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The in vitro interaction between purified bovine liver and sperm DNA with somatic histones, to form nucleosomes, and with bovine and salmon protamines were studied. DNAse or microccocal nuclease digestion of liver DNA-histone reassociated chromatin produced the expected polynucleosome type of fragments. Electrophoretic patterns of digested sperm-DNA nucleosomes were different. Micrococcal nuclease digestion produced mainly fragments smaller than 100 bp and some nucleosome-type particles. Under DNAse activity most of the products were smaller than 100 bp, indicating an increased susceptibility of the sperm DNA-histone complexes to the hydrolytic activity of both nucleases, particularly toward DNAse I. This differential susceptibility was confirmed by sucrose gradient spectrophotometric analysis. Acridine orange (AO) staining of histone-DNA reassociated nucleosomes showed significant differences in fluorescence intensity, sperm DNA-histone complexes being almost twice as fluorescent as liver DNA-histone complexes. On the contrary, liver DNA/protamine complexes stained with AO were consistently more fluorescent than sperm DNA-protamine complexes. Finally, no differences in either fluorescence intensity or spectra were observed when liver and sperm DNA were stained with AO after interaction with salmon protamines. The data suggest that sperm DNA has important structural characteristics that differentiates it from somatic DNA. These differences seem to be species specific and must surely play an important role on the determination of the dramatic sequence of that participates sperm chromatin organization. [ABSTRACT FROM AUTHOR]

The evolution of reproductive barriers is the first step in the formation of new species and can help us understand the diversification of life on Earth. These reproductive barriers often take the form of hybrid incompatibilities, in which alleles derived from two different species no longer interact properly in hybrids 1-3 . Theory predicts that hybrid incompatibilities may be more likely to arise at rapidly evolving genes 4-6 and that incompatibilities involving multiple genes should be common 7,8 , but there has been sparse empirical data to evaluate these predictions. Here we describe a mitonuclear incompatibility involving three genes whose protein products are in physical contact within respiratory complex I of naturally hybridizing swordtail fish species. Individuals homozygous for mismatched protein combinations do not complete embryonic development or die as juveniles, whereas those heterozygous for the incompatibility have reduced complex I function and unbalanced representation of parental alleles in the mitochondrial proteome. We find that the effects of different genetic interactions on survival are non-additive, highlighting subtle complexity in the genetic architecture of hybrid incompatibilities. Finally, we document the evolutionary history of the genes involved, showing signals of accelerated evolution and evidence that an incompatibility has been transferred between species via hybridization., (© 2024. The Author(s).)

Large superovulatory doses of gonadotrophins result in reduced fertility in laboratory and large domestic animals and it has been postulated that some of the superovulated oocytes are derived from abnormal follicles which would not ovulate under normal physiological stimuli. Follicular growth, follicular maturation and atresia, ovulation and the nidation of the fertilized oocyte require intense tissue remodelation which can be accomplished only through the action of hydrolytic enzymes. We have studied the activities and sub-cellular distribution of three lysosomal enzymes (acid phosphatase, N-acetyl-beta-D-glucosaminidase and beta-glucuronidase) in the follicular fluid, granulosa and theca cells of preovulatory follicles and in the endometrial tissue of immature Wistar rats injected with 4 (control) or 40 (superovulated) IU of pregnant mare serum gonadotrophin (PMSG). Enzyme activities were from four to ten times higher in theca than in granulosa cells. This difference was particularly important in the case of beta-glucuronidase. Large preovulatory follicles tended to have higher activities of lysosomal enzymes in the free fraction of all the compartments studied. This difference was remarkable in theca cells where free enzymes would be required to help ovulation. Forty IU of PMSG induced higher activities of acid phosphatase in theca and granulosa cells than 4 IU, but in endometrial tissue this latter dose of PMSG was more efficient to induce higher activities of this enzyme. The endometrial bound fraction of N-acetyl-beta-D-glucosaminidase was almost three times higher than the free activity. This behavior was also observed in endometrial beta-glucuronidase but only in the control rats. The results observed in follicular fluid were less homogeneous. The activities of glucosaminidase and acid phosphatase were two to three times higher in rats overstimulated with 40 IU of PMSG than in the control rats, whereas the activities of beta-glucuronidase were lower in the superovulated rats. Our results suggest that alterations in the process of tissue remodeling required for ovulation of mature, normal oocytes and for nidation of the fertilized ovum may be important factors to explain pregnancy failure in the PMSG superovulated female.

Binding of N-formyl-methionyl-L-leucyl-[3H]phenylalanine (fML[3H]Ph) to human ejaculated spermatozoa and to its isolated plasma membrane was studied. Our data confirm the presence of specific receptors for f-MLPh in the human spermatozoa and suggest that whole spermatozoa receptors exist in two affinity states, one high-affinity, low-capacity specific receptor (Kd = 12.3 +/- 0.5 nM, n = 22,285 +/- 65,008 binding sites per sperm cell) and a second one (Kd = 700 +/- 47 nM) that is not saturable, indicating a low-affinity, high-capacity nonspecific site. In contrast, sperm membrane showed only one class of binding site (Kd = 6.4 +/- 0.12 nM), which was statistically different from that of the high-affinity binding site of intact spermatozoa. To explain this difference we discuss the possibility that first, the two binding affinities represent two interconvertible states of a single receptor population, which, depending on the metabolic activity of spermatozoa, may change its physicochemical properties; or second, they reflect two different processes, binding and/or transport into the spermatozoa.

The effect of cupric ions on the initiation protein synthesis rate of the human endometrium was studied. Addition of copper to the complete ribosomal system decreased the binding of [3H]Met-tRNA(i) to the isolated ribosomes with a plateau at about 70% inhibition with concentrations higher than 150 microM. The initiation activity was GTP-dependent with a maximum at 2 mM. This activity was very rapid, requiring 5 min to complete the reaction. Incubation of isolated initiation factors with copper (300 microM) inhibited the formation of the ternary complex. When the complete system was reconstituted with salt-washed ribosomes after ternary complex formation, no significant change on the inhibition pattern was observed. Addition of initiation factors to 5-min preincubated salt-washed ribosomes with 300 microM copper, after the elimination of excess copper, induced only a 12% decrease on Met-tRNA(i) binding. This effect was not modified by the presence of Sparsomycin, an elongation inhibitor. It was concluded that copper interferes with the initiation process, probably at the ternary complex formation level.