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Kinya Nishimura

Publications and source records attributed to Kinya Nishimura.

10 recordsLinked to original sources
PubMed2006

Evolution of the maturation rate collapses competitive coexistence.

Most theoretical studies on character displacement and the coexistence of competing species have focused attention on the evolution of competitive traits driven by inter-specific competition. We investigated the evolution of the maturation rate which is not directly related to competition and trades off with the birth rate and how it influences competitive outcomes. Evolution may result in the superior competitor becoming extinct if, initially, the inferior competitor has a lower, and the superior one a higher, maturation rate at the coexistence equilibrium. This counterintuitive result is explained by an explosive increase in the adult population of the inferior competitor as a result of the more rapid evolution of its maturation rate, which is caused by differences in the intensity and direction of selection on the maturation rates of the two species and in their adult densities, which are related to differences in their life histories. Thus, a life history trait trade-off with a competitive trait may cause a competitive ecological coexistence to collapse.

Animals↗
PubMed2005

Genetic basis of phenotypic plasticity for predator-induced morphological defenses in anuran tadpole, Rana pirica, using cDNA subtraction and microarray analysis.

Anuran tadpoles (Rana pirica) are induced to develop a higher tail and a bulgy body as predator-specific morphological responses when they are exposed to predatory larval salamanders. Subtractive hybridization was performed using induced tadpole body skin and normal tadpoles' body skin. A total of 196 clones showed higher expression, and 104 clones showed lower expression, when they formed bulgy bodies. In the subtraction, carboxypeptidase B, trypsinogen, elastase I, fibrinogen, elastase II, triacyl-glycerol lipase, and alpha1-antitrypsin genes showed lower expression. In contrast, RT-like protein, bullous pemphigoid antigen, phosphoserine aminotransferase, uromodulin, tetranectin, chaperonin-like protein, zinc finger protein, osteonectin, aldehyde dehydrogenase, Sec 23A protein, and ribosomal protein showed higher gene expression. Microarray analysis was also performed using this subtracted cDNA (nine replicates). Results of the microarray data essentially corresponded with those of the subtraction data, and the degree of the suppressed genes was much stronger than that of the expressed genes. Carboxypeptidase B showed the strongest suppression, and its inhibition range was from 1/100 to 3/100 compared with that of control body skin. Strong suppression was also observed with trypsinogen, elastase I, fibrinogen, and elastase II as well. These results can be interpreted as increases of fibrinolysis by strong depression of both carboxypeptidase B and other genes simultaneously, resulting in the retention of blood vessels and facilitating the circulation of blood. Expression was observed in phosphoserine aminotransferase, aldehyde dehydrogenase, RT-related protein, chaperonin-like protein, tetranectin, bullous pemphigoid antigen, uromodulin, and Sec 23A protein. They were significantly (p<0.05) increased and were at least 1.5 times greater compared with the control. From the appearance, it seems that the bulgy shaped body is highly connecting to the bullous pemphigoid (BP) antigen that causes the skin blistering disorder, and tetranectin and uromodulin may be related to the extracell matrix through myogenesis, protein secretion, and ion transport, respectively. Since the RT-related protein gene derived from retrotransposon (L1) is known to disrupt mammalian transcriptomes, retrotransposon may be involved with phenotypic plasticity for morphological defense by Rana prica against predator threat.

Animals↗
PubMed2005

Tissue hyperoxygenation promotes oxidative metabolism in motor unit.

Some mutant hemoglobin (Hb) variants are found with lowered O2 affinity. Low oxygen affinity is reported to increase the O2 availability in peripheral tissues (Kunert et al. [1996] Microvasc. Res. 52:58-68). In the present study, we used a mouse model carrying two low-affinity Hb variants, Titusville and Presbyterian, to evaluate the chronic in vivo influence of lowered oxygen affinity on the neuromuscular system. Our model mice showed an increased voluntary running ability compared with wild-type littermates. In the tibialis anterior (TA) muscle of mutant mice, the glycolytic fibers were converted to oxidative ones in where the activity of the mitochondrial marker enzyme succinate dehydrogenase (SDH) was up-regulated. We report that the spinal ventral horn motoneurons innervating TA skeletal fibers also showed higher mitochondrial oxidative enzyme activity. This phenomenon was evidenced by increased SDH activity and electron microscopic (EM) mitochondrial electronic density in these motoneurons. Our data suggest that, as the result of adaptation to the tissue hyperoxygenation, energy metabolism in the neuron-muscle motor unit is augmented and thus function of the motor unit is promoted.

Adenosine Triphosphatases↗
PubMed2005

Are the incidences of cardiac events during noncardiac surgery in Japan the same as in the United States and Europe?

In Japan, an ever-present problem in the preoperative evaluation of patients with ischemic heart disease is that although such evaluations are based on Western data, these data serve as the basis for determining perioperative risk in Japanese patients. To remedy this problem, the Cardiac Ischemia and Anesthesia Research Committee was formed in 1997 and has conducted studies of perioperative complications in noncardiac surgery in Japan. In two retrospective studies in 1997, the proportions of patients with ischemic heart disease were 3.9% and 3.1%, approximately one tenth the rates reported in Europe and the United States. The incidences of perioperative cardiac complications in patients with ischemic heart disease were 16.4% and 13.2%, not widely divergent from rates reported in Europe and the United States. To investigate the baseline characteristics involved in perioperative complications, we conducted a prospective study of 237 patients classified as having intermediate risk for perioperative cardiac complications according to the American College of Cardiology/American Heart Association Guidelines for Perioperative Cardiovascular Evaluation for Noncardiac Surgery. We found that the prominent factor in intraoperative cardiac complications was the presence of hypertension (odds ratio = 2.911). Factors contributing to postoperative cardiac complications included those reflecting coronary lesion severity and cardiac dysfunction (history of heart failure; odds ratio = 6.884, coronary risk index grade; odds ratio = 2.884, and a history of intervention; odds ratio = 4.774).

Adult↗
PubMed2005

[Which is more useful for central venous catheterization? A comparison between a 22 gauge metal needle (Argyle) and a 24 gauge plastic cannula with a metal needle (Insyte)].

BACKGROUND: Central venous catheterization is commonly performed by puncturing the internal jugular vein. However, placement of central venous catheters is not without risk. We compared the Argyle and the Insyte in terms of usefulness and incidence of complications during central venous catheterization. METHODS: Twenty adult patients for cardiac operation were randomly allocated into two groups; 10 patients in the Argyle group (Group A) and 10 patients in the Insyte group (Group B). RESULTS: In both groups, no kinking or stucking of the guide wire occurred during insertion. No accidental puncture of the carotid artery occurred in Group B, while it occurred in one case in Group A. The time required for insertion of the guide wire was not significantly different between the two groups, though it tended to be shorter in Group B than in Group A (19.3 +/- 14.6 sec vs 34.6 +/- 34.0 sec). On ultrasonography, the Argyle was observed to compress the internal jugular vein and to be prone to penetrate both anterior and posterior walls. CONCLUSIONS: Using the Argyle makes it a little more difficult to place the needle in the appropriate venous lumen. We conclude that central venous catheterization with the Insyte was quicker and safer than with the Argyle.

Adult↗
PubMed2004

Bulgy tadpoles: inducible defense morph.

Predator induced morphological defenses are marked morphological shifts induced directly by cues associated with a predator. Generally, remote cues, i.e., chemical substances emitted from predators or injured conspecifics, are considered to be ideal signals to induce morphological change in aquatic environments rather than close cues, i.e., close chemical or tactile cues, since chemical substances that can propagate over relatively long distances and persist for a long period may allow organisms to keep safe and to deliberately change their morph. In fact, most organisms adopting an inducible morphological defense utilize remote chemical cues to detect predation risk and to produce morphological defenses. In this paper, we report a unique and functionally well designed inducible morphological defense strategy where the induction process requires close cues from a predator. The tadpoles of Rana pirica exhibited a bulgy bodied morphology when threatened with predation by larval salamanders, Hynobius retardatus, in close proximity. Predation trials and a function experiment showed that the induced bulgy morph is an adaptive defense phenotype against the gape-limited predator larval H. retardatus. Furthermore, R. pirica tadpoles use two adaptive strategies in terms of cost saving, i.e., adjustment of the extent of bulginess according to predation risk and reversibility by actual shrink of bulgy body after removing the predation threat. In general, R. pirica hatch earlier than H. retardatus. In natural ponds, during the early developmental stage R. pirica tadpoles live in close proximity to young H. retardatus larvae. As they grow, the salamanders gradually become serious predators and the predator-prey interaction becomes intimate. After a while, predation, cannibalism and metamorphosis decrease the number of salamanders in the ponds, and the predator-prey interaction weakens. Such a phenology in the predator-prey interaction allows the evolution of a close-cue detection system and adaptive cost-saving strategies. Our results highlight that the characteristics of the inducible defense depend on the intensity and specificity of the predator-prey system.

Adaptation, Physiological↗
PubMed2004

Evolution of cannibalism: referring to costs of cannibalism.

A rational explanation for cannibalism is that it would be favored under conditions of crowding of conspecific individuals and/or low availability of alternative prey with the fear of starvation, so as to maximize individual fitness. Cannibalism has, however, not evolved and is not maintained by a simple individual optimization, while it has evolved and is maintained as a game among population members. We analysed the attainable state of an evolutionary cannibalism game within a framework that reflects the minimum essence of cause-effect in the cannibalism phenomenon. Cannibalism is predator-prey interaction among conspecifics. Immediate direct payoffs (survival in the interaction among conspecifics) and indirect payoffs (growth results in potential productivity and survival against the threat of starvation) would be included. No morphological specialization and no size priority of cannibalism individuals are assumed as conservative situations in which we analyse the possibility of cannibalism. Cannibalism would be possible under the conservative condition, if initially the wild population's cannibalism rate is not sufficiently lower than a threshold value. Crowding and/or low availability of alternative prey with the fear of starvation facilitates cannibalism evolution. Energy gain from conspecific prey would be attenuated by costs of counterattacks by conspecific victims and by challenge cost of its own. Discounting net intake energy required in the arms race for cannibalism challenge result in a relative disadvantage of having a high cannibalism rate and makes an evolutionary equilibrium of low cannibalism rate, even when potential profitability of conspecific prey is high.

Animals↗
PubMed2004

Variant evolutionary trees under phenotypic variance.

Evolutionary branching, which is a coevolutionary phenomenon of the development of two or more distinctive traits from a single trait in a population, is the issue of recent studies on adaptive dynamics. In previous studies, it was revealed that trait variance is a minimum requirement for evolutionary branching, and that it does not play an important role in the formation of an evolutionary pattern of branching. Here we demonstrate that the trait evolution exhibits various evolutionary branching paths starting from an identical initial trait to different evolutional terminus traits as determined by only changing the assumption of trait variance. The key feature of this phenomenon is the topological configuration of equilibria and the initial point in the manifold of dimorphism from which dimorphic branches develop. This suggests that the existing monomorphic or polymorphic set in a population is not an unique inevitable consequence of an identical initial phenotype.

Adaptation, Physiological↗
PubMed2002

Human substance P receptor undergoes agonist-dependent phosphorylation by G protein-coupled receptor kinase 5 in vitro.

G protein-coupled receptor kinases (GRKs) phosphorylate agonist-occupied G protein-coupled receptors, leading to receptor desensitization. Seven GRKs, designated GRK1 through 7, have been characterized. GRK5 is negatively regulated by protein kinase C. We investigated whether human substance P receptor (hSPR) is a substrate of GRK5. We report that membrane-bound hSPR is phosphorylated by purified GRK5, and that both the rate and extent of phosphorylation increase dramatically in the presence of substance P. The phosphorylation has a high stoichiometry (20+/-4 mol phosphate/mol hSPR) and a low K(m) (1.7+/-0.1 nM). These data provide the first evidence that hSPR is a substrate of GRK5.

Amino Acid Sequence↗