Biomedical subjects

A Yoshida

Publications and source records attributed to A Yoshida.

At least 199 records · Page 11Linked to original sources

PubMed2000

[New examination methods for macular disorders--application of diagnosis and treatment].

To establish a diagnosis or evaluate the efficacy of treatment for macular disorders, we need methods to evaluate the anatomical and functional changes of these disorders. In this article, we describe several studies that we have conducted for 2 years. In section 1, we report our new methods for making a diagnosis and evaluating visual function in macular disorders. In section 2, we describe our trials of these examination methods in treatment. Here is the summary of our results. In section 1, to examine the structures of the macular area, we used a retinal thickness analyzer (RTA), a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph, HRT), and optical coherence tomography (OCT) to measure retinal thickness and assess retinal microstructures. We compared retinal imaging analysis of various macular diseases obtained with these three instruments. With the RTA, we obtained good three-dimensional macular images displayed on a retinal thickness map, but the retinal thickness map did not demonstrate the thickened retina with dense retinal hemorrhages, and high backscattering from hard exudates might obscure the vitreoretinal interface. The HRT three-dimensional topographic image clearly showed the undulation of the retinal surface. However, it took a relatively long time to obtain the HRT image, and we sometimes could not obtain good topographic images because of fixation movement. Examination with the OCT allows confirmation of the retinal cross-sectional structures, such as retinoschisis or cystoid spaces and the vitreomacular interface, such as vitreous traction, that cannot be detected using other conventional methods with high resolution, but high reflectivity from dense hemorrhages obscured the deeper layers of the retinal structures. Measurement of retinal thickness obtained with both the RTA and OCT is highly reproducible, and there was significant correlation between the retinal thicknesses measured with the two instruments. We believe that these three instruments might contribute significantly to early, accurate diagnosis and better monitoring of the therapeutic effects of vitrectomy for macular diseases. In the future, if these fundus imaging analysis instruments can achieve higher resolution and can analyze three-dimensional retinal images, they will provide better information to clinically evaluate macular diseases. We demonstrated vitreous examination and examination from the retinal surface to the deeper retinal layer at the macular area using a scanning laser ophthalmoscope (SLO). The SLO examination with an argon laser and a large confocal aperture was useful for conducting kinetic examination of the vitreous opacity above the macula. With a diode laser and a ring aperture (dark-field mode), it was possible to examine the retina from the deeper retinal layer to the choroids. On the other hand, the SLO also allows us to conduct a functional examination of fixation. We demonstrated that the referred retinal locus of fixation may change during the follow-up period in patients whose central fixation is impaired due to macular disease, and we showed that the fixation behavior was related to the visual acuity. Therefore, the SLO is an ideal instrument for determining the visual field and the visual acuity before and after treatment in patients with macular disease, because of its precise localization of the examination point by directly observing the fundus and by monitoring fixation behavior. Our new program installed in the SLO allows us to complete the quantitative retinal sensitivity evaluation within 2 minutes, which is difficult to do using a conventional SLO program. Furthermore, we demonstrated for the first time that minute functional changes in the retina can be detected by the SLO under low background illuminance. Such changes cannot be detected under conventional conditions. In addition, the extrafoveal visual acuity of normal subjects and patients with macular disease was studied using this new SLO program. The iso-acuity lines could be illustrated by summarizing these results in normal subjects. The SLO acuity of the horizontal meridian is significantly better than that of the vertical meridian, and even in the nasal area adjacent to the optic disc, an acuity of better than 0.1 could be achieved. To evaluate macular function, we also investigated the blood flow of the choroid (CF), the retina (RF), and the choriocapillaris at the fovea (CCF). We investigated the CF in patients with age-related macular degeneration (AMD) using pulsatile ocular blood flow (POBF) measurements. In patients with exudative AMD, the POBF was significantly lower than in patients with nonexudative AMD or in control subjects. Decreased CF may play a role in the development of choroidal neovascularization in AMD. RF was measured using laser Doppler velocimetry (LDV). (ABSTRACT TRUNCATED)

Animals↗

PubMed1999

Distribution pattern of inhibitory and excitatory synapses in the dendritic tree of single masseter alpha-motoneurons in the cat.

Little is known about the differences in the distributions of inhibitory and excitatory synapses in the dendritic tree of single motoneurons in the brainstem and spinal cord. In this study, the distribution of gamma-aminobutyric acid (GABA)-, glycine-, and glutamate-like immunoreactivity in axon terminals on dendrites of cat masseter alpha-motoneurons, stained intracellularly with horseradish peroxidase, was examined by using postembedding immunogold histochemistry in serial ultrathin sections. The dendritic tree was divided into three segments: primary (Pd) and distal (Dd) dendrites and intermediate (Id) dendrites between the two segments. Quantitative analysis of 175, 279, and 105 boutons synapsing on 13 Pd, 54 Id, and 81 Dd, respectively, was performed. Fifty percent of the total number of studied boutons were immunopositive for GABA and/or glycine and 48% for glutamate. Among the former, 27% showed glycine immunoreactivity only and 14% were immunoreactive to both glycine and GABA. The remainder (9%) showed immunoreactivity for GABA only. As few as 3% of the boutons were immunonegative for the three amino acids. Most boutons immunoreactive to inhibitory amino acid(s) contained a mixture of spherical, oval, and flattened synaptic vesicles. Most boutons immunoreactive to excitatory amino acid contained clear, spherical, synaptic vesicles with a few dense-cored vesicles. When comparisons of the inhibitory and excitatory boutons were made between the three dendritic segments, the proportion of the inhibitory to the excitatory boutons was high in the Pd (60% vs. 37%) but somewhat low in the Id (46% vs. 52%) and Dd (44% vs. 53%). The percentage of synaptic covering and packing density of the inhibitory synaptic boutons decreased in the order Pd, Id, and Dd, but this trend was not applicable to the excitatory boutons. The present study provides possible evidence that the spatial distribution patterns of inhibitory and excitatory synapses are different in the dendritic tree of jaw-closing alpha-motoneurons.

Animals↗

PubMed1999

Crystal structure of the RNA-dependent RNA polymerase of hepatitis C virus.

BACKGROUND: Hepatitis C virus (HCV) is the major etiological agent of hepatocellular carcinoma, and HCV RNA-dependent RNA polymerase (RdRp) is one of the main potential targets for anti-HCV agents. HCV RdRp performs run-off copying replication in an RNA-selective manner for the template-primer duplex and the substrate, but the structural basis of this reaction mechanism has still to be elucidated. RESULTS: The three-dimensional structure of HCV RdRp was determined by X-ray crystallography at 2.5 A resolution. The compact HCV RdRp structure resembles a right hand, but has more complicated fingers and thumb domains than those of the other known polymerases, with a novel alpha-helix-rich subdomain (alpha fingers) as an addition to the fingers domain. The other fingers subdomain (beta fingers) is folded in the same manner as the fingers domain of human immunodeficiency virus (HIV) reverse transcriptase (RT), another RNA-dependent polymerase. The ribose-recognition site of HCV RdRp is constructed of hydrophilic residues, unlike those of DNA polymerases. The C-terminal region of HCV RdRp occupies the putative RNA-duplex-binding cleft. CONCLUSIONS: The structural basis of the RNA selectivity of HCV RdRp was elucidated from its crystal structure. The putative substrate-binding site with a shallow hydrophilic cavity should have ribonucleoside triphosphate (rNTP) as the preferred substrate. We propose that the unique alpha fingers might represent a common structural discriminator of the template-primer duplex that distinguishes between RNA and DNA during the replication of positive single-stranded RNA by viral RdRps. The C-terminal region might exert a regulatory function on the initiation and activity of HCV RdRp.

Amino Acid Sequence↗

PubMed1999

Factors that predict intrahepatic recurrence of hepatocellular carcinoma in 81 patients initially treated by percutaneous ethanol injection.

BACKGROUND: In Japan, where liver transplantation has not been used to treat patients with hepatocellular carcinoma (HCC), percutaneous ethanol injection (PEI) has been employed for those with small HCCs that are not amenable to surgical resection. In the current study, the authors evaluated PEI as a treatment for HCC patients by studying recurrence rates and survival after treatment. They then examined the clinicopathologic factors that predicted patterns of local and distant intrahepatic recurrence. METHODS: For 81 patients who underwent PEI as initial therapy between 1990 and 1997, the cumulative recurrence and survival rates and their correlations with 16 clinicopathologic factors were studied using the Kaplan-Meier method. RESULTS: The 3-year overall cumulative rates of intrahepatic recurrence and survival were 81% and 84%, respectively. At the end of the observation period, intrahepatic recurrence was detected in 56 patients (69%). In 21 (38%) of 56 patients, local recurrences were significantly associated with earlier stages of underlying cirrhosis, decreased indocyanine green retention at 15 minutes (ICG R15), larger tumor size, and histologically advanced tumor grade. Distant intrahepatic recurrence was also significantly associated with liver function and ICG R15. CONCLUSIONS: PEI is most effective as the initial treatment for patients with well-differentiated HCC when the tumor is less than 15 mm in greatest dimension. However, local recurrence depends predominantly on the biologic characteristics of the tumor, regardless of the efficacy of PEI. Surgical resection of HCC should be considered, especially for patients with mild liver dysfunction.

Aged↗

PubMed1999

Three metal ions at the active site of the Tetrahymena group I ribozyme.

Metal ions are critical for catalysis by many RNA and protein enzymes. To understand how these enzymes use metal ions for catalysis, it is crucial to determine how many metal ions are positioned at the active site. We report here an approach, combining atomic mutagenesis with quantitative determination of metal ion affinities, that allows individual metal ions to be distinguished. Using this approach, we show that at the active site of the Tetrahymena group I ribozyme the previously identified metal ion interactions with three substrate atoms, the 3'-oxygen of the oligonucleotide substrate and the 3'- and 2'-moieties of the guanosine nucleophile, are mediated by three distinct metal ions. This approach provides a general tool for distinguishing active site metal ions and allows the properties and roles of individual metal ions to be probed, even within the sea of metal ions bound to RNA.

Animals↗

PubMed1999

Mouse CAF1, a mouse homologue of the yeast POP2 gene, complements the yeast pop2 null mutation.

The yeast POP2 protein (Pop2p) is a component of a global transcription regulatory complex and is required for gene expression of many genes in Saccharomyces cerevisiae. We constructed POP2 deletion plasmids encoding various Pop2p regions under the native POP2 promoter and found that the minimum functional region was located in two-thirds of the carboxyl terminal region. A mouse homologue of the POP2 gene (mCAF1), which corresponds to the Pop2p minimum region, partially rescued the growth defect of pop2 null mutant cells. Addition of the Pop2p amino terminal region to mCAF1 strengthened the suppression. mCAF1 also weakly suppressed the relatively high expression of the SUC2 gene of pop2 cells under glucose-repressing conditions; however, it failed to suppress the defect of full expression of the SUC2 gene under glucose-derepressing conditions. Our findings clearly demonstrate that a mammalian homologue can substitute for the yeast POP2 gene in some aspect.

Animals↗

PubMed1999

Light and electron microscopic immunocytochemical study on the innervation of the pineal gland of the tree shrew (Tupaia glis), with special reference to peptidergic synaptic junctions with pinealocytes.

Conventional and immunocytochemical, light- and electron-microscopic studies on the innervation of the pineal gland of the tree shrew (Tupaia glis) were made. Neuropeptide Y (NPY)-immunoreactive fibers, which were abundantly distributed in the gland, disappeared almost completely after superior cervical ganglionectomy, suggesting that these fibers are mostly postganglionic sympathetic fibers. By contrast, tyrosine hydroxylase (TH)-immunoreactive fibers, which were less numerous than NPY-fibers, remained in considerable numbers in ganglionectomized animals, indicating the innervation of TH-positive fibers from extrasympathetic sources. Bundles of substance P (SP)- or calcitonin gene-related peptide (CGRP)-immunoreactive fibers, entering the gland at its distal end, were left intact after ganglionectomy. SP-fibers were numerous, but CGRP-fibers were scarce in the gland. SP-immunoreactive fibers were myelinated and nonmyelinated, and were regarded as peripheral fibers because of the presence of a Schwann cell sheath. NPY- and SP-immunoreactive fibers and endings were mainly localized in the pineal parenchyma. NPY-immunoreactive endings synapsed frequently, and SP-positive ones did less frequently, with the cell bodies of pinealocytes. The results suggest that NPY and SP directly control the activity of pinealocytes. Sections stained for myelin showed that thick and less thick bundles of myelinated fibers entered the gland by way of the habenular and posterior commissures, respectively. Under the electron microscope, the bundles were found to contain also unmyelinated fibers. A considerable number of nerve endings synapsing with the cell bodies of pinealocytes remained in ganglionectomized animals; these endings were not immunoreactive for TH or SP. Such synaptic endings may be the terminals of commissural fibers.

Animals↗

PubMed1999

Unusually high expression of N-acetylglucosaminyltransferase-IVa in human choriocarcinoma cell lines: a possible enzymatic basis of the formation of abnormal biantennary sugar chain.

Structural analysis of the sugar chains of human chorionic gonadotropin (hCG) has revealed that abnormal biantennary structures appear specifically on hCG in the urine of choriocarcinoma patients. However, the enzymatic and molecular mechanisms of the biosynthesis of abnormal biantennary sugar chains have not yet been elucidated. In this report, the enzyme activities and the expression levels of mRNAs of N-acetylglucosaminyltransferases (GnT)-I to -V, beta-1,4-galactosyltransferase, and alpha-mannosidase II in normal human placentae and three human choriocarcinoma cell lines were investigated. GnT-IV activities in choriocarcinoma cell lines were increased from 16- to 66-fold and GnT-III activity was increased from 15- to 25-fold as compared with those in human placentae, whereas other enzyme activities were not increased significantly. The mRNA expression levels generally correlated with their enzyme activities. Among the two GnT-IV genes found in human tissues only GnT-IVa gene was strongly expressed in the cancer cells: from three to seven times as much as in the normal tissue, whereas that of GnT-IVb remained constant. On the basis of these results, we proposed that ectopic expression of GnT-IVa gene should occur along with the malignancy of trophoblastic tissues, and that the increased GnT-IV activity should be the main cause of the formation of abnormal biantennary sugar chains in choriocarcinoma. A possible enzymatic basis of the biosynthesis of abnormal biantennary sugar chains is discussed.

Carbohydrate Metabolism↗

PubMed1999

Codon optimization effect on translational efficiency of DNA vaccine in mammalian cells: analysis of plasmid DNA encoding a CTL epitope derived from microorganisms.

Interspecific difference of codon usage is one of the major obstacles for effective induction of specific immune responses against bacteria and protozoa by DNA immunization. Using genes encoding major histocompatibility complex class I-restricted cytotoxic T-lymphocyte (CTL) epitopes, derived from an intracellular bacterium, Listeria monocytogenes and a mouse malaria parasite, Plasmodium yoelii, we report here that the codon optimization level of the genes is not precisely proportional to, but does correlate well with the translational efficiency in mammalian cells, which is concomitantly associated with the induction level of specific CTL response in the mouse. These results suggest that DNA immunization using the gene codon-optimized to mammals through the entire region is very effective.

Animals↗

PubMed1999

Postoperative prediction of and strategy for metastatic recurrent hepatocellular carcinoma according to histologic activity of hepatitis.

BACKGROUND: The hepatitis activity index (HAI) score describes the histologic status of accompanying chronic hepatitis and was established by pathologists. The aim of this study was twofold: 1) to investigate the correlation between intrahepatic metastatic recurrence (IM) and the HAI score of the noncancerous region of the liver and 2) to estimate the usefulness of postoperative preventive chemotherapy in patients with hepatocellular carcinoma (HCC). METHODS: The study included 158 consecutive patients who underwent curative resection for HCC and had been observed for > 1 year. Based on the HAI scores of the noncancerous region the patients were classified into 3 groups: those with mild hepatitis (n = 33) (i.e., with HAI scores of 0-5), those with moderate hepatitis (n = 77) (with HAI scores of 6-9), and those with severe hepatitis (n = 48) (those with HAI scores of > or = 10). In addition, a prospective randomized trial of postoperative adjuvant chemotherapy was performed for 21 patients with moderate hepatitis. RESULTS: The patients in the moderate hepatitis group were found to be at higher risk for IM recurrence within 2 years after HCC resection compared with those patients in the mild (P = 0.05) and severe (P < 0.01) hepatitis groups. The incidences of more than two tumors and portal vein involvement in patients with moderate hepatitis were much higher than in those patients with mild or severe hepatitis. Multivariate analysis showed that intraoperative bleeding volume, the number of nodules, portal vein involvement, and moderate hepatitis were independent predictive factors for IM recurrence free survival. Ten patients with moderate hepatitis had received postoperative intrahepatic arterial chemotherapy (2-3 courses with a maximum dose of 80 mg of cisplatin and 10 mg of mitomycin C at 1-month intervals) for the last 3 years. Although the number of patients was small, the therapy improved the disease free survival rate significantly compared with 11 patients who received no therapy. CONCLUSIONS: The patients with moderate hepatitis (HAI score of 6-9) had the highest rate of IM recurrence among the three HAI groups. Postoperative hepatic arterial chemotherapy may be useful in improving the rate of disease free survival after surgery among these patients.

Aged↗

PubMed1999

Decreased expression of Th2 type cytokine mRNA contributes to the lack of allergic bronchial inflammation in aged rats.

Sensitized Brown Norway rats are known to develop eosinophilic bronchial inflammation and airway hyperresponsiveness after Ag exposure. However, we have previously observed that sensitized aged rats of the same strain failed to develop such allergic inflammation. In the present study, we investigated age-associated changes of cytokine mRNA expression in bronchoalveolar lavage (BAL) cells. Both young (8- to 10-wk-old) and aged (100- to 120-wk-old) Brown Norway rats were sensitized with OVA, and BAL was performed 24 h after OVA inhalation challenge. Semiquantitative RT-PCR analysis of BAL cells showed that the cells from aged rats preferentially expressed Th1 type cytokine (IFN-gamma) mRNA, whereas cells from young animals expressed more Th2 type cytokine mRNAs including those for IL-4 and IL-5. Decreased expression of Th2 type cytokine transcripts in aged animals was further confirmed by quantitative analysis, competitive RT-PCR of BAL cells, and in situ hybridization. The age-associated changes of cytokine profile were not restricted to BAL cells but were a general feature of lymphocytes, as shown by examination of popliteal lymph nodes draining the site of sensitization. These findings suggest that decreased allergic inflammation in aged animals is attributable to age-dependent impairment of Th2 generation in response to Ag.

Age Factors↗

PubMed1999

Poisoning of human DNA topoisomerase I by ecteinascidin 743, an anticancer drug that selectively alkylates DNA in the minor groove.

Ecteinascidin 743 (Et743, National Service Center 648766) is a potent antitumor agent from the Caribbean tunicate Ecteinascidia turbinata. Although Et743 is presently in clinical trials for human cancers, the mechanisms of antitumor activity of Et743 have not been elucidated. Et743 can alkylate selectively guanine N2 from the DNA minor groove, and this alkylation is reversed by DNA denaturation. Thus, Et743 differs from other DNA alkylating agents presently in the clinic (by both its biochemical activities and its profile of antitumor activity in preclinical models). In this study, we investigated cellular proteins that can bind to DNA alkylated by Et743. By using an oligonucleotide containing high-affinity Et743 binding sites and nuclear extracts from human leukemia CEM cells, we purified a 100-kDa protein as a cellular target of Et743 and identified it as topoisomerase I (top1). Purified top1 was then tested and found to produce cleavage complexes in the presence of Et743, whereas topoisomerase II had no effect. DNA alkylation was essential for the formation of top1-mediated cleavage complexes by Et743, and the distribution of the drug-induced top1 sites was different for Et743 and camptothecin. top1-DNA complexes were also detected in Et743-treated CEM cells by using cesium chloride gradient centrifugation followed by top1 immunoblotting. These data indicate that DNA minor groove alkylation by Et743 induces top1-mediated protein-linked DNA breaks and that top1 is a target for Et743 in vitro and in vivo.

Alkylation↗

PubMed1999

Selective coupling of mouse brain metabotropic sigma receptor with recombinant Gi1.

Various sigma (sigma) ligands including (+)-pentazocine stimulated [35S]GTPgammaS binding in synaptic membranes from the mouse cerebellum. The (+)-pentazocine-stimulated [35S]GTPgammaS binding was blocked by the treatment of membranes with pertussis toxin (PTX), but completely recovered by the reconstitution of PTX-treated membranes with recombinant Gi1, but not with GoA. These findings suggest that metabotropic sigma receptors are selectively coupled to Gi1 protein.

Animals↗

PubMed1999

A TSH/dibutyryl cAMP activated Cl-/I- channel in FRTL-5 cells.

An iodide (I) and chloride (Cl) channel has been identified in the continuously cultured FRTL-5 thyroid cell line using a cell attached patch clamp technique. The channel is activated by TSH and dibutyryladenosine cyclic monophosphate (Bt2-cAMP) but not by phorbol 12-myristate 13-acetate (TPA). Gluconate can not replace chloride or iodide and the channel is impermeable to Na+,K+ and tetraethylammonium ions. The current-voltage relationship demonstrates that the single channel current is a linear function of the clamp voltage. Single channel currents reversed at a pipette potential close to 0 mV. The mean single channel conductance was 60 pS for Cl- and 50 pS for I-. From the I-V relationship there was a strong outward rectification with Cl-, and a complete block with I-, in the single channel current above +40 mV. The feature of the channel is manifested in the single channel records by four distinct, equally spaced conductance levels. We suggest the channel is important for the transport of I and Cl ions across the apical membrane into the colloid space and is important for hormone synthesis and follicle formation.

Animals↗

PubMed1999

Activation of Gi1 by lysophosphatidic acid receptor without ligand in the baculovirus expression system.

Lysophosphatidic acid (LPA) receptor has been attracting many neuroscientists' concerns, since it was reported to have a potential role in the neurogenesis, which occurs in the ventricular zone of the developing and adult brain. In the present experiments using baculovirus expression system, the LPA receptor encoded by ventricular zone gene 1 (Edg-2/Vzg-1) was found to be functionally coupled to Gi1, Goa, and G11, but not to GS. The coexpression of LPA receptor markedly decreased the expression of G protein alphai1 or alphaoa subunit, while the basal [35S]GTPgammaS binding significantly increased in the Gi1-preparation. The Scatchard Plot analysis indicates that the expression of LPA-receptor (Edg-2/Vzg-1) showed stimulation of Gi1 without agonist. These results suggest the Edg-2/Vzg-1 has an intrinsic acctivity on Gi1.

Animals↗

PubMed1999

Cloning and characterization of a novel gene, striamin, that interacts with the tumor suppressor protein p53.

Expression analysis of a novel cDNA isolated from immortal murine fibroblasts revealed a single transcript of 3.0 kilobase pairs that was highly expressed in mouse and human striated muscle and in mouse heart. The gene has therefore been named striamin. Its expression was confined to skeletal muscle types with a fast glycolytic (2B) contractile phenotype. It was also detected in C2C12 mouse myoblasts and was down-regulated during in vitro myogenesis. The cDNA has a single open reading frame encoding a predicted 16.8-kDa protein of 149 amino acids with no homology to known proteins. Microinjection and transfection of green fluorescence protein-tagged striamin demonstrated that it localizes to the nucleus. Coimmunoprecipitations revealed that it can interact with p53 (a positive marker for myoblast differentiation) in vivo and in vitro. Furthermore, it repressed p53 activity in p53-mediated reporter assays. Fluorescence in situ hybridization with a mouse P1 genomic clone localized the gene to chromosome 12C3, which is syntenic to human chromosome 14q21-22.

Amino Acid Sequence↗

PubMed1999

Enhancing effects of salicylate on tonic and phasic block of Na+ channels by class 1 antiarrhythmic agents in the ventricular myocytes and the guinea pig papillary muscle.

OBJECTIVE: To study the interaction between salicylate and class 1 antiarrhythmic agents. METHODS: The effects of salicylate on class 1 antiarrhythmic agent-induced tonic and phasic block of the Na+ current (INa) of ventricular myocytes and the upstroke velocity of the action potential (Vmax) of papillary muscles were examined by both the patch clamp technique and conventional microelectrode techniques. RESULTS: Salicylate enhanced quinidine-induced tonic and phasic block of INa at a holding potential of -100 mV but not at a holding potential of -140 mV; this enhancement was accompanied by a shift of the hinfinity curve in the presence of quinidine in a further hyperpolarized direction, although salicylate alone did not affect INa. Salicylate enhanced the tonic and phasic block of Vmax induced by quinidine, aprindine and disopyramide but had little effect on that induced by procainamide or mexiletine; the enhancing effects were related to the liposolubility of the drugs. CONCLUSIONS: Salicylate enhanced tonic and phasic block of Na+ channels induced by class 1 highly liposoluble antiarrhythmic agents. Based on the modulated receptor hypothesis, it is probable that this enhancement was mediated by an increase in the affinity of Na+ channel blockers with high lipid solubility to the inactivated state channels.

Action Potentials↗

PubMed1999

Physiologic and morphologic properties of motoneurons and spindle afferents innervating the temporal muscle in the cat.

Little is known about physiology and morphology of motoneurons and spindle afferents innervating the temporalis and on synaptic connections made between the two. The present study was aimed at investigating the above issues at the light microscopic level by using the intracellular recording and horseradish peroxidase or biotinamide labeling techniques and by the use of succinylcholine (SCh) for the classification of spindle afferents in the cat. Temporalis motoneurons had dendritic trees that ranged from a spherical form to an egg-shaped form. The shape deformation was more prominent for the dendritic trees made by motoneurons located closer to the nuclear border. No axon collaterals of the motoneurons were detected. On the basis of the values for the dynamic index after SCh infusion, temporalis spindle afferents were classified into two populations: presumptive groups Ia and II. The spindle afferents terminated mainly in the supratrigeminal nucleus (Vsup), region h, and the dorsolateral subdivision (Vmo.dl) of the trigeminal motor nucleus (Vmo). The proportion of group Ia afferent terminals was lower in the Vsup than that of group II afferents. In the Vmo.dl, the proportion of group Ia afferent terminals was nearly even throughout the nucleus, but that of group II afferent terminals increased in the more outlying regions. The proportion of terminal distribution in the central region of Vmo.dl was higher for group Ia than group II. The frequency of contacts (presumptive synapses) made by a single spindle afferent on a motoneuron was higher for group Ia than group II. The present study provided evidence that the central organization of spindle afferent neurons is different between groups Ia and II.

Animals↗