Targeting Homologous Recombination in Notch-Driven C. elegans Stem Cell and Human Tumors

Mammalian NOTCH1-4 receptors are all associated with human malignancy, although exact roles remain enigmatic. Here we employ glp-1(ar202), a temperature-sensitive gain-of-function C. elegans NOTCH mutant, to delineate NOTCH-driven tumor responses to radiotherapy. At ≤20°C, glp-1(ar202) is wild-type, whereas at 25°C it forms a germline stem cell⁄progenitor cell tumor reminiscent of human cancer. We identify a NOTCH tumor phenotype in which all tumor cells traffic rapidly to G2⁄M post-irradiation, attempt to repair DNA strand breaks exclusively via homology-driven repair, and when this fails die by mitotic death. Homology-driven repair inactivation is dramatically radiosensitizing. We show that these concepts translate directly to human cancer models.     

A New Real-Time PCR for the Detection of Plasmodium ovale wallikeri

It has been proposed that ovale malaria in humans is caused by two closely related but distinct species of malaria parasites: P. ovale curtisi and P. ovale wallikeri. We have extended and optimized a Real-time PCR assay targeting the parasite’s small subunit ribosomal RNA (ssrRNA) gene to detect both these species. When the assay was applied to 31 archival blood samples from patients diagnosed with P. ovale, it was found that the infection in 20 was due to P. ovale curtisi and in the remaining 11 to P. ovale wallikeri. Thus, this assay provides a useful tool that can be applied to epidemiological investigations of the two newly recognized distinct P. ovale species, that might reveal if these species also differ in their clinical manifestation, drugs susceptibility and relapse periodicity. The results presented confirm that P. ovale wallikeri is not confined to Southeast Asia, since the majority of the patients analyzed in this study had acquired their P. ovale infection in African countries, mostly situated in West Africa.     

Induction of porphobilinogen oxygenase and porphobilinogen deaminase in rat blood under conditions of erythropoietic stress

Porphobilinogen is the substrate of two enzymes: porphobilinogen deaminase and porphobilinogen-oxygenase. The first one transforms it into the metabolic precursors of heme and the second diverts it from this metabolic pathway by oxidizing porphobilinogen to 5-oxopyrrolinones. Rat blood is devoid of porphobilinogen-oxygenase under normal conditions while it carries porphobilinogen-deaminase activity. When the rats were submitted to hypoxia (p_O2 = 0.42 atm) for 18 days, the activity of porphobilinogen-oxygenase appeared at the tenth day of hypoxia and reached the maximum at the 14–16th day. It decreased to a half after 2 days (half-life of the enzyme) and disappeared after 4 days of return to normal oxygen pressure. Porphobilinogen-deaminase activity increased after the first day of hypoxia, reached a maximum at the 14–16th day and did not decrease to normal values until the 15th day after return to normal oxygen pressure. The activities of both prophobilinogen-oxygenase and porphobilinogen-deaminase were induced by administration of erythropoietin. When rats were made anaemic with phenylhydrazine, porphobilinogen-oxygenase activity also appeared in the blood cells. Although the reticulocyte concentration was higher when compared to that obtained under hypoxia, the activities of the oxygenase obtained under both conditions were comparable. Porphobilinogen-deaminase activity was always closely related to the reticulocyte content. The appearance of porphobilinogen-oxygenase under the described erythropoietic conditions was due to a de novo induction of the enzyme, as shown by its inhibition with actinomycin D and cycloheximide. Porphobilinogen-oxygenase as well as porphobilinogen-deaminase were present in the rat bone marrow under normal conditions. Their activities increased in phenylhydrazine treated rats. The properties and kinetics of porphobilinogen-oxygenase from the rat blood and bone marrow were determined and found to differ in several aspects.     

Stimulation of endothelial cell binding of lymphocytes by tumor necrosis factor

Lymphokines and monokines have been reported to affect endothelial cell (EC) morphology and function. In experiments here described, we have demonstrated that recombinant tumor necrosis factor (TNF) stimulates the adhesion of T lymphocytes to confluent monolayers of human umbilical vein EC. The increase in adhesion induced by TNF was EC-specific inasmuch as preincubation of the lymphocytes with TNF did not alter binding, and preincubation of human dermal fibroblasts with TNF did not increase their inherently low adhesiveness for lymphocytes. Stimulation of T-EC binding occurred after treatment of the EC with as little as 0.01 U/ml (1 pg/ml) of TNF. In kinetic experiments, preincubation of EC with TNF for 4 hr resulted in optimal adhesion. TNF-treated EC retained their increased adhesiveness after fixation with paraformaldehyde, suggesting that TNF stimulated binding by increasing the expression or accessibility of EC surface receptors for lymphocytes. Although antibodies to the lymphocyte function-associated antigen 1 alpha- or beta-chains on the T cell markedly inhibited unstimulated T-EC binding, such antibodies had no effect on the increase in EC adhesiveness induced by TNF, indicating that the increased binding resulted from the generation of an alternate binding receptor on the EC membrane. These findings provide additional evidence that cytokines participate in the mobilization of mononuclear cells in the chronic inflammatory reaction by stimulation of the adhesiveness of endothelium for circulating lymphocytes.     

Superinduction of T lymphocyte-endothelial cell (EC) binding by treatment of EC with interleukin 1 and protein synthesis inhibitors

We have previously reported that marked enhancement of the in vitro binding of lymphocytes to endothelial cell (EC) monolayers is observed after stimulation of the EC with interleukin 1 (IL 1). To determine whether new protein synthesis was required for this effect of IL 1, EC were incubated with IL 1 in the presence of cycloheximide or puromycin. Three different effects of these protein synthesis inhibitors on T-EC binding were observed. First, preincubation of the EC with both IL 1 and an inhibitor blocked the increase in binding if the inhibitor was present during both the preincubation and the 1 hr duration of the T-EC binding assay, suggesting that new protein synthesis is required for the enhancement of T-EC adhesion by IL 1. Second, preincubation of the EC with low doses of the inhibitors (0.1 to 1 microgram/ml) in the absence of IL 1 consistently increased T-EC binding, even if the inhibitors were present during the T-EC adhesion assay; in addition, the inhibitors additionally increased the stimulatory effect of IL 1 if the EC were washed free of the inhibitor before the assay step. The binding-enhancing effect of low concentrations of cycloheximide could be inhibited by an antibody to the CDw18 complex on the T cell, suggesting an up-regulation of the ligand on the EC involved in CDw18-dependent T cell adhesion. Third, higher concentrations of the inhibitors (3 to 10 micrograms/ml) were toxic for the EC in the presence of IL 1, possibly due to the combined blocking effect of IL 1 and inhibitors on EC protein synthesis.     

Molecular characterization of β-thalassemia in Czechoslovakia

Summary We have identified different -thalassemia mutations in 93 members of 34 families of Czech or Slovakian descent using gene amplification, hybridization with specific ³²P-labeled oligonucleotide probes, sequencing of amplified DNA, and gene mapping. The GA mutation at IVS-I-1 was found in 18 families; other Mediterranean mutations were IVS-II-1 (GA), IVS-II-745 (CG), IVS-I-110 (GA), and codon 39 (CT); these were present in 9 additional families. The GT mutation at codon 121, known to cause Heinzbody -thalassemia, was present in 3 families, and the frameshift at codons 82/83 (-G), first described in the Azerbaijanian population, in 2 families. A newly discovered allele was a frameshift at codons 38/39 (-C). One -thalassemia allele was incompletely characterized. We observed in 2 families a TC mutation at position +96 UTR (untranslated region) relative to the termination codon; this mutation likely is a rare polymorphism, -Thalassemia was rare; only one person carried the -^3.7 heterozygosity, and one other had a yet to be identified -thalassemia-1, while seven had the ^{anti 3.7} triplication.     

Interleukin 1 increases the binding of human B and T lymphocytes to endothelial cell monolayers

Lymphocyte binding to specialized high-endothelial venules (HEV) in lymph nodes and Peyer's patches is the first step in normal lymphocyte emigration and recirculation. The development and maintenance of HEV in these lymphoid organs are thought to be immunologically controlled. Because postcapillary venules in chronic inflammatory tissue often resemble the HEV of lymphoid tissue and may also be a site of lymphocyte emigration, examination of the effects of immunologic and inflammatory mediators on endothelial cells (EC) may provide important information about the physiology of both normal lymphocyte recirculation and chronic inflammation. It is reported here that treatment of human umbilical vein EC monolayers in vitro with affinity-purified human interleukin 1 (IL 1) markedly enhances the binding of both B and T lymphocytes. Increased binding was observed within 1 h of treatment of EC with as little as 0.04 U/ml IL 1. This effect of IL 1 was EC-specific, because pretreatment of T cells or human skin fibroblasts with IL 1 did not increase the binding of lymphocytes. Stimulation of binding required active EC metabolism because incubation of EC with IL 1 at 4 degrees C, or prior fixation of EC, prevented enhanced binding. The action of IL 1 was not associated with EC damage. The secretion of IL 1 by macrophages and perhaps other cells in inflammatory lesions may exert a positive feedback signal on EC to enhance further emigration of lymphocytes into the inflammatory focus.     

Rapid Activation of Tyrosine Hydroxylase in Response to Nerve Growth Factor

Abstract: Nerve growth factor protein (NGF) was found to rapidly promote the activation of tyrosine hydroxylase in cultured rat PC 12 pheochromocytoma cells. PC 12 cultures were exposed to NGF for periods of less than 1 h and the soluble contents of homogenates prepared from the cells were assayed for tyrosine hydroxylase activity. Under these conditions, the specific enzymatic activity was increased by 60 ± 10% (n = 13) in comparison with that in untreated sister cultures. The increase was half maximal by 2–5 min of exposure and at NGF concentrations of about 10 ng/ml (0.36 n M ). Antiserum against NGF blocked the effect. Tyrosine hydroxylase activity could also be rapidly increased by NGF in cultures of PC12 cells that had been treated with the factor for several weeks in order to produce a neuron-like phenotype. This was achieved by withdrawing NGF for about 4 h and then readding it for 30 min. The NGF-induced increase of tyrosine hydroxylase activity in PC12 cultures was not affected by inhibition of protein synthesis and therefore appeared to be due to activation of the enzyme. Kinetic experiments revealed that NGF brought about no change in the apparent K_m of the enzyme for tyrosine or for co-factor (6-methyltetrahydropteridine), but that it did significantly increase the apparent maximum specific activity of the enzyme. These observations suggest that NGF (perhaps released by target organs) could promote a rapid and local enhancement of noradrenergic transmission in the sympathetic nervous system.     

Substance P affects the GABAergic system in the hypothalamo-pituitary axis

In the present work we examined the effect of the neutralization of endogenous substance P by the administration of an anti-substance P serum (ASPS) on GABA concentration in the anterior pituitary in hyperprolactinemic conditions induced by 5-hydroxytryptophan or by grafting anterior pituitaries. ASPS reduced the increase in the anterior pituitary GABA concentration induced by hyperprolactinemia. In vitro experiments showed that substance P inhibited K⁺-evoked GABA efflux from hypothalamic fragments and decreased GABA concentration in the anterior pituitary but ASPS increased it. Our results demonstrate that substance P modifies hypothalamic GABA release and anterior pituitary GABA concentration and suggest that an interaction exists between substance P and GABA.