bluuebunny/crossref_metadata_2025 huggingface dataset:
Medroxyprogesterone, immunosuppression, and conceptus size in Peromyscus
Authors: Bell Floyd E. , Palmer Jennifer S. , Dawson Wallace D.
Published: June 2005

Effects of exogenous medroxyprogesterone acetate (MPA) on skin transplant retention and conceptus size were studied in the deer mouse, Peromyscus maniculatus, and the oldfield mouse Peromyscus polionotus. Daily injections of 2 mg MPA significantly prolonged survival of allografts in P. maniculatus and transspecific grafts between P. maniculatus and P. polionotus. Allografts were retained significantly longer than transspecific grafts (17.2 vs 12.4 days) on MPA‐treated P. maniculatus. Near‐term fetal and placental sizes and weights were not detectably influenced by daily 1‐mg MPA injections given to the mother from the 5th through the 19th day of pregnancy. The data are discussed relative to the possible immunosuppressive role of progestins in protecting the allogeneic conceptus from maternal immune rejection.
Sodium ion concentrations in uterine flushings from “implanting” and “delayed implanting” mice
Authors: Van Winkle Lon J. , Campione Allan L. , Webster Douglas P.
Published: June 2005

The uteri of mice were flushed with isotonic marnnitol (1) on the day of implantation during normal pregnancy or (2) during delay of implantation. The Na+ concentration in flushings was reduced during diapause but had increased by 65% 24 h after progesterone‐treated ovariectomized mice received estrogen injections. The results suggest that the apparent metabolic quiescence of diapausing blastocysts may, in part, be a consequence of lower (Na+) in the uterus during delay of implantation.
Cellular aspects of allograft rejection in marine sponges of the genus Polymastia
Authors: Van de Vyver Gysèle , Barbieux Bruno
Published: June 2005

Allograft rejection processes of two taxonomically related sponge species, Polymastia robusta and Polymastia mamillaris, have been studied at the cellular level. Grafts in parabiosis have been made by pairing papillae. They were investigated using histology and scanning and transmission electron microscopy.

In Polymatia robusta, allografts undergo progressive rejection with adhesion. A few days after grafting, archaeocytes and collencytes migrate toward the zone of contact and fall into line on either side of this zone. The narrow space which separates the grafted papillae is progressively filled up with collagen fibers thanks to which the parabionts are firmly held together. Allografts of Polymastia mamillaris never fuse to each other; the specimens are completely and directly rejected. In this species, the cell migration to the zone of contact is not followed by their alignment nor by deposition of a collagen layer. Autografts made in similar conditions succeed in all cases in both species.

These experiments demonstrate for the first time that sponges, even taxonomically closely related, may develop different but defined processes of rejection.
Adaptations for reflection of bioluminescent light in the gas bladder of Leiognathus equulus (perciformes: Leiognathidae)
Authors: McFall‐Ngai Margaret J.
Published: June 2005

The gas bladder of leiognathid fishes functions not only in buoyancy but also in reflection of bioluminescent light from the circumesophageal light organ. Purine distribution, quality (guanine/hypoxanthine ratio), and concentration, as the basis for reflectivity, were assayed enzymatically for different portions of the gas bladder lining of the common leiognathid, Leiognathus equulus (Forskal). For highly reflective areas, the percentage of tissue wet mass and dry mass represented by purine was also determined. The results indicate that total purine content in the reflective areas of the leiognathid bladder was significantly higher than values determined for other similar, shallow water fishes; instead, purine content in these reflective areas was similar to that known for very deep‐dwelling fishes, in which heavy purine deposition is correlated with high pressures and high oxygen concentrations in the bladder. In addition, the results show that differential purine distribution within the bladder correlates strikingly with the path of bioluminescent light. The dorsal bladder lining, the primary site of incident luminescence, had extremely high purine concentrations (averaging 2.80 mg/cm2), whereas the secondary reflective surfaces, the lateral (1.81 mg/cm2) and ventral (1.22 mg/ cm2) portions, although high in purine content, had concentrations significantly lower than the dorsum. Areas through which light is transmitted, the light organ‐bladder interface (0.09 mg/cm2) and the posterior region (0.19 mg/ cm2), were greatly reduced in purine content. The enhancement of purine in the reflective portions of the bladder and the correlation of the differential distribution of purines with the path of light indicate that the L. equulus gas bladder is exquisitely adapted to function as a reflector of bioluminescent light.
Immediate and delayed effects of vincristine administered during early postimplantation stages of murine embryogenesis
Authors: Wan Yu‐Jui , Wu Tsung‐Chieh , Damjanov Ivan
Published: June 2005

Vincristine was given to pregnant mice on day 7½ of pregnancy and the teratogenic effects of this treatment were assessed 2 and 3 days thereafter. Most of the embryos in litters removed on day 9½ of pregnancy (2 days after treatment) were morphologically normal, whereas on day 10½ most embryos were either developmentally retarded by the treatment or malformed. The morphologically “normal” embryos removed on day 9½ of pregnancy were cultured in vitro for 24 h. During this procedure more than 50% of them showed growth retardation or abnormal development. These data indicate that exposure of early postimplantation embryos to vincristine has an immediate teratogenic and embryocidal action, and also a delayed effect which becomes apparent only several days after exposure and following an ostensibly “normal” period of embryonic development.
Dynamics of pigment pattern formation in the zebrafish, Brachydanio rerio. III. Effect of anteroposterior location of three‐day lateral line melanophores on colonization by the second wave of melanophores
Authors: Milos Nadine , Dingle Allan D. , Milos Joseph P.
Published: June 2005

The mode of colonization of the lateral line melanophore band of the zebrafish, Brachydanio rerio, by the second wave of melanophores has been investigated. This stripe forms in two consecutive stages. First, there is an initial migration and reorientation of pigment cells in an anteroposterior wave into the site to form an interrupted stripe. Following this, a round of melanophores differentiates directly at the site and fills in the gaps between the initial cells. An analysis of the distributions of initial and second wave melanophores along the stripe site has shown that both groups of cells are selective as to localization. Initial wave melanophores colonize more anterior somite areas than do second wave melanophores. However, both groups of cells exhibit preferential colonization of the same anterior sites. It is suggested that second wave melanophores attempt to colonize the same somite areas of the stripe as the initial wave of melanophores but are forced to move to more posterior locations due to the presence of initial wave melanophores anteriorly. Observations were also made on later stages of development of the lateral line melanophore band. These melanophores retain the ability to migrate. Some of them reorient out onto the flank and contribute to the juvenile flank pigment pattern.
Correlation of increased intraacrosomal pH with the hamster sperm acrosome reaction
Authors: Working Peter K. , Meizel Stanley
Published: June 2005

This study describes investigations of the importance of intraacrosomal pH in the hamster sperm acrosome reaction (AR). Washed cauda epididymal sperm were capacitated in vitro in a medium containing 2 mM Ca2+, 144 mM Na +, and 3 mM K +. Such sperm underwent a significant increase in the number of AR within 10 min after the addition of the Mg2+ −ATPase (adenosine triphosphatase) inhibitors DCCD (20,μM) or NBD‐Cl (10 μM) or the proton ionophore FCCP (6 μg/ml) at 3.5 hr of incubation or after addition of NH4Cl (3 mM) at 4 hr of incubation. Addition of the mitochondrial electron transport inhibitor rotenone (2.5 μM) at 3.5 hr or of NaCl (3 mM) or KCl (3 mM) at 4 hr did not stimulate AR over control levels, suggesting that the stimulation of AR by the other compounds was not directly due to depletion of acrosomal adenosine triphosphate (ATP) or alteration of the acrosomal transmembrane potential. The AR also was not stimulated by either DCCD or FCCP added prior to 3 hr of incubation of sperm, whereas both compounds were increasingly effective at stimulating AR with increasing length of preincubation of sperm before the addition of the test compounds.

The intraacrosomal pH of sperm incubated in low [K+] (0.6–0.9 mM) for 3.5 hr rose by at least one pH unit (as measured with the fluorescent dye 9‐aminoacridine) within 15–30 min after raising extracellular [K + ] to 4.2–4.5 mM. The pH rise occurred even in the presence of the Ca2+‐chelator EGTA (2 mM). Either FCCP (8μg/ml) or DCCD (20 μM), but not rotenone (2.5 μM), plus K+ (3.6 mM), raised the intraacrosomal pH of sperm incubated for 3 hr in low [K+] within 10 min after addition. No pH rise occurred in the absence of additional K +.

These results demonstrate that the intraacrosomal pH of the hamster sperm becomes more alkaline in a process not requiring high concentrations of external Ca2+, but requiring K +. The results of this and previous studies lead us to suggest here that the intraacrosomal pH rise may be mediated via a change in K+ and H+ permeability of sperm head membranes, which allows K+ influx and H+ efflux, and via inhibition of an acrosomal Mg2+ −ATPase proton pump. We propose that the permeability changes and the consequent alkalinization of the acrosomal interior are important steps in late capacitation and/or the mammalian AR.
Cytokinesis: Furrowing activity in nucleated endoplasmic fragments of fertilized sand dollar eggs
Authors: Rappaport R.
Published: June 2005

When the sand dollar egg surface is extensively disrupted by contact with an expanding oil drop, and the egg contents are squeezed out by mechanical pressure, the denuded endoplasm is rapidly covered by a new surface. The original egg surface alters its appearance as the area that it covers diminishes, and the original and the new surfaces become different in appearance and behavior. If a mitotic apparatus is pushed into the endoplasmic fragment, the fragment surface undergoes furrowing activity, which is synchronous with typical cyclical changes in the appearance of the mitotic apparatus. In this circumstance, furrows develop later and progress more slowly than normal. Furrows formed soon after the operation usually regress, but those developing in conjunction with subsequent cell cycles are more nearly normal and are frequently permanent.
Preliminary investigations on the possible antimicrobial properties of tunicate blood cell vanadium
Authors: Rowley Andrew F.
Published: June 2005

Tunicates have the unique ability to accumulate and store metals such as vanadium. In the sea squirt, Ciona intestinalis, this element is stored in phagocytic blood cells termed granular amoebocytes and vacuolar hyaline amoebocytes. Incubation of bacteria and amoebocytes together results in the phagocytosis of these particles with subsequent fusion of the vanadium‐containing vaeuoles with the bacteria‐laden phagosomes. This process may be important in the intracellular digestion of such microorganisms.
Acid‐base balance and Na+ regulation in rainbow trout during exposure to, and recovery from, low environmental pH
Authors: Holeton G. F. , Booth J. H. , Jansz G. F.
Published: June 2005

Rainbow trout in simulated hard water were exposed to pH 4 for 4 days, followed by 3 days at pH 7, to evaluate both the effects of lowered water pH on the mechanisms of acid‐base balance and iono‐regulation, and the ability of the fish to recover from the pathophysiological consequences of this form of acid stress. Prior to the acid stress, the fish maintained a relatively constant internal acid‐base balance. Na+ was absorbed from the surrounding water. At pH 4 a net uptake of H+ ions from the water resulted in acidaemia combined with a significant reduction in plasma [HCO3−]. Plasma [Na+] increased for the first 24 hours of acid exposure before falling to levels significantly lower than the preacidification values. Hematocrit remained above the preacidification levels throughout the period of acid stress. Upon returning to pH 7 the normal acid‐base status was restored within 24 hours. Na+ was absorbed from the water, and plasma [Na+] returned almost to control levels within 24 hours. Hematocrit fell rapidly and remained depressed throughout the 3‐day recovery period. The results suggest that the physiological effects of short‐term exposure to low water pH are probably entirely reversible.
Entrainment of daily serum gonadotropin cycles in the goldfish to photoperiod, feeding, and daily thermocycles
Authors: Hontela Alice , Peter Richard E.
Published: June 2005

Female fish were kept under 16L:8D/20°C in November and April and the onset of light and/or feeding times were shifted by several hours in the experimental groups. Photoperiod and feeding entrained significant fluctuations in serum gonadotropin hormone (GTH) levels when the onset of light and the first daily feeding were 4 hr apart, but not when they were 10 hr apart. Fish were subjected to 16L:8D for 14–16 days in February, and to either a constant warm (20°C) or a diurnal sinusoidal (12–20°C) temperature regime, the warmth being imposed during photophase or scotophase. While relatively high, uniform serum GTH levels were found throughout the 24‐hr period in fish subjected to constant warmth, warm temperature during the day promoted fluctuations in serum GTH levels, and warmth during night resulted in relatively low, uniform serum GTH levels.
Immunohistochemical localization of laminin within the mouse ovary
Authors: Wordinger Robert J. , Rudick Victoria L. , Rudick Michael J.
Published: June 2005

Laminin, a noncollagenous glycoprotein, was observed in the mouse ovary using a direct immunofluorescence technique. Laminin was localized within the basal lamina underlying growing and atretic ovarian follicles, blood vessels, and the germinal epithelium. In addition, laminin was also present at the periphery of individual corpora lutea cells. The presence of laminin in the basal lamina underlying ovarian follicles may be important for the passage of material between the follicle cells and the connective tissue stroma. In addition, its location around the corpora lutea cells may reflect an involvement in cell to cell contact as well as intercellular communication.
Precocious hatching of Ilyanassa obsoleta embryos exposed to CaCl2 or KCl1
Authors: Sullivan Charles H.
Published: June 2005

Ilyanassa obsoleta embryos are enclosed within a maternally produced capsule until hatching around day 8 of development. Hatching occurs when a chemical hatching substance is released from embryos that dissolves the capsule plug, providing a means of escape for the embryos. The activity of the hatching substance can be detected in homogenates of prehatching embryos and its release can be rapidly triggered by incubating prehatching capsules in solutions of CaCl2 or KCl. With both homogenization and cationinduced release, hatching activity has been detected in embryos as early as day 5, 2 days before the onset of significant hatching. Therefore, the hatching substance is synthesized in advance of hatching, with release, rather than synthesis, being the controlling step in the hatching process.
Nuclear kinetics during cleavage in a dipteran egg
Authors: Lundquist Anders , Löwkvist Bertil
Published: June 2005

The numbers of intravitelline and periplasmic nuclei have been determined throughout pregastrular development in the Calliphora egg. The intravitelline nuclear divisions are synchronous and the peripheral divisions are parasynchronous. In spite of this, the total number of nuclei is lower than 2n from the middle part of intravitelline cleavage and onward. This is probably caused mainly by loss of nuclei during midintravitelline cleavage. Proportionally less important losses may occur during subsequent stages. The vitellophage nuclei are secondarily derived. Most of them are formed by the migration of nuclei from all regions of the syncytial blastoderm. This migration takes place mainly during the early part of the interphase following after the completion of the nuclear divisions. Vitellophage formation, the primary somatic differentiation process, is thus radically different in Calliphora and Drosophila. As a consequence, the total number of nuclei is higher just before gastrulation in the Calliphora egg.
Fertilization of mammalian eggs by sperm injection
Authors: Markert Clement L.
Published: June 2005

Mammalian sperm normally fertilize eggs in the ampulla of the oviduct after a long trip through the female reproductive tract. During this trip, the sperm become capacitated to fertilize but must overcome substantial barriers in the form of egg investments before reaching the plasma membrane of the egg. Once inside the egg the head of the sperm responds to cytoplasmic factors to decondense and form a pronucleus. All the problems of sperm penetration of the egg and its investments can be circumvented by injecting the sperm into the egg with a micropipette. Such injected sperm can participate normally in the subsequent events, typical of fertilized eggs, that lead to the formation of embryos. Sperm can also be injected into normally fertilized eggs to produce a third pronucleus and a triploid embryo.

To avoid the mechanical problems of capturing a swimming sperm with a micropipette, the sperm suspension can be sonicated to break off the sperm tails. The resulting sperm heads can easily be injected into unfertilized eggs to induce the normal events of fertilization. With these injection procedures it is possible to test the fertilizing capacity of foreign sperm, of defective sperm, and even of “dead” sperm. We have found that the phenotype of the sperm does not reflect the genotype in terms of fertilizing ability after microinjection. Immotile and grossly defective sperm of the mouse when injected into the egg produce the same reactions that are produced by fertilization with healthy robust sperm. Thus we conclude that the complex set of interactions normally required for sperm to penetrate the egg investments and to fertilize the egg are biologically unnecessary and can be circumvented by direct injection of the sperm into the egg.
Interspecific hybrids and chimeras in mice
Authors: Rossant J. , Croy B. A. , Clark D. A. , Chapman V. M.
Published: June 2005

Interspecific hybrids and chimeras in mammals provide unique tools for investigating problems in genetics and embryology, because of the degree of disparity between the two component genotypes. We have attempted to produce hybrids and chimeras between Mus musculus, the laboratory mouse, and Mus caroli, a wild species of mouse from Southeast Asia. M. musculus and M. caroli do not normally interbreed, although sterile hybrids can be produced at a low rate by artificial insemination. Extrinsic problems of genotypic incompatibility between the fetus and the maternal environment seem to be involved in poor hybrid survival, since M. caroli blastocysts also die when transferred to the M. musculus uterus. Death is associated with the generation of maternal T‐cells which are cytotoxic to M. caroli target cells in vitro. It is not yet clear whether this immune response is the primary cause of death or is secondary to breakdown of some other components of the fetal‐maternal interaction. It is clear, however, that it is the trophoblast layer that mediates survival or death of the foreign embryonic cells in the M. musculus juterus, since M. caroli inner cell mass cells can survive to term after injection into M. musculus blastocysts: Viable interspecific chimeras result. Even more convincing evidence is provided by the production of viable M. caroli offspring by trophoblast vesicle reconstitution using trophoblast of M. musculus genotype and inner‐cell mass of M. caroli type. Studies of properties of isolated trophoblast tissues have indicated that M. caroli trophoblast may differ from M. musculus in both its antigenic and immunosuppressive properties. Elucidation of trophoblast‐uterine interactions in these various interspecific pregnancies is being aided by the development of an in situ marker system, which can distinguish cells of the two species in sectioned material by in situ hybridization with a M. musculus satellite DNA probe. This same marker is also proving a very powerful tool for analyzing cell lineage development in chimeras.
Murine trisomy: Developmental profiles of the embryo, and isolation of trisomic cellular systems
Authors: Gropp A. , Winking H. , Herbst E. W. , Claussen C. P.
Published: June 2005

Many questions related to the development and the phenotypic expression of trisomy (Ts) are amenable to systematic investigation in a mouse model that allows the induction of Ts 1 to 19 by a breeding design of mice heterozygous for Robertsonian metacentric chromosomes. Some Ts do not survive the first critical phase of organogenesis on days 11 to 12 of fetal development; others as Ts 12, 14, 16, 18, and 19, have a life span until or beyond birth. Model type studies of the morphogenesis of developmental anomalies (e.g. craniocerebral, cardiovascular, or placental) are possible in Ts with a longer developmental span, and Ts 16 of the mouse is considered as a natural model of human trisomy 21. The eventual breakdown and death of the trisomic organism are inevitable. There is considerable interest to find ways for rescue and longer survival of Ts in competitive developmental systems, as e.g., in Ts ⟷ 2n blastocyst chimeras, or by isolation of trisomic cellular or tissue systems. Thus, the transfer of Ts hemopoietic stem cells of the fetal liver to irradiated adult recipients is a means of studying the functional capacities and maturation of trisomic hemopoiesis and lymphopoiesis. Both are almost completely restored by Ts 12, 14, 18, and 19 stem cell transplantation with survival periods of more than 6 months. But in other Ts, as of chromosomes 13 or 16, such capacity of reconstitution is impaired. The stepwise analysis of the effects of chromosome triplication on the cell level, in isolated functional systems and in the embryonic organism, is a promising way to understand the phenotypic expression of genome anomalies in complex developmental processes.
Placentation
Authors: Benirschke Kurt
Published: June 2005

Placental development differs greatly among members of different taxa. Not only does blastocyst attachment take place at different times, the penetration of trophoblast varies considerably. From an epitheliochorial relationship between fetus and mother to the hemochorial placentation of taxa, such as the higher primates, the trophoblast becomes increasingly exposed to maternal immune recognition which may be one cause of rejection in interspecific embryo transfers or hybridization. Shape of uterus and endometrium and genetic factors govern the morphologic form of the placenta. The paper reviews ungulate placentation, successes and failures of interspecific embryo transfers, and the scant knowledge of genetic determinants in primate placentas.
Energy metabolism of arthropods and mollusks during environmental and functional anaerobiosis
Authors: Gäde Gerd
Published: June 2005

During environmental anaerobiosis, when the whole organism is exposed to anoxic conditions caused by external, physical factors in the microhabitat, arginine phosphate, glycogen, and aspartate (only mollusks) are the substrates for the metabolism. Main end products formed are lactate (Crustacea, Xiphosura, some Gastropoda and Bivalvia), alanine, succinate, and the volatile fatty acids, propionate and acetate (most Gastropoda and most Bivalvia). Because of reduction of the overall metabolism in bivalves, utilization and production rates of substrates and end products, respectively, are low. They are generally faster in Crustacea, which do not reduce their metabolism.

During functional anaerobiosis, when the muscle tissue becomes anoxic because of increased work done by the animal, energy is derived from arginine phosphate and glycogen. The main end products formed are lactate (Crustacea), octopine (active Gastropoda and Bivalvia), and strombine/alanopine (some gastropod species). Utilization rates of the phosphagen and production rate of lactate and opines are sometimes more than 500‐fold higher than during environmental anaerobiosis. These strong variations in the glycolytic flux are probably regulated by the influence of the phosphagen and adenylates on regulatory enzymes and by the NADH/NAD ratio.
Cell multiplication and blastoderm development in relation to egg envelope formation during uterine development of quail (Coturnix coturnix japonica) embryo
Authors: Stepińska Urszula , Olszańska Bozenna
Published: June 2005

The relationship between the number of cells and blastoderm development to the formation of the egg envelopes is established for the uterine period of quail embryogenesis. On the basis of this relationship, the developmental stage of the embryo can be estimated without destroying the egg or dissecting the embryo. Data are also presented on the number of cells in the quail embryo at the time of egg laying and during the first hours of incubation. These data are critically compared to those in other reports dealing with quail and chick embryos.
Identification of an hemipteran juvenile hormone: In vitro biosynthesis of JH III by Dysdercus fasciatus
Authors: Bowers W. S. , Marsella P. A. , Evans P. H.
Published: June 2005

Corpora allata of the African cotton stainer, Dysdercus fasciatus Sign. (Hemiptera: Pyrrhocoridae), produce radiolabeled methyl‐10,11‐epoxy‐3,7,11‐trimethyldodeca‐2E,6E‐dienoate (JH III) when cultured in a medium containing L‐[methyl‐14C] methionine. Similar in vitro studies show JH III biosynthesis by cultured corpora allata of Lygaeid and Pentatomid species. This is the first identification of a juvenile hormone in Hemiptera.
Cellular aspects of alloimmune reactions in sponges of the genus Axinella II. Axinella verrucosa and Axinella damicornis
Authors: Buscema Marco , Van de Vyver Gysèle
Published: June 2005

The analysis and understanding of immune reactions in sponges are presently impaired by numerous discrepancies and inconsistencies between the results obtained for different species that make critical judgment difficult. In order to determine the possible influence of experimental procedures, parabiotic allografts were performed on Axinella verrucosa and Axinella damicornis. Three reactions were observed in allogrfts of Axinella verrucosa: acceptance, nonfusion, and chronic rejection. The acceptance reaction differed from the fusion of control autografts by a transient phase of dense cell accumulation between the parabionts. Nonfusion resulted in the virtual absence of reaction between the incompatible sponges. Chronic rejection was characterized by: 1) intensive cell migration and accumulation of collencytes in the zone of contact; 2) regular alignment of these cells on each side of that zone; 3) deposition of a collagen barrier that progressively joined but demarcated the parabionts. Some sponges presented nonfusion or chronic rejection depending on their graft partner. All allografts in Axinella damicornis displayed a chronic rejection reaction, which was essentially similar, but more intense and faster, than in Axinella verrucosa. However, in Axinella damicornis, the parabionts which were separated by the barrier became independent instead of joined. Reasons for and the implications of such a diversity of immune reactions in sponges are discussed.
Neural crest cell behavior in white and dark larvae of Ambystoma mexicanum: Differences in cell morphology, arrangement, and extracellular matrix as related to migration
Authors: Spieth J. , Keller R. E.
Published: June 2005

Melanocytes of white (d/d) larvae of the Mexican axolotl (Ambystoma mexicanum) are confined to the dorsal midline of the trunk region, whereas in dark (D/‐) larvae they are spread laterally on the flank as well, where they contribute to the normal pigment pattern of the trunk. Pigment cell migration in the subepidermal space of white larvae is inhibited by the white epidermis (Dalton '50; Keller et al., '82). The present scanning electron microscopic study describes a well‐defined sequence of changes in shape and arrangement of neural crest cells during and after their segregation from the neural tube in both dark and white axolotls. The morphology of the neural crest cells migrating in the subepidermal pathway of dark larvae is correlated with their motile behavior and pattern of migration in vivo, as described by time‐lapse cinemicrography (Keller and Spieth, '83). Also, the structures of the matrix material in the subepidermal space of dark and white axolotls differ in ways that may be related to the epidermal inhibition of migration in the latter. Numerous possibilities for contact guidance offered by the structure and topography of the substrata, neighboring cells, and the extracellular matrix in the migration path are described and discussed.
Contraction of an embryonic epithelium, the enveloping layer of the medaka (Oryzias latipes), a teleost
Authors: Fluck R. A. , Killian C. E. , Miller K. , Dalpe J. N. , Shih T.‐M.
Published: June 2005

The enveloping layer (EVL), a simple epithelium that forms the outer covering of the blastoderm of the teleost embryo, contracted in situ when it was exposed to the calcium ionophore A23187. This contraction was inhibited by cytochalasin D and occurred in a Ca2+‐free medium. When the EVL was detached from the rest of the embryo, it contracted into a tight ball. Detached EVLs contracted fully in Na+‐, K+‐, SO4−2−, Mg2+‐, or glucose‐free medium but only partially in medium containing less than 10 μM free Ca2+ Contraction was inhibited by the polyvalent cations La3+, Ni2+, Co2+, and Mn2+ but not by the “calcium antagonists” D 600, verapamil, nifedipine, or papaverine; it was only slightly inhibited by the “calcium antagonist” diltiazem. The contraction was inhibited by cytochalasin B (1 μg/ml) and cytochalasin D (1 μg/ml) but not by demecolcine (0.35 mM) or colchicine (1 mM). The effects of lowered free Ca2+ and the cytochalasins were reversible.

The contraction of EVLs permeabilized by the detergent Brij 58 was ATP and Ca2+ dependent. In the presence of 5 mM MgATP, the EVLs contracted only when the medium contained at least 1 μM free Ca2+. Three other nucleotides—ITP, GTP, and CTP—also supported contraction but at a lower rate than ATP. The contraction of permeabilized EVLs was inhibited by cytochalasin B (1 μg/ml), N‐ethylmaleimide (6 mM), but not by 10 μM vanadate.

Dissociated cells of the EVL underwent circus movement, which was inhibited nearly completely by cytochalasin B, cytochalasin D, and La3+ and inhibited partially by Ni2+, Mn2+, and Co2+. Although the EVLs contain acetylcholine (1.2 pmol/EVL), the amount did not change significantly during contraction. The cholinergic antagonists d‐tubocurarine and atropine sulfate and the cholinergic agonist carbamylcholine had no effect on the contraction.

We conclude that the contraction of detached EVLs is an ATP‐, Ca2+‐dependent phenomenon and that part of the Ca2+ required for contraction enters the cytoplasm from the medium. Microtubules have no apparent role in the contraction, but microfilaments probably do. Acetylcholine apparently has no role in the contraction.
The influence of flank dermis on limb regeneration in the newt, Notophthalmus viridescens
Authors: Tank Patrick W.
Published: June 2005

The ability of nonlimb skin to support forelimb regeneration was studied in the newt, Notophthalmus viridescens. When forelimb skin was replaced by skin removed from the flank followed by amputation through the graft, 96% of the limbs did not regenerate. Varying the orientation of the skin graft around the limb did not affect this outcome. When limb stumps were covered by flank epidermis independent of flank dermis, normal forelimb structures regenerated (86%). When flank dermis was grafted to the limb independent of flank epidermis, 66% of experimental limbs did not regenerate. When flank skin was grafted proximal to the regenerate at several times after amputation (3, 9, or 15 days), 72% of the experimental limbs did not regenerate. Finally, limb stumps that contained no dermis at the level of amputation underwent normal regeneration (86%). These results indicate that flank skin does not support forelimb regeneration in the newt. The dermal component of flank skin is responsible for this outcome.
Forelimbs of the newt Notophthalmus viridescens continuously denervated for up to six weeks prior to amputation do not regenerate
Authors: Scadding Steven R.
Published: June 2005

It has been suggested that urodele forelimbs become “addicted” to innervation, because they will not regenerate in the absence of nerves. Recently, evidence has been provided that indicates that if axolotl forelimbs are denervated for 3 or 4 wk prior to amputation, they will regenerate in the absence or near absence of nerves since the addiction is broken and regeneration can occur (Wallace, '81). The present investigation was designed to determine if forelimbs of the newt Notophthalmus viridescens could regenerate in the absence of nerves when the forelimbs were maintained in a denervated state for several weeks prior to amputation. Thus, newts had their forelimbs denervated by transection of the brachial plexus at intervals of 0, 2, 4, 6 wk prior to forelimb amputation through the radius and ulna. Denervations were repeated at 2‐wk intervals to prevent regrowth of the nerves. After amputation, the limbs were observed and the degree of regeneration observed. The results indicated that regardless of the length of the prior denervation period, denervated limbs consistently failed to regenerate. In the newt, it appears that long‐term denervation does not significantly modify the requirement for nerves during forelimb regeneration.
Renal handling of phosphate, calcium, sodium, and potassium in intact and parathyroidectomized Rana pipiens
Authors: Sasayama Yuichi , Clark Nancy B.
Published: June 2005

Renal excretion of phosphate, calcium, sodium, and potassium in intact and parathyroidectomized male Rana pipiens was studied by renal clearance techniques using 14C‐inulin. In intact frogs, 57% of filtered phosphate, 60% of filtered calcium, 97% of filtered sodium, and 89% of filtered potassium was reabsorbed by the renal tubules. Following parathyroidectomy, the rate of reabsorption of phosphate became significantly higher than that of the intact frog, and the relative phosphate clearance (fractional excretion) decreased. These changes corresponded with a gradual rise in serum phosphate values. There was no major effect on excretion patterns of calcium, sodium, or potassium after parathyroidectomy. These results suggest that in frogs the parathyroid glands strongly influence phosphate excretion patterns but have little effect on the excretion of calcium, sodium, or potassium.
Separation and labeling of specific subpopulations of Botryllus blood cells
Authors: Schlumpberger Jay M. , Weissman Irving L. , Scofield Virginia L.
Published: June 2005

Blood cells of the colonial tunicate Botryllus were separated by density gradient centrifugation in Percoll. Unseparated blood cells were used to immunize mice for development of hybridoma cell lines producing anti‐Botryllus monoclonal antibodies. These antibodies identify specific subpopulations of blood cells, indicating possible divisions of these cells into defined subgroups sharing particular differentiation antigens. Additional studies utilizing fluorescein‐conjugated lectins also revealed differential binding to density‐ and monoclonal antibody‐defined blood cell fractions. These methods allow separation of the different Botryllus blood cell types for functional studies.
Electron microscopic studies of planarian regeneration. IV. Cell division of neoblasts in Dugesia dorotocephala
Authors: Morita Michio , Best Jay Boyd
Published: June 2005

There has been disagreement regarding the source of new cells for planarian regeneration. Electron microscopy was used to study this problem in surgically decapitated asexual Dugesia dorotocephala. Comparison of the fine structural morphology of cells found in prophase, metaphase, anaphase, and telophase with those of various cell types in interphase shows that the mitotic cells and resulting daughter cells are all neoblasts. This mitosis, which appears quite classical, was observed in the parenchyma of preexisting tissue but not in the regeneration blastema. This accords with previous observations indicating that blastema cells are already differentiated out of the neoblast stage, and the present observation that mitotic activity appears restricted to neoblasts. However, persistence of neoblast characteristics, e.g., numerous free, or poly‐, ribosomes and diminished, but still prominent, nuclear satellite material, indicate recent differentiation of blastema cells from neoblasts. Previous studies have shown a basal mitotic rate in the parenchymal neoblasts of uninjured asexual planarians. This mitotic incidence remains the same for the first day, then increases to a maximum on the second and third days following decapitation. Despite an exhaustive search involving construction of electronmicrographic montages of all or most of the wound area and adjacent tissue at various times ranging from 1 to 72 hours after decapitation, no evidence of cellular dedifferentiation was observed. Joint consideration of present and previous results indicate that new specialized cells, whether required for normal turnover replacement, asexual reproduction, or reconstitutive regeneration, are all differentiated from parenchymal neoblasts which maintain their numbers by mitotic production of more neoblasts.
Changes in protein phosphorylation during the maturation of mammalian oocytes in vitro
Authors: Crosby Ian M. , Osborn Jeremy C. , Moor Robert M.
Published: June 2005

Cumulus‐enclosed sheep oocytes were cultured in gonadotrophin‐containing medium for up to 9 hr and were then incubated for 3 hr in the presence of [32P]phosphate. The incorporation of 32P into TCA‐insoluble material was measured, and oocyte proteins were separated by one‐ and two‐ dimensional gel electrophoresis.

Incorporation of [32P]phosphate into protein increased after 3 hr of culture and again after 9 hr, the time of germinal vesicle breakdown (GVBD). Qualitative and quantitative changes in the phosphorylation of proteins occurred over the 12‐hr period studied. One of the most prominent changes was the appearance of a band of Mr 33,000, which was absent at 0–3 hr but appeared with increasing intensity with longer periods of culture. Two‐dimensional electrophoresis revealed that the bulk of material in this band was a neutral polypeptide. No significant incorporation of [32P]phosphate was found in ribosomal extracts of oocytes.
An improved method for destroying mouse blastomeres electrically inside the zona pellucida and the in vitro development of the surviving blastomeres
Authors: Tojo Hideaki , Ogita Zen‐Ichi
Published: June 2005

An improved method for isolating mouse blastomeres by electrically destroying the other blastomeres inside the zona pellucida is described. Instruments required are two micromanipulators connected to an inverted microscope and an electronic stimulator equipped with an isolator. The target blastomere in which a glass microelectrode is inserted disintegrates completely within a few seconds after a direct current is applied. Complete destruction of a blastomere requires more than 60 μA delivered at 8 V. Destruction of blastomeres occurred mainly as a result of the medium penetrating the blastomere due to the change of membrane potential in both the zona and the blastomere. Most one‐half, two‐quarter, and three‐quarter embryos obtained in this way developed in vitro into normal blastocysts (76.4–86.2%). By contrast, there was a marked decrease (35.3%) of developmental potential in one‐quarter embryos. The results indicate that the present method is an improvement over previous methods of obtaining mammalian blastomeres inside the zona pellucida.
A daily rhythm in heat tolerance in the salt marsh fish Fundulus heteroclitus
Authors: Bulger Arthur J.
Published: June 2005

1)A daily rhythm in heat tolerance occurs in Fundulus heteroclitus acclimated to temperatures of 12°C or 27°C; the rhythm persists at least 30 days in the laboratory in the absence of any thermal fluctuation. 2) The significance of the rhythm appears to be anticipation of daily temperature changes in a highly fluctuating thermal environment. 3) A normal photoperiod is necessary for the full expression of the rhythm, although it appears to have a weak endogenous component which persists in darkness.
Pressure inhibition of starfish oocyte maturation: Temporal aspects
Authors: Cloud J. G.
Published: June 2005

High hydrostatic pressure reversibly inhibits 1‐methylade‐nine (1‐MA)‐induced maturation of starfish oocytes; the objective of this investigation was to describe more fully the nature of this inhibition. Oocytes incubated at atmospheric pressure following a 90‐min period with 1‐MA at high pressure and the removal of exogenous 1‐MA immediately after the reduction in pressure failed to mature. Furthermore, the time required for germinal vesicle breakdown at atmospheric pressure in oocytes preincubated with 1‐MA for 15 min at high pressure was not less than the time required for untreated control oocytes. From a comparison of the percentage of oocytes that matured when incubated at atmospheric or elevated pressure with or without ammonium (20 mM), an inhibitor of 1‐MA that appears to act during an initial step of the hormone dependent period, it was found that the inhibitory action of pressure and ammonium was additive. Inhibition of oocyte maturation was reversible even after 20 hr of incubation at high pressure, but the percentage of oocytes that matured when subsequently incubated at atmospheric pressure was reduced in those oocytes incubated at the elevated pressure with 1‐MA. Taken together, these results suggest that high pressure, like ammonium, inhibits an initial step in the maturational process and that oocytes incubated with 1‐MA at high pressure have a reduced responsiveness to 1‐MA when subsequently incubated at atmospheric pressure.
Further evidence that formation of the neural tube requires elongation of the nervous system
Authors: Jacobson Antone G.
Published: June 2005

In previous papers, we have correlated rapid elongation of the midline of the neural plate with the time of closure of the plate into a tube in the newt embryo and at one stage of the chick embryo. We proposed a model in which stretching of the midline of the plate causes the plate to buckle out of the plane and roll into a tube. In this paper, I show for another stage of development in the chick embryo, the period of closure of the brain tube, that rapid elongation of the nervous system accompanies closure of the tube. If elongation of the brain plate causes formation of the tube, then treatments that stop tube formation should also stop brain elongation. I tested this hypothesis by using low fluences of UV irradiation, known to stop tube formation (Davis, '44), and measuring the effects on elongation of the brain plate. The open plates of UV‐irradiated embryos failed to elongate normally. Furthermore, photoreactivation with longer wavelengths of light reversed the UV effects and allowed closure of the tube in UV‐irradiated embryos. These embryos elongated their brains.
An analysis of Sciara ocellaris gynandromorphs and the morphogenetic fate map of presumptive adult cuticular structures
Authors: Mori Lyria , Perondini André L. P.
Published: June 2005

Gynandromorphs have been collected in different crosses of Sciara ocellaris involving the mutation sepia. Gynandromorphs develop only from heterozygous zygotes. The mean proportion of male tissue in these gynandromorphs is variable and related to the genotype of the parental females, and is higher when the cytoplasm of the egg is under the influence of sepia. The results give support for the hypothesis of the existence of a cytoplasmic component involved in the process of X‐chromosome elimination in the embryo of sciarid flies. The distribution of phenotypes in the adult gynandromorphs is nonrandom. The frequency with which each of the 27 cuticular structures is XO is higher for the anterior parts of the body and decreases toward the posterior. A morphogenetic fate map placing the origin of these cuticular structures on the blastoderm surface was constructed. The map agrees in its general features and in the calculated mapping function with those previously made for other insects.
Hormonal regulation of the annual pelage color cycle in the Djungarian hamster, Phodopus sungorus. I. Role of the gonads and the pituitary
Authors: Duncan Marilyn J. , Goldman Bruce D.
Published: June 2005

The Djungarian hamster exhibits an agouti pelage in the summer and a predominantly white pelage in the winter. This pelage color cycle is known to be regulated by the length of the daily photoperiod probably acting through the pineal gland, as is the seasonal cycle of reproductive function with which it is closely correlated (Figala et al., '73; Hoffmann, '78b). The possibility of a causal relationship between the decline in gonadal hormone secretion and the coat color change occurring in short photoperiod was examined. Gonadectomized and intact male and female hamsters were exposed to either long (16L:8D) or short (10L:14D) photoperiod for several months. Gonadectomy neither induced the change to the winter pelage color in long photoperiod‐housed animals, nor prevented either the change to the winter pelage or the spontaneous return to summer pelage color in short photoperiod‐housed animals. Chronic implants of testosterone in castrated males delayed and attenuated the short photoperiod‐induced coat color change. Administration of ovine prolactin (100 μg/day) stimulated pigmentation in hamsters with the winter pelage, whereas administration of a αMSH (30 μg/ day) was without effect. These results suggest that changes in pelage color may be regulated largely by changes in pituitary prolactin secretion and modified to some extent by changes in gonadal steroid hormone secretion.
Forskolin and mouse oocyte maturation in vitro
Authors: Sato Eimei , Koide S. S.
Published: June 2005

Oocytes isolated from mature follicles undergo spontaneous maturation when cultured in vitro. Forskolin, an adenylate cyclase stimulator, inhibited resumption of meiosis of cumulus‐free mouse oocytes in vitro. Germinal vesicle breakdown (GVBD) was prevented in more than 85% of the oocytes treated by forskolin at concentrations of 20 μg/ml and higher. The inhibiting effect of forskolin was dose‐dependent and reversible. FSH, LH, FSH plus LH, estrogen, progesterone, and estrogen plus progesterone did not reverse the block induced by forskolin in cumulus‐free and cumulus‐enclosed oocytes. The present results suggest that intracellular cAMP may play a role in the regulation of oocyte maturation.
Patterned regeneration of internal femoral structures in the cockroach, Periplaneta americana L.
Authors: Kaars C. , Greenblatt S. , Fourtner C. R.
Published: June 2005

The morphology of the nerve and tracheal supply to the extensor tibiae muscle in normal legs was compared to that in regenerate legs. In normal femurs, the extensor nerve and trachea extend along the posterior surface of the extensor muscle. The nerve and trachea are closely associated and branch coincidently at regular intervals. In regenerate femurs, the nerve and trachea are not closely associated with each other, and both structures differ from normals in their branching patterns. The results suggest that tissue level interactions during regeneration differ from those during embryogenesis.