Summary: Brief ischemia induced tolerance to subse quent ischemia in the hippocampal neurons. Male Mon golian gerbils were subjected to 2 min of ischemia in an awake condition. This ischemic insult only rarely pro duced neuronal damage in the gerbil brain. One day (n = 9), 2 days (n = 9), or 4 days (n = 10) following the first brief ischemia, the animals (double-ischemia group) were subjected to the second ischemia for 5 min. The single ischemia group received a sham procedure instead of the first ischemia and was identically subjected to the second ischemia I day (n = 9), 2 days (n = 10), and 4 days (n = 13) following the sham procedure. One week following the second ischemia, all gerbils were perfusion fixed and the neuronal density in the hippocampal CA I sector was measured. In double-ischemia groups, the neuronal denThe brain is particularly vulnerable to distur bances of energy metabolism, such as ischemia, an oxia, hypoglycemia, or status epilepticus (Auer and Siesj6, 1988; Siesj6 and Bengtsson, 1989). Even a brief episode of ischemia destroys certain groups of ischemia-sensitive neurons. These selectively vul nerable neurons are found in the hippocampal CA 1 sector, in the dorsolateral striatum, in certain layers of the cerebral cortex, and in the cerebellar cortex (Wieloch, 1985). Among these vulnerable cells in the brain, hippocampal CAl pyramidal cells have been the most extensively studied. Following brief ischemia, CA 1 pyramidal cells recover energy me tabolism (Pulsinelli and Duffy, 1983; Arai et a!. , 1986) and electrophysiological activity (Suzuki et a!., 1983). The fine structure of CA 1 pyramidal cells is maintained well until they are disintegrated 3 or 4Received July 18 , 1990 ; revised August 27 , 1990 ; accepted Au gust 31 , 1990 .Ad dress correspondence and reprint requests to Dr . T . Kirino at Department of Neurosurgery , Teikyo University School of Medicine , 7-3-\ Kaga , It abashi-ku , Tokyo 173 , Japan .Abbreviation used: hsp70 , 70-kDa heat-shock protein . 299sity per I-mm length of the pyramidal cell layer was 103.4 ± 93. 1 (SD) in the I-day subgroup, 125. 6 ± 64. 2 in the 2-day subgroup, and 176. 2 ± 93.7 in the 4-day subgroup, while the density in normal gerbils was 254.7 ± 18.6. The average neuronal density in the single-ischemia group was much lower than that in the double-ischemia group (whole control group: 10. 9 ± 27.4). Immunostaining using monoclonal antibody raised against 70-kDa heat-shock protein revealed an increase in 70-kDa heat-shock protein in the CAl area following 2 min of ischemia. Very brief ischemia induces heat-shock proteins and, presumably, thereby renders neurons more tolerant to subsequent metabolic stress.

A key reason for the persistently grim statistics associated with metastatic ovarian cancer is resistance to conventional agents, including platinum-based chemotherapies. A major source of treatment failure is the high degree of genetic and molecular heterogeneity, which results from significant underlying genomic instability, as well as stromal and physical cues in the microenvironment. Ovarian cancer commonly disseminates via transcoelomic routes to distant sites, which is associated with the frequent production of malignant ascites, as well as the poorest prognosis. In addition to providing a cell and protein-rich environment for cancer growth and progression, ascitic fluid also confers physical stress on tumors. An understudied area in ovarian cancer research is the impact of fluid shear stress on treatment failure. Here, we investigate the effect of fluid shear stress on response to platinum-based chemotherapy and the modulation of molecular pathways associated with aggressive disease in a perfusion model for adherent 3D ovarian cancer nodules. Resistance to carboplatin is observed under flow with a concomitant increase in the expression and activation of the epidermal growth factor receptor (EGFR) as well as downstream signaling members mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) and extracellular signal-regulated kinase (ERK). The uptake of platinum by the 3D ovarian cancer nodules was significantly higher in flow cultures compared to static cultures. A downregulation of phospho-focal adhesion kinase (p-FAK), vinculin, and phospho-paxillin was observed following carboplatin treatment in both flow and static cultures. Interestingly, low-dose anti-EGFR photoimmunotherapy (PIT), a targeted photochemical modality, was found to be equally effective in ovarian tumors grown under flow and static conditions. These findings highlight the need to further develop PIT-based combinations that target the EGFR, and sensitize ovarian cancers to chemotherapy in the context of flow-induced shear stress. Keywords: ovarian cancer; epidermal growth factor receptor (EGFR); mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK); extracellular signal-regulated kinase (ERK); chemoresistance; fluid shear stress; ascites; perfusion model; photoimmunotherapy (PIT); photodynamic therapy (PDT); carboplatin J. Clin. Med. 2020, 9, 924 3 of 27 anatomical structures [4,[27][28][29][30]]. An area that remains understudied is the effect of fluid shear stress on response to chemotherapy and the modulation of molecular pathways associated with aggressive disease [11,16,17,31]. J. Clin. Med. 2020, 9, x FOR PEER REVIEW 3 of 27 Figure 1. (A) A schematic of ovarian cancer metastases involving tumor cells or clusters (yellow) shedding from a primary site and disseminating along ascitic currents of peritoneal fluid (green arrows) in the abdominal cavity. Ovarian cancer typically disseminates in four common abdominopelvic sites: (1) cul-de-sac (an extension of the peritoneal cavity between the r...

Following brief cerebral ischemia, tolerance to subsequent ischemia is induced in the hippocampal neurons. In this experiment, recovery of protein synthesis was investigated autoradiographically in gerbils with induced tolerance. The animals were subjected to single forebrain ischemia for 5 min (5-min ischemia group) or 2 min (2-min ischemia group). To observe the effect of tolerance acquisition, double forebrain ischemia (double ischemia group), 2-min ischemia followed by 5-min ischemia was induced 2 days later. At various recirculation periods (90 min, 6 h, 1 day, and 4 days following ischemia), animals received a single dose of L-[2,3-3H]valine. In the 5-min ischemia group, protein synthesis in the CA1 sector was severely suppressed during the period from 90 min to 1 day of recirculation and never returned to the normal level even at 4 day of recirculation. In the 2-min ischemia group, protein synthesis recovered gradually and returned to near normal at 4 days of recirculation. On the other hand, in the double ischemia group, recovery of protein synthesis in the CA1 sector was rapid. At 1 day of recirculation, protein synthesis returned to near normal. Protein synthesis in the CA2 sector was inhibited during the 4 days of recirculation in this group. The present study revealed an early recovery of protein synthesis in the hippocampal CA1 neurons in the gerbil with induced tolerance. We suggest that recovery of protein synthesis is essential for the survival of neurons exposed to transient ischemia.