Novel mutations in the HPS1 gene among Puerto Rican patients.

Hermansky-Pudlak syndrome (HPS) is a disorder of oculocutaneous albinism (OCA) and platelet storage pool deficiency. Eight different disease-causing genes have been identified, whose gene products are thought to be involved in the biogenesis of lysosome-related organelles. HPS type 1 (HPS-1) is the most common HPS subtype in Puerto Rico, with a frequency of 1:1800 in the northwest of the island due to a founder mutation, i.e. a 16-bp duplication in exon 15 of the HPS1 gene (c.1472_1487dup16; p.H497QfsX90). We identified three Puerto Rican HPS-1 patients who carried compound heterozygous HPS1 mutations. One patient was heterozygous for c.937G>A, causing a missense mutation (p.G313S) at the 3 splice junction of exon 10. This mutation resulted in activation of a cryptic intronic splice site causing an aberrantly spliced HPS1 mRNA that included 144-bp of intronic sequence, producing 11 novel amino acids followed by a stop codon. The other two patients were heterozygous for the previously reported c.972delC in HPS1, resulting in a frameshift and a premature stop codon (p.M325WfsX6). These findings indicate that, among Puerto Ricans, other HPS1 mutations apart from the 16-bp duplication should be considered in the analysis of this population.

Clinical and cellular characterisation of Hermansky-Pudlak syndrome type 6.

BACKGROUND: In the last decade, Hermansky-Pudlak syndrome (HPS) has arisen as an instructive disorder for cell biologists to study the biogenesis of lysosome related organelles (LROs). Of the eight human HPS subtypes, only subtypes 1 through 5 are well described. AIM: To characterise extensively the HPS-6 subtype, caused by defects in HPS6, a subunit of the biogenesis of lysosome related organelles complex-2 (BLOC-2). METHODS: Mutation analysis for the HPS6 gene was performed on DNA from our group of unclassified HPS patients. The clinical phenotype of patients with HPS6 mutations was then carefully ascertained, and their cultured dermal melanocytes were employed for cellular immunofluorescence studies. RESULTS: Molecular studies showed a variety of mutations in the single exon HPS6 gene, including frame shift, missense, and nonsense mutations as well as a approximately 20 kb deletion spanning the entire HPS6 genomic region. Cellular studies revealed that the melanogenic proteins tyrosinase and tyrosinase related protein 1 failed to be efficiently delivered to the melanosomes of HPS-6 patients, explaining their hypopigmentation. Clinical studies indicated that HPS-6 patients exhibit oculocutaneous albinism and a bleeding diathesis. Importantly, granulomatous colitis and pulmonary fibrosis, debilitating features present in HPS subtypes 1 and 4, were not detected in our HPS-6 patients. CONCLUSION: The HPS-6 subtype resembles other BLOC-2 defective subtypes (that is, HPS-3 and HPS-5) in its molecular, cellular and clinical findings. These findings are not only important for providing a prognosis to newly diagnosed HPS-6 patients, but also for further elucidation of HPS function in the biogenesis of LROs.

Ulysses radio and plasma wave observations in the jupiter environment.

The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded new evidence of whistler-mode radiation within the magnetosphere. Observations of aurorallike hiss provided evidence of a Jovian cusp. The source direction and polarization capabilities of URAP have demonstrated that the outer region of the lo plasma torus supported at least five separate radio sources that reoccurred during successive rotations with a measurable corotation lag. Thermal noise measurements of the lo torus densities yielded values in the densest portion that are similar to models suggested on the basis of Voyager observations of 13 years ago. The URAP measurements also suggest complex beaming and polarization characteristics of Jovian radio components. In addition, a new class of kilometer-wavelength striated Jovian bursts has been observed.

Augmentation of hematoporphyrin uptake and in vitro-growth inhibition of L1210 leukemia cells by succinylacetone.

Succinylacetone (SA; 4,6-dioxoheptanoic acid), a specific inhibitor of delta-aminolevulinic acid dehydrase (ALAD) (the second enzyme of the heme biosynthetic pathway), was tested for its effect in L1210 cells from inbred DBA/2 mice. ALAD from broken L1210 cells was completely inhibited by 1 microM SA, but in whole cells activity was decreased only 83% after incubation of the cells with 2.5 mM SA for 3 days. When incubated with hematoporphyrin (HP), L1210 cells rapidly took up porphyrin from the medium, and this uptake could be augmented by pretreatment of the cells with SA; but this enhancement of porphyrin uptake occurred gradually over a period of days. When SA-treated and untreated L1210 cells were incubated with increasing concentrations of HP in the medium, SA-treated cells reached the saturation concentration of cellular porphyrin at lower medium HP concentrations than did untreated cells. Growth of L1210 cells could be inhibited by 2 mM SA or more. Addition of increasing amounts of serum to cultures of cells containing SA did not reverse the growth inhibition due to SA. Porphyrin uptake from HP in the medium in nonmalignant fibroblast line 3T3 was much lower than in L1210 cells and could not be enhanced by incubation of the cells with SA.

Uptake of hematin and growth of malignant murine erythroleukemia cells depleted of endogenous heme by succinylacetone.

Heme levels and growth of malignant murine erythroleukemia cells in heme-free medium are drastically reduced by incubation of these cells in the presence of 4,6-dioxoheptanoic acid [succinylacetone (SA)]. When hematin was added to the culture medium of heme-depleted cells, the intracellular heme levels returned to normal, and growth inhibition produced by SA was also reversed. However, when cells depleted of heme by growth in heme-free medium containing SA were placed in heme-free medium without SA, heme levels were restored to normal, and growth was resumed. Hematin uptake in both untreated and heme-depleted malignant murine erythroleukemia cells exhibited biphasic kinetics, with a rapid phase of about 2 min followed by a slower uptake. The rate of uptake of exogenous hematin was slightly greater at 37 degrees than at 20 degrees. Although supplementation of heme-free medium with exogenous hematin increased total cellular heme in both untreated and heme-depleted malignant murine erythroleukemia cells, the fraction of heme in the 20,000 X g sediment was unaffected. A nonmalignant fibroblastic cell line, 3T3, exhibited little or no capacity to take up exogenous hematin.

Sertoli cells are capable of proliferation into adulthood in the transition region between the seminiferous tubules and the rete testis in Wistar rats.

Sertoli cells (SCs) play a crucial role in testis differentiation, development and function, determining the magnitude of sperm production in sexually mature animals. For over 40 years, it has been considered that these key testis somatic cells stop dividing during early pre-pubertal phase, between around 10 to 20 days after birth respectively in mice and rats, being after that under physiological conditions a stable and terminally differentiated population. However, evidences from the literature are challenging this dogma. In the present study, using several important functional markers (Ki-67, BrdU, p27, GATA-4, Androgen Receptor), we investigated the SC differentiation status in 36 days old and adult Wistar rats, focusing mainly in the transition region (TR) between the seminiferous tubules (ST) and the rete testis. Our results showed that SCs in TR remain undifferentiated for a longer period and, although at a lesser degree, even in adult rats proliferating SCs were observed in this region. Therefore, these findings suggest that, different from the other ST regions investigated, SCs residing in the TR exhibit a distinct functional phenotype. These undifferentiated SCs may compose a subpopulation of SC progenitors that reside in a specific microenvironment capable of growing the ST length if needed from this particular testis region. Moreover, our findings demonstrate an important aspect of testis function in mammals and opens new venues for other experimental approaches to the investigation of SC physiology, spermatogenesis progression and testis growth. Besides that, the TR may represent an important site for pathophysiological investigations and cellular interactions in the testis.

The Sertoli cell: one hundred fifty years of beauty and plasticity.

It has been one and a half centuries since Enrico Sertoli published the seminal discovery of the testicular 'nurse cell', not only a key cell in the testis, but indeed one of the most amazing cells in the vertebrate body. In this review, we begin by examining the three phases of morphological research that have occurred in the study of Sertoli cells, because microscopic anatomy was essentially the only scientific discipline available for about the first 75 years after the discovery. Biochemistry and molecular biology then changed all of biological sciences, including our understanding of the functions of Sertoli cells. Immunology and stem cell biology were not even topics of science in 1865, but they have now become major issues in our appreciation of Sertoli cell's role in spermatogenesis. We end with the universal importance and plasticity of function by comparing Sertoli cells in fish, amphibians, and mammals. In these various classes of vertebrates, Sertoli cells have quite different modes of proliferation and epithelial maintenance, cystic vs. tubular formation, yet accomplish essentially the same function but in strikingly different ways.

Small tubules, surprising discoveries: from efferent ductules in the turkey to the discovery that estrogen receptor alpha is essential for fertility in the male.

Efferent ductules are small, delicate tubules that connect rete testis with the head of the epididymis, first identified by de Graaf in 1668. Although difficult to find in routine dissection, the ductules are an essential component of the male reproductive tract and in larger mammals occupy up more than 50% of the caput epididymidis. My introduction to research began with the study of efferent ductules in the domestic turkey, and to my surprise these small structures with kidney-like function become the core for numerous discoveries throughout my scientific career. In this review, only two discoveries that I found interesting will be discussed: cilia that line the efferent ductule lumen and estrogen receptors that play an essential role in regulating fluid reabsorption. A potential link between these two discoveries was uncovered in the study of efferent ductule effects observed in the estrogen receptor knockout mouse and following toxic exposure to the fungicide benomyl.

The ultrastructure of collagen in the dermis of tight-skin (Tsk) mutant mice.

A recently discovered dominant mutation in C57/B10 mice called tight-skin (Tsk) results in hypertrophy of certain collagenous tissues including the dermis and hypodermis. The skin of heterozygotes (Tsk/+) is indurated and substantially stiffer than that of the normal animals (+/+). In this study, an electron microscopical comparison of the skin of these animals revealed that the fibrous architecture of the hypertrophic reticular dermis of Tsk/+ mice is more disorganized than that of the +/+ mice and in many areas, the collagen fibrils are more densely packed. The abundance of fibroblasts with distended endoplasmic reticulum in both the dermis and hypodermis of Tsk/+ mice is consistent with increased collagen synthesis. Several of the changes in the dermis and hypodermis of the Tsk/+ mice are similar to changes reported in sclerodermatous skin of man. Surprisingly, an apparent abnormality in the morphology of some of collagen fibrils in the skin of Tsk/+ mice was found to be at least as prevalent in the "normal" +/+ mice. The reticular dermis of both animals contain scattered fibrils which are much larger in diameter than normal and often have a twisted appearance resulting from either helical grooves in the surface of the fibril or discrete branches which twist about one another.

Estrogen receptor expression in developing epididymis, efferent ductules, and other male reproductive organs.

The distribution of estrogen receptors (ER) in developing reproductive organs of male BALB/c mice was determined by 3H-estradiol steroid autoradiography. Efferent ductules, urogenital sinus and Wolffian ducts, and their derivatives, the epididymis, ductus deferens, seminal vesicles, coagulating glands, prostate, and bulbouretheral glands (BUGs), were examined from 16 days fetal (gestation = 19-20 days) to 10 days postnatal. All fetal reproductive organs strongly expressed mesenchymal ER. Stromal cells of these organs remained ER+ at later times. However, smooth muscle cells in organs such as the ductus deferens, BUG, prostate, and caudal epididymis were only weakly ER+ or ER- after their differentiation from mesenchyme, although fibroblasts interspersed within the smooth muscle remained strongly ER+. Efferent ductules were the first site of epithelial ER expression in the developing male tract; this organ expressed epithelial ER on day 16 of gestation and subsequently. Wolffian ducts and urogenital sinus did not contain epithelial ER on day 16 of gestation. Epididymis began expressing epithelial ER soon after its differentiation, on day 19 of gestation. A clear gradient of ER expression was noted in the regions of the developing epididymis, with the efferent ducts and the initial segment of the epididymis containing 3-fold more silver grains per epithelial cell than more distal regions of the epididymis. Epithelium of the seminal vesicle and coagulating gland was initially ER-, but became weakly ER+ at day 6 postnatal and later. The epithelium of all other organs (ductus deferens, prostate, and BUGs) never expressed ER at any time.

Increased sperm production in adult rats after transient neonatal hypothyroidism.

In the preceding paper it was shown that transient neonatal hypothyroidism induced by treatment of rats from birth to day 25 with the goitrogen 6-propyl-2-thiouracil (PTU) is associated with increases in testis wt and DNA content of up to 80% during adulthood. The testis changes were accompanied by similar, though less marked, increases in the wt and DNA content of epididymis and accessory organs. The purpose of this study was to assess sperm production in these enlarged testes and measure changes in sperm reserves in the epididymis. Testes and epididymides were obtained from control rats or rats given PTU from birth to day 25 (designated "treated") at 90, 135, 160, and 180 days of age. Daily sperm production (DSP), efficiency of sperm production (DSP/g testis), and epididymal sperm reserves were measured in all animals. Compared to controls, DSP of the treated rats was increased by 83%, 86%, 136%, and 132% at 90, 135, 160, and 180 days, respectively. Thus, in the treated rats, DSP, like testis wt, plateaued at day 160. In addition, efficiency of sperm production was increased by 15%-30% at all ages in treated animals. Epididymal sperm reserves were also increased in treated rats at all ages, but the correlation between DSP and epididymal sperm reserves was weak. Sperm motility and concentration in caudal epididymal fluid of adult males treated from birth to day 25 with PTU were normal. These males were fertile and sired litters in which pup wt and pup number were normal. These results indicate that neonatal hypothyroidism in rats is associated not only with increased testis size but also with increased efficiency of sperm production, resulting in increases in DSP of up to 140% in these animals during adulthood. Maximal sperm production is reached at 160 days of age in treated rats (compared to 100 days in controls), coinciding with the attainment of final testicular size. This system represents the first experimental model in which such large increases in sperm production can be produced. The neonatal PTU treatment does not appear to impair fertility or alter sperm characteristics when these animals become adults and may be a useful system with which to study factors which normally regulate sperm production.

Adult testicular enlargement induced by neonatal hypothyroidism is accompanied by increased Sertoli and germ cell numbers.

Our previous studies have shown that transient neonatal hypothyroidism, induced by treatment with the reversible goitrogen 6-propyl-2-thiouracil (PTU), increases testicular size and daily sperm production in the adult rat by up to 82% and 136%, respectively. The objective of the present study was to examine morphological and functional changes in adult seminiferous tubules associated with PTU-induced increases in testicular size and sperm production. Sprague-Dawley rats were treated with PTU from birth to day 25 or left untreated; for morphometry, all testes were fixed by vascular perfusion at 90 days of age. Although testicular weight was increased 62% in treated rats, gross pathological changes were not evident in these organs, and spermatogenesis appeared morphologically normal. The percent area of testis occupied by seminiferous tubules was equal in control and treated testes, but mean seminiferous tubule diameter and length were increased in the PTU-treated testis. The adult number of Sertoli cells in treated testes was increased by 157%, and the numbers of leptotene spermatocytes and round spermatids were increased 84% and 93%, respectively. These results demonstrate that increases in Sertoli cell numbers result in increased sperm production and support the idea that Sertoli cells are the major regulators of the magnitude of sperm production. Although the round spermatid to Sertoli cell ratio was reduced by nearly 30%, the number of round spermatids per g testis was increased by 14%. This increased efficiency of sperm production was accomplished by an increased density of Sertoli cells along the basement membrane and an increased height of the seminiferous epithelium. Despite the large increase in Sertoli cell numbers in treated rats, Northern blot analysis using Sertoli cell-specific cDNA probes for transferrin and androgen-binding protein indicated that relative steady state levels of mRNAs per Sertoli cell for these two secretory proteins were similar in control and treated rats at 90 days of age.

Leydig cells increase their numbers but decline in steroidogenic function in the adult rat after neonatal hypothyroidism.

Administration of the goitrogen, 6-propyl-2-thiouracil (PTU), to suckling rat pups from birth through day 24 postpartum as a 0.1% solution in the mother's drinking water increases adult testis size and sperm production by about 80% and 140%, respectively, without affecting peripheral testosterone levels. The objectives of this study were to determine whether adult Leydig cell numbers were altered in PTU-treated rats and whether the steroidogenic function of these cells was normal. The number of Leydig cells per testis at 180 days increased by 69% in PTU-treated compared to control rats, whereas the average Leydig cell volume declined by about 20%. Steroidogenic function assessed in isolated adult Leydig cells decreased after neonatal PTU treatment. LH-stimulated testosterone production was reduced by 55% in Leydig cells from treated rats, commensurate with a 50% decline in the number of hCG-binding sites in these cells. The difference in steroidogenic potential was even more striking after incubations with saturating concentrations of steroid substrate, 22(R)-hydroxycholesterol; Leydig cells from treated males produced 73% less testosterone than controls. Therefore, this decrease in testosterone production may be partially due to a reduction in the numbers of LH receptors, but also reflects the impaired steroidogenic potential of these cells. These results clearly show that the dramatic increase in adult Leydig cell number after neonatal PTU treatment is counterbalanced by a permanent decline in Leydig cell steroidogenic function, producing no net change in peripheral testosterone levels.

The differential fate of mesonephric tubular-derived efferent ductules in estrogen receptor-alpha knockout versus wild-type female mice.

We investigated mesonephric tubular-derived efferent ductules in female wild-type (WT) and estrogen receptor-alpha knockout (ERalphaKO) mice from late fetal to adult life. On gestational day 17, efferent ductules in both fetal WT and ERalphaKO females were well developed and morphologically similar, although one third the size of the male counterpart. Unexpectedly, efferent ductules with a ciliated epithelium were still present on postnatal day 10 in WT and ERalphaKO females. By day 23, however, marked phenotypic differences occurred in efferent ductules of WT and ERbetaKO vs. ERalphaKO female mice. In the latter, efferent ductules became hypertrophied and dilated, whereas only small tubules remained in WT and ERbetaKO adult mice. The serum testosterone concentrations were similar in 21- to 25-day-old ERalphaKO, heterozygous, and WT female mice, suggesting that increased testosterone was not inducing enlargement of efferent ductules in ERalphaKO females. In conclusion, remnants of efferent ductules persisted in normal adult female mice, although these structures were greatly reduced in size compared with efferent ductules in ERalphaKO female mice. The underlying mechanism inducing hypertrophy and dilation of efferent ductules in ERalphaKO females is not clear, but secretory and/or reabsorptive function of female efferent ductules may involve ERalpha.

Germ cells of the mouse testis express P450 aromatase.

Estrogen production within the testis has been a subject of considerable controversy for many years. Several studies have shown that both Sertoli and Leydig cells produce estrogen during different stages of development. Therefore, we have conducted experiments to localize aromatase, a cytochrome P450 enzyme that converts androgen to estrogen, within the testis. First, P450 aromatase (P450arom) was localized in germ cells of the adult mouse testis by immunocytochemistry, using an antiserum generated against purified human placental cytochrome P450arom. In the germinal epithelium, P450arom was located primarily in the Golgi region of round spermatids, throughout the cytoplasm of elongating spermatids, and along the flagella of late spermatids. Second, localization of P450arom within the germinal epithelium was supported by Western blot analysis of isolated germ cells. Third, Northern blot analysis using a mouse P450arom cDNA probe indicated that the mRNA for the mouse P450arom was present in testicular germ cells. Fourth, P450arom activity was measured in germ cells by the 3H2O water assay. Based upon these observations, we conclude that germ cells are a site of estrogen synthesis in the adult mouse testis.

Developmental hormonal profiles accompanying the neonatal hypothyroidism-induced increase in adult testicular size and sperm production in the rat.

Neonatal treatment with the reversible goitrogen 6-N-propyl-2-thiouracil (PTU) results in a near doubling of testicular size and a 25% increase in the efficiency of spermatogenesis, without affecting circulating testosterone (T) levels in adult rats. The objectives of the present study were to examine the effects of neonatal PTU treatment on the pattern of testicular growth and circulating levels of anterior pituitary (FSH, LH, PRL, GH, and TSH), gonadal [immunoreactive inhibin-alpha (irI alpha) and T], and thyroid (T3 and T4) hormones over the first 100 days of life. Treatment of rats with PTU from birth to 24 days of age significantly reduced testicular weights between 10 and 60 days of age. However, the duration of testicular growth was extended in treated males, resulting in a 68% increase at 100 days of age. Serum gonadotropin levels in treated males were reduced throughout the experimental period, typically remaining between 50-70% of control levels. The characteristic robust prepubertal FSH peak was absent in PTU-treated males. Initially high until 20 days of age, irI alpha levels characteristically declined to adult levels (200-300 pg/ml) in control males. In treated males, irI alpha levels were reduced during the period of hypothyroidism, increased between 30 and 60 days, and then declined, but remained significantly higher (1.7- to 2-fold greater) than those observed in control males. Serum T levels were similar in treated and control males. Control males demonstrated increased T levels beginning at 45 days of age, earlier than observed in treated males; however, similar peak T levels were observed in all males. PTU treatment significantly suppressed serum GH and PRL and led to a 14-fold increase in circulating TSH during the period of treatment. However, unlike the gonadotropins, these hormones returned to control levels after PTU treatment, suggesting that the reduced levels of FSH and LH observed are not due to a generalized reduction in pituitary function. Serum T4 and T3 levels returned to control levels within 15 days after the removal of PTU. These results demonstrate that the neonatal PTU treatment-induced increases in adult testicular size and sperm production were not due to increased levels of FSH at any point in development. On the contrary, the observed increases occur in spite of chronically reduced FSH levels.

Hematin therapy for acute porphyria.

1. A therapeutic trial of intravenous hematin is presented. Eleven cases of AIP and one of VP who did not improve with conventional treatment (high carbohydrate intake) received this new agent. 2. Urinary ALA, PBG and, when possible, uroporphyrin and coproporphyrin were used to monitor the chemical response to the treatment. Objective clinical parameters of hypertension and tachycardia were followed when present in addition to subjective estimates of acute porphyric symptomatology (abdominal pain, backache, extremity pain and paresthesias, weakness, depression, etc.). 3. At a dosage of approximately 3 mg/kg, diminution of urinary ALA and PBG excretion was achieved in every patients. Hypertension and tachycardia improved in those instances where they were observed in association with the attack. Also, subjective improvements in the clinical status of the patients were observed frequently. 4. Hematin appears to be a promising therapeutic agent for the treatment of acute attack forms of porphyria.

Grand mal seizures and acute intermittent porphyria. The problem of differential diagnosis and treatment.

A 36-year-old white man had both acute intermittent porphyria and long-standing idiopathic grand mal seizures. Diphenylhydantoin apparently adversely affected both the clinical and biochemical parameters of the acute intermittent porphyria. Comparison of urinary levels of the porphyrin precursors, delta aminolevulinic acid and porphobilinogen, under controlled diet conditions before and after withdrawal of diphenylhydantoin, showed that this drug accounted for approximately one-half of the porphyrin precursor excretion. Significant clinical improvement of the porphyria followed withdrawal of the diphenylhydantoin. Bromides appeared to be approximately as effective as diphenylhydantoin for seizure control in this patient.

Oestrogen, its receptors and function in the male reproductive tract - a review.

Oestrogen is synthesized in the male reproductive system by at least three different cell types; Sertoli, Leydig and germ cells. Although testosterone is recognized as the primary sex steroid in man, oestrogen is produced in sizable quantities in the testis, as well as the brain and is found in extremely high concentrations in the semen of several species. The high concentration of oestrogen in rete testis fluid of the rodent is now thought to be derived from the conversion of testosterone to estradiol by P450 aromatase in germ cells of the testis and spermatozoa traversing the reproductive tract. This new major source of oestrogen would target oestrogen receptors in the male reproductive tract, in particular the efferent ductules, which contain the highest concentration of oestrogen receptor-alpha. This recent data raises new hypotheses regarding the role of oestrogen in the function of the male reproductive system. The oestrogen receptor-alpha knockout mouse was used to help define the function of oestrogen in the male. It was found that oestrogen receptor-alpha is essential for fluid reabsorption in the efferent ductules and in the absence of expression the male is infertile.

Sperm, a source of estrogen.

This review article discusses a novel nontraditional site of estrogen synthesis and the potential targets of estrogen action within the male reproductive system. Our laboratories have recently demonstrated that developing spermatids in several species contain aromatase, the cytochrome P450 enzyme responsible for converting androgens into estrogens. The enzyme was localized by immunocytochemistry and the protein's presence was confirmed by Western blot analysis. Northern blot analysis and in situ hybridization were used to corroborate the presence of mRNA for aromatase. It appears that the aromatase message precedes the synthesis of the protein, and the protein remains in the spermatids several days after the message disappears. The enzyme is located along the tail of newly released sperm and is active in the epididymal sperm as well as in the developing germ cells of the testis. This unique discovery is the basis for our overall hypothesis that estrogen, synthesized by sperm, plays a role in the regulation of epididymal function proportional to the number of sperm being transported. The presence of an estrogen source within the ductal lumen is of special importance to the study of epididymal function because the regulatory mechanisms in this region remain unclear, particularly for the efferent ductules and initial segment regions, although estrogen receptors have been identified in the ductal epithelium. An understanding of the role that estrogen plays in the function of the epididymis may provide benefits in several areas including the treatment of abnormalities in epididymal function, the potential development of a male contraceptive, and insight into the causes of adult epididymal lesions induced by neonatal exposure to estrogenic compounds such as diethylstilbestrol.