Transcriptional regulatory region and DNA methylation analysis of TNNI1 gene promoters in Gaoyou duck skeletal muscle (Anas platyrhynchos domestica).

1. The slow skeletal muscle troponin I (TNNI1) gene has been found to be specifically expressed in slow muscle fibres and plays an important role in muscle development. The aim of this study was to determine the active control area of duck TNNI1 and identify the potential cis-regulatory elements in the promoter. 2. In this study, the TNNI1 promoter was first cloned by genome walking and the sequences were analysed using bioinformatics software. Firefly luciferase reporter gene vectors, driven by a series of constructs with progressive deletions, were used to identify the core transcriptional regulatory region of the duck TNNI1 gene. The methylation status of the CpG island in the TNNI1 promoter was detected in skeletal muscle on embryonic days 21 and 27, by bisulphite sequencing PCR (BSP). 3. The results showed two CpG islands presented in the promoter region, with one of the CpG islands located in the core transcriptional regulatory region (-2078/-885 bp). The total methylation levels of the 14 CpG sites were not altered between breast and leg muscles on embryonic days 21 and 27. However, four CpG sites (loci of positions 4, 11, 13, and 14) showed dramatically different methylation levels between breast and leg muscles at embryonic days 21 and 27. Analysis showed that multiple CpG sites had a significant correlation between the methylation levels of the CpG sites and mRNA expressions in skeletal muscle. Multiple transcription factor binding sites including Sp1, c-Myc, Oct-1 and NF-kB motifs were identified and might be responsible for transcriptional regulation of the TNNI1 gene. 4. These findings contribute to further understanding of the fundamental mechanism for transcriptional regulation of the TNNI1 gene in ducks.

Effect of cadmium in feed on organs and meat colour of growing pigs.

One hundred and ninety-two barrows (Duroc x Landrace x Yorkshire, initial weight 27.7 kg) were used to investigate the effects of cadmium in feed on the function of selected organs and meat colour of growing pigs. The pigs were randomly allocated into four different treatments. Each treatment included three replications with 16 pigs per replicate. The animals were fed corn-soybean basal diet and supplemented with 0, 0.5, 5.0, 10.0 mg/kg cadmium (as CdCl(2)), respectively. The feeding trial ended when the average body weight of the pigs reach 90 kg. The results showed that, compared with controls, addition of 10 mg/kg cadmium to the diet resulted in significant elevations of relative weight of liver and spleen by 18.3% (p<0.05) and 19.7% (p<0.05) respectively, and of serum glutamic-pyruvic transaminase (GPT) and glutamic-oxaloacetic transaminase (GOT) activities by 17.8% (p<0.05) and 27.4% (p<0.05) respectively; and significant decreases of Na(+)/K(+)-ATPase activity in the liver by 24.6% (p<0.05), the redness of longissimus dorsi by 26.6% (p<0.05) and 24.9% (p<0.05) at 0.75 h and 16 h post mortem, respectively, and of the myoglobin content of longissimus dorsi by 19.4% (p<0.05). No changes were found in these indices above when the pigs were fed the diet supplied with 0.5 or 5 mg/kg cadmium (p>0.05), nor in renal functions among cadmium-treatment treatments (p>0.05) as indicated is the activities of urinary N-acetyl-beta-D-glucosaminidase (NAG) and alkaline phosphatase (ALP) and the content of urinary protein. The study indicated the adverse effects of 10 mg/kg cadmium in feed on liver functions and meat colour of growing pigs.

[Observation on phrenic discharges induced by bicuculline or picrotoxin in spinal rabbits].

The respiratory activity of spinal cord-transected animals was reinvestigated on 71 rabbits. Under light urethane anesthesia and paralyses by gallamine, the spinal cord was transected at either C1 or C2 level, and phrenic discharges were monitored in 43 rabbits. After cordotomy, tonic phrenic discharges were observed in 25 of the 43 spinal rabbits. No spontaneous rhythmic phrenic activities appeared in any of the animal. Respiratory-like, long lasting phrenic bursts (lasting longer than 0.25s) or convulsive-like, short lasting phrenic bursts (lasting shorter than 0.1s on the average) were induced by administration of bicuculline (BCL, 20 micrograms/10 microliters-40 micrograms/20 microliters, intra-subarachnoid space, i.s.s.) in 24 spinal rabbits or picrotoxin (PIC, 20 micrograms/20 microliters, i.s.s. or 3-5 mg/kg i.v.) in 13 spinal rabbits. According to the pattern of the recruitment and de-recruitment of the phrenic discharges, the long lasting phrenic bursts may be divided into three types: Type I, average frequency 23.5 +/- 2.3 cycles/min (BCL), incidence 58.5% (BCL) or 67.7% (PIC); Type II, average frequency 33.8 +/- 4.7 cycles/min (BCL), incidence 39.3% (BCL) or 32.3% (PIC); Type III, average frequency 21.3 +/- 2.8 cycles/min (BCL), incidence 2.2% (BCL) or 3.3% (PIC). The duration of the evoked phrenic discharges was 60.0 +/- 18.9 min (BCL) or 42.0 +/- 0.8 min (PIC). The type I and type II showed respiratory-like discharges, accounting for more than 97.8% of the incidence of the long lasting phrenic bursts. It is suggested that the endogenous GABA system in spinal cord might exert a tonic inhibitory action on the spinal "respiration" activity.