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.Blood-Brain Barrier: Specialized non-fenestrated tightly-joined ENDOTHELIAL CELLS with TIGHT JUNCTIONS that form a transport barrier for certain substances between the cerebral capillaries and the BRAIN tissue.Rete Testis: The network of channels formed at the termination of the straight SEMINIFEROUS TUBULES in the mediastinum testis. Rete testis channels drain into the efferent ductules that pass into the caput EPIDIDYMIS.Spermatogenesis: The process of germ cell development in the male from the primordial germ cells, through SPERMATOGONIA; SPERMATOCYTES; SPERMATIDS; to the mature haploid SPERMATOZOA.Sertoli Cells: Supporting cells projecting inward from the basement membrane of SEMINIFEROUS TUBULES. They surround and nourish the developing male germ cells and secrete ANDROGEN-BINDING PROTEIN and hormones such as ANTI-MULLERIAN HORMONE. The tight junctions of Sertoli cells with the SPERMATOGONIA and SPERMATOCYTES provide a BLOOD-TESTIS BARRIER.Cryptorchidism: A developmental defect in which a TESTIS or both TESTES failed to descend from high in the ABDOMEN to the bottom of the SCROTUM. Testicular descent is essential to normal SPERMATOGENESIS which requires temperature lower than the BODY TEMPERATURE. Cryptorchidism can be subclassified by the location of the maldescended testis.Leydig Cells: Steroid-producing cells in the interstitial tissue of the TESTIS. They are under the regulation of PITUITARY HORMONES; LUTEINIZING HORMONE; or interstitial cell-stimulating hormone. TESTOSTERONE is the major androgen (ANDROGENS) produced.Blood-Testis Barrier: A specialized barrier, in the TESTIS, between the interstitial BLOOD compartment and the adluminal compartment of the SEMINIFEROUS TUBULES. The barrier is formed by layers of cells from the VASCULAR ENDOTHELIUM of the capillary BLOOD VESSELS, to the SEMINIFEROUS EPITHELIUM of the seminiferous tubules. TIGHT JUNCTIONS form between adjacent SERTOLI CELLS, as well as between the ENDOTHELIAL CELLS.Spermatids: Male germ cells derived from the haploid secondary SPERMATOCYTES. Without further division, spermatids undergo structural changes and give rise to 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.Spermatogonia: Euploid male germ cells of an early stage of SPERMATOGENESIS, derived from prespermatogonia. With the onset of puberty, spermatogonia at the basement membrane of the seminiferous tubule proliferate by mitotic then meiotic divisions and give rise to the haploid SPERMATOCYTES.Seminiferous Epithelium: The epithelium lining the seminiferous tubules composed of primary male germ cells (SPERMATOGONIA) and supporting SERTOLI CELLS. As SPERMATOGENESIS proceeds, the developing germ cells migrate toward the lumen. The adluminal compartment, the inner two thirds of the tubules, contains SPERMATOCYTES and the more advanced germ cells.Blood-Retinal Barrier: A specialized transport barrier, in the EYE, formed by the retinal pigment EPITHELIUM, and the ENDOTHELIUM of the BLOOD VESSELS of the RETINA. TIGHT JUNCTIONS joining adjacent cells keep the barrier between cells continuous.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.Spermatocytes: Male germ cells derived from SPERMATOGONIA. The euploid primary spermatocytes undergo MEIOSIS and give rise to the haploid secondary spermatocytes which in turn give rise to SPERMATIDS.Blood-Air Barrier: The barrier between capillary blood and alveolar air comprising the alveolar EPITHELIUM and capillary ENDOTHELIUM with their adherent BASEMENT MEMBRANE and EPITHELIAL CELL cytoplasm. PULMONARY GAS EXCHANGE occurs across this membrane.Testosterone: A potent androgenic steroid and major product secreted by the LEYDIG CELLS of the TESTIS. Its production is stimulated by LUTEINIZING HORMONE from the PITUITARY GLAND. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to DIHYDROTESTOSTERONE or ESTRADIOL.Testicular Diseases: Pathological processes of the TESTIS.Testicular Neoplasms: Tumors or cancer of the TESTIS. Germ cell tumors (GERMINOMA) of the testis constitute 95% of all testicular neoplasms.Tight Junctions: Cell-cell junctions that seal adjacent epithelial cells together, preventing the passage of most dissolved molecules from one side of the epithelial sheet to the other. (Alberts et al., Molecular Biology of the Cell, 2nd ed, p22)Communication Barriers: Those factors, such as language or sociocultural relationships, which interfere in the meaningful interpretation and transmission of ideas between individuals or groups.Permeability: Property of membranes and other structures to permit passage of light, heat, gases, liquids, metabolites, and mineral ions.Sperm Count: A count of SPERM in the ejaculum, expressed as number per milliliter.Organ Size: The measurement of an organ in volume, mass, or heaviness.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.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.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.Germ Cells: The reproductive cells in multicellular organisms at various stages during GAMETOGENESIS.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).Orchitis: Inflammation of a TESTIS. It has many features of EPIDIDYMITIS, such as swollen SCROTUM; PAIN; PYURIA; and FEVER. It is usually related to infections in the URINARY TRACT, which likely spread to the EPIDIDYMIS and then the TESTIS through either the VAS DEFERENS or the lymphatics of the SPERMATIC CORD.Spermatic Cord Torsion: The twisting of the SPERMATIC CORD due to an anatomical abnormality that left the TESTIS mobile and dangling in the SCROTUM. The initial effect of testicular torsion is obstruction of venous return. Depending on the duration and degree of cord rotation, testicular symptoms range from EDEMA to interrupted arterial flow and testicular pain. If blood flow to testis is absent for 4 to 6 h, SPERMATOGENESIS may be permanently lost.Sexual Maturation: Achievement of full sexual capacity in animals and in humans.Scrotum: A cutaneous pouch of skin containing the testicles and spermatic cords.Tissue Distribution: Accumulation of a drug or chemical substance in various organs (including those not relevant to its pharmacologic or therapeutic action). This distribution depends on the blood flow or perfusion rate of the organ, the ability of the drug to penetrate organ membranes, tissue specificity, protein binding. The distribution is usually expressed as tissue to plasma ratios.Occludin: A MARVEL domain protein that plays an important role in the formation and regulation of the TIGHT JUNCTION paracellular permeability barrier.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Capillary Permeability: The property of blood capillary ENDOTHELIUM that allows for the selective exchange of substances between the blood and surrounding tissues and through membranous barriers such as the BLOOD-AIR BARRIER; BLOOD-AQUEOUS BARRIER; BLOOD-BRAIN BARRIER; BLOOD-NERVE BARRIER; BLOOD-RETINAL BARRIER; and BLOOD-TESTIS BARRIER. Small lipid-soluble molecules such as carbon dioxide and oxygen move freely by diffusion. Water and water-soluble molecules cannot pass through the endothelial walls and are dependent on microscopic pores. These pores show narrow areas (TIGHT JUNCTIONS) which may limit large molecule movement.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.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.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.Organ Specificity: Characteristic restricted to a particular organ of the body, such as a cell type, metabolic response or expression of a particular protein or antigen.Blood-Aqueous Barrier: The selectively permeable barrier, in the EYE, formed by the nonpigmented layer of the EPITHELIUM of the CILIARY BODY, and the ENDOTHELIUM of the BLOOD VESSELS of the IRIS. TIGHT JUNCTIONS joining adjacent cells keep the barrier between cells continuous.Sex Differentiation: The process in developing sex- or gender-specific tissue, organ, or function after SEX DETERMINATION PROCESSES have set the sex of the GONADS. Major areas of sex differentiation occur in the reproductive tract (GENITALIA) and the brain.Orchiectomy: The surgical removal of one or both testicles.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.Fertility: The capacity to conceive or to induce conception. It may refer to either the male or female.Ovary: The reproductive organ (GONADS) in female animals. In vertebrates, the ovary contains two functional parts: the OVARIAN FOLLICLE for the production of female germ cells (OOGENESIS); and the endocrine cells (GRANULOSA CELLS; THECA CELLS; and LUTEAL CELLS) for the production of ESTROGENS and PROGESTERONE.Sex-Determining Region Y Protein: A transcription factor that plays an essential role in the development of the TESTES. It is encoded by a gene on the Y chromosome and contains a specific HMG-BOX DOMAIN that is found within members of the SOX family of transcription factors.Zonula Occludens-1 Protein: A 195-kDa zonula occludens protein that is distinguished by the presence of a ZU5 domain at the C-terminal of the molecule.DNA, Complementary: Single-stranded complementary DNA synthesized from an RNA template by the action of RNA-dependent DNA polymerase. cDNA (i.e., complementary DNA, not circular DNA, not C-DNA) is used in a variety of molecular cloning experiments as well as serving as a specific hybridization probe.Seminal Vesicles: A saclike, glandular diverticulum on each ductus deferens in male vertebrates. It is united with the excretory duct and serves for temporary storage of semen. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)In Situ Hybridization: A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes.Electric Impedance: The resistance to the flow of either alternating or direct electrical current.Blood-Nerve Barrier: The barrier between the perineurium of PERIPHERAL NERVES and the endothelium (ENDOTHELIUM, VASCULAR) of endoneurial CAPILLARIES. The perineurium acts as a diffusion barrier, but ion permeability at the blood-nerve barrier is still higher than at the BLOOD-BRAIN BARRIER.Sex Determination Processes: The mechanisms by which the SEX of an individual's GONADS are fixed.Follicle Stimulating Hormone: A major gonadotropin secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Follicle-stimulating hormone stimulates GAMETOGENESIS and the supporting cells such as the ovarian GRANULOSA CELLS, the testicular SERTOLI CELLS, and LEYDIG CELLS. FSH consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity.Gonads: The gamete-producing glands, OVARY or TESTIS.Sertoli Cell Tumor: Gonadal neoplasm composed entirely of SERTOLI CELLS or may have a component of GRANULOSA CELLS. Some of the Sertoli cell tumors produce ESTROGEN or ANDROGENS, but seldom in sufficient quantity to cause clinical symptoms such as FEMINIZATION or masculinization (VIRILISM).Cell Membrane Permeability: A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Orchiopexy: A surgical procedure in which an undescended testicle is sutured inside the SCROTUM in male infants or children to correct CRYPTORCHIDISM. Orchiopexy is also performed to treat TESTICULAR TORSION in adults and adolescents.Gene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Dibutyl Phthalate: A plasticizer used in most plastics and found in water, air, soil, plants and animals. It may have some adverse effects with long-term exposure.Mice, Inbred C57BLTime Factors: Elements of limited time intervals, contributing to particular results or situations.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Blotting, Northern: Detection of RNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.Health Services Accessibility: The degree to which individuals are inhibited or facilitated in their ability to gain entry to and to receive care and services from the health care system. Factors influencing this ability include geographic, architectural, transportational, and financial considerations, among others.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.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.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Reproduction: The total process by which organisms produce offspring. (Stedman, 25th ed)Luteinizing Hormone: A major gonadotropin secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Luteinizing hormone regulates steroid production by the interstitial cells of the TESTIS and the OVARY. The preovulatory LUTEINIZING HORMONE surge in females induces OVULATION, and subsequent LUTEINIZATION of the follicle. LUTEINIZING HORMONE consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH and FSH), but the beta subunit is unique and confers its biological specificity.Epidermis: The external, nonvascular layer of the skin. It is made up, from within outward, of five layers of EPITHELIUM: (1) basal layer (stratum basale epidermidis); (2) spinous layer (stratum spinosum epidermidis); (3) granular layer (stratum granulosum epidermidis); (4) clear layer (stratum lucidum epidermidis); and (5) horny layer (stratum corneum epidermidis).Seminoma: A radiosensitive, malignant neoplasm of the testis, thought to be derived from primordial germ cells of the sexually undifferentiated embryonic gonad. There are three variants: classical (typical), the most common type; anaplastic; and spermatocytic. The classical seminoma is composed of fairly well differentiated sheets or cords of uniform polygonal or round cells (seminoma cells), each cell having abundant clear cytoplasm, distinct cell membranes, a centrally placed round nucleus, and one or more nucleoli. In the female, a grossly and histologically identical neoplasm, known as dysgerminoma, occurs. (Dorland, 27th ed)Testicular Hormones: Hormones produced in the testis.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.Claudins: A large family of transmembrane proteins found in TIGHT JUNCTIONS. They take part in the formation of paracellular barriers and pores that regulate paracellular permeability.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.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.Animals, Newborn: Refers to animals in the period of time just after birth.Meiosis: A type of CELL NUCLEUS division, occurring during maturation of the GERM CELLS. Two successive cell nucleus divisions following a single chromosome duplication (S PHASE) result in daughter cells with half the number of CHROMOSOMES as the parent cells.Varicocele: A condition characterized by the dilated tortuous veins of the SPERMATIC CORD with a marked left-sided predominance. Adverse effect on male fertility occurs when varicocele leads to an increased scrotal (and testicular) temperature and reduced testicular volume.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Spermatic Cord: Either of a pair of tubular structures formed by DUCTUS DEFERENS; ARTERIES; VEINS; LYMPHATIC VESSELS; and nerves. The spermatic cord extends from the deep inguinal ring through the INGUINAL CANAL to the TESTIS in the SCROTUM.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.Inhibins: Glycoproteins that inhibit pituitary FOLLICLE STIMULATING HORMONE secretion. Inhibins are secreted by the Sertoli cells of the testes, the granulosa cells of the ovarian follicles, the placenta, and other tissues. Inhibins and ACTIVINS are modulators of FOLLICLE STIMULATING HORMONE secretions; both groups belong to the TGF-beta superfamily, as the TRANSFORMING GROWTH FACTOR BETA. Inhibins consist of a disulfide-linked heterodimer with a unique alpha linked to either a beta A or a beta B subunit to form inhibin A or inhibin B, respectivelySOX9 Transcription Factor: A SOXE transcription factor that plays a critical role in regulating CHONDROGENESIS; OSTEOGENESIS; and male sex determination. Loss of function of the SOX9 transcription factor due to genetic mutations is a cause of CAMPOMELIC DYSPLASIA.Mice, Hairless: Mutant strains of mice that produce little or no hair.Genes, sry: The primary testis-determining gene in mammalians, located on the Y CHROMOSOME. It codes for a high mobility group box transcription factor (TRANSCRIPTION FACTORS) which initiates the development of the TESTES from the embryonic GONADS.Diethylhexyl Phthalate: An ester of phthalic acid. It appears as a light-colored, odorless liquid and is used as a plasticizer for many resins and elastomers.Claudin-5: A claudin subtype that is found localized to TIGHT JUNCTIONS in VASCULAR ENDOTHELIAL CELLS. The protein was initially identified as one of several proteins which are deleted in VELOCARDIOFACIAL SYNDROME and may play an important role in maintaining the integrity of the BLOOD-BRAIN BARRIER.Intestinal Mucosa: Lining of the INTESTINES, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. In the SMALL INTESTINE, the mucosa is characterized by a series of folds and abundance of absorptive cells (ENTEROCYTES) with MICROVILLI.