Conception rates after artificial insemination or embryo transfer in lactating dairy cows during summer in Florida

The objective was to compare conception rates to embryo transfer relative to AI, during summer heat stress, in lactating dairy cows. Holstein cows (n = 180; 50 to 120 d postpartum) were allocated randomly to 1 of 3 groups: artificial insemination (AI, n = 84), embryo transfer using either embryos collected from superovulated donors (ET-DON, n = 48), or embryos produced in vitro (ET-IVF, n = 48). Embryos from superovulated donors were frozen in 10% glycerol and were rehydrated in a 3-step procedure, in decreasing concentrations of glycerol in a sucrose medium before transfer. Embryos produced in vitro were frozen in 1.5 M ethylene glycol, thawed and transferred without rehydration. Blood samples were collected from AI and ET recipients on Days 0, 7 and 22 for measurement of progesterone in plasma. Conception rate was estimated for the three groups at Day 22 (progesterone > 1 ng/mL) and confirmed at Day 42 by palpation per rectum. Conception rate estimates at Day 22 did not differ among groups (AI, 60.7%; ET-DON, 60.4%; ET-IVF, 54.2%), but conception rates at Day 42 differed (AI, 21.4%; ET-DON, 35.4%; ET-IVF, 18.8%; AI versus ET: P > 0.10 and ET-DON versus ET-IVF: P < 0.05). In cows considered pregnant at 22 d but diagnosed open at 42 d, the interestrous intervals were 28.8 +/- 2.2, 35.2 +/- 3.5 and 31.6 +/- 2.9 d, respectively, for AI, ET-DON and ET-IVF groups. Transfer of embryos collected from nonheat-stressed superovulated donors significantly increased conception rates in heat stressed dairy cattle. However, transfer of IVF-derived embryos had no advantage over AI. Where appropriate mechanisms are in place to attenuate the effects of heat stress, embryo transfer using frozen-thawed donor embryos increases conception rates.     

International Rice Research Institute: roles and challenges as we enter the genomics era

The International Rice Research Institute (IRRI) was established in 1960 by the Rockefeller (New York, NY, USA) and Ford Foundations (New York, NY, USA) in response to food scarcity problems in the developing world. Today, it is the world's leading international research and training center for rice. Based in the Philippines, with operations in 11 other countries, it is one of 16 Future Harvest Centers funded by the Consultative Group on International Agricultural Research (CGIAR), an association of public and private donor agencies.     

On the effects of spatial heterogeneity on the persistence of interacting species

 The dynamics of two interacting theoretical populations inhabiting a heterogeneous environment are modelled by a system of two weakly coupled reaction–diffusion equations having spatially dependent reaction terms. Longterm persistence of both populations is guaranteed by an invasibility condition, which is itself expressed via the signs of certain eigenvalues of related linear elliptic operators with spatially dependent lowest order coefficients. The effects of change in these coefficients upon the eigenvalues are here exploited to study the effects of spatial heterogeneity on the persistence of interacting species through two particular ecological topics of interest. The first concerns when the location of favorable hunting grounds within the overall environment does or does not affect the success of a predator in predator–prey models, while the second concerns cases of competition models in which the outcome of competition in a spatially varying environment differs from that which would be expected in a spatially homogeneous environment. Received: 9 June 1997     

Evidence that proteins S1, S11 and S21 directly participates in the binding of transfer RNA to the 30S ribosome.

In a previous publication1 we reported that the tyrosine selective reagent, tetraitromethane, causes complete inactivation of E. coli 30S ribosomes for poly U directed non-enzymatic phe-tRNA binding. This inactivation was demonstrated to be due to the chemical modification of the protein moiety of the ribosome. We have no identified the proteins of the 30S particle inactivated by this modification. Using a method of ribosome reconstruction we have found that unmodified proteins S1, S11, and S21 are essential for the restoration of the phe-tRNA binding activity of tetranitromethane inactivated ribosomes. We propose that these three proteins are intimately involved in the 30S ribosome binding site for tRNA.     

Chemical inactivation of Escherichia coli 30 S ribosomes with maleic anhydride: identification of the proteins involved in polyuridylic acid binding.

Modification of 30 S ribosomal subunits by the protein-modifying reagent maleic anhydride was found to inactivate the particles for polyuridylic acid binding. Reconstitution of 30 S ribosomes using 16 S RNA, maleylated total 30 S protein, and purified, unmodified proteins demonstrated that S4, S11, S12, S13 and S18 are involved in poly(U) binding. Modified 30 S subunits contain all the ribosomal proteins and show normal sedimentation characteristics, indicating that the inactivation is not simply due to the gross alteration of the particles. Correlation of these results with those of other workers is discussed.     

Peptides as requirement for immunotherapy of the guinea-pig line-10 tumor with endotoxins

Summary The transplantable line-10 hepatocellular carcinoma of guinea-pigs has been used as a model for the study of immunotherapy of malignant tumors. Cure rates of up to 100% have been obtained with ReGl-CM from 0 antigen-deficient (Re) mutant strains of Enterobacteriaceae, provided they were combined with mycobacterial trehalose dimycolate (cord factor, P3). Whereas highly endotoxic LPS extracts from all wild-type strains so far tested have failed to cause tumor regression, acid hydrolysis of such LPS samples led to residual fractions (RESI) that cross-reacted serologically with ReGl-CM samples (Chang and Nowotny, 1975) and provided cure rates up to 100%. RESI from Serratia marcescens was essentially nonpyrogenic and 100 times less lethal for chick embryos than potent endotoxins. Antigenic material associated with endotoxic extracts appears to be cryptic or sterically hindered from being effective in wild-type LPS but is exposed in ReGl and RESI samples.Reduction of the aminoacid content of ReGl-CM by microparticulate silica gel chromatography or by treatment with Triton X-100 significantly lowered the ability to bring about tumor regression without affecting endotoxicity. Antitumor activity could be restored by the addition of synthetic N-acetyl-muramyl-l-seryl-d-isoglutamine (MDP) or a nontoxic lipoid side fraction recovered during the isolation of ReGl-CM, which contained a small amount of peptidic substances. It is concluded that the addition of peptidic material, which may act as an adjuvant, to endotoxins is required to make them useful for immunotherapy of the weakly immunogenic line-10 tumor.Chemical procedures known to detoxify endotoxins while retaining adjuvanticity, such as succinylation and phthalylation, resulted in complete loss of endotoxicity and tumor-regressive potency of ReGl-CM. Transesterification with sodium methoxide led to a water-soluble phase, which cured 50% of tumor-bearing animals even though lethality and pyrogenicity were reduced by 100 times and 50 times, respectively. Thus there was no direct correlation between endotoxic potency and tumor-regressive activity. In addition, our findings indicate that a low level of toxicity may be required to obtain optimal levels of tumoricidal action.Abbreviations P3 trehalose dimycolate isolated by microparticulate silica gel chromatography (Ribi et al., 1974) - LPS lipopolysaccharide from wild-type gram-negative bacteria - ReGl endotoxic glycolipids from Re mutant gram-negative bacteria - CM chloroformmethanol - PW phenol-water - PCP phenol-chloroform-petroleum ether - ReGl-CM ReGl-PW, ReGl-PCP refer to ReGl extracted with CM, PW, or PCP, respectively - ACP acetone-precipitated by-product of ReGl-CM - B1, B2, B4 chromatographic fractions of ReGl-CM - lipid A hydrochloric acid hydrolyzate of LPS or ReGl - RESI organic solvent-insoluble fraction of lipid A (Chang and Nowotny, 1975) - KDO keto-3-deoxyoctonate - BSA bovine serum albumin - CWS cell wall skeleton of BCG (Bacillus Calmette-Guérin) - PPD purified protein derivative (tuberculoprotein) - TAP tuberculin-active peptide - MDP N-acetyl-muramyl-l-seryl-d-isoglutamine     

Aryl hydrocarbon hydroxylase and 16α-hydroxylase in cultured human lymphocytes

Aryl hydrocarbon hydroxylase and 16-hydroxylase were examined in intact, cultured human lymphocytes. The two microsomal mixed-function oxygenases had different pH optima and showed competitive inhibition for enzyme induction and activity. Population distributions were lognormal for both enzymes, giving apparent evidence for polygenic control. Induced levels of AHH were slightly higher among first-order relatives of lung or colon cancer patients than in the control group. The correlation coefficient (r) for AHH and SAH co-inducibility was –0.08, indicating no correlation and suggesting the absence of association between the two enzymes in man.Supported in part by NIH Contract NO1-CP5-5626 and NTSU Faculty Grants 34984 and 34815.National Science Foundation Predoctoral Trainee.     

Identification and characterization of plasmids in hydrogen uptake positive and hydrogen uptake negative strains ofRhizobium japonicum

Modifications were made of published procedures to allow routine isolation of plasmids fromRhizobium japonicum. The plasmid profiles of a series of H₂ uptake positive and H₂ uptake negative strains were compared. None of the strains ofR. japonicum with high H₂ uptake activities exhibited discernible plasmids, while most of the strains, with little or no H₂ uptake activity, showed plasmids with molecular weights ranging from approximately 49–290 x10⁶. An examination of H₂ uptake negative mutants derived from an H₂ uptake positive parent revealed two discernible plasmid bands in nonrevertible mutants but no detectable plasmids in revertible mutants or in the parent strain from which mutants were derived.     

A multiscale model for avascular tumor growth

The desire to understand tumor complexity has given rise to mathematical models to describe the tumor microenvironment. We present a new mathematical model for avascular tumor growth and development that spans three distinct scales. At the cellular level, a lattice Monte Carlo model describes cellular dynamics (proliferation, adhesion, and viability). At the subcellular level, a Boolean network regulates the expression of proteins that control the cell cycle. At the extracellular level, reaction-diffusion equations describe the chemical dynamics (nutrient, waste, growth promoter, and inhibitor concentrations). Data from experiments with multicellular spheroids were used to determine the parameters of the simulations. Starting with a single tumor cell, this model produces an avascular tumor that quantitatively mimics experimental measurements in multicellular spheroids. Based on the simulations, we predict: 1), the microenvironmental conditions required for tumor cell survival; and 2), growth promoters and inhibitors have diffusion coefficients in the range between 10(-6) and 10(-7) cm2/h, corresponding to molecules of size 80-90 kDa. Using the same parameters, the model also accurately predicts spheroid growth curves under different external nutrient supply conditions.