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Biomedical subjects

X Tang

Publications and source records attributed to X Tang.

333 records · Page 19Linked to original sources
PubMedDate not supplied

Retinoblastoma protein complexes with C/EBP proteins and activates C/EBP-mediated transcription.

The retinoblastoma protein (RB) recruits histone deacetylase (HDAC) to repress E2F-mediated transactivation that plays a critical role in cell cycle regulation. RB is also involved in activation of expression of a number of tissue specific- and differentiation-related genes. In this study, we examined the mechanism by which RB stimulated the expression of a differentiation-related gene, the surfactant protein D (SP-D), which plays important roles in innate host defense and the regulation of surfactant homeostasis. We demonstrated that RB specifically stimulated the activity of human SP-D gene promoter. The RB family member, p107 but not p130, also increased SP-D promoter activity. Activation by RB was mediated through a NF-IL6 (C/EBP beta) binding motif in the human SP-D promoter, and this sequence specifically bound to C/EBP alpha, C/EBP beta, and C/EBP delta. RB formed stable complexes with all three C/EBP family members. RB small pocket (amino acid residues 379-792), but not the C-pocket (amino acid residues 792-928), was necessary and sufficient for its interaction with C/EBP proteins. Furthermore, we demonstrated that the complexes containing RB and C/EBP proteins directly interacted with C-EBP binding site on DNA. These findings indicate that RB plays a positive, selective, and direct role in the C/EBP-dependent transcriptional regulation of human SP-D expression.

Amino Acid Motifs↗
PubMedDate not supplied

Pneumocystis carinii pneumonia in patients being registered for smear-negative pulmonary tuberculosis in Malawi.

The National TB Control Programme of Malawi registers and treats large numbers of patients with chronic cough for smear-negative pulmonary tuberculosis (PTB). Smear-negative PTB is diagnosed according to clinical and radiographic criteria, as mycobacterial cultures are not routinely available. In an area of high HIV seroprevalence there is a concern that other opportunistic infections apart from TB, such as Pneumocystis carinii, may be missed owing to lack of diagnostic facilities. The aims of this study were to investigate (i) the extent of P. carinii pneumonia (PCP) in patients about to be registered for smear-negative PTB; (ii) whether there were any clinical or radiological features that could help identify PCP in the absence of more detailed investigations; and (iii) the treatment outcome of PCP patients. A cohort of 352 patients who were about to be started on treatment for smear-negative PTB were investigated further in 1997-99 by clinical assessment, HIV testing and bronchoscopy. HIV sero-prevalence was 89% (278/313). A total of 186 patients underwent bronchoscopy and bronchoalveolar lavage, and PCP was diagnosed by indirect immunofluorescence or polymerase chain reaction in 17 (9%) of this subgroup. Dyspnoea was significantly more common in PCP cases compared to non-PCP cases (RR 1.35; 95% CI 1.24-1.48; P = 0.008), but discrimination between the groups was difficult using clinical criteria alone. The outcome of PCP cases was poor despite management with high-dose co-trimoxazole and secondary co-trimoxazole prophylaxis, with a median survival of 4 months (25-75% range: 2-12 months).

Adult↗
PubMedDate not supplied

Inhibition of the mutagenicity of 2-nitrofluorene, 3-nitrofluoranthene and 1-nitropyrene by flavonoids, coumarins, quinones and other phenolic compounds.

When 56 flavonoids, 32 coumarins, five naphthoquinones, 12 anthraquinones and five structurally-related compounds were tested for their antimutagenic potencies with respect to mutagenicities induced by 2-nitrofluorene (2-NF), 3-nitrofluoranthene (3-NFA) and 1-nitropyrene (1-NP) in Salmonella typhimurium TA98 distinct structure-activity relationships were detected. First, the tetracyclic nitroarenes 3-NFA and 1-NP were in general more effectively antagonized by potent antimutagenic flavonoids and coumarins than the tricyclic 2-NF, while there were only minor differences with quinones. Secondly, antimutagenicity of natural compounds of plant origin correlated with the aglyconic nature 10 of a total of 15 glycosides were inactive, four flavonoid glycosides exerted antimutagenicity but to a distinctly lower degree than the corresponding aglycones. Thirdly, within flavonoids, coumarins and anthraquinones positive correlations were found between antimutagenic potency and the polarity of a molecule with the existence of an optimum of activity within flavonols and anthraquinones. However, polarity seemed to be unimportant within the chalcone and naphthoquinone series. Among flavonoids, the parent compounds flavone and flavanone were inactive, but all flavones and many flavonoids with phenolic hydroxyl groups exerted antimutagenicity. Antimutagenic potency reached a maximum with the presence of four hydroxyl functions-luteolin, kaempferol-though the position of hydroxyls was also a determinant of antimutagenic potency. Methylation of phenolic hydroxyl groups, however, always reduced antimutagenicity. A carbonyl group at carbon 4 was essential for antimutagenicity: two catechins and anthocyanidins each were inactive. On the other hand, ring C of the flavane nucleus was not essential for antimutagenicity: chalcones and dihydrochalcones were potent antimutagens. Among coumarins, the parent compound showed antimutagenicity against 1-NP and 3-NFA, although dihydrocoumarin, methylcoumarins and compounds with bulky substituents were inactive. Otherwise, antimutagenic activity depended on the presence of polar hydroxyl, amino or carboxyl groups at carbons 3, 4 or 7 but was diminished by interactions of hydroxyl groups vicinal to carbon 7. Again, antimutagenic potencies were reduced by alkylation or acetylation. Among furanocoumarins xanthotoxin exerted strong and bergapten moderate antimutagenicity, while psoralen (except against 3-NFA), isopimpinellin and the furanochromanones visnagin and khellin were inactive. Among anthraquinones, the principles delineated here were valid again, resulting in potent antimutagenicity of most phenolic compounds and inactivity of anthraquinone itself. Among compounds structurally related to anthraquinones, anthrone, acridone and xanthone exerted antimutagenicity, anthrone being the most potent one, while thioxanthone and 9-fluorenone were inactive. All naphthoquinones were potent antimutagens irrespective of the presence of methyl or hydroxyl functions. Plumbagin, 2-methyl-5-hydroxynaphthoquinone, however, showed exceptional antimutagenicity.

Animals↗
PubMedDate not supplied

Inhibition of the mutagenicity of 2-nitrofluorene, 3-nitrofluoranthene and 1-nitropyrene by vitamins, porphyrins and related compounds, and vegetable and fruit juices and solvent extracts.

When 21 vitamins including related compounds haemin, chlorophyllin, chlorophyll, biliverdin and bilirubin, as well as juices from five fruits and 25 vegetables and solvent extracts from the residues of fruits and vegetables were tested for their antimutagenic potencies with respect to mutagenicity induced by 2-nitrofluorene (2-NF), 3-nitrofluoranthene (3-NFA) and 1-nitropyrene(1-NP) in Salmonella typhimurium TA98 the following results were obtained. The tetracyclic nitroarenes 3-NFA and 1-NP were in general more effectively antagonized by potent antimutagenic compounds than the tricyclic 2-NF. beta-Carotene, retinol, retinal, retinoic acid, retinol palmitate, riboflavin 5'-phosphate, alpha-tocopherol, vitamins B12, C, K1 and K3 as well as biliverdin, bilirubin, chlorophyll, chlorophyllin and haemin exerted antimutagenicity against the nitroarenes cited previously. All other vitamins were inactive. While part of the juices were inactive, juices from cauliflower, carrots, chives, radishes and spinach exerted weak antimutagenic activities. However, weak to moderate co-mutagenic effects were seen with grapes, kiwi, pineapple, eggplant, celeriac, chicory greens, fennel leaves and radishes and strong effects with peppers which were not caused by the presence of growth-promoting factors. Most solvent fractions were inactive but fractions containing chlorophyll exerted antimutagenicity.

Antimutagenic Agents↗
PubMedDate not supplied

Mucosa-associated lymphoid tissue (MALT) lymphoma of the stomach progressing to overt B cell malignancy.

A 70 year old man, who underwent subtotal gastrectomy under the diagnosis of reactive lymphoid hyperplasia 6 years earlier, suffered from diffuse large-cell-type B cell lymphoma in the remnant stomach. Retrospectively reviewed, the initial lesion was consistent with mucosa-associated lymphoid tissue (MALT) lymphoma, a low-grade B cell malignancy, based upon histologic, cytologic and immunohistochemical features. Both the initial and recurrent tumors revealed the phenotypes of mantle zone cells, DBA44-positive. It is noteworthy that the overt lymphoma cells retained the capacity for inducing germinal center-like nodules consisting of LN1 and DNA7-positive cells even in the invading site. The diagnosis of reactive lymphoid hyperplasia of the stomach should be made after careful exclusion of the possibility of MALT lymphoma.

Aged↗
PubMedDate not supplied

Phrenic and intercostal repetitive nerve stimulation: a useful electroneurophysiological method to detect the respiratory status of myasthenia gravis patients.

OBJECTIVE: To get a comprehensive recognition about the profile of phrenic repetitive nerve stimulation (PRNS) and intercostal repetitive nerve stimulation (IRNS) in healthy people, to investigate the electrophysiological features about respiratory function of myasthenia gravis (MG) patients, and to detect the predictive value of IRNS and PRNS on the respiratory deterioration of MG patients during the pulse treatment with large dosage of adrenal corticosteroid. SUBJECTS AND METHODS: Bilateral PRNS and IRNS with stimulation frequency of 3 and 5 Hz were tested in 28 healthy people and 113 MG patients; limb and cranial repetitive nerve stimulation (RNS), clinical score and forced vital capacity (FVC) were also recorded from those MG patients. Further more, PRNS and IRNS of 36 MG patients were tested 3 days before the beginning of their adrenal corticosteroid pulse treatment, FVC, clinical score and respiratory changes of the MG patients were simultaneously observed. RESULTS: For healthy people, there were no significant differences in the results of PRNS or IRNS in different age, sex and testing sides. After combining the left result with the right one, the amplitude decrement percentage in PRNS and IRNS was less than 7%. PRNS had more technical difficulty than IRNS. For 113 MG patients, FVC was dependent on the values of PRNS, IRNS and facial RNS. A subclinical respiratory dysfunction was found in patients with type I and II MG. The abnormal rate of PRNS in type IIb MG was similar to that in type III and IV MG, even though a difference in the percentage of amplitude decrement between them was observed. Meanwhile, both the abnormal rate and the percentage of amplitude decrement of IRNS had no difference between type IIb MG and type III and IV MG. The general incidence of abnormal PRNS and abnormal IRNS were higher than those of decreased FVC and clinical dyspnea, and the sensitivity of PRNS in type IIa MG patients was higher than that of IRNS. Among 36 MG patients under the adrenal corticosteroid pulse treatment, 14 showed the newly clinical dyspnea or worsened original one 2 to 13 days after the beginning of the therapy. There were significant difference of the above parameters between the patients with and without respiratory deterioration during the treatment. Logistic regression analysis showed that when the mean value of the bilateral IRNS amplitude decrement was larger than 30%, the odds ratio of the occurrence of the respiratory deterioration was 19.523, for both 3 and 5 Hz stimulation. CONCLUSIONS: It is recommended that PRNS and IRNS will be defined as abnormal when their amplitude reduces more than 15%. PRNS and IRNS are neurophysiological indices reflecting the damage of respiratory muscles in MG, they are helpful in evaluating the clinical condition correctly and making the classification of MG properly. It is necessary to test the PRNS and IRNS in type II MG patients regularly. Although the respiratory damage during the adrenal corticosteroid treatment was correlated with PRNS, IRNS, FVC, MG clinical score and type, only IRNS had predictive value on the respiratory deterioration during the treatment.

Adrenal Cortex Hormones↗