scholarly journals Molecular control of irreversible bistability during trypanosome developmental commitment

2015 ◽  
Vol 211 (2) ◽  
pp. 455-468 ◽  
Author(s):  
Maria Rosa Domingo-Sananes ◽  
Balazs Szöőr ◽  
Michael A.J. Ferguson ◽  
Michael D. Urbaniak ◽  
Keith R. Matthews
Keyword(s):  
Isotope Labeling ◽  
Data Set ◽  
Bistable Switch ◽  
Molecular Control ◽  
Developmental Transitions ◽  
Mammalian Blood ◽  
Parasite Populations ◽  
Translational Inhibitor ◽  
New Protein

The life cycle of Trypanosoma brucei involves developmental transitions that allow survival, proliferation, and transmission of these parasites. One of these, the differentiation of growth-arrested stumpy forms in the mammalian blood into insect-stage procyclic forms, can be induced synchronously in vitro with cis-aconitate. Here, we show that this transition is an irreversible bistable switch, and we map the point of commitment to differentiation after exposure to cis-aconitate. This irreversibility implies that positive feedback mechanisms operate to allow commitment (i.e., the establishment of “memory” of exposure to the differentiation signal). Using the reversible translational inhibitor cycloheximide, we show that this signal memory requires new protein synthesis. We further performed stable isotope labeling by amino acids in cell culture to analyze synchronized parasite populations, establishing the protein and phosphorylation profile of parasites pre- and postcommitment, thereby defining the “commitment proteome.” Functional interrogation of this data set identified Nek-related kinase as the first-discovered protein kinase controlling the initiation of differentiation to procyclic forms.

Electron probe x-ray microanalysis and electron microscopy of amino acid absorption and transport by the small intestine: inhibition by chemical poisons and correlation to the elemental composition of the epithelial cells

1986 ◽  
Vol 44 ◽  
pp. 134-135
Author(s):  
A. J. Tousimis
Keyword(s):  
Small Intestine ◽  
Amino Acid ◽  
Epithelial Cells ◽  
Elemental Composition ◽  
Isotope Labeling ◽  
Structural Components ◽  
X Ray ◽  
Human Small Intestine ◽  
Transport Studies

The elemental composition of amino acids is similar to that of the major structural components of the epithelial cells of the small intestine and other tissues. Therefore, their subcellular localization and concentration measurements are not possible by x-ray microanalysis. Radioactive isotope labeling: I131-tyrosine, Se75-methionine and S35-methionine have been successfully employed in numerous absorption and transport studies. The latter two have been utilized both in vitro and vivo, with similar results in the hamster and human small intestine. Non-radioactive Selenomethionine, since its absorption/transport behavior is assumed to be the same as that of Se75- methionine and S75-methionine could serve as a compound tracer for this amino acid.

Hemolysis of erythrocytes by the hemolytic system from the blood-feeding stable fly, Stomoxys calcitrans

1992 ◽  
Vol 50 (1) ◽  
pp. 690-691
Author(s):  
H. J. Kirch ◽  
G. Spates ◽  
R. Droleskey ◽  
W.J. Kloft ◽  
J.R. DeLoach
Keyword(s):  
Blood Feeding ◽  
Stomoxys Calcitrans ◽  
Stable Fly ◽  
Digestive Physiology ◽  
Transmission Electron ◽  
Erythrocyte Lysis ◽  
Mammalian Blood ◽  
Bovine Erythrocytes ◽  
Potential Tool

Blood feeding insects have to rely on the protein content of mammalian blood to insure reproduction. A substantial quantity of protein is provided by hemoglobin present in erythrocytes. Access to hemoglobin is accomplished only via erythrocyte lysis. It has been shown that midgut homogenates from the blood feeding stable fly, Stomoxys calcitrans, contain free fatty acids and it was proposed that these detergent-like compounds play a major role as hemolysins in the digestive physiology of this species. More recently sphingomyelinase activity was detected in midgut preparations of this fly, which would provide a potential tool for the enzymatic cleavage of the erythrocyte's membrane sphingomyelin. The action of specific hemolytic factors should affect the erythrocyte's morphology. The shape of bovine erythrocytes undergoing in vitro hemolysis by crude midgut homogenates from the stable fly was examined by scanning and transmission electron microscopy.

scholarly journals Molecular Basis of In Vivo Resistance to Sulfadoxine-Pyrimethamine in African Adult Patients Infected withPlasmodium falciparum Malaria Parasites

1998 ◽  
Vol 42 (7) ◽  
pp. 1811-1814 ◽  
Author(s):  
Leonardo K. Basco ◽  
Rachida Tahar ◽  
Pascal Ringwald
Keyword(s):  
Dihydrofolate Reductase ◽  
Point Mutations ◽  
Gene Mutations ◽  
Adult Patients ◽  
Wild Type ◽  
Dihydropteroate Synthase ◽  
Reductase Gene ◽  
Parasite Populations

ABSTRACT In vitro sulfadoxine and pyrimethamine resistance has been associated with point mutations in the dihydropteroate synthase and dihydrofolate reductase domains, respectively, but the in vivo relevance of these point mutations has not been well established. To analyze the correlation between genotype and phenotype, 10 Cameroonian adult patients were treated with sulfadoxine-pyrimethamine and followed up for 28 days. After losses to follow-up (n = 1) or elimination of DNA samples due to mixed parasite populations with pyrimethamine-sensitive and pyrimethamine-resistant profiles (n = 3), parasite genomic DNA from day 0 blood samples of six patients were analyzed by DNA sequencing. Three patients who were cured had isolates characterized by a wild-type or mutant dihydrofolate reductase gene (with one or two mutations) and a wild-type dihydropteroate synthase gene. Three other patients who failed to respond to sulfadoxine-pyrimethamine treatment carried isolates with triple dihydrofolate reductase gene mutations and either a wild-type or a mutant dihydropteroate synthase gene. Three dihydrofolate reductase gene codons (51, 59, and 108) may be reliable genetic markers that can accurately predict the clinical outcome of sulfadoxine-pyrimethamine treatment in Africa.

scholarly journals Fluconazole MIC and the Fluconazole Dose/MIC Ratio Correlate with Therapeutic Response among Patients with Candidemia

2005 ◽  
Vol 49 (8) ◽  
pp. 3171-3177 ◽  
Author(s):  
Cornelius J. Clancy ◽  
Victor L. Yu ◽  
Arthur J. Morris ◽  
David R. Snydman ◽  
M. Hong Nguyen
Keyword(s):  
Therapeutic Response ◽  
Geometric Mean ◽  
Therapeutic Failure ◽  
Response To Therapy ◽  
Success Rates ◽  
Therapeutic Success ◽  
Data Set ◽  
In Vitro Susceptibility ◽  
Dose Dependent

ABSTRACT We tested 32 Candida isolates recovered in the early 1990s from the bloodstreams of patients with candidemia for in vitro susceptibility to fluconazole and determined if MIC and/or the daily dose of fluconazole/MIC ratio correlated with the response to therapy. This is a unique data set since 87.5% (28/32) of patients were treated with fluconazole doses now considered to be inadequate (≤200 mg), which contributed to high therapeutic failure rates (53% [17/32]). The geometric mean MIC and dose/MIC ratio for isolates associated with therapeutic failure (11.55 μg/ml and 14.3, respectively) differed significantly from values associated with therapeutic success (0.95 μg/ml and 219.36 [P = 0.0009 and 0.0004, respectively]). The therapeutic success rates among patients infected with susceptible (MIC ≤ 8 μg/ml), susceptible-dose dependent (S-DD) (MIC = 16 or 32 μg/ml), and resistant (MIC ≥ 64 μg/ml) isolates were 67% (14/21), 20% (1/5), and 0% (0/6), respectively. A dose/MIC ratio >50 was associated with a success rate of 74% (14/19), compared to 8% (1/13) for a dose/MIC ratio ≤50 (P = 0.0003). Our data suggest that both fluconazole MIC and dose/MIC ratio correlate with the therapeutic response to fluconazole among patients with candidemia. In clinical practice, dose/MIC ratio might prove easier to interpret than breakpoint MICs, since it quantitates the effects of increasing fluconazole doses that are alluded to in the S-DD designation.

scholarly journals Properties of precise firing synchrony between synaptically coupled cortical interneurons depend on their mode of coupling

2015 ◽  
Vol 114 (1) ◽  
pp. 624-637 ◽  
Author(s):  
Hang Hu ◽  
Ariel Agmon
Keyword(s):  
Firing Rate ◽  
Electrical Coupling ◽  
Gamma Oscillations ◽  
Inhibitory Synapses ◽  
Data Set ◽  
Temporal Precision ◽  
Gamma Frequency ◽  
Rate Dependent ◽  
Cortical Interneurons

Precise spike synchrony has been widely reported in the central nervous system, but its functional role in encoding, processing, and transmitting information is yet unresolved. Of particular interest is firing synchrony between inhibitory cortical interneurons, thought to drive various cortical rhythms such as gamma oscillations, the hallmark of cognitive states. Precise synchrony can arise between two interneurons connected electrically, through gap junctions, chemically, through fast inhibitory synapses, or dually, through both types of connections, but the properties of synchrony generated by these different modes of connectivity have never been compared in the same data set. In the present study we recorded in vitro from 152 homotypic pairs of two major subtypes of mouse neocortical interneurons: parvalbumin-containing, fast-spiking (FS) interneurons and somatostatin-containing (SOM) interneurons. We tested firing synchrony when the two neurons were driven to fire by long, depolarizing current steps and used a novel synchrony index to quantify the strength of synchrony, its temporal precision, and its dependence on firing rate. We found that SOM-SOM synchrony, driven solely by electrical coupling, was less precise than FS-FS synchrony, driven by inhibitory or dual coupling. Unlike SOM-SOM synchrony, FS-FS synchrony was strongly firing rate dependent and was not evident at the prototypical 40-Hz gamma frequency. Computer simulations reproduced these differences in synchrony without assuming any differences in intrinsic properties, suggesting that the mode of coupling is more important than the interneuron subtype. Our results provide novel insights into the mechanisms and properties of interneuron synchrony and point out important caveats in current models of cortical oscillations.

scholarly journals Quality control in scRNA-Seq can discriminate pacemaker cells: the mtRNA bias

2021 ◽  
Author(s):  
Anne-Marie Galow ◽  
Sophie Kussauer ◽  
Markus Wolfien ◽  
Ronald M. Brunner ◽  
Tom Goldammer ◽  
...  
Keyword(s):  
Quality Control ◽  
Cardiac Tissue ◽  
High Energy ◽  
Tissue Type ◽  
Pacemaker Cells ◽  
Data Set ◽  
Public Data ◽  
Standard Quality ◽  
Mitochondrial Transcripts

AbstractSingle-cell RNA-sequencing (scRNA-seq) provides high-resolution insights into complex tissues. Cardiac tissue, however, poses a major challenge due to the delicate isolation process and the large size of mature cardiomyocytes. Regardless of the experimental technique, captured cells are often impaired and some capture sites may contain multiple or no cells at all. All this refers to “low quality” potentially leading to data misinterpretation. Common standard quality control parameters involve the number of detected genes, transcripts per cell, and the fraction of transcripts from mitochondrial genes. While cutoffs for transcripts and genes per cell are usually user-defined for each experiment or individually calculated, a fixed threshold of 5% mitochondrial transcripts is standard and often set as default in scRNA-seq software. However, this parameter is highly dependent on the tissue type. In the heart, mitochondrial transcripts comprise almost 30% of total mRNA due to high energy demands. Here, we demonstrate that a 5%-threshold not only causes an unacceptable exclusion of cardiomyocytes but also introduces a bias that particularly discriminates pacemaker cells. This effect is apparent for our in vitro generated induced-sinoatrial-bodies (iSABs; highly enriched physiologically functional pacemaker cells), and also evident in a public data set of cells isolated from embryonal murine sinoatrial node tissue (Goodyer William et al. in Circ Res 125:379–397, 2019). Taken together, we recommend omitting this filtering parameter for scRNA-seq in cardiovascular applications whenever possible.

In vitro effectiveness of biapenem against IMP-producing Enterobacteriaceae

2021 ◽  
Vol 70 (10) ◽  
Author(s):  
Kazuyoshi Gotoh ◽  
Makoto Miyoshi ◽  
I Putu Bayu Mayura ◽  
Koji Iio ◽  
Osamu Matsushita ◽  
...  
Keyword(s):  
Therapeutic Option ◽  
Small Data ◽  
Limited Data ◽  
Data Set ◽  
Content Type ◽  
Link Type ◽  
Almost All ◽  
New Treatments ◽  
Time Kill

The options available for treating infections with carbapenemase-producing Enterobacteriaceae (CPE) are limited; with the increasing threat of these infections, new treatments are urgently needed. Biapenem (BIPM) is a carbapenem, and limited data confirming its in vitro killing effect against CPE are available. In this study, we examined the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of BIPM for 14 IMP-1-producing Enterobacteriaceae strains isolated from the Okayama region in Japan. The MICs against almost all the isolates were lower than 0.5 µg ml−1, indicating susceptibility to BIPM, while approximately half of the isolates were confirmed to be bacteriostatic to BIPM. However, initial killing to a 99.9 % reduction was observed in seven out of eight strains in a time–kill assay. Despite the small data set, we concluded that the in vitro efficacy of BIPM suggests that the drug could be a new therapeutic option against infection with IMP-producing CPE.

scholarly journals Enhancer-associated H3K4 methylation safeguards in vitro germline competence

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tore Bleckwehl ◽  
Giuliano Crispatzu ◽  
Kaitlin Schaaf ◽  
Patricia Respuela ◽  
Michaela Bartusel ◽  
...  
Keyword(s):  
Primordial Germ Cells ◽  
Transcriptional Activators ◽  
H3k4 Methylation ◽  
Developmental Transitions ◽  
Intrinsic Factors ◽  
Germline Genes ◽  
Enhancer Function ◽  
Differentiation Efficiency ◽  
Post Implantation

AbstractGermline specification in mammals occurs through an inductive process whereby competent cells in the post-implantation epiblast differentiate into primordial germ cells (PGC). The intrinsic factors that endow epiblast cells with the competence to respond to germline inductive signals remain unknown. Single-cell RNA sequencing across multiple stages of an in vitro PGC-like cells (PGCLC) differentiation system shows that PGCLC genes initially expressed in the naïve pluripotent stage become homogeneously dismantled in germline competent epiblast like-cells (EpiLC). In contrast, the decommissioning of enhancers associated with these germline genes is incomplete. Namely, a subset of these enhancers partly retain H3K4me1, accumulate less heterochromatic marks and remain accessible and responsive to transcriptional activators. Subsequently, as in vitro germline competence is lost, these enhancers get further decommissioned and lose their responsiveness to transcriptional activators. Importantly, using H3K4me1-deficient cells, we show that the loss of this histone modification reduces the germline competence of EpiLC and decreases PGCLC differentiation efficiency. Our work suggests that, although H3K4me1 might not be essential for enhancer function, it can facilitate the (re)activation of enhancers and the establishment of gene expression programs during specific developmental transitions.

The ecology of host-finding behaviour and parasite transmission: past and future perspectives

Parasitology ◽  
1994 ◽  
Vol 109 (S1) ◽  
pp. S31-S39 ◽  
Author(s):  
J. G. Rea ◽  
S. W. B. Irwin
Keyword(s):  
Host Finding ◽  
Life Cycles ◽  
Reproductive Value ◽  
Costs And Benefits ◽  
Evolutionary Mechanisms ◽  
High Fecundity ◽  
Environmental Signals ◽  
Community Organisation ◽  
Parasite Populations

SUMMARYHost location by parasites can be achieved by either active or passive mechanisms. In spite of their significance, the efficacy of these methods has been little researched. High fecundity in parasites is discussed in terms of the role it plays in dispersal and transmission. Some concepts developed by mainstream behavioural ecologists are outlined and their relevance to parasitology is indicated. ‘Reproductive value’ is recommended as an appropriate measure of the costs and benefits of behavioural acts. Although costs of reproduction have been rarely studied in parasites, they are likely to occur in cosexual insects, nematodes and crustaceans. Experiments using captive hosts and/orin vitrocultivation could help in the construction of realistic optimality models. We suggest that r- and K-selection theory could assist in the study of the evolution of parasite behaviour. We discuss how parasite populations are dispersed and controlled and consider the implications of overdispersion. WTe outline three sources of signals to which parasites may respond and suggest that understanding evolutionary mechanisms and community organisation of parasites and hosts requires evaluation of fundamental behavioural responses to environmental signals. The study of closely related groups of parasites and their hosts may advance our knowledge of the evolution of parasite life cycles and the evolutionary costs and benefits of behavioural acts.

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