bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of proline synthesis during osmotic stress in the copepod Tigriopus californicus
Authors: Burton Ronald S.
Published: June 2005

The marine copepod Tigriopus californicus shows rapid adjustment of intracellular proline and alanine pools in response to salinity stress. Small increases in salinity (on the order of 2 ppt or 50 mOsmoles) are sufficient to elicit proline synthesis in animals acclimated to 50% seawater. Increases in osmolarity achieved by adding organic solutes to a 50% seawater medium also elicited proline (but not alanine) synthesis. In constant 50% seawater, label from 14C‐(U)‐glucose is incorporated into the free alanine and glutamate (but not proline) pools; only the proline pool shows a monotonic increase in specific activity following transfer to 100% seawater. To demonstrate that glutamate is a proline precursor, 14C‐(U)‐glutamate was provided to animals maintained in 50% seawater (control) and animals transferred to 100% seawater; salinity change resulted in the rapid increase in alanine and proline concentrations, with proline (and not alanine) achieving specific activities similar to that of the glutamate pool. Taken together, these results indicate that small hyperosmotic stimuli result in the induction of proline synthesis from glutamate. The regulation of proline synthesis involves mechanisms discrete from those regulating the concentrations of other FAA functioning in osmotic response.
Regulation of phosphofructokinase in the foot muscle of Patella caerulea (L.) during exposure to air
Authors: Lazou Antigone
Published: June 2005

The effects of 4 hours and 8 hours of exposure to air on the kinetic properties of phosphofructokinase (PFK) and the maximal activity of glycogen phosphorylase were studied in order to evaluate the role of these enzymes in glycolytic rate control and metabolic depression during air exposure of Patella caerulea foot muscle.

Air exposure resulted in stable modifications of the kinetic properties of PFK including changes in S0.5 for fructose‐2,6‐phosphate (fructose‐6‐P), Hill coefficient, Ka values for adenosine monophosphate (AMP), fructose‐2,6‐biphosphate (fructose‐2,6‐P2), and I50 for adenosine triphosphate (ATP) and phosphoenolpyruvate (PEP), the direction of changes being generally consistent with the production of a less active form in the air exposed tissue. Air exposure did not affect maximal activity of glycogen phosphorylase nor the percentage of active α form. In contrast, changes in the tissue content of fructose‐2,6‐P2 were observed.

Incubation of PFK preparations with protein kinase second messengers (cyclic adenosine mono‐phosphate [cAMP] and cyclic guanosine monophosphate [cGMP]) lead to an increase in the enzyme activity and affinity for the substrate whereas treatement with alkaline phosphatase reversed these effects. The data suggest that modification of PFK kinetics during air exposure is probably mediated via a phosphorylation‐dephosphorylation mechanism.
Protective effects of manganese, cobalt, nickel, and barium against a calcium paradox in the isolated frog heart
Authors: Touraki Maria , Beis Isidoros
Published: June 2005

The effect of inorganic slow channel blockers on the calcium paradox in the frog heart was examined. Addition of the divalent cations of manganese, cobalt, nickel, or barium during calicium depletion protected the frog heart against a calcium paradox. This protective effect was indicated by reduced protein release, maintenance of electrical activity, and recovery of mechanical activity during reperfusion.

Tissue calcium determination results showed that in the control paradox in the absence of divalent cations, there is an efflux of calcium from myocardial cells during calcium depletion and a massive influx of calcium during the following reperfusion, leading to a calcium overload. Divalent cations protected frog myocardial cells, when present in the calcium‐free perfusion medium, by reducing both calcium efflux during calcium depletion and the massive calcium influx during reperfusion.

The effectiveness of the added divalent cations showed a strong dependence upon their ionic radius. The most potent inhibitors of the calcium paradox in the frog heart were the divalent cations having an ionic radius closer to the ionic radius of calcium.

These results are discussed in terms of the possible mechanism involved in the protective effect of manganese, cobalt, nickel, and barium.
Identification of a stretch‐activated monovalent cation channel from teleost urinary bladder cells
Authors: Chang Wenhan , Loretz Christopher A.
Published: June 2005

The urinary bladder of euryhaline teleosts is an important osmoregulatory organ which absorbs Na+, Cl−, and water from urine. Using patch clamp technique, single stretch‐activated channels, which were permeable to K+ and Na+ (PNa/PK ≈︁ 0.75) and had conductances of 55 and 116 pS, were studied. In excised, inside‐out patches which were voltage‐clamped in the physiological range of membrane potential, the single‐channel open probability (P0) was low (≈︁0.02), and increased to a maximum of 0.9 with applied pipette suction. Single‐channel conductance also increased with suction. The channels showed adaptation to applied suction and relaxed to a steady‐state activity about 20 seconds after application of suction. The P0 increased up to 0.9 with strong membrane depolarization (Vm = 0 to + 80 mV); however, there was little dependence of P0 on membrane potential in the physiological range. The kinetic data suggest that there is one conducting state and at least two non‐conducting states of the channel. The open‐time constant increased with suction but remained unchanged with membrane potential (Vm = −70 to + 60 mV). The mean closed‐time of the channel decreased with suction and membrane depolarization. These results demonstrate the presence of a non‐selective monovalent cation channel which may be involved in cell volume regulation in the goby urinary bladder. Additionally, this channel may function as an enhancer of Na+ influx and K+ efflux across the bladder cell as part of transepithelial ion transport if it is located in apical membrane.
The influence of denervation on grafted hindlimb regeneration of larval Xenopus laevis
Authors: Filoni Sergio , Bernardini Sergio , Cannata Stefano M.
Published: June 2005

The aim of the present research is to ascertain whether in larval Xenopus laevis nerve‐independence for the regeneration of early stage limbs and nerve‐dependence of late stage limbs observed in a previous work (Filoni and Paglialunga, '90) is related to extrinsic (systemic) factors or to intrinsic changes taking place in the limb cells themselves during development. In this paper the regenerative capacity of early and late stage hindlimbs under the same extrinsic conditions, insofar as both are grafted onto the denervated hindlimbs of host larvae at the same developmental stage, is studied. All the grafted limbs are amputated after the host larvae have reached stage 57–58 (according to Nieuwkoop and Faber, '56).

In experiment I, the grafted limb is amputated at stage 52, at the thigh level; in experiment II, the grafted limb is amputated at stage 54–55, at the tarsalia level; in experiment III the grafted limb is amputated at stage 57, at the tarsalia level. In all three experiments, together with the grafted limb, also the host limb is amputated at the tarsalia level.

The results show that while grafted limbs amputated at stages 52 and 54–55 regenerate in the absence of nerves, grafted limbs amputated at stage 57 cannot. The failure of late stage grafted limbs to regenerate cannot be explained in terms of an immune‐type inhibiting reaction since it has been observed also in denervated autografted limbs and in the host limbs.

Since all the grafted limbs are in the same environmental conditions, the results show that in larval Xenopus laevis nerve‐independence for regeneration of early stage limbs and nerve‐dependence of late stage limbs are not related to factors extrinsic to the limb but to intrinsic changes taking place in the limb cells themselves during development.
Region‐specific expression of scutate scale type beta keratins in the developing chick beak
Authors: Shames Rose B. , Knapp Loren W. , Carver Wayne E. , Sawyer Roger H.
Published: June 2005

This study shows that different patterns of scutate scale type beta keratins are accumulated in the three adjacent structures of the embryonic chick beak: periderm, egg tooth, and cornified beak. The cornified beak accumulates all of the beta keratins of scutate scale except pp2,3. The periderm, which is the outermost, multilayered covering of the whole embryonic beak, accumulates only beta keratins 2,3, and p2,3 of the scutate scale pattern. The egg tooth, which is the rounded elevation on the dorsal surface of the upper beak, and the embryonic claw accumulate greatly reduced levels of 2,3 and p2,3 compared to scutate scale. Like cornified beak, the claw does not accumulate pp2,3, but both tissues express a potentially new beta keratin, beta keratin 8. Neither the histidine rich “fast” proteins (HRPs), which are expressed in embryonic scutate scales and feathers, nor the avian cytokeratin associated proteins (cap‐1 and cap‐2), which are expressed in scutate and reticulate scales, are expressed in any of the embryonic beak structures or in the claw. The implications of these findings with regard to regulation of terminal differentiation of avian skin are discussed.
Morphological basis of “growling” in the king cobra, Ophiophagus hannah
Authors: Young Bruce A.
Published: June 2005

A bioacoustic analysis is conducted on the defensive sounds produced by 21 species of snakes. The “typical” snake hiss is described as having a broad‐frequency span (from roughly 3,000 to 13,000 Hertz) and a dominant frequency near 7,500 Hertz. The “growl” of the king cobra (Ophiophagus hannah) differs from the “typical” snake hiss in consisting solely of frequencies below 2,500 Hertz, with a dominant frequency near 600 Hertz. Structural analysis of the upper respiratory tract of O. hannah suggests that the “growl” is produced by tracheal diverticula functioning as low‐frequency resonating chambers. This hypothesis is supported in several ways. An acoustic analysis of a mechanical model of the trachea demonstrates the potential for these diverticula to produce resonance effects. A “growl” also occurs in the mangrove ratsnake (Gonyosoma oxycephalum), a species that also has tracheal diverticula. Flushing the respiratory tract of G. oxycephalum with helium produces a shift of over 1,000 Hertz in the “growl,” a shift that is indicative of a resonance effect.
Anaerobic glycolysis in the dental plate retractor muscles of the New Zealand hagfish Eptatretus cirrhatus during feeding
Authors: Baldwin J. , Davison W. , Forster M. E.
Published: June 2005

Hagfish lack jaws, and the teeth are carried on a cartilagenous dental plate associated with the large longitudinal and tubular retractor muscles. Previous studies had shown that the retractors had intracellular pH buffering capacities among the highest reported for vertebrate muscle, and as these animals indulge in bursts of feeding within the hypoxic body cavity of dead fish it was of interest to examine the role of anaerobic glycolysis in powering the dental plate retractor muscles. Both retractors of the New Zealand hagfish Eptatretus cirrhatus contain only large diameter white muscle fibres (X = 200μm), and show low capillary:fibre ratios relative to the red and pink fibres of the general body musculature. These white fibres are characterized by sparsely distributed small mitochondria with poorly developed inner membranes, low activities of enzymes unique to aerobic ATP production, and moderate activities of glycolytic enzymes. During bursts of continuous feeding for periods of from 1.5 to 6.45 min there was a linear increase in lactate concentration at rates of 19.6 and 17.4 μmol lactate min−1 g−1 wet wt muscle, respectively, for the longitudinal and tubular retractors, reaching a maximum of 132 μmol lactate g−1 wet wt muscle. While the glycolytic flux in the hagfish retractors during feeding may not reach levels encountered in white muscle of burst swimming tuna, the actual lactate concentrations achieved are among the highest ever reported for normal muscle work by unrestrained animals.
Chronology and morphology of temperature‐dependent sex determination
Authors: Wibbels Thane , Bull James J. , Crews David
Published: June 2005

Temperature sensitivity and gonadal differentiation were studied in a turtle, Trachemys scripta, with temperature‐dependent sex determination. Sex determination was sensitive to both the duration and magnitude of incubation temperature. Temperature exerted an “all or none” effect on the ovarian or testicular nature of most gonads, but affected the length of ovaries in a graded fashion. Collectively, the results indicate that sex determination is controlled by the quantitative effect of temperature during a period beginning prior to (histologically detectable) sexual differentiation and extending to a time when initial sex specific changes are evident in the gonads.
Homeoboxes in cnidarians
Authors: Schierwater Bernd , Murtha Michael , Dick Matthew , Ruddle Frank H. , Buss Leo W.
Published: June 2005

Homeoboxes have previously been documented from various phyla of triploblastic, coelomate and pseudocoelomate, animals. We report here the first homeoboxes from cnidarians, a phylum of diploblastic organisms thought to occupy a near‐basal position in metazoan phylogeny. We have sequenced three partial (77 bp) fragments of Antennapedia (Antp) class homeoboxes from the hydroids Hydractinia symbiolongicarpus and Eleutheria dichotoma. A pair of fragments, Cnox‐2‐Hs and Cnox‐2‐Ed, from the two species differ in nucleotide sequences but have identical derived amino acid sequences. A gene tree produced by parsimony analysis shows that these two fragments cluster within the Antp homeobox lineage. The third fragment, Cnox‐1, clusters as a sister group of the other Antp class homeoboxes.
Acid‐base balance and ion transfers in the spiny dogfish (Squalus acanthias) during hypercapnia: A role for ammonia excretion
Authors: Claiborne J. B. , Evans David H.
Published: June 2005

The effect of hypercapnia on the acid‐base balance and acid‐equivalent transfers has been measured in the dogfish Squalus acanthias. Previous reports on Squalus are not in agreement as to the role played by compensatory acid‐base transfers between the animal and the water during hypercapnia.

Cannulated animals were maintained in a closed circuit, seawater recirculation system. Plasma pH, Cco2 (from which Pco2 and [HCO3−] were calculated), and transfers of NH4+ and HCO3−‐equivalent ions between the fish and the water, were measured during 24 hours of hypercapnic exposure (Pco2: 8–10 torr) and a subsequent 8–24 hour normocapnic recovery period.

Respiratory acidosis resulted in a plasma pH depression, which was then almost completely compensated (within ˜ 0.1 pH unit) over 24 hours by a ˜ 20 mM increase in plasma [HCO3 ]. In contrast to previous studies on elasmobranch acid‐base regulation, hypercapnia induced a rapid 3 × increase in not only HCO3−‐equivalent uptake but also branchial ammonia (NH4+) excretion. These transfers combined for a net Δ H+ loss to the water of 5.5 mmol kg−1. During the normocapnic period, net Δ H+ was reversed to −6.9 mmol kg−1, nearly completely due to HCO3‐efflux.

Several lines of evidence point to the contribution of gill Na+/NH4+ exchange to the total ammonia excreted during hypercapnia, whereas NH3 diffusion predominates during the recovery period. Likewise, Cl−/HCO3− or Cl−/OH− exchange may enhance the uptake of HCO3− during hypercapnia.
Embryonic retinal ablation and post‐metamorphic optic nerve crush: Effects upon the pattern of regenerated retinotectal connections
Authors: Underwood Lauren Wunsh , Nelson Paula , Noelke Elizabeth , Ide Charles F.
Published: June 2005

We examined relationships between healing observed during embryonic Xenopus retinal and optic nerve regeneration and resultant visuotectal pattern formation. Dorsal (D) and nasoventral (NV) 1/3 sized eye fragments were surgically created in stage 32 Xenopus laevis embryos. Gross anatomical healing modes of these fragments were examined 2 days post‐surgery (stage 43). Healing was categorized according to the degree of cell movements observed. Animals were reared through metamorphosis and electrophysiologic mapping techniques were employed on those animals whose eyes regenerated. All D 1/3 fragments showed normal (non‐duplicated) projections to the tectum; most (80%) of the healing observed showed little cell movements (the remaining 20% showed substantial cell movements, yet failed to show duplicated projections). Most NV 1/3 fragments (73%) formed two mirror image projections to the contralateral midbrain optic tectum (pattern duplication). Most (88%) of the healing observed among these animals showed massive cell movements in the ventral retinal region (the remaining 12% showed moderate cell movements). The remaining NV 1/3 fragments (27%) showed moderate cell displacement and failed to show duplicated projections). These data are compatible with a cell‐movement:intercalary cell division hypothesis in which duplication is dependent upon specific positional confrontation and subsequent cell division.

In additional studies, in adult animals, the optic nerves of eyes with duplicated projections were crushed and allowed to regenerate for 1 year. Duplicated projections were restored, indicating that developmental and maturational factors are probably not responsible for duplicative pattern formation; rather, information intrinsic to the eye, possibly created during healing interactions and/or fiber ingrowth to the tectum, underlies duplicate innervation of the tectum.
Prolactin‐dependent seasonal changes in pelage: Role of the pineal gland and dopamine
Authors: Badura Lori L. , Goldman Bruce D.
Published: June 2005

The Siberian hamster displays seasonal changes in pelage that are dependent upon fluctuations in circulating prolactin levels. Pinealectomy prevented the decrease in serum prolactin and molt to the winter pelage displayed by castrated males housed under a short‐day photoperiod. A dopaminergic antagonist, pimozide, enhanced prolactin levels in both pinealectomized and shamoperated animals under both long and short photoperiods. In the short‐day animals, this effect of pimozide was associated with a prevention of the development of winter pelage. These results indicate that seasonal prolactin levels and related pelage changes are dependent upon the integrity of the pineal gland. However, basal prolactin levels under different photoperiod conditions appear to be only partly regulated by the actions of the dopaminergic system.
Eyestalk ablation in female crabs: Effects on egg characteristics
Authors: Lachaise Fabienne , Goudeau Marie , Carpentier Gilles , Saidi Bassima , Goudeau Henri
Published: June 2005

Eyestalk ablation in Crustacea eliminates the inhibitory hormonal effects exerted by the eyestalk neuroendocrine center on ovarian growth. Planning to use crab eggs throughout the year as a model for physiological cell research, we performed a preliminary study to examine the characteristics of eggs that originated from eyestalk‐ablated females. Here we discuss the data that deal with the characteristics of eggs at fertilization and during the first 40 h of embryonic development. We found that eyestalk ablation in female crabs did not modify the resumption of egg meiosis that is stimulated by sea water, nor did it affect the electrical and cortical responses of eggs to fertilization. We also found that eyestalk ablation in females did not result in any changes in the nature of the two major ecdysteroids that are usually found in crabs' eggs (ponasterone A and 20‐hydroxyecdysone) or in their respective precursors (25‐deoxyecdysone and ecdysone) in eggs tested from 0 to 40 h post‐spawning. The respective variations in the concentrations of the four ecdysteroids were the same during this period as in control eggs. However, eyestalk ablation in females induced a striking decrease in the concentration of ponasterone A (60%) in eggs 30 to 40 h post‐spawning. Furthermore, eyestalk ablation in females promoted an increase in the titer of ponasterone A in the ovaries of about 2‐ and 20‐fold, at egg‐laying and 40 hours afterwards. This difference is discussed in terms of possible perturbations in either the synthesis of ponasterone A at the ovarian level, or its metabolism in spawned eggs.
Autocrine and paracrine role of steroids during spermatogenesis: Studies in Squalus acanthias and Necturus maculosus
Authors: Callard Gloria V.
Published: June 2005

Due to a cystic mode of spermatogenesis and zonal testes, the spiny dogfish shark (Squalus acanthias) and salamander (Necturus maculosus) are advantageous for studying the relationship between steroidogenesis and germ cell development. Direct analysis of steroidogenic enzymes and steroid receptors in staged tissue samples, together with light and electron microscopic observation, suggests that androgens and estrogens produced by Sertoli cells or Leydig cells immediately before or after spermiation serve as intratesticular regulators of events specific to premeiotic stages of spermatogenesis. These correlative data are consistent with limited observations in mammalian testis and provide a conceptual framework for direct testing of functional interactions between spermatogenesis and steroidogenesis in future studies.
In vivo and in vitro evidence for the role of hormones in fish spermatogenesis
Authors: Cochran Roger C.
Published: June 2005

In an attempt to discern general mechanisms by which specific hormones control certain aspects of fish spermatogenesis, we focus on a single fish species (Fundulus heteroclitus), and, by analogy, generalize to other fishes. At least three androgenic steroids (testosterone, 11‐ketotestosterone, 11β‐hydroxytestosterone) are present in the serum of Fundulus heteroclitus, but only testosterone appears to be associated with spermatogenesis in vitro as well as in vivo. 11‐Ketotestosterone appears to be associated with spermiation in vivo, but has not yet been tested for its ability to cause spermiation in vitro. The preponderant androgen present in the serum, 11β‐hydroxytestosterone, does not appear to be directly associated with spermatogenic process either in vitro or in vivo.

In F. heteroclitus, in vivo studies indicate that at least two different gonadotropins are produced, on that primarily causes steroid production and a second that causes testicular growth. Indirect evidence suggests that production of these gonadotropins is seasonal in terms of both their amounts and their relative proportions.
Early innervation of abdominal swimmeret muscles in developing lobsters
Authors: Kirk Mark D. , Govind C. K.
Published: June 2005

The swimmerets in the abdomen of the lobster Homarus americanus are paired external appendages whose back and forth propulsive movements are brought about largely by a group of power and return stroke muscles located in the lateral abdominal cavity. We find functional innervation of these muscles by several excitatory axons and a single inhibitor in embryonic and stage 1 larval lobsters before the external appendages are even formed. This early innervation is via a few nerve bundles in which branches of the motor axons are intertwined in a complex manner. As the swimmerets develop to maturity in later larval and juvenile stages, the innervation consisting usually of several excitor and a single inhibitor synaptic terminals becomes localized to individual muscles. Patterned synaptic activity in these muscles was not seen in the embryonic and larval stages but has been shown in early juvenile stages, when it coincides with the onset of rhythmic movement of the swimmerets. Consequently, such early innervation of the swimmeret muscles may be influential in establishing the central circuitry for the generation of patterned activity, a possibility that was discounted in a previous study (Proc. Natl. Acad. Sci. USA, 70:954–958).
The role of hormones in the acquisition of sperm motility in salmonid fish
Authors: Miura Takeshi , Yamauchi Kohei , Takahashi Hiroya , Nagahama Yoshitaka
Published: June 2005

In salmonid fish, spermatozoa taken from the testes are immotile, but acquire motility during their passage through the sperm duct. Using male masu salmon (Oncorhynchus masou), we found that gonadotropin‐induced testicular production of 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17α,20β‐DP), the oocyte maturation‐inducing hormone of salmonid fish, is responsible for the acquisition of sperm motility. However, neither testosterone (T) nor 11‐ketotestosterone (11‐KT), the two major androgens in teleost fish, were effective. We also present evidence that 17α,20β‐DP action is mediated through an increase in sperm duct pH, which in turn increases the cAMP content of sperm allowing the acquisition of motility.
Sulfation is required for mobility of veliger larvae of Concholepas concholepas (Mollusca; Gastropoda; Muricidae)
Authors: Urrea Rodrigo , González Mauricio , Inestrosa Nibaldo C. , Brandan Enrique
Published: June 2005

The sulfation reaction seems to be a critical biochemical process during early steps of development. We have evaluated the effect of sulfation on the mobility of veliger larvae of the gastropod Concholepas concholepas. It was found that incubation of larvae in low‐sulfate artificial sea water had strong inhibitory effect on mobility. The use of sodium chlorate, a specific inhibitor of sulfation, also resulted in a strong inhibition of larval mobility. At the biochemical level, the synthesis of proteoglycans (PGs) and detergent‐soluble sulfoproteins and sulfolipids was specifically inhibited by chlorate, without affecting either total protein synthesis or phosphorylation. Intracellular levels of the sulfate donor 3′‐phosphoadenosine 5′‐phosphosulfate (PAPS) were decreased to 4% by chlorate treatment, indicating that this molecule is also involved in sulfation of marine invertebrates. Both effects of chlorate, the inhibition of sulfation and the larval mobility, were reversible. It is therefore concluded that sulfation is required for larval mobility in the mollusc C. concholepas. © 1992 Wiley‐Liss, Inc.
Cooling rate influences cryoprotectant distribution and organ dehydration in freezing wood frogs
Authors: Costanzo Jon P. , Lee Richard E. , Wright Michael F.
Published: June 2005

Ice formation in the freeze‐tolerant wood frog (Rana sylvatica) induces the production and distribution of the cryoprotectant, glucose. Concomitantly, organs undergo a beneficial dehydration which likely inhibits mechanical injury during freezing. Together, these physiological responses promote freezing survival when frogs are frozen under slow cooling regimes. Rapid cooling, however, is lethal. We tested the hypothesis that the injurious effects of rapid cooling stem from an inadequate distribution of glucose to tissues and an insufficient removal of water from tissues during freezing. Accordingly, we compared glucose and water contents of five organs (liver, heart, skeletal muscle, eye, brain) from wood frogs cooled slowly or rapidly during freezing to — 2.5°C. Glucose concentrations in organs from slowly cooled frogs were significantly elevated over unfrozen controls, but no significant increases occurred in rapidly cooled frogs. Organs from slowly cooled frogs contained significantly less water than did those from controls, whereas water contents from rapidly cooled frogs generally were unchanged. Rapid cooling therefore inhibited the production and distribution of cryoprotectant and organ dehydration during freezing. This inhibition may result from an accelerated, premature failure of the cardiovascular system. © 1992 Wiley‐Liss, Inc. © 1992 Wiley‐Liss, Inc.
The zona pellucida binds the mature form of an oviductal glycoprotein (oviductin)
Authors: St‐Jacques Sylvie , Malette Brigitte , Chevalier Simone , Roberts Kenneth D. , Bleau Gilles
Published: June 2005

The use of a monoclonal antibody (MAb) specific for the oviductal zona pellucida (ZP) of the hamster has demonstrated that a new antigen (oviductin) is acquired by the ZP during transit of the oocyte in the oviduct. The epitope that is recognized by the MAb bears a terminal N‐acetyl‐D‐galactosamine residue. We conducted a study in order to determine whether this immunoreactivity of the oviductal ZP results from the addition of the terminal sugar residue to a preformed ZP protein or from the transfer of the mature glycoprotein produced by oviductal secretory cells. We measured the incorporation of [35S]methionine into proteins using four different incubation systems: cumulus oophorus (CO) alone, CO in the presence of oviductal fluid, CO co‐incubated with empty oviducts, and CO within intact oviducts. At the end of the incubation period, the ZP, vitelli, dispersed cumulus without oocyte, oviducts, and culture medium were isolated and analyzed for their protein content by sodiumdodecylsulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), autoradiography, and immunodetection. The cumulus cells synthesized several proteins, independently of the oviductal environment; however, none of these proteins corresponded to oviductin. The ZP and the vitelli of cumulus oophorus that were incubated either alone or in the presence of oviductal fluid did not contain radioactive oviductin. When the oviduct (empty or intact) was present in the incubation system, radiolabeled oviductin was synthesized and secreted into the incubation medium. The ZP picked up a detectable amount of radioactive antigen only in the system in which intact oviducts were incubated. These results demonstrate that the entire molecule of oviductin (including its antigenic determinant) is produced by the oviduct and subsequently becomes associated with the ZP of the oocyte. © 1992 Wiley‐Liss, Inc.
Cervical kinematics during drinking in developing chickens
Authors: Heidweiller Jan , Van Der Leeuw Angelique H. J. , Zweers Dr. Gart A.
Published: June 2005

Development of head neck motion patterns is studied in drinking chickens to examine (1) general motion principles, (2) ontogenetic changes in these patterns, and (3) whether pattern changes are due to scaling effects during growth. Behavioral patterns are analyzed by high speed filming, radiography, and calculation of rotation patterns for each joint during all movement patterns.

Flexibility and variability are great, but representative kinematic patterns are selected for immersion, upstroke, and tip‐up phases. Five principles were found that control cervical motion. Two principles maximize rotation efficiency: the geometric and lever arm principles. Two trajectory compensating principles occur; one controls compensation for overflexion, and the other corrects curved into straight trajectories of head motion. One principle occurs that minimizes rotation force if large forces tend to develop in one joint. This principle results in a characteristic cervical motion pattern (“bike chain” pattern).

There are three developmental periods: (1) hatchlings (2) chickens 1 to 4 weeks old (1–4W), and (3) older than 4 weeks. Each period is characterized by different kinematic patterns. In 1–4W chicks, the rotation force is minimized. In older stages, the cervical joints rotate according to geometric and lever arm principles. The totally different motion pattern in hatchlings results from a different behavioral reaction to water and the influence of large centrifugal forces. Transitions in cervical motion patterns are connected to effects of scaling, primarily changes in head and body weights. Changes in motion patterns are not related to changes in anatomical characters such as flexion extremes and relative length of each vertebra since these are similar in all stages. © 1992 Wiley‐Liss, Inc.
Localization of β‐endorphin‐like immunoreactivity in the nervous system of the adult newt, Notophthalmus viridescens
Authors: Vethamany‐Globus Swani , Michener Gregory
Published: June 2005

Using indirect immunofluorescence methods, we have localized for the first time in the newt, Notophthalmus viridescens, β‐endorphin (β‐ep)‐like immunoreactivity in the neurons of spinal ganglia (SPG), spinal cord (SPC), as well as in the hypothalamic region of the brain. An examination of serially sectioned SPG showed that the β‐ep‐positive neurons, cell bodies, and nerve fibers were distributed at all levels of SPG. Peripheral regions of the perikarya of β‐ep‐positive SPG neurons exhibited intense staining for β‐ep, the central nuclear region remaining nonreactive. In SPC, brightly staining fibers were seen entering the afferent nociceptive input areas, namely the Lissauer's tracts, substantia gelatinosa, and the dorsal ascending columns. Dot‐fiber immunofluorescence pattern was observed throughout the gray matter of SPC representing β‐ep‐positive, secondary sensory neurons as well as interneurons. Also, discrete cluster of neurons located deep in the gray matter of SPC stained positively to β‐ep antisera. This study not only demonstrates for the first time the presence of β‐ep like material in the newt, more specifically in SPG and SPC, but also raises the question of a possible link between β‐ep and newt limb regeneration as previous work has shown that SPG support limb regeneration in a denervated‐amputated newt forelimb. © 1992 Wiley‐Liss, Inc.
Preloading of micromolar intracellular Ca2+ during capacitation of Sicyonia ingentis sperm, and the role of the pHi decrease during the acrosome reaction
Authors: Lindsay Leann L. , Clark Wallis H.
Published: June 2005

In studying the mechanism controlling the sperm acrosome reaction (AR) in the marine shrimp Sicyonia ingentis, intracellular Ca2+ and pH were measured using the fluorescent indicators Fura‐2 and Fluo‐3 for Ca2+, and SNARF‐1 for pH. Capacitated sperm possessed an apparent resting Ca2+ concentration of 1–2 μM which remained constant upon induction of the AR with egg water. Uncapacitated sperm had extremely low Ca2+ levels and did not respond to egg water. These results suggest that, while in other species the Ca2+ is elevated to micromolar levels during initiation of the AR, S. ingentis sperm are preloaded with Ca2+ during capacitation and the trigger for the AR is downstream of the Ca2+ increase. The notion that Ca2+ influx is not involved at the actual time of the AR in capacitated S. ingentis sperm is supported by the inability of Ca2+ ionophore A23187 to induce the AR and the ineffectiveness of Ca2+ channel antagonists to block egg water‐induced AR. Measurements of capacitated sperm pH showed a significant decrease during the first 10–15 min of the AR, which did not correlate temporally to either acrosomal exocytosis (at 5 min post‐induction) or filament formation (after 45 min). Inhibition of egg protease activity required for induction of filament formation did not inhibit the pH drop, indicating that intracellular acidification is not the final trigger for filament formation, although it may be required prior to action of the protease. © 1992 Wiley‐Liss, Inc.
Behavioral thermoregulation by hypoxic rats
Authors: Dupré R. Keith , Owen T. Lon
Published: June 2005

To address whether a shift in hypothalamic thermal setpoint might be a significant factor in induction of hypoxic hypothermia, behavioral thermoregulation was examined in 7 female Sprague‐Dawley rats implanted with radiotelethermometers for deep body temperature (Tb) measurement in a thermocline during normoxia (PO2 = 125 torr) and hypoxia (PO2 = 60 torr). Normoxic rats (TNox) selected a mean ambient temperature of 19.7 ± 1.4 (SE) °C and maintained Tb at 37.0 ± 0.2°C. Hypoxic rats selected a significantly higher ambient temperature (THox = 28.6 ± 2.2°C) but maintained Tb significantly lower at 35.5 ± 0.3°C. Without a thermal gradient (ambient temperature = 25°C), Tb during hypoxia was 35.4 ± 0.4°C. The maintenance of a lower body temperature during hypoxia through behavioral thermoregulation despite having warmer temperatures available supports the hypothesis that the thermoregulatory setpoint of hypoxic rats is shifted to promote thermoregulation at a lower Tb, effectively reducing oxygen demand when oxygen supply is limited. © 1992 Wiley‐Liss, Inc.
Ultimobranchial body and parathyroid glands of the freshwater snake Natrix piscator in response to vitamin D3 administration
Authors: Srivastav Ajai K. , Rani Ladli
Published: June 2005

Vitamin D3 (20 I.U./100 g body wt) was administered to the freshwater snake Natrix piscator for 15 days. Elevation of serum calcium and inorganic phosphate levels was observed after the treatment. The ultimobranchial body became active whereas the parathyroid glands exhibited reduced activity. © 1992 Wiley‐Liss, Inc.
Activation of Xenopus Laevis eggs in the absence of intracellular Ca activity by the protein phosphorylation inhibitor, 6‐dimethylaminopurine (6‐DMAP)
Authors: Zhang Shi Cui , Masui Yoshio
Published: June 2005

Xenopus laevis eggs pricked or microinjected with water or saline in medium containing a limited quantity of free Ca (1.0 to 2.0 μM) remain unactivated for at least 6 hr, even after transfer to oocyte medium containing Ca at higher concentrations (0.5–1.0 mM). These injected eggs, when later pricked in oocyte medium or exposed to A23187 or urethane are fully capable of activation. This confirms the observations of Wangh ('89). However, eggs injected in this Ca‐limited medium (CaLM) with 6‐DMAP as well as those simply exposed to this drug undergo changes characteristic of activation, including cortical contraction, cortical granule breakdown, a loss of MPF and CSF activities, and pronuclear formation. The time required for 6‐DMAP to induce egg activation is inversely correlated to its concentration. Interestingly, eggs that have been injected with EGTA, and thus are unable to respond to activation stimuli such as pricking and A23187 or urethane treatment, can also be activated by exposure to 6‐DMAP. In contrast, eggs exposed to or injected with a 6‐DMAP analogue (6‐aminopurine or puromycin) or a protein synthesis inhibitor (cycloheximide or emetine or puromycin) are not activated. As well, eggs injected in CaLM with 6‐DMAP simultaneously with a phosphatase inhibitor (NaF or ammonium molybdate) fail to become activated. Although 6‐DMAP‐activated eggs remain at the pronucleus stage so long as 6‐DMAP is present, they resume cell cycle activities after the drug is with‐drawn. They form cleavage furrows, disassemble pronuclear envelopes, and recondense chromosomes. Also, MPF activity reappears and cycles at least twice, peaking each time shortly before cleavage furrow formation. These results suggest that activation of Xenopus eggs arrested at metaphase II by inhibition of protein phosphorylation does not require intracellular Ca release and that maintenance of the egg at metaphase II depends upon continuous protein phosphorylation. © 1992 Wiley‐Liss, Inc.
Glycerol is a colligative antifreeze in some northern fishes
Authors: Raymond James A.
Published: June 2005

Many polar marine fishes produce macromolecular antifreezes that act in a non‐colligative way to prevent freezing. In this report, a new type of freezing avoidance is described in which the rainbow smelt, Osmerus mordax dentex, in addition to producing a macromolecular antifreeze, avoids freezing by increasing the osmolality of its body fluids. In smelt living in −2.0°C water, osmolality exceeded 1.0 M, making it among the highest found in bony fishes, and the only known case of a near isosmotic condition in a marine teleost. High osmolalities, but less extreme than those shown in the rainbow smelt, were found in another smelt species and two species of greenling. The high osmolalities in each species are largely due to glycerol, an osmolyte that has not previously been reported in fishes. Glycerol appears to be produced only at subzero temperatures, and in the rainbow smelt reaches its highest concentration, 0.4 M, at environmental temperatures near the freezing point of seawater. © 1992 Wiley‐Liss, Inc.
Synthesis and secretion of low molecular weight cuticular proteins during heat shock in the tobacco hornworm, Manduca sexta
Authors: Lohmann Catherine M. Fittinghoff , Riddiford Lynn M.
Published: June 2005

In the tobacco hornworm, Manduca sexta, heat shock normally elicits synthesis of the classic heat‐shock proteins. A 1‐hr heat shock of 42°C and above can also increase the relative synthesis of certain 12–18 kD proteins in the epidermis. These 12–18 kD proteins were identified as cuticular proteins for several reasons. Like cuticular proteins, they appear only in the epidermis. They can be precipitated from epidermal homogenates with an antiserum to larval cuticle. The same conditions that increased labeled 12–18 kD proteins in the epidermis also increased labeled 12–18 kD proteins in the cuticle. Some of the epidermal increase may result from a partial inhibition of secretion to the cuticle during 46°C heat shock, causing abnormal accumulation in the epidermis. However, slight increases also occur at lower temperatures, which do not inhibit secretion detectably. Preliminary results also indicate that total quantities of at least one cuticular protein mRNA may increase during heat shock, either because of increased transcription or increased mRNA stability. © 1992 Wiley‐Liss, Inc.
Physiological cost of pregnancy in a viviparous lizard (Sceloporus jarrovi)
Authors: Demarco Vincent , Guillette Louis J.
Published: June 2005

The V̇o2 (standard metabolic rate; cc · h−1) of pregnant Sceloporus jarrovi increases to a maximum near term. Immediately following parturition, V̇o2 decreases sharply. Approximately 93.6% of the V̇o2 of late pregnant S. jarrovi is due to litter and non‐reproductive female V̇o2. The difference between measures of the V̇o2 of late pregnant lizards and late pregnant V̇o2 estimated by summing litter and nonreproductive V̇o2 (6.4%) represents the physiological cost of maintaining a litter. This estimate of the physiological cost of pregnancy in S. jarrovi is similar to that reported for mammals; however, it is lower than other estimates of the cost of pregnancy in reptiles. Estimates of litter metabolism were obtained by measuring maximum embryo metabolism, using an in vitro technique and multiplying embryo V̇o2 by litter size. These results suggest that others have overestimated the physiological cost of pregnancy in reptiles because maximum litter V̇o2 has been underestimated. Others have suggested that viviparity is an expensive mode of reproduction because the physiological cost of supporting a litter is an important component of an individual's reproductive effort. Data presented here support the alternative hypotheses that the cost of supporting a litter is not high and constitutes a small fraction of the energy apportioned into reproduction. © 1992 Wiley‐Liss, Inc.
Modulation of meiotic arrest in mouse oocytes by guanyl nucleotides and modifiers of G‐proteins
Authors: Downs Stephen M. , Buccione Roberto , Eppig John J.
Published: June 2005

Guanyl nucleotide binding‐proteins, or G‐proteins, are ubiquitous molecules that are involved in cellular signal transduction mechanisms. Because a role has been established for cAMP in meiosis and G‐proteins participate in cAMP‐generating systems by stimulating or inhibiting adenylate cyclase, the present study was conducted to examine the possible involvement of G‐proteins in the resumption of meiotic maturation. Cumulus cell‐free mouse oocytes (denuded oocytes) were maintained in meiotic arrest in a transient and dose‐dependent manner when microinjected with the nonhydrolyzable GTP analog, GTPγS. This effect was specific for GTPγS, because GppNHp, GTP, and ATPγS were without effect. Three compounds, known to interact with G‐proteins, were tested for their ability to modulate meiotic maturation: pertussis toxin, cholera toxin, and aluminum fluoride (AlF4−). Pertussis toxin had little effect on maturation in either cumulus cell‐enclosed oocytes or denuded oocytes when meiotic arrest was maintained with dibutyryl cAMP (dbcAMP) or hypoxanthine. Cholera toxin stimulated germinal vesicle breakdown (GVB) in cumulus cell‐enclosed oocytes during long‐term culture, but its action was inhibitory in denuded oocytes. AlF4− stimulated GVB in both cumulus cell‐enclosed oocytes and denuded oocytes when meiotic arrest was maintained with hypoxanthine but was much less effective in dbcAMP‐arrested oocytes. In addition, AlF4− abrogated the inhibitory action of cholera toxin in denuded oocytes and also that of follicle‐stimulating hormone (FSH) in cumulus cell‐enclosed oocytes. Cholera toxin or FSH alone each stimulated the synthesis of cAMP in oocyte‐cumulus cell complexes, whereas pertussis toxin or AlF4− alone were without effect. Both cholera toxin and AlF4− augmented the stimulatory action of FSH on cAMP. These data suggest the involvement of guanyl nucleotides and G‐proteins in the regulation of GVB, although different G‐proteins and mediators may be involved at the oocyte and cumulus cell levels. Cholera toxin most likely acts by ADP ribosylation of the α subunit of Gs and increased generation of cAMP, whereas AlF4− appears to act by antagonizing a cAMP‐dependent step.
Extracellular and intracellular acid‐base regulation in crustaceans
Authors: Wheatly Michele G. , Henry Raymond P.
Published: June 2005

This article attempts to review mechanisms of intra‐ (ICF) and extracellular fluid (ECF) acid‐base balance and the contribution each makes to whole animal acid‐base homeostasis in an evolutionary progression of crustaceans (marine, freshwater, semi‐ and fully terrestrial). ICF pH (pHi) is regulated to preserve the functional integrity of enzymes involved in cell metabolism. The ECF is the intermediary between cellular acid/base production and whole animal exchange at the primary epithelia, the gills, and antennal gland. In vivo regulation of pHi is discussed under selected environmental conditions. Compensatory mechanisms include intracellular buffering and transmembrane exchange of acidic/base equivalents including primarily an Na + /H + /HCO3 −/Cl− mechanism and an Na + /H + exchanger. Acid‐base values and regulation in the ECF (which may be subcompartmented in selected tissues) differ in aquatic versus terrestrial species. The latter have higher PCO2 (and lower pH) associated with reduced ventilation due to the higher O2 capacitance of air. Correspondingly they can regulate ECF pH (pHe) by respiratory control of PCO2; terrestrial species also depend upon mobilization of exoskeletal CaCO3 to buffer protons. In aquatic species the primary mechanism of acid‐base regulation is via electroneutral ion exchangers (Na +/acidic equivalent; Cl −/basic equivalent) primarily at the branchial epithelium but also apparent in the renal tubule in species that produce dilute urine (hyperosmo/ionoregulators). Evidence is presented for dynamic regulation of unidirectional branchial and renal ion fluxes for purposes of acid‐base regulation. Quantitatively the antennal gland typically contributes only 10% of the overall response. Stoichiometrically, whole animal acidic/basic equivalents exchanged at these epithelia originate predominantly in the ICF compartment (50‐‐95%). Future perspectives emphasize the need to better understand how pH compensation or in some cases tolerance is related to cellular function. © 1992 Wiley‐Liss, Inc.