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The aim of the project was to determine whether the rate of contaminant blood cultures could be reduced by using a team of dedicated phlebotomists. Comparisons were made between adult patients requiring blood cultures for suspected bacteremia on medical and surgical units before and after the introduction and withdrawal of a dedicated blood culture team. The results showed that a significant reduction in the contaminant blood culture rate was achieved by the blood culture team (P < 0.001; chi(2) test). Therefore, in our experience, the rate of contaminant blood cultures can be reduced in a teaching hospital by using a team of dedicated phlebotomists. Calculations made with our data and those published by others suggest that cost savings from reducing false-positive blood cultures are greater than the cost of the blood culture team.

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The use of computed tomography (CT) in the management of patients who are hemodynamically stable with symptoms suggestive of ruptured abdominal aortic aneurysm and in hemodynamically unstable patients without palpable or known aortic aneurysms was analyzed in a retrospective study. One hundred forty-two CT scans were performed; 48 patients had abdominal aortic aneurysms and 35 had no evidence of rupture or retroperitoneal blood. Ten patients had CT scans that showed evidence of rupture, and three patients had CT scans that were thought to be indeterminate for rupture, probably inflammatory. Forty patients underwent laparotomy. Excluding the three patients with inflammatory aneurysms, the results of CT scanning were compared with the findings at laparotomy. The sensitivity of CT scanning for the diagnosis of retroperitoneal blood in the presence of abdominal aortic aneurysm was 77% and the specificity was 100%, with an overall accuracy of 92%. An algorithm for the management of the patient with symptoms suggestive of a ruptured aneurysm is presented.

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A technique has been described to salvage upper arm graft fistulas using expanded polytetrafluoroethylene grafts by subcutaneous extension to the infraclavicular axillary vein. The axillary vein is exposed through an infraclavicular incision near the lateral end of the clavicle by splitting the pectoralis major muscle and by dividing or retracting the pectoralis minor muscle medially. A new segment of polytetrafluoroethylene graft is anastomosed to the axillary vein, and then to the old graft segment. This technique was employed in six patients over a 12 month period, with a 24 month graft patency rate of 84 percent. The advantage over a new access graft is immediate hemodialysis through a puncture of the preserved arterial limb of the polytetrafluoroethylene graft.

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Aortocaval fistulization is usually manifested by signs of rupture of an aneurysm or of the large fistula. Absence of symptoms is unusual with this rare complication. Two cases of asymptomatic aortocaval fistula are presented. An awareness of this possibility should facilitate management when unexpected venous bleeding is encountered.

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Leishmaniasis is an intracellular protozoal infection for which host defense is believed to depend on cellular immune mechanisms. The in vitro proliferative responses of lymphocytes from patients with leishmaniasis and from control subjects to leishmanial antigens were examined. Only lymphocytes from patients responded to 1 microgram of leishmanial antigen/ml, whereas both patient and control lymphocytes responded to 10 micrograms/ml. The nonspecific responses were most likely not due to a mitogenic component in the antigen preparation because cord blood lymphocytes failed to respond at all concentrations of antigen tested. Both specific and nonspecific responses to leishmanial antigens were elicited in purified populations of thymus-derived (T) cells. This lymphocyte proliferation assay can be applied to the assessment of antigen-specific responsiveness of T cells from patients who represent the spectrum of host defense against leishmaniasis.

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Antigen preparations derived from Plasmodium falciparum-infected erythrocytes (but not from uninfected erythrocytes) can stimulate the in vitro proliferation of peripheral blood lymphocytes from malaria-sensitized as well as nonsensitized donors. The possibility that the nonspecific responses might be due to a parasite-derived B-cell mitogen has been previously suggested since polyclonal hypergammaglobulinemia is a frequent accompaniment of malaria infection. To test this hypothesis, we investigated the in vitro proliferative responses of purified T- and B-cell populations to malaria antigens. T but not B cells responded to the antigens. The addition of small numbers of T cells restored the ability of purified B cells to respond to lectin mitogens but not to malaria antigens. Falciparum malaria infection was associated with an increase in T-cell but not in B-cell proliferation in vivo, as assessed by the spontaneous tritiated thymidine incorporation of lymphocytes during a brief incubation in vitro. Our observations suggest that extracts of malaria parasites do not contain a B-cell mitogen but are antigenic as well as mitogenic for T cells.

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Previously, 10 BALB/c T cell lines (Thy 1.2+, Ig-) were shown to express different combinations of Ly 1 and Ly 2 antigens. The possible immunologic function(s) of these tumor cells was determined by investigating the effects of these cells on the responses to mitogens, the mixed lymphocyte response (MLR), and the generation of cell-mediated lysis (CML) by normal spleen cells. Five T cell lines, P1798 and BALENTL 3, 5, 8, and 9, continued to synthesize DNA after exposure to large doses of irradiation. Only BALENTL 4, 6, 7, and 14 (Ly 1-(2+)) and BALENTL 13 (Ly 1+(2-)) were radiosensitive and therefore amenable to study. BALENTL 4 and 14 gave significant suppression of the MLR between BALB/c and C57BL/6; BALENTL 14 also inhibited the generation of BALB/c effector cells against C57BL/6 spleen cells. None of these T cell lines had any effect on the proliferative response of BALB/c spleen cells induced by concanavalin A. However, there was approximately 50% suppression of the phytohemagglutinin response of BALB/c spleen cells by BALENTL 14.

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The kinetics of various specific and nonspecific immunologic responses were examined in BALB/c mice infected with 17X nonlethal Plasmodium berghei yoelii (a self-limiting infection). The sequence of events after infection was characterized by rapid sensitization of splenic T cells to malaria antigen and polyclonal B cell activation, followed by a period of depressed splenic proliferative responses in vitro to mitogens (PHA and LPS) and malaria (specific) antigen. At the same time, suppressed primary in vitro splenic PFC responses to trinitrophenyl-aminoethylcarbamylmethyl-Ficoll (TNP-F) were seen. This suppression was an active process requiring adherent cells. During this period, levels of antimalarial antibody also increased exponentially. As the infection was cleared, splenic malaria antigen-specific proliferative responses were again observed and splenic PFC and in vitro mitogen responses returned to preinfection levels after variable periods of time. Both splenic proliferative responses to malaria antigen and antimalarial antibody responses remained persistently elevated. In addition, some responses were examined in mice infected with 17X lethal P.b. yoelii (a fatal infection); in comparison to the early responses of mice infected with the nonlethal substrain, there was a decrease and delay in the development of a splenic T cell response to malaria antigen and a blunted antimalarial antibody response.

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Transplanted lymphomas (Thy 1.2+, Ig-) of BALB/c mice, induced by the injection of 1-ethyl-1-nitrosourea, were adapted for growth as in vitro lines to provide potential tools for investigation of T lymphocyte differentiation and functions. All these tissue culture lines maintained the same pattern of surface differentiation antigens (Ly, TL, and Thy-1 antigens) as they had expressed during in vivo passages: BALENTL 13 was Thy 1.2+, TL.2-, and Ly 1+2-. BALENTL 3, 4, 5, 6, 7, 8, and 14 were Thy 1.2+, TL.2+, and Ly 1-2+. P1798 and BALENTL 9 were Thy 1.2+, TL.2+, and Ly 1-2+. There were various levels of terminal transferase activity present among these T cell tumor lines. The range of variation was from 4.6 units/10(8) cells to 29.3 units/10(8) cells (normal thymocytes, 5.0 units/10(8) cells). This 6-fold variation in TdT activity was present even among those cell lines which were Ly 1-2+, TL+. Most cultures lines had chromosome numbers near 40 and generation times of 11 to 22 hr. There were no significant morphologic changes after the adaptation of these tumors in culture except an increase in cytoplasmic C-type virus particles.

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B-cell-deficient C57B1/6J mice (suppressed from birth with goat anti-mu) and controls (treated from birth with normal goat serum) were infected with Trypanosoma rhodesiense. There was a significant (P less than 0.01) decrease in duration of survival of the mu-suppressed mice compared with that of controls. Whereas both mu-suppressed and control mice had an initial rise in parasitemia of similar magnitude, only the control mice exhibited a subsequent period during which the parasitemia fell to undetectable levels. In control mice, immunization with irradiated organisms prevented the development of detectable parasitemia after challenge with viable trypanosomes. However, immunization did not alter the course of infection in B-cell-deficient mice. These results indicate that immunity to T. rhodesiense infection in mice is dependent on B-cell immunocompetence.

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Evidence from various systems suggests that thymus-derived lymphocytes can affect the quality of antibody responses by recognizing various portions of the immunoglobulin receptor of bone-marrow-derived thymus-independent lymphocytes. A model for this process is proposed involving two antigen-specific mature T helper cells, one of which also is specific for immunoglobulin determinants. These two cells act synergistically. Evidence from adoptive secondary antibody responses demonstrates that both cells are antigen-specific T cells and that the immunoglobulin-recognizing T helper cell is absent from experimentally agammaglobulinemic mice. This cell is termed an "immunoglobulin-dependent T cell" because its activation requires the presence of immunoglobulin.

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The effect of administration of live Bacillus Calmette-Guerin (BCG), a nonspecific immunostimulant, on the course of experimental cutaneous leishmaniasis in mice was investigated. BALB/c mice were injected in the footpad with Leishmania tropica, NIH S-strain; in mice that were not pretreated with BCG this produced a reproducible fatal infection characterized by local inflammation, regional lymphadenopathy, and dissemination of parasites with hepatosplenomegaly. In mice that were pretreated with BCG and similarly infected with L. tropica there was a reduction in the severity of cutaneous disease and a significant (p less than 0.005) decrease in mortality without evidence of visceralization.

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The cellular basis of immunity to sporozoites was investigated by examing the effect of immunization of T and B cell-deficient C57BL/6N X BALB/c AnN F1 (BLCF1) mice compared to immunocompetent controls. Immunization of T cell-deficient (ATX-BM-ATS) BLCF1 mice with x-irradiated sporozoites did not result in the generation of protective immunity. The same immunization protocols protected all immunocompetent controls. In contrast, B cell-deficient (micron-suppressed) BLCF1 mice were protected by immunization in the majority of cases. The absence of detectable serum circumsporozoite precipitins or sporozoite neutralizing activity in the micron-suppressed mice that resisted a sporozoite challenge suggests a minor role for these humoral factors in protection. These data demonstrate a preeminent role for T cells in the induction of protective immunity in BLCF 1 mice against a P. berghei sporozoite infection.

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The course of infection with 17X nonlethal Plasmodium berghei yoelii was examined in BALB/c mice which were deficient in either T cells or B cells. Markedly increased parasitemia and mortality were observed in athymic (nude) mice which had been backcrossed on a BALB/c background (T cell deficient) compared to similar mice which had been grafted with neonatal BALB/c thymus, and were also observed in BALB/c mice suppressed from birth with goat antiserum to mouse mu-chain (B cell deficient) compared to age- and sex-matched BALB/c controls. These results establish the requirement for the presence of both T cells and B cells for effective resistance to an intercurrent infection with 17XNL P.b. yoelii in adult BALB/c mice. Mechanisms by which the requirement for both T cells and B cells could be explained were discussed. The model of mu suppression was shown to be a valuable tool for an evaluation of the cellular basis of immunity to an infectious disease.

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After infection with a nonlethal strain of murine malaria (17XNL Plasmodium berghei yoelli), BALB/c mice are then resistant to a lethal strain (17XL P.b. yoelli). BALB/c mice were infected with 17XNL, anc challenged 3 weeks later, after clearing their parasitemias, with 17XL. Three weeks thereafter, spleen cells from such immune animals were used to define an early peaking T-dependent (anti-theta sensitive) antigen-specific proliferative response when incubated in vitro with 17XL infected RBC, or a saline soluble 17XL antigen preparation. T dependent responsiveness of spleen cells from uninoculated control animals to the 17XL antigen preparation was also observed, but demonstrated a much different (delayed) kinetics from that observed with immune cells.

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