Effects of gonadotropin-releasing hormone at initiation of the 5-d timed artificial insemination (AI) program and timing of induction of ovulation relative to AI on ovarian dynamics and fertility of dairy heifers

Two experiments evaluated the effects of the first GnRH injection of the 5-d timed artificial insemination (AI) program on ovarian responses and pregnancy per AT (P/AI), and the effect of timing of the final GnRH to induce ovulation relative to AT on P/AI. In experiment 1, 605 Holstein heifers were synchronized for their second insemination and assigned randomly to receive GnRH on study d 0 (n = 298) or to remain as untreated controls (n = 307). Ovaries were scanned on study d 0 and 5. All heifers received a controlled internal drug-release (CIDR) insert containing progesterone on d 0, a single injection of PGF(2 alpha),, and removal of the CIDR on d 5, and GnRH concurrent with timed AT on d 8. Blood was analyzed for progesterone at AI. Pregnancy was diagnosed on d 32 and 60 after AI. Ovulation on study d 0 was greater for GnRH than control (35.4 vs. 10.6%). Presence of a new corpus luteum (CL) at PGF(2 alpha),, injection was greater for GnRH than for control (43.1 vs. 20.8%), although the proportion of heifers with a CL at PGF(2 alpha) did not differ between treatments and averaged 87.1%. Progesterone on the day of AT was greater for GaRH than control (0.50 +/- 0.07 vs. 0.28 +/- 0.07 ng/mL). The proportion of heifers at AI with progesterone <0.5 ng/mL was less for GURH than for control (73.8 vs. 88.2%). The proportion of heifers in estrus at AI did not differ between treatments and averaged 66.8%. Pregnancy per AI was not affected by treatment at d 32 or 60 (GnRH = 52.5 and 49.8% vs. control = 54.1 and 50.0%), and pregnancy loss averaged 6.0%. Responses to GnRH were not influenced by ovarian status on study d 0. In experiment 2, 1,295 heifers were synchronized for their first insemination and assigned randomly to receive a CIDR on d 0, PGF(2 alpha) and removal of the CIDR on d 5, and either GnRH 56 h after PGF(2 alpha) and AI 16 h later (OVS56, n = 644) or GnRH concurrent with AI 72 h after PGF(2 alpha) (COS72; n = 651). Estrus at AI was greater for COS72 than for OVS56 (61.4 vs. 47.5). Treatment did not affect P/AI on d 32 in heifers displaying signs of estrus at AI, but COS72 improved P/AI compared with OVS56 (55.0 vs. 47.6%) in those not in estrus at AI. Similarly, P/AI on d 60 did not differ between treatments for heifers displaying estrus, but COS72 improved P/AI compared with OVS56 (53.0 vs. 44.7%) in those not in estrus at AI. Administration of GnRH on the first day of the 5-d timed AI program resulted in low ovulation rate and no improvement in P/AI when heifers received a single PGF(2 alpha) injection 5 d later. Moreover, extending the proestrus by delaying the finAI GnRH from 56 to 72 h concurrent with AI benefited fertility of dairy heifers that did not display signs of estrus at insemination following the 5-d timed AI protocol.

Effects of sperm concentration and straw volume on motion characteristics and plasma, acrosomal, and mitochondrial membranes of equine cryopreserved spermatozoa

The advantages of using cryopreserved semen in equine reproduction are well known. During cryopreservationl spermatozoa undergo many changes that lead to a decrease in fertility. There is no agreement on the ideal sperm dose and concentration to maximize fertility rates. Thus, the objectives of this experiment were to evaluate sperm motion by computer-assisted analysis (CASA), sperm membrane integrity and function with fluorescence probes of cryopreserved sperm at three concentrations: 100 (C100), 200 (C200) and 400 x 10(6) sperm/mL (C400), and two straw volumes (0.50 and 0.25 mL). There was no interaction between sperm concentration and storage volume (P > .05). Sperm motion characteristics were influenced by concentration (C100 > C200 > C400; P < .05). Curvilinear velocity (VCL) in 0.25-mL straws had higher average values (P < .05). Membrane integrity and function were not changed by straw volume (P > .05). However, sperm concentration changed the percentage of cells with intact plasma membrane (C100 > C200 > C400; P < .05) and the percentage of cells with high mitochondrial membrane potential (C100 = C200; P > .05 and C400 < C100 and C200; P < .05). According to this experiment, the best freeing method was that involving 100 x 10(6) sperm/mL, regardless of straw volume.

Quantum nonlinear dynamics of continuously measured systems

Classical dynamics is formulated as a Hamiltonian flow in phase space, while quantum mechanics is formulated as unitary dynamics in Hilbert space. These different formulations have made it difficult to directly compare quantum and classical nonlinear dynamics. Previous solutions have focused on computing quantities associated with a statistical ensemble such as variance or entropy. However a more diner comparison would compare classical predictions to the quantum predictions for continuous simultaneous measurement of position and momentum of a single system, in this paper we give a theory of such measurement and show that chaotic behavior in classical systems fan be reproduced by continuously measured quantum systems.

Finite Element Analysis of 2 Immediate Loading Systems in Edentulous Mandible: Rigid and Semirigid Splinting of Implants

Purpose: The objective of this study was to evaluate the stress on the cortical bone around single body dental implants supporting mandibular complete fixed denture with rigid (Neopronto System-Neodent) or semirigid splinting system (Barra Distal System-Neodent). Methods and Materials: Stress levels on several system components were analyzed through finite element analysis. Focusing on stress concentration at cortical bone around single body dental implants supporting mandibular complete fixed dentures with rigid ( Neopronto System-Neodent) or semirigid splinting system ( Barra Distal System-Neodent), after axial and oblique occlusal loading simulation, applied in the last cantilever element. Results: The results showed that semirigid implant splinting generated lower von Mises stress in the cortical bone under axial loading. Rigid implant splinting generated higher von Mises stress in the cortical bone under oblique loading. Conclusion: It was concluded that the use of a semirigid system for rehabilitation of edentulous mandibles by means of immediate implant-supported fixed complete denture is recommended, because it reduces stress concentration in the cortical bone. As a consequence, bone level is better preserved, and implant survival is improved. Nevertheless, for both situations the cortical bone integrity was protected, because the maximum stress level findings were lower than those pointed in the literature as being harmful. The maximum stress limit for cortical bone (167 MPa) represents the threshold between plastic and elastic state for a given material. Because any force is applied to an object, and there is no deformation, we can conclude that the elastic threshold was not surpassed, keeping its structural integrity. If the force is higher than the plastic threshold, the object will suffer permanent deformation. In cortical bone, this represents the beginning of bone resorption and/or remodeling processes, which, according to our simulated loading, would not occur. ( Implant Dent 2010; 19:39-49)

Patch dynamics and metapopulation theory: the case of successional species

We present a mathematical framework that combines extinction-colonization dynamics with the dynamics of patch succession. We draw an analogy between the epidemiological categorization of individuals (infected, susceptible, latent and resistant) and the patch structure of a spatially heterogeneous landscape (occupied-suitable, empty-suitable, occupied-unsuitable and empty-unsuitable). This approach allows one to consider life-history attributes that influence persistence in patchy environments (e.g., longevity, colonization ability) in concert with extrinsic processes (e.g., disturbances, succession) that lead to spatial heterogeneity in patch suitability. It also allows the incorporation of seed banks and other dormant life forms, thus broadening patch occupancy dynamics to include sink habitats. We use the model to investigate how equilibrium patch occupancy is influenced by four critical parameters: colonization rate? extinction rate, disturbance frequency and the rate of habitat succession. This analysis leads to general predictions about how the temporal scaling of patch succession and extinction-colonization dynamics influences long-term persistence. We apply the model to herbaceous, early-successional species that inhabit open patches created by periodic disturbances. We predict the minimum disturbance frequency required far viable management of such species in the Florida scrub ecosystem. (C) 2001 Academic Press.

Cervical range of motion discriminates between asymptomatic persons and those with whiplash

Study Design. A comparative study of cervical range of motion in asymptomatic persons and those with whiplash. Objectives. To compare the primary and conjunct ranges of motion of the cervical spine in asymptomatic persons and those with persistent whiplash-associated disorders, and to investigate the ability of these measures of range of motion to discriminate between the groups. Summary of Background. Evidence that range of motion is an effective indicator of physical impairment in the cervical spine is not conclusive. Few studies have evaluated the ability to discriminate between asymptomatic persons and those with whiplash on the basis of range of motion or compared three-dimensional in vivo measures of range of motion in asymptomatic persons and those with whiplash-associated disorders. Methods. The study participants were 89 asymptomatic volunteers (41 men, 48 women; mean age 39.2 years) and 114 patients with persistent whiplash-associated disorders (22 men, 93 women; mean age 37.2 years) referred to a whiplash research unit for assessment of their cervical region. Range of cervical motion was measured in three dimensions with a computerized, electromagnetic, motion-tracking device. The movements assessed were flexion, extension, left and right lateral flexion, and left and right rotation. Results. Range of motion was reduced in all primary movements in patients with persistent whiplash-associated disorder. Sagittal plane movements were proportionally the most affected. On the basis of primary and conjunct range of motion, age, and gender, 90.3% of study participants could be correctly categorized as asymptomatic or as having whiplash (sensitivity 86.2%, specificity 95.3%). Conclusions. Range of motion was capable of discriminating between asymptomatic persons and those with persistent whiplash-associated disorders.

Solid-state NMR structure determination of melittin in a lipid environment

Solid-state C-13 NMR spectroscopy was used to investigate the three-dimensional structure of melittin as lyophilized powder and in ditetradecylphosphatidylcholine (DTPC) membranes. The distance between specifically labeled carbons in analogs [1-C-13]Gly3-[2-C-13]Ala4, [1-C-13]Gly3-[2-C-13]Leu6, [1-C-13]Leu13-[2-C-13]Ala15, [2-C-13]Leu13-[1-C-13]Ala15, and [1-C-13]Leu13-[2-C-13]Leu16 was measured by rotational resonance. As expected, the internuclear distances measured in [1-C-13]Gly3-[2-C-13]Ala4 and [1-C-13]Gly3-[2-C-13]Leu6 were consistent with alpha -helical structure in the N-terminus irrespective of environment. The Internuclear distances measured in [1-C-13]Leu13-[2-C-13]Ala15, [2-C-13]Leu13-[1-C-13]Ala15, and [1-C-13]Leu13-[2-C-13]Leu16 revealed, via molecular modeling, some dependence upon environment for conformation in the region of the bend in helical structure induced by Pro14. A slightly larger interhelical angle between the N- and C-terminal helices was indicated for peptide in dry or hydrated gel state DTPC (139 degrees -145 degrees) than in lyophilized powder (121 degrees -139 degrees) or crystals (129 degrees). The angle, however, is not as great as deduced for melittin in aligned bilayers of DTPC in the liquid-crystalline state (similar to 160 degrees) (R. Smith, F. Separovic, T. J. Milne, A. Whittaker, F. M. Bennett, B. A. Cornell, and A. Makriyannis, 1994, J. Mol, Biol 241:456-466). The study illustrates the utility of rotational resonance in determining local structure within peptide-lipid complexes.

Enzymology, structure, and dynamics of acetohydroxy acid isomeroreductase

Acetohydroxy acid isomeroreductase is a key enzyme involved in the biosynthetic pathway of the amino acids isoleucine, valine, and leucine. This enzyme is of great interest in agrochemical research because it is present only in plants and microorganisms, making it a potential target for specific herbicides and fungicides. Moreover, it catalyzes an unusual two-step reaction that is of great fundamental interest. With a view to characterizing both the mechanism of inhibition by potential herbicides and the complex reaction mechanism, various techniques of enzymology, molecular biology, mass spectrometry, X-ray crystallography, and theoretical simulation have been used. The results and conclusions of these studies are described briefly in this paper.

Structural Dynamics in (ND4)2[Cu(D2O)6](SO4)2

The extended X-ray absorption fine structure spectroscopy (EXAFS) of (ND4)(2)[CU(D2O)(6)](SO4)(2) at 5, 14,100, 200, and 298 K is reported. This indicates that the Cu-O bond lengths of the Cu(D2O)(6)(2+) ion do not change significantly within this temperature range, which contrasts with EPR results and X-ray and neutron diffraction experiments, which imply that two of the Cu-(D2O) bonds converge in length as the temperature is raised. The EXAFS measurements thus confirm that the bond distances yielded by the diffraction experiments refer to the average positions of ligands involved in a dynamic equilibrium in which the directions of the long and intermediate bonds of the Jahn-Teller distorted Cu(D2O)(6)(2+) ion are interchanged in the crystal lattice. Analysis of the displacement parameters is consistent with this interpretation, as are the wave functions calculated using a model involving Jahn-Teller vibronic coupling and the influence of lattice strain interactions.

Three-dimensional orthotropic viscoelastic finite element model of a human ligament

Ligaments undergo finite strain displaying hyperelastic behaviour as the initially tangled fibrils present straighten out, combined with viscoelastic behaviour (strain rate sensitivity). In the present study the anterior cruciate ligament of the human knee joint is modelled in three dimensions to gain an understanding of the stress distribution over the ligament due to motion imposed on the ends, determined from experimental studies. A three dimensional, finite strain material model of ligaments has recently been proposed by Pioletti in Ref. [2]. It is attractive as it separates out elastic stress from that due to the present strain rate and that due to the past history of deformation. However, it treats the ligament as isotropic and incompressible. While the second assumption is reasonable, the first is clearly untrue. In the present study an alternative model of the elastic behaviour due to Bonet and Burton (Ref. [4]) is generalized. Bonet and Burton consider finite strain with constant modulii for the fibres and for the matrix of a transversely isotropic composite. In the present work, the fibre modulus is first made to increase exponentially from zero with an invariant that provides a measure of the stretch in the fibre direction. At 12% strain in the fibre direction, a new reference state is then adopted, after which the material modulus is made constant, as in Bonet and Burton's model. The strain rate dependence can be added, either using Pioletti's isotropic approximation, or by making the effect depend on the strain rate in the fibre direction only. A solid model of a ligament is constructed, based on experimentally measured sections, and the deformation predicted using explicit integration in time. This approach simplifies the coding of the material model, but has a limitation due to the detrimental effect on stability of integration of the substantial damping implied by the nonlinear dependence of stress on strain rate. At present, an artificially high density is being used to provide stability, while the dynamics are being removed from the solution using artificial viscosity. The result is a quasi-static solution incorporating the effect of strain rate. Alternate approaches to material modelling and integration are discussed, that may result in a better model.

Stochastic gauges in quantum dynamics for many-body simulations

Quantum dynamics simulations can be improved using novel quasiprobability distributions based on non-orthogonal Hermitian kernel operators. This introduces arbitrary functions (gauges) into the stochastic equations. which can be used to tailor them for improved calculations. A possible application to full quantum dynamic simulations of BEC's is presented. (C) 2001 Elsevier Science B.V. All rights reserved.

Haptic information stabilizes and destabilizes coordination dynamics

Goal-directed, coordinated movements in humans emerge from a variety of constraints that range from 'high-level' cognitive strategies based oil perception of the task to 'low-level' neuromuscular-skeletal factors such as differential contributions to coordination from flexor and extensor muscles. There has been a tendency in the literature to dichotomize these sources of constraint, favouring one or the other rather than recognizing and understanding their mutual interplay. In this experiment, subjects were required to coordinate rhythmic flexion and extension movements with an auditory metronome, the rate of which was systematically increased. When subjects started in extension on the beat of the metronome, there was a small tendency to switch to flexion at higher rates, but not vice versa. When subjects: were asked to contact a physical stop, the location of which was either coincident with or counterphase to the auditor) stimulus, two effects occurred. When haptic contact was coincident with sound, coordination was stabilized for both flexion and extension. When haptic contact was counterphase to the metronome, coordination was actually destabilized, with transitions occurring from both extension to flexion on the beat and from flexion to extension on the beat. These results reveal the complementary nature of strategic and neuromuscular factors in sensorimotor coordination. They also suggest the presence of a multimodal neural integration process-which is parametrizable by rate and context - in which intentional movement, touch and sound are bound into a single, coherent unit.