Sperm Maturation: The maturing process of SPERMATOZOA after leaving the testicular SEMINIFEROUS TUBULES. Maturation in SPERM MOTILITY and FERTILITY takes place in the EPIDIDYMIS as the sperm migrate from caput epididymis to cauda epididymis.Epididymis: The convoluted cordlike structure attached to the posterior of the TESTIS. Epididymis consists of the head (caput), the body (corpus), and the tail (cauda). A network of ducts leaving the testis joins into a common epididymal tubule proper which provides the transport, storage, and maturation of SPERMATOZOA.Spermatozoa: Mature male germ cells derived from SPERMATIDS. As spermatids move toward the lumen of the SEMINIFEROUS TUBULES, they undergo extensive structural changes including the loss of cytoplasm, condensation of CHROMATIN into the SPERM HEAD, formation of the ACROSOME cap, the SPERM MIDPIECE and the SPERM TAIL that provides motility.Sperm Head: The anterior portion of the spermatozoon (SPERMATOZOA) that contains mainly the nucleus with highly compact CHROMATIN material.Sperm Count: A count of SPERM in the ejaculum, expressed as number per milliliter.Sperm Capacitation: The structural and functional changes by which SPERMATOZOA become capable of oocyte FERTILIZATION. It normally requires exposing the sperm to the female genital tract for a period of time to bring about increased SPERM MOTILITY and the ACROSOME REACTION before fertilization in the FALLOPIAN TUBES can take place.Echidna: An oviparous burrowing mammal of the order Monotremata native to Australia, Tasmania, and New Guinea. It has hair mingled with spines on the upper part of the body and is adapted for feeding on ants.Testis: The male gonad containing two functional parts: the SEMINIFEROUS TUBULES for the production and transport of male germ cells (SPERMATOGENESIS) and the interstitial compartment containing LEYDIG CELLS that produce ANDROGENS.Epididymal Secretory Proteins: Proteins secreted by the epididymal epithelium. These proteins are both tissue- and species-specific. They are important molecular agents in the process of sperm maturation.Sperm-Ovum Interactions: Interactive processes between the oocyte (OVUM) and the sperm (SPERMATOZOA) including sperm adhesion, ACROSOME REACTION, sperm penetration of the ZONA PELLUCIDA, and events leading to FERTILIZATION.Sperm Transport: Passive or active movement of SPERMATOZOA from the testicular SEMINIFEROUS TUBULES through the male reproductive tract as well as within the female reproductive tract.Spermatogenesis: The process of germ cell development in the male from the primordial germ cells, through SPERMATOGONIA; SPERMATOCYTES; SPERMATIDS; to the mature haploid SPERMATOZOA.Infertility, Male: The inability of the male to effect FERTILIZATION of an OVUM after a specified period of unprotected intercourse. Male sterility is permanent infertility.Acrosome: The cap-like structure covering the anterior portion of SPERM HEAD. Acrosome, derived from LYSOSOMES, is a membrane-bound organelle that contains the required hydrolytic and proteolytic enzymes necessary for sperm penetration of the egg in FERTILIZATION.Fertilization: The fusion of a spermatozoon (SPERMATOZOA) with an OVUM thus resulting in the formation of a ZYGOTE.Sperm Motility: Movement characteristics of SPERMATOZOA in a fresh specimen. It is measured as the percentage of sperms that are moving, and as the percentage of sperms with productive flagellar motion such as rapid, linear, and forward progression.Sperm Tail: The posterior filiform portion of the spermatozoon (SPERMATOZOA) that provides sperm motility.Semen: The thick, yellowish-white, viscid fluid secretion of male reproductive organs discharged upon ejaculation. In addition to reproductive organ secretions, it contains SPERMATOZOA and their nutrient plasma.Fertility: The capacity to conceive or to induce conception. It may refer to either the male or female.Vasectomy: Surgical removal of the ductus deferens, or a portion of it. It is done in association with prostatectomy, or to induce infertility. (Dorland, 28th ed)Ejaculation: The emission of SEMEN to the exterior, resulting from the contraction of muscles surrounding the male internal urogenital ducts.Vasovasostomy: Surgical anastomosis or fistulization of the spermatic ducts to restore fertility in a previously vasectomized male.Sapindus: A plant genus of the family SAPINDACEAE that contain SAPONINS.Spermatids: Male germ cells derived from the haploid secondary SPERMATOCYTES. Without further division, spermatids undergo structural changes and give rise to SPERMATOZOA.Seminal Plasma Proteins: Proteins found in SEMEN. Major seminal plasma proteins are secretory proteins from the male sex accessory glands, such as the SEMINAL VESICLES and the PROSTATE. They include the seminal vesicle-specific antigen, an ejaculate clotting protein; and the PROSTATE-SPECIFIC ANTIGEN, a protease and an esterase.Genitalia, Male: The male reproductive organs. They are divided into the external organs (PENIS; SCROTUM;and URETHRA) and the internal organs (TESTIS; EPIDIDYMIS; VAS DEFERENS; SEMINAL VESICLES; EJACULATORY DUCTS; PROSTATE; and BULBOURETHRAL GLANDS).Clusterin: A highly conserved heterodimeric glycoprotein that is differentially expressed during many severe physiological disturbance states such as CANCER; APOPTOSIS; and various NEUROLOGICAL DISORDERS. Clusterin is ubiquitously expressed and appears to function as a secreted MOLECULAR CHAPERONE.Sperm Injections, Intracytoplasmic: An assisted fertilization technique consisting of the microinjection of a single viable sperm into an extracted ovum. It is used principally to overcome low sperm count, low sperm motility, inability of sperm to penetrate the egg, or other conditions related to male infertility (INFERTILITY, MALE).ADAM Proteins: A family of membrane-anchored glycoproteins that contain a disintegrin and metalloprotease domain. They are responsible for the proteolytic cleavage of many transmembrane proteins and the release of their extracellular domain.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Sperm Midpiece: The middle piece of the spermatozoon is a highly organized segment consisting of MITOCHONDRIA, the outer dense fibers and the core microtubular structure.Androgens: Compounds that interact with ANDROGEN RECEPTORS in target tissues to bring about the effects similar to those of TESTOSTERONE. Depending on the target tissues, androgenic effects can be on SEX DIFFERENTIATION; male reproductive organs, SPERMATOGENESIS; secondary male SEX CHARACTERISTICS; LIBIDO; development of muscle mass, strength, and power.Oocytes: Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).Vas Deferens: The excretory duct of the testes that carries SPERMATOZOA. It rises from the SCROTUM and joins the SEMINAL VESICLES to form the ejaculatory duct.Vacuolar Proton-Translocating ATPases: Proton-translocating ATPases that are involved in acidification of a variety of intracellular compartments.Mice, Inbred ICROrchiectomy: The surgical removal of one or both testicles.Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Sperm Banks: Centers for acquiring and storing semen.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Semen Preservation: The process by which semen is kept viable outside of the organism from which it was derived (i.e., kept from decay by means of a chemical agent, cooling, or a fluid substitute that mimics the natural state within the organism).Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Sexual Maturation: Achievement of full sexual capacity in animals and in humans.Zona Pellucida: A tough transparent membrane surrounding the OVUM. It is penetrated by the sperm during FERTILIZATION.Electrophoresis, Polyacrylamide Gel: Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Semen Analysis: The quality of SEMEN, an indicator of male fertility, can be determined by semen volume, pH, sperm concentration (SPERM COUNT), total sperm number, sperm viability, sperm vigor (SPERM MOTILITY), normal sperm morphology, ACROSOME integrity, and the concentration of WHITE BLOOD CELLS.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Fluorescent Antibody Technique: Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.Reverse Transcriptase Polymerase Chain Reaction: A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.Proteins: Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.Glycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.