bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of the muscle and heart lactate dehydrogenases of the New Zealand hagfish, Eptatretus cirrhatus: Functional and evolutionary implications
Authors: Baldwin J. , Davison W. , Forster M. E.
Published: June 2005

Hagfish possess two lactate dehydrogenase (LDH) subunit types that combine to form only the two homotetramers LDHA4 and LDHB4. Similarities in the kinetic properties of these isozymes from Myxine glutinosa have been attributed to the anaerobic nature of the hagfish heart and the failure of LDHB4 to diverge in function since the ancient A‐B gene duplication. The LDHA4 and LDHB4 isozymes purified from the New Zealand hagfish Eptatretus cirrhatus display more divergent properties which are consistent with the more efficient oxygen delivery system and aerobic lifestyle of this species. This, together with recent reinterpretations of LDH subunit evolution, leads to the conclusion that the unusual properties of hagfish LDH isozymes can be attributed to metabolic adaptation rather than to the conservation of features present in the ancestral LDH of vertebrates.
Transferrin, alpha‐fetoprotein, and albumin in plasma of quail‐chick chimeras during embryonic development
Authors: Martin B. , Denoulet P.
Published: June 2005

Heterospecific chimeras obtained by blastoderm recombination between 36h quail embryos and chick yolk sacs were used as an in ovo model to determine the respective contribution of yolk sac and embryo in plasma protein during development. Analysis of quail and chick embryo plasma proteins by 2D‐PAGE and peptide mapping showed that it was possible to readily distinguish both albumin and transferrin from these two avian species. No distinction could be established between chick and quail alpha‐fetoprotein using these criteria. The presence of quail‐ and chick‐type albumin and transferrin was then assayed in chimera blood at two stages of embryonic development. We show that transferrin and albumin of both avian species are found at 7 and 12 days of incubation. This result obtained in ovo suggest that both yolk sac (chick) and embryo (quail) contribute, at least, to albumin and transferrin synthesis during development.
Regeneration of the foreleg tibia and tarsi of Ephippiger ephippiger (Orthoptera: Tettigoniidae)
Authors: Lakes Reinhard , Mücke Alfred
Published: June 2005

The regenerative power of Ephippiger ephippiger (Tettigoniidae) after the experimental removal at hatching of both tibia and tarsi of the foreleg was investigated. The lost leg parts were successively regenerated with increasing degrees of morphological differentiation. This process has an effect on the postembryonic development because, subsequently, the first larval stage is prolonged. In adults, the regenerated limb is one‐quarter of the length of normal tibia and tarsi together, but it often has the gross morphology of a normal leg. The pattern of innervation and the distribution of receptor is completely changed, and the complex tibial organ is not reformed. The tympanic nerve is missing, and the axons of the regenerated receptor cells form new nerves that join the leg nerve.

Physiological recordings of acoustic‐vibratory, ventral nerve cord neurons revealed the possibility of excitatory input from the contralateral, intact acoustic receptors. However, the magnitude of the response is not fully restored. Behavioral experiments showed that the operated animals are not able to compensate for the unilateral deprivation of sensory input and fail in localization of the conspecific song.
Mating‐induced release of granules by the endocrine dorsal body cells of the snail Helisoma duryi (Mollusca)
Authors: Saleuddin A. S. M. , Ashton Mary Lou , Khan Hamid R.
Published: June 2005

The hermaphrodite snail Helisoma duryi reproduces preferentially by cross‐fertilization. Virgin and castrated snails lay an insignificant number of egg masses. The fine structure of its endocrine dorsal bodies (DB), which regulate reproduction, has been studied in reproductively inactive virgin and castrated snails and in reproductively active mated snails, using tannic acid staining and autoradiography after injection of [3H]leucine. The DB cells of the mated snails appear synthetically active, containing scattered rough endoplasmic reticulum (RER) and probably smooth endoplasmic reticulum (SER), many Golgi complexes, and putative DB hormone‐containing granules. On the other hand, the DB cells of the virgin and castrated snails appear synthetically inactive, containing RER in circular stacks, few Golgi complexes, many lipid droplets, and scattered glycogen. Mitochondria appear slender in mated snails, whereas those in virgin and castrated snails appear large and spherical. With tannic acid treatment, the processes of the DB cells of mated snails exhibited more released granules than those of virgin and castrated snails. Many silver grains were seen on RER, Golgi complexes, and mitochondria in the autoradiographs of the DB cells of mated snails. It is suggested that the DB cells of the reproductively active snails are synthetically more active than those in virgin and castrated snails and that the DB cells may produce peptide hormone as well as a steroid hormone.
Daily variation in maternal and fetal weight gain in mice and hamsters
Authors: Davis Fred C.
Published: June 2005

Daily variation in maternal and fetal weight gain was measured in hamsters (Mesocricetus auratus) and in mice (Mus musculus, C57Bl) with free access to food or under restricted feeding schedules. Pregnant hamsters with free access to food and water were weighed twice a day and fetuses were collected twice a day from 10.5 to 14.5 days after fertilization. In three experiments, pregnant mice were given free access to food and water or were allowed food for 12 hours a day or for 6 hours a day. Pregnant mice were weighed twice a day and in the restricted feeding experiments, fetuses were collected every 6 hours from 12.0 to 14.5 days after fertilization. Pregnant mice and hamsters with free access to food showed a daily rhythm in weight gain with greater gain at night. There was no evidence of a daily rhythm in the weight gain of hamster fetuses. Mouse fetuses showed greater weight gain during two 6‐hour intervals each day, the second half of each night and the second half of each day. The 12‐hour variation was seen in both wet and dry fetal weight. A 24‐hour rhythm in fetal growth was previously described in rats (Barr: Teratology, 7:283–288, 1973). Results in rats and mice indicate that fetal growth is modulated on a daily basis. The different periodicity observed in rats and mice might be related to the different ages of the fetuses examined.
Pineal sensitivity to nighttime swimming stress changes during the active season in Richardson's ground squirrels (Spermophilus richardsonii)
Authors: Tannenbaum Michael G. , Reiter Russel J. , Hurlbut Edward C. , Vaughan Mary K. , Gonzalez‐Brito Aldo , Troiani Maureen E.
Published: June 2005

Melatonin synthesis in the pineal gland, which is primarily regulated by the environmental lighting regime, can also be influenced by other factors that elicit modifications in sympathetic tone. The objectives of this study were to determine if forced swimming alters the normal pattern of melatonin production in the pineal gland of the Richardson's ground squirrel (Spermophilus richardsonii). In early June, the squirrels were forced to swim for 10 min during the photophase or during the scotophase. In mid‐July squirrels swam only during the scotophase. Animals were sacrificed 15, 30, or 60 min after the onset of swimming. Activities of pineal N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) were assessed by radioenzyme assay, and pineal melatonin content was measured by radioimmunoassay. Daytime swimming elicited no major changes in enzyme activity or pineal melatonin. In June, swimming at night prevented the normal rises in NAT activity and pineal melatonin seen in nonswimming controls. In contrast, the pineals of squirrels that were tested 6 weeks later in mid‐July did not appear to be as sensitive to nighttime swimming, as there were only minor differences in both NAT activity and melatonin content compared to controls. These results demonstrate that forced nighttime swimming, unlike several other aversive stimuli, can evoke changes in the normal pattern of pineal melatonin production in this species. Furthermore, the pineal's response to such stimuli may not be stable over the course of the active season.
Molecular analyses of gene expression during sea star spermatogenesis
Authors: Boom J. D. G. , Smith M. J.
Published: June 2005

We have investigated actin gene expression during the annual spermatogenic cycle of Pisaster ochraceus by Northern blot analyses of testes RNAs pooled from defined spermatogenic stages. Specific probes for cytoplasmic (Cy) and muscle (M) actin gene products detect 2.3 and 2.1 kb transcripts, respectively. In addition, actin‐coding sequence probes detect a third, much larger (3.5 kb) transcript designated FAT. Preliminary sequence analyses of two cDNAs representing portions of the FAT transcript show over 90% homology to Pisaster Cy actin at the amino acid level but only 80% nucleotide identity.

The expression patterns of these three transcripts, plus two spermiogenic indicator transcripts (H3 histone and β‐tubulin), were determined over the cycle. The Cy transcript is seen at all stages but is ten‐ to 100‐fold higher early in the cycle when mitotic activity predominates. The M transcript appears at the onset of gonadal growth and is maintained at constant levels through spermatogenesis consistent with the expansion of the muscular sheath surrounding the testes. The FAT, H3 histone, and β‐tubulin transcripts reach their highest levels in ripe testes when spermiogenic activity is maximal. The homology of the FAT transcript to actin, and its pattern of expression, suggest the hypothesis that this transcript may encode acrosomal actin.
Anisotropic gas diffusion in the shell membranes of the hen's egg
Authors: Ar A. , Girard H.
Published: June 2005

The area‐specific diffusive conductances for oxygen and carbon dioxide of the isolated eggshell compound membrane (CSM), in perpendicular direction (the shortest way between hard shell and chorioallantois), on day 16 of incubation, are 3.38 and 2.00 mmol/(cm2·d·kPa), respectively. Calculated Krogh constants of the CSM for oxygen (K) in lateral (parallel to the shell) and perpendicular (to the shell) directions show marked anisotropy in diffusive properties. The lateral K is about 100 times the perpendicular K. Analysis shows that eggshell pore density is closely structured to match the diffusive properties of the CSM, ensuring a quasihomogenization of gas pressures in the CSM among adjacent pores. During incubation regional P (and P) changes within the CSM may occur as a result of covering relatively small fractions of eggshell. The CSM contributes little to the overall O2 transport resistance in the live egg.
Changes in the testicular binding of luteinizing hormone and plasma testosterone concentrations in the Djungarian hamster subjected to different photoperiods and temperatures and effects of long‐term testosterone treatment on the binding
Authors: Tsutsui Kazuyoshi , Kawashima Seiichiro , Masuda Atsuko , Oishi Tadashi
Published: June 2005

The effects of artificial photoperiod, temperature, and long‐term testosterone treatment on testicular luteinizing hormone (LH) binding were studied in adult male Djungarian hamsters. In hamsters transferred to long‐day (LD; 16 hr light, 8 hr dark) photoperiod 8 weeks after adaptation in short‐day (SD; 8 hr light, 16 hr dark) photoperiod of 25°C, testicular growth was associated with an increase in the total LH binding per two testes and a decrease in LH binding per unit testicular weight. Plasma testosterone levels reached a peak 47 days after transfer to LD and tended to decrease thereafter, while the testes continued growing. In contrast, when hamsters reared under LD conditions at 25°C for 12 weeks were transferred to SD, testicular regression was associated with a decrease in plasma testosterone and the total LH binding per two testes and an increase in LH binding per unit testicular weight. A significant decrease in LH binding per unit weight compared to SD controls was observed in those hamsters exposed to SD with continuous testosterone treatment. The testosterone treatment tended to induce decrease in the total LH binding. Scatchard plot analyses of the binding suggested that changes in LH binding were due to changes in the number of binding sites. When sexually mature male hamsters were subjected for 8 weeks to two different ambient temperatures (7°C and 25°C) and photoperiods (LD and SD), the difference between the two temperature groups was statistically not significant regarding the weights of testes, epididymides, and prostates; plasma testosterone levels; and LH binding in either LD or SD group. These results suggest that photoperiod is a more important environmental factor than temperature for the regulation of testicular activity and LH receptors and that testosterone reduces the number of LH receptors per unit testicular weight in adult male Djungarian hamsters.
Embryonic cellular organization: Differential restriction of fates as revealed by cell aggregates and lineage markers
Authors: Bernacki Susan H. , McClay David R.
Published: June 2005

Cleavage‐stage Lytechinus variegatus embryos were dissociated and the cells were aggregated in an experimental system designed to address questions of embryonic organizational capability. Using monoclonal antibodies against stage‐ and structure‐specific antigens, it was determined that germ‐layer specific molecules were expressed in the expected locations in aggregates and that the germ layers differentiated in the normal temporal sequence, but the dorsoventral axis of the embryo was not reestablished properly. In other experiments individual rhodamine‐labeled blastomeres were incorporated into unlabeled aggregates. Micromeres localized and differentiated normally. Mesomeres, however, which in normal embryos form only ectoderm, were found to change their specified fate and participate in gut formation.

The sequence of aggregate organization revealed other properties of the embryo. Ectodermal and endodermal epithelia formed via two temporally distinct epithelialization events. Ectoderm separated from a mass of interior cells at about 12 hrs, and endoderm compacted from the interior cells at about 20 hr. A lathrytic agent that prevents gut formation in normal embryos also prevented gut formation in aggregates; however, it did not affect formation of the ectoderm. Hence, formation of the triploblastic structure in aggregates appears to be dependent upon developmentally regulated, distinct cell adhesion events.
Vasculogenesis and angiogenesis: Two distinct morphogenetic mechanisms establish embryonic vascular pattern
Authors: Poole Thomas J. , Coffin J. Douglas
Published: June 2005

We are using a monoclonal antibody, QH‐1, as a label for angioblasts in quail embryos to study vascular development. Our previous experiments showed that major embryonic blood vessels, such as the dorsal aortae and posterior cardinal veins, develop from angioblasts of mesodermal origin that appear in the body of the embryo proper (Coffin and Poole: Development, 102:735–748, '88). We theorized that there are two separate processes for blood vessel development that occur in quail embryos. One mechanism termed “vasculogenesis” forms blood vessels in place by the aggregation of angioblasts into a cord. The other mechanism, termed “angiogenesis,” is the formation of new vessels by sprouting of capillaries from existing vessels. Here we report the results of microsurgical transplantation experiments designed to determine the extent of cell migration taking place during blood vessel formation. Comparison of the chimeras to normal embryos suggests that the vascular pattern develops, in part, from the normally restricted points of entry of angioblasts into the head from the ventral and dorsal aortae. Transplantations of quail mesoderm (1–15 somite stage) into the head of 5–15 somite chick hosts resulted in extensive sprouting and in migration of single and small groups of angioblasts away from the graft sites. Transplantations into the trunk resulted in incorporation of the graft into the normal vascular pattern of the host. Lateral plate mesoderm was incorporated into the dorsal aortae and individual sprouts grew between somites and along the neural tube to contribute to the intersomitic and vertebral arteries, respectively.
Mullerian‐duct regression in the American alligator (Alligator mississippiensis): Its morphology and testicular induction
Authors: Austin Harriet B.
Published: June 2005

In most vertebrates, the mullerian ducts differentiate into the oviducts or uterus in the female but regress in the male. Regression is caused by a testicular glycoprotein, mullerian‐inhibiting substance (MIS), in mammals and birds. However, neither the morphology nor the cause of regression has been characterized in ectothermic vertebrates. In the present study, both these topics were addressed in the American alligator. To examine the morphology of regression, males were sampled shortly before and after hatching, and the mullerian ducts and gonads were removed for histological examination. In addition, female hatchlings were castrated and implanted with testicular grafts from male hatchlings to determine if the substance responsible for regression in this species is produced by the testes. Control females were implanted with grafts of muscle tissue. The morphology of mullerian‐duct regression in male alligators is similar to that in mammals and birds. A characteristic “epithelial cuff” forms, followed by a loss of the basement membrane and the eventual loss of both epithelial and stromal cells. The testicular grafts caused a significant reduction in the size of the mullerian duct as well as the appearance of an epithelial cuff consistent with normal mullerian‐duct regression. Therefore, the mullerian‐duct regressor in the American alligator is probably produced by the testes as it is in mammals and birds.
Absence of extrahepatic lipid oxidation in a freshwater elasmobranch, the dwarf stingray Potamotrygon magdalenae: Evidence from enzyme activities
Authors: Singer Thomas D. , Ballantyne James S.
Published: June 2005

Measurements of key enzymes in several metabolic pathways in five tissues were undertaken in a freshwater elasmobranch, the dwarf stingray Potamotrygon magdalenae, with special emphasis on enzymes of lipid and ketone body oxidation. The metabolic organization of this freshwater elasmobranch resembles that of the marine elasmobranchs studied to date with some slight differences noted. As has been observed in marine elasmobranchs, lipid oxidation occurs largely in the liver. Other tissues, especially heart, may rely on the oxidation of other substrates, in particular amino acids. Amino acids appear to be very important metabolites for both oxidative and gluconeogenic tissues perhaps because of a reduced requirement for urea synthesis. Ketone bodies, especially beta‐hydroxybutyrate, although less important in the freshwater elasmobranch than in marine forms, can be used by both marine and freshwater elasmobranchs, and this distinguishes them metabolically from all teleosts examined to date.
Greatly elevated and sustained secretion of oxytocin by bovine granulosa cells in serum‐free culture
Authors: Luck M. R.
Published: June 2005

Bovine granulosa cells were cultured in collagen (Vitrogen 100)‐pretreated wells using defined medium to study the secretion of oxytocin and progesterone under serum‐free conditions. Secretion of oxytocin began spontaneously after the first day and was maintained at a high level during a 1 week culture period. Addition of serum to the medium reduced oxytocin concentrations by up to 90%. There were positive exponential relationships between oxytocin and progesterone concentrations and the inoculated cell density (range, 1.67 to 23.4 × 105 cells/ml/well). The results indicate that neither serum nor gonadotrophins are required for in vitro differentiation of bovine granulosa cells and that addition of serum may attenuate subsequent hormone secretion. This culture system should provide a better in vitro model for the study of ovarian oxytocin secretion than those previously described.
Dolichol phosphorylation occurs via a CTP‐dependent reaction in Artemia larvae
Authors: Horst Michael N.
Published: June 2005

The phosphorylation of dolichol in larval stages of the brine shrimp, Artemia salina, has been investigated. The dolichol kinase has been assayed in crude microsomes; the enzyme requires CTP as phosphoryl donor and calcium as divalent cation. Activity increases with both incubation time and added microsomal protein. The product of the reaction has been characterized by chromatographic and enzymatic procedures. With gamma‐32P CTP as substrate, the apparent Km for CTP is 24 μM. Enzymatic activity is stimulated fivefold by exogenous dolichol. The specific activity of the enzyme increases with the frequency of molting. Dolichol kinase activity was detectable in membranes prepared from dormant Artemia cysts. The low level in dormancy may anticipate the critical role of the enzyme during hatching.
Hyolingual feeding systems of the Plethodontidae: Comparative kinematics of prey capture by salamanders with free and attached tongues
Authors: Larsen John H. , Beneski John T. , Wake David B.
Published: June 2005

High‐speed cinematography (500 fps) was used to analyze quantitatively the kinematics of terrestrial prey capture in Bolitoglossa occidentalis, B. mexicana, Ensatina esch‐scholtzii, Plethodon glutinosus, Desmognathus quadramaculatus, Hynobius kimurae, and H. nebulosus. The gape cycle of these salamanders is highly stereotyped. In B. occidentalis the mouth is opened by a combination of cranial elevation and mandibular depression. The gape increases dramatically during tongue retraction, thus allowing the prey to be delivered to the rear of the oral cavity without being impeded by the marginal teeth. The absence of a feeding function for these teeth apparently has resulted in their reduction and/or morphological alteration in some bolitoglos‐sines. Observed differences in jaw rotation between successful and unsuccessful prey capture attempts appear to be biomechanical phenomena and not adjustments by the salamander in response to neural feedback.

Tongue projection is most rapid and highly accurate in the two bolitoglossines and Ensatina. The distance to which the tongue can be protracted from the mouth is 7% snout‐vent length in D. quadramaculatus, P. glutinosus, H. kimurae, and H. nebulosus (attached protrusible tongue); 15% in E. eschscholtzii (attached projectile tongue); and 30% in B. occidentalis (free projectile tongue). Even though tongue protraction is significantly faster in salamanders with projectile tongues than those with protrusible tongues, the range of times for the entire gape cycle is generally similar for all salamanders (ca. 100 ms). However, less derived salamanders spend a shorter period preparing the tongue for firing and more time in its projection than E. eschscholtzii and B. occidentalis. One obvious advantage for increasing the speed of tongue protraction is that it decreases the prey's available escape time. In the supergenus Bolitoglossa prey are limited to small, active invertebrates by a combination of stereotyped feeding behavior, a small tongue pad, and a lightweight hyolingual apparatus that is projected extremely fast.

While all terrestrial salamanders possess the same basic feeding system, the bolitoglossines have evolved an impressive array of unique specializations for capturing small, rapidly moving prey. This suite of characters has enabled the tribe to radiate rapidly into a vast variety of microhabitats.
Oxygen‐binding properties of cephalopod blood with special reference to environmental temperatures and ecological distribution
Authors: Brix O. , Bårdgard A. , Cau A. , Colosimo A. , Condò S. G. , Giardina B.
Published: June 2005

The oxygen‐binding properties of the blood of the cephalopods Todarodes sagittatus, Loligo vulgaris, Architeuthis monachus, and Octopus vulgaris were studied in relation to temperature and pH. The data obtained at pH 7.4 were compared with previously reported data on nine species of cephalopod over the actual range of temperatures at which the animals live in an attempt to define the role of temperature as an effector in the process, and to demonstrate the extent to which temperature influences the ecological range of the various species.

For most cephalopods we found Bohr and Haldane factors of lower than −1.0, a result that implies that the Bohr shift does not facilitate the unloading of O2, but may improve the loading of O2 with increased ventilation. The functional significance of the Bohr and Haldane effects appears, thus, to involve stabilization of pH by the isohydric transport of CO2.

Our results further demonstrated a significant decrease in oxygen affinity with temperature for all cephalopods studied. This relationship was more pronounced for the cephalopods from colder waters than for those from the tropics. Furthermore, a significant increase in cooperativity with decreasing affinity for oxygen was found when we compared these oxygen‐binding parameters at pH 7.4 and at the temperatures of the natural habitats of the various cephalopods. The respective relationships between the Hill coefficient (n50) and the oxygen tension at half‐saturation (P50) allowed us to separate the cephalopods into three distinct groups: 1) the Sepia species; 2) all the squids except Architeuthis; and 3) all the Octopus species, plus Architeuthis and Nautilus, this third group being the most sluggish group examined. Furthermore, the most sluggish species, those in group 3, have the highest reported functional buffer capacities, 7–19 mM CO2 · pH−1 · mM O2−1, while the more active species have functional buffer capacities in the range of 4–7 mM CO2 · pH−1 · mM O2−1. The relationship between P50 and n50 optimizes the utilization of O2 over the entire range of P50 reported.
Effects of magnetic resonance imaging (MRI) on the formation of mouse dentin and bone
Authors: Kwong‐Hing A. , Sandhu H. S. , Prato F. S. , Frappier J. R. H. , Kavaliers M.
Published: June 2005

The effects of magnetic resonance imaging (MRI) on dentin and bone formation in mice were examined using standard autoradiographic and liquid scintillation procedures. It was observed that exposure to a standard 23.2 min clinical multislice MRI (0.15T) procedure caused a significant increase in the synthesis of the collagenous matrix of dentin in the incisors of mice. There were no significant effects on alveolar and tibial bone matrix synthesis. These results suggest that the magnetic fields associated with MRI can affect the activity of cells and/or tissues that are involved in rapid synthetic activity.
Acquisition of endogenous ecotropic MuLV can occur before the late one‐cell stage in the genital tract of SWR/J‐RF/J hybrid females
Authors: Richoux Véronique , Panthier Jean‐Jacques , Salmon Anne‐Marie , Condamine Hubert
Published: June 2005

Endogenous ecotropic MuLV proviral loci are acquired by the progeny of some [SWR/J × (SWR/J × RJ/J)F1] N2 hybrid females obtained by two successive backcrosses of RF/J mice onto the SWR/J background. This results most likely from an infection of early embryos or oocytes by MuLV particles originating from maternal tissues. However, the time and site of infection are not yet known. Using oviductal transfers of embryos at the one‐cell stage, we show here that three of 88 N3 embryos from [SWR/J × (SWR/J × RF/J)F1] N2 hybrid females transferred to virus‐free foster mothers harbored new proviral integrations, whereas none of 61 SWR/J embryos transferred to [SWR/J × (SWR/J × RF/J)F1] N2 hybrid females had acquired any proviruses. These data support the infection of oocyte and/or early one‐cell embryo as the initial event leading to new proviral insertions.
Synthetic neuropeptide antagonists stimulate in vitro thyrotropin and growth hormone secretion by hatchling turtle pituitaries
Authors: Denver Robert J. , Licht Paul
Published: June 2005

The effects of synthetic antagonists to mammalian vasoactive intestinal polypeptide (VIP), corticotropin‐releasing hormone (CRH), and growth hormone‐releasing hormone (GHRH) on in vitro thyrotropin (TSH) and growth hormone (GH) secretion by pituitaries of hatchling slider turtles (Pseudemys scripta elegans) were investigated in hopes of understanding the mechanism(s) of action of the native neuropeptides. Pituitary glands were incubated individually in wells, and the culture medium was changed every 2 hr. After determination of basal secretion rates for one 2 hr period, glands were incubated in medium with or without VIP antagonist (100 or 500 nM) for 2 hr followed by two 2 hr periods with antagonist plus 2.5 nM VIP. VIP alone had no effect on TSH or GH secretion at this dose; however, both TSH and GH secretion were significantly elevated by the high dose of the VIP antagonist plus VIP (2.9‐fold). In another experiment, glands were exposed to 2.5 μg/ml (500–750 nM) antagonists to VIP, CRH, or GHRH for four 2 hr incubation periods. The GHRH and VIP antagonists stimulated significant increases in TSH secretion above basal release, whereas the CRH antagonist produced a significant stimulation of TSH but not GH release, an observation that is consistent with our earlier report for other CRH‐like peptides (Denver and Licht: J. Exp. Zool., 251:306–315, '89a). Maximum stimulation by the antagonists (3.5‐ to 5‐fold) was comparable to maximum stimulation by the native neuropeptides at doses ranging from 25 to 250 nM. These results demonstrate that synthetic peptides that can act as antagonists of neuropeptide actions in mammalian systems have agonistic effects on in vitro TSH and GH secretion by turtle pituitaries. These observations also lend support to the hypothesis that neuropeptide control of the ectotherm pituitary is generally less specific than in mammals.
Calcium requirement and increased association with bovine sperm during capacitation by heparin
Authors: Handrow R. R. , First N. L. , Parrish J. J.
Published: June 2005

The requirement for external Ca+2 during capacitation of ejaculated bovine sperm with heparin and changes in sperm‐associated 45Ca+2 during capacitation were investigated in vitro. Sperm capacitation was evaluated by ability to undergo an acrosome reaction (AR) upon exposure to lysophosphatidylcholine. The percentage of sperm which were capacitated during a 4 h incubation with heparin increased exponentially with increased exposure time to 2 mM Ca+2. When sperm were incubated with or without heparin in the presence of 45CaCl2, there was no difference in the amount of 45Ca+2 associated with sperm initially or at 1 h of incubation. Incubation with heparin resulted in a greater amount of sperm‐associated 45Ca+2 at 2, 3, and 4 h as compared to sperm incubated without heparin. The amount of 45Ca+2 associated with sperm during capacitation was unaffected by washing with 2 mM EGTA‐5 mM LaCl3. Glucose (5 mM) inhibited the effects of heparin on sperm‐associated 45Ca+2 and on capacitation. The inhibitory effects of glucose could be overridden by 8‐bromo‐cAMP. The results suggest that the requirement for external Ca+2 during capacitation with heparin may be related to an increased association of external Ca+2 with sperm.
Early events in peptide‐stimulated ecdysteroid secretion by the prothoracic glands of Manduca sexta
Authors: Smith Wendy A. , Gilbert Lawrence I.
Published: June 2005

The prothoracic glands of the tobacco hornworm, Manduca sexta, have been an advantageous model for investigating the cellular mechanisms underlying hormone‐stimulated ecdysteroid secretion in insects. The cerebral neuropeptide prothoracicotropic hormone (PTTH) is currently thought to activate the prothoracic glands via a calcium‐dependent increase in cAMP synthesis, activation of cAMP‐dependent protein kinase, and protein phosphorylation (Gilbert et al.: Bioessays, 8:153–158, '88). The present paper discusses current research regarding early changes in cell function elicited by PTTH, with emphasis on the regulation of cAMP synthesis and degradation and the involvement of translational events in PTTH action.
Gonadotropin‐induced luminal formation in the seminiferous tubules and efferent ductules in young frogs: Light and electron microscopic study
Authors: Kobayashi Tohru , Iwasawa Hisaaki
Published: June 2005

To clarify the mechanism of fluid secretion in the testes at the time of gonadotropin‐induced spermiation, young Rana nigromaculata were used. As a morphological index of fluid secretion, luminal formation of the seminiferous tubules, and efferent ductules were observed. The following changes were seen by the administration of hCG or frog pituitary: first, the luminal formation of the seminiferous tubules was seen; next, tubular expansion became evident, and finally, luminal formation and expansion were observed in the efferent ductules. These changes were preceded by the separation of cell contact among Sertoli cells and of cell contact between Sertoli cells and the cells of efferent ductules only in the center and the swelling of Sertoli cells and cells of efferent ductules. With regard to the flow of fluid at the time of spermiation, the present results indicate the possibility that there is a difference in the ability for fluid secretion between Sertoli cells and the ductule cells.
Innervation of the lobster limb rotator muscle: Physiology and fine structure
Authors: Wiens T. J. , Govind C. K.
Published: June 2005

The rotator muscle in the walking legs of the lobster Homarus americanus is innervated by two axons, an excitor and an inhibitor. The identities of each of these axons and their neuromuscular synaptic properties were determined by electrophysiological methods, and quantitative data on the fine structure of their synaptic terminals was obtained via serial thin‐section electron microscopy. The inhibitory axon to the rotator muscle was shown by simultaneous recordings from various pairs of muscles during axonal stimulation to be the common inhibitor (CI), shared in particular but not exclusively with the flexor muscle and the stretcher muscle. Only the stretcher muscle receives additionally the specific stretcher inhibitor (SI) axon. The rotator muscle appeared electrophysiologically homogeneous and CI exerted a moderate effect on all its fibers, as reflected in membrane hyperpolarization and in the accelerated decay and reduced summation of excitatory junctional potentials. Inhibitory neuromuscular terminals, recognizable in electron micrographs by their ellipsoid‐shaped synaptic vesicles, were fewer in number but had larger synapses than their excitatory counterparts. These synapses supported several active zones. The excitatory axon to the rotator muscle was found to be a specific one of the four excitors of the flexor muscle. Excitatory junctional potentials were also found to be uniform throughout the muscle, being very small initially but facilitating significantly. Excitatory neuromuscular terminals were recognizable by their spherical vesicles, and their smaller synapses supported only one or two active zones. Although excitatory and inhibitory terminals were co‐localized, intimate synaptic contact between them was not seen, supporting the indirect electrophysiological evidence of the absence of presynaptic inhibition.
Disconnected corpora allata provide a novel assay for allatostimulating factors
Authors: Couillaud Franck , Girardie Adrien
Published: June 2005

In the African locust, corpora allata deprived of brain neural connection exhibit a very low and reproducible rate of juvenile hormone (JH) biosynthesis. They were used to develop a novel in vitro assay for allatostimulating factors. A methanol brain extract stimulated the JH production of disconnected corpora allata by a factor of 20‐ to 30‐fold. Brain extract stimulation was dose‐dependent from 0.5 to 1 brain equivalent and maximum from 1 to 4. A slight allatostimulating activity was also found when using a methanol extract of the corpora cardiaca or of the corpora allata.
Influence of the tail graft on axial polarity in planarian regeneration
Authors: Kurabuchi Shingo , Kishida Yoshikazu
Published: June 2005

The freshwater planarian Dugesia japonica was used to examine the influence on the axial polarity of a tail piece transplanted into the following three regions: in experiment I posterior to the head; in experiment II just anterior to the pharynx; and in experiment III in the postpharyngeal region. The hosts were transversely amputated at a level 0.5 mm posterior to the grafted site at various times after transplantation. After this procedure, the regenerating blastemas from the posterior cut ends of the hosts were examined to determine if they were the head or the tail. The regeneration of the head occurred as a result of the reversal of the original anteroposterior polarity of the planarian body.

In experiment I, when the hosts were amputated immediately after transplantation, a head regenerated in about 50% of the cases. The longer the time after amputation, the higher the rate of head regeneration, and the reversal of polarity was completed within 7 days or more after transplantation. In experiment II, the rate of head regeneration was lower than that in the first experiment at every time point after posterior amputation. In experiment III, a reversal of polarity was also observed, but the rate of head regeneration gradually decreased after the 4th day from the time of amputation, and the tail completed its regeneration on the 10th day in all cases. Based on these results, a discussion is presented on the role of the tail in axial polarity during its regeneration.
Explanation for naturally occurring supernumerary limbs in amphibians
Authors: Sessions Stanley K. , Ruth Stephen B.
Published: June 2005

The occasional occurrence of high frequencies of limb abnormalities, including extra limbs, in natural populations of amphibians has long been a puzzle. In this paper we report the discovery of a population in which such limb abnormalities appear to be caused by a parasitic flatworm (trematode) that uses amphibians as intermediate hosts. The cercarial larval stage of the trematode attacks amphibians, penetrating the skin to form cysts (metacercariae). The cysts are preferentially localized in the cloacal region, including the developing hind limb regions in larvae of both frogs (Hyla regilla) and salamanders (Ambystoma macrodactylum). A wide range of limb abnormalities are seen, including duplicated limb structures ranging from extra digits to several extra whole limbs. We hypothesize that these limb abnormalities result from localized regulatory responses of developing and regenerating limb tissues to mechanical disruption caused by the trematode cysts. We have tested this idea by implanting inert resin beads into developing limb buds of frogs and salamanders. Since this treatment can cause supernumerary limb structures, our hypothesis is sufficient to explain the naturally occurring extra limbs.
In vitro effect of osmotic pressure and cortisol on prolactin cell physiology in the coho salmon (Oncorhynchus kisutch) during the parr‐smolt transformation
Authors: Kelley Kevin M. , Nishioka Richard S. , Bern Howard A.
Published: June 2005

The pituitary of the coho salmon (Oncorhynchus kisutch) was studied during the parr‐smolt transformation. Changes in pituitary prolactin (PRL) synthetic rate and influences of osmotic pressure (OP) and cortisol on PRL cell activity were investigated in vitro. After 20‐hr incubations in the presence of 35S‐methionine, tissue and medium were separated and subjected to SDS‐polyacrylamide gel electrophoresis; bands stained with Coomassie Blue R‐250 (= total PRL) and bands on X‐ray film resulting from autoradiography of the gels (= newly synthesized PRL) were quantified by soft laser densitometry. Physiological changes in medium OP exerted no detectable effect on the % release of total or newly synthesized PRL (35S‐PRL), whereas some differences, mostly in the % release of 35S‐PRL, were detected when extraphysiological medium OPs were used. Since OP effects on GH release are similar, these results suggest that OP has no specific direct effect on PRL release under physiological conditions. PRL synthetic rate during the parr‐smolt transformation increased beginning in mid‐February and peaked in mid‐March, but fell to undetectable levels in mid‐April; a second peak in PRL synthesis was observed in mid‐May. These data are in accord with reports on plasma levels of PRL, which further indicate that cortisol levels increase during the April decline in PRL levels. Our in vitro studies demonstrate that cortisol inhibits pituitary PRL synthesis and content in a dose‐related manner and also inhibits the % release of total and 35S‐PRL, suggesting that cortisol may be an important regulator of PRL cell activity during the parr‐smolt transformation.
Trypsin‐like hatching protease from mouse embryos: Evidence for the presence in culture medium and its enzymatic properties
Authors: Sawada Hitoshi , Yamazaki Kimie , Hoshi Motonori
Published: June 2005

Enzymatic properties of a protease involved in hatching of mouse embryos were examined. A trypsin‐like protease, which most efficiently hydrolyzed t‐butoxycarbonyl‐Leu‐Ser‐Thr‐Arg‐4‐methylcoumaryl‐7‐amide, was demonstrated in culture medium of mouse hatching embryos. The enzyme was strongly inhibited by diisopropyl fluorophosphate, phenylmethanesulfonyl fluoride, leupeptin, antipain, Nα‐tosyl‐l‐lysyl‐chloromethane, soybean trypsin inhibitor, and Trasylol, but not or weakly inhibited by p‐chloromercuribenzoic acid, EDTA, E‐64, pepstain, chymostatin, and bestatin, suggesting a trypsin‐like serine proteinase. The protease activity in the medium gradually elevated during the course of hatching, whereas the embryo‐associated activity showed no significant change. Furthermore, pyroglutamyl‐Leu‐argininal, the strongest inhibitor for the enzyme among peptidyl argininals, all of which are potent trypsin inhibitors, showed the strongest inhibition toward hatching. Thus, a trypsin‐like protease secreted from hatching embryos into the culture medium may participate in mouse hatching, probably as a hatching enzyme.
Activation of taurine efflux in hypotonically stressed elasmobranch cells: Inhibition by stilbene disulfonates
Authors: Goldstein Leon , Brill Susan R. , Freund Ellen V.
Published: June 2005

Hypotonic stress activates taurine efflux from elasmobranch cells. The transport mechanism involved in this efflux is not known. In this study we show that the hypotonic‐activated taurine efflux from skate (Raja erinacea) erythrocytes and dogfish (Squalus acanthias) rectal gland tubules is inhibited by stilbene disulfonates. These results suggest that the anion transporter (Band‐3) is involved in the efflux activation mechanism.
Temperature‐adaptive differences between the M4 lactate dehydrogenases of stenothermal and eurythermal sciaenid fishes
Authors: Coppes Zulema L. , Somero George N.
Published: June 2005

The effects of temperature on the apparent Michaelis‐Menten constant (Km) of pyruvate were determined for M4‐lactate dehydrogenases (LDHs) of 15 species of the teleost family Sciaenidae from habitats differing in average temperature and temperature range. The central question addressed was whether adaptive difference in the effect of temperature on an important kinetic parameter, Km, reflect selection based on the range of temperatures experienced by the species, the highest temperature encountered by the species, or both of these factors.

For the M4‐LDHs of all 15 species, the Km of pyruvate was conserved between 0.1 and 0.4 mM pyruvate over the species' physiological temperature range. However, large increases in Km of pyruvate commonly were found at temperatures a few degrees C above the species' upper habitat temperature. Distinctions were found between the responses of the enzymes of eurythermal and stenothermal sciaenids. For the most eurythermal species, e.g., Sciaenops ocellatus, Micropogonias undulatus, and Roncador stearnsii, Km of pyruvate varied only about twofold between 10 and 30°C, the temperatures which encompass most of the habitat ranges of these species. For the most stenothermal species, e.g., Cynoscion striatus and Micropogonias furnieri, with habitat temperature ranges of 14–18°C, sharp increases in Km occurred at temperatures above 20°C. We hypothesize that thermal stability of Km values is more strongly selected by maximal habitat temperature than by the amount of variation in habitat temperature, and that adaptation to high temperatures may pre‐adapt enzymes for eurythermal function.
Extraction of vanadium‐binding substance (vanadobin) from a subpopulation of signet ring cells newly identified as vanadocytes in ascidians
Authors: Michibata Hitoshi , Uyama Taro
Published: June 2005

We have previously extracted vanadobin, a substance binding vanadium ions in ascidian blood cells. The present study examined which of several types of blood cell contains this substance, using a combination of cell fractionation, chromatographies, and neutron activation analysis. The vanadium‐containing blood cell type, so‐called vanadocyte, is the signet ring cell in Ascidia sydneiensis samea as well as A. ahodori, and vanadobin was extracted from a homogenate of signet ring cells, but not from morula cells, although the latter have previously been considered to be the vanadocytes.
Ontogenetic changes in proteins and isozyme expression in larval and juvenile bonefish (Albula)
Authors: Pfeiler Edward , Almada Ernestina , Vrijenhoek Robert C.
Published: June 2005

Developmental changes in soluble proteins and 16 enzymes were followed in metamorphosing leptocephalous larvae and juveniles of the bonefish (Albula sp.) using polyacrylamide gel and starch gel electrophoresis. Metamorphosis was characterized by relatively rapid and pronounced changes in amounts of specific proteins and in expression of different enzymes and isozymes. These effects are assumed to reflect changes in activity of structural genes. The metamorphic change from a largely gelatinous larval body matrix to the juvenile morphology involves a dramatic increase in muscle development. A corresponding increase was observed in the expression of the A4 isozyme of lactate dehydrogenase and the A2 isozyme of creatine kinase, isozymes characteristic of muscle tissue. Increased expression of various isozymes and a specific protein (Mr ∼ 14,000) was also observed in developing eye tissue. Differential expression of isozymes of malate dehydrogenase, lactate dehydrogenase, and glucose‐6‐phosphate isomerase, in early metamorphosing larvae collected from shallow water and deeper water, suggests that the near‐shore environment may be an important factor in “triggering” the metamorphic period.
Development in culture of the chick embryo from fertilized ovum to hatching
Authors: Naito M. , Nirasawa K. , Oishi T.
Published: June 2005

An experiment was carried out to investigate whether thick albumen is essential for the normal development of the chick embryo. Fertilized ova recovered from the oviducts of hens were cultured in vitro and transferred to recipient eggshells with (method A) or without (method B) replacement of the thick albumen by thin albumen. Embryos from freshly laid eggs were transferred to recipient eggshells with (method C) or without (method E) replacement of the thick albumen by thin albumen or with replacement of the thick albumen by thin albumen diluted with solution of salts (method D). Embryos were then incubated until hatching. The rates of hatching of the cultured embryos were 34.4%, 16.2%, 50.0%, 6.9–26.7%, and 47.5% for methods A, B, C, D, and E, respectively. Thus the rate of hatching of cultured fertilized ova was increased by replacement of the thick albumen by thin albumen at the blastoderm stage. Chicks obtained by method A reached maturity and produced viable offspring, and this technique provides an improved method for the culture of fertilized ova to hatching.