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Biomedical subjects

K Koga

Publications and source records attributed to K Koga.

At least 181 records · Page 10Linked to original sources
PubMed1993

Preconditioning improves energy metabolism during reperfusion but does not attenuate myocardial stunning in porcine hearts.

BACKGROUND: It has been reported that a brief period of coronary occlusion and reperfusion slows the rate of ATP depletion during subsequent sustained ischemia as well as limiting infarct size. However, it has not yet been determined whether ischemic preconditioning also has an effect on the functional and metabolic recovery of stunned myocardium. Our study was designed to address this problem. METHODS AND RESULTS: Farm pigs were anesthetized with fluothane and randomly assigned to either a control group or a preconditioned group. The control group (n = 15) underwent 15 minutes of coronary occlusion followed by 120 minutes of reperfusion. The preconditioned group (n = 14) underwent two episodes of 5-minute occlusion and 5-minute reperfusion followed by 15 minutes of occlusion and 120 minutes of reperfusion. This protocol was designed to exclude the stunning effect of the preconditioning procedure itself as much as possible besides preconditioning the heart. A pair of ultrasonic crystals was implanted in the area at risk perfused by the left anterior descending coronary artery. 31P-nuclear magnetic resonance spectroscopy and sonomicrometry were performed alternately. Regional myocardial blood flow (RMBF) was determined with colored microspheres. At 15 minutes of sustained ischemia, phosphocreatine (Pcr), ATP, and intracellular pH were significantly better preserved in the preconditioned group (Pcr: control/preconditioned, 1 +/- 1%/14 +/- 1%; ATP:control/preconditioned, 66 +/- 2%/74 +/- 2%; pH:control/preconditioned, 6.32 +/- 0.07/6.52 +/- 0.05; P < .05). After reperfusion, ATP increased progressively and was almost normalized at 120 minutes of reperfusion in the preconditioned group (control/preconditioned, 73 +/- 4%/95 +/- 3%; P < .05). Overshoot of Pcr (which indicates that the energy generating system is operating better than energy utilizing system) persisted in preconditioned hearts but disappeared rapidly in controls (control/preconditioned, 104 +/- 3%/130 +/- 3% after 120 minutes of reperfusion). There was no significant difference in percent segment shortening (%SS), RMBF, and hemodynamics between the two groups throughout the experiment (%SS: control/preconditioned, 29.8 +/- 5.9%/28.8 +/- 6.3% of baseline after 120 minutes of reperfusion). CONCLUSIONS: Preconditioning improves energy metabolism during reperfusion, although it does not attenuate myocardial stunning for at least 2 hours after reperfusion.

Adenosine Triphosphate↗
PubMed1993

Prismatic displacement of vision induces transient changes in the timing of eye-hand coordination.

Eye-hand coordination was investigated during a task of finger pointing toward visual targets viewed through wedge prisms. Hand and eye latencies and movement times were identical during the control condition and at the end of prism exposure. A temporal reorganization of eye and hand movements was observed during the course of adaptation. During the earlier stage of prism exposure, the time gap between the end of the eye saccade and the onset of hand movement was increased from a control time of 23 to 68 msec. This suggests that a time-consuming process occurred during the early prism-exposure period. The evolution of this time gap was correlated with the evolution of pointing errors during the early stage of prism exposure, in such a way that both measures increased at the onset of prism exposure and decreased almost back to control values within about 10 trials. However, spatial error was not entirely corrected, even late in prism exposure when the temporal organization of eye and hand had returned to baseline. These data suggest that two different adaptive mechanisms were at work: a rather short-term mechanism, involved in normal coordination of spatially aligned eye and hand systems, and a long-term mechanism, responsible for remapping spatially misaligned systems. The former mechanism can be strategically employed to quickly optimize accuracy in a situation involving misalignment, but completely adaptive behavior must await the slower-acting latter mechanism to achieve long-term spatial alignment.

Adult↗
PubMed1993

Human space experiments in SL-J: preparation and conducted.

This experiment investigated how human beings achieve visual stability during body movements, including fine motion on the ground. When humans are exposed to an environment with different gravity vectors, the programmed behavior on the ground must be changed, that is, it is reprogrammed. This is called habituation or familiarization. This experiment focuses on visual, vestibular and somatosensory perception coordination and how it changes in microgravity as compared to a 1-G environment. We examined these issues under microgravity during the mission Spacelab Japan [correction of Japane] (SL-J) mission with the cooperation of the Japanese Payload Specialist (PS), Dr. Mohri. In this paper we describe how the first human life science experiments were conducted and how the data processed is being.

Adaptation, Physiological↗
PubMed1993

[Congenital nasal stenosis--new concept and its cases].

Congenital nasal stenosis is a new disease concept which was reported, for the first time, by Knegt-Junk et al in 1988. The authors experienced 10 cases of this disease from 1986 to 1990. Radiography revealed that transverse width of the bony nasal passage of these patients was smaller than that of normal infants. Infants with nasal stenosis showed respiratory distress after birth and half of them had a low body weight and/or other congenital defects. Our patients were treated by nasal or oral intubation or by installation of nasal vasoconstrictor into the nasal passage. Four cases showed improvement up to 4 months of age, 6 others after 6 months of age. Tracheostomy was performed in one case. We must differentiate this disease from incomplete choanal atresia or nasal aperture stenosis. Our cases were similar to that of Knegt-Junk et al. We speculate that the congenital origin of this disease stems from a disturbance in embryologic development of the middle third of the face. Accordingly, we measured the diameter of the nasal passage radiography and recognized a narrow transverse width in the bony portion of the nose.

Ephedrine↗
PubMed1993

[Usefulness of polymerase chain reaction (PCR) technique in making early diagnosis and treatment of cytomegalovirus and Pneumocystis carinii-pneumonia in patients with hematological neoplasms].

Recently, the incidence of opportunistic infections in patients with hematological neoplasms has been markedly increasing. However, early and definitive diagnosis and treatment of these infections remain difficult. In this study, we report three patients, a 47-year-old female with ATL, a 54-year-old female with CML and a 65-year-old female with ATL. All these cases were complicated with pneumonia caused by Pneumocystis carinii (Pc) or cytomegalovirus (CMV). They were successfully treated with sulfamethoxazole/trimethoprim or ganciclovir after detection of the respective microorganisms from sputum samples in the early stage of the infections by polymerase chain reaction (PCR) method. The above clinical evidence demonstrated the PCR technique to be a rapid and sensitive diagnostic procedure for the detection of Pc or CMV and to be helpful for the early initiation of appropriate treatment of the infections in patients with hematological neoplasms.

Aged↗
PubMed1992

Cerebral myxopapillary ependymoma.

A rare case of myxopapillary ependymoma is reported. The tumor occurred in the cerebral hemisphere of an 8-year-old girl and had no relationship to the lateral ventricles. Microscopically, it showed abundant mucin production around papillary or reticular structures. Immunohistochemically, these tumor cells were weakly positive, with glial fibrillary acidic protein demonstrated in part of the tumor and vimentin strongly demonstrated throughout the tumor. The results may indicate the poorly differentiated nature of this tumor. This is the second reported case of intracranial myxopapillary ependymoma.

Brain Neoplasms↗
PubMed1992

Reversibility of energy metabolism and intracellular pH after cerebral ischaemia evaluated by 31P-MRS.

We have previously developed a reproducible model of transient forebrain ischaemia in rats by bilateral carotid artery occlusion combined with temporary increase of ICP. With this model, reversibility of the energy metabolism and intracellular pH (pHi) was investigated by 31P-MRS during 120 min of recirculation in three groups of, respectively, 30, 60, and 120 min of ischaemia. With the induction of ischaemia, ATP and phosphocreatine (PCr) disappeared, and measurement of pHi showed severe acidosis in all rats. In the 30 min ischaemia group, both energy metabolism and pHi recovered almost completely. In the 60 min ischaemia group, ATP recovered to 74% of control values, but pHi showed full recovery. In the 120 min ischaemia group, ATP recovered to about 50% of control values, and recovery of pHi was variable. Showing logarithmical changes during recirculation in ATP and PCr, the rate of metabolic recovery was fast during 60 min of recirculation, but it decreased and reached plateau thereafter in all groups. Recovery of pHi was affected by ATP levels, and was precipitously accelerated as ATP levels exceeded 50% of pre-ischaemic values. These results suggest that prolongation of the duration of ischaemia limits the restoration of the energy state, and the quality of pHi recovery after cerebral ischaemia is affected by the degree of ATP recovery during 60 min of recirculation.

Adenosine Triphosphate↗
PubMed1992

Gene structure and multiple mRNA species of Drosophila melanogaster aldolase generating three isozymes with different enzymatic properties.

Genomic clones encoding the Drosophila aldolase gene were isolated and the organization of the gene was determined. The protein-coding region spanning nearly 3.5 kb consists of five coding exons (exon 2, 3, 4 alpha, 4 beta, and 4 gamma). The insect exon 2 corresponds to exons 2 to 7 of vertebrate aldolase genes and thus appears to have been formed by the fusion of these 6 exons into a single exon during evolution. The Drosophila aldolase gene is predicted to generate mRNAs for three isozymes (alpha-, beta-, and gamma-types) from the primary transcripts by alternative usage of the final three exons. The reverse transcriptase-PCR assay revealed the occurrence of mRNAs for the three isozymic forms at different developmental stages, and tissue-specific expression was also found to occur in adult flies. In addition to the usual type mRNA species for the alpha-, beta-, and gamma-isozymes, two novel forms of mRNAs, alpha beta- and beta gamma-type mRNAs, were detected tissue-specifically in adult flies, although their functions are unpredictable. The alpha beta-mRNA is an alpha-type mRNA in which exon 4 beta remains unspliced, while the beta gamma-mRNA is a beta-type mRNA with the exon 4 gamma remaining unspliced. Recombinant enzymes expressed in Escherichia coli were all active and exhibited different enzymatic properties.

Amino Acid Sequence↗
PubMed1992

Metabolism of tegafur in rat liver observed by in vivo 19F magnetic resonance spectroscopy and chromatography.

Metabolism of tegafur in the rat liver was observed by in-vivo 19F magnetic resonance spectroscopy (MRS). After MRS observation, tegafur and q-fluorouracil (5-FU) in the liver were determined by a chromatographic method for comparison with the results of 19F-MRS. Rats were divided into 3 groups: 1) CCl4-induced liver injury group, 2) uracil combined group, 3) control group. Catabolism to fluoro-beta-alanine was suppressed in both the liver injury group and the uracil combined group. Low peaks of 5-FU and fluoronucleotides could be found only in the uracil combined group. The result of 19F MRS observation of each group was in agreement with the result of determination of tegafur and 5-FU by chromatography. This showed that substances which could be observed by 19F-MRS were in proportion to all intracellular fluoro-containing substances. 19F-MRS can provide direct information on the metabolism of fluoropyimidines non-invasively and it might be a useful aid in choosing suitable chemotherapy for patients.

Alanine Transaminase↗
PubMed1992

[A case report of a burn produced by the probe of a pulse oximeter].

We experienced a case of burn produced by the pulse oximeter probe at the finger of a patient. Patient was a 75-year old man scheduled to transurethral prostatectomy. The pulse oximeter probe made by Physio-Control Co. was attached at his finger and was connected to a pulse oximeter manufactured by Ohmeda Co. Soon after the start of Spo2 measurement the anesthetist became aware of abnormal heating of the probe and removed it immediately. But unfortunately a small thermal injury was formed at patient's finger. Abnormally excessive current went through the detector diode and heated the finger probe. Attention to correct connection between the pulse oximeter probe and the finger is necessary before use.

Aged↗
PubMed1992

[Significance of detection of specific IgE in Anisakis-related diseases].

Anisakis larvae which parasitize sea fishes sometimes cause not only anisakiasis but also such allergic reactions as mackerel-induced urticaria. We prepared AlaSTAT by using excretory/secretory antigens from Anisakis larvae to detect specific IgE in various patients groups. The AlaSTAT positive rate was 87.5% in gastric anisakiasis patients who were endoscopically diagnosed, while it was 66.7% in patients who had acute abdominal pain but no larva detected. Ascariasis in the common bile duct was 0%. The positive rate in mackerel-induced urticaria patients was 75.0%, while it was 8.3% and 10.0% in patients with urticaria of unknown origin and normal controls, respectively. Based on these data, the detection of specific IgE using AlaSTAT is useful in elucidating the cause of urticaria or acute abdominal pain, such as Anisakis.

Animals↗
PubMed1992

In vivo 19F MR spectroscopic study of metabolism of 5-fluorotryptophan in rat liver.

The metabolism of 5-fluorotryptophan in rat liver was examined by in vivo 19F MR spectroscopy. After i.v. injection of 200 mg/kg b.w. of 5-fluorotryptophan the substance was noted immediately as a strong peak, which decreased gradually. Another peak appeared about 40 min after the injection. The chemical shift value of this peak was 1.6 ppm from that of 5-fluorotryptophan. Kynurenine is known to be a major metabolite of tryptophan in the liver. We synthesized 5-fluorokynurenine from 5-fluorotryptophan by ozonolysis. The chemical shift value of 5-fluorokynurenine was confirmed to be coincident with that of the metabolite peak. This strongly suggests that the metabolite peak of 5-fluorotryptophan observed in this study was the 5-fluorokyrurenine signal. We also applied this method for the CCl4-injured liver. In the liver injury group, the metabolite peak appeared slowly and the intensity was low compared to that of the normal group, though the peak of 5-fluorotryptophan decreased similarly as in the normal liver. These results suggest that the decrease of 5-fluorotryptophan is due mainly to the renal excretion, as the injured liver could not metabolize 5-fluorotryptophan.

Animals↗
PubMed1991

Neural and humoral controlling mechanisms of cardiovascular functions in man under weightlessness simulated by water immersion.

To clarify how neural and humoral mechanisms operate to control cardiovascular functions in man under weightlessness, the response of sympathetic nerve activity was observed in healthy human subjects by means of microneurographic technique with the changes of several hemodynamic parameters and hormonal responses during thermoneural head-out water immersion. Muscle sympathetic nerve activity was markedly suppressed by head-out immersion, concomitantly with a reduction of the leg volume, an increase of the stroke volume and a reduction of total peripheral resistance. At the same time, plasma level of norepinephrine, vasopressive and antidiuretic hormones (ADH, aldosterone, renin activity, angiotensin I-II) were reduced, while vasodepressive and diuretic hormone (ANP) was markedly increased. The systemic blood pressure was maintained almost unchanged during head-out water immersion. The suppressive response of sympathetic nerve activity seemed to be age-dependent. This response was less prominent in the elderly than in young subjects. It is concluded that the suppressive response of muscle sympathetic activity plays an important role to maintain hemodynamic homeostasis under weightlessness to compensate for the cephalad fluid shift and the resultant increase of the stroke volume in cooperation with the hormonal responses.

Adolescent↗
PubMed1991

Absolute structure-cytotoxic activity relationships of steganacin congeners and analogues.

The cytotoxic activities of optically pure and racemic steganacin congeners and analogues against KB cells in culture and the inhibitor activity of cilia regeneration in Tetrahymena were studied with regard to absolute and relative configurations. The stereochemical requirements of dibenzocyclooctadiene lignan lactones for activity were clarified.

4-Butyrolactone↗