Negative allometry of leaf xylem conduit diameter and double-wall thickness: implications for implosion safety.

Xylem conduits have lignified walls to resist crushing pressures. The thicker the double-wall (T) relative to its diameter (D), the greater the implosion safety. Having safer conduits may incur higher costs and reduced flow, while having less resistant xylem may lead to catastrophic collapse under drought. Although recent studies have shown that conduit implosion commonly occurs in leaves, little is known about how leaf xylem scales T vs D to trade off safety, flow efficiency, mechanical support, and cost. We measured T and D in > 7000 conduits of 122 species to investigate how T vs D scaling varies across clades, habitats, growth forms, leaf, and vein sizes. As conduits become wider, their double-cell walls become proportionally thinner, resulting in a negative allometry between T and D. That is, narrower conduits, which are usually subjected to more negative pressures, are proportionally safer than wider ones. Higher implosion safety (i.e. higher T/D ratios) was found in asterids, arid habitats, shrubs, small leaves, and minor veins. Despite the strong allometry, implosion safety does not clearly trade off with other measured leaf functions, suggesting that implosion safety at whole-leaf level cannot be easily predicted solely by individual conduits' anatomy.

Long-term effect of a GnRH-based immunocontraceptive on feral cattle in Hong Kong.

Increasing human-wildlife conflicts worldwide are driving the need for multiple solutions to reducing "problem" wildlife and their impacts. Fertility control is advocated as a non-lethal tool to manage free-living wildlife and in particular to control iconic species. Injectable immunocontraceptives, such as GonaCon, stimulate the immune system to produce antibodies against the gonadotrophin-releasing hormone (GnRH), which in turn affects the release of reproductive hormones in mammals. Feral cattle (Bos indicus or Bos taurus) in Hong Kong are an iconic species whose numbers and impacts on human activities have increased over the last decade. Previous studies have proven that a primer vaccination and booster dose of GonaCon in female cattle are safe and effective in reducing pregnancy levels one year post-treatment. The aims of this project were 1. to evaluate the longevity of the effect of GonaCon in feral cattle up to four years post-vaccination; and 2. to assess if a second booster dose of GonaCon, administered at either two or four years post-vaccination, extends the contraceptive effect in this species. Vaccination with GonaCon, administered as a primer and booster dose, was effective in causing significant infertility in free-living cattle for at least three years post-vaccination, with the percentage of pregnant animals in the vaccinated group decreasing from 76% at vaccination to 35%, 19% and 7% in years 2, 3 and 4 post-vaccination, compared with 67% at vaccination to 50%, 57% and 14% respectively in the control group. A second booster dose of GonaCon administered either 2 or 4 years after vaccination rendered 100% of the Treated cattle infertile for at least another year. These results suggested that vaccination with GonaCon can reduce feral cattle population growth and that a second booster dose can extend the longevity of the contraceptive effect.

Effect of redo varicocelectomy on semen parameters and pregnancy outcome: An original report and meta-analysis.

Recurrence following varicocelectomy is an important cause of treatment failure and persistence of subnormal semen parameters. This original study was combined with a systemic review and meta-analysis aiming to evaluate the efficacy of redo varicocelectomy on male fertility potential and pregnancy outcome. The retrospective study included 32 patients who underwent microsurgical subinguinal varicocelectomy for patients with recurrent varicocele. Changes in semen parameters and hormone profiles before and after surgery were compared. The literature review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and included seven articles in addition to our original report. Results of the original study revealed statistically significant improvements in sperm concentration, progressive motility, total motile sperm count and normal morphology following redo varicocelectomy. The meta-analysis results echoed those reported in our original study and depicted significant improvements in sperm concentration (mean difference [MD] = +20.281 million/ml, p < 0.001), total motility (MD = +9.659%, p = 0.001), total motile sperm count (MD = +23.258 million sperm, p < 0.001) and normal morphology (MD = +4.460%, p < 0.001). Overall pregnancy outcome was reported in seven studies with a rate of 34.6%. No significant changes were noted in any of the collected hormone results both in this original report and in the meta-analysis. In conclusion, redo varicocelectomy has a beneficial role on male fertility potential and can be offered for men with recurrent varicocele as directed by their individual clinical condition.