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D S Irvine

Publications and source records attributed to D S Irvine.

At least 37 records · Page 2Linked to original sources
PubMed1998

Relative impact of oxidative stress on the functional competence and genomic integrity of human spermatozoa.

Reactive oxygen metabolites are known to disrupt sperm-oocyte fusion, sperm movement, and DNA integrity; however, the relative sensitivities of these elements to oxidative stress are unknown. In this study these factors were assessed in human spermatozoa exposed to increasing levels of oxidative stress achieved through the stimulation of endogenous oxidant generation with NADPH or direct exposure to hydrogen peroxide. At low levels of oxidative stress, DNA fragmentation was significantly reduced while the rates of sperm-oocyte fusion were significantly enhanced. As the level of oxidative stress increased, the spermatozoa exhibited significantly elevated levels of DNA damage (p < 0.001) and yet continued to express an enhanced capacity for sperm-oocyte fusion. At the highest levels of oxidative stress, extremely high rates of DNA fragmentation were observed but the spermatozoa exhibited a parallel loss in their capacities for movement and oocyte fusion. These studies emphasize how redox mechanisms can either enhance or disrupt the functional and genomic integrity of human spermatozoa depending on the intensity of the oxidative stimulus. Because these qualities are affected at different rates, spermatozoa exhibiting significant DNA damage are still capable of fertilizing the oocyte. These results may have long-term implications for the safety of assisted conception procedures in cases associated with oxidative stress.

DNA↗
PubMed1998

A novel signal transduction cascade in capacitating human spermatozoa characterised by a redox-regulated, cAMP-mediated induction of tyrosine phosphorylation.

Capacitation is a priming event that renders mammalian spermatozoa responsive to signals originating from the cumulus-oocyte complex. The attainment of a capacitated state is dependent upon an increase in tyrosine phosphorylation and results in the acquisition of responsiveness to physiological agonists such as progesterone and ZP3. In this study we have shown that this capacitation-dependent increase in tyrosine phosphorylation is controlled by a unique redox-regulated, cAMP-mediated, signal transduction cascade. Either stimulation of reactive oxygen species generation or elevation of intracellular cAMP induced increases in phosphotyrosine expression by human spermatozoa and enhanced their responsiveness to progesterone. Ultimate convergence of the redox- and cAMP-regulated pathways was indicated by the ability of the protein kinase A inhibitor, H89, to block both modes of signal transduction. Furthermore, the fact that the redox-regulated pathway could be silenced by catalase, while this enzyme had no effect on the cAMP-mediated response, indicated that oxidant generation must lie upstream from cAMP in the reaction sequence. In keeping with this conclusion, a functional association was demonstrated between the redox status of human spermatozoa and their cAMP content. The continuous production of reactive oxygen species was also shown to be necessary for the protein kinase A-tyrosine phosphorylation axis to remain functional. If the generation of oxidising conditions during capacitation was prevented with 2-mercaptoethanol, 2-deoxyglucose or the flavoprotein inhibitor, diphenylene iodonium, then cAMP could no longer trigger tyrosine phosphorylation. These data support a model for human sperm capacitation as a redox-regulated process, involving a unique sequence of interactive events including reactive oxygen species production, elevation of intracellular cAMP, stimulation of protein kinase A and the induction of tyrosine phosphorylation. This is the first report of such a signal transduction cascade and may have implications for the functional significance of reactive oxygen metabolites in other cell types.

Catalase↗
PubMed1997

Field trial of a diluent for the transportation of human semen at ambient temperatures.

OBJECTIVE: To examine the ability of a citrate-yolk buffer extender to preserve human semen samples at ambient temperatures over a 25- to 30-hour period. DESIGN: Human semen samples were diluted 1:1 with citrate-yolk buffer or homologous seminal plasma and transported at ambient temperature between two distant locations (London to Edinburgh, United Kingdom). Various criteria of semen quality then were assessed before and after 25 to 30 hours storage and transportation in these diluents. SETTING: An institutional research laboratory and a private fertility clinic. PATIENT(S): Samples were provided by 21 donors of unknown fertility and 7 asthenozoospermic patients. INTERVENTION(S): The diluent used to preserve human semen comprised an egg yolk buffer supplemented with fructose and citrate. MAIN OUTCOME MEASURE(S): Aspects of semen quality assessed included movement, hyaluronate penetration, viability, acrosome reaction, and reactive oxygen species generation. RESULT(S): The deterioration of semen quality at ambient temperatures could be prevented by the presence of citrate-yolk buffer, permitting the accurate analysis of oxidative stress and human sperm function, 25 to 30 hours postejaculation. CONCLUSION(S): Citrate-yolk buffer offers considerable promise as a medium for the ambient temperature storage and transportation of human semen.

Acrosome↗
PubMed1997

Declining sperm quality: a review of facts and hypotheses.

A substantial body of evidence has accumulated in recent years suggesting that human semen quality may be deteriorating. This has been associated with evidence of other changes in male reproductive health, including increases in congenital malformations and testis cancer in men, and associated problems in wildlife. Unfortunately the evidence remains inconclusive. It has been suggested that these changes may be due to environmental xenoestrogens acting during development. Although there is now a large quantity of data indicating that this is a plausible hypothesis, evidence of causality, rather than association, remains to be provided. The potential importance of these changes for human health is considerable, and urgent research is required to clarify the situation.

Data Collection↗
PubMed1997

Semen analysis performed by different laboratory teams: an intervariation study.

Some recent studies have indicated that sperm concentration has decreased during the last 50 years. However, comparisons between laboratories have revealed that geographical differences seem to exist and that any decrease may not be global. One point of criticism concerning comparison of results from different laboratories has been that some of the discrepancies detected could reflect the lack of standardized methods used in the different laboratories. Four teams, each consisting of one physician and one technician from groups which have recently published data on semen quality, met in order to evaluate the variability between their laboratories on semen analysis. Twenty-six fresh semen samples from unselected men were analysed. The groups analysed the samples according to the normal practice in their laboratories, using their own equipment. The variation between laboratories was estimated through a random effects model. For sperm concentration and semen volume assessment a remarkable consistency between laboratories was detected, in contrast to the very considerable inter-individual variation. For sperm motility and morphology assessments interlaboratory consistency was much poorer. In conclusion, evaluation of sperm motility and morphology characteristics requires further standardization in order to achieve comparable data from different laboratories. However, semen volume and sperm concentration are characteristics which can be compared reliably between laboratories, when similar methodologies are used.

Adolescent↗
PubMed1997

Laboratory techniques for semen analysis: a Scottish survey.

OBJECTIVE: To survey the techniques used by Scottish laboratories to undertake semen analysis in the context of the investigation of infertility. DESIGN: A telephone survey. SETTING/SUBJECTS: Laboratories in Scotland performing semen analysis. RESULTS: Thirty-one laboratories reported performing semen analysis for infertility. There was a lack of consistency in the instructions given to patients in several areas, including the period of abstinence prior to producing the specimen and the delivery of the specimen to the laboratory within an appropriate time after ejaculation. Only 19% of laboratories reported using a positive displacement pipette in the dilution of semen and only 26% used phase contrast microscopy for routine semen analysis. The minimum normal values quoted by laboratories for sperm concentration ranged from 20 x 10(6)/ml to greater than 50 x 10(6)/ml. The normal values quoted for sperm morphology ranged from at least 30% normal forms to at least 88% normal forms. Only 13% of laboratories participated in any form of internal or external quality control for semen analysis. CONCLUSIONS: Semen analysis is fundamental to the clinical work up of the infertile couple but, unlike most other laboratory investigations, it is not a standardised test in Scotland. Factors which are known to influence the results such as the advice given to patients about collecting specimens and the methods and equipment used by technicians vary widely. There is not even a consensus on the normal values quoted. This has implications for clinical decisions based on semen analysis and for future accreditation of laboratories.

Clinical Laboratory Techniques↗
PubMed1996

The extragenomic action of progesterone on human spermatozoa is influenced by redox regulated changes in tyrosine phosphorylation during capacitation.

Capacitation had no effect on the ability of progesterone to elicit a rapid calcium transient in the acrosomal domain of human spermatozoa but had a marked influence of the ability of this steroid to induce a biological response. The development of this responsiveness to progesterone appeared to be redox regulated in that it was promoted by the stimulation of reactive oxygen species generation and inhibited by the presence of antioxidants, including catalase and membrane permeant thiols. The ability of redox conditions to influence the biological responsiveness of human spermatozoa did not involve changes in the dynamics of the calcium transients induced by progesterone but was causally linked with clear differences in tyrosine phosphorylation. We conclude that the ability of human spermatozoa to respond to the calcium transients induced by progesterone depends on a background of phosphotyrosine expression that can be profoundly influenced by the redox status of the spermatozoa during capacitation.

Humans↗
PubMed1996

Superoxide dismutase in human sperm suspensions: relationship with cellular composition, oxidative stress, and sperm function.

Sensitive techniques have been developed for monitoring superoxide dismutase (SOD) activities in human sperm preparations. In contradiction to the protective role normally assigned to SOD, populations of defective spermatozoa recovered from the low density region of Percoll gradients were found to have three times more SOD than functionally competent preparations pelleting in high density Percoll. SOD activity was negatively correlated with the movement characteristics of human spermatozoa and their capacity for oocyte fusion, and positively associated with the induction of peroxidative damage. SOD activity was also highly correlated with other markers of the cytoplasmic space, creatine kinase (CK), and glucose-6-phosphate dehydrogenase (G-6-PDH). We conclude that while SOD may play a physiological role in maintaining a balance between O2.- and H2O2, high levels of this enzyme are associated with impaired sperm function because (a) the human spermatozoon is highly susceptible to the cytotoxic effects of H2O2, (b) O2.- is an important mediator of normal sperm function, and (c) high SOD activities reflect errors in spermatogenesis associated with germ cell exfoliation and the retention of excess residual cytoplasm by the spermatozoa.

Acrosome↗
PubMed1996

Protective effect of antioxidants on the impairment of sperm motility by activated polymorphonuclear leukocytes.

OBJECTIVE: To test the ability of antioxidants to reduce the loss of sperm motility caused by reactive oxygen species generated by polymorphonuclear leukocytes (PML). DESIGN: Standardized preparations of leukocyte-contaminated semen were created by suspending known concentrations of purified spermatozoa and PML in seminal plasma. After the stimulation of reactive oxygen species generation with phorbol ester, the spermatozoa were washed and incubated in culture medium before an analysis of their movement. The ability of antioxidants to counteract the free radical-induced loss of sperm motility observed under these circumstances was assessed. SETTING: An institutional research laboratory. PARTICIPANTS: The semen was obtained from normal volunteers. INTERVENTIONS: The following were tested: vitamins C and E, dimethylsulfoxide, catalase, hypotaurine, N-acetylcysteine, and reduced glutathione. MAIN OUTCOME MEASURES: Reactive oxygen species generation was monitored by luminol-dependent chemiluminescence. Sperm motility was assessed manually and by computer-aided semen analysis. RESULTS: Consistent impairment of sperm motility and average path velocity was observed in the presence of activated PML. This effect was reduced by the concomitant presence of glutathione, N-acetylcysteine, hypotaurine, and catalase. CONCLUSION: Antioxidants can protect against the damaging effect of leukocyte-derived reactive oxygen species on sperm movement and may be of clinical value in assisted conception procedures.

Antioxidants↗
PubMed1996

Studies on the development of diluents for the transportation and storage of human semen at ambient temperature.

Storage of human semen samples at ambient temperature for 24 h resulted in a significant loss of sperm motility from a mean 45.1 +/- 1.8% to 13.8 +/- 1.1% (n = 148). This motility loss was associated with a significant increase in the osmolality of the seminal plasma and the induction of peroxidative damage to the spermatozoa. Both of these detrimental changes could be prevented by diluting the original semen sample 1:1 with a citrate-egg yolk, buffer (CYB). In the presence of this extender all aspects of semen quality were efficiently preserved for 24 h, including sperm movement, penetration of a cervical mucus substitute, the acrosome reaction and sperm-oocyte fusion. CYB extension also permitted the use of chemiluminescent tests of leukocyte contamination to be performed on semen samples stored for 24 h at ambient temperatures. As a preservation medium, CYB was found to be superior to alternative formulations lacking citrate and storage at ambient temperatures was preferable to 4 degrees C. Significant improvements in motility retention were also observed when CYB was supplemented with pentoxifylline, although this treatment significantly stimulated peroxidative damage in the spermatozoa. However, if the pentoxifylline was combined with antioxidants then this collateral peroxidative damage could be reduced and the performance of CYB significantly enhanced. These results have implications for the design of diluents permitting the long-term storage and transportation of human semen samples at ambient temperatures.

Animals↗
PubMed1996

Prediction of the in-vitro fertilization (IVF) potential of human spermatozoa using sperm function tests: the effect of the delay between testing and IVF.

To examine the diagnostic significance of several criteria of semen quality and to determine whether their prognostic value is eroded by the time interval between assessment and the attempt at in-vitro fertilization (IVF) with embryo transfer, 73 couples undergoing IVF and embryo transfer therapy were studied. The ability of human spermatozoa to achieve fertilization in vitro was examined in relation to the conventional semen profile, sperm morphology, the computer-aided assessment of sperm movement, ionophore-induced acrosome reaction, acridine orange staining, and chemiluminescent signals induced by phorbol ester and N-formyl-methionyl-leucyl-phenylalanine (FMLP). Spermatozoa were examined both in semen and after preparation on Percoll, some weeks prior to IVF. Fertilization rates were noted to be significantly correlated with elements of sperm movement characteristics, sperm morphology, and reactive oxygen species generation. Prediction of fertilization rates in a stepwise multiple regression analysis was obtained using four variables: sperm morphology, FMLP-induced chemi-luminescence and sperm movement characteristics (beat cross frequency and straightness) (r approximately 0.5). When multiple logistic regression analysis was used to predict which samples would achieve fertilization rates above and below a 50% threshold, three variables of predictive value including linearity, average path velocity and FMLP-induced chemiluminescence were selected. Combination of these variables classified the samples achieving good or poor fertilization with an overall accuracy of 83.6%. The time interval between semen assessment and IVF had little effect on the predictive value of these tests. In conclusion, the fertilizing ability of human spermatozoa is related to sperm morphology, attributes of sperm movement and reactive oxygen species production. The time delay between testing and IVF did not appear to affect predictive accuracy.

Acridine Orange↗
PubMed1996

Home ovulation testing in a donor insemination service.

The use of home ovulation testing kits in donor insemination (DI) has been proposed to increase patient and clinic convenience while not compromising fecundity rates. Such a system was introduced into our DI service in December 1994, and we here report an audit of experience over 6 months. Patients were offered home or laboratory luteinizing hormone (LH) testing, and those requesting home testing were asked to store an aliquot of tested urine for subsequent assay in the laboratory allowing retrospective analysis of the accuracy of cycle timing. Insemination using cryopreserved semen was performed on the day home testing predicted ovulation, or on the day an LH surge was detected in the laboratory, and on the following day. Pregnancy rates were significantly reduced in home testers: 3.4% per cycle (174 cycles, 64 women) versus 12.7% (110 cycles, 53 women) over the same time period (P < 0.005, 95% confidence interval 6.5-18.9). Urine samples from 140 cycles from 51 women using home testing were analysed. There were insufficient data in nine to allocate the cycle. Of home tested cycles, 37 (28%) were inseminated on a day other than the first day of the LH surge. In 13 of these insemination was performed after the first day of the LH surge. Incorrect treatment was associated with high baseline LH, but those with 'late' treatment had low basal LH concentrations, similar to those correctly treated. Analysis of individual urine samples showed that the positive predictive value of home testing was 72%. These results suggest that home ovulation testing results in reduced chance of pregnancy, with increased frustration for both patients and clinic staff. This may be particularly so in women with high baseline LH concentrations.

Adult↗
PubMed1996

The extragenomic action of progesterone on human spermatozoa: evidence for a ubiquitous response that is rapidly down-regulated.

Image analysis techniques have been used to demonstrate that progesterone induces a rapid calcium transient in the acrosomal domain of greater than 90% of human spermatozoa (n = 2354). These results are at variance with previous reports, suggesting that progesterone receptors are only expressed on a small subpopulation of these cells, by virtue of their ability to bind fluorescent probes incorporating progesterone 3- (O-carboxymethyl) oxime conjugated to BSA. In the present study, we could confirm that such probes only bound to a small proportion of human spermatozoa (3.01 +/- 0.29%; n = 7557) although 91.79 +/- 1.8% of the same sperm populations exhibited a calcium transient in response to progesterone. These results indicate that the binding of labeled progesterone conjugates to human spermatozoa does not reflect the size of the progesterone responsive population; the response elicited by this steroid is essentially ubiquitous. Progesterone action was shown to involve an influx of extracellular calcium via mechanisms that did not involve voltage sensitive- or second messenger operated-channels, phospholipase C, or G proteins. Despite previous evidence suggesting that progesterone action might involve a GABAA receptor/chloride channel, neither GABA nor the GABA agonist muscimol had any effect on intracellular calcium concentrations in human spermatozoa or influenced their functional competence. The only factor that disrupted the responses of human spermatozoa to progesterone was this steroid itself. Progesterone exposure induced a prolonged period of refractoriness to further stimulation that influenced the capacity of these cells to generate calcium transients, and their ability to exhibit a biological response to changes in intracellular calcium. There are implications in these results for our understanding of the extragenomic action of progesterone on human spermatozoa and the clinical manipulation of this system for the assessment and suppression of human sperm function.

Binding Sites↗
PubMed1996

Glutathione as a treatment for male infertility.

The excessive generation of reactive oxygen species (ROS) by abnormal spermatozoa and by contaminating leukocytes has been identified as one of the few defined aetiologies for male infertility. As a consequence, work has begun on evaluating the role of antioxidants in the management of these patients. Glutathione plays a significant role in the antioxidant defences of the spermatogenic epithelium, the epididymis, and perhaps in ejaculated spermatozoa. The use of antioxidants in vitro appears to be of value in preserving fertilizing capacity, although no clinical data are available. Glutathione administered in vivo to patients who may have infertility secondary to excessive oxidative stress appears to act at the epididymis and during spermatogenesis, to improve the function of ejaculated spermatozoa. However, fertility studies have not yet been conducted. Controlled studies of glutathione and other antioxidants in patients with defined ROS pathology are urgently required.

Antioxidants↗
PubMed1995

Predicting the fertilizing potential of human sperm suspensions in vitro: importance of sperm morphology and leukocyte contamination.

OBJECTIVE: To determine the relationships between sperm function tests and fertilization of human oocytes in vitro. DESIGN: Analysis of infertile patients undergoing IVF therapy. SETTING: Diagnostic Andrology Laboratory and Assisted Conception Service. PATIENTS: Forty-one couples who underwent IVF-ET therapy were studied. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The ability of human spermatozoa to achieve fertilization in vitro was examined in relation to numerous criteria of semen quality, including the conventional semen profile, the computer-aided assessment of sperm movement, ionophore-induced acrosome reaction, acridine orange staining, sperm morphology, and chemiluminescent signals induced by phorbol ester and N-formyl-methionyl-leucyl-phenylalanine (FMLP). RESULTS: Significant correlations were observed between fertilization rates and several attributes of the sperm preparations, including elements of sperm function (acrosome reaction), movement (percentage motile, hyperactivation, the amplitude of lateral sperm head displacement), morphology (normal morphology, midpiece defects, multiple anomalies index), nuclear normality (acridine orange staining), and reactive oxygen species generation (chemiluminescence induced by phorbol ester and FMLP). In a stepwise multiple regression analysis, an accurate prediction of fertilization rates was obtained using a multiple regression equation incorporating six variables of which sperm morphology and FMLP-induced chemiluminescence were the most informative. CONCLUSIONS: A set of criteria have been identified that accurately predict the fertilizing potential of human sperm suspensions in vitro and that place particular emphasis on sperm morphology and the degree of leukocyte contamination.

Acridine Orange↗