Biomedical subjects

T Sun

Publications and source records attributed to T Sun.

At least 55 records · Page 3Linked to original sources

PubMed1999

Signal joint formation is inhibited in murine scid preB cells and fibroblasts in substrates with homopolymeric coding ends.

During B and T lymphocyte development, immunoglobulin and T cell receptor genes are assembled from the germline V, (D) and J gene segments (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Adv. Immunol. 56, 27-150). These DNA rearrangements, responsible for immune system diversity, are mediated by a site specific recombination machinery via recognition signal sequences (RSSs) composed of conserved heptamers and nonamers separated by spacers of 12 or 23 nucleotides (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Adv. Immunol. 56, 27-150). Recombination occurs only between a RSS with a 12mer spacer and a RSS with a 23mer spacer (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Adv. Immunol. 56, 27-150). RAG1 and RAG2 proteins cleave precisely at the RSS-coding sequence border leading to flush signal ends and coding ends with a hairpin structure (Eastman, M., Leu, T., Schatz, D., 1996. Initiation of V(D)J recombination in vitro obeying the 12/23 rule. Nature 380, 85-88; Roth, D.B., Menetski, J.P., Nakajima, P.B., Bosma, M.J., Gellert, M., 1992. V(D)J recombination: broken DNA molecules with covalently sealed (hairpin) coding ends in scid mouse thymocytes. Cell 983-991: Roth, D.B., Zhu, C., Gellert. M., 1993. Characterization of broken DNA molecules associated with V(D)J recombination. Proc. Natl. Acad. Sci. USA 90, 10,788-10,792; van Gent, D., McBlane, J.. Sadofsky, M., Hesse, J., Gellert, M., 1995. Initiation of V(D)J recombination in a cell-free system. Cell 81, 925-934). Signal ends join, forming a signal joint. The hairpin coding ends are opened by a yet unknown endonuclease, and are further processed to form the coding joint (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Ad. Immunol. 56, 27-150.) The murine scid mutation has been shown to affect coding joints, but much less signal joint formation. In this study we demonstrate that the murine scid mutation inhibits correct signal joint formation when both coding ends contain homopolymeric sequences. We suggest that this finding may be due to the function of the SCID protein as an assembly component in V(D)J recombination.

Animals↗

PubMed1999

Participant satisfaction and value in American Academy of Dermatology and American Cancer Society skin cancer screening programs in Massachusetts.

BACKGROUND: More than 1 million Americans have attended the American Academy of Dermatology's Melanoma/Skin Cancer Screening Programs since 1985. However, there have been no reports of the participants' perceived value, satisfaction, and benefits of skin cancer screening. OBJECTIVE: We attempted to measure the benefits and subsequent screening practices of persons with presumptive positive screening diagnoses. METHODS: A self-administered questionnaire was sent to participants with positive screening diagnoses in Massachusetts. RESULTS: Of the 643 respondents, 81% rated their satisfaction as high and 84% had similar ratings for the value of the screening. Screenings apparently led to an increase in self-screening (60% before screening compared with 84% after screening). CONCLUSION: Although screening appears to have relatively strong benefits, further studies should be conducted nationally.

Adult↗

PubMed1999

Determination of domoic acid in phytoplankton by high-performance liquid chromatography of the 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate derivative.

Domoic acid is the toxin that can cause amnesic shellfish poisoning. In this work, a new precolumn derivatization reagent, 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate, was used to react with domoic acid to form a stable unsymmetrical urea derivative, which was readily analyzed by reversed-phase HPLC with fluorescence detection. The one-step derivatizing method is rapid and straightforward. The method was applied to detect domoic acid in phytoplankton using a 3.9 x 150 mm Nova-Pak, 4 microm, C(18) column.

Aminoquinolines↗

PubMed1999

Expression of the fusion protein recombinant human granulocyte-macrophage colony stimulating factor and leukemia inhibitory factor in a baculovirus vector system.

A fusion gene coding human granulocyte-macrophage colony stimulating factor (GM-CSF) and leukemia inhibitory factor (LIF) cDNAs was inserted into the transfer vector pSXIVVI+ X3 with the control of Syn and XIV promoters. The Sf9 cells (Spodoptera frugiperda) were co-transfected with the recombinant plasmid and TnNPV DNA (Trichoplusia ni nuclear polyhedrosis virus DNA). The fusion protein recombinant human granulocyte-macrophage colony stimulating factor (GM-CSF) and leukemia inhibitory factor (LIF) could be synthesized in cells infected with recombinant virus at a level of about 23% of their total cellular protein. Activity analysis of the fusion protein in infected cells revealed that it exhibited the dual activities of GM-CSF and LIF. Western blot analysis of the expressed fusion protein in infected larvae showed that the virus-mediated fusion protein, with a molecular weight of approximately 35 kDa, is confirmed with immunoreactivity.

Journal Article↗

PubMed1999

Medical students' knowledge, attitudes, skills, and practices of cancer prevention and detection.

BACKGROUND: Surveys of U.S. physicians show deficiencies in cancer detection and counseling skills. Thus, there is a compelling need to provide skills teaching during medical school for cancers with preventable mortality and for counseling techniques for smoking prevention and cessation. METHODS: In advance of the integration of initiatives for cancer education into the medical school curriculum, the authors conducted a baseline survey of students' knowledge, attitudes, skills, practices, observation, and training (KASPOT) related to cancer education. Eighty-one percent of Boston University School of Medicine students (n = 499) completed surveys. RESULTS: The students reported higher levels of KASPOT for breast and cervical cancers, compared with skin cancer examination or tobacco use cessation or prevention counseling. More than half of third- and fourth-year students reported that too little emphasis was given to cancer control education. CONCLUSIONS: It appears that students' practice and skills for detection of the most common cancer (skin cancer), and for cancers with the greatest mortality (tobacco-related cancers) are deficient. Revisions in medical students' curricula should seek to address these shortcomings.

Clinical Competence↗

PubMed1999

Characterization of the analgesic and anti-inflammatory activities of ketorolac and its enantiomers in the rat.

The marked analgesic efficacy of ketorolac in humans, relative to other nonsteroidal anti-inflammatory drugs (NSAIDs), has lead to speculation as to whether additional non-NSAID mechanism(s) contribute to its analgesic actions. To evaluate this possibility, we characterized (R,S)-ketorolac's pharmacological properties in vivo and in vitro using the nonselective cyclooxygenase (COX) inhibitors [indomethacin (INDO) and diclofenac sodium (DS)] as well as the selective COX-2 inhibitor, celecoxib, as references. The potency of racemic (R,S)-ketorolac was similar in tests of acetic acid-induced writhing, carrageenan-induced paw hyperalgesia, and carrageenan-induced edema formation in rats; ID50 values = 0.24, 0. 29, and 0.08 mg/kg, respectively. (R,S)-ketorolac's actions were stereospecific, with (S)-ketorolac possessing the biological activity of the racemate in the above tests. The analgesic potencies for (R,S)-, (S)-, and (R)-ketorolac, INDO, and DS were highly correlated with their anti-inflammatory potencies, suggesting a common mechanism. (R,S)-ketorolac was significantly more potent than INDO or DS in vivo. Neither difference in relative potency of COX inhibition for (R,S)-ketorolac over INDO and DS nor activity of (S)-ketorolac at a number of other enzymes, channels, or receptors could account for the differences in observed potency. The distribution coefficient for (R,S)-ketorolac was approximately 30-fold less than for DS or INDO, indicating that (R,S)-ketorolac is much less lipophilic than these NSAIDs. Therefore, the physicochemical and pharmacokinetics properties of (R,S)-ketorolac may optimize the concentrations of (S)-ketorolac at its biological target(s), resulting in greater efficacy and potency in vivo.

Acetic Acid↗

PubMed1999

[The changes in endogenous growth factors and their relation with wound healing].

OBJECTIVE: To explore the effects of endogenous growth factors on the formation of scars and ulcers after trauma or burn. METHODS: The amounts of endogenous epidermal growth factor (EGF), tumor necrosis factor(TNF) and nitric oxide (NO) in scar and the developing granulation tissues after trauma or burn were determined and their relation with the wound healing were studied. RESULTS: The results showed that EGF, TNF and NO could be found in all scars and the granulation tissues, but their concentration varied with different tissues, sex and age of patients. In male patients or youngsters, the amounts of EGF, TNF and NO in scars were much greater than those in granulation tissues. CONCLUSIONS: The results indicated that the growth factors are necessary for wound healing, but insufficiency or overproduction of the endogenous growth factors may lead to the development of chronic ulcers or scar formation after trauma or burn.

Adult↗

PubMed1999

[Transcranial approach to the orbit: a microanatomical study].

OBJECTIVE: To provide detailed knowledge of microanatomy and parameters for transcranial approach to the orbit. METHOD: Three intraorbital approaches were studied by dissecting and measuring 20 adult cadaveric heads under x5 to 25 magnification. RESULTS: The medical approach was directed through the space between the superior oblique and the levator palpebrae superior muscles, which was selected for lesions located in the medial part of the orbital apex. The central approch was directed through the space between the levator palpebrae superior and the superior rectus muscles. There were two variants of the central approach, the choice of which depends on whether the frontal nerve was retracted medially or laterally. The approach was selected for lesions located in the midportion of the intraorbital segment of the optic nerve. The lateral approach was directed through the space between the superior and the lateral rectus muscle. There were two variants of the lateral approach, the choice of which was determined by whether the superior ophthalmic vein is retracted medially or laterally. This approach was selected for lesions located in the superior, inferior or lateral part of the orbital apex as well as the superior orbital fissure. CONCLUSION: This research provides a microanatomical foundation for avioding the important nerves and vessels damage in transcranial to orbital surgery.

Adult↗

PubMed1998

T-cell lymphoma associated with natural killer-like T-cell reaction.

We report a case of T-cell lymphoma showing in the peripheral blood (PB) exclusively T-lymphocytes with suppresser T-cell preponderance and a high percentage of natural killer (NK) marker positive cells by flow cytometry. A T-cell receptor (TCR) gene analysis of the PB leukocytes demonstrated rearrangements of TCRalpha, TCRbeta, and TCRgamma genes. Therefore, the phenotype and genotype appeared to be consistent with an NK-like T-cell leukemia/lymphoma. However, when the PB lymphocytes were separated by size, it was found that 80% of NK marker positive cells were in the smaller cell population, while the neoplastic cells were in the large cell gate. A diagnosis of T-cell lymphoma with reactive NK-like T-cells was finally confirmed by demonstrating the presence of both large atypical lymphoid cells and large granular lymphocytes (LGL) on PB smears. Although immunoperoxidase stain of bone marrow and colon showed positive T-cell markers in the tumor cell population, cytoplasmic granules could not be identified in tissue sections and, thus, a distinction between T-cell lymphoma and NK-like T-cell lymphoma could not be made by light microscopy until NK markers were studied. CD57 was demonstrated immunohistochemically in small lymphocytes but not in the large tumor cells in the colon. Electron microscopy, however, demonstrated LGL reaction to the lymphoma cells in the colonic biopsy. NK-like T-cell lymphoma usually carries a poorer prognosis than peripheral T-cell lymphoma, thus the distinction of these neoplasms is important. This study emphasizes that T-cell lymphoma may cause an LGL reaction or proliferation. If the lymphoma cells were of the same size as LGL, flow cytometric studies may have misled the diagnosis to NK-like T-cell-lymphoma.

Aged↗

PubMed1998

Ischemia and reperfusion impair the gene expression of endogenous basic fibroblast growth factor (bFGF) in rat skeletal muscles.

Our previous studies showed that the amount of endogenous basic fibroblast growth factor (bFGF) was reduced after ischemia and reperfusion insult. One of the mechanisms involved in the decrease of endogenous bFGF is the increased destruction of this growth factor associated with oxygen free radical activation and inflammation. We hypothesized that the wounding also impairs the secretion of bFGF and examined the bFGF gene expression in skeletal muscles after ischemia and reperfusion insult. In this study, a rat leg ischemia (4 h) and reperfusion (24 h) injury model was prepared and the in situ hybridization method and reverse transcriptase polymerase chain reaction technique (RT-PCR) were used to evaluate the bFGF gene expression and its localization in control (normal) and injured rat skeletal muscles. The results showed that the bFGF mRNA expression was localized in the cytoplasm in control skeletal muscle, especially at the periphery inside the cells. According to the intensity of the stain, four main classes of fibers could be identified: strongly, moderately, weakly, and negatively stained fibers. Based on the positive stain, about 82% of the total fibers examined were positive for bFGF mRNA stain. In ischemic or ischemic and reperfused rat skeletal muscles, the localization of bFGF mRNA expression was similar to that in normal skeletal muscles, but only 52% in ischemic muscles and 22% in ischemic and reperfused muscles had positive bFGF mRNA staining. RT-PCR confirmed a significant decrease in bFGF mRNA expression in ischemic and reperfused rat skeletal muscles. These results suggest that the acute ischemia and reperfusion not only induce the destruction of endogenous bFGF molecule, which is stored at the extracellular matrix of the fibers, but also downregulate the bFGF gene expression. The simultaneous dysregulation of endogenous bFGF gene expression and decreased synthesis of bFGF protein suggest a possible role of this growth factor in delayed wound healing.

Animals↗

PubMed1998

Pax6 influences the time and site of origin of glial precursors in the ventral neural tube.

Neuroepithelial precursors in the ventral ventricular zone (VZ) of the spinal cord generate motor neurons (MNs) and interneurons, and then a subset of precursors starts to produce oligodendrocyte progenitors (OLPs). We show that OLPs originate in the ventral-most part of the Pax6-positive VZ, which at earlier times generates somatic (Isl2/Lim3-positive) MNs. In Small eye (Pax6-deficient) mice, the origin of OLPs is shifted dorsally and both OLPs and Isl2/Lim3 MNs are delayed. We suggest that somatic MNs and OLPs are generated sequentially from a common set of MN-OL precursors whose position in the VZ is influenced by Pax6. Neuron-glia fate switching might be a preprogrammed property of these precursors or a response to feedback from newly generated neurons. OLs developed normally in explants of Isl1(-/-) spinal cords, which lack MNs, arguing against feedback control and suggesting that the neuron-glia switch is an intrinsic developmental program in a specific subset of neural precursors.

Animals↗

PubMed1998

Gland atrophy following retrograde injection of methyl violet as a treatment in chronic obstructive parotitis.

OBJECTIVE: The purpose of this study was to evaluate the clinical effectiveness of retrograde injection of 1% methyl violet as a treatment for chronic obstructive parotitis. STUDY DESIGN: Sixteen patients with chronic obstructive parotitis were treated with retrograde injection of 1% methyl violet. Pretreatment evaluation and assessment of the treatment effect were performed by clinical and imaging methods, including sialography and sonography of the treated glands. RESULTS: Clinical symptoms following treatment included initial acute swelling and then a decrease in parotid swellings; the final outcome was a clinical cure of the affected glands characterized by disappearance of all symptoms, absence of secretion, and complete obliteration of the main duct orifice. Posttreatment imaging showed total atrophy of the diseased glands. CONCLUSION: Retrograde injection of 1% methyl violet caused total atrophy of the diseased glands and brought about complete relief in all 16 patients, with no detectable side effects.

Adolescent↗

PubMed1998

Defining the minimal portion of the retinoblastoma protein that serves as an efficient substrate for cdk4 kinase/cyclin D1 complex.

We have determined the minimal portion of the retinoblastoma protein (Rb) that can serve as an efficient substrate for in vitro phosphorylation by cdk4 kinase-D1 cyclin. Kinetic measurements indicate that in vitro, a 15-kDa fragment that represents the C-terminus of Rb can serve equally well as a substrate when compared with the larger 56-kDa fragment of Rb, which contains the A, B and C domains. By comparison, peptide substrates appear to be 1000-fold less efficient. Furthermore, mutational analysis indicates that not all of the five phosphorylation sites within this minimal C domain are phosphorylated equally by cdk4/D1. Ser795 is the preferred phosphorylation site, whereas the four remaining sites Ser807, Ser811, Thr821 and Thr826 are phosphorylated to a much lesser degree. Truncations of the C domain from the carboxy terminus indicate that almost all of this domain is required for efficient phosphorylation. These data suggest that the structural context of the phosphorylation site within the substrate is critical for its phosphorylation by the cdk4/D1 kinase.

Animals↗

PubMed1998

Phytochrome regulation and differential expression of gibberellin 3beta-hydroxylase genes in germinating Arabidopsis seeds.

Despite extensive studies on the roles of phytochrome in photostimulated seed germination, the mechanisms downstream of the photoreceptor that promote germination are largely unknown. Previous studies have indicated that light-induced germination of Arabidopsis seeds is mediated by the hormone gibberellin (GA). Using RNA gel blot analyses, we studied the regulation of two Arabidopsis genes, GA4 and GA4H (for GA4 homolog), both of which encode GA 3beta-hydroxylases that catalyze the final biosynthetic step to produce bioactive GAs. The newly isolated GA4H gene was expressed predominantly during seed germination. We show that expression of both GA4 and GA4H genes in imbibed seeds was induced within 1 hr after a brief red (R) light treatment. In the phytochrome B-deficient phyB-1 mutant, GA4H expression was not induced by R light, but GA4 expression still was, indicating that R light-induced GA4 and GA4H expression is mediated by different phytochromes. In contrast to the GA4 gene, the GA4H gene was not regulated by the feedback inhibition mechanism in germinating seeds. Our data demonstrate that expression of GA 3beta-hydroxylase genes is elevated by R light, which may result in an increase in biosynthesis of active GAs to promote seed germination. Furthermore, our results suggest that each GA 3beta-hydroxylase gene plays a unique physiological role during light-induced seed germination.

Amino Acid Sequence↗

PubMed1998

The Arabidopsis RGA gene encodes a transcriptional regulator repressing the gibberellin signal transduction pathway.

The recessive rga mutation is able to partially suppress phenotypic defects of the Arabidopsis gibberellin (GA) biosynthetic mutant ga1-3. Defects in stem elongation, flowering time, and leaf abaxial trichome initiation are suppressed by rga. This indicates that RGA is a negative regulator of the GA signal transduction pathway. We have identified 10 additional alleles of rga from a fast-neutron mutagenized ga1-3 population and used them to isolate the RGA gene by genomic subtraction. Our data suggest that RGA may be functioning as a transcriptional regulator. RGA was found to be a member of the VHIID regulatory family, which includes the radial root organizing gene SCARECROW and another GA signal transduction repressor, GAI. RGA and GAI proteins share a high degree of homology, but their N termini are more divergent. The presence of several structural features, including homopolymeric serine and threonine residues, a putative nuclear localization signal, leucine heptad repeats, and an LXXLL motif, indicates that the RGA protein may be a transcriptional regulator that represses the GA response. In support of the putative nuclear localization signal, we demonstrated that a transiently expressed green fluorescent protein-RGA fusion protein is localized to the nucleus in onion epidermal cells. Because the rga mutation abolished the high level of expression of the GA biosynthetic gene GA4 in the ga1-3 mutant background, we conclude that RGA may also play a role in controlling GA biosynthesis.

Alleles↗

PubMed1998

Characterization of a region upstream of exon I.1 of the human CYP19 (aromatase) gene that mediates regulation by retinoids in human choriocarcinoma cells.

The biosynthesis of estrogens is catalyzed by aromatase P450 (P450arom), the product of the CYP19 gene. The tissue-specific expression of the CYP19 gene is regulated by means of tissue-specific promoters through the use of alternative splicing mechanisms. Thus, transcripts containing various 5'-untranslated termini are present in ovary, brain, adipose stromal cells, and placenta. Sequence corresponding to untranslated exon I.1 is present uniquely in 5'-termini of transcripts expressed in human placenta and choriocarcinoma cells, as a consequence of expression driven by a distal promoter, I.1. The goal of the present study was the identification of regulatory elements in this promoter region. Various deletion mutations of the upstream flanking region of exon I.1 were constructed using the PCR or restriction enzyme digestion. The genomic fragments were fused upstream of the luciferase reporter gene. These constructs were transfected into human choriocarcinoma (JEG3) cells. The longest construct employed, -924/+10 bp, expressed the highest luciferase reporter gene activity. The -64/+10 bp and -125/+10 bp constructs showed no reporter gene expression. Transfection of the -201/+10 bp construct resulted in reporter gene expression, but at a lower level than that of the -924/+10 bp construct, and this expression was induced by serum as well as by LG69 and TTNPB, ligands specific for RXR and RAR respectively, as well as by vitamin D. These results parallel the actions of the ligands on aromatase activity. Mutation or deletion of an imperfect palindromic sequence (AGGTCATGCCCC) located at -183 to -172 bp upstream of the transcriptional start site of exon I.1 resulted in loss of basal- and retinoid-induced reporter gene expression. Gel retardation analysis using nuclear extracts of JEG3 cells treated with retinoids and the imperfect palindromic sequence as probe, showed that proteins present in the nuclear extracts bound to this sequence in a specific fashion. The binding activities were elevated by incubation of the cells with LG69 and TTNPB, ligands specific for RXR and RAR respectively. Binding of nuclear proteins to the palindromic sequence was displaced either by anti-RXR alpha serum or by anti-VDR serum, suggesting the formation of a heterodimer of RXR alpha and VDR. These results suggest that the imperfect palindromic sequence upstream of exon I.1 plays an important but novel role in the regulated expression of the CYP19 gene in choriocarcinoma cells.

Aromatase↗

PubMed1998

A histochemical examination of the staining of kainate-induced neuronal degeneration by anionic dyes.

Anionic dyes, notably acid fuchsine, strongly stain the nuclei and cytoplasm of neurons severely damaged by injury or disease. We provide detailed instructions for staining nervous tissue with toluidine blue and acid fuchsine for optimal demonstration of injured neurons. Degeneration was induced in the hippocampus of the mouse by systemic administration of kainic acid, and the resulting acidophilia was investigated using paraffin sections of the Carnoy- or Bouin-fixed brains. The affected cells were bright red with the toluidine blue-acid fuchsine sequence. Their nuclei were stainable also with alkaline Biebrich scarlet and with the 1,2-naphthoquinone-4-sulfonic acid-Ba(OH)2 method; all staining was blocked by benzil but was relatively refractory to deamination by HNO2. These properties indicated an arginine-rich protein. The nuclei were strongly acidophilic in the presence of a high concentration of DNA (strong Feulgen reaction), and acidophilia could not be induced in normal neuronal nuclei by chemical extraction of nucleic acids. The cytoplasmic acidophilia of degenerating hippocampal neurons was due to a protein rich in lysine (extinguished by alkalinity, easily prevented by deamination, and unaffected by benzil). Stainable RNA was absent from the perikarya of the affected cells, but normal neuronal cytoplasm did not become acidophilic after extraction of nucleic acids. We suggest that kainate-induced cell death is preceded by increased production of basic proteins, which become concentrated in the nucleus and perikaryon. Groups of small, darkly staining neurons were seen in the cerebral cortex in control and kainate-treated mice. These shrunken cells were purple with the toluidine blue-acid fuchsine stain, and were attributed to local injury incurred during removal of the unfixed brain.

Animals↗

PubMed1998

[Analyse on the epidemiological characteristics of brucellosis and in Inner Mongolia through the observation of the change among Brucella species].

This article analysed the epidemiological characteristics of Brucellosis in Inner Mongolia. Data had been collected for the last fourty years since 1,937 on the changes of Brucella species in their distribution, variation, toxicity, types, etc. The authors pointed out that changes of Brucella species played a decisive role in changing the epidemiological patterns, while intentionally active or passive intervention importantly contributed to the change of Brucella species. It was emphasized that the survey on Brucella species and the dynamic change of epidemiological features were closely related which should not be ignored for the forecasting of Brucellosis epidemics.

Animals↗