bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biochemical Factors Governing the Steady-State Estrone/Estradiol Ratios Catalyzed by Human 17β-Hydroxysteroid Dehydrogenases Types 1 and 2 in HEK-293 Cells
Authors: Sherbet Daniel P. , Guryev Oleg L. , Papari-Zareei Mahboubeh , Mizrachi Dario , Rambally Siayareh , Akbar Sharareh , Auchus Richard J. 
Published: June 2009

AbstractHuman 17β-hydroxysteroid dehydrogenase types 1 and 2 (17βHSD1 and 17βHSD2) regulate estrogen potency by catalyzing the interconversion of estrone (E1) and estradiol (E2) using nicotinamide adenine dinucleotide (phosphate) cofactors NAD(P)(H). In intact cells, 17βHSD1 and 17βHSD2 establish pseudo-equilibria favoring E1 reduction or E2 oxidation, respectively. The vulnerability of these equilibrium steroid distributions to mutations and to altered intracellular cofactor abundance and redox state, however, is not known. We demonstrate that the equilibrium E2/E1 ratio achieved by 17βHSD1 in intact HEK-293 cell lines is progressively reduced from 94:6 to 10:90 after mutagenesis of R38, which interacts with the 2′-phosphate of NADP(H), and by glucose deprivation, which lowers the NADPH/NADP+ ratio. The shift to E2 oxidation parallels changes in apparent Km values for purified 17βHSD1 proteins to favor NAD(H) over NADP(H). In contrast, mutagenesis of E116 (corresponding to R38 in 17βHSD1) and changes in intracellular cofactor ratios do not alter the greater than 90:10 E1/E2 ratio catalyzed by 17βHSD2, and these mutations lower the apparent Km of recombinant 17βHSD2 for NADP(H) only less than 3-fold. We conclude that the equilibrium E1/E2 ratio maintained by human 17βHSD1 in intact cells is governed by NADPH saturation, which is strongly dependent on both R38 and high intracellular NADPH/NADP+ ratios. In contrast, the preference of 17βHSD2 for E2 oxidation strongly resists alteration by genetic and metabolic manipulations. These findings suggest that additional structural features, beyond the lack of a specific arginine residue, disfavor NADPH binding and thus support E2 oxidation by 17βHSD2 in intact cells.
Chorionic Gonadotropin Regulates Prostaglandin E Synthase via a Phosphatidylinositol 3-Kinase-Extracellular Regulatory Kinase Pathway in a Human Endometrial Epithelial Cell Line: Implications for Endometrial Responses for Embryo Implantation
Authors: Banerjee Prajna , Sapru Kavita , Strakova Zuzana , Fazleabas Asgerally T. 
Published: June 2009

Abstract
Successful implantation necessitates modulation of the uterine environment by the embryo for a specific period of time during the menstrual cycle. Infusion of chorionic gonadotropin (CG) into the oviducts of baboons to mimic embryo transit induces a myriad of morphological, biochemical, and molecular changes in the endometrium. Endometrial epithelial cells from both baboons and humans when stimulated by CG in vitro, activates a cAMP-independent MAPK pathway leading to prostaglandin E2 (PGE2) synthesis. This study shows that in the human endometrial cell line, HES, CG, acting via its G-protein coupled receptor, phosphorylates protein kinase B, c-Raf, and ERK1/2 in a phosphatidylinositol 3-kinase (PI3K)-dependent manner. Furthermore, ERK1/2 phosphorylation is independent of the signaling paradigms of Gαs, GαI, and epidermal growth factor receptor (EGFR) transactivation, typical of gonadal cells, indicating an alternative signaling pattern in the endometrium. After phosphorylation by CG, ERK1/2 translocates to the nucleus in a time-dependent manner. Downstream of ERK1/2, CG activates the nuclear transcription factor, Elk1, also in a PI3K-MAPK-dependent manner. Lastly, we show that in HES cells, this pathway regulates the expression of the microsomal enzyme PGE2 synthase (mPTGES), a terminal prostanoid synthase responsible for PGE2 synthesis. CG regulates the mPTGES promoter and also induces mPTGES synthesis in HES cells via the PI3K-ERK1/2 pathway. We suggest that this alternative PI3K-ERK-Elk pathway activated by CG regulates prostaglandin production by the endometrial epithelium and serves as an early trigger to prepare the endometrium for implantation.
ASCOM Controls Farnesoid X Receptor Transactivation through Its Associated Histone H3 Lysine 4 Methyltransferase Activity
Authors: Kim Dae-Hwan , Lee Jeongkyung , Lee Bora , Lee Jae W. 
Published: June 2009

Abstract
Activating signal cointegrator-2 (ASC-2), a coactivator of multiple nuclear receptors and transcription factors, belongs to a steady-state complex named ASCOM (for ASC-2 complex), which contains histone H3 lysine 4 (H3K4) methyltransferase MLL3 or its paralog MLL4. ASC-2 binds to many nuclear receptors in a ligand-dependent manner through its two LxxLL motifs. Here we show that the first LxxLL motif of ASC-2 shows relatively weak but specific interaction with the nuclear receptor farnesoid X receptor (FXR) and that ASCOM plays crucial roles in FXR transactivation. Our results reveal that ASC-2, MLL3, and MLL4 are recruited to FXR target genes in a ligand-dependent manner. We further show that the recruitment of MLL3 requires ASC-2 and that FXR ligand induces not only expression of FXR-target genes but also their H3K4 trimethylation in a manner dependent on the presence of ASC-2, MLL3, and MLL4. In addition, MLL3 and MLL4 function redundantly with FXR transactivation. Correspondingly, expression of FXR target genes is partially impaired in mice expressing an enzymatically inactivated mutant form of MLL3, and these mice show disrupted bile acid homeostasis. Overall, these results suggest that ASCOM-MLL3 and ASCOM-MLL4 play redundant but essential roles in FXR transactivation via their H3K4 trimethylation activity.
Limiting factors to encapsulation: the combined effects of dissolved protein and oxygen availability on embryonic growth and survival of species with contrasting feeding strategies
Authors: Brante Antonio , Fernández Miriam , Viard Frédérique 
Published: June 2009

SUMMARYEncapsulation is a common strategy among marine invertebrate species. It has been shown that oxygen and food availability independently constrain embryo development during intracapsular development. However, it is unclear how embryos of species with different feeding strategies perceive these two constraints when operating jointly. In the present study, we examined the relative importance of dissolved albumen, as a food source, oxygen condition and their interaction on embryonic growth and the survival of two calyptraeid species, Crepidula coquimbensis and Crepidula fornicata,exhibiting different embryo feeding behaviours (i.e. presence vsabsence of intracapsular cannibalism). Two oxygen condition treatments(normoxia and hypoxia) and three albumen concentrations (0, 1 and 2 mg l–1) were studied. In addition, albumen intake by embryos was observed using fluorescence microscopy. Our study shows that embryos of both species incorporated dissolved albumen but used a different set of embryonic organs. We observed that embryo growth rates in C. coquimbensis were negatively affected only by hypoxic conditions. Conversely, a combination of low albumen concentration and oxygen availability slowed embryo growth in C. fornicata. These findings suggest that oxygen availability is a limiting factor for the normal embryo development of encapsulated gastropod species, regardless of feeding behaviour or developmental mode. By contrast,the effect of dissolved albumen as an alternative food source on embryo performance may depend on the feeding strategy of the embryos.
Do cephalopods communicate using polarized light reflections from their skin?
Authors: Mäthger Lydia M. , Shashar Nadav , Hanlon Roger T. 
Published: June 2009

SUMMARYCephalopods (squid, cuttlefish and octopus) are probably best known for their ability to change color and pattern for camouflage and communication. This is made possible by their complex skin, which contains pigmented chromatophore organs and structural light reflectors (iridophores and leucophores). Iridophores create colorful and linearly polarized reflective patterns. Equally interesting, the photoreceptors of cephalopod eyes are arranged in a way to give these animals the ability to detect the linear polarization of incoming light. The capacity to detect polarized light may have a variety of functions, such as prey detection, navigation, orientation and contrast enhancement. Because the skin of cephalopods can produce polarized reflective patterns, it has been postulated that cephalopods could communicate intraspecifically through this visual system. The term `hidden' or`private' communication channel has been given to this concept because many cephalopod predators may not be able to see their polarized reflective patterns. We review the evidence for polarization vision as well as polarization signaling in some cephalopod species and provide examples that tend to support the notion – currently unproven – that some cephalopods communicate using polarized light signals.
A supracellular system of actin-lined canals controls biogenesis and release of virulence factors in parasitoid venom glands
Authors: Ferrarese Roberto , Morales Jorge , Fimiarz Daniel , Webb Bruce A. , Govind Shubha 
Published: June 2009

SUMMARY
Parasitoid wasps produce virulence factors that bear significant resemblance to viruses and have the ability to block host defense responses. The function of these virulence factors, produced predominantly in wasp venom glands, and the ways in which they interfere with host development and physiology remain mysterious. Here, we report the discovery of a specialized system of canals in venom glands of five parasitoid wasps that differ in their infection strategies. This supracellular canal system is made up of individual secretory units, one per secretory cell. Individual units merge into the canal lumen. The membrane surface of the proximal end of each canal within the secretory cell assumes brush border morphology, lined with bundles of F-actin. Systemic administration of cytochalasin D compromises the integrity of the secretory unit. We show a dynamic and continuous association of p40, a protein of virus-like particles from a Drosophila parasitoid, L. heterotoma, with the canal and venom gland lumen. Similar structures in three Leptopilina species and Ganaspis xanthopoda,parasitoids of Drosophila spp., and Campoletis sonorenesis,a parasitoid of Heliothis virescens, suggest that this novel supracellular canal system is likely to be a common trait of parasitoid venom glands that is essential for efficient biogenesis and delivery of virulence factors.
The behavioural, digestive and metabolic characteristics of fishes with different foraging strategies
Authors: Fu Shi-Jian , Zeng Ling-Qing , Li Xiu-Ming , Pang Xu , Cao Zhen-Dong , Peng Jiang-Lan , Wang Yu-Xiang 
Published: June 2009

SUMMARY
To test the hypothesis that digestion has a more notable physiological effect on ambush foragers than on active foragers, we investigated the behavioural, digestive and metabolic characteristics, as well as the postprandial locomotory capacity, of four species of juvenile fish distributed along the Yangtze River, China, with distinct foraging strategies. The ambush foraging southern catfish (Silurus meridionlis) had the fewest movements per minute (MPM), lowest per cent time spent moving (PTM), slowest critical swimming speed (Ucrit), lowest maintenance metabolism(V̇O2rest) and lowest maximum locomotory metabolism(V̇O2max). However, the southern catfish had the highest feeding level and maximum feeding metabolism(V̇O2peak) and the greatest decrease in Ucrit after consumption of a large meal. Thus, this fish is highly adapted to its ambush behavioural strategy and sedentary life style. In the herbivorous grass carp (Ctenopharyngodon idellus), a low digestive capacity led to little change in postprandial locomotory performance, which benefits its frequent grazing behaviour. In this species, the greater amount of energy spent on routine activity and avoiding predators versus Ucrit might be related to its herbivorous life style and high predation risk. The active foraging crucian carp(Carassius auratus) adopts a unique high energy cost strategy that allows for high capacity in both routine activity and digestion, and the great flexibility of its cardio-respiratory capacity (increased V̇O2max after feeding) guarantees a small decrease in Ucrit even after maximum feeding. Finally, the sluggish foraging darkbarbel catfish(Pelteobagrus vachelli) has low digestive and locomotory capacity,but its energy-efficient venomous defence strategy may be related to its abundance. These results show that the digestive, behavioural and metabolic strategies differ among these fish species. The locomotory capacity in the sedentary fishes decreased profoundly after feeding, whereas it decreased little or not at all in the active fishes. The maintenance of high locomotory capacity after eating in the active fishes is probably related to a large metabolic capacity, a lower digestive capacity or an improvement in cardio-respiratory capacity after feeding.
Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight
Authors: Werner Y. L. , Pylka J. , Schneider H. , Seifan M. , Walkowiak W. , Werner-Reiss U. 
Published: June 2009

SUMMARYThe dimorphic ear of the bullfrog, Rana catesbeiana, has long been enigmatic. The male's tympanic membrane (TM) area approximates twice the area of the female's; however, similar size differences in the area of the columellar footplate were not observed between the sexes. Hence, the male's hearing is expected to be more sensitive than the female's but this is not the case. Asking what offsets the advantage of the large TM, we applied a series of experiments to the auditory system. Male and female audiograms based on stimulation with airborne sound and on both multi-unit responses from the brain and alternating cochlear potentials (`microphonics') showed equal sensitivity and a small difference in frequency response; at low frequencies the male was more sensitive than the female. Amputating the columella and stimulating the stump with mechanical vibration showed that for an equal microphonic response, the male's footplate vibrated with lower amplitude than the female's footplate. Mechanically stimulating the TM of the intact ear replicated this result, excluding the involvement of the mechanical lever. The TM of the male weighs five times the TM of the female, and artificial loading of the TM of either sex greatly reduced the ear's sensitivity. Hence, the male's excessive area ratio (TM to columellar footplate) is offset by the heavier cartilage cushion on the male's TM, damping the TM's response to sound. This is corroborated by experimentally artificially loading the TM. The product of area ratio and footplate vibration amplitude would result in similar stimulation of the inner ear in the two sexes.
A study of synchronisation between the flagella of bull spermatozoa, with related observations
Authors: Woolley David M. , Crockett Rachel F. , Groom William D. I. , Revell Stuart G. 
Published: June 2009

SUMMARYFlagellar synchronisation has been observed between bull spermatozoa as they swam in a viscous medium, confined to a glass surface. This process is of interest in understanding the regulation of flagellar oscillation in general. Exact and persisting synchrony between bull spermatozoa occurred only when the spermatozoan heads were tightly coupled mechanically. For these cells, viscous coupling between the flagella was not by itself sufficient to establish synchronisation. Immediately on synchronisation, with the spermatozoan heads superposed, the paired spermatozoa showed rises in conjoint beat frequency,wave velocity and swimming velocity, i.e. in nearly all cases, the new conjoint values were greater than those shown by either of the two singleton spermatozoa. In our interpretation of these results, we put forward hydrodynamic arguments for seeing the primary change as a rise in wave velocity, via a decreased viscous resistance to bend propagation. Mechanistically, the rise in beat frequency is mysterious unless, as we suggest, it is consequential to the rise in wave velocity, and mediated by an as-yet-unknown mechanical feedback process. The rise in swimming velocity is not surprising given the rise in wave velocity but there is evidence for an additional influence due to a subtle re-orientation of the conjoint spermatozoan heads, such that they experienced less frictional drag.
Targets for TNFα-induced lipolysis in gilthead sea bream(Sparus aurata L.) adipocytes isolated from lean and fat juvenile fish
Authors: Cruz-Garcia Lourdes , Saera-Vila Alfonso , Navarro Isabel , Calduch-Giner Josep , Pérez-Sánchez Jaume 
Published: June 2009

SUMMARY
The present study aimed to analyze adiposity heterogeneity and the role of liver X receptor (LXRα) and peroxisome proliferator-activated receptors(PPARs) as targets of tumour necrosis factor-α (TNFα) in gilthead sea bream (Sparus aurata L.). The screening of 20 fish at the beginning of the warm season identified two major groups with fat and lean phenotypes. Fat fish showed increased liver and mesenteric fat depots. This increased adiposity was concurrent in the adipose tissue to enhanced expression of lipoprotein lipase (LPL) whereas mRNA levels of the hormone-sensitive lipase (HSL) remained almost unchanged. The resulting LPL/HSL ratio was thereby highest in fat fish, which suggests that this group of fish has not reached its peak fat storage capacity. This is not surprising given the increased expression of PPARγ in the absence of a counter-regulatory raise of TNFα. However, this lipolytic cytokine exerted dual effects in primary adipocyte cultures that differ within and between lean and fat fish. One set of fat fish did not respond to TNFαtreatment whereas a second set exhibited a lipolytic response (increased glycerol release) that was apparently mediated by the downregulated expression of PPARβ. In lean fish, TNFα exerted a strong and non-transcriptionally mediated lipolytic action. Alternatively, TNFαwould inhibit lipid deposition via the downregulated expression of adipogenic nuclear factors (PPARγ and LXRα). TNFα targets are therefore different in fish with lean and fat phenotypes, which is indicative of the complex network involved in the regulation of fish lipid metabolism.
African lungfish,Protopterus annectens, possess an arginine vasotocin receptor homologous to the tetrapod V2-type receptor
Authors: Konno Norifumi , Hyodo Susumu , Yamaguchi Yoko , Kaiya Hiroyuki , Miyazato Mikiya , Matsuda Kouhei , Uchiyama Minoru 
Published: June 2009

SUMMARYIn tetrapods, arginine vasopressin and its counterpart, arginine vasotocin(AVT), are involved in renal water conservation through vascular V1a-type and tubular V2-type receptors, and only the former has thus far been cloned in fish. We successfully cloned the V1a-type and V2-type AVT receptor from the kidney of the African lungfish, Protopterus annectens, and the deduced amino acid sequences exhibited high homology with amphibian V1a- and V2-type receptors, respectively. Functional analysis showed that AVT addition to CHO cells transfected with lungfish V1a-type receptor increased[Ca2+]i in a concentration-dependent manner, whereas CHO cells transfected with lungfish V2-type receptor responded with cAMP accumulation after AVT stimulation. Lungfish V2-type receptor mRNA was strongly expressed in the heart and kidney, while V1a-type receptor mRNA was ubiquitously expressed in all the tissues examined. In the kidney,immunohistochemistry using a specific antibody to lungfish V2-type receptor showed localization in the basolateral area of the cells in the late part of the distal tubules. Artificial estivation (EST) for 90 days significantly increased plasma osmolality and sodium and urea concentrations. There was no significant difference in the V2-type receptor mRNA and protein expression levels in the kidney between the freshwater and EST lungfish, while the AVT precursor mRNA level in the hypothalamus was remarkably higher in the EST lungfish. Our results indicate that African lungfish possess a functional V2-type receptor similar to that in tetrapods, suggesting that elevated plasma AVT during estivation exerts a renal tubular antidiuretic effect through the V2-type receptor expressed in the distal segments of lungfish kidney.
Hyperunstable matrix proteins in the byssus of Mytilus galloprovincialis
Authors: Sagert Jason , Waite J. Herbert 
Published: June 2009

SUMMARY
The marine mussel Mytilus galloprovincialis is tethered to rocks in the intertidal zone by a holdfast known as the byssus. Functioning as a shock absorber, the byssus is composed of threads, the primary molecular components of which are collagen-containing proteins (preCOLs) that largely dictate the higher order self-assembly and mechanical properties of byssal threads. The threads contain additional matrix components that separate and perhaps lubricate the collagenous microfibrils during deformation in tension. In this study, the thread matrix proteins (TMPs), a glycine-, tyrosine- and asparagine-rich protein family, were shown to possess unique repeated sequence motifs, significant transcriptional heterogeneity and were distributed throughout the byssal thread. Deamidation was shown to occur at a significant rate in a recombinant TMP and in the byssal thread as a function of time. Furthermore, charge heterogeneity presumably due to deamidation was observed in TMPs extracted from threads. The TMPs were localized to the preCOL-containing secretory granules in the collagen gland of the foot and are assumed to provide a viscoelastic matrix around the collagenous fibers in byssal threads.
Lift and drag performance of odontocete cetacean flippers
Authors: Weber Paul W. , Howle Laurens E. , Murray Mark M. , Fish Frank E. 
Published: June 2009

SUMMARYCetaceans (whales, dolphins and porpoises) have evolved flippers that aid in effective locomotion through their aquatic environments. Differing evolutionary pressures upon cetaceans, including hunting and feeding requirements, and other factors such as animal mass and size have resulted in flippers that are unique among each species. Cetacean flippers may be viewed as being analogous to modern engineered hydrofoils, which have hydrodynamic properties such as lift coefficient, drag coefficient and associated efficiency. Field observations and the collection of biological samples have resulted in flipper geometry being known for most cetacean species. However,the hydrodynamic properties of cetacean flippers have not been rigorously examined and thus their performance properties are unknown. By conducting water tunnel testing using scale models of cetacean flippers derived via computed tomography (CT) scans, as well as computational fluid dynamic (CFD) simulations, we present a baseline work to describe the hydrodynamic properties of several cetacean flippers. We found that flippers of similar planform shape had similar hydrodynamic performance properties. Furthermore, one group of flippers of planform shape similar to modern swept wings was found to have lift coefficients that increased with angle of attack nonlinearly, which was caused by the onset of vortex-dominated lift. Drag coefficient versus angle of attack curves were found to be less dependent on planform shape. Our work represents a step towards the understanding of the association between performance, ecology, morphology and fluid mechanics based on the three-dimensional geometry of cetacean flippers.