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V Pohl

Publications and source records attributed to V Pohl.

At least 19 recordsLinked to original sources
PubMed1997

Activation of cyclic AMP-dependent kinase is required but may not be sufficient to mimic cyclic AMP-dependent DNA synthesis and thyroglobulin expression in dog thyroid cells.

Thyrotropin (TSH), via a cyclic AMP (cAMP)-dependent pathway, induces cytoplasmic retractions, proliferation, and differentiation expression in dog thyroid cells. The role of cAMP-dependent protein kinase (PKA) in the induction of these events was assessed by microinjection into living cells. Microinjection of the heat-stable inhibitor of PKA (PKI) inhibited the effects of TSH, demonstrating that activation of PKA was required in this process. Overexpression of the catalytic (C) subunit of PKA brought about by microinjection of the expression plasmid pC alpha ev or of purified C subunit itself was sufficient to mimic the cAMP-dependent cytoplasmic changes and thyroperoxidase mRNA expression but not to induce DNA synthesis and thyroglobulin (Tg) expression. The cAMP-dependent morphological effect was not observed when C subunit was coinjected with the regulatory subunit (RI or RII subunit) of PKA. To mimic the cAMP-induced PKA dissociation into free C and R subunits, the C subunit was coinjected with the regulation-deficient truncated RI subunit (RIdelta1-95) or with wild-type RI or native RII subunits, followed by incubation with TSH at a concentration too low to stimulate the cAMP-dependent events by itself. Although the cAMP-dependent morphology changes were still observed, neither DNA synthesis nor Tg expression was stimulated in these cells. Taken together, these data suggest that in addition to PKA activation, another cAMP-dependent mechanism could exist and play an important role in the transduction of the cAMP signal in thyroid cells.

Animals↗
PubMed1996

Calbindin localization in African giant rat kidney (Cricetomys gambianus).

Cricetomys gambianus are rodents living in savanna and follow area. They can live with restricted drinking water eating fresh food. Therefore their kidney may have some adaptive mechanisms for ion/water homeostasis compared to usual laboratory rats. In this study we have looked for calbindin, an intracellular calcium binding protein previously found in distal convoluted tubules from all mammalian species that have been studied and able to increase, in vitro, Ca2+ reabsorption. We have shown by using in situ hybridization, immunoblotting and immunohistochemistry that calbindin was expressed in three different portions of the distal nephron of the African giant rat. Calbindin was found in distal convoluted tubules, in cortical collecting tubules and in outer medullary collecting ducts. By contrast, in laboratory rat, calbindin was only found in distal convoluted tubules and undetectable in medullary collecting ducts. Thick ascending limb of Henle's loop were calbindin negative as shown by double immunolabelling using anti-uromucoid (Tamm-Horsfall protein). As previously shown in laboratory rat and rabbit, transcellular Ca2+ movement seems to be facilitated by calbindin in renal tubules segments predominantly actively transporting Ca2+, it may be suggested that in African giant rat, outer medullary collecting ducts may also actively transport Ca2+. As calretinin, another intracellular calcium binding protein highly homologous to calbindin but whose function is still conjectural has been suspected to be expressed in kidney, we have looked and not found any calretinin in both adult rat species.

Animals↗
PubMed1995

Parvalbumin expression during developmental differentiation of the rat ovary.

Parvalbumin (PV) is a high-affinity Ca(2+)-binding protein which is expressed in a limited number of vertebrates tissues and restricted to a few distinct cell types. It has been shown by biochemical methods to be present in the adult rat ovary, but cellular localizations or developmental appearance have not been described until now. This study describes the presence of PV and its transcripts, analyzed by immunohistochemistry and in situ hybridization, respectively, during the postnatal development of the rat ovary: 13 developmental stages between day 1 and day 83 were examined. In ovaries 1-16 days old, neither PV mRNA nor PV was observed in any caaaaaaaaaaaaaay. By contrast, starting from day 18 postpartum, both PV mRNA and PV were detected in low amounts, simultaneously with the onset of differentiation of secondary intestitial gland cells in the ovarian interfollicular stroma. PV and its transcripts were primarily detected in conspicuous patches of interstitial gland tissue and in the differentiated thecal cells around the large follicles, and PV appeared to be fully expressed 33 days after birth. The parallel time courses of PV mRNA and PV accumulation during developmental differentiation, and the appearance of a steroid-producing cellular phenotype as well as the strict cellular colocalization of these two features, strongly suggest involvement of PV in the steroid metabolism of these cells, as earlier proposed for the Leydig cells of the testis. According to this hypothesis, we also show that suppression of gonadotrophic hormone production by hypophysectomy of adult rats totally suppresses PV production in parallel with the disappearance of the morphological features typical of steroid-producing cells in the remaining interstitial tissue of the ovary.

Animals↗
PubMed1994

Expression of thyrotropin receptor (TSH-R), thyroglobulin, thyroperoxidase, and calcitonin messenger ribonucleic acids in thyroid carcinomas: evidence of TSH-R gene transcript in medullary histotype.

We studied the expression of the TSH receptor (TSH-R), thyroglobulin (Tg), thyroperoxidase (TPO), and calcitonin (CT) genes in a total of 53 tissues from 30 patients with thyroid carcinoma and from 9 patients with benign thyroid diseases. By Northern blot analysis of total RNA preparations, CT mRNA was expressed in all cases (n = 6) of medullary thyroid carcinoma (MTC). Surprisingly, 3 of them expressed the TSH-R mRNA, in association with the Tg and TPO mRNAs in 1. The presence of the TSH-R transcript in the neoplastic C-cells was confirmed in 1 MTC by in situ hybridization using a mixture of 3 oligonucleotide probes derived from dog TSH-R cDNA. With various degrees of expression, all differentiated thyroid carcinomas (20 papillary and 2 follicular) expressed TSH-R, Tg, and TPO, but not CT mRNAs. On the contrary, samples from 2 patients with anaplastic carcinoma did not express TSH-R, Tg, or TPO mRNA, but 1 of them expressed CT mRNA. All of the transcripts obtained from thyroid carcinomas (both primary and metastatic) were of the same size as the transcripts from normal or benign thyroid tissues, with the exception of 2 cases of differentiated thyroid cancer, in which TSH-R mRNA of lower mol wt (approximately 4.0 kilobases) was found in the absence of alteration in cDNA size and restriction map. The main conclusions of our study are that 1) the TSH-R gene is expressed in some MTC, which supports, at molecular level, the hypothesis of the existence of mixed follicular-medullary thyroid tumors; and 2) the expression of TSH-R, Tg, and TPO in undifferentiated thyroid cancer is lost.

Blotting, Northern↗
PubMed1993

Thyroperoxidase mRNA in quiescent and proliferating thyroid epithelial cells: expression and subcellular localization studied by in situ hybridization.

Using in situ hybridization procedure, we have investigated the regulation and the cellular localization of thyroperoxidase (TPO) messenger RNA accumulation as a marker of differentiation in dog thyroid epithelial cells in primary culture. The response to different mitogens (TSH acting through cAMP, EGF and TPA) has been compared. TPO mRNA accumulation was exquisitely dependent on a continuous TSH/cAMP stimulation. It was induced within 1 h in the whole cell population from a very low basal level. This effect was inhibited by the cAMP-independent mitogens EGF and TPA. By contrast, the TSH-induction of TPO mRNA accumulation was observed irrespectively of the proliferative activity of the cells, i.e. in the presence or the absence of insulin, which is required for mitogenesis. The short half-life of TPO mRNA (+/- 2 h) implies that it was continuously transcribed during TSH/cAMP-dependent cell cycling. As compared to another thyroid differentiation marker, thyroglobulin mRNA (Pohl et al., J. Cell Biol. 111, 663-672 (1990)), TPO mRNA accumulation differed by the rapidity of its control by cAMP, the pattern of its intercellular heterogeneity, and the unexpected segregation to a perinuclear region, probably the nuclear envelope that constitutes a specialized part of the endoplasmic reticulum. Despite these differences, both TPO and thyroglobulin gene transcriptions are unequivocally compatible with the cell cycle when induced by cAMP, at variance with the generally observed antagonism between growth and differentiation expression.

Animals↗
PubMed1992

Calretinin in rat ovary: an in situ hybridization and immunohistochemical study.

Calretinin is a cytosolic calcium-binding protein of the calmodulin superfamily, with high homology with calbindin D28k. The only cells in which calretinin has been described so far are neurons, in the central nervous system and in retina. In the present work, we describe the expression of the calretinin gene in the interstitial cells of rat ovary. Immunohistochemistry, using a calretinin-specific antibody, allowed to detect the protein from 19 days after birth. Western blot from ovary homogenates confirmed the labelling of a 29 kDa band, the size of calretinin. In situ hybridization confirmed immunochemical data; calretinin transcripts were clearly shown in the same cell population. This represents the first description of calretinin outside the nervous system. Its function in ovary remains to be determined.

Animals↗
PubMed1992

Differential regulation of thyrotropin receptor and thyroglobulin mRNA accumulation at the cellular level: an in situ hybridization study.

Regulation of TSH receptor (TSHr) mRNA accumulation has been investigated in canine thyrocytes in primary culture by in situ hybridization experiments; the effects of the mitogenic thyrotropin (TSH), epidermal growth factor (EGF), and phorbol ester TPA (12-O-tetradecanoylphorbol-13-acetate) have been compared. Apart from their mitogenic action, TSH enhances, while EGF and phorbol ester inhibit, the expression of differentiation. The TSHr gene was transcribed in almost all the cells cultured in control conditions (serum free medium supplemented with insulin). Addition of TSH slightly upregulated (twofold) the expression (mRNA) of the TSHr gene. This positive effect was maintained for 20 and 44 h of treatment. EGF and TPA reduced transiently the TSHr mRNA accumulation but did not suppress it. In these different conditions, the TSHr mRNA was homogeneously distributed within the cell population. This contrasted strongly with the effects of TSH, EGF, and TPA on the expression of the thyroglobulin gene, a prominent marker of thyroid cell differentiation: in this case, the regulation was much tighter (high range of stimulation by TSH, strong inhibition by EGF, and suppression of Tg gene expression by TPA) and displayed a great variability of the level of individual cellular response. The fact that the TSHr gene was little modulated and remained expressed regardless of the treatment may reflect the physiological role of the receptor which is the main connection of the thyrocyte to the regulation network.

Animals↗
PubMed1991

Various facets of the intercellular heterogeneity in thyroid primary culture.

The mechanisms that generate the intercellular heterogeneity of functional and proliferation responses in a tissue are generally unknown. In thyroid gland, this heterogeneity is peculiarly marked and it was suggested that it could result from the coexistence of (epi)genetically different subpopulations of thyrocytes. As summarized in this short review, qualitative or quantitative intercellular heterogeneities have been found at each levels of our "in situ" investigations of morphological, differentiation and proliferative responses of unselected dog thyrocytes in primary culture. These different heterogeneities are unrelated at the individual cell level, which does not indicate the coexistence in thyroid of cell subpopulations stably expressing special properties. Nevertheless, using a double labeling methodology that allows to trace the proliferative behavior of some cells, we show how cell division may stably affect further proliferation responses and how a local synchrony of the dividing cells can result in a stable heterogeneity with a regional, patchy pattern, which resembles the one characterizing multinodular goiter.

Animals↗
PubMed1990

Differentiation expression during proliferative activity induced through different pathways: in situ hybridization study of thyroglobulin gene expression in thyroid epithelial cells.

In canine thyrocytes in primary culture, our previous studies have identified three mitogenic agents and pathways: thyrotropin (TSH) acting through cyclic AMP (cAMP), EGF and its receptor tyrosine protein kinase, and the phorbol esters that stimulate protein kinase C. TSH enhances, while EGF and phorbol esters inhibit, the expression of differentiation. Given that growth and differentiation expression are often considered as mutually exclusive activities of the cells, it was conceivable that the differentiating action of TSH was restricted to noncycling (Go) cells, while the inhibition of the differentiation expression by EGF and phorbol esters only concerned proliferating cells. Therefore, the capacity to express the thyroglobulin (Tg) gene, the most prominent marker of differentiation in thyrocytes, was studied in proliferative cells (with insulin) and in quiescent cells (without insulin). Using cRNA in situ hybridization, we observed that TSH (and, to a lesser extent, insulin and insulin-like growth factor I) restored or maintained the expression of the Tg gene. Without these hormones, the Tg mRNA content became undetectable in most of the cells. EGF and 12-0-tetradecanoyl phorbol-13-acetate (TPA) inhibited the Tg mRNA accumulation induced by TSH (and/or insulin). Most of the cells (up to 90%) responded to both TSH and EGF. Nevertheless, the range of individual response was quite variable. The effects of TSH and EGF on differentiation expression were not dependent on insulin and can therefore be dissociated from their mitogenic effects. Cell cycling did not affect the induction of Tg gene. Indeed, the same cell distribution of Tg mRNA content was observed in quiescent cells stimulated by TSH alone, or in cells approximately 50% of which had performed one mitotic cycle in response to TSH + insulin. Moreover, after proliferation in "dedifferentiating" conditions (EGF + serum + insulin), thyrocytes had acquired a fusiform fibroblast-like morphology, and responded to TSH by regaining a characteristic epithelial shape and high Tg mRNA content. 32 h after the replacement of EGF by TSH, cells in mitosis presented the same distribution of the Tg mRNA content as the rest of the cell population. This implies that cell cycling (at least 27 h, as previously shown) did not affect the induction of the Tg gene which is clearly detectable after a time lag of at least 24 h. The data unequivocally show that the reexpression of differentiation and proliferative activity are separate but fully compatible processes when induced by cAMP in thyrocytes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

[Ileus after appendicitis in children].

A relatively frequent and alarming complication of appendicitis in children is ileus. The authors submit an analysis of 41 cases of ileus with a time interval of 3 days to 8 years after appendectomy. In eight patients conservative treatment was successful, and 33 children were operated with the finding of intraabdominal adhesions (23 times), bands (3 times), abscesses and adhesions (7 times). Two children were re-operated on account a relapsing ileus. None of the children died. Prophylaxis of ileus after appendectomy is ineffective and uncertain, therefore the authors emphasize early diagnosis and early operation of the appendicitis but warn against inadequately considered appendectomy.

Appendectomy↗
PubMed1989

Calbindin-D28 in mammalian brain, retina, and endocrine pancreas: immunohistochemical comparison with calretinin.

Calbindin 28K and calretinin are very similar calcium binding proteins which are both present in the central nervous system (CNS). They respectively bind 4 and 5 Ca++ ions. We have compared by immunohistochemistry and in situ hybridization their localisation in the brain and the retina. The two proteins are generally expressed in different neurons with a few neurons containing both calcium binding proteins. Calbindin 28K is also present in the endocrine system. We have examined the cellular distribution of calbindin in the pancreatic endocrine cells of chick, rat and human and found variable distribution among the different endocrine cell types. We also describe the presence of calbindin in RINm5F cells, an insulin-producing tumor cell line derived from a radiation-induced rat insulinoma.

Animals↗
PubMed1989

Electrical analogs for monitoring vascular properties in artificial heart studies.

The problem of choosing parametric descriptions of the systemic vascular bed suitable for monitoring beat-to-beat changes in peripheral vascular properties is considered. Three simple models with two, three, and five elements are compared, essentially exploiting the Akaike information criterion combined with reasonable requirements for estimate accuracy. Analysis of pressure data, which are either simulated by the five-element model or measured on a mock circulatory system during abrupt changes in peripheral resistance, suggests guidelines for model selection. In particular, the five-element model exhibits very close adherence to physical reality by allowing for reflection, while the classical windkessel model provides the most reproducible estimates.

Cardiovascular Physiological Phenomena↗
PubMed1989

Tracking time-varying properties of the systemic vascular bed.

The problem of tracking changes in viscoelastic properties of the systemic arterial bed is considered and a recursive estimation procedure, belonging to the class of output-error algorithms with adjustable compensator, is developed and discussed. By means of computer simulations, suitable values are determined for the key design variable which controls the tradeoff between tracking ability and noise sensitivity of the algorithm. In this way, the algorithm allows on-line estimation of arterial compliance, peripheral resistance, and characteristic impedance on the basis of aortic pressure and flow signals. Furthermore, the results obtained from data numerically simulated, as well as measured on a mock circulatory system, demonstrate that the dominant arterial time-constant can be tracked by the algorithm using only measurements of the aortic pressure during diastole.

Algorithms↗
PubMed1988

Structure of chick chromosomal genes for calbindin and calretinin.

The chick chromosomal gene for calbindin (the 28,000 Mr intestinal calcium-binding protein) was cloned, and all the exons and flanking regions were sequenced. The promoter region contains typical ATAAA and GGGCGG boxes, the latter being unusual in "non-housekeeping" genes. Three polyadenylation signals are found in the calbindin gene that correspond to the three known mRNAs. Transcription termination is not efficient because homology with consensus sequences found downstream from the polyadenylation signal is weak. There are ten introns, most of which do not fall at homologous positions, neither with respect to the sixfold repeating structure of the calbindin protein, nor with respect to previously sequenced genes for calmodulin and other calcium-binding proteins. The gene for the related protein calretinin was cloned and partially sequenced. The introns are in the same positions in the calretinin and calbindin genes. The introns have apparently been inserted during the divergence of the calcium-binding protein superfamily.

Animals↗
PubMed1987

Structural organization of the 5' region of the thyroglobulin gene. Evidence for intron loss and "exonization" during evolution.

More than one third of thyroglobulin (1190 residues out of 2750) is made of one peptide motif repeated ten times in tandem. Segments unrelated to the motif interrupt this structure at various places. The corresponding gene region, which extends over 40 x 10(3) bases, was studied in detail. All exon borders and exon/intron junctions were localized precisely and sequenced, and their positions were correlated with the repetitive organization of the protein. When intron positions were compiled on a consensus sequence of all repeats, three categories of introns were observed. Except between repeats numbers 5 and 6, an intron was invariably found within the Cys codon making the limit of each motif. This category of intron most probably reflects the serial duplication events responsible for the evolution of this region of the gene. All other introns, except no. 2, are found at positions were the repetitive structure is disrupted by "inserted" peptides. We present the hypothesis that this second category of introns was already present in the original unit before the first duplication. Thereafter, they would have experienced either complete loss (some units do not contain any intron) or partial or total exonization, resulting in the slipping of intronic material into coding sequence. Intron no. 2, finally, separates motif no. 1 at a position on the boundary between two segments presenting sequence homology. This last type of intron probably reflects an initial duplication event at the origin of a primordial thyroglobulin gene motif. With all these characteristics, the thyroglobulin gene is presented as a paradigm for the analysis of the fate of introns in gene evolution.

Amino Acid Sequence↗
PubMed1987

Structural organization of the bovine thyroglobulin gene and of its 5'-flanking region.

The structural organization of the bovine thyroglobulin gene has been investigated by a combination of Southern genomic blotting and direct analysis of cloned gene fragments isolated from a chromosomal DNA library. The entire locus is spread over more than 200,000 base pairs which makes it one of the largest eukaryotic genes studies to date. The coding information is scattered into at least 42 exons, 34 of which have been precisely identified. A different evolutionary origin of the 5' and 3' regions of the gene is supported by the highly different proportion of exonic material they contain (12% and 3%, respectively) and by the existence of sequence homology between the 3' region of thyroglobulin and acetylcholinesterase. Detailed sequence analysis of the 5' region of the gene and its flanking segment demonstrated that a significant homology exists between bovine and human thyroglobulin sequences, except for the presence within the ruminant promoter region of a 220-base-pair sequence belonging to the bovine monomer repeated family.

Animals↗