scholarly journals Novel In Vivo and In Vitro Pharmacokinetic/Pharmacodynamic-Based Human Starting Dose Selection for Glofitamab

2021 ◽  
Author(s):  
Nicolas Frances ◽  
Marina Bacac ◽  
Katharine Bray-French ◽  
François Christen ◽  
Heather Hinton ◽  
...  
Keyword(s):  
Dose Selection ◽  
Starting Dose ◽  
Selection For

Improvement of effectiveness in maize breeding

2006 ◽  
Vol 54 (3) ◽  
pp. 351-358 ◽  
Author(s):  
P. Pepó
Keyword(s):  
Recurrent Selection ◽  
Genetic Manipulation ◽  
Field Testing ◽  
Tissue Cultures ◽  
Maize Breeding ◽  
Breeding Programmes ◽  
Speed Up ◽  
Selection For

Plant regeneration via tissue culture is becoming increasingly more common in monocots such as maize (Zea mays L.). Pollen (gametophytic) selection for resistance to aflatoxin in maize can greatly facilitate recurrent selection and the screening of germplasm for resistance at much less cost and in a shorter time than field testing. In vivo and in vitro techniques have been integrated in maize breeding programmes to obtain desirable agronomic attributes, enhance the genes responsible for them and speed up the breeding process. The efficiency of anther and tissue cultures in maize and wheat has reached the stage where they can be used in breeding programmes to some extent and many new cultivars produced by genetic manipulation have now reached the market.

Biochemical and genetic characterization of a yeast TFIID mutant that alters transcription in vivo and DNA binding in vitro

1992 ◽  
Vol 12 (5) ◽  
pp. 2372-2382
Author(s):  
K M Arndt ◽  
S L Ricupero ◽  
D M Eisenmann ◽  
F Winston
Keyword(s):  
Amino Acid ◽  
Dna Binding ◽  
Direct Repeat ◽  
Single Amino Acid ◽  
Wild Type ◽  
Dna Binding Specificity ◽  
Selection For

A mutation in the gene that encodes Saccharomyces cerevisiae TFIID (SPT15), which was isolated in a selection for mutations that alter transcription in vivo, changes a single amino acid in a highly conserved region of the second direct repeat in TFIID. Among eight independent spt15 mutations, seven cause this same amino acid change, Leu-205 to Phe. The mutant TFIID protein (L205F) binds with greater affinity than that of wild-type TFIID to at least two nonconsensus TATA sites in vitro, showing that the mutant protein has altered DNA binding specificity. Site-directed mutations that change Leu-205 to five different amino acids cause five different phenotypes, demonstrating the importance of this amino acid in vivo. Virtually identical phenotypes were observed when the same amino acid changes were made at the analogous position, Leu-114, in the first repeat of TFIID. Analysis of these mutations and additional mutations in the most conserved regions of the repeats, in conjunction with our DNA binding results, suggests that these regions of the repeats play equivalent roles in TFIID function, possibly in TATA box recognition.

scholarly journals Mutagenesis and ultraviolet inactivation of transforming DNA of Haemophilus influenzae complexed with a Bacillus subtilis protein that alters DNA conformation.

1996 ◽  
Vol 43 (1) ◽  
pp. 107-114 ◽  
Author(s):  
J K Setlow ◽  
B C Setlow ◽  
P Setlow
Keyword(s):  
Bacillus Subtilis ◽  
Haemophilus Influenzae ◽  
Dna Conformation ◽  
Erythromycin Resistance ◽  
Bacillus Subtilis Spore ◽  
Pyrimidine Dimers ◽  
Resistance Markers ◽  
Selection For

The wild-type Bacillus subtilis spore protein, SspCwt, binds to DNA in vitro and in vivo and changes the conformation of DNA from B to A. Synthesis of the cloned SspCwt gene in Escherichia coli also causes large increases in mutation frequency. Binding of SspCwt to transforming DNA from Haemophilus influenzae made the DNA resistant to ultraviolet (UV) radiation. The mutant protein, SspCala, which does not bind DNA, did not change the UV resistance. The UV sensitivity of the DNA/SspCwt complex was not increased when the recipients of the DNA were defective in excision of pyrimidine dimers. These data indicate that the H. influenzae excision mechanism does not operate on the spore photoproduct formed by UV irradiation of the complex. Selection for the streptomycin- or erythromycin-resistance markers on the transforming DNA evidenced significant mutations at loci closely linked to these, but not at other loci. SspCwt apparently entered the cell attached to the transforming DNA, and caused mutations in adjacent loci. The amount of such mutations decreased when the transforming DNA was UV irradiated, because UV unlinks linked markers.

scholarly journals Multiple gonococcal opacity proteins are expressed during experimental urethral infection in the male.

1994 ◽  
Vol 179 (3) ◽  
pp. 911-920 ◽  
Author(s):  
A E Jerse ◽  
M S Cohen ◽  
P M Drown ◽  
L G Whicker ◽  
S F Isbey ◽  
...  
Keyword(s):  
Antigenic Variation ◽  
Outer Membrane Proteins ◽  
Predominant Type ◽  
Detectable Difference ◽  
Single Protein ◽  
Selection For ◽  
Opacity Proteins ◽  
Strain Fa1090

The opacity (Opa) proteins of Neisseria gonorrhoeae are a family of outer membrane proteins demonstrating phase and antigenic variation. N. gonorrhoeae strain FA0190 has 11 opa loci that encode at least 8 antigenically distinct Opa proteins. To determine if expression of one Opa protein or a subset of them is favored during gonococcal infection, we inoculated Opa-negative variants of strain FA1090 intraurethrally into male volunteers. The Opa phenotype of gonococci isolated from urine and urethral swab cultures from nine infected subjects was determined. Opa proteins were expressed in a large proportion of the reisolates from the infected subjects. Gonococci cultured from urine or urethral swab samples from six of the subjects were uniformly Opa positive, with the predominant Opa variants differing among subjects. Three different Opa proteins were represented as the predominant type in at least one subject each. In three subjects, there was more heterogeneity in Opa phenotype of the reisolates, including the presence of Opa-negative variants. An increase in the proportion of isolates expressing multiple Opa proteins occurred over time in most subjects. Passage of the inoculum in vitro did not result in similar changes in Opa expression. There was no detectable difference in infectivity of an Opa-negative variant and one expressing an Opa protein (OpaF) that was highly represented in reisolates from the original nine subjects. Reisolates from three infected volunteers inoculated with the OpaF variant showed continued expression of OpaF alone or in conjunction with other Opa proteins. These results demonstrate that there is strong selection for expression of one or more Opa proteins by strain FA1090 in vivo, but that no single protein is preferentially expressed during early infection in the male urethra.

scholarly journals Modelling of Systemic versus Pulmonary Chloroquine Exposure in Man for COVID-19 Dose Selection

2020 ◽  
Author(s):  
Ghaith Aljayyoussi ◽  
Rajith KR Rajoli ◽  
Henry Pertinez ◽  
Shaun H Pennington ◽  
W. David Hong ◽  
...  
Keyword(s):  
Therapeutic Potential ◽  
Systemic Circulation ◽  
Dose Effect ◽  
Dose Selection ◽  
Pulmonary Exposure ◽  
Drug Concentrations ◽  
Treatment Dose ◽  
Relationship Of

ABSTRACTChloroquine has attracted intense attention as a potential clinical candidate for prevention and treatment of COVID-19 based on reports of in-vitro efficacy against SARS-CoV-2. While the pharmacokinetic-pharmacodynamic (PK-PD) relationship of chloroquine is well established for malaria, there is sparse information regarding its dose-effect relationship in the context of COVID-19.Here, we explore the PK-PD relationship of chloroquine for COVID-19 by modelling both achievable systemic and pulmonary drug concentrations. Our data indicate that the standard anti-malarial treatment dose of 25mg/kg over three days does not deliver sufficient systemic drug exposures for the inhibition of viral replication. In contrast, PK predictions of chloroquine in the lungs using in-vivo data or human physiologically-based PK models, suggest that doses as low as 3mg/kg/day for 3 days could deliver exposures that are significantly higher than reported antiviral-EC90s for up to a week. Moreover, if pulmonary exposure is a driver for prevention, simulations show that chronic daily dosing of chloroquine may be unnecessary for prophylaxis purposes. Instead, once weekly doses of 5mg/kg would be sufficient to achieve a continuous cover of therapeutically active pulmonary exposures.These findings reveal a highly compartmentalised distribution of chloroquine in man that may significantly affect its therapeutic potential against COVID-19. The systemic circulation is shown as one site where chloroquine exposure is insufficient to inhibit SARS-CoV-2 replication. However, if therapeutic activity is driven by pulmonary exposure, it should be possible to reduce the chloroquine dose to safe levels. Carefully designed randomized controlled trials are urgently required to address these outstanding issues.

scholarly journals Metastatic cells are preferentially vulnerable to lysosomal inhibition

2018 ◽  
Vol 115 (36) ◽  
pp. E8479-E8488 ◽  
Author(s):  
Michael J. Morgan ◽  
Brent E. Fitzwalter ◽  
Charles R. Owens ◽  
Rani K. Powers ◽  
Joseph L. Sottnik ◽  
...  
Keyword(s):  
Tumor Cells ◽  
Expression Patterns ◽  
Selective Vulnerability ◽  
Molecular Alterations ◽  
Metastatic Cells ◽  
Lung Colonization ◽  
Potential Biomarker ◽  
Selection For

Molecular alterations that confer phenotypic advantages to tumors can also expose specific therapeutic vulnerabilities. To search for potential treatments that would selectively affect metastatic cells, we examined the sensitivity of lineage-related human bladder cancer cell lines with different lung colonization abilities to chloroquine (CQ) or bafilomycin A1, which are inhibitors of lysosome function and autophagy. Both CQ and bafilomycin A1 were more cytotoxic in vitro to highly metastatic cells compared with their less metastatic counterparts. Genetic inactivation of macroautophagy regulators and lysosomal proteins indicated that this was due to greater reliance on the lysosome but not upon macroautophagy. To identify the mechanism underlying these effects, we generated cells resistant to CQ in vitro. Surprisingly, selection for in vitro CQ resistance was sufficient to alter gene expression patterns such that unsupervised cluster analysis of whole-transcriptome data indicated that selection for CQ resistance alone created tumor cells that were more similar to the poorly metastatic parental cells from which the metastatic cells were derived; importantly, these tumor cells also had diminished metastatic ability in vivo. These effects were mediated in part by differential expression of the transcriptional regulator ID4 (inhibitor of DNA binding 4); depletion of ID4 both promoted in vitro CQ sensitivity and restored lung colonization and metastasis of CQ-resistant cells. These data demonstrate that selection for metastasis ability confers selective vulnerability to lysosomal inhibitors and identify ID4 as a potential biomarker for the use of lysosomal inhibitors to reduce metastasis in patients.

scholarly journals Confounding Factors in the Interpretation of Preclinical Studies

2019 ◽  
Vol 38 (3) ◽  
pp. 228-234 ◽  
Author(s):  
Laura Dill Morton ◽  
Martin Sanders ◽  
William J. Reagan ◽  
Torrie A. Crabbs ◽  
Maralee McVean ◽  
...  
Keyword(s):  
Clinical Pathology ◽  
Early Death ◽  
Study Data ◽  
Dose Selection ◽  
Study Planning ◽  
Complicating Factors ◽  
Final Interpretation ◽  
Design Factors

A number of issues may arise during the conduct of a study which can complicate interpretation of in vitro and in vivo datasets. Speakers discussed the implications of differing interpretations and how to avoid complicating factors during study planning and execution. Consideration needs to be given to study design factors including defining objectives, consideration of expected pharmacological effects, dose selection and drug kinetics, species used, and vehicle selection. In addition, the effects of vivarium temperature effects on various endpoints, how to control variables affecting clinical pathology, and how early death animals, common background findings, and artifacts can affect histopathology interpretation all play into the final interpretation of study data.

scholarly journals Selection for Loss of p53 Function in T-Cell Lymphomagenesis Is Alleviated by Moloney Murine Leukemia Virus Infection in myc Transgenic Mice

2001 ◽  
Vol 75 (20) ◽  
pp. 9790-9798 ◽  
Author(s):  
Euan W. Baxter ◽  
Karen Blyth ◽  
Ewan R. Cameron ◽  
James C. Neil
Keyword(s):  
Transgenic Mice ◽  
Leukemia Virus ◽  
Moloney Murine Leukemia Virus ◽  
Tumor Cell Lines ◽  
Wild Type ◽  
Allele Loss ◽  
Selection For

ABSTRACT Thymic lymphomas induced by Moloney murine leukemia virus (MMLV) have provided many examples of oncogene activation, but the role of tumor suppressor pathways in these tumors is less clear. These tumors display little evidence of loss of heterozygosity, and MMLV is only weakly synergistic with the Trp53 null genotype, suggesting that viral lymphomagenesis involves mechanisms which do not require mutational loss of Trp53function. To explore this relationship in greater depth, we infected CD2-myc transgenic mice with MMLV and examined the role of Trp53 in the genesis of these tumors. Most (19 of 27) of the tumors from MMLV-infected, CD2-myc Trp53 +/− mice retained the wild-typeTrp53 allele in vivo while tumors of uninfected CD2-myc Trp53 +/− mice invariably showed allele loss from a significant fraction of primary tumor cells. The functional integrity of the Trp53gene in these tumors was indicated by ongoing allele loss or selection for mutational stabilization during in vitro propagation and by the radiosensitivity of selected Trp53 +/−tumor cell lines. An inverse correlation was noted between retention of the wild-type Trp53 allele and expression of p19ARF, providing further evidence of negative-feedback control of the latter by p53. However, expression of p19ARFdoes not appear to be counterselected in the absence of p53, and its integrity in Trp53 +/− tumors was indicated by its transcriptional upregulation on Trp53 wild-type allele loss in vitro in selected tumor cell lines. The role of MMLV was investigated further by analysis of proviral insertion sites in tumors of CD2-myc transgenic mice sorted forTrp53 genotype. A proportion of tumors showed insertions at Runx2, an oncogene which has been shown to collaborate independently with CD2-myc and with theTrp53 null genotype, and at a novel common integration site (ptl-1) on chromosome 8. Genotypic analysis of the panel of tumors suggested that neither of these integrations is functionally redundant with loss of p53, but it appears that the combination of the MMLV oncogenic program with the CD2-myc oncogene relegates p53 loss to a late step in tumor progression or in vitro culture. While the means by which these tumors preempt the p53 tumor suppressor response remains to be established, this study provides further evidence that irreversible inactivation of this pathway is not a prerequisite for tumor development in vivo.

scholarly journals Extraepitopic Compensatory Substitutions Partially Restore Fitness to Simian Immunodeficiency Virus Variants That Escape from an Immunodominant Cytotoxic-T-Lymphocyte Response

2004 ◽  
Vol 78 (5) ◽  
pp. 2581-2585 ◽  
Author(s):  
Thomas C. Friedrich ◽  
Christopher A. Frye ◽  
Levi J. Yant ◽  
David H. O'Connor ◽  
Nancy A. Kriewaldt ◽  
...  
Keyword(s):  
Cytotoxic T Lymphocyte ◽  
Chronic Phase ◽  
Escape Mutant ◽  
Gag Protein ◽  
Immunodeficiency Virus ◽  
Rate Of Escape ◽  
Selection For ◽  
Cytotoxic T Lymphocyte Response

ABSTRACT Selection for escape mutant immunodeficiency viruses by cytotoxic T lymphocytes (CTL) has been well characterized and may be associated with disease progression. CTL epitopes accrue escape mutations at different rates in vivo. Interestingly, certain high-frequency CTL do not select for escape until the chronic phase of infection. Here we show that mutations conferring escape from immunodominant CTL directed against an epitope in the viral Gag protein are strongly associated with extraepitopic mutations in gag in vivo. The extraepitopic mutations partially restore in vitro replicative fitness of viruses bearing the escape mutations. Constraints on epitope sequences may therefore play a role in determining the rate of escape from CTL responses in vivo.

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