bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scanning electron microscopy of primordial germ cells in early chick embryos
Authors: Lee Hsin‐Yi , Nagele Robert G. , Goldstein Mark M. 
Published: June 2005

AbstractPrimordial germ cells (PGCs) of the early chick embryo were examined using scanning electron microscopy. Temporal changes in the form and distribution of surface projections were found to be correlated with migratory phases of PGCs. Non‐migrating PGCs were spherical to ovoid with relatively smooth surfaces. Their transition to the migratory phase was first evidenced by a burst of membrane activity. Migrating PGCs became somewhat flattened against the underlying hypoblast (which serves as the substratum for their migration) and exhibited blebs and lamellar processes. The lamellar processes were most prominent at the leading edges of actively migrating PGCs. Overall results of the present study indicate that PGCs found in the germinal crescent area of early chick embryos actively migrate on the dorsal surface of the hypoblast towards posterior embryonic regions.
Glucose effect on respiration: Possible mechanism for capacitation in guinea pig spermatozoa
Authors: Rogers B. Jane , Chang Lana , Yanagimachi Ryuzo 
Published: June 2005

AbstractGuinea pig sperm respiration was determined in minimal capacitation medium (MCM) with different energy sources. The ZO2 observed for spermatozoa suspended in media containing pyruvate and lactate was 35.7 ± 5.9, pyruvate alone, 27.9 ± 3.8 and D‐glucose alone 3.4 ± 1.1. When D‐glucose was added to spermatozoa rapidly respiring in media containing pyruvate as the only exogenous energy source, an immediate suppression in respiration was observed. Further reduction was caused by continued addition of D‐glucose. Fructose and mannose also produced a suppression in respiratory rate. However, lactose, fucose, sucrose, L‐glucose, and galactose did not alter the respiratory rate. The suppression of respiration by metabolizable sugars is paralleled by a suppression of acrosome reaction in guinea pig spermatozoa. The possibility that suppression of respiration is the mechanism for retardation of capacitation and the subsequent acrosome reaction by D‐glucose and other metabolizable sugars is suggested.
Peroxidase absorption in the ascidian gut
Authors: Burighel Paolo 
Published: June 2005

AbstractProtein absorption in the colonial ascidian Botryllus schlosseri was investigated by electron microscopic cytochemistry using horseradish peroxidase (HRP) as a tracer. Colonies were kept in HRP dissolved in seawater; entire guts were excised at selected intervals and processed for electron microscopy using the technique of Graham and Karnovsky for demonstration of HRP activity.The absorption of HRP takes place in cells of the stomach and intestine, characterized by brush borders and large supranuclear vacuoles (vacuolated cells). Zymogenic cells and mucous cells did not show evidence of HRP uptake.In the vacuolated cells HRP is absorbed by pinocytic invaginations of the apical plasmalemma and appears to be localized in numerous apical microvesicles, in subapical macrovesicles and in the large supranuclear vacuoles. It appears probable that the macrovesicles and vacuoles are important sites of intracellular digestion. However, some differences in ultrastructure and in the pattern of HRP uptake were observed between vacuolated cells of the distal intestine and those of the stomach and proximal intestine.The results indicate that ascidians are able to absorb macromolecules which are naturally occurring in the gut or derive from incomplete extracellular digestion.
Histochemical evidence for enzyme differences in crustacean fast and slow muscle
Authors: Ogonowski Mark M. , Lang Fred 
Published: June 2005

AbstractHistochemical techniques were developed for characterizing fast and slow muscles of crustaceans. When crayfish or lobster abdominal muscles were tested for myofibrillar ATPase activity, fast muscle stained darkly and slow muscle stained lightly. When tested for NADH diaphorase activity, as a sign of oxidative capacity, slow muscle stained darkly around the sarcolemma while fast muscle stained lightly. In contrast, the results suggested that swimmeret muscles are more heterogenous in their properties. These histochemical techniques provide a simple but efficient method for elucidating the enzymatic profile of crustacean muscles. They should prove useful for characterizing the diversity of these muscles and for investigating the causes of this diversity.
Sexual differentiation and germ cell transfer in the colonial ascidian Botryllus schlosseri
Authors: Sabbadin Armando , Zaniolo Giovanna 
Published: June 2005

AbstractThe sexual differentiation in the colonial ascidian Botryllus schlosseri was considered with respect to colony sexualization and sexualization of the single zooids of the same blastogenic generation.The colony sexualization was investigated histologically in a series of young colonies reared in the laboratory and fixed periodically throughout a sequence of blastogenic generations. The newly set colonies lack gonad blastemata; next, germ cells appear and several generations are involved in various phases of hyposexuality prior to the appearance of generations in which mature both eggs and sperm.The sexual contribution of the zooids of the same generation was found to vary according to an intrinsic bilateral asymmetry (the gonadogenic potential differs both contralaterally in each zooid and between zooids of a different, dextral or sinistral, parental origin) and in proportion to the quantity of germ cells that have been transferred from preceding generations.The transfer of germ cells from one to the following generations was investigated by fusing colonies of opposite pigment genotypes, then crossing the separated parabionts to a common genotype, and scoring the offspring pigment phenotypes. This experiment has shown that not only immature oocytes but also undifferentiated cells were exchanged between the parabionts and then gradually matured as eggs or sperm in a prolonged series of generations.The primordial germ cells differ in size from hemoblasts, the source of hemocytes. However, further experiments are needed in order to decide between the two contrasting hypotheses of germ cell origin: either segregation from the atrial epithelium of buds or development from hemoblasts.
Rathke's pouch morphogenesis in the chick embryo
Authors: Jacobson Antone G. , Miyamoto David M. , Mai S.‐H. 
Published: June 2005

AbstractOrigin of Rathke's pouch ectoderm is complex. Anterior neural ridge and plate extend and reflect ventrally, then caudad, under the head into the subcephalic pocket. At least pouch roof and part of the walls form from ventral neural ridge. Pouch roof anchors to brain floor along the ventral suture line. Pouch tip, floor, and the rest of the walls are from stomodeal ectoderm. Pouch tip anchors to prechordal plate, and floor to Seessel's pocket along the midline.The prosencephalon bulges ventrally, bending attached pouch roof at right angles to pouch floor. The pouch tip is a pivotal point about which the head of the embryo enfolds. Cranial flexure bends the head ventrally, then caudad, folding the pouch roof parallel to its floor. Prosencephalon floor elongation stretches attached pouch roof. That these forces help form the pouch is shown in experiments in which parts are surgically altered, or glass rods are placed in brain cavity or in the foregut to stop the movements and thereby affect pouch formation.Pouch wall formation is due to accumulation of mesenchyme beneath lateral, unattached ectoderm. The full length of pouch floor ectoderm is present in early embryos and is gradually incorporated into the pouch as the walls form. The pouch does not invaginate nor change its position relative to the brain floor. The true infundibulum evaginates from brain floor over the pouch tip on the fifth day of incubation, which also is when an earlier, more caudal structure called “infundibulum” disappears.
The induction of collagenase and acid phosphatase by thyroxine in resorbing tadpole gills in vitro
Authors: Derby Albert , Jeffrey John J. , Eisen Arthur Z. 
Published: June 2005

AbstractExplants of tadpole gills were cultured in Hanks balanced salt solution or in Hanks supplemented with thyroid hormone. Gills in control media maintain their integrity in vitro while those treated with thyroxine undergo resorption. The activity of collagenase in the media increases in parallel with thyroxine induced resorption and is accompanied by a decrease in tissue collagen levels. T4 induced gill resorption is also associated with an increase in the specific activity of acid phosphatase. However, this increase is not the result of a significant increase in total enzyme activity but rather the result of a differential loss in total protein concentration in thyroxine treated gills as compared to control.
Anhydrobiosis in nematodes: Permeability during rehydration
Authors: Crowe John H. , O'Dell Steven J. , Armstrong David A. 
Published: June 2005

Abstract1. Inorganic ions and primary amines are leaked from anhydrobiotic and quick‐dried nematodes, Aphelenchus avenae, when they are plunged from dry air into water.2. Anhydrobiotic nematodes leak about one‐third as fast as quick‐dried ones.3. When the water content is increased above about 20% by exposing the animals to moist air before immersing them in water, the leakage rate in both anhydrobiotic and quick‐dried worms is diminished.4. The rate of leakage is inversely correlated with the glycerol contents of the worms at the time they are placed in water.
In vitro development of core cells of the inner cell mass of the mouse blastocyst: Effects of conditioned medium
Authors: Atienza‐Samols Sui Bi , Sherman Michael I. 
Published: June 2005

AbstractBlastocysts submitted to two rounds of immunosurgery give rise to cores of presumptive ectoderm cells, many of which do not survive for more than 48 hours when cultured individually. Precoating of the culture plates with conditioned medium (CM) from PYS‐2 cells increases the incidence with which cores regenerate an outer layer. This procedure also improves the survival frequency of the cores, but only for a limited period of time. The small number of cores which survive for two weeks or more, either in uncoated or CM‐coated plates, give rise to an array of cell types, including giant cells resembling trophoblast.
Gonadotropin stimulation of the expansion of cumulus oophori isolated from mice: General condition for expansion in vitro
Authors: Eppig John J. 
Published: June 2005

AbstractGonadotropin Stimulation of the Expansion of Cumulus Oophori Isolated from Mice: General Conditions for Expansion In VitroThe hormonal stimulation of cumulus expansion (mucification) was studied using oocyte‐cumulus cell complexes isolated from Graafian follicles of C57BL/6J mice. Cumulus expansion was stimulated in vitro with human chorionic gonadotropin (HCG) and highly purified rat follicle stimulating hormone (FSH) in Whitten's medium containing fetal bovine serum (FBS). Highly purified rat luteinizing hormone failed to stimulate cumulus expansion. The 50% maximal stimulating concentration of FSH was found to be about 3–4 ng/ ml. Cumulus expansion was also stimulated by dibutyryl cyclic adenosine monophosphate (DBcAMP), but not by dibutyryl cyclic guanosine monophosphate or butyrate. Neither progesterone, testosterone, nor 17β‐estradiol stimulated cumulus expansion. Expanded cumuli were dispersed by hyaluronidase.The stimulation of cumulus expansion by FSH, HCG or DBcAMP required the presence of FBS. The active component of serum had a molecular weight greater than 10,000 daltons and did not require the association of a steroid for activity. Since DBcAMP does not stimulate cumulus expansion in the absence of FBS, it is suggested that the serum factor(s) is involved after the step of FSH stimulation of cAMP production by the complex.The cumulus does not expand if FSH is added to cultures after seven hours of spontaneous oocyte maturation, when the oocytes are at late metaphase I or early anaphase I of meiosis. Therefore, the changes which occur in the oocytecumulus cell complex during spontaneous oocyte maturation affect the ability of the complex to respond to FSH and bring about the expansion of the cumulus.
The Focal differentiation of pigment cells
Authors: Whimster I. W. 
Published: June 2005

AbstractA study has been made of the normal development and of the regeneration after excision of the groups of large pigment cells which form the spotted skin pattern of the gecko Eublepharis macularius, together with the effects of neonatal graft transplantation on this pattern. The results all indicate strongly that such groups of specialized pigment cells are not clones but the product of an induction process. This is then compared with the neural reflex mechanism by which the skin pattern of Chamaeleo dilepis is formed.
Autoradiographic and electron microscopic studies of minced cardiac muscle regeneration in the adult newt, Notophthalmus viridescens
Authors: Bader David , Oberpriller John 
Published: June 2005

AbstractThe regenerative response of minced cardiac muscle grafts in the adult newt was studied using autoradiography and electron microscopy. One‐sixteenth to one‐eighth of the newt ventricle was amputated, minced, and returned to the wounded ventricle. At five days after grafting, no reorganization of graft muscle pieces was apparent and there was degeneration of much of the muscle graft. Another, smaller population of 5‐day myocytes had euchromatic nuclei and intact sarcolemmae. In 10‐ and 16‐day grafts, continuity between ventricular and graft lumina was established and coalescence of graft pieces was apparent. Ultrastructurally, 10‐ and 16‐day graft myocytes appeared to have fewer myofibrillae and increased amounts of rough endoplasmic reticulum, polyribosomes, Golgi complexes, and dense bodies when compared to uninjured ventricular myocytes. The peak of proliferative activity of graft cells was observed at 16 days. Electron microscopic autoradiography revealed breakdown of myofibrillar structure in labeled myocytes, whereas in myocytes in the later stages of mitosis only scattered myofilaments and no Z bands were present. By 30 days, grafts appeared as an integrated structure composed primarily of cardiac muscle. Myocytes of 30‐day grafts were observed in various stages of myofibrillogenesis and contained numerous 10‐nm filaments. Seventy‐day graft myocytes had numerous well organized myofibrillae and intercellular junctions similar to those seen in uninjured ventricular myocytes.
Light‐induced acceleration of retina development in a mouth‐brooding teleost
Authors: Grün Gerd 
Published: June 2005

AbstractRearing animals in the dark had been shown to be either without effect on the development of the retina or to result in a reduction or a delay of retinal maturation. In the present study, the influence of light on a retina which normally develops under contitions of very dim light has been investigated. When 3‐day‐old embryos of the mouth‐brooding teleost Tilapia leucosticta are placed into a continuously lighted environment, from day 6 on, optic tract diameter and inner plexiform layer thickness increase up to day 10 or 12. In the dark‐reared retina, this increase occurs only after day 10. Similarly, synaptic junctions of the inner plexiform layer appear at about day 6 in the light‐reared retina and increase continuously on following days, whereas in the retina of embryos reared in darkness, they appear at day 7 and do not increase essenially before day 11. These and other data suggest that continuous light induces a precocious growth of retinal structures. The first differences between light‐ and dark‐reared retinae appear synchronously with the beginning of receptor cell development and prior to the first synaptic junctions. A nonneurally mediated effect of light on the retinal ganglion cells in consequently assumed.
Acrosin does not appear to be bound to the inner acrosomal membrane of bull spermatozoa
Authors: Shams‐Borhan Gabriele , Huneau Daniel , Fléchon Jacques‐Edmond 
Published: June 2005

AbstractFerritin‐conjugated soybean tryps in inhibitor was used for the ultrastructural localization of acrosin in bull spermatozoa following acrosomal disruption. The ferritin label was observed in the anterior segment of the acrosome in disrupted cells only. Emptied acrosomes were labeled, mostly on the external surface of their outer membrane. Labeling was also found on the material bound to detached acrosomal caps. However, at no time could the ferritin label be found on the inner acrosomal membrane. It is concluded that acrosin activity is not present on the inner acrosomal membrane but is lost from the acrosomal matrix as the acrosomal reaction proceeds.
Feeding in water snakes: An electromyographic study
Authors: Cundall David , Gans Carl 
Published: June 2005

AbstractSynchronized cinematography and electromyography were used to study feeding behavior in water snakes, Nerodia rhombifera and Nerodia fasciata. While these species swallow their prey by alternate movements of the right and left toothed bones of the skull, the muscles show bilateral asymmetric activity during each movement.Opening of one side of the mouth is initiated by protraction of the palatomaxillary arch and slight depression of the mandible. These movements serve to disengage the teeth from the surface of the prey and correlate with activity of the protractors of the palatomaxillary arch and quadrate. Continued opening results primarily from rotation of the braincase around its longitudinal axis. During the latter half of the opening phase, the rates of protraction of both palatomaxillary arch and mandible increase; this correlates with increased activity of the depressor mandibulae, several of the mandibular adductors and three of the four cervical muscles analyzed. The cervical muscles appear to restrain the prey during the fast segment of mouth opening when the toothed bones reach their maximum displacements from the surface of the prey.Closing of the mouth is initiated by rapid depression of the palatopterygoid joint which correlates with a cessation of activity of the levator pterygoidei. Immediately thereafter, the posterior end of the maxilla is depressed and slightly retracted and the mandible tends to be protracted and slightly adducted. These movements correlate with synchronized activity of the palato‐maxillary protractors, the pterygoideus and the depressor mandibulae. The rest of the closing phase consists primarily of adduction and retraction of the palatomaxillary and mandibular elements relative to the braincase; the toothed bones remain fixed to the surface of the prey while the braincase is moved forward. EMGs indicate that the complex bone movements of the latter stage of mouth opening and the initial stage of mouth closing are dependent upon the simultaneous firing of a number of morphologically antagonistic muscles.
Cyclic AMP derivatives stimulate the chondrogenic differentiation of the mesoderm subjacent to the apical ectodermal ridge of the chick limb bud
Authors: Kosher Robert A. , Savage Mary P. , Chan Sai‐Chung 
Published: June 2005

AbstractRecent studies indicate that one of the major functions of the apical ectodermal ridge (AER) of the embryonic chick limb bud is to maintain mesenchymal cells directly subjacent to it (i.e., cells extending 0.4–0.5 mm from the AER) in a labile, undifferentiated condition. Furthermore, when mesenchymal cells are freed from the AER's influence, either artifically or as a result of normal polarized proximal‐to‐distal limb outgrowth, they are freed to commence cytodifferentiation. In a preliminary attempt to investigate at a molecular level the mechanism by which the AER exerts its “negative” effect on the cytodifferentiation of subridge mesenchymal cells, we have examined the effect of a variety of agents that elevate cyclic AMP levels on the chondrogenic differentiation of the unspecialized subridge mesoderm of the limb bud in an organ culture system. Dibutyryl‐ and 8‐hydroxy‐cyclic AMP elicit a dose‐dependent increase in the rate and amount of cartilage matrix formation and a corresponding dose‐dependent increase in sulfated glycosaminoglycan accumulation by subridge mesoderm explants. The stimulatory effect of suboptimal concentrations of cyclic AMP derivatives is potentiated by the addition of theophylline. The stimulatory effect is limited to cyclic AMP derivatives, since dibutyryl‐cyclic GMP and 5′‐AMP have no effect. Thus agents that elevate intracellular cyclic AMP levels stimulate the chondrogenic differentiation of the unspecialized subridge mesoderm of the embryonic chick limb bud.
An ultrastructural study of epididymal mouse spermatozoa binding to zonae pellucidae in vitro: Sequential relationship to the acrosome reaction
Authors: Saling Patricia M. , Sowinski Janice , Storey Bayard T. 
Published: June 2005

AbstractMouse sperm bind to the zona pellucida of the egg prior to penetration of the zona and entry into the perivitelline space. The question then arises: when does the acrosome reaction occur relative to these processes? An Ultrastructural study of mouse epididymal sperm bound to the surface of the zona and in the privitelline space was undertaken to clarify this point. Cumulus‐free mouse eggs were inseminated in either a complete defined culture medium capable of supporting in vitro fertilization or in Tris/NaCl buffer containing Ca+2. Both media support sperm binding to the zona to the same extent; binding is complete in 15 minutes. Unbound sperm were removed by a step gradient density centrifugation to yield a preparation of eggs with sperm firmly bound. All sperm in the perivitelline space had undergone the acrosome reaction. Sperm bound at the surface of the zonae pellucidae of eggs recovered at ten minutes after insemination all had intact acrosomes. At 40 minutes after insemination, half of the sperm were intact; the other half were in the initial stages of the acrosome reaction. At 90 minutes after insemination, 12% of the sperm had undergone the full acrosome reaction and were starting to penetrate the zona; of the balance, half were in various stages of the acrosome reaction, while half were still intact. These findings support the hypothesis that the sequence of the early reactions leading to fertilization in the mouse is: intact sperm binding to zona; acrosome reaction at the zona surface; penetration of the zona.
Relationships between eye factors and lens‐forming transformations in the cornea and pericorneal epidermis of larval Xenopus laevis
Authors: Bosco Luigi , Filoni Sergio , Cannata Stefano 
Published: June 2005

AbstractLarval Xenopus laevis at stage 56 (Nieuwkoop and Faber, '56) were subjected to various types of lentectomy:

simple lentectomy, from the pupillary space after incision of outer and inner cornea;
lentectomy from the dorsal region of the eye;
lentectomy from the dorsal region of the eye and simultaneous incision of the outer cornea;
lentectomy from the dorsal region of the eye and simultaneous incision of the outer and inner cornea.
The results obtained show that the outer cornea underwent lens‐forming transformations only when the inner cornea had been incised, thus permitting direct communication between the lentectomized eye environment and the outer cornea (Experiments I‐IV). No lens regeneration occurred when the inner cornea was left intact (Experiments II, III). It was concluded that the factor(s) allowing the lens‐forming transformations of the outer cornea is not an aspecific nutritional factor(s) but a more specific factor(s) that cannot reach the outer cornea when the inner cornea is intact. Therefore, the absence of the lens and sufficient nutrient available to the outer cornea are not enough to allow lens regeneration from the outer cornea.When lens removal was carried out through the dorsal part of the eye (Experiments III‐IV) the lens regenerated from the pericorneal epidermis of this region in a large number of cases.