bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of successive generations of ether treatment on penetrance and expression of the bithorax phenocopy in Drosophila melanogaster
Authors: Ho M. W. , Tucker C. , Keeley D. , Saunders P. T. 
Published: June 2005

AbstractEther treatment of embryos in successive generations results in the progressive increase in penetrance of the bithorax phenocopy in both a massbred and an inbred line of Drosophila melanogaster without artificial selection for the phenocopy. The involvement of cumulative cytoplasmic modifications is suggested by the results of recipiocal crosses between the treated massbred line and its foundation stock, and by the lingering effects observed when ether treatment is withheld in later generations.Regression analyses showed that the effect of successive generations of ether treatment on penetrance is cumulative and direct, and not mediated by possible effects on viability.Ether treatment carried out on embryos at four consecutive age intervals in the 14th generation suggests that the effects of long‐term etherisation are as follows: an increased tendency to phenocopy at all ages tested; an extension of the critical period during which the phenocopy can be induced; and an increased resistance to the lethal effects of ether in older embryos.The remarkable consistency in every aspect of the response in the two different lines—one containing at least 20 times as much genetic variation as the other—points to the existence of systematic organismic properties which do not depend on specific alleles in specific genes.The possible evolutionary significance of our results is discussed.
Thyroid and skin‐shedding in the rat snake (Ptyas korros)
Authors: Chiu K. W. , Leung M. S. , Maderson P. F. A. 
Published: June 2005

AbstractEpidermal‐thyroid relationships were studied in thyroidec‐tomized (;Tx) Ptyas korros kept at 23°C by observing changes in shedding frequency (;SF), body weight, oxygen consumption rate (;OCR), and postsurgical survival. Tx animals showed increased SFs but lost weight and eventually died, as did Tx animals receiving 3‐mono‐iodotyrosine injections. However, injections of 3, 5‐diiodothyronine inhibited shedding and the animals survived longer. OCRs were similar in all control and experimental groups. It is concluded that among thyroid secretions, only iodothyronines inhibit shedding. Snake shedding is concluded not to reflect general metabolic status as it does in lizards.
Mating‐type‐specific loss of conjugation competence by irritation in Euplotes vannus
Authors: Lueken W. , Gaertner M. , Breer H. 
Published: June 2005

AbstractIn order to characterize differences in mating types in Euplotes vannus, two cell populations of complementary mating types were mixed and exposed to a pattern of irritation (switching schedule of agitation and rest). Cells costimulate each other, as is seen from courtship behavior during still intervals, but do not pair. Prolonged periods of treatment cause distinctly reduced cell interactions. After 72 hr they have ceased completely: Overstimulated cells have lost their ability to conjugate. However, with fresh cells of mating types, which are different from both constituents of the mixture, overstimulated cells mate normally as judged by time course, cycloheximide‐sensitivity, and concanavalin A (ConA) binding. Conjugation competence thus is selectively lost only for that mating type which has been the partner in the perturbated mixture. The required classification of pairs with regard to mating‐type combinations were confirmed by several identification procedures using amicronucleates and doublets. The observed phenomena during the mating‐type‐specific loss of conjugation ability are consistent with the concept that this is due to a physiological disappearance of a specific mating substance, which might correspond to the receptor side of the extended gamone‐receptor hypothesis of Miyake ('81).
Preparation and cross‐reactivity of anti‐avian glutamine synthetase antibody
Authors: Smith Darwin D. , Vorhaben Jean E. , Campbell James W. 
Published: June 2005

AbstractRabbit antibody to chicken liver mitochondrial glutamine synthetase was purified by immunoaffinity chromatography for analysis of the immunological relatedness of vertebrate glutamine synthetases. The antibody cross‐reacted with enzymes from representitives of all five vertebrate classes, indicating a high degree of evolutionary conservatism in the structure of the enzymes. A unique aspect of the immunological similarity of these enzymes is that it exists between cytosolic and mitochondrial enzymes which are, in general, immunologically distinct. The antibody did not cross‐react with two insect glutamine synthetases. Compositional difference indices, calculated from the amino acid compositions of glutamine synthetases from several species, gave a mean estimate of over 80% sequence homology for the vertebrate enzymes. The avian mitochondrial enzyme gave a mean 78% homology with the mammalian cytosolic enzyme.
Sustained branchial apnea in the Australian short‐finned eel, Anguilla australis
Authors: Smith D. G. , Duiker W. , Cooke I. R. C. 
Published: June 2005

AbstractBranchial and cutaneous O2 uptake as well as branchial ventilatory stroke volume and frequency were measured by twin‐chamber respirometry in conscious unoperated eels (Anguilla australis) at 20°C. The branchial ventilatory pattern comprised alternating periods of apnea and eupnea, together constituting a “Standard Breathing Cycle” (SBC = 1 apneic period plus the ensuing period of eupnea). SBC time in 17 eels averaged 15.5 min of which only 23% was devoted to eupnea. Reduction of the PO2 of inspired water from 155 to 80 torr significantly increased the proportion of time devoted to eupnea to 49% of SBC time without significantly changing SBC time. Absolute cutaneous O2 uptake (5.8 ml O2·h−1·kg−1) was largely independent of the frequency or occurrence of eupnea, with the relative contribution of the skin to total O2 uptake averaging 47%. The histological appearance of the skin in A. australis is very similar to that described in A. anguilla: eel skin is only poorly vascularized. It was concluded that the skin may contribute to O2 requirements other than its own, and that this adaptation is a consequence of the unusual intermittent pattern of gill ventilation.
Evidence for inherent morphogenetic properties of the myogenic regions of the embryonic chick wing
Authors: Searls Robert L. 
Published: June 2005

AbstractThe dorsal and ventral myogenic regions were isolated from the right and left wings of donor chick embryos. After removal of the ectoderm, the myogenic regions were grafted into the dorsal myogenic region of the right wing of host embryos in normal or reversed proximal‐distal orientation. All grafts were made so that the surface of the graft originally in contact with ectoderm was dorsal. It was expected that myogenic regions grafted into the myogenic region would participate in the normal formation of the host wing. However, after 7 days of further development many of the host wings had developed abnormal cartilages. To investigate the interactions between the tissue of the host and the tissue of the graft and the source of the tissue giving rise to ectopic cartilages, the donor embryos were labeled with tritiated thymidine. The location and shape of the graft were recorded at the time of the operation. The host wings and adjacent body wall were fixed 1, 3, and 4 days after the operation, sectioned, and prepared as autoradiographs. The location of the grafted cells in the host wing was determined by reconstructing the host wing and adjacent body wall. Serial sections and the reconstructions were examined to discover the correlates of abnormal cartilage formation. The following observations were made: 1) Grafts from the dorsal region of the right and left wing in normal orientation participated in the formation of the groove at the base of the wing ventral to the nineteenth somite that produces the extensor surface of the elbow. Grafts from the ventral region of the right and left wing in normal orientation, and all grafts in reversed orientation, did not participate in the formation of the groove. 2) Grafts in normal orientation increased in length on the axis of the humerus and did not increase in width. Grafts in reversed orientation increased in both length and width. Increase in width caused the graft to extend into the proximo‐caudal corner of the wing. 3) Wings with grafts from the dorsal regions of the right and left wings in normal orientation were not clearly abnormal 4 days after the operation. When the groove ventral to the nineteenth somite did not form normally, ectopic cartilage differentiated where the groove should have been from grafted cells of the myogenic region. Increase in width of the graft into the proximo‐caudal corner of the wing produced an increased mass of graft cells ventral to the nineteenth somite and an increased amount of ectopic cartilage.
Can differences in limb regeneration ability between individuals within certain amphibian species be explained by differences in the quantity of innervation?
Authors: Scadding Steven R. 
Published: June 2005

AbstractIn some species of amphibians, the regenerative response to limb amputation is not uniform. For example, regenerative ability varies from one individual to another within the species Xenopus laevis, Ambystoma maculatum, and Amphiuma tridactylum. In many species, limb regenerative ability declines with increasing age. The objective of this investigation was to determine if this variation in regenerative ability can be explained by variation in the quantity of innervation. In each of the above‐named species, limbs were amputated and allowed to regenerate. The quantity of innervation (percentage of cross‐sectional area of amputated surface occupied by nerves) was measured in the amputated part of the limb as close as possible to the amputation surface. The presence, rate, or extent of limb regeneration in that specific limb was then compared to the quantity of innervation at the amputation surface. The results indicated that there was no correlation between innervation and the rate or extent of regeneration in Xenopus laevis or Ambystoma maculatum. On the other hand, in Amphiuma tridactylum, those limbs that regenerated were the ones that had the highest levels of innervation. In Ambystoma maculatum, the quantity of innervation was measured at five different stages, from early larvae to mature adult. The results showed that the quantity of innervation was highest during the larval period, reaching a maximum at the late larval stage before declining greatly to the adult level. It appears that the decline in regenerative ability in the adult cannot be attributed solely to a reduction in innervation to below the threshold level.
The culture of chick embryo mesoderm cells in hydrated collagen gels
Authors: Sanders E. J. , Prasad S. 
Published: June 2005

AbstractChick embryo mesoderm cells at various stages of differentiation were cultured in three‐dimensional matrices of hydrated collagen. The tissues used were: stage 5 mesoderm from regions adjacent to the primitive streak; stage 12 mesoderm, comprising somitic, unsegmented (segmental plate) and lateral plate mesoderm; and stage 18 sclerotome. Explants were examined by phase contrast microscopy, including time‐lapse, and scanning and transmission electron microscopy. The cells showed an increased ability to adhere to, and move in, the collagen gel with advancing stage. Of the stage 12 tissues, the unsegmented mesoderm was initially the slowest to grow out of the explant. Sclerotome cells showed by far the greatest ability to move within the gel. Where the collagen fibrils were randomly oriented, the cell morphology was polypodial and advancing lamellipodia showed clear undulations at their leading edges. A distinction was drawn between these undulations and the classical major ruffles which are seen in two‐dimensional culture to uplift and pass back along the cell surface. The latter were not seen in the collagen matrix and were presumably suppressed by the three‐dimensional culture configuration while the leading edge undulations were not. Ultrastructural examination showed that the cells possessed patches of amorphous material on their surface, which was sometimes interposed between the plasma membrane and collagen fibrils. Addition of hyaluronie acid (2 mg/ml) had an effect only the segmented mesoderm, where outgrowth was enhanced. Although the addition of plasma fibronectin (50 μg/ml) to the cultures did not affect any of the tissues, the removal of this substance, by antifibronectin antiserum or by the use of fibronectin depleted serum, inhibited outgrowth in most cases. The only tissue not reproducibly inhibited in this way was sclerotome. Alignment of the collagen fibres by the explants was observed, accompanied by an elongation of the outgrowing cells which, in bipolar form, preferentially moved up and down the aligned tracts. Scanning electron microscopy suggested that cell processes attached to, and presumably exerted tension on, bundles of fibrils thereby pulling them into line. Cell‐to‐cell contact was not accompanied by contact paralysis as judged by time‐lapse micrography.
Endocrine regulation of spermatogenesis in Nereis diversicolor (Annelida Polychaeta): Experimental study of the control of meiotic differentiation
Authors: Bertout Marc 
Published: June 2005

AbstractIn Nereidae, spermatogenesis is regulated by a hormone secreted by the supraesophageal ganglion (brain hormone). The hormonal concentration decreases with worm age. Spermatogonial proliferation in young worms proceeds under a high hormonal level whereas differentiation of spermatozoa in aged worms occurs in the absence of brain hormone. Spermatogonia were removed from the endocrine influence of the brain in vitro by the organ culture method. Isolated parapodia produced spermatozoa after 13 days. Control cultures were obtained by associating a parapodium with the prostomium of a young worm. It seems that the brain hormone inhibits the spermatocyte differentiation since removal of the brain results in increased RNA synthesis, followed by DNA replication, meiosis, and spermiogenesis (Bertout, '83).Modalities of the hormonal control of meiosis, especially at the level of the RNA syntheses related to meiotic differentiation, were investigated. Effects of reintroducing the hormonal influence during meiotic differentiation were studied through parapodium‐prostomium associations at various time after the brain inhibition has been lifted. Effects or RNA inhibitors (actinomycin D, α‐amanitin, cordycepin) were also tested. The results lead us to propose a hypothesis according to which brain hormone would interfere with molecular events related to the transition from the stage of spermatogonial proliferation (mitotic behavior) to the stage of meiotic differentiation (meiotic behavior).
Calcium‐binding phosphoprotein particles in the extrapallial fluid and innermost shell lamella of clams
Authors: Marsh M. E. , Sass R. L. 
Published: June 2005

AbstractA calcium‐binding phosphoprotein has been isolated from the extrapallial fluid of clams where it occurs as discrete particles 30–40 nm in diameter at a concentration of 1.5–6.0 mM with respect to organic phosphate. The particles were isolated by nitration and differential centrifugation procedures. In particles obtained from Rangia cuneata, 90 mole % of the amino acid residues are aspartic acid (21.7%), serine (29.1%), histidine (34.6%), and lysine (4.6%). In Mercenaria mercenaria particles 95% of the residues are aspartic acid (20.1%), serine and threonine (26.9%), histidine (36.0%), and glycine (11.4%). The serine and threonine residues may be fully phosphorylated.Particles from Rangia contain 1.45 moles of calcium plus magnesium and 0.24 moles of inorganic phosphate per mole of organic phosphate, and in Mercenaria particles these values are 1.29 and 0.164 respectively. Calcium and magnesium probably bind to organic phosphate and aspartic acid residues, and inorganic phosphate may bind secondarily through calcium and magnesium.In Rangia, the innermost shell lamella (ISL) is a single continuous layer which forms the inner surface of the shell dorsal to the pallial attachment. It contains no crystalline mineral but is firmly attached to the mineral in the underlying calcined layer. The presence of phosphoprotein particles in the ISL was demonstrated by electron microscopy and amino acid analysis. Phosphoprotein particles are not present in the bulk shell; however, their occurrence in the extrapallial fluid and ISL coupled with their affinity for mineral ions suggests that the particles have an intermediary roll in shell deposition or dissolution.
Formation of a functional apical ectodermal ridge from nonridge ectoderm in limb buds of chick and quail embryos
Authors: Murphy Michael J. , Gasseling Mary T. , Saunders John W. 
Published: June 2005

AbstractIn an attempt to impede the inductive communications between the apical ectodermal ridge (AER) of the wing bud and its underlying mesoderm, we lined the apex of the trypsin‐isolated ectodermal hull of the chick limb bud with stage 23 or 25 quail back‐skin ectoderm or nonridge limb ectoderm. We then inserted a stage 21 chick wing‐bud mesodermal core into this hull with its apex against the putative barrier. Reciprocally, quail limb components were united with a barrier of chick nonridge limb ectoderm. Such composites, grafted to host chick embryos, usually formed wings comparable in perfection to those obtained when ectodermal and mesodermal elements are recombined and grafted without a lining ectodermal layer. The reestablishment of a normal vascular pattern in the composite limbs was delayed compared to controls, suggesting that the interposed layer of cells interferes, initially at least, with the communication between the AER and subjacent mesoderm, and that this interference delays the development of, particularly, the veinous channels draining the limb bud.Histological study of Feulgen‐stained preparations showed that the interposed ectodermal cells begin moving into the overlying ectoderm as early as 6 h after grafting, populating the AER and adjoining ectoderm. By 48–50 h the ridge and adjacent ectoderm are composed entirely, or almost so, of cells of the interposed type. The original ridge cells are apparently displaced into the amniotic fluid, and the cells invading from below take over the functional attributes of the AER, inducing the growth of terminal limb parts.
In vitro estrogen modulation of pituitary and progesterone‐induced oocyte maturation in Rana pipiens
Authors: Lin Yu‐Wai P. , Schuetz Allen W. 
Published: June 2005

AbstractThe role of estrogen in the process of hormone‐induced meiotic maturation was investigated using in vitro culture of Rana pipiens ovarian follicles and isolated oocytes. Estrogen alone was ineffective in triggering maturation and did not act synergistically when combined with progesterone. Instead, slight inhibitory effects on oocyte maturation were observed when estrogen was added to the culture medium simultaneously with progesterone. Prolonged estrogen pretreatment (1–8 hr) was seen to be increasingly effective in inhibiting progesterone‐induced germinal vesicle breakdown (GVBD). Washing follicles after estrogen pretreatment diminished the inhibitory effects, suggesting continued presence of estrogen was necessary for maximal inhibition. Progesterone‐induced GVBD was inhibited by estrogen in denuded oocytes (follicle wall removed) indicating that estrogen acts directly on the oocyte. Incorporation of radioactive progesterone into ovarian follicles was not inhibited regardless of the estrogen concentration used. This suggests that estrogen inhibits oocyte maturation by raising intrafollicular threshold to progesterone rather than by suppressing hormone incorporation into ovarian follicles. Next, the action of estrogen on frog pituitary homogenate (FPH)‐induced GVBD was examined. Although both progesterone and FPH‐induced GVBD were inhibited by estrogen, the latter was remarkably more susceptible and did not require estrogen pretreatment. Furthermore, increased concentration of progesterone, but not FPH, overcame the inhibitory action of estrogen. The results suggest that estrogen may exert its inhibitory effects on gonadotropin action at more than one site. Estrogen can o modulate either the maturation‐inducing action of progesterone directly at the oocyte level or the suppression of progesterone production by the follicle cell. Hence, estrogen may play an important role as an endogenous regulator of oocyte meiotic maturation.
Parthenogenetic activation of mouse oocytes in vitro with ethanol and benzyl alcohol
Authors: Cuthbertson K. S. Roy 
Published: June 2005

AbstractTreatment in vitro of ovulated mouse oocytes for 5–10 min with 4.5–8.6% ethanol or 0.24–0.4% benzyl alcohol was found to induce parthenogenetic activation. Suppression of the second polar body with cytochalasin D and subsequent culture in vitro gave a high yield of parthenogenetic morulae and blastocysts (up to 85% overall). Fifty percent of transferred diploid parthenogenones implanted, 14% developed into egg cylinders, and 8% formed somites and developed as far as the forelimb‐bud stage.
The organization of flexion‐evoking interneurons in the abdominal nerve cord of the crayfish, Procambarus clarkii
Authors: Larimer James L. , Jellies John 
Published: June 2005

AbstractIntracellular recording and dye injection was used to investigate the flexion‐evoking interneurons in the isolated abdominal nerve cord of the crayfish, Procambarus clarkii. The interneurons described in this study have all of the characteristics of cells called flexion command fibers in earlier works. These interneurons show cell bodies in all of the abdominal ganglia, all are interganglionic, and those with posteriorly directed axons enter the terminal caudal ganglion. Some cells were found in as many as eight different preparations, supporting the idea that these interneurons are identified cells. In addition to presenting evidence for identities, evidence was obtained for serial homology in this premotor system. A summary of the general organization of the flexion premotor apparatus is offered. It consists primarily of parallel elements (command interneurons) that are either bipolar or monopolar whose axonal projections course to the terminal caudal ganglion or rostrally into the thoracic region, perhaps into the cerebral ganglion. When activated singly, these parallel elements do not recruit additional interneurons but there are data to suggest that several of these elements could act in concert and interact in a low‐gain fashion to produce coordinated positioning behavior.
Effects of abrasion and Na+ on dactyl‐mediated chemoreception in mature kelp crabs, Pugettia producta (Randall)
Authors: Hamilton K. A. , Case J. F. 
Published: June 2005

AbstractExtracellular recordings from the mixed sensory nerves innervating the abraded dactylopodites of the kelp crab, Pugettia producta (Randall), indicate that at least some chemoreceptors and mechanoreceptors remain functional. The chemoreceptors of the abraded dactyls are sensitive to both the concentration and chemical nature of the stimulants. The responses of the chemoreceptors, but not of the mechanoreceptors, are reduced when choline is substituted for sodium in the stimulant solutions. Only chemoreception is blocked by the topical application of tetrodotoxin (TTX) to the dactyls; partial reversal of the blockage occurs with time. The differential blockage of receptor activity by low Na+ and TTX is consistent with the idea that spike initiation occurs more distally in the dendrites of the chemosensory neurons than in the mechanosensory neurons. The relevance of this to the ability of at least some abraded dactyl setae to remain functional in a long‐lived, nonmolting crab is considered.