bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional specificity of anuran larval skin during metamorphosis: Transdifferentiation of tadpole tail‐epidermis
Authors: Kinoshita Tsutomu , Sasaki Fumie , Watanabe Kyozo 
Published: June 2005

AbstractDuring metamorphosis of the anuran tadpole, dorsal skin of the larva develops into adult back‐skin, whereas tail‐skin disappears simultaneously with resorption of the tail. Although it has been shown by transplantation experiments that the regional specificity is intrinsically determined in the respective skin, survival of a tail‐skin graft to the body has also been reported. In order to resolve the contradiction, developmental changes of back‐and tail‐skin grafts transplanted to the same tadpole were examined using an electron microscope. Back‐skin transplanted to the tail developed into adult‐type back‐skin, regardless of degeneration of the surrounding tail tissue. When tail‐skin was transplanted to the back region, collagen layers of the dermis degenerated during the early stage of metamorphosis. As metamorphosis progressed, however, fibroblasts derived from the adjacent back region formed collagen fibers in the subepidermis and the new dermis slowly replaced the regressive graft dermis. Epidermis of this tail‐skin graft remained intact, transforming into flattened epithelium and some epidermal cells clearly proliferated during metamorphosis. Furthermore, the epidermis formed secretory glands that are characteristic of adult back‐skin and survived even after metamorphosis. These results suggest that the tail‐epidermis is able to survive if the tissue is translocated under appropriate conditions prior to the beginning of tail resorption.
Selective sequestration of an oviductal fluid glycoprotein in the perivitelline space of mouse oocytes and embryos
Authors: Kapur Raj P. , Johnson Lincoln V. 
Published: June 2005

AbstractPreviously, we identified a 215 kd glycoprotein, GP215, which is associated with postovulatory oocytes and embryos, but not with preovulatory oocytes (Kapur and Johnson, '85). In this paper a polyclonal antibody that specifically recognizes GP215 has been used to study the distribution of the molecule in association with ova and preimplantation embryos and in the female reproductive tract. GP215 is present in epithelial cells lining the cranial portions of the oviduct and in oviductal fluid, ovarian bursal fluid, and medium conditioned by oviductal tissue in vitro. Immunofluorescence assays of the ovum and early embryo show that GP215 is sequestered in the perivitelline space. Since preovulatory oocytes exposed to bursal fluid in vitro acquire GP215, we hypothesize that GP215 is synthesized and secreted by the oviductal epithelium and secondarily associates with the ovulated oocyte. Sequestration of GP215 within the perivitelline space is relatively specific since mouse serum albumin, a major constituent of oviductal fluid, and other high molecular weight proteins are not similarly retained. These observations indicate that the composition of the perivitelline space may be significantly different from the greater environment external to the zona pellucida such that fertilization and early development of mammalian ova potentially take place in a distinct perivitelline microenvironment.
Properties of muscle phosphorylase b from a hagfish, Paramyxine atami
Authors: Yonezawa Satoshi 
Published: June 2005

AbstractPhosphorylase b was purified to homogeneity from the muscle of a hagfish (Paramyxine atami), as judged by electrophoretic and immunological criteria. The purified enzyme was partially but not fully activated by AMP, and its conversion into the a form resulted in a three‐fold increase in activity. The enzyme was stimulated by SO42−, and kinetic experiments showed that SO42− markedly increased the affinity of enzyme toward substrates: in the presence and absence of 0.35 M SO42−, the apparent Km values of hagfish phosphorylase b were 0.04 and 1.3% for glycogen, 8.7 and 66 mM for glucose 1‐phosphate, and 0.05 and 1.0 mM for AMP, respectively.Electrophoretic and immunological data indicated that the hagfish possessed a single molecular form of phosphorylase, like the lamprey. Some immunological relatedness between the hagfish enzyme and the enzyme from lamprey or skate was demonstrated.
Enzymatic esterification of exogenous retinol and 3,4‐didehydroretinol in the retinal pigment epithelium
Authors: Tsin Andrew T. C. 
Published: June 2005

AbstractThe kinetics of esterification of exogenous retinol by cell membranes prepared from the crude homogenate of the frog retinal pigment epithelium was studied. The formation of retinyl palmitate from added retinol was directly assayed by high performance liquid chromatography (HPLC). A linear relationship was observed between the amount of protein (up to 2 mg) in the incubation medium and the amount of retinyl palmitate formed. At room temperature, this reaction took less than 2 hours to complete. By varying the substrate concentration in the incubation medium, the reciprocal of initial velocity of the reaction (nmol retinyl palmitate formed per hour) was plotted against the reciprocal of substrate concentration (nmol of retinol). This double‐reciprocal plot shows that the apparent Km of the reaction was 10 μM with an apparent Vmax of 9.1 nmol of retinyl palmitate per hour per mg protein. When this assay was repeated in the presence of 3,4‐didehydrortinol (20 μM), the kinetics of the reaction showed the pattern of that of a competitive inhibitor, suggesting that 3,4‐didehydroretinol competes with retinol for the same active site for esterification. The esterification of 3,4‐didehydroretinol resulted in the formation of 3,4‐didehydroretinyl palmitate, which was also measured by HPLC. The amount of 3,4‐didehydroretinyl palmitate formed by this reaction decreased in proportion to increased retinol concentration in the incubation mixture. This further confirms that a competition exists between the esterification of retinol and 3,4‐didehydroretinol by retinal pigment epithelium of the frog.
Observations on fissiparity and spontaneous regeneration in two strains of agamic planarians (Dugesia gonocephala and Dugesia tigrina)
Authors: Zaccanti Francesco , Farne' Patrizia 
Published: June 2005

AbstractCephalic age “E,” fission interval “I,” and the number of animals produced at any fission crisis “S” have been defined as characteristic parameters for the fission cycles in two strains of agamic planarians (Dugesia gonocephala and Dugesia tigrina). Variations of weight, total amount of DNA, and total amount of RNA during standard fissiparous cycles have been measured for the same strains. The following results have been obtained. 1) The cephalic age “E” influences fissiparous reproduction: in samples of D. gonocephala, using heads regenerated for 10 months or more, the number of animals produced at any fission crisis “S” increases; by contrast, the fission interval “I” decreases in samples of D. tigrina with heads regenerated for 3 month or more. 2) The fissiparous cycle may be divided into three periods, based upon variations in weight and the total amount of DNA; an increase of these quantities was observed during the middle period. 3) Two periods of accumulation of RNA were observed at approximately the middle and the end of the fissiparous cycle, respectively. The results have been interpreted according to a model that involves a negative cephalic control of fissiparity and a preliminary organisation of regenerative blastema during the last part of the fissiparity cycle.
Stages and rates of normal development in the holostean fish, Amia calva
Authors: Ballard William W. 
Published: June 2005

AbstractThirty‐one stages in the normal development of the “living fossil” bony fish, Amia calva, are morphologically defined so as to identify the length of time after fertilization. Experiments were conducted and their results recorded in a study of morphogenetic cell movements in early embryos of this species, as reported previously (Ballard, '84) and in a paper that follows this one in this volume. Rates of progress through these stages are charted at several fairly constant temperatures. External and internal cell displacements from late cleavage to early organogenesis are described from living material and serial sections. Apperarance and changes in organogenesis are also described from dissections of all later stages to the time of disappearance of the yolk and onset of feeding, and they are correlated with earlier published descriptions which were based on specimens inadequately defined by body length or time from fertilization or hatching.
Plasma prolactin, thyroxine, triiodothyronine, testosterone, and luteinizing hormone during a photoinduced reproductive cycle in mallard drakes
Authors: Sharp P. J. , Klandorf H. , McNeilly A. S. 
Published: June 2005

AbstractThe temporal relationships between plasma concentrations of prolactin, thyroxine (T4) and triiodothyronine (T3) were determined in a group of six wild mallard drakes during the development and maintenance of longday refractoriness after transfer from 6 h light: 18 h darkness (6L:18D) to 20L:4D for 24 weeks. As shown by changes in the plasma concentrations of luteinizing hormone (LH) and testosterone, the birds came into breeding condition and then became long‐day refractory within 5 weeks of photostimulation. Long‐day refractoriness was maintained for the remainder of the study. Plasma prolactin began to increase immediately after photostimulation, although not as fast as the increases in plasma LH and testosterone. The concentration of plasma T4 also increased after photostimulation but, as shown by decreased plasma LH and testosterone levels, only after the birds had become long‐day refractory. The development of long‐day refractoriness was thus directly correlated with an increased plasma prolactin and not with a change in plasma concentration of T4. Plasma T3 decreased after photostimulation but returned to prestimulation values as the birds became long‐day refactory and remained stable for the remainder of the study. Concentrations of plasma T4 and prolactin returned to baseline values after about 15 weeks photostimulation showing that the long‐term maintenance of long‐day refractoriness is not directly related to continuously high plasma concentrations of either hormone.
Effect of cytochalasin B and demecolcine on freeze–thaw survival of murine embryos in vitro
Authors: Prather R. S. , First N. L. 
Published: June 2005

AbstractThe effects of cytochalasin B (CB), a microfilament inhibitor, and demecolcine (DC), a microtubule inhibitor, on freeze‐thaw survival and culture survival of early cleavage stage mouse embryos, was evaluated. In the first experiment, eight‐cell mouse embryos were frozen in dimethylsulfoxide (DMSO) or DMSO + 0.1 μg/ml DC + 7.5 μg/ml CB. In the second experiment, eight‐cell embryos were dehydrated and cultured in the presence of either DMSO, DMSO + DC, DMSO + CB, or DMSO + DC + CB for 45 min prior to rehydration and culture to simulate the osmotic and chemical changes encountered during the dehydration and rehydration procedures, but without the consequences of freezing and thawing. In the third experiment, additional eight‐cell embryos were frozen in either DMSO, DMSO + DC, DMSO + CB, or DMSO + DC + CB. The survival of embryos frozen in DMSO (75%) was significantly higher (P < 0.01) than that of embryos frozen in DMSO + DC + CB (55%). No differences (P = 0.55) were observed after a 48‐hr culture period in the development of embryos dehydrated, cultured, and rehydrated but not frozen. Embryos frozen in the presence of both DC and CB had a lower (P = 0.06) survival rate (55%) than that of embryos frozen in the presence of DMSO, DC, or CB (˜ 70%). These results suggest that both microfilaments and microtubules have a role in maintaining the structural integrity of the plasma membrane during the freeze–thaw process and that the loss of either loss does not seem to be detrimental to survival, but the loss of both results in lower survival.
Forelimb regeneration in the postmetamorphic bullfrog: Stimulation by dimethyl sulfoxide and retinoic acid
Authors: Cecil Mark L. , Tassava Roy A. 
Published: June 2005

AbstractTo examine the effects of retinoic acid and dimethyl sulfoxide on regenerative ability of anuran amphibians, the left forelimbs of 60 postmetamorphic froglets of Rana catesbeiana (bullfrogs) were amputated through the distal zeugopodium. Fifteen of the froglets had their left forelimb stumps immersed in dimethyl sulfoxide (DMSO) for 3 minutes, once immediately after amputation and once on each of 5 subsequent days. Another 15 frogs had their left forelimb stumps immersed in a 0.01 M solution of retinoic acid dissolved in DMSO for the same period of time. The remaining 30 control froglets received no treatment to their forelimb stumps. The untreated group of froglets did not regenerate structures distal to the amputation surface, while all limbs in both treated groups produced regenerates by 120 days postamputation. Regenerates of limbs treated with both DMSO alone and DMSO combined with retionic acid, although hypomorphic, were composed of multiple cartilage elements, which in many cases (46.7%) were organized as patterns partially resembling the skeletal arrangement of a normal forelimb. All of these regenerates exhibited bundles of striated muscle. In addition, nearly half (46.7%) of the regenerates in the DMSO + retinoic acid group possessed two separate regenerate outgrowths. The results demonstrate that young bullfrogs (Rana catesbeiana) possess a latent epimorphic regenerative capability, which can be stimulated by topical application to the wound surface of DMSO alone or DMSO combined with retionic acid.
Adipose tissue of Drosophila melanogaster: VII. Distribution of nuclear DNA amounts along the anterior–posterior axis in the larval fat body
Authors: Butterworth F. M. , Rasch E. M. 
Published: June 2005

AbstractThe DNA content of fat body nuclei was measured cytophotometrically as a function of position along an anterior–posterior (A–P) axis of the tissue throughtout larval development. There was a dramatic 55‐fold increase in the average amount of DNA per nucleus during the first 3 days of this period, but there was no further increase during the final day. However, the rate of increase had regional specificity. The amount of DNA per nucleus correlated significantly with its position along the A–P axis of the tissue: nuclei in a posterior direction contain gradually increasing amounts of DNA. There was up to a seven‐fold difference between the smallest anterior and largest posterior nucleus. In addition, for three of the ages studied there was a subgradient in the posterior region with a slope that was considerably steeper than that of the overall tissue gradient. The tissue has three characteristic morphological regions, anterior, medial, and posterior, which can be recognized early in development and which are maintained throughout the larval period. The distribution of nuclear DNA classes determined for cells in each region for the final 2 days of larval life became fixed before the final day of development. The significance of the DNA gradient in terms of a protein storage gradient is discussed.
Hight concentrations of methemoglobin in five species of temperate marine teleosts
Authors: Graham Mark S. , Fletcher Garth L. 
Published: June 2005

AbstractBlood samples from five species of marine teleosts were assayed for methemoglobin (metHb) levels during winter and summer acclimatization. There was at least 7% total hemoglobin in the met‐form in all species, and as high as 27% in one species, the Atlantic cod (Gadus morhua).There was significant seasonal variation in metHb levels for three of the five species, the highest values occurring during the winter months; cunners (Tautogolabrus adspersus) 15.6% in winter and 10.1% in the summer, shorthorn sculpin (Myoxocephalus scorpius) 20.0% in the winter and 8.19% in the summer, longhorn sculpin (Myoxocephalus octodecemspinosus) 17.3–21.6% in the winter and 8.12% in the summer. The winter flounder (Pseudopleuronectes americanus) and the Atlantic cod maintained metHb concentrations constant throughout the year: 13% and 27%, respectively.There does not appear to be any relationship between the activity of a fish and the level of metHb in its blood.
The ultrastructure and physiology of the tergotrochanteral depressor muscle of the housefly, Musca domestica
Authors: Schouest L. P. , Anderson M. , Miller T. A. 
Published: June 2005

AbstractThe gross morphology, ultrastructure, and the physiological properties of the tergotrochanteral depressor muscle (TTM) of the housefly are described. Under transmission and scanning electron microscopy, the TTM is a highly modified multinucleated tubular muscle of the synchronous class of insect muscle. Mitochondria appear few in number (5% of muscle volume) but there is an extensive sarcoplasmic reticulum (20% of muscle volume). Two types of neuromuscular junctions were observed, but these junctions are considered functionally similar. Three neurons innervate the muscle, and when the muscle is orthodromically stimulated, three well‐defined thresholds are observed. Under repeated stimulation, the TTM fatigues rapidly but recovers in a short time. The TTM has a long “length constant” of 132.1 μm, 7.3 μF/cm2 membrane capacity, and a specific resistance of 394 Ωcm2.The tergotrochanteral or “jumping” muscle has a behaviorally unique function. It is used only in the jump response preparatory to flight. TTM development is believed to have coevolved with an associated giant neuron to optimize the escape behavior response (response time 2.5 msec) in the housefly. The muscle has become specialized and more massive to increase the jump response. The TTM appears to be adapted physiologically and ultrastructurally for fast response and short twitch duration times.
A possible mechanism of action of 17β‐estradiol in stimulation of fertilization in vitro
Authors: Sjöblom Peter , Lindahl Per Eric 
Published: June 2005

AbstractThe effects of 17β‐estradiol (E2) on sperm‐egg interactions in the mouse were investigated. It was shown that E2 induces adhesiveness of the sperm head, expressed as sperm‐sperm and sperm‐egg binding. Since the concentration dependence of this process was similar to that observed for stimulation of in vitro fertilization by E2, it is suggested that induction of adhesiveness or initiation of processes that cause adhesiveness of the sperm head are of biological significance as preparatory steps for fertilization. Finally, the content of E2 in mouse eggs was determined and found to be 0.2 pg/egg, equally distributed between the oocyte together with the zona pellucida and the follicular cells with their associated intercellular matrix. The intraovum concentration is estimated as 10−6 M.
The releasing action of calcium upon cyclic AMP‐dependent meiotic arrest in hamster oocytes
Authors: Racowsky Catherine 
Published: June 2005

AbstractThe effect of increasing cytoplasmic calcium on cyclic adenosine monophosphate (cAMP)‐dependent meiotic arrest (%GV where GV is germinal vesicle) in hamster oocytes was investigated. The hypotheses tested were that 1) calcium is required for the spontaneous maturation of hamster oocytes, 2) elevation of calcium in the oocyte‐cumulus complex can antagonize cAMP‐dependent meiotic arrest, and 3) the intraoocyte level of cAMP remains unchanged, but heterologous metabolic coupling decreases, concomitant with calcium‐stimulation of germinal vesicle breakdown (GVBD). Levels of cAMP were elevated by culturing cells in the presence of dibutyryl cAMP (dbcAMP), isobutylmethylxanthine (IBMX) or forskolin and intracellular levels of calcium were manipulated by altering the CaCl2 concentration in the medium and/or by utilizing EGTA or A23187. Intracellular cAMP was determined by RIA, functional metabolic coupling was assessed by determination of the fraction of radiolabeled uridine marker transferred from the cumulus mass to the fraction of radiolabeled uridine marker transferred from the cumulus mass to the oocyte, and meiotic stage was determined cytogenetically.Compared with the proportion of oocytes that underwent meiotic maturation in control medium containing 1.53 mM CaCl2, that of cumulus‐free (denuded) oocytes was unaffected by culture in the absence of added CaCl2, while that of cumulus‐enclosed (intact) oocytes was significantly decreased (%GV = 59.5 ± 4.8 and 4.2 ± 0.9 in 0 and 1.53 mM CaCl2, respectively, P < 0.001, where GV is germinal vesicle). EGTA prevented, in a dose‐dependent manner, the spontaneous maturation of denuded oocytes that occurred in 0 mM CaCl2 (ID50 = 0.05 mM, where ID50 is the dose of EGTA that inhibited GVBD in 50% cultured oocytes). In contrast, compared with the control, less than 1 mM EGTA failed to increase the %GV of intact oocytes, although 5 mM EGTA significantly increased meiotic arrest. The %GVBD of oocytes cultured in medium containing 0 mM CaCl2 was dose‐dependent on A23187 for both intact oocytes (ID50 = 3.0 μM) and for denuded oocytes cultured in the presence of 0.5 mM EGTA (ID50 = 2.7 μM). Elevated extracellular calcium significantly antagonized dbcAMP‐maintained meiotic arrest in both types of oocyte and the %GV was significantly correlated with the pH of the medium [(r) = −0.78 and −0.60 for intact and denuded oocytes, respectively, P < 0.001 in both cases]. Both CaCl2 and A23187 induced dose‐dependent antagonistic effects on forskolin‐maintained meiotic arrest in intact oocytes but neither antagonism was accompanied by significant dose‐dependent decreases in either the intraoocyte content of cAMP or the extent of heterologous metabolic coupling. These data indicate that calcium plays a central regulatory role in meiotic resumption in hamster oocytes but that the action of this cation is not mediated by modulation of the level of cAMP within the oocyte.
Avian spermatozoa penetrate zona‐free hamster oocytes In vitro
Authors: Samour Jaime , Moore Harry D. , Smith Caroline A. 
Published: June 2005

AbstractAfter collection from the cloaca of adult males, budgerigar spermatozoa were incubated in modified BWW medium at pH 8.3. By light microscopy, many spermatozoa (> 100 per oocyte) were seen to be bound to the oolemma, and a small proportion (1–2 spermatozoa) were judged to have undergone fusion and penetration of the vitellus, as indicated by complete decondensation of their chromatin. The latter finding was confirmed at the electron microscope level by the presence of sperm nucleus, midpiece and tail in egg cytoplasm. This finding is discussed in relation to events at fertilization in the different Phyla.
New function for the granular skin glands of the eastern long‐toed salamander, Ambystoma macrodactylum columbianum
Authors: Williams Thomas A. , Larsen John H. 
Published: June 2005

AbstractWhile it has been accepted for over 50 years that salamanders use their tails for fat storage, no caudal adipose tissue was detected in the eastern long‐toed salamander, Ambystoma macrodactylum columbianum. We provide evidence to show that a proteinaceous material, sequestered in the epidermally derived caudal granular skin glands, is the storage product. An increase in the size of these glands, at the expense of fat deposits in the tail, is interpreted as a solution to a conflict between two of the tail's major functions: nutrient storage and predator deterrence. Loss of caudal lipid allows for larger granular glands. With more secretory product available for defense, the possibility of the salamander's surviving an encounter with a predator is apparently enhanced. Storing protein is energetically beneficial because salamander diets are primarily protein, and its has been demonstrated by previous investigators that converting protein to fat for storage is metabolically inefficient.