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Biomedical subjects

J Gong

Publications and source records attributed to J Gong.

At least 109 records · Page 6Linked to original sources
PubMed1997

Clinical correlates of interferon gamma production in patients with tuberculosis.

To determine if the capacity to produce interferon (IFN) gamma is related to the clinical manifestations of tuberculosis, we correlated Mycobacterium tuberculosis-induced IFN-gamma production by peripheral blood mononuclear cells (PBMCs) with clinical, radiographic, and laboratory variables for 63 human immunodeficiency virus (HIV)-negative patients and 43 HIV-positive patients with tuberculosis. For HIV-negative patients whose chest radiographs showed moderately advanced disease, the mean IFN-gamma concentration +/- SD was 1,639 +/- 388 pg/mL, whereas that for patients with far-advanced disease was 327 +/- 100 pg/mL (P = .0001). For HIV-infected patients who had only pleuropulmonary disease, the mean IFN-gamma concentration was 1,002 +/- 257 pg/mL, whereas that for patients with disease outside the lungs and pleura was 149 +/- 55 pg/mL (P = .0004). Multivariate analysis confirmed that the radiographic extent of disease and the site of disease were the only independent predictors of IFN-gamma production in HIV-negative and HIV-infected patients (P < or = .001). We conclude that reduced IFN-gamma production by PBMCs is a marker of severe tuberculosis in both HIV-negative and HIV-infected patients with tuberculosis.

AIDS-Related Opportunistic Infections↗
PubMed1997

Group-specific 16S rRNA hybridization probes for determinative and community structure studies of Butyrivibrio fibrisolvens in the rumen.

Oligonucleotide probes covering three phylogenetically defined groups of Butyrivibrio spp. were successfully designed and tested. The specificity of each probe was examined by hybridization to rRNAs from an assortment of B. fibrisolvens isolates as well as additional ruminal and nonruminal bacteria. The sensitivity of the hybridization method was determined by using one of the probes (probe 156). When RNA was extracted from a culture of OB156, the probe was able to detect target cells at densities as low as 10(4) cells/ml. When 10(4) or more target cells/ml were added to cattle rumen samples, detectable hybridization signals were obtained with 1,000 ng of total RNA loaded onto the nylon membrane. In contrast, the sensitivity was reduced to 10(6) target cells/ml at 100 ng of RNA per slot. The probes were used to type 19 novel Butyrivibrio isolates. The phylogenetic placement was confirmed by partial 16S rRNA gene sequencing. The use of the probes in community-based studies indicated that the Butyrivibrio groups examined in this paper did not represent a significant portion of the bacterial 16S rRNA pool in the rumen of the cattle, sheep, and deer examined.

Animals↗
PubMed1997

Managed care. Dealing with the dual eligible population.

This is the first of a two-part series reviewing the genesis of managed care programs for persons dually eligible for Medicare and Medicaid. Part two will profile several state programs, exploring their impact on long term care.

Eligibility Determination↗
PubMed1997

[IR and UV-vis spectra of nitrogen-doped fullerene].

Nitrogen-doped fullerene derivative's IR and UV-vis spectra are reported. Some of the C60 IR silent modes are activated due to nitrogen atom reducing C60 molecular symmetry. UV-vis spectrum indicates nitrogen is donor.

English Abstract↗
PubMed1997

Role of alpha 5 beta 1 integrin in determining malignant properties of colon carcinoma cells.

We characterized the expression of alpha 5 beta 1 integrin in two distinct phenotypes of colon carcinoma cell lines. Highly invasive colon cell lines (designated Group I cell lines) expressed higher levels of integrin alpha 5 beta 1 mRNA and protein than did poorly invasive colon cell lines (designated Group III cell lines). The relatively high expression of integrin alpha 5 beta 1 in Group I cell lines resulted in strong enhancement of cell adhesion to fibronectin (FN) tissue culture plates, whereas Group III cell lines showed little or no enhancement of cell adhesion by coating. There was no significant difference between Group I and Group III cell lines with respect to cell adhesion to laminin and collagen IV. Cell adhesion to FN in Group I cells was mainly mediated by integrin alpha 5 beta 1 because a monoclonal anti-alpha 5 subunit antibody could block cell adhesion to FN, whereas anti-alpha 2 and anti-alpha 3 antibodies had no effect on cell adhesion to FN. The divergence of alpha 5 beta 1 expression in these two distinct colon carcinoma phenotypes suggested that high expression of alpha 5 beta 1 might contribute to malignant progression in this model system. To test this hypothesis, GEO cells, a Group III cell line that did not express alpha 5 integrin, were transfected with the alpha 5 subunit. Stable transfection of alpha 5 sense cDNA into a typical GEO-limiting dilution clone led to the expression of alpha 5 subunit mRNA and cell surface alpha 5 beta 1 protein. The alpha 5 sense transfectants showed enhanced attachment to FN-coated plates and were more tumorigenic when the cells were injected into athymic nude mice. These results indicate that inappropriately high alpha 5 beta 1 integrin expression contributes to malignant progression in colon carcinoma.

Animals↗
PubMed1996

Mutations at a glycine loop in aminolevulinate synthase affect pyridoxal phosphate cofactor binding and catalysis.

5-Aminolevulinate synthase catalyzes the first step of the heme biosynthetic pathway in animals, fungi, and some bacteria. The enzyme belongs to a large family of enzymes that use pyridoxal 5'-phosphate as an essential cofactor. We previously analyzed the informational content contained in each residue of a conserved glycine loop, which we proposed to form part of the cofactor binding site [Gong, J., & Ferreira, G. C. (1995) Biochemistry 34, 1678-1685]. We found that Gly-142 and -144 contain high informational content, and we identified G144A, G144S, G144T, and G142C as functional mutants. Here, the catalytic parameters, cofactor affinities, and spectral and thermostability properties of these four glycine mutants are determined to examine the function of the glycine loop. In addition, computer models of the glycine loops from the wild-type and mutant enzymes were generated, using glycogen phosphorylase b as the structural template. G144A, G144S, G144T, and G142C displayed lower affinity than the wild-type enzyme for the cofactor, reflected in the 8.5-, 8-, 24.5-, and 15-fold increases, respectively, in the dissociation constant value for binding of the cofactor. While the turnover numbers for G144A, G144S, G144T, and G142C were 43%, 39%, 21%, and 6% of the wild-type value, respectively, the K(m) values for both substrates remained unchanged, with the exception of the G142C K(m)Gly, which showed a 4-fold increase. The UV-visible and CD spectra of Gly-144 mutants were similar to those of the wild type; however, the spectral properties of G142C suggest that this mutant binds the cofactor in a different mode at the active site. G144A, G144S, G144T, and G142C were also found to be less stable than the wild-type enzyme, with the thermotransition temperature, T1/2, determined to be 3.5, 3, 3.5, and 5 degrees C, respectively, lower than that of the wild-type enzyme. Collectively, computer modeling of the wild-type and mutant forms of the ALAS glycine loop and biochemical and spectroscopic characterization of G144A, G144S, G144T, and G142C strongly suggest that the conserved glycine loop in 5-aminolevulinate synthase is a pyridoxal 5'-phosphate cofactor binding motif.

5-Aminolevulinate Synthetase↗
PubMed1996

Cytometry of cyclin proteins.

Cyclins are key components of the cell cycle progression machinery. They activate their partner cyclin-dependent kinases (CDKs) and possibly target them to respective substrate proteins within the cell. CDK-mediated phosphorylation of specific sets of proteins drives the cell through particular phases or checkpoints of the cell cycle. During unperturbed growth of normal cells, the timing of expression of several cyclins is discontinuous, occurring at discrete and well-defined periods of the cell cycle. Immunocytochemical detection of cyclins in relation to cell cycle position (DNA content) by multiparameter flow cytometry has provided a new approach to cell cycle studies. This approach, like no other method, can be used to detect the unscheduled expression of cyclins, namely, the presentation of G1 cyclins by cells in G2/M and of G2/M cyclins by G1 cells, without the need for cell synchronization. Such unscheduled expression of cyclins B1 and A was seen when cell cycle progression was halted, e.g., after synchronization at the G1/S boundary by inhibitors of DNA replication. The unscheduled expression of cyclins B1 or E, but not of A, was also observed in some tumor cell lines even when their growth was unperturbed. Likewise, whereas the expression of cyclins D1 or D3 in nontumor cells was restricted to an early section of G1, the presentation of these proteins in many tumor cell lines also was seen during S and G2/M. This suggests that the partner kinase CDK4 (which upon activation by D-type cyclins phosphorylates pRB committing the cell to enter S) is perpetually active throughout the cell cycle in these tumor lines. Expression of cyclin D also may serve to discriminate G0 vs. G1 cells and, as an activation marker, to identify the mitogenically stimulated cells entering the cell cycle. Differences in cyclin expression make it possible to discriminate between cells having the same DNA content but residing at different phases such as in G2 vs. M or G2/M of a lower DNA ploidy vs. G1 cells of a higher ploidy. The expression of cyclins D, E, A and B1 provides new cell cycle landmarks that can be used to subdivide the cell cycle into several distinct subcompartments. The point of cell cycle arrest by many antitumor agents can be estimated with better accuracy in relation to these compartments compared to the traditional subdivision into four cell cycle phases. The latter applications, however, pertain only to normal cells or to tumor cells whose phenotype is characterized by scheduled expression of cyclins. As sensitive and specific indicators of the cell's proliferative potential, the cyclins, in particular D-type cyclins, are expected to be key prognostic markers in neoplasia.

Animals↗
PubMed1996

Effect of protease inhibitors on early events of apoptosis.

Proteolysis is an early event of apoptosis which appears to be associated with activation of the endonuclease which is responsible for internucleosomal DNA cleavage. The present study was designed to reveal the possible role of proteolysis in other early events, such as chromatin condensation, nuclear breakdown, and destabilization of in situ DNA double-stranded structure. Apoptosis of human leukemic HL-60 cells and rat thymocytes was induced by different agents, including DNA topoisomerase inhibitors, an RNA antimetabolite, and the glucocorticosteroid, prednisolone. DNA degradation was evaluated by pulsed field and conventional gel electrophoresis and by the presence of in situ DNA strand breaks. DNA stability was estimated by the measure of its sensitivity in situ to denaturation. Chromatin condensation, nuclear breakdown, and other morphological changes were monitored by interference contrast and UV microscopy following cell staining with the DNA-specific fluorochrome 4',6-diamidino-2- phenylindole. Several irreversible or reversible serine protease inhibitors prevented internucleosomal DNA degradation, nuclear breakdown, and destabilization of DNA double-stranded structure. The effective inhibitors, however, did not prevent the onset of chromatin condensation, nor the loss of the fine structural framework, nor the initial step of DNA cleavage generating DNA fragments of >=50 kb in size. The data indicate that in both cell systems the activity of proteases sensitive to the inhibitors tested is needed for internucleosomal DNA cleavage to occur. The data also suggest that these proteases may be involved in dissolution of the nuclear envelope. Because nuclear matrix proteins and histones stabilize DNA in situ, and the decrease in DNA stability which occurs during apoptosis is precluded by the inhibitors, it is likely that serine proteases may degrade DNA stabilizing proteins. The activity of these proteases, however, appears needed neither for DNA cleavage to >=50-kb fragments nor for the onset of chromatin condensation which is associated with dissolution of the structural framework of the nucleus.

Animals↗
PubMed1996

Tubing loops as a model for cardiopulmonary bypass circuits: both the biomaterial and the blood-gas phase interfaces induce complement activation in an in vitro model.

We describe here a model for the study of blood/surface and blood/air interaction as encountered in cardiopulmonary bypass (CPB) circuits. Polyethylene tubing was filled with serum or blood and closed end to end into loops whereby the volume of the remaining air bubble was inversely varied with respect to that of the fluid. The loops were rotated vertically in a water bath at 37 degrees C. The profiles of C3a, iC3, and TCC generation were similar to those observed at surgery, involving CPB. Soluble heparin and heparan sulfate inhibited both C3a and TCC formation, but surface-conjugated heparin had only a minor effect. Binding of C3 and/or C3 fragments to the heparin surface was much reduced compared to the amine matrix to which heparin was linked, but compared with the polyethylene surface the effect was less pronounced. These data suggest that, in addition to the biomaterial surface, the blood-gas interface seems to play an important role in the activation of complement and that this activation is inhibitable by high concentrations of soluble glucose aminoglycans.

Biocompatible Materials↗
PubMed1996

Breast cancer-associated antigen, DF3/MUC1, induces apoptosis of activated human T cells.

Given the plethora of well-documented breast carcinoma-associated antigens in humans including MAGE-1, -2 and -3, mutated p53, p21ras, HER-2/neu and DF3/MUC-1, coupled with evidence that humoral and cytotoxic T-cell responses against these antigens exist, the central dilemma facing tumor immunologists is why the host immune response is so inefficient. One possibility is that tumor cells themselves are either inefficient or ineffective antigen-presenting cells (APCs). The failure of tumor cells to function as APCs may be due to their inability to process and present the antigen, the absence or insufficient numbers of adhesion and costimulatory molecules or, potentially, the secretion of inhibitory cytokines. Therefore, we sought to determine whether human breast cancer cell lines could function as APCs and, if not, to identify mechanism(s) responsible for this defect. Here, we show that human breast cancer cell lines fail to present alloantigen. This defect does not reside in their inherent capacity to present antigen but rather is due to apoptosis of activated T cells induced by exposure to the breast carcinoma-associated mucin antigen, DF3/MUC1. These results support the hypothesis that DF3/MUC1 may contribute to the paucity of clinically significant anticarcinoma-specific immune responses.

3T3 Cells↗
PubMed1996

Unscheduled expression of cyclins D1 and D3 in human tumour cell lines.

D-type cyclins are involved in regulation of cell traverse through G1 primarily by activating the cyclin-dependent kinase 4 (CDK4) and targeting it to the retinoblastoma tumour suppressor protein. There is a vast body of evidence that defective expression of D-type cyclins is associated with tumour development and/or progression. Immunocytochemical detection of D cyclins combined with multiparameter flow cytometry makes it possible to measure the expression of these proteins in individual cells in relation to their cell cycle position without the need for cell synchronization. This approach was used in the present study to compare the cell cycle phase specific expression of cyclins D3 and D1 in human normal proliferating lymphocytes and fibroblasts, respectively, with nine tumour cell lines of different lineage. During exponential, unperturbed growth, expression of cyclin D1 in fibroblasts from donors of different age, or cyclin D3 in lymphocytes, was limited to mid-G1 cells: Less than 7% of the cells entering S phase or progressing through S and G2 were cyclin D positive. In contrast, expression of either cyclin D1 or cyclin D3 in tumour cell lines of different lineage was not limited to G1 phase. Namely, over 80% of the cells in S and G2+M were cyclin D positive in eight of the nine cell lines studied. The data indicate that while expression of cyclin D1 or D3 in normal cells is discontinuous, occurring transiently in G1, these proteins are expressed in some tumour lines persistently throughout the cell cycle. This suggests that the partner kinase CDK4 is perpetually active throughout the cell cycle in these tumour lines.

Cell Cycle↗
PubMed1996

16S rDNA analysis of Butyrivibrio fibrisolvens: phylogenetic position and relation to butyrate-producing anaerobic bacteria from the rumen of white-tailed deer.

Complete 16S rDNA sequences of six strains of Butyrivibrio fibrisolvens, including the type strain (ATCC 19171), were determined. The type strain was found to have less than 89% sequence similarity to the other isolates that were examined. The five plasmid-bearing strains formed a closely related cluster and three of these strains (OB156, OB157 and OB192) were very highly related (> 99%), indicating that they are isolates of the same genomic species. The phylogenetic position of Butyrivibrio was found to be within the subphylum Clostridium, of Gram-positive bacteria. The closest relatives to the type strain were Eubacterium cellulosolvens and Cl. xylanolyticum and the closest relatives to the separately clustered strains were Roseburia ceciola, Lachnospira pectinoschiza and Eubacterium rectale.

Animals↗
PubMed1996

Effects of spectral smearing on phoneme and word recognition.

The principal goal was to measure the effects, on speech perception, of loss of spectral detail in the acoustic signal. Spectral smearing was produced by multiplying the speech waveform by low-pass filtered noise. Performance was measured in normal adults as the percentage of phonemes correctly repeated in lists of monosyllabic words. A smearing bandwidth of 250 Hz (i.e., each tonal component of the instantaneous spectrum replaced by a 250-Hz band of noise) had a small but significant effect on phoneme recognition. A smearing bandwidth of 8000 Hz was required to reduce phoneme recognition to a value that was indistinguishable from that produced by complete smearing. Vowels were somewhat more susceptible to the effects of spectral smearing than were consonants, and initial consonants were more susceptible than were final consonants. In an analysis of errors, place of consonant articulation was more susceptible than either manner of articulation or voicing. These findings are attributable to differences in the relative importance of spectral and temporal cues. Word recognition was more susceptible to the effects of spectral smearing than was phoneme recognition, but this finding was predictable on the basis of the known nonlinear relationship between the two measures. In a second experiment, smearing bandwidths of 707 and 2000 Hz increased phoneme recognition threshold by 12.9 and 16.4 dB, respectively, compared to that found without smearing. (Phoneme recognition threshold is defined, here, as the signal-to-noise ratio at which phoneme recognition is 50% of the value obtained in quiet.) The data are consistent with the hypothesis that reduced spectral resolution affects phoneme recognition to the extent that it reduces access to the formant patterns in the spectral envelope.

Adult↗
PubMed1996

Absence of a prominent Th2 cytokine response in human tuberculosis.

Depressed Th1 responses are a prominent feature of human tuberculosis, but an enhanced Th2 response has not been detected in peripheral blood T cells stimulated in vitro with Mycobacterium tuberculosis. In disease due to Mycobacterium leprae, Th2 cells predominate in tissue lesions of patients with extensive disease but are absent from peripheral blood. To determine if Th2 cells are present in tissue lesions of tuberculosis patients, we evaluated patterns of cytokine expression in lymph nodes from tuberculosis patients with or without human immunodeficiency virus infection and in controls without tuberculosis. Gamma interferon and interleukin-10 (IL-10) mRNA expression in tuberculosis patients with or without human immunodeficiency virus infection was high, whereas IL-4 expression in the same patients was low. Immunolabeling studies showed that macrophage production of IL-12 was increased in lymph nodes from tuberculosis patients, that gamma interferon was produced by T cells, and that IL-10 was produced by macrophages rather than Th2 cells. These results indicate that Th2 responses are not enhanced either systemically or at the site of disease in human tuberculosis.

HIV Infections↗
PubMed1995

Induction of apoptosis by 5-azacytidine: drug concentration-dependent differences in cell cycle specificity.

There are conflicting data in the literature as to whether cytotoxicity of the cytidine antimetabolite 5'-azacytidine (AZC) is a consequence of its incorporation into RNA, DNA, or both. Because apoptosis appears to be the predominant mode of tumor cell death after treatment with most antitumor drugs, and in the case of some drugs, the proclivity of the cell to undergo apoptosis varies depending on the cell cycle position, this study was aimed toward elucidating whether induction of apoptosis by AZC is cell cycle phase specific. Human promyelocytic leukemic HL-60 cells were treated with varying concentrations of AZC, and flow cytometric methods that identify apoptotic cels and provide information about the cell cycle distribution of the apoptotic and nonapoptotic cell populations were used. At 2-6 microM concentrations of AZC, the cells in the G1 phase preferentially underwent apoptosis, whereas the cells in G2-M were particularly resistant. Although incorporation of bromouridine into RNA was suppressed at that low AZC concentration, the rate of 5'-bromo-2-deoxyuridine incorporation into DNA was not significantly affected. At an AZC concentration of 8-40 microM, no cell cycle phase specificity in induction of apoptosis was apparent, but both the rate of 5'-bromo-2-deoxyuridine incorporation into DNA and bromouridine into RNA were reduced in proportion to drug concentration. The data suggest that the mechanism of cell killing by AZC may be different, depending on its concentration. Namely, whereas incorporation of AZC into RNA may play a predominant role in the induction of cytotoxicity of G1 cells at low drug concentrations, the perturbation of both RNA and DNA metabolism may be responsible for triggering cell death in the G1 and S phases, as is seen at higher concentrations of this antimetabolite.

Apoptosis↗
PubMed1995

Autocrine transforming growth factor beta 1 modulates the expression of integrin alpha 5 beta 1 in human colon carcinoma FET cells.

Transforming growth factor beta (TGF-beta) has been extensively studied as an exogenous agent that stimulates the expression of extracellular matrix proteins and their cell-surface integrin receptors in a variety of cell types. However, the recent demonstration of autocrine TGF-beta growth effects in a number of cell types suggests that the steady-state expression of extracellular matrix and integrin proteins and their biological activity may also be under autocrine TGF-beta control. Previously, we reported that repression of autocrine TGF-beta 1 activity by constitutive expression of a full-length TGF-beta 1 antisense cDNA led to abrogation of autocrine negative TGF-beta and, as a result, increased tumorigenicity and anchorage-independent growth of a poorly tumorigenic, well-differentiated colon carcinoma cell line designated FET (Wu, S., Theodorescu, D., Kerbel, R. S., Willson, J. K. V., Mulder, K. M., Humphrey, L. E., and Brattain, M. G. (1992) J. Cell Biol. 116, 187-196). Consequently, we have used this model system to study the effects of repression of autocrine TGF-beta 1 activity on the expression of integrin alpha 5 beta 1 and integrin alpha 5 beta 1-mediated cell adhesion to fibronectin. The expression of the integrin alpha 5 subunit was reduced in TGF-beta 1 antisense transfected FET cells at both mRNA and protein levels as determined by RNase protection assays and immunoprecipitation, respectively. Autocrine TGF-beta 1 had no effect on the transcription of integrin alpha 5 and beta 1 subunits, indicating that autocrine TGF-beta 1 may regulate integrin alpha 5 beta 1 expression at the post-transcriptional level. The diminished expression of integrin alpha 5 beta 1 on the cell surface led to the reduced adhesion of TGF-beta 1 antisense transfected cells to fibronectin. This phenomenon could be reversed by treatment with exogenous TGF-beta 1.

Cell Adhesion↗
PubMed1995

Aminolevulinate synthase: functionally important residues at a glycine loop, a putative pyridoxal phosphate cofactor-binding site.

5-Aminolevulinate synthase catalyzes the first step of the heme biosynthetic pathway in nonplant higher eukaryotes. The enzyme functions as a homodimer and requires pyridoxal 5'-phosphate as its cofactor. Lysine-313 in murine erythroid aminolevulinate synthase has been identified as the residue involved in the Schiff base linkage with pyridoxal 5'-phosphate [Ferreira, G. C., Neame, P. J., & Dailey, H. A. (1993) Protein Sci. 2, 1959-1965]. However, other residues involved in binding and orienting the cofactor remain unknown. We studied the informational content of each residue within an 11 amino acid glycine-rich region, which we propose to be part of the phosphate-binding motif, based on amino acid sequence comparison with other pyridoxal 5'-phosphate-dependent enzymes and nucleotide-binding proteins. Partial random mutagenesis of this region in murine erythroid aminolevulinate synthase gene was followed by an efficient biological selection, using a hemA- Escherichia coli strain to recover functional unnatural enzymes. Among the total of 5444 variants produced, 283 were found to be functional. DNA sequencing results of 226 functional mutants indicated that most residues in this region contained a low informational content, being able to tolerate several other amino acid substitutions. However, three residues, namely, Arg-149, Gly-142, and Gly-144, were found to contain high informational content; Arg-149 was conserved in all of the functional mutants sequenced, while Gly-142 and Gly-144 could only tolerate alanine replacement. Two codon-specific random libraries of Arg-149, and Gly-142 and -144, respectively, were constructed to test further the stringency of these three positions.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Aminolevulinate Synthetase↗