Expression of creatine kinase isoenzyme during oogenesis and embryogenesis in the mouse

Creatine kinase activity was discovered in the growing mouse oocyte and in the preimplantation embryo. Changes in the enzyme activity during the growth and maturation of the egg and during the development of the embryo up to the blastocyst stage were determined. Close similarity of the protein to the brain-type isoenzyme of creatine kinase was established immunochemically. The kinetic parameters of the brain-type isoenzyme (M. R. Iyengar, C. E. Fluellen, and C. W. L. Iyengar, 1982, J. Muscle Cell Motil. 3, 231–246) and the pattern of development-associated changes in activity suggest a possible role for creatine kinase in maintaining the reported high ATP/ADP ratio (L. Ginsberg and N. Hillman, 1975, J. Reprod. Fertil. 43, 83–90), which is essential for the biosynthetic activities of the embryo.     

Cortical vesicle exocytosis in isolated cortices of sea urchin eggs: Description of a turbidometric assay and its utilization in studying effects of different media on discharge

Cortices of unfertilized sea urchin eggs can be isolated in suspension and will discharge the attached cortical vesicles (CVs) in response to calcium. We describe a simple turbidometric assay for monitoring the Ca²⁺-induced discharge of these vesicles and also compare the discharge of vesicles isolated in a high salt medium (primarily KCl) with a medium more closely simulating the internal milieu of the cell (primarily potassium gluconate and glycine). Discharge in response to calcium is similar in both media, requiring approximately 6 μM calcium for one-half maximal discharge. There are, however, significant differences in morphology and protein composition of the two types of preparations (more proteins present in the glycine cortices) and also in the rate of discharge of the vesicles in response to calcium (KCl cortices with $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ 6 sec as opposed to 30 sec in the glycine cortices). The glycine cortices gradually lose their ability to respond to calcium but retention of calcium sensitivity is considerably aided by inclusion of ATP in the media; ATP has no apparent effect on discharge of the KCl cortices. The glycine cortices, as opposed to the KCl cortices, exhibited variation in calcium sensitivity during the breeding season and in the number of vesicles which would not break down in response to added calcium (referred to as refractory vesicles). The question of which type of cortex preparation most closely simulates the in vivo situation is discussed, and the view is presented that the glycine cortices most closely resemble the in vivo situation.     

Behavior of lactating rats in a dual-chambered maternity cage

Videotape sampling of behavior in a dual-chambered apparatus indicates that the continuous monitoring of the amount of time a mother spends in the cage with its litter can be taken as a valid reflection of maternal behavior. Nursing is the principal behavior of lactating females while in the compartment with their litters; lying still, consummatory behavior, and activity occur with greater frequency in the cage away from the litter. Both the time that mothers spend with their litters and nursing behavior displayed a 24-hr rhythm with crest values occurring during the period of light.     

Localization of glycoprotein glycosyltransferases in the Golgi apparatus of rat and mouse testis

Golgi fractions prepared from rat testis have been shown to be enriched in the following glycoprotein glycosyltransferases: N-acetylglucosaminyltransferase, 47-fold, galactosyltransferase, 33-fold, and N-acetylglucosaminide fucosyltransferase, 15-fold. Appreciably lower transferase levels were obtained in other subcellular fractions. In the mouse, Golgi fractions were prepared from testis homogenates, testis cell suspensions and partially purified testis germinal cells; these fractions were also enriched in the above glycoprotein glycosyltransferases. Electron microscopic analysis indicated that a major portion of the total transferase activity was located in the Golgi apparatus of both rat and mouse testis although these experiments could not rule out the possible presence of some transferase activity in other organelles.     

The influence of rotor speed on the sedimentation behavior in sucrose gradients of high molecular weight DNA's

Anomalous sedimentation behavior has been observed for high molecular weight duplex DNA's in sucrose gradients. The sedimentation rate of DNA's having molecular weights of 10⁸ or higher is influenced by high centrifugal fields. The change in the sucrose sedimentation coefficient due to this effect, S^RPM_suc-S⁰_suc, is equal to 1 × 10^?48M^3.65( The anomalous behavior is not influenced by DNA concentration at sufficiently low concentrations. Because of the smallness of the coefficient this effect has not been previously detected for DNA's the size of T2 or smaller at rotor speeds below 40000 RPM. For example, the relative sedimentation coefficient of T2 DNA at 65 000 RPM is only 9% less than at 10000 RPM. However, the sedimentation profile of heterogeneous high molecular weight [(100 – 350) × 10⁶] E. coli DNA is severely altered even at moderate rotor speeds (37000 RPM). Therefore, it seems advisable to use low rotor speeds when sedimenting high molecular weight DNA's.     

The effect of cyclic nucleotides on purine biosynthesis and the induction of PRPP synthetase during lymphocyte activation

The activation of lymphocytes has been used to study the regulation of mammalian gene expression. Concanavalin A (Con A) added to mouse spleen lymphocytes in serum-free medium leads to an increase in the rate of DNA synthesis as great as 1000 fold, commencing 20 hr after its addition. Prior to 20 hr, the rate of purine synthesis increases 10–100 fold as measured by accumulation of the purine intermediate, formyl glycineamide ribonucleotide (FGAR). Addition of dibutyryl cyclic GMP to the lymphocyte suspensions results in a 10 fold increase in the rate of DNA synthesis in the absence of Con A and enhances both purine synthesis and DNA synthesis in its presence. The activity of phosphoribosyl pyrophosphate synthetase (PRPP synthetase), an enzyme central to purine and pyrimidine biosynthesis, is increased 2–10 fold during the activation. The increase begins to appear 8 hr after Con A addition and requires concomitant protein synthesis. The induced PRPP synthetase activity is stimulated by the presence of cyclic GMP in the enzyme assay. Addition of dibutyryl cyclic AMP to Con A-stimulated lymphocytes inhibits FGAR production, the stimulation of DNA synthesis, and the appearance of cyclic GMP-sensitive PRPP synthetase. These studies suggest that cyclic nucleotides play a significant role in the molecular mechanism of lymphocyte activation, the regulation of purine biosynthesis, and of eucaryotic genetic expression.     

Isolation of ouabain-resistant human diploid fibroblasts

Seventeen clones resistant to the cytotoxic action of ouabain were isolated in culture by direct selection from 5 independent strains of diploid human fibroblasts. Resistant clones were recovered at frequencies on the order of 10^?7 per wild type cell selected from populations treated with the mutagen EMS, but no resistant cells were detected among 10⁸ unmutagenized cells. Most selected clones remained ouabain-resistant following further propagation in the absence of drug. The growth of wild type cells was inhibited by 50% at ouabain concentrations of 2–5 × 10^?8 M, while resistant clones required 15–180 fold higher drug concentrations to cause equivalent inhibition. Ouabain-resistant clones showed increased resistance of K+ transport function to ouabain inhibition that paralleled their increased resistance to growth inhibition. Initial experiments suggest that under selective conditions the resistant diploid fibroblasts differ significantly from wild type in binding of ³H-ouabain per unit surface area. The ouabain-resistant cells were similar to wild type in transport properties unrelated to ouabain inhibition. Resistant cells had normal karyotypes and senesced with a lifespan similar to control clones. The ouabain-resistant phenotypes of these diploid human fibroblast isolates apparently reflect point mutations that specifically affect the Na+/K+ transport ATPase with respect to ouabain-binding and/or response to bound ouabain.     

THE EFFECTS OF PREDATION ON THE AGE AND SIZE OF MATURITY OF PREY

The effects of nonselective predation on the optimal age and size of maturity of their prey are investigated using mathematical models of a simple life history with juvenile and adult stages. Fitness is measured by the product of survival to the adult stage and expected adult reproduction, which is usually an increasing function of size at maturity. Size is determined by both age at maturity and the value of costly traits that increase mean growth rate (growth effort). The analysis includes cases with fixed size but flexible time to maturity, fixed time but flexible size, and adaptively flexible values of both variables. In these analyses, growth effort is flexible. For comparison with previous theory, models with a fixed growth effort are analyzed. In each case, there may be indirect effects of predation on the prey's food supply. The effect of increased predation depends on (1) which variables are flexible; (2) whether increased growth effort requires increased exposure to predators; and (3) how increased predator density affects the abundance of food for juvenile prey. If there is no indirect effect of predators on prey food supply, size at maturity will generally decrease in response to increased predation. However, the indirect effect from increased food has the opposite effect, and the net result of predation is often increased size. Age at maturity may either increase or decrease, depending on functional forms and parameter values; this is true regardless of the presence of indirect effects. The results are compared with those of previous theoretical analyses. Observed shifts in life history in response to predation are reviewed, and the role of size-selective predation is reassessed.