Participation in sport and physical activity in head and neck cancer survivors: associations with quality of life.

BACKGROUND: Head and neck cancer (HNC), and its treatment, is associated with significant side-effects which can affect quality of life (QOL). Physical activity (PA) is known to improve a number of QOL measures. We aimed to determine the prevalence of PA pre- and post-treatment of HNC and to determine associations with QOL. METHODS: A questionnaire-based survey of 172 patients pre- and post-treatment for HNC. RESULTS: A total of 62.2% of patients met current UK PA guidelines pre-treatment, reducing to 40.1% following treatment. There was a significant decrease in Metabolic equivalent task minutes/week post-treatment, with 71% of participants reporting less PA after diagnosis (P < 0.001). Swimming and cycling remained the two most practiced sports. There was a positive correlation between the post-treatment PA and QOL (P < 0.001). CONCLUSION: These data suggest that PA may improve QOL following treatment for HNC. We believe that further studies are warranted.

Patient reported outcome measures in septorhinoplasty surgery.

INTRODUCTION: Surgical procedures incorporating a cosmetic element such as septorhinoplasty and otoplasty are currently under threat in the National Health Service (NHS) as they are deemed to be procedures of 'limited clinical benefit' by many primary care providers. Patient reported outcome measures (PROMs), which assess the quality of care delivered from the patients' perspective, are becoming increasingly important in documenting the effectiveness of such procedures. METHODS: The Rhinoplasty Outcomes Evaluation (ROE) questionnaire, a validated PROM tool, was used to assess patient satisfaction in 141 patients undergoing septorhinoplasty surgery over a 90-month period at the University Hospital Southampton NHS Foundation Trust. RESULTS: Overall, 100 patients with a mean follow-up period of 36 months completed the study. The mean ROE score was 73.3%. In addition, 75% of patients questioned were happy with the final result of their operation and 83% would undergo the procedure again if required. These benefits occurred irrespective of age, sex and primary versus revision surgery, and were maintained for up to 71 months following surgery. CONCLUSIONS: This study has shown that patients are generally satisfied with their functional and cosmetic outcomes following septorhinoplasty surgery. These results help support the case for septorhinoplasty surgery to continue being funded as an NHS procedure.

The role of small molecules in sperm capacitation.

Mammalian spermatozoa released into an appropriate environment in vitro can capacitate but then may undergo spontaneous acrosome reactions. Since successful sperm interaction with the zona pellucida of an unfertilized oocyte requires an intact sperm plasma membrane, spontaneous acrosome loss is biologically undesirable because it renders spermatozoa non-fertilizing. Several small molecules (fertilization promoting peptide [FPP], adenosine, calcitonin and adrenaline), found in various body fluids including seminal plasma, have been shown to regulate capacitation in vitro. They initially accelerate capacitation but then inhibit spontaneous acrosome loss, allowing spermatozoa to maintain their fertilizing potential. Specific receptors for all these molecules are present on mammalian spermatozoa and their activation by the appropriate ligands leads to modulation of membrane-associated adenylyl cyclase activity and production of cAMP, stimulating cAMP production in uncapacitated cells and inhibiting it in capacitated cells. Boar spermatozoa have been shown to respond in vitro to adenosine and FPP, suggesting that the addition of these molecules to sperm samples used for artificial insemination could be beneficial in helping spermatozoa maintain fertilizing potential until they reach their target.

Calcitonin acts as a first messenger to regulate adenylyl cyclase/cAMP and mammalian sperm function.

Calcitonin stimulates capacitation in uncapacitated mouse spermatozoa and then inhibits spontaneous acrosome loss in capacitated cells, responses similar to those elicited by fertilization promoting peptide (FPP), a peptide known to regulate the adenylyl cyclase/cAMP pathway. This study investigated the hypothesis that calcitonin also modulates this pathway. Calcitonin significantly stimulated cAMP production in uncapacitated spermatozoa and then inhibited it in capacitated cells; the magnitude of both stimulatory and inhibitory changes was similar to that obtained with FPP but the inhibitory responses to FPP preceded those of calcitonin. This possibly reflects the involvement of two different adenosine receptors in response to FPP compared with one calcitonin receptor. Calcitonin receptors were located on the acrosomal cap and the flagellum, the midpiece having a greater abundance than the principal piece. Although both calcitonin and adenosine receptors are found in the head and flagellum, there was no evidence for cross-talk between them. Chlortetracycline investigations to determine the minimum extracellular Ca(2+) requirement for responses to calcitonin revealed that calcitonin significantly stimulated capacitation in Ca(2+)-deficient medium but FPP did not. Calcitonin also significantly stimulated cAMP production under these conditions, and similarly preincubated suspensions, when diluted into +Ca(2+) medium, were significantly more fertile in vitro than untreated controls. These results indicate that calcitonin, like FPP, acts as a first messenger to regulate the production of cAMP and mammalian sperm function, but the differences in Ca(2+) requirements suggest that calcitonin and FPP may regulate different isoforms of adenylyl cyclase.

17beta-Estradiol and environmental estrogens significantly affect mammalian sperm function.

BACKGROUND: Compounds with estrogenic activity can affect reproductive function in mammals. This study investigated possible effects of 17beta-estradiol (E(2)) and three weakly estrogenic environmental estrogens on mammalian sperm capacitation and fertilizing ability in vitro. METHODS: Uncapacitated and capacitated mouse sperm suspensions were incubated for 30 min in the presence of E(2), genistein (Gen), 8-prenylnaringenin (8-PN) and nonylphenol (NP), and then assessed using chlortetracycline (CTC) fluorescence analysis. In addition, treated uncapacitated sperm suspensions were tested for changes in fertilizing ability. RESULTS: In uncapacitated cells, E(2) at >or=1 micromol/l and Gen, 8-PN and NP at >or=0.001 micromol/l, significantly stimulated capacitation and acrosome reactions. Hydroxytamoxifen (an estrogen antagonist) did not inhibit responses to any of these compounds. In capacitated cells, E(2) had no effect, but the other three compounds significantly stimulated acrosome reactions. Added to uncapacitated suspensions, 10 micromol/l E(2), 0.1 micromol/l Gen and 0.1 micromol/l 8-PN all significantly stimulated sperm fertilizing ability ( approximately 76% oocytes fertilized) compared with untreated control sperm ( approximately 36%). CONCLUSIONS: This study provides the first evidence that E(2) and environmental estrogens can significantly stimulate mammalian sperm capacitation, acrosome reactions and fertilizing ability, with the environmental estrogens being much more potent than E(2). The inability of hydroxytamoxifen to block these responses suggests that classical estrogen receptors may not be involved. Whether these responses have effects on fertility in vivo remains to be determined, along with the mechanisms of action involved.

ESHRE basic semen analysis courses 1995-1999: immediate beneficial effects of standardized training.

BACKGROUND: Many reports have shown problems with the high variability in results of semen analyses. The Special Interest Group in Andrology (SIGA) of the European Society of Human Reproduction and Embryology (ESHRE) implemented a standardized training course which has been run in different regions of the world on more than 20 occasions since 1994. The aim of the present analysis was to investigate to what extent training resulted in any immediate effects on the variability of assessments made by different observers. METHODS: The variability in participants' results from the beginning to the end of each course was analysed in eight courses given between 1995 and 1999. RESULTS: For assessments of sperm concentration, motility, vitality and morphology, substantial improvement was seen over the duration of the course. CONCLUSIONS: A comprehensive, structured training course does lead to substantial reductions in inter-observer variability in semen analysis. This supports our contention that providing a thorough theoretical background and repeated practical training, combined with daily feedback of results, is highly effective in raising the technical skills of laboratory personnel performing semen analysis.

Fertilization promoting peptide--a possible regulator of sperm function in vivo.

Fertilization promoting peptide (FPP), a tripeptide related to thyrotrophin releasing hormone (TRH), is found in seminal plasma. Recent evidence obtained in vitro suggests that FPP may play an important role in regulating sperm fertility in vivo. Specifically, FPP initially stimulates nonfertilizing (uncapacitated) spermatozoa to "switch on" and become fertile more quickly, but then arrests capacitation so that spermatozoa do not undergo spontaneous acrosome loss and therefore do not lose fertilizing potential. These responses are mimicked, and indeed augmented, by adenosine, known to regulate the adenylyl cyclase (AC)/cAMP signal transduction pathway. Both FPP and adenosine have been shown to stimulate cAMP production in uncapacitated cells but inhibit it in capacitated cells, with FPP receptors somehow interacting with adenosine receptors and G proteins to achieve regulation of AC. These events affect the tyrosine phosphorylation state of various proteins, some being important in the initial "switching on," others possibly being involved in the acrosome reaction itself. Calcitonin and angiotensin II, also found in seminal plasma, have similar effects in vitro on uncapacitated spermatozoa and can augment responses to FPP, suggesting that all four molecules may be involved in regulating availability of cAMP. It is plausible that these molecules have similar effects in vivo, affecting fertility by stimulating and then maintaining fertilizing potential. Either reductions in the availability of FPP, adenosine, calcitonin, and angiotensin II or defects in their receptors could contribute to male infertility. These exciting results may provide new approaches for diagnostic tests and treatments of certain categories of male infertility.

Calcitonin, angiotensin II and FPP significantly modulate mouse sperm function.

Fertilization-promoting peptide (FPP) regulates the adenylyl cyclase (AC)/cAMP pathway to elicit capacitation-dependent responses, stimulating capacitation in uncapacitated spermatozoa and then arresting it in capacitated cells, thereby inhibiting spontaneous acrosome reactions. Like FPP, calcitonin and angiotensin II are found in seminal plasma and so might affect sperm function; this study investigated responses in uncapacitated and capacitated mouse spermatozoa to these three peptides. Both calcitonin (5 ng/ml) and angiotensin II (1 and 10nmol/l), like FPP (100nmol/l), significantly stimulated capacitation, assessed using chlortetracycline (CTC) fluorescence and fertilization in vitro analyses. Combinations of two or three peptides, at high and low, non-stimulatory concentrations, were more stimulatory than the individual peptides, suggesting that they may act on the same signalling pathway, plausibly AC/cAMP; preliminary data indicate that calcitonin does stimulate cAMP production. In capacitated cells, FPP and calcitonin elicited pertussis toxin-sensitive inhibition of spontaneous acrosome loss, suggesting involvement of inhibitory G proteins; angiotensin II had no detectable effect. When all three peptides were used, angiotensin II did not interfere with inhibitory responses to FPP/calcitonin. These results suggest that angiotensin II, calcitonin and FPP may somehow modulate the AC/cAMP signal transduction pathway, but the precise mechanisms involved have yet to be elucidated.

Fertilization promoting peptide and adenosine, acting as first messengers, regulate cAMP production and consequent protein tyrosine phosphorylation in a capacitation-dependent manner.

Fertilization promoting peptide (FPP) and adenosine have been shown to act as first messengers, regulating availability of the second messenger cAMP by initially stimulating cAMP production in uncapacitated spermatozoa and then inhibiting it in capacitated cells. This study investigated possible capacitation-related changes in protein tyrosine phosphorylation in response to FPP and adenosine. Time-dependent changes in phosphorylation of proteins of approximately 30-140 kDa were observed in both uncapacitated and capacitated suspensions, the general level of phosphorylation being markedly greater in capacitated cells. In the presence of FPP, phosphorylation was stimulated in uncapacitated but inhibited in capacitated spermatozoa, compared with untreated control samples. Adenosine, cholera toxin, and CGS-21680, a stimulatory A(2a) adenosine receptor agonist, also stimulated phosphorylation in uncapacitated spermatozoa, while Gln-FPP, a competitive inhibitor of FPP, blocked responses to FPP. In capacitated cells, FPP's inhibition of phosphorylation was abolished when cells were treated with FPP in the presence of pertussis toxin. Consistent with the capacitation-dependent effects of FPP and adenosine on cAMP production, these results support the hypothesis that FPP and adenosine modulate sperm function by regulating the AC/cAMP signaling pathway and, consequently, protein tyrosine phosphorylation. Of particular significance is the identification of several phosphoproteins showing FPP-induced alterations in phosphorylation. In uncapacitated spermatozoa, proteins of approximately 116, 95, 82, 75, 66, 56, and 42 kDa showed increased phosphorylation, while in capacitated cells, phosphoproteins of approximately 116, 95, 82, 75, 70, 66, 56, and 50 kDa showed decreased phosphorylation. This suggests that these particular proteins may be involved in stimulation and arrest of capacitation, respectively.

Both fertilization promoting peptide and adenosine stimulate capacitation but inhibit spontaneous acrosome loss in ejaculated boar spermatozoa in vitro.

Both fertilization promoting peptide (FPP) and adenosine stimulate capacitation and inhibit spontaneous acrosome loss in epididymal mouse spermatozoa; these responses involve modulation of the adenylyl cyclase (AC)/cAMP signal transduction pathway. However, it was unclear whether these responses were restricted to the mouse or possibly common to many mammalian species. To address this question, the response of boar spermatozoa to FPP and/or adenosine was evaluated. FPP is found in nanomolar concentrations in seminal plasma of several mammals, but not the pig. When cultured in caffeine-containing Medium 199 for 2 hr, chlortetracycline fluorescence evaluation indicated that neither FPP nor adenosine stimulated boar sperm capacitation per se but did inhibit spontaneous acrosome loss. However, in caffeine-free medium, FPP and adenosine both stimulated capacitation and inhibited spontaneous acrosome loss, suggesting that boar spermatozoa have receptors for both FPP and adenosine. Gln-FPP, a competitive inhibitor of FPP in mouse spermatozoa, has recently been shown to inhibit mouse sperm responses to adenosine as well, suggesting that FPP receptors and adenosine receptors interact in some way. Used with boar spermatozoa, Gln-FPP also significantly inhibited responses to both FPP and adenosine. These responses suggest that mechanisms whereby FPP and adenosine can regulate sperm function, via AC/cAMP, are of considerable physiological significance. Mouse, human, and now boar spermatozoa have been shown to respond to FPP, suggesting that these mechanisms may be common to many mammalian species. We also suggest that the effects of FPP and adenosine could also be exploited to maximize monospermic fertilization in porcine in vitro fertilization.

New insights into possible causes of male infertility.

Male subfertility/infertility is acknowledged to contribute significantly to infertility problems experienced by couples. In some instances, morphological and/or physiological defects known to interfere with normal sperm function can be identified. However, in others, no obvious cause of fertilization failure can be identified. The recent introduction of molecular methods has made it possible to diagnose more subtle defects that could affect the function of spermatozoa produced by some males. For others, though, the problems may result from defects in the physiological mechanisms that need to be activated in spermatozoa so that they 'switch on' functionally following their release from the male reproductive tract. Capacitation, the term applied to this 'switching on', encompasses a number of changes that, collectively, confer fertilizing potential on sperm cells. This article focuses on two extrinsic factors, one a protein and one a very small peptide, that become associated with spermatozoa either in the epididymis or following contact with seminal plasma. These factors modulate capacitation in vitro in ways that could be very relevant to fertilization in vivo, possibly helping to maximize the fertilizing potential of the few cells that reach the site of fertilization. In some men, defects in either of the factors and the systems they modulate could result in defective fertilization. However, by understanding the underlying mechanisms, it may prove possible to develop new diagnostic techniques and new therapeutic treatments to alleviate the infertility.

Modulation of adenylyl cyclase by FPP and adenosine involves stimulatory and inhibitory adenosine receptors and g proteins.

FPP and adenosine modulate the adenylyl cyclase (AC)/cAMP signal transduction pathway in mammalian spermatozoa to elicit a biphasic response, initially stimulating capacitation and then inhibiting spontaneous acrosome loss. This study addressed the hypothesis that responses to FPP involve interactions between receptors for FPP and adenosine, the biphasic responses involving stimulatory and inhibitory adenosine receptors. Gln-FPP, a competitive inhibitor of FPP, significantly inhibited binding of an adenosine analogue and responses to adenosine, especially in capacitated suspensions, consistent with interaction between FPP and adenosine receptors. CGS-21680 (1 microM), a stimulatory A2a adenosine receptor agonist, significantly stimulated capacitation and cAMP in uncapacitated cells, while cyclopentyl adenosine (1 microM), an inhibitory A1 adenosine receptor agonist only affected capacitated cells, inhibiting spontaneous acrosome loss. Responses to FPP and adenosine were inhibited in uncapacitated cells by a selective A2a antagonist and in capacitated cells by a selective A1 antagonist; subsequent investigations indicated possible involvement of G proteins. Like FPP, cholera toxin stimulated capacitation and cAMP production in uncapacitated cells, suggesting involvement of a G protein with a Galphas subunit. In contrast, pertussis toxin prevented FPP's inhibition of both spontaneous acrosome loss and cAMP production, suggesting involvement of a Galphai/o subunit. Immunoblotting evidence revealed the presence of proteins of the appropriate molecular weights for Galphas, Galphai2, Galpha i3, and Galphao subunits. This study provides the first direct evidence suggesting the involvement of two different types of adenosine receptors and both Galphas and Galphai/o subunits in the regulation of capacitation, resulting in modulation of AC activity and availability of cAMP.

New insights into the t-complex and control of sperm function.

The mouse t-complex, located on chromosome 17, contains genes known to influence male, but not female, fertility. Although some t-complex genes are recessive lethals, t-chromosomes are maintained in the population by transmission ratio distortion. When male mice heterozygous for the t-chromosome mate with wild-type females, most offspring will possess the t-chromosome, indicating a link between t-complex genes and sperm function. Several proteins coded for by t-complex genes have been localised in the sperm flagellum, suggesting roles relating to motility. Another t-complex protein appears able to regulate the adenylyl cyclase/cAMP signal transduction pathway, known to play an important role in capacitation. Defective motility and/or failure to capacitate ("switch on") would result in poorly fertile or infertile spermatozoa. Given the existence of human homologues for many genes in the t-complex and the prevalence of "male factor" infertility, information obtained about the t-complex not only will provide insight into basic biological mechanisms but may be of future clinical relevance as well.

Role of fertilization promoting peptide (FPP) in modulating mammalian sperm function.

Fertilization promoting peptide (FPP), structurally similar to thyrotrophin releasing hormone, is produced by the prostate gland and secreted into seminal plasma. Recent in vitro studies have provided evidence that FPP elicits biologically relevant responses in mouse, human and boar spermatozoa. In the presence of nanomolar concentrations of FPP, spermatozoa become fertilizing more quickly and then are inhibited from undergoing spontaneous acrosome loss, an event that would make them non-fertilizing. In vivo, these responses would be very important in maximizing the availability of potentially fertilizing spermatozoa. Adenosine, which can elicit the same responses as FPP, is known to modulate the adenylyl cyclase(AC)/cAMP signal transduction pathway; current evidence indicates that FPP and adenosine act via separate receptors on the same signal transduction pathway. Mouse spermatozoa are known to have adenosine receptors and a putative receptor for FPP (TCP-11) has been identified. Unlike many surface receptors, TCP-11 has no obvious transmembrane regions whereby modulation of AC could occur. Recent evidence suggests that FPP receptors may dimerize with adenosine receptors to activate the signaling pathway, with stimulatory adenosine receptors involved in the stimulation of capacitation, but inhibitory receptors involved in inhibition of spontaneous acrosome loss. These results indicate that FPP plays an important role in normal sperm function and that it might be used in new therapeutic strategies designed to alleviate some causes of sperm dysfunction.

FPP modulates mammalian sperm function via TCP-11 and the adenylyl cyclase/cAMP pathway.

Fertilization promoting peptide (FPP; pGlu-Glu-ProNH2), which is found in seminal plasma, promotes capacitation but inhibits spontaneous acrosome loss in mammalian spermatozoa in vitro. Adenosine, known to modulate the adenylyl cyclase (AC)/cAMP pathway, elicits these same responses whereas FPP + adenosine produces an enhanced response, leading to the hypothesis that FPP and adenosine modulate the same signal transduction pathway but act via different receptors. TCP-11, the product of a t-complex gene, is the putative receptor for FPP: Fab fragments of anti-TCP-11 antibodies have the same effect as FPP on mouse spermatozoa and Gln-FPP, a competitive inhibitor of FPP, also competitively inhibits responses to the Fab fragments. In the present study, specific binding of 3H-FPP to sperm membranes was significantly inhibited by 200 nM Gln-FPP and anti-TCP-11 Fab fragments (1/25 dilution), thus confirming that FPP, Gln-FPP, and Fab fragments compete for the same binding site. In addition, spermatozoa treated with A23187 to induce the acrosome reaction bound significantly less 3H-FPP than untreated cells, suggesting that a large proportion of the FPP binding sites are associated with the acrosomal cap region; TCP-11 is located in this region. In other experiments, 100 nM FPP significantly stimulated cAMP production in mouse sperm membranes, permeabilized cells and intact cells. Furthermore, Gln-FPP inhibited production of cAMP in response to FPP but not to adenosine (10 microM) or its analogue NECA (100 nM), supporting the involvement of two different receptors. Finally, anti-TCP-11 Fab fragments (1/25 dilution) significantly stimulated cAMP production, whereas low Fab (1/200; nonstimulatory when used alone) plus adenosine (10 microM) significantly enhanced the stimulation of capacitation by adenosine. These results support the hypotheses that TCP-11 is the receptor for FPP and that FPP<-->TCP-11 interactions modulate AC/cAMP.

Fertilization promoting peptide: an important regulator of sperm function in vivo?

Fertilization promoting peptide (FPP; pGlu-Glu-ProNH2), a tripeptide structurally related to thyrotrophin releasing hormone, is produced by the prostate gland and released into seminal plasma. Recent studies carried out in vitro have revealed that FPP elicits biologically important responses in both mouse and human spermatozoa. In the presence of physiological concentrations of FPP (50-100 nmol l(-1)), uncapacitated spermatozoa undergo accelerated capacitation and so become potentially fertilizing more quickly, while capacitated spermatozoa are inhibited from undergoing spontaneous acrosomal exocytosis, an event that would make them non-fertilizing. In vivo, these responses would be very important since relatively few spermatozoa reach the site of fertilization; FPP could help to ensure that these were potentially fertilizing cells. A putative receptor (TCP-11) for FPP has been identified in mice. The gene for TCP-11 (which has a human homologue) maps to the t-complex, a region known to contain genes affecting male fertility. Current evidence indicates that FPP and TCP-11 act by modulating the activity of adenylyl cyclase and hence production of cAMP, a signal transduction pathway shown to be important in the acquisition of fertilizing ability. These results suggest that FPP plays an important role in normal fertility and that insufficient FPP could reduce fertility. Prostatic dysfunction can lead to decreased synthesis of FPP and increased synthesis of FPP-related peptides with reduced biological activity, both of which could compromise fertility in vivo. Given that 'male factor' infertility is a common contributor to subfertility in couples, it may prove possible to develop new therapeutic treatments, for at least some males, using FPP. In addition, this ligand-receptor pair could provide a novel target for male contraception.

Modulation of mammalian sperm function by fertilization promoting peptide (FPP).

Fertilization promoting peptide (FPP; pGlu-Glu-ProNH2) is produced by the prostate gland and secreted into seminal plasma. When added to uncapacitated mouse and human sperm suspensions, it stimulates capacitation as demonstrated by both cytological changes and increased fertilizing ability in vitro. When added to capacitated suspensions, FPP inhibits spontaneous acrosome loss but cells retain high fertility in vitro. Adenosine elicits similar responses to FPP in both uncapacitated and capacitated cells and FPP + adenosine has a greater effect on uncapacitated cells than either used individually. We have proposed that these two molecules modulate the same pathway (adenylate cyclase/cAMP) but act via different receptors. The structure of FPP is crucial for bioactivity: loss of the terminal amide group abolishes activity and substitution of the central glutamic acid can markedly alter activity. Most recently we have found that stimulation of TCP-11, the product of the mouse t-complex gene Tcp-11, elicits responses indistinguishable from those obtained with FPP and we have hypothesized that the protein TCP-11 is the receptor for FPP. The existence of a human homologue for Tcp-11 suggests that the gene product, in conjunction with FPP, could play an important role in human fertility.

Interactions between a decapacitation factor and mouse spermatozoa appear to involve fucose residues and a GPI-anchored receptor.

Epididymal mouse spermatozoa have a surface-associated decapacitation factor (DF) that can be removed precociously by centrifugation, resulting in acceleration of capacitation and increased fertilizing ability. Addition of exogenous DF to capacitated suspensions inhibits fertilizing ability and reverses capacitation in acrosome-intact cells. DF appears to regulate a Ca2+-ATPase, located primarily in the post-acrosomal region. The present investigations of DF<-->spermatozoon interaction indicate that DF can be removed from uncapacitated cells by treatment with phosphatidylinositol-specific phospholipase C (PIC), suggesting the involvement of a glycosylphosphatidylinositol (GPI) moiety. However, exogenous DF cannot reassociate with PIC-treated spermatozoa, suggesting that DF may bind to spermatozoa via a GPI-anchored receptor. DF binding appears to involve fucose residues, since depletion of endogenous DF followed by brief exposure to fucose (0.1-10 mM) prevented DF reassociation with cells. Furthermore, 5 mM fucose could displace DF from uncapacitated cells, accelerating capacitation and resulting in a higher proportion of fertilized oocytes, with increased polyspermy, than obtained with untreated controls. FITC-labelled fucosylated BSA bound specifically to the postacrosomal region, binding being inhibited by both excess fucose and crude DF. UEA I, a lectin with specificity for fucose residues, bound to the postacrosomal region of cells preincubated in fucose but not crude DF, and blocked DF binding to DF-depleted cells. These results are consistent with the DF binding, via fucose residues, to a GPI-anchored receptor. Fucose binding sites are in the same region where Ca2+-ATPase, the enzyme regulated by DF, has been localized; these results support the hypothesis that DF modulates capacitation by regulating enzyme activity and hence the intracellular Ca2+ concentration.

Sperm capacitation and the acrosome reaction.

To achieve successful fertilization under normal circumstances in vivo, mammalian spermatozoa must first undergo capacitation and then the acrosome reaction, an exocytotic event that allows cells to penetrate the zona pellucida and fuse with the oocyte plasma membrane. These complex events permit spermatozoa to achieve fertilizing ability at the right time in the right place, important considerations since relatively few sperm cells actually reach the site of fertilization in vivo. Several mechanisms that may be involved in regulating the acquisition of fertilizing ability are considered. In vivo, selective pressures placed on the initial population of spermatozoa help ensure that the 'fittest' spermatozoa are able to fertilize. Since intracytoplasmic sperm injection bypasses this selection process, it is best used only in cases where spermatozoa are judged to be incapable of achieving normal fertilization in vitro.