Supraglottic airway device to improve ventilation success and reduce pulmonary aspiration during cardio-pulmonary resuscitation by basic life support rescuers: a randomised cross-over human cadaver study

Objectives: Early airway management during cardiopulmonary resuscitation (CPR) prevents aspiration of gastric contents. Endotracheal intubation is the gold standard to protect airways, but supraglottic airway devices (SGA) may provide some protection with less training. Bag-mask ventilation (BMV) is the most common method used by rescuers. We hypothesized that SGA use by first rescuers during CPR could increase ventilation success rate and also decrease intragastric pressure and pulmonary aspiration.Methods: We performed a randomized cross-over experimental trial on human cadavers. Protocol A: we assessed the rate of successful ventilation (chest rise), intragastric pressure, and CPR key time metrics. Protocol B: cadaver stomachs were randomized to be filled with 300 mL of either blue or green serum saline solution through a Foley catheter. Each rescuer was randomly assigned to use SGA or BMV during a 5-minute standard CPR period. Then, in a crossover design, the stomach was filled with the second colour solution and another 5-minute CPR period was performed using the other airway method. Pulmonary aspiration, defined as the presence of coloured solution below the vocal cords, was assessed by a blinded operator using bronchoscopy. A generalized linear mixed model was used for statistical analysis.Results: Protocol A: Forty-eight rescuers performed CPR on 11 cadavers. Median ventilation success was higher with SGA than BMV: 75.0% (IQR: 59.8-87.3) vs. 34.7% (IQR: 25.0-50.0), (p = 0.003). Gastric pressure and differential (maximum minus minimum) gastric pressure were lower in the SGA group: 2.21 mmHg (IQR: 1.66; 2.68) vs. 3.02 mmHg (IQR: 2.02; 4.22) (p = 0.02) and 5.70 mmHg (IQR: 4.10; 7.60) vs. 8.05 mmHg (IQR: 5.40; 11.60) (p = 0.05). CPR key times were not different between groups. Protocol B: Ten cadavers were included with 20 CPR periods. Aspiration occurred in 2 (20%) SGA procedures and 5 (50%) BMV procedures (p = 0.44).Conclusion: Use of SGA by rescuers improved the ventilation success rate, decreased intragastric pressure, and did not affect key CPR metrics. SGA use by basic life support rescuers appears feasible and efficient.

Comparative expression of hCG β-genes in human trophoblast from early and late first-trimester placentas

Human chorionic gonadotropin (hCG) displays a major role in pregnancy initiation and progression and is involved in trophoblast differentiation and fusion. However, the site and the type of dimeric hCG production during the first trimester of pregnancy is poorly known. At that time, trophoblastic plugs present in the uterine arteries disappear, allowing unrestricted flow of maternal blood to the intervillous space. The consequence is an important modification of the trophoblast environment, including a rise of oxygen levels from about 2.5% before 10 wk of amenorrhea (WA) to ∼8% after 12 WA. Two specific β-hCG proteins that differ from three amino acids have been described: type 1 (CGB7) and type 2 (CGB3, -5, and -8). Here, we demonstrated in situ and ex vivo on placental villi and in vitro in primary cultures of human cytotrophoblasts that type 1 and 2 β-hCG RNAs and proteins were expressed by trophoblasts and that these expressions were higher before blood enters in the intervillous space (8-9 vs. 12-14 WA). hCG was immunodetected in villous mononucleated cytotrophoblasts (VCT) and syncytiotrophoblast (ST) at 8-9 WA but only in ST at 12-14 WA. Furthermore, hCG secretion was fourfold higher in VCT cultures from 8-9 WA compared with 12-14 WA. Interestingly, VCT from 8-9 WA placentas were found to exhibit more fusion features. Taken together, we showed that type 1 and type 2 β-hCG are highly expressed by VCT in the early first trimester, contributing to the high levels of hCG found in maternal serum at this term.

Review: Human trophoblast fusion and differentiation: lessons from trisomy 21 placenta

The syncytiotrophoblast layer plays a major role throughout pregnancy, since it is the site of numerous placental functions, including ion and nutrient exchange and the synthesis of steroid and peptide hormones required for fetal growth and development. Inadequate formation and regeneration of this tissue contributes to several pathologies of pregnancy such as intrauterine growth restriction and preeclampsia, which may lead to iatrogenic preterm delivery in order to prevent fetal death and maternal complications. Syncytiotrophoblast formation can be reproduced in vitro using different models. For the last ten years we have routinely purified villous cytotrophoblastic cells (CT) from normal first, second and third trimester placentas and from gestational age-matched Trisomy 21 placentas. We cultured villous CT on plastic dishes to follow the molecular and biochemical aspects of their morphological and functional differentiation. Taking advantage of this unique collection of samples, we here discuss the concept that trophoblast fusion and functional differentiation may be two differentially regulated processes, which are linked but quite distinct. We highlight the major role of mesenchymal-trophoblast cross talk in regulating trophoblast cell fusion. We suggest that the oxidative status of the trophoblast may regulate glycosylation of proteins, including hCG, and thereby modulate major trophoblast cell functions.

315. HOMEOBOX GENES ARE DIFFERENTIALLY EXPRESSED IN PRIMARY VILLOUS AND EXTRAVILLOUS TROPHOBLAST CELL LINEAGES DURING EARLY PREGNANCY

During human placental development trophoblast cells differentiate along either the villous cytotrophoblast (VCT) lineage to form the syncytiotrophoblast (ST) or the invasive extravillous cytotrophoblast (EVCT) lineage (1). Abnormalities in early differentiation processes are characteristic of poor placentation, which is associated with fetal growth restriction (FGR) and pre-eclampsia (PE), the major clinical complications of human pregnancy (2). A large family of homeobox gene transcription factors controls “cell-fate decisions” during development (3), but the expression profile and role of homeobox genes in the human trophoblast cell lineages is not well understood. The aim of the study was to determine homeobox gene expression in primary cultures of mononuclear VCT (2h) and EVCT (2 h) obtained from first trimester human chorionic villi of 8–12 weeks of gestation and in vitro differentiated ST (72 h) and invasive EVCT (48 h), respectively. The isolation and characterization of freshly isolated VCT, EVCT and in vitro differentiated ST and invasive EVCT were performed as described previously (1,4). The homeobox gene mRNA profile was performed using PCR arrays in a pooled sample of VCT and EVCT (n = 6 in each group) and further validated by real-time PCR. Homeobox gene expression studies revealed MSX2 mRNA levels were the highest in VCT (2 h) but undetectable in EVCT (2 h). Further comparisons of homeobox gene expression in in vitro differentiated ST to invasive EVCT showed marked increase in MSX2, DLX3, DLX4 and MEIS1 mRNA levels in ST, which are regulators of cellular differentiation in many studies. Homeobox genes HLX and HHEX, which are implicated in regulating cellular proliferation showed decreased mRNA levels in ST compared to invasive EVCT. Our results demonstrated several known placental and novel homeobox genes are differentially expressed in trophoblast cell lineages. Functional studies of these candidate genes will provide a better understanding of the molecular mechanisms of early placental development. (1) Tarrade et al. (2001) Lab Invest. 81, 1199–1211.(2) LokeYW and King A (1995) Cell Biology and Immunology, Cambridge ed.(3) J Cross et al. (2002) Recent Progress in Hormone Research 57: 221–234.(4) Handschuh et al. (2007) Placenta, 28, 175–184.

Indomethacin, a cox inhibitor, enhances 15-PGDH and decreases human tumoral C cells proliferation

High levels of prostaglandins (PGs) are currently found in tumoral cells, due to expression of the inducible PGs synthesis enzyme, the cyclooxygenase 2 (COX 2). Non Steroidal Anti Inflammatory Drugs (NSAIDs) possess an antitumoral effect related, in a large extend, to the inhibition of this enzyme. It was recently suggested that the decreased activity of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), the key enzyme catabolysing PGs, may be responsible too for experimentally induced colon tumor enhancement. We report here, for the first time, that indomethacin, an NSAID, decreased TT cell proliferation, derived from a human Medullary Thyroid Carcinoma (MTC). This effect is time and concentration-dependent. Moreover, indomethacin enhanced expression and activity of 15-PGDH. The 15-PGDH levels were negatively correlated with TT cell proliferation (r = -0.52, p < 0.001). Indomethacin, known to decrease COX levels and activity, could also act in modifying catabolism of PGs. This suggests that 15-PGDH is involved in tumoral development, and could therefore be considered as a target for NSAIDs.

Indomethacin increases 15-PGDH mRNA expression in HL60 cells differentiated by PMA

We previously reported an induction of 15-hydroxyprostaglandin dehydrogenase type I mRNA (15-PGDH) expression accompanied by a decrease in prostaglandin E2(PGE2) levels during cord blood monocytes differentiation into preosteoclastic cells by 1,25 dihydroxyvitamin D3 (1,25 (OH)2D3). These results suggested a role of prostaglandin (PG) enzymes in adhesion and/or differentiation of monocytes. In the present work, we studied modulation of gene expression of PG metabolism enzymes mRNAs in HL60 cells differentiated by phorbol myristate acetate (PMA) into the monocyte/macrophage lineage. We showed that adhesion of HL60 induced by PMA causes an increase of cyclooxygenase 2 (COX 2) and 15-PGDH mRNAs. When adding indomethacin, a non steroidal antiinflammatory drug known to inhibit COX activity, the cells remained attached and expressed large amounts of 15-PGDH mRNA while COX 2 mRNA expression remained unchanged. Indomethacin, in association with PMA can consequently exert a dual control on key enzymes of PGE2 metabolism without modifying adhesion of the cells.

Influence of laminin substratum on cell proliferation and CALC I gene expression in medullary thyroid carcinoma C cell lines

Medullary thyroid carcinoma (MTC) originates from C cells, which secrete calcitonin (CT) and CT gene-related peptide (CGRP), the two splice peptide products of the CALC I gene. Normal and hyperplastic C cells are intrafollicular, in contact with the basement membrane (BM) that is maintained around the differentiated tumors. To investigate the relationships between MTC evolution and BM constituents, we examined the modifications induced by laminin-1 and -2 (merosin), two isoforms colocalized in the follicular BM, on three MTC cell lines: murine rMTC 6-23 and CA-77 cells, and human TT cells. Laminin exerted a mitogenic activity on rMTC 6-23 and on TT cells, causing a concurrent decrease in both CT and CGRP mRNA levels and production of the peptides. Conversely, laminin reduced the proliferation rate and enhanced CGRP synthesis and secretion in CA-77 cells. This antiproliferative response, which coincides with an increase in differentiation markers, is comparable to that reported in normal cells and also in the neoplastic Caco-2 cell line. This suggests that laminin could exert opposite effects depending on the stage of tumor evolution.

Retinoic acid abolishes the calcitonin gene-related peptide autocrine system in F9 teratocarcinoma cells

Calcitonin gene-related peptide (CGRP), expressed predominantly in F9 embryonal carcinoma cells, is both a potent chemotactic agent and an autocrine growth factor for these cells. We analyzed the effect of retinoic acid (RA)-induced differentiation of F9 cells into primitive parietal endoderm-like cells, on CGRP production and the CGRP responsiveness of these cells. Poly(A) RNA extracted from F9 cells and analysed by Northern blotting and hybridization with a CGRP probe showed a specific band of about 1200 bases corresponding to mature CGRP mRNA. This band was not detected in F9 cells treated for 6 days with RA (differentiated primitive parietal endoderm-like cells) or in PYS cells (established parietal endoderm-like cell line). During RA-induced differentiation of F9 cells, CGRP mRNA levels fell within 24 h after treatment and were almost undetectable after 2 days. RA treatment also reduced CGRP secretion by F9 cells; the effect was maximal at 3 days and remained stable thereafter. Similarly, RA rapidly reduced adenylate cyclase responsiveness to chicken CGRP (cCGRP) and human CGRP (hCGRP). An 80% fall in cAMP release into the culture medium in the presence of CGRP was observed after 24 h of RA treatment. These results demonstrate that RA rapidly abolishes the CGRP autocrine system involved in the proliferation of F9 cells, at the same time inducing their differentiation into primitive parietal endoderm. They point to the interaction between retinoic acid and growth factors in the regulation of cell proliferation and differentiation.

Modulation of interleukin-1 receptor expression by transforming growth factor-beta in cultured rabbit articular chondrocytes: analysis by reverse transcription-polymerase chain reaction

Interleukin-1 receptor type I (IL-1RI) expression in cultured rabbit articular chondrocytes (RAC) was studied by reverse transcription-polymerase chain reaction (RT-PCR). A cDNA probe specific for the rabbit IL-1RI gene was constructed using primers derived from the sequence data of the human, murine and chick receptors. Transforming growth factor-beta 1 (TGF beta-1) was shown to transiently increase the level of expected 900-bp PCR product at 1 h of incubation and decrease the expression at 48 and 72 h with no effect at 24 h. In receptor binding assays using [125I]-IL-1 alpha, TGF beta decreased IL-1R bioactivity at all time points. These results suggest that TGF beta-induced down-regulation of IL-1 RI could be responsible for its ability to antagonize the effect of IL-1 and that TGF beta may have a role in the repair of articular cartilage.

An isoform of the human calcitonin receptor is expressed in TT cells and in medullary carcinoma of the thyroid

We amplified, using the polymerase chain reaction and calcitonin receptor (CTR) specific primers, RNA extracted from medullary thyroid carcinoma (MTC) and the derived TT cell line. Both secrete large amounts of calcitonin. Electrophoresis of amplification products revealed, in both cases, an ethidium bromide-stained band that hybridized to a CTR probe. Sequencing the band amplified from TT cells revealed an open reading frame identical to the sequence of H-CTR but lacking 16 amino acids in the first intracellular loop. This demonstrates the existence of an mRNA coding for a subtype of H-CTR which is expressed in TT cells and MTC.

Specific immunostaining for CCP II, a novel calcitonin carboxyl terminal peptide encoded by the calcitonin/CGRP gene

Alternative splicing of the primary transcript of the CALC I gene in thyroid C-cells results predominantly in calcitonin (CT) mRNA (exons 1-4), whereas CGRP mRNA (exons 1, 2, 3, 5, and 6) is mainly produced in neuronal cells. The CT mRNA encodes for a protein precursor containing an amino terminal peptide, CT, and a carboxyl terminal peptide (CCP I). CGRP precursor is composed of the same amino terminal peptide and CGRP. Recently we reported the presence of a third mature transcript of the CALC I gene in human medullary thyroid carcinoma (MTC) tissues. This transcript encodes for a precursor containing the amino terminal peptide CT and a novel carboxyl terminal peptide, CCP II. This finding was further confirmed in the TT-cell line derived from a human MTC. We produced monoclonal antibodies against CCP II and developed a rapid and specific immunofluorescence method for this peptide. We demonstrated CCP II-specific immunoreactivity in TT-cells and in MTC tissues. CCP II labeling was relatively homogeneous in contrast to CT and CGRP, which presented striking heterogeneity for intensity of labeling. Therefore, CCP II mRNA is translated in tumor cells in an apparently constitutive way.

Calcitonin gene-related peptide: an autocrine growth factor with regulatory activity in vitro

We show that an autocrine system for calcitonin gene-related peptide (CGRP) exists in F9 teratocarcinoma cells. Synthesis of CGRP by F9 cells was demonstrated by measuring the peptide concentration in cells and medium and by determining specific mRNA in cells. During six days of culture, CGRP secretion did not vary significantly in the medium, while intracellular CGRP and CGRP mRNA levels increased. F9 cells contained a CGRP-sensitive adenylate cyclase system and CGRP increases the accumulation of cAMP in the culture medium. Interestingly affinity purified antibodies against CGRP specifically inhibited growth of F9 cells by 50%. CGRP therefore stimulates F9 cell growth by an autocrine process, suggesting that CGRP may be a growth factor during early embryogenesis.

CCP II: a novel calcitonin carboxy terminal peptide is expressed in normal thyroid tissue

We have recently identified in medullary thyroid carcinoma the existence of a second calcitonin messenger, generated by a splicing between the 3' coding region of exon 4 and exon 5 of Calc I gene. It differs from the first one in its 3' coding sequence and codes for a calcitonin precursor which generates the same N terminal peptide, calcitonin and a specific 21 amino acid carboxy terminal peptide differing from Katacalcin by its 8 last amino acids. We searched for the expression of this new messenger in normal human thyroid tissue by Northern and by polymerase chain reaction techniques. This second calcitonin messenger was expressed in 4/4 normal thyroids and 4/5 medullary thyroid carcinoma tissue samples. The expression of this second messenger is apparently a common occurrence in C cells whether normal or tumoral.

Effects of calcitonin on human trophoblastic cells in culture: absence of autocrine control

The purpose of this work was to investigate the effects of calcitonin (CT) on trophoblastic cells with respect to cAMP levels and human chorionic gonadotrophin (hCG) secretion in cultured cells from first-trimester and term placentas and in a choriocarcinoma cell line (JEG-3). The expression of the CT gene was investigated to elucidate a putative autocrine control of CT during pregnancy. The addition of salmon CT (10(-10) M and above) resulted in concentration-dependent increases in cAMP secretion by normal trophoblastic cells from term and first-trimester placentas. Moreover, CT was found to increase cAMP secretion preferentially in completely differentiated cells, i.e. after 4-7 days in culture. Addition to the culture medium of JEG-3 cells slightly increased cAMP secretion only at a concentration of 10(-8) M. The basal level of hCG in the medium was found to be higher in the first-trimester than in the term trophoblast culture, but salmon CT induced an increase in hCG secretion by term placenta cells only. CT gene expression in our experimental model was investigated to elucidate a putative autocrine control of CT action during pregnancy. It was not found to be expressed in syncytiotrophoblast cells from either first-trimester or term placenta cells by the method used. Our data demonstrate the absence of autocrine control of CT effects in trophoblastic cells, and suggest that CT is likely to exert its effect preferentially on differentiated cells.

Calcitonin and calcitonin gene-related peptide are chemotactic for F9 embryonal carcinoma cells

The chemotactic effect of calcitonin (CT) gene products was tested on F9 teratocarcinoma cells, which are an in vitro model of early embryonic development. CT and CT gene-related peptide (CGRP) induce a significant chemotactic response (chemotactic index, 40-50). The order of potency is: chicken CGRP greater than or equal to salmon CT greater than or equal to human CGRP. Human CT is a less potent chemotactic agent (chemotactic index, 15). Compared to other well known peptides with chemotactic activity, such as platelet-derived growth factor (no activity) and transforming growth factor-beta (chemotactic index, 5), CGRP and CT appear to be very active in attracting F9 cells in the Boyden chamber assay. Interestingly, CT and CGRP exhibit little chemotactic effect toward differentiated teratocarcinoma cells (i.e. retinoic acid-treated F9 cells or parietal endodermal PYS cells). While salmon CT and chicken CGRP activate adenylate cyclase activity in F9 cell membranes by 7- to 8-fold, higher concentrations (greater than 10(-10) M) of these peptides are required to stimulate cAMP formation than are required to mediate the chemotactic effect of these peptides. These data imply the possible involvement of CT gene products in regulating cell migration during early embryonic development.

Study of calcitonin and thyroglobulin gene expression in human mixed follicular and medullary thyroid carcinoma

mRNAs were isolated from 2 patients suffering from a familial form of a rare variant of medullary carcinoma of the thyroid (MTC), called mixed follicular and medullary carcinoma. The presence of calcitonin (CT) and thyroglobulin (Tg) mRNAs was checked by northern and in situ hybridization and compared with immunohistochemical results. In each case, mRNAs hybridizing to probes specific for CT and Tg were detected. Both proteins were quantified by radioimmunoassay determination in tissue extracts. Patient 1 had 20 ng Tg and 68 ng CT per micrograms total protein, and patient 2 had 0.4 ng Tg and 1.7 ng CT per micrograms total protein. Northern analysis showed that mixed carcinoma expressed several species of both CT mRNAs and Tg mRNAs. The main Tg transcripts present in neoplastic cells (8.5 and 4.8 kb for patient 1 and patient 2) were identical to or smaller than those of normal thyroid tissue (8.5 kb). The tumor CT mRNA (1 kb) was identical to that of normal tissue. In situ hybridization confirmed the presence of CT and Tg mRNA in the great majority of tumor cells. Furthermore, the presence of small amounts of organified iodine was evidenced by analytical ion microscopy in 35% of these cells. This raises an important question regarding the histogenesis of this tumor.

PCR amplification of CGRP II mRNA. Variable expression in tumoral and non-tumoral human thyroid

Two genes code for calcitonin gene-related peptides (CGRPs). One expresses by tissue-specific alternate splicing calcitonin and CGRP I mRNAs, the other CGRP II mRNA. Calcitonin is the marker of sporadic or hereditary human medullary thyroid carcinoma (MTC). CGRP II expression is not well established in normal or tumoral thyroid. After amplification by polymerase chain reaction, CGRP I and II mRNAs were detected in six cases of MTC associated with other endocrine neoplasia (MEN IIa) and in two cases of isolated MTC. CGRP I was detected in all non-C cell tumoral thyroids (6 samples), CGRP II was barely detectable in three out of six cases. CGRP II could be a specific tumoral marker of MTC.

Predicted structure of rabbit N-terminal, calcitonin and katacalcin peptides

Poly A rich RNA was extracted from rabbit thyroid and cDNA obtained by the action of reverse transcriptase. The cDNA was used to construct a library in lambda GT 11. Screening of the library with a radio-labelled probe specific for human calcitonin allowed the isolation of a clone containing an open reading frame with a high homology with human and murine exon 4 of calcitonin/calcitonin gene-related peptide gene. This sequence codes for a typical calcitonin precursor. We deduced the amino acid sequence of rabbit N-terminal peptide, calcitonin and katacalcin.

Increase in calcitonin mRNA levels in rats at high risk of C cell tumours is genetically determined

C-cells tumours are frequent (50%) in old WAG/Rij rats. In comparison to the original Wistar strain, three month old WAG/Rij rats are characterized by higher calcitonin synthesis and secretion, in addition to a genetically transmitted loss of calcitonin binding sites in the outer renal medulla. In order to determine if the increase of calcitonin gene expression is also of genetic origin, we quantified calcitonin and its specific messenger in the thyroid glands of second generation (Wistar x WAG/Rij) hybrids. These parameters ranged from low Wistar like to higher WAG/Rij like values. The amount of calcitonin messenger in the thyroid was highly correlated to the release of the hormone in plasma elicited by a calcium challenge and inversely correlated with the number of its binding sites in the kidney. Our results suggest that an enhanced expression of the calcitonin gene is genetically transmitted, probably as a consequence of the mutation involved in the loss of renal calcitonin binding sites. It may represent the first event leading to malignancy.

Actinomycin D inhibits the rapid increase in translatable calcitonin mRNA provoked by acute calcium stimulation

Calcium, injected to rats, elicits a rapid increase in translatable calcitonin mRNA, by acting probably at the post-transcriptional level, as no change in calcitonin mRNA could be detected by hybridization assay. In this study we have measured calcitonin mRNA extracted from rats subjected or not to acute hypercalcemia and pretreated or not with actinomycin D. Calcitonin mRNA was quantified by its ability to direct the synthesis of calcitonin (CT) precursors in a cell free system and by hybridization to a 32P cDNA probe specific for CT mRNA. Actinomycin D, injected 5 hours before calcium administration, decreased the incorporation of 3H adenine in liver and thyroid, but did not inhibit the rise in plasma levels of calcium and CT (measured by radioimmunoassay). The antibiotic was able to inhibit the eightfold increase in translatable mRNA elicited by calcium administration in the control animals. Hybridizable CT mRNA levels were not modified by the treatments. Thus the increase in translatable CT mRNA after calcium stimulation is independent of CT secretion and is probably due to post-transcriptional modifications involving the expression of other gene(s).

Circadian rhythms of calcitonin gene expression in the rat

The daily changes in rat thyroid calcitonin and its specific mRNA concentrations, and the relationship between their dynamics and the plasma levels of calcitonin, calcium and phosphate over a 24-h period were investigated. The circulating calcitonin concentration rose during the daily dark period when plasma calcium and phosphate levels were minimal, indicating that plasma calcitonin rhythm cannot be generated directly by a linear effect of calcium on hormone secretion. Moreover, we established that the expression of the calcitonin gene also exhibited periodic dynamics observable at the pretranslational level: the gland content of hybridizable specific calcitonin RNA displayed daily rhythms; specific RNA levels peaked during the light period and were minimal during the first part of the dark period. Significant changes in thyroid calcitonin concentrations also occurred over a 24-h period. Statistical analyses which distinguished between variations over the 24-h period and residual variations were performed to test the relationships between the various parameters. The daily rhythms of hybridizable RNA, thyroid calcitonin and plasma minerals appeared to be in phase, while the plasma calcitonin concentration displayed variations out of phase with these rhythms. The implication of the correlations observed on the residual variations is discussed in comparison with the temporal relationship between the daily variations. The results fit the hypothesis that hormone production and secretion are self-oscillating processes. Plasma concentrations of calcium and phosphate might play a role in the synchronization of the calcitonin metabolism periodicity.

Elevated levels of calcitonin mRNA: a marker for the spontaneous development of medullary thyroid carcinoma in rats

The aging WAG/Rij rats (a Wistar derived strain) develop spontaneously medullary thyroid carcinoma with a high frequency (50%). We have studied calcitonin biosynthesis in Wistar and WAG/Rij rats strains in order to determine if early changes in this parameter occurred in the WAG/Rij strain. Thyroidal and plasma CT levels were measured in three months old WAG/Rij and Wistar rats before and after acute calcium challenge. Total RNA was extracted from thyroid glands and specific CT messenger RNA levels estimated by dot and Northern blot analysis with a 32P-labeled probe specific for CT mRNA. The capacity of mRNA to direct synthesis of CT precursor was also measured by translation in an in vitro system. Though mean basal circulating CT levels were equivalent in both strains, CT release after calcium stimulation was much increased in the WAG/Rij rat. CT content of the glands and CT mRNA levels were two fold higher in the WAG/Rij strain. Thus, in this strain, CT biosynthesis and secretion were increased long before the development of a C-cell carcinoma.

Calcitonin-like immunoreactivity and calcitonin gene expression in the placenta and in the mammary gland of the rat

Recently, the presence of monomeric CT in plasma and milk was reported by others in a lactating woman surgically thyroidectomized. Similarly, the placenta was thought to be a possible source of CT. Since such findings were based exclusively on immunological arguments, we have investigated the CT gene expression in these rat tissues. CT mRNAs were detected by dot-blot hybridization of total RNAs extracted from rat tissues with a 32P-labelled human CT cDNA probe. Subcellular fractions of each tissue were screened for CT-like immunoreactivity using two different antibodies. With one antibody, extracts of the mammary gland and placenta both produced full displacement of labelled human CT from the antiserum and serial dilutions of the extracts gave displacement curves parallel to that of synthetic human CT, which suggests immunological similarity. However, dilution curves were not parallel for the second antibody, and for both antisera, CT-like immunoreactivity was found in all subsellular fractions from nuclei to cytosols. Immunoprecipitation of translation products from poly (A)+RNAs of placenta showed two major bands around 30 kD. Under stringent conditions, the weak hybridization of placental RNAs seen by dot-blot under less stringent conditions disappeared. Northern analyses of total RNAs from the placenta failed to detect mRNA of 1 k base size like in thyroid glands, but hybridization under weak stringent conditions occurred with larger mRNAs (around 4.4 and 2.4 k bases). Immunoprecipitation of translation products from mRNAs of rat mammary glands showed three major bands around 46, 30 and 20 kD. Dot-blot hybridization of total RNAs extracted from mammary glands was also negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Potassium administration and calcitonin mRNA level in the rat

We have investigated the acute effects of elevated plasma potassium concentrations on the calcitonin (CT) mRNA level measured by dot-blot hybridization. Plasma CT levels were significantly increased (X2) 30 min after potassium administration (1.2 mmol, KCl/100 g body weight) in adult female rats; a trend towards increased values was observed 10 min after treatment. No change in plasma calcium concentration was induced by the elevated extracellular potassium levels. The amount of CT mRNA measured by dot-blot hybridization was statistically significantly increased 10 min and 30 min (around 47-55%) after potassium treatment. This finding was confirmed by a Northern blot analysis. It is suggested for the first time that the potassium-induced CT release is associated with a slight increase in CT mRNA level. The increased CT secretion was probably mediated through a rise in the ionized calcium concentration of the C-cell.

Sequence and expression of the chicken calcitonin gene

The avian calcitonin gene was isolated and sequenced; two mRNAs are expressed by tissue-specific alternate splicing. The peptides encoded by the mRNAs are the protein precursors of either calcitonin or calcitonin gene-related peptide (CGRP). Calcitonin is expressed predominantly in ultimobranchial bodies and CGRP in brain.

Increased level of calcitonin mRNA after 1,25-dihydroxyvitamin D3 injection in the rat

Vitamin D metabolites are able to change plasma calcitonin (CT) levels, but nothing is known about a possible effect at the CT gene level. Here we have investigated the acute effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on the CT biosynthetic activity of thyroid glands from adult rats. Plasma CT levels were significantly increased (X2) 1 and 2 h after 1,25-(OH)2D3 injection in the face of unchanged plasma calcium values. The thyroidal CT content also was unchanged. A 2-fold increase in CT mRNA level measured by dot-blot hybridization occurred 1 and 2 h after 1,25-(OH)2D3 administration. Expression of CT gene products was examined in the rabbit reticulocyte lysate cell-free translation assay. After polyacrylamide gel electrophoresis, specific immunoprecipitates were autoradiographed and quantified by integration. A single precursor of Mr approximately equal to 15 000 could be specifically immunoprecipitated with CT antisera. A 3-4-fold rise in translatable CT mRNA activity was observed 1 and 2 h after 1,25-(OH)2D3 injection. Thus, parallel changes in CT mRNA level, CT mRNA activity and plasma CT levels were observed in adult female rats after administration of 1,25-(OH)2D3. These findings demonstrate for the first time that 1,25-(OH)2D3 enhanced CT gene expression in the face of unchanged plasma calcium levels.

Calcitonin mRNA activity in young obese (fa/fa) Zucker rats

Alterations in both calcitonin (CT) secretion and plasma calcium were recently described in adult obese Zucker rats. We have investigated the CT biosynthetic activity of thyroid glands in 30-day-old obese Zucker rats (fa/fa), and their controls (Lean). Plasma calcium level was significantly increased (+0.6 mg/dl) in obese animals, but plasma phosphate was unchanged. Plasma CT levels measured by radioimmunoassay (RIA) were significantly decreased in fatty (0.50 +/- 0.03 vs 0.68 +/- 0.03 ng/ml in Leans; P less than 0.001), but thyroidal hormone content was not different between Lean and fatty rats (68.7 +/- 5.1 in Leans vs 60.5 +/- 3.6 ng/gland in fatty rats). mRNA was extracted from 10 thyroids, and translated in a rabbit reticulocyte lysate (NEN) in the presence of [35S]methionine. After polyacrylamide gel electrophoresis, specific immunoprecipitates were autoradiographed and quantified by integration. A 50% decrease in translatable CT mRNA was observed in fatty rats. In basal conditions, the biosynthetic activity of C cells in obese rats correlates with the secretion rate of the hormone in the face of unchanged thyroidal CT contents.

Rapid increase of calcitonin-specific mRNA after acute hypercalcemia

The regulation of calcitonin (CT) secretion by calcium was studied by measuring CT mRNA extracted from thyroids of normal rats subjected to acute calcium stimulation in vivo. The 15000-Mr primary translation product of CT mRNA was identified by immunoprecipitation using specific antibodies. While total mRNA and total radioactivity incorporated after translation of total mRNA remained unaffected by the calcium stimulation, a fourfold increase in radioactivity incorporated in CT primary translation product occurred as early as 2 min after calcium administration. This peak coincided with a rise in plasma levels of the hormone and preceded a detectable decrease in tissue stores. These results suggest that calcium ion, either directly or indirectly via its action on intracellular stores of the hormone or its precursors, causes a rapid increase in cell levels of translatable CT mRNA. In view of the extremely short time (2 min) in which this increase occurs, the action is probably at the post-transcriptional level as no increase in CT mRNA levels could be detected by hybridization assay using a specific cDNA probe for human CT mRNA.

Cell free translation of chicken calcitonin messenger RNA

The primary step of calcitonin biosynthesis was studied in a normal organ: chicken ultimobranchial gland, a tissue particularly rich in calcitonin secretory cells. Poly(A)-rich RNA was extracted and purified from ultimobranchial organs and translated in a reticulocyte lysate in the presence of labelled methionine. Polyacrylamide gel electrophoresis of specific immunoprecipitates revealed a major band of Mr 14 500 and a band of Mr 13 300. Thus, in chicken the precursor of calcitonin is a Mr 14 500 polypeptide. The minor component of Mr 13 300 could represent limited processing by the reticulocyte lysate.