Endogenous peroxidase activity in primary culture of human thyroid cells. Localization and measurement

Intracellular localization of and an assay method for endogenous peroxidase (PO) activity were studied using primary culture of thyroid cells obtained from patients with hyperthyroidism. PO activity was visualized by cytochemical reaction and was located mainly in perinuclear cisternae and rough endoplasmic reticulum. With increased culture time, the number of cells showing positive PO activity and amount of the enzyme reaction product in individual cells showed a parallel decrease. For measurement of PO activity, cultured thyroid cells were frozen and thawed and then incubated with citric acid buffer solution containing o-phenylenediamine (opd) and hydrogen peroxide. After incubation, the optical density (OD) of the solution colorized by endogenous peroxidase was measured at 405 nm using a microplate reader. About 1 X 10(4) cells were sufficient for assay of PO activity. Using the above method to assay PO activity and sandwich enzyme immunoassay for thyroglobulin (TG), chronological changes in the PO activity and TG concentration in the culture medium were examined. Although the cells showed no decrease in number, PO activity and TG concentration decreased chronologically. When the ratio of PO activity to TG concentration was calculated, in 3 cases the ratio was almost constant, and in the remaining two, it decreased chronologically. The present biochemical method thus seems useful for determining peroxidase activity of cultured thyroid en masse.     

Convergence of hepatoportal glucose-sensitive afferent signals to glucose-sensitive units within the nucleus of the solitary tract

Units which are activated by ascending impulses from the liver within the nucleus of the solitary tract (NTS) were identified by electrical stimulation delivered to the hepatic branch of the vagus. Responses of descending units were eliminated by a collision test. The units which showed decreased firing rates during portal infusion of isotonic glucose solution were also glucose-sensitive so that they showed decreased firing rates during topical application of glucose by means of micro-electro-osmotic techniques. It is concluded that glucose-sensitive neurons exist within the NTS and also that they are functionally linked with hepatoportal glucose-sensitive afferent units.     

Accumulation of somatic hypermutation and antigen-driven selection in rapidly cycling surface Ig+ germinal center (GC) B cells which occupy GC at a high frequency during the primary antihapten response in mice

Well-developed germinal centers (GC) contain rapidly dividing surface immunoglobulin-negative (sIg^-) B cells (centroblasts), and most of their progeny are sIg⁺ B cells (centrocytes) in a resting state. It has been predicted that somatic hypermutation occurs in centroblasts, whereas antigen-driven selection takes place in centrocytes. The present analysis indicates that murine GC B cells bearing sIg with specificity for an immunizing antigen are in a rapidly cycling state and increase exponentially in number to occupy spleen GC at high frequency during the 1st week after primary immunization; however, the number of these cells is significantly reduced in the 2nd week of immunization. During that period, these proliferating sIg⁺ GC B cells accumulate somatic hypermutations with nucleotide exchanges indicative of affinity maturation. These sIg⁺ GC B cells co-express B7-2, ICAM-1, and LFA-1, and have potent antigen-presenting activity which results in T cell activation in vitro. These observations indicate that the sIg⁺ GC B cells accumulate somatic hypermutations and undergo antigen-driven selection through proliferation, probably upon activation by T cells. This sIg⁺ GC B cell population may represent cell cycling centrocytes; however, the possibility that these may represent centroblasts undergoing re-expression of sIg could not be excluded.     

Comparative study on deletions of the dystrophin gene in three Asian populations

The frequency and distribution of deletions of 19 deletion-prone exons clustered in two hot spots in the proximal and central regions of the dystrophin gene were compared in three populations from Singaporean, Japan, and Vietnam. DNA samples obtained from 105 Singaporean, 86 Japanese, and 34 Vietnamese Duchenne muscular dystrophy patients were examined by polymerase chain reaction amplification. Deletions of the examined exons were found in 51.2% of Japanese patients but in 40.0% or less of the Singaporeans and Vietnamese. About two thirds of the deletions were localized in the central region and the remaining deletions were clustered at the proximal region. The most commonly deleted exons at the central deletion hot spot were exon 50 in the Singaporean, exons 49 and 50 in the Japanese, and exon 51 in the Vietnamese population. At the proximal deletion hot spot, the most commonly deleted exons were exons 6 and 8 in the Singaporeans, exons 12 and 17 in the Japanese, and exons 8 and 12 in the Vietnamese. Two cases each from Singapore and Japan had large-scale gross mutations spanning both deletion hot spots. Our results suggest that, although the presence and frequency of the two deletion hot spots may be similar in the three Asian populations analyzed, the distribution and frequency of deletions among the different exons can vary as a result of population-specific intronic sequences that predispose individuals to preferential deletion breakpoints. Received: May 20, 2002 / Accepted: July 1, 2002     

Apoptosis of colorectal adenocarcinoma (COLO 201) by tumour necrosis factor-alpha (TNF-α) and/or interferon-gamma (IFN-γ), resulting from down-modulation of Bcl-2 expression

Fas antigen is constitutively expressed in the normal colon epithelium, but considerably diminished in most colorectal carcinomas. In the present study, we examine the relationship between Fas antigen expression and apoptosis using the colorectal carcinoma cell line COLO 201, on which a low grade of Fas antigen is expressed. Anti-Fas antibody had no effect on the induction of apoptosis of COLO 201. However, TNF-α and/or IFN-γ, independently and additively, up-regulated Fas antigen expression on COLO 201 and induced apoptosis in a dose-dependent manner. Both cytokines also increased the COLO 201 sensitivity to anti-Fas antibody, resulting from the down-modulation of Bcl-2 and the up-regulation of Bax. These findings indicate that cytokine(s) plus anti-Fas antibody (which mimics natural Fas ligand) are more effective in inducing apoptosis of COLO 201 than cytokine(s) alone. These findings suggest that immunotherapy in combination with cytokine(s) and lymphokine-activated killer (LAK) cells will become a more effective therapy for cancer than cytokine(s) or LAK cells alone, since the Fas ligand is expressed on activated T cells, natural killer cells and macrophages.     

The effect of a specific thromboxane A2 antagonist, AA-2414 on airway hyperresponsiveness induced by ozone exposure in dogs]

To determine whether thromboxane A2 (TxA2) is involved in airway hyperresponsiveness induced by ozone exposure, we studied the effect of a specific TxA2 antagonist, AA-2414 on ozone-induced airway hyperresponsiveness in seven dogs. Airway responsiveness to inhaled methacholine was determined by modified Astograph (7 Hz oscillation method), and numbers of neutrophils in the peripheral blood, neutrophil counts in bronchoalveolar lavage fluid (BALF), the levels of TxB2 and 6-keto-Prostaglandin F1 alpha (6-keto-PGF1 alpha) in BALF were measured before and after ozone exposure, and after ozone exposure with pretreated AA-2414. Ozone exposure was carried out for 2 hr at an ozone level of 3.06 +/- 0.06 ppm (mean +/- SE). Airway responsiveness to inhaled methacholine increased significantly after ozone exposure (p less than 0.01), and the hyperresponsiveness induced by ozone exposure was inhibited significantly by pretreated AA-2414 (p less than 0.01). Numbers of neutrophils in the peripheral blood and neutrophil counts in BALF increased after ozone exposure, and these increase were not inhibited by pretreated AA-2414. There was no apparent change in the levels of TxB2 in BALF after ozone exposure and after ozone exposure with pretreated AA-2414, however the levels of 6-keto-PGF1 alpha in BALF decreased after ozone exposure and after ozone exposure with pretreated AA-2414 (p less than 0.1). These results suggest that TxA2 plays an important role in the development of airway responsiveness after ozone exposure in dogs, and ozone-induced airway hyperresponsiveness may not be associated with the hyperproduction of TxA2 but with the relative increase of TxA2 due to the decrease of PGI2.     

DETECTION OF HBsAg IN THE PANCREAS

Hepatitis B surface antigen (HBsAg) has been reported to be present in other organs than the liver.^3,9 So far as our knowledge is concerned, however, any report of cases dealing with pancreatic diseases induced by hepatitis B virus (HBV) has not been described in the English and Japanese literature. We report an autopsy case with a pancreatic lesion characterized by damage of both exocrine and endocrine epithelial cells with inflammatory response, which were immunohistochemically found to be positive for HBsAg, and electron-microscopically to possess core-like particles In the nucleus and cytoplasm.     

Mixed Medullary-Follicular Carcinoma of the Thyroid Immunohistochemical and Electron Microscopic Studies

A case of mixed medullary follicular carcinoma of the thyroid is reported. Grossly, the tumor was a solid, grayish white, well circumscribed mass without lymph node metastasis. Microscopically, the tumor showed both medullary and follicular areas. The follicular areas occupied discrete portions of the tumor, and were considered to be neoplastic. Tumor cells in the medullary area were polyhedral or spindle-shaped. There was no amyloid deposition within the tumor. Immunohistochemically, tumor cells in the medullary area were positive for calcitonin and negative for thyroglobulin. Some cells lining the follicles were positive for thyroglobulin. By electron microscopy, two types of tumor cell were observed. One type contained numerous cytoplasmic secretory granules, whereas the other type had few granules and showed a prominent rough endoplasmic reticulum. These findings suggested that this mixed medullary follicular carcinoma of the thyroid presented neoplastic changes within a common cell lineage.     

Functionality of chimeric Rev proteins of HIV/SIV

Studies on functional compatibility of various Rev proteins derived from all known human and simian immunodeficiency virus subgroups have shown that this essential gene product is not always exchangeable among the viruses. In an attempt to map the region of Rev proteins responsible for the observed nonreciprocal complementation, hybrid genomic Rev expression vectors were constructed by exchanging the first and second exons ofrev genes, and were examined for their abilities to activate reporter clones by transfection. With one exception, the second coding exon ofrev gene determined the functional specificity of Rev proteins.