Concentration-dependent isoflurane effects on withdrawal reflexes in pigs and the role of the stimulation paradigm

In this prospective two-phase experimental trial, 10 pigs were anaesthetized twice with isoflurane only. In the first phase, the individual minimum alveolar concentration (MAC) was determined and in the second phase the effects on withdrawal reflexes of increasing end-tidal isoflurane concentrations (from 1.6% to 2.8%) were assessed. Single, 10 and 60 repeated electrical stimulations were used to evoke withdrawal reflexes which were recorded and quantified by electromyography. Recruitment curves for reflex amplitude for increasing stimulation intensities and isoflurane concentrations were constructed. Isoflurane MAC was 1.9+/-0.3%. Reflexes evoked by repeated stimulation were suppressed at isoflurane concentrations significantly higher than those which suppressed complex movements during MAC determination (P=0.014 and P=0.006 for 10 and 60 repeated stimuli respectively). Isoflurane up to 2.8% was still not able to abolish reflex activity evoked by repeated stimulations in all pigs. Single stimulation reflexes were suppressed at significantly lower concentrations than repeated stimulation reflexes (P=0.008 and P=0.004 for 10 and 60 repeated stimuli, respectively). Reflex amplitude was significantly correlated with isoflurane concentration (P<0.001, r=-0.85) independent of the individual MAC. The findings indicate that the level at which isoflurane suppresses withdrawal reflexes is dependent on the stimulation paradigm (single vs. repeated electrical stimulation), and there is limited value in expressing reflex withdrawal suppression in terms of MAC as purposeful and reflex movements are independently affected by isoflurane in individual animals.

The implementation of a tobacco dependence education curriculum in a Swiss Dental Hygiene School - an 8-year review

OBJECTIVE The aim of our investigation was to review the implementation of a comprehensive tobacco dependence education (TDE) curriculum at the Medi School of Dental Hygiene (MSDH), Bern, Switzerland, 2001-2008. METHODS In 2001, new forms to record patients' tobacco use history and willingness to quit were created for all the MSDH patients. In 2002, a new theoretically based tobacco dependence treatment protocol was implemented into the MSDH curriculum. Students received instruction on how to provide brief tobacco use dependence interventions as well as maintain detailed records of patient tobacco use and cessation interventions for every smoker at all dental hygiene visits. RESULTS In 2002, 17 lecture hours were added to the following subjects: pathology, periodontology, preventive dentistry, pharmacology and psychology. During the same time period, 2213 patients (56.9% women) have visited the MSDH. Smoking status was recorded in 85.7% of all the patients (30.2% smokers). Brief tobacco use interventions were recorded in 36.8% of all smokers while 7.6% of these have reported to quit smoking. CONCLUSIONS Overall, the new TDE curriculum was successfully implemented and accepted by the MSDH faculty. Applications in the clinical practice, however, may still be improved to better identify smokers and increase initial and follow-up interventions potentially leading to higher quit rates.

Quantitative assessment of the nociceptive withdrawal reflex in healthy, non-medicated experimental sheep

This study aimed to characterize the nociceptive withdrawal reflex (NWR) and to define the nociceptive threshold in 25 healthy, non-medicated experimental sheep in standing posture. Electrical stimulation of the dorsal lateral digital nerves of the right thoracic and the pelvic limb was performed and surface-electromyography (EMG) from the deltoid (all animals) and the femoral biceps (18 animals) or the peroneus tertius muscles (7 animals) was recorded. The behavioural reaction following each stimulation was scored on a scale from 0 (no reaction) to 5 (strong whole body reaction). A train-of-five 1 ms constant-current pulse was used and current intensity was stepwise increased until NWR threshold intensity was reached. The NWR threshold intensity (It) was defined as the minimal stimulus intensity able to evoke a reflex with a minimal Root-Mean-Square amplitude (RMSA) of 20 μV, a minimal duration of 10 ms and a minimal reaction score of 1 (slight muscle contraction of the stimulated limb) within the time window of 20 to 130 ms post-stimulation. Based on this value, further stimulations were performed below (0.9It) and above threshold (1.5It and 2It). The stimulus-response curve was described. Data are reported as medians and interquartile ranges. At the deltoid muscle It was 4.4 mA (2.9–5.7) with an RMSA of 62 μV (30–102). At the biceps femoris muscle It was 7.0 mA (4.0–10.0) with an RMSA of 43 μV (34–50) and at the peroneus tertius muscle It was 3.4 mA (3.1–4.4) with an RMSA of 38 μV (32–46). Above threshold, RMSA was significantly increased at all muscles. Below threshold, RMSA was only significantly smaller than at It for the peroneus tertius muscle but not for the other muscles.

Short-Term Plasticity in a Computational Model of the Tail-Withdrawal Circuit in Aplysia.

The tail-withdrawal circuit of Aplysia provides a useful model system for investigating synaptic dynamics. Sensory neurons within the circuit manifest several forms of synaptic plasticity. Here, we developed a model of the circuit and investigated the ways in which depression (DEP) and potentiation (POT) contributed to information processing. DEP limited the amount of motor neuron activity that could be elicited by the monosynaptic pathway alone. POT within the monosynaptic pathway did not compensate for DEP. There was, however, a synergistic interaction between POT and the polysynaptic pathway. This synergism extended the dynamic range of the network, and the interplay between DEP and POT made the circuit responded preferentially to long-duration, low-frequency inputs.

Correlates of tobacco cessation counseling among Hispanic physicians in the US: a cross-sectional survey study.

BACKGROUND: Physician advice is an important motivator for attempting to stop smoking. However, physicians' lack of intervention with smokers has only modestly improved in the last decade. Although the literature includes extensive research in the area of the smoking intervention practices of clinicians, few studies have focused on Hispanic physicians. The purpose of this study was to explore the correlates of tobacco cessation counseling practices among Hispanic physicians in the US. METHODS: Data were collected through a validated survey instrument among a cross-sectional sample of self-reported Hispanic physicians practicing in New Mexico, and who were members of the New Mexico Hispanic Medical Society in the year 2001. Domains of interest included counseling practices, self-efficacy, attitudes/responsibility, and knowledge/skills. Returned surveys were analyzed to obtain frequencies and descriptive statistics for each survey item. Other analyses included: bivariate Pearson's correlation, factorial ANOVAs, and multiple linear regressions. RESULTS: Respondents (n = 45) reported a low level of compliance with tobacco control guidelines and recommendations. Results indicate that physicians' familiarity with standard cessation protocols has a significant effect on their tobacco-related practices (r = .35, variance shared = 12%). Self-efficacy and gender were both significantly correlated to tobacco related practices (r = .42, variance shared = 17%). A significant correlation was also found between self-efficacy and knowledge/skills (r = .60, variance shared = 36%). Attitudes/responsibility was not significantly correlated with any of the other measures. CONCLUSION: More resources should be dedicated to training Hispanic physicians in tobacco intervention. Training may facilitate practice by increasing knowledge, developing skills and, ultimately, enhancing feelings of self-efficacy.

Hispanic physicians' tobacco intervention practices: a cross-sectional survey study

Background U.S. Hispanic physicians constitute a considerable professional collective, and they may be most suited to attend to the health education needs of the growing U.S. Hispanic population. These educational needs include tobacco use prevention and smoking cessation. However, there is a lack of information on Hispanic physicians' tobacco intervention practices, their level of awareness and use of cessation protocols, and the type of programs that would best address their tobacco training needs. The purpose of this study was to assess the tobacco intervention practices and training needs of Hispanic physicians. Methods Data was collected through a validated survey instrument among a cross-sectional sample of self-reported Hispanic physicians. Data analyses included frequencies, descriptive statistics, and factorial analyses of variance. Results The response rate was 55.5%. The majority of respondents (73.3%) were middle-age males. Less than half of respondents routinely performed the most basic intervention: asking patients about smoking status (44.4%) and advising smoking patients to quit (42.2%). Twenty-five percent assisted smoking patients by talking to them about the health risks of smoking, providing education materials or referring them to cessation programs. Only 4.4% routinely arranged follow-up visits or phone calls for smoking patients. The majority of respondents (64.4%) indicated that they prescribe cessation treatments to less than 20% of smoking patients. A few (4.4%) routinely used behavioral change techniques or programs. A minority (15.6%) indicated that they routinely ask their patients about exposure to tobacco smoke, and 6.7% assisted patients exposed to secondhand smoke in understanding the health risks associated with environmental tobacco smoke (ETS). The most frequently encountered barriers preventing respondents from intervening with patients who smoke included: time, lack of training, lack of receptivity by patients, and lack of reimbursement by third party payers. There was no significant main effect of type of physician, nor was there an interaction effect (gender by type of physician), on tobacco-related practices. Conclusion The results indicate that Hispanic physicians, similarly to U.S. physicians in general, do not meet the level of intervention recommended by health care agencies. The results presented will assist in the development of tobacco training initiatives for Hispanic physicians.

Short-Term Plasticity in a Computational Model of the Tail-Withdrawal Circuit in Aplysia.

The tail-withdrawal circuit of Aplysia provides a useful model system for investigating synaptic dynamics. Sensory neurons within the circuit manifest several forms of synaptic plasticity. Here, we developed a model of the circuit and investigated the ways in which depression (DEP) and potentiation (POT) contributed to information processing. DEP limited the amount of motor neuron activity that could be elicited by the monosynaptic pathway alone. POT within the monosynaptic pathway did not compensate for DEP. There was, however, a synergistic interaction between POT and the polysynaptic pathway. This synergism extended the dynamic range of the network, and the interplay between DEP and POT made the circuit responded preferentially to long-duration, low-frequency inputs.

Diffusion and implementation of a tobacco prevention program: A replication study

Tobacco use is a major health hazard, and the onset of tobacco use occurs almost entirely in the teenage years. For this reason, schools are an ideal site for tobacco prevention programs. Although studies have shown that effective school-based tobacco prevention programs exist, all too frequently these programs are not used. In order for effective programs to achieve their potential impact, strategies for speeding the diffusion of these programs to school districts and seeing that, once adopted, programs are implemented as they are intended, must be developed and tested.^ This study (SC2) set out to replicate the findings of an earlier quasi-experimental study (The Smart Choices Diffusion Study, or SC1) in which strategies based on diffusion theory and social learning theory were found to be effective in encouraging adoption and implementation of an effective tobacco prevention program in schools. To increase awareness and encourage adoption, intervention strategies in both studies utilized opinion leaders, messages highlighting positive aspects of the program, and modeling of benefits and effective use through videotape and newsletters. To encourage accurate implementation of the curriculum, teacher training for the two studies utilized videotaped modeling and practice of activities by teachers. SC2 subjects were 38 school districts that make up one of Texas' 20 education service regions. These districts had served as the comparison group in SC1, and findings for the SC1 comparison and intervention groups were utilized as historic controls.^ SC2 achieved a 76.3% adoption rate and found that an average of 84% of the curriculum was taught with an 82% fidelity to methods utilized by the curriculum. These rates and rates for implementation of dissemination strategies were equal to or greater than corresponding rates for SC1. The proportion of teachers implementing the curriculum in SC2 was found to be equal to SC1's video-trained districts but lower than the SC1 workshop-trained group.^ SC2's findings corroborate and support the findings from the earlier study, and increase our confidence in its findings. Taken together, the findings from SC2 and SC1 point to the effectiveness of their theory-based intervention strategies in encouraging adoption and accurate implementation of the tobacco prevention curriculum. ^

Anatomical organization of the memory underlying sensitization in the siphon-withdrawal reflex circuit of {\it Aplysia californica}

Previous studies have shown that short-term sensitization of the Aplysia siphon-withdrawal reflex circuit results in multiple sites of change in synaptic efficacy. In this dissertation I have used a realistic modeling approach (using an integrate-and-fire scheme), in conjunction with electrophysiological experiments, to evaluate the contribution of each site of plasticity to the sensitized response.^ This dissertation contains a detailed description of methodology for the construction of the model circuit, consisting of the LFS motor neurons and ten interneurons known to convey excitatory input to them. The model replicates closely the natural motor neuron firing response to a brief tactile stimulus.^ The various circuit elements have different roles for producing circuit output. For example, the sensory connections onto the motor neuron are important for the production of the phasic response, while the polysynaptic interneuronal connections are important for producing the tonic response.^ The multiple sites of plasticity that produce changes in circuit output also have specialized roles. Presynaptic facilitation of the sensory neuron to LFS connection enhances only the phasic component of the motor neuron firing response. The sensory neuron to interneuron connections primarily enhance the tonic component of the motor neuron firing response. Also, the L29 posttetanic potentiation and the L30 presynaptic inhibition primarily enhance the tonic component of the motor neuron firing response. Finally, the information content at the various sites of plasticity can shift with changes in stimulus intensity. This suggests that while the sites of plasticity encoding memory are fixed, the information content at these sites can be dynamic, shifting in anatomical location with changes in the intensity of the test stimulus.^ These sites of plasticity also produce specific changes in the behavioral response. Sensory-LFS plasticity selectively increases the amplitude of the behavioral response, and has no effect on the duration of the behavioral response. Interneuronal plasticity (L29 and L30) affects both the amplitude and duration of the behavioral response. Other sensory plasticity also affect both the amplitude and duration of the behavioral response, presumably by increasing the recruitment of the interneurons, which provide all of the effect on duration of the behavioral response. ^

The ethanolic fermentation pathway supports respiration and lipid biosynthesis in tobacco pollen

Rapid pollen tube growth requires a high rate of sugar metabolism to meet energetic and biosynthetic demands. Previous work on pollen sugar metabolism showed that tobacco pollen carry out efficient ethanolic fermentation concomitantly with a high rate of respiration (Bucher et al ., 1995). Here we show that the products of fermentation, acetaldehyde and ethanol, are further metabolised in a pathway that bypasses mitochondrial PDH. The enzymes involved in this pathway are pyruvate decarboxylase, aldehyde dehydrogenase and acetyl-CoA synthetase. Radiolabelling experiments show that during tobacco pollen tube growth label of C-14-ethanol is incorporated into CO2 as well as into lipids and other higher molecular weight compounds. A role for the glyoxylate cycle appears unlikely since activity of malate synthase, a key enzyme of the glyoxylate cycle, could not be detected.

Accuracy of the withdrawal reflex for localization of the site of cervical disk herniation in dogs: 35 cases (2004-2007)

OBJECTIVE To evaluate the accuracy of neurologic examination versus magnetic resonance imaging (MRI) in localization of cervical disk herniation and evaluate the usefulness of withdrawal reflex testing in dogs. DESIGN Retrospective case series. ANIMALS 35 client-owned dogs with a single-level cervical disk herniation as determined via MRI. PROCEDURES 1 of 2 board-certified neurologists performed a complete neurologic examination in each dog. Clinical signs of a cervical lesion included evidence of neck pain and tetraparesis. The withdrawal reflex was used for neuroanatomic localization (C1-C5 or C6-T2). Agreement between results of neurologic and MRI examinations was determined. RESULTS Agreement between neurologic and MRI diagnoses was 65.8%. In 11 dogs in which the lesion was clinically localized to the C6-T2 segment on the basis of a decreased withdrawal reflex in the forelimbs, MRI revealed an isolated C1-C5 disk lesion. In 1 dog, in which the lesion was suspected to be at the C1-C5 level, MRI revealed a C6-T2 lesion. Cranial cervical lesions were significantly associated with an incorrect neurologic diagnosis regarding site of the lesion. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the withdrawal reflex in dogs with cervical disk herniation is not reliable for determining the affected site and that a decreased withdrawal reflex does not always indicate a lesion from C6 to T2.

Antinociceptive effect of buprenorphine and evaluation of the nociceptive withdrawal reflex in foals.

OBJECTIVE To elicit and evaluate the NWR (nociceptive withdrawal reflex) in 2 and 11 day old foals, to investigate if buprenorphine causes antinociception and determine if the NWR response changes with increasing age. The effect of buprenorphine on behaviour was also evaluated. STUDY DESIGN Prospective, experimental cross-over trial. ANIMALS Nine Norwegian Fjord research foals. METHODS Buprenorphine, 10 μg kg(-1) was administered intramuscularly (IM) to the same foal at 2 days and at 11 days of age. The NWR and the effect of buprenorphine were evaluated by electromyograms recorded from the left deltoid muscle following electrical stimulation of the left lateral palmar nerve at the level of the pastern. Mentation, locomotor activity and respiratory rate were recorded before and after buprenorphine administration. RESULTS We were able to evoke the NWR and temporal summation in foals using this model. Buprenorphine decreased the root mean square amplitude following single electrical stimulation (p < 0.001) in both age groups, and increased the NWR threshold following single electrical stimulation in 2 day old foals (p = 0.0012). Repeated electrical stimulation at 2 Hz was more effective to elicit temporal summation compared to 5 Hz (p < 0.001). No effect of age upon the NWR threshold was found (p = 0.34). Sedation when left undisturbed (11 occasions), increased locomotor activity when handled (9 occasions) and tachypnea (13 occasions) were common side-effects of buprenorphine. CONCLUSION AND CLINICAL RELEVANCE These findings indicate that buprenorphine has antinociceptive effect in foals. Opioid side effects often recognized in adult horses also occur in foals.