Use of spin labels and electron spin resonance spectroscopy to characterize membranes of bovine sperm: effect of butylated hydroxytoluene and cold shock

Post-thaw quality of ram sperm frozen with different concentrations of low-density lipoproteins associated with non-enzymatic antioxidants

The cryopreservation reduces ram sperm quality, decreasing the pregnancy rate of ewes inseminated with thawed sperm. Hence, we aimed to improve the post-thaw quality of ram sperm replacing egg yolk on Tris-Glucose extender with different concentrations of LDL (2 or 8%), associated with the addition of 10 mM non-enzymatic antioxidants (ascorbic acid, hydroxytoluene butylate, ascorbyl palmitate, and trehalose). Semen samples were collected from six rams, split into different treatments, and frozen. After thawing, kinematic (CASA), structural (propidium iodide and carboxyfluorescein diacetate) and functional (hypoosmotic test) sperm membrane integrity was assessed. Total motility, VCL, and LIN were also assessed in thawed samples during 3 h of incubation (38 °C). The results showed that hydroxytoluene butylate at 10 mM in Tris-Glucose extender with 8% LDL improved velocity parameters immediately post-thaw compared with Tris-Glucose egg yolk extender, as well as prevented the reduction of total motility and VCL after incubation. There was no benefit of adding ascorbic acid and trehalose. Moreover, for the first time, it was shown the motility impairment promoted by ascorbyl palmitate to ram sperm.

Short-term storage sperm of coho salmon (Oncorhynchus kisutch) at 4 °C: Effect of sperm: Extender dilution ratios and antioxidant butyl-hydroxytoluene (BHT) on sperm function

Short-term storage of semen is a necessary key procedure in fish; it allows maximizing the use of gametes. Nevertheless, sperm quality decreases during storage has been associated with oxidative stress damage due to an increase in reactive oxygen species (ROS) during storage. This study was designed to optimize a short-term storage protocol for Coho salmon (Oncorhynchus kisutch) spermatozoa, evaluating the effect of extender dilution and the addition of butyl-hydroxytoluene (BHT) antioxidant on sperm function parameters. In the first experiment, fresh semen was diluted in Storfish®: extender dilution (1:2 and 1:3) and a control sample undiluted and stored at 4 °C for 7-days. In both experiments motility (MO), viability and integrity of plasma membrane, mitochondrial membrane potential (MMP) and superoxide anion level (O₂^-) were evaluated at 0, 3 and 7 days. Result shows that, 1:3 dilution maintained a higher sperm function for a longer period time. In the second experiment, spermatozoa were suspended in Storfish® (1:3) supplemented with two different concentrations of BHT (1.0 mM and 2.0 mM) and a control sample without antioxidant and stored at 4 °C for 7 days. The results demonstrated that, antioxidant-supplemented samples greater MO than control samples (P < 0.05). The viability remained >75% during storage in all groups. MMP was higher in 2.0 mM BHT compared to 1.0 mM and control (P < 0.05), in addition, this concentration reduced O₂^- level (P < 0.05). In conclusion, sperm: extender dilution 1:3 and adding of 2.0 mM BHT in sperm storage extender may enhance protection sperm function in Oncorhynchus kisutch against effects harmful of the oxidative stress during the in vitro storage.

Effect of butylated hydroxytoluene (BHT) on the cryopreservation of common carp (Cyprinus carpio) spermatozoa

The aim of the present study was to test the effects of butylated hydroxytoluene (BHT) on the cryopreservation of common carp spermatozoa. BHT is widely used in the cryopreservation of the spermatozoa of different animal species and successfully sustains the characteristics of spermatozoa during freezing and thawing, but it has not previously been used with fish. After sampling, common carp spermatozoa were diluted with an extender composed of modified Kurokura's extender, 10% DMSO, and 10% egg yolk containing 0.0001, 0.001, 0.01, 0.1, 1, 2.5, 5, or 10mM BHT and subsequently frozen in liquid nitrogen. The post-thaw spermatozoa characteristics (i.e., progressive motility percentage (%), duration of progressive motility (s), fertilization rate (%), and eyed-eggs rate (%)) were evaluated and compared with those of the control group. There were significant increases in the percentage of progressive motility and the duration of progressive motility at the concentrations of 0.1 and 0.001mM BHT (P<0.05). The duration of post-thawed spermatozoa progressive motility at 0.001mM BHT was significantly greater than that of the other groups (39.6±0.4s, P<0.05), and the fertilization rates and eyed-eggs rates were also higher following the 0.1 and 1mM BHT treatments. BHT at concentrations of more than 1mM caused sperm immobility during the preparatory stages of the sperm freezing. We concluded that 0.001-0.1mM BHT can be beneficial for the cryopreservation of common spermatozoa.

Effects of different concentrations of BHT on microscopic and oxidative parameters of Mahabadi goat semen following the freeze-thaw process

Oxidative damage to sperm is one of the main causes for decline in motility and fertility of frozen-thawed sperm. Thus, it is crucial to use cryoprotectant agents in extender in order to prevent lethal intracellular ice crystal formation. The present study aims to evaluate the effects of different concentrations of the antioxidant butylated hyroxytoluene (BHT) on sperm parameters post-thaw. Semen was diluted into five equal aliquots of extender containing different concentrations of BHT (0, 0.5, 1, 2 and 4mM), aspirated into 0.25 mL straws, and equilibrated at 5°C for 2h. After equilibration, straws were frozen in liquid nitrogen vapor and plunged into liquid nitrogen for storage. Sperm parameters, including motility and progressive motility, viability, membrane integrity, acrosome integrity and capacitation status, were assessed. Malondialdehiyde (MDA) and glutathione peroxidase (GSH-PX) activity were also evaluated after freezing-thawing. Results of this experiment show that addition of 1mM of BHT to the extender for freezing of goat semen can improve motility, progressive motility and viability (P<0.05) and reduce the MDA level (P<0.01). HOST (hypo-osmotic swelling test), acrosome integrity, capacitation status and GSH-PX were not affected by the concentrations of BHT (P>0.05). Therefore, we conclude that the optimum concentration of BHT for cryopreservation of goat semen is 1mM.

Survival and Fertility of Boar Spermatozoa After Freeze-Thawing in Extender Supplemented With Butylated Hydroxytoluene

This study evaluated the protective effect of butylated hydroxytoluene (BHT), a lipid-soluble antioxidant, against cryopreservation injuries to boar spermatozoa. In experiment 1, the lowest BHT concentrations able to reduce lipid peroxidation in boar spermatozoa were determined. Nine BHT concentrations (ranging from 0.025 to 3.2 mM) were evaluated, and the lowest (P <.05) production of malondialdehyde (MDA), as an indicator of lipid peroxidation, was obtained when BHT ranged from 0.2 to 1.6 mM. In experiment 2, sperm survivability was evaluated when BHT was added to a postthaw freezing extender by measuring the degree of sperm lipid peroxidation (using MDA production) and by measuring parameter such as motility, plasma membrane and acrosome integrity, and cell apoptosis. The ability of thawed spermatozoa to fertilize in vitro-matured oocytes and of embryos to develop to the blastocyst stage in vitro was also assessed. Pooled sperm-rich fractions collected from 3 mature Pietrain boars were frozen in 0.5-mL straws after dilution with lactose-egg yolk-glycerol-Orvus ES Paste extender supplemented with 0, 0.2, 0.4, 0.8, and 1.6 mM BHT. Postthaw sperm survival, evaluated 30 and 150 minutes after thawing, was higher in BHT-treated spermatozoa, being significant (P <.05) when the freezing extender was supplemented with 0.2, 0.4, and 0.8 mM BHT. The addition of BHT to the freezing extender resulted in a significant (P <.05) decrease in the MDA concentration in thawed spermatozoa, irrespective of the level of BHT used. BHT had no effect on oocyte cleavage rates, but the development to blastocyst was improved for embryos derived from spermatozoa frozen in extender supplemented with 0.4 mM BHT (16% vs 29% of blastocysts per total oocytes; P <.05). In conclusion, under the conditions tested in the present study, the addition of BHT to the freezing extender improved the overall efficiency of thawed boar spermatozoa.

Effect of ultraviolet C irradiation on human sperm motility and lipid peroxidation

PURPOSE

Ultraviolet C (UVC) irradiation of aqueous solutions is known to be a good source of reactive oxygen species (ROS). The aim of this study is to examine the effect of increasing doses of UVC irradiation, in the presence and absence of the antioxidant butylated hydroxytoluene (BHT), on human sperm motility and lipid peroxidation of its membranes.

MATERIALS AND METHODS

Human sperm samples were irradiated with UVC light (254 nm) for different periods of time. A computer-assisted semen analysis of sperm motility was carried out after UV irradiation. The percentage of motile sperm (%MOT), progressive motility, straight line velocity (VSL), curvilinear velocity (VCL) and the percentage of linearity (%LIN) were evaluated. The level of lipid peroxidation of sperm membranes was estimated by measurement of the thiobarbituric acid reactive substances (TBARS).

RESULTS

UVC irradiation of human spermatozoa produced a diminution of the sperm motility (%MOT, progressive motility, VSL, VCL, %LIN), viability and, concomitantly, an increase of the level of lipid peroxidation of the sperm membranes. The observed effects of the UVC irradiation were prevented by addition of the antioxidant BHT, indicating that the effects of UVC on the tested sperm parameters are mediated by an important rise in lipid peroxidation of the sperm membrane.

CONCLUSION

Lipid peroxidation of the human sperm plasma membrane leads to a decrease in the sperm motility (%MOT, progressive motility, VSL, VCL, %LIN) and viability. The protective effect of BHT on the UVC-irradiated sperm cells indicates the effects of ROS on sperm function.

Effect of butylated hydroxytoluene on bull spermatozoa frozen in egg yolk-citrate extender

Effect of butylated hydroxytoluene (BHT) on the quality of frozen-thawed Holstein bull sperm in egg yolk-citrate extender was evaluated. High quality semen samples were diluted in egg yolk-citrate extenders containing 0, 0.5, 1, 2 and 4 mM BHT and subsequently frozen in liquid nitrogen. Pre-freeze and post-thaw progressive motility, and live/dead ratio and acrosomal integrity of 200 sperm per slide, stained with Eosin-Nigrosin and Giemsa, were evaluated at 0, 2 and 4 h after thawing. There was a significant decrease in forward motility, livability and acrosomal integrity up to 4 h after thawing the frozen sperm. Upon thawing, sperm progressive motility at 1 mM BHT was significantly (P<0.001) higher (11%) than other groups, but percentages of live sperm and live sperm with intact acrosomes were higher at 0.5 mM BHT. BHT at 4 mM BHT caused a significant decrease in motility, livability and acrosomal integrity during preparatory stages of freezing sperm. It is concluded that 0.5-1.0 mM BHT can be beneficial for freezing Holstein bull spermatozoa in egg yolk-citrate diluent, when inseminated immediately after thawing.

Interrelationship between plasma membrane integrity, mitochondrial membrane potential and DNA fragmentation in cryopreserved bovine spermatozoa

The objective of this flow cytometric study was to examine plasma membrane integrity, mitochondrial membrane potential (MMP) and the degree of DNA fragmentation of cryopreserved bovine sperm immediately (0 h) and 3 h after thawing and to compare the results with each other and with the fertility of bulls. Cryopreserved spermatozoa from 4 consecutive ejaculates of 20 bulls were examined. Percentages of plasma membrane intact sperm (PMI) and sperm showing a high MMP (HMMP), respectively, were determined by the SYBR14/PI- and the JC-1 assays. DNA fragmentation was analysed by the standard deviation of the DNA fragmentation index (SD-DFI) and the percentage of sperm with a high degree of DNA fragmentation (%DFI) by using SCSA(TM). The mean non-return rate on day 56 (NRR 56) ranged from 63.7% to 78.0% (mean +/- SD: 71.8% +/- 3.7%). Mean values for PMI and HMMP decreased from 37.4% +/- 6.8% to 31.2% +/- 6.1% and from 38.8% +/- 7.1% to 23.8% +/- 7.7% respectively. SD-DFI increased from 56.9% +/- 8.0% to 69.0% +/- 12.9% and %DFI from 6.4% +/- 2.5% to 12.4% +/- 5.8%. The correlation between PMI 0 h and HMMP 0 h (r = 0.95; p < 0.0001) was higher (p < 0.05) than that between PMI 3 h and HMMP 3 h (r = 0.88; p < 0.0001). %DFI 0 h was neither related to PMI 0 h nor to HMMP 0 h (p > 0.05), nor was there a correlation (p > 0.05) between DFI 3 h and PMI 3 h; but %DFI 3 h and HMMP 3 h were significantly correlated (r = -0.31; p < 0.05). SD-DFI and %DFI 3 h were the only parameters related to NRR 56 (r = -0.58; p < 0.05). In conclusion, plasma membranes and mitochondria are similarly affected by the freezing and thawing process, but not during the incubation period after thawing.

Pellet-freezing of Damascus goat semen in a chemically defined extender

During the breeding season of goats (12 bucks and 64 does) in Egypt, five experiments were conducted using a chemically defined cryoextender (CDE) to investigate: (1) the influence of rates of semen dilution (1:2, 1:4 and 1:19) and methods of thawing of frozen semen pellets (dry thawing versus wet thawing) on sperm progressive motility (SPM), sperm acrosome abnormalities (SAA) and rate of lipid peroxidation in semen as measured by malonaldehyde (MAL) production, and (2) the effect of insemination of does in natural (n = 38) and cloprostenol-synchronized (n = 26) estrus with frozen semen on their kidding rates and prolificacy. Semen (two successive ejaculates/buck) was collected twice a week via an AV and only ejaculates of >2500 x 10(6) sperm/ml and 70% SPM were diluted in one step at 30 degrees C with the CDE, cooled to 5 degrees C over a 4h-period, frozen in the form of 0.30 ml pellets and stored in liquid nitrogen for 72 h. The results revealed that post-thaw SPM of semen diluted at a rate of 1:4 was significantly (P < 0.01) higher than that of semen diluted at the other rates. Dilution of semen at a rate of 1:19 (< or =151 x 10(6) sperm/ml) not only minimized (P < 0.01) pre-freeze and post-thaw SPM, but also augmented (P < 0.01) pre-freeze and post-thaw rates of lipid peroxidation as evidenced by the high level of MAL production and the ability of antioxidants (1mg/ml EDTA, 200 U/ml bovine liver catalase, 0.61 mg/ml reduced glutathione and 0.11 mg/ml sodium pyruvate) to restore (P < 0.01) pre-freeze and post-thaw SPM. Frozen semen pellets exposed to dry thawing had a greater percentage of SPM (P < 0.01) as well as lower values of SAA and MAL (P < 0.01) than those exposed to wet thawing. Although the kidding rates did not vary significantly among does in natural (55.26%) and synchronized (53.85%) estrus, a higher (P < 0.05) prolificacy was obtained after their insemination in natural (1.81+/-0.16) rather than in synchronized (1.22+/-0.11) estrus.

Effect of antioxidants on preservation of motility,viability and acrosomal integrity of equine spermatozoa during storage at 5 degrees C

Preservation of liquid semen at 5 degrees C is an important technique in the breeding management of horses. Oxidative damage to spermatozoa during storage is a potential cause of the decline in motility and fertility during hypothermic storage of liquid semen. The objective of this study was to evaluate the use of water-soluble and lipid-soluble antioxidants to improve the maintenance of motility of equine spermatozoa at 5 degrees C during storage for 72 to 96 h. In Experiment 1, the effect of addition of catalase on the maintenance of motility, viability and acrosomal integrity was determined. Semen was collected, and these treatments were applied: catalase (0, 100 or 200 U/mL) in nonfat, dried skim milk extender (NFDSM; with or without seminal plasma) or 10% seminal plasma + NFDSM. Motility was determined by computerized semen analysis (CASA) at 0, 24, 48 and 72 h. Viability and acrosomal integrity were determined at 72 h of storage. There was no significant treatment effect on the maintenance of sperm motility during 72 h storage. In Experiment 2, the effect of adding lipid-soluble antioxidants on maintenance of motility was evaluated. Semen was diluted to a final concentration of 25 x 10(6) sperm/mL in NFDSM containing butylated hydroxytoluene (BHT; 2.0, 1.0, or 0.5 mM), Vitamin E (4.0, 2.0, 1.0 mM), or Tempo (2.0, 1.0, or 0.5 mM). Although the addition of BHT significantly reduced (P < 0.05) progressive motility during storage compared to the control, there were no positive treatment effects of either Vitamin E or Tempo on maintenance of motility. In Experiment 3, the effect of adding water-soluble antioxidants on maintenance of motility was evaluated. Semen was diluted in NFDSM containing these treatments: Trolox (2.0 mM), Tempo (1.0 mM), Vitamin C (0.45 mg/mL), BSA (3% w/v), combinations of these antioxidants, or control. Adding these water-soluble antioxidants did not significantly improve the maintenance of motility during cooled storage at 5 degrees C. In conclusion, adding the enzyme scavenger, catalase, or a variety of lipid- and water-soluble antioxidants did not significantly improve the maintenance of motility during liquid semen storage at 5 degrees C.

Protection of boar spermatozoa from cold shock damage by 2-hydroxypropyl-beta-cyclodextrin

This study examined whether 2-hydroxypropyl-beta-cyclodextrin (HBCD) could play a role in protecting spermatozoa from cold shock, as judged by motility parameters, intact acrosomes, and membrane integrity. Motility parameters were assessed by a computer-assisted sperm motility analysis (CASA) system, and the acrosome and membrane integrity were evaluated by fluorescent staining with FlTC-labeled peanut agglutinin and SYBR-14 plus Propidium Iodide, respectively. The addition of HBCD to the BF5 extender significantly increased the percentages of spermatozoa with intact acrosomes and increased membrane integrity after cold shock. The motility, progressive motility, and progressive velocity of the cold-shocked spermatozoa in the presence of HBCD were significantly higher than in the absence of HBCD. In contrast, further supplement of HBCD with cholesterol-3-sulfate (a cholesterol analogue) resulted in a decrease in all the aforementioned criteria, suggesting that the ability of HBCD to protect spermatozoa from cold shock injury is blocked by saturating the cholesterol binding sites of HBCD. It is therefore concluded that HBCD protects spermatozoa against cold shock injury, possibly due to its ability to remove membrane cholesterol.

Basic aspects of frozen storage of semen

Basic concepts of cryopreservation and the causes of cryoinjury are reviewed. The possible roles of cryoprotectants and additives are considered in the context of their putative interactions with the sperm plasma membrane. Modern approaches to the laboratory assessment of spermatozoa after freeze-thawing are also briefly discussed.

Electron paramagnetic resonance spectroscopy for the investigation of the fluidity of human spermatozoa plasma membranes: a feasibility study

Spermatozoal membrane perturbations may play a role in abnormal sperm functions. The objective of this investigation was to study the feasibility of measuring membrane fluidity of isolated human sperm by electron paramagnetic resonance (EPR) spectroscopy and to compare the order parameter of spectra obtained from the sperm plasma membranes of living sperm of fertile men with that of infertile men. Ejaculates of infertile and fertile men were washed and the spermatozoa labelled with 5-doxylstearic acid (5-DSA) and 16-doxylstearic-acid (16-DSA) (10 nmol per 4 x 10(7) sperm). The reporter group of 5-DSA partitions into the outer, hydrophilic part of the sperm plasma membrane, whereas that of 16-DSA is distributed in the inner hydrophobic part. The following results were obtained: (i) the lowest measurable cell count was 3.6 to 7 x 10(6) sperm and the interassay variance of the order-parameter s was < 1%; (ii) swim-up experiments revealed a higher fluidity of sperm with a higher percentage of motility; (iii) sperm membranes of infertile patients exhibited a decreased fluidity of their plasma membranes in the polar interface region of 5-DSA compared with volunteer semen donors and fertile men (P=0.002). No difference of membrane fluidity was found between the different groups using 16-DSA. It is concluded that EPR spectroscopy can be used to study the fluidity of sperm plasma membranes in fertile and infertile men.

Viability, susceptibility to peroxidation and fatty acid composition of boar semen during liquid storage

The changes in viability, susceptibility to peroxidation and fatty acid composition of total phospholipid were studied in boar spermatozoa during 5 day liquid storage in a standard or alpha-tocopherol (alphaT) enriched diluent. The sperm rich fraction of the ejaculates was collected from 6-month old boars. Sperm viability progressively decreased during storage and alphaT inclusion into the diluent significantly inhibited this trend. alphaT inclusion also decreased significantly peroxidation (TBARS production of spermatozoa). Spermatozoa stored in the treatment diluent became rapidly enriched in alphaT with a concomitant decrease of alphaT content in the medium. The proportion of polyunsaturates, mainly 22:6n-3, decreased with a complementary increase in the content of the saturates, mainly 18:0. The inclusion of alphaT into the diluent was effective in totally preventing the significant decrease of 22:6n-3 observed in sperm phospholipid in the control samples during the storage period. It is concluded that the alphaT inclusion in the boar semen diluent increased cell viability through its prevention of an oxidative reduction in the levels of the major polyunsaturated fatty acids, namely 22:6n-3.

Human spermatozoa glycerol permeability and activation energy determined by electron paramagnetic resonance

The permeability of human spermatozoa to glycerol and its activation energy were determined using electron paramagnetic resonance (EPR) techniques. EPR was used to monitor the aqueous cell volume change vs. time during the glycerol permeation process using the aqueous spin label 15N-tempone and the membrane impermeable broadening agent potassium trioxalatochromiate (chromium oxalate). The permeation process was completed in tens of seconds, requiring the use of a stopped-flow methodology. The glycerol permeability coefficient (Pg) was determined by fitting a simple theoretical model to the experimental data. The permeabilities of human spermatozoa in 1 molar and 2 molar glycerol at 20 degrees C are (10.3 +/- 0.3).10(-4) cm/min (mean +/- S.D.) and (6.0 +/- 1.4).10(-4) cm/min, respectively. The permeabilities of human spermatozoa in 2 molar glycerol at 30, 20, 10, and 0 degrees C are (8.3 +/- 1.3).10(-4) cm/min, (6.0 +/- 1.4).10(-4) cm/min, (2.1 +/- 0.4).10(-4) cm/min, and (1.1 +/- 0.3).10(-4) cm/min, respectively. The activation energy (Ea) for glycerol permeation between 30 degrees C and 0 degrees C was found to be 11.6 kcal/mol.

Categorical data analysis of the effect on bull fertility of butylated hydroxytoluene addition to semen extenders prior to freezing

Butylated hydroxytoluene is an antioxidant that has antiviral properties and sustains sperm viability during freezing and thawing. A field trial involving 11 bulls and 19,000 AI was conducted to determine whether addition of .5 mM butylated hydroxytoluene to whole milk extender during seminal processing affected bull fertility as estimated by nonreturn rates generated by cows bred to the bulls. Effects of bull, batch of semen nested within bull, treatment, and month of AI were studied. Nonreturn rates were recorded for each month for every bull, batch of semen (ejaculates pooled on a given day), and treatment combination. Because some bulls had < 6 batches of semen, the original experimental design was reduced to two smaller designs. Categorical data analysis with maximum likelihood estimation was used for analysis of nonreturn rates. The results from three models were used to interpret the data. The nonreturn rates were approximately 73.9% for the butylated hydroxytoluene treatment and 74.1% for the control. In all models, bull effect was significant, but batch, month of AI, and treatment had no effect on bull fertility. Addition of .5 mM butylated hydroxytoluene to whole milk extender during semen processing did not affect bull nonreturn rates.

Effects of cryopreservation procedures on sperm membranes

Empirical approaches to semen cryopreservation have resulted in the production of young in a broad range of species. However, acceptable levels of fertility in most domestic animal species has not been achieved. In this review, an attempt has been made to describe the complexity of the sperm plasma membrane and the many steps in a cryopreservation procedure where membrane perturbations can occur. Improvement in sperm cryopreservation procedures will require a careful consideration of the complexity of the sperm plasma membrane, the interaction of its components and the influence of cooling, freezing and thawing on these interactions.

Protective action of aromatic compounds against cold-shock injuries in boar spermatozoa

Butylated hydroxytoluene has been known to protect spermatozoa from cold shock injury. To determine whether such protective action is a common property of aromatic compounds, the effect of 14 hydrophobic and 2 hydrophilic aromatic compounds on the protection of boar spermatozoa from cold shock was investigated. The majority of the hydrophobic compounds tested provided protection; the hydrophilic compounds were ineffective. Of the aromatic compounds tested, naphthalene was most effective in reducing the effect of cold shock on motility and acrosomal integrity of boar spermatozoa.

Differential effects of butylated hydroxytoluene analogs on bull sperm subjected to cold-induced membrane stress

Previous reports established that butylated hydroxy toluene (BHT) minimized cold-induced membrane rupture in sperm from several species. No data regarding the specificity of its effect is available. In this study 25 BHT analogs were tested for their effect on bovine sperm membrane stability. Fourteen were membrane lytic at 25 degrees C and 6 were neither membrane lytic nor membrane stabilizing. The remaining 5 compounds, a family of 2,6-tert-butyl phenols with substitutions at position 4 of hydrogen, methyl (BHT), ethyl, butyl, hexyl, or octyl, afforded effective membrane protection to cold shock. Since membrane protection is a function of both the ability of a compound to partition into the membrane and a molecule's effectiveness once there, an analysis of each analog's membrane partitioning, assessed by measuring the cellular analog/cholesterol ratio, showed the following extents of transfer for the analogs: ethyl = butyl greater than methyl = hydrogen greater than hexyl greater than octyl. Thus, an optimum chain length exists for partitioning from micellar donors into cells. A separate experiment established that all analogs, when incorporated in equivalent amounts, protect equally plasma and mitochondrial membranes from cold shock. No effect on acrosomal membrane stability was noted. BHT, but not the other analogs, reduced sperm motility. Addition of egg yolk to extender containing BHT analog protected sperm motility from cold shock but had little effect on membrane stabilization. Analysis of sperm membrane compartments revealed that little to no analog was partitioned into the outer acrosomal membrane or the plasma membrane overlying the acrosome, but rather was localized in other portions of the sperm. We conclude that (a) the effective BHT analogs, if partitioned into the membrane, are indistinguishable with regard to their capacity to eliminate cold-induced membrane lysis; (b) membrane-linked events (e.g., motility) are uniquely disrupted by a subset of this analog family; and (c) when concentrations of egg yolk and BHT analogs are carefully controlled, unique synergistic effects are noted.

Evaluation of butylated hydroxytoluene as a cryopreservative added to whole or skim milk diluent for bull semen

Effect of five concentrations of butylated hydroxytoluene on the percent motility and percent intact acrosomes was evaluated for bull sperm frozen and thawed in whole and skim milk diluents. Twelve ejaculates were frozen in .5-ml straws in moving nitrogen vapor after each ejaculate was split among the five butylated hydroxytoluene treatments within the two diluents. Prefreeze and postthaw percent motility and postthaw percent intact acrosomes were evaluated at 0 and 4 h. Before freezing, sperm motilities were similar in whole or skim milk diluents with and without butylated hydroxytoluene. Upon thawing, sperm motility was 10 percentage points higher in whole milk diluent containing .5 and .75 mM butylated hydroxytoluene than in samples without it. After 4 h, percentage motile sperm was similar among all whole milk treatments. Sperm motility was similar among all skim milk treatments at both 0 and 4 h. Percent intact acrosomes were similar among all treatments for each diluent. Oxidation in whole milk diluent stored at 4 degrees C for 1 wk was reduced in the presence of 1.0, 2.0, and 4.0 mM butylated hydroxytoluene.

Motility, heat, and lactate production in ejaculated bovine sperm

Effects of various inhibitors on motility, heat, and lactate production of ejaculated bovine sperm were determined in the presence of antimycin A and rotenone. erythro-9-[3-(2-Hydroxynonyl)]adenine (EHNA) and polyvinylpyrrolidone (PVP-360) stopped motility and reduced heat or lactate production by 30-50%. Carbodiimides resulted in loss of motility and a reduction of metabolism by 60-75%. Quercetin treatment, which enhanced rather than inhibited motility, depressed heat and lactate production by 50-60%. Since mechanical immobilization reduced heat production by only 30%, the question arises as to what other cellular processes are major contributors to the energy budget. Inhibitors of ion flux had little-to-no effect on heat or lactate production, suggesting that neither mitochondrial nor Na+/K+ ATPases were major ATP-requiring processes. Calcium flux at the plasma membrane also was minimal and previous reports eliminated glycolytic substrate cycling as major consuming processes for ATP. Although quercetin inhibited lactate production in intact cells, no effect of quercetin on cell-free glycolysis and the ATPase activities of isolated dynein was detected. Quercetin did, however, inhibit ATPase activity of plasma membrane, suggesting that this unidentified ATPase may contribute to the formation of ADP and Pi required for lactate production by the intact cell. We propose (a) that the bioenergetic costs of motility are divided between regulatory events and dynein-microtubule interaction (dynein ATPase), (b) that some of the membrane-related processes may be "inefficient," and (c) that quercetin may render these steps more "efficient," in a manner analogous to its action on the Na+/K+ pump of Ehrlich ascites tumor cells.

Isolation and characterization of the plasma membrane of rat cauda epididymal spermatozoa

Cauda epididymal rat spermatozoa were isolated by flushing the excised epididymis and the plasma membrane was detached by a nitrogen cavitation treatment (500 psi, 10 minutes equilibration at 4 C). Membrane vesicles were recovered after sucrose gradient centrifugation. Portions of the sperm surface releasing the plasma membrane were assessed by light microscopy of fluoroscein isothiocyanate-succinylated concanavalin A-treated spermatozoa and by transmission electron microscopy. Plasma membrane was detached from the region overlying the acrosome from most spermatozoa and from the middle-piece overlying the mitochondria from some cells. Thus, the fraction analyzed was derived from at least two portions of the sperm surface. The fractions from the sucrose density gradient were analyzed for gross chemical composition (phospholipid, protein and sterol) and the protein components were detected after electrophoresis under denaturing conditions; the peak fractions (at density approximately 1.13 g/ml) were judged homogeneous. Replicate analyses of such preparations established mass ratios of protein to phospholipid of 0.63, total sterol to phospholipid of 0.18, and demosterol to cholesterol of 0.32. The molecular composition of the phospholipid fraction was determined to be 10% phosphatidylserine (mole percent), 3% phosphatidylinosital, 3% sphingomyelin, 31% phosphatidylethanolamine, 27% phosphatidylcholine, 10% diphosphatidylglycerol and 5% of an unknown component. Fatty acyl analyses of the phospholipid fraction revealed that approximately 70% of the residues consisted of palmitoyl (16:0) and stearoyl (18:0) acyl groups, with the balance distributed among various unsaturated acyl groups (18:1, 22:3, 22:4 and 22:5); about 40% of the recovered phospholipids represented ether acyl phosphatides. Differences in the lipid composition of rat vesicles described here and similar vesicles isolated from ram and boar spermatozoa (described previously) are discussed. The partitioning of the nitroxyl spin label 3-doxylheptane into vesicles isolated from rat and ram spermatozoa was assessed by electron paramagnetic resonance spectroscopy at temperatures between 4 C and 26 C; no difference in the response of the spin label in the two vesicle preparations was detected.

The role of membrane-active lipids in the protection of ram spermatozoa during cooling and storage

The interactions of ram spermatozoa with exogenous liposomes of varying composition were studied, with the aim of examining the mechanisms by which some lipids protect against cold-induced damage during cryostorage. Liposomes containing various preparations of phosphatidylcholine and cholesterol enhanced sperm survival during storage at 5 degrees C, both in terms of motility and acrosomal integrity. A membrane-fluidizing agent, A2C, was slightly deleterious in this respect. Cholesterol-containing liposomes were not superior in their effects to those prepared without cholesterol. Thus stabilization of the plasma membrane by cholesterol loading may be unimportant. When sodium vanadate was used as a functional probe of membrane integrity, the cryoprotective effects of lipids were apparent despite increased plasma membrane permeability. Incubation of spermatozoa with positively charged liposomes, containing stearylamine, caused considerable loss of motility and acrosomal damage, coupled with cellular aggregation. There was also some evidence that the presence of calcium lessened the effectiveness of liposomes in protecting spermatozoa against damage during cooling.

Cytotoxicity of commonly used nitroxide radical spin probes

Since nitroxide radical spin probes are used frequently to test biophysical properties of cells, their use should be restricted to conditions that do not perturb normal cell growth and viability. Eight commonly used nitroxide radical spin probes have been tested for their effects on the survival of CHO cells. These include water-soluble spin probes Tempol, Tempamine, CTPO, CTPC and 4-maleimido-Tempo, and lipid soluble spin probes 5-Doxyl-, 12-Doxyl-, and 16-Doxylstearates. With the exception of 4-maleimido-Tempo, none of the water soluble spin labels inhibited cell survival at concentrations as high as 1 mM. At concentrations of 75 microM and higher, 4-maleimido-Tempo inhibited cell survival in a dose dependent manner. At concentrations commonly used for spin labeling of cells (30-50 microM) none of the lipid soluble spin probes tested was cytotoxic. At 100 microM only 5-Doxylstearate inhibited cell survival, whereas 12-Doxylstearate and 16-Doxylstearate had no effect.

Effect of phenolic antioxidants on microbial growth

Antioxidants belong to a class of compounds used to retard oxidation of chemicals in foods. These compounds, such as BHA, BHT, TBHQ, PG, etc. are approved to be used in foods by government agencies. In the past 10 years considerable interest has been directed to the antimicrobial properties of these compounds due to the observations by various scientists that many of these compounds can suppress the growth of viruses, protozoa, bacteria, yeast, and molds and their subsequent production of toxic materials in foods. Thus, the dual purpose usage of these compounds (i.e., antioxidation and antimicrobial) has been the subject of many research papers. This review is designed to summarize major publications on this subject as well as present some detailed studies on the effect of major antioxidants on bacteria and mold generated in the laboratory of the author in recent years.

Proton involvement with the light-induced hindrance of spin label motion in the lumen of spinach thylakoids

The light-induced hindrance of spin label motion increases linearly with light intensity. However, it has not been possible to unambiguously demonstrate light saturation due to the very high rates of spin label reduction at high light intensity. The light-induced hindrance of spin label motion may be mimicked in the dark by subjecting thylakoids to appropriately low pH regimes. Uncouplers such as gramicidin-D and methylamine reduce the light-induced hindrance to dark levels as does ethylenedinitrilotetraacetate (EDTA) treatment. Valinomycin plus KCl which destroys the electric potential is only partially effective in reducing the light-induced hindrance. These results indicate that protons in the aqueous lumen of the thylakoids are closely involved with the observed light-induced hindrance of spin label motion.

Water permeability of mammalian cells as a function of temperature in the presence of dimethylsulfoxide: correlation with the state of the membrane lipids

The water permeability of V-79 Chinese hamster lung fibroblasts was determined by measuring the rate of cell shrinkage in hypertonic medium using a cell sizer. The water permeability appears to follow Arrhenius kinetics as a function of temperature with a sharp discontinuity at 21 degrees C. An activation energy of 7.0 +/- 1.6 kcal/mole was found below 21 degrees C and 22.8 +/- 3.1 kcal/mole above 21 degrees C. The correlation time of rotation of the spin label 2,2-dimethyl-5-dodecyl-5-methyloxazolidine-N-oxide was measured as a function of temperature in the cellular membranes, and shows a break at 20 degrees C. A discontinuity was also found in the membrane to water partitioning of the spin label 2,2-dimethyl-5-pentyl-5-butyloxazolidine-N-oxide near 20 degrees C. These breaks may correspond to a membrane lipid phase transition. Dimethylsulfoxide, in the concentration range of 0.2--0.5 M, decreases the water permeability by a factor of two.

Inactivation of the enveloped bacteriophage phi6 by butylated hydroxytoluene and butylated hydroxyanisole

Butylated hydroxytoluene (BHT) is a potent inactivator of the enveloped bacterial virus ø6 at concentrations as low as 3 x 10(-5) M. The viral envelope is not removed by BHT treatment, in contrast to the effects of exposure to the detergent Triton X-100. BHT-treated viruses are morphologically indistinguishable from controls but are defective in their ability to attach to the host cell. Temperature at the time of exposure was found to be a crucial factor in the effectiveness of BHT against ø6. A precipitous drop in the degree of inactivation by 3 x 10(-5) M BHT occurred when the temperature was lowered from 20 to 15 C. Calcium ions were found to potentiate the effect of BHT, particularly at lower temperatures where BHT alone was relatively ineffective. Barium and strontium, but not magnesium, were also effective in enhancing the activity of BHT. A structurally related molecule, butylated hydroxyanisole (BHA), was also found to inactivate ø6 virus, but higher concentrations were required than with BHT. Both BHT and BHA are commonly used as food additives, have apparent low toxicity to humans and other animals, and are potentially useful as antiviral agents.