## 1 Introduction  
In vitro analyses of behavioral, physiological and morphological cell responses are often a preliminary to in vivo studies. The objective of the present study was the combinatorial use of new methods to characterize cell modifications in response to a given treatment. To this purpose, we have studied the effects of cell exposure to reduced glutathione (GSH) on an olfactory neuroblast cell line (13s24).  
Glutathione holds a special place among antioxidant molecules: it is the most abundant small molecular weight thiol compound of living cells [1]. Although it is a small molecule composed of only three amino acids, it cannot enter directly inside cells. It is broken down in the extracellular space by the enzyme ectoprotein \(\gamma\)-glutamyl transpeptidase to produce dipeptides and free amino acids that are then absorbed by cells to intracellularly resynthesize GSH [2, 3]. Reduced glutathione (GSH) is a well-known direct antioxidant and a substrate of several antioxidant enzymes [4]. Glutathione participates to numerous cellular regulations: antioxidant protection, thiol-disulfide exchange of peptides and proteins, cell signaling, gene expression, detoxification of toxic compounds, etc. [5]. Studies have shown that it is excreted by cells such as liver cells [6], lymphoid cells [7], gallbladder [8], and cancer cells [9], supporting the hypothesis of local extracellular activities. Specific transport of GSH through the blood-brain barrier has been described [10]. Glutathione is abundant in the brain (in the range of millimolar) and exerts a protective effect against oxidative stress in neurons [11,12]. The endogenous production of oxidative stress is considered the main endogenous factor of aging, and dysregulation of glutathione homeostasis has been linked to loss of neurons in age-related diseases such as Parkinson's, Alzheimer's, and [PERSON]'s [13]. In a recent study, we demonstrated that both adhesion strength and cell volume are directly regulated by the extracellular GSH concentrations [14]. Both cell adhesion and reactive oxygen species (ROS) play a crucial role in neurogenesis through regulation of proliferation and differentiation [15,16]. Because GSH plays a crucial role as an antioxidant and causes marked cellular changes, cell exposure to GSH is a suitable situation for testing new technological approaches.  
In the present study, experiments were carried out on a non-cancerous immortalized cell line representing sensory olfactory neuron precursors (13s24) [17]. This study of olfactory neuroblasts is of particular interest since (1) the olfactory epithelium is the only location where the brain is in direct contact with the environment and thus exposed to partial oxygen pressure and potential oxidative stress higher than other brain cells, and (2) olfactory sensory neurons are continuously renewed during live from olfactory precursors (neuroblasts) [18].  
For this purpose, we performed a combinatorial study of cell physiological and morphological properties using highly sensitive methods to measure in real-time experiments, adhesion strength (xCELLigence), physical parameters (cell surface occupancy, size, and cell shape), cellular behavior such as motility (HoloMonitor) and changes in refractive index within the cells (Nanolive). The effects on size and shape were validated, after optimized time of exposure with GSH, using fluorescent markers by flow cytometry. Results show that GSH induced both a reduction in adhesion strength and an increase in cell volume. These findings reveal an unexpected role of GSH in the regulation of cell volume and adhesion strength, suggesting that each cell is able to control its own volume. Although the methods studied measure different parameters, their main interest lies in the fact that they are in real-time and do not require marking.