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Biomedical subjects

K Arita

Publications and source records attributed to K Arita.

At least 127 records · Page 7Linked to original sources
PubMed1995

Effect of cabergoline, a dopamine agonist, on estrogen-induced rat pituitary tumors: in vitro culture studies.

Cabergoline (CG) is a dopamine agonist that inhibits secretion of prolactin (PRL) and growth hormone. The purpose of this study was to investigate the PRL-lowering effect and antitumor effect of CG on estradiol-induced rat pituitary tumors in vitro and to elucidate these mechanisms. We compared the effects of CG with those of bromocriptine (BC) in terms of the inhibition of hormone secretion as well as antitumor effects on rat pituitary tumors. Primary cultures of dissociated pituitary tumor cells were used in these studies. A significant inhibition of prolactin (PRL) secretion was observed for both drugs within 12 h after treatment, and the inhibitory effects of CG and BC were antagonized by sulpiride or haloperidol. Inhibitory effect on PRL secretion after 12-h BC or CG pretreatment was more pronounced with CG than BC treatment at all time points. PRL secretion in group pretreated with CG was significantly suppressed at 72 h when compared to that of vehicle. Inhibition of de novo PRL synthesis was better demonstrated in the CG group. These findings suggest that CG has a higher affinity for the D2 receptor of pituitary cells as compared to BC and may preferentially inhibit PRL secretion rather than PRL production. An antitumor effect of CG has been confirmed at a lower dosage than that of BC.

Animals↗
PubMed1995

Anterior pituitary function in patients with nonfunctioning pituitary adenoma: results of longitudinal follow-up.

Studies of anterior pituitary function in patients treated for nonfunctioning pituitary adenomas have been limited by their short duration. The purpose of the present study was to examine pituitary function longitudinally among three types of patients: those with complete tumor removal (group A); those with subtotal or partial adenomectomy (group B); and those in group B who underwent additional radiation therapy (group C). The subjects were 33 patients whose anterior pituitary function was evaluated by provocative tests such as insulin induced hypoglycemia, thyrotropin releasing hormone administration test and luteinizing hormone releasing hormone administration test. They underwent preoperative evaluation and postoperative reevaluations at 2 weeks, 3 months, 6 months and annually thereafter, for over 10 years. Anterior pituitary function was restored within a year after surgery, if at all. No additional function was restored after one year from treatment. In group A, no one developed impairment of anterior pituitary function after one year from surgery. In group B, however, new impairment was noted at intervals, due to tumor regrowth. In Group C, deficiencies developed after one year, irrespective of tumor regrowth. In conclusion, lifelong endocrinological follow-up is recommended for patients receiving postoperative irradiation, and for patients with potential for tumor regrowth. On the other hand, patients with total adenomectomy may be exempted from periodic endocrinological follow-up if they do not need postoperative hormonal replacement therapy.

Adenoma↗
PubMed1995

Secretion of growth hormone (GH)-releasing hormone by GH-producing pituitary adenoma assessed by cell immunoblot analysis.

To detect growth hormone-releasing hormone (GHRH) secreted by monodispersed human GH-producing pituitary adenoma cells, the cell immunoblot assay was performed. GHRH-secreting cells were observed in 3 cases of GH-producing pituitary adenomas. The incidence of GHRH-secreting cells in the total cell populations was 0.24-3.42%. By contrast, no GHRH-secreting cells were observed in 2 cases of clinically nonfunctioning pituitary adenomas. The findings obtained by immunohistochemical studies for adenohypophysial hormones and for nuclear antigens of proliferative activity revealed that the incidence of GHRH-secreting cells is more related to the frequency of GH cells than to the proliferative activity in GH-producing pituitary adenomas.

Adenoma↗
PubMed1995

Changes of motor evoked potentials in global and focal ischemic models of cats.

In order to evaluate the significance of motor evoked potentials (MEPs) in central nervous system monitoring, the authors conducted two sets of experiments using feline ischemic models. Twenty-three adult mongrel cats were divided into two groups: global (n = 9) and focal ischemic (n = 14) groups. In the case of global ischemia, which was induced by hypovolemic hypotension due to blood letting, deterioration of the D wave began when the mean arterial blood pressure (MABP) approached 45 mmHg, and regional cerebral blood flow (rCBF) dropped to 40% of control. Complete disappearance of the D wave was observed below 30 mmHg in MABP and 20% of control in rCBF. In the case of focal ischemia, which was induced by transorbital occlusion of the middle cerebral artery, the percentages of rCBF at which the D wave disappeared ranged from 9 to 20%. Changes in the amplitude of the D wave--an increase and following decrease--preceded the prolongation of its latency. In contrast with the D wave I waves were too easily affected by ischemia. Moreover, rCBF at the point of disappearance of the I wave varied greatly. In conclusion, the D wave is stable in mild ischemia and is a reliable indicator of critically profound ischemia (%rCBF < 40%). Monitoring the D wave of MEPs seems to be a useful method for avoiding the deterioration of motor function by ischemic insult.

Animals↗
PubMed1995

[A case of pineal germinoma presenting with severe amnesia].

Patients who have a pineal germinoma usually present with symptoms of intracranial hypertension or disturbances in vertical ocular motion but rarely present with amnesia. We recently encountered a case of pineal germinoma accompanied by severe amnesia, but not by hydrocephalus. A 32-year-old, right-handed man was admitted with severe memory disturbance which had gradually worsened in the preceding three months. On admission, he was alert and cooperative. His speech was well preserved and not fabricated. He had neither symptoms of intracranial hypertension or visual disturbance. There was no manifestation of interhemispheric disconnection symptoms. His immediate and semantic memory was preserved, however, his recent and antegrade episodic memory was severely impaired. The amnesia involved both verbal and visual modalities. He could recall only 1 out of 5 objects in 5 minutes. He was orientated to people, but not to time and place. And his motivation was severely affected. Magnetic resonance imaging (MRI) showed a heterogeneously enhanced tumor in the splenium and pineal body that extended into the bilateral ventricular trigon through major forceps and was accompanied by edema in the retrosplenial region. The bilateral crura of the fornix was obscured by the tumor. The enlarged pineal body was slightly compressing the upper colliculus but hydrocephalus was not observed. The tumor, which was partially excised through a right parietal corticotomy, had features typical of a germinoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

MRI of pituitary adenomas: the position of the normal pituitary gland.

The position of the normal pituitary gland, assessed using gadolinium - enhanced MRI was compared with the position found at surgery for pituitary adenoma in 25 patients. The tumours were five microadenomas and 20 macroadenomas. Using T1-weighted imaging, the anterior lobe could be differentiated on the sagittal image in five patients (20%) and on the coronal image in four (16%). The high intensity of the posterior lobe could be differentiated using T1-weighted sagittal imaging in 13 patients (52%). The normal pituitary gland, which enhanced more strongly than tumour, could be differentiated using Gd-DTPA-enhanced MRI on the sagittal images in 22 cases (88%) and on the coronal image in 17 (68%). In seven patients, the normal pituitary gland surrounded the tumour; it was displaced superiorly in 14 cases and superioposterorly in two but in no case was it displaced anteriorly or downwards.

Adenoma↗
PubMed1994

Displacement of the normal pituitary gland by sellar and juxtasellar tumours: surgical-MRI correlation and use in differential diagnosis.

We compared the position of the normal pituitary gland as estimated by gadolinium (Gd)-DTPA-enhanced MRI, with its position at surgery in 40 patients with intra- and juxtasellar tumours: 22 pituitary adenomas, 4 craniopharyngiomas, 7 meningiomas, 2 germinomas, and 5 Rathke cleft cysts. In 37 of these, the normal gland showed more intense contrast enhancement than the adjacent tumour, from which it could be differentiated by Gd-DTPA-enhanced MRI, especially in the sagittal plane. The direction of displacement of the normal pituitary gland correlated well with tumour type, so that its position proved helpful in the differential diagnosis. The normal gland was typically displaced superiorly by pituitary adenomas, inferiorly by craniopharyngiomas, and anteriorly by germinomas. It showed variable displacement by Rathke cleft cysts, and was not usually displaced by meningiomas.

Adenoma↗
PubMed1994

Clinical evaluation of 33 patients with histologically verified germinoma.

We evaluated 33 patients with histologically verified germinoma between 1978 and 1992. The patients consisted of 23 men and 10 women between 6 and 32 years of age. All patients underwent either biopsy, partial resection, or total resection. All patients received radiotherapy, and all had a complete remission. Recurrence occurred in three patients. Two recurrences were outside of the irradiated area. Though there were four deaths, none were caused by germinoma. Three resulted from the inadequate hormonal replacement. Accurate staging of patients with germinoma using magnetic resonance imaging (MRI), including whole spinal MRI, and development of a radiochemotherapy or chemotherapy method that preserves the hypothalamic-pituitary axis function are needed.

Adolescent↗
PubMed1994

A case of Cushing's disease accompanied by Rathke's cleft cyst: the usefulness of cavernous sinus sampling in the localization of microadenoma.

A 42-year-old man presented with classical symptoms of Cushing's disease. Endocrinological examinations indicated the presence of a adrenocorticotropin-(ACTH) producing pituitary adenoma. Magnetic resonance imaging showed a cystic sellar lesion, which had features of a Rathke's cleft cyst, whereas the adenoma was not depicted. The ratio of blood ACTH concentration between cubital vein, left, and right cavernous sinus was 1: 1.4: 20. During transsphenoidal surgery, in addition to the Rathke's left cyst, a tiny adenoma was detected beneath the left pituitary lobe. Cavernous sinus sampling is a useful auxiliary in the localization of an ACTH-producing adenoma, as in this case.

Adenoma↗
PubMed1994

Comparison of three-dimensional phase-contrast magnetic resonance angiography with three-dimensional time-of-flight magnetic resonance angiography in cerebral aneurysms.

Magnetic resonance angiography (MRA) can be divided into two types: namely, the phase-contrast (PC) method and the time-of-flight (TOF) method. The purpose of this study is to determine which method is better suited to demonstrate cerebral aneurysms. In a total of 27 cerebral aneurysms confirmed by cerebral angiography, both three-dimensional (3-D) PC and 3-D TOF methods were performed, and the corresponding findings were compared with conventional cerebral angiographic findings. Aneurysm visualization was grouped into three categories: "good" when clearly distinguishable, "fair" if distinguishable when reconstructed, and "poor" if completely undistinguishable. All MRAs were independently interpreted by two neurosurgeons in our institute. Sensitivity was 92.6% when MRA was performed with the TOF method, whereas it was 70.4% when performed with the PC method. In conclusion, the TOF method was more useful for demonstrating the aneurysms than the PC method due to its higher spatial resolution and shorter imaging time.

Adult↗
PubMed1994

Effect of vinconate on long-term potentiation in a mossy fiber-CA3 system of guinea pig hippocampal slices.

We investigated the effect of vinconate on the long-term potentiation of population spikes following the stimulation of mossy fibers in the CA3 pyramidal layer of hippocampal slices from guinea pig brain. Vinconate (10(-7) and 10(-6) M) dose-dependently augmented the long-term potentiation in the mossy fiber-CA3 system. This effect was reduced by treatment with scopolamine at a concentration of 10(-6) M, which showed no significant change in the long-term potentiation in a mossy fiber-CA3 system. These results suggest that vinconate may augment long-term potentiation in the mossy fiber-CA3 system partly via activation of the cholinergic system.

Animals↗
PubMed1994

Pituitary function in patients with Rathke's cleft cyst: significance of surgical management.

The pituitary function of patients with Rathke's cleft cyst before and after surgery was investigated to clarify the significance of surgery and operative indications. The authors have treated 19 patients with Rathke's cleft cyst. There were panhypopituitarism in 2 patients (11%), amenorrhea and/or galactorrhea in 3 (16%), diabetes insipidus in 4 (21%), and visual disturbance in 9 (47%). All the patients underwent systematic endocrinological examination and were found to have various degrees of pituitary dysfunction. Panhypopituitarism was endocrinologically confirmed in 2 patients. Hyperprolactinemia was observed in 4. These patients underwent aspiration of the cyst contents and biopsy of the cyst wall. Postoperative follow-up endocrinologic evaluation performed more than 3 months after surgery showed improvement in pituitary function in 9 out of 13 patients (69%). Amenorrhea and/or galactorrhea recovered or improved in 100% of patients and visual disturbance improved in 89%. However, diabetes insipidus and panhypopituitarism did not improve postoperatively, in any patient. The results of the present study indicate that the incidence of pituitary dysfunction in patients with Rathke's cleft cyst is higher than suspected and in most cases surgical intervention improves pituitary function and the clinical status of the patient. Therefore, surgical treatment is recommended even when the patient has only mild symptoms or signs, including pituitary dysfunction, to prevent irreversible panhypopituitarism.

Adolescent↗
PubMed1994

Germinoma of the medulla oblongata--case report.

A 32-year-old female presented with medulla oblongata germinoma manifesting as numbness in the extremities. Computed tomography demonstrated a mass in the medulla oblongata expanding into the fourth ventricle. The tumor was partially removed. Immunohistochemical staining of the tumor specimen demonstrated large epithelioid cells positive for placental alkaline phosphatase, and syncytiotrophoblastic cells positive for beta subunit of human chorionic gonadotropin. Some epithelioid cells were also positive for cytokeratin. She received 44 Gy of irradiation to the posterior fossa and 20 Gy whole spinal irradiation. No signs of recurrence have occurred for 9 years. Patients with medulla oblongata germ cell tumor are comparatively older than those with other intracranial germ cell tumors and have two X chromosomes. All tumors were diagnosed as germinoma, and caused symptoms of involvement of the lower cranial nerves and the lower brain stem without pyramidal tract signs.

Adult↗
PubMed1994

[Late phase II clinical study of RP56976 (docetaxel) in patients with non-small cell lung cancer].

A late phase II clinical study of RP56976 (Docetaxel) was conducted in patients with non-small cell lung cancer. Patients with non-small cell lung cancer in Stage IIIB and Stage IV not previously treated were enrolled. Docetaxel was administered at a dose of 60 mg/m2 based on the results of a phase I and an early phase II clinical study, and the efficacy and safety were examined. Of the 77 patients enrolled, 72 patients were evaluated to have completed the scheduled course of treatment by the Evaluation Committee. A partial response (PR) was seen in 18 patients, and the overall response rate was 25.0%. The response rate classified by clinical stage was 28.0% (7/25) in patients with Stage IIIB and 23.4% (11/47) in patients with Stage IV. Hematological adverse reactions included leukopenia of Grade III or more in 53.3% (40/75) and neutropenia of Grade III or more in 86.7% (65/75) as specified in the Adverse Event Reporting Form proposed by the Japan Society for Cancer Therapy. Other major adverse reactions included alopecia, asthenia, and fever, all of which were tolerable. From these results, the efficacy of docetaxel for the treatment of non-small cell lung cancer was confirmed.

Adolescent↗
PubMed1994

[Clinical efficacy of arbekacin in deep MRSA infection. Including follow-up study after the termination of chemotherapy].

We analyzed the efficacy of arbekacin (ABK) using monotherapy or combined therapy on deep MRSA infection to find the most adequate usage of the drug. We also followed-up the isolation incidence of MRSA after the end of chemotherapy. The results are summarized as follows: 1. Clinical efficacy of ABK on 29 pneumonia and 3 septicemia due to MRSA was 42.9% in ABK monotherapy (9 patients), 62.5% in combined therapy with ABK and minocycline (9 patients), 100% with ABK and imipenem/cilastatin (IPM/CS) (7 patients), and 100% with ABK and other drugs (7 patients). 2. As for microbiological efficacy, combined therapy with ABK and IPM/CS or other drug was superior to other methods. Among patients from whom two or more species of bacteria were isolated, causative bacteria persisted in many cases, and some replacements occurred. 3. Kidney functions deteriorated in two patients that underwent monotherapy or combined therapy with ABK and IPM/CS, but they recovered when therapy was completed the completion. 4. In the three month follow-up study after ABK therapy, we found four cases of renewed infections after disappearance of MRSA. When just decreases in the number of MRSA resulted upon the chemotherapy, the relapse occurred in all cases. 5. Above results indicate that ABK is effective in MRSA infection, and combined therapy with beta-lactams is superior to other methods in serious MRSA infections. We also suggest that chemotherapy should be continued until the complete disappearance of MRSA is achieved.

Adult↗