Comparametric equations with practical applications in quantigraphic image processing

It is argued that, hidden within the flow of signals from typical cameras, through image processing, to display media, is a homomorphic filter. While homomorphic filtering is often desirable, there are some occasions where it is not. Thus, cancellation of this implicit homomorphic filter is proposed, through the introduction of an antihomomorphic filter. This concept gives rise to the principle of quantigraphic image processing, wherein it is argued that most cameras can be modeled as an array of idealized light meters each linearly responsive to a semi-monotonic function of the quantity of light received, integrated over a fixed spectral response profile. This quantity depends only on the spectral response of the sensor elements in the camera. A particular class of functional equations, called comparametric equations, is introduced as a basis for quantigraphic image processing. These are fundamental to the analysis and processing of multiple images differing only in exposure. The "gamma correction" of an image is presented as a simple example of a comparametric equation, for which it is shown that the underlying quantigraphic function does not pass through the origin. Thus, it is argued that exposure adjustment by gamma correction is inherently flawed, and alternatives are provided. These alternatives, when applied to a plurality of images that differ only in exposure, give rise to a new kind of processing in the "amplitude domain". The theoretical framework presented in this paper is applicable to the processing of images from nearly all types of modern cameras. This paper is a much revised draft of a 1992 peer-reviewed but unpublished report by the author, entitled "Lightspace and the Wyckoff principle."

Predictors of post-hospital employment status for psychiatric patients in Hong Kong: from perceptions of rehabilitation professionals to empirical evidence

Fifty participants with mental illness and a concrete discharge plan were selected from two mental hospitals in Hong Kong and assessed on their Psychosocial support by the Chinese Version of the Significant Others Scale, social vocational competence using the Workshop Behavior Checklist and the Vocational Social Skills Scale, medical history, work history, and demographic variables. At three months after discharge, the employed participants (n = 12) were shown to have better psychosocial support and social vocational competence than the unemployed participants (n = 24) by univariate comparison. The employed and unemployed participants did not differ in their medical and work history, and demographic variables. Implications of the results for rehabilitation programming are discussed.

Effects of a butterfly scale microstructure on the iridescent color observed at different angles

Multilayer thin-film structures in butterfly wing scales produce a colorful iridescence from reflected sunlight. Because of optical phenomena, changes in the angle of incidence of light and the viewing angle of an observer result in shifts in the color of butterfly wings. Colors ranging from green to purple, which are due to nonplanar specular reflection, can be observed on Papilio blumei iridescent scales. This refers to a phenomenon in which the curved surface patterns in the thin-film structure cause the specular component of the reflected light to be directed at various angles while affecting the spectral reflectivity at the same time by changing the optical path length through the structure. We determined the spectral reflectivities of P. blumei iridescent scales numerically by using models of a butterfly scale microstructure and experimentally by using a microscale-reflectance spectrometer. The numerical models accurately predict the shifts in spectral reflectivity observed experimentally.

Coccolith ultrastructure and biomineralisation

The relationship between calcite biomineralisation and coccolith ultrastructure is analysed across the diversity of calcifying haptophytes. The emphasis is on integration of evidence from crystallographic and ultrastructural studies but additional relevant information from biochemical and phylogenetic work is reviewed. We attempt to identify aspects of ultrastructure which are most likely to be the product of self-organising processes. The principal topics reviewed are heterococcolith rim nucleation, including reassessment of the V/R model; crystal growth regulation in heterococcoliths; holococcolith biomineralisation; and the diversity of other biomineralisation modes in haptophytes. It is concluded that the diverse range of calcareous structures produced by haptophytes probably has a common phylogenetic origin and is produced via operation of a limited set of mainly shared genetic and biochemical pathways. Copyright 1999 Academic Press.

Structure of a voltage-dependent K+ channel beta subunit

The integral membrane subunits of many voltage-dependent potassium channels are associated with an additional protein known as the beta subunit. One function of beta subunits is to modify K+ channel gating. We have determined the structure of the conserved core of mammalian beta subunits by X-ray crystallography at 2.8 A resolution. Like the integral membrane component of K+ channels, beta subunits form a four-fold symmetric structure. Each subunit is an oxidoreductase enzyme complete with a nicotinamide co-factor in its active site. Several structural features of the enzyme active site, including its location with respect to the four-fold axis, imply that it may interact directly or indirectly with the K+ channel's voltage sensor. This structure suggests a mechanism for coupling membrane electrical excitability directly to chemistry of the cell.

Impaired apoptotic deletion of myelin basic protein-reactive T cells in patients with multiple sclerosis

T cell responses to myelin basic protein (MBP) may play an important role in the pathogenesis of multiple sclerosis (MS). If MBP-reactive T cells are involved in the disease processes and undergo clonal activation and expansion, their precursor frequency would be increased in patients with MS. The frequency of MBP-reactive T cells is also influenced by regulatory mechanisms in vivo, including apoptotic deletion. In this study, we examined changes in the frequency of MBP-reactive T cells in patients with MS as a function of the apoptotic deletional mechanism in vivo, using a cell culture-based assay. A significantly increased frequency of MBP-reactive T cells was found in patients with MS relative to healthy individuals only when Fas-ligand antibody was used to block apoptosis. This result indicates that a significant proportion of MBP-reactive T cells are sensitive to apoptosis and are not deleted in vivo in patients with MS, as opposed to healthy individuals, thus suggesting a functional deficit in apoptotic deletional mechanism. Surviving Fas-sensitive MBP-reactive T cell lines represent distinct subpopulations preferentially recognizing the 111-139 region of MBP and exhibiting a Th2 cytokine profile. The findings are relevant to our understanding of regulation of MBP-reactive T cells in vivo in MS.

Rhetoric to Practice: The Challenge of Collaboration of Academe and Industry

Community health nursing is a complex practice that encompasses nurses working in many diverse settings. This article discusses the development of a project which focused on better preparation of students for potential employment in community settings. The formation of the working team and the development of the curriculum is outlined. A focus is given to the linking of primary health care principles in the teaching and facilitation of students within hospital and community settings. Comprehensive conclusions cannot be made yet from the project's preliminary findings. However, the process of collaboration has demonstrated several issues. These will have an impact on everyone who has been part of this project, and the issues are discussed in this article. The article provides an overview of the first year of collaboration of a 4-year project.

Intraneuronal ApoE in human visual cortical areas reflects the staging of Alzheimer disease pathology

Alzheimer disease (AD) is marked by progressive loss of cortical neurons with associated cognitive decline. Multiple genetic and environmental factors likely contribute to this progressive loss. Such genetic factors include the polymorphic locus (APOE) that encodes apolipoprotein E (apoE). In order to investigate a possible correspondence between cellular localization of apoE and the neuropathology of AD, we examined the distribution of apoE-immunoreactive neurons in visual cortical areas with different apparent susceptibility to AD neuropathology (areas 17-primary sensory, 18-secondary sensory, and inferior temporal-association cortex) at different stages of AD pathology as described by Braak and Braak. We found that intraneuronal apoE was present at all these stages, however, only in visual cortical regions known to be vulnerable to AD. In the late stages, the laminar distribution of apoE-immunoreactivity matched the distribution of other markers of AD pathology, especially modified tau. These data support previous findings that intraneuronal apoE in neocortex is common in aged, nondemented controls and demonstrate that it may be more common in regions at risk for AD pathology. Thus, intraneuronal accumulation of apoE may be an attribute of cortical neurons that are more vulnerable to age-related injury with the presence of apoE antedating the classical indices of late-onset AD pathology.

Curriculum collaboration and the Ottawa Charter: a nursing initiative

The World Health Organization (WHO) and the International Council of Nurses (ICN) have been consistent in their call for nurses to be involved with Primary Health Care (PHC). This paper will demonstrate how an innovative partnership between the School of Nursing, Flinders University of South Australia (FUSA) and Noarlunga Health Services (NHS) has been instrumental in developing an undergraduate nursing curriculum which has the potential to guide future nursing practice. The Community Enrichment Project (CEP) has been an example of health promotion in practice and demonstrates how a PHC philosophy can permeate all levels of health care.

CD30 (Ki-1)-positive primary cutaneous T-cell lymphoma: report of spontaneous resolution

A 28-year-old man in whom CD50 (Ki-1)-positive cutaneous large cell lymphoma manifested as multiple widespread ulcerated nodules; which developed over a 2-week period, is reported. The lymphoma was composed of large anaplastic cells in large clusters, with scattered eosinophils, neutrophils and small lymphocytes. Extensive staging investigations revealed no extra-cutaneous disease. No treatment was given because, within weeks of presentation, the nodules began to regress spontaneously and the patient remains disease-free 20 months later.

All-optical code-division multiple-access applications: 2(n) extended-prime codes

A new family of 2(n) codes, called 2(n) extended-prime codes, is proposed for all-optical code-division multiple-access networks. Such 2(n) codes are derived from so-called extended-prime codes so that their cross-correlation functions are not greater than 1, as opposed to 2 for recently proposed 2(n) prime codes. As a result, a larger number of active users can now be supported by the new codes for a given bit-error rate than can be by 2(n) prime codes, while power-efficient, waveguide-integrable all-serial coding and correlating configurations proposed for the 2(n) prime codes can still be employed.

The biomimetics of enamel: a paradigm for organized biomaterials synthesis

The formation of enamel takes place through a sequence of processes that can be mimicked in inorganic materials chemistry. This chapter describes the generic features of enamel biomineralization in terms of a house-building analogy. Four stages are identified: supramolecular preorganization and spatial patterning; interfacial molecular recognition in inorganic nucleation; vectorial crystallization; and pattern evolution and hierarchy. Each of these concepts can be translated into synthetic approaches to the formation of inorganic materials with organized architectures. An example of applying this biomimetic paradigm is described. Supersaturated water-in-oil microemulsions have been used to synthesize microskeletal calcium phosphates by controlled nucleation and vectorial growth in constrained reaction environments. The results of these preliminary studies suggest that biomimetic concepts could be useful in the fabrication of biomaterial implants with controlled porosity and microstructure.

Vitamin B-6 normalizes the altered sulfur amino acid status of rats fed diets containing pharmacological levels of niacin without reducing niacin's hypolipidemic effects

Niacin (nicotinic acid) in large doses (> 2 g) has been increasingly the choice of lipid-lowering agent by clinicians. However, the potential risks of the use of high doses of the vitamin have not been critically considered in the same way as has the use of other lipid-lowering drugs. The present study provides evidence that pharmacological levels of niacin interfere with the metabolism of methionine, leading to hyperhomocysteinemia and hypocysteinemia. Male Sprague-Dawley rats were fed a semisynthetic diet supplemented with either 400 or 4000 mg niacin/kg (compared with 47 mg/kg diet in the control diet). In Experiment 1, feeding these diets for 3 wk resulted in a dose-related increase in the plasma and urine methionine concentrations while cysteine levels were decreased. This altered methionine metabolism was accompanied by a lower plasma vitamin B-6 concentration in niacin-supplemented rats compared with controls. In Experiment 2, the methionine and cysteine levels in plasma and urine were normalized when vitamin B-6 (10 mg/kg diet) was added to the diet containing 4000 mg niacin/kg and fed for 6 wk. This experiment also showed that plasma and urine homocysteine concentrations were increased by niacin and normalized by vitamin B-6. The hypolipidemic action of niacin was unaffected by the presence of vitamin B-6. These results indicate that niacin at large dosages interferes with methionine metabolism by affecting vitamin B-6 status. The treatment of dyslipidemia with simultaneous administration of niacin and vitamin B-6 could be a better therapy than the use of niacin alone.

Video orbits of the projective group a simple approach to featureless estimation of parameters

We present direct featureless methods for estimating the eight parameters of an "exact" projective (homographic) coordinate transformation to register pairs of images, together with the application of seamlessly combining a plurality of images of the same scene, resulting in a single image (or new image sequence) of greater resolution or spatial extent. The approach is "exact" for two cases of static scenes: (1) images taken from the same location of an arbitrary three-dimensional (3-D) scene, with a camera that is free to pan, tilt, rotate about its optical axis, and zoom, or (2) images of a flat scene taken from arbitrary locations. The featureless projective approach generalizes interframe camera motion estimation methods that have previously used a camera model (which lacks the degrees of freedom to "exactly" characterize such phenomena as camera pan and tilt) and/or which have relied upon finding points of correspondence between the image frames. The featureless projective approach, which operates directly on the image pixels, is shown to be superior in accuracy and the ability to enhance the resolution. The proposed methods work well on image data collected from both good-quality and poor-quality video under a wide variety of conditions (sunny, cloudy, day, night). These new fully automatic methods are also shown to be robust to deviations from the assumptions of static scene and no parallax.

A physiologically based pharmacokinetic model for arsenic exposure. II. Validation and application in humans

A physiologically based pharmacokinetic model (PB-PK) for inorganic arsenic exposure in humans has been developed. This model is an extension of a PB-PK model for hamsters and rabbits, with adjustments for body weight, metabolic rates, and absorption rates. It describes the absorption, distribution, metabolism, and excretion of arsenate, arsenite (As(III)), methyl arsonate, and dimethyl arsinate, the four major metabolites of inorganic arsenic. The routes of intake considered are inhalation of arsenic dust and fumes and oral intake of arsenic via drinking water and food. The PB-PK model for the oral exposure route is validated using data on urinary excretion after repeated oral exposure to As(III) as well as after exposure to inorganic As via drinking water. Absorption by inhalation is validated using data on urinary excretion after occupational exposure to arsenic trioxide dust and fumes. In both cases, the model gives satisfactory results for urinary excretion of the four As metabolites. The PB-PK model is also used in the description of the effects on the kinetics of exposure via different routes and for the simulation of various realistic exposure scenarios.

Agrin is synthesized by retinal cells and colocalizes with gephyrin [corrected]

At the neuromuscular junction, motoneuron-derived agrin is concentrated in the basal lamina of the synaptic cleft where it is responsible for the formation of the postsynaptic apparatus. As a step toward understanding agrin's role in the developing central nervous system, we have characterized agrin in retinal cell cultures as well as in the intact retina. Agrin was synthesized and secreted by cultured retinal cells and at least part of this agrin was active in acetylcholine receptor aggregation. Punctate anti-agrin immunoreactivity was associated with the cell bodies and processes of retinal neurons. Double labeling with antibodies against agrin and against the synapse-associated molecule gephyrin demonstrated that approximately half of the gephyrin clusters colocalized with the punctate agrin immunoreactivity in vitro. In the in vivo retina, more than 80% of the gephyrin clusters colocalized with extracellular agrin. These data indicate that agrin is concentrated at synapses in the retina as it is at the neuromuscular junction.

Immunomagnetic isolation of magnetoferritin-labeled cells in a modified ferrograph

Pan T, helper, and cytotoxic lymphocytes were isolated from the human peripheral blood mononuclear cell fraction by antibody staining, ferritin labeling, and deposition on glass slides. Two distinct forms of ferritin were used: one was native horse spleen ferritin, and the other was magnetoferritin. Magnetoferritin was obtained by reconstituting the horse spleen ferritin iron core with superparamagnetic magnetite instead of the usual paramagnetic ferrihydrite crystal. The cell deposition on microscopic glass slides in the magnetic field was obtained by an instrument that was adapted from an industrial magnetic deposition analyzer, the ferrograph. The identity of cells in the magnetic deposits was confirmed by comparing the cell fractions in the feed and in the eluate with the use of flow cytometry. The immunostaining protocol amplified the number of ferritin molecules per cell surface antigen 20-70 times. Magnetoferritin, but not native ferritin, imparted a sufficient magnetic moment to cells to deplete the labeled cell population between 67 and 88% of its initial concentration in a magnetic field of 1.67 Tesla (T), a field gradient of 2.57 T/mm, and a flow rate of 0.01 ml/min. This study showed that the magnetic moment of magnetoferritin was sufficient for immunomagnetic isolation of lymphocytes from mononuclear cell preparations in the modified ferrograph.

A physiologically based pharmacokinetic model for arsenic exposure. I. Development in hamsters and rabbits

A physiologically based pharmacokinetic model for exposure to inorganic arsenic in hamsters and rabbits has been developed. The model in its present state simulates three routes of exposure to inorganic arsenic: oral intake, intravenous injection, and intratracheal instillation. It describes the tissue concentrations and the urinary and fecal excretions of the four arsenic metabolites: inorganic As(III) and As(V), methylarsonic acid, and dimethylarsinic acid. The model consists of five tissue compartments, chosen according to arsenic affinities: liver, kidneys, lungs, skin, and others. The model is based on physiological parameters, which were scaled according to body weight. When physiological parameters were not available, the data for the model were obtained by fitting (tissue affinity, absorption rate, and metabolic rate constants). The excretions of the arsenic metabolites in urine and feces are well simulated with the model for both species. Further validation of the arsenic metabolite concentrations in the tissues and in vitro measurements of the tissue affinity constants are discussed.

Biochemical and functional characterization of basal lamina-bound agrin in the chick central nervous system

Agrin is a high-molecular weight extracellular matrix molecule, initially purified from the electric organ of the marine ray Torpedo californica, which induces on the surface of cultured myotubes the formation of postsynaptic specializations similar to those found at the neuromuscular junction. Agrin immunoreactivity is highly concentrated in the basal lamina of the synaptic cleft but is also found in a number of other tissues where its function is not known. We characterized agrin associated with two basal laminae from the central nervous system, the inner limiting membrane of the retina and the mesencephalic external limiting membrane. A major broad band with an apparent molecular weight of > 300 kDa was identified in immunoblots of isolated basal laminae from retina, mesencephalon, kidney and muscle, showing that basal lamina-bound agrin from the central nervous system and that from non-neural tissues have similar molecular sizes. Agrin is stably but not covalently bound to the inner limiting membrane and could be completely removed only with strong detergents. Agrin could be partially extracted with buffers that are also able to partially release acetylcholine receptor aggregation activity from the neuromuscular junction or from the electric organ. Despite these immunological and biochemical similarities, agrin from both central nervous system-derived basal laminae was not able to induce acetylcholine receptor aggregation on cultured myotubes. This shows that functionally different agrin isoforms are associated with basal laminae in the central nervous system compared to the neuromuscular junction or the electric organ.

[General automated documentation and performance data on the surgical intensive care unit--the theoretical concept of the Regensburg Surgical University Clinic]

Documentation is becoming an ever more time-consuming task due to the need to document increasing ICU productivity, quality management and cost-assessment data. Automatic charting of on-line monitoring data, therapeutic-device data, clinical laboratory data, microbiological data, radiological data and other data reduces documentation time significantly. One of the major advantages of PDMS in the SICU is the quality of the documentation and with better documentation the therapist is able to improve the quality of care. Not only the physician, but also nurses and physiotherapists are able to benefit from these advantages. Our concept, SURGIC (Department of Surgery, University Regensburg, Germany, Intensive Care), stands for: widely automated documentation, work orientation, including physicians, nurses' and physiotherapists' tasks, minimal dataset for simple use and perfect overview, costs assessments, scientific dataset, SICU PDMS as a part of the clinical information system, and professional support by a software-house is necessary.

Outcome of high-dose therapy and autologous transplantation in non-Hodgkin's lymphoma based on the presence of tumor in the marrow or infused hematopoietic harvest

PURPOSE

To evaluate the outcomes in 65 consecutive patients with non-Hodgkin's lymphoma (NHL) undergoing high-dose therapy (HDT) and autologous transplantation based on initial marrow involvement and the presence or absence of minimal disease in the hematopoietic harvests.

PATIENTS AND METHODS

Patients with any history of histologic evidence of marrow tumor underwent autologous peripheral-blood stem-cell transplantation (PSCT), whereas others underwent autologous bone marrow transplantation (ABMT). Patients who underwent ABMT were further segregated retrospectively into two groups depending on whether there was evidence by cell culture and/or Southern analysis of minimal tumor in the marrow harvest.

RESULTS

Comparable proportions (58% to 60%) of patients in each of the two groups (PSCT and ABMT) achieved a complete clinical remission (CR) at 100 days. For patients who achieve a CR, the actuarial relapse-free survival rate at 5 years for PSCT patients who received a tumor-negative apheresis harvest was 64%, compared with 57% for patients who received a tumor-negative bone marrow harvest and 17% for patients who received a histologically negative but minimally contaminated bone marrow harvest. Lymphoma grade and phenotype were not significant predictors of outcome.

CONCLUSION

The observation that survival was significantly better in the groups of patients who received tumor-negative harvests and worse for patients who received minimally contaminated harvests suggests that tumor cells, even at minimal levels, reinfused in the transplanted harvest are responsible for progression in a proportion of patients who achieve a CR following HDT, although other biologic characteristics of the tumor could also be important. A relatively good outcome can be achieved with HDT and PSCT, even in patients with a significant marrow tumor burden.

Valproic acid treatment of learning disorder and severely epileptiform EEG without clinical seizures

Using a single-patient (n = 1) clinical trial, we studied a 7-year-old boy who presented with unsatisfactory progress in school and whose electroencephalogram had very active independent frontal spike discharges. He had not had clinical seizures. The patient was randomized to receive valproic acid, 125 mg twice daily, (four periods) or matching placebo (four periods) over 8 weeks. Primary endpoints were the Wechsler Intelligence Scale for Children-Revised Coding sub-test and a handwriting sample. Behavior was monitored using teacher's and parent's Conners questionnaires. His score on the Wechsler Intelligence Scale for Children-Revised Coding subtest was significantly improved while he was taking valproic acid (P = .03). His electroencephalogram improved from a pretreatment recording of 28 spike discharges per minute to a normal recording while on valproic acid. We conclude that in this patient, valproic acid had a cognitive enhancing effect, probably by reducing epileptiform discharges.

Initial assessment of magnetoferritin biokinetics and proton relaxation enhancement in rats

RATIONALE AND OBJECTIVES

We evaluated the biokinetics and proton relaxation enhancement of magnetoferritin, a recently developed class of superparamagnetic iron oxides, in rats.

METHODS

"Equine" magnetoferritin was administered intravenously at 5 mg protein and 1.4 mg Fe/kg in nude rats carrying subcutaneous xenografted human small-cell lung carcinoma with and without preinjection of 100 mg/kg equine apoferritin. Blood clearance, in vivo biodistribution, and proton relaxation enhancement were assessed by variable field relaxometry, immunohistochemistry, and magnetic resonance (MR) imaging at 1.5 T.

RESULTS

Magnetoferritin clearance from blood followed biexponential kinetics, with a short initial half-life of 1.4-1.7 min. A second, longer component lasted for several hours. Histochemical staining, MR imaging, and ex vivo relaxometry revealed rapid uptake of magnetoferritin in the liver, spleen, and lymph nodes. There was no difference in biodistribution after apoferritin preinjection.

CONCLUSION

In the rat, equine magnetoferritin is rapidly sequestered by cells of the reticuloendothelial system, with no direct involvement of ferritin receptors. These properties may allow the use of magnetoferritin as an MR contrast agent for the liver and spleen.

Controlled Biomineralization of Magnetite (Fe(inf3)O(inf4)) and Greigite (Fe(inf3)S(inf4)) in a Magnetotactic Bacterium

A slowly moving, rod-shaped magnetotactic bacterium was found in relatively large numbers at and below the oxic-anoxic transition zone of a semianaerobic estuarine basin. Unlike all magnetotactic bacteria described to date, cells of this organism produce single-magnetic-domain particles of an iron oxide, magnetite (Fe(inf3)O(inf4)), and an iron sulfide, greigite (Fe(inf3)S(inf4)), within their magnetosomes. The crystals had different morphologies, being arrowhead or tooth shaped for the magnetite particles and roughly rectangular for the greigite particles, and were coorganized within the same chain(s) in the same cell with their long axes along the chain direction. Because the two crystal types have different crystallochemical characteristics, the findings presented here suggest that the formation of the crystal types is controlled by separate biomineralization processes and that the assembly of the magnetosome chain is controlled by a third ultrastructural process. In addition, our results show that in some magnetotactic bacteria, external environmental conditions such as redox and/or oxygen or hydrogen sulfide concentrations may affect the composition of the nonmetal part of the magnetosome mineral phase.

Synthesis and Structure of an Iron(III) Sulfide-Ferritin Bioinorganic Nanocomposite

Amorphous iron sulfide minerals containing either 500 or 3000 iron atoms in each cluster have been synthesized in situ within the nanodimensional cavity of horse spleen ferritin. Iron-57 Mössbauer spectroscopy indicated that most of the iron atoms in the 3000-iron atom cores are trivalent, whereas in the 500-iron atom clusters, approximately 50 percent of the iron atoms are Fe(III), with the remaining atoms having an effective oxidation state of about +2.5. Iron K-edge extended x-ray absorption fine structure data for the 500-iron atom nanocomposite are consistent with a disordered array of edge-shared FeS(4) tetrahedra, connected by Fe(S)(2)Fe bridges with bond lengths similar to those of the cubane-type motif of iron-sulfur clusters. The approach used here for the controlled synthesis of bioinorganic nanocomposites could be useful for the nanoscale engineering of dispersed materials with biocompatible and bioactive properties.

Classical and quantum magnetic phenomena in natural and artificial ferritin proteins

Artificial ferritin has been synthesized with control of both the magnetic state (antiferromagnetic or ferrimagnetic) and the particle size over an ofer of magnitude in the number of iron atoms. The magnetic properties of the artificial ferritin were compared with those of natural horse spleen ferritin in a range of temperatures (20 millikelvin to 300 kelvin) and fields (1 nanotesla to 27 tesla). In the classical regime, the blocking temperature was found to correlate with the average particle size. A correlation was also observed in the quantum regime between the resonance frequency of macroscopic quantum tunneling of the Néel vector and the particle size. At high magnetic fields (to 27 tesla), a spin flop transition with a strong dependence on orientation was seen in the natural ferritin, providing evidence of antiferromagnetism in this system.

Reconstitution of manganese oxide cores in horse spleen and recombinant ferritins

The formation of Mn(III) oxyhydroxide (MnOOH) cores within the nanoscale cavity of the iron storage protein ferritin has been investigated by electron microscopy and visible absorption spectroscopy. At pH 8.9, discrete amorphous MnOOH cores were formed within horse spleen apoferritin at a range of metal:protein ratios, as well as in ferritin molecules seeded with a small ferrihydrite nucleus. Analysis of the resultant core size distributions showed that the reconstitution of horse spleen apoferritin with Mn(II) was similar to that observed previously for Fe(II) reconstitution in recombinant human L-chain ferritin, suggesting that horse spleen apoferritin does not exhibit Mn(II) oxidase activity at pH 8.9. Reconstitution with MnOOH shows essentially "all-or-nothing" behavior in which many protein molecules remain unmineralized whilst others are loaded to maximum capacity. Kinetic studies showed no significant differences between horse spleen ferritin, recombinant H- and L-chain homopolymers, and H-chain variants containing site-directed modifications at the ferroxidase and putative Fe nucleation centers. Our results indicate that the reconstitution of ferritin with MnOOH cores proceeds by a nonspecific pathway. We propose that the outer surface of the protein inhibits the development of MnOOH nuclei in bulk solution whereas the inner surface is inactive, enabling nucleation and growth to proceed unperturbed within the cavity. One possibility is that differences in the general polyelectrolyte properties of these two surfaces, rather than site-specific charges, account for the "Janus" behavior of the molecule. A similar mechanism might also increase the specificity of iron oxide mineralization in ferritins that lack ferroxidase centers.

Inorganic Overgrowth of Aragonite on Molluscan Nacre Examined by Atomic Force Microscopy

The nacre (mother-of-pearl) that forms the irridescent inner layers of mollusc shells is a highly ordered microlaminate composite of aragonite crystals and biopolymers with a strength and fracture resistance that far exceed those of the mineral crystals themselves. The processes governing the biofabrication of this material by the secretory cells of the mantle are complex and only partially understood. We have used the atomic force microscope (AFM) to investigate the aqueous solution conditions under which mineral growth can occur on the nacreous layer of the shell of the bivalve mollusc Atrina sp. In situ imaging of the mature nacre surface exposed to a pH-controlled environment of natural seawater with added carbonate ions reveals that inorganic overgrowth of aragonite can occur within the ranges of pH and inorganic ion concentrations found in the molluscan extrapallial fluid from which the mineral is produced during biological shell growth. Thus, we posit that once nucleation has occurred, nacreous tablets could grow inorganically in the extrapallial space; the role of proteins and other macromolecules may be limited to initiating growth or controlling morphology through selective adsorption and spatial constraint on the growing crystal.

Once daily lisinopril and captopril in hypertension: a double blind comparison using ambulatory monitoring

AIM

To validate and compare the 24-hour antihypertensive efficacy of the angiotensin-converting-enzyme inhibitors, captopril and lisinopril.

METHODS

A randomised, doubleblind, doubledummy crossover study was performed with single-blind placebo run-in and washout periods and titration opportunities during therapeutic phases (captopril 25mg, 50mg and 100mg daily, lisinopril 10mg, 20mg and 40mg daily). The study was monitored using standard office blood pressure measurements, clinical and laboratory assessment. 24 patients of either sex and between 18 and 70 years with essential hypertension were enrolled, 20 met randomisation criteria (of sitting diastolic pressure 95-115mmHg), 3 withdrew from the study during its active phase and one was excluded from analysis having been found retrospectively to have not met randomisation criteria at the appropriate visit. Predetermined endpoints were blood pressure levels during different time periods of ambulatory monitoring performed at the end of each placebo or treatment phase.

RESULTS

In the 17 patients who completed the protocol, lisinopril produced a greater reduction of blood pressure at all time periods although the differences were not all statistically significant. The differences were most marked 19-24 hours post dosage time when pressures (systolic/diastolic) during lisinopril therapy were lower than during captopril by 18.0/14.5 mmHg (p < 0.001 for both). As measured by clinic pressures, lisinopril also achieved a considerably higher degree of blood pressure control with less dose titration.

CONCLUSION

In this study, lisinopril proved a more effective once daily antihypertensive agent than captopril, especially in the last 6 hours of the 24-hour dosage interval.

Further characterisation of forms of haemosiderin in iron-overloaded tissues

The biochemical and biophysical properties of isolated haemosiderins have been compared to that of another iron-containing protein, termed prehaemosiderin, which sediments through chaotropic potassium iodide only after 20 h of ultracentrifugation, in contrast to that of haemosiderin which is recovered after 2 h of ultracentrifugation. The iron/protein ratio and iron/phosphate ratio were less that that of the corresponding haemosiderin, while the elemental composition was also reduced in many of the prehaemosiderin samples. Mossbauer spectroscopy and electron diffraction identified the predominant presence of ferrihydrite in prehaemosiderin species even though the secondary haemochromatosis haemosiderin iron cores were essentially goethite-like. The majority of the prehaemosiderins isolated showed the presence of an additional peptide band at 17 kDa in addition to that at 21 kDa. Further Mossbauer studies of haemosiderin isolated from untreated secondary haemochromatosis patients showed that goethite was the predominant form of iron present, thereby indicating that the presence of this form of ferrihydrite was not wholly attributable to chelation therapy.

Intracellular ionic consequences of dietary salt loading in essential hypertension. Relation to blood pressure and effects of calcium channel blockade

To study the ionic basis of salt sensitivity in hypertension, 19F-, 13P-, and 23Na-nuclear magnetic resonance techniques were used to measure cytosolic free calcium (Cai), pH (pHi), free magnesium (Mgi), and sodium (Nai) in erythrocytes of essential hypertensive subjects (n = 19). Individuals were studied for 2 mo each on low- (UNaV < 50 meq/d) and high- (UNaV > 200 meq/d) salt diets, with the concomitant administration of nifedipine (10 mg t.i.d.) or placebo tablets for 1 mo of each diet. Salt loading elevated Cai and Nai while suppressing Mgi and pHi; these changes occurred predominantly in salt-sensitive subjects (n = 9). Nifedipine blunted the pressor response to salt loading > 50% (delta diastolic BP [high-low salt vs placebo] = 5 +/- 2 vs 14 +/- 2 mmHg, P < 0.05) and reversed salt-induced ionic changes, lowering Cai and elevating Mgi and pHi. Regardless of the definition of salt sensitivity, continuous relationships were observed between the pressure response to salt loading, the levels of Cai (r = 0.726, P < 0.001), Nai (r = 0.747, P < 0.001), and pHi (r = -0.754, P < 0.001), and the salt-induced change in Mgi (r = -0.757, P < 0.001). Altogether, these results emphasize the reciprocal and coordinate nature of intracellular ionic changes in response to dietary salt loading and calcium channel blockade in essential hypertension. They suggest that salt sensitivity is mediated by cellular calcium accumulation from the extracellular space, in association with magnesium depletion and acidification. Lastly, interpretation of intracellular ion measurements in the future will require concurrent assessment of dietary salt intake.

Crystal Tectonics: Construction of Reticulated Calcium Phosphate Frameworks in Bicontinuous Reverse Microemulsions

The chemical construction of organized architectures is an important aspect of innovative materials synthesis. Bicontinuous water-filled microemulsions can be used as preorganized systems for the fabrication of crystalline calcium phosphate materials with extended reticulated microstructures. These macroporous materials are formed by mineralization reactions located within the interconnecting water channels of the bicontinuous network. The resulting materials represent replicas of the microemulsion architecture, but the pore sizes are incommensurate, suggesting that secondary modifications in the bicontinuous microstructure occur during crystal growth. Synthetic macroporous calcium phosphates could have uses in biomaterial implants.

Prenatal diagnosis and post-mortem study of a fetus with mosaic trisomy 14 due to a dic(14)(p11)

Amniocentesis at 17 weeks' gestation revealed a mosaic karyotype--46,XX/46,XX,-14,+dic(14)(p11). No abnormalities were detected on ultrasound. Growth and placentation were normal. The fetus was examined after termination of pregnancy and micrognathia and pulmonary hyperlobation were the only abnormalities detected. Several tissues were set up for cytogenetics, including fetal skin, kidney, ovary, and placenta. The diagnosis was confirmed by these studies. The level of mosaicism varied between tissues, with the trisomy 14 cell line highest in amniotic fluid.

Magnetoferritin: characterization of a novel superparamagnetic MR contrast agent

A protein-encaged superparamagnetic iron oxide has been developed and characterized by using horse spleen apoferritin as a novel bioreactive environment. The roughly spherical magnetoferritin molecules, 120 A in diameter, are composed of a monocrystalline maghemite or magnetite core 73 A +/- 14 in diameter. Except for the additional presence of iron-rich molecules of higher molecular weight, the appearance and molecular weight (450 kd) of magnetoferritin are identical to that of natural ferritin; the molecules are externally indistinguishable from their precursor, with a pI (isoelectric point) in the range 4.3-4.6. The measured magnetic moment of the superparamagnetic cores is 13,200 Bohr magnetons per molecule, with T1 and T2 relaxivities (r1 and r2) of 8 and 175 L.mmol-1 (Fe).sec-1, respectively, at body temperature and clinical field strengths. The unusually high r2/r1 ratio of 22 is thought to arise from ideal core composition, with no evidence of crystalline paramagnetic inclusions. T2 relaxation enhancement can be well correlated to the field-dependent molecular magnetization, as given by the Langevin magnetization function, raised to a power in the range 1.4-1.6. With its nanodimensional biomimetic protein cage as a rigid, convenient matrix for complexing a plethora of bioactive substances, magnetoferritin may provide a novel template for specific targeting of selected cellular sites.

Self-assembled microstructures from 1,2-ethanediol suspensions of pure and binary mixtures of neutral and acidic biological galactosylceramides

Optical and electron microscopy were employed to characterize microstructures formed by thermal mechanical treatment of glycol suspensions of various pure and binary mixtures of the brain-derived galactosphingolipids hydroxy fatty acid cerebroside (HFA-Cer), non-hydroxy fatty acid cerebroside (NFA-Cer) and sulfatide (S-Cer). Negative staining indicated some new features of the neutral cerebroside suspensions in glycol. HFA-Cer formed a small fraction of both unilamellar cylinders (ULCs) (lumina ca. 27 nm) and giant multilamellar cochleates in addition to the typical nonhelical multilamellar cylinders (MLCs) (lumina ca. 10-30 nm). NFA-Cer formed a gel composed of a significant fraction of very long ULCs (lumina ca. 17 nm) without helical substructure, in addition to multilamellar helical structures such as ribbons and cylinders (lumina ca. 70 nm). Anisotropic lamellar micelle-shards of NFA-Cer were also detected by negative staining. S-Cer formed short ULCs (lumina ca. 44 nm) with no obvious helical substructure. Complex mixture data are thought to result from thermodynamic and kinetic factors. HFA-Cer is highly insoluble and promotes a network of rigid intralamellar hydrogen bonding that tends to exclude other lipids. NFA-Cer stabilizes helical defects in the lamellae, and S-Cer enhances disorder or micellization. The processes of microstructure nucleation and lipid phase separation were affected by mixtures such that metastable microstructures were trapped or the length of lamellar cylinders was altered.