Removal of gemcitabine-induced senescent cancer cells by targeting glutaminase1 improves the therapeutic effect in pancreatic ductal adenocarcinoma.

Insufficient cancer treatment can induce senescent cancer cell formation and treatment resistance. The characteristics of induced senescent cancer (iSnCa) cells remain unclear. Pancreatic ductal adenocarcinoma (PDAC) has a low and nondurable response rate to current treatments. Our study aimed to analyze the properties of iSnCa cells and the relationship between cellular senescence and prognosis in PDAC. We evaluated the characteristics of gemcitabine-induced senescent cancer cells and the effect of senescence-associated secretory phenotype (SASP) factors released by iSnCa cells on surrounding PDAC cells. The relationship between cellular senescence and the prognosis was investigated in 50 patients with PDAC treated with gemcitabine-based neoadjuvant chemotherapy. Exposure to 5 ng/mL gemcitabine-induced senescence, decreased proliferation and increased senescence-associated ß-galactosidase-cell staining without cell death in PDAC cells; the expression of glutaminase1 (GLS1) and SASP factors also increased and caused epithelial-mesenchymal transition in surrounding PDAC cells. iSnCa cells were selectively removed by the GLS1 inhibitor bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide (BPTES) through apoptosis induction. Cellular senescence was induced in PDAC cells via insufficient gemcitabine in subcutaneous tumor model mice. GLS1 expression was an independent prognostic factor in patients with PDAC who received gemcitabine-based neoadjuvant chemotherapy. This is the first study to identify the relationship between senescence and GLS1 in PDAC. Low-dose gemcitabine-induced senescence and increased GLS1 expression were observed in PDAC cells. Cellular senescence may contribute to treatment resistance of PDAC, hence targeting GLS1 in iSnCa cells may improve the therapeutic effect.

COVID-19 vaccine effectiveness against severe COVID-19 requiring oxygen therapy, invasive mechanical ventilation, and death in Japan: A multicenter case-control study (MOTIVATE study).

INTRODUCTION: Since the SARS-CoV-2 Omicron variant became dominant, assessing COVID-19 vaccine effectiveness (VE) against severe disease using hospitalization as an outcome became more challenging due to incidental infections via admission screening and variable admission criteria, resulting in a wide range of estimates. To address this, the World Health Organization (WHO) guidance recommends the use of outcomes that are more specific to severe pneumonia such as oxygen use and mechanical ventilation. METHODS: A case-control study was conducted in 24 hospitals in Japan for the Delta-dominant period (August-November 2021; "Delta") and early Omicron (BA.1/BA.2)-dominant period (January-June 2022; "Omicron"). Detailed chart review/interviews were conducted in January-May 2023. VE was measured using various outcomes including disease requiring oxygen therapy, disease requiring invasive mechanical ventilation (IMV), death, outcome restricting to "true" severe COVID-19 (where oxygen requirement is due to COVID-19 rather than another condition(s)), and progression from oxygen use to IMV or death among COVID-19 patients. RESULTS: The analysis included 2125 individuals with respiratory failure (1608 cases [75.7%]; 99.2% of vaccinees received mRNA vaccines). During Delta, 2 doses provided high protection for up to 6 months (oxygen requirement: 95.2% [95% CI:88.7-98.0%] [restricted to "true" severe COVID-19: 95.5% {89.3-98.1%}]; IMV: 99.6% [97.3-99.9%]; fatal: 98.6% [92.3-99.7%]). During Omicron, 3 doses provided high protection for up to 6 months (oxygen requirement: 85.5% [68.8-93.3%] ["true" severe COVID-19: 88.1% {73.6-94.7%}]; IMV: 97.9% [85.9-99.7%]; fatal: 99.6% [95.2-99.97]). There was a trend towards higher VE for more severe and specific outcomes. CONCLUSION: Multiple outcomes pointed towards high protection of 2 doses during Delta and 3 doses during Omicron. These results demonstrate the importance of using severe and specific outcomes to accurately measure VE against severe COVID-19, as recommended in WHO guidance in settings of intense transmission as seen during Omicron.

Endometrioid Carcinoma of the Uterine Corpus With a Micropapillary Component: A Novel Prognostic Factor For Metastasis.

BACKGROUND/AIM: Micropapillary pattern is a morphologically distinctive form of carcinoma composed of small, hollow, or morula-like clusters of cancer cells surrounded by clear stromal spaces. The neoplastic cells characteristically display a reverse polarity, also known as an ''inside-out'' growth pattern, that is linked to higher frequencies of lymphovascular invasion and lymph nodal metastasis. To the best of our knowledge, it has not been previously recognized in uterine corpus. CASE REPORT: We report 2 cases of endometrioid carcinoma of the uterine corpus with a micropapillary component. In these cases, histological examination identified an endometrioid carcinoma that had invaded the myometrial layer. The carcinoma cells that constructed the micropapillary components were immunohistochemically positive for EMA. They lined the stromal facing surface of the cell membrane, confirming the inside-out growth pattern, and D2-40 immunohistochemistry confirmed lymphovascular invasion of carcinoma cells. CONCLUSION: We believe that the micropapillary pattern linked to higher frequencies of lymphovascular invasion and lymph nodal metastasis may be one of the most important invasive patterns in endometrioid carcinomas of the uterine corpus for predicting aggressive malignant potential, prognosis, and recurrence, although further, larger studies are required to evaluate its clinical significance.

A Ruptured Mucinous Cystadenocarcinoma of the Pancreas Extensively Evaluated Before and After the Rupture: A Case Report.

ABSTRACT: Pancreatic mucinous cystic neoplasm (MCN) rarely ruptures because of their surrounding fibrotic capsules and has never been reported with detailed information regarding prerupture and postrupture states. We report a case of MCN rupture where performed emergency surgery was performed while waiting for elective surgery. A 54-year-old woman was referred to our department for a pancreatic cystic tumor with slight abdominal pain. A cystic tumor with a nodular lesion was found, with a contrast effect measuring 78 mm in diameter. On day 21, the patient visited our hospital complaining of increased abdominal pain, but few signs of peritonitis were observed. Tests conducted revealed moderate ascites, marginal shrinkage of the cyst diameter, and a slight elevation of inflammatory markers. We suspected an MCN rupture and immediately performed distal pancreatectomy. Brown turbid ascites and rupture of the anterior wall of the cyst were observed. In the ascites, amylase levels were not elevated, and bacterial cultures were negative. The histopathological diagnosis was noninvasive mucinous cystadenocarcinoma. At 9 months after surgery, she started chemotherapy because of a recurrence of the peritoneal dissemination. This case provided valuable insight into the rupture of MCNs using thorough imaging techniques, laboratory, and physical findings before and after rupturing.

Prognostication of Ovarian Function after Ovarian Torsion Using Intraoperative Indocyanine Green Angiography.

STUDY OBJECTIVE: To quantitatively evaluate the blood flow in ovaries (ischemic ovaries) that underwent torsion using indocyanine green angiography (ICGA) and assess the use of ICGA as an indicator for functional preservation of the ovaries. DESIGN: In vivo animal study. SETTING: The University of Yamanashi Animal Experimentation Center. SUBJECTS: Eighteen female Wistar albino rats. INTERVENTIONS: As an alternative to ovarian torsion, we occluded an ovary in each rat for 24 hours, after which we performed ICGA before and after releasing ischemia and extracted the following 8 parameters: Fmax (maximum F value before releasing ischemia); Tmax (time taken from the onset of an increase in F to reaching Fmax); T½max (time taken from the onset of an increase in F to reaching half of Fmax); slope (Fmax/Tmax); time ratio (T½max/Tmax); F'max (maximum F value after releasing ischemia); reperfusion rate (F'max/Fmax); and reperfusion gap (F'max - Fmax). Four weeks later, we counted the total number of primordial and primary follicles and classified the rats into functional and nonfunctional groups. MEASUREMENTS AND MAIN RESULTS: On the basis of the total number of primordial and primary follicles, 13 rats had "functional" ovaries on the clamped side, and 5 rats had "nonfunctional" ovaries. The area under the curve values for each parameter were as follows: Fmax, 0.908; Tmax, 0.569; T½max, 0.546; time ratio, 0.746; slope, 0.877; F'max, 0.723; reperfusion rate, 0.938; and reperfusion gap, 0.862. CONCLUSION: ICGA can be used to quantitatively evaluate ovaries that have been subjected to ischemia, and the magnitude of fluorescence intensity can be an excellent predictor of ovarian necrosis. Quantifying the degree of reperfusion immediately after the release of ischemia can be an equally excellent predictor of necrosis.

A safe and simple procedure for laparoscopic hepatectomy with combined diaphragmatic resection.

Diaphragmatic resection may be required beneath the diaphragm in some patients with liver tumors. Laparoscopic diaphragmatic resection is technically difficult to secure in the surgical field and in suturing. We report a case of successful laparoscopic hepatectomy with diaphragmatic resection. A 48-year-old man who underwent laparoscopic partial hepatectomy for liver metastasis of rectal cancer 20 months ago underwent surgery because of a new hepatic lesion that invaded the diaphragm. The patient was placed in the left hemilateral decubitus position. The liver and diaphragm attachment areas were encircled using hanging tape. Liver resection preceded diaphragmatic resection with the hanging tape in place. Two snake retractors were used to secure the surgical field for the inflow of CO2 into the pleural space after diaphragmatic resection. The defective part of the diaphragm was repaired using continuous or interrupted sutures. Both ends of the suture were tied with an absorbable suture clip without ligation. In laparoscopic liver resection with diaphragmatic resection, the range of diaphragmatic resection can be minimized by performing liver resection using the hanging method before diaphragmatic resection. The surgical field can be secured using snake retractors. Suturing with an absorbable suture clip is conveniently feasible. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13691-021-00506-x.

Leptomeningeal metastasis from cervical cancer: Report of two cases and a review of the literature.

Leptomeningeal metastases from cervical cancer are extremely rare, with only 24 cases reported in the English-language literature. Leptomeningeal metastasis (LM) is usually a late event, but it can develop at any stage. A 44-year-old woman presented with vertigo, tinnitus, diminution of hearing, and a cervical tumor at the initial visit. She underwent whole brain radiotherapy and systemic chemotherapy. Five months after the initial visit, her condition deteriorated rapidly and she died. A 49-year-old woman underwent surgery and pelvic radiotherapy for cervical cancer. She underwent resection of lung metastases 2 years later and received systemic chemotherapy for lymph node metastases 4 years later. Five years after the initial visit, the patient suddenly presented with diplopia, headache, and vomiting; her clinical course was fulminant and she died. Most patients with LM present with diverse clinical manifestations and deteriorate rapidly despite multiple treatment modalities. Gynecologic oncologists should be aware of this rare complication.

[A Case of Advanced Hepatocellular Carcinoma That Caused Rapid Re-Growth Due to Lenvatinib Withdrawal].

Lenvatinib is reported to have a stronger angiogenesis-inhibiting effect in hepatocellular carcinoma(HCC)than sorafenib, but in many cases dose reduction and withdrawal are required due to the occurrence of adverse events. We report 12 cases of using lenvatinib for advanced HCC in our hospital together with a case of rapid re-growth due to withdrawal of lenvatinib. In 2 cases, metastases of HCC were controlled and radically resected. All patients required lenvatinib withdrawal due to Grade 3 adverse event, except for 2 cases that started with dose reduction. There were 3 cases in which drug withdrawal was required for 2 weeks or more, and in 2 of them, rapid re-growth of tumor was observed during the drug withdrawal and the treatment could not be continued. Although the use of lenvatinib may results in tumor shrinkage, suggesting that prolonged drug withdrawal may make disease management difficult. It is important to manage adverse events and minimize days of drug withdrawal by reducing the dose and systematically discontinuing the drug.

Bioactivity of alginetin, a caramelization product of pectin: Cytometric analysis of rat thymic lymphocytes using fluorescent probes.

Alginetin is the major product formed from pentoses and hexurionic acids. Alginetin is producted by cooking process of food including pection, a naturally-occurring polysacharride found in many plants. However, the biological interaction and toxicity of alginetin are not known at all. The aim of the present study was to investigate the cellular actions of alginetin on rat thymic lymphocytes. The effects of alginetin on the cell were examined using flow cytometry with fluorescent probes. Alginetin increased cellular content of non-protein thiols ([NPT]i) and elevated intracellular Zn2+ levels ([Zn2+]i). Chelation of intracellular Zn2+ reduced the effect of alginetin on [NPT]i, and chelation of external Zn2+ almost completely diminished alginetin-induced elevation of [Zn2+]i, indicating that alginetin treatment increased Zn2+ influx. Increased [NPT]i and [Zn2+]i levels in response to alginetin were positively correlated. Alginetin protected cells against oxidative stress induced by hydrogen peroxide and Ca2+ overload by calcium ionophore. It is considered that the increases in [NPT]i and [Zn2+]i are responsible for the cytoprotective activity of alginetin because NPT attenuates oxidative stress and Zn2+ competes with Ca2+. Alginetin may be produced during manufacturing of jam, which may provide additional health benefits of jam.

Triphenyltin disrupts intracellular Zn2+ homeostasis in rat thymic lymphocytes.

Triphenyltin (TPT), previously used as an agricultural fungicide and industrial antifoulant, is now considered an environmental pollutant. The effect of TPT on human health is concerning due to its presence as a contaminant in seafood. In this study, the changes in intracellular Zn2+ concentration ([Zn2+]i) and cellular content of nonprotein thiols ([NPT]i) induced by triphenyltin chloride (TPTCH), were measured in rat thymic lymphocytes. This was studied by flow-cytometry using the fluorescent probes FluoZin-3-AM and 5-chloromethylfluorescein diacetate (5-CMF-DA). Incubation with TPTCH, at 0.1 µM or more (up to 3 µM), increased [Zn2+]i in a concentration-dependent manner. The TPTCH-induced elevation in [Zn2+]i was due to the increase in membrane Zn2+ permeability and intracellular Zn2+ release. Incubation with TPTCH at 0.3 µM significantly increased [NPT]i levels, whereas the addition of an intracellular Zn2+ chelator had no effect on the same. TPT at higher concentrations (1 or 3 µM) reduced [NPT]i. TPT may disturb intracellular Zn2+ signaling in lymphocytes that disturbs cellular functions.

Our experience of repeat laparoscopic liver resection in patients with recurrent hepatocellular carcinoma.

BACKGROUND: Repeat liver resection is an effective treatment approach for patients with recurrent hepatocellular cell carcinoma (HCC). However, the surgical feasibility and oncological significance of repeat laparoscopic liver resection (r-LLR) remain unproven. This study evaluates and compares the clinical outcomes of non-anatomic r-LLR applied towards recurrent HCC, with those of primary LLR (p-LLR) for primary HCC. METHODS: This retrospective study reports 104 patients with HCC, treated with LLR between 2014 and 2018. Twenty eight of these patients underwent r-LLR for recurrent HCC. The clinical and surgical variables were reviewed for all cases. RESULTS: The analysis was limited to non-anatomic resection across both groups (r-LLR: 89% (25/28) vs. p-LLR: 80% (61/76)). There were no statistically significant differences about patient background between the two groups, with the exception of Child-Pugh classification. r-LLR surgical techniques included single-site laparoscopic adhesiolysis (32%, 8/25), Pringle maneuver (8%, 2/25), and crush-clamp method using BiClamp for hepatic parenchymal transection (72%, 18/25). No severe postoperative complications were observed in the r-LLR group. Postoperative hospital stays and procedure-related postoperative survival were similar for both groups. CONCLUSIONS: Non-anatomical r-LLR renders comparable surgical and oncological outcomes. Our data suggest that non-anatomical r-LLR is a safe and feasible therapeutic approach to recurrent HCC.

Successful management of aberrant right hepatic duct during laparoscopic cholecystectomy: a rare case report.

BACKGROUND: Anatomic variants of the biliary tree present challenges to surgical management during laparoscopic cholecystectomy and affect perioperative outcomes. An aberrant right hepatic duct connecting into the cystic duct is a practically important variation because of the susceptibility to serious postoperative refractory bile leakage. We report a successful case of laparoscopic cholecystectomy in the aberrant right hepatic duct of a patient diagnosed with chronic cystitis. CASE PRESENTATION: A 49-year-old man was referred to our department for treatment of chronic cholecystitis. Magnetic resonance cholangiopancreatography indicated that the cystic duct branched from the common bile duct and an aberrant bile duct connected to the cystic duct. Intraoperative cholangiography revealed that the bile duct was not confluent to the major right branch of the intrahepatic bile duct and drained a narrow area. Preoperative magnetic resonance cholangiopancreatography had diagnostic value. Furthermore, intraoperative cholangiography with the Critical View of Safety method was paramount to achieving safe cholecystectomy based on confirmation of the biliary anatomy and the drainage area of the aberrant right hepatic duct. CONCLUSION: We encountered a rare but clinically significant case of laparoscopic cholecystectomy. This case suggests that precise understanding of the anatomy and drainage area of the aberrant right hepatic duct preoperatively and intraoperatively can lead to safe cholecystectomy.

Modification of cell vulnerability to oxidative stress by N-(3-oxododecanoyl)-L-homoserine-lactone, a quorum sensing molecule, in rat thymocytes.

N-(3-oxododecanoyl)-l-homoserine-lactone (ODHL), a quorum sensing molecule, affects intracellular Zn2+ concentration ([Zn2+]i) and cellular levels of nonprotein thiols ([NPT]i) of rat thymic lymphocytes, both of which are assumed to affect cell vulnerability to oxidative stress. Therefore, it is interesting to examine the effects of ODHL on the cells under oxidative stress. ODHL augmented the cytotoxicity of H2O2, but not calcium ionophore A23187. ODHL potentiated the H2O2-induced elevation of [Zn2+]i, wherein, it greatly attenuated the H2O2-induced increase in intracellular Ca2+ concentration. ODHL did not affect [NPT]i in the presence of H2O2. Therefore, we conclude that the elevation of [Zn2+]i is involved in the ODHL-induced potentiation of H2O2 cytotoxicity. Our findings suggest that ODHL modifies cell vulnerability to oxidative stress in host cells.

Membrane hyperpolarization and depolarization of rat thymocytes by azoxystrobin, a post harvest fungicide.

Azoxystrobin, a broad-spectrum fungicide, has been increasingly used in the agricultural industry. In Japan in 2018, azoxystrobin at five times the normal limit was detected in a shipment of Australian barley that had been used in food products. Therefore, the effects of azoxystrobin need to be carefully examined to predict potential adverse reactions in humans. In this study, the effects of azoxystrobin on the membrane potential and intracellular Ca2+ levels of thymocytes have been photochemically examined using flow cytometry. Azoxystrobin hyperpolarized plasma membrane potential. This hyperpolarization appeared to be due to the activation of Ca2+-dependent K+ channels, as both the removal of extracellular Ca2+ and addition of charybdotoxin attenuated the observed hyperpolarization. In the presence of quinine, an anti-malarial drug that blocks Ca2+-dependent K+ channels, azoxystrobin depolarized the membranes instead. Azoxystrobin increased intracellular Ca2+ levels in a concentration-dependent manner through the influx of extracellular Ca2+ and intracellular release of Ca2+, as confirmed by reduction in azoxystrobin-induced response in the absence of extracellular Ca2+. It appears likely that azoxystrobin at micromolar concentrations modifies membrane ion permeability in thymocytes. Since changes in membrane potential and intracellular Ca2+ levels occur during typical physiological lymphocyte responses, azoxystrobin may disturb lymphocyte function.

Laparoscopic resection of retroperitoneal paraganglioma behind the Spiegel lobe in a kyphotic patient: A rare case report.

Extra-adrenal paraganglioma is a rare form of neuroendocrine neoplasm capable of catecholamine secretion. The surgical risks associated with the tumor location are compounded in this case of a kyphotic patient. This report presents the successful application of laparoscopy on extra-adrenal paraganglioma located behind the Spiegel lobe in a kyphotic patient. The operation was performed after 1 week of α-blocker administration. The laparoscopic approach, with the patient in the left hemilateral decubitus position on a rotating table, provided optimal access for safe tumor resection after complete hepatic right lobe mobilization. The patient's postoperative course was uneventful. Based on the results, the laparoscopic approach can be a safe and effective method for resecting extra-adrenal paraganglioma in the challenging case of a kyphotic patient.

Zinc-dependent and independent actions of hydroxyhydroquinone on rat thymic lymphocytes.

Coffee contains hydroxyhydroquinone (HHQ). HHQ is one of the by-products released during bean roasting. Therefore, it is important to elucidate the bioactivity of HHQ to predict its beneficial or adverse effects on humans. We studied zinc-dependent and independent actions of commercially procured synthetic HHQ in rat thymocytes using flow cytometric techniques with propidium iodide, FluoZin-3-AM, 5-chloromethylfluorescein diacetate, and annexin V-FITC. HHQ at 1050 µM elevated intracellular Zn2+ levels by releasing intracellular Zn2+. HHQ at 10 µM increased cellular thiol content in a zinc-dependent manner. However, HHQ at 30-50 µM reduced cellular thiol content. Although the latter actions of HHQ (30-50 µM) were suggested to increase cell vulnerability to oxidative stress, HHQ at 0.3-100 µM significantly protected cells against oxidative stress induced by H2O2. The process of cell death induced by H2O2 was delayed by HHQ, although both H2O2 and HHQ increased the population of annexin V-positive living cells. However, HHQ at 10-30 µM promoted cell death induced by A23187, a calcium ionophore. HHQ at 10-30 µM exerted contrasting effects on cell death caused by oxidative stress and Ca2+ overload. Because HHQ is considered to possess diverse cellular actions, coffee with reduced amount of HHQ may be preferable to avoid potential adverse effects.

Short-term outcomes of robotic-assisted versus conventional laparoscopic radical hysterectomy for early-stage cervical cancer: A single-center study.

AIM: Our hospital adopted laparoscopic surgery for early-stage cervical cancer in August 1998, with robot-assisted surgery implemented in October 2013. This study aimed to compare short-term outcomes for conventional laparoscopic radical hysterectomy (LRH) and robot-assisted radical hysterectomy (RARH) and assess the technical feasibility of RARH for early-stage cervical cancer. METHODS: We retrospectively compared operative time, blood loss, number of resected lymph nodes, length of postoperative hospital stay, rate of positive vaginal margin and perioperative complications between two groups of 121 patients (LRH group, n = 57; RARH group, n = 64) with stage IA2 to IIB, among 164 patients who underwent endoscopic radical hysterectomy for early-stage cervical cancer performed between January 2010 and December 2017 by an expert surgeon, excluding cases of para-aortic lymphadenectomy. RESULTS: No differences in patient background, in terms of age and body mass index, were identified. For the LRH/RARH groups (mean ± standard deviation), results obtained were as follows: operative time, 211 ± 38/280 ± 59 min (P < 0.01); blood loss, 219 ± 114/370 ± 231 mL (P < 0.01); number of resected lymph nodes, 38.5 ± 15.9/50.2 ± 18.2 (P < 0.01); length of postoperative hospital stay, 11.6 ± 3.3/11.3 ± 4.8 days (P = 0.67); and perioperative complications with Clavien-Dindo classification of grade III or higher, 1.8/7.8% (P = 0.13). CONCLUSION: The operative time was significantly longer and blood loss greater in the RARH than LRH group. A greater number of lymph nodes were removed in the RARH group. However, these differences seem to be within a clinically acceptable range, showing that RARH is as feasible and safe as LRH in terms of short-term outcomes.

Captan-induced increase in the concentrations of intracellular Ca2+ and Zn2+ and its correlation with oxidative stress in rat thymic lymphocytes.

Captan, a phthalimide fungicide, is considered to be relatively nontoxic to mammals. There is a possibility that captan affects membrane and cellular parameters of mammalian cells, resulting in adverse effects, because of high residue levels. To test the possibility, we examined the effects of captan on rat thymic lymphocytes using flow-cytometry with appropriate fluorescent probes. Treatment with 10 and 30 µM captan induced apoptotic and necrotic cell death. Before cell death occurred, captan elevated the intracellular concentrations of Ca2+ and Zn2+ and decreased the concentration of cellular thiol compounds. These captan-induced phenomena are shown to cause cell death and are similar to those caused by oxidative stress. Captan also elevated the cytotoxicity of hydrogen peroxide. Results indicate that 10 and 30 µM captan cause cytotoxic effects on mammalian cells. Despite no report on the significant environmental toxicity hazard of captan in humans, it may exhibit adverse effects, described above, on wild organisms.

Hyperpolarization by N-(3-oxododecanoyl)-l-homoserine-lactone, a quorum sensing molecule, in rat thymic lymphocytes.

To study the adverse effects of N-(3-oxododecanoyl)-l-homoserine-lactone (ODHL), a quorum sensing molecule, on mammalian host cells, its effect on membrane potential was examined in rat thymic lymphocytes using flow cytometric techniques with a voltage-sensitive fluorescent probe. As 3-300 µM ODHL elicited hyperpolarization, it is likely that it increases membrane K+ permeability because hyperpolarization is directly linked to changing K+ gradient across membranes, but not Na+ and Cl- gradients. ODHL did not increase intracellular Ca2+ concentration. ODHL also produced a response in the presence of an intracellular Zn2+ chelator. Thus, it is unlikely that intracellular Ca2+ and Zn2+ are attributed to the response. Quinine, a non-specific K+ channel blocker, greatly reduced hyperpolarization. However, because charybdotoxin, tetraethylammonium chloride, 4-aminopyridine, and glibenclamide did not affect it, it is pharmacologically hypothesized that Ca2+-activated K+ channels, voltage-gated K+ channels, and ATP-sensitive K+ channels are not involved in ODHL-induced hyperpolarization. Although the K+ channels responsible for ODHL-induced hyperpolarization have not been identified, it is suggested that ODHL can elicit hyperpolarization in mammalian host cells, disturbing cellular functions.