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At least 505 records · Page 28Linked to original sources
PubMed2001

Preliminary studies on the effect of dehydroepiandrosterone (DHEA) on both constitutive and phytohaemagglutinin (PHA)-inducible IL-6 and IL-2 mRNA expression and cytokine production in human spleen mononuclear cell suspensions in vitro.

In order to gain further insight into the potential immunological benefits of oral administration of DHEA we have examined its effects on the constitutive and PHA-inducible expression by human spleen cell suspensions in vitro of IL-6 and IL-2. This was studied at both the mRNA and protein levels. The quantification of specific mRNA was undertaken using commercially available quantitative polymerase chain reaction kits. These studies, which were performed on suspensions from six individual spleens, revealed that 10(-5) M DHEA did not impair the expression of IL-6 at either the mRNA or protein level, but may have slightly enhanced the latter. In contrast, IL-2 mRNA levels were increased on most occasions, whilst IL-2 secretion was decreased, albeit slightly. Additional studies revealed that cyclosporin (approx. 10(-5) M) and dexamethasone (10(-7) M) readily inhibited these responses and the production of other cytokines, including interferon-gamma and tumour necrosis factor-alpha. These preliminary studies suggest that high doses of DHEA do not readily inhibit the production of IL-6, and indeed other cytokines, by PHA-stimulated secondary human lymphoid tissue suspensions in vitro. They may also partially explain the meagre immunomodulatory effects noted in some DHEA replacement studies in humans.

Adjuvants, Immunologic↗
PubMed2006

Amplification of MET may identify a subset of cancers with extreme sensitivity to the selective tyrosine kinase inhibitor PHA-665752.

The success of molecular targeted therapy in cancer may depend on the selection of appropriate tumor types whose survival depends on the drug target, so-called "oncogene addiction." Preclinical approaches to defining drug-responsive subsets are needed if initial clinical trials are to be directed at the most susceptible patient population. Here, we show that gastric cancer cells with high-level stable chromosomal amplification of the growth factor receptor MET are extraordinarily susceptible to the selective inhibitor PHA-665752. Although MET activation has primarily been linked with tumor cell migration and invasiveness, the amplified wild-type MET in these cells is constitutively activated, and its continued signaling is required for cell survival. Treatment with PHA-665752 triggers massive apoptosis in 5 of 5 gastric cancer cell lines with MET amplification but in 0 of 12 without increased gene copy numbers (P = 0.00016). MET amplification may thus identify a subset of epithelial cancers that are uniquely sensitive to disruption of this pathway and define a patient group that is appropriate for clinical trials of targeted therapy using MET inhibitors.

Antineoplastic Agents↗
PubMed1995

The phytohaemagglutinin (PHA) skin test as an indicator of stress-induced changes in immune reactivity in pigs.

The present study describes two experiments to standardize the phytohaemagglutinin (PHA) skin test as an indicator of lymphocyte reactivity in pigs after exposure to stressful situations in practical pig husbandry. The first experiment was a dose-response experiment. No time dose interaction was found, so the pattern of the reaction was the same for all doses used, although the magnitude of the reaction differed. The second experiment was carried out to determine stress-induced changes in lymphocyte reactivity. One half of a group of 48 pigs was exposed to stress (mixing, moving, and an increased stocking density). The immune reactivity to intradermally injected PHA of stressed animals differed significantly (P < 0.01) from that of unstressed controls. The reaction of stressed animals can be characterized by a delayed reaction with a lower peak. It can be concluded that frequent measurements are preferable to single measurements when the effects of stress on immunological processes are studied.

Animals↗
PubMed1975

Kinetic study of T lymphocytes after sensitization against soluble antigen. III. Potentiation and suppression of the PHA response by antigen-activated lymphocytes of low density.

Lymph node cells of ovalbumin-sensitized rats were separated on the basis of buoyant density into fractions reciprocally enriched in cells responsive to ovalbumin or phytohemagglutinin (PHA). Recombination of high density and low density fractions in varying proportions resulted in potentiation or suppression of the DNA synthetic response to PHA in culture. The response of cultures containing equal numbers of high and low density cells was markedly greater than the sum of the two populations stimulated separately. However, when decreasing numbers of low density cells were cultured with a constant number of high density cells, profound suppression was observed.

Animals↗
PubMed1975

Halothane inhibition of rna and protein synthesis of PHA-treated human lymphocytes.

Cultured human lymphocytes treated with phytohemagglutinin (PAH) ahd higher rates of RNA and protein synthesis, as judged by incorporation of the labelled precursors -3H-URIDINE AND -14C-leucine, than did control cultures without PHA. These cultures were prepared from cells of the same donor, as were a third set of cultures which were equilibrated with 2 per cent halothane. The increased rates of RNA and protein synthesis six and 16 hours after PHA ADDITION WERE INHIBITED BY THE HALOTHANE, MODESTLY AT SIX HOURS AND STRIKINGLY AT 16 HOURS. These experiments provide further evidence that halothane prevents recruitment of resting cells into the active cycle of cell division.

Carbon Radioisotopes↗
PubMed1999

Chemokine receptor-usage of clinical HIV-1 isolates obtained from patients with HIV-1 infection in late clinical stages using PHA-blast.

In the present sudy, chemokine receptor-usage of primary HIV-1 isolates was examined using U87-CD4 cells expressing chemokine receptors CCR3, CCR5 and CXCR4. HIV-1 was isolated from the peripheral blood mononuclear cells (PBMC) and/or plasma of eight HIV-1-infected individuals in late CDC-II and CDC-IV clinical stages using PHA-blast prepared from the PBMC of healthy blood donors. The primary HIV-1 isolates from patients in late CDC-II stage rarely infected monocyte-derived macrophages in the present study, whereas most isolates from patients in the CDC-IV stage infected the macrophages. In the experiments using U87-CD4 cells expressing chemokine receptors, the isolates from patients in the late CDC-II stage infected U87-CD4 cells expressing CXCR4, but not U87-CD4 cells expressing CCR5. In contrast, most isolates from patients in the CDC-IV stage infected both U87-CD4 cells expressing CXCR4 or CCR5. The isolates which infected both U87-CD4 cells were supposed to contain dual tropic HIV-1 or a mixture of CXCR4-tropic and CCR5-tropic HIV-1s. Analysis of the deduced amino acid sequence of the V3 region in proviral env gene showed that the V3 region in U87-CD4 cells infected with CXCR4-tropic HIV-1 isolates was largely different from that in the cells infected with CCR5-tropic isolates, but were highly similar to that in cells infected with dual tropic isolates. These results suggest that PHA-blasts may preferentially support the replication of the CXCR4-tropic and dual tropic HIV-1s, and that CXCR4-tropic and dual tropic HIV-1s are also present in peripheral blood from patients in the late stage of the asymptomatic phase.

Amino Acid Sequence↗
PubMed1977

UVA-induced inhibition of proliferation of PHA-stimulated lymphocytes from humans treated with 8-methoxypsoralen.

Lymphocytes from healthy human donors were used as a model system for studying the combined effect of 8-methoxypsoralen (8-MOP) plus UVA. Two hours after oral administration of therapeutic doses of the drug enough 8-MOP was taken up in vivo by the circulating peripheral lymphocytes to cause significant inhibition of phytohaemagglutinin induced lymphocyte proliferation when the cells were exposed in vitro to UVA irradiation. The inhibition of proliferation as monitored by a reduced 3H-thymidine incorporation into cellular DNA was shown to be UVA-dose dependent. Control cultures of 8-MOP containing lymphocytes which were not UVA irradiated showed normal blast transformation. In lymphocytes obtained from the same donors prior to 8-MOP intake, PHA-induced lymphocyte transformation was not impaired by UVA irradiation. In 8-MOP containing lymphocytes exposed repeatedly to UVA during the 72 h culture period a cumulative effect of irradiation could be observed. A varying sensitivity towards 8-MOP plus UVA was noted when the cells were irradiated at different times after PHA stimulation. The cells were most vulnerable to UVA irradiation during the DNA-synthesis phase of the proliferating lymphocytes. The results suggest that dermal inflammatory infiltrates containing locally proliferating lymphocytes are influenced by systemic photochemotherapy since UVA penetrates well into the dermis.

Cell Cycle↗
PubMed1978

Commercial PHA preparations contain different mitogenic components.

Three commercially available purified phytohaemagglutinin (PHA) preparations have been examined both chemically and biologically. Marked differences were observed in both composition and mitogenic effect on lymphocytes; the existence of at least two distinct mitogenic fractions in PHA was confirmed.

Amino Acids↗
PubMed1979

Restimulation of PPD-stimulated lymphocytes: decreased responsiveness of prestimulated cells to a second challenge with PPD and PHA.

Lymphocytes stimulated with purified protein derivative (PPD) were inhibited in their response to a second stimulation with PPD or phytohaemagglutinin (PHA). The degree of inhibition was related to the PPD concentration during prestimulation, the dose-response curve for inhibition resembling very much that of stimulation. The decreased reactivity was neither due to a toxic effect of PPD nor to altered proliferation kinetics of the prestimulated cells. Lymphocytes preincubated for 6 h or 16 days with PPD were equally refractory, and the non-reactivity persisted even if the cells were incubated without stimulant for 1 week or more. The prestimulated cells were able to suppress the PHA stimulation of fresh lymphocytes. These results indicate that the decreased reactivity of the prestimulated lymphocytes is due to the action of suppressor lymphocytes, generated during the primary stimulation.

Cell Division↗
PubMed1991

The Projections of Mitral Cells from Small Local Regions of the Olfactory Bulb: An Anterograde Tracing Study Using PHA-L (Phaseolus vulgaris Leucoagglutinin).

Numerous anatomical and electrophysiological studies have demonstrated a lack of simple point-to-point topographical relationships between the olfactory bulb and primary olfactory projection areas. They reveal instead, a complex pattern of divergence and convergence. Furthermore, several authors reported that a single mitral cell could project onto different widely spaced cortical regions of the olfactory cortex. In the present study, we attempted to label the projections of a few mitral cells so close together so that they might be assumed to be connected to the same glomerulus, and to determine if these cells had similar patterns of axonal projections. For this purpose small Phaseolus vulgaris leucoagglutinin (PHA-L) injections were performed in the olfactory bulb of adult rats. We found that labelling two to five mitral cells, lying close together in the mitral cell layer, resulted in well-delineated patches of labelled fibres in the cortex. The number of patches was not related to the number of labelled mitral cells but the fibre density in each patch increased with the number of PHA-L filled somata in the olfactory bulb. We conclude that mitral cells lying close together in the mitral cell layer have similar patterns of axonal projections. Functional implications of such an organization in olfactory coding is discussed.

Journal Article↗
PubMed1980

Inhibitory ability of adherent blood cells from patients with chronic myeloid leukaemia on DNA-synthesis in non-adherent leukaemic cells and PHA-stimulated lymphocytes.

Mononuclear blood cells were isolated from patients with different types of leukaemia and studied in vitro with regard to cell functions - adhesiveness, phagocytosis, DNA synthesis and inhibitory effects of adherent cells on non-adherent leukaemic cells and PHA stimulated lymphocytes. Cells from patients with chronic myeloid leukaemia (CML) adhered to the plastic surface of the culture dishes and showed esterase staining reactions as monocytes/macrophages. They showed a normal capacity to ingest Candida albicans, while the digestion capacity appeared reduced. Non-adherent cells from CML showed a high ability to incorporate thymidine, indicating DNA synthesis. Adhesive cells from patients with CML inhibited DNA synthesis in nonadherent CML cells and in PHA-stimulated lymphocytes to about the same extent as adhesive cells from normal donors. Blood cells from acute myeloid leukaemia and chronic lymphocytic leukaemia showed on adhesiveness and a very low spontaneous thymidine incorporation.

Adult↗
PubMed1996

Human pregnancy serum suppresses the proliferative response of lymphocytes to autologous PHA-activated T lymphoblasts.

PROBLEM: We have previously demonstrated that human serum can suppress the proliferative response in autologous mixed lymphocyte reaction (AMLR) in which phytohemagglutinin (PHA)-activated T lymphoblasts act as stimulators (T-TPHA AMLR). The aim of the present work was to determine whether pregnancy serum (PS) possesses an inhibitory capacity similar or different in magnitude. METHODS: Sixteen PS were added to T-TPHA AMLR cultures and the proliferative response was compared with that in the presence of human serum. The effect of PS on the IL-2 dependent proliferation of PHA-activated T Lymphoblasts was examined as well. RESULTS: PS induced a significantly more pronounced suppression of T-TPHA AMLR than human serum (P < 0.05). One PS tested was not inhibitory but rather stimulatory. This PS was obtained from a woman who subsequently had IUGR. The inhibition is related to the existence of a serum inhibitory factor and not to the lack of a serum supporting factor. PS inhibited not only T-TPHA AMLR of the same woman but also T-TPHA AMLR of other individuals as well, implying that the inhibitor is a non-MHC restricted factor. IL-2 dependent cell proliferation was not inhibited by PS, implying that the inhibitor detected in T-TPHA AMLR is not a general cell proliferation inhibitor. CONCLUSIONS: These results suggest that a non-MHC restricted inhibitory factor present in PS may play an important biological role in regulating local immune responses in the fetal-placental unit mediated by autoreactive T cells restricted to autologous activated T lymphocytes.

Antilymphocyte Serum↗
PubMed1986

Immune function in patients with previous yersinia arthritis: lymphocyte responses to PHA and Staphylococcus aureus strain Cowan I.

Evidence has accumulated that, first, polymorphonuclear leukocytes (PMN) and humoral factors such as fragments of complement components may regulate immune response, and second, PMN function is enhanced in HLA-B27-positive subjects. We therefore used a whole-blood culture technique to study lymphocyte proliferation in response to phytohaemagglutinin-P (PHA) in blood samples obtained from patients with previous yersinia arthritis and from healthy subjects with or without HLA-B27. In another series of experiments, mononuclear cells were separated from peripheral blood and lymphocyte responses to Staphylococcus aureus strain Cowan I, a B-cell mitogen in fetal calf serum, and to PHA in pooled normal human serum were determined. The patients and the control subjects were always tested simultaneously. The results showed no significant differences between the subject groups. This suggests that humoral factors and enhanced neutrophil function do not exert remarkable effects on in vitro lymphocyte responses to mitogens in HLA-B27-positive subjects.

Arthritis, Infectious↗
PubMed1992

Beta-endorphin concentrations in resting peripheral mononuclear cells and after treatment with PHA or serotoninergic drugs in human aging, Alzheimer's disease, and Down's syndrome.

We measured the concentrations of beta-endorphin in resting peripheral blood mononuclear cells obtained from normal subjects of different ages and from age-matched patients with Down's syndrome or Alzheimer's disease. We also measured beta-endorphin concentrations in peripheral blood mononuclear cells obtained from subjects of different ages after treatment with PHA or serotoninergic drugs. The results show that in normal subjects the concentrations of the peptide increase after 30 years of age and remain constant up to 99 years. After stimulation with PHA, the release of beta-endorphin in cells from subjects older than 30 years increases, leading to a decrease in contents, whereas it is unchanged in younger subjects. In patients with Down's syndrome or Alzheimer's disease, beta-endorphin concentrations in peripheral blood mononuclear cells behave similarly to those in age-matched normal subjects. Treatment in vivo with the serotoninergic agonist chlorimipramine induces an increase in beta-endorphin concentrations in peripheral blood mononuclear cells that is significantly greater in subjects over 30 years old than in younger subjects.

Adult↗
PubMed2004

Environmentally induced foregut remodeling by PHA-4/FoxA and DAF-12/NHR.

Growth and development of the Caenorhabditis elegans foregut (pharynx) depends on coordinated gene expression, mediated by pharynx defective (PHA)-4/FoxA in combination with additional, largely unidentified transcription factors. Here, we used whole genome analysis to establish clusters of genes expressed in different pharyngeal cell types. We created an expectation maximization algorithm to identify cis-regulatory elements that activate expression within the pharyngeal gene clusters. One of these elements mediates the response to environmental conditions within pharyngeal muscles and is recognized by the nuclear hormone receptor (NHR) DAF-12. Our data suggest that PHA-4 and DAF-12 endow the pharynx with transcriptional plasticity to respond to diverse developmental and physiological cues. Our combination of bioinformatics and in vivo analysis has provided a powerful means for genome-wide investigation of transcriptional control.

Animals↗
PubMed1995

Regulated expression of the Alcaligenes eutrophus pha biosynthesis genes in Escherichia coli.

A novel poly-beta-hydroxybutyrate (PHB) production system in which the expression and gene dosage of the Alcaligenes eutrophus pha biosynthetic operon were effectively regulated by cultivation temperature was constructed in Escherichia coli. The pha operon was fused to the negatively regulated tac promoter and cloned into a vector in which the copy number is temperature dependent. A two-phase process was employed to produce PHB during fed-batch growth. In the growth phase, the culture was maintained at a low temperature. Under this condition, the plasmid copy number was depressed and the number of LacI proteins was sufficient to repress tacupha transcription. The production phase was initiated by temperature upshift. At the elevated temperature, the number of plasmids surpassed the number of LacI repressors, which resulted in rapid induction of tacupha transcription, synthesis of poly-beta-hydroxyalkanoate-specific proteins, and polymer synthesis. During the production phase, the PHB production rate was 1.07 g of PHB liter-1 h-1 under optimized conditions. This rate is comparable to that of bacteria which naturally produce this polymer.

Alcaligenes↗
PubMed1995

Role of fadR and atoC(Con) mutations in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesis in recombinant pha+ Escherichia coli.

Recombinant Escherichia coli fadR atoC(Con) mutants containing the polyhydroxyalkanoate (PHA) biosynthesis genes from Alcaligenes eutrophus are able to incorporate significant levels of 3-hydroxyvalerate (3HV) into the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)]. We have used E. coli fadR (FadR is a negative regulator of fatty acid oxidation) and E. coli atoC(Con) (AtoC is a positive regulator of fatty acid uptake) mutants to demonstrate that either one of these mutations alone can facilitate copolymer synthesis but that 3HV levels in single mutant strains are much lower than in the fadR atoC(Con) strain. E. coli atoC(Con) mutants were used alone and in conjunction with atoA and atoD mutants to determine that the function of the atoC(Con) mutation is to increase the uptake of propionate and that this uptake is mediated, at least in part, by atoD+. Similarly, E. coli fadR mutants were used alone and in conjunction with fadA, fadB, and fadL mutants to show that the effect of the fadR mutation is dependent on fadB+ and fadA+ gene products. Strains that were mutant in the fadB or fadA locus were unable to complement a PHA biosynthesis pathway that was mutant at the phaA locus (thiolase), but a strain containing a fadR mutation and which was fadA+ fadB+ was able to complement the phaA mutation and incorporated 3HV into P(3HB-co-3HV) to a level of 29 mol%.

Acetyl Coenzyme A↗