Biomedical subjects

S Sasaki

Publications and source records attributed to S Sasaki.

At least 19 recordsLinked to original sources

PubMed1992

Ultrastructural study of skein-like inclusions in anterior horn neurons of patients with motor neuron disease.

We investigated the ultrastructure of skein-like inclusions (SI) in 11 patients with motor neuron disease. SI mainly consisted of bundles of filaments. Each filament was approximately 15-25 nm in diameter and had a tubular profile on transverse sections. SI occasionally appeared to contain electron-dense material similar to Bunina bodies (BB), and in clusters of SI, electron-dense material closely resembling BB with vesicles were scattered among the bundles of filaments or were directly attached to the filaments, suggesting a close relationship between SI and BB. We also infer that SI might be the precursor of Lewy body-like hyaline inclusions (LBHI), on the basis of the frequent presence of in-between structures, the coexistence of SI and LBHI, the detection of tubular profiles (component of SI) in LBHI, the far greater frequency with which SI were observed compared with LBHI, and the occasional connection between ubiquitin-positive SI and LBHI observed in preceding immunocytochemical studies.

Aged↗

PubMed1992

Regulation mechanisms of intracellular pH of Xenopus laevis oocyte.

Intracellular pH values (pHi) of Xenopus oocytes were optically measured using a fluorescent dye, 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The oocytes were loaded with dye by incubation with a membrane-permeable form (BCECF-AM). Mean pHi of the oocytes in pH 7.6 solution was 7.69. Increasing ambient pCO2 rapidly decreased pHi and estimated buffering power was 23.8 mM/pH unit. Changing ambient HCO3- from 5 to 30 mM did not alter pHi. After incubation in a Na(+)-free solution, Na+ addition to the bath rapidly increased pHi and this response was blocked by amiloride (ED50 2 microM). The addition of NH4Cl to the bath caused an initial transient increase in PHi followed by a secondary decrease. The secondary decrease was greatly inhibited by a histidine specific reagent, diethylpyrocarbonate. It was also slightly inhibited by ouabain, Ba2+ and furosemide, but not by amiloride. These data suggest that (1), fluorescence technique is applicable to PHi measurements of Xenopus oocytes; (2), Xenopus oocytes have an amiloride sensitive Na+/H(+)-exchange, and permeabilities to CO2, NH3, and NH+4. These observation may be useful in studying the relationship between pHi and oocytes development, and the expression of acid/base transporters in Xenopus oocytes.

Ammonia↗

PubMed1992

Expressions of receptor gene for hepatocyte growth factor in kidney after unilateral nephrectomy and renal injury.

The renal expressions of the receptor gene (c-met) for hepatocyte growth factor (HGF) were examined in unilateral nephrectomy (UNX), renal ischemia or folic acid administration. The levels of c-met mRNA were increased rapidly in all rat models at 6h after the operations. On the other hand, the expression of c-met mRNA in a kidney cell line (MDCK cells) was down-regulated for 8 h after HGF addition, indicating that c-met mRNA induction in rat models may be independent of the stimulated production of HGF. The stimulated expression of c-met in these models suggest that HGF may play an important role in renal hypertrophy after UNX and regeneration after ischemic or nephrotoxic injury.

Animals↗

PubMed1992

Loss of thyroid hormone receptor activity in primary cultured rat hepatocytes is reversed by 2-mercaptoethanol.

In primary cultures of rat hepatocytes, specific thyroid-hormone-binding activity diminished with time and was hardly detectable at 24 h. In accordance with the loss of 3,5,3'-tri-iodothyronine (T3) binding, responses to the hormone disappeared, as indicated by low induction of the thyroid-hormone-responsive gene S14. In contrast, thyroid hormone receptor proteins were present, as determined by immunostaining with a specific antibody against the receptor. Thus the loss of T3 binding was due to receptor inactivation. After various attempts to restore the T3-binding activity, we found that 2-mercaptoethanol, a reducing agent, when added to the culture medium restored the hormone binding activity in a dose- and time-dependent manner. The observed kinetics and experiments using cycloheximide suggested that mercaptoethanol prevented inactivation of the newly synthesized receptors. Oxidoreductive conditions within cells may have a role in determining the level of activity of thyroid hormone receptors.

Animals↗

PubMed1992

Hepatocyte growth factor is a paracrine factor for renal epithelial cells: stimulation of DNA synthesis and NA,K-ATPase activity.

The expressions of mRNAs of hepatocyte growth factor (HGF) and its receptor (c-met) and its effects were examined in cultured renal epithelial cell lines (OK, LLCPK1, and MDCK cells) and rat mesangial cells in primary culture. Northern blot analysis revealed the presence of HGF mRNA in mesangial cells, but not in epithelial cells. c-met mRNA was detected in epithelial cells, but not in mesangial cells. HGF stimulated [3H]-thymidine incorporation (DNA synthesis) dose-dependently in OK and LLCPK1 cells, but not in MDCK and mesangial cells. Ouabaine sensitive rubidium uptake (Na,K-ATPase activity) was stimulated by 63% with HGF (10 ng/ml) treatment for 16hr in MDCK cells. The results suggest that HGF is produced in the kidney, at least in mesangial cells and works on epithelial cells to stimulate the proliferation and/or to modify cell functions in a paracrine manner.

Animals↗

PubMed1992

Structure of the pine (Pinus thunbergii) chlorophyll a/b-binding protein gene expressed in the absence of light.

A gene for chlorophyll a/b-binding protein (cab) of pine (Pinus thumbergii) was isolated and sequenced. The gene (cab-6) contains an intron at a position equivalent to the type II cab genes of angiosperms. Transcript mapping analyses show that the amount of the mRNA in the dark is about half of that in the light. The cab-6 gene is expressed in dark-grown seedlings at a very high level, differing from angiosperm cab genes which are induced by light. The cab-6 gene typifies the coniferous plant cab genes in light-independent gene expression.

Amino Acid Sequence↗

PubMed1992

Trigeminal excitation of dorsal neck motoneurones in the cat.

Excitation of dorsal neck motoneurones evoked by electrical stimulation of primary trigeminal afferents in the Gasserian ganglion has been investigated with intracellular recording from alpha-motoneurones in the cat. Single stimulation in the Gasserian ganglion ipsi- and contralateral to the recording side evoked excitatory postsynaptic potentials (EPSPs) in motoneurones innervating the lateral head flexor muscle splenius (SPL) and the head elevator muscles biventer cervicis and complexus (BCC). The gasserian EPSPs were composed of early and late components which gave the EPSPs a hump-like shape. A short train of stimuli, consisting of two to three volleys, evoked temporal facilitation of both the early and late EPSP components. The latencies of the gasserian EPSPs ranged from 1.6 to 3.6 ms in SPL motoneurones and from 1.6 to 5.8 ms among BCC motoneurones. A rather similar latency distribution between 1.6 and 2.4 ms was found for ipsi- and contralateral EPSPs in SPL and BCC motoneurones, which is compatible with a minimal disynaptic linkage between primary trigeminal afferents and neck motoneurones. Systematic transections of the ipsi- and contralateral trigeminal tracts were performed in the brain stem between 3 and 12 mm rostral to the level of obex. The results demonstrate that both the ipsi- and contralateral disynaptic and late gasserian EPSPs can be mediated via trigeminospinal neurones which take their origin in the nucleus trigeminalis spinalis oralis. Transection of the midline showed that the contralateral trigeminospinal neurones cross in the brain stem. Systematic tracking in and around the ipsilateral trigeminal nuclei demonstrated that the axons of ipsilateral trigeminospinal neurones descend just medial to and/or in the medial part of the nucleus. Spinal cord lesions revealed a location of the axons of the ipsilateral trigeminospinal neurones in the lateral and ventral funiculi. Interaction between the ipsi- and contralateral gasserian EPSPs showed complete summation of the disynaptic EPSP component, while the late components were occluded by about 45%. These results show that the disynaptic EPSPs are mediated by separate trigeminospinal neurones from the ipsi- and contralateral side, while about half of the late EPSPs are mediated by common neurones which receive strong bilateral excitation from commissural neurones in the trigeminal nuclei. Spatial facilitation was found in the late gasserian EPSP but not in the disynaptic gasserian EPSP by conditioning stimulation of cortico- and tectofugal fibres. Disynaptic pyramidal and tectal EPSPs, which are mediated by reticulospinal neurones, were facilitated by a single stimulation in the gasserian ganglion at an optimal interval of 2 ms.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Descending projections of Forel's field H neurones to the brain stem and the upper cervical spinal cord in the cat.

1. Descending projections from Forel's field H (FFH) to the brain stem and upper cervical spinal cord were studied in cats. 2. Following implantation of HRP pellets into the spinal gray matter (C1-C3) or in the ponto-medullary reticular formation, the nucleus reticularis pontis caudalis (NRPC) or in the nucleus reticularis gigantocellularis (NRG), numerous neurones were retrogradely labelled in FFH on the ipsilateral side. In the former cases, the sizes of labelled neurones were medium-large (20-40 microns in diameter) while both small and medium-large neurones were labelled in the latter cases. 3. The lowest levels of spinal projection of single FFH neurones (n = 70) were assessed by antidromic spikes elicited by stimulating electrodes placed in C1, C3 and C7. The majority (59%) projected to C1 (but not to C3), about 27% to C3 (but not to C7), and only 14% to C7. 4. Axonal trajectories of single FFH neurones in C1-C3 segments were investigated by antidromic threshold mapping methods. The stem axons of spinal-projecting FFH neurones descended in the ventral or in the ventrolateral funiculi and the collaterals were projected to neck motor nuclei (lamina IX, Rexed 1954) and laminae V-VIII. The conduction velocities were estimated as 8-37 m/s from the antidromic latencies. 5. Axonal trajectories of 7 FFH neurones were investigated in the ponto-medullary reticular formation. All were antidromically activated from C1. In six neurones, the stem axons were located in the ventral part of the central tegmental tract and collaterals were projected to the NRPC and/or the NRG. Some of them projected to the inferior olive and the nucleus prepositus hypoglossi as well. The stem axon, in the remaining cell, was in the most dorso-medial part of the medial longitudinal fasciculus and collaterals were projected mainly to the dorsal part of the NRPC and the NRG, and also to the medial vestibular nucleus. 6. Anterograde transport of WGA-HRP injected into FFH revealed that in the upper cervical spinal cord, stem axons were found in the ventral funiculus and ventral part of the lateral funiculus. Collateral projections and presumed bouton-like deposits were observed in the laminae VI-IX, especially in their medial part. In the brain stem, dense bundles of the descending fibres were found in the central and the medial tegmental tracts and in the medial longitudinal fasciculus. FFH neurones projected densely to the caudal half of the NRPC and to the rostral half of the NRG.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Mono- and disynaptic pathways from Forel's field H to dorsal neck motoneurones in the cat.

1. We analysed the synaptic actions produced by Forel's field H (FFH) neurones on dorsal neck motoneurones and the pathways mediating the effects. 2. Stimulation of ipsilateral FFH induced negative field potentials of several hundred microvolts with the latency of about 1.1 ms in the medial ponto-medullary reticular formation, being largest in the ventral part of the nucleus reticularis pontis caudalis (NRPC), and in the dorsal part of the nucleus reticularis gigantocellularis (NRG). 3. Stimulation of ipsilateral FFH induced excitatory postsynaptic potentials (EPSPs) in 90% (47/52) and inhibitory postsynaptic potentials (IPSPs) in 19% (10/52) of the reticulospinal neurones (RSNs) in the NRPC and the NRG. Latencies of the EPSPs and IPSPs were 0.7-3.0 ms, the majority of which were in the monosynaptic range. The monosynaptic connexions were confirmed by spike triggered averaging technique both in excitatory (n = 4) and inhibitory (n = 2) pathways. 4. Single stimulation of FFH induced EPSPs at the segmental latencies of 0.3-1.0 ms in neck motoneurones, which were clearly in the monosynaptic range. Repetitive stimulation of FFH produced marked temporal facilitation of EPSPs in neck motoneurones. The facilitated components of the EPSPs had a little longer latencies and their amplitude reached several times as large as that evoked by single stimulation in all the tested motoneurones. These facilitated excitations are assumed to be mediated by RSNs in the NRPC and NRG, since RSNs were mono- and polysynaptically fired by stimulation of FFH and they were previously shown to directly project to neck motoneurones. 5. EPSPs were induced in 91% (82/91) of motoneurones supplying m. biventer cervicis and complexus (BCC; head elevator), 10% (3/29) of motoneurones supplying m. splenius (SPL; lateral head flexor). Likewise, stimulation of FFH produced EMG responses in BCC muscles, while not in SPL muscle. Thus FFH neurones produce excitations preferentially in BCC motoneurones. 6. Systematic tracking in and around FFH revealed that the effective sites for evoking above effects were in FFH and extended caudally along their efferent axonal course. 7. These results suggested that FFH neurones connect with neck motoneurones (chiefly BCC, head elevator) mono-, di- and/or polysynaptically and are mainly concerned with the control of vertical head movements.

Animals↗

PubMed1992

Synthesis in vitro of very long chain fatty acids in Vibrio sp. strain ABE-1.

The activity of fatty acid synthetase (FAS) from Vibrio sp. strain ABE-1 required the presence of acyl carrier protein and was completely inhibited by thiolactomycin, an inhibitor specific for a type II FAS. These observations indicate that this enzyme is a type II FAS. Analysis by gas-liquid chromatography of the reaction products synthesized in vitro from [2-14C]malonyl-CoA by the partially purified FAS revealed, in addition to 16- and 18-carbon fatty acids which are normal constituents of this bacterium, the presence of fatty acids with very long chains. These fatty acids were identified as saturated and mono-unsaturated fatty acids with 20 up to as many as 30 carbon atoms. The longest fatty acids normally found in this bacterium contain 18-carbon atoms. These results suggest that the FAS from Vibrio sp. strain ABE-1 has potentially the ability to synthesize fatty acids with very long chains.

Acyl Carrier Protein↗

PubMed1992

Pericapillary rosettes in the human spinal cord.

We have found large eosinophilic bodies in the pericapillary regions of the gray and white matter in the human spinal cord. These are entirely different from the previously reported pericapillary inclusion bodies (PIB). We have designated them pericapillary rosettes (PR), since they consist of clusters of round or ovoid structures of various sizes which form rosettes around the transversely sectioned capillaries. Positive staining with silver impregnation and anti-neurofilament antibody, the presence of the myelin around the bodies and the accumulation of neurofilaments within them indicate that axonal swelling is associated with the formation of PR. These bodies are not observed in individuals aged less than 30 years, and afterwards they increase in proportion to age. Over the age of 80, they are almost always found in the spinal cord, particularly in the gray matter of both the anterior and posterior horns at the thoracic and lumbar levels. Thus, the development of PR is closely related to the aging process.

Adolescent↗

PubMed1992

Sporadic amyotrophic lateral sclerosis with extensive neurological involvement.

We report an autopsy case of respirator-assisted long-survival sporadic amyotrophic lateral sclerosis (ALS) with extensive involvement extending beyond the motor system. The involved areas included the globus pallidus, subthalamic nucleus, red nucleus, substantia nigra, Clarke's column, intermediolateral nucleus, Onuf's (Onufrowicz) nucleus, middle root zone of the posterior column, and the spinocerebellar tract. There was no impairment of ocular movements. Such sporadic ALS cases with extensive involvement extending beyond the motor system may constitute a distinct subgroup of this disease that differs from long-survival ALS (with or without respirator support) in which only the motor system is affected.

Aged↗

PubMed1992

Effects of non-collagenous proteins on the formation of apatite in calcium beta-glycerophosphate solutions.

The effects of the non-collagenous proteins; osteonectin, bone Gla protein and dentine phosphoprotein, on the formation of apatite were studied in calcium beta-glycerophosphate solutions containing catalytic amounts of alkaline phosphatase under physiological conditions. In the system used, calcium phosphate precipitates de novo at levels of supersaturation precisely determined through the enzymatic hydrolysis of beta-glycerophosphate. At 1.7 mM of calcium beta-glycerophosphate, calcium phosphate precipitated when inorganic phosphate accumulated to about 1.4 mM. In the presence of the proteins, however, a greater accumulation of inorganic phosphate was needed for calcium phosphate to precipitate, suggesting that a higher degree of supersaturation, though still a slight undersaturation with respect to dicalcium phosphate dihydrate, is required for calcium phosphate to precipitate in the presence of the proteins. At the same protein (micrograms/ml) concentration, dentine phosphoprotein was approximately four times as effective as bone Gla protein, which was about twice as effective as osteonectin in delaying precipitation. The proteins also retarded subsequent crystal growth, with apatite formed in the presence of the more inhibitory proteins having the smallest crystals, especially in width.

Alkaline Phosphatase↗

PubMed1992

Esophageal tracheoplasty for congenital tracheal stenosis.

Two infants with congenital long tracheal stenosis underwent operation by means of an esophageal tracheoplasty. The first patient had previously undergone tracheal reconstruction using the pericardium. Although ventilation improved somewhat following this procedure, the pericardial patch suddenly ruptured 12 days after the operation, requiring an immediate esophageal tracheoplasty. The esophageal portion of the reconstructed trachea epithelialized 1 month later, with the lumen maintaining its proper size. However, the patient died 3 months after the second tracheoplasty. The cause of death was thought to be due to complications arising from prolonged high-pressure use of mechanical ventilation. He had been on a respirator for 6 months before the first tracheoplasty. The second patient has been doing well with no recurring respiratory problems for 25 months now. Her reconstructed trachea has adapted with her growth. This technique should be considered along with other forms of treatment for tracheal reconstruction because it is relatively simple and pliable.

Bronchography↗

PubMed1992

Increase in diameter of the axonal initial segment is an early change in amyotrophic lateral sclerosis.

We measured the diameter of the most distal portion of the axonal initial segment, the neuronal size of anterior horn cells, and the length of the axon hillock plus the initial segment (AH+IS) in the lumbar spinal cord in motor neuron disease. Three patients with amyotrophic lateral sclerosis (ALS) and one with lower motor neuron disease (LMND) were compared with 11 controls. Serial plastic sections stained with toluidine blue and electron micrographs were studied. A total of 214 axons directly emanating from the somata (n = 207) and the primary dendrites (n = 7) were observed in the patients. Approximately 19% of the proximal myelinated axons (24 axons out of 155 in ALS, and 17 axons out of 59 in LMND) were swollen at the first internode, and most of the swellings extended to the middle portion of the initial segment. Electron microscopy showed that the swellings of the proximal axons (the initial segment and the first internode) directly connected with their somata consisted mainly of accumulations of 10-nm neurofilaments. The average diameter of the most distal initial segment was markedly larger in ALS (n = 155) (P less than 0.0001) and LMND (n = 59) (P less than 0.0001) than in the controls (n = 258). Moreover, the average diameter of the most distal portion of even normal-appearing initial segments of the non-swollen axons was larger in ALS (n = 131) (P less than 0.0001) than in the controls. The perikarya and axon hillocks connected with the normal-appearing and swollen proximal axons and their dendrites almost always appeared normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyotrophic Lateral Sclerosis↗

PubMed1992

Descending pathways mediating disynaptic excitation of dorsal neck motoneurones in the cat: facilitatory interactions.

Facilitatory interactions between disynaptic EPSPs evoked from the contralateral tectum, ipsilateral tegmentum and contra- and/or ipsilateral pyramid have been investigated in dorsal neck motoneurones of the cat. Monosynaptic convergence on common intercalated neurones was found from ipsi- and contralateral pyramidal, contralateral tectal and ipsilateral tegmental fibres. In addition, disynaptic facilitation was observed from ipsilateral pyramidal fibres on disynaptic contralateral pyramidal EPSPs. Transection of cortico-fugal fibres in the pyramid showed that the location of the interactions occurred in the lower brain stem, suggesting that reticulospinal neurones are mediating the effects.

Afferent Pathways↗

PubMed1992

Descending pathways mediating disynaptic excitation of dorsal neck motoneurones in the cat: brain stem relay.

The location of intercalated neurones mediating disynaptic excitation from tectum, tegmentum and pyramids to dorsal neck motoneurones has been investigated by: (a) recording field potentials in the lower brain stem evoked from the above systems, (b) systematic stimulation in the brain stem during intracellular recording from motoneurones innervating the splenius, biventer cervicis and complexus muscles, and (c) comparing the effects of lesions of the brain stem with kainic acid on the disynaptic EPSPs elicited from the above three systems. Electrical stimulation of the contralateral superior colliculus evoked monosynaptic field potentials which were largest in the caudal pontine reticular formation rostral to the abducens nucleus and in the rostral part of the medullary reticular formation caudal to the abducens nucleus. Likewise, stimulation of the ipsilateral tegmentum (the cuneiform and subcuneiform nucleus) evoked field potentials which were large in the caudal medulla and small in the pons. In contrast, stimulation of the contralateral tegmentum was ineffective in evoking field potentials. Stimulation of the pyramid 2-3 mm rostral to the obex elicited monosynaptic field potentials in the reticular formation of the lower brain stem that were only about 25% of those from the superior colliculus. In contrast to the field potentials from the superior colliculus, the pyramidal ones were large in the medulla and small in the pons. Lesions of the reticular formation in the lower brain stem by unilateral kainic acid injection caused disappearance of disynaptic EPSPs in motoneurones from the above three systems. These results strongly suggest that the intercalated neurones mediating pyramidal, tectal and tegmental EPSPs are reticulospinal neurones in the lower brain stem. Systematic stimulation in various locations of the lower brain stem showed that monosynaptic EPSPs were evoked from the regions of the reticular formation which received projection from the above three descending systems. The effective regions for evoking the EPSPs in splenius (SPL) were located somewhat more dorsally than for biventer cervicis and complexus (BCC) motoneurones. The descending axons of presumed reticulospinal neurones were stimulated with electrodes placed in medial, middle and lateral positions at the spinomedullary junction. Monosynaptic EPSPs in SPL and BCC motoneurones were evoked from the medial and middle electrodes but not from the lateral electrode.

Afferent Pathways↗

PubMed1992

The preclinical safety evaluation of human monoclonal antibody against cytomegalovirus.

The human monoclonal antibody against cytomegalovirus (Mab C23) was examined pharmacokinetically and toxicologically as part of the preclinical studies prior to approval for human use. Rats given repeated intravenous administrations of Mab C23 produced no antibodies against Mab C23 and maintained a blood Mab C23 level in a dose-dependent manner. However, pregnant rabbits produced antibodies against Mab C23. The half-life of Mab C23 in plasma was 15.9 days in rats, which was similar to that of normal human serum gamma-globulin (NHSG). Neither behavioral effects nor circulatory disturbance was found in mice, rats, and dogs even after a single intravenous injection of 100 or 200 mg/kg, which corresponds to 50 or 100 times the intended clinical dosage. The repeated doses of 2, 10, or 20 mg/kg of Mab C23 on six occasions with 1- or 2-week intervals elicited a transient decrease in leukocyte counts in rats given 10 or 20 mg/kg, but no adverse effects in cynomolgus monkeys. Mab C23 did not cause any reproductive or developmental toxicity when administered to rats and rabbits at dose levels of 20 mg/kg or less. However, pregnant animals showed lower plasma levels of Mab C23 than non-pregnant animals. The chromosomal aberration test disclosed no clastogenicity in human lymphocytes. An immunostaining for Mab C23 revealed no localizations in several tissues of cynomolgus monkeys given intravenous doses of Mab C23.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗