Yasutaka Noda

Regional characteristics of stress-induced increases in brain noradrenaline release in rats

Male Wistar rats were exposed to immobilization stress for various periods (1 to 5 hr) with or without an IP injection of probenecid at 400 mg/kg. The regional characteristics of stress-induced increases in noradrenaline (NA) release in the rat brain related to the time-course of stress were demonstrated by measuring levels of the major metabolite of NA, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4). Increases in MHPG-SO4 levels occurred mainly within the first hr of stress in the hypothalamus, amygdala and thalamus, while the peak elevations of the metabolite levels were delayed in the hippocampus, cerebral cortex, pons + medulla oblongata and basal ganglia. According to the accumulation of MHPG-SO4 during each 1-hr period of stress, regional characteristics of NA release were classified into the following four types based upon regions where the most marked increase in MHPG-SO4 levels occurs mainly: (1) within the first hr of stress (the hypothalamus, amygdala and thalamus), (2) during the first and second hr (the hippocampus and cerebral cortex), (3) during the third hr (the basal ganglia) and (4) to the same extent from the first to the fourth hr of stress (the pons + medulla oblongata). These results suggest that noradrenergic neurons in different brain regions respond differentially to stress and reflect their own characteristic patterns depending upon nature and time-course of the stressor.

Regional responses of rat brain noradrenergic neurones to acute intense stress.

Contents of noradrenaline (NA) and its principal metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), in six brain regions of the rat were monitored simultaneously during 180 min of acute intense stress, i.e., electric tail shock under immobilization. In the hypothalamus and amygdala, NA contents decreased rapidly, and subsequently remained at the decreased levels while MHPG-SO4 contents increased progressively. The hippocampus and cerebral cortex showed more delayed changes in NA and MHPG-SO4 contents than the above regions. In the pons+med. obl., no decreases of NA contents were observed at any time, but MHPG-SO4 contents increased significantly. Neither NA nor MHPG-SO4 content changed significantly in the basal ganglia except for a transient increase of NA. These results suggest that, during acute intense stress, each brain region responds differently and the NA content is maintained at a decreased level despite continuously enhanced release of the amine.

Cerebral blood flow and metabolism in experimental hydrocephalus.

Cerebral blood flow and metabolism were studied in experimental hydrocephalus which was produced by intracisternal injection of kaolin in cats, rabbits and rats. Measurements were carried out in varied stages of hydrocephalus. Local cerebral blood flow (l-CBF) was measured by the hydrogen clearance method. Assessment of cerebral metabolism was made biochemically in the brain tissues of various regions, including water content, Na, K, lactate, pyruvate, lipids, ATP, cyclic AMP, catecholamines and monoamine metabolites. Blood flow studies were performed in the cerebral cortex, periventricular white matter, thalamus and midbrain reticular formation in hydrocephalic cats. In all of these regions, l-CBF decreased to about half of the control in both acute and chronic stages of hydrocephalus. CO2 reactivity to CBF was impaired only in the acute stage, while autoregulation of CBF was preserved in the hydrocephalic brain. Water content of the brain tissue increased temporarily only within the periventricular white matter of hydrocephalic rabbits concomitant with increase in Na and decrease in K. Transient increase in the lactate and lactate/pyruvate ratios was also observed in the frontal lobe tissue. In hydrocephalic rats, decrease in phospholipids and cholesterol was observed parallel with the degree of ventricular dilatation. ATP and cyclic AMP decreased biphasically in both acute and chronic stages. On the other hand, increase in concentrations of norepinephrine, dopamine, homovanillic acid, and 5-hydroxyindoleacetic acid became evident in the chronic stage of hydrocephalus. From the above results, it is concluded that the hydrocephalic brain sustained considerable disturbance of metabolism in all modalities in association with decreased blood flow, which is sufficient to explain the clinical symptoms of hydrocephalus.

Muscarinic and nicotinic effects on yawning and tongue protruding in the rat

Physostigmine, an anticholinesterase agent, elicited yawning with a marked protrusion of the tongue and teeth chattering. Yawning and chattering were also observed after pilocarpine, a cholinergic agonist predominantly acting upon muscarinic receptors. Apomorphine at low doses (0.1-0.5 mg/kg), which preferentially activates presynaptic dopamine autoreceptors, elicited yawning, whereas at high doses (1-2 mg/kg) it produced stereotypy. Yawning induced by both cholinergic agonists and apomorphine was inhibited by scopolamine, a muscarinic receptor blocking agent, but not by methylscopolamine, a peripheral anticholinergic agent and mecamylamine, a nicotinic receptor blocking agent. Low dose (0.02 mg/kg) of haloperidol, which has been reported to block presynaptic dopamine autoreceptors, inhibited apomorphine-induced yawning but did not affect cholinergic agonist-induced yawning. Physostigmine-elicited tongue protruding was inhibited by mecamylamine. The results imply that yawning behavior is essentially associated with the stimulation of central muscarinic receptors, and that physostigmine also induces tongue protruding by activating the central nicotinic receptors.

MORPHOLOGICAL COMPARISONS AND HYPOTHESES ON THE ORIGIN OF POLYPLOIDS IN PARTHENOGENETIC FASCIOLA SP

It is known that Fasciola sp. from Japan and the Republic of Korea consist of diploids (2n = 2x = 20), triploids (2n = 3x = 30), and mixoploids with diploid and triploid cells. Triploids are distributed over Asia and Hawaii. Abnormal spermatogenesis and parthenogenetic reproduction are the main characteristics of Fasciola sp. Here we measured 21 different morphological parameters of diploid and triploid flukes of Fasciola sp. obtained from Japan and the Republic of Korea. Statistical analysis showed that diploid and triploid flukes were morphologically different. No bivalents or trivalents could be detected in diploid and triploid flukes, respectively. Based on our findings, we speculate that parthenogenetic diploids, triploids, and mixoploids (2x/3x) of Fasciola sp. are genetically related to each other.

Effects of a Long-Term Inhalation of Fragrances on the Stress- Induced Immunosuppression in Mice

The aim of this study was to determine the effects of the long-term application of various fragrances on the suppression of immune response induced by high-pressure stress in mice. The immune response was analyzed based on plaque-forming cell (PFC) count, using mice sensitized with sheep red blood cells. The decreased PFC involving thymic involution induced by high-pressure stress in mice was restored by exposing the stressed mice to tuberose, lemon, oakmoss and labdanum for 24 h following exposure to stress. The decreased PFC and thymic involution from stress were restored by exposure to lemon and oakmoss, but not to tuberose and labdanum when the mice were exposed to those fragrances continuously for 3 weeks before the stress was given, followed by exposure to the same fragrances for 24 h after the stress. The decreased PFC and thymic involution from stress were restored by exposure to lemon and labdanum for 24 h after the stress, but not to tuberose over 3 weeks before the stress was given. These data suggest that the neuroimmunomodulatory effects of fragrances may be affected by tolerance depending on the kinds of fragrances in the case of a long-term application.

Atrial natriuretic peptide (ANP): a study of ANP and its mRNA in cardiocytes, and of plasma ANP levels in non-obese diabetic mice.

SummaryAtrial natriuretic peptide (ANP) levels in cardiocytes and plasma were examined by using immunohistochemistry, electron microscopy, and radioimmunoassay in non-obese diabetic mice (NOD). Cardiocyte ANP mRNA expression was measured by the polymerase chain reaction method. ANP immunoreactivity in the auricular cardiocytes was more prominent in hyperglycemic mice (NOD-h) than in normoglycemic mice (NOD-n). Ultrastructural examination showed that auricular cardiocytes of the NOD-h group contained more cytoplasmic granules than cells of the NOD-n group. Ultrastructural morphometry indicated that the number of granules per auricular cardiocyte was significantly larger in the NOD-h group than in the NOD-n group. (P<0.01), whereas the granule diameter was significantly smaller in the NOD-h group (P<0.01). Radioimmunoassay showed that ANP levels in the NOD-h auricular cardiocytes were significantly higher than those in the NOD-n cardiocytes (P<0.01); the opposite was true in plasma. Cardiocyte ANP mRNA expression was lower in the NOD-h group than in the NOD-n group.

The oocyte of triploid fluke receiving intrusion of sperm from a diploid fluke-evidence for the origin of tetraploids in Paragonimus westermani

An experiment was conducted to elucidate the origin of tetraploids (2n = 4x = 44) of Paragonimus westermani that occur together with diploid (2n = 2x = 22) and triploid (2n = 3x = 33) types in Liaoning Province, the Peoples Republic of China. Metacercariae of the diploid type, obtained from Hyogo Prefecture, Japan, and those of the triploid type from Tsushima, Nagasaki Prefecture, Japan, were mixed and inoculated into dogs and cats. The following results were obtained. The flukes were found in pairs within cysts in random combinations of 2x + 2x, 2x + 3x, and 3x + 3x (7:15:7). Oocytes in the oviduct were at stages from diplotene to metaphase. In a triploid fluke encysted with a diploid fluke, the primary oocytes were intruded by sperms from the diploid fluke. In the primary oocytes of diploid as well as triploid flukes, from diplotene to diakinesis, the homologues of the nucleolar chromosomes were heteromorphic as far as the size of the short arm was concerned. This implies that the triploid is an autotriploid generated in an ancestral diploid population that was polymorphic for the nucleolar chromosome.

Pathological Studies on the Brain of Congenital Hydrocephalic Rats

An experimental model of congenital hydrocephalus of the Lewis strain rats was successfully bred and maintained for 14 generations in our institute by repeated brother-sister matings in litter-mates of an accidentally bred mutant rat with hydrocephalus since 1981. The overall incidence of hydrocephalus was 20%. However, in litter-mates without head enlargement, we found occult hydrocephalus at autopsy. Adding these latent cases, the total incidence of hydrocephalus became approximately 30%.

Experimental fascioliasis in the rat-like hamster, Tscherskia triton, and other rodent hosts

Experimental infection with Fasciola hepatica and parthenogenetic Fasciola sp. in laboratory animals have been conducted in rats and rabbits. Inoculation of less than 5 metacercariae into rat-like hamsters, Tscherskia triton, is sufficient to establish Fasciola infections. The prepatent period of F. hepatica and the parthenogenetic Fasciola sp. in T. triton was shorter than that in rats and rabbits, suggesting that T. triton is a suitable experimental model for these flukes. In contrast, F. gigantica infection in T. triton did not yield adult flukes; T. triton, is therefore, considered to be an unsuitable host for F. gigantica. The cotton rat, Sigmodon hispidus, was an unsuitable host for the parthenogenetic Fasciola sp.