bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of prolactin and the gonads in seasonal physiological changes in the collared lemming (Dicrostonyx groenlandicus)
Authors: Gower Barbara A. , Nagy Tim R. , Stetson Milton H.
Published: June 2005

On a seasonal basis, collared lemmings undergo a number of physiological and morphological changes. Short photoperiod exposure results in a molt to a white pelage, an increase in body weight, a reduction in relative body fat content, an increase in relative water content, and the development of a bifid claw. Treatment with the dopamine agonist, CB‐154, resulted in a reduction in serum prolactin and the development of the white pelage in lemmings housed under 16L:8D, while treatment with the dopamine antagonist, sulpiride, prevented the winter molt in animals transferred to 8L:16D. Castration under 16L:8D resulted in an increase in body weight and an enlargement of the bifid claw. Castrated animals also molted more readily when treated with CB‐154 and developed a relatively greater carcass water content. Treatment with CB‐154 increased relative carcass fat content. These findings suggest that, in the collared lemming, seasonal changes in pelage parameters are regulated by prolactin, with gonadal hormones playing a modulating role. Body weight, water content, and bifid claw size appear to be influenced by gonadal hormones. © 1993 Wiley‐Liss, Inc.
Characterization of phosphotyrosyl protein phosphatase from the hepatopancreas of the shrimp Penaeus japonicus (Crustacea: Decapoda)
Authors: Chuang Nin‐Nin , Wang Pei‐Cheng
Published: June 2005

Phosphotyrosyl protein phosphatase, purified from the hepatopancreas of Panaeus japonicus, is a monomeric enzyme with a relative mass (Mr) of 28,000, as estimated by size‐exclusion FPLC on a SuperoseTM 12. It has a hydrophobic domain and can be extracted with the detergent CHAPS. The specific activity of the purified enzyme was 9,800 units/mg of protein. The purified enzyme had an isoelectric point less than 4.6, and an optimal pH of 6.5 with either a synthetic peptide or autophosphorylated receptors for insulin as the substrate. The purified phosphotyrosyl protein phosphatase from shrimp hepatopancreas dephosphorylated human and shrimp receptors for insulin and was inactivated by ZnCl2, LiCl, MgCl2, and NaF. © 1993 Wiley‐Liss, Inc.
Development of the ectopically transplanted primordium of epithelial hypophysis (anterior neural ridge) in Bufo japonicus embryos
Authors: Kikuyama Sakae , Inaco Hiroo , Jenks Bruce G. , Kawamura Kosuke
Published: June 2005

It has recently been demonstrated that the epithelial pituitary of the toad is not stomodeal, but placodal, in origin. The placodal cells in the anterior part of the neural ridge (ANR) of the open neurulae are the exclusive source of the epithelial pituitary gland. The present study was undertaken to see the self‐differentiating ability of these cells in an ectopic environment. Bufo japonicus embryos at the tailbud stage received implants of either the ANR from open‐neurula‐stage embryos, or the pituitary primordium from tailbud‐stage embryos (the ANR derivative beneath the forebrain floor) into the tail. Development of the pars intermedia and the pars distalis was monitored immunohistochemically using antisera against both synthetic α melanophore‐stimulating hormone (αMSH) and bullfrog prolactin (PRL). Neither the immunoreactive αMSH cells nor the immunoreactive PRL cells differentiated from the neural ridge when it was dislocated from the original site at the open neurula stage. On the other hand, in grafts of the pituitary primordium transplanted from the tailbud‐stage embryos, immunoreactive PRL cells developed invariably and immunoreactive αMSH cells were detected at an incidence of 72%. The significance of the role of brain tissue surrounding the pituitary anlage in differentiation of the pars intermedia and pars distalis is discussed. © 1993 Wiley‐Liss, Inc.
Circadian timing of a daily rhythm of hemolymph insulin‐like peptide titers inHelisoma(Mollusca)
Authors: Sevala V. M. , Sevala V. L. , Kunigelis S. C. , Saleuddin A. S. M.
Published: June 2005

The hemolymph titers of insulin‐like peptide inHelisoma duryihave been determined using a radioimmunoassay. When animals were raised in a mixed photoperiod (12L:12D), the titer displayed two significant peaks of immunoreactivity during photophase, one after “lights on” (08:00 h) and the other before “lights off” (18:00 h). During the entire scotophase the titer remained low. This daily rhythm is maintained in continuous darkness and differing temperature regimes with a period of approximately 24 h. The free running period of the rhythm is temperature compensated. Therefore the hemolymph insulin‐like peptide titer is controlled by a circadian timing system. In older non‐growing snails, the titer was high without significant oscillations. Since the insulin‐like peptide is involved in shell growth and/or shell regeneration inHelisoma, circadian modulation can provide a precise control of shell growth and/or shell regeneration in this species. © 1993 Wiley‐Liss, Inc.
Probing the functions of endogenous lectins: Effects of a monoclonal antibody against the neural crest‐stage lectin of Xenopus laevis on trunk development
Authors: Milos Nadine C. , Frunchak Yvette N. , Mohamed Zarina
Published: June 2005

Trunk neural crest of Xenopus laevis has been confronted prior to migration with whole or fragments of a monoclonal antibody raised against the carbohydrate‐binding site of the endogenous neural crest‐stage galactoside binding lectin (Milos et al.: Anat. Embryol., 182:319–327 '90). External fin formation was inhibited in confronted regions but extensive internal matrix develops suggesting interiorization of fin tissue. In the regions of missing fin, the myotomes overgrew the neural tube and dorsal root ganglion neuronal numbers became more variable. Melanophore numbers in regions of missing fin did not change but a significantly greater proportion of the pigment cells localized on the muscle surface that had overgrown the neural tube suggesting that the pigment cell population redistributed itself to occupy a greater myotomal area. © 1993 Wiley‐Liss, Inc.
Seasonal testosterone levels in leydig and sertoli cells of the snapping turtle (Chelydra serpentina) in natural populations
Authors: Mesner Peter W. , Mahmoud I. Y. , Cyrus Rodney V.
Published: June 2005

Leydig cells were enzymatically separated from the seminiferous tubules and were then purified by isoosmotic Percoll gradient centrifugation so that steroidogenic activity in the two sites could be measured separately. After purification, the cells in fractions 29–31 were identified as Leydig cells since these tested positively for 3β hydroxysteroid dehydrogenase activity (3β HSD), had steroidogenic ultrastructural features (smooth endoplasmic reticulum), and were capable of synthesizing testosterone (T) in vitro. The rest of the fractions tested negatively for the 3β HSD activity and were incapable of synthesizing detectable amounts of T. Sertoli cells from seminiferous tubules also showed the above steroidogenic properties. The T concentration of intratubular origin (Sertoli cells) was low prior to spermatogenesis but began to rise at the onset of the spermatogenic phase (late May to early June). The level of Sertoli T increased steadily during the summer. In late August to early September intratubular T reached a peak that coincided with spermiation and maximal testicular development. Leydig cells (interstitial origin) were more active prior to spermatogenesis, producing large amounts of T at a time of minimal testicular mass. The sharply rising T concentrations peaked in May or early June (mating period). After the onset of spermatogenesis, T of interstitial origin began to drop until early August to early September when, like T of intratubular origin, it peaked in synchrony with spermiation and maximal testes development. During September the testes regressed rapidly and T from both sources declined significantly. Throughout the cycle the Leydig cells appeared to be the major site of testosterone synthesis. © 1993 Wiley‐Liss, Inc.
Unreduced diploid eggs produced by interspecific hybrids between Oryzias latipes and O. curvinotus
Authors: Sakaizumi Mitsuru , Shimizu Yasushi , Matsuzaki Takashi , Hamaguchi Satoshi
Published: June 2005

Male hybrids produced from reciprocal crosses between Oryzias latipes and O. curvinotus are sterile, whereas females do lay eggs. Fertilized by the sperm of one of the parental species, such eggs develop into triploid males and females. We examined allozyme patterns of triploids that developed from the eggs fertilized by sperms of non‐parental strains of O. latipes or a closely related species, O. luzonensis. Expression of three allelic products in triploid offsprings indicated unreduced diploidy of the eggs produced by the hybrid females.

In order to test the clonality of the diploid eggs produced by the hybrid females, we examined the progeny of hybrid females for their immunological clonality and DNA content. Progeny of a hybrid female crossed with a male of an inbred strain of O. latipes was demonstrated to belong to a single immunological clone. Differences in frequency of hypotriploidy and mosaicism were observed between strains of O. latipes that produced hybrid females.

Because O. latipes is a fish that is used widely as a model organism in experimental biology, the hybrid females that produce unreduced diploid eggs provide a unique model with which to examine the underlying causes of polyploidy and clonal reproduction in vertebrates. © 1993 Wiley‐Liss, Inc.
A structural and functional polymorphism in the hemoglobin O2 transport system of the blood clam Noetia ponderosa
Authors: Mangum Charlotte P. , Cockey Elizabeth M.
Published: June 2005

A sample of arcid blood clams (Noetia ponderosa) from the Atlantic coast of Virginia had red blood cells containing a hemoglobin composed of only one electrophoretically separable component. Both the red blood cells and hemoglobin extracts had a moderately high oxygen affinity. A sample from the Gulf of Mexico had red blood cells containing hemoglobins composed of two components. According to previous reports, this population contains a homodimer of one chain and a heterodimer of that chain plus another. Both the red blood cells and the hemoglobin extracts had a much lower oxygen affinity. Thus, in this species, the O2 carrier is qualitatively (and, according to the previous report, quantitatively) polymorphic, and the polymorphism is reflected in respiratory properties as well as quaternary structure. The origin of the different hemoglobin phenotypes, however, is not yet clear. © 1993 Wiley‐Liss, Inc.
Evolution of oviductal gestation in amphibians
Authors: Wake Marvalee H.
Published: June 2005

Oviductal retention of developing embryos, with provision for maternal nutrition after yolk is exhausted (viviparity) and maintenance through metamorphosis, has evolved independently in each of the three living orders of amphibians, the Anura (frogs and toads), the Urodela (salamanders and newts), and the Gymnophiona (caecilians). In anurans and urodeles obligate viviparity is very rare (less than 1% of species); a few additional species retain the developing young, but nutrition is yolk‐dependent (ovoviviparity) and, at least in salamanders, the young may be born before metamorphosis is complete. However, in caecilians probably the majority of the approximately 170 species are viviparous, and none are ovoviviparous. All of the amphibians that retain their young oviductally practice internal fertilization; the mechanism is cloacal apposition in frogs, spermatophore reception in salamanders, and intromission in caecilians. Internal fertilization is a necessary but not sufficient exaptation (sensu Gould and Vrba: Paleobiology 8:4–15, '82) for viviparity. The salamanders and all but one of the frogs that are oviductal developers live at high altitudes and are subject to rigorous climatic variables; hence, it has been suggested that cold might be a “selection pressure” for the evolution of egg retention. However, one frog and all the live‐bearing caecilians are tropical low to middle elevation inhabitants, so factors other than cold are implicated in the evolution of live‐bearing. Viviparity might facilitate life in a rigorous environment, but likely is not “caused” by such an existence. © 1993 Wiley‐Liss, Inc.
Monotreme development with particular reference to the extraembryonic membranes
Authors: Hughes R. L.
Published: June 2005

This paper considers many of the salient features of monotreme development, particularly morphogenesis of the extraembryonic membranes.

The uterine endometrium of both monotremes and marsupials exhibits a progesterone driven luteal phase where accelerated utilization of endometrial nutrients is evidenced by a rapid post‐primitive streak expansion in the dimensions of the extraembryonic membranes. Monotremes share with marsupials, birds, and reptiles an unspecialized vertebrate mode of genesis of the embryonic disc on the peripheral surface of the yolk‐sac.

The fused vascularized respiratory chorioallantois is estimated to have a functional life of not more than the terminal 4 to 5 days of the monotreme incubation period. This time interval is of a slightly greater order of magnitude than that found in marsupials with a fused chorioallantois, so far described, but in the context of the proportional elapse of post‐primitive streak organogenesis would fall within the marsupial grade.

The dominant extraembryonic membrane for nutritive and respiratory function in both monotremes and marsupials is the yolk‐sac.

This contribution shows that monotremes and marsupials share a much larger suite of developmental anatomical features than previously reported. The evolutionary biologist is confronted with the challenge of how to assign an appropriate weighting to these features as marsupials are considered by many researchers to be allied phylogenetically more closely with eutherian mammals than with monotremes. © 1993 Wiley‐Liss, Inc.
Development and structure of the placenta and fetal membranes of nonhuman primates
Authors: King Barry F.
Published: June 2005

This survey examines placental and fetal membrane structure, function, and development in nonhuman primates. It will focus on these aspects of fetal membranes in species exemplifying the two main types of primate placentation. The chorioallantoic placentas of most strepsirhine primates (e.g., lorises and lemurs), are diffuse, villous and epitheliochorial in structure. Villi are stout, usually unbranched and interdigitate with indentations in the uterine lining. Early in gestation trophoblast cells are columnar but with advancing gestational age considerable thinning of the interhemal membrane occurs. The villous tips have indented regions that appear to be involved in absorption of histotroph. Accessory placental structures known as areolae or chorionic vesicles occur in many strepsirhines. These are cup‐shaped specializations that develop opposite the mouths of uterine glands and appear active in absorption of glandular secretions. In addition, most strepsirhines are characterized by a large yolk sac early in gestation, a transient choriovitelline placenta, and most have a large allantoic sac. In strepsirhines, amniogenesis occurs by folding. In contrast, the chorioallantoic placentas of most haplorhines are discoidal, villous, and hemochorial. The species emphasized in the review are macaque monkeys. The placental villi are covered by a layer of syncytiotrophoblast; the latter is active in maternal‐fetal transport and hormone synthesis. In some haplorhines, extravillous trophoblast invades deeply into the endometrium and also into spiral arteries supplying the placenta. Other fetal membranes include 1) nonvillous chorion (chorion laeve); there is evidence supporting both an absorptive and synthetic role for trophoblast of the chorion laeve; 2) yolk sac, which is unusual in that a secondary yolk sac is formed. The yolk sac has both synthetic and absorptive functions in early gestation; and 3) amnion; amniogenesis in haplorhines occurs by cavitation. © 1993 Wiley‐Liss, Inc.
Embryonic diapause in vertebrates
Authors: Mead Rodney A.
Published: June 2005

Embryonic diapause occurs in many species of vertebrates, but the physiological mechanisms which control this fascinating process are exceedingly different in the diverse groups which employ this reproductive strategy. In nonmammalian species and some bats, reduction in rate of embryonic development is temperature dependent, but this is not the case in most mammals. Development becomes arrested at the blastocyst stage of embryogenesis in mammals which exhibit delayed implantation, whereas postimplantation development is continuous but retarded in species exhibiting delayed development. The hormonal control of diapause is remarkably different in the various species. Pituitary secretion of prolactin prevents implantation in the tammar wallaby but hastens renewed development and implantation in the mink and spotted skunk. Ovariectomy results in the eventual death of blastocysts in mustelids but induces renewed development and implantation in the armadillo. Luteal function, as evidenced by elevated progesterone secretion, is essentially constant in the roe deer and armadillo, whereas the luteal cells fail to complete their differentiation and secrete low levels of progesterone in carnivores. Progesterone will induce implantation in the tammar wallaby, but estrogen is required to induce renewed development and implantation in rodents. Neither progesterone and/or estrogens appear to be capable of stimulating implantation in carnivores. The uterus plays an important role in maintaining the embryos in a viable state throughout the period of diapause. In many species the uterus undergoes histological changes and secretes increased amounts of protein, yet we still do not understand the role, if any, these proteins play in initiating renewed embryonic development. Thus the phenomenon of embryonic diapause still holds many mysteries for scientists to solve. © 1993 Wiley‐Liss, Inc.
Developmental changes in the acetylcholine influence on heart muscle of Rana catesbeiana: in situ and in vitro effects
Authors: Pelster Bernd , Burggren Warren W. , Petrou Steven , Wahlqvist Inger
Published: June 2005

The influence of acetylcholine (ACh) on cardiac performance of larval (Taylor Kollros [TK] stages II‐XVIII) and postmetamorphic (3–609 g) Rana catesbeiana was analyzed in situ (circulatory system intact) and in vitro (isolated heart or ventricular strip preparations).

Topical application of ACh to the heart in situ resulted in a dose‐dependent decrease in heart rate and in a slight decrease in systolic ventricular pressure in all developmental stages. Injection of acetylcholine in to the ventricle lumen in situ caused a dose‐dependent transient decrease in systolic ventricular pressure, with little heart rate effect. Intraventricular ACh injection also changed the hemodynamic coupling between ventricle and conus arteriosus, generating a biphasic pressure profile in the conus due to sequential contractions of the ventricle and of the conus. In situ the sensitivity of the ventricle to ACh decreased during larval development, with the lowest sensitivity in small postmetamorphic adults.

ACh applied in vitro to cardiac muscle strips or small hearts produced a negative inotropic effect. The ACh dose necessary to induce a 50% reduction in muscle strip contraction force in vitro decreased substantially during larval development, indicating an increase in ACh sensitivity with development.

The effects of ACh both in vitro and in situ were diminished or eliminated by topical application or injection of atropine, suggesting the presence of muscarinic cholinergic receptors. After preincubation with the acetylcholinesterase blocker eserine, injection of ACh in to the conus arteriosus decreased systolic ventricular pressure with a delay of 4–10 seconds, probably representing the minimum blood circulation time.

The observed inotropic and chronotropic responses result from the action of ACh on cardiac muscle, primarily affecting systolic ventricular pressure, and on the cardiac pacemaker, mainly influencing heart rate. These responses occur as early as TK, stage II, indicating a well‐developed set of mechanisms to regulate cardiovascular performance early in development. © 1993 Wiley‐Liss, Inc.
In vitro motilities of the unconventional myosins, brush border myosin‐I, and chick brain myosin‐V exhibit assay‐dependent differences in velocity
Authors: Wolenski Joseph S. , Cheney Richard E. , Forscher Paul , Mooseker Mark S.
Published: June 2005

Two types of in vitro motility assays are currently used for examining the mechanochemical properties of purified myosins. The Nitella bead movement assay (Sheetz and Spudich: Nature 303:31–35, 1983) allows determination of both velocity and directionality of movement, but is of limited utility because of the fragile nature of the dissected Nitella internodal cells. On the other hand, the sliding actin filament assay (Kron and Spudich: Proc. Natl. Acad. Sci. U.S.A. 83:6272–6276, 1986) is technically much simpler to perform than the Nitella assay, and is suitable for the study of numerous physiological parameters. As it is currently used, however, the sliding actin filament assay does not indicate the directionality of motor movement. Previous studies have demonstrated that the velocities of filament‐forming conventional myosins‐II from either muscle or nonmuscle cells are comparable in both motility assays (Umemoto and Sellers: J. Biol. Chem. 265:14864–14869, 1990). However, similar studies using unconventional myosins are lacking. In the present report we have compared the rates of two structurally distinct unconventional myosins: brush border (BB) myosin‐I and chick brain (CB) myosin‐V (p190‐calmodulin), using the sliding actin filament and Nitella‐based in vitro motility assays. These two unconventional myosins differ from conventional myosins in that they appear unable to associate in to bipolar filaments, and have extended rod‐like neck domains which bind multiple calmodulin light chains in a Ca2+‐sensitive manner. Unlike conventional myosins, both of these unconventional myosins exhibit motility rates using the Nitella assay (BB myosin‐I:∼10 nm/s; CB myosin‐V:∼30 nm/s) that are 5‐to 10‐fold slower than that determined for these myosins using the sliding filament assay (BB myosin‐I: 40–67 nm/s; CB myosin‐V: 260–340 nm/s). © 1993 Wiley‐Liss, Inc.
Threshold photoperiods for the induction of short day traits in collared lemmings (Dicrostonyx groenlandicus)
Authors: Nagy Tim R. , Gower Barbara A. , Stetson Milton H.
Published: June 2005

When exposed to short photoperiod collared lemmings undergo a number of physiological and morphological changes including an increase in body weight, a change in body composition, development and enlargement of the bifid “digging” claw, and a molt to a white winter pelage. We investigated the threshold photoperiods for the induction of these traits in male and female lemmings born and raised under a 22L:2D photoperiod and transferred at weaning (19 days of age) to various other photoperiods. Male lemmings showed the characteristic increase in body weight when exposed to 16 hr of light or less per day whereas females required a photoperiod of 14 hr of light or less per day to elict an increase in body weight. The thresold photoperiods for the increase in bifid claw size were 16 and 18 hr of light per day in male and female lemmings, respectively. The molt to the white winter pelage began under a longer photoperiod in females (16L:8D) than in males (14L:10D). Testes and seminal vesicles were significantly inhibited by photoperiods of 22L:2D and 20L:4D. Likewise, uterine weights were inhibited by maintenance on a photoperiod of 22L:2D. Taken together, these data show that the threshold photoperiods for the induction of the short day traits in collared lemmings are both trait‐ and sex‐dependent. These observations also suggest that under some conditions, exposure to long photoperiods can inhibit sexual maturation. © 1993 Wiley‐Liss, Inc. © 1993 Wiley‐Liss, Inc.
Interactions between the pharyngeal jaw apparatus, feeding behaviour, and ontogeny in the cichlid fish, Haplochromis piceatus: A study of morphological constraints in evolutionary ecology
Authors: Galis Frietson
Published: June 2005

I found evidence of a morphological constraint on the food choice of young stages of a cichlid fish. The constraint is not a developmental one because it is not imposed by developmental changes. I found no evidence of developmental constraints. In gradual transitions developmental constraints may be rare, in contrast to their regular occurrence in sudden transitions. I suggest that flexible muscle activation and reserve capacity (structural capacity in excess of functional demand) provide organisms with mechanisms that buffer against the effects of form changes and as such facilitate ontogenetic and evolutionary changes.

A mathematical model for piercing prey in the pharyngeal jaws is applied to a juvenile cichlid fish. The maximum possible biting forces and the best biting directions were calculated. Piercing forces were measured that were generated when natural prey were pierced. The results were compared with the feeding behaviour in the laboratory and in the field and with results from an adult. The model predicts great flexibility of the pharyngeal jaw apparatus. Furthermore, the model predicts that a shift in biting point, prey size, or predator size leads to changes in muscle recruitment. The m.transversus ventralis is predicted to play an important role in pharyngeal biting.

The model explains why large fish can easily pierce Chaoborus larvae and pupae, whereas a fish of 2.5 cm is just able to pierce larvae (symmorphosis) and is unable to pierce pupae. The inability of small fish to pierce pupae is due to a morphological constraint. This constraint is imposed by the size of the cross‐sectional areas of the muscles that generate the biting force. © 1993 Wiley‐Liss, Inc.
Mechanisms of osmoregulation in the green alga Dunaliella salina
Authors: Thompson Guy A.
Published: June 2005

The halotolerant alga, D. salina, offsets the high (up to 5 M) external NaCl concentration in its environment by maintaining a nearly equivalent level of intracellular glycerol. Cells experiencing sudden hypoosmotic shock respond initially by volume expansion and then convert glycerol to osmotically inactive starch. Within 2 min following dilution of cells from 1.7 M NaCl to 0.85 M NaCl, their volume and surface area increase by 50%. Concurrently, the plasma membrane phosphatidylinositol 4,5‐bisphosphate (PIP2) level falls by 30% due to hydrolysis by a GTP‐binding, protein‐activated phospholipase C that produces inositol trisphosphate and diacylglycerol (DAG). Following the short‐lived rise of PIP2‐derived DAG, a second and larger peak of DAG is produced by the hydrolysis of phosphatidylcholine and through de novo synthesis. Since protein kinase C is not detectably stimulated, DAG may act through the alternative pathway of increasing actin nucleation sites, thereby facilitating expansion of the cell's cytoskeleton. D. salina contains a family of at least 4 low molecular weight (28–30 kDa) GTP‐binding proteins. The major one of these (28 kDa) is immunologically cross‐reactive with antibodies to the yeast ypt1 protein that is involved in intracellular vesicle trafficking. The D. salina 28 kDa protein may play a similar role in facilitating the plasma membrane expansion triggered by hypoosmotic shock. During this expansion, which features a massive fusion of cytoplasmic vesicles with the plasma membrane, there is significant translocation of the 28 kDa GTP‐binding protein from the ER‐enriched microsomal fraction to the plasma membrane, chloroplast, and cytosol. Factors regulating these translocations are under study. © 1994 Wiley‐Liss, Inc.
Dealing with salt stress in animal cells: The role and regulation of glycine betaine concentrations
Authors: Dragolovich Julia
Published: June 2005

Glycine betaine is the end product of a two step oxidation of choline. Although glycine betaine is a common osmolyte in the cells of many species, the mechanism(s) regulating its synthesis in response to hyperosmotic stress has not been thoroughly studied in animals. We localized glycine betaine production in the mitochondrial matrix of cardiac cells from the horseshoe crab (Limulus polyphemus). Isolated Limulus mitochondria take up choline and convert it to glycine betaine. The uptake rate is stimulated by exposure to hyperosmotic medium and mediated in part by a Na+‐dependent, high affinity transporter. The increased choline concentrations in hyperosmotically stressed mitochondria result in increased glycine betaine concentrations. Thus, choline transport by Limulus mitochondria is the rate‐limiting step in glycine betaine synthesis. Oysters (Crassostrea virginica) appear to have a different regulatory strategy. Oysters from the Atlantic Ocean accumulate more glycine betaine than oysters from the Chesapeake Bay when hyperosmotically stressed. Gill mitochondria isolated from both oyster populations take up choline at similar rates. However, the Atlantic Coast oyster mitochondria synthesize 3–4 times as much glycine betaine as their Bay counterparts. Thus, in oysters, the regulatory step may be at the level of the synthetic enzymes. © 1994 Wiley‐Liss, Inc.
Vitellogenin in the surface mucus of tilapia (Oreochromis mossambicus): Possibility for uptake by the free‐swimming embryos
Authors: Kishida Mitsuyo , Specker Jennifer L.
Published: June 2005

Tilapia (Oreochromis mossambicus) produce two forms of vitellogenin, designated tVTG‐200 and tVTG‐130 to indicate the molecular masses (kDa) of their monomeric forms. The female of this species broods the embryos in her mouth, and they nip at her sides. Enzyme‐linked immunosorbent assays (ELISAs) and Western blots using the antisera to tVTG‐200 and tVTG‐130 were used in this study to show the presence of tVTGs in the surface mucus of vitellogenic females and estradiol (E2)‐treated male tilapia. Gut extracts from the free‐swimming embryos exhibited a displacement curve in ELISAs for tVTG‐200 and tVTG‐130. Western blot analyses of the esophagus/ stomach extract of the embryo showed no intact tVTGs, although proteins at 20.8 and 18.1 kDa were detected by the antiserum to tVTG‐200 and a protein at 106 kDa by the antiserum to tVTG‐130, which were similar to the proteins found in the extract of the yolk sac. Immunocytochemistry for tVTG‐200 and tVTG‐130 demonstrated positive cross‐reaction in the gut content of the embryo. However, gut extracts from embryos which were separated from the mother showed cross‐reactivity in ELISAs similar to those taken from the embryos hatched in the mouth of the mother. The availability of VTGs in the mucus of the mother raises the possibility of continued nutrient supply from the mother for post‐hatched embryonic tilapia. Alternative sources of the yolk protein‐like substances inside the gut of the embryos are considered. © 1994 Wiley‐Liss, Inc.
Acid‐base status of a pulmonate land snail (Helix aspersa) and a prosobranch amphibious snail (Pomacea bridgesi) during dormancy
Authors: Scholnick David A. , Snyder Gregory K. , Spell Angel R.
Published: June 2005

Changes in metabolism and acid‐base status were compared during dormancy in the pulmonate land snail Helix aspersa and a prosobranch amphibious snail Pomacea bridgesi. The typical condition of higher blood PCO2 and bicarbonate levels for air‐breathing versus water‐breathing vertebrates was shown for the two snail species. When exposed to dry air for 24 hr, both species depressed oxygen uptake by about 65%. In Pomacea, hypercapnia (increase in hemolymph PCO2 from 5.5 to 18 torr) resulting from dormancy produced no significant change in pH due to large increases in bicarbonate (over 17 mmol/l). In Helix, on the other hand, hypercapnia (increase in hemolymph PCO2 from 13 to 18 torr) resulting from dormancy produced a significant decrease in pH and a less than 7 mmol/l increase in bicarbonate. Pre‐existing high levels of bicarbonate in Helix may prevent compensation of hypercapnia resulting from dormancy, similar to the case described for air‐breathing vertebrates. Complete compensation of respiratory acidosis during the first 24 hr of dormancy in Pomacea suggests that metabolic rate suppression is independent of pH. © 1994 Wiley‐Liss, Inc.
Weak applied voltages interfere with amphibian morphogenesis and pattern
Authors: Metcalf M. E. Mourey , Borgens Richard B.
Published: June 2005

We have imposed steady DC electric fields over developing gastrula and neurula stage axolotls,Ambystoma mexicanum. These applied voltages were meant to confound cues provided by endogenous currents and fields that we have measured and believe to be controls of pattern and morphogenesis during early development. Applied voltages in the physiological range (25–75 mV/mm) cause severe disruption of development when imposed over neurulae whose orientation within the field is random or fixed. In the latter case, developmental defects are more likely to occur at that end of the neurula (rostral or caudal) that faces the cathode, or negative pole, of the applied field. In neurulae whose orientation within the field was fixed, the lowest magnitude producing developmental abnormality was between 5 and 25 mV/mm. Physiological measurement of the embryonic transepithelial potential (TEP) when perturbed by artificially applied voltages demonstrates that ectoderm facing the cathode is hyperpolarized, while ectoderm facing the anode is depolarized at all fields strengths tested. These data show that the electrical polarity of embryonic ectoderm is predictably disrupted by applied voltages. Though applied voltages exert this same effect on the ectoderm of gastrulae, exposure only during gastrulation does not lead to developmental abnormality. This observation demonstrates that the applied electric field does not harm the embryo in some non‐specific way and further emphasizes the stages of neurulation as those most sensitive to artificially applied or endogenous voltages. These data strongly support the notion the polarized natural voltages within amphibian embryos are controls of their emerging pattern. © 1994 Wiley‐Liss, Inc.
Gender specific developmental transformation of a cockroach bifunctional muscle
Authors: Stokes Darrell R. , Malamud Jean G. , Schreihofer Derek A.
Published: June 2005

Adult male and female cockroaches,Periplaneta americana, differ in their capacity for sustained flight. Tethered 20 day adult males flap their wings about 15 min; females 12 seconds. Males are less massive and have greater total wing area than do females, with wing loading only about half that of the female. The basalar muscle, a major wing depressor in flight, is also sexually dimorphic. In males it is 1.5× more massive and has a cross sectional area 1.2× greater than the female homologue. Muscle fibers of the adult male and female basalar muscles are ultrastructurally and biochemically distinct. Female fibers have a myofilament array similar to that of other non‐flight locomotory muscles, with 10–12 actin filaments surrounding each myosin filament. Adult male fibers typically have six actin filaments around each myosin filament. The male fibers also appear to be more oxidative. The volume density of mitochondria is about 3× greater and the specific activity for citrate synthase, an oxidative indicator, is 3.5× greater in male fibers than in female fibers. Male basalar muscle shows an enhanced ability to resist fatigue when its motoneurone is stimulated at flight frequency; homologues from the male terminal nymph and 20 day adult female are both highly fatiguable. The basalar muscle of both male and female terminal nymphs are similar in ultrastructural and biochemical profile and are not greatly different from the adult female. In male roaches there may be important neuronal or hormonal inputs at about the time of the terminal molt to adulthood that direct the transformation of the basalar muscle in time for the assumption of a new behavioral role—flight. © 1994 Wiley‐Liss, Inc.
Toxic effects of b̃‐aminopropionitrile treatment on developing chicken skin
Authors: Marsh Randall G. , Gallin Warren J.
Published: June 2005

β‐aminopropionitrile (BAPN), a compound that inhibits crosslinking of collagen, has been widely used to examine the function of collagen in developing tissues. We used BAPN to examine the function of collagen during the formation and patterning of feather rudiments in embryonic chicken skin. Organ cultures of skin were treated with different concentrations of BAPN and examined for changes in morphology, histology, and extent of collagen crosslinkage. Increasing concentrations of BAPN led to striped patterns of feather rudiments, increases in feather rudiment diameter, and increases in skin thickness in cultured skin. These changes in morphology were paralleled by a progressive decrease in collagen crosslinkage as the concentration of BAPN was increased. However, these changes were also paralleled by an increase in cell death in the epidermis. Culture of monolayers of separated epidermal and dermal cells in the same concentration range of BAPN that altered feather development in the organ cultures showed that BAPN killed epidermal cells but not dermal cells. Our reults suggest that developmental alterations caused by BAPN may, in some cases, be due to acute toxicity to specific cell types, and not simply to inhibition of collagen crosslinkage. © 1994 Wiley‐Liss, Inc.
Mosaic expression of an Hprt transgene integrated in a region of Y heterochromatin
Authors: Pravtcheva Dimitrina D. , Wise Thomas L. , Ensor Nancy J. , Ruddle Frank H.
Published: June 2005

The sensitivity of small transgenes to position effects on their expression suggests that they could serve as indicators of the chromatin properties at their integration site. In particular, they might be expected to provide information on the functional properties of mammalian heterochromatin. We have produced a transgenic line that carries a mouse Hprt minigene on the Y chromosome. In situ hybridization localized the transgene to the heterochromatic portion of the Y. Analysis of transgene expression by isoelectric focusing indicated that the transgene is expressed in a mosaic pattern, and expressing cells have different levels of transgene activity. These findings can be explained as a position effect variegation induced by Y heterochromatin. However, two other transgenes, located at autosomal sites, also showed mosaic activity. If the mosaic transgene expression is attributed to the influence of the chromatin at the insertion site, the Y heterochromatin would appear less potent than some autosomal regions at inducing variegation. An alternative explanation consistent with our results is that the mosaic expression is a semi‐autonomous characteristic of these transgene loci. Transgene‐expressing and non‐expressing cells differed in their ability to grow and be cloned in vitro, indicating that cellular differentiation affected the chromatin structure of the transgene locus on the Y. Karyotype analysis of male mice with the Y‐linked transgene and from control male mice carrying the human HPRT transgene, or the mouse Pgk‐1 gene at autosomal sites, indicated that the transgene‐carrying Y is prone to non‐disjunction, generating cells with two (or more) or no Y chromosomes in equal proportion. Further studies will determine if the propensity of this Y chromosome to mitotic errors is also observed in vivo. © 1994 Wiley‐Liss, Inc.
Rapid induction of a hyperciliated phenotype in zinc‐arrested sea urchin embryos by theophylline
Authors: Stephens R. E.
Published: June 2005

Zinc ions, present since fertilization, will arrest embryos of the sea urchin Tripneustes gratilla at the hatched blastula stage, but such embryos lack long cilia, the usual characteristic of animalized embryos. Eventually these embryos will express a minimal long cilia phenotype, with a mean population < 1.4 times that of control blastulae, but only after contemporaneous control embryos gastrulate. Theophylline will rapidly but minimally animalize embryos when added after hatching, but its inductive ability decreases as the embryos gastrulate. Theophylline‐animalized embryos produce cilia whose mean population length is > 1.5 times that of control blastulae. At any point from the time of hatching up until control embryos complete gastrulation, theophylline added to zinc‐arrested embryos will induce a hyperciliated phenotype with a mean population length nearly 3 times that of control blastulae. The elongation of cilia is immediate and significantly exceeds the rate of normal ciliary regeneration. Initially requiring the presence of theophylline, the hyperciliated phenotype becomes stable as control embryos begin gastrulation and, when deciliated, the induced embryos will regenerate hyperlong cilia in the absence of theophylline. The time dependence for both induction and phenotype stability would suggest that certain timing mechanisms are still operative in zinc‐arrested embryos. This inducible system should facilitate studies of length control during ciliary elongation and regeneration. © 1994 Wiley‐Liss, Inc.
Morphological and functional changes accompanying the acquisition of meiotic competence in ovarian goat oocyte
Authors: De Smedt Véronique , Crozet Nicole , Gall Laurence
Published: June 2005

In order to determine at which follicular size goat oocytes were capable of resuming and completing meiosis, we evaluated their ability to mature in vitro and measured their maturation promoting factor (MPF) activity by histone H1 kinase assay. The results indicated that goat oocyte meiotic competence developed progressively in follicles ranging from 0.5 to 3 mm, the oocytes acquired the ability to resume meiosis in follicles of 0.5–0.8 mm, to reach metaphase I (MI) in follicles of 1–1.8 mm, and to reach metaphase II (MII) in follicles larger than 3 mm. The presence of MPF activity was first observed in oocytes arrested at early prometaphase I and reached a maximum level in oocytes blocked in metaphase I (MI). In the second part of this study, RNA synthesis and nucleolar changes were analyzed during the growth period. The acquisition of meiotic competence was accompanied by nucleolar compaction and a dramatic decrease in RNA synthesis. Changes in protein patterns were also analyzed, but only slight differences were observed among oocytes from the different classes. © 1994 Wiley‐Liss, Inc.
Influence of gonad‐stimulating substance on ovarian 1‐methyladenine levels responsible for germinal vesicle breakdown and spawning in the starfish Asterina pectinifera
Authors: Mita Masatoshi , Nakamura Masaru
Published: June 2005

In starfish oocytes, 1‐methyladenine (1‐MeAde) induces not only germinal vesicle breakdown (GVBD) but also follicular envelope breakdown (FEBD), releasing the oocytes from the ovaries, i.e., spawning. This study was undertaken to examine changing levels of 1‐MeAde within ovaries of the starfish Asterina pectinifera after treatment with gonad‐stimulating substance (GSS). 1‐MeAde production in ovaries was markedly dependent on GSS concentration. Although the period until oocyte release from the ovaries was shortened to as little as 19 min when the GSS concentration was increased to 0.1 mg/ml, about 5 min of treatment with GSS (0.1 mg/ml) was sufficient for induction of oocyte release, involving GVBD and FEBD. Almost the same duration of treatment with 1‐MeAde at a concentration of 0.1 μM was required for spawning. Since the increase in the 1‐MeAde level was correlated with a parallel rise in ovary wet weight, the internal content of 1‐MeAde in ovaries was estimated to be 1 g wet weight ovary/ml. The content of 1‐MeAde within the ovaries was calculated to reach about 0.18 μM during 5 min of GSS treatment. It is thus concluded that the 1‐MeAde content is sufficient to induce GVBD and FEBD of oocytes in starfish ovary. © 1994 Wiley‐Liss, Inc.
Fertilization of the lamprey (Lampetra japonica) eggs: Implication of the presence of fast and permanent blocks against polyspermy
Authors: Kobayashi Wataru , Yamamoto Tadashi S.
Published: June 2005

We have carried out a morphological examination to analyze the mechanism of monospermic fertilization in the lamprey, Lampetra japonica. Upon insemination, many sperm passed through a “tuft” of jelly that is found only on the animal pole area of the egg and underwent the acrosome reaction after they came into contact with the outer surface of the two‐layered vitelline envelope. The acrosomal filaments were admitted into the envelope and their tips touched the ooplasmic surface. The Hoechst dye transfer method revealed that a single sperm showed intense fluorescence before its nucleus penetrated the vitelline envelope; this indicated the actual fusion of the gametes. No other sperm with acrosomal filaments fluoresced, however. These findings indicate that a fast block against polyspermy is established at the plasma membrane level and prevents additional sperm‐egg fusion.

The separation of the ooplasmic surface from the vitelline envelope (perivitelline space formation) was initiated beneath the margin of the animal pole region and progressed toward the animal and vegetal poles of the egg. At this stage, the head of a fertilizing sperm passed through the thickness of the vitelline envelope. The nuclei of supernumerary sperm were unable to enter the inner layer of the vitelline envelope. During the early phase of the perivitelline space formation at the animal pole region, many thin threads and one, or a small number, of the thick projection(s) of the ooplasm connected the envelope with the vitellus. A fertilizing sperm invariably moved along one of the thin threads and was embedded in the ooplasm at the animal pole region. Cytochalasin B inhibited sperm from passing through the inner layer of the vitelline envelope. When ionophore‐activated eggs were inseminated, the tips of the acrosomal filaments were prevented from touching the ooplasmic surface by the intervening presence of the perivitelline space. None of these sperm passed through the vitelline envelope. These findings suggest that the fusion of the acrosomal filament with the egg plasma membrane is a prerequisite for the passage of sperm through the inner layer of the vitelline envelope. Furthermore, actin‐mediated ooplasmic activity is probably involved in the passage. We conclude that the formation of the perivitelline space at the animal pole region contributes to the establishment of a permanent block against polyspermy in the lamprey egg. © 1994 Wiley‐Liss, Inc.
Contribution of dietary and loading changes to the effects of suspension on mouse femora
Authors: Simske S. J. , Broz J. J. , Fleet M. L. , Schmeister T. A. , Gayles E. C. , Luttges M. W.
Published: June 2005

The present study assessed the contributions of feeding changes and unloading to the overall measured effects of 2‐wk hindlimb (Tail) suspension on the mouse femora. Feeding changes were addressed by considering the effects of matched feeding among suspended and control mice. The effects of hind limb unloading were considered by comparing suspended mice to mice equipped identically (though not suspended) and matched‐fed. The feeding and unloading aspects of suspension appear to cause distinctly differing effects on the stereotypic modeling of the femora. Matched‐feeding was accompanied by increased resorption surface in comparison to suspended mice, while unloading led to reduced bone formation at the mid‐diaphysis of the femora. Reduced mineral content was observed in the bones of suspended mice when compared to the other mice groups, but without increased resorption surface. Thus, the unloading aspects of the antiorthostatic suspension protocol apparently causes reduced formation and mineralization in the femur. © 1994 Wiley‐Liss, Inc.