Modelling self assembly of natural silk solutions.

We present a tentative interpretation of the origin of nematic liquid crystalline order exhibited by various natural silk fibroin solutions, notably those of orb-weaving spiders and the domestic silkworm Bombyx mori. It is thought that liquid crystalline rheology is exploited during the spinning process. We discuss in this approach the response of the liquid crystalline phase diagram to equilibrium physiological conditions and to parameters characterising the amino acid sequence of the fibroin molecules. The phase diagram is sensitive in this latter respect to sequence mutations, such that it may constitute a source of evolutionary selection pressure.

THE PHYSICAL AND CHEMICAL MICROSTRUCTURE OF THE ACHATINA FULICA EPIPHRAGM.

Microstructural characterization of Achatina fulica Bowdich, 1822 epiphragms and mucus secretions was performed to address two questions: what are the structure and composition of the reinforcing inorganic phase in the epiphragms, and what enables a durable epiphragm to form quickly in comparison to other biomineralized materials? Characterization was performed by a combination of light microscopy (relying on a variety of contrast modes), wet chemical tests, environmental scanning electron microscopy (including the use of energy dispersive X-ray analysis to obtain compositional data), and X-ray diffraction. The morphology of the inorganic phase promotes mechanical interlocking and presents a large surface for binding to the organic matrix. Strong binding occurs between the organic and inorganic phases. The inorganic phase adopts the calcite structure; its composition is Ca(0.912) Mg(0.088) CO(3). Epiphragms can form quickly because pre-grown crystals of the inorganic reinforcing phase are co-deposited with the mucus matrix. Unlike other biomineralized material, the crystals are not solution-grown in situ on an organic template in the final product.

A simple method for orienting silk and other flexible fibres in transmission electron microscopy specimens.

When microstructures are characterized by transmission electron microscopy (TEM), the interpretation of results is facilitated if the material can be sectioned in defined orientations. In the case of fibres, it is especially useful if transverse and longitudinal sections can be obtained reliably. Here we describe a procedure for orienting spider silk and other flexible fibres for TEM investigation. Prior to embedding in epoxy resin, the silk is wound around a notched support made from polyester film. No glue is required. After the silk and its supporting film have been embedded and the resin has been cured the film can be peeled away to reveal nearly perfectly orientated silk threads. Both transverse and longitudinal sections can then be cut with a microtome. The method can be extended to obtain sections at any intermediate orientation.

Fluctuation-entanglement mechanism for director anchoring at nematic polymer surfaces.

The existence of polymeric entanglements in a polymer nematic liquid crystal modifies the Frank elastic description governing director deformation. We present a calculation of the director fluctuation contribution to polymer nematic surface tension, in which we supplement the usual Frank terms with a damping term due to entanglements. We infer an effective surface anchoring potential, going to zero as n ln n in the limit of low entanglement density n. The anchoring easy axis depends on the relative magnitudes of the Frank constants governing director elasticity. We comment on generalizing the approach to take into account polydomain structure.

[Cutaneous lupus erythematosus following argon laser treatment]. / Lupus érythémateux cutané déclenché par le laser argon.

BACKGROUND: It is well known that exposure to ultraviolet light can trigger lupus manifestations. Other light sources may have the same effect. We report a case of argon laser-induced lupus erythematosus. CASE REPORT: A 59-year-old women developed an erythematous edematous infiltrated and sensitive lesion over the right cheek ten days after an argon laser treatment of the retina. The lesion spread towards the chin despite antibiotic treatment. Histology examination of a biopsy specimen and direct immunofluorescence suggested the diagnosis of cutaneous lupus erythematosus. The lesions regressed in one month with hydroxychloroquine (400 mg/d) treatment. DISCUSSION: Our patient developed argon laser induced cutaneous lupus erythematosus. It is known that ultraviolet light and non-ultraviolet frequencies (x-rays, visible light) can induce lupus manifestations. One case of discoid lupus erythematosus after argon laser has been reported. In our case, due to a technical error the laser beam was directed onto the ipsilateral cheek during the laser treatment of the retina. The low-energy beams used in ophthalmology would explain the absence of local burn but would be sufficient to trigger lupus. This case demonstrates that argon laser, a visible blue or green beam, can provoke cutaneous lupus erythematosus even if there is no heat-induced burn. It is important to be aware of this adverse effect due to the widespread use of lasers in dermatology, particularly for the treatment of cutaneous lupus lesions.

Addressing sexuality in intensive care: an addition to the curriculum.

A range of views of sexuality is explored, concluding that sexuality is more than sexual orientation. A review of the literature revealed that little attention is given by nurses in intensive care to meeting those needs of patients which relate to their sexuality. Vignettes, taken from practice, are given as examples of where the sexuality of a patient has been a significant element and these are used to examine nurses' attitudes to sexuality. An evaluation of two teaching sessions is given.

The effect of post-spin drawing on spider silk microstructure: a birefringence model.

Measurements of optical birefringence have been used to characterise the effect of mechanical history on supramolecular structure in major ampullate silk from Nephila clavipes (golden orb weaver) spiders. Birefringence modelling is demonstrated to be a powerful technique for obtaining quantitative information on supramolecular rearrangement in response to macroscopic strain. Temporary and permanent birefringence changes measured as a function of strain and strain rate are interpreted in terms of two types of microstructural response: increased molecular alignment in all the microstructural phases present is accompanied by decreased lateral register within crystallographically ordered phases. Significant implications of these studies for the commercial processing of silks and silk-like biopolymers are discussed.

Spider (Araneus diadematus) cocoon silk: a case of non-periodic lattice crystals with a twist?

Transmission electron microscopy was used to investigate the supramolecular structure of Araneus diadematus (garden spider) cocoon silk. Electron diffraction patterns contain features which are consistent with the presence of non-periodic lattice crystals, i.e. highly frustrated crystalline regions as identified previously in the major ampullate silk (MAS, dragline) of Nephila clavipes spiders. The diffraction patterns further suggest that crystals in A. diadematus cocoon silk may be twisted parallel to the chain direction, offering a potential explanation for the lower tensile stiffness of this fibre relative to MAS.

Mucus liquid crystallinity: is function related to microstructural domain size?

The size of liquid crystalline domains formed in partially dried giraffe saliva is found to be an order of magnitude greater than that previously documented for slug pedal mucus. A correlation between (a) intrinsic liquid crystalline domain size and (b) the scale of surface topography over which the mucus is required to provide lubrication is postulated. The scale of mucus microstructure can be related, via a simple model, to two significant material constants: the elastic constant K for distortion of molecular alignment in the liquid crystalline state, and the anchoring energy I at the liquid crystal/substrate interface. In turn, the quantity K is expected to depend on fundamental molecular characteristics of the constituent mucin, such as molecular weight and degree of glycosylation. The possibility that observations of mucus microstructure might serve as a diagnostic tool for mucus defects at the molecular level is suggested.

Expanding practice and obtaining consent.

The Scope of Professional Practice liberates nurses, midwives and health visitors from previous role constraints, while keeping the focus on the patient. Some of the adjustments to the scope of practice require the individual practitioner to obtain explicit verbal or written consent.

Non-periodic lattice crystals in the hierarchical microstructure of spider (major ampullate) silk.

A commonly adopted model for the microstructure of Nephila clavipes major ampullate silk (MAS) is similar to that used for Bombyx mori (silkworm) silk: a simple composite wherein discrete, essentially perfect crystals are dispersed throughout an amorphous protein matrix. However, inconsistencies arise when researchers using complementary microstructural characterisation techniques attempt to explain their results within that framework. We present here the findings of our parallel studies in x-ray diffraction, electron microscopy, and molecular modeling. These results, combined with other data gleaned from the literature, lead us to propose a revised description of the spider silk microstructure. The new model recognizes that the 70-500 nm sized ordered regions in MAS cannot be constructed from a simple motif of repeating monomers, and develops the concept of non-periodic lattice (NPL) crystals to characterize these structures. The local composition, symmetry, and perfection of order vary over distances that are small compared to the size of an NPL crystal.

Does the APACHE II scoring system equate with the Nottingham Patient Dependency System? Can these systems be used to determine nursing workload and skill mix?

The development of a holistic patient dependency system for intensive care in Nottingham has enabled nursing staff to analyse their patient's needs more comprehensively and relate them to existing staffing levels. A recent publication (Chellel et al., 1995) implied that some units were using medical scoring systems to predict workload and that practitioners were dissatisfied with current scoring systems. Patient dependency scores were correlated with APACHE II scores by regression analysis on 1,743 patients from the Adult Intensive. Care Unit at the University Hospital, Nottingham. Analysis revealed that APACHE II had little ability to predict patient dependency and, therefore, is unreliable at predicting nursing workload and skill mix.

A phenomenological study of ethical decision-making experiences among senior intensive care nurses and doctors concerning withdrawal of treatment.

The study compared and contrasted the experiences of senior doctors and nurses ethical decision making concerning the withdrawal of treatment. Doctors generally took the primary role in ethical decision making, leaving nurses acting as information brokers. Nurses suffered moral distress as a result of the decision to withdraw treatment, whilst doctors suffered moral dissonance. Doctors and nurses needed to come to terms with withdrawal of treatment. A model of communication which will enhance collaborative, multidisciplinary ethical decision making is suggested.

A survey of current ventilator circuit changes in intensive care units in England.

A survey of intensive care units (England) aimed at identifying current practices in ventilator circuit changes. A random sample of 180 units were surveyed, 152 (84%) questionnaires were returned. The results demonstrated a wide range of current practices regarding circuitry and related respiratory equipment changes. Tentative recommendations for practice are suggested based on current knowledge and evidence from previous studies.

Coexistence of Meyerson's with Sutton's naevus after sunburn.

We described the simultaneous occurrence of perinaevic eczema (Meyerson's naevi) and Sutton's halo naevus in one patient. Characteristic clinical and histological features of perinaevic eczema were found around four benign melanocytic naevi on the limbs. In addition, the patient had a typical Sutton's naevus on the back. The association of Meyerson's naevi and Sutton's naevus has been reported only once in the past literature. Both diseases appeared a few weeks after a severe sunburn. The role of sun exposure in the development of eczematiform and/or vitiligoid reactions around melanocytic naevi is discussed.

Liquid crystalline order in mucus.

NASA: Mucus plays an exceptionally wide range of important biological roles. It operates as a protective, exchange, and transport medium in the digestive, respiratory, and reproductive systems of humans and other vertebrates. Mucus is a polymer hydrogel. It is secreted as discrete packages (secretory granules) by specialized secretory cells. Mucus hydrogel is stored in a condensed state inside the secretory granules. Depending upon the architecture of their constituent macromolecules and on the composition of the solvent, polymer gels can form liquid crystalline microstructures, with orientational order being exhibited over optically resolvable distances. Individual mucin molecules consist of alternating rigid segments (heavily glycosylated; hydrophilic) and flexible segments (nonglycosylated; hydrophobic). Polymer molecules consisting of rigid units linked by flexible spacers are frequently associated with liquid crystalline behavior, which again raises the possibility that mucus could form anisotropic fluid phases. Suggestions that mucins may be self-associating in dilute solution have previously been challenged on the basis of sedimentation-equilibrium studies performed on mucus in which potential sites of association were competitively blocked with inhibitors. However, the formation of stable liquid crystalline phases does not depend on the existence of inter- or intramolecular associations; these phases can form on the basis of steric considerations alone.^ieng

Pre-operative shaving in gynaecology.

The authors describe a small scale study conducted to examine the practice of pre-operative shaving in women undergoing gynaecological surgery. The results show that the practice of shaving was not uniform among the wards surveyed and that there were differences in the method used, area shaved and times at which the patient was shaved. Recommendations for practice are suggested.