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See detailIdentification and modulation of a growth hormone-binding protein in rainbow trout (Oncorhynchus mykiss) plasma during seawater adaptation.
Sohm, F.; Manfroid, Isabelle ULg; Pezet, A. et al

in General and Comparative Endocrinology (1998), 111(2), 216-24

A soluble protein that specifically bound 125I-human growth hormone (hGH) was identified in rainbow trout plasma, using HPLC-gel filtration. The binding affinity of the protein for hGH was 1.2 x 10(9)M-1 ... [more ▼]

A soluble protein that specifically bound 125I-human growth hormone (hGH) was identified in rainbow trout plasma, using HPLC-gel filtration. The binding affinity of the protein for hGH was 1.2 x 10(9)M-1. 125I-rainbow trout GH (tGH) was also able to bind to the protein albeit with a lower affinity (6.6 x 10(7)M-1) than hGH. Crosslinking experiments using 125I-hGH revealed two specific bands of 150 and 130 kDa. The complex 125I-hGH-BP could be precipitated by a monoclonal anti-GH receptor antibody, suggesting a close relationship between the plasma GH-BP and the GH receptor. A fourfold increase in the hGH binding to the GH-BP was shown 48 h after transfer of the fishes from freshwater to seawater. The increase in binding was related to a high binding capacity without significant changes in binding affinity. These results suggest a potential role of this related GH-BP as an index of GH effects during seawater adaptation in salmonids. [less ▲]

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See detailTrypsin and Trypsinogen from an Antarctic Fish: Molecular Basis of Cold Adaptation
Genicot, S.; Rentier-Delrue, Françoise ULg; Edwards, D. et al

in Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology (1996), 1298(1), 45-57

Trypsin from Antarctic fish Paranotothenia magellanica displays molecular and kinetic properties typical of enzymes produced by psychrophilic organisms. The enzyme has a high catalytic efficiency at low ... [more ▼]

Trypsin from Antarctic fish Paranotothenia magellanica displays molecular and kinetic properties typical of enzymes produced by psychrophilic organisms. The enzyme has a high catalytic efficiency at low and moderate temperatures and is rapidly inactivated at temperatures higher than 30 degrees C. The nucleotide sequence was determined after mRNA extraction and cDNA synthesis. The cDNA encodes a pretrypsinogen which includes a seven residue activation peptide containing only three acidic residues preceeding the 222 amino-acid mature enzyme. A three-dimensional model of the enzyme was built. Structural parameters possibly involved in the adaptation to cold have been derived from comparison with the three-dimensional structure of the bovine enzyme. Among them are the lack of Tyr-151 in the substrate binding pocket, an overall decrease in the number of salt bridges and hydrophobicity and the increase in the surface hydrophilicity. [less ▲]

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See detailDifferential effects of gonadotropin-releasing hormone, dopamine and somatostatin and their second messengers on the mRNA levels of gonadotropin IIb subunit and growth hormone in the teleost fish, tilapia
Melamed, P.; Gur, G.; Elizur, A. et al

in Neuroendocrinology (1996)

In cultured pituitary cells of tilapia, gonadotropin-releasing hormone (GnRH; 10 nM 4-24 h), elevation of cyclic AMP (by 10 microM forskolin or 0.2 mM 3-isobutyl-1-methylxanthine: IBMX 0.5-36 h) or ... [more ▼]

In cultured pituitary cells of tilapia, gonadotropin-releasing hormone (GnRH; 10 nM 4-24 h), elevation of cyclic AMP (by 10 microM forskolin or 0.2 mM 3-isobutyl-1-methylxanthine: IBMX 0.5-36 h) or activation of protein kinase C (PKC; by 12.5 nM tetradecanoyl phorbol-13-acetate: TPA, 0.5-24 h) all increased gonadotropin (GtH) II beta steady state mRNA levels by three to four-fold. The involvement of PKA and PKC in the GnRH stimulatory effect on both GtH release and GtH II beta mRNA levels was corroborated by use of the PKA and PKC inhibitors, H89 and GF109203X, respectively (100 nM) which attenuated the GnRH effect. Incubation with actinomycin D (8 microM, 4-21 h) after preexposure for 24 h to either forskolin (10 microM) or TPA (12.5 nM), revealed that rates of transcript degradation were slower in forskolin-treated cells (T 1/2 = 14.1 h) than in control or TPA-treated cells (T 1/2 = 8.47 or 8.38 h), suggesting a stabilizing effect on the mRNA. Dopamine (DA; 10 microM, 4-36 h) had no apparent effect on steady state mRNA levels of GtH II beta, but reduced GtH release by as much as 75%. Steady state levels of growth hormone (GH) mRNA were not affected by exposure to GnRH (10 nM, 4-24 h), although GH release was more than doubled. Similarly, activation of PKC (by TPA 12.5 nM, 1.5-36 h), which was shown to be essential for the GnRH-stimulatory effect on GH release, did not alter levels of the GH transcript, but increased GH release by more than fivefold. DA (10 microM, 4-24 h) moderately increased GH transcript levels (160%) with similar kinetics but lower potency than direct elevation of cAMP (by 10 microM forskolin or 0.2 mM IBMX, 0.5-36 h) which increased transcript levels by more than fourfold. The involvement of PKA in the DA effect was confirmed when the PKA inhibitor H89 (100 nM, 15 min prior to DA exposure) attenuated the DA effect on GH mRNA levels. Exposure of cells to actinomycin D (8 microM, 2-16 h) after treatment with forskolin (10 microM, 24 h) led to a slower rate of transcript degradation than in control cells (T 1/2 = 6.5 h vs. T 1/2 = 4.36 h), suggesting that cAMP also elicits a stabilizing effect on GH mRNA. Somatostatin (100 nM, 0.5-36 h) had no clear effect on GH transcript levels, but reduced GH release by as much as 90%. These results suggest that activation of either cAMP-PKA or PKC pathways can, possibly by different mechanisms, stimulate mRNA levels of the GtH II beta gene, but that only the cAMP-PKA pathway stimulates GH mRNA levels. It would appear therefore that GnRH, although stimulating GH release, does not regulate GH transcription in this fish. [less ▲]

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See detailThe effect of gonadal development and sex steroids on growth hormone secretion in the male tilapia hybrid (Oreochromis niloticus x O. aureus O;
Melamed, P.; Eliahu, N.; Ofir, M. et al

in Fish Physiology and Biochemistry (1995)

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See detailAbsence of tiGh effect on adaptability to brackish water in Tilapia (Oreochromis niloticus)
Auperin, B.; Leguen, I.; Rentier-Delrue, Françoise ULg et al

in General and Comparative Endocrinology (1995)

The aim of this study was to investigate the possible role of growth hormone in the adaptation of tilapia (Oreochromis niloticus) to brackish water and to analyze its interactions with prolactin in this ... [more ▼]

The aim of this study was to investigate the possible role of growth hormone in the adaptation of tilapia (Oreochromis niloticus) to brackish water and to analyze its interactions with prolactin in this process. Plasma levels of growth hormone do not change upon transfer to brackish water. Treatment of intact tilapia in fresh water with growth hormone prior to transfer did not enable the fish to preadapt to brackish water: the duration of the hydromineral imbalance after transfer was the same in treated animals and controls. The major osmoregulatory role of prolactin in fresh water led us to test the hypothesis that prolactin might antagonize the effect of growth hormone on adaptation to brackish water. Growth-hormone-treated hypophysectomized animals, however, exhibited no increased osmoregulatory capacity as compared to hypophysectomized controls, confirming the absence of a growth-hormone-related osmoregulatory effect. When prolactin and growth hormone were coinjected, growth hormone also proved unable to oppose the Na+ retaining effect of prolactin, in both brackish and fresh water. Surprisingly, hypophysectomized animals adapt better to brackish water than do sham-operated animals. This result is discussed in light of the effects of prolactin and cortisol on osmoregulation in brackish water and we suggest that an important event which allows O. niloticus to adapt to hyperosmotic environment is the reduction of plasma PRL upon transfer to brackish water. [less ▲]

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See detailCellular and molecular aspects of thymic T-cell education to neurohypophysial peptides
Geenen, Vincent ULg; Martens, Henri ULg; Vandersmissen, Eric et al

in Excerpta Medica (1995), 1098

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See detailCellular and molecular aspects of thymic T-cell education to neurohypophysial peptides
Geenen, Vincent ULg; Vandersmissen, Eric; Martens, Henri ULg et al

in Yoshida, Sho; Saito, Toshikazu; Kurokawa, Kiyoshi (Eds.) Neurohypophysis - Recent Progress of Vasopressin and Oxytocin Research (1995)

Our studies have shown that oxytocin (OT) is the dominant peptide of the neurohypophysial (NHP) family that is expressed by thymic epithelial/nurse cells (TEC/TNC). Both in specific RIA and ICC analyses ... [more ▼]

Our studies have shown that oxytocin (OT) is the dominant peptide of the neurohypophysial (NHP) family that is expressed by thymic epithelial/nurse cells (TEC/TNC). Both in specific RIA and ICC analyses, vasopressin (VP) immunoreactivity is considerably lower in TEC. OT is not secreted by TEC/TNC, but it is presented as the self antigen of the NHP family to developing pre-T cells. The process of T-cell education in recognizing the NHP family involves an active cooperation between this neuroendocrine gene/protein family and the immunoglobulin family. This cooperation is illustrated by the identification in plasma membranes of human TEC of a 55-kDa protein bearing a neurophysin (10 kDa), as well as a MHC class I heavy chain-related domain (45 kDa). Since both OT and VP genes are transcribed in the thymus, the site of this cooperation should be located at posttranscriptional level. From these data, it appears that thymic T-cell education to the NHP family involves specific pathways which are not strictly superimposible to those dlineated using peripheral dedicated APC. Although MHC class I pathways are needed, it appears that thymic T-cell education to NHP self is not restricted in an allelic fashion. This offers significant advantages for the selection of the human T-cell repertoire. Furthermore, the absence of a tight MHC allelic restriction in the process of T-cell education to neuroendocrine self opens novel perpectives for the prevention of autoimmune endocrine disorders such as insulin-dependent diabetes mellitus. [less ▲]

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See detailRegulation of gill prolactin receptors in tilapia (Oreochromis niloticus) after a change in salinity or hypophysectomy
Auperin, B.; Rentier-Delrue, Françoise ULg; Martial, Joseph ULg et al

in Journal of Endocrinology (1995), 145(2), 213-20

Prolactin (PRL) receptors in gill tissue have been analyzed in tilapia (Oreochromis niloticus) after transfer from fresh water (FW) to brackish water (BW). This study has indicated the presence of only ... [more ▼]

Prolactin (PRL) receptors in gill tissue have been analyzed in tilapia (Oreochromis niloticus) after transfer from fresh water (FW) to brackish water (BW). This study has indicated the presence of only one class of tilapia PRL (tiPRL) receptor whatever the salinity. After transfer, however, the percentage of specific binding of the two forms of tiPRL (tiPRLI and tiPRLII) increased significantly. Scatchard analysis of tiPRLI binding indicated an increase in receptor affinity, an effect which was not accompanied by any change in receptor specificity. Transfer to BW also caused the number of tiPRL receptors to increase rapidly, remaining high in fish adapted to BW for 28 days. Based on the sharp reduction in plasma tiPRLI and tiPRLII levels after transfer to BW, one possible explanation may be that tiPRL itself is an important factor regulating the number of free receptors. This hypothesis finds support in the fact that the number of tiPRL receptors also increased in hypophysectomized fish reared in FW. However, the absence of change in receptor affinity after hypophysectomy suggested that yet other factors are involved in tiPRL receptor regulation during the transfer from FW to BW. The paradoxically high numbers of tiPRL receptors in the gills of BW-adapted tilapia, even though PRL is known to be a FW-adapting hormone, is discussed with regard to the environment in which tilapia live. [less ▲]

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See detailCrystal structure of recombinant triosephosphate isomerase from Bacillus stearothermophilus. An analysis of potential thermostability factors in six isomerases with known three-dimensional structures points to the importance of hydrophobic interactions
Delboni, Luis F; Mande, Shekhar C; Rentier-Delrue, Françoise ULg et al

in Protein Science : A Publication of the Protein Society (1995), 4(12), 2594-604

The structure of the thermostable triosephosphate isomerase (TIM) from Bacillus stearothermophilus complexed with the competitive inhibitor 2-phosphoglycolate was determined by X-ray crystallography to a ... [more ▼]

The structure of the thermostable triosephosphate isomerase (TIM) from Bacillus stearothermophilus complexed with the competitive inhibitor 2-phosphoglycolate was determined by X-ray crystallography to a resolution of 2.8 A. The structure was solved by molecular replacement using XPLOR. Twofold averaging and solvent flattening was applied to improve the quality of the map. Active sites in both the subunits are occupied by the inhibitor and the flexible loop adopts the "closed" conformation in either subunit. The crystallographic R-factor is 17.6% with good geometry. The two subunits have an RMS deviation of 0.29 A for 248 C alpha atoms and have average temperature factors of 18.9 and 15.9 A2, respectively. In both subunits, the active site Lys 10 adopts an unusual phi, psi combination. A comparison between the six known thermophilic and mesophilic TIM structures was conducted in order to understand the higher stability of B. stearothermophilus TIM. Although the ratio Arg/(Arg+Lys) is higher in B. stearothermophilus TIM, the structure comparisons do not directly correlate this higher ratio to the better stability of the B. stearothermophilus enzyme. A higher number of prolines contributes to the higher stability of B. stearothermophilus TIM. Analysis of the known TIM sequences points out that the replacement of a structurally crucial asparagine by a histidine at the interface of monomers, thus avoiding the risk of deamidation and thereby introducing a negative charge at the interface, may be one of the factors for adaptability at higher temperatures in the TIM family. Analysis of buried cavities and the areas lining these cavities also contributes to the greater thermal stability of the B. stearothermophilus enzyme. However, the most outstanding result of the structure comparisons appears to point to the hydrophobic stabilization of dimer formation by burying the largest amount of hydrophobic surface area in B. stearothermophilus TIM compared to all five other known TIM structures. [less ▲]

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See detailHypothalamic and Thyroidal Regulation of Growth Hormone in Tilapia
Melamed, P. M.; Eliahu, N. A.; Levavi-Sivan, Berta et al

in General and Comparative Endocrinology (1995), 97

A radioimmunoassay (RIA) for recombinant tilapia growth hormone (GH) was established and validated. The ability of various hypothalamic factors to regulate GH secretion in the tilapia hybrid (Oreochromis ... [more ▼]

A radioimmunoassay (RIA) for recombinant tilapia growth hormone (GH) was established and validated. The ability of various hypothalamic factors to regulate GH secretion in the tilapia hybrid (Oreochromis niloticus x Oreochromis aureus) was studied. Somatostatin1-14 (SRIF1-14; 10-100 micrograms/kg) was found to reduce circulating GH levels in a dose-dependent manner. SRIF1-14 (0.1-1000 nM) inhibited GH release from perifused pituitary fragments (ED50 0.83 nM). Human growth hormone-releasing hormone fragment 1-29 (hGHRH1-29; 100 micrograms/kg) doubled circulating GH levels and modestly stimulated GH secretion in vitro. Carp growth hormone-releasing hormone (cGHRH) stimulated GH secretion in vitro to a similar degree at the same dose (1 microM). Injection of salmon gonadotropin-releasing hormone (sGnRH) superactive analog (10-100 micrograms/kg) increased plasma GH levels sixfold. sGnRH also stimulated GH release in vitro (ED50 142.56 nM). Dopamine (0.1-10 microM) and the D1 DA receptor agonist SKF 38393 increased GH secretion from perifused pituitary fragments dose-relatedly. Thyrotropin-releasing hormone (TRH) had no effect on GH secretion from perifused pituitary fragments, but increased plasma GH levels, as did bovine thyroid stimulating hormone (bTSH). The increased plasma GH in the bTSH-treated fish coincided with a dramatic increase in T4; however, TRH increased GH without changing T4 levels. T3 increased the synthesis of GH by isolated pituitaries (incorporation of [3H]leucine). SRIF1-14 seems to be a most potent hypothalamic regulator of GH secretion in tilapia; sGnRH and DA both increased GH secretion, although sGnRH elicited considerably greater responses at lower doses. Two forms of GHRH increased GH levels, although the unavailability of the homologous peptide prevented an accurate evaluation of its importance in regulating GH secretion. The thyroid axis (TRH, TSH, and T3) stimulates both synthesis and release of GH, although TRH did not appear to have a direct effect on the level of the pituitary. [less ▲]

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See detailEvidence that two tilapia (Oreochromis niloticus) prolactins have different osmoregulatory functions during adaptation to a hyperosmotic environment
Auperin, B.; Rentier-Delrue, Françoise ULg; Martial, Joseph ULg et al

in Journal of Molecular Endocrinology (1994), 12(1), 13-24

Two forms of prolactin (tiPRLI and tiPRLII), with only 69% sequence identity, have been previously described in the cichlid fish tilapia (Oreochromis species). In the present study we have attempted to ... [more ▼]

Two forms of prolactin (tiPRLI and tiPRLII), with only 69% sequence identity, have been previously described in the cichlid fish tilapia (Oreochromis species). In the present study we have attempted to investigate the biological activity of these two prolactin forms during adaptation to a hyperosmotic environment. For this purpose, we have developed two highly sensitive (sensitivity: 0.05 ng/ml) and specific (cross-reactivity < 0.04%) radioimmunoassays for tiPRLI and tiPRLII, using recombinant hormones. When fish were directly transferred from fresh to brackish water, the measured levels of plasma tiPRLI and tiPRLII dropped abruptly until 12 h after transfer. Thereafter, plasma tiPRLII remained stable (around 0.5 ng/ml) until the end of the experiment, whereas plasma tiPRLI continued to decrease to undetectable levels. These different patterns of change are reflected in the calculated ratio of plasma tiPRLII to tiPRLI, which increased from 2-3 in fresh water-adapted fish to over 10 in fish which had spent 3 days or more in brackish water. The pituitary contents of tiPRLI and tiPRLII varied in a qualitatively similar fashion after transfer to brackish water. The tiPRLI content dropped continuously after 12 h, reaching one-twelfth of its initial level after 2 weeks. The pituitary tiPRLII content, on the other hand, did not decrease significantly until day 7, and after a 2-week exposure to brackish water it had only decreased by 50%. When injected into tilapia adapted to brackish water, both ovine prolactin and recombinant tiPRLI induced a clear dose-dependent ion-retaining effect. In contrast, the effect induced by tiPRLII treatment was markedly smaller and not dose-dependent. Northern blot analysis of tiPRL mRNAs using either a tiPRLI or a tiPRLII cDNA probe indicated the presence of two mRNAs differing in size: a 1.7 kb mRNA coding for tiPRLI and a 1.3 kb mRNA coding for tiPRLII. After transfer to brackish water, levels of the two mRNAs decreased similarly. The present study indicates that, in O. niloticus, the two forms of prolactin have different osmoregulatory roles during adaptation to brackish water. Accordingly, their synthesis are differentially regulated after transfer to a hyperosmotic environment, presumably at a post-transcriptional level. [less ▲]

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See detailCharacterization of a single prolactin (PRL) receptor in tilapia (Oreochromis niloticus) which binds both PRLI and PRLII
Auperin, B.; Rentier-Delrue, Françoise ULg; Martial, Joseph ULg et al

in Journal of Molecular Endocrinology (1994), 13(3), 241-51

In tilapia, there are two forms of prolactin (PRL) whose effects on sodium and chloride movements differ and depend on the living environment of the fish. To see whether different receptors or the same ... [more ▼]

In tilapia, there are two forms of prolactin (PRL) whose effects on sodium and chloride movements differ and depend on the living environment of the fish. To see whether different receptors or the same receptor mediates these different effects, we have characterized the specific binding of both forms of tilapia (ti)PRL in two osmoregulatory organs, the gill and kidney. Two recombinant tiPRLs were used for this analysis. The recombinant hormones had the same properties as the native hormones in a tilapia gill radioreceptor assay. Specific binding to gill and kidney membranes was increased by optimizing the quality of the tissue preparations (physiological state of fish, membrane preparation) and the incubation conditions (pH, salt concentrations, temperature, time). Under these optimized conditions, we detected only one class of high affinity PRL receptor in gill and kidney. Its binding affinity was higher for tiPRLI than for tiPRLII in both gill and kidney (for tiPRLI the respective affinity values were 2.9 and 2.3 x 10(10) per M, for tiPRLII they were 1.9 and 0.5 x 10(10) per M). In competition studies, tiPRLI was more potent, followed by tiPRLII and ovine (o)PRL. tiGH and oGH did not significantly displace either tiPRL. The receptor we have characterized thus recognizes quite specifically both tiPRLs. [less ▲]

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See detailCalcitropic effect of recombinant prolactins in Oreochromis mossambicus
Flik, G.; Rentier-Delrue, Françoise ULg; Wendelaar-Bonga, S. E.

in The American Physiological Society (1994)

Homologous recombinant tilapia prolactins 1 and 2 were tested for calcitropic activity in tilapia Oreochromis mossambicus. Injection of both PRLs induced hypercalcemia that resulted for an enhanced ... [more ▼]

Homologous recombinant tilapia prolactins 1 and 2 were tested for calcitropic activity in tilapia Oreochromis mossambicus. Injection of both PRLs induced hypercalcemia that resulted for an enhanced calcium influx via the gills and a decreased calcium efflux. Both PRLs increased the density of the Ca2+-transporting Ca2+-adenosinetriphosphatase in a plasma membrane preparation of the branchial epithelium. Dose-response studies demonstrated that the PRL-1 was roughly twofold more potent than PRL2 in inducing hypercalcemia, in enhacing basal levels of cortisol and in stimulating opercular ionocyte density. But both PRL were equipotent in stimulating the dermal mucocyte frequency. [less ▲]

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See detailDetection of mRNA encoding an antibacterial-metalloprotein (MPII) by in situ hybridization with a cDNA probe generated by PCR in the worm nereis diversicolor
Salzet-Raveillon, B.; Rentier-Delrue, Françoise ULg; Dhainaut, A.

in Cellular and Molecular Biology (1993)

Based on partial amino acid sequence of an antibacterial-metalloprotein (MPII) consisting of a N-terminal fragment (1-33th) and an 43 amino acids long internal fragment, two oligonucleotides primers were ... [more ▼]

Based on partial amino acid sequence of an antibacterial-metalloprotein (MPII) consisting of a N-terminal fragment (1-33th) and an 43 amino acids long internal fragment, two oligonucleotides primers were synthesized and used to generate a cDNA fragment by the PCR method. The specificity of the PCR synthesized 220 bp fragment was verified by hybrid-arrest translation and sequencing. In situ hybridization performed with this cDNA fragment on Nereis diversicolor whole body defined two specific sites of recognition: a cluster of cells floating in the coelom and two types of muscles (perineural and oblique). Finally, the chronological expression of the MPII was postulated. [less ▲]

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See detailHomologous recombinant growth hormone and calcium metabolism in the tilapia oreochromis mossambicus, adapted to freshwater
Flik, G.; Atsma, W.; Fenwick, J. C. et al

in Journal of Experimental Biology (1993)

Homologous recombinant tilapia growth hormoe was tested for its effect on calcium metabolism in freshwater tilapia Oreochromis mossambicus. A comparison of the role of GH and prolactin in calcium ... [more ▼]

Homologous recombinant tilapia growth hormoe was tested for its effect on calcium metabolism in freshwater tilapia Oreochromis mossambicus. A comparison of the role of GH and prolactin in calcium regulation of the tilapia led to the conclusion that GH has specific calciopropic effects on freshwater Tilapia that differ from those of prolactin. [less ▲]

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See detailCloning and overexpression of the triosephosphate isomerase genes from psychrophilic and thermophilic bacteria. Structural comparison of the predicted protein sequences
Rentier-Delrue, Françoise ULg; Mande, Shekhar C; Moyens, Sylvianne et al

in Journal of Molecular Biology (1993), 229(1), 85-93

We focused on the temperature adaptation of triosephosphate isomerase (TIM; E.C. 5.3.1.1.) by comparing the structure of TIMs isolated from bacterial organisms living in either cold or hot environments ... [more ▼]

We focused on the temperature adaptation of triosephosphate isomerase (TIM; E.C. 5.3.1.1.) by comparing the structure of TIMs isolated from bacterial organisms living in either cold or hot environments. The TIM gene from psychrophilic bacteria Moraxella sp. TA137 was cloned and its nucleotide sequence determined. Its deduced amino acid sequence revealed 34% identity with the thermophilic bacteria Bacillus stearothermophilus TIM. Expression vectors were constructed and recombinant Moraxella TA137 and Bacillus stearothermophilus TIMs were overproduced and purified to homogeneity. Recombinant TIM inactivation constants (Ki), measured at various temperatures, compared to those of the mesophilic Escherichia coli recombinant TIM clearly show that Moraxella TA137 and B. stearothermophilus TIMs have respectively psychrophilic and thermophilic characteristics. To try to elucidate the structure-thermolability and structure-thermostability relationship, factors affecting the overall stability of these two TIMs were examined, based on the alignment with the mesophilic chicken TIM, the three-dimensional structure of which is already known. From this comparison, it appears that the adaptability of TIM to high temperature is favored by better stabilizing residues for the helix dipole as well as better helix-forming residues whereas the adaptability of TIM to low temperature seems to reside in the nature of helix-capping residues. [less ▲]

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See detailThe 16-kilodalton N-terminal fragment of human prolactin is a potent inhibitor of angiogenesis
Clapp, Carmen; Martial, Joseph ULg; Guzman, Raphaël C et al

in Endocrinology (1993), 133(3), 1292-9

The formation of a new blood supply, angiogenesis, is an essential component of carcinogenesis and unrestricted tumor growth. A substance capable of inhibiting angiogenesis would be of considerable ... [more ▼]

The formation of a new blood supply, angiogenesis, is an essential component of carcinogenesis and unrestricted tumor growth. A substance capable of inhibiting angiogenesis would be of considerable therapeutic potential in the treatment of cancer. We previously reported that the 16-kilodalton N-terminal fragment of rat PRL (16K rPRL) was a potent inhibitor of capillary endothelial cell proliferation via a novel receptor. We now report that the nanomolar concentrations of recombinant human 16K PRL inhibit basal and basic fibroblast growth factor- or vascular endothelial growth factor-stimulated growth of bovine brain capillary endothelial cells. 16K human (h) PRL also inhibits stimulation of human umbilical vein endothelial cell proliferation by basic fibroblast growth factor. The organization of endothelial cells into capillary-like structures in type I collagen gels is also prevented by 16K hPRL. Furthermore, in an in vivo assay, the chick embryo chorioallantoic membrane assay, 16K hPRL as well as 16K rPRL were potent inhibitors of capillary formation. 16K hPRL, like 16K rPRL, maintains its biological activity as a partial PRL agonist at PRL receptors on mammary gland epithelial cells. These data demonstrate for the first time that the biological activity of 16K rPRL is not unique and that similar fragments of hPRL are active. The antiangiogenic activity of these molecules is conserved across avian and mammalian species. That 16K hPRL is a potent antiangiogenic factor in in vitro and an in vivo assay raises the exciting potential of this peptide being capable of inhibiting tumor growth. [less ▲]

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See detailMolecular Biology of tilapia prolactins
Swennen, E.; Sekkali, B.; Poncelet, A. C. et al

in Fundamental and applied research for aquaculture (1993)

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See detailReplacing the (beta alpha)-unit 8 of E.coli TIM with its chicken homologue leads to a stable and active hybrid enzyme
Mainfroid, Véronique; Goraj, Karine; Rentier-Delrue, Françoise ULg et al

in Protein Engineering (1993), 6(8), 893-900

In order to investigate how structural modifications interfere with protein stability, we modified a (beta alpha)-unit in E.coli triosephosphate isomerase (TIM), a typical (beta alpha)-barrel protein ... [more ▼]

In order to investigate how structural modifications interfere with protein stability, we modified a (beta alpha)-unit in E.coli triosephosphate isomerase (TIM), a typical (beta alpha)-barrel protein, assuming that the pseudosymmetrical beta-barrel can be divided into eight successive loop/beta-strand/loop/alpha-helix motifs. We replaced the eighth (beta alpha)-unit of E.coli TIM with the corresponding chicken (beta alpha)-unit. The substitution, involving the replacement of 10 of the 23 residues of this (beta alpha)-unit, was evaluated first by modelling, then experimentally. Modelling by homology suggests how the amino acid replacements might be accommodated in the hybrid E.coli/chicken TIM (ETIM8CHI). Both natural and hybrid recombinant TIMs, overproduced in E.coli, were purified to homogeneity and characterized as to their stability and kinetics. Our kinetic studies show that the modification performed here leads to an active enzyme. The stability studies indicate that the stability of ETIM8CHI is comparable to that of the wild type TIM. [less ▲]

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