Analysis of flow rate and pressure in syringe-based wound irrigation using Bernoulli's equation.

The objective of this study was to examine the dependence of the pressure level in the wound area on the height of the syringe needle from the wound, the gauge of the needle, and the flow rate using the Bernoulli equation. This study was the control-volume analysis using the Bernoulli equation. At a given height of the syringe needle from the wound, the gauge of the syringe needle was fixed, and the pressure in the wound area, which depended on the flow rate of the irrigation solution discharged from the tip of the needle, was calculated according to the Bernoulli equation and the definition of the flow rate. At a constant flow rate of the irrigation solution, the velocity of the irrigation solution discharged through the syringe needle decreased (7.80 → 0.80) with an increase in the diameter of the needle (18G → 14G). At a constant inner diameter of the needle, the velocity of the irrigation solution increased with a reduction in the flow rate of the solution. As the velocity of the irrigation solution increased, the pressure in the wound area increased. As the height of the syringe needle from the wound area increased, the pressure in the wound area increased. In order to maintain the pressure of 8-15 psi when nurses perform syringe-based irrigation, it is necessary to set the flow rate of the cleaning solution from 3.5 cc/s to less than 4.8 cc/s for 19G. In addition, 20G maintains the flow rate of the solution at 2.6 cc/s or more and less than 3.5 cc/s, 22G maintains the flow rate of solution at 1.3 cc/s or more and less than 1.8 cc/s, and 25G maintains the flow rate of solution at 0.5 cc/s. This study provides nurses with a reference for the flow rate at which syringe-based irrigation can be performed while maintaining the appropriate pressure based on fluid dynamics, which can be used as the basis for wound nursing standards.

Rapid degradation of replication-dependent histone mRNAs largely occurs on mRNAs bound by nuclear cap-binding proteins 80 and 20.

The translation of mammalian messenger RNAs (mRNAs) can be driven by either cap-binding proteins 80 and 20 (CBP80/20) or eukaryotic translation initiation factor (eIF)4E. Although CBP80/20-dependent translation (CT) is known to be coupled to an mRNA surveillance mechanism termed nonsense-mediated mRNA decay (NMD), its molecular mechanism and biological role remain obscure. Here, using a yeast two-hybrid screening system, we identify a stem-loop binding protein (SLBP) that binds to a stem-loop structure at the 3'-end of the replication-dependent histone mRNA as a CT initiation factor (CTIF)-interacting protein. SLBP preferentially associates with the CT complex of histone mRNAs, but not with the eIF4E-depedent translation (ET) complex. Several lines of evidence indicate that rapid degradation of histone mRNA on the inhibition of DNA replication largely takes place during CT and not ET, which has been previously unappreciated. Furthermore, the ratio of CBP80/20-bound histone mRNA to eIF4E-bound histone mRNA is larger than the ratio of CBP80/20-bound polyadenylated ß-actin or eEF2 mRNA to eIF4E-bound polyadenylated ß-actin or eEF2 mRNA, respectively. The collective findings suggest that mRNAs harboring a different 3'-end use a different mechanism of translation initiation, expanding the repertoire of CT as a step for determining the fate of histone mRNAs.

Translation initiation on mRNAs bound by nuclear cap-binding protein complex CBP80/20 requires interaction between CBP80/20-dependent translation initiation factor and eukaryotic translation initiation factor 3g.

In the cytoplasm of mammalian cells, either cap-binding proteins 80 and 20 (CBP80/20) or eukaryotic translation initiation factor (eIF) 4E can direct the initiation of translation. Although the recruitment of ribosomes to mRNAs during eIF4E-dependent translation (ET) is well characterized, the molecular mechanism for CBP80/20-dependent translation (CT) remains obscure. Here, we show that CBP80/20-dependent translation initiation factor (CTIF), which has been shown to be preferentially involved in CT but not ET, specifically interacts with eIF3g, a component of the eIF3 complex involved in ribosome recruitment. By interacting with eIF3g, CTIF serves as an adaptor protein to bridge the CBP80/20 and the eIF3 complex, leading to efficient ribosome recruitment during CT. Accordingly, down-regulation of CTIF using a small interfering RNA causes a redistribution of CBP80 from polysome fractions to subpolysome fractions, without significant consequence to eIF4E distribution. In addition, down-regulation of eIF3g inhibits the efficiency of nonsense-mediated mRNA decay, which is tightly coupled to CT but not to ET. Moreover, the artificial tethering of CTIF to an intercistronic region of dicistronic mRNA results in translation of the downstream cistron in an eIF3-dependent manner. These findings support the idea that CT mechanistically differs from ET.