Direct observation of different surface structures on high-resolution images of native halorhodopsin

Halorhodopsin (HR) was investigated with atomic force microscopic techniques (AFM) in aqueous solution. Two-dimensional (2D) crystals of HR were obtained by purifying an HR membrane fraction with the same buoyant density as the purple membrane (HR-PM) from the overexpressing strain Halobacterium salinarum D2. The membrane patches of HR were immobilized on mica. Images with a resolution up to 14 A were recorded. Crystals showed an orthogonal structure and the orientation of the molecules showed p42(1)2 symmetry; thus, alternate tetramers are inverted in the membrane. The crystal surface was found to display different structures depending on the imaging force used, indicating that some parts of the HR molecule are more rigid but others more compressible. From samples with single tetramers missing in the crystalline patches dimensions of the unit cell could be determined. Helix-connecting loops in single molecules of halorhodopsin were assigned. The images indicate that the large extracellular BC loop covers the whole molecule and is very flexible.

Perlustrin, a Haliotis laevigata (abalone) nacre protein, is homologous to the insulin-like growth factor binding protein N-terminal module of vertebrates

The 84-amino-acid-long sequence of perlustrin showed homology of the abalone nacre protein to the N-terminal domain of mammalian insulin-like growth factor binding proteins (IGFBPs). Despite the evolutionary distance between mollusks and mammals, the sequence identity was 40% including 12 conserved cysteines. However, the residues which were suggested recently to bind IGF-II in a complex with IGFBP-5 were conserved only partially. Nevertheless, perlustrin bound human IGFs with K(D) approximately 10(-7) M. This was the same affinity range as measured before for the interaction of isolated IGFBP-5 N-terminal domains with IGFs. Moreover, perlustrin bound bovine insulin with only approximately two- to sevenfold lower affinity than IGFs. Sequence similarity and growth factor binding identified perlustrin unequivocally as a member of the IGFBP family, the first found in an invertebrate biomineral. Nacre is known to contain proteinaceous factors which promote bone formation in vitro and in vivo. Bone contains IGFBPs which influence bone metabolism in many ways by modulating either IGF effects or IGF independently. Thus, perlustrin may provide a first clue at the molecular level to what these two phylogenetically rather distant biomineralization systems have in common.

[Effectiveness of Formica rufa and autologous blood injection in patients with ankylosing spondylitis: a double-blind randomized study]

While complementary medicine and homeopathy is becoming an increasingly prominent part of the health care practices, there is a lack of controlled studies concerning their effectiveness. In our study, we wanted to answer the question whether a combination of Formica rufa D6 and reinjection of the patient's own blood is superior to injection of placebo. 104 patients with ankylosing spondylitis entered a prospective, randomized, double-blind study. During four weeks they received twice weekly either 1 ml of Formica rufa D6 in combination with 0.5 ml of blood or 1.5 ml NaCl intramuscular. Before and after therapy, mobility, thoracic excursion and doctor's overall assessment were measured in addition to patient's health status, using a German version of the Arthritis Impact Measurement Scales, before and after therapy as well as four, twelve, and twenty-four weeks later. We were not able to detect any statistical difference between treatment and placebo group in any of the parameters measured. Therefore, the therapy under study may not be regarded effective.

The amino-acid sequence of the abalone (Haliotis laevigata) nacre protein perlucin. Detection of a functional C-type lectin domain with galactose/mannose specificity

Perlucin isolated from abalone nacre consists of 155 amino acids including a glycosylated asparagine. The sequence of the first 130 amino acids shows a high similarity to the C-type carbohydrate-recognition domains of asialoglycoprotein receptors and other members of the group of C-type lectins but also a weaker similarity to related proteins without carbohydrate-binding activity. This C-type module is followed by a short C-terminal domain containing two almost identical sequence repeats with a length of 10 amino acids. Solid phase assays show a divalent metal ion-dependent binding of perlucin to (neo)glycoproteins containing D-galactose or D-mannose/D-glucose indicating that perlucin is a functional C-type lectin with broad carbohydrate-binding specificity. Our results also indicate that it may be difficult to predict carbohydrate-binding specificity and the occurrence of alternative binding configurations by amino-acid sequence comparisons and homology modeling.

Simulating the response of a standing operator to vibration stress by means of a biomechanical model

Under vibration stress the compressive forces transmitted in the joints of a standing operator are composed of nearly static and oscillating force parts. Because these forces can hardly be measured they were assessed by means of a biomechanical model. In the model, 27 rigid bodies with 103 degrees of freedom represent the segments of the human body. 106 force elements imitate the muscles of the trunk and the legs. At first, the model parameter were varied so that for the simulated sitting posture the model fits the seat-to-head transmissibility given in the literature and in ISO/CD 5982. For the standing posture, the transfer functions between the ground acceleration and the oscillating forces in the ankle, the knee, the hip, and the motion segment L3-L4 were computed. According to the moduli of these functions the forces in the ankles are higher than those in the knees or the hips and they nearly come up to the forces in the lumbar spine. Further the results of the simulation indicate that under equal vibration stress in the standing and the sitting posture the differences between the compressive forces in the lumbar spine are small.

Bacterial turgor pressure can be measured by atomic force microscopy

We report a study of the deformability of a bacterial wall with an atomic force microscope (AFM). A theoretical expression is derived for the force exerted by the wall on the cantilever as a function of the depths of indentation generated by the AFM tip. Evidence is provided that this reaction force is a measure for the turgor pressure of the bacterium. The method was applied to magnetotactic bacteria of the species Magnetospirillum gryphiswaldense. Force curves were generated on the substrate and on the bacteria while scanning laterally. With the mechanical properties so gained we obtained the spring constant of the bacterium as a whole. Making use of our theoretical results we determined the turgor pressure to be in the range of 85 to 150 kPa.

Imaging microtubules and kinesin decorated microtubules using tapping mode atomic force microscopy in fluids

The atomic force microscope has been used to investigate microtubules and kinesin decorated microtubules in aqueous solution adsorbed onto a solid substrate. The netto negatively charged microtubules did not adsorb to negatively charged solid surfaces but to glass covalently coated with the highly positively charged silane trimethoxysilylpropyldiethylenetriamine (DETA) or a lipid bilayer of 1,2-dipalmitoyl-3-dimethylammoniumpropane. Using electron beam deposited tips for microtubules adsorbed on DETA, single protofilaments could be observed showing that the resolution is up to 5 nm. Under conditions where the silane coated surfaces are hydrophobic, microtubules opened, presumably at the seam, whose stability is lower than that of the bonds between the other protofilaments. This led to a "sheet" with a width of about 100 nm firmly attached to the surface. Microtubules decorated with a stoichiometric low amount of kinesin molecules in the presence of the non-hydrolyzable ATP-analog 5'-adenylylimidodiphosphate could also be adsorbed onto silane-coated glass. Imaging was very stable and the molecules did not show any scan-induced deformation even after hundreds of scans with a scan frequency of 100 Hz.

Description of the relation between the forces acting in the lumbar spine and whole-body vibrations by means of transfer functions

OBJECTIVE

The purpose of this study was to display the relationships between the forces transmitted in the spine and the accelerations of the vibrating seat.

BACKGROUND

Investigations reveal that exposure to whole-body vibration can induce degenerative changes in the lumbar spine. Elevated spinal forces are probably the crucial component in the pathogenesis of this disease.

DESIGN AND METHODS

The spinal forces are simulated by means of a biomechanical model, where 16 rigid bodies represent the upper body and the arms of a sitting operator. The relationships between seat accelerations and spinal forces are displayed as frequency-dependent transfer functions.

RESULTS

Spinal forces are not only elevated in the direction parallel to the vibration excitation but also in the two other orthogonal vibration directions. According to the magnitudes of the transfer functions the highest oscillating parts of the forces are reached at frequencies below 10 Hz.

CONCLUSIONS

Using the transfer functions, the time course of the spine forces can be computed and a new kind of weighting function can be derived which enables a force related weighting of the seat acceleration. RelevanceVibration induced health risks are commonly assessed by the weighted acceleration (ISO 2631-1). These weighting factors resulted from subjective magnitude sensation. It is argued that a more valid assessment will be obtained if the accelerations are weighted in relation to spinal forces. These forces cannot be measured directly under vibration. However, they can be simulated by means of biomechanical models.

In situ determination of sulfide turnover rates in a meromictic alpine lake

A push-pull method, previously used in groundwater analyses, was successfully adapted for measuring sulfide turnover rates in situ at different depths in the meromictic Lake Cadagno. In the layer of phototrophic bacteria at about 12 m in depth net sulfide consumption was observed during the day, indicating active bacterial photosynthesis. During the night the sulfide turnover rates were positive, indicating a net sulfide production from the reduction of more-oxidized sulfur compounds. Because of lack of light, no photosynthesis takes place in the monimolimnion; thus, only sulfide formation is observed both during the day and the night. Sulfide turnover rates in the oxic mixolimnion were always positive as sulfide is spontaneously oxidized by oxygen and as the rates of sulfide oxidation depend on the oxygen concentrations present. Sulfide oxidation by chemolithotrophic bacteria may occur at the oxicline, but this cannot be distinguished from spontaneous chemical oxidation.

Purification and characterization of perlucin and perlustrin, two new proteins from the shell of the mollusc Haliotis laevigata

Two new proteins, named perlucin and perlustrin, with M(r) 17,000 and 13,000, respectively, were isolated from the shell of the mollusc Halotis laevigata (abalone) by ion-exchange chromatography and reversed-phase HPLC after demineralization of the shell in 10% acetic acid. The sequence of the first 32 amino acids of perlucin indicated that this protein belonged to a heterogeneous group of proteins consisting of a single C-type lectin domain. Perlucin increased the precipitation of CaCO(3) from a saturated solution, indicating that it may promote the nucleation and/or the growth of CaCO(3) crystals. With pancreatic stone protein (lithostathine) and the eggshell protein ovocleidin 17, this is the third C-type lectin domain protein isolated from CaCO(3) biominerals. This indicates that this type of protein performs an important but at present unrecognized function in biomineralization. Perlustrin was a minor component of the protein mixture and the sequence of the first 33 amino acids indicated a certain similarity to part of the much larger nacre protein lustrin A.

Conventional ventilation versus high-frequency oscillation: hemodynamic effects in newborn babies

OBJECTIVE

We conducted a prospective study to assess the hemodynamic effects of conventional mechanical ventilation (CMV) compared with high-frequency oscillation (HFO) in newborn babies with respiratory distress syndrome.

METHODS

A total of 18 consecutive term and preterm infants were examined by two-dimensional M-mode and pulsed Doppler echocardiography.

RESULTS

Five patients had to be excluded, three of them because of increasing cardiovascular support after initiation of HFO. The remaining 13 infants (seven males, six females) had a median gestational age of 33 wks (range, 25-40) and a birth weight of 2350 g (range, 790-3600). Patients entered the study at 21 hrs (range, 5-69) of life, receiving total maintenance fluid of 90 mL/kg/day (range, 60-120). Five babies (38%) needed continuous inotropic support. HFO was used as a rescue therapy in infants who failed with CMV. In all 13 patients, HFO significantly impaired cardiac performance compared with CMV by decreasing aortic velocity-time integral: median, 10.2 cm (range, 6.0-14.6) vs. 8.3 cm (range, 5.3-12.4; p<.002); stroke volume: median, 3.8 mL (range, 1.6-6.8) vs. 3.2 mL (range, 1.3-5.9; p<.002); and cardiac index: 281 mL/min/kg of body weight (range, 177-579) vs. 200 mL/min/kg of body weight (range, 156-591; p<.002). Fractional shortening was also significantly reduced: median, 0.31% (range, 0.24-0.44) vs. 0.29% (range, 0.20-0.34; p<.01), because of a significantly smaller left ventricular diastolic diameter during HFO: median, 1.4 cm (range, 1.0-1.9) vs. 1.4 cm (range, 0.9-1.8; p<.05), with a median difference of -0.07 cm (range, -0.4-0.2). HFO also causes a significant decrease in heart rate-corrected left ventricular ejection time: median, 0.25 sec (range, 0.23-0.28) vs. 0.23 sec (range, 0.21-0.26; p < .02) and heart rate-corrected velocity of circumferential fiber shortening (Vcfc): median, 1.3 circ/sec (range, 1.0-1.6) vs. 1.2 circ/sec (range, 0.9-1.4; p<.05). Left ventricular end-systolic wall stress (LVESWS; g/cm2) remained stable. The correlation between Vcfc and LVESWS did not show any significance (CMV, r2 = .2; HFO, r2 = .09). The regression line between Vcfc and LVESWS showed a higher y-intercept and steeper slope during CMV than during HFO. Heart rate, mean arterial pressure, and left ventricular systolic diameter remained unchanged.

CONCLUSIONS

In newborn babies, HFO significantly decreased left ventricular cardiac output caused by reduced left ventricular filling and HFO decreased contractility at higher mean airway pressures than with CMV.

Effects of modification of the allocation system on ischemia duration and costs of heart transplantation. Transplantation Cooperation UNI-NRW

BACKGROUND

In order to optimize regional utilization of transplantable thoracic organs, the seven university hospitals in North-Rhine-Westfalia have formed a transplant cooperation meanwhile approved by Eurotransplant.

METHODS

Heart transplant and organ donation activities of the cooperating hospitals in the year before the foundation of the cooperation (period A, 7/95 - 6/96) and in the year thereafter (period B, 7/96 - 6/97) were retrospectively analysed.

RESULTS

In period A, a total of 39 heart transplants and 74 heart donations were performed, whereas in period B 67 heart transplantations and 78 heart donations could be achieved. The regional utilization of the donor organs increased from 4% to 30% with a significantly shorter ischemia time of regionally or locally allocated donor hearts than of nationally or internationally allocated ones.

CONCLUSIONS

A high rate of regional or local heart transplant procedures with short ischemia times clearly demonstrate the benefits of a regionalization of heart transplant medicine for medical as well as economical reasons.

Three-dimensional biomechanical model for simulating the response of the human body to vibration stress

Several investigations have revealed that long-term exposure to whole-body vibrations can induce low back pain. In analogy to materials handling, the health risk can be assessed if the forces transmitted in the spine during vibration are known. To estimate the forces a biomechanical model has been developed in which the human trunk, neck, head and arms are represented by 16 rigid bodies. An additional body simulates the vibrating seat. The bodies are connected by visco-elastic joint elements, and 56 force elements imitate the trunk and neck muscles. The motion equations are derived by means of the dynamics of systems of rigid bodies, and the motions are simulated in three directions. The frequency-response functions between the accelerations of the seat and the head satisfactorily correspond to data reported in the literature. The spine forces are composed of a static part, due to body posture, and a vibration-induced part. The relation between the oscillating parts of the forces transmitted from seat to pelvis and the spine forces are also described by frequency-response functions. To assess the health risk the simulated spine forces must be compared with the strength of the spine, bearing in mind that this is dependent on the number of load cycles.

Dominance of the BV17 element in nickel-specific human T cell receptors relates to severity of contact sensitivity

Hypersensitivity to nickel (Ni) represents the most common manifestation of contact allergy in humans. The role of metal-specific T cells in this disease is well established, but the molecular interactions involved in their activation are poorly understood. We examined the T cell receptor (TCR) repertoire in T cells activated with either NiSO4 or NiSO4-treated human serum albumin from six allergic patients. For the three most hyperreactive donors, we found a strong over-representation of the TCR BV17 element. TCR sequencing for one of these donors revealed an additional skewing for AV1 as well as a selection for an N region encoded argine at position 95 of the BV17 complementarity determining region (CDR)3. Since Arg is not known to participate in Ni complexing, we suppose that this selection is driven by contacts with peptide rather than nickel. However, the CDR1 of BV17 contains a unique combination of amino acids (HDA) that bears similarities to known motifs in Ni-binding proteins or peptides. We therefore propose that the severe hypersensitivity reactions found in BV17 over-expressors may be the result of Ni2+ ions bridging the germ-line-encoded BV17 CDR1 loop to corresponding sites in the major histocompatibility complex/peptide complex and thereby creating a superantigen-like enhancement of weak TCR-peptide contacts.

Estimation of spine forces under whole-body vibration by means of a biomechanical model and transfer functions

BACKGROUND

Several investigations reveal that long-term exposure to whole-body vibrations can induce degenerative changes in the lumbar spine. In analogy to the activities of lifting or carrying loads, an assessment of the health risk should be possible if the forces transmitted in the spine during vibration stress are known.

METHODS

To estimate the spine forces a biomechanical model was developed. In the model the human trunk, neck, and head were represented by 10 rigid bodies connected by visco-elastic elements. Some 56 force elements imitated the muscles of the body. The motion equations of the model were derived by means of the dynamics of systems of rigid bodies.

RESULTS

The transfer functions of the model accelerations in x- and z-direction satisfactorily corresponded to data reported in the literature. Transfer functions were computed between the forces transmitted from the seat to the pelvis and in the lumbar spine, respectively.

CONCLUSION

The forces between seat and pelvis were measured, then the spine forces were computed by means of the transfer functions. To assess the health risk the computed forces must be compared with the strength of the spine because the strength is dependent on the age and gender of the worker and decreases with the number of load cycles.

Protein tracking and detection of protein motion using atomic force microscopy

Height fluctuations over three different proteins, immunoglobulin G, urease, and microtubules, have been measured using an atomic force microscope (AFM) operating in fluid tapping mode. This was achieved by using a protein-tracking system, where the AFM tip was periodically repositioned above a single protein molecule (or structure) as thermal drifting occurred. Height (z-piezo signal) data were taken in 1 - or 2-s time slices with the tip over the molecule and compared to data taken on the support. The measured fluctuations were consistently higher when the tip was positioned over the protein, as opposed to the support the protein was adsorbed on. Similar measurements over patches of an amphiphile, where the noise was identical to that on the support, suggest that the noise increase is due to some intrinsic property of proteins and is not a result of different tip-sample interactions over soft samples. The orientation of the adsorbed proteins in these preliminary studies was not known; thus it was not possible to make correlations between the observed motion and specific protein structure or protein function beyond noting that the observed height fluctuations were greater for an antibody (anti-bovine IgG) and an enzyme (urease) than for microtubules.

Measuring the viscoelastic properties of human platelets with the atomic force microscope

We have measured force curves as a function of the lateral position on top of human platelets with the atomic force microscope. These force curves show the indentation of the cell as the tip loads the sample. By analyzing these force curves we were able to determine the elastic modulus of the platelet with a lateral resolution of approximately 100 nm. The elastic moduli were in a range of 1-50 kPa measured in the frequency range of 1-50 Hz. Loading forces could be controlled with a resolution of 80 pN and indentations of the platelet could be determined with a resolution of 20 nm.

Imaging soft samples with the atomic force microscope: gelatin in water and propanol

We have imaged mica coated with thin gelatin films in water, propanol, and mixtures of these two liquids by atomic force microscopy (AFM). The elastic modulus (Young's modulus) can be tuned from 20 kPa to more than 0.1 GPa depending on the ratio of propanol to water. The resolution is best in pure propanol, on the order of 20 nm, and becomes worse for the softer samples. The degradation in resolution can be understood by considering the elastic indentation of the gelatin caused by the AFM tip. This indentation becomes larger and thus the contact area becomes larger the softer the sample is. Therefore this study may be used to estimate the resolution to be expected with an AFM on other soft samples, such as cells. Nondestructive imaging was possible only by imaging at forces < 1 nN. This was difficult to achieve in contact mode because of drift in the zero load deflection of the cantilever, supposedly caused by temperature drift, but straightforward in tapping mode.

High-yield selection criteria for cranial computed tomography after acute trauma

OBJECTIVE

To develop and prospectively evaluate criteria for selecting head-injured patients requiring cranial CT.

METHODS

A two-phased prospective observational study design was implemented at a university ED. Physicians completed a form with 51 variables for 540 patients in Phase I. Ten high-yield variables were identified and prospectively tested on 273 patients in Phase II. Prediction rule performance for identification of patients with abnormal CT scans was determined.

RESULTS

The combined criteria had a sensitivity of 97% for CT-scan abnormalities in Phase I; sensitivity was 96% in Phase II. Negative predictive values were 97% and 94%, respectively. Prevalence of disease in Phase I was 17%; prevalence in Phase II was 16%. Had the Phase I criteria been implemented during Phase II, 43 of 273 patients (16%) would not have been scanned, including two patients with positive results who did not require operative intervention.

CONCLUSIONS

Fifty-one clinical variables from head-injured patients were narrowed to ten of statistical significance and consistent interpretation for prospective evaluation. Patients with none of these criteria were found to be at low risk of having sustained significant head injury.

Succession of putative peri-implant pathogens after root-form and plate-form implant placement in partially dentate adult monkeys

This report describes the succession of putative peri-implant pathogens in partially dentate monkeys after dental implantation and prosthetic reconstruction. Tooth and implant (6 root-end form, 4 blade-vent implants) sites in eight monkeys were monitored microbiologically and clinically during the pre-implant stage, abutment connection stage, bridge placement stage, and three and six months after the bridge placement stage. Tooth and implant sites were cleaned monthly post-extraction. Microbiological studies included dark field microscopy, selective and non-selective culture, and primary phenotypic characterization of culture isolates. After implant surgery, the median proportion of several putative peri-implant pathogens studied were significantly elevated. Following fixture placement, P. intermedia replaced P. melaninogenica as the predominant Black Pigmented Anaerobic Bacilli (BPAB) in the mouth. After abutment connection stage, levels of P. intermedia, A. actinomycetemcomitans, F. nucleatun, Haemophilus sp. and spirochetes were significantly elevated at implant and tooth sites. Three months after bridge installations, P. intermedia and A. actinomycetemcomitans remained significantly elevated at implant sites. At six months after bridge installation, levels of P. intermedia, F. nucleatum and A. actinomycetemcomitans declined significantly relative to levels at three months. Porphyromonas sp. and spirochetes were not significantly elevated although their levels correlated with gingival redness. P. intermedia, Porphyromonas sp. and spirochetes levels correlated significantly with probing depth. Correlation was detected between P. gingivalis and spirochetes; and between A. actinomycetemcomitans and F. nucleatum. Our studies show a transitional increase in levels of several organisms resembling putative pathogens of human peri-implant infection, associated with implant placements in partially edentulous mouths and supports early prophylactic interventions to control their levels.

[Balloon dilatation of postoperative and congenital aortic isthmus stenoses]

From July 1987 to December 1992, 52 patients underwent balloon-angioplasty of aortic coarctation at three units of pediatric cardiology in Austria (Graz = 35 patients, Innsbruck = 15 patients, and Vienna = 2 patients). 35 patients had postoperative and 17 had native coarctation. Mean age at intervention was 7 10/12 years with 2 patients under 1 year and 5 patients over 18 years old. The mean relation balloon diameter-coarctation diameter was 2.6 +/- 0.9. The blood pressure gradient between upper and lower extremities decreased from a mean of 44 +/- 16 mm Hg to 15 +/- 13 mm Hg (p < 0.0001). The diameter of the stenosed segment was increased from 5 +/- 3 mm to 8.5 +/- 3.5 mm (p < 0.0001). Native coarctation showed a significantly better result in respect to decrease of the gradient (36 +/- 12 mm Hg) than did postoperative coarctations (25 +/- 19 mm Hg) (p < 0.03). 13 patients did not respond adequately to angioplasty. 10 patients out of this group had tubular narrowings and belonged to the group of postoperative coarctations, whereas localized stenoses in native coarctations gave the best results. Localized wall irregularities were found in 4 patients with native coarctation. Balloon angioplasty of postoperative and native coarctations in childhood and adolescence is a secure and effective means of treatment and should be considered as therapy of first choice. The best results can be found in the group of the circumscript type of stenoses in native coarctation, whereas long and tubular stenoses in the group of postoperative coarctations give less satisfying results.

Direct observation of enzyme activity with the atomic force microscope

The height fluctuations on top of the protein lysozyme adsorbed on mica were measured locally with an atomic force microscope operated in tapping mode in liquid. Height fluctuations of an apparent size of 1 nanometer that lasted for about 50 milliseconds were observed over lysozyme molecules when a substrate (oligoglycoside) was present. In the presence of the inhibitor chitobiose, these height fluctuations decreased to the level without the oligoglycoside. The most straightforward interpretation of these results is that the height fluctuations correspond to the conformational changes of lysozyme during hydrolysis. It is also possible, however, that the height fluctuations are, at least in part, the result of a different height or elasticity of the transient complex of lysozyme plus the substrate.

A dominant negative mutant of PG13 suppresses transcription from a cauliflower mosaic virus 35S truncated promoter in transgenic tobacco plants

TGA1a and PG13 constitute a family of tobacco basic leucine zipper (bZIP) proteins that bind to activating sequence-1 (as-1), which is one of the multiple regulatory cis elements of the cauliflower mosaic virus (CaMV) 35S promoter. After truncation of the CaMV 35S promoter down to position -90 (CaMV 35S [-90] promoter), transcription stringently depends on the presence of as-1, which is recognized by nuclear DNA binding proteins called ASF-1. The role of the TGA1a/PG13 bZIP family in the formation of ASF-1 and in transcriptional activation of the CaMV 35S (-90) promoter has not yet been demonstrated in vivo. We constructed transgenic tobacco plants expressing a mutant of potato PG13, which lacks its wild-type DNA binding domain. This mutant acts as a trans-dominant inhibitor of ASF-1 formation and of expression from the CaMV 35S (-90) promoter, showing that PG13 can specifically interact with proteins necessary for these processes. Although we did not observe any other obvious phenotypic changes, these transgenic plants are a potentially valuable tool in identifying whether TGA1a and PG13 are involved in controlling promoters encoded in the plant genome.

[5-10-year results with the straight-shaft Müller prosthesis]

103 patients with 106 Müller straight stem prostheses could be evaluated clinically and radiologically after an average follow-up period of 6.8 years (range 5 to 10 ys.). Although until now no revision for aseptic loosening has become necessary 3 p.c. of the stems and 11 p.c. of the acetabular components showed radiological loosening. The clinical results were rated as satisfactory. After surgery 67 p.c. of the patients were completely painfree, 28 p.c. still had slight pain, 4 p.c. moderate and 1 p.c. severe pain. The investigation concentrated particularly on radiographic changes of the interface of the femur. Whereas radiolucency typically was non-progressive and located in the proximal part of the femur we found an increasing atrophy of the cortical bone on the calcar. Moreover, we found a continuous and increasing subsidence of the stem during the whole period of observation. At the time of follow up 56 p.c. of the straight stems had subsided about 2 mm and more. Calcar atrophy and radiolucency were significantly less present in femurs with a tapered medullary canal than in those with a cylindrical shape.

Mapping interaction forces with the atomic force microscope

Force curves were recorded as the sample was raster-scanned under the tip. This opens new opportunities for imaging with the atomic force microscope: several characteristics of the samples can be measured simultaneously, for example, topography, adhesion forces, elasticity, van der Waals, and electrostatic interactions. The new opportunities are illustrated by images of several characteristics of thin metal films, aggregates of lysozyme, and single molecules of DNA.

Granula motion and membrane spreading during activation of human platelets imaged by atomic force microscopy

The redistribution of platelet constituents during activation is essential for their physiological function of maintaining hemostasis. We report here about real time investigations of the activation of native human platelets under physiological conditions from the initial formation of filopodia to the fully spread form by atomic force microscopy. We followed the trafficking of granules and their interaction with the plasma membrane within single cells. Our results show movement of certain granula towards the lamellipodia. Analysis of this rearrangement and the subsequent enlargement of the platelet surface reveals details of the membrane spreading process. Images of living cells are presented that show the distribution of cytoskeletal components and membrane-bound filaments at a resolution of better than 50 nm. The local minimum forces between the tip and the platelets were estimated to be smaller than 60 pN. A model for the elastic contributions of the glycocalix to the tip/membrane interaction was developed using the theory of grafted polymers.

Actin binding to lipid-inserted alpha-actinin

The interaction of alpha-actinin with lipid films and actin filaments was investigated. First alpha-actinin was incorporated in lipid films at the air/water interface. Injection of alpha-actinin into the subphase of a lipid monolayer led to a significant increase of the surface pressure only for lipid films consisting of a mixture of a negatively charged lipid with a high proportion of diacylglycerol. These alpha-actinin-containing films were transferred onto silanized quartz slides. Photobleaching experiments in the evanescent field allowed quantification of the lateral number density of the lipid-bound alpha-actinin. In combination with the area increase from the monolayer experiments, the photobleaching measurements suggest that alpha-actinin is incorporated into the lipid film in such a way that actin binding sites are accessible from the bulk phase. Binding experiments confirmed that the alpha-actinin selectively binds actin filaments in this configuration. We also showed that, in contrast to actin filaments which are adsorbed directly onto planar surfaces, the alpha-actinin-bound actin filaments are recognized and cleaved by the actin-severing protein gelsolin. Thus we have constructed an in vitro system which opens new ways for investigations of membrane-associated actin-binding proteins and of the physical behavior of actin filaments in the close neighborhood to membranes.

In vitro activation of human platelets triggered and probed by atomic force microscopy

We report on the activation of human platelets probed by atomic force microscopy under nearly physiological conditions. We could image native platelets in different stages of activation at a resolution of about 100 nm. Intracellular structures within the platelets could be resolved without staining. Furthermore we could trigger and follow the activation process of individual platelets, demonstrating that the platelets are still intact and are not destroyed or severely harmed by this novel imaging process.

Sub-gingival microflora in Macaca mulatta species of rhesus monkey

The Macaca mulatta species of rhesus monkey is one of several non-human primate (nhp) models for periodontal disease. This report presents the bacteriology of the gingival sulci in M. mulatta monkeys. Three sub-gingival sites (maxillary right central incisor, the disto-buccal of the mandibular left second molar and mesio-buccal of the mandibular right second molar) of 9 monkeys were evaluated clinically before scaling and 7 days after scaling. Plaque samples were obtained from sub-gingival sites before clinical examination and studied bacteriologically by dark field microscopy, selective and non-selective culture, and by primary phenotypic characterizations of culture isolates. Several gingival sites presented with mild gingival inflammation. Anaerobic and facultatively anaerobic bacteria were the predominant flora colonizing the gingival sulci. The major microbial groups were Haemophilus species (100% of sites; percentage of total anaerobic count (TAC): 21-51), Peptostreptococcus micros (89%, 7.5-29.5), Actinomyces sp. (85%, 7-27), Fusobacterium nucleatum (90%, 5-8), Actinobacillus actinomycetemcomitans (73%, 1.3-12), black-pigmented anaerobic rods (BPAR) (80%, 0.6-6.5) and oral streptococci (80%, 0.2-1.0). Microbial groups detected less often were Wolinella sp. (66%, 0-2.6), Capnocytophaga sp. (30%), Eikenella corrodens (4.7%, 0), Campylobacter sp. (28%, 0-0.1) and spirochetes (4.7%, 0-0.07). Seven days after gingival sites were scaled, the plaque score and indices for gingival inflammation declined significantly. The gingival flora after scaling were characterized by lower proportions of the Actinomyces sp., P. micros and BPAR; and increased proportions of the oral streptococci, relative to pre-scaling levels.(ABSTRACT TRUNCATED AT 250 WORDS)

From molecules to cells: imaging soft samples with the atomic force microscope

Since its invention a few years ago, the atomic force microscope has become one of the most widely used near-field microscopes. Surfaces of hard sample are imaged routinely with atomic resolution. Soft samples, however, remain challenging. An overview is presented on the application of atomic force microscopy to organic samples ranging from thin ordered films at molecular resolution to living cells. Fundamental mechanisms of the image formation are discussed, and novel imaging modes are introduced that exploit different aspects of the tip-sample interaction for local measurements of the micromechanical properties of the sample. As examples, images of Langmuir-Blodgett films, which map the local viscoelasticity as well as the friction coefficient, are presented.

An improved biomechanical model for simulating the strain of the hand-arm system under vibration stress

In order to define relationships between the vibration stress and the strain of the human hand-arm system a biomechanical model was developed. The four masses of the model representing the hand, the forearm and the upper arm were connected by dampers and springs in two perpendicular directions. Simulating muscle activity, damped torsion springs were included additionally. The motions of the model were described by a differential matrix equation which was solved by using a 'transfer matrix routine' as well as by numerical integration. Thus, functions with harmonic or transient time courses could be selected as an excitation. The simulated vibrations were compared with those of other hand-arm models. The forces and torques transmitted between the masses, and the energy dissipated by the dampers were computed for several combinations of exciter frequencies and accelerations. The dependence of torques upon excitation agreed fairly well with the behaviour of the arm muscles under vibration as described by various investigators. At frequencies above 100 Hz the energy was dissipated mainly by the dampers between the masses near to the exciter. Transferring this result to the hand-arm system it shows that at high frequencies energy is dissipated by the hand and its palmar tissues and this might be one cause for the incidence of vibration-induced white finger disease.

Child health care policy and delivery in France

Medical and social protection of mothers, infants, and children began in France more than a century ago. A number of laws and regulations have improved the system, which is discussed in detail. The discussion includes an overview of health policy, service delivery, and the financing of care. Is the current French system of Maternal and Child Health responsible for the good health of today's children? This question is addressed through selected examples. Finally, failures and short-comings of the system are described, including the persistence of underserved groups, unequal access to care, and other problems. Solutions are feasible, and some are now being implemented.

[Treatment of advanced pancreatic cancer with 5-fluorouracil, 4-epidoxorubicin and mitomycin C (FEM II). From the Chemotherapy of Gastrointestinal Tumors Group]

In a multicentre phase II trial, 20 patients with advanced pancreatic carcinoma were treated with 5-fluorouracil, 4-epidoxorubicin and mitomycin C, in which 4-epidoxorubicin was administered by escalated dose and split course (FEM II). From among 12 patients evaluable for response, 2 partial and 1 minimal remission were observed, suggesting a response rate of 25%. Four patients (30%) showed a no change and 5 progression. The median survival of all patients was 3.4 months, of the responders 8.4 months, of those with no change 5.2, and of those showing progression 3.4 months. Considerable nausea/vomiting and leukopenia was observed. The preliminary data suggest that the FEM II regimen does not offer any progress in terms of efficacy, survival and toxicity for advanced pancreatic carcinoma.

Resizing--what two Detroit Hospitals learned, achieved. Interview by Lynn D. Kahn

Mike Fritz has spent his entire career with Harper Grace Hospitals, a subsidiary corporation of Detroit Medical Center. After 25 years with the hospitals and three years as their president and chief executive officer, Fritz resigned earlier this summer. During the time he served as CEO, Fritz and his management team undertook a dramatic resizing initiative--one that has proven to be effective for both 650-bed Harper Hospital and 300-bed Grace Hospital. In an interview with Lynn D. Kahn, Health Care Strategic Management's managing editor, Fritz discusses what led to the resizing, how it was undertaken and what it accomplished.