The overall PD group (21 rats) was randomly divided into three subgroups. The PD + L-DOPA 8 mg group and the PD + L-DOPA 6 mg group (seven rats each) were given intraperitoneal injections of 8 mg and 6 mg, respectively, of L-DOPA (Sigma-Aldrich, Buchs, Switzerland) together with 15 mg/kg of benserazide (Sigma-Aldrich, Buchs, Switzerland) diluted in NaCl 0.9%, once a day for 21 days, while the PD + saline group (seven rats) received saline injections only. The naive group (seven healthy rats) received the same treatment as the PD + L-DOPA 8 mg group. The experimenter analyzing the behavior was blinded to the injection conditions.
L dopa
Manufactured by Merck Group
Sourced in United States, Germany, Spain, Macao, China, Italy, Sweden, Japan, United Kingdom, France, Switzerland, Australia, Canada, Poland, India, Israel
L-DOPA is a laboratory product manufactured by Merck Group. It is a chemical compound used as a precursor in the synthesis of various pharmaceutical and research-related substances. The core function of L-DOPA is to serve as a starting material or intermediate in chemical reactions and processes. No further details or interpretations are provided.
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Lab products found in correlation
Mushroom tyrosinase, by Merck Group (53 mentions)
Kojic acid, by Merck Group (44 mentions)
Dimethyl sulfoxide (dmso), by Merck Group (37 mentions)
α msh, by Merck Group (33 mentions)
L tyrosine, by Merck Group (32 mentions)
Benserazide, by Merck Group (25 mentions)
Fetal bovine serum (fbs), by Thermo Fisher Scientific (23 mentions)
Arbutin, by Merck Group (22 mentions)
Tyrosinase, by Merck Group (22 mentions)
2 2 diphenyl 1 picrylhydrazyl (dpph), by Merck Group (18 mentions)
Quercetin, by Merck Group (16 mentions)
Gallic acid, by Merck Group (16 mentions)
Benserazide hydrochloride, by Merck Group (15 mentions)
Penicillin streptomycin, by Thermo Fisher Scientific (14 mentions)
Sodium hydroxide (naoh), by Merck Group (12 mentions)
Dopamine, by Merck Group (11 mentions)
Ascorbic acid, by Merck Group (11 mentions)
Triton x 100, by Merck Group (11 mentions)
Trolox, by Merck Group (11 mentions)
6 ohda, by Merck Group (9 mentions)
444 protocols using l dopa
1
Investigating L-DOPA Dosage Effects in Parkinson's Rat Model
2
Selective Depletion of Meso-Cortical Dopamine
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Rats were anesthetized with chloral hydrate (400 mg kg−1, i.p.). Thirty minutes before surgery, rats received an i.p. injection of desipramine hydrochloride (25 mg kg−1; Sigma) in order to prevent noradrenergic terminals from taking up 6-OHDA65 (link). To selectively deplete meso-cortical dopamine innervation to the M1, 8 μg of 6-OHDA (Sigma, St Louis, MO, USA) dissolved in 2 μl of sterile 0.9% saline and 0.02% ascorbic acid (or 2 μl of 0.9% saline for sham injection) was injected into bilateral M1 forelimb territory at a rate of 1 μl min−1 respectively. The micro-syringe for injection stayed in the brain for 15 min in order to prevent backflow of solution. For levodopa (L-DOPA)-treated group, 6-OHDA lesioned or sham-operated animals received intraperitoneal injection of L-DOPA (Sigma) 30 min before behaviour training. L-DOPA was given at a dose of 15 mg kg−1 dissolved in vehicle solution (saline with 0.1% ascorbic acid), combined with the peripheral decarboxylase inhibitor benserazide-HCl (Sigma) at a dose of 15 mg kg−1.
3
Modeling Parkinson's Disease Dyskinesia
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The rats were anesthetized with pentobarbital sodium (purchased from the Chinese domestic market) 50 mg/kg (IP), positioned in a stereotaxic frame and injected 6-OHDA (Sigma Aldrich) into the medial forebrain bundle at the following coordinates relative to bregma and dural surface, in mm: tooth bar position -3.3, AP = -1.8, ML = -2, DV = -8.6 (18ug 6-OHDA). Two weeks after surgery the animals were injected apomorphine HCl (Sigma Aldrich, given IP) and contralateral full body turns were recorded over 30 minutes. Only rats with rotational scores ≥180 turns/30 minutes were selected for the next experimental stage. To generate L-DOPA-induced dyskinesia, one day after the apomorphine-induced rotation test the rats were administered daily 6 mg/kg L-DOPA (Sigma Aldrich) and 15 mg/kg benserazide HCl (purchased from the Chinese domestic market), hereafter denoted as L-DOPA, for 21 days. Thereafter, the rats that had not developed dyskinesia were excluded from the study, and the rats with total axial, limb, orolingual and locomotive abnormal involuntary movement (AIM) scores ≥28 points/120 minutes were kept on a treatment regimen of at least two injections of L-DOPA per week to maintain stable AIM scores. The rats with stable AIM scores were allocated to groups balanced with respect to AIM severity and treated with the drugs or drug combinations as described in the figure legends.
4
Assessing Parkinson's-like Motor Deficits in Mice
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The modified constant speed rotarod assay was performed as previously described.29 (link), 36 (link) After a training period when each mouse attained stable baseline levels of performance staying at 15 r.p.m. for 60 s, mice received several trials at 15, 25, 35 and 44 r.p.m. rotation speed with 60-s maximum trial length and 5-min intervals between individual trials. Two maximal values per speed per day were used to calculate the average, which was used for subsequent statistical analyses.
For the open field test, mice were placed individually into an open arena and monitored for 5 min via video camera. The resulting data were analyzed using the image processing system EthoVision 3.0 (Noldus Information Technology, Wageningen, Netherlands) and Any-maze 4.82 (Stoelting Co., Wood Dale, IL, USA). For each sample, the system recorded position, object area and the status of defined events to calculate the traveled distance.
To follow the effects of L-3,4-dihydroxyphenylalanine (l -DOPA) on locomotor performance, 17 weeks post Tam (wpT) injection control and Dicerfl/fl/DATCreERT2 mice were tested in the modified rotarod assay before and immediately after an intraperitoneal injection of 20 mg/kg l -DOPA (Sigma-Aldrich) complemented with 12 mg/kg benserazide (Sigma-Aldrich).
For the open field test, mice were placed individually into an open arena and monitored for 5 min via video camera. The resulting data were analyzed using the image processing system EthoVision 3.0 (Noldus Information Technology, Wageningen, Netherlands) and Any-maze 4.82 (Stoelting Co., Wood Dale, IL, USA). For each sample, the system recorded position, object area and the status of defined events to calculate the traveled distance.
To follow the effects of L-3,4-dihydroxyphenylalanine (
5
Melanocyte Purity Determination: Tyrosinase Assay
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Purity of melanocytes was determined by visual observation of cell morphology and histochemical analyses. Melanocytes were morphologically identified based on their characteristic dendritic morphology with multiple long processes and variable pigmentation. Tyrosinase (TYR) activity in melanocytes was assayed via L-DOPA reaction as previously described (27 (link)): culture media were removed and melanocytes rinsed twice in PBS, fixed for 20 min in fixative solution (ethanol:chloroform:acetic acid = 6:3:1), washed three times with PBS, and then incubated at 37°C for 18 h in the dark with 10 mM L-DOPA (Sigma, USA). Negative control melanocytes were incubated in the absence of L-DOPA. After incubation, the melanocytes were rinsed with distilled water, dehydrated, and mounted. Melanocytes that stained positive for TYR activity were observed via light microscopy.
6
Motor Function Assays in Mice
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Two behavioural tests for motor function assay were used, the open field test and CatWalk XT gait analysis. Experimenters were blinded to genotypes during behavioural testing as previously described (Angeby-Moller et al., 2008 (link)).
l -DOPA (25 mg/kg, i.p.; Sigma) or saline vehicle (0.9%, i.p.) was administered 30 min before each session in a counterbalanced manner. The peripheral decarboxylase inhibitor benserazide (12.5 mg/kg, i.p.; Sigma) was administered 20 min before l -DOPA while saline-treated animals received an additional injection of saline at the same time point.
7
Mushroom Tyrosinase Inhibition Assay
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The measurement of Mushroom tyrosinase activity was modified from the published method [65 (link),66 (link)]. l - Tyrosine (Bio Basic, Ontario, Canada) or l - DOPA (Sigma Chemical, St. Louis, MO, USA) were used as substrates for monophenolase and diphenolase activity, respectively. Each sample was diluted to a series of concentrations (0.039, 0.078, 0.156, 0.3125, 0.625, 1.25, 2.5, and 5 mg/mL). Mushroom tyrosinase (Sigma Chemical, St. Louis, MO, USA) was dissolved in 0.1 M phosphate buffer (pH = 6.8) to obtain the final concentration of 100 units/mL. The reaction was started by adding 40 µL of sample solution, 80 µL of phosphate buffer, 40 µL of Mushroom tyrosinase, and 40 µL of substrates (1.5 mM l - tyrosine or 2.5 mM l - DOPA solution). After incubation at room temperature for 15 min, the l - dopachrome formation was measured at 475 nm. The percentage of Mushroom tyrosinase inhibition was calculated using the following equation:
where A = vehicle control, B: = vehicle control without Mushroom tyrosinase, C = sample mixed with Mushroom tyrosinase, and D = sample without Mushroom tyrosinase. The results were expressed as IC50 values (the concentration that caused 50% Mushroom tyrosinase inhibition).
where A = vehicle control, B: = vehicle control without Mushroom tyrosinase, C = sample mixed with Mushroom tyrosinase, and D = sample without Mushroom tyrosinase. The results were expressed as IC50 values (the concentration that caused 50% Mushroom tyrosinase inhibition).
8
Tyrosinase Enzyme Isolation and Activity Assay
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The tyrosinase enzyme was isolated from potato and purified by using the method described by the literature.63 (link) Tyrosinase activity was determined through measuring the oxidation of 3,4-dihydroxyphenylalanine (l -DOPA, Sigma), which was constructed by Pomerantz et al.:64 (link) 50 μL of enzyme extract was added to 450 μL of 0.05 M phosphate buffer (pH 6.8) containing 50 μM chelators, and the mixture was preincubated at 30 °C for 10 min, 500 μL of 5 mM l -DOPA solution was then added, and the increase in absorption at 475 nm (ε = 3600 M cm–1) due to the formation of DOPA chrome was monitored as a function of time. The initial rate could be used to estimate the tyrosinase activity and the control was a blank containing 1% DMSO.
9
Tissue-Specific L-dopa Metabolism
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The whole blood, colon contents, jejunum, and brain tissues of SD rats (n = 6) were collected. Colonic contents were pooled and suspended in anaerobic medium (Aobox) at a ratio of 1:20 (g/mL), the mixtures were centrifuged at 800 g (4°C) for 10 min, and then collected the supernatant for culture. Tissues were pooled and weighed, then homogenized with 5 mM phosphate buffer (pH = 7.4) at the ratio of 1:5 (g/ml). The incubation systems of rat intestinal bacteria, tissue homogenate, and whole blood were treated with L‐dopa (0.3 mM, Sigma) and L‐dopa (0.3 mM) + PIP (10 or 20 μg/mL), respectively. The intestinal bacterial cultures were incubated in an anaerobic chamber, while tissues or blood incubation systems were incubated at 37°C for 12 and 24 h, and then the incubation was terminated with three‐fold acetonitrile. After centrifugation at 12,000 g for 10 min, the supernatants were collected for HPLC‐FLD analysis.
10
EEP Modulates Melanin Production in C. neoformans
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C. neoformans was treated with EEP at concentrations of 0.5, 1 and 2 mg/mL for 2 h at 37 °C [18 (link)]. Yeasts were then cultured in the L-3,4-dihydroxyphenylalanine (L-DOPA) minimal medium (15 mM glucose, 10 mM MgSO4, 29.4 mM KH2PO4, 13 mM glycine and 3 mM thiamine; pH 5.5), with 1 mM L-DOPA (Sigma-Aldrich, St. Louis, MO, USA) and incubated in a dark chamber at 30 °C and in a shaking incubator for 5 days. The melanin pigment production was observed daily. To confirm the viability of yeast cells, the cells were diluted, adjusted to 5 × 105, 5 × 104 and 5 × 103 cells/mL, and dropped on a SDA plate. After 48 h of incubation at 37 °C, the number of colony-forming units (CFUs) were counted [19 (link)].
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