bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium transport across isolated gill epithelium of Carcinus
Authors: Lucu Čedomil
Published: June 2005

Preparations of posterior gills isolated from postmoult shore crabs (Carcinus mediterraneus) that had been acclimated to dilute seawater were used for calcium‐transport studies. Gills were perfused and bathed with saline of identical composition, with 45Ca2+ ions added exclusively to the bathing solution or the perfusate for measurement of unidirectional influx or efflux, respectively. The unidirectional influx of calcium (5.57 ± 0.95 μmol h−1 per g gill fresh weight) significantly exceeded the efflux (3.15 ± 1.02 μmol h−1 per g gill fresh weight), indicating a net transgill influx of calcium.

Calcium influxes were inhibited when La3+ ions were added apically (IC50 = 7 × 10−6 mol 1−1) or basolaterally (IC50 = 1.6 × 10−6 mol 1−1). In addition, basolaterally applied La3+ ions inhibited effluxes with an IC50 of 3.0 × 10−7 mol 1−1. Amiloride had no significant effect on the unidirectional fluxes of calcium. Influxes of calcium gave a sigmoidal curve when plotted against the external concentration of calcium in the bath. The Hill coefficient (2.66 ± 0.20) suggested that there are at least two or three Ca2+ carrier systems that are active during the influxes of calcium. Moreover, apically added La3+ ions produced a concentration‐dependent inhibition of calcium influx, which is discussed in terms of inhibition of apically located calcium channels. By contrast, the inhibitory action of La3+ ions at the basolateral gill surfaces is discussed in terms of an effect on ATP‐dependent calcium transport and the Na+/Ca2+ exchanger. © 1994 Wiley‐Liss, Inc.
Effects of lung reduction on rheotactic performance in amphibian larvae
Authors: Bruce Richard C. , Beachy Christopher K. , Lenzo Paul G. , Pronych Scott P. , Wassersug Richard J.
Published: June 2005

In this study we test the hypothesis that lung reduction in amphibians is a larval adaptation to reduce buoyancy and facilitate rheotaxis in lotic environments. Larvae of the spotted salamander Ambystoma maculatum (family Ambystomatidae) were raised from eggs with (= control) and without (= experimental) access to the air‐water interface. The experimental larvae developed significantly smaller and more solidified lungs than the controls. Although mean snout‐vent length did not differ between the control and experimental groups, the latter had a significantly greater mean body mass, indicating greater specific gravity in experimentals versus controls. To evaluate rheotactic behavior, larvae were subjected to a water current in an artificial stream. The distance and time required to establish a purchase on the stream bottom were recorded. Although the times did not differ, the distances displaced downstream were significantly less in experimental than in control larvae. We conclude that lung reduction and solidification reduce buoyancy and enhance rheotactic ability in salamander larvae. These findings suggest that lunglessness in plethodontid salamanders evolved as an adaptation to stream environments. © 1994 Wiley‐Liss, Inc.
Patterns of DNA synthesis and mitotic activity during the intermoult of Daphnia
Authors: Beaton Margaret J. , Hebert Paul D. N.
Published: June 2005

Among insects, the epidermal cell cycle pattern is related to the type of ontogenetic development. In taxa undergoing complete metamorphosis, cells are commonly maintained in the G2 stage of interphase between bouts of cell division. In crustaceans, as in insects exhibiting incomplete metamorphosis, it is believed that cells ordinarily remain in G1 for much of the intermoult, with DNA replication occurring late in the moult cycle followed closely by cell division. The present study reveals a differing pattern of epidermal cell division in two distantly related members of the cladoceran crustacean genus Daphnia. Cell cycle kinetics were examined in the last juvenile instar of each species using DNA content determinations and estimates of mitotic frequency. These analyses confirm that each epidermal cell possessed the diploid DNA amount, completed a single cell cycle, and remained in G1 for the majority of the instar. However, DNA replication occurred shortly after moulting and was followed by intense mitotic activity so that cell proliferation was restricted to a short period soon after ecdysis. Cell densities during the instar increased by approximately 60 and 100% for D. pulex and D. magna, respectively. © 1994 Wiley‐Liss, Inc.
Effect of dark rearing on the eye of Gryllus bimaculatus Crickets
Authors: Deruntz Philippe , Palévody Claude , Lambin Michel
Published: June 2005

Studies of the visual fields of six species of crickets have shown that the extent of these visual fields is related more to the nature of their habitat than to the phyletic proximity of the species. The present experiments were conducted to determine the influence of light itself on the development of the eye in young Gryllus bimaculatus. When these insects were maintained in total darkness from the first stages of ontogenetic development, they exhibited morphogenetic changes which seem to result in better light energy reception (more numerous ommatidia, smaller interommatidial angles). However, electron microscopic studies revealed fine structural modifications, which are likely to affect vision adversely. We discuss these changes in terms of the visually guided locomotion of the insects in their natural habitat. © 1994 Wiley‐Liss, Inc.
Androgen receptor in the harderian glands of the golden hamster: Characterization and the effects of androgen deprivation, the pituitary, and gender
Authors: McBlain William A. , Hoffman Roger A. , Buzzell Gerald R.
Published: June 2005

The Harderian glands of the golden hamster were found, by a competitive binding assay using [3H]mibolerone as the ligand, to have a high affinity androgen receptor. In intact male hamsters, this receptor was present in both cytosolic and nuclear KCl‐extractable fractions. Castration or hypophysectomy led to 3‐ to 5‐fold increases in the concentrations of cytosolic receptor with decreased dissociation constants. Hypophysectomy with maintenance of prolactin levels (by removal of pituitaries and their implantation either in the sella turcica or under the kidney capsule) had no effect on androgen receptor binding, compared to hypophysectomy alone. Female hamsters had androgen receptor levels which were 2 to 4 times higher than those of intact males. Hypophysectomy led to elevated receptor binding in ovariectomized female hamsters and this rise was prevented by maintaining prolactin levels. Binding of [3H]mibolerone in male glands was effectively inhibited by 5α‐dihydrotestosterone, whereas the parent molecule, testosterone, required approximately a 10‐fold greater molar excess to achieve the same amount of inhibition. Estradiol and progesterone were relatively poor inhibitors of the observed binding of [3H]mibolerone, while dexamethasone was ineffective. Sucrose gradient studies indicated that the Harderian androgen receptor migrated to the 8S region, as expected for this receptor in molybdate‐containing gradients. These results indicate that the androgen receptor in the hamster Harderian gland is a 5α‐dihydrotestosterone receptor. © 1994 Wiley‐Liss, Inc.
Electrophoretic characterization of equine oviductal fluid
Authors: Willis P. , Sekhar K. N. C. , Brooks P. , Fayrer‐Hosken R. A.
Published: June 2005

To characterize further the events involved in fertilization and early embryonic development in the mare, effect of the estrous cycle on oviductal fluid proteins was investigated. Five mares had indwelling cannulas placed in their oviducts so that fluid could be collected throughout the estrous cycle. Daily fluid volumes were recorded and mares were monitored for signs of standing estrus. Oviductal fluid samples were pooled across mares according to stage of cycle (either estrus or nonestrus) for further analysis. Two‐dimensional polyacrylamide gel electrophoresis (PAGE) was used to determine proteins present in estrus‐associated and nonestrus‐associated equine oviductal fluid as compared to blood serum from the same mares. Oviductal fluid volumes increased significantly during estrus to an average of 3.94 ml/24 hr from 1.44 ml/24 hr during nonestrus. Total oviductal protein increased significantly from 24.6 mg/24 hr during nonestrus to 53.9 mg/24 hr during estrus. One‐dimensional PAGE demonstrated that the proteins in equine oviductal fluid were present throughout the cycle and also common to equine serum. Reducing conditions revealed one band at 106 kDa detected only in nonestrus‐associated oviductal fluid, while nonreducing conditions revealed bands at 48 and 25 kDa that were present in oviductal fluid in general. Two‐dimensional PAGE demonstrated three 50 kDa proteins that were detected only in estrus‐associated oviductal fluid and several 24 kDa proteins detected only in nonestrus‐associated oviductal fluid. Those proteins found only in estrus‐associated oviductal fluid may be vital to the fertilization process, while those found only in nonestrus‐associated oviductal fluid may be vital to early embryonic development. © 1994 Wiley‐Liss, Inc.
Comparison between the sulfated polysaccharides from larval and adult ascidians
Authors: Pavão Mauro S. G. , Lambert Charles C. , Lambert Gretchen , Mourão Paulo A. S.
Published: June 2005

Previously we reported the occurrence of novel sulfated polysaccharides in the tunic of adult ascidians (Mourão and Perlin [1987], Eur. J. Biochem., 166:431–436; Pavão et al. [1989a], J. Biol. Chem., 264:9972–9979). In the present study we compare the polysaccharides from larval and adult ascidians. They differ markedly in electrophoretic mobility and chemical composition. Thus, larvae of ascidians contain a complex sulfated polysaccharide composed of D‐glucose, L‐fucose, and L‐galactose, whereas the adult tunics have a single sulfated L‐galactan. This result may reflect changes in the metabolic pathways involved in the biosynthesis of these sulfated polysaccharides after metamorphosis of the ascidian. © 1994 Wiley‐Liss, Inc.
Embryonic expression pattern of amyloid protein precursor suggests a role in differentiation of specific subsets of neurons
Authors: Salbaum J. Michael , Ruddle Frank H.
Published: June 2005

Immunohistochemical analysis revealed the temporal and spatial expression pattern of the amyloid protein precursor (APP) during the development of the mouse embryo. APP was first detected at day 9.5 of gestation in motor neurons of the hind brain and the spinal cord. APP proteins were also evident in cells of the floor plate, and in neurons of the cranial, dorsal root, and sympathetic ganglia shortly after their formation. Except for floor plate cells, APP expression was restricted to differentiated neurons. Comparison with the expression of microtubule‐associated protein 2 (MAP‐2), a marker for neurodifferentiation, showed that APP is expressed on a subset of differentiated neurons. APP can also serve as an early marker for the developing nuclei of the hind brain. The onset of APP expression in neurons appeared to be correlated with axonal outgrowth, whereas later expression of APP may be associated with functional specialization in the developing nervous system. © 1994 Wiley‐Liss, Inc.
Binding of starfish and sea cucumber sperm attractants to whole sperm and sperm fragments
Authors: Miller Richard L. , Crawford Dwight
Published: June 2005

Binding of starfish and sea cucumber sperm attractants to whole, living spermatozoa and to separated, purified, sperm heads and tails was measured by assaying for loss of sperm attracting activity from solution. Starfish sperm attractant bound mainly to whole sperm or isolated sperm tails and much less, or not at all, to isolated sperm heads. Binding of starfish attractant to sea cucumber sperm or sperm fragments did not occur, nor did sea cucumber sperm attractant bind to starfish sperm or sperm fragments. However, sea cucumber attractant bound equivalently to separated sea cucumber sperm heads and tails. Starfish sperm attractant remained bound to whole sperm or isolated sperm tails if they were frozen‐thawed, but was released if the sperm or sperm fragments were heated. Starfish attractant did not bind to sperm that was previously killed by heat or freezing and thawing but did bind to formalin‐fixed, sea water‐washed sperm. Removal of the sperm membrane using Triton X‐100 eliminated the ability to bind sperm attractant. Although the ratio of the surface areas of tails to heads was approximately 1.5 to 1, up to 10 times more sperm attractant bound to starfish sperm tails than to heads. These results are similar to the binding pattern of the motility‐activating, egg jelly‐derived peptides speract (SAP‐I) and alloresact (SAP‐IIB) to sea urchin sperm heads and tails. They suggest that starfish and sea cucumber sperm attractants bind to sperm membranes in a manner similar to the sperm activating peptides of sea urchins. © 1994 Wiley‐Liss, Inc.
Structural analysis of photosystem I polypeptides using chemical crosslinking
Authors: Armbrust Trent S. , Odom William R. , Guikema James A.
Published: June 2005

Thylakoid membranes, obtained from leaves of 14 d soybean (Glycine max L. cv. Williams) plants, were treated with the chemical crosslinkers glutaraldehyde or 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide (EDC) to investigate the structural organization of photosystem I. Polypeptides were resolved using lithium dodecyl sulfate polyacrylamide gel electrophoresis, and were identified by western blot analysis using a library of polyclonal antibodies specific for photosystem I subunits. An electrophoretic examination of crosslinked thylakoids revealed numerous crosslinked products, using either glutaraldehyde or EDC. However, only a few of these could be identified by western blot analysis using subunit‐specific polyclonal antibodies. Several glutaraldehyde dependent crosslinked species were identified. A single band was identified minimally composed of PsaC and PsaD, documenting the close interaction between these two subunits. The most interesting aspect of these studies was a crosslinked species composed of the PsaB subunit observed following EDC treatment of thylakoids. This is either an internally crosslinked species, which will provide structural information concerning the topology of the complex PsaB protein, a linkage with a polypeptide for which we do not yet have an immunological probe, or a masking of epitopes by the EDC linkage at critical locations in the peptide which is linked to PsaB. © 1994 Wiley‐Liss, Inc.
Comparative assessment of the polypeptide profiles from lateral and primary roots of Phaseolus vulgaris L
Authors: Westberg Jeffrey , Odom William R. , Guikema James A.
Published: June 2005

In Phaseolus vulgaris, primary roots show gravitational sensitivity soon after emerging from the seed. In contrast, lateral roots are agravitropic during early development, and become gravitropic after several cm growth. Primary and lateral root tissues were examined by polyacrylamide gel electrophoresis, coupled with western blotting techniques, to compare proteins which may contribute to the acquisition of gravitational sensitivity. Root tips and zones of cell elongation were compared for each root type, using immunological probes for calmodulin, α‐actin, α‐tubulin, and proteins of the plastid envelope. Lateral roots contained qualitatively less calmodulin, and showed a slightly different pattern of actin‐related epitope proteins, than did primary root tissues, suggesting that polypeptide differences may contribute to the gravitational sensitivity which these root types express. © 1994 Wiley‐Liss, Inc.
Insect gravitational biology: Ground‐based and shuttle flight experiments using the beetle Tribolium castaneum
Authors: Bennett R. L. , Abbott M. K. , Denell R. E.
Published: June 2005

Many of the traditional experimental advantages of insects recommend their use in studies of gravitational and space biology. The fruit fly, Drosophila melanogaster, is an obvious choice for studies of the developmental significance of gravity vectors because of the unparalleled description of regulatory mechanisms controlling oogenesis and embryogenesis. However, we demonstrate that Drosophila could not survive the conditions mandated for particular flight opportunities on the Space Shuttle. With the exception of Drosophila, the red flour beetle, Tribolium castaneum, is the insect best characterized with respect to molecular embryology and most frequently utilized for past space flights. We show that Tribolium is dramatically more resistant to confinement in small sealed volumes. In preparation for flight experiments we characterize the course and timing of the onset of oogenesis in newly eclosed adult females. Finally, we present results from two shuttle flights which indicate that a number of aspects of the development and function of the female reproductive system are not demonstrably sensitive to microgravity. Available information supports the utility of this insect for future studies of gravitational biology. © 1994 Wiley‐Liss, Inc.
Development of the brine shrimp Artemia is accelerated during spaceflight
Authors: Spooner Brian S. , Metcalf Janet , DeBell Lynnette , Paulsen Avelina , Noren Winn , Guikema James A.
Published: June 2005

Developmentally arrested brine shrimp cysts have been reactivated during orbital spaceflight on two different Space Shuttle missions (STS‐50 and STS‐54), and their subsequent development has been compared with that of simultaneously reactivated ground controls. Flight and control brine shrimp do not significantly differ with respect to hatching rates or larval morphology at the scanning and transmission EM levels. A small percentage of the flight larvae had defective nauplier eye development, but the observation was not statistically significant. However, in three different experiments on two different flights, involving a total of 232 larvae that developed in space, a highly significant difference in degree of flight to control development was found. By as early as 2.25 days after reactivation of development, spaceflight brine shrimp were accelerated, by a full instar, over ground control brine shrimp. Although developing more rapidly, flight shrimp grew as long as control shrimp at each developmental instar or stage. © 1994 Wiley‐Liss, Inc.
Eicosanoid synthesis by warm‐and cold‐acclimated American bullfrog (Rana catesbeiana) brain
Authors: Martinez Jeanelle M. , Chapunoff David , Romero Melissa A. , Herman Ceil A.
Published: June 2005

Previous studies in bullfrogs have demonstrated the presence of leukotriene (LT)C4 binding sites in the brain. However, synthesis of eicosanoids by brain tissue has not been examined. Because prostaglandin (PG) synthesis differs in warm‐ and cold‐acclimated bullfrog lung tissue, this study compared the synthesis of prostaglandins and leukotrienes in brains from warm‐(22°C) and cold‐acclimated (5°C) animals. Initial experiments determined that leukotriene and prostaglandin production rates were greatest during the initial 30 min time period. Therefore, tissues were incubated in Munsick's solution and gassed with 95% O2, 5% CO2 for 30 min. Media were analyzed by radioimmunoassay for LTC4, LTB4, PGE2, PGF2α, TXB2, and 6‐keto PGF1α. In warm‐acclimated bullfrog brains, production was as follows: LTC4 > PGE2 > 6‐keto PGF1α, thromboxane (TX)B2, LTB4, and PGF2α. Brain tissues from cold‐acclimated animals incubated at 22°C produced significantly greater quantities of PGE2 and 6‐keto PGF1α than did brains from warmacclimated animals. Stimulation of TXB2 levels was observed when the animal was stunned with a blow to the head prior to decapitation. Indomethacin, a cyclooxygenase inhibitor, decreased prostaglandin but not leukotriene synthesis. Epinephrine (4 × 10−8M), the amphibian sympathetic postganglionic neurotransmitter, stimulated leukotriene synthesis by brains from warm‐acclimated bullfrogs, and the effect was blocked with the 5‐lipoxygenase inhibitor MK‐886 (5 × 10−5M). These results clearly indicate that the bullfrog brain synthesized both leukotrienes and prostaglandins. Further studies are necessary to determine their function in the amphibian central nervous system. © 1994 Wiley‐Liss, Inc.
Culture of rat renal medullary tissue in media made hyperosmotic with NaCl and urea
Authors: Isabelle M. E. , Githens S. , Moses R. L. , Bartell C. K.
Published: June 2005

During antidiuresis, the rat kidney maintains a variable and steep osmotic gradient from the cortex (300 mOsm) to the inner medulla (at least 2,600 mOsm). Therefore, cells in the renal medulla must be able to adapt to a variably hyperosmotic environment. We have examined the ability of tissue fragments taken from various points on the cortical‐medullary axis to survive and grow when cultured in media made hyperosmotic with urea and NaCl. Survival and growth were measured by the explants' ability to produce epithelial outgrowths. At osmotic concentrations of 1,100 and 1,200 mOsm, only explants from the inner medulla produced epithelial outgrowths. At 700 mOsm, all explants produced outgrowths but outgrowth size was a function of position on the cortical‐medullary axis, with inner medullary fragments producing the largest outgrowths. Growth was most rapid at all osmolalities when the Na+:urea ratio was 1:1. These results are consistent with the hypothesis that renal medullary cells are adapted to elevated concentrations of Na+ and urea. Both explants and epithelial outgrowths were examined using light and electron microscopy. Physical continuities between the epithelial outgrowths and collecting duct epithelium in the explants, as well as the ultrastructural characteristics of the outgrowths at 700 mOsm, indicated that the outgrowths may have originated from collecting duct epithelium. © 1994 Wiley‐Liss, Inc.
Establishment and maintenance of claw bilateral asymmetry in snapping shrimps
Authors: Young R. E. , Pearce J. , Govind C. K.
Published: June 2005

The paired asymmetric chelae, or claws, in snapping shrimps, Alpheus heterochelis, differ in form and function; the major, or snapper, claw is grossly enlarged, has a hammer and socket, and functions in agonistic displays, while the minor, or pincer, claw is small and slender and functions in burrowing and feeding. The paired claws are symmetrical and undifferentiated in the larval and early juvenile stages but differentiate on a random basis into a snapper and a pincer claw by the sixth juvenile stage. Removal of one of the paired claws in the third or fourth juvenile stage results in the intact claw developing into a snapper, suggesting that differential use initially determines claw type. However, claw bilateral asymmetry may be altered in adults as removal of the snapper claw causes transformation of the existing pincer into a snapper while a new pincer regenerates at the old snapper site. To test the hypothesis that inhibitory influences from the transforming pincer‐to‐snapper claw may limit the newly regenerating claw to a pincer type, we observed the effects of closer muscle tenotomy and nerve lesions in the intact transforming claw on the type of claw regenerated at the old snapper site. With mild tenotomy in which the tendon is cut at its attachment to the moveable dactyl but the closer muscle and its innervation is otherwise intact, a pincer claw regenerates similar to the control animals. However, with radical tenotomy in which the tendon is removed from the claw and the closer muscle and its innervation is severely disrupted, either a pincer or snapper claw regenerates. Lesioning of the large nerve 2 by itself or together with the small nerve 1 (but not nerve 1 by itself) in the intact transforming claw also permits regeneration of either a pincer or snapper claw at the old snapper site. Thus, neural influences from the transforming pincer‐to‐snapper claw restrict regeneration of the contralateral claw to a pincer type thereby ensuring bilateral asymmetry in adult shrimps. © 1994 Wiley‐Liss, Inc.
In vivo evidence that the premature death (p) mutation of Ambystoma mexicanum affects an early segregating subpopulation of neural crest cells
Authors: Graveson Ann C. , Armstrong John B.
Published: June 2005

The premature death (p) mutation of Ambystoma mexicanum causes a variety of abnormalities and rapid degeneration in homozygous embryos. We have previously determined that the differentiative ability of the chondrogenic neural crest is severely deficient in these embryos. In this study, we demonstrate that the axial specification of the defective neural crest cells is normal, since their major migration routes are the same as those of wild‐type cells from the same axial levels. In addition, we use a series of transplantations and extirpations to show that other neural crest cell populations are also affected by the mutation. The defects observed in p/p embryos, therefore, suggest a role for the neural crest in the morphogenesis of the gills in the establishment of a functional circulatory system, and perhaps in the proper development of other organ systems. We propose that the subset of neural crest cells which are affected by the mutation may represent an intermediate subpopulation produced during the segregation of the neural crest. © 1994 Wiley‐Liss, Inc.
The influence of male‐specific genes on female muscle fiber types: Studies on the sex‐reversed (Sxr) mouse
Authors: Stickland Neil C. , O'Shaughnessy Peter J.
Published: June 2005

Previous experiments on the effects of either male castration or injection of androgens have concluded that levels of androgens are responsible for different muscle fiber type proportions between the sexes. However, these conclusions are based on invasive techniques which may involve secondary factors. The sex‐reversed (Sxr) mouse is genetically female (X/X) but phenotypically male due to the presence of part of the short‐arm of the Y chromosome containing the testis determining gene (Tdy). Serum testosterone in this mouse is in the low normal range and therefore provides a model for investigating the possible control of muscle fiber types by male specific genetic factors.

Ten males, ten females, and ten Sxr mice of approximately 60 days of age were used, together with ten males weight‐matched to the females. The animals were killed and biceps brachii and soleus muscles removed and prepared for routine muscle histochemistry. Body and muscle weights were similar in the males and Sxr mice and significantly greater than in the females and the weight‐matched males. Muscle fiber sizes in biceps brachii reflected the differences in muscle weights and there were no significant differences in fiber type proportions for this muscle. In the soleus muscle, the percentage of slow, oxidative (SO) fibers was higher in the female mice than in any other group. Furthermore, although the fast, oxidative, glycolytic (FOG) fibers were larger in the heavier animals, SO fibers were largest in the female mice.

The results indicate that, although the size of FOG and fast, glycolytic (FG) fibers may be a result of work‐load hypertrophy related to body weight, the proportion and size of SO fibers in the soleus is directly influenced by genetic factors derived from the Y‐chromosome, probably Tdy. © 1994 Wiley‐Liss, Inc.
Directional light transmission in the pineal window of Atlantic salmon (Salmo salar L.) may be used for solar orientation
Authors: Nordtug Trond , Berg Ole Kristian , Melø Thor Bernt
Published: June 2005

The pineal window of adult Atlantic salmon (Salmo salar) (fork length 45–55 cm) is highly transparent, apart from a roof‐like (mean angle 120° ± 5°), bony structure formed by the pineal plates. On each side of the bony pineal plates there is a white lining which acts like an optical diffusor. The forward scattering of an incident narrow laser beam by the pineal plates was observed by an optical fibre and a diode array. The direction for maximum intensity of the scattered light below the pineal plates is refracted with respect to the incidence angle, and the half‐width of the scattered light intensity is 22°. Furthermore, the maximum transmittance of a light ray, with an incidence angle μ with respect to the pineal plates, depends upon μ according to a (1 + cosμ) function. Hence, each pineal plate of the laminar roof grossly receives light from the corresponding hemisphere and projects and assembles the rays on to the pineal organ at an angle of about 30° relative to the vertical plane along the body axis. In spite of the light scattering by the pineal window, a polarization factor of 0.60 was found at the level of the pineal organ for linearly polarized incident light.

The hypothesis is proposed that these properties have ultimately evolved as a directional aid enabling the fish to orient by the directionality of the sunlight. © 1994 Wiley‐Liss, Inc.
Possible involvement of arachidonic acid and eicosanoids in metamorphic events in Hydractinia echinata (Coelenterata; hydrozoa)
Authors: Leitz T. , Beck H. , Stephan M. , Lehmann W. D. , De Petrocellis L. , Di Marzo V.
Published: June 2005

Upon induction of metamorphosis, larvae of the marine hydroid Hydractinia echinata release [14C]‐arachidonic acid from previously labeled endogenous sources. The lipoxygenase inhibitors nordihydroguaiaretic acid and 5,8,11,14‐eicosatetraynoic acid inhibited metamorphosis induced by Cs+ and 1,2‐sn‐dioctanoylglycerol, whereas the inhibitors of cyclooxygenase, indomethacin, and acetylsalicylic acid were ineffective, suggesting a role for lipoxygenase metabolites of arachidonic acid in induction of metamorphosis. Lipoxygenase products in Hydractinia echinata were isolated and identified by gas chromatography/mass spectrometry. 8‐ and 12‐HETE were the most abundant metabolites. In cytosolic fractions from larvae activity of an arachidonic acid metabolizing enzyme, presumably a lipoxygenase, was found. The metabolic product was identified by 1H‐NMR and chiral phase HPLC as 8(R)‐HETE. Its production was strongly inhibited by NDGA, but not by indomethacin. © 1994 Wiley‐Liss, Inc.
Metabolic depression in land snails: In vitro analysis of protein kinase involvement in pyruvate kinase control in isolated Otala lactea tissues
Authors: Brooks Stephen P. J. , Storey Kenneth B.
Published: June 2005

Isolated tissues from the land snail Otala lactea were used to examine the relationship between protein kinase activity and phosphorylation‐induced changes associated with metabolic depression. Hepatopancreas and foot muscle were removed from active and estivating land snails and incubated in vitro under aerobic and anoxic conditions. Pyruvate kinase (PK), cAMP‐dependent protein kinase (PKA), and protein kinase second messenger compounds (cyclic AMP and inositol 1,4,5‐triphosphate) were measured after incubating the tissues for 4 hours. Pyruvate kinase from the hepatopancreas of active snails was phosphorylated during anoxic incubations as indicated by changes in the I50 value for L‐alanine. However, measurements of PKA activity and of cellular cAMP concentrations suggested that PKA activity was lower in these incubated tissues. When foot muscle was used as the tissue source, incubation under anoxic conditions produced no changes in PK activity even though PKA activity was drastically reduced. Analysis of changes in inositol 1,4,5‐triphosphate concentrations after tissue incubation showed that they were not consistent with changes in PK activity in either organ. These results suggest that PKA and Ca2+/phospholipid‐dependent protein kinase C do not phosphorylate PK during anoxia in land snails. The differences between values measured in incubated tissues and those measured in vivo suggest that isolated O. lactea tissues are not a good in vitro model system for studying metabolic changes associated with depressed metabolism. © 1994 Wiley‐Liss, Inc.
Seasonal and daily variations in the plasma gonadotropin II response to a LHRH analog and serotonin in Atlantic croaker (Micropogonias undulatus): Evidence for mediation by 5‐HT2 receptors
Authors: Khan Izhar A. , Thomas Peter
Published: June 2005

The effects of serotonin (5‐hydroxytryptamine; 5‐HT) alone, and in combination with luteinizing hormone‐releasing hormone analog (LHRHa), on plasma levels of maturational gonadotropin (GtH II) in the post‐vitellogenic female and spermiating male Atlantic croaker were investigated during mid‐light, late‐light, mid‐dark, and late‐dark phases of the day‐night (12 hr light: 12 hr dark) cycle. Although LHRHa stimulated GtH II secretion throughout the day‐night cycle, maximal stimulation was observed during the mid‐dark phase. Serotonin significantly potentiated LHRHa‐induced GtH II secretion at all time points tested except during the late‐dark phase. The plasma GtH II response to LHRHa was markedly reduced, and the response to 5‐HT was abolished in regressed Atlantic croaker. Pretreatment of the fish with a 5‐HT2 antagonist, LY 53,857 maleate, almost completely abolished the stimulatory effect of 5‐HT on LHRHa‐induced GtH II secretion, whereas a 5‐HT1 antagonist, methiothepin mesylate, failed to influence the stimulatory effect of 5‐HT on GtH II secretion. In addition, a 5‐HT2 agonist, (±) DOI hydrochloride, potentiated the effect of 5‐HT on basal and LHRHa‐induced GtH II secretion, while a 5‐HT1 agonist, m‐chlorophenylpiperazine dihydrochloride, did not. The results clearly demonstrate timeand season‐dependent stimulatory effects of LHRHa and 5‐HT on plasma GtH II levels in Atlantic croaker. Moreover, the stimulatory effect of 5‐HT appears to be mediated by 5‐HT2 receptors in this species. © 1994 Wiley‐Liss, Inc.
Amphibian cross‐fertilization and polyspermy
Authors: Gómez Marta I. , Cabada Marcelo O.
Published: June 2005

A string of oocytes from Bufo arenarum (Ba) was inseminated with spermatozoa from Ba, Leptodactylus chaquensis (Lch), or Bufo paracnemis (Bp). Homologous insemination resulted in monospermic eggs and normal development, while in the case of heterologous fertilization both polyspermy and abnormal development were the rule. Oocytes from Ba inseminated with homologous spermatozoa, when reinseminated 30 sec after the first insemination with heterologous spermatozoa, exhibit a high rate of polyspermy and abnormal development. A lower rate of abnormalities was observed when reinsemination was carried out 60 sec after the first insemination. Normal development and an absence of polyspermy were observed in the case of eggs reinseminated 300 sec after initial insemination. This result indicated that the electrophysiological blockage of fertilization either was not triggered or was ineffective. The establishment of the permanent blockage of polyspermy, either by artificial activation of oocytes or as a result of their incubation with the products of the cortical granules, inhibited penetration of Ba eggs by heterologous sperm. © 1994 Wiley‐Liss, Inc.
Role of P‐450 aromatase in sex determination of the diamondback terrapin, Malaclemys terrapin
Authors: Jeyasuria Pancharatnam , Roosenburg Willem M. , Place Allen R.
Published: June 2005

Sex determination in the diamondback terrapin, Malaclemys terrapin, is temperature‐dependent. Eggs incubated at 31°C, and above, hatch in approximately 45 days as females. Eggs incubated below 27°C hatch in about 60 days as males. Sex is not reversible after hatching. Nest temperatures in the wild can be as low as 20°C and as high as 37°C with as much as a 10°C diel cycle. The shortest incubation time measured in nature was 56 days and the longest approaching 120 days. Nests in our study site produced predominantly (> 95%) male hatchlings. Treatment of developing embryos with estrogen produces females at male producing temperatures while treatment with fadrozole (a nonsteroidal aromatase inhibitor) induces partial male‐like gonads. Treatment with a steroidal aromatase inhibitor (4‐hydroxyandrostenedione, 4‐OHA) had no effect on sex determination. Both fadrozole and 4‐OHA are potent competitive inhibitors (Ki approximately 40–50 nM) for terrapin in vitro aromatase activity. These findings are consistent with aromatase expression being a key step in sex determination of terrapins. We have cloned a partial single copy P‐450 aromatase from the terrapin using a cDNA library constructed from ovarian mRNA. This partial clone is highly homologous to other vertebrate aromatases. © 1994 Wiley‐Liss, Inc.
Molecular mechanisms of TSD in reptiles: A search for the magic bullet
Authors: Spotila James R. , Spotila Loretta D. , Kaufer Norbert F.
Published: June 2005

Significant progress has been made in understanding mechanisms of genetic sex determination. The ZFY gene encodes a zinc finger protein but is not the primary signal in sex determination. The SRY gene is the testis determining gene in man, mouse, rabbit, and probably marsupial mouse and wallaby. Temperature dependent sex determination probably involves a modification of development of the indifferent gonad due to differential expression of one or more specific DNA sequences whose behavior is controlled by some temperature sensitive process or to differential action of a gene product such as a protein. There are ZFY and SRY‐like genes in reptiles. We cloned and sequenced a portion of the ZFY gene (Zft) from snapping turtle (Chelydra serpentina) that is found in both sexes. We cloned and sequenced portions of SRY‐like genes (Sra for SRY‐related‐autosomal) from snapping turtle. Similar genes are found in alligator (Alligator mississippiensis) and lizards. Cladistic analysis suggests that there are two or three major families of SRY‐like genes in vertebrates in addition to sex specific SRY genes located on the Y chromosome of eutherian and marsupial mammals. When placed on a phylogenetic tree these data indicate that Sras were present in early tetrapods. Sequestering of the SRY gene on the Y chromosome probably happened only once and this may have been the defining moment that set the mammalian line of Therapsid reptiles apart from other reptilian groups. © 1994 Wiley‐Liss, Inc.
Postecdysial cuticle alteration in the blue crab, Callinectes sapidus: Synchronous changes in glycoproteins and mineral nucleation
Authors: Shafer Thomas H. , Roer Robert D. , Midgette‐Luther Carol , Brookins Teresa A.
Published: June 2005

In order to investigate the control of the onset of postecdysial mineralization of the cuticle of the blue crab, Callinectes sapidus Rathbun, EDTA‐soluble proteins and glycoproteins were analyzed at short intervals after ecdysis by SDS‐PAGE. Gels were either stained with silver, blotted to polyvinylidene difluoride membranes and stained with periodic acid/Schiff reagent (PAS), or blotted to nitrocellulose membranes and probed with a variety of lectins [particularly the mannose‐binding lectins concanavalin A(Con A) and Galanthus nivalis agglutinin (GNA)]. Pieces of cuticle were also tested for their ability to nucleate calcite in vitro. A major change occurred in the biochemistry of the cuticle between 1 and 3 hr after ecdysis. This change, which we term the post‐ecdysial cuticle alteration (PECA), involved 1) loss of a major 66 kDa glycoprotein band, 2) decrease in Con A binding by a 79 kDa protein band, 3) complete loss of PAS‐reactivity of both 66 and 79 kDa proteins, 4)gain in Con A affinity of an existing band at 73 kDa, and 5) an increase in the intrinsic ability of cell‐free cuticle pieces to mineralize, as measured by the in vitro calcite crystal nucleation assay. © 1995 Wiley‐Liss, Inc.
Sensitive assay for cholesterol in biological membranes reveals membrane‐specific differences in kinetics of cholesterol oxidase
Authors: Crockett Elizabeth L. , Hazel Jeffrey R.
Published: June 2005

Quantification of cholesterol in biological membranes from a variety of sources is an important step toward understanding cholesterol's roles in membranes function. We extend to biological membranes the fluorometric/enzymatic approach (cholesterol oxidase) to measures cholesterol, originally described for whole cells (Heider and Boyett [1978] J. Lipid Res., 19: 514–518; Gamble et al. [1978] J. Lipid Res., 19: 1068–1070) and serum (Huang et al. [1975] Clin Chem., 21: 1605–1608). This method has a detection limit of 0.3 μg cholesterol. As revealed by comparison with high‐performance liquid chromatography, the fluorometric/enzymatic method with biological membranes is accurate (within 4% and 8% for intestinal and hepatic plasma membranes, respectively). The assay may be completed within 3 to 4 hours and requires neither lipid extraction nor chromatographic techniques. Kinetics of the cholesterol oxidase reaction are membrane‐specific, and first‐order rate constants (k) are positively correlated with membrane order. © 1995 Wiley‐Liss, Inc.
Prolactin receptor concentrations in the skin of mink during the winter fur growth cycle
Authors: Rose Jack , Garwood Todd , Jaber Basem
Published: June 2005

The objectives of this study were to determine: 1) if the skin of mink might be a target organ for prolactin (PRL) by establishing if PRL binding sites (receptors) exist in the cell membranes of skin, and 2) if PRL receptor concentrations change during onset and progression of the winter fur growth cycle. Skin was collected on October 6, 1992 for characterization of PRL receptors and from July through December 1992 (N = 3 mink/month) to evaluate possible changes in PRL receptor concentrations during the fur growth cycle. PRL receptors were quantified using125I‐ oPRL in a validated radioreceptor assay. Scatchard analysis of saturation data revealed a single class of high‐affinity (Kd=5.21 × 10−11±. 84M), low capacity (Bmax= 27.03 ± 3.37 fmoles/mg) binding sites. Only oPRL (40% displacement) and to a lesser extent oGH (3% displacement) inhibited the binding of125I‐oPRL to mink skin cell membranes. No inhibition of125I‐oPRL binding to membranes occurred in the presence of a 500‐fold excess of bTSH of oLH, indicating that the receptors were hormone specific. Concentrations of125I‐oPRL receptors during the onset and development of winter fur growth (July through November) exhibited no significant change. However, following completion of the winter fur growth cycle (December 1) PRL receptor concentration was significantly higher than all preceding months. The greater binding observed at that time may reflect a change in tissue sensitivity, in preparation for growth of the summer pelage. These data suggest to us that the skin of mink is a target organ for PRL and are consistent with the hypothesis that part of the affects of PRL on fur growth occur directly at the level of the skin. © 1995 Wiley‐Liss, Inc.
Cytoskeletal organization in clusters of isolated polarized skate hepatocytes: Structural and functional evidence for microtubule‐dependent transcytosis
Authors: Henson John H. , Capuano Stephanie , Nesbitt David , Hager David N. , Nundy Surajit , Miller David S. , Ballatori Nazzareno , Boyer James L.
Published: June 2005

Isolated hepatoctes from the marine vertebrate Raja erinacea (the little skate) retain their structural and functional integrity as clusters of cells formed around a single tubular bile canaliculus, and therefore can be used as a model of polarized hepatocytes in situ. In this study we used confocal and conventional epifluorescence microscopy in conjunction with fluorescent markers and immunocytochemistry to examine the structure and function of the cytoskeleton in these cells. Actin filaments in the hepatocyte clusters were found cortically and also concentrated in a pericanalicular array, while microtubules disrupting agent, nocodazole, resulted in the microtubules depolymerizing from the basolateral surfaces towards the apical surface, indicating that the microtubules were oriented with their plus ends at the basolateral surface and their minus ends at the apical surface. Nocodazole was also found to disrupt the ability of clusters to transcytose a fluorescent bile salt derivative into their canalicular lumens. We detected cytoplasmic dynein in skate hepatocyte homogenates by Western blotting using an anti‐dynein intermediate chain anti‐body, and immunofluorescent staining of intact hepatocytes revealed a punctate vesicular pattern. The polarized arrangement of microtubules, the presence of cytoplasmic dynein, and the inhibition of bile salt secretion by nocodozole are consistent with the microtubule cytoskeleton playing a fundamental role in the mediation of transcytosis, endocytosis, and bile excretory function in these hepatocytes. These polarized isolated skate hepatocytes represent an excellent experimental model for the in vitro study of hepatic transport, and allow for important comparative studies aimed at elucidating the evolutionarily conserved nature of various hepatocyte structures amongst the vertebrates. © 1995 Wiley‐Liss, Inc.
Influence of pH and temperature on hemolysis by adult Schistosoma mansoni membranes
Authors: Kasschau Margaret R. , Byam‐Smith Mary P. , Gentry Deborah S. , Watson Fay N.
Published: June 2005

Membrane fractions from homogenized adult Schistosoma mansoni are known to lyse host red blood cells (RBC's), Which serve as an important nutrient source for the parasite, In order to learn more about the homolytic process, we investigated the effects of pH and temperature on the steps involved in the hemolytic process. For maximum schistosome induced hemolysis to occur the worm lytic agent must be in the contact with RBCs in a low pH (pH 5.1), high temperature (37°C) environment for a short time (30 min), after which hemolysis occurs at both pH 7.5 and 5.1 At pH 7.5 the hemolytic process is relatively temperature independent and highly concentration dependent. Dose‐response experiments suggest that a multi‐hit process of hemolysis is probably involved. Temperature and dextran experiments suggest that a pore is formed in the RBC membrane at pH 7.5 At pH 5.1 hemolysis is temperature dependent and not very concentration dependent. Dose‐response data suggest that a single‐hit process of hemolysis is utilized at low pH. The hemolytic process at pH 7.5, the pH of the host blood, and pH 5.1, the approximate pH of the worm gut, appears to be very different. © 1995 Wiley‐Liss, Inc.
Comparative study of Msx‐1 expression in early normal and vitamin A‐deficient avian embryos
Authors: Chen Yiping , Kostetskii Igor , Zile Maija H. , Solursh Michael
Published: June 2005

Homeobox‐containing genes may play an important role in establishing embryonic patterns during development of vertebrates. Retinoic acid is able to induce expression of Hox genes in cells in culture and to alter expression patterns in the developing vertebrate embryos. Using wholemount in situ hybridization, we have examined and compared the expression patterns of a homeobox‐containing gene, Msx‐1, in early normal and vitamin A‐deficient quail embryos. At gastrulation stage, Msx‐1 is primarily expressed in the posterior half of both normal and vitamin A‐deficient embryos. However, the gene is expressed wider and stronger in the vitamin A‐deficient embryos. At neurulation stages, Msx‐1 is continuously expressed in the posterior region up to Hensen's node and in the edge of the neural fold in both normal and vitamin A‐deficient embryos. Notably, in the vitamin A‐deficient embryos, Msx‐1 is expressed more strongly and is also expressed ectopically in the anterior and precardiac regions. These results provide evidence that endogenous retinoids are involved in the normal expression of Msx‐1 in avian embryo and that the expression of Msx‐1 is downregulated by endogenous and physiological retinoids in vivo during early avian embryogenesis. © 1995 Wiley‐Liss, Inc.