weeks. Stockings were a problem for 49 (53%) patients.

Conclusions: Although we would like all our patients to mobilize early after varicose vein surgery, the traditional long walk is unrealistic. Support stockings cause difficulties in over half the patients. Postoperative care and advice for varicose vein surgery need re-thinking.

[Anterior and posterior default mode networks impairments in minimal hepatic encephalopathy]

OBJECTIVE

To investigate the functional connectivity (FC) impairments within anterior and posterior default mode networks (aDMN and pDMN) for cirrhosis with minimal hepatic encephalopathy (MHE), and to analyze relationship between DMNs alterations with neurocognitive impairments.

METHODS

From March 2009 to December 2011, a total of 43 cirrhotic patients without MHE (NMHE groups), 32 cirrhotic patients with current MHE (MHE groups), and 21 healthy controls were recruited in this study. All resting-state fMRI datasets were preprocessed and normalized into standard brain space. Two universal templates for aDMN and pDMN were applied to generate spatial patterns for aDMN and pDMN for each participate by dual regression. One sample t test were analyzed within groups, and one way ANOVA (analysis of variance) were performed to calculate the different FCs within aDMN and pDMN among groups. Additional correlation analysis was performed between different FCs within two DMNs and behavior scores.

RESULTS

Within aDMN, FC of MHE patients were significantly deceased than controls and NMHE groups in right superior frontal gyrus (SFG)/ bilateral medial frontal gyrus (MFG); while within pDMN, FC of MHE patients were significantly increased than controls and NMHE groups in right superior temporal gyrus (STG)/ middle temporal gyrus (MTG) and left cuneus/ bilateral calcarine gyri (one way ANOVA, P<0.01, cluster sizes>40, AlphaSim correction). The FC alterations in those region were significantly correlated with neurocognitive test scores (Pearson correlation coefficient, P<0.05).

CONCLUSION

Dual regression based aDMN and pDMN method was firstly applied to investigated functional connectivity impairments in MHE patients' brain. Functional deficits were endogenous within aDMN, while functional connectivity was compensatory enhancements within pDMN. These compensatory enhancements indicated that patients with current MHE had the potential to additionally recruit more neurological resource to accomplish the specific actions. Therefore, the alterations of dual regression based aDMN and pDMN can be potential neuroimaging biomarkers for MHE studies.

Decreased miR-452 expression in human colorectal cancer and its tumor suppressive function

MicroRNA-452 (miR-452) is dysregulated in some human malignancies, and is correlated with tumor progression. However, its expression and function in human colorectal cancer (CRC) remain unclear. The aim of our study was to explore the effects of miR-452 in CRC tumorigenesis and development. Using reverse transcription quantitative real-time polymerase chain reaction, we detected miR-452 expression in CRC cell lines and primary tumor tissues. We also examined the association between miR-452 expression and clinicopathological factors. We then investigated the effects of miR-452 on the biological behavior of CRC cells. miR-452 expression was significantly downregulated in CRC compared with the adjacent noncancerous tissues. A low level of miR-452 was associated with larger tumor size, deeper invasion depth, and advanced TNM stage. Multivariate Cox regression analysis identified decreased miR-452 expression as an independent factor predicting poor prognosis for CRC patients. In addition, in vitro functional analysis showed that overexpression of miR-452 in HCT116 cells reduced cell proliferation, promoted cell apoptosis, and inhibited cell invasion and migration. These findings indicate that miR-452acts as a tumor suppressor in CRC, and would serve as a novel molecular therapeutic agent for the treatment of the disease.

How pinning and contact angle hysteresis govern quasi-static liquid drop transfer

This paper presents both experimental and numerical simulations of liquid transfer between two solid surfaces with contact angle hysteresis (CAH). Systematic studies on the role of the advancing contact angle (θa), receding contact angle (θr) and CAH in determining the transfer ratio (volume of the liquid transferred onto the acceptor surface over the total liquid volume) and the maximum adhesion force (Fmax) were performed. The transfer ratio was found to be governed by contact line pinning at the end of the transfer process caused by CAH of surfaces. A map based on θr of the two surfaces was generated to identify the three regimes for liquid transfer: (I) contact line pinning occurs only on the donor surface, (II) contact line pinning occurs on both surfaces, and (III) contact line pinning occurs only on the acceptor surface. With this map, an empirical equation is provided which is able to estimate the transfer ratio by only knowing θr of the two surfaces. The value of Fmax is found to be strongly influenced by the contact line pinning in the early stretching stage. For symmetric liquid bridges between two identical surfaces, Fmax may be determined only by θa, only by θr, or by both θa and θr, depending on the magnitude of the contact angles. For asymmetric bridges, Fmax is found to be affected by the period when contact lines are pinned on both surfaces.

JAK-STAT and G-protein-coupled receptor signaling pathways are frequently altered in epitheliotropic intestinal T-cell lymphoma

Epitheliotropic intestinal T-cell lymphoma (EITL, also known as type II enteropathy-associated T-cell lymphoma) is an aggressive intestinal disease with poor prognosis and its molecular alterations have not been comprehensively characterized. We aimed to identify actionable easy-to-screen alterations that would allow better diagnostics and/or treatment of this deadly disease. By performing whole-exome sequencing of four EITL tumor-normal pairs, followed by amplicon deep sequencing of 42 tumor samples, frequent alterations of the JAK-STAT and G-protein-coupled receptor (GPCR) signaling pathways were discovered in a large portion of samples. Specifically, STAT5B was mutated in a remarkable 63% of cases, JAK3 in 35% and GNAI2 in 24%, with the majority occurring at known activating hotspots in key functional domains. Moreover, STAT5B locus carried copy-neutral loss of heterozygosity resulting in the duplication of the mutant copy, suggesting the importance of mutant STAT5B dosage for the development of EITL. Dysregulation of the JAK-STAT and GPCR pathways was also supported by gene expression profiling and further verified in patient tumor samples. In vitro overexpression of GNAI2 mutants led to the upregulation of pERK1/2, a member of MEK-ERK pathway. Notably, inhibitors of both JAK-STAT and MEK-ERK pathways effectively reduced viability of patient-derived primary EITL cells, indicating potential therapeutic strategies for this neoplasm with no effective treatment currently available.

Fast Liquid Transfer between Surfaces: Breakup of Stretched Liquid Bridges

In this work, a systematic experimental study was performed to understand the fast liquid transfer process between two surfaces. According to the value of the Reynolds number (Re), the fast transfer is divided into two different scenarios, one with negligible inertia effects (Re ≪ 1) and the other with significant inertia effects (Re > 1). For Re ≪ 1, the influences of the capillary number (Ca) and the dimensionless minimum separation (H(min)* = H(min)/V(1/3), where H(min) is the minimum separation between two surfaces and V is the volume of liquid) on the transfer ratio (α, the volume of liquid transferred to the acceptor surface over the total liquid volume) are discussed. On the basis of the roles of each physical parameter, an empirical equation is presented to predict the transfer ratio, α = f(Ca). This equation involves two coefficients which are affected only by the surface contact angles and H(min)* but not by the liquid viscosity or surface tension. When Re > 1, it is shown for the first time that the transfer ratio does not converge to 0.5 with the increase in the stretching speed.

Electric field modification of magnetism in Au/La2/3Ba1/3MnO3/Pt device

The La_2/3Ba_1/3MnO₃ film is deposited in a CMOS-compatible Pt/Ti/SiO₂/Si substrate with the oxygen pressure of 10 Pa for investigating magnetoelectric effect. Bipolar resistive switching effect with excellent endurance and retention is observed in this Au/La_2/3Ba_1/3MnO₃/Pt device. Through this effect, a significant nonvolatile change of magnetization is obtained in this device as well. The change of magnetization can be understood by the break and repair of the -Mn³⁺-O²⁻-Mn⁴⁺- chains induced by the electric field through the oxygen vacancies migration. The resistance and magnetization of the Au/La_2/3Ba_1/3MnO₃/Pt device can be simultaneously manipulated by the electric field, which makes it to be a promising candidate for the multifunctional memory devices.

[Effect of core ceramic surface treatment on the failure behavior of two bilayered all-ceramic structures]

OBJECTIVE

To evaluate the effect of core ceramic surface treatment on the failure behaviors of two bilayered all- ceramic structures.

METHODS

Lithium disilicate glass-ceramic (LDG, IPS e.max Press) and Zirconia(Cercon) specimens were divided into 4 groups(n=12) according to the following surface treatment methods: ground successively to 1 000(group A), 600(group B) and 320(group C) grit silicon carbide(SiC) papers and sandblasted with 110 µm aluminum oxide particle(group D, as control). Surface roughness was measured using a profilometer. After veneer sintering, the flexural strength σ was measured with biaxial flexure test and the reliability of strength was analyzed with Weibull distribution. Failure modes and fractographic patterns were analyzed by optical stereo and scanning electron microscopy (SEM).

RESULTS

For LDG, no significant difference was found for the flexural strength values among groups (F=0.406, P=0.750). No significant difference was found in Weibull modulus among groups(the confidence bounds overlapped with each other). SEM and optical stereo observation results showed that all the bilayered LDG specimens failed cohesively. For zirconia, Mean flexural strength values were (541 ± 75), (533 ± 73), (529 ± 78) and (640 ± 95) MPa for groups A, B, C and D, respectively, and group D demonstrated a significantly higher flexural strength compared to the other three groups(P<0.05). No significant difference were found among groups(the confidence bounds overlapped with each other). Specimens in all groups failed mainly adhesively, while those in group D presented lower percentage of adhesive failure.

CONCLUSIONS

Core ceramic surface treatment has no influence on the failure behaviors of LDG based bilayered structures. Sandblasting can increase the flexural strength of bilayered zirconia structures by reducing the incidence of delamination.

Association between two single nucleotide polymorphisms of interleukin-27 gene and increased cryptorchidism risk

Growing evidences have suggested the association between interleukin-27 and cryptorchidism. We aimed to investigate the relationship between IL-27 polymorphisms and cryptorchidism susceptibility. A total of 519 males were enrolled in a case-control study (150 cases and 369 normal subjects). The variants were discriminated using polymerase chain reaction-restriction fragment length polymorphism methods. The proportions of the major allele for rs153109 and rs17855750 were A and T with frequencies of 0.56 and 0.85 in cases and 0.51 and 0.91 in controls respectively (P values = 0.002, P value = 0.002). The heterozygous genotype of rs153109 and 17855750 was A/G and T/G with frequencies of 0.62 and 0.25 in cases and 0.39 and 0.17 in controls respectively (P values <0.001, P values <0.001). The A allele and A/G genotype of rs153109 polymorphisms contribute to increase cryptorchidism susceptibility, and G allele and T/G genotype of rs17855750 also contribute to increase cryptorchidism susceptibility, which implies that these allele and genotypes may be risk factors for the development of cryptorchidism.

Modulation of Purkinje cell complex spike waveform by synchrony levels in the olivocerebellar system

Purkinje cells (PCs) generate complex spikes (CSs) when activated by the olivocerebellar system. Unlike most spikes, the CS waveform is highly variable, with the number, amplitude, and timing of the spikelets that comprise it varying with each occurrence. This variability suggests that CS waveform could be an important control parameter of olivocerebellar activity. The origin of this variation is not well known. Thus, we obtained extracellular recordings of CSs to investigate the possibility that the electrical coupling state of the inferior olive (IO) affects the CS waveform. Using multielectrode recordings from arrays of PCs we showed that the variance in the recording signal during the period when the spikelets occur is correlated with CS synchrony levels in local groups of PCs. The correlation was demonstrated under both ketamine and urethane, indicating that it is robust. Moreover, climbing fiber reflex evoked CSs showed an analogous positive correlation between spikelet-related variance and the number of cells that responded to a stimulus. Intra-IO injections of GABA-A receptor antagonists or the gap junction blocker carbenoxolone produced correlated changes in the variance and synchrony levels, indicating the presence of a causal relationship. Control experiments showed that changes in variance with synchrony were primarily due to changes in the CS waveform, as opposed to changes in the strength of field potentials from surrounding cells. Direct counts of spikelets showed that their number increased with synchronization of CS activity. In sum, these results provide evidence of a causal link between two of the distinguishing characteristics of the olivocerebellar system, its ability to generate synchronous activity and the waveform of the CS.

Liquid transfer mechanism between two surfaces and the role of contact angles

The transfer ratio of quasi-static liquid transfer was found to strongly depend on the difference between the receding contact angles of the two surfaces. In contrast to traditional thinking, the transfer ratio was quite insensitive to the adhesion force between the solid and the liquid when the liquid bridge broke.

Production and repair of implant-induced microdamage in the cortical bone of goats after long-term estrogen deficiency

SUMMARY

By using an ovariectomized goat model, we found that estrogen depletion decreases bone quality and makes it susceptible to screw-induced mechanical microdamage. Both diffuse microdamage and linear cracks accumulated up to 3 weeks after screw implantation, and the microdamage was repaired gradually after 4-8 months.

INTRODUCTION

The aim of this study was to observe the effect of long-term estrogen deficiency on the creation and repair of microdamage in cortical bone adjacent to bone screw.

METHODS

Cortical bone screws were placed in the tibial diaphyses 28 months after ovariectomy (OVX) or sham operation (Sham-Op) in female goats. The goats were euthanized at 0 day, 21 days, 4 months, and 8 months after screw implantation. Microdamage morphology and repair were examined in peri-screw bone using histomorphometric method, and the nanomechanical properties of peri-screw bone were examined with nanoindentation testing.

RESULTS

Tibiae from ovariectomized goats in which screws had been placed had significantly higher levels of diffuse microdamage and significantly more linear cracks than those from sham goats, and the diffuse microdamage was more obvious than linear cracks in the region adjacent to the implant. Both diffuse microdamage and linear cracks accumulated up to day 21 and then gradually repaired at 4 and 8 months after surgery. The trend for bone remodeling in each group was consistent with changes in the level of microdamage. Nanoindentation testing showed that both elastic modulus and hardness in peri-screw bone were significantly decreased in OVX group compared to Sham-Op group. The hardness and elastic modulus also showed a downward trend up to 4 months after screw implantation and then exhibited some recovery after 8 months.

CONCLUSIONS

Estrogen depletion decreases bone quality and makes it vulnerable to screw-induced mechanical damage, which may compromise the initial stability of an orthopedic implant.

Investigating univariate temporal patterns for intrinsic connectivity networks based on complexity and low-frequency oscillation: a test-retest reliability study

Intrinsic connectivity networks (ICNs) are composed of spatial components and time courses. The spatial components of ICNs were discovered with moderate-to-high reliability. So far as we know, few studies focused on the reliability of the temporal patterns for ICNs based their individual time courses. The goals of this study were twofold: to investigate the test-retest reliability of temporal patterns for ICNs, and to analyze these informative univariate metrics. Additionally, a correlation analysis was performed to enhance interpretability. Our study included three datasets: (a) short- and long-term scans, (b) multi-band echo-planar imaging (mEPI), and (c) eyes open or closed. Using dual regression, we obtained the time courses of ICNs for each subject. To produce temporal patterns for ICNs, we applied two categories of univariate metrics: network-wise complexity and network-wise low-frequency oscillation. Furthermore, we validated the test-retest reliability for each metric. The network-wise temporal patterns for most ICNs (especially for default mode network, DMN) exhibited moderate-to-high reliability and reproducibility under different scan conditions. Network-wise complexity for DMN exhibited fair reliability (ICC<0.5) based on eyes-closed sessions. Specially, our results supported that mEPI could be a useful method with high reliability and reproducibility. In addition, these temporal patterns were with physiological meanings, and certain temporal patterns were correlated to the node strength of the corresponding ICN. Overall, network-wise temporal patterns of ICNs were reliable and informative and could be complementary to spatial patterns of ICNs for further study.

Low-dose risedronate sodium protects bone cells after abrupt oestrogen withdrawal

OBJECTIVE

To investigate the effects of low-dose risedronate sodium on the in vitro cellular profile of osteoblasts, adipocytes, osteocytes and osteoclasts in a rat model of abrupt oestrogen deficiency.

METHODS

Oestrogen deficiency was induced by ovariectomy in 24 female rats. The rats were treated with low-dose (0.24 μg/kg) or high-dose (2.4 μg/kg) risedronate sodium for 4 days presurgery, continuing every 3 days until 15 days postsurgery. Osteogenic and adipogenic differentiation were determined in cultured bone marrow cells by alkaline phosphatase and Oil Red O staining, respectively, and by osteogenic and adipogenic gene expression. Osteoclast formation was measured in bone marrow cells stimulated with macrophage colony-stimulating factor and receptor activator of nuclear factor κB ligand, and stained with tartrate-resistant acid phosphatase. Osteocyte apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelling assay and B-cell lymphoma-2 (Bcl-2) immunohistochemistry.

RESULTS

Low-dose risedronate sodium enhanced osteoblast differentiation, suppressed adipocyte differentiation and osteoclast formation, and reduced osteocyte apoptosis through regulation of Bcl-2 and Bcl-2-associated X protein.

CONCLUSIONS

Low-dose risedronate sodium may have clinical benefit in protecting against bone loss after abrupt oestrogen deficiency.

Altered regional homogeneity patterns in adults with attention-deficit hyperactivity disorder

PURPOSE

Investigating the discriminative brain map for patients with attention-deficit/hyperactivity disorder (ADHD) based on feature selection and classifier; and identifying patients with ADHD based on the discriminative model.

MATERIALS AND METHODS

A dataset of resting state fMRI contains 23 patients with ADHD and 23 healthy subjects were analyzed. Regional homogeneity (ReHo) was extracted from resting state fMRI signals and used as model inputs. Raw ReHo features were ranked and selected in a loop according to their p values. Selected features were trained and tested by support vector machines (SVM) in a cross validation procedure. Cross validation was repeated in feature selection loop to produce optimized model.

RESULTS

Optimized discriminative map indicated that the ADHD brains exhibit more increased activities than normal controls in bilateral occipital lobes and left front lobe. The altered brain regions included portions of basal ganglia, insula, precuneus, anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), thalamus, and cerebellum. Correlation coefficients indicated significant positive correlation of inattentive scores with bilateral cuneus and precuneus, and significant negative correlation of hyperactive/impulsive scores with bilateral insula and claustrum. Additionally, the optimized model produced total accuracy of 80% and sensitivity of 87%.

CONCLUSION

ADHD brain regions were more activated than normal controls during resting state. Linear support vector classifier can provide useful discriminative information of altered ReHo patterns for ADHD; and feature selection can improve the performances of classification.

Modeling liquid bridge between surfaces with contact angle hysteresis

This paper presents the behaviors of a liquid bridge when being compressed and stretched in a quasi-static fashion between two solid surfaces that have contact angle hysteresis (CAH). A theoretical model is developed to obtain the profiles of the liquid bridge given a specific separation between the surfaces. Different from previous models, both contact lines in the upper and lower surfaces were allowed to move when the contact angles reach their advancing or receding values. When the contact angles are between their advancing and receding values, the contact lines are pinned while the contact angles adjust to accommodate the changes in separation. Effects of CAH on both asymmetric and symmetric liquid bridges were analyzed. The model was shown to be able to correctly predict the behavior of the liquid bridge during a quasi-static compression/stretching loading cycle in experiments. Because of CAH, the liquid bridge can have two different profiles at the same separation during one loading and unloading cycle, and more profiles can be obtained during multiple cycles. The maximum adhesion force generated by the liquid bridge is found to be influenced by the CAH of surfaces. CAH also leads to energy cost during a loading cycle of the liquid bridge. In addition, the minimum separation between the two solid surfaces is shown to affect how the contact radii and angles change on the two surfaces as the liquid bridge is stretched.

Type II EATL (epitheliotropic intestinal T-cell lymphoma): a neoplasm of intra-epithelial T-cells with predominant CD8αα phenotype

In this multicentre study, we examined 60 cases of Type II enteropathy-associated T-cell lymphoma (EATL) from the Asia-Pacific region by histological review, immunohistochemistry and molecular techniques. Patients were mostly adult males (median age: 58 years, male:female 2.6:1), presenting with abdominal pain (60%), intestinal perforation (40%) and weight loss (28%). None had a history of coeliac disease and the median survival was only 7 months. Histologically, these tumours could be divided into (i) central tumour zone comprising a monotonous population of neoplastic lymphocytes, (ii) peripheral zone featuring stunted villi and morphologically atypical lymphocytes showing epitheliotropism, and (iii) distant mucosa with normal villous architecture and cytologically normal intra-epithelial lymphocytes (IELs). Characterized by extensive nuclear expression of Megakaryocyte-associated tyrosine kinase (MATK) (87%) and usually a CD8(+)CD56(+) (88%) cytotoxic phenotype, there was frequent aberrant expression of CD20 (24%). T-cell receptor (TCR) expression was silent or not evaluable in 40% but of the remainder, there was predominant expression of TCRαβ over TCRγδ (1.6:1). In keeping with the normal ratio of IEL subsets, CD8(+) cases showed predominant CD8αα homodimer expression (77%), regardless of TCR lineage. These tumours constitute a distinct entity from classical EATL, and the pathology may reflect tumour progression from IEL precursors, remnants of which are often seen in the distant mucosa.