Biomedical subjects
Publications and source records attributed to R J Howard.
After CMV infection, significant reduction in directed neutrophil migration persisted through 21 days; reduction of random migration persisted through 14 days. The duration of these defects coincide with other immune derangements and increased susceptibility to lethal bacterial infections.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Mature asexual stages of the malaria parasite Plasmodium Knowlesi synthesize proteins of Mr 180 000-225 000 that are expressed on the outer membrane of infected erythrocytes and which vary antigenically such that different parasite clones are specifically agglutinated with homologous antibody. Other non-agglutinable clones have been prepared which fail to express variant antigen on infected cells. Two agglutinable clones of different variant antigen phenotypes and a non-agglutinable cone were examined to determine the proportion of total malarial proteins represented by variant antigens. Malarial proteins were labelled with various radioactive amino acids and the sodium dodecyl sulphate--polyacrylamide gel patterns for the three clones compared by fluorography. The patterns were indistinguishable, the variant antigens being undetectable in analyses of total malarial proteins. Furthermore, these antigens were not detected by Coomassie Blue-staining of total cellular proteins after electrophoresis. Sodium dodecyl sulphate and Triton X-100 extracts of labelled cells were immunoprecipitated using a panel of sera of defined agglutination specificity. The variant antigens could not be detected in the fluorographic patterns of total malarial antigens immunoprecipitated by these sera. In contrast, after lactoperoxidase catalysed radio-iodination of intact schizont-infected cells, the 125I-variant antigens on the cell surface were identified by demonstrating their accessibility both to antibody and to trypsin with intact cells. Thus, the variant antigens are quantitatively very minor malarial proteins that can only be detected by methods which selectively analyse the subset of proteins on the erythrocyte surface.
Two malaria parasites, Plasmodium knowlesi and P. falciparum, when passaged in splenectomized hosts alter or fail to express parasite-dependent antigens on the surface membrane of erythrocytes infected with mature parasites. Experiments with cloned populations of P.knowlesi show this change to be phenotypic and to be modulated by the spleen of the host. In addition, the induction of antigen variation in P. knowlesi malaria apparently requires two factors: specific antibody and the spleen. Along with the altered expression of P. knowlesi variant antigen on the infected erythrocyte surface, there is a decrease in parasite virulence in non-splenectomized monkeys. It is suggested that the spleen-dependent expression of malarial antigens on the parasitized erythrocyte may be an adaptation of the malaria parasite for survival in the presence of a potentially destructive spleen-mediated host immunity.
We have defined the surface protein antigens on Plasmodium gallinaceum zygotes using radioiodination methods and rabbit anti-zygote serum which blocks transmission of the parasite to Aedes aegypti mosquitoes. Fifteen protein bands (1-15) in the molecular weight range of 40 000-240 000 and one band at the bromophenol blue dye marker were labelled by the lactoperoxidase and IODOGEN (1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenylglycoluril) methods. The localization of these radioiodinated components on the cell surface was confirmed in two ways: (1) They were completely degraded by trypsin or Streptomyces griseus protease treatment of intact viable zygotes. (2) They were immunoprecipitated following incubation of intact zygotes with antibody prior to detergent solubilization. Reactivity with immune rabbit serum demonstrated that the major surface immunogens were components with Mr 240 000, 200 000, 180 000, 80 000, 55 000, 50 000 and the band at the dye marker. A band of Mr 180 000 was shown immunologically to be a host serum protein selectively adsorbed to the zygote surface. The identity of this protein and the significance of its adsorption to the surface of the zygote are unknown.
Erythrocytes infected with Plasmodium falciparum develop knob-like protrusions on their membranes. Knobby (K+) parasites of the FCR-3 (Gambian) strain have been shown to possess a histidine-labelled protein of apparent molecular weight 80 000 which is absent from knobless (K-) variants of the same strain. Here we report similar findings with K+ and K- parasites of another strain, the Malayan Camp strain, and also with cloned K+ and K- parasites of the FCR-3 strain. A histidine-labelled protein unique to the two K+ parasites was identified as a broad band with an apparent molecular weight of 89 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The presence of this protein in both K+ Malayan Camp parasites and K+ FCR-3 (Gambian) parasites and its absence from K- parasites of both strains is consistent with this protein being a major component of knobs.
Explore the source record for details and available documents.
Erythrocytes infected with mature asexual stages of Plasmodium knowlesi express a new surface antigen such that rhesus monkey antisera specifically agglutinate these cells. Cloned parasites can express different antigenic variants of this antigen. The variant antigen has been identified by comparison of the surface membrane antigens of a clone and of an antigenic variant of that clone of different agglutination phenotype. After lactoperoxidase labeling, 125I-labeled proteins of Mrs 210,000 and 190,000 with one clone and of Mrs 205,000 with the antigenic variant were only immunoprecipitated by antisera containing homologous anti-variant antibody. Antigens of the same Mr from each clone were labeled by [35S]methionine incorporation during parasite growth and also specifically immunoprecipitated only by agglutinating antisera. Therefore, the variant antigens are malarial proteins rather than modified host proteins.
We studied the effect of clindamycin on phagocytosis of Bacteroides fragilis (MIC = 0.05 mg/l). In the in-vitro test system phagocytosis of Bact. fragilis was less than 11% for the first 30 min of incubation. At 60 min, 25-50% of Bact. fragilis were phagocytosed. At 90 min, phagocytosis increased to 60% of the bacterial inoculum and did not increase thereafter. When clindamycin (0.02 mg/l) was incubated with neutrophils for 2 h prior to exposure to bacteria, there was no increase in phagocytosis. When clindamycin (0.02 mg/l) was incubated with bacteria for 2 h before exposure to neutrophils, phagocytosis increased to 23.1 +/- 5.9 (S.D.) per cent at 30 min compared to 1.1 +/- 15.1% (P less than 0.05) for bacteria not exposed to clindamycin. There was no difference in phagocytosis between the two groups at 60 and 90 min. One-fifth the MIC (0.01 mg/l) but not 0.004 mg/l also led to increased phagocytosis at 30 min but not at 60 min if previously incubated with clindamycin. Thus, clindamycin potentiates phagocytosis of Bact. fragilis. It can act directly on bacteria and promote phagocytosis, although the clinical importance of this last mode of action is not currently known.
Explore the source record for details and available documents.
Variant antigens appear on the surface of Plasmodium knowlesi-infected erythrocytes as the asexual parasite matures and are detected by antibody-mediated schizont-infected cell agglutination (SICA). We now show that cloned parasites can undergo antigenic variation in nonsplenectomized monkeys. In addition, we previously described a new P. knowlesi phenotype in which uncloned parasites passaged in splenectomized monkeys were no longer agglutinable by immune sera. We have designated this new phenotype SICA[-] and the one expressing the variant antigen SICA[+]. Cloned parasites can also switch from SICA[+] to SICA[-] in splenectomized monkeys. The switch from SICA[+] to SICA[-] is a gradual process that requires sequential subpassage in several monkeys. After passage in one monkey, the agglutination titer decreased 4- to 16-fold. Decreased agglutination was associated with decreased antibody binding on all infected erythrocytes as measured by fluorescein-conjugated anti-rhesus monkey immunoglobulin. The asexual malaria parasite can therefore alter its expression of variant antigen in response to the host environment (antivariant antibody or splenectomy). When cloned SICA[-] parasites were inoculated into intact monkeys, two courses of parasitemia were observed: fulminant parasitemia (greater than 20%) and parasitemia that was controlled. Fulminant infections were associated with conversion of the parasite from SICA[-] to SICA[+], i.e., from nonexpression to expression of the variant antigen on the erythrocyte surface. Parasitized erythrocytes remained SICA[-] in those infections that were controlled. It appears, therefore, that the expression of the variant antigen on the erythrocyte surface may influence parasite virulence.
Defective murine cytomegalovirus (MCMV) antigen-specific proliferation, induced by treatment of MCMV-infected mice with either antilymphocyte globulin (ALG), prednisolone, or both agents, was eventually restored following the cessation of immunosuppression. At 100 and 278 days following the end of immunosuppressive therapy splenic lymphocytes from infected and subsequently immunosuppressed mice responded significantly in vitro to soluble MCMV antigen after having lost this response immediately upon initiation of immunosuppression. Circulating specific antibodies and mitogen-induced blast transformation were comparable between infected mice and infected mice that also were immunosuppressed. At 278 days following the cessation of immunosuppression splenocytes from infected mice that had been treated with ALG yielded greatly increased background proliferation. Nylon-wool adherence was used to obtain enriched populations of T cells, and B cells and monocytes from MCMV-infected mice. While T cells alone did not respond in vitro to MCMV antigen, recombining B cells and monocytes with the T cells reconstituted in vitro proliferation. Defective lymphocyte proliferation to MCMV for an extended period of time following the end of immunosuppressive therapy indicated a prolonged inability to respond to an active MCMV infection. Identification of the cellular basis for the proliferation defect might lead to the development of effective immunotherapy.
A double-blind, randomized study of gentamicin and netilmicin, each in combination with cefoxitin, was done to compare their respective efficacy and toxicity in patients with serious systemic infection. Thirty-seven surgical patients were evaluated for efficacy and 46 patients were evaluated for toxicity. The most frequently cultured organisms were Escherichia coli (15), Klebsiella sp (9), Proteus sp (6), and Bacteroides sp (4). For 23 patients treated with gentamicin-cefoxitin (G-C), the clinical response was favorable in 20/21 (95.2%) evaluable cases, and elimination or marked reduction of 33/34 (97.1%) organisms was achieved. For 14 patients treated with netilmicin-cefoxitin (N-C), the clinical response was favorable in 13/13 (100%) evaluable cases, and 19/20 (95%) organisms were eliminated or markedly reduced. Nephrotoxicity was defined as an increase in serum creatinine to greater than 25% over baseline with an absolute rise of at least 0.5 mg/100 ml to a value greater than or equal to 1.3 mg/100 ml. Based on these criteria, nephrotoxicity was seen in 2/27 (7.4%) patients treated with G-C and in 3/19 (15.8%) patients treated with N-C. Ototoxicity was defined as a greater than 20 dB loss at any frequency. Based on these criteria, ototoxicity was seen in 5/27 (18.5%) patients treated with G-C and 2/19 (10.5%) patients treated with N-C. The data show no significant difference in toxicity and suggest that netilmicin and gentamicin are both highly effective in combination with cefoxitin in patients who have serious infections after surgery.
Monoclonal antibodies (MAb) against gametes of the chicken malaria Plasmodium gallinaceum have been derived. All reacted with the surface of extracellular gametes of the parasite in immunofluorescent antibody reactions and all agglutinated both male and female gametes. In the absence of active complement one mu isotype MAb, la 1-D5, mediated at least 95% suppression of infectivity of the parasites to Aedes aegypti mosquitoes. Individually, MAb of the gamma 1 or gamma 2a isotypes mediated only slight suppression in the absence of active complement. Certain combinations of these MAb, however, suppressed parasite infectivity by 90 to 95%. Suppression of infectivity by the MAb was shown to be mainly due to their effects on the events leading up to or including fertilization. Certain gamma 2a isotype MAb, which otherwise mediated minimal or no suppressive effect, completely abolished infectivity of the parasites if complement was present. No target antigen could be identified by immunoprecipitation of Triton X-100 extracts of surface radioiodinated zygotes or gametes of P. gallinaceum for the mu isotype MAb. All gamma isotype MAb precipitated the same three proteins of 240,000, 56,000, and 54,000 daltons under reducing conditions on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, from extracts of radioiodinated male and female gametes. These surface proteins on gametes of both sexes of P. gallinaceum thus appear to include target antigens of anti-gamete transmission blocking immunity.
Metastases to the heart are rarely diagnosed before death. In this report the authors describe what they believe is the first case of metastasis from embryonal carcinoma of the testis to the heart that was successfully removed. Nine years after orchiectomy for embryonal carcinoma of the testis a 32-year-old man was found to have a right atrial tumour. The preliminary diagnosis was myxoma, but because of his previous testicular cancer and a metastatic deposit that had been found 6 years earlier, a diagnosis of cardiac metastasis seemed more likely. The tumour, removed from the lateral wall of the right atrium, had the same histologic features as the original embryonal carcinoma and the metastatic deposit. The patient made a smooth recovery.
Explore the source record for details and available documents.
Explore the source record for details and available documents.