Ultralow freezer for gene expression analysis

要理解认知的细胞基础，关键需要在细胞分辨率下评估同一动物在多个时期的行为中大脑广泛区域的神经活动模式。事实上，一种名为通过荧光原位杂交(CATFISH)对时间活动进行细胞室分析的敏感技术通过可视化即刻早期基因(IEGs)的转录来实现这种区分。参与信息处理的神经元立即转录出在核内持续几分钟可见的IEG。随后，处理后的mRNA被转位到细胞质中，浓度在~30min达到峰值。由于信使核糖核酸可以在两个独立的细胞隔间中分解，因此有可能在同一动物的两个行为时期识别活跃的神经元。此外，在行为过程中转录IEG的细胞比例与电生理记录产生的估计相同。因此，与功能磁共振成像或正电子发射计算机断层扫描一样，鲶鱼在同一受试者中提供大规模重复的神经元活动测量，但具有细胞分辨率，以检查调节认知的神经网络中的信号和可塑性。这一新的实验系统使我们能够检查神经网络中的信号和可塑性，这些神经网络是信息处理和存储的基础。事实上，使用这种方法，已经可以可视化与海马体的空间处理、顶叶后皮质的运动处理以及杏仁核和眼眶额叶皮质的取食行为相关的神经元。然而，这一领域的进一步工作非常需要超低冰柜。由于将实验诱导的杂交产量差异降至最低所固有的实际限制，组织存储数天或数周是不可避免的。在这些期间，在保持RNA完整性的温度下存储的可用性对所产生的数据的质量至关重要。

Understanding the cellular basis of cognition critically requires the assessment of patterns of neural activity over widespread regions of the brain during multiple epochs of behaviour in the same animal at cellular resolution. In fact, a sensitive technique, termed cellular compartment analysis of temporal activity by fluorescence in situ hybridization (catFISH) permits such discrimination by visualizing the transcription of immediate-early genes (IEGs). Neurons engaged in information processing immediately transcribe IEGs that are visible for several minutes within the nucleus. Subsequently, processed mRNA is trans-located to the cytoplasm, peaking in concentration at ~30 min. Because mRNA can be resolved in two independent cellular compartments, it is possible to identify active neurons during two behavioural epochs in the same animal. Moreover, the proportion of cells transcribing IEGs during behaviour equals estimates generated by electrophysiological recording. Thus, like fMRI or PET, catFISH provides large-scale repeated neuronal activity measurements in the same subject, but with the cellular resolution to examine signalling and plasticity in neural networks mediating cognition. This new experimental system allows us to examine signalling and plasticity in neural networks that underlie information processing and storage.  In fact, using this method it has been possible to visualize neurons associated with spatial processing in the hippocampus, movement processing in posterior parietal cortex, and feeding behaviour in the amygdala and orbitofrontal cortex.  Further work in this area, however, critically requires an ultra-low freezer.  The practical constraints inherent in  minimizing experimentally-induced variation in hybridization yield make the storage of tissue for days or weeks unavoidable. During these periods, the availability of storage at temperatures that maintain the integrity of RNA is critical to the quality of the data that is generated.