Biomedical subjects

K Kurosumi

Publications and source records attributed to K Kurosumi.

At least 19 recordsLinked to original sources

PubMed1997

Proteolytic processing of pro-opiomelanocortin occurs in acidifying secretory granules of AtT-20 cells.

Using antibodies specific for pro-opiomelanocortin (POMC), amidated joining peptide (JP), and the prohormone convertase PC1, we showed immunocytochemically that PC1 in a corticotrophic tumor cell line, AtT-20, was co-localized either with POMC or with amidated JP in secretory granules, and also confirmed that POMC was cleaved mainly in secretory granules. Analysis using DAMP (3- [2,4-dinitroanilino]-3'-amino-N-methyldipropylamine) as the pH probe suggested a correlation between POMC processing and acidic pH in the secretory granules. Bafilomycin A1, a specific inhibitor of vacuolar-type H(+)-ATPase, completely inhibited POMC processing and caused constitutive secretion of the unprocessed precursor. By contrast, chloroquine, a weak base that is known to neutralize acidic organelles, was unable to inhibit POMC processing. Electron microscopic analysis revealed that, in AtT-20 cells treated with bafilomycin A1, the trans-Golgi cisternae were dilated and few secretory granules were present in the cytoplasm. These observations suggest that acidic pH provides a favorable environment for proteolytic processing of POMC by PC1 but is not required, and that integrity of the trans-Golgi network and sorting of POMC into secretory granules are important for POMC processing.

Animals↗

PubMed1993

Morphofunctional study on prolactin-producing cells of the anterior pituitaries in adult male rats following thyroidectomy, thyroxine treatment and/or thyrotropin-releasing hormone treatment.

An immunoelectron-microscopic and morphometric study was carried out on the anterior pituitary prolactin (PRL) cells of adult male Wistar rats treated with a combination of thyroidectomy and administration of L-thyroxine (T4) and/or synthetic thyrotropin-releasing hormone (TRH) in order to clarify the effects of changes in the hypothalamus-pituitary-thyroid axis on the ultrastructure and function of PRL cells. After thyroidectomy, PRL cells underwent atrophy and hypofunction of their cell organelles, but these changes tended to be restored to their normal level by T4 treatment. On the other hand, the administration of TRH to intact rats produced hypertrophy and hyperfunction in the PRL cells, although this treatment had no effect on the PRL cells of thyroidectomized rats. However, treatment with a combination of T4 and TRH had a strong effect and led to hypertrophy and hyperfunction in the PRL cells of thyroidectomized rats. Serum and pituitary PRL levels were measured by radioimmunoassay (RIA) for a comparison with the morphological results. They correlated well with the morphological changes. These results indicate that TRH stimulates PRL secretion in the presence of thyroid hormone, and that the thyroid hormone plays an important role in the basic maintenance of PRL cell function and its reactivity to TRH.

Animals↗

PubMed1993

Influence of exogenously administered oxytocin on prolactin-producing cells in adult male rats as revealed by immuno-electron microscopy.

Prolactin-producing cells (PRL cells) identified by immuno-electron microscopy were studied in male rats with chronic intraperitoneal injection of synthetic oxytocin (OT). The PRL cells are usually classified into three types: the immature type containing round secretory granules about 100 nm in diameter with poorly developed cell organelles; the intermediate type containing medium-sized (150-250 nm in diameter) secretory granules with moderately developed cell organelles; and mature type containing large pleomorphic secretory granules ranging from 300 to 700 nm in diameter with well-developed cell organelles. In male rats, the intermediate type comprises typical PRL cells that constitute about 50% of all immunoreactive PRL cells. Chronic intraperitoneal OT administration to rats caused morphologically hypertrophic and hyperfunctioning PRL cells which are identified as mature type PRL cells. The frequency of occurrence of the mature type PRL cells increased after treatment. The contents of pituitary and serum PRL as measured by radioimmunoassay essentially paralleled the morphological results. These data indicate that OT may play a physiological role in PRL secretion as a releasing factor, and that OT administration causes the interconversion of the three types of PRL cells, indicating the mature type to be at the most activated state of secretory function.

Animals↗

PubMed1992

The alpha-subunit of glycoprotein hormones exists in the prolactin secretory granules of the bullfrog (Rana catesbeiana) pituitary gland.

Our recent finding that the number of immunoreactive alpha-subunit cells was invariably greater than the total number of immunoreactive gonadotropin (GTH) and thyrotropin (TSH) cells in the bullfrog (Rana catesbeiana) pituitary gland raises the possibility that the alpha-subunit also exists in pituitary cells other than GTH and TSH cells. The present study demonstrates that there are a considerable number of immunoreactive prolactin (PRL) cells that are also stained with antibody against the alpha-subunit when adjacent sections are immunocytochemically examined. Neither immunoreactive growth hormone nor adrenocorticotropin cells are stained with the antibody against the alpha-subunit. The specificity of the antibody against the alpha-subunit and of that against PRL was demonstrated by preabsorption test, non-competitive binding test, and immunoblot analysis. Double-immunolabeling with gold particles of different sizes for the alpha-subunit and PRL revealed that most of the immunolabeled PRL-secretory granules are also labeled with the alpha-subunit antibody. The gold particles indicating the presence of the alpha-subunit were mostly found in the peripheral zone of the secretory granules.

Animals↗

PubMed1992

A certain step of proteolytic processing of proopiomelanocortin occurs during the transition between two distinct stages of secretory granule maturation in rat anterior pituitary corticotrophs.

To obtain antibodies specific for precursor POMC and its cleaved peptides, we prepared synthetic peptides corresponding to the cleavage site (ST-1) between ACTH and beta-lipotropic hormone moieties of POMC and to amidated joining peptide (JP; ST-3) and generated their polyclonal antibodies in rabbits. The anti-ST-1 serum immunoprecipitated only POMC in the extract of AtT-20 cells. In addition to a similar immunoprecipitation examination, an immunoabsorption test showed that anti-ST-3 serum recognizes cleaved peptides, 16K amino-terminal peptide, and JP, but not POMC precursor. Double immunolabeling with gold particles of different sizes for the precursor POMC and its cleaved peptides revealed that the former was localized in electron-dense secretory granules, whereas the latter was found in the electron-lucent secretory granules in the same ultrathin cryosections. Colocalization of POMC and its cleaved peptides in the same secretory granules was rarely observed. Only POMC immunolabeling was detected in the Golgi cisternae. These results suggest that a certain step of proteolytic processing of POMC occurs in the secretory granules during the transition between the two distinct stages of secretory granule maturation in the rat anterior pituitary corticotroph.

Adrenocorticotropic Hormone↗

PubMed1992

Light and electron microscopic immunocytochemistry of TSH-like cells occurring in the pars tuberalis of the adult male rat pituitary.

Morphological characteristics of TSH-immunoreactive cells (TSH-like cells) in the pars tuberalis (PT) of intact adult male rats were studied by light and electron microscopic immunocytochemistry. TSH-like cells in the rat PT can be classified into three types by light microscopy: 1) cells diffusely stained throughout the cytoplasm, 2) diffusely weak stained cells containing a strongly stained spot in the paranuclear region; 3) cells with a strongly stained spot in the paranuclear region without diffuse reaction. We call the latter two cell types "spot cells". Electron microscopic immunocytochemistry revealed that the latter two cells reacted very strongly in the Golgi apparatus. The spot cells were localized throughout the PT from rostral to caudal extremities as well as the ventral surface area of the pars distalis (PD) which was connected to the PT. The cytoplasm of the TSH-cells in the PD proper was strongly and diffusely stained with anti-TSH serum, while there was no spot-like staining in any cells. The spot cells demonstrated by electron microscopy contained a well developed Golgi apparatus, many microvesicles and a few secretory granules. These immunocytochemical results clearly showed two apparently distinct types of TSH-immunoreactive cells between the PT and PD in the intact adult male rat adenohypophysis. This morphological distinction of TSH-immunoreactive cells suggests functional differences in these cells.

Animals↗

PubMed1992

[A case of the emergency salvage from the thrombotic occlusion of the Fontan conduit in tricuspid atresia].

The thrombotic occlusion of the Fontan conduit is one of the most fatal complications after Fontan procedure. Its survival case by the successful emergency surgery is reported. A 17-year-old male who had undergone Fontan procedure three years before for tricuspid atresia, using the expanded PTFE graft of 19 mm in internal diameter, had several episodes of palpitation due to probable paroxysmal atrial fibrillation. He suddenly complained chest oppression feeling and suffered paroxysmal atrial tachycardia following after atrial fibrillation. The radionuclide angiocardiography was performed immediately, which revealed clearly that the Fontan conduit had occluded by the thromboembolism in spite of the prophylactic anticoagulant therapy. Then the emergency surgery was performed successfully, in which the occluded Fontan conduit was replaced with another expanded PTFE graft of 20 mm in internal diameter under the extracorporeal circulation. It seemed that the inducement of this thrombotic occlusion of the Fontan conduit was paroxysmal atrial fibrillation. We emphasize the importance of the prevention of arrhythmias in the postoperative care of the Fontan procedure. Additionally we do emphasize the usefulness of the radionuclide angiocardiography which is available and non-invasive. Especially, first-pass study is much informative to elucidate the circulatory states in the cardiac anomalies.

Adolescent↗

PubMed1991

Ultrastructural immunocytochemistry of the adenohypophysis in the rat: a review.

Immunocytochemistry has made great strides in the morphology of endocrine glands, especially the adenohypophysis, because the localization of hormones can be clearly demonstrated by this method in the microscopic preparations both for light and electron microscopy. In the adenohypophysis, electron microscopic immunocytochemistry is useful for identifying the producer cell of each hormone. The second contribution is its application to the cell biology of secretion mechanisms. The pituitary hormones, their precursors, derivatives, and fragments were artificially synthesized and their antibodies were produced. Using these antibodies the intracellular sites of synthesis, condensation, processing, and sorting were studied under the electron microscope. The ultrastructure of each cell organelle and its alteration due to the changing function was studied. It was proved that the intracisternal granules in the thyroidectomy cells contain thyroid-stimulating hormone (TSH). The trans-Golgi network or GERL contains a peculiar supporting structure, intracisternal skeleton. Transport of secretory granules may be performed in relation to the microtubules, actin, and some related substances. The most frequently observed mode of hormone release in the adenohypophysis is exocytosis. Sometimes multigranular exocytosis occurs. Vesiculation of membrane around the secretory granules often occur inward or outward. The inward vesiculation forms pinocytotic vesicles, through which the membrane material may be retrieved. The outward vesiculation forms vesicle-like fragments of cytoplasm being discarded to the extracellular space. By these mechanisms the surface area of the cell is maintained constantly.

Animals↗

PubMed1991

Differential appearance of the subunits of glycoprotein hormones (LH, FSH, and TSH) in the pituitary of bullfrog (Rana catesbeiana) larvae during metamorphosis.

The ontogeny of gonadotrophs and thyrotrophs in the bullfrog pituitary was examined immunohistochemically using monoclonal antibodies against bullfrog lutropin beta-subunit (LH beta), follitropin beta-subunit (FSH beta) and its alpha-subunit, and polyclonal anti-human thyrotropin beta-subunit (TSH beta) serum. Immunoreactive alpha-subunit- and TSH beta-, but not FSH beta- and LH beta-containing cells were observed at embryonic stage 24 (Shumway's classification). Immunoreactive FSH beta cells first appeared at Taylor-Korllos stage V, and immunoreactive LH beta cells at stage X. Throughout metamorphosis, several gonadotrophs containing both FSH and LH were found in the ventrocaudal region, but most gonadotrophs contained only FSH. Immunoreactive alpha-subunit cells were always more frequent than the sum of immunoreactive beta-subunit cells, which was confirmed by quantitative studies using immunohistochemical and RIA techniques.

Animals↗

PubMed1991

Intracellular sites of proteolytic processing of pro-opiomelanocortin in melanotrophs and corticotrophs in rat pituitary.

A synthetic peptide (ST-1) corresponding to the cleavage site between ACTH and beta-lipotropic hormone moieties of murine pro-opiomelanocortin (POMC) was constructed and its polyclonal antibody was generated. This antiserum immunoprecipitated only POMC from extracts of AtT-20 cells. Moreover, an antiserum raised against porcine ACTH immunoprecipitated both ACTH[1-39] and POMC. When ultra-thin frozen sections of melanotrophs in rat pars intermedia were immunolabeled with anti-ST-1 followed by protein A-gold, gold particles indicating the presence of POMC were selectively found in the electron-dense secretory granules in the Golgi area. In addition, the immunolabeling was also observed in the cisternae of the Golgi apparatus and rough endoplasmic reticulum. In contrast, with a polyclonal antibody specific for alpha-melanocyte-stimulating hormone the gold particles were found exclusively in the electron-lucent secretory granules, with none seen in the electron-dense secretory granules. With anti-ACTH serum, gold particles were observed in the electron-dense and -lucent secretory granules. In corticotrophs in the pars distalis, many gold particles indicating the presence of POMC were observed in the Golgi and peripheral secretory granules, but the percentage of immunolabeling in the peripheral secretory granules varied from cell to cell. On the other hand, ACTH immunolabeling was found in almost all the secretory granules. This finding suggests that the processing of POMC in corticotrophs might occur in the relatively peripheral granules. These results suggest that the intracellular sites of POMC processing are somewhat different between melanotrophs and corticotrophs in the pituitary.

Adrenocorticotropic Hormone↗

PubMed1991

Immunoelectron microscopic studies of gonadotrophs in the male and female rat anterior pituitaries, with special reference to their changes with aging.

Gonadotrophs immunocytochemically identified with an antibody to LH beta were studied in both male and female rats of various ages, viz., 2, 14 and 23 months after birth. The rat gonadotrophs are classified into two cell types, i.e., Type I containing large (300-700 nm) and small (150-200 nm) secretory granules, and Type II containing only small (100-200 nm) secretory granules. In normal young adults, the male rat pituitary contains a large number of Type I cells (more than 90% of all gonadotrophs), whereas the female pituitary contains much more Type II cells (more than 70%) than Type I cells. With age, Type I gonadotrophs in the male rat pituitary decrease remarkably to less than 25%, while Type II cells constitute more than 70% at the age of 23 months; the ratio of Type I to Type II comes to be the same as in the female. The main cause of this change is the decrease in the number of large secretory granules as the animal ages. FSH and LH levels in both the pituitary and serum were determined by radioimmunoassay. Pituitary FSH content decreased gradually in the male with age, while that in the female showed no change. LH content in the male decreased slowly, but LH in the female increased with aging. The large secretory granules indicating the presence of FSH markedly decreased with aging. The Type II cells contain only small secretory granules which probably contain LH. Thus the results of morphological counting of each type of gonadotroph and those of radioimmunoassay of gonadotropins during aging were essentially parallel. Some signs of degeneration were observed in the gonadotrophs in the aged rat pituitaries.

Aging↗

PubMed1991

[A review: classification and ultrastructures of the anterior pituitary cells and their role in function of hormone secretion].

Anterior pituitary cells first were classified by their staining behaviour in light microscopic preparations. Later they were classified according to the type of hormone they produce. Although even electron microscopy has been routinized, the functional classification of anterior pituitary cells was not easy. Experimental morphology that was mainly based on observation of the anterior pituitary after extirpation of target endocrine organs was the only method for identifying the probable function of each cell type in the anterior pituitary. The use of antibody against each hormone, that is immunohisto(cyto-)chemistry at light and electron microscopic level, was an epoch-making innovation in the technique for studying endocrine morphology. The technique revealed two or three morphologically different types in each cell group containing the same hormone. These subtypes in cell classification by immuno-electron microscopy are related to the age and sex of the animal. Cell biological research using electron microscopy, especially immunocytochemistry, clarified mechanisms concerning various steps in hormone production, for example, the synthesis of peptide hormones (precursors) in the rough endoplasmic reticulum; transfer to the Golgi apparatus; modification and processing of precursor peptides during the passage through Golgi stacks and the trans-Golgi network that corresponds to GERL; the moving of secretory granules; the mechanism of exocytosis and related membrane events; and the activity of lysosomes related to such endocrine functions as crinophagy and the recycling of membrane constituents retrieved from the cell surface after exocytosis of secretory granules.

Age Factors↗

PubMed1990

Immunocytochemical localization of the subunits of glycoprotein hormones (LH, FSH, and TSH) in the bullfrog pituitary gland using monoclonal antibodies and polyclonal antiserum.

Using beta and alpha subunits of bullfrog follitropin (FSH) III (pI 6.2), which were highly purified by HPLC, we generated three monoclonal antibodies (MCAs) to FSH beta subunit (FSH beta) and six to FSH alpha subunit (FSH alpha). They were produced by hybridomas derived from the myeloma X63.Ag8.653 and spleen lymphocytes from mice immunized with each subunit. Non-competitive binding tests revealed that one of the MCAs against FSH beta (BF3B25) bound strongly to intact FSH and its beta subunit, but not FSH alpha, lutropin (LH), LH alpha, and LH beta. The immunoblotting results also showed a similar immunological specificity for BF3B25. Cross-reactivity of bullfrog FSH against BF3B25 was 19.4%, when compared with FSH beta in the competitive inhibition assay system. On the other hand, noncompetitive binding tests and immunoblotting results showed that one of the MCAs against FSH alpha (BF3A20) bound strongly to intact LH and FSH and their alpha subunits, but not their beta subunits. The inhibition curves obtained using the alpha subunits of LH and FSH were similar. In the sexually mature bullfrog pituitary, immunoreactive FSH cells stained with MCA BF3B25 were distributed throughout the pars distalis, except for the rostral region, and were polygonal in shape, with well-developed cytoplasm. With respect to distribution and histological characteristics, the immunoreactive LH cells were very similar to the immunoreactive FSH cells when consecutive sections were stained with LH beta-specific MCA (BL4B11). However, immunoreactive TSH cells, revealed by anti-human TSH beta serum, formed clusters in the ventrocentral region of the pars distalis. In young adult pituitary, almost all of the gonadotrophs showed the coexistence of FSH and LH, but some gonadotrophs contained only FSH. The number of immunoreactive alpha-subunit cells stained by BF3A20 was always higher than the sum of the numbers of cells stained by the three beta-subunit-specific antibodies.

Animals↗

PubMed1990

[Elective prosthetic valve reoperation to relieve unacceptably high gradient].

Pressure gradients of Lillehei-Kaster valve (13 patients), Omniscience valve (26 patients) and Omnicarbon valve (7 patients) in the aortic position were evaluated by Doppler echocardiography. Twenty-three out of 46 patients revealed unacceptably high gradients. Seven prostheses were removed because the valve design that they had high gradients across them. Clinical findings including left ventricular function and symptoms improved after the reoperation. Patients who underwent aortic valve replacement with this series of valve prostheses should be followed up cautiously.

Aortic Valve↗

PubMed1989

Ultrastructural observation of the trans-Golgi associated plate-like cisterna in the secretory cells of the rat anterior pituitary gland with special reference to the intracisternal skeleton.

A well-developed plate-like cisterna (PLC) associated with trans-Golgi elements was observed in the Golgi apparatus of secretory cells in the rat anterior pituitary gland. This structure corresponds to the trans-most sacculotubular network. The PLC maintains a remarkably uniform thickness of about 33 nm, as measured between the outer leaflets of its unit membrane structure. As to the mechanism by which this peculiar construction of the PLC is maintained, pillar-like structures were noted in the PLC intracisternal space, apparently acting as supports to keep the intermembrane distance constant. The PLC was especially well developed in hypertrophied cells such as gonadotrophs following castration. One noteworthy feature was that the PLC frequently ran parallel with the rough endoplasmic reticulum (RER), maintaining a constant distance from the latter in hypertrophied cells, but no membrane continuity between the PLC and RER was seen.

Animals↗

PubMed1989

Postnatal development of thyrotrophs in the rat anterior pituitary as studied by immunogold electron microscopy.

Thyrotrophs (TSH cells) of the rat anterior pituitary identified by immunogold electron microscopy were classified into three subtypes according to their morphological characteristics: Immature type TSH cells are oval with a few small secretory granules (50-100 nm in diameter) and poorly developed cell organelles. These cells are frequently found in the neonatal stage between birth and 10 days of age. The intermediate type is polygonal or stellate, containing a moderate number of medium sized secretory granules (80-120 nm in diameter) and moderately or well developed cell organelles. Cells of this type are often found between 10 and 30 days of age. Mature type cells are large and polygonal in shape, and contain many large secretory granules (120-180 nm in diameter) and well developed cell organelles. Cells of the last type are frequently found at more than 30 days of age. At 45 days of age the mature type TSH cells make up about 70% of all TSH cells. The proportion of immature type cells was shown to decrease while the proportion of the mature type TSH cells increases, as the animal grows.

Animals↗

PubMed1989

Localization of fibronectin in the folliculo-stellate cells of the rat anterior pituitary by the double bridge peroxidase-antiperoxidase method.

The localization of fibronectin was demonstrated in the rat anterior pituitary by the highly sensitive double bridge peroxidase-antiperoxidase (PAP) method. The fibronectin immunopositive cells were characterized by stellate-like morphology. The cells immunostained for fibronectin were observed to be identical to those for S-100 protein in adjacent mirror sections, whereas the S-100 protein has been specifically immunodetected in the folliculo-stellate (FS) cells of the anterior pituitary. The present study indicates that the fibronectin is present in the FS cells, suggesting that FS cells might play a role in the regulation of pituitary function through the interaction of fibronectin with hormone secreting cells.

Animals↗

PubMed1989

The immature type of pro-opiomelanocortin cell of the rat anterior pituitary as observed by immunogold electron microscopy.

The perinatal development of glandular cells in the rat anterior pituitary producing pro-opiomelanocortin (POMC), the precursor protein of peptide hormones including adrenocorticotropin (ACTH), melanocyte-stimulating hormones (MSH) and endorphins was studied by an immunoelectron microscopic technique using the colloidal gold-antibody method. The POMC cells are classified into the following three types: 1) an immature type, 2) an intermediate type, and 3) a mature type, which correspond to Types III, I and II of the ACTH cells, respectively. The average size of the secretory granules in POMC cells varies widely, measuring 98.6 +/- 8.5 nm in the immature type, 111.4 +/- 6.7 nm in the intermediate type, and 139.3 +/- 23.1 nm in the mature type. The immature type comprises more than 90% of the POMC cells in the late fetal stage, but decreases in number after birth. The intermediate type reaches a peak at 8 days (female) or 33 days (male), while the mature type is that most frequently observed at 45 days, i.e., more than 50-60% of the total POMC cells, when the immature type decreases to about 15%.

Adrenocorticotropic Hormone↗