Specialist nurse in Europe: education, regulation and role.

BACKGROUND: The concept of a 'specialist nurse' has existed for many years and related education programmes are proliferating. However, while literature clearly outlines the roles and practice of registered nurses and advanced practice nurses, those of specialist nurses remain unclear and nursing specializations across Europe need clarifying. AIM: This pilot study aimed to explore the competencies, education requirements and regulation of specialist nurses in Europe. DESIGN: A descriptive cross-sectional survey. METHODS: An online questionnaire named 'Specialist nurse and specialization in Europe' was sent to 550 members of the European Federation of Nurse Educators and ten members of the European Specialist Nurses Organizations. Snowball sampling was then used to build a convenience sample of nurse educators, clinical nurses and specialist nurses, national nursing association members, and chief nursing officers from all European countries. Besides quantitative aspects, responses to open-ended questions were analysed using a qualitative content analysis process. RESULTS: A total of 77 experts from 29 European countries responded to the questionnaire. Findings highlighted variations in titles, levels and length of education, certification, regulation and scope of practice for specialized nurses in Europe. Analysis of the promoted competencies revealed dominant clinical and technical aspects of the role with a high level of knowledge. CONCLUSIONS: The study emphasized the need to improve standards for education, certification and regulation for specialist nurses. Interpretation of the role and competencies is diverse with a weak presence of health policy that would enhance and develop the specialities. IMPLICATIONS FOR NURSING AND HEALTH POLICY: To address the current lack of provisions for automatic recognition of specialist nurses, common training frameworks corresponding to the relevant level of the European Qualifications Framework should promote lifelong learning and mobility, and enhance levels of health care and patient safety.

Postgraduate training in surgery: From theory to practice.

INTRODUCTION: Postgraduate training is a time-honored entity, the goal of which was to develop and ensure the acquisition of new medical knowledge for the medical profession. MATERIAL AND METHODS: The main goal of this retrospective study is to analyze the current situation of postgraduate training in surgical disciplines within the framework of the French Universities. We studied the legal texts found in the LéxisNéxis® and Légifrance® sites up until December 1, 2018; references were sought from the Web of Science repository. RESULTS: Postgraduate training in France is mandatory from the legal point of view. Currently there are two possibilities for validation of postgraduate training: either through a recognized continuing professional development (CPD) organization controlled by the National Agency of Continuing Professional Development (NACPD), or by asking for certification through an official accreditation council (AC) (one exists for each surgical specialty), controlled by the High Health Authority that can automatically provide the equivalence of passing through the NACPD organization. DISCUSSION: The continuing education process remains complex. It could well be modified in the near future by the creation of a new certification procedure. With regard to surgical education, whether it concerns the CPD or the accreditation process, the goal is to decrease patient risk and to be an integral part of the overall policy to decrease health care costs. The role of professional national counsels will be more and more important; this is an advantage for each of the surgical specialties. Nonetheless, from the regulatory viewpoint, the decree concerning the role of National Professional Councils has not yet been published in the Journal Officiel de la République Française (French Republic official journal) at the time of writing. CONCLUSIONS: Currently two systems are available for surgeons to comply with the 2016 legislative obligation of continuing education: CPD which is run by the NACPD, and the accreditation process, run by an AC and controlled by the HAS; in the first instance, surgeons can ask for reimbursement from the NACPD and in the second, request that the National Health Insurance Fund for Salaried Employees cover a portion of the litigation insurance premium. LEVEL OF EVIDENCE: Retrospective study: level of evidence IV.

No-go decision: A newly identified adverse event in orthopaedic surgery - causes and medico-legal implications.

BACKGROUND: No-go designates a decision not to perform surgery when it becomes apparent that safety and/or feasibility requirements are not met. No-go decisions can occur at any time between patient admission to a hospital department and immediately before the first incision. The primary objective of this study was to assess the causes of no-go decisions reported as healthcare-associated adverse events (HAAEs). HYPOTHESIS: Most no-go decisions in orthopaedic surgery are related to problems with medical devices. MATERIAL AND METHODS: A preliminary retrospective study assessed HAAEs reported over the 1-year period from 1st October 2014 to 30th September 2015, using the risk-management tool ALARM. A prospective survey was then performed by emailing a 15-item questionnaire to the 1828 members of Orthorisq (the French orthopaedic surgeon accreditation agency). Responses were either yes/no or open. Statistical comparisons were performed, using the paired Wilcoxon signed-rank test to estimate p values. RESULTS: Among reported HAAEs, 5.6% were no-go decisions. Of the 101 reported no-go decisions, 43.5% and 45.2% were due to problems with managing implantable medical devices in the retrospective and prospective assessments, respectively. In over 85% of cases, surgery was cancelled or postponed. Over half the no-go decisions were associated with unnecessary anaesthesia. Checklist completion was performed in only half the cases and was not associated with no-go decisions (p>0.8). DISCUSSION: This study provides descriptive data on no-go decisions in orthopaedic surgery. Healthcare professionals use many methods to enhance patient safety by preventing adverse events or diminishing their impact. Errors in managing implantable medical devices are the leading cause of no-go decisions. The current checklist is not appropriate for managing implantable medical devices in orthopaedic surgery, in part because it does not include checking devices upon receipt. Before surgery, patients should be informed of the risk of a no-go decision, since unnecessary anaesthesia occurs in over half the cases. LEVEL OF EVIDENCE: IV, prospective study.

The concept of a waiting period for preoperative patient consent: Prospective study of 51 shoulder arthroscopy cases.

INTRODUCTION: The French Code of Public Health (CSP) does not explicitly require that patients should be given a certain amount of time to think about a procedure, except for cosmetic surgery, where 15 days is required (Art. L 6322-2 CSP). We hypothesized that patients require a waiting period during their decision-making process for scheduled shoulder arthroscopy procedure. MATERIALS AND METHODS: This prospective observational study of 51 patients analysed the concept of a waiting period based on a 10-item questionnaire. A comparative statistical approach was used and the P values were calculated using a paired Wilcoxon rank-sum test. RESULTS: Of the 51 patients, 42 (82%) rejected the concept of a waiting period before the procedure and 37 patients (73%) did not want a mandatory waiting period imposed by law. DISCUSSION: This study looked at the decision-making process during scheduled orthopaedic surgery and differentiated between the conscious and unconscious approach corresponding to an active and passive waiting period. A waiting period does not allow patients to make a conceptually deliberative decision that conforms to the criteria defined by the French Health Authority. This study rejects the need for a mandatory waiting period imposed on surgeons and patients as it does not integrate itself into the informative model of ethical decision-making for scheduled shoulder arthroscopy. TYPE OF STUDY: Prospective, observational; level of evidence IV.

Expression and localization of alpha-fetoprotein mRNA and protein in human early villous trophoblasts.

Alpha-fetoprotein (AFP) is a major plasma protein produced during human fetal life. It is a good marker for several possible disorders affecting gestation. We previously reported that afp gene expression, which takes place mainly in yolk sac and fetal liver, also occurs in normal human placenta, specifically in early pregnancy. The aim of the present study was to determine the precise location of AFP synthesis sites within the placental villi. In situ hybridization and immunohistochemical experiments were performed on sections obtained from placentas of first-trimester and full-term pregnancies. We found that the pattern of afp gene expression was restricted to specific villous trophoblastic areas in early placentas. Both afp transcripts and AFP protein were mainly located in discontinuous regions, at junctions between two villi and at budding sites. In contrast, no AFP expression was detected in the cytotrophoblastic extravillous proliferative zone or in other placental cell types. According to the earlier studies, no AFP synthesis was detected in placental villous tissue from full-term pregnancies, using in situ hybridization and immunohistochemistry.

Phorbol esters down-regulate alpha-fetoprotein gene expression without affecting growth in fetal hepatocytes in primary culture.

The effects of phorbol esters (phorbol-12,13-dibutyrate, PDB) on alpha-fetoprotein expression and cell growth were assayed by using fetal hepatocytes in primary culture. PDB acts synergistically with epidermal growth factor (EGF) to specifically decrease alpha-fetoprotein (AFP) mRNA levels, without affecting the expression of other genes of the same family, such as albumin and Vitamin D-binding protein (DBP). This effect is PDB-dose dependent, maximal effects being at 10 ng/ml. The implication of protein kinase C (PKC) in this effect seems clear since bisindolylmaleimide (BIS), a specific PKC inhibitor, completely blocks the PDB effect on AFP expression. Nuclear run-on experiments show that the decrease in AFP mRNA levels is mainly due to an inhibition in the transcription rate of the gene. Determination of PKC activities shows that fetal hepatocytes contain mainly Ca(2+)-independent isoenzymes, which patterns of activation was not modified by EGF plus PDB treatment with respect to PDB treatment. We have found that MAPK and JNK activities, c-jun and c-fos mRNA levels and AP-1 binding activity are notably increased when cells are incubated with both EGF and PDB, PDB does not stimulate growth of fetal hepatocytes, measured either as [3H]-thymidine incorporation into DNA or by cell cycle analysis using flow cytometry. All these results suggest that activation of PKC may affect liver gene expression rather than cell growth in fetal hepatocytes.

Rat yolk sac explants as a system for studying the regulation of endodermal genes: down-regulation of the alpha-fetoprotein gene by dexamethasone and phorbol ester.

The visceral yolk sac is a fetal membrane with essential placental functions. It is the major site of synthesis of alpha-fetoprotein (AFP), the most abundant plasma protein in the fetus. We developed a system of rat yolk sac explants in serum-free culture medium to study the regulation of endodermal gene expression in yolk sac. The explanted yolk sac tissues retained their double-sided morphology for up to 48 hours. The epithelial cells of both layers remained tightly joined on a basement membrane as seen by light and electron microscopy. This probably accounts for the continued expression of several endodermal cell-specific markers. The levels of mRNA encoding AFP, vitamin D-binding protein (DBP), hepatocyte nuclear factor 1alpha and beta transcription factors did not change during the 48-hour culture period. This reflects the stability of the differentiation state of the yolk sac endodermal cells. Dexamethasone and phorbol ester (TPA) specifically reduced the AFP mRNA level without affecting that of DBP. This suggests that these transduction pathways are functional in the yolk sac during this period of gestation and could be involved in the physiological down-regulation of AFP gene expression before birth. All these results show that this serum-free culture of rat yolk sac explants is a valuable system for further investigating the action of natural compounds and pharmacological drugs on endodermal gene expression during the embryonic and fetal periods.

In rat uterus 17 beta-estradiol stimulates a calcium-binding protein similar to the duodenal vitamin D-dependent calcium-binding protein.

A calcium-binding protein (CaBP) similar to rat duodenal vitamin D-dependent CaBP was identified in rat uterus. Uterine CaBP and duodenal CaBP had the same mol wt (9,000-10,000), exhibited the same calcium-dependent electrophoretic mobility, and were immunologically identical. The localization of CaBP in the rat uterus was explored using indirect immunoperoxidase methods, and by CaBP RIA in the endometrium and myometrium after enzyme separation. In the endometrium CaBP was found in the cytoplasm of the stroma cells but not in the epithelium or in the glandular cells. In the myometrium, it was located inside the smooth myometrial fibers. Hormonal regulation of CaBP was shown to differ in the uterus and duodenum. Duodenal CaBP concentrations increased in response to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and were not influenced by ovariectomy or sex steroids administration. By contrast, CaBP synthesis fell drastically in the uterus of ovariectomized rats, but was greatly enhanced by low physiological doses of 17 beta-estradiol. This effect of 17 beta-estradiol on uterine CaBP was dose dependent. Medroxyprogesterone and more especially 1,25(OH)2D3 exerted no such stimulating effect on uterine CaBP. In vitamin D-deficient ovariectomized rats, administration of 17 beta-estradiol alone restored the uterine CaBP concentrations to normal and this potency contrasted with the apparent inability of 1,25(OH)2D3 to affect the uterine CaBP concentrations. Our data suggest that, unlike duodenal CaBP regulation, the expression of the CaBP gene in rat uterus is predominantly controlled by 17 beta-estradiol.

Presence of immunoreactive vitamin D-binding protein in rat yolk sac endodermal cells.

The visceral yolk sac is, in the rat, an organ which possesses true placental functions. We recently showed that yolk sac is involved in the control of metabolism and action of vitamin D in the fetoplacental unit, since its endodermal cells contain a 24-hydroxylase for vitamin D metabolites and the 1,25-dihydroxyvitamin D receptor. In the present work, by using indirect immunoperoxidase staining, we demonstrate that an immunoreactive vitamin D-binding protein (DBP) is present in this yolk sac throughout embryonic and fetal development. It is mainly located at the apex of the endodermal cells. Immunoprecipitation studies of radioactive proteins synthesized in vitro by yolk sac explants showed that yolk sac DBP, in contrast to alpha-fetoprotein, is not synthesized in situ by yolk sac. This result, combined with the location of DBP at the apex of the endodermal cells which face the uterus, strongly suggests that yolk sac DBP is of maternal origin. The concomitant presence in the endodermal cells of this DBP, of the 1,25-dihydroxyvitamin D receptor, and of the system hydroxylating vitamin D metabolites in position 24, certainly has considerable physiological significance.

Alpha-fetoprotein gene expression in early and full-term human trophoblast.

Alpha-fetoprotein (AFP) is a major serum glycoprotein synthesized during fetal life mainly by the yolk sac and the fetal liver. At term, it reaches high concentrations in the maternal intervillous blood, which is in direct contact with the placental trophoblastic microvillous membrane, and this suggests the placental origin of the AFP at the fetal-maternal interface. We used several experimental approaches to investigate the expression of AFP gene and fetal protein production in early gestation and term placentas. RT-PCR and immunological studies clearly identified AFP messenger RNA and AFP protein in the placental villi from first trimester of pregnancy. The AFP gene was also expressed in highly purified cytotrophoblasts from early placentas, and enzymo-immunoassay showed that AFP protein was synthesized and secreted by early cytotrophoblasts. AFP was also detected in the cytoplasm of these cells by immuno-cytochemistry. However, none of these methods detected any expression of the AFP gene in full-term placental villi or in cultured trophoblasts. These findings demonstrate that both AFP mRNA and protein are present in trophoblastic cells early in pregnancy. The absence of AFP gene expression in term placental villi also suggests, that the AFP at the fetal-maternal interface is attributable to a notable transplacental passage of AFP from fetal blood in late pregnancy.

Chicken ovalbumin upstream promoter-transcription factor, hepatocyte nuclear factor 3, and CCAAT/enhancer binding protein control the far-upstream enhancer of the rat alpha-fetoprotein gene.

We have further characterized the most distal of the three alpha-fetoprotein (AFP) enhancers required for expression of the AFP gene in fetal hepatocytes and yolk sac endodermal cells. Almost total rat AFP enhancer 3 (E3) activity is driven by a 160-bp fragment at -6 kb containing three target regions for nuclear proteins that cooperate to stimulate transcription from the AFP and the thymidine kinase promoters in HepG2 hepatoma cells. Region 1, recently shown to be crucial for correct function of the enhancer in liver of transgenic mice, is recognized by two sets of transcription factors that bind to partly overlapping sites, 1a and 1b, in a noncooperative and nonexclusive manner. Site 1a contains a motif, AGGTCA, which is recognized by chicken ovalbumin upstream promoter transcription factors (COUP-TFs), but not by hepatocyte nuclear factor 4. Hepatocyte nuclear factor 3 (HNF3) and CCAAT/enhancer binding protein (C/EBP), which bind to regions 2 and 3, respectively, are likely responsible for the liver-specific E3 action. They play a key role by acting in synergy. The participation of nuclear receptors such as COUP-TFs, with C/EBP and HNF3, in the tight control of the distal AFP enhancer is a new, and perhaps key, step toward understanding the regulation and function of this enhancer, which may remain active throughout development.

Modulation of the far-upstream enhancer of the rat alpha-fetoprotein gene by members of the ROR alpha, Rev-erb alpha, and Rev-erb beta groups of monomeric orphan nuclear receptors.

Expression of the oncodevelopmental alpha-fetoprotein (AFP) gene is tightly regulated and occurs in the yolk sac, fetal liver and intestine, and cancerous liver cells. Transcription of the AFP gene is under the control of three enhancers that are very tissue specific. We have shown that the most upstream of these enhancers, located at -6 kb, works through the combined action of liver-enriched factors and nuclear receptors that bind to three regions of this DNA regulatory element. This study showed that orphan nuclear receptors of the ROR alpha, Re-verb alpha, and Rev-erb beta groups can bind as monomers with high affinity and specificity to an evolutionarily conserved AGGTCA motif in the functionally important region 1 of this AFP enhancer. Transient transfection experiments performed with human HepG2 hepatoma cells showed that overproduction of ROR alpha 4 stimulated the activity of the AFP enhancer in a dose-dependent manner, while that of Rev-erb alpha and Rev-erb beta had the opposite effect. These effects were highly specific and required the integrity of the AGGTCA motif. The action of these nuclear receptors also occurred in the context of the entire 7-kb regulatory region of the rat AFP gene. These results suggest that altering the amounts or activities of these orphan receptors in cells of hepatic or endodermal origin could modulate AFP gene expression in response to a variety of developmental or carcinogenic stimuli.

Regulation of alpha-foetoprotein gene expression by fatty acids and fibrates.

Alpha-foetoprotein (AFP), the major plasma protein in the foetus, is mainly synthesized by yolk sac and foetal liver. It binds polyunsaturated fatty acids and probably controls their metabolism and action. We investigated the effects of fatty acids and fibrates on expression of the AFP gene using two complementary approaches. Treatment with 5-8-11-14 eicosatetraynoic acid (ETYA), an analogue of arachidonic acid, specifically led to lower AFP mRNA levels in cultured rat yolk sac explants whereas treatment with palmitic or oleic acid did not. Clofibric acid and fenofibrate also gave lower AFP mRNA levels. Transient transfection experiments with HepG2 hepatoma cells showed that ETYA and clofibric acid decreased the transcriptional activity of the 7 kb regulatory region of the rat AFP gene. The 330 bp AFP promoter was identified as a target for these down regulating effects.

[Several transcription factors participate in the functioning of the alpha-fetoprotein gene promoter]. / Plusieurs facteurs de transcription participent au fonctionnement du promoteur du gène alpha-foetoprotéine.

The oncodevelopmentally regulated alpha-fetoprotein (AFP) gene offers a very good model system to better understand the molecular mechanisms which dictate the specificity of gene expression in liver and control its tight modulation in the course of development and carcinogenesis. Transcription factors of the CCAAT/enhance-binding protein (C/EBP), hepatocyte nuclear factor-1 (HNF-1), and nuclear factor-1 (NF-1) families can bind in vitro to the promoter of the rat AFP gene, which makes the expression of the AFP gene specific to the liver. We have evaluated the influence of some of these factors on the activity of the AFP promoter by transfection of HepG2 hepatoma cells with the appropriate expression vector plus a CAT plasmid under the control of the AFP promoter. A similar plasmid bearing the rat albumin promoter was used as a control. C/EBP alpha, and C/EBP beta acted as transactivators on the AFP promoter, while LIP, a truncated form of C/EBP beta, was a potent negative regulator of the promoter. Interestingly, HNF-1 beta was found to be more potent than HNF-1 alpha in activating the AFP promoter in the HepG2 cells. This effect was highly promoter and cell specific since it did not occur with the rat albumin promoter or in Chinese hamster ovary cells. HNF-1 beta, which is produced earlier than HNF-1 alpha during liver development, would thus have the greater influence on the AFP promoter in early development. Our results pointed to a key role that NF1 might play in the functioning of the AFP promoter. Indeed, overexpression of NF1 induced a specific decrease in the activity of the AFP promoter. Competition between NF1 and HNF-1 for binding to their overlapping binding sites on the AFP promoter would be critical for modulating its activity.

Members of the CAAT/enhancer-binding protein, hepatocyte nuclear factor-1 and nuclear factor-1 families can differentially modulate the activities of the rat alpha-fetoprotein promoter and enhancer.

The promoter of the rat alpha-fetoprotein (AFP) gene, which makes the expression of the developmentally regulated AFP gene specific to the liver, is a putative target for transcription factors of the CAAT/enhancer-binding protein (C/EBP), hepatocyte nuclear factor-1 (HNF-1) and nuclear factor-1 (NF-1) families. We have evaluated the influence of these factors on the activity of the AFP promoter by transfection of HepG2 hepatoma cells with the appropriate expression vector plus a CAT plasmid under the control of the AFP promoter. A similar plasmid bearing the rat albumin promoter was used as a control. C/EBP alpha, C/EBP beta and D-binding protein (DBP) acted as trans-activators on the AFP promoter, whereas liver inhibitory protein (LIP), a truncated form of C/EBP beta, was a potent negative regulator of the promoter. C/EBP alpha also bound to and stimulated the activity of the AFP enhancer at -2.5 kb. Interestingly, HNF-1 beta was found to be more potent than HNF-1 alpha in activating the AFP promoter. This effect was specific, as it did not occur with the rat albumin promoter. HNF-1 beta, which is produced earlier than HNF-1 alpha during liver development, would thus have the greater influence on the AFP promoter in early development. Both HNF-1s allowed expression of the AFP promoter in cells of nonhepatic origin. Overexpression of NF-1 induced a specific decrease in the activity of the AFP promoter. This strongly suggests that competition between NF-1 and HNF-1 for binding to their overlapping binding sites on the AFP promoter is critical for modulating its activity. Thus changing combinations of these trans-acting factors may tightly modulate the AFP promoter activity in the course of liver development and carcinogenesis.

A liver-specific factor and nuclear factor I bind to the rat alpha-fetoprotein promoter.

Proteins putatively involved in the transcriptional control of rat (alpha-fetoprotein (AFP) gene expression in the liver were identified by analyzing the in vitro binding of proteins from nuclear extracts of fetal and adult rat livers to the cloned rat AFP promoter region (-197 to +48) using a combination of gel shift and DNase I footprinting assays. Three stable and specific high affinity complexes (I, II, and III) were detected by gel shift analysis of fetal rat liver extracts. Complex II was specific to extracts from fetal liver while the two others (I and III) were also formed with extracts from adult liver. Complex I was highly liver-specific since it was not detected with extracts of kidney, spleen, and brain. DNase I and gel shift competition experiments using a synthetic oligonucleotide indicated that it is formed upon binding of a liver-specific factor to region -65 to -46 of the rat AFP promoter. This region, perfectly conserved in the rat, mouse, and man, had been previously shown to be crucial for liver-specific expression of the mouse AFP gene. The binding of this liver-specific factor to this DNA region may thus represent a key step in the specificity of expression of AFP gene in liver. Gel shift and DNase I footprinting competition experiments showed that complex III was formed by binding of the widely distributed nuclear factor I to the rat AFP promoter in the region -125 to -100. It is potentially significant that, in extracts from fetal liver, nuclear factor is also involved with another binding factor in the formation of the stage-specific complex II.

Gel-permeation high-performance liquid chromatography as a powerful technique for rapid analysis of calcitriol (1,25-dihydroxycholecalciferol) receptors.

We used gel-permeation high-performance liquid chromatography to detect cytosolic and nuclear calcitriol (1,25-dihydroxycholecalciferol) receptors. This new convenient technique allowed accurate separation of the calcitriol receptor from other vitamin D-binding proteins. Compared with sucrose-density-gradient centrifugation, it has several advantages including, in particular, its rapidity.

Regulation of rat yolk sac 25-hydroxy- and 1,25-dihydroxyvitamin D3 24-hydroxylase activities.

The yolk sac of the pregnant rat which functions as a true placenta is a target organ for vitamin D. This tissue can hydroxylate in position 24 both 25-hydroxy- and 1,25-dihydroxyvitamin D3 (25-OHD3 and 1,25-(OH)2D3). The present report describes an in vitro model for the study of 1,25-(OH)2D3 action on the further metabolism of 25-OH[3H]D3 and 1,25-(OH)2[3H]D3 by yolk sac. The tissue explants were preincubated with 1,25-(OH)2D3 for 18 h in a serum-free culture medium. Physiological concentrations of 1,25-(OH)2D3 were the most effective in stimulating (7.5-fold) the 1,25-(OH)2D3 24-hydroxylase, while the 25-OHD3 24-hydroxylase stimulation (4-fold) required a 1,25-(OH)2D3 concentration of 10(-7) M. The stimulating effect of 1,25-(OH)2D3 on the 1,25-(OH)2D3 24-hydroxylase was temperature-dependent, and, since its was inhibited by actinomycin D and cycloheximide, required de novo protein synthesis. 1,24,25-(OH)3D3, 25-OHD3, and 24,25-(OH)2D3 were 10- to 1000-fold less potent than 1,25-(OH)2D3 in inducing the 1,25-(OH)2D3 hydroxylase. Our results strongly suggest that 1,25-(OH)2D3 regulated the 1,25-(OH)2D3 24-hydroxylase by a receptor-mediated process. Furthermore, 1,25-(OH)2D3 at 10(-9) M induced within 4 h an increase of its own degradation and the formation of an as yet unidentified major 1,25-(OH)2[3H]D3 metabolite. We conclude that the yolk sac can participate in the regulation of 1,25-(OH)2D3 concentration in the fetoplacental unit.

Rat alpha-fetoprotein promoter and proximal enhancer direct expression of the nls-lacZ reporter gene in embryonic yolk sac, gut, and eustachian canal of transgenic mice.

The alpha-fetoprotein (AFP) gene is expressed mainly in the yolk sac, liver and intestine during embryonic and fetal life. We have analyzed the activities of some of the rat AFP regulatory elements in vivo, using transgenic mice bearing the LacZ gene with a nuclear localization signal (nls-lacZ) placed under the control of the rat AFP promoter and the most proximal enhancer regions (from -3,127 to +102). Four of the six transgenic lines, with two genetic backgrounds, had highly specific reproducible patterns of transgene expression on embryonic days E10.5, E12 and E15. Analyses were performed on the whole embryo and histologically. There was nuclear staining in the yolk sac endodermal cells and in the epithelial cells of the intestine, indicating that the proximal enhancer and promoter drive expression in these cells where the AFP gene is actively transcribed. The pharyngo-tympanic canal was also stained in the transgenic embryos. But there was no expression of the lacZ transgene in the embryonic liver, indicating that additional sequences of rat genomic DNA are required for correct expression in the liver.