On the ultrastructure of follicles and isolated follicular granulosa cells of porcine ovary

Summary The endoplasmic reticulum in granulosa cells of primary, secondary, and small tertiary follicles of the porcine ovary is sparse and largely of the granular type.In granulosa cells of large tertiary follicles the endoplasmic reticulum shows distinct signs of proliferation. Some cells even contain whorls of endoplasmic reticulum membranes, essentially of the agranular variety.Direct continuity between endoplasmic reticulum membranes of the granular and agranular type as well as the continuous increase in agranular membranes suggest that these membranes may originate from the granular membranes.Granulosa cells isolated from large tertiary follicles by microdissection and keptin vitro show essentially the same ultrastructure as granulosa cells of intact large tertiary follicles.Some lipid droplets appear to be localized in cavities of the endoplasmic reticulum. It is suggested that the droplets contain precursor material for steroid hormone synthesis.Finally, the development of the agranular endoplasmic reticulum including the appearance of whorls in some granulosa cells of large tertiary follicles indicates that steroid synthesis may occur in such follicular granulosa cells.Read at the Meeting of the Swedish Society for Pathology in Umeå, September 25, 1965 (Bjersing, 1966).This investigation was supported by grants from the Swedish Medical Research Council (Projects No. 13 X-78-01, 12 X-78-02, and 12 X-78-03).     

The polypeptide structure and assembly of Ly-2/3 heterodimers

Mild reduction of mature, thymic Ly-2/3 heterodimers of M _r 67 000 resulted in dissociation into three individual polypeptide chains, , , and , of respective M _r values 38000, 35000, and 30000. The and chains were both immunoprecipitated by a monoclonal antibody directed to the Ly-2.1 epitope whereas the Ly-3.1 antibody bound only the chain. The possibility that the and chains of each heterodimer established their interchain links within a labile precursor protein in which a and segments were fused was considered but discounted by the finding that in mice heterozygous for both Ly-2 and Ly-3 loci, the Ly-2 product of one chromosome was not exclusively joined to Ly-3 structures coded by the same chromosome. By utilizing ionic detergents which selectively alter the charge of intrinsic membrane proteins, both Ly-2 and Ly-3 polypeptides were shown to have membrane insertion sites. It is suggested that as a consequence of their likely synthesis on membrane-bound polysomes, newly synthesized Ly-2 and Ly-3 structures accumulate within the same subcellular compartment — the membranes of the rough endoplasmic reticulum. Their elevated concentration within this space may facilitate a low affinity binding interaction between Ly-2 and Ly-3 which is later stabilized by interchain disulfide bond formation.Abbreviations used in this paper BSA bovine serum albumin - DOC sodium deoxycholate - DTT dithiothreitol - HA hemagglutinin - HTAB hexadecyltrimethylammonium bromide - RER rough endoplasmic reticulum - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - TX100 Triton X-100     

Fine structure of the Wolffian duct and cytodifferentiation of the epididymis in fetal rats

Summary The fine structure of the Wolffian duct and alterations that occur with the differentiation of the epididymis have been studied in fetal rats ranging in length from 5 to 22 mm (12 to 19 days gestation). Contents of the columnar Wolffian duct cells include basal and perinuclear granular endoplasmic reticulum, sparse apical agranular endoplasmic reticulum, elongate mitochondria, and a small Golgi complex. Large membrane-bounded dense bodies contain cellular organelles and may represent parts of degenerating cells ingested by phagocytosis. During the development of the epididymis from the Wolffian duct in older fetuses, intracytoplasmic confronting cisternae of the granular endoplasmic reticulum become numerous, and the agranular reticulum in the apical part of the cell increases moderately in abundance. Concomitantly, the apical cell surface is modified. Many microvilli are formed, indentations of the plasma membrane appear between the microvilli, and the number of coated vesicles in the apical cytoplasm increases. These changes closely follow the onset of androgen secretion by the fetal testis, and it is suggested that they may occur in response to androgen. The relation of these differentiations to known adult functions of the epididymis is discussed.This study was supported by a research grant from the American Cancer Society (E-500), Program Project HD-02282 of the National Institutes of Health, and Health Sciences Advancement Award FR-02084 from the National Institutes of Health. The author is the recipient of a Research Career Development Award from the National Institute of General Medical Sciences. He wishes to acknowledge the technical assistance of Mrs. Heather Taylor.     

Potential of somatic embryogenesis in Prunus avium immature zygotic embryos

For the purpose of developing somatic embryogenesis in Prunus avium L., immature zygotic embryos, collected from five donor trees and sorted into two size classes (C1: 2.5–3.5 and C2: 3.6–4.5 mm), received various experimental treatments. When cultured for 10 days on an inductive medium containing 18.1 M 2,4-dichlorophenoxyacetic acid (2,4-d) and 9.3 M kinetin, then transferred to fresh medium without growth regulators, 2.5% of the C1 class cotyledons expressed direct somatic embryogenesis. C2 class cotyledons were less responsive. The response was also influenced by the chosen donor tree. In a few cases, spontaneous germination occurred. The presence of a root meristem was clearly demonstrated by histological examination of longitudinal sections. The replacement of half the amount of 2,4-d, present in the inductive medium mentioned above, by the same quantity of naphthaleneacetic acid reduced the incidence of somatic embryogenesis. Conversely, a rhizogenic response was strongly enhanced. When submitted to an inductive medium containing indoleacetic acid and zeatin without any subcultures for 3 months, C1 class cotyledons were the most morphogenic and developed leaves and cotyledon-like structures.Abbreviations BA 6-benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid - IBA indolebutyric acid - NAA -naphthaleneacetic acid     

The distribution and form of the endoplasmic reticulum during spermatogenesis in the crayfish,Cambaroides japonicus

Summary The form and differentiation of the endoplasmic reticulum has been studied in the developing sperm of the crayfish, Cambaroides japonicus. Throughout development a relationship between the nuclear envelope and cytoplasmic portion of the endoplasmic reticulum has been shown to exist. Furthermore, large contributions of material from the nuclear envelope to extranuclear cytoplasmic systems has been noted in the development of early spermatids and nearly mature sperm.A sequential predominance of several types of endoplasmic reticulum has been described in the differentiating sperm. An agranular vesicular reticulum is the most common in the early stages although annulate lamellar stacks and rough surfaced stacks are scattered randomly throughout the cytoplasm. Blebs of the nuclear envelope appear to contribute rough surfaced reticulum to the cytoplasmic system in the early spermatid. A fusion of vesicular elements results in the formation of the dense filamentous reticulum which is typical of the nearly mature sperm. Densely packed lamellae develop on the nuclear envelope in the maturing sperm and are connected to both the nuclear envelope and filamentous endoplasmic reticulum. The possible relationships of these lamellar groups to mitochondria or Golgi is discussed.Supported in part by Grant No B-2314 of the National Institute of Neurological Diseases and Blindness, U.S. Public Health Service.Predoctoral Research Fellow of the National Institute of Neurological Diseases and Blindness, U.S. Public Health Service.     

Tubular structures associated with the endothelial endoplasmic reticulum in glomerular capillaries of Rhesus monkey and nephritic man

Summary Round bodies, tubular profiles and crystalline images have been studied by electron microscopy in the endothelium of seven normal young Rhesus monkeys and in the renal glomerular endothelium of two nephritic human patients. The crystalline images are most frequently formed by aggregation of round bodies, 200–240 Å in diameter. In Rhesus monkeys a variety of crystalline images are seen. On the contrary, in nephritic patients round bodies and tubular profiles are rare and less organized. In the glomerular endothelium of two normal men they were not found.The results obtained suggest that the round bodies, the tubular profiles and the crystalline images result from sectioning of a system of undulating tubules associated with the smooth endoplasmic reticulum. In nephritic patients the formation of such a tubular system could represent a change taking place within the affected cells as a pathologic response to the disease.This work was supported by U.S. Public Health Service (N.H.I.), Grant AI-04527-03-04, and by the Consiglio Nazionale delle Ricerche (C.N.R.), Contributo 115/0815/0-1365. The Authors are greatly indebted to Miss Hermina Spiele for skilful technical assistance.     

Ultrastructural changes in granulosa lutein cells and progesterone levels during preimplantation,implantation, and early placentation in the western spotted skunk

Summary The ultrastructure of corpora lutea obtained during the preimplantation, implantation and early postimplantation periods has been studied in 20 western spotted skunks. Fine structure of granulosa lutein cells was correlated with progesterone levels. The corpus luteum of the prolonged (7 month) preimplantation period contained undifferentiated small granulosa cells and differentiated large granulosa lutein cells. The former ranged in size between 12 and 20 and the latter between 20 and 45 . The ratio of small and large cells was about equal in an animal 2 days prior to nidation whereas only few small cells and numerous large cells were observed in an animal estimated to be 8 to 12 hours from nidation. Occasionally small cells were observed amidst large ones during the 24 hour nidation period, i.e. adhesion of trophoblast with the luminal uterine epithelium, but small cells were absent in animals after this period. Small cells had some smooth and rough endoplasmic reticulum, rod-shaped mitochondria with platelike cristae, small Golgi complex, and relatively smooth plasma membranes. Large lutein cells had abundant smooth endoplasmic reticulum, membranous whorls of smooth endoplasmic reticulum, usually round mitochondria with tubular and lamellar cristae, a well developed Golgi complex, variable amounts of lipid droplets, and highly plicated and ruffled plasma membranes. Peripheral plasma progesterone levels during the prolonged preimplantation period ranged between 1.1 and 7.9 ng/ml, but during implantation it was between 8 and 16.6 ng/ml. It is suggested that plasma progesterone levels fluctuate during the time of implantation and should not be regarded as a basis to predict actual nidation in the western spotted skunk.This research was supported in part by Grant Number HD06556 from the National Institute of Child Health and Human Development.     

Enzymic synthesis of the trisaccharide core region of the carbohydrate chain ofN-glycoprotein

Transmannosylation from mannotriose (Man1-4Man1-4Man) to the 4-position at the nonreducing end N-acetylglucosaminyl residue ofN,N-diacetylchitobiose was regioselectively induced through the use of -d-mannanase fromAspergillus niger. The enzyme formed the trisaccharide Man1-4GlcNAc1-4GlcNAc (3.7% of the enzyme-catalysed net decrease ofN,N-diacetylchitobiose) from mannotriose as a donor andN,N-diacetylchitobiose as an acceptor. Mannobiose (Man1-4Man) was also shown to be useful as a donor substrate for the desired trisaccharide synthesis.Abbreviations Man d-mannose - (M _n) (n=1–5) -linkedn-mer of mannose - GlcNAc₂ 2-acetamido-2-deoxy--d-glucopyranosyl-(1–4)-2-acetamido-2-deoxy-d-glucose     

The mode of secretion of α-amylase in barley aleurone layers

The involvement of the endomenbrane system of barley (Hordeum vulgare L.) aleurone cells in the secretion of gibberellin-induced hydrolases has been investigated at the biochemical level. Our results show that at least 40–60% of the -amylase activity in homogenates of aleurone layers occurs in a membrane-bound, latent form. The latent -amylase can be assayed quantitatively following disruption of membranes by treatment with Triton X-100, ethanol, sonication, or osmotic shock and shear. The association of -amylase with the membrane is not an artifact arising from homogenization of the tissue, and acid protease is also enriched in the same subcellular fraction as the -amylase. The membrane fraction with which the -amylase is associated has many properties of the endoplasmic reticulum (ER). When membranebound -amylase is prepared in buffers containing 3 mM MgCl₂ two fractions from a sucrose step gradient contain most of the -amylase activity. These fractions are enriched in the ER marker enzyme, NADH-dependent cytochrome-c reductase, and show densities characteristic of smooth and rough ER during subsequent purification on continuous gradients. In step gradients prepared with ethylenediaminete-traacetic-acid-treated membranes, -amylase activity is contained primarily in one fraction having the density of smooth ER. Electron microscopy of the purified fractions is consistent with -amylase being associated with smooth and rough ER. However, it has not been ruled out that the enzyme is also associated with plasma membrane, Golgi membranes, or tonoplast. Examination of the isoenzyme patterns of secreted, of total-homogenate and of membrane-associated -amylases, as well as the results from pulsechase experiments using L-[³H]leucine for labeling of -amylase, are all consistent with the hypothesis that membrane-associated -amylase is an intermediate in the secretory process.Abbreviations CNTPE N-carbobenzoxy-L-tyrosine p-nitrophenylester - Cyt oxidase Cytochrome oxidase - ER endoplasmic reticulum - EDTA ethylenediaminetetraacetic acid - GA₃ gibberellic acid - IDPase inosine diphosphatase - K⁺-ATPase pH 6.5 K⁺-stimulated adenosine triphosphatase - MES 2-(N-morpholino)ethanesulfonic acid - MOPS 3-(N-morpholino)propanesulfonic acid - NADH: Cyt c reductase cyanide-insensitive NADH-linked cytochrome-c reductase - RER rough endoplasmic reticulum - Tris tris-(hydroxymethyl)-aminomethane     

The effects of oestrogens and other steroid hormones on the ultrastructure of the liver of Xenopus laevis Daudin

Summary Administration of oestradiol-17 to Xenopus laevis Daudin results in profound modifications of hepatic ultrastructure. In all liver cells there is a considerable proliferation of the granular endoplasmic reticulum and an increase in the electron density of the nucleolus. The amount of stored glycogen is depressed. Injection of pregnant mare serum gonadotrophin causes a similar response in intact females but not in males or ovariectomized females, suggesting an indirect effect of this hormone by stimulation of ovarian oestrogen secretion. Oestradiol benzoate, oestrone and oestriol are also able to effect the described response, though in the last case the changes are less complete. Testosterone propionate, progesterone, and cortisone acetate are inert in this respect.Supported by a grant from the Agricultural Research Council (A. G. 24/28) to Professor J. M. Dodd.     

The endomembrane sheath: a key structure for understanding the plant cell?

Summary Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this streaming, F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.Abbreviations EMSy endomembrane system - EMSh endomembrane sheath - PCC plasmalemmal control center     

Ultrastructural analysis of the sperm cells of mature pollen of maize,Zea mays

Summary Ultrastructural analysis of the mature viable unhydrated pollen of maize,Zea mays from dehiscent anthers shows that the sperm cells are physically distant, each bounded by an envelope comprising their own plasma membrane and the inner plasma membrane of the vegetative cell. The chondriome is unusual in containing one or more filamentous complexes, up to 12m in length appressed to the side of the sperm nucleus. The extensions at each end of the elongate sperm cells contain longitudinally-oriented arrays of endoplasmic lamellae. In a three-dimensional reconstruction of serial thin sections, there is a long J-shaped sperm, c. 35 × 5m and up to 1m in thickness, sited within pointed evaginations of the vegetative nucleus and a second shorter sperm c. 20 × 5m and up to 3.5m in thickness.Abbreviations PA-TCH-SP periodic acid-thiocarbohydrazide-silver proteinate - DAPI 4,6-diamino-2-phenylindole - SC sperm cell - Sn sperm nucleus - Ua-Pb Uranyl acetate-lead citrate staining - ER endoplasmic reticulum     

Fine structure of the flagellar apparatus of gametesin situ and motile zygotes of the green algaUlothrix flacca var.Roscoffensis (Ulotrichales) (Chlorophyta)

Summary This fine structural study ofUlothrix flacca (Dillw.) ThuretRoscoffensis variety (Berger-Perrot), a marineUlothrix, describes in detail the flagellar apparatus configuration of gametesin situ in the gametangia and in motile zygotes. The gametes's flagellar apparatus shows two basal bodies overlapping at their proximal end at a 30° angle, in an 11/5 o'clock configuration or with a counterclockwise absolute orientation. The basal bodies are interconnected by a non-striated band or capping plate. They are wrapped in their proximal part by an electron-dense sheath and obtured by a bilobed terminal cap. A cruciate microtubular root system having a 4-2-4-2 alternation pattern is present. A striated microtubule associated component (S.M.A.C.) or system I fibres accompany the two membered root R₂. The system II fibres or rhizoplasts along with striated bands associated to the microtubular roots, were not observed and are presumed to be absent.In the motile zygotes, the basal bodies are paired in a cruciate pattern. During the fusion process, two basal bodies, one of each pair, slide in a face to face position with a slight displacement into the 11/5 o'clock direction; the other two make a 30° counterclockwise rotation, thus making a 60° angle between the two basal bodies of each pair instead of 30° in the gamete.After comparison with the flagellar apparatus of other green alga gametes, it is concluded that the taxonomic affinities ofUlothrix flacca var.Roscoffensis, lie with theUlvophyceae sensuStewart andMattox 1978.Abbreviations CP capping plate - ER endoplasmic reticulum - G Golgi body - LG lipid globule - M mitochondria - MS presumed mating structure - N nucleus - R ₂,R ₄ microtubular roots - SH sheath - SMAC striated microtubule associated component - TC terminal cap - V vacuole - Ve vesicles in the anterior papilla - 1, 2, 1, 2 basal bodies numerotation     

Cloning of the ugp region containing the structural genes for the pho regulon-dependent sn-glycerol-3-phosphate transport system of Escherichia coli

Summary Using a novel positive selection method for G3P transport activity, phages that carry either all or part of ugp, the genes of the pho regulon-dependent G3P transport system of Escherichia coli were isolated from a library of EcoRI fragments of Escherichia coli established in gt7. By subcloning EcoRI fragments carried by the different phages into the multicopy plasmids pACYC184 and pUR222, it was shown that two chromosomal fragments of 6.0 and 6.6 kb are required for the expression of ugp, whereas all the structural information is located on the 6.6 kb EcoRI fragment. A restriction map of the cloned DNA was established and the extent of ugp genes determined by Tn5 insertions. Using ugp-lacZ fusions, it could be shown that the ugp region consists of at least two different operons that are transcribed in the same direction (counterclockwise) on the E. coli chromosome.Abbreviations DHBP 3,4-dihydroxibutyl-1-phosphonate - G3P sn-glycerol-3-phosphate - G3PBP glycerol-3-phosphate binding protein - IPTG isopropyl--d-thiogalactopyranoside - XG 5-bromo-4-chloro-3-indolyl--d-galactopyranoside     

The immune response of allophenic mice to the synthetic polymer GLΦ

The immune response of allophenic mice of type C57BL/6(A × SJL) F₁ to GL administered in complete Freund's adjuvant was tested. Control mice of the three strains C57BL/6, A, and SJL are all nonresponders to this antigen. However, the F₁ generations of C57BL/6 × A, C57BL/6 × SJL, and A × SJL were all responders to the antigen, so that the complementarity of at least two genes is confirmed. The allophenic mice showed no further complementation beyond the F₁ generation, a result which may argue against the possibility that more than two genes control the response to GL in these mouse strains. Characterization of the allophenic mice over several months showed that they exhibit chimeric drift, both in their coat color and in peripheral white blood cell population. There is no apparent correlation of coat color to the lymphocyte composition of the mice at any one time. The mice are true chimeras, since killing of the two populations of white blood cells with two different anti-H-2 sera produced a 100 percent killing. The immune response of individual allophenic mice to GL showed a good correlation to the number of A × SJL lympho-cytes in the animal.Abbreviations used in this paper are GL an amino acid polymer of 57 %l-glutamic acid, 38%l-lysine, and 5%l-phenylalanine - GLT¹⁵ an amino acid polymer ofl-glutamic acid,l-lysine, and 15 %l-tyrosine - (T,G)-A-L an amino acid polymer having a polylysine backbone with side chains of polyd-l-alanine, terminating in short sequences of tyrosine and glutamic acid - GAT₁₀ an amino acid polymer of 60%l-glutamic acid, 30%l-alanine, and 10%l-tyrosine - GLA₅ an amino acid polymer of 57%l-glutamic acid, 38%l-lysine, and 5%l-alanine - DNP 2,4 dinitrophenyl - BGG bovine gamma globulin - FCS fetal calf serum - PWBC peripheral white blood cell - SWBC spleen white blood cell - T cell thymus-derived lymphocyte - B cell bone marrow-derived lymphocyte     

Further studies on ultrastructure of plants infected withPetunia ringspot virus

Summary New methods of fixation and embedding have revealed in plants infected withPetunia ringspot some structural features not described before. These include the X-bodies, 80 per cent of which are formed by tubular elements which are responsible for the positive staining specific for Golgi apparatus. The tubular elements are morphologically similar to agranular endoplasmic reticulum as described in some animal cells. The rest of the inclusion is formed by normal cytoplasmic elements in which are embedded long rod-shaped tubules 600 Å wide and more than 7,000 Å long, cross sections of which are formed by 10 subunits. These subunits are arranged in a helical way to form the large tubules. These subunits are probably the actual virus particles, which would be icosahedral and would form tubular crystals. Icosahedral virus particles would also form true crystalline inclusions.It is not known what the role of the agranular endoplasmic reticulum and of some dense osmiophilic bodies found in it may be in the multiplication of the virus. However, these components induced by the virus infection probably result in the manufacture of some proteins or other substances necessary for virus multiplication.     

Pleconax Rafin. — eine bis heute unbeachtete Silenoideen-Gattung (Caryophyllaceae)

Zusammenfassung Die zwischen den Arten der SektionConoimorpha Otth (UntergattungConocalyx Willk.) der GattungSilene und den übrigen Arten derselben Gattung sowie aller übrigen Gattungen der TribusLychnideae A. Br. existierenden Unterschiede berechtigen zur Abtrennung dieser Sektion (Untergattung) als selbständige GattungPleconax Rafin. Nach bisherigen Untersuchungen gehören in diese Gattung folgende Arten und Unterarten:Pleconax ammophila (Boiss.)ourková mit subsp.ammophila und subsp.carpathae (Chowdhuri)ourková,P. amphorina (Pomel)ourková,P. conica (L.)ourková mit subsp.conica und subsp.conomaritima (D.Jord. et P.Pan.)ourková,P. coniflora (Nees)ourková,P. conoidea (L.)ourková,P. lydia (Boiss.)ourková,P. macrodonta (Boiss.)ourková,P. multinervia (Wats.)ourková,P. sartorii (Boiss. etHeldr.)ourková,P. subconica (Friv. emend. D.Jord. et P.Pan.)ourková mit subsp.subconica und subsp.grisebachii (David.)ourková sowieP. tempskyana (Freyn etSint.)ourková. Die angeführten nomenklatorischen Umkombinationen werden hier zum ersten Male veröffentlicht.     

Histochemical demonstration of Δ 5-3β- and 17β-hydroxysteroid dehydrogenase activities in porcine ovary

Summary In histochemical investigations with the ditetrazolium salt tetranitro blue tetrazolium as final hydrogen acceptor, ⁵-3-hydroxysteroid dehydrogenase activity was found in theca interna of sexually mature and even prepuberal sows. In the granulosa cells both ⁶-3-hydroxysteroid and 17-hydroxysteroid dehydrogenase reactions were negative except in specimens from some sows in puberty or oestrus. The corpora lutea showed a positive ⁵-3-hydroxysteroid dehydrogenase activity which was somewhat more pronounced during the first week of dioestrus than in other phases of the oestrous cycle.Abbrevations NAD nicotinamide-adenine dinucleotide - NADH₂ reduced NAD - NADP nicotinamide-adenine dinucleotide phosphate - NADPH₂ reduced NADP Read at the Meeting of Umeå Medical Society in Umeå, January 25, 1966 (Bjersing, 1967).This investigation was supported by grants from the Swedish Medical Research Council (Projects No. 13X-78-01, 12X-78-02, and 12X-78-03).     

Struktur und quantitatives Verhalten des perimitochondrialen granulären endoplasmatischen Retikulums der Mäuseleber

Zusammenfassung In normalen Leberzellen der Maus wurde das quantitative Verhalten des perimitochondrialen granulären endoplasmatischen Retikulums untersucht. 74% der Mitochondrien zeigen Beziehungen zum granulären endoplasmatischen Retikulum. Die einzelnen Mitochondrien werden zu 52%19,5 von den Membranen des granulären endoplasmatischen Retikulums bedeckt. Je Mikrometer Membranstrecke sind auf der mitochondriennahen Seite des granulären endoplasmatischen Retikulums 21 und auf der mitochondrienfernen Seite 20 Ribosomen zu finden, was der Zahl im übrigen granulären endoplasmatischen Retikulum entspricht. Die Befunde stellen die Grundlage für Untersuchungen des perimitochondrialen granulären endoplasmatischen Retikulums unter pathologischen Bedingungen dar.

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Structure and quantitative behaviour of the perimitochondrial granular endoplasmic reticulum in the liver cells of the mouse

Summary The perimitochondrial granular endoplasmic reticulum in normal mouse liver cells has been investigated quantitatively. 74% of the mitochondria are in association with the granular endoplasmic reticulum. The individual mitochondrion is covered by the membranes of the granulated E. R. in 52%19.5. The outer surface of the endoplasmic membrane, facing the mitochondrion, is occupied by 21 ribosomes per m; the corresponding surface of the membrane facing the free cytoplasm is occupied by 20 ribosomes per m. These data are in agreement with those of that fraction of the E. R., which is not in association with mitochondria. These findings represent a basis for investigations of the perimitochondrial endoplasmic reticulum under pathological conditions.

     

Die submikroskopische Struktur der Assimilatleitbahnen von Polytrichum commune

Summary In the young part of the stem of Polytrichum commune the protoplasts of the two types of conducting cells, the leptoids and parenchyma cells, are nearly identically equipped with cell organelles and cytoplasmic structures. Both types contain a nucleus, chloroplasts, mitochondria, and dictyosomes. The endoplasmic reticulum builds characteristic cisterns in form of hollow cylinders extending from one end wall to the other. The cisterns are connected with many plasmodesmata, which occur only in the end walls. Leptoids have oblique end walls with 16 to 20 plasmodesmata per m², and parenchyma cells show cross walls perpendicular to the axis with 9 to 12 plasmodesmata per m².Since the leptoids are supposed to be the pathways for the longitudinal transport of assimilates (Eschrich and Steiner, 1967, 1968), it is of interest that early in their development these elements undergo a change in their protoplasmatic structure. Two to 3 cm below the apical cell the protoplasts degenerate and show lysosome-like structures. The endoplasmic reticulum and other structures are deformed or dissolved; the plasmodesmata are constricted by callose deposits. At the same level the parenchyma cells still retain the original structure of their protoplasts.Thus, assimilates moving upward in one row of leptoids may penetrate the whole lumen of the leptoids at lower levels, but they are restricted to the cisterns of the endoplasmic reticulum at higher levels of the stem.