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Biomedical subjects

T Sakaguchi

Publications and source records attributed to T Sakaguchi.

At least 289 records · Page 16Linked to original sources
PubMed1987

Structural comparison of the cleavage-activation site of the fusion glycoprotein between virulent and avirulent strains of Newcastle disease virus.

The nucleotide sequence of the mRNA encoding the fusion (F0) protein of a virulent strain of Newcastle disease virus was determined. A single open reading frame in the sequence encodes a protein of 553 amino acids with a calculated molecular weight of 59058. The amino acid sequence predicted several structural features involving the fusion-inducing hydrophobic stretch (residues 117-142) and the cleavage-activation site (residues 112-116) to generate the disulfide-linked F1 and F2 subunits. The cleavage-activation site as well as a part of the fusion-inducing sequence were compared among a series of virulent and avirulent strains by the chain-termination method using a synthetic oligonucleotide primer. It was found that without exception, the cleavage-activation site of virulent strains consisted of two dibasic residues with an intervening glutamine, Arg-Arg-Gln-Arg-Arg, whereas the corresponding region of avirulent strains was made of a sequence with single basic residues scattered among uncharged residues, Gly-LysArg-Gln-GlySer-Arg. On the basis of these observations and the previous results showing a strict correlation between the pathogenicity and the cleavability of the fusion protein of NDV (Y. Nagai, H-D. Klenk, and R. Rott, Virology, 72, 494-508, 1976), we propose the importance of the dibasic residues for efficient proteolytic activation of the fusion protein and for the pantropic property of NDV. Some strains were found to have Leu-Ile-Gly as the N-terminus of F1, whereas others contained Phe-Ile-Gly, indicating that Phe-X-Gly is not always conserved at F1 N-terminus of paramyxovirus.

Amino Acid Sequence↗
PubMed1987

The mode of projections of single locus coeruleus neurons to the cerebral cortex in rats.

Axonal distributions of single locus coeruleus neurons within the cerebral cortex were examined with antidromic stimulation technique combined with cortical lesions (frontal lobotomy and lobectomy). In urethan-anesthetized rats, stimulating electrodes were implanted in 10 points extending over nearly the entire cerebral cortex, and antidromic responses of single locus coeruleus neurons to stimulation of these stimulus sites were analysed. Fifty percent of locus coeruleus neurons examined were activated antidromically from at least one cortical point in the cerebral cortex. The pattern and extent of axonal distributions of single locus coeruleus neurons in the cortex appeared to vary from cell to cell. From the results obtained in rats with the cortical lesions, it is concluded that in addition to locus coeruleus neurons with intracortical axons running from rostral to caudal, there are the neurons projecting to the occipital cortex without innervating the frontal cortex and those projecting simultaneously to the frontal and occipital cortex with two axonal branches. There was no topographic order between the recording sites within the locus coeruleus and the projection sites in the cortex.

Afferent Pathways↗
PubMed1987

The effect of intrahypothalamic injections of glucose on sympathetic efferent firing rate.

Electrical stimulation of the ventromedial hypothalamus of anesthetized rats, produced an increase in temperature of brown adipose tissue. The magnitude of increase in temperature was linearly related to the frequency (Hz) of electrical stimulation of the hypothalamus. Microinjection of glucose into the ventromedial hypothalamus produced a dose-dependent increase in firing rate of the sympathetic nerves to brown adipose tissue, whereas comparable volumes of physiological saline had no effect. Destruction of neurons in the ventromedial hypothalamus with injections of kainic acid completely blocked the stimulatory effect of glucose on the firing rate of nerves to the brown adipose tissue. These studies support the hypothesis that glucose sensitive neurons in the ventromedial hypothalamus can directly modulate sympathetic nerves supplying brown adipose tissue.

Action Potentials↗
PubMed1987

Alterations in gastric acid secretion following hepatic vagotomy at a stage of development in rats.

The relation of gastric acid secretion to the hepatic vagal section was examined in consideration of developmental stages of a rat. Acid outputs in rats deprived of food for 22 hr before the experiment were estimated with or without insulin. The animals were classified into five groups according to their body weights at the experiments (50, 100, 200, 300 and 400 g). Hepatic vagotomy was effective in decreasing acid output in all of the groups treated with food deprivation and insulin, and it was found that there was a close relationship between the output and glucose concentration in the portal blood. In rats treated only with food deprivation, hepatic vagotomy produced different effects for the five groups; the vagotomy failed to cause acid response when the rats weighed about 300 and 400 g, while in the animals weighing about 50, 100 and 200 g acid outputs were reduced following the vagotomy. It was noted that the sensitivity to hypoglycemia in the acid output was greater in the young rats than the older ones. Results suggest that function of the hepatic vagal nerve may be prominent in modulating acid secretion in an earlier stage of development when the animals are most sensitive to hypoglycemia.

Aging↗
PubMed1987

Intrahypothalamic injection of insulin decreases firing rate of sympathetic nerves.

Injection of picomolar quantities of insulin into the ventromedial hypothalamus of rats significantly reduced the firing rate of sympathetic nerves that supply interscapular brown adipose tissue. The minimal firing rate was reached in 2 min, and the effect was gone within 4 min. The effect of insulin was dose-related and did not occur when comparable volumes of physiological saline were injected into the ventromedial hypothalamus. Destruction of neurons in the ventromedial hypothalamus by injection of kainic acid abolished the inhibitory effects of insulin. These data suggest that insulin may play a role in modulating the sympathetic firing rate to thermogenically important tissues.

Adipose Tissue↗
PubMed1987

Cell-mediated immunity caused by beryllium compounds.

Cells of spleen and lymph nodes were obtained from mice subcutaneously injected with BeCl2 once a week over a 6-week period. These cells were washed twice in cold phosphate-buffered saline and suspended at a final concentration of 2 x 10(7) cells in 1 ml of buffer. Subsequently, 0.5 ml of the suspension was injected into normal mice intravenously (passive transfer). The findings of the experiments using these mice are summarized as follows: (1) The footpad reaction test was performed 24 hrs after passive transfer. The mice receiving spleen cells or lymph node cells from mice sensitized with BeCl2 developed significant footpad swelling 24 and 48 hrs after challenge of BeCl2 as the antigen. (2) After passive transfer with sensitized spleen cells or lymph node cells the ears of the mice were painted with 7% BeCl2 in ethyl alcohol. Ears of these mice showed significant swelling as compared with those of controls. (3) The migration of peritoneal cells from mice receiving spleen or lymph node cells from sensitized mice was inhibited when tested in medium containing the antigen of BeCl2. From our present experiments, it was suggested that the beryllium sensitizing ability was related to active as well as passive cell-mediated immunity.

Animals↗
PubMed1987

Postnatal development of electrical activity in the locus ceruleus.

1. A method for adapting a standard stereotaxic frame for use with neonatal rats as young as postnatal day 1 (PD 1) was devised, and single-unit extracellular recordings were obtained from neurons in the locus ceruleus (LC) in urethan-anesthetized rats during different stages in development from PD 1 to PD 34. 2. The spontaneous firing pattern of neonatal LC neurons was characterized by long silent periods punctuated by brief epochs of sporadic firing. At PD 7-14, LC neurons exhibited periodic occurrences of irregular firing that lasted for 20-30 s. By PD 20, the pattern and rate of spontaneous activity were virtually indistinguishable from that of adults. 3. Conditioning stimulation of the dorsal noradrenergic bundle (DNB), given 10-200 ms prior to a test stimulus to the DNB, markedly reduced the amplitude of the antidromic action potentials to the test stimulus and sometimes resulted in spike decomposition. This refractoriness of the soma-dendritic membrane of LC cells was significantly attenuated with development and approached adult levels after PD 18. 4. Antidromic responses elicited by DNB stimulation were followed by a phase of inhibition or inhibition-excitation. Postactivation excitation was most prominent in cells that were not spontaneously active, and decreased steadily throughout development, probably because of the steady increase in spontaneous firing rate seen during maturation. 5. Although the conduction velocity of LC axons increased steadily from birth through PD 26, conduction time remained unchanged. 6. Neonatal LC neurons were equally sensitive to noxious and nonnoxious somatosensory stimuli. As development proceeded, LC neurons became less sensitive to innocuous somatosensory stimuli such as air puffs and tactile stimuli while simultaneously becoming more sensitive to noxious stimuli. Auditory and visual stimuli became effective for the first time at PD 14 and PD 12, respectively. 7. These results indicate that the electrical activity of LC neurons in the developing brain is intimately related to input from peripheral sensory sources. Therefore, the influence of the LC on the developing brain may occur predominantly through sensory input.

Aging↗
PubMed1987

Effects of feeding behavior of rats of a cryptic peptide from the C-terminal end on prepro-growth hormone-releasing factor.

An amidated peptide derived from cleavage of the C-terminal of prepro-GRF [prepro-GRF-(78-107)NH2] and designated CTPG or anorectin was injected ip and into the third ventricle of rats, and food intake and body weight were measured. An acute injection of 0.2, 0.5, or 1.0 microgram CTPG (anorectin; 60, 150, or 300 pmol) into the third ventricle produced a significant dose-related reduction in food intake in the hungry rat during the 12-h dark period. Water intake was suppressed 30% by 1.0 microgram (300 pmol), but the lower doses had no effect. The highest dose (1 microgram or 300 pmol) produced a small rise in glucose concentration 5 min after injection into the third ventricle, which returned to the control value by 15 min. Anorectin increased the sympathetic efferent firing rate 3, 6, and 24 h after a single injection. Intraperitoneal injection of 2.0, 5.0, and 20 micrograms, however, had no significant effect on food or water intake. Chronic infusion into the third ventricle at a rate of 50 ng/h for 7 days produced a persistent reduction in food intake and a steady fall in body weight. The chronically infused rats had a significantly higher level of sympathetic activity, as measured by the firing rate of sympathetic nerves innervating the interscapular brown adipose tissue. These studies raise the possibility that anorectin released during processing of GRF might be involved in the modulation of feeding behavior.

Animals↗
PubMed1987

Effects of propentofylline on disorder of learning and memory in rodents.

Effects of a newly synthesized xanthine derivative propentofylline (3,7-dihydro-3-methyl-1-(5-oxohexyl)-7-propyl-1H-purine-2,6-dione) on learning and memory of rodents were examined in the two different paradigms. In a shuttle box active avoidance paradigm, propentofylline (25 mg/kg/day, p.o.) improved the decreased learning ability of 12-month-old spontaneously hypertensive rats. Normotensive Wistar-Kyoto rats at a comparable age showed rapid acquisition of avoidance learning, which was not influenced by propentofylline. Step-down passive avoidance task was carried out as the other paradigm. The protein synthesis inhibitor cycloheximide (CXM) induced amnesia in young adult mice. Propentofylline improved the memory deficit when intraperitoneally administered 30 min before the retention test, and it also prevented the development of amnesia when injected 15 min before CXM. These results suggest that propentofylline ameliorates the disturbed learning and memory.

Amnesia↗
PubMed1987

[Immunological study of beryllium workers].

Immunological health surveys of Beryllium (Be) workers in a copper-beryllium casting factory were made 10 times during the 5-year period from 1981 to 1985. The total number of Be workers was 150. 1) Macrophage migration inhibition test was performed by an agarose plate method using Be as antigen with peritoneal cells from guinea pigs and small amounts of Be worker's blood. We found that 1 out of 22 healthy Be workers (4.5%) that migration index (MI) was below 80% after 24 h and 5 (22.7%) after 48 h. The mean of MI in Be workers showed significant low value as compared with that of the control group (p less than 0.01). 2) It was found that the serum complement titer tended to be lower in Be workers than in the control group. The serum complement titer of 3 to 6 subjects showed to be less than 30 U/ml every survey. 3) Although a few showed the abnormal levels in serum immunoglobin (IgG, IgA and IgE), the means of these immunoglobin levels were not markedly changed and they were in the normal ranges, respectively. 4) MI values significantly correlated with IgE level in Be workers, that is y= -8.9 x + 997.8 (r = -0.473, p less than 0.05). These results suggest that macrophage migration inhibition test and serum complement titer were of value for assaying of sensitivity to Be and immune responses in Be workers.

Beryllium↗
PubMed1987

Sensation of thirst in normal and laryngectomized man.

The purpose of this study was to evaluate the role of the larynx in sensation of thirst and to identify precise areas responsible for the sensation in normal and laryngectomized groups. The present analysis showed that the laryngectomized group was less aware of the sensation and less able to localize it than the normal group. Both groups localized the sensation from the base of the tongue to the larynx as well as in the pharynx.

Adult↗
PubMed1987

Differences in drinking behavior between normal and laryngectomized man.

The properties of drinking in normal and laryngectomized groups were examined. Drinking associated with meals was more frequent in the 76 young and 37 older normal subjects than the 25 laryngectomized persons. The laryngectomized group preferred tea and coffee to water to alleviate thirst sensation, while such a preference was hardly seen in either normal group. Results suggest that the larynx may contribute not only to thirst sensation but may be associated with preference in drinking.

Adult↗
PubMed1987

[Changes in protein and RNA synthesis following acute hindbrain ischemia].

Protein and RNA synthesis of the brain is affected by focal transient ischemia. Protein synthesis is depressed by the depletion of energy metabolism during ischemia, and its recovery following recirculation is slower than restoration of energy metabolism. On the other hand, RNA synthesis is more tolerable to ischemia than protein synthesis. Present study has designed to evaluate changes of protein and RNA synthesis of the brain after ischemia. We used a hindbrain ischemia model of gerbils, and quantitative autoradiography was applied for estimation of regional protein and RNA synthesis. The model was made by occluding the basilar artery for 15 minutes and recirculating afterwards. 14C-valine was used as a tracer for protein synthesis. In the ischemic group, protein synthesis was inhibited extremely in the medial thalamus, inferior colliculus, gray matter of the pons and midbrain, and cerebellum, RNA synthesis by salvage pathway was evaluated using tracer doses of 14C-uridine. It increased 1.6-2.4 folds of sham controls in the thalamus, and gray matter of the pons and midbrain. De novo synthesis of RNA was evaluated using 14C-carbamoylphosphate and 14C-NaHCO3. 14C-NaHCO3 antoradiogram showed inhibition of tracer incorporation into RNA and protein fraction in the ischemic lesions. 14C-carbamoylphosphate autoradiogram showed no significant change. These results indicate that protein synthesis is inhibited after ischemia but response of RNA synthesis to ischemia is not uniform. De novo synthesis of RNA is inhibited following ischemia, but RNA synthesis by salvage pathway increases in the ischemic lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1987

[Clinico-pathological study of autopsy cases of nonresected gastric cancer in the young and old].

To elucidate the difference between the natural history of gastric cancer in young and old patients, this study was carried out. Fifty-four cases were studied, representing the autopsy findings of gastric cancer patients who did not undergo operation. The characteristics of the gastric cancer in the young patients were as follows: had infiltrative macroscopical types, had histologically diffuse types, had deeper and wider infiltration, showed a severer invasion into the vessels, and, showed marked lymphatic disseminated, and distant metastasis. The elderly, in comparison, showed various types of gastric cancers. The extension of the cancer in the old group was significantly, less than in the young, even in the same diffuse type. The period from the onset to death was almost same in both groups. The age of the host seems one of the important factors influencing the natural history of gastric cancer.

Adult↗
PubMed1987

[A case of serous papillary adenocarcinoma of the ovary initially suspected to be a uretero-vaginal fistula].

A case of serous papillary adenocarcinoma of the ovary initially suspected to be an uretero-vaginal fistula is reported. The patient was a 57-year-old female with the complaint of urinary leakage from the vagina. Because she had undergone a supravaginal hysterectomy for myoma uteri 10 years earlier, a uretero-vaginal fistula was initially suspected. However, the fistula was not recognized from the findings of excretory and retrograde pyelographies. Chemical analysis of the vaginal discharge was similar to serum rather than urine. Gynecological examination showed the presence of an ovarian tumor. Right oophorectomy and extirpation of remaining cervix combined with partial resection of rectum was performed. From the pathological finding that the tumor consisted of serous papillary adenocarcinoma, the vaginal discharge was confirmed to originate from the tumor. Ovarian tumors with serous discharge from the vagina seem to be very rare.

Cystadenocarcinoma↗
PubMed1986

Effects of D-glucose anomers on sweetness taste and insulin release in man.

Insulin release was examined in human subjects after lingual applications of D-glucose and its anomers. A dose-dependent increase in the insulin release was noted following the application of equilibrated D-glucose consisting of 36% alpha- and 64% beta-anomer. The response was not reproduced after administration of atropine. The magnitude of insulin release produced by alpha-anomer was different from that induced by beta-anomer in men who could not differentiate between sweetness of the two anomers. Results indicate that recognition of sweetness in the cortex is unrelated to the insulin response, and suggest that a subcortical mechanism may detect qualitative differences in taste and produce the oral phase of insulin secretion via vagus action in humans.

Adult↗