Digital Variance Angiography in Lower-Limb Angiography with Metal Implants.

PURPOSE: The presence of metal implants may reduce angiographic image quality due to automated beam adjustments. Digital variance angiography (DVA) is reported to be superior to digital subtraction angiography (DSA) with increased contrast-to-noise ratio (CNR) and better image quality. The aim of the study was to evaluate whether DVA could counterbalance the image quality impairment of lower-limb angiographies with metal implants. MATERIALS AND METHODS: From November 2019 to January 2020, 85 raw lower-limb iodine contrast angiograms of 12 patients with metal implants were processed retrospectively with DVA analyses. For objective comparison, CNR of DSA and DVA images was calculated and the ratio CNRDVA/CNRDSA was determined. Visual image quality was evaluated in a paired comparison and by a five-grade Likert scale by three experienced radiologists. RESULTS: The CNR was calculated and compared in 1252 regions of interest in 37 image pairs containing metal implants. The median ratio of CNRDVA/CNRDSA was 1.84 with an interquartile range of 1.35-2.32. Paired comparison resulted in 84.5% in favour of DVA with an interrater agreement of 83.2% (Fleiss κ 0.454, p < 0.001). The overall image quality scores for DSA and DVA were 3.64 ± 0.08 and 4.43 ± 0.06, respectively (p < 0.001, Wilcoxon signed-rank test) with consistently higher individual ratings for DVA. CONCLUSION: Our small-sample pilot study shows that DVA provides significantly improved image quality in lower-limb angiography with metal implants, compared to DSA imaging. The improved CNR suggest that this approach could reduce radiation exposure for lower-limb angiography with metal implants. LEVEL OF EVIDENCE: Level 4, case studies.

Cortical cytoplasmic filaments of cleaving eggs: a structural element corresponding to the contractile ring.

A sheath consisting of filaments 50-70 A in diameter has been demonstrated in association with the expanded, leading margins of the cleavage furrow in unilaterally and symmetrically cleaving eggs of a jellyfish and a polychaete worm, respectively. The observations suggest that the filament system might provide a structural basis for the existence of the contractile gel that, according to a hypothesis by Marsland and Landau, accomplishes cleavage. The filamentous sheath is present only in the furrow region and is arranged in an arcuate manner in unilaterally cleaving eggs and circumferentially in symmetrical cleavage. The filaments appear to be of finite length, and a number of them must overlap to span the length of the furrow. Contraction may be accomplished if the filaments slide relative to each other. However, contraction per se was experimentally not demonstrated in the studied systems. The disappearance of microvilli and the merocrine type secretion of mucoid droplets at the interdigitating or "spinning" membrane region of unilateral cleavage suggest that the unfolding of a pleated membrane and the insertion of intracytoplasmic membranes might contribute, at least in part, to the necessary extra cell membrane.

Unique envelope of a jellyfish ovum: the armed egg.

The eggs of Bougainvillia multitentaculata are spawned with an envelope consisting of a single layer of cnidocvtes. The cnidocytes are surficial On eggs, cleavage stages, and young blastulae. During gastrulation, the cnidocytes are Incorporated intO the ectoderm and become an integral part of the planula.

Early mouse embryo intracisternal particle: Fourth type of retrovirus-like particle associated with the mouse.

Electron microscopy combined with a quantitative analysis was used to study the virus-like particles appearing in oocytes and preimplantation embryos of nine mouse strains: inbred AKR, NZB, BALB/c, and C3H/He; randomized Swiss; inbred DDK; noninbred Peru; and randombred Q and MF1. Main findings were as follows: 1) The omnipresence was noted in mice of a fourth type of retrovirus-like particle (referred to as epsilon-particle) clearly distinguishable from the known A-, B-, and C-type particles and resembling more closely the R-type particles of the hamster. 2) epsilon-Particles occur transiently within the endoplasmic reticulum of early cleavage-stage embryos and have not yet been observed in either oocytes or later embryos, in normal adult tissues, or in tumors. 3) Intracisternal A-particles, identical to those seen generally in mouse tumors, also occurred in oocytes and early embryos but by far in smaller numbers than did epsilon-particles. 4) The production of epsilon- and A-particles exhibited exactly inverse patterns of developmental stage dependence. These patterns were basically similar, regardless of the mouse strain examined. 5) In contrast, the mode of occurrence of C-type particles was subject to a great strain-dependent variation.

Changes in embryonic 8-cell nuclei transferred by means of cell fusion to mouse eggs.

Metaphase II and activated mouse oocytes were fused with 8-cell blastomeres, and morphological changes in the transferred nuclei were followed using light and electron microscopy. In metaphase II oocytes, blastomere nuclei underwent premature chromosome condensation (PCC) typical for S-phase nuclei: chromatin pulverization. Then an abortive spindle was formed without evident microtubule organizing centers. Blastomere chromosomes condensed to a lesser degree than meiotic chromosomes and lacked mature functional, trilaminar kinetochores. After parthenogenetic activation of these oocytes, blastomere chromosomes followed, in synchrony with oocyte chromatin, a similar route of changes (anaphase, telophase) and then reformed interphase nuclei of the pronuclear type. Remodeling of 8-cell nucleus thus occurred, but the integrity of the chromatin set was frequently disturbed by formation of micronuclei. If blastomere fusion with oocytes was done close to activation (either before or after parthenogenetic stimulation), the chances of remodeling of the nuclei decreased, because PCC was not regularly induced in all oocytes. In hybrids produced 60 min or later after oocyte activation, blastomere nuclei were maintained in interphase without any structural modifications. Multiple experiments in the mouse have shown that the nuclei from 8-cell stage transferred to enucleated oocytes and egg cells are not capable of substituting for pronuclear functions. Possible reasons for impaired functional reprogramming of 8-cell nucleus in the mouse are discussed in light of our present findings on the morphology of nuclei transferred before and after oocyte activation.

Effects of cold and of isopropyl-N-phenylcarbamate on the second meiotic spindle of mouse oocytes.

The meiotic spindle of ovulated mouse oocytes are cold sensitive similar to the mitotic spindles of somatic cells and unicellular organisms. On crushed ice, the spindle microtubules were disorganized between 15 and 60 min of treatment: continuous microtubules depolymerized at first, then kinetochore fibers followed. MTOCs also dispersed during the cold treatment while kinetochores remained intact. The effects of isopropyl-N-phenylcarbamate (IPC) on the reorganization of the meiotic spindle of mouse oocytes were studied after cold disorganization. This drug is an antimitotic agent which appears to act on cells lacking centrioles (higher plants, amoeba, alga) as oocytes do. In ovulated mouse oocytes, IPC disturbed microtubule orientation and the relative distance between MTOCs and chromosomes. However this herbicide did not seem to act on polymerized microtubules and its action was apparently reversible. The disturbances in microtubule orientation are probably due to the displacement of chromosomes and MTOCs, which are loci of microtubule polymerization.

A centriole-free Drosophila cell line. A high voltage EM study.

The problem of the absence of centrioles in cells of the 1182-4 line of Drosophila melanogaster has been reexamined with high voltage electron microscopy. A hypotonic treatment of the cells before fixation allowed a clear recognition of centrioles in 1 micron thick sections. Three different approaches were used to determine the presence of absence of centrioles in a Kc control cell line and in the 1182-4D cell line. 1) 1500 random 0.5 micron thick sections representing the equivalent of 60 whole cells of the 1182-4D line show no centrioles. In contrast, nearly all centrioles of the Kc cells were detected by this examination. 2) In a blind test 10 grids with either Kc or 1182-4D cells were correctly identified by the operator. In Kc cells, 4 to 6 diplosomes were observed by grid square on about 300 cell profiles, while no centrioles were seen in the sections of 1182-4D cells. 3) Complete serial sections 1 micron thick of whole 1182-4D cells were screened for presence or absence of centriole. No centriole was seen in any section. We conclude that these Drosophila 1182-4D cells, which have been maintained in culture for several years, are free of centrioles.

Remodelling of thymocyte nuclei in activated mouse oocytes: an ultrastructural study.

Oocyte-thymocyte mouse cell hybrids were produced using polyethylene glycol (PEG) and examined at the ultrastructural level. Fusion was accomplished either before or after activation of metaphase II oocytes. In both experimental variants thymocyte nuclei undergo remodelling which comprises the following sequence of events: nuclear envelope breakdown, initial chromatin condensation, and subsequent decondensation, nuclear envelope reformation and formation of nucleoli. In hybrids produced before oocyte activation but activated within a short time and cultured for several hours the thymocyte nuclei become identical to the female pronucleus. In the second variant (fusion with activated oocytes) the degree of remodeling of thymocyte nuclei is variable. Our observations demonstrate that between metaphase II, telophase of meiosis and early female pronuclear stages the mouse oocyte contains all "factors" necessary for remodelling of differentiated somatic nuclei and their development as if they were pronuclei.

Desmosomes: their occurrence between adjacent primary oocytes in polyovular follicles in the rabbit.

In polyovular, primordial follicles in the rabbit, desmosomes are found between apposing oocyte surfaces. Morphologically these desmosomes correspond closely to those described in epithelia of vertebrates. The desmosomes alternate with other junctions which are probably gap junctions.

[Egg-spermatozoid relation: a phenomenon of fusion of membranes]. / Relations oeuf/spermatozoide: phenomenes de fusion de membranes.

PIP: Spermatozoa, during their migration from the epididymus to the female genital tract, undergo a complex series of transformation and fusion of membranes. The first fusion takes place as soon as spermatozoa get in contact with the pellucid zone. Other, and more important fusions, happen between the plasmic membrane of the ovocyte and the equatorial segment of the spermotozoon, and between the cortical membranes and the plasmic membrane of the ovocyte. The lipid components of the 2 membranes seem to cause both fusions.^ieng

[Phagocytosis of spermatozoa by cumulus oophorus cells of cultured calf follicles]. / La phagocytose des spermatozoïdes par les cellules du cumulus oophorus de follicules de veau en culture

Cells of the cumulus oophorus of the calf show intense phagocytotic activity under various in vitro conditions after insemination. The spermatozoa utilized were bull spermatozoa either only washed or washed and treated by various means to induce capacitation. The cumuli cultured in a simple salt medium with BSA or with FSH, LH and prolactin, phagocytise intensely; up to 8-10 spermatozoa may be incorporated per cell. Washed sperm is taken up with the same intensity as those treated for capacitation. Mouse sperm is incorporated also. Calf cumulus cells thus appear to demonstrate a general phagocytotic activity. This phagocytotic activity may represent a primary defense against polyspermy in case too many spermatozoa should be present in the ampulla at time of ovulation.

In vitro ovulation of trout oocytes: effect of prostaglandins on smooth muscle-like cells of the theca.

Ovulation (active expulsion of oocyte from the mature follicle) of trout follicles matured in vivo can be induced in vitro by adding PGF2alpha at doses of 1 and 5 mug/ml. PGE2 is ineffective. The in vitro induction of ovulation by PGF2alpha is inhibited in a calcium free medium or by inhibitors of calcium influx, particularly by Mn++ and La+++, suggesting the ovulation process implies active contraction of the smooth muscle cells of the theca. A significant but partial inhibition is also observed with cytochalasin B (1 and 5 mug/ml) demonstrating that contraction of other cell types than muscle, containing actin-like filaments, may also participate in the process.

Activation of paternally derived regulatory mechanism in early mouse embryo.

A stage-specific occurrence of retrovirus-like elements (intracisternal particles) is regularly observed within the endoplasmic reticulum of early mouse embryos. A quantitative electron microscopic study was carried out on hybrid embryos issued from the matings between high- and low-producer mouse strains of intracisternal particles. The low-producer character behaved as dominant in all these crosses, and this enabled us to demonstrate the activation of paternally introduced regulatory mechanism in two-cell embryos and morulae. There was no sign of maternal effect in the results of reciprocal crosses.

Cytochalasin D treatment induces meiotic resumption in follicular sheep oocytes.

Ovine cumulus-enclosed oocytes collected from antral follicles (3-5 mm in diameter) were cultured in vitro with 2 x 10(6) granulosa cells/ml in the presence or absence of gonadotropins or in the presence of cytochalasin D (CD). The maturation rate was assessed after 24 h of culture. In the control group, in the presence of gonadotropins (follicle-stimulating hormone-luteinizing hormone (FSH-LH; -10 micrograms/ml) 100% of the oocytes reached metaphase II. Whereas intercellular junctions were no longer present after 6-7 h of culture, germinal vesicle breakdown (GVBD) occurred by the same time. In contrast, in the absence of gonadotropin, the majority of the oocytes (59%) remained blocked in GV stage. The inhibition exerted by the granulosa cells on meiotic resumption was overcome when the cumulus-oocyte complexes (COCs) were incubated in CD (5 micrograms/ml) for 6 h at the beginning of the culture. Under these conditions, 85% of the oocytes matured with extrusion of the first polar body. Cytological analysis by cytofluorescence (NBD phallacidin) and electron microscopy showed that, after 6 h of treatment, CD provoked a redistribution of the microfilaments, mainly in the cumulus cells and to a lesser extent in the oocyte cortex. Intercellular junctions disappeared concomitantly with a significant decrease of the intercellular transport of tritiated uridine. The initiation of GVBD occurred at the same time. These results indicate that the resumption of meiosis was correlated with a loss of both junctional complexes (intermediate and gap junctions) between the cumulus cells and the oocyte.

De novo formation of centrioles in parthenogenetically activated, diploidized rabbit embryos.

In rabbit oocytes activated parthenogenetically by repetitive electric pulses, centrioles develop de novo in blastocysts. Centrioles were not observed in earlier stages of development, not until the blastocoele is formed. Up to the morula stage (between 8-32 cells), a filamentous, electron-dense material develops and aggregates with a small vesicle fraction within the well developed Golgi apparatus. A spherical to ovoid electron dense mass forms, which is comparable to the deuterosome or to the blepharoplast. The quantity of the electron dense material enlarges and it seems to give rise to the centriole "generating complex". Centrioles arise in all three differentiated cell types of the blastocysts, the mural and polar trophoblasts and the embryonal cell mass at the same time. Some of the forming centrioles in parthenotes have a co-linear arrangement, as in control blastocysts. It is not yet known whether the co-linearly arranged centrioles represent a maturation phase, prior to the formation of the usual diplosome, with centrioles oriented perpendicularly to each other. Nor is it known whether the forming centrioles are functioning as the polar organizer of the mitotic spindle or if they can perform any other centriolar function.

'Blebbing' of the nuclear envelope of mouse zygotes, early embryos and hybrid cells.

In the mouse zygote and in two-cell stage embryos the inner leaflet of the nuclear envelope of pronuclei and that of blastomere and polar body II nuclei evaginate, forming multiple blebs within the perinuclear space, which contains a granular material. Blebbing exists only in oocytes activated by sperm in vivo or in vitro, or parthenogenetically by treatment with ethanol or puromycin. The germinal vesicle and an interphase nucleus formed after treatment of the oocyte at metaphase I by puromycin do not form blebs. Formation of blebs is specifically located in the cell cycle. The burst of the blebbing activity occurs during the first half of the cell cycle in one-cell embryos and in the earliest interphase period in the second cell cycle. Blebbing ceases from the beginning of the third cell cycle. The occurrence in the cytoplasm of 'double-layered' vesicles containing granular material resembling bleb contents and the disappearance of blebs from the nuclear envelope by the end of the cell cycle provide evidence that blebs represent a step in the transport of some material from the nucleus to the cytoplasm. Ethanolic phosphotungstic acid does not stain blebs, suggesting the absence of basic protein in their contents. Blebbing can be induced in somatic (thymocyte) and embryonic (blastomere of 8-cell stage embryo) nuclei following cell hybridization with activated oocytes. Their response to the oocyte cytoplasm by initiating blebbing depends on: (1) the position of the host cell in its cell cycle at the moment of hybridization, and (2) the time spent by the foreign nuclei in the host cytoplasm following cell fusion. If donor nuclei are introduced close to the time of activation, they start to produce blebs at the time corresponding to the initiation of blebbing by the female pronucleus in the first cell cycle. If foreign nuclei are introduced a few hours after activation they must be incubated in the host cytoplasm for some time before initiation of bleb formation, provided that the host pronucleus has initiated blebbing by that time. The existence of blebbing in nuclei formed only after oocyte activation, and the timing and the general occurrence of this event during the earliest cleavage stages of almost every mammalian embryo, suggest that this special nucleocytoplasmic transport plays a specific role at the beginning of development.

Post-fusion reaction of mouse oocyte cortex to incorporated thymocyte cells.

Ovulated alcohol-activated or inactivated mouse oocytes were fused with mouse thymocytes. Activated oocytes react to the presence of foreign nuclei by forming in the peripheral cytoplasm incorporation cones. In this region the cell membrane is smooth and a cortical layer of thin filaments underlies it. It resembles the fertilization cone. In non-activated oocytes a layer of thin cortical filaments of the same thickness is formed over the foreign chromatin but the surface protuberance (cone) is absent. These results suggest that the cortical alteration in the oocyte architecture may be a general reaction of the oocyte surface to various chromatins introduced, not only to sperm chromatin. The role of oocyte activation in the evolution of these cortical changes is discussed.

Relationship between sperm nucleus remodelling and cell cycle progression of fragments of mouse parthenogenotes.

Nucleate and anucleate fragments of parthenogenetically activated mouse oocytes, as well as cybrids obtained by fusion of anucleate fragments (cytoplasts) of maturing and activated matured oocytes were fertilized at different time after activation. Remodelling of the sperm nucleus was studied by electron microscopy at 1.5 and 3 h after fertilization and, in addition, at 14 h in cybrids. Results show that 1) the nuclear envelope of the sperm nucleus can break down when the insemination takes place after the end of M-phase, but the capacity of the parthenote cytoplasm to remodel the sperm nucleus is restricted in time. 2) Male chromatin can decondense within the old, unbroken nuclear envelope, but in such cases formation of a male pronucleus, one of the two nuclei of zygote possessing inactive nucleoli, is never observed.

Centrosomes with striated rootlets in rabbit zygotes.

An electron microscopic study of the rabbit zygote has shown the presence of numerous paracrystalline structures (PSs) around the pronuclei. The majority of these structures are situated in the narrow space between pronuclei. The PSs during interphase are associated with small dense knobs, and filamentous material; some of them, namely those situated in the internuclear space, are also associated with striated rootlets. The PS and its appendages form a complex which nucleates microtubules during interphase and phase M. The structure of these complexes changes with the cell cycle. Striated rootlets disappear at G2/M. Dense knobs and filamentous material separate from the PS, become loose and associate with numerous microtubules at the poles of the first mitotic spindle. PSs and their associated structures are considered to be a newly discovered morphological form of the centrosome.

In vitro maturation of sheep ovarian oocytes.

An in vitro system has been developed which induces full meiotic maturation in 98% ovarian sheep oocytes isolated from follicles 2-6 mm in diameter. 45.7% of these were fertilized, determined by the presence of two pronuclei, extrusion of the second polar body and the presence of the sperm flagellum. This culture system was used to describe the morphological changes during meiotic maturation, examining the nucleus, the cytoplasm and cumulus (corona)-oocyte relationship. 24 h are required for maturation of sheep oocytes. The culture medium must contain FSH, LH (10 micrograms/ml of each), estradiol-17 beta (1 micrograms/ml) and coculture of 10(6) mural granulosa cells in suspension (Crozet et al., 1987). Nuclear changes were the first evident transformations, showing that chromatin condensation leads to nuclear deformation, to germinal vesicle breakdown and to formation of the first and second meiotic metaphases. The axis of both spindles are oriented perpendicularly to the egg membrane. At each pole a bent disc composed of filamentous material represents the microtubule organizing centers (MTOC). The key event may be the initiation and control of chromosome condensation. Cytoplasmic changes include the development of a cortical layer of 1-4 microns thickness poor in cell organelles. Golgi complexes are localized in three distinct areas with possibly different functions: (1) around the germinal vesicle; (2) in the oocyte cortex, of regular distance; (3) in the central part of the oocyte. Cortical granules (CG) of different maturation stages (condensation) form clusters near the peripheral Golgi complexes while at Meta I they form a nearly continuous single layer. At Meta II the CGs are apparently anchored to the cell membrane by means of small spokes. The cumulus (corona) cells are attached by junctional complexes to each other and to the oocyte. Foot processes cross the zona and indent the oocyte. The termini are gradually exteriorized and contacts must be broken to isolate the oocyte. The sum of all the above changes represent meiotic maturation.