bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantification and localization of ornithine decarboxylase in the embryonic palate
Authors: Gawel‐Thompson Kathleen J. , Greene Robert M.
Published: June 2005

Ornithine decarboxylase (ODC; EC4.1.1.17), the key enzyme in polyamine biosynthesis, and intracellular polyamines increase rapidly and markedly in tissues and cells that are actively proliferating as well as differentiating and decrease as these processes cease. ODC activity has also been implicated as playing a role in the proliferation and differentiation of cells derived from the developing palate. Ornithine decarboxylase activity was thus quantified and ODC localized in the developing murine palate in vivo. Levels of ODC activity showed little variation during the ontogeny of the palate, averaging 126 pmol CO2/mg protein/hr. When difluoromethylornithine (DFMO), an irreversible inhibitor of ODC activity, was administered to pregnant mice throughout the period of palate development (days 11–14), palatal tissue ODC activity was reduced by 85%. No craniofacial malformations were observed, however. The lack of a teratogenic effect by DFMO treatment could be due to sufficient remaining ODC activity in craniofacial tissue and/or maintenance of intracellular polyamine levels by the activity of a polyamine transport system. The activity of this system was demonstrated by the ability of palatal tissue in vivo to take up radiolabeled putrescine. The presence of a polyamine transport system was previously suggested by the demonstration of such a system in palate mesenchymal cells in vitro.

Dramatic temporal and spatial shifts in tissue patterns of immunolocalization for ODC in developing palatal tissue were also seen. Immunostaining for ODC was evenly distrubuted in oral, nasal, and medial edge palate epithelial cells on day 12 of gestation. The basal aspects of epithelial cells were, however, more intensely stained. Mesenchymal cells exhibited a peri‐nuclear immunostaining pattern. On days 12 and 13 of gestation, the staining patterns for ODC in palate epithelial and mesenchymal cells were comparable. On day 14 of gestation, all regions of the palate epithelium, particularly the medial edge epithelia, were immunostained for ODC, whereas the intensity of staining in the mesenchymal cells was significantly reduced. This study represents essential initial observations toward understanding the role that ODC may play in normal craniofacial development. © 1992 Wiley‐Liss, Inc.
Characterization of leukotriene C4 binding sites in the brain of the American bullfrog, Rana catesbeiana
Authors: Herman Ceil A. , Charlton Gregory A. , Chiono Matt
Published: June 2005

In this study, specific binding sites for [3H]‐LTC4 on membrane preparations from American bullfrog (Rana catesbeiana) brain were characterized. Binding assays were done in the presence of serine (5mM) borate (10 mM) for 30 min at 23°C. Under these conditions, no metabolism of LTC4 to LTD4 occurred. Specific binding of [3H]‐LTC4 reached steady state within 10 min, remained constant for 60 min, and was reversible with the addition of 1,000‐fold excess unlabelled LTC4. Scatchard analysis of the binding data indicated a single class of binding sites with an estimated Kd of 89.83 nM and Bmax of 43.79 pmol/mg protein. Competition binding studies demonstrated that LTD4 and LTE4 were ineffective in displacing [3H]‐LTC4 from its binding site. The Ki for LTC4 was 51 nM. S‐decylglutathione, glutathione and hematin had Ki values of 44, 312,602, and 25,576 nM, respectively. The mammalian cysteinyl leukotriene antagonist L‐660,711 inhibited specific binding of [3H]‐LTC4, with a Ki of 87,149 nM. Guanosine‐5′‐0‐3‐thiotriphosphate (GTPγS) did not affect specific binding of [3H]‐LTC4 indicating that, like mammalian LTC4 receptors, a Gi protein is not involved in the transduction mechanism. The LTC4 binding site in bullfrog brain demonstrates both similarities and differences from its mammalian counterpart. © 1992 Wiley‐Liss, Inc.
The problem of the number of tarsomeres in the regenerated cockroach leg
Authors: Tanaka Akira , Akahane Hitomi , Ban Yukari
Published: June 2005

There are 5 tarsomeres in the normal cockroach leg, but this number is often reduced in regenerated legs. In order to examine this complicated situation, fore‐, mid‐, and hindlegs of German cockroaches were amputated at 11 different tarsal levels and at 18 different times during the last instar. When tarsi were amputated at or proximal to the 3rd tarsomere, 4‐segmented tarsi regenerated. When legs were amputated distal to the 3rd tarsomere, the regenerated tarsi had 5 segments. Three‐segmented tarsi rarely regenerated when legs were amputated proximal to the 3rd tarsomere and in the latter half of the instar period. The lengths of all tarsomeres of regenerated tarsi were measured together with those of unoperated contralateral tarsomeres, and the ratios of the former to the latter were calculated. The ratios ranged from 28 to 138% for the various tarsomeres and levels of amputation. From a comparison of the ratios and morphological observations, it was suggested that the 3rd tarsomere of the normal 5‐segmented tarsus has disappeared in the regenerated 4‐segmented tarsus. Pads and disto‐lateral spines of tarsomeres were observed on unoperated and regenerated tarsi. It was of interest that double spines were often found on the 4‐segmented tarsi, mostly on the 2nd tarsomere, just proximal to the position of the missing 3rd tarsomere. This observation supported the idea that the 3rd tarsomere has not simply disappeared, but has probably fused with the 2nd tarsomere. © 1992 Wiley‐Liss, Inc.
Immunological characterization of oviductal glycoproteins associated with the zona pellucida of the golden hamster egg
Authors: Abe Hiroyuki , Ookata Kayoko , Abe Miki , Oikawa Taneaki
Published: June 2005

Three monoclonal antibodies (MAbs) were produced against materials obtained from the golden hamster oviduct. The MAbs (C11E8, C8B11, and A3D5) selectively reacted with the zona pellucida (ZP) of oviductal eggs. An immunohistochemical study demonstrated that all MAbs bound strongly to the epithelial cells of the oviduct and, to a lesser extent, of the uterus, the cervix, and the vagina. Weak reactions were also observed with some other tissues. All immunohistochemical reactions were completely eliminated by treatment of tissues with periodic acid, suggesting that the antigenic determinants that react with the MAbs are carbohydrate in nature. Antigens that reacted with the MAbs were characterized by immunoblotting analyses of 1‐ or 2‐dimensional polyacrylamide gels after electrophoresis to fractionate tissue extracts under reducing conditions. With the oviductal extract, C11E8 and A3D5 specifically bound to broad bands that corresponded to macromolecules of more than 200 and 160 kD, respectively, whereas C8B11 reacted with a broad range of macromolecules, with the strongest reactivity being detected at molecular weights (MWs) higher than 160 kD. The macromolecules that reacted with the MAbs had carbamilation trains, suggestive of extensive microheterogeneity with respect to charge and size. Similar substances of high MW were not detected in extracts of tissues from the other reproductive organs. In addition, one MAb‐positive oviductal antigen bound to the ZP of ovarian eggs, but the others did not bind to the ZP of ovarian eggs. This result indicates that the binding activity is specific for the oviductal glycoproteins. We have thus established clones that produce 3 different MAbs with strong affinity for oviduct‐specific glycoproteins, one of which is associated with the ZP of the golden hamster. © 1992 Wiley‐Liss, Inc.
Inhibition of Ca2+ uptake in freshwater carp, Cyprinus carpio, during short‐term exposure to aluminum
Authors: Verbost Pieter M. , Lafeber Floris P. J. G. , Spanings Franciscus A. T. , Aarden Elisabeth M. , Bonga Sjoerd E. Wendelaar
Published: June 2005

In carp exposed to pH 5.2 in fresh water, the Ca2+ influx from the water is reduced by 31% when compared to fish in water of neutral pH. At pH 5.2, the Ca2+ influx but not Na+ uptake is decreased by aluminum (Al). Al reduces Ca2+ influx dose‐dependently: a maximum 55% reduction was observed after 1–2 h exposure to 200 μg·1−1 (7.4 μM) Al. Branchial Ca2+ efflux is less sensitive to Al and affected only by exposure for more than 1 h to high Al concentrations. Na+ influx is not affected by concentrations Al up to 400 μg·1−1. Na+ efflux, similarly to Ca2+ efflux, increased when fish were exposed for more than 1 h to 400 μg·l−1 Al. © 1992 Wiley‐Liss, Inc.
Mechanisms by which calcium ionophore and phorbol ester modulate steroid production by goldfish preovulatory ovarian follicles
Authors: Kraak Glen Van Der
Published: June 2005

Recent studies have shown that agents that increase intracellular calcium content (calcium ionophore A23187) and activate protein kinase C (phorbol 12‐myristate 13‐acetate; PMA) modulate basal and cAMP‐stimulated steroid production by goldfish preovulatory ovarian follicles. This report describes studies evaluating sites in the steroidogenic cascade (pre‐ and postadenylyl cyclase) influenced by calcium and protein kinase C. PMA (12.5–400 nM) inhibits hCG stimulated cAMP production, whereas phorbol 12, 13‐dideconate, an inactive phorbol ester that does not activate protein kinase C, was without effect. Earlier studies suggested that PMA also acts post cAMP formation, but this action was shown to be exerted prior to cholesterol side‐chain cleavage as metabolism of 25‐hydroxycholesterol to testosterone was not inhibited by PMA. A high dosage of A23187 (4000 nM) inhibited the stimulatory action of hCG on cAMP and testosterone production; lower dosages of A23187 were without effect. In contrast, a wide range of A23187 dosages (250–4,000 nM) enhanced conversion of 25‐hydroxycholesterol to testosterone. This effect appears to be exerted at the level of the cholesterol side‐chain cleavage enzyme as A23187 did not affect conversion of exogenous pregnenolone to testosterone. These data demonstrate specific regulatory actions of calcium and protein kinase C at multiple sites in the steroidogenic cascade both proximal and distal to cAMP generation. © 1992 Wiley‐Liss, Inc.
Development of the chick chorioallantoic capillary plexus under normoxic and normobaric hypoxic and hyperoxic conditions: A morphometric study
Authors: Burton G. J. , Palmer M. E.
Published: June 2005

Fertile eggs from the domestic fowl were incubated under normobaric normoxic (21% O2), hypoxic (14% O2), and hyperoxic (40% O2) conditions in order to examine the influence of the prevailing oxygen level on the growth and maturation of the chorioallantoic memorane. Eggs were sampled at regular stages throughout incubation for morphometric analysis. Under normoxic conditions, maturation of the capillary plexus occurred in two distinct stages, both of which contributed to a reduction in the thickness of the air‐blood barrier. Between days 6 and 10, the capillaries sprouted and fused to form a dense plexus. Subsequently, between days 10 and 14, this plexus invaginated into the chorionic epithelium. Differentiation of the chorioallantoic membrane appeared maximal by the end of this period. Hypoxia resulted in diminished growth of the embryo and chorioallantoic membrane, but in accelerated maturation of the capillary plexus. Hyperoxia had a less marked effect but appeared to retard the final invagination of the plexus, resulting in a thicker air‐blood barrier. © 1992 Wiley‐Liss, Inc.
An aerodynamic valve in the avian primary bronchus
Authors: Wang Ning , Banzett Robert B. , Nations Christopher S. , Jenkins Farish A.
Published: June 2005

The segmentum accelerans in geese is a constriction in the caudal end of the primary bronchus. Experimental evidence suggests that this part of the airway functions as an inspiratory aerodynamic valve, accelerating the incoming airstream past the ventrobronchial openings. The luminal diameter of the segmentum accelerans dilates in the presence of elevated CO2 levels, probably through relaxation of smooth muscle. Physiological control of the segmentum acelerans may permit inspiratory aerodynamic valving to be maintained throughout a wide range of ventilatory flows. © 1992 Wiley‐Liss, Inc.
Acid‐base regulation in pulmonate molluscs
Authors: Barnhart M. Christopher
Published: June 2005

Evidence is presented for a role of CO2 in acid‐base regulation by air‐breathing gastropods. In the land snail Otala lactea, alterations of PCO2 account for pH adjustment during acute temperature change and in compensation for metabolic acidosis. CO2 release from the gastropod lung appears to be more closely coupled with ventilation than is O2 uptake, because O2 uptake is limited to a greater extent by diffusion through the lung epithelium. Cutaneous CO2 release may account for half of CO2 release from active snails, and the loss of this route during withdrawal into the shell partly accounts for elevation of CO2 during dormancy. Further CO2 accumulation and consequent acidosis during dormancy is attributable to hypoventilation of the lung. Although respiratory acidosis appears to be involved in metabolic depression during dormancy, the mechanism of influence on cellular metabolism is unknown and is probably indirect. Unlike the respiration of whole animals, respiration of isolated tissues of Otala is insensitive to PCO2. © 1992 Wiley‐Liss, Inc.
Mechanisms of ion and acid‐base regulation at the gills of freshwater fish
Authors: Goss G. G. , Perry S. F. , Wood C. M. , Laurent P.
Published: June 2005

This review examines the branchial mechanisms utilized by freshwater fish to regulate internal acid‐base status and presents a model to explain the underlying basis of the compensatory processes. Rainbow trout, Oncorhynchus mykiss, and brown bullhead, Ictalurus nebulosus, were examined under a variety of experimental treatments which induced respiratory and metabolic acid‐base disturbances. Acid‐base regulation was achieved by appropriate adjustments of Na + and Cl− net fluxes across the gills which, in turn, were accomplished by variable contributions of three different branchial mechanisms: 1) differential changes in Na+ and Cl− diffusive effluxes, 2) changes in internal substrate (H+, HCO3 −) availability, and 3) morphological adjustments to the gill epithelium. Differential diffusive efflux of Na+ over Cl− was involved only during periods of metabolic alkalosis. The importance of internal substrate availability was demonstrated using a two‐substrate model. According to the model, ionic flux rates (JinCl−, JinNa +) are determined not only by the concentration of the external ion (Na+, Cl−) but also by the concentration of the internal counterion (H+, HCO3−). This system provides for an “automatic negative feedback” to aid in the compensation of metabolic acid‐base disturbances. Morphological alteration of the gill epithelia and the associated regulation of chloride cell (CC) fractional area is an essential third mechanism which is especially important during respiratory acid‐base disturbances. Specifically, fish vary the availability of the CC associated Cl−/HCO3 − exchange mechanism by physical covering/uncovering of CCs by adjacent pavement cells. © 1992 Wiley‐Liss, Inc.
Control and consequences of adrenergic activation of red blood cell Na+/H+ exchange on blood oxygen and carbon dioxide transport in fish
Authors: Thomas Serge , Perry Steve F.
Published: June 2005

The catecholamines, adrenaline and noradrenaline, are released into the circulation of fish during a variety of physical and environmental disturbances that share the common feature of a requirement for enhanced blood oxygen transport. Indeed, the dominant factor controlling the mobilization of catecholamines from chromaffin tissue is a depression of blood oxygen content usually coinciding with a reduction of hemoglobin‐O2 (Hb‐O2) binding to 50–60% saturation. The elevation of plasma catecholamine levels, under such conditions, activates a β‐adrenergic cyclic AMP‐dependent Na + /H+ exchanger on the red blood cell (rbc) membrane. The adrenergic responsiveness of the rbc Na + /H+ exchanger to catecholamines varies both within and between species. Such inter‐ and intra‐specific differences may reflect, in part, the availability of cell surface β‐adrenoceptors that are functionally coupled to adenylate cyclase.

The activation of rbc Na + /H + exchange and the accompanying profound adjustments of intracellular and extracellular acid‐base status, nucleoside triphosphate (NTP) levels, and cooperativity of Hb‐O2 binding have important consequences on both O2 and CO2 transfer and transport in the blood that vary markedly at the sites of oxygenation (the gill) and deoxygenation (the tissues) thereby enabling simultaneous amelioration of O2 loading and unloading. At the gill, oxygen transfer is enhanced owing to increases in Hb‐O2 affinity and capacity while at the tissues, oxygen delivery is facilitated by a reduction of Hb‐O2 affinity. This reduction in affinity at the tissues is a consequence of the combined effects of increased cooperativity of Hb‐O2 binding and a rise in venous PCO2 (PvCO2) caused by the titration of HCO3 − by H+ extruded by the rbc Na + /H+ exchanger. This elevation of PvCO2 may contribute to the rise in arterial PCO2 (PaCO2) observed after adrenergic activation of rbc Na + /H+ exchange that is caused primarily by impairment of rbc CO2 excretion related to modification of the intracellular acid‐base status. © 1992 Wiley‐Liss, Inc.
Tissue specificity of crustacean tropomyosin
Authors: Miyazaki Jun‐Ichi , Makioka Toshiki , Fujiwara Yoshihiro , Hirabayashi Tamio
Published: June 2005

The tropomyosin isoform distribution in muscle and nonmuscle tissues of crustaceans was investigated by two‐dimensional gel electrophoresis and immunoreplica tests. All five crustacean species examined in this study showed extensive molecular heterogeneity and tissue specificity of tropomyosin. The results were different from those previously reported with the horseshoe crab, that is, horseshoe crab tropomyosin was heterogeneous but not tissue‐specific. In this respect, therefore, the distribution of crustacean tropomyosin isoforms is more similar to that of vertebrate tropomyosin isoforms rather than that of horseshoe crab tropomyosin isoforms. Furthermore, crustacean nonmuscle tissues contained tropomyosin isoforms of high electrophoretic mobilities, which were possible counterparts of so‐called vertebrate nonmuscle isoforms of low molecular weights. However, it is rather difficult to expect that each tropomyosin isoform has a tissue‐specific function, since the patterns of isoform composition were not consistent among the examined crustaceans except for those of cardiac isoforms, which were unique to the hearts in all the examined crustaceans and correlated with the expression of presumed actin of compound peptides, which specifically appeared in the hearts. Therefore, the cardiac isoforms of crustacean tropomyosin are suggested to play tissue‐specific regulatory roles. © 1992 Wiley‐Liss, Inc.
Presence of gonadotropin‐releasing hormone immunoreactivity in dogfish and skate brains
Authors: Lovejoy D. A. , Ashmead B. J. , Coe I. R. , Sherwood N. M.
Published: June 2005

Gonadotropin‐releasing hormone (GnRH) immunoreactivity was studied in two species of elasmobranchs, spiny dogfish (Squalus acanthias) and black skate (Bathyraja kincaidii). Immunoreactive material in brain sections was identified using the avidin‐biotin technique with the horseradish peroxidase reaction. Although there were a few GnRH immunoreactive cells, GnRH fibers were greatest in the telencephalon of both species and were associated primarily with the terminal nerve system. In the dogfish, many immunoreactive fibers extended towards the ventromedial surface of the caudal forebrain. This site may be the locus for neurosecretion. GnRH fibers were found in the preoptico‐hypophyseal tract of dogfish, but not in the media eminence or pituitary. Immunoreactive material was less abundant in other regions of the brain, although a diffuse fiber network throughout the brain including the brain stem was observed. © 1992 Wiley‐Liss, Inc.
Analysis of puberty‐accelerating pheromones
Authors: Price Monica A. , Vandenbergh John G.
Published: June 2005

Two experiments were performed to test putative puberty‐accelerating pheromones. In the first experiment, 37 weanling female house mice of the ICR strain were exposed to 1 of the following 3 treatments: an airborne mixture of 0.05 M isoamylamine and 0.05 M isobutylamine, fresh male mouse urine, or distilled water, as the control. Neither the amine mixture nor the male urine accelerated first estrus in the mice following airborne exposure to these compounds. In the second experiment, 37 weanling female mice of the same strain were exposed to the same chemicals as in the first experiment by direct contact to the oro‐nasal groove. The mixture of isoamylamine and isobutylamine did not accelerate puberty, but direct contact with the male urine accelerated puberty as evidenced by uterine weights. © 1992 Wiley‐Liss, Inc.
Intratesticular control of spermatogenesis in the frog, Rana esculenta
Authors: Minucci Sergio , Di Matteo Loredana , Fasano Silvia , Baccari Gabriella Chieffi , Pierantoni Riccardo
Published: June 2005

Adult intact and hypophysectomized (PDX) frogs, Rana esculenta, were treated with a gonadotropin releasing hormone agonist (GnRHA, HOE 766) and/or cyproterone acetate (CPA), the antiandrogen, in order to investigate the regulation of primary spermatogonial (I SPG) multiplication in vertebrates. Treatment with GnRHA (injections containing 900 ng administered for 12 days on alternate days) caused a significant increase of the mitotic index (MI) of I SPG in PDX animals and a further MI increase of SPG was observed when 0.66 mg CPA was given concomitantly with GnRHA. The treatment with 0.66 mg CPA in combination with GnRHA also increased secondary spermatocyte (II SPC) appearance. Moreover, number of nests containing spermatids (SPT) decreased as CPA, in combination with GnRHA, was administered in increasing doses (0.33 and 0.66 mg/injection). Intact animals treated with CPA (0.66 mg/injection) showed a time‐dependent I SPG multiplication increase which reached highest values after 28 days. Secondary SPC also proliferated until day 28; meanwhile the number of nests containing SPT decreased. Neither testosterone nor R5020 (a progestin which is not converted to androgens) modified the basal and GnRHA‐induced spermatogonial proliferation. These results confirm that in the frog, Rana esculenta, spermatid formation is impaired by CPA treatment and that I SPG multiplication is enhanced by a direct effect of GnRHA; moreover, we suggest that the abence of spermatides constitutes a signal promoting spermatogonial proliferation. © 1992 Wiley‐Liss, Inc.
Whole‐body and plasma concentrations of steroids in the turtle, Trachemys scripta, before, during, and after the temperature‐sensitive period for sex determination
Authors: White Richard B. , Thomas Peter
Published: June 2005

To examine endogenous steroid levels during early sexual differentiation in a reptile, we measured whole‐body and plasma steroid concentrations in a turtle (Trachemys scripta) throughout embryogenesis using radioimmunoassays. Whole embryos contained testosterone, estradiol, progesterone, and corticosterone before the temperature‐sensitive period for sex determination (TSP) (stage 14). The concentration of each of these steroids increased significantly between stage 14 and the initiation of the TSP (stage 16), but no increases were evident between stage 16 and the middle of the TSP (stage 18). No sex differences in steroid content were observed prior to the TSP (stage 14). However, presumptive male embryos (26°C incubation temperature) contained significantly more testosterone and estradiol than presumptive females (31°C incubation temperature) during the TSP (stages 16 and 18), and males contained more progesterone than females at stage 18. Plasma samples collected during the TSP (beginning at stage 17+) contained testosterone, estradiol, progesterone, androstenedione, and corticosterone. Progesterone and corticosterone were present in the highest concentrations, followed by androstenedione. Testosterone and estradiol were found in plasma at lower, similar concentrations except at stage 17+, when estradiol levels were ∼3‐fold higher than testosterone levels in both sexes. The only significant sex difference found in plasma steroid levels was for estradiol at stage 19, with males having higher levels than females. Our results demonstrate the presence of a rich steroid milieu throughout early development and support our previous findings that embryonic tissues can synthesize each of these steroids in vitro. Furthermore, a role for sex steroids in the process of sexual differentiation is strongly suggested. © 1992 Wiley‐Liss, Inc.
Inhibitory role of sex steroid in the regulation of ovarian follicle‐stimulating hormone receptors during pregnancy
Authors: Tsutsui Kazuyoshi
Published: June 2005

The present study was conducted to determine the role of sex steroids in the regulation of FSH receptors in pregnant rats. In the normal physiological condition, FSH bindings per unit ovarian weight (density of binding) and per 2 ovaries (total binding) increased during days 14–21 gestation. Scatchard plot analyses of the binding suggested that the increase in FSH binding was due to an increase in the number of FSH‐binding sites. The plasma FSH concentration in pregnant rats was stable during the receptor change. In contrast, the plasma estradiol‐17β concentration continuously increased from gestation day 14 to 21, and the testosterone level showed a large peak on gestation day 18. Estradiol‐17β (one silastic plate containing 13 mg crystal)‐implanted pregnant rats during 14–21 days of gestation induced significant decreases in the total FSH binding and ovarian weight on gestation day 21. Estradiol administration increased the plasma estradiol level 2.3‐fold but did not change the FSH level. Testosterone or 5 α‐dihydrotestosterone, a nonaromatizable androgen, did not influence the binding level under the same dose treatment. In contrast, continuous treatment with aminoglutethimide (2 plates containing 20 mg crystal), an inhibitor of adrenocortical steroidogenesis, for 7 days significantly increased the total FSH binding without a significant change in the ovarian weight. The plasma titers of estradiol and testosterone in pregnant rats treated with aminoglutethimide were reduced by 37% and 51%, respectively. Aminoglutethimide did not influence plasma FSH levels. These results suggest that circulating estradiol acts as a negative factor in the regulation of ovarian FSH receptors, at least during the second half of pregnancy. Other factor(s) that is (are) independent of sex steroids and FSH may contribute to FSH receptor induction. © 1992 Wiley‐Liss, Inc.
Sex differences in adrenal function in the lizard Cnemidophorus sexlineatus: II. Responses to acute stress in the laboratory
Authors: Grassman Mark , Hess David L.
Published: June 2005

Circulating concentrations of plasma corticosterone and gonadal steroids were measured intact and gonadectomized male and female lizards (Cnemidophorus sexlineatus) following acute stress (handling) in the laboratory. There was a significant increase in plasma corticosterone after stress. Whereas intact females exhibited greater concentrations of corticosterone relative to intact males, ovariectomized females exhibited lower concentrations of corticosterone relative to castrated males. In addition to sex differences in corticosterone responses to gonadectomy, progesterone was elevated by stress in both intact and ovariectomized females but not in males. Corticosterone adjusted for castration and handling in males was negatively correlated with the plasma androgen level. The adrenal responsiveness of males to acute stress may be attenuated by androgens presumably secreted by the testis. Not only does adrenal function influence reproduction, but adrenal responses differ between males and females, and appear to be influenced by the gonadal axis. The sex differences in adrenal responses to stress likely reflect different reproductive strategies and nutritional requirements of males and females during the breeding season. © 1992 Wiley‐Liss, Inc.
The role of hypoglossal sensory feedback during feeding in the marine toad, Bufo marinus
Authors: Nishikawa Kiisa C. , Gans Carl
Published: June 2005

Behavioral observations demonstrate that bilateral deafferentation of the hypoglossal nerves in the marine toad (Bufo marinus) prevents mouth opening during feeding. In the present study, we used high‐speed videography, electromyography (EMG), deafferentation, muscle stimulation, and extracellular recordings from the trigeminal nerve to investigate the mechanism by which sensory feedback from the tongue controls the jaw muscles of toads. Our results show that sensory feedback from the tongue enters the brain through the hypoglossal nerve during normal feeding. This feedback appears to inhibit both tonic and phasic activity of the jaw levators. Hypoglossal feedback apparently functions to coordinate tongue protraction and mouth opening during feeding. Among anurans, the primitive condition is the absence of a highly protrusible tongue and the absence of a hypoglossal sensory feedback system. The hypoglossal feedback system evolved in parallel with the acquisition of a highly protrusible tongue in toads and their relatives. © 1992 Wiley‐Liss, Inc.
The role of protein kinase C in reorganization of the cortical cytoskeleton during the transition from oocyte to fertilization‐competent egg
Authors: Capco David G. , Tutnick Joel M. , Bement William M.
Published: June 2005

Fertilization‐competent amphibian eggs (metaphase II) are programmed to undergo an actin‐myosin based contraction of the cortical cytoplasm (i.e., cortical contraction) in response to an elevation of intracellular‐free calcium which accompanies fertilization. This ability to undergo cortical contraction is acquired within a few hours after the meiotically‐arrested oocyte is triggered to resume meiosis by exposure to progesterone. This report examines the timing of changes in the contractile potential of the cortical cytoplasm as the oocyte becomes the egg, and in addition, the signal transduction events which induce these changes. We use the bisected oocyte system developed by Christensen et al. ('84; Nature 310: 150‐151) to assess the changes in cortical potential during the meiotic resumption. Immediately after progesterone treatment (less than 5% of the way through the meiotic resumption) the cortex acquires the ability to form a contractile ring, an ability which gradually disappears during the meiotic resumption. Eighty percent of the way through the meiotic resumption the cortex of the hemisphere rapidly acquires the ability to undergo cortical contraction. In contrast, when bisected in a medium containing protein kinase C (PKC) agonists, the cortex of the hemisphere undergoes cortical contraction much earlier (i.e., 50% through the meiotic resumption). In addition, treatment of oocytes with PKC agonists alone can mimic the complete spectrum of changes in cortical potential induced by progesterone, suggesting that PKC has a role in reorganization of the cortical cytoskeleton which occurs as a normal response to progesterone. In support of this, antagonists of PKC block the progesterone‐induced reorganization of the cortical cytoskeleton. © 1992 Wiley‐Liss, Inc.
Seasonal changes of the adrenocortical response to stress in birds of the Sonoran desert
Authors: Wingfield John C. , Vleck Carol M. , Moore Michael C.
Published: June 2005

Many avian species of the North American Sonoran desert, e.g., the black‐throated sparrow, Amphispiza bilineata, cactus wren, Campylorhynchus brunneicapillus, and curve‐billed thrasher, Toxostoma curvirostre, can potentially breed from March/April to August. It is possible that, at least in summer, intense heat and aridity may have inhibitory effects on breeding by precipitating a stress response. Stress typically results in a rise in secretion of adrenocorticosteroid hormones that then inhibit reproduction by suppressing release of gonadal hormones. However, we found that plasma levels of corticosterone were not higher during summer, compared with winter, even in 1989 when summer temperatures were higher than normal. In June 1990, temperatures were also above normal and soared to the highest level recorded in Arizona (50°C). Plasma levels of corticosterone during June were high in black‐throated sparrows, but less so in two other species (Abert's towhee, Pipilo aberti, and Inca dove, Scardafella inca) found in more shady riparian and suburban habitat with constant access to water. The adrenocortical response to stress (as measured by the rate of corticosterone increase following capture) was reduced in the hottest summer months in black‐throated sparrows, cactus wrens, and curve‐billed thrashers, but less so in Abert's towhee an Inca dove. These data suggest that at least some birds breeding in the open desert with restricted access to water are able to suppress the classical adrenocortical response to stress. The response is then reactivated in winter after breeding has ceased. It is possible that this stress modulation may allow breeding to continue despite severe heat. Analysis of plasma from these species indicated that the apparent modulation of the adrenocortical response to stress was not an artifact of reduced affinity or capacity of corticosterone binding proteins. © 1992 Wiley‐Liss, Inc.
Renal clearance measurements of electrolytes in embryonic chickens
Authors: Clark N. B. , Feng J. Q. , Murphy M. J.
Published: June 2005

Plasma ion concentrations and renal functions were examined in chick embryos after 9, 12, and 15 days of incubation. Plasma calcium and phosphate values rise steadily and significantly between days 9 and 15 of development. Values of other plasma ions (sodium, potassium, magnesium, sulfate) remain more or less the same during this developmental period. Glomerular filtration rates and urine flow rates decline steadily and significantly during this period of embryogenesis when expressed relative to body weight. Renal clearance values of calcium decrease between day 9 (16% of filtered calcium is excreted) and day 15 (4%). The latter value is the same as in birds after hatching and indicates that calcium is being conserved by the kidney of the chick during late embryogenesis. Other ions that appear to be conserved by the embryonic kidney are sodium and sulfate, whereas high percentages of filtered phosphate, potassium, and magnesium are excreted. Except for calcium, there was no significant difference between the renal handling of ions by the mesonephric kidney (functional in 9 day embryos) and the metanephric kidney (predominant in the 15 day embryos). © 1993 Wiley‐Liss, Inc.
Developmental anomalies of Xenopus embryos following microinjection of SPARC antibodies
Authors: Purcell Laura , Gruia‐Gray Jasmine , Scanga Sam , Ringuette Maurice
Published: June 2005

The function of SPARC (Secreted Protein, Acidic, Rich in Cysteine) in early embryonic development was assayed by microinjecting affinity‐purified antibodies directed against SPARC into the blastocoel cavity of Xenopus embryos. Microinjection of SPARC antibodies did not appear to interfere with development until late neurulation. By hatching, a broad spectrum of external developmental anomalies were observable, including bent embryonic axes, accentuated ventral masses, shortened embryonic axes, and lack of visible eye pigment. Histological sections of injected embryos demonstrated that lack of visible eye pigmentation was often associated with deformities in eye development. Bending and shortening of the embryonic axis was associated with highly disorganized myo‐tome patterns and loss of segmental boundaries. The results indicate a requirement for SPARC in the early morphological development of several tissues in Xenopus. © 1993 Wiley‐Liss, Inc.
Relationship between local cell division and cell displacement during regeneration of embryonic Xenopus eye fragments
Authors: Underwood Lauren Wunsh , Carruth Marc R. , Vandecar‐Ide Annette , Ide Charles F.
Published: June 2005

We examined the relationship between early healing modes and extra cell division (via tritiated thymidine incorporation) during embryonic retinal regeneration. Nasal (N) and dorsal (D) one‐third sized eye fragments were surgically created in stage 32 Xenopus laevis embryos. Embryos were injected with tritiated thymidine two days postsurgery (stage 43), and then fixed and processed for autoradiography one day postinjection (stage 46). Histological analysis revealed that all nasal one‐third sized fragments showed cell displacement in healing regions. These displaced cells were located in the ventral retinal region and showed heavy thymidine label incorporation. Alternatively, most dorsal one‐third sized fragments showed little cell displacement during healing; in addition, no extra thymidine incorporation was evident. A minority of dorsal one‐third sized fragments showed cell displacement during healing, and also showed significant local label ventrally through all regions of the eye. Therefore, in both dorsal and nasal one‐third sized retinal fragments, when cell displacements were observed during early healing, associated mitosis was apparent in ventral retinal regions. Furthermore, by 60 hours postsurgery, all eyes which showed cell displacements during healing were greater in volume than those eyes which showed little cell displacement. Increases in volume appear to be derived from a combination of both cells migrating in from underlying optic stalk tissue and from related extra cell division during healing. These data further support a model which predicts that specific healing interactions which involve cell displacement during embryonic retinal regeneration and subsequent intercalary growth underlie visuotectal pattern formation. © 1993 Wiley‐Liss, Inc.
Effects of reproductive state on molt in the Japanese quail
Authors: Hall M. R. , Laouar L. , Ivings W.
Published: June 2005

Molt is induced in quail when they are transferred from photostimulatory long daylengths of 18L, with a fully active reproductive system, to short daylengths of 8L, when the reproductive system regresses. Gonadal steroids, but not gonadotrophins, inhibit molt in male and female Japanese quail. Molt can be induced in long‐term photostimulated (18L) quail by withdrawing gonadal steroids 1) by transferring quail to 8L, 2) by castrating males and maintaining them on a photoperiodic regime of 18L, or 3) by treating females or males with the antiestrogen, tamoxifen. In contrast, treatment of male quail with the antiandrogen, flutamide, does not induce molt even though androgen secretion is inhibited and androgen‐dependent tissues regress. Neither the exact mode of action nor the metabolite of gonadal steroids which inhibits molt is known, although estradiol is capable of inhibiting molt in females and to a lesser extent in males. Plasma levels of thyroxine are consistently elevated during molt. © 1993 Wiley‐Liss, Inc.
Embryonic mouse pre‐metatarsal development in organ culture
Authors: Klement Brenda J. , Spooner Brian S.
Published: June 2005

Embryonic mouse pre‐metatarsals were removed from embryos at 13 days of gestation and cultured in a defined, serum‐free medium for up to 15 days. By histological analysis, we observe that the cultured pre‐metatarsal tissue undergoes a similar developmental profile as pre‐metatarsals growing normally in vivo. The initial mesenchyme condensation regions undergo differentiation and morphogenesis to form distinct rods made up of cartilage tissue. A marker of this differentiation step is the synthesis of type II collagen. Metabolic labelling, pepsin digestion, SDS‐PAGE, and autoradiography were used to demonstrate this protein when cartilage tissue is present in the cultures. After additional culture time, terminal chondrocyte differentiation and morphogenesis take place in specific regions of the cartilage rods to form bands of hypertrophied chondrocytes. One marker of this differentiation step is the synthesis of the enzyme alkaline phosphatase. We have measured the activity of this enzyme throughout the culture period and see a substantial increase at the time of terminal chondrocyte differentiation. Another feature of hypertrophied chondrocytes is that the matrix around the cells becomes calcified. Calcified matrix in our cultured pre‐metatarsals was visualized by staining with alizarin red. By supplementing the defined culture medium with ITS, we observed that terminal chondrocyte differentiation took place in a shorter culture time. Supplementation of the medium with serum results in a similar acceleration of terminal differentiation, and, with additional culture time, an osteoid‐like matrix forms around the central region of the rods. © 1993 Wiley‐Liss, Inc.
On the existence of epithelial chloride channels in intact frogs and crayfish
Authors: Zetino Ana M. , Kirschner Leonard B.
Published: June 2005

Chloride channels in isolated amphibian skins have been shown to be open (high PCi) when the transepithelial potential (TEP) across the skin is >30 mV, inside positive, and [Cl−] in the external medium is high. In the absence of either of these signals PCl is much lower. Using Cl− efflux as a criterion, it is shown here that when the same cues are presented to intact frogs, channels open as in the in vitro preparation. The augmented efflux is partially inhibited by high I− in both preparations. However, salt‐depleted frogs do not show channel opening, differing in this regard from isolated skins.

Elevating external [Cl−] resulted in an even larger efflux stimulation in crayfish than in frogs. The TEP in these animals is usually small and sometimes blood negative; it does not appear to play a role in augmenting the efflux. Gluconate and NO3− also caused Cl efflux to increase markedly. Salt‐depletion reduced the stimulation by high [Cl−] but did not abolish it as in frogs. Iodide had no effect on chloride efflux in crayfish. The results may indicate that gated channels exist in these animals, but interpretation is complicated by the possibility that the augmented efflux is due to exchange diffusion. © 1993 Wiley‐Liss, Inc.
Biochemistry, localization, and physiology of carbonic anhydrase in the gills of euryhaline crabs
Authors: Böttcher K. , Siebers D.
Published: June 2005

Carbonic anhydrase, found at high levels in crustacean gill, is capable of catalyzing the formation of CO2 in the forward reaction or the production of HCO3− in the reverse reaction. Thus the enzyme may participate in both respiratory and ion regulatory functions. Its subcellular distribution in crab gill epithelial cells suggests that a large proportion of the enzyme is membrane‐bound, where it would be available to pharmacological treatment with membrane‐impermeable carbonic anhydrase inhibitors. These studies suggest that the enzyme plays a central role in CO2 excretion. Treatment with the permeable inhibitor acetazolamide affects osmoregulation and ion transport in addition to CO2 excretion, suggesting that the cytosolic form of carbonic anhydrase may provide HCO3 − for Cl−/HCO3 − exchange and H+ for Na+ /H+ exchange across the gill epithelium. © 1993 Wiley‐Liss, Inc.
Evidence for an alternative route of phosphoenolpyruvate metabolism in mature nucleated Rana ridibunda erythrocytes
Authors: Kaloyianni Martha , Beis Isidoros
Published: June 2005

The presence of phosphoenolpyruvate carboxykinase (PEPCK) activity in the direction of oxaloacetate formation in Rana ridibunda erythrocytes was detected. In addition, the levels of all the individual enzymes leading from phosphoenolpyruvate (PEP) to succinate production have been determined in Rana ridibunda hemolysates. Incubation of the intact red cells in the presence of the PEPCK activity inhibitors, quinolinic, and mercaptopicolinic acid resulted in the inhibition of the succinate levels whereas the pyruvate levels were increased. The flow of carbon through PEPCK indicates its participation to an alternative route of PEP metabolism with the advantage of two additional molecules of adenosine triphosphate (ATP) production per glucose molecule catabolized. The possible mechanisms that could control the flow of PEP either towards pyruvate or towards oxaloacetate in Rana ridibunda erythrocytes are discussed. © 1993 Wiley‐Liss, Inc.
Control of intrinsic buccal muscles by motoneurons B11, B15, and B16 in Aplysia californica
Authors: Jordan Robert , Cohen Kevin P. , Kirk Mark D.
Published: June 2005

To further define the control of intrinsic buccal muscles by identified motoneurons B11, B15, and B16 in Aplysia californica, we made physiological recordings from semi‐intact and isolated preparations of the buccal ganglia and buccal mass. B15 and B16 were previously known to innervate muscle 15 (also called the accessory radula closer muscle). We show here that these motoneurons also innervate other buccal muscles ipsilateral to their cell bodies; for example, B15 reliably innervates and can cause contraction in intrinsic muscle 14. Likewise, B11 appears to innervate all of the intrinsic buccal muscles, but elicits contractions only in I4. The form and time course of synaptic plasticity displayed by these motoneurons is common to all the muscles they innervate. No evidence for electrical coupling between fibers of adjacent muscles could be obtained, suggesting that all recorded innervation is direct. Like B15 and B16 (Cohen et al., '78), B11 neuromuscular synapses appear to be cholinergic, since they are reversibly antagonized by hexamethonium and d‐tubocurarine (acetylcholine [ACh] receptor antagonists). In addition, direct application of ACh elicits depolarizing responses and contractions in I4 which are also blocked by hexamethonium. Application of glutamate and GABA do not elicit depolarizations or contractions in I4 or I5. We conclude that these motoneurons control radula position through complex synaptic actions on multiple intrinsic buccal muscles, using ACh as their conventional transmitter. © 1993 Wiley‐Liss, Inc.
Ultrastructure of mature sperm and eggs of the brooding hermaphroditic chiton, Lepidochitona fernaldi Eernisse 1986, with special reference to the mechanism of fertilization
Authors: Buckland‐Nicks John A. , Eernisse Douglas J.
Published: June 2005

Most chitons are gonochoric and free spawning with fertilization occurring in seawater. Brooding hermaphroditic chitons retain their embryos in the pallial groove but whether the eggs are fertilized internally in the female genital tract or externally in the pallial groove was not previously known. Furthermore, the transition to this mode of reproduction could be expected to involve other changes in the functional morphology of eggs and sperm. We describe for the first time observations on live spawning, as well as the ultrastructure of sperm and eggs, in the brooding hermaphrodite, Lepidochitona fernaldi.

Sperm and eggs are spawned through common gonoducts and the eggs are self‐fertilized in the pallial groove. Sperm structure is unmodified from that typical of other Lepidochitonidae, which suggests that the medium filling the pallial groove is seawater and not some more viscous fluid. The egg hull is reduced in this species to a series of flattened hexagonal plates that block access to sperm. Sperm must, therefore, penetrate the egg in between hull plates. In this region are located numerous micropores that provide more direct access to the vitelline layer beneath the hull. This region also overlies an area of the egg membrane that is rich in microvilli. The biological significance of these results is discussed with reference to the evolution of self‐fertilization. © 1993 Wiley‐Liss, Inc.