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.

5-Fluorouracil, 4-epidoxorubicin, and mitomycin C (FEM) combination chemotherapy for advanced gastric carcinoma. A phase-II trial by the "chemotherapiegruppe gastrointestinaler tumoren (CGT)"

In a phase-II-trial 40 patients with advanced gastric cancer were treated with 5-fluorouracil, 4-epidoxorubicin, mitomycin C (FEM) combination therapy. Twenty-five out of 30 patients with measurable disease were evaluable for response after 8 weeks of treatment. Seven patients achieved a partial remission (PR), suggesting a response rate of 28%. Ten patients had no change (NC) and 8 patients showed progression (P). The median time to progression for patients with PR was 7.2 months and for patients with NC 6.3 months. Median survival time for all patients was 5.3 months, for patients with PR and NC 9.9 months. WHO grade 3 toxicity appeared in 3% (WBC and nausea/vomiting) and 15% (alopecia) of patients. The data suggest that this regimen is not more active, but is better tolerated than the original FAM schedule. Therefore it seems suitable for out-patient treatment, for elderly patients and for those who cannot be treated by more aggressive drugs.

Four systems develop regionally organized HMO

Plans to establish HealthPlus HMO, Inc.--a joint venture of the Sisters of St. Francis Health Services, Ancilla Systems, Daughters of Charity Health Systems-East Central, and Holy Cross Health System--began in 1984 with a feasibility study to assess the potential for an HMO in Indiana. Goals set by the four systems included protecting and expanding hospitals' market share and physicians' patient bases; establishing local HMO ownership; and providing health education, preventive care, and comprehensive treatment at affordable costs. During the organizational phase, participants created a 12-member board of directors with three representatives from each system, selected the name HealthPlus, and contracted with a management company to direct the HMO's planning and development phases. HealthPlus adopted a regional organizational structure, which allows financial risk to be shared among three regions, and a primary care physician model for the delivery of services. As of January 1987, the joint venture had 16 participating hospitals, 345 primary care physicians, more than 1,000 consulting specialists, and a membership of 13,100. HealthPlus now offers a triple-option product in partnership with a preferred provider organization and an insurance carrier and has developed non-health-related products with the insurance carrier as well.

Dose dependence of breath hydrogen and methane in healthy volunteers after ingestion of a commercial disaccharide mixture, Palatinit

Breath hydrogen and methane were determined by gas chromatography in eleven normal individuals given a low-fibre, mixed diet (control) and after ingestion of 20-50 g Palatinit/d, an equimolar mixture of D-glucosyl-alpha(1----1)-D-mannitol and D-glucosyl-alpha(1----6)-D-glucitol (Isomalt). A linear relation was found (r 0.85; P less than 0.001) between the amount of Palatinit ingested and breath H2 per 10 h in subjects who did not exhale methane. If methane was formed in addition to H2, the sum of both gases followed a linear dose-effect relation. The mouth-to-caecum time, indicated by the first increase in breath H2 after ingestion, was shortened by about half, yet no sign of diarrhoea was observed. Stool weight and stool frequency did not change significantly. The linear relation between a dose of 20-50 g Palatinit and exhalation of H2 (eventually plus methane) indicated that a relatively constant fraction of the dose given underwent cleavage and absorption in the small intestine, the remainder being transported into the large bowel. Microbial gas formation in the colon as well as the fractional transfer of these gases into the expiratory air occurred at fixed proportions, thus allowing an insight into colonic microbial contributions to carbohydrate utilization in the human large bowel.

Effect of Acarbose on the production of hydrogen and methane and on hormonal parameters in young adults under standardized low-fibre mixed diets

Short and middle term effects of Acarbose were studied in volunteers on a standardized, low-fibre, mixed diet for the development of tolerance phenomena with gas exhalations and some peptide hormone levels as main parameters. Both hydrogen and methane were measured quantitatively as diurnal profiles. Acarbose caused an about 20-fold increase of H2 exhalation and had only moderate effects on methane production, indicating the presence of fermentable carbohydrates in the large bowel. Methanogenic individuals exhaled significantly less H2 than did non-methanogenic subjects. Changes in blood glucose, serum insulin, GIP, gastrin, and plasma glucagon, caused by Acarbose, reflected delayed glucose absorption and were plausible within the regulatory framework of carbohydrate assimilation. When the Acarbose regime was maintained for 5 weeks on a controlled diet, abdominal sensations like e.g. meteorism declined remarkably while carbohydrate fermentation remained high and lowered GIP was sustained. Thus functional responses of the gastro-intestinal tract to altered carbohydrate supplies, elicited by Acarbose, were found by 3 independent parameters: anaerobic gas production, peptide hormone levels, and subjective abdominal sensations. The objective parameters seem to remain constant in the longer run, while subjective parameters show long-term adaptation.

[Accidents on circular bench saws (author's transl)]

For an expert opinion in a lawsuit regarding the suspicion of self-mutilation the physical data of an accident on a circular saw bench have been investigated. The result was as follows: The time required for severing a human forearm of 6 cm diameter is 40 to 80 ms depending on the feeding power. The impulse of 13 to 15 Ns necessary for severing an arm in only 1/10 to 2/10 of the impulse a slipping person exerts when striking the disk. The standard time data for such accidents indicated in the scientific literature are much too high.