Biomedical subjects

Y Nakai

Publications and source records attributed to Y Nakai.

At least 19 recordsLinked to original sources

PubMed1992

Ultrastructural studies of medullary synaptic inputs to vasopressin-immunoreactive neurons in the supraoptic nucleus of the rat hypothalamus.

Direct projections from the A1/C1 catecholaminergic cell group in the caudal ventrolateral medulla oblongata to neurons containing vasopressin (VP) in the supraoptic nucleus (SON) were studied electron microscopically by a double-labeling technique which combines anterograde tracing after injection of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the A1/C1 cell group with VP immunocytochemistry. WGA-HRP-labeled axon terminals originating from neurons in the A1/C1 cell group were found to make synaptic contacts with VP-immunoreactive cell bodies and dendrites in the SON, most often forming axo-dendritic synapses. This indicates that VP-containing neurosecretory neurons in the SON receive monosynaptic catecholaminergic input from the A1/C1 cell group.

Animals↗

PubMed1992

Retinoic acids inhibit activation-induced apoptosis in T cell hybridomas and thymocytes.

Apoptosis is induced in immature thymocytes and T cell hybridomas upon stimulation via the TCR/CD3 complex. This phenomenon appears to be related to negative selection of T cell clones in the thymus. In T cell hybridomas, it has been shown that glucocorticoids inhibit TCR/CD3-mediated apoptosis, whereas glucocorticoids alone induce apoptosis. All-trans-retinoic acid (RA) at 0.1 to 10 microM also inhibited TCR/CD3-mediated apoptosis assessed by DNA fragmentation and cytolysis, but RA alone hardly induced apoptosis. RA enhanced the effects of glucocorticoids to induce apoptosis and to inhibit TCR/CD3-mediated apoptosis. TCR/CD3-mediated stimulation can be mimicked by the combination of ionomycin, a calcium ionophore, and PMA, an activator of protein kinase C, and the combination-induced DNA fragmentation was also inhibited by RA. RA, however, failed to inhibit the combination-induced increase in intracellular Ca2+ concentration or the combination-induced translocation of protein kinase C from the cytosolic fraction to the particulate fraction. Time course studies of RA addition into the culture indicated that a 3- to 6-h delay in the addition of RA did not reduce its inhibitory effect on anti-CD3-induced DNA fragmentation. These results suggest that RA interferes with the apoptotic process at some point after its initiation stage. It has been suggested that negative selection involves not only TCR/CD3-mediated signals but also LFA-1-mediated signals. RA at 0.01 to 1 microM significantly inhibited the induction of thymocyte apoptosis by co-immobilized mAb to CD3 and LFA-1 molecules. RA by itself hardly induced apoptosis, but enhanced glucocorticoid-induced apoptosis. The results suggest that thymic selection might be influenced by RA at near-physiologic concentrations. The receptors of glucocorticoids and RA belong to the erbA oncogene-related steroid hormone receptor superfamily. Thyroid hormones and 1 alpha,25-dihydroxy vitamin D3, whose receptors also belong to the superfamily, failed to modulate apoptosis in both T cell hybridomas and thymocytes.

Animals↗

PubMed1992

Noradrenergic innervation of vasopressin-containing neurons in the rat hypothalamic supraoptic nucleus.

The noradrenergic innervation of vasopressin (VP)-containing neurons in the supraoptic nucleus (SON) of the rat hypothalamus was studied electron microscopically by using double-labeling immunocytochemistry combining the pre-embedding peroxidase-anti-peroxidase method with post-embedding immunocolloidal gold staining. Noradrenaline-like immunoreactive axon terminals were found to make synaptic contacts with neurophysin II-like immunoreactive neurons in the SON. This provides morphological evidence for noradrenergic control of neuronal activity of VP-containing neurons at the SON level.

Adrenergic Fibers↗

PubMed1992

Immunochemical characterization of rat testicular asparagine synthetase.

We studied immunochemical properties of rat testicular asparagine synthetase. Western blot analysis of testis extract with polyclonal antibody raised against purified asparagine synthetase revealed an immunoreactive band at 62 kDa. The pancreas, brain, thymus, and spleen also showed 62-kDa bands. The intensities of these bands were roughly proportional to the specific activities of the enzyme in these tissues. The antibody showed some degree of cross-reactivity to asparagine synthetases from human, beef, pig, mouse, guinea pig, chicken, and frog, but not carp. But the enzyme from human HL-60 cells and lower vertebrates reacted with the antibody less strongly than enzyme from rats. The N-terminal amino acid sequence of the enzyme, determined by the Edman degradation method, in 10 recovered residues was identical to that of human asparagine synthetase deduced from corresponding cDNA (I.L. Andrulis et al., 1987, Mol. Cell. Biol. 7, 2435-2443). Immunohistochemical staining of the testis showed the presence of asparagine synthetase mainly in Sertoli cells in the seminiferous tubules.

Amino Acid Sequence↗

PubMed1992

Regulation of interleukin-1 receptors on AtT-20 mouse pituitary tumour cells.

To study the cellular mechanisms of interleukin-1 (IL-1) in the pituitary corticotroph, we studied the properties of IL-1 receptors on a mouse pituitary ACTH-producing cell line, AtT-20. Scatchard plot analysis revealed a single type of receptor with a Kd (dissociation constant) of 93 pM, and 482 binding sites/cell. [125I]IL-1 alpha binding competed with IL-1 alpha and IL-1 beta in an equimolar fashion. A 24 h pre-incubation with either CRH, epinephrine or nor-epinephrine increased the [125I]IL-1 alpha binding sites in the AtT-20 cells and conversely, a similar pre-incubation with either dexamethasone or tumour necrosis factor-alpha (TNF alpha) decreased them without affecting the affinity of the receptors in either case.

Adrenocorticotropic Hormone↗

PubMed1992

Mechanism of induction of micronuclei and chromosome aberrations in mouse bone marrow by multiple treatments of methotrexate.

Methotrexate (MTX), an inhibitor of dihydrofolate reductase (DHFR), slightly induced micronuclei and this induction of micronuclei was enhanced by multiple treatments with the drug (Yamamoto et al., 1981; Hayashi et al., 1984; CSGMT/JEM.MMS, 1990). More micronuclei and chromosomal aberrations in mouse bone marrow cells were induced by multiple than by single treatment. The MTX level in mouse plasma and bone marrow showed little (or no) differences between single and quadruple treatments several hours after the injection(s). On the other hand, the DHFR activity in bone marrow cells 3 h after one and four injections was decreased to approximately 38 and 0%, respectively, of that in non-treated mice. Furthermore, the intracellular MTX level in the bone marrow cells (but not in total bone marrow) after four injections was about 10-fold higher than that after one injection. The amount of MTX bound to protein 3 h after four injections, as assayed by gel filtration (Sephadex G-25), was approximately 8-fold greater than after one injection. Therefore, the multiple-dose effects of MTX on the induction of micronuclei and chromosomal aberrations may be explained by the intracellular accumulation of MTX resulting in an enhancement of enzyme inhibition.

Animals↗

PubMed1992

TRH regulation of tracheal tension through vagal preganglionic motoneurons.

TRH-immunoreactive nerve terminals innervate the ambiguous nucleus in the rabbit. Vagal preganglionic motoneurons that innervate the trachea, were revealed by HRP histochemistry in the rostral part of the ambiguous nucleus and the dorsal motor nucleus of the vagus. HRP histochemistry plus TRH immunocytochemistry revealed that TRH-immunoreactive axon terminals synapsed on ambiguous nucleus neurons retrogradely labeled by HRP injection into tracheal smooth muscle and the superior laryngeal nerve. Microinjection of 50 ng TRH into the rostral ambiguous nucleus caused slight dilation followed by constriction, which was inhibited by atropine and vagotomy. Results show that central TRH-containing neurons regulate tracheal tension through synapses on vagal preganglionic motoneurons that innervate tracheal smooth muscle.

Animals↗

PubMed1992

GABAergic innervation of serotonergic neurons in the dorsal raphe nucleus of the rat studied by electron microscopy double immunostaining.

A double immunocytochemical method combining the preembedding PAP technique and the postembedding immunogold technique was used to examine interactions between GABAergic and serotonergic neurons in the same tissue sections of the dorsal raphe nucleus of the rat. A large number of immunogold stained GABAergic axon terminals were found to be presynaptic to strongly PAP immunostained serotonergic perikarya and dendrites. The types of synapses were mostly symmetrical although a few asymmetrical ones were also found. No axo-axonic synapse between the GABAergic axon terminals and the serotonergic neuronal profiles was found. These results suggest that GABAergic neurons could modulate serotonergic neurons in the dorsal raphe nucleus through synaptic relations.

Animals↗

PubMed1992

Responses of plasma adrenocorticotropic hormone, cortisol, and cytokines during and after upper abdominal surgery.

There is currently accumulating evidence for bidirectional communication between the neuroendocrine and immune systems. Various cytokines have been suggested to be involved in the stimulation of stress hormone secretion during the times of infection and inflammation. To assess the possible involvement and pathophysiologic significance of cytokines in the mechanisms responsible for the perioperative stress response of the hypothalamo-pituitary-adrenal axis, we observed the changes of plasma adrenocorticotropic hormone and cortisol levels together with those of plasma endotoxin and cytokine levels. In patients undergoing pancreatoduodenectomy, perioperative stimulation of adrenocorticotropic hormone and cortisol secretion was accompanied by a significant elevation of plasma cytokine levels. Application of epidural block up to the upper thoracic levels failed to suppress this stress response effectively. In patients undergoing unilateral total hip replacement, the response of plasma hormone levels was smaller and briefer with no significant increase of plasma cytokine levels. Application of epidural block up to the lower thoracic levels suppressed this hormonal response almost completely. In patients undergoing pancreatoduodenectomy, a significant elevation of plasma endotoxin level was followed by a gradual but significant elevation of plasma tumor necrosis factor alpha and interleukin-6 levels. It seems likely that the stimulatory effects of these cytokines on the secretion of adrenocorticotropic hormone and cortisol might be involved in the development of the greater and more prolonged stress response of hypothalamo-pituitary-adrenal axis. Our present study suggests that not only neural input from the surgical wound but also stimulation of cytokine production were responsible for the development of the stress response of the hypothalamo-pituitary-adrenal axis during and after upper abdominal surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1992

Pulsatile umbilical venous flow and its clinical significance.

OBJECTIVE: To determine the prevalence and significance of pulsatile waveforms from the umbilical vein. SETTING: A tertiary referral clinic for high risk pregnancies. SUBJECTS: 209 fetuses from 24-41 weeks gestation. MAIN OUTCOME MEASURES: The presence of pulsatile waveforms in the umbilical vein and the pregnancy outcome. RESULTS: 9/209 fetuses demonstrated pulsatile waveforms and seven had severe growth retardation or congenital anomalies of the heart. Pulsatile flow and abnormalities of the inferior vena cava waveforms were observed in these seven but not in the two infants who were born at term. Double pulsations are described for the first time. CONCLUSION: Examination of the umbilical venous waveform for pulsatile flow is a useful test as it indicates the presence of asphyxial cardiomyopathy or congenital heart lesions.

Blood Flow Velocity↗

PubMed1992

Germ line-restricted supernumerary (B) chromosomes in Eptatretus okinoseanus.

Cytogenetic studies were performed on two types of Japanese hagfish (Eptatretus okinoseanus) that eliminate about 45% (type A) and 55% (type B) of their DNA from presumptive somatic cells during the differentiation of somatic cells. The observations revealed inter- and intraindividual variations in the number of chromosomes in germ cells of both types of hagfishes. Although the modal number of chromosomes in the germ cells was 54 in both types, the percentage of cells with the modal number was rather low (38.6% [51/132] in five specimens of type A and 22.7% [25/110] in eight specimens of type B). In addition, one of seven type B specimens clearly had a modal number of 62 chromosomes. Another specimen of type B had a bimodal distribution of chromosome numbers, with peaks of 54 and 59 chromosomes. The observation of interindividual variations was supported by data on the amount of DNA in germ cells of type B specimens. However, these variations were rarely observed in somatic cells. These results suggest that supernumerary (B) chromosomes are maintained in germ cells and are eliminated together with some other chromosomes and/or chromatin from somatic cells.

Aneuploidy↗

PubMed1992

Changes in serum erythropoietin levels during chemotherapy for lung cancer.

Serial serum erythropoietin (EPO) levels were measured in 12 adult lung cancer patients during cancer chemotherapy. In major cases, EPO levels increased significantly after chemotherapy while the hemoglobin (Hb) remained at initial levels. EPO fell gradually or rapidly to initial levels after a peak, although the patients were anemic. The increase of EPO levels was linearly related to the decrease in Hb (y = 17.48x + 1.003). The mechanism of the rapid increase of EPO is not simply explained by anemia, but might be related to new synthesis, corresponding to depressed bone marrow.

Adult↗

PubMed1992

Distribution and characterization of immunoreactive corticostatin in the hypothalamic-pituitary-adrenal axis.

Using an antiserum against synthetic rabbit corticostatin-1 (CS-1), we established a specific RIA for CS-1 and examined its distribution in various tissues, including the hypothalamic-pituitary-adrenal axis. Among the tissues examined, the highest levels of CS-1-like immunoreactivity (-LI) were found in the lung and spleen. CS-1-LI was also detected at relatively high levels in the pituitary, adrenal medulla, and small intestine, while it was barely detectable in the hypothalamus. Immunocytochemical studies revealed the widespread distribution of CS-1 in these tissues. Plasma CS-1 levels averaged 7.8 ng/ml and increased to 185.4 ng/ml in the presence of infection. CS-1-LI in the adrenal gland, small intestine, and hypothalamus also increased in rabbits with active inflammation. These data suggest that CS-1 may modify the hypothalamic-pituitary-adrenal axis in an endocrine or paracrine manner in response to infection.

Animals↗

PubMed1992

Detection of serum antibodies in Eimeria tenella-infected chickens by enzyme linked immunosorbent assay (ELISA) with merozoite and oocyst antigens.

Soluble antigens prepared from sporulated oocytes and second generation merozoites of E. tenella were used for enzyme linked immunosorbent assay (ELISA) to investigate antibody in sera of two breeds of chickens, i.e. commercial broilers and SPF single comb white leghorn layers, which were experimentally infected with E. tenella. In broilers inoculated with oocysts at 15 days of age, ELISA values increased rapidly after day 19 post inoculation (PI) and reached the maximum lebel on days 29 and 32 PI against both merozoite and oocyst antigen. The values against merozoite antigen were significantly higher than those against oocyst antigen. In SPF layers infected at 15 days of age, the values increased gradually after 7 days PI. There were no significant differences between values against two antigens. Generally, the values in broilers tended to be higher than those in SPF layers, especially against merozoite antigen. In broilers inoculated with oocysts at 1 and 15 days of age, ELISA values increased rapidly and reached the maximum level on days 11 and 20 post second inoculation (PSI) against merozoite and oocyst antigens respectively and then the values against merozoite antigen decreased. The values against merozoite antigen were markedly higher than those against oocyst antigen. In SPF layers inoculated twice, the values reached the highest on day 11 PSI as in the case of broiler; however, after that day, the values against both antigens decreased. The sera reacted similarly against both antigens. The values against merozoite antigen were significantly higher in broilers than in SPF layers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Chemotherapy in small cell lung cancer--from view point of dose intensity.

Results of chemotherapy trials for small cell lung cancer carried out for the past 5 years were analyzed from view point of dose intensity. Early study of CDDP+EP+ADM (1985 to 1987) showed moderate response rate (RR) of 72% with MST of 369 days. Succeeding alternative protocol of CDDP+EP+VCR/CPM+ADM+MTX (1989-1990) showed improved RR of 88% and MST of 13 months. Actual dose and interval for the alternating regimen was superior to the single arm regimen. Projected relative dose intensity against MAOP protocol including 6 drugs common to our regimen was 0.86 and delivered RDI was 0.61 with comparable RR and MST. The results may indicate that change of dose intensity within the conventional range does not result in major advantage or disadvantage for substantial prolongation of the survival in SCLC patients.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1992

Appropriate conditions for the plaque forming cell (PFC) assay in rats and effects of cyclophosphamide on PFC response.

The appropriate conditions for the plaque forming cell (PFC) assay using rat splenocytes were determined and effects of cyclophosphamide on PFC response were investigated using these conditions. The number of PFCs produced by immunization with a suspension of sheep red blood cells (SRBCs) was higher with i.v. injection than with i.p. injection. Subcutaneous injection of the suspension did not produce PFCs. The highest PFC response was observed when the number of PFCs was determined 4 days after i.v. immunization with 0.5 ml of a 1% SRBC suspension. Cyclophosphamide (3, 10, 30, 100 and 300 mg/kg, p.o.) dose-dependently decreased PFC response under the above-mentioned optimal conditions, and decreased PFC responses were noted even at the very low dose of 3 mg/kg: a dose at which a decrease in the number of PFCs has not been reported in studies using mice. From these results, the appropriate conditions for the PFC assay in rats are considered to be i.v. immunization with 0.5 ml of a 1% SRBC suspension and determination of the number of PFCs 4 days after immunization. Furthermore, it is considered that the PFC assay using rats might be more sensitive to immunosuppressive agents than that using mice.

Age Factors↗

PubMed1992

Pathogenic factors responsible for glucose intolerance in patients with NIDDM.

To define the pathogenic factors responsible for glucose intolerance in NIDDM, we estimated insulin secretory capacity, SI, and SG in 11 healthy, nondiabetic subjects and 9 NIDDM patients who had no SI impairment. All subjects studied were nonobese and normotensive. Each underwent a 75-g OGTT and a modified FSIGT: glucose was administered (300 mg/kg body weight), and insulin was infused (20 mU/kg over 5 min) from 20 to 25 min after the administration of glucose. SI and SG were estimated by Bergman's minimal-model method. The insulin response to oral glucose was significantly lower in NIDDM patients than in normal control subjects. First-phase insulin secretion expressed as the integrated area of plasma insulin above the basal level during the first 20 min was much smaller in NIDDM subjects (214 +/- 112 pM.min) than in control subjects (4643 +/- 885 pM.min, P < 0.01). SI was not statistically different in normal control subjects (1.27 +/- 0.18 x 10(-4) min-1.pM-1) versus diabetic patients (1.62 +/- 0.33 x 10(-4) min-1.pM-1). However, SG was significantly lower in diabetic subjects (1.11 +/- 0.17 x 10(-2) min-1) than in control subjects (2.35 +/- 0.26 x 10(-2) min-1, P < 0.01). These results suggest that impaired insulin secretion and decreased SG are the factors responsible for glucose intolerance of Japanese NIDDM patients with normal insulin sensitivity. Because SI and SG are the factors responsible for glucose intolerance of NIDDM patients with insulin resistance, it is conceivable that decreased SG is common in NIDDM patients regardless of their SI index.

Adult↗

PubMed1992

Microvasculature of normal and hydropic labyrinth.

The microvasculature of the inner ear in guinea pigs and humans was observed with a scanning electron microscope using corrosion casting method. Alterations in the inner ear vasculature which occurred in association with experimental endolymphatic hydrops were also investigated. The results thus obtained are summarized as follows: 1. In the cochlea and vestibule, the arteries, coiled arterioles, and the veins are endowed with their respective characteristic morphologic features and play a role in the regulatory mechanisms of circulation. 2. The point in humans which is most different from guinea pigs was that coiled arterioles in the cochlea and the coil-like traveling of the anterior vestibular artery is not outstanding. 3. Arteriovenous anastomoses were demonstrated to exist in lateral wall of cochlea and utricular macula, a finding suggesting the existence of a regulatory mechanism for local blood flow. 4. Endolymphatic hydrops was noted to be preferentially associated with vascular abnormalities in the lateral wall of the cochlear duct and in the saccular macula, among other vestibular structures.

Animals↗