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Biomedical subjects

M Imai

Publications and source records attributed to M Imai.

At least 487 records · Page 27Linked to original sources
PubMed1985

[The effect of reduced glutathione on the changes of lipid-peroxide concentration in shock states--clinical and experimental studies].

Lipoperoxide changes and the effect of reduced glutathione (GSH) on that were investigated in cardiopulmonary bypass and endotoxin shock states. In human cardiopulmonary bypass, 26 patients with congenital heart disease were studied and the following results were obtained. Serum lipoperoxide concentration in control group increased in 30 and 60 min after bypass. On the other hand, in the reduced glutathione pretreatment group (100 mg/kg), this change was not observed. In both groups, beta-glucuronidase activity had a tendency to increase after bypass, and it had a close correlation between serum lipoperoxide concentration and beta-glucuronidase activity. In endotoxin shock rats, the results were as follows. 3 hours after injection of endotoxin (10 mg/kg), hepatic lipoperoxide concentration increased and superoxide dismutase (SOD) activity decreased, and hepatic Chemiluminescence counts had a tendency to increase. There was no significant change in serum lipoperoxide concentration after 3 hr, but a significant elevation was observed only after 6 hr. In the reduced glutathione pretreatment group (1,000 mg/kg), serum and hepatic lipoperoxide concentration, hepatic SOD activity, and hepatic Chemiluminescence counts were unchanged. These results suggest that lipoperoxide may increase in shock states and GSH administration may be useful to inhibit lipoperoxide formation.

Adolescent↗
PubMed1984

A two-site sandwich radioimmunoassay of beta 2-microglobulin with monoclonal antibodies.

Among 21 batches of monoclonal antibodies raised against beta 2-microglobulin (anti-beta 2m), 6 reacted with soluble beta 2m, as well as with beta 2m present in association with HLA heavy chains on the surface of leukocytes. The remaining 15 anti-beta 2m antibodies bound with soluble beta 2m, but failed to react with beta 2m on the cell surface. No monoclonal anti-beta 2m antibodies revealed precipitin lines when they were tested against beta 2m in immunodiffusion. When 2 anti-beta 2m antibodies with different specificities were mixed together, however, they developed a precipitin line against beta 2m. Based on these observations, there was only 1 epitope on beta 2m that was available for the binding with a monoclonal anti-beta 2m antibody with either specificity. This allowed the development of a solid-phase radioimmunoassay in which beta 2m in test specimens was sandwiched between immobilized anti-beta 2m of 1 specificity and radiolabeled anti-beta 2m of a heterologous specificity in a single step. Monoclonal antibodies with at least 2 different specificities would be required for developing a sandwich-type immunoassay of polypeptides, such as beta 2m, that do not display 2 or more epitopes of the same specificity.

Animals↗
PubMed1984

ECG changes during cerebral angiography. An analysis of 334 patients--942 cerebral angiographies.

We have analyzed HR changes greater than 20% among 334 patients and 942 cerebral angiographies. A tachycardial effect was seen in 14.9% of patients, while a bradycardial effect was seen in 7.1% including two patients having cardiac standstill (0.5%). These two patients were examined without atropine premedication after subarachnoid hemorrhage. Patients under 19 years of age, unpremedicated with atropine sulfate and suffering from subarachnoid hemorrhage secondary to ruptured aneurysm or arteriovenous malformation showed a significantly high incidence of bradycardia. On the other hand, patients with the neoplastic disease and having an initial sinus bradycardia showed a significantly high incidence of a tachycardial effect.

Adolescent↗
PubMed1984

Isolation and characterization of rho mutants of Escherichia coli with increased transcription termination activities.

A novel type of rho mutants, rhos, with increased transcription termination activities have been isolated. A termination defective rho mutation rho-ts702 (formerly designated nitA702), which causes temperature-sensitive cell growth, was found to be dominant over the wild-type allele in relieving mutational polarity. The rhos mutations were derived as temperature-resistant revertants of rho-ts702 carried by lambda transducing phage. They exhibited dominance over rho-ts702 leading to restoration of polarity. When the rhos mutations were introduced into the Escherichia coli chromosome, they caused increased polarity in the trp and lac operons. The rhos mutants were classified into two groups in terms of their terminator specificity: The first group demonstrated increased termination efficiencies against all terminators tested, whereas the second exhibited various efficiencies, either more than or less than the normal level depending on the terminator. The cellular content of p protein in each rhos strain was significantly lower than that in the rho+ strain. Moreover, in an in vitro transcription system, purified ps proteins showed increased termination activities against the trpE pseudoterminators. These results indicate that the rhos phenotype is due to qualitative alterations, rather than quantitative increases, of the p protein. The reduced content of ps enforces the current notion that the rho gene is autogenously regulated by rho-dependent transcriptional attenuation.

Base Sequence↗
PubMed1984

Effects of solute concentration on vasopressin stimulated cyclic AMP generation in the rat medullary thick ascending limbs of Henle's loop.

We examined effects of osmolality or sodium concentration on vasopressin induced cyclic AMP generation in the medullary thick ascending limbs isolated from collagenase treated rat kidneys. Vasopressin-stimulated cyclic AMP generation was increased as a function of NaCl concentration of the incubation medium. Addition of sucrose was also effective in enhancing the vasopressin-stimulated cyclic AMP, whereas addition of urea was without effect. When incubation medium was made hypertonic with sodium cyclamate, vasopressin-stimulated cyclic AMP generation was also enhanced. When choline chloride was used instead of sodium cyclamate, only an insignificant increase in the hormone-stimulated cyclic AMP generation was observed. These results suggest that the responsiveness of the rat medullary thick ascending limbs to vasopressin is regulated, at least in part, by transmembrane osmotic gradient.

Animals↗
PubMed1984

Functional heterogeneity of the descending limbs of Henle's loop. I. Internephron heterogeneity in the hamster kidney.

By using the in vitro microperfusion technique, were examined functions of the descending limbs of Henle's loop obtained from either the short-loop nephron (SDL) or the upper portion of the long-loop nephron of hamsters (LDLu). Morphological distinctions between these segments were confirmed by light and electron microscopic observations. Both segments were highly permeable to water. The LDLu was highly permeable to sodium and to chloride: efflux coefficients (10(-7) cm2 x s-1) for 22Na and 36Cl were 41.0 +/- 5.4 and 3.8 +/- 0.6, respectively. The SDL were less permeable to sodium and to chloride: efflux coefficient for 22Na and 36Cl were 2.9 +/- 1.4 and 0.9 +/- 0.2, respectively. In contrast, the SDL was more permeable to urea as compared to the LDL, efflux coefficients for urea being 5.1 +/- 1.4 vs 1.4 +/- 0.3, respectively. When composition of the perfusate was identical to that of the bathing fluid, no transepithelial voltage was demonstrated. The volume flux was very small or undetectable. From these observations, we propose that the internephron heterogeneity must be taken into consideration for constructing a model of countercurrent system in the renal medulla.

Animals↗
PubMed1984

Functional heterogeneity of the descending limbs of Henle's loop. II. Interspecies differences among rabbits, rats, and hamsters.

Permeability properties of the descending limbs of Henle's loop were compared among rabbits, hamsters, and rats by measuring transepithelial voltage (Vt) across the isolated renal tubules perfused in vitro. From the deflection of the Vt when the composition of the bathing fluid was varied, the permeabilities of sodium and of potassium relative to chloride (Pna/PCl and PK/PCl, respectively) were determined in either the descending limbs of the short-loop nephron (SDL) or the segments of the upper protion of the long-loop nephron (LDLu). In hamsters and rats, the values of PNa/PCl of the LDLu (3.98 +/- 0.66 and 5.03 +/- 0.79) were higher than those of the SDL (0.68 +/- 0.03 and 0.61 +/- 0.00). In contrast, in rabbits the value of PNa/PCl of the LDLu (0.96 +/- 0.05) was only slightly higher than that of the SDLu (0.75 +/- 0.03). The similar tendency was also noted in the values of PK/PCl. In hamsters and rats, the PK/PCi ratios were 4.90 +/- 0.82 and 6.44 +/- 0.90, respectively, in the LDLu and 1.09 +/- 0.04 and 1.02 +/- 0.0, respectively in the SDL. When a transepithelial osmotic gradient was imposed by adding raffinose to the bath, a lumen-negative streaming voltage of about -8 mV was generated in the hamster and the rat LDLu. Taken together with the findings in the preceding paper, these observations support the view that the descending limbs of rabbits are different from those of hamsters and rats in that internephron heterogeneity is less remarkable, and that the LDLu of hamsters and rats is highly permeable to sodium and to potassium as well as to water.

Animals↗
PubMed1984

Distribution of alpha-adrenergic receptors in the rabbit nephron.

In order to determine the distribution of alpha-adrenergic receptors within a nephron, a method was used to determine the specific binding of [3H]-prazosin to isolated fragments of rabbit renal tubules. When 10(-8) moles/liter [3H]-prazosin was incubated with proximal convoluted tubules, 61.4% of total binding was accounted for specific binding. The [3H]-prazosin binding to the proximal convoluted tubule was a linear function of the tubular length and reversible. It was inhibited with 10(-4) moles/liter phenoxybenzamine by about 60%, and with 10(-4) moles/liter norepinephrine by about 25%, but not with either atenolol or isoproterenol. No specific binding of [3H]-prazosin was observed in the proximal straight tubule and in the cortical collecting tubule. These data are in good agreement with the view that alpha-1 adrenergic receptors are mainly distributed in the proximal convoluted tubules.

Animals↗
PubMed1984

Effects of parathyroid hormone and calcitonin on stop-flow patterns of cyclic AMP, sodium, potassium, calcium and inorganic phosphate in thyroparathyroidectomized rabbits.

Conventional stop-flow studies were performed in thyroparathyroidectomized rabbits in order to examine the effects of parathyroid hormone (PTH) and calcitonin on urinary excretion of 3',5'-cyclic adenosine monophosphate (cAMP), Na, K, Ca, and inorganic phosphate (Pi). PTH markedly increased excretion of cAMP in the distal as well as in the proximal fractions. PTH increased Na concentration at the proximal and the distal fractions. K concentration was increased with PTH in all segments, and two prominent peaks were observed at the late proximal and the terminal fractions. Although changes in the pattern of Ca concentration after PTH were similar to those of Na, the pattern of Ca concentration normalized by Na concentration (Ca/Na) showed a decrease in Ca concentration in the late distal fractions. PTH increased Pi concentration in two portions, the proximal and the late distal fractions. Calcitonin slightly increased excretion of cAMP at the midfractions. Calcitonin did not cause any significant changes in the patterns of Na and Pi, but increased Ca concentration in the early distal fractions and K concentration in the late proximal fractions. From these findings we suggest: (a) nephrogenous cAMP responsive to each hormone partly corresponds to nephron distribution of hormone-dependent adenylate cyclase; (b) the sites of action of these hormones are quite distinct in the rabbit kidney; (c) the distal nephron segments play important roles in anticalciuric and phosphaturic actions of PTH, and (d) mechanisms of increases in K excretion by these two hormones may be different.

Adenylyl Cyclases↗
PubMed1983

A two-site sandwich radioimmunoassay of human fibroblast (beta-) interferon with monoclonal antibodies.

Monoclonal antibodies were produced against human fibroblast (beta-)interferon (IFN-beta). Four of them were directed to the determinant designated a, while the remaining 3 to another determinant named b. An IFN molecule was found to bear one each of a and b determinants arranged in such a manner that the occupation of a with the corresponding antibody did not interfere with the binding of b to its corresponding antibody, and vice versa. This allowed the development of a 2-site sandwich radioimmunoassay in which antibody to b was immobilized on wells of a microtiter plate and the bound antigen was detected by the radiolabeled antibody to a. The 2-site sandwich radioimmunoassay detected, with a high sensitivity, IFN-beta either induced from fibroblast or produced by Escherichia coli harboring the gene of IFN-beta.

Animals↗