'Evolutionary poker': an agent-based model of interactome emergence and epistasis tested against Lenski's long-term E. coli experiments.

A simple agent-based model is presented that produces results matching the experimental data found by Lenski's group for ≤50,000 generations of Escherichia coli bacteria under continuous selective pressure. Although various mathematical models have been devised previously to model the Lenski data, the present model has advantages in terms of overall simplicity and conceptual accessibility. The model also clearly illustrates a number of features of the evolutionary process that are otherwise not obvious, such as the roles of epistasis and historical contingency in adaptation and why evolution is time irreversible ('Dollo's law'). The reason for this irreversibility is that genomes become increasingly integrated or organized, and this organization becomes a novel selective factor itself, against which future generations must compete. Selection for integrated or synergistic networks, systems or sets of mutations or traits, not for individual mutations, confers the main adaptive advantage. The result is a punctuated form of evolution that follows a logarithmic occurrence probability, in which evolution proceeds very quickly when interactomes begin to form but which slows as interactomes become more robust and the difficulty of integrating new mutations increases. Sufficient parameters exist in the game to suggest not only how equilibrium or stasis is reached but also the conditions in which it will be punctuated, the factors governing the rate at which genomic organization occurs and novel traits appear, and how population size, genome size and gene variability affect these.

A Biomechanical Study of Hyoid Bone and Laryngeal Movements During Swallowing Comparing the Blom Low Profile Voice Inner Cannula and Passy-Muir One Way Tracheotomy Tube Speaking Valves.

The aim of this prospective, consecutive, cohort study was to investigate the biomechanical effects, if any, of the Blom low profile voice inner cannula and Passy-Muir one-way tracheotomy tube speaking valves on movement of the hyoid bone and larynx during swallowing. Ten adult patients (8 male, 2 female) with an age range of 61-89 years (mean 71 years) participated. Criteria for inclusion were ≥18 years of age, English speaking, and ability to tolerate both changing to a Blom tracheotomy tube and placement of a one-way tracheotomy tube speaking valve with a fully deflated tracheotomy tube cuff. Digitized videofluoroscopic swallow studies were performed at 30 frames/s and with each patient seated upright in the lateral plane. A total of 18 swallows (three each with 5 cc bolus volumes of single contrast barium and puree + barium × 3 conditions) were analyzed for each participant. Variables evaluated included larynx-to-hyoid bone excursion (mm), maximum hyoid bone displacement (mm), and aspiration status under three randomized conditions: 1. Tracheotomy tube open with no inner cannula; 2. Tracheotomy tube with Blom valve; and 3. Tracheotomy tube with Passy-Muir valve. Blinded reliability testing with a Pearson product moment correlation was performed on 20 % of the data. Intra- and inter-rater reliability for combined measurements of larynx-to-hyoid bone excursion and maximum hyoid bone displacement was r = 0.98. Intra- and inter-rater reliability for aspiration status was 100 %. No significant differences (p > 0.05) were found for larynx-to-hyoid bone excursion and maximum hyoid bone displacement during swallowing based upon an open tracheotomy tube, Blom valve, or Passy-Muir valve. Aspiration status was identical for all three randomized conditions. The presence of a one-way tracheotomy tube speaking valve did not significantly alter two important components of normal pharyngeal swallow biomechanics, i.e., hyoid bone and laryngeal movements. Aspiration status was similarly unaffected by valve use. Clinicians should be aware that the data do not support placement of a one-way tracheotomy tube speaking valve to reduce prandial aspiration.

Management of the anxious dental patient.

The anxious patient in the dental office reacts with panic and inability to cooperate with necessary treatment. It is the dentist's responsibility to recognize and assuage the patient's anxiety on both psychological and medical levels. The diagnosis, etiology and treatment of anxiety will be investigated and presented as any other disease entity. It is an illness that contributes to dental neglect and subsequent pain, disease and dysfunction. The purpose of this paper is to discuss the recognition and etiology of patient anxiety and to offer treatment solutions and behavior modification techniques. The discussion will include psychological insight as well as the use of anxiolytics and nitrous oxide-oxygen (N2O-O2) sedation to ameliorate the symptoms. Finally, a presentation will be made of the modern application of philosophic dicta of Plato and Aristotle in which the doctor is considered a philosopher who values the concept of self-healing based on the doctor-patient relationship. These techniques and concepts of totality in diagnosis and treatment are applicable today just as they were 17 centuries ago.

Clinical identification of head and neck lymphadenopathy: a diagnostic obligation.

The purpose of this article is to reinforce the need for all dental clinicians to perform a complete lymph node examination on every patient, regardless of age, gender, or chief complaint. As early diagnosis provides for the best prognosis, head and neck lymph node palpation may be the earliest indicator of infection or neoplasia. This article provides the rationale for lymph node examination, the palpation techniques for the clinician to utilize, and the anatomic locations and descriptions of lymph nodes.

Epiglottis is not essential for successful swallowing in humans.

Controversy has continued for well over 100 years regarding the role of the epiglottis in deglutition. We describe the effect of isolated epiglottectomy on swallowing success in a case series of 3 adult human subjects with isolated epiglottectomy due to trauma, surgery, or cancerous erosion. The patients were 42, 51, and 70 years of age, and swallowing was analyzed objectively with videofluoroscopy. All subjects exhibited successful swallowing with all food types: thin liquid, puree, and solid food. Specifically, the patient with traumatic epiglottectomy exhibited rapid swallowing success, the patient with surgical epiglottectomy exhibited a short period of dysphagia due to postoperative edema, followed by swallowing success, and the patient with epiglottectomy due to cancerous erosion of the entire epiglottis exhibited long-term adaptation, with successful swallowing maintained. We conclude that the epiglottis is not essential for successful swallowing in humans, because individuals can readily adapt to isolated epiglottectomy and avoid tracheal aspiration.

Hyoid bone and laryngeal movement dependent upon presence of a tracheotomy tube.

The aim of this prospective, consecutive study was to investigate the biomechanical effects, if any, of the presence of a tracheotomy tube and tube cuff status, tube capping status, and aspiration status on movement of the hyoid bone and larynx during normal swallowing. Seven adult patients (5 male, 2 female) with an age range of 46-82 years (mean = 63 years) participated. Criteria for inclusion were no history of cancer of or surgery to the head and neck (except tracheotomy), normal cognition, normal swallowing, and ability to tolerate decannulation. Digital videofluoroscopic swallowing studies were performed at 30 frames/s and with each patient seated upright in the lateral plane. Variables evaluated included maximum hyoid bone displacement and larynx-to-hyoid bone approximation under three randomized conditions: tracheotomy tube in and open with a 5-cc air-inflated cuff; tracheotomy tube in and capped with deflated cuff; and tracheotomy tube out (decannulated). Differences between maximum hyoid bone displacement and larynx-to-hyoid approximation (cm) based on presence/absence of a tracheotomy tube, tube cuff status, and tube capping status were analyzed with the Student's t test. Reliability testing with a Pearson product moment correlation was performed on 21% of the data. No significant differences (p > 0.05) were found for both maximum hyoid bone displacement and larynx-to-hyoid bone approximation during normal swallowing based on tracheotomy tube presence, tube cuff status, or tube capping status. Intraobserver reliability for combined measurements of maximum hyoid displacement and larynx-to-hyoid approximation was r = 0.97 and interobserver reliability for the absence of aspiration was 100%. For the first time with objective data it was shown that the presence of a tracheotomy tube did not significantly alter two important components of normal pharyngeal swallow biomechanics, i.e., hyoid bone movement and laryngeal excursion. The hypothesis that a tracheotomy tube tethers the larynx thereby preventing hyoid bone and laryngeal movement during normal swallowing is not supported.

Differentiation and immune function of human dendritic cells following infection by respiratory syncytial virus.

RSV causes annual epidemics of bronchiolitis in winter months resulting in the hospitalization of many infants and the elderly. Dendritic cells (DCs) play a pivotal role in coordinating immune responses to infection and some viruses skew, or subvert, the immune functions of DCs. RSV infection of DCs could alter their function and this could explain why protection after natural RSV infection is incomplete and of short duration. In this study, this interaction between DCs and RSV was investigated using a human primary culture model. DCs were generated from purified healthy adult volunteer peripheral blood monocytes. Effects of RSV upon DC phenotype with RSV primed DCs was measured using flow cytometry. Changes to viability and proliferation of cocultured DCs and T-cells were determined using microscopy with fluorescent dyes (Hoechst 33342 and propidium iodide). DC maturation was not prevented by the RSV challenge. RSV infected a fraction of DCs (10-30%) but the virus replicated slowly in these cells with only small reduction to cell viability. DCs challenged with RSV stimulated T-cell proliferation less well than lipopolysaccharide. This is the first study to demonstrate RSV infection of human monocyte derived DCs and suggests that the virus does not significantly interfere with the function of these cells and potentially may promote cellular rather than humoral responses.

Role in the inspiratory off-switch of vagal inputs to rostral pontine inspiratory-modulated neurons.

Neurons of the pontine respiratory group (PRG) in the region of the nucleus parabrachialis medialis and the Kolliker-Fuse nucleus are believed to play an important role in promoting the inspiratory (I) off-switch (IOS). In decerebrate gallamine-paralyzed cats ventilated with a cycle-triggered pump system (lung inflation during the neural I phase), we studied the effects of vagal (V) afferent inputs on firing of I-modulated neurons (the most numerous population in PRG) and on I duration. The predominant V effect on unit activity was inhibitory, as shown by two types of test: (a) withholding of inflation during an I phase, which produced increase of unit firing and of its respiratory modulation (58/66 neurons in 14 cats), indicating disinhibition due to removal of phasic V input; (b) delivery of afferent V stimulus trains during a no-inflation I phase, which produced decrease of unit firing and of its respiratory modulation (20 neurons). In addition, application of V input during the neural expiratory (E) phase, which lengthened E phase duration, produced no effect on the neurons' firing, suggesting that the inhibition during I was presynaptic in origin. The results may be interpreted by the hypothesis that the medullary late-I presumptive IOS neurons receive excitatory inputs from the PRG I-modulated neurons as well as from V afferents.. With relatively strong V input, this pontine excitatory output is reduced by inhibition, whereas with relatively weak V input that excitatory output is increased due to reduction of inhibition. Thus the pontine and the V influences on the IOS can operate in a complementary manner dependent on state.

Different types of barosensory synaptic inputs to rostral ventrolateral medulla neurons of the rat.

Neurons situated in the rostral ventrolateral medulla (RVLM) with descending axons to the spinal cord and that are modulated by different baroreceptor inputs are considered the main central generators of vasomotor activity. In the urethane-anesthetized, curarized rat, we recorded intracellular potentials from 14 neurons located in the RVLM and investigated their barosensory properties by analysis of the relation between neuronal membrane potential (MP), including spike potentials, and high-pressure barosensory activity, which was indicated by arterial blood pressure (BLPR). Time-domain (cross-correlations or triggered averaging) and frequency-domain (autospectra and coherences) analysis showed that 7 of 14 neurons had cardiac-cycle-correlated rhythms. EXCITATORY CARDIAC-CYCLE-RELATED MODULATION: One type of barosensitive neuron, with strong cardiac-related activity, was antidromically activated from the spinal cord and received inhibitory inputs from aortic nerve stimulation. These neurons had strong pulse-modulated activity consisting of EPSPs and spike potentials locked to the cardiac cycle and occurring at the end of diastole. INHIBITORY CARDIAC-CYCLE-RELATED MODULATION: Another type of barosensitive neuron showed hyperpolarizations locked to the cardiac cycle that started during late diastole and ended during the systolic period, but which had little relation to spike firing. The hyperpolarizations might be due to either IPSPs or disfacilitation. RESPIRATORY AND CARDIAC MODULATION: Some neurons also showed modulation of synaptic potentials and/or spike firing locked to the oscillation produced by ventilator pressure. It is suggested that the different types of cardiac- and respiratory-related rhythm reflect different functional roles of neurons in baroreceptor regulation of vasomotor activity.

Testosterone inhibits the prostaglandin F2alpha-mediated increase in intracellular calcium in A7r5 aortic smooth muscle cells: evidence of an antagonistic action upon store-operated calcium channels.

Testosterone-induced vasodilatation is proposed to contribute to the beneficial effects associated with testosterone replacement therapy in men with cardiovascular disease, and is postulated to occur via either direct calcium channel blockade, or through potassium channel activation via increased production of cyclic nucleotides. We utilised flow cytometry to investigate whether testosterone inhibits the increase in cellular fluorescence induced by prostaglandin F(2alpha) in A7r5 smooth muscle cells loaded with the calcium fluorescent probe indo-1-AM, and to study the cellular mechanisms involved. Two-minute incubation with testosterone (1 microM) significantly inhibited the change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) (3.6+/-0.6 vs 7.6+/-1.0 arbitrary units, P=0.001). The change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) was also significantly attenuated in the absence of extracellular calcium (3.6+/-0.3 vs 15.6+/-0.7 arbitrary units, P=0.0000002), and by a 2-min incubation with the store-operated calcium channel blocker SK&F 96365 (50 microM) (4.7+/-0.8 vs 8.1+/-0.4 arbitrary units, P=0.003). The response was insensitive to similar incubation with the voltage-operated calcium channel blockers verapamil (10 microM) (12.6+/-1.2 vs 11.9+/-0.2 arbitrary units, P=0.7) or nifedipine (10 microM) (13.9+/-1.3 vs 13.3+/-0.5 arbitrary units, P=0.7). Forskolin (1 microM) and sodium nitroprusside (100 microM) significantly increased the cellular concentration of cyclic adenosine monophosphate and cyclic guanosine monophosphate respectively, but testosterone (100 nM-100 microM) had no effect. These data indicate that the increase in intracellular calcium in response to prostaglandin F(2alpha) occurs primarily via extracellular calcium entry through store-operated calcium channels. Testosterone inhibits the response, suggesting an antagonistic action upon these channels.

Rhythmic properties of neurons in the rostral ventrolateral medulla of the rat in vitro: effects of clonidine.

The rostral ventrolateral medulla (RVLM) is thought to be the main central site for generation of tonic sympathetic activity. In the rat in vitro slice preparation, we used intracellular recordings to identify different populations of neurons in the RVLM: 43 spontaneously active neurons with regular (R) or irregular (I) patterns of spike firing and 10 silent neurons. The degree of regularity was quantified by the coefficient of variation (CV = SD/mean) of interspike interval durations, as well as by the rhythmic properties of the spike autospectrum and autocorrelation. The distribution of CVs was clustered: R and I neurons were defined as those with CVs 12% (n = 22), respectively. The R-type and I-type neurons resemble the type II and type I neurons, respectively, which were previously characterized in the RVLM in vivo as barosensitive and bulbospinal. Both types may be important in generation of sympathetic tone. Clonidine (1-100 microM) was applied to 10 R-type neurons and 16 I-type neurons. The firing of 21/26 was depressed to the point of silence. However, 18/26 neurons were excited earlier in the perfusion. The later depression of firing occurred in both I and R neurons and in different cases was associated with either hyperpolarization or depolarization.

Respiratory cycle timing and fast inspiratory discharge rhythms in the adult decerebrate rat.

In supracollicular decerebrate paralyzed adult rats, neural respiration was monitored by bilateral phrenic recordings. In the study of respiratory cycle timing, the effects of vagal afferent input (lung inflation) on respiratory phase durations resembled those seen in decerebrate cats. 1) Withholding lung inflation during neural inspiration (I) produced lengthening of I phase duration by 46% (mean, n = 11). 2) Maintaining lung inflation during neural expiration (E) produced lengthening of E phase duration by 112% (mean, n = 4). In the study of fast rhythms in inspiratory discharges, phrenic nerve autospectra and bilateral (left-right) phrenic coherences in 16 rats revealed two types of fast rhythm: 1) high-frequency oscillation (HFO), which had significant coherence peaks (n = 9, range 106-160 Hz, mean 132 Hz); and 2) medium-frequency oscillation (MFO), which had autospectral peaks but no distinct coherence peaks (n = 11, range 46-96 Hz, mean 66 Hz). These rhythms resembled MFOs and HFOs in the decerebrate cat, but the modal frequency range was about twice as large. In addition, these frequency values differed markedly from the 20-40 Hz of the rhythms found in earlier studies in neonatal in vitro preparations; the difference may be due to developmental immaturity.

Solubilized zona pellucida proteins and progesterone induce calcium influx and the acrosome reaction in capacitated dog spermatozoa.

Spermatozoa from the sperm-rich fractions of the semen of 6 beagle dogs were capacitated and the effect of both zona pellucida (ZP) proteins and progesterone on calcium flux and the acrosome reaction measured. Sperm calcium flux was determined using the dual wavelength calcium probe indo-1/AM (6 microM) in a flow cytometric assay (one ejaculate from each dog examined; n = 6). No calcium flux was observed in the negative control treatments (RPMI medium or DMSO). Both heat-solubilized bitch ZP proteins and progesterone caused a similar response characterized by a gradual but marked influx of calcium ions which was sustained over 2 min. Acrosomal status was assessed by indirect immunofluorescence using a specific monoclonal antibody following 1 hr incubation for each treatment (four ejaculates from each dog examined; n = 24). The level of acrosomal exocytosis was very high for samples treated with ZP proteins (70.3 +/- 2.1%) and progesterone (84.6 +/- 1.5%) and was significantly different from the respective controls (P < 0.001). Interestingly the patterns of calcium flux in response to both ZP proteins and progesterone were in contrast to the situation in other species studied to date raising the possibility that the mechanism for triggering the acrosome reaction may be different in dog spermatozoa. In addition the high degree of progesterone-induced acrosomal exocytosis compared to other species raises the probability that the majority of dog spermatozoa are already undergoing the acrosome reaction before they reach the egg ZP.