Biomedical subjects

Z Jin

Publications and source records attributed to Z Jin.

At least 55 records · Page 3Linked to original sources

PubMed2000

Bax is a transcriptional target and mediator of c-myc-induced apoptosis.

The c-Myc oncoprotein is a transcription factor involved in cellular transformation as well as apoptotic cell death. We show here that over-expression of c-Myc delivered by an adenovirus vector up-regulates endogenous proapoptotic bax mRNA and protein expression in human cells. In contrast, the cytotoxic tumor necrosis factor-related apoptosis-inducing ligand induces cell death without up-regulating bax expression. c-Myc/Max heterodimers bind to canonical E-box elements located in the bax promoter region as demonstrated by electrophoretic mobility shift analysis and DNaseI foot-printing assays. Analysis of bax regulatory region mutants suggests a model involving myc-dependent activation as well as relief of repression through distinct E-box elements. c-Myc-null cells are deficient in bax-promoter activation as compared with wild-type c-Myc-expressing cells. Overexpression of c-Myc in serum-starved human or mouse embryonic cells leads to apoptosis which is significantly reduced in the presence of growth factor-containing serum. c-Myc-induced apoptosis appears to be deficient in bax-null as compared with bax-wild-type mouse embryonic fibroblasts. The results suggest that the cell death-promoting gene bax is directly downstream of c-Myc in a pathway leading to apoptosis.

Adenoviridae↗

PubMed2000

Total synthesis of everninomicin 13,384-1--Part 4: explorations of methodology; stereocontrolled synthesis of 1,1'-disaccharides, 1,2-seleno migrations in carbohydrates, and solution- and solid-phase synthesis of 2-deoxy glycosides and orthoesters.

Methods for the stereocontrolled construction of 1,1'-disaccharides, 2-deoxy glycosides, and orthoesters are reported. Specifically, a tin-acetal moiety was utilized to fix the anomeric stereochemistry of a carbohydrate acceptor leading to an efficient and stereoselective synthesis of 1,1'-disaccharides, while a newly discovered 1,2-phenylseleno migration reaction in carbohydrates opened entries to 2-deoxy glycosides and orthoesters. Thus, reaction of 2-hydroxy phenylselenoglycosides with DAST led to 2-phenylselenoglycosyl fluorides which reacted with carbohydrate acceptors to afford, stereoselectively, 2-phenylselenoglycosides. The latter compounds could be reductively deselenated to 2-deoxy glycosides or oxidatively converted to orthoesters via the corresponding ketene acetals.

Aminoglycosides↗

PubMed2000

Distinct methylation patterns of two APC gene promoters in normal and cancerous gastric epithelia.

The adenomatous polyposis coli (APC) tumor suppressor gene is mutationally inactivated in both familial and sporadic forms of colorectal cancers. In addition, hypermethylation of CpG islands in the upstream portion of APC, a potential alternative mechanism of tumor suppressor gene inactivation, has been described in colorectal cancer. Because a subset of both gastric and colorectal cancers display the CpG island methylator phenotype, we hypothesized that epigenetic inactivation of APC was likely to occur in at least some gastric cancers. APC exhibits two forms of transcripts from exons 1A and 1B in the stomach. Therefore, we investigated CpG island methylation in the sequences upstream of exons 1A and 1B, i.e., promoters 1A and 1B, respectively. We evaluated DNAs from 10 gastric cancer cell lines, 40 primary gastric cancers, and 40 matching non-cancerous gastric mucosae. Methylated alleles of promoter 1A were present in 10 (100%) of 10 gastric cancer cell lines, 33 (82.5%) of 40 primary gastric cancers, and 39 (97.5%) of 40 noncancerous gastric mucosae. In contrast, promoter 1B was unmethylated in all of these same samples. APC transcripts from exon 1A were not expressed in nine of the 10 methylated gastric cancer cell lines, whereas APC transcripts were expressed from exon 1B. Thus, expression from a given promoter correlated well with its methylation status. We conclude that in contrast to the colon, methylation of promoter 1A is a normal event in the stomach; moreover, promoter 1B is protected from methylation in the stomach and thus probably does not participate in this form of epigenetic APC inactivation.

Adolescent↗

PubMed2000

Helium plasma source time-of-flight mass spectrometry: off-cone sampling for elemental analysis

In this paper, an atmospheric pressure, helium microwave-induced plasma (MIP) ion source coupled with an orthogonal acceleration time-of-flight mass spectrometer (TOFMS) is explored for elemental analysis. Studies of the relationship between ion signals and sampling distance of the MS reveal that background signals can be suppressed dramatically without sacrificing the signal intensities of analytes when the microwave plasma plume is off the tip of the sampler orifice. This "off-cone" ion sampling mode provides a technique to obtain nearly "clean" background spectra and, thus, eliminates the spectral interference from entrainment air and the working-gas species, making it possible to sensitively determine isotopes that suffered from spectral interference in ICPMS and MIPMS (such as 40Ca, 52Cr, 55Mn, and 56Fe). On the other hand, since the high-temperature plasma is kept away from the sampler aperture, off-cone sampling places little demand on the cooling device and the lifetime of the sampler plate can be extended. The instrumental system can provide a fairly good mass resolution of 1100 (fwhm). The detection limits (3sigma) in the tens of picograms per milliliter level for the elements studied can be achieved with a digital oscilloscope. These detection limits can be easily improved with an advanced detection system, which is currently available in commercial markets.

Journal Article↗

PubMed2000

A field-portable plasma source monitor for real-time air particulate monitoring

In this research, a novel portable instrument for on-site, real-time air particulate monitoring was developed. It is highly desirable to use microwave plasmas for on-site, real-time environmental and occupational hazard monitoring because they can be sustained with various gases at relatively low power and possess excellent detection capabilities for both metal and nonmetal air pollutants. In the new instrument design, a microwave plasma was selected as an excitation source and was used in conjunction with atomic emission spectrometry. A small, integrated spectrometer with a charge-coupled detector (CCD) was used for optical signal detection. An efficient, in situ air-sampling system was developed for direct sampling of air particles into the plasma. Characterization and calibration of the new instrument were achieved with an in-house-fabricated high-efficiency nebulization-desolvation system. Tolerance of the microwave argon plasma source to air introduction was tested, and the operational parameters were optimized. Analytical performance and the feasibility of the newly developed portable instrument for aerosol particle analysis were evaluated. Some advantages and possible applications of the new instrument are discussed. The instrument provides an innovative tool for rapid environmental and occupational hazard monitoring.

Journal Article↗

PubMed2000

Atrophy and high intensity lesions: complementary neurobiological mechanisms in late-life major depression.

The primary objective of our study was to examine the role of atrophy, high intensity lesions and medical comorbidity in the pathophysiology of major depressive disorder in the elderly (late-life MDD). Our sample was comprised of 51 patients with late-life MDD and 30 non-depressed controls. All subjects were scanned on 1.5 tesla magnetic resonance imaging scanner (MRI) and absolute and normalized measures of brain and lesion volumes were obtained and used for comparison between groups. Patients with MDD had significantly smaller frontal lobe volumes, together with larger whole brain lesion volumes when compared with controls (p < .05). Whole brain lesion volumes correlated significantly (r = 0.41, p = .006) with overall medical comorbidity. The odds ratio (OR) for existing MDD increases significantly with a decrease in frontal lobe volume and an increase in whole brain lesion volumes (p < .05). Our findings suggest that atrophy and high intensity lesions represent relatively independent pathways to late-life MDD. While medical disorders lead to neuropathological changes that are captured on MR imaging as high intensity signals, atrophy may represent a relatively autonomous phenomenon. These findings have broad implications for the pathophysiology of mood disorders and suggest that complementary neurobiological processes may lead to cumulative neuronal injury thereby predisposing to clinical depression.

Age of Onset↗

PubMed2000

Ovarian gonadoblastoma with mixed germ cell tumor in a woman with 46, XX karyotype and successful pregnancies.

An extremely rare case of unilateral gonadoblastoma with mixed germ cell tumor arising in the ovary of a 27-year-old woman with 46,XX karyotype and two successful pregnancies is reported. The mixed germ cell tumor was composed of choriocarcinoma, embryonal carcinoma, yolk sac tumor, immature teratoma and dysgerminoma. The patient has been well, without evidence of disease for over 10 years since her first surgery and adjuvant chemotherapy.

Adult↗

PubMed2000

Lymph node trafficking and antigen presentation by endobronchial eosinophils.

Because eosinophils recruited into the airways in allergic diseases are exposed to inhaled allergens, we evaluated whether eosinophils within the endobronchial lumen can function in vivo as antigen-presenting cells for inhaled antigens. We recovered eosinophils from the airways after aerosol antigen challenge in sensitized mice or from the peritoneal cavities of IL-5 transgenic mice and fluorescently labeled these cells ex vivo. These labeled cells, instilled intratracheally into normal mice, migrated into draining paratracheal lymph nodes and localized to T cell-rich paracortical areas. The homing of airway eosinophils to lymph nodes was not governed by eotaxin, because CCR3(-/-) and CCR3(+/+) eosinophils migrated identically. Airway eosinophils, recovered after inhalational antigen challenge in sensitized mice, expressed MHC class II and costimulatory CD80 and CD86 proteins and functioned in vitro as CD80- and CD86-dependent, antigen-specific, antigen-presenting cells. Moreover, when instilled into the airways of antigen-sensitized recipient mice, airway eosinophils recovered after inhalational antigen challenge stimulated antigen-specific CD4(+) T cell proliferation within paratracheal lymph nodes. Thus, eosinophils within the lumina of airways can process inhaled antigens, traffic to regional lymph nodes, and function in vivo as antigen-presenting cells to stimulate responses of CD4(+) T cells.

Animals↗

PubMed2000

Characterization of epstein-barr virus-infected mantle cell lymphoma lines.

It has been reported that Epstein-Barr virus (EBV) resides in resting B cells in vivo. However, an ideal in vitro system for studying EBV latent infection in vivo has not yet been established. In this study, a mantle cell lymphoma line, SP53, was successfully infected with a recombinant EBV containing a neomycin-resistant gene. The EBV-carrying SP53 cells were obtained by selection using G418. They expressed EBER-1, EBNAs, and LMP1; this expression pattern of the EBV genes was similar to that in a lymphoblastoid cell line (LCL). However, proliferation assay showed that the EBV-carrying SP53 cells have a doubling time of 73 h, compared with 57 h of SP53 cells. Transplantation of 10(8) SP53 cells to nude mice formed tumors in 4 of 10 mice inoculated, but the EBV-carrying SP53 cells did not. Unexpectedly, EBV infection reduced the proliferation and tumorigenicity of SP53 cells. However, the EBV-carrying SP53 cells showed higher resistance to apoptosis induced by serum starvation than did the SP53 cells. The inhibition of proliferation and the resistance to apoptosis induced in SP53 cells by EBV infection indicate that this cell line might to some extent provide a model of in vivo EBV reservoir cells.

Animals↗

PubMed2000

[Effects of tumor necrosis factor-alpha on proliferation and intracellular free calcium concentration in endothelium of human umbilical vein endothelial cells].

OBJECTIVE: To Observe the effects of tumor necrosis factor-alpha (TNF-alpha) on cell proliferation and Intracellular free calcium concentration ([Ca2+]i) in endothelium of human umbilical vein endothelial cells (HUVEC) and investigate the pathogenesis of pregnancy induced hypertension syndrome (PIH). METHODS: Confluent monolayer of HUVEC was directly incubated with TNF-alpha at following final concentrations: 500, 1,000, 2,000 U/ml for 24 hours. The percentages of different cellcycles and [Ca2+]i were measured by flow cytometry and fluorospectrophotmetry. RESULTS: Incubated with TNF-alpha, the endothelial cells were elongated and transformed into fibroblast-like cells. Border of nucleus was sharp, clarity, and cells were in regular shape. But there were abnormal granules in cytoplasma and some cells detached at the concentrotion of 2,000 U/ml of TNF-alpha. Stimulated by TNF-alpha, the percentage of cellcycles from phase G0 + G1 to S and G2 + M decreased significantly and it was dose-dependent [Ca2+]i increased significantly and dose-dependent as well. CONCLUSION: TNF-alpha may injure endothelium directly and inhibit its proliferation and repair through the changes of [Ca2+]i level. It may play an important role in the pathogenesis of PIH.

Calcium↗

PubMed2000

Leukoplakia and angiopoiesis resistance of Herba Erigerontis.

OBJECTIVE: To evaluate the effects of Herba Erigerontis on angiopoiesis and carcinogenesis; to seek an effective drug for prevention of leukoplakia progression to carcinoma and to stop the mechanism of angiopoiesis. METHODS: Carcinomatous conversions of golden hamster cheek pouches induced by Salley way and inhibited by Herba Erigerontis. Ink perfusion, analysis of images, resin cast form of micro-vessel, a-SMA detection and histopathological examination were applied to observe their changing patterns. RESULTS: The rate of leukoplakia conversion to tumor of the Herba Erigerontis group was half that of model group. The proportion of normal cells was approximately 4 times greater than that of model. The a-SMA levels of the Herba Erigerontis treated group was higher than that of model (P < 0.001). There was no significant difference between angeion vessel area and density (P > 0.05) in these 2 groups, which were elevated compared to the control. Nevertheless, the resin casts of the microvasculature in the Herba Erigerontis group showed that its configuration and spatial arrangement was similar to the control group. CONCLUSIONS: Herba Erigerontis has the function of inhibiting leukoplakia progression to tumor. This may be due to its ability to upregulate the expression of a-SMA. It has no obvious effect on angio-hyperplasia and expansion in the course of leukoplakia progression to tumor. However, it may preserve the angio-configuration and spatial arrangement and keep intact the angeion vessel wall. Its mechanism of promoting blood circulation may be through removing blood stasis and benign angiopoiesis so as to resist carcinogenesis.

Actins↗

PubMed2000

[Effects of estrogen on experimental tooth movement in osteoporosis rats].

OBJECTIVE: To investigate the effects of estrogen on the orthodontic tooth movement and alveolar bone in osteoporosis rats. METHODS: Thirty 3 month-old female sprague-dawley rats were divided randomly into three groups (control, osteoporosis and estrogen). In the three groups, the distances of tooth movement and the number of osteoclast were measured and compared. Histologic changes were observed. RESULTS: Compared with the control group, in first month, the distances of orthodontic tooth movement was increased by 43.3% in osteoporosis group and by 30.7% in estrogen group; the number of osteoclast was increased by 64.4% and by 32.9% respectively. In second month, the distances were increased by 68.5% in osteoporosis group and by 24.9% in estrogen group; the number of osteoclast was increased by 68.7% and by 15.0% respectively. In addition, estrogen promoted the alveolar bone-forming and inhibited the bone resorption. CONCLUSION: It is suggested that the estrogen may affect the rate of orthodontic tooth movement on postmenopausal osteoporosis patient.

Animals↗

PubMed2000

[Ultrastructural observation of E. coli K12 treated with antibacterial peptide CM4].

The effect of antibacterial peptide CM4 of Bombyx mori against E. coli K12 was investigated using scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The ultrastructural changes of E. coli K12 were observed by the challenge of the purified antibacterial peptide CM4. The results showed that the antibacterial peptide caused a series of pathological changes on E. coli. SEM and TEM revealed aggregates of bacteria and SEM revealed wrinkled bacterial surfaces in the early stage. Thereafter, plasmolysis was observed with irregular holes appearing in the two ends of bacteria and the cytoplasmic contents of the cells leaking out. Finally, bacteria became empty vesicles and disintegrated into small fragments subsequently. Comparatively, the bacterial membrane was normal and the bacterial structure remained intact in the control group.

Animals↗

PubMed2000

[Trannasal-transsphenoidal endoscopic surgery of the sphenoid sinus and the sella turcica].

OBJECTIVE: The primary objective of this study is reporting our experience with transnasal endoscopic technique to management of the sphenoidal and the sellar lesions. METHOD: Forty one patients were management under endoscope who suffered from pituitary adenomas, craniopharyngioma and sphenoidal lesions, et al. RESULTS: In forty one cases of the sphenoidal and the sellar lesions, thirty two surgeries were successful. One patient died of bleeding, five developed the foramen of nasal septum, the adhesion of nasal cavity was complicated in three patients. CONCLUSION: The endoscope has the advantage of improved visualization, angled view, and a wide panoramic perspective. The transnasal-transspheniodal endoscopic technique is a effective, minimally invasive approach. But there are its disadvantages and occurred severe complication. Surgeons should be understood its feasibility, limits and indication.

Adolescent↗

PubMed2000

[Hyperconjugation, characteristic infrared absorption of methylsulfones and crystal structures of selected aromaticsulfones].

A branched absorption peak with medium intensity at (970 +/- 20) cm-1 appears only in the infrared spectra of methylsulfones. The below mentioned aromaticsulfones are chosen to reveal the specificity. Crystal and molecular parameters of CH3CONH-C6H4-SO2R(R = -CH3, -CH2CH2OH)-CH2CONH2, are determined by application of single crystal diffraction of X-ray through Nicolet R3M/E diffracometer. The existence of hyperconjugation and its natures in group -SO2CH3, confirmed by further analyses on the parameters, result in the specificity of IR absorption of the group, which is proved characteristic and can be used to identify methylsulfones. The first part describes the detection results, ascertains their crystal and molecular structures, and shows that the aromaticsulfone exists as cross linking multi-molecules when R = -CH2CONH2 or as double molecules when R = -CH2CH2OH because of H bonds. The second part covers analyses on their molecular structures. The analyses demonstrate the hyperconjugation between sigma S-C and pi S-C in group -SO2CH3. The sigma C-H hyperconjugate with pi S-O. The strength of hyperconjugated bond C-H decreases and its length tends longer. Due to the effect, the bond S-C is not a pure single bond sigma, but one which possesses a certain degree of a double bond. Its IR wave number, between those of sigma S-C and pi S-C, attributes to the medium branched peak at (970 +/- 20) cm-1. The peak branch reflects two groups of the most stable hyperconjugating conformational isomers. The hyperconjugation is weakened by the substitution of one non H group for one H atom in -SO2CH3 and if the non H group does not conjugate with pi S-O, the absorption at (970 +/- 20) cm-1 disappears as a characteristic peak. The intensity of absorption at (970 +/- 20) cm-1 conforms to the intensity of hyperconjugation between pi S-O and its adjacent sigma C-H. The third part introduces syntheses of the products, crystal preparations and their detections through X-ray diffraction.

English Abstract↗

PubMed2000

[Application of UV spectrophotometry in the detection of magnetization effect].

Compared the UV absorption spectra of some magnetized samples with them of unmagnetized samples(the pure solvents and unmagnetized solutions as the reference substances separately), we found the wavelength of absorption didn't change, but strength of absorption of all magnetized compounds changed. When unmagnetized solutions is selected as reference substances, there may be a peak of magnetic effect in UV absorption spectra. Furthermore, the different magnetization time made the absorbance change in varying degrees. This research will play an important role for the study of possible mechanism of magnetic field effect on chemical reaction.

Magnetics↗

PubMed1999

Age of onset of depression and quantitative neuroanatomic measures: absence of specific correlates.

The purpose of our study was to examine the relationship between volumetric neuroanatomic measures and age of onset of illness in subjects with late-life major depression. Our sample was composed of 51 elderly subjects with Major Depressive Disorder who were scanned using a 1.5-tesla GE magnetic resonance imaging scanner with head coil. Absolute total and focal brain volumes were obtained together with quantified estimates of high intensity lesions. The relationship of these measures to onset age was examined using a regression while adjusting for subjects' current age and total intracranial volume. There was no significant linear relationship between age of onset of the first episode and any of the neuroanatomic measures examined. These data do not support the notion that neuroanatomical contributions to depression increase with a later age of onset of illness.

Brain↗

PubMed1999

Model for lentivirus capsid core assembly based on crystal dimers of EIAV p26.

Two crystal forms of recombinant p26 capsid protein (CA) from the equine infectious anemia virus (EIAV) have in common an antiparallel four-helix bundle dimer interface between N-terminal domains (NTDs). The dimer interface provides a lenient scaffold to accommodate the wide sequence variation in these helices within lentivirus CA. Pairs of dimers weakly associate to form exact or approximate D2 symmetry tetramers. In one of the two crystal forms, the tetramers are linked via dimerization of C-terminal domains (CTDs). We propose that the observed NTD and CTD homodimer interactions are involved in the assembly of the lentivirus capsid. The NTD homodimer shape readily suggests a model for the mature capsid core, based on hexagonal packing with dimensions and surface topology resembling described EIAV capsid cores. Combining available data for human immunodeficiency virus and EIAV CA, we also propose an assembly pathway for maturation of the lentivirus capsid core following proteolytic cleavage of the gag polyprotein precursor.

Amino Acid Sequence↗