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Biomedical subjects

M Takata

Publications and source records attributed to M Takata.

At least 271 records · Page 15Linked to original sources
PubMed1988

Renal and systemic vascular conductances in renal wrap hypertension in rabbits.

The contribution of renal vascular conductance to the fall in total peripheral conductance during the development of renal wrap hypertension was determined in conscious rabbits. Measurements were made 28 days after renal wrap (n = 9) or sham operation (n = 8). Blood pressure was about 50 mmHg higher in the wrapped group as compared to the sham-operated group. This was due to a fall in total peripheral conductance of about 42%. Cardiac output was not significantly different between wrap and sham groups. Renal vascular conductance was 0.42 ml/min per mmHg lower in the wrap compared to the sham-operated group (P less than 0.001). Total peripheral conductance was 3.93 ml/min per mmHg lower in the wrap compared to the sham group (P less than 0.01). The reduction in renal vascular conductance in wrapped rabbits, which is probably due to compression caused by the thickening renal capsule, accounts for about 10% of the fall in total peripheral conductance. We suggest that this mechanically induced reduction in renal conductance is involved in the initiation and maintenance of the hypertension, but is only a minor contributor to the overall change in blood pressure.

Animals↗
PubMed1988

Does cytosolic free calcium concentration in platelets reflect tone and structural changes of resistance vessels?

To investigate tone and vascular changes of resistance vessels as related to cytosolic free calcium concentration [( Ca2+]i) in platelets, we measured forearm vascular resistance and free calcium concentration in platelets from 10 essential hypertensives and 15 normotensives. The [Ca2+]i in platelets was significantly higher in essential hypertensives than in normotensives (184 +/- 43 versus 146 +/- 23 nmol/l, P less than 0.01). The [Ca2+]i levels in platelets were significantly correlated with both systolic (r = 0.50, P less than 0.05) and diastolic blood pressures (r = 0.57, P less than 0.01). Resting vascular resistance and minimal vascular resistance were significantly higher in essential hypertensives than in normotensives (30.6 +/- 12.6 and 2.57 +/- 1.30 versus 16.3 +/- 8.0 and 1.47 +/- 0.63 mmHg/ml per min per 100 ml, P less than 0.05 and P less than 0.01, respectively). Both resting and minimal vascular resistance were significantly correlated with [Ca2+]i in platelets (r = 0.40 and P less than 0.05, r = 0.55 and P less than 0.01, respectively). These results suggest that [Ca2+]i in platelets reflects [Ca2+]i in vascular smooth muscle cells and may be a significant determinant of not only tone but also structural changes of resistance vessels.

Adult↗
PubMed1988

Decreased renal responses to atrial natriuretic peptide in renal wrap hypertension.

1. The effects of atrial natriuretic polypeptide (ANP) on renal function were examined in renal wrap hypertensive rabbits and sham operated rabbits. 2. ANP (2 micrograms/min) induced hypotension, but did not produce significant diuresis, natriuresis or change in the glomerular filtration rate (GFR) in renal wrap hypertensive rabbits (n = 8). 3. In sham operated normotensive rabbits (n = 4), ANP induced significant diuresis (230%) and increased GFR by about 40%. 4. Thus, ANP was markedly less effective in the impaired kidneys of renal wrapped rabbits than in normal kidneys.

Animals↗
PubMed1987

Properties of stereotyped series of postsynaptic potentials in hypoglossal motoneurons.

A stereotyped series of postsynaptic potentials produced in cat hypoglossal motoneurons by stimulation of the cerebral cortex, the inferior alveolar nerve or the lingual nerve was studied. These include an excitatory postsynaptic potentials (EPSP) and subsequently 3 different types of inhibitory postsynaptic potentials (IPSPs). The first is a short-lasting IPSP which was blocked by strychnine administration. The second is a gamma-aminobutyric acid (GABA) IPSP which was blocked by picrotoxin administration. This IPSP was sensitive to membrane polarization and dependent on a conductance increase. The third is a long-duration hyperpolarizing potential which was enhanced by the injection of picrotoxin and insensitive to membrane polarization. Moreover, we have demonstrated that the amplitude of cortically induced EPSPs decreased greatly with depolarization.

Animals↗
PubMed1987

Cytotoxic T lymphocyte clone recognizing self idiotype: its regulatory role in antibody production.

MOPC 104E idiotype-specific cytotoxic T lymphocyte (CTL) clones were established. The clone KA1.02 specifically killed MOPC 104E cells and inhibited anti-dextran antibody production in an idiotype-specific manner. Both cytotoxicity and antibody inhibition were restricted to the cross-reactive idiotype and class I histocompatibility antigen. The data presented here provide definitive evidence that the self idiotype is the immunogenic determinant recognized by T lymphocytes in association with the major histocompatibility complex product. A regulatory role of CTL in antibody response is proposed.

Animals↗
PubMed1987

Corticofugal inhibitory effects on lingually induced postsynaptic potentials in cat hypoglossal motoneurons.

The suppression of lingually or cortically induced postsynaptic potentials produced by conditioning stimulation of the cerebral cortex or the lingual nerve was studied in cat hypoglossal motoneurons. We have demonstrated that lingually or cortically induced inhibitory postsynaptic potentials were effectively suppressed by a conditioning stimulus of the cerebral cortex or the lingual nerve. In hypoglossal motoneurons after blocking inhibitory postsynaptic potentials by the administration of strychnine, lingually induced excitatory postsynaptic potentials and spikes were effectively suppressed by cortical stimulation. Whereas, a conditioning stimulus of the lingual nerve suppressed only a long-latency excitatory postsynaptic potential evoked by a test stimulus of the cerebral cortex, while a short-latency excitatory postsynaptic potential was unaffected. Picrotoxin and bicuculline appeared to act by reducing the suppression of lingually induced excitatory postsynaptic potentials produced by cortical conditioning stimulation.

Action Potentials↗
PubMed1987

Ultrastructural and immunological studies of virus particles observed in a T-cell line derived from a mouse spontaneous lymphoma.

Intracytoplasmic type A virus particles in clusters, associated with budding, immature type B and mature type B-like particles were observed in a T-cell line derived from a spontaneous lymphoma of an A/J mouse. These particles shared the antigenic determinants with murine mammary tumor virus from RIII, C3H, and GR strains as revealed by both indirect immunofluorescence and immunoperoxidase methods at ultrastructural level.

Animals↗
PubMed1987

Membranoproliferative glomerulonephritis associated with chronic hepatitis B in adults: pathogenetic role of HBsAg.

Two adult cases of membranoproliferative glomerulonephritis (MPGN) associated with chronic hepatitis B were reported. Serum HBsAg, HBeAg and anti-HBc were positive. Glomerular changes were essentially the same in both patients and consistent with MPGN type III. Immunofluorescence microscopy revealed diffuse granular and lumpy deposits of IgG, IgA, IgM, C1q and C3 along glomerular capillary walls and in mesangial areas. Granular deposition of HBsAg was observed along capillary walls and in mesangial areas, and the staining patterns were similar to those of immunoglobulins and complements in both patients. Glomerular deposition of HBeAg, however, was negative in one case, and only slight and segmental in the other case. These findings suggest that HBsAg rather than HBeAg may play a role in the pathogenesis of MPGN associated with hepatitis B virus infection in adults.

Antibodies, Viral↗
PubMed1987

Differences in vasodilating action between ketanserin, a 5-HT2-serotonergic receptor antagonist, and terazosin, an alpha 1-adrenoceptor antagonist, in anesthetized rabbits.

It has not yet been demonstrated clearly whether the antihypertensive action of ketanserin is due to 5-hydroxytryptamine type-2 (5-HT2)-serotonergic receptor blockade or to alpha 1-adrenergic receptor blockade. The present study was performed to evaluate in vivo the antihypertensive action of ketanserin in comparison with that of terazosin, a selective alpha 1-adrenoceptor antagonist. The changes of renal blood flow (RBF) after intrarenal injection of phenylephrine, 5-HT, or angiotensin II were measured in anesthetized rabbits. RBF responses induced by these vasoconstrictors with or without pretreatment with ketanserin (0.2, 1.0, and 5.0 mg/kg, i.v.) or terazosin (0.04, 0.2, and 1.0 mg/kg, i.v.) were examined. Following intrarenal injection, RBF decreased by 20.8%, 22.7%, and 23.0% respectively, without ketanserin and also decreased by 21.0%, 21.6%, and 24.4%, respectively, without terazosin. Following pretreatment with a small dose of ketanserin or terazosin, the vasoconstricting effects of phenylephrine were attenuated by 20% or 62% (delta% changes in RBF), respectively. The effects of 5-HT on RBF responsiveness were blocked by ketanserin in a dose-dependent manner. Ketanserin did not modify the RBF responses to angiotensin II. These findings indicate that the antihypertensive effect of ketanserin, to a certain extent, depends on the blockade of the 5-HT2-serotonergic receptor in addition to that of the alpha 1-adrenoceptor, whereas the renin-angiotensin system is not involved in the hypotensive effects of ketanserin.

Animals↗
PubMed1987

The role of L3T4-positive T lymphocytes in the generation of anti-tumor immunity in the mouse.

The role of L3T4-positive lymphocytes in the generation of anti-tumor immunity against syngeneic murine plasmacytoma was investigated. The induction of in vitro primary and secondary cytotoxic T lymphocytes against MOPC-104E plasmacytoma of BALB/c origin was completely inhibited by the addition of monoclonal anti-L3T4 antibody (GK1.5) during the culture period. The possible participation of L3T4-positive lymphocytes in the induction of cytotoxic T lymphocytes was confirmed by the pretreatment of non-immune or immune splenocytes with GK 1.5 plus complement followed by in vitro stimulation with the tumor. The treatment abrogated the ability to generate killer T cell activity. Because the effector killer T lymphocytes were not affected by GK1.5 plus complement treatment, the results strongly suggest that the L3T4-positive lymphocytes might be acting as helper cells for the generation of killer T lymphocytes. The in vivo effect of GK1.5 on anti-tumor immunity was then investigated. Tumor cell growth in mice which received GK1.5 injections was significantly accelerated and the mean survival time of the mice was shorter than that in control groups. On the other hand, mice with established anti-tumor immunity produced by hyperimmunization of tumor cells were affected differently from non-immune mice, showing 50% tumor incidence on day 30 after viable tumor challenge. The present study supports the contention that the L3T4-positive T lymphocytes, probably helper T cells, play a crucial role in the establishment of anti-tumor immunity.

Animals↗
PubMed1987

Effect of the anticomplementary agent, K-76 monocarboxylic acid, on experimental immune complex glomerulonephritis in rats.

We examined the effect of the anticomplementary agent K-76 monocarboxylic acid (K-76COOH), which is known to inhibit C5 activity, on immune complex glomerulonephritis in rats. Bovine serum albumin (BSA) nephritis was induced in rats by subcutaneous immunization and daily intravenous administration of BSA. K-76COOH (30 mg/kg) was administered intraperitoneally twice daily for 4 weeks. It was shown that K-76COOH would significantly reduce the development of proteinuria in the early stage of BSA nephritis, but it failed to suppress proteinuria in the late stage. There was no significant difference in glomerular changes between treated animals and non-treated controls. These findings suggest that C5, and the terminal complement components may play a significant role in protein excretion in the early stage of immune complex glomerulonephritis.

Animals↗
PubMed1986

Cortically and lingually induced postsynaptic potentials in trigeminal motoneurons after axotomy.

The membrane properties and the efficacy of excitatory and inhibitory synapses were studied in cat masseteric motoneurons (Mass Mns) after axotomy. In axotomized Mass Mns the slope of the primary range in the frequency-current relationship showed a higher gain than that of normal Mass Mns. The safety of antidromic invasion was increased and the initial segment component of antidromic action potentials could not be separated from the soma-dendritic component. In normal Mass Mns a single shock delivered to the orbital gyrus or the lingual nerve induced long-lasting inhibitory postsynaptic potentials (IPSPs). In two-thirds of Mass Mns explored 30 days after axotomy, a single shock delivered to the orbital gyrus or the lingual nerve evoked a mixture of inhibitory and excitatory synaptic potentials. In Mass Mns 50 days after axotomy, we have demonstrated that the major fraction of the total sample of explored Mass Mns showed long-lasting excitatory postsynaptic potentials followed by IPSPs. The results suggest that in Mass Mns, axotomy is followed by the decline of synaptic efficacy of inhibitory rather than of excitatory synapses.

Animals↗
PubMed1986

Effects of antifibrotic substances on pancreatic fibrosis following acute necrotizing pancreatitis.

This study was designed to search for a way to inhibit pancreatic fibrosis following acute pancreatitis. Experimental necrotizing pancreatitis was induced by a freezing procedure in the pancreas of male Wistar rats. After the freezing procedure, the rats were divided into 3 groups: nothing addition was done to the control group, while the other 2 groups received daily intraperitoneal administration of antifibrotic substances (colchicine or L-azetidine-2-carboxylic acid (AZC)) for 6 weeks. Pancreatic enzymes in the serum were not markedly influenced by administration of antifibrotic substances, and there were no differences in the ratios of dry to wet weights of the pancreas between groups with and without these drugs. After freezing, the hydroxyproline levels in the pancreas of the control group increased from 1 to 4 weeks and then decreased during the 5th and 6th weeks. All groups receiving colchicine or AZC exhibited a significant decrease in the hydroxyproline levels at 2 to 4 weeks compared with the control group (P less than 0.01). Histological examination also showed the inhibition of pancreatic fibrosis, agreeing with changes in the hydroxyproline levels in groups receiving colchicine or AZC. These results suggest that administration of antifibrotic substances, colchicine and AZC, have the possibility of inhibiting pancreatic fibrosis following acute pancreatitis.

Animals↗
PubMed1986

Properties of postsynaptic potentials evoked in hypoglossal motoneurons by inferior alveolar nerve stimulation.

The properties of excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) produced in cat hypoglossal motoneurons by inferior alveolar nerve stimulation were studied. The percentage magnitude of a short- and a long-lasting component in inferior alveolar-induced IPSPs was measured by application of double shocks separated by 80- to 90-ms intervals to the inferior alveolar nerve. As a result, the protruder motoneurons received synaptic input primarily from the afferent fibers in both the ipsilateral and the contralateral inferior alveolar nerve generating the long-lasting IPSP. In addition, the retractor motoneurons received afferent fibers from the bilateral inferior alveolar nerves to generate the short- and the long-lasting IPSP. With respect to the properties of EPSPs, we have demonstrated that the amplitude of inferior alveolar-induced EPSPs decreased greatly with depolarization.

Animals↗