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Biomedical subjects

M Takata

Publications and source records attributed to M Takata.

At least 217 records · Page 12Linked to original sources
PubMed1993

Regression of vascular structural changes and calcium metabolism in patients with essential hypertension after long-term monotherapy with enalapril.

We investigated the effect of one year of enalapril monotherapy on vascular structural changes and calcium metabolism in ten patients with essential hypertension. BP decreased from 169-10/103 +/- 10 mmHg during the placebo period to 138-12/82 +/- 10 mmHg after enalapril therapy. Minimal vascular resistance assessed by the venous occlusion technique with strain-gauge plethysmography was higher in the hypertensive patients than in the normotensive subjects (2.7 +/- 1.2 vs. 1.2 +/- 0.3 mmHg/ml/min per 100 ml tissue, P < 0.01). Although the elevated minimal vascular resistance seen in essential hypertensives decreased to 1.7 +/- 0.5 mmHg/ml/min per 100 ml tissue after enalapril (P < 0.01), it remained higher than that of normotensives (P < 0.05). Cytosolic free calcium ([Ca2+]i) in platelets measured by a Qiun-2 fluorescent indicator was higher in essential hypertensives than in normotensives (189 +/- 38 nM and 138 +/- 14 nM, respectively; P < 0.01). [Ca2+]i of essential hypertensives was reduced to 138 +/- 19 nM after treatment. Plasma renin activity was significantly increased after enalapril. Although plasma ionized calcium concentration did not change, parathyroid hormone was significantly increased after enalapril (from 0.36 +/- 0.22 to 0.58-0.32 ng/ml, P < 0.05). During the placebo period, minimal vascular resistance was correlated with [Ca2+]i (r = 0.62, P < 0.01). There was a close relationship between the changes in minimal vascular resistance and [Ca2+]i (r = 0.78, P < 0.01); however the change in minimal vascular resistance was not associated with changes in BP, catecholamine or parathyroid hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Synaptic potentials produced in jaw-closer and jaw-opener motoneurons by palatal stimulation.

Excitation and inhibition of temporal and digastric motoneurons (Temp. and Dig. Mns) during transient jaw closing, the so-called jaw-closing reflex, were studied in cats. Application of diffuse pressure stimulation to the posterior palatal surface produced the jaw-closing reflex and it was found that mechanosensory inputs from the posterior palatal mucosa produce depolarizing potentials on the Temp. Mns responsible for jaw closure during the jaw-closing reflex. We have demonstrated that in one-third of 27 explored Temp. Mns the initial bursts of spikes were elicited before the onset of jaw closure, suggesting that these cells contribute to initiate jaw closure during the jaw-closing reflex. The remaining cells probably contributed to maintain the occlusal phase. Furthermore, it was found that mechanosensory inputs from the posterior palatal mucosa produce a hyperpolarization-depolarization sequence in the Dig. Mns responsible for the jaw-closing reflex. In addition, when pressure stimulation was applied to the anterior palatal mucosa, sustained jaw opening was elicited and an increase of firing frequency of Dig. Mns occurred 40 ms before the onset of jaw opening and continued for 80 ms.

Animals↗
PubMed1992

Characterization of suppressor T cell clones derived from a mouse tolerized with conjugates of ovalbumin and monomethoxypolyethylene glycol.

The induction of antigen-specific tolerance in mice by conjugates of ovalbumin (OVA) and monomethoxypolyethylene glycol (mPEG) previously had been shown to be associated with the generation of antigen-specific suppressor T (Ts) cells. For the elucidation of the nature of these Ts cells, five nonhybridized OVA-specific Ts cell clones were generated from the spleen cells of a BDF1 mouse which had been immunosuppressed by the tolerogenic conjugate, OVA(mPEG)12. The cloned Ts cells were maintained in vitro by periodic stimulation with OVA and feeder cells and were able to suppress the in vitro antibody production in an OVA-specific and MHC class I (H-2Kd or H-2Dd)-restricted manner. All these Ts cell clones were shown to be Thy1.2+, CD4-, CD5-, CD8+, and to express CD3 and the alpha beta heterodimer of the T cell receptor. The cell-free extracts of these cells contained soluble suppressor factors which could mimic in vitro the suppressive activity of the intact cells. In contrast to cytotoxic T lymphocytes (CTL), none of the cloned Ts cells were endowed with cytolytic activity as revealed in the perforin-mediated microhemolysis and in the 18-hr51Cr release assays. These results demonstrate that (i) OVA-specific Ts cell clones can be generated from mice pretreated with OVA(mPEG)12 by employing conventional T cell culture techniques, and (ii) these Ts cells are functionally different from conventional CD8+ CTL.

Animals↗
PubMed1992

Stimulative effects of cadmium on bone resorption in neonatal parietal bone resorption.

Effects of cadmium on bone resorption were investigated using neonatal mouse parietal bone culture system. Cadmium at 0.5 microM and above stimulated hydroxyproline release as well as 45Ca release. As cadmium-stimulated bone resorption was inhibited by calcitonin, bone resorption induced by cadmium is osteoclast-mediated bone resorption. CI-1, collagenase inhibitor, depressed cadmium-stimulated bone resorption in a dose-dependent manner. Osteoblasts are also involved in cadmium-induced bone resorption. Indomethacin-inhibited cadmium-stimulated bone resorption and cadmium-treated bones released prostaglandin E2 to a greater extent than untreated bones. Cadmium-stimulated bone resorption was shown to be dependent on the production of prostaglandin E2. 3-Isobutyl-1-methylxanthine potentiated cadmium-stimulated bone resorption and verapamil depressed it. It is possible that an increase in levels of cAMP and calcium ion in bone cells is involved in cadmium-induced bone resorption. From these results, cadmium was found to stimulate osteoclast-mediated bone resorption which is dependent on prostaglandin E2. Second messengers in cadmium-induced bone resorption may be cAMP and calcium ion.

Animals↗
PubMed1992

Altered renal response to enhanced endogenous 5-hydroxytryptamine after tryptophan administration in essential hypertension.

1. To examine the pathophysiological significance of 5-hydroxytryptamine (serotonin) in essential hypertension, we compared the renal response to intrarenally formed 5-hydroxytryptamine by oral dosing with its precursor, L-tryptophan (2 g), in nine patients with essential hypertension and in six subjects with normotension. 2. Before tryptophan administration, urinary excretion of 5-hydroxytryptamine was significantly higher in the hypertensive group than in the normotensive group (66 +/- 8 versus 36 +/- 6 ng/min, P less than 0.05), whereas renal plasma flow and glomerular filtration rate did not differ between the two groups. After dosing with tryptophan, urinary excretion of 5-hydroxytryptamine significantly increased to the same plateau level in both groups (366 +/- 55 ng/min in the hypertensive group and 365 +/- 64 ng/min in the normotensive group). Significant and equivalent decreases in renal plasma flow were observed in the early phase after tryptophan administration in both groups (-8.5 +/- 3.4% in the hypertensive group and -8.2 +/- 1.7% in the normotensive group). Thereafter, renal plasma flow increased to above the baseline value in normotensive subjects, whereas this late vasodilatation was absent in the hypertensive group. Glomerular filtration rate significantly decreased at the time of the fall in renal plasma flow in the normotensive group (106.8 +/- 7.8 to 92.7 +/- 8.5 ml min-1 1.73 m-2, P less than 0.05), whereas it remained unchanged in the hypertensive group (108.2 +/- 6.2 to 110.4 +/- 6.3 ml min-1 1.73 m-2, not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Purification of human blood basophils using negative selection by flow cytometry.

Basophils were purified from peripheral blood of normal donors using Percoll discontinuous gradients and negative selection by flow cytometry. The mean purity of basophils obtained was 84.7 +/- 4.1 (s.d.)% (range 77.3-90.0%, n = 13). The overall yield of these procedures was 16.0 +/- 2.6% (range 11.0-19.9%, n = 13), and cell viability of purified basophils exceeded 90%. Properties of highly purified basophils obtained by flow cytometry did not differ from those of partially enriched basophil preparations from Percoll discontinuous gradients in respect of: (i) intracellular histamine content; (ii) percentage of spontaneous histamine release in buffer; and (iii) percentage of histamine release triggered by ionophore A 23187 or anti-IgE. Moreover, purified basophils responded chemotactically to complement C5a in a dose-dependent manner. These findings suggest that our procedure for purification of human basophils does not affect the functions of basophils and may be useful for in vitro studies on the role of basophils in hypersensitivity reactions such as bronchial asthma.

Basophils↗
PubMed1992

Phenotypic progression of a rat lymphoid cell line immortalized by human T-lymphotropic virus type I to induce lymphoma/leukemia-like disease in rats.

Rat lymphoid cells, TARS-1, immortalized by coculture with adult T-cell leukemia cells, were intraperitoneally injected into 65 newborn, inbred WKAH/Hkm rats. In most of the rats, tumor nodules were discernible 7 to 15 days after transplantation but were completely rejected within 5 to 6 weeks. Two rats with no tumor nodules exhibited gait disturbances and paralysis of the hind legs 3 to 4 weeks after transplantation. Histological and hematological examinations revealed that a lymphoma/leukemia-like disease had developed in one of the two rats, and the T-lymphoid cell line WLeuk-1 was established from peripheral blood mononuclear cells from this rat. When the WLeuk-1 cells were transplanted into newborn WKAH/Hkm rats, the animals died of a lymphoma/leukemia-like disease within several weeks after transplantation, in contrast to their rejection of the TARS-1 cells. Southern blot and karyotype analyses revealed that WLeuk-1 cells had retained the marker chromosomes and human T-lymphotropic virus type I (HTLV-I) integration patterns of the parent cell line, TARS-1. The additional specific chromosome abnormalities 3p+,t (12;13), and Xq+ were found in the WLeuk-1 cells. Moreover, the expression of HTLV-I structural proteins was slightly depressed in WLeuk-1 cells, while that of the transacting factors p40tax and p21x, but not that of p27rex, was enhanced about fivefold compared with that in TARS-1. The transactivating function of p40tax was intact in WLeuk-1, as evidenced by enhanced interleukin-2 receptor alpha chain expression. These results suggest that aberrant expression of HTLV-I regulatory genes and alteration of cellular genes were associated with the phenotypic progression of the WLeuk-1 cell line.

Animals↗
PubMed1992

Superior and inferior vena caval flows during respiration: pathogenesis of Kussmaul's sign.

Respiratory induced changes in superior (QSVC) and inferior (QIVC) vena caval flows and abdominal pressures were evaluated in anesthetized closed-chest dogs. QSVC and QIVC were measured with ultrasound transit time flow probes (n = 5), and general (Pab) and regional subdiaphragmatic (Pd) abdominal pressures were measured by air-filled balloons (n = 5), during two respiratory maneuvers produced by phrenic nerve stimulation, i.e., simulated spontaneous inspiration (SSI), and Mueller maneuver (MM), with the airway occluded to minimize diaphragmatic descent. With hypervolemia: during SSI, QSVC decreased, QIVC increased, and right atrial pressure increased (P less than 0.05) despite a decrease in esophageal pressure (Pes), i.e., Kussmaul's sign; during MM, both QSVC and QIVC increased (P less than 0.05) without Kussmaul's sign. The ratios delta Pab/delta Pes and delta Pd/Pes were larger during SSI than MM (P less than 0.01). With hypovolemia: during SSI and MM, QSVC increased and QIVC decreased with a venous pressure gradient across the diaphragm (P less than 0.05), consistent with development of a vascular waterfall. These results suggest that 1) changes in abdominal pressure may affect the patterns of QSVC and QIVC during respiration, depending on blood volume status; 2) a prolonged inspiration with hypovolemia may decrease QIVC because of the development of a vascular waterfall; 3) QSVC and QIVC may be interdependent during respiration; and 4) the essential mechanism of Kussmaul's sign is a substantially larger inspiratory increase in abdominal pressures produced by diaphragmatic descent compared with the decrease in intrathoracic pressure under hypervolemic conditions, rather than the presence of pericardial pathology or right heart dysfunction.

Animals↗
PubMed1992

Influence of pericardial constraint on atrioventricular interactions.

The effects of the pericardial constraint in control, tamponade, and absent pericardium conditions was studied in 18 anesthetized open-chest dogs. Atrial pressures and systolic and diastolic inflow volumes per beat in the superior (SVC), inferior vena cavae (IVC), and pulmonary vein (PV) were measured. With increasing tamponade, 1) the systolic-diastolic distribution of venous flow became almost exclusively systolic in the SVC (P less than 0.001) and IVC (P less than 0.05), as the gamma-descent disappeared; 2) similar but lesser left-sided changes occurred in PV flows (P less than 0.001) and pressure; and 3) the systolic-diastolic distribution of venous flow was modulated by heart rate. The results imply that during tamponade 1) increased pericardial liquid pressure associated with an increased pericardial constraint couples reciprocal atrial and ventricular volume changes; 2) the atria fill during ventricular ejection (atrioventricular interaction); 3) total heart volume must have been relatively constant throughout a cardiac cycle; and 4) differences in right and left heart compliances may explain persistent diastolic PV flow. Pericardiotomy produced a small increase in the ratio of diastolic to systolic venous inflow volumes (P less than 0.025), suggesting that normally the pericardium has a minor influence on atrioventricular interaction, the volume changes in the atria and ventricles being relatively uncoupled. With severe tamponade, a homogeneous pericardial fluid column tightly couples atrial and ventricular volume changes and accounts for the characteristic changes in atrial pressure waveforms and patterns of venous flow.

Animals↗
PubMed1992

Effects of inspiratory diaphragmatic descent on inferior vena caval venous return.

To explain the contradictory results in the literature regarding the effects of inspiratory diaphragmatic descent on inferior vena caval (IVC) venous return, we evaluated changes in total IVC flow as well as regional splanchnic and nonsplanchnic IVC flows by use of ultrasound flow probes placed around the thoracic and subhepatic abdominal IVC during phrenic nerve stimulation (PNS) in anesthetized open-chest dogs. With the abdomen closed (n = 6), PNS under hypervolemic conditions increased the total IVC flow by enhancing the splanchnic IVC flow, with a transient decrease in the nonsplanchnic IVC flow (P less than 0.05). Under hypovolemic conditions, PNS initially increased the total IVC flow but later decreased the total IVC flow by reducing the nonsplanchnic IVC flow, associated with a venous pressure gradient in the IVC across the diaphragm (P less than 0.05), consistent with development of a vascular waterfall. With the abdomen widely open, the mobile abdominal contents eviscerated, and the subhepatic IVC occluded (n = 5), PNS increased the splanchnic IVC flow associated only with an increase in focal contact pressure over the liver without any increase in general abdominal pressure (Pab) (P less than 0.05). These results suggest that our previously proposed concept of abdominal vascular zone conditions (J. Appl. Physiol. 69: 1961-1972, 1990) is useful as a global approximation to understand the effects of respiratory-induced changes in Pab's on the total and regional IVC venous return. Nonhomogeneous distribution of Pab's during diaphragmatic descent may need to be considered to explain all aspects of the behavior of the intact IVC system.

Animals↗
PubMed1992

Effects of the platelet-activating factor antagonists CV-6209 and CV-3988 on nephrotoxic serum nephritis in the rat.

Platelet-activating factor (PAF) is known as an important mediator in the pathogenesis of glomerular injury. In the present study, we evaluated the effect of the specific PAF antagonists CV-6209 and CV-3988 on accelerated nephrotoxic serum nephritis (NTN) in the rat. The amount of urinary protein excretion was significantly less in the rats treated with CV-6209 or CV-3988 on the 5th and 7th day of treatment than in the nontreated controls. The results of light- and immunofluorescence-microscopic examination did not demonstrate any favorable effect on glomerular changes by these PAF antagonists. However, CV-6209 protected against the loss of glomerular anionic charges in rats with NTN. Thus, it is suggested that PAF is a potent mediator of protein excretion, and that the loss of glomerular anionic charges is an important mechanism for the mediation of PAF in glomerulonephritis.

Animals↗
PubMed1992

[Effects of a specific thromboxane A2 synthetase inhibitor on lymphocyte and neutrophil functions in adult intractable asthmatics].

To clarify whether thromboxane A2 (TXA2) is involved in type III and IV allergy, or so called "cell-mediated allergy", we studied the effect of a specific TXA2 synthetase inhibitor, sodium ozagrel (OKY-046) on peripheral blood mononuclear cells and neutrophils in adult intractable asthmatics. The results revealed, firstly, that lymphocyte blastogenesis and interleukin-2 (IL-2) production from peripheral blood mononuclear cells stimulated by PHA and Candida antigen in intractable asthmatics was significantly suppressed dose-dependently by OKY-046. Secondly, there was a tendency that neutrophil chemotactic factor (NCF) and eosinophil chemotactic factor (ECF) from peripheral blood mononuclear cells stimulated by Candida antigen in intractable asthmatics were suppressed by OKY-046. Thirdly, leukotriene (LTC4) and superoxide (O2-) production from peripheral blood neutrophils in intractable asthmatics was significantly suppressed dose-dependently by OKY-046. That is, OKY-046 has a suppressive effect on type IV allergy caused by lymphocyte activation and on mediator release from neutrophils. These results suggest that TXA2 plays an important role in the development of bronchial asthma and OKY-046 might be a useful drug in the treatment of intractable asthmatics.

Adult↗
PubMed1992

Total and regional bone mineral density by dual photon absorptiometry in patients on maintenance hemodialysis.

To evaluate bone loss in renal osteodystrophy, we measured total and regional (head, trunk, pelvis, leg and arm) bone mineral density (BMD) by dual photon absorptiometry in 72 patients on maintenance hemodialysis (HD). We also examined the validity of serum carboxy-terminal parathyroid hormone (C-PTH) and intact-PTH as an indicator of secondary hyperparathyroidism. Total BMD correlated inversely with age in female patients (r = -0.57, p less than 0.01), but not in male patients. Female patients older than 50 years were omitted from analysis to exclude the effect of menopause on bone. Among clinical and biochemical parameters, only trunk BMD correlated inversely with the duration of HD (r = -0.26, p less than 0.05). Head, trunk and total BMD correlated inversely with serum alkaline phosphatase, C-PTH and intact-PTH, while pelvis BMD did not. Leg and arm BMD also correlated inversely with serum intact-PTH, but not with serum C-PTH. The serum level of C-PTH correlated positively with the duration of HD (r = 0.40, p less than 0.005), while intact-PTH did not. As compared with 18 control male volunteers aged 25-42 years, trunk, pelvis, leg, arm and total BMD were significantly lower in male patients on HD aged 22-49 years, whereas head BMD did not differ significantly between the two groups. The percent decrease of BMD was most prominent in the trunk (-19.6%, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1992

Cytosolic free calcium concentration in platelets in patients with renovascular hypertension and primary aldosteronism.

To investigate the role of cytosolic free calcium, [Ca2+]i, in secondary hypertension, the levels in platelets from 14 secondary hypertensives (7 renovascular hypertension, 7 primary aldosteronism) were compared with those from 21 essential hypertensives and 15 normotensives by means of the fluorescent indicator, quin-2. The mean BP was significantly higher in both the secondary hypertensives and essential hypertensives (122 +/- 8 and 124 +/- 12 mmHg) than in the normotensives (89 +/- 10 mmHg). Cytosolic free calcium in platelets was significantly higher in the essential hypertensives, but not in the secondary hypertensives, compared with the normotensives (182 +/- 34, 141 +/- 17, 138 +/- 15 nM respectively). There was no significant difference in platelet [Ca2+]i between renovascular hypertension and aldosteronism (142 +/- 19 versus 139 +/- 16 nM). There was no correlation between platelet [Ca2+]i and plasma renin activity, plasma aldosterone concentration or plasma noradrenaline concentration in the three groups. Thus, the increase in platelet [Ca2+]i seen in essential hypertension was not found in patients with secondary hypertension. Our results suggest that the cytosolic calcium handling of secondary hypertensive patients with renal artery stenosis or primary aldosteronism differs from that of essential hypertensives.

Adult↗
PubMed1991

Downregulation of helper T cells by an antigen-specific monoclonal Ts factor.

The findings of previous studies in this laboratory demonstrating that conjugates of human monoclonal (myeloma) IgG (HIgG) and monomethoxypolyethylene glycol (mPEG) were able to induce in mice antigen-specific tolerance and CD8+ suppressor T (Ts) cells were confirmed in the present study. An extract (TsF) of a nonhybridized clone of Ts cells (viz., clone 23.32), which had been derived from spleen cells of mice tolerized with HIgG(mPEG)26, was shown to possess antigen-specific suppressive activity. This monoclonal TsF was able to specifically suppress in vitro antibody formation only if it was present from the beginning of the culture. From the results of the cellular dissection of the system used it was concluded that (i) the TsF had no effect on fully differentiated primed B cells or plasma cells, and (ii) the TsF inactivated carrier-primed Th cells when the culture contained concomitantly naive CD8+ T cells, accessory cells, and antigen. These data support the view that the monoclonal TsF exerted its downregulating effect on Th cells only if it could first interact with a CD8+ T cell, in the presence of accessory cells and antigen.

Animals↗