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Adaptive humoral immunity and immunoprophylaxis
Published in Gabriel Virella, Medical Immunology, 2019
When the proper sum of specific signals and costimulatory signals is received by the B cell, clonal proliferation and differentiation ensue. Since each immunogen presents a multitude of epitopes, a normal immune response is polyclonal, i.e., involves many different clones recognizing different epitopes of an immunogen. The induction of an immune response requires some time, for activation of all the relevant cells, and for proliferation and differentiation of B cells into plasma cells. Thus, there is always a lag phase between the time of immunization and the time when antibodies become detectable. It must be noted that while most activated B cells will become antibody-producing plasma cells, some will become memory cells (see discussion later in chapter).
DNA Repair During Aging
Published in Alvaro Macieira-Coelho, Molecular Basis of Aging, 2017
In 1935 Hollaender and Curtis34 published a paper on the effect of sublethal doses of UV irradiation on E. coli suspensions. They discovered that: The retarded growth (lag) phase of the irradiated bacteria was extended considerably over the control. This extension apparently depends on the energy applied to the suspension. When the bacteria had completed their growth, the suspension with the control and that with the irradiated bacteria contained the same number of organisms, andA careful determination of the lag phase revealed that where the control culture changed little in number of bacteria during this phase, the culture which had survived irradiation increased in number quite rapidly in the earlier part of the lag phase and then slowed down more or less for a certain time before it came into the log phase, thus producing a modified extension of the lag phase. The growth curve of the control rising in the beginning of the lag phase actually crossed the curve of the exposed culture and in the end an extension of the lag phase was induced by the radiation. The total number of viable bacteria of the exposed culture had increased during the lag phase. These increases were so pronounced that in the time during which the control culture showed a change in number of not more than 10 to 15%, the exposed culture had increased up to, or more than, 100%.
Biology of microbes
Published in Philip A. Geis, Cosmetic Microbiology, 2006
When microorganisms are first introduced into fresh media, no immediate increase in cell numbers occurs. This is referred to as the lag phase. All cultures go through a lag phase if the medium is different from the one the organisms were transferred from or when the organisms are not in exponential phase. The lag phase may be the result when cells are old and depleted of ATP or it may be due to essential cofactors or ribosomes that must be synthesized before binary fission can occur. The lag phase is especially long if an inoculum is from an old culture. Sometimes the lag phase can be avoided entirely if an inoculum is transferred during log phase into a fresh medium of the same composition.
Effects of platelets activated by different agonists on fibrin formation and thrombin generation
Published in Platelets, 2023
Ivan A. Muravlev, Anatoly B. Dobrovolsky, Olga A. Antonova, Svetlana G. Khaspekova, Alexey V. Mazurov
Platelets treated with the same agonists and prepared in the same way as in PRA (sedimentation in 96-well plates) were tested for their ability to accelerate thrombin generation. Tissue factor with minimum amount of phospholipids was used as a trigger reagent. As in PRA, in TGT platelets were exposed to endogenous thrombin formed after initiation of the coagulation cascade. Typical thrombin generation curves are given in Figure 3 and statistical data in Table II. Very low concentrations of thrombin were detected when the reaction was performed without platelets. Platelets which were not treated with exogenous agonists induced a 3- to 4-fold increase in endogenous thrombin potential (ETP), thrombin peak and maximum rate of thrombin generation. The effect on lag phase was much less pronounced: it shortened by about 15%. Incubation with exogenous agonists had no effect on lag phase and ETP (lag phase slightly shortened only in the presence of A23187) but markedly increased peak and maximum rate of thrombin generation. Thrombin generation was accelerated almost in the same order as fibrin formation in PRA: A23187 >> collagen > arachidonic acid > TRAP > ADP ≈ no agonist. Weak effect of TRAP in TGT could be explained by its competition with exogenous thrombin.
The impact of converting a power plant from coal to natural gas on pediatric acute asthma
Published in Journal of Asthma, 2022
Robert Clemons, Maiying Kong, Kahir Jawad, Yana Feygin, Kerry Caperell
For the primary analysis, we used segmented Poisson regression of interrupted timeseries data to examine changes in the rate of asthma-related visits in Louisville that were associated with the transition to cleaner fuel by Louisville Gas and Electric. There were two time periods—before and after July 1, 2015. Interrupted time-series analysis does not require an intervention to be introduced overnight, but the period of implementation should be well defined so it can be considered separate. While we select July 1, 2015 as our cut-point for analysis, it took LGE 2–3 months to implement all changes to their power plant. As such, we hypothesized a short lag phase would exist until a significant decrease in pediatric asthma ED visits was observed. In our time-series analysis, a priori, we selected a slope change, following a lag impact model. All analyses were conducted using SAS, version 9.4 (SAS Institute Inc), and 2-sided p < 0.05 was considered statistically significant.
Engineered PLGA microspheres for extended release of brexpiprazole: in vitro and in vivo studies
Published in Drug Development and Industrial Pharmacy, 2021
Bangqing Wu, Lijun Wu, Yingju He, Zongning Yin, Li Deng
In summary, brexpiprazole loaded PLGA microspheres with spherical and porous structures were successfully prepared via a facile O/W emulsion-solvent evaporation method. In vitro brexpiprazole release from PLGA microsphere formulations showed a triphasic release profile, with an initial burst release, followed by a lag phase and then a secondary zero-order release phase. In vivo, these microspheres exhibited a biphasic release curve with an initial burst followed by a clear zero-order release phase. The lack of a lag phase in vivo might be the result of complex internal environment. In addition, the release rate of the drug in vivo was faster. Both in vitro and in vivo release data suggest that the microspheres have controlled and sustained release potential, which offers an alternative treatment option for patients with schizophrenia.