Outcome after reinfection following reimplantation hip arthroplasty

Between 1976 and 1992, reinfection developed in 34 patients treated for an infected total hip arthroplasty with removal of the prosthesis and implantation of another prosthesis. These patients included 15 men and 19 women with a mean age of 62 years. Infection recurred an average of 2.2 years after reimplantation of the new prosthesis. Followup after the diagnosis of reinfection averaged 5.1 years. Reinfection after an attempt at reimplantation total hip arthroplasty was seldom compatible with a good functional outcome. Resection arthroplasty was reliable in eradicating reinfection but led to poor function and was associated with persistent pain. Although reimplantation of a third prosthesis allowed 3 patients to achieve an excellent result, the 8 hips that failed a third reimplantation attempt had the worst functional results in this study. The results from the present series suggest that reinfection after an attempt at reimplantation is a contraindication to further attempts at a 1-stage reimplantation of another prosthesis. Those patients in whom the same single microorganism has been identified from the failed primary total hip and from the failed first reimplantation, however, may be reasonable candidates for an attempt at a 2-stage reimplantation of a third prosthesis, particularly when a deficiency in prior antibiotic therapy or surgical technique can be identified.     

15N NMR relaxation studies of calcium-loaded parvalbumin show tight dynamics compared to those of other EF-hand proteins

Dynamics of the rat alpha-parvalbumin calcium-loaded form have been determined by measurement of 15N nuclear relaxation using proton-detected heteronuclear NMR spectroscopy. The relaxation data were analyzed using spectral density functions and the Lipari-Szabo formalism. The major dynamic features for the rat alpha-parvalbumin calcium-loaded form are (1) the extreme rigidity of the helix-loop-helix EF-hand motifs and the linker segment connecting them, (2) the N and C termini of the protein being restricted in their mobility, (3) a conformational exchange occurring at the kink of helix D, and (4) the residue at relative position 2 in the Ca2+-binding sites having an enhanced mobility. Comparison of the Ca2+-binding EF-hand domains of alpha-parvalbumin-Ca2+, calbindin-Ca2+, and calmodulin-Ca2+ shows that parvalbumin is probably the most rigid of the EF-hand proteins. It also illustrates the dynamical properties which are conserved in the EF-hand domains from different members of this superfamily: (1) a tendency toward higher mobility of NH vectors at relative position 2 in the Ca2+-binding loop, (2) a restricted mobility for the other residues in the binding loop, and (3) an overall rigidity for the helices of EF-hand motifs. The differences in mobility between parvalbumin and the two EF-hand proteins occur mainly at the linker connecting the pair of EF hands and also at the C terminus of the last helix. In parvalbumin-Ca2+, these two regions are characterized by a pronounced rigidity compared to the corresponding more mobile regions in calbindin-Ca2+ and calmodulin-Ca2+.     

Nitric oxide as an autocrine regulator of sodium currents in baroreceptor neurons

Arterial baroreceptors are mechanosensitive nerve endings in the aortic arch and carotid sinus that play a critical role in acute regulation of arterial blood pressure. A previous study has shown that nitric oxide (NO) or NO-related species suppress action potential discharge of baroreceptors. In the present study, we investigated the effects of NO on Na+ currents of isolated baroreceptor neurons in culture. Exogenous NO donors inhibited both tetrodotoxin (TTX) -sensitive and -insensitive Na+ currents. The inhibition was not mediated by cGMP but by NO interaction with channel thiols. Acute inhibition of NO synthase increased the Na+ currents. NO scavengers (hemoglobin and ferrous diethyldithiocarbamate) increased Na+ currents before but not after inhibition of NO synthase. Furthermore, NO production in the neuronal cultures was detected by chemiluminescence and immunoreactivity to the neuronal isoform of NO synthase was identified in fluorescently identified baroreceptor neurons. These results indicate that NO/NO-related species function as autocrine regulators of Na+ currents in baroreceptor neurons. Modulation of Na+ channels may represent a novel response to NO.     

Patellar component resection in revision and reimplantation total knee arthroplasty

Between 1979 and 1995, 34 knees in 31 patients had a revision or reimplantation total knee arthroplasty in which the patellar component could not be reinserted. The patellar bone stock in each of those cases was compromised markedly and precluded adequate prosthetic fixation. The mean followup after the revision operation was 3.5 years (range, 2-14 years). The Knee Society knee score improved from a mean of 59 points preoperatively to a mean of 75 points postoperatively. The function score improved from a mean of 46 points preoperatively to a mean of 69 points postoperatively. Complications occurred in five patients: one patient sustained a patellar fracture that required no additional treatment; one experienced intermittent episodes of patellar subluxation; one had a recurvatum deformity develop and was treated with a brace; one had persistent knee stiffness and had four manipulations; and one patient had an extensor lag of 30 degrees develop. Twenty-six patients were satisfied with the results of their revision operations and five were dissatisfied. Ten patients had persistent knee symptoms referable to the patellofemoral articulation: mild pain in three; moderate pain in six; and severe pain in one. This study suggests that resection of the patellar component during revision or reimplantation total knee arthroplasty may be a reasonable approach for patients with markedly compromised patellar bone stock; however, mild or moderate anterior knee pain can be expected to persist in as much as 1/3 of these patients.     

Neuropsychological assessment of the college football player

The application of neuropsychological assessment procedures to the evaluation of athletes has recently become an area of intense interest and debate and has led to the development of research initiatives at both the amateur and the professional level. However, to date, only a handful of research studies have been completed that have addressed the special issues that accompany the use of neuropsychological assessment instruments with athletes. This article reviews the past use of psychological testing in sports and presents a model of neuropsychological assessment that is currently being utilized in the National Football League. In addition, the extension of this approach to major college football is discussed and test-retest data from a sample presented to provide the basis for comparison of athletes who have suffered a concussion. Recommendations of a national panel of neuropsychologists who are involved in the evaluation of athletes are presented in hopes of encouraging new research initiatives in this area.     

Toxoplasma gondii bradyzoites form spontaneously during sporozoite-initiated development

Tachyzoites (VEG strain) that emerge from host cells infected with Toxoplasma gondii sporozoites proliferate relatively fast and double their number every 6 h. This rate of growth is intrinsic, as neither the number of host cells invaded nor host cell type appears to influence emergent tachyzoite replication. Fast tachyzoite growth was not persistent, and following approximately 20 divisions, the population uniformly shifted to slower growth. Parasites 10 days post-sporozoite infection doubled only once every 15 h and, unlike emergent tachyzoites, they grew at this slower rate over several months of continuous cell culture. The spontaneous change in tachyzoite growth rate preceded the expression of the bradyzoite-specific marker, BAG1. Within 24 h of the growth shift, 2% of the population expressed BAG1, and by 15 days post-sporozoite infection, 50% of the parasites were positive for this marker. Spontaneous BAG1 expression was not observed in sporozoites or in tachyzoites during fast growth (through day 6 post-sporozoite inoculation), although these tachyzoites could be induced to express BAG1 earlier by culturing sporozoite-infected cells at pH 8.3. However, alkaline treatment also reduced the replication of emergent tachyzoites to the rate of growth-shifted parasites, supporting a link between reduced parasite growth and bradyzoite differentiation. The shift to slower growth was closely correlated with virulence in mice, as the initially fast-growing emergent tachyzoites were avirulent (100% lethal dose, >10(4) parasites), while a mutant VEG strain (MS-J) that is unable to growth shift caused 100% mortality in mice inoculated with 10 parasites. Parasites recovered from gamma interferon knockout mice inoculated with emergent tachyzoites grew at a slow rate and expressed BAG1, confirming that the replication switch occurs in animals and in the absence of a protective immune response.     

An Implicit Learning Task Activates Medial Temporal Lobe in Patients With Parkinson's Disease.

Recent studies provide evidence for an interaction between a declarative memory system, dependent on the medial temporal lobe (MTL), and a habit memory system, dependent on the basal ganglia. Using functional MRI, the authors studied this interaction when 1 system was compromised by neurological disease. Neural activity when performing a habit-learning task was compared in normal controls and subjects with Parkinson's disease (PD). Patients with PD showed less activation in the caudate nucleus and greater activation in a region of prefrontal cortex that has been associated with explicit memory retrieval. Patients with PD also showed activation of the MTL during the weather-prediction task. These findings are consistent with an interaction between memory systems of the MTL and the striatum. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Defective pancreatic beta-cell glycolytic signaling in hepatocyte nuclear factor-1alpha-deficient mice

Mutations in the hepatocyte nuclear factor-1alpha (HNF-1alpha) gene cause maturity onset diabetes of the young type 3, a form of type 2 diabetes mellitus. In mice lacking the HNF-1alpha gene, insulin secretion and intracellular calcium ([Ca2+]i) responses were impaired following stimulation with nutrient secretagogues such as glucose and glyceraldehyde but normal with non-nutrient stimuli such as potassium chloride. Patch clamp recordings revealed ATP-sensitive K+ currents (KATP) in beta-cells that were insensitive to suppression by glucose but normally sensitive to ATP. Exposure to mitochondrial substrates suppressed KATP, elevated [Ca2+]i, and corrected the insulin secretion defect. NAD(P)H responses to glucose were substantially reduced, and inhibitors of glycolytic NADH generation reproduced the mutant phenotype in normal islets. Flux of glucose through glycolysis in islets from mutant mice was reduced, as a result of which ATP generation in response to glucose was impaired. We conclude that hepatocyte nuclear factor-1alpha diabetes results from defective beta-cell glycolytic signaling, which is potentially correctable using substrates that bypass the defect.     

Refractive changes after pediatric intraocular lens implantation

PURPOSE: To report refractive changes after cataract surgery and intraocular lens implantation in infants and children. METHODS: In an ongoing prospective study, the refractive errors of all patients younger than 18 years undergoing intraocular lens implantation were determined at 6 weeks, 3 months, 6 months, and 1 year, and at least yearly thereafter. All patients with greater than 6 months of follow-up were included in the study. RESULTS: Eighty-three eyes of 81 patients were identified. Cataracts were traumatic in 32 eyes (38%) and developmental in 42 eyes (50%). At implantation, the mean (+/-SD) age was 6.3 +/- 4.6 years (range, 9 months to 17 years). The mean follow-up was 26.6 months (range, 6 months to 6.6 years). Patients 0 to 2 years old at the time of implantation demonstrated a mean myopic shift of -3.00 diopters during a mean follow-up period of 2.5 years. Patients 2 to 6 years old at the time of implantation demonstrated a mean myopic shift of -1.50 diopters in a similar follow-up period. Children aged 6 to 8 years experienced a mean myopic shift of -1.80 diopters during a mean follow-up period of 3.0 years, while children older than 8 years at the time of intraocular lens implantation experienced a mean myopic shift of -0.38 diopters during a mean follow-up period of 1.8 years. On average, the operated-on eye showed a greater mean myopic shift than the fellow eye. No statistically significant differences in refractive change were found in comparing amblyopic to nonamblyopic eyes, traumatic to nontraumatic cataracts, or primary to secondary intraocular lenses. CONCLUSIONS: Our data demonstrate a trend toward increasing postoperative myopia in pediatric patients undergoing intraocular lens implantation. This myopic shift is greatest in the younger age groups and persists until at least 8 years of age. There is much variability in the postoperative refractive changes, and predicting exactly when and where the refraction will stabilize for an individual patient is difficult.     

Radiation dose and image quality in spiral computed tomography: multicentre evaluation at six institutions

The purpose of this study was to evaluate the correlation of radiation dose with image quality in spiral CT. Seven clinical protocols were measured in six different radiological departments provided with four different types of high specification spiral CT scanners. Central and surface absorbed doses were measured in acrylic. The practical CT dose index (PCTDI) was calculated for seven clinical examination protocols and one standardized protocol using identical parameters on four different spiral CT scanners with a dedicated ionization chamber inserted into PMMA phantoms. For low contrast measurements, a cylindrical three-dimensional (3D) phantom (different sized spheres of defined contrast) was used. Image noise was measured with a cylindrical water phantom and high contrast resolution with a Perspex hole phantom. Image quality phantoms were scanned using the parameters of the clinical protocols. Images were randomized, blinded and read by six radiologists (one from each institution). PCTDI values for four different scanners varied up to a factor between 1.5 (centre) and 2.2 (surface) for the standardized protocol. A greater degree of variation was observed for seven clinical examination protocols of the six radiological departments. For example, PCTDI varied up to a factor between 1.7 (cerebrum protocol) and 8.3 (abdomen paediatric protocol). Low contrast resolution correlates closely with dose. An improvement in detection from 8 mm to 4 mm sized spheres needs approximately a ten-fold increase in dose. Noise shows a moderate correlation with PCTDI. High contrast resolution of clinical protocols is independent of PCTDI within a certain range. Differences in modern CT scanner technology seem to be of less importance for radiation exposure than selection of protocol parameters in different radiological institutes. Future discussion on guidelines regarding optimal (patient adapted) tube current for clinical protocols is desirable.