Period Of Muscle Research Articles

Effect of flowing water on the pharmacokinetic properties of norfloxacin in channel catfish (Ictalurus punctatus) after single-dose oral administration.

The recirculating aquaculture system (RAS) is a widely used, water-saving and efficient aquaculture model. However, bacterial diseases are common in farmed fish reared at high densities. Although antibiotics effectively treat these diseases, developing efficient methods to increase drug clearance in fish and decrease the concentrations of antibiotic residues in aquatic products is essential. This study evaluates the effect of flowing water in the RAS on norfloxacin (NOR) pharmacokinetics in channel catfish (Ictalurus punctatus). Channel catfish were randomly divided into the control group (RAS group) and the experimental group (flow-through aquaculture system group) (120 individuals/group). A NOR dose of 20mg/kg was then orally administered to the fish. Plasma, muscle, liver and kidney samples were collected up to 168 h after treatment. NOR concentrations were measured using liquid chromatography-mass spectrometry, and pharmacokinetic parameters were calculated using a non-compartmental method. Flowing water had a significant effect on the plasma pharmacokinetics and tissue distribution of NOR, increasing NOR clearance in the kidney, muscle and plasma. The time to maximum concentration of NOR was shorter in the plasma and longer in the kidney and liver. Moreover, flowing water increased the maximum concentration of NOR in the kidney, muscle and plasma and decreased the area under the concentration-time curve from time 0 to the last measurable concentration in the liver and plasma. Flowing water decreased the withdrawal period in muscle from 10 to 6 days. These results indicate that flowing water can potentially increase NOR clearance in channel catfish.

Progressive Improvement in Static Glabellar Lines After Repeated Treatment With DaxibotulinumtoxinA for Injection.

DaxibotulinumtoxinA for Injection (DAXI) is a novel botulinum toxin in development that has demonstrated efficacy on dynamic glabellar lines. To evaluate the effect of repeated DAXI treatment on static glabellar lines. This post hoc analysis included adults with moderate or severe dynamic glabellar lines who were treated with 40U DAXI in the SAKURA clinical program. Glabellar line severity was evaluated through validated subject and investigator scales. Overall, 568 subjects received 3 DAXI treatments. Most subjects were White (92.3%) and female (85.7%). At baseline, 9.0% and 27.3% of subjects had no static glabellar lines based on subject and investigator assessment, respectively. Four weeks after DAXI Treatment Cycle 1, the proportion of subjects with no static glabellar lines increased to 57.9% and 64.8% based on subject and investigator assessment, respectively. At Week 4 after DAXI Treatment Cycles 2 and 3, the proportion further increased to 68.7% and 71.5%, respectively, based on subject assessment and 75.0% and 77.6% based on investigator assessment. Subjects who received repeated DAXI treatment showed progressive improvement in their static glabellar lines. The extended duration of therapeutic benefit with DAXI on dynamic glabellar lines likely provides a long period of muscle inactivity/hypoactivity, during which dermal remodeling can occur.

Post-mortem activity of the glycogen debranching enzyme and change in the glycogen pools in porcine M. longissimus dorsi from carriers and non-carriers of the RN − gene

Glycogen debranching enzyme (GDE) is together with glycogen phosphorylase responsible for the degradation of glycogen. The present study compares the post-mortem activity of GDE and breakdown of the glycogen pools in M. longissimus dorsi of RN − carrier pigs and in wild type animals. The activity of GDE ( n = 14) and pH ( n = 20) was measured 0.5, 3, 5, 24 and 48 h post-mortem. The change in pro-glycogen and in macro-glycogen content ( n = 20) was followed until 216 h post-mortem and the transcription level of GDE, glycogenin and glycogen synthase m-RNA ( n = 19) were measured 0.5 h post-mortem. Both the activity of GDE and the transcription level of GDE were found to be similar in RN − carriers and wild type animals shortly after slaughter. However, the activity declined faster in wild type animals compared with RN − carriers with increasing time post-mortem. The contents of both pro-glycogen and macro-glycogen were higher in RN − carriers compared with wild type animals, and further, the proportion of macro-glycogen was higher in RN − carriers compared with wild type animals. During the post-mortem period, only degradation of pro-glycogen was observed in both genotypes. The decrease in pH was faster and the ultimate pH lower in RN − carriers than in wild type animals. It was suggested that the higher GDE activity in the late phase of the post-mortem period in muscles from RN − carriers renders the extended pH decrease in these muscles.

Effects of Removal of Muscle Receptor Organ Input on the Temporal Structure of Non-Giant Swimming Cycles in the Crayfish, Cherax Destructor

Most studies of the muscle receptor organs (MROs) of decapod crustaceans have focused on their role in local reflex loops. This may not be their only function. We examine their involvement in the regulation of non-giant swimming cycles by removing stretch receptor (SR) input from the MROs in abdominal segments 2-5 of the crayfish Cherax destructor. SR input was left intact in two control groups, one of which had sham surgery and the other no surgery at all. We recorded electromyograms (EMGs) from selected uropod muscles during tailflipping in sequences of non-giant swimming in tethered animals. The removal of SR input had a significant effect. The opener muscle period was shorter in the experimental group than in either of the control groups. This suggests that by using SR afference, crayfish sacrifice speed for increased control of the swimming movement.

Ipsilateral motor control in pathological left-handedness

Left-handedness may be associated with early brain injury and re-organization of motor control. In a 27-year-old man with pathological left-handedness, transcranial magnetic stimulation (TMS) was used to look for evidence that the ipsilateral right hemisphere contributed to control of his recovered right arm. TMS of each hemisphere elicited normal motor evoked potentials (MEPs) in contralateral arm muscles. Furthermore, TMS of the right motor cortex elicited electromyogram (EMG) silent periods in muscles of the right hand and elicited MEPs in more proximal muscles of the right arm. In contrast, TMS of the left motor cortex had no effect on the EMG in muscles of the left arm. In control subjects, these asymmetries in the effects of ipsilateral cortical stimulation were not observed. We suggest that pathological left-handedness may be a marker for increased functionality of ipsilateral cortical representations in the course of recovery from early brain injury.

Hormonal regulation of motor unit size and synaptic strength during synapse elimination in the rat levator ani muscle

Previous anatomical studies suggest that androgen regulates synapse elimination in the androgen-sensitive levator ani(LA) muscle of the rat. Androgen treatment beginning on postnatal day 7 (P7) prevents some of the normal loss of multiaxonal innervation in this muscle. The present study used physiological techniques to measure the number and size of LA motor units during the synapse elimination period in muscles from normals, and castrates treated with either testosterone propionate or oil. The number of increments in LA twitch tension as nerve stimulation intensity increased, a measure of the number of motor units, was the same at the end (P28) of synapse elimination as near the beginning (P7) of this process. This result indicates that motoneuronal cell death does not contribute to synapse elimination in the LA. Moreover, androgen during this period did not influence the number of LA motor units. In contrast, between P7 and P28, there was a dramatic decline in the size of LA motor units, as indicated by a decrease in the percentage of twitch or tetanus tension of individual motor units relative to the maximal twitch or tetanus tension of the whole muscle. In addition, androgen treatment of castrated males during this period prevented some of the normal decline in the size of LA motor units. Estimates of the number of inputs per LA muscle fiber derived from the number of LA motor units and their average size indicate that androgen maintains polyneuronal innervation in the LA muscle. This finding supports previous anatomical studies suggesting that androgen can prevent synapse elimination in this muscle. The strength of LA synapses was also examined by measuring the tetanus: twitch ratio of individual motor units and by measuring the safety margin of LA synapses. Both measurements indicated that the average strength of LA synapses increases during synapse elimination. Moreover, androgen appeared to spare synapses from elimination without increasing their strength, since androgen-treated muscles generally had larger motor units but the same mean tetanus:twitch ratio and safety margins as untreated LA muscles except at P28, when synapses in androgen-treated LA muscles had appreciably lower safety margins than normal. These results suggest that androgen regulates synapse elimination through a mechanism(s) independent of synaptic strength.

Postmortem Changes in Muscle

The topic of the postmortem period in muscle has a rich history of scientific accomplishment. It is a topic being vigorously pursued at present with new approaches both by seasoned investigators and by a new generation of meat scientists. I must emphasize to you that I am confident it is a topic critically important to improvements in the industry which produces and distributes meat for human consumption. Postmortem change is a topic I feel comfortable with because I took my training and conducted my early work in the area—and that at a time of high activity and major accomplishments. There is a large number of excellent reviews recorded in the literature. I will not attempt to replay them here, but rather use the license of flexibility granted me to develop the concept of the crucial importance scientific work in the area of postmortem change plays in the economically important factor of meat quality.So there is my thesis—I believe that research on postmortem change. in muscle is leading to the situation which will allow control of meat quality to the extent that the industry will be able to respond to changing demands of the consumer, and do so rather rapidly.

Investigations of the silent period in muscles of region of face

Investigations of the silent period in muscles of region of face

Dependence of latent period in muscle on strength of stimulus.

THE so-called latent period, which includes latency relaxation, has an important bearing on theories of excitation coupling. It is surprising then that systematic studies1,2 of this phenomenon do not mention the role of the stimulus. The reason is that, with the frog sartorius, increasing strength of stimulus above twice the threshold value apparently produces no significant effect on the latency, while below this value the effects may conceivably be dismissed as due to ‘recruitment of fibres’. Even here, however, latency relaxation increases and may reach as much as 1 per cent of tetanus tension at ten times threshold field-strength.

The temperature coefficient of the rate of conduction and of the latent period in muscle

The temperature coefficient of the rate of conduction and of the latent period in muscle