bluuebunny/crossref_metadata_2025 huggingface dataset:
Angiotensin Peptides As Neurotransmitters/ Neuromodulators In The Dorsomedial Medulla
Authors: Diz Debra I , Jessup Jewell A , Westwood Brian M , Bosch Susan M , Vinsant Sherry , Gallagher Patricia E , Averill David B
Published: March 2003

1. The present review provides an update on evidence of the neurotransmitter pathways and location of receptors within the nucleus tractus solitarii (NTS) mediating the baroreflex and other haemodynamic actions of angiotensin (Ang) II.

2. A series of studies suggests a significant role for substance P in the acute cardiovascular and carotid sinus chemoreceptor facilitatory actions of AngII in the NTS. The use of antisense oligonucleotides to AT1 receptors indicates both pre‐ and post‐synaptic AngII receptors are likely to be involved in these actions.

3. With respect to baroreceptor reflex actions, it is clear that endogenous AngII impairs the gain for operation of the baroreceptor reflex, because AT1 receptor antagonists facilitate reflex function. This effect is either independent of substance P or involves inhibition of release. Moreover, initial data obtained using antisense oligonucleotides to AT1 receptors suggest that, in the NTS, the effect of endogenous AngII on the baroreceptor reflex is mainly due to presynaptic actions on vagal or carotid sinus afferent fibres. In contrast, the level of endogenous AngII within the NTS appears to have variable effects on activation of cardiopulmonary vagal afferent fibres by phenylbiguanide. These results indicate a divergence of effects of AngII on reflexes evoked by these two different types of sensory input.

4. Use of transgenic rats with alterations in brain angiotensin peptides allowed us to assess the effect of long‐term alterations in brain Ang peptides on reflex function. We studied (mRen2)27 transgenic rats (TGR(mRen2)) with high brain medulla AngII levels and transgenic rats with angiotensinogen (Aogen) antisense linked to glial fibrillary acidic protein promoter (TGR(ASrAogen)) with greatly reduced brain Aogen. The reflex evoked by activation of cardiac vagal chemosensitive afferent fibres was enhanced in TGR(ASrAogen), whereas the baroreceptor reflex control of heart rate was attenuated in TGR(mRen2), further confirming a divergence of effects of AngII on these two sensory modalities.

5. The overall results are consistent with a sustained inhibitory effect of AngII on the baroreceptor reflexes, with dose‐dependent or activation‐dependent effects on cardiac vagal afferent fibre activation. Moreover, alterations in substance P pathways may contribute to the actions of AngII on reflex function.
The Baroreflex And Beyond: Control Of Sympathetic Vasomotor Tone By Gabaergic Neurons In The Ventrolateral Medulla
Authors: Schreihofer Ann M , Guyenet Patrice G
Published: March 2003

1. Barosensitive, bulbospinal neurons in the rostral ventrolateral medulla (RVLM), which provide the major tonic excitatory drive to sympathetic vasomotor neurons, are prominently inhibited by GABA.

2. A major source of the GABAergic inhibition to presympathetic RVLM neurons arises from an area immediately caudal to the RVLM, known as the caudal ventrolateral medulla (CVLM).

3. Arterial baroreceptor afferents projecting to the nucleus tractus solitarius (NTS) provide a major tonic excitatory input to GABAergic CVLM neurons. These CVLM cells are a critical component for baroreflex‐mediated changes in presympathetic RVLM neuronal activity, sympathetic nerve activity (SNA) and arterial pressure (AP).

4. Some GABAergic CVLM neurons are tonically activated by inputs independent of arterial baroreceptors or the NTS, providing a GABAergic‐mediated inhibition of the presympathetic RVLM neurons that is autonomous of baroreceptor inputs.

5. GABAergic CVLM neurons appear to play two distinct, yet important, roles in the regulation of sympathetic vasomotor tone and AP. They dampen immediate changes in AP via the baroreflex and tonically inhibit the activity of the presympathetic RVLM neurons by baroreceptor‐independent mechanisms. This baroreceptor‐independent, GABAergic inhibition of presympathetic RVLM neurons may play an important role in determining the long‐term level of sympathetic vasomotor tone and AP.
Neurotransmitters In Central Cardiovascular Regulation: Glutamate And Gaba
Authors: Gordon Frank J , Sved Alan F
Published: March 2003

1. The role of the amino acidsL‐glutamate and GABA as neurotransmitters in central pathways regulating cardiovascular function is briefly summarized.
Involvement Of Oxidative Stress In Bee Venom‐Induced Inhibition Of Na+/Glucose Cotransporter In Renal Proximal Tubule Cells
Authors: Han Ho Jan , Park Soo Hyun , Lee Jang Hern , Yoon Byeong Cheol , Park Kwon Moo , Mar Woong Chon , Lee Hye Jung , Kang Sung Keel
Published: March 2003

1. The present study was conducted to examine the involvement of oxidative stress in bee venom‐induced inhibition of the Na+/glucose cotransporter (α‐methyl‐d‐glucopyranoside (α‐MG) uptake), a typical functional marker of proximal tubules, in primary cultured rabbit renal proximal tubule cells (PTC).

2. Bee venom (≥ 1μg/mL) increased lipid peroxide (LPO) formation over 30 min. The increase in [3H]‐arachidonic acid (AA) release and LPO formation and the inhibition ofα‐MG uptake induced by bee venom (1μg/mL) and melittin (a major component of bee venom; 0.5μg/mL) were blocked byN‐acetyl‐l‐cysteine, vitamin C and vitamin E, anti‐oxidants.

3. Bee venom‐ and melittin‐induced increases in LPO formation and inhibition ofα‐MG uptake were significantly prevented by mepacrine and AACOCF3, phospholipase A2inhibitors. In addition, nordihydroguaiareic acid (a lipoxygenase inhibitor) and econazole (a cytochrome P‐450 epoxygenase inhibitor), but not indomethacin (a cyclo‐oxygenase inhibitor), prevented bee venom‐ and melittin‐induced increases in LPO formation and inhibition ofα‐MG uptake.

4. Nordihydroguaiareic acid prevented bee venom‐ and melittin‐induced increases in Ca2+uptake. Moreover, anti‐ oxidants significantly prevented bee venom‐ and melittin‐induced increases in Ca2+uptake.

5. In conclusion, bee venom inhibitsα‐MG uptake via the phospholipase A2–oxidative stress–Ca2+signalling cascade in primary cultured rabbit renal proximal tubule cells.
Statistical Techniques For Comparing Measurers And Methods Of Measurement: A Critical Review
Authors: Ludbrook John
Published: March 2003

1. Clinical and experimental pharmacologists and physiologists often wish to compare two methods of measurement, or two measurers.

2. Biostatisticians insist that what should be sought is not agreement between methods or measurers, but disagreement or bias.

3. If measurements have been made on a continuous scale, the main choice is between the Altman–Bland method of differences and least products regression analysis. It is argued that although the former is relatively simple to execute, it does not distinguish adequately between fixed and proportional bias. Least products regression analysis, although more difficult to execute, does achieve this goal. There is almost universal agreement among biostatisticians that the Pearson product–moment correlation coefficient (r) is valueless as a test for bias.

4. If measurements have been made on a categorical scale, unordered or ordered, the most popular method of analysis is to use the kappa statistic. If the categories are unordered, the unweighted kappa statistic (K) is appropriate. If the categories are ordered, as they are in most rating scales in clinical, psychological and epidemiological research, the weighted kappa statistic (Kw) is preferable. But Kw
corresponds to the intraclass correlation coefficient, which, like r for continuous variables, is incapable of detecting bias. Simple techniques for detecting bias in the case of ordered categorical variables are described and commended to investigators.
Caffeine Decreases The Expression of Na+/K+‐Atpase and the Type 3 Na+/H+ Exchanger In Rat Kidney
Authors: Lee JongUn , Ha Jeong Hoon , Kim Sunmi , Oh YoonWha , Kim Soo Wan
Published: March 2003

1. The aim of the present study was to explore the mechanisms underlying the renal effects of caffeine.

2. Male Sprague‐Dawley rats were treated with caffeine, consisting of a single oral bolus (0.2%, 20 mL/kg) followed by supplementation in drinking water (0.2%) for 1 day. Rats treated the same but given water without caffeine served as controls.

3. The expression of α1‐ and β1‐subunits of Na+/K+‐ATPase,
the type 3 Na+/H+ exchanger (NHE3) and aquaporin‐1 was determined in the kidney by western blot analysis.

4. To explore possible involvement of local humoral mediators, the tissue expression of nitric oxide synthase (NOS) proteins was determined by western blot analysis and the expression of atrial natriuretic peptide (ANP) mRNA was determined by semiquantitative reverse transcription–polymerase chain reaction.

5. Following treatment with caffeine, the expression of α1‐ and β1‐subunits
of Na+/K+‐ATPase, as well as that of NHE3, was decreased. Accordingly,
the catalytic activity of Na+/K+‐ATPase was decreased. In contrast, the expression of aquaporin‐1 was not altered significantly.

6. The expression of the endothelial isoform of NOS was increased, along with tissue nitrite/nitrate levels. The expression of ANP mRNA was increased.

7. It is suggested that caffeine decreases Na+/K+‐ATPase and NHE3 activities and increases nitric oxide and ANP activities in the kidney.
Cellular Signalling In Arteriolar Myogenic Constriction: Involvement Of Tyrosine Phosphorylation Pathways
Authors: Murphy Timothy V , Spurrell Brian E , Hill Michael A
Published: March 2003

1. An increase in transmural pressure in arterioles results in a shortening of vascular smooth muscle cells, with subsequent constriction of the vessel. The mechanisms underlying this myogenic contraction are not fully understood; however, the obligatory role of increases in intracellular [Ca2+] and myosin light chain phosphorylation have been demonstrated.

2. The myogenic response shows a relationship with smooth muscle cell membrane potential and influx of extracellular Ca2+ through voltage‐operated
Ca2+ channels (VOCC). Mechanically sensitive channels and possibly
release of Ca2+ from intracellular stores may play a role. However,
there are other components of myogenic contraction that cannot be explained by a
Ca2+–MLCK mechanism, for example the initial sensing of
alterations in transmural pressure, whether sustained myogenic constriction involves
myofilament Ca2+ sensitization or remodelling of the vessel wall in response to a maintained increase in transmural pressure.

3. In an attempt to investigate these areas, recent studies have examined a role for tyrosine phosphorylation pathways in pressure‐induced contraction of arterioles. In rat pressurized cremaster arterioles, tyrosine kinase inhibitors dilated vessels showing spontaneous myogenic tone and tyrosine phosphatase inhibitors caused vasoconstriction. However, pressure‐induced myogenic constriction of vessels persisted in the presence of these agents. Biochemical studies revealed that phosphotyrosine formed at a relatively slow rate (significant after 5 min, with maximal increase after approximately 15 min) in response to increased vessel transmural pressure, in contrast with myosin light chain phosphorylation or the time‐course of myogenic constriction itself (maximum within 1 min).

4. Taken together, these observations support the idea of a role for tyrosine phosphorylation pathways in longer‐term responses to increased transmural pressure rather than acute myogenic constriction. Phosphotyrosine formation was also more closely correlated to vessel wall tension (pressure × diameter) than the diameter of the arterioles alone. The identity of the tyrosine‐phosphorylated proteins requires further investigation; however, there is some evidence supporting roles for cSrc‐type tyrosine kinases and p44 mitogen‐activated protein kinase. The longer‐term responses of blood vessels to increased transmural pressure that may involve tyrosine phosphorylation pathways include maintenance of myogenic constriction and vessel wall remodelling.
Effect of calcium on the vascular contraction induced by cobra venom cardiotoxin
Authors: Kwan CY , Kwan TK , Huang SJ
Published: March 2003

1. The cytotoxic effects of cardiotoxin (CTX) purified from Cobra venom were tested in endothelium‐denuded rat aortic ring preparations in tissue organ baths and the effect of extracellular Ca2+ on the cytotoxic effect of CTX was investigated using a digital dynamic calcium imaging technique.

2. At 10 µmol/L, CTX induced a slowly developing and sustained contraction that amounted to approximately 50% of the maximal contraction induced by 80 mmol/L KCl. At high concentrations (> 15 µmol/L), CTX caused irreversible damage to the smooth muscle contractile function. However, washout of CTX at its peak contraction did not affect the subsequent contraction to either KCl or phenylephrine.

3. Contraction induced by CTX was dependent on the Ca2+concentration in the external solution. A maximal contractile response to CTX was obtained in medium containing 1–2.5 mmol/L Ca2+. This contractile response induced by CTX decreased with higher Ca2+ concentrations and was completely diminished when 7 mmol/L Ca2+, 3 mmol/L Ni2+ or 30 µmol/L tetrandrine (a non‐selective calcium channel blocker) was present in the external solution before addition of CTX to the bath.

4. The above observations were supported by the calcium imaging work performed with cultured aortic smooth muscle cells from Wistar‐Kyoto rats, in which CTX was shown to induce the elevation of cytosolic Ca2+ in the presence, but not in the absence, of 2.5 mmol/L extracellular Ca2+. Increasing the extracellular Ca2+ concentration to 7 mmol/L, the addition of 3 mmol/L Ni2+ or inclusion of 30 µmol/L tetrandrine inhibited the elevation of cytosolic Ca2+ induced by CTX.

5. These results suggest that: (i) a CTX‐sensitive internal calcium store does not exist in rat aortic smooth muscle; (ii) the contractile effect CTX is associated with a Ca2+ influx process; and (iii) CTX interacts extracellularly with the plasma membrane at the level of the calcium channels, as well as anionic sites to which Ca2+ and other inorganic cations bind.
Regulation of K+ channels underlying the slow afterhyperpolarization in enteric afterhyperpolarization‐generating myenteric neurons: Role of calcium and phosphorylation
Authors: Vogalis Fivos , Harvey John R , Neylon Craig B , Furness John B
Published: March 2003

1. Myenteric afterhyperpolarization‐generating myenteric (AH) neurons serve as intrinsic primary afferent neurons of the enteric nervous system and generate prolonged or slow afterhyperpolarizing potentials (slow AHP). The slow AHP is generated by an increase in a Ca2+‐activated K+ conductance (gK‐Ca) and is inhibited by enteric neurotransmitters leading to increased excitability.

2. Using cell‐attached patch‐clamp recordings from AH neurons, we have shown that K+ channels with an intermediate unitary conductance (IK channels) open following action potential firing.

3. In excised patches from AH neurons, we have identified an IK‐like channel that can be activated by submicromolar levels of cytoplasmic Ca2+ and is not voltage dependent.

4. Application of the catalytic subunit of cAMP‐dependent protein kinase to the cytoplasmic surface of inside‐out patches inhibits the opening of IK‐like channels previously activated by Ca2+.

5. The IK‐like channels are resistant to external tetraethylammonium (5 mmol/L) and apamin (0.3–1 µmol/L), but are inhibited by clotrimazole (10 µmol/L).

6. Our present data support the idea that an increase in the open probability of IK‐like channels in AH neurons following an increase in cytoplasmic [Ca2+] is responsible for the slow AHP and their opening is modulated by kinases.
Restoration of arterial baroreflex function contributes to organ protection in spontaneously hypertensive rats treated with long‐term hydrochlorothiazide mixture
Authors: Lu Ze‐An , Xie He‐Hui , Xu Li‐Ping , Yin An‐Fan , Miao Chao‐Yu , Su Ding‐Feng
Published: March 2003

1. Hydrochlorothiazide mixture (HCTM) is widely used in China for the treatment of hypertension. This mixture consists of hydrochlorothiazide, triamterene, reserpine, hydralazine and chlordiazpoxide, with small (one‐third to one‐fifth of normal) doses of each drug. The present study was designed to investigate the effects of this mixture on blood pressure, blood pressure variability (BPV), baroreflex sensitivity (BRS) and end‐organ damage in spontaneously hypertensive rats (SHR).

2. The HCTM was mixed in the rat chow and rats were treated for 4 months. After treatment, rats were catheterized and their blood pressure, BPV and BRS were measured in the conscious state. Organ damage was examined after these measurements had been completed.

3. It was found that HCTM not only decreased blood pressure and BPV, but also ameliorated impaired BRS in SHR. The HCTM had an obvious effect on organ protection in SHR.

4. The HCTM prevented left ventricular hypertrophy and this effect was mainly related to a decrease in systolic blood pressure. The effects of HCTM on preventing renal atrophy were mainly determined by BRS. Baroreflex sensitivity was the most important determinant for predicting organ damage in HCTM‐treated SHR.

5. In conclusion, long‐term treatment of rats with HCTM prevented hypertensive organ damage. Restoration of arterial baroreflex function contributes to organ protection in SHR treated in the long term with HCTM.
Synergism between β2‐adrenoceptor agonists and subtype‐selective α1A‐adrenoceptor antagonists in the tocolytic effect on pregnant rat uterus in vitro
Authors: Mihályi A , Gáspár R , Csonka D , Falkay G
Published: March 2003

1. Despite great efforts in recent decades, premature birth is still a leading cause of perinatal morbidity and mortality. β2‐Adrenoceptor agonists are frequently used as tocolytics, although their use is rather controversial. Previous animal studies have revealed that blockade of α1A‐adrenoceptors results in relaxation of the pregnant rat myometrium.

2. The aim of the present study was to investigate the uterus relaxant effect of the β2‐adrenoceptor agonists (terbutaline, ritodrin) applied together with the subtype‐selective α1A‐adrenoceptor antagonists (WB 4101, 5‐methylurapidil) in an in vitro rat model. The main objective of the experiments was to clarify whether there was an additive or a potentiating synergism between the two drug classes.

3. Myometrial rings were taken from female, 22‐day pregnant (end‐term) Sprague‐Dawley rats. Electrical field stimulation (EFS) was used to elicit rhythmical contractions. Non‐cumulative concentration–response curves were constructed to the β2‐adrenoceptor agonists and the α1A‐adrenoceptor antagonists alone and to β2‐adrenoceptor agonists co‐administered with the α1A‐adrenoceptor antagonists.

4. Both groups of drugs inhibited EFS‐induced contractions in a dose‐dependent way. Administering the β2‐adrenoceptor agonists in combination with the α1A‐adrenoceptor antagonists resulted in a significant decrease in the EC50 and an increase in the maximal contraction inhibiting effect.

5. The potentiating synergism that has been revealed between β2‐adrenoceptor agonists and α1A‐adrenoceptor antagonists in the uterus relaxant effect may be of great clinical importance because it could improve the efficacy of therapy of preterm delivery.
Prevalence of overweight and hypertension in Tanzania: Special emphasis on resting energy expenditure and leptin
Authors: Kuga Sachiko , Njelekela Marina , Noguchi Takanori , Kanda Tomo , Yamori Masashi , Sato Toshiaki , Miki Tomohiro , Ikeda Katsumi , Nara Yasuo , Mtabaji Jacob
Published: March 2003

1. In the present study we investigated the difference in the distribution of selected cardiovascular disease risk factors among three middle‐aged Tanzanian populations with different lifestyles.

2. The prevalence of hypertension and overweight was higher in urban areas than in rural areas. Plasma leptin concentration was also highest in urban areas. Based on these results, we speculated that overweight in the urban population may be partly due to adiposity.

3. Resting energy expenditure was lower in urban areas than in other areas for both genders. These findings suggest that the high prevalence of overweight in the urban population may be partly due to low physical activity levels.
Localization of mitochondrial large ribosomal RNA in the myoplasm of the early ascidian embryo
Authors: Oka Takuya , Amikura Reiko , Kobayashi Satoru , Yamamoto Hiroki , Nishida Hiroki
Published: March 2003

Mitochondrial large ribosomal RNA (mtlrRNA) is transferred out of mitochondria and associates with germinal granules in Drosophila and Xenopus embryos. It has been revealed that mtlrRNA outside of mitochondria is required for formation of the germ‐line progenitor, or pole cells in Drosophila. In the present study, the distribution of mtlrRNA was examined in embryos of the ascidian, Halocynthia roretzi, during cleavage stages by whole‐mount in situ hybridization. Until the 4‐cell stage, the distribution of mtlrRNA coincided with that of mitochondria, which are localized to the cortical cytoplasm in the posterior region of the embryos. Both mitochondria and mtlrRNA were preferentially partitioned into muscle‐lineage blastomeres during cleavage stages. After the 8‐cell stage, a discrepancy in intracellular localization of mitochondria and mtlrRNA became evident. Mitochondria translocated into central yolkless cytoplasm, while mtlrRNA remained in the posterior cortex in the posterior muscle‐lineage blastomeres. The significance of the cortical localization of mtlrRNA in muscle precursor cells in ascidian embryos is obscure. However, the results suggest that mtlrRNA is also transferred out of mitochondria in early ascidian embryos and may play some roles in developmental processes.
Origin of the gonad in the juvenile of a solitary ascidian, Ciona intestinalis
Authors: Yamamoto Masamichi , Okada Toshiaki
Published: March 2003

In the just‐metamorphosed juveniles of Ciona intestinalis, a round mass of tissue debris derived from the resorbed tadpole tail is situated in the broad space enclosed by the peritoneal membrane and the epidermis around the ventral side of the esophagus. In living juveniles, the origin of the gonad rudiment was traced back to the mass of tissue debris. Electron microscopically, the round mass was a clump of irregular‐shaped phagocytotic cells engulfing degenerated cell fragments. On the surface of the cell clump, a small number of singly occurring round cells were found and identified as primordial germ cells on the basis of morphological continuity to obvious germ cells in later stages. Presence of nuage around the nucleus characterized the germ cells. In a few days the germ cells assembled to form a solid slender body (gonad rudiment) together with smaller somatic cells. The gonad rudiment left the space around the esophagus, moving into the narrow mesenteric space connecting the stomach and intestine on the fourth day after metamorphosis. It gradually increased in size by proliferation of the germ cells and somatic cells. The solid gonad rudiment changed into an oval vesicle with an eccentrically located cavity on about the seventh day after metamorphosis. The vesicle comprised a thinner wall made of a simple epithelium without germ cells and a thicker wall containing germ cells and somatic cells.
Studies on fertilization of the teleost. II. Nuclear behavior and changes in histone H1 kinase
Authors: Iwamatsu Takashi , Shibata Yasushi , Yamashita Masakane
Published: March 2003

In order to understand the dynamic responses of gamete nuclei upon fertilization in the fish, Oryzias latipes, the relationship between changes in the activity of histone H1 kinase and nuclear behavior was examined during fertilization. Kinase activity rapidly decreased concomitant with the initiation of the propagative exocytosis of cortical alveoli following sperm attachment to the egg plasma membrane post‐insemination (PI). Activity again increased 30 min PI. Similar changes in kinase activity, migration and syngamy of pronuclei, and subsequent cleavage were observed with aphidicolin or actinomycin D treatment, except that formation of abnormal metaphase chromosomes was retarded in aphidicolin‐treated zygotes. Pretreatment of unfertilized eggs with cycloheximide or 6‐dimethylaminopurine (6‐DMAP) caused no nuclear changes. The activity of histone H1 kinase in these eggs rapidly declined following sperm penetration and exocytosis, but did not undergo subsequent increase in the presence of these inhibitors. In these eggs with low histone H1 kinase activity, the fertilization process from sperm penetration to syngamy occurred normally, but the pronuclear membrane did not break down and the chromosomes did not condense. The present data suggest that in fish eggs, DNA replication as well as the synthesis and phosphorylation of proteins, especially cyclin B, are required for normal formation of metaphase chromosomes at the first cleavage, but not for fertilization events from sperm penetration through to nuclear migration resulting in syngamy.
Dorsoventral differential distribution of collagen type XIV around the spinal cord is regulated by the ectoderm
Authors: Fukushima Mikiko , Hirano Shigeki , Tanaka Hideaki
Published: March 2003

Regional specification in the nervous system is a critical issue in nervous system morphogenesis. Along the dorsoventral axis of the spinal cord, ventral inductive signals of the notochord and floor plate, and dorsal ones of the epidermal ectoderm are essential. Collagen type XIV is uniquely distributed around the spinal cord with a gradient of dorsal high and ventral low at the early developmental stages of the chick embryo. In the present study it was found that collagen type XIV expression around the spinal cord was entirely regulated by the ectoderm and that even the ventralizing tissues, the notochord and floor plate, themselves could be influenced to express this molecule by the ectoderm.
The vasa‐like gene, olvas, identifies the migration path of primordial germ cells during embryonic body formation stage in the medaka, Oryzias latipes
Authors: Shinomiya Ai , Tanaka Minoru , Kobayashi Tohru , Nagahama Yoshitaka , Hamaguchi Satoshi
Published: March 2003

The medaka homolog of the Drosophila vasa gene, olvas (Oryzias latipes vas) was obtained using polymerase chain reaction of medaka cDNA from the testis and ovary. The spatio‐temporal expression pattern of olvas transcripts was observed by in situ hybridization on gonads and embryos. The transcripts for olvas were exclusively detected in the cytoplasm of germ cells in the testis and ovary, not in gonadal somatic cells. In the early developmental stages, each blastomere possessed the maternal transcripts of olvas, which disappeared during gastrula stages. At the late gastrula stage, specific expression of olvas was observed only in germline cells located at the posterior shield. Embryos after the hybridization were examined histologically, and the distribution and migration path of primordial germ cells (PGC) during early stages of embryonic‐body formation were revealed using the olvas gene as a germline cell marker. The PGC were translocated from the posterior shield to both sides of the embryonic body via the inner embryonic body in the medaka.
Suppression of polydactyly of the Gli3 mutant (extra toes) by δEF1 homozygous mutation
Authors: Moribe Hiroki , Takagi Tsuyoshi , Kondoh Hisato , Higashi Yujiro
Published: March 2003

Digit patterning is established through multiple genetic interactions. δ‐Crystallin enhancer/E2‐box factor (δEF1) is a zinc finger and homeodomain containing repressor protein, and is expressed in the posterior half of the forelimb bud and in the entire hindlimb bud during the early stage of limb development. The δEF1‐deficient mutant mice display various skeletal abnormalities, among which inferior ossification and abnormal patterning of autopodial bones are similar to those observed in Hox and Gli gene mutants. Gli3 mutant mice, extra toes (Xt), exhibit pre‐axial polydactyly losing the identity of digit I. It is demonstrated here that δEF1null(lacZ) homozygosity suppressed formation of the extra digit, uniquely of the hindlimb, in both Gli3XtJ heterozygous and homozygous mutants, but with no restoration of digit I identity. In Gli3XtJ mutants, the Hoxd13 expression domain was expanded more dramatically in homozygotes. In Gli3XtJ;δEF1null(lacZ) double homozygous mutants, Hoxd13 expression once expanded in Gli3XtJ homozygous mutant was reduced, more conspicuously in the hindlimbs, which may account for hindlimb‐restricted suppression of formation of the extra digit. The data suggest the possibility that the extent of Hoxd13 expression along the distal margin of the limb bud is determinative in defining the digit number.
Conversion from mitosis to meiosis: Morphology and expression of proliferating cell nuclear antigen (PCNA) and Dmc1 during newt spermatogenesis
Authors: Yazawa Takashi , Yamamoto Takashi , Nakayama Yuki , Hamada Shuji , Abé Shin‐ichi
Published: March 2003

The conversion from mitosis to meiosis is a phenomenon specific to the cellular progenitors of gametes; however, the mechanism or mechanisms responsible for this conversion are poorly understood. To this end, some morphological and molecular changes that occur during the initiation of meiosis in newt spermatogenesis are reported in the present paper. In situ morphologic studies revealed that spermatogonial stages comprise two phases: early mitotic generations (G1–G4) and late mitotic generations (G5–G8). Morphologic conversion from secondary spermatogonia to primary spermatocytes occurred during the intermediate stage of premeiotic DNA replication. The expression of proliferating cell nuclear antigen (PCNA), a DNA polymerase‐delta auxiliary protein, in spermatogonia was weak in G1, highest during DNA synthesis (S), decreased in G2 and was not detectable in dividing cells. Complementary DNA for newt homologs of DMC1 (disrupted meiotic cDNA), which is an Escherichia coli RecA‐like protein specifically active during meiosis, were isolated. The newt Dmc1 mRNA was first expressed significantly during the preleptotene stage and this continued into the spermatid stage. These observations present a basis for investigating the mechanism(s) controlling the conversion of newt spermatogonial cells from mitosis to meiosis.
T‐targets: Clues to understanding the functions of T‐box proteins
Authors: Tada Masazumi , Smith J. C.
Published: March 2003

Members of the T‐box gene family have been identified in both vertebrates and invertebrates, where they play key roles in the regulation of embryonic development, and particularly in morphogenesis and the assignment of cell fate. T‐box proteins act as transcription factors which regulate the expression of downstream effector genes. This review focuses on the identification of T‐box target genes and the basis of T‐box functional specificity.
Origin and evolution of the neural crest: A hypothetical reconstruction of its evolutionary history
Authors: Wada Hiroshi
Published: March 2003

The neural crest has long been regarded as one of the key novelties in vertebrate evolutionary history. Indeed, the vertebrate characteristic of a finely patterned craniofacial structure is intimately related to the neural crest. It has been thought that protochordates lacked neural crest counterparts. However, recent identification and characterization of protochordate genes such as Pax3/7, Dlx and BMP family members challenge this idea, because their expression patterns suggest remarkable similarity between the vertebrate neural crest and the ascidian dorsal midline epidermis, which gives rise to both epidermal cells and sensory neurons. The present paper proposes that the neural crest is not a novel vertebrate cell population, but may have originated from the protochordate dorsal midline epidermis. Therefore, the evolution of the vertebrate neural crest should be reconsidered in terms of new cell properties such as pluripotency, delamination–migration and the carriage of an anteroposterior positional value, key innovations leading to development of the complex craniofacial structure in vertebrates. Molecular evolutionary events involved in the acquisitions of these new cell properties are also discussed. Genome duplications during early vertebrate evolution may have played an important role in allowing delamination of the neural crest cells. The new regulatory mechanism of Hox genes in the neural crest is postulated to have developed through the acquisition of new roles by coactivators involved in retinoic acid signaling.
Characteristics of Sasa nipponica grassland as a summer forage resource for sika deer on Mt Ohdaigahara, central Japan
Authors: YOKOYAMA SHOTARO , SHIBATA EI'ICHI
Published: March 2003

Recently, the sika deer, Cervus nippon Temminck, population has increased on Mt Ohdaigahara, central Japan. The dwarf bamboo, Sasa nipponica Makino et Shibata, is a primary forage plant for sika deer in this area. To demonstrate the characteristics of S. nipponica grassland, especially as summer forage for sika deer, the habitat use intensity of sika deer was estimated by fecal densities, and biomass, growth rate, removal by deer and crude protein content were examined. Sika deer utilized the S.␣nipponica grassland on Mt Ohdaigahara during summer when the biomass, growth rate and crude protein content of S. nipponica were high. The recent increase in the deer population seems to be partly due to S.␣nipponica grassland being a favorable summer habitat.
Plasticity of flower longevity in Corydalis ambigua
Authors: YASAKA MICHIYASU , NISHIWAKI YUKI , KONNO YASUO
Published: March 2003

We investigated the longevity of individual flowers of Corydalis ambigua Cham. et Schlecht. during different periods of pollinator activity and at different temperatures. To measure potential (unpollinated) flower longevity of C. ambigua, this study was conducted at forest islands where pollinator visits were scarce. The longevity of individual flowers of C. ambigua indicated high plasticity. The longevity of unpollinated flowers in natural pollination ranged from 2 to 25 days and continuously decreased with the date of flower opening. The temperature increased as the flowering season progressed. Furthermore, the greenhouse transplanting experiment showed that higher temperatures shorten the life span of flowers. The longevity of pollinated flowers subjected to hand pollination of newly opened flowers was shorter than that of unpollinated flowers in natural pollination regardless of the date of flower opening. These results showed that not only high temperature but also pollination shortens flower longevity. We discuss the role of plasticity in flower longevity for C. ambigua in relation to pollination success and reduction in the maintenance cost of the flowers.
Use of carbon and nitrogen isotope ratios in termite research
Authors: Tayasu Ichiro
Published: March 2003

In this paper, I review carbon and nitrogen isotopic (natural abundance levels) studies of termites. The carbon isotope ratio of CH4 emitted from termites, together with the emission rates of CO2, CH4 and H2, showed several trends corresponding to the kinds of symbiotic microbes and feeding habits. The fraction of methane oxidized in the nest structure was estimated by comparing carbon isotope ratio of CH4 emitted from the nest with that produced by termites in the nest. Symbiotic nitrogen fixation in the gut of termites has been shown to have a significant contribution to the nitrogen economy in some wood‐feeding termites. The carbon isotope ratio distinguishes between C4 from C3 plants, and the fractional contribution of grass in the diet can thereby be estimated. The carbon and nitrogen isotope ratios in termites are discernible among soil‐feeders, fungus cultivators and wood‐feeders. Wood/soil‐interface feeders have intermediate values between wood‐ and soil‐feeders, and thus carbon and nitrogen stable isotope ratios are assumed to characterize the degree of humification of the material consumed by termites. It is suggested that carbon and nitrogen isotope ratios are useful indicators of the functional position of termites in the decomposition process. A similar isotope pattern has been obtained in earthworms, suggesting that isotope signatures might be useful parameters in investigating detritivorous animals in general.
Effect of immigration on a chaotic insect population
Authors: Gonzalez‐Andujar Jose L.
Published: March 2003

Recently, the most convincing evidence of complex dynamics and chaos in biological populations has been presented for Tribolium castaneaum, a classic laboratory model insect. In this note, the robustness of this system is investigated and a constant immigration term is added to the adult population equation. It has been found that such perturbation to the model can either have a complicating effect (when the isolated system is periodic) or a simplifying one (when the system is chaotic in isolation).
Linking microhabitat availability and local density of rainbow trout in low‐gradient Japanese streams
Authors: Urabe Hirokazu , Nakano Shigeru
Published: March 2003

Quantification of reach‐based microhabitat availability for rainbow trout (Oncorhynchus mykiss), considering their microhabitat requirements in two low‐gradient streams, northern Japan, was attempted to test for habitat space limitation of local trout density. Underwater observations revealed that fish selected microhabitats of moderate current velocity, relatively greater depth and shorter distance to overhead cover in both streams, although habitat features used and available differed slightly between the streams. Habitat space for fish potentially available in the channel environment was evaluated using principal component analysis (PCA) of both available and used microhabitat. A close relationship was evident in both streams between reach‐based microhabitat availability and fish density, which was assessed by a three‐pass removal method. Direct estimates of fish microhabitat availability using PCA can contribute to accurate predictions of local fish density and provide insight into the mechanisms responsible for fish–habitat relationships in streams.
Population structure and dynamics of an evergreen shade herb, Ainsliaea apiculata (Asteraceae), with special reference to herbivore effects
Authors: HORI YOSHIMICHI , YOKOI TOMOKO
Published: March 2003

The population structure and dynamics of Ainsliaea apiculata, a forest understory evergreen herb widely distributed in Japan, was examined in a Chamaecyparis obtusa forest in Ibaraki Prefecture, central Japan (36Â°51′N, 140Â°33′E; 750 m a.s.l.). The mean population growth rate (λ) calculated from the transition matrices for 4 years was 0.69 per year, predicting that the population size will decrease remarkably. There was a significant positive correlation between the survival of old leaves and the growth of new shoots in the following year. The shoots, especially new leaves, were damaged severely by herbivores (caterpillars of Leioptilus sp.). The survival rate of leaves formed in the previous spring to the next spring was remarkably low (41–54%). The growth of new shoots depended mainly on the reserves contained in old shoots, especially those in old leaves. New shoots of A. apiculata began to develop in spring, even though they were formed in autumn of the previous year. A defoliation experiment also showed that the removal of old shoots at the beginning of the growing season significantly inhibited the growth of new shoots. Damage to old shoots by herbivores severely influenced the growth and population dynamics of A. apiculata.
Light, nutrients and primary productivity in Lake Biwa: An evaluation of the current ecosystem situation
Authors: Urabe Jotaro , Sekino Tatsuki , Nozaki Kentaro , Tsuji Akihiro , Yoshimizu Chikage , Kagami Maiko , Koitabashi Tadatoshi , Miyazaki Tatsuo , Nakanishi Masami
Published: March 2003

Simple correlation and multiple regression analyses were performed to examine the relationship between primary productivity and environmental factors in the north basin of Lake Biwa. The primary production rates used in the analyses were estimated monthly or bimonthly during the growing season (April–November) in 1992, 1996 and 1997 with the 13C method. Elemental (C, N and P) contents of seston were used to assess nutrient conditions. Analyses revealed that 86% of variance in depth‐integrated primary production rates (areal PP) can be explained by changes in light intensity, and sestonic C, N and P concentrations. Water temperature had no effect on areal PP. To assess relative effects of light and nutrients on PP, the P:B ratio was estimated by normalizing PP with sestonic C. The areal P:B ratio correlated most significantly with the sestonic N:P ratio, followed by light intensity. When regression analyses were made at each depth, however, the P:B ratio correlated significantly only with the sestonic N:P ratio at 0 and 1 m depths, while light intensity was also incorporated into the regressions at deeper than 2.5 m. In these regressions, the P:B ratio was negatively correlated with sestonic N:P ratio but positively with light intensity. The results suggest that the primary production rate in this lake was mainly limited by P relative to N supply rates, but was not free from light limitation in a large part of the epilimnion. In Lake Biwa, the vertical water mixing regime as well as the nutrient supply seem to be important in determining the growth and composition of primary producers, since the surface mixing layer extends into 10–15 m depths during most of the growing season.
Diversity in specific gravity and water content of wood among Bornean tropical rainforest trees
Authors: Suzuki Eizi
Published: March 2003

Wood properties were measured for trees in lowland dipterocarp forests in West Kalimantan. In 1993 and 1994, 353 samples of 286 species were collected from trunk base of trees of approximately 5 cm in diameter, and the specific gravities (SG: oven dry weight/fresh volume) and water contents of wood including bark were measured. The SG of each species ranged from 0.21 to 0.84, and the mean Â± SD was 0.53 Â± 0.13. The wide range of SG suggests that the forest had a high diversity in wood properties. The most dominant and diversified genus in this area was Shorea, and the SG of 15 species varied from 0.21 to 0.71. The range covered SG of pioneer (six Macaranga, 0.29–0.43) and small trees in primary forests (nine Eugenia and 10 Xanthophyllum, 0.55–0.77). The SG average for tree species of secondary forests of 2–6 years old was 0.31. It was significantly smaller than that of primary forests (0.58). In a primary dipterocarp forest plot, light‐wood species grew faster in diameter than heavy‐wood species. Water content ranged from 0.26 to 0.76. Heavy wood had low water content. Among light‐wood species, some (Shorea, Artocarpus) had low water contents and others (Ficus) had high water contents. Some riverine trees also had high water contents. These wood properties appear strongly related to the life history of trees and successional stage.
Nitrogen content in feces and the diet of Sika deer on the Boso Peninsula, central Japan
Authors: Asada Masahiko , Ochiai Keiji
Published: March 2003

Fecal and rumen nitrogen content of Sika deer (Cervus nippon Temminck 1838) on the Boso Peninsula, central Japan, were analyzed concerning their seasonal fluctuations and local differences at four areas on the Boso Peninsula. The mean fecal nitrogen was high in August and low in February in all the areas. The seasonal variation, however, was relatively small. This may be the result of the following reasons: the Boso deer feed on evergreen broad‐leaves containing a high and stable nitrogen content in winter; little snow falls there; and the deer consume foods relatively low in nitrogen in summer. The fecal and rumen nitrogen content in both summer and winter depended on deer density.
Caste developmental system of the Japanese damp‐wood termite Hodotermopsis japonica (Isoptera: Termopsidae)
Authors: Miura Toru , Hirono Yoshiyuki , Machida Mitsuyo , Kitade Osamu , Matsumoto Tadao
Published: March 2003

Caste developmental pathways of the Japanese damp‐wood termite Hodotermopsis japonica Holmgren were estimated by measuring body parts. From the size distribution of head‐width, seven peaks were recognized in populations of larvae. Of these peaks, the seventh has a wide range and variance, indicating that it represents several instars. The individuals that make up the seventh peak, which take the role of workers (pseudergate), are suggested to enter the nymphal stage(s), which has brachypterous wing buds, prior to becoming alates. The pseudergates appear to be totipotent, that is, capable of differentiating into any caste, including reproductives and soldiers. Sixth instars and pseudergates have the potential to become soldiers via a presoldier stage. Although the evolution of caste systems in termites is controversial, the linear developmental pathway found in this study is thought to be the typical pattern in lower termites. Sexual discrimination was also investigated, males and females being easily distinguished by examining the seventh abdominal sternites of individuals older than fourth instar larvae. Both sexes appear to follow the same caste developmental pathway.
Spatial genetic relationships in a population of the Japanese wood mouse Apodemus argenteus
Authors: Ohnishi Naoki , Saitoh Takashi , Ishibashi Yasuyuki
Published: March 2003

Space‐related relationships between individuals were investigated during the breeding season in a natural population of Apodemus argenteus (Temminck) by using the catch‐mark‐release method and microsatellite DNA markers. Several overlapping patterns of home ranges in breeding males and females were observed. Although this species is thought to be monogamous, DNA analysis revealed polygynous mating. In adults, relatedness between sexes was generally low and no apparent spatial genetic structure was observed. In juveniles, however, relatedness and geographical distance be‐tween individuals were significantly negatively correlated. The relatedness between adult females decreased with distance, whereas there was not such a correlation in males. Long‐distance movements were observed in current‐year‐born males. The differences in spatial genetic structure between adults and juveniles are thought to be produced by male‐biased natal dispersal.
Interspecific effects of grey squirrels (Sciurus carolinensis) on the space use and population demography of red squirrels (Sciurus vulgaris) in conifer plantations
Authors: Wauters Luc A. , Lurz Peter W. W. , Gurnell John
Published: March 2003

Interspecific competition between red squirrels and grey squirrels was investigated by comparing the population demography, spacing behavior and habitat use of red squirrels in two large conifer plantations in northern England: one site had only red squirrels (the ‘red‐only’ site), in the other both red and grey squirrels occurred (the ‘red–grey’ site). Despite more abundant food at the red–grey site, red squirrel densities (0.26 ha−1 at the red–grey site, 0.29 ha−1 at the red‐only site), adult survival rates and the breeding rates of females were similar at both study sites. Grey squirrels at the red–grey site occurred at higher densities (0.92–1.1 ha−1) than did the reds and tended to have higher breeding rates. In the presence of grey squirrels, the recruitment pattern of red squirrels changed and there was little recruitment of subadults. The juvenile recruitment rate in the red–grey site (13%) was much lower than in the red‐only site (50%). Grey squirrels, in contrast, had higher juvenile recruitment rates at the red–grey site (41%). The core areas of the home ranges of red squirrels in the red–grey site were more strongly overlapped by grey squirrels than by conspecifics. Red squirrels did not select the habitat with the best tree seed crop (Scots pine) but preferred dense Sitka spruce plantations; they appeared to avoid the Scots pine area with its high grey squirrel density. Data on foot length and body condition indicated decreased body growth in young red squirrels when grey squirrels were present. Our data suggest that adult red squirrels suffered little from interspecific competition with grey squirrels and that the key factor is decreased juvenile recruitment in red squirrels.