Characteristics of a tandem system of ionization chambers in X-ray beams, mammography level

Two parallel plate ionization chambers (inserted in slab phantoms) recently assembled at IPEN were studied in relation to their operational characteristics for use in quality control of X-ray beams, mammography level. The chambers present only one difference: one has an inner collecting electrode made of graphite and the other, of aluminum. These chambers make up a tandem system, which may be employed to verify X-ray beams energy constancy, by the confirmation of half-value layers and effective energies, and to determinate air kerma rates. The chambers presented good results for the operational tests, as recommended internationally.

Purification, amino-acid sequence and partial characterization of two toxins with anti-insect activity from the venom of the South American scorpion Tityus bahiensis (Buthidae)

We report here the isolation by a two-step chromatographic procedure of two new toxins from the South American scorpion Tityus bahiensis. Their amino-acid sequences and some of their biological features were established. The two toxins have different biological properties. Toxin TbIT-I had almost no activity or pharmacological effects in vertebrate tissues whereas it was lethal to house flies (LD50 80.0 ng/house fly). In contrast, Tb2-II was active against both mammals (intracerebroventricular injection of 100 ng/mouse was lethal) and insects (LD50 40.0 ng/house fly). The amino-acid sequences of these toxins were established and found to be similar (60-95%) to previously described beta-toxins from the Tityus genus. Based on the available comparative information, this study attempts identify possible structure-function relationships that may be responsible for the differences in bioactivity displayed by these toxins.

Screening of expression libraries using ELISA: identification of immunogenic proteins from Tityus bahiensis and Tityus serrulatus venom

The present report describes the use of ELISA with cDNA expression libraries in the identification of immunogenic proteins. The methodology described was applied using libraries constructed with mRNA isolated from Tityus serrulatus and Tityus bahiensis venom glands. In addition we describe for the first time the sequence of a neurotoxin from Tityus bahiensis venom gland named TbTx5 whose amino acid sequencing showed 93% similarity with the Tityus bahiensis TbTx IV-5 neurotoxin. The methodology described can be used for the generation of an immunogenic bank in order to contribute to genome and proteome projects.

Immunochemotherapy in American cutaneous leishmaniasis: immunological aspects before and after treatment

In this study, we evaluated the immune response of patients suffering from cutaneous leishmaniasis treated with two distinct protocols. One group was treated with conventional chemotherapy using pentavalent antimonium salts and the other with immunochemotherapy where a vaccine against cutaneous leishmaniasis was combined with the antimonium salt. Our results show that, although no differences were observed in the necessary time for complete healing of the lesions between the two treatments, peripheral blood mononuclear cells from patients treated by chemotherapy showed smaller lymphoproliferative responses at the end of the treatment than those from patients in the immunochemotherapy group. Furthermore, IFN-gamma production was also different between the two groups. While cells from patients in the chemotherapy group produced more IFN-gamma at the end of treatment, a significant decrease in this cytokine production was associated with healing in the immunochemotherapy group. In addition, IL-10 production was also less intense in this latter group. Finally, an increase in CD8+ -IFN-gamma producing cells was detected in the chemotherapy group. Together these results point to an alternative treatment protocol where healing can be induced with a decreased production of a potentially toxic cytokine.

Coinfection with Toxoplasma gondii inhibits antigen-specific Th2 immune responses, tissue inflammation, and parasitism in BALB/c mice infected with Leishmania major

Lesion size, cellular infiltration, and tissue parasitism in the footpads of BALB/c mice infected with Leishmania major were all dramatically inhibited during acute but not chronic infection with Toxoplasma gondii. Similarly, acute but not chronic toxoplasmosis at the time of infection with L. major had a strong inhibitory effect on development of acquired immune responses mediated by Th2 lymphocytes. In contrast, no major changes in Leishmania-specific Th1-mediated responses were observed in mice coinfected with T. gondii.

Metabolic abnormalities in hypertension

Hypertension is often accompanied by a host of metabolic defects. Investigations have shown an association between insulin resistance, hyperinsulinemia, central/visceral obesity, and hypertension. Recent interest has focused on the fact that untreated hypertensive individuals have compensatory hyperinsulinemia, are resistant to insulin-mediated glucose uptake, and frequently have coexisting lipid abnormalities. Data from prospective studies appear to indicate that fasting hyperinsulinemia is an independent predictor of coronary artery disease. Additionally, there is evidence that hyperinsulinemia and diabetes eliminate the normal sex differences in the prevalence of coronary artery disease. The salutary effects of ovarian hormones on the prevalence of hypertension and cardiovascular disease in postmenopausal women are well established. Hyperandrogenism, in particular elevated serum levels of dehydroepiandrosterone sulfate, is believed to be a risk factor promoting sex-specific impairments of glucose and lipid metabolism, obesity, and hypertension in women. Clinical and epidemiologic evidence have linked elevated blood pressure to disturbances in lipoprotein metabolism, fibrinolytic activity, plasminogen activation inhibitor levels, and dyslipidemia. This review briefly presents the current understanding of various metabolic disturbances associated with hypertension, the pathophysiologic mechanisms involved, and the significance of the interplay between them relative to the complications of this disease.

Effects of antihypertensive therapy on platelet cytosolic calcium responses to low density lipoprotein cholesterol

This study examines the effects of antihypertensive therapy on platelet cytosolic calcium [Ca2+]i responses to low-density lipoprotein cholesterol (LDL) and vasopressin (AVP) in 15 patients (50-80 years) participating in the Hypertension Optimal Treatment International Study. All patients (diastolic blood pressure (DBP) > or = 100 mm Hg and < or = 115 mm Hg) were treated with the calcium antagonist felodipine (10 mg p.o.) with or without addition of enalapril (up to 20 mg daily as needed) to lower diastolic pressures to < 85 mm Hg. This antihypertensive therapy lowered DBP (104 +/- 0.8 to 78 +/- 1.6 mm Hg, P < 0.0001), but had no effect on basal [Ca2+]i or AVP-stimulated [Ca2+]i responses. Basal platelet [Ca2+]i following antihypertensive therapy (49 +/- 3.4 ng/ml) were not different from those prior to therapy (52 +/- 4.7 ng/ml). Additionally, [Ca2+]i responses to AVP following therapy (554 +/- 74 units) were not different from those prior to treatment (595 +/- 49 units). Following antihypertensive therapy, [Ca2+]i responses to 200 micrograms/ml of LDL were decreased fourfold (P < 0.05). These results suggest that antihypertensive therapy with a calcium channel blocker may potentially impact the atherogenic process by reducing the platelet [Ca2+]i rise, and potentially the aggregatory response, to LDL.

IL-12 is required for natural killer cell activation and subsequent T helper 1 cell development in experimental leishmaniasis

Infection of mice with the protozoan Leishmania major is an established in vivo model for the definition of factors that contribute to CD4+ T helper cell subset development. In the current study, a central role for IL-12 in directing both the innate and adaptive immune responses to L. major is established. We show that in vivo neutralization of IL-12 eliminates the NK cell cytotoxic response and IFN-gamma production by lymph node cells from 2-day L. major-infected C3H mice. Moreover, anti-IL-12 treatment abrogated Th1 cell development and enhanced Th2 cell development. Consistent with these results, elevated IL-12 p40 production and an increase in the number of IL-12 p40-producing cells were observed within 1 day of infection in C3H mice. Because BALB/c mice lack an early NK cell response or a Th1-type immune response after L. major infection, we investigated the possibility that they had a defect in the ability to produce IL-12. Surprisingly, L. major infection stimulated IL-12 p40 production in BALB/c mice early after infection. Further studies suggest that BALB/c mice are unable to generate an early IFN-gamma response because of the simultaneous production of IL-12 and cytokines that inhibit IL-12 function, such as TGF-beta, IL-4, and IL-10. Together, these data show that IL-12 regulates the immune response to L. major, but that even when IL-12 is induced, Th1 cell development may be interrupted by simultaneous production of inhibitory cytokines.

IL-12 is required for natural killer cell activation and subsequent T helper 1 cell development in experimental leishmaniasis

Infection of mice with the protozoan Leishmania major is an established in vivo model for the definition of factors that contribute to CD4+ T helper cell subset development. In the current study, a central role for IL-12 in directing both the innate and adaptive immune responses to L. major is established. We show that in vivo neutralization of IL-12 eliminates the NK cell cytotoxic response and IFN-gamma production by lymph node cells from 2-day L. major-infected C3H mice. Moreover, anti-IL-12 treatment abrogated Th1 cell development and enhanced Th2 cell development. Consistent with these results, elevated IL-12 p40 production and an increase in the number of IL-12 p40-producing cells were observed within 1 day of infection in C3H mice. Because BALB/c mice lack an early NK cell response or a Th1-type immune response after L. major infection, we investigated the possibility that they had a defect in the ability to produce IL-12. Surprisingly, L. major infection stimulated IL-12 p40 production in BALB/c mice early after infection. Further studies suggest that BALB/c mice are unable to generate an early IFN-gamma response because of the simultaneous production of IL-12 and cytokines that inhibit IL-12 function, such as TGF-beta, IL-4, and IL-10. Together, these data show that IL-12 regulates the immune response to L. major, but that even when IL-12 is induced, Th1 cell development may be interrupted by simultaneous production of inhibitory cytokines.

Switch from a type 2 to a type 1 T helper cell response and cure of established Leishmania major infection in mice is induced by combined therapy with interleukin 12 and Pentostam

Successful treatment in allergic, autoimmune, and infectious diseases often requires altering the nature of a detrimental immune response mediated by a particular CD4+ T helper (Th) cell subset. While several factors contribute to the development of CD4+ Th1 and Th2 cells, the requirements for switching an established response are not understood. Here we use infection with Leishmania major as a model to investigate those requirements. We report that treatment with interleukin 12 (IL-12), in combination with the antimony-based leishmanicidal drug Pentostam, induces healing in L. major-infected mice and that healing is associated with a switch from a Th2 to a Th1 response. The data suggest that decreasing antigen levels may be required for IL-12 to inhibit a Th2 response and enhance a Th1 response. These observations are important for treatment of nonhealing forms of human leishmaniasis and also demonstrate that in a chronic infectious disease an inappropriate Th2 response can be switched to an effective Th1 response.

Infection with Leishmania major induces interleukin-12 production in vivo

Experimental infections of mice with the protozoan parasite Leishmania major provide an excellent model for defining the conditions required for generation of CD4+ Th1 and Th2 cells in vivo. Since interleukin-12 (IL-12) has been implicated in the development of Th1 cells, we investigated whether L. major stimulates IL-12 production in vitro or in vivo. Surprisingly, macrophages cultured in vitro failed to produce IL-12 following L. major infection. In contrast, lymph node cells from C3H mice infected for 2 days with L. major produced elevated levels of IL-12. In order to determine if the inability to stimulate IL-12 production was limited to in vitro infections, we infected macrophages in vivo by inoculating L. major into the peritoneal cavity. Peritoneal cells isolated 24 h later exhibited a significant increase in the number of cells producing IL-12. In addition, supernatants harvested from these cells following culture contained elevated levels of IL-12. These data indicate that L. major infection induces increased IL-12 production in mice.

The adjuvant effect of interleukin-12 in a vaccine against Leishmania major

Protection induced by vaccination depends on the capacity of the vaccine to elicit an appropriate immune response. In leishmaniasis, protection requires leishmanial-specific CD4+ T helper (TH) cells. Vaccination of BALB/c mice with leishmanial antigens and interleukin-12 (IL-12) promoted the development of leishmanial-specific CD4+ TH1 cells. These mice were resistant to subsequent infection with Leishmania major. Thus, IL-12 is an effective adjuvant for the initiation of protective cell-mediated immunity against leishmaniasis and may be an important component in other vaccines that need to induce cell-mediated immunity.

Immune responses associated with susceptibility of C57BL/10 mice to Leishmania amazonensis

Leishmaniae are protozoans which, depending upon both the host and parasite species, can cause either a healing or nonhealing infection. While C57BL/10 mice are able to heal following infection with Leishmania major, they fail to heal following infection with Leishmania amazonensis. In order to address the role of Th1 and Th2 cell responses in the outcome of these infections in C57BL/10 mice, gamma interferon (IFN-gamma) and interleukin-4 (IL-4) production was assessed. While cells from L. major-infected C57BL/10 mice produced high levels of IFN-gamma, cells from L. amazonensis-infected animals produced little or no IFN-gamma. On the other hand, IL-4 was produced only by cells from L. amazonensis-infected C57BL/10 mice, but this production was restricted to the first few weeks of infection. Later in infection, when lesions were evident, no IL-4 was detected. Treatment of BALB/c mice with a monoclonal antibody (11B11) directed against IL-4 induced a dramatic reduction in L. amazonensis lesions. This reduction was associated with a decrease in IL-4 levels and an increase in IFN-gamma production. However, only a slight reduction in lesion sizes and parasite numbers was observed when anti-IL-4-treated C57BL/10 mice were infected with L. amazonensis. These results suggest that IL-4 may have an important role in mediating susceptibility to L. amazonensis in BALB/c mice, as previously demonstrated for L. major. More importantly, however, the data suggest that susceptibility to L. amazonensis in C57BL/10 mice is due to the absence of a Th1 cell response, rather than to the presence of a Th2 cell response.

Immune responses and protection induced in mice by an industrialized vaccine against American cutaneous leishmaniasis

An industrialized vaccine against American cutaneous leishmaniasis was compared to a laboratory made vaccine in its ability to induce cellular and humoral immune responses in mice. No differences were observed between seric IgG levels or lymphoblastic proliferation response of mice immunized with either vaccine. Antigenic composition, evaluated by SDS-PAGE, was identical in both preparations. Protection induced in mice against a challenge with infective parasites was also compared. The level of protection obtained with the industrialized vaccine was comparable to that induced by the laboratory made preparation. The results showed that the industrialization process did not alter the efficacy of the vaccine.

Evidence for the occurrence of LDL receptors in extracts of schistosomula of Schistosoma mansoni

Schistosomula of Schistosoma mansoni were shown to contain proteins on their surface membranes which bind iodinated human low density lipoproteins (125I-LDL). Treatment of the parasites with trypsin decreased the binding in comparison with untreated controls. Membrane-bound, acetone-insoluble proteins were extracted from the schistosomula with Triton X-100 and the extract in liposome form was incubated with 125I-LDL at room temperature. After incubation a complex was formed between the proteins present in the extract and 125I-LDL, as shown by a filter binding assay. 125I-LDL binding to filters was proportional to the amount of protein in the extract; it was inhibited by unlabelled LDL and VLDL and by EDTA. Binding of 125I-LDL to proteins present in the liposome suspension containing the Triton X-100 extract followed saturation kinetics, indicating the occurrence of receptors for lipoproteins in the extract.