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Biomedical subjects

F Murakami

Publications and source records attributed to F Murakami.

At least 163 records · Page 9Linked to original sources
PubMed1983

Synaptic inputs of feline rubrospinal neurons from the parietal association cortex, pretectum and medial lemniscus, and their lesion-induced sprouting.

Synaptic inputs of rubrospinal (RN) neurons from the cerebral cortex, pretectal area (PRT), and medial lemniscus (ML) were investigated electrophysiologically in the cat. Stimulation of the ipsilateral parietal association cortex (PASC) and secondary sensory area (SII) produced slow-rising about 3 msec rise time monosynaptic EPSPs which were, in some cases, followed by hyperpolarizations, similar to the sensorimotor cortex (SM)-induced PSPs previously observed. Stimulation of the contralateral cerebral cortex never produced detectable PSPs. Topographical arrangement of PASC-rubral projection was found. Stimulation of the lateral part of PASC induced EPSPs predominantly in RN cells innervating the cervicothoracic spinal segments, while stimulation of the medial part of PASC produced EPSPs predominantly in RN cells innervating the lumbosacral cord. Furthermore, PASC-induced EPSPs were more frequently recorded at the rostral half of RN than at the caudal half. Monosynaptic EPSPs and multisynaptic IPSPs were induced by stimulation of the ipsilateral PRT and ML. PRT- and ML-induced EPSPs had times-to-peak of 1.0 +/- 0.4 msec (mean +/- S.D.) and 1.6 +/- 0.5 msec, respectively, which were intermediate to those of the cerebral peduncle (CP)- and nucleus interpositus of the cerebellum (IP)-induced EPSPs. Furthermore, sensitivity of amplitudes of PRT-induced EPSPs to membrane hyperpolarization was intermediate to those of CP- and IP-EPSPs, and that of ML-induced EPSPs was lower than that of IP-EPSPs. Therefore, it is likely that synapses of PRT and ML fibers are formed between the distal dendrites where CP-rubral synapses terminate and soma where IP-rubral synapses terminate. PASC-induced EPSPs after chronic IP and SM lesions had a new fast-rising component and the effectiveness of ML stimulation to induce the unit spike of RN cells was clearly increased in IP and SM lesioned cats. It was suggested that PASC-rubral fibers sprouted and formed new synapses at the proximal portions of soma-dendritic membranes of RN cells after IP and SM destructions. Collateral fibers to RN cells of the pyramidal tract were also shown to sprout new synapses following IP and ML lesions.

Animals↗
PubMed1982

A quantitative study of synaptic reorganization in red nucleus neurons after lesion of the nucleus interpositus of the cat: an electron microscopic study involving intracellular injection of horseradish peroxidase.

A quantitative electron microscopic analysis of the corticorubral projection was performed in the red nucleus (RN) of adult cats to determine morphological correlates of synaptic reorganization that occur following a lesion of the interpositus nucleus (IP). Corticorubral synaptic endings were identified by lesioning the sensorimotor cortex 2-6 days before electrophysiological experiments. Horseradish peroxidase (HRP) was injected into electrophysiologically identified RN neurons. Sagittal sections 100 micrometers thick were cut and reacted by diaminobenzidine. Sections containing HRP-positive neurons were selected and embedded in Epon. In normal cats, degenerating corticorubral terminals in the RN region frequently made contact with dendritic profiles, having small cross-sections, while a few made contact with somatic profiles. Similar results were obtained when degenerating terminals making contact with HRP-filled dendrites were analyzed. In the experimental animals, the cortical lesion was performed more than 8 weeks after lesion of the IP. In these animals, degenerating corticorubral terminals were frequently found on proximal dendrites and somata in RN region and HRP-positive neurons in contrast to the findings in normal cats. The results indicate that new corticorubral synapses were formed on proximal dendrites and somata of RN neurons as a consequence of IP lesions.

Animals↗
PubMed1982

Multiple molecular forms of acetylcholine receptors in cultured skeletal muscle cells: subcellular localization and characterization.

Skeletal muscle cells of newborn rats, cultured in the absence of neuronal influence, were found to contain two types of cell surface acetylcholine receptors as demonstrated by isoelectric focusing. The isoelectric points of the two types of receptors were indistinguishable from those of junctional and extrajunctional types of receptors in mature animals. The cultured cells had two classes of intracellular alpha-bungarotoxin (alpha BT) binding components; one had the same sedimentation coefficient as that of surface receptors (9S), and the other had much smaller apparent molecular weights. Only a single major component was detected by isoelectric focusing analysis of the 9S intracellular alpha BT binding component, with a pI value close to that of the extrajunctional receptor. These results suggest that the junctional and extrajunctional types of receptors may be synthesized through a common precursor.

Animals↗
PubMed1982

Genetics of lattice degeneration of the retina.

First-degree relatives of proband patients with lattice degeneration of the retina revealed a significantly higher prevalence of the disease than the prevalence in the general population: the former had the disease about three times as frequently as the latter. The observed data were analyzed in terms of their accordance with recognized genetic models. The inheritance pattern did not fit well to a monogenic mode of inheritance, and it was hypothesized that a polygenic or multifactorial mode of inheritance is the most likely for lattice degeneration of the retina.

Adolescent↗
PubMed1981

Reciprocal connections between the nucleus interpositus of the cerebellum and precerebellar nuclei.

Reciprocal excitatory connections which give rise to reverberatory activity were investigated by intracellular recording and retrograde horseradish peroxidase (HRP) transport. Neurons in the interpositus nucleus (IP) were activated antidromically from the nucleus reticularis tegmenti pontis (NRTP) and paramedian reticular nucleus (PMRN). Stimulation of these nuclei and lateral reticular nucleus (LRN) elicited monsynaptic EPSPs in IP neurons. PMRN neurons could be activated antidromically as well as orthodromically from IP. HRP-positive neurons were found in NRTP, PMRN and LRN following injection of HRP into IP. Neuronal connections of IP-NRTP-IP, IP-PMRN-IP and IP-RN-LRN-IP were suggested as possible components of reverberating circuits.

Animals↗
PubMed1981

Congenital hereditary retinoschisis: evolution at the initial stage.

Two male infants with congenital hereditary retinoschisis are presented. The disease was detected when they were 11 and 20 months old, respectively, and they were followed up during the subsequent months. Initially, they both revealed a tremendously elevated retinoschisis lesion in both equatorial an peripheral retina, which was associated with foveal retinoschisis. The peripheral ballooning retinoschisis regressed gradually in the following months, and a relatively flat retinoschisis was left. It was proposed that the early stage of the disease is characterized by a bullous retinoschisis followed by its spontaneous regression during the first several years of life. A survey of the literature favors our view.

Child, Preschool↗
PubMed1979

Therapy and prognosis of status convulsivus in childhood.

The record of 67 cases under 15 years of age who were hospitalized during status convulsivus from 1975 to 1978, the 348 cases who visited the hospital for the first time with epilepsy (Oct. 1977 to Sept. 1978) and the 32 cases who were hospitalized during status epilepticus from 1969 to 1974 and who are being followed up as outpatients were studied. The frequency of status epilepticus was 8% among epileptic children. There was no difference in the frequency of incidence between male and female. Patients with mental retardation, however, were revealed to have status epilepticus twice to three times more frequently as compared to cases without mental retardation. The major seizure types of status epilepticus in childhood were generalized tonic clonic convulsion and unilateral clonic convulsion. In 25% of the cases, status epilepticus was the first ictal manifestation. The major cause of status convulsivus was epilepsy, followed by encephalitis and encephalopathy, but cases due to brain tumor were rare. The drug of first choice for status convulsivus is diazepam. If there is any difficulty in controlling status convulsivus with diazepam, it may be worthwhile to consider what the problem is, causes of status convulsivus, seizure type, or basic disease of the patient. The effective dose of diazepam was within the range of 0.3--0.5 mg/kg. When the effect is not sufficient, the dose of diazepam should be increased to 1 mg/kg while watching the general condition of the patient. Factors affecting the prognosis of status convulsivus were its cause, duration, onset age and effectiveness of therapy during the acute stage. The frequency of cases who suffered disability after status epilepticus was 56%. (transient disability 43%, permanent disability 13%) The most frequent type of transient disability was hemiplegia. Most epileptic children who had repetitive status convulsivus revealed psychomotor retardation before first status. Factors which cause repetitive status seem to be hemispheric brain damage or diffuse corticocentrencephalic damage.

Adolescent↗
PubMed1978

A role of anti-"LD" antibody in induction of active enhancement in rat heart allografts.

Heart allografts from S-D to Wistar rats pretreated with 5 x 10(7) spleen cells taken from donor strain 1 or 2 weeks before, survived indefinitely. Sera taken from the pretreated rats showed high lymphocytotoxic titers and obvious blocking activity against LMC of immunized Wistar spleen cells. Even though the sera were exhaustively absorbed with RBC, this blocking activity was not impaired, although CDC was reduced. The active prolongation of graft survival, therefore, correlates with the presence of anti-LD antibody.

Animals↗
PubMed1977

Analysis of unitary EPSPs mediated by the newly-formed cortico-rubral synapses after lesion of the nucleus interpositus of the cerebellum.

1. Unitary EPSPs were recorded intracellularly from neurons of the red nucleus (RN) by stimulating the cortico-rubral fibers in normal cats as well as those with chronic lesion of interpositus nucleus (IP) of the cerebellum. 2. Two groups of unitary EPSPs were recorded in cats with IP lesion. One consisted of cortico-rubral unitary EPSPs with a shorter time to peak and larger amplitude than those in normal cats. The other consisted of unitary EPSPs of the normal range. 3. The appearance of the fast rising group of cortico-rubral EPSPs caused by IP lesions was theoretically predictable based on Rall's compartmental model by assuming that new synapses were formed close to the soma of the RN cells. 4. The amplitude of the fast rising EPSPs increased more prominently by hyperpolarizing the membrane potential than that of the slowly rising ones. 5. It was concluded that the fast rising group of unitary EPSPs which appeared following IP lesion was due to the formation of new synapses on the proximal portion of the soma-dendritic membrane of RN cell.

Animals↗
PubMed1977

Properties of the synaptic transmission of the newly formed cortico-rubral synapses after lesion of the nucleus interpositus of the cerebellum.

1. Properties of synaptic transmission during and after repetitive activation of the newly formed cortico-rubral were examined in the red nucleus neurons (RN) of cats after lesions of the nucleus interpositus of the cerebellum (chronic cats) as well as in normal ones. 2. A prominent facilitation of the amplitude of cortico-rubral unitary EPSPs was observed in both normal and chronic cats when a stimulus to the cerebral peduncle (CP) was preceded by another stimulus by 2-50 msec. 3. Time course of the facilitation shows that it attains maximum at the interval of about 3 msec and decays approximately exponentially lasting for 50 msec or more. 4. When three successive stimuli of identical intensity were applied to CP, the degree of facilitation was more prominent than that for double shock. 5. There was a positive correlation between the time to peak of the cortico-rubral EPSPs and their maximum value of facilitation. 6. The posttetanic potentiation of the cortico-rubral EPSPs was observed after tetanic stimulation to CP in chronic and normal cats. It lasts for a few minutes in both cases.

Animals↗
PubMed1977

Connectin, an elastic protein of muscle. Comparative Biochemistry.

Connectin, an elastic protein, was isolated from both skeletal and cardiac muscles of various species of vertebrates, and also from smooth muscles (gizzard) of the chicken. The amino acid compositions of these preparations were very similar. Connectin was also obtained from claw and tail muscles of the crayfish, but preparations from clam adductor muscles and insect thoracic muscles were heavily contaminated with collagen and resilin, respectively. Connectin-like protein was obtained from cell membranes of erythrocytes and fluorescent anti-connectin staining suggested that it is located on the cytoplasmic surface of the membrane. An attempt to isolate an elastic protein from insoluble residues of amoebae of the slime mold and those of bacterial cell body (Salmonella) was inconclusive. The present comparative bio-chemical study has shown that connectin or connectin-like protein is widely distributed in various types of muscles and in some nonmuscle cells.

Amino Acids↗