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Biomedical subjects

M Kojima

Publications and source records attributed to M Kojima.

At least 775 records · Page 43Linked to original sources
PubMed1985

Development of slow Ca2+-Na+ channels during organ culture of young embryonic chick hearts.

Young (3-days-old) embryonic chick hearts have slowly-rising spontaneous action potentials, dependent on tetrodotoxin-insensitive slow Na+ channels. When the hearts were placed into organ culture for 5-11 days, action potential duration was markedly increased by 260-370%, and a notch appeared between the initial spike phase and the plateau phase in some hearts. The spike amplitude was mainly dependent on [Na]0, whereas the plateau amplitude was dependent on [Ca]0. Thus, the young embryonic hearts develop slow Ca2+-Na+ channels (while retaining the slow Na+ channels) during organ culture, and the spike phase and the plateau phase of the slow action potentials are mainly dependent on currents through slow Na+ channels and through slow Ca2+-Na+ channels, respectively. The effects of Mn2+ (a specific blocker of slow Ca2+-Na+ channels) and verapamil (a blocker of slow Na+ channels as well as of slow Ca2+-Na+ channels) on the spike phase and the plateau phase were examined. Mn2+ (0.5 mM) and verapamil (5 microM) depressed the plateau duration and overshoot. Verapamil did not decrease the maximum rate of rise (Vmax), but Mn++ produced a small, but significant, decrease. High concentrations (10/30 microM) of verapamil depressed the action potential amplitude and Vmax, and abolished the spontaneous action potentials. These results indicate that slow Ca2+-Na+ channels appear de novo during organ culture of young embryonic hearts.

Action Potentials↗
PubMed1985

Sex-dependent induction of hepatic enzymes for mutagenic activation of a tryptophan pyrolysate component, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]-indole, by feeding in mice.

Male and female BALB/c X DBA/2 F1 mice were treated with a diet containing 0.02% 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]-indole (Trp P-1), a hepatocarcinogenic tryptophan pyrolysate component, and the capacities of subcellular fractions of the liver to catalyze the mutagenic activation of Trp P-1 and its analogue Trp P-2 (4-demethylated Trp P-1) were examined by the in vitro Salmonella test with strain TA 98. In mice on control diet, both 9000 X g supernatant (S-9) and microsomal fractions from female mice livers displayed only 1.1- to 1.3-fold higher capacities for the mutagenic activation of either Trp P-1 or Trp P-2 than did those from male mice livers. When mice were treated with the Trp P-1 diet for 1 week, the S-9 activity in male mice for the Trp P-1 mutagenesis did not change, but that in females was increased to 2.5-fold of the female control. Treatment of mice with the dietary Trp P-1 for 2 weeks increased the S-9 activities to 2.8-fold in males and 4.9-fold in females of the same sex controls and the increased S-9 activities were not significantly changed by additional Trp P-1 feeding for 2 weeks. Similar changes in the S-9 activity were observed for the Trp P-2 mutagenesis. The overall changes in the S-9 activities induced by feeding Trp P-1 were reflected in the isolated microsomes. However, microsomes derived from the same volume of S-9 used exhibited only about one-half (Trp P-1) or one-third (Trp P-2) of the activity of the respective complete S-9 mixtures. Addition of liver cytosolic fractions (105,000 X g supernatants) from untreated or Trp P-1-treated mice to microsomes resulted in enhanced activities. Cytosols alone did not activate the compounds to mutagens. The microsome-mediated mutagenicity of either Trp P-1 or Trp P-2 was diminished by removal of NADPH from the assay system. It was also inhibited by addition of 7,8-benzoflavone and to a lesser extent by SKF 525A. Enzyme(s) for the mutagenic activation of Trp P-1 was induced by an i.p. injection of 3-methylcholanthrene to mice and to a lesser extent by an injection of phenobarbital, but no sex differences were observed in these enzyme inductions as opposed to the Trp P-1 feeding.(ABSTRACT TRUNCATED AT 400 WORDS)

Aminopyrine N-Demethylase↗
PubMed1985

[Treatment of primary empty sella with intractable headache via the transsphenoidal approach].

Two cases of primary empty sella with intractable headache were treated via the transsphenoidal approach. One patient was a fifty-three-year-old female with right upper nasal quadrantanopsia and intractable retrobulbar pain and the other was fourty-six-year-old female with continuous retrobulbar pain with a history of transient right temporal hemianopsia. Both cases were diagnosed by metrizamide CT cisternography. They had normal endocrinological functions. They did not respond to drug therapy and were treated surgically. In each case, the dura mater of the floor of the sella was elevated with lyophilized human dura mater and bone fragments obtained during the procedure. In the former case, significant improvement of visual field defect was not obtained but the retrobulbar pain disappeared completely after the operation. In the latter case which had intractable headache for six months, the symptom disappeared just after the operation. Until now, retroorbital pain has not recurred in both cases for several months. Primary empty sella has been considered to be a benign condition except in some cases with CSF rhinorrhea or with visual disturbance. Headache which is often accompanied to primary empty sella has rarely been treated surgically because it is difficult to know whether the headache is related to the empty sella or not. Another reason may be that there is few available data concerning to the efficacy of surgical treatment. Headache caused by stretching of the dura of the floor of the sella is usually frontal or retrobulbar, continuous, profound and intractable.(ABSTRACT TRUNCATED AT 250 WORDS)

Empty Sella Syndrome↗
PubMed1985

[Estrogen-induced pituitary tumors--in relation to the changes in the pituitary gland after estrogen withdrawal].

Pituitary tumors were induced in female rats of Wistar strain by administration of estradiol valerate (E2) and the effect of estrogen withdrawal on E2-induced tumors were studied to elucidate the nature of the induced tumors. Ten mg of E2 was administered to 100 rats intraperitoneally once every 2 weeks, totally four times. Experimental animals were sacrificed at 1 week before, 2, 6, 10, and 14 weeks after stopping injection of E2. The incidence of pituitary tumor and hyperplasia (Table 1). Pituitary glands in each animals were examined and were classified into three groups, namely pituitary tumor, hyperplasia, and normal gland according to histological findings. The incidence of pituitary tumors was highest in rats sacrificed 6 weeks after E2 withdrawal. Pituitary tumors became less frequent and hyperplasias and normal glands became more frequent in rats sacrificed thereafter. Pituitary weight (Table 2, Fig. 1) Irrespective of timing of sacrifice, the weight of pituitary gland (mean +/- SE) was 134 +/- 70 mg in the group which were judged as having a pituitary tumor, 38 +/- 17 mg in the hyperplasia group, and 17 +/- 5 mg in the normal group, respectively. Pituitary weight of control rats were 12 +/- 3 mg. The tumor group had a significantly heavier pituitary weight than hyperplasia and normal groups (p less than 0.01). In each group, there was no significant difference of pituitary weights between animals sacrificed at different intervals after E2 withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1985

[Clinical analysis of large and/or invasive pituitary adenomas].

To establish a more reasonable therapeutic guide line for large and/or invasive pituitary adenomas, 257 cases of pituitary adenoma were analyzed. Among 83 cases with slight or moderate suprasellar extension (Wilson's Grade II-A & B) in the pre-CT era, 57 patients were alive at the time of follow-up (mean follow-up period: 12.7 years). Death of unspecified causes other than cancer, myocardial infarction, etc. were reported in nine patients. Among 60 cases of Grade II-A & B in the post-CT era, 59 patients were alive (mean follow-up: 3.4 years). Comparing these groups, cases with huge suprasellar extension (Grade C) had much worse prognosis. Only two patients were alive among 14 cases of Group C in the pre-CT era. Seven cases of death with unspecified causes were reported. In the 13 cases of Group C in the post-CT era, 12 patients were alive but at least four of them were severely handicapped. In 10 cases with sphenoid invasion (Grade IV) in the pre-CT era, only two were alive. In the group of Grade IV in the post-CT era, one patient died and three patients were operated repeatedly. Severe complications of irradiation therapy occurred in seven patients (mean interval: 6.6 years) among 120 cases of irradiated pituitary adenomas in every category. Among six cases with histological malignancy, three were operated repeatedly; among the latter group, two patients died and the third showed intracranial metastases. The present data indicate that large and/or invasive pituitary adenomas have a pessimistic prognosis, although adenomas with mild or moderate simple suprasellar extension have fairly good prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1984

Sexual differences in the topographical distribution of serotonergic fibers in the anterior column of rat lumbar spinal cord.

Sexual dimorphism in the topographical organization of immunoreactive serotonergic fibers has been shown for the first time in the anterior column of the rat lumbar cord. A characteristic preferential arrangement of serotonergic fibers on the small cell column composed of anterior horn motoneurons, which have been proved to send their axons to the cremaster muscle, was demonstrated at the lumbar segments (L1-L2) of male rats, using the immunoperoxidase technique with antiserum against serotonin. A similar finding was also observed in female rats, but was less prominent than in males. Comparative analysis of the cell numbers and the size of neuronal somata of the aforementioned nucleus, done using retrograde transport of fluorescent dye (DAPI) via axonal fibers coursing down the genitofemoral nerve to the cremaster muscle, gave significantly larger values in males. The sexual difference in the serotonergic innervation pattern was, in consequence, surmised to be caused by the cytoarchitectonic contrast ascertained in the lumbar anterior column. Furthermore, there may be a striated muscle endowed with some active functions homologous to those of the male cremaster muscle in the female rat.

Animals↗
PubMed1984

Fluorescence histochemical study on the noradrenergic control to the anterior column of the spinal lumbosacral segments of the rat and dog, with special reference to motoneurons innervating the perineal striated muscles (Onuf's nucleus).

The organization of noradrenergic fibers in the lumbosacral anterior column of rats and dogs was examined in detail using a modification of a highly sensitive glyoxylic acid fluorescence histochemical method. In both rat and dog, there were greater concentrations of fluorescing noradrenergic fibers around the motoneurons innervating the perineal striated muscles (Onuf's nucleus) than around other motoneuronal groups. The preferential accumulation of noradrenergic fibers in Onuf's nucleus may indicate that the noradrenergic neuron system in the spinal cord of rodents and carnivores is closely related to the functional peculiarities of the perineal striated muscles, including the external anal and urethral sphincter muscles.

Animals↗