Photonic Source of Heralded Greenberger-Horne-Zeilinger States

Generating large multiphoton entangled states is of main interest due to enabling universal photonic quantum computing and all-optical quantum repeater nodes. These applications exploit measurement-based quantum computation using cluster states. Remarkably, it was shown that photonic cluster states of arbitrary size can be generated by using feasible heralded linear optics fusion gates that act on heralded three-photon Greenberger-Horne-Zeilinger (GHZ) states as the initial resource state. Thus, the capability of generating heralded GHZ states is of great importance for scaling up photonic quantum computing. Here, we experimentally demonstrate this required building block by reporting a polarisation-encoded heralded GHZ state of three photons, for which we build a high-rate six-photon source (547±2  Hz) from a solid-state quantum emitter and a stable polarization-based interferometer. The detection of three ancillary photons heralds the generation of three-photon GHZ states among the remaining particles with fidelities up to F=0.7278±0.0106. Our results initiate a path for scalable entangling operations using heralded linear-optics implementations.

[Utilization of video consultation in cardiovascular lipid treatment]

BACKGROUND

Video consultation is a possibility for physician-patient communication independent of the location; however, only limited information is available for the possibility of sole use since 2018.

METHODS

After the implementation of video consultation (Viomedi) in lipid consultations at the Medical University Mainz, the patients in the first quarter of 2022 were assessed depending on the possibility, suitability and readiness to participate. Included were patients under lipid management and long COVID patients. After treatment an online survey was carried out on the utilization and appraisal.

RESULTS

Of the 134 patients 29.1% were inclusively treated (3 refusals). All subjects (16 replies) reported having managed (very) well. Advantages were seen in counselling and follow-up. Problems were feared with respect to technology and possible disorders. Data protection aspects played a subordinate role. In comparison to telephone calls, a significant improvement in the physician-patient relationship (p-value = 0.00027), the quality of treatment and information (p-value both = 0.00044), the access to care (p-value = 0.0053) and the communication (p-value = 0.021) was assumed. An improvement in access to care (p-value = 0.021) and the quality of information (p-value = 0.034) was seen in comparison to personal contact. The main problems were a lack of experience, technical requirements, technical problems and unpunctuality of the practitioner. The flexibility, low effort and the pleasant consultation were all praised. All subjects wanted to use the video consultation again.

CONCLUSION

Video consultation can represent a supplement to treatment of patients under lipid management. The correct use requires exact planning and further research.

Detection of herpesvirus capsids in transmission electron microscopy images using transfer learning

The detailed analysis of secondary envelopment of the Human betaherpesvirus 5/human cytomegalovirus (HCMV) from transmission electron microscopy (TEM) images is an important step towards understanding the mechanisms underlying the formation of infectious virions. As a step towards a software-based quantification of different stages of HCMV virion morphogenesis in TEM, we developed a transfer learning approach based on convolutional neural networks (CNNs) that automatically detects HCMV nucleocapsids in TEM images. In contrast to existing image analysis techniques that require time-consuming manual definition of structural features, our method automatically learns discriminative features from raw images without the need for extensive pre-processing. For this a constantly growing TEM image database of HCMV infected cells was available which is unique regarding image quality and size in the terms of virological EM. From the two investigated types of transfer learning approaches, namely feature extraction and fine-tuning, the latter enabled us to successfully detect HCMV nucleocapsids in TEM images. Our detection method has outperformed some of the existing image analysis methods based on discriminative textural indicators and radial density profiles for virus detection in TEM images. In summary, we could show that the method of transfer learning can be used for an automated detection of viral capsids in TEM images with high specificity using standard computers. This method is highly adaptable and in future could be easily extended to automatically detect and classify virions of other viruses and even distinguish different virion maturation stages.

FIB and MIP: understanding nanoscale porosity in molecularly imprinted polymers via 3D FIB/SEM tomography

We present combined focused ion beam/scanning electron beam (FIB/SEM) tomography as innovative method for differentiating and visualizing the distribution and connectivity of pores within molecularly imprinted polymers (MIPs) and non-imprinted control polymers (NIPs). FIB/SEM tomography is used in cell biology for elucidating three-dimensional structures such as organelles, but has not yet been extensively applied for visualizing the heterogeneity of nanoscopic pore networks, interconnectivity, and tortuosity in polymers. To our best knowledge, the present study is the first application of this strategy for analyzing the nanoscale porosity of MIPs. MIPs imprinted for propranolol - and the corresponding NIPs - were investigated establishing FIB/SEM tomography as a viable future strategy complementing conventional isotherm studies. For visualizing and understanding the properties of pore networks in detail, polymer particles were stained with osmium tetroxide (OsO₄) vapor, and embedded in epoxy resin. Staining with OsO₄ provides excellent contrast during high-resolution SEM imaging. After optimizing the threshold to discriminate between the stained polymer matrix, and pores filled with epoxy resin, a 3D model of the sampled volume may be established for deriving not only the pore volume and pore surface area, but also to visualize the interconnectivity and tortuosity of the pores within the sampled polymer volume. Detailed studies using different types of cross-linkers and the effect of hydrolysis on the resulting polymer properties have been investigated. In comparison of MIP and NIP, it could be unambiguously shown that the interconnectivity of the visualized pores in MIPs is significantly higher vs. the non-imprinted polymer, and that the pore volume and pore area is 34% and approx. 35% higher within the MIP matrix. This confirms that the templating process not only induces selective binding sites, but indeed also affects the physical properties of such polymers down to the nanoscale, and that additional chemical modification, e.g., via hydrolysis clearly affects that nature of the polymer.

Preservation of protein fluorescence in embedded human dendritic cells for targeted 3D light and electron microscopy

In this study, we present a correlative microscopy workflow to combine detailed 3D fluorescence light microscopy data with ultrastructural information gained by 3D focused ion beam assisted scanning electron microscopy. The workflow is based on an optimized high pressure freezing/freeze substitution protocol that preserves good ultrastructural detail along with retaining the fluorescence signal in the resin embedded specimens. Consequently, cellular structures of interest can readily be identified and imaged by state of the art 3D confocal fluorescence microscopy and are precisely referenced with respect to an imprinted coordinate system on the surface of the resin block. This allows precise guidance of the focused ion beam assisted scanning electron microscopy and limits the volume to be imaged to the structure of interest. This, in turn, minimizes the total acquisition time necessary to conduct the time consuming ultrastructural scanning electron microscope imaging while eliminating the risk to miss parts of the target structure. We illustrate the value of this workflow for targeting virus compartments, which are formed in HIV-pulsed mature human dendritic cells.

Optimizing Surveillance for South American Origin Influenza A Viruses Along the United States Gulf Coast Through Genomic Characterization of Isolates from Blue-winged Teal (Anas discors)

Relative to research focused on inter-continental viral exchange between Eurasia and North America, less attention has been directed towards understanding the redistribution of influenza A viruses (IAVs) by wild birds between North America and South America. In this study, we genomically characterized 45 viruses isolated from blue-winged teal (Anas discors) along the Texas and Louisiana Gulf Coast during March of 2012 and 2013, coincident with northward migration of this species from Neotropical wintering areas to breeding grounds in the United States and Canada. No evidence of South American lineage genes was detected in IAVs isolated from blue-winged teal supporting restricted viral gene flow between the United States and southern South America. However, it is plausible that blue-winged teal redistribute IAVs between North American breeding grounds and wintering areas throughout the Neotropics, including northern South America, and that viral gene flow is limited by geographical barriers further south (e.g., the Amazon Basin). Surveillance for the introduction of IAVs from Central America and northern South America into the United States may be further optimized through genomic characterization of viruses resulting from coordinated, concurrent sampling efforts targeting blue-winged teal and sympatric species throughout the Neotropics and along the United States Gulf Coast.

Electron tomography and cryo-SEM characterization reveals novel ultrastructural features of host-parasite interaction during Chlamydia abortus infection

Chlamydia (C.) abortus is a widely spread pathogen among ruminants that can be transmitted to women during pregnancy leading to severe systemic infection with consecutive abortion. As a member of the Chlamydiaceae, C. abortus shares the characteristic feature of an obligate intracellular biphasic developmental cycle with two morphological forms including elementary bodies (EBs) and reticulate bodies (RBs). In contrast to other chlamydial species, C. abortus ultrastructure has not been investigated yet. To do so, samples were fixed by high-pressure freezing and processed by different electron microscopic methods. Freeze-substituted samples were analysed by transmission electron microscopy, scanning transmission electron microscopical tomography and immuno-electron microscopy, and freeze-fractured samples were analysed by cryo-scanning electron microscopy. Here, we present three ultrastructural features of C. abortus that have not been reported up to now. Firstly, the morphological evidence that C. abortus is equipped with the type three secretion system. Secondly, the accumulation and even coating of whole inclusion bodies by membrane complexes consisting of multiple closely adjacent membranes which seems to be a C. abortus specific feature. Thirdly, the formation of small vesicles in the periplasmic space of RBs in the second half of the developmental cycle. Concerning the time point of their formation and the fact that they harbour chlamydial components, these vesicles might be morphological correlates of an intermediate step during the process of redifferentiation of RBs into EBs. As this feature has also been shown for C. trachomatis and C. pneumoniae, it might be a common characteristic of the family of Chlamydiaceae.

Criteria impacting the cellular uptake of nanoparticles: a study emphasizing polymer type and surfactant effects

A detailed understanding of the particle-cell interaction is essential and of immense interest in order to create a "specific carrier" for each particular application. In this paper, the effect of the surfactant type (non-ionic vs ionic) and polymer nature on the cellular uptake of fluorescent polystyrene and poly(L-lactide) nanoparticles was studied on HeLa cells. Nanoparticles in a size range from 100 to 160 nm were synthesized by the miniemulsion process. The particles were detected in cells by confocal laser scanning fluorescence microscopy and flow cytometry. It was found that the influence of the surface charge is greater than that of the polymer type itself. In fact, particles stabilized with cationic surfactant were incorporated in a large number irrespective of polymer type. Cellular pathways at ultrastructural level were studied by transmission electron microscopy in more detail to shed light on the particle-cell interaction based on the material properties. The criteria governing the cellular uptake of nanoparticles based on the polymer and surfactant types are finally established.

Recovery of mechano-electrical transduction in rat cochlear hair bundles after postnatal destruction of the stereociliar cross-links

Mechano-electrical transduction (MET) in the stereocilia of outer hair cells (OHCs) was studied in newborn Wistar rats using scanning electron microscopy to investigate the stereociliar cross-links, Nomarski laser differential interferometry to investigate stereociliar stiffness and by testing the functionality of the MET channels by recording the entry of fluorescent dye, FM1-43, into stereocilia. Preparations were taken from rats on their day of birth (P0) or 1–4 days later (P1–P4). Hair bundles developed from the base to the apex and from the inner to outer OHC rows. MET channel responses were detected in apical coil OHCs on P1. To study the possible recovery of MET after disrupting the cross-links, the same investigations were performed after the application of Ca²⁺ chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) and allowing the treated samples to recover in culture medium for 0–20 h. We found that the structure and function were abolished by BAPTA. In P0–P1 samples, structural recovery was complete and the open probability of MET channels reached control values. In P3–P4 samples, complete recovery only occurred in OHCs of the outermost row. Although our results demonstrate an enormous recovery potential of OHCs in the postnatal period, the structural component restricts the potential for therapy in patients.

Experimental realization of Dicke states of up to six qubits for multiparty quantum networking

We report the first experimental generation and characterization of a six-photon Dicke state. The produced state shows a fidelity of F=0.56+/-0.02 with respect to an ideal Dicke state and violates a witness detecting genuine six-qubit entanglement by 4 standard deviations. We confirm characteristic Dicke properties of our resource and demonstrate its versatility by projecting out four- and five-photon Dicke states, as well as four-photon Greenberger-Horne-Zeilinger and W states. We also show that Dicke states have interesting applications in multiparty quantum networking protocols such as open-destination teleportation, telecloning, and quantum secret sharing.

High-resolution cryo-SEM allows direct identification of F-actin at the inner nuclear membrane of Xenopus oocytes by virtue of its structural features

The nuclear envelope of Xenopus laevis stage VI oocytes was studied in a high-resolution field emission cryo-scanning electron microscope to compare the level of structural preservation obtainable by different procedures of specimen preparation. All approaches generally allowed frequent detection of long filaments of about 10 nm in diameter that were attached to the nuclear envelope's inner membrane facing the nuclear interior. Structural details of these 10-nm filaments, however, could not be unveiled by standard procedures of specimen preparation and analysis, including critical point drying and imaging at room temperature. In contrast, after freeze-drying and imaging at -100 degrees C, the 10-nm filament type was found to be composed of distinct globular subunits of approximately 5 nm in diameter that were arranged in a helical manner with right-handed periodicity. Stereoscopic images showed that some of these filaments were lying directly on the membrane whereas others appeared to hover at a certain distance above the nuclear envelope. The appearance of these filaments was highly similar to that of in vitro polymerized F-actin analysed in parallel, and closely resembled the structural characteristics of F-actin filaments described earlier. By virtue of their structural features we therefore conclude that these filaments at the nuclear periphery represent F-actin. The high level of structural resolution obtainable by field emission cryo-SEM illustrates the potential of this method for studying details of biological structures in a subcellular context.

Freeze-substitution: the addition of water to polar solvents enhances the retention of structure and acts at temperatures around -60 degrees C

High-pressure freezing followed by freeze substitution and plastic embedding is becoming a more widely used method for TEM sample preparation. Here, we have investigated the influence of solvents, fixative concentrations and water content in the substitution medium on the sample quality of high-pressure frozen, freeze-substituted and plastic embedded mammalian cell culture monolayers. We found that the visibility of structural details was optimal with acetone and that extraction increased with both increasing and decreasing solvent polarity. Interestingly, the addition of water to polar solvents increased the sample quality, while being destructive when added to apolar solvents. The positive effect of water addition is saturable in acetone and ethanol at 5%(v/v), but even addition of up to 20% water has no negative effect on the sample structure. Therefore, a medium based on acetone containing fixatives and 5% water is most optimal for the substitution of mammalian cell cultures. In addition, our results suggest that the presence of water is critical for the retention of structure at temperatures around -60 degrees C.

Penetration and growth of DPPC/DHPC bicelles inside the stratum corneum of the skin

The effect of dipalmitoyl phosphatidylcholine (DPPC)/dihexanoyl phosphatidylcholine (DHPC) bicelles on the microstructure of pig stratum corneum (SC) in vitro was evaluated. The physicochemical characterization of these nanoaggregates revealed small disks with diameters around 15 nm and a thickness of 5.4 nm. Upon dilution, the bicelles grow and transform into vesicles. Cryogenic scanning electron microscopy (cryo-SEM) images of the SC pieces treated with this system showed vesicles of about 200 nm and lamellar-like structures in the intercellular lipid areas. These vesicles probably resulted from the growth and molecular rearrangement of the DPPC/DHPC bicelles after penetrating the SC. The presence of lamellar-like structures is ascribed to the interaction of the lipids from bicelles with the SC lipids. The bicellar system used is suitable to penetrate the skin SC and to reinforce the intercellular lipid areas, constituting a promising tool for skin applications.

Timing and patterns of recurrences and deaths from prostate cancer following adjuvant pelvic radiotherapy for pathologic stage T3/4 adenocarcinoma of the prostate

To determine the timing and patterns of late recurrence after radical prostatectomy (RP) alone or RP plus adjuvant radiotherapy (RT). Between 1970 and 1983, 159 patients underwent RP for newly diagnosed adenocarcinoma of the prostate and were found to have positive surgical margins, extracapsular extension and/or seminal vesicle invasion. Of these, 46 received adjuvant RT and 113 did not. The RT group generally received 45-50 Gy to the whole pelvis, then a boost to the prostate bed (total dose of 55-65 Gy). In the RP group, 62% received neoadjuvant/adjuvant androgen deprivation vs 17% in the RT group. Patients were analyzed with respect to timing and patterns of failure. Only one patient was lost to follow-up. The median follow-up for surviving patients was nearly 20 years. The median time to failure in the surgery group was 7.5 vs 14.7 years in the RT group (P=0.1). Late recurrences were less common in the surgery group than the RT group (9 and 1% at 10 and 15 years, respectively vs 17 and 9%). In contrast to recurrences, nearly half of deaths from prostate cancer occurred more than 10 years after treatment. Deaths from prostate cancer represented 55% of all deaths in these patients. Recurrences beyond 10 years after RP in this group of patients were relatively uncommon. Despite its long natural history, death from prostate cancer was the most common cause of mortality in this population with locally advanced tumors, reflecting the need for more effective therapy.

[Does the orientation of the IOL in the eye play a role? Imaging quality of foldable intraocular lenses measured utilizing point spread function (PSF-measurement) and scanning electron microscopy cross-sectional images]

BACKGROUND

Foldable intraocular lenses (IOLs) are established in ophthalmic surgery and increasingly more complex geometries are available. This study investigates different designs of the optics of the IOL as well as the imaging quality of these optics utilizing electron microscopic photographs and mathematical approximations.

METHOD

Included in this study were two different lens powers of common IOLs (+ 13 D and + 26 D). All studied IOLs were processed depending upon their water content: Aqueous IOLs with up to 25 % water content were fixed with 2.5 % glutaraldehyde in 0.1 M phosphate buffer (mPP), and then contrasted with 2 % OsO (4) and processed in an alcohol series of 30 - 100 % propanol. Subsequently, the IOLs were transferred into EPON (epoxy resin) and polymerization took place at 60 degrees C. After hardening, the samples were cut out with a leaves saw and divided into halves. Afterwards these were polished with glass and diamond knifes at the ultramicrotom (Ultracut, Rückert-Jung). After coal vaporization measurement took place in the scanning electron microscope (DSM 962, Zeiss). In the case of dry stored IOLs, the samples were sputtered with Au-Pd 20 nm and afterwards measurement was performed as described above. The measurement of the optical imaging quality was performed with correctly and inversely oriented IOLs according to the standard EN ISO 11979 -- 2 by means of a measuring system which works on the basis of the point spread function (PSF) and/or the modulation transfer function (MTF). From this the Strehl ratio was computed in each case.

RESULTS

Utilizing a correlation of the electron microscopic investigation of the optics of different IOLs with their imaging quality (Strehl ratio), we were able to show that the optical design of the IOL has substantial influence on the imaging quality of an intraocular lens. In particular, with non-symmetrical designs of the optics (e. g., AR40 e; AMO) the orientation of an IOL in the eye is crucial; i. e., the Strehl ratio increased thereby from 0.68 to 0.87.

CONCLUSIONS

The design of asymmetrical optics is crucial and much attention should be paid to the fact that the imaging quality can substantially be affected. A correct orientation of the lens within the eye is very important with these asymmetrical optics.

Quantitative analysis of keratin filament networks in scanning electron microscopy images of cancer cells

The keratin filament network is an important part of the cytoskeleton. It is involved in the regulation of shape and viscoelasticity of epithelial cells. The morphology of keratin networks depends on post-translational modifications of keratin monomers. In-vitro studies indicated that network characteristics, such as filament crosslink density, determines the biophysical properties of the filament network. This report presents a quantitative method for the morphological analysis of keratin filament networks. Visualization of filaments was based on prefixation extraction of epithelial cells and scanning electron microscopy (SEM). SEM images were processed by a skeletonization algorithm to obtain a graph structure that represents individual filaments as well as their connections. This method was applied to investigate the effects of transforming growth factor alpha (TGFalpha) on the morphology of keratin networks in pancreatic cancer cells. TGFalpha contributes to pancreatic cancer progression and activates signalling pathways phosphorylating keratin monomers. Using this new method, a significant alteration to the keratin network morphology could be detected in response to TGFalpha.

Experimental one-way quantum computing

Standard quantum computation is based on sequences of unitary quantum logic gates that process qubits. The one-way quantum computer proposed by Raussendorf and Briegel is entirely different. It has changed our understanding of the requirements for quantum computation and more generally how we think about quantum physics. This new model requires qubits to be initialized in a highly entangled cluster state. From this point, the quantum computation proceeds by a sequence of single-qubit measurements with classical feedforward of their outcomes. Because of the essential role of measurement, a one-way quantum computer is irreversible. In the one-way quantum computer, the order and choices of measurements determine the algorithm computed. We have experimentally realized four-qubit cluster states encoded into the polarization state of four photons. We characterize the quantum state fully by implementing experimental four-qubit quantum state tomography. Using this cluster state, we demonstrate the feasibility of one-way quantum computing through a universal set of one- and two-qubit operations. Finally, our implementation of Grover's search algorithm demonstrates that one-way quantum computation is ideally suited for such tasks.

Full characterization of a three-photon Greenberger-Horne-Zeilinger state using quantum state tomography

We have performed the first experimental tomographic reconstruction of a three-photon polarization state. Quantum state tomography is a powerful tool for fully describing the density matrix of a quantum system. We measured 64 three-photon polarization correlations and used a "maximum-likelihood" reconstruction method to reconstruct the Greenberger-Horne-Zeilinger state. The entanglement class has been characterized using an entanglement witness operator and the maximum predicted values for the Mermin inequality were extracted.

Quantum nonlocality obtained from local states by entanglement purification

We have applied an entanglement purification protocol to produce a single entangled pair of photons capable of violating a Clauser-Horne-Shimony-Holt Bell inequality from two pairs that individually could not. The initial poorly entangled photons were created by a controllable decoherence that introduced complex errors. All of the states were reconstructed using quantum state tomography which allowed for a quantitative description of the improvement of the state after purification.

Influence of chemical and freezing fixation methods in the freeze-fracture of stratum corneum

A comparison between two fixation techniques for freeze-fracture was established. Stratum corneum (SC) samples from pig epidermis were fixed using high-pressure freezing (HPF) and using plunging in propane freezing; the latter after chemical fixation. Then, frozen samples were freeze-fractured, coated with platinum-carbon, and visualized using a high-resolution low-temperature scanning electron microscope and a transmission electron microscope. Our results indicate that the plane of freeze-fracture was different depending on the fixation and freezing methodology used. In the samples frozen by HPF without chemical fixation, the fracture plane laid mainly between the lipid lamellae. However, when chemical fixation and plunging in propane freezing was used, the fracture plane did not show preference to a specific way. Plunging in propane freezing of chemically fixed samples, on the other hand, provides a more homogeneous fracture behaviour. Thus, depending on the methodology used, we can favour a visualization of either lipid or protein domains of the SC. These results could be very useful in future ultrastructural studies in order to facilitate the microscopic visualization and interpretation of the complex images such as those of SC and even of other samples in which different domains coexist.

Distributing entanglement and single photons through an intra-city, free-space quantum channel

We have distributed entangled photons directly through the atmosphere to a receiver station 7.8 km away over the city of Vienna, Austria at night. Detection of one photon from our entangled pairs constitutes a triggered single photon source from the sender. With no direct time-stable connection, the two stations found coincidence counts in the detection events by calculating the cross-correlation of locally-recorded time stamps shared over a public internet channel. For this experiment, our quantum channel was maintained for a total of 40 minutes during which time a coincidence lock found approximately 60000 coincident detection events. The polarization correlations in those events yielded a Bell parameter, S=2.27+/-0.019, which violates the CHSH-Bell inequality by 14 standard deviations. This result is promising for entanglement-based freespace quantum communication in high-density urban areas. It is also encouraging for optical quantum communication between ground stations and satellites since the length of our free-space link exceeds the atmospheric equivalent.

Recent progress in freeze-fracturing of high-pressure frozen samples

Pancreatic tissue, bacteria and lipid vesicles were high-pressure frozen and freeze-fractured. In addition to the normal holder, a new type of high-pressure freezing holder was used that is particularly suitable for suspensions. This holder can take up an EM grid that has been dipped in the suspension and clamped in between two low-mass copper platelets, as used for propane-jet freezing. Both the standard and the new suspension holder allowed us to make cryo-fractures without visible ice crystal damage. High-pressure frozen rat pancreas tissue samples were cryo-fractured and cryo-sectioned with a new type diamond knife in the microtome of a freeze-etching device. The bulk fracture faces and blockfaces were investigated in the frozen-hydrated state by use of a cryo-stage in an in-lens SEM. Additional structures can be made visible by controlled sublimation of ice ('etching'), leading to a better understanding of the three-dimensional organization of organelles, such as the endoplasmic reticulum. With this approach, relevant biological structures can be investigated with a few nanometre resolution in a near life-like state, preventing the artefacts associated with conventional fixation techniques.

[Intensive care of delirium syndromes]

Delirium is mental dysfunctions occurring as impaired attentional and memory systems with disturbances of consciousness, affectivity, psychomotor activity and sleep patterns. Numerous factors and underlying diseases may be responsible for these non-specific symptoms. Therefore, a thorough evaluation of preadmission history and current clinical status, supplemented by laboratory and extended technical diagnostic procedures, are always required. If delirium occurs in connection with emergency admission to hospital, an organic disease can most regularly be found. Due to its rapid time of onset and minor side-effects, the intravenous injection of 2.0 g gamma-hydroxybutyric acid is preferred for sedation of extremely agitated patients. Neuroleptic drugs are indicated in psychiatric patients. A central anticholinergic syndrome in the early postoperative period causative of the symptoms of delirium may respond to intravenous injection of physostigmine. Most of the time, however, these acute disturbances of brain function are best treated by correction of homeostatic imbalances, restoration of cardiovascular and respiratory stability and alleviation of pain. Postoperative delirium occurring two or more days later is frequently due to respiratory distress, followed by sepsis, alcohol withdrawal and many other causes including heart failure, exsiccosis and side-effects of drugs. In intensive care patients, delirium may be caused, for example, by withdrawal (alcohol, opioids, benzodiazepines), the onset of sepsis (often venous catheter related), side-effects of drugs, problems of communication, sleep deprivation and others. Treatment should focus on finding the right approach. Personal care should be intensified and include help from family members. Most problems arise from agitated, non-cooperative patients. Treatment with clonidine, gamma-hydroxybutyric acid or neuroleptic drugs like perazin and haloperidol may be required to reduce agitation and the activation of sympathetic influence.

Freeze substitution of high-pressure frozen samples: the visibility of biological membranes is improved when the substitution medium contains water

Biological membranes are often poorly visible with the electron microscope after high-pressure freezing and freeze-substitution. The water content of the sample and of the substitution medium is one factor among others that strongly influences membrane visibility. In order to investigate this effect, high-pressure frozen yeast cells, rat-pancreas tissue and arthropod tissue were freeze-substituted with and without adding water to the substitution medium. The visibility of the biological membranes was generally improved if the substitution medium contained 1-5% water. The effect was especially pronounced in yeast cells, where membrane visibility was poor after freeze-substitution with water-free medium but good after addition of 5% water to the substitution medium.

Calcium stores in differentiated Dictyostelium discoideum: prespore cells sequester calcium more efficiently than prestalk cells

Dictyostelium discoideum pseudoplasmodia exhibit a gradient of the cytosolic free Ca2+-concentration ([Ca2+]i) along their anterior-posterior axis involved in cell-type specific differentiation. [Ca2+]i is high in prestalk and low in prespore cells. We determined the content and localization of calcium and other elements in cryosectioned cells of pseudoplasmodia and fruiting bodies by X-ray microanalysis. Granular stores rich in Ca, Mg and P were identified. Average Ca was higher in prespore than prestalk granules (225vs 111 mmol/kg dry weight). Total Ca stored in granules was also higher in prespore than prestalk cells. The amount of P and S in granules differed between the two cell types indicating different store composition. In spores mean granular Ca was 120 mmol/kg dry weight. Stalk cells had smaller granules with 360 mmol Ca/kg dry weight. Complementary to microanalysis, vesicular Ca2+-fluxes were studied in fractionated cell homogenates. The rate of Ca2+-uptake was higher in pellet fractions of prespore than prestalk amoebae (4.7 vs 3.4 nmol/min x mg). Ca2+-release was greater in supernatant fractions from prestalk than prespore cells (16.5vs 7.7 nmol/10(8)cells). In summary, prestalk and prespore cells possess qualitatively different, high-capacity stores containing distinct amounts of Ca and probably being involved in regulation of the anterior-posterior [Ca2+]i-gradient.

Liposomes as protective agents of stratum corneum against octyl glucoside: a study based on high-resolution, low-temperature scanning electron microscopy

The ability of phosphatidylcholine (PC) liposomes to protect pig stratum corneum (SC) against the action of the nonionic surfactant octyl glucoside (OG) was investigated "in vitro" using double-layer coating for high-resolution, low-temperature scanning electron microscopy. This technique has been useful in preventing drying artifacts in the study of biological materials. The treatment of SC with OG led to a perturbation mainly in the corneocytes. However, the incubation of the tissue with liposomes prior to the OG treatment resulted in a progressive decrease in these perturbations and, consequently, in the progressive protection of the SC against the action of the surfactant.

Immunohistochemical demonstration of hyaluronan and its possible involvement in axolotl neural crest cell migration

Hyaluronan (HA), an extracellular matrix component, is involved mainly in the control of cell proliferation, neural crest and tumor cell migration, and wound repair. We investigated the effect of hyaluronan on neural crest (NC) cell migration and its ultrastructural localization in dark (wild-type) and white mutant embryos of the Mexican axolotl (Ambystoma mexicanum, Amphibia). The axolotl system is an accepted model for studying mechanisms of NC cell migration. Using a biotinylated hyaluronan binding protein (HABP), major extracellular matrix (ECM) spaces, including those of NC cell migration, reacted equally positive on cryosections through dark and white embryos. Since neural crest-derived pigment cells migrate only in subepidermal spaces of dark embryos, HA does not seem to influence crest cell migration in vivo. However, when tested on different alternating substrates in vitro, migrating NC cells in dark and white embryos prefer HA to fibronectin. In vivo, such an HA migration stimulating effect might exist as well, but be counteracted to differing degrees in dark and white embryos. The ultrastructural localization of HA was studied by means of transmission electron microscopic immunohistochemistry using HABP and different protocols of standard chemical fixation, cryofixation, embedding, and immunolabeling. The binding reaction of HA to HABP was strong and showed an equal distribution throughout ECM spaces after both standard chemical fixation/freeze substitution and cryofixation. A preference for the somite or subepidermal side was not observed. Following standard fixation/freeze substitution HABP-labeled "honeycomb"-like networks reminiscent of fixation artifacts were more prominent than labeled fibrillar or irregular net-like structures. The latter predominated in adequately frozen specimens following high-pressure freezing/freeze substitution. For this reason fibrillar or irregular net-like structures very likely represent hyaluronan in the complex subepidermal matrix of the axolotl embryo in its native arrangement.

Structural modifications in the stratum corneum by effect of different solubilizing agents: a study based on high-resolution low-temperature scanning electron microscopy

The action of different solubilizing agents (chloroform-methanol mixtures and the nonionic surfactant octyl glucoside, OG) on the structural organization of the stratum corneum (SC) was investigated by means of the double-layer high-resolution low-temperature scanning electron microscopy technique. Chloroform-methanol mixtures were able to remove mainly the lipid without a significant loss of cohesion in the SC tissue. However, OG treatment caused a partial disaggregation of the corneocytes and their envelopes and, at a macroscopic level, a loss of cohesion in the whole SC tissue. As for lipid domains, after OG treatment the formation of rough structures was detected, probably associated with the disorder in the lipid lamellae. The formation of these new structures could be attributable to the interaction of the lipids with the proteins liberated from the corneocytes. Hence, a direct correlation may be established between the preservation of the structure of the corneocytes and the corneocyte envelope and the cohesion of the whole SC tissue.

Biological ultrastructure as revealed by high resolution cryo-SEM of block faces after cryo-sectioning

Ultrastructural information was obtained by imaging the block face of high-pressure-frozen cryo-sectioned biological samples in a high-resolution cryo-SEM. Cryo-sectioning leads to a well-defined flat artificial surface in contrast to cryo-fracturing. Typical artefacts of cryo-sections such as compression and crevasses were not visible on the block face. The ultrastructural features known from resin sections and from freeze-fractures could also be found on the block faces. The cytoplasms show particles of different size which most likely represent proteins. The effects of radiation damage could be reduced considerably by applying the double layer coating technique and backscattered electron imaging. High quality cryo-sections are only obtained from vitrified material. Reasonably flat block faces were, however, also obtained from adequately frozen microcrystalline samples, thereby facilitating ultrastructural studies in the frozen hydrated state.

Electron microscopic investigation of water occlusions in intercellular spaces in the inner cortex of lucerne nodules

It is unclear to what extent oxygen diffusion pathways through the cortex of the nitrogen-fixing zone of indeterminate nodules are liquid filled and whether a blockage of these pathways is involved in varying nodule oxygen permeability to control nitrogenase activity. We examined the proportion of water-filled intercellular spaces of lucerne (Medicago sativa L.) nodules with cryo-scanning electron microscopy. This technique allows for direct observation of water accumulation. Thirty percent of all intercellular spaces in the inner cortex of lucerne nodules were liquid filled. Decreasing the nodule oxygen permeability by detopping of the plant or by increasing the rhizospheric oxygen partial pressure to 80 kPa had no statistically significant effect on the water distribution in the intercellular spaces. Therefore, the hypothesis of a continuous aqueous diffusion barrier in the inner cortex could not be supported. The abundance of glycoproteins in intercellular spaces of the inner cortex was investigated with immunoelectron microscopy. No alteration due to detopping or after increase of the rhizospheric oxygen partial pressure was observed. Therefore, our results do not support the hypothesis of a short-term regulation of oxygen permeability by blockage of diffusion pathways through morphological changes in the cortex region of the nitrogen-fixing zone of lucerne nodules.

Double-layer coating for field-emission cryo-scanning electron microscopy--present state and applications

Imaging of fast-frozen samples is the most direct approach for electron microscopy of organic material. It prevents chemical fixation and drying artifacts. Frozen samples can be replicated and imaged in the transmission electron microscope (TEM), or they can be directly visualized in the cryo-scanning electron microscope (cryo-SEM). Double-layer coating combines these two techniques and many of their advantages. With this method, the frozen bulk sample is coated similar to the TEM-replica technique with, for example, a shadow of platinum (at an angle of 45 degrees) and an additional layer of carbon. Then, the sample is cryo-transferred to an SEM equipped with a cold stage and imaged with the material-dependent backscattered electron signal that shows the platinum distribution. With this method, charging artifacts and the effects of beam damage are significantly reduced. Although currently the resolution of the replica technique cannot be surpassed, the method greatly facilitates the processing of brittle, rapidly frozen samples because no replica cleaning is necessary. This makes the method especially suitable for high-pressure frozen samples.

IGF-I and bFGF differentially influence atrial natriuretic factor and alpha-smooth muscle actin expression in cultured atrial compared to ventricular adult rat cardiomyocytes

In the present study, we compare expression, storage and secretion of the atrial natriuretic factor (ANF) in atrial and ventricular adult rat cardiomyocytes (aARC and vARC) in long-term culture. The influence of insulin-like growth factor-I (IGF-I) and of basic fibroblast growth factor (bFGF) on ANF production and secretion, as well as on the expression of a structural component, alpha-smooth muscle actin (alpha-sm actin), was studied in the two cell types. Antibodies against alpha-ANF were used for immunocytochemical localization of ANF. aARC contained more ANF-granules than vARC, and they were distributed throughout the cell bodies. Quantitative determination of ANF storage and secretion was done by radioimmunoassay (RIA; 125I), and it was demonstrated that aARC stored and secreted ANF 18- and 16-times more, respectively, when compared to vARC. Immuno-electron microscopy confirmed that ANF storing secretory granules were present in both types of cardiomyocytes. Expression of ANF and alpha-sm actin in aARC and vARC responded differently to treatment with either IGF-I or bFGF. In aARC, neither IGF-I nor bFGF had an influence on expression of ANF. In vARC, expression of ANF was downregulated by IGF-I and upregulated by bFGF with regard to both immunoreactivity and message. In contrast to vARC, expression of alpha-sm actin was not affected by IGF-I in aARC, whereas bFGF produced a strong upregulation similar to that found in vARC. Mitogen-activated protein kinases (MAPK) 42 and 44, though, were equally activated by bFGF and IGF-I in both aARC and vARC.

Full-thickness skin grafts from eyelids to penis, plus split-thickness grafts in chronic balanitis xerotica obliterans

Balanitis xerotica obliterans is a progressive, sclerotic, constrictive scar-forming disease process of the penile prepuce that can involve the frenulum and urethral meatus. Full-thickness skin grafting from the upper eyelids supplemented with split-thickness skin grafting was successfully used in a patient to end a 57-year symptomatic course.

Light damage in rod outer segments: the effects of fixation on ultrastructural alterations

PURPOSE

In this electron microscopical study, we compared effects of chemical fixation versus cryofixation on the ultrastructure of acute rod outer segment alterations in the rat retina.

METHODS

The alterations were induced by toxic levels of diffuse white light. Albino rats were exposed to 2000 lux for 30 min. Samples from one eye of each animal were fixed by high pressure freezing and samples from the other eye were fixed by standard glutaraldehyde procedures.

RESULTS

Light exposed retina showed major differences in their rod outer segments, inner segments and photoreceptor synaptic regions in chemical fixation. In particular gross vesiculations of outer segment membranes were produced in light exposed experiments. In contrast, in cryo-fixed samples such prominent changes were not observed in outer segment membranes. There was, however, occasional formation of small vesicles and a reduction of the cilium diameter in response to light damage. In the dark adapted control group the morphology of chemically fixed and cryo-fixed photoreceptors was similar.

CONCLUSIONS

We conclude, that cryo-fixed samples better represent the living state of the retina, because high pressure freezing is a purely physical method and acts much faster than chemical fixation.

Double-layer coating for high-resolution low-temperature scanning electron microscopy

Specimen damage caused by mass loss due to electron beam irradiation is a major limitation in low-temperature scanning electron microscopy of bulk specimens. At high primary magnifications (e.g., 100,000 x) a hydrated sample is usually severely damaged after one slow scan (about 3000 e-nm-2). The consequences of this beam damage are significantly reduced by coating the frozen-hydrated sample with a 5-10-nm-thick carbon layer. Since this layer covers up surface details, the sample is first unidirectionally shadowed with a thin heavy metal layer (e.g., 2 nm of platinum) that is in close contact with the biological surface (double layer coating). This heavy metal layer can be visualized in field-emission scanning electron microscopy with the material-dependent backscattered electron signal. The method allows for routine observation of large frozen-hydrated samples. By use of an in-lens field-emission SEM and a sensitive backscattered electron detector, structural information comparable to that obtained with the transmission electron microscopy freeze-fracture replica technique can be achieved.

Comparison of ultrastructure of germinating pea leaves prepared by high-pressure freezing-freeze substitution and conventional chemical fixation

High-pressure freezing-freeze substitution (HPF-FS) methods were applied to germinating pea leaves. Good ultrastructural preservation without visible freezing damage was obtained up to 200 microns in thickness. Compared to conventional chemical fixation (CF), cellular membranes were smoother without undulation, and organelles appeared more turgid. The matrices of cytoplasm and organelles were denser and more homogeneous. The features imply that HPF-FS samples retain more substances and ultrastructure closer to the living state. There were differences in membrane stainability among organelles in HPF-FS specimens, which were not seen after CF. Bundles of microfilaments were observed frequently after HPF-FS.

Immortalization of rat hepatocytes by fusion with hepatoma cells. I. Cloning of a hepatocytoma cell line with bile canaliculi

Hepatocytoma (HPCT) hybrid cells were obtained by fusion of cultured rat hepatocytes with Fao Reuber hepatoma cells H35 by polyethylene glycol treatment. Surviving cells were cloned in HAT (hypoxanthine-aminopterine-thymidine)/ouabain medium and propagated in cell lines over 80 passages. Morphological criteria were chosen to allow differentiation of the clones into two types of cells: 1) Type I cells which formed irregular cell layers, lacked contact inhibition and resembled the parental Fao hepatoma cells and 2) type II cells, which proliferated in monolayer cultures, exhibited contact inhibition during growth in culture plates and formed bile canaliculi thereby resembling cultured hepatocytes by phenotype. Bile canaliculi were absent in type I clones and Fao cells. One particular type II clone 1E3 was studied in detail. These cells formed bile canaliculi sealed by tight junctions and were comparably polarized as cultured hepatocytes. They expressed canalicular antigen B10, canalicular aminopeptidase N, and even secreted the fluorescent bile acid derivative NBD-cholate into the canalicular lumen. This type of HPCT cells lacked malignancy by tests in vivo and in vitro, and contained 110 +/- 5 chromosomes. The cells were considered to represent an immortalized hepatocyte-like cell line.

Scanning electron microscopy of high-pressure-frozen sea urchin embryos

High-pressure-freezing permits direct cryo-fixation of sea urchin embryos having a defined developmental state without the formation of large ice crystals. We have investigated preparation protocols for observing high-pressure-frozen and freeze-fractured samples in the scanning electron microscope. High-pressure-freezing was superior to other freezing protocols, because the whole bulk sample was reasonably well frozen and the overall three-dimensional shape of the embryos was well preserved. The samples were either dehydrated by freeze-substitution and critical-point-drying, or imaged in the partially hydrated state, using a cold stage in the SEM. During freeze-substitution the samples were stabilized by fixatives. The disadvantage of this method was that shrinking and extraction effects, caused by the removal of the water, could not be avoided. These disadvantages were avoided when the sample was imaged in the frozen-hydrated state using a cold-stage in the SEM. This would be the method of choice for morphometric studies. Frozen-hydrated samples, however, were very beam sensitive and many structures remained covered by the ice and were not visible. Frozen-hydrated samples were partially freeze-dried to make visible additional structures that had been covered by ice. However, this method also caused drying artifacts when too much water was removed.