Different strategies for auditory word recognition in healthy versus normal aging.

To explore the effects of commonly encountered pathology on auditory recognition strategies in elderly participants, magnetoencephalographic (MEG) brain activation patterns and performance were examined in 30 elderly [18 controls and 12 elderly with mild cognitive impairment (MCI) or probable Alzheimer's disease (AD)]. It was predicted that participants with known pathology would reveal different networks of brain activation, compared to healthy elderly, which should correlate with poorer performance. Participants heard a list of words representing common objects, twice. After 20 minutes a list of new and old words was presented and participants judged whether each word was heard earlier. MEG responses were analyzed using a semiautomated source modeling procedure. A cluster analysis using all subjects' MEG sources revealed three dominant patterns of activity which correlated with IQ and task performance. The highest performing group revealed activity in premotor, anterior temporal, and superior parietal lobes with little contribution from prefrontal cortex. Performance and brain activation patterns were also compared for individuals with or without abnormalities such as white matter hyperintensities and/or volume reduction evidenced on their MRIs. Memory performance and activation patterns for individuals with white matter hyperintensities resembled the group of MCI/AD patients. These results emphasize the following: (1) general pathology correlates with cognitive decline and (2) full characterization of the health of elderly participants is important in studies of normal aging since random samples from the elderly population are apt to include individuals with subclinical pathology that can affect cognitive performance.

Reciprocal control of the conformational state of the sarcoplasmic reticulum calcium channel protein by polarization and depolarization in the transverse tubule.

We attached the conformational probe methylcoumarin acetate (MCA) specifically to the junctional foot protein (JFP) moiety of triads, and monitored conformational changes in the JFP during polarization and depolarization of the T-tubule moiety. The MCA fluorescence decreased upon T-tubule polarization, and the fluorescence changes were blocked by preventing T-tubule polarization or by a nimodipine block of the T-tubule-to-sarcoplasmic reticulum communication. Depolarization of the T-tubule reversed the MCA fluorescence decrease which had been produced by T-tubule polarization. These results suggest that the conformational and functional states of the JFP are regulated by T-tubule polarization and depolarization in a reciprocal fashion.

Neomycin: a novel potent blocker of communication between T-tubule and sarcoplasmic reticulum.

Ca2+ release from the sarcoplasmic reticulum (SR) was induced in isolated triads by direct stimulation of the SR moiety by polylysine, or stimulation via chemical depolarization of the transverse tubule (T-tubule) moiety. Polylysine-induced release was blocked by neomycin with an IC50 (the concentration for half-maximal inhibition) of 0.3 microM. However, the IC50 for neomycin block of depolarization-induced Ca2+ release sharply decreased in a voltage-dependent fashion, and it was 5.3 nM at a maximal extent of T-tubule depolarization. These results suggest that the high affinity binding of neomycin to the triad leads to the specific blocking of the signal transmission from T-tubule to SR.

Fluororuby as a marker for detection of acute axonal injury in rat spinal cord.

Axonal damage is a common pathological consequence of spinal cord injury. Previous studies have detected axonal injury with silver stains for degeneration or immunohistochemistry for alterations in components such as beta-amyloid precursor protein, neurofilament or ubiquitin. Fluororuby has recently been introduced as a neuronal tracer in studies of spinal cord injury and regeneration. Our study was carried out to determine whether Fluororuby can be used to identify injured axons and monitor the time course of axonal damage. Adult rats underwent needle puncture injury to the white matter in the midline and lateral spinal cord at T11. At the same time, 0.05 microl of Fluororuby was injected into the cord at the same sites. After survival times ranging from 6 h to 3 weeks, spinal cords were cut into longitudinal frozen sections and examined with confocal microscopy. Fluororuby was found to label key features of axonal injury including axonal swelling, retraction balls and disrupted axons. Damaged axons close to the injury site were consistently labeled within 6 h, with indications of swollen and disconnected axons spreading further from the site during the first week. Fewer injured axons were labeled after 1 week survival, but the marker revealed longer distances of degenerating axons both distal and rostral to the injury site. Our findings indicate that Fluororuby is a quick, sensitive, reliable and technically simple fluorescent marker for early stages of acute axonal injury and degeneration.

Insulin doses in children using conventional therapy for insulin dependent diabetes.

The objective of this project was to develop plots of daily insulin dosages by percentile in diabetic children and to analyze various factors, such as metabolic control, age, and duration of diabetes that might influence the insulin prescription. Patients in extremely poor metabolic control (HbA1C > 9.8%) and patients with less than 1 year of diabetes were excluded from analysis. Patients were aged 2-21 years and the mean age at diagnosis was 8 years. Thirty-two percent of the patients were younger than 5 years and 15% were older than 15 years at diagnosis. Ninety-nine percent of patients used both regular and intermediate-acting (NPH or Lente) insulin 10-30 min before breakfast and again in the evening. Ten percent of the patients used only regular insulin at supper but used intermediate-acting insulin at bedtime. Insulin doses varied between 0.3 and 1.2 U/kg/day in prepubertal children (mean, 0.8 U/kg/day) and 0.5 and 1.8 U/kg body weight/day in pubertal children (mean, 1.25 U/kg/day). Average insulin doses in boys and girls were similar, except at ages 10-13, when the dose was significantly higher in girls. The insulin dose declined after age 17 in both genders to a value at age 21 that was 20-30% lower than the highest dose during pubertal years. Insulin dose did not correlate with duration of disease after 2 years, the ratio of morning to evening insulin, the ratio of regular to intermediate-acting insulin, or body mass. There was a slight association between higher insulin doses and higher glycosylated hemoglobin values. The results indicate that insulin requirements vary over a wide range in a group of children with metabolic control ranging from 'excellent' to 'fair' and correlate primarily with age and pubertal development. About 25% of prepubertal children and 50% of pubertal and post-pubertal children use more than 1 U insulin/kg/day--a dose commonly believed to be an 'upper limit' by many health professionals. The data should provide guidelines for the range of insulin dosing required to achieve fairly good to excellent control in diabetic children of various ages.

Signal transmission and transduction in excitation-contraction coupling.

For the better understanding of the molecular mechanism of E-C coupling, two key questions remain to be resolved: (a) how the excitation signal elicited in the T-tubule membrane is transmitted to the ryanodine receptor, RyR (signal transmission), and (b) how the signal transmitted from the T-tubule to the RyR is translated into the action of opening the sarcoplasmic reticulum Ca2+ channel to induce Ca2+ release and muscle contraction (signal transduction). Our recent studies on E-C coupling with the use of the isolated triads and synthetic peptides have provided several pieces of new information. It appears that the signal transmission is mediated by the voltage-controlled binding of the Thr671-Leu690 region (Trigger) of the cytoplasmic II-III loop of the dihydropyridine receptor alpha 1 a subunit to the putative activator site on the RyR. The transmitted signal is translated to the action of channel opening by mediation of rapid conformational changes occurring in the RyR. Upon T-tubule polarization the Glu724-Pro760 region of the loop (Blocker) replaces the RyR-bound Trigger. This reprimes the RyR to the original conformational state.

Metallic wear debris in acetabular osteolysis in a mechanically stable cementless total hip replacement: report of a case.

Wear debris has evolved as the primary etiology of mechanical loosening of cemented as well as uncemented total hip arthroplasty. Osteolysis results from particle formation, and this has been most commonly reported to be secondary to polyethylene wear debris. This article demonstrates that metallic particle debris will also result in significant osteolysis. The two sources in this case are cobalt-chromium (Co-Cr) particles from the acetabular component and titanium-alloy (Ti) particles from the Morse taper junction and the Ti-alloy femoral head. However, it is likely that polyethylene debris also contributed to the osteolysis, because a titanium head was used and we know this results in increased poly wear.

Immunophenotypic pattern of childhood acute lymphoblastic leukemia.

Full text is available as a scanned copy of the original print version.

A practical approach to incidental findings in neuroimaging research.

OBJECTIVE: We describe the systematic approach to incidental findings (IFs) used at the Mind Research Network (MRN) where all MRI scans receive neuroradiologist interpretation and participants are provided results. METHODS: From 2004 to 2011, 8,545 MRI scans were acquired by 45 researchers. As mandated by MRN's external institutional review board, all structural sequences were evaluated by a clinical neuroradiologist who generated a report that included recommendations for referral if indicated. Investigators received a copy of their participants' reports, which were also mailed to participants unless they specifically declined. To better understand the impact of the radiology review process, a financial analysis was completed in addition to a follow-up phone survey to characterize participant perceptions regarding receiving their MRI scan results. RESULTS: The radiologist identified IFs in 34% of the 4,447 participants. Of those with IFs (n = 1,518), the radiologist recommended urgent or immediate referral for 2.5% and routine referral for 17%. For 80.5%, no referral was recommended. Estimated annual cost for this approach including support for the neuroradiologist, medical director, and ancillary staff is approximately $60,000 or $24/scan. The results of the retrospective phone survey showed that 92% of participants appreciated receiving their MRI report, and the majority stated it increased their likelihood of volunteering for future studies. CONCLUSIONS: Addressing IFs in a cost-effective and consistent manner is possible by adopting a policy that provides neuroradiology interpretation and offers participant assistance with clinical follow-up when necessary. Our experience suggests that an ethical, institution-wide approach to IFs can be implemented with minimal investigator burden.

Effects of Focus Film Distance (FFD) variation on entrance testicular dose in lumbar-pelvic radiography.

INTRODUCTION: With the steady increase in public and professional concern regarding the biological effects of ionising radiation, there is a need for both the Chiropractic and Radiography professions to improve imaging techniques for the lowering of patient radiation doses. Lumbar radiographs are essential in chiropractic general practice for biomechanical diagnosis and postural analysis. Detailed anatomical measurements are taken from spinal radiographs for the determination of various biomechanical alterations for clinical purposes. The quality of spinal radiograph is dependent on a number of factors, including Focus Film Distance (FFD), magnification ratios, penumbra, contrast and density. Variation in FFD will vary magnification factor (MF) and Penumbra. OBJECTIVES: The study aims to investigate the relationship between FFD and received radiation dose to patients, where the radiation dose to the testes may be significantly lowered whilst still maintaining acceptable image quality. METHODS: Radiographic images and dosimetry were obtained with a Seimans wall-mounted X-ray unit. All anterior/posterior (AP) and lateral lumbar-pelvic radiographs were taken of an anthromorphological phantom that resembles human tissues, at both 100cm and 200cm FFD. Five central beam air doses were measured for all parameters to demonstrate patient entrance doses. RESULTS: For AP lumbar-pelvic radiography, increasing FFD by a factor of two resulted in an approximately 30% decrease in entrance dose to the testes. For lateral lumbar-pelvic radiography a two fold increase in FFD resulted in a 70% reduction in entrance dose. CONCLUSIONS: The study suggests for the first time that an FFD of 200 cm, which is largely utilised by the chiropractic profession, is an efficient method of minimising radiation dose to patient, during lumbar radiography.

Correlating motion palpation with functional x-ray findings in patients with low back pain.

Objectives: To determine whether a correlation between motion palpation findings and abnormal coupling patterns, as viewed in lumbar functional X-rays, can be demonstrated in low back pain (LBP) patients.Design: A prospective observational study of patients who present to a chiropractic clinic for assessment of low back pain.Subjects: The sample population consisted of 27 consecutive patients presenting with LBP between the ages of 20-50 year old and who were capable of pain free lateral lumbar flexion.Intervention: All subjects underwent motion palpation to determine whether a "fixation" at the L4/5 existed. All had lumbar spine X-rays in an anterior-posterior (AP) and bilateral AP lateral flexion position. X-rays were then analyzed to determine whether the coupling pattern at L4/5 was considered abnormal.Results: In those patients with a perceived L4/5 motion restriction no coupling patterns where found in 6 cases (22.4%) and normal coupling patterns in 13 cases (48%). In those patients who presented with LBP and no motion findings at L4/5 no coupling was observed in 4 cases (14.8%) and normal coupling in another 4 cases (14.8%). The chi-squared test demonstrated no statistical differences (p>0.05) between the motion fixation at L4/5 and coupling patterns from lateral flexion X-rays.Conclusion: It is of particular interest to note that the presence of the L4/5 fixation was not associated with abnormal coupling but conversely was frequently observed to be associated with normal coupling patterns. A simple correlation between a single motion palpation finding of a restriction at a L4/5 facet and an alteration in coupling patterns could not be supported.

A cervical manikin procedure for chiropractic skills development.

OBJECTIVE: To determine whether chiropractic students can effectively acquire adjustive skills for the cervical spine by utilizing a Thrust in Motion Cervical (TMC) manikin and to evaluate its value as a teaching aid. A pilot study was formulated and incorporated into the skills tutorial program at Macquarie University. Centre for Chiropractic in Sydney, Australia. DESIGN AND SETTING: A prospective study was performed on chiropractic students with no prior experience in performing spinal adjustments. SUBJECTS: Twenty subjects were selected randomly from a population of 75 students about to commence their 4th-yr Master's of Chiropractic program. INTERVENTION: Students who formed the experimental group (n = 6) did not perform any thrusting maneuvers on human subjects while practicing Diversified chiropractic cervical spinal techniques. They practiced the adjustive thrust only on the TMC manikin. The control group (n = 14) learned in the established "hands-on" approach, performing thrusting maneuvers on fellow student subjects. Both groups were supervised, taught and examined in an otherwise identical fashion. RESULTS: The data indicate there is no significant difference between the examination scores of the student group that practiced on the TMC manikin (average, 2.17 points) compared with the controls (2.13 points), with a confidence interval at p = .985, assuming that 0.5 marks is clinically important in these examination results. Interexam reliability was acceptable (Pearson's r = .73) for both experimental and control examination performances. CONCLUSION: The null hypothesis is accepted, and no significant difference in student examination performance was found between those who learned thrusting on the manikin alone and those who learned on fellow students. Further, for the first time, a manikin has been shown to be effective in teaching chiropractic skills. The implications of the TMC manikin procedure will revolutionize the acquisition of motor learning skills that are essential for chiropractic skills training.

Identification of the minimum essential region in the II-III loop of the dihydropyridine receptor alpha 1 subunit required for activation of skeletal muscle-type excitation-contraction coupling.

We have previously shown that among several peptides encompassing various regions of the II-III loop of the dihydropyridine receptor alpha 1 subunit, only one peptide corresponding to the Thr671-Leu690 region (designated as peptide A) activated ryanodine binding to and induced calcium release from the sarcoplasmic reticulum [El-Hayek et al. (1995) J. Biol. Chem. 270, 22116-22118]. To further localize within peptide A the minimum unit essential for activating the sarcoplasmic reticulum calcium release channel, we synthesized variously truncated forms of peptide A and examined their ability to activate ryanodine binding. We found that the carboxy-terminal 10-residue region of peptide A encompassing Arg681-Leu690 (peptide As-10; s, skeletal muscle-type sequence) activated ryanodine binding in a RyR1-specific manner and induced calcium release even more efficiently than the 20-residue peptide A. Further truncation of one or more residue(s) of peptide As-10 virtually abolished both functions of activating ryanodine binding and inducing Ca2+ release. The activating ability of As-10 seems to be determined by at least two factors: (1) the distribution of the positively charged residues, and (2) the skeletal muscle-type amino acid sequence, as deduced from the comparison of various peptides with modified structures. These results provide evidence that the minimum essential unit for the in situ trigger of skeletal muscle excitation-contraction coupling is localized in the Arg681-Leu690 region of the II-III loop of the alpha 1 subunit of the dihydropyridine receptor.

Volatile anesthetics selectively alter [3H]ryanodine binding to skeletal and cardiac ryanodine receptors.

The effect of clinical concentrations of volatile anesthetics on ryanodine receptors of cardiac and skeletal muscle sarcoplasmic reticulum was evaluated using [3H]ryanodine binding. At 2 volume percent, halothane and enflurane stimulated binding to cardiac SR by 238% and 204%, respectively, while isoflurane had no effect. In contrast, halothane and enflurane had no effect on [3H]ryanodine binding to skeletal ryanodine receptors, while isoflurane produced a significant stimulation. These results suggest that volatile anesthetics interact in a site-specific manner with ryanodine receptors of cardiac or skeletal muscle to effect Ca2+ release-channel gating.

Postulated role of interdomain interaction within the ryanodine receptor in Ca(2+) channel regulation.

Localized distribution of malignant hyperthermia (MH) and central core disease (CCD) mutations in N-terminal and central domains of the ryanodine receptor suggests that the interaction between these domains may be involved in Ca(2+) channel regulation. To test this hypothesis, we investigated the effects of a new synthetic domain peptide DP4 corresponding to the Leu(2442)-Pro(2477) region of the central domain. DP4 enhanced ryanodine binding and induced a rapid Ca(2+) release. The concentration for half-maximal activation by agonists was considerably reduced in the presence of DP4. These effects of DP4 are analogous to the functional modifications of the ryanodine receptor caused by MH/CCD mutations (viz. hyperactivation of the channel and hypersensitization of the channel to agonists). Replacement of Arg of DP4 with Cys, mimicking the in vivo Arg(2458)-to-Cys(2458) mutation, abolished the activating effects of DP4. An N-terminal domain peptide DP1 (El-Hayek, R., Saiki, Y., Yamamoto, T., and Ikemoto, N. (1999) J. Biol. Chem. 274, 33341-33347) shows similar activation/sensitization effects. The addition of both DP4 and DP1 produced mutual interference of their activating functions. We tentatively propose that contact between the two (N-terminal and central) domains closes the channel, whereas removal of the contact by these domain peptides or by MH/CCD mutations de-blocks the channel, resulting in hyperactivation/hyper-sensitization effects.

Effects of perchlorate on depolarization-induced conformational changes in the junctional foot protein and Ca2+ release from sarcoplasmic reticulum.

Perchlorate is one of the most potent activators of skeletal muscle excitation-contraction (E-C) coupling reported in the literature, but the detailed mechanism of its action remains to be elucidated. In an attempt to further resolve the mode of perchlorate action, the effects of increasing concentrations of perchlorate on the voltage-dependent (T-tubule-mediated) and voltage-independent portions of Ca2+ release were investigated using the isolated triad model. Low concentrations of perchlorate (< or = 10 mM) activated SR Ca2+ release only when the T-tubule moiety was chemically depolarized. Higher concentrations of perchlorate (30-100 mM), on the other hand, produced significant activation of SR Ca2+ release, regardless of whether or not the T-tubule was depolarized. In order to gain further insights, we monitored the conformational change in the junctional foot protein (JFP), which presumably is an important intermediate step in E-C coupling [Yano, M., El-Hayek, R., & Ikemoto, N. (1995) J. Biol. Chem. 270, 3017-3021], using the fluorescently labeled triad preparation. Again, low concentrations of perchlorate (< or = 10 mM) produced a preferential activation of voltage-dependent protein conformational change, while higher concentrations of perchlorate produced significant activation of voltage-independent protein conformational change. An increase in the ryanodine binding by perchlorate occurred only in the higher concentration range where the voltage-independent protein conformational change was activated. These results suggest that perchlorate activates E-C coupling by acting on at least two different steps: at lower concentrations, on the T-tubule-to-JFP signal transmission step; at higher concentrations, on the JFP directly.

Conformational changes in the junctional foot protein/Ca2+ release channel mediate depolarization-induced Ca2+ release from sarcoplasmic reticulum.

In an attempt to monitor the kinetic events occurring in the junctional foot protein (JFP) during excitation-contraction coupling, the JFP moiety of isolated triads was covalently labeled in a site-directed manner with methylcoumarin acetate (MCA) using a recently developed technique (Kang, J.J., Tarcsafalvi, A., Carlos, A.D., Fujimoto, E., Shahrokh, Z., Thevenin, B.J.M., Shohet, S.B., and Ikemoto, N. (1992) Biochemistry 31, 3288-3293). Chemical depolarization of the transverse tubular system (T-tubule) moiety of labeled triads after appropriate priming induced first a rapid increase of the fluorescence intensity of the JFP-bound MCA probe, and then sarcoplasmic reticulum (SR) Ca2+ release. Upon increasing the magnitude of T-tubule depolarization by increasing the magnitude of T-tubule depolarization by increasing the degree of ionic replacement, both the amplitude of the MCA fluorescence change and the amount of released Ca2+ increased in parallel. Blockers of T-tubule-to-SR communication, such as nimodipine and low concentration of neomycin, inhibited both the MCA fluorescence change and the SR Ca2+ release. In contrast, the release blocking concentration of Mg2+ (2 mM) inhibited only SR Ca2+ release without affecting the fluorescence change. These results suggest that upon T-tubule depolarization the original state of the JFP (R) isomerizes to an activated state with higher MCA fluorescence (*R), which in turn changes into a subsequent state in which the release channel is open (*Ro):R-->*R-->*Ro.

A conformational change in the junctional foot protein is involved in the regulation of Ca2+ release from sarcoplasmic reticulum. Studies on polylysine-induced Ca2+ release.

We investigated both conformational changes in the junctional foot protein (JFP) and Ca2+ release from sarcoplasmic reticulum (SR) in parallel after stimulation of triadic vesicles by the JFP-specific ligand, polylysine. To monitor protein conformational change, the JFP was labeled in a site-directed fashion with the fluorescent conformational probe methylcoumarin acetate (MCA) (Kang, J. J., Tarcsafalvi, A., Carlos, A. D., Fujimoto, E., Shahrokh, Z., Thevenin, B. J.-M., Shohet, S. B., and Ikemoto, N. (1992) Biochemistry 31, 3288-3293). The induction of SR Ca2+ release by polylysine produced a rapid increase in the fluorescence intensity of the JFP-bound MCA. The polylysine concentration dependence of the fluorescence change was essentially the same as that of Ca2+ release, suggesting that the two events are tightly coupled. However, the rate constant of MCA fluorescence change was much larger than that of Ca2+ release; i.e. the conformational change preceded Ca2+ release. Prevention of protein conformational change by lysine (0.2 M) inhibited Ca2+ release from SR. Inhibition of Ca2+ release by Mg2+ (5 mM), however, had little effect on the conformational change. These results suggest that binding of polylysine to the JFP produces conformational changes in the protein, which in turn activates the Ca2+ channel, leading to Ca2+ release from the SR.