A comparison of the in vivo kinetics of Plasmodium falciparum ring-infected erythrocyte surface antigen-positive and -negative erythrocytes.

Ring-infected erythrocyte surface antigen (RESA)-positive, Plasmodium falciparum-negative red blood cells (RBCs) are cells from which the malaria parasite has been removed by the host without the destruction of the erythrocyte ("pitting"). The survival of RESA-RBCs in vivo was assessed in 14 severe and 6 uncomplicated falciparum malaria patients. The mean RESA-RBC life of 183 hours (95% confidence interval [CI], 136-246) was longer than the median parasite clearance time of 66 hours (range, 30-108 hours) but shorter than the mean red cell life of 1027 hours (95% CI, 840-1213) (P =.0004), with a median ratio of 0.2:1.0 (range, 0.1-0.7). The estimated median percentage of parasites pitted/body transit was 0.003% (range, 0.001%-0.05%). The rate of rise of the RESA-RBC count during the first 24 hours after antimalarial treatment was significantly faster (P =.036) and the subsequent RESA-RBC survival significantly shorter (P =.017) after treatment with an artemisinin derivative than after treatment with quinine. Parasitization of red cells leads to changes in the erythrocyte that shorten their survival even if the parasite is removed subsequently.     

DLA-identical bone marrow grafts after low-dose total body irradiation: the effect of canine recombinant hematopoietic growth factors

Previous studies found that bone marrow (BM) allografts from DLA- identical littermates resulted in survival of two thirds of recipient dogs after otherwise lethal doses of 450 to 600 cGy of total body irradiation (TBI) because of successful allografts or autologous recovery after rejection of the allografts. The current study asked whether survival could be further improved by treating allograft recipients with recombinant canine granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF), or G-CSF/SCF. Of 21 dogs, 14 (67%) receiving allografts but no growth factors survived, 10 with successful allografts (including 5 mixed chimeras) and 4 with autologous recovery; whereas 7 animals died, 5 from infections during BM aplasia and 2 from acute graft-versus-host disease. By comparison, 30 of 34 dogs (88%) receiving hematopoietic growth factors in addition to the BM graft survived, 17 with successful allografts (including 10 mixed chimeras) and 13 with autologous recovery; whereas 4 died, all with infection related to BM aplasia after rejection of the allograft. Survival was similar for recipients of G-CSF, SCF, or the combination of G-CSF and SCF. Logistic regression analyses, which accounted for possible effects of TBI dose, showed a trend for improved survival in dogs receiving growth factors (P = .09), no change in allogeneic engraftment (P = .74), and a slight increase in autologous recovery (P = .22). In agreement with previous data, we found that grafts of BM from DLA-identical littermates improved survival of recipient dogs exposed to low but otherwise lethal doses of TBI. A further improvement in survival could be achieved by additional treatment with G-CSF, SCF, or G-CSF/SCF. Results suggest that treatment by hematopoietic growth factors along with BM grafts should be considered for victims of radiation accidents.     

Quality control of multidrug resistance assays in adult acute leukemia: correlation between assays for P-glycoprotein expression and activity

We have compared multiple assays for the P-glycoprotein (Pgp/MDR1) phenotype in fresh and thawed adult acute leukemia to validate and quantitate measures for the expression and function of Pgp. The results are related to the Pgp-expressing KB8 and KB8-5 call lines. The most sensitive assay was the measurement of modulation of the rhodamine 123 (R123) fluorescence by 2 micromol/L PSC833, followed by the modulation of the probe calcein-AM. We also found a good intralaboratory and interlaboratory correlation between the values of the R123/PSC833 assay for fresh as well as thawed samples. In addition, the affects of PSC833 on 3H-daunorubicin (DNR) accumulation, DNR fluorescence, and 3H- vincristine accumulation were very similar. The correlation between the DNR/PSC833 and R123/PSC833 test was r = .86 (N = 51). The modulation of drug accumulation by 8 micromol/L verapamil was the some as the PSC833 effect for DNR (117%, N = 21), but was higher for vincristine in every single case (161% v 121%, N = 22; P< .001), indicating additional verapamil effects, not related to Pgp. The correlation of the staining of viable cells for Pgp with the monoclonal antibody MRK16 was r = .77 (N = 52) for the R123/PSC833 functional test and r = .84 (N = 50) for the DNR/PSC833 test. From these results it could be calculated that a maximal increase of the mean DNR accumulation of about 50% can be achieved by blocking Pgp pump activity with PSC833 in leukemic blast samples with the highest mean Pgp expression. Subpopulations of blast calls with higher Pgp activity are likely to be present. Their relevance has to be studied further. The methods outlined here allow the reliable, quantitative monitoring of the Pgp/MDR1 phenotype in leukemias in multicentered, clinical Pgp modulation studies.     

Establishment and characterization of an Epstein-Barr virus transformed cell line with strong phagocytic activity

An immunoglobulin M (IgM)-positive cell line, Ms 28, apparently spontaneously transformed by Epstein-Barr virus (EBV) was established from peripheral blood cells of a patient with immature myeloblastic leukemia. It has been characterized according to phenotype, cytochemistry, and membrane antigen pattern. The cell line expresses lymphoid markers like CD 19, CD 22, and CD 30 and synthesizes and secretes IgM. Monocyte markers CD 11c, CD 14, and CD 15 are absent. Neither interleukin-1 (IL-1), nor tumor necrosis factor (TNF-alpha) are produced. But Ms 28 cells show strong phagocytic activity and engulf Latex particles and sheep RBCs (SRBCs) that need not to be opsonized. The phagocytic activity can be inhibited by chloroquine. Both phagocytosis and EBV nuclear-antigen (EBNA) expression can be observed in one and the same cell. Ms 28 cells might be useful to study immunologic activities like antigen processing and presentation.     

The regulatory subunit of Escherichia coli aspartate carbamoyltransferase may influence homotropic cooperativity and heterotropic interactions by a direct interaction with the loop containing residues 230-245 of the catalytic chain.

A recent x-ray structure of aspartate carbamoyltransferase (carbamoyl-phosphate: L-aspartate carbamoyl-transferase, EC 2.1.3.2) with phosphonoacetamide bound [Gouaux, J. E. & Lipscomb, W. N. (1990) Biochemistry 29, 389-402] shows an interaction between Asp-236 of the catalytic chain and Lys-143 of the regulatory chain. Asp-236 is part of the loop containing residues 230-245 (240s) of the catalytic chain that undergoes a significant conformational change between the tight and the relaxed states of the enzyme. Furthermore, side-chain interactions between the 240s loop and other portions of the enzyme have been shown to be important for the low activity and low affinity of the tight state and the high activity and high affinity of the relaxed state. To determine whether the intersubunit link between Lys-143 of the regulatory chain and Asp-236 of the catalytic chain is important for either homotropic cooperativity and/or the heterotropic interactions in aspartate carbamoyltransferase, site-specific mutagenesis was used to replace Asp-236 with alanine. The mutant enzyme exhibits full activity and a loss of both homotropic cooperativity and heterotropic interactions. Furthermore, the aspartate concentration at half the maximal observed specific activity is reduced by approximately 8-fold. The mutant enzyme exhibits normal thermal stability but drastically altered reactivity toward p-hydroxymercuribenzoate. The catalytic subunit of the mutant and wild-type enzymes have very similar properties. These results, in conjunction with previous experiments, suggest that the intersubunit link involving Asp-236 is involved in the stabilization of the 240s loop in its tight-state position and that the regulatory subunits exert their effect on the catalytic subunits by influencing the position of the 240s loop.     

Media and scientific communication about the COVID-19 pandemic and the repercussions on the population's mental health: A protocol for a systematic review and meta-analysis

Background:Good communication strategies are essential in times of crisis, such as the coronavirus pandemic. The dissemination of inaccurate information and the need for social isolation to control coronavirus disease 2019 (COVID-19) have shown a negative impact on the population, causing damage to mental health, with the appearance or worsening of symptoms of stress, fear, anxiety, and depression. Thus, the systematic review study is intended to gather evidence on the impact of information about COVID-19 on the mental health of the population.Methods:This systematic review protocol is conducted using the guidelines of the preferred reporting items for systematic reviews and meta-analyses protocols and the Cochrane Handbook for Systematic Reviews of Interventions. The review aims to include published studies that address the exposure of the general population to information about COVID-19, through observational and experimental studies, which consider the following outcomes: fear, stress, anxiety, and depression. Thus, a comprehensive research strategy will be conducted in the following databases: PubMed / Medline, Scopus, Web of Science, EMBASE, Science Direct, CINAHL, PsycINFO and Cochrane Central Register of Controlled Trials (CENTRAL). Two independent reviewers will perform all procedures, such as study selection, data collection, and methodological evaluation. Disagreements will be forwarded to a third reviewer. RevMan 5.3 software will be used for data analysis.Results:This systematic review will provide evidence of the influence of access to and consumption of media and scientific information about COVID-19 on the mental health of the population. It will consider information about the characterization of the study and the population studied, clinical and epidemiological information on mental health, and data on access to and consumption of media and scientific information.Discussion:The results should inform about the consequences of communication about the new coronavirus on the emergence or worsening of psychological and psychiatric symptoms, allowing to develop strategies to achieve effective communication of information to promote the mental health of the population.Systematic review registration number:PROSPERO CRD42020182918