bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pituitary and gonadal responses to the long-term pulsatile administration of gonadotrophin-releasing hormone in fetal fetal sheep
Authors: Thomas G B , Brooks A N 
Published: December 2004

Abstract
The fetal hypothalamo–pituitary–gonadal axis reaches a peak in activity at mid-gestation and this is followed by a period of suppression which persists until the onset of puberty. The decline in gonadotrophic activity during late gestation is thought to reflect the maturation of central and peripheral feedback signals. In order to establish if sustained pituitary responsiveness is rate limiting to the reinstatement of reproductive function, we have examined the endocrine consequences of repeated pulsatile GnRH administration to male and fetal sheep during late gestation. Beginning on day 121 of gestation (term=145 days) chronically catheterized fetal sheep were given i.v. pulses of either 500 ng GnRH or saline every 2 h for 14 days. Pituitary and gonadal responses were assessed by measuring changes in plasma concentrations of LH, FSH, inhibin and testosterone (in male fetuses) in response to the first pulse of GnRH on day 1 and to the corresponding pulse on days 4, 7, 10 and 14. In response to the first pulse of GnRH there was an immediate release of LH, with the peak response being significantly (P<0·01) greater than on subsequent days. In male fetuses each pulse of LH was followed by a rise in plasma testosterone concentrations within 40–60 min. The amplitude of these testosterone responses increased significantly (P<0·01) after 9 days of treatment despite a decline in the plasma LH response. Basal FSH concentrations increased progressively (P<0·05) during pituitary stimulation with GnRH in both male and female fetuses. Immunoreactive inhibin concentrations were significantly (P<0·05) higher in males than in females, and there was a gradual increase throughout the experimental period irrespective of treatment. We observed no inverse correlation between inhibin and FSH concentrations. These data show that pulsatile administration of GnRH to fetal sheep during late gestation results in sustained re-activation of pituitary–gonadal function. The decline in fetal gonadotrophins, which is a characteristic feature of late gestation, is therefore likely to result from inadequate GnRH secretion from the fetal hypothalamus rather than an inhibition of pituitary function by peripheral feedback signals.
Journal of Endocrinology (1997) 153, 385–391
Effects of season, protein and nutritional state on glucose tolerance during an annual cycle of growth in young red deer stags
Authors: McMahon C D , Corson I D , Littlejohn R P , Stuart S K , Veenvliet B A , Suttie J M 
Published: December 2004

Abstract
Two hypotheses were tested in gonad-intact, young (aged 6–18 months), growing red deer stags during an annual growth cycle. First, that glucose clearance rate is faster during summer than during winter. Secondly, that increased dietary protein availability will enhance winter growth.
Stags were randomly assigned into one of two groups: group 1 (n=5) had 16% while group 2 (n=6) had 48% of dietary protein naturally protected against fermentative degradation in the rumen. Total crude protein and energy remained similar for each diet (12 and 14% respectively for protein and 11 MJ metabolisable energy/kg dry matter). Stags were kept indoors in individual pens for 12 months and given monthly intravenous glucose tolerance tests (IVGTT), at a dose of 200 mg/kg, in the fed and fasted (48 h) states to determine both growth and steady-state tissue requirements. Protein level had no effect on food intake, weight gain, insulin kinetics, or glucose clearance rate. In the fed state, insulin peak (highest level after IVGTT) increased (P<0·01) from October (139 pmol/l) to December (247 pmol/l (s.e.d.=42) and remained elevated during the summer, before declining (P<0·01) from February (223 pmol/l) to April (130 pmol/l) (s.e.d.=25). Glucose clearance rate was faster (P<0·05) in December (1·69 litres/min) than June (0·61 litres/min) in the fed state (s.e.d.=0·30), and decreased (P<0·05) from February (1·75 litres/min) to April (0·92 litres/min) (s.e.d.=0·39). During fasting, the pattern of glucose clearance was similar to that observed in the fed state, but the amplitude was lower, while the pattern for insulin peak was similar to that of the fed state.
We concluded first, that additional protected protein does not benefit growth during winter. Secondly, we concluded from the fasted, steady-state data that stags are insulin resistant during summer. Thirdly, despite insulin resistance, data on the fed state demonstrated that stags have higher tissue energy requirements during summer growth.
Journal of Endocrinology (1997) 154, 275–283
Responsiveness of chicken embryonic somatotropes to somatostatin (SRIF) and IGF-I
Authors: Piper M M , Porter T E 
Published: December 2004

Abstract
We have previously demonstrated that chicken embryonic somatotropes are responsive to GHRH shortly after they differentiate. In contrast, relatively little is known about the regulation of GH secretion by somatostatin (SRIF) and IGF-I during chicken embryonic development. In the present study, anterior pituitary cells were isolated from day 16, 18 and 20 embryos and subjected to reverse hemolytic plaque assays (RHPAs) for chicken GH to assess the effect of SRIF and IGF-I on basal GH release and SRIF on GHRH-stimulated GH secretion. We found that all three ages responded to SRIF, under both basal and stimulated conditions. SRIF inhibition of basal GH release was evident for day 18 and 20 cells by 9 h, while 18 h were required for day 16 cells. After 18 h, 10−11 m SRIF depressed basal GH secretion by day 16 and 18 cells, while 10−9 m SRIF was required to depress GH plaque percentages by day 20 cells. GHRH stimulated GH release from all ages tested. After 2 h, SRIF partially suppressed GHRH-stimulated GH release by day 20 cells. After 6 h, day 18 cells responded to SRIF, reducing the percentage of plaque-forming cells under GHRH stimulated conditions. After 18 h, the percentage of day 16 cells forming GH plaques was reduced for cells treated with GHRH and SRIF, compared with cells treated with GHRH alone. All ages examined also responded to IGF-I. After 36 h, GH release by day 16 and 18 cells was decreased when exposed to IGF-I. While IGF-I decreased the relative amount of GH secreted per somatotrope on day 20, a paradoxical increase in the percentage of cells secreting GH was noted. These results indicate that anterior pituitary somatotropes are responsive to SRIF and IGF-I during late embryonic development of chickens.
Journal of Endocrinology (1997) 154, 303–310
Differential effects of GH stimulation on fasting and prandial metabolism and plasma IGFs and IGF-binding proteins in lean and obese sheep
Authors: McCann J P , Loo S C , Aalseth D L , Abribat T 
Published: December 2004

Abstract
The effect of body condition per se on plasma IGFs and IGF-binding proteins (IGFBPs) and the whole-body metabolic responses to recombinant DNA-derived bovine GH (rbGH) in both the fed and the fasted state were determined in lean and dietary obese sheep (n=6/group). Sheep at zero-energy balance and equilibrium body weight were injected s.c. for 12 days with 100 μg/kg rbGH immediately before their morning feeding. Before GH treatment, fasting plasma concentrations of insulin (17·0 ± 1·9 vs 7·5 ± 0·7 μU/ml), IGF-I (345 ± 25 vs 248 ± 10 ng/ml), glucose (52·6 ± 1·1 vs 48·3 ± 0·7 mg/dl), and free fatty acid (FFA) (355 ± 45 vs 229 ± 24 nmol/ml) were greater (P<0·05) and those of GH (1·1 ± 0·2 vs 2·6 ± 0·3 ng/ml) were lower (P<0·05) in obese than in lean sheep. Fasting concentrations of IGF-II and glucagon were not affected (P>0·05) by obesity. GH concentrations were increased equivalently by 6–9 ng/ml in lean and obese sheep during GH treatment. GH caused an immediate and a marked fivefold increase in the fasting insulin level in obese sheep but only minimally affected insulin concentration in lean sheep. The increment in fasting glucose during GH treatment was greater (P<0·05) in obese (8–12 mg/dl) than in lean (2–5 mg/dl) sheep. Frequent measurements in the first 8 h after feeding and injection of excipient (day 0) or the first (day 1), sixth (day 6) and twelfth (day 12) daily injection of GH showed that prandial metabolism in both groups of sheep was affected minimally by GH. However, GH treatment on day 1 (not days 6 or 12) acutely attenuated the feeding-induced suppression of plasma FFA in both groups of sheep and this effect was significantly greater in obese than in lean sheep.
Although obese sheep were hyposomatotropic, the basal and GH-induced increases in plasma IGF-I concentrations were greater (P<0·05) in obese than in lean sheep. Plasma IGF-II was unaffected by obesity and was not increased by GH stimulation. Western ligand blotting showed that IGFBP-3 accounted for approximately 50–60% of the plasma IGF-I binding capacity in sheep respectively both before and during GH treatment. Basal plasma levels of IGFBP-2 were lower (P<0·05) and those of IGFBP-3 greater (P<0·05) in obese compared with lean sheep. GH increased the level of IGFBP-3 equally in lean and obese sheep, but suppressed the expression of IGFBP-2 more (P<0·05) in lean than in obese sheep. We concluded that the diabetogenic-like actions of GH in sheep were exaggerated markedly by obesity, and were expressed more during the fasted than the fed states. The effects of GH stimulation on the endocrine pancreas may be selective for β-cells and preferentially enhanced by obesity. GH regulation of IGF-I and the IGFBPs differs in lean and obese sheep.
Journal of Endocrinology (1997) 154, 329–346
Tissue-specific changes in angiotensin II receptors in streptozotocin-diabetic rats
Authors: Brown L , Wall D , Marchant C , Sernia C 
Published: December 2004

Abstract
While there have been reports on changes in the renin–angiotensin system and angiotensin II (AT) receptors in diabetes, there is no agreement on the nature of these changes. This study has characterised specific AT receptors in the heart, kidney, liver and adrenal glands of the streptozotocin (STZ)-diabetic rat using radioligand binding studies with the radioligand 125I-[Sar1,Ile8]-angiotensin II. Left ventricular AT receptor density increased by 135% 4 weeks after treatment and by 206% 12 weeks after treatment; in the liver, AT receptor density increased by 476% (4 weeks) and 263% (12 weeks) and in the adrenal gland by 236% (4 weeks) and 109% (12 weeks). In contrast, renal AT receptor density decreased by 49% (4 weeks) and 36% (12 weeks). Competition-displacement assays with losartan, an AT1-selective ligand, showed that the proportion of AT receptor subtypes remained unchanged. STZ treatment decreased plasma angiotensinogen by 72% (4 weeks) and 67% (12 weeks) and increased plasma renin concentration after 12 weeks; plasma renin activity and aldosterone concentrations remained unchanged. Treatment with human insulin (5 U/day) attenuated changes in plasma angiotensinogen and AT receptor density except in the left ventricle. We conclude that there are major changes in AT receptors in the STZ-diabetic rat that are tissue-specific and time-dependent. Plasma angiotensinogen and renin secretion change in directions that result in the maintenance of plasma renin activity and aldosterone concentration.
Journal of Endocrinology (1997) 154, 355–362
Prolegomena zum experimentellen Engineering des genetischen Codes durch Erweiterung seines Aminosäurerepertoires
Authors: Budisa Nediljko 
Published: December 2004

AbstractDie Proteinsynthese und ihre Verbindung mit dem genetischen Code spielten lange Zeit eine zentrale Rolle in der Biologie. Der schnelle experimentelle Fortschritt führte im vergangenen Jahrzehnt zu einer nahezu kompletten Beschreibung dieser Prozesse. Weitere wichtige Experimente ergaben Hinweise dafür, dass die natürliche Protein‐Translationsmaschinerie neu programmiert werden kann, um viele nichtkanonische Aminosäuren genetisch zu codieren. Tatsächlich lassen die 20 kanonischen Aminosäuren, die im universellen genetischen Code verwendet werden, viele wünschenswerte Funktionalitäten vermissen, etwa Halogen‐, Keto‐, Cyan‐, Azido‐, Nitroso‐, Nitro‐ oder Silylgruppen sowie CC‐ oder CC‐Bindungen. Die Fähigkeit, genetisch eine derartige chemische Vielfalt zu codieren, wird uns ermöglichen, lebende Zellen wie Bakterien neu zu programmieren, sodass sie maßgeschneiderte Proteine mit vielseitigen Funktionen exprimieren. An der Schnittstelle von Biologie, Chemie und Physik entwickelt sich mit dem Engineering des genetischen Codes ein aufstrebendes Forschungsgebiet.
Cryostructuration of polymer systems. XXIV. Poly(vinyl alcohol) cryogels filled with particles of a strong anion exchanger: Properties of the composite materials and potential applications
Authors: Savina Irina N. , Hanora Amro , Plieva Fatima M. , Galaev Igor Y. , Mattiasson Bo , Lozinsky Vladimir I. 
Published: December 2004

AbstractA composite material produced from a poly(vinyl alcohol) cryogel with entrapped particles of the strong anion‐exchange resin Amberlite is presented. The properties of the composite material depended strongly on whether the resin was used in OH− form or Cl− form. The ion‐exchange filler in OH− form caused both a significant reinforcement of the composite material and an increase in the gel fusion temperature. These effects were thought to be associated with the additional ionic bonding between the continuous and disperse phases. Beads 200–600 μm in size were prepared from the composite material and used in expanded‐bed ion‐exchange chromatography for the capture of the negatively charged solutes benzoate and lactate from the suspension of negatively charged cells. The plausibility of the approach has been demonstrated on model systems composed of yeast cells and benzoate and with a real fermentation broth produced after lactic acid fermentation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 529–538, 2005
Flow‐induced crystallization in the injection molding of polymers: A thermodynamic approach
Authors: Kim Kyuk Hyun , Isayev A. I. , Kwon Keehae 
Published: December 2004

AbstractThe prediction of the crystallinity and microstructure that develop in injection molding is very important for satisfying the required specifications of molded products. A novel approach to the numerical simulation of the skin‐layer thickness and crystallinity in moldings of semicrystalline polymers is proposed. The approach is based on the calculation of the entropy reduction in the oriented melt and the elevated equilibrium melting temperature by means of a nonlinear viscoelastic constitutive equation. The elevation of the equilibrium melting temperature that results from the entropy reduction between the oriented and unoriented melts is used to determine the occurrence of flow‐induced crystallization. The crystallization rate enhanced by the flow effect is obtained by the inclusion of the elevated equilibrium melting temperature in the modified Hoffman–Lauritzen equation. Injection‐molding experiments at various processing conditions were carried out on polypropylenes of various molecular weights. The thickness of the highly oriented skin layer and the crystallinity in the moldings were measured. The measured data for the microstructures in the moldings agree well with the simulated results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 502–523, 2005
Bioengineering functional copolymers: V. Synthesis, LCST, and thermal behavior of poly(N‐isopropyl acrylamide‐co‐p‐vinylphenylboronic acid)
Authors: Çimen E. K. , Rzaev Zakir M. O. , Pişkin E. 
Published: December 2004

AbstractNew boron‐containing stimuli‐responsive (pH‐ and temperature‐sensitive) copolymers were synthesized and characterized. Structure and composition of copolymers were determined by FTIR and 1H‐NMR spectroscopy, and elemental analysis and titration (N and B contents for NIPA and VPBA unit, respectively). By DSC and XRD measurements, it is established that the synthesized copolymers have a semicrystalline structure due to formation of intra‐ and/or intermolecular H‐bonded supramolecular architecture. The copolymer composition–structure–property relationship indicates semicrystalline structure of copolymers with different compositions, degrees of crystallinity, and thermal and stimuli‐responsive behaviors depends on the content of boron‐containing monomer linkage. Results of DSC, DTA, and TGA analyses indicated that copolymers have Tg and Tm and high thermal stability. These water‐soluble and temperature‐ and pH‐sensitive amphiphilic copolymers can be used as polymeric carries for delivery of biological entities for diverse biomedical use, including boron neutron capture therapy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 573–582, 2005
Relationship between the morphological structure and mechanical properties of copper‐in‐hydrophilic polymer gradient composite films
Authors: Tang Jianguo , Che Yanke , Liu Haiyan , Wang Yao 
Published: December 2004

AbstractThis investigation was focused on the influence of polymer hydrophilicity on the morphological structure and mechanical properties of copper‐in‐polymer gradient composite films (CPGCFs). The ion motion and reduction in swelling cathode films under an electric field were the core of the gradient morphology formation of a metal region in the polymer matrix. The morphological study of CPGCFs revealed that the hydrophilicity of poly(vinyl alcohol) was helpful in forming a continuously deposited layer. The nanoclusters (40 nm) aligned into a branchlike form in the copper‐rich region in the poly(vinyl alcohol) matrix. On the basis of the fuzzy interface between the poly(vinyl alcohol) matrix and copper nanoclusters, a complex interaction between them was inferred. The reduced copper affected the mechanical properties of CPGCFs. The maximum load of CPGCFs could be enhanced by 25% to 167.0 N with optimal electrochemical reduction, but the elongation was depressed. An excess of reduced copper in the polymer matrix reduced both the strength and elongation of CPGCFs. The moduli of related samples showed trends similar to those of the strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 539–545, 2005
Superabsorbent resin of acrylic acid/ammonium acrylate copolymers synthesized by ultraviolet photopolymerization
Authors: Weiqing Ruan , Jinliang Qiao , Yuli Huang , Aijie Niu 
Published: December 2004

AbstractA new method of synthesizing a superabsorbent resin (SAR) from an acrylic acid/ammonium acrylate copolymer by direct UV photopolymerization was studied. The effects of the degree of neutralization of acrylic acid, the photoinitiators, the crosslinking agents, and the UV‐light exposure time on the water absorbency (Q) were investigated. The results showed that Q of an SAR based on Irgacure 1700 or Irgacure 1800 and Irgacure 651 was high, reaching about 1200 mL/g, but under the same conditions, Q was low for an SAR based on other photoinitiators. The UV absorption spectrum proved that the photoinitiators matched the UV light source. Among the crosslinking agents, N,N′‐methylene bisacrylamide was more efficient than the others at a small concentration and a high value of Q. 13C‐NMR spectrometry was used to identify the mechanism of the crosslinking reaction through the esterification of hydroxyethyl acrylate (HEA) and 2‐hydroxypropyl acrylate with carboxylic acid group in acrylic acid/ammonium acrylate copolymerization, but the efficiency of the crosslinking reaction by esterification was lower than that of the copolymerization of vinyl groups in the crosslinking agent. Q of the acrylic acid/ammonium acrylate copolymer for the SAR reached 1255 mL/g under certain conditions (degree of neutralization of acrylic acid = 75%, Irgacure 651 concentration = 0.2 wt %, [HEA] = 0.2 wt %, exposure time = 10 min). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 546–555, 2005
Comparative bioavailability of two brands of atenolol 100 mg tablets (Tensotin and Tenormin) in healthy human volunteers
Authors: Najib Naji M. , Idkaidek Nasir , Adel Ayman , Mohammed B. , Al‐Masri Sahar , Admour Isra' , Alam S. Mahmood , Dham Ruwayda , Qumaruzaman  
Published: December 2004

AbstractA bioequivalence study of two oral formulations of 100 mg atenolol was carried out in 24 healthy volunteers following a single dose, two‐sequence, cross‐over randomized design at the International Pharmaceutical Research Centre (IPRC), as a joint venture with Al‐Mowasah Hospital, Amman, Jordan. The two formulations were Tensotin (Julphar, UAE) as test and Tenormin (Zeneca, UK) as reference product. Both test and reference tablets were administered with 240 ml of water to each subject after an overnight fast on 2 treatment days separated by a 1 week washout period. After dosing, serial blood samples were collected for a period of 36 h. Whole blood was analysed for atenolol by a sensitive, reproducible and accurate HPLC method with fluorescence detection capable of detecting atenolol in the range of 20–1600 ng/ml with a limit of quantitation of 20 ng/ml. Various pharmacokinetic parameters including AUC0−t, AUC0−∝, Cmax, Tmax, T1/2 and λZ were determined from blood concentrations of both formulations and found to be in good agreement with reported values. AUC0−t, AUC0−∝, and Cmax were tested for bioequivalence after log‐transformation of data using ANOVA and 90% confidence interval and were found within the acceptable range of 80%–125%. Based on these statistical inferences, it was concluded that Tensotin is bioequivalent to Tenormin. Copyright © 2004 John Wiley & Sons, Ltd.
Pharmacokinetics of a novel antiangiogenic agent KR‐31831 in rats
Authors: Kim Sook J. , Lee Hong I. , Ji Hye Y. , Moon Ya , Paek In B. , Lee Sunkyung , Yi Kyu Y. , Yoo Sun D. , Lee Hye S. 
Published: December 2004

AbstractThis study reports the absorption, dose‐linearity and pharmacokinetics of a novel antiangiogenic agent KR‐31831 in rats after i.v. and oral administration at doses of 5, 10 and 25 mg/kg on both occasions. Concentrations of KR‐31831 were determined by a validated LC/MS/MS assay method. After i.v. injection, plasma concentration‐time profiles showed multi‐compartmental characteristics, and there were no significant differences in Cl (20.8–27.7 ml/min/kg) and dose‐normalized AUC (178.1–231 µg·min/ml based on the 5 mg/kg dose) as a function of dose. However, Vss was significantly increased at the 25 mg/kg dose (4931 ml/kg) compared with those (2288–2421 ml/kg) at lower doses. Subsequently, t1/2 was increased from 143–159 min at the lower doses to 304 min at the 25 mg/kg dose. The altered VSS was found to be a result of reduced plasma protein binding at relatively high concentrations. Following oral administration (doses 5–25 mg/kg), the absolute oral bioavailability ranged from 37.8% to 46.3%, and there were no significant alterations in dose‐normalized AUC, Tmax, Cmax and t1/2 as a function of dose. The extent of urinary excretion was low for both i.v. (0.35%–0.54%) and oral (0.13%–0.33%) doses. Further discussions on the chemical and microsomal stability were included. In conclusion, dose‐independent absorption kinetics were observed at oral doses from 5 to 25 mg/kg in rats. Orally administered KR‐31831 could be eliminated mainly by the liver metabolic pathway. Copyright © 2004 John Wiley & Sons, Ltd.