bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in morphology and cell proliferation during vitamin A‐lnduced mucous metaplasia of developing chick scale cultured in vitro
Authors: Tanaka Shoji 
Published: June 2005

AbstractThroughout the process of vitamin A (V‐A)‐induced mucous metaplasia of the scale epidermis of a 12‐day chick embryo, changes in the activities of cell proliferation were investigated in reference to morphological changes. In both the control and V‐A cultures after 5 days, a dynamic steady state was established among the stratified layers which differentiated into keratinizing epidermis during the first 7 days.In the control, cell proliferates within only the basal layer and the cell cycle time, except Tg2, increased during 30 days of culture. In the V‐A culture, this tendency was reversed in each parameter between day 10 and day 13, when symptoms of mucous metaplasia became morphologically prominent. On day 13 in the V‐A culture, superficial cornified cell layers were sloughed off as whole sheets and concurrently DNA synthesis was reactivated throughout the entire cell layers of the epithelium.The correlation between two of five cell cycle times (Tgc, Tg1, Ts, Tg2, Tm) was statistically treated as linear regression lines and gave highly significant coefficients in every case. The regression coefficients between Ts and Tgc and Ts and Tgl in V‐A culture are significantly (P < 0.01) smaller than those in the control. It was found that V‐A induced sequential alterations in mucous metaplasia with respect both to morphology and proliferation activity in the epidermis of the chick embryo.
BHC‐lnduced molt inhibition in the fresh water rice field crab (Oziotelphusa senex senex fabricius)
Authors: Reddy P. Sreenivasula , Bhagyalakshmi A. , Ramamurthi R. 
Published: June 2005

AbstractBHC‐induced molt inhibition in the crab, Oziotelphusa senex senex Fabricius, apparently by triggering the release of molt inhibition hormone (MIH).
Autoradiographic visualization of beta adrenergic receptors in fish melanophores
Authors: Komatsu Koichiro , Yamada Koji 
Published: June 2005

AbstractAutoradiographic demonstration of beta adrenergic receptors was achieved light microscopically in melanophores of isolated scales of a teleost fish, Oryzias latipes. [3H]hydroxybenzylisoproterenol, a beta adrenergic agonist, and [3H]propranolol, a beta adrenergic antagonist, were used as radioligands. In the autoradiograms, photographic grains of considerably high density were found to be distributed evenly over all parts of the surface of melanophores. Since the density of the grains was observed to decrease significantly in the presence of excess amounts of nonlabeled ligands, the results indicate the actual existence of beta adrenergic receptors in the present melanophores. This substantiates the findings obtained by other physiological and pharmacological methods that beta‐adrenergic receptors may exist and be involved in melanosome‐dispersion response of fish melanophores.
Electrical activities of a type of electroretinogram recorded from the ocellus of a jellyfish, Polyorchis penicillatus (hydromedusae)
Authors: Weber Christian 
Published: June 2005

AbstractAn electroretinogram (ERG), evoked by light stimuli, was recorded from ocelli of Polyorchis penicillatus (Hydromedusae). The ERG is a polyphasic response with a positive potential change at the onset of illumination followed by a slower biphasic pulse, and a positive deflection at the cessation of illumination which is followed by a series of high‐frequency pulses. The most striking features of the initial pulse are its latency‐log intensity relation and the gradation of pulse amplitude with respect to the intensity of the light stimulus and to different wavelengths. Maximum spectral sensitivity lies around 530 nm. Response patterns induced by shadowing and repeated stimulation of light‐ and dark‐adapted ocelli are described. Morphological structures which could give rise to the mass response of the ocellus are discussed.
Pattern development in palleal buds of the polystyelid ascidian, Polyandrocarpa misakiensis: Bud grafting induces bilateral asymmetry conversion through polarity reversal
Authors: Kawamura Kazuo , Watanabe Hiroshi 
Published: June 2005

AbstractPrevious work has shown that the anteroposterior axis and the transverse axis of the palleal buds of some botryllid and polystyelid ascidians develop in a predictable manner, depending on the position of the buds on the parental lateral wall. In the present study, three kinds of homopleural and heteropleural bud grafts were performed to invert the presumptive bud axes. The results show that the polarity of the bud A‐P axis can be inverted with relative ease, depending on the duration of the connection of the bud with a host adult zooid. Concurrently with the reversal of this axis, the normal pattern of body asymmetry is reversed. When both the presumptive anteroposterior and transverse axes are inverted, the future zooid develops the same body asymmetry pattern as its parent. Body asymmetry conversion was induced most efficiently (22.8%) when buds were amputated and grafted with reversed proximodistal axis on the host mantle wall. The polarities of zooid body patterns are transmitted through subsequent (asexual) blastogenic generations. This work shows that the future body pattern of a bud depends on the two axial polarities of its parent.
The relation of Na and Cl extrusion in Opsanus beta, the gulf toadfish, acclimated to seawater
Authors: Kormanik Gregg A. , Evans David H. 
Published: June 2005

AbstractA model has been proposed by Silva et al. ('77) to describe the manner by which Cl extrusion occurs across the gills of the eel and seawater fish in general. Aspects of the model include (1) passive distribution of Na across the gill surface, and (2) Cl extrusion dependent on Na‐K‐ATPase and thus dependent on the transport of Na.In order to test various aspects of this model, we examined, using the appropriate radiotracers, the relationship of Na and Cl efflux in the gulf to adfish, Opsanus beta. The model of Silva et al. does not apply to the toadfish because (1) Na cannot be passively distributed across the gills of the toadfish, because the transepithelial potential is several millivolts negative with respect to seawater, and (2) Cl efflux (unlike Na efflux) is not dependent on external K. Additionally, Cl efflux is dependent on the seawater Na concentration, and both Na and Cl efflux are dependent on seawater HCO3. Thus Na and Cl efflux appear to be linked in the toadfish, but not as proposed in the model suggested by Silva et al.
Incorporation of synthesized and dietary hydrocarbons into the cuticle and hepatopancreas of the scorpion Paruroctonus mesaensis
Authors: Hall Richard L. , Hadley Neil F. 
Published: June 2005

AbstractMeasurable amounts of cuticular and hepatopancreas lipids were synthesized by the scorpion Paruroctonus mesaensis from [14C]‐labeled acetate, propionate, mevalonate, and leucine when animals were acclimated to 35°C and incubated for at least 72 hours. Labeled hydrocarbons comprised less than 1.5% of the activity in lipids, with most of the labeled hydrocarbons associated with the hepatopancreas. The hepatopancreas was also the site of most lipid synthesis in scorpions injected with [3H]H0. Incorporation of the latter into hydrocarbons relative to other lipid classes increased from 0.9% in 72 hours to 8.4% by day 10 in fed animals, with slightly higher values in starved scorpions. After 3 months, activity in cuticular hydrocarbons increased coincident with a decrease in hepatopancreas activity. Scorpions maintained on crickets (Acheta domesticus) which contain few n‐alkanes showed a marked decrease in cuticular n‐alkanes after 10 weeks, while scorpions maintained on grasshoppers (Trimerotropis pallidipennis) which are n‐alkane‐rich showed a corresponding increase in their cuticular n‐alkanes. Scorpions fed crickets injected with labeled n‐alkanes (C25, C27, C29) incorporated these unchanged into their cuticular hydrocarbons. These results are evidence that lipid synthesis is consistent with the low metabolic rate of the scorpion and that the synthesized hydrocarbons which slowly accumulated in the cuticle were supplemented by diet‐specific branched and n‐alkanes.
Oocyte maturation in the amago salmon (Oncorhynchus rhodurus): In vitro effects of salmon gonadotropin, steroids, and cyanoketone (an inhibitor of 3β‐hydroxy‐Δ5‐steroid dehydrogenase)
Authors: Young Graham , Kagawa Hirohiko , Nagahama Yoshitaka 
Published: June 2005

AbstractThe effect of partially purified chinook salmon gonadotropin (SG‐G100) and a number of steroids on the induction of germinal vesicle breakdown (GVBD) in amago salmon (Oncorhynchus rhodurus) oocytes (with intact follicle layers) was investigated in vitro. SG‐G100 was effective only at the highest concentration tested (1 μg/ml). 17α,20β‐Dihydroxy‐4‐pregnen‐3‐one (17α,20β‐diOHprog) was the most potent maturation‐inducing steroid tested, followed by 17α‐hydroxyprogesterone. Testosterone or deoxycorticosterone (DOC) enhanced the rate of GVBD in response to SG‐G100. DOC also enhanced the response to 17α,20β‐diOHprog but testosterone was without effect, suggesting that DOC has a direct action on the oocyte while testosterone probably acts at the level of the follicle. Estradiol‐17β had no effect on GVBD in response to SG‐G100 or 17α,20β‐diOHprog.The action of SG‐G100 was shown to be dependent on the synthesis of a second Δ4 steroidal mediator of maturation since cyanoketone, a specific inhibitor of 3β‐hydroxy‐Δ5‐steroid dehydrogenase, completely abolished the maturational effects of the gonadotropin and pregnenolone but not Δ4 steroids. Radioimmunoassay of media in which oocytes were induced to mature in vitro with SG‐G100 revealed significantly elevated levels of progesterone and 17α,20β‐diOHprog. Estradiol‐17β levels, high in control media, were only elevated twofold by SG‐G100. Levels of the two progestogens were extremely low or nondetectable in media in which oocytes were incubated with cyanoketone, while estradiol‐17β levels remained high. These results are discussed in relation to other evidence indicating that 17α,20β‐diOHprog is the naturally occurring maturation‐inducing steroid of amago salmon. The role of other steroid hormones, particularly the possible involvement of corticosteroids, in the control of final oocyte maturation in teleosts is explored.
Two examples of monoamniotic monozygotic twinning in diploid parthenogenetic mouse embryos
Authors: Kaufman Matthew H. 
Published: June 2005

AbstractIn experiments in which diploid parthenogenetic mouse embryos cultured entirely in vitro from the one‐cell stage to the blastocyst were transferred to suitable recipients and maintained in “delay” for about 3 days before implanting. about 25–40% subsequently developed to somite‐containing stages. In all, over 30 such embryos were examined. Most were morphologically normal, and equivalent to fertilized development observed on the 9th–11th days of pregnancy. A few embryos, however, had neural tube abnormalities, but of greatest interest were two sets of monoamniotic monozygotic twins. It is unclear whether the twins in some way resulted from the parthenogenetic condition, or from the “delayed” state. The present examples are discussed in the context of previous observations of monozygotic twinning in the mouse and man.
Oscillatory activity of maturation promoting factor (MPF) in extracts of Rana pipiens eggs
Authors: Masui Yoshio 
Published: June 2005

AbstractDejellied Rana pipienseggs were crushed by centrifugation and clear extracts were prepared by further centrifugation at 150,000 × G for 2 h. The extracts were kept at 0°C for 2 to 3 weeks. At intervals during the storage period, 80‐nl aliquots were injected into ovarian oocytes to assay maturation promoting factor (MPF). In most cases, MPF activity disappeared from the extracts on day 3 or 4, but reappeared on the following days and persisted 2 or 3 days at high levels before disappearing again. The cycle of MPF activity in extracts was repeated fairly regularly a few times during storage of the extracts. The average period of the oscillation was 5.05 + 1.25 days. If a single extract was assayed by oocytes from different frogs, all the assays exhibited exactly the same patterns of changes in MPF activity during storage of the extract. This indicates that the oscillations in MPF activity observed during storage of the extracts reflect changes in MPF activity intrinsic to the extracts, rather than fluctuations in the sensitivity of recipient oocytes to MPF. The reappearance of MPF activity in stored extracts was sensitive to Ca and dependent on Mg ions. The MPF activity that recurred periodically in cold‐stored extracts was indistinguishable from that contained in fresh extracts, since oocytes induced to mature by the recurring MPF activity had chromosomes condensed to meiotic metaphase and were capable of cleavage when injected with a sperm suspension. The oscillatory behavior of MPF activity observed in this study may be comprehended on a conceptual basis by aid of a kinetic model.
In vitro ovulation of hamster oocytes depends on contraction of follicular smooth muscle cells
Authors: Talbot Prudence , Chacon R. S. 
Published: June 2005

AbstractSmooth muscle cells (SMC) of the hamster follicle contract prior to ovulation, and their contraction produces a V‐shaped constriction in the base of the follicle. We have determined when basal constrictions first appear in follicles removed from females at various preovulatory times by examining stained, thick sections with a brightfield microscope. The time to ovulation was controlled by injecting the female with human chorionic gonadotropin (hCG). The shape of the follicle was classified as flat, small V, medium V, or large V depending on the size of the basal constriction. Twenty‐nine out of 30 follicles removed 12 hours after the hCG injection had flat bases or small V‐shaped constrictions. However, by 12.5 and 13.0 hours after hCG injection, 45 and 54%, respectively, of the follicles had medium and large V‐shaped constrictions in their bases. Transmission electron microscopy was used to confirm that flat follicles had uncontracted SMC, follicles with small V's had uncontracted or slightly contracted SMC, and follicles with medium and large V's had highly contracted SMC. When 12 hour follicles were removed from females and cultured in vitro, ovulation did not occur. Microscopic examinations showed that SMC had not contracted in these follicles during culture. Some (36.6%) 12.5 hour follicles and most (69.9%) 13 hour follicles ovulated when cultured in vitro. The majority of those which failed to do so, did not have contracted SMCs. We interpret these data to mean that in hamsters follicular SMC begin to contract in some follicles between 12–12.5 hours after the hCG injection. If contraction has begun in vivo, then the ovary may be removed from the female and ovulation will occur during in vitro culture. If contraction has not begun in vivo, it will not do so using the in vitro conditions described in this study and ovulation will not occur. These observations are consistent with the idea that the contraction of follicular SMC is necessary for hamster ovulation, and suggest that either stretch or neurotransmitters may initiate SMC contraction in vivo.
Neural crest ablation and limb morphogenesis
Authors: Shoobridge R. , Velkou D. , McCredie J. 
Published: June 2005

AbstractLeft caudal neural crest was ablated by diathermy in 2‐day‐old chick embryos, to injure the region of sensory sciatic innervation before the appearance of the hind‐limb bud. Embryos were fixed immediately, 24 hr and 14 days later, for examination of the effects of the ablation upon neural crest, neural tube, somitic mesoderm, and subsequent limb development. All embryos examined immediately and at 24 hr after ablation showed damage to the left neural crest, but the injury extended deeper into neural fold or tube, across the midline, and into somitic mesoderm. Of 17 chicks which survived to 16 days, 7 had gross deformity of the left leg and 10 had morphologically normal legs. Deformed chicks had a significant reduction in the mass of dorsal root ganglia on the operated side but no reduction in the area of the spinal cord. Operated chicks without limb deformities showed reduction of spinal cord but not of dorsal root ganglia. This suggests that limb morphogenesis may be quantitatively related to neural crest but not to neural tube. This possibility is considered in the light of previous publications. However, the experimental limitation of the diathermy method leaves the final conclusion open to interesting speculation and to future examination by improved experimental design.
Scaling of the brain and the eye cooling system in birds: A morphometric analysis of the Rete ophthalmicum
Authors: Midtgård Uffe 
Published: June 2005

AbstractA morphometric analysis has been made of the rete ophthalmicum which is a functional arteriovenous heat exchange system in the heads of birds. The morphological data were obtained from histological sections of the rete from 40 species of birds covering a weight range of 20,000‐fold. The maximal number of retial arteries, the length, the diameter of the arteries, the total arterial cross‐sectional area, and the maximal exchange area have been expressed in terms of allometric equations. Other parameters important for the countercurrent heat exchange effect have been estimated or calculated. By use of simple physical laws for ideal heat exchangers, it is shown that the temperature decrease of the arterial blood passing the rete is rather constant over a wide range in body weight, but larger than previously reported body‐to‐brain temperature differences. The results are consistent with the heat exchange function of the rete and provide support for the idea that the rete, besides serving as a cooling system for the brain, also may be important in reducing heat loss from the eye.
Studies on factors affecting the timing of early morphogenetic events during starfish embryogenesis
Authors: Mita Izumi 
Published: June 2005

AbstractEggs of the starfish Asterina pectinifera were divided into two equal‐sized parts with fine glass needles after the first polar body formation, and nucleate halves were fertilized. Half embryos thus formed continued to divide and developed into morphologically normal, but dwarf bipinnariae. In order to explore possible mechanisms which determine the time of onset of early morphogenetic events, the timing of initiation of asynchronous cleavages, blastulation, and gastrulation was compared between half and whole embryos. The following results were obtained: (1) half eggs divided synchronously until the ninth cleavage, but the asynchronous cleavages started one division earlier in half embryos compared with whole embryos; (2) blastulation started at the 256‐cell stage in both half and whole embryos; (3) half embryos initiated gastrulation at almost the same time as did whole embryos; and (4) the average number of constituent cells of half gastrulae was about 2500, while that of normal gastrulae was about 4500. These results indicate that (a) the start of the asynchronous cleavages, is closely associated with the nucleocytoplasmic ratio, but not with the number of cell divisions; (b) the timing of blastulation is not affected by the altered nucleo‐cytoplasmic ratio; and (c) the timing of gastrulation is not determined by the number of cell divisions.
Neural differentiation in fly CNS transplants cultured in vivo
Authors: Nässel D. R. , Sivasubramanian P. 
Published: June 2005

AbstractTo study the influence of afferent retinal innervation on neuronal organization in the CNS during differentiation in the fly Sarcophaga bullata, we transplanted larval CNS with or without eye imaginal discs into freshly pupariated animals. After metamorphosis and eclosion of the adult flies, the transplants were recovered and analyzed histologically.Optic lobes transplanted with eye disc differentiated fully like normal in situ optic lobes. In transplants without discs the outermost optic neuropil, the lamina, did not differentiate at all, and the more central ones, medulla, lobula, and lobula plate, were reduced in volume. Although certain neuron types present in normal optic lobes could be identified, the strict columnar and layered organization of these neuropils was no longer apparent in the eyeless transplants.The experiments confirm the earlier notion that afferent innervation strongly influences normal differentiation in the peripheral optic lobes of insects, whereas more central neuropil regions are less dependent on the retinal innervation. In addition, we show that the formation of the normal pattern of dendritic arborizations as well as strict columns and layers in these lobes seems to require retinal and/or laminar input.
Keratin diversity in the reptilian epidermis
Authors: Wyld Jean A. , Brush Alan H. 
Published: June 2005

AbstractThe ϕ keratins extracted from individual turtles and snakes were compared. The extent and nature of the molecular differentiation associated with the production of structurally distinct epidermal tissues was determined. The electrophoretic comparisons, molecular weight, and chemical fractionation indicate that these tissues contain unique proportions of the constituent keratin monomers specific to each species. This pattern of differentiation is similar to that previously observed for avian scale, claw, and beak, and for mammalian horn and hoof. This suggests that several “scale‐like” structures with distinctive chemical properties may be produced by a single individual without the synthesis of wholly unique proteins. The implications of these observations for the evolution of mammalian hair and avian feathers are discussed.
Obligatory hibernation for completion of vitellogenesis in the lizard Lacerta vivipara J.
Authors: Gavaud Jacqueline 
Published: June 2005

AbstractHibernation in Lacerta vivipara from Massif Central (1,000–1,200 m) lasts 6–7 months and is immediately followed by vitellogenesis, gestation, and parturition within a short period of time (May–August). Suppression of hibernation by maintaining females in active life (food and high temperatures) inhibits the resumption of ovarian growth in spring: i.e., the reproductive system remains indefinitely refractory to high temperatures. In order for vitellogenesis to be completed, females need to hibernate below S–10°C with sufficient duration (“amount of cold” thresholds). The prolongation of the exposure of females to low temperature beyond the minimal stay gradually improves their ability to complete vitellogenesis: The number of females responding increases, and the heat requirement for the onset of ovarian growth decreases.
Limb regeneration to digit stages occurs in well‐fed adult newts after hypophysectomy
Authors: Tassava Roy A. 
Published: June 2005

AbstractExperiments were designed to determine the maximum survival time and extent of limb regeneration of well‐fed adult newts (Notophthal‐mus viridescens) after complete hypophysectomy.Adult newts were either well‐fed or fasted for 3 weeks at which time hypophysectomies were performed. Forelimbs were amputated 5 days posthypophy‐sectomy. Fasted hypophysectomized newts did not survive beyond 4 weeks, and limb regeneration was either absent or abortive. All of the well‐fed newts survived to 3 weeks posthypophysectomy, and even at 6 weeks posthypophy‐sectomy showed 30% survival. In the complete absence of the pituitary gland, many of the fed newts regenerated limbs to digit stages. It is concluded that pituitary hormones are not an absolute requirement for limb regeneration of adult newts. Newts in good nutritional condition at the time of hypophysectomy survive longer and their limbs regenerate to more advanced stages.