Studies on the morphology of the isolated perfused rabbit ovary

Summary Ovulation was induced in rabbits by intravenous administration of human chorionic gonadotrophin (HCG), and 4–5 h later the ovaries were isolated and introduced into an in-vitro perfusion system containing synthetic medium with albumin. Rupture of follicles occurred in vitro within the physiological time range (mean 11.3 h after injection of HCG), although with a reduced frequency. Preovulatory and ruptured follicles were studied in detail by light and electron microscopy.In the granulosa layer of ruptured or preovulatory follicles cytoplasmic blebbing activity, disappearance of CallExner bodies and differentiation toward luteinized cells were found. Perhaps the most important sign of normal preovulatory development in vitro was that the basement membrane surrounding the granulosa layer was penetrated by projections of granulosa cells. In the absence of this penetration phenomenon the granulosa layer prolapsed out of the follicle. Immediately before rupture, follicles showed marked degeneration, restricted to the outer layers of the apical wall, which is compatible with the hypothesis that degradative enzymes are released close to the surface of preovulatory follicles.Although the majority of follicles that ovulated under in-vitro conditions showed the same kind of morphological alterations as can be seen in vivo, occasional atypical ruptures occurred without any overt signs during perfusion. Also technical manipulations of the perfusion system, e.g., nonphysiological increase of perfusion pressure, could force follicles to rupture. This illustrates the importance of careful morphological study of all ovaries perfused in vitro before conclusions are drawn.     

The isolated perfused rabbit ovary — A model for studies of ovarian function

Summary In the present investigation the ultrastructure of isolated rabbit ovaries, perfused with different media for various time periods, was studied. The steroid hormone production by the perfused ovary was also determined. Perfusion with Medium 199 results in prominent interstitial ovarian oedema which increases with perfusion time. Even after the addition of 6–10 % Dextran T40, oedema appears in the interstitial tissue of the ovary. Perfusion solutions with osmotically active colloid particles of large molecular size (Dextran T70; average molecular weight 70,000 and bovine serum albumin), cause less distortion in the ovarian structure, and ultrastructurally the ovarian tissues appear essentially the same as in the control ovaries.The results indicate that the perfused rabbit ovary, under strictly controlled conditions, can be used as an experimental model for studies of various aspects of ovarian function, including follicular rupture.     

Structural alterations of rabbit ovarian follicles after mating with special reference to the overlying surface epithelium

Summary Rabbit ovarian preovulatory follicles and in particular the overlying surface epithelium were studied by morphological and ultrahistochemical means at different times after mating.By light microscopy an increase of cytoplasmic granules was found in the surface epithelium at the follicle apex 4 h after mating. The granules increased in amount and showed maximal accumulation 8–9 h after mating. They then disappeared at the same time as the connective tissue elements in the underlying tunica albuginea and theca externa disintegrated.Transmission electron microscopy showed that the membrane-bounded granules or dense bodies fused with one another and by 8 h after mating they often changed character and appeared more electron lucent. Furthermore, open communications were found between altered granules and vacuoles and between vacuoles and the extracellular space below the epithelium. Acid phosphatase reaction product was localized to the granules and Golgi cisternae. Not all the dense bodies were enzyme positive. At later stages, close to the time of follicle rupture, the epithelial cells were attenuated and thin, with only a few granules.By scanning electron microscopy it was found that the epithelial cells at the follicle apex increased in size approaching the time of follicle rupture and that their microvilli decreased in number and in size. At 8 h and later, the contours of intracellular granules could be visualized.The results of this study were similar to those found when rabbits were induced to ovulate by HCG-stimulation. This further strengthens the hypothesis that the surface epithelium contributes proteolytic enzymes which help to disintegrate the follicle apex prior to rupture.     

Further studies of the surface epithelium covering preovulatory rabbit follicles with special reference to lysosomal alterations

Summary The fine structure of the surface epithelium over preovulatory rabbit follicles was examined parallel with visualization of acid phosphatase at the electron microscopical level. Small enzyme positive vesicles were pinched off from the Golgi cisternae and similar vesicles fused and got incorporated into larger lysosomes of dense body type. Some lysosomes appeared in direct continuity with tubular enzyme positive structures. Other possible ways of increase of the lysosomal pool are indicated and discussed.As in previous studies a maximal accumulation of lysosomes was found in the apical epithelium at 8 h after an ovulatory dose of human chorionic gonadotrophin (HCG); thereafter a gradual loss of lysosomes ensued. Before the lysosomes disappeared from the surface epithelium they changed in character. They became more electron-lucent and revealed a fine-fibrillar matrix. Dense bodies deep in the cell interior appeared to communicate with each other and with the extracellular space below the surface epithelium. Openings were never seen towards the peritoneal cavity. The loss of lysosomal content from the apical surface epithelium before follicle rupture appeared in many respects similar to the histamine release process in mast cells.The findings support our working hypothesis that the surface epithelium over Graafian follicles is an essential source of proteolytic enzymes and that these may be released extracellularly and actively contribute to the dissolution of the follicular apex before rupture.This investigation was supported by grants from the Swedish Medical Research Council (Projects No. B74-12X-78-09C and B75-12X-78-10A). The technical assistance of Miss Ingalis Fransson and Miss Kerstin Nilsson is greatly appreciated     

Ovulation and the mechanism of follicle rupture

Summary The rabbit Graafian follicles are encircled by a capillary network between the theca interna and the avascular membrana granulosa. After injection of an ovulatory dose of human chorionic gonadotrophin (HCG) the theca interna cells showed an increase in the amount of smooth endoplasmic reticulum, lipid droplets and mitochondria with tubular cristae. In addition, considerably more junctions, similar to the abutment nexuses of granulosa cells were found; annular nexuses also appeared. At 4 hours after injection of HCG a prominent oedema was evident in the theca interna layer, particularly in the apical region.Small fenestrations in the endothelium of the blood capillaries increased in amount after HCG injection, and close to the time of ovulation, large gaps or perforations, 1–3 in diameter, were found in the thin, distended part of the endothelial cells. The surrounding basement membrane became fragmented and partly lost, so that a seemingly free passage from the capillary lumen to the interstitium was eventually established. Leakage of fluid, causing interstitial oedema, presumably proceeds until the pressure in the pericapillary interstitium has risen to the pressure in the capillaries. Some hours before and up to ovulation the pericapillary interstitium has also broad communications with the cavity of the follicles. Therefore, both pressure and fluid can be passed from the capillaries-via the interstitium-to the follicle antrum. However, influx of fluid with subsequent follicle expansion and ovulation-at constant pressure-does not occur until the tensile strength of the follicle wall has decreased.This investigation was supported by grants from the Swedish Medical Besearch Council (Projects No. B72-12X-78-07A, B73-12X-78-08B and B74-12X-78-09C). The technical assistance of Miss Ingalis Fransson, Miss Kerstin Nilsson, and Mrs. Ulla-Britt Westman is greatly appreciated.     

Follicle growth in the ovary of the rabbit after ovulation-inducing application of human chorionic gonadotropin

Summary The growth of tertiary follicles, i.e., the proliferation of cells in the stratum granulosum and in the capillary network of the theca interna, after injection of ovulation-inducing human chorionic gonadotropin (HCG), was investigated in the rabbit by means of autoradiographic and morphometric methods.Based on the frequency distribution of follicles with different sizes and on the labeling index (LI) of granulosa cells as a function of follicle size and of time prior to and after HCG stimulation, two groups of tertiary tollicles can be distinguished: growing (250–900 m in diameter) and mature (>900 m in diameter) elements. The growth of both groups is influenced by the release of gonadotropins.After HCG stimulation, follicles belonging to the first group grow rapidly. During, and a short time after ovulation, almost all non-ruptured follicles larger than 600 m in diameter become atretic. Within 35–50 h the ruptured and atretic mature follicles (>900 m in diameter) are replaced by follicles out of the group of growing follicles.From these results the following concept for regulation of follicle growth is derived: In principle, all growing follicles possess the potential to develop into mature follicles. When a sufficient number of mature follicles is generated, these mature follicles determine the number of succeeding growing follicles. Follicles that are not required for providing mature follicles become atretic as soon as they reach a diameter of 700 m. When the majority of mature follicles is lost during ovulation (by rupture or atresia), this inhibition regulated by mature follicles is abolished, and all of the growing follicles again are capable to develop into mature follicles.The relative amount of capillaries in the theca interna of growing and mature follicles remains constant with increasing follicle size. This means that the capillary network grows parallel to the increasing size of follicles. No differences are found between intact and atretic follicles; advanced atretic follicles were excluded from this study.The labeling index (LI) of granulosa cells in the stratum granulosum and of endothelial cells in the theca interna, as a function of follicle size and of time after HCG stimulation, are closely correlated. A change in the LI of granulosa cells is usually followed with a certain delay by a similar alteration of the LI of endothelial cells in the theca interna. This suggests that granulosa cells have a certain regulatory function on capillary growth.     

Structural changes occurring during atresia in sheep ovarian follicles

Summary The structural changes that characterize primary, secondary and tertiary atresia in sheep Graafian follicles have been studied by means of histological, histochemical and ultrastructural techniques.In primary atresia vacuoles representing swollen endoplasmic reticulum are prominent along the antral border together with disorganized granulosa cells containing pyknotic nuclei. Phagocytic cells, which increase in number as atresia progresses, were seen within the membrana granulosa and are considered to be transformed granulosa cells. Even in follicles classified as nonatretic, a few antral vacuoles and occasional pyknotic nuclei are present.During secondary atresia there is a large increase in the number of cells with pyknotic nuclei; many of these nuclei had been extruded and had fused to form the characteristic Feulgen-positive atretic bodies found along the edge of the antral cavity. These bodies usually have a diameter of up to 15 m but occasionally reached as much as 400 m. A second area of degeneration is frequently present in the membrana granulosa, two or three cell layers from the basal lamina, and it is at this level that exfoliation of granulosa cells occurs in tertiary atresia. In contrast to the membrana granulosa, there are during secondary atresia, only slight indications of degeneration in the cumulus.In tertiary atresia the membrana granulosa is highly disorganized; the atretic bodies are often fewer in number than at earlier stages. The basal lamina remains essentially intact. It is at this stage that the first clear signs of degeneration occur in the theca interna. Despite some disintegration of the cumulus, the integrity of the oocyte is maintained and its nucleus remains vesicular.Changes in the thecal microcirculation may play a key role in atresia: adjacent to the basal lamina of non-atretic follicles, there is a well-developed capillary network which is significantly reduced as atresia progresses.The authors are greatly indebted to Dr. H.M. Dott and Mr. G.C. Foster for carrying out the analysis with the Quantimet image analysing computer. The skilled technical assistance of Mrs. Linda Collins is also gratefully acknowledged     

Effect of melengestrol acetate on the bovine ovary

Summary To investigate the relation of ovarian morphology to increased body weight gain during administration of melengestrol acetate (17-acetoxy-6-methyl-16-methylenepregna-4,6-diene-3,20-dione, or MGA, a progestagen), ovaries of 100 Holstein dairy heifers were examined for characteristics of follicular maturation, signs of lipid secretion, and the presence of steroid-producing-type cell organelles. The heifers were fed either a normal or a high-protein level ration with or without 0.30–0.45 mg daily of MGA from 2.5 months of age to the age of first estrus or to breeding age (120 cm withers height). The high-level ration effect was not consistently mediated by the special development of ovarian structures. MGA effect, like the weight-gain effect, was consistently evident after the time of first estrus. MGA suppressed estrus and ovulation, and resulted in the presence in the ovary, after regression of corpora lutea, of an increased number of large follicles. The largest follicles corresponding in structure to developing proestrous, mature estrous, or early atretic follicles contained hypertrophied theca interna cells showing lipid secretion signs and ultrastructural characteristics of steroid synthesis. The majority of the largest follicles, however, were atretic or late atretic and did not contain steroid-type cells. The development of replacement follicles was evident in ovaries with late atretic largest follicles. The weight-gain effect of MGA may therefore be associated with a steroidogenic, probably estrogenic, effect in the cow.Dedicated to Prof. W. Bargmann of Kiel.This investigation was supported by scholarships of the Ministère Français des Affaires Étrangères and the Alexander von Humboldt-Stiftung to Dr. J. Priedkalns.Drs. R. G. Zimbelman and L.S. Goyings of the Upjohn Company, Kalamazoo, Michigan, and Drs. D.E. Pritchard, R.W. Purchas, H.A. Tucker, H.D. Hafs, and L.J. Boyd of the Department of Dairy Science, Michigan State University, East Lansing, Michigan, designed and conducted a study on the effects of melengestrol acetate on Holstein heifers and provided ovaries for this investigation. The author wishes to thank Dr. J. W. Lauderdale of the Upjohn Company for aid in statistical analyses; the Department of Veterinary Anatomy, University of Minnesota, St. Paul, Minnesota, and the Laboratoire d'Histologie de l'École Nationale Vétérinaire de Lyon, for assistance in the processing of the ovarian tissues for electron microscopic examination; and the Laboratoire d'Histophysiologie du Collège de France, Paris, for providing facilities for a part of the histochemical study of the ovaries.A brief report of this investigation has been presented to the Société des Sciences Vétérinaires de Lyon (Priedkalns, 1971).     

Effect of clomiphene citrate on the rabbit ovary

Summary The effect of clomiphene citrate on the rabbit ovary was studied in mature nulliparous rabbits pretreated with three consecutive doses ranging from 0.01–10.0 mg/kg per day. With increasing doses a trend of decrease in mean ovarian weight (mg/kg body weight) is observed 2 days after termination of treatment. Five days later a significant increase occurs, which then subsides again to control values on day 12 after termination of treatment. During this period, no matings or injections of luteinizing hormone were performed to trigger ovulation; consequently no ovulations are observed. Folliculogenesis appears as normally; number and morphology of follicles are within normal ranges. No endogenous, spontaneous gonadotropin surges are detected in blood serum up to the 7th day after termination of treatment (2 and 10 mg doses). The surface epithelium of the ovary resembles normal germinal epithelium; however, after treatment with high doses a secretory-like activity is observed, accompanied with ultrastructural changes.Supported by the Deutsche Forschungsgemeinschaft, Special Program on Biology and Clinics of Reproduction. (Grant Be 524/7-7).Visiting Scientist from the Department of Obstetrics and Gynecology, Hadassah University Hospital, Jerusalem, Israel.     

The mature mesonephric nephron of the rabbit embryo

Summary In freeze-fracture replicas of the entire cross-fractured mesonephros of 18 day rabbit embryos the basolateral and luminal cell faces of the different nephron segments were studied and compared with their metanephric counterparts. In the proximal tubule, the shallow zonula occludens exhibited only 1–2 strands and resembled the corresponding metanephric zonula, a very leaky type, which was found with a considerable paracellular flow component in sites of isotonic reabsorption. Gap junctions were restricted to the proximal tubule and were seen more frequently in its terminal segment. The distal tubule harboured two types of tight junctions. The most common type, a band of 5–8 closely parallel strands, matched the zonula occludens of the metanephric straight distal tubule. The observed particle density of the basolateral membrane (2,500±328/m²) was less than that of the proximal tubule (2,642±306). In addition, the collecting tubule exhibited a zonula occludens of the tight variety similar to that which occurred in the metanephric collecting duct. Rod-shaped particles of the luminal membrane were mainly concentrated in some of the intercalated cells but also had developed on principal cells, and occasionally, in the distal tubule. The Wolffian duct, with a deep tight zonula occludens, had an obviously rather inactive epithelium with no conspicuous transport-linked membrane specializations.     

Pericytes and perivascular microglial cells in the basal forebrain of the neonatal rabbit

Summary Three types of pericytes outline the vascular bed in Golgi preparations of the newborn rabbit brain. Elongate cells (Type I) are restricted to capillaries, elements resembling smooth muscle cells (Type II) surround vessels of intermediate size, and large flat forms (Type III) cover the surface of arterioles and venules. Electron microscopy shows all types to be located within a well defined perivascular basement membrane. It also reveals the presence of filaments in the cytoplasm of some pericytes resembling the myofilaments of smooth muscle cells. It suggests the possibility that some pericytes are capable of contraction and may participate in regulating blood flow in small vessels.Microglia cells bear no resemblance to pericytes in terms of their shape, distribution or staining characteristics. Microglia cells are located outside the vascular basement membrane (external basal lamina) in the brain parenchyma, and they vary in form according to their location and the character of the surrounding extracellular space. This study does not support the hypothesis that microglia cells arise from pericytes but indicates that they originate either by in situ division or from hematogenous elements that enter the brain by crossing the vessel wall.Support provided by N.I.H. Grants No. NS 10864 and NS 07938 from the U.S. Public Health Service.     

Effects of high and low preovulatory concentrations of progesterone on ovulation from the isolated perfused rabbit ovary

Rabbit ovaries were isolated surgically before the ovulatory gonadotrophin stimulation and perfused in vitro. Untreated, control ovaries never ovulated. Ovaries treated in vitro with ovine LH ovulated 10-14 h later and the oocytes had undergone germinal vesicle breakdown (GVB). LH induced increases in progesterone secretion from the treated ovaries. A 3 beta-hydroxysteroid dehydrogenase blocker ('Compound A') effectively reduced progesterone secretion into the perfusate and follicular fluid to very low levels but had no effect on ovulation rate or on oocyte maturation. Excessively high progesterone levels were obtained artificially in perfusates by addition of exogenous steroid; the number of ovaries ovulating was markedly reduced but there was no effect on oocyte maturation. It is concluded that the rise in progesterone that normally occurs immediately after the LH surge is not a prerequisite for ovulation in the rabbit. However, progesterone may have a modifying effect on LH-induced follicle rupture when at a pharmacologically high level.     

Changes in the surface morphology of the rabbit endometrium related to the estrous and progestational stages of the reproductive cycle

Summary Changes occurring on the surface of the uterine luminal epithelium of the rabbit during the estrous and progestational stages of the reproductive cycle were examined by scanning and transmission electron microscopy. The findings demonstrate that the uterine epithelium, or endometrium, contains two cell types: ciliated cells and nonciliated, microvillous cells. In estrous animals, ciliated cells, although not very numerous, were usually observed in small groups. However, at increasing intervals of time following mating, ciliated cells progressively disappeared from the endometrium until approximately eight to ten days post coitum, when they became scare. From several hours to four to five days following mating, extensive changes occurred on the surfaces of microvillous cells. When observed by TEM, these elements contained organelles typical of cells involved in the synthesis and secretion of glycoproteins. Furthermore, microvillous cells during this period displayed numerous apical protrusions of different sizes and shapes and containing material of varying electron density. Parallel SEM examinations of the same material confirmed the presence of these protrusions. Some of the protrusions appeared as spheroidal masses attached to the cytoplasm by means of a cytoplasmic strand. Other surface masses were clearly unattached to the cell surface and were distributed (1) on the surface of microvillous cells, (2) on the cilia of adjacent ciliated cells, and (3) on the surface of spermatozoa.Changes occurring on the luminal surface during the early postcoital period are interpreted as an expression of morphodynamic processes likely involving coupled secretion (exocytosis) and resorption (endocytosis) of luminal material. The observations presented here also demonstrate that between six and ten days post coitum, the rabbit endometrium contained increasing numbers of enlarged, nonciliated cells that probably arose by the fusion of smaller, microvillous elements.The work reported here was supported by C.N.R. contracts No. CT 760128809 and CT 77014239 (to P.M.) and NIH. Grant HD-04274 (to J.V.B.)     

Post-coital depletion of dense-core vesicles from the external layer of the rabbit median eminence

Summary The effects of mating on the depletion of osmiophilic material from dense-core vesicles (DCV) within the external layer of the rabbit median eminence (ME) were investigated. Two different populations of DCV were demonstrated within the ME external layer of the non-mated control animals. A plot of the diameters of these vesicles showed two peaks, one at 90–100 nm, and the other at 120–130 nm. These two populations of DCV were found in separate axons and axon terminals in contact with, or near the perivascular spaces of, portal capillaries. Within these axons and terminals an occasional membrane profile or vesicle ghost was also observed.The same two populations of DCV were evident in the ME external layer of animals that were sacrificed at 10 minutes post-coitus. In these experimental animals, the number and size of the smaller population of DCV were the same as those of the none-mated controls. However, there was an obvious decrease in the number of the large (120–130nm) DCV, together with a simultaneous marked increase in the number of vesicle ghosts. These ghosts had a mean diameter of 137±14 nm. On the basis of their size, it is suggested that the vesicle ghosts represent large DCV that have been depleted of their content following mating. Ultrastructural evidence for the depletion of osmiophilic material from the large DCV of mated animals is provided.According to previous writers the smaller DCV within the ME are aminergic, whereas the larger DCV may contain releasing factors (RF). Our findings provide further morphological evidence to support this hypothesis. Furthermore, RF and biogenic amines appear to be contained within separate nerve terminals in the rabbit ME.This investigation was supported by grants to Drs. D. G. Montemurro and R. P. Singh from the Medical Research Council of Canada. The authors gratefully acknowledge the technical assistance of Miss A. Overweel and Mrs. S. Griffin.     

Evidence for basal secretion in the subcommissural organ of the adult rabbit

Summary Morphological evidence is presented supporting the possibility of basal secretion into hypendymal capillaries of the adult rabbit subcommissural organ (SCO). The synthetic apparatus of the SCO cell is described as well as the heterogeneous granules and vesicles which are concentrated in the basal processes bordering a widened perivascular space. The origin of the electron dense granules, of which two fairly distinct subgroups are found, is discussed.A binding of secretory sacs to the lateral plasma membrane is seen. The possibility of a lateral secretion is supported by the presence of a system of extracellular channels between SCO cells which are filled with a flocculent material resembling that of the secretory sacs.Nerve perikarya which are separated from the SCO by only a few glial fibers are demonstrated. Synapses are described in nerve fascicles bordering on the hypendymal capillaries. The possibility of an innervation of the hypendymal region is discussed as well as possible nervous connections with the pineal gland.This work was supported by grants from Statens almindelige Videnskabsfond, Copenhagen.     

Heterotopic allotransplantation of isolated aortic cells

Summary Smooth muscle cells were enzymatically isolated from the tunica media of the aorta of 5-day-old rats. Following in vitro exposure to colloidal thorium dioxide particles the cells displayed numerous lysosomes filled with these particles. Intramuscular injection of isolated cells into the tongues of young rats of the same strain, resulted in the formation by both freshly isolated and thorium dioxide-labeled cells of a characteristic tissue similar to that found in the intact aortic wall. Thus, the transplants consisted of typical smooth muscle cells surrounded by an extracellular matrix consisting of a microfibrillar network, patches and fibers of elastin, collagen fibrils and small polygonal granules believed to represent proteoglycans. This system can be used for experimental studies on the production of extracellular matrix components and on other functions of arterial smooth muscle cells growing outside the vascular wall.The technical assistance of Ms. Karin Blomgren and the secretarial assistance of Ms. Inger Åhrén are gratefully acknowledgedFinancial support was obtained from the Swedish Medical Research Council (proj. no. 12X-03355), the King Gustaf V 80th Birthday Fund, the M. Bergvall Foundation, the A.O. Swärd Foundation, and from the Funds of the Karolinska Institutet     

The amino acid sequence of the rabbit lutropin beta subunit

The amino acid sequence of the beta subunit of rabbit lutropin (lLH) has been determined. The amino terminus of about 97% of the beta subunit has a two amino acid extension (pyro-Glu-Pro) compared to other lutropin beta sequences. Overlapping peptides from trypsin and chymotrypsin digestions of the performic acid-oxidized beta subunit and trypsin digestion of the S-aminoethylated cysteine beta subunit were isolated by chromatography on TSK Fractogel 40F and high-pressure liquid chromatography (HPLC). Sequencing was by a combination of the dansyl-Edman method and the direct Edman method. Amide placements were established by HPLC analysis of the PTH amino acid derivatives. The proposed sequence of lLH subunit is: This sequence is highly homologous to the other known lutropin beta subunits, especially rat and pig lutropin beta (91%). Partial cleavage of the peptide bond between Asp-79 and Pro-80 was observed during cyanogen bromide treatment. Rabbit thyrotropin and thyrotropin beta subunit copurified with lLH and lLH except at a final chromatography on Sephadex G-100.     

Studies on the innervation of the endometrium

Summary The innervation of the endometrium of rabbit, rat, mink, mongoose and pig has been investigated electron microscopically. Large bundles of nerve fibers can be observed in the connective tissue spaces within the basal layer of the endometrium. Unmyelinated nerve fibers enter the lamina functionalis, terminal nerve fibers penetrate the basal lamina and make contact with the glandular and the cavum epithelial cells. The terminal axons contain abundant synaptic vesicles, dense core vesicles and mitochondria. To date, no specialized presynaptic or postsynaptic membranes have been found.Supported by the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg (Grants Ku 210/5 and Be 524/4).Dedicated to Prof. Dr. Drs. h.c. Wolfgang Bargmann on his 70th birthday in friendship and admiration.