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Biomedical subjects

H Karibe

Publications and source records attributed to H Karibe.

32 records · Page 2Linked to original sources
PubMed1994

Mild intraischemic hypothermia suppresses consumption of endogenous antioxidants after temporary focal ischemia in rats.

Oxidative damage by free radicals has been proposed as a mechanism of cerebral injury due to ischemia and reperfusion. Hypothermia protects against ischemic necrosis; however, its effect on oxidative stress has not been investigated. In this study, the effects of hypothermia on oxidative stress were studied by determining consumption of endogenous antioxidants after temporary focal ischemia in rats. Thirty-two Sprague-Dawley rats anesthetized with 1.5% isoflurane underwent 3 h of middle cerebral artery occlusion under hypothermic (33 degrees C) or normothermic (37 degrees C) conditions followed by 3 h of normothermic reperfusion. In the first study (n = 8 per group), intraischemic hypothermia suppressed the reduction of tissue concentrations of endogenous antioxidants, ascorbate (P < or = 0.05), and glutathione (P < or = 0.05) in ischemic cortex but not in caudoputamen. In a parallel study (n = 8 per group), hypothermia reduced tissue damage in ischemic frontoparietal cortex (P < or = 0.05), but not in caudoputamen. Laser-Doppler estimates of cortical blood flow showed that intraischemic hypothermia significantly attenuated early postischemic hyperperfusion (P < or = 0.01) and delayed postischemic hypoperfusion (P < or = 0.01). These results demonstrate that intraischemic mild hypothermia reduces oxidative stress and cell injury after prolonged focal ischemia followed by reperfusion. The reduction of oxidative stress by hypothermia may be related indirectly to attenuation of postischemic blood flow changes.

Animals↗
PubMed1994

Mild intraischemic hypothermia reduces postischemic hyperperfusion, delayed postischemic hypoperfusion, blood-brain barrier disruption, brain edema, and neuronal damage volume after temporary focal cerebral ischemia in rats.

Mild to moderate hypothermia (30-33 degrees C) reduces brain injury after brief (< 2-h) periods of focal ischemia, but its effectiveness in prolonged temporary ischemia is not fully understood. Thirty-two Sprague-Dawley rats anesthetized with 1.5% isoflurane underwent 3 h of middle cerebral artery occlusion under hypothermic (33 degrees C) or normothermic (37 degrees C) conditions followed by 3 or 21 h of reperfusion under normothermic conditions (n = 8/group). Laser-Doppler estimates of cortical blood flow showed that intraischemic hypothermia reduced both postischemic hyperperfusion (p < or = 0.01) and postischemic delayed hypoperfusion (p < or = 0.01). Hypothermia reduced the extent of blood-brain barrier (BBB) disruption as estimated from the extravasation of Evans blue dye at 6 h after the onset of ischemia (p < or = 0.01). Hypothermia also reduced the volume of both brain edema (p < or = 0.01) and neuronal damage (p < or = 0.01) as estimated from Nissl-stained slides at both 6 and 24 h after the onset of ischemia. These results demonstrate that mild intraischemic hypothermia reduces tissue injury after prolonged temporary ischemia, possibly by attenuating postischemic blood flow disturbances and by reducing vasogenic edema resulting from BBB disruption.

Animals↗
PubMed1994

Delayed induction of mild hypothermia to reduce infarct volume after temporary middle cerebral artery occlusion in rats.

Deep to moderate hypothermia (24 degrees to 30 degrees C) during focal cerebral ischemia reduces infarct volume but must be initiated before the onset of ischemia to be effective and has deleterious pulmonary, myocardial and neurological effects. It is not known whether mild hypothermia (32 degrees to 33 degrees C) protects against ischemic neuronal damage, whether hypothermia induced after the onset of ischemia has protective effects, or whether these effects are associated with alterations in cortical blood flow. In this study, mild whole-body hypothermia was induced in rats just before or 10, 30, or 60 minutes after the onset of 2 hours of temporary middle cerebral artery occlusion; rewarming began immediately after reversal of occlusion and normothermia was maintained throughout 22 hours of reperfusion. Infarct volume, measured 24 hours after the end of reperfusion, was significantly smaller in rats made hypothermic within 30 minutes after the onset of ischemia than in normothermic controls; hypothermia induced at 60 minutes of ischemia did not reduce infarct volume. Cortical blood flow, measured by laser Doppler ultrasound flowmetry, was not significantly different between groups during ischemia; however, postischemic cortical blood flow correlated positively with total infarct volume. These results indicate that mild hypothermia initiated during temporary focal ischemia in rats can reduce infarct volume without attenuating the reduction in cortical blood flow.

Animals↗
PubMed1992

Ca(2+)-independent contraction of uterine smooth muscle induced by vanadate and its inhibition by Ca2+.

Vanadate, 30 microM, contracts uterine smooth muscle of estrogen-dominated non-pregnant rats in Ca(2+)-free medium after preincubation with 3 mM EGTA. In spite of the phosphorylation of the myosin light chain during this contraction, studies with fura-2 suggested that this contraction was not accompanied by an increase in the cytosolic Ca2+ level. Inhibitors of the myosin light chain kinase and protein kinase C partly inhibited this contraction. Vanadate seems to enter the cell through anion channels to inhibit phosphatases, resulting in phosphorylation via basal activities of the myosin light chain kinase and protein kinase C. An increase in the cytosolic free Ca2+ level resulted in relaxation of the contracting muscle in the same manner as in the oxytocin-induced Ca(2+)-free contraction.

Alkaloids↗
PubMed1992

Calcium ion itself inhibits Ca-free contraction of various smooth muscles in response to adrenergic and cholinergic stimulations and to TPA in the absence of Ca channel blocker and EGTA.

1. Smooth muscles such as thoracic aorta, stomach and vas deferens contract tonically in the absence of Ca ion (Ca) in response to various agonists such as norepinephrine, carbachol and TPA. 2. Addition of Ca alone to the Ca-free medium relaxes the muscle that has been contracting in response to the agonist in the Ca-free medium. 3. Ca itself has an inhibitory action on the contraction. 4. Acidification of the medium relaxes the muscle as Ca does, but weakly.

Animals↗
PubMed1991

Involvement of protein kinase C in Ca(2+)-independent contraction of rat uterine smooth muscle.

The contribution of protein kinase C to the contraction by oxytocin of rat uterine longitudinal smooth muscle in Ca(2+)-free solution was investigated. Immunological analysis revealed that type II (beta) and III (alpha) protein kinase C subspecies were present in rat uterine smooth muscle. The pretreatment of a diacylglycerol kinase inhibitor R59022 to accumulate diacylglycerol potentiated the Ca(2+)-independent contraction. The contractile activity was diminished with the depletion of protein kinase C, when the contraction was evoked repeatedly by oxytocin during the prolonged exposure to a tumor-promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate. These results suggested the involvement of protein kinase C in oxytocin-induced contraction in Ca(2+)-free solution.

Animals↗
PubMed1991

Oxytocin contracts rat uterine smooth muscle in Ca2(+)-free medium without any phosphorylation of myosin light chain.

Contraction of rat uterine smooth muscle related to phosphorylation state of myosin light chain under various conditions was investigated. In the Ca2(+)-containing medium, both high K+ and oxytocin induced marked contraction of the muscle accompanied by pronounced phosphorylation of myosin light chain. In the Ca2(+)-free medium, although both vanadate and oxytocin induced slight contraction, phosphorylation of myosin light chain was only evident for vanadate but not for oxytocin. It was suggested that another mechanism distinct from myosin light chain phosphorylation might be involved in Ca2(+)-independent contraction of uterine smooth muscle elicited by oxytocin.

Animals↗
PubMed1991

Calcium reversal, relaxation by calcium ion of various smooth muscles contracted by carbachol, norepinephrine or a phorbol ester in calcium-ion free medium.

1. Ca reversal was reported on the longitudinal smooth muscle of rat uterus and the fundic part of the circular smooth muscle of guinea pig stomach; that is, addition of Ca ion to the Ca-free bathing solution in which the muscle is contracting to oxytocin or carbachol, respectively, relaxes the muscle. 2. We tested whether this inhibitory action of Ca ion is seen in other smooth muscles including vascular, air way, gastric and genital smooth muscles. 3. We found that Ca reversal was observed in the smooth muscle of rat thoracic aorta contracted by norepinephrine or by a phorbol ester, TPA, guinea pig tracheal smooth muscle contracted to carbachol, fundic smooth muscle of rat stomach to carbachol, corporal and antral smooth muscle of guinea pig stomach to carbachol and rat vas deferens to norepinephrine. 4. Ca reversal was observed not only when the muscle contracted by an agonist of the surface receptor such as oxytocin, norepinephrine or carbachol but also by a phorbol ester that is believed to cause contraction in the cell by activating phosphorylation. 5. Thus, we conclude that Ca reversal is a universal phenomenon in smooth muscles.

Animals↗
PubMed1990

Effects of ouabain and EGTA on the inhibitory effect of Ca2+ on guinea pig stomach smooth muscle ('Ca reversal').

Guinea pig stomach smooth muscle is known to show sustained contraction when treated with carbachol (CCh) in Ca-free solution containing 2 X 10(-3) M EGTA ('Ca-free contraction'). After pretreatment of the muscle with a Ca antagonist (D-600, nicardipine or nifedipine), addition of 10(-4) M Ca2+ (pCa 4.0) relaxed this CCh-induced Ca-free contraction ('Ca reversal'), but without pretreatment with a Ca antagonist, Ca2+ evoked contraction. In a Ca buffer containing 2 X 10(-3) M EGTA, low concentrations of Ca2+, 10(-8)-3 X 10(-7) M (pCa 8.0-6.5), relaxed the Ca-free contraction dose dependently ('Ca reversal'), whereas concentrations higher than 10(-6) M Ca2+ (pCa 6.0-) reversed this relaxation back to contraction. EGTA at 5 X 10(-3) or 10(-2) M potentiated the Ca reversal, whereas no reversal occurred in a Ca buffer containing 10(-3) M EGTA. This Ca reversal was inhibited in K(+)-depleted, Ca-free solution and by ouabain in Ca buffer containing EGTA (5 X 10(-3) or 10(-2) M). These results show that Ca reversal of guinea pig stomach smooth muscle occurs at low concentrations of Ca2+ and that its mechanism is related to ouabain-sensitive processes, such as the function of Na(+)-K+ ATPase.

Animals↗
PubMed1990

Inhibitory effects of protein kinase inhibitors and cytoskeletal inhibitors on Ca2(+)-free contraction of rat uterus.

In rat uterine smooth muscle, sustained Ca2(+)-free contraction was observed by oxytocin in Ca2(+)-free solution. This Ca2(+)-free contraction was effectively inhibited by protein kinase inhibitors and cytoskeletal inhibitors but myosin-light chain kinase (MLCK) inhibitors were not so effective. Simultaneous addition of a protein kinase inhibitor and a cytoskeletal inhibitor caused synergistic inhibition. These results suggest that the mechanism for Ca2(+)-free contraction involves some protein kinase and cytoskeletal elements rather than MLCK.

Alkaloids↗
PubMed1990

[The method of esthetic crown restoration with composite resin jacket crown in primary molars].

The term "esthetics" has recently been also used in the dental field, and a field called esthetic dentistry is increasingly being noted. The number of not only adult but also pediatric patients who visit for treatment aiming at esthetic recovery is being increased. Inpedodontics, composite resin of the coronal color is generally used in the restoration of deciduous incisors. However, the method using metal crowns for the deciduous teeth is used for the deciduous molars at present. We applied a composite resin jacket crown to the deciduous molar in a way similar to that of esthetic crown restoration for the anterior teeth. The surgical procedure before crown preparation varied slightly according to the presence or absence of pulpal treatment of vital teeth and with non-vital teeth, but the application was performed as follows: 1) Desensitization of pulp, pulpal treatment and core construction. 2) Preparation of crown. 3) Selection, trial set and occlusal equilibration of a metal crown for the deciduous tooth. 4) Precision impression with a silicone impression material. 5) Removal of the metal crown for the deciduous tooth from the impression material. 6) Making of an under-cut to the abutment tooth on the buccal lingual side. 7) Filling of the impression with chemical polymerization resin. 8) Application of pressure in the oral cavity. 9) Adjustment of edge and crown forms. Thus, the preparation method for the composite resin jacket crown was relatively simple. Since this surgery, the patient has been followed up for 1 year and 6 months, and no specifically troublesome points have been observed clinically. The patient and her parents are satisfied with the results.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1989

Ca2+-independent contraction of uterine smooth muscle.

Rat uterine smooth muscle shows sustained contraction to oxytocin in Ca2+-free medium with EGTA, that is called "Ca-free contraction"(1). Participation of the rise in cytosolic free Ca2+ in this Ca-free contraction was tested. In Ca-free contraction, the cytosolic free Ca2+ level was not changed at all as measured with fura-2. Further, the chelation of cytosolic free Ca2+ with quin-2 did not at all affect Ca-free contraction. These results strongly suggest that Ca-free contraction is not triggered by Ca2+.

Aminoquinolines↗
PubMed1989

[Study on thermal pulp testing of immature permanent teeth].

The duration of reaction to cool stimulation was investigated in 185 normal maxillary right and left central and lateral incisors from 55 pediatric patients aged from 6 to 15 years, who were brought to the Department of Pedodontics of Nippon Dental University Hospital, and from 9 students aged from 19 to 20 years in the School of Dental Technology and Hygiene affiliated with Nippon Dental University by using Dichloro-Difluoro-Methane coolants [PULPER (G-C Dental Industrial Corp.) and PULPOFLUORANE (Septodont Co.)] in order to determine the efficacy of thermal pulp testing for mature and immature permanent teeth. The results obtained are as follows: 1) The mean duration of reaction to cool stimulation according to the type of teeth was 0.93 sec for the maxillary left lateral incisors, 0.91 sec for the maxillary left central incisors, 0.88 sec for the maxillary right central incisors and 0.95 sec for the maxillary right lateral incisors, showing no statistically significant difference in the duration between the tooth types. 2) The duration of reaction to cool stimulation according to age was shortened with aging except for the 6-year-old patients. 3) The patients were divided into those 10 years old or younger and those older than 10 years because the tooth roots of the maxillary anterior teeth are developed at 10 years of age. The mean duration of reaction to cool stimulation was 1.02 sec in the group with immature permanent teeth, which consisted of patients aged 10 years or younger, while it was 0.82 sec in the group with mature permanent teeth, which consisted of patients aged 11 years or older.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗