Counterion, temperature, and time modulation of nanometric chiral ribbons from gemini-tartrate amphiphiles.

Amphiphile supramolecular assemblies result from the cooperative effects of multiple weak interactions between a large number of subcomponents. As a result, prediction of and control over the morphologies of such assemblies remains difficult to achieve. Here, we described the fine-tuning of the shape, size, and morphology transitions of twisted and helical membranes formed by non-chiral dicationic n-2-n gemini amphiphiles complexed with chiral tartrate anions. We have reported that such systems express the chirality of the tartrate components at a supramolecular level and that the mechanism of the chiral induction by counterions involves specific anion cation recognition and the induction of conformationally labile chirality in the cations. Here, we demonstrate that the morphologies and dimensions of twisted and helical ribbons, as well as tubules, can be controlled and that interconversion between these structures can be induced upon modifying temperature, upon introducing small amounts of additives, or slightly modifying molecular structure. Specifically, electron microscopy, IR spectroscopy, and small-angle X-ray scattering show that (i) varying the hydrophobic chain length or adding gemini having bromide counterions (1%) or the opposite enantiomer (10%) leads to an increase of the diameter of membrane tubules from 33 to 48.5 nm; (ii) further addition (1.5%) of gemini bromide or a slight increase in temperature induces a transition from tubules to twisted ribbons; (iii) the twist pitch of the ribbons can be continuously tuned by varying enantiomeric excess; and (iv) it was also observed that the morphologies of these ribbons much evolve with time. Such unprecedented observations over easy tuning of the chiral supramolecular structures are clearly related to the original feature that the induction of chirality is solely due the counterions, which are much more mobile than the amphiphiles.

Effects of a managed chiropractic benefit on the use of specific diagnostic and therapeutic procedures in the treatment of low back and neck pain.

OBJECTIVE: The aim of this study was to measure the effects of a managed chiropractic benefit on the rates of specific diagnostic and therapeutic procedures for the treatment of back pain and neck pain. DESIGN: This study is a retrospective analysis of claims data from a managed-care health plan over a 4-year period. The use rates of advanced imaging, surgery, inpatient care, and plain-film radiographs were compared between employer groups with and without a chiropractic benefit. RESULTS: For patients with low back pain, the use rates of all 4 studied procedures were lower in the group with chiropractic coverage. On a per-episode basis, the rates in the group with coverage were reduced by the following: surgery (-32.1%); computed tomography (CT)/magnetic resonance imaging (MRI) (-37.2%); plain-film radiography (-23.1%); and inpatient care (-40.1%). On a per-patient basis, the rates were reduced by the following: surgery (-13.7%); CT/MRI (-20.3%); plain-film radiography (-2.2%); and inpatient care (-24.8%). For patients with neck pain, the use rates were reduced per episode in the group with chiropractic coverage as follows: surgery (-49.4%); CT/MRI (-45.6%); plain-film radiography (-36.0%); and inpatient care (-49.5%). Per patient, the rates were surgery (-31.1%); CT/MRI (-25.7%); plain-film radiography (-12.5%); and inpatient care (31.1%). All group differences were statistically significant. CONCLUSION: For the treatment of low back and neck pain, the inclusion of a chiropractic benefit resulted in a reduction in the rates of surgery, advanced imaging, inpatient care, and plain-film radiographs. This effect was greater on a per-episode basis than on a per-patient basis.

Chiropractic as spine care: a model for the profession.

BACKGROUND: More than 100 years after its inception the chiropractic profession has failed to define itself in a way that is understandable, credible and scientifically coherent. This failure has prevented the profession from establishing its cultural authority over any specific domain of health care. OBJECTIVE: To present a model for the chiropractic profession to establish cultural authority and increase market share of the public seeking chiropractic care. DISCUSSION: The continued failure by the chiropractic profession to remedy this state of affairs will pose a distinct threat to the future viability of the profession. Three specific characteristics of the profession are identified as impediments to the creation of a credible definition of chiropractic: Departures from accepted standards of professional ethics; reliance upon obsolete principles of chiropractic philosophy; and the promotion of chiropractors as primary care providers. A chiropractic professional identity should be based on spinal care as the defining clinical purpose of chiropractic, chiropractic as an integrated part of the healthcare mainstream, the rigorous implementation of accepted standards of professional ethics, chiropractors as portal-of-entry providers, the acceptance and promotion of evidence-based health care, and a conservative clinical approach. CONCLUSION: This paper presents the spine care model as a means of developing chiropractic cultural authority and relevancy. The model is based on principles that would help integrate chiropractic care into the mainstream delivery system while still retaining self-identity for the profession.

The selection effects of the inclusion of a chiropractic benefit on the patient population of a managed health care organization.

OBJECTIVE: The aim of this study is to measure the selection effects of the inclusion of a chiropractic benefit on a managed care health plan. DESIGN: An analysis of enrollment data from a managed care health plan over a 4-year period was conducted. Employers could select the managed care plan with or without a chiropractic care benefit. Comparisons of demographic and comorbid characteristics were made between employees who had the chiropractic benefit and those who did not, and between individuals who self-selected chiropractic care and those who self-selected medical care. RESULTS: The cohort with chiropractic coverage was younger with fewer subjects in the older age group (>65 years; 6.5% vs 9.6%) and more subjects in the younger age group (0-17 years; 31.9% vs 26.2%). The mean age of the group with coverage was 32.9 compared with 35.5 in the group without coverage. Comparing self-selected chiropractic patients to self-selected medical patients, there were fewer subjects older than 65 years in the chiropractic group (4.9% vs 9.2%) and fewer subjects aged 0 to 17 years (9.4% vs 19.4%). In 6 of the 8 comorbid conditions studied, the rates were lower in the cohort with chiropractic coverage compared with the group without coverage. The rates of comorbid conditions in self-selected chiropractic patients were lower in all 8 categories compared with self-selected medical patients. CONCLUSION: The inclusion of a chiropractic benefit in a health plan produces a modest favorable selection processes resulting in a slightly younger patient population with fewer comorbidities. At the level of patient self-selection, chiropractic patients are considerably younger and healthier than comparable medical patients.

Photoinduced morphism of gemini surfactant aggregates.

The photochemical behaviour of an azobenzene chromophore inserted in a gemini surfactant imparts photocontrol to the resulting amphiphile assemblies, including the collapse, upon irradiation, of the multi lamellar vesicles formed in aqueous solution.

Aggregation behaviors of gemini nucleotide at the air-water interface and in solutions induced by adenine-uracil interaction.

Cationic gemini surfactants having nucleotides as counterions (called nucleo-gemini hereafter) were synthesized and their aggregation behavior at air-water surfaces as well as in bulk solutions were studied. Fluid solutions of these nucleo-gemini surfactants show transitions to hydrogels upon addition of complementary nucleoside bases or other nucleo-gemini surfactants having complementary bases as counterions. The FTIR-ATR measurements show that the carboxylate groups of uridine form hydrogen bonds with the amine groups of adenosine. The aggregation behavior was also confirmed at the air-water interface by Brewster angle microscopy as well as surface pressure measurements; the monolayer of a gemini nucleotide was observed to undergo a transition to multilayers when nucleosides with complementary bases were added into the subphase. Isotherm curves of surface pressure monitored in parallel show a decrease in molecular area upon addition of such nucleosides.

Chiropractic care: is it substitution care or add-on care in corporate medical plans?

An analysis of claims data from a managed care health plan was performed to evaluate whether patients use chiropractic care as a substitution for medical care or in addition to medical care. Rates of neuromusculoskeletal complaints in 9e diagnostic categories were compared between groups with and without chiropractic coverage. For the 4-year study period, there were 3,129,752 insured member years in the groups with chiropractic coverage and 5,197,686 insured member years in the groups without chiropractic coverage. Expressed in terms of unique patients with neuromusculoskeletal complaints, the cohort with chiropractic coverage experienced a rate of 162.0 complaints per 1000 member years compared with 171.3 complaints in the cohort without chiropractic coverage. These results indicate that patients use chiropractic care as a direct substitution for medical care.

Cation modulation of bicelle size and magnetic alignment as revealed by solid-state NMR and electron microscopy.

The influence of salts (KCl, NaCl, CaCl(2), and MgCl(2)) on bicelles (bilayered micelles) made of dimyristoylphosphatidylcholine (DMPC, molar fraction X = 78%) and dicaproylphosphatidylcholine (DCPC) was investigated by solid-state (31)P- and (2)H NMR as well as by freeze-fracture electron microscopy. Sizes were determined from (2)H- and (31)P NMR on the basis of a model that incorporated a planar bilayer and a (half-torus) curved rim representing the DMPC and DCPC regions of the bicelle, respectively. Good agreement was shown with sizes determined independently from freeze-fracture electron microscopy images. In the presence of K(+) and Na(+), bicelles have diameters of approximately 300 A while in the presence of Ca(2+) and Mg(2+); their diameter increases to approximately 500 A. Bicelle magnetic alignment is considerably improved by the presence of salts. The optimum salt concentration for such an effect ranges from 50 to 200 mM. Bicelles are magnetically aligned for temperatures roughly ranging from 30 degrees C to 40 degrees C with monovalent cations; this range is slightly extended in the presence of divalent salts. In this temperature range, the dynamics of the long-chain hydrocarbon region of the bicelle (leading to a bicelle thickness of 38 A) and of water is about the same independently of cation nature and concentration. However, at higher temperatures, considerable differences in water dynamics are observed between systems with monovalent and divalent cations. In these conditions, the system consists of a mixture of micelles and extended bilayers, which show residual macroscopic alignment in the magnetic field.