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Biomedical subjects

J Yamada

Publications and source records attributed to J Yamada.

At least 325 records · Page 18Linked to original sources
PubMed1990

The spontaneously epileptic rat (SER), a zitter*tremor double mutant rat: histopathological findings in the central nervous system.

The spontaneously epileptic rat (SER), a mutant homozygous for both zitter and tremor genes, exhibits absence-like seizures and tonic convulsions without external stimulation from 7 to 8 weeks of age. Histopathological studies of the central nervous system revealed the following abnormalities. The 35-day-old SERs which exhibit body tremor, and which have never shown seizures, had marked vacuolation and hypomyelination in the brainstem and cerebellum. The vacuoles were produced by splitting of the myelin sheaths and swelling of the dendrites and were related to primary swelling of the astrocytes. The 2- to 3-month-old SERs with staggering gait and seizures showed focal axonal swelling ('torpedo') and advanced vacuolation in the granular cell layer of the cerebellum in addition to the abnormalities observed at 35 days of age. Degenerative neurons and spheroidal bodies were observed in the substantia nigra and ventral tegmental nucleus. These brain areas are known to be related to tonic convulsions in the several experimental models. The SER is believed to be a useful tool for the investigation of the relationship between the structure and function of the central nervous system in epilepsy. It is probable that the more severe changes in the cerebellum are responsible for the staggering gait.

Animals↗
PubMed1990

Participation of the peroxisomal beta-oxidation system in the chain-shortening of PCA16, a metabolite of the cytosine arabinoside prodrug, YNKO1, in rat liver.

When PCA16, a metabolite of the cytosine arabinoside prodrug YNKO1, was incubated with isolated rat hepatocytes, time-dependent H2O2 generation was found. When the hepatocytes obtained from clofibrate-treated rat liver were used as an enzyme source, PCA16-dependent production of H2O2 was increased by around 6-fold. The activity of peroxisomal beta-oxidation for PCA16 assayed by H2O2 generation was 3-fold higher than that for palmitic acid, whereas the activity of mitochondrial beta-oxidation for PCA16 assayed by ketone body production was much less than that for palmitic acid. A subcellular distribution study revealed that the distribution of the activities of beta-oxidation and fatty acyl-CoA oxidase for PCA16-CoA coincided with those of cyanide-insensitive palmitoyl-CoA-dependent beta-oxidation and catalase, a marker enzyme of peroxisomes. The profile of the cofactor requirement for beta-oxidation of PCA16-CoA in isolated peroxisomes was similar to that for palmitoyl-CoA oxidation, and the reaction was not inhibited by KCN. The formation of CoA derivative prior to beta-oxidation reaction was essential. HPLC analysis of metabolites after incubation of PCA16-CoA with isolated peroxisomes demonstrated the production of four metabolites, two of which were identified as PCA14 and PCA12 by fast atomic bombardment-mass spectrometry. These results indicate that peroxisomal beta-oxidation participates in the shortening of the alkyl-side chain of PCA16 and plays an important role in the formation of antileukemic cytosine arabinoside from YNKO1.

Animals↗
PubMed1990

Effect of intermittent infusions of somatostatin on growth hormone secretion in unrestrained male rats with hypothalamic deafferentation.

The effect of intermittent infusions of somatostatin (SS) on growth hormone (GH) secretion was studied in unrestrained adult male rats deprived largely of SS influence on the medial basal hypothalamus by anterolateral deafferentation (AL-cut). In addition, the influence of hypothalamic surgery on the plasma GH response to beta-endorphin (beta-END) was observed. In sham-operated rats, high-amplitude GH pulses separated by low baseline levels occurred at 185 min intervals. In rats with AL-cut, GH pulses were difficult to identify upon visual appraisal and baseline plasma GH levels became significantly higher than those of sham-operated rats. When AL-cut was performed unilaterally (half-AL-cut), low amplitude GH pulses separated by elevated baseline GH levels occurred at frequent intervals. The amount of GH secreted during 6 h was significantly reduced in rats with AL-cut or half-AL-cut as compared to that of sham-operated rats. The plasma GH response to intracerebroventricular injection of beta-END (4 micrograms) was abolished in AL-cut rats, and the response was significantly reduced in half-AL-cut rats as compared to that of sham-operated rats. When AL-cut rats were subjected to repeated infusions of SS (30 micrograms/kg b. wt./h, 150 min) separated by 30 min control periods, a large rebound of GH secretion was observed after removal and the amount of GH secreted during 6 h became comparable to that of sham-operated rats. The results suggest that SS plays important roles in the dynamic secretion of GH.

Animals↗
PubMed1990

Distinct gelation mechanism between linear and branched (1--3)- beta-D-glucans as revealed by high resolution solid state 13C NMR.

We have recorded high-resolution 13C-NMR spectra of linear (curdlan) and branched (lentinan, HA-beta-glucan and its polyol and aldehyde derivatives) (1----3)-beta-D-glucans in hydrate and gel states, in order to gain insight into their gelation mechanism. Network structure of curdlan turned out to be highly heterogeneous from its motional state, from liquid-like, through intermediate, to solid-like domains. They are studied by a variety of experiments, conventional high-resolution NMR by broad-band decoupling, high-power decoupling with magic angle spinning (MAS), and cross-polarization-magic-angle-spinning (CP-MAS). Nevertheless, we found that conformations of these distinct liquid-like and solid-like domains exhibit an identical single helix conformation with a small proportion of a triple helix form, supporting our previous view as to the gelation mechanism. In contrast, the network structure of branched (1----3)-beta-D-glucans in the gel state arises mainly from the triple helix conformation. This means that gelation of branched (1----3)-beta-D-glucan proceeds from partial association of the triple helical chains, previously proposed for gelation of a linear glucan. Furthermore, we found that conversion from the single chain to the single helix was not achieved readily by hydration of over 8 h at 96% R.H. for branched glucan but the triple helix form is obtained when these samples are hydrated fully as in gel state.

Carbohydrate Conformation↗
PubMed1990

A study of growth regulators of renal cortical tubular cells in the rabbit liver.

Two growth regulators, a growth stimulator for cultured renal tubular cells and a growth inhibitor, were observed in this study in rabbit liver homogenate after a unilateral nephrectomy. These regulators appeared in the liver on the third day after this nephrectomy, decreased on the seventh day, and disappeared by the fourteenth day. The growth stimulatory activity, termed a tubular cell growth factor (TuCGF), was a heat- and acid stable 15 to 20 KDa protein. The additive effects of TuCGF on the epidermal growth factor (EGF), the insulin-like growth factor-I (IGF-I), and the fibroblast growth factor (FGF) were observed; the results suggest that TuCGF differs from EGF, IGF-I, or FGF. In contrast, the growth inhibitory activity, termed a tubular cell growth inhibitor (TuCGI), was a heat- and acid-labile protein with a molecular weight of about 150 to 200 KDa. This factor potently inhibited the DNA synthesis of tubular cells in the presence of insulin and EGF. These results suggest that TuCGI is not identical with transforming growth factor-beta (TGF-beta). The regulation of these activities by target cell density is also discussed.

Animals↗
PubMed1990

Immunohistochemical study of peptide-containing nerves in the gastrointestinal tract of the Japanese field vole, Microtus montebelli.

The distribution and relative frequency of nerves containing immunoreactivity for substance P (SP), vasoactive intestinal polypeptide (VIP), gastrin-releasing polypeptide (GRP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and menthionine-enkephalin (MENK) were studied by immunohistochemistry in the gastrointestinal tract of the herbivorous Japanese field vole, Microtus montebelli.

Animals↗
PubMed1990

Insulin sensitivity in patients with anorexia nervosa and bulimia.

Insulin sensitivity was studied using the euglycemic insulin clamp technique in 5 female patients with anorexia nervosa and 4 females with bulimia. The results were compared with those of 15 male patients with non-insulin-dependent diabetes mellitus. Euglycemic insulin clamp is performed for 2 h using the Biostator, during which time insulin was infused at a rate of 0.77 mU kg-1 min-1. Fasting plasma glucose and immunoreactive insulin tended to be lower in patients with anorexia nervosa than in those with bulimia (69.8 +/- 6.7 vs 75.9 +/- 7.7 mg/dl, and 5.9 +/- 2.0 vs 9.8 +/- 3.4 U/ml). The mean metabolic clearance rate (MCR) was 9.2 +/- 3.9 ml kg-1 min-1 for patients with anorexia nervosa, 5.1 +/- 2.2 ml kg-1 min-1 for patients with bulimia, and 3.8 +/- 0.3 ml kg-1 min-1 for patients with diabetes mellitus. However, one anorectic had a significantly high MCR. One anorectic and 3 bulimics had a significantly low MCR. These results suggest that insulin sensitivity varied in patients with anorexia nervosa, whereas it tended to decrease in some patients with bulimia but not to the same degree as in patients with diabetes mellitus.

Adult↗
PubMed1990

Effects of serotonin on blood glucose and insulin levels of glucose- and streptozotocin-treated mice.

Effects of serotonin (5-HT) on plasma glucose and serum insulin levels were studied in mice. In normal mice, 5-HT induced a dose-dependent hypoglycemia and an increase in serum insulin levels. 5-HT significantly inhibited glucose-induced hyperglycemia and increased glucose-stimulated insulin release. However, in streptozotocin-induced diabetic mice, 5-HT changed neither the glucose nor insulin levels. These results strongly suggest that 5-HT-induced hypoglycemia is brought on by increasing serum insulin levels.

Animals↗
PubMed1990

Behavioural characteristics of wild jumping or running episodes in the double mutant spontaneously epileptic rat.

Spontaneously epileptic rats (SER) are homozygous for two mutations, zitter (zi) and tremor (tm), and spontaneously exhibit both absence-like seizure and tonic convulsion. In addition, wild jumping or running episodes sometimes appear without any previous stimuli. We recorded the behaviour on a video camera and/or a vibration response apparatus to examine the behavioural characteristics. All wild jumping or running episodes appeared within 27 s after termination of tonic convulsion with a frequency of 2.1%, and the episode could be detected even in the dark by using the vibration response apparatus. A rapid increase of high motor activity around the episodes was recorded as a single peak with high amplitude by the vibration response apparatus. The wild jumping or running episode appeared in all 4 SER at 8-14 weeks of age with a variable frequency, 0-9 times in the light period and 0-6.7 times in the dark period 8 h each week. Thus, the wild jumping or running episode was found to occur not only during the light period but also during the dark period without any significant difference in frequency.

Animals↗
PubMed1990

Delayed postnatal behavioral development in spontaneously epileptic rats and tremor rats, and poor operant performance in spontaneously epileptic rats.

Postnatal behavioral development and learning ability of operant performance were examined in spontaneously epileptic rats (SER: zi/zi, tm/tm), and the original tremorous mutant strains of rats, tremor rats (tm/tm) and zitter rats (zi/zi) and their controls. Before the eyes opened, the increase in body weight and the age of achieving the righting reflex on a surface were no significantly different between the SER and their littermates without epileptic seizures (SER-N: zi/zi, tm/+ or zi/zi, +/+), and between tremor rats and the original strain Kyo: Wistar rats. After the eyes opened, the increase in body weight, age of achieving the righting reflex in air and traction performance, and the development of rotarod performance, were delayed in SER and tremor rats in comparison with other groups of rats. The zitter rats were apparently inferior in their development of rotarod performance in comparison with the same zitter homozygous SER-N. Operant performance was more inferior in SER than in SER-N and in tremor rats than in Kyo: Wistar rats. The differences were much more marked between SER and SER-N than between tremor and Kyo: Wistar rats. Thus, homologous tm genes and the coexistence of homologous tm and zi genes have an inhibitory effect on postnatal behavioral development and learning ability.

Animals↗
PubMed1990

Sensitivity of spontaneously epileptic rats to external stimuli that induce seizures.

The sensitivity of spontaneously epileptic rats (SER), double homozygotes of zitter and tremor mutations, to external stimuli that induce seizures was studied in comparison with tremor (tm/tm) and zitter (zi/zi) rats, and with normal Kyo: Wistar and F 344/N rats. Touching their body, a blinking light (1200 lux, 1 sec interval) or a big sound (8 and 12 kHz, 95 dB) induced tonic extension only in the SER. The response frequency was 22 to 44% at 9 weeks of age and 75 to 100% at 13 weeks of age. Electric stimulus at 30 mA induced tonic-clonic convulsions in all Kyo: Wistar and F 344/N rats. At 20 mA the incidence of seizures decreased with age, from 100% at 5 weeks of age to 33% at 13 weeks of age in Kyo: Wistar rats and from 100 to 71% in F344/N rats. In SER, 10-mA stimuli induced tonic extension at 9 and 13 weeks of age, and 20 and 30 mA induced tonic convulsions, generalized or partial convulsions, and wild jumping or running episodes at 5, 9 and 13 weeks of age. At 30 mA, the incidence of convulsive seizures decreased with age in both tremor (tm/tm) and zitter (zi/zi) rats. Apparently external stimuli acted as simple triggers in the induction of tonic extension, since characteristic tonic extension is induced in the SER by each of the stimuli used in the present study, and induced convulsions closely resembled spontaneously occurring convulsions. The threshold of external stimuli in the induction of tonic extension became lower with aging in the SER, indicating that they are appropriate models for evaluating anticonvulsant drugs, as reported previously.

Acoustic Stimulation↗
PubMed1990

A survey of endocrine cells in the pancreas of the echidna (Tachyglossus aculeatus) with special reference to pancreatic motilin cells.

Pancreatic endocrine cells were examined in a primitive egg-laying mammal, the echidna, using immunohistochemistry. Immunoreactive endocrine cells were observed using antisera to insulin, glucagon, somatostatin, avian pancreatic polypeptide and bovine pancreatic polypeptide. In addition, motilin-immunoreactive cells were identified in both the endocrine and exocrine pancreas of pouch-young and adult echidnas using three types of motilin antisera. Since the motilin-immunoreactive cells did not cross-react with any other pancreatic hormones tested, they are identified as an independent endocrine cell type.

APUD Cells↗
PubMed1990

An immunohistochemical study on the distribution of endocrine cells in the gastrointestinal tract of the musk shrew, Suncus murinus.

The endocrine cells in the gastrointestinal tract of the musk shrew were studied immunohistochemically. Eleven kinds of endocrine cells, immunoreactive for serotonin, somatostatin, gastrin, cholecistokinin, gastric inhibitory polypeptide, motilin, secretin, neurotensin, pancreatic glucagon, enteroglucagon and bovine pancreatic polypeptide, were revealed. In the stomach, serotonin-, somatostatin-, gastrin-, pancreatic glucagon- and enteroglucagon-immunoreactive cells were detected. The first three types of cells predominated and were more abundant in the pyloric glands than in the other stomach regions. In the small intestine, all types of endocrine cells were found, each having different distributions and relative frequencies. In the large intestine, 10 types of endocrine cells except cholecystokinin-immunoreactive cells were detected. Serotonin- and bovine pancreatic polypeptide-immunoreactive cells were more numerous in the large intestine than in the small intestine.

Animals↗
PubMed1990

An immunohistochemical study of endocrine cells in the proximal duodenum of eight marsupial species.

The proximal duodenum of eight marsupial species, (koala, common brushtail possum, ring-tailed possum, common wombat, great grey kangaroo, parma wallaby, short-nosed bandicoot and tiger cat) were investigated immunohistochemically using 12 specific antisera for gut hormones. Several types of immunoreactive cells were seen on the intestinal villi and in crypts of these species: 9 types in the koala; 8 types in the common brushtail possum; 7 types in the common wombat; 6 types in the short-nosed bandicoot and 5 types in the ringtailed possum, great grey kangaroo, parma wallaby and tiger cat. Gastrin-, somatostatin-, motilin- and serotonin-immunoreactive cells were seen in all species examined. A few BPP-, enteroglucagon-, CCK-, secretin-, GIP- and neurotensin-immunoreactive cells were seen but only in few species. A few substance P-immunoreactive cells were detected only in the koala. Immunoreactive cells were also seen in Brunner's glands: 5 types in the parma wallaby; 3 types in the great grey kangaroo and tiger cat; 2 types in the koala and common wombat; 1 type in the short-nosed bandicoot. No immunoreactive cells were found in Brunner's glands of the common brushtail possum.

Animals↗
PubMed1990

The use of the orthographic lexicon in reading kana words.

A lexical decision task was used to investigate the dual-route hypothesis that, in reading words conventionally written in katakana, a Japanese syllabic script, lexical access may be achieved by both a process of assembled segmental phonology and the use of a visual orthographic lexicon. The variables examined were lexicality (words and nonwords), kana type (katakana and hiragana), string length (long and short), and vocal interference (silence and concurrent vocalization). The main effects of the first three variables were significant, but more important, we found that subjects could be divided into two groups--phonological assemblers and orthographic lexicon users. Words that assume sighting were also identified. Collectively, the results were interpreted to uphold the dual-route hypothesis and to reject the common view that kana words are accessed on the basis of phonological mediation alone.

Adult↗
PubMed1990

An ultrastructural study on gastric endocrine cells in the stomach gland patch of the koala Phascolarctos cinereus.

The endocrine cells in the stomach gland patch of the koala (Phascolarctos cinereus) were studied ultrastructurally. They were classified into 3 types based on the ultrastructural profiles of their endocrine granules and tentatively categorized as type I, II, and III endocrine cells. Type I cells contained round granules that were for the most part larger than those observed in the other 2 cell types. The granules ranged from moderate to relatively high in electron density. Type II cells were angular in shape and characterized by the presence of granules that were polymorphous in profile. Contents of the endocrine granules in type II cells also showed a range of high to moderate electron density. Type III cells were oval or pyramidal in shape. They contained highly polymorphous granules that were round, oval, dumbbell-like or comma in shape and characterized by the presence of a clear space or halo separating the high to low electron-dense core from the limiting membrane of granules. Type III cells were observed most often whereas type I and II cells were a less frequent observation.

Animals↗
PubMed1990

An immunohistochemical study of endocrine cells of the alimentary tract of the King's skink (Egernia kingii).

The gastrointestinal tract of the King's skink (Egernia kingii) was examined for the presence of fifteen regulatory peptides, two proteinases and an amine by immunohistochemical methods. Immunoreactivity was detected for somatostatin, gastrin, motilin, bovine pancreatic polypeptide, pepsinogen and serotonin, but not for avian pancreatic polypeptide, gastric inhibitory peptide, secretin, cholecystokinin, enteroglucagon, pancreatic glucagon, gastrin-releasing polypeptide, neurotensin, vasoactive inhibitory polypeptide, leu-enkephalin or chymosin. The six peptides detected in E. kingii have been previously found in the gastrointestinal tract of squamate reptiles; however, immunoreactivity for other peptides previously detected in squamates, in particular another skink, was not observed. In addition, chromogranin was found to be effective in the detection of endocrine cells though its specificity was unknown.

Animals↗