Electro-acupuncture Reduces Neuronal Apoptosis Linked to Bax and Bcl-2 Expression in the Spinal Cords of Cats Subjected to Partial Dorsal Root Ganglionectomy

While electro-acupuncture (EA) has been well known to contribute towards neuroplasticity occurring in both the central and the peripheral nervous system after injury, the underlying mechanism remains largely unknown. This study evaluated the effects and the possible mechanism of EA on neuronal apoptosis in the spinal cords of cats subjected to the removal of L₁–L₅ and L₇–S₂ dorsal root ganglion, sparing the L₆ dorsal root ganglion. EA treatment decreased the number of TUNEL-positive apoptotic cells in lamina II of the L₃ and L₆ cord segments at 7 and 14 days post operation (dpo). This EA-mediated neuroprotection is associated with a decrease in the number of Bax immunoreactive neurons and an increase in the number of Bcl-2 immunoreactive neurons. Furthermore, Western blot and RT-PCR analysis revealed a significant downregulation of Bax protein and its mRNA, but an upregulation of Bcl-2 in the dorsal horn of L₃ and L₆ cords at both 7 and 14 dpo. The present findings suggest that EA could inhibit neuronal apoptosis in dorsal root deafferentated cat spinal cords, possibly by Bax downregulation and Bcl-2 upregulation. Wei Zhao and Qi Zhao contributed equally to this work.     

How Modification of Accessible Lysines to Phenylalanine Modulates the Structural and Functional Properties of Horseradish Peroxidase: A Simulation Study

Horseradish Peroxidase (HRP) is one of the most studied peroxidases and a great number of chemical modifications and genetic manipulations have been carried out on its surface accessible residues to improve its stability and catalytic efficiency necessary for biotechnological applications. Most of the stabilized derivatives of HRP reported to date have involved chemical or genetic modifications of three surface-exposed lysines (K174, K232 and K241). In this computational study, we altered these lysines to phenylalanine residues to model those chemical modifications or genetic manipulations in which these positively charged lysines are converted to aromatic hydrophobic residues. Simulation results implied that upon these substitutions, the protein structure becomes less flexible. Stability gains are likely to be achieved due to the increased number of stable hydrogen bonds, improved heme-protein interactions and more integrated proximal Ca²⁺ binding pocket. We also found a new persistent hydrogen bond between the protein moiety (F174) and the heme prosthetic group as well as two stitching hydrogen bonds between the connecting loops GH and F′F″ in mutated HRP. However, detailed analysis of functionally related structural properties and dynamical features suggests reduced reactivity of the enzyme toward its substrates. Molecular dynamics simulations showed that substitutions narrow the bottle neck entry of peroxide substrate access channel and reduce the surface accessibility of the distal histidine (H42) and heme prosthetic group to the peroxide and aromatic substrates, respectively. Results also demonstrated that the area and volume of the aromatic-substrate binding pocket are significantly decreased upon modifications. Moreover, the hydrophobic patch functioning as a binding site or trap for reducing aromatic substrates is shrunk in mutated enzyme. Together, the results of this simulation study could provide possible structural clues to explain those experimental observations in which the protein stability achieved concurrent with a decrease in enzyme activity, upon manipulation of charge/hydrophobicity balance at the protein surface.     

Neurofilaments and Orthograde Transport Are Reduced in Ventral Root Axons of Transgenic Mice that Express Human SOD1 with a G93A Mutation

Mice engineered to express a transgene encoding a human Cu/Zn superoxide dismutase (SOD1) with a Gly⁹³ → Ala (G93A) mutation found in patients who succumb to familial amyotrophic lateral sclerosis (FALS) develop a rapidly progressive and fatal motor neuron disease (MND) similar to amyotrophic lateral sclerosis (ALS). Hallmark ALS lesions such as fragmentation of the Golgi apparatus and neurofilament (NF)-rich inclusions in surviving spinal cord motor neurons as well as the selective degeneration of this population of neurons were also observed in these animals. Since the mechanism whereby mutations in SOD1 lead to MND remains enigmatic, we asked whether NF inclusions in motor neurons compromise axonal transport during the onset and progression of MND in a line of mice that contained ∼30% fewer copies of the transgene than the original G93A (Gurney et al., 1994). The onset of MND was delayed in these mice compared to the original G93A mice, but they developed the same neuropathologic abnormalities seen in the original G93A mice, albeit at a later time point with fewer vacuoles and more NF inclusions. Quantitative Western blot analyses showed a progressive decrease in the level of NF proteins in the L5 ventral roots of G93A mice and a concomitant reduction in axon caliber with the onset of motor weakness. By ∼200 d, both fast and slow axonal transports were impaired in the ventral roots of these mice coincidental with the appearance of NF inclusions and vacuoles in the axons and perikarya of vulnerable motor neurons. This is the first demonstration of impaired axonal transport in a mouse model of ALS, and we infer that similar impairments occur in authentic ALS. Based on the temporal correlation of these impairments with the onset of motor weakness and the appearance of NF inclusions and vacuoles in vulnerable motor neurons, the latter lesions may be the proximal cause of motor neuron dysfunction and degeneration in the G93A mice and in FALS patients with SOD1 mutations.Neurofilaments (NFs)¹ comprise the major class of neuron-specific intermediate filaments and are the most abundant cytoskeletal components found in large myelinated axons (for reviews see Nixon, 1993; Fuchs and Weber, 1994). NFs are heteropolymers formed by three subunits known as the high (NFH; 110 kD), middle (NFM; 95 kD), and low (NFL; 62 kD) molecular weight NF proteins, all of which are synthesized in neuronal perikarya and transported in the SCa phase (i.e., slow component a) of axonal transport at ∼0.2 to 1.2 mm/d (Lasek and Hoffman, 1976). Other cytoskeletal components (e.g., actin, tubulin) are transported three to four times faster in the SCb of slow axonal transport (Hoffman and Lasek, 1980).The carboxy termini or tail domains of NFH and NFM harbor tandem repeats of lysine-serine-proline (KSP) motifs, and the serine in this motif may be phosphorylated under both physiological and pathological conditions (Jones and Williams, 1982; Julien and Mushynski, 1982; Black and Lee, 1988; Lee et al., 1988a ,b; Clark and Lee, 1991; Giasson and Mushynski, 1996). Normally, the serines in these motifs become highly phosphorylated only after NFH and NFM have been transported into axons where this phosphorylation regulates the caliber of axons (de Waegh et al., 1992; Cole et al., 1994; Tu et al., 1995). In a variety of human neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Parkinson''s disease (PD), as well as in neurotoxin-induced neuropathies, such as those that result from exposure to aluminum and acrylamide (Troncoso et al., 1985; Yase, 1988; Johnson and Jope, 1988; Johnson et al., 1990; Strong, 1994), NF inclusions typically form in the perikarya and processes of neurons, and these inclusions contain highly phosphorylated NFH and NFM (Tu et al., 1997a ,b). The major functions of NFs are to provide mechanical support, especially in large myelinated axons, and to regulate axonal caliber. Thus, disruption of the NF network has been hypothesized to play a mechanistic role in the degeneration of selectively vulnerable neurons that accumulate inclusions in a subset of human neurodegenerative disease (Lee et al., 1994; Julien, 1995). Significantly, this hypothesis has been supported by several recent studies of a number of different lines of transgenic mice that develop an ALS-like phenotype, including prominent NF inclusions in motor neurons that subsequently degenerate (Côté et al., 1993; Xu et al., 1993; Eyer and Peterson, 1994; Lee et al., 1994; Tu et al., 1997a ). Since only variations in the number of KSP motifs in NFH have been observed in some ALS patients (Figlewicz et al., 1994), other factors may lead to disruption of the NF network in neurodegenerative disorders. For example, mutations in the Cu/Zn superoxide dismutase gene (SOD1), which occurs in ∼20% of familial ALS (FALS) kindreds, lead to perturbations of the NF network (for recent review see Tu et al., 1997b ). FALS (as well as sporadic ALS) is a motor neuron disease (MND) characterized by progressive motor weakness due to the selective degeneration of motor neurons, many of which accumulate NF inclusions before their demise (Schmidt et al., 1987; Hill et al., 1991; Hirano, 1991; Tu et al., 1997b ). Transgenic mice that express one of four different mutant forms of the human SOD1 gene recapitulate many of the hallmarks of FALS including a fatal, progressive motor neuron weakness, the selective loss of motor neurons (Gurney et al., 1994; Ripps et al., 1995; Wong et al., 1995; Bruijn et al., 1997), fragmentation of the Golgi apparatus (Mourelatos et al., 1996), and the accumulation of NF inclusions in motor neurons that are vulnerable to degenerate (Dal Canto and Gurney, 1994, 1995, 1997; Tu et al., 1996). The precise mechanisms that lead to the selective degeneration of neurons in authentic ALS as well as in transgenic mouse models of this disorder remain enigmatic, but there is evidence to suggest that NF inclusions may impede axonal transport and thereby contribute to the degeneration of affected neurons (Collard et al., 1995). Alternatively, other studies suggest that NF inclusions may compromise the viability of affected neurons by sequestering vital organelles (Tu et al., 1997a ). Thus, the present study exploited a classic experimental paradigm to determine if axonal transport in the ventral roots was impaired in transgenic mice that expresses human SOD1 with a Gly⁹³→ Ala mutation (G93A) and develop an ALS-like phenotype.     

Chloroquine Intoxication Induces Ganglioside Storage in Nervous Tissue: A Chemical and Histopathological Study of Brain, Spinal Cord, Dorsal Root Ganglia, and Retina in the Miniature Pig

Abstract :
The effect of chronic chloroquine intoxication on lipid composition, particularly the gangliosides, was studied in the nervous system of miniature pigs, type Göttingen. The tissues examined were cerebrum, spinal cord, dorsal root ganglia and retina. Chloroquine was given in the diet in doses of 2.0-3.5 g/kg food. The intoxication of the pigs was started at the age of 100–240 days and continued for 177-219 days. The control pigs received the same diet without chloroquine. The ganglioside concentration was increased in all the tissues examined. Dorsal root ganglia and retina were the tissues affected most and showed a twofold increase. This corresponded to the light and electron microscopically demonstrated extensive storage process in the perikarya of dorsal root ganglion cells and inner ganglion cells of the retina. Under light microscopy the storage material was granular, intensely PAS-positive and dissolved by paraffin embedding. The electron microscopical equivalent consisted of conglomerates of membranous lysosomal residual bodies. In cerebrum the ganglioside concentration was increased by 12%. Storage in the brain varied widely between different systems and types of cells. The allocortex was much more affected than the isocortex. Certain inhibitory ganglion cell types, such as the basket cells, exhibited the most massive storage of all. The spinal medulla was morphologically less involved but showed approximately the same ganglioside increase, though not statistically significant. With the exception of cerebrum the increase in the tissues examined involved all the individual gangliosides, most severely ganglioside GM2 and three fucogangliosides. In cerebrum only the ganglioside GM2 was increased more than the other gangliosides. Chloroquine intoxication did not affect the concentration of phospholipids or cholesterol in the cerebrum, spinal cord or dorsal root ganglia, but in retina the acidic phospholipids were significantly increased.     

Effect of Extracellular Potassium on Ouabain-Sensitive Consumption of High-Energy Phosphate by Crayfish Giant Axons: A Study of the Energy Requirement for Transport in the Steady State

Crayfish axons exposed to a high or low extracellular K+ concentration ([K+]o) maintain intracellular Na+ and K+ concentrations constant, for up to 3 h, by adjusting both the Na+/K+ transport "coupling ratio" and turnover rate in compensation for changes in ion fluxes due to altered electrochemical gradients. These findings give rise to the prediction that the steady-state consumption of high-energy phosphate (approximately P) [ATP and phospho-L-arginine (Arg-P)] is inversely proportional to the [K+]o, i.e., directly proportional to the product of membrane conductance and magnitude of the transmembrane electrochemical gradients for Na+ and K+. This investigation was designed to test this hypothesis. The [K+]o did not influence total approximately P consumption (Q approximately P) of the axon. For a [K+]o between 0.5 and 21.6 mM, Q approximately P averaged 52.8 +/- 4.7%/h (n = 44) of the initial [ATP] + [Arg-P]. Unlike total Q approximately P, the ouabain-sensitive portion of Q approximately P was markedly influenced by [K+]o. In 0.5 mM K+o, ouabain poisoning reduced Q approximately P to 8%/h, a result indicating that 85% of the total Q approximately P was ouabain sensitive. For 1.35 mM K+o, the ouabain-sensitive portion was 66%; at 5.4 mM K+o, 45%; and at 13.5 mM K+o, 41%. There was a small but significant increase in the ouabain-sensitive Q approximately P at 21.6 mM K+o, compared with Q approximately P at 5.4 mM K+o. The pattern of effect of [K+]o on Q approximately P was similar to its effect on the electrical power content of the Na+ and K+ electrochemical gradients. In contrast to the generally accepted Na+ flux (JNa)/approximately P stoichiometry of 3, an actual ratio of JNa/approximately P stoichiometry of approximately 33:1 was calculated for the experiments reported here, a result suggesting that cells in a zero-membrane current steady state utilize efficient energy conservation mechanisms that may not operate under non-steady-state conditions.     

Ultrastructural Analysis of the Terminals of Various Somatosensory Pathways in the Ventrobasal Complex of the Raft Thalamus: An Electron-Microscopic Study Using Wheatgerm Agglutinin Conjugated to Horseradish Peroxidase as an Axonal Tracer

We used wheatgerm agglutinin conjugated to horseradish peroxidase (WGA:HRP) as an anterograde tracer to label the terminals of the lemniscal, spinothalamic, and trigeminothalamic pathways in the ventrobasal complex of the rat thalamus (VB). The use of benzidine dihydrochloride (BDHC) as the chromogen allowed us to view the labeled profiles with the electron microscope and permitted us to compare the morphology of the terminals from the various pathways. We found that all the labeled somatosensory pathways terminate in the VB in the form of large terminals that contain round synaptic vesicles and make numerous asymmetrical synaptic contacts, usually with dendritic protrusions and proximal dendrites. The present results demonstrate that pathways conveying noxious and non-noxious somatosensory information terminate upon thalamic neurons with synaptic terminals having similar morphological features.     

The Absence of CYP3A5*3 Is a Protective Factor to Anticonvulsants Hypersensitivity Reactions: A Case-Control Study in Brazilian Subjects

Although aromatic anticonvulsants are usually well tolerated, they can cause cutaneous adverse drug reactions in up to 10% of patients. The clinical manifestations of the antiepileptics-induced hypersensitivity reactions (AHR) vary from mild skin rashes to severe cutaneous drug adverse reactions which are related to high mortality and significant morbidity. Genetic polymorphisms in cytochrome P450 genes are associated with altered enzymatic activity and may contribute to the risk of AHR. Here we present a case-control study in which we genotyped SNPs of CYP2C19, 2C9 and 3A5 of 55 individuals with varying severities of AHR, 83 tolerant, and 366 healthy control subjects from São Paulo, Brazil. Clinical characterization was based on standardized scoring systems and drug patch test. All in vivo investigation followed the ENDA (European Network of Drug Allergy) recommendations. Genotype was determined by real time PCR using peripheral blood DNA as a template. Of all 504 subjects, 65% were females, 45% self-identified as Afro-American, 38% as Caucasian and 17% as having non-African mixed ascendancy. Amongst 55 subjects with AHR, 44 had severe cutaneous drug adverse reactions. Of the 46 drug patch tests performed, 29 (63%) were positive. We found a strong association between the absence of CYP3A5*3 and tolerant subjects when compared to AHR (p = 0.0002, OR = 5.28 [CI95% 2.09–14.84]). None of our groups presented positive association with CYP2C19 and 2C9 polymorphisms, however, both SNPs contributed to separation of cases and tolerants in a Classification and Regression Tree. Our findings indicate that drug metabolism genes can contribute in the tolerability of antiepileptics. CYP3A5*3 is the most prevalent CYP3A5 allele associated with reduced enzymatic function. The current study provides evidence that normal CYP3A5 activity might be a protective factor to aromatic antiepileptics-induced hypersensitivity reactions in Brazilian subjects.     

Regional Distribution of Calcitonin Gene-Related Peptide-, Substance P-, Cholecystokinin-, Met5-Enkephalin-, and Dynorphin A (1–8)-Like Materials in the Spinal Cord and Dorsal Root Ganglia of Adult Rats: Effects of Dorsal Rhizotomy and Neonatal Capsaicin

Biochemical mapping of five different peptide-like materials--calcitonin gene-related peptide (CGRP), substance P (SP), Met5-enkephalin (ME), cholecystokinin (CCK), and dynorphin A (1-8) (DYN)--was conducted in the dorsal and ventral zones of the spinal cord at the cervical, thoracic, and lumbar levels in 3-month-old rats 10 days after unilateral dorsal rhizotomy at the cervical level (C4-T2) or after neonatal administration of capsaicin (50 mg/kg s.c.). In control rats, all peptide-like materials were more abundant in the dorsal than in the ventral zone all along the spinal cord. However, in both zones, absolute concentrations of CGRP, SP, ME, and CCK were significantly higher at the lumbar than at the cervical level. Rhizotomy-induced CGRP depletion (-85%) within the ipsilateral dorsal zone of the cervical cord was more pronounced than that due to neonatal capsaicin (-60%), a finding suggesting that this peptide is contained in both capsaicin-sensitive (mostly unmyelinated) and -insensitive (myelinated) primary afferent fibers. In contrast, similar depletions of SP (-50%) were observed after dorsal rhizotomy and neonatal capsaicin treatment, as expected from the presence of SP only in the capsaicin-sensitive small-diameter primary afferent fibers. Although the other three peptides remained unaffected all along the cord by either intervention, evidence for the existence of capsaicin-insensitive CCKergic primary afferent fibers could be inferred from the increased accumulation of CCK (together with SP and CGRP) in dorsal root ganglia ipsilateral to dorsal root sections.     

In Vivo Molecular Imaging and Histological Analysis of Changes Induced by Electric Pulses Used for Plasmid DNA Electrotransfer to the Skin: A Study in a Dorsal Window Chamber in Mice

Electropermeabilization/electroporation (EP) is a physical method that by application of electric pulses to cells increases cell membrane permeability and enables the introduction of molecules into the cells. One of the uses of EP in vivo is plasmid DNA electrotransfer to the skin for DNA vaccination. EP of tissues induces reduction of blood flow and, in combination with plasmid DNA, induction of an immune response. One of the EP protocols for plasmid DNA electrotransfer to the skin is a combination of high-voltage (HV) and low-voltage (LV) pulses. However, the effects of this pulse combination on skin-vessel blood flow are not known. Therefore, using intravital microscopy in a dorsal window chamber in mice and fluorescently labeled dextrans, the effects of one HV and eight LV pulses on skin vasculature were investigated. In addition, a detailed histological analysis was performed. Image analysis of fluorescence intensity changes demonstrated that EP induces a transient constriction and increased permeability of blood vessels as well as a “vascular lock.” Histological analysis revealed rounding up of endothelial cells and stacking up of erythrocytes at 1?h after EP. In addition, extravasation of erythrocytes and leukocyte infiltration accompanied by edema were determined up to 24?h after EP. In conclusion, our results show that blood flow modifying effects of EP in skin contribute to the infiltration of immune cells in the exposed area. When combined with plasmid DNA for vaccination, this could enable the initial and prolonged contact of immune cells with encoded therapeutic proteins.     

The Effect of Non-Contact Conditions in a Splinted Fixed Partial Denture on the Load Sharing Mechanism: A Finite Element Study

A computer-aided design model for a fixed partial denture was constructed and used in a finite element analysis to study the overall load sharing mechanism between the fixed partial denture and oral structures while the denture base rested on the alveolar ridge.To investigate the consequences of non-contact conditions,three additional models were generated incorporating a uniform clearance of 0.125 mm,0.25 mm,and 0.5 mm,respectively.A 100 N static load located at the free end of the prosthesis was applied while the distal portion of the jaw was set fixed.The results show that whilst releasing the ridge almost entirely,the presence of the clearance drastically increased the load on the splinting teeth.A pull-out force on the canine tooth of about 44 N was computed,accompanied by a mesio-distal moment of about 500 N.cm.The combination of which was similar to the tooth extraction maneuver performed by the dentist.In contrast,the second premolar was found to bear a push-in force of almost 115N.The first molar,though barely solicited in the contact condition,became substantially loaded in non-contact conditions,which validates the choice of sacrificing three teeth to support the denture.     

A Novel Approach to Determining a Population-Level Threshold in Ecological Risk Assessment: A Case Study of Zinc

A novel approach to population-level assessment was applied in order to demonstrate its utility in estimating and managing the risk of zinc in a water environment. Much attention has been paid to population-level risk assessment, but there have been no attempts to determine a “safe” population-level concentration as an environmental criterion. Based on the published results of toxicity tests for various species, we first theoretically derived a threshold concentration at which a population size is unchanged due to the adverse effects of zinc exposure. To derive a zinc concentration that will protect populations in natural environments, we adopted the concept of species sensitivity distribution. Assuming the threshold concentrations of a set of species are log-normally distributed, we calculated the 95% protection level of zinc (PHC₅ :population-level hazardous concentration of 5% of species), which is 107 μg/L. Meanwhile, the 95% protection criterion (HC₅) based on conventional individual-level chronic toxicity, was calculated to be 14.6 μg/L. The environmentally “safe” concentration for a population-level endpoint is about 7 times greater than that for an individual-level endpoint. The proposed method provides guidance for a pragmatic approach to population-level ecological risk assessment and the management of chemicals.     

A Physician's Perspective on the Incorporation of Pictograms as a Supplement to Medical Instructions in Chile: A Pilot Study

Introduction and objectivesCurrent models of health care are progressively migrating to more participatory models, where for treatment to achieve results that last over time, there must be effective communication between the patient, his or her caregivers, and health professionals. Although the use of pictograms in the context of medical instructions has been widely studied, in our country, there are no studies about their usefulness, or which set of symbols should be used by the systems. This work aims to present the first step towards the development of platforms that automatically suggest pictograms to supplement medical instructions for primary care settings in Chile.Materials and methodsIn this pilot study, we collected and analyzed the physicians' opinions on the selection of medical instructions that later will automatically be supplemented by the software that is under construction. We designed an expert validation survey using a set of 66 medical instructions with pictograms. This survey provided three rating options for each medical instruction: Not necessary (supplementing the instruction with a pictogram does not carry any value), Useful (supplementing the instruction with a pictogram may help patients to understand and remember the instruction), and Essential (supplementing the instruction with a pictogram is essential). Seventy-one physicians responded to the survey.Results22 out of 66 medical instructions were considered “essential” by >=51% of the experts, and 12 of the 66 were considered to be “useful but not essential” by >=51% of the experts.ConclusionResults of our survey validate the potential use of pictograms as a complement to better comprehension of medical instructions in our country.     

Work of Breathing into Snow in the Presence versus Absence of an Artificial Air Pocket Affects Hypoxia and Hypercapnia of a Victim Covered with Avalanche Snow: A Randomized Double Blind Crossover Study

Presence of an air pocket and its size play an important role in survival of victims buried in the avalanche snow. Even small air pockets facilitate breathing. We hypothesize that the size of the air pocket significantly affects the airflow resistance and work of breathing. The aims of the study are (1) to investigate the effect of the presence of an air pocket on gas exchange and work of breathing in subjects breathing into the simulated avalanche snow and (2) to test whether it is possible to breathe with no air pocket. The prospective interventional double-blinded study involved 12 male volunteers, from which 10 completed the whole protocol. Each volunteer underwent two phases of the experiment in a random order: phase “AP”—breathing into the snow with a one-liter air pocket, and phase “NP”—breathing into the snow with no air pocket. Physiological parameters, fractions of oxygen and carbon dioxide in the airways and work of breathing expressed as pressure-time product were recorded continuously. The main finding of the study is that it is possible to breath in the avalanche snow even with no air pocket (0 L volume), but breathing under this condition is associated with significantly increased work of breathing. The significant differences were initially observed for end-tidal values of the respiratory gases (EtO₂ and EtCO₂) and peripheral oxygen saturation (SpO₂) between AP and NP phases, whereas significant differences in inspiratory fractions occurred much later (for F_IO₂) or never (for F_ICO₂). The limiting factor in no air pocket conditions is excessive increase in work of breathing that induces increase in metabolism accompanied by higher oxygen consumption and carbon dioxide production. The presence of even a small air pocket reduces significantly the work of breathing.     

Deformation of Filamentous Escherichia coli Cells in a Microfluidic Device: A New Technique to Study Cell Mechanics

The mechanical properties of bacterial cells are determined by their stress-bearing elements. The size of typical bacterial cells, and the fact that different time and length scales govern their behavior, necessitate special experimental techniques in order to probe their mechanical properties under various spatiotemporal conditions. Here, we present such an experimental technique to study cell mechanics using hydrodynamic forces in a microfluidic device. We demonstrate the application of this technique by calculating the flexural rigidity of non-growing Escherichia coli cells. In addition, we compare the deformation of filamentous cells under growing and non-growing conditions during the deformation process. We show that, at low forces, the force needed to deform growing cells to the same extent as non-growing cells is approximately two times smaller. Following previous works, we interpret these results as the outcome of the difference between the elastic response of non-growing cells and the plastic-elastic response of growing cells. Finally, we observe some heterogeneity in the response of individual cells to the applied force. We suggest that this results from the individuality of different bacterial cells.     

The Response of Physicians to a Mailed Questionnaire: A Study in Ontario,Manitoba and British Columbia

During 1965, 1585 questionnaires were sent to physicians in British Columbia, Manitoba and Ontario to elicit information about persons who had died and in whom a chronic non-specific respiratory disease had been recorded on the registration of death. The response rate to the first letter of enquiry was 54.1%. This was improved to 76.5% when the enquiry was sent by registered mail, and to 90.6% by a registered special appeal. The final response rate was 93.8% for British Columbia, 92.8% for Manitoba and 89.5% for Ontario. Although response varied with the time of the year, there was no evident relationship between response rate and characteristics of the physician. Physician characteristics studied were place and year of graduation and the nature of practice. Acceptable and high response rates to mailed questionnaires eliciting clinical data from physicians can be obtained if the investigator''s concern is demonstrated by sending the request in successive waves to the diminishing group of non-respondents.