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Biomedical subjects

K Koga

Publications and source records attributed to K Koga.

At least 19 recordsLinked to original sources
PubMed2002

Effects of gonadotropin-releasing hormone analog treatment on skin condition.

The skin is a target organ of estrogens. Thus, theoretically, a hypoestrogenic state induced by gonadotropin-releasing hormone analog (GnRHa) treatment may have effects on skin condition. The aim of this study was to evaluate skin condition during GnRHa treatment. Sixteen premenopausal women undergoing GnRHa treatment for 16 weeks, as a presurgical treatment for uterine leiomyomas, were studied. Measurement of serum estradiol levels and epidermal hydration, and evaluation of subjective findings on skin condition using a questionnaire, were performed every 4 weeks during the treatment period. Serum estradiol levels were significantly suppressed at 4 weeks of treatment, and remained low afterwards. Epidermal hydration measured by corneometer did not show any significant difference at any time point examined, compared with that before treatment. No particular subjective findings relating to the skin (dryness, wrinkling, roughness, pigmentation, itching, formication, reaction to cosmetics) were reported during treatment, whereas complaints about hot flushes and sweating were notable. The results of this preliminary study support the notion that GnRHa treatment for 16 weeks is unassociated with apparent changes in skin condition.

Adult↗
PubMed2001

Altered psychomotor behaviors in mice lacking pituitary adenylate cyclase-activating polypeptide (PACAP).

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been conserved remarkably during evolution and is widely expressed in the mammalian brain. In Drosophila, mutation of the PACAP homologue results in behavioral defects, including impaired olfaction-associated learning and changes in ethanol sensitivity. Here, we report the generation of mice lacking the PACAP gene (PACAP(-/-)). PACAP(-/-) mice were born in the expected Mendelian ratios but had a high early-mortality rate. The surviving adult PACAP(-/-) mice displayed remarkable behavioral changes; they exhibited hyperactive and explosive jumping behaviors in an open field, increased exploratory behavior, and less anxiety in the elevated plus maze, emergence, and novel-object tests. Analysis of PACAP(-/-) mice brains revealed that the serotonin metabolite 5-hydroxyindoleacetic acid was slightly decreased in the cortex and striatum compared with wild-type mice. The present study provides evidence that PACAP plays a previously uncharacterized role in the regulation of psychomotor behaviors.

Animals↗
PubMed2001

Formation of ordered ice nanotubes inside carbon nanotubes.

Following their discovery, carbon nanotubes have attracted interest not only for their unusual electrical and mechanical properties, but also because their hollow interior can serve as a nanometre-sized capillary, mould or template in material fabrication. The ability to encapsulate a material in a nanotube also offers new possibilities for investigating dimensionally confined phase transitions. Particularly intriguing is the conjecture that matter within the narrow confines of a carbon nanotube might exhibit a solid-liquid critical point beyond which the distinction between solid and liquid phases disappears. This unusual feature, which cannot occur in bulk material, would allow for the direct and continuous transformation of liquid matter into a solid. Here we report simulations of the behaviour of water encapsulated in carbon nanotubes that suggest the existence of a variety of new ice phases not seen in bulk ice, and of a solid-liquid critical point. Using carbon nanotubes with diameters ranging from 1.1 nm to 1.4 nm and applied axial pressures of 50 MPa to 500 MPa, we find that water can exhibit a first-order freezing transition to hexagonal and heptagonal ice nanotubes, and a continuous phase transformation into solid-like square or pentagonal ice nanotubes.

Journal Article↗
PubMed2001

Linearization and integration of DNA into cells preferentially occurs at intrinsically curved regions from human LINE-1 repetitive element.

A bent DNA library was constructed from human genomic DNA, from which a new clone belonging to the human LINE-1 sequence family was isolated and characterized. This clone, with a length of 378 base pairs and termed HBC-1 (human bent clone-1), contained an intrinsically occurring curved DNA structure. By permutation analysis, the center of curvature of this fragment was mapped onto the nucleotide position 886 from the 5' terminus of the complete LINE-1 sequence. Reporter plasmids, which contain HBC-1, were effectively integrated into human chromosome, indicating that the bent DNA structure provides a preferential donor site for the integration of human LINE-1 sequences. The present finding may provide an explanation as to why some inactivated LINE-1 sequences on human chromosomes carry the deletion at their 5' termini.

3T3 Cells↗
PubMed2001

Expression of angiopoietin-2 in human glioma cells and its role for angiogenesis.

In highly vascular malignant glioma, glioma cells themselves may express angiogenic factors and induce angiogenesis. Recent studies have shown that novel angiogenic factors, angiopoietin-1 (Ang1) and -2 (Ang2), play important roles in the modulation of vasculogenesis and angiogenesis. In this study, we determined Ang2 mRNA expression in cultured human malignant glioma cells (U105, U251, and U373 MG) by reverse transcriptase-PCR. Western blot analysis and immunocytochemical analysis with antihuman Ang2 antibody revealed that Ang2 protein was expressed and secreted by these cells. Furthermore, hypoxia increased the Ang2 protein level in cultured glioma cells. Serial sections of 32 human glioma tissues (14 glioblastomas, eight anaplastic astrocytomas, seven astrocytomas, and three pilocytic astrocytomas) were immunostained against Ang2, vascular endothelial growth factor, Tie2, von Willebrand factor, and alpha smooth muscle actin. The immunoreactivity of each angiogenic factor was higher in malignant gliomas than in low-grade gliomas. Ang2 protein was detected not only in endothelial cells but also in glioma cells, and its expression was prominent in both the area surrounding the necrosis and the periphery of glioblastomas. In the area surrounding necrosis, Ang2 was highly expressed and tumor vessels showed regression. In the tumor periphery, Ang2 was highly expressed and many small vessels stained positively for von Willebrand factor but not for alpha smooth muscle actin, suggesting angiogenesis. Statistical analysis revealed that the Ang2 expression was negatively correlated with vessel maturation in malignant gliomas and that vascular endothelial growth factor expression was positively correlated with vessel maturation in low-grade gliomas (P < 0.05). These results suggest that glioma cells themselves express Ang2 and that expression may be induced by hypoxic stimulation and may play a crucial role in the vessel maturation, angiogenesis, and vessel regression in malignant glioma.

Adolescent↗
PubMed2001

Hypothermia reduces glutamate efflux in perilymph following transient cochlear ischemia.

The effect of hypothermia on ischemic injury of the cochlea in gerbils was studied with particular regard to glutamate efflux in the perilymph. Under normothermic conditions interruption of the blood supply to the cochlea for 15 min caused a remarkable elevation of the compound action potential (CAP) threshold, and an increase in perilymphatic glutamate. The CAP threshold recovered to some extent with reperfusion, but not to preischemic levels. CAP thresholds, under hypothermic conditions and with reperfusion, recovered promptly to near pre-ischemic levels, while glutamate concentration did not change. These results, together with electron microscopy studies, suggest that hypothermia prevents hearing loss primarily through reduction of glutamate efflux at the synopses between inner hair cells and primary afferent auditory neurons.

Animals↗
PubMed2001

[Results of treatment of out-of-hospital cardiopulmonary arrest patients transferred to the UOEH hospital].

We have accepted patients suffering out-of-hospital cardiopulmonary arrest (CPA) since September 1997. In this study, we retrospectively reviewed the etiology of CPA and the outcome of the patients. We also investigated the effects of the pre-hospital cardiopulmonary resuscitation (CPR) by a bystander or emergency life-saving technicians (ELST) on the restoration of spontaneous circulation. Seventy-seven patients were transferred to our hospital from September 1997 to April 2000, 10 of who underwent bystander (basic) CPR. All the patients underwent advanced CPR by the attending physician immediately after admission to the emergency room. The etiology of CPA was categorized into three groups: (1) unknown endogenous disease (43 patients, 56%), (2) exacerbation of previous disease such as heart, respiratory or cerebrovascular disease (12 patients, 15%), (3) accident or suicide (22 patients, 29%). Spontaneous circulation of 30 patients was restored temporary, but only two patients recovered fully and were discharged from the hospital. The rate of restored spontaneous circulation of the CPA patients with bystander CPR was higher compared to that of the CPA patients without bystander CPR. The two fully recovered patients underwent bystander CPR. The CPR by ELST did not affect the resuscitated rate significantly. These results indicate that the most common etiology of CPA is unknown endogenous disease, and the rate of full recovery is very low (2.6%). This study suggests that bystander CPR may contribute to an improved outcome of the patients suffering out-of-hospital CPA.

Adolescent↗
PubMed2001

Radiographic diagnosis of congenital bony nasal stenosis.

Congenital bony nasal stenosis (CBNS) is a rare condition that causes respiratory distress in neonates. Between 1986 and 1996, we encountered 13 cases of CBNS. Recently, CT measurements have been used to evaluate the features of this type of stenosis, but no satisfactory investigation of the severity of bony nasal stenosis has been reported. We compared the nasal width (NW), facial width (FW), and interorbital distance (IOD) measured from occipitofrontal (Caldwell's) projections of plain radiographs in nine CBNS patients and nine normal infants. NW was significantly narrower in the CBNS patients than in the controls, and never exceeded the IOD in any of the CBNS patients. This measuring method can be used to diagnose CBNS, because NW in normal subjects of all age groups is always greater than IOD on Caldwell's view. We also investigated one patient radiographically, to determine how NW increased until the age of 4 years. However, there was no significant change in nasal width, although the FW increased significantly. This method seems useful for determining the severity of stenosis, and its simplicity makes it useful for routine investigation of breathing difficulty in neonates and infants. We review and discuss the CT images of CBNS reported in the literature.

Constriction, Pathologic↗
PubMed2001

Reward-related neuronal activities in basal ganglia of domestic chicks.

We aimed to reveal what is coded in the basal ganglia of domestic chicks. In the water-reinforced 'go' task, chicks learned to peck selectively at a colored bead in order to obtain a drop of water. Out of 38 units obtained, seven showed excitatory activities specifically during the reward period. In the food-reinforced go/no-go task, chicks learned to discriminate two colors to obtain mash food after a delay period. They also learned to ignore another color, which was not associated with a reward. Out of 27 units obtained, four showed excitatory activities during the cue period, specifically when a food reward was anticipated. LPO neurons may code qualities of the obtained rewards, and also chick's anticipation of the forthcoming rewards.

Action Potentials↗
PubMed2001

7,8-Dihydropterin-6-carboxylic acid as light emitter of luminous millipede, Luminodesmus sequoiae.

A luminous millipede. Luminodesmus sequoiae, emits light centered at a wavelength of 500 nm. To determine the light emitter of this bioluminescent system, fluorescent compounds were isolated from pulverized cuticles. NMR and MS spectra of these compounds showed them to be pterin derivatives. Furthermore, proton/deuterium (H/D) exchange experiments by ESI-Q-TOF-MS and -MS/MS measurements have proved to be a powerful tool for elucidating these heteroaromatic compounds. Finally, we have concluded that 7,8-dihydropterin-6-carboxylic acid, a new natural product, is the light emitter of Luminodesmus bioluminescence.

Animals↗
PubMed2001

Occurrence of ovalbumin in ovarian yolk of chicken during oogenesis.

Yolk specimens from chicken ovaries during oogenesis gave a positive signal for ovalbumin as analyzed by Western blotting, indicating that the ovarian yolk contains ovalbumin. Northern blotting and reverse transcriptase-polymerase chain reaction gave a negative signal for ovalbumin mRNA in the liver and other organs except oviduct, whereas the laying hen serum was found to indicate immunologically the presence of ovalbumin. It was therefore assumed that ovalbumin synthesized in the oviduct might partly be secreted into the blood circular system, from which it is taken up into the oocyte.

Animals↗
PubMed2001

Role of interaction between two silkworm RecA homologs in homologous DNA pairing.

Recombinant BmRad51 and BmDmc1, silkworm homologs of the Escherichia coli RecA proteins catalyzing the homologous DNA pairing, were purified from E. coli cells carrying expression vectors. These possessed different enzymatic properties in the joint molecule formation between single-stranded circular DNA and homologous linear double-stranded DNA. The requirement of single-stranded circular DNA for the efficient reaction was twofold higher in BmRad51 than in BmDmc1. Although able to mediate the joint molecule formation independently, a complex of the two enzymes formed prior to single-stranded DNA binding was found to have augmented efficiency of the pairing reaction.

Animals↗
PubMed2001

Icosahedron-fcc transition size by molecular dynamics simulation of Lennard-Jones clusters at a finite temperature.

We studied finite-temperature ensembles of solid clusters produced by cooling liquid droplets either by evaporation or by a thermostat through a molecular dynamics calculation using the Lennard-Jones potential. The ensembles consist of either single or binary component clusters with 25% of the atoms 8% smaller in diameter than the other 75%. These clusters (380 clusters in total) exhibit various structures in the size range of n=160-2200, where n is the number of atoms in a cluster. For increasing size, the clusters show a gradual transition from icosahedral to a variety of structures: decahedral, face centered cubic, a small amount of hexagonal, and some icosahedral structures. They are asymmetrical or faulted. Electron diffraction patterns calculated with average structure factors of clusters after grouping them into several size regions are very similar to those experimentally observed. The size transition is around n=450 for single component clusters whatever the cooling process, evaporation or thermostat. This size is smaller than the experimental transition size estimated for argon clusters formed in a supersonic expansion. The transition size for binary component clusters is around n=600 for evaporative cooling, and larger for thermostatic cooling. The larger transition size found for the binary component clusters is consistent with the large icosahedral Au-Fe and Au-Cu alloy clusters observed experimentally.

Journal Article↗
PubMed2001

Hypothermia prevents hearing loss and progressive hair cell loss after transient cochlear ischemia in gerbils.

The effects of hypothermia on ischemia-reperfusion injury of the cochlea were studied in gerbils. Hearing was assessed by sequentially recording compound action potentials before, during and after the ischemia. The degree of hair cell loss in the organ of Corti was evaluated in specimens stained with rhodamine-phalloidin and the dye Hoechst 33342. Ischemic insult was applied to the animals by occluding the bilateral vertebral arteries for 15 min under normothermic or hypothermic (rectal temperature 32 degrees C) conditions. Interruption of the blood supply to the cochlea caused a tremendous increase in the compound action potential threshold, which usually recovered to some extent with reperfusion. In the ischemia/normothermic group, the threshold did not return to the pre-ischemic level. The average increase in the threshold seven days after ischemia was 20.0 dB. Histologically, the hair cell loss increased gradually until four days after the ischemic insult. On the seventh day, the mean loss of inner and outer hair cells at the basal turn was 31.1 % and 2.4 %, respectively. In the ischemia/hypothermic group, the threshold returned to the pre-ischemic level within 30 min after reperfusion and remained stable thereafter. The mean loss of inner and outer hair cells on the seventh day was 0.1 % and 0.2 %, respectively. These results indicate that hypothermia can prevent inner ear damage, which otherwise occurs after transient ischemia of the cochlea.

Animals↗
PubMed2001

Comparison of no airway device, the Guedel-type airway and the Cuffed Oropharyngeal Airway with mask ventilation during manual in-line stabilization.

STUDY OBJECTIVE: To compare two different types of oropharyngeal airway: the Guedel-type oral airway and the Cuffed Oropharyngeal Airway (COPA), with respect to the effectiveness of positive-pressure ventilation (PPV) through a face mask in patients with in-line stabilization of the head and neck. DESIGN: Prospective, randomized, crossover study. SETTING: University hospital. PATIENTS: 30 ASA physical status I and II patients undergoing elective surgery. INTERVENTIONS: General anesthesia was induced with propofol and muscle relaxation was produced with vecuronium. In a random sequence, no airway device, the Guedel-type airway, and the COPA were used in each patient while applying a face mask and lifting the jaw forward. MEASUREMENTS AND MAIN RESULTS: Tidal volumes were measured during PPV in each option. The position of the distal tip of each airway was assessed using a fiberscope, and the resulting views were graded and compared. When the Guedel-type airway was used, tidal volumes (V(T)s; means +/- SD) were significantly greater (12.3 +/- 4.5 mL/kg) than those with no airway device (8.5 +/- 4.5 mL/kg) (p < 0.001). When the COPA was used, V(T)s (14.6 +/- 4.4 mL/kg) were significantly greater than those with the Guedel-type airway (p < 0.05). The grade of the fiberscopic view through the distal tip was significantly better with the COPA than with the Guedel-type airway (p < 0.05). CONCLUSIONS: Although clinical differences often appear trivial, the COPA is more effective on mask ventilation than the Guedel-type airway when used in patients with manual in-line stabilization.

Adult↗
PubMed2001

Development of the fiber neutron monitor for the energy range 15-100 MeV on the International Space Station (ISS).

In order to investigate the space environment, a new neutron monitor has been prepared. The sensor consists of scintillation fibers (FIB) and will be on board the exposed facility of the Japanese Experimental module (Kibo) of the International Space Station (ISS). The sensor is one of the instruments which measures the particle and plasma environment around the ISS. The sensor will be used by the cosmonauts who work on the ISS, to help them avoid a strong particle radiation which may arrive soon. We believe that such an alert is necessary for the cosmonauts to prevent unnecessary radiation from the sun. Furthermore, the sensor will be very useful in understanding the particle acceleration mechanism at the solar surface. The design of the Engineering Model (EM) was finished and its properties were investigated. This report discusses these results.

Equipment Design↗
PubMed2001

Real-time measurement of low-energy-range neutron spectra on board the space shuttle STS-89 (S/MM-8).

We have developed a real-time, Bonner Ball-type (neutron energy range is from thermal to 15 MeV) neutron spectral measurement system (Bonner Ball Neutron Detector (BBND)) for use on board the International Space Station (ISS). From measurements taken inside STS-89 (S/MM-8), we successfully distinguished neutrons from protons and other particles in a mixed radiation field; a task hitherto considered difficult. Although the experimental period was short, only 3.5 days (January 24-27, 1998), we were able to obtain energy spectral data and the Earth's neutron dose-equivalent map for the ISS orbital conditions (altitude 400 km, orbit inclination angle 51.6 degrees). A method for calculating the neutron energy spectrum and compensating for the particle interaction with the sensors is also described in detail.

Aluminum↗