The culture of doubt: Do medical students really experience clinical uncertainty when they should?

Uncertainty is a fundamental aspect of medical practice, necessitating incorporation into undergraduate medical training. The integrative model of uncertainty tolerance (UT) developed by Hillen and Han serves as a comprehensive framework for exploring clinical uncertainty. While studies have extensively examined UT dimensions, including sources, responses, and moderators, the factors influencing the perception of uncertainty stimuli remain underexplored. However, students' ability to perceive uncertainty and their approach to uncertain stimuli play a crucial role in enabling them to develop adaptive responses to uncertainty, necessary for their comfort in these situations. Defining uncertainty as a metacognitive state suggests significant variability in its perception among individuals and within an individual over time. Moreover, several studies have demonstrated the substantial influence of various individual and contextual factors on how individuals perceive and respond to uncertainty. In this paper, the authors present multiple hypotheses to address the question of whether students genuinely perceive uncertainty stimuli when they should. The authors argue that students' personal relationship with their knowledge is essential in their ability to identify clinical uncertainty, particularly concerning the limits of medical knowledge. Therefore, they propose that an academic culture fostering doubt, through exposing students to a variety of perspectives, would enhance their ability to identify uncertainty zones in a clinical situation at an early stage. Drawing on Dewey's situational theory, the authors emphasize the importance of better understanding, in a work setting, the influence of contextual and situational characteristics on individual perceptions of uncertainty. In line with this idea, ethnographic studies would offer valuable insights into identifying the relationship between the students, their work environment, and their perception of clinical uncertainty.

Interictal Cognitive Deficits in Migraine Sufferers: A Meta-Analysis.

While a significant proportion of the population suffer from migraine, the existing research literature does not provide a clear indication as to whether migraineurs experience objective cognitive deficits outside of acute migraine attacks. This meta-analysis was conducted to investigate which cognitive domains if any were affected by migraine, by synthesising the existing research quantitatively. The meta-analysis was prospectively registered with the PROSPERO International prospective register of systematic reviews (registration no.: CRD42019134138). A search of the electronic databases PubMed, Ovid MEDLINE, and PsycINFO was conducted for journal articles published between January 1980 and January 2020. Seventeen studies met the inclusion criteria, allowing for the calculation of pooled effect sizes between migraineurs (with and without aura) and healthy controls in the several cognitive domains. During the interictal period, migraineurs demonstrated a moderate, negative effect on complex attention immediate and delayed memory, spatial cognition, and executive functioning. This effect was not attributable to migraine history, attack frequency, or participant age. However, the lack of performance validity testing, and limited data on mood symptomatology and migraine medication use in the included studies may be confounds potentially overestimating the magnitude of effect. Comparison with a clinical control group, which may have accounted for some these extraneous variables, was unable to be conducted. Recommendations for comprehensive future neuropsychological research are provided.

Role of intravascular ultrasound imaging during endovascular interventions of failing hemodialysis access grafts.

BACKGROUND: Arteriovenous (AV) access graft complications represent a serious complication in patients undergoing hemodialysis. Angiography is one method of visualizing them. However, angiography is not always an effective means of detecting lesions that occur in this context. Intravascular ultrasound (IVUS) is an adjunct modality used to identify stenoses responsible for failing access by identifying multiple stenoses, including those that are most severe. The purpose of this study was to define the value of IVUS in patients with failing AV access grafts by comparing digital subtraction angiography (DSA) alone with DSA followed by IVUS. METHODS: This was a single-center randomized study comparing IVUS with DSA in patients with failing hemodialysis access grafts. It consisted of 100 randomized hemodialysis patients presenting with failing AV access who were being considered for endovascular intervention. Interventions in the control group were guided by DSA alone, whereas interventions in the test group were guided by DSA followed by IVUS. Patients were observed for 6 months after intervention. The primary end point was the time in days to AV access graft failure after the index intervention, expressed as median and interquartile range. Secondary analyses included influence of DSA and IVUS on index procedure decision-making and percentage of patients with AV access graft reinterventions or discontinuation through 3 and 6 months. RESULTS: Median time to first AV graft reintervention or discontinuation was 61 days in the test group and 30 days in the control group (P = .16), with analysis limited to patients who experienced reintervention or discontinuation (n = 59). IVUS resulted in a change in treatment plan in 76% (44/58) of patients, with no treatment change after IVUS in 24% (14/58) of patients. At 6 months, approximately 35% of patients in both the control and test groups remained free from reinterventions (P = .88). At 6 months, approximately 75% of patients in the control group and 80% of patients in the test group remained free from AV graft discontinuation or abandonment (P = .45). CONCLUSIONS: This pilot study suggests that addition of IVUS to standard angiography during endovascular interventions of failing hemodialysis access grafts holds potential to extend the time to the first reintervention. The data support the design and execution of an adequately powered randomized trial with longer follow-up to reliably discern the clinical benefit of IVUS as an addition to standard angiography in the setting of failing AV access grafts.

Mayer-Rokitansky-Küster-Hauser syndrome patients' interest, expectations and demands concerning uterus transplantation.

OBJECTIVE: To better understand patients' conditions and expectations before starting a uterus transplantation (UTx) program for women suffering from Mayer-Rokitansky-Küster-Hauser syndrome (MRKH syndrome). METHOD: A web-based survey was conducted among MRKH patients via the French national association network from March to August 2020. The questionnaire comprised twenty-eight questions about their desire for parenthood, their condition's characteristics and previous reconstructive procedures, opinions and knowledge about UTx. RESULTS: Among the 148 participants, 88 % reported a desire for parenthood, and 61 % opted for UTx as their first choice to reach this aim. The possibility of bearing a child and having the same genetic heritage were the main motivations. Once informed about the usual course of an UTx protocol, only 13 % of the participants changed their mind and 3 out of 4 of them opted for UT. CONCLUSION: Uterus transplantation seems to be the first option to reach motherhood in patients suffering from MRKH syndrome. The development of UTx programs could meet the demands of this already well-informed population.

Estimation of the prevalence of uterine infertility and its different causes in France according to data from a literature review.

INTRODUCTION: Uterine infertility (UI) is defined as the complete absence of a uterus (absolute uterine infertility or AUI) or the presence of a non functional uterus (non-absolute uterine infertility or NAUI). The exact prevalence of uterine infertility is currently unknown. Our aim was to assess the number of French women concerned by Uterine Infertility according to a recent literature review. MATERIALS AND METHODS: We have previously conducted a systematic review of the literature on UI and its various causes in the world. Based on these study and demographic data of 2022 from INSEE (Institut National de la Statistique et des Études Économiques), we attempted to estimate the number of women under 40 years of age in France affected by potential UI using direct standardization. RESULTS AND DISCUSSION: Based on the estimation from INSEE data, approximately 2066 women of childbearing age would have MRKH syndrome in France, 380 the Androgen Insensitivity Syndrome and 3700 had an haemostasis hysterectomy in France. We did not find data on the prevalence of hysterectomies before the age of 40 in France. For the following pathologies: uterine malformations, radiation uterus, synechiae, myomas and adenomyosis there was a huge amount of missing data, which does not allow us to estimate the number of potentially infertile patients. CONCLUSION: Prevalence of UI is poorly known. UI probably concerns several thousand patients in France. The creation of a UI registry would make enable to assess the number of patients potentially eligible for adoption, uterus transplantation or even surrogacy.

Improving Environmental Health in Schools.

School environmental conditions have immediate and long-term effects on student health and learning. Relying on disconnected, inconsistent, voluntary, or unenforced environmental standards has not resulted in sufficient protection of students from toxic insults. Furthermore, the United States public school system was not prepared to navigate a potentially deadly infectious disease like COVID-19. Although Department of Education agencies have policies to establish clean and safe learning spaces, deficiencies are evident. This article highlights common environmental challenges in schools and opportunities for improvement. Voluntary adoption of rigorous environmental policies by grassroots efforts alone is unlikely to occur in all school systems. In the absence of a legally enforced requirement, the dedication of sufficient resources to update infrastructure and build the environmental health workforce capacity is equally unlikely to occur. Environmental health standards in schools should not be voluntary. Science-based standards should be comprehensive, and part of an actionable, integrated strategy that includes preventive measures and addresses environmental health issues sustainably. Establishing an Integrated Environmental Management approach for schools will require a coordinated capacity-building effort, community-based implementation efforts, and enforcement of minimal standards. Schools will need ongoing technical support and training for staff, faculty, and teachers sufficient to enable them to assume greater oversight and responsibility for environmental management of their schools. Ideally, a holistic approach will include all environmental health components, including IAQ, IPM, green cleaning, pesticide and chemical safety, food safety, fire prevention, building legacy pollutant management, and drinking water quality. Thus, creating a comprehensive management system with continuous monitoring and maintenance. Clinicians who care for children can serve as advocates for children's health beyond their clinic walls by advising parents and guardians to be aware of school conditions and management practices. Medical professionals have always been valued and influential members of communities and school boards. In these roles they can greatly assist in identifying and providing solutions to reduce environmental hazards in schools.

Fibroblast growth factor-21 (FGF21) analogs as possible treatment options for diabetes mellitus in veterinary patients.

Fibroblast growth factors (FGFs) are involved in numerous metabolic processes. The endocrine subfamily of FGFs, consisting of FGF19, FGF21, and FGF23, might have beneficial effects in the treatment of diabetes mellitus (DM) and/or obesity. The analog with the greatest potential, FGF21, lowers blood glucose levels, improves insulin sensitivity, and induces weight loss in several animal models. In this review we summarize recent (pre)clinical findings with FGF21 analogs in animal models and men. Furthermore, possible applications of FGF21 analogs for pets with DM will be discussed. As currently, information about the use of FGF21 analogs in pet animals is scarce.

In which cases should endometrial destruction be performed during an operative hysteroscopy? Clinical practice guidelines from the French College of Gynaecologists and Obstetricians (CNGOF).

OBJECTIVE: To provide guidelines from the French College of Obstetricians and Gynaecologists (CNGOF), based on the best evidence available, concerning the impact of endometrial destruction on bleeding and endometrial cancer risk reduction in patients candidates for operative hysteroscopy. METHODS: Recommendations were made according to AGREE II and the GRADE® (Grading of Recommendations Assessment, Development and Evaluation) systems to determine separately the quality of evidence (QE) and in the level of recommendation. RESULTS: In a retrospective study comparing the incidence of endometrial cancer in 4776 patients with menorrhagia treated with endometrial destruction vs 229 945 patients with a medical treatment. There was a non-significant reduced risk of developing endometrial cancer (HR, 0.45; 95% CI, 0.15-1.40; p = .17). In premenopausal women, five studies compared the incidence of endometrial cancer in patients treated with endometrial ablation/destruction (EA/D) to the incidence of endometrial cancer in a comparable population of women from national registers, all of which show reduced risk of endometrial cancer after endometrectomy. In case of menopausal metrorrhagia, the prevalence of endometrial cancer is 9%, by analogy with the results found in premenopausal patients, the combination of endometrial ablation during operative hysteroscopy seems justified. In a retrospective cohort of 177 non-menopausal patients treated with myomectomy for metrorrhagia and/or menorrhagia, a significantly better control of bleeding at 12 months was found when myomectomy was combined with endometrectomy using roller-ball (OR: 0.18 [95% Cl 0.05-0.63]; p = 0.003). CONCLUSION: In premenopausal women with heavy menstrual bleeding, when an operative hysteroscopy is performed, it is recommended to propose an endometrial ablation/destruction in order to prevent the risk of endometrial cancer, (QE3) and to prevent recurrence of bleeding (QE2). In menopausal women, it is probably recommended to also perform an endometrial ablation/destruction in case of operative hysteroscopy in order to prevent the risk of endometrial cancer (QE1).

[Uterus transplantation, current prospect and future indications. State of art with review of literature]. / La transplantation utérine : essor de la technique chirurgicale, nouvelles indications. État de l'art avec revue de la littérature.

OBJECTIVES: The aim of this review is to summarize the development of UT on worldwide and to develop the new questions posed by this technique in 2020. METHODS: According to the PRISMA model, via Pubmed, we searched for publications containing the keywords: uterus transplantation; UT and cryopreservation from 2000 to 2020. RESULTS: At least 76 UTx have been carried out around the world and 19 healthy babies were born. The main indication remains the uterine agenesis (MRKH Syndrome>85% cases) then the history of hysterectomy (hemorrhage of the delivery or cervical cancer) and the non-functional uterus (Asherman's syndrome, diffuse adenomyosis). The 2 types of donors (living and deceased) are developed representing respectively 75% and 25% of the TU; the success rate in terms of return of rules is better in the living donor group and is 79% vs 68% in the deceased donor group. The choice of donor type must take into account the constraints of both procedures. Surgical complications (grade III) for the donor are estimated to be 14% mainly represented by ureter wounds. Technical simplifications concerning the venous return of the graft but also the carrying out of robot-assisted surgery would reduce the operating time for the donor and facilitate the collection process. CONCLUSION: TU is a complementary alternative to GPA and adoption allowing patients to be surrogates, legal and biological of the baby. An extension of the indications to patients with non absolute uterine infertility is in the process of democratization.

[Guidelines for Clinical Practice of the French College of Obstetricians and Gynecologists 2021: Prophylactic procedures associated with gynecologic surgery]. / Recommandations pour Pratique Clinique du Collège des Gynécologues Obstétriciens français 2021 : gestes prophylactiques associés en chirurgie gynécologique.

OBJECTIVE: To draw up recommendations on the use of prophylactic gynecologic procedures during surgery for other indications. DESIGN: A consensus panel of 19 experts was convened. A formal conflict of interest policy was established at the onset of the process and applied throughout. The entire study was performed independently without funding from pharmaceutical companies or medical device manufacturers. The panel applied the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system to evaluate the quality of evidence on which the recommendations were based. The authors were advised against making strong recommendations in the presence of low-quality evidence. Some recommendations were ungraded. METHODS: The panel studied 22 key questions on seven prophylactic procedures: 1) salpingectomy, 2) fimbriectomy, 3) salpingo-oophorectomy, 4) ablation of peritoneal endometriosis, 5) adhesiolysis, 6) endometrial excision or ablation, and 7) cervical ablation. RESULTS: The literature search and application of the GRADE system resulted in 34 recommendations. Six were supported by high-quality evidence (GRADE 1+/-) and 28 by low-quality evidence (GRADE 2+/-). Recommendations on two questions were left ungraded due to a lack of evidence in the literature. CONCLUSIONS: A high level of consensus was achieved among the experts regarding the use of prophylactic gynecologic procedures. The ensuing recommendations should result in improved current practice.

Management of borderline ovarian tumours during pregnancy: Results of a French multi-centre study.

OBJECTIVE: To assess the diagnostic and prognostic characteristics of borderline ovarian tumours (BOTs) detected during pregnancy, and to establish an inventory of French practices. MATERIALS AND METHODS: A retrospective multi-centre case study of 14 patients treated for BOTs, diagnosed during pregnancy between 2005 and 2017, in five French pelvic cancerology expert centres, including data on clinical characteristics, histological tumour characteristics, surgical procedure, adjuvant treatments, follow-up and fertility. RESULTS: The mean age of patients was 29.3 [standard deviation (SD) 6.2] years. Most BOTs were diagnosed on ultrasonography in the first trimester (85.7 %), and most of these cases (78.5 %) also underwent magnetic resonance imaging to confirm the diagnosis (true positives 54.5 %). Most patients underwent surgery during pregnancy (57 %), with complete staging surgery in two cases (14.3 %). Laparoscopy was performed more frequently than other procedures (50 %), and unilateral adnexectomy was more common than cystectomy (57.5 %). Tumour size influenced the surgical approach significantly (mean size 7.5 cm for laparoscopy, 11.9 cm for laparoconversion, 14 cm for primary laparotomy; P = 0.08), but the type of resection did not. Most patients were initially diagnosed with International Federation of Gynecology and Obstetrics stage IA (92.8 %) tumours, but many were upstaged after complete restaging surgery (57.1 %). Most BOTs were serous (50 %), two cases had a micropapillary component (28.5 %), and one case had a micro-invasive implant. BOTs were bilateral in two cases (14.2 %). Mean follow-up was 31.4 (SD 14.8) months. Recurrent lesions occurred in two patients (14.2 %) and no deaths have been recorded to date among the study population. CONCLUSION: BOTs remain rare, but this study - despite its small sample size - supports the hypothesis that BOTs during pregnancy have potentially aggressive characteristics.

[Borderline Ovarian Tumours: CNGOF Guidelines for Clinical Practice - Value of Tumor Markers]. / Tumeurs frontières de l'ovaire. Recommandations pour la pratique clinique du CNGOF ­ Pertinence des marqueurs tumoraux.

OBJECTIVES: To evaluate the diagnostic value of serum biomarkers in the management strategy of borderline ovarian tumours (BOT) to make management recommendations. METHODS: English and French review of literature from 1990 to 2019 based on publications from Pubmed, Medline, Cochrane, with keywords: borderline ovarian tumors, tumour markers, CA125, CA19 9, ACE, CA72 4, TAG72, HE4, ROMA, mucinous, serous, mucinous, endometrioid ovarian tumours, peritoneal implants, recurrence, overall survival, follow-up. Among 1000 references, 400 were selected and only 30 were screened for this work. RESULTS: Literature review: there is low evidence in literature concerning the discriminating value of serum tumour biomarkers (CA125, CA19-9, CEA, CA72-4, HE4) and specific score between presumed benign ovarian tumour/BOT/ovarian cancer (LE4). Serum CA125 antigen is higher in case of serous borderline ovarian tumour (LE4), increase with the tumor height, the FIGO stage, notably in case of serous borderline ovarian tumor. However, a normal value rate of serum CA125 antigen does not rule out a BOT (LE4). The preoperative positivity rate of CA19 9 in case of TFO is relatively lower than that of CA125 and is higher in mucinous TFO. The preoperative rate of serum CA19 9 antigen increases with the tumour height and the FIGO stage (LE4) and are higher in case of mucinous BOT (LE4). Preoperative rates of serum HE4 are not different between histologic type of BOT. A high level of serum biomarkers (CA125) is a predictive factor of peritoneal implants (LE4) and an independent predictive factor of recurrence (CA125) (LE4). RECOMMENDATIONS: no recommendation can be made about the use of serum tumour biomarkers (CA125, CA19-9, CEA, CA72-4, HE4) or specific score in order to distinguish benign ovarian tumor/borderline ovarian tumor/ovarian cancer in case of indeterminate mass. In case of suspicion of mucinous ovarian tumour on imaging, the systematic dosage of serum CA19-9 antigen can be proposed (grade C). In case of an ovarian indeterminate mass on imaging; dosage of serum HE4 and C125 is recommended. If preoperative dosage of serum tumor biomarkers is normal, their systematic dosage is not recommended in the follow-up of BOT (grade C). If preoperative dosage of CA125 is high, the systematic dosage of CA125 is recommended in the follow-up of BOT with no precisions about the rhythm and the duration of the follow-up (grade B).

[Guidelines for surgical management of gynaecological cancer during pandemic COVID-19 period - FRANCOGYN group for the CNGOF]. / Prise en charge chirurgicale des cancers gynécologiques en période de pandémie COVID-19 ­ Recommandations du Groupe FRANCOGYN pour le CNGOF.

INTRODUCTION: Recommendations for the management of patients with gynecological cancer during the COVID-19 pandemic period. MATERIAL AND METHOD: Recommendations based on the consensus conference model. RESULTS: In the case of a COVID-19 positive patient, surgical management should be postponed for at least 15 days. For cervical cancer, the place of surgery must be re-evaluated in relation to radiotherapy and Radio-Chemotherapy-Concomitant and the value of lymph node staging surgeries must be reviewed on a case-by-case basis. For advanced ovarian cancers, neo-adjuvant chemotherapy should be favored even if primary cytoreduction surgery could be envisaged. It is lawful not to offer hyperthermic intraperitoneal chemotherapy during a COVID-19 pandemic. In the case of patients who must undergo interval surgery, it is possible to continue the chemotherapy and to offer surgery after 6 cycles of chemotherapy. For early stage endometrial cancer, in case of low and intermediate preoperative ESMO risk, hysterectomy with bilateral annexectomy associated with a sentinel lymph node procedure should be favored. It is possible to consider postponing surgery for 1 to 2 months in low-risk endometrial cancers (FIGO Ia stage on MRI and grade 1-2 endometrioid cancer on endometrial biopsy). For high ESMO risk, it ispossible to favor the MSKCC algorithm (combining PET-CT and sentinel lymph node biopsy) in order to omit pelvic and lumbar-aortic lymphadenectomies. CONCLUSION: During COVID-19 pandemic, patients suffering from cancer should not lose life chance, while limiting the risks associated with the virus.

Synchrotron infrared reflectivity measurements of iron at high pressures.

The infrared reflectance of iron was studied using high-pressure synchrotron radiation methods up to 50 GPa at room temperature in a diamond anvil cell of 1000-8000 cm(-1) (1.25-10 microm). The magnitude of the reflectivity shows a weak pressure dependence up to the transition from the body centered cubic (alpha) to hexagonal close packed (epsilon) phase transition, where a discontinuous change in both the slope and magnitude of the reflectivity was observed. Reflectance spectra were corrected for diamond absorption and treated with a Kramers-Kronig analysis to extract the optical constants; the emissivity of iron was derived from Kirchoff's law. The pressure and wavelength dependence of the emissivity is characterized by an empirical function for 1.5-1.9 microm; this wavelength range is useful for spectroradiometric temperature measurements from 1000 K up to approximately 2500 K. Alpha-Fe is a nonideal emitter; however, epsilon-Fe behaves as an almost perfect greybody in the infrared up to the highest pressures of the measurements. Temperature measurements based on the spectroradiometry of iron samples should take into account the wavelength dependent emissivity below the alpha-epsilon phase transition at approximately 13 GPa.

Tumor-promoting phorbol esters inhibit procollagen synthesis at a pretranslational level in JB-6 mouse epidermal cells.

Collagen synthesis was inhibited in JB-6 mouse epidermal cells after exposure to 12-O-tetradecanoylphorbol-13-acetate under conditions leading to irreversible neoplastic transformation. In vitro translation and hybridization studies demonstrated a dramatic decrease in collagen mRNA in 12-O-tetradecanoylphorbol-13-acetate-treated cells, suggesting that the inhibition of collagen synthesis in response to 12-O-tetradecanoylphorbol-13-acetate is due to regulation at a pretranslational level.

[Pap smear before 25 years old]. / La pratique du frottis cervico-vaginal avant 25 ans.

OBJECTIVES: Current French recommendations advocate cervical-vaginal screening for cervical cancer from age 25 whereas earlier screening is mostly found in current clinical practice although its consequences are not well understood. METHODS: A literature review using the MedLine database on the natural history of HPV infections, cytological screening, management of cytological and histological anomalies in adolescents and young women. RESULTS: The adolescent and young woman have some characteristics that distinguish them from adult women: a high prevalence of HPV infections (making the use of the HPV test unprofitable), accompanied by a higher clearance; frequency of minor cytological abnormalities (for which a cytological surveillance without colposcopy is sufficient) and low-grade histological lesions of low grade the usual prognosis of which is complete recovery; and rarity of CIN3 lesions and absence of invasive lesions, allowing no treatment in patients with CIN2 lesions and compliant to cytological and colposcopic surveillance. CONCLUSION: Cervical screening in the adolescent and young woman is not a logical attitude and the discovery of cytological or histological lesions requires specific behavior in this particular population.

Vitamin A-induced density-dependent inhibition of L-cell proliferation.

Retinoic acid, the acid form of vitamin A, was found to have an inhibitory effect on the proliferation of L-929 mouse cells. Cultures treated with retinoic acid (5.0 mug/ml) were shown to cease proliferation at cell densities corresponding to confluent monolayers (10.0+/-1.0 X 10(4) cells/cm2). Control cultures, however, continued to proliferate and consistently reach densities two to four times higher than those of treated cultures. Viability was determined by trypan blue exclusion, and the results (80-90 percent viable) excluded cytotoxicity as an explanation of decreased proliferation. Replenishing the medium on confluent retinoic acid-treated cultures failed to stimulate further proliferation, while control cells continued to grow exponentially with each medium change. Therefore, the cessation of cell proliferation at confluence did not result from medium depletion. Studies of cell growth after seeding at relatively low cell densities have indicated that retinoic acid-treated cultures had greater nutritional requirements than did control cultures. Cell-cloning experiments have shown that DNA synthesis was not blocked, since clones formed by cells seeded with retinoic acid contained an average of 27 cells after 9 days of incubation (indicating between four and five cell divisions). However, clones developing from treated cells had fewer cells per clone (27 vs. 54) and were less dense than control clones. These data suggested the restoration of contact inhibition (topoinhibition) to L-929 cells treated with retinoic acid.

Inhibition by tumor-promoting phorbol esters of procollagen synthesis in promotable JB6 mouse epidermal cells.

The JB6 mouse epidermal cell line has been developed to study promotion of neoplastic transformation in vitro. Treatment of JB6 cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) or other tumor promoters resulted in the irreversible acquisition by JB6 cells of tumorigenicity in nude mice and anchorage-independent growth in soft agar. As previously reported, one of the biochemical responses that occurs during TPA treatment is a greater than 75% reduction in a mannose-labeled glycoprotein with an apparent molecular weight of 180,000. This TPA-sensitive glycoprotein has now been identified on the basis of collagenase and pepsin sensitivity as procollagen pro-alpha 1(I) chain. [3H]proline labeling also demonstrated a parallel decrease in the 150,000 procollagen pro-alpha 2(I) component. Two nonphorbol promoters, mezerein and epidermal growth factor, were also active in decreasing procollagen synthesis. Promotion-sensitive and promotion-resistant clonal derivatives of JB6 showed similar basal levels of collagen synthesis as well as similar degrees of TPA-dependent procollagen loss indicating that the collagen decrease may be necessary but is not sufficient to produce the promotion response. Comparison of chemically transformed mouse epidermal cell lines with paried nontransformants suggests the reduced procollagen synthesis is a stably acquired phenotypic change and may therefore be involved in maintenance of the transformed phenotype as well as in its induction.

Four-day duration of tumor promoter exposure required to transform JB6 promotion-sensitive cells to anchorage independence.

The JB6 mouse epidermal cell lines have been developed to study promotion of neoplastic transformation in vitro. Treatment of JB6 cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) at 1 to 100 ng/ml results in the irreversible acquisition of tumorigenicity in nude mice and anchorage-independent growth. Among the biochemical responses which occur during TPA treatment is a decrease in procollagen synthesis. During a study of the possible role of H2O2 in the process of promotion, it was observed that catalase purchased commercially would inhibit TPA promotion as well as the reduction of collagen synthesis in a dose-dependent manner. A highly purified catalase preparation failed to demonstrate the TPA blocking activity, suggesting that this activity was due to a contaminating factor. We have separated the TPA blocking factor from the catalase itself using concanavalin A affinity chromatography. The factor is a Mr 60,000 glycoprotein showing TPA hydrolase activity. The enzyme, which is similar to a murine liver-derived TPA hydrolase, produces a single phorbol product from TPA that has been identified as phorbol-13-acetate. TPA hydrolase was used to terminate TPA action in soft agar. This made it possible to establish that approximately 4 days of exposure to phorbol esters are required for promotion of transformation in the JB6 model system.