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The adsorption and degradation capacities of dichlorodiphenyltrichloroethane (DDT) on a photocatalyst composed of TiO 2 supported on the mesoporous material MCM-41 (TiO 2 /MCM-41) were investigated using density functional theory and real-time density functional theory methods. The van der Waals interactions within the PBE functional were adjusted by using the Grimme approach. The adsorption of DDT was evaluated through analyses involving adsorption energy, Hirshfeld atomic charges, Wiberg bond orders, molecular electrostatic potential, noncovalent interaction analysis, and bond path analysis. The findings reveal that DDT undergoes physical adsorption on pristine MCM-41 or MCM-41 modified with Al or Fe due to the very small bond order (only about 0.15-0.18) as well as the change in total charge of DDT after adsorption is close to 0. However, it chemically adsorbs onto the TiO 2 /MCM-41 composite through the formation of Ti···Cl coordination bonds because the maximum bond order is very large, about 1.0 (it can be considered as a single bond). The adsorption process is significantly influenced by van der Waals interactions (accounting for approximately 30-40% of the interaction energy), hydrogen bonding, and halogen bonding. MCM-41 is demonstrated to concurrently function as a support for the TiO 2 photocatalyst, creating a synergistic effect that enhances the photocatalytic activity of TiO 2 . Based on the computational results, a novel photocatalytic mechanism for the degradation of DDT on the TiO 2 /MCM-41 catalyst system was proposed., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Introduction: Brain cancer is the leading cause of cancer-related deaths in children and the majority of childhood brain tumors are diagnosed without determination of their underlying etiology. Little is known about risk factors for childhood brain tumors in Vietnam. The objective of this case-control study was to identify maternal and perinatal factors associated with brain tumors occurring in young Vietnamese children and adolescents., Methods: We conducted a hospital-based case-control study at Viet Duc University Hospital in Hanoi, Vietnam. Cases consisted of children with brain tumors aged 0-14 years old admitted to the hospital from January 2020 to July 2022 while the controls were age and sex-matched hospitalized children diagnosed with head trauma. Perinatal characteristics were abstracted from hospital medical records and maternal medical, behavioral, and sociodemographic factors were collected through in-person interviews. Conditional logistic regression models were used to examine maternal and perinatal factors associated with childhood brain tumors., Results: The study sample included 220 children (110 cases and 110 controls) whose average age was 8.9 years and 41.8% were girls. Children born to mothers aged greater than 30 years at the time of the child's birth had a higher risk of childhood brain tumors compared to those born to mothers aged from 18 to 30 years old (OR = 2.55; 95% CI: 1.13-5.75). Additionally low maternal body mass index prior to the current pregnancy of <18.5 kg/m 2 significantly increased the odds of having a child with a brain tumor in relation to normal maternal body mass index from 18.5-22.9 kg/m 2 (OR = 3.19; 95% CI: 1.36 - 7.50)., Conclusion: Advanced maternal age and being markedly underweight were associated with an increased odds of having a child with a brain tumor. A population-based study with larger sample size is needed to confirm and extend the present findings., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Introduction: Breast cancer remains one of the major cancers worldwide. In Asia, breast cancer is leading both incidence and mortality rates. Health-related quality of life (HRQoL) studies play an important role in clinical treatment. This systematic review aimed to summarize the evidence of HRQoL and associated factors among patients with breast cancer in low-and-middle-income countries (LMICs) in Asia., Method: Performed according to PRISMA guidelines for systematic review, the studies were searched from three databases (PubMed, Cochrane, Scopus) up to November 2020. The studies which met the predefined eligibility criteria were selected, extracted, and assessed the quality according to the Newcastle-Ottawa Scale (NOS) tool., Results and Discussion: A total of 2,620 studies were searched on the three databases, of which 28 met the selection criteria, then, were included in the systematic review. The Global Health Status (GHS) score of breast cancer patients based on the EORTC QLQ-C30 questionnaire ranged from 56.32 ± 25.42 to 72.48 ± 15.68. The overall HRQoL scores using the FACT-G and FACT-B instruments ranged from 60.78 ± 13.27 to 82.23 ± 12.55 and from 70.29 ± 13.33 to 108.48 ± 19.82, respectively. Factors affecting HRQoL of patients with breast cancer included age, education level, income, marital status, lifestyle, tumor stage, method, and treatment duration. Patient's income showed a consistent effect on HRQoL while the remaining factors reported inconsistent findings across the studies. In conclusion, the HRQoL of breast cancer patients in LMICs in Asia was low and affected by several sociodemographic factors which should be studied more in future research., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Ngo, Nguyen, Nguyen, Vo, Phung, Pham, Vo, Dang, Nguyen Le Bao and Duong.)

Introduction: Autoimmune bullous dermatoses (ABD) represent a heterogeneous group of blistering disorders that may be debilitating with high morbidity. Clinical, histological, and direct immunofluorescence (DIF) studies are essential in establishing an accurate diagnosis of ABD, which is essential for its clinical management. Our study objective was to perform a systematic evaluation of ABD cases in a patient population at an academic medical center in Ho Chi Minh City, Vietnam, and determine the degree of concordance of clinical, histological, and DIF findings in ABD. Methodology: A systematic retrospective cross-sectional study was performed on 92 patients diagnosed with ABD by clinical, histological, and DIF studies at the University of Medicine and Pharmacy in Ho Chi Minh City, Vietnam, between September 2019 and September 2021. The clinical histories, H and E stained tissue sections, and DIF stains were evaluated by pathologists at the University of Medicine and Pharmacy. Results: ABD was evaluated as a whole and subdivided into an intraepidermal blister subgroup and a subepidermal blister subgroup. The analysis of paired diagnostic methods (clinical, histological, and DIF) for concordance with the final diagnosis was performed and showed that there were no statistically significant differences between the paired methods (McNemar’s test, p > 0.05). There was moderate concordance between the clinical, histological, and DIF diagnoses among all ABD cases (Brennan-Prediger coefficient Kappa test, κBP = 0.522, CI = 0.95). In the intraepidermal blister subgroup, the diagnostic accuracies of the histology and DIF stains were comparable to each other, and both were more accurate than a clinical diagnosis alone. In the subepidermal blister subgroup, there was no statistically significant difference in each pair of the three diagnostic methods (clinical, histological, and DIF) (McNemar’s test, p > 0.05). The concordance between the clinical, histological, and DIF diagnoses was high for the intraepidermal blister subgroup (Kappa test, κBP = 0.758, CI = 0.95). However, the concordance between the clinical, histological, and DIF diagnoses was slight for the subepidermal blister subgroup (Kappa test, κBP = 0.171, CI = 0.95). Conclusion: Histological evaluation is highly accurate in the diagnosis of the intraepidermal blister subgroup, but it is not as accurate in the diagnosis of the subepidermal blister subgroup in the Vietnamese patient cohort in which clinical, histological, and DIF studies were performed. DIF stains are a crucial diagnostic tool for ABD in this patient population.

Background: The model of trauma in Vietnam has changed significantly over the last decade and requires reforming medical education to deal with new circumstances. Our aim is to evaluate this transition regarding the new target by analyzing trauma and the medical training system as a whole., Objective: This study aimed to establish if medical training in the developing country of Vietnam has adapted to the new disease pattern of road trauma emerging in its economy., Methods: A review was performed of Vietnamese medical school, Ministry of Health, and Ministry of Education and Training literature on trauma education. The review process and final review paper were prepared following the guidelines on scoping reviews and using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flowchart., Results: The current trauma training at the undergraduate level is minimal and involves less than 5% of the total credit. At the postgraduate level, only the specialties of surgery and anesthesia have a significant and increasing trauma training component ranging from 8% to 22% in the content. Trauma training, which focuses on practical skills, accounts for 31% and 32% of the training time of orientation courses for young doctors in "basic surgery" and "basic anesthesia," respectively. Other relevant short course trainings, such as continuing medical education, in trauma are available, but they vary in topics, facilitators, participants, and formats., Conclusions: Medical training in Vietnam has not adapted to the new emerging disease pattern of road trauma. In the interim, the implementation of short courses, such as basic trauma life support and primary trauma care, can be considered as an appropriate method to compensate for the insufficient competency-related trauma care among health care workers while waiting for the effectiveness of medical training reformation., (©Ba Tuan Nguyen, Toi Lam Phung, Thi Hong Hanh Khuc, Van Anh Thi Nguyen, Christopher Leigh Blizzard, Andrew Palmer, Huu Tu Nguyen, Thang Cong Quyet, Mark Nelson. Originally published in JMIR Medical Education (https://mededu.jmir.org), 24.01.2022.)

Introduction: Coronavirus disease 2019 (COVID-19) has significantly affected health care workers (HCWs), including their mental health. However, there has been limited evidence on this topic in the Vietnamese context. Therefore, this study aimed to explore COVID-19-related, psychological stress risk factors among HCWs, their concerns and demands for mental health support during the pandemic period. Methods: We employed a cross-sectional study design with convenience sampling. An online, self-administered questionnaire was used and distributed through social media among medical and non-medical HCWs from April 22 to May 12, 2020. HCWs were categorized either as frontline or non-frontline. We measured the prevalence of psychological stress using the Impact of Event Scale-Revised (IES-R) instrument. Multivariate binary logistic regression analysis was performed to identify risk factors associated with psychological stress among HCWs. Results: Among the 774 enrolled participants, 761 (98.3%) eligible subjects were included in the analysis. Most respondents were females (58.2%), between 31 and 40 years of age (37.1%), lived in areas where confirmed COVID-19 cases had been reported (61.9%), medical HCWs (59.9%) and practiced being at the frontline (46.3%). The prevalence of stress was 34.3%. We identified significant risk factors such as being frontline HCWs (odds ratio [OR] = 1.77 [95% confidence interval [CI]: 1.17-2.67]), perceiving worse well-being as compared to those before the COVID-19 outbreak [OR = 4.06 (95% CI: 2.15-7.67)], and experiencing chronic diseases [OR = 1.67 (95% CI: (1.01-2.77)]. Majority (73.9%) were concerned about testing positive for COVID-19 and exposing the infection to their families. Web-based psychological interventions that could provide knowledge on managing mental distress and consulting services were highly demanded among HCWs. Conclusion: The prevalence of psychological stress among HCWs in Vietnam during the COVID-19 pandemic was high. There were also significant risk factors associated with it. Psychological interventions involving web-based consulting services are highly recommended to provide mental health support among HCWs., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Nguyen, Nguyen, Pham, Duong, Gloria, Vo, Vo and Phung.)

Competing Interests: Competing interest statement: C.L.S. is employed through Torreyana Corp, San Diego, CA; Blackhawk Genomics, Concord, CA; and Advagenix, Rockville, MD. Volunteer activities of C.L.S. include those for College of American Pathologists, Northfield, IL, and Clinical Laboratory Standards Institute, Wayne, PA. T.J.O. is a Member, Scientific Advisory Committee, MioDx and Integrated Nano-Technologies. A.W.I.L.’s laboratory receives sponsorships from AstraZeneca (HK) Ltd. and MSD (HK) Ltd. for providing selected companion diagnostic tests free to public patients. N.C. is an employee at Quest Diagnostics, Inc. F.A.M. is an employee and stock option holder at Castle Biosciences, Inc. A.B.C. is paid teaching faculty for the American Medical Informatics Association Clinical Informatics Board Review Course and receives small honoraria as well as travel reimbursement to speak at multiple scientific and professional medical society meetings. T.L.P. has been consulted (compensated) for Bio-Rad, Inc. and is Director of Pathology Strategies for the Sturge Weber Foundation (compensated). H.E.W. has employment through Viapath, a majority National Health Service-owned independent pathology service provider; has been a paid faculty member at Kingston University, accepted paid accommodation and subsistence as an invited speaker to Cytocell User Group meeting for the United Kingdom and Ireland, and accepted paid event registration as an invited speaker to Digital Pathology/Global Engage meeting. H.E.W.’s laboratory received scholarship funds from The International Council for Standardization in Haematology for providing JAK2 testing. The other authors (K.F., E.A.B., P.M., N.R.P., K.P.P., B.S., M.S., M.L.G., S.M.M., H.F., and S.O.) do not have any affiliations, memberships, funding, or financial holdings that might be perceived as affecting the objectivity of this article.

To investigate whether endothelial Akt1 activation is sufficient to induce vascular tumor formation in the skin, we have developed a skin graft model in which a skin fragment from transgenic donor mice with inducible and endothelial cell-specific overexpression of activated Akt1 (myrAkt1) is grafted into the skin of wild type recipient mice. The donor skin successfully engrafts after two weeks and, more importantly, vascular tumor develops at the site of transgenic skin graft when myrAkt1 expression is turned on. This skin graft model is a novel approach to investigate the biological impact of a key signal transduction molecule in a temporal, localized and organ-specific manner., (Copyright © 2017 The Authors; exclusive licensee Bio-protocol LLC.)

Blockade of angiogenesis can retard tumour growth, but may also paradoxically increase metastasis. This paradox may be resolved by vessel normalization, which involves increased pericyte coverage, improved tumour vessel perfusion, reduced vascular permeability, and consequently mitigated hypoxia. Although these processes alter tumour progression, their regulation is poorly understood. Here we show that type 1 T helper (T H 1) cells play a crucial role in vessel normalization. Bioinformatic analyses revealed that gene expression features related to vessel normalization correlate with immunostimulatory pathways, especially T lymphocyte infiltration or activity. To delineate the causal relationship, we used various mouse models with vessel normalization or T lymphocyte deficiencies. Although disruption of vessel normalization reduced T lymphocyte infiltration as expected, reciprocal depletion or inactivation of CD4 + T lymphocytes decreased vessel normalization, indicating a mutually regulatory loop. In addition, activation of CD4 + T lymphocytes by immune checkpoint blockade increased vessel normalization. T H 1 cells that secrete interferon-γ are a major population of cells associated with vessel normalization. Patient-derived xenograft tumours growing in immunodeficient mice exhibited enhanced hypoxia compared to the original tumours in immunocompetent humans, and hypoxia was reduced by adoptive T H 1 transfer. Our findings elucidate an unexpected role of T H 1 cells in vasculature and immune reprogramming. T H 1 cells may be a marker and a determinant of both immune checkpoint blockade and anti-angiogenesis efficacy.

Cutis laxa is characterized by dramatic wrinkling of skin that is lacking in elasticity due to inherent defects in dermal elastic fibers. Cutis laxa can be caused by genetic and metabolic disorders. It can also be acquired, possibly resulting from inflammatory processes with destruction of elastic fibers. This report describes a 26-year old woman who developed acquired cutis laxa and cutaneous mastocytosis leading to premature aging. She represents a unique co-occurrence of these two separate disease entities. To our knowledge, there has been only one published case report of acquired cutis laxa occurring in association with urticaria pigmentosa in a 4-year old girl. Our case would be a second case that exhibits the coexistence of these two disorders in an adult female.

Vascular tumors are endothelial cell neoplasms whose mechanisms of tumorigenesis are poorly understood. Moreover, current therapies, particularly those for malignant lesions, have little beneficial effect on clinical outcomes. In this study, we show that endothelial activation of the Akt1 kinase is sufficient to drive de novo tumor formation. Mechanistic investigations uncovered opposing functions for different Akt isoforms in this regulation, where Akt1 promotes and Akt3 inhibits vascular tumor growth. Akt3 exerted negative effects on tumor endothelial cell growth and migration by inhibiting activation of the translation regulatory kinase S6-Kinase (S6K) through modulation of Rictor expression. S6K in turn acted through a negative feedback loop to restrain Akt3 expression. Conversely, S6K signaling was increased in vascular tumor cells where Akt3 was silenced, and the growth of these tumor cells was inhibited by a novel S6K inhibitor. Overall, our findings offer a preclinical proof of concept for the therapeutic utility of treating vascular tumors, such as angiosarcomas, with S6K inhibitors., (©2014 American Association for Cancer Research.)

Vascular tumors are endothelial cell neoplasms whose cellular and molecular mechanisms, leading to tumor formation, are poorly understood, and current therapies have limited efficacy with significant side effects. We have investigated mechanistic (mammalian) target of rapamycin (mTOR) signaling in benign and malignant vascular tumors, and the effects of mTOR kinase inhibitor as a potential therapy for these lesions. Human vascular tumors (infantile hemangioma and angiosarcoma) were analyzed by immunohistochemical stains and western blot for the phosphorylation of p70 S6-kinase (S6K) and S6 ribosomal protein (S6), which are activated downstream of mTOR complex-1 (mTORC1). To assess the function of S6K, tumor cells with genetic knockdown of S6K were analyzed for cell proliferation and migration. The effects of topical rapamycin, an mTOR inhibitor, on mTORC1 and mTOR complex-2 (mTORC2) activities, as well as on tumor growth and migration, were determined. Vascular tumors showed increased activation of S6K and S6. Genetic knockdown of S6K resulted in reduced tumor cell proliferation and migration. Rapamycin fully inhibited mTORC1 and partially inhibited mTORC2 activities, including the phosphorylation of Akt (serine 473) and PKCα, in vascular tumor cells. Rapamycin significantly reduced vascular tumor growth in vitro and in vivo. As a potential localized therapy for cutaneous vascular tumors, topically applied rapamycin effectively reduced tumor growth with limited systemic drug absorption. These findings reveal the importance of mTOR signaling pathways in benign and malignant vascular tumors. The mTOR pathway is an important therapeutic target in vascular tumors, and topical mTOR inhibitors may provide an alternative and well-tolerated therapy for the treatment of cutaneous vascular lesions.

Tumors are composed of cancer cells but also a larger number of diverse stromal cells in the tumor microenvironment. Stromal cells provide essential supports to tumor pathophysiology but the distinct characteristics of their signaling networks are not usually considered in developing drugs to target tumors. This oversight potentially confounds proof-of-concept studies and increases drug development risks. Here, we show in established murine and human models of breast cancer how differential regulation of Akt by the small GTPase RhoB in cancer cells or stromal endothelial cells determines their dormancy versus outgrowth when angiogenesis becomes critical. In cancer cells in vitro or in vivo, RhoB functions as a tumor suppressor that restricts EGF receptor (EGFR) cell surface occupancy as well as Akt signaling. However, after activation of the angiogenic switch, RhoB functions as a tumor promoter by sustaining endothelial Akt signaling, growth, and survival of stromal endothelial cells that mediate tumor neoangiogenesis. Altogether, the positive impact of RhoB on angiogenesis and progression supercedes its negative impact in cancer cells themselves. Our findings elucidate the dominant positive role of RhoB in cancer. More generally, they illustrate how differential gene function effects on signaling pathways in the tumor stromal component can complicate the challenge of developing therapeutics to target cancer pathophysiology.

Objective: We evaluated the stages of VEGF-A(164) driven angiogenesis that are inhibited by therapeutic doses of rapamycin and the potential role of S6K1 in that response., Methods and Results: We assessed the effects of rapamycin on the several stages of angiogensis and lymphangiogenesis induced with an adenovirus expressing VEGF-A(164) (Ad-VEGF-A(164)) in the ears of adult nude mice. Rapamycin (0.5 mg/kg/d) effectively inhibited mTOR and downstream S6K1 signaling and partially inhibited Akt signaling, likely through effects on TORC2. The earliest stages of angiogenesis, including mother vessel formation and increased vascular permeability, were strikingly inhibited by rapamycin, as was subsequent formation of daughter glomeruloid microvasular proliferations. However, later stage formation of vascular malformations and lymphangiogenesis were unaffected. Retrovirally delivered isoforms and shRNAs demonstrated that S6K1 signaling plays an important role in early VEGF-A(164)-angiogenesis., Conclusions: Rapamycin potently inhibited early and mid stages of VEGF-A(164)-driven angiogenesis, but not late-stage angiogenesis or lymphangiogenesis. Rapamycin decreased phosphorylation of both Akt and S6, suggesting that both the TORC1 and TORC2 pathways are impacted. Inhibition of S6K1 signaling downstream of mTOR is a major component of the antiangiogenesis action of rapamycin.

Chronic activation of Akt signaling in the endothelium recapitulates the salient features of a tumor vasculature and can be inhibited by rapamycin, an inhibitor of mammalian target of rapamycin. This led to the hypothesis that the antitumor efficacy of rapamycin may be partially dependent on its ability to inhibit endothelial Akt signaling, making rapamycin an antiangiogenic agent and endothelial Akt pathway inhibitor. Dose-response studies with rapamycin showed that primary human endothelial cells and fibroblasts had a bimodal Akt response with effective reductions in phosphorylated Akt (pAkt) achieved at 10 ng/mL. In contrast, rapamycin increased pAkt levels in tumor cell lines. When tumor-bearing mice were treated with rapamycin doses comparable to those used clinically in transplant patients, we observed strong inhibition of mammary tumor growth. To test whether Akt activation in the endothelium was rate-limiting for this antitumor response, we engineered mouse mammary tumor virus-polyoma virus middle T antigen mice with endothelial cell-specific expression of constitutively activated Akt. We observed that the antitumor efficacy of rapamycin was reduced in the presence of elevated endothelial Akt activation. Just as we observed in MCF7 cells in vitro, rapamycin doses that were antiangiogenic resulted in increased pAkt levels in total mouse mammary tumor virus-polyoma virus middle T antigen tumor lysates, suggesting that tumor cells had an opposite Akt response following mammalian target of rapamycin inhibition compared with tumor endothelial cells. Together, these data support the hypothesis that endothelial Akt signaling in the tumor vasculature is an important target of the novel anticancer drug rapamycin.

Endothelial cells in growing tumors express activated Akt, which when modeled by transgenic endothelial expression of myrAkt1 was sufficient to recapitulate the abnormal structural and functional features of tumor blood vessels in nontumor tissues. Sustained endothelial Akt activation caused increased blood vessel size and generalized edema from chronic vascular permeability, while acute permeability in response to VEGF-A was unaffected. These changes were reversible, demonstrating an ongoing requirement for Akt signaling for the maintenance of these phenotypes. Furthermore, rapamycin inhibited endothelial Akt signaling, vascular changes from myrAkt1, tumor growth, and tumor vascular permeability. Akt signaling in the tumor vascular stroma was sensitive to rapamycin, suggesting that rapamycin may affect tumor growth in part by acting as a vascular Akt inhibitor.

Insulin inhibits apolipoprotein B (apoB) secretion by primary rat hepatocytes through activation of phosphoinositide 3-kinase (PI 3-K). Current studies demonstrate that the PI 3-K inhibitor wortmannin inhibits both basal and insulin-stimulated PI 3-K activities. Wortmannin and LY 294002, two structurally distinct PI 3-K inhibitors, prevent insulin-dependent inhibition of apoB secretion in a dose-dependent manner. To link PI 3-K activation to insulin action on apoB, we investigated whether insulin induced localization of activated PI 3-K to the endoplasmic reticulum (ER), where apoB biogenesis is initiated. Insulin action results in a significant redistribution of PI 3-K to a low density microsome (LDM) fraction containing apoB protein and apoB mRNA. Insulin stimulates a significant increase in PI 3-K activity associated with insulin receptor substrate-1 as well as an increase in insulin receptor substrate-1/PI 3-K mass in LDM. Subfractionation of LDM on sucrose density gradients shows that insulin significantly increases the amount of PI 3-K present in an ER fraction containing apoB. Insulin stimulates PI 3-K activity in smooth and rough microsomes isolated from rat hepatocytes, the latter of which contain rough ER as demonstrated by electron microscopy. Studies indicate that 1) PI 3-K activity is necessary for insulin-dependent inhibition of apoB secretion by rat hepatocytes; 2) insulin action leads to the activation and localization of PI 3-K in an ER fraction containing apoB; and 3) insulin stimulates PI 3-K activity in the rough ER.

Insulin inhibition of the secretion of apolipoprotein B (apo B) was studied in primary cultures of rat hepatocytes by using brefeldin A (BFA), an inhibitor of protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus, and by using the phosphatidylinositol 3-kinase (PI 3-K) inhibitor wortmannin. Incubation of hepatocytes with BFA (10 micrograms/ml) for 1 h inhibited the subsequent secretion of apo B, albumin and transferrin for up to 3 h. BFA treatment resulted in the time-dependent accumulation in cells of [14C]leucine-labelled proteins and apo B. Under conditions where insulin decreased total apo B (cell plus secreted), BFA blocked the insulin-dependent effect. These results suggest that export of apo B from the ER is a prerequisite for the observed insulin effect. Treatment of hepatocytes with wortmannin for 20 min abolished insulin inhibition of apo B secretion, suggesting that the insulin effect on the apo B pathway involves activation of PI 3-K. Enzyme inhibitor studies indicate that chymostatin and (+)-(2S,3S)-3-[(S)-methyl-1-(3-methylbutylcarbamoyl)-butylcarba moyl]-2- oxiranecarboxylate (E-64-c) partially block insulin effects on apo B compared with leupeptin, which had no discernible effect. The cell-permeable derivative of E-64-c, EST, and N-Ac-Leu-Leu-norleucinal (ALLN) were most effective in blocking insulin effects on apo B. These results suggest that insulin action on apo B in primary rat hepatocytes involves (1) vesicular movement of apo B from the ER; (2) activation of PI 3-K and (3) a cellular protease that is either a cysteine- or calcium-activated neutral protease.