Doped nanomaterial facilitates 3D printing target plate for rapid detection of alkaloids in laser desorption/ionization mass spectrometry.

This work aims to rapidly detect toxic alkaloids in traditional Chinese medicines (TCM) using laser desorption ionization mass spectrometry (LDI-MS). We systematically investigated twelve nanomaterials (NMs) as matrices and found that MoS2 and defect-rich-WO3 (D-WO3) were the best NMs for alkaloid detection. MoS2 and D-WO3 can be used directly as matrices dipped onto conventional ground steel target plates. Additionally, they can be conveniently fabricated as three-dimensional (3D) NM plates, where the MoS2 or D-WO3 NM is doped into resin and formed using a 3D printing process. We obtained good quantification of alkaloids using a chemothermal compound as an internal standard and detected related alkaloids in TCM extracts, Fuzi (Aconiti Lateralis Radix Praeparata), Caowu (Aconiti Kusnezoffii Radix), Chuanwu (Aconiti Radix), and Houpo (Magnoliae Officinalis Cortex). The work enabled the advantageous "dip and measure" method, demonstrating a simple and fast LDI-MS approach that achieves clean backgrounds for alkaloid detection. The 3D NM plates also facilitated mass spectrometry imaging of alkaloids in TCMs. This method has potential practical applications in medicine and food safety. Doped nanomaterial facilitates 3D printing target plate for rapid detection of alkaloids in laser desorption/ionization mass spectrometry.

[Effects of intracerebroventricular microinjection of L-arginine on exercise capacity and expression of nitric oxide in rat hypothalamus].

OBJECTIVE: To explore the relationship between nitric oxide (NO) in central nervous system and exercise-induced fatigue stress and to study the effect of L-arginine (L-Arg), as a substrate of nitric oxide, on the exercise capacity and NO content in the exhausted rat brain and blood. METHODS: Through an implanted cannula, the normal saline or L-Arg was microinjected into rat's intracerebroventrical for consecutive four days. Then an acute exhaustive model (on the speed of 18 m/min, an inclination of 5 degrees) was established with animal treadmill. The time of exercise till exhaustion was recorded, and the total workload was calculated that represented the exercise capacity. Nitrate and nitrite (NO3/NO2-, NOx-) levels in blood, hypothalamus and hippocampus were assayed. RESULTS: Both the time of exercise till exhaustion and total workload in the LArg group increased respectively by 51.8% and 50.08% (P < 0.05), compared with those in the control. The NOx- content in hypothalamus in the L-Arg group (8.93 +/- 1.83) micromol/g pro was larger than that in the control (4.25 +/- 0.79) micromol/g pro, (P < 0.01). There was no significant difference in NOx- content in brain and hippocampus between the two groups. The total workload was positively correlated with NOx- concentration in hypothalamus (P < 0.01). However, there was no correlation between workload and changes in hippocampus NOx- content at fatigue. CONCLUSION: Intracerebroventricular microinjection of L-Arg may enhance the exercise capacity and lead to up-regulation of NO by means of L-Arg-NO signal path in the hypothalamus. Hypothalamus may be a key site in brain in the modulation of physiological exercise.