Showing papers on "Acrosome reaction published in 1974"

Capacitation of mammalian spermatozoa.

Abstract: The need for a physiological change in mammalian spermatozoa in the female genital tract as a prerequisite for fertilization was first recognized by Austin (1951) and Chang (1951) in the rabbit, and the change was termed “capacita­tion” (Austin, 1952). They found that if epididymal or ejaculated spermatozoa were introduced into the oviduct of the female rabbit before ovulation, eggs were fertilized. However, when the spermatozoa were introduced into the female after ovulation, few-if any-eggs were fertilized. In other words, the eggs lost the ability to be fertilized before the spermatozoa became capacitated.

Report of a workshop: Maturation of the fertilizing ability of mammalian spermatozoa in the male and female reproductive tract.

Abstract: This summarizes the proceedings of a workshop sponsored in January 1973 by the Reproductive Biology Section of NIH and the Center for Population Research of the National Institute for Child Health and Human Development on the complex posttesticular phase of sperm maturation in the epididymis uterus and fallopian tubes. It covers the physiology of the spermatozoa in the epididymis and its possible implications for fertility control; the physiology of the spermatozoa in the female reproductive tract including the process of capacitation substances which inhibit sperm head enzymes and the possible modes of action of the sperm and egg; and the character of the sperm cell itself. Each step of the fertilization process is detailed with areas of needed research indicated. The mechanisms involved in induction of the acrosome reaction the factors which determine sperm penetration of the zona the chemical nature of the sperm receptors on zona and vitelline surface the nature of the nuclear decondensation factor in the ooplasm are all cited as essential to understanding of the mechanism involved in conception and should be the focus of modern cell biology.

Hamster sperm hyaluronidase. II. Its release from sperm in vitro in relation to the degenerative and normal acrosome reaction.

Abstract: Hamster sperm incubated in vitro were used to determine: (1) when hyaluronidase is released from sperm undergoing acrosome detachment, i.e., either a degenerative or normal acrosome reaction, and (2) what ultrastructural changes occur in the acrosomes of living sperm during hyaluronidase release. Sperm were incubated up to 4 hours in normal saline, Ham's F-10, or heat pretreated blood serum. At hourly intervals, the percentages of live (motile) and acrosome reacted sperm were counted, and the supernatant from each sperm sample was assayed for hyaluronidase activity. In normal saline, sperm died during the incubation period, underwent a degenerative acrosome reaction, and gradually released hyaluronidase. In Ham's F-10, sperm lived throughout the incubation period, did not undergo acrosome detachment, and did not release detectable amounts of hyaluronidase. In heat pretreated blood serum, sperm death did not occur during the incubation period, a surge of hyaluronidase release was complete by 1 hour of incubation, and additional hyaluronidase activity was not detected in the incubation medium between 3 and 4 hours when the normal acrosome reaction was observed. The fine structure of the acrosome was unaltered immediately after the release of hyaluronidase in serum. It was concluded that more than 50% of the mechanically extractable hamster sperm hyaluronidase was released by a factor present in serum and that this release occurred prior to and independently of the normal acrosome reaction. The partial release of hyaluronidase in serum prior to the occurrence of a normal acrosome reaction may indicate that this enzyme has a bifunctional role in reproduction.

The release of hyaluronidase from guinea-pig spermatozoa during the course of the normal acrosome reaction in vitro.

Abstract: Hamster spermatozoa incubated in heat-pretreated blood serum release 55 to 60% of their total hyaluronidase activity by the end of 1 hr of incubation; little increase in activity is found in the incubation medium at later time intervals up to 4 hr (Rogers & Morton, 1973; Talbot & Franklin, 1974b). This release occurs well before and independently of a normal acrosome reaction, i.e. detachment of the acrosome from motile spermatozoa as observed with phasecontrast microscopy (Talbot & Franklin, 1974b). Vesiculation between the outer acrosomal membrane and plasma membrane does not occur before the surge of hyaluronidase release which takes place between time zero and 1 hr of incubation (Talbot & Franklin, 1974b). Lewis & Ketchel (1972a, 1973) demonstrated that the release of hyaluronidase from rabbit spermatozoa incubated in postovulatory uterine fluid is "related to the completion of the process of capacitation". Although acrosome detachment is not easily monitored for this species, their data imply that hyaluronidase release occurs before a normal acrosome reaction. The complex incubation media used for studies of both hamster and rabbit spermatozoa contain a macromolecular factor (s) which promotes hyaluronidase release in vitro (Lewis & Ketchel, 1972b; Rogers & Morton, 1973; Talbot & Franklin, 1974b). Recently, several chemically defined media have been developed which support the occurrence ofa normal acrosome reaction in guinea-pig spermatozoa (Barros, Berrios & Herrera, 1973; Barros, 1974). This investigation was undertaken to compare the release of hyaluronidase from guinea-pig sperm¬ atozoa incubated in a chemically defined medium with its release from guineapig and hamster spermatozoa incubated in heat-pretreated blood serum. In the first experiment, the time course of hyaluronidase release from guinea-pig spermatozoa incubated in a chemically defined medium was monitored. Spermatozoa from the cauda epididymidis ofsexually mature males were washed twice in 4 ml normal saline. Falcon centrifuge tubes (catalogue No. 2095) containing minimum capacitation medium (MCM) (Barros, 1974)

Separation of human serum components capable of inducing the acrosome reaction in hamster spermatozoa

Abstract: serum by Sephadex gel filtration (Morton & Bavister, 1974). The proteinrich fractions potentiate this activity and effectively induce the acrosome reaction. Here, we describe attempts to determine the type of protein that may be involved. The methods used to prepare the motility-stimulating fraction from human serum and for assessing its activity were as previously described (Morton & Bavister, 1974). To help identify which serum component induced the acrosome reaction, serum proteins were chromatographically separated on Sephadex G-150 (5 ml pooled human serum fractionated on 130 ml bed volume G-150 in a 1\m=.\\m=x\90cm column, fraction size 1\m=.\6ml, flow rate 10 ml/hr). Protein was monitored by absorption at 280 nm with an LKB Uvicord II (see Text-fig. 1). The G-150 column was calibrated with Blue Dextran, human IgG, bovine

The acrosome reaction in the sperm of the shipworm Bankia australis Calman (Bivalvia, Mollusca).

Abstract: The ultrastructure of the acrosome reaction in the sperm of the teredo, Bankia australis, is described. In brief, the reaction consists of three phases: (a) formation of a bleb and membrane fusion, (b) disappearance of the longitudinally oriented fibrils, and (c) outward flaring and disappearance of the osmiophilic granule. The osmiophilic granule appears to consist of prism-like structures. The axial rod never lengthens during the acrosome reaction.

Fractionation of hamster sperm-capacitating components from human serum by gel filtration

Abstract: Efficient capacitation of hamster spermatozoa can be induced by follicular fluid (Barros & Austin, 1967; Yanagimachi, 1969a, b) and blood sera of several species (Barros & Garavagno, 1970; Yanagimachi, 1970a; Talbot, Franklin & Fussell, 1974). Two components are involved: one is dialysable, heat-stable and stimulates sperm motility, while the other is non-dialysable, heat-labile and induces the acrosome reaction (Yanagimachi, 1969a). Our understanding of capacitation and the acrosome reaction might be enhanced if the nature and mode of action of these factors were known. Blood serum is an easily available source of both factors and this preliminary report describes the recovery of the sperm motility-stimulating activity from human serum. Fresh human serum was heated to 56\s=deg\Cfor 30 min to destroy unidentified toxic factor(s) (Yanagimachi, 1970a). The serum was chromatographed on Sephadex G-25 (medium grade) and equilibrated in Tyrode's solution supplemented with 0\m=.\33mm-sodium pyruvate, 0\m=.\01 mg phenol red/ml, 100 i.u. penicillin/ml and 10 mg Dextran T70 (Pharmacia)/ml. Equilibration in culture medium avoided further dilution of the fractions in the test system. Protein elution was monitored with a L.K.B. Uvicord II measuring absorption at 280 nm and columns were pumped under positive pressure at a flow rate of about 50 ml/cm2/hr. Column calibration was carried out with Blue Dextran (Pharmacia) and potassium ferricyanide. The fraction size was approximately 5% bed volume. In order to test the fractions, 200-μ1 aliquots were placed under paraffin oil in plastic tissue culture dishes (Falcon Plastics) and equilibrated with 5% C02 in air at 37°C. Hamster epididymal spermatozoa were added to the drops so that the final sperm concentration was about 1 106/ml, and the drops were then reincubated. At intervals between 1 and 6 hr, the percentage of motile spermatozoa and the degree of sperm motility in each drop were estimated, and a 'sperm motility index' was calculated as previously described (Bavister, 1974). The proportion of motile spermatozoa showing the acrosome reaction was also noted at 3 and 6 hr. The 'sperm motility-stimulating activity' was constantly found to elute

Capacitation of sperm: as a function of the oviduct

Abstract: Capacitation is defened as a physiological change of sperm in the female reproductive tract which makes it capable of penetrating the ovum. 1st there is the removal or neutralization of the decapacitation factor. 2nd sperm seem to require an acrosome reaction and finally there is a release or activation of lytic sbustances that allow the sperm to pass through the outer investments of the egg. Capacitation is needed in many species including the human. Requirements vary with the species. A precise environment more than a special agent seems to be needed. In rabbits there is need for some special female reproductive tract factor which is sensitive to the hormonal state of the animal. This chapter describes 5 bioassays that measure capacitation of sperm. In Changs original assay sperm are incubated usually in the female reproductive tract of the rabbit (capacitation) and then transferred to the oviduct of another test rabbit which has been given an ovulating injection of luteinizing hormone or human chorionic gonadotropin 12-14 hours previously. Ova are recovered from the test rabbit at 10-30 hours after introducing the sperm. The control test is by placing nonincubated sperm in the contralateral oviduct of the test rabbit. Sperm became capacitated in the uterus in 5-6 hours but required 11 hours in the oviduct. There are several variations of this method. In vitro fertilization is now possible in some species by incubating sperm in blood serum follicular fluid or reproductive tract fluid. After sperm are placed with ova the ova are observed for any sign of fertilization. Any treatment of sperm which will allow them to fertilize ova is considered to have capacitated the sperm. Removal of tetracycline fluorescence from sperm has not been confirmed as effective capacitation. Other tests indicate sperm surface changes during capacitation. Changes in the acrosome have been observed. Ultrastructural studies with the scanning electron microscope have shown changes. A differential staining procedure has been used. Electroanalytical techniques are being developed. Mechanisms involved in the capacitation process involve removal of the decapacitation factor (DF) and activation of acrosomal enzymes. The female tract inactivates antifertility agents DF included bound to the sperm head surface. Activation of acrosomal enqymes is accomplished by removal of inhibitors. The rabbit oviduct behaves differently from the uterus. Estrogen appears to be stimulatory but progestagen may counteract actions of estrogen. If capacitation could be stopped a contraceptive method could be developed. Capacitation does not seem to occur in the pseudopregnant rabbit uterus. The end result of capacitation is to enhance contact between ova and sperm by the release of lytic substances allowing sperm to pass through the cumulus and corona cells around the ova and to penentrate the zona pellucida. The lytic agent permitting penetration of the zona pellucida is a trypsinlike enzyme. Preventing the activation or release of this enzyme is being attempted.

The Properties of Rabbit Sperm Membranes in Contact with Electrode Surfaces

Abstract: In dilute suspensions of sperm cells there is electrode noise due to the changes in the electrical double layer during contacts of the suspended cells with the electrode surface. The noise frequency, the number of current fluctuations above one nanoampere per unit time, depends upon the concentration of cells, the potential at the electrode surface and the presence of adsorbed material at the electrode. We have studied the electrode noise due to suspensions of rabbit sperm cells, and have obtained information about the properties of the cell membranes and their ability to adsorb or interact with substances in the environment. The observed differences in the noise frequency between ejaculated and epididymal sperm cells indicate that the ejaculated sperm cell does not adsorb material as readily. The titration of sperm cell suspensions with Zn++ ions shows a lower negative surface charge on the epididymal sperm cell, in agreement with published values on cell electrophoresis. The experiments reported here demonstrate that there are significant changes in the membranes of sperm cells at the later stages of maturation which are independent of membrane charge and affect the ability of the cells to adsorb material. Such adsorption processes could be the first stages of physiological processes (e.g. “sperm capacitation”, “acrosome reaction”) that are known to occurin vivo, and that play important roles in fertilization.

In Vitro Fertilization and its Uses in Animals and Man

Abstract: Fertilization is the process in which spermatozoon and ovum come together and unite to form a zygote. Initially, the sperm cell penetrates through the surrounding cellular investments, the zona pellucida, and into the vitellus of the ovum. Fertilization proceeds as the sperm head enlarges to form the male pronucleus and, following activation of the ovum, the female chromatin condenses to form the female pronucleus. Ovum activation denotes the resumption of meiosis which proceeds from metaphase II to completion. Male and female pronuclei develop and come into apposition, pronuclear membranes break down, and the chromosomes from male and female gametes intermix. Mitosis begins and fertilization is concluded with the first mitotic metaphase which is rapidly followed by cleavage into a two-cell embryo. Fertilization takes approximately 12 hours in the rabbit and roughly twice that in large domestic animals including (wo)man.