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Biomedical subjects

M Takata

Publications and source records attributed to M Takata.

At least 253 records · Page 14Linked to original sources
PubMed1990

Influence of the pericardium on ventricular loading during respiration.

The influence of the pericardium on ventricular loading during respiration was studied in 17 acutely instrumented anesthetized dogs. Changes in intrapericardial surface pressures (Ppe) on the ventricles were measured by use of air-filled flat latex balloons during acute changes in ventricular loading with the chest open or during negative intrathoracic pressure (NITP) produced by phrenic nerve stimulation with the chest closed. Ppe always demonstrated a phasic change within a cardiac cycle, with its maximum near end diastole and minimum near end systole, and a waveform similar to ventricular dimensions measured by sonomicrometer crystals. With the chest open we found that 1) inferior vena caval constriction decreased Ppe on both ventricles at end diastole (P less than 0.01), 2) aortic constriction increased Ppe on both ventricles at end systole and end diastole (P less than 0.05), and 3) pulmonary artery constriction increased Ppe on the right ventricle (RV) (P less than 0.01) while decreasing Ppe on the left ventricle (LV) at end diastole (P less than 0.05). Thus regional Ppe over a ventricle is influenced by changes in ventricular loading conditions. During NITP with lung volume either constant or increased, Ppe over the anterolateral LV decreased less than two independent extrapericardial measures of intrathoracic pressure, and this resulted in an increased transpericardial pressure at end systole (P less than 0.05) and end diastole (P less than 0.01). During NITP with increased transpericardial pressure, Ppe over the anterior LV, lateral LV, and RV inflow showed small regional differences, but all decreased less than esophageal pressure (P less than 0.01). These results sugges that the increase in transpericardial pressure during late diastole to early systole, produced by increases in ventricular volume during NITP, could effectively attenuate the increases in ventricular preload and afterload caused by respiration, analogous to a negative feedback loop.

Animals↗
PubMed1990

Effects of abdominal pressure on venous return: abdominal vascular zone conditions.

The effects of changes in abdominal pressure (Pab) on inferior vena cava (IVC) venous return were analyzed using a model of the IVC circulation based on a concept of abdominal vascular zone conditions analogous to pulmonary vascular zone conditions. We hypothesized that an increase in Pab would increase IVC venous return when the IVC pressure at the level of the diaphragm (Pivc) exceeds the sum of Pab and the critical closing transmural pressure (Pc), i.e., zone 3 conditions, but reduce IVC venous return when Pivc is below the sum of Pab and Pc, i.e., zone 2 conditions. The validity of the model was tested in 12 canine experiments with an open-chest IVC bypass. An increase in Pab produced by phrenic stimulation increased the IVC venous return when Pivc-Pab was positive but decreased the IVC venous return when Pivc - Pab was negative. The value of Pivc - Pab that separated net increases from decreases in venous return was 1.00 +/- 0.72 (SE) mmHg (n = 6). An increase in Pivc did not influence the femoral venous pressure when Pivc was lower than the sum of Pab and a constant, 0.96 +/- 0.70 mmHg (n = 6), consistent with presence of a waterfall. These results agreed closely with the predictions of the model and its computer simulation. The abdominal venous compartment appears to function with changes in Pab either as a capacitor in zone 3 conditions or as a collapsible Starling resistor with little wall tone in zone 2 conditions.

Abdomen↗
PubMed1990

IgA nephropathy and hepatitis B virus. IgA nephropathy unrelated to hepatitis B surface antigenemia.

The incidence and pathogenetic role of hepatitis B surface antigen (HBsAg) were evaluated in patients with IgA nephropathy. Among 130 consecutive patients with IgA nephropathy, HBs antigenemia was detected in 4 patients (3.1%). Serum antibody to hepatitis B core antigen was positive in these 4 patients indicating that they were persistent carriers of hepatitis B virus. Serum hepatitis B e antigen (HBeAg) was detected in 1 patient, and antibody to HBeAg was positive in the other 3 patients. The incidence of HBs antigenemia was not significantly higher than the 2.0% of the general population. An immunofluorescent study in the renal tissues from the 4 IgA-nephritic patients with HBs antigenemia did not demonstrate HBsAg or HBeAg in the glomeruli. These findings suggest that HBsAg appears to play no role in the pathogenesis of IgA nephropathy.

Adolescent↗
PubMed1990

Development of hypertension from unilateral renal artery stenosis in conscious dogs.

The renal and systemic changes after stenosis of the left renal artery (n = 5) or sham stenosis (n = 6) in conscious dogs were studied sequentially over 25 days. Stenosis produced a prompt rise in arterial pressure, which was at all times due to reduced peripheral vascular conductance, with no increase in cardiac output despite initial evidence of mild fluid retention. The decrease in peripheral conductance was attributable to 1) the stenotic kidney (25% of the total and due to the mechanical effect of the stenosis itself), 2) the nonstenotic kidney (about 15% of the total and not caused by angiotensin II), and 3) the nonrenal vasculature (60%). The decrease in conductance in the nonrenal vasculature was due partly to angiotensin II, but there was also a gradually developing non-angiotensin II component. Acute administration of captopril caused significantly greater changes in arterial pressure and peripheral conductance throughout the period of stenosis than before stenosis (and greater than in sham-stenosis dogs), indicating that angiotensin II was constricting the peripheral vasculature even when plasma renin levels were no longer elevated. In the stenotic kidneys, captopril produced a fall in renal vascular resistance, but renal blood flow did not rise because there was an approximately equal rise in the resistance of the stenosis. There was no evidence for a role for the autonomic nervous system in the hypertension, as ganglion blockade (pentolinium) had similar hemodynamic effects before and after stenosis. Thus, the hypertension was due at all times to reduced peripheral conductance, with the two kidneys responsible for 40% of this reduced conductance.

Animals↗
PubMed1990

Studies on the antitumor-promoting activity of naturally occurring substances. II. Inhibition of tumor-promoter-enhanced phospholipid metabolism by umbelliferous materials.

Ninety-five extracts prepared from 14 kinds of Umbelliferous materials were studied to determine their effects on tumor-promoter-induced phenomena in vitro. Of the materials, 5 Chinese crude drugs, two Bai-Hua Qian-Hu classified as Q-I and Q-II types, the root of Peucedanum praeruptorum Dunn., Zi-Hua Qian-Hu, the root of P. decursivum Maxim., Tang-Bai-Zhi, the root of Angelica dahurica Benth, et Hook. var. pai-chi Kimura, Hata et Yen., Dang-Gui, the root of A. acutiloba Kitagawa and 2 Umbelliferous plants, ashita-ba. A. keiskei Koidz., and ama-nyuu, A. edulis Miyabe, showed potent inhibitory effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated 32Pi incorporation into phospholipids of cultured cells. From the active fraction of the crude drug "Tang-Bai-Zhi," imperation (1), isoimperatoin (2), oxypeucedanin (3), pabulenol (4), neobyakangelicol (5) and byakangelicin (6) were identified as active or inactive principles. Compound 4 had not previously been isolated from Tang-Bai-Zhi, A. dahurica var. pai-chi. We also discuss the structure-activity relationship among the above 6 kinds of linear-type furanocoumarins, together with 3 kinds of antitumor-promoter coumarins having the same skeleton, psoralen (7), bergapten (8) and xanthotoxin (9), obtained from "ashita-ba" (eaten as a vegetable in Japan). Among the compounds in the present experiment, compounds 1 and 2 showed potent inhibitory activity at the concentration of 50 micrograms/ml and 3-9 were found to have less or no activity.

Animals↗
PubMed1990

Reversal of left ventricular hypertrophy by terazosin in hypertensive patients.

To assess the reversibility of left ventricular hypertrophy (LVH) during terazosin therapy, we studied changes in LVH as determined by echocardiography and humoral parameters before and after three and 12 months of terazosin monotherapy in ten patients. Blood pressure decreased within four weeks of treatment and the antihypertensive effect was sustained throughout 12 months. Left ventricular mass index decreased significantly from 126 +/- 22 g/m2 to 109 +/- 24 g/m2 and 98 +/- 23 g/m2 after 3 and 12 months respectively. Interventricular septum (11.2 to 9.8 and 9.0 mm) and posterior wall thickness (10.4 to 9.6 and 8.8 mm) also decreased significantly, whereas left ventricular internal dimensions were unchanged. Total peripheral resistance decreased significantly after initiation of treatment, but cardiac output did not change. Plasma volume, plasma renin activity and plasma noradrenaltine levels were unchanged by terazosin. Thus, terazosin monotherapy reversed LVH associated with decreased peripheral resistance. It is suggested that the reversal of LVH by terazosin is mainly due to the reduction in ventricular afterload and that humoral factors are not involved in its mechanism.

Adrenergic alpha-Antagonists↗
PubMed1989

Neural mechanism generating firing patterns in jaw motoneurons during the food-induced response in Aplysia kurodai. I. Identification and characterization of premotor neurons.

1. In each right and left buccal ganglia of Aplysia kurodai, we identified 4 premotor neurons impinging on the ipsilateral jaw-closing and -opening motoneurons. Three of them (MA1 neurons) had features of multifunctional neurons. Current-induced spikes in the MA1 neurons produced excitatory junction potentials (EJPs) in the buccal muscle fibers. In addition, tactile stimulation of the buccal muscle surface produced a train of spikes in the MA1 neurons without synaptic input. The other neuron (MA2) had only a premotor function. 2. The MA1 and MA2 neurons had similar synaptic effects on the jaw-closing and -opening motoneurons. Current-induced spikes in the premotor neurons gave rise to monosynaptic inhibitory postsynaptic potentials (IPSPs) in the ipsilateral jaw-closing motoneurons. Simultaneously, spikes in one of the MA1 neurons and the MA2 also gave rise to monosynaptic excitatory postsynaptic potentials (EPSPs) in the ipsilateral jaw-opening motoneuron. 3. The IPSPs and the EPSPs induced by spikes in the premotor neurons were reversibly blocked by d-tubocurarine and hexamethonium, respectively, suggesting that the MA1 and MA2 neurons are cholinergic. 4. When depolarizing and hyperpolarizing current pulses were passed into one premotor neuron, attenuated but similar potential changes were produced in another randomly selected premotor neuron in the same ganglion, suggesting that they are electronically coupled.

Animals↗
PubMed1989

Hemodynamic and endocrinological effects of a new selective alpha 1-blocking agent, terazosin, in patients with essential hypertension. Results of long-term treatment.

Thirteen patients with essential hypertension were treated with an alpha 1-adrenoceptor antagonist, terazosin (1 to 4 mg/day) for 12 months. To assess the mechanism of its antihypertensive effect, the hemodynamic and endocrinological responses to terazosin were determined before, 3, and 12 months after the administration of terazosin. Blood pressure significantly decreased within 2 weeks after the start of terazosin and its effect was sustained throughout the 12 month period. Pulse rate did not change except slight increase in the third month. The hemodynamic studies revealed that total peripheral resistance significantly decreased and cardiac output slightly increased, indicating that the antihypertensive effect of terazosin is mainly produced by its vasodilation. Blood volume and plasma volume did not change. Although plasma renin activity remained the same, plasma aldosterone significantly decreased in response to terazosin. Plasma noradrenaline increased in the third month, but returned to the baseline level in the twelfth month. Thus, terazosin monotherapy lowered blood pressure throughout one year without drug tolerance including volume expansion and/or accentuation of renin-angiotensin-aldosterone system or sympathetic function.

Adrenergic alpha-Antagonists↗
PubMed1989

Beta 2 microglobulin expression in normal melanocytes, nevocellular nevi, and malignant melanomas.

Expression of beta 2 microglobulin (beta 2M), a light chain of class 1 HLA antigen, was studied in normal melanocytes and in benign and malignant melanocytic tumors by use of immunohistochemical methods. By immunoelectron microscopy, normal melanocytes were shown to express beta 2M on the cell surface. In lentigo maligna melanomas and acral lentiginous melanomas, the mean percentages of beta 2M-positive tumor cells were significantly lower in thick (greater than 1.50 mm) primary lesions and metastases than in thin (less than or equal to 1.50 mm) primary lesions. The evidence suggests that melanocyte-derived melanoma clones with a low grade of malignancy preserve class 1 HLA expression, and that the clones with a high grade of malignancy tend to lose the antigen expression. Nevus cells in common nevi have little or no expression of beta 2M. In halo nevi, however, beta 2M were detected on nevus cells in the lesions associated with inflammatory infiltration. Immunohistochemical analyses of the cellular composition of the inflammatory cells in halo nevi demonstrated the presence of cytotoxic T cells together with helper/inducer T cells, Langerhans cells, and macrophages. It appears that nevus cells of halo nevi are destroyed by cytotoxic T cells and that class 1 HLA antigens expressed on nevus cells play an important role in the target cell recognition and lysis by specific cytotoxic T cells.

Adult↗
PubMed1989

Augmentation of human cytotoxic T lymphocytes against autologous tumor by a factor released from human monocytic leukemia cell line.

A human acute monocytic leukemia cell line, THP-1, releases a factor which activates human cytotoxic (killer) T lymphocytes (CTL) against autologous tumor in vitro. The factor, named cytotoxic (killer) T cell activating factor (KAF), is an acidic protein of 70,000 to 100,000 dalton molecular size. Peripheral blood leukocytes from two patients, bearing epithelioid sarcoma or malignant schwannoma, were cultured for 7 days with individual autologous tumor to induce CTL directed to the corresponding tumor. Monocyte-depleted peripheral leukocytes generated lesser CTL activity than the monocyte-containing leukocyte population. However, the KAF was able to replace the monocyte function. The KAF acted at the CTL generation phase as well as the effector phase. The KAF-activated killer cells possessed CD4-8+ surface phenotype. The CTL killed autologous tumor or other unrelated tumor cell lines only when they shared some of the HLA class I antigens. It was also demonstrated that the KAF does not activate killer cells without proper antigenic stimuli, because the KAF-augmented CTL possess specificity against autologous tumor or other HLA-A or -B matched tumor cell lines. The therapeutic applicability of human KAF for anti-tumor CTL therapy against autologous tumor is discussed.

Adult↗
PubMed1989

Renal effects of atrial natriuretic peptide in conscious rabbits with renal wrap hypertension.

Atrial natriuretic peptide (ANP, 2 micrograms/min) was infused intravenously into rabbits four weeks after renal wrap or sham operation. Mean arterial pressure (MAP) averaged 132 +/- 4 mmHg in the renal wrapped rabbits and 89 +/- 3 mmHg in the sham rabbits, and glomerular filtration rate (GFR) was significantly lower in the hypertensive rabbits (6.2 +/- 1.0 ml/min) than in sham rabbits (8.9 +/- 0.7 ml/min). In sham rabbits, ANP caused a significant diuresis, natriuresis and increase in GFR. Enalapril pretreatment blunted these responses. In the hypertensive rabbits, ANP reduced mean arterial pressure but did not cause significant diuresis or natriuresis or change in GFR. Enalapril pretreatment did not significantly alter this response to ANP. In separate experiments, nitroprusside was infused to lower arterial pressure in hypertensive rabbits by a similar amount to that achieved with ANP and this reduced GFR, sodium and urine excretion rates. Thus ANP maintained GFR and sodium excretion in hypertensive rabbits compared to an equihypotensive dose of nitroprusside. In summary, ANP did not cause natriuresis or diuresis in renal wrapped kidneys at a dose which was effective in normal kidneys, but did maintain GFR, sodium and water excretion rates, compared to an equally hypotensive dose of nitroprusside.

Animals↗
PubMed1989

[A new variety of neurocutaneous melanosis: benign leptomeningeal melanocytoma associated with extensive Mongolian spot on the back].

A 38-year-old Japanese man presented with a blue macule on the back. A spinal meningeal tumor at the C3-C5 levels was detected radiologically and excised. The histological findings in the biopsy specimen from the blue macule were consistent with an extensive Mongolian spot. The histological diagnosis of the meningeal tumor was benign melanocytoma. The case was thought to be a new variety of neurocutaneous melanosis.

Adult↗
PubMed1988

Excitatory and inhibitory postsynaptic potentials in cat hypoglossal motoneurons during swallowing.

The postsynaptic potentials produced in cat genioglossus and styloglossus motoneurons (GG- and SG-Mns) during swallowing were studied. During swallowing elicited by placing water on the dorsum of the tongue, the GG-muscle discharged for 80-210 ms (mean +/- S. D. 123 +/- 31 ms, N = 59) and was abruptly suppressed, and the SG-muscle began discharging in synchrony with the GG-muscle and discharged for 200-360 ms (mean +/- S. D. 247 +/- 36 ms, N = 59). The GG- and the SG-Mns were identified if unitary muscle activity followed the induced spike of the motoneuron one-for-one. During swallowing, excitatory postsynaptic potentials (EPSPs) were evoked in the SG-Mns regardless of the respiratory drive on the SG-Mns, and inhibitory postsynaptic potential (IPSP) or EPSP-IPSP was evoked on the GG-Mns regardless of the respiratory drive on the GG-Mns. By increasing the intracellular concentration of chloride ions, the IPSP elicited in the GG-Mn during swallowing was turned into a depolarizing potential. In immobilized cats, a depolarizing potential and a depolarizing-hyperpolarizing potential sequence was evoked successively on a tongue retractor motoneuron and a tongue protruder motoneuron by repetitive electrical stimulation of the superior laryngeal nerve.

Action Potentials↗
PubMed1988

Therapeutic results of primary aldosteronism with special reference to renal or renovascular lesions.

A study was made of 9 patients with primary aldosteronism due to aldosterone-producing adenoma (APA) and 8 subjects with idiopathic adrenal hyperplasia (IHA) to clarify the pathogenesis of sustained hypertension after surgical or non-surgical treatment. Following each treatment, a complete improvement of hypertension was obtained in 12 patients (6 APA, 6 IHA), while 5 (3 APA, 2 IHA) showed still hypertensive status. Renal or renovascular lesions were prominent only in the hypertension-unchanged group. Under regular sodium diet, the ratio of urinary excretion of sodium to creatinine of this hypertensive group was significantly lower than that of the hypertension-improved group. However, the results of other renal function tests were similar in both groups. After respective treatments, suppressed plasma renin activity and elevated plasma aldosterone concentration were improved in all patients. In addition, patients of both groups showed normal response of the renin-aldosterone system following diuretic and dietary induced sodium and volume depletion. Based on these findings, renal or renovascular lesions appear to play an important role in the pathogenesis of maintenance of hypertension in this disorder after respective treatments.

Adenoma↗
PubMed1988

Magnetic resonance imaging in the diagnosis of tumors of the liver.

To evaluate the usefulness of magnetic resonance (MR) imaging in the diagnosis of liver tumors, MR imaging was performed in 70 patients, 30 with normal or cirrhotic liver, 15 with benign tumors and 25 with malignant tumors. MR imaging was carried out with a 0.5-Tesla superconducting magnet and was made using a spin-echo technique, from which T1 and T2-weighted images were obtained, and also T1 and T2 values were measured. Hemangiomas and cysts were demonstrated as sharply circumscribed homogeneous masses of low- or high-intensity on each image. Hepatomas were revealed as low-, iso- and high-intensity masses on both images. The minimum size of hepatoma detected, 1 cm in diameter, exhibited uniform intensity. Large hepatomas showed a mosaic pattern of different intensities, a low-intensity area around the mass, and a capsular pattern. The majority of metastatic tumors demonstrated a characteristic irregularity at the periphery of the mass. There were significant differences in T1 and T2 values between benign and malignant tumors. These results suggest that MR imaging is useful not only in the detection but also in the differentiation of liver tumors and can permit evaluation of the architecture of the tumor.

Adenocarcinoma↗
PubMed1988

The effects of cadmium, copper or zinc on formation of embryonic chick bone in tissue culture.

Femurs from 9-day-old chick embryo were cultivated for 6 days by the roller-tube method in the presence of Cd, Cu or Zn. Cd (5.0 microM and above) and Cu (2.5 microM and above) caused a decrease in collagen content of both diaphysis and epiphysis, mainly due to inhibition of collagen synthesis. In addition, Cd and Cu each showed a tendency to inhibit an increase in Ca content of diaphysis, where intraperiosteal ossification could be observed. Alkaline phosphatase (ALP) activity was decreased by Cd (5.0 microM and above) or Cu (10 microM and above) in diaphysis. On the other hand, Zn at 50 microM and above inhibited an increase in Ca content of the diaphysis with a remarkable elevation of ALP activity in the medium. At this time, Zn did not decrease the collagen content of the diaphysis so strongly. Histological observations revealed that Cd and Cu each decreased both calcified and uncalcified osteoid tissue at 2.5 microM, while Zn at 100 microM decreased calcified tissue but increased uncalcified osteoid tissue. As Zn accumulated particularly in diaphysis and deposited at the edge of calcified tissue, it was suggested that Zn inhibited calcification physicochemically. It was concluded that Cd or Cu would induce bone damage represented by osteoporosis, whereas Zn would induce osteomalacia.

Alkaline Phosphatase↗
PubMed1988

Role of zinc in protection against cadmium-induced toxicity in formation of embryonic chick bone in tissue culture.

To clarify a possible mechanism of zinc (Zn)-induced tolerance to cadmium (Cd) toxicity on bone formation, femurs from 9-day-old chick embryos were cultured for 6 days by the roller-tube method in the presence of Cd (2, 4 or 9 microM) and/or Zn (60 microM). Zn prevented a decrease in bone growth caused by Cd at 4 and 9 microM. An increase in calcium (Ca) content of diaphysis was inhibited by Zn in both the presence and absence of Cd. Histologically, Zn protected a Cd-induced degenerative change of mesenchymal cells in the periosteum and that of osteoblasts around the trabecula at each Cd level. At 60 microM Zn, Cd accumulated less in the bone at 2 microM but more at 9 microM. From these results, it was concluded that Zn prevented Cd-induced toxicity in the process of ossification except calcification in a culture system by two different mechanisms, i.e. a decreasing Cd accumulation at a low level of Cd and probably an induction of metallothionein (MT)-like protein at a high level of Cd.

Alkaline Phosphatase↗