bluuebunny/crossref_metadata_2025 huggingface dataset:
The histochemical identification of primordial germ cells in diploid parthenogenetic mouse embryos
Authors: Kaufman M. H. , Schnebelen M. T.
Published: June 2005

An attempt has been made to improve the early post‐implantation development potential of diploid parthenogenetic mouse embryos by transferring parthenogenetic blastocysts to one uterine horn of a pseudopregnant recipient and a similar number of fertilized embryos to the contralateral horn. In control studies, diploid parthenogenetic embryos were transferred to both uterine horns of appropriate recipients. Unfortunately no obvious advantage appeared to be gained by carrying out the former manoeuvre. A significant improvement in the development potential of the parthenogenones could have indicated that their poor post‐implantation survival might have been associated with a deficiency, possibly of hormonal origin, in the functioning of their decidual reaction. However, sufficient somite‐containing parthenogenetic embryos were obtained in this study to allow a comparison to be made between them and fertilized embryos that were morphologically at a comparable stage of development. The parthenogenones were found to have a markedly smaller crown–rump length than their fertilized counterparts. A high proportion of both the parthenogenetic and fertilized embryos were subsequently fixed and appropriately stained in order to localize alkaline phosphatase activity. The analysis of this material clearly demonstrated that parthenogenetic mouse embryos are in fact capable of producing primordial germ cells. The latter were recognized by their morphology, histochemical staining appearance, and characteristic location, being found in the early ‘turned’ embryos within the dorsal mesentery in close proximity to the developing gut tube, and in the more advanced limb‐bud stage embryos within the gonadal ridges.
Relationship between calcium binding sites and membrane fusion during the acrosome reaction induced by lonophore in ram spermatozoa
Authors: Watson P. F. , Plummer J. M.
Published: June 2005

Ram spermatozoa treated with the ionophore A23187, to induce the acrosome reaction, were fixed in pyroantimonate‐osmium in order to demonstrate calcium at an ultrastructural level. Prior to vesiculation, granules of precipitate occurred at points of contact between plasma and outer acrosomal membranes, suggesting a discrete role for calcium during membrane fusion. The earliest stages of vesiculation always occurred in the region just anterior to the equatorial segment and it was this same site where a marked concentration of precipitate, indicating calcium binding sites, could be demonstrated.
Secretion of prolactin‐synergizing activity (synlactin) by the liver of ectothermic vertebrates in vitro
Authors: Delidow Beverly C. , Hebert Nora , Steiny Susan , Nicoll Charles S.
Published: June 2005

Recent work in our laboratory indicated that the liver of rats and pigeons secretes a prolactin synergist (synlactin) in vitro. We have investigated the secretion of this activity by the liver of nine species of ectothermic vertebrates. Liver from three teleosts (goby, salmon, and tilapia), four amphibians (Ambystoma, Necturus, bullfrog, and grass frog) and two reptiles (turtle and anole) was diced, washed, and incubated for 3 hr in isotonic medium. After dialysis, the liver incubation media (LIM) were tested with and without prolactin (PRL) in the local pigeon crop‐sac bioassay. The LIM for turtle, larval bullfrog, freshwater salmon, and 5% seawater‐adapted goby significantly augmented the local crop‐sac response to PRL, but the LIM from anole, adult bullfrog, grass frog, fasted larval Ambystoma, Necturus, 100% seawater‐adapted goby, and tilapia did not contain synergizing activity. We conclude that synlactin is secreted by the liver of several species representing three of the major ectothermic classes of vertebrates. It is significant that in two cases, larval bullfrog and 5% seawater‐adapted goby, the presence of synlactin occurs in physiological states in which PRL is active. In the opposite cases (adult frog and 100% seawater‐adapted goby) the activity was not detectable. We also found that the liver of larval and adult bullfrogs and tilapia released a factor in vitro that had proliferative activity in the crop‐sac. This activity appears to be distinct from synlactin.
Effects of the lethal yellow (Ay) and recessive yellow (e) genes on the population of epidermal melanocytes in newborn mice
Authors: Tamate Hidetoshi B. , Hirobe Tomohisa , Takeuchi Takuji
Published: June 2005

Very few melanocytes can be detected by the DOPA reaction in the dorsal epidermis of newborn lethal yellow mice (Ay/a). Nevertheless, the epidermis contains a considerable number of melanoblasts (cells positive for the combined DOPA‐premelanin reaction). On the other hand, numerous melanocytes as well as melanoblasts are found in the dorsal epidermis of black mice (a/a). The number of epidermal melanoblasts is smaller in (Ay/a than in a/a mice even though the same number of melanocytes is found in the dermis of these animals. It seems probable that the product of the Ay gene suppresses either the differentiation or the proliferation of epidermal melanoblasts.

The number of melanoblasts plus melanocytes in day‐17 embryos from a cross between Ay/a and a/a mice shows a bimodal distribution. It seems possible that half of the embryos were Ay/a and possessed a reduced number of melanoblasts and melanocytes. This result seems to suggest that the Ay gene is active at this embryonic stage.

In contrast to the case for the epidermis from Ay/a mice, numerous DOPA‐positive melanocytes were detected in the epidermis from e/e mice. However, the total number of melanoblasts plus melanocytes in e/e epidermis did not differ from that in Ay/a epidermis, suggesting that the mode of action of the e gene in the epidermis is different from that of the Ay gene.
Presence of a substance crossreacting with cortical alveolar material in “yolk vesicles” of growing oocytes of Oryzias latipes
Authors: Masuda Kaori , Iuchi Ichiro , Iwamori Masao , Nagai Yoshitaka , Yamagami Kenjiro
Published: June 2005

A large number of spherical bodies, a major insoluble component of cortical alveolus, were isolated from blastulae of medaka, Oryzias latipes. Spherical body material was found to be abundant in carbohydrates, especially in galactose and hexosamine, and total carbohydrate content amounted to about 1.3 times that of protein. Immunohistochemical studies using anti‐spherical body antiserum as a probe revealed that a substance crossreacting with spherical body material was localized only in “yolk vesicles” of growing oocytes and later in cortical alveoli of full‐grown oocytes. Thus the present results identified immunochemically yolk vesicle material with cortical alveolar material, supporting the view that the yolk vesicle is a precursory structure of cortical alveolus.
Metamorphosis of the American eel, Anguilla rostrata Le Seur: II. Structural reorganisation of the locomotory musculature
Authors: Egginton Stuart
Published: June 2005

Skeletal muscle types show a differential response in both organization and morphology on transition from non‐migratory (yellow eel) to migratory (silver eel) life‐history stages. Volume density, Vv, and surface density, Sv, of intracellular components and the capillary network reflect structural limits to aerobic metabolism, and parallel changes seen in metabolic potential using enzyme activity measurements. Increased capacity for aerobic ATP supply is apparently derived from an increase in mitochondrial Vv from 16% to 22% of slow fiber volume in silver eels. Cristae Sv appears not to vary with the level of aerobic metabolism: Sv (cst, mit) is 46.8 and 44.0 μ2 · μm−3 in slow muscle fibers of yellow and silver eel, respectively, and 38–43 μ2 · μm−3 in fast fibers. The large amount of intracellular lipid in slow fibers of silver eel, around 25% of fiber volume, contrasts with only 4% in fibers of yellow eel. This is consistent with the contention that mature, migratory fish rely heavily on lipid metabolism.

Maturation appears to induce only minor changes in fast muscle morphology, reflecting a potentially constant work capacity and suggesting that the slow muscle system supports the increased energy demand for extensive locomotion. Change in relative proportion of slow muscle, from 8.6% to 14.4% of total muscle mass, is largely due to cellular hypertrophy. This amplifies the cellular reorganization, increasing total mitochondrial volume of slow muscle from 0.7% to 1.6 cm3 for 100g yellow and silver eels, respectively. Changes in skeletal muscle during transition from yellow to silver life‐history stages are therefore both qualitative and quantitative, and represent a true metamorphosis.
Local light stimulation of melanophores of a teleost, Zacco temmincki
Authors: Iga Tetsuro , Takabatake Ikuo
Published: June 2005

Responses of melanophores of the teleost, Zacco temmincki, to local light stimulation were examined in preparations of isolated scales. The melanophores induced the aggregation of melanosomes in darkness and their dispersion in light. Local illumination of a melanophore in the melanosome‐dispersed state inhibited centripetal migration of melanosomes only in the stimulated area. Local illumination of a pigment‐free branch of a melanophore with aggregated melanosomes generally brought about pigment dispersion into the stimulated area. However, when that area was at a significant distance from the edge of the central melanosome mass, the melanosomes never migrated into the irradiated area. Local illumination of the centrosphere of a cell inhibited the full aggregation of melanosomes in the dispersed and aggregated state. The degree of the inhibition depended on the size of the irradiated area. The result suggest that photoreceptive sites are distributed over the whole of a cell, and that the movements of melanosomes are regulated locally in a very precise manner.
Avian hepatic T‐3 production by two pathways of 5′‐monodeiodination: Effects of fasting and patterns during development
Authors: Hughes Thomas E. , McNabb F. M. Anne
Published: June 2005

Two forms of iodothyronine 5′‐monodeidinase (5′‐D) were studied in liver homogenates from adult and developing quail. The influence of fasting in adults and corticosterone treatment in embryonic quail on 5′‐D also were examined. Liver homogenates were assayed for 5′‐D activity in the presence of abundant substrate (T4) and cofactor (dithiothreitol; DTT). Generation of T3 during a 15 min incubation at 37°C was assessed by an ethanolbased RIA. In adults, both Type I [the fraction of activity inhibited by propylthiouracil (PTU)] and a putative Type II (the PTU‐insensitive fraction) were present in liver homogenates. Type II activity typically comprised about 30% of Total activity.

Type I activity first appeared on day 15 of the 16.5 day incubation period, increased 20‐fold to peak at hatching, then gradully declined to reach adult levels by 21 days of age. Type II activity was present at all developmental stages and was highest during the perinatal period. Corticosterone treatment in vivo on day 13 of development induced increases in both Type I and Type II activities in liver homogenates 24‐ and 48‐h after treatment.

This study demonstrates that in avian liver a putative Type II 5′‐D activity (generally considered to be lacking in mammalian‐liver) is present and may be important in the maintenance of minimal concentrations of tissue T3 during fasting. Both types of 5′‐D contribute to the developmental pattern of serum T3 concentrations. Type II comprises a large proportion of total activity during late embryonic life; Type I becomes predominant at the beginning of the perinatal period. Corticosterone is capable of inducing increases in both Type I and Type II activities during late embryonic life.
Cytoplasmic control of chromosome diminution in Ascaris suum
Authors: Oliver Brian C. , Shen Sheldon S.
Published: June 2005

The elimination of portions of chromosomes (chromosome diminution) in Ascaris sp. is an early event associated with divisions of somatic blastomeres. Germ‐line blastomeres do not undergo diminution during cell division. It has been proposed that the occurrence of chromosome diminution is under the control of morphogenetic determinant(s) in the ooplasm, which are fixed into specific blastomeres by the cleavage process. The nature of the morphogenetic determinant(s) contained in the cytoplasm remains an enigma. Two problems with the Ascaris sp. system have been an impermeable extra embryonic (ascaroside) layer and the difficulty of scoring interphase nuclei as somatic (diminished) or germ‐line (non‐diminished). We have successfully permeabilized the ascaroside layer by puncture with micropipettes. We also report a Ba(OH)2 C‐banding technique, which preferentially stains germ‐line limited chromatin in anaphase, telophase, and interphase nuclei. These two techniques have allowed us to (1) produce early embryos with multinucleated blastomeres (coenocytic embryos) of Ascaris suum and (2) assay for the effects on chromosome diminution brought about by these altered cytoplasmic environments. The patterns of diminution seen in one‐cell and two‐cell coenocytic embryos strongly suggest the presence of cytoplasmic determinats. Since chromosome diminution serves as a marker of blastomere commitment, these determinants may also play a role in the commitment of blastomeres to the germ‐line.
Genetic variation in Drosophila melanogaster for the life‐shortening effects of random lighting regimes
Authors: Ringo John M. , Dowse Harold B. , Lagasse Steven , Ezzy Stephen
Published: June 2005

A daily random light‐dark regime (RLD), in which the onset of the photophase occurred at a random time of the 24‐h day, significantly shortened the life span of adult Drosophila melanogaster in 8 out of 23 strains tested. For the eight sensitive strains, the mean percent decrement in LT50 ± SE was 11.2 ± 0.6 d; for ten resistant strains, the mean decrement was 5.1 ± 0.8 d; for the remaining 5 strains, which could not be unambiguously classified as sensitive to RLD, the mean decrement was 8.6 ± 1.1 d. Strains homozygous for whole chromosomes (either X or one of the two large autosomes) exhibited continuous variation for sensitivity to clock shifting. No chromosome accounted for a disproportionate share of the variation, suggesting a multigenic basis for this phenotype. The LT50 in a normal, constant light‐dark regime (CLD) ranged from 31.7 d to 65.3 d, with chromosome 2 contributing most heavily to this variation. The correlation between LT50 and percent decrement in LT50 was not significant (r = .23, df = 21, P > .20). In most sensitive strains, RLD and CLD groups did not begin to differ in percent surviving until after .5 of CLD LT50; after this critical point, RLD animals started dying at an increased rate. RLD may be stressful by disrupting temporal organization of physiological processes immediately following phase shifts, during the period marked by transients in observed phase response.
Actin filament bundle in the acrosome of abalone spermatoza
Authors: Shiroya Yoko , Hosoya Hiroshi , Mabuchi Issei , Sakai Yoshi T.
Published: June 2005

The localization of actin filaments in abalone sperm was investigated using 7‐nitrobenz‐2‐oxa‐1,3,‐diazole‐phallacidin (NBD‐phallacidin) as a specific probe for actin filaments. Fluorescence staining of intact sperm revealed the localization of actin filaments in the axial rod. After the acrosome reaction the fluorescent rod elongated to form the acrosomal process, which signified the elongation of actin filaments. More definite identification of the bundle of filaments in the axial rod as filamentous actin was indicated by decoration with myosin subfragment 1 (S1). The actin filaments in both the unreacted and reacted sperm all appeared decorated with S1, and the polarity was found to be unidirectional with the arrowheads pointing towards the nucleus. When Triton X‐100‐treated unreacted sperm were incubated in exogenous G‐actin, actin monomers assembled on the “barbed end” of the actin filaments of the axial rod. These results suggest that the elongation of the acrosomal process occurs via polymerization of endogenous G‐actin at the tip (the barbed end) of the axial rod.
Responses to reversed NH3 and NH4+ gradients in a teleost (Ictalurus punctatus), an elasmobranch (Raja erinacea), and a crustacean (Callinectes sapidus): Evidence for NH4+/H+ exchange in the teleost and the elasmobranch
Authors: Cameron James N.
Published: June 2005

Ammonia excretion rates of channel catfish, Ictalurus punctatus, little skate (Raja erinacea), and blue crab (Callinectes sapidus) were measured in experimental regimes which permitted simultaneous assessment of the partial pressure gradients for nonionized NH3 and the chemical concentration gradients of NH4+. Under conditions of low external ammonia, the average ammonia excretion was +295 μM kg−1 h−1 for catfish, + 149 μM kg−1 h−1 for blue crabs, and +59 μM kg−1h−1 for skates with partial pressure gradients of +72.5 μTorr, + 413 μTorr, and +24.4 μTorr, respectively; and [NH4+] gradients of +189 μM l−1, +643 μM l−1, and +107 μM l−1 (positive indicating greater from inside to medium). When the external ammonia was increased to 1.15 mM l−1, both gradients were reversed, and the net ammonia movement was initially from the external water into all three species. In the catfish the inward movement ceased, however, and ammonia excretion eventually resumed in the face of reversed gradients of both NH3 partial pressure and [NH4+]. Unidirectional Na+ influx, indicative of a Na+/NH4+ exchange, did not increase. The ammonia data, changes in titratable acidity, and net apparent H+ efflux were all consistent with a linked extrusion of internal NH4+ for external H+. Incorporation of such an exchange into a computer simulation model of the ammonia equilibrium and exchange system duplicated the experimental data. Other hypotheses failed to match experimental data, or failed to predict internal ammonia levels lower than outside. In the crab, internal ammonia levels rose rapidly to concentrations and partial pressures above the external medium until excretion was reestablished, with no evidence of maintenance of a reversed gradient. In the skate, internal concentrations rose appreciably in the first hour and continued to rise for 6–8 h, with no resumption of ammonia excretion. The interspecies differences appear to be due at least partly to differences in ammonia permeability of the gills.
Regenerate epithelium and skin glands of the adult newt react to the same monoclonal antibody
Authors: Tassava Roy A. , Johnson‐Wint Barbara , Gross Jerome
Published: June 2005

A search for specific proteins involved in newt limb regeneration, using monoclonal antibodies against forelimb blastemas, led to the detection of an antigen in the regenerate epithelium. Fluorescent‐antibody‐labeled cells first appeared just prior to blastema outgrowth. From bud through early digit stages this antibody reacted with nearly all of the regenerate epithelial cells. Other tissues also reacted, including nerve, blood vessels, and gastrointestinal tract. The behavior of the reactive cells in the regenerate epithelium, and their close association with immediately adjacent skin glands, raises several new possibilities for the origin of the regenerate epithelium.
Pineal melatonin: Circadian rhythm and variations during the hibernation cycle in the ground squirrel, Spermophilus lateralis
Authors: Stanton Toni L. , Craft Cheryl M. , Reiter Russel J.
Published: June 2005

Variations in pineal melatonin content throughout a 24‐hour period and during different phases of the hibernation bout cycle were studied in the golden‐mantled ground squirrel (Spermophilus lateralis). In addition to pineal melatonin, the circadian variation in the activities of pineal N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) were also investigated in summer animals maintained at 22 ± 2°C, on a light:dark (L:D) schedule of 12:12 hr for 1 month (lights on at 08.00 hr). Pineal glands were collected from six animals in each group at 1200, 1600, 2000, 2400, 0200, 0400, and 0800 hr. Changes in pineal melatonin content during the hiberation bout cycle were investigated in ground squirrels housed at 4 ± .05°C in relative darkness (1.9–3.4 lux; 10:14 LD). Pineal glands were obtained between 12:00 and 18:00 hr from 30 animals during one of three phases of the cycle (deep hibernation, euthermic interbout, and entrance into hibernation). Pineal melatonin was also measured for comparison in six winter euthermic animals that were housed at 22 ± 2°C, on a L:D schedule of 10:14 hr. Melatonin was measured in individual pineal glands by radioimmunoassay. The daily melatonin rhythm in S. lateralis was characterized by a marked increase in pineal melatonin during the dark phase, in which peak nighttime values were nearly 20‐fold greater than daytime basal levels. The daily rhythm for NAT activity paralleled the changes in melatonin, showing a peak activity at 0200 hr that was 45 times greater than mean daytime values. No significant variation was observed in HIOMT activity. Pineal melatonin levels in winter animals were lowest during the state of deep hibernation. Melatonin content was increased significantly in the interbout phase within 1 hr postarousal (p < .01). A significant decline was evident in interbout animals that were sacrificed 6–8 hr postarousal and in animals that were in the entrance phase of hibernation (p < .01), although these values remained significantly higher compared to hibernation.
Myofiber death plays a role in determining fiber type composition in the claw closer muscles of the snapping shrimp, Alpheus heterochelis
Authors: Quigley Michael M. , Mellon Deforest
Published: June 2005

Marine shrimp of the genus Alpheus exhibit a remarkable reversal of asymmetry in their great claws. This unique phenomenon includes transition of the closer muscle in one claw from a muscle of mixed fiber type into a homogenous slow muscle. We have developed monoclonal antibodies that specifically recognize fast and slow myosin heavy chain (MHC), and have used these as immunohistochemical markers to follow the fate of different myofiber types during this transformation. This analysis reveals a strikingly specific necrosis of the fast fibers. The onset of fiber degeneration appears linked to the molt cycle and occurs rapidly once started. This represents the first example of programmed myofiber death as a mechanism used in crustacean muscle development.
Solute effects on mitochondria from an elasmobranch (Raja erinacea) and a teleost (Pseudopleuronectes americanus)
Authors: Ballantyne J. S. , Moon T. W.
Published: June 2005

Varying osmolarity with sucrose/KCI media resulted in similar effects on the oxidation of glutamate by mitochondria isolated from the livers of an elasmobranch, Raja erinacea, and a teleost, Pseudopleuronectes americanus. In both species trimethylamine oxide (TMAO) inhibited mitochondrial oxidation of glutamate. Urea penetrated the inner mitochondrial membrane of both species and equilibrated with a ratio ureai/ureao of unity. Urea had little effect on the oxidation of glutamate in both species at concentrations as high as 760 mM. Addition of urea (urea/TMAO, 2:1) did not overcome the detrimental effects of TMAO in the mitochondria of either species. In the case of the elasmobranch, the osmolarity of the urea/TMAO media giving the optimal rate of respiration was hypoosmotic with respect to the intracellular osmolarity. The rate of glutamate oxidation steadily declined as osmolarity increased above this value. Assuming the osmotic profile obtained with the urea/TMAO (2:1) medium resembled most closely the in vivo situation, higher rates of oxidation or organic solutes at low osmolarity would help deplete the cell of these solutes and could contribute to cell volume regulation during hypoosmotic stress.

It is suggested that two broad classes of intracellular solutes can be defined based on their effects on mitochondrial respiration. Solutes such as K+, C1−, and TMAO penetrate the inner mitochondrial membrane slowly or not at all. Increasing concentrations of these solutes result in lower rates of oxidation. This capacity may be important in regulating intracellular levels of organic solutes during osmotic stress. Solutes such as urea rapidly penetrate the cell and inner mitochondrial membrane reducing the mitochondrial volume changes associated with osmotic stress. The known detrimental effects of urea on protein structure may prevent its exclusive use as an intracellular osmotic effector.
Organisation of Xenopus egg cytoplasm: Response to simulated microgravity
Authors: Smith Rosamund C. , Neff Anton W.
Published: June 2005

The cytoplasm of Xenopus fertilised eggs appears to be organised into three major compartments based primarily on the uneven distribution of yolk platelets. There is a shift of these yolk compartments during the first cell cycle that is thought to be involved in the dorsal/ventral morphogenesis of the embryo. The involvement of gravity in Xenopus cytoplasmic organisation and in compartment shifts was addressed by examining, cytologically, the yolk compartments in embryos that developed under the simulated microgravity conditions of the horizontal clinostat. The cytoplasmic organisation into yolk compartments was found to be maintained, and the asymmetric movements of compartments still occurred in eggs that developed on the clinostat. It is suggested that the organisation of Xenopus egg cytoplasm into discrete compartments relies on forces other than those involving gravity (i.e., not density differences), and that the compartment shifts that take place during the first cell cycle are active movements.

The variation in compartment size and composition observed from batch to batch of eggs, and to a lesser extent from egg to egg, during this study was addressed.
Cyclic AMP stimulation of Cl− secretion by the opercular epithelium: The basolateral chloride uptake mechanism
Authors: Degnan Kevin J.
Published: June 2005

The isolated, short‐circuited opercular epithelium of Fundulus heteroclitus, secretes Cl− by a mechanism dependent on the presence of serosal Na+ and inhibited by bumetanide and furosemide. Under serosal Na+‐free conditions the active Cl− secretion is abolished. However, subsequent elevations of intracellular cyclic AMP (cAMP) levels with isoproterenol or forskolin stimulated Cl− secretion markedly. This stimulation was unaffected by SITS, DIDS, methazolamide, and HCO−3‐free solutions, but was blocked by furosemide and bumetanide. Determinations of relative intracellular 36Cl− levels showed a Na+ dependence of intracellular 36Cl− in epithelia not stimulated by isoproterenol and a Na+ independence of intracellular 36Cl− in isoproterenol stimulated epithelia. In both conditions, the intracellular 36Cl− was bumetanide sensitive. The results indicate that cAMP stimulation of Cl− secretion can occur by a Na+‐independent, loop diuretic‐inhibitable mechanism, which may be operative even in the presence of Na+. Whether this is a separate Cl− uptake mechanism or a cAMP‐induced alteration in the normal Na+‐dependent mechanism could not be determined. In either instance, an alternative to the Na+ gradient as a source of energy for Cl− uptake into the cell across the basolateral membrane is required.
Neoplastic transformation in the planarian: I. Cocarcinogenesis and histopathology
Authors: Hall Frederick , Morita Michio , Best Jay Boyd
Published: June 2005

Although several investigators have reported that exposure to mammalian carcinogens induces abnormal tumorlike growths and teratogenic remodeling in planarians, there is no general agreement that these, or comparable responses in any other invertebrates, model mammalian carcinogenesis. To investigate this question, freshwater planarians of the species Dugesia dorotocephala were exposed to culture water containing an initiator and a promoter, either alone or in combination. Cadmium, a potent carcinogen, was used as an initiator in the protocol. Treatment with sublethal concentrations of cadmium sulfate produced a benign, but persistent, tumor in a small percentage of the planarians. The addition of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), a phrobol ester and well‐known promoter, to the cadmiumcontaining solutions resulted in the induction of a progressive, potentially lethal, transplantable tumor in a large proportion of the treated flatworms. Light and electron microscopy revealed this particular tumor to be composed both of immature cells and of a single mature cell type: newly differentiated, but transformed, reticular cells. Further examination of the infiltrating tissue formations elucidated the profile of differentiation, from a population of mitotically active transformed stem cells through the transitional stages in the associated reticuloma. These results suggest that (1) the freshwater planarian displays the major phenomenology of mammalian cocarcinogenesis and that (2) the planarian reticuloma models several important features of a neoplastic stem cell disease.
The effect of the presence of adult fishes, gonad homogenates, and embryo homogenates on the dispersion‐reaggregation phase during early embryonic development of the annual fish Nothobranchius korthausae
Authors: Levels P. J. , van Tits L. J. H. , Denucé J. M.
Published: June 2005

The effect of the presence of adults of the annual fish Nothobranchius korthausae on development of eggs of this species was investigated. If the eggs were incubated in glass tanks together with adult females, embryonic development was prolonged during the dispersion‐reaggregation phase. Furthermore, gonadal homogenates as well as homogenates of oocytes and fertilized eggs or embryos (until the prehatching stage) also caused prolongation of the dispersion‐reaggregation phase. This prolongation was attributed to a longer lasting reaggregation, although the occurrence of a brief diapause I could not be ruled out.

We suggest that gonads of adult annual fishes, especially females, contain one or more pheromonelike agents that are released into the water and induce a prolongation of the dispersion‐reaggregation phase of the deposited eggs. By increasing or decreasing the amount of agent released, the adults would be able to affect embryonic development. The fact that homogenates of oocytes and fertilized eggs had the same effect on egg development indicates that also the eggs may be a source of this agent. Therefore, it probably plays a function during (normal) embryonic development.
Integumentary uptake of acetate and propionate (VFA) by Tubifex sp, a freshwater oligochaete. II. Role of VFA as nutritional resources and effects of anaerobiosis
Authors: Hipp Erich , Bickel Ursula , Mustafa Tariq , Hoffmann Klaus H.
Published: June 2005

The freshwater oligochaete Tubifex tubifex is able to absorb 14C‐labeled short‐chain carboxylic acids (VFA) from ambient water (Hipp et al., '86). In this paper evidence is given that VFA are transported across the body surface (autoradiography) and not taken up to any significant extent by bacteria or accumulated on the surface layer. Absorbed carboxylic acids are metabolized, as shown by the appearance of label in respiratory Co2 as well as in glycogen content. Rates of uptake are determined by the metabolic state of the worms. Under anoxic conditions, uptake is rapidly reduced. However, only 30 to 60 minutes of aerobic recovery were needed to regain aerobic control levels of uptake. Comparison of potential rates of VFA accumulation to rates of oxidative metabolism suggest that acetate and propionate might serve as an important nutritional supplement to these benthic freshwater animals.
Serotonin regulation of gill cAMP production, Na, and water uptake in freshwater mussels
Authors: Scheide John I. , Dietz Thomas H.
Published: June 2005

Active Na transport in freshwater mussels was stimulated by addition of 10−4 M serotonin (5‐HT) in the bath. Carrier kinetics apply to serotonin‐stimulated Na uptake with no effect on the affinity (Km 10−4 M). The Jmaxi was increased 350% over controls to 5.83 μeq (g dry tissue · h)−1. Amiloride reversibly inhibited the 5‐HT‐stimulated Na influx. Serotonin also caused a net water uptake of 0.36 ml H2O (g dry tissue · h) −1, due, in part, to a reduction in renal filtration. When mussel gill tissue was incubated in pondwater containing 10−4 M 5‐HT, cAMP content increased 2.5 times control levels within the first minute and then declined toward control values by 20 minutes. Theophylline (10−3 M) in the incubation medium prevented this decline. Dopamine, epinephrine, or norepinephrine (10−4 M in pondwater) increased gill cAMP concentrations; L‐dopa did not. Both 5‐HT and dopamine significantly increased gill cAMP concentration at 10−5 M.
Role of the neural retina in newt (Notophthalmus viridescens) lens regeneration in vitro
Authors: Connelly Thomas G. , Green M. Sean , Sahijdak Walter M. , Loyd Robert M.
Published: June 2005

Removal of the lens from the eye of an adult newt (Notophthalmus viridescens) is followed by regeneration of a new lens from the dorsal iris epithelial cells at the pupillary margin. This process is dependent upon the neural retina for its normal completion in vivo and in vitro. To examine the relationship between the retina and lens regeneration, we have conducted experiments that delimit the time period during which the retinal presence is critical (in vivo) and have investigated the influence of extracts of the retina on the progress of regeneration (in vitro).

In vivo, removal of the retina at day 11 seriously retards further progression of regeneration while removal of the retina at day 15 does not retard regeneration significantly. This defines a “critical period” in regeneration of the lens during which the retina is required.

Explantation of regenerates 11 or 12 days after lentectomy to organ culture medium enriched with either crude retinal homogenate or extracts prepared from chick or bovine retinas according to Courty et al. ('85, Biochimie, 67:265–269) reveals that the progress of regeneration can be supported in culture by the crude extract. This is the first demonstration of complete iris‐lens trnsformation in culture in the presence of retinal extract.

It is possible that the retina acts indirectly by promoting passage of the iris epithelial cells through the critical number of mitoses required before redifferentiation into lens cells can occur (as proposed by Yamada, '77, Monogr. Dev. Biol., 13:126). It is also possible that the retina acts by directly instructing the iris cells to redifferentiate. Our experiments provide some indirect support for the first possibility but do not distinguish between them at this time.
The cellular basis of the calcium dependence of GnRH‐stimulated gonadotropin release from frog, Rana pipiens, pituitaries
Authors: Porter David A. , Licht Paul
Published: June 2005

An in vitro superfusion system was used in an attempt to identify the cellular systems involved in the Ca2+ dependence of gonadotropin‐releasing hormone (GnRH) actions in the frog, Rana pipiens. Superfusion with 5 μM A23187 (a calcium ionophore) or phorbol myristate acetate (an analog of diacylglycerides) caused marked increases in luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) secretion. Exclusion of Ca2+ from the medium prevented the stimulatory effects of PMA. The potent stimulator of adenylate cyclase, forskolin, caused only slight stimulation of LH and FSH secretion, which was also prevented by removal of Ca2+. The cytoskeletal disruptive agents colchicine, nocodazole, and cytochalasin B, and the calmodulin inhibitors, trifluoperazine and pimozide, had no significant effects on the action of GnRH. Overall, these results indicate that the major mechanisms of Ca2+ involvement in the response to GnRH by the frog pituitary are similar to that of mammals, with the possible exceptions of lesser roles for calmodulin and the cytoskeleton in the frog. The study suggests that polyphosphatidyl‐inositol‐diacylglyceride metabolism may be critical in understanding the mechanism of GnRH action in frogs.
Effect of ouabain on the meiotic maturation of stage IV–V Xenopus laevis oocytes
Authors: Penna Mary Jo , Wasserman William J.
Published: June 2005

Full‐grown stage VI Xenopus laevis oocytes (1,200 to 1,300μm) respond to progesterone stimulation by undergoing a series of physiological and morphological changes that are referred to as meiotic maturation. Oocytes in earlier stages of oogenesis (I through V) do not undergo these changes and remain in prophase arrest when exposed to this steroid. We have found that oocytes ranging from 850 μm (stage IV) to 1,000 μm (stage V) are capable of responding to progesterone under the appropriate conditions. Oocytes ≥ 850 μm in diameter underwent germinal vesicle breakdown (GVBD) after 10–12 hr of exposure to progesterone when ouabain was added to the medium at a concentration > 2.5 × 10−6M. Under this culture condition, progesterone was now able to induce a 0.3‐ to 0.4‐unit increase in the intracellular pH of stage IV–V oocytes, a 4‐ to 5‐fold increase in 40s ribosomal protein S‐6 phosphorylation, and a 2.3‐fold increase in their rate of protein synthesis. All of these physiological changes are characteristic of full‐grown stage VI oocytes undergoing meiotic maturation. In addition, we have found that oocytes ≥ 750 μm are capable of amplifying maturation promoting factor (MPF) in their cytoplasm leading to GVBD. Therefore, stage IV–V Xenopus oocytes have the potential for undergoing meiotic maturation, but they are blocked at a point in prophase that appears to be alleviated by the combination of progesterone and ouabain.
Circadian and circannual rhythms of melatonin in plasma of male white‐tailed deer and the effect of oral administration of melatonin
Authors: Bubenik G. A. , Smith P. S.
Published: June 2005

Circadian levels of melatonin (M) were determined in plasma of four male white‐tailed deer sampled hourly in September for 24 h via indwelling jugular catheter. Concentrations of M, detected by the radioimmunoassay rise with the onset of darkness, peak at 1.00 h (265 pg/ml) and then quickly decline to baseline levels (60 to 70 pg/ml) maintained during the scotophase. Orally administered M (5 mg, given at 13:00 h) induced a rapid elevation of plasma M (peak 980 pg/ml at 15:00 h) followed by a decline to baseline (100 pg/ml) reached at 22:00 h. The usual midscotophase peak was abolished by exogenous M administration. Seasonal midscotophase levels of M (determined in three samples taken 45 min apart between 23:00 and 1:00 h reach maximum in December (1530 pg/ml) followed by decline to minimum (69 to 90 pg/ml) observed between May and July. The data indicate that: 1) similarly to other mammals, deer exhibit peak level of M during the dark phase; 2) 5 mg of M given orally caused a rapid elevation of M levels in blood followed by a depression of the normally present night‐time peak; and 3) midscotophase levels of M exhibit very pronounced seasonal fluctuations which might be related to yearly cycles, such as the reproduction, hair molt, and antler growth.
Effect of mammalian gonadotropins on testosterone secretion in male alligators
Authors: Lance Valentine A. , Vliet Kent A.
Published: June 2005

Male farm‐reared alligators were injected with mammalian FSH, LH, hCG, prolactin, or saline. A blood sample was taken immediately prior to injection of hormone and at 24 h postinjection. Testosterone concentrations in the plasma were then determined by radioimmunoassay. Only the alligators injected with FSH showed a significant increase in plasma testosterone. In a second series of experiments male alligators were injected with ovine LH, ovine FSH, or saline and bled at 0, 2, 4, 16, and 24 h postinjection. Again, only the alligators injected with FSH showed significant increases in plasma testosterone at 16 and 24 h postinjection. Mammalian LH does not appear to stimulate testosterone secretion in male alligators.
Utilization of aspartate transcarbamylase activity in the study of neuroendocrinal control of gametogenesis in Mytilus edulis
Authors: Mathieu Michel
Published: June 2005

Studies on the endocrine control exerted upon cellular multiplication in mussel mantle tissue (the site of the gonad in this species) are rendered difficult by its extremely heterogeneous nature and require the use of a quantifiable bioassay. Measurement of specific ATCase activity gives a good estimation of pyrimidine biosynthesis; in mussels, the specific activity of this enzyme is highest in the mantle tissue and is closely correlated to the gonadosomatic index. Stimulatory action of cerebral ganglia in organ culture experiments are associated with increases of specific ATCase activity. Antimitotic substances, such as 5 fluorouracile or arabinocytosine on the other hand, induce a decrease of ATCase activity in mantle explants. The utilization of ATCase activity measurements, in the study of gametogenic controls, is proposed in species in which the gonad is not a differentiated organ.
Isolation and characterization of a polarized isolated hepatocyte preparation in the skate Raja erinacea
Authors: Smith D. J. , Grossbard M. , Gordon E. R. , Boyer J. L.
Published: June 2005

Hepatocytes of the small skate (Raja erinacea) were isolated by collagenase perfusion and evaluated by a variety of functional and morphologic criteria. Cell yield was 1.45 × 108 ± 1.3 × 107 cells per isolation, and as long as 8 h after isolation 98% of the hepatocytes excluded Trypan blue and no leakage of lactate dehydrogenase (LDH) or cell associated potassium could be detected. Oxygen consumption averaged 1.6 ± 0.5 nmol/min/mg cell protein, was not stimulated by 1 mM succinate, and also remained stable for up to 8 h following isolation. However, 2,4,‐dinitrophenol (5 × 10−5 M) produced a 55% increase in oxygen utilization while ouabain, (1 mM) or sodium removal decreased oxygen consumption by 31 ± 6 and 33 ± 7%, respectively, indicating that a significant portion of the cells energy utilization is coupled to the activity of plasma membrane Na+, K+‐ATPase.

Light microscopic studies showed that the individual hepatocytes had diameters of 28 ± 5 μm and contained large lipid droplets. Electron microscopy revealed groups of three to five cells with normal ultrastructure and tight junctions and desmosomes surrounding a single bile canaliculus.

These studies indicate that skate hepatocytes can be isolated in high yield that retain their structural polarity in the form of clusters of cells formed around a single bile canaliculus. These hepatocytes remain morphologically intact and metabolically stable for a prolonged period of time. Isolated skate hepatocyte preparations should be a useful experimental model to study hepatic metabolism in marine species, not only because of their viability but also because they retain their apical and basolateral membrane polarity, a feature that is usually lost in other isolated hepatocyte preparations.
Regulation of embryonic diapause in Artemia: Environmental and physiological signals
Authors: Drinkwater Laurie E. , Crowe John H.
Published: June 2005

Environmental cues terminating embryonic diapause and a potential regulatory mechanism involving depressed pH were investigated in the encysted embroyos of the brine shrimp, Artemia. Two species, Artemia franciscana and Artemia monica, were used for this comparative study. To determine if alteration of intracellular pH (pHi) can terminate diapause, the pHi of diapause cysts was manipulated by exposure to NH3 and CO2. Alkalinization did not result in activation of cysts from either species but acidification activated A. franciscana cysts. A. monica did not respond to acidification. The pHi of aerobic diapausing embryos was determined using 31P nuclear magnetic resonance spectroscopy. During diapause, embryos from both species had pHi's similar to those reported for activated (nondiapause) embryos, indicating that diapause is not imposed by depressed pHi, as is the case during suppression of metabolism under anaerobic conditions. Diapause embryos were exposed to varying conditions of temperature, salinity, and oxygen to determine what conditions are necessary to break diapause. A. franciscana cysts were activated by cold temperature or salinites above 2.0 M NaCl, while A. monica cysts only responded to cold temperature. The availability of oxygen did not influence either population's ability to terminate diapause. The results are discussed with respect to each population's environment and potential mechanisms of diapause regulation.
Protein synthesis during imaginal disc pattern regulation
Authors: Greenberg Robert M. , Adler Paul N.
Published: June 2005

We have examined the pattern of protein synthesis during wing disc pattern regulation. Although in vivo culture dramatically alters the pattern of abundant protein synthesis in wing discs, only one protein—RG38—changes specifically in response to pattern regulation. This polypeptide, previously identified as being nonuniformly distributed in wing and haltere discs, is synthesized in a graded distribution across the wing disc. During wing disc pattern regulation, it acts as a molecular marker for regeneration of particular wing disc regions. Thus, the rate of RG38 synthesis increases during regeneration (by fragments with initial low levels) with kinetics that parallel those for regeneration as scored by the presence of adult cuticular structures.
Pacemaker region in a rhythmically contracting embryonic epithelium, the enveloping layer of Oryzias latipes, a teleost
Authors: Barber B. , da Cruz M. J. B. , DeLeon J. , Fluck R. A. , Hasenfeld M. P. , Unis L. A.
Published: June 2005

The primary objectives of this study were (1) to determine the embryonic stage at which the Oryzias latipes enveloping layer (EVL) begins to contract rhythmically, and (2) to determine where these contractions arise within the EVL. Using time‐lapse video recording, we showed that the contractions begin at stage 14 (the stage of the embryonic shield) and arise in the ventral region of the EVL, which is centered at 180° longitude from the embryonic shield. We have called this the pacemaker region for the contractions. Using fluorescein diacetate as a vital stain, we showed that the ventral region of the EVL continues to act as a pacemaker even after the EVL is detached from the rest of the egg.

Rhythmic contractile activity ceased when we removed a group of about 130 cells — 10% of the total EVL— from the pacemaker region; comparably large wounds elsewhere had no effect on the contractions. When we cut detached EVLs into ten pieces, only 2.4 ± 1.8 (X ± SD, N = 11) of them contracted rhythmically, even though a considerably larger proportion of the EVL cells participate in the contractions in undisturbed blastoderms. We conclude that the pacemaker cells are necessary for rhythmic contractile activity and that cells outside this region do not contract spontaneously.

The contractile waves are propagated at a velocity of 14–54 μm sec−1. This value, which is two to three orders of magnitude slower than the propagation of epithelial action potentials, is similar to the rate of propagation of waves of increased cytosolic Ca2+ in other systems.

We propose that the medaka EVL is a good system in which to study certain aspects of epithelial morphogenesis.