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Biomedical subjects

T Hirata

Publications and source records attributed to T Hirata.

At least 199 records · Page 11Linked to original sources
PubMed1996

Surgical treatment for invasive thymoma, especially when the superior vena cava is invaded.

BACKGROUND: We analyzed the operative outcome of extensive surgery for invasive thymoma, especially in those with thymomas invading the superior vena cava, the left innominate vein, or both. METHODS: We treated 41 patients with invasive thymoma, including 34 stage III, 5 stage IVa, and 2 stage IVb thymomas. Thirty-eight patients received radiotherapy preoperatively or postoperatively. In 12 patients with invasion of the superior vena cava or innominate vein, we performed angioplasty, reconstruction, or both. RESULTS: The overall 5-year survival rate was 77% and the 10-year survival rate was 59%. In the stage III group, there was a significant difference between those with complete and those with incomplete resection. Ten of 12 patients who had angioplasty with or without reconstruction of the superior vena cava or innominate vein survived without recurrence of the tumors. CONCLUSION: Angioplasty and vascular reconstruction are recommended because successful treatment for invasive thymomas depends on complete resection of the tumors.

Adolescent↗
PubMed1996

Effective 30-hour preservation of canine lungs with modified ET-Kyoto solution.

BACKGROUND: With the aim of developing a preservation solution that can preserve donor lungs reliably for a long time, we prepared a modified ET-Kyoto solution by adding N-acetylcysteine, nitroglycerin, and dibutyryl adenosine 3', 5'-cyclic phosphate to the previously reported ET-Kyoto solution, which contains trehalose, gluconate, and hydroxyethyl starch. In this study, we examined the efficacy of modified ET-Kyoto solution in 30-hour lung preservation. METHODS: Twenty five pairs of adult mongrel dogs were divided into four groups. Donor lungs were flushed with modified ET-Kyoto solution (n = 9), with ET-Kyoto solution (n = 6), with University of Wisconsin solution group (n = 6), or with ET-Kyoto solution plus the solvents of nitroglycerin (ethanol and propylene glycol) (n = 4), then stored at 4 degrees C for 30 hours. All animals were treated with prostaglandin E1. Left lungs were transplanted and reperfused for 6 hours. RESULTS: With respect to arterial oxygen tension, peak inspiratory pressure, and wet-to-dry lung weight ratio, modified ET-Kyoto solution was significantly superior to ET-Kyoto solution. The modified ET-Kyoto solution was significantly superior to University of Wisconsin solution with respect to survival rate, arterial oxygen tension, and wet-to-dry lung weight ratio. Ultrastructural findings supported these results. CONCLUSIONS: These results suggest that modified ET-Kyoto solution is superior to University of Wisconsin solution for 30-hour lung preservation.

Acetylcysteine↗
PubMed1996

Inhibition of glutamine synthetase reduces ammonia-induced astrocyte swelling in rat.

Astrocyte hypertrophy and swelling occur in a variety of pathophysiological conditions, including diseases associated with hyperammonemia. Ammonia is rapidly incorporated into glutamine by glutamine synthetase localized in astrocytes. We tested the hypotheses that (1) 6 h of hyperammonemia (500-600 microM) is adequate for producing astrocyte enlargement, and (2) astrocyte enlargement is attenuated by inhibition of glutamine synthetase with methionine sulfoximine. Pentobarbital-anesthetized rats received an intravenous infusion of either sodium or ammonium acetate after intraperitoneal pretreatment with vehicle, methionine sulfoximine (0.8 mmol/kg) or buthionine sulfoximine (4 mmol/kg), an analogue that does not inhibit glutamine synthetase. Hyperammonemia produced enlarged cortical astrocytes characterized by (1) decreased electron density of cytoplasmic matrix in perikaryon, processes and perivascular endfeet, (2) increased circumference of nuclear membrane, (3) increased numbers of mitochondria and rough and smooth endoplasmic reticulum in perikarya and large processes, and (4) less compact bundles of intermediate filaments. Pretreatment with methionine sulfoximine, but not buthionine sulfoximine, attenuated the decrease in cytoplasmic density and the increase in nuclear circumference; most perivascular endfeet remained as dense as occurred with sodium acetate infusion. However, increased numbers of organelles in expanded perikarya and large processes occurred after methionine sulfoximine treatment with and without ammonium acetate infusion. In separate groups of rats, hyperammonemia produced an increase in cortical tissue water content which was inhibited by methionine sulfoximine, but not buthionine sulfoximine. We conclude that clinically-relevant levels of hyperammonemia can cause astrocyte enlargement within 6 h in vivo characterized by both watery cytoplasm and increased organelles indicative of a cellular metabolic stress and altered astrocyte function. The watery cytoplasm component of astrocyte enlargement depends on glutamine synthesis rather than on ammonium ions per se, and is possibly caused by the osmotic effect accumulated glutamine.

Ammonia↗
PubMed1996

A newly developed solution enhances thirty-hour preservation in a canine lung transplantation model.

Ischemia and reperfusion cause the production of oxygen free radicals. These damage grafts or disrupt normal vascular homeostatic mechanisms, with a parallel reduction in endothelial nitric oxide and adenosine 3',5'-cyclic monophosphate levels. We hypothesized that lung preservation failure may be related to these events. To improve lung preservation, we prepared a new ET-Kyoto solution, which contains N-acetylcysteine (a radical scavenger), nitroglycerin (to elevate the nitric oxide level), and dibutyryl adenosine 3',5'-cyclic monophosphate (to elevate the adenosine 3',5'-cyclic monophosphate level) and examined its efficacy in a canine single-lung transplantation model. Lungs were flushed with new ET-Kyoto solution (group I, n = 9), basal ET-Kyoto solution (group II, n = 6), basal ET-Kyoto solution plus ethanol and propylene glycol (solvents of nitroglycerin; group III, n = 6), or low-potassium dextran glucose solution (group IV, n = 6), and stored at 4 degrees C for 30 hours. After left single-lung transplantation, the right main bronchus and right pulmonary artery were ligated and the functions of the transplanted lung were assessed for 6 hours. Arterial oxygen tension was significantly higher in group I than in groups II, III, and IV (p < 0.05). Peak inspiratory pressure and wet-to-dry lung weight ratio were significantly lower in group I than in groups II and IV (p < 0.01). Histologic and ultrastructural studies showed better preservation in group I than in groups II, III, and IV. We conclude that the new ET-Kyoto solution provides enhanced 30-hour lung preservation.

Animals↗
PubMed1996

Immunological and chemical types of reversible hypothyroidism; clinical characteristics and long-term prognosis.

OBJECTIVE: Spontaneous improvement occurs in about one-half of patients with primary hypothyroidism who reside in an iodine-sufficient area of Japan, but the pathogenetic factors related to reversible hypothyroidism are still not fully understood. We therefore investigated the clinical features and prognosis of patients with reversible hypothyroidism with or without iodine excess and antithyroid antibodies. DESIGN: Amelioration of hypothyroidism was diagnosed when the elevated serum TSH concentrations (serum TSH concentration > or = 40 mU/l) decreased by 50% or more during an iodine restriction period of 2-15 weeks without replacement therapy. Reversible hypothyroidism occurred in a post-partum group (n = 20) and a non-post-partum group (n = 91). The latter was then further classified into chemical (n = 28), immunological (n = 20), and mixed (n = 43) groups, according to the presence of iodine excess (serum non-hormonal iodine level > 50 micrograms/l or a history of excess iodine ingestion), antithyroid autoantibody, or both, respectively. MEASUREMENTS: Clinical characteristics and long-term prognosis were compared among the four groups. The rate at which hypothyroidism recovered was expressed as the number of days required for a 50% decrease in the serum TSH concentration. The level of thyroid echogenicity was measured by 10-MHz ultrasonography. RESULTS: In the chemical group, the mean age, male:female ratio, and serum non-hormonal iodine concentrations were all higher than those in the immunological group. The estimated rate at which hypothyroidism recovered was rapid (6.1 +/- 3.1 (mean +/- SD) days), the levels of thyroid echogenicity were near normal, and a histological examination (n = 7) revealed either colloid goitre or a normal thyroid in the chemical group. In the immunological and post-partum groups, the recovery rate was slow (16.8 +/- 9.6 days and 16.2 +/- 5.8 days, respectively). The levels of thyroid echogenicity were markedly reduced but increased after the spontaneous recovery of the thyroid function in both groups. Aspiration cytology suggested lymphocytic infiltration in all patients examined in the immunological (n = 6) and post-partum groups (n = 4). Relapse to overt hypothyroidism was observed more frequently in the immunological (38%) and mixed groups (35%) than in the chemical group (5%). CONCLUSION: Thyroid damage was more severe, recovery slower and the rate of relapse higher in the immunological than in the chemical type of reversible hypothyroidism.

Adult↗
PubMed1996

Association between family history and gastric carcinoma among young adults.

The relationship between family history of gastric carcinoma and gastric carcinoma in Japanese under 40 years of age was analyzed. The subjects were 108 gastric carcinoma patients (86% were diffuse type) at 9 hospitals in the Kanto area of Japan. Firstly, incidence of gastric carcinoma among the parents of the subjects were compared with that in the general population. Observed/expected (O/E) ratios (P-value) were 1.8 (0.06) for all subjects, 1.3 (0.62) for male subjects, 2.1 (0.04) for female subjects, 0.5 (0.41) for early carcinoma, 2.6 (P<0.01) for advanced carcinoma, 2.3 (0.22) for intestinal-type carcinoma and 1.7 (0.13) for diffuse-type carcinoma. Association between gastric carcinoma and parents' history of gastric carcinoma was strong among women and regarding advanced carcinoma, and the difference in O/E ratios between early and advanced carcinoma was remarkable. Secondly, factors related to advanced-stage gastric carcinoma were analyzed. Histological type (diffuse and intestinal types) was not related, but family history of gastric carcinoma among parents and grandparents was related to advanced stage, and the relationship was independent of other factors. The odds ratio (95% confidence interval) was 3.3 (1.1-9.9). Family history may be related to stage of gastric carcinoma through its relationship to the manner or speed of the tumor's progression. We hypothesis that some genetic factor exists which is involved both in progression from early to advanced stage and in occurrence of gastric carcinoma.

Adolescent↗
PubMed1996

Association between thyroid cancer of cribriform variant and familial adenomatous polyposis.

A case of a 20 year old Japanese woman who developed thyroid cancer exhibiting unusual cribriform structures while being followed up for familial adenomatous polyposis/Gardner's syndrome is reported. The patient presented with osteomas, pigmented retinal lesions, and adenomas of the duodenum and the papilla of Vater, in addition to numerous adenomatous polyps in the colorectum. On ultrasonography, the thyroid cancer was localised to the right lobe and was identified as an irregular, internal echo tumour with a peripheral hypoechoic zone, measuring 1.8 cm in diameter. Histological examination of the resected tumour showed a concomitance of papillary proliferation and cribriform structures with follicles of varying sizes. These features can be distinguished from sporadic thyroid cancer.

Adenocarcinoma↗
PubMed1996

Impaired pial arteriolar reactivity to hypercapnia during hyperammonemia depends on glutamine synthesis.

BACKGROUND AND PURPOSE: Acute hyperammonemia causes glutamine and water accumulation in astrocytes and loss of the cerebral blood flow response selectively to CO2. We tested whether extraparenchymal pial arterioles not subjected directly to mechanical compression by swollen astrocyte processes also lose hypercapnic reactivity and whether any such loss can be attenuated by inhibiting glutamine synthesis during hyperammonemia. METHODS: Pentobarbital-anesthetized rats were pretreated intravenously with either saline vehicle, methionine sulfoximine (0.83 mmol/kg), which inhibits glutamine synthetase and potentially gamma-glutamylcysteine synthetase, or buthionine sulfoximine (4 mmol/kg), which inhibits gamma-glutamylcysteine synthetase. Three hours after pretreatment, cohorts received an intravenous infusion of either sodium or ammonium acetate for 6 hours. Pial arteriolar diameter was measured with radiolabeled microspheres during normocapnia and 10 minutes of hypercapnia. RESULTS: With sodium acetate infusion, pial arteriolar diameter increased during hypercapnia in groups pretreated with vehicle (23+/-3% [mean+/-SE]; n=6), methionine sulfoximine (37+/-11%; n=5), and buthionine sulfoximine (32+/-3%; n=5). With ammonium acetate infusion, pial arteriolar diameter increased only in the group pretreated with methionine sulfoximine (31+/-4%; n=8) but not in those pretreated with vehicle (-2+/-4%; n=8) or buthionine sulfoximine (4+/-4%; n=6). Methionine sulfoximine, but not buthionine sulfoximine, also prevented loss of the cerebral blood flow response to hypercapnia, an increase in cortical tissue water content, and an increase in pressure under the cranial window during normocapnia in hyperammonemic rats. In contrast to hypercapnia, hypoxemia increased arteriolar diameter 30+/-7% (n=5) during ammonium acetate infusion. CONCLUSIONS: Loss of the blood flow response to hypercapnia during acute hyperammonemia is not due simply to swollen astrocyte processes passively impeding blood flow because extraparenchymal resistance arterioles also lose their reactivity selectively to hypercapnia. Lost reactivity depends on glutamine synthesis rather than on ammonium ions per se and may reflect indirect effects of astrocyte dysfunction associated with glutamine accumulation or possibly effects of glutamine on nitric oxide production.

Acetates↗
PubMed1996

Dermatofibrosarcoma protuberans. CT findings with pathologic correlation in 6 cases.

PURPOSE: To characterize the CT findings of dermatofibrosarcoma protuberans. MATERIAL AND METHODS: CT and pathologic specimens of 6 patients with dermatofibrosarcoma protuberans (5 in the trunk and 1 in the leg) were retrospectively reviewed. RESULTS: CT clearly defined the tumors in the dermis and subcutaneous tissue with a characteristic, if not pathognomonic, protrusion. On postcontrast CT, 3 tumors showed marginal enhancement and central low density, while the others showed homogeneous enhancement. Pathologically, the marginal enhancement on CT corresponded to fibrosarcomatous changes, and the central low density to necrosis. The tumors with homogeneous enhancement had no sarcomatous changes. CONCLUSION: CT allows detection and precise anatomic localization of dermatofibrosarcoma protuberans. Marginal enhancement with central low density on CT may suggest a relatively poor prognosis.

Adult↗
PubMed1996

Cervical discitis associated with spinal epidural abscess caused by methicillin-resistant staphylococcus aureus.

A 53-year-old male developed fever, nuchalgia, shoulder pain, and sore throat after a partial sigmoidectomy. He suffered sudden onset of quadriplegia about 5 days later. Magnetic resonance (MR) imaging indicated the characteristic appearance of C5-6 intervertebral disc herniation. However, anterior discectomy showed that he had cervical discitis associated with spinal epidural abscess. Continuous pus drainage from the abscess and vigorous antibiotic therapy were undertaken after surgery. He improved and could walk with assistance. MR imaging with gadolinium can be useful in diagnosing pyogenic spinal infection (epidural abscess, osteomyelitis, and discitis), but care should be taken in MR image interpretation since spinal epidural abscess associated with discitis may mimic disc herniation. Axial MR images are important to distinguish this rare disease from other cervical disorders.

Abscess↗
PubMed1996

Oxygen metabolism after cardiopulmonary bypass.

We hypothesized that the relationship between oxygen delivery (DO2) and oxygen consumption (VO2) in patients undergoing cardiopulmonary bypass (CPB) may differ from the normal physiologic state because of oxygen debts acquired during CPB. Blood gas analysis and hemodynamic parameters were repeatedly measured for determination of DO2 and VO2 in 40 patients undergoing CPB every 8 hours during the first 48 hours postoperatively. Twenty patients of acute myocardial infarction (AMI) also were studied in the same protocol as controls. In the CPB group, a regression analysis showed that VO2 was significantly dependent on DO2, even within the physiologic range of DO2 (>500 ml/min/m2); VO2=121+0.0844 DO2 (R=0.25, p=0.023). However, such supply-dependent oxygen consumption was not observed in the AMI patients. Perioperative parameters which had a significant relationship with oxygen extraction rate (VO2/DO2 x 100) were Hb concentration, cardiac index, systemic vascular resistance, age of the patients, duration of CPB, SaO2 and SvO2. These results suggest that patients undergoing CPB need a much higher oxygen supply to recover from the oxygen debt during open heart surgery.

Cardiopulmonary Bypass↗
PubMed1996

Dilation of gelatin-sealed knitted dacron prosthesis.

OBJECTIVE: Postoperative dilation of gelatin-sealed knitted dacron prostheses (Gelseal, Vascutek, Scotland UK) was studied. EXPERIMENTAL DESIGN: Prospective study. SETTING: Institutional clinical research. MATERIALS AND METHODS: Ten patients who underwent aortic repair for abdominal aortic aneurysm (AAA) with the Gelseal graft were studied (Group A). Prior to and immediately following the implantation, the diameter of Gelseal was measured with slide calipers. The external diameter was examined by CT scan 4 weeks following the surgery. Another 10 patients, who had undergone AAA repair with the Gelseal graft more than 2 years earlier (Group B), also were examined by CT scan. Early and late dilation of Gelseal was estimated and the data from the two groups were compared. MEASURES: In Group A, the preimplantation external diameter was 22.6 +/- 2.3 mm while the mean package size (PS) used was 18.7 +/- 2.1 mm prior to implantation. Just after the implantation, the external diameter changed to 22.7 +/- 2.4 mm. Four weeks later, it averaged 24.0 +/- 2.2 mm. In Group B, the PS averaged 19.2 +/- 2.0 mm, while the external diameter measured by CT scan averaged 27.8 +/- 3.4 mm at a mean of 31.3 months following the surgery. RESULTS: Prior to implantation, the external diameter was 1.21 times that of the PS. Following implantation, it was 1.21 times (immediately after), 1.28 times (4 weeks later), and 1.45 times (31.3 months later) of the PS. CONCLUSIONS: At an average of 31.3 months following implantation, the external diameter was 45% larger than the PS. Considering that the external diameter was 21% larger than the PS even prior to implantation, the actual dilation rate is estimated as 24% of the PS in the late postoperative period.

Aged↗
PubMed1996

[Veno-arterial bypass and intraaortic balloon pumping for profound right heart failure--a case report of perioperative right heart infarction].

A combination of veno-arterial bypass (VAB) and intraaortic balloon pumping (IABP) was applied to a 54-year-old male patient whose right heart function was severely damaged immediately following aortic valve replacement. A diagnosis of perioperative myocardial infarction was made with findings of severe hypokinesis of the right heart, new Q wave with ST elevation, and increased cardiac escaping enzyme. The VAB was maintained wih a pump flow rate of 2.0-2.5 L/min. The system was exchanged to the second one 42 hours after the surgery. According to repeated on/off testing, the VAB was successfully weaned on the 5th postoperative day followed by weaning IABP on the 6th postoperative day. This case report shows a recovery from isolated right heart failure by an immediate switching from a cardiopulmonary bypass to VAB and IABP.

Aortic Valve↗