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Biomedical subjects

K Soga

Publications and source records attributed to K Soga.

At least 37 records · Page 2Linked to original sources
PubMed1999

Growth and development in Arabidopsis thaliana through an entire life cycle under simulated microgravity conditions on a clinostat.

The effects of simulated microgravity conditions produced by a horizontal clinostat on the entire life cycle of Arabidopsis thaliana ecotype Columbia and Landsberg erecta were studied. Horizontal clinorotation affected little germination of seeds, growth and development of rosette leaves and roots during early vegetative growth stage, and the onset of the bolting of inflorescence axis and flower formation in reproductive growth stage, although it suppressed elongation of inflorescence axes. The clinorotation substantially reduced the numbers of siliques and seeds in Landsberg erecta, and completely inhibited seed production in Columbia. Seeds produced in Landsberg erecta on the clinostat were capable of germinating and developing rosette leaves normally on the ground. On the other hand, growth of pin formed mutant (pin/pin) of Arabidopsis ecotype Enkheim, which has a unique structure of inflorescence axis with no flower and extremely low levels of auxin polar transport activity, was inhibited and the seedlings frequently died during vegetative stage on the clinostat. Seed formation and inflorescence growth of the seedlings with normal shape (pin/+ or +/+) were also suppressed on the clinostat. These results suggest that the growth and development of Arabidopsis, especially in reproductive growth stage, is suppressed under simulated microgravity conditions on a clinostat. To complete the life cycle probably seems to be quite difficult, although it is possible in some ecotypes.

Arabidopsis↗
PubMed1999

Increased molecular mass of hemicellulosic polysaccharides is involved in growth inhibition of maize coleoptiles and mesocotyls under hypergravity conditions.

Elongation growth of dark grown maize (Zea mays L cv. Cross Bantam T51) coleoptiles and mesocotyls was suppressed by hypergravity at 30 g and above. Acceleration at 300 g significantly decreased the mechanical extensibility of cell walls of both organs. Hypergravity increased the amounts of hemicellulose and cellulose per unit length in mesocotyl walls, but not in coleoptile walls. The weight average molecular masses of hemicellulosic polysaccharides were also increased by hypergravity in both organs. On the other hand, the activities of beta-glucanases extracted from coleoptile and mesocotyl cell walls were decreased by hypergravity. These results suggest that the decreased activities of beta-glucanases by hypergravity cause an increase in the molecular mass of hemicellulosic polysaccharides of both organs. The upshift of molecular mass of hemicellulosic polysaccharides as well as the thickening of cell walls under hypergravity conditions seems to be involved in making the cell wall mechanically rigid, thereby inhibiting elongation growth of maize coleoptiles and mesocotyls.

Acceleration↗
PubMed1999

Morphogenesis of rice and Arabidopsis seedlings in space.

Seedlings of rice (Oryza saliva L.) and Arabidopsis (A. thaliana L.) were cultivated for 68.5 hr in the RICE experiment on board during Space Shuttle STS 95 mission, and changes in their growth and morphology were analyzed. Microgravity in space stimulated elongation growth of both rice coleoptiles and Arabidopsis hypocotyls by making their cell walls extensible. In space, rice coleoptiles showed an inclination toward the caryopsis in the basal region and also a spontaneous curvature in the same direction in the elongating region. These inclinations and curvatures were more prominent in the Koshihikari cultivar compared to a dwarf cultivar, Tan-ginbozu. Rice roots elongated in various directions including into the air on orbit, but two thirds of the roots formed a constant angle with the axis of the caryopsis. In space, Arabidopsis hypocotyls also elongated in a variety of directions and about 10% of the hypocotyls grew into the agar medium. No clear curvatures were observed in the elongating region of Arabidopsis hypocotyls. Such a morphology of both types of seedlings was fundamentally similar to that observed on a 3 D clinostat. Thus, it was confirmed by the RICE experiment that rice and Arabidopsis seedlings perform an automorphogenesis under not only simulated but also true microgravity conditions.

Arabidopsis↗
PubMed1999

Changes in mechanical properties of the cuticle and lipid accumulation in relation to adult diapause in the bean bug, Riptortus clavatus.

Photoperiodically controlled adult diapause in the bean bug, Riptortus clavatus (Thunberg) (Heteroptera: Alydidae) was due to suppression of corpus allatum activity under short-day conditions. The mechanical extensibility of the cuticle of the pronotum was significantly higher in nondiapause adults reared under long-day conditions than in diapause adults reared under short-day conditions. Furthermore, diapause adults accumulated significantly larger amount of lipids than nondiapause ones. It was then examined whether these two characteristics of adult diapause also depend on activity of the corpus allatum, by removal of the corpus allatum and transection of the nervi corporis allati. Even after these two kinds of surgery, adults responded to photoperiod and showed similar differences both in mechanical properties of the cuticle and in lipid content between long-day and short-day conditions. Therefore, inactivity of the corpus allatum is not responsible for the stiffer cuticle or higher lipid accumulation in diapause adults.

Journal Article↗
PubMed1999

Inhibition of reproductive growth of Arabidopsis in airtight vessels.

Airtight vessels have various advantages for space experiments. However, Arabidopsis thaliana plants scarcely produced seeds when grown in such vessels. The mechanism by which reproductive growth is inhibited in airtight vessels was studied. The length of the flower stalk was shorter when the plants were grown in airtight vessels. Thus, there was a possibility that the inhibition of reproductive growth was due to the inhibition of vegetative growth. However, even when the plants which has grown under non-airtight conditions and has reached to the flowering stage were transferred to airtight vessels, silique formation was inhibited, suggesting that the airtight environment directly influences reproductive growth. In airtight vessels, anther dehiscence was inhibited, which appears to be the cause of inhibition of silique formation and seed development. Reproductive growth recovered when silica gel was added to the vessels. These results suggest that in airtight vessels, high humidity causes a suppression of anther dehiscence, resulting in the inhibition of reproductive growth. Therefore, the control of humidity by ventilation should be taken into consideration in designing a growth chamber for space experiments.

Arabidopsis↗
PubMed1999

Hypergravity increases the molecular mass of xyloglucans by decreasing xyloglucan-degrading activity in azuki bean epicotyls.

Elongation growth of dark-grown azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara) epicotyls was suppressed by hypergravity at 30 x g and above. Acceleration at 300 x g significantly decreased the mechanical extensibility of cell walls. The amounts of cell wall polysaccharides (pectin, hemicellulose-II and cellulose) per unit length of epicotyls increased under the hypergravity condition. Hypergravity also increased the amounts and the weight-average molecular mass of xyloglucans in the hemicellulose-II fraction, while decreasing the activity of xyloglucan-degrading enzymes extracted from epicotyl cell walls. These results suggest that hypergravity increases the amounts and the molecular mass of xyloglucans by decreasing xyloglucan-degrading activity. Modification of xyloglucan metabolism as well as the thickening of cell walls under hypergravity conditions seems to be involved in making the cell wall mechanically rigid, thereby inhibiting elongation growth of azuki bean epicotyls.

Cell Wall↗
PubMed1999

Retinal artery air embolism in dogs: fluorescein angiographic evaluation of effects of hypotension and hemodilution.

UNLABELLED: Cerebral air embolism can cause cerebral complications after open heart surgery. The duration of cerebral artery occlusion by air embolism is thought to vary depending on the conditions. However, no study has evaluated factors affecting the duration of occlusion. In this study, we examined the effects of blood pressure and hemodilution on the duration of retinal artery occlusion caused by air embolism in dogs. The duration of retinal artery occlusion caused by the injection of 0.6 mL of air into the common carotid artery was measured by fluorescein angiography and compared among the following three periods: a control period, during which the mean blood pressure (MBP) was maintained at 80 mm Hg; a hypotension period, during which MBP was decreased to 60 mm Hg by exsanguination; and a hypotension plus hemodilution period, during which an additional exchange of blood with hydroxyethyl starch solution was performed and MBP was maintained at 60 mm Hg. When MBP was lowered from 80 to 60 mm Hg, the duration of retinal artery occlusion was prolonged from 34+/-39 to 166+/-90 s (P < 0.01). In dogs with MBP of 60 mm Hg, hemodilution (12.0+/-0.9 to 7.3+/-0.5 g/dL hemoglobin concentration) shortened the duration from 166+/-90 to 75+/-50 s (P < 0.05). Our results demonstrate that hypotension prolongs and hemodilution shortens the duration of retinal artery occlusion caused by air embolism. IMPLICATIONS: We evaluated the effects of blood pressure and hemodilution on the duration of retinal artery occlusion caused by air embolism by retinal fluorescein angiography. Hypotension prolonged and hemodilution shortened the duration of retinal artery occlusion caused by air embolism.

Animals↗
PubMed1999

Primary duodenal MALT lymphoma.

Primary duodenal MALT lymphoma (MALToma) is a very rare neoplasm arising from the mucosa-associated lymphoid tissue of the duodenum. We report a 55-year-old woman with MALToma located in the descending duodenum and accompanying Helicobacter pylori infection of the stomach. We performed operative resection due to involvement of the papilla of Vater and submucosal tumor infiltration. Despite wide mucosal spreading, postoperative examination revealed only a small amount of MALToma cells infiltrating into the submucosa. No invasion into the adjacent structure or metastasis to regional lymph nodes was confirmed, suggesting the disease could have been controlled by eradication of Helicobacter pylori.

Duodenal Neoplasms↗
PubMed1995

[The hazards of coronary revascularization under hypothermic ventricular fibrillation].

Since January 1992 till June 1994, we experienced 22 cases of coronary revascularization (CABG) under hypothermic ventricular fibrillation (Vf) in patients with unclampable ascending aorta (Group 2). We compared them with patients undergoing conventional CABG with cardioplegic cardiac arrest (Group 1). All these 362 cases were primary isolated CABG. Comparing preoperative patient profile, patients of Group 2 were older (Group 1: 64.3 +/- 8.5, Group 2: 68.2 +/- 6.7 year old, p < 0.05), had more unstable angina (Group 1: 20.3%, Group 2: 54.5%, p < 0.001), and had more severe NYHA classification (Group 1: 2.22 +/- 0.55, Group 2: 2.73 +/- 0.46, p < 0.05) than Group 1. There were no significant difference between both groups about other factors. Comparing post operative complication, low output syndrome (Group 1: 2.6%, Group 2: 18.2%, p < 0.005) perioperative myocardial infarction (PMI) (Group 1: 4.4%, Group 2: 36.4%, p < 0.0001) ventricular tachycardia (VT) (Group 1: 1.4%, Group 2: 18.2%, p < 0.0001), respiratory failure (Group 1: 3.8%, Group 2: 18.2%, p < 0.005), and post operative hospital death (Group 1: 2.9%, Group 2: 18.2%, p < 0.0005) occurred more frequent in Group 2 than Group 1. Other complication (renal failure, wound infection, cerebrovascular accident, rethoracotomy for bleeding) equally occurred in both groups. Long Vf time (mean 92.8 minutes) and low perfusion pressure during Vf (mean 60.0 mmHg) were suspected to be major cause of high incidence of PMI and VT in Group 2. But there were no correlation between Vf time, perfusion pressure and occurrence of PMI and/or VT.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

[Risk factors of wound infection following cardiac surgery and antimicrobial prophylaxis].

To make investigation about risk of wound infection following cardiac surgery, we analyzed cases of primary aorto-coronary bypass surgery and/or primary valvular surgery. Cases required respirator for longer than 2 days, and those with drainage tube for longer than 5 days were excluded from this study, because these cases had antimicrobial agent postoperatively as therapeutic use rather than prophylactic use. Those received preoperative antimicrobial agent for infectious endocarditis and so on were also excluded for the same reason. 523 cases were entered this study. These cases received cefazolin (CEZ) postoperatively as prophylaxis. Sternal wound and leg/groin wound were separately analyzed. Risk factors (age, sex, diabetes mellitus, unstable angina, use of intraaortic balloon, internal thoracic artery harvest, re-exploration, previous myocardial infarction, NYHA classification, emergent operation, operation time, extracorporeal circulation time, blood product use, preoperative blood hemoglobin concentration, preoperative serum albumin, preoperative creatinine clearance (Ccr), duration of drainage tube insertion, body surface area, daily dose of CEZ, duration of prophylaxis) were examined using univariate (Chi square test was used for contingency table analysis, unpaired t test was used to compare averages) and multiple regression analysis. For sternal wound infection, only Ccr showed significant (P = 0.027) correlation. For leg/groin wound infection, 2 factors (smaller daily dose of CEZ: P = 0.009, more severe NYHA class: P = 0.03) showed significant correlation. To investigate appropriate duration of CEZ prophylaxis, cases were divided into 2 groups, those had CEZ within 48 hours postoperatively (group S) and those had CEZ for longer than 48 hours (group L).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗