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Biomedical subjects

K Koga

Publications and source records attributed to K Koga.

At least 127 records · Page 7Linked to original sources
PubMed1998

[Two cases of functioning parathyroid cysts].

Two cases of functioning cysts are reported. The first patient was a 48-year-old man who underwent percutaneous cyst puncture for a palpable mass in the neck at another hospital. Hypercalcemic crisis brought the patient to Koga General Hospital. The second patient was a 69-year-old woman with the complaint of discomfort in the right neck of several years duration and with a palpable mass identified on physical examination at a local hospital. Both patients had high serum calcium and parathyroid hormone (PTH) levels and were diagnosed as having functioning parathyroid cysts by imaging studies including ultrasonography, computed tomographic scan, magnetic resonance imaging and scintigraphy. After parathyroidectomy, their serum calcium and PTH levels became normal, but calcium supplement was necessary in the first patient. To our knowledge, these are the 40th and 41st cases reported in the Japanese literature.

Aged↗
PubMed1998

[2,8-dihydroxyadenine urolithiasis due to partial deficiency of adenine phosphoribosyltransferase: a case report].

A 35-year-old female was referred to our clinic with a complaint of left flank pain in 1993. Drip infusion pyelography showed a filling defect of 25 x 24 mm in size in the left ureteropelvic junction. Computed tomography and ultrasonography revealed it as the renal stone. Percutaneous nephroureterolithotomy and extracorporeal shock-were lithotomy were performed. The stone was composed of 2,8-dihydroxyadenine (DHA). The patient was diagnosed as having a partial deficiency of adenine phosphoribosyltransferase (APRT) from the low APRT activity and a genotype of a compound heterozygote APRT*J/APRT*Q0 by T-cell analysis. The urinary excretion of 2,8-DHA crystals disappeared by the postoperative treatment with allopurinol. Cases of 2,8-DHA urolithiasis reported in the Japanese literature are discussed.

Adenine↗
PubMed1997

Comparative study of toborinone (OPC-18790) and milrinone on energy metabolism in microembolized guinea pig hearts.

The effects of toborinone (OPC-18790) and milrinone on cardiac function and energetics were compared in microembolized guinea pig hearts. Male guinea pig hearts were perfused according to the Langendorff method and microembolization was induced by injecting microspheres. The hearts were then treated with toborinone (10 microM), milrinone (4 microM), and vehicle. Energy metabolism in hearts was assessed by 31-phosphorus magnetic resonance spectroscopy (31P-MRS). Microembolization produced a decrease in coronary perfusion flow (CPF), left ventricular developed pressure (LVP), and peak LVdP/dt by about 50% concomitantly with a decrease in creatine phosphate (PCr) and ATP and an increase in inorganic phosphate (Pi) and Pi/PCr ratio. Toborinone and milrinone increased peak LVdP/dt, an index of contractility, by 15 +/- 2% and 18 +/- 3%, respectively. Milrinone increased heart rate (HR) by 22 +/- 4% but toborinone did not change HR. Toborinone did not change PCr, ATP, Pi, Pi/PCr, and intracellular pH (pHi) compared with the vehicle. On the other hand, milrinone decreased PCr and increased Pi and Pi/PCr compared with toborinone or vehicle. These results suggest that the different effects between toborinone and milrinone on energy metabolism in microembolized hearts may be due to the difference of chronotropic action between these drugs. Thus toborinone, a positive inotropic agent without chronotropic action, may be effective in acute treatment of ischemic heart failure.

Animals↗
PubMed1997

Effects of vasodilators on the signal intensity of perfluorocarbon monitored by in vivo 19F-NMR spectroscopy.

The effects of vasodilators on peripheral vessels were examined by monitoring the 19F-NMR signal of perfluorocarbon in vivo. Nitroglycerin, a venodilator that acts mainly on venous smooth muscle, increased the signal intensity of FC-43, whereas hydralazine, a typical arteriolar dilator that acts on arteriolar smooth muscle, decreased the signal intensity. These results indicate that the in vivo effects of vasodilators on smooth muscles of the venous and arterial systems are reflected by their effects on the signal intensity of FC-43.

Animals↗
PubMed1997

Effect of peripheral nerve injury on nuclear magnetic resonance relaxation times of rat skeletal muscle.

RATIONALE AND OBJECTIVES: The authors evaluate the changes in magnetic resonance (MR) relaxation times of rat skeletal muscles in vivo after nerve injury and during neural recovery, and determine the major determinants of relaxation times. MATERIALS: Magnetic resonance relaxation times, blood volume, and water and fat content were examined after nerve injury and during recovery with time course. RESULTS: Nerve injury led to longer T2 values compared with controls, but there were no significant changes in T1 values. After the initial prolongation of T2 after nerve injury, no changes were observed. Neural recovery resulted in a return of T2 values to normal. The time course of changes in blood volume was similar to that of changes in T2, and T2 values were correlated strongly with 19-fluorine-MR spectroscopy estimates of blood volume (r2 = 0.94). CONCLUSIONS: T2 values may be useful to monitor recovery after nerve injury and may be related to the blood volume in skeletal muscle.

Animals↗
PubMed1997

Damage to the laryngeal mask by residual fluid in the cuff.

It has been suggested that, in some situations, the cuff of the laryngeal mask should be filled with fluid. We speculated that this practice might damage the device during sterilisation in an autoclave. We studied whether injection of a small volume of water into the cuff of the laryngeal mask and subsequent sterilisation affected the integrity of the cuff. First, a pressure-volume relationship for each of 20 new masks was obtained by inflating the cuff with increasing volumes of air (5-45 ml). The masks were then randomly allocated into four groups (W0, W0.25, W0.5 or W1.0), 0, 0.25, 0.5 or 1.0 ml of water was injected into the cuff and the mask was then sterilised in an autoclave. After sterilisation, the shape of the cuff was examined and pressure-volume relationships were obtained again. The baseline intracuff pressures were similar in the four groups. After sterilisation, the pressure was significantly lower in groups W0.25, W0.5 and W1.0 than in group W0 (p < 0.05). Two masks in group W1.0 lost their integrity, resulting in herniation of and rupture of the cuff. We conclude that the cuff of the laryngeal mask should not be inflated with fluid unless the device is discarded afterwards.

Equipment Failure↗
PubMed1997

Effect of the size of a tracheal tube and the efficacy of the use of the laryngeal mask for fibrescope-aided tracheal intubation.

We randomly allocated 60 patients with normal airways into three groups to compare the ease of fibrescope-aided tracheal intubation using 8.0-mm internal diameter (group F8) and 6.0-mm (group F6) reinforced tracheal tubes and to evaluate the efficacy of the laryngeal mask as an aid for fibreoptic tracheal intubation (group L). In group F8 tracheal intubation was optimal in 2 of 20 patients and in two patients in whom intubation over the fibrescope was difficult the attempts resulted in inadvertent oesophageal intubation. In group F6 intubation was always successful and significantly easier than in group F8 (p < 0.005; 95% confidence interval for the difference in the proportion of the optimal intubation grade: 20-70%). In group L tracheal intubation was optimal in 18 of 20 patients and easier than in group F6 (p = 0.014; 95% confidence interval for difference: 10-60%). In both groups F6 and L tracheal intubation was completed within less than about 1 min. We conclude that conventional fibrescope-aided tracheal intubation with a 6.0-mm tracheal tube is easier than with an 8.0-mm tube and that the laryngeal mask facilitates fibrescope-aided tracheal intubation.

Adult↗
PubMed1997

Enhancement of glucose uptake in stunned myocardium: role of glucose transporter.

This study quantifies the myocardial glucose uptake and clarifies the pathway of augmented glucose uptake in myocardium reperfused after a brief period of ischemia (stunned myocardium). The glucose uptake rate was determined from the time course of the sugar phosphate (SP) resonance in rat myocardium (d[SP]/dt) with 31P nuclear magnetic resonance after the substitution of glucose with its analog 2-deoxyglucose. The d[SP]/dt in stunned myocardium [1.03 +/- 0.05 (SE) micromol x g wet wt(-1) x min(-1); n = 8] increased significantly compared with nonischemic control myocardium (0.18 +/- 0.03 micromol x g wet wt(-1) x min(-1); n = 8; P < 0.0001), reaching the maximal stimulatory uptake rate during exposure to insulin (1.05 +/- 0.04 micromol x g wet wt(-1) x min(-1); n = 8). Twenty minutes after reperfusion, the d[SP]/dt was still augmented (0.41 +/- 0.05 micromol x g wet wt(-1) x min(-1); n = 5; P < 0.05 vs. control myocardium). To elucidate further the mechanism of augmented glucose uptake, N6-(L-2-phenylisopropyl)-adenosine (PIA; 100 micromol/l), a potent blocker of the glucose transporter, was administered to stunned hearts and, as a control, to insulin-stimulated hearts. PIA significantly and comparably inhibited the increase in d[SP]/dt in stunned myocardium (0.36 +/- 0.07 micromol x g wet wt(-1) x min(-1); n = 4; P < 0.0001 vs. without PIA) and in insulin-stimulated myocardium (0.38 +/- 0.02 micromol x g wet wt(-1) x min(-1); n = 4; P < 0.0001 vs. without PIA). These results indicate that the augmented glucose uptake in stunned myocardium is maintained by the glucose transporter, the amount of which is almost equal to that which can be maximally recruited by insulin.

Adenosine Triphosphate↗
PubMed1997

Time course of recovery from nerve injury in skeletal muscle: energy state and local circulation.

This study examined the time course of recovery from nerve injury on energy state assessed by phosphorus-31 magnetic resonance spectroscopy and local circulation dynamics by fluorine-19 magnetic resonance spectroscopy in skeletal muscles of rats. The hindlimb muscles that had undergone unilateral sciatic nerve compression for 2 wk (CN) were compared with sham-operated (SO) muscles and with muscles that had the compression removed after 2 wk and were allowed to recover for 4 wk (R4) or for 6 wk (R6). The energy state and local circulation dynamics of CN muscles were less than those of SO muscles (P < 0.01). The energy state of R4 muscles remained at levels similar to CN muscles, whereas the local circulation dynamics improved but not back to SO values. In R6 muscles, both parameters returned to SO values. These results showed that the recovery processes of circulation precede those of energy state in skeletal muscles.

Animals↗
PubMed1997

Contribution of hydrophobicity of nonionic detergents to membrane lipid fluidity and disopyramide uptake by rat intestinal brush-border membrane vesicles.

The contribution of hydrophobicity of different types of detergents to disopyramide uptake by rat small intestinal brush-border membrane vesicles was studied in relation to their membrane lipid fluidity and the physicochemical parameters of the detergents, i.e., hydrophile-lipophile balance (HLB). Span-, Tween-type detergents or glycerol esters at non-solubilizing concentrations (0.01-0.05% (w/v)) decreased the extent of maximum uptake of the drug in the presence of outward H(+)-gradient, but not in the absence of the gradient. The fluorescence anisotropy of the vesicles using diphenylhexatriene (DPH), as reflected by its incorporation into the membrane inner lipid layer, decreased with the addition of all detergents used. In contrast, that of the vesicles using trimethylammoniumphenyl phenylhexatriene (TMA-DPH), which reflected its incorporation into the membrane outer lipid layer, increased depending on the concentration of Tween-type detergents except for Tween 81 and Tween 85, glycerol esters (MO-500, MO-750, ML-500 and ML-750); it decreased with the addition of Span-type detergents, Tween 81 and glycerol ester (MO-310). Therefore, the membrane lipid fluidity change of the outer leaflet, rather than the inner lipophilic domain, of the membrane vesicles caused by the detergents was found to be dependent on the hydrophobicity, but not on the type of detergent. This seems to correlate with the inhibitory effects on the facilitated uptake of the drug by the membrane vesicles.

Animals↗
PubMed1997

[Asymmetric synthesis using chiral bases].

Studies have been made to design chiral bidentate lithium amides and chiral tetradentate amines, and to explore the use of these chiral bases for enantioselective formation and reactions of lithium enolates. Chiral bidentate lithium amides having a chiral amide nitrogen made by virtue of chelation were successfully applied to the enantioselective deprotonation reaction of prochiral cyclic ketones, the kinetic resolution of racemic cyclohexanone derivatives by deprotonation, and the regioselective deprotonation of optically active 3-keto steroids. Structures of some of these chiral bidentate lithium amides in the solid state and in solution were elucidated by X-ray and NMR spectroscopic analyses. By the use of chiral tetradentate amines, enantioselective reactions of lithium enolates with electrophiles, such as alkylation, protonation, and Michael addition, proceeded successfully. Examples of catalytic enantioselective deprotonation, alkylation, and protonation by the present strategy are also presented and discussed.

Magnetic Resonance Spectroscopy↗
PubMed1997

Three cases of renal angiomyolipoma.

We report three non-typical cases of renal angiomyolipoma including clinical features, imaging examinations (with ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI) and angiography) and histological findings. Microaneurysms observed by angiography were common to the three cases and were considered to be an important finding in the diagnosis of renal angiomyolipoma. Moreover, the short tau inversion recovery (STIR) method of MRI, which suppresses photon signals of fat, was considered to be useful for the diagnosis. Case 1 was accompanied by spontaneous rupture, Case 2 was difficult to diagnose because of little fat tissue and Case 3 revealed a very small tumor.

Adolescent↗
PubMed1997

Comparative measurement of visual stability in Earth and cosmic space.

Three theories have been suggested as to the cause of space motion sickness: 1) eye and vestibular sensory mismatch, 2) abnormal shift of body fluids producing increased intracranial pressure and 3) pre-warning signals for unpleasant physical situations by self-produced neurotoxic substances released in the body. We are interested in the possible functional disabilities/incongruities of eye, head and body movements in 0-G. Space motion sickness might be explained from the viewpoint of lack of coordination of the movements of the eye and head. It is important to ascertain the significance of gravity in the maintenance of human visual stability. We will examine the coordination of Japanese Payload Specialist (JPS) eye and head movement by electrooculogram and neck muscle electromyogram recordings, as well as obtaining a subjective evaluation of visual stability from the PS during space flight. We hypothesize that 1) poor performance of the eye movement will be observed, 2) unusual neck muscle activity will be observed and 3) there will be decreased visual stability in micro gravity. We obtained all digital data and VCR taped image data in [TEXT MISSING]

Aerospace Medicine↗
PubMed1997

Inflammatory pseudotumor of the liver--MR imaging findings.

Using retrospective studies, we have investigated the possibility of obtaining characteristic findings of inflammatory pseudotumor of the liver by magnetic resonance (MR) imaging. We examined 8 patients (involving 8 masses) who had been histologically diagnosed as having an inflammatory pseudotumor in the liver. The histological studies were performed on an excised specimen of 1 mass, and on aspiration needle biopsy specimens and the clinical courses of the other 7 masses. T1 weighted images (T1WI) and T2 weighted images (T2WI) were obtained on MR imaging. MR imagings were analyzed for visualized patterns, patterns of internal structure and patterns of contrast enhancement of dynamic MR imaging. The 8 masses were visualized as hypointense on T1WI and hyperintense on T2WI by MR imaging. Dynamic MR imaging revealed that 1 mass was markedly enhanced peripherally while another mass was homogeneously enhanced, and that enhancement was most marked immediately after injection of contrast medium and then gradually disappeared. Vessels were observed in 4 masses (the portal vein in 2 masses, the hepatic vein in 1 mass, and portal and hepatic veins in 1 mass), and these vessels were clearly visualized on T1WI. The MR imaging findings from the early stage of an inflammatory pseudotumor showed a pattern similar to that of hepatic tumors with rich blood flow. The portal vein or hepatic vein was found in the tumor in half the patients, suggesting that this characteristic was useful for diagnosis of an inflammatory pseudotumor in the liver.

Aged↗
PubMed1997

Telescience for the reduced gravity flight experiments.

To improve the efficiency of the preliminary experiments for the JEM, the telescience capabilities have been implemented into the parabolic flight experiments on the small jet plane. In this paper, we will describe the results of the 1st telescience support experiments using the two commercial airline telephone system. In the experiments, these lines have been used not only for the voice communication, but also for the data transfer, such as FAX, still TV image transmission, and data transfer. Utilizing these capability, human physiological experiment was tested as the sample experiment. The parabolic flights were done in the two major training/testing area, that are C & K area.

Aerospace Medicine↗
PubMed1997

[What the gravity environment enables us to attain].

How human beings achieve visual stability during body movements in space was investigated. When humans are exposed to an environment with different gravity environment, the pre-programmed behavior on the ground must be changed and should be re-programmed. This is habituation or familiarization. Present 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 the microgravity during the mission Spacelab Japan (SL-J) mission with the cooperation of the Japanese Payload Specialist (RS), Dr. Mohri. In this paper we describe how the first human life science experiments were conducted and showed the unusual muscle cooperation between gravity specific and non-gravity specific muscle over the mission days.

Adaptation, Physiological↗