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Biomedical subjects

M Kudo

Publications and source records attributed to M Kudo.

At least 361 records · Page 20Linked to original sources
PubMed1987

Ultrastructural analyses of afferent terminals in the subthalamic nucleus of the cat with a combined degeneration and horseradish peroxidase tracing method.

The synaptic organization of the feline subthalamic nucleus (STN) was studied electron microscopically. Following horseradish peroxidase (HRP) injections into the globus pallidus (GP) and electrolytic lesions of the nucleus tegmenti pedunculopontinus pars compacta (TCP) in the same cat, both degenerating and HRP-labeled terminals were found in the STN with abundant retrogradely HRP-labeled neurons. Degenerating terminals of TPC origin were medium-sized and characterized by asymmetric synaptic contacts. They synapsed widely on the STN neuronal surface, including the somata, dendrites of varying dimensions, dendritic spines and vesicle-containing processes. They formed 25.1%, 65.1%, 4.7%, and 4.7%, respectively, of all TPC efferent terminals. Some of the postsynaptic components were labeled with HRP. Occasionally both degenerating terminals and HRP-labeled terminals were in synaptic contact with the same HRP-labeled neuron: therefore, afferents of TPC and GP converge on the same STN projection neuron. In order to discover the origin of these HRP-labeled terminals, a mixed solution containing HRP and kainic acid was injected into the GP. Numerous degenerating terminals were observed to synapse with HRP-labeled STN neurons, but no HRP-labeled terminal was observed. These degenerating terminals were similar in appearance to the above-mentioned HRP-labeled terminals. They were characterized by their relatively large size, predominantly symmetric synapses, and preferential distribution on the somata and large or medium-sized dendrites. They formed 39.6%, 20.1%, and 31.1%, respectively, of all GP efferent terminals. Therefore, it became clear that both the HRP-labeled terminals of the first experiment and the degenerating terminals of the second experiment originated from the GP. Following surgical ablations of the primary sensorimotor cortex (Cx), some axon terminals in the STN showed degeneration. These degenerating terminals were small and formed asymmetric synapses mainly with dendritic spines, small dendrites and vesicle-containing processes. They formed 48.0%, 28.0%, and 12.0%, respectively, of all Cx efferent terminals. These electron microscopic investigations reveal the convergence of TPC and GP afferents and that STN projection neurons relay the TPC and pallidal inputs directly to the GP.

Afferent Pathways↗
PubMed1987

[Stimulated corticosterone production by alpha-human atrial natriuretic polypeptide with increased cyclic GMP production].

Several studies on the effects of atrial natriuretic polypeptide (ANP) on aldosterone production using isolated adrenal cells have been reported, and they have consistently demonstrated the reduced production of aldosterone by ANP. However, the results on the corticosterone production are sundry. Since ANP selectively activates particulate guanylate cyclase, a possibility could exist that cyclic GMP is the second messenger of ANP signal transduction. In order to demonstrate unequivocally a correlation of cyclic nucleotide levels with the ANP-induced steroidogenesis, we investigated the effects of various concentrations of alpha-human atrial natriuretic polypeptide (alpha-hANP) on aldosterone, corticosterone, cyclic AMP and cyclic GMP production in isolated glomerulosa and fasciculata cells of the rats. Rat glomerulosa and fasciculata cells were obtained by enzymatic digestion of the adrenals of male Wistar rats. The cell pellet was suspended in Hanks balanced salt solution-0.1% BSA buffer and distributed in 900 microliter aliquots to 12 X 75 mm glass tubes. The samples were preincubated for 90 min. in a 37 degrees C water bath under an atmosphere of 5% CO2/95% O2. Aliquots of the test samples were added in a 100 microliter volume and incubated for 4 hr. Total volume of the incubation mixture is 1.0 ml. Aldosterone, cyclic AMP and cyclic GMP were measured by radioimmunoassay and corticosterone was determined by fluorimetric method. The results indicated that alpha-hANP inhibited the secretion of aldosterone and corticosterone in rat glomerulosa cells. Alpha-hANP significantly decreased cyclic AMP production in the rat glomerulosa cells, while it markedly stimulated cyclic GMP production.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1987

Electron microscopic study of the rubrocerebellar projection in the cat.

Rubral neurons sending axons to the cerebellar anterior interpositus nucleus (AIN) in the cat were identified light microscopically by labeling them with horseradish peroxidase (HRP). The synaptic organization of these rubral neurons and of their afferents from the cerebral motor cortex and the AIN was also analyzed electron microscopically by combined anterograde degeneration and retrograde HRP-labeling techniques. In the light microscopic study, either HRP or a mixture of HRP and kainic acid was injected into the AIN. Both of the injections resulted in retrograde labeling of rubrocerebellar projection neurons in the red nucleus on the contralateral side. The labeled neurons were distributed throughout the rostrocaudal extent of the red nucleus: some lay in clusters. Most labeled neurons were small to medium-sized, although some were large. The injection of HRP into the AIN also resulted in anterograde labeling of cerebellorubral projection fibers terminating in a wider area of the red nucleus on the contralateral side of the injection, whereas the injection of a mixture of HRP and kainic acid showed no anterograde labeling of fibers or terminals. In one set of electron microscopic observations, HRP injections into the AIN were combined with ablation of the motor cortex. Degenerating axon terminals were occasionally found to synapse with both dendrites and neuronal somata labeled with HRP retrogradely. In another set of electron microscopic observations, a mixture of HRP and kainic acid was injected into the AIN in order to label rubrocerebellar projection neurons retrogradely and to bring about degeneration in the cerebellorubral projection fibers anterogradely. Abundant degenerating axon terminals were observed to make axosomatic synaptic contacts with rubral neurons labeled with HRP retrogradely and also with unlabeled rubral neurons. These results indicate that cerebrorubrocerebellar and rubrocerebellorubral monosynaptic circuitries exist which constitute one of the cerebrocerebellar linkages, as well as those linkages via the inferior olivary complex and the pontine nuclei.

Animals↗
PubMed1987

Relationship between genital ridge formation and settlement site of primordial germ cells in chick embryos.

Chick embryos from stage 15 to stage 18, which is the most frequent extravasation period, were investigated by means of serial sections and light microscopy in order to learn the detailed relationship between the settlement sites of the primordial germ cells (PGCs) and the forming genital ridge. PGCs circulating in the vascular system came out of the small vessels in the splanchnopleure posterior to the vitelline artery. This PGC extravasation was limited to an area about 1.2 mm caudal to the vitelline artery. After the extravasation, the PGCs entered the neighboring thickened coelomic epithelium of the splanchnopleure. This thickened epithelium, which had incorporated the PGCs, changed the location toward the future gonadal site with the advance of development. At stage 16, the thickened portion of the epithelium was located in the splanchnopleure; then it moved toward the somatopleure via the coelomic angle; finally, at stage 18, this epithelium occupied the region between coelomic angle and the mesonephros which corresponded to the future genital ridge. This means that the thickened epithelium of the splanchnopleure which initially incorporated the PGCs becomes the superficial epithelium of the genital ridge in more advanced stages. The thickened portion of the epithelium of the splanchnopleure at stage 16 is thought to be the definitive gonadal anlage.

Animals↗
PubMed1987

Confronting cisternae in pituitary gland thyrotrophs of congenitally hypothyroid mice.

Confronting cisternae were found in pituitary thyrotrophs of congenitally hypothyroid mice. These confronting cisternae rapidly reverted back to ordinary rough endoplasmic reticulum following thyroxine administration. Confronting cisternae were not observed in the thyrotrophs of euthyroid control mice. Our results strongly suggest that confronting cisternae are a peculiar form of rough endoplasmic reticulum which appears under certain conditions of enhanced cellular metabolism.

Animals↗
PubMed1987

Syntactic pattern analysis of 5'-splice site sequences of mRNA precursors in higher eukaryote genes.

The signals which direct the excision of introns from eukaryotic pre-mRNA are not yet well understood. In order to define the signals for 5'-splice sites of mRNA splicing, nucleotide sequences including 5'-splice junctions of mammalian pre-mRNAs are analysed by means of syntactic pattern analysis. Taking this approach, we infer the grammatical rules which specify 5'-splice sites and construct a finite automaton which is the recognizer of the nucleotide sequences at 5'-splice sites. By scanning the automaton along nucleotide sequences, we can identify the positions of 5'-splice junctions with a degree of discrimination of up to 94-97% in the known genes, while the degree of prediction is in the range 50-55% in new genes.

Algorithms↗
PubMed1987

[Early combined carcinoma and malignant lymphoma in the stomach associated with tonsillar malignant lymphoma--report of a case].

This report deals with a histologic demonstration of a combined tumor of early signet ring cell carcinoma and lymphoma of the stomach in a 52-year-old Japanese man. The Gastric carcinoma was found by a systemic work up for a tonsillar lymphoma. The relationship between the malignant lymphomas of the stomach and of the tonsil is not clear in this case. The carcinoma and lymphoma of the stomach were both small, and the depth of invasion was localized to the mucosa and submucosa, respectively. The lymphoma was observed just beneath the cancer and was a diffuse, large cell type, and of the same histologic typing as the tonsillar lymphoma. Based on the broader size of the carcinoma, it is considered that the carcinoma probably induced the lymphoma in the stomach. This of an early combined tumor of carcinoma and lymphoma of the stomach is, to our knowledge, the first to be reported in the literature.

Adenocarcinoma, Mucinous↗