bluuebunny/crossref_metadata_2025 huggingface dataset:
Osmotic and ionic regulation during hypoxia in the medicinal leech, Hirudo medicinalis L.
Authors: Hildebrandt Jan‐Peter , Zerbst‐Boroffka Irene
Published: June 2005

The concentrations of inorganic and organic ions and osmolality in the blood of the medicinal leech, Hirudo medicinalis, were determined during normoxia and hypercapnic and hypocapnic hypoxia. In normoxic animals, the blood sodium concentration was 124.5 ± 4.2 mmol/l and the total cation concentration was 132.2 ± 4.3 mEq/l (mean ± S.D.). Major anionic compounds were chloride (40.8 ± 1.6 mmol/l), bicarbonate (8.4 ± 1.3 mmol/l), and organic anions (42.5 ± 2.3 mEq/l). Among the latter, malate accounts for 30.4 ± 2.2 mEq/l. The nature of the remaining anion fraction, which balances cation and anion concentrations in leech blood, remains unknown.

Within 96 h of hypercapnic hypoxia, the amount of organic osmolytes in leech tissue increased from the control level of 56.6 ± 9.1 to 158.3 ± 19.5 μmol/g dry weight. An even higher amount of organic acids was accumulated within 96 h of hypocapnic hypoxia (218.0 ± 53.7 μmol/g dry weight). A possible reason for this is that lactate, which is a major end‐product of hypocapnic hypoxia, cannot be excreted to the external medium as easily as propionate.

The accumulation of blood organic acids generating osmotic stress in the animals was compensated by an equimolar decrease in sodium and chloride ion concentrations. In hypercapnic animals these changes resulted in a constant osmotic concentration of the blood (200 mosmol/kg H2O) during the experimental period. Between 24 and 96 h of hypocapnic hypoxia, however, the increase in the osmotic gradient between animal and medium was correlated with further net water uptake and the obvious deterioration of the volume‐ and ion‐regulatory mechanisms in these animals. © 1992 Wiley‐Liss, Inc.
Epibolic extension of the presumptive ectodermal layer of embryos of the newt Cynops pyrrhogaster before and during gastrulation
Authors: Komazaki Shinji
Published: June 2005

Epibolic extension of the presumptive ectodermal layer (PEL) was investigated in embryos of the newt Cynops pyrrhogaster before and during gastrulation. The PEL was composed of only one layer of columnar cells at all stages examined. The cells of the PEL became elongated from the blastula to the early gastrula stage. They were most elongated at the early gastrula stage and then shortened during gastrulation. Present observations suggest that changes in cell shape of the PEL play an important role in the control of the epibolic extension of the newt embryos.

The morphology and movement of the isolated cells from the PEL were examined in an attempt to elucidate the role of cell movement in epibolic extension of the PEL. Blebbing and vermiform cells which showed active cell movement appeared at the early blastula stage. The blebbing cells, which formed large hyaline blebs that moved around the circumference of each cell, appeared in large numbers at the early blastula stage. The frequency of the blebbing cells decreased from the early blastula to the early gastrula stage and increased again during gastrulation. The vermiform cells, which had an elongated cell body and moved in a worm‐like manner, increased in frequency from the early blastula to the early gastrula stage. The relative number of such vermiform cells was maximal at the early gastrula stage and decreased abruptly during gastrulation. These results suggest that the elongation of the cells of the PEL is controlled by the active cell movement which resembles that of a worm. © 1992 Wiley‐Liss, Inc.
Body temperature rhythm of the tree shrew, Tupaia belangeri
Authors: Refinetti Roberto , Menaker Michael
Published: June 2005

The circadian rhythm of body temperature of the tree shrew Tupaia belangeri was studied by telemetry. The amplitude of the daily (or circadian) variation was found to be much larger than that of most endotherms (amplitude ∼ 5°C) and the bimodal shape of the rhythm differed from the cosine waveform that characterizes the temperature rhythms of most other species. In free‐running conditions, as well as in the entrained state, the temperature rhythm remained synchronized to the rhythm of locomotor activity. © 1992 Wiley‐Liss, Inc.
Cleavage inhibition by cell shape change
Authors: Rappaport R.
Published: June 2005

The division mechanism of animal cells is positioned by the mitotic apparatus. The mitotic apparatus determines the position by a pattern of regional inequality of its effect on the surface and cortex. Because the effect of the asters decreases with distance, the location of the division plane can be manipulated geometrically. It follows that cytokinesis should be preventable by imposition of a cell shape that prevents the normal pattern of unequal aster effect. The shape that inhibits division reveals something of the normal pattern of aster effect as well as the nature of the immediate response of the surface to the aster.

In 13 of 13 experiments, sand dollar (Echinarachnius parma) eggs fail to cleave when the polar and subpolar regions are extruded in the mitotic axis, although some surface contraction may develop in the extruded region. Extrusion was accomplished by sucking the appropriate regions into opposed pipets. A computer model of the relative aster effect in this circumstance indicates that the minimum is at the equator, and the maximum is in the extruded regions. These experiments indicate that furrows do not form where the aster effect is minimal. Previous experiments showed that cells divide when cells are artificially constricted in the equatorial plane where the aster effect is maximal. Together, the geometrical experiments strongly suggest that furrowing activity occurs in maximally affected areas. These results are consistent with the equatorial contraction theory of cell division, but inconsistent with the aster relaxation theory. © 1992 Wiley‐Liss, Inc.
Role of humidity in the seasonal reproduction of male spotted munia, Lonchura punctulata
Authors: Sikdar Malabika , Kar Anand , Prakash Prem
Published: June 2005

A systematic long‐term study was made on the possible involvement of humidity in the reproduction of male spotted munia. Both high humidity (90 ± 2%) and continuous illumination (LL) exhibited precocious gonadal development, indicating positive involvement of these 2 factors in the reproduction of this bird. Delay in testicular regression by 2 months in high humidity treated birds suggests a greater role for humidity than photoperiod. © 1992 Wiley‐Liss, Inc.
Electrophoretic studies of meiotic segregation in inter‐ and intraspecific hybrids among East Asian species of the genus Oryzias (Pisces: Oryziatidae)
Authors: Sakaizumi Mitsuru , Shimizu Yasushi , Hamaguchi Satoshi
Published: June 2005

Three species of Oryzias, namely, O. curvinotus, O. luzonensis, and four subspecific groups of O. latipes, have been found in East Asia. In order to elucidate the genetic relationships among theses species, fertility and meiotic segregation in hybrids were examined. Fertile males and females and normal segregation were observed in intraspecific crosses of O. latipes and in interspecific hybrids between O. luzonensis and O. curvinotus. By contrast, male sterility and production of non‐reductional 2nd eggs by female were observed in interspecific crosses between O. latipes and O. curvinotus. Similar results were obtained with luzonensis‐latipes hybrids. These results demonstrated that O. luzonensis and O. curvinotus are closely related, and that reproductive isolation is complete between O. latipes and O. luzonensis and between O. latipes and O. curvinotus. © 1992 Wiley‐Liss, Inc.
Gonadal involvement in sexual size dimorphism in the African bullfrog (Pyxicephalus adspersus)
Authors: Hayes Tyrone , Licht Paul
Published: June 2005

Sexual size dimorphism was investigated in the African bullfrog (Pyxicephalus adspersus), a species in which adult males are about 2.5 times larger than females. Growth profile analysis revealed that males and females begin to diverge in growth rates at 4 weeks postmetamorphosis, concurrent with the appearance of differentiated gonads. At the end of 300 days, males were about 75% heavier and 20% longer than females (females remained previtellogenic). The difference was attributable primarily to an extended period of accelerated linear growth in males between days 166 and 195, and an extended period of accelerated weight gain between days 139 and 166. Surgical gonadectomy did not affect growth in males or females. Reduced plasma steroid levels, failure to show steroid response to GnRH injection, and abolishment of male agonistic behaviors confirmed the completeness of gonadectomy. In addition, there was no correlation between plasma steroid hormones and size or growth rate. The current study suggests that gonadal hormones may not play an “activational” role in establishing sexually dimorphic growth patterns. Sexual size dimorphism may be due to either “organizational” hormonal effects or genetic control of growth patterns. © 1992 Wiley‐Liss, Inc.
Anti‐P450lpr antiserum inhibits specific monooxygenase activities in LPR house fly microsomes
Authors: Wheelock Geoffrey D. , Scott Jeffrey G.
Published: June 2005

Monooxygenase activity in microsomes from the LPR strain of house fly (Musca domestica L.) was inhibited by anti‐P450lpr, an antiserum specific for house fly cytochrome P450lpr, Anti‐P450lpr did not inhibit house fly cytochrome P450 reductase or rat cytochrome P450 monooxygenase assays, consistent with specific inhibition of P450lpr. Anti‐P450lpr inhibited the ability of cytochrome P450 reductase to reduce carbon monoxide treated LPR microsomal cytochrome P450, up to 49% of the total, showing that inhibition of cytochrome P450 reduction is the major mechanism of inhibition. Anti‐P450lpr inhibited 98% of methoxyresorufin‐O‐demethylase activity and all the benzo(a)pyrene hydroxylase activity in LPR microsomes, but none of the pentoxyresorufin‐O‐dealkylase activity. The antiserum partially inhibited ethoxyresorufin‐O‐dealkylase and ethoxycoumarin‐O‐dealkylase activity. These results demonstrate that methoxyresorufin‐O‐demethylase activity and benzo(a)pyrene hydroxylase activity are characteristic substrates for P450lpr activity in the LPR strain of house fly. © 1992 Wiley‐Liss, Inc.
The duration of the effectiveness of vitamin A at causing proximodistal duplication in regenerating limbs of the axolotl, Ambystoma mexicanum, in relation to whole body retinoid levels
Authors: Johnson Keith J. , Scadding Steven R.
Published: June 2005

Urodele amphibians regenerate their limbs after amputation. Normally, only those parts of the limb distal to the plane of amputation are regenerated. However, retinoids are capable of inducing proximodistal (PD) duplication such that structures already present proximal to the plane of amputation are duplicated in the regenerating limb. PD duplication can be induced by retinoids even if amputation occurs some time after the retinoid treatment. Thus, the purpose of this investigation was to determine for how long after administration, retinoids were effective at inducing PD duplication, and to determine whether this persistent effectiveness was due to some change in the cells of the limb or to residual levels of retinoids in the body. Thus, forelimbs of larval axolotls, Ambystoma mexicanum, were amputated at various times in relation to retinol palmitate (RP) treatment to investigate the relationship between the induction of proximodistal duplications and the timing of the retinoid treatment. RP induced PD duplications when amputation was delayed for up to 2 weeks after cessation of the retinoid treatment. To measure the levels of retinoids actually present within the body, axolotls were treated with RP, and whole body retinoid levels were colorimetrically assayed during and after the RP treatment. Since high levels of retinoids were present for several weeks after the cessation of the treatment, we conclude that the induction of PD duplications, when amputation is delayed until after the RP treatment, is due to the persistence of retinoids in the axolotl body. © 1992 Wiley‐Liss, Inc.
Characterization and partial purification of sperm‐activating substance from eggs of the herring, Clupea palasii
Authors: Morisawa Masaaki , Tanimoto Satomi , Ohtake Hideki
Published: June 2005

Spermatozoa of the herring, Clupea palasii, were immotile in a solution of isotonic to seminal plasma but swimming was initiated in a hypertonic solution such as 60% seawater. This suggests that hyperosmolality is a factor for the initiation of sperm motility in herring. The motility of herring spermatozoa in hypertonic solution remained very low but became active in “egg water,” suggesting that a sperm‐activating substance is released from unfertilized eggs and diffuses into the surrounding environment to promote fertilization. The activity of the egg water was heat stable and nondialyzable, and was lost upon digestion with the proteolytic enzyme, pronase E; thus the substance is a protein. During procedures for partial purification using gel‐filtration chromatography on Sephadex G‐75, the substance was found to be very adherent to the Sephadex beads when buffer solution or the lower salt solution was used as the eluate instead of 0.5 M NaCl. This suggests that the sperm‐activating substance might be attached to the surface of eggs in the relatively lower ionic environment of the female reproductive organ and is released from the eggs when they are spawned into the high salt environment of seawater. © 1992 Wiley‐Liss, Inc.
Glutamine metabolism in elasmobranch and agnathan muscle
Authors: Chamberlin M. E. , Ballantyne J. S.
Published: June 2005

Glutamine metabolism was investigated in the little skate (Raja erinacea), spiny dogfish (Squalus acanthias), and hagfish (Myxine glutinosa). Amino acid analysis revealed that dogfish plasma glutamine concentration was 11.6 nmol/ml, whereas 48‐fold higher levels, 0.56 μmol/gm, were found in the red muscle. Mitochondria were isolated from the red muscle of the skate and dogfish. The isolation procedure yielded well‐coupled mitochondria, which oxidize glutamine and β‐hydroxybutyrate more rapidly than any other substrate tested. Palmitoyl carnitine was not oxidized, confirming previous studies that elasmobranch red muscle has a negligible capacity for fatty acid oxidation. Glutaminase and glutamine synthetase were measured in the muscle of the hagfish, dogfish, as well as several tissues of the skate. The brain and red muscle have the highest activities of glutaminase, and the activity in dogfish muscle is the highest reported for any muscle. Glutamine synthetase activity is highest in the brain, liver, and kidney, whereas the activity of this enzyme is low or not detectable in elasmobranch and hagfish muscle. The high glutaminase/glutamine synthetase ratio in the muscle indicates that the metabolic organization of elasmobranch and agnathan muscle is geared toward glutamine catabolism. The present study shows that, in addition to β‐hydroxybutyrate, glutamine is an important fuel for elasmobranch red muscle. © 1992 Wiley‐Liss, Inc.
Thyroid involvement in photoperiodically induced testicular and body weight cycles of the black‐headed bunting, Emberiza melanocephala
Authors: Devi Ksh. Pratima , Lal P.
Published: June 2005

In the black‐headed bunting, Emberiza melanocephala, thyroidectomy suppressed the amplitude of light‐induced testicular growth and accelerated the onset of photorefractoriness. Extirpation of the thyroid glands during progressive phase inhibited further testicular growth and led to immediate testicular regression when performed during peak phase of a photostimulated cycle. The inhibitory influence of thyroidectomy on light‐induced testicular growth was fully reversed by daily im injection of L‐T4 at a dose level of 2 μg/bird/day. Neither thyroidectomy nor L‐T4 had any effect on the regressing testes of thyroidectomized buntings. Body weight which was about 26 g increased to about 37 g within 15 days of photostimulation by 20L/4D. Removal of thyroid glands suppressed light‐induced increase in body weight and resulted in premature decline. The inhibitory influence of thyroidectomy on body weight depended upon lipid reserves at the time of operation, an effect which could be reversed by daily im treatments of L‐T4 at dose level 2 μg/bird/day. It is suggested that in the black‐headed buntings thyroid hormones are required for sustaining light‐induced increase in the testes and body weight and may not necessarily be involved in the development of photorefractory states—gonadal and metabolic. © 1992 Wiley‐Liss, Inc.
Monoclonal antibody ST1 identifies an antigen that is abundant in the axolotl and newt limb stump but is absent from the undifferentiated regenerate
Authors: Yang Eric V. , Shima David T. , Tassava Roy A.
Published: June 2005

Monoclonal antibodies (mAb) utilized in regeneration studies to date identify antigens that are up‐regulated in the blastema. We obtained a monoclonal antibody, designated ST1 (Stump 1), that is reactive to an extracellular matrix (ECM) antigen exhibiting the opposite distribution; ST1 is an abundant antigen of the limb stump soft tissues but is absent from within the blastema. The border between abundance and absence of mAb ST1 reactivity was sharp and extended as a concavity into the stump. This distinct dichotomy led to further studies relevant to understanding how this extracellular matrix antigen is modulated during regeneration. mAb ST1 reactivity decreased in the internal tissues at the distal end of the limb prior to blastema formation and remained absent until the onset of differentiation. The initial decrease in mAb ST1 reactivity was dependent on the combined effects of injury and the wound epithelium but was nerve independent. At blastema stages of regeneration, the distribution of tenascin, ascertained by mAb MT1 reactivity, closely matched the area without reactivity to mAb ST1. The spatial and temporal distribution of the ST1 antigen in unamputated limbs and during regeneration did not correspond to any previously described ECM component. © 1992 Wiley‐Liss, Inc.
Polarity of responsiveness to sperm and artificial stimuli in medaka eggs
Authors: Iwamatsu T. , Onitake K. , Nakashima S.
Published: June 2005

Experiments were performed to ascertain the polarity of responsiveness to sperm and to artificial stimuli in the egg of teleost, the medaka Oryzias latipes. When the eggs were stimulated by sperm or by microinjection of inositol‐trisphosphate or calcium ions, exocytosis of cortical alveoli began earlier at the animal pole than at the equatorial or vegetal pole regions. The propagation velocity of the exocytosis wave through the cortex was constant to the antipode of the egg. When denuded (dechorionated) eggs were inseminated, the number of spermatozoa that penetrated into the cortical cytoplasm was greater in the animal hemisphere than in the vegetal hemisphere. Most of the swollen sperm heads were found around the animal pole area. This distribution pattern of the sperm heads was also observed in both cytochalasin B‐ and colchicine‐treated eggs. These results suggest that there is polarity in the medaka egg regulating the affinity of the plasma membrane for sperm and the responsiveness of the cortex to sperm or artificial stimuli. © 1992 Wiley‐Liss, Inc.
Heat flux, oxygen flux, and mitochondrial redox state as a function of oxygen availability and ciliary activity in excised gills of Mytilus edulis
Authors: Doeller Jeannette E. , Kraus David W. , Shick J. Malcolm , Gnaiger Erich
Published: June 2005

The ciliated gill of bivalve molluscs is situated at an interface between animal and environment. Cilia propel water past the gills to deliver oxygen and nutrition to the animal. Ciliary activity is driven by dynein ATPases and requires a continual supply of ATP at a rate sufficient to match the rate of ATP hydrolysis. Control of the balance between ATP supply and demand in the ciliated gill, and how this balance may be altered by environmental stresses, is unknown. In this pilot study, metabolic flux of excised gills from the marine mussel Mytilus edulis was examined in response to oxygen availability and to serotonin‐stimulated ciliary activity. Heat flux and oxygen flux were measured simultaneously with calorespirometry. In parallel experiments, the redox state of mitochondrial cytochromes was determined with in vivo spectrophotometry. Above 4 kPapO2, heat flux was supported by aerobic metabolism. Anoxic heat flux was less than 5% of aerobic heat flux. Heat and oxygen fluxes nearly doubled in gills in the presence of 10 μM serotonin; however, half‐maximal pO2 for heat and oxygen fluxes and for reduction of mitochondrial cytochromes remained unchanged from control levels. In gills having inactive cilia in half‐strength seawater, half‐maximal pO2 for heat and oxygen fluxes and for cytochrome reduction nearly doubled compared with values in full‐strength seawater. These data indicate that limitation to oxygen delivery imposed by boundary layers may be reduced when ciliary beat frequency is elevated, leading to enhanced oxygen flux to intracellular mitochondria which matches the increased energy demand by the cilia. © 1993 Wiley‐Liss, Inc.
Ontogeny of the capacity for homeoviscous adaptation in white sturgeon (Acipenser transmontanus)
Authors: Buddington Randal K. , Hazel Jeffrey R. , Doroshov Serge I. , Van Eenennaam Joel
Published: June 2005

Most fish species tolerate a narrower range of temperatures during their early life history. To ascertain whether this might be related to development of the capacity to regulate membrane fluidity (homeoviscous adaptation), we examined the fatty acid composition of tissue phospholipids from developing white sturgeon eggs, embryos, and prefeeding larvae incubated at temperatures both within the range of natural spawning temperatures (14°), and above (20°) and below (8°). Mortality was highest at low temperature, with the greatest losses prior to neurulation. High temperature also resulted in increased mortality relative to 14°, with peak mortality between neurulation and hatch. At a constant temperature of 14°, significant changes in the fatty acid composition of tissue phospholipids were observed during development, but the patterns of change were altered by development at low and high temperature. Contrary to homeoviscous theory, embryos incubated at low temperature exhibited a decline in the ratio of unsaturated to saturated fatty acids (U/S ratio). In contrast, posthatch larvae exposed to low and high temperature exhibited, respectively, higher and lower U/S ratios than larvae maintained at 14°, implying that the capacity for homeoviscous adaptation is acquired at the time of hatch. Although the lack of a homeoviscous response by embryos may account for low survival at temperature extremes, the specific influences of the observed changes in phospholipid fatty acid composition on the biophysical properties of cell membranes remain to be determined. © 1993 Wiley‐Liss, Inc.
The accumulation of vanadium and manifestation of an antigen recognized by a monoclonal antibody specific to vanadocytes during embryogenesis in the vanadium‐rich ascidian, Ascidia sydneiensis samea
Authors: Uyama Taro , Uchiyama Junko , Nishikata Takahito , Satoh Noriyuki , Michibata Hitoshi
Published: June 2005

The present experiments, using a combination of thermal‐neutron activation analysis for the determination of vanadium and an immunofluorescence method for the recognition of the manifestation of an antigen specific to vanadocytes, clearly revealed the time at which ascidians gain their unusual ability to accumulate vanadium ions during their development. Significant accumulation of these ions was observed after metamorphosis. Two and half months after fertilization, the amount of vanadium in juveniles was about 930 ng per individual, a concentration corresponding to more than 5 orders of magnitude greater than that in unfertilized eggs. A vanadocyte‐specific antigen, recognized by a monoclonal antibody specific to the signet ring cells, first appeared in the body wall after metamorphosis. Three weeks after metamorphosis, the antigen became evident within the cytoplasm of the coelomic cells, which have a single, small vacuole. One and a half months after metamorphosis, signet ring cells appeared for the first time and were specifically recognized by the monoclonal antibody. It is suggested that the accumulation of the vanadium coincides with the differentiation of the vanadocytes during the development of ascidians. © 1993 Wiley‐Liss, Inc.
Mesodermal cell adhesion to fibronectin‐rich fibrillar extracellular matrix is required for normal Rana pipiens gastrulation
Authors: Johnson Kurt E. , Darribère Thierry , Boucaut Jean‐Claude
Published: June 2005

New observations on thin strips of cells from the leading edge of the involuting presumptive mesoderm explanted onto FN‐coated substrata show a striking preferential cellular emigration from the leading edge of explants. Microinjected probes (Fab′ anti‐FN, Fab' anti‐integrin and RGD‐peptides) that disrupt cell adhesion to the FN‐matrix on basal surface of the blastocoel roof also disrupt normal anuran gastrulation, producing blocked embryos with no adhesion of leading edge mesodermal cells to the blastocoel roof, abnormal epiboly, and defects of mesodermal cell spreading across the basal surface of the blastocoel roof toward the animal pole. These results show that the FN‐rich fibrillar extracellular matrix on the basal surface of the blastocoel roof is required for normal gastrulation in Rana pipiens embryos. © 1993 Wiley‐Liss, Inc.
Factors involved in the development of and decline in photoperiodism as it relates to the gonadal activity of a spring‐spawning bitterling, Acheilognathus tabira
Authors: Shimizu Akio , Hanyu Isao
Published: June 2005

The involvement of changes in photoperiodism in gonadal activity was investigated in the spring‐spawning bitterling, Acheilognathus tabira, in which photoperiodism develops during the summer and declines during the winter. In spring, gonadal development occurred without a need for photoperiodic stimulation and independently of the preceding photoperiod (9 hours or 12 hours light; 9L or 12L) during the winter. This observation indicates that the natural photoperiod during the corresponding season is not responsible for the decline in photoperiodism. Fish kept at moderate temperatures (16°C or 22°C) during the winter eventually achieved gonadal maturation, even under short daylength conditions (11L), indicating that low temperature during the winter is not necessary for the decline in photoperiodism. Both treatment with moderate temperature and long days (22°C, 15L) treatment and treatment with moderate temperature and short days (22°C, 11L) induced the development of photoperiodism during the summer, an indication that neither high temperatures during the summer nor long days during the early summer are necessary for the development of photoperiodism in this species. Since the natural photoperiod and temperature conditions during the corresponding seasons are not responsible for the changes in photoperiodism, these changes are probably caused by an internal factor such as circannual rhythm.

Alteration of the photoperiodic regime from 11L to even fewer hours of daylight during the period when photoperiodism was declining did not affect subsequent gonadal development. The nature of the changes in photoperiodism in this species is, therefore, a rapid switchover of the responsiveness to daylength rather than a gradual change in the critical daylength for gonadal development. © 1993 Wiley‐Liss, Inc.
Gonadal differentiation and secretions of estradiol and testosterone of the ovaries of Rana catesbeiana tadpoles treated with 4‐hydroxyandrostenedione
Authors: Yu Nai‐Wen , Hsu Chih‐Yun , Ku Hung‐Hai , Chang Li‐Tze , Liu Hwan‐Wun
Published: June 2005

Laparotomized female tadpoles of Rana catesbeiana at TK stages X–XII, about 9 months old, were implanted intraperitoneally with empty capsules or capsules containing 4‐hydroxyandrostenedione (4‐OHA), known as an aromatase inhibitor in vertebrates. Histology, gonosomatic index, and secretions of estradiol (E2) and testosterone (T) of the ovaries were investigated. Three months after the treatment, histological examination revealed various degrees of sex reversal in the ovaries treated with 4‐OHA and 79% (57 in 72) were transformed into testes. The ovaries of control tadpoles, however, displayed normal histological appearance. Radioimmunoassay showed that secretion of E2 was decreased while that of T was increased in 4‐OHA treated ovaries. The gonosomatic index displayed a decline tendency from control females through experimental animals to untreated control males. These results indicated that activity of aromatase in the ovaries was inhibited by 4‐OHA, resulting in accumulation of T which induced transformation of the ovaries into testes. © 1993 Wiley‐Liss, Inc.
The yolk syncytial layer of Fundulus: Its origin and history and its significance for early embryogenesis
Authors: Trinkaus J. P.
Published: June 2005

Because of its importance in early embryogenesis, the developmental history of the yolk syncytial layer (YSL) of Fundulus has been investigated in detail. As in other teleosts, the Fundulus YSL forms mainly by collapse of certain marginal blastomeres which then merge with the cytoplasm of the yolk cell peripheral to the blastoderm. Nuclei enter the yolk cell from these open blastomeres variably during cleavages 8–11, but most frequently at cleavages 9 and 10. After entry, the first nuclei divide five times and later nuclei divide with them. Thus, nuclei that have invaded at the next cleavage divide four times, etc. When the first YSL nuclei cease dividing, all other YSL nuclei cease dividing with them. These YSL mitoses occur in metachrony. Two or more metachronous waves progress through the YSL cytoplasm at each mitosis. After each nuclear division, the YSL increases in width and its nuclei are quite evenly spaced. After the 5th and last mitosis, when the YSL is at its widest, it contracts in its animal‐vegetal axis. This slow contraction has two major effects: 1) narrowing of the YSL, accompanied by crowding of its nuclei and their disappearance beneath the blastoderm to nucleate the internal YSL; 2) epibolic expansion of the I‐YSL and the blastoderm, followed soon after by other cell movements of gastrulation. This YSL transition, therefore, sets the stage for the onset of gastrulation. It is preceded by increased duration and variability of succeeding mitoses and, in particular, duration of their interphases, a decrease and deceleration in the rate of the last metachronous waves, and, finally, by the complete cessation of mitosis and the entry of YSL nuclei into permanent interphase. © 1993 Wiley‐Liss, Inc.
Relative roles of jelly layers in successful fertilization of Bufo japonicus
Authors: Omata Setsuko
Published: June 2005

The uterine eggs of Bufo japonicus are invested with four jelly layers, J1, J2, J3, and J4, from inner to outer, respectively. When eggs were inseminated with serially diluted sperm suspensions, a higher concentration of sperm was required for successful fertilization of dejellied uterine eggs in solubilized jelly preparation than fertilization of fully jellied uterine eggs. When the eggs taken from different portions of oviduct were inseminated, the eggs invested with J1J2J3 were fertilized as effectively as fully jellied uterine eggs. Those with J1J2 were fertilized at lower frequency but those with J1 and a thin J2 were hardly fertilizable. Eggs artificially invested with J3J4 were less fertilizable than the J1J2 eggs, but addition of J3J4 to J1 and a thin J2 made eggs as fertilizable as the J1J2 eggs. Observations on the sperm penetrating the jelly indicated that these differences in fertilizability were dependent on two variables: an increased number of sperm penetrating into J3 and J4, and an increased rate of acrosome reacted sperm in J1 and J2. © 1993 Wiley‐Liss, Inc.
Isolation and partial characterization of the sperm motility initiation factor from eggs of the pacific herring, Clupea pallasi
Authors: Pillai Muralidharan C. , Shields Tammy S. , Yanagimachi Ryuzo , Cherr Gary N.
Published: June 2005

Previously, we have demonstrated that sperm from the Pacific herring, Clupea pallasi, remain immotile upon spawning into the surrounding medium and initiate motility only upon contact with the micropyle area of the chorion (Yanagimachi et al., '92, Dev. Growth Differ., 34:447–461). In the present study we have purified a chorion‐bound sperm motility initiating factor (SMIF) and have found it to be a 105 kDa glycosylated polypeptide. The isolated factor was highly bioactive, stimulating prolonged motility in >90% of the cells in vitro. The 105 kDa glycoprotein showed affinity for Con A on western blots. Furthermore, in intact eggs, Con A was localized to only the micropyle area, indicating that SMIF is restricted to this region of the chorion. © 1993 Wiley‐Liss, Inc.
Ion transport in the gill epithelium of aquatic crustacea
Authors: Lucu Čedomil
Published: June 2005

In recent years a convincing body of knowledge has been accumulated indicating transport mechanisms for osmolytes in marine and brackish water Crustacea. Cuticle and epithelium cell layers serve as selective communications for the exchange of ions and small organic molecules between crustacean gills and their environment. The following apparent permeability coefficients in the Carcinus posterior gill epithelia was measured: PRb : PNa : PCl = 1.7 : 1.0 : 0.1.

In addition to the presence of ouabain sensitive unidirectional Na exchange (Ja…︁>b) located on the basolateral gill surface, there is also located an oppositely‐directed, ouabain‐sensitive Rb (K) unidirectional flux. Basolaterally applied ouabain inhibits NH4 fluxes (Jb…︁>a) and seems to interact with the Na/K exchanger, in which NH4 appears to substitute for K. In isolated perfused posterior gills, amiloride affected sodium fluxes and transbranchial potentials, supporting the possible presence of an Na/H exchanger. A unique electrogenic 2Na/H antiporter present in membrane vesicles of marine invertebrates has been discussed with the aim to integrate the knowledge at the different functional levels.

Branchial cell acidification was studied in Carcinus hemilamellae microspectrofluorimetrically using the fluorescent dye BCECF. In the case when hemilamellae were immersed in Na‐free solution, intracellular acidification was not affected by amiloride. In addition, in perfused gill epithelia in DSW (200 mM Na) identical with the bathing solution, acetazolamide‐inhibited acidification of the perfused medium was observed.

The effects of the inhibitors on the transbranchial potentials (TBP) and their role in the ion transport mechanisms of the crustacean gills are reported. © 1993 Wiley‐Liss, Inc.
Transport of amino acids by marine invertebrates
Authors: Preston Robert L.
Published: June 2005

Marine invertebrates transport amino acids and other organic solutes across their body surfaces. This surface absorption, in some instances, may contribute significantly to the overall nutritional requirements for an organism. Amino acids are accumulated against gradients as high as 106:1 to 107:1 (intracellular:extracellular concentration). The transport mechanism that has been consistently observed to account for this process is Na dependent cotransport. A review of the general characteristics of these transport systems characterized in marine invertebrate epithelia indicates certain common features: Na dependency with coupling coefficients of 2:1 or 3:1 (Na:amino acid translocated), influx coupled to membrane potential, and low intracellular Na activity. Under these conditions Na cotransport can readily account for gradients approaching 107:1. These transport systems may play a role in acquisition of nutrients by marine invertebrates, but it has also been suggested that they may play additional roles in osmoregulation, nutrient conservation, and chemo‐reception. © 1993 Wiley‐Liss, Inc.
Cyclic nucleotide regulation of methyl farnesoate synthesis by the mandibular organ of the lobster, Homarus americanus
Authors: Tsukimura B. , Kamemoto F. I. , Borst D. W.
Published: June 2005

Mandibular organ (MO) synthesis of methyl farnesoate (MF) is negatively regulated by extracts of the sinus gland, a neuroendocrine organ in the lobster eyestalk. Sinus gland extracts significantly increased cyclic GMP (cGMP) levels in the MO in vitro, but had no effect on cyclic AMP (cAMP) levels. Extracts of two other neuroendocrine tissues, the brain and thoracic ganglion, did not affect either cAMP or cGMP levels. In vitro treatment of MO with 8‐bromo‐cGMP (a cGMP analog) significantly decreased MF synthesis at concentrations of 10−7 M to 10−4M. Higher concentrations of 8‐bromo‐cAMP (10−5M to 10−4M) were required for significant decreases in MF synthesis. Forskolin and IBMX decreased MF synthesis at a concentration of 10−5M, but had no effect at lower concentrations (10−8M to 10−6M). These data suggest that cGMP is a second messenger for the sinus gland factor that inhibits MF synthesis in the MO. © 1993 Wiley‐Liss, Inc.
Regulation of ecdysteroid biosynthesis in crayfish Y‐organs: I. Role of cyclic nucleotides
Authors: Sedlmeier Dietrich , Fenrich Renate
Published: June 2005

Ecdysteroidogenesis in crustacean Y‐organs is negatively regulated by the so‐called molt‐inhibiting hormone (MIH), which is thought to inhibit the ecdysteroid pathway either directly through phosphorylation of the key enzyme(s) and/or through action on the synthesis of these enzymes. In the present study the role of cyclic nucleotides in the mode of action of MIH in the astacuran Orconectes limosus was investigated. Orconectes Y‐organs were incubated in vitro with sinus gland conditioned medium (SGCM) and cyclic AMP (cAMP) and cyclic GMP (cGMP) levels were measured. A striking increase of cGMP values (4 to 43 pmoles/mg protein) was observed after 2 hours, whereas cAMP levels were unchanged. Using the established in vitro bioassay for the measurement of inhibitory action on ecdysteroid release from Y‐organs (Soumoff and O'Connor, '82) the potential of dBcAMP, dBcGMP, forskolin, and IBMX to diminish this release was demonstrated, suggesting a possible role of both cyclic nucleotides in the mode of action of MIH. The present findings are discussed in view of the effect of MIH‐material on cyclic nucleotide levels in crab Y‐organs (Mattson, '86). © 1993 Wiley‐Liss, Inc.
Regulation of ecdysteroid biosynthesis in crayfish Y‐organs: II. Role of cyclic nucleotide‐dependent protein kinases
Authors: Von Gliscynski Ursula , Sedlmeier Dietrich
Published: June 2005

The ecdysteroid production of the crustacean molting gland, the Y‐organ, is known to be suppressed by the so‐called molt inhibiting hormone (MIH), a neuropeptide from the X‐organ‐sinus gland complex. Cyclic nucleotides appear to be involved in intracellular effects of MIH in Y‐organs. In the crab Cancer antennarius cAMP synthesis seems to be an initial event in MIH action, while in crayfish results indicate a more important role for cGMP in intracellular effects of MIH. To gain a better understanding of the intracellular mechanisms we examined the cAMP‐ and cGMP‐dependent protein kinase (A‐ and G‐kinase) activity in Y‐organs of the crayfish Orconectes limosus at different molting stages induced by eyestalk ablation. The activity ratio of cGMP‐dependent protein kinase was lower for premolt animals (0.51) than for intermolt animals (0.81), indicating a more pronounced activation of G‐kinase in Y‐organs of intermolt animals by endogenous cGMP. Moreover, preincubation of Y‐organs from destalked animals with sinus gland extract reestablished a G‐kinase activity ratio characteristic for intact animals. On the contrary, the activity ratio of A‐kinase did not vary depending on molting stage and was not altered by sinus gland extract. These results strongly suggest that MIH action in Orconectes limosus Y‐organ is mediated by cGMP rather than by cAMP. © 1993 Wiley‐Liss, Inc.
Seasonal conditions determine the manner of skin rejection in reptiles
Authors: Afifi Ahmed , Mohamed El Rashdy , Ridi Rashika El
Published: June 2005

During summer, 33%, 52%, and 15% of lizards Chalcides ocellatus rejected first set skin allografts (time between day of first sign of rejection and end point), respectively in an acute (11–14 days), subacute (15–20 days), and chronic (21–24 days) manner. Second set grafts were rejected in an acute fashion (8–13 days). Examination of histological samples from grafted areas revealed evident lymphoid cell aggregations in allo‐ but not in autografts. This suggests that graft rejection results from an immunological reaction against allogeneic cells. In the other seasons, all skin allotransplanted lizards rejected the graft in a chronic manner: in 46–132 days during autumn, 31–79 days in winter, and 40–78 days during spring. These data indicate that graft rejection in reptiles is under the control of seasonal conditions. © 1993 Wiley‐Liss, Inc.
Atrophy of nerve and neuropil following limb loss and regeneration in adult snapping shrimps, Alpheus heterochelis
Authors: McTeague J. A. , Govind C. K.
Published: June 2005

Changes in the nervous system were examined in adult snapping shrimps Alpheus heterochelis following the removal and regeneration of the minor or pincer cheliped. In order to compensate for differences amongst animals, the regenerated pincer side was compared to the contralat‐eral pristine major or snapper cheliped. In control shrimps with pristine pincer and snapper chelipeds, the number of axons in the nerves at the base of the ganglion on the pincer side constitute 74.4% of the number on the snapper side while the volume of the pincer neuropil constitutes 94.3% of its snapper counterpart. Following the removal of the pincer cheliped and the regeneration of a smaller one at the next molt, the number of axons in the nerves drops to 41.6% and the neuropil volume is reduced to 80.3% of its pristine snapper counterpart. This atrophy of the nerve and neuropil is further exaggerated following the removal of the pincer cheliped over four successive intermolts. On the regenerated pincer side, the number of axons drops to 8.5% and the neuropil volume to 61.4% compared to the pristine snapper side. Thus, loss of almost all of the peripheral sensory axons reduces the neuropil by about one third. The remaining two‐thirds of the neuropil volume is presumably comprised of input from central elements. © 1993 Wiley‐Liss, Inc.
Prolactin and interrenal hormone balance in adult specimens of Xenopus laevis exposed to hyperosmotic stress for up to one week
Authors: Guardabassi Antonietta , Muccioli Giampiero , Andreoletti Gian Emilio , Pattono Paola , Usai Pasquale
Published: June 2005

Adult female specimens of Xenopus laevis were exposed to diluted artificial seawa‐ter for up to 1 week. Statistically significant increases were observed in serum levels of aldosterone and corticosterone, concomitant with a drop in levels of prolactin (PRL) receptors in the cell membranes of the epidermis and kidney, which can be taken as an indicator of the levels of circulating PRL. The changes in hormone levels were detected after 1 day, being followed by a gradual restoration of the initial mean levels of these hormones when the exposure to hyperosmotic stress was extended for up to 2 or 7 days. Comparison of the above results with those previously obtained in Xenopus after longer exposure (15 days) to brackish water substantiates the necessity of recording possible initial fluctuations, as well as any changes that occur over the course of longer exposure during which time adaptation to environmental changes are likely to take place. The reverse responses, which may be not independent of one another, in terms of levels of corticoids and PRL in the animals exposed to hyperosmotic stress, are discussed.

A survey of the literature suggests that, in Xenopus, as in the case of other less strictly water‐dwelling amphibians, PRL is one of the hormones required for life in fresh water. © 1993 Wiley‐Liss, Inc.
Bilateral eye formation in the eyeless mutant Mexican salamander following unilateral, partial excision of neural fold tissues: A quantitative study
Authors: Brun Rudolf B.
Published: June 2005

Previous results showed that ectopic neural fold grafts, performed unilaterally during neurulation on eyeless mutant axolotl embryos, frequently stimulated eye formation bilaterally. The analysis of the eyeless mutant was expanded in order to obtain quantitative data on the effect of various types of neural fold grafts. While performing these experiments, significant eye formation occurred in controls. Larvae in which neural fold tissues were not grafted but only partially removed at neurula stages formed eyes in some experiments, but not in others. In those cases that eyes did form, partial removal of the posterior neural fold of the prospective ear region stimulated eyes to differentiate more frequently than partial removal of the anterior neural fold of the prospective nose area. In both cases, unilateral neural fold ectomy frequently resulted in bilateral eye formation. There was a positive correlation between the amount of posterior neural fold tissues excised and the frequency of cases in which eyes formed. This increase was roughly 10% if the posterior neural fold excision was performed bilaterally instead of unilaterally.

A comparison of eye formation between neural fold excision experiments and ectopic neural fold grafts was performed. There was a statistically significant different between anterior and posterior neural fold operations, but not between grafting and excision experiments. I interpret these results to suggest that there is a signal in the posterior neural fold of the eyeless mutant that prevents eye formation. This signal can be neutralized most efficiently by wounding of the posterior neural folds. In addition, the results provide strong evidence that the effect of wounding propagates from posterior to anterior regions, as well as from one side of the developing neuroepithelium to the other. © 1993 Wiley‐Liss, Inc.
Eggshell formation in Bdelloura candida, an ectoparasitic turbellarian of the horseshoe crab Limulus polyphemus
Authors: Huggins Luke G. , Waite J. Herbert
Published: June 2005

The marine triclad Bdelloura candida (Turbellaria) episodically deposits stalked eggshells onto the gill lamellae of the horseshoe crab Limulus polyphemus. Ultrastructural and biochemical analyses indicate that the eggshells consist of primary inner and secondary outer layers. Protein of the primary layer is rich in glycine, aspartate/asparagine, serine, and 3,4‐dihydroxyphenylalanine (Dopa). In this regard it resembles the eggshell compositions of other members of the phylum Platyhelminthes. The primary layer appears to be derived from precursors produced in the vitelline cells of the flatworm. Each egg‐laying episode consumes all of the precursor‐containing vitel‐line cells. A Dopa‐containing protein, vitelline protein 1 (Vp1), has been isolated from B. candida and resembles the primary eggshell layer in its composition. Vp1 has an apparent molecular weight of 34.4 and an acidic pI. Dopa‐containing proteins are presumed to be directly involved in the cross‐linking reactions that accompany quinone‐tanning. The secondary outer layer of the eggshell may serve to adhere the eggshell to the gill. Its amino acid composition is unlike that of the primary eggshell and nothing is known about its precursors. © 1993 Wiley‐Liss, Inc.