Metformin blocks mitochondrial membrane potential and inhibits sperm motility in fresh and refrigerated boar spermatozoa

Metformin is clinically used to treat diabetes. Given its role‐impacting metabolism, metformin has been also added to semen cryopreservation media showing specie‐dependent effects. We aimed to investigate metformin effects in both fresh (38.5°C for 2, 24 hr) and refrigerated (17°C for 10 days) boar spermatozoa. Metformin (2 hr) does not affect fresh sperm viability, membrane lipid organization nor acrosome integrity. However, metformin (24 hr) blocks sperm ΔΨm and significantly reduces % motile spermatozoa (65%), % progressive spermatozoa (50%), % rapid (100%), velocities VCL (69%), VSL (86%), VAP (78%) and motility coefficients. Metformin‐including extender does not modify sperm viability, membrane lipid organization or acrosome integrity. Furthermore, it significantly reduces high ΔΨ‐population spermatozoa at refrigeration day 4. Metformin also significantly reduces sperm motility during refrigeration. Summarizing, metformin inhibits both boar sperm ΔΨ and motility in any sperm condition studied: fresh and refrigerated. These findings dissuade metformin as an additive to improve boar sperm quality.     

Fish mortality due to acute ammonia exposure

Abstract. Fish mortality in the River Umia, near Villagarcia de Arosa, Pontevedra, Spain, which occurred after a discharge from a food sewage works, is studied. Physico-chemical parameters of water samples from sewage and from the River Umia were studied and concentrations of ammonia sufficiently high to cause toxic effects in fish (702 mg/1 and 302 mg/1 as total ammonia) were found. The toxicity of two concentrations of ammonia was investigated on goldfish, Carassius auratus (L.), using water quality values the same as found in the River Umia, to obtain the same concentrations of un-ionized ammonia (2·13 mg/1 and 0·91 mg/1). Fish exposed to high concentrations died within 24 h and three of six, which were exposed to the lowest concentration died within 96h. All fish at first showed symptoms of hyper excitability and hyperventilation, and at times of rest showed a decrease in respiration. Post-mortem findings generally included gill congestion and haemorrhage.     

Scanning Single-Electron Transistor Microscopy: Imaging Individual Charges

A single-electron transistor scanning electrometer (SETSE)-a scanned probe microscope capable of mapping static electric fields and charges with 100-nanometer spatial resolution and a charge sensitivity of a small fraction of an electron-has been developed. The active sensing element of the SETSE, a single-electron transistor fabricated at the end of a sharp glass tip, is scanned in close proximity across the sample surface. Images of the surface electric fields of a GaAs/AlxGa1-xAs heterostructure sample show individual photo-ionized charge sites and fluctuations in the dopant and surface-charge distribution on a length scale of 100 nanometers. The SETSE has been used to image and measure depleted regions, local capacitance, band bending, and contact potentials at submicrometer length scales on the surface of this semiconductor sample.