Improved Hodgkin-Huxley type model for neural action potentials.

The simple Goldman-Hodgkin-Katz model for resting-state membrane potentials has been generalized to provide a new nonlinear theoretical model for action potentials in perfused axons. Our minimalistic model appeals naturally to physically based electrodiffusion principles to describe electric-current densities inside sodium and potassium-ion channels whereas the 1952 Hodgkin-Huxley model describes such current densities in an ad hoc way. Although the two models share similar schemes for the kinetics of ion-channel gating, our relaxation times for channel gating are simpler, being independent of membrane potential. Like the theoretical model of Hodgkin and Huxley, based primarily on experimental data at [Formula: see text], our dynamical system behaves as a 4-dimensional resonator exhibiting subthreshold oscillations. Although our present analysis refers to experiments at [Formula: see text], re-parameterizations of this model should permit consideration of action potentials at alternative temperatures. The predicted speed of propagating action potentials in giant axons of squid at [Formula: see text] is in excellent agreement with the Hodgkin-Huxley experimental value at [Formula: see text]. In cases where our model predictions differ from those of the Hodgkin-Huxley model, new experiments will be required to determine which model is more accurate.

Evaluation of Protective Equipment Used Among Motorbike Riders.

INTRODUCTION: This study compared outcomes between patients injured at a motorbike track, which requires riders to follow safety equipment guidelines, and those involved in recreational riding where safety equipment usage is voluntary. METHODS: A retrospective review was conducted of all patients presenting with motorbike-related injuries at an American College of Surgeons verified level-I trauma center between January 1, 2009 and December 31, 2013. Data collected included demographics, injury details, safety equipment use, hospitalization details, and discharge disposition. Comparisons were made regarding protective equipment usage. RESULTS: Among the 115 patients admitted, more than half (54.8%, n = 63) were injured on a motorbike track, and 45.2% (n = 52) were injured in a recreational setting. The majority of patients were male (93.9%), Caucasian (97.4%), and between the ages of 18 to 54 (64.4%). Helmet usage was higher among track riders (95.2%, n = 60) than recreational riders (46.2%, n = 24, p < 0.0001). Comparisons of injury severity and outcomes between those who wore protective equipment and those who did not were not significant. CONCLUSION: Even though track riders wore protective equipment more than recreational riders, there was no difference between the groups regarding injury severity or hospital outcomes. These results suggested that motocross riders should not rely on protective equipment as the only measure of injury prevention.

Repeat head imaging in blunt pediatric trauma patients: Is it necessary?

BACKGROUND: Children with confirmed brain injury usually undergo follow-up computed tomography (CT) scan of the head within 24 hours of admission. To date, no evidence exists to validate the diagnostic or therapeutic value of these repeat CTs. The purpose of this study was to (1) evaluate progression of traumatic brain injuries, (2) determine if routine repeat imaging changes management, and (3) compare the efficacy of recognizing worsening hemorrhage with serial neurological examination versus repeat imaging. METHODS: A 5-year retrospective review was conducted of all patients aged under 18 years with blunt traumatic head injury (n = 95). Data included demographics, type and size of intracranial hemorrhage, exam findings, diagnostic and management changes, and hospital outcomes. RESULTS: Most patients (68.4%) had at least one repeat CT; of these, 67.7% (n = 44) showed no change or reduced hemorrhage. In only one patient did a repeat CT scan result in a surgical procedure; however, that CT scan was prompted by a change in neurological status. Among patients with more than two repeat head CTs, 42.9% led to a change in management, most frequently an additional CT scan. Presence of neurological symptoms was associated with having repeat CT scans (p = 0.025). Changes in Glasgow Coma Scale score were associated with increased hemorrhage (p = 0.012) but not repeat scans (p = 0.496). In the majority of cases, increased hemorrhage only resulted in an additional head CT and prolonged intensive care unit stay. Excluding patients who arrived with brain death, there was no difference in mortality between patients with and without repeat imaging. CONCLUSION: Findings from this study support a selective approach for repeating head CTs with emphasis on changes in neurological symptoms and Glasgow Coma Scale score. Prospective studies on timing and indications for repeat CT scans are needed to support development of clinical guidelines. LEVEL OF EVIDENCE: Therapeutic study, level III.

Pediatric trauma system models: do systems using adult trauma surgeons exclusively compare favorably with those using pediatric surgeons after initial resuscitation with an adult trauma surgeon?

BACKGROUND: A shortage of pediatric surgeons exists. The purpose of this study was to evaluate pediatric outcomes using pediatric surgeons vs adult trauma surgeons. METHODS: A review was conducted at 2 level II pediatric trauma centers. Center I provides 24-hour in-house trauma surgeons for resuscitations, with patient hand-off to a pediatric surgery service. Center II provides 24-hour in-house senior surgical resident coverage with an on-call trauma surgeon. Data on demographics, resource utilization, and outcomes were collected. RESULTS: Center I patients were more severely injured (injury severity score = 8.3 vs 6.2; Glasgow coma scale score = 13.7 vs 14.3). Center I patients were more often admitted to the intensive care unit (52.2% vs 33.5%) and more often mechanically ventilated (12.9% vs 7.7%), with longer hospital length of stay (2.8 vs 2.3 days). However, mortality was not different between Center I and II (3.1% vs 2.4%). By logistic regression analyses, the only variables predictive of mortality were injury severity score and Glasgow coma scale score. CONCLUSION: As it appears that trauma surgeons' outcomes compare favorably with those of pediatric surgeons, utilizing adult trauma surgeons may help alleviate shortages in pediatric surgeon coverage.

Evaluation of chest tube administration of tissue plasminogen activator to treat retained hemothorax.

BACKGROUND: When retained hemothorax occurs, video-assisted thoracoscopy or thoracotomy is performed, but recently, tissue plasminogen activator (tPA) has been used. This study evaluated intrapleural tPA use for retained traumatic hemothoraces. METHODS: A retrospective review was conducted of trauma patients treated with intrapleural tPA for retained hemothorax. Data included demographics, past medical and surgical histories, injury details, treatment details, and outcomes. RESULTS: Seven patients (median age = 47 years, male = 6, blunt trauma = 6) met study criteria. All patients received a chest tube. Six patients later received computed tomography-guided drains for tPA infusion. Number of tPA treatments per patient varied from 1 to 5. Median total tPA dosage was 24 mg. Median time from injury to chest tube placement was 11 days and from chest tube placement to first tPA treatment was 4 days. No patients required a video-assisted thoracoscopy; however, 1 patient required thoracotomy. There were no deaths or bleeding complications attributed to intrapleural tPA. CONCLUSION: Although future studies are needed to identify optimum treatment guidelines, intrapleural tPA appears to be a safe and efficacious treatment option.

A long-term bacteriological and immunological study in Holstein-Friesian cattle experimentally infected with Mycobacterium avium subsp. paratuberculosis and necropsy culture results for Holstein-Friesian cattle, Merino sheep and Angora goats.

The aims were to longitudinally evaluate the interferon-gamma (IFN-gamma) test in comparison to faecal culture and the absorbed ELISA in a cattle infection model for Johne's disease and to determine the adult infection status, by necropsy and tissue culture, of sheep, goats and cattle infected as young animals. Clinical disease, faecal culture results and immunological responses for Merino sheep [Stewart, D.J., Vaughan, J.A., Stiles, P.L., Noske, P.J., Tizard, M.L.V., Prowse, S.J., Michalski, W.P., Butler, K.L., Jones, S.L., 2004. A long-term study in Merino sheep experimentally infected with Mycobacterium avium subsp. paratuberculosis: clinical disease, faecal culture and immunological studies. Vet. Microbiol. 104, 165-178] and Angora goats [Stewart, D.J., Vaughan, J.A., Stiles, P.L., Noske, P.J., Tizard, M.L.V., Prowse, S.J., Michalski, W.P., Butler, K.L., Jones, S.L., 2006. A long-term study in Angora goats experimentally infected with Mycobacterium avium subsp. paratuberculosis: clinical disease, faecal culture and immunological studies. Vet. Microbiol. 113, 13-24], in the same experiments as the Holstein-Friesian cattle, have been described. Two longitudinal experiments involving Holstein-Friesian cattle challenged with either bovine or ovine strains of Mycobacterium avium subsp. paratuberculosis (Map) have been conducted over a period of 54 and 35 months, respectively. Blood samples for the IFN-gamma test and the absorbed ELISA and faecal samples for bacteriological culture were taken pre-challenge and monthly post-challenge. Cell-mediated (CMI) responses were substantially higher for the bovine Map strain during the 42-month period following dosing but then declined in the remaining 12 months. However, for the ovine Map challenge and control groups, CMI responses were not significantly different from each other. None of the cattle developed clinical disease and only one of the cattle in the bovine Map gut mucosal tissue challenged group was a persistent faecal shedder and also an ELISA antibody responder which developed after shedding commenced. Culture of tissues, following necropsy at the completion of the experiments, showed no evidence of infection in any of the challenged cattle and sheep for either the bovine or ovine Map strain in contrast to positive cultures for challenged goats in the same experiments. The tissues from the control cattle, sheep and goats were culture negative. The cattle were less susceptible to the bovine and ovine Map strains than goats and sheep with the goats being the least naturally resistant.

A long-term study in Angora goats experimentally infected with Mycobacterium avium subsp. paratuberculosis: clinical disease, faecal culture and immunological studies.

Two longitudinal experiments involving Angora goats challenged with either bovine or ovine strains of Mycobacterium avium subspecies paratuberculosis (Map) have been conducted over a period of 54 and 35 months, respectively. Blood samples for the interferon-gamma (IFN-gamma) test and the absorbed ELISA and faecal samples for bacteriological culture were taken pre-challenge and monthly post-challenge. Persistent shedding, IFN-gamma production, seroconversion and clinical disease occurred earlier with the bovine Map gut mucosal tissue challenge inoculum than with cultured bacteria. The IFN-gamma responses of the gut mucosal tissue and bacterial challenge groups were substantially and consistently higher than those of the control group. The in vivo and cultured cattle strains were much more pathogenic for goats than the sheep strains with persistent faecal shedding, seroconversion and clinical disease occurring in the majority of bovine Map challenged goats. With the ovine Map, 3 goats developed persistent antibody responses but only one of these goats developed persistent faecal shedding and clinical disease. However, there was no significant difference between the IFN-gamma responses of the tissue challenged, bacterial challenged and control groups. Compared with sheep, the ELISA appeared to have higher sensitivity and the IFN-gamma test lower specificity.

A long-term study in Merino sheep experimentally infected with Mycobacterium avium subsp. paratuberculosis: clinical disease, faecal culture and immunological studies.

Two longitudinal experiments involving Merino sheep challenged with either bovine or ovine strains of Mycobacterium avium subsp. paratuberculosis (Map) have been conducted over a period of 54 and 35 months, respectively. Blood samples for the interferon-gamma test, the absorbed ELISA and faecal samples for bacteriological culture were taken pre-challenge and monthly post-challenge. Infections were induced with either a bovine or ovine strain of Map in separate experiments with infections being more easily established, in terms of faecal bacterial shedding and clinical disease when the challenge inoculum was prepared from gut mucosal tissue than cultured bacteria. The patterns of response for shedding and clinical disease were similar. Cell-mediated immune responses were proportionally elevated by at least an order of magnitude in all sheep dosed with either a bovine or ovine strain of Map. Conversely, antibody responses were only elevated in a relatively small proportion of infected sheep. Neither of the clinically affected tissue challenged sheep developed an antibody response despite the presence of persistent shedding and the development and decline in cell-mediated immunity. The results indicated that for sheep the interferon-gamma test may be useful for determining if a flock has been exposed to ovine Johne's disease.

Structures of HCN-Mgn (n=2-6) complexes from rotationally resolved vibrational spectroscopy and ab initio theory.

High-resolution infrared laser spectroscopy has been used to determine the structures of HCN-Mgn complexes formed in helium nanodroplets. The magnesium atoms are first added to the droplets to ensure that the magnesium complexes are preformed before the HCN molecule is added. The vibrational frequencies, structures, and dipole moments of these complexes are found to vary dramatically with cluster size, illustrating the nonadditive nature of the HCN-magnesium interactions. All of the complexes discussed here have the nitrogen end of the HCN pointing towards the magnesium clusters. For Mg3, the HCN binds to the "threefold" site, yielding a symmetric top spectrum. Although the HCN-Mg4 complex also has C3v symmetry, the HCN sits "on-top" of a single magnesium atom. These structures are confirmed by both ab initio calculations and measurements of the dipole moments. Significant charge transfer is observed in the case of HCN-Mg4, indicative of charge donation from the lone pair on the nitrogen of HCN into the lowest unoccupied molecular orbital of the Mg4.

Improving understanding of research consent disclosures among persons with mental illness.

OBJECTIVE: The objective of this study was to evaluate alternative procedures for improving the understanding of research consent disclosures by persons who have mental illness. METHODS: Three groups participated in the study: persons with schizophrenia (N=79), persons with depression (N=82), and a healthy control group (N=80). The participants were guided through an informed consent process in which two factors were manipulated. One was the structure of the disclosure form; either a typical disclosure form involving standard dense text was used, or a graphically enhanced form was used. The other was the interpersonal process: the presence or absence of a third-party facilitator, with iterative feedback given to participants for whom a facilitator was not present. Participants' understanding of the disclosure was assessed with the use of recall tests that involved paraphrasing and recognition tests that involved multiple choice. RESULTS: The mean understanding scores did not differ significantly between the depression and control groups, and the mean scores of the schizophrenia group were significantly lower than those of the other two groups. Neither the graphically enhanced consent disclosure form nor the presence of a third-party facilitator was associated with improved understanding. The use of iterative feedback was associated with improvement in comprehension scores in all groups. CONCLUSIONS: The use of a feedback procedure in the consent disclosure process during the recruitment of persons who are mentally ill may be a valuable safeguard for ensuring adequate understanding and appropriate participation in research.

Probing the structure of metal cluster-adsorbate systems with high-resolution infrared spectroscopy.

High-resolution infrared laser spectroscopy was used to obtain rotationally resolved infrared spectra of adsorbate-metal complexes. The method involves forming the bare metal clusters in helium nanodroplets and then adding a molecular adsorbate (HCN) and recording the infrared spectrum associated with the C-H stretching vibration. Rotationally resolved spectra were obtained for HCN-Mg(n) (n = 1 to 4). The results suggest a qualitative change in the adsorbate-metal cluster bonding with cluster size.

Effects of bilateral olivocochlear lesions on vowel formant discrimination in cats.

Operant conditioning procedures were used to measure the effects of bilateral olivocochlear lesions on the cat's discrimination thresholds for changes in the second formant frequency (deltaF2) of the vowel /epsilon/. Three cats were tested with the formant discrimination task under quiet conditions and in the presence of continuous broadband noise at signal-to-noise ratios (S/Ns) of 23, 13, and 3 dB. In quiet, vowel levels of 50 and 70 dB produced average deltaF2s of 42 and 47 Hz, respectively, and these thresholds did not change significantly in low levels of background noise (S/Ns = 23 and 13 dB). Average deltaF2s increased to 94 and 97 Hz for vowel levels of 50 and 70 dB in the loudest level of background noise (S/N = 3 dB). Average deltaF2 thresholds in quiet and in lower noise levels were only slightly affected when the olivocochlear bundle was lesioned by making bilateral cuts into the floor of the IVth ventricle. In contrast, post-lesion deltaF2 thresholds in the highest noise level were significantly larger than pre-lesion values; the most severely affected subject showed post-lesion discrimination thresholds well over 200 Hz for both 50 and 70 dB vowels. These results suggest that olivocochlear feedback may enhance speech processing in high levels of ambient noise.

For-profit versus non-profit freestanding psychiatric inpatient facilities: an update.

Although several studies have examined the trend toward the decreasing differentiation of non-profit from for-profit general hospitals, few have focused on freestanding psychiatric hospitals. This study updates previous research that used psychiatric hospital data from calendar year 1986 with data from 1990. In addition, a preliminary examination of the influence of market competition on the behavior of non-profit psychiatric facilities was conducted. Results confirm a converging trend between for-profit and non-profit facilities that is related, in part, to competition.

Rehabilitation of lower limb traumatic amputees: the Sandy Gall Afghanistan Appeal's experience.

Physical rehabilitation after lower limb traumatic amputation due to acts of war has not yet been investigated. It has been shown that patients suffering non-war injuries rehabilitate well. This study shows that despite the difficult circumstances and limited resources available in an area of conflict, good rehabilitation of war victims is possible. However, economic rehabilitation is worse than that seen in non-war populations. Given that this type of injury is very common in war zones worldwide, this failure of economic rehabilitation may represent a major healthcare issue.

Old and new: a comparison of state psychiatric hospitals.

The study examined whether state hospitals in operation before deinstitutionalization still carry vestiges of older models of psychiatric care. Using a national database, the authors compared 166 state hospitals built before 1949 with 80 state hospitals built after that time. The old hospitals treated fewer children and adolescents, received more state funding and less third-party funding, had fewer professional clinical staff, spent less on salaries and maintenance, and had more beds, a lower turnover rate, and a longer average length of stay. Findings suggest that planners and policymakers should take into account a facility's history when attempting to introduce innovations.

Early failure of titanium alloy femoral components: a quantitative radiological analysis of osteolytic and granulomatous change.

Shot blasted titanium alloy femoral components with a coarse finish were withdrawn from use in 1987 following reports of early component failure. We reviewed all coarse titanium femoral stems used in primary total hip arthroplasty in our institution between 1985 and 1987 and compared them to a similar stem made of vitallium which was also used over the same period. We found that, at an average of 5.2 years following implantation, over two-thirds of titanium components were associated with endosteal lysis. In many of the cases the early lytic changes were asymptomatic with significant bone loss occurring prior to presentation. We discuss our findings in relation to revision surgery. We advocate that all those with coarse stem titanium components should be positively reviewed to detect early lytic change before extensive bone destruction occurs.

The Guildford elbow.

A new unconstrained elbow replacement is described and the results of 44 primary and 5 revision operations assessed. A high incidence of pain relief (82%) and functional improvement (73%) was achieved. However 23% of primary replacements later underwent loosening as assessed radiologically and 12% have undergone revision for pain. Minor complications not affecting the final result occurred in 28%. The causes and significance of the complications are analysed.

Cubital bursitis.

We describe two cases of bursitis at the insertion of the biceps tendon. They presented as swellings in the cubital fossa with symptoms of median nerve irritation. The aetiology was probably mechanical trauma; both patients were cured by operation.