Manipulation of the oocyte: possible damage to the spindle apparatus

Oocytes are structured, polarized cells. For high developmental potential, it is essential that the distribution of organelles and molecules, and the function of meiotic spindles remain intact during handling of oocytes in assisted reproduction. Spindles are dynamic cell organelles. Spindle formation depends on activity of motor proteins, energy supply and temperature. Disturbances in spindle function may predispose oocytes to aneuploidy or maturation arrest. Thus, perturbation of the cytoskeletal integrity of oocytes may critically influence the fate of the embryo. Recently, enhanced polarizing microscopy has been developed for non-invasive analysis of spindle morphology in living mammalian oocytes. Chemically induced dynamic alterations have been characterized in the spindle in individual mouse oocytes and it has been shown that spindle aberrations are predictive of risks for non-disjunction. Spindle imaging identified adverse, irreversible effects of handling in living human oocytes (for instance, the extreme susceptibility of human oocytes to cooling). Also, oocyte immaturity may be detected. Selection of metaphase II oocytes and an injection site for intracytoplasmic sperm injection (ICSI) that avoids spindle damage may increase the yield of euploid embryos. The detection of genetic, environmentally induced, or treatment-related defects in oocyte maturation by non-invasive spindle imaging can improve quality control and assist in the selection of morphologically normal oocytes for assisted reproduction.     

The Prevention of Positioning Injuries During Gynecologic Surgery. Guideline of the DGGG,OEGGG and SGGG (S2k Level,AWMF Registry Number 015/077, October 2020)

Purpose Positioning injuries are relatively common, forensically highly relevant complications of gynecologic surgery. The aim of this official AWMF S2k-guideline is to provide statements and recommendations on how to prevent positioning injuries using the currently available literature. The literature was evaluated by an interdisciplinary group of experts from professional medical societies. The consensus on recommendations and statements was achieved in a structured consensus process. Method The current guideline is based on the expired S1-guideline, which was updated by a systematic search of the literature and a review of relevant publications issued between February 2014 and March 2019. Statements were compiled and voted on by a panel of experts. Recommendations The guideline provides general and specific recommendations on the prevention, diagnosis and treatment of positioning injuries. Key words: gynecologic surgery, positioning injuries, prevention     

Rehabilitation of adolescent patients with scoliosis—what do we know? A review of the literature

Different opinions exist about the efficacy of conservative scoliosis treatment. Because this divergence of opinion corresponds to a great variety of standards applied, it is also not surprising that the results of conservative treatment differ a lot. Scoliosis normally does not have such dramatic effects that immediate surgery would be indicated. Moreover, it is clear that functional and physiological impairments of scoliosis patients—including pain, torso deformity, psychological disturbance and pulmonary dysfunction—require therapeutic intervention. The triad of out-patient physiotherapy, intensive in-patient rehabilitation and bracing has proven effective in conservative scoliosis treatment in central Europe. Indication, content and results of the individual treatment procedures are described and discussed. The positive outcomes of this practice validate a policy of offering conservative treatment as an alternative to scoliosis patients, including those for whom surgery is discussed.     

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

The pyroclastic aggregate concrete of Trajan’s Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime–volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium–aluminum-silicate–hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8–0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45–0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.The builders of the monuments of Imperial Rome (from 27 BCE, when Octavian became Emperor Augustus, through the fourth century CE) used pyroclastic volcanic rock to create unreinforced concrete structures with dramatic vaulted spans, as at the Markets of Trajan (110 CE) (1, 2) (Fig. 1A). The concrete foundations, walls, and vaulted ceilings are composed of decimeter-sized volcanic tuff and brick coarse aggregate (caementa) bound by volcanic ash–lime mortar (Fig. 1B). The conglomeratic fabric of the concretes is analogous to sedimentary rocks made of coarse rock fragments and a matrix of finer grained material. The concretes have resisted structural scale failure during moderate-magnitude earthquakes (<8 on the Mercalli–Cancani–Sieberg intensity scale) associated with slip on Appennine fault systems 80–130 km to the northeast, as well as chemical decay associated with repeated inundations of foundations and walls by Tiber River floods (3–5). To date, at least six episodes of moment magnitude 6.7–7 ground shaking and damage to monuments have been recorded since 508 CE (4). The concrete structures contain common macroscale fractures, with rough surfaces that link by complex segment overlap and bridging, and either follow or traverse caementa interfacial zones (Fig. 1C). Many monuments remain in active use as residences, offices, museums, and churches. In addition to the Markets of Trajan, these include the Theater of Marcellus (44–13 BCE), Mausoleum of Hadrian (123–39 CE), Pantheon (ca. 126 CE), and Baths of Diocletian (298–306 CE). The monuments that did undergo sectional failure, for example at the Colosseum (70–90 CE), Baths of Caracalla (ca. 215 CE), and Basilica of Maxentius (ca. 313 CE), mainly did so in Late Antiguity or the Middle Ages, when they were several centuries old and had become vulnerable through subsurface instabilities; problematic structural design; removal of marble and travertine dimension stone, columns, and cladding; and lack of regular maintenance (4, 6, 7).Open in a separate windowFig. 1.Markets of Trajan concretes. (A) Great Hall, vaulted ceiling and brick-faced concrete walls; reprinted with permission from Archives, Museo Fori Imperiali. (B) Drill core with Pozzolane Rosse volcanic ash (harena fossicia) mortar and conglomeratic aggregate (caementa). (C) Fractures in vaulted ceiling, Grande Emiciclo: 1, crack follows caementa perimeter; 2, crack traverses caementa. Wall concrete contains ∼88 vol % pyroclastic rock: 45–55% tuff (and brick) as caementa, ∼38% volcanic ash pozzolan, and ∼12% lime paste, with 3:1 ash:lime volumetric ratio (de Architectura 2.5.1) in the mortar (18).The pozzolanic mortar perfected by Roman builders during first century BCE (8) is key to the durability of concrete components in structurally sound monuments well maintained over two millennia of use. [Pozzolans, named after pumiceous ash from Puteoli (now, Pozzuoli) in the Campi Flegrei volcanic district, react with lime in the presence of moisture to form binding cementitious hydrates (9)]. By the Augustan era (27 BCE–14 CE), after experimenting with ash mixtures for >100 y, Romans had a standardized mortar formulation using scoriaceous ash of the mid-Pleistocene Pozzolane Rosse pyroclastic flow (Fig. S1) that substantially improved the margin of safety associated with increasingly daring structural designs (10, 11). They used this mortar formulation in the principal Imperial monuments constructed in Rome through early fourth century CE (8). Pozzolane Rosse erupted at 456 ± 3 ka from nearby Alban Hills volcano (12), filling valleys and covering topographic plateaus across the Roman region; the ash has a highly potassic tephritic composition (13). Romans made the architectural mortars by calcining limestone at ∼900 °C to produce quicklime [CaO], hydrating the quicklime to form portlandite [Ca(OH)₂], a trigonal calcium hydroxide] putty, and laboriously incorporating granular Pozzolane Rosse ash. This is the red and black excavated sand (harena fossicia) described by the Roman architect Vitruvius in first century BCE (de Architectura 2.4.1–2.4.3; 2.5.1–2.5.3) (14). The strongly alkaline portlandite solution attacks the surfaces of the scoriaceous pozzolan; volcanic glass and silicate mineral textures dissociate; their alkali ions dissolve in the liquid phase; and calcium is adsorbed on the scoria surfaces, forming cementitious hydrates (9). These phases are regarded as central to the chemical durability that is an essential component of the impressive record of survival of many monuments, but their role in resisting mechanical degradation through obstructing microcrack propagation has never been examined.Fracture-mechanical properties offer important insight into a cementitious material’s long-term survivability (i.e., its ability to absorb energy from applied loads without failing catastrophically). Two common properties are uniaxial tensile strength [f_t (megapascals)], which refers to the stress at which a macrocrack initiates, and fracture energy [G_F (joules per square meter)], the amount of mechanical work required to propagate a macrocrack to create one square unit of new surface area (15). Experimental characterization of the fracture behavior of the Imperial-age mortar through tests of ancient material is difficult, because it occurs in narrow, irregular zones that are bonded to caementa (Fig. 1B), and the heterogeneous fabric of the concrete requires large test dimensions (16). We therefore duplicated the Imperial-age mortar using the volcanic ash–quicklime proportions described by Vitruvius (de Architectura 2.4–2.5) (14) and petrographic and mineralogical characterization of mortar samples from the Great Hall of Trajan’s Markets (17) to formulate a mix design that closely mimics the Trajanic formulation. Fracture-mechanical properties, as well as Young’s modulus, were previously determined at 28, 90, and 180 d hydration via an innovative arc-shaped three-point bending test (18) that reproduced half-slices of hollow 20-cm-diameter drill cores from the Great Hall (Fig. 1B), so that the behavior of the mortar reproduction can be compared with that of Trajanic concrete in a future experimental testing program. All measured properties increase with age, with the 180-d mortar producing values for Young’s modulus and uniaxial tensile strength around 1/10 of modern structural concrete, whereas fracture energy is close to one-half (Fig. S2) of the crack arrays in the reproduction at 28, 90, and 180 d hydration provide visualization of millimeter-scale fracture processes to which macroscale toughness associated with previously published G_F values are attributed (18). X-ray microdiffraction experiments with synchroton radiation are a critical analytic component, because they provide very fine-scale identifications of the cementitious mineral assemblage that evolved over 1,900 y. The Markets of Trajan concrete provides a proven prototype for innovations in monolithic concretes (19) that are reinforced by a clast-supported conglomeratic fabric at the macroscale and an enduring crystalline fabric at the microscale. New concrete materials formulated with pyroclastic aggregate based on the Imperial Roman prototype could reduce carbon emissions, produce crystalline cementitious reinforcements over long periods of time, enhance durability in seismically active regions, and extend the service life of environmentally sustainable buildings.

Table 1.

Mechanical properties of mortar reproductions

GABAA and GABAB receptors in locus coeruleus: effects of blockers

Racemic baclofen, (-)-baclofen and muscimol depressed all spontaneously firing locus coeruleus neurons tested in a slice preparation. Racemic phaclofen (100 microM; 1 mM) moderately antagonized the effects of racemic baclofen without antagonizing those of muscimol. Bicuculline (10, 30, 100 microM) potently antagonized the action of muscimol without affecting the inhibition of baclofen. Phaclofen and bicuculline had no pronounced effect on the spontaneous discharge rate of cells. The results suggests that there are GABAA and GABAB receptors in the locus coeruleus.     

Increased acetylcholine and quisqualate responsiveness after blockade of GABAB receptors.

The aim of this study was to gain further insight into the function of cortical GABAB receptors. In chloral hydrate-anaesthetized rats, microiontophoretic administration of the GABAB receptor blocker CGP 35348 induced a moderate increase in firing of spontaneously active neurons in the rostral and caudal sensorimotor cortex. This increase in cell firing was accompanied by a reduction in the baclofen-induced inhibition of cell activity. In contrast to the GABAA receptor antagonist bicuculline methiodide, CGP 35348 did not induce any paroxysmal discharges. The excitatory responses of rostral cortical neurons elicited by iontophoretically applied acetylcholine and quisqualate were potentiated in most neurons after both microiontophoretic and intravenous administration of CGP 35348. The potentiation was observed in the absence of any change in the spontaneous firing rate. These effects were dose-dependent for both routes of administration. The potentiation of the quisqualate response was reversed by intravenously applied baclofen. In conclusion, these findings suggest that cortical GABAB receptors are involved in the control of cortical neuronal excitability.