Stress preconditioning of semen before cryopreservation improves fertility and increases the number of offspring born: a prospective randomised study using a porcine model.

The aim of the present study was to investigate the effect of applying sublethal stress treatment at room temperature, before cryopreservation (hydrostatic pressure (HP): 40MPa, 80min) of 34 boar ejaculate samples, on post-thawed motility and sow fertility. Sows (n=102) were randomly allocated into equal groups inseminated with HP-treated or untreated frozen-thawed semen. Sows were inseminated twice, 10h apart, with 6×10(9) spermatozoa per dose without oestrus synchronisation. Rates of non-return of oestrus and pregnancy, and total numbers of piglets and live piglets were significantly higher (P<0.05) in the HP-treated group. There was also a numerical, albeit non-significant (P>0.05), improvement in the farrowing rate in the HP-treated group. Although the number of live piglets per litter decreased approximately 15% in both groups by 42 days after farrowing, but this remained significantly higher in the HP-treated group. Although total and progressive sperm motility were significantly (P<0.001) higher in the HP-treated group, there were no significant differences (P>0.05) in these parameters between pregnant and non-pregnant sows in either group; thus motility can indicate, but not predict, improved fertility. In conclusion, HP treatment, with sperm cryopreservation, increases in vitro sperm motility and improves reproductive performance without adversely affecting the health of the piglets.

Stress preconditioning of boar spermatozoa: a new approach to enhance semen quality.

Semen preparation and cryopreservation require finely adjusted procedures. Gametes are sensitive to environmental stresses, so in vitro procedures aim to minimize the inevitable harmful conditions. Applying stress to precondition cells has only been investigated recently. Studies demonstrated that by utilizing a well defined and properly applied hydrostatic pressure (HP) stress treatment to spermatozoa before in vitro storage, cryopreservation or insemination, cell survival and fertility improved compared with untreated controls. The birth of healthy piglets from treated fresh or frozen-thawed semen demonstrates the in vivo safety of the procedure. Although the biological mechanism is still unclear, several processes incorporating cellular stress response might explain the observations. This paper summarizes results, background, aspects and considerations of HP treatment for porcine semen. The new principle, i.e. to improve the stress tolerance by a defined sublethal stress may outline a new strategy in assisted reproductive technologies with unique theoretical and practical consequences.

The cation radicals of free base and zinc bacteriochlorin, bacteriochlorophyll, and bacteriopheophytin.

One-electron oxidation of zinc tetraphenylbacteriochlorin and its metal-free base yielded stable cation radicals. Electron spin resonance hyperfine splittings were assigned by selective deuterations. These results indicate that the protons of the saturated rings of the bacteriochlorins carry large spin densities, in accord with molecular orbital calculations. Comparison in vitro of the optical spectra of bacteriochlorins and their cation radicals with those of bacteriochlorophyll show close correspondence and suggest that the electron spin resonance data from the former may also prove a guide to the biological molecule. The surprising similarity in properties between the radicals of free base and zinc bacteriochlorins is maintained in the chlorophylls: cation radicals of bacteriopheophytin and methyl pheophorbide (the free bases of bacteriochlorophyll and methyl chlorophyllide, respectively) exhibit electron spin resonance properties similar to those of their magnesium-containing derivatives. The possibility that metal-free chlorophylls participate in photosynthesis is discussed.