Relationship among cattle breed and anabolic implant protocol relative to feedlot performance: Growth, temperament, feeding behavior, carcass traits, and economic return.

Recent research has suggested that different cattle breed types may respond differently to anabolic implant protocols of varying intensity. Therefore, the purpose of this research was to compare anabolic implant protocols in feedlot steers of 2 different breed types. Sixty steers were stratified by weight and breed in a 2 × 3 factorial design examining 2 different breeds: Angus (AN; n=38) or Santa Gertrudis influenced (SG; n=22), and 3 implant strategies: no implant (CON; n=20), a moderate intensity implant protocol (d0 implant: Revalor-G, d56 implant: Revalor-IS, d112 implant: Revalor-S; MI; n=20), or a high intensity implant protocol (d0 implant: Revalor-IS, d56 implant: Revalor-S, d112 implant: Revalor-200; HI; n=20). Steers were randomly placed into pens equipped with GrowSafe bunks to collect dry matter intake and feeding behavior. All animals were fed the same diet. Weight, chute score, exit velocity, serum, rectal temperature, hip height and 12th rib fat thickness were collected approximately every 28 d over a 196 d period. Serum urea nitrogen (SUN) was evaluated as well. Total average daily gain was increased (P < 0.0001) in both the HI and MI steers compared to the CON steers by 29.4% and 26%, respectively. A treatment × breed interaction was observed (P < 0.0001) for hip height, with AN-CON steers being shorter (P < 0.0007) than AN-HI, SG-CON, SG-MI, and SG-HI steers. A breed × treatment interaction was observed (P < 0.004) for chute score and rectal temperature, with SG-HI and SG-MI steers having increased chute scores (P < 0.001) when compared to AN-HI, AN-MI, AN-CON, and SG-CON throughout the course of the trial. Additionally, SG-HI and SG-MI steers had an increased rectal temperature (P < 0.004) compared to AN-HI, AN-MI, AN-CON, and SG-CON steers. A breed effect was observed (P = 0.002) for SUN with AN steers having increased (P = 0.002) SUN concentration compared to SG sired steers, in addition to a treatment effect (P < 0.0001), with CON steers having a higher (P < 0.0001) SUN concentration than MI and HI steers, regardless of breed. The MI implant protocol increased net return per head, on average, by $97.28, regardless of breed, while the HI implant protocol increased net return by only $80.84. Taken together, despite the cattle breed types responding differently to the different anabolic implant protocols at times, a moderate intensity anabolic implant protocol was optimal in this experiment for steers raised in a temperate climate.

Structure determination of the phiX174 closed procapsid.

The structure of a procapsid of the single-stranded DNA bacteriophage ++phiX174 was determined to 3.5 A resolution. The crystal space group was I213 with a unit-cell length of 774 A. The unit cell contained 16 icosahedral virus particles, each situated on a crystallographic threefold axis. Thus, there are two independent one-thirds of a particle per asymmetric unit, and a total of 40-fold non-crystallographic redundancy. To aid in the interpretation of the packing arrangement, crystals were prepared for thin sectioning and analyzed by electron microscopy. Oscillation X-ray diffraction data was collected on image plates using synchrotron radiation and oscillation angles of either 0.25 or 0.30 degrees. A low-resolution 6.5 A data set collected from a single frozen crystal was particularly helpful in the structure determination, because of its completeness and internal consistency. The initial particle orientations were determined using self-rotation functions, while the initial position of one particle was determined from a Patterson map. The structure was solved by molecular replacement real-space averaging using a model based on a cryo-electron microscopy reconstruction as a starting point for the phase determination. The initial structure determination used the data between 20 and 13 A resolution, which was then extended one reciprocal lattice point at a time to 6.5 A resolution. At this point, a 3.5 A resolution data set compiled from a number of crystals collected at 277 K was introduced. Phase extension and averaging continued to 3.5 A resolution after re-determining the particle positions and orientations. The amino-acid sequences of most of the D, F and G proteins and part of the B protein could be unambiguously built into the 3.5 A electron-density map. Partial crystallographic refinement yielded an R factor of 31.6%, consistent with the relatively low resolution and lack of completeness of the data.

Structure of a viral procapsid with molecular scaffolding.

The assembly of a macromolecular structure proceeds along an ordered morphogenetic pathway, and is accomplished by the switching of proteins between discrete conformations as they are added to the nascent assembly. Scaffolding proteins often play a catalytic role in the assembly process, rather like molecular chaperones. Although macromolecular assembly processes are fundamental to all biological systems, they have been characterized most thoroughly in viral systems, such as the icosahedral Escherichia coli bacteriophage phiX174. The phiX174 virion contains the proteins F, G, H and J. During assembly, two scaffoldingproteins B and D are required for the formation of a 108S, 360-A-diameter procapsid from pentameric precursors containing the F, G and H proteins. The procapsid contains 240 copies of protein D, forming an external scaffold, and 60 copies each of the internal scaffolding protein B, the capsid protein F, and the spike protein G. Maturation involves packaging of DNA and J proteins and loss of protein B, producing a 132S intermediate. Subsequent removal of the external scaffold yields the mature virion. Both the F and G proteins have the eight-stranded antiparallel beta-sandwich motif common to many plant and animal viruses. Here we describe the structure of a procapsid-like particle at 3.5-A resolution, showing how the scaffolding proteins coordinate assembly of the virus by interactions with the F and G proteins, and showing that the F protein undergoes conformational changes during capsid maturation.

Atomic structure of the degraded procapsid particle of the bacteriophage G4: induced structural changes in the presence of calcium ions and functional implications.

Bacteriophage G4 and phiX174 are members of the Microviridae family. The degree of similarity of the structural proteins ranges from 66% identity of the F protein to 40% identity of the G protein. The atomic structure of the phiX174 virion had previously been determined by X-ray crystallography. Bacteriophage G4 procapsids, consisting of the structural proteins F, G, D, B, H, and small traces of J but no DNA, were set up for crystallization. However, the resultant crystals were of degraded procapsid particles, which had lost the assembly scaffolding proteins D and B, resulting in particles that resembled empty virions. The structure of the degraded G4 procapsid has been determined to 3.0 angstrom resolution. The particles crystallized in the hexagonal space group P6(3)22 with unit cell dimensions a=b=414.2(5) angstrom and c=263.0(3) angstrom. The diffraction data were collected at the Cornell High Energy Synchrotron Source (CHESS) on film and image plates using oscillation photography. Packing considerations indicated there were two particles per unit cell. A self-rotation function confirmed that the particles were positioned on 32 point group special positions in the unit cell. Initial phases were calculated to 6 angstrom resolution, based on the known phiX174 virion model. Phase information was then extended in steps to 3.0 angstrom resolution by molecular replacement electron density modification and particle envelope generation. The resulting electron density map was readily interpretable in terms of the F and G polypeptides, as occur in the mature capsid of phiX174. In a few regions of the electron density map there were inconsistencies between the density and the published amino acid sequence. Redetermining the amino acid sequence confirmed that the density was correct. The r.m.s. deviation between the Calpha backbone of the mature capsid of phiX174 and the degraded G4 procapsid was 0.36 angstrom for the F protein and 1.38 angstrom for the G protein. This is consistent with the greater conservation of the F protein compared to the G protein sequences among members of the Microviridae family. Functionally important features between phiX174 and G4 had greater conservation. Calcium ions (Ca2+) were shown to bind to G4 at a general site located near the icosahedral 3-fold axis on the F protein capsid, equivalent to sites found previously in phiX174. Binding of Ca2+ also caused the ordering of the conserved region of the DNA binding protein J, which was present in the degraded procapsid particle in the absence of DNA.

Effects of waveform on comfort during neuromuscular electrical stimulation.

Electrical stimulation is a commonly used clinical tool, but subject and patient comfort is still a major problem retarding its widespread application. Stimulus waveform in combination with pulse duration can play a major part in subject comfort. An asymmetric balanced biphasic square waveform was perceived as comfortable and was clinically effective in stimulating wrist flexor and extensor muscles. Subjects preferred the square waveforms over a paired spike monophasic waveform. In the larger quadriceps muscle group, a symmetric biphasic square wave was perceived as more comfortable than either a monophasic paired spike or any of three medium frequency waveforms. There seemed to be, however, a small subpopulation of subjects who consistently preferred the medium frequency waveforms. Medium frequency stimulation should be tried for those patients who have considerable difficulty adapting to the sensory input inherent with the use of surface electrical stimulation.

Response of single alpha motoneurons to high-frequency pulse trains. Firing behavior and conduction block phenomenon.

Studies were conducted on 25 cats to document the discharge rates of alpha motoneurons during stimulation of the sciatic nerve at frequencies from 100 to 10,000 pulses per second (pps). In addition, the feasibility of using high-frequency pulse trains to block the conduction of action potentials was investigated. Two cuff electrodes were placed around the proximal portion of the left sciatic nerve, and recordings of antidromic potentials were taken from single fibers of the L7 ventral root. When stimulating through the more proximal electrode, discharge rates were generally equal to or were subharmonics of the stimulation rate up to 1,000 pps. Firing often decreased in rate during 3-min runs. At 2,000-10,000 pps, fibers responded briefly at rates of several hundred per second but stopped firing within seconds after stimulus initiation. After cessation of response to the high-frequency pulse train, action potentials generated at 50 pps at the more distal electrode did not propagate to the recording electrodes. The 'electrical block' so induced was maintained for up to 20 min, and recovery following termination of the pulse train was complete within 1 s.

Effects of waveform parameters on comfort during transcutaneous neuromuscular electrical stimulation.

Twenty-three females between the ages of 19 and 35 were studied in order to compare the effects of variations in pulse duration, waveform symmetry, and source regulation on comfort during quadriceps surface stimulation at amplitudes necessary to produce 27 Nm torque. Stimulation parameters compared were: 1) 50 and 300 microseconds pulse durations, 2) asymmetrical and symmetrical biphasic waveforms, and 3) current and voltage source regulation. Subjects overwhelmingly preferred the 300 microseconds pulse duration regardless of waveform or source regulation, strongly preferred the symmetrical biphasic waveform, and had inconsistent preference for either regulated voltage or regulated current sources.

Acute and chronic implantation of coiled wire intraneural electrodes during cyclical electrical stimulation.

The posterior tibial nerves of 18 rabbits were intraneurally implanted with coiled wire electrodes for up to 9 weeks to evaluate their usefulness for neuromuscular electrical stimulation. In one group an electrode was implanted and removed in one leg while the other leg was chronically implanted. A second group was chronically implanted without electrical stimulation in one leg and implanted with cyclical electrical stimulation applied through the electrode in the other leg. No significant changes in nerve conduction velocities between the time of implantation and up to 9 weeks post-implantation were observed in either the stimulated or the non-stimulated nerves. Little change in motor current threshold was observed beyond 10 days post-implantation. The nerves showed little or no histologic demyelination or denervation in most specimens, although in about 40% of the nerves, a bulbous formation of connective tissue was observed at electrode entry and exit sites with some demyelination in these regions. The spinal cords showed no histologic abnormalities in either group. The gastrocnemius and soleus muscles showed only occasional signs of denervation. One cat was implanted in both the posterior tibial and peroneal nerves of each leg for a 4-year period. Threshold current showed very little change during the implantation period. The nerves showed minimal focal demyelination at the electrode site and the muscles showed normal fibers.

Effects of electrical stimulation on spinal spasticity.

Seven spinal cord injured (SCI) patients with clinical signs of knee-joint spasticity were tested with the Wartenberg pendulum test and an electrogoniometer. All patients were subjected to four channel rhythmical electrical stimulation of the knee muscles for three consecutive days. In five patients some improvement of spasticity was achieved. No increase of spasticity was observed in any patient. Combining results from two separate but similar studies it is contended that about one-half of randomly selected SCI patients with knee joint spasticity might benefit by electrical stimulation.

Effect of electrical stimulation on spasticity in hemiparetic patients.

Cyclical electrical stimulation has been applied to 10 hemiparetic patients with clinical signs of knee joint spasticity. The programme included 30 minutes of stimulation to the hamstrings followed by another 30 minutes of stimulation to the hamstrings and quadriceps. None of the patients experienced increased spasticity. The reduction in spasticity ranged from none to substantial with some other beneficial side-effects. No conclusions could be drawn as to whether hamstring stimulation is preferred to combined stimulation or to quadriceps stimulation alone. It is suggested that small portable stimulators be introduced for chronic use in spastic patients after an optimum stimulation regimen is individually established for each patient.

Electrode effectiveness during transcutaneous motor stimulation.

Four types of electrodes were evaluated for clinical effectiveness in electrically stimulating the quadriceps muscles to gain knee extension for time periods lasting up to 4 days. These electrodes included self-adhering pregelled pads, solvent-activated conductive tape, carbonized conductive silicone rubber, and felt-covered metal plates. The electrodes were compared for ability to produce knee extension torque, electrical impedance, ease of application, durability, comfort, and skin reactivity. Felt-pad electrodes soaked in tap water or saline produced the highest mean torque and lowest electrical impedance, which made them excellent choices for single session stimulation. Carbon-rubber electrodes with either gel produced slightly less torque, slightly higher impedances, and only minor skin reactions. They were relatively easy to apply, and the majority remained intact for the duration of the study period. They were found to be most suitable for prolonged functional electrical stimulation of the quadriceps. Stimulation using pregelled electrodes produced the lowest torque, and they displayed consistently higher electrical impedance. Even though they were easiest to apply and survived better than the other electrodes, they also produced the most skin reactions. The torque and electrical impedance of the activated-tape electrodes were extremely variable and unpredictable, and the process of application was long and involved, making them clinically impractical for either long or short stimulation.

Positional feedback and electrical stimulation: an automated treatment for the hemiplegic wrist.

Positional feedback (PF) and electrical stimulation were combined in a new treatment modality for facilitating wrist extension in stroke patients. Thirty adult hemiparetic patients lacking normal voluntary wrist extension were randomly placed in control and study groups. The control group received conventional therapy while the study group received positional feedback stimulation training (PFST) in addition to conventional treatment. At the end of the 4-week program, study patients showed a 280% increase in isometric extension torque when the wrist was positioned in 30 degrees of extension and 70% increase when positioned in 30 degrees of flexion. Control patients showed no significant changes in torque. Study patients made an average 200% gain in selective range of motion over their starting levels while controls made only a 50% increase. Treatment using automated PFST equipment allows controlled repetitive isotonic exercise and facilitation of wrist extension without continuous one-on-one therapist/patient supervision.