Differences in Specific Mass Density Between Dinoflagellate Life Stages and Relevance to Accumulation by Hydrodynamic Processes

One previously unstudied aspect of differences between sexual and asexual life stages in large-scale transport and accumulation is density (mass per unit volume) of cells in each life stage. The specific density was determined for Scrippsiella lachrymosa cells in medium with and without nitrogen (N) enrichment through density-gradient centrifugation. Growth medium without N addition is often called "encystment medium" when used for the purpose of resting cyst formation in cyst-forming dinoflagellates; mating gametes are usually seen after 2-3 days. Significant differences in specific density were found after 2 days in encystment medium simultaneously with the observation of typical gamete swimming behavior and mating. The specific density of cells in encystment medium was 1.06 g · cm^-3 ; whereas, the specific density of cells in growth medium was 1.11 g · cm^-3 . Cells in encystment medium were found to have significantly increased lipid content, reduced chlorophyll content, and reduced internal complexity. The findings may explain differential transport of less dense and chemotactically aggregating gametes into surface blooms in contrast to denser vegetative cells that perform daily vertical migration and do not aggregate. Passive accumulation of non-migrating gametes into layers in stagnant water also can be explained, as well as sinking of zygotes when the storage of highly dense starch increases. Resting cysts had a density of over 1.14 g · cm^-3 and would sink to become part of the silt fraction of the sediment. We suggest that differences in behavior and buoyancy between sexual and asexual life stages cause differences in cell accumulation, and therefore large-scale, environmental transport could be directly dependent upon life-cycle transitions.

Gradient sperm selection for reproductive techniques in cattle: Is Isolate a suitable replacement for Percoll?

In assisted reproductive techniques, it is essential to perform a sperm selection to obtain spermatozoa with high motility and membrane integrity for in vitro fertilisation (IVF) and high-DNA integrity for intracytoplasmic sperm injection (ICSI). In this study, we evaluated whether Isolate^® was a suitable substitute for Percoll^® for assisted reproductive techniques. Commercial cryopreserved bovine semen was used after selection in both gradients, and plasma and acrosome membrane integrity, reactive oxygen species (ROS) levels, DNA integrity and mitochondrial membrane potential (ΔΨm) were assessed by flow cytometry. Motility parameters were also evaluated by CASA system. A similar percentage of spermatozoa with intact plasma membrane, acrosome integrity and high ΔΨm was observed in both sperm selection methods, but only Percoll^® showed higher percentage of spermatozoa with intact plasma and acrosome membrane compared to the post-thawing group. No differences were observed in the motility, ROS, DNA fragmentation and on the in vitro embryo production in all experimental groups. In conclusion, the selection of bovine spermatozoa with Isolate^® generates spermatozoa with similar quality parameters and embryonic development compared to Percoll^® providing a suitable alternative sperm selection method for assisted reproductive techniques in this species.

Flow cytometric characterization of peripheral blood leukocyte populations of 3 neotropical snake species: Boa constrictor, Bothrops jararaca, and Crotalus durissus

BACKGROUND

The reptilian immune system is represented by innate, humoral, and cell-mediated mechanisms, involving different types of blood leukocytes. The development of optimized methods for the advanced study of origin and function of reptilian blood leukocytes is needed.

OBJECTIVES

The purpose of the study was to optimize leukocyte density gradient isolation protocols from snake peripheral blood samples, and characterize recovered cells by flow cytometry based on size and internal complexity for a qualitative and semi-quantitative assessment of leukocyte populations in one boa (Boa constrictor), and 2 viper species (Bothrops jararaca, Crotalus durissus).

METHODS

Blood samples from 30 snakes (10 from each species, 5 males and 5 females) were collected in tubes with sodium heparin. Fresh blood was centrifuged with either ficoll-paque PLUS or percoll density gradients for leukocyte isolation. Flow cytometric leukocyte gates were defined based on size (forward scatter [FSC]) and internal complexity (side scatter [SSC]). Relative leukocyte differential counts after sorting the cells in these gates in one snake for each species were compared to conventional light microscopic differential counts on unsorted isolated leukocytes.

RESULTS

There was no statistical difference in the relative leukocyte populations, including heterophils, azurophils, and small and large lymphocytes between samples isolated by ficoll or percoll. Four leukocyte gates were identified based on their location in FSC/SSC cytograms. The relative leukocyte differential counts after sorting in single animals showed some agreement with the light microscopy differential count on unsorted cells.

CONCLUSIONS

Based on FSC and SSC, 4 distinct leukocyte populations were found in ficoll or percoll density gradient isolated leukocytes from peripheral blood from boa and viper species. Further optimization of the technique should allow the performance of functional assays.

Isolation of granulosa cells from follicular fluid; applications in biomedical and molecular biology experiments

BACKGROUND

Recently, a lot of research has been conducted to investigate the molecular mechanisms of the low quality of oocytes with granulosa cells (GCs). GCs are one of the major cell types found in follicular fluid and purification of these cells from the follicular fluid is very important for further studies. Although, there are different techniques of purification, a method for separation of highly-pure and minimally-damaged cells is necessary. In this paper, we presented a novel method for high purification of GCs with a large quantity and high purity.

MATERIALS AND METHODS

Follicular fluid was collected from patients who referred for in vitro fertilization and GCs in follicular fluid were extracted by Ficoll, Percoll and Red blood cell lysing buffer (RLB) methods. Then purity of extracted GCs was assessed by flow cytometry and morphological properties of GCs were observed by differential interference contrast microscopy. The purity of deoxyribonucleic acid and ribonucleic acid extracts was examined by NanoDrop 1000, pre-restriction fragment length polymorphism and electrophoresis techniques. Quality and quantity of extracting GCs were affected during the cell separation procedures.

RESULTS

Our results showed that each of purification method can affect quality and quantity of extracted cells.

CONCLUSION

RLB method for extraction of GCs was shown to be a convenient procedure in comparison with Ficoll and Percoll methods.

Separating X-bearing human spermatozoa through a discontinuous Percoll density gradient proved to be inefficient by double-label fluorescent in situ hybridization

PURPOSE

Double-label fluorescence in situ hybridization (FISH) was used to evaluate the efficiency of separating X- and Y-chromosome-bearing spermatozoa through 12-step discontinuous Percoll gradients.

METHODS

Liquefied normal semen samples from 10 healthy donors were overlaid onto 25% Percoll and centrifuged. Parts of the sperm pellet were saved as control, while the remaining portion was separated by 12-step Percoll gradient. After centrifugation, the spermatozoa in the 80% Percoll layer were collected. The X:Y ratio of the control and separated spermatozoa was verified by double-label FISH (CEP SOX/SGY probes) and scored blindly by one observer. Differences in the X:Y ratios between matched groups were analyzed by paired t tests.

RESULTS

The overall average labeling efficiency was 99.2%. A significant enrichment (P = 0.02) of X-bearing spermatozoa was obtained in Percoll separated fractions (mean X:Y ratio = 52.2:46.4) compared with the control group (X:Y ratio = 49.5:48.4). Discontinuous Percoll gradients also decreased the proportion of aneuploid spermatozoa (from 1.0 to 0.8%), but the differences were nonsignificant.

CONCLUSIONS

Discontinuous Percoll separation did increase the X:Y ratio significantly, but the enrichment of X-bearing spermatozoa is insufficient for clinical use in preconceptional sex selection.

Silane-coated silica particle colloid processing of human sperm

PURPOSE

The purpose of this study was to determine differences in the quality of human sperm processed through different lots of silane-coated silica particle colloid solutions. The objectives were to compare (a) sperm kinematic parameters, (b) the sperm acrosome status, (c) the membrane integrity of the head and tail regions, (d) the DNA normality, and (e) the heat-inducible hyperactivation motility after processing sperm through either a Silane-coated silica particle colloid solution, a Percoll solution, or a simple centrifuge sperm wash (control).

METHODS

Sperm cells were derived from pooled cryopreserved-thawed specimens of several donors (n = 10). The pooled sperm were divided and processed through either the centrifuge wash, the 90:47% two-layer Percoll, or one of three lots of silane-coated silica particle colloidal solutions from three vendors. Aliquots of sperm cells were analyzed using the Hamilton-Thorn HTM-C motility analyzer for differences in kinematics and hyperactivation. Sperm were also analyzed for membrane integrity at both head and tail regions, normal morphology, acrosome status, and viability. Sperm undergoing apoptosis were determined using the acridine orange stain. Processed sperm were also incubated at 40 degrees C for 4 hr and the quality of the sperm was assessed using the heat-induced hyperactivation and motility parameter.

RESULTS

The data showed that after sperm processing, the number of sperm recovered was higher for the three lots of colloids (silane-coated silica particle colloid solutions) compared with Percoll processing. Total sperm motility was higher in the colloidal washes compared with the control. There were no differences in motility between Percoll- and colloid-processed sperm. In contrast, the percentages of sperm exhibiting progressive motility or hyperactivation varied among the different lots of colloid solutions. The Percoll wash solution yielded the highest percentage of sperm with intact tail membranes, whereas some lots of colloid solutions disrupted sperm head membranes. The percentages of sperm undergoing apoptosis varied for the different lots of colloid solutions. There was a marked increase in hyperactivation associated with one colloid solution after heat induction.

CONCLUSIONS

The results demonstrated variability in the different lots of silane-coated silica particle colloid solutions for processing sperm. Each lot of colloid solution excelled at improving different sperm parameters. The silane-coated silica particle colloid solutions were shown to be effective in recovering motile sperm compared with Percoll but the types of motility and sperm quality varied for the different lots of colloid solutions. Due to the variability in lots of silane-coated silica colloid solutions, reported studies based on only one lot or one source of colloid solution may be difficult to interpret. Furthermore, it may be advantageous to select the best lot of silane-coated silica particle colloid solution to produce the highest number of sperm exhibiting the ideal parameters for use in assisted reproduction technologies.

Improved motile sperm recovery by a hyperosmotic Percoll gradient

PURPOSE

Our purpose was to investigate whether a new, relatively hyperosmotic Percoll gradient, Enhance-S, can improve total motile sperm recovery rates compared with the commonly used Percoll gradient Perception.

METHODS

Semen specimens from each of 17 donors were divided into two equal aliquots. One part was washed using Percoll Perception, while the other was prepared using Percoll Enhance-S.

RESULTS

Compared to the unwashed specimen, sperm motion characteristics (motility and velocity) improved significantly after Percoll separation using either the Perception or the Enhance-S gradient. There was no difference in motility or velocity in spermatozoa recovered after wash with either of the two preparations. However, the total motile sperm recovery was significantly higher using the Percoll Enhance-S gradient than with the Percoll Perception gradient (P < 0.0024).

CONCLUSION

The new Percoll Enhance-S gradient provides significantly more total motile sperm than the Percoll Perception gradient.

Flow cytometric characterization of bovine blood neutrophil phagocytosis of fluorescent bacteria and zymosan particles

A Flow Cytometric method for the evaluation of the phagocytic capacity of bovine blood neutrophils is described. The neutrophils were isolated from bovine blood by a one step discontinuous gradient of Percoll. By this technique of isolation, 90 ± 2.8 % (mean ± s) of the granulocytes in the whole blood were recovered.

Isolated neutrophils were incubated with FITC labeled S. aureus or zymosan particles in a ratio of 1:20 and 1:10, respectively, and a final serum concentration of 10 %. Phagocytosis was terminated after 15 min and the number of extracellular bacteria or zymosan particles and the percentage of phagocytic granulocytes were registered by Flow Cytometry (FCM). FCM and microscopic studies revealed that eosinophils play a minor role in the phagocytosis of bacteria. The neutrophils were the main population of the granulocytes which were actively phagocytic. Variation among cows in the ability of their blood neutrophils to phagocytize bacteria was evident.