Koshin Adachi

Radioimmunoassay for orexin A.

A radioimmunoassay for orexin A has been developed. Anti-orexin A antiserum was raised in New Zealand white rabbits immunized with a conjugate of synthetic orexin A with bovine serum albumin. This antibody did not crossreact with orexin B, hypothalamic hormones, pituitary hormones, neuropeptides or gut hormones. Radioiodination of orexin A was performed with the chloramin T method, followed by purification of radioiodinated material on Sephadex G-25 column. Orexin A was extracted from tissues using acid-acetone. The assay was performed with a double antibody system. The dilution curve of acid-acetone-extracts of rat hypothalamus in the radioimmunoassay system was parallel to the standard curve. The recovery of tissue orexin A was about 80%,and the intra-assay and inter-assay variations were 5.2% and 7.8%, respectively. Orexin A was found in the hypothalamus, cerebrum and testis. These data suggest that this assay system is suitable for the measurement of tissue orexin A and that orexin A is found in the central nervous system and testis.

Concentrations of Immunoreactive Thyrotropin-Releasing Hormone in Spinal Cord of Patients with Amyotrophic Lateral Sclerosis

Concentrations of immunoreactive thyrotropin-releasing hormone (ir-TRH) were measured by specific radioimmunoassay in the spinal cord of six patients with amyotrophic lateral sclerosis (ALS) and seven with non-neurological diseases. Ir-TRH concentrations were the highest in the anterior horn, compared with other areas of the spinal cord, both in nonneurological diseases and ALS. Ir-TRH concentrations in the anterior horn of ALS were significantly lower than in nonneurological diseases, but were the same in both groups in other parts of the spinal cord (e.g. posterior horn, frontal part, lateral and central part, posterior part). Ir-TRH concentrations in rat spinal cords were stable for up to seven hours when spinal cord was stored after death at 4°C or 22°C. An elution profile of methanol-extracted human spinal cord on Sephandex G-10 column was identical to that of synthetic TRH. The cell population in the anterior horn in ALS was decreased markedly. The findings suggest that TRH is present in the human spinal cord and its decreased concentrations in the anterior horn of ALS may be due to a decrease in the cell population.

Lack of change in indoleamine metabolism in spinal cord of patients with amyotrophic lateral sclerosis

Indoleamine metabolism was determined by high-performance liquid chromatography with electrochemical detection in the cervical spinal cord of patients with amyotrophic lateral sclerosis (ALS) and controls with non-neurological diseases. The concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were the highest in the ventral horn compared with other regions of the spinal cord both in ALS and controls. There was no significant change in the concentration of 5-HT in any region of the spinal cord between ALS and controls. In addition, the concentration of 5-HIAA in ALS was lower than that in controls, however, no statistical significance was observed.

Effect of vitamin E deficiency on rat brain monoamine metabolism

We investigated the effects of vitamin E deficiency on the monoamine metabolism in the rat brain. Male Wistar rats fed on the vitamin E deficient diet for 24 weeks were analyzed. At 28 weeks, they showed a reduced growth rate (52% of reduction), muscle atrophy, a motor weakness of hind limbs and disturbance of gait. The concentrations of monoamines, their precursors and metabolites in the brain were simultaneously determined using high performance liquid chromatography (HPLC) coupled with a coulometric detection with electrode array system. In addition, tryptophan hydroxylase activity was measured. The dopamine (p = 0.009) and serotonin (p = 0.04) levels in the brain stem of vitamin E deficients rats were significantly lower than in the controls, whereas their precursors tyrosine (p = 0.0009) and tryptophan (p = 0.0065) levels in the brain stem were significantly higher than in the controls. Moreover, tryptophan hydroxylase activity (p = 0.0005) in the brain stem of vitamin E deficient brains was significantly lower than in the controls. All statistical comparisons were done using non-parametric tests (Mann-Whitney U test). These results suggest that vitamin E deficiency may play a role in the disturbance of monoamine metabolism in rat brain.

Polyamine concentrations in the brain of vitamin B12-deficient rats.

To study the pathophysiology of the neuronal degeneration in vitamin B12 deficiency, we investigated the concentrations of the polyamines putrescine, spermidine, and spermine in brain regions and liver using high-performance liquid chromatography with fluorescence detection. Male Wistar rats were fed either a control or vitamin B12-deficient diet for 20 weeks. No remarkable behavioral changes were observed. Serum vitamin B12 and hepatic methionine concentrations were significantly lower and hepatic homocysteine was elevated in rats fed vitamin B12-deficient diet than in controls. Vitamin B12 deficiency was associated with decreased concentrations of spermidine, spermidine in liver and some regions of brain, although there were no observed abnormalities in behavior. These results suggest that vitamin B12 deficiency may play a role in neuronal degeneration through the disturbance of polyamine concentrations in rat brain.

Concentrations of thyrotropin-releasing hormone in the brain of ataxic mice.

Concentrations of thyrotropin-releasing hormone (TRH) were studied in the brain of the Weaver ataxic mouse, the Purkinje cell degenerative ataxic mouse (pcd-ataxic mouse) and the cytosine arabinoside (ara-C)-induced ataxic mouse. The brain tissue was dissected into 4 parts, e.g., hypothalamus, cerebrum, cerebellum and brain stem. TRH concentrations in each part of the brain were measured by radioimmunoassay. TRH concentrations in the brain of Weaver ataxic mice were significantly higher in the cerebellum and brain stem than in the controls. In pcd-ataxic mice, the TRH concentrations in the brain were significantly higher in the cerebrum and brain stem. In ara-C-induced ataxic mice, the concentrations were significantly higher in the cerebrum, cerebellum and brain stem. TRH levels in the hypothalamus of ataxic mice did not differ from those of controls. The elution profile of methanol-extracted cerebellum of ataxic mice on Sephadex G-10 was identical to that of synthetic TRH. These findings suggest that changes in the TRH concentrations in the brain play a pathophysiological role in ataxic mice.

Concentrations of thyrotropin-releasing hormone in the brain of patients with amyotrophic lateral sclerosis

Concentrations of thyrotropin-releasing hormone (TRH) were measured by a specific radioimmunoassay in the brain of 11 patients with amyotrophic lateral sclerosis (ALS) and 6 controls (myocardial infarction, gastric cancer, multiple myeloma, cerebrovascular disease, amyloid neuropathy). TRH was found in all parts of the dissected brain tissues (pedunculus cerebri, corpus callosum, capsula interna, motor area) in patients with ALS and controls. The TRH concentrations in the brain of patients with ALS were significantly lower in the pedunculus cerebri, compared with controls, and tended to decrease in the motor area and corpus callosum, but not significantly. Changes in TRH concentrations did not always correlate with pathohistological changes. These findings suggest that TRH is widely distributed in the human brain and decreases in some part of the ALS brain.

Nociceptin Stimulates Thyrotropin Secretion in Rats

Effects of nociceptin on thyrotropin (TSH) and thyrotropin-releasing hormone (TRH) secretion in rats were studied. Nociceptin (150 μg/kg) was injected intravenously and rats were serially decapitated after the injection. The effects of nociceptin on TRH release from the hypothalamus and TSH release from the anterior pituitary in vitro were also investigated. TRH and thyroid hormones were measured by individual radioimmunoassays. TSH was determined by enzyme immunoassay. TRH contents in the hypothalamus decreased significantly after nociceptin injection, whereas plasma TRH concentrations showed no changes. Plasma TSH concentrations increased significantly in a dose-related manner. The TRH release from the hypothalamus was enhanced significantly in a dose-related manner with the addition of nociceptin. The TSH release from the anterior pituitary in vitro was not affected by the addition of nociceptin. The plasma thyroxine and 3,3′,5-triiodothyronine levels did not change significantly after nociceptin administration. The inactivation of TRH by plasma or hypothalamus in vitro after nociceptin injection did not differ from that of controls. The findings suggest that nociceptin acts on the hypothalamus to stimulate TRH and TSH secretion.

Levels of somatostatin and cholecystokinin in the brain of ataxic mutant mice.

Changes in immunoreactive somatostatin (SOM) and cholecystokinin (CCK-8) levels in the cerebellum and cerebrum were investigated in three types of genetically-determined ataxic mutant mice: rolling mouse Nagoya (RMN), weaver, and Purkinje cell degeneration (PCD) mice. The cerebellar pathology in each of these types differs. The concentration of both SOM and CCK-8 (ng/mg weight) was significantly higher in the cerebellum and the cerebrum of the three types of ataxic mutant mice than in these regions in the respective controls. SOM and CCK-8 content (ng/organ) was significantly higher in PCD and RMN than in controls but this was not in the weaver mice. The possible involvement of both peptides in manifestations of ataxia is discussed.

Simultaneous determination of catechols in thalamic slices with liquid chromatography/electrochemistry.

A method was developed for the simultaneous determination of dopamine (DA), epinephrine (E), norepinephrine (NE), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-methoxy-4-hydroxyphenylglycol (MHPG), as well as L-3,4-dihydroxyphenylalanine (L-DOPA) with liquid chromatography (LC) using electrochemical (EC) detection. With a ODS column and a mobile phase consisting of a sodium acetate-citrate with heptasulfonic acid, this method was applied on simultaneous determination of catechols released from thalamic slices of ddY mouse. The pretreatment of the bathing medium required only centrifugation, and the supernatant was injected directly into the LCEC system. The high potassium stimulation of catecholaminergically innervated thalamic slices led to increase in the levels of DA, NE, DOPAC and MHPG, especially of NE, but not that of L-DOPA itself. In the present study, we designed to make simultaneous determination of catechols released from thalamic slices for estimation of the physiological status of catecholaminergic neuronal activity.