bluuebunny/crossref_metadata_2025 huggingface dataset:
Germ cell differentiation in mouse adrenal glands
Authors: Zamboni Luciano , Upadhyay Shakti
Published: June 2005

The differentiation of germ cells in the adrenal glands of 26 male and female Swiss albino mice was studied in sequential stages of development, from day 12½ of intrauterine life to postnatal day 21; the study was performed by means of high‐resolution light microscopy and electron microscopy. In 12½‐ and 13‐day‐old embryos, the ectopic cells had morphologic characteristics typical of primordial germ cells, whereas in 14‐ and 15‐day‐old fetuses they were identifiable as oogonia. In male and female fetuses from day 17 to term, all ectopic germinal elements entered meiotic prophase, reached diplotene, and differentiated into oocytes in perfect adherence to mouse ovarian timetables. In the postnatal animals, females as well as males, all oocytes progressed through the postmeiotic phase of growth just as they normally do in ovarian follicles, and, in the 2‐ and 3‐week‐old animals, they displayed features identical to those exhibited by oocytes in large antral follicles, including a zona pellucida. Germinal elements were no longer seen in the adrenals of animals older than 3 weeks. Our study shows that mammalian germ cells are capable of developing even outside the gonads, and that in ectopic sites they all differentiate as oocytes irrespective of their genetic sex.
Nuclear transplantation in mouse embryos
Authors: McGrath James , Solter Davor
Published: June 2005

The ability of foreign nuclei to support development in nuclear transplantation manipulations has proven an effective means to assess the consequences of nuclear differentiation. In addition, nuclear transplantation might serve to define the persistence and role of maternally inherited cytoplasmic constitutents during embryogenesis. We have extended the use of a technique that enables the efficient transfer of one‐cell‐stage pronuclei into the cytoplasm of enucleated mouse embryos, and have successfully transferred two‐, four‐, eight‐cell‐stage and inner cell mass (ICM) cell nuclei. We have also used this technique as a means to determining that the stage‐specific embryonic antigen, SSEA‐3, is a cytoplasmic contribution of the unfertilized ovum. The potential value of this technique in determining the developmental capacity of nuclei from various embryonic stages, and in determining nuclear/cytoplasmic origins of early embryonic gene products, is discussed.
Intra‐ and interspecific embryo transfer
Authors: Kraemer Duane C.
Published: June 2005

The procedures that are collectively referred to as embryo transfer (ET) have many uses. They were first used as research tools to study fetal‐maternal physiology. Since the first successful mammalian embryo transfer in 1890, ET has been utilized for enhancement of genetic selection; diagnosis and treatment of infertility; control of infectious disease transmission; screening for genetic defects; propagation of rare and endangered species; and the study of developmental biology. Most of the embryo transfers have been intraspecific. A listing of the species includes rabbit, rat, sheep, mouse, goat, cattle, pig, hamster, ferret, mink, horse, baboon, cat, dog, water buffalo. In two species, rhesus monkey and humans, the successful embryo transfers have been limited to within‐animal, homologous replacement of the embryos. There have been a few successful interspecific embryo transfers. The most common were between Bos taurus and B. indicus cattle. Other interspecific transfers involved Bos gaurus and B. taurus, cattle; Ovis musimon and O. aries, sheep; Equus asinus and E. caballus, horses. There are several examples of integeneric embryo transfers in which embryos implanted but did not develop to term: sheep and goat, mouse and rat. The factors that determine the degree of compatibility between embryos and uteri of various species and genera are not clearly understood. The ability to hybridize successfully is probably a dependable indication of compatibility for embryo transfer. The limits of tolerance for differences between the donor and recipient in such factors as placental structure and gestation length have not been defined, but the recently developed technique of inner cell mass transfer will be very useful in such studies.
Alternatives to lactic acid: Possible advantages
Authors: Fields Jeremy H. A.
Published: June 2005

Many groups of invertebrates use metabolic strategies that do not lead to the accumulation of lactate during periods of hypoxia or anoxia. These animals may accumulate some combination of the following: alanine, octopine, alanopine, strombine, acetate, propionate, 2‐methylbutyrate, 2‐meth‐ylvalerate, and succinate. An organism may derive a benefit from production of an alternative end product when the yield of ATP per mole of glucose 6‐phosphate is greater than that found in lactate production. Formations of succinate, propionate, 2‐methylbutyrate, and 2‐methylvalerate have been shown to yield more ATP in a few species. This analysis can be extended to the formation of alanine, as this is accompanied by the conversion of aspartate to succinate.

Formations of octopine, alanopine, or strombine apparently do not increase the yield of ATP per mole of glucose 6‐phosphate, because the enzymes forming these compounds are functionally analogous to lactate dehydrogenase. A potential advantage of producing these compounds might be maintenance of a constant intracellular osmotic pressure during periods of anoxia. The significance of this is uncertain, because if lactate were to accumulate, the expected change in osmotic pressure appears to be trivial. Another possible advantage of accumulating octopine, alanopine, or strombine, would be the ability to maintain a lower NADH/NAD+ ratio as compared with the accumulation of lactate. This might assist the organism in maintaining a high rate of glycolysis by reducing the inhibition of glyceraldehyde 3‐phosphate dehydrogenase by NADH. Other possibilities are smaller perturbations of the acid–base balance of the cell, or producing a compound that has less effect on the catalytic and regulatory properties of enzymes in the cell.
Properties of amino acid transport in preimplantation rabbit embryos
Authors: Miller J. G. O. , Schultz G. A.
Published: June 2005

The kinetics, specificity, time dependency, Na+ dependency, and exchange behavior of the uptake of methionine, as a model for the uptake of the neutral amino acids, was investigated in rabbit eggs, morulae, and 6‐day blastocysts. Uptake by the blastocyst was physically resolved into components representing uptake into the cellular and cavity compartments. The kinetic data for all material, except the cellular compartment of the blastocyst, could be described mathematically by the parallel activity of a saturable and a linear transport system. The Km decreased from 91 μM in the unfertilized egg to 38 μM in the fertilized egg to 13 μM in the 69‐hr morula. The Km of uptake into blastocysts was 131 μM. The Vmax of uptake into the whole blastocyst was calculated to be about 5000 times that of uptake into the egg. Competition of methionine uptake by other amino acids indicated that the egg had somewhat more “L‐like” transport specificity than subsequent developmental stages, while the system(s) in the blastocyst were reactive with most neutral amino acids. Uptake into the egg, 69‐hr morula, and the cellular compartment of the blastocyst reached a steady state with time, in contrast to uptake into the 76‐hr morula and the cavity compartment of the blastocyst. Compatible with this, was the observation that eggs and 69‐hr morula, but not blastocysts, exhibited considerable efflux into amino acid‐containing media. The cavity compartment of the blastocyst may, however, act as a reservoir of amino acids for the cellular compartment. The Na+ dependency of transport was unchanged throughout the developmental period studied in this investigation.
TMAO (trimethylamine oxide)‐independence of oxygen affinity and its urea and ATP sensitivities in an elasmobranch hemoglobin
Authors: Weber Roy E.
Published: June 2005

Urea and trimethylamine oxide (TMAO), the major osmolytes in the body fluids of marine elasmobranch fishes, are known to exert counteracting effects on the functions of a variety of enzymes and other proteins of vertebrates (cf. Yancey et al., '82). Although urea raises the O2 affinity of the hemoglobin (Hb) of Squalus acanthias and reduces its sensitivity to the major allosteric cofactor, ATP, the oxygenation reactions of the Hb are insensitive to TMAO, reflecting the absence of urea‐TMAO counteraction in the absence or in the presence of the phosphate.
Fluorescent localization of calcium at sites of cell attachment and spreading
Authors: Moran Denis
Published: June 2005

Chlorotetracycline (CTC), a calcium‐chelating fluorescent probe identifies and localizes calcium when applied to cultured neural crest cells. The fluorescence occurs at specific membrane regions involved in cell attachment and spreading as well as with the formation of cytoskeletal stress fibers (actin microfilament bundles). The observed CTC reaction indicates that calcium sequestration and the development of these membrane‐cytoskeletal features share a temporal and spatial pattern. Thus, the selective availability of calcium may be an important determinant of cell morphogenesis.
Intracellular optical physiology of the eye of the pyralid moth Amyelois
Authors: Bernard Gary D. , Owens Elizabeth D. , Hurley Andrea Voss
Published: June 2005

As in most nocturnal moths, the eyes of pyralid moths contain crystalline tracts formed by long, thin, distal extensions of the photoreceptor cells. Eyes of pyralid moths are unusual, however, because these thin extensions of the photoreceptor cells contain both pigment granules and rhabdomeric microvilli. Published anatomical and optical studies show that granules of both the photoreceptor cells and the primary/secondary pigment cells migrate as pyralid eyes adapt to light.

The purpose of this paper is to describe noninvasive optical methods that characterize quantitatively the migration of pigment granules of both photoreceptor cells and pigment cells within the eye of the adult pyralid moth Amyelois. We find that: 1) Short, dim, monochromatic flashes (5 sec; 350–600 nm; quantum flux Q = 1010−1012 photons/cm2/sec) delivered to the dark‐adapted eye cause migration of the granules within photoreceptor cells, but no migration of the granules within pigment cells. The shape of a response is simple for the dimmest flashes and is complex for the brighter flashes. 2) The 12 photoreceptor cells that contribute microvilli to the distal rhabdom in each ommatidium are of three spectral types, maximally sensitive at about 350, 430, and 530 nm, respectively. 3) Short, bright flashes (Q > 1013) or long flashes (duration > 1 min; Q > 4 × 1012) delivered to the dark‐adapted eye cause migration of granules within pigment cells as well as receptor cells. Action spectra (350–665 nm) for movements of pigment‐cell granules are dominated by green‐receptors, with minor input from UV‐receptors and negligible input from the blue‐receptors.
Notochord formation in the Mexican salamander (Ambystoma mexicanum) is different from notochord formation in Xenopus laevis
Authors: Brun Rudolf B. , Garson John A.
Published: June 2005

The cytoskeletons of cells from gastrula and neurula stages of the Mexican salamander (Ambystoma mexicanum) and the African clawed toad (Xenopus laevis) were analyzed. Bundles of intermediate filaments were found in the superficial layer of the epidermis in neurulae (but not in gastrulae) of both organisms. The bundles (tonofilaments) were observed in the forming notochord of the axolotl but not in the differentiating notochord in Xenopus. Serial semithin sections demonstrated that the notochord develops from invaginated deep cells in Xenopus, but from invaginated superficial layer in the axolotl. Scanning electron microscopy of neurula stages from the axolotl and from Xenopus laevis confirmed this difference in notochord formation. This dissimilarity in notochord formation seems to be a typical difference between anurans and urodeles as was clearly pointed out by Ruffini ('25). This has implications for the fate maps published by Vogt ('29). The considerable differences in early embryonic development suggest to us that the salamanders (urodeles) and frogs and toads (anurans) are not monophyletic in origin.
Electrophysiological effects of cholinergic agents on the CNS of a nicotine‐resistant insect, the tobacco hornworm (Manduca sexta)
Authors: Morris Catherine E.
Published: June 2005

To assess the relative sensitivity of Manduca sexta central nervous system (CNS) to nicotine and other cholinergic agonists, global electrophysiological recording techniques were used. Comparisons were made between the tobacco hornworm and Periplaneta americana. Cords were tested in intact and partially desheathed conditions using two different recording methods (differential recording of activity in interganglionic connectives and non‐electrolyte gap recording of potentials developed in the ganglion). Both recording methods indicate that the Manduca tissue is about 100‐fold less sensitive to nicotine than Periplaneta, suggesting that mechanisms local to the CNS contribute to Manduca's ability to subsist on a nicotine‐rich diet. The threshold for response of desheathed Manduca cords to nicotine (during 5‐min exposures) is 5 × 10−5 M nicotine. Desheathing increases the sensitivity of the Manduca CNS to nicotine but does not make the tissue equally as responsive as the Periplaneta CNS. The cholinergic agonists acetylcholine, muscarine, lobeline, and tetramethylammonium and the anticholinesterase, eserine, all induce neural activity in Manduca, indicating that the tissue is not intrinsically insensitive to cholinergic agents. The tertiary amide N'‐methylnicotinamide potentiates the toxicity of nicotine to the Manduca CNS.
Larval innervation of the lobster claw closer muscle
Authors: Hill R. H. , Govind C. K.
Published: June 2005

The excitatory innervation of the claw closer muscle in the three larval (1st, 2nd, 3rd stage) and first postlarval (4th stage) forms of the lobster Homarus americanus was determined principally by electrophysiology. In the 3rd and 4th stages only two excitatory axons were found. One of these had a larger spike with a shorter latency and elicited a larger muscle EJP and a twitch‐like closing of the dactyl compared to the other axon, which had a smaller spike with a longer latency and elicited smaller EJPs and a slow closing of the dactyl with repetitive stimulation. These two axons resemble, respectively, the fast and slow axons of the adult muscle. In the 2nd stage only two excitor axons were demonstrated, one of which resembled the fast axon in evoking large EJPs with regenerative responses. In the 1st stage, excitatory innervation is present, though the number and character of the axons remain unknown. Motor axons, therefore, innervate the claw closer muscle right from the time of hatching and are completely differentiated into fast and slow types by the end of the larval period of development.
Evidence suggesting the importance of fatty acids and the fatty acid moieties of sperm membrane phospholipids in the acrosome reaction of guinea pig spermatozoa
Authors: Fleming Alan D. , Yanagimachi Ryuzo
Published: June 2005

When guinea pig spermatozoa were preincubated 1 hr in Ca2+‐free medium containing dilysocardiolipin (100–125 μg/ml) then exposed to Ca2+, the majority underwent an immediate acrosome reaction. Monolyso‐cardiolipin was much less effective and the native cardiolipin was totally ineffective. Some fatty acids added to the medium could also render the spermatozoa capable of undergoing their acrosome reactions, arachidonic acid in methyl ester form being most potent. It is known that sperm membrane contains phospholipase A which cleaves membrane phospholipids into lysophospholipids and fatty acids. Most lysophospholipids are known to be potent acrosome reaction–promoting agents. As some forms of fatty acids are also potent acrosome reaction–promoting agents, both products of membrane phospholipid hydrolysis by phospholipase A (i.e., both fatty acids and lysophospholipids) may work synergistically to effect the conversion of stable sperm membranes to a fusion competent state capable of engaging in the acrosome reaction.
Two healing patterns correlate with different adult neural connectivity patterns in regenerating embryonic Xenopus retina
Authors: Ide Charles F. , Reynolds Patrick , Tompkins Robert
Published: June 2005

Nasal and temporal one‐third‐sized eye fragments, formed by ablation at stage 32–33 of Xenopus laevis embryos, heal and, in about 50% of the cases, survive to make eyes in the postmetamorphic animal which have mappable visuotectal projections. The majority of nasal one‐third eyes have duplicate projections whereas the majority of temporal one‐third eyes have unduplicated projections. Most nasal one‐third eye fragments and a minority of temporal eye fragments heal by the extrusion of cells from the center of the cut edge into the region of the ablation, forming a tongue of cells between the distal cut edges. This healing pattern is correlated with duplicated visuotectal projections. Most temporal one‐third fragments and a minority of nasal one‐third fragments heal by rounding up; that is, the distal cut edges collapse to meet in the region of the ablation. This healing pattern is correlated with the formation of unduplicated visuotectal projections. During tongue formation, neurons and undifferentiated cells are transferred from the original fragment into the tongue in a disorderly array, but quickly re‐form normal retinal order. We propose that the tongue cells retain their original determination to connect to the same tectal positions as the fragment from which they originated, despite their new positions, and that this mosaicism, coupled with cell movement into the tongue, established duplicate visuotectal projections.
Sources of calcium for embryonic development in eggs of the snapping turtle Chelydra serpentina
Authors: Packard Mary J. , Short Terry M. , Packard Gary C. , Gorell Thomas A.
Published: June 2005

Flexible‐shelled eggs of snapping turtles (Chelydra serpentina) were analyzed for calcium content at different times in incubation to determine sources of mineral for developing embryos and to characterize the pattern of its mobilization. Yolk and albumen of freshly laid eggs contained 11.70 and 0.16 mg of calcium, respectively. Almost all calcium was withdrawn from the yolk during incubation, but this calcium was not sufficient to satisfy requirements of embryos. Calcium contained within eggs increased to 27 mg between oviposition and hatching owing to mobilization of approximately 15 mg of calcium from the calcareous eggshell. Thus, embryonic snapping turtles obtain slightly more than half (56%) of the calcium required for development from the eggshell, with the remainder (44%) coming from stores present in the yolk at oviposition.
Acetylcholine promotes progesterone‐induced maturation of Xenopus oocytes
Authors: Dascal Nathan , Yekuel Rivkah , Oron Yoram
Published: June 2005

Progesterone‐induced maturation of follicle‐enclosed and denuded Xenopus laevis oocytes was significantly shortened by a concomitant exposure to acetylcholine. The promotion of maturation by acetylcholine was blocked by the specific muscarinic antagonist atropine. The action of acetylcholine was dose dependent, and the neurotransmitter was effective at very low concentrations. Progesterone progressively reduced the electrophysiological responses of X. laevis oocytes to acetylcholine, which completely disappeared close to the time of germinal vesicle breakdown. Progesterone alone did not elicit any electrophysiological responses. The in vitro effect of acetylcholine on oocyte maturation might reflect a physiological influence of the cholinergic system on an in vivo maturation process.
Conspecific odor detection by the male broad‐headed skink, Eumeces laticeps: Effects of sex and site of odor source and of male reproductive condition
Authors: Cooper William E. , Vitt Laurie J.
Published: June 2005

Olfactory stimuli are sufficient for detection and discrimination of sex of conspecific lizards by the male broad‐headed skink, Eumeces laticeps, a member of a large group of lizards with pronounced chemosensory abilities, the Autarchoglossa.

The capacity of male broad‐headed skinks to detect conspecific odors was assessed by measuring tongue extrusion rates in response to odor stimuli presented on moist cotton applicators. Tongue‐flick rates of postreproductive males were siginificantly higher for clocal odors of postreproductive conspecif‐ics of both sexes than to distilled water and higher to female than male odors over the initial 20‐ and 60‐sec intervals. In a second experiment using testosterone‐treated males and estrogen‐injected females, testosterone‐treated males emitted significantly more tongue flicks to female cloacal odors than to the other stimuli, and two males bit applicators bearing male odors. Testosterone did not affect reaction to male cloacal odors, but markedly increased tongue flick rates in response to cloacal odors of estrogen‐treated females. Post reproductive males also responded to female, but not male, skin odors at a significantly higher rate than to water. Possible sources and presumed adaptive significance of conspecific odors are discussed.
Quail melanoblast migration in two breeds of fowl and in their hybrids: Evidence for a dominant genic control of the mesodermal pigment cell pattern through the tissue environment
Authors: Hallet Marie‐Martine , Ferrand Raymond
Published: June 2005

In the Silkie fowl large numbers of melanocytes invade most internal tissues and organs. The factors involved in this internal pigment cell pattern were studied by grafting quail neural tube segments into White Leghorn, White Silkie, and F1 hybrids (White Silkie male × White Leghorn female). Sections of quail neural tube five somites long, excised at the level of the last formed somites, were grafted isotopically and isochronically. Various tissues and organs (mesenteries, muscles, testis, ovary, mesonephros, metane‐phros, and adrenals) excised from the internal region corresponding to the peripheral transverse strip of quail melanocytes, were studied after staining by the Feulgen‐Rossenbeck technique.

Despite some variations in pigment cell density, Silkie and hybrid grafted embryos exhibited an extensive quail internal pigmentation similar to the melanocyte distribution in the Silkie breed. In white Leghorn host embryos, the internal pigmentation remained limited. These results show the part played by tissular factors in the expression of the Silkie pigment phenotype and that this genetic tissular character is dominant.

On the contrary, White Leghorn embryos, grafted with Silkie neural tube segments, never exhibited any internal pigmentation; the melanocytes deriving from the grafted Silkie neural tube were only localized at the dermoepidermal level. Thus, the migrating and/or differentiating capabilities of the Silkie premelanoblasts are different from those of quail premelanoblasts. The sex‐linked inhibitor of the White Leghorn tissue interferes at the level of the pigment cells of chickens but not of quails.
Relationship between muscle size and motoneurone survival in temporarily paralyzed embryos
Authors: McLennan Ian S.
Published: June 2005

Neuronal cell death has been postulated to occur as a consequence of there being a limited availability of target. This hypothesis was examined by delaying the onset of motoneurone cell death, by temporary paralysis of chick embryos, until the size of the target had increased. Despite the availability of this enlarged periphery, the extent of cell death was unaltered, although the rate of cell death was retarded. It is argued that the extent of cell death is not simply related to target size and may instead be governed by differences in the capacity of particular motoneurones to compete successfully for target cells.
Influence of ethanol on chromosome segregation during the first and second meiotic divisions in the mouse egg
Authors: Kaufman M. H. , Bain I. M.
Published: June 2005

This study was carried out to investigate the influence of ethanol on chromosome segregation during the first and second meiotic divisions. Female mice were given a single intragastric injection of a dilute solution of ethanol either just before or at various times after the HCG injection for inducing superovulation. The mice were mated, and the chromosome constitution of fertilized eggs was determined at the first cleavage mitosis. The technique employed allowed the male‐ and female‐derived pronuclear sets to remain as two discrete groups. Exposure from 1.5 h before to 17 h after the HCG injection induced a high incidence of aneuploidy (15–25%) involving in over 90% of cases only one chromosome, so that either 19 or 21 instead of the normal complement of 20 chromosomes were present in one of the two sets (a previous study using a “marker” chromosome has demonstrated that the nondisjunction induced here invariably involves the female set). We suggest these findings draw attention to the susceptibility of chromosome segregation in female germ cells to interference by ethanol and that the mode of action is likely to be via interference with the normal functioning of the spindle apparatus. It is possible that interference with meiotic chromosome segregation by spindle‐acting agents such as ethanol might account for a proportion of human spontaneous abortions with similar chromosomal defects where no other obvious cause is apparent.
Environmental salinity and the thyroidal response to thyrotropin in juvenile coho salmon (Oncorhynchus kisutch)
Authors: Specker Jennifer L. , Richman N. Harold
Published: June 2005

The effect of environmental salinity on the thyroidal response, measured by plasma concentrations of thyroxine (T4), to exogenous bovine thyrotropin (bTSH) was assessed early and late in the smoltification of coho salmon (Oncorhynchus kisutch). A single injection of 100 mlU bTSH significantly increased plasma T4 concentrations in fish in both fresh water and seawater, and both early (March 19) and late (May 24) in smoltification. In fish transferred to seawater, the increase in T4 titers was somewhat earlier and its duration shorter, suggesting an environmentally induced change in the kinetics of T4 entry and exit from the blood stream. The overall response to TSH was greater near the beginning (March 19) of the smoltification‐associated T4 increase than near the end (May 24), suggesting a development‐related change in thyroid function.
Electrophoretic analysis of pancreatic proteases and zymogen‐activating factors in the mouse
Authors: Isobe Masaharu , Ogita Zen‐Ichi
Published: June 2005

Mouse pancreatic proteases were analyzed by one‐ and two‐dimensional electrophoresis. Active proteases that existed in the luminal fluid were separated into at least eight bands in 8% polyacrylamide gel. Pancreatic proteases activated by intestinal extract were separated into at least seven bands. The mobilities of these bands were exactly the same as those of proteases in the luminal fluid except for those of the most cathodal band. Two kinds of trypsin (Try‐I group and Try‐II) and one kind of chymotrypsin (Chy‐I) were determined by specific and nonspecific protease staining. Try‐I group and Try‐II were derived from different trypsinogens (Try G‐I group and Try G‐II), whereas Chy‐I was derived from a single chymotrypsinogen (Chy G). Although Try G‐II was activated by both intestinal extract and by bovine trypsin, Try G‐I group activated only by intestinal extract. Intestinal‐activating factors were analyzed by two‐dimensional electrophoresis. Mouse enterokinase (enteropeptidase, EC 3.4.4.8), which can activate bovine trypsinogen, had a slow mobility. In the intestine of the mouse there are several activating factors in addition to enterokinase. Although it is unclear what intestinal‐activating factors can activate Chy G, there is a factor that can convert chymotrypsinogen into chymotrypsin directly. These data suggest that intestinal‐activating factors play an important role in the activating mechanisms of mouse pancreatic zymogens.
Bipartite axiation follows incomplete epiboly in zebrafish embryos treated with chemical teratogens
Authors: Baumann Martin , Sander Klaus
Published: June 2005

Medial clefts in the axis of the trunk region are malformations known from many chordates and are mostly referred to as rachischisis anterior. In teleosts, rachischisis was previously ascribed either to secondary rifting of a single uniform axial rudiment, or to the establishment of two (half) axes and body halves physically separate from the very beginning. In order to decide between these conflicting interpretations, we treated zebrafish embryos during blastodisc stages and epiboly with several chemical teratogens causing rachischisis anterior. Treatment with ethanol, Colcemid®, hydroxyurea, or cyclohex‐imide was found to delay the proliferation and movements of the deep cells more strongly than the timing of cell differentiation, so that the deep cells embark on organogenesis before having reached their destinations in the uniform germ shield. Treatment with α‐amanitin, on the other hand, seems primarily to affect the periblast and enveloping layer; the incomplete epiboly observed in these layers appears to restrain deep cell epiboly physically and thus to cause rachischisis. In both instances, the split condition of the embryo's trunk region is clearly due to the ectopic formation of physically separate body halves right from the beginning, a mode we call bipartite axiation. We also describe secondary anomalies specific for individual teratogens, and briefly discuss the possible origins of rachischisis anterior among other chordates including man.
Lysosomes fuse with one half of alga‐bearing phagosomes during the reestablishment of the European green hydra symbiosis
Authors: McNeil P. L. , McAuley P. J.
Published: June 2005

Sorting of native Chlorella algae during the reestablishment of the European green hydra symbiosis occurs after phagocytosis by host digestive cells, when approximately half the algae subsequently disappear, either by exocytosis or by digestion. Using electron microscopical and cytochemical techniques we have assessed the morphological integrity of algae after phagocytosis and characterized fusion between alga‐bearing phagosomes and host‐digestive cell lysosomes.

Five hours after initiation of phagocytosis of algae, approximately 45% were associated with lead reaction product of the lysosomal enzyme acid phosphatase. Some individual alga‐bearing phagosomes had fused, forming large phagolysosomes which contained numbers of algae at various stages of digestive degradation. Thus, sorting may result from the failure of about half of the algae phagocytosed by European digestive cells to prevent lysosome fusion with their phagosomes, and hence their digestion by lysosomal enzymes. Acid phosphatase reaction product was not associated with vacuoles containing established algal or bacterial symbionts.

Pretreatment of algae with cationic agents increased the number of algae sorted for digestion, and it also perturbed algal release of photosynthate. It is suggested that algae prevent lysosomal fusion through release of photosynthate, and that sorting is a result either of a rate competition between lysosomal fusion and its inhibition by algae, or of only a proportion of algae releasing photosynthate above the threshold level needed to prevent lysosomal fusion.
Regulation of melanization of tobacco hornworm larval cuticle in vitro
Authors: Hiruma Kiyoshi , Riddiford Lynn M.
Published: June 2005

When tobacco hornworm larvae (Manduca sexta) are allatectomized 5–6 hr before head capsule slippage in the molt to the fifth (final) larval instar, the new cuticle melanizes 3 hr before ecdysis. After explantation between 7 and 3 hr before the onset of melanization, the new cuticle was found to melanize in vitro in Grace's medium only if β‐alanine was removed. When explanted at the onset of melanization, the presence of β‐alanine had no effect on melanization. The addition of either dopa or dopamine was found to be necessary for complete melanization of pieces explanted before the onset of melanization with 0.3 mM of either dopa or dopamine being optimal. Both of these compounds were incorporated into the cuticular melanin. In this optimal medium, melanization occurred over about a 9‐hr period after a 5‐ to 6‐hr lag period presumably required for adjustment to the medium. Fifty ng/ml 20hydroxyecdysone was found to inhibit melanization of pieces explanted 7 hr but not 3 hr before melanization. The hormone neither inhibited uptake of dopa into the epidermis nor prevented melanization in the cuticle once the prophenoloxidase in the premelanin granules was activated. Therefore, 20hydroxyecdysone may inhibit the activation of the phenoloxidase in the premelanin granules, or may inhibit the incorporation of dopa into the granules.
Neural tube occlusion precedes rapid brain enlargement
Authors: Schoenwolf Gary C. , Desmond Mary E.
Published: June 2005

Histological examination of early vertebrate embryos during rapid brain enlargement (an event partially driven by fluid pressure) reveals that the spinal cord lumen is occluded. Occlusion (if it is not merely a fixation artifact) may confine neural tube fluid to brain regions and seal off the ventricles before posterior neuropore closure. We injected neural tubes of living chick embryos with dyes, asking: (1) is occlusion real; and (2) does occlusion precede brain enlargement? Both questions were answered affirmatively. Experimental analyses of occlusion and brain enlargement are in progress.
The thiol‐disulfide balance during maturation of Xenopus laevis oocytes
Authors: Heidemann Steven R. , Hamborg Marlyn A.
Published: June 2005

We measured several of the components involved in the thioldisulfide balance of immature and mature oocytes of Xenopus laevis: total soluble native sulfhydryl, reduced and oxidized glutathione, native sulfhydryl content of soluble protein, and disulfide content of soluble protein. None of these values changed during maturation. Both the immature and mature oocyte were characterized by a relatively high disulfide to sulfhydryl ratio. We also measured native sulfhydryl content of germinal vesicle proteins and enucleated oocyte proteins in immature oocytes. Contrary to early cytochemical findings, our measurements suggest that the germinal vesicle has a lower concentration of protein sulfhydryl than does the cytoplasm.
Regulation of glycolysis in the mouse blastocyst during delayed implantation
Authors: Nieder Gary L. , Weitlauf Harry M.
Published: June 2005

The rate of oxidation of glucose is reduced in mouse embryos in the prolonged free living phase associated with delayed implantation and increases when the embryos are reactivated by estrogen. To determine how these changes in metabolism are regulated, several aspects of glucose metabolism were evaluated in dormant and reactivated blastocysts: 1) Embryos were exposed to 14C‐pyruvate in vitro and evolved 14CO2 was measured. It was found that the rate of production of CO2 was equal in the two types of blastocysts, suggesting that aerobic pathways are fully functional during delayed implantation. 2) Production of lactate in the presence of O2 was measured and a decrease of 30% was found in delayed implanting embryos, suggesting that the overall regulatory mechanism for glucose metabolism resides in the glycolytic portion of the pathway. 3) Capacity for uptake and phosphorylation of glucose was evaluated using 3H‐2‐deoxyglucose and was found to be equal in the two types of embryos. 4) Total amounts of the rate‐controlling enzymes for glycolysis (i.e., hexokinase and phosphofructokinase) in lysates of delayed and reactivated embryos were found to be equal, indicating that amounts of these enzymes are not limiting in delayed implantation. 5) Lactate production, measured under anaerobic conditions, was found to be equal, demonstrating that it is not the capacity for glycolysis but a difference in the degree of allosteric inhibition that is responsible for reduced glucose oxidation in delayed implantation. 6) Levels of ATP, ADP, and hexose‐6‐phosphates were found to be consistent with allosteric inhibition of the glycolytic pathway at phosphofructokinase during delay and a release of this inhibition with reactivation. In addition, finding a high ATP/ADP ratio in delayed implanting blastocysts indicates that the associated depression of macromolecular synthesis is not due to limited energy supply. Rather it suggests that the reduction in glucose metabolism is probably due to a decrease in energy demand.
Evidence for specific binding of uncapacitated boar spermatozoa to porcine zonae pellucidae in vitro
Authors: Peterson R. N. , Russell L. D. , Hunt W. P.
Published: June 2005

Washed ejaculated boar sperm and sperm from the cauda epididymis bind to the zona pellucida of fixed porcine eggs in large numbers. Sperm incubated in the presence of dextran sulfate (8 K daltons or 500 K daltons) or fucoidan and then washed no longer bind to eggs. Other acid carbohydrates (heparin, chondroitin sulfates, inositol hexasulfate, carboxymethylcellulose) fail to block sperm‐egg binding even when added directly to sperm‐egg suspensions. Seminal plasma and the seminal vesicle secretion contain basic proteins which bind tightly to sperm and bind reversibly to eggs preventing sperm from binding to eggs. When dextran sulfate or fucoidan are mixed with the vesicular secretion, from which seminal plasma basic proteins originate (Hunt et al., '83), the secretion loses the capacity to prevent sperm from binding to eggs; this suggests that seminal vesicle proteins can bind to the same site on zonae as do sperm and thus seminal plasma may modify sperm‐egg interactions.

Corpus and cauda epididymal sperm also bind in large numbers to the zona pellucida of isolated eggs but high concentrations of caput sperm, which exhibit high motility in the presence of caffeine, bind only in few numbers. Thus a component that enhances sperm‐zona binding is apparently formed on the plasma membranes of uncapacitated sperm during passage through the epididymis. This finding, and an earlier observation that antibodies raised against uncapacitated sperm plasma membranes block sperm‐egg binding in vivo (Peterson et al., '83) suggest that this component may be involved in sperm zona interaction in vivo.
Histochemical and biochemical localization of mannitol oxidase in the snail Helix aspersa
Authors: Vorhaben Jean E. , Smith Darwin D. , Campbell James W.
Published: June 2005

The tissue distribution of mannitol oxidase in the snail Helix aspersa has been determined by histochemical and biochemical techniques. Highest activity was found within the alimentary canal and digestive gland where the enzyme presumably acts on ingested naturally occurring polyols, especially mannitol.
The in vitro uptake and distribution of 3H‐fucose and 3H‐mannose in the crayfish retina: A light and electron microscope autoradiographic study
Authors: Hafner G. S.
Published: June 2005

The in vitro uptake and distribution of 3H‐fucose and 3H‐mannose in the crayfish retina was studied using light and electron microscope autoradiography. Animals maintained on a 12:12 light‐dark (L‐D) cycle were incubated for 8 hr in the light beginning at their normal light‐onset time. Both sugars were incorporated into components of the rhabdom microvillous membrane, as indicated by the progressive increase in labeling of this structure during the incubation period. Fucose was initially concentrated in the Golgi apparatus of the receptor cells, where distinct grain clusters were seen after 15‐min incubation in the light. A similar concentration of fucose was also seen in the accessory reflecting pigment cells, as well as neurons and glia of the lamina ganglionaris. After 1 hr and longer, the eighth cell rhabdomere and the distal portion of the main rhabdom appeared more heavily labeled than the proximal region of the rhabdom. With mannose, a more diffuse cytoplasmic label was observed, and there was no evidence of heavy Golgi labeling. The diffuse label in the cytoplasm with mannose was followed by a general increase in labeling over the rhabdom, which was more uniform in comparison with fucose. The pattern of labeling seen in the crayfish photoreceptor with these two sugars is similar to that reported in the vertebrate photoreceptor. The progressive labeling of the rhabdom during the time when membrane loss is also taking place suggests that both aspects of the renewal process in the crayfish occur simultaneously during the period of the light cycle examined. It is proposed that the labeling pattern represents the incorporation of these sugars into glycoproteins present in the microvillous membrane and that one or both of these sugars may be components of the photopigment in these membranes.
Stump currents in regenerating salamanders and newts
Authors: Borgens R. B. , McGinnis M. E. , Vanable J. W. , Miles E. S.
Published: June 2005

We report here that a variety of salamanders and newts from differing habitats all drive a steady ionic electric current out of the forelimb stump tip after forelimb amputation. Several hours after amputation the density of this stump current ranges from about 10 to 100 μA/cm2 in most species, and declines with time.

In most cases, the magnitude of the stump current is dependent on the concentration of Na+ in the external medium (an artificial pondwater), suggesting that the well‐known Na+‐dependent transcutaneous voltage described in amphibia (particularly frogs) is the EMF for this stump current. These measurements add to those previously reported for the North American red spotted newt (Notophthalmus viridescens), and suggest that electrical changes following amputation of urodele limbs are widespread among members of this group.
Effects of photoperiods and melatonin on planarian asexual reproduction
Authors: Morita Michio , Best Jay Boyd
Published: June 2005

Asexual planarians of the species Dugesia dorotocephala exhibit a distinct day‐night rhythm of fissioning under the influence of normal photoperiod; fissioning occurs only at night. This rhythm is broken by continuous illumination, continuous darkness, or by decapitation. The fissioning rate increases when planarians are exposed to light for less than 1 hr/day or when they are decapitated. These results suggest that the planarian head, probably brain, releases a substance that inhibits fissioning, and that the synthesis and release of this substance are closely related to the environmental photoperiod. Furthermore, fissioning of decapitated planarians is suppressed by continuous treatment with melatonin in their culture water. Fissioning resumes when these are returned to normal culture water. Interestingly, fissioning occurs at night when decapitates are treated with melatonin in the daytime, while it is observed in the daytime with night‐time melatonin treatment. These results are consistent with the hypothesis that melatonin release from brain mediates the influence of environmental photoperiods on fissioning.
Cardiac output and tissue blood flow in the abalone, Haliotis cracherodii (Mollusca, Gastropoda)
Authors: Jorgensen D. D. , Ware S. K. , Redmond J. R.
Published: June 2005

Little is known about the characteristics of hemolymph (blood) flow in animals with open circulatory systems. We measured cardiac output and blood flow to specific tissues in the black abalone, Haliotis cracherodii, a gastropod mollusk. The use of thermodilution allowed us to make repeated measurements of cardiac output and cardiac stroke volume over relatively short time intervals (5–10 heart beats) in resting, unrestrained abalone while disturbing the animals minimally. Anatomical studies of the abalone circulation showed that the arterial system terminated in small diameter (approaching 10–20 μm in some cases) lacunar tissue spaces. Because of this, we used radioactive microspheres (which must be trapped in the tissue vasculature) to measure blood flow rates to selected tissues. The major findings of our study were that 1) cardiac output in the black abalone ranged from about 100 to 150 ml · kg−1 · min−1, and was highly correlated with body size; 2) weight‐specific cardiac stroke volume was about 5 ml · kg−1, considerably larger than that of a mammal; 3) tissue blood flow rates ranged from 10 ml · 100 g−1 · min−1 (foot muscle) to 80 ml · 100 g−1 · min−1 (nephridial tissue), similar to typical tissue blood flow rates in mammals. Our data suggest that the blood in the abalone is directed to the tissues not in proportion to percent total body weight the tissues represent (as might be expected in an open vascular system), but apparently in proportion to tissue metabolic rate.
Photoaffinity labeling of the ouabain binding site in Na, K‐ATPase in developing brine shrimp
Authors: Churchill Lynn , Hall Clifford C. , Peterson Gary L. , Ruoho Arnold E. , Hokin Lowell E.
Published: June 2005

Analysis of purified Na,K‐ATPase from brine shrimp nauplii by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis reveals two large (α) subunits [G.L. Peterson, R.D. Ewing, S.R. Hootman, and F.P. Conte (1978) J. Biol. Chem. 253:4762]. The band with lower mobility in a neutral or alkaline gel is designated α1 and the band with higher mobility α2. Ouabain prevents dephosphorylation of both α1 and α2 as documented by gel analysis, but a higher concentration of ouabain is required to prevent dephosphorylation of α2. The photoaffinity label, [3H]4′(2‐ethyldiazomalonyl) digitoxigenin monodi‐gitoxiside, specifically labels α in a ouabain‐protectable manner without labeling other contaminating proteins in the preparation. Greater than 93% of the total ouabain‐protectable labeling of the α subunits is associated with α1. The photoaffinity label, [3H]4‴ (2‐ethyldiazomalonyl) digitoxin, specifically labels α1 and β in a ouabain‐protectable manner without labeling other contaminating proteins. These data show that in the brine shrimp the third digitoxose residue of digitoxin binds in a region in which the α1 and β chains are in close proximity. Less than 5% of the specific ouabain‐protectable labeling of total α is associated with α2. These studies indicate that cardioactive steriods have higher affinity for the α1 subunit.
A reversal in relative mobility of the two large subunits of brine shrimp (Na+ + K+)‐adenosinetriphosphatase
Authors: Churchill Lynn
Published: June 2005

The two large subunits of brine shrimp Na,K‐ATPase can be resolved by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis at neutral pH and at acidic pH. These subunits appear to reverse their positions on the gel relative to each other when resolved at acidic pH relative to neutral pH. The migration of both subunits is apparently affected by charge, even in the presence of 2.5% sodium dodecyl sulfate.
Ascites tumor fluid and bovine serum albumin as supplements in presomite mouse embryo cultures
Authors: Meneses Juanito J. , Pedersen Roger A.
Published: June 2005

The growth of presomite mouse embryos in culture was studied using mouse Ehrlich ascites tumor fluid and bovine serum albumin as supplements to the tissue culture medium. The best development was observed with a mixture of 10–20% ascites fluid and 2% bovine serum albumin. During 48 h of culture under these condition, embryos grew from egg cylinders to complex structures with neural folds and other organ rudiments. Most embryos had beating hearts, numerous pigmented red blood cells, and a fused chorioallantoic placenta. The results suggest that factors in ascites fluid support differentiation and growth of mouse embryos. Addition of bovine serum albumin was also beneficial for development. Differential sister chromatid staining of cultured embryos showed that ascites fluid increased the rate of clel proliferation as compared with medium containing bovine serum albumin alone, or bovine serum albumin and fetal calf serum. These results with abundant, and readily available supplements may facilitate certain studies of mouse embryo development.