Neuropeptide Y: some viewpoints on a multifaceted peptide in the normal and diseased nervous system

Using immunohistochemical and in situ hybridization methodologies the localization of neuropeptide tyrosine (NPY) and two of its receptors, the Y1- and the Y2-receptor (R), has been analysed in various tissues in normal animals and animals subjected to different experimental procedures as well as animals with a genetic and an acquired disease. (1) Dorsal root ganglion (DRG) neurons are discussed with special focus on the effect of peripheral nerve injury. In normal DRG neurons NPY cannot be detected, whereas Y1-R mRNA and Y1-R-like immunoreactivity (LI) are strongly expressed. The Y1-Rs decorate the membrane of the cell soma and are not transported peripherally into the axonal branches. Y2-R mRNA levels are low. After axotomy there is a marked increase in NPY, a decrease in Y1-Rs and an increase in Y2-Rs. The Y2-R is transported centrifugally. These findings suggest that NPY-ergic mechanisms participate in the adaptive changes of sensory neurons in response to injury. (2) Using specific antibodies the cellular and subcellular localization of the Y1-R protein have been analysed in cerebral blood vessels. The results demonstrate high concentrations of receptors in smooth muscle cells around pial arterioles with lower numbers in large vessels on the basal surface of the brain. In many regions the receptors 'disappear' after the arterioles have entered the brain tissue. At the ultrastructural level the receptors are found both on the endothelial and peripheral side of the muscle cells as well as laterally, where muscle cells oppose each other. The receptor protein is often associated with small vesicles. No NPY-positive nerve fibers were found around the Y1-R-rich arterioles, but they were only seen around the arteries with low Y1-R levels. The Y1-R-rich arterioles were, however, seen close to numerous NPY-positive fibers originating from central interneurons. These findings raise the possibility that centrally originating NPY can influence cerebral blood flow, possibly by stimulating NPY-Rs on the peripheral side of the muscle cells. However, also blood borne NPY, released under special conditions, such as stress from sympathetic nerves and the adrenal medulla and transported with blood, may stimulate receptors on the endothelial side of the smooth muscle cells. (3) In the arcuate nucleus Y1- and Y2-Rs are found, whereby the Y1-Rs are located in its ventro-medial portion and co-localized with POMC peptides, and the Y2-R in its ventromedial part, partly co-localized with NPY. NPY nerve endings makes synaptic contact with the POMC/Y1-R-positive neurons. In a mouse model for genetic anorexia very high levels of NPY were observed in arcuate neurons as compared to control mice. However, NPY mRNA levels were not different between the two groups. Taken together these findings are in good agreement with the view that NPY in the arcuate nucleus plays an important role in regulating feeding behaviour. (4) After intracerebral prion inoculation in mice an upregulation of NPY mRNA levels was observed in CA3 pyramidal neurons, and this effect was seen at a time point just before the first behavioural symptoms were manifested. At approximately the same time there was a dramatic decrease in Y2-R binding in strata oriens and radiatum of the CA1 region of the hippocampus, whereas in other regions no changes or much smaller changes were observed. Also, there was only a very slight decrease in Y2-R mRNA levels in CA3 neurons. It thus appears as if the prion disease prevents ligand binding to the Y2-R, perhaps by influencing traffic of receptor proteins, possibly at the level of cell membrane-associated caveolae, which have been implicated in the conversion of normal protein to scrapie protein. It is possible that these changes in NPY-ergic mechanisms may underlie some of the central symptoms associated with the prion disease. (ABSTRACT TRUNCATED)

Assessing hepatitis A virus epidemic stochastic process in eight cities in China in 1990

BACKGROUND

In The People's Republic of China in 1990, the age-specific seroprevalence of hepatitis A was investigated in eight large cities.

METHODS

A stochastic model, the two-state Markov chain, was applied to hepatitis A virus seroprevalence data by age group. An age-specific risk rate, Markov Risk Rate (MRR), and its weighted sum, Total MRR, are defined and used as novel measure indices to prioritize age groups for allocating vaccine or to decide in which cities vaccine should be used to prevent hepatitis A.

RESULTS

In 1990, the MRR1- in Xi'an, Jinan, Ha'erbin and Huhehaote, and the MRR10- in Chongqing were over 40. The MRR10- in Xi'an, Nanjing, Jinan and Ha'erbin and the MRR20- in Chongqing and Nanjing were over 20. The Total MRR in Chongqing and Ha'erbin were over 160, which was higher than the warning value.

CONCLUSIONS

All age groups whose MRR was over 20 are strongly recommended to be vaccinated first. Chongqing and Ha'erbin are cities at high risk of a hepatitis A virus epidemic in the 1990s and therefore should be under close surveillance.

Aspartate-279 in aminolevulinate synthase affects enzyme catalysis through enhancing the function of the pyridoxal 5'-phosphate cofactor

5-Aminolevulinate synthase (ALAS) catalyzes the first step in the heme biosynthetic pathway in nonplant eukaryotes and some prokaryotes, which is the condensation of glycine with succinyl-coenzyme A to yield coenzyme A, carbon dioxide, and 5-aminolevulinate. ALAS requires pyridoxal 5'-phosphate as an essential cofactor and functions as a homodimer. D279 in murine erythroid enzyme was found to be conserved in all aminolevulinate synthases and appeared to be homologous to D222 in aspartate aminotransferase, where the side chain of the residue stabilizes the protonated form of the cofactor ring nitrogen, thus enhancing the electron sink function of the cofactor during enzyme catalysis. D279A mutation in ALAS resulted in no detectable enzymatic activity under standard assay conditions, and the conservative D279E mutation reduced the catalytic efficiency for succinyl-CoA 30-fold. The D279A mutation resulted in a 19-fold increase in the dissociation constant for binding of the pyridoxal 5'-phosphate cofactor. UV-visible and CD spectroscopic analyses indicated that the D279A mutant binds the cofactor in a different mode at the active site. In contrast to the wild-type and D279E mutant, the D279A mutant failed to catalyze the formation of a quinonoid intermediate upon binding of 5-aminolevulinate. Importantly, this partial reaction could be rescued in D279A by reconstitution of the mutant with the cofactor analogue N-methyl-PLP. The steady-state kinetic isotope effect when deuteroglycine was substituted for glycine was small for the wild-type enzyme (kH/kD = 1.2 +/- 0.1), but a strong isotope effect was observed with the D279E mutant (kH/kD = 7.7 +/- 0.3). pH titration of the external aldimine formed with ALA indicated the D279E mutation increased the apparent pKa for quinonoid formation from 8.10 to 8.25. The results are consistent with the proposal that D279 plays a crucial role in aminolevulinate synthase catalysis by enhancing the electron sink function of the cofactor.

Growth of virulent and avirulent Mycobacterium tuberculosis strains in human macrophages

Mycobacterium tuberculosis H37Rv causes progressive disease in animals, whereas the H37Ra strain does not. The relevance of this difference in virulence to human infection is uncertain because these strains have been shown to have similar growth rates in human macrophages. To evaluate the intracellular growth of M. tuberculosis strains in macrophages under conditions similar to those encountered in vivo, we infected human monocyte-derived macrophages with H37Ra, H37Rv, or one of four isolates from tuberculosis patients at a low bacillus-to-macrophage ratio. H37Rv and the patient isolates grew significantly faster than H37Ra, based on the numbers of CFU and acid-fast bacilli. These findings did not result from extracellular mycobacterial growth, differential macrophage viability, or bacillary clumping. In contrast to other published results, these findings indicate that the virulence characteristics of M. tuberculosis strains in animal models are relevant to human tuberculosis infection.

Disruption of fibronectin binding to the alpha 5 beta 1 integrin stimulates the expression of cyclin-dependent kinases and DNA synthesis through activation of extracellular signal-regulated kinase

The alpha 5 alpha 1 integrin, a fibronectin receptor, has been implicated in the control of cell growth and the regulation of gene expression. We report that disruption of ligation between alpha 5 alpha 1 and fibronectin by integrin alpha 5 subunit or fibronectin monoclonal antibodies stimulated DNA synthesis in growth-arrested FET human colon carcinoma cells. This stimulation only occurred when monoclonal antibody was added in the early G1 phase of the cell cycle after release from quiescence by fresh medium. Stimulation of DNA synthesis by alpha 5 or fibronectin antibody was concentration- and time-dependent. FET cells expressed alpha 4 beta 1 integrin (another fibronectin receptor); however, addition of anti-human integrin alpha 4 monoclonal antibody had no effect on DNA synthesis. Treatment with alpha 5 monoclonal antibody led to a marked increase in the expression of CDK4 in G1 phase of the cell cycle and consequently increased the phosphorylation of retinoblastoma protein. alpha 5 monoclonal antibody treatment increased both cyclin A- and cyclin E-associated kinase activity which was accompanied by increased protein levels of CDK2 and cyclin A. Western blotting of immunoprecipitates demonstrated increased CDK2-cyclin E and CDK2-cyclin A complexes in cells treated with alpha 5 monoclonal antibody. Furthermore, disruption of alpha 5 alpha 1/fibronectin ligation activated mitogen-activated protein kinase p44 and p42 (extracellular signal-regulated kinase 1 and 2). Pretreatment of the cells with a specific inhibitor of MEK-1, PD98059, blocked the alpha 5 monoclonal antibody-induced mitogen-activated protein kinase activity. In addition PD98059 prevented alpha 5 monoclonal antibody-induced DNA synthesis. Since alpha 5 alpha 1 ligation to fibronectin is associated with decreased growth parameters, our results indicate that ligation of alpha 5 alpha 1 integrin to fibronectin results in suppressed mitogen-activated protein kinase activity which in turn inhibits cyclin-dependent kinase activity in growth-arrested cells.

Isolation of mycobacterium-reactive CD1-restricted T cells from patients with human immunodeficiency virus infection

Because CD1-restricted T cells lack CD4 but produce IFN-gamma in response to nonpeptide mycobacterial antigens, they could play a unique role in immunity to tuberculosis. We studied CD1-restricted T cells in the context of HIV infection by expanding CD4(-) T cell lines from 10 HIV-infected patients. Upon stimulation with Mycobacterium tuberculosis antigen or upon exposure to macrophages infected with M. tuberculosis, these T cell lines proliferated, produced IFN-gamma, and showed cytolytic T cell (CTL) activity against macrophages pulsed with mycobacterial antigen, findings consistent with a protective role against M. tuberculosis. Anti-CD1b antibodies abrogated T cell proliferation, IFN-gamma production, and CTL activity, demonstrating that these T cells are CD1 restricted. IFN-gamma production in response to M. tuberculosis was enhanced by antitransforming growth factor-beta in 8/10 lines, and by IL-15 in 2/10 lines. IFN-gamma production was augmented in a nonantigen-specific manner by IL-12 in 4/8 lines. When live HIV was cocultured with CD1-restricted T cell lines, p24 antigen and proviral DNA were not detected, indicating that the T cells were not infectable with HIV. Vaccination strategies aimed at activation and expansion of M. tuberculosis-reactive CD1-restricted T cells in HIV-infected patients may constitute a novel means to provide protection against tuberculosis, while minimizing the risk of enhancing HIV replication through stimulation of CD4(+) cells.

Regulation of ubiquitin-conjugating enzymes by glutathione following oxidative stress

Upon oxidative stress cells show an increase in the oxidized glutathione (GSSG) to reduced glutathione (GSH) ratio with a concomitant decrease in activity of the ubiquitinylation pathway. Because most of the enzymes involved in the attachment of ubiquitin to substrate proteins contain active site sulfhydryls that might be covalently modified (thiolated) upon enhancement of GSSG levels (glutathiolation), it appeared plausible that glutathiolation might alter ubiquitinylation rates upon cellular oxidative stress. This hypothesis was explored using intact retina and retinal pigment epithelial (RPE) cell models. Exposure of intact bovine retina and RPE cells to H2O2 (0.1-1.7 micromol/mg) resulted in a dose-dependent increase in the GSSG:GSH ratio and coincident dose-dependent reductions in the levels of endogenous ubiquitin-activating enzyme (E1)-ubiquitin thiol esters and endogenous protein-ubiquitin conjugates and in the ability to form de novo retinal protein-125I-labeled ubiquitin conjugates. Oxidant-induced decrements in ubiquitin conjugates were associated with 60-80% reductions in E1 and ubiquitin-conjugating enzyme (E2) activities as measured by formation of ubiquitin thiol esters. When GSH levels in RPE cells recovered to preoxidation levels following H2O2 removal, endogenous E1 activity and protein-ubiquitin conjugates were restored. Evidence that S thiolation of E1 and E2 enzymes is the biochemical link between cellular redox state and E1/E2 activities includes: (i) 5-fold increases in levels of immunoprecipitable, dithiothreitol-labile 35S-E1 adducts in metabolically labeled, H2O2-treated, RPE cells; (ii) diminished formation of E1- and E2-125I-labeled ubiquitin thiol esters, oligomerization of E225K, and coincident reductions in protein-125I-labeled ubiquitin conjugates in supernatants from nonstressed retinas upon addition of levels of GSSG equivalent to levels measured in oxidatively stressed retinas; and (iii) partial restoration of E1 and E2 activities and levels of protein-125I-labeled ubiquitin conjugates in supernatants from H2O2-treated retinas when GSSG:GSH ratios were restored to preoxidation levels by the addition of physiological levels of GSH. These data suggest that the cellular redox status modulates protein ubiquitinylation via reversible S thiolation of E1 and E2 enzymes, presumably by glutathione.

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.

Induction of antigen-specific antitumor immunity with adenovirus-transduced dendritic cells

Transduction of dendritic cells (DC) can result in presentation of tumor-associated antigens and induction of immunity against undefined epitopes. The present studies demonstrate adenovirus (Ad)-mediated transduction of the beta-galactosidase gene in mouse DC. Similar transductions have been obtained with the gene encoding the DF3/MUC1 tumor-associated antigen. We show that the Ad-transduced DC are functional in primary allogeneic mixed lymphocyte reactions. Mice immunized with Ad-transduced DC develop cytotoxic T lymphocytes that are specific for the beta-galactosidase or DF3/MUC1 antigens. The results also demonstrate that Ad MUC1-transduced DC induce a specific response which inhibits the growth of DF3/MUC1-positive tumors. These findings support the usefulness of Ad-transduced DC for in vivo immunization against tumor-associated antigens.

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.

Significance of leukocyte concentration in the performance of the quantitative cytomegalovirus (CMV) antigenemia assay

BACKGROUND

The quantitative cytomegalovirus-antigenemia (CMV-Ag) assay is an important technology in the regimen of tests utilized in the care and management of acquired immunodeficiency syndrome (AIDS) and other immunocompromised patient groups. Performance of this assay is contingent upon the appropriate processing of the polymorphonuclear leukocyte (PMNL) compartment of the peripheral blood. However, a cell input standard in the performance of the CMV-Ag assay, has not been established. Interpretive differences between laboratories utilizing the CMV-Ag assay may reflect this lack of test uniformity.

OBJECTIVES

To determine the effect of different PMNL concentrations on the quantitation of CMV in peripheral blood. The leukocyte concentration resulting in optimal rates of viral detection, will be compared with the shell vial assay-indirect immunofluorescent assay (SVA-IFA), and conventional tube culture (TC-CPE).

STUDY DESIGN

A total of 74 freshly collected blood specimens were tested by the CMV-Ag assay, using cytospin preparations consisting of 2 x 10(5), 4 x 10(5) and in preliminary experiments, 8 x 10(5) PMNLs/slide. Data obtained from these studies were compared to SVA-IFA and TC-CPE. Viral load was monitored among 11 symptomatic patients through sequential testing of these patients at the start of ganciclovir (GCV), foscarnet (PFA), or combination drug therapy.

RESULTS

Among 74 blood specimens tested by the CMV-Ag assay, cytospin preparations consisting of 4 x 10(5) compared with 2 x 10(5) PMNLs/slide, affected a mean positive cell increase of 215% (P = 0.03). PMNL slide preparations consisting 8 x 10(5) cells produced background levels which prevented accurate reading of slides. The CMV-Ag assay was more sensitive than the SVA-IFA, but equivalent to TC-CPE. Among 11 patients started on drug therapy, viral load was markedly reduced in 8 within 2-3 weeks; three patients (2 deceased within 3 weeks after receiving therapy), showed no decrease in viral load. One patient was identified as harboring a PFA resistant strain.

CONCLUSIONS

A PMNL concentration of 4 x 10(5) cells facilitated the reading of CMV-Ag assay slide preparations. The modified CMV-Ag assay furthermore, is applicable in the monitoring of viral load for the tracking of susceptible or resistant CMV strains.

Single-cell cytokine analysis of gamma delta T cell responses to nonpeptide mycobacterial antigens

TCR gamma delta T cells are considered important in the rapid immune response to intracellular infection. We investigated the early response of peripheral blood gamma delta T cells to the nonpeptide Ag isopentenyl pyrophosphate and to its synthetic analogue ethyl pyrophosphate. In healthy donors, an increase in the number of gamma delta T cells was detected as soon as 4 days after stimulation with the nonpeptide Ags. Single-cell analysis of cytokine production was performed by intracellular staining of IFN-gamma and IL-4. gamma delta T cells were found to rapidly expand and produce IFN-gamma in response to nonpeptide Ags. Furthermore, IL-12 augmented the IFN-gamma response. In contrast, gamma delta T cells from the majority of HIV+ donors did not expand or express IFN-gamma in response to nonpeptide Ags, even in the presence of IL-12. These findings indicate a role for nonpeptide-reactive gamma delta T cells in effective cell-mediated immunity for intracellular pathogens.

Single-cell cytokine analysis of gamma delta T cell responses to nonpeptide mycobacterial antigens

TCR gamma delta T cells are considered important in the rapid immune response to intracellular infection. We investigated the early response of peripheral blood gamma delta T cells to the nonpeptide Ag isopentenyl pyrophosphate and to its synthetic analogue ethyl pyrophosphate. In healthy donors, an increase in the number of gamma delta T cells was detected as soon as 4 days after stimulation with the nonpeptide Ags. Single-cell analysis of cytokine production was performed by intracellular staining of IFN-gamma and IL-4. gamma delta T cells were found to rapidly expand and produce IFN-gamma in response to nonpeptide Ags. Furthermore, IL-12 augmented the IFN-gamma response. In contrast, gamma delta T cells from the majority of HIV+ donors did not expand or express IFN-gamma in response to nonpeptide Ags, even in the presence of IL-12. These findings indicate a role for nonpeptide-reactive gamma delta T cells in effective cell-mediated immunity for intracellular pathogens.

Quantitative comparison of mu opioid receptor mRNA in selected CNS regions of alcohol naive rats selectively bred for high and low alcohol drinking

We combined solution hybridization, ribonuclease protection and microdissection techniques to quantitatively compare the anatomical distribution of mu receptor mRNA in discrete brain regions of alcohol naive rats selectively bred for high and low alcohol drinking (HAD and LAD lines, respectively). The solution hybridization assay is highly sensitive and can detect mu opioid receptor mRNA in a 100-fold linear range from 4 to 421 amol. HAD and LAD rats exhibited a similar level of mu receptor mRNA in all central nervous system (CNS) regions examined except for the inferior colliculus. Our data suggest that the steady-state level of mu receptor mRNA is not associated with genetic differences in alcohol drinking behavior.

Induction of antitumor activity by immunization with fusions of dendritic and carcinoma cells

Dendritic cells (DCs) are potent antigen-presenting cells that prime naive cytotoxic T-cells (CTLs). In this study, we have fused DCs with MC38 carcinoma cells. The fusion cells were positive for major histocompatibility (MHC) class I and II, costimulating molecules and intercellular cell adhesion molecule-1 (ICAM-1). The results show that the fusion cells stimulate naive T cells in the primary mixed lymphocyte reaction (MLR) and induce MC38 tumor-specific CTLs in vivo. Antibody-mediated depletion experiments demonstrate that induction of CD4+ and CD8+ CTLs protects against challenge with tumor cells. We also show that immunization with the fusion cells induces rejection of established metastases. These findings represent the first demonstration that fusions of DCs and tumor cells can be used in the treatment of cancer.

[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.

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.

Makatoxin I, a novel toxin isolated from the venom of the scorpion Buthus martensi Karsch, exhibits nitrergic actions

Buthus martensi Karsch venom exhibits nitrergic action in rat anococcygeus muscle (ACM). We have purified a novel toxin, makatoxin I (MkTx I), which exhibits nitrergic action, to homogeneity from this venom by a combination of gel-filtration, cation-exchange chromatography, and reverse-phase chromatography. Its purity was assessed by capillary electrophoresis and mass spectrometry. Its molecular weight was found to be 7031.71 +/- 2.88 as calculated from electrospray mass spectrographic data. The complete amino acid sequence was elucidated by sequencing of reduced and S-pyridylethylated toxin and a carboxyl-terminal peptide, P55-64, generated by the cleavage of toxin with endoproteinase Lys-C. The complete sequence of MkTx I is GRDAYIADSENCTYTCALNPYCNDLCTKNGAKSGYCQWAGRYGNACWCIDLPDKVPIRISGSCR. This toxin is composed of 64 amino acid residues and contains 8 half-cystine residues. Structurally, MkTx I has high similarity to Bot I and Bot II when compared with toxins from other scorpion species. The effects of MkTx I on nitrergic responses were investigated using the rat isolated ACM mounted in Krebs solution (37 degrees C, 5% CO2 in O2). MkTx I (2 microg/ml) markedly relaxed the carbachol-precontracted ACM; the relaxation was inhibited by the stereoselective inhibitor of nitric oxide synthase, Nomega-nitro-L-arginine methyl ester (50 microM). Thus, MkTx I is the first alpha-toxin that can mediate nitrergic responses in the rat isolated ACM.

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.

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.

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.

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.

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.