A spectrophotometric procedure for the determination of objective measurements of equine spermatozoan motility

A spectrophotometric procedure was developed and evaluated for the objective measurement of equine spermatozoan motility. A 100 mul sample of a sperm suspension, prepared by the removal of seminal plasma, was layered under a column of optically clear medium in a specially designed spectrophotometric cuvette maintained at 37 degrees C. Changes in light transmittance above the interface of the sperm suspension and medium were recorded on chart paper. As sperm cells swam into the medium, a decrease in light transmittance was recorded as a deflection on the chart paper. Chart recordings were analyzed for the height (cm) and time (min) to the peak deflection. To standardize the procedure, a fixed number of cells (1x10(9)) were used to prepare suspensions of 300x10(6) cells/ml. Coefficients of variation for mean values obtained under these conditions after the evaluation of five ejaculates from a given stallion were estimated at between 10 and 12%. Correlations between swim-up measurements and computer-assisted semen analysis demonstrated that the percentage of motile cells and mean velocity (mum/sec) of motile cells influenced swim-up measurements. Described here is a simple and inexpensive procedure to determine objective measurements of spermatozoan motility that may have application in semen evaluation and fertility testing in the stallion.     

Differentiation of species in Gonioloboceras

The type specimen ofGonioloboceras goniolobum (Meek), rediscovered by Spath in the British Museum, is the foundation for a more accurate comparative study of this and other species ofGonioloboceras.Gonioloboceras described asG. goniolobum byElias in 1938 is differentiated asGonioloboceras schmidti, new species. Suture sets (new term) for several growth stages inG. goniolobum (Meek),G. welleriSmith,G. schmidtiElias, G.eliasiMiller &Owen, andG. asiaticumLibrovitch are assembled and used for differentiation of the species.The Kazakhstan goniatite faunule containingG. asiaticum is considered of very late Pennsylvanian age.     

The photosynthetic F1-α3β3 and α1β1 catalytic core complexes

Minimal photosynthetic catalytic F₁() core complexes, containing equimolar ratios of the and subunits, were isolated from membrane-bound spinach chloroplast CF₁ and Rhodospirillum rubrum chromatophore RrF₁. A CF₁-₃₃ hexamer and RrF₁-₁₁ dimer, which were purified from the respective F₁() complexes, exhibit lower rates and different properties from their parent F₁-ATPases. Most interesting is their complete resistance to inhibition by the general F₁ inhibitor azide and the specific CF₁ inhibitor tentoxin. These inhibitors were earlier reported to inhibit multisite, but not unisite, catalysis in all sensitive F₁-ATPases and were therefore suggested to block catalytic site cooperativity. The absence of this typical property of all F₁-ATPases in the ₁₁ dimer is consistant with the view that the dimer contains only a single catalytic site. The ₃₃ hexamer contains however all F₁ catalytic sites. Therefore the observation that CF₁-₃₃ can bind tentoxin and is stimulated by it suggests that the F₁ subunit, which is required for obtaining inhibition by tentoxin as well as azide, plays an important role in the cooperative interactions between the F₁-catalytic sites.Abbreviations CF₀F₁ chloroplast F₀F₁ - CF₁ chloroplast F₁ - CF₁ chloroplast F₁ subunit - CF₁ chloroplast F₁ subunit - CF₁() a complex containing equal amounts of the CF₁ and subunits - MF₁ mitochondrial F₁ - RrF₀F₁ Rhodospirillum rubrum F₀F₁ - RrF₁ R. rubrum F₁ - RrF₁ R. rubrum F₁ subunit - RrF₁ R. rubrum F₁ subunit - RrF₁() a complex containing equal amounts of the RrF₁ and subunits - Rubisco Ribulose-1,5-bisphosphate carboxylase - TF₁ thermophilic bacterium PS3 F₁     

Homology modeling by the ICM method

Five models have been built by the ICM method for the Comparative Modeling section of the Meeting on the Critical Assessment of Techniques for Protein Structure Prediction. The targets have homologous proteins with known three-dimensional structure with sequence identity ranging from 25 to 77%. After alignment of the target sequence with the related three-dimensional structure, the modeling procedure consists of two subproblems: side-chain prediction and loop prediction. The ICM method approaches these problems with the following steps: (1) a starting model is created based on the homologous structure with the conserved portion fixed and the noncon-served portion having standard covalent geometry and free torsion angles; (2) the Biased Probability Monte Carlo (BPMC) procedure is applied to search the subspaces of either all the nonconservative side-chain torsion angles or torsion angles in a loop backbone and surrounding side chains. A special algorithm was designed to generate low-energy loop deformations. The BPMC procedure globally optimizes the energy function consisting of ECEPP/3 and solvation energy terms. Comparison of the predictions with the NMR or crystallographic solutions reveals a high proportion of correctly predicted side chains. The loops were not correctly predicted because imprinted distortions of the backbone increased the energy of the near-native conformation and thus made the solution unrecognizable. Interestingly, the energy terms were found to be reliable and the sampling of conformational space sufficient. The implications of this finding for the strategies of future comparative modeling are discussed. © 1995 Wiley-Liss, Inc.     

Initiation of superovulation in mares 5 or 12 days after ovulation using equine pituitary extract with or without GnRH analogue

Cyclic mares were assigned to 1 of 3 treatments (n=15 per group): Group 1 received equine pituitary extract (EPE; 25 mg, i.m.) on Day 5 after ovulation; Group 2 received EPE on Day 12 after ovulation; while Group 3 received 3.3 mg of GnRH analogue (buserelin implant) on the day of ovulation and 25 mg, i.m. EPE on Day 12. Mares in each group were given 10 mg PGF(2)alpha on the first and second day of EPE treatment. The EPE treatment was continued daily until the first spontaneous ovulation, at which time 3,300 IU of human chorionic gonadotropin (hCG) were given to induce further ovulations. Mares in estrus with a >/=35 mm follicle were inseminated every other day with pooled semen from 2 stallions. Embryo recovery was attempted 7 days after the last ovulation. Follicular changes and embryo recovery during 15 estrous cycles prior to treatment were used as control data. During treatment, the number of follicles >/=25 mm was higher (P<0.05) for Day 5 than for Day 12 or control mares, but the number for Day-5 mares was similar (P>0.05) to that of mares treated with buserelin implants (Group 3). Initiation of EPE treatment on Day 5 resulted in a greater (P<0.05) number of ovulation (2.9) than on Day 12 (1.1) or in the control mares (1.3) but not in the buserelin-treated mares (1.8). The number of embryos recovered from mares in the Day 5 (1.2), Day 12 (1.0), buserelin (0.9) and control (0.9) groups was similar (P>0.05). The conclusions were 1) EPE initiated in early diestrus increased follicular development and ovulation and 2) treatment with GnRH analogue marginally improved response to EPE treatment.     

Effects of linear cooling rate on motion characteristics of stallion spermatozoa

Three experiments were designed to analyze the effects of cooling rate on survival of stallion spermatozoa in a milk-based extender, at 0 to 96 hours after reaching the desired temperature. The samples were warmed to 37 degrees C and were evaluated by computer-assisted analysis of sperm motility. In Experiment 1, rate of cooling between 37 and 20 degrees C was evaluated. Sperm motion was not affected by cooling at plunge, -0.42 or -0.28 degrees C/minute. However, storage of spermatozoa at 5 degrees C after slow cooling below 20 degrees C was superior to storage at 20 degrees C. In Experiment 2, 3 cooling rates from 37 degrees to 5 degrees C were evaluated. Cooling at either -0.05 or -0.7 degrees C/minute was superior (P<0.05) to plunging spermatozoa to 5 degrees C. Cooling at -0.05 degrees C/minute rather than -0.7 degrees C/minute maximized the percentage of motile spermatozoa and their curvilinear velocity. In Experiment 3, cooling rates from 20 to 5 degrees C were evaluated, with all samples cooled at -0.7 degrees C/minute from 37 to 20 degrees C. Sperm motion was similar (P>0.05) after cooling below 20 degrees C at -0.012, -0.05 or -0.10 degrees C/minute, and the 2 slower rates were superior (P<0.05) to cooling at -0.3 degrees C/minute. It was concluded that stallion spermatozoa can be cooled rapidly from 37 to 20 degrees C, but should be cooled at 相似文献   

High‐Voltage‐Driven Surface Structuring and Electrochemical Stabilization of Ni‐Rich Layered Cathode Materials for Li Rechargeable Batteries

Layered lithium–nickel–cobalt–manganese oxide (NCM) materials have emerged as promising alternative cathode materials owing to their high energy density and electrochemical stability. Although high reversible capacity has been achieved for Ni‐rich NCM materials when charged beyond 4.2 V versus Li⁺/Li, full lithium utilization is hindered by the pronounced structural degradation and electrolyte decomposition. Herein, the unexpected realization of sustained working voltage as well as improved electrochemical performance upon electrochemical cycling at a high operating voltage of 4.9 V in the Ni‐rich NCM LiNi_0.895Co_0.085Mn_0.02O₂ is presented. The improved electrochemical performance at a high working voltage at 4.9 V is attributed to the removal of the resistive Ni²⁺O rock‐salt surface layer, which stabilizes the voltage profile and improves retention of the energy density during electrochemical cycling. The manifestation of the layered Ni²⁺O rock‐salt phase along with the structural evolution related to the metal dissolution are probed using in situ X‐ray diffraction, neutron diffraction, transmission electron microscopy, and X‐ray absorption spectroscopy. The findings help unravel the structural complexities associated with high working voltages and offer insight for the design of advanced battery materials, enabling the realization of fully reversible lithium extraction in Ni‐rich NCM materials.     

Ceruloplasmin: Macromolecular Assemblies with Iron-Containing Acute Phase Proteins

Copper-containing ferroxidase ceruloplasmin (Cp) forms binary and ternary complexes with cationic proteins lactoferrin (Lf) and myeloperoxidase (Mpo) during inflammation. We present an X-ray crystal structure of a 2Cp-Mpo complex at 4.7 Å resolution. This structure allows one to identify major protein–protein interaction areas and provides an explanation for a competitive inhibition of Mpo by Cp and for the activation of p-phenylenediamine oxidation by Mpo. Small angle X-ray scattering was employed to construct low-resolution models of the Cp-Lf complex and, for the first time, of the ternary 2Cp-2Lf-Mpo complex in solution. The SAXS-based model of Cp-Lf supports the predicted 1∶1 stoichiometry of the complex and demonstrates that both lobes of Lf contact domains 1 and 6 of Cp. The 2Cp-2Lf-Mpo SAXS model reveals the absence of interaction between Mpo and Lf in the ternary complex, so Cp can serve as a mediator of protein interactions in complex architecture. Mpo protects antioxidant properties of Cp by isolating its sensitive loop from proteases. The latter is important for incorporation of Fe³⁺ into Lf, which activates ferroxidase activity of Cp and precludes oxidation of Cp substrates. Our models provide the structural basis for possible regulatory role of these complexes in preventing iron-induced oxidative damage.