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Z Li

Publications and source records attributed to Z Li.

At least 19 recordsLinked to original sources
PubMed2025

HLA-E and NKG2A Mediate Resistance to BCG Immunotherapy in Non-Muscle-Invasive Bladder Cancer.

Bacillus Calmette-Guérin (BCG) is the first-line therapy for high-grade non-muscle-invasive bladder cancer (NMIBC), yet many patients experience recurrence due to immune evasion. We identify HLA-E and NKG2A as mediators of adaptive resistance involving chronic activation of NK and T cells in BCG-unresponsive tumors. Prolonged IFN-γ exposure enhances HLA-E and PD-L1 expression on recurrent tumors, accompanied by the accumulation of NKG2A+ NK and CD8 T cells. HLA-Ehigh tumor cells preferentially cluster near CXCL12-rich stromal regions with dense effector cell presence, underscoring a spatially segregated tumor architecture. Although cytotoxic lymphocytes retain effector potential, their activity is restrained by HLA-E/NKG2A and PD-L1/PD-1 pathways located in their immediate neighborhood within the bladder tumor microenvironment. These data reveal a spatially organized immune escape program that limits anti-tumor immunity. Our findings support dually targeting NKG2A and PD-L1 checkpoint blockade as a rational, bladder-sparing strategy for patients with BCG-unresponsive NMIBC.

BCG-unresponsive↗
PubMed1992

Prognostic factors for survival of patients with bidimensionally measurable metastatic hormone-refractory prostatic cancer treated with single-agent chemotherapy.

BACKGROUND: A range of response proportions have been reported using the same single-agent inpatients with hormone refractory prostatic cancer. To assess whether these results were due to imbalances in prognostic factors, the authors evaluated a series of prognostic factors for survival in patients with prostatic cancer treated with chemotherapy. METHODS: Complete data sets were available in 146 patients, in whom 27 individual variables were considered in univariate analysis. Significant factors (P < 0.05) were then evaluated using regression analysis along with transformations of the data to obtain a Cox and exponential model. The derived model was then evaluated on an independent data set from the National Cancer Institute treated with suramin. RESULTS: In univariate analysis in order of significance, the serum alkaline phosphate (0.0018), serum lactic dehydrogenase (0.006), prior radiation therapy (0.007), serum aspartate amino transferase (0.02), presence of liver disease (0.033), and pretreatment Karnofsky performance status (0.04) were associated with survival. In the regression analysis, only the log-transformed lactic dehydrogenase (LDH) and normal versus abnormal alkaline phosphatase were significant. This model was confirmed with an independent data set from patients treated with the putative growth factor inhibitor suramin. CONCLUSIONS: This analysis emphasizes important factors that can be used to stratify patients in future phase II and III trials.

Aged↗
PubMed1992

In vitro biosynthesis of GbOse4Cer (globoside) and GM2 ganglioside by the (1-->3) and (1-->4)-N-acetyl beta-D-galactosaminyltransferases from embryonic chicken brain. Solubilization, purification, and characterization of the transferases.

(1-->4)-N-Acetyl-beta-D-galactosaminyltransferase (GalNAcT-1) and (1-->3)-N-acetyl-beta-D-galactosaminyltransferase (GalNAcT-2), which are involved in the in vitro biosynthesis of GM2 and GbOse4Cer glycosphingolipids, respectively, have been solubilized and separated by differential detergent extraction from a membrane preparation of 19-day-old embryonic chicken brain. The separated GalNAcT-1 activity had a pH optima of 7.8-8.0, and the separated GalNAcT-2 activity a single pH optimum of 7.2. Furthermore, the partially purified GalNAcT-2 preparation catalyzed the transfer of N-acetylgalactosamine from UDP-D-[3H]GalNAc to only GbOse3Cer and nLcOse5Cer. Both GalNAcT-1 and GalNAcT-2 activities were purified to approximately 316- and 428-fold, respectively, by use of UDP-hexanolamine-Sepharose 4B affinity-column chromatography. However, the partially purified GalNAcT-1 preparation appeared to be active only with GM3, lactosylceramide, and lactotriaosylceramide. The proposed linkage of the N-acetylgalactosamine unit incorporated into GM3 is beta-D-GalpNAc-(1-->4)-GM3 from the isolation of [3H]threitol after hydrolysis of the desialylated, lead tetraacetate-treated, enzymic product, beta-D-GalpNAc-(1-->4)-beta-D-[6-3H]Galp-(1-->4)-beta-D-Glcp-(1-->1)-Cer . In addition, beta-D-GalpNAc-(1-->3)-GbOse3Cer was produced, as shown by the identification of 2,4,6-tri-O-methyl-galactose after permethylation and hydrolysis of the GalNAcT-2 enzymic product, GalpNAc-[6-3H]Galp--->Gal-->Glc-->Cer.

Animals↗
PubMed1992

Fatty acid-enhanced binding of flavin mononucleotide to bacterial luciferase measured by steady-state fluorescence.

Bacterial luciferase catalyzes the oxidation of reduced flavin mononucleotide and tetradecanal resulting in the emission of light. We have investigated the interactions of a recombinant luciferase from a terrestrial bacterium Xenorhabdus luminescens with the reaction products, FMN and myristic acid, using steady-state fluorescence spectroscopy. Quenching of the intrinsic fluorescence and FMN fluorescence on binding of FMN to luciferase was found to be greatly stimulated in the presence of myristic acid, corresponding to a reduction of more than 30-fold in the FMN dissociation constant of the enzyme. In addition, the FMN-luciferase complex exhibits distinct fatty acid-dependent fluorescence properties. These results indicate that luciferase forms a ternary complex with FMN and myristic acid with a significantly different conformation from that of the binary FMN-luciferase complex.

Enterobacteriaceae↗
PubMed1992

Practical usage concentrations of monensin have non-specific actions other than as a sodium ionophore in rat parotid acinar cells.

Monensin is used as a sodium ionophore to examine the effect of Na+ on cellular function in a variety of cell types. In the present study, we investigated the effects of different concentrations of monensin on the signal transduction system in exocrine parotid acinar cells. Monensin increased cytosolic free Na+ concentration, measured by the Na+ indicator sodium-binding benzofuran isophthalate in a concentration-dependent manner (0.01 to 100 microM). Likewise, monensin concentration-dependently increased amylase release and intracellular Ca2+ concentration in the presence and the absence of extracellular Ca2+. Low concentrations (0.01 to 1 microM) of monensin did not release Ca2+ from non-mitochondrial intracellular pools in permeabilized cells with saponin but high concentrations (10 and 100 microM) of monensin which are of practical usage did. Monensin itself did not change the cyclic AMP accumulation, whereas high concentrations (10 and 100 microM) but not low concentrations (0.01 to 1 microM) of monensin inhibited cyclic AMP accumulation elevated by isoproterenol in the presence and absence of extracellular Na+. These results indicate that high concentrations of monensin, which are practically used, have nonspecific actions in rat parotid acinar cells, and lower concentrations of monensin are recommended for use as a sodium ionophore.

Adenosine Triphosphate↗
PubMed1992

Functional neuronal binding sites for oxytocin in the ventromedial hypothalamus of the guinea pig after gonadectomy.

Castration in rats of either sex has been shown to markedly decrease hypothalamic oxytocin binding in the ventromedial hypothalamus and this can be reversed by injecting gonadal steroids. We wondered whether castration exerts similar effects on homologous oxytocin binding sites present in the guinea pig hypothalamus. Adult male guinea pigs were castrated and killed 2-90 days later. Binding sites for oxytocin in the ventromedial nucleus and neuronal responses to this peptide were little affected by gonadectomy, in contrast to what is observed in the rat under similar experimental conditions. The steroid dependency of hypothalamic oxytocin receptors appears therefore to be species dependent.

Animals↗
PubMed1992

RNase PH is essential for tRNA processing and viability in RNase-deficient Escherichia coli cells.

RNase PH is a Pi-dependent exoribonuclease that can act at the 3' terminus of tRNA precursors in vitro. To obtain information about the function of this enzyme in vivo, the Escherichia coli rph gene encoding RNase PH was interrupted with either a kanamycin resistance or a chloramphenicol resistance cassette and transferred to the chromosome of a variety of RNase-resistant strains. Inactivation of the chromosomal copy of rph eliminated RNase PH activity from extracts and also slowed the growth of many of the strains, particularly ones that already were deficient in RNase T or polynucleotide phosphorylase. Introduction of the rph mutation into a strain already lacking RNases I, II, D, BN, and T resulted in inviability. The rph mutation also had dramatic effects on tRNA metabolism. Using an in vivo suppressor assay we found that elimination of RNase PH greatly decreased the level of su3+ activity in cells deficient in certain of the other RNases. Moreover, in an in vitro tRNA processing system the defect caused by elimination of RNase PH was shown to be the accumulation of a precursor that contained 4-6 additional 3' nucleotides following the -CCA sequence. These data indicate that RNase PH can be an essential enzyme for the processing of tRNA precursors.

Escherichia coli↗
PubMed1992

Expression of the cardiac Na(+)-Ca2+ exchanger in insect cells using a baculovirus vector.

We constructed a recombinant baculovirus containing cardiac Na(+)-Ca2+ exchanger cDNA under control of the polyhedrin promoter. When either Sf9 or Sf21 insect cells are infected with the recombinant baculovirus, both Na(+)-Ca2+ exchanger protein and Na(+)-Ca2+ exchange activity are expressed at high level. The exchanger protein can be detected either by immunoblot or by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole cell lysate. At maximal expression, the exchanger protein comprises about 3-5% of total cell protein. The Na(+)-Ca2+ exchanger can be purified by alkaline extraction of infected cells followed by elution from a Bio-Rad Prep Cell. The expressed exchanger, in contrast to the native sarcolemmal exchanger, is not glycosylated. Sf9 cells expressing the exchanger are intensely stained by anti-exchanger antibodies as observed by immunofluorescence. The expressed exchanger is predominantly in the cell plasma membrane since it is susceptible to extracellular trypsin. In 45Ca2+ flux experiments, the expressed Na(+)-Ca2+ exchange activity is about 4-fold higher than that in cultured neonatal rat heart cells. The expressed exchanger was also analyzed electrophysiologically using whole cell patch clamp techniques. The characteristics of inward exchange currents in infected Sf21 cells are very similar to those of ventricular myocytes, although of a larger magnitude.

Animals↗
PubMed1992

Transmembrane region of wild-type and mutant M13 coat proteins. Conformational role of beta-branched residues.

Although transmembrane (TM) segments of integral membrane proteins are putatively alpha-helical in conformation, beta-sheet promoters (Val, Ile, Thr) often account for approximately 40% of TM residue composition. We are examining the conformational role(s) of these residues, using as a model system the major coat protein of the filamentous bacteriophage M13. This 50-residue protein, which is located at the Escherichia coli host membrane during phage reproduction, contains a prototypic 19-residue hydrophobic midregion (residues 21-39: YIGYAWAMVVVIVGATIGI). Using "Eckstein" site-directed mutagenesis, we have generated several viable M13 coat protein mutants with beta-branched amino acid substitutions within their TM region. Mutant coat proteins, including Ile32----Val (I32V) and Ala27----Thr (A27T), were obtained in milligram quantities by growing M13 mutant phages in liter preparations, confirming that these coat proteins are capable of assuming their normal biological function(s) in phage reproduction. Circular dichroism spectroscopy performed in the membrane-mimetic medium of deoxycholate micelles indicated comparable alpha-helical contents of mutants I32V and A27T to wild-type protein. 13C nuclear magnetic resonance experiments with mutant A27T demonstrated that the combination of additional beta-branched content and introduction of an -OH substituent induced chemical shift and temperature-dependent changes and influenced the local protein environment at sites up to 12 residues remote from the mutation site. In contrast, mutant I32V (of which a salient feature is a mid-TM pentavaline segment) behaved very similarly to wild-type coat. These findings are interpreted in terms of the range of TM secondary structure and stability which can be accommodated by viable M13 coat protein mutants.

Amino Acid Sequence↗
PubMed1992

Desmosome assembly in MDCK epithelial cells does not require the presence of functional microtubules.

Desmosomes, complex multisubunit structures that assemble at sites of cell-cell contact, are important components of the epithelial junctional complex. Desmosome assembly requires the coordinated interaction at the plasma membrane of at least 8 cytoplasmic and integral membrane proteins organized into two structurally and functionally distinct domains, the cytoplasmic plaque and membrane core. Previous studies (Pasdar et al., J. Cell Biol., 113:645-655) provided evidence that cytokeratin filaments and microtubules may regulate transfer and assembly of cytoplasmic plaque and membrane core proteins, respectively. To determine directly the role of microtubules in these processes, Madin-Darby canine kidney (MDCK) cells were treated with nocodazole or colchicine to disrupt the microtubular network. Biochemical analysis of the different components of the cytoplasmic plaque and membrane core domains revealed little or no effect of nocodazole or colchicine on the kinetics of synthesis, post-translational modifications, transfer of proteins to the plasma membrane or their metabolic stability in the presence or absence of cell-cell contact. Likewise, immunofluorescence analysis of desmosome formation demonstrated an apparently normal desmosome assembly in the presence of nocodazole or colchicine upon induction of cell-cell contact. These results indicate that an intact microtubular network is not necessary for the processing or transport of the desmosomal membrane core glycoproteins to the plasma membrane in the absence or presence of cell-cell contact. Furthermore, the integration of the cytoplasmic plaque and membrane core domains induced by cell-cell contact at the plasma membranes of adjacent cells does not require the presence of functional microtubules.

Animals↗
PubMed1992

Sensory nerve endings in the puborectalis and anal region of the fetus and newborn.

The study was carried out in seven fetuses (ovulation ages were 16, 18, 20, 22, 26, 28, and 31 weeks, respectively) and in five full-term newborn babies. The modified Bielschowsky method and Barker's block silver impregnation were used. It was found that the muscle spindle was arranged in the puborectalis and the external sphincter muscles from the 20th week onward; the tendon organ was located in association with the musculo-tendinous junction of the puborectalis from the 20th week onward; the Pacinian corpuscle lay in the plane of cleavage between the internal anal sphincter and the external anal sphincter from the 22nd week onward, and in the presacral space from the 28th week onward, and the later lagged behind the former in development; the globular endings lay in the presacral space from the 28th week onward; and the free nerve ending was distributed in the epithelium of the anal mucosa and the epidermis around the anus from the 31st week onward. These sensory nerve endings tend to mature gradually with increasing age. It was concluded that these endings may be responsible for the reflex of the external anal sphincter and the anal sensation.

Anal Canal↗
PubMed1992

Enhanced incorporation of [14C]glucosamine into glycosaminoglycans of aortic neointima of balloon-injured and cholesterol-fed rabbits in vitro.

Glycosaminoglycans (GAG), which form the elementary constituent of extracellular matrix proteoglycans (PG), are implicated in the pathogenesis of atherosclerosis, mainly due to their lipoprotein binding capability and their abundance in a developing lesion during atherogenesis. However, the reasons for the increment of GAG content are poorly understood. In the present study, the influence of two well known atherogenic factors on arterial GAG synthesis were examined by estimating the incorporation of [14C]glucosamine into aortic GAG in an in vitro incubation system. Radioactivity associated with GAG was taken to represent their synthesis. GAG synthesis by neointimal tissue of rabbit aortas, 12 weeks following balloon catheter deendothelialization was measured and compared in rabbits fed a normal or 0.25% cholesterol supplemented diet for the preceding 6 weeks. In normolipaemic rabbits synthesis was found to be 12,438 +/- 173, 17,884 +/- 1390 and 15,960 +/- 1355 dpm/mg dry defatted tissue from uninjured (control), deendothelialized (DEA) and reendothelialized (REA) areas of rabbit aortas, respectively. This incorporation of radioactivity was significantly greater in hypercholesterolaemic rabbits corresponding to 13,426 +/- 239, 32,670 +/- 3077 and 27,496 +/- 3287 in the control, DEA and REA, respectively. The results demonstrated a synergistic effect of cholesterol feeding and arterial endothelial denudation in stimulating GAG synthesis. Although GAG synthesis was found to be stimulated by either cholesterol feeding or arterial injury, the stimulation by cholesterol feeding alone was only marginal. Further, results show a much higher retention of newly synthesized GAG by the tissue from REA. This study provided a possible explanation for increased GAG content in a developing proliferative lesion.

Animals↗
PubMed1992

Microprocedure for in situ nick translation of chromosomes.

We have modified the procedure of in situ nick translation to shorten the autoradiographic exposure time from 1 month to 3 days and reduce the volume of nick translation solution by a factor of at least 10. The modified procedure can be carried out on individually chosen chromosome spreads. The procedure was used on chromosome spreads of three related lines of mouse mammary epithelium (+SA, -SA, CL-S1) with different degrees of tumorigenicity. We found that the autoradiographic silver grains that are observed following in situ nick translation were often placed at the apparent junction site of chromosome translocations or at the breakpoint of chromosomal pieces. We found also that silver grains were located above double minute chromosomes, which suggests that there are active genes in double minutes.

Cell Line↗
PubMed1992

A cytotonic, cholera toxin-like protein produced by Campylobacter jejuni.

1. Campylobacter jejuni is a major cause of gastroenteric infection. 2. This organism appears to produce both cytotonic and cytotoxic virulence factors. 3. We report here that culture filtrates of some clinical isolates of C. jejuni induce elongation of Chinese hamster ovary (CHO) cells in vitro but do not cause inhibition of fluid absorption in the rat ileum. 4. These culture filtrates contain low levels of a protein which cross-reacts immunologically with the cholera toxin. 5. The cholera toxin-like protein of C. jejuni behaved identically to cholera toxin on non-denaturing polyacrylamide gel electrophoresis. 6. Under denaturing conditions, however, this protein displayed no subunit structure and a molecular weight of approximately 50 kDa with many higher molecular weight aggregates. 7. In conclusion, isolates of C. jejuni produced small amounts of enterotoxin when grown in vitro. 8. The toxin cross-reacted immunologically with cholera toxin and has a similar native structure, but does not appear to possess subunits.

Animals↗
PubMed1992

The selection of portal aperture using interactively displayed Beam's Eye Sections.

Portal apertures are often defined by wax-pencil lines drawn on simulator films. The simulator-film images suffer degradation due to X ray absorption and scatter in tissues proximal to and distal to the intended target volume. We describe a method for avoiding the degradation by using a 3-D dataset to produce high-contrast section images with a user-defined orientation. The calculation of these Beam's Eye Section (BES) images requires a set of medium-to high-resolution transverse section data (the 3-D dataset), as well as a medium- to high-performance computer workstation. These CT-like section images, providing more contrast and detail than a projection (that is, a simulator or Digitally Reconstructed Radiograph [DRR]) image, should allow for more accurate selection of portal apertures. The BES image plane is oriented perpendicular to the central axis of a user-selected beam. Once the user has created a beam, the system allows the user to step along that beam with a new BES image produced at each step. Contours manually drawn on these BES images are ultimately projected onto a DRR image. The outermost segments of these sometimes crisscrossing contours (the union of all projected areas) accurately defines the portal aperture needed to encompass the target at all levels.

Computer Simulation↗
PubMed1992

Expression and purification of kringle 4-type 2 of human apolipoprotein (a) in Escherichia coli.

The most frequently occurring kringle 4 domain of human apolipoprotein (a), Kringle 4-subtype 2 (K4(2)), was expressed as a fusion protein with the maltose binding protein in Escherichia coli using the "tac" promoter. Although the fusion protein was expressed without a signal sequence, 25% was secreted into the periplasmic space; the remainder was found associated with the soluble cytosolic fraction. The fusion protein was readily isolated from whole cell lysate by amylose agarose affinity chromatography. Although a factor Xa cleavage site was engineered into the fusion protein, it was found that release of the K4(2) protein was most conveniently achieved by proteolysis with subtilisin A. The cleavage product produced in this way was shown to be intact K4(2) with only the first three amino acid residues of the leading flanking peptide missing, as judged by N-terminal sequence analysis. K4(2) was isolated from the hydrolysate by FPLC on a Mono-Q column with a yield of 170 +/- 30 micrograms/g wet cells. The resulting protein was monomeric in phosphate-buffered saline as judged by size-exclusion chromatography and appeared to be folded as shown by spectroscopic and immunological assays. The recombinant K4(2) did not bind to either lysine- or proline-Sepharose, suggesting that the ligand binding activities of lipoprotein (a) may reside in the other kringle domains of apolipoprotein (a).

ATP-Binding Cassette Transporters↗
PubMed1992

Plasminogen activator activity and thymidine incorporation in avian granulosa cells during follicular development and the periovulatory period.

The hormonal and second messenger regulation of plasminogen activator (PA) activities in avian granulosa and theca cells has been documented. However, the physiological role(s) of PAs in the avian ovary remains poorly understood. The present studies were designed to evaluate PA activity in hen granulosa cells collected from the most mature (F1) preovulatory follicle at three discrete time points relative to a spontaneous ovulation and from follicles collected at various stages of follicular development. Levels of PA activity in the granulosa layer of the F1 follicle declined by greater than 90% as follicles were collected closer to their anticipated time of ovulation (e.g., from 17-16 h to 0.75-0.15 h; p less than 0.05). Timing of tissue collection was confirmed by evaluation of serum progesterone levels, which peaked as expected at the 6-5-h time point. During follicular development, PA activity was several times greater in rapidly growing follicles (6-12 mm, 1-3 wk prior to ovulation) than in slowly growing (1-5 mm) or preovulatory (F3 and F1) follicles (p less than 0.05). Granulosa cells of these rapidly growing follicles also incorporated significantly higher levels of 3H-thymidine than did granulosa cells of mature follicles (p less than 0.05), suggesting a higher level of DNA synthesis. Similarly, granulosa cells of the mitotically active germinal disc region of the F1 granulosa layer were found to possess at least 3-fold higher (p less than 0.05) levels of PA activity and a 2-fold greater level of 3H-thymidine incorporation than the more mature granulosa cells isolated from the remaining F1 granulosa layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗