bluuebunny/crossref_metadata_2025_split huggingface dataset:
Different subsets of axonal guidance cues are essential for sensory neurite outgrowth to cutaneous and muscle targets in the dorsal ramus of the embryonic chick
Authors: Tosney Kathryn W. , Hageman Martha S. 
Published: June 2005

AbstractThe dorsal ramus nerve diverges dorsally from each spinal nerve to innervate the epaxial muscle and dermis that are derived in situ from each dermamyotome. The outgrowth of both the sensory and motor components of this nerve are sensitive to the proximity of the dermamyotome. Motoneurons display a direct target response that is not dependent upon the concurrent outgrowth of sensory neurites (Tosney: Dev. Biol. 122:540–588, 1987). Likewise, the outgrowth of sensory neurites could be directly dependent on the dermamyotome. Alternatively, sensory neurites could be dependent on motor axons that in turn require the dermamyotome for outgrowth. To distinguish between these possibilities, motor outgrowth was abolished by unilateral ventral neural tube deletion and the patterns of subsequent sensory neurite outgrowth were assessed. The cutaneous nerve branch formed in all cases. In contrast, neither of the epaxial muscle nerves formed in the absence of epaxial motoneuron outgrowth. Furthermore, sensory neurites could not be detected diverging into muscle from the cutaneous nerve or entering muscle via other novel routes. We conclude that motoneurons are essential for sensory outgrowth to epaxial muscle but not to cutaneous targets. It is clear that different subsets of navigational cues guide sensory afferents to muscle and to cutaneous destinations.
Regional identity is established before gastrulation in the Xenopus embryo
Authors: Turner A. , Snape A. M. , Wylie C. C. , Heasman J. 
Published: June 2005

AbstractRegional differences in cell recognition properties along the animal‐vegetal axis of Xenopus laevis embryos were investigated by using an in vitro cell sorting assay. Dissociated cells were obtained from defined regions of blastula‐ and early gastrula‐stage embryos. Binary combinations of cells from different regions, or from the same region at different ages, were aggregated in stationary culture. Labelling of one population in each pair with a cell‐autonomous dye allowed the degree of sorting out in the resulting aggregates to be scored. In combinations of cells from animal caps (prospective ectoderm) and vegetal masses (prospective endoderm), sorting was detectable at the equivalent of late blastula stage and increased with developmental age to the gastrula stage.In addition, cells from the same region but different stages sorted from each other, indicating temporal changes in regional identity. Marginal cells (prospective mesoderm) sorted strongly from vegetal cells but only weakly from animal cells.These results indicate the presence of regional identity in the form of specific recognition properties in cells of the Xenopus blastula. We suggest that these properties act to establish and maintain coherent cell populations, corresponding to the primary germ layers, prior to gastrulation. These results account for the gradual restriction in developmental capacity of blastomeres seen previously in single‐cell transplantation experiments from this laboratory.
Invagination of the otic placode: Normal development and experimental manipulation
Authors: Hilfer S. Robert , Esteves Ruth A. , Sanzo James F. 
Published: June 2005

AbstractThe inner ear forms from paired ectodermal primordia that lie to either side of the developing hindbrain. Initially each primordium forms a shallow depression in the ectodermal surface. Invagination to form an otic pit coincides with the formation of several deep folds in the epithelial surface. An initial fold appears parallel to the embryonic axis and at the junction of the rhombencephalon with somitomeric mesoderm. This is followed by formation of cranial and caudal folds perpendicular to the axis and minor folds that are within the pit formed by earlier folding. The central region of the otic primordium remains in close apposition to the lateral surface of the neural tube during the process of fold formation, until the otic pit becomes quite deep. At that time, mesenchymal cells penetrate between the two layers.Experimental analysis of invagination supports the conclusion that otic invagination is controlled differently from that of similar organ primordia, such as the eye and thyroid. Whereas these other primordia can be stimulated to undergo normal morphogenetic shape changes precociously by treatments that presumably activate motile processes in the cytoskeleton, the same conditions have little effect on the otic placode. Similarly, neither inhibitors of calcium transport nor inactivators of calmodulin activity prevent otic pit formation, while these drugs block invagination of other primordia. These results suggest that otic invagination may be caused by changes in the surrounding tissues rather than by an activation of motility within the primordium.
Aromatic alcohol oxidase: A new membrane‐bound H2O2‐generating enzyme in alimentary tissues of the slug Arion ater
Authors: Mann Vincent , Large Andrew , Khan Sultan , Malik Zulfiqar , Connock Martin J. 
Published: June 2005

AbstractWe employed a sensitive spectrophotometric technique to detect H2O2‐generating enzymic activities capable of utilizing aldehydes or alcohols as substrates. We analysed tissue homogenates and subcellular fractions of the terrestrial slug Arion ater. Of the tissues tested, those of the alimentary system (especially crop and digestive gland) had the greatest activity and generated H2O2 when supplied with a variety of alcohol and aldehyde substrates. Aldehyde oxidase activity was soluble and had high apparent affinity for benzaldehyde. This activity is probably analogous to mammalian aldox (aldehyde oxidase; E.C.1.2.3.1), since it could use an artificial electron acceptor system and greatly preferred benzaldehyde to hypoxanthine. However, it differed from guinea pig liver aldehyde oxidase in that salicylaldehyde was a potent inhibitor rather than a substrate. Alcohol oxidase activity was particulate but not localised in mitochondria or peroxisomes. In digestive gland, it was localised differently from mannitol oxidase. In crop, the subcellular sites are either the same or inseparable by isopycnic density gradient centrifugation in sucrose gradients. Activity was at least ten times greater with aromatic alcohols than with ethanol, propanol, or butanol. No activity was detected with methanol, and the enzyme could not utilise an artificial electron acceptor system or pyridine nucleotides. Aromatic alcohol oxidase differed from mannitol oxidase with respect to temperature and pH sensitivity and in exhibiting greater apparent affinity for its substrates. The alcohol oxidase accepted a wide variety of aromatic alcohols as substrates. In several respects it resembled the corresponding enzyme of wood‐rot fungi, implying that the slug utilises dietary lignin or lignin precursors. Possible dietary, microbicidal, and detoxifying roles are considered for slug aldehyde and alcohol oxidases.
Neuropeptides influencing in vitro pituitary hormone secretion in hatchling turtles
Authors: Denver Robert J. , Licht Paul 
Published: June 2005

AbstractStatic culture techniques were used to examine the effects of neuropeptides on thyrotropin (TSH), growth hormone (GH), and luteinizing hormone (LH) secretion by turtle pituitaries (Pseudemys scripta). Pituitaries were exposed to 2.5–2,500 nM thyrotropin‐releasing hormone (TRH), ovine corticotropin‐releasing hormone (oCRH), sauvagine (SV), carp urotensin I (UI), rat growth hormone‐releasing hormone (rGHRH), human GHRH (hGHRH), carp GHRH‐like immunoreactive peptide (cGHRH‐LIP), vasoactive intestinal peptide (VIP), arginine vasotocin (AVT), salmon gonadotropin‐releasing hormone (sGnRH) or chicken II GnRH (cGnRH). Medium concentrations of TSH, GH, and LH were estimated by RIA. Significant dose responses in TSH secretion were observed with TRH, oCRH, rGHRH, and hGHRH; VIP was also a potent stimulator of TSH, but a dose response was not observed. The two CRH‐like molecules, SV and UI, also stimulated TSH at the single dose tested (25 nM). All these neuropeptides had similar potencies. In one test in which PRL was measured, it was stimulated by 25 nM TRH but not by an equivalent dose of the CRH‐like neuropeptides. GH secretion was elevated by TRH, rGHRH, hGHRH, and VIP. oCRH at the highest dose (250 nM) stimulated GH, but SV and UI had no effect on GH at the single dose tested (25 nM). Neither AVT, cGHRH‐LIP, nor the two GnRH molecules had any effect on TSH or GH secretion. Data obtained by bioassay of TSH in representative samples were consistent with results of RIA.In contrast to the diversity of neuropeptides affecting pituitary TSH and GH, only GnRH stimulated significant and marked increases in LH secretion. AVT produced a small increase in LH output at the higher doses tested (250 and 2,500 nM), and all other neuropeptides were inactive at all doses. Taken together with other comparative data, these results suggest that in ectothermal vertebrates, TSH and GH responses are generally not as specific for neuropeptides as they are in normal mammals but may resemble mammals in certain abnormal states. However, there is not a clear phylogenetic pattern in which neuropeptides may be stimulatory to TSH or GH. The gonadotropes in both ectotherms and mammals appear to be relatively specific for molecules of the GnRH family.
Adolescence in Euplotes octocarinatus
Authors: Kuhlmann Hans‐Werner , Heckmann Klaus 
Published: June 2005

AbstractTen mating types are known for the hypotrich ciliate Euplotes octocarinatus. The mating types are determined by four codominant alleles that control the production of four gamones. The gamones induce mature cells of certain other mating types to get ready for conjugation. That the cells respond only to gamones that they do not synthesize themselves is rationalized by assuming that mating competence is specified by gamone‐specific receptors and that cells express receptors only for those gamones they do not synthesize themselves.Here we show that exconjugant clones are initially composed of cells that neither release gamones nor respond to gamones. If cells are heterozygous and therefore capable of producing two gamones, they start at a clonal age of about 15 fissions to synthesize first one gamone and five to ten fissions later a second gamone. Later still, their capacity to respond to gamones develops, first for one gamone and then five to ten fissions later for a second gamone. Cells responding in maturity to three gamones often acquire this capacity in three steps. These results support our assumption that in E. octocarinatus the gamones are perceived by gamone‐specific receptors. We propose that the genes coding for these gamone receptors are derepressed individually in clonal development. The same is assumed for the derepression of the genes that code for the four gamones. We further propose that the cells have the capacity to synthesize receptors for all four gamones, but they down‐regulate those receptors to which they synthesize a corresponding gamone.
The temporal pattern of vitellogenin synthesis in Drosophila grimshawi
Authors: Kambysellis Michael P. , Hatzopoulos Polydefkis , Craddock Elysse M. 
Published: June 2005

AbstractThe temporal pattern of protein production and, in particular, vitellogenin protein synthesis during the sexual maturation of Drosophila grimshawi females has been studied in vivo by briefly feeding the flies with 35S‐methionine and 3H‐amino acids. The overall level of incorporation was very low in young flies; it then progressively increased to reach a maximum with the onset of sexual maturity at 13–15 days. Sodium dodecyl sulfate—polyacrylamide gel electrophoresis (SDS‐PAGE) analyses revealed three classes of proteins: those synthesized throughout the age spectrum, which constitute the majority of protein species; proteins synthesized primarily or only in young flies; and proteins synthesized only by the older flies. In this Drosophila species, the three vitellogenins (V1, V2, and V3) appeared to be synthesized in a two‐phase pattern. In the first phase, small quantities of V1 and V2 were detected immunologically in the fat body and hemolymph of newly emerged and 1 day‐old flies. These proteins did not accumulate in the hemolymph or the ovaries, apparently being unstable proteins. The second phase commenced in early vitellogenesis (7–9 days of age) with synthesis in the fat body of small quantities of V1 and V2, followed by V3 proteins. These proteins were secreted and accumulated in the hemolymph and 24 h later were found in the ovaries. Their quantities increased rapidly and a steady state of synthesis, release into the hemolymph, and uptake by the ovaries was reached by days 13–15. We have estimated that during the steady state of vitellogenin synthesis, a fly can synthesize in 24 h at least 152 μg of vitellogenins, which is more than 2% of its body weight, at an average rate of about 6.3 μg vitellogenins/h. About 2 μg of this are synthesized in the fat body, and about 4 μg in the ovaries. These findings are discussed in terms of their physiological implications and contrasted with the available data on Drosophila melanogaster.
Functional organization of cerebral microvasculature in a marsupial, the Northern Quoll (Dasyurus hallucatus)
Authors: Snyder Gregory K. , Gannon Bren , Baudinette R. V. , Nelson John 
Published: June 2005

AbstractCapillaries within the central nervous system (CNS) of eutherian mammals form meshworks with numerous anastamoses, whereas capillaries in the CNS of marsupials consist entirely of hairpin‐like loops, without anastamotic interconnections. Counter‐current blood flow in capillary loops may have been important in the evolutionary development of a cerebral vascular supply. However, loops are not found in eutherian mammals, perhaps because of a limited benefit to the diffusive conductance of gases.
Comparative study of ureogenesis in freshwater, air‐breathing teleosts
Authors: Saha N. , Ratha B. K. 
Published: June 2005

AbstractThe ureogenic potential of five species of freshwater, air‐breathing teleosts was studied. The activity of all five enzymes of the ornithine‐urea (c‐u) cycle could be assayed in four out of the five species. The enzymatic activities were generally high. Physiological levels of ammonia and urea and of enzymes of the o‐u cycle have been considered to be associated with the potential for terrestrial life in different species. The species having an efficient o‐u cycle had low levels of ammonia and high levels of urea in various tissues. Ammonia was the major excretory product in the aquatic medium in all five air‐breathing species. However, the rate of excretion of urea was greater than that of exclusively freshwater teleosts reported earlier. There was apparently no diurnal variation in the rates of excretion of ammonia. The rate of excretion of urea was significantly higher during the night than during the day in only two of the species examined, namely, Heteropneustes fossilis and Anabas testudineus. These observations strengthen our earlier suggestion that active ureogenesis through a functional o‐u cycle does exist in some freshwater, air‐breathing teleosts.
Effects of the organophosphate insecticides diazinon and parathion on bobwhite quail embryos: Skeletal defects and acetylcholinesterase activity
Authors: Meneely Gail A. , Wyttenbach Charles R. 
Published: June 2005

AbstractBobwhite quail eggs were injected at 48 or 72 hr of incubation with various doses of the organophosphate (OP) insecticides diazinon or parathion and the embryos were examined after an additional 48 hr of incubation by both histological and cartilage‐staining methods. Bobwhite embryos did not display the notochordal folding or vascular enlargement reported for OP‐injected chicken embryos. Cartilage staining of embryos injected with insecticide at 72 hr of incubation and recovered at day 12 of incubation revealed severe shortening and contortion of the vertebral axis, as well as tibiotarsal, rib, and sternum defects. Parath on was more potent in causing skeletal defects than diazinon. No type I defects (micromelia, parrot beak) were detected. Radiometric acetylcholinesterase (AChE) assays of whole embryo homogenates were performed for day 6, 9, and 12 diazinon‐injected and control embryos. Diazinon effected drastic reductions in AChE activity. Although the AChE and axial skeletal responses of bobwhite embryos to OP injection are similar to those reported in the literature for other species, some major differences in the bobwhite response were noted: namely, the absence of notochordal folding in the young bobwhite embryo and the absence of type I defects at day 12. These differences suggest that further studies with the bobwhite quail would be useful in clarifying the mechanisms involved in OP‐induced teratogenesis.
De novo synthesis and release of polypeptides from cyclic and early pregnant porcine oviductal tissue in explant culture
Authors: Buhi W. C. , Vallet J. L. , Bazer F. W. 
Published: June 2005

AbstractThe objective of the present study was to identify and characterize in a limited manner the major de novo oviductal secretory proteins (OSP) synthesized and released by the porcine oviduct. Oviductal tissue was collected on various days of the estrous cycle (EC) and early pregnancy (EP) and cultured in a modified minimal essential medium supplemented with 100 μCi L‐[3H]‐leucine. Oviductal secretory activity, as measured by the rate of incorporation of 3H‐leucine (dpm/mg wet tissue weight) into nondialyzable macromolecules, was greatest(P < .01) between days 0 and 2 and reached its lowest levels on days 10 to 15. There was no difference between left and right side or pregnancy status. This increased rate of incorporation at proestrus and estrus is temporally associated with elevated levels of estrogen. Incorporation rate for ampulla was greater than for the isthmus. Analysis of oviductal culture medium by one‐dimensional sodium dodecyl sulphate‐polyacrylamide gel electrophoresis and fluorography revealed three protein bands of relative molecular weight (Mr) 335,000, 115,000, and 85,000, which were associated with proestrus, estrus, and metestrus and were not detectable on other days. All three proteins also incorporated 3H‐glucosamine. The 115,000 Mr band was the major 3H‐glucosamine‐labeled protein. Two protein bands (Mr 60,000 and 20,000) were expressed with increasing progesterone during diestrus. Other de novo synthesized protein bands appear to be present throughout the EC and EP with little modulation by estrogen or progesterone. Thus, this study demonstrates that for the porcine oviduct, the increase in the incorporation rate of 3H‐leucine into OSP by both whole oviduct and ampulla and de novo synthesis and secretion of three glycoproteins, Mr 335,000,115,000, and 85,000, were associated with proestrus and estrus when events such as fertilization and early cleavage stages of embryo development occurred.
In vitro fertilization of gonadotropin‐stimulated leopard cat (Felis bengalensis) follicular Oocytes
Authors: Goodrowe Karen L. , Miller Anne M. , Wildt David E. 
Published: June 2005

AbstractBased on techniques developed for the domestic cat, in vitro fertilization (IVF) studies were conducted in the taxonomically related leopard cat (Felis bengalensis). Adult females received pregnant mares' serum gonadotropin (PMSG) followed 80 or 84 h later by human chorionic gonadotropin (hCG) on two to four occasions over a 40‐day to 27‐month interval. Oocytes were collected laparoscopically from ovarian follicles 25–27 h after hCG and co‐cultured with processed, homologous spermatozoa (37°C, 5% CO2 in air, humidified atmosphere) for 30–36 h. There was no apparent ovarian refractoriness to repeated treatments with exogenous gonadotropins. Overall, the mean number of mature follicles present and the total number of oocytes and proportion of immature oocytes collected did not differ (P > 0.05) between the 80 h (4.9 ± 0.9; 4.7 ± 1.2; 14.9%, respectively) and 84 h (5.6 ± 1.4; 5.4 ± 1.7; 22.2%, respectively) gonadotropin interval groups. However, the proportion of mature leopard cat oocytes fertilized in vitro, as determined by embryonic cleavage, was increased (P < 0.005) by extending the interval between PMSG and hCG from 80 (17.5%) to 84 (52.4%) h. These data 1) demonstrate that, compared to the domestic cat, the ovaries of the leopard cat are less responsive to a given PMSG/hCG treatment; 2) indicate that leopard cat follicular oocytes can be recovered readily by laparoscopy and are capable of becoming fertilized in vitro; and 3) suggest that IVF may be a viable approach for producing embryos and perhaps enhancing captive propagation of rare Felidae.
Human chorionic gonadotropin (hCG) induces gonad reversal in a protogynous fish, the bluehead wrasse, Thalassoma bifasciatum (teleostei, labridae)
Authors: Koulish S. , Kramer C. R. 
Published: June 2005

AbstractFemale to male successive hermaphroditism (protogyny) is common in several groups of marine fish. Thalassoma bifasciatum, the bluehead wrasse (Labridae), found in the reefs of the Caribbean normally undergoes sex reversal after receiving behavioral cues. This report deals with the successful use of human chorionic gonadotropin (hCG) in inducing gonad reversal in this species. Eighty percent (n = 40) of the treated fish showed signs of reversal in 1–6 weeks; only 11% (n = 54) of the control (nontreated) group showed signs of reversal during the same period. The number of fish undergoing reversal increased with the length of the treatment period, 55% after 1 week, 100% after 6 weeks. A bluehead color pattern, typical of the terminal male phase, also appeared more frequently in the longer treated groups. To determine the efficacy of hCG in inducing gonad reversal, morphological criteria for reversal had to be established. For the majority of treated fish, the presence of both spermatogenic cysts and degenerating oocytes was sufficient to label these gonads unambiguously as undergoing reversal. However, at the extremes of this process, i.e., onset (early) and endpoint (late) stages, ambiguity could arise in identifying a gonad as undergoing reversal, and, therefore, key criteria were established for these stages. In our hands, the most consistent and reliable criterion for the early stage reversal was appearance of male germ line cells, clusters of “spermatogonial‐like” cells. For the late stage, recognizable remnants of late‐state oocytes had to be present. Some details of the histological changes that occur during early, middle, and late stages of reversal are also described. It is suggested that these results with hCG shed new light on the endocrine control of gonad reversal in T. bifasciatum.
Cold shock induces actin reorganization and polyspermy in sea urchin eggs
Authors: Santella Luigia , Monroy Alberto 
Published: June 2005

AbstractThe effect of low temperature on the cortical actin system and polyspermy in sea urchin eggs was studied. Eggs cold‐shocked at 3°C for 1 hour formed a cortical system of polymerized actin and were polyspermic when fertilized. These effects were completely reversible following a 7–20 minute recovery period at room temperature. The present data raises the possibility that actin, or components of the egg cytoskeleton, regulate sperm entry in sea urchin eggs.