bluuebunny/crossref_metadata_2025 huggingface dataset:
Endurance training adaptations modulate the redox–force relationship of rat isolated slow‐twitch skeletal muscles
Authors: Plant David R , Gregorevic Paul , Warmington Stuart A , Williams David A , Lynch Gordon S
Published: March 2003

1. Studies have shown that, in isolated skeletal muscles, maximum isometric force production (Po) is dependent on muscle redox state. Endurance training increases the anti‐oxidant capacity of skeletal muscles, a factor that could impact on the force‐producing capacity following exogenous exposure to an oxidant. We tested the hypothesis that 12 weeks treadmill training would increase anti‐oxidant capacity in rat skeletal muscles and alter their response to exogenous oxidant exposure.

2. At the conclusion of the 12 week endurance‐training programme, soleus (slow‐twitch) muscles from trained rats had greater citrate synthase (CS) and catalase (CAT) activity compared with soleus muscles from untrained rats (P < 0.05). In contrast, CAT activity of extensor digitorum longus (EDL; fast‐twitch) muscles from trained rats was not different to EDL muscles of untrained rats. The CS activity was lower in EDL muscles from trained compared with untrained rats (P < 0.05).

3. Equilibration with exogenous hydrogen peroxide (H2O2, 5 mmol/L) increased the Po of soleus muscles from untrained rats for the duration of treatment (30 min), whereas the Po of EDL muscles was affected biphasically, with a small increase initially (after 5 min), followed by a more marked decrease in Po (after 30 min). The H2O2‐induced increase in Po of soleus muscles from trained rats was less than that in untrained rats (P < 0.05), but no differences were observed in the Po of EDL muscles following training.

4. The results indicate that 12 weeks endurance running training conferred adaptations in soleus but not EDL muscles. These adaptations were associated with an attenuation of the oxidant‐induced increase in Po of soleus muscles from trained compared with untrained rats. We conclude that endurance training‐adapted soleus muscles have a slightly altered redox–force relationship.
Peripheral injection of risperidone, an atypical antipsychotic, alters the bodyweight gain of rats
Authors: Ota Miyuki , Mori Keiji , Nakashima Akira , Kaneko Yoko S , Fujiwara Kentaro , Itoh Mitsuyasu , Nagasaka Akio , Ota Akira
Published: March 2003

1. Risperidone is an atypical antipsychotic drug that possesses 5‐hydroxytryptamine 5‐HT2 receptor antagonism combined with milder dopamine D2 receptor antagonism.

2. Excessive bodyweight gain is one of the side‐effects of antipsychotics. Risperidone treatment causes a greater increase in the body mass of patients than treatment with conventional antipsychotics, such as haloperidol. Therefore, the present study was undertaken in order to address the aetiology of the risperidone‐induced bodyweight change in rats by examining the expression of leptin, an appetite‐regulating hormone produced in white adipose tissue (WAT), and uncoupling protein (UCP)‐1, a substance promoting energy expenditure in the brown adipose tissues (BAT).

3. Eight‐week‐old male rats were injected subcutaneously with risperidone (0.005, 0.05 or 0.5 mg/kg) twice daily for 21 days. Both bodyweight and food intake were monitored daily. On day 21, rats were decapitated and their serum leptin and prolactin concentrations were measured. Expression levels of leptin, Ucp1 and β3‐adrenoceptor (β3‐AR) genes in WAT and BAT were quantified using real‐time polymerase chain reaction amplification.

4. Injection of 0.005 mg/kg risperidone into rats increased food intake and the rate of bodyweight gain, as well as the augmentation of leptin gene expression in WAT. Injection of 0.05 mg/kg risperidone increased food intake and leptin gene expression in WAT, but the rate of bodyweight gain was not affected. Injection of 0.5 mg/kg risperidone caused a reduction in bodyweight gain, as well as enhanced Ucp1 gene expression in BAT and serum prolactin concentrations. The serum leptin concentration and β3‐AR gene expression in WAT and BAT were not affected by injection of 0.5 mg/kg risperidone.

5. Although the changes in food intake observed in risperidone‐injected rats were rationalized neither by serum leptin nor prolactin concentrations, the reduction in the rate of bodyweight gain following injection of 0.5 mg/kg can be explained, in part, by increased energy expenditure, as revealed by the remarkable increase in the UCP‐1 mRNA expression level in BAT. The role of leptin in risperidone‐induced alterations in bodyweight gain remain to be clarified.
Effects of second‐generation histamine H1 receptor antagonists on the active avoidance response in rats
Authors: Nishiga Miyuki , Fujii Yoko , Konishi Masako , Hossen Maria Alejandra ,   Chiaki Kamei
Published: March 2003

1. The aim of the present study was to establish a new schedule of active avoidance response in rats to estimate the central effects of second‐generation histamine H1 receptor antagonists.

2. With the new schedule, a rat was placed into a dark room. A sliding door was opened after a delay of 5 s and, unless the animal moved into the lit room, an electric shock was delivered for 3 s. With the conventional schedule, the sliding door was opened immediately after the rat was placed into the dark room.

3. Ketotifen, at a dose of 50 mg/kg, showed no significant effect on the retrieval of active avoidance response with the conventional schedule. However, with the new schedule, the drug caused significant inhibition of retrieval of the response, even at a dose of 10 mg/kg.

4. Epinastine showed no significant effect on retrieval of the active avoidance response, even at a dose of 50 mg/kg with the new schedule.

5. Cetirizine, at a dose of 50 mg/kg, caused a significant effect, indicating that cetirizine, at this dose, markedly inhibits memory retrieval.

6. Both olopatadine and loratadine had potent effects; at doses of 20 and 50 mg/kg, respectively, these agents showed significant inhibitory effects on retrieval of the response.

7. In conclusion, we have developed a new schedule of active avoidance response that can be used to estimate the central effects of second‐generation histamine H1 receptor antagonists.
Cardiovascular reflex responses after intrathecal ω‐conotoxins or dexmedetomidine in the rabbit
Authors: Blake Duncan W , Wright Christine E , Scott David A , Angus James A
Published: March 2003

1. The effects of thoracic intrathecal doses (1 µg/kg) of the α2‐adrenoceptor agonist dexmedetomidine and ω‐conotoxins MVIIA and CVID on vasoconstrictor and heart rate responses to acute central hypovolaemia were studied in seven chronically instrumented rabbits.

2. Gradual inflation of an inferior vena cava cuff to reduce cardiac index (CI) by 8% per minute induced progressive vasoconstriction and an increase in heart rate (phase I). At approximately 40% of resting CI, there was sudden decompensation with failure of vasoconstriction and decrease in mean arterial pressure (MAP; phase II).

3. Both intrathecal MVIIA and CVID decreased resting CI (by 20% at 3 h), but only MVIIA significantly reduced resting MAP (P = 0.003). Dexmedetomidine resulted in transient bradycardia, but no other significant change in the resting circulation. With simulated haemorrhage, the relationship between CI and vascular conductance was shifted after MVIIA (1–3 h after injection) so that there was less vasoconstriction and a reduced increase in heart rate by the end of phase I compared with other treatments (P = 0.002 and P = 0.009, respectively). One hour after injection, dexmedetomidine reduced the slope of the phase I vasoconstrictor response (P = 0.03), but did not significantly alter the end‐point of the response. With failure of vasoconstriction and the onset of phase II, vascular conductance was higher after MVIIA compared with controls. Both conotoxins caused progressive failure of vasoconstriction rather than recovery during phase II (P < 0.001).

4. Intrathecal injections of these drugs to control chronic pain may compromise cardiovascular responses to changes in central blood volume. At the single doses studied, there were significant differences between the responses to simulated haemorrhage after MVIIA or dexmedetomidine compared with CVID, with the prolonged effect after MVIIA most likely to be of clinical significance.
Relationship between anti‐oxidant activities and doxorubicin‐induced lipid peroxidation in P388 tumour cells and heart and liver in mice
Authors: Liu Qi‐Yuan , Tan Benny KH
Published: March 2003

1. The present study found that, compared with mouse heart and liver, P388 ascitic tumour had significantly lower superoxide dismutase (SOD) activity and that compared with the mouse liver, the heart had significantly lower SOD and catalase activities, as well as a lower glutathione content.

2. At 7.5 mg/kg, doxorubicin (DOX), a superoxide radical inducer, induced significant lipid peroxidation only in the tumour, whereas 15.0 mg/kg DOX induced lipid peroxidation in both the tumour and heart, but not in the liver.

3. Overall, the results of the present study suggest that the differential anti‐oxidant activities in P388 ascitic tumour, heart and liver in mice may explain their differential responses and, hence, susceptibility to DOX‐induced lipid peroxidation.
The renal medullary interstitium: focus on osmotic hypertonicity
Authors: Sadowski Janusz , Dobrowolski Leszek
Published: March 2003

1. There has been continued interest in the functional role of the renal medullary interstitium and intense research in this area has furnished new information regarding the extent, dynamics and mechanisms determining fluctuations in medullary osmotic hypertonicity.

2. Any change in the tonicity (interstitial solute concentration) indicates an imbalance of the rate of solute delivery to the interstitium (by tubular transport) and solute removal therefrom (by the microcirculation). It is often difficult to establish whether alteration of the delivery or removal triggered the change in medullary tissue tonicity.

3. Newer in vivo studies have confirmed earlier predictions and indirect evidence indicating that the rate of NaCl transport in the ascending limb of the loop of Henle is the major determinant of medullary ionic hypertonicity.

4. The hypothesis of a ‘washout’ of medullary solutes during increased medullary blood flow (MBF) has been re‐evaluated. A novel experimental approach has provided direct evidence of a modest dissipation of medullary solutes with increasing MBF and a modest accumulation of solutes with decreasing MBF.

5. Increasing evidence is reviewed indicating that medullary tonicity is not only a regulated variable, but also that it may itself modulate the activity of multiple local endocrine and paracrine control systems and thereby affect local microcirculation and the function of medullary interstitial and tubular cells.
Pyruvate‐dependent preconditioning and cardioprotection in murine myocardium
Authors: Flood Amanda , Hack Benjamin D , Headrick John P
Published: March 2003

1. Whether pyruvate inhibits or can actually initiate myocardial preconditioning is unclear and whether pyruvate provides protection via its action as a ‘cosubstrate’ with glucose or via alternative mechanisms also remains controversial. We examined effects of a high concentration of pyruvate (10 mmol/L) alone or with 15 mmol/L glucose in mouse hearts subjected to 20 min ischaemia and 30 min reperfusion.

2. Provision of 10 mmol/L pyruvate alone or as a cosubstrate markedly reduced ischaemic contracture and enhanced postischaemic recovery. Time to contracture was increased from approximately 3 min to over 8 min, peak contracture was reduced from 90 mmHg to less than 60 mmHg and postischaemic pressure development was also improved. Effects on contracture were independent of the presence of pyruvate during ischaemia and improved postischaemic recovery was evident with pre‐ischaemic pyruvate perfusion.

3. Cardioprotection did not require the presence of pyruvate during ischaemia or reperfusion and effects of pyruvate pretreatment could be mimicked by pretreatment with 1 mmol/L dichloroacetate (DCA), an activator of pyruvate dehydrogenase.

4. Myocardial adenosine efflux and Ca2+ content were elevated (by 215 and 65%, respectively) following pretreatment with pyruvate, potentially triggering a preconditioned state. A role for adenosine A1 receptors is supported by lack of added protection with pyruvate in hearts transgenically overexpressing adenosine A1 receptors.

5. Collectively, these observations demonstrate that pre‐ischaemic treatment with pyruvate or DCA provides a beneficial preconditioning‐like effect in ischaemic and postischaemic myocardium. The response appears unrelated to glycolytic inhibition, but may be mediated via transient changes in adenosine levels and/or cellular Ca2+.
Comparison of the in vitro neuromuscular activity of venom from three australian snakes (Hoplocephalus stephensi, Austrelaps superbus and Notechis scutatus): Efficacy of tiger snake antivenom
Authors: Hodgson Wayne C , Eriksson Christer O , Alewood Paul F , Fry Bryan G
Published: March 2003

1. Tiger snake antivenom, raised against Notechis scutatus venom, is indicated not only for the treatment of envenomation by this snake, but also that of the copperhead (Austrelaps superbus) and Stephen's banded snake (Hoplocephalus stephensi). The present study compared the neuromuscular pharmacology of venom from these snakes and the in vitro efficacy of tiger snake antivenom.

2. In chick biventer cervicis muscle and mouse phrenic nerve diaphragm preparations, all venoms (3–10 µg/mL) produced inhibition of indirect twitches. In the biventer muscle, venoms (10 µg/mL) inhibited responses to acetylcholine (1 mmol/L) and carbachol (20 µmol/L), but not KCl (40 mmol/L). The prior (10 min) administration of 1 unit/mL antivenom markedly attenuated the neurotoxic effects of A. superbus and N. scutatus venoms (10 µg/mL), but was less effective against H. stephensi venom (10 µg/mL); 5 units/mL antivenom attenuated the neurotoxic activity of all venoms.

3. Administration of 5 units/mL antivenom at t90 partially reversed, over a period of 3 h, the inhibition of twitches produced by N. scutatus (10 µg/mL; 41% recovery), A. superbus (10 µg/mL; 25% recovery) and H. stephensi (10 µg/mL; 50% recovery) venoms. All venoms (10–100 µg/mL) also displayed signs of in vitro myotoxicity.

4. The results of the present study indicate that all three venoms contain neurotoxic activity that is effectively attenuated by tiger snake antivenom.
Development and evaluation of a simple calorimeter for the measurement of resting metabolism
Authors: Tamura Toshiyo , Ichinoseki Noriko , Yoshimura Takumi , Torii Yoshihiko
Published: March 2003

1. A simple calorimeter based on the measurement of oxygen uptake has been developed.

2. A respiratory simulator was used to evaluate oxygen uptake at different flow rates. A known concentration of mixed gases flows into the calorimeter via the respiratory simulator. Oxygen concentration and flow rate were measured and stored to memory for further analysis.

3. Results indicate that large errors occur at low flow rates, but that the error is less than 5% under normal conditions.

4. This device can be used to measure oxygen uptake under resting conditions.
Examination of the reliability of the portable calorimeter
Authors: Igawa Shoji , Sakamaki Mikako , Miyazaki Masami
Published: March 2003

1. The present study was performed in order to determine the reliablility of the portable calorimeter.

2. Resting energy expenditure (REE) was measured by two different apparatuses: one was the typical gas analyser, the other was the portable calorimeter.

3. Although there are differences among individuals, unless the subject has been exposed to severe physical activity prior to the measurement, a suitable resting time prior to the measurement of resting metabolic rate is 10 min.

4. For the measurement of resting metabolic rate, fluctuations in respiratory quotient (RQ) are extremely small; there is greater fluctuation due to variations in respiration. Therefore, for the screening of energy consumption, the use of a fixed value for RQ is sufficient when measuring only oxygen uptake.

5. Respiratory fluctuations vary from person to person and it is not possible to make stable measurements in 1 or 2 min. Therefore, a suitable measurement time for resting metabolic rate is from 3 to approximately 6 min.

6. The results indicate that this portable calorimeter is a useful apparatus for measuring REE in the field.
Acrosome reaction in spermatozoa of the hagfish Eptatretus burgeri (Agnatha)
Authors: Morisawa Sachiko
Published: March 2003

Fertilization of the hagfish or myxiniformes, a member of the most primitive vertebrate group and an animal of phylogenic interest, is unknown. Here, induction of an acrosome reaction for spermatozoa in the hagfish, Eptatretus burgeri, was successfully achieved by treatment of mature spermatozoa with ionomycin and excess Ca2+. The spermatozoon produced an acrosomal process that elongated from the apex of the long sperm head. The reaction bears resemblance to that of invertebrate spermatozoa rather than that of vertebrate spermatozoa. The result provides insights into the phylogenetical changes that have occurred in this sperm reaction.
Dual specificity of activin type II receptor ActRIIb in dorso‐ventral patterning during zebrafish embryogenesis
Authors: Nagaso Hideyuki , Suzuki Atsushi , Tada Masazumi , Ueno Naoto
Published: March 2003

Members of the transforming growth factor‐β (TGF‐β) superfamily are thought to regulate specification of a variety of tissue types in early embryogenesis. These effects are mediated through a cell surface receptor complex, consisting of two classes of ser/thr kinase receptor, type I and type II. In the present study, cDNA encoding zebrafish activin type II receptors, ActRIIa and ActRIIb was cloned and characterized. Overexpression of ActRIIb in zebrafish embryos caused dorsalization of embryos, as observed in activin‐overexpressing embryos. However, in blastula stage embryos, ActRIIb induced formation of both dorsal and ventro‐lateral mesoderm. It has been suggested that these inducing signals from ActRIIb are mediated through each specific type I receptor, TARAM‐A and BMPRIA, depending on activin and bone morphogenetic protein (BMP), respectively. In addition, it was shown that a kinase‐deleted form of ActRIIb (dnActRIIb) suppressed both activin‐ and BMP‐like signaling pathways. These results suggest that ActRIIb at least has dual roles in both activin and BMP signaling pathways during zebrafish embryogenesis.
Myotube morphology, and expression and distribution of collagen type I during normal and low score normal avian satellite cell myogenesis
Authors: Velleman Sandra G. , McFarland Douglas C.
Published: March 2003

Myogenic satellite cells are essential for postnatal muscle growth and the regeneration of muscle in response to injury. An understanding of how the extracellular matrix affects satellite cell activity, and the temporal and spatial expression of extracellular matrix macromolecules is largely unknown. In the avian genetic muscle weakness, low score normal (LSN), satellite cell proliferation and differentiation rates are significantly lower than that observed in normal chicken satellite cells, which may be attributed to a late embryonic increase in the expression of decorin. Satellite cell‐derived morphological properties, collagen type I expression, and the spatial distribution of collagen type I were investigated during normal and LSN satellite cell proliferation and differentiation. These studies showed a decrease in LSN myotube length and the number of nuclei per myotube. Collagen type I expression was similar between the LSN and normal satellite cell cultures during the course of proliferation and differentiation. However, the spatial distribution of collagen type I was altered in the LSN cultures 48 h after the initiation of fusion. The LSN cultures exhibited a premature extracellular distribution of collagen type I compared to the normal satellite cells.
Mitochondrial small ribosomal RNA is present on polar granules in early cleavage embryos of Drosophila melanogaster
Authors: Kashikawa Maki , Amikura Reiko , Nakamura Akira , Kobayashi Satoru
Published: March 2003

In Drosophila, formation of the germline progenitors, the pole cells, is induced by polar plasm localized in the posterior pole region of early embryos. The polar plasm contains polar granules, which act as a repository for the factors required for pole cell formation. It has been postulated that the factors are stored as mRNA and are later translated on polysomes attached to the surface of polar granules. Here, the identification of mitochondrial small ribosomal RNA (mtsrRNA) as a new component of polar granules is described. The mtsrRNA was enriched in the polar plasm of the embryos immediately after oviposition and remained in the polar plasm throughout the cleavage stage until pole cell formation. In situ hybridization at an ultrastructural level revealed that mtsrRNA was enriched on the surface of polar granules in cleavage embryos. Furthermore, the localization of mtsrRNA in the polar plasm depended on the normal function of oskar, vasa and tudor genes, which are all required for pole cell formation. The temporal and spatial distribution of mtsrRNA is essentially identical to that of mitochondrial large ribosomal RNA (mtlrRNA), which has been shown to be required for pole cell formation. Taken together, it is speculated that mtsrRNA and mtlrRNA are part of the translation machinery localized to polar granules, which is essential for pole cell formation.
Regulatory interrelations among topographic molecules CBF1, CBF2 and EphA3 in the developing chick retina
Authors: Yamagata Masahito , Mai Angela , Pollerberg G. Elisabeth , Noda Masaharu
Published: March 2003

It has been shown that topographic expression of two winged‐helix transcription factors, CBF1/c‐qinand CBF2, and a receptor tyrosine kinase EphA3 (Mek4/Cek4) play important roles in establishing the topographic retinotectal projection map along the rostrocaudal axis. The interrelationship among these topographic molecules in the chick retina was studied during development. The topographic expression of CBF1 and CBF2 preluded the graded expression of EphA3, but their precise expression profiles did not exactly fit together. However, interestingly, CBF1 and CBF2 were properly expressed, together with EphA3, in immortalized cell lines derived from the quail retina, which maintained position‐specific characteristics. The expression of another topographic molecule SOHo‐1, the sensory organ homeobox‐1 transcription factor, was separate from EphA3 expression. Ectopic expression of CBF1 usingin ovoelectroporation repressed the expression of CBF2, and misexpression of CBF2 influenced the graded localization of EphA3 in the retina, albeit imperfectly. Taken together, it is suggested that retinal cells first begin to express CBF1 or CBF2 according to their topographic positions, generate cellular descendants in which the expression of CBF1 and CBF2 is maintained cell‐autonomously, and then establish the nasotemporal gradient of EphA3 under the control of CBF2, although indirect.
Cyclic AMP‐ and calmodulin‐dependent phosphorylation of 21 and 26 kDa proteins in axoneme is a prerequisite for SAAF‐induced motile activation in ascidian spermatozoa
Authors: Nomura Mamoru , Inaba Kazuo , Morisawa Masaaki
Published: March 2003

Sperm activating and ‐attracting factor (SAAF), derived from the egg of the ascidian Ciona, activates sperm motility through adenosine 3′:5′‐cyclic monophosphate (cAMP)‐synthesis. A demembranated preparation of intact immotile sperm without SAAF was shown to require cAMP for reactivation. However, a demembranated preparation of intact motile sperm treated with SAAF did not require cAMP for reactivation, suggesting that cAMP is a prerequisite factor for SAAF‐dependent activation of sperm motility. Furthermore, a cAMP‐dependent protein kinase (PKA) inhibitor, H‐89, was found to inhibit sperm motility. During in vivo or in vitro activation of sperm motility by SAAF or cAMP, a 26 kDa axonemal protein and 21 kDa dynein light chain were phosphorylated, respectively, suggesting the involvement of PKA‐dependent phosphorylation of these proteins in sperm activation. The calmodulin antagonist, W‐7, and an inhibitor of calmodulin‐dependent myosin light chain kinase, ML‐7, also inhibited the activation of sperm motility. Inhibition was reversed by the addition of phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine. Demembranated preparations of immotile sperm in the presence of W‐7 or ML‐7 were reactivated by cAMP, suggesting that calmodulin participated in sperm activation and that cAMP synthesis was followed by activation of a calmodulin‐dependent mechanism.
Applications of microelectroporation for studies of chick embryogenesis
Authors: Yasuda Kunio , Momose Tsuyoshi , Takahashi Yoshiko
Published: March 2003

A technique by which genes can be introduced into the cells and tissues of developing embryos has great potential for studying the roles of genes during vertebrate embryogenesis. The ‘microelectroporation’ technique, in which DNA is introduced into cells within a restricted area of developing chick embryos with high reproducibility, was developed by the authors. In this review, the advantages and applications of this microelectroporation technique for developmental studies and functional analysis of genes in chick embryos is discussed.
Matrix metalloproteinases regulate mesonephric cell migration in developing XY gonads which correlates with the inhibition of tissue inhibitor of metalloproteinase‐3 by sry
Authors: Nishino Koichiro , Yamanouchi Keitaro , Naito Kunihiko , Tojo Hideaki
Published: March 2003

In the mouse, the sex determining gene Sry, on the Y chromosome, controls testis differentiation during embryogenesis. Following Sry expression, indifferent XY gonads increase their size relative to XX gonads and form cord‐like structures with the adjacent mesonephros, providing XY gonad somatic cells. This mesonephric cell migration is known to depend on Sry, but the molecular mechanism of mesonephric cell migration remains unknown. In this study, it was shown that cells expressing Sry induced proliferation of mesonephric cells migrating into male gonads, and inhibited expression of the tissue inhibitor of metalloproteinases (TIMP)‐3 gene, which is the endogenous inhibitor of matrix metalloproteinases (MMP). In addition, the mesonephric cell migration was blocked by a chemically synthesized inhibitor of MMP in a gonad/mesonephros organ co‐ culture system with enhanced green fluorescent protein transgenic embryos. The findings indicate that MMP may play a critical role in mesonephric cell migration, and the function of MMP may be regulated by a Sry– TIMP‐3 cascade. These findings are an important clue for the elucidation of testicular formation in developing gonads.
Electron microscopic observations of karyogamy in the fish egg
Authors: Iwamatsu Takashi , Kobayashi Hirokuni
Published: March 2003

In the initial step of pronuclear association in fertilized fish eggs, the female and male pronuclei (containing large nucleolus‐like bodies) were juxtaposed in the center of the blastodisc and formed nucleoplasmic projections along adjacent surfaces. After contact of the pronuclei, small internuclear bridges joining them were formed by fusion at several regions of the nuclear envelope projections. No specific site of fusion or breakdown of nuclear envelopes was recognized in the pronuclei during karyogamy. In the advanced stage, clumps of condensing chromatin appeared in the nucleoplasm of the newly fused pronuclei. The number and diameter of the internuclear bridges increased gradually by progressive fusion in many regions, finally yielding a spherical zygote nucleus. Following complete formation of the zygote nucleus, the pronuclear envelope began to break down concomitantly with shrinkage of the nucleoplasm, which was highly convoluted around the entire nuclear surface. The nucleoplasm containing chromosomes then mingled with the perinuclear cytoplasm.
β‐Catenin in early development of the lancelet embryo indicates specific determination of embryonic polarity
Authors: Yasui Kinya , Li Guorong , Wang Yong , Saiga Hidetoshi , Zhang Peijun , Aizawa Shinichi
Published: March 2003

The lancelet (amphioxus) embryo develops from a miolecithal egg and starts gastrulation when it is approximately 400 cells in size, in a fashion similar to that of some non‐chordate deuterostomes. Throughout this type of gastrulation, the embryo develops characteristics such as the notochord and hollow nerve cord that commonly appear in chordates. β‐Catenin is an important factor in initiating body patterning. The behavior and developmental pattern of this protein in early lancelet development was examined in this study. Cytoplasmic β‐catenin was localized to the animal pole after fertilization and then was incorporated asymmetrically into the blastomeres during the first cleavage. Asymmetric distribution was observed at least until the 32‐cell stage. The first nuclear localization was at the 64‐cell stage, and involved all of the cells. At the initial gastrula stage, however, concentrated β‐catenin was found on the dorsal side. LiCl treatment affected the asymmetric pattern of β‐catenin during the first cleavage. LiCl also changed distribution of nuclear β‐catenin at the initial gastrula stage: distribution extended to cells on the animal side. Apparently associated with this change, expression domains of goosecoid, lhx3 and otx also changed to a radially symmetric pattern centered at the animal pole. However, LiCl‐treated embryos were able to establish embryonic polarity. The present study suggests that in the lancelet embryo, polarity determination is independent of dorsal morphogenesis.
Foot formation in Hydra: Commitment of the basal disk cells in the lower peduncle
Authors: Kobayakawa Yoshitaka , Kodama Rie
Published: March 2003

Foot regeneration in the freshwater hydra Pelmatohydra robusta was examined using a monoclonal antibody AE03 as a marker. This antibody specifically recognizes mucous‐producing ectodermal epithelial cells in the basal disk, but not cells in the peduncle region located just above the basal disk in the foot. When the basal disk was removed by amputation at the upper or lower part of the peduncle, AE03‐positive (basal disk) cells always appeared at the regenerating tip of the footless polyp approximately 12–16 h later. When a small piece of tissue was cut out from the upper or lower peduncle region, the tissue invariably turned into a smooth spherical or oblong shape within a few hours. AE03 signal appeared in these spheres variably depending on their origin: when tissue pieces were derived from the lower peduncle, the signal appeared in nearly all pieces and often covered the entire surface of the pieces within 24 h. In contrast, the signal appeared in less than 10% of pieces derived from the upper peduncle. Furthermore, the signal seldom covered more than half of the surface of these pieces. When maintained for many days, pieces derived from the upper peduncle often regenerated tentacles, whereas those from the lower peduncle seldom did. These and other observations suggest that epithelial cells in the peduncle can rapidly differentiate into basal disk cells when the basal tissue is removed. However, cells in the upper peduncle are not irreversibly committed to differentiate into basal disk cells because, when cut out as small tissue pieces, they could remain AE03 negative and become tentacle cells. In contrast, the cells in the lower peduncle apparently are irreversibly committed to differentiate into basal disk cells, as they always turned rapidly into AE03‐positive cells once they were physically separated from (and freed from the influence of) the basal disk itself, regardless of the separation methods used.
Bidder's organ in the toad Bufo marinus: Effects of orchidectomy on the morphology and expression of lamina‐associated polypeptide 2
Authors: Brown Federico D. , Del Pino Eugenia M. , Krohne Georg
Published: March 2003

The Bidder's organ is an undeveloped ovary located anterior to the testis in male true toads (Bufonidae). The presence of sperm and oocytes, derived from the primordial germ cells of the male toad, provides an exceptional condition for the study of germ cell differentiation in vertebrates. In this study, the effects of orchidectomy on morphology and on lamina‐associated polypeptide 2 (LAP2) expression were investigated in the Bidder's organ of Bufo marinus. To characterize bidderian oocytes, oogenesis in the ovary was divided into six stages. It was found that ovarian and bidderian oocytes were morphologically identical. To determine the expression of LAP2 isoforms, oocytes from the ovary and the Bidder's organ were examined by sodium dodecylsulfate–polyacrylamide gel electrophoresis and immunoblotting. In amphibians, LAP2β is expressed in somatic cells, whereas LAP2ω is expressed in oocytes. The Bidder's organ normally contained previtellogenic oocytes of less than 150 µm in diameter that expressed LAP2β. However, the organ in some male toads contained a few larger oocytes, resulting in the faint detection of LAP2ω. After orchidectomy, bidderian oocytes grew and strongly expressed LAP2ω. Moreover, as in the ovary, LAP2ω was upregulated in bidderian oocytes of 240 µm in diameter. This work represents the first demonstration of the molecular similarity between ovarian and bidderian oocytes.
In vitro Cre/loxP system in cells from developing gonads: Investigation of the Sry promoter
Authors: Ito Masanori , Yokouchi Kou , Naito Kunihiko , Endo Hitoshi , Hakamata Yoji , Miyazaki Jun‐ichi , Tojo Hideaki
Published: March 2003

There have been few studies on the regulatory elements of the Sry gene, mainly because no Sry‐expressing cell lines have yet been established. This paper describes a useful tool for investigating the regulation and upstream region of Sry by means of the in vitro Cre/loxP system. Using plasmids containing the 9.9 kb mouse genomic Sry previously shown to induce testis development in XX transgenic mice, we constructed a Sry/Cre fusion gene plasmid in which Cre expression is controlled by the 5′ and 3′ untranslated regions of mouse Sry. To distinguish between male and female gonads of 11.5 days post‐coitus (d.p.c.) fetuses, double transgenic fetuses carrying both the CAG (cytomegalovirus enhancer and β‐actin promoter)/loxP/lacZ transgene on the autosome and the green fluorescent protein transgene ubiquitously expressed on the Y chromosome were produced by crossing between two transgenic mouse lines. When Sry/Cre plasmids were transfected into the cells that had been prepared from the gonads, brains and livers of double transgenic fetuses, only a small number of X‐gal‐stained cells were detected among the primary cultured cells from male and female gonads, and none were detected among the cells from the other tissues. The X‐gal‐positive cells were negative for alkaline phosphatase, indicating that these cells were somatic cells expressing Sry. The Sry/Cre plasmids with a 0.4 kb upstream region of Sry yielded a large number of X‐gal‐positive cells in the cells from gonads, including various tissues of 11.5 d.p.c. fetuses, indicating the loss of the tissue‐specific expression of Sry. The Sry/Cre with a 1.4 kb upstream region maintained tissue‐specific activity of Sry. The results indicate that the present in vitro Cre/loxP system using transgenic mice is a simple and useful system for investigating the regulatory element of sex determination‐related genes, including Sry.
Mate choice by males of the hermit crab Pagurus filholi: Do males assess ripeness and/or fecundity of females?
Authors: Goshima Seiji , Kawashima Tetsuya , Wada Satoshi
Published: March 2003

Males of the hermit crab, Pagurusfilholi, often grasp the edges of shells occupied by females and drag them during the mating season. This behavior was experimentally confirmed to be a precopulatory guarding behavior displayed by males for ripe females, and males were found to recognize females which were within about 5 days of spawning. Most theoretical models for mating preference assume the choosing sex (the male in the present case) has complete reproductive information about potential mates, and predict that males will preferably choose more fecund females and/or females that will require less guarding time (i.e. that will spawn sooner) as partners. Several male‐choice experiments between two ripe females, both previously guarded by other males, were carried out to examine the above predictions. Males did not prefer females of larger size, higher fecundity or with less time remaining until spawning. These results suggest that males may not have complete information about potential partners, rather that male hermit crabs may adopt a mating strategy of pairing with the first ripe female they encounter. Even with such incomplete mate assessment, males may enhance their reproductive success by recognizing ripe females that will spawn within a given time (about 5 days in the present case).
Effects of population size and pollinator limitation on seed‐set ofPrimula sieboldiipopulations in a fragmented landscape
Authors: Matsumura Chizuru , Washitani Izumi
Published: March 2003

Female reproductive success, fruit and seed‐set and factors affecting them were measured for 3 years (1995–1997) for 24 populations ofPrimula sieboldiiE. Morren, a threatened Japanese plant species in a highly fragmented landscape in southern Hokkaido. The smaller populations (genets <=; 3) set almost no seeds consistently during the study years. In larger populations (genets >= 7), proportions of failed flowers without damage from fungi or herbivores were relatively high, but fruit set per flower varied among the populations in 1995. Correlations of fruit (r= 0.589,P= 0.011) and seed‐ set (r= 0.688,P< 0.01) with population pollinator availability were highly significant. In 1995, pollination failure would be the most plausible reason for the variation in reproductive success among the populations. However, pollinator availability was relatively high in all populations in 1996 and 1997. In these years, higher proportions of fruit failed because of antagonistic biological interactions. In the populations with poor pollinator availability in 1995, mean fruit and seed‐sets were greater in the long‐styled morph than in the short‐styled morph. Such between‐morph differences are thought to be caused by partial self‐compatibility of the long‐styled morph and the results of hand pollination experiments support this hypothesis.
Asymmetric interactions between plants and seed‐harvesting ants in a Mediterranean pasture
Authors: López F. , Acosta F. J. , Serrano J. M.
Published: March 2003

A four‐year study on the interactions between plants and seed‐harvesting ants in a Mediterranean pasture is reviewed in this paper. As previously reported in many studies on plant–herbivore interactions, ant–plant relationships are also asymmetric; plants had a larger impact on herbivore dynamics than vice versa. However, the asymmetry did not refer to population dynamics but rather to animal foraging strategies. Ants did not exert a significant influence on vegetation dynamics in terms of plant abundance. The main constraints underlying vegetation change were self‐regulation and rainfall. In contrast, the structural characteristics and abundance of vegetation had a significant impact on several important features of food harvesting by ants. This influence was not only associated with their feeding requirements but also with their foraging activities.
Influence of leaf litter quality on the colonization and consumption of stream invertebrate shredders
Authors: Motomori Kayoko , Mitsuhashi Hiromune , Nakano Shigeru
Published: March 2003

The importance of leaf litter quality for colonization and consumption by two caddisflies (Goerodes satoi and Hydatophylax festivus) and an amphipod (Sternomoera yezoensis) was examined by laboratory and field experiments in a forested headwater stream in northern Japan. Initial values of leaf litter toughness and the carbon to nitrogen (C : N) ratio, both of which varied among the three most common tree species, oak (Quercus crispula), maple (Acer mono) and alder (Alnus hirsuta), decreased dramatically in the field experiment. The density of Hydatophylax was greatest in alder leaf litter characterized by the lowest C : N ratio among the three, with C : N ratio being the only predictor of their density. In contrast, lesser toughness was the only factor facilitating colonization by Sternomoera, the density of which was greatest in the softest maple litter. Neither toughness nor C : N ratio could be used to predict colonization by Goerodes. In the laboratory experiment, in which the shredders were reared on the aforementioned types of leaf litter, following conditioning periods of 1 week and 1 month (six separate trials), the litter consumption rate decreased with toughness in both Sternomoera and Hydatophylax, and with C : N ratio in the latter. However, the consumption rate of Goerodes was influenced by neither of the above, indicating that Sternomoera and Hydatophylax, but not Goerodes, selectively colonized the leaf litter available as a food resource in the stream. Both chemical and physical qualities of leaf litter play an important role in determining species‐specific colonization by invertebrate shredders.
Fallen leaves and unpalatable plants as alternative foods for sika deer under food limitation
Authors: Takahashi Hiroshi , Kaji Koichi
Published: March 2003

Feeding behavior and rumen contents of sika deer (Cervus nippon Temminck) under food limitation were studied on Nakanoshima Island, Hokkaido. During the phase of population growth, the deer subsisted on tree bark and twigs, deciduous leaves and dwarf bamboos (Sasa spp.) in the winter. After a crash in population, the deer began feeding on the fallen leaves of deciduous trees and continued to do so throughout the year. They also ate unpalatable plants Cephalotaxus harringtonia var. nana Rehd., Senecio cannabifolius Less. and Cynanchum caudatum Maxim. as winter foods, which used to remain untouched by deer, and had accordingly expanded their distributions, following a decrease in the amount of dwarf bamboos available. These facts suggest that sika deer drastically shift their foods and exploit alternative foods under conditions of food limitation.
Feedback regulation of constant leaf standing crop in Sasa tsuboiana grasslands
Authors: Konno Yasuo
Published: March 2003

The standing crop of current leaves of Sasa tsuboiana was measured on the upper slopes of Mount Horai, Shiga prefecture, central Japan. Upper one‐year‐old branches in the canopy produced greater mass of current leaves than lower ones. Furthermore, culms in artificially thinned plots produced larger leaf mass per culm than those in control plots. These results reveal that leaf production is positively correlated with light intensity. Therefore, when the leaf standing crop in a given year is somewhat smaller than usual, it may increase in the following year because the branches will receive stronger light. This feedback regulation causes uniformity in the horizontal distribution of the leaf standing crop. The constancy of the leaf standing crop throughout dense stands of different heights indicates that a common equilibrium value of the leaf standing crop exists. This uniform distribution leads to an almost‐uniform weak light intensity under the canopy of S. tsuboiana, and can consequently exclude other plant species.
Adaptive significance of vegetative sprouting for a tropical canopy tree, Scaphium longiflorum (Sterculiaceae), in a peat swamp forest in Central Kalimantan
Authors: Yamada Toshihiro , Kumagawa Yoshie , Suzuki Eizi
Published: March 2003

Scaphium longiflorum Ridley (Sterculiaceae), a common canopy tree in peat swamp forests in the Far East, produces vegetative sprouting in its juvenile stage. We investigated morphological features and allometric properties of the species in a peat swamp forest in Central Kalimantan, Indonesia, to determine under what conditions ramets are produced and discuss the adaptive significance of the vegetative sprouting in a peat swamp environment. Larger juveniles were more toppled, and the toppled ones sprouted vegetatively. Therefore, the vegetative sprouting acts as a countermeasure for a shoot’s mechanical failure and fall on an unstable peat soil. We propose three hypotheses to explain the reason why larger juveniles are more often toppled in a peat swamp environment.
Self‐thinning lines differ with fertility level
Authors: Morris E. Charles
Published: March 2003

The effect of variations in fertility level of the substrate on the self‐thinning lines followed by populations ofOcimum basilicumL. was investigated experimentally by establishing populations over a range of densities at two fertility levels. Populations from each fertility level followed different self‐thinning lines for shoot biomass. Self‐thinning began at a lower biomass in populations grown at the higher fertility level; the subsequent slope of the thinning line was −0.5 for these stands on a log shoot biomass versus log density plot. The slope of the self‐thinning line was flatter (−0.29) at the lower fertility level. Fitting the self‐thinning line by the Structural Relationship rather than the Major Axis made little difference to line estimates. Biomass packing differed with fertility level, with plants from the higher fertility stands requiring more canopy volume for given shoot biomass than plants from lower fertility levels. Biologically, this would mean shoot competition intensified more rapidly at the higher fertility level as biomass accumulated in stands. The difference in slope between fertility levels was associated with changes above‐ and belowground. The radial extension of the canopy versus shoot mass relationships of individual plants differed with fertility level. Plants at the lower fertility level allocated more biomass to root growth, and had less leaf area per unit root length. The differences in slope of the self‐thinning lines may have been because of differences in the radial extension of the canopy versus shoot mass relationships of individual plants at each fertility level, and/or to an increase in root competition at the lower fertility level.
Trophic polymorphism in introduced bluegill in Japan
Authors: Yonekura Ryuji , Nakai Katsuki , Yuma Masahide
Published: March 2003

We demonstrate that bluegill (Lepomis macrochirus) introduced from their native North American source to Lake Biwa in Japan showed considerable trophic and morphological variations (morphs). Three morphs were found for larger bluegills, specialized in three distinct resources (i.e. plankton, benthic invertebrates and aquatic plant), and two morphs were found for smaller bluegills, specialized in two slightly different prey taxa (i.e. calanoid and cyclopoid plankton). These morphs, especially for the large size class, can be distinguished primarily by differences in midbody length and depth. The dietary specialization and morphological differentiation among individuals were considered to be a result of different requirements for efficient resource utilization, which is a unique example of trophic polymorphism occurring in an introduced fish species in a species‐rich fish community.