The Connection between the Seminiferous Tubules and the Rete Testis in the Domestic Fowl (Gallus Domesticus) Morphological Study

The tubules connecting the seminiferous tubules proper to the rete testis in the fowl were studied with the aid of light and electron microscopy. The material examined ultrastructurally was fixed by vascular perfusion through the thoracic aorta. The seminiferous tubules were joined to the rete testis in three different ways; they were either linked by a terminal segment and a tubulus rectus, by a terminal segment only, or opened directly into the rete cavities. The terminal segment of the seminiferous tubules was lined with columnar cells (modified Sertoli cells). These cells were characterized by having an indented nucleus with a prominent nucleolus, many mitochondria, a sizable Golgi apparatus, electron dense bodies and many cytoplasmic protrusions into the lumen. Intraepithelial lymphocytes as well as macrophages in the lumina of the terminal segment, the tubuli recti and the rete testis were also observed. Myoid cells were found in the boundary tissue of the terminal segment.     

Effect of Testosterone on Development of the Lumen in Seminiferous Tubules of the Rat*

Der Einfluß von Testosteron auf die Entwicklung des Lumens der Tubuli seminiferi der Ratte Obwohl systemisch zugeführtes Testosteron die postnatale Reifung der Bestandteile in den Tubuli seminiferi von hypophysektomierten Ratten und Mäusen beeinflussen kann, löst es nicht dieselbe Entwicklungsstufe aus, die bei gesunden, normalen Kontrolltieren beobachtet wird. Im Hinblick auf Berichte einer frühzeitigen Spermatogenese-Entwicklung bei androgenproduzierenden Leydig-Zelltumoren war die vorliegende Studie darauf angelegt, zu analysieren, ob hohe Lokalwerte von Testosteron die Entwicklung der Tubuli seminiferi beschleunigen kann. Hierzu wurden Testosteronpellets unter die Tunica albuginea des rechten Hodens von 7 Tage alten Ratten implantiert. Nach 17, 23 und 28 Lebenstagen war die Entwicklung der Tubuli seminiferi, wie aus der Formation des Tubuluslumens geschlossen wurde, weiter ausgedehnt bei den behandelten Hoden als bei den kontralateralen und scheinoperierten Kontrollen. Der Tubulusdurchmesser war nicht unbedingt mit der Lumen-Formation korreliert. Die Untersuchung demonstriert nach Ansicht der Autoren, daß hohe Lokal-Werte von Testosteron die Entwicklung der Tubuli seminiferi der Ratte beschleunigte; das bedeutet, daß der Tubulusdurchmesser keine gültige Basis für die Beurteilung der Entwicklung eines Hodens ist. Es wird die Schlußfolgerung gezogen, daß Testosteron diesen Effekt über seine Wirkung auf die Sertoli-Zellen bewirkt.     

The Terminal Segment of the Seminiferous Tubules and the Blood-Testis Barrier Before and After Efferent Ductule Ligation in the Rat

The ultrastructure of modified Sertoli cells in the terminal segment of the seminiferous tubules in the rat was studied in material fixed by perfusion through the thoracic or the abdominal aorta. The central lumen of the terminal segment was not distinct under normal conditions, but became quite evident with an increased intratesticular pressure caused by efferent ductule ligation. The modified Sertoli cells were characterized by a marked increase in number of microtubules and microfilaments, extensive inter-Sertoli cell junctions, vacuolated cytoplasm, and considerably dilated intercellular spaces. Three types of specialized cell contacts were found between modified Sertoli cells: typical inter-Sertoli cell junctions, desmosome-like devices, and septate-like tight junctions. These specialized cell contacts were efficient in preventing lanthanum to penetrate into the lumen of the terminal segment both before and after efferent ductule ligation. Moreover, it was found that typical inter-Sertoli cell junctions prevented lanthanum penetration into the adluminal compartment of the seminiferous tubules even after efferent ductule ligation.     

Scanning Electron Microscopy of Mechanically Isolated Seminiferous Tubules of the Rat Testis

Rasterelektronenmikroskopie von mechanisch isolierten Tubuli seminiferi des Rattenhodens
Mittels der Rasterelektronenmikroskopie wurden mechanisch isolierte Tubuli seminiferi des Rattenhodens eingehend untersucht. Es wird festgestellt, daß die Oberfläche der Tubuli aus lymphoiden Endothelzellen gebildet wird. Diese Zellen umgeben vollständig die Tubuli seminiferi und bilden das innere Futter des lymphatischen Zwischenraumes, der rundherum um den Tubulus seminiferus liegt. Zwischen den Zellen befinden sich Vertiefungen, die mit den Fenestrierungen korrespondieren, welche man in der Transmissionselektronenmikroskopie sieht.     

Functional and Structural Aspects of the Rat Seminiferous Tubules after Treatment with Exogenous Cyproterone Acetate, Testosterone, Progesterone and Oestradiol

Cyproterone acetate, testosterone propionate, progesterone and oestradiol were given to adult rats for 30 days, and the effects on the seminiferous tubules were studied. The contractility of the seminiferous tubules was not affected by cyproterone acetate or progesterone, but was totally abolished by testosterone and oestradiol. The effects of these steroids on spermatogenesis were studied histologically and electron microscopically.
Cyproterone acetate was observed to induce a clear-cut increase in the lipid content of the Sertoli cells and mitochondrial changes in all stages of the cycle of the seminiferous epithelium.
The increase of lipid content was smaller with progesterone. Oestradiol caused an accumulation of phagocytosed lipid material in Sertoli cells. These steroids did not change the protein composition of the rete testis fluid.     

The Mechanism of Transport of Testosterone through the Walls of the Seminiferous Tubules of the Rat Testis

A specific saturable carrier-mechanism probably involving facilitated diffusion has been shown to be involved in the transport of testosterone into seminiferous tubule fluid (STF) and rete testis fluid (RTF). This carrier does not transport DHT and its capacity for testosterone is not affected by increasing the concentration of DHT in the blood.     

A Quantitative Structural Model of the Testis of Fertile Males with Normal Sperm Counts

The morphology of testicular biopsies of 8 healthy fertile men with proven normal sperm counts was studied using stereological techniques. Quantitative estimations were made of different cellular compartments in the testicular biopsies. The experimental errors of observation, homogeneity of the section, accuracy of the measurements and errors caused during the preparation of the sections were studied. A stereological model of the human testis comprising all compartments was designed. The present observations on the stereological parameters were compared with the results in literature; generally a good agreement was found.
This stereological model enabled the authors to establish the quantitative correlations that exist between the separate compartments of the human testis. The tubular length density was positively correlated with the tubular surface density. The tubular surface density showed a negative correlation with the volume density of the germinal cell nuclei. The tubular volume density showed a negative correlation with the volume density of the Leydig cells. The intra-tubular volume density correlated negatively with the volume density of the Leydig cells and with the volume density of the remaining extra-tubular tissue. The intra-tubular tissue density correlated negatively with the volume density of the intra-tubular space.     

Hormonal Milieu of the Seminiferous Tubules in the Normal and Cryptorchid Rat

The intratesticular concentration of androgens seems to be of more importance for normal spermatogenesis than the concentration of androgens in the peripheral blood.
Therefore, the levels of testosterone, 5α - dihydrotestosterone (DHT), androstenedione and FSH in the interstitial fluid of the rat testis were determined by radioimmunoassay. The following concentrations were obtained from the interstitial fluid of normal rats and from rats cryptorchid between 60 and 90 days of age: Testosterone 137 ± 25 (mean ± SEM) and 271 ± 34 ng/ml, DHT 11 ± 2 and 22 ± 5 ng/ml, androstenedione 8 ± 2 and 20 ± 4 ng/ml, respectively. The sum of testosterone and DHT in serum did not differ in the two groups. Serum FSH concentrations were significantly increased in the cryptorchid rats (942 ± 73 ng/ml) as compared to the control rats (600 ± 38 ng/ml). These elevated levels were also found in the testicular interstitial fluid (425 ± 33 ng/ml in controls, 641 ± 43 ng/ml in cryptorchid rats). It is thus evident that in the cryptorchid rat, both FSH and androgens are available to the seminiferouse tubules in significantly elevated amounts. Since these are the only hormones which are known to be of importance in spermatogenesis, the impaired Sertoli cell function and depletion of germinal cells in cryptorchidism is not due to an absolute shortage of stimulatory hormones.     

On the Problem of the Phagocytic Capacity of Sertoli Cells Electron Microscopic Study in the Rat

Zum Problem der phagozytotischen Aktivität der Sertoli-Zellen Elektronenmikroskopische Studie bei der Ratte
Um die phagozytotische Aktivität der Sertolizelle zu untersuchen, wurden folgende Versuche angestellt: Kolloidale Kohle-Lösung oder Thoriumdioxyd mit einer Teilchengröße von 0,01–0,03 μm in einer 2%igen Lösung wurde über eine Infusionspumpe mit einer Geschwindigkeit von 50 μl pro min. in den Rattenhoden injiziert. Die Injektion wurde entweder in die intertubulären Zwischenräume unter der Tunica albuginea oder in das Lumen der Tubuli seminiferi verabfolgt. 30 bis 240 Minuten nach der Injektion wurde das Gewebe durch Perfusion mit 2% Glutaraldehyd fixiert und für die Elektronenmikroskopie eingebettet. Es ergab sich folgendes: 1) Partikel, welche in die intertubulären Zwischenräume injziert waren, konnten die Tubuluswand nicht durchdringen und wurden entweder von den Makrophagen des Bindegewebes phagozytiert oder über die Lymphgefäße abgeräumt. 2) Innerhalb der Tubuli seminiferi applizierte Partikel wurden von den Sertolizellen nicht phagozytiert und blieben im Lumen liegen. Das Verhalten der Sertolizellen war dem der Phagozyten nicht vergleichbar, da sie gegenüber den inerten Partikeln keine Phagozytose-Aktivität zeigten. Diese Resultate stimmen mit der Interpretation überein, wonach die fortlaufende Beseitigung von Zelltrümmern durch die Sertolizellen eher von einer autophagischen Auflösung als von einer Makrophagenphagozytose abhängig ist.     

Correlations between the Quantitative Morphology of the Human Testis and Sperm Production The Testis of Healthy Men with Normal Sperm Counts

Stereology was used as a morphometric method to study the testicular biopsies of 8 healthy volunteers with a proven fertility and normal sperm counts.
The geometrical mean of the sperm density and total sperm count of 2 semen samples were correlated with the measured and calculated stereological parameters. The volume density of the germinal cell nuclei ( r = 0.72) and the intra-tubular tissue volume density ( r = 0.81) were significantly correlated with the sperm density. A significant correlation was demonstrated between the total sperm count and the volume density of the germinal cell nuclei ( r = 0.71) and the volume density of the Leydig cells ( r =–0.70).
Using stepwise multiple regression analysis the prediction of the observed variance of the log sperm density was feasible ( r = 0.996; P = 0.0007) with 4 stereological parameters: the volume density of the germinal cell nuclei (positive correlation), the volume density of the tubular wall (negative correlation), the volume density of the Leydig cells (negative correlation) and the tubular surface density (positive correlation).
The observed variance of the log total sperm count was predicted ( r = 0.96; P = 0.003) with 3 stereological parameters: the volume density of the germinal cell nuclei (positive correlation), the volume density of the Leydig cells (negative correlation) and the volume density of the blood vessels (negative correlation).     

Specialized Cell Contacts and the Blood-testis Barrier in the Seminiferous Tubules of the Domestic Fowl (Gallus domesticus)

The ultrastructure of Sertoli-Sertoli and Sertoli-germ cell surface specializations in the domestic fowl was studied in material fixed by vascular perfusion through the thoracic aorta. Three main types of surface specializations were found between adjacent Sertoli cells. These are focal tight junctions, desmosome-like devices, and a specialization characterized by the presence of long and dilated subsurface cisternae of rough endoplasmic reticulum. Typical inter-Sertoli cell junctions similar to those of mammals were absent. Germ cells were attached to Sertoli cells mainly by desmosome-like devices of varying appearance. The junctions between Sertoli cells and elongating or elongated spermatids, "the mantle", consisted of only slight condensations of filamentous material in the Sertoli cell. The tight junctions between adjacent Sertoli cells were efficient in preventing lanthanum from passing towards the lumen beyond the level of the spermatogonia.     

On the Morphology of the Transitional Zone of the Seminiferous Tubule and the Rete Testis in Man

Die Morphologie der Übergangszonen zwischen Samenkanälchen und Rete testis beim Menschen
Die Übergangszonen zwischen den Tubuli seminiferi und den Tubuli recti des Rete testis beim Menschen wurden licht-und elektronenmikroskopisch untersucht.
Es ließen sich drei Anastomosierungstypen darstellen: End-zu-End-Anastomosen, End-zu-Seit-Anastomosen und Seit-zu-End-Anastomosen. Im Terminalsegment besteht das Keimepithel aus modifizierten Sertolizellen, zwischen denen vereinzelt Spermatogonien liegen. Das Tubuluslumen ist eng, die Lamina propria ist dick. Am Abschluß des Tubulus seminiferus sind die modifizierten Sertolizellen lippenartig in das Lumen des Tubulus rectus vorgewölbt. Die Sertolizellen des Terminalsegments sind gegenüber den normalen Sertolizellen charakteristisch verändert: die Zellkerne sind oval und glatt begrenzt, perinukleäre Einschlüsse fehlen, im apikalen Bereich des Zytoplasmas befinden sich zahlreiche Lipidtropfen und Residualkörper. Im gesamten Zytoplasma sind Mikrotubuli und Mikro-filamente vermehrt. Die Lamina propria besteht aus einer Basalmembran und aus unregelmäßig angeordneten Myofibroblasten, zwischen denen dicke Bündel kollagener Fibrillen das Terminalsegment ringförmig umschließen. Am Anfang der Tubuli recti findet man häufig ektopische Inseln des modifizierten Keimepithels, die um ein bindegewebiges Zentrum angeordnet sind.     

Ontogeny and cellular origin of an interleukin-1 -like factor in the reproductive tract of the male rat

We have recently isolated an interleukin-1 (IL-1)-like factor from the rat testis, which originates from the seminiferous tubules and is a protein with an MW of 17,000 and a pI of 5-6. This paper reports on the appearance of the IL-1-like factor during postnatal development and investigates its cellular origin further. IL-1 activity was measured by a murine thymocyte proliferation assay. Very low IL-1 activity was present in culture medium conditioned by seminiferous tubules from rats aged 10 or 20 days. From 30 days of age, increasing amounts were detected, reaching a maximum level in adult animals (60-90 days). No IL-1 activity was found in medium conditioned by peritubular cells. Sertoli cell-enriched seminiferous tubules obtained from experimentally cryptorchid or from prenatally irradiated rats produced much higher levels of IL-1 activity than did those obtained from intact testes. IL-1 activity was detected in efferent duct fluid after ligation of the efferent ducts for 24 h, indicating that the IL-1-like factor was secreted into the tubular lumen. Low levels of IL-1 activity were detected in extracts of epididymal tissue and epididymal sperm, whereas ejaculated seminal plasma, seminal vesicle fluid and extracts of seminal vesicles (together with the coagulating glands) and ventral and dorsolateral prostate lacked IL-1 activity. Instead, seminal plasma inhibited testicular IL-1 activity dose-dependently without affecting cell viability in the thymocyte cultures. Although its biological function remains to be defined, our results indicate that the testicular IL-1-like factor is produced by Sertoli cells and that its appearance during development coincides with the initiation of active spermatogenesis in the rat testis.     

Ontogeny and cellular origin of a rat seminiferous tubule factor(s) that inhibits LH-dependent testosterone production by interstitial cells in vitro

Previous studies have shown the presence of a peptide in spent media from incubated seminiferous tubules (SMST), which inhibits LH stimulation of testosterone production by rat Leydig cells in vitro. The present study has investigated whether the secretion of this inhibitor changes during development in the rat. Seminiferous tubules obtained from rats aged 10, 20, 25, 30, 35, 40, 42, 50 or 60 days were incubated at 32 degrees C for 24 h. Spent media from these incubations were then added to interstitial cells isolated from the testes of rats aged 60 days. Spent media from rats aged 10-30 days had no effect on basal or oLH-stimulated testosterone production by interstitial cells during 3-h incubation. Significant inhibition of LH-stimulated testosterone production was, however, observed with SMST from rats aged 35-60 days. Spent media prepared using tubules from normal, prenatally irradiated (Sertoli cell-enriched) or seminiferous tubules, depleted of peritubular cells, had no effect on basal, but inhibited LH-stimulated, testosterone production. Spent media from peritubular cell cultures had no effect on basal or LH-stimulated testosterone production by interstitial cells. The inhibitory effect of SMST was also dependent on the age of the rats providing the target cells. Interstitial cells from rats aged 10, 20, 50 or 60 days were responsive to the inhibitor while cells from rats aged 30 and 40 days were not. The results of the present study demonstrate that the seminiferous tubule factor(s), which inhibits LH action on interstitial cells, is first secreted at 35 days, a time when the most mature germ cells present are in the early maturation phase. Moreover, interstitial cells are responsive to this factor in both immature (10-20 day-old) and mature (50-60 day-old) rats, but not at ages in between these times. It is suggested that the adult Sertoli cell is the major source of the interstitial cell inhibitor.     

枸杞、黄芪对大鼠睾丸支持细胞功能的影响

目的:探讨中药枸杞、黄芪对大鼠睾丸支持细胞(Sertoli细胞)功能的作用及机制。方法:对18~22 d的SD大鼠睾丸Sertoli细胞进行分离培养,用MTT法检测枸杞(50、100、200、400μg/m l枸杞多糖)、黄芪(12.5、25、50、100 g/L黄芪提取液)对Sertoli细胞增殖的影响,用一步法RT-PCR方法检测枸杞、黄芪对正常培养状态和过氧化物(H2O2)损伤状态下Sertoli细胞抑制素(INH)βB亚基转录的影响。结果:高浓度枸杞(400μg/m l)、黄芪(100 g/L)对Sertoli细胞的增殖有促进作用(P<0.05),高浓度杞芪合剂(400μg/m l枸杞+100 g/L黄芪)对Sertoli细胞增殖有明显促进作用(P<0.01);在正常培养状态下,枸杞、黄芪及杞芪合剂对Sertoli细胞INHβB亚基的转录具有明显促进作用(P<0.01);在过氧化物(H2O2)损伤状态下,Sertoli细胞INHβB亚基的转录明显降低(P<0.01),黄芪对Sertoli细胞INHβB亚基的转录水平具有上调作用(P<0.05),枸杞、杞芪合剂对其转录水平具有明显上调作用(P<0.01)。结论:枸杞、黄芪及杞芪合剂对体外培养的Sertoli细胞INHβB亚基的转录具有促进和保护作用。