bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vasculogenesis and angiogenesis: Two distinct morphogenetic mechanisms establish embryonic vascular pattern
Authors: Poole Thomas J. , Coffin J. Douglas 
Published: June 2005

AbstractWe 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

AbstractIn 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

AbstractMeasurements 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

AbstractBovine 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

AbstractThe 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

AbstractHigh‐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

AbstractThe 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

AbstractThe 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

AbstractEndogenous 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractTo 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

AbstractThe 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

AbstractIn 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

AbstractThe 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.