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H Waki

Publications and source records attributed to H Waki.

At least 37 records · Page 2Linked to original sources
PubMed1999

Total synthesis of a cholinergic neuron-specific ganglioside GT1a alpha: a high affinity ligand for myelin-associated glycoprotein (MAG).

An efficient total synthesis of a cholinergic neuron-specific ganglioside GT1a alpha (IV3NeuAcIII6NeuAcII3NeuAc-GgOse4Cer) is described. The suitably protected sialyl-alpha(2-->6)-gangliotriose (III6NeuAc-GgOse3) derivative was glycosylated with the phenyl 2-thioglycoside of sialic acid in the presence of N-iodosuccinimide (NIS) and trimethylsilyl trifluoromethane-sulfonate (TMSOTf) in acetonitrile medium, giving the disialogangliotriose (III6NeuAcII3NeuAc-GgOse3) derivative which contains both sialyl-alpha(2-->6)-GalNAc and sialyl-alpha(2-->3)-Gal structures (Route I). This pentasaccharide was efficiently synthesized also by the coupling of (methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto -2-nonulopyranosylonate)-(2-->6)-2-deoxy-3,4-O-isopropylidene-2-ph thalimido-D-galactopyranosyl trichloroacetimidate with 2-(trimethylsilyl)ethyl (methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto -2-nonulopyranosylonate)-(2-->3)-(2,6-di-O-benzyl-beta-D-galactopy ranosyl)-(1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside, followed by conversion of the phthalimido group to the acetamido group (Route II). O-Deisopropylidenation and further glycosylation with methyl (methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-gala ct-2-nonulopyranosylonate)-(2-->3)-2,4,6-tri-O-benzoyl-1-thio-b eta-D-galactopyranoside, promoted by dimethyl(methylthio)sulfonium triflate (DMTST), gave the desired trisialogangliotetraose (IV3NeuAcIII6NeuAcII3NeuAc-GgOse4) derivative, which was converted stepwise into the title ganglioside GT1a alpha by the introduction of the ceramide part and then complete deprotection. The ganglioside obtained was shown to be identical with the native GT1a alpha on TLC-immunostaining.

Animals↗
PubMed1999

Correlation of dietary food intakes and serum lipid fatty acids in urban senior citizens.

Fatty acid compositions of serum lipids from elderly people (65 to 79 years old) in Koganei City of Tokyo were determined, and their correlation with dietary food intakes were examined. Cholesterol esters, triglycerides and lecithin revealed characteristic fatty acid profiles, respectively. Lecithin contained large amounts of eicosapentanoic and docosahexanoic acids (EPA and DHA) which belong to n-3 fatty acids as compared to other lipids. Sex differences in the fatty acid composition were found only in lecithin among serum lipids. Percentages of n-3 fatty acids were higher in males than in females, and were found to be positively correlated with the intake of fish. On the other hand, linoleic acid and n-6 fatty acids were shown to have positive correlations with beans. Arachidonic acid among n-6 had weak but significant correlations with eggs and milk.

Aged↗
PubMed1999

Frequency distribution of axon diameters in the left aortic nerve of the rat raised in space--Neurolab Program.

INTRODUCTION: To study development of the aortic baroreflex mechanisms under conditions of microgravity, we carried out the various experiments in the neonate rats aged 25 days raised in microgravity for 16 days (flight: FLT group) in Neurolab program (STS-90, space shuttle Columbia, launch date: Apr 17, '98. Some results of the experiments were already reported. The results of histological examination of the aortic nerve which is the afferent of the aortic baroreflex showed that the number of unmyelinated fibers in FLT was significantly less in than those in two control groups and there was no difference between FLT and each control group in the analysis of myelin. In the present paper, the frequency distribution of axon diameters of the left aortic nerves in FLT was compared to that in two ground control groups to examine the growth of the aortic nerve fibers in space. METHODS: After breeding Sprague-Dawley rats for 16 days in the shuttle in space and in the animal center in the Kennedy space center, a total of 43 deeply anesthetized rats were perfused with 1% parahormaldehyde and 1% glutaraldehyde or 4% parahormaldehyde solution buffered at pH7.4 with 0.12 M phosphate solution. Concerning the control groups, one group was the asynchronous ground control (AGC) group in which the rats were housed in the same cages as those on the shuttle, and the other was the vivarium ground control (VIV) group in which the rats were housed in commercial cages. The cervical region of the left aortic nerve which is a branch of the vagus was cut off and stored in the same fixative as that used for perfusion, and postfixed in the solution of 1% OsO4, for 2 hours within 24 hours after the perfusion. The fixed specimens were embedded in epoxy resin blocks by the usual method for electron microscopy following dehydration. Electron microscopic montages of transverse sections of these nerve trunks were made from the five left aortic nerves in each group. The magnification of the montages was approximately 13400 times. The long and short axes (a and b) of the nerve fibers and the myelin thickness (T) were measured with a caliper and the axon diameters (R were calculated by following formula: R2=[(a-2T)2+(b-2T)2]/2.

Animals↗
PubMed1998

Gangliosides and sialylcholesterol as modulators of synaptic functions.

Gangliosides were shown to enhance the release of acetylcholine from synaptosomes on stimulation. The influx of calcium ion into synaptosomes on membrane depolarization was increased by gangliosides. This was hypothesized to be an underlying mechanisms for the enhancement of acetylcholine release. Studies using calcium channel blockers revealed that four distinct types of voltage-dependent calcium channels occurred in cerebrocortical synapses, and that the N-type was primarily responsible for the evoked release of acetylcholine. An additional result suggests that gangliosides may act mainly on the N-type calcium channel. Cholinergic-specific gangliosides, Chol-1 alpha, were assumed to participate in the mechanism of high-affinity choline uptake. These two different actions of gangliosides were found to be mimicked by synthetic ganglioside analogs. Calcium influx was increased by alpha-sialylcholesterol, and choline uptake was accelerated by beta-sialylcholesterol. Gangliosides and sialylcholesterol having these apparently beneficial effects were shown to ameliorate decreased functions of synapses from aged brains.

Acetylcholine↗
PubMed1998

Effect of the mono- and tetra-sialogangliosides, GM1 and GQ1b, on long-term potentiation in the CA1 hippocampal neurons of the guinea pig.

Effects of the mono- and tetra-sialogangliosides, GM1 and GQ1b, on long-term potentiation (LTP) were investigated in the CA1 neurons of guinea-pig hippocampal slices. The magnitude of LTP induced by a strong tetanus (100 Hz, 100 pulses) was not significantly affected by application of either ganglioside. In contrast, when LTP was induced by a weak tetanus (100 Hz, 4 pulses), a significantly greater LTP was induced in the presence of either ganglioside. Similarly, when slices were incubated in low-Ca2+ (1.0-1.1 mM) medium for more than 2 h, the LTP was usually small or absent, but showed a significant increase in amplitude of population spike (A-PS) when the slices were incubated with either GM1 or GQ1b (4-5 microg/ml). In addition, the application of GQ1b (4 microg/ml) reversed the blocking effect of an NMDA-receptor antagonist, APP-5 (10 microM), on the induction of LTP and resulted in forming LTP. Based on these findings, we conclude that GM1 and GQ1b exert positive modulatory effects on the induction of LTP in hippocampal CA1 neurons and suggest that GM1 and GQ1b may participate in the induction of LTP as donors of Ca2+ ions.

Animals↗
PubMed1998

Histological analysis of the aortic nerve in the rat raised in space (Rapid communication on Neurolab Project).

To study development of the aortic nerve baroreflex under conditions of microgravity, we examined the cross section of the left aortic nerve (LAN), which is the afferent of the baroreflex, in the neonate rats aged 25 days raised in microgravity on the space shuttle Columbia (flight:FLT group) for 16 days. In this paper, we report a part of the result obtained from the data of the myelinated fibers of LAN analyzed with an electron microscope. Two kind of ground control groups were compared to the FLT group; one was asynchronous ground control (AGC) group where the rats were housed in the same cage as that on the shuttle, and the other was vivarium(VIV) group where the rats were housed in a commercial cage. The LANs in each group were extirpated the from rats perfused with a fixative and embedded for histological analysis. We observed the transverse sections of LAN and took pictures of several areas (magnified to x 2K to x 200K). No irregular myelination was found in all fibers of FLT group when they were compared with two control groups. The thickness of myelin of the maximally myelinated fibers were 0.55 +/- 0.17 micrometer in FLT(n=5), 0.45 +/- 0.10 micrometer in AGC(n=5), and O.47 +/- 0.06 micrometer meter in VIV(n=5). There was no significant difference among three groups (unpared t-test). The results suggest that there is no effect of space environment on the myelin formation of each nerve fiber in the aortic nerve.

Animals↗
PubMed1997

Gangliosides enhance KCl-induced Ca2+ influx and acetylcholine release in brain synaptosomes.

Effects of gangliosides GM1 and GQ1b on cholinergic synaptic functions were investigated using synaptosomes prepared from mouse brain cortices. Treatment of synaptosomes with GM1 and GQ1b increased high K(+)-evoked acetylcholine (ACh) release in a bell-shaped dose-dependent manner. The peaks of the effects were found to be at 1-5 microM for GM1 and 5-10 microM for GQ1b. ACh synthesis and the levels of ACh in synaptosomes were not affected by the ganglioside treatment. Both gangliosides enhanced depolarization-induced influx of calcium ions into synaptosomes. These results indicate that GM1 and GQ1b gangliosides increase evoked ACh release by modulating voltage-dependent calcium channels in the synaptic plasma membranes. The effect of GM1 on calcium ion influx remained after repetitive washings, but was almost completely abolished when the bound GM1 was removed by trypsin. This indicates that the fraction of GM1 which was tightly bound to, but not incorporated in synaptic plasma membranes, is responsible for activating the calcium channels.

Acetylcholine↗
PubMed1996

Gangliosides expressed in human breast cancer.

Breast tumors that were histopathologically diagnosed as invasive ductal carcinoma were examined in relation to their abnormal expression of gangliosides. Total ganglioside levels that were expressed as lipid-bound sialic acids were significantly higher in breast tumor tissues than in normal mammary tissues. Two kinds of unusual gangliosides were found to be expressed in many cases of breast tumors. One was a group of O-acetylated gangliosides, such as O-acetyl-GD3 and O-acetyl-GT3. They are known as fetal gangliosides, which appear in fetal brains. The other was an N-glycolylneuraminic acid-containing ganglioside, N-glycolyl-GM3, which had not been previously found in normal human tissues. The finding that unusual gangliosides are expressed in breast tumors may provide the basis for their immunological diagnosis and vaccine therapy.

Breast Neoplasms↗
PubMed1996

A novel ganglioside, 9-O-acetyl GD1b, is recognized by serum antibodies in Guillain-Barré syndrome.

A hitherto undescribed ganglioside was detected in a crude ganglioside fraction of bovine brain using an IgM M-protein binding to Gal beta 1, 3GalNAc residue. We purified and identified it as 9-O-acetyl GD1b based on results of alkali treatment that yielded GD1b and results of fast atom bombardment-mass and gas chromatography-mass spectrometries. 9-O-acetyl GD1b was also found to be present in human peripheral nerve tissue. The reactivities of the serum antibodies from patients with Guillain-Barré syndrome to 9-O-acetyl GD1b, GD1b, and GM1 were determined by ELISA and TLC immunostaining. Nineteen of 85 serum samples from Guillain-Barré syndrome patients had antibodies that bound to 9-O-acetyl GD1b: 14 of the positive samples also reacted with GM1 and GD1b, three reacted with GM1 but not with GD1b, one with GD1b but not with GM1, and one with neither GM1 nor GD1b. These results show that a subset of patients with Guillain-Barré syndrome had antibodies that react with 9-O-acetyl GD1b; therefore, this ganglioside can serve as a target antigen against the antibodies present in Guillain-Barré syndrome.

Animals↗
PubMed1996

[Measurement of the common carotid arterial flow during parabolic flight in the anesthetized rat].

To measure the blood flow of a common carotid artery (CCA) during parabolic flight in the rat, we developed an animal double hold box (ADHB) made of styrene expanded form for the anesthetized rat to keep the animal at a proper posture in an aircaft. Twelve anesthetized rats weighing 291-342 g were surgically operated to mount a ultrasound flowmeter probe (1 mm size,1RS:Transonic Systems Inc.) around the right CCA and to insert a catheter into the right axillar artery for blood pressure measurement. These animals were held comfortably in ADHBs which were placed on the rack installed in the aircraft (MU-300). A total of 27 parabolic flights was performed and the blood flow was measured accurately in 9 rats. This special animal holding facility is useful for various types of animal experiments in an aircraft.

Animals↗
PubMed1994

Characteristics of gangliosides including O-acetylated species in growth cone membranes at several developmental stages in rat forebrain.

Growth cones, the motile tips of extending neuronal processes, are involved in accurate synaptogenesis. To study the developmental changes in ganglioside composition including O-acetylated gangliosides in growth cones, we analyzed the gangliosides in growth cone membranes (GCM) prepared from rat forebrains at different developmental stages. At several stages, GCM contained significantly larger amounts of gangliosides than the other membrane subfractions. The ganglioside content of GCM increased in amount with development. Moreover, in GCM, the relative amount of GD3 gradually decreased, and that of GD1a dramatically increased. There were significant differences in the composition of ganglioside species between GCM and the perinuclear plasma membrane subfraction (NM); most importantly, GCM had a higher ratio of GD1a to GM3 plus GD3 than NM. There were three different O-acetylated gangliosides in GCM: O-acetyl-GD3, O-acetyl-GT1b, and O-acetyl-GQ1b. The molar ratio of O-acetyl-GD3 decreased in GCM at later stages (5% of the total gangliosides at embryonic day 17, to 1% at postnatal day 5). However, those of the other two O-acetylated gangliosides were almost constant (1-2% of the total). Our results show that there are significant differences in ganglioside content and composition between the membrane subfraction of growth cones and the perinuclear portion. This suggests that several species of gangliosides, including O-acetyl-GD3, play a role in growth cone function.

Acetylation↗
PubMed1994

Facile methods for isolation and determination of gangliosides in a small scale: age-related changes of gangliosides in mouse brain synaptic plasma membranes.

A quantitative isolation method for gangliosides from small sizes of samples has been developed. Total lipids were separated into gangliosides and other lipids using Phenyl Sepharose column chromatography. Gangliosides were recovered in a yield of 99%. Determination of gangliosides was performed by gas chromatography--mass spectrometry using a selected ion-monitoring technique. These combined methods can provide quantitative isolation and determination of gangliosides from as little as 10 mg fresh brain tissues or 0.5 mg protein of membrane fractions. The present methods were successfully applied to the analysis of gangliosides from mouse brain synaptic plasma membranes to reveal that the ganglioside contents and composition remain constant from adult to senescence.

Aging↗
PubMed1994

Changes of blood volume distribution by postural changes in rats.

During a space flight the human body responds to many different gravities. The launching of the rocket, the weightlessness, the re-entry of the spacecraft, and other factors influence the astronaut's body. The fluid shifts and the effect on the cardiovascular system arising from these gravitational changes have been frequently studied in space medicine by using body tilting, lower body negative pressure (LBNP) and centrifugal accelerators. There exist, however, few reports about the changes in whole body blood volume distribution caused by body tilting. These changes can be measured using radioisotopes: scintigraphy using 99mTechnetium-labeled human serum albumin (99mTc-HSA), etc. In humans, however, because the visual field of the scintillation camera is so small, the simultaneous measurement of whole body blood volume distribution cannot be done during body tilting. We therefore used rats, whose whole bodies can be encompassed within the visual field of the camera, and we discussed the changes in blood volume distribution induced by body tilting. We also measured the blood concentrations in each organ by using whole body autoradiography in mice, and discussed the effect of postural changes on some abdominal organs.

Abdomen↗
PubMed1993

Differential fatty acid release from CA1 and CA3 regions of rat hippocampal slices under hypoxia and hypoglycemia.

Rat hippocampal slices were subjected to hypoxia and/or hypoglycemia for 10 min, and free fatty acids released in CA1 and CA3 regions were separately analyzed. Fatty acid accumulation in CA1 was not so significant under hypoglycemia, but very prominent under hypoxia. Free fatty acid levels in CA3 were much less than those in CA1 even under hypoxia plus hypoglycemia. This observation seems to be consistent with the selective vulnerability of CA1 neurons seen in in vivo ischemia. The decreasing order of accumulation of free fatty acid species in CA1 was C16:0 > C18:0 > C18:1 > C20:4 > C22:6. The increment fold as compared to control level was decreasing as follows: C22:6, 28 times; C20:4, 13 times, C18:1, 10 times; C18:0 = C16:0, 3 times. The present experimental conditions using hippocampal slices provided a good in vitro model to prove the selective hypoxic damages of the CA1 subfield in terms of free fatty acid release in association with the membrane degradation.

Animals↗
PubMed1993

Isolation and characterization of a trisialyllactosylceramide, GT3, containing an O-acetylated sialic acid in cod fish brain.

An O-acetylated ganglioside that generated a trisialyllactosylceramide or GT3 by base treatment was found for the first time in cod fish brain. This ganglioside was isolated by high-performance liquid chromatography, and characterized by fast atom bombardment mass spectrometry, and proton nuclear magnetic resonance spectroscopy in addition to chemical analysis. The structure was identified as a modified GT3 in which the external sialic acid is O-acetylated at the C-9 position. The chemical structure is as follows: II3(9-O-Ac-NeuAc2-8NeuAc2-8NeuAc2-3)Lac Cer.

Acetylation↗