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Biomedical subjects

A Ishihara

Publications and source records attributed to A Ishihara.

At least 73 records · Page 4Linked to original sources
PubMed2000

Effect of hypobaric hypoxia on rat soleus muscle fibers and their innervating motoneurons: a review.

Mammalian skeletal muscle fibers are classified into three basic types based on their enzyme histochemical profiles: fast-twitch glycolytic (FG), fast-twitch oxidative glycolytic (FOG), and slow-twitch oxidative (SO) types. The type-shift of fibers from FOG to SO in the slow soleus muscle of rats occurs during postnatal growth. Our previous studies have demonstrated that hypoxic exposure inhibits a growth-related type-shift of fibers from FOG to SO in the rat soleus muscle, irrespective of the duration and age at which the animals are exposed to hypoxia. Our previous studies have also revealed that a high percentage of FOG fibers in the soleus muscle of the hypoxia-adapted rats is found only under hypoxic conditions. Furthermore, we have found that these adaptations in fibers of the rat soleus muscle correspond well with those in motoneurons at the ventral horn of the spinal cord that innervate the muscle fibers.

Adaptation, Physiological↗
PubMed2000

[Imaging studies and surgical approach to postoperative maxillary cysts].

Surgical treatment for postoperative maxillary cysts (POMC) can be performed using the peroral method, or the endonasal method which is less invasive. Recently, the percentage of cases in which the endonasal method is employed has increased with the widespread use of endoscopy and advancement in imaging techniques. However, the peroral method is still necessary in some cases. During the 5-year period from July 1994 to June 1999, we operated on 29 patients (31 sides) for POMC. The endonasal method was used for 22 sides, and the peroral method was needed for the remaining 9 sides. Following analysis of the CT scans and MR images, we concluded that it is difficult to employ the endonasal method in the following cases; 1) Cysts located in the lateral or anteroinferior portion of the maxillary sinus 2) Small cysts 3) Cysts with a bony wall.

Cysts↗
PubMed2000

[A 59-year-old woman with recurrent convulsive seizures, cerebral infarctions, dementia, and intracranial calcifications].

A 59-year-old woman with recurrent seizures and progressive dementia is reported. Her past history and familial history were unremarkable. She became short-tempered at 56 years old (Oct. 1991). She had the first seizure attack and was admitted to a hospital at March 4, 1993, with prolonged disturbance of consciousness and subsequent mental deterioration. Her brain CT showed multiple small calcifications in the subcortical white matter and pons. The laboratory data including blood count, serum chemistry, serological studies and CSF was normal. MRI and digital subtraction angiography of the cranial vessels were unremarkable. There was a decrease in accumulation in the right cerebral hemisphere on 123I IMP SPECT. Despite anti-convulsant therapy, she had recurrent seizures several times, with gradual worsening of her mental state. She had the latest seizure attack and was transferred to Matsusaka Chuo Hospital, on August 29, 1993. After the attack she had been in the apallic state, and died on Nov. 13, 1995. This case was discussed in a neurological CPC. The discussants suggested that the isolated angiitis of the central nervous system caused secondary seizures and cerebral infarctions. Post-mortem examination revealed the CNS findings of vasculitis at various stages, calcification or mineralization mainly in the subcortical white matter and pons, massive cerebral infarctions with massive exudate, fresh and old small bleedings and exudate around the inflamed or calcified vessels. The white matter degeneration resembled that of Binswanger leukoencephalopathy. The final pathological diagnosis was isolated angiitis of the central nervous system since there was no inflammatory changes or atherosclerotic change of the blood vessels in the extracranial organs.

Calcinosis↗
PubMed2000

[Intra-arterial infusion chemotherapy with docetaxel for locally advanced breast cancer and inflammatory breast cancer].

From 1998 to 2000, we performed neoadjuvant intra-arterial infusion chemotherapy using docetaxel (60 mg/m2) a few times with 5 patients with local advanced breast cancer and inflammatory breast cancer. Therapeutic effects included 3 cases of PR among the breast tumor patients and downstaging was obtained 2 cases. No critical side effects were found due to this chemotherapy. We could perform mastectomy in all the cases. We consider intra-arterial infusion using docetaxel to be highly effective with few side effects in cases of advanced breast cancer.

Adenocarcinoma↗
PubMed2000

Effects of 9 weeks of hindlimb unloading on motor performances in adult rats.

It has been reported that abnormal steps associated with an ankle hyper-extension during walking were observed in adult rats after 2 weeks of hindlimb suspension (Canu and Falempin, 1997 & 1998). But such phenomena were normalized after 7 days of reambulation recovery. Canu and Falempin (1996) suggested that the spinal cord has a capacity to generate a well-organized pattern of locomotion even after a period of muscle disuse. There are, however, no reports about the effects of more prolonged suspension on motor performances. In the present study, 7 weeks old male rats were hindlimb-unloaded by tail suspension for 9 consecutive weeks and landing performances in response to drop from head-down, head-up, or supine position were investigated during 8 weeks of recovery. Posture maintenance during right-left translation was also checked.

Animals↗
PubMed2000

Effects of 9 weeks hindlimb suspension on neuromuscular activity patterns in rat.

It is well known that gravitational unloading induces muscle atrophy associated with a shift of fiber type in slow-twitch muscle. Ishihara et al. (1996 & 1997) reported that 2 weeks of spaceflight caused a decrease in succinate dehydrogenase activities of ventral horn and dorsal root ganglion neurons in rats. Significant effects on motor performance are also induced in both human (Kozlovskaya et al., 1981) and rats (Canu and Falempin, 1997), but these changes are reversible. However, it is not known how neuromuscular function respond to long-term gravitational unloading. Therefore, the current study was carried out to investigate the effects of 9 weeks of hindlimb suspension on the neuromuscular function and mass in hindlimb muscles in rats.

Animals↗
PubMed2000

Responses of motor and sensory neurons of rodents to spaceflight.

Spinal motoneurons innervating skeletal muscles comprised predominantly of high oxidative fibers, i.e. slow oxidative and fast oxidative glycolytic, have higher oxidative enzyme activities than motoneurons innervating skeletal muscles comprised primarily of low oxidative fibers, i.e. fast glycolytic. These findings suggest that there is a close relationship between the oxidative phosphorylation capacity of a motoneuron and of the muscle fibers that it innervates. Since some skeletal muscles become faster and less oxidative after 4-14 days of spaceflight, it might be expected that oxidative enzyme activities in some motoneurons also may decrease after spaceflight. In addition, there is significant muscular atrophy after even short spaceflights and, therefore, it may be expected that some motoneurons associated with these muscles also would atrophy. In the present paper, we examine the issue of whether spaceflight induces changes in the oxidative enzyme activity and/or size of spinal motoneurons.

Animals↗
PubMed1999

The novel neuropeptide Y Y(1) receptor antagonist J-104870: a potent feeding suppressant with oral bioavailability.

Neuropeptide Y (NPY) is known to induce robust feeding through the action of NPY receptors in the hypothalamus. Among the subtypes of NPY receptors, Y(1) receptors may play a key role in feeding regulation. In the present study, we demonstrated that a novel Y(1) antagonist, J-104870, shows high selectivity and potency for the Y(1) receptor with an anorexigenic effect on NPY-mediated feeding. J-104870 displaced [(125)I]peptide YY (PYY) binding to cloned human and rat Y(1) receptors with K(i) values of 0.29 and 0.54 nM, respectively, and inhibited the NPY (10 nM)-induced increase in intracellular calcium levels (IC(50) = 3.2 nM) in cells expressing human Y(1) receptors. In contrast, J-104870 showed low affinities for human Y(2) (K(i) > 10 microM), Y(4) (K(i) > 10 microM), and Y(5) receptors (K(i) = 6 microM). In rat hypothalamic membranes, J-104870 also completely displaced the binding of [(125)I]1229U91, which is known to bind to the typical Y(1) receptor, with a high affinity (K(i) = 2.0 nM). Intracerebroventricular (ICV) injection of J-104870 (200 microg) significantly suppressed NPY (5 microg)-induced feeding in satiated Sprague-Dawley rats by 74%. Furthermore, ICV and oral administration of J-104870 (200 microg and 100 mg/kg, respectively) significantly suppressed spontaneous food intake in Zucker fatty rats. These findings suggested that J-104870 is a selective and potent nonpeptide Y(1) antagonist with oral bioavailability and brain penetrability. In addition, the anorexigenic effect of J-104870 clearly revealed the participation of the Y(1) receptor in NPY-mediated feeding regulation. The potent and orally active Y(1) antagonist J-104970 is a useful tool for elucidating the physiological roles of NPY in obesity.

Administration, Oral↗
PubMed1999

Expanded expression of heme oxygenase-1 (HO-1) in the hypothalamic median eminence of aged as compared with young rats: an immunocytochemical study.

This study was performed to examine the differences in expression of heme oxygenase protein with age using immunocytochemistry. We compared the contents of HO-1 and HO-2 between young and aged rats using immunocytochemical methods. Stronger HO-1 expression was detected in the internal layer of the median eminence (ME) of aged than of young rats. Moreover, the cells expressing HO-1 were larger in the aged than the young animals. Electron microscopy indicated these cells with HO-1-like immunoreactivity (HO-1-LI) to be astrocytes. These findings suggested that the expression of HO-1 increased in the ME with age. The significance of this increased expression of HO-1 with age will be discussed briefly.

Aging↗
PubMed1999

Regulation of cell movement is mediated by stretch-activated calcium channels.

Intracellular calcium regulates many of the molecular processes that are essential for cell movement. It is required for the production of actomyosin-based contractile forces, the regulation of the structure and dynamics of the actin cytoskeletons, and the formation and disassembly of cell-substratum adhesions. Calcium also serves as a second messenger in many biochemical signal-transduction pathways. However, despite the pivotal role of calcium in motile processes, it is not clear how calcium regulates overall cell movement. Here we show that transient increases in intracellular calcium, [Ca2+]i, during the locomotion of fish epithelial keratocytes, occur more frequently in cells that become temporarily 'stuck' to the substratum or when subjected to mechanical stretching. We find that calcium transients arise from the activation of stretch-activated calcium channels, which triggers an influx of extracellular calcium. In addition, the subsequent increase in [Ca2+]i is involved in detachment of the rear cell margin. Thus, we have defined a mechanism by which cells can detect and transduce mechanical forces into biochemical signals that can modulate locomotion.

Animals↗
PubMed1999

Metabolic and morphological stability of motoneurons in response to chronically elevated neuromuscular activity.

The purpose of this study was to determine the plasticity of spinal motoneuron size and succinate dehydrogenase activity in response to increased levels of neuromuscular activation and/or increased target size. The plantaris muscles of adult rats were functionally overloaded for one or 10 weeks via the removal of the soleus and gastrocnemius muscles bilaterally. In addition, one group of functionally overloaded rats at each time period was trained daily (1 h/day) on a treadmill. The plantaris muscle on one side in each rat was injected with the fluorescent tracer Nuclear Yellow two days prior to the end of the study to retrogradely label the associated motor pool. At one week, the plantaris weight was increased compared to control, whereas there was no change in motoneuron size. Succinate dehydrogenase activity was unaffected in either the muscle or motoneurons. At 10 weeks, the plantaris muscle weight was larger and the succinate dehydrogenase activity lower in the functionally overloaded rats compared to age-matched controls. Training further increased the hypertrophic response, whereas the succinate dehydrogenase activity returned to control levels. In contrast, mean motoneuron size and succinate dehydrogenase activity were similar among the three groups. These data indicate that overload of a specific motor pool, involving both an increase in activation and an increase in target size, had a minimal effect on the size or the oxidative potential of the associated motoneurons. Thus, it appears that the spinal motoneurons, unlike the muscle fibers, are highly stable over a wide range of levels of chronic neuromuscular activity.

Animals↗
PubMed1999

Effects of ovariectomy on bone morphology in maxillae of mature rats.

Postmenopausal oestrogen deficiency results in bone loss (osteoporosis) in humans and experimental animals. The loss of trabecular bone in the ovariectomized (OVX) rat provides a useful experimental model of post-menopausal osteoporosis. At 5 months after ovariectomy of 3-month-old female rats, the mid and distal femurs and maxillae were dissected and processed for quantitative backscattered electron microscopic examinations. Histomorphometric analysis of femurs in OVX rats showed significant loss in metaphyseal trabecular bone areas compared with sham-operated controls; no significant bone loss was observed in the cortical bone areas of mid-diaphyses in OVX rats. Net bone areas in the maxillae of OVX rats was similar to that of sham-operated controls. Bone structure of maxillae in OVX rats was also similar to that in controls. Our results suggest that, in this animal model of osteoporosis, prominent bone loss occurs mainly in the bone areas formed by endochondral ossification such as distal femurs, but those areas formed by intramembranous ossification such as mid-femurs and maxillae sustained less effects by OVX.

Animals↗
PubMed1999

Succinate dehydrogenase activities of fibers in the rat extensor digitorum longus, soleus, and cardiac muscles.

Succinate dehydrogenase (SDH) activities and cross-sectional areas (CSAs) of different types of fibers in the superficial (EDLs) and deep (EDLd) regions of the extensor digitorum longus and soleus (SOL) muscles and the left ventricular muscle of the heart (HEART) of 10-week-old male rats were determined using quantitative histochemistry and a computer-assisted image processing system. The fibers were classified as type I, type IIA, type IIB, or type IIC according to their histochemically assessed adenosine triphosphatase activities. The mean SDH activity was higher and the mean CSA was smaller in type IIA fibers than in type IIB fibers in both the EDLs and EDLd. The mean SDH activity of type IIA fibers in the SOL was higher than that of type I fibers. Fibers in the HEART showed the highest mean SDH activity and the smallest mean CSA among all fiber types in the muscles examined. There was an inverse correlation between CSA and SDH activity for the different fiber types in different muscles. These data suggest that the SDH activity of fibers in muscle is fiber type- and size-specific, and that the highest SDH activity of fibers in the left ventricular muscle of the heart contributes to their functional properties, i.e., high fatigue resistance.

Animals↗