The phrase "activated directly" is correct and usable in written English.
It can be used in contexts where something is triggered or turned on without any intermediaries or additional steps.
Example: "The system can be activated directly by pressing the main power button."
Alternatives: "triggered immediately" or "turned on directly".
Thus, the pathways shown could be activated directly by ligand-independent activity of cytoplasmic mutant TNFR1 and/or indirectly by exogenous proinflammatory cytokines (TNF, IL-6, IL-1).
However, mTOR can be activated directly by amino acids, causing a subsequent stimulation of p70S6K activity [ 12, 13].
PLC γ is activated directly upon binding to the phosphorylated Ret receptors, while ERK1/2 activation requires the participation of several signaling intermediates.
In addition, ILCs lack recombination-activating gene (RAG), meaning that unlike B and T cells, ILCs can be activated directly (Spits and Cupedo, 2012; Spits et al., 2013).
cAMP is synthesized by adenylate cyclases, which may be activated directly by stress.
Constantinople, C.M. & Bruno, R.M. Deep cortical layers are activated directly by thalamus.
Ladle slag with higher alumina could not be activated directly by carbon dioxide to gain strength.
The prepaid plan can be activated directly from the iPad and, because there is no contract, can be canceled at anytime".
ON and OFF midget, ON and OFF parasol, and small bistratified ganglion cells could all be activated directly to fire a single spike with submillisecond latency using brief pulses of current within established safety limits.
Our data further suggest that the A11 nucleus may not be activated directly by trigeminohypothalamic afferents.
Furthermore, cellular studies in primary TG neurons and in heterologous TRPV4-expressing cells suggest that TRPV4 can be activated directly by formalin to gate Ca(2+).
