Biomedical subjects

H Yagi

Publications and source records attributed to H Yagi.

At least 127 records · Page 7Linked to original sources

PubMed1997

DNA fragmentation is not the primary event in glucocorticoid-induced thymocyte death in vivo.

Thymocyte death has been recognized as one of the best models for studying apoptosis. Our recent study, however, indicated that most thymocytes die without DNA fragmentation and become terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end-labeling-positive (TUNEL+) only after being phagocytosed by macrophages. In this study, we used histological techniques using the TUNEL method, histochemistry, immunohistochemistry, and transmission electron microscopy as well as flow cytometry to examine in vivo the effect of glucocorticoid (GC), a well-known agent for inducing thymocyte apoptosis in vitro, on thymocyte death to determine whether or not DNA fragmentation was the first event of GC-induced thymocyte death. At 2 h and 4 h after GC injection, a large number of cortical thymocytes were TUNEL+. Most TUNEL+ cells were aggregated to form clusters. Double staining of the section showed that the TUNEL+ thymocytes were phagocytosed by acid phosphatase+ and Mac-2+ macrophages. An ultrastructural study indicated that a far greater number of small pyknotic thymocytes were present in the cortex of the GC-treated thymus than were observed in the control thymus, that all those pyknotic thymocytes were TUNEL-, and moreover, that at the electron microscopic level, TUNEL+ cells were all phagocytosed by macrophages. Flow cytometric analysis did not detect a single TUNEL+ thymocyte even 4 h after the GC treatment, suggesting that virtually no free dead thymocytes were present after DNA fragmentation. These results indicate that, consistent with our previous findings with normal thymocyte death and B cell death in the germinal centers, DNA fragmentation is not involved in the cell death process of the GC-induced rapid thymocyte death in vivo.

Animals↗

PubMed1997

Ultrastructural analysis of mouse thymocyte subpopulations.

To understand the lineage relationship and to define morphological characteristics of each thymocyte subset, we have performed ultrastructural analysis of highly purified thymocyte subpopulations. By flow cytometry, five subpopulations were sorted based on the expression of CD4 and CD8 and on cell size (forward scatter): large and small CD4+8+, CD4-8-, CD4+8-, and CD4-8+ thymocytes. Small CD4+8+ thymocytes were the smallest among lymphoid cells, and had a round and smooth cell outline with condensed nuclei, the cytoplasm was scanty and the cell organelles were not developed, suggesting the majority of this subset might be inactive by morphological criteria. CD4+8- thymocytes appeared to be similar to peripheral CD4+ T cells. The CD4-8- thymocyte subset contained morphologically immature cells in terms of cell size, presence of cell surface villi, and euchromatic appearance of the nucleus. CD4-8+ thymocytes heterogeneous in cell size, nuclear chromatin contents and amount of cytoplasm, could be divided into two distinct types. Type 1 CD4-8+ thymocytes were intermediate in size, and therefore similar to peripheral mature CD8+ T cells. Type 2 CD4-8+ thymocytes were large and irregular in shape (large CD4-8+) with irregular-shaped and euchromatic nuclei. Large CD4-8+ cells were, thus, considered to be at the transitional stage from CD4-8- to CD4+8+. At least two groups of large CD4+8+ cells were ultrastructurally classified by the nuclear chromatin content. Large CD4+8+ cells with heterochromatic nuclei were round with a smooth cell membrane, whereas large CD4+8+ cells with euchromatic nuclei were spherical with projections. Cytological features of heterochromatic large CD4+8+ cells are similar to those of small CD4+8+ thymocytes except for cell size. Euchromatic large CD4+8+ cells could be regarded as active blasts potentially leading to mature cells. Taken together, this is the first report that describes the ultrastructural characteristics of each thymocyte subset highly purified by flow cytometry.

Animals↗

PubMed1997

Rare earth element, Al, and Sc partition between soil and Caatinger wood grown in north-east Brazil by instrumental neutron activation analysis.

Seven representative wood species constituting Caatinger forest in north-east Brazil were chosen to analyze La, Ce, Sm, Eu, Yb, Sc, and Al by instrumental neutron activation analysis (INAA). Soil profiles were prepared where the trees were downed. Then soil and root samples from each horizontal soil layer, as well as the upper part of the wood, ground-level bark, and the bark at 1 m above were collected. In woods, the rare earth element (REE) was found to be mainly accumulated in root, which concentration was in the same order as that of soil. In all samples, concentration of La and Ce were found to be about ten times higher than those of the other REEs. The REE accumulation became higher, in both root and soil, in the order of La, Ce, and Sm. The partition rate of La and Eu was higher from soil to root, whereas Ce tended to be concentrated from root to bark. In the case of bark, there was no tendency of specific REE accumulating from ground level to the upper part. The correlation of La concentration to the other REE was higher in root than that of corresponding soil. Roots also showed higher correlation of REE to Al and Sc than that of soil or bark.

Aluminum↗

PubMed1997

Role of cytochrome P450 enzyme induction in the metabolic activation of benzo[c]phenanthrene in human cell lines and mouse epidermis.

The environmental contaminant benzo[c]phenanthrene (B[c]Ph) has weak carcinogenic activity in rodent bioassays; however, the fjord region diol epoxides of B[c]Ph, B[c]Ph-3,4-diol 1,2-epoxides (B[c]PhDE), are potent carcinogens. To determine the role of cytochrome P450 isozymes in the activation of B[c]Ph in MCF-7 cells and the low activation of B[c]Ph in mouse skin, cells of the MCF-7 and the human hepatoma HepG2 cell lines were treated with the potent Ah receptor agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) prior to exposure to B[c]Ph for 24 h. Mice were treated topically with 1 microg of TCDD or vehicle (control) for 73 h and then with 2 micromol of B[c]Ph for 24 h. In MCF-7 cells, TCDD exposure increased B[c]PhDE-DNA adduct levels more than 3-fold with a 10-fold increase in the (-)-B[c]PhDE-2-dA(t) adduct. Treatment of HepG2 cells with TCDD prior to B[c]Ph application did not increase B[c]PhDE-DNA binding. Total B[c]PhDE-DNA adducts increased 3-fold in TCDD-treated mouse epidermis: the majority of the increase resulted from (+)-B[c]PhDE-1-dA adducts. Analysis of P450 enzymes by Western blotting detected a large increase of P4501B1 but almost no increase in P4501A1 in MCF-7 cells exposed to 10 microM B[c]Ph for 24 or 48 h. In HepG2 cells, there were no detectable levels of P4501A1 or P4501B1 after treatment with 10 microM B[c]Ph for 24 h. In contrast, topical application of 2 micromol of B[c]Ph to mouse skin for 48 or 72 h increased P4501A1, but no P4501B1 was detected. As a measure of P450 activity, the metabolism of 7,12-dimethylbenz[a]anthracene (DMBA) was analyzed in microsomes prepared from MCF-7 and HepG2 cells exposed to 0.1% DMSO, 10 microM B[c]Ph, or 10 nM TCDD for 24 or 48 h and from mouse epidermis treated with 1 microg of TCDD, or vehicle control for 72 h, or 2 micromol of B[c]Ph for 48 h. The levels of DMBA metabolites were low or undetectable in microsomes from B[c]Ph-treated MCF-7 and HepG2 cells, but a metabolite pattern consistent with P4501A1 metabolism of DMBA was present in B[c]Ph-exposed mouse epidermal microsomes. TCDD-treated MCF-7 cells, HepG2 cells, and mouse epidermis had DMBA metabolism patterns characteristic of P4501A1 activity. Microsomes from TCDD-treated human cells formed a higher proportion of the proximate carcinogenic metabolite DMBA-3,4-dihydrodiol (16% of total identified metabolites) than TCDD-treated mouse epidermis (2%). In mouse epidermis, the weak ability of B[c]Ph to increase hydrocarbon-metabolizing activity and the increase in mainly P4501A1, leading to formation of the less carcinogenic stereoisomer B[c]PhDE-1, may explain the low carcinogenic activity of B[c]Ph. In a human mammary carcinoma cell line, treatment with B[c]Ph increases mainly P4501B1 and results in formation of a higher proportion of the more carcinogenic B[c]PhDE-2. This indicates that cells in which B[c]Ph treatment increases P4501B1 levels effectively activate B[c]Ph to potent carcinogenic metabolites.

Animals↗

PubMed1997

A novel point mutation of thyroid hormone receptor beta gene in a family with resistance to thyroid hormone.

Resistance to thyroid hormone (RTH) is characterized by variable tissue hyporesponsiveness to thyroid hormone caused by mutations of thyroid hormone receptor beta (TRbeta) gene. We found a novel point mutation of the TRbeta gene in a family (F123) with RTH, a transition of a guanine to adenine at nucleotide 1215, which replaced the normal Met-310 with Ile. This substitution was found in only one allele of affected family members. In vitro transcription and translation of this mutant TRbeta demonstrated a 12-fold reduction of the affinity for triiodothyronine (T3) compared with the wild type TRbeta. Thyroid function tests were similar to a previously reported RTH family (F99) who had a different mutation in the same codon (Thr 310).

Adolescent↗

PubMed1997

T-cell proliferation to superantigen-releasing Staphylococcus aureus by MHC class II-bearing keratinocytes under protection from bacterial cytolysin.

Skin colonization with Staphylococcus aureus may exacerbate skin disorders by activation of lesional T cells with release of superantigens. Although T cells are effectively stimulated by staphylococcal superantigens in the presence of epidermal accessory cells, it remains to be elucidated whether in vivo cutaneous colonization with S. aureus can activate T cells. We examined how T cells are stimulated in the presence of keratinocytes by mitomycin C (MMC)-treated S. aureus that are unable to propagate but retain their ability to produce superantigens. Peripheral blood mononuclear cells (PBMCs) proliferated well in response to MMC-treated superantigen-producing S. aureus and bacterial supernatants. When purified T cells were cultured with MMC-treated S. aureus or supernatant in the presence of interferon-gamma-pre-treated keratinocytes, the supernatant, but not MMC-treated S. aureus, stimulated T cells. MMC-treated S. aureus had a cytotoxic effect on keratinocytes. Furthermore, keratinocytes were highly susceptible to alpha-toxin compared with monocytes and B cells functioning as accessory cells in PBMCs. This suggests that a lack of response of T cells to S. aureus plus keratinocytes is due to damage of superantigen-presenting function of keratinocytes by cytolysin. The activity of alpha-toxin was much less stable than that of superantigen during incubation. Given that S. aureus-colonized skin provides circumstances in which viable keratinocytes are exposed to superantigens but not to active cytolysin(s), skin-infiltrating T cells may be effectively stimulated by S. aureus.

Adult↗

PubMed1997

Resistance to thyroid hormone caused by two mutant thyroid hormone receptors beta, R243Q and R243W, with marked impairment of function that cannot be explained by altered in vitro 3,5,3'-triiodothyroinine binding affinity.

Resistance to thyroid hormone (RTH) is a syndrome of reduced responsiveness to thyroid hormone caused by mutations in the thyroid hormone receptor beta (TRbeta) gene. Mutant TRbetas exhibit variable degrees of impaired T3 binding resulting in reduced T3-mediated function. The dominant mode of inheritance is attributed to the ability of mutant TRbetas to interfere with the function of the wild-type (WT) TR, a phenomenon known as dominant negative effect (DNE). We recently identified two families with RTH having mutations in amino acid 243 (R243Q and R243W) in whom the mechanism of RTH appears to be distinct from that of other natural TRbeta mutations. These mutations, which are located in the hinge domain of the TRbeta, do not significantly alter the binding affinity for T3, measured in vitro. The present study was undertaken to characterize the properties of these mutant TRbetas to understand the molecular basis of the RTH phenotype. Two other mutant TRbeta producing RTH with mild (320H) and severe (345R) impairment of T3 binding were studied in parallel. The results demonstrate that TRbetas 243Q and 243W could be translocated into the nucleus where they exerted normal ligand-independent repression of positively regulated thyroid hormone response elements. Yet, the addition of 10 nmol/L T3 failed to normalize the transactivation (16-13% of WT) and revert the DNE exerted by the two TRbeta mutants. In contrast, at this T3 concentration, the transactivation function of 320H was significantly higher (50% of WT), and the DNE was completely abolished, in keeping with the mild clinical form of RTH. Formation of 243Q and 243W homodimers on thyroid hormone response elements could not be as readily prevented by T3 as those formed by the WT and 320H TRbetas. These results suggest that the substitution of R243 in TRbeta produces RTH by increasing the propensity for the formation of tightly bound homodimers or by reduction of the receptor affinity for T3 only after it binds to DNA.

Animals↗

PubMed1997

Heterogeneity of mouse thymic macrophages: I. Immunohistochemical analysis.

As the first step toward understanding the identity and functions of thymic macrophages in situ, we examined the phenotypic heterogeneity of mouse thymic macrophages in tissue sections by the immunohistochemical double staining method with four monoclonal antibodies (F4/80, Mac-2, anti-CD32/16 and anti-I-A antibodies) as macrophage markers. Morphologically, three types of macrophages were identified: dendritic, round and flat-shaped. Dendritic macrophages were scattered throughout the thymus, and most of them were stained by all four markers. Among these macrophages, those at the cortico-medullary region (CMR) expressed a high intensity of CD32/16 antigen. Round macrophages were also distributed throughout the thymus; most of them, however, were localized in the cortico-medullary region to the medulla. These cells were F4/80-negative, Mac-2-positive, CD32/16-negative and I-A-positive. In contrast, round macrophages located at the cortex expressed F4/80. Flat-shaped macrophages were localized at the subcapsular region of the cortex where active lymphopoiesis was observed. This type was positive for F4/80 and CD32/16, but negative for Mac-2. Furthermore, most of the three types of thymic macrophages showed intense reactions of the I-A antigen within the cytoplasm in addition to the expression of I-A antigen on the cell membrane. These results indicate that morphological characteristics of thymic macrophages at different locations reflect phenotypic variations detected in immunohistochemistry, and suggest that these different type macrophages may play distinct roles at various locations in thymocyte development in the thymus.

Animals↗

PubMed1997

Glucocorticoid-induced thymocyte death in the murine thymus: the effect at later stages.

SUMMARY: Although glucocorticoid has been considered to cause thymocyte apoptosis in vitro, few studies have presented its in vivo effect. We report here on kinetics of glucocorticoid-induced murine thymocyte death in vivo by the TUNEL method. TUNEL-positive cells were observed as early as at 2 h after intraperitoneal injection of glucocorticoid. Most TUNEL-positive thymocytes were phagocytosed by acid phosphatase positive macrophages. "Free" (not phagocytosed) TUNEL-positive cells were not detected at early stages (by 4 h). At 6 to 8 h after the injection, the number of phagocytosed thymocytes per individual macrophage had reached its maximum, and at 8 to 12 h many ruptured macrophages ingesting too many dying thymocytes became noticeable. During the process, no additional macrophages appeared to be mobilized to the thymus. At 6 to 8 h after the injection, however, coincidentally with the fact that macrophages had become unable to further ingest dying lymphocytes, dead cells were left unphagocytosed, and ultimately became "free" positive cells, probably due to some proteolytic process ongoing within the thymus. As late as at 12 h, morphological examination revealed that epithelial cells seemed to begin engulfing thymocytes, almost simultaneously with the start of rupture of the macrophages due to the ingestion of too many thymocytes. Epithelial cells were readily identified by desmosomes and tonofilaments, in addition to euchromatic nuclei. Altogether, these results suggest that: 1) even though thymocytes were exposed to glucocorticoid in vivo, most of them were not TUNEL-positive unless they were phagocytosed; 2) even after most macrophages had ingested too many cells at later stages, macrophages in other locations did not migrate to the thymus; and finally, 3) deletion of damaged thymocytes was also carried out by thymic epithelial cells, though not frequently, at around 12 h and later.

Animals↗

PubMed1997

Subacute and chronic prurigo effectively treated with recombination interferon-gamma: implications for participation of Th2 cells in the pathogenesis of prurigo.

Subacute and chronic prurigo is notoriously resistant to usual therapies. Four of five patients with a subacute or chronic form of prurigo responded well to daily intravenous injections of recombinant interferon-gamma (rIFN-gamma) (0.25-2 x 10(6) Japan Reference Unit (JRU; 1 JRU roughly corresponds to 4 NIH units) daily, for 10-14 days). In one patient examined, the dermal portion of lesional skin before the treatment contained considerable amounts of mRNA for interleukin (IL)-4, IL-5, and IL-10, indicative of infiltration of Th2 cells. Furthermore, the administration of rIFN-gamma selectively down-regulated mRNA for Th2 cytokines, IL-4 and IL-10 in peripheral blood mononuclear cells. These findings suggest that Th2 cells play a pathogenic role in these types of prurigo and that rIFN-gamma exerts its efficacy by inhibiting Th2 cells. Our pilot study suggests that the systemic administration of rIFN-gamma is a therapeutic alternative for the treatment of recalcitrant prurigo.

Adult↗

PubMed1997

[Clinicopathological features of interstitial pneumonia associated with amyopathic dermatomyositis].

We studied clinicopathological characteristics of interstitial pneumonia associated with amyopathic dermatomyositis. The subjects comprised two men and three women, and their mean age was 58.2 years. All subjects had cruptions specific for dermatomyositis, but had no signs of myositis. They all presented with acutely or subacutely developed coughing and dyspnea. Results of tests for anti-Jo-1 antibody were negative in all cases. Chest X-ray films showed infiltrations or streaky shadows, or both in the middle and lower lung fields. Analysis of bronchoalveolar lavage fluid revealed abnormally high percentages of lymphocytes and neutrophils. In one patients a specimen obtained by open lung biopsy showed homogeneous cell infiltrations in alveolar septa and regional alveolar damage. That patient was successfully treated with cyclosporin and corticosteroids in early phase of the disease. The other four patients received immunosuppressive agents after respiratory failure developed. All four died despite having received high-dose corticosteroid and immunosuppressive therapy. Examination of autopsy specimens showed diffuse alveolar damage.

Acute Disease↗

PubMed1997

Wells' syndrome: a pathogenic role for circulating CD4+CD7- T cells expressing interleukin-5 mRNA.

Wells' syndrome, or eosinophilic cellulitis, is a rare dermatosis characterized histologically by a dermal infiltrate of eosinophils, lymphocytes and histiocytes between collagen bundles and amorphous or granular eosinophilic deposits on collagen, constituting flame figures. We report a 54-year-old woman with eosinophilic cellulitis whose peripheral blood showed a marked eosinophilia and a high proportion of CD4+CD7- cells before treatment. Reverse transcriptase-polymerase chain reaction revealed that CD4+CD7- cells, but neither CD4+CD7+ nor CD4-CD8+ cells, in the circulating mononuclear cells expressed mRNA for interleukin (IL)-5, the major cytokine involved in eosinophilia. The proportion of CD4+CD7- cells decreased, and expression of mRNA for IL-5 disappeared in the peripheral blood, when the disease was treated by the administration of intravenous recombinant interferon-gamma. These findings suggest that circulating CD4+CD7- T cells play a pivotal role in the pathogenesis of eosinophilic cellulitis by producing IL-5.

Antigens, CD7↗

PubMed1996

The Marrara syndrome: a hypersensitivity reaction of the upper respiratory tract and buccopharyngeal mucosa to nymphs of Linguatula serrata.

The Marrara syndrome, like Halazoun in Lebanon, is a hypersensitivity reaction of the upper respiratory tract and buccopharyngeal mucosa to nymphs of Linguatula serrata. The condition follows the consumption of Marrara which consists of raw liver, lungs, trachea and rumen of goats and sheep infected with larvae of L. serrata. The adult worm is found in the nasal passages of dogs. Sheep and goats are infected by eggs from infected dogs. A survey that included 240 adult individuals in a village of endemic L. serrata infection in the Sudan showed that 20% experienced symptoms of allergic nasopharyngitis (Marrara syndrome) following the consumption of raw viscera of goats or sheep at least once in their life. In a prospective study of 24 patients who reported to hospital with the Marrara syndrome, the clinical features included itching in the throat and nose, unilateral conductive deafness, tinnitus and facial palsy. Secondary bacterial infection caused suppurative otitis media. Adult L. serrata parasites were found in the nasal passages of 56 and 47% of male and female dogs in the endemic area. Nymphs were recovered from the mesenteric lymph nodes, lungs and livers of goats in the area.

Adult↗

PubMed1996

Unusual pKa of the carboxylate at the putative catalytic position of the thermophilic F1-ATPase beta subunit determined by 13C-NMR.

Glutamic acid-190 in the beta subunit of F1-ATPase from thermophilic Bacillus PS-3 (TF1) was reported to be essential for the ATPase activity. The mutant TF1beta subunit in which Glu-190 had been substituted by cysteine was carboxymethylated with 13C-labeled monoiodoacetic acid. The pKa value of the carboxymethylene group at the 190 position was determined as 5.6 +/- 0.4 by 13C-NMR. On the basis of this value, the pKa of the carboxylate of Glu-190 of the TF1beta subunit was estimated to be 6.8 +/- 0.5. The unusually high pKa could play a role in the catalytic mechanism of F1-ATPase.

Adenosine Diphosphate↗

PubMed1996

Absence of fetal liver hematopoiesis in mice deficient in transcriptional coactivator core binding factor beta.

Core binding factor beta (CBF beta) is considered to be a transcriptional coactivator that dimerizes with transcription factors core binding factor alpha 1 (CBFA1), -2, and -3, and enhances DNA binding capacity of these transcription factors. CBF beta and CBFA2, which is also called acute myeloid leukemia 1 gene, are frequently involved in chromosomal translocations in human leukemia. To elucidate the function of CBF beta, mice carrying a mutation in the Cbfb locus were generated. Homozygous mutant embryos died between embryonic days 11.5-13.5 due to hemorrhage in the central nervous system. Mutant embryos had primitive erythropoiesis in yolk sac but lacked definitive hematopoiesis in fetal liver. In the yolk sac of mutant embryos, no erythroid or myeloid progenitors of definitive hematopoietic origin were detected, and the expression of flk-2/flt-3, the marker gene for early precursor cells of definitive hematopoiesis, was absent. These data suggest that Cbfb is essential for definitive hematopoiesis in liver, especially for the commitment to early hematopoietic precursor cells.

Animals↗

PubMed1996

Immunohistochemical analysis of proliferating cell nuclear antigen, p53 protein and nm23 protein, and nuclear DNA content in transitional cell carcinoma of the bladder.

BACKGROUND: Transitional cell carcinoma (TCC) of the bladder displays an unpredictable biologic behavior and the morphologic methods of grading tumor malignancy are often insufficient to predict the clinical outcome of patients with TCC of the bladder. Thus, the new indicator should reliably reflect prognosis. In this study, the authors determined the prognostic significance of proliferating cell nuclear antigen (PCNA), p53 protein, and nm23 protein, as well as nuclear DNA content in specimens with TCC of the bladder. METHODS: Paraffin embedded materials taken from 77 patients with nonmetastatic untreated TCC of the bladder (classified as pTa-3b, NO, MO) treated with total cystectomy were employed in this study. PCNA expression, p53 protein and nm23 protein immunoreactivities, and the parameters for nuclear DNA content such as 2c deviation index (2cDI) and 5c exceeding rate (5cER) were evaluated using a computer-assisted image analyzer, and the results were compared with histologic findings and clinical outcome. RESULTS: PCNA expression positively correlated with p53 protein and nm23 protein immunoreactivities, 2cDI value, and 5cER. In addition, histologic grade positively correlated with all of these five parameters. Similarly, pT category and disease progression positively correlated with all of the five parameters, except for nm23 protein immunoreactivity. In tumors with high genetic instability as judged by 2cDI and 5cER, both PCNA expression and p53 protein immunoreactivity were elevated, whereas nm23 protein immunoreactivity was not. However, the percent coefficient of variation in PCNA expression was smaller than that observed in p53 protein immunoreactivity in each group of genetic instabilities. In univariate analysis, prognostic potential was found with histologic grade, pT category, PCNA expression, p53 protein immunoreactivity, 2cDI value, and 5cER, but was not noted in nm23 protein immunoreactivity. Multivariate analysis indicated that quantity and intensity of PCNA expression (chi 2 = 8; P = 0.0047 for quantity and chi 2 = 8.71; P = 0.0032 for intensity) and 2cDI value (chi 2 = 5.52; P = 0.0019) were independent variables of histologic grade and pT category when predicting survival. However, p53 protein and nm23 protein immunoreactivities and 5cER were not of independent significance. CONCLUSIONS: The tumor growth fraction as assessed by PCNA immunostaining is an independently significant predictor for survival of patients with TCC of the bladder.

Adult↗

PubMed1996

Defect of thymocyte emigration in a T cell deficiency strain (CTS) of the mouse.

As bone marrow progenitors migrate to the thymus, differentiate into immunologically competent T cells, then leave the thymus and home to the peripheral lymphoid organs, each migration or homing is an essentially critical process for T cell differentiation. Homing of thymocytes into peripheral lymphoid organs has been extensively analyzed. On the contrary, little is known about the mechanism whereby mature thymocytes emigrate from the thymus to peripheral lymphoid organs. In this work, we show that the mutant T cell deficiency strain (CTS) of mouse, previously described as a peripheral T cell deficiency strain, has a novel defect of mature thymocyte emigration process. Flow-cytometric analysis demonstrated a marked decrease in T lymphocytes in peripheral lymphoid organs and an accumulation of mature thymocytes in the thymus. Histologic study revealed the high concentration of thymocytes within the giant perivascular space at thymic corticomedullary junction. These accumulating cells closely resemble normal peripheral T lymphocytes in terms of cell surface phenotype and responsiveness to mitogens or allogeneic cells. They were found to express the Mel-14 Ag, the homing receptor to lymph nodes, and had a high capability of homing to peripheral lymphoid organs when explanted thymocytes were injected i.v. The intrathymic labeling methods detected hardly any emigrating CTS thymocytes from the thymus. These results indicate that emigration defect lies in the thymus of CTS mice, and suggest that this mutation is due to abnormal releasing mechanisms occurring between the thymus and the bloodstream. Complete delineation of the precise mechanisms of this defect, however, requires further studies.

Animals↗

PubMed1996

Fatty acids selectively inhibit eukaryotic DNA polymerase activities in vitro.

The in vitro relationship between eukaryotic DNA polymerases and fatty acids was investigated. Some fatty acids strongly inhibited the activities of DNA polymerase alpha and/or beta in vitro. The kinetics of inhibition by linoleic acid showed that DNA polymerase alpha was non-competitively inhibited with respect to the DNA template and substrate (dTTP), while DNA polymerase beta was inhibited competitively with both DNA and substrate.

Animals↗