bluuebunny/crossref_metadata_2025 huggingface dataset:
Pheromonal regulation of the mouse estrous cycle by a heterogenotypic male
Authors: Barkley M. , DeLeon D. Delgado , Weste R.
Published: June 2005

The role of male pheromones in estrous cyclicity was studied in mice selected for different reproductive traits. When females are exposed to males of their own strain, estrous cycles are highly regular in females selected for increased embryo survival (line E). In contrast, cycle regularity is reduced by exposure of line E females to males from a strain characterized by irregular estrous cycles (line CN‐). To investigate the inhibition of estrous cyclicity and the role of androgen in this phenomenon, line E females were housed in the olfactory presence of E males and later rehoused with one of the following: intact or castrated males of line E (homogenotypic condition) or line CN‐heterogenotypic condition) or castrated CN‐ males provided with testosterone replacement. A final exposure to homogenotypic (line E) males was provided. Estrous cyclicity was decreased when line E females were rehoused with intact or castrated CN‐ males. Metestrus was prolonged by intact CN‐ males, whereas diestrus was prolonged in the presence of castrated CN‐ males. Androgen treatment did not enable castrated CN‐ males to prolong metestrus. These results demonstrate that: 1) heterogenotypic pheromones inhibit estrous cyclicity in line E; and 2) the inhibitory influence of line CN‐males on line E estrous cyclicity is mediated by factors in addition to or other than testosterone. © 1993 Wiley‐Liss, Inc.
Maintenance of high extracellular pH does not influence cell pH or metabolism in submerged anoxic bullfrogs
Authors: Wasser Jeremy S. , Jackson Donald C. , Chang Susan Y. , Warburton Stephen J.
Published: June 2005

We compared extracellular and intracellular acid‐base states in paralyzed bullfrogs subjected to 4 h of anoxic submergence at 15°C with or without maintenance of extracellular pH at preanoxic levels by bicarbonate infusion. We also assessed anaerobic metabolism under these conditions by measuring tissue lactate and glycogen concentrations in liver, heart, and skeletal muscle. Although bicarbonate infusion resulted in a significantly higher arterial blood pH (pHe) than saline infusion, intracellular pH (pHi) of heart and skeletal muscle, as determined by the DMO equilibration technqiue, were not significantly different after 4 h of anoxia. We were also unable to demonstrate any differences in anaerobic metabolic rate, since both tissue lactate accumulation and glycogen depletion were identical in bicarbonate‐ and saline‐infused frogs in the tissues studied. We conclude that (1) alterations in the extracellular acid‐base state by bicarbonate infusion are not necessarily reflected in the intracellular compartment, perhaps due to powerful intracellular buffering processes, and (2) maintenance of an alkaline extracellular pH during anoxia in bullfrogs does not influence the anaerobic metabolic rate. We could not, however, rule out a possible role for intracellular pH in regulating anaerobic metabolism during anoxia in frogs. © 1993 Wiley‐Liss, Inc.
Effects of cytochalasin B on calcium transport by 1,25(OH)2D3‐ or PTH‐treated chick embryonic yolk sac in vitro and in vivo
Authors: Lee S. Kyeong , Clark Nancy B.
Published: June 2005

The present study was done to elucidate the mechanism(s) by which calcium is taken up or transported across the yolk sac membrane of the embryonic chick. We examined the effect of various inhibitors or experimental conditions on the uptake of calcium in vitro. Treatment with ouabain, verapamil, antimycin A and calcium ionophore A23187; substitution of choline for sodium or potassium in the buffer; or incubation of the tissue at 0°C had no significant effect on calcium uptake by the yolk sac membrane. Dinitrophenol (DNP) and lanthanum chloride (LaCl2) reduced 45Ca uptake from day 6 and 9 embryos by 15% and 30%, respectively. Cytochalasin B decreased the uptake of 45Ca in yolk sac membrane disks of day 6 embryos, but not in older embryos. The effects of cytochalasin B were explored further in embryos pretreated with either 1,25(OH)2D3 or PTH, both of which enhance calcium uptake. Cytochalasin B decreased calcium uptake in 9‐day and 12‐day vitamin D‐treated embryos to about 60% of their hormone‐enhanced level and also decreased PTH‐stimulated 45Ca uptake into yolk sac disks by about 50% in embryos of all age groups tested.

We also examined the effect of cytochalasin B on 45Ca transport across the yolk sac membrane in vivo. Cytochalasin B did not affect this transport in control (vehicle‐treated) embryos. However, it significantly decreased the enhanced in vivo 45Ca transport in day‐9 and ‐12 vitamin D‐treated embryos approximately 30% and 45%, respectively. Additionally, cytochalasin B decreased the transport of calcium from yolk to blood by about 40% in PTH‐treated day‐9 embryos. These results indicated that both calcium uptake and transport by hormone‐stimulated yolk sac membranes involves endocytosis but that some other mechanism(s) must also be involved. © 1993 Wiley‐Liss, Inc.
Morphological and distributional changes in the eosinophilic granule cell (EGC) population of the rainbow trout (Oncorhynchus mykiss walbaum) intestine following systemic administration of capsaicin and substance P
Authors: Powell Mark D. , Wright Glenda M. , Burka John F.
Published: June 2005

Intestinal eosinophilic granule cells (EGCs) of the rainbow trout (Oncorhynchus mykiss) have been likened to mammalian mast cells and degranulate in response to stimulation by capsaicin and substance P. This investigation was conducted to examine the effects of capsaicin and substance P on the trout intestinal EGC population and to quantify the different morphologies following systemic administration. Rainbow trout were injected intraperitoneally with capsaicin, substance P, serotonin, or vehicle controls (0.5 ug/g body weight). Fish were killed at timed intervals and the mid intestine was processed for light and electron microscopy. The number of EGCs which could be observed in the stratum compactum was quantified for each treatment over the time course of the experiment. EGCs could be classified ultrastructurally into 1 of 5 categories based on their granule morphology. The cell frequencies and relative proportion of each cell class were analyzed statistically. The frequency of EGCs in the stratum compactum of fish injected with capsaicin or substance P significantly decreased post‐injection (P < 0.05) compared to controls (saline‐ and BSA‐injected fish). Serotonin had no effect on EGC frequency, morphology, or distribution as compared with saline. Stimulation with capsaicin and substance P resulted in time‐dependent changes in both EGC granule morphology and distribution within the intestinal mucosa. Following an apparent migration of EGCs to the lamina propria and degranulation, small granuled EGC‐like cells appeared first in the lamina propria and then later in the stratum compactum. The significance of the stratum compactum as a depot for intestinal EGCs and the site for EGC maturation is discussed. © 1993 Wiley‐Liss, Inc.
Ectoderm promotes differentiation of the presumptive ventral mesoderm in early gastrulae of Bufo arenarum
Authors: Casal Fernando H. Campos , Manes Mario E.
Published: June 2005

Cultures of both isolated and conjugated explants from early gastrulae of Bufo arenarum were prepared for a study of the development of ventral mesoderm. Only combinations including components of the deep ventral marginal zone and the animal pole successfully differentiated into blood cells (erythrocytes). Histological studies indicated that, while prospective mesodermal cells constituted the only source of such cells, prospective ectodermal cells provided the necessary stimulus for this kind of differentiation. Differentiated cultures, in which the tracer of cell‐lineage fluorescein dextran amine was used to label these components, confirmed the above conclusions. These findings are discussed in the context of current concepts about the formation of mesoderm. © 1993 Wiley‐Liss, Inc.
Specificity of binding of zona pellucida glycoproteins to sperm proacrosin and related proteins
Authors: Williams R. M. , Jones R.
Published: June 2005

A major regulatory site for species specificity of fertilization in mammals lies at the level of sperm binding to the zona pellucida. This implies a high degree of complementarity between gamete receptor molecules. One putative receptor molecule on spermatozoa is proacrosin/ acrosin which binds to zona pellucida glycoproteins (ZPGPs) non‐enzymically and with high affinity. The mechanism of recognition involves polysulphate groups in a particular stereochemical orientation and it has been suggested that this may contribute to species specificity of sperm‐egg binding. In the present work this hypothesis has been tested by challenging 125I‐labelled ZPGPs from pig, cow, and hamster eggs to recognize heterologous sperm proacrosins as well as a variety of sequencerelated and unrelated proteins. Results show that pig and cow 125I‐ZPGPs bind readily to boar, ram, and bull proacrosin but do not recognize guinea‐pig proacrosin or any of the polysulphate binding proteins from rat, hamster, or mouse spermatozoa. Hamster 125I‐ZPGPs also recognise boar, ram, and bull proacrosin as well as a range of unidentified proteins in pH3 extracts of hamster, rat, and mouse spermatozoa. The binding of ZPGPs to a variety of proteins not related to proacrosin is strongest to those with a high content of basic residues (i.e., pI > 8.5), although the secondary folding of the target protein is of major importance as boar proacrosin (pI 6.75) has the highest binding capacity of all proteins tested. Cross‐reaction of ZPGP probes was not observed to guinea‐pig proacrosin, suggesting that in this species the conformation of the protein is different to other sperm proacrosins. These results suggest that there are significant differences in the affinity of ZPGP‐proacrosin and ZPGP‐protein interactions to contribute to species specificity of sperm‐egg binding. © 1993 Wiley‐Liss, Inc.
Dopamine reduces intensity of serotonin‐induced spawning in the zebra mussel Dreissena polymorpha (Pallas)
Authors: Fong Peter P. , Noordhuis Ruurd , Ram Jeffrey L.
Published: June 2005

The effect of dopamine (DA) on serotonin (5‐HT)‐induced spawning in the zebra mussel Dreissena polymorpha (Pallas) was tested. Administration of 1 mM DA with either 0.3 mM or 0.5 mM 5‐HT significantly delayed spawning and reduced its intensity in both males and females compared with 5‐HT controls. In dose‐response experiments, a minimal DA concentration of 0.3 mM was necessary to delay spawning and reduce male spawning intensity to levels below that of the 5‐HT control. Mussels treated with 5‐HT‐DA or DA alone opened their valves initially, but after 1 hour most valves were closed and both inhalent and exhalent siphons appeared extended, squeezed, and narrow, with reduced aperture openings. Possible mechanisms for the observed reduction in spawning intensity are discussed. © 1993 Wiley‐Liss, Inc.
Steroid metabolism in the cortex and the medulla of the early fetal bovine ovary
Authors: Juárez‐Oropeza M. A. , Álvarez‐Fernández G. , López V. , Kawa S. , Pedernera E.
Published: June 2005

Suspensions of cells obtained from the cortex and the medulla of the ovary of early bovine fetuses of 4–10 cm in crown‐rump (C‐R) length were used for studies of the metabolism of radiolabeled exogenous steroid precursors. Tritiated dehydroepiandrosterone, androstenedione, and testosterone were employed as precursors and their metabolic products were evaluated after separation by thin‐layer chromatography. The extent of conversion of tritiated dehydroepiandrosterone to androstenedione was higher in cells from medulla than in those from the cortex. Androstenedione was metabolized mainly to estrone, and the percent of transformation was similar in the cortex and the medulla, but the rate of formation of 17β‐estradiol was higher in the medulla than in the cortex. Furthermore, cells obtained from the cortex and the medulla aromatized testosterone to 17β‐estradiol at a similar rate. In all cases, the percent of transformation was higher in ovaries from fetuses of 4.0 cm in C‐R length than those from fetuses of 9.0–10.0 cm in C‐R length. These data suggest that, in the bovine fetal ovary, the activity of 3β‐hydroxysteroid dehydrogenase/isomerase and 17β‐hydroxysteroid dehydrogenase predominates in the medulla, whereas aromatase activity is similar in the cortex and the medulla of the early fetal bovine ovary. © 1993 Wiley‐Liss, Inc.
Regulation of prostaglandin E and F production in the goldfish testis
Authors: Wade Michael G. , Kraak Glen Van Der
Published: June 2005

The present studies have investigated the putative role of activators of different signal transduction pathways in the regulation of prostaglandin (PG) production by goldfish testis pieces in vitro. The protein kinase C activator (PKC) phorbol 12‐myristate 13‐acetate (PMA: 1.56‐400 nM) and calcium ionophore A23187 (62.5‐4000 nM) stimulated PGE and F production in a dose and time‐dependent fashion. There was no synergism between A23187 and PMA in stimulating PG production. PGE levels were at least 4.5 times higher than PGF levels. The phorbol ester 4α phorbol didecanoate (400 nM), which does not activate PKC, had no effect on PGE production. The synthetic diacylglycerol 1‐oleoyl‐2‐acetyl‐sn‐glycerol (100 μM), but not 1,2‐dioctanoyl‐sn‐glycerol (100 μ), stimulated PGE production. Although the gonadotropin analog human chorionic gonadotropin (1 IU/ml), adenylate cyclase activator forskolin (2 μM) and testosterone (5 ng/ml) had no effect, the cyclic nucleotide phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine (1 mM) and cyclic adenosine‐3′,5′‐monophosphate analog dibutyryladenosine‐3′,5′‐monophosphate (2 mM) inhibited PMA (400 nM) and A23187 (1 μM)‐stimulated PGE production. PMA and A23187 (400 nM and 1 μM, respectively)‐stimulated PGE production was inhibited by phospholipase A2 inhibitors 4‐bromophenacyl bromide, quinacrine and chloroquine (all 6.25‐400 μM) and by diacylglycerol lipase inhibitor RHC 80267 (10–100 μM), suggesting that both lipases are involved in the release of precursor fatty acids for PG synthesis by goldfish testis tissue. These data, in conjunction with earlier studies showing that PGE stimulates testosterone production by goldfish testis pieces, lend support to the contention that locally produced PGs of the E series modulate testicular steroidogenesis in teleosts. © 1993 Wiley‐Liss, Inc.
Gastrulation and mesoderm morphogenesis in the white sturgeon
Authors: Bolker J. A.
Published: June 2005

This study presents a detailed description of gastrulation in the white sturgeon, Acipenser transmontanus, using scanning electron microscopy, histology, and time‐lapse filming and video microscopy. This morphological analysis describes the similarity of gastrula structure in the sturgeon and the amphibian Xenopus laevis, and suggests that the species share many developmental mechanisms. It also identifies important differences, such as the equatorial dorsal lip in sturgeon, and provides a basis for interpreting experiments that test the effect of these differences on gastrulation. The onset of gastrulation in the sturgeon is marked by the appearance of a blastoporal equatorial pigment line that forms as the apices of bottle cells contract and concentrate surface pigment granules. Bottle cell formation at the blastopore lip and involution of surface material through the blastopore are strikingly similar to the equivalent processes in amphibian embryos. As gastrulation continues, a distinct cleft of Brachet forms between pre‐involution and post‐involution material. Following involution, the prospective axial mesoderm located on the dorsal surface of the late blastula (Ballard and Ginsburg: J. Exp. Zool., 213:69–103, 1980) ingresses from a central zone in the posterior archenteron roof surface in a process that is unlike any in Xenopus, but resembles events in other amphibians (Purcell, 1992; Smith: Dev. Biol., 98:250–254, 1983; King: Biol. Bull., 4:287–300, 1903). The detailed comparison of similarities and differences in gastrulation in different vertebrate lineages yields insights into the function and versatility of common developmental mechanisms. © 1993 Wiley‐Liss, Inc.
The mechanism of gastrulation in the white sturgeon
Authors: Bolker J. A.
Published: June 2005

Gastrulation in the white sturgeon, Acipenser transmontanus, involves many of the same processes as in the amphibian Xenopus laevis, but the timing and relative importance of these processes are altered so that they function appropriately in a different type of egg. In both species, convergence and extension result from a combination of radial and mediolateral cell intercalation. In sturgeons, where the blastopore lip forms at the equator, an early phase of thinning and extension of the animal cap moves the marginal zone below the equator during late blastula and early gastrula stages. This early extension without convergence is followed by convergent extension of the dorsal marginal zone after its displacement vegetally. When the animal cap is removed before gastrulation, precluding the initial extension that moves the marginal zone below the equator, autonomous convergence of the lower marginal zone produces an equatorially constricted embryo. Dorsal explants of sturgeon embryos undergo convergent extension similar to that documented in Xenopus (Keller and Danilchik: Development, 103:193–209, 1988), with distinct zones of extension in the involuting and non‐involuting marginal zone regions. The extension of cultured explants demonstrates that this morphogenetic behavior is intrinsic to the dorsal tissue. These results show that normal gastrulation depends not only on the function of these independent morphogenetic mechanisms, but also on their mechanical context in the embryo. Experimental analyses and comparison of gastrulation in similar embryos, such as those of Xenopus and sturgeons, reveal both common developmental mechanisms, and variation in their roles. © 1993 Wiley‐Liss, Inc.
Effect of follicle cells and steroidogenesis on maturation and fertilization in vitro of pig oocytes
Authors: Nagai T. , Ding J. , Moor R. M.
Published: June 2005

Follicle cell numbers, steroidogenesis, and culture conditions were manipulated in a series of experiments designed to identify their effect during in vitro maturation of pig oocytes upon meiotic cycle progression, sperm penetration and male pronuclear formation. In Experiment 1 a static culture system was used to determine the effect of follicle cell numbers on maturation. When the follicle cell number was 3.5 × 103 cells per complex or less, cell cycle progression to metaphase II (M‐II) and male pronuclear formation were both low (<30%). Increasing follicle cell numbers to 15 × 103 per complex significantly enhanced both meiotic maturation (93%) and male pronuclear formation (83%). A further 10‐fold increase in follicle cell numbers (150 × 103), however, reduced subsequent male pronuclear formation (33%).

The purpose of Experiment 2 was to determine whether the observed follicle cell effects were influenced by the type of culture system used for oocyte maturation. Comparisons were made between both static and non‐static forms of culture. Meiotic progression was significantly depressed when non‐static culture systems were used for the maturation of oocyte‐cumulus complexes containing low numbers of somatic cells (<15 × 103 cells). However, the addition of somatic cells (follicle shells) to non‐static, but not static, culture systems significantly enhanced male pronuclear formation in all groups irrespective of the number of cumulus cells in the oocyte complex.

Experiment 3 investigated the effects of the steroid environment on maturation and male pronuclear formation. The addition of high levels of progesterone (1 mg/ml) from the beginning of maturation was detrimental for maturation. More interestingly, inhibition of steroidogenesis using an inhibitor of 20α‐cholesterol oxidase was without effect on meiotic progression or sperm penetration but reduced male pronuclear formation. The combined results demonstrate the importance of appropriate somatic support of oocytes as measured by their subsequent capacity to induce normal pronuclear formation after fertilization. Furthermore, studies on the required hormonal environment support published data showing that progesterone is required during maturation for subsequent male pronuclear formation. © 1993 Wiley‐Liss, Inc.
Interactions of temperature and steroids on larval growth, development, and metamorphosis in a toad (Bufo boreas)
Authors: Hayes Tyrone , Chan Ruth , Licht Paul
Published: June 2005

The effects of temperature and steroids [testosterone (T), estradiol (E2), and cortico‐sterone (B)] on premetamorphic growth and development were investigated in the toad (Bufo boreas). The effects of steroids were both temperature and age dependent. In the first experiment, steroids (1.1–1.4 μM) were administered by dissolving them in the water beginning 1 day after hatching at 22°C or 27°C. At 22°C, B inhibited growth (P < 0.001) but had no significant effect on development. Forelegs never emerged in B‐treated animals and all died before complete tail resorption. Discontinuation of B treatment allowed normal growth and metamorphosis, but the resulting post‐metamorphic animals were significantly shorter (snout‐vent length, P < 0.001) than after other treatments. At 22°C, T and E2 had no effect on larval growth and development or size at metamorphosis (P > 0.05), but T induced early foreleg emergence (FLE) (P < 0.005). At 27°C, B was fatal after 2 weeks of treatment, and T and E2 inhibited growth (P < 0.001) and development (P < 0.001), but did not affect time to FLE.

In a second experiment at 27°C, treatment with 1.1 μM B starting 15 days after hatching induced early metamorphic events (P < 0.001), such as tail resorption and emergence of the left foreleg (but not the right), but jaw and head restructuring failed to occur. All B‐treated animals died before complete tail resorption. © 1993 Wiley‐Liss, Inc.

In a third experiment, 0.275 and 1.11 μM B, starting at day 43 (stage 43), induced early FLE (P < 0.05) and decreased snout‐vent length at tail resorption (P < 0.005) without a dose effect. A higher dose of B (4.44 μM) decreased snout‐vent length at tail resorption and time to FLE (P < 0.05) but did not affect body weight at metamorphosis (P > 0.05). Animals in this experiment survived to complete tail resorption and transformed normally. The actions of B in these experiments closely resemble those observed with administration of thyroid hormones, suggesting that steroids may interact with endogenous thyroid hormones.
Targeted single‐cell induction of gene products in Caenorhabditis elegans: A new tool for developmental studies
Authors: Stringham Eve G. , Candido E. Peter M.
Published: June 2005

Heat shock promoters have been employed to achieve tightly regulated expression of transformed genes in a wide variety of model systems including tissue culture cells, bacteria, yeast, Drosophila, and more recently Caenorhabditis elegans. Here we investigate the feasibility of using a laser microbeam to induce a sub‐lethal heat shock response in individual cells of C. elegans. We demonstrate that in transgenic strains carrying heat shock promoter‐lacZ fusions, single cell expression of β‐galactosidase in a variety of cell types of endodermal, mesodermal, or ectodermal origin can be achieved after pulsing with a laser. A tissue‐general, inducible promoter can therefore be converted into one of single cell specificity which can be induced rapidly at any point in development, offering unique opportunities to study cell‐cell interactions in C. elegans. This technique defines a new approach to generate mosaic animals and may be adaptable to other organisms or tissues. © 1993 Wiley‐Liss, Inc.
Responses of isolated vela of nudibranch larvae to inducers of metamorphosis
Authors: Pires Anthony , Hadfield Michael G.
Published: June 2005

Larvae of the aeolid nudibranch Phestilla sibogae metamorphose in response to a water‐soluble factor derived from their adult prey, the coral Porites compressa. Destruction of the velum, a ciliated larval swimming and feeding organ, is one of the major morphogenic events that occurs during metamorphosis. Previous work established that whole larvae metamorphose in response to the natural coral‐derived inducer (CI) and to choline, and shed the velum without completing metamorphosis in response to hydrogen peroxide (H2O2). In the present study, excised velar lobes were maintained in vitro while their responses to known inducers of metamorphosis were examined. In this way direct tissue‐level morphogenic effects of inducers could be discerned. Isolated velar lobes were unaffected by CI and by choline (5 mM). “Donor” larvae (each of which had supplied a single velar lobe used in these experiments) and unoperated controls lost their vela in response to both treatments. These results are consistent with the hypothesis that morphogenic effects of CI are mediated by the central nervous system. H2O2 (0.2 mM) caused disintegration of isolated velar lobes, and caused nearly all donor and unoperated larvae to shed their vela. © 1993 Wiley‐Liss, Inc.
Two GnRHs fluctuate in correlation with androgen levels in the male frog Rana esculenta
Authors: Fasano Silvia , Goos Henk J. Th. , Janssen Coby , Pierantoni Riccardo
Published: June 2005

ChickenII‐(cII‐) and salmon (s‐) GnRH levels have been measured in the male frog Rana esculenta during the annual cycle. The presence of pituitary binding activity for both peptides and plasma androgen levels has been investigated in order to give insight into the significance of the dual control exerted by the GnRH forms present in the R. esculenta brain. ChickenII‐ and s‐GnRHs showed high values during the spring‐summer period. Conversely, while cII‐GnRH peaked in February, s‐GnRH declined slowly from February until May. Plasma androgen levels increased as the peptides decreased during the autumn‐winter period. Still high androgen levels (but significantly lower as compared with winter concentrations) were found during spring. Using iodinated cII‐GnRH, GnRH binding sites were detected in pituitary preparations when the corresponding peptide concentration decreased in the brain. On the contrary, no binding sites were found using labeled s‐GnRH. Our results indicate that cII‐GnRH has a hypophysiotropic activity, while the role of s‐GnRH needs to be further investigated. © 1993 Wiley‐Liss, Inc.
Detection of insulin receptors in newt liver and forelimb regenerates and the effects of local insulin deprivation on epimorphic regeneration
Authors: Foty Ramsey A. , Liversage Richard A.
Published: June 2005

Previous in vivo and in vitro studies indicate that insulin is required in adult newt forelimb regeneration. The objectives of the current study were 1) to detect insulin receptors in the liver (a classical target organ for insulin) and once verified, detection of insulin receptors in the adult newt forelimb regenerate; and 2) to determine whether locally implanting insulin antibody‐soaked hydrolyzed polyacrylamide beads (hypa beads) into a regenerating forelimb blastema would affect its growth and/or differentiation. The results show that insulin receptors are detectable in the plasma membranes of newt liver and forelimb regenerates. Radioiodinated bovine insulin binding is time‐dependent and specific; unlabeled bovine insulin competes with labeled insulin for binding to NLPM more effectively than does insulin‐like growth factor‐I, guinea pig insulin, and glucagon. The newt hepatic insulin receptor binds insulin with high affinity (1.1 nM−1) and low capacity (63 ± 8 fmoles/mg). The size of the alpha subunit of the newt insulin receptor is 130 kDA and that of the beta subunit is 95 kDa. The β subunits undergo insulin‐stimulated phosphorylation in response to insulin. An autoantibody against the human insulin receptor recognizes the newt receptor protein. Insulin receptors are also detectable in 15 and 20 day newt forelimb regenerates. Specific immunogold labelling of the receptor‐bound antibody appears to be restricted to the cellular processes of the regenerate. Implanting hypa beads soaked with purified insulin antibody into regenerating adult newt forelimbs results in abnormal growth and differentiation of the regenerates, confirming that insulin plays an essential role in adult newt forelimb regeneration. © 1993 Wiley‐Liss, Inc.
Uterogestation and placentation in elasmobranchs
Authors: Hamlett William C. , Eulitt Allison M. , Jarrell Robert L. , Kelly Matthew A.
Published: June 2005

Elasmobranch fishes utilize a variety of means to provide nourishment for their developing young. All employ internal fertilization and sperm storage within the female genital tract. Some elasmobranchs, including all the skates and some sharks, are oviparous. In these species, fertilized eggs are enclosed in a tough egg case that is secreted by the nidamental or shell gland. The female lays the egg cases and development is entirely dependent on the yolk stores sequestered in the yolk sac. Upon oviposition, the embryo weighs less than the fertilized egg. The majority of elasmobranchs are viviparous, however, and utilize a variety of strategies to provide nourishment and satisfy respiratory demands of the developing young. Some sharks simply retain their young in the dilated posterior segment of the oviduct. In its simplest form, the maternal uterus does not provide any additional nutrients to the embryos. Other elasmobranchs develop secretory uterine villi that produce nutrient histotroph to supplement oocyte yolk stores. Uterine secretions find their zenith in the stingrays. Following yolk depletion, the uterine lining hypertrophies into secretory appendages termed trophonemata. The process by which the uterine secretions, also known as uterine milk or histotroph, are elaborated resembles the production of breast milk in higher vertebrates, and the milk is rich in protein and lipid. Concurrent with growth of the embryos, the vascular bed of the trophonemata enlarges to form sinusoids that project out to the surface to form a functional respiratory membrane. In lamnoid sharks, following yolk use, the embryos develop precocious dentition and feed on intrauterine eggs and siblings. There is generally one fetus per uterus and it grows to enormous proportions of up to 4 feet in length. In placental sharks the yolk sac is not withdrawn to become incorporated into the abdominal wall. Instead, it lengthens to form an umbilical cord and the yolk sac becomes modified into a functional epitheliochorial placenta. © 1993 Wiley‐Liss, Inc.
Maternal–embryonic relations in viviparous teleosts
Authors: Schindler Joachim F. , Hamlett William C.
Published: June 2005

Teleosts do not possess uteri and ovulation occurs into the ovarian lumen. Hence, osteichthyan viviparity is characterized by intrafollicular gestation or intraluminal gestation (within the ovarian cavity), and thus, the ovary functions both in egg production and maintenance of the developing embryos. Because there is no attachment between embryonic and maternal tissues, maternal‐embryonic exchange of gas, electrolytes, nutrients, metabolic waste, and possibly effector molecules and immunoglobulins is mediated by embryotrophe. In several instances it has been demonstrated that embryotrophic proteins originate from maternal serum rather than from elaboration within ovarian tissues. In intraluminal gestation, the ovarian wall becomes hypervascularized and the inner ovarian epithelium lining the ovarian cavity secretes embryotrophe. Trophotaeniae provide extraembryonic endodermal exchange surfaces in many species undergoing intraluminal gestation. There is a strong indication of a trophotaenial membrane binding system for proteins containing appreciable amounts of lysine. In intrafollicular gestation, yolk, pericardial and coelomic sacs play a major role in physiologic exchange. In most instances, intrafollicular gestation is associated with extraembryonic fine structural modifications consistent with respiratory and osmoregulatory functions. The postulated role in nutrient transfer requires experimental evidence. In matrotrophic viviparous teleosts, the gut may provide an effective absorptive surface. On the other hand, the skin, and perhaps the gills and buccopharyngeal tissue, serve as respiratory surfaces. As yet, no experimental evidence suggests exchange of metabolites at these sites. © 1993 Wiley‐Liss, Inc.
Uses and limitations of mammalian fetal membranes and placenta for phylogenetic reconstruction
Authors: Luckett W. Patrick
Published: June 2005

Comparative studies on the development of the mammalian fetal membranes and placenta, and discussions of the possible evolutionary significance of these data, have been carried out for more than a century. Throughout much of this period, however, such data were considered in isolation from cranioskeletal and other biological findings, so that only rarely were placental features incorporated into comparative assessments of mammalian evolution. Evolutionary interpretations of the fetal membrane evidence were commonly based on the concept of overall similarity, and most placentologists were strongly influenced by the widely accepted hypothesis that living “insectivores” were closely related to the ancestral eutherian mammals.

Mossman's emphasis on the use of all available developmental data on the fetal membranes and placenta, rather than simply the nature of the definitive placenta, marked a turning point in the history of using such findings for assessing eutherian mammalian evolution. Recent advances in the methodology of phylogenetic inference, with emphasis on evaluating convergence versus homology, and on distinguishing between relatively primitive versus derived homologous similarities shared by two or more taxa, have provided a sound framework for the phylogenetic analysis of fetal membrane data. Character analysis of mammalian fetal membrane traits provides a mechanism for testing phylogenetic hypotheses formulated by cranioskeletal features. It is emphasized in this study that fetal membrane data have their greatest input into assessing mammalian phylogeny when they are evaluated in conjunction with the available cranioskeletal and molecular evidence. © 1993 Wiley‐Liss, Inc.
Development and characteristics of placentation in a carnivore, the domestic cat
Authors: Leiser Rudolf , Koob Bärbel
Published: June 2005

Among the carnivores, development of the fetal membranes and placentation have now been particularly well studied in the domestic cat (Felis catus). Initially, the cat conceptus is bordered by a primitive and a precontact chorion. This becomes part of a temporary choriovitelline placenta which is subsequently supplanted by a chorioallantoic placenta. Following thiphasic process of implantation (which involves apposition, adhesion, and intrusion), the chorioallantoic placenta forms a zonary girdle which separates two paraplacental cupules. These cupules are subdivided from base to tips into 1) extravasate zones with hematomal areas and solid junctional areas containing intermingled fetal and maternal tissue, 2) free polar zones with almost no feto‐maternal contact, and 3) interplacental polar zones freely projecting into the uterine lumen or, near the end of pregnancy, facing comparable regions of neighboring fetuses.

The placental girdle consists of a lamellar zone characterized by elongate, parallel fetal (chorionic) and maternal (septal) lamellae, a junctional zone where fetal and maternal tissues face each other and intimately intermingle, and a zone of pure endometrial glands. In the lamellar zone the interhemal membrane (placental barrier) is of the endotheliochorial type. As pregnancy progresses, cytotrophoblast in the interhemal barrier contributes to the formation of syncytiotrophoblast and is gradually reduced from being a continuous layer to only scattered cells. The syncytiotrophoblast is usually separated from endothelial cells of the maternal capillaries by a thickened basal lamina (the interstitial membrane) or faces persisting endometrial connective tissue containing some enlarged decidual cells.

The efficiency of maternal‐fetal physiological exchange depends not only upon the thickness of the interhemal membrane, which in reduced in places to 1.5 μm, but also upon the materno‐fetal blood flow interrelationship. This is of the simple crosscurrent type in the cat. © 1993 Wiley‐Liss, Inc.
A comparative study on the fusogenic nature of echinoderm and nonechinoderm phagocytes in vitro
Authors: Dan‐Sohkawa Marina , Suzuki Junko , Towa Shuichi , Kaneko Hiroyuki
Published: June 2005

Phagocytes obtained from six echinoderm and four nonechinoderm species are compared in culture with respect to their ability to form syncytium. It is shown that phagocytes of all echinoderm species examined form an extensive syncytium while those of three nonechinoderm species shoe no such activity. Phagocytes of an ascidia, on the other hand, formed a less extensive type of syncytium known as a multinucleate giant cell. Kinetic analyses of the process of fusion were performed. Phagocytes of the asteroid, Asterina pectinifera, fuse more readily when transferred to culture condition in an aggregated state than as single cells. The extraordinarily fusogenic nature of echinoderm phagocyte is discussed in relation to the calcareous body wall structure of the echinoderms. © 1993 Wiley‐Liss, Inc.
Specific phosphorylation of membrane proteins of Mr 44, 000 and Mr 32,000 by the autophosphorylated insulin receptor from the hepatopancreas of the Shrimp Penaeus monodon (Crustacea: Decapoda)
Authors: Lin Chung‐Liang , Wang Pei‐Chen , Chuang Nin‐Nin
Published: June 2005

The insulin receptor, purified from the hepatopancreas of the shrimp Penaeus monodon, is a hydrophobic heterodimer of subunits with relative masses (Mr) of 70,000 and 58, 000, as estimated by FPLC on Superose™12 and SDS‐PAGE. Only the subunit of Mr 70,000 was autophosphorylated after the addition of insulin. The autophosphorylation occurred specifically at Tyr residues, as demonstrated by the specific subsequent dephosphorylation by the phosphotyrosyl protein phosphatase from the hepatopancreas of the shrimp Penaeus monodon. Proteins of Mr 44,000 and Mr 32,000 on the plasma membrane from the hepatopancreas of the shrimp Panaeus monodon were phosphorylated by the autophosphorylated insulin receptor from the shrimp hepatopancreas, but not by that from the human placenta. The detergent, Triton X‐100, caused noticeable enhancement of the autophosphorylation of both shrimp and human insulin receptors. © 1993 Wiley‐Liss, Inc.
Consequences of splenectomy on the compensatory mechanism of cutaneous respiration in the newt
Authors: Frangioni Giuliano , Borgioli Gianfranco
Published: June 2005

The spleen of the newt Triturus cristatus carnifex (Laurenti) hoards erythrocytes when the animal is well oxygenated and releases these into circulation when the animal becomes hypoxic. This mechanism allows the newts, amphibians with prevalently cutaneous respiration, to adapt to both environmental and metabolic changes.

Splenectomized specimens were anesthetized with chlorbutol (to eliminate movement and lung respiration) and observed in five different conditions: at 18°C in humid air, stirred water, and still water, and at 6°C and 33°C in humid air. The study demonstrates that the newt does not have substitute sites for erythrocyte accumulation. However, though the spleenless specimens are incapable of controlling their cutaneous oxygen supply, they can regulate their blood volume, which diminishes with decreasing temperature causing marked variations in the erythrocyte concentration and hematocrit value.

The splenectomized specimens, raised for over a year at 18°C, present typically steatosic livers, with lipid droplets and extremely low hepatocyte glycogen levels, indicating a state of chronic hypoxia due to the prevalently aquatic habits of the newt. In fact, the spleenless newts have significantly fewer erythrocytes (P < 0.001) than the unoperated animals‐‐a total volume of 2.27 ± 0.46 ml per 100 g of body weight compared to 2.74 ± 0.29 (mean ± standard deviation). The limited quantity of erythrocytes can provide adequate oxygen only at low temperatures and in an airy environment or in moving water, while an immobile animal in still water undergoes hypoxia due to the formation around it of an hypoxic =diffusion boundary layer= caused by the low coefficient of oxygen diffusion in water. © 1993 Wiley‐Liss, Inc.
Gonadotropin‐releasing hormone (GnRH) binding characteristics in the testis of goldfish (Carassius auratus)
Authors: Pati Debananda , Habibi Hamid R.
Published: June 2005

Gonadotropin‐releasing hormone (GnRH) binding sites were characterized in the goldfish testis using an analog of salmon GnRH ([D‐Arg6, Trp7, Leu8, Pro9‐NEt]‐GnRH; sGnRH‐A) as a labeled ligand. Binding of sGnRH‐A to goldfish testicular membrane homogenate was found to be saturable, reversible, and dependent on time, temperature, and tissue concentration. Addition of unlabeled sGnRH‐A displaced the bound 125 I‐sGnRH‐A in a dose‐related manner. Hill plot as well as Scatchard analysis indicated the presence of two classes of binding sites, a high affinity/low capacity site and a low affinity/high capacity site in the goldfish testis. Bound 125I‐sGnRH‐A was also found to be displaceable by sGnRH ([Trp7, Leu8]‐GnRH) and cGnRH‐II ([His5, Trp7, Tyr8,]‐GnRH) which occur naturally in the goldfish brain. sGnRH‐A and cGnRH‐II were found to bind with greater affinity than sGnRH to the goldfish testicular GnRH binding sites. The findings provide the first characterization of testicular GnRH binding sites in a teleost species. © 1993 Wiley‐Liss, Inc.
Regulation of mammalian brain cell volume
Authors: Law R. O.
Published: June 2005

Maintenance of brain cell volume is of crucial importance for normal central nervous system (CNS) function. This review considers volume regulation primarily in response to disturbances of body fluid osmolality. Brain cells counter the tendency to swell or shrink by appropriate adjustment of their internal osmotic potential. This is achieved by loss or uptake of inorganic ions and low molecular weight organic solutes (osmolytes). The latter comprise mainly amino acids, myoinositol, choline, and methylamines. Taurine may be of particular importance in volume control, especially in young animals. Brain cell volume regulation, however, is only one contributory factor to maintenance of constant brain volume (water content), and operates in parallel with important alterations in bulk fluid and electrolyte movement across the blood‐brain barrier and between the interstitium and cerebrospinal fluid, which themselves moderate the requirement for transient alteration in cell volume during acute osmotic imbalance. Although altered cerebral content of inorganic ions and osmolytes are usually regarded as responses, respectively, to acute and chronic osmotic disturbances, osmolytes (especially taurine) may also participate in short‐term cell volume regulation. © 1994 Wiley‐Liss, Inc.
Hypoosmotic volume regulation in bivalves: Protein kinase C and amino acid release
Authors: Deaton Lewis E.
Published: June 2005

Phorbol esters potentiate the release of free amino acids from isolated ventricles and gills of the mussel, Geukensia demissa, when the tissues are incubated in hypoosmotic seawater. Phorbol esters do not affect the release of amino acids from tissues in isosmotic seawater. Inhibitors of protein kinase C depress the release of amino acids from isolated ventricles in hypoosmotic seawater by 25–30%. Calmodulin antagonists did not inhibit the efflux of amino acids from isolated ventricles in hypoosmotic seawater.

The level of inositol 1,4,5‐triphosphate does not change in isolated ventricles incubated in either hypoosmotic or isosmotic seawater. In contrast, there is a transient increase in the level of diacylglycerol in ventricles exposed to hypoosmotic seawater. The increase is detectable 0.5 min after transfer of the tissue to hypoosmotic seawater; 2 min after transfer, there is no difference between tissues incubated in isosmotic and hypoosmotic media.

These results suggest that protein kinase C plays a role in the modulation of the release of amino acids from ventricle and gill cells in G. demissa. © 1994 Wiley‐Liss, Inc.
Stimulation of skeletal growth by thyroid hormone administrations in the rainbow trout, Oncorhynchus mykiss
Authors: Takagi Yasuaki , Hirano Joe , Tanabe Hiroshi , Yamada Juro
Published: June 2005

Effects of 3, 5, 3′‐triiodo‐L‐thyronine (T3) on the skeletal growth in yearlings of rainbow trout were studied. Groups of rainbow trout maintained at 10–14°C under a natural photo‐period were fed daily to satiation with diets supplemented with 0, 5, 25, and 50 ppm T3 for 2 months. Histological preparations of the ceratobranchial cartilage and pharyngeal bone were observed under a light microscope to compare histomorphometric parameters. The T3 administrations significantly increased plasma T3 (25 and 50 ppm diets) and fork length (50 ppm diets), and depressed the condition factor (25 and 50 ppm diets). Chondrocytes in the hypertrophic zone of the cartilage markedly increased both in size and number (25 and 50 ppm diets). A significant enlargement of osteoid of the bone was observed (50 ppm diets). Bone formation (25 and 50 ppm diets) and resorption (5, 25 and 50 ppm diets) were activated. The results indicated that the oral administration of T3 can stimulate the growth of both cartilage and bone in the rainbow trout. © 1994 Wiley‐Liss, Inc.
Peritrophic matrix of the black fly Simulium vittatum: Formation, structure, and analysis of its protein components
Authors: Ramos Alfredo , Mahowald Anthony , Jacobs‐Lorena Marcelo
Published: June 2005

The peritrophic matrix (PM) (same as peritrophic membrane) is secreted by the midgut epithelium of insects and completely surrounds the ingested food. The PM is likely to influence disease transmission by hematophagous insects. As a prelude to a more detailed examination of PM function, we report on morphological and molecular studies of the PM type 1 (PM1) from Simulium vittatum. The blood meal induces major changes in epithelial cell morphology: cells become flattened, microvilli decrease dramatically in number, and organelles redistribute in the cytoplasm. The PM1 forms within minutes of the blood meal. After 6 h the PM1 has reached its maximum thickness (approximately 13 μm) and strength. Two‐dimensional gel electrophoresis reveals two major PM1‐specific proteins of 66 and 61 kDa. Synthesis of these PM1 proteins is likely to be induced by the blood meal, since they are not detectable prior to blood feeding. The time course of accumulation and disappearance of the PM1 proteins closely correlates with the appearance and disappearance of the PM1 itself. © 1994 Wiley‐Liss, Inc.