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Biomedical subjects

K Ichikawa

Publications and source records attributed to K Ichikawa.

At least 415 records · Page 23Linked to original sources
PubMed1986

Characterization of regulation of thyrotropin (TSH) receptor function in thyroid plasma membrane: interaction between TSH receptor function and activation of adenosine 3',5'-monophosphate-dependent protein kinase.

The changes in the characteristics of thyrotropin (TSH) binding to thyroid plasma membranes during the activation of cyclic AMP-dependent protein kinase in the membranes were studied. Preincubation of thyroid plasma membranes with TSH or cyclic AMP reduced the maximal binding capacity but increased the association rate for TSH binding. In double reciprocal analysis, a marked reduction of the total number of binding sites and association constant was observed in the membranes treated with cyclic AMP. These reductions were also observed in the membranes preincubated with buffer alone. The degree of these reductions, however, was greater in the membranes pretreated with cyclic AMP. During incubation of the membranes with buffer alone, cyclic AMP formation (activation of adenylate cyclase) was observed though the degree of the formation was lower than that induced by TSH. The results suggested that not only TSH receptor release from thyroid plasma membrane but also the modification of TSH binding activity in the membrane is produced by cyclic AMP-dependent protein kinase.

Adenylyl Cyclases↗
PubMed1985

[Induction of cytosolic proteins controlling mitochondrial protein synthesis by thyroid hormone].

The effect of thyroid hormone on the generation of modulators of mitochondrial protein synthesis was investigated. The modulators were present in the 150,000 X g supernatant (S-150) prepared from Wistar rat liver and kidney. A stimulator was found in the liver, and an inhibitory modulator was present in kidney tissue. Generation of these modulators was stimulated by T4 administration to the animals. Both the stimulatory and inhibitory modulators were inactivated by pretreatment with trypsin or boiling. The molecular weight of these modulators was estimated by gel filtration study and for both the stimulatory and inhibitory modulator proteins was approximately 10,000 daltons. The results suggested that thyroid hormone regulates mitochondrial protein synthesis through the stimulation of synthesis of mitochondrial protein synthesis modulators, and that the tissue specific modulators (stimulatory in liver and inhibitory in kidney) can be produced by the hormone.

Animals↗
PubMed1985

Temporal aspects of the electroretinogram in cone-rod dystrophy.

Twelve patients with cone-rod dystrophy were studied in terms of the temporal aspects of electroretinography (ERG). The peak time of scotopic b-wave was within normal limits in all patients, while the amplitude was reduced in nine patients. The normal peak time of the scotopic-b wave may help explain rod involvement with normal or only slightly elevated final rod thresholds of subjective dark adaptation. The peak time of photopic b-wave and 30-Hz flicker response was normal in four patients and significantly delayed or nonrecordable in eight patients. Such variations of peak time in photopic and 30-Hz flicker ERG may reflect the stage of the disease or may be caused by the different hereditary mode.

Adult↗
PubMed1985

Light and electron microscopic localization of L-alpha-hydroxyacid oxidase in rat kidney revealed by immunocytochemical techniques.

Light and electron microscopic localization of L-alpha-hydroxyacid oxidase (L-HOX) in rat kidney was studied by means of immunocytochemical techniques. Isozymes A and B of L-HOX were purified from rat liver and kidney, respectively. The apparent molecular weights of the subunits of the isozymes A and B were 35,800 and 33,500 daltons, respectively, by a slab gel electrophoresis. Antibodies to the isozymes were raised in rabbits. Anti(isozyme A) is not cross-reactive with the isozyme B and vice versa anti(isozyme B) not with the isozyme A. Using anti-isozyme B, semithin sections of Epon-embedded material and ultrathin sections of Lowicryl K4M-embedded material were stained by immunoenzyme and protein A-gold techniques, respectively. By light microscopy, fine discrete granular staining was noted in proximal tubules, but not in distal tubules including thick and thin limbs of Henle and collecting tubules. By electron microscopy, gold particles representing the antigen sites for L-HOX B were confined exclusively to peroxisomes, in which most of the gold particles were localized in electron dense peripheral matrix, but little in central matrix with low electron density. The results indicate that L-HOX B does not homogeneously distribute in peroxisomes of rat kidney but might be associated with some substructure within peroxisome matrix.

Alcohol Oxidoreductases↗
PubMed1985

Intra-axonal polysaccharide deposits in the peripheral nerve seen in adult polysaccharide storage myopathy.

This is the first report of an adult polysaccharide storage myopathy demonstrating polysaccharide deposits within the axons of the peripheral nerve. Histochemical and electron-microscopic studies revealed that the intra-axonal deposits were basophilic, PAS-positive, diastase-resistant, and composed of filamentous and granular material. The structural similarity among the polysaccharide deposits in our case, amylopectin-like materials in type IV glycogenosis, Lafora bodies, corpora amylacea, and polyglucosan bodies is discussed.

Adult↗
PubMed1985

Models for transmitter activation process in retinal rod outer segments to flash stimuli.

It has been generally accepted that transmitter molecules, which participated in the visual transduction process in retinal rod outer segments, are activated by bleached rhodopsin molecules serially one by one (serial activation model). This serial activation model accounts for some experimental observations, but not the quick and amplified activation of transmitter molecules. In this study, two models are proposed and solutions from the differential equations of the models are compared quantitatively with experimental observations. The two models proposed in this study are the serial-parallel activation model and the parallel-parallel activation model. In the serial-parallel activation model, rhodopsin molecules are activated by bleached rhodopsin molecules. Transmitter molecules are activated both by bleached and activated rhodopsin molecules. In the parallel-parallel activation model, both rhodopsin and transmitter molecules are activated by bleached and activated rhodopsin molecules. The time taken to activate 90% of transmitter molecules after flash stimuli, which bleaches 10(-4)% of rhodopsin, is 5.94 s, 3.91 ms and 23.7 microseconds for the serial, serial-parallel and parallel-parallel activation models, respectively. As contrasted to the serial activation model in which transmitter activation proceeds too slow, the present serial-parallel and parallel-parallel activation models can reproduce transmitter activation quick enough to account for the experimental observations.

Animals↗
PubMed1985

Peripharyngeal space invasion of head and neck cancer--incidence, mechanisms, and management.

We studied the incidence and mode of development of peripharyngeal invasion from head and neck cancers by both retrospective examination of our 127 patients and tracing the dynamics of lymph flow from the hypopharyngeal wall to the peripharyngeal space. We also presented three experiences of the surgical approach to the peripharyngeal invasion by our modification of Attia's technique. Peripharyngeal space invasions occur frequently in a direct or indirect way when meso- or hypopharyngeal or posterior oral cancer invades deeply into the muscle layers and extends to the palatine arch, retromolar region, pharyngoepiglottic fold, pharyngeal tongue, or posterior buccal mucosa. The lymph flow was revealed to move quickly from the lateral hypopharyngeal wall to the base of the skull and occasionally to the opposite side. The peripharyngeal space invasions were successfully removed under a wide surgical field without injuring the important nerves and vessels and with preservation of mandibular function. We should cover all routes for extension of head and neck cancers, including the peripharyngeal space, in the diagnosis and management of these conditions.

Head and Neck Neoplasms↗
PubMed1985

Evidence for induction by thyroid hormone of cytosolic proteins which control mitochondrial protein synthesis.

The effect of thyroid hormone on the generation of modulators of mitochondrial protein synthesis was investigated. The modulators were present in the 150,000 X g supernatant (S-150) prepared from Wistar rat liver and kidney. In young rats (50 g BW), a stimulator was found in liver, and an inhibitory modulator was present in kidney tissue. Generation of these modulators was stimulated by T4 administration to the animals. In aged rats (200 g BW), the production of an inhibitory modulator in both liver and kidney was stimulated by thyroid hormone administration. Both the stimulatory and inhibitory modulators were inactivated by pretreatment with trypsin. The mol wt of these modulators was estimated by gel filtration study, and for both the stimulatory and inhibitory modulator proteins was approximately 10,000. The results suggested that thyroid hormone regulates mitochondrial protein synthesis through the stimulation of synthesis of mitochondrial protein synthesis modulators and that the tissue-specific modulators (stimulatory in liver and inhibitory in kidney) can be produced in young animals. In aged animals, however, it is postulated that thyroid hormone stimulates biosynthesis of an inhibitory modulator in both liver and kidney.

Aging↗
PubMed1985

Black (or brown) adrenal cortical adenoma: its characteristic features on computed tomography and endocrine data.

Seventeen patients with adrenal adenoma causing Cushing's syndrome, eight patients with Cushing's disease due to hypersecretion of ACTH, and five patients with primary aldosteronism due to an aldosteronoma were studied for their computed tomographic (CT) patterns, hormonal profiles, and macroscopic and microscopic findings of the adrenal gland. Black (or brown) adrenal adenomas were found in 71% of the patients with Cushing's syndrome, but not in patients with aldosteronoma. The adrenal tissue of patients with Cushing's disease was predominantly yellow. The number of compact cells was larger in black or brown adenomas than in yellow tumors or hyperplastic adrenal tissue. In patients with Cushing's syndrome, urinary excretion of 17-ketosteroids (17-KS) and serum aldosterone concentrations were lower in those with black or brown adenomas than in those with yellow adenomas (P less than 0.05). Patients with Cushing's disease had even higher 17-KS and serum aldosterone levels. No difference was found in serum cortisol concentrations and dexamethasone suppressibility in two types of adenomas causing Cushing's syndrome. Visual estimation of radiological density of the adrenal tissue relative to the kidney on CT scan and quantitative measurement of it by CT number revealed a difference between the two types of adrenal tumors causing Cushing's syndrome. Adrenal tumors with decreased density on CT scan were yellow adenomas with predominantly clear cells, and those with equal or increased density were black or brown adenomas with predominantly compact cells. All aldosteronomas had decreased density and consisted of clear cells. It is suggested that black or brown adenomas of the adrenal gland have higher radiological density and accompanying lower serum aldosterone and urinary 17-KS levels than ordinary yellow tumors. The abundance of compact cells may have some significance for the development of this particular type of adrenal tumor.

17-Hydroxycorticosteroids↗
PubMed1985

Bile duct lesions and diminution in number of intrahepatic bile ducts in asymptomatic primary biliary cirrhosis.

Morphological changes of interlobular bile ducts in asymptomatic or symptomatic primary biliary cirrhosis (PBC) and chronic hepatitis with ductal lesions were investigated. It was supposed that bile duct lesions found in PBC and chronic hepatitis could be distinguished histologically. There were identical epithelial changes between symptomatic PBC and asymptomatic one, but granulomas were more often found in asymptomatic PBC than in symptomatic PBC. Numbers of interlobular bile ducts per portal tract and the rates of portal tracts without interlobular duct in asymptomatic PBC were intermediate between symptomatic PBC and chronic hepatitis. Serial sections revealed that some bile ducts were able to be followed by ductules in asymptomatic PBC. From these results, numbers of interlobular bile ducts are undoubtedly decreased in asymptomatic PBC but not so much as in symptomatic one. This observation may be attributable partially for taking asymptomatic course.

Aged↗