Metabolic activity of sperm cells: correlation with sperm cell concentration, viability and motility in the rabbit.

The resazurin reduction test (RRT) is a useful technique to assess the metabolic rate of sperm cells. RRT depends on the ability of metabolically active cells to reduce the non-fluorescent dye resazurin to the fluorescent resorufin. The aim of this study was to develop a vital fluorometric method to evaluate metabolic activity of rabbit sperm cells. Twenty-five rabbit males were included in the study. Viability and morphology, motility and metabolic activity were evaluated using an eosin-nigrosin staining, a computer-assisted semen analysis (CASA) and the RRT, respectively. Spearman rank correlation analysis was used to determine the correlation between RRT and semen parameters. After evaluation, a concentration of 10 × 106 sperm cells/ml was selected for further experiments with RRT. No significant correlation was found between the RRT results and the motility parameters. However, after RRT a significant positive correlation between relative fluorescence units and the percentage of alive spermatozoa (r = 0.62; P = 0.001) and a negative one with the percentage of sperm cells with acrosomic abnormalities (r = -0.45; P < 0.05) were detected. The vital assessment of metabolic rate of sperm cells by RRT could provide more information about semen quality than other routine semen analysis, correlating with sperm viability and acrosome status information.

Daily exposure to summer circadian cycles affects spermatogenesis, but not fertility in an in vivo rabbit model.

Heat stress (HS) in mammals is a determining factor in the deterioration of spermatogenesis and can cause infertility. The aim of this study was to evaluate the effect of continuous summer circadian cycles on semen production, sperm cell features, fertility, prolificacy, and fecal cortisol metabolites from rabbits kept under an in vivo HS model. We split randomly 60 New Zealand White rabbits into two temperature-controlled rooms: The control group was maintained at comfort temperature (18 °C-22 °C) and an HS group, where the environmental temperature was programmed to increase from 22 °C to 31 °C and be maintained for 3 hours to this temperature at the central part of the day. Fecal cortisol metabolites were assessed to evaluate the stress conditions. Seminal parameters were analyzed. Although animals exposed to HS showed higher values of fecal cortisol metabolites (P = 0.0003), no differences were detected in fertility or prolificacy. Semen samples from HS males showed a significant decrease (P < 0.05) with respect to the controls in the percentage of viable spermatozoa (80.71% vs. 74.21%), and a significant (P ≤ 0.01) increase in the percentage of acrosomic abnormalities (22.57% vs. 36.96%) and tailless spermatozoa (7.91% vs. 12.83). Among motility parameters, no differences were found. This study describes a model of HS simulating a continuous summer daily cycle that allows periods of time to recover as it occurs under natural conditions. Although negative effects have been detected in several sperm parameters, fertility and prolificacy were not affected, suggesting a recovery of the reproductive function when normal conditions are reestablished.

Biobanked Amphibian Samples Confirmed To Species Level Using 16S rRNA DNA Barcodes.

The DNA barcoding technique is often used as a tool for validating species identity in biobanks. In the case of amphibians, the mitochondrial DNA (mtDNA) 16S ribosomal RNA (rRNA) gene is reported to fulfill the requirements of a universal DNA barcoding marker. The 16S primers are designed to specifically bind to the 16S rRNA gene, which is a very well-conserved mtDNA gene sequence in amphibians. DNA was extracted from thirteen known but different species of amphibians within the Zoological Society of London/Amphibian Ark's cryobank. After this, the DNA was amplified and analyzed by (1) the traditional DNA barcoding procedure that involves conventional polymerase chain reaction (PCR) and DNA sequencing and (2) a novel procedure, involving real-time PCR and melting temperatures. Both procedures used the same 16S primers. Successful DNA amplification and validation to the species or genus level was achieved in 10 out the 13 cases using the traditional approach. Nevertheless, after real-time PCR and melting temperature analysis, some variability was found between Common Frog samples but more concerning, the same melting temperature was recorded in unrelated species (Common Toad, Common Frog and Amazon Milk Frog), despite their 16S sequences exhibiting a high degree of variability. We conclude that traditional DNA barcoding using 16S rRNA sequences is suitable for validating the specific identity of amphibian samples within biobanks and that modification of the current 16S real-time PCR and melting temperature analysis is required before it can be employed as a cheaper and faster alternative.