Is the callus shape an optimal response to a mechanobiological stimulus?

After bone trauma, the natural response to restore bone function is the formation of a callus around the fracture. Although several bone healing models have been developed, none have effectively perceived early callus formation and shape as the result of an optimal response to a mechanobiological stimulus.In this paper, we investigate which stimulus regulates early callus formation. An optimal design problem is formulated, and several objective functions are defined, each using a different mechanobiological stimulus. The following stimuli were analysed: the interfragmentary strain, the second invariant of the deviatoric strain tensor and a generic inflammatory factor. Different regions for callus formation were also evaluated, such as the gap region, the periosteum and the periosteum border. Each stimulus was computed using the finite element method, and the callus shape was optimised using the steepest descent method.The results demonstrated that the inflammatory factor approach, the interfragmentary strain and the second invariant of the deviatoric strain tensor over the inner gap provided the best results when compared with histological callus shapes. Therefore, this work suggests that callus growth can be an optimal mechanobiological response to either local mechanical instability and/or local inflammatory reaction.     

Excitatory effect of dopamine on oxytocin and vasopressin reflex releases in the rat

The involvement of dopamine in the release of oxytocin and vasopressin was investigated in lactating rats during suckling or after changes in plasma osmolality. The effects of intraventricular injections of dopamine, agonists and antagonists, were tested on electrical unit activity of oxytocinergic or vasopressinergic cells in the paraventricular nucleus, on intramammary pressure (index of oxytocin release) and diuresis (index of vasopressin release).In urethane-anaesthetized lactating suckled rats, dopamine (1 μg), apomorphine (2.5 and 5 μg) facilitated the established milk-ejection reflex, increasing the frequency and the amplitude of neurosecretory bursts of oxytocinergic cells. They also triggered the reflex in lactating rats without milk-ejections during suckling. The small doses injected were in no way such as to induce an acceleration in firing rate of oxytocinergic cells or an increase in mammary pressure.In alcohol-loaded rats, during water diuresis, dopamine (2 μg) and apomorphine (5 μg) activated the depressed vasopressinergic cells and inhibited diuresis. These facilitatory effects were progressive, reaching a maximum 10–15 min after injection.Haloperidol (5 μg) and α-flupentixol (10 μg) had an inhibitory effect on both types of neurosecretory cells in urethane-anaesthetized rats. They prevented the reflex activation of oxytocinergic cells induced by suckling and of vasopressinergic cells after a hyperosmotic stimulus (1 ml i.p 9% NaCl solution). These inhibitory effects were not of the ‘all-or-none’ type.So, we can postulate that dopamine regulates the reflex release of oxytocin and vasopressin in the hypothalamus. On the one hand, dopamine permits and controls the periodic activation of oxytocinergic cells as long as the mothers are being suckled. On the other hand, it modulates the activity of vasopressinergic cells whenever the plasma osmolality changes.     

电刺激对大鼠脑梗塞康复中星形细胞与神经元的影响

目的：探讨大鼠急性脑梗塞后的康复机制。方法：用易卒中型双肾双夹型肾血管性高血压大鼠复制大脑中动脉闭塞模型,随机分为电刺激治疗组（简称治疗组）和对照组,用走平衡木法评价大鼠康复功能。于电刺激治疗后第1、3、6、9周末在脑梗塞灶边缘区观察神经元与星形胶质细胞的超微结构,胶质酸性蛋白表达,神经丝蛋白和微管相关蛋白2表达,神经元凋亡及脑微血管舒张情况。结果：治疗组从3－9周末瘫痪肢体功能恢复较对照组明显,在脑梗塞边缘区上述表达及脑微血管舒张数量均较对照组高（P＜0．05）。结论：电刺激治疗可以促进瘫痪肢体功能恢复,其机理可能是电刺激增加星形胶质细胞增殖,增强神经元活性,激发脑微血管舒张。     

Paravertebral extramedullary hematopoiesis associated with improvement of anemia in congenital dyserythropoietic anemia type II

Thoracic masses resulting from extramedullary hematopoiesis developed in two sisters of Moroccan origin with congenital dyserythropoietic anemia type II (HEMPAS). In one patient, the diagnosis of extramedullary hematopoiesis was confirmed histologically. The appearance of extramedullary foci of hematopoiesis mimicking mediastinal tumors has not been previously described in HEMPAS. These masses result from persistent erythropoietic stimulation associated with chronic hemolytic anemia. In both patients, detection of the asymptomatic masses was preceded by normalization of hemoglobin levels. Thus unexpected correction of a chronic refractory anemia associated with the appearance of mediastinal masses might be the heralding manifestation of an effective extramedullary hemopoiesis.     

Modulation of sensitivity to alcohol by cortical and thalamic brain regions

The nucleus accumbens core (AcbC) is a key brain region known to regulate the discriminative stimulus/interoceptive effects of alcohol. As such, the goal of the present work was to identify AcbC projection regions that may also modulate sensitivity to alcohol. Accordingly, AcbC afferent projections were identified in behaviorally naïve rats using a retrograde tracer which led to the focus on the medial prefrontal cortex (mPFC), insular cortex (IC) and rhomboid thalamic nucleus (Rh). Next, to examine the possible role of these brain regions in modulating sensitivity to alcohol, neuronal response to alcohol in rats trained to discriminate alcohol (1 g/kg, intragastric [IG]) vs. water was examined using a two‐lever drug discrimination task. As such, rats were administered water or alcohol (1 g/kg, IG) and brain tissue was processed for c‐Fos immunoreactivity (IR), a marker of neuronal activity. Alcohol decreased c‐Fos IR in the mPFC, IC, Rh and AcbC. Lastly, site‐specific pharmacological inactivation with muscimol + baclofen (GABA_A agonist + GABA_B agonist) was used to determine the functional role of the mPFC, IC and Rh in modulating the interoceptive effects of alcohol in rats trained to discriminate alcohol (1 g/kg, IG) vs. water. mPFC inactivation resulted in full substitution for the alcohol training dose, and IC and Rh inactivation produced partial alcohol‐like effects, demonstrating the importance of these regions, with known projections to the AcbC, in modulating sensitivity to alcohol. Together, these data demonstrate a site of action of alcohol and the recruitment of cortical/thalamic regions in modulating sensitivity to the interoceptive effects of alcohol.     

Cone dysfunction and supernormal scotopic electroretinogram with a high-intensity stimulus

An unusual form of scotopic electroretinogram with a bright white stimulus, which consisted of a rectangular a-wave of normal amplitude and a b-wave of supernormal amplitude, was recorded in three patients with cone dysfunction. In addition to poor visual acuity, abnormal color vision and reduced amplitude of the photopic electroretinogram, these patients showed a 2-log unit elevation of the dark-adaptation threshold. Funduscopic examination and fluorescein angiography revealed fine granular pigment disturbances at the mascula. The relationship between the response of the dark-adapted electroretinogram versus stimulus intensity was unique to these patients. The b-wave thresholds were elevated by 1 log unit. The b-waves were reduced in amplitude and markedly delayed in implicit time to dim stimuli, but supernormal in amplitude and normal in implicit time to bright stimuli.Abbreviations GMP guanosine monophosphate     

Accessing vulnerable children’s lived experiences through visual stimuli illustrations (VSI)

One challenge that is often encountered when researching with children is finding effective research tools targeting younger children in sub-Saharan Africa. Consequently, many childhood experiences for those in adversity are less reported due to limitations in research tools to capture their lived experiences. This article explores the choice, design and use of visual stimulus illustrations (VSI) as a research tool to access lived experiences of orphans and vulnerable children (OVC) who enrol into early childhood development and education centres within low-resourced areas in Nairobi – Kenya. This paper views VSI with a range of participatory engagements to meaningfully benefit the younger OVC directly as a medium through which they can access, engage, interrogate, identify and ventilate their lived experiences, thus providing insights into the less researched domains of their childhood experiences.     

腰椎间盘突出症与腰椎间盘突出症合并阻塞性睡眠呼吸暂停患者的对比研究

目的 探究腰椎间盘突出症（LDH）与阻塞性睡眠呼吸暂停（OSA）之间的关联,为LDH的临床诊治策略及治疗方案提供参考依据。方法 选取2018年1月—2020年3月中国医科大学附属第一医院骨科行外科手术治疗的485例LDH患者,按是否合并OSA进行分组研究。结果 485例LDH患者中合并OSA的307例,发生率为63.3%。LDH合并OSA组主观症状、临床症状、日常活动受限程度日本骨科协会（JOA）腰痛评分低于单纯LDH组（P <0.05）;两组膀胱功能JOA评分比较,差异无统计学意义（P> 0.05）;LDH合并OSA组视觉模拟评分法（VAS）评分高于单纯LDH组（P <0.05）。Pfirrmann 5级评分法中4、5级例数构成比LDH合并OSA组较单纯LDH组高（P <0.05）。两组患者的硬膜撕裂率、神经受损率、血肿率、切口感染率等并发症发生率比较,差异无统计学意义（P>0.05）。单纯LDH组与LDH合并OSA组术后3、6、12和24个月静息状态下JOA和VAS评分比较,采用重复测量设计的方差分析,结果：(1)不同时间点的JOA和VAS评分有差异（...     

Peri-ictal normalization of visual cortex excitability in migraine: an MEG study

To delineate if the change in cortical excitability persists across migraine attacks, visual evoked magnetic fields (VEF) were measured in patients with migraine without aura during the interictal ( n  = 26) or peri-ictal ( n  = 21) periods, and were compared with 30 healthy controls. The visual stimuli were checkerboard reversals with four different check sizes (15', 30', 60' and 120'). For each check size, five sequential blocks of 50 VEF responses were recorded to calculate the percentage change of the P100m amplitude in the second to the fifth blocks in comparison with the first block. At check size 120', interictal patients showed a larger amplitude increment than controls [28.1 ± 38.3% ( s.d. ) vs. 8.7 ± 21.3%] in the second block and a larger increment than peri-ictal patients in the second (28.1 ± 38.3% vs. −3.2 ± 19.2%), fourth (22.7 ± 31.2% vs. −5.7 ± 22.3%) and fifth (20.5 ± 30.4% vs. −10.8 ± 30.1%) blocks ( P  < 0.05). There was no significant difference at other check sizes or between peri-ictal patients and controls. In conclusion, there may be peri-ictal normalization of visual cortical excitability changes in migraine that is dependent on the spatial frequency of the stimuli and reflects a dynamic modulation of cortical activities.